Issue published May 1, 1971

A n isotope dilution method, using ³²P-labeled pyrophosphate, has been developed for the measurement of inorganic pyrophosphate (PP₁) in human plasma. The specificity of the method was better than 90% as assessed by elution patterns during ion-exchange chromatography, by paper chromatography, and by incubation with inorganic pyrophosphatase. The 99% confidence limits for a single estimation of plasma PP₁ was ±13%. There were no differences in plasma PP₁ between men and women, but the values in young people (0-15 yr) were slightly higher than in older people. The mean concentration (±SE) of PP₁ in the plasma of 73 men and women was 3.50 ±0.11 μmoles/liter (0.217 ±0.007 μg P/ml) and the normal range (99% limits) was 1.19-5.65 μmoles/liter (0.074-0.350 μg P/ml).It has been suggested that PP₁ may be important in calcium metabolism because PP₁ can prevent the precipitation of calcium phosphates in vitro and in vivo, and can slow the rates at which hydroxyapatite crystals grow and dissolve. Plasma PP₁ was therefore measured in several disorders of bone. Normal values were found in osteogenesis imperfecta, osteopetrosis, “acute” osteoporosis, and primary hyperparathyroidism. Plasma PP₁ was invariably raised in hypophosphatasia. The excess of PP₁ in plasma might be the cause of the defective mineralization in hypophosphatasia and the function of alkaline phosphatase in bone may be to act as a pyrophosphatase at sites of calcium deposition.

I n order to investigate the possible role of the renin-angiotensin system in the regulation of intrarenal hemodynamics in hemorrhagic hypotension (HH), seven mongrel dogs have been studied under the following conditions: (a) Control, (b) HH (mean arterial pressure 70 mm Hg), and (c) HH + alpha adrenergic blockade by phenoxybenzamine (HH + POB). The following parameters were obtained for the right kidney: Intrarenal distribution of blood flow and local blood flow rates (¹³³Xe washout technique); total renal blood flow (RBF) on the basis of the clearance and extraction ratio of PAH and the arterial hematocrit; plasma renin concentrations in the renal artery and vein by the method of Boucher and his associates; and renin release into the renal circulation.Alpha adrenergic blockade reverted the typical redistribution of intrarenal blood flow observed under HH. In hemorrhage, arterial and venous renin concentrations increased by a factor of 3.4 and 4.8 respectively. A further small increase was observed during HH + POB with the respective factors increasing to 4.8 and 5.3, as compared with control values. The renin release into the circulation increased by a factor of 1.2 in HH and 4.0 in HH + POB. Whereas in HH there seemed to be a relationship between increased renin concentrations or renin release, and the redistribution of blood flow, no such correlation was found during α-adrenergic blockade. From these observations it is concluded that renin alone is unable to maintain the typical redistribution of RBF seen during hemorrhage. Circumstantial evidence points to a permissive role of the renin-angiotensin system in the pathogenesis of the patchy cortical hypoperfusion caused by sympathoadrenergic mechanisms during hemorrhagic hypotension.

T he relation of neuraminidase to morbidity and mortality was examined in patients with Haemophilus influenzae, meningococcal, and pneumococcal meningitis. Ten strains of H. influenzae and eight strains of meningococci from infected cerebrospinal fluid (CSF) did not elaborate neuraminidase. Each of 27 strains of pneumococci from infected CSF elaborated both neuraminidase and N-acetylneuraminic acid (NANA) aldolase. There was no correlation between amount of neuraminidase secreted in vitro and survival of patients.Values for free and total NANA concentrations were derived from admission CSF samples of 63 patients with meningitis; 18 patients infected with Neisseria meningitidis, 10 with H. influenzae and 35 with Diplococcus pneumoniae. Mean values for total NANA were elevated in each type of bacterial meningitis; however, abnormal concentrations of free CSF NANA were detected only in 17 patients with pneumococcal meningitis. 11 of 18 patients with pneumococcal meningitis showing normal free CSF NANA concentrations were cured, whereas only 4 patients with abnormal free NANA levels survived without residua. Both coma and bacteremia occurred significantly more often among patients with elevated concentrations of free CSF NANA. The association of elevated concentrations of free CSF NANA with coma and with an adverse prognosis suggested that neuraminidase may be a factor in the pathogenesis of penumococcal meningitis.

