Issue published January 1, 1971

T he endogenous production of carbon monoxide (˙V_CO) in newborn infants was measured by serial determinations of blood carboxyhemoglobin during rebreathing in a closed system. Mean ˙V_CO in nine full-term infants was 13.7 ±3.6 μl CO/kg per hr (SD), and in four erythroblastotic infants ˙V_CO ranged from 37 to 154 μl CO/kg per hr preceding exchange transfusion. Mean red cell life-span (MLS) and total bilirubin production were calculated from ˙V_CO. MLS in normal newborns was 88 ±15 days (SD), and bilirubin production was 8.5 ±2.3 mg/kg per 24 hr. This is more than twice the amount of bilirubin normally produced in the adult per kilogram of body weight. Normal infants achieved a net excretion of bilirubin of at least 5.6 ±2.3 mg/kg per 24 hr (SD) as calculated from the bilirubin production and the measured rise in serum bilirubin concentration.The measurement of ˙V_CO should prove valuable in the study of red blood cell survival and bilirubin metabolism in the newborn infant.

T he fate and distribution of isotopic manganese administered as a single carrier-free dose of 200 μCi of maleate-⁵⁴Mn to 12 rhesus monkeys was studied at different time periods from the 6th hr to the 278th day. Whole-body activity was measured, and all body organs and tissues and different parts of the central nervous system (CNS) were evaluated for specific activity, exponential analysis, and relative retention. Exponential analysis revealed a pattern of discharge with a fast and a slow component for the whole body and for many of the viscera. All parts of the CNS and, to a lesser degree, the thyroid and muscle showed an almost steady state of activity after the initial uptake. While the whole body and most organs and tissues appeared to discharge their radioactivity with the passage of time, first rapidly and then gradually, the CNS, endocrine glands, and muscle tissues showed persistent levels of specific activity. All components of the brain exhibited increasing relative retention, the lentiform nucleus and the cerebellum showing this more. It is suggested that the selective vulnerability of the brain in manganese miners might result from this inability on the part of the CNS to discharge the ⁵⁴Mn with time. This investigation confirms and amplifies our earlier similar study on the rat.

A new radioimmunoassay for human parathyroid hormone (PTH) in serum, which can measure the hormone present in 94% of the normal sera tested, is described. It is based on the ability of human PTH to compete with ¹³¹I-labeled bovine PTH for binding to an antiserum directed against porcine PTH. This antiserum distinguishes between human PTH extracted from parathyroid adenomata and that present in hyperparathyroid sera. Evidence is given to suggest that this is due to immunochemical changes in the hormone extracted from adenomata and not to immunochemical heterogeneity of the hormone present in serum.Physiologic data supporting the validity and specificity of the assay are presented. Induced episodes of hypercalcemia and hypocalcemia resulted in appropriate responses in serum immunoreactive PTH (IPTH) in normal subjects and in patients with Paget's disease of bone. In normals, there was a progressive increase in serum IPTH in the late afternoon and evening, suggesting a diurnal secretory rhythm. A negative correlation was found between the serum calcium and serum IPTH over the normal range of serum calcium values; a positive correlation was found between these variables in patients with primary hyperparathyroidism. There was apparent overlap between serum IPTH values in normal subjects and patients with primary hyperparathyroidism, but formal discriminate analysis of values for serum calcium and IPTH demonstrated separation of these two groups, without overlap.

I ntrarenal transport of urate-2-¹⁴C was studied in anesthetized rats using the microinjection technic. During saline diuresis, small volumes of urate-2-¹⁴C (0.24-0.48 mM) and inulin-³H were injected into surface proximal and distal convoluted tubules, and ureteral urine was collected serially. Total (74-96%) and direct (57-84%) urate recovery increased significantly the more distal the puncture site. Delayed recovery (±20%) remained approximately the same regardless of localization of the microinjection. After proximal injections, total and direct recoveries of urate-2-¹⁴C were significantly higher in rats treated with probenecid, pyrazinoate, or PAH than during saline diuresis alone, while the excretion rates were comparable after distal injection. Delayed recovery was not altered by drug administration. The decreased proximal reabsorption of urate is presumably due to an effect of the drugs on the luminal membrane of the nephron. For perfusion at high urate concentrations, nonradioactive urate was added to the injectate (0.89-1.78 mM). Urate-2-¹⁴C recovery was almost complete and there was no delayed excretion, demonstrating saturation kinetics. These findings are compatible with a carrier-mediated mechanism for urate transport probably located at the luminal border of the proximal tubular epithelium. No definitive evidence for urate secretion was found in these studies.

