P M Henson, R B Johnston Jr
Rhesus monkeys were fed corn or coconut oil-based diets for 3-6 mo to determine effects on the composition of all lipoprotein classes and on the metabolism of high density lipoproteins (HDL). Major findings included the following. Coconut oil feeding increased concentrations of all classes of plasma lipoproteins without altering lipoprotein size, suggesting an increase in particle number. The percentage of saturated fatty acids in the cholesteryl esters (CE) of low density lipoproteins (LDL) and HDL reached 40% with coconut oil feeding. This value probably constitutes a minimum estimate of the CE which were of intracellular rather than intraplasmic origin. The CE in LDL and HDL were nearly identical suggesting virtually complete equilibration by the core lipid transfer reaction. The CE in very low density lipoproteins, in contrast, were significantly more saturated than those in LDL and HDL irrespective of diet. Lower HDL levels on the corn oil diet were associated with higher fractional catabolic rates for both apolipoprotein A-I (0.42 vs. 0.31 d-1) and apolipoprotein A-II (0.45 vs. 0.30 d-1).
K S Chong, R J Nicolosi, R F Rodger, D A Arrigo, R W Yuan, J J MacKey, S Georas, P N Herbert
Free-flow micropuncture experiments were performed to examine ammonia transport separately in early and late proximal convoluted tubule (PCT) of the rat. In control rats, ammonia was secreted along the early PCT but was reabsorbed along the late PCT. In rats with chronic metabolic acidosis, ammonia secretion along the early PCT was increased compared with controls, and ammonia absorption by the late PCT was converted to small net ammonia secretion. In the acidotic rats, ammonia secretion rate in the early PCT was six times higher than that in the late PCT. Thus, most or all of ammonia secretion by the PCT occurred along its early portion. In control and acidotic rats, luminal NH3 concentration in the early PCT was significantly higher than that in the late PCT, indicating that ammonia is not in diffusion equilibrium throughout the renal cortex. It is proposed that differences in ammonia transport rate in early vs. late PCT may be due to differences in ammonia production rate and/or to differences in the rate of an ammonia backflux that detracts from net ammonia secretion.
D W Good, T D DuBose Jr
We investigated the effects of the antifolate methotrexate on intracellular folate pools of human myeloid precursor cells (MPCs). Immature MPCs, representing 3.2% of the original marrow population, were selected from normal human bone marrow by immune rosetting. The intracellular folate pools were labeled by incubation with 5 X 10(-8) M [3H]5-formyl-FH4 and were quantitated by high performance liquid chromatography. The predominant folates were 5-methyl-tetrahydrofolate (5-methyl-FH4) (36%), 10-formyl-FH4 (41.4%), 5-formyl-FH4 (12.3%), and FH4 (10.3%). A 12-h exposure to 1 microM methotrexate (MTX) resulted in a 34% reduction in the intracellular concentration of 10-formyl-FH4, a 61% decrease in 5-formyl-FH4, and a 62% decrease in 5-methyl-FH4, as well as the appearance and progressive expansion of the FH2 and 10-formyl-FH2 pools. These changes were maximal after 4 h of incubation with MTX. Paralleling the changes in folates, particularly the increase in FH2, were a 64% reduction in myeloid colony formation and a 77% depression of de novo purine synthesis after 4 h of MTX. We conclude that MTX does not produce quantitative depletion of 10-formyl-FH4 and that its antipurine effect may be mediated by direct inhibition of de novo purine synthesis by FH2 and, at later time points, by MTX polyglutamates.
J Baram, C J Allegra, R L Fine, B A Chabner
Hereditary angioneurotic edema (HANE) results from deficiency of complement 1 inhibitor (C1 INH). In type I HANE, C1 INH is present in serum at levels 5-30% of normals. Using cultured monocytes and biosynthetic labeling of proteins, C1 INH was detected in supernatants of cells from HANE patients at levels 20% of those detected in normals. The intracellular reduction of C1 INH in patients' monocytes approached 50%. The study of C1 INH messenger RNA (mRNA) by Northern blot analysis indicated that in HANE patients' monocytes a message of normal size is present at about half the concentration of that from normal cells. One of the patients analyzed showed the presence of a genetically inherited abnormal mRNA (1.9 kb) in addition to the normal mRNA (2.1 kb). Southern blot analysis of DNA from peripheral blood leukocytes did not show any difference in quantity or in sizes of endonuclease restriction fragments between patients and normals. The defect(s), therefore, in type I HANE is pretranslational, but is not due to a deletion or to a major chromosomal rearrangement.
M Cicardi, T Igarashi, F S Rosen, A E Davis 3rd
We have investigated glucose transport proteins in isolated human adipocytes. Using the cytochalasin B binding assay to measure glucose transporters in subcellular membrane subfractions, we found that insulin induced translocation of intracellular glucose transporters to the cell surface. Isoelectric focusing of glucose transporters photolabeled with [3H]cytochalasin B revealed two distinct glucose transporter isoforms in low density microsomes focusing at pH 5.6 and pH 6.4, but only the pH 5.6 isoform was detectable in plasma membranes and only the pH 6.4 form was found in the high density microsomes. Insulin recruited only the pH 5.6 glucose transporter from the low density microsomes to the plasma membrane with no effect on the pH 6.4 transporter isoform. The results suggest that the pH 6.4 species is an immature form of the glucose transporter initially located in the high-density microsome fraction, which then migrates to the low-density microsomes where it matures (converted to pH 5.6 species) and becomes available for insulin-mediated recruitment to the plasma membrane.
S Matthaei, W T Garvey, R Horuk, T P Hueckstaedt, J M Olefsky
Adenosine analogs were used to investigate the cellular mechanisms by which adenosine may alter renal tubular function. Cultured rabbit cortical collecting tubule (RCCT) cells, isolated by immunodissection, were treated with 5'-N-ethylcarboxamideadenosine (NECA), N6-cyclohexyladenosine (CHA), and R-N6-phenylisopropyladenosine (PIA). All three analogs produced both dose-dependent inhibition and stimulation of RCCT cell cyclic AMP (cAMP) production. Stimulation of cAMP accumulation occurred at analog concentrations of 0.1 microM to 100 microM with the rank order of potency NECA greater than PIA greater than CHA. Inhibition occurred at concentrations of 1 nM to 1 microM with the rank order of potency CHA greater than PIA greater than NECA. These effects on cAMP production were inhibited by 1,3-diethyl-8-phenylxanthine and isobutylmethylxanthine. CHA (50 nM) blunted AVP- and isoproterenol-stimulated cAMP accumulation. This modulation of hormone-induced cAMP production was abolished by pretreatment of RCCT cells with pertussis toxin. Prostaglandin E2 production was unaffected by 0.1 mM CHA. These findings indicate the presence of both inhibitory (A1) and stimulatory (A2) receptors for adenosine in RCCT cells. Moreover, occupancy of the A1 receptor causes inhibition of both basal and hormone-stimulated cAMP formation through an action on the inhibitory guanine nucleotide-binding regulatory component, Ni, of the adenylate cyclase system.
