bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of endotoxin on capillary permeability to macromolecules
Authors: Chien S. , Sinclair D. G. , Dellenback R. J. , Chang C. , Peric B. , Usami S. , Gregersen M. I.
Published: December 2017

The intravenous injection of Escherichia coli endotoxin (3 mg/kg) into dogs caused an increase in lymph flow from the thoracic duct. The lymph concentrations of macromolecules (dextran with mol. wt. of 250,000, albumin-I131, and endogenous proteins) increased and the lymph-to-plasma ratios approached 1. These results indicate that E. coli endotoxin causes an increase in capillary permeability to both the fluid and the macromolecules in plasma. The increase in capillary permeability for albumin-I131 was greater than that for dextran with mol. wt. of 250,000. Eighty minutes after endotoxin, the lymph flow returned to normal, but albumin-I131 and dextran injected at this time were still transferred into the thoracic duct lymph at enhanced rates.
An hypothesis for discovery of inhibitors of gastric acid secretion
Authors: LeFevre Marian E. , Gohmann Edmund J. , Rehm Warren S.
Published: December 2017

Davenport discovered that thiocyanate inhibits gastric acid secretion. The original working hypothesis, that this action of thiocyanate is due to inhibition of carbonic anhydrase, was successful in stimulating further work but is now no longer tenable. We propose a new working hypothesis according to which the inhibitory action is dependent on the presence of a nitrogen with a pair of unshared electrons. This hypothesis was tested by studying the effects of nitrite, cyanate, and ammonium ions on the in vitro frog's stomach. It was found that the addition of these compounds to the nutrient side reversibly inhibits H+ secretion in the same concentration range as that found for thiocyanate, i.e., 0.5–10 mm. Reduction of the H+ rate to approximately zero was associated with an increase in the transmucosal potential difference and electrical resistance to levels characteristic of the resting stomach. Acetate and nitrate in the same and higher concentrations did not inhibit the H+ rate. The hypothesis has been fruitful in that three new gastric inhibitors have been discovered, and it is hoped that it will be successful in stimulating much further work before it too becomes untenable.
Acute subtraction alkalosis from gastric juice loss in dogs
Authors: Grantham Jared J. , Schloerb Paul R.
Published: December 2017

The clinical syndrome of acute metabolic alkalosis secondary to pyloric obstruction and vomiting was simulated in 50 dogs by draining gastric juice through a cannula gastrostomy. This study was designed to quantify changes in body electrolyte and water utilizing radioisotope-dilution methods. Total body chloride decreased 43% with good correlation between the decrease in plasma chloride concentration and the decrease in total body chloride. Body sodium decreased 21% with no change in plasma sodium concentration. Body potassium decreased 20% but was not significantly related to the decrease in plasma potassium concentration. A highly significant correlation was obtained between plasma potassium and the product of blood hydrogen and intracellular potassium content. Intracellular pH (DMO) did not change significantly. Body water decreased 16% with isotonic loss of 169 mEq Na + K per liter body water. Sodium chloride solution alone corrected the alkalosis and acidified the urine. Potassium administration was necessary to prevent hypokalemia and aggravation of the cellular potassium deficit during rehydration. This study helps clarify the differences in body composition between the acute alkalosis of gastric juice loss and the alkalosis resulting from prolonged potassium depletion, sodium loading, and excess adrenocorticosteroid administration.
Cardiovascular responses to severe hypercapnia of short duration
Authors: Manley Emmett S. , Nash Clinton B. , Woodbury R. A.
Published: December 2017

Dogs under pentobarbital anesthesia were employed in an investigation of the effect of abrupt, severe hypercapnia upon blood pressure, heart rate, and force of myocardial contraction. Electrocardiographic activity and arterial blood pH were also monitored. Hypercapnia was induced for 10-min periods with 15 and 30% CO2 in oxygen. The studies were undertaken in nontreated animals and animals treated with atropine, reserpine, chlorisondamine, P-286, or bilateral adrenalectomy. Severe hypercapnia was shown to be depressant to the cardiovascular parameters evaluated, but blood pressure and contractile force normally demonstrated compensation to this depression. Parasympathetic blockade with atropine did not reduce the depression observed in the nontreated dogs during hypercapnia. Results obtained with other pretreated animals indicate that compensation occurs primarily via sympathetic activation. Adrenal activation may assume importance in compensation to 30% CO2, but intact adrenals were not necessary for survival during hypercapnia. No arrhythmias (excluding bradycardia) were observed during or immediately following exposure to either concentration of CO2.
Effect of varying coronary perfusion on ventricular function in isolated dog hearts
Authors: Buckley N. M. , Porter E. P. , Jedeikin L. A.
Published: December 2017

