Conversion of Thyroxine (T4) to triiodothyronine (T3) in athyreotic human subjects

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Abstract

Studies of the possibility that thyroxine (T4) is converted to 3.5,3′-triiodo-L-thyronine (T3) in the extrathyroidal tissues in man have been conducted in 13 patients, all but two of whom were athyreotic or hypothyroid, and all of whom were receiving at least physiological replacement doses of synthetic sodium-L-thyroxine.

Authors

Lewis E. Braverman, Sidney H. Ingbar, Kenneth Sterling

Correction of metabolic deficiencies in the leukocytes of patients with chronic granulomatous disease

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Abstract

Polymorphonuclear leukocytes from patients with chronic granulomatous disease (CGD) exhibit metabolic and bactericidal deficiencies that may be the result of inadequate production of H2O2. A hydrogen peroxide-generating system was, therefore, inserted into CGD leukocytes. This was accomplished by allowing the cells to phagocytize latex spherules coated with glucose oxidase. This produced an amelioration in the known metabolic deficiencies of these cells during phagocytosis: (a) intracellular (catalatic) formate oxidation dependent upon hydrogen peroxide production was enhanced fourfold; and (b) hexose monophosphate shunt activity, which other workers have shown to be at least partially dependent upon the availability of H2O2, was markedly stimulated. These data strengthen the evidence that the fundamental metabolic lesion in CGD cells during phagocytosis is indeed deficient production of hydrogen peroxide, probably, as previously shown, due to diminished oxidase for reduced nicotinamide adenine dinucleotide.

Authors

Robert L. Baehner, David G. Nathan, Manfred L. Karnovsky

Mechanisms regulating the renal excretion of sodium during pregnancy

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Observations were made on the relation of the renin-angiotensin-aldosterone system and renal hemodynamic function to sodium balance in 43 pregnant dogs. Daily balance studies revealed that about 30-40% of ingested sodium was retained during the last half of pregnancy; during the same period, potassium balance was also positive but to a lesser extent. For groups of pregnant dogs, plasma renin activity (n = 14) and aldosterone secretion (n = 19) were significantly higher than normal; however, in some animals one or both functions were normal even though sodium retention was present. In contrast, plasma renin substrate concentration was consistently elevated during pregnancy in seven dogs. In a group of nine dogs in which both aldosterone secretion and plasma renin activity were measured, aldosterone secretion was elevated in the three dogs with the highest values for plasma renin activity; in two of the remaining six animals aldosterone secretion was elevated but plasma renin activity was normal or only slightly increased. The sequestration of sodium and water into the uterine contents was defined quantitatively in this study but evidence was lacking to support the idea that such changes led to renin release. The glomerular filtration rate (GFR) was significantly elevated throughout pregnancy but a significant decrease from the high level of mid-pregnancy occurred during the last half of pregnancy; this decrease in GFR probably contributed to the sodium retention. Administration of a large dose of deoxycorticosterone acetate (DOCA) to dogs in late pregnancy produced marked sodium retention but “escape” from the sodium-retaining steroid occurred. The data demonstrate that although increased activity of the renin-angiotensin-aldosterone system was frequently present during pregnancy, a normal rate of aldosterone secretion occurred. This finding and the observed “escape” from DOCA suggest the existence of sodium-retaining mechanisms other than the mechanism provided by a high plasma level of aldosterone.

Authors

Charles A. Robb, James O. Davis, J. Alan Johnson, Edward H. Blaine, Edward G. Schneider, John S. Baumber

