bluuebunny/crossref_metadata_2025 huggingface dataset:
Rate and affinity in human red blood cell sugar transport
Authors: LeFevre Paul G.
Published: December 2017

After addition of any of six penetrant aldoses to suspensions of washed human erythrocytes at body temperature, serial samples were taken for analysis of sugar distribution between cells and medium. The progress of equilibration was analyzed in terms of a simple carrier model previously proposed for monosaccharide transport in these cells, by which the sugar movements are characterizable by two constants, one of which defines the affinity of the sugar for the transport system's reactive site, the other expressing the rate of diffusion of the sugar-carrier complex through the cell membrane. The experiments show the latter constant to be nearly invariant among the several sugars, although the affinity constants and the net transfer times cover a wide range. This finding implies that the identity of the passenger sugar molecule does not seriously influence the diffusivity of the sugar-carrier complex. Certain contrary results recently published are questioned on the basis of an oversimplification in the formal analysis by which the data were interpreted.
Effect of bilateral nephrectomy on pressor response to renin
Authors: Blaquier Pedro , Hoobler Sibley W. , Schroeder John , Gomez Arthur , Kreulen Tom
Published: December 2017

In rats treated with ganglion-blocking agents, potentiation of the pressor response to renin appears from 4 to 24 hr after bilateral nephrectomy has been performed, but the response to norepinephrine and angiotensin remains unchanged. Further studies support the theory that there is an activator or an inhibitor which influences the renin-angiotensinogen reaction. Production or storage of such a substance seems to be in the renal tissue.
Alterations in food and water intake after hypothalamic lesions in the rat
Authors: Smith Roland W. , McCann S. M.
Published: December 2017

Electrolytic lesions in the lateral hypothalamus produced aphagia and adipsia. One rat remained adipsic until sacrifice 283 days after operation; 11 rats with lesions continued to drink water while refusing ground laboratory chow. This effect lasted until sacrifice, 8–13 days postlesions, suggesting that areas regulating water and food intake are separable. Lesions designed to induce diabetes insipidus were produced in rats in which variable renal water loss had been eliminated by prior nephrectomy. Rats with lesions drank significantly more than nephrectomized controls during the 2-day observation period. The experiment was repeated, but food was withheld and controls were subjected to sham hypothalamic operation. In this group water intake was greater and weight loss less in rats with lesions than in sham-operated controls, though the difference was less than that in the presence of food. Although the difference in water intake was small, the results suggest that destruction of an inhibitory drinking center may contribute to polydipsia in diabetes insipidus. Water intake may be stimulated by lateral and inhibited by medial areas in the hypothalamus.
Monopolar and bipolar stimulation of the brain
Authors: Stark Paul , Fazio Giovanni , Boyd Eugene S.
Published: December 2017

Intracranial self-stimulation experiments in the dog using a two-wire electrode, with each wire used as a monopolar electrode and the combination as a bipolar electrode, show that monopolar stimulation may produce either a higher or a lower rate of response than that produced by bipolar stimulation. A theoretical consideration of the changes in current density around the electrode when it is changed from a monopolar to a bipolar electrode shows that such differences are to be expected. The exact location of the structure being stimulated with reference to the two electrode tips will determine whether the structure is subjected to a higher current density on monopolar or on bipolar stimulation.
Anaerobic myocardial metabolism
Authors: Shea Thomas M. , Watson Richard M. , Piotrowski Stanley F. , Dermksian George , Case Robert B.
Published: December 2017

Metabolic changes occurring during coronary insufficiency were studied in ten dogs by progressively reducing the rate of blood flow to the perfused left main coronary artery, while maintaining aortic pressure constant. Seven animals exhibited a net myocardial lactate production at low coronary flows, averaging 2.8 mg/min. The remaining animals showed a decreased lactate uptake which fell from an average 40 to 1.8% at the lowest flows. A rise in left atrial pressure occurred coincident with the alteration of lactate metabolism in all animals. Calculated coronary vascular resistance fell from an average 2.33 to 1.24 units, and in each case reached the minimum value at the onset of the metabolic changes. These results indicate that left ventricular failure, anaerobic myocardial metabolism, and maximal coronary arteriolar dilatation occur at the same time during inadequate myocardial blood flow.
Turnover rates of acid-soluble nucleotides in hind leg muscles of dystrophic mice
Authors: Zymaris Michael C. , Saifer Abraham , Volk Bruno W.
Published: December 2017