The effects of coronary perfusion on ventricular function have been studied in isolated ventricle preparations working under different conditions. Coronary flow, oxygen consumption, ventricular stroke work, rate of ventricular pressure change during isovolumetric contraction (dPC), and diastolic ventricular pressure (DVPm) and pressure/inflow ratio were determined. Maintenance of coronary flow and oxygen consumption in 5 experiments did not prevent irreversible changes in DVPm, stroke work, and dPC when the right ventricle was acutely overloaded. These ventricles did not accumulate water. Decreasing coronary perfusion pressure at constant arterial oxygen content in 11 experiments led to inconsistent changes in DVPm, stroke work and dPC. Decreasing arterial oxygen content at constant coronary perfusion pressure in 10 experiments led to increased DVPm but inconsistent changes in stroke work and dPC. There was an inverse relationship between DVPm and oxygen consumption in the variable perfusion experiments, but not in the overloading experiments. Ventricular function did not change significantly with time in 6 experiments in which the conditions of workload and coronary perfusion were kept constant. It was concluded that irreversible changes in performance of acutely overloaded ventricles could be independent of coronary flow, myocardial water content, or duration of experiment.
Cardiac muscle mechanics and ventricular performance: force and time parameters
Authors: Downing S. Evans , Sonnenblick Edmund H.
Published: December 2017

Studies were designed to determine parameters of force and velocity derived from isolated cardiac muscle mechanics which would permit comparison with related performance characteristics in the intact ventricle. In the papillary muscle, for a wide range of resting muscle lengths, tension developed isometrically (Po) was found a linear function of initial muscle length and proportional to the extent of isotonic shortening (δL). Length-tension curves obtained isotonically were virtually identical to those obtained isometrically. In the intact heart stroke volume is a function of δL. Ventricular end-diastolic pressure is a function of resting muscle length. As increments of resting muscle length increased δL, increasing ventricular end-diastolic pressure augmented stroke volume. Increasing the load carried by the muscle (afterload) at a given resting muscle length increased work performed by the papillary muscle. Similarly, increasing aortic pressure increased stroke work for a given ventricular end-diastolic pressure in the intact heart. In the papillary muscle time to maximal δL was an inverse function of maximal velocity of shortening (Vmax), but independent of both Lr and afterload. The inverse relation of time to max δL and Vmax were shown for norepinephrine and frequency. In the intact heart time to peak ventricular pressure, was found to be largely independent of ventricular end-diastolic and aortic pressures and inversely related to the inotropic state of the myocardium. Contractility of the papillary muscle strictly defined by Vmax and Po, was thus characterized by time to maximal δL, as well as δL. Contractility of the ventricle at a given ventricular end-diastolic pressure could then be defined by stroke volume and peak pressure time, which are indices of force and velocity.
Effect of catecholamines on respiration of cerebral cortex and hypothalamus in female rats
Authors: Moguilevsky Jaime Alberto , Trifaró Jose M. , Foglia Virgilio G. , Schiaffini Omar
Published: December 2017

Epinephrine and norepinephrine in vitro produced a significant elevation in the oxygen uptake of hypothalamus in diestrus rats. No changes were observed in the respiratory activity of cerebral cortex and hypothalamus during the estrus. An increase in the oxygen consumption of diestrus hypothalamus was obtained by the injection of pheniprazine; reserpine decreases the oxidative activity of cerebral cortex during diestrus and that of the hypothalamus during the estrus. It is suggested that the changes reported herein are related to modifications of the catecholamine levels in the hypothalamus during the sexual cycle.
Decreased nephron population resulting from increased ureteral pressure
Authors: Malvin Richard L. , Kutchai Howard , Ostermann Fred
Published: December 2017

The glucose Tm and GFR were determined for each kidney in anesthetized dogs. After three control periods a hydrostatic pressure was applied to one ureter. This resulted in a decrease in GFR over all ranges of ureteral pressures. Tm glucose remained essentially unchanged until the ureteral pressure was elevated to more than 30% of mean blood pressure. At ureteral pressures greater than this, Tm glucose was significantly depressed. The data were used in an attempt to calculate the range and the mean glomerular capillary pressure.
Regulation of cellular histamine content by modulators of glucose metabolism
Authors: Tidball M. E.
Published: December 2017

When rabbits are anesthetized with ether, both their total platelet histamine (TPH) and number of circulating platelets (PC) decline, then rise, then fall again. Splenectomy abolishes the rise indicating that this represents a splenic response to the ether anesthesia. The loss of TPH is greater than platelet loss signifying that histamine release occurs during ether anesthesia. Histamine release and the splenic response are prevented by pretreating animals with phenoxybenzamine, suggesting that epinephrine causes both of these effects. Glucose, infused into splenectomized or phenoxybenzamine-treated animals, causes changes in TPH and PC without loss of platelet histamine, demonstrating that elevated blood glucose, or insulin released in response to this, plays a role in the conservation of platelet histamine. The results extend previous in vitro observations to the intact animal with respect to the relation of epinephrine and insulin through glucose to platelet histamine content. They add further impetus to the concept that cellular histamine content is regulated by physiologic mechanisms which serve other homeostatic functions in living cells.
Relationships between electrical activities of antrum and duodenum
Authors: Allen George L. , Poole Elmon W. , Code Charles F.
Published: December 2017

This study attempted to determine whether the slow basic electrical rhythms of the antrum and the duodenum were related, and to search for relationships between the fast electrical activities of the two regions. Observations were made on five healthy, trained, unanesthetized dogs by means of detecting electrodes surgically implanted on the walls of the antrum and duodenum. No relationship was found, in either fasted or fed dogs, between the slow electrical rhythms of the antrum and duodenum. Feeding increased the fast activity in the antrum and in the duodenum, and under these circumstances, the fast activity in the duodenum was related to the slow basic electrical rhythm of the antrum.
Effect of hypothalamic lesions on rat anaphylaxis
Authors: Luparello Thomas J. , Stein Marvin , Park C. Dick
Published: December 2017