T he utilization of circulating maltose was compared to that of glucose in six normal fasting subjects after intravenous injection of 25 g of either sugar. Blood samples were obtained over a 2 hr period and were assayed for free fatty acids (FFA), insulin, glucose, and total reducing substances. Urine was collected for 2 hr after maltose administration and assayed enzymatically for glucose and maltose. Blood glucose concentrations did not increase after maltose infusion, although a significant rise in total reducing substances was noted, indicating the presence of this disaccharide in the blood. Less than 3% of the administered maltose was excreted in the urine either as maltose or glucose. Initially, there was a fourfold increase in serum insulin concentration after glucose and a threefold increase after maltose infusion. Therefore, serum insulin concentrations gradually declined in a similar manner for both sugars. The plasma FFA at 15 min decreased 371 uEq/liter after glucose and 338 uEq/liter after maltose infusion.In other studies, 10 g maltose containing 5 μCi maltose-U-¹⁴C were injected into five human subjects and expired CO₂ collected for 6 hr. Maximal ¹⁴CO₂ specific activity was noted at 170 min and a mean of 61.1% of the injected radioactivity was recovered as ¹⁴CO₂. Less than 8% of the injected ¹⁴C was excreted in the urine.These results indicate that maltose administered intravenously has similar metabolic effects when compared to glucose, and may be efficiently utilized as a carbohydrate substrate. The oxidation of intravenously administered maltose-U¹⁴C to ¹⁴CO₂ demonstrates that circulating maltose is readily metabolized. A solution of maltose could provide twice the mass of sugar (and of calories) per milliliter as an equimolar solution of glucose. Parenterally administered maltose may be of clinical value and should be further studied.

I nfluences of estrogen and progesterone on the development of hyperinsulinemia and augmented pancreatic islet insulin secretion during pregnancy were assessed in this study. Groups of female rats were injected subcutaneously for 21 days with varying daily dosages of estradiol benzoate or progesterone in oil. On day 21, pancreatic islets were isolated by a collagenase method. Total insulin secretion was measured after 90-min incubations of 10 islets in buffered medium containing glucose. Higher physiologic dosages of estradiol or progesterone, singly or in combination, significantly increased islet secretion above values of untreated control rats and were comparable to augmented islet responses of term, 3-wk pregnant rats. Diameter and protein content of islets obtained from steroid-treated and pregnant rats exceeded control measurements in these instances. However, 2-hr preincubations of control islets with 1 or 10 μg/ml of either steroid did not influence subsequent glucose-stimulated insulin output.In related studies, plasma insulin responses during 30 min intravenous glucose tolerance tests were significantly above control responses in term-pregnant rats and animals receiving comparable dosages of steroids for 3 wk. Unlike pregnancy or progesterone treatment, estradiol administration alone or with progesterone significantly lowered postchallenge plasma glucose concentrations.These results indicate that estradiol and progesterone contribute to enhanced islet insulin secretion and plasma insulin responses to glucose administration during pregnancy. This change is not acutely produced but can be related to hypertrophy of islets following chronic hormonal administration. Although the data do not distinguish between direct and indirect beta-cytotrophic effects of these sex steroids, metabolic actions of estradiol and progesterone may differ, since estrogen treatment lowers plasma glucose curves following the induction of hyperinsulinemia.

P lacental transport of vitamin B₁₂ was studied in the pregnant rat in two series of experiments. In the first series animals were given cyanocobalamin-⁵⁷Co intravenously at various stages of gestation. High specific activity tracer was used and doses of B₁₂ were 1-2 ng per animal. The rats were killed from 15 min to 24 hr after injection and the fetuses, placentas, and serum were assayed for radioactivity. In the second series using uninjected animals, absolute amounts of vitamin B₁₂ in fetuses and placentas were measured at stages of gestation from day 12 through day 20.There was a progressive increase in B₁₂ transferred to the fetus during gestation. Although the quantity of vitamin B₁₂ transported per 24 hr was proportional to fetal weight, the amount transported per gram of placenta increased tenfold from day 10 through day 19. Uptake of tracer B₁₂ by placenta was initially rapid; however, no radioactivity appeared in the fetus until 2 hr after injection. The actual amount of B₁₂ in placenta increased throughout gestation, and the placental concentration of B₁₂ was greater than maternal plasma and fetal tissue concentrations at all times measured.These data suggest that the ability of placenta to transport B₁₂ increased throughout gestation, and that the rate-limiting step in the transport process was either the passage of B₁₂ from the maternal to the fetal side of placenta or the transfer from placenta into fetal plasma.