L J Arend, W K Sonnenburg, W L Smith, W S Spielman
The function of macrophage C3 receptors was assessed in vivo by measuring the clearance of C3-sensitized autologous erythrocytes in seven acquired immunodeficiency syndrome (AIDS) patients, eight healthy homosexual men, eight healthy heterosexual men, and four infected controls. Healthy heterosexual men had an initial clearance of 50.1 +/- 2.0% of the inoculum, with a release of a small portion of these cells (10.9 +/- 1.3%) into the circulation. Healthy homosexual men had a greater initial clearance of 66.0 +/- 4.2% (P less than 0.01) followed by a similar release (14.0 +/- 3.3%). AIDS patients had an initial clearance of 60.6 +/- 7.5% but had a relatively large release of cells (25.6 +/- 3.2%) (P less than 0.005 vs. heterosexuals; P less than 0.05 vs. homosexuals), suggesting a failure of macrophage phagocytosis. Infected controls had an initial clearance of 59.4 +/- 4.9%, with a release of 19.6 +/- 3.8% (P = NS vs. AIDS). These data, in addition to Fc-receptor dysfunction, demonstrate a global reticuloendothelial system dysfunction in AIDS patients. This may contribute to their frequent infections with opportunistic pathogens and inappropriate immune responses against these microorganisms.
B S Bender, J F Bohnsack, S H Sourlis, M M Frank, T C Quinn
Purified murine colony-stimulating factors (CSF) recombinant interleukin 3 (IL-3), natural CSF-1, and recombinant granulocyte-macrophage (GM) CSF were assessed in vivo for their effects on BDF1 mouse bone marrow and spleen granulocyte-macrophage (CFU-GM), erythroid (BFU-E), and multipotential (CFU-GEMM) progenitor cells in untreated mice and in mice pretreated with purified iron-saturated human lactoferrin (LF). The CSF and LF preparations did not contain detectable endotoxin (less than 0.1 ng). Mice pretreated with LF were more sensitive to the effects of CSF. In mice pretreated with LF, 2,000 U IL-3 or 20,000 U CSF-1 significantly enhanced the cycling status and absolute numbers of all progenitors, whereas 20,000 U GM-CSF significantly increased the cycling status of CFU-GM and CFU-GEMM, but had no effect on cycling of BFU-E or on numbers of any of the progenitors. The effects of CSF in mice pretreated with LF were not mimicked by 0.1-100 ng E. coli lipopolysaccharide.
H E Broxmeyer, D E Williams, S Cooper, R K Shadduck, S Gillis, A Waheed, D L Urdal, D C Bicknell
Human urine is osmoprotective for enteric bacteria, permitting E. coli to grow with high concentrations of NaCl and other salts and even higher concentrations of sucrose and mannitol but not urea. The active material in urine is soluble in methanol and is precipitated by ammonium reineckate at acid pH. Using gel filtration and high-pressure liquid chromatography, we have identified two major osmoprotective compounds in urine. One is glycine betaine; the other is proline betaine as demonstrated by nuclear magnetic resonance, mass spectrum scanning, and chemical synthesis. Proline betaine has not been described previously to our knowledge in vertebrate tissues. It is known to be a cell volume-regulating agent for marine red algae and the euryhaline mollusk Elysia chloritica. We suggest that the presence of glycine and proline betaines in human urine may reflect an osmoprotective role for the kidney and that they protect bacteria in the urine only fortuitously.
S T Chambers, C M Kunin
Although maneuvers augmenting atrial volume and/or stretch also augment plasma levels of atrial natriuretic factor (ANF), the role of ANF in modulating renal sodium and water handling has not been defined. Water immersion to the neck (NI) was employed to assess the ANF response to acute volume expansion in 13 seated sodium-replete normal subjects. ANF increased promptly and markedly from 7.8 +/- 1.8 to 19.4 +/- 3.8 fmol/ml, then declined to 6.3 +/- 1.4 fmol/ml after 60 min recovery. Concomitantly, NI increased urine flow rate (V) (2.0 +/- 0.6 to 7.0 +/- 0.9 ml/min; P less than 0.001) and sodium excretion (UNaV) (92 +/- 12 to 191 +/- 15 mu eq/min; P less than 0.001), and decreased PRA (-66 +/- 3%) and plasma aldosterone (-57 +/- 6%). Increases of plasma ANF ranged from less than 20% to over 12-fold. Similarly, the natriuretic response to NI varied markedly from none to 500%. There was a strong correlation between peak ANF and peak UNaV (r = 0.67; P less than 0.025), but none between peak V and peak plasma ANF (r = -0.10; P greater than 0.5). These findings suggest that an increase in plasma ANF contributes to the natriuretic response to NI, implying a physiological role for ANF in modulating volume homeostasis in humans.
M Epstein, R Loutzenhiser, E Friedland, R M Aceto, M J Camargo, S A Atlas
DNA from nine hemophilia B patients who produce anti-factor IX inhibitors (antibodies), including two brothers, was analyzed by the Southern blotting method and hybridization with factor IX cDNA, intragenomic, and 3'-flanking probes. Two inhibitor patients were shown to have total deletions of the factor IX gene. Two other inhibitor patients, the brothers, were shown to have a presumably identical complex rearrangement of the factor IX gene involving two separate deletions. The first deletion is of approximately 5.0 kb and removes exon e. The second deletion is between 9 and 29 kb and removes exons g and h but leaves exon f intact. An abnormal Taq I fragment at one end of the deletion junctions acted as a marker for the inheritance of hemophilia B in the patients' family. Five other inhibitor patients have a structurally intact factor IX gene as detected by this method. Our studies indicate that whereas large structural factor IX gene defects predispose hemophilia B patients to developing an anti-factor IX inhibitor, the development of an inhibitor can be associated with other defects of the factor IX gene.
R J Matthews, D S Anson, I R Peake, A L Bloom
Accumulation of aluminum in bone is a frequent finding in patients requiring chronic dialysis and is associated with considerable morbidity and/or mortality. Until now, evidence seemed to point to relatively low circulating levels of parathyroid hormone as a contributing factor, but because levels of parathyroid hormone and calcitriol are interrelated, calcitriol might be also involved. In this study we employed an animal model to evaluate the single and combined effects of parathyroid hormone and calcitriol on bone aluminum accumulation. The results show significantly less aluminum accumulation in calcitriol-replete dogs independent of the presence or absence of parathyroid hormone. These results indicate that low levels of calcitriol may play a role in the development of aluminum related bone disease. Further studies are needed to demonstrate whether administration of calcitriol in patients with renal insufficiency will prevent development of aluminum-related bone disease.
