Issue published March 1, 1971

T he possibility that alterations in the rate or efficiency of energy utilization could be involved in the control of cellular oxygen consumption by thyroid hormone was examined in right ventricular papillary muscles isolated from normal euthyroid cats and cats with experimentally induced hyperthyroidism and hypothyroidism. Energy production in the muscles was inhibited and isolated from the process of energy utilization by exposure to iodoacetic acid and nitrogen. After resting or performing variable amounts of contractile element work under isometric conditions, muscles were frozen, and the total amount of chemical energy (∼ P = creatine phosphate + ATP) used was determined. The resting rate of energy utilization in muscles from euthyroid animals was 0.78±0.07 μmoles/g per min of ∼ P. This rate was elevated in muscles from hyperthyroid cats to 1.00±0.09 μmoles/g per min and decreased in muscles from hypothyroid cats to 0.23±0.14 μmoles/g per min. Isometrically contracting muscles from cats with hypothyroidism utilized only 64% as much energy as muscles from euthyroid cats while performing 81% as much contractile element work at a moderately decreased level of contractile state. Muscles from hyperthyroid cats utilized an average of 41% more energy than did muscles from euthyroid cats while contracting an identical number of times and performing an equal amount of contractile element work at a slightly increased level of contractile state. These results suggest that thyroid hormone directly influences the rate of cellular energy utilization. Furthermore, the increase in energy utilization in muscles from hyperthyroid cats could not be attributed entirely to observed alterations in contractile behavior, which indicates that excess thyroid hormone may decrease the efficiency of the conversion of cellular energy to work. However, the opposite effect, an increased efficiency of energy utilization, was not observed in muscles from hypothyroid cats. Thus, it is concluded that the calorigenic effects of thyroid hormone may be explained, at least in part, by alterations in the process of energy utilization.

T his study correlated levels of activated fibrinolysis with the presence, extent, and rate of resolution of angiographically documented pulmonary emboli. Pulmonary emboli demonstrable by angiography were associated with detectable fibrin split products in the serum of 24 of 25 patients. In the absence of increased fibrin split products, pulmonary emboli large enough to be demonstrated by angiography were found in only 2 of 25 positive pulmonary angiograms. Spontaneous resolution of pulmonary emboli could not be correlated with the the concentration or persistence of fibrin split products but did correlate well with the presence of a reversible precipitating cause.Thrombophlebitis in the absence of clinical evidence of pulmonary embolism was not associated with increased concentrations of fibrin split products in eight of nine patients. The one patient with increased fibrin split product concentration had evidence on lung scan of silent pulmonary embolism.

T he cause of hypoxemia was studied in 21 patients with no previous heart or lung disease shortly after an episode of acute pulmonary embolism. The diagnosis was based on pulmonary angiography demonstrating distinct vascular filling defects or “cutoffs.” It was found that virtually all of the hypoxemia in patients with previously normal heart and lungs could be accounted for on the basis of shunt-like effect. The magnitude of the shunting did not correlate with the percent of the pulmonary vascular bed occluded nor with the mean pulmonary artery pressure. The shunts tended to gradually recede over about a month after embolism. Patients without pulmonary infarction were able to inspire 80-111% of their predicted inspiratory capacities, and this maneuver temporarily diminished the observed shunt. Patients with pulmonary infarcts were able to inhale only to 60-69% of predicted inspiratory capacity, and this did not reverse shunting. These data suggest that the cause of right-to-left shunting in patients with pulmonary emboli is predominantly atelectasis.When the elevation of mean pulmonary artery pressure was compared to cardiac index per unit of unoccluded lung, it fell within the range of pulmonary hypertension predicted from published data obtained in patients with exercise in all except one case. This observation suggests that pulmonary vasoconstriction following embolism is not important in humans, although these data are applicable only during the time interval in which our patients were studied and in patients receiving heparin.

H ealthy adult dogs were subjected to stepwise reduction of nephron population so as to create the transition from normal renal function to advanced renal insufficiency. Studies were performed at each level of renal function. Glomerular filtration rate (GFR), renal phosphate clearance, and serum radioimmunoassayable parathyroid hormone (PTH) levels were measured. Two groups of animals were studied. In one, phosphorous intake was maintained at 1200 mg/day. As GFR declined, fractional phosphate excretion rose reciprocally, and PTH levels increased over 20-fold. In the second group, phosphorous intake was maintained at less than 100 mg/day. As GFR fell, fractional phosphate excretion changed little, and no increment in PTH levels occurred. The data suggest that the control system regulating phosphate excretion contributes importantly to the pathogenesis of secondary hyperparathyroidism in advancing renal insufficiency.