S tudies of adipose tissue cellularity were carried out in a group of nonobese adult male volunteers who gained 15-25% of their body weight as the result of prolonged high caloric intake. Adipose cell size (lipid content per cell) was determined in tissue obtained from three subcutaneous sites (gluteal, anterior abdominal wall, and triceps) and total adipose cell number estimated from measurement of total body fat.Five experimental subjects gained an average of 16.2 kg of body weight, of which 10.4 kg was determined to be fat. Expansion of the adipose mass was accompanied by a significant and relatively uniform increase in fat cell size in each subcutaneous site tested. Total adipose cell number did not change as a result of weight gain and expansion of the adipose depot in adult life. Subsequent loss of weight and restoration of original body fat was associated with a reduction in adipose cell size at each subcutaneous site, but no change in total number. In two control subjects who neither gained nor lost weight there were no changes in total adipose cell number or cell size. These observations suggest that expansion and retraction of the adipose depot in adult life is accompanied by changes in adipose cell size only.Significant differences in both the size and total number of adipose cells were observed between subjects in both the experimental and control groups. In addition, within individuals of both groups there were significant differences in cell size when adipose cells from the three subcutaneous sites were compared. These findings indicate that wide variations in adipose cell size and number exist in nonobese individuals having similar adipose depot sizes.

H istamine has positive inotropic and chronotropic effects on the heart which are not abolished by beta adrenergic-blocking agents. Since the positive inotropic and chronotropic effects of other hormones on the heart are thought to be mediated by cyclic 3′,5′-AMP, we examined the effect of histamine on adenyl cyclase in particulate preparations of guinea pig, cat, and human myocardium. Histamine at the peak of its dose-response curve, 3 × 10^-4moles/liter, produced approximately a 300% increase in cyclic 3′,5′-AMP accumulation in the guinea pig, 60% in the cat, and 90% in the human heart particles. Half-maximal activity for the histamine mediated activation of adenyl cyclase in the guinea pig was 9 × 10^-6moles/liter, almost identical with that observed for norepinephrine in the same preparation. DL-Propranolol, 1 × 10^-5moles/liter, did not abolish the activation of adenyl cyclase produced by histamine but did abolish the activation produced by norepinephrine. In contrast, diphenhydramine hydrochloride, Benadryl, 8 × 10^-5moles/liter, abolished the activation of adenyl cyclase by histamine but not that produced by norepinephrine. These data suggest that there are at least two receptor sites in guinea pig heart mediating the activation of adenyl cyclase, one responsive to histamine, the other to norepinephrine. In addition, combined maximal doses of histamine and norepinephrine produced completely additive effects on the activation of adenyl cyclase, which suggests that at least two separate adenyl cyclase systems are present in the heart, each responsive to one of these hormones. However, definitive proof would require physical separation of the two enzymes.

T he activation energy (E_A) for the diffusion of water across the epithelial cell layer of the toad bladder was determined in the absence and presence of vasopressin. An experimental approach was employed which minimized the effects of unstirred layers and the thick supporting layer of the bladder on the measurement of water diffusion. E_A in the absence of vasopressin was 11.7 ±1.4 kcal·mole^-1; after vasopressin it was 10.6±1.1 kcal·mole^-1. The difference between the two values was not significant. The results are consistent with an increase in the number rather than the size of aqueous channels in the cell membrane, a finding which differs from the generally held view that the hormone increases the radius of pores in the membrane.

T he ability of heavy microsomes and mitochondria, isolated from the control and failing hearts of genetically dystrophic hamsters (BIO 14.6 strain), to accumulate calcium was examined. The rate and extent of energy-linked calcium binding (in the absence of oxalate) by the heavy microsomes of the failing heart were markedly depressed. The calcium uptake (in the presence of 5 mM oxalate) by the heavy microsomes of the failing heart was similar to that of the control heart. On the other hand, both the rate and extent of energy-linked calcium binding (in the absence of Pi and succinate) and calcium uptake (in the presence of 4 mM Pi and 5 mM succinate) by mitochondria were greatly reduced in the failing heart in comparison to the control. No difference in the total adenosine triphosphatase activities (Ca⁺⁺-Mg⁺⁺ stimulated) of heavy microsomes or mitochondria was observed between the control and failing hearts. These results indicate an abnormality of subcellular membranes of the failing heart to bind calcium and support the growing conviction concerning the defective “calcium pump” as a molecular abnormality associated with a moderate degree of congestive heart failure.

