The human Ia-like antigens, selectively expressed on B lymphocytes, are now recognized to be closely associated with, or identical to, the gene products of the major histocompatibility complex responsible for stimulation in the mixed lymphocyte reaction. The leukemic B lymphocytes of patients with chronic lymphocytic leukemia express these antigens very well. In the present study they were readily detected by several techniques utilizing both allo- and heteroantisera. However, the leukemic B cells from most patients were found to be extremely poor stimulating cells in the mixed lymphocyte reaction. This was particularly apparent when comparisons were made on a B-cell basis with isolated normal B lymphocytes.
We have developed a double-antibody radioimmunoassay for the quantitative measurement of human goblet cell mucin (GCM) in order to study intestinal mucus in human and other species. The assay used 3H-labeled mucin as the antigen, rabbit antisera, and sheep anti-rabbit IgG antisera as the second antibody. A number of applications of the assay were investigated. A survey of human tissues revealed that mucins of the rectum, colon, and small intestine had identical affinity for the rabbit antibody, whereas lung eyelid conjunctiva, esophagus, and stomach reacted less strongly. GCM concentration ranged from 1.9 to 14 microgram mucin protein/mg tissue protein in the small and large intestine, respectively. The radioimmunoassay was also found to be useful as a marker during the isolation of GCM from human ileal extracts, where it indicated that a 10,000-fold purification had been achieved. Antigenic determinants of the mucin did not rely upon ABH blood group-specific terminal sugars in oligosaccharide chains. A comparison of mucins among various species revealed a partial species specificity of the GCM antibody. Human GCM cross-reacted with dog, monkey, and rabbit mucins, but not with mucins of rat, pig, toad, and oyster. Organ distributions of cross-reactive mucins in rabbit tissues indicated a pattern that was qualitatively similar to that seen in human tissues. Possible implications of these findings for autoimmune diseases are briefly discussed.
The myopathy associated with vitamin D deficiency has not been well characterized, and it is not known if weakness is a result of a specific effect of vitamin D deficiency on skeletal muscle. Chicks were raised from hatching on a vitamin D-deficient diet, and by 3 wk of age were hypocalcemic and appeared weak. Tension generated by triceps surae during repetitive stimulation of posterior tibial nerve was significantly less than that developed by chicks given vitamin D3 supplements (309 g tension/g wet weight of triceps surae, SD 60, for vitamin D-deficient chicks; 470, SD 77, for vitamin D3-treated chicks, P < 0.01). Histochemical and electron microscopic examination of skeletal muscles of these chicks showed no abnormalities, and there were no electrophysiologic evidences of motor nerve or neuromuscular junction dysfunction. The concentration of ATP in skeletal muscle of the vitamin D-deficient chicks (5.75 μmol/g wet weight, SD 0.17) was not significantly different from that in vitamin D-treated chicks (5.60, SD 0.50). There was no correlation between strength and serum calcium, serum inorganic phosphate, or skeletal muscle inorganic phosphate. Relaxation of tension after tetanic stimulation was slowed in the vitamin D-deficient chicks (20.6 ms, SD 1.7, vs. 15.4, SD 1.3, in vitamin D-treated chicks and 15.3, SD 1.0, in normal control chicks), and in vitro 45Ca++ transport by sarcoplasmic reticulum from the vitamin D-deficient chicks was reduced. Calcium content of mitochondria prepared from leg muscles of vitamin D-deficient chicks (24 nmol/mg mitochondrial protein, SD 6) was considerably lower than that of mitochondria from normal control chicks (45, SD 8) or from chicks treated with vitamin D for 2 wk or more (66-100, depending upon level and duration of therapy). Treatment of the vitamin D-deficient chicks from hatching with sufficient dietary calcium to produce hypercalcemia did not significantly raise skeletal muscle mitochondrial calcium content (31 nmol/mg mitochondrial protein, SD 7) and did not prevent weakness. These studies demonstrate objective weakness as a result of myopathy in vitamin D-deficient chicks, and provide evidence that vitamin D deficiency has effects on skeletal muscle calcium metabolism not secondary to altered plasma concentrations of calcium and phosphate.
This free-flow micropuncture study examined the dependence of bicarbonate reabsorption in the rat superficial proximal convoluted tubule to changes in filtered bicarbonate load, and thereby the contribution of the proximal tubule to the whole kidney's response to such changes. The independent effects of extracellular fluid (ECF) volume expansion and of acidosis on proximal bicarbonate reabsorption were also examined.
The effect of testosterone (DT) and thyroxin (L-T4) on erythropoiesis and erythropoietin (Ep) production was studied in control and nephrectomized sheep fetuses beginning at about 100 d of gestation. Fetuses were given injections of either 1.2 mg/d x 13 of L-T4, 12 mg, once every 5 d x 3 of DT or the vehicle alone. Fetal plasma samples for Ep determinations were obtained before and at intervals after the start of the treatment. Reticulocyte and hematocrit levels, and the percent erythrocyte-59Fe uptake values were used to assess erythropoiesis in each fetus. No Ep was detected in plasmas of control fetuses, while significant amounts of Ep were present in plasma obtained from DT- and L-T4-treated intact fetuses. Bilateral nephrectomy did not diminish the Ep response to DT and L-T4. In both intact and nephrectomized fetuses, treatment with DT resulted in the production of significantly greater amounts of Ep than L-T4. The rise in Ep in all groups was accompanied by increases in reticulocytes (2.2 +/- 0.2% vs L-T4:8.1 +/- 0.4% and DT:7.6 +/- 0.7%), percent erythrocyte-59Fe uptake (20.5 +/- 2.9% vs. L-T4:36.7 +/- 3.8% and DT:39.1 +/- 4.0%) and hematocrit (31.2 +/- 2% vs. L-T4:41.8 +/- 3% and DT:48.6 +/- 4.2%). The enhanced erythropoiesis in all groups of nephrectomized fetuses was dependent upon the presence of Ep, because the administration of anti-Ep to these fetuses resulted in the suppression of erythropoiesis in all three groups. These data demonstrate that (a) DT and L-T4 are effective promoters of extrarenal Ep production, thereby enhancing erythropoiesis in intact and nephrectomized fetuses; (b) DT is a stronger stimulus of extrarenal Ep formation than L-T4; and (c) Ep is required for the expression of the erythropoietic effects of L-T4 and DT.
Properties of delta-aminolevulinic acid synthetase in erythroblasts of patients with pyridoxine-responsive anemia were investigated with special reference to the protease in mitochondria of erythroblasts. delta-Aminolevulinic acid synthetase activity in erythroblasts of patients with this disease before treatment was extremely decreased, whereas it gradually increased in parallel with the improvement of anemia by the therapy with pyridoxal phosphate. The amount of apo-delta-aminolevulinic acid synthetase in erythroblasts before treatment was also extremely diminished. Apparent affinity to pyridoxal phosphate of the apo-delta-aminolevulinic acid synthetase obtained from erythroblasts of the patients was almost the same as that of normal controls. The activity of a new protease which is considered to be engaged in the regulation of delta-aminolevulinic acid synthetase levels in mitochondria of erythroblasts was shown to be in normal range in erythroblasts of the patients. On the other hand, apo-delta-aminolevulinic acid synthetase obtained from the patients was extremely sensitive to the protease. These results indicate that disturbance of heme synthesis characteristic to pyridoxine-responsive anemia could be ascribed to the hypercatabolism of delta-aminolevulinic acid synthetase caused by the increased susceptibility to the controlling protease in erythroblasts.