H H Malluche, M C Faugere, R M Friedler, C Matthews, P Fanti
The cell surface phenotype of peripheral blood lymphocytes (PBL) of systemic lupus erythematosus (SLE) patients was characterized with the anti-2H4 monoclonal antibody that defines the human suppressor inducer subset. The T4+2H4+ population of cells has been shown to be critical for the activation of T8+ suppressor cells. Patients with SLE has a markedly decreased percentage of T4+2H4+ cells (13 +/- 2%) in their PBL compared with normal controls (21 +/- 1%) (P less than 0.001). This reduction was greatest in patients with active SLE, especially those with renal disease. Serial analysis of patients with SLE and renal disease showed a correlation between percent positive circulating T4+2H4+ cells and disease activity. Moreover, there was a significant correlation between a low percentage of T4+2H4+ cells and decreased suppressor-inducer function in autologous mixed lymphocyte reaction-activated T4+ cells from SLE patients. Thus, a deficiency exists in SLE patients with active renal disease in the T4+2H4+ suppressor-inducer T cell subset.
C Morimoto, A D Steinberg, N L Letvin, M Hagan, T Takeuchi, J Daley, H Levine, S F Schlossman
We assessed the time-dependent impact of estradiol on properties of the luteinizing hormone (LH) pulse signal in 12 hypoestrogenemic postmenopausal volunteers studied basally and after 1, 5, 10, and 30 d of estradiol delivery via an intravaginal Silastic ring. Computerized analysis of the plasma LH time series revealed a significant decrease in LH pulse frequency within 24 h of estrogen treatment, followed by a secondary increase (days 5 and 10), and then a sustained decline (day 30) in LH pulsatility. Estradiol also significantly suppressed incremental and maximal (but not fractional) LH pulse amplitudes in a biphasic manner. In contrast, LH peak duration was invariant until day 30 of estradiol replacement. These observations indicate that the well recognized biphasic actions of estradiol on mean serum LH concentrations can be modeled in relation to specific and time-dependent alterations in LH pulse frequency and amplitude.
J D Veldhuis, W S Evans, A D Rogol, M O Thorner, P Stumpf
To define glycemic thresholds for activation of glucose counterregulatory systems and for symptoms of hypoglycemia, we measured these during stepped reductions in the plasma glucose concentration (in six 10-mg/dl hourly steps) from 90 to 40 mg/dl under hyperinsulinemic clamp conditions, and compared these with the same measurements during euglycemia (90 mg/dl) under the same conditions over 6 h in 10 normal humans. Arterialized venous plasma glucose concentrations were used to calculate glycemic thresholds of 69 +/- 2 mg/dl for epinephrine secretion, 68 +/- 2 mg/dl for glucagon secretion, 66 +/- 2 mg/dl for growth hormone secretion, and 58 +/- 3 mg/dl for cortisol secretion. In contrast, the glycemic threshold for symptoms was 53 +/- 2 mg/dl, significantly lower than the thresholds for epinephrine (P less than 0.001), glucagon (P less than 0.001), and growth hormone (P less than 0.01) secretion. Thus, the glycemic thresholds for activation of glucose counterregulatory systems during decrements in plasma glucose lie within or just below the physiologic plasma glucose concentration range, and are substantially higher than the threshold for hypoglycemic symptoms in normal humans. These findings provide further support for the concept that glucose counterregulatory systems are involved in the prevention, as well as the correction, of hypoglycemia.
N S Schwartz, W E Clutter, S D Shah, P E Cryer
Immunosuppressive effects of E-series prostaglandins have been demonstrated in many in vitro assays of immune responsiveness as well as in autoimmune diseases. To explore the mechanisms underlying prostaglandin E1 (PGE1)-associated immunosuppression in autoimmunity, we treated SJL mice immunized to produce immune-mediated interstitial nephritis with PGE1, PGF2 alpha, or vehicle alone. Mice receiving PGE1 treatment do not develop interstitial nephritis, nor do they display delayed-type hypersensitivity (DTH) to the immunizing renal tubular antigen preparation. The observed immunosuppression is critically dependent on PGE1 administration during the period of effector T cell induction. We therefore investigated the effect of PGE1 on the in vitro induction of DTH effector T cells reactive to renal tubular antigens (SRTA). PGE1 inhibits effector T cell induction in a dose-dependent, reversible manner, but has no inhibitory effect on fully differentiated DTH effector cells or SRTA-reactive cell lines. The PGE1 effect is indirect and mediated via nonspecific suppressor lymphokines. This suppression can be overcome by recombinant interleukin 1 (IL-1), which suggests a mechanism related to either diminished IL-1 secretion or target cell sensitivity to IL-1.
C J Kelly, R B Zurier, K A Krakauer, N Blanchard, E G Neilson
Studies were done to determine whether the minimal model approach and the glucose clamp measure equivalent indices of insulin action. Euglycemic glucose clamps (glucose, G: 85 mg/dl) were performed at two rates of insulin (I) infusion (15 and 40 mU/min per m2) in 10 subjects (body mass index, BMI, from 21 to 41 kg/m2). Insulin sensitivity index (SI) from clamps varied from 0.15 to 3.15 (mean: 1.87 +/- 0.36 X 10(-2) dl/[min per m2] per microU/ml), and declined linearly with increasing adiposity (versus BMI: r = -0.97; P less than 0.001). SI from modeling the modified frequently sampled intravenous tolerance test varied from 0.66 to 7.34 X 10(-4) min-1 per microU/ml, and was strongly correlated with SIP(clamp) (r = 0.89; P less than 0.001). SI and SIP(clamp) were similar (0.046 +/- 0.008 vs. 0.037 +/- 0.007 dl/min per microU/ml, P greater than 0.35); the relation had a slope not different from unity (1.05 P greater than 0.70) and passed through the origin (P greater than 0.40). However, on a period basis, SI exceeded SIP(clamp) slightly, due to inhibition of hepatic glucose output during the FSIGT, not included in SIP(clamp). These methods are equivalent for assessment of overall insulin sensitivity in normal and insulin-resistant nondiabetic subjects.
