bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrophoresis of serum proteins and body fluid volumes during cold acclimation
Authors: Shields J. L. , Platner W. S. , Neubeiser R. E.
Published: December 2017

Albino rats exposed to 4° ± 2.0°C were sacrificed at 10, 20, 30 and 40 days. Serum electrophoretic patterns showed a marked decrease in the albumin fraction at 20, 30 and 40 days. Percentage increases in alpha1 and beta fractions occurred at different time periods but are interpreted as only apparent changes accompanying the greater albumin fall. Gamma globulin decreased at 10 and 40 days exposure. Alpha2 increased at all sampling periods and retained statistical significance when calculated as per cent of total globulins. Hematocrit remained unchanged throughout the sampling period. Plasma volume increased and remained elevated to the 40-day period. Thiocyanate space increased at the 10- and 20-day periods and subsequently declined, approaching control values at 40 days. Muscle water remained essentially unchanged despite suggestive changes in electrophoretic patterns of soluble muscle proteins. It appears that changes in plasma volume and osmotically active proteins are not complementary and act to the detriment of the animal during cold acclimation.
Hypoxia and ammonia toxicity
Authors: Warren Kenneth S. , Schenker Steven
Published: December 2017

Ammonia toxicity was strikingly potentiated by short periods of hypoxia. The toxicity (ld50) of ammonium chloride administered intravenously to mice after 2 minutes in 15% oxygen was the same as that in 21% oxygen. However, its toxicity began to increase when they were exposed to 13% oxygen, and was markedly enhanced by each 2% decrement in oxygen concentration. The effect of a maximal lethal dose in 7% oxygen could be completely reversed in a matter of seconds by transferring the mice to 21% oxygen. Ninety-nine per cent oxygen did not alter the ld50, but significantly prolonged life. Hypoxia had a relatively slight effect on Metrazol toxicity. Blood pH was unchanged by the short periods of hypoxia prior to ammonia injection. Furthermore, measurements of brain ammonia concentrations following a standard dose of ammonium chloride at 21, 11 and 7% oxygen revealed that hypoxia had no effect on ammonia uptake or detoxication by the brain. It appeared therefore, that hypoxia directly potentiated the toxic effect of ammonia on the brain.
Urea enhancement of water reabsorption in the renal medulla
Authors: Jaenike John R.
Published: December 2017

In the dog, osmotic diuresis produced by the infusion of urea results in a higher rate of abstraction of solute-free water, at any given osmolal clearance, than does mannitol or sodium chloride diuresis. It is proposed that the ratio of urea to nonpermeating solute within the fluid entering the collecting duct system will influence the degree to which the urine can be concentrated and to which solute-free water can be abstracted from an isotonic precursor fluid. Urea, as a result of its ability to permeate the collecting duct epithelium, is relatively ineffective in opposing the osmotic force resulting from the presence of a hypertonic sodium chloride solution in the peritubular space. The osmotic movement of water out of the collecting duct is consequently limited primarily by the concentration of nonpermeating solute within the tubular fluid. Since during the infusion of urea the relative concentration of nonpermeating solute within the tubular lumen is reduced, the potential for water abstraction from this fluid is accordingly enhanced.
Strontium-calcium interrelationships in the mature rat
Authors: Thompson Roy C. , Palmer Ray F.
Published: December 2017

Page 95: Roy C. Thompson and Ray F. Palmer, "Strontium-calcium interrelationships in the mature rat." In table 1, the third and fourth lines under the heading Single Dose Retention are transposed. The numbers 766†, +9, 52† go with the 2% calcium diet and the numbers 721, –3, 49 go with the 0.5% calcium diet.
Erythropoietic recovery and residual injury in rats exposed repeatedly to x-rays
Authors: Baum Siegmund J.
Published: December 2017

Rats exposed repeatedly to 300-r x-rays showed a decrease in Fe59 incorporation which attained its lowest point 48 hours postirradiation. Thereafter iron uptake increased until normal values were measured. This return to normalcy was delayed further with each newly repeated irradiation. On any day during the recovery period Fe59 uptake decreased exponentially with repeated x-irradiations. This decrease is a measure of residual injury to the erythropoietic system. Since, after each repeated irradiation, a reduced amount of Fe59 was incorporated at the beginning of the recovery period, while the rate of recovery was similar, it is postulated that the decrease in radio iron uptake is due to an impairment in the functional capacity of the stem cells to proliferate erythrocytes. A working hypothesis for the calculation of erythrocyte stem cell damage is presented. Although the functional capacity of the stem cells to produce erythrocytes was reduced, the daily red cell turnover was normal. Only when this reduction was below a certain limit did a permanent anemia ensue.
Metabolic changes in the intact rat and excised tissues after thyroidectomy
Authors: Nielson R. R. , Loizzi R. F. , Klitgaard H. M.
Published: December 2017

The oxygen consumption of the intact rat and selected excised tissues was determined for 28 days following surgical thyroidectomy. By the 3rd day, the whole-animal basal metabolism showed a reduction to 90% of the normal value followed by a continuous fall to the basal level of 71% on the 7th day. In general, the excised tissues followed a similar pattern to that of the thyroidectomized intact animal. Heart, psoas and liver nearly paralleled the changes found in the whole animal, having correlation coefficients of 0.93, 0.93 and 0.97, respectively. Diaphragm ( r = 0.84) decreased sharply to 73% by day 3 then less rapidly to 42% on the final day of the study. Kidney ( r = 0.75) showed no decrease until day 2 then fell to a minimal value of 82% on day 20. Brain ( r = 0.77) declined only 16% reaching the basal level of 84% of normal 24 days after thyroidectomy.
Identification of mitochondria by osmotic swelling and tetrazolium staining
Authors: Miller A. T. , Gunn L. D.
Published: December 2017