T he kinetic characteristics of galactose-l-phosphate uridyl transferase have been determined in homogenates of human liver biopsies obtained from control subjects and in 50-fold purified enzyme preparations from liver obtained at autopsy. A standardized assay procedure employing linear kinetics was used to assess the enzyme activity in homogenates of liver biopsy specimens from five control subjects and four patients with congential galactosemia with demonstrated absence of the enzyme activity in red blood cells. Activity of control specimens ranged from 11.8 to 17.2 mμmoles of UDPgalactose formed per min mg of protein. Liver of two galactosemic patients, both Caucasian, possessed no detectable enzyme activity (less than 1-2% of normal). The tissue of two others, both Negro, who are known to be capable of metabolizing intravenously administered galactose, contained easily detectable enzyme at approximately 10% of the controls. No alternate enzymatic activity for formation of UDPgalactose was found in the liver of Negroes with galactosemia that was as active as the residual galactose-l-phosphate uridyl transferase. The data suggest that the residual liver enzyme activity accounts for the ability of Negroes with galactosemia to metabolize limited but significantly large quantities of galactose.

T he two enzymes required for de novo glutathione synthesis, glutamyl cysteine synthetase and glutathione synthetase, have been demonstrated in hemolysates of human erythrocytes. Glutamyl cysteine synthetase requires glutamic acid, cysteine, adenosine triphosphate (ATP), and magnesium ions to form γ-glutamyl cysteine. The activity of this enzyme in hemolysates from 25 normal subjects was 0.43±0.04 μmole glutamyl cysteine formed per g hemoglobin per min. Glutathione synthetase requires γ-glutamyl cysteine, glycine, ATP, and magnesium ions to form glutathione. The activity of this enzyme in hemolysates from 25 normal subjects was 0.19±0.03 μmole glutathione formed per g hemoglobin per min. Glutathione synthetase also catalyzes an exchange reaction between glycine and glutathione, but this reaction is not significant under the conditions used for assay of hemolysates. The capacity for erythrocytes to synthesize glutathione exceeds the rate of glutathione turnover by 150-fold, indicating that there is considerable reserve capacity for glutathione synthesis. A patient with erythrocyte glutathione synthetase deficiency has been described. The inability of patients' extracts to synthesize glutathione is corrected by the addition of pure glutathione synthetase, indicating that there is no inhibitor in the patients' erythrocytes.

T he effect of acute extracellular volume expansion with saline on the intrarenal distribution of glomerular filtrate, was studied in dogs utilizing micropuncture techniques in which samples were obtained by both recollection and from new tubules.Recollection was examined in seven dogs during continuous hydropenia and in five dogs during continuous saline diuresis. Recollection was associated with an increase in nephron flow rate of 8% during hydropenia and 27% during saline diuresis. In addition, during continuous saline diuresis, shortened transit times and lowered intratubular pressures were recorded in previously punctured tubules. Despite increased tubular flow, fractional reabsorption was unchanged.Nephron glomerular filtration rates (gfr) were measured during hydropenia and then after acute volume expansion in 10 dogs. In the repunctured tubules gfr rose 38% more than total glomerular filtration rate (GFR). In contrast, when new tubules were punctured during volume expansion, nephron gfr and total GFR changed proportionately. The disproportionate rise in nephron gfr after volume expansion noted with the recollection technique appears to be artifactual when contrasted to micropuncture of new tubules. With acute volume expansion, fractional reabsorption decreased 15% in recollected samples and 16% in newly sampled tubules. Increased nephron gfr cannot account for the fall in fractional reabsorption. It is concluded that in dogs, saline diuresis is not associated with redistribution of filtrate from deep to superficial nephrons, and that the fall in proximal fractional reabsorption is caused by diminished absolute reabsorption.

L eft ventricular catheterization was carried out in 40 patients with acute myocardial infarction. Left ventricular end-diastolic pressure (LVEDP) was elevated in 85% of the patients studied. In 14 patients with apparently uncomplicated infarcts, LVEDP averaged 15 mm Hg, and cardiac index (2.98 liter/min/m²), stroke volume (38.3 ml/m²), and stroke work (49.2 g-m/m²) were within normal limits. In 12 patients with clinical signs of left ventricular failure, LVEDP averaged 29.9 mm Hg, cardiac index was at the lower limit of normal (2.79 liter/min/m²), but stroke volume (31.6 ml/m²) and stroke work (37.3 g-m/m²) were reduced. In 14 patients with clinical signs of shock, LVEDP averaged significantly lower than in the heart failure group (21.1 mm Hg), but cardiac index (1.59 liter/min/m²), stroke volume (16.5 ml/m²), and stroke work (11.1 g-m/m²) were markedly reduced. A large presystolic atrial “kick” (average amplitude 9.5 mm Hg) was an important factor in the high LVEDP in the patients with heart failure but not in those with shock. The first derivative of left ventricular pressure was significantly lower in shock than in the nonshock group. Although right atrial pressure (RAP) and LVEDP were significantly correlated (r = 0.49), wide discrepancies in individual patients rendered the RAP an unreliable indicator of the magnitude of left ventricular filling pressure.These data show the following: (a) LVEDP is usually elevated in acute myocardial infarction, even in absence of clinical heart failure; (b) cardiac output apparently is supported by increased LVEDP and compensatory tachycardia; (c) in patients with shock, left ventricular function usually is markedly impaired, but inadequate compensatory cardiac dilatation or tachycardia could contribute to the reduced cardiac output in some individuals; (d) lower LVEDP in shock than in heart failure may represent differences in left ventricular compliance.