T he resting membrane potential difference (Em) of skeletal muscle was measured in 26 normal human subjects, 7 patients with mild illness, and 21 patients with severe, debilitating medical disorders. A closed transcutaneous approach to the muscle was made by needle puncture and the Em was measured utilizing standard Ling electrodes. Measurements revealed an Em of -88 ±3.8 mv in healthy subjects and -89 ±2.1 mv in patients hospitalized for minor medical problems. The mean Em in 21 in-hospital patients, judged to be severely ill clinically from a variety of causes, was -66.3 ±9.0 mv. Open deltoid muscle biopsies were performed in 7 of the healthy subjects and in 13 of the severely ill group. Estimation of the intra-extracellular water partition was made by calculating the chloride space from the previously measured Em. Analysis of the muscle samples revealed no significant difference in the intra-extracellular potassium ratios of the two groups biopsied. Intracellular Na⁺ concentrations were uniformly increased in the muscle samples of the severely ill subjects and averaged 42.3% higher than those of the normal subjects. The mechanisms which might account for the elevation of intracellular Na⁺ and a depression of Em independent of changes in intra-extracellular K⁺ ratios are discussed and it is suggested that this defect may be a generalized cellular abnormality which is a common quality of serious illnesses.

A ssays of ribonuclease activity in components of mature and immature mammalian erythroid cells indicate that RNase activity is present both in the membrane-free hemolysate and the washed membranes. Erythroid cell RNase exists in an active and latent form. The majority of total cell RNase activity is in the latent state, and is localized to the erythroid cell membrane. Both total and latent RNase activity decline as the cell matures. The latent RNase is released from its relatively firm attachment to the cell membrane and activated by centrifugation or, optimally, by exposure to 4 M urea. The active sites of membrane-associated RNase are apparently oriented toward the inner side of the cell membrane. The properties of the latent membrane-bound RNase which is activated by urea, including K_m, pH optimum, inhibition of enzyme activity by cations, and response to metabolic inhibitors, do not differ significantly from those of the soluble RNase in the membrane-free hemolysate, suggesting that there is only one type of RNase in the erythroid cell. Binding of Rnase to the erythroid cell membrane stabilized the enzyme against inactivation during incubation at 37°C, and the findings suggest that membrane-bound RNase may play a particular part in degrading ribosomes. The findings indicate that the cell membrane has a major role in RNA metabolism in the maturing mammalian erythroid cell.

R enal proximal tubular transport of salt and water has been examined using isolated perfused rabbit tubules. In this method direct measurements can be made under controlled conditions not readily achieved in vivo. The results are in general agreement with previous micropuncture studies in other species, supporting the validity of both sets of measurements.In the present studies, absorption of sodium salts and water occurred without change in the concentration of Na in the lumen except when a poorly reabsorbed solute (raffinose) was present, in which case, mean concentration of Na in the lumen reached a steady-state value 33-35 mEq liter^-1 less than in the bath. The tubule is very permeable to sodium salts (sodium permeability = 9.3 × 10^-5 cm sec^-1, σ_NaCl = 0.68-(0.71) and to water (hydraulic conductivity [L_p] = 2.9 to 6.3 × 10^-5 cm sec^-1 atm^-1). Net reabsorptive flux of Na was only 20% of the unidirectional Na flux.The steady-state concentration difference for Na in the presence of raffinose and σ_NaCl in the present studies was the same as previously found by micropuncture in the rat. On the other hand Na permeability, net Na transport rate, and L_p were all from one-half to one-third as great in the isolated rabbit tubule as in the rat in vivo. Apparently, although the transport mechanisms appear to be basically the same in the two species, there are fewer transport units and passive permeability paths per unit length in the rabbit tubule than in the rat.

T he mechanism of glomerulotubular balance was investigated by microperfusion of the rat proximal tubule at two different rates before and after contriction of the aorta sufficient to produce a 50% reduction in whole kidney filtration rate and plasma flow. At a perfusion rate of 28 nl/min the absolute rate of proximal tubular reabsorption averaged 4.80±0.28 nl/mm·min in the absence of aortic constriction. Reducing the perfusion rate by one-half resulted in only a 22% decrease in the absolute rate of reabsorption, and imbalance between load and reabsorption resulted as fractional reabsorption of the perfused volume increased from 0.56 to 0.83 at 3 mm length of perfused tubule. These observations support other studies indicating that changing the load presented to the individual proximal tubule does not change reabsorptive rate sufficiently to result in glomerulotubular balance. Aortic constriction decreased the absolute rate of proximal tubular reabsorption approximately 50%, resulting in imbalance between load and reabsorption at the higher perfusion rate (fractional reabsorption of the perfused volume fell to 0.23 at 3 mm). Thus, the decrease in proximal tubular reabsorption necessary for glomerulotubular balance will occur independent of a change in the load presented for reabsorption. Balance between load and reabsorption was produced artificially by combining aortic constriction and a reduction in perfusion rate proportional to the reduction in whole kidney filtration rate. Mathematical analysis of the data suggests that the absolute rate of reabsorption along the accessible length of the proximal tubule is constant and is not proportional to the volume of fluid reaching a given site. Thus, there appears to be no contribution to glomerulotubular balance of any intra- or extratubular mechanism directly coupling load and the rate of proximal tubular reabsorption. It is concluded that glomerulotubular balance during aortic constriction is a consequence of hemodynamic effects of the maneuver to decrease filtration rate and the rate of proximal tubular reabsorption independently but in an approximately proportional manner.