When tissue homogenates were diluted in sucrose solutions of decreasing concentration or in distilled water, there was a graded resistance of the mitochondria to osmotic swelling, and even in distilled water some granules having the electron microscopic appearance of mitochondria did not swell. After pretreatment with distilled water, mitochondria incubated at 37°C in the presence of iodophenyl tetrazolium and succinate showed distinct formazan granules within the swollen mitochondria. There was satisfactory agreement between mitochondrial counts based on osmotic swelling in distilled water and on staining with tetrazolium.
Anode break excitation and Pflüger's law
Authors: Wright Ernest B. , Ooyama Hiroshi
Published: December 2017

The relations between the nodes of stimulating current and excitation were studied on frog nerve with special emphasis on anode break excitation. The threshold for anode break excitation was several times greater than cathode make threshold. Following an exceedingly strong anodal pulse, there is a period of marked reduction in anode break threshold. The data indicate that anode break excitation in whole nerve results from node membrane breakdown, as concluded in a previous investigation on the single Ranvier node. The many confusing results often obtained in demonstrating Pflüger's law on whole nerve were found to be attributable to populations of nerve fibers in whole nerve and are readily explained by the results of single-fiber experiments.
Accumulation of uric acid by slices of kidney cortex
Authors: Platts Margaret M. , Mudge Gilbert H.
Published: December 2017

Accumulation of uric acid by surviving slices of renal cortex occurs by active transport. On the basis of substrate and inhibitor effects, the cellular mechanism has many features in common with that for p-aminohippurate accumulation. Uptake was most marked in the chicken, rabbit and guinea pig. Active accumulation could not be demonstrated for man, the mongrel dog or the rat. Agents that are uricosuric in man inhibited accumulation in the species studied. However, the bidirectional transport of uric acid across the renal tubule poses methodological problems that may not be completely resolved in in vitro studies.
Clearance of exogenous vasopressin from plasma of dogs
Authors: Lauson Henry D. , Bocanegra Manuel
Published: December 2017

Bovine Pitressin was infused intravenously into five pentobarbital-anesthetized dogs (13–24 kg) at constant rates (33.3–382 mu/min.) for 121–198 minutes in 10 experiments. Arterial plasma, obtained just before the end of the infusion, was assayed for antidiuretic hormone concentration in conscious, hydrated female dogs. Total plasma clearance was calculated as the quotient, Pitressin infusion rate/Pitressin concentration in arterial plasma. Pitressin clearance was equivalent to 16.1% of the plasma volume per minute (range 10.2–25.7%/min.). The Pitressin clearance averaged 2.2 times as large as concurrent glomerular filtration rate (creatinine clearance) and 0.63 as large as effective renal plasma flow ( p-aminohippurate clearance). In five of the experiments, arterial plasma, obtained 15 minutes after cessation of the infusion, had an average Pitressin concentration of 14% of the steady-state concentration. On the assumption, as a crude first approximation, that the disappearance was semilogarithmic, the averaged data indicate, for this first 15-minute interval, that 12.9% of the ‘apparent’ volume of Pitressin distribution was cleared per minute, that the half-life was 5.4 minutes, and that the ‘apparent’ volume of distribution of Pitressin was only about 14% larger than the plasma volume.
Hypothalamic influences on heterotropic pituitary in the rat
Authors: Florsheim Warner H. , Knigge Karl M.
Published: December 2017

Anterior pituitaries from neonate rats grew well in the eyes of hypophysectomized recipients and supported a considerable degree of thyroid function as judged by a number of tests. Anterior hypothalamic lesions in the ‘thyrotropin area’ had no effect upon the growth or function of these grafts. The results are discussed with respect to the neurohumoral theory of hypothalamic control over pituitary thyrotropic function.
Effects of submergence on cardiac cycle and rate in aquatic and terrestrial birds
Authors: Bond Charles F. , Douglas Steven D. , Gilbert Perry W.
Published: December 2017

Electrocardiograms were recorded for various aquatic and terrestrial birds with heads submerged and then returned to air. Instantaneous cardiac rates were calculated and P-R and Q-T intervals were measured at selected times. Bradycardia developed in all birds during submergence, but was most pronounced and longest sustained in aquatic birds. Upon emergence, aquatic birds and pigeons developed instantly a compensatory tachycardia; cardiac rate in the others gradually returned to the presubmergence level. In the first 15 seconds of submersion, P-R and Q-T intervals remained constant in all birds except pheasants, but in ducks undergoing prolonged submergence the Q-T interval increased significantly. This Q-T interval increase lagged approximately 60 seconds behind the onset of bradycardia. Diving ducks were like dabblers, supporting further the hypothesis that differences in their underwater activity cannot be explained by vascular differences. These observations on minimally restrained wild birds are consistent with the hypothesis of a differential vascular control of oxygen during diving. For underwater activity, aquatic birds utilize mechanisms appearing to some extent in all birds.
Transport of monovalent anions by isolated small intestine of the rat
Authors: Clarkson T. W. , Rothstein A. , Cross A.
Published: December 2017