The present study investigated the effect of anterior and posterior hypothalamic lesions on lethal anaphylaxis in the rat. Three groups of animals—control, posterior hypothalamic lesioned, and anterior hypothalamic lesioned—were sensitized to ovalbumin and subsequently challenged with various doses of the antigen. Dose-mortality curves were plotted for the control and two experimental groups. The three curves were demonstrated to be parallel. Ovalbumin was significantly less potent in the animals with anterior hypothalamic lesions than in both the control rats and those with posterior lesions. The protective action of anterior hypothalamic lesions against lethal anaphylaxis in the rat is discussed in terms of neuroendocrine processes, parasympathetic-sympathetic effects and antibody formation.
Preference for sodium chloride over lithium chloride by adrenalectomized rats
Authors: Harriman Arthur E. , Kare Morley R.
Published: December 2017

The experiment tested the hypothesis that adrenalectomized rats can discriminate, as measured by preference, between equimolar NaCl and LiCl solutions on the basis of taste. An adrenalectomized experimental group was given long-term, two-bottle drinking tests with NaCl opposite distilled water, and later with LiCl opposite distilled water. In a subsequent series of brief two-bottle tests, the rats selected NaCl over LiCl more frequently and in greater quantities. Control groups lacking either prior experience with LiCl opposite distilled water or adrenalectomy failed to manifest the preference. Presumably, the experimental group acquired the ability to discriminate between the solutions in the preliminary long-term drinking tests in which there was ample opportunity for the rats to experience the differential postingestional effects of the compounds.
Biliary and fecal clearance of endogenous thyroid hormone in cold-acclimated rats
Authors: Cottle W. H.
Published: December 2017

The increase in fecal excretion of thyroid hormone by rats as a result of cold acclimation may result from a more rapid biliary excretion of the hormone and/or from a reduction in reabsorption of hormone from the intestinal tract. In the present study cold acclimation was found to increase both biliary and fecal clearances of endogenously labeled hormone. No evidence was found, under the conditions of the experiment, to support the possibility that the greater volume of food eaten in some way reduces reabsorption. Feeding a commercial rat chow led to higher values of both fecal and biliary clearances than feeding a test diet. Significant reabsorption of hormone was not evident. The linear correlation between fecal and biliary clearances indicates the removal of the hormone by the liver and excretion via the bile is the major mechanism governing rate of excretion in the feces.
Pressor effect of renin
Authors: Haas Erwin , Goldblatt Harry
Published: December 2017

The pressor activity of renin administered intravenously at various rates and at various states of purity was measured and the effects of anesthesia, heparinization, and atropinization were investigated. Under all of these conditions, the blood pressure of normotensive and hypertensive dogs was elevated considerably throughout the period of infusion and for some time thereafter. The pressor activity of single doses of angiotensin and of renin was abolished and that of norepinephrine was inhibited, up to 85%, during the infusion of renin. The refractory state (socalled tachyphylaxis) to renin is not specific, since the continuous infusion of methoxamine likewise abolished the pressor activity of superimposed single doses of renin or angiotensin. At a very high rate of infusion, renin caused two exceptional and highly abnormal effects, the return of the blood pressure to the base line during the infusion, and the failure of the infused renin to inhibit the pressor action of single doses of norepinephrine.
Potentiation and intrinsic regulations in mammalian heart muscle
Authors: Seoane Antonio Bonnet
Published: December 2017

Repeated paired stimuli (S1–S2) were applied to isolated atrial and ventricular preparations. Isometric force and transmembrane action potentials were recorded at different S1–S2 intervals. At the intervals where S2 evokes an action potential, developed force gradually attains a higher level during the S1–S2 train. This mechanical behavior is quantitatively dependent on the timing of S2. Potentiation is graded during the electrical relative refractory period and related to the amplitude of the premature electrical response. This relationship was confirmed under conditions of massive response, where propagation was suppressed and the whole muscle was activated at once. Potentiation can be augmented by interposing multiple (premature) action potentials between driven beats. By increasing the S1–S2 interval the premature contraction becomes evident and increases while the first one (driven) decreases. Mechanical events are delayed one cycle after the electrical ones. Three factors are proposed to account for the intrinsic inotropic regulation: a potentiating factor related to the action potential; an ionic compartment; and a restitution factor.
Glucose metabolism in mice
Authors: Baker Nome , Huebotter Robert
Published: December 2017

Sixty normal mice were given single intravenous injections of glucose-U-C14. At varying times between 1 and 60 min following injection, either respiratory CO2 was collected or the animals were decapitated and blood, liver, and extrahepatic tissues were analyzed for glucose content and specific activity. In addition, C14 appearing in extrahepatic, nonglucose compounds soluble in 70% ethanol was determined. Data analysis indicated that all of the glucose in the postabsorptive mouse behaves as a single well-mixed pool which turns over with a half-time of approximately 5 min. Most glucose carbon utilized in the first 5 min was found in extrahepatic tissues. When half of the injected dose had been converted to nonglucose compounds, only 1.5% of the administered C14 was found in respiratory CO2. The respiratory C14O2 specific activity-time curve when compared to body glucose-C14 and extrahepatic tissue nonglucose-C14 at varying times indicated that glucose was oxidized to CO2 by way of a large intermediate pool of carbon and that a major part of the total CO2 produced by the postabsorptive mouse was derived from relatively nonlabeled sources of carbon.
Exchange diffusion of chloride in frog gastric mucosa
Authors: Durbin R. P. , Kitahara S. , Stahlmann K. , Heinz E.
Published: December 2017