O bstruction of a major branch of the left coronary artery in a previously normal ventricle is not usually associated with shock, experimentally or clinically. To examine the early hemodynamic alterations which may determine the course of ischemia when myocardial scar exists from previous infarction, 16 animals were successfully studied 9 wk after obstruction of the left circumflex artery. Acute ischemia during thrombus formation in the anterior descending artery of intact anesthetized dogs with scar was compared with animals undergoing the same procedure in the absence of scar (group 1). In the chronic animals, two types of hemodynamic responses were observed. Group 2 was characterized by heart failure usually persisting through 3 hr, and group 3 by a different ventricular volume response and rapidly developing shock. The weight of ischemic and scar areas were comparable and coronary blood flow (⁸⁵Kr method) to the ischemic site was reduced to a similar extent. Animals in groups 1 and 2 remained normotensive and had similar elevations of left ventricular enddiastolic volume (indicator dilution method) during the initial 60 min of ischemia. Group 2 had a significantly larger rise of end-diastolic pressure, presumably related to altered elastic properties associated with scar of subendocardial distribution.Group 3 had a stroke volume decline that was not significantly greater than group 2 and both groups had an initial rise of peripheral vascular resistance. Despite a nearly fourfold increase of left ventricular end-diastolic pressure, there was a significant decline of left ventricular end-diastolic volume in group 3. This preceded the onset of hypotension in group 3, with arterial pressure declining to a greater extent than stroke volume, usually culminating in cardiac standstill. Group 3 was distinguished by the presence of transmural scar, which was postulated to influence contiguous ischemic tissue in diastole so as to diminish ventricular volume. By analogy with the hemodynamics of acute pericardial tamponade, a reflex pathway activated in the myocardium in response to reduced end-diastolic volume has been suggested as a mechanism for the arterial hypotension.

P rocessing of RNA in the toad bladder was analyzed by polyacrylamide-gel electrophoresis to determine whether aldosterone causes any changes in the 1 hr before it potentiates transport of sodium ion. No change was found in the quantity or in the specific activity of bulk RNA labeled with uridine-5-³H. In vivo and in vitro with either uridine-5-³H or with methionine-(methyl)-³H as precursors, processing of RNA was extremely slow. Heterodisperse RNA was obvious after 30 min of continuous labeling, but labeling of the 40S precursor of ribosomal RNA was not apparent for 60 min. Labeling of mature 28S and 18S RNA first became apparent after 8 hr. ∼7S RNA was the principal fastmigrating species labeled at 30 min, and 4S RNA was not heavily labeled until 1 hr. Aldosterone (5 × 10^-7 mole/liter) produced no changes. If care were not taken to inhibit metabolism of native bacteria colonizing the bladder, bacterial RNA of high specific activity predominated. We conclude that RNA metabolism in the toad bladder is extraordinarily slow, that a major acceleration of de novo synthesis in response to physiologic doses of aldosterone was not demonstrable, and that some reports to the contrary may have been influenced by artifacts from bacterial RNA metabolism. Earlier evidence for obligatory alterations in RNA metabolism during the latent period is not strong.

S erum levels of complement components and of C3 nephritic factor (C3NeF) were measured serially in two patients with membrano-proliferative glomerulonephritis who were subjected to bilateral nephrectomy and maintained by peritoneal dialysis for 2 wk before renal transplantation. In both patients, low levels of C3 and high levels of preformed alpha 2D, a C3 breakdown product, were present before nephrectomy and remained essentially unchanged during the anephric period. With transplantation, C3 levels rose towards normal and alpha 2D disappeared from the serum. The serum of both patients contained detectable amounts of C3NeF, a factor which has been shown to react with a cofactor found in normal serum to form an enzyme, designated C3 lytic nephritic factor (C3LyNeF), which will cleave C3 to form the breakdown products, β1A and alpha 2D. The level of C3NeF was high in one patient before nephrectomy, increased somewhat during the anephric period, and fell after transplantation. In the other patient, the C3NeF level was initially lower, remained relatively constant during the anephric period, and was not significantly affected by transplantation. In both patients, levels of C4 and C5 were either normal or elevated over the period of the study and bore no relationship to the C3 level. The following conclusions can be drawn from the data. The high levels of alpha 2D during the anephric period and the disappearance of this protein as C3 levels approach normal at the time of transplantation indicate that the low C3 levels were largely the result of C3 breakdown rather than diminished synthesis. The presence of C3NeF in detectable amounts in both patients suggest that C3LyNeF, formed by the reaction of C3NeF and cofactor, was responsible for the low C3 levels. Finally, the lack of effect of nephrectomy on C3, alpha 2D, and C3NeF levels indicate that the site of C3 breakdown was extrarenal and that C3NeF and cofactor are at least in large part of extrarenal origin.