Monovalent anions could be divided into three groups, according to relative rates of absorption along the small intestine. Group 1 (chloride, bromide, iodide, nitrate and thiocyanate) moved at approximately equal rates in both the ileal and the jejunal regions. Group 2 (bicarbonate, acetate, propionate and phosphate) moved preferentially in the jejunum. Group 3 (iodate) did not move in either region. Radioisotope flux measurements indicated that the low rate of transport of group 2 in the ileum was owing to decreased permeability. All anions tested invariably moved down the electrochemical potential gradient. There is a correlation between the three anion groupings and their physicochemical properties suggesting that group 1 anions move preferentially along aqueous channels, and group 2 anions diffuse through lipid regions in the undissociated, acidic form. In this respect, both the mucous coating of the mucosal cells and the preferential release of hydrogen ions on the mucosal side of the jejunum, as a result of lactic-acid production, have an essential function in the absorption of group 2 anions.
Strain difference in thyroidal iodide-concentrating ability of the rat
Authors: Silverstein Emanuel , Lee Stephanie
Published: December 2017

T/S ratio, thyroid weight, and plasma protein-bound iodine (PBI) concentration were obtained in four strains of rats. Significant strain differences were found for T/S ratio and thyroid weight. Differences in PBI concentration were not significant. The T/S ratio varied inversely with the ratio of thyroid weight to body weight. No significant correlation was observed among T/S ratio, PBI, and thyroid histologic appearance.
Effects of hydrocortisone and adrenalectomy on uptake of α-aminoisobutyric acid
Authors: Kaplan S. A. , Nagareda C. Susan
Published: December 2017

Effects of adrenalectomy and hydrocortisone injection on distribution of α-aminoisobutyric acid (AIB) were measured in tissues of 16 groups of mice. Administration of hydrocortisone resulted in uniformly increased uptake of AIB by the liver and, less consistently, decreased uptake by lymphoid tissues and increased excretion by the kidneys. Experiments were also conducted which showed that little if any AIB is incorporated into proteins of the mouse. The experiments are consistent with a growing body of evidence that adrenal steroids lead to increased protein synthesis by the liver despite the induction of negative nitrogen balance in the body as a whole.
Changes in plasma free fatty acid concentrations on passage through the dog kidney
Authors: Hohenleitner Frank J. , Spitzer John J.
Published: December 2017

To measure the renal removal of free fatty acids from the plasma, simultaneous determinations of this metabolite were performed in a systemic artery and a renal vein in the anesthetized dogs. Renal plasma flow was also determined by the PAH method, and the renal uptake of free fatty acids was calculated. Concentrations of free fatty acids in renal venous plasma were usually lower than the arterial concentrations. The arteriovenous differences were statistically highly significant. The results also suggested that the degree of free fatty acid removal was proportional to the arterial concentration of this metabolite.
Motor unit area in a rat muscle
Authors: Norris Forbes H. , Irwin Richard L.
Published: December 2017

Single motor axons to rat peroneus longus were isolated in the ventral root. The muscle was then explored with a microelectrode during stimulation of the axon. The muscle fibers supplied by the axon were identified by the intracellular depolarization potentials evoked by axon stimulation. In ten experiments the muscle fibers of a motor unit were rather widely scattered. This indicates that in certain motor units all the muscle fibers are not grouped together within one area of the muscle.
Active relaxation of unstriated muscle produced by epinephrine
Authors: Singh Inderjit , Singh Sunita I. , Dhalla Naranjan Singh
Published: December 2017

The frog's stomach muscle and the guinea pig's uterus relax without application of any external force when treated with epinephrine; this relaxation is accompanied by increased oxygen consumption, hence it is postulated that relaxation produced by epinephrine is an active process. Ultimately the oxygen consumption decreases with relaxation, suggesting that contraction is also an active process. It is postulated, therefore, that unstriated muscle contains two contractile mechanisms, one that relaxes actively and the other passively.
Relationship of pyruvate and lactate during anaerobic metabolism. V: Coronary adequacy
Authors: Huckabee William E.
Published: December 2017

Veno-arterial differences of pyruvate and lactate across the myocardium in chloralose-anesthetized dogs were very variable; in any one animal they changed continually with time despite constant blood flow and arterial blood concentrations. There was a systematic tendency of v-a lactate to vary with v-a pyruvate, as expressed in the calculated "Δ excess lactate," which remained nearly constant (or, if blood flow changed, bore a constant ratio to (a-v)O2). No change in Δ excess lactate from control values occurred in nonhypoxic experiments despite marked changes in v-a differences, arterial blood composition, and coronary flow. Cardiac Δ excess lactate became positive in most animals breathing 10% O2 in N2; output of excess lactate was also observed in all those in which moderate muscular exercise was induced. This anaerobic metabolism, or change in the relationship between pyruvate and lactate exchanges, was interpreted as an indication that O2 delivery response was not adequate to meet cardiac tissue requirements during such mild stresses when judged by the standards of adequacy of the basal state.
Transmembrane resistance of smooth muscle cells
Authors: Barr Lloyd
Published: December 2017