Richard N. Bergman, Rudy Prager, Aage Volund, Jerrold M. Olefsky
The subendothelial space of normal rat liver contains the constituent proteins of a basal lamina, as judged by immunohistochemical study of tissue sections. However, it is unknown whether these proteins constitute a complex with effects on hepatocellular function. We have examined this question, using normal rat hepatocytes cultured on substrata of matrix proteins as a model of the interaction between cells and basal lamina in vivo. In cultures on a type I collagen substratum, albumin secretion decreased progressively after 2 d. By contrast, when cells were cultured on a laminin-rich gel matrix, albumin secretion was stable for at least 3 wk; other functions and ultrastructural morphology were similarly maintained. None of the individual matrix proteins effectively substituted for the gel matrix, suggesting that full support of hepatocellular function requires a complex of matrix proteins. We speculate that a cause of hepatocellular dysfunction in acute inflammation is disruption of this matrix and alteration of its interaction with the hepatocyte plasma membrane.
D M Bissell, D M Arenson, J J Maher, F J Roll
Serum from some seropositive (RF+) rheumatoid arthritis (RA) patients contains relatively high concentrations of monomeric (7S) IgM molecules. Seven S IgM molecules fail to bind the Fc portion of IgG, unlike 19S IgM RFs that bind aggregated IgG in classical RF assays. Some pentameric IgM RFs are marked by crossreactive idiotypes (RCRI) defined by prototypic monoclonal RFs. In previous studies, we observed that a proportion of pokeweed mitogen (PWM) induced plasma cells from RA patients' blood lymphocytes express the major RCRI as assayed by indirect immunofluorescence with polyclonal anti-RCRI antibodies. In this study, 7S IgM obtained from three different RF+ RA patients inhibits specific anti-RCRI intracytoplasmic staining of PWM induced RF+ RA-derived plasma cells. These 7S molecules also block polyclonal anti-RCRI antibodies from reacting with red blood cells bearing 7S IgM molecules from RF+ patients with RA or Waldenstrom's macroglobulinemia. We conclude that some 7S IgM molecules in the serum of RF+ RA patients are marked by the major RCRI idiotype and are related to 19S monoclonal and polyclonal RFs.
V R Bonagura, L Mendez, N Agostino, B Pernis
We investigated the structure of the 107-kD thyroid protein recognized as microsomal antigen. Solubilized microsomes were incubated with affinity gels consisting of IgG, from thyroiditis patients or controls, linked to Reacti-gel. Eluates were analyzed by SDS polyacrylamide electrophoresis and Western blot. 107- and 101-kD proteins were augmented in eluates from gels containing patient IgG and had microsomal antigenicity. In a Western blot of microsomes run under unreduced conditions, poorly defined large proteins were identified by antibody. When eluted electrophoretically and reanalyzed in reducing conditions, they demonstrated the 107-kD antigen. The 107-kD protein identified in reducing conditions was extracted and reanalyzed under nonreducing conditions. Large molecular mass proteins were then observed. On two-dimensional electrophoresis, a 107-kD antigen was isolated with isoelectric point of 7.0. The microsomal antigen may be complexes or multimers of a 107-kD peptide with isoelectric point of 7.0.
N Hamada, L Portmann, L J DeGroot
Hemoglobin Mississippi (HbMS: beta 44ser----cys) has anomalous properties that include disulfide linkages with normal beta-, delta-, gamma-, and alpha-chains, and the formation of high molecular weight multimers. While heterozygotes for HbMS are clinically and hematologically normal and carriers of the beta +-thalassemia gene in our family had mild microcytic anemia, the proband with HbMS-beta +-thalassemia had a hemoglobin level of 7 g/dl, mean corpuscular volume (MCV) of 68 fl, reticulocytes of 2-6%, HbF of 18%, marked anisocytosis and poikilocytosis, and splenomegaly, all features of thalassemia intermedia. With oxidant stress, her erythrocytes developed multiple dispersed Heinz bodies, but HbMS was only mildly unstable. HbMS was susceptible to proteolytic degradation in the presence of ATP. The unexpectedly severe clinical findings in HbMS-beta +-thalassemia may result from the proteolytic digestion of HbMS, as well as the excessive alpha-chains characteristic of beta +-thalassemia, which combined provide the increment of cellular damage that results in the phenotype of thalassemia intermedia.
M H Steinberg, J G Adams 3rd, W T Morrison, D J Pullen, R Abney, A Ibrahim, R F Rieder
Serum-denatured TBG (dnTBG) measured in 32 families deficient in native TBG (nTBG) was undetectable in all subjects with complete nTBG deficiency and was high in 2 of 16 families with partial nTBG deficiency. nTBG (in mean micrograms per decaliter +/- SD) in members of the Quebec and Montreal families, respectively were: 258 +/- 54 and 230 in affected men, 747 +/- 190 and 927 +/- 90 in affected women, and 1568 +/- 151 and 1300 +/- 195 in unaffected relatives. Corresponding mean dnTBG levels were: 14.3 +/- 2.9 and 21.3 in affected men, 8.6 +/- 1.0 and 11.6 +/- 3.1 in affected women, and less than 2.1 and less than 2.6 in unaffected relatives. All were euthyroid with normal free thyroxine and thyrotropin levels. In comparison to common type TBG, TBG-Quebec was more heat labile by 10 degrees C and TBG-Montreal by 12 degrees C. The degree of dnTBG elevation and nTBG lability at 37 degrees C were correlated (r = 0.99). Isoelectric focusing showed cathodal shift of all TBG bands: TBG-Quebec by 0.06 isoelectric points (pI) and TBG-Montreal by 0.02 pI. These two TBG variants represent different mutations most likely affecting the polypeptide chain of the molecule. Their inheritance is X-chromosome linked. The instability of these TBGs at 37 degrees C may lead to more rapid degradation in vivo resulting in low nTBG and high dnTBG concentrations in serum.
J Takamatsu, S Refetoff, M Charbonneau, J H Dussault
We have applied a sensitive assay to analyze lupus and Sjögren's syndrome autoantibodies in 40 normal sera. Seven of these bound Ro/Sjögren's syndrome A antigen (SSA). Although this binding was 1,000-fold lower than the highest anti-Ro/SSA level measured from patients, it was inhibited by human Ro/SSA. Positive normal serum-bound Ro/SSA in Western immunoblots and binding activity was demonstrated in the F(ab')2 fragment of IgG. Affinity purification of normal anti-Ro/SSA IgG increased the specific anti-Ro/SSA binding by greater than 17-fold. This purified antibody formed a Ro/SSA precipitin and had a relative affinity for Ro/SSA identical to that of Ro/SSA precipitin-positive patients. These data demonstrate that the anti-Ro/SSA present in healthy normal donors is true autoantibody. Anti-La/Sjögren's syndrome B antigen (SSB) autoantibodies were found in 3 of the 40 normal sera, while none bound nuclear ribonucleoprotein (Sm). Finding low levels of anti-Ro/SSA and anti-La/SSB among normals may indicate that anti-Ro/SSA and anti-La/SSB occur in disease by enhancement of a preexisting immune response.