The turnover rates of the acid-soluble nucleotides in skeletal muscle were compared in mice with dystrophic muscularis and in normal mice. At various time intervals after a subcutaneous injection of radioactive phosphate, both dystrophic mice and their normal littermates were sacrificed. The nucleotides were extracted from the hind limb musculature, chromatographically resolved, and determined quantitatively. Specific activities were calculated from the radioactivity measurements made on the separated acid-soluble nucleotides. The turnover rates for the ADP, DPN, and GTP fraction (absolute or fractional) were significantly higher in the muscle of the dystrophic mice than those obtained for normal mouse muscle. Little or no differences were found in the fractional turnover rates of the AMP, ATP, and GDP components derived from both types of tissue. Studies dealing with the rate of absorption of radioactive phosphate, as well as the phosphate levels in the plasma and whole blood of these animals, were included.
Parietal cell mass and distribution in stomachs of Wistar rats
Authors: Bralow S. P. , Komarov S. A.
Published: December 2017

Parietal cell mass (PCM) and distribution of parietal cells were studied by the technique of Cox and Barnes ( Proc. Soc. Exptl. Biol. Med. 60: 118, 1945) except that mucosal sections were excised perpendicular to the antral margins rather than parallel to the curvatures. Highly significant correlations were found between PCM with age ( r = 0.9522) and with body weight ( r = 0.9319) in animals between 30 and 112 days of age. Each of the factors determining PCM—parietal cell count per unit area, surface area, glandular mucosal thickness and volume—was closely associated with age with its own specific pattern which, in all cases, could be accurately expressed by parabolic regressions. Distribution of parietal cells with respect to area or volume was not uniform or subject only to random variation, as reported by others; but cell counts were found to be a second degree polynomial function of the distance from antral margin.
Vascular resistance and arterial pressure in autoperfused dog hind limb
Authors: Hanson Kenneth M. , Johnson Paul C.
Published: December 2017

Arterial and venous vascular resistance was studied in 30 isolated dog hind limbs. The preparations were autoperfused from the contralateral femoral artery through a short piece of polyethylene tubing. By application of the isogravimetric technique of Pappenheimer and Soto-Rivera the capillary pressure was determined and the arterial and venous resistances were separately calculated. As arterial pressure in the limbs was progressively reduced from approximately 100 mm Hg down to 20 mm Hg the arterial resistance decreased in 25 of the 30 experiments. The reduction in resistance was particularly evident at arterial pressures below 50 mm Hg. The venous resistance remained relatively constant as the arterial pressure was reduced; a significant rise was seen in only three experiments. Arterial and venous blood oxygen and carbon dioxide contents were determined at various levels of blood flow in ten of the experiments. In general, as the blood flow was decreased, venous oxygen content decreased and carbon dioxide content increased, while oxygen consumption fell. It is concluded that autoregulation of blood flow in the hind limb may, in part, be due to tissue hypoxia. It cannot be explained by the tissue pressure hypothesis.
Effect of structural analogues on intestinal accumulation of glycine
Authors: Spencer Richard P. , Weinstein Janet , Sussman Arthur , Bow Ted M. , Markulis Mary Anne
Published: December 2017

Glycine uptake (1 x 10–3 m) by hamster intestinal segments in vitro was studied after 20 min of incubation both in the absence and presence of various analogues (5 x 10–3 m). A variety of chemical relatives of glycine with modifications of the —COOH, —NH2, or α-hydrogen groups or with double modifications (such as ethanol) were without effect on glycine accumulation. Thus under these conditions glycine could not be displaced by its analogues. Three compounds, however, all α-amino acids, were effective in depressing glycine uptake (allylglycine, α-phenylglycine, l-alanine). Data are presented showing that two of these inhibitors are themselves transported and hence likely competed with the amino acid transport system. α-Aminoisobutyric acid and N-methylglycine, both known to be transported by the gut, did not interfere with glycine accumulation. In addition to oxalic acid, other succinic dehydrogenase inhibitors (hydrocinnamic acid, glutaric acid, malonic acid at 5 x 10–3 m) were without major depressant effect on glycine accumulation by this system.
Response of chronic denervated gastric pouches of rats to food and histamine
Authors: Alphin R. S. , Lin T. M.
Published: December 2017