The two-color method originally described by Van Rood et al. (Van Rood, J. J., A. Van Leeuwen, and J. S. Ploen. 1976. Simultaneous detection of two cell populations by two-color fluorescence and application to the recognition of B-cell determinants. Nature (Lond.). 262: 795-797) for the typing of homologous leukocytic antibodies, D-region was used for the detection of antilymphocyte antibody (ALA) in systemic lupus erythematosus. In this method, surface immunoglobulin-bearing cells were identified with fluorescein isothiocyanate-labeled anti-immunoglobulin and nuclei of killed cells were stained with ethidium bromide. Therefore, cell type (T or B) of the target cells can be identified without fractionating them. ALA was detected in 87% of lupus sera and had a preferential reactivity with T cells. Its major immunoglobulin class was shown to be immunoglobulin (Ig)M.
Vascular and metabolic effects of circulating epinephrine and norepinephrine have been studied in relation to the plasma concentration of these amines in dogs. Intravenous infusion of epinephrine or norepinephrine (0.1, 0.5, and 2.5 nmol x kg-1 x min-1) raised the plasma concentration of the infused amine by 2.5 , 13, and 63 nM from resting levels of 2.4 and 3.6 nM, respectively. Blood flow to isolated adipose tissue; skeletal muscle preparations; and plasma levels of glycerol, glucose, and cyclic AMP were measured. Epinephrine and norepinephrine displayed a distinct selectivity with regard to both vascular and metabolic effects. Epinephrine caused significant vasoconstriction in adipose tissue already at a plasma concentration of 5 nM, whereas no significant effect was seen on skeletal muscle vascular resistance. Norepinephrine, on the other hand, caused significant vasoconstriction in skeletal muscle at 5 nM but had no vasoconstrictor effect in adipose tissue. Epinephrine was more potent than norepinephrine in increasing plasma cyclic AMP and glucose, whereas the converse was true for plasma glycerol. Epinephrine had significant effects on plasma cyclic AMP at 5 nM and on plasma glucose and glycerol at 15 nM. Norepinephrine, on the other hand, had significant effects on plasma glycerol at 5 nM, plasma cyclic AMP at 15 nM and plasma glucose only at 65 nM. It is suggested that these response patterns are related to a preferential action of epinephrine on beta 2-adrenoceptors and a preferential action of norepinephrine on beta 1-adrenoceptors. Our results support the view that both epinephrine and norepinephrine may act as circulating hormones, because vascular and metabolic effects of both amines were seen at plasma concentrations encountered during various kinds of stress in animals and man.
Livers from normal and nephrotic rats were perfused by the nonrecirculating technique. Nephrosis was studied on the 7th d after the injection of puromycin animonucleoside. Amino acid-labeled lipoproteins (d < 1.21) were isolated from the perfusion medium by agarose column chromatography or by sequential density ultracentrifugation. In both groups of animals, in addition to very low density lipoproteins and nascent high density lipoproteins, column chromatography revealed the presence of a peak of 2-3 × 106 daltons. This peak contained lipoproteins of densities corresponding to <1.006, 1.006 < d < 1.02, and 1.02 < d < 1.06, which indicated that rat liver secretes a heterogeneous mixture of triglyceride-rich lipoproteins.
Pulmonary macrophages (PAM) metabolically activated benzo[a]pyrene [B(a)P] and its proximate carcinogenic metabolite, (±)trans 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (7,8-diol), to ultimate mutagens that were detected in cocultivated Chinese hamster V79 cells. Increases in the frequency of ouabainresistant (Or) mutations and sister chromatid exchanges were found in V79 cells only when they were cocultivated with both PAM and the chemical procarcinogens. 7,8-Diol caused higher frequencies of both Or mutations and sister chromatid exchanges than did the parent compound, B(a)P. When metabolically activated by PAM the mean Or mutation frequency caused by B(a)P was 9 Or mutants/106 surviving V79 cells per 106 PAM and a 10-fold interindividual variation (range, 2-21) was found. The mean Or mutation frequency caused by 7,8-diol was 64 and a ninefold interindividual variation (range, 14-120) was found. In the absence of PAM, the Or mutation frequency in V79 cells was one or less Or mutant per 106 survivors. 7,8-Benzoflavone, an inhibitor of mixed function oxidases, reduced the frequencies of Or mutations and of sister chromatid exchanges in V79 cells caused by 7,8-diol and B(a)P. As expected 7,8-benzoflavone did not influence the frequency of Or mutations caused by one of the ultimate mutagens derived from B(a)P and 7,8-diol, (±)7β, 8α-dihydroxy-9α, 10α-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene. These data are consistant with the hypothesis that PAM may play a role in the activation of environmental chemical procarcinogens.
A 34-year-old Black woman had severe megaloblastic anemia in childhood. Initially, and over the years, she responded well to massive doses of parenteral cobalamin (Cbl) or oral folic acid. Metabolic reactions involving Cbl and folate enzymes were normal during both relapse and remission except for the absence of thymidylate synthetase in relapse. Amino acid analyses of urine and plasma showed no significant abnormalities. Neither cystathionine, homocystine, formiminoglutamic acid, nor methylmalonic acid was detected in the urine. The serum Cbl level was repeatedly elevated even when the patient was receiving only folic acid therapy. The elevation of the vitamin in the serum was found to be a result of markedly increased levels of transcobalamin II (TC II), as identified by several physicochemical techniques. The patient's TC II-Cbl shared immunologic properties with normal TC II but did not facilitate or impede the uptake of Cbl or Cbl bound to normal TC II, respectively, by human cells.
Antibodies to T cells present in the plasma of patients with active systemic lupus erythematosus (SLE) plus complement are able to eliminate concanavalin A-induced suppressor function for the proliferative responses of T cells to allogeneic lymphocytes (MLR) and of B cells to pokeweed mitogen (PWM). Such antibodies were found to be effective in eliminating suppressor function only when T cells were treated before activation; there was no effect when treatment was performed after activation. These studies indicate that the antibodies preferentially interact with a T cell necessary for the generation of suppressor cells, rather than with mature, activated suppressor cells. Studies of individual SLE patients indicate that the same defects observed in SLE T cells were induced in normal T cells by plasma from that patient. Such observations suggest that many T-cell defects associated with active SLE may not be intrinsic T-cell abnormalities, but, rather, secondary effects of anti-T-cell antibodies. Studies of the T-cell subpopulations responsible for suppression of the MLR and PWM responses indicate that only T gamma cells (T cells bearing receptors for the Fc portion of immunoglobulin [Ig]G) acted as precursors of suppressor cells for the MLR, whereas both T gamma and T non-gamma cells (T cells not bearing receptors for the Fc portion of IgG) could be activated to suppress the PWM response. Consistent with this observation, SLE anti-T-cell antibodies that preferentially killed T gamma cells preferentially eliminated suppressor cells for the MLR.
Adrenal responsiveness to angiotensin II (AII) and the diastolic blood pressure responses to saralasin were studied in 19 patients with high renin essential hypertension (HREH) on a 10-meq Na+/100 meq K+ diet. The increment in plasma renin activity (PRA) between supine and upright positions was used as an estimate of the acute stimulation of the adrenal gland by endogenous AII; the normal increment in plasma aldosterone divided by the increment in PRA was >3.8. 7 of 19 had abnormal upright posture responses with significantly greater mean PRA increments (24±6 ng/ml per h) and significantly smaller plasma aldosterone increments 47 ± 16 ng/dl) (P < 0.036) compared to the increments observed in HREH patients with normal adrenal responsiveness (PRA = 15 ± 1 ng/ml per h; plasma aldosterone = 87 ± 17 ng/dl). When AII was infused at doses of 0.1-3 ng/kg per min, only patients with normal posture responses had normal plasma aldosterone increments; plasma aldosterone levels failed to significantly increase even at the highest infusion rate in the patients with the abnormal upright posture responses. The AII competitive inhibitor, saralasin (0.3-30 μg/kg per min) was then infused to study the occurrence of angiotensinogenic hypertension in both HREH subgroups. The mean decline in diastolic blood pressure to saralasin in the subnormal adrenal responsive patients (−15 ± 3 mm Hg) was significantly greater than in the normal adrenal responsive group (−3 ± 2 mm Hg) (P < 0.02).