K K Gaither, O F Fox, H Yamagata, M J Mamula, M Reichlin, J B Harley
We tested the hypothesis that there is an enhanced rate of hypoxanthine salvage in two siblings with hereditary xanthinuria. We radiolabeled the adenine nucleotide pool with [8-14C]adenine and examined purine nucleotide degradation after intravenous fructose. The cumulative excretion of radioactivity during a 5-d period was 9.7% and 9.1% of infused radioactivity in the enzyme-deficient patients and 6.0 +/- 0.7% (mean +/- SE) in four normal subjects. Fructose infusion increased urinary radioactivity to 7.96 and 9.16 X 10(6) cpm/g creatinine in both patients and to 4.73 +/- 0.69 X 10(6) cpm/g creatinine in controls. The infusion of fructose increased total urinary purine excretion to a mean of 487% from low-normal baseline values in the patients and to 398 +/- 86% in control subjects. In the enzyme-deficient patients, the infusion of fructose elicited an increase of plasma guanosine from undetectable values to 0.7 and 0.9 microM. With adjustments made for intestinal purine loss, these data support the hypothesis that there is enhanced hypoxanthine salvage in hereditary xanthinuria. Degradation of guanine nucleotides to xanthine bypasses the hypoxanthine salvage pathway and may explain the predominance of this urinary purine compound in xanthinuria.
F A Mateos, J G Puig, M L Jiménez, I H Fox
The mechanism for the increased glucose transport response to insulin in adipose cells from chronically hyperinsulinemic rats was examined. Rats were infused with insulin s.c. for 2 wk. Isolated adipose cells were incubated with and without insulin, 3-O-methylglucose transport was measured, and glucose transporters in subcellular membrane fractions were assessed by cytochalasin B binding. Adipose cells from insulin-treated rats showed no change in basal but a 55% increase in insulin-stimulated glucose transport activity compared with those from control rats (7.1 +/- 0.8 vs. 4.6 +/- 0.5 fmol/cell per min, mean +/- SEM) and a corresponding increase in the concentration of glucose transporters in the plasma membranes (44 +/- 5 vs. 32 +/- 6 pmol/mg of membrane protein). In the low-density microsomes, glucose transporter concentrations in both basal and insulin-stimulated states were the same, but the total numbers were greater in cells from the insulin-treated rats because of a 39% increase in low-density microsomal protein. Therefore, chronic experimental hyperinsulinemia in the rat enhances the stimulatory action of insulin on glucose transport in the adipose cell by increasing the concentration of glucose transporters in the plasma membranes. This results from an enlarged intracellular pool due to increased intracellular protein and enhanced glucose transporter translocation in response to insulin.
B B Kahn, E S Horton, S W Cushman
We have examined the constitutive and inducible secretion of platelet-derived growth factor (PDGF)-like proteins in a variety of human hemopoietic cell lines. The highest levels of secreted protein were noted in four human erythroleukemia lines which, in addition to erythroid lineage markers, express one or more megakaryocytic lineage markers. Induction of these lines by 12-O-tetradecanoylphorbol-13-acetate enhanced the expression of megakaryocytic markers and increased secretion of PDGF-like proteins several fold. In concert with these changes, there was significant induction of c-sis/PDGF-B messenger RNA (mRNA) expression in all lines, whereas one line showed significant concurrent induction of PDGF-A mRNA expression. Whether PDGF-like secretion is part of the stem cell-like phenotype displayed by these lines or is secondary to their leukemic transformation remains to be determined. Nevertheless, these lines provide new cellular models for studying the expression and function of PDGF analogs in hemopoietic cells.
T Papayannopoulou, E Raines, S Collins, B Nakamoto, M Tweeddale, R Ross
Thrombospondin (TSP) is a multifunctional platelet glycoprotein synthesized by a variety of cells in culture including monocytes and macrophages. We now report that 125I-TSP binds specifically, saturably, and reversibly to mouse peritoneal macrophages and to cells of the monocyte-like human cell line U937 with dissociation constants of 6.7-14.5 X 10(-8) M and 3-4 X 10(5) binding sites per cell. TSP mediates an adhesive interaction between thrombin-stimulated platelets and both U937 cells and human blood monocytes. Using a sensitive rosetting assay, we found that monocytes were not rosetted by resting platelets whereas greater than 90% were rosetted by thrombin-stimulated platelets. Monoclonal and polyclonal anti-TSP antibodies markedly inhibited rosetting as did TSP itself. Neither control antibodies nor heparin, fibronectin, fibrinogen, nor the fibronectin adhesion tetrapeptide Arg-Gly-Asp-Ser inhibited rosetting. TSP may thus serve as a molecular bridge linking activated platelets with monocytes at sites of early vascular injury. Such interaction may be of critical importance in the regulation of thrombosis and the initiation of atherosclerosis.
R L Silverstein, R L Nachman
Histidyl-proline diketopiperazine (His-Pro DKP) cells in the pancreas of human fetuses aged between 12 and 19 wk were localized by the indirect antibody-enzyme method on semithin sections. To study their fine structure, two techniques were used: a superimposition technique consisting of comparison of the same cells in semithin and electron microscopic preparations, and an immunocytochemical technique on ultrathin sections using the unlabeled antibody peroxidase-antiperoxidase method. Our results show that (a) the same cells are positive for both His-Pro DKP and glucagon/glicentin, (b) His-Pro DKP immunoreactive cells possess extremely electron-opaque secretory granules, implying that these cells correspond to the A cells, and (c) His-Pro DKP immunoreactivity is found over the secretory granules. We hypothesize that the two peptides His-Pro DKP and thyrotropin-releasing hormone (TRH) have independent origins, since TRH is found in the B cells.