Microelectrodes were used to obtain evidence that the cell membrane of vertebrate intestinal smooth muscle cells has a resistance comparable to those obtained for other muscle types. The membrane is thus a barrier of low permeability across which diffusion potentials occur. Resistance measurements between cell interiors and the bathing solution averaged 103.8 megohms and a specific membrane resistance of 980 ohms cm2 was calculated on the assumption that the cells are discrete, 100 µ long and 6 µ in width, and shaped like two cones base to base. Resistance measurements between two cell interiors less than 0.5 mm apart averaged 236.0 megohms. Since the double-cell resistance is twice the single-cell resistance, it is concluded that no low resistance pathways between cells exist. This finding is in agreement with electron micrographs showing transverse membranes across the intercellular connections. The implications of these resistance values are discussed relative to propagation, methods of recording, and the nature of the "bioelectric generator."
Active transport of calcium by intestine: action and bio-assay of vitamin D
Authors: Schachter David , Kimberg Daniel V. , Schenker Harris
Published: December 2017

Vitamin D is required for the active transport of calcium in vitro. Small doses of vitamins D2 and D3 restore the mechanism in depleted rats, and this provides a sensitive bio-assay for the vitamin, independent of an antirachitic effect. Vitamin D influences calcium transfer in all segments of the small intestine, and maximal increments are observed in the duodenum. The effect of vitamin D requires oxidative metabolism in vitro, is maximal where active transport is maximal, and the sterol increases the maximal rates of active transport of calcium. Consequently, vitamin D influences calcium transport by affecting primarily the active mechanism rather than by simple diffusion. Experiments with various monosaccharides demonstrate that two distinct steps are involved in the active transport mechanism in duodenum. Vitamin D is required for both of the steps.
Sex difference in histamine metabolism in the rat
Authors: Netter K. J. , Cohn V. H. , Shore P. A.
Published: December 2017

Female rats excrete much more free endogenous histamine than do males. The sex difference lies in histamine catabolism rather than biosynthesis, since females excrete, unchanged, a much higher percentage of injected histamine than do males. Investigation of the activity in vitro of the major histamine metabolizing enzymes, diamine oxidase (DAO) and imidazol-N-methyl transferase (IMT), showed no sex difference in distribution or activity, nor was there a sex difference in the activity of liver methionine-activating enzyme. Measurement of the biologic half-life of injected histamine revealed no sex difference in normal rats, in rats treated with the DAO inhibitor, aminoguanidine (AG), or in rats after nephrectomy, which removes almost all of IMT activity. A combination of AG and nephrectomy, however, resulted in a marked sex difference, which did not appear to be due to histamine conjugation or to liver drug-metabolizing enzymes. The findings suggest that male rats possess a minor histamine-metabolizing pathway which females lack.
Secretion of potassium and acidification in collecting ducts of mammalian kidney
Authors: Hierholzer Klaus
Published: December 2017

As part of an investigation of the site of potassium secretion, potassium and inulin clearances were measured simultaneously in golden hamsters during infusion of KCl, acetazoleamide and sodium sulfate. Potassium clearance exceeded that of inulin, indicating that K must have been secreted into the tubular fluid. Utilizing the microcatheterization technique, tubular fluid was drawn from the collecting duct system of the golden hamster during sulfate diuresis. In the first series of experiments carried out during KCl infusion, evidence was obtained of a contribution by the distal portion of the collecting duct system to K secretion. In a second series, without KCl infusion, pH measurements demonstrated that acidification occurs in the same segment, confirming results obtained by previous investigators. However, both secretion of potassium ions and of hydrogen ions cannot be confined completely to the distal collecting duct system under conditions of sulfate diuresis, but must also occur in more proximal parts of the nephron.
Endocrine influences on tissue serotonin content of the rat
Authors: Resnick Robert H. , Smith George T. , Gray Seymour J.
Published: December 2017

The effect of endocrine influences on the serotonin concentration of rat brain and gastrointestinal viscera was determined by a spectrophotofluorimetric technique. Animals subjected to the removal of hypophysis, adrenals, parathyroids, thyroid, or testes showed no change in tissue 5-hydroxytryptamine (5-HTA) content. A significant increase in gastric 5-HTA concentration was observed after pituitary section, but this result was attributed to gastric atrophy. Morphological studies of the stomach revealed a loss of parenchymal cell elements with preservation of the enterochromaffin system after hypophysectomy. The administration of corticotropin, testosterone, or methacholine chloride to healthy animals did not produce any alterations in 5-HTA levels. This study indicates that tissue serotonin stores in the rat are unaffected by profound endocrine changes. The stability of gastrointestinal serotonin content was also demonstrated after drug-induced cholinergic stimulation.
Tissue distribution of thyroxin analogues and their effects on cholesterol metabolism
Authors: Duncan Charles H. , Best Maurice M.
Published: December 2017

Four thyroxin analogues, l-triiodothyronine, d-triiodothyronine, tetraiodothyropropionic acid, and tetraiodothyroformic acid, labeled with I131, were injected intravenously into male rats and the tissue distributions of radioactivity determined at intervals of 40 min, 2 hr, and 6 hr. Of the two analogues that have been shown to exert an effect on cholesterol metabolism, which is accentuated relative to their other metabolic activities, d-triiodothyronine and tetraiodothyroformic acid, only the former was disproportionately concentrated by the liver. The liver to skeletal muscle concentration ratio of tetraiodothyroformic acid did not differ appreciably from those of l-triiodothyronine and tetraiodothyropropionic acid, which do not display an accentuated effect on cholesterol metabolism. It is concluded that the effect on cholesterol metabolism relative to other metabolic activities of thyroxine analogues is not determined solely by their tissue distributions.
Seasonal and starvation-induced changes in enzymatic pattern of frog nephron
Authors: Karnovsky Morris J. , Himmelhoch S. Ralph
Published: December 2017