Smaller very low density lipoprotein (VLDL) remnants interact more readily with tissues than do larger “intact” VLDL. This may be related to changes in the availability of VLDL apoproteins on the surface of the lipoproteins. To test this hypothesis VLDL were incubated at 37°C with bovine milk lipase (LPL), and the abilities of LPL-treated VLDL preparations to compete with 125I-low density lipoproteins (LDL) for interaction with cultured normal human fibroblasts were measured. At the same time, the immunologic activities of these preparations were also tested by double antibody radioimmunoassay. Triglyceride (TG) contents of VLDL fell by 30-90% during incubation with LPL and, on zonal ultracentrifugation, VLDL of faster Svedberg unit of flotation (Sf1.063) rates (>150) were gradually converted to smaller VLDL with lower Sf rates (21-60). LPL-treated VLDL competed two to five times more effectively with 125I-LDL for binding to cellular receptors than did control VLDL. Control VLDL incubated with heat-inactivated LPL at 37°C, or with active LPL at 4°C had unaltered cell reactivities and TG contents compared with VLDL incubated without any enzyme. The direct uptake and degradation of LPL-treated VLDL was also assessed by using VLDL 125I-labeled in apoprotein (Apo)B. LPL-treated VLDL-125I-ApoB were taken up and degraded by fibroblast at greater rates than were control VLDL-125I-ApoB. Thus, hydrolysis of VLDL lipids was accompanied by an increased ability of VLDL to interact with fibroblasts. The immunoreactivity of ApoB in the same VLDL preparations, expressed as the “apparent ApoB contents” of LPL-treated VLDL, increased by 10-50% (P < 0.02) in those assays that contained anti-LDL antisera, but the ApoB of control VLDL remained constant. However, assays that contained antisera directed against ApoB isolated from VLDL did not distinguish between LPL-treated and control VLDL. Thus, VLDL lipid hydrolysis was accompanied by changes in the immunoreactivity of VLDL-ApoB, which probably reflect changes in the disposition of ApoB on the surface of VLDL. The altered disposition of ApoB on VLDL “remnants” may be related to their enhanced interaction with cells.
We have examined the plasma Factor VIII/von Willebrand factor (FVIII/vWF) molecule from 16 patients with von Willebrand's disease, and have found no evidence of a significant decrease of carbohydrate content in 15 of these patients. FVIII/vWF was isolated by preparative counter immunoelectrophoresis directly from plasma using antibody to Factor VIII-related antigen, reduced in sodium dodecyl sulfate in the presence of urea, and electrophoresed in 5% polyacrylamide gels to separate the FVIII/vWF subunit from other proteins. Duplicate gels were stained by either the periodic acid-Schiff (PAS) reaction or by Coomassie Brilliant Blue G250. The ratio of Coomassie: PAS was determined by spectrophotometric scanning of the gels. Transferrin was used as an internal reference standard. The ratio for 23 normal individuals was 2.4±0.38 and the observed range was 1.8-3.8. 15 patients with von Willebrand's disease fell within this range. One patient independently reported as having decreased FVIII/vWF carbohydrate was also studied by this technique. A ratio of 6.8 was found, indicative of decreased, though not absent, carbohydrate. Cold insoluble globulin did not represent a significant contaminant in these analyses. 11 of the von Willebrand's disease patients with normal FVIII/vWF carbohydrate had abnormal crossed immunoelectrophoretic patterns characterized by absence of the less anodic forms of Factor VIII-related antigen. Four patients had normal patterns. These studies indicate that an absence or decrease of PAS reactive FVIII/vWF carbohydrate is not a consistent abnormality in von Willebrand's disease.
This study explores how dietary lipids are digested when intraduodenal bile salts are low or absent. Long-chain triglycerides emulsified with phosphatidylcholine were found to be hydrolyzed very slowly by pancreatic lipase alone, as if the surface layer of phospholipids enveloping the triglycerides impeded the action of the enzyme. Colipase enhanced triglyceride hydrolysis severalfold, both when added before or after the lipase. Hydrolysis became even more rapid when the emulsion was first incubated with pancreatic phospholipase. Hydrolysis of long-chain triglycerides was also severely impeded when other proteins were added to the system, probably because they adsorbed to the oil-water interface of the emulsion droplets. It was previously known that bile salts can relieve such inhibition, presumably by desorbing the adsorbed proteins. Colipase was found to enhance hydrolysis severalfold in a dose-dependent manner even in the absence of bile salts, i.e., it could partially or completely relieve the inhibition depending upon the amount and the type of inhibitory protein added to the system. Prior exposure of a protein-coated triglyceride emulsion to another lipase also enhanced the rate at which pancreatic lipase could then hydrolyze the lipids. Most dietary triglycerides are probably presented for intestinal digestion in emulsions covered by proteins and/or phospholipids. These emulsions would be hydrolyzed slowly by pancreatic lipase alone. However, through the action of the lipase in stomach contents and of pancreatic phospholipase and through the lipolysis-promoting effects of collipase, these triglycerices can be rather efficiently hydrolyzed, even in the absence of bile salts.
Low-density lipoproteins (LDL) receptor activity, as reflected by LDL degradation, was stimulated by the addition of insulin to cultures of human skin fibroblasts. These changes occurred independently of the glucose concentration of the incubation medium and occurred whether or not LDL receptor activity was suppressed. A comparison of the saturation kinetics of LDL receptor activity in the presence and absence of insulin indicated that insulin produced a 35% increase in Vmax with no difference in "apparent Km". These results suggest that insulin enhances LDL receptor activity by increasing the number of LDL receptors rather than by influencing binding affinity. In confirmation, LDL degradation by receptor negative cells was not enhanced by insulin. Sterol synthesis from [14C]acetate was also stimulated by insulin, but egress of cholesterol and cellular cholesterol content were unaffected by the hormone. The effect of insulin on LDL receptors was not dependent on its known ability to enhance cellular DNA synthesis and proliferation, because insulin stimulated LDL receptor activity in cells kept quiescent by maintenance in plasma-derived serum that was devoid of platelet derived growth factor. Nevertheless, the effect of insulin in enhancing LDL receptor number, coupled with stimulation of endogenous cholesterol synthesis, provides a mechanism whereby the cell could theoretically increase its supply of cholesterol during times of additional need.
In previous studies of two patients with polycythemia vera (PV) and heterozygous at the X-linked locus for glucose-6-phosphate dehydrogenase (G-6-PD), only type A isoenzyme was found in non-lymphoid hematopoietic cells. However, some granulocytic and erythrocytic colonies grown in vitro had type B G-6-PD and therefore arose from presumably normal progenitors. In this study we exposed marrow cells from these same two patients to high-specific activity tritiated thymidine (3HTdR) before culture to kill cells actively synthesizing DNA. Individual granulocytic colonies were plucked and tested for G-6-PD after 14 d of culture. The frequency of type B colonies rose after exposure to 3HTdR from 8/101 to 11/36 in patient 1 and from 0/32 to 6/31 in patient 2 (P less than 0.003). No increase in the frequency of normal erythroid bursts after 3HTdR exposure was seen, implying that in PV, early granulopoiesis, and erythropoiesis are regulated differently. The results demonstrated that only type A granulocytic colonies, arising from the abnormal clone, were removed by the 3HTdR. In addition, for patient 2, statistical analysis indicated there was an absolute increase in normal granulocytic colonies detected in culture. Thus, PV clonal colony-forming units in culture (CFU-C) cycle more rapidly than do normal CFU-C and may suppress proliferation of normal CFU-C in vitro.