The effect of fasting, diet, and actinomycin D on insulin secretion in the rat

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The present studies were performed to elucidate the mechanisms responsible for the impairment of glucose-stimulated insulin secretion observed in fasting. Rats fasted for 48 hr displayed marked impairment in their insulin secretory response to both oral and intravenous glucose. Glucose-stimulated insulin secretion was restored within 24 hr by refeeding; actinomycin D given before refeeding blocked the expected return of normal glucose-stimulated insulin secretion despite adequate food intake. Fasted rats refed a diet devoid of carbohydrate failed to display a return of normal insulin secretory responsiveness to oral glucose in contrast to rats fed isocalorically a high carbohydrate diet. Differences in insulin secretion in fed, fasted, and fasted-refed rats could not be attributed to changes in pancreatic insulin content. There was no significant difference in the insulin secretory response to aminophylline of fed, fasted, or fasted-refed rats. The intermittent pulsing of fasted rats with hyperglycemic episodes by the injection of small amounts of glucose (500 mg) intraperitoneally every 8 hr ameliorated the impairment of glucose-stimulated insulin secretion characteristic of the fasting state. These results suggest that the impairment of glucose-stimulated insulin secretion during fasting and its restoration by refeeding are regulated by changes in a glucose-inducible enzyme system in the pancreatic beta cell.

Authors

N. J. Grey, S. Goldring, D. M. Kipnis

A method for the calculation of the relative contributions of recruitment and enhancement to human eccrine sweating

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Abstract

The rate of eccrine sweating has been studied by collecting samples in unventilated capsules from human subjects following subdermal or intradermal injections of acetyl-β-methylcholine and under moderate total body heat exposure. The rate of sweating in a given area of skin could increase by recruitment of fresh glands, enhanced output of the already active glands, or some combination of both.

Authors

Juan Carlos Fasciolo, Gregory L. Totel, Becky B. Johnson, Robert E. Johnson

The detection of cell-bound antibody on complement-coated human red cells

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Abstract

This study sought to elucidate the mechanism by which human red cells, in a variety of clinical settings, become coated in vivo with autologous complement components in the absence of anti-red cell autoantibodies demonstrable by standard methods. By means of a newly developed complement-fixing antibody consumption test, previously undetectable red cell-bound γG globulin could be detected and quantified. By this technique, the complement-coated red cells of 13 of 16 patients were shown to carry abnormally high numbers of γG molecules per cell, which were nevertheless below the level for detection by the direct antiglobulin test. Eluates were made from the red cells of seven of these patients and each eluate, when sufficiently concentrated, was capable of sensitizing normal human red cells (with γG antibodies) to give a positive indirect antiglobulin test with anti-γG serum. In the presence of fresh normal serum, six of the eluates so tested were capable of fixing complement to normal human red cells. The antibodies in the red cell eluates did not exhibit Rh specificity and did not react with nonprimate red cells. When studied by sucrose gradient ultracentrifugation, the γG antibodies to human red cells in these eluates sedimented in the 7S region. It is concluded that in many patients in whom direct antiglobulin tests reveal only cell-bound complement, the complement fixation is mediated in vivo by small quantities of “warm-reacting” erythrocyte autoantibodies of the γG class.

Authors

Bruce C. Gilliland, John P. Leddy, John H. Vaughan

Warfarin metabolism in man: identification of metabolites in urine

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After administration of the coumarin anticoagulant racemic warfarin to normal humans, seven fluorescent compounds were chromatographically separated from extracts of their urine. Four of these were identified using mass spectrometry, thin-layer chromatography, and ultraviolet absorption spectroscopy. One metabolic pathway, reduction of the acetonyl side chain of warfarin, resulted in the formation of a second asymmetric carbon atom, and two diastereoisomer alcohols were identified. These warfarin alcohols are structurally similar to pharmacologically active coumarin derivatives. They have not been reported in animal studies. In addition, 6- and 7-hydroxywarfarin were identified. These are the first studies to document the metabolic fate of warfarin in the normal human.

Authors

Richard J. Lewis, William F. Trager

Catabolism of heme in vivo: comparison of the simultaneous production of bilirubin and carbon monoxide

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The quantitative relationship between the catabolism of heme and the formation of bilirubin and carbon monoxide (CO) was studied in untreated rats and in animals treated with phenobarbital or the porphyrogenic drug, allylisopropylacetamide (AIA). A novel metabolic chamber permitting continuous collection of the bile and breath was utilized for quantitation of bilirubin-14C and 14CO after the administration of hematin-14C or glycine-14C.