Oxidative and hydrolytic enzyme activities in the nephron of the frog were investigated using histochemical and spectrophotometric techniques. The distal tubule was found to possess high activities of enzymes of glycolysis and the Krebs cycle, as well as high cytochrome oxidase activity, but had only slight activities of the hexose-monophosphate shunt enzymes. The proximal tubule had high activities of glycolytic enzymes, enzymes of the hexose-monophosphate shunt, and enzymes of the Krebs cycle, except for succinic dehydrogenase, which was present in very low activity. Proximal tubular cytochrome oxidase was found to vary according both to the season and to environ mental conditions. In freshly caught summer frogs it was present in high activity, but in winter frogs or summer frogs starved for periods of 10–30 days, no proximal tubular cytochrome oxidase could be detected, although other proximal tubular enzyme activities remained unchanged as far as could be histochemically determined. The specific activity of cytochrome oxidase in mitochondrial fractions was found to decrease by about 50% in the kidneys of starved and winter frogs, as compared with summer frogs.
Development of an insulin-sensitive glucose transport system in chick embryo hearts
Authors: Guidotti Guido , Foà Piero P.
Published: December 2017

Glucose uptake, sorbitol space, and total water content were measured in chick embryo hearts at various stages of development, in control aerobic and anaerobic conditions and after the addition of insulin, 2,4-dinitrophenol (DNP), or ouabain to the incubation medium. In 5-day-old hearts, glucose uptake is relatively high; sorbitol distributes itself rapidly in a volume of about 90 ml/ 100 g of fresh tissue; insulin, DNP, and ouabain have no effect on glucose uptake, sorbitol space, or tissue water; anoxia increases glucose uptake, but has no effect on sorbitol space or tissue water. In 7-day-old hearts, glucose uptake and sorbitol diffusion are slower and sorbitol space reaches values of about 90 ml/100 g of fresh tissue only after 2 hr of incubation. In 10-day-old hearts, glucose uptake is still lower; sorbitol space remains below 50 ml/100 g of fresh tissue; insulin, DNP, anoxia, and ouabain cause significant increases in glucose uptake, but do not modify sorbitol space or tissue water. These results are consistent with the hypothesis that the 5-day-old chick embryo heart is freely permeable to glucose and to sorbitol and that a "membrane" capable of regulating the transport of glucose appears between the 7th and 10th day of embryonic development. No evidence of stimulation of glucose phosphorylation by insulin, DNP, or ouabain was obtained.
Heparin-released lipolytic and esterolytic activities of human and rabbit plasmas
Authors: Shore B. , Shore V.
Published: December 2017

The enzymes released into both human and rabbit plasmas by heparin injection hydrolyzed, in addition to triglyceride moieties of lipoproteins, a number of mono- and diglycerides of C16 and C18 fatty acids after in vitro addition of the unemulsified glycerides to the plasma. In human postheparin plasma, these enzymes also hydrolyzed glycerides of butyric and caproic acids. The pure triglycerides and methyl or ethyl esters of C16 and C18 fatty acids were not substrates. The heparin-released activities for the hydrolysis of glycerides added in vitro persisted after all activity for the lipolysis of lipoproteins had been destroyed by heat. These activities also differed from lipoprotein lipase activity with respect to the effects of 1 m NaCl, dialysis, and aging the plasma at 4 C. It appears that heparin releases into the blood more than one enzyme or more than one form of an enzyme which may be involved in a stepwise degradation to fatty acids and glycerol of the triglyceride moieties of lipoproteins of density less than 1.007 g/ml.
Variations in pyridine nucleotides in liver of fetal, newborn, and adult guinea pigs
Authors: Räihä Niels C. R.
Published: December 2017

Concentrations of oxidized diphosphopyridine nucleotide (DPN) and oxidized triphosphopyridine nucleotide (TPN), reduced diphosphopyridine nucleotide (DPNH) and reduced triphosphopyridine nucleotide (TPNH) were determined enzymatically in fetal, newborn, and adult guinea pig liver. Acid-soluble nucleotides were determined by anion-exchange chromatography in fetal and adult guinea pig liver. The concentration of DPN shows a slight increase from a mean of 418.0 mµmoles/g liver in fetal liver to 533.3 mµmoles/g in the adult. DPNH is low in fetal liver, 26.0 mµmoles/g, increasing rapidly after birth to the adult value of 127.0 mµmoles/g. The concentration of TPN is low in both fetal and adult liver and could not be determined accurately. TPNH increases from 125.0 mµmoles/g in fetal liver to a mean of 185.0 mµmoles/g in adult liver. Anoxia increases the concentration of DPNH in both fetal and adult liver, whereas TPNH tends to decrease, especially in fetuses near term. No effect on DPN and TPN was found. The other acid-soluble nucleotides determined are present in fetal liver in a lower concentration than in the adult liver. Results are discussed in relation to the high fat content of the fetal liver.
Regulation of food intake in the goldfish
Authors: Rozin Paul , Mayer Jean
Published: December 2017