Chloride flux from nutrient to secretory surface of frog gastric mucosa was observed to be maximal with isotonic NaCl as the secretory solution, and was depressed in varying amounts by the replacement of NaCl with other sodium salts or nonelectrolytes. In particular, bicarbonate ion in the secretory solution lowered Cl flux, but not because of an increase in pH. On the contrary, increasing the partial pressure of CO2 to maintain a normal secretory pH produced a further decrease in Cl flux. This decrement was similar to that due to increasing CO2 pressure only, so that effects of bicarbonate ion and CO2 were additive. The largest reduction in Cl flux was found with nonelectrolytes in the secretory solution. According to a previous hypothesis, the different degrees of flux depression reflect different affinities of the replacement solute for a transport or exchange carrier substance in the mucosal membrane. Although a similar but smaller effect on Cl flux was found in cellulose membranes, the evidence indicates that the effect in the functioning gastric mucosa is not exclusively physico-chemical in origin.
Biochemistry of brown fat and liver of cold-acclimated hamsters
Authors: Chaffee R. R. J. , Allen J. R. , Cassuto Y. , Smith R. E.
Published: December 2017

Studies were made of the effects of cold acclimation on the weight, the total protein content, and the enzymatic activity of brown fat of hamsters. For comparison, some enzymatic assays were also conducted on liver preparations. The mass of the brown fat doubled, as did the per cent protein, and there was a large increase in its mitochondrial and microsomal content. Brown fat mitochondria of cold-acclimated hamsters show striking increases in respiration associated with both ß-hydroxybutyrate and α-glycerophosphate, which indicates that there may be an enhanced capacity to degrade fats. On the other hand there was no change in succinoxidase, and a lowered respiration associated with isocitrate. Thus the mitochondrial catabolic activity involving the citric acid cycle may not be enhanced. Brown fat microsomal NADPH- and NADH-cytochrome c reductases were both increased in response to cold exposure which should be of significance in increasing heat production. Brown fat mitochondria show a respiration rate associated with α-glycerophosphate and isocitrate which is about 300– 400% higher than that of liver mitochondria. It is concluded that there is an increase in thermogenic capacity of the brown fat of the hamster during cold acclimation.
Lipid metabolism in cultured cells. III. Cholesterol excretion process
Authors: Bailey J. Martyn
Published: December 2017

Mammalian cells grown in tissue culture have been shown previously to take up considerable quantities of cholesterol from the growth medium. When cells grown on cholesterol-C14 supplemented medium were transferred to unlabeled medium containing serum, excretion of cholesterol into the outside medium took place. When cell cholesterol was labeled by intracellular synthesis from mevalonate-C14 precursor, it also was excreted readily into the serum medium. This excretion did not take place in serum-free medium and was found to be stimulated by a nondialyzable, thermolabile component of human serum. Horse, chicken, calf, and rabbit serum also showed stimulation ability. The process of cholesterol excretion appears to be of general occurrence. It was found in both strains of cultured cells examined (mouse fibroblasts and lymphoblasts) and also in strips of rabbit aorta incubated in vitro.
Intracellular distribution of tritiated bilirubin during hepatic uptake and excretion
Authors: Brown William R. , Grodsky Gerold M. , Carbone John V.
Published: December 2017

Physiologic amounts of bilirubin-H3 were injected into normal rats and the distribution of isotope was determined in serum, subcellular fractions of the liver, and bile at intervals during the phases of uptake and excretion. Recovery in the three spaces after 2, 5, 15, and 30 min was 75–85%, indicating little bilirubin entered the extrahepatic tissues. At 5 min, 50% of the dose (excluding trapped serum bilirubin-H3) was in the liver, a bilirubin concentration greater than in serum; biliary excretion of bilirubin was less than 3%. By 30–60 min, most of the label was excreted in the bile as intact, diazotizable and crystallizable bilirubin. Bilirubin-H3 appeared principally in the hepatic cell sap at a rate and concentration too high for an albumin-linked transfer. No differences in the distribution of isotope in subcellular fractions were detectable during the phases of uptake or excretion or when the quantity injected was increased 20–40 times. Thus, intracellular distribution was primarily a constant function of intracellular bilirubin concentration. When compared to in vitro experiments, significant amounts of bilirubin accumulated within the microsomes and the acid hydrolase-rich fraction (lysosomes) but not in the mitochondrial or nuclear fractions.
Epinephrine and organ blood flow: effects of hyperthyroidism, cocaine, and denervation
Authors: Wurtman Richard J. , Kopin Irwin J. , Horst Dale , Fischer Josef E.
Published: December 2017