T he pulmonary vasopressor response to acidemia was studied in intact dogs in a hemodynamically separated lobe which was pump perfused with systemic arterial or venous blood at a fixed rate. The magnitudes of the lobar vasopressor responses to perfusion with blood rendered acidic by infusions of hydrochloric lactic, and acetic acids, and by hypercapnia (membrane oxygenator) were significantly different. Although the PH of the perfusing blood in each group fell to similar extents (pH 7.1-7.0), the lobar pressor response was greatest with hydrochloric acid (HCl), smaller with lactic and acetic acids, and absent with hypercapnia. A lobar vasopressor response also occurred during lobar perfusion with blood which had been extracorporeally acidified with HCl or acetic acid, but then returned to control pH by infusions of sodium bicarbonate and Tris before reaching the lung. A lobar vasopressor response also resulted from pump perfusion of the lobar artery with femoral venous blood during perfusion of the isolated ipsilateral femoral artery with similarly treated aortic blood. However, no lobar vasopressor response resulted from pump perfusion of the lobar artery with blood removed transseptally from a right pulmonary vein during acidification (HCl) of the right pulmonary artery (to pH 7.0).The data indicate that, in this experimental preparation involving closed-chest dogs spontaneously breathing air or 35% oxygen, the lobar vasopressor response to infusions of acidifying agents is not directly related to the pH of blood actually perfusing the lobar vessels. Additionally, the vasopressor response is prevented by prior perfusion of the acidified blood through a pulmonary vascular bed but not by prior perfusion through the femoral vascular bed. Although these experiments do not establish the mediation of the lobar vasopressor response, activation of vasoactive agents in blood at or near the acidification site is suggested.In these experiments, the acidemia was produced under conditions which are not like the usual ones of developing metabolic acidosis or alveolar hypercapnia, in that strong acids were directly infused into blood which perfused only one lung lobe. The mediation of the present pressor responses and of those found in the more usual forms of experimental and clinical acidosis may therefore be dissimilar.

L ysates of mixed human leukocyte suspensions released histamine from intact human leukocytes in vitro. Microgram quantities of leukocyte lysate protein released up to 90% of the total available histamine. The mixed leukocyte lysates were separated by differential centrifugation into nuclear (800 g pellet), lysosomal (25,000 g pellet), and postlysosomal supernatant (25,000 g supernatant) fractions. The degree of separation of the lysosomal from the other two fractions was assessed by measuring the relative activities of four lysosomal enzymes. The average distribution of enzyme activity was 11 ±2% (mean ±1 SD), 72 ±10%, and 17 ±8% for the nuclear, lysosomal, and supernatant fractions respectively. The histamine-releasing activity was equally distributed between the lysosomal and supernatant fractions, each of which had 5-fold greater activity than the nuclear fraction.Purified suspensions of platelets, lymphocytes, and granulocytes were prepared, and the lysates of these suspensions all had histamine-releasing activity. Centrifugation at 100,000 g for 18 hr sedimented the histamine-releasing activity from all three types of lysate. After 20% ethanol fractionation for the preparation of cationic protein, only the activity from the platelet lysates was found in the 20% ethanol insoluble fraction.These mediators of histamine release from human platelets, lymphocytes, and granulocytes may play a role in the development of the vasodilation and increased vascular permeability which characterize the acute inflammatory response.

A coordinate relationship between the activities of two sequential enzymes in the de novo pyrimidine biosynthetic pathway has been demonstrated in human red cells. The two enzymes, orotidylate phosphoribosyltransferase and decarboxylase are responsible for the conversion of orotic acid to uridine-5′-monophosphate. Fractionation of red cells, on the basis of increase of specific gravity with cell age, has revealed that these two enzymes have a marked but equal degree of lability in the ageing red cell. It is postulated that orotidylate phosphoribosyltransferase and decarboxylase form an enzyme-enzyme complex, and that the sequential deficiency of these two enzymes in hereditary orotic aciduria may reflect a structural abnormality in this complex.In patients receiving allopurinol, the activities of both enzymes are coordinately increased, and this increase appears to be due, at least in part, to stabilization of both orotidylate phosphoribosyltransferase and decarboxylase in the ageing red cell. Allopurinol ribonucleotide is an in vitro inhibitor of orotidine-5′-monophosphate decarboxylase and requires the enzyme hypoxanthineguanine phosphoribosyltransferase for its synthesis. However, the administration of allopurinol to patients lacking this enzyme results in orotidinuria and these patients have elevated orotidylate phosphoribosyltransferase and decarboxylase activities in their erythrocytes. Evidence is presented that the chief metabolite of allopurinol, oxipurinol, with a 2,4-diketo pyrimidine ring is capable of acting as an analogue of orotic acid. It is postulated that the in vivo formation of oxipurinol ribonucleotide, catalyzed by orotidylate phosphoribosyltransferase, after allopurinol administration, leads to inhibition of orotidine-5′-monophosphate decarboxylase. This inhibition results in the urinary excretion of excessive amounts of orotidine and orotic acid, and “pseudo-substrate” stabilization of orotidylate phosphoribosyltransferase and decarboxylase.