P Leduque, I M Jackson, A Kervran, S Aratan-Spire, P Czernichow, P M Dubois
Arginine-vasopressin (AVP) immunoreactivity (Ir) has been found to be elevated in platelet-rich plasma. PlatAVP was defined as platelet-rich plasma Ir minus platelet-poor plasma Ir (Pavp). PlatAVP, Pavp, and synthetic AVP were found to have identical retention time on high performance liquid chromatography analysis and similar mobility on thin-layer chromatography. During a standard osmotic suppression-stimulation test, Pavp increased with plasma osmolality (Posm, mosmol/kg H2O); Pavp (pg/ml) = 0.98 (Posm -274.4), r = 0.57, P less than 0.001, n = 65; but PlatAVP was not significantly correlated with Posm and remained at 5 pg/ml. This PlatAVP concentration was estimated to represent a true intraplatelet AVP concentration of 0.4 to 3.7 X 10(-9) M. Binding studies on intact human platelets demonstrated specific binding sites for [3H]AVP (n = 16; BMax = 98 +/- 30 binding sites/platelet; Kd = 0.72 +/- 0.24 nM). This in vitro affinity association constant (Kd) was close to the estimated in vivo intraplatelet AVP concentration. Measurement of PlatAVP could estimate vasopressin bound to a specific platelet receptor.
D G Bichet, M F Arthus, J N Barjon, M Lonergan, C Kortas
Two Salmonella typhi mutants, 541Ty (Vi+) and 543Ty (Vi-), auxotrophic for p-aminobenzoate and adenine, were evaluated as live oral vaccines. 33 volunteers ingested single doses of 10(8), 10(9), or 10(10) vaccine organisms, while four others received two 2 X 10(9) organism doses 4 d apart. No adverse reactions were observed. Vaccine was recovered from coprocultures of 29 of 37 vaccinees (78%) and from duodenal string cultures of two; repeated blood cultures were negative. The humoral antibody response to S. typhi O, H, Vi, and lysate antigens in serum and intestinal fluid was meager. In contrast, all vaccinees manifested cell-mediated immune responses. After vaccination, 69% of vaccinees overall and 89% of recipients of doses greater than or equal to 10(9) responded to S. typhi particulate or purified O polysaccharide antigens in lymphocyte replication studies but not to antigens of other Salmonella or Escherichia coli. All individuals, postvaccination, demonstrated a significant plasma-dependent mononuclear cell inhibition of wild S. typhi.
M M Levine, D Herrington, J R Murphy, J G Morris, G Losonsky, B Tall, A A Lindberg, S Svenson, S Baqar, M F Edwards
We studied the regulation of thromboxane (TX) synthesis in promyelocytic leukemia cells during macrophage differentiation. Cells treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) showed rates of TXB2 synthesis from exogenous arachidonic acid that exceeded that of control cells by a factor of up to 81. Cells treated with sn-1,2-dioctanoylglycerol (diC8) showed similarly high TXB2 synthesis rates when diC8 was added concomitantly with a subthreshold concentration of TPA or when given in multiple doses. These activities depended on de novo synthesis of prostaglandin H (PGH) synthase because: microsomal PGH synthase activity showed large increases in Vmax values, and mass measurements of PGH synthase revealed the presence of PGH synthase in differentiating cells whereas the enzyme was undetectable in control cells. These results indicate that macrophage differentiation is associated with stimulation of TXB2 synthesis that requires both activation of protein kinase C and de novo synthesis of PGH synthase.
M Goerig, A J Habenicht, R Heitz, W Zeh, H Katus, B Kommerell, R Ziegler, J A Glomset
The antibody domain controlling reactions between platelet membranes and drug-dependent (dd) antibodies from patients with thrombocytopenia induced by cinchona alkaloids was studied using F(ab')2, Fab, and Fc fragments made from purified dd-IgG. By direct binding radioimmunoassay (RIA) measurements, 20,000 to 50,000 antibody molecules bound per platelet equivalent of purified platelet membranes at apparent saturation with three different antibodies. F(ab')2 and Fab fragments bound to platelet membranes drug dependently but Fc fragments did not. The ability of dd-IgG fragments to compete with intact IgG was quantitatively measured by RIA and by complement fixation. F(ab')2 and Fab competed with intact IgG at an 8:1 and greater than 50:1 molar ratio, respectively, in RIA, and at a 1.6-3:1 and 44-75:1 ratio, respectively, by complement fixation assays. Fc did not compete with IgG in either assay. We conclude that the Fab domain supports attachment of dd antibody to the platelet surface.
M E Smith, D M Reid, C E Jones, J V Jordan, C A Kautz, N R Shulman
Gram-negative septicemia elicits multiple abnormalities of the coagulation system. Although products of coagulation can lead to clot formation, thereby potentiating organ damage, recent work has shown that low concentrations of thrombin can protect animals from the shock state. Because these amounts of thrombin also lead to formation in vivo of the anticoagulant enzyme, activated protein C, we examined the role of protein C in modulation of Escherichia coli shock in baboons. First, we infused activated protein C and lethal concentrations of E. coli organisms, which prevented the coagulopathic, hepatotoxic, and lethal effects of E. coli. Second, using an antibody to protein C we blocked protein C activation in vivo to determine if this influenced the response to lethal and sublethal concentrations of E. coli organisms. Under these conditions the response to lethal concentrations of E. coli organisms was made more severe and the response to sublethal concentrations of E. coli was made lethal. The coagulopathic, hepatotoxic, and lethal responses in this latter case were prevented by infusion of exogenous protein C.
F B Taylor Jr, A Chang, C T Esmon, A D'Angelo, S Vigano-D'Angelo, K E Blick
Antibodies in sera from newly diagnosed insulin-dependent diabetes mellitus (IDDM) patients are directed to a human islet cell protein of relative molecular mass (Mr) 64,000. Since IDDM seems to develop after a prodromal period of beta-cell autoimmunity, this study has examined whether 64,000 Mr antibodies could be detected in 14 individuals who subsequently developed IDDM and five first degree relatives who have indications of altered beta-cell function. Sera were screened by immunoprecipitation on total detergent lysates of human islets and positive sera retested on membrane protein preparations. Antibodies to the 64,000 Mr membrane protein were consistently detected in 11/14 IDDM patients, and in all 5 first degree relatives. 10 IDDM patients were already positive in the first samples, obtained 4-91 mo before the clinical onset of IDDM, whereas 1 patient progressed to a high 64,000 Mr immunoreactivity, at a time where a commencement of a decline in beta-cell function was detected. 64,000 Mr antibodies were detected before islet cell cytoplasmic antibodies (ICCA) in two patients. In the control groups of 21 healthy individuals, 36 patients with diseases of the thyroid and 5 SLE patients, the 64,000 Mr antibodies were detected in only one individual, who was a healthy sibling to an IDDM patient. These results suggest that antibodies against the Mr 64,000 human islet protein are an early marker of beta-cell autoimmunity and may be useful to predict a later development of IDDM.