Experiments were done in normal rats to assess kidney, single nephron, and tubuloglomerular feedback responses during renin-angiotensin blockade with the converting enzyme inhibitor (CEI) SQ 20881 (E. R. Squibb & Sons, Princeton, N. Y.) (3 mg/kg, per h). Converting enzyme inhibition was documented by complete blockade of vascular responses to infusions of angiotensin I (600 ng/kg). Control plasma renin activity was 12.5±2.7 ng angiotensin I/ml per h (mean±SEM) and increased sevenfold with CEI (n = 7). There were parallel increases in glomerular filtration rate from 1.08±0.05 to 1.26±0.05 ml/min and renal blood flow from 6.7±0.4 to 7.5±0.5 ml/min. During CEI infusion absolute and fractional sodium excretion were increased 10-fold. Proximal tubule and peritubular capillary pressures were unchanged. Single nephron glomerular filtration rate (SNGFR) was measured from both proximal and distal tubule collections; SNGFR based only on distal collections was significantly increased by CEI. A significant difference was observed between SNGFR values measured from proximal and distal tubule sites (6.0±1.6 nl/min) and this difference remained unchanged after CEI administration. Slight decreases in fractional absorption were suggested at micropuncture sites beyond the late proximal tubule, whereas early distal tubule flow rate was augmented by CEI. Tubuloglomerular feedback activity was assessed by measuring changes in proximal tubule stop-flow pressure (SFP) or SNGFR in response to alterations in orthograde microperfusion rate from late proximal tubule sites. During control periods, SFP was decreased 11.2±0.4 mm Hg when the perfusion rate was increased to 40 nl/min; during infusion of CEI, the same increase in perfusion rate resulted in a SFP decrement of 6.7±0.5 mm Hg (P<.001). When late proximal tubule perfusion rate was increased from 0 to 30 nl/min, SNGFR was decreased by 15.0±1.2 nl/min during control conditions, and by 11.3±1.3 nl/min during CEI infusion. Attenuation of feedback responsiveness during CEI was also observed at lower perfusion rates with both techniques. These results indicate that blockade of the renin-angiotensin system with CEI reduces the activity of the tubuloglomerular feedback mechanism which may mediate the observed renal vasodilation.
Diet-induced alterations in thyroid hormone concentrations have been found in studies of long-term (7 mo) overfeeding in man (the Vermont Study). In these studies of weight gain in normal weight volunteers, increased calories were required to maintain weight after gain over and above that predicted from their increased size. This was associated with increased concentrations of triiodothyronine (T3). No change in the caloric requirement to maintain weight or concentrations of T3 was found after long-term (3 mo) fat overfeeding. In studies of short-term overfeeding (3 wk) the serum concentrations of T3 and its metabolic clearance were increased, resulting in a marked increase in the production rate of T3 irrespective of the composition of the diet overfed (carbohydrate 29.6 +/- 2.1 to 54.0 +/- 3.3, fat 28.2 +/- 3.7 to 49.1 +/- 3.4, and protein 31.2 +/- 2.1 to 53.2 +/- 3.7 microgram/d per 70 kg). Thyroxine production was unaltered by overfeeding (93.7 +/- 6.5 vs. 89.2 +/- 4.9 microgram/d per 70 kg). It is still speculative whether these dietary-induced alterations in thyroid hormone metabolism are responsible for the simultaneously increased expenditure of energy in these subjects and therefore might represent an important physiological adaptation in times of caloric affluence. During the weight-maintenance phases of the long-term overfeeding studies, concentrations of T3 were increased when carbohydrate was isocalorically substituted for fat in the diet. In short-term studies the peripheral concentrations of T3 and reverse T3 found during fasting were mimicked in direction, if not in degree, with equal or hypocaloric diets restricted in carbohydrate were fed. It is apparent from these studies that the caloric content as well as the composition of the diet, specifically, the carbohydrate content, can be important factors in regulating the peripheral metabolism of thyroid hormones.
Under certain conditions, exogenously administered cholecystokinin (CCK) or its COOH-terminal octapeptide can terminate feeding and cause behavioral satiety in animals. Furthermore, high concentrations of CCK are normally found in the brains of vertebrate species. It has thus been hypothesized that brain CCK plays a role in the control of appetite. To explore this possibility, a COOH-terminal radioimmunoassay was used to measure concentrations of CCK in the cerebral cortex, hypothalamus, and brain stem of rats and mice after a variety of nutritional manipulations. CCK, mainly in the form of its COOH-terminal octapeptide, was found to appear in rat brain shortly before birth and to increase rapidly in cortex and brain stem throughout the first 5 wk of life. Severe early undernutrition had no effect on the normal pattern of CCK development in rat brain. Adult rats deprived of food for up to 72 h and rats made hyperphagic with highly palatable diets showed no alterations in brain CCK concentrations or distribution of molecular forms of CCK as determined by Sephadex gel filtration of brain extracts. Normal CCK concentrations were also found in the brains of four strains of genetically obese rodents and in the brains of six animals made hyperphagic and obese by surgical or chemical lesioning of the ventromedial hypothalamus. It is concluded that despite extreme variations in the nutritional status of rats and mice, CCK concentrations in major structures of the brain are maintained with remarkable constancy.
To investigate a possible action of insulin on the glomerulus, the binding 125I-insulin to the isolated glomeruli prepared from rat kidney was examined. When incubated at 22 degrees C, 125I-insulin binding proceeded with time and reached a steady state at 45 min at which time nonspecific binding was less than 25% of total binding. A small fraction of 125I-insulin was degraded during incubation. This binding was specific to insulin in that it was inhibited by unlabeled porcine and beef insulins and to a lesser extent by porcine proinsulin and desalanine-desasparagine insulin, but not by glucagon, parathyroid hormone, vasopressin, calcitonin, and angiotensin II. Increasing concentrations of nonlabeled insulin displaced 125I-insulin binding in a dose-dependent fashion. Scatchard plot of the data was curvilinear consistent with either two classes of receptors with different affinities or a single class of receptors that demonstrate negative cooperativity. The addition of excess nonlabeled insulin to the glomeruli preincubated with 125I-insulin resulted in a rapid dissociation of approximately or equal to 70% of bound 125I-insulin. Insulin decreased the increments in glomerular cyclic AMP levels by epinephrine and by prostaglandin E2, but not those by histamine. These data showed the presence of specific insulin receptors in the glomeruli, and that insulin action may be, at least in part, through modulation of glomerular cyclic AMP concentrations. Such action of insulin may underlie the alteration in glomerular ultrafiltration and the glomerular ultrafiltration and the development of glomerular lesions in diabetes mellitus, a disease in which insulin deficiency or the tissue resistance to insulin exists.
The initial step in the degradation pathways of proline and hydroxyproline is catalyzed by proline oxidase and hydroxyproline oxidase, yielding delta 1-pyrroline-5-carboxylate and delta 1-pyrroline-3-hydroxy-5-carboxylate, respectively. The second step is the oxidation of delta 1-pyrroline-5-carboxylate to glutamate and delta 1-pyrroline-3-hydroxy-5-carboxylate to gamma-hydroxy-glutamate. To determine if this second step in the degradation of proline and hydroxyproline is catalyzed by a common or by separate enzyme(s), we developed a radioisotopic assay for delta 1-pyrroline-3-hydroxy-5-carboxylate dehydrogenase activity. We then compared delta1-pyrroline-3-hydroxy-5-carboxylate dehydrogenase activity with that of delta 1-pyrroline-5-carboxylate dehydrogenase in fibroblasts and leukocytes from type II hyperprolinemia patients, heterozygotes, and controls. We found that cells from type II hyperprolinemia patients were deficient in both dehydrogenase activities. Furthermore, these activities were highly correlated over the range found in the normals, heterozygotes, and patients. We conclude from these data that a common delta 1-pyrroline-5-carboxylate dehydrogenase catalyzes the oxidation of both delta 1-pyrroline-5-carboxylate and delta 1-pyrroline-3-hydroxy-5-carboxylate, and that this activity is deficient in type II hyperprolinemia.