A n effort to examine certain aspects of the adaptation in potassium excretion associated with nephron reduction was made in dogs with unilateral remnant kidneys. A constant intake of potassium was maintained by tube feeding and studies were performed before and after removal of the intact control kidney. The removal of the intact kidney created the need for the remaining nephrons of the remnant kidney to increase their rate of potassium excretion markedly. Sodium intake was held constant either at a normal or a low level. Mineralocorticoid hormone activity was maintained either at a high level by the administration of 0.2 mg 9-α-fluorohydrocortisone daily or at a low level by performing bilateral adrenalectomy and administering a minimal maintenance dose of deoxycorticosterone acetate (DOCA) and cortisol. Potassium excretion per nephron increased strikingly within 18 hr of contralateral nephrectomy and by 7 days, excretion rates were 600% of control values for the remnant kidney. More potassium was excreted in the first 5 hr after administration of a test dose of potassium by the remnant kidney alone in the postnephrectomy state than by both the remnant and intact kidneys in the prenephrectomy state. 24 hr excretion of potassium by the remnant kidney postnephrectomy averaged 92% of the administered load of potassium. The adaptation in potassium excretion was independent of the concurrent rate of sodium excretion and of mineralocorticoid hormone activity and persisted during constriction of the renal artery, a stimulus which presumably decreased distal delivery of sodium. The adaptation and the continued modulation of potassium excretion could not be explained adequately by an increase in impermeant anion excretion per nephron. Finally, known changes in hydrogen ion excretion per nephron associated with nephron reduction are in a direction opposite to those which would explain the acquired kaliuresis per nephron.

I n order to determine whether an adrenergic mechanism is involved in the secretion of growth hormone and insulin, the effect of adrenergic-blocking or -stimulating agents on plasma human growth hormone (HGH), immunoreactive insulin, blood free fatty acids (FFA), and glucose levels was studied in normal human subjects.The intravenous infusion of propranolol, a beta adrenergic-blocking agent, caused a rise in plasma HGH, a transient decrease in blood FFA, and no significant change in plasma insulin. This increase in plasma HGH was inhibited either by the combined administration of isoproterenol, a beta adrenergic-stimulating agent, along with propranolol or by oral glucose loading immediately before the start of propranolol infusion. The concomitant administration of epinephrine and propranolol brought about a rise in plasma HGH comparable with that produced by propranolol alone, without any significant change in blood FFA. Alpha adrenergic blockade by the intravenous infusion of phenotolamine significantly suppressed plasma HGH responses to insulin-induced hypoglycemia and to arginine infusion, and enhanced plasma insulin response to arginine infusion. It also stimulated lipid mobilization significantly.The intravenous infusion of alpha adrenergic-stimulating agents, phenylephrine and methoxamine, caused an increase in plasma HGH, a slight decrease in blood FFA, and no significant change in plasma insulin. This increase in plasma HGH was significantly inhibited by the simultaneous administration of phentolamine along with methoxamine. On the contrary, a beta adrenergic stimulant, isoproterenol, raised plasma insulin and blood FFA, and abolished the plasma HGH response to propranolol. Another beta stimulator, isoxsuprine, raised blood FFA but not plasma insulin.It is concluded that either beta adrenergic blockade or alpha stimulation enhances HGH secretion and inhibits insulin secretion and fat mobilization, whereas either alpha blockade or beta stimulation stimulates insulin secretion and fat mobilization and inhibits HGH secretion.

I n a series of 40 patients treated with L-asparaginase for various neoplastic diseases, 6 patients had generalized anaphylactic reactions to L-asparaginase. Each of these reactors had antibodies detectable by passive hemagglutination, but precipitins were detectable in only one of this group of six patients. That patient had received two courses of the enzyme. 1 wk after the anaphylactic reaction, complement-fixing antibodies were present in all the patients that were studied. Specific reagin antibodies (IgE) were demonstrated in one patient by the release of histamine from his leukocytes after incubation in vitro with L-asparaginase.Binding of L-asparaginase to serum antibodies after incubation in vitro was detected by selective precipitation of the complexes with 30% ammonium sulfate or by ultracentrifugation. Total inactivation of the enzyme did not occur even at optimal proportions or at antibody excess.Passive hemagglutinating antibodies to L-asparaginase were present in all patients who had an allergic reaction at least 1 day before the reaction occurred, when that sample was available, and were absent in all patients who did not manifest clinical allergy. Titration of antibodies by passive hemagglutination may thus provide a means of predicting impending anaphylaxis in this system, particularly when coupled with a sudden decrease in circulating levels of L-asparaginase activity.