T hree adult human subjects were maintained for 7 days (period I) on a protein-free formula diet containing the minimum daily requirements of the eight essential amino acids plus 40 g glycine. During the last 5 days of this period, the average daily nitrogen balances for the three subjects were +0.52, +0.71, and +0.30 g, respectively. During the next 7 days (period II), valine was withdrawn from the diet, and the glycine ration increased by an equimolar amount. During the last 5 days of period II, average daily nitrogen balances declined to -1.82, -1.61, and -1.87 g, respectively. In the final period of 7 days (period III), the keto analogue of valine, α-ketoisovaleric acid, was added to the diet in a quantity equimolar to the minimum daily requirement of valine. During the last 5 days of this period, average daily nitrogen balances improved to -0.02, -0.18, and -0.83 g, respectively. Analogous experiments in three subjects involved the withdrawal from the diet of phenylalanine (period II) and replacement by its keto analogue, phenylpyruvic acid (period III). The average daily nitrogen balances were as follows: period I: +1.04, +0.96, and +0.53 g; period II: -1.45, -1.83, and -1.94 g; period III: +0.07, +0.11, and -0.52 g.The data demonstrate that man can convert α-ketoisovaleric acid and phenylpyruvic acid to the corresponding essential amino acids, valine and phenylalanine. The efficiency of these conversions is considerably less than 100%.

A physiological explanation for sustained hyperosmolality was sought in a patient with histiocytosis. During 23 days of observation with only sodium intake regulated at 100 mEq daily, elevation (mean 310 mOsm/kg of water) and fluctuation (range 298-323) of the fasting plasma osmolality were recorded. The presence of endogenous vasopressin was indicated by the patient's ability to concentrate the urine to as high as 710 mOsm/kg of water with a creatinine clearance of 84 cc/min, and by dilution of the urine in response to alcohol. The failure of increasing fluid intake to as high as 6.2 liters daily to lower the plasma osmolality indicated that deficient fluid intake was not solely responsible for the elevated plasma osmolality. Hypertonic saline infusion during water diuresis resulted in the excretion of an increased volume of dilute urine. The water diuresis continued despite a rise in plasma osmolality from 287 to 339. An isotonic saline infusion initiated during hydropenia resulted in a water diuresis which continued despite a rise in the plasma osmolality from 303 to 320. Stable water diuresis induced during recumbency by either oral ingestion of water or intravenous infusion of normal saline was terminated by orthostasis and resumed with the return to the recumbent position. Antecedent alcohol ingestion blocked the antidiuresis of orthostasis. The data are interpreted as indicating impairment of the osmoreceptor mechanism as the primary cause of the hyperosmolar syndrome. They also indicate that vasopressin secretion was regulated primarily by changes in effective blood volume. Chlorpropamide was found to be an effective treatment for the syndrome.

W ater diuresis was produced in anesthetized hypophysectomized, cortisone-treated dogs by infusion of 2.5% dextrose. Alpha adrenergic blockade of the left kidney produced by infusion of phenoxybenzamine in the left renal artery was associated with a significantly (P < 0.05) greater rate of urine flow (V) and free water excretion (C_H2O) in the left kidney than in the right despite similar glomerular filtration rates (GFR) (17 ± 1.3 ml/min, left; 18 ±0.9 ml/min, right). Sodium excretion (U_NaV) was similar in the two kidneys (3 and 5 μEq/min).When beta adrenergic stimulation of the left kidney was superimposed on alpha blockade by the addition of isoproterenol to the left renal artery infusate, GFR remained unchanged and similar in the two kidneys, as V and C_H2O increased significantly (P < 0.01) in the left kidney but not in the right. When isoproterenol was discontinued, V and C_H2O returned towards control in the left kidney and remained unchanged in the right. The ratios of the left kidney to the right during control, isoproterenol, and postcontrol were 1.22, 1.65, and 1.35, respectively, for V and 1.36, 1.90, and 1.44, respectively, for C_H2O. Sodium excretion remained unchanged and similar in the two kidneys throughout the study.The results indicate that blockade of alpha adrenergic activity inhibits the increased proximal tubular sodium reabsorption which anesthesia induces in the dog.Beta adrenergic stimulation appears to decrease proximal tubular sodium reabsorption but does not prevent virtually complete reabsorption of the increased quantity of delivered sodium by the ascending limb of the loop of Henle and the distal tubule. These changes in sodium reabsorption presumably are not associated with changes in colloid osmotic pressure or hydrostatic pressure in the peritubular capillary inasmuch as cortical and non-cortical plasma flow, filtration fraction, and mean arterial pressure in the left kidney were unchanged. Thus, isoproterenol probably produced its effects through a direct action on the renal tubule, possibly through the mediation of the adenyl cyclase system.