I ncorporation of L-leucine-¹⁴C into proteins and immunoglobulins in vitro was determined in jejunal biopsy specimens from normal volunteers, patients with celiac sprue before and after introduction of gluten into the diet, patients with Whipple's disease in remission, and patients with immune deficiency states.Values for incorporation of L-leucine-¹⁴C into total and soluble protein by biopsies from five celiac sprue patients on a gluten-free diet were within, or slightly above, the 95% confidence limits for control data. One patient with celiac sprue and with normal intestinal histology had a normal value for incorporation into IgA; the other four patients with flat mucosas had elevated values. In Whipple's disease in remission, values for incorporation into total protein and IgA were within the control limits, whereas incorporation into soluble protein was increased. Patients with hypogammaglobulinemia or IgA deficiency had normal or elevated values for incorporation into total and soluble proteins; in these cases, however, no incorporation into IgA was detected.Biopsies from the four celiac sprue patients studied revealed that with introduction of gluten into the diet (a) incorporation into total protein, soluble protein, or both, increased; (b) incorporation into IgA increased in all patients, and in two instances the increase was greater than the increase in incorporation into total protein; and (c) incorporation into IgM increased in all patients. The changes during gluten administration usually occurred before changes in gastrointestinal absorptive function or in concentration of IgA in serum could be detected.These results indicate that gluten challenge stimulates increased local intestinal synthesis of immunoglobulins in patients with celiac sprue. The reaction occurs within days and it is possible that it plays a primary role in the pathogenesis of the disease.

S keletal muscle of guinea pigs is composed of at least three types of fibers which are distinguishable by their kinetic and histochemical properties. Fast twitch muscles may be histochemically red or white; fragmented sarcoplasmic reticulum (FSR) prepared from both types of fast twitch muscles has identical calcium-accumulating capacity (maximal calcium uptake) and calcium-concentrating ability. FSR from slow twitch muscles accumulates less total calcium, but the calcium-concentrating ability is equal to that of fast twitch muscles. The slower rate of calcium accumulation by FSR of slow twitch muscles correlates with a prolonged relaxation time.

T o clarify the role of insulin and growth hormone (HGH) in regulating substrate production for body fuel during prolonged starvation, 6 normal subjects and 10 HGH-deficient dwarfs were fasted for 6 days. Four of these dwarfs received HGH during the fast.Blood glucose concentration decreased a mean 15 mg/100 ml in both controls and HGH-treated dwarfs, but decreased 50 mg/100 ml in untreated dwarfs. The final level at which the blood glucose stabilized was significantly higher in the former two groups (65 ±1.0 mg/100 ml and 88 ±19 mg/100 ml, respectively, versus 39.0 ±4.0 mg/100 ml in the untreated dwarfs). The decline in plasma insulin concentration showed a comparable pattern, decreasing from a similar basal level to 7.7 ±0.4 μU/ml in controls, 8.8 ±1.1 μU/ml in dwarfs treated with HGH, and to a significantly lower level of 3.8 ±1.1 μU/ml in untreated dwarfs. When glucose concentrations were plotted against paired insulin values, the correlation in both dwarfs and normals was significant. In normals, no correlation existed at any time between plasma HGH levels and plasma concentration of either glucose or free fatty acid.Free fatty acid, β-hydroxybutyrate, and acetoacetate increased respectively in normals to peak concentrations in plasma of 1.55 ±0.11, 2.87 ±0.23, and 0.77 ±0.09 mmoles/liter. Untreated dwarfs had significantly greater values of all three (mean maximal concentration: FFA = 2.16 ±0.17 mmoles/liter, β-hydroxybutyrate = 4.11 ±0.34 mmoles/liter, and acetoacetate = 1.16 ±0.10 mmoles/liter). Values returned toward normal in HGH-treated dwarfs. The cahnges in plasma concentrations of β-hydroxybutyrate and acetoacetate were not due to changes in renal excretion.In starvation, the relation between insulin on the one hand and glucose and free fatty acid on the other hand is maintained in the absence of HGH. However, the setting of blood glucose concentration at which this relation takes place is decreased in the absence of HGH. This results in a lower than normal insulin level and, consequently, in a higher than normal free fatty acid concentration.