Authors

Stephen A. Landaw, Edward W. Callahan Jr., Rudi Schmid

The effect of dialysates and ultrafiltrates of plasma of saline-loaded dogs on toad bladder sodium transport

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In order to obtain direct evidence for the existence of a natriuretic hormone, dialysates and ultrafiltrates of plasma of dogs expanded with saline were tested for effects on sodium transport by the toad urinary bladder. Dialysate was obtained by dialysis of blood in vivo in a clinical dialyzer and by dialysis in vitro of small volumes of blood using a miniature model of the clinical dialyzer. Ultrafiltrates were prepared using selective molecular filters which permit passage of substances on the basis of molecular weight and three dimensional configuration.

Authors

Vardaman M. Buckalew Jr., F. Jesus Martinez, Wesley E. Green

Cholinesterase activity of motor end plate in human skeletal muscle

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The activity and properties of cholinesterase of the motor end plate in human intercostal muscle were studied in the isolated muscle membrane. This preparation was used because cholinesterase activity of the membrane preparation was localized in the motor end plate without contamination of cholinesterase of other muscle components. Under the experimental conditions, cholinesterase in a human end plate hydrolyzed 1.21 × 108 molecules of acetylcholine per msec, which is smaller than hydrolysis of 2.69 × 108 by a motor end plate of rat intercostal muscle. Studies with cholinesterase inhibitors and specific substrates indicated that about 90% of cholinesterase of human motor endplates is acetylcholinesterase, and about 10% is pseudocholinesterase. The end plate cholinesterase had an optimal pH of 7.8 and a Michaelis-Menten constant of 4.15 mmoles/liter, and was stable at 4°C for at least 4 wk. Motor end plates were estimated to contain only about 2% of the total cholinesterase activity of human intercostal muscle, compared with about 20% in rat tibialis anterior muscle. The difference is due to the lower cholinesterase activity of the motor end plate and higher cholinesterase activity of non-end plate components in human muscle than in rat muscle. The isolated muscle membrane provides a useful preparation for the study of the properties of motor end plate in human skeletal muscle.

Authors

Tatsuji Namba, David Grob

Renal metabolic response to acid-base changes: II. The early effects of metabolic acidosis on renal metabolism in the rat

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The early renal metabolic response was studied in rats made acidotic by oral feeding of ammonium chloride. 2 hr after feeding of ammonium chloride there was already significant acidosis. Urinary ammonia also increased after ammonium chloride ingestion and at 1½ hr was significantly elevated. In vitro gluconeogenesis by renal cortical slices was increased at 2 hr and thereafter increased steadily. Ammonia production by the same slices was also increased at 2 hr, but thereafter fell and at 6 hr had decreased to levels which, although higher than those of the control, were lower than those obtained from the rats acidotic for only 2 hr. There was no correlation between in vitro gluconeogenesis and ammonia production by kidney slices from rats during the first 6 hr of acidosis, but after 48 hr of ammonium chloride feeding, these two processes were significantly correlated. The early increase in renal gluconeogenesis was demonstrable with both glutamine and succinate as substrates.

Authors

George A. O. Alleyne

Metabolism of β-sitosterol in man

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The metabolism of β-sitosterol was compared to that of cholesterol in 12 patients. Sterol balance methods were supplemented by radiosterol studies, with the following results. (a) Plasma concentrations of β-sitosterol ranged from 0.30 to 1.02 mg/100 ml plasma in patients on intakes of β-sitosterol typical of the American diet. Plasma levels were raised little when intakes were increased greatly, and on fixed intakes they were constant from week to week. On diets devoid of plant sterols, the plasma and feces rapidly became free of β-sitosterol. (b) The percentage of esterified β-sitosterol in the plasma was the same as for cholesterol. However, the rate of esterification of β-sitosterol was slower than that for cholesterol. (c) Specific activity-time curves after simultaneous pulse labeling with β-sitosterol-3H and cholesterol-14C conformed to two-pool models. The two exponential half-lives of β-sitosterol were much shorter than for cholesterol, and pool sizes were much smaller. Values of turnover for β-sitosterol obtained by the sterol balance method agreed closely with those derived by use of the two-pool model. There was no endogenous synthesis of β-sitosterol in the patients studied; hence, daily turnover of β-sitosterol equaled its daily absorption. Absorption of β-sitosterol was 5% (or less) of daily intake, while cholesterol absorption ranged from 45 to 54% of intake. (d) About 20% of the absorbed β-sitosterol was converted to cholic and chenodeoxycholic acids. The remainder was excreted in bile as free sterol; this excretion was more rapid than that of cholesterol. (e) The employment of β-sitosterol as an internal standard to correct for losses of cholesterol in sterol balance studies is further validated by the results presented here.