A ngiotensin II was determined by radioimmunoassay in systemic arterial, pulmonary arterial, and renal venous plasma and in renal hilar lymph in dogs. Levels of the peptide were determined prior to and during progressive graded hemorrhage or reduction in renal perfusion pressure. Levels of angiotensin II in plasma consistently rose during transit through the lung indicating pulmonary conversion of angiotensin I to angiotensin II. On the other hand, angiotensin II in the renal vein plasma was less than that in arterial plasma indicating renal extraction of the peptide from plasma. When renal hilar lymph was sampled under similar conditions, angiotensin II in lymph was consistently higher than that in arterial or renal venous plasma. Furthermore, in some experiments angiotensin II in lymph increased at a time when the concentration in plasma was undetectable. No evidence was found to indicate that angiotensin II in plasma entered renal lymph. It was concluded that angiotensin II levels in lymph reflected the concentration of angiotensin II in renal tissue. The data further suggested that angiotensin II is partially removed from arterial plasma by hydrolysis during transit through the kidney.

C ultured fibroblasts from a young girl with ketotic hyperglycinemia were unable to oxidize propionate-¹⁴C to ¹⁴CO₂, but oxidized methylmalonate-¹⁴C and succinate-¹⁴C normally. This block in propionate catabolism was shown to result from a lack of propionyl-CoA carboxylase activity. The carboxylase deficiency was not due to the presence of an intracellular inhibitor and it was not corrected by biotin, a known cofactor for the enzyme. Both of her parents' fibroblasts had approximately 50% of normal propionyl-CoA carboxylase activity. These results demonstrate that ketotic hyperglycinemia and propionicacidemia are the same disease, caused by a mutation of the propionyl-CoA carboxylase apoenzyme, which is inherited as an autosomal recessive trait. This enzymatic localization provides an explanation for the remarkable clinical and chemical similarity between ketotic hyperglycinemia and methylmalonicaciduria and offers a potential means of antenatal detection of this disorder.

T he relation of cyclic 3′,5′-adenosine monophosphate to platelet function has been studied by investigating the influence of this compound and of its N⁶-2′-0-dibutyryl derivative on platelet aggregation and other aspects of platelet behavior after demonstration of adenyl cyclase activity in disrupted platelets.Dibutyryl cyclic AMP inhibited platelet aggregation induced by ADP, epinephrine, collagen, and thrombin. Cyclic AMP was also inhibitory but was less effective. The platelet “release reaction” was also inhibited; specifically, there was inhibition of the induction of platelet factor 3 activity and of the release of labeled 5-hydroxytryptamine. Platelet swelling produced by ADP was not inhibited.The action of dibutyryl cyclic AMP did not result from contamination with 5′-AMP, nor was it attributable to production of 5′-AMP by plasma enzymes. Dibutyryl cyclic AMP was degraded to 2′-O-monobutyryl cyclic AMP and to cyclic AMP in plasma, but plasma exhibited no cyclic nucleotide phosphodiesterase activity, and the production of 5′-AMP did not occur. The in vitro effects of dibutyryl cyclic AMP were associated with uptake of the compound by platelets.Adenyl cyclase activity of platelet homogenates was demonstrated with production of 9.27 × 10^-11 (±2.62 × 10^-11) mole cyclic AMP per min per 10¹⁰ platelets. The activity was increased by NaF and by prostaglandin PGE₁ and was decreased by epinephrine. The effect of epinephrine was blocked by phentolamine but not by propanolol. Adenyl cyclase activity was also inhibited by collagen, 5-hydroxytryptamine, and thrombin. ADP, dibutyryl cyclic AMP, and cyclic AMP did not alter adenyl cyclase activity.These observations are consistent with the hypothesis that platelet aggregation is favored by a decrease in platelet cyclic AMP and inhibited by an increase in cyclic AMP.