Plasma fibrinopeptide B (Bβ1-14 or FPB) immunoreactivity was studied by radioimmunoassay in patients who received intrauterine infusion of hypertonic saline to terminate pregnancy. FPB immunoreactivity increased with thrombin treatment (TIFPB) suggesting the presence of a larger FPB-containing peptide, since purified FPB is not altered by thrombin, whereas thrombin increases the immunoreactivity of Bβ1-42 (which includes FPB) 10-fold. TIFPB immunoreactivity in plasma, drawn 4 h after hypertonic saline infusion eluted from Sephadex G-50 similarly to isolated Bβ1-42. Streptokinase, incubated with normal plasma progressively generated TIFPB immunoreactivity, which showed a major component which eluted from Sephadex G-50 similarly to Bβ1-42. Streptokinase generated TIFPB much more rapidly in reptilase-treated plasma that contains fibrin I, (which still includes FPB), indicating that fibrin I is preferred over fibrinogen as a substrate for plasmin cleavage of arginine (Bβ42)-alanine (Bβ43). Serial studies were then made in 10 patients receiving intrauterine hypertonic saline. Fibrinopeptide A (FPA) levels rose immediately, reached a peak between 1 and 2 h, were declining at 4 h, and were normal at 24 and 48 h. TIFPB levels rose slightly in the 1st h, reached a peak at 4 h, and had returned to base-line values at 24 h. Serum fibrinogen degradation product levels were unchanged at 1 h, reached their highest level at 4 h, and were still markedly elevated at 24 and 48 h. Fibrinogen levels dropped slightly being lowest at 4 and 24 h. Platelet counts declined in parallel with the fibrinogen levels over the first 4 h, but continued to decrease through 48 h. Beta thromboglobulin (βTG) levels generally paralleled FPA levels whereas platelet factor 4 (PF4) levels showed only slight changes. The data indicate that immediately after intrauterine hypertonic saline infusion thrombin is formed that cleaves FPA from fibrinogen to produce fibrin I and releases βTG and PF4 from platelets. Later plasmin cleaves Bβ1-42 from fibrin I to produce fragment X, which is further degraded to form serum fibrinogen degradation products. This sequence of proteolysis indicates that plasmin action on fibrin I serves as a mechanism that regulates fibrin II formation by removing the Bβ chain cleavage site, which is required for thrombin action in converting fibrin I to fibrin II.
When serum complement is activated by either the classical or alternative pathways, a factor with an apparent 80,000 mol wt is generated that is chemotactic for human dermal fibroblasts. The origin of this serum-derived chemotactic factor (SDCF) is not known; however, it may be a cleavage product from C5 because it is inactivated by monospecific antiserum to human C5, and it is not generated when the complement system is activated in human serum deficient in C5. SDCF is not chemotactic for human neutrophils or monocytes. Because SDCF is generated when serum complement is activated, it may function in vivo to attract connective tissue fibroblasts to sites of inflammatory reactions in which the complement system participates.
Cultured mononuclear cells from human peripheral blood produce a soluble factor (MCF) that stimulates collagenase and prostaglandin E2 (PGE2) release by cultured rheumatoid synovial cells up to several hundred fold. These target rheumatoid synovial cells lack conventional macrophage markers. To determine which mononuclear cells are the source of MCF, purified populations of monocyte-macrophages, thymus-derived (T) lymphocytes, and bone marrow-derived (B) lymphocytes were prepared. The monocyte-macrophages alone produced levels of MCF that were proportional to cell density but unaffected by phytohemagglutinin or pokeweed mitogen. No detectable collagenase activity was produced by the cultured monocyte-macrophages or lymphocytes. Purified T lymphocytes produced levels of MCF approximately or equal to 1--3% those of purified monocyte-macrophages in the presence or absence of the above lectins. Purified T lymphocytes modulated the production of MCF by the monocyte-macrophages, however, in a manner dependent upon relative cell densities and the presence of lectins. For example, at optimal ratios of T lymphocytes: monocyte-macrophages, MCF production was markedly stimulated by pokeweed mitogen. Thus, interactions of T lymphocytes and monocyte-macrophages could be important in determining levels of MCF, which regulate collagenase and PGE2 production by target synovial cells in inflammatory arthritis.
The role of fibrinogen as a cofactor for platelet aggregation was examined by measuring the binding of 125I-labeled human fibrinogen to gel-filtered human platelets both before and after platelet stimulation by ADP and epinephrine. Platelet stimulation by ADP resulted in the rapid, reversible binding of fibrinogen to receptors on the platelet surface. Fibrinogen binding increased as the concentration of ADP was increased from 0.1 to 2 microM, reaching a plateau at higher ADP concentrations. Binding occurred only after platelet stimulation and in the presence of divalent cations. However, fibrinogen binding did not occur to ADP-stimulated platelets from three patients with Glanzmann's thrombasthenia. Analysis of fibrinogen binding as a function of increasing fibrinogen concentration demonstrated that maximal platelet stimulation exposed approximately or equal to 45,000 binding sites per platelet with a dissociation constant of 80--170 nM. These fibrinogen binding parameters were essentially the same whether ADP or epinephrine was the platelet-stimulating agent. Thus, these studies demonstrate that platelet stimulation by ADP and epinephrine exposes a limited number of fibrinogen receptors on the platelet surface. Furthermore, these data suggest that the fibrinogen molecules bound to the platelet as a consequence of platelet stimulation are directly involved in the platelet aggregation response.
Our recent in vivo studies have suggested that intrapituitary l-thyroxine (T4) to 3,5,3′-triiodo-l-thyronine (T3) conversion with subsequent nuclear binding of T3 is an important pathway by which circulating T4 can inhibit thyrotropin release. The present studies were performed to evaluate various physiological and pharmacological influences on these two processes in rat anterior pituitary tissue. Intact pituitary fragments were incubated in buffer—1% bovine serum albumin containing 0.14 ng/ml [131I]T3 and 3.8 ng/ml [125I]T4. Nuclei were isolated after 3 h of incubation and the bound iodothyronines identified by paper chromatography. There was 0.3-1% [125I]T3 contaminating the medium [125I]T4, and this did not change during incubation. Nuclear [125I]T4 was not decreased by 650-fold excesses of medium T3 or T4, suggesting that it was nonspecifically bound. The ratio of nuclear to medium [131I]- and [125I]T3 were expressed as nuclear counts per minute per milligram wet weight of tissue:counts per minute per microliter medium. Intrapituitary T4 to T3 conversion was evidenced by the fact that the nuclear:medium (N:M) ratio for [131I]T3 was 0.45±0.21, whereas that for [125I]T3 was 2.23±1.28 (mean±SD, n = 51). A ratio (R), the N:M [125I]T3 divided by the N:M [131I]T3, was used as an index of intrapituitary T4 to T3 conversion. Increasing medium T3 concentrations up to 50 ng/ml caused a progressive decrease in the N:M ratio for both T3 isotopes, but no change in the value for R, indicating that both competed for the same limited-capacity nuclear receptors. Increasing concentrations of medium T4 caused no change in the N:M [131I]T3 but did cause a significant decrease in R in three of four experiments. These results suggest saturation of T4-5′-monodeiodination occurred at lower T4 concentrations than saturation of nuclear T3 binding sites. In hypothyroid rats, the N:M ratios for both [131I]T3 and [125I]T3 were increased (P < 0.005), but R was three-fold higher than in controls (P < 0.005). Animals given 10 μg T4/100 g body wt per d for 5 d had significantly decreased N:M ratios for both [131I]T3 and [125I]T3, as well as a decreased value for R. In fasted rats, neither N:M ratio was depressed, although hepatic T4 to T3 conversion in the same animals was 50% of control (P < 0.005). Iopanoic acid (13 μM), but not 6-n-propylthiouracil (29 μM), decreased the N:M [125I]T3 with a significant decrease in the value for R (P < 0.025 or less). Neither sodium iodide (6 μM) nor thyrotropin-releasing hormone (7-700 nM) affected the T3 N:M ratios. These results indicate that intrapituitary T4 to T3 conversion is stimulated in hypothyroidism and depressed in T4-treated animals, whereas opposite changes occur in hepatic T4-5′-monodeiodination. Unlike liver, anterior pituitary T4-5′-monodeiodination is not affected by fasting or incubation with 6-n-propyl-2-thiouracil, but T4 to T3 conversion is inhibited in both by iopanoic acid. These results indicate that there are important differences between anterior pituitary and other tissues in the regulation of T4-5′-monodeiodination.