The intravenous administration of 1 µg l-epinephrine increases the fraction of the cardiac output, measured by K42 uptake, which is delivered to the rat heart. This effect of the catecholamine is potentiated in hyperthyroidism or by a single injection of cocaine. One microgram of epinephrine causes no change in the fractional perfusion of the innervated rat salivary gland, but produces a marked decrease following chronic sympathetic denervation. Processes which interfere locally with the inactivation of circulating epinephrine by binding in sympathetic nerve endings thus potentiate its effects on regional perfusion.
Absorption of albumin from alveoli of perfused dog lung
Authors: Schultz Alvin L. , Grismer Jerome T. , Wada Shohachi , Grande Francisco
Published: December 2017

An iodinated albumin solution was instilled into the isolated perfused dog lung through a bronchial catheter. During the 5-hr period following instillation, 6.4% of the iodinated albumin dose was absorbed from the lung into the pulmonary perfusion blood. Fifty-seven percent of the absorbed radioactivity passed through an Amberlite resin column indicating that absorption occurred as large protein molecules. Fractionation of the plasma protein-bound radioactivity on a diethylaminoethyl-cellulose column demonstrated that absorption of the iodinated albumin from the lung had been predominantly as intact albumin molecules. Since the pulmonary lymphatic drainage was interrupted in the perfused lung, absorption of the albumin must have been directly from the alveoli into the pulmonary capillary blood. It is concluded that in the isolated lung the primary mechanism for removal of albumin from the pulmonary alveoli is slow absorption of intact albumin directly into the pulmonary blood.
Effects of arteriovenous fistula on systemic and pulmonary circulations
Authors: Nakano Jiro , Schryver Christian De
Published: December 2017

The effects of arteriovenous fistulas of different magnitudes on cardiovascular dynamics were studied in anesthetized dogs. It was found that A-V fistula decreases mean systemic arterial pressure, effective systemic blood flow, total and pulmonary peripheral resistances, whereas it increases heart rate, total cardiac output, stroke volume, left atrial pressure, pulmonary arterial pressure, and systemic peripheral resistance. The magnitude of the above hemodynamic changes was essentially proportional to the size of the fistula. At equivalent increments in total cardiac output produced by A-V fistula and blood transfusion, the former condition causes a greater increase in pulmonary arterial pressure than the latter, although both conditions decrease the pulmonary peripheral resistance by the same degree. It was also found that, at equivalent left atrial pressures, left ventricular stroke work with A-V fistula was greater than that with blood transfusion.
Initial cardiovascular adjustment to exercise in dogs with chronic cardiac denervation
Authors: Donald David E. , Shepherd John T.
Published: December 2017

In three normal dogs and in six dogs with cardiac denervation, there was a rapid increase in cardiac output (electromagnetic flowmeter) from the start of exercise. The denervated group showed an average delay of 25 sec in reaching plateau values of cardiac output and a deficit of 18% in the accumulated flow over the first minute of running; augmentation of output was due principally to a rapid increase in stroke volume since acceleration of heart rate was slow. In normal dogs, the augmentation of output came from a rapid increase in heart rate. The steady-state values for cardiac output and oxygen consumption were similar in the two groups as was the pattern of oxygen consumption in the first minutes of exercise and the manner in which the oxygen debt was repaid. This suggested that the denervated dogs extracted more oxygen from the circulating blood in the first moments of running. The changes with exercise in aortic blood pressure were similar in the two groups.
D-C potential changes in rabbit brain during slow-wave and paradoxical sleep
Authors: Kawamura H. , Sawyer C. H.
Published: December 2017

A study has been made of d-c potential changes in the brain during various states of sleep and wakefulness in the unrestrained unanesthetized rabbit with chronically implanted electroencephalogram and d-c electrodes. In preliminary acute experiments with an occipital bone reference electrode, the direction of the d-c potential change induced by stimulation of the midbrain reticular formation was the same in cortical and subcortical sites. With frontal and occipital bones as reference points the cortical d-c potential changes were similar to one another, but arousal stimuli readily elicited positive d-c shifts with the frontal reference electrode. In the chronic rabbit with an occipital reference electrode, cortical and hypothalamic d-c potentials shifted strongly to the positive side during slow-wave sleep and after injection of pentobarbital; from these conditions stimulation of the reticular formation induced a marked negative shift. During paradoxical sleep both cortical and subcortical d-c electrodes showed negative shifts similar to those seen during an arousal reaction. Grooming and eating elicited strong positive shifts in both cortical and hypothalamic d-c electrodes.
Contraction of lactating rat mammary gland in response to direct mechanical stimulation
Authors: Grosvenor Clark E.
Published: December 2017

Experiments were performed to determine whether the mammary gland myoepithelium of the lactating rat responds to direct mechanical stimulation. Rat pups on postpartum day 14 obtained 8.6 and 12.2% of the total extractable milk in the mammary glands in 31–41 min from anesthetized spinal cord-sectioned and sham-operated mothers, respectively. The mammary glands of both groups responded with a rise in intramammary pressure following mechanical stimulation of the skin overlying the cannulated mammary gland. The responses occurred after a latent period of 1–2 sec, attained an amplitude of 1–13 cm H2O, and lasted 8–18 sec. Summation of the responses did not occur. Temporary fatigue of the response could be induced with repetitive stimuli. Stimulation of mammary glands contralateral to or adjacent to the cannulated gland never produced a response in the cannulated gland. The exposed mammary gland responded to lightly applied mechanical stimulation with alveolar contractions confined to the area of stimulus contact. Each rat responded to intravenous oxytocin (25 mU) with a 10–29 cm H2O intramammary pressure rise of 4–31 min duration.
Effects of insulin on liver glycogen synthesis and breakdown in the dog
Authors: Bishop J. S. , Steele R. , Altszuler N. , Dunn A. , Bjerknes C. , de Bodo R. C.
Published: December 2017