I n a 19 yr old male with familial hyperkalemic periodic paralysis, paralysis was consistently induced by the administration of potassium chloride, corticotropin-gel, and a variety of glucocorticoids (dexamethasone, 6-methylprednisolone, triamcinolone) but not by mineralocorticoids (D-aldosterone, deoxycorticosterone) or by adrenocorticotropin (ACTH)-gel plus metyrapone. Induced attacks were virtually identical with spontaneous attacks, being associated, after a latent period of a few hours, with a rise in plasma K⁺ and HCO₃^- and a simultaneous fall in plasma Na⁺ and Cl^- concentrations to an extent implying exchange of 1 K⁺ with 2 Na⁺ and 2 Cl^- between extracellular and intracellular fluid. ACTH-induced paralysis was preceded by rising serum inorganic P, and associated with increased plasma glucose, blood lactate, and serum creatine phosphokinase concentrations. In normal subjects ACTH, cortisol, and triamcinolone administration failed to change plasma electrolytes or strength, while ingestion of KCl produced no weakness and smaller changes in plasma K and Na than in the patient.Since the patient and normal subjects showed the same changes in renal excretion of K after the administration of cortisol and KCl, it seems likely that paralysis in the patient resulted from abnormally slow uptake (and/or excessive loss) of K by the muscle cells, possibly caused by an abnormal “ion-exchange pump.” Normal adrenocortical function and absence of a peak in plasma 11-hydroxycorticoid (11-OHCS) concentration preceding spontaneous paralysis, indicated that spontaneous paralysis did not result from changes in cortisol secretion. Similar hyperkalemic paralysis was precipitated by ACTH-gel in a brother and first cousin of the propositus. Administration of acetazolamide and fludrocortisone reduced the rise in plasma K concentration and prevented the weakness which otherwise invariably followed KCl administration to the patient. He and two close relatives have been completely protected from severe attacks of paralysis in the past 14 months by treatment with these two medications.

P ure amylase was isolated from pancreata and parotid glands of the baboon, an animal which has a serum amylase level and renal clearance of amylase (C_Am) similar to man. After bolus injection, both pancreatic and salivary amylase rapidly disappeared from the serum in a monoexponential fashion with a mean serum half-time of approximately 83 min. Only about 24% of the amylase cleared from the serum appeared in the urine indicating that the majority of amylase was removed from the serum by an extraurinary mechanism. The C_Am by the kidney was constant over a wide range of serum amylase levels and the ratio of C_Am/C_In, which averaged 3.0%, was not influenced by mannitol diuresis. This suggests that the renal excretion of amylase results from glomerular filtration without appreciable tubular reabsorption. Pancreatic amylase was consistently cleared more rapidly by the kidney than was the baboon's endogenous amylase while salivary amylase was consistently cleared less rapidly than endogenous amylase.The findings in this study provide insight into several of the following clinically observed phenomena: (a) the short serum half-time of amylase accounts for the transient nature of serum amylase elevations in pancreatitis; (b) the extra-urinary removal of amylase accounts for the maintenance of relatively normal amylase levels in uremia; and (c) the more rapid renal clearance of pancreatic amylase compared to salivary amylase may explain the disproportionate elevation of the urinary amylase excretion rate relative to the serum amylase level in acute pancreatitis.

T he effects of oral ethanol administration on blood glucose and lactate concentrations, lactate inflow and outflow rates, and lactate incorporation into glucose were investigated in eight human volunteers. Lactate incorporation into glucose, lactate turnover, and lactate inflow and outflow rates were determined during an 8 hr constant infusion of 100 μCi of lactate-U-¹⁴C. Ethanol was administered by mouth at hourly intervals, 60 ml of bonded whiskey initially and 30 ml/hr thereafter. Blood lactate concentrations increased precipitously after the administration of ethanol, reached a plateau within 120-180 min, and remained constant thereafter despite the continued administration of ethanol. Before ethanol, the lactate turnover rate was 0.76 mmoles/kg per hr ±0.05 (SEM) and lactate inflow and outflow rates were closely balanced. During the administration of ethanol, the lactate inflow rate was unchanged, but the lactate outflow rate was significantly inhibited, decreasing to 50% of the inflow rate. Despite the continued administration of ethanol, equilibrium between lactate inflow and outflow was restored within 120-180 min and coincided temporally with establishment of a constant blood lactate concentration. Lactate oxidation was unaltered by ethanol, but lactate incorporation into glucose was significantly inhibited. Lactate incorporation into glucose was reduced within 30 min of the administration of ethanol, and nadir values were reached within 120-180 min. Lactate incorporation into glucose remained constant thereafter at rates that were only 30% of those observed in the absence of ethanol. The results of these studies indicate that ethanol-induced hyperlacticacidemia is due to decreased lactate disposal rather than increased lactate production.