Goldfish were trained to press a lever. This response was followed by the delivery of a pellet of food. The fish were then allowed continuous access to the lever under controlled conditions, and their food intake was measured. Goldfish distribute their feeding responses fairly evenly over time, within the limits of the lighting cycle. Some fish eat mainly at night, some during the day, and others seem to be indifferent to the lighting cycle. Goldfish decrease their food intake by one-half to one-third in response to a drop in ambient temperature from 25 to 15 C, and show a corresponding increase in food intake when the temperature returns to 25 C. Goldfish increase their food intake significantly in response to dilution of their normal diet with kaolin, and thus seem to eat for calories or nutrient value.
Action of secretin on pancreatic secretion
Authors: Christodoulopoulos John B. , Jacobs Walter Harvey , Klotz Arthur P.
Published: December 2017

Dogs with chronic duodenal fistulas were used for quantitative collections of pancreatic juice after single rapid injections of secretin and continuous intravenous administration of secretin. Measurement of volume and pH and analysis for bicarbonate and chloride, amylase, lipase, leucine aminopeptidase (LAP), glutamic oxalacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) were performed. Single rapid injections of secretin resulted in consistently reproducible responses on the same day. Apparent maximal stimulatory effect could not be achieved with single rapid injections of secretin even when quantities greater than that reported by others were used. Amylase concentrations were high after single rapid injections but fell off quickly suggesting a "washing out" effect. With continuous secretin stimulation after 120–180 min of collection, a fall in bicarbonate concentration and a rise in chloride concentration were obtained despite the maintenance of high volume. Exhaustion of pancreatic secretion was not achieved even after 12 hr of continuous intense stimulation. In one continuous experiment 23.8 ml pancreatic juice/10 min was obtained. GOT, GPT, and LAP were present sporadically in low variable concentrations.
Iron 59 incorporation into erythrocytes of hamsters after irradiation
Authors: Lohmann W. , Glasgow J. L. , Perkins W. H.
Published: December 2017

The effect of 800 r of whole-body Co60-γ- and X-irradiation on the incorporation of citrate-Fe59 into erythrocytes of male hamsters was investigated. Iron 59 was given intraperitoneally immediately postirradition, and serial blood samples were obtained. The nonirradiated control animals showed a progressive increase in the Fe59 activity of the erythrocytes, reaching a maximum in 4–5 days. After a 5-day plateau, the activity gradually decreased. The Fe59 activity of the irradiated animals decreased, initially, then increased gradually. After 7 days the incorporation rate of Fe59 was 27% by the X-irradiated and 22% by the Co60-γ-irradiated animals, using the controls as 100% values. Ten days later the incorporation rate was 40% by the X-irradiated animals. None of the Co60-γ-irradiated animals survived 10 days, but all of the X-irradiated animals survived. In the X-irradiated animals, the leukocyte counts rose, initially, then decreased and returned, gradually, to preirradiation levels after 30 days. The specific Fe59 activity of different organs of irradiated and control hamsters is reported.
Cerebral O2 in exposures to O2 at atmospheric and higher pressure, and influence of CO2
Authors: Bean John W.
Published: December 2017

In polarographic experiments on anesthetized dogs and rats, a shift from breathing air to breathing oxygen at atmospheric pressure, and also at a high pressure (OHP) of 5 atm, raised availability of oxygen to the brain to levels well maintained throughout the exposure (20–55 min). Decompression reversed these effects. Cerebral vasoconstriction which may have occurred in OHP was apparently insufficient to prevent pronounced elevation of cerebral O2 or to protect against O2 toxicity. In simultaneous recordings from two regions, the occurrence of cyclic changes, frequently out of phase, suggest the involvement of a reciprocating cerebral vascular control mechanism between different regions. Addition of CO2 to the OHP, to give concentrations of 0.8–1.7%, usually raised the O2 availability and tended to precipitate asynchronous cyclic O2 changes; apparently brain vasculature does not necessarily react en masse to CO2. The data suggest there are wide variations in Po2, Pco2, and pH in circumscribed regions of the brain, for which the internal jugular venous blood is not a reliable index. Such regions may serve to precipitate manifestations of O2 toxicity.
Renal regulation of acid-base balance in the bullfrog
Authors: Yoshimura Hisato , Yata Masateru , Yuasa Minoru , Wolbach Robert A.
Published: December 2017

Renal mechanisms for the maintenance of acid-base balance were studied in the normal bullfrog, during metabolic and respiratory acidosis, and after carbonic anhydrase inhibition. Following intravenous administration of 0.3–12 mmole HCl/ kg, as 0.1 n HCl, urinary pH (initially pH 6.3–7.7) did not change significantly. However, urinary ammonia excretion increased more than twofold, and within 3–5 days the cumulative increase was equivalent to the acid load given. Despite the increased ammonia excretion, chloride excretion did not increase after acid loading. In both normal and acidotic bullfrogs ammonia excretion was correlated with an increase in urinary pH. Respiratory acidosis in the small frog, Rana limnocharis, produced by exposure to 6.4% CO2 in air, induced neither urinary acidification nor increased ammonia excretion; both urinary sodium and bicarbonate excretion increased. When renal carbonic anhydrase was inhibited by acetazoleamide injection, urine flow, sodium excretion, and bicarbonate excretion increased markedly, urinary pH increased slightly, and urinary ammonia excretion remained unchanged. These renal responses to acidosis are compared with those of the acidotic dog.
Specificity of carnitine action on fatty acid oxidation by heart muscle
Authors: Fritz Irving B. , Kaplan Eli , Yue Kenneth T. N.
Published: December 2017