S erial changes in circulating triglyceride, free fatty acids (FFA), insulin, and glucose have been measured in human subjects fed sucrose as the sole source of calories for 2- or 3-day periods. The sucrose was given either during the day with overnight fasting (19 subjects) or as continual 3-hour meals during the day and night (seven subjects). Insulin was infused overnight in five additional subjects on the day-feeding regimen to determine the effect on triglyceride concentration.The concentration of triglyceride increased during the study in all subjects, but there was a clear diurnal pattern in the response which was present even in the continual feeding studies. The rise in triglyceride occurred mainly overnight, and during the day there was frequently a fall in the concentration. The overnight increase was significantly less when insulin was infused. There were also diurnal fluctuations in FFA and insulin in both daytime and continual feeding regimens. The plasma FFA, like triglyceride, rose during the night and fell during the day while the insulin rose during the day and fell overnight.Separate statistical analysis of the daytime and overnight changes revealed that the changes in triglyceride were significantly but negatively correlated with changes in insulin during both periods. The changes in triglyceride and FFA were positively correlated during the day but not significantly related during the night. The data show that when sucrose is eaten for 2 or 3 days, there is a general increase in triglyceride concentration upon which are superimposed major diurnal fluctuations in the concentrations of triglyceride, insulin, and FFA. It is suggested that the highly significant inverse relationship between changes in triglyceride and insulin may be mediated through an effect of insulin on triglyceride removal.

T he present study was prompted by the observation that, in patients with chronic renal failure being followed at this center, renal osteodystrophy developed almost exclusively in those who were treated by chronic hemodialysis at home rather than in our center. A systematic comparison was made between the 10 patients with roentgenographic evidence of the bone disease and 18 patients without demonstrable bone disease. The two groups were similar in age, sex, nature of renal disease, and duration of dialysis. The mean duration of kidney disease was almost 2 yr longer in the patients without bone disease than in those with bone disease. Other significant differences related to where the hemodialysis was performed and to the calcium concentration in the dialysate (6.0-7.4 mg/100 ml in the hospital and 4.9-5.6 mg/100 ml at home). If the unknown factors related to where the dialysis was performed were of no consequence, the major factor contributing to the production of bone disease observed in these patients was the use of a dialysate with a calcium concentration less than 5.7 mg/100 ml.

P lasma concentration of immunoreactive parathyroid hormone (IPTH) was measured in 18 patients who had been on a hemodialysis program for longer than 6 months. A negative correlation was found between the predialysis plasma concentration of IPTH and the mean concentration of calcium in the dialysate previously used: plasma concentrations of IPTH were higher in patients dialyzed against a calcium concentration between 4.9 and 5.6 mg/100 ml than in patients dialyzed against a calcium concentration of 6.0 mg/100 ml or more. Plasma concentrations of IPTH also were higher in patients with bone disease than in patients without bone disease. Furthermore, a positive correlation was found between predialysis plasma concentrations of IPTH and calcium, and between mean predialysis concentration of IPTH and phosphate. To obviate the possibility that individual differences in susceptibility could have accounted for the observed effects of plasma phosphate and of dialysate calcium, a 2 × 2 factorial study was conducted in seven of these patients to examine the independent effects of perturbation of each of these factors. It was observed that plasma concentration of IPTH was lowest with the combination of high dialysate calcium and low plasma phosphate, highest with the combination of low dialysate calcium and high plasma phosphate, and intermediate with the two other combinations. It is concluded that both dialysate calcium and plasma phosphate are important determinants of parathyroid function in these patients.

A large per cent of rheumatoid synovial fluids contain chemotactic activity for rabbit granulocytes (neutrophilic). The chemotactic activity is, in large part, related to the fifth (C5) and sixth (C6) components of human complement; a combination of physical-chemical techniques indicates the activity to be attributable to C567 and C5a, a cleavage product of C5. Many rheumatoid synovial fluids contain a C5-cleaving enzyme which, on the basis of substrate specificity and susceptibility to inhibitors, is very similar to an enzyme extractable from lysosomal granules of human and rabbit granulocytes. Inflammatory nonrheumatoid synovial fluids contain chemotactic activity that is related to cleavage products (C3a) of the third component of human complement (C3). Also found in these fluids is a C3-cleaving enzyme capable of producing C3a. Of the other synovial fluids examined, lupus fluids were remarkable by their total lack of chemotactic activity. These findings record for the first time the presence of complement-derived chemotactic factors in pathological human fluids.