S Baekkeskov, M Landin, J K Kristensen, S Srikanta, G J Bruining, T Mandrup-Poulsen, C de Beaufort, J S Soeldner, G Eisenbarth, F Lindgren
Bombesin, a polypeptide derived from frog skin, has been shown to stimulate gastrin release from the gastric antrum in vivo and in vitro. To elucidate the mechanisms of this effect, we developed a method to culture isolated and enriched G cells from canine stomach. After digestion of antral mucosa with collagenase and EDTA, dispersed cells were fractionated by counterflow elutriation then cultured on a collagen support. Bombesin and three molecular forms of canine gastrin-releasing peptides all stimulated gastrin release from G cells in a dose-dependent manner. The effect of bombesin was suppressed by somatostatin and potentiated by dibutyryl cyclic AMP (10(-3) M) but not by carbachol (10(-6) M). Extracellular calcium depletion attenuated the stimulation of gastrin release by bombesin but not by forskolin. These findings suggest that the bombesin family peptides directly activate G cells through calcium-dependent mechanisms to cause gastrin release.
K Sugano, J Park, A H Soll, T Yamada
To explain the transient anemia and poikilocytosis seen during infancy in hereditary elliptocytosis (HE), we resealed erythrocyte (RBC) ghosts from affected children or their elliptocytic parents with 2,3-diphosphoglycerate (DPG) (0-8 mM), a compound that dissociates membrane skeletons, then measured ghost mechanical stability in the ektacytometer. Without added 2,3-DPG, ghost mechanical stability was subnormal in infantile poikilocytosis (IP) and HE but was even more abnormal in hereditary pyropoikilocytosis (HPP). Addition of 2,3-DPG (2.55 mM) to IP or HE ghosts, decreased their stability to that of HPP ghosts (without 2,3-DPG). Nonphysiological 2,3-DPG levels (6-8 mM) were required to elicit a similar effect in normal ghosts. The data suggest that free 2,3-DPG, present in neonatal RBC as a consequence of diminished binding to HbF, may render HE susceptible to in vivo fragmentation. The developmental switch from fetal to adult hemoglobin, by diminishing available free 2,3-DPG, may explain the abatement of poikilocytosis and hemolytic anemia that accompanies maturation.
W C Mentzer Jr, T A Iarocci, N Mohandas, P A Lane, B Smith, J Lazerson, T Hays
Contractile dysfunction in stunned myocardium could result from a decrease in the intracellular free [Ca2+] transient during each beat, a decrease in maximal Ca2+-activated force, or a shift in myofilament Ca2+ sensitivity. We measured developed pressure (DP) at several [Ca]0 (0.5-7.5 mM) in isovolumic Langendorff-perfused ferret hearts at 37 degrees C after 15 min of global ischemia (stunned group, n = 13) or in a nonischemic control group (n = 6). At all [Ca]0, DP was depressed in the stunned group (P less than 0.001). Maximal Ca2+-activated pressure (MCAP), measured from tetani after exposure to ryanodine, was decreased after stunning (P less than 0.05). Normalization of the DP-[Ca]0 relationship by corresponding MCAP (Ca0 sensitivity) revealed a shift to higher [Ca]0 in stunned hearts. To test whether cellular Ca overload initiates stunning, we reperfused with low-[Ca]0 solution (0.1-0.5 mM; n = 8). DP and MCAP in the low-[Ca]0 group were comparable to control (P greater than 0.05), and higher than in the stunned group (P less than 0.05). Myocardial [ATP] observed by phosphorus NMR failed to correlate with functional recovery. In conclusion, contractile dysfunction in stunned myocardium is due to a decline in maximal force, and a shift in Ca0 sensitivity (which may reflect either decreased myofilament Ca2+ sensitivity or a decrease in the [Ca2+] transient). Our results also indicate that calcium entry upon reperfusion plays a major role in the pathogenesis of myocardial stunning.
H Kusuoka, J K Porterfield, H F Weisman, M L Weisfeldt, E Marban
Patient C.M. presented platelet function defects symptomatic of Glanzmann's thrombasthenia. However, analysis of surface-labeled platelets by SDS-polyacrylamide gel electrophoresis revealed the usual presence of the major glycoproteins, including GP IIb and GP IIIa. Platelet fibrinogen was not detected. Analysis of Triton X-100 extracts of Ca2+-washed C.M. platelets by crossed immunoelectrophoresis (CIE) showed normal amounts of GP IIb-IIIa complexes. However, when samples were electrophoresed through an agarose gel containing 125I-fibrinogen, the usual binding of fibrinogen to GP IIb-IIIa did not occur. Furthermore, the GP IIb-IIIa complexes showed an increased sensitivity to dissociation with EDTA, either after Triton X-100 solubilization or in the intact platelet membrane. For example, after incubation with EDTA at room temperature, the patient's platelets bound little of the monoclonal antibodies AP-2 or T10 (anti-GP IIb-IIIa complex) although normally binding Tab (anti-GP IIb). Patient C.M. appears to represent a subgroup of thrombasthenia where platelets contain unstable GP IIb-IIIa complexes unable to support fibrinogen binding.
A T Nurden, J P Rosa, D Fournier, C Legrand, D Didry, A Parquet, D Pidard
Expression of the cardiac myosin isozymes is regulated during development, by hormonal stimuli and hemodynamic load. In this study, the levels of expression of the two isoforms (alpha and beta) of myosin heavy chain (MHC) during cardiac hypertrophy were investigated at the messenger RNA (mRNA) and protein levels. In normal control and sham-operated rats, the alpha-MHC mRNA predominated in the ventricular myocardium. In response to aortic coarctation, there was a rapid induction of the beta-MHC mRNA followed by the appearance of comparable levels of the beta-MHC protein in parallel to an increase in the left ventricular weight. Administration of thyroxine to coarctated animals caused a rapid deinduction of beta-MHC and induction of alpha-MHC, both at the mRNA and protein levels, despite progression of left ventricular hypertrophy. These results suggest that the MHC isozyme transition during hemodynamic overload is mainly regulated by pretranslational mechanisms, and that a complex interplay exists between hemodynamic and hormonal stimuli in MHC gene expression.
S Izumo, A M Lompré, R Matsuoka, G Koren, K Schwartz, B Nadal-Ginard, V Mahdavi
Prostaglandin (PG) D2, the predominant prostanoid released from activated mast cells in humans is initially metabolized by reduction of the C-11 keto function to yield 9 alpha,11 beta-PGF2. In this study the airways effects of 9 alpha,11 beta-PGF2 were compared with those of its epimer 9 alpha,11 alpha-PGF2 (PGF2 alpha) and PGD2. 9 alpha,11 beta-PGF2 was a potent contractile agonist of isolated guinea pig trachea and 4-mm human airways in vitro; the potencies of the PGs relative to PGD2 (= 1.00) being 0.65 (NS) and 4.08 (P less than 0.001) for 9 alpha,11 beta-PGF2, and 0.52 (P less than 0.01) and 2.40 (P less than 0.001) for PGF2 alpha, respectively. When inhaled by asthmatic subjects, 9 alpha,11 beta-PGF2 was a potent bronchoconstrictor agent, being approximately equipotent with PGD2 and 28-32 times more potent than histamine (P less than 0.01). These studies suggest that 9 alpha,11 beta-PGF2 is at least equipotent with PGD2 as a bronchoconstrictor agonist, and in being a major metabolite of PGD2, could contribute to the bronchoconstrictor effect of this mast cell-derived mediator in asthma.