Experimental myocardial ischemia produced in dogs by proximal left anterior descending coronary artery ligation is accompanied by relatively rapid (1 h) increases in the number of (-) [3H]dihydroalprenolol binding sites without changing their dissociation constants in ischemic left ventricular tissue. The changes, persist for at least 8 h and are accompanied by marked decreases in myocardial tissue ischemic region norepinephrine content. In contrast, in the same canine model 1 h of proximal left anterior descending coronary artery ligation did not result in a significant change in the number of [3H]quinuclidynl benzilate binding sites of their dissociation constants. However, the number of [3H]quinuclidynl benzilate binding sites (muscarinic cholinergic receptors) are 50--70% greater than (-) [3H]dihydroalprenolol binding sites (beta adrenergic receptors) in canine left ventricular tissue. Thus, the data suggest that proximal left anterior descending coronary artery occlusion for 1 h significantly increases the number of beta adrenergic receptors in ischemic left ventricular tissue without changing the number of muscarinic cholinergic receptors. Whether the ischemia-produced increase in cardiac beta-receptor content is causally related to increased cyclic AMP levels that develop in ischemic tissue and/or an etiologic factor in arrhythmias originating from ischemic myocardial tissue will have to be determined in additional studies.
In 1971, thyroid function was evaluated in 15 unselected patients whose only therapy for diffuse toxic goiter was a course of thionamide drug treatment completed 20-27 yr earlier. One patient was frankly hypothyroid by clinical and laboratory criteria. The remaining 14 patients appeared clinically euthyroid and had a normal serum thyroxine (T4) concentration and thyroid radioiodine uptake (RAIU). Nevertheless, only 6 of 14 appeared to be entirely normal according to more refined criteria. The serum thyrotropin (TSH) concentration was markedly elevated in one patient and above the normal range (1.6±2.0; mean±2 SD) in five others. Thyroid stimulation with exogenous TSH revealed subnormal responses of the serum T4I, RAIU, or both, in 7 of 11 patients tested. An abnormal iodideperchlorate discharge test was found in 5 of 10 patients and appeared most abnormal in patients with abnormal RAIU responses to TSH. Fluorescent antimicrosomal antibody was found in the serum of 12 of the 15 patients, in contrast to an expected frequency of 7% in normal individuals of the same age.
Poison oak, ivy, and sumac dermatitis is a T-cell-mediated reaction against urushiol, the oil found in the leaf of the plants. This hapten is extremely lipophilic and concentrates in cell membranes. A blastogenesis assay employing peripheral blood lymphocytes obtained from humans sensitized to urushiol is described. The reactivity appears 1--3 wk after exposure and persists from 6 wk to 2 mon. The dose-response range is narrow, with inhibition occurring at higher antigen concentrations. Urushiol introduced into the in vitro culture on autologous lymphocytes, erythrocytes and heterologous erythrocytes produces equal results as measured by the optimal urushiol dose, the intensity of reaction, and the frequency of positive reactors. This suggests that the urushiol is passed from introducer to some other presenter cell. Although the blastogenically reactive cell is a T cell, there is also a requirement for an accessory cell, found in the non-T-cell population, for reactivity. Evidence is presented that this cell is a macrophage.
[14C]Arachidonic acid incubated with human neutrophils was esterified into phospholipids and triglycerides. Stimulation of these labeled neutrophils with ionophore A23187 (2 microM) results in release of [14C]arachidonate from phospholipid and its metabolism to prostaglandin E2 and 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE), a lipoxygenase product. The released arachidonate is also metabolized to a polar lipid of unknown composition here disignated compound A. 5-HETE was found to be released into the medium and then taken up again by the cells. To determine its metabolic fate, [14C]5-HETE was prepared biosynthetically, purified, and incubated with stimulated, unlabeled neutrophils. Most of the radioactivity entered the cells and was esterified into phospholipids and triglycerides. The radiolabeled complex lipids were saponified, and the released fatty acids cochromatographed with authentic 5-HETE. The esterification of 5-HETE, a hydroxylated fatty acid, into membrane phospholipids may be an example of a more generalized mechanism for altering membrane characteristics.
The natriuresis and concomitant decline in absolute proximal reabsorption (APR) that occur in rats in response to saline loading are blunted markedly when renal perfusion pressure is reduced immediately before, but not after, the volume load. To ascertain the mechanism responsible for these differences between early clamp (EC) vs. late clamp (LC), intracapillary and interstitial determinants of peritubular capillary uptake of APR were measured in seven LC and seven EC Munich-Wistar rats before and after isotonic saline loading (80% body wt). With volume expansion in LC animals, we observed a marked decline in APR (averaging 11±1 nl/min), associated with large increases in urinary sodium excretion rate, which averaged 8±2 μeq/min. In EC, the changes in urinary sodium excretion rate (+1±0 μeq/min) and APR (−3±1 nl/min) with volume expansion were smaller in magnitude. Since peritubular capillary reabsorption coefficient and mean peritubular transcapillary hydraulic pressure difference did not change with saline loading in LC, the marked fall in APR was attributed primarily to a measured large decline in mean peritubular transcapillary oncotic pressure difference (δ̄π̄). Despite an equivalent mean fall in δ̄π̄ with volume expansion in EC, near-constancy of APR was found to be associated with a simultaneous and equivalent decline in mean peritubular transcapillary hydraulic pressure difference (a consequence of decreased mean peritubular capillary hydraulic pressure), which effectively offset the fall in δ̄π̄. These results demonstrate the importance of hydraulic pressure patterns of the peritubular capillaries in modulating APR and are consistent with the view that Starling forces across the postglomerular microcirculation play a fundamental role in determining APR.
Effects of neomycin were studied on serum cholesterol and fecal steroids in hypercholesterolemic patients during a short treatment period (4 wk) and a long treatment period (16 mo), using small (1.5 g/d) and large (up to 6 g/d) doses alone and in combination with cholestyramine. In the short-term low-dose study the decrease in serum cholesterol by 21% was associated with a proportionate increase in fecal cholesterol elimination as neutral sterols through impaired cholesterol absorption. Serum cholesterol remained low and fecal steroid excretion remained elevated in the long-term neomycin study. Increasing the dosage from 1.5 to 6 g/d at the end of the 16-mo period brought about a further slight decrease in serum cholesterol and a small further increase in fecal neutral and acidic steroids. The increases in fecal bile acids and fat but not in neutral sterols were positively correlated with the increases in the neomycin dosage. Thus, large neomycin doses can also cause bile acid malabsorption. In another series of patients, a decrease (25%) in serum cholesterol by cholestyramine was associated with a proportional increase in the fecal elimination of cholesterol (2.5-fold) as bile acids. The inclusion of neomycin in cholestyramine therapy further increased fecal steroid output (solely as neutral sterols) by only about one-fifth of that due to cholestyramine, but further decreased serum cholesterol almost to the same extent (-17%) as cholestyramine alone. The overall decrease was 38%, no side effects occurred, and the patients found combination therapy convenient. Neomycin decreased serum cholesterol in different studies by 10±2, 17±4, and 12±4% per 100 mg/d of the increment in fecal steroids, the respective decrease for cholestyramine being only 2.2±0.5%. Thus, neomycin effectively reduced serum cholesterol by a relatively small increase in cholesterol elimination (via cholesterol malabsorption) compared with cholestyramine-induced bile acid malabsorption.