T o evaluate the effects of parathyroid hormone and cyclic adenosine monophosphate on proximal tubular sodium and phosphate reabsorption, micropuncture studies were performed on dogs that received a highly purified preparation of parathyroid hormone (PTH), dibutyryl cyclic 3′,5′-adenosine monophosphate (cyclic AMP), 5′-AMP, and saline. PTH resulted in a 30-40% inhibition of sodium and phosphate reabsorption in the proximal tubule unassociated with a rise in either total kidney or single nephron glomerular filtration rate (GFR). The bulk of the phosphate rejected proximally was excreted in the final urine while sodium excretion rose minimally despite the marked proximal inhibition, consistent with the presence of reabsorptive sites in the distal nephron for sodium but not phosphate. The infusion of dibutyryl cyclic AMP either systemically or directly into the renal artery inhibited proximal sodium and phosphate reabsorption in the absence of changes in either total kidney or single nephron GFR, resembling the effects of PTH quantitatively and qualitatively. In contrast, another adenine nucleotide, 5′-AMP, did not inhibit the reabsorption of either sodium or phosphate. These observations support the thesis that renal effects of PTH are mediated via stimulation of renal cortical adenyl cyclase. The infusion of a moderate saline load, 25 ml/kg, also produced a similar inhibition of proximal tubular fractional sodium and phosphate reabsorption with a marked phosphaturia but only minimal natriuresis. Thus, changes in sodium and phosphate reabsorption occur in parallel in the proximal tubule when sodium reabsorption is inhibited either with volume expansion or with administration of “specific” phosphaturic agents such as PTH or cyclic AMP. These data are consistent with the thesis that phosphate reabsorption is dependent upon proximal tubular sodium reabsorption wherein the phosphaturic effect of PTH might be the result of a primary inhibition of proximal tubular sodium reabsorption mediated by adenyl cyclase stimulation.

G lucose oxidation to CO₂ in man at the fasted, steady state has been investigated in normal, hypothyroid, patients by monitoring the specific activity of plasma glucose and expired CO₂ after intravenous injection of glucose-1-¹⁴C, glucose-6-¹⁴C, and sodium bicarbonate-²⁴C in tracer amounts. Making certain stoichiometric assumptions about the oxidation of the C-1 and C-6 carbons of glucose to CO₂, the data are incorporated into a multicompartmental model describing the kinetics of plasma glucose, plasma bicarbonate, and the conversion of glucose to CO₂ by the hexose monophosphate pathway and all other series and parallel pathways which oxidize glucose carbon to CO₂ (EMP-TCA). This formulation separates the distribution kinetics of glucose and bicarbonate from the kinetics of glucose oxidation to CO₂. It allows the calculation of a minimal fraction (ϕ_t) of glucose irreversibly oxidized to CO₂ which is based entirely on the duration of the experimental data. This calculation is independent of the extrapolative implications of the model beyond the experimental interval and of the particular model chosen to fit the data. All modeling and data fitting were performed on a digital computer with the SAAM program.Based on a 300 min experiment the analysis suggests that in hypothyroidism there is a decrease in the rate of glucose metabolized irreversibly (ρG). There is also a decrease in the minimal fraction (ϕ₃₀₀) which is completely oxidized to CO₂ by way of the EMP-TCA. ρG and ϕ₃₀₀ are 0.56 and 0.42 mmole/min respectively as compared to 0.89 and 0.50 mmole/min respectively in normals. However, the fraction of the C-1 of glucose metabolized irreversibly which undergoes oxidation to CO₂ by the hexose monophosphate pathway (Ψ) is not different from normal (0.07 and 0.07 respectively). The hyperthyroid studies suggest that ρG and ϕ₃₀₀ are within the normal range (1.01 and 0.46 mmoles/min respectively as compared to 0.89 and 0.50 mmole/min respectively in normals). However, Ψ is decreased to less than half the normal value (0.03 as compared to 0.07 in normals).

K idney tissue from 97 patients was studied by immunofluorescent techniques using antiserum to purified properdin. All patients with acute poststreptococcal glomerulonephritis showed deposition of properdin and the third component of complement (C3), either as “humps” on the basement membrane, or in the mesangium. In all cases of chronic membranoproliferative glomerulonephritis, properdin and C3 were localized in the glomeruli, most commonly in a lobular pattern on the basement membrane. Activation of C3 by the properdin system may explain the depressed serum levels of C3 and terminal complement components even though levels of earlier components are normal, and the deposition of C3, often without immunoglobulins, in the kidneys of patients with acute glomerulonephritis or chronic membranoproliferative glomerulonephritis.