Authors

Gerald Salen, E. H. Ahrens Jr., Scott M. Grundy

Mechanism of excessive purine biosynthesis in hypoxanthine-guanine phosphoribosyltransferase deficiency

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Certain gouty subjects with excessive de novo purine synthesis are deficient in hypoxanthineguanine phosphoribosyltransferase (HG-PRTase [EC 2.4.2.8]). The mechanism of accelerated uric acid formation in these patients was explored by measuring the incorporation of glycine-14C into various urinary purine bases of normal and enzyme-deficient subjects during treatment with the xanthine oxidase inhibitor, allopurinol.

Authors

Leif B. Sorensen

The biological and immunological properties of pork and beef insulin, proinsulin, and connecting peptides

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The recently discovered hormone precursors, pork and beef proinsulins, their respective connecting peptides, and beef proinsulin intermediates have been compared to insulin in their ability to stimulate the conversion of glucose-U-14C to 14CO2 and lipids in isolated fat cells. The concentrations of beef and pork proinsulins required to achieve the same biological effect were respectively, 15 and 10 times that of insulin. Beef proinsulin intermediates required only 2.6 times the concentration of insulin for the same effect. Pork and beef connecting peptides in high or low concentrations alone or in combination with proinsulin, insulin, or proinsulin intermediates showed no biological effect on the isolated fat cell system. The insulin-like activity of beef and pork proinsulins on the isolated fat cell system was not abolished with pancreatic trypsin or kallikrein inhibitors. Pork insulin antiserum inhibited the biological activity of pork insulin and proinsulin as well as that of beef insulin or proinsulin. Pork proinsulin antiserum also inhibited the insulin-like activity of both pork insulin and proinsulin. By the radioimmunoassay method, pork insulin antiserum bound only ¼ to [unk] as much proinsulin as insulin. Beef proinsulin intermediates, on the other hand, were found to react with the pork insulin antiserum to an extent nearly equal to that of insulin. These data suggest that (a) proinsulin exhibits its effect on the isolated fat cells independent of its conversion to insulin, (b) connecting peptides have no biological effect under present experimental conditions, and (c) in comparison to insulin, immunological reactivity of proinsulin is greater than its biological activity using our pork insulin antiserum; thus, the comparison of antibody specificity with the fat cell receptor specificity suggests that the biological site of action is different from the immunologic site.

Authors

Abbas E. Kitabchi

On the influence of extracellular fluid volume expansion and of uremia on bicarbonate reabsorption in man

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Abstract

The patterns of bicarbonate reabsorption during increasing plasma concentrations were studied in subjects with a range of glomerular filtration rates (GFR) from 170 to 2 ml/min. In a group of five subjects with GFR values above 30 ml/min, paired bicarbonate titration studies were performed first under conditions which minimized extracellular fluid (ECF) volume expansion, and second under conditions which were conducive to exaggerated expansion of ECF volume. In patients with GFR values below 30 ml/min, a single protocol was employed. Studies also were performed on two patients with far advanced renal disease who were nephrotic and exhibited a sodium-retaining state. When ECF volume expansion was minimized in the nonuremic subjects, values for bicarbonate reabsorption were well in excess of the usually accepted Tm level and over the range of plasma bicarbonate concentrations employed, no evidence of a Tm phenomenon was observed. A similar pattern emerged in the two nephrotic patients despite the presence of uremia. However, with both exaggerated expansion of ECF volume (GFR greater than 30) and in patients with advanced renal disease in the absence of exaggerated ECF volume expansion a tendency towards saturation kinetics for bicarbonate reabsorption was demonstrable. In comparing the minimized with the exaggerated expansion studies, evidence emerged for a decrease in both bicarbonate reabsorption per unit of GFR and the absolute rate of bicarbonate reabsorption. When ECF volume expansion was exaggerated in uremic patients after stable rates of bicarbonate reabsorption had been achieved, a decrease in reabsorption per unit of GFR and in absolute bicarbonate reabsorption occurred. The possible relationship of the factors controlling sodium excretion to the observed patterns of bicarbonate reabsorption is considered in the text.