T he effect of ethanol on the interrelationship of lactate and glucose metabolism was investigated in eight human volunteers. Lactate and glucose kinetics and intervconversion rates were determined by the sequential administration of L-(+) lactate-U-¹⁴C and glucose-1-¹⁴C over an 8 hr period. After a 12 hr fast, the glucose turnover and recycling rates were 94.0 ±3.8 (SEM) and 13.7 ±1.1 mg/kg per hr, respectively. Approximately 50% of the glucose turnover or 40.7 ±2.1 mg/kg per hr was converted to lactate, accounting for 50% of the lactate turnover rate. Lactate turnover and lactate conversion to glucose were 81.8 ±6.2 and 16.7 ±1.1 mg/kg per hr, respectively. Approximately 20% of the glucose turnover was derived from lactate under these conditions. During the administration of ethanol, the blood lactate concentration doubled and the lactate turnover rate declined slightly. Lactate conversion to glucose was markedly inhibited, decreasing from 16 to 5 mg/kg per hr, and the per cent of the glucose turnover derived from lactate decreased from 18 to 6. Despite the marked inhibition of lactate conversion to glucose, neither the blood glucose concentration nor the glucose turnover rate changed. Both glucose recycling and glucose conversion to lactate were decreased, indicating that ethanol inhibited peripheral glucose utilization. There was no difference in the degree of inhibition of lactate incorporation into glucose produced by ethanol when nonfasted subjects were compared with two subjects who had fasted for 48-72 hr despite the presence of hypoglycemia in the latter.These results indicate that starvation is not a prerequisite for ethanol inhibition of gluconeogenesis from lactate in humans but is necessary for the development of hypoglycemia. Inhibition of lactate incorporation into glucose in nonfasted subjects is probably masked by a concomitant increase in glycogenolysis which prevents hypoglycemia. Ethanol decreases glucose conversion to lactate as well as lactate conversion to glucose, thus inhibiting the Cori cycle.

T o determine whether chronic exposure to hypoxia during adulthood produces alterations in the control of ventilation, measurements of the resting ventilatory response to hypoxia and hypercapnia, as well as ventilatory response to hypoxia during exercise, were carried out in a group of 10 long-term (3-39 yr) non-native residents of Leadville, Colo. (elevation 3100 m). A group of 8 subjects native to Leadville was also studied and 10 low altitude subjects of Denver, Colo. (elevation 1600 m) served as controls. Hypoxic ventilatory drive was measured as the shape parameter A of isocapnic ˙VE-PA_o2 curves. In the non-native high altitude resident this parameter averaged 43% of the value for low altitude controls (P<0.05) denoting a diminished ventilatory response to hypoxia. The degree of attenuation was related to the length of time spent at high altitude. In the high altitude natives the parameter A averaged 9.6% of control (P<0.01). Similarly hypercapnic ventilatory drive as measured by the slope of the isoxic ˙VE-PA_co2 lines was reduced in the non-native residents to 65% of control (P<0.05) and in the natives averaged 54% of control (P<0.01).In contrast with these findings at rest induction of hypoxia during exercise produced an increase in ventilation comparable to that in the controls in both groups of highlanders.Hence chronic exposure to hypoxia during adulthood in man results in marked attenuation of the ventilatory response to hypoxia at rest and this is a function of the length of exposure to hypoxia. This attenuation of the ventilatory response to hypoxia was associated with a decrease in hypercapnic ventilatory drive. The fact that hypoxic ventilatory drive was almost completely absent while hypercapnic drive was only partially reduced parallels closely the more important role of the peripheral chemoreceptors in mediating ventilatory responses to hypoxia than to hypercapnia. This suggests that the alterations in ventilatory control at altitude are due to failure of peripheral chemoreceptor function.

T he electrophoretic mobility and activity of NADH-methemoglobin reductase in erythrocytes of patients with hereditary methemoglobinemia, obligatory heterozygotes, and normal subjects were examined. Six distinct electrophoretic variants were found in studies of erythrocytes from members of ten different families. Five variants (Boston Slow, Duarte, Princeton, Puerto Rico, and California) were associated with significant methemoglobinemia and moderate to marked decreases in enzymic activity. Precise correlations between levels of NADH-methemoglobin reductase activity, electrophoretic mobility, and clinical severity of methemoglobinemia, however, could not be drawn. One variant (Boston Fast) was associated with almost normal activity and very minimal methemoglobinemia. Nine members from three generations of two Italian families were found to have two bands with NADH-methemoglobin reductase activity in their erythrocytes, one with normal mobility and one with a mobility identical with that of Boston Fast. No functional or clinical impairment could be attributed to this abnormality. The observations made in this investigation were consistent with an autosomal recessive mode of inheritance of multiple alleles for NADH-methemoglobin reductase. As has been shown to be true for hemoglobin and glucose-6-phosphate dehydrogenase, multiple aberrations in the NADH-methemoglobin reductase of human erythrocytes apparently exist, some with and some without functional consequences.Two bands with NADPH-methemoglobin reductase activity with electrophoretic mobilities distinct from those of the NADH-methemoglobin reductase were found in human erythrocytes. These bands were normal in hemolysates of erythrocytes from patients with hereditary methemoglobinemia, but were absent from the hemolysate of erythrocytes deficient in NADPH-methemoglobin reductase activity. These latter erythrocytes, however, contained normal concentrations of methemoglobin and had a normal ability to reduce methemoglobin in vitro. These observations were most consistent with the thesis that the NADH-methemoglobin reductase, distinct from any NADPH-methemoglobin reductase, was the major system responsible for the reduction of methemoglobin to hemoglobin in human erythrocytes.