We studied the effect of furosemide on pulmonary oxygen exchange, lung liquid, and central hemodynamics in dogs with pulmonary capillary leak induced by intravenous oleic acid (OA). 2 h after OA, triple indicator-dilution lung liquid volume and pulmonary shunt (Qs/Qt) doubled despite normal pulmonary capillary wedge pressure in 16 dogs compared with dogs not given OA in which no variable change during the same time. Six edematous dogs were then treated with furosemide (1 mg/kg), and 2 h later they showed significant reductions in Qs/Qt and lung liquid. In contrast, six other edematous dogs not given furosemide increased Qs/Qt and lung liquid during the same time. The changes in edema after furosemide could not be attributed to altered wedge or colloid osmotic pressures, and similar changes in Qs/Qt and lung liquid with furosemide were observed in four nephrectomized dogs. We conclude that pulmonary vasoactive effects of furosemide account for reduced shunt and edema in canine pulmonary capillary leak. These effects of furosemide differ from those in cardiogenic pulmonary edema, and suggest a different rationale for diuretic therapy in low-pressure pulmonary edema. Analysis of count rates from 51Cr-labeled erythrocytes and 125I-labeled albumin in lungs excised from 12 dogs indicated that the composition of excess lung liquid did not change with furosemide, and was 50% plasma, 25% blood, and 25% crystalloid.
To investigate whether skeletal muscle is resistant to insulin in insulinopenic states, insulin binding and biological effects on glucose utilization were studied in isolated soleus muscles from 24- or 48-h-fasted mice and from streptozotocin-diabetic mice. Both 48-h fasting and diabetes led to an increase in insulin binding at insulin concentrations <3.4 nM. In both states, submaximal concentrations of insulin were also more effective in stimulating muscle 2-deoxyglucose uptake and glycogen synthesis, and in activating glycogen synthase. This resulted in a two- to fourfold leftward shift in the insulin dose-response curves in muscles from both groups compared with control. No change in insulin binding or biological effects was detected in muscles from 24-h-fasted mice. Maximal insulin effectiveness on 2-deoxyglucose uptake and glycolysis was either unchanged or only slightly enhanced in 48-h-fasted mice and in diabetic animals, compared with controls. Maximal insulin effects on glycogen synthesis and glycogen synthase activation were unaltered by fasting or diabetes. Basal glucose uptake and glycolysis were similar in all groups of mice. In conclusion, when soleus muscles from 48-h-fasted mice and from diabetic mice are compared with controls it can be observed that, (a) at low insulin concentrations insulin binding is increased and insulin effectiveness in stimulating glucose transport and metabolism is enhanced; (b) biological responses to maximally effective insulin concentrations are either unaltered or slightly increased; (c) basal rates of glucose transport and metabolism are essentially unaltered. These results indicate that in insulinopenic states soleus muscle is not insulin resistant in vitro but is hypersensitive to low concentrations of insulin, and normally responsive to maximally effective doses of the hormone.
The addition of bacterial lipopolysaccharide (LPS) from Escherichia coli 0111:B4 or Salmonella minnesota R595 to plasma (or serum) resulted in a marked reduction of the hydrated buoyant density of the parent LPS (0111:B4 [d = 1.44 g/cm3] and R595 [d = 1.38 g/cm3]), to d less than 1.2 g/cm3. This reduction in buoyant density to less than 1.2 g/cm3 of the LPS required plasma (or serum) lipid. Delipidation of plasma (or serum) by extraction with n-butanol/diisopropyl ether (40/60, vol:vol) prevented the conversion of the parent LPS to a form with d less than 1.2 g/cm3. Reversal of the effect of delipidation was accomplished by the addition of physiologic concentrations of high density lipoprotein (HDL). In contrast, as much as two times normal serum concentration of low density or very low density lipoprotein were ineffective. The ability of normal plasma (or serum) to inhibit the pyrogenic activity of LPS, lost after delipidation, was also restored after the addition of HDL. Preliminary results suggested that prior modifications of the LPS, probably disaggregation, may be required before interaction with HDL.
Immune complex-induced vascular damage can be markedly suppressed by treatment of rats with either prostaglandin (PG)E1 or its stable derivative, 15-(S)-15-methyl PGE1, but not with PGF2 alpha. In addition, PGD2 and PGE2 also show suppressive effects. The PGE1 derivative is considerably more effective than PGE1 and shows potent anti-inflammatory activity even after oral administration. Suppression of the vasculitis reaction is reflected by a greatly diminished increase in vasopermeability, indicating little or no vascular damage. In suppressed animals, the infiltration of neutrophils is greatly reduced, and those leukocytes that have appeared at tissue sites fail to show phagocytic uptake of immune complexes. In suppressed animals, the skin sites nevertheless show deposits of immune complexes and C3 fixation in vascular walls. Neutrophils harvested from the blood of rats treated with PGE1 show depressed responsiveness in chemotaxis and in enzyme secretion after incubation with chemotactic peptide. These studies indicate that certain PG have potent anti-inflammatory activity, which may be related to their effects on leukocytes.
The monoclonal immunoglobulin (Ig)M from 5 to 16 patients with Waldenström's macroglobulinemia and a polyneuropathy shared cross-idiotypic antigenic determinants as demonstrated by hemagglutination and hemagglutination inhibition experiments as well as by precipitin reactions. This reactivity was located to the Fab (and not Fc) fragment of the protein. The IgM from 73 patients with macroglobulinemia but without neuropathy all gave negative reactions. In contrast, the monoclonal IgG from a patient with polyneuropathy also possessed similar idiotypic determinants. Since cross-idiotypic determinants are usually related to the combining site of a monoclonal Ig, this finding suggests that the monoclonal Ig of these patients may mediate the nerve injury via their antibody activity, which could be directed either to a nerve antigen or to some component involved in the pathogenesis of the neuropathy.
Prostaglandins (PG) of the E series, PGE1 and PGE2 (PGEs), can induce elevations of intracellular cyclic AMP (cAMP) among thymus-derived (T) lymphocytes (T cells) and inhibit their reactivity. For example, 0.1 μM of PGEs induces a two- to threefold increase of intracellular cAMP among human peripheral blood T cells and a 20-30% suppression of their blastogenic response to phytohemagglutinin. However, this suppression actually represents the net reactivity of T-cell populations demonstrating quite different responses to PGEs. Fractionation of T-enriched populations on a discontinuous density gradient yields a population of high density cells whose phytohemagglutinin-induced blastogenic response is suppressed 60%; a population of intermediate density cells whose response is suppressed 20%; and a population of low density T cells whose response is not suppressed, but is enhanced 20% by both of the PGEs. The diametrically opposite responses of low and high density T cells to the PGEs is not related to any difference in their intrinsic mitogen reactivity nor is it influenced by interactions with other T cells, bone marrow-derived (B) cells, or monocytes. Moreover, the distinct blastogenic response of low and high density T cells to PGEs does not simply correlate with PGE-mediated activation of adenylate cyclase. PGE2 induced comparable absolute and identical relative increases of intracellular cAMP among the low and high density T cells. Cholera toxin, a potent activator of adenylate cyclase, and exogenous 8-bromo cAMP mimicked the effects of the PGEs on these two T-cell populations. These data demonstrate that T cells are heterogeneous with regard to their response to the PGEs. Thus, PGEs should be considered as potential regulators rather than as universal suppressors for T-cell reactivity. Moreover, the effect of PGEs on the blastogenic response of a given T-cell population depends upon intracellular events which occur subsequent to elevations of cAMP.