Authors

Eduardo Slatopolsky, Phillip Hoffsten, Mabel Purkerson, Neal S. Bricker

Effects of experimental heart failure on the capacity of glucagon to augment myocardial contractility and activate adenyl cyclase

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Although glucagon exerts positive inotropic effects in patients with no or mild impairment of cardiac function, similar effects are not consistently observed in patients with chronic heart failure. Accordingly, the inotropic effects of glucagon on papillary muscles from normal cats and cats in which right ventricular failure had been produced for 4-145 days by pulmonary artery banding were compared. At the peak of the concentration-response curve, glucagon increased peak isometric tension (T) in normal muscles from 4.4±0.4 to 6.6±0.5 g/mm2 (P <0.001), and maximum rate of tension development (dT/dt) from 16.9±0.9 to 25.1±1.6 g/sec per mm2 (P < 0.001). In contrast, glucagon produced no significant increases in T or dT/dt in failure muscles. The percentage increases in T and dT/dt caused by norepinephrine were the same in muscles from normal and failing hearts. Since the cardiac effects of glucagon and norepinephrine may be mediated by adenyl cyclase, responsiveness of adenyl cyclase was determined in particulate fractions of the right ventricle. Glucagon activated adenyl cyclase in normal, but had no effect in failure preparations. Norepinephrine-induced activation of adenyl cyclase, however, was unaltered by failure. Thus, in contrast to norepinephrine, glucagon loses the capacity to augment myocardial contractility and activate adenyl cyclase in hearts derived from cats in chronic failure.

Authors

Herman K. Gold, Kirk H. Prindle, Gerald S. Levey, Stephen E. Epstein

Effects of hyperlipoproteinemias and their treatment on the peripheral circulation

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The purpose of this study was to determine the effect of familial hyperlipoproteinemia (HLP) on peripheral vascular disease (PVD) and the extent to which the vascular disease (PVD) and the extent to which the vascular disease is modified by treatment of the lipoprotein disorder. PVD was detected plethysmographically by observing a diminished peak reactive hyperemia blood (PRHBF) following ischemia. The value for PRHBF in the extremity demonstrating the lowest response in 32 normal subjects (age 19-50 yr) was 39.6±1.5 SEM, ml/min per 100 g. Patients with untreated HLP. who had PRHBF below the lower limit of normal, were 2 of 11 type II, 9 of 12 type III, 1 of 10 type IV. As a group, patients with type III HLP showed diminished PRHBF (26.6 ±3.0 ml/min per 100 g, P <0.01). In view of the high incidence of PVD and the striking reduction in serum lipids and complete resorption of xanthomas observed in type III HLP with therapy, six patients were studied before and after 3-6 months of treatment with a therapeutic diet and clofibrate. PRHBF in the most severely affected extremity increased markedly, from 20.4 ±1.6 to 31.9 ±1.8 ml/min per 100 g (P<0.01), indicating a dramatic increase in maximum blood flow to this extremity. In two type III patients with PVD not treated, no change in PRHBF occurred over 5 months. In two other type III patients the PRHBF increased 17% during the first 25 days of therapy concomitant with a 30% reduction in whole blood viscosity. Over the next 120 days, blood viscosity decreased only an additional 4.6% whereas the PRHBF increased 57%, indicating that the observed changes seen in the PRHBF with therapy of type III patients can be only minimally accounted for by changes in the viscosity of the blood. Thus, patients with type III HLP are particularly susceptible to the development of PVD and objective improvement of PVD can occur with medical treatment of this lipid transport disorder.