S tudies on bacteria have suggested that morphine-like drugs have effects on the cell membrane. To determine the effect of this class of drugs on a mammalian cell, we selected the rabbit peritoneal exudate granulocyte, which undergoes striking membrane changes during phagocytosis. We examined the effect in vitro of the morphine analogue, levorphanol on phagocytosis and metabolism by granulocytes incubated with and without polystyrene particles or live Escherichia coli. Levorphanol (1 or 2 mmoles/liter) decreased: (a) acylation of lysolecithin or lysophosphatidylethanolamine in the medium (which is stimulated about two-fold during phagocytosis) both at rest (40%) and during phagocytosis (60%); (b) uptake of latex particles and Escherichia coli, as judged by electron microscopy; (c) killing of live Escherichia coli (10-fold); (d) ¹⁴CO₂ production from glucose-1-¹⁴C during phagocytosis by at least 80%; (e) K⁺ content of granulocytes (35%); (f) oxidation of linoleate-1-¹⁴C by 50%, and its incorporation into triglyceride by more than 80%. However, levorphanol stimulated 2 to 3-fold the incorporation of linoleate-1-¹⁴C or palmitate-1-¹⁴C into several phospholipids. Glucose uptake, lactate production, and adenosine triphosphate (ATP) content are not affected by the drug. Thus, levorphanol does not appear to exert its effects through generalized metabolic suppression.Removal of levorphanol by twice resuspending the granulocytes completely reverses all inhibition.In line with observations on bacteria, it appears that the complex effects of levorphanol on granulocytes may be due at least in part to an effect on the cell membrane.

T he mechanism of bacterial uptake of vitamin B₁₂, the spectrum of microorganisms capable of such uptake, and the factors involved were the subject of this study. Bacterial uptake of vitamin B₁₂ was found to be at least a two stage process. A primary uptake phase which was rapid (1 min or less), pH dependent, nontemperature dependent, did not require viable organisms and was insensitive to either the metabolic inhibitor dinitrophenol or to the sulfhydryl inhibitor N-ethyl-maleimide. Protein denaturation (formalin treatment or autoclaving) abolished all B₁₂ uptake. This primary uptake phase is thought to represent adsorption to binding or “receptor” sites on the cell wall. Second stage uptake was slower, pH and temperature dependent, required living bacteria, and was abolished by either dinitrophenol or N-ethyl-maleimide. This phase is dependent upon metabolic processes and may reflect transfer of B₁₂ from surface “receptor” sites into the bacterial cell. Although differences among organisms were observed in total 1 hr uptake, number of surface “receptor” sites, and relative avidities for B₁₂, all organisms except Streptococcus fecalis shared the two stage mechanism. Two Gram-positive organisms. Bacillus subtilis and Group A streptococcus, demonstrated the highest 1 hr vitamin B₁₂ uptake values; Gram-negative bacteria required 2,000-10,000 the number of organisms for comparable uptake. Binding constants (K_m) varied from 5.05 ±1.67 × 10^-10M for B. subtilis to 6.18 ±3.08 × 10^-9M for Klebsiella pneumoniae which approximate the Km for human intrinsic factor (0.38 × 10^-10M). Competition between bacteria and intrinsic factor for vitamin B₁₂ may be inferred from the similarity of these constants.These observations suggest that a variety of enteric and nonenteric organisms, not requiring exogenous B₁₂, may play a role in the pathogenesis of the vitamin B₁₂ malabsorption found in the intestinal bacterial overgrowth syndromes.

A new human antigen is reported which is present only on blood neutrophils. A neutrophil-specific antigen, designated NA1, has previously been identified in two unrelated families, and was shown to be involved in fetomaternal incompatibility and the development of isoimmune neonatal neutropenia in five newborns. In the present paper, a second antigen, designated NB1, is identified in four families with seven affected children. Antibodies that react with this second antigen are shown to produce selective agglutination of neutrophils but not other blood cells. They are neither absorbed by cells prepared from solid tissues nor by non-neutrophilic blood cells.By family and population studies, NB is shown to be distinct from NA, representing an independent genetic locus. 68% of the New York population are homozygous for NB1, 29% heterozygous, and 3% negative. The NB locus is shown to be independent from those of HL-A and other known leukocyte antigens. No evidence for linkage between NA, NB, and red cell antigens was obtained.