A patient with erythropoietic protoporphyria was studied to determine the sites of excess protoporphyrin formation. The patient's protoporphyrin was pulse labeled by the simultaneous administration of the precursors 2-glycine-¹⁴C and 3,5-δ-aminolevulinic acid-³H; δ-aminolevulinic acid preferentially labels the hepatic pool. Blood and feces were studied at intervals for the next 14 days. Protoporphyrin was extracted from erythrocytes, plasma, and feces, identified by thin-layer chromatography, and quantitated spectrophotometrically, and its specific activity was determined by liquid scintillation spectrometry. Analysis of the kinetic and isotopic data indicated at least two sources of protoporphyrin, one localized in the erythroid cells, a second in the liver. The liver was responsible for the majority of the excess protoporphyrin. This report thus provides evidence of a genetic porphyria exhibiting an abnormality of porphyrin biosynthesis in at least two tissues. We propose that the disease, erythropoietic protoporphyria, be renamed erythrohepatic protoporphyria.

S tudies were carried out to determine the influence of the chronic level of arterial carbon dioxide tension upon the buffering response to acute changes in arterial carbon dioxide tension. After chronic adaptation to six levels of arterial CO₂ tension, ranging between 35 and 110 mm Hg, unanesthetized dogs underwent acute whole body CO₂ titrations. In each instance a linear relationship was observed between the plasma hydrogen ion concentration and the arterial carbon dioxide tension. Because of this linear relationship, it has been convenient to compare the acute buffering responses among dogs in terms of the slope, dH⁺/dPaco₂. With increasing chronic hypercapnia there was a decrease in this slope, i.e. an improvement in buffer capacity, which is expressed by the equation dH⁺/dPaco₂=-0.005 (Paco₂)_chronic + 0.95. In effect, the ability to defend pH during acute titration virtually doubled as chronic Paco₂ increased from 35 to 110 mm Hg.The change in slope, dH⁺/dPaco₂, was the consequence of the following two factors: the rise in plasma bicarbonate concentration which occurs with chronic hypercapnia of increasing severity, and the greater change in bicarbonate concentration which occurred during the acute CO₂ titration in the animals with more severe chronic hypercapnia. These findings demonstrate the importance of the acid-base status before acute titration in determining the character of the carbon dioxide titration curve. They also suggest that a quantitative definition of the interplay between acute and chronic hypercapnia in man should assist in the rational analysis of acid-base disorders in chronic pulmonary insufficiency.

T he hemodynamic effects of tachycardia induced by atrial pacing were investigated in left ventricular failure of acute and healing experimental myocardial infarction in 20 intact, conscious dogs. Myocardial infarction was produced by gradual inflation of a balloon cuff device implanted around the left anterior descending coronary artery 10-15 days prior to the study. 1 hr after acute myocardial infarction, atrial pacing at a rate of 180 beats/min decreased left ventricular end-diastolic pressure from 19 to 8 mm Hg and left atrial pressure from 17 to 12 mm Hg, without change in cardiac output. In the healing phase of myocardial infarction 1 wk later, atrial pacing decreased left ventricular end-diastolic pressure from 17 to 9 mm Hg and increased the cardiac output by 37%. This was accompanied by evidence of peripheral vasodilation. In two dogs with healing anterior wall myocardial infarction, left ventricular failure was enhanced by partial occlusion of the circumflex coronary artery. Both the dogs developed pulmonary edema. Pacing improved left ventricular performance and relieved pulmonary edema in both animals. In six animals propranolol was given after acute infarction, and left ventricular function deteriorated further. However the pacing-induced augmentation of cardiac function was unaltered and, hence, is not mediated by sympathetics.The results show that the spontaneous heart rate in left ventricular failure of experimental canine myocardial infarction may be less than optimal and that maximal cardiac function may be achieved at higher heart rates.