Glucose-C14 was given intravenously in trace amount, as an initial dose followed by continuous infusion, to measure glucose-C12 release by the liver, and total glucose uptake from plasma by the tissues. The glycogen content of liver and the C14 incorporated into the glycogen and the nonglycogen constituents of liver were measured by analysis of percutaneous biopsy samples. Glucose 6-C14 was used to show that direct uptake and conversion to liver glycogen (without passage through three carbon intermediates) of tagged blood glucose molecules was the source of almost all the C14 of glycogen Insulin infusion at 0 1–0.2 U/kg per hr, iv, along with glucose to limit hypoglycemia, stopped glycogen loss, decreased glucose-C12 release, increased glucose uptake from the plasma by the tissues and brought about the incorporation of plasma glucose-C14 units into liver glycogen. Incorporation of C14 into the nonglycogen constituents of the liver was increased much less. Glucose infusion, presumed to stimulate endogenous insulin secretion, produced similar effects. In earlier periods of insulin infusion the outstanding hepatic effects were decreases in glycogen loss and glucose-C12 release. In later periods the outstanding further effect was a great increase in the use of plasma glucose-C14 for liver glycogen synthesis.
Physiological effects of the noble gases on frog sciatic nerve and gastrocnemius muscle
Authors: Gottlieb Sheldon F. , Weatherly J. M.
Published: December 2017

Evidence has been obtained which indicates that pressures up to 200 psi (gauge pressure) of helium, neon, nitrogen, or argon have no adverse effects on the ability of frog gastrocnemius muscles to produce tension when stimulated either directly or indirectly via the nerve. These gas tensions were without effect on nerve threshold and ability of nerve to conduct impulses. Experiments revealed that high tensions of gases do not result in fatiguing muscle at a faster rate than at 1 atm air. Krypton may have had a slight inhibitory effect on muscle ability to produce tension. Xenon or nitrous oxide, 100 psi, exerted a profound inhibitory effect on ability of gastrocnemius muscles to produce tension. These two gases appeared to have primarily a direct effect on muscle. On isolated sciatic nerve preparations, it was found that 100 psi xenon or 80 psi nitrous oxide exerted a slight depressing effect on nerve excitability. As the Pxe or Pn2o increased, nerve excitability decreased at a more rapid rate. The decreased nerve excitability was completely reversible.
Muscle stretch and theories of contraction
Authors: Alexander Robert S. , Johnson Peter D.
Published: December 2017

Frog sartorius muscle was loaded with a small cup to which mercury could be added or removed with a motor-driven syringe to achieve dynamic loading cycles. Intermittent stimulation during the loading and unloading cycle very significantly reduced the creep of the resting muscle. Analysis of the data indicates that contraction acts to reset the resting length of the muscle system as well as evoke the contractile response. On the basis of the available evidence, it is suggested that a resetting of the cross linkages between the myosin rods and the actin filaments during contraction is the most plausible explanation of this interaction between the contractile mechanism and the viscoelastic state of the resting muscle.
Functional separation of adrenergic and cholinergic fibers to skeletal muscle vessels
Authors: Dorr Lawrence D. , Brody Michael J.
Published: December 2017

The hypothesis that sympathetic innervation to skeletal muscle vasculature contains functionally distinct adrenergic and cholinergic fibers was investigated utilizing the dog isolated perfused gracilis muscle. The use of hemicholinium in an attempt to abolish cholinergic dilatation, but not adrenergic constriction, in response to intermittent nerve stimulation was not successful. Continuous nerve stimulation produced vasoconstriction which was maintained for the duration of stimulation. Conversely, when cholinergic vasodilatation was unmasked, continuous stimulation resulted in a dilator response which disappeared rapidly. These experiments suggested that release of the adrenergic transmitter could not be dependent upon an intermediate cholinergic link in the sympathetic nerve. This postulate was supported further by experiments utilizing electrical stimulation of medullary vasoconstrictor areas. Whereas cholinergic vasodilatation was unmasked routinely by peripheral stimulation following reserpine, guanethidine or ß-TM 10, this response was never seen when medullary vasoconstrictor neurons were activated following these agents. It was concluded that sympathetic cholinergic nerves to skeletal muscle vessels possess a purely vasodilator function, and do not play an intermediate role involving release of the adrenergic transmitter.
Role of cerebral fluids in control of respiration as studied in unanesthetized goats
Authors: Pappenheimer J. R. , Fencl V. , Heisey S. R. , Held D.
Published: December 2017