The volume output and hydrochloric acid secretion from the denervated gastric pouch of the rat in response to food and histamine were studied. Food was given at three dose levels—1.25, 2.5, and 5.0 g—and histamine (as free base) was given subcutaneously at dose levels of 0.34, 0.7, 1.4, and 2.8 mg/kg. The results show that the chronic denervated gastric pouch of the rat responds in a graded manner to both food and histamine in a certain dose range. Although rats are not as sensitive to histamine as humans and dogs, the chronic gastric pouch of the conscious rat is far more sensitive to histamine than the stomach of the pyloric-ligated or anesthetized rat. The feasibility of using this preparation for testing the effect of agents inhibiting food- or histamine-stimulated gastric secretion is discussed.
Micropuncture study of renal excretion of water, K, Na, and Cl in Necturus
Authors: Bott Phyllis A.
Published: December 2017

Inulin, sodium, potassium, and chloride were determined on identical samples of serum and fluid collected from the kidney tubules of Necturus under urethan anesthesia. Inulin fluid-serum ratios obtained were as follows: highest ratios for proximal tubules approximated 2, indicating a reabsorption of about 50%, of filtered water; highest ratios for distal tubules were near 3.4; ratios for sodium remained near 1 in proximal tubules, tending to be lowest near the ends of the segments. There was an abrupt drop in sodium concentration in the early part (thin segment) of the distal tubules, which may be made possible by the better oxygen supply in this region. Chloride ratios rose to 1.12 in the proximal tubules and chloride concentrations fell over the same region, as did sodium. Potassium ratios remained close to 1 in the proximal tubules, indicating that up to one-half of the filtered potassium may be reabsorbed there. Distal tubule potassium ratios showed great variability, some being higher and some lower than 1.
Peptide synthesis in bone marrow: insulin and thyroxin effects
Authors: Necheles Thomas F.
Published: December 2017

Myeloid marrow was rapidly removed from femurs of fasting young rabbits, sectioned, and incubated in Krebs-bicarbonate-CO2-oxygen buffer with appropriate C14-labeled precursors. All manipulations were designed to preserve the architecture of the tissue. After 1 hr the protein or nucleic acid-adenine was isolated and purified. Insulin, 0.01 U/ml added in vitro, stimulated histidine-2(ring)-C14 incorporation into protein by 26 ± 1.4%; alkali-treated insulin was inactive. Thyroxin elicited a 49.4 ± 2.1% stimulation at an optimum concentration of 10–7 m. Triiodothyronine, but not diiodothyronine, also had a significant effect. Insulin increased incorporation of carbon from adenosine-8-C14 into adenine of ribonucleic acid and deoxyribonucleic acid. Thyroxin, on the other hand, was without consistent effect on this process. Thyroxin stimulated significantly the incorporation of C14 of glycine-2-C14 into adenine. The possibility that part of the anabolic effect of thyroxin on bone marrow may arise from a stimulus to incorporation of precursors into purines is suggested.
Adrenal cortex and neurohypophyseal deficiency in salt and water homeostasis of rats
Authors: Friedman Sydney M. , Sréter Frank A. , Nakashima Miyoshi , Friedman Constance L.
Published: December 2017