T he effect of salicylate on the metabolism of peripheral blood lymphocytes in tissue culture was investigated. Lymphocytes incubated with sodium salicylate at a concentration of 30 mg/100 ml showed increased glucose consumption, lactic acid production, and oxygen consumption, evidence for uncoupling of oxidative phosphorylation. No decrease in cell number or viability (trypan blue dye exclusion) was noted in salicylate-treated cultures. Normal DNA, RNA, and total protein synthesis measured by radioisotope incorporation was depressed in the salicylate-treated cultures. Increased DNA synthesis after the addition of a mitogen (PHA) or antigen (PPD) to the culture was strikingly suppressed by salicylate. The degree of suppression was proportional to the concentration of salicylate used. The effect on RNA and protein synthesis in stimulated lymphocytes was much less pronounced. Acetylsalicylic acid was found to be as active as sodium salicylate in suppressing DNA synthesis, but the p-OH congener (p-OH benzoic acid) did not alter cell respiration, glycolysis, viability, or DNA synthesis. The salicylate effect was reversible as evidenced by return of cellular reactivity upon removal of the drug from the media.

T he mechanism of renal potassium wasting in renal tubular acidosis associated with the Fanconi syndrome (type 2 RTA) was investigated in 10 patients, each of whom had impaired proximal renal tubular reabsorption of bicarbonate as judged from a greater than 15-20% reduction of renal tubular bicarbonate reabsorption (THCO₃^-) at normal plasma bicarbonate concentrations. When the plasma bicarbonate concentration ([HCO₃^-]p) was experimentally increased to normal levels in three patients with a fractional potassium excretion (C_K/C_in) of less than 1.0 during acidosis, C_K/C_in and urinary potassium excretion (U_KV/C_in) increased strikingly and concurrently with a striking increase in urinary sodium (U_NaV/C_in) and bicarbonate (U_HCO3^-V/C_in) excretion. When [HCO₃^-]p was increased to normal levels in two patients with a C_K/C_in of greater than 1.0 during acidosis and in whom U_NaV/C_in and U_HCO3^-V/C_in were already markedly increased, C_K/C_in did not increase further. When [HCO₃^-]p was decreased to subnormal levels in a patient given ammonium chloride, U_KV/C_in, C_K/C_in, and U_HCO3^-V/C_in decreased concurrently. In the six patients in whom [HCO₃^-]p was maintained at normal levels (oral alkali therapy) for 2 months or longer, C_K/C_in was directly related to the urinary excretion rates of sodium and bicarbonate, hence was directly related to the magnitude of reduction of THCO₃^- at normal [HCO₃^-]p; C_K/C_in was greater than 0.55 in all six patients and greater than 1.0 in four.In eight patients with classic RTA (type 1 RTA), proximal renal tubular reabsorption of bicarbonate was largely intact as judged from a trivial reduction of THCO₃^- at normal [HCO₃^-]p. When [HCO₃^-]p was either increased from subnormal to normal levels, or decreased from normal to subnormal levels, U_HCO3^-V/C_in remained essentially constant, and U_KV/C_in did not change significantly. When correction of acidosis was sustained, U_HCO3^-V/C_in remained a trivial fraction of that filtered, and C_K/C_in was consistently less than 0.55.These results provide evidence that renal potassium wasting in type 2 RTA is physiologically separable from that in type 1 RTA and in part the result of a reduction in the rate at which the proximal tubule reabsorbs bicarbonate and the distal delivery of supernormal amounts of sodium bicarbonate. With an increased stimulus to distal sodium reabsorption, indicated by the finding of hyperaldosteronism, delivery to the distal nephron of supernormal amounts of sodium with the relatively impermeant bicarbonate anion would be expected to increase intraluminal negativity in the distal nephron, and as a consequence, increase potassium secretion and promote renal potassium wasting.

H eterologous antiserum was prepared in rabbits against highly purified human antihemophilic factor (AHF, factor VIII). This antiserum blocked the clot-promoting properties of AHF and, when suitably absorbed, formed a single precipitin line against AHF upon immunoelectrophoresis. Material antigenically similar to normal AHF was detected in normal amounts in plasma concentrates in each of 22 patients with classic hemophilia, in a patient with an acquired circulating anticoagulant against AHF, and in a patient with deficiencies both of AHF and proaccelerin (factor V). AHF-like antigen was present in normal human serum. In contrast, material antigenically related to AHF was found in decreased amounts in the concentrates prepared from the plasma of 11 patients with von Willebrand's disease. The experiments described suggest that von Willebrand's disease is a disorder in which a true deficiency of AHF exists. Whether the AHF-like material found in classic hemophilia is nonfunctional through a defect in structure or through the intervention of an inhibitor has not been shown.

T he relation between functional antihemophilic factor (AHF) activity and AHF-like antigen was studied in the plasma of 25 known carriers of hemophilia. In 23 cases, this relationship was significantly different from that in normal women, at the 99% limit of confidence. In contrast, among families in which only one case of hemophilia had occurred, only five of nine mothers could be identified as carriers. This observation suggests that in some instances the hemophilia arose from a newly mutant gene. The data are consistent with the hypothesis that the proportion of antigen to AHF activity in carriers is determined by random activation or inactivation of the X chromosome.