T he question of whether the carotid sinus baroreceptors modulate myocardial performance remains controversial. Several studies that have stressed their importance have been criticized because the possible role of cerebral ischemia and of other important variables was not eliminated. To reinvestigate this problem, we studied 21 dogs placed on total cardiopulmonary bypass. In each of these animals the carotid sinus regions were isolated and perfused with fully oxygenated blood at a constant flow rate; perfusion pressure was changed by varying the resistance to outflow from the isolated segments. Several indices of myocardial performance were assessed: right and left ventricular contractile force with Walton-Brodie strain gauge arches; the maximal rate of change in contractile force, dF/dt; the pressure developed within an isovolumic balloon inserted into the left ventricle; and the maximal rate of change of this pressure, dP/dt. When the pressure distending the carotid sinuses was raised from an average value of 34.1 ±2.8 (SEM) mm Hg to 190.1 ±4.7 mm Hg, right ventricular contractile force fell 14.9 ±2.3% (P < 0.001); right ventricular dF/dt decreased 16.7 ±3.0% (P < 0.01); left ventricular contractile force declined 14.9 ±3.3% (P < 0.01); left ventricular dF/dt fell 19.3 ±4.0% (P < 0.01); peak systolic pressure in the isovolumic balloon declined 18.2 ±3.7% (P < 0.001); and dP/dt decreased 34.1 ±4.0% (P < 0.01). Prior adrenalectomy and vagotomy and maintenance of heart rate at a constant level did not influence these results. The inverse relation between carotid sinus perfusion pressure and the indices of contractility that was observed in this investigation strongly suggests that the carotid sinus baroreceptors are an important regulatory mechanism in the control of myocardial performance.

S tudies of the rate of extrathyroidal conversion of thyroxine (T4) to 3,5,3′-triiodo-L-thyronine (T3) were carried out in rats. Total body homogenates were prepared and extracted with ethanol 48, 72, and 96 hr after the intravenous injection of ¹²⁵I-T4. ¹³¹I-T3 was added, and the paper chromatographic purification of T3 was effected by serial elution and rechromatography in three paper and one thin-layer cycles. The ratio of ¹³¹I-T3 and ¹²⁵I-T3 counting rates in the final chromatograms, which was identical in three different paper chromatography systems, was used to calculate the proportion of ¹²⁵I-T3 to ¹²⁵I-T4 in the original homogenates. In order to discount the effects of in vitro monodeiodination of T4 during extraction and chromatography, we killed control animals immediately after injection of ¹²⁵I-T4 and processed them in a similar fashion to the experimental groups. The average ratio of ¹²⁵I-T3 to ¹²⁵I-T4 in carcass extracts of animals killed between 48 and 96 hr after isotopic injection was 0.08 whereas the average ratio of ¹²⁵I-T3 to ¹²⁵I-T4 in chromatograms of control animals was 0.01. On the basis of the proposed model, calculations indicated that about 17% of the secreted T4 was converted to T3. Assuming values cited in the literature for the concentration of nonradioactive T3 in rat plasma, these findings would suggest that about 20% of total body T3 is derived by conversion from T4. Moreover, since previous estimates have suggested that in the rat, T3 has about 3 to 5 times greater biologic activity than T4, these results also raise the possibility that the hormonal activity of T4 may be dependent in large part on its conversion to T3.A necessary assumption in calculating T4 to T3 conversion in this and other studies is that the 3′ and 5′ positions are randomly labeled with radioiodine in phenolic-ring iodine-labeled T4. Evidence supporting this assumption was obtained in the rat by comparing the amount of labeled T3 produced after injection of phenolic and nonphenolic-ring iodine-labeled T4.

L ow density lipoproteins (LDL) and high density lipoproteins (HDL) from the plasma of patients with familial lecithin: cholesterol acyltransferase (LCAT) deficiency have been characterized by gel filtration, analytical ultracentrifugation, and gel electrophoresis, and their relative content of lipid and protein has been determined. The LDL of d 1.019-1.063 g/ml show marked heterogeneity. A subfraction of the LDL emerges from columns of 2% agarose gel with the void volume, has corrected flotation rates (S_f°) in the range of 20-400, and contains 4-10 times as much unesterified cholesterol, phosphatidylcholine, and triglyceride per mg protein as normal LDL. A major subfraction of the LDL emerges from the gel in the same general position as normal LDL, but exhibits somewhat higher flotation rates and contains 1.5-3 times as much unesterified cholesterol and phosphatidylcholine and 13 times as much triglyceride per mg protein. The HDL, shown to be heterogeneous in earlier studies, are mainly comprised of molecules which have flotation rates of F_1.20 3-20, migrate in the α₁-α₂ region on electrophoresis, and contain about 12 times as much unesterified cholesterol and 5 times as much phosphatidylcholine per mg protein as normal HDL. Smaller molecules are also detected, which have flotation rates of F_1.20 0-3, migrate in the prealbumin region on electrophoresis, and contain only slightly more unesterified cholesterol and phosphatidylcholine per mg protein than normal HDL.