Carnitine (ß-hydroxy, γ-trimethylammonium butyrate), at concentrations of 10–5 m and more, increased the oxidation of long-chain fatty acids severalfold by heart muscle particulates incubated under optimal conditions. CoA dependency could be demonstrated in the presence of carnitine but not in its absence. Of a variety of compounds tested for carnitinelike activity, only acetylcarnitine and ß-hydroxy, γ-dimethylaminobutyrate ("norcarnitine") influenced palmitate oxidation in the assay system. Activity was abolished by removal of the hydroxyl group on the ß carbon; by replacement of the carboxyl group with either a cyano, an alcohol, or an amide grouping; or by substitution of an amino group for the trimethylammonium moiety of the molecule. Nonspecifically tritium-labeled carnitine was not degraded by heart particulates during incubation, indicating that carnitine acted catalytically to enhance fatty acid oxidation. The physiological significance of the data was discussed.
Effect of amino acid imbalance on food intake and preference
Authors: Sanahuja Juan C. , Harper Alfred E.
Published: December 2017

Effects of an amino acid imbalance, caused by adding 3.8% of an amino acid mixture lacking histidine to a diet containing 6% of beef fibrin, on the food intake and food preference of protein-depleted rats are described. After being depleted, animals fed the balanced or imbalanced diets ate equal amounts for 3 days, then both growth rate and food intake of those fed the imbalanced diet dropped. When protein-depleted rats were fed the balanced or imbalanced diet together with a protein-free diet, neither group ate the protein-free diet during the first 3 days. Thereafter, animals fed the imbalanced diet began to eat the protein-free diet in preference to the imbalanced diet, even though the latter would support growth and the former would not. Animals fed ad libitum the balanced diet or the imbalanced diet plus histidine did not eat the protein-free diet at all. These observations indicate that both food intake and food selection are influenced by the amino acid pattern of the diet.
Movements of lactate and pyruvate in pregnant uterus
Authors: Huckabee William E. , Metcalfe James , Prystowsky Harry , Barron Donald H.
Published: December 2017

Anesthetized goats were studied at various stages of pregnancy. Lactate and pyruvate concentrations were determined in maternal blood (artery and uterine vein) and in fetal blood (umbilical artery and vein) A great variety of concentrations was found at all sites, and no systematic effect of gestational age was noted. There were also no systematic effects of absolute concentrations on arteriovenous (A-V) differences or on absolute rates of exchange of lactate and pyruvate between pregnant uterus and maternal blood (A-V x uterine blood flow). There was no systematic effect of the concentrations in either mother or fetus on those of the other. The direction of exchanges on the two sides of the placenta (i.e., between placenta and mother or between placenta and fetus) were not necessarily consistent. It was concluded that passive movement of either substance between the two blood streams was improbable and, furthermore, that the difference between the two levels could not be taken to represent the concentration gradient along which transfer occurred. The concentration and the metabolic activity in the placenta appeared to be unknown factors essential to an understanding of the heterogeneous values observed.
Cardiovascular responses to insulin in the absence of hypoglycemia
Authors: Pereda Santiago A. , Eckstein John W. , Abboud François M.
Published: December 2017

Cardiovascular responses to intravenous administration of insulin were studied in lightly anesthetized dogs treated with a neuromuscular blocking agent. An early transient pressor response was observed. This abrupt increase in arterial pressure appeared 2–9 min after insulin was given. It was accompanied by increases in cardiac output and right atrial pressure. It occurred in the presence of hyperglycemia and in the absence of hypoglycemia. It was not altered by glucagon but it could be antagonized by ganglionic and adrenergic blocking drugs and by pentobarbital. The response could be produced when insulin was given in the carotid artery in doses that caused no effect when injected in a systemic vein. The experiments suggest that insulin may have a direct action on the brain.
Release of rabbit platelet histamine by serum in vitro
Authors: Tidball M. E. , Shore P. A.
Published: December 2017

Freshly prepared defibrinated serum rapidly releases the histamine content of rabbit platelets. The presence of calcium ion is required for this action. Releasing activity of the serum factor slowly declines on aging of the serum. Release is inhibited by heparin or by tosylarginine methyl ester, but not by soybean trypsin inhibitor. Release is also promoted by thrombin, which again is inhibited by heparin. The serum factor does not appear to be preformed thrombin since thrombin is effective in the absence of calcium ion. The findings suggest that the serum factor may be blood thromboplastin which acts directly on platelets or indirectly through the generation of thrombin.
Specificity of zinc pathway through the body: turnover of Zn65 in the mouse
Authors: Cotzias George C. , Borg Donald C. , Selleck Bernell
Published: December 2017

An isotopic study is presented which shows that zinc metabolism is controlled by at least two homeostatic mechanisms which act at the sites of absorption and of intestinal excretion, respectively. Zinc was the only element which, when used as a metabolic load, accelerated the elimination of Zn65. Among its neighbors in the transition series, copper and gallium were ineffectual. Among the members of group II of the elements cadmium decelerated the excretion of Zn65 slightly, whereas magnesium was without demonstrable effect. The significance of these findings relative to the specificity of zinc's pathway through the body is discussed.
Seasonal variations in caloric intake of dogs living in an arctic environment
Authors: Durrer John L. , Hannon John P.
Published: December 2017