Respiratory responses to inhaled CO2 were measured in unanesthetized goats during repeated perfusions of the ventriculocisternal system through chronically implanted cannulas. [HCO3–] and pH were measured in carotid loop blood and cisternal outflow. Average steady-state alveolar ventilation increased fourfold when cerebrospinal fluid (CSF)-[HCO3–] was reduced from 30 to 15 mm/liter at constant, normal CO2 pressure or threefold when CSF pH changed from 7.32 to 7.21 at constant, normal CSF-[HCO3–]. Sensitivity was two- to sevenfold greater than reported for anesthetized animals. At constant CSF pH the ventilatory response to inhaled CO2 was 60% of the isobicarbonate response. Pco2 in cisternal outflow was shown to approximate that in cerebral tissue. HCO3– flux was measured as a function of CSF-[HCO3–] and concentration profiles between CSF and capillary blood were considered. Alveolar ventilation is a single linear function of [H+] in tissue fluid located two-thirds to three-fourths of the distance along the functional concentration gradient of HCO3– between CSF and blood at all values of Pco2 and CSF-[HCO3–] which we investigated.
Tolerance of dog lung to hyperthermic perfusion
Authors: Reed William A.
Published: December 2017

Hyperthermia of the left lung of the dog was produced by pulmonary artery perfusion in 29 animals. It was found that the lung tolerates tissue temperatures up to 43 C for periods as long as 60 min without significant permanent disturbance of structure or function as measured by blood gas analysis, angiography, and contralateral pulmonary artery ligation. Elevation of the lung temperature above 43 C for periods longer than 10–12 min resulted in partial or total destruction of pulmonary tissue. Data are presented regarding perfusion techniques, factors affecting lung tolerance to hyperthermia, and possible areas for future study.
Experimental heart block: effect on myocardial catecholamine concentration
Authors: Kaiser George C. , Jellinek Max , Cooper Theodore , Hanlon C. Rollins
Published: December 2017

Surgically induced complete heart block in the dog results in decreased levels of myocardial catecholamines. Sham operations which involve atriotomy and manipulation of the atrial septum cause less significant changes. These reductions in myocardial catecholamine levels may be due to destruction of adrenergic, intracardiac nerves or to a relatively increased utilization of catecholamines.
Metabolism of the renal medulla
Authors: Bernanke David , Epstein Franklin H.
Published: December 2017

Slices of the inner medulla of kidneys removed from hydropenic dogs were incubated with glucose and succinate under aerobic and anaerobic conditions. When theoretical maximum ATP generation was calculated from oxygen uptake and lactate production, the calculated energy production from oxidative degradation of glucose was twice that from glycolysis. Hypertonic solutions of NaCl and urea, in concentrations comparable to those present in vivo, depressed both lactate production from glucose and oxygen uptake in succinate to the same extent. Studies of CO2 generation by medullary slices from labeled glucose in 100% O2 showed a C1/C6 ratio of 3.7, compared to 1.7 for cortex. It is suggested that oxidative metabolism may play a critical role in the renal medulla of intact animals in providing energy for active transport of sodium and thereby facilitating the process by which urine is concentrated.
Fatty acid metabolism in segments of rat intestine
Authors: Porte Daniel , Entenman Cecil
Published: December 2017

The in vitro metabolism of albumin-bound palmitic acid-1-C14 by segments of small intestine was studied. Tissue uptake, esterification, and oxidation of the fatty acid were measured separately and found to respond independently to altered incubation conditions. Uptake was reversible, and did not require glucose or oxygen. It was not inhibited by fluoride or arsenate. Esterification required both glucose and oxygen, but was unaffected by insulin. It was depressed by succinate and almost completely inhibited by fluoride and arsenate. Oxidation was a minor fate for fatty acid. It was independent of glucose but inhibited by succinate, fluoride, and arsenate. Sodium taurocholate stimulated uptake, but not esterification, as has been previously reported. The possible significance of the reversible tissue uptake reaction is discussed.
Effect of thyrotropin and thyroxine on serum malic and isocitric dehydrogenases
Authors: Benson S. G. , Murphy L. J. , Klitgaard H. M.
Published: December 2017

The effect of altered levels of thyrotropin and thyroxine on NAD- and NADP-linked enzyme systems in the rat was studied. Serum malic and isocitric dehydrogenases were determined in normal, iodine-deficient, thyroidectomized, thyroxine-treated, thyroxine- and TSH-treated, and hypophysectomized animals. Serum malic dehydrogenase was found to be significantly increased in those metabolic states where an elevation of TSH could be predicted. This change in enzyme activity appeared to be independent of expected circulating thyroxine levels. Serum isocitric dehydrogenase was unaffected by the above treatments. Thyrotropin did not appear to regulate directly serum malic dehydrogenase activity. The physiologic significance of these findings is not known.
Weak electrotonic interaction between neighboring visceral smooth muscle cells
Authors: Sperelakis Nick , Tarr Merrill
Published: December 2017