A n abnormal hemoglobin, termed Hb Savannah, was found in red cell hemolysate of a young Caucasian girl with severe hemolytic anemia. The presence of this unstable variant became evident when inclusion bodies appeared rapidly upon exposure of red cells to redox dyes and a large percentage of hemoglobin in hemolysate precipitated on warming to 65°C. Treatment of the hemoglobin with p-hydroxymercuribenzoate (PMB) caused a rapid dissociation into monomers; starch-gel electrophoresis of PMB-treated hemoglobin showed the presence of abnormal β-chains. Data from structural studies of isolated β-chains indicated substitution of a valyl residue for the normally occurring glycyl residue at position 24, which corresponds to helical residue B6. A similar substitution but with an arginine replacing the glycyl residue has been observed in Hb Riverdale-Bronx. The glycine to valine substitution will change the relationship of the B and the E helices which results in extensive conformational changes in the β-chain. This change presumably causes an increased dissociation of the hemoglobin molecule into dimers and probably monomers, and a decreased stability of the αβ-dimers. The hemoglobin abnormality may be the result of a fresh mutation because the abnormality is not present in the parents nor in any of the seven siblings.

T he mechanical behavior of isolated cat, rat, and dog ventricular muscle was examined during hypoxia and after reoxygenation. During hypoxia, an early abbreviation of tension duration was followed by a decline in the rate of tension development. After reoxygenation, a marked, early prolongation of tension development and relaxation time was invariably observed with little, if any, increase in peak tension. As recovery progressed, the duration of contraction gradually shortened as tension returned to control levels. This phenomenon was also observed in the intact dog heart after release of a coronary artery ligature. Isometric tension gauges sewn to ischemic portions of the left ventricle demonstrated that after reinstitution of coronary flow, segment tension duration “outlasts” the duration of left ventricular pressure development and is associated with ventricular irritability. Epicardial electrograms showed shortening of the QT interval within the ischemic segment with prolongation of the QT interval after release of the coronary ligature. Prolongation of tension development during recovery from hypoxia was not observed in experiments with rat skeletal muscle. These observations identify localized mechanical abnormalities during recovery from myocardial ischemia which may be important in the syndrome of acute coronary heart disease.

I n two patients with classic renal tubular acidosis (RTA) and in two patients with RTA associated with the Fanconi syndrome, renal potassium wasting persisted despite sustained correction of acidosis: (a) during moderate degrees of hypokalemia, daily urinary excretion of potassium exceeded 80 mEq in each patient; (b) during more severe degrees of hypokalemia, daily urinary excretion of potassium exceeded 40 mEq in two patients and 100 mEq in another. These urinary excretion rates of potassium are more than twice those observed in potassium-depleted normal subjects with even minimal degrees of hypokalemia. The persistence of renal potassium wasting may have resulted in part from hyperaldosteronism, since urinary aldosterone was frankly increased in two patients and was probably abnormally high in the others relative to the degree of their potassium depletion. The hyperaldosteronism persisted despite sustained correction of acidosis, a normal sodium intake, and no reduction in measured plasma volume, and was not associated with hypertension; its cause was not defined. In the two patients with classic RTA, neither renal potassium wasting nor hyperaldosteronism could be explained as a consequence of a gradient restriction on renal H⁺ - Na⁺ exchange because the urinary pH remained greater than, or approximately equal to, the normal arterial pH or considerably greater than the minimal urinary pH attained during acidosis. The findings provide no support for the traditional view that renal potassium wasting in either classic RTA or RTA associated with the Fanconi syndrome is predictably corrected solely by sustained correction of acidosis with alkali therapy.

V itamin D in all body tissues was radio-labeled by supplementing completely vitamin D-deficient weanling rats with oral vitamin D₃-4-¹⁴C for 2 wk. All vitamin D was then withheld, and radioactivity and vitamin D content in a variety of organs and tissues were measured. Adipose tissue was found to contain by far the greatest quantity of radioactivity throughout the 3 month experimental period. Immediately after supplementation, half of the total radioactivity in adipose tissue corresponded to unaltered vitamin D₃, and the other half to polar metabolites and esters of vitamin D₃ and unidentified peak II. 1 month later there was approximately the same proportion but a decrease in the total quantity of each form. We conclude that adipose tissue is the major storage site for vitamin D₃ in its several forms. Unaltered vitamin D₃ was the principal storage form observed and presumably a source available for conversion to other metabolites during deprivation.