Authors

Robert Zelis, Dean T. Mason, Eugene Braunwald, Robert I. Levy

Differences in primary cellular factors influencing the metabolism and distribution of 3,5,3′-L-triiodothyronine and L-thyroxine

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Administration of phenobarbital, which acts exclusively on cellular sites, results in an augmentation of the liver/plasma concentration ratio of L-thyroxine (T4) in rats but no change in the liver/plasma concentration ratio of L-triiodothyronine (T3). Whereas phenobarbital stimulates the fecal clearance rate both of T3 and T4, it increases the deiodinative clearance rate of T4 only. These findings suggest basic differences in the cellular metabolism of T3 and T4. Further evidence pointing to cellular differences was obtained from a comparison of the distribution and metabolism of these hormones with appropriate corrections for the effect of differential plasma binding. The percentage of total exchangeable cellular T4 within the liver (28.5) is significantly greater than the corresponding percentage of exchangeable cellular T3 within this organ (12.3). Extrahepatic tissues bind T3 twice as firmly as T4. The cellular metabolic clearance rate (= free hormone clearance rate) of T3 exceeds that of T4 by a factor 1.8 in the rat. The corresponding ratio in man, 2.4, was determined by noncompartmental analysis of turnover studies in four individuals after the simultaneous injection of T4-125I and T3-131I. The greater cellular metabolic clearance rate of T3 both in rat and man may be related to the higher specific hormonal potency of this iodothyronine.

Authors

Jack H. Oppenheimer, Harold L. Schwartz, Harvey C. Shapiro, Gerald Bernstein, Martin I. Surks

Hemolysis of “stress” reticulocytes: a source of erythropoietic bilirubin formation

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The formation of bilirubin-14C was measured in rats given transfusions of red blood cells containing 14C-labeled hemoglobin heme. Per cent conversion of hemoglobin-14C to bilirubin was 4 times greater with transfusion of “stress” reticulocytes from rats responding to hemorrhage than with normal reticulocytes from unstimulated donors. When the increased number of labeled reticulocytes produced by hemorrhaged donors was also considered, the total magnitude of labeled bilirubin formation was almost 20 times higher with stress as compared to normal reticulocytes. The findings were not influenced by splenectomy of either donor or recipient rats, iron loading of donors, or bleeding of recipients. However, bilirubin-14C formation fell off progressively as studies were performed at longer intervals after erythroid stimulation.

Authors

Stephen H. Robinson, Maria Tsong

Nature of fetal hemoglobin in the Greek type of hereditary persistence of fetal hemoglobin with and without concurrent β-thalassemia

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The fetal hemoglobin in the affected members of three Greek families with the hereditary persistence of fetal hemoglobin has only γ-chains of the type with alanine in position 136. Although certain Negro families had been considered to have only this type of γ-chains in their fetal hemoglobin, further studies required that they be reclassified. Consequently, the Greek cases are the sole examples of this class among the heterozygotes for the hereditary persistence of fetal hemoglobin. In Greek double heterozygotes for β-thalassemia and the hereditary persistence of fetal hemoglobin, fetal hemoglobin is increased above the level of hemoglobin F in simple heterozygotes and γ-chains with glycine in position 136 become apparent. In these individuals, γ-chains with alanine in position 136 apparently derive from the chromosome for the hereditary persistence of fetal hemoglobin and are present in the hemoglobin F with γ-chains of both types from the chromosome for β-thalassemia. When these data are correlated with earlier knowledge of the genetic state of the Greek individuals, modifications of our previous ideas about deletions as the genetic basis of the hereditary persistence of fetal hemoglobin must be considered.

Authors

T. H. J. Huisman, W. A. Schroeder, George Stamatoyannopoulos, Nicole Bouver, J. Roger Shelton, Joan Balog Shelton, Gerald Apell

Genetic control of the phenobarbital-induced shortening of plasma antipyrine half-lives in man

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Abstract

Authors