T he low density lipoproteins (LDL) of d 1.019-1.063 g/ml of patients with familial lecithin: cholesterol acyltransferase (LCAT) deficiency show marked heterogeneity when viewed with the electron microscope. At least two types of particles are present, one large and the other small. The large particles predominate in a LDL subfraction of large molecular weight isolated by gel filtration on 2% agarose gel. They appear to be flattened structures with diameters mainly in the range of 900-1200 A. The small particles predominate in a LDL subfraction of smaller molecular weight isolated by filtration on the same type of gel. They are 210-250 A in diameter and are similar to normal LDL in size and shape.The high density lipoproteins (HDL) also are heterogeneous. The majority of particles are disc-shaped structures 150-200 A in diameter. The discs are mainly present in stacks which have a periodicity of 50-55 A and a variable length. Each disc appears to be made up of a rosette of smaller globular units 50 A in diameter. The appearance of these large molecular weight HDL contrasts with that of normal HDL, which are 70-100 A in diameter and aggregate in monolayers that show hexagonal packing of particles. A small percentage of the patients' HDL consists of structures 45-60 A in diameter. These predominate in a smaller molecular weight HDL subfraction isolated by gel filtration on Sephadex G200. The particles are present in monolayer aggregates but never form stacked structures similar to those seen in the large molecular weight HDL subfraction.

T he sequential changes in the concentration and pattern of circulating luteinizing hormone (LH) and follicle-stimulating hormone (FSH)¹ following bilateral ovariectomy were determined in 10 premenopausal women. The initial (1st wk) and delayed (3 wk) secretory responses of serum LH and FSH as related to the phases of the menstrual cycle were examined. Ovariectomy during follicular phase was accompanied by a prompt and much greater rise in both LH and FSH during the 1st wk. This rapid rise was followed by a transient decline between the 7th and 10th day which resulted in a biphasic pattern. In contrast, a slower and progressive rise in serum LH and FSH was observed in subjects ovariectomized during luteal phase of the cycle. The quantitative secretion (area under the curve) during the 1st wk after ovariectomy was significantly greater in patients operated on during the follicular phase than during the luteal phase for both LH (P < 0.05) and FSH (P < 0.01). Thereafter, a similar pattern of gonadotropin rise was observed for patients ovariectonized during either phase of the cycle and reached a plateau by the end of the 3rd wk. At this time, the mean LH concentration increased 6-fold for follicular phase surgery and 8-fold for luteal phase surgery. The mean serum FSH concentration increased 8-fold for follicular phase surgery and 12-fold for luteal phase surgery. The net increase in serum FSH level was higher than that in the serum LH level after surgery in both phases of the cycle and thus a reversal of FSH/LH ratio occurred. These data provide indirect evidence that the phase of ovarian steroid secretion may exert a quantitative influence on the gonadotropin turnover rate within the hypothalamic-pituitary system. The augmented gonadotropin release and the reversal of FSH/LH ratio following ovariectomy presumably could be due to an increased gonadotropin net synthesis which is more pronounced for FSH than for LH.

A fter the relief of 24 hr of complete unilateral ureteral obstruction in the dog, the experimental kidney is characterized by a decrease in filtration rate and an increase in fractional and often absolute excretion of sodium before and after the administration of mannitol. In the hydrated state, the failure to conserve sodium is associated with increases in fractional free water clearance and fractional sodium supply to water-freeing sites signifying that the augmented sodium excretion is derived from a proximal source. In the hydropenic state there is decreased fractional free water reabsorption, and sometimes free water excretion, in the postobstructive kidney. An early plateau in free water reabsorption is associated with an increased fractional excretion of sodium. These findings are attributed to the early development of distal nephron impermeability to water as a result of enhanced distal tubular supply and transport of sodium. There is a decrease in maximal tubular reabsorptive capacity (Tm) of glucose in the post-obstructive kidney which is, however, less marked than the decrease in filtration rate. The fall in filtration rate is to some extent likely due to a dropping out of nephrons from the circulation while the remaining nephrons are hypoperfused. The magnitude of the sodium reabsorptive defect is markedly exaggerated as the concentration of nonreabsorbable solute (mannitol) in the glomerular perfusate is increased. It is concluded that the postobstructive increase in sodium excretion during mannitol administration is in part due to a limit in the capacity to reabsorb sodium against a concentration gradient in the proximal tubule.