The role of adrenal cortex and neurohypophysis in controlling the equilibrium distribution and handling of water, sodium, and potassium was studied for a 2-week period in rats deprived of these glands. Adrenal deficiency is characterized by a loss of sodium from both extracellular and intracellular compartments (gastrocnemius, aorta) and a shift of water into cells. The sodium gradient, [Na]o/[Na]i, remains relatively unchanged. There is a marked fall in the potassium gradient, [K]i/[K]o, due in large part to the shift of water and in smaller part to a translocation of potassium. Neurohypophyseal deficiency is characterized mainly by an increase in intracellular sodium both in amount and concentration. A salt load administered by stomach tube tends to be excessively retained when cell sodium is low and excessively rejected when it is high. Animals deprived of both adrenal and neurohypophyseal function show an intermediate pattern. The pattern of salt and water distribution in either deficiency thus depends in part on the activity of the remaining gland. It is suggested that adrenal insufficiency and diabetes insipidus are counterpoint states.
Combined effects of Pitressin and aldosterone on adrenal and neurohypophyseal deficiency
Authors: Friedman Sydney M. , Sréter Frank A. , Nakashima Miyoshi , Friedman Constance L.
Published: December 2017

The equilibrium distribution of water, sodium, and potassium was studied in rats given Pitressin tannate with aldosterone for 2 weeks in the absence of both adrenal and neurohypophysis. The characteristic effects of each hormone can be elicited in the presence of the other. The final equilibrium in each case is a close approximation of the sum of the opposing actions.
Inhibition of adrenal secretion of epinephrine during infusion of catecholamines
Authors: Robinson Robert L. , Watts Daniel T.
Published: December 2017

The effect of intravenous infusion of epinephrine or norepinephrine on the secretion of epinephrine by the adrenal was studied in dogs. The epinephrine content of adrenal venous blood was assayed on the rat uterus, automatically stimulated. The infusion of epinephrine or norepinephrine at a rate which produced an increase in blood pressure inhibited the output of epinephrine by the adrenal. If the rate of infusion of catecholamines was too slow to increase the blood pressure, or if the increase in blood pressure was prevented by a pressure compensator, secretion of epinephrine was not inhibited. A good correlation exists between the per cent decrease in epinephrine secretion and the per cent increase in blood pressure produced by infusion of catecholamines. It appears that the inhibition of epinephrine secretion during infusion of catecholamines is produced reflexly by the induced increase in blood pressure. In two experiments the aortic epinephrine concentration exceeded the adrenal venous epinephrine concentration during infusion of epinephrine, suggesting an uptake of epinephrine by the adrenal gland.
Effect of stretch on O2 consumption of resting and active frog sartorius muscle
Authors: Whalen W. J. , Collins L. C. , Berry H.
Published: December 2017

Oxygen consumption and resting and developed tension were measured simultaneously while the length of the muscle was increased by known increments. The Qo2 of resting muscle increased about 1% for each 1% extension beyond the relaxed length. Both resting tension and length were directly related to Qo2. In a stimulated muscle, Qo2 and frequency of contraction showed a highly significant correlation. The Qo2 of a stimulated muscle increased as the length and total tension (developed plus resting) increased. Neither Qo2 nor the increment in Qo2 above the resting level correlated significantly with developed tension. These latter findings differ from the results predicted from heat-liberation experiments. The results found here are not markedly different from those we found in heart muscle.
Bulk flow and diffusion in the cerebrospinal fluid system of the goat
Authors: Heisey S. R. , Held D. , Pappenheimer J. R.
Published: December 2017

Ventriculocisternal perfusions were carried out on chronically prepared, unanesthetized goats. Measurements were made of steady-state rates at which inulin, fructose, creatinine, urea, K, Na, and labeled water (TOH) were removed from perfusion fluid at various hydrostatic and osmotic pressures. The ventricular system is virtually impermeable to inulin. Inulin is removed from subarachnoid spaces by bulk absorption at rates which vary linearly with hydrostatic pressure. Net absorption ceases at –15 cm H2O. Rate of net formation of cerebrospinal fluid (CSF) is equal to inulin clearance plus the difference between outflow and inflow rates; normally it averages 0.16 cm3 min–1 and is essentially independent of hydrostatic pressures in the range –10 to +30 cm H2O. Net rate of formation is linearly related to total osmotic pressure differences between plasma and CSF. The coefficient of osmotic flow is greater than that measured from diffusion of TOH, as in other porous membranes. Passive permeability characteristics resemble those of the vasopressin-treated toad bladder.
Microelectrode study of dorsal spinocerebellar tract
Authors: Kitai S. T. , Morin F.
Published: December 2017