R adioisotope studies of bilirubin turnover, ferrokinetics, and red cell survival (⁵¹Cr) in a patient with erythrocyte PK deficiency have provided evidence for prompt reticulocyte sequestration and destruction by the reticuloendothelial system. More mature erythrocytes appeared to survive well despite their deficiency of PK. PK-deficient reticulocytes, dependent upon oxidative phosphorylation for ATP production, are exquisitely sensitive to cyanide- or nitrogen-induced mitochondrial inhibition. If oxidative phosphorylation is unavailable, ATP levels decline rapidly, producing alterations in the cell membrane which allow massive losses of potassium and water. The result is a shrunken, spiculated, viscous cell whose rheologic properties would favor its sequestration by the reticuloendothelial system. Those reticulocytes with particularly low levels of PK exhibit very low glycolytic rates and thus are uniquely reliant upon oxidative phosphorylation. Other reticulocytes, better endowed with PK activity, can meet the increased ATP requirements of young erythrocytes. Upon reaching maturity, such cells have diminished ATP needs and can, therefore, survive despite their enzyme deficiency.

T he recent reports of the effect of 2,3-diphosphoglycerate (2,3-DPG) on hemoglobin affinity for oxygen suggested that this substance may play a role in man's adaptation to acidosis and alkalosis.A study of the effect of induced acidosis and alkalosis on the oxyhemoglobin dissociation curve of normal man was therefore carried out, and the mechanisms involved in the physiological regulation of hemoglobin oxygen affinity examined.In acute changes of plasma pH there was no alteration in red cell 2,3-DPG content. However, there were changes in hemoglobin oxygen affinity and these correlated with changes in mean corpuscular hemoglobin concentration (MCHC). With maintained acidosis and alkalosis, red cell 2,3-DPG content was altered and correlated with the changes in hemoglobin oxygen affinity. Both of these mechanisms shift the hemoglobin oxygen dissociation curve opposite to the direct pH (Bohr) effect, and providing the rate of pH change is neither too rapid nor too large, they counteract the direct pH effect and the in vivo hemoglobin oxygen affinity remains unchanged.It is also shown that approximately 35% of the change in hemoglobin oxygen affinity resulting from an alteration in red cell 2,3-DPG, is explained by effect of 2,3-DPG on the red cell pH.

T o elucidate the mechanism by which phototherapy reduces serum bilirubin, studies were performed on the catabolism of labeled bilirubin in homozygous jaundiced Gunn rats before, during, and after a period of exposure to 1700 foot candles of daylight fluorescent light. Following equilibration with the body pool of an intravenously administered tracer dose of ³H- or ¹⁴C-bilirubin, radioactive and diazo reactive compounds were excreted in the bile at a slow, steady rate and plasma specific activity declined semilogarithmically. Subsequent exposure to light caused a marked increase in the biliary excretion of radioactive and diazoreactive compounds. Fecal and urinary radioactivity increased also but remained minor fractions of the total excreted radioactivity. After extinguishing the lights, these variables reverted gradually to control values. Spectral and chromotographic analysis of the excreted pigments and their azopigments demonstrated that the increased biliary radioactivity during phototherapy consisted of two roughly equal fractions: (a) unconjugated bilirubin, excreted at rates comparable to the output of conjugated bilirubin in the bile of normal nonjaundiced rats; and (b) water-soluble bilirubin derivatives, chromatographically identical with those found in Gunn rat bile under control lighting conditions but different from the products of photodecomposition of bilirubin in vitro. In some animals, phototherapy produced little decline in plasma bilirubin despite comparable acceleration of bilirubin catabolism. This was attributed tentatively to increased synthesis of early labeled bilirubin in these animals.

T he lysates of peripheral cells as well as the serum from some patients with chronic myelogenous leukemia, contained a macromolecular factor which bound tritiated folic acid. Bound tracer folate filtered through Sephadex G-75 and G-100 columns with the early effluent and appeared with the inner volume through a Sephadex G-200 column. Bound tracer could not be extracted from solution by coated charcoal or the anion exchange resin Dowex 2-X8 and could not be reduced to tetrahydrofolate by folate reductase. The velocity of the binding reaction was very rapid and dissociation of bound tracer extremely slow. Binding decreased sharply below pH 5.0 and the binding factor as well as the folate-binder complex, resisted 56°C for 30 min. The binding factor in the leukemic lysate could be separated from endogenous folate reductase by filtration through a G-75 Sephadex column.Competitive inhibition studies demonstrated little or no inhibition of binding of tritiated folic acid by formyltetrahydrofolate and methyltetrahydrofolate. Diopterin (pteroyldiglutamate), pteropterin (pteroyltriglutamate), methotrexate, and dihydrofolate inhibited binding of tracer folate but not as effectively as unlabeled folic acid.The function of this folate binder is unknown. However, that it reacts with dihydrofolate suggests some relationship (physiologic or pathologic) to DNA synthesis since this folate cofactor is essential for the de novo synthesis of thymidylate from deoxyuridylate. In addition, these findings also suggest that the binding of methotrexate may, like folate, inhibit its reaction with folate reductase, and thus be a mechanism by which leukemic cells become resistant to this drug.