The kinetics for mesangial uptake and transport of radiolabeled aggregated human immunoglobulin (Ig)G (AHIgG125I) deviated markedly from normal in male Sprague-Dawley rats with ureteral obstruction. Four experimental groups, each containing 25 rats, were used: (a) bilateral ureteral ligation (BUL) with release of one ureter 24 h later; (b) unilateral ureteral ligation with release 24 h later [UUL(R)]; (c) unilateral ureteral ligation without release (unreleased) [UUL(U)]; (d) uremia-control, which consisted of rats with ligated left ureter and a severed right ureter. A similar number of sham-operated rats served as control for each group. AHIgG125I (45 mg/100 g body wt) was given intravenously 1 h after release of the ureteral obstruction (25 h after ureteral obstruction or sham surgery). Groups of five control and five experimental animals were sacrificed at 2, 4, 8, 16, and 24 h after injection.
Hypocalcemia during magnesium (Mg) depletion has been well described, but the precise mechanism(s) responsible for its occurrence is not yet fully understood. The hypocalcemia has been ascribed to decreased parathyroid hormone (PTH) secretion as well as skeletal resistance to PTH. Whereas the former is well established, controversy exists as to whether or not Mg depletion results in skeletal resistance to PTH. These studies examine the skeletal response to PTH in normal dogs and dogs fed a Mg-free diet for 4-6 mo. Isolated tibia from normal (serum Mg 1.83±0.1 mg/100 ml) and experimental dogs (serum Mg 1.34±0.15 mg/100 ml) were perfused with Krebs-Henseleit buffer during a constant infusion of 3 ng/ml of synthetic bovine PTH 1-34 (syn b-PTH 1-34). The arteriovenous (A-V) difference for immunoreactive PTH (iPTH) across seven normal bones was 37.5±3%. In contrast, the A-V difference for iPTH was markedly depressed to 10.1±1% across seven bones from Mg-depleted dogs. These findings correlated well with a biological effect (cyclic AMP [cAMP] production) of syn b-PTH 1-34 on bone. In control bones, cAMP production rose from a basal level of 5.8±0.2 to 17.5±0.7 pmol/min after syn b-PTH 1-34 infusion. In experimental bones, basal cAMP production was significantly lower than in controls, 4.5±0.1 pmol/min, and increased to only 7.1±0.4 pmol/min after syn b-PTH 1-34 infusion. Even when PTH concentrations were increased to 20 ng/ml, cAMP production by experimental bones was lower than in control bones perfused with 3 ng/ml. Histological examination of bones from Mg-deficient dogs showed a picture compatible with skeletal inactivity. These studies demonstrate decreased uptake of iPTH and diminished cAMP production by bone, which indicates skeletal resistance to PTH in chronic Mg deficiency.
Prostaglandins have been postulated to participate in the regulation of salt excretion during acute volume expansion. The present papillary and cortical micropuncture studies were designed to examine the effect of prostaglandin synthesis inhibitors on segmental chloride transport during hydropenia (with and without meclofenamate) and 10% volume expansion (with and without both meclofenamate and indomethacin). Both inhibitors significantly decreased the urinary excretion rate of prostaglandins E2 and F2α. Clearance studies on the intact right kidney demonstrated no effect of either agent on glomerular filtration rate, but a significant reduction in chloride excretion during hydropenia and volume expansion was observed. To assess the specific site(s) of enhanced chloride reabsorption, absolute and fractional chloride delivery was measured in the late proximal tubule, thin descending limb of Henle, and the early and late distal tubules. In addition, the fraction of filtered chloride remaining at the base and tip of the papillary collecting duct was compared to that fraction remaining at the superficial late distal tubule. During hydropenia, meclofenamate had no effect on fractional chloride delivery out of the superficial late distal tubule or the juxtamedullary thin descending limb of Henle, but significantly reduced the fraction of chloride delivered to the base of the papillary collecting duct. During volume expansion, neither meclofenamate nor indomethacin had an effect on absolute chloride delivery out of the proximal tubule or the thin descending limb of Henle. However, absolute chloride delivery to the early distal tubule was significantly reduced, and was associated with a decrease in fractional chloride reabsorption in this segment. Furthermore, the fraction of chloride delivered to the base of the collecting duct was significantly reduced. Fractional reabsorption along the terminal 1 mm of the collecting duct was not altered by either meclofenamate or indomethacin. These results suggest that inhibitors of prostaglandin synthesis result in an increase in chloride reabsorption in the superficial loop of Henle, and in segments between the superficial late distal tubule and the base of the collecting duct. The results are consistent with the view that prostaglandins inhibit chloride transport in the thick ascending limb of Henle, and/or the cortical and outer medullary collecting tubule.
Eosinophil leukocytes have been reported to have a major role in host defense against invasive, migratory phases of helminth infestations, yet the relative larvicidal abilities of eosinophils and neutrophils have not been thoroughly examined. This study examined the killing of newborn (migratory phase) larvae of Trichinella spiralis during incubation by human granulocytes in vitro. The assay employed cultue of larvae with cells, sera, and reagents in microtiter wells with direct counting of surviving larvae after incubation. Killed larvae appeared to be lysed. Verification of the microplate assay was obtained by demonstrating complete loss of infectivity of larvae incubated with leukocytes and immune serum. In the presence of optimal immune serum concentrations, purified neutrophils or eosinophils achieved ≥95% killing of larvae at cell:larva ratios of 2,000:1 or greater. Fresh normal serum prompted slight (19%) killing by leukocytes at a cell:larva ratio of 9,000:1. Cells plus heat-inactivated normal serum and all sera preparations in the absence of leukocytes killed <8% of the larvae. The activity of immune serum was opsonic. Cells adhered to larvae that had been preincubated in immune serum, and immunofluorescent studies indicated that such preopsonized larvae were coated with immunoglobulin (Ig)G. However, preopsonized larvae lost opsonic activity and surface IgG during incubation for 3 h in medium lacking immune serum.
Studies were performed to ascertain the effect of urushiol analogues on the in vitro lymphocyte blastogenesis elicited by urushiol in peripheral blood lymphocytes taken from individuals sensitized to poison oak or ivy. Urushiol is a mixture of alkylcatechols composed of a catechol ring coupled to mono-, di-, or tri-unsaturated C-15 or C-17 carbon side chains. Each of these two moieties, catechol ring and side chain, was tested for its role in eliciting reactivity. Analogues tested represented the catechol ring (3-methylcatechol), the mono- or di-unsaturated side chain (oleic or linoleic acid), and the saturated side chain coupled to a catechol ring (pentadecylcatechol), a blocked catechol ring (heptadecylveratrole), or a resorcinol (pentadecylresorcinol). Urushiol with a blocked catechol ring (urushiol dimethyl ether) was also included.
Deoxyadenosine and deoxyguanosine are toxic to human lymphoid cells in culture and have been implicated in the pathogenesis of the immunodeficiency states associated with adenosine deaminase and purine nucleoside phosphorylase deficiency, respectively. We have studied the relative incorporation of several labeled nucleosides into DNA and into nucleotide pools to further elucidate the mechanism of deoxyribonucleoside toxicity. In the presence of an inhibitor of adenosine deaminase [erythro-9-(2-hydroxy-3-nonyl)adenine [EHNA], 5 μM], deoxyadenosine (1-50 μM) progressively decreased the incorporation of thymidine, uridine, and deoxyuridine into DNA, but did not affect uridine incorporation into RNA. This decrease in DNA synthesis was associated with increasing dATP and decreasing dCTP pools. Likewise, incubation of cells with deoxyguanosine caused an elevation of dGTP, depletion of dCTP, and inhibition of DNA synthesis.
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