C R Beasley, C Robinson, R L Featherstone, J G Varley, C C Hardy, M K Church, S T Holgate
Epidermal growth factor (EGF) has been reported to stimulate adrenocorticotropin hormone (ACTH), growth hormone and prolactin secretion from pituitary tissue in vitro, and in large doses evokes ACTH secretion in adult sheep in vivo. In order to assess a possible role for EGF in the pituitary hyperfunction characteristic of the in utero fetus, we measured changes in plasma immunoreactive ACTH concentrations after acute administration of saline, purified mouse EGF or synthetic ovine corticotropin releasing factor (CRF) to chronically catheterized fetal sheep. Both CRF and EGF were associated with increases in plasma immunoreactive ACTH concentrations. Peak values 60 min after 10-micrograms injections of either EGF or CRF increased from baseline ACTH values of 61 +/- 11 pg/ml to 191 +/- 37 and 178 +/- 25 pg/ml, respectively. Dose-response studies indicate that at low doses (less than 20 micrograms) EGF is as potent a stimulus for ACTH release as CRF. EGF infusion was not associated with detectable changes in circulating CRF, catecholamines, arginine vasopressin levels, or plasma growth hormone concentrations. We speculate that EGF may be important in the regulation of pituitary function in the developing mammalian fetus.
D H Polk, M G Ervin, J F Padbury, R W Lam, A L Reviczky, D A Fisher
We report here a unique variant of alpha spectrin in a kindred with hereditary elliptocytosis. This novel red blood cell-membrane protein migrated to a position between the normal alpha- and beta-spectrin subunits in SDS polyacrylamide gel electrophoresis. It was identified as an alpha spectrin by its binding to anti-alpha spectrin antibodies, by the absence of a phosphorylation site, and by the normal 1:1 stoichiometry between total alpha- and beta-spectrin molecules. The quantity of the alpha-spectrin mutant, expressed as a percentage of the total alpha spectrin, varied from 9.9-45.2% among six affected individuals. Two-dimensional electrophoretic analysis of spectrin tryptic digests was qualitatively normal but showed a decreased quantity of a normal alpha IV fragment. The variable quantity of alpha-spectrin mutant among family members correlated directly with the increased percentage of spectrin dimers in cold low ionic strength spectrin extracts (r = 0.92) and inversely with red blood cell ghost mechanical stability (r = -0.98). The data suggest that this new alpha-spectrin mutant is responsible for decreased spectrin dimer-dimer association and for red cell instability in affected individuals.
P A Lane, R L Shew, T A Iarocci, N Mohandas, T Hays, W C Mentzer
An understanding of the regulatory mechanisms that govern the humoral immune response will be facilitated by the availability of techniques for the measurement of specific antibody production in vitro. We have developed an enzyme-linked immunosorbent assay system for the measurement of in vitro anti-DNA antibody production by peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus. Using this technique, the PBMC from 74% of serologically active SLE patients produced levels of anti-DNA antibodies that were greater than 2 SD above the mean of 18 +/- 9 IU/ml for normal subjects. Furthermore, the addition of 3I, a monoclonal anti-idiotypic antibody that recognizes a cross-reactive determinant on anti-DNA antibodies, was shown to specifically inhibit anti-DNA production in vitro.
A Epstein, M Greenberg, B Diamond, A I Grayzel
We have investigated the molecular basis of the marked elevation in erythrocyte adenosine deaminase (ADA) activity in a kindred with hereditary hemolytic anemia. Red cell ADA-specific activity was verified to be 70- to 100-fold normal levels. Western blots demonstrated a corresponding increase in erythrocyte ADA-specific immunoreactive protein. Analysis of genomic DNA revealed no evidence for amplification or major structural changes in the ADA gene. ADA-specific messenger RNA (mRNA) from proband reticulocytes was comparable in size and amount to mRNA from control reticulocytes. Translation of proband poly A+ reticulocyte mRNA in a rabbit reticulocyte lysate system and immunoprecipitation of 35S-labeled protein products with anti-ADA antibody yielded a band of approximately 42,000 apparent mol wt that was absent in translation products from control reticulocyte mRNAs. These data suggest that the increased ADA activity in red cells in this disorder results from the increased translation of an aberrant ADA mRNA.
E G Chottiner, H J Cloft, A P Tartaglia, B S Mitchell
Starvation for a single essential amino acid induced differentiation of the human promyelocytic leukemia line HL-60 into morphologically and functionally mature granulocytes. Differentiation occurred when protein synthesis was inhibited up to 90% but was not simply secondary to growth arrest or protein synthesis inhibition, because neither glucose starvation nor treatment with protein synthesis inhibitors induced differentiation. Induction of differentiation by an aminoacyl tRNA synthetase inhibitor and the effect of cycloheximide and puromycin on amino acid-starved cells suggested an important regulatory role of tRNA molecules during differentiation.
R B Pilz, G Van den Berghe, G R Boss
Deficiency of a family of three leukocyte adhesion molecules (Leu-CAM) is associated with recurrent and life-threatening bacterial infections in man. Each of the three antigens, Mo1, LFA-1, and Leu M5 has a distinct alpha subunit noncovalently associated with a common beta subunit that appears to be required for the expression of these antigens on the cell surface. To investigate the molecular basis of Leu-CAM deficiency, we studied leukocytes from four unrelated patients suffering from complete or partial Leu-CAM deficiency using immunoprecipitation of metabolically labeled proteins, RNA extraction, and Northern blot analysis. We found that B cells from all four patients synthesized a normal sized beta subunit precursor that either failed to "mature" or matured only partially to the membrane expressed form. B cells from all four patients also had a single normal sized beta subunit mRNA of approximately 3.4 kb. Leu-CAM deficiency, in these unrelated patients, is not due to the absence of the beta chain gene or to aberrant splicing of its mRNA and are consistent with a defective beta subunit gene resulting in abnormal posttranslational processing of the synthesized molecule.
N Dana, L K Clayton, D G Tennen, M W Pierce, P J Lachmann, S A Law, M A Arnaout