The electrotonic spread of current was determined by double microelectrodes cemented at various distances. A bridge circuit enabled transmembrane potentials to be recorded at zero distance from injected current. At interelectrode distances of 100 µ or greater, with the electrodes oriented parallel to the cell axes, current flow of 20 x 10–9 amp through one intracellular electrode produced almost no change in potential at the second electrode. At interelectrode distances of 40 µ or less, similar currents through a given electrode pair produced either a substantial or a small change in potential depending on the impalement. With transverse electrode orientation, no substantial interactions occurred at distances of 17 µ or greater. Various criteria, including the congruous decline in resting potential on both channels, indicated when both electrodes impaled the same cell. The degree of electrotonic spread did not depend on the interelectrode distance per se at close distances. Thus, current flow through one cell does not have substantial effect on the transmembrane potentials of adjacent cells.
Cardiac pacemaker potentials at different extra- and intracellular K concentrations
Authors: Vassalle Mario
Published: December 2017

Transmembrane potentials were recorded from mammalian Purkinje fibers. Adding saccharose to the bathing solution slowed the spontaneous rate, probably as a result of cell shrinkage and an increase in the intracellular K concentration. An opposite result was found with hypotonic medium. In solutions containing 5.4 mm K the fibers were quiescent. Lowering K to 2.7 mm left the membrane resting potential unchanged but decreased the membrane conductance to half. There was only a minor effect of extracellular K on membrane conductance during the plateau of the action potential. Spontaneous firing regularly started when extracellular K was reduced to or below 2.7 mm. This was preceded by subthreshold oscillations which increased in amplitude. A low K conductance associated with a sizeable difference between membrane potential and potassium equilibrium potential seem to be essential for spontaneous activity to occur in cardiac tissue.
Vascular resistance of dog foreleg during hemorrhagic shock
Authors: Familiar Robert G.
Published: December 2017

Anesthetized dogs were submitted to conventional bleeding and reinfusion procedures so as to be able to compare vascular pressure gradients in the forelimb during acute hemorrhage with those recorded subsequently during the development of normovolemic shock. In some animals venous outflow from the limb was recorded to permit calculation of vascular resistances. The results demonstrate a marked increase in arterial and small vessel resistance during shock as compared to the changes observed in acute hemorrhage. Venous resistance also was appreciably greater during shock than during acute hemorrhage, which would argue against the possibility that the hemodynamic failure in shock might relate to a generalized collapse of venomotor tone. The data also show a tendency toward elevation of large vein pressure in shock, interpreted as signifying some degree of cardiac failure.
Relations among activity, blood flow, and vascular state in skeletal muscle
Authors: Wright D. L. , Sonnenschein R. R.
Published: December 2017

The relation between stimulus interval and performance of skeletal muscle was investigated under conditions of controlled and spontaneous blood flow. Vascular resistance, arteriovenous oxygen saturation difference, oxygen consumption, and peak isometric tension and blood flow were used as indices of muscle performance. In all cases vascular resistance decreased while oxygen consumption increased as the stimulus interval was shortened. The relative contributions of alteration flow (where permitted) and alteration of arteriovenous oxygen difference to changes in oxygen consumption were assessed. The latter proved to be the more important contributor. The apparent oxygen cost per unit of tension change rate decreased to a nearly steady level as the stimulus interval shortened. Changes in these variables brought about by intra-arterial infusion of acetylcholine or d-tubocurarine were shown. The results illustrate some features of the myovascular interaction which occurs during muscular activity. A model of the blood flow-oxygen consumption relation, based on considerations of oxygen extraction, is presented.
Fibrinogen destruction in the cadaver: Effects of antemortem stress and inhibitors
Authors: McKenzie J. M. , Celander D. R. , Guest M. M.
Published: December 2017

The blood of healthy, well-fed dogs remained completely fluid following hypoxic death. Clots were not observed for several hours after death and fibrinogen levels fell gradually. Injections of heparin or antifibrinolysin into unstressed dogs just before death impeded the disappearance of fibrinogen. In dogs from the same group which had been exposed to a mild stress a solid coagulum formed in the heart and major blood vessels soon after death. Prothrombin activity and fibrinogen concentration increased and accelerator globulin levels fell during the stress period. The results indicate that postmortem loss of fibrinogen in the dog is a normal occurrence in the unstressed animal and that a stress involving little or no tissue trauma may cause a postmortem coagulation of the blood. Results of experiments involving antemortem injections of heparin or antifibrinolysin indicate that both the fibrinolytic and coagulation systems must be intact if destruction of fibrinogen is to proceed in the cadaver.
Role of transmural pressure in local regulation of blood flow through kidney
Authors: Haddy F. J. , Scott J. B.
Published: December 2017

In the kidney of the anesthetized dog, the pressure in an occluded hilar lymphatic vessel was used as an index of tissue pressure. While elevation of renal vein pressure produced a large rise in lymphatic pressure, reduction of renal artery pressure had little effect. Similarly, while elevation of vein pressure at constant flow produced an almost equal rise in lymphatic pressure, large changes in blood flow and hence artery pressure had little effect, despite evidence of local regulation of resistance. Intra-arterial injection of vasoactive agents at constant flow, which produced large changes in renal artery pressure, had little effect on lymphatic pressure. Sudden transient increase in renal blood flow sometimes produced changes in perfusion pressure which could have resulted from active constriction subsequent to rise in transmural pressure. These findings provide little support for the tissue pressure theory of autoregulation but suggest that tissue pressure does participate in the vascular response to elevated vein pressure. The study also provides some evidence for a vascular myogenic response to change in renal vascular transmural pressure.