The seasonal variations in the average daily caloric intake and body weight of five Husky dogs and five beagle dogs were measured over 12- and 8-month periods, respectively, during which the average monthly temperature ranged from +17 C to –22 C. The caloric intake of the Huskies rose from a midsummer low of 49 kcal/kg/day to a November high of 87 kcal/kg/day. Mid- and late winter values averaged about 79 kcal/kg/day. During late winter there was no relationship between the day-to-day temperature and caloric intake. In the beagles, acute and later chronic exposure to cold in March caused a marked increase (80–131 kcal/kg/day) in caloric intake. They, like the Huskies, tended toward minimum values (85 kcal/kg/day) during the summer. With the onset of winter the beagles increased their intake to a high of 144 kcal/kg/day in November. Overall, these data showed that the relative magnitude of the seasonal changes were quite similar in both groups of dogs and suggested that seasonal changes in insulation are supplementary to seasonal changes in caloric intake.
Estrous and circadian periodicity and electroshock convulsions in rats
Authors: Woolley Dorothy E. , Timiras Paola S.
Published: December 2017

The threshold and pattern of electroshock seizures of 100 mature rats during the estrous cycle were investigated. It was observed a) that the threshold for minimal seizures was highest during diestrus, lower during proestrus, and lowest during estrus; and b) that the duration of tonic flexion during maximal seizures was longest during diestrus and shortest during estrus. These findings indicate that convulsive reactivity in the rat is lowest during diestrus, higher during proestrus, and highest during estrus. This heightened reactivity during estrus may be the expression of an increased central excitability as a result of high levels of circulating estradiol during this phase. It was also observed that electroshock thresholds were significantly lower between 9:00 and 11:00 pm than between 1:00 and 3:00 pm when illumination was from 7:00 am to 7:00 pm. These day-night differences or circadian rhythms in thresholds were quantitatively larger than changes seen during the estrous cycle. Finally, convulsions produced by these methods did not appear to alter the regularity of the estrous cycle.
A hypothalamic luteinizing-hormone-releasing factor
Authors: McCann S. M.
Published: December 2017

Crude acidic extracts of rat stalk-median eminence tissue evoked an ovarian ascorbic acid depletion on intravenous injection into immature rats pretreated with gonadotropins. Response was linearly related to logarithm of the dose. Various parts of the hypothalamus were extracted, and the major activity was found to reside in the stalk-median eminence region. Activity of this stalk-median eminence extract (SME) was relatively heat stable as compared to luteinizing hormone (LH) activity of rat anterior pituitary extract. SME was partially inactivated by pepsin and completely inactivated by tryptic digestion. Intravenous SME did not elevate the already high plasma LH levels in untreated ovariectomized rats but evoked a significant elevation in plasma LH of ovariectomized, estrogenized donors, whereas an extract of cerebral cortex was ineffective in this latter type of test animal. Pitressin also failed to influence LH titer of such donors. Increasing doses of estrogen or estrogen plus progesterone failed to block this effect of SME. SME also increased LH activity in plasma of ovariectomized rats in which release of LH had been blocked by lesions in the median eminence. It elevated LH activity in plasma of normal donors but had no significant effect on plasma LH activity of hypophysectomized animals. It was concluded that a hypophysial LH-releasing factor resides in stalk-median eminence tissue, and reasons were advanced for believing this to be a hormonal effect.
Conjugation and biliary excretion of corticosteroids by isolated perfused liver
Authors: Berliner D. L. , Leong G. F. , Cazes D. M. , Berliner M. L.
Published: December 2017

The metabolic capacities of the liver on cortisol and corticosterone were studied using the isolated perfused rat liver with cannulated biliary duct, a preparation in which temperature, blood pressure, and injection mass can be rigidly maintained. The infused steroids were 4-C14-labeled compounds in trace amount (3–5 µg). The major transformation achieved by the liver is conjugation of the steroids, which renders them water soluble and rapidly excretable in the bile. The half-lives (T1/2) of the steroids we found in blood are shorter than those reported for intact animals; however, differences in the T1/2 of the metabolic products of both steroids (cortisol > corticosterone), speed of excretion (cortisol < corticosterone), and rate of conjugation (cortisol < corticosterone) were found to be in agreement with those found in the in vivo studies. Whereas, in normal humans, most of the steroids are excreted in the urine as ß-glucuronides and sulfates, these types of conjugates accounted for less than 30% of the water-soluble compounds recovered from the bile in the present study. Finally, none of the originally injected steroid was found to be present in the bile.
Submandibular salivary gland weight increase by administration of isoproterenol to rats
Authors: Wells Herbert
Published: December 2017

Administration of isoproterenol, like amputation of lower incisor teeth, resulted in a marked increase in both the fresh and dry weights of the submandibular salivary glands of rats. There was a linear relationship between the percent increase in gland weight and the dose of isoproterenol between 10 and 160 mg/kg/day. Ten days after cessation of isoproterenol administration, the weight of the enlarged glands had receded to control levels. Although prior unilateral extirpation of the superior cervical ganglion inhibited the response to incisor amputation of the submandibular gland on the operated side, both glands enlarged to the same extent following administration of isoproterenol. When isoproterenol administration was combined with amputation of the incisors, the effects on gland weight were additive.