The dorsal spinocerebellar tract (DSCT) at C-1, C-2, and the lower medulla level was studied with microelectrodes in lightly anesthetized cats. All responses were obtained from the stimulation of the ipsilateral side of the body. The sensory modalities activating the total of 242 fibers studied were touch (53%), pressure (31%), touch and pressure (2%), and joint movement (14%). Responses to touch were more numerous for the forelimb, while responses to pressure and to joint movement were more numerous for the hind limb. Regardless of modalities the trunk was significantly less represented in the DSCT than the limbs. Tactile and pressure peripheral fields were restricted (i.e., a few hairs of a paw) and large (i.e., more than one segment of a limb). The ratio of restricted to large fields for touch was 7 to 1, and for pressure 5 to 1. Fibers activated by joint movements adjusted their frequency of firing to the degree of displacement and to the rate of the movement. There was no evidence for a separate anatomical segregation of fibers responding to a single sensory modality.
Hormonal factors in the rat's tolerance to altitude
Authors: DeBias Domenic A.
Published: December 2017

The survival period of adrenalectomized rats, which are less tolerant than normal rats to reduced barometric pressure (equiv. to altitude of 27,800 ft), can be extended when the animals are pretreated with adequate amounts of cortisol. Pretreatment of adrenalectomized animals with somatotropin (0.5 mg/100 g body wt.) did not have any significant effect on tolerance to simulated altitude, but when somatotropin was administered simultaneously with a subeffective dose of cortisol, tolerance to altitude was significantly increased. Thyroidectomy did not have a beneficial effect on survival of adrenalectomized animals, but pretreatment of adrenalectomized-thyroidectomized rats with 3 mg cortisol, which is inadequate to protect the adrenalectomized animal against exposure to simulated altitude, significantly increased survival rate. A possible mechanism whereby lesser amounts of cortisol are effective in prolonging survival of thyroidectomized-adrenalectomized rats exposed to low barometric pressure may be a decrease in catabolism of the steroid in hypothyroid animals.
Cholinesterase and active sodium transport in frog skin
Authors: Koblick D. C. , Goldman M. H. , Pace Nello
Published: December 2017

In each of a series of 16 experiments, unpigmented ventral skin was removed from a frog of the species Rana pipiens. The skin was divided into three parts; two of these were used for duplicate determinations of cholinesterase activity, the third for measurement of bioelectric activity as manifested by the short-circuit current, the two kinds of measurement being made during the same time period. The product moment correlation coefficient for these two variables was found to be +0.87. The best fitting straight line, calculated for these data by the method of least squares, is represented by the equation: I = –5.7 + 19.5 R, where I is the short-circuit current in microamperes per square centimeter and R is the cholinesterase activity in micromoles per square centimeter per hour.
Differential effect of fixed acid and carbon dioxide on ammonia toxicity
Authors: Warren Kenneth S , Schenker Steven
Published: December 2017

Changes in pH have been found to alter the toxicity of ammonia. Most of the studies have been performed with fixed acid or base, but the use of CO2 has recently attracted attention. Theoretically, however, these two methods of altering pH may not have similar effects. Fixed acid or base will penetrate tissue barriers poorly, thus causing an alteration in extracellular fluid-intracellular fluid pH gradient and a change in ammonia distribution. The alteration of pH gradient on inhalation of CO2 is usually of a much smaller degree, as the gas crosses membranes with ease. Consequently, the redistribution of ammonia will tend to be less marked. A comparison was made, therefore, between the effect on ammonia toxicity of equivalent plasma pH changes produced by both methods. The greater the reduction of blood pH with HCl infusion the greater the degree of protection afforded to mice against ammonium bicarbonate toxicity. Similar changes in pH produced by CO2 inhalation either had no effect or exacerbated ammonia toxicity. Concomitantly, HCl caused a marked diminution in the passage of a test dose of ammonia into the brain whereas CO2 had little or no effect.
Water and chloride exchange across the gall bladder of the anesthetized dog
Authors: Kang Doo Hee , Hong Suk Ki
Published: December 2017

The gall bladder was cannulated in the anesthetized dog and various solutions were introduced into it, in order to study the exchange characteristics of the gall bladder wall to water, as well as to various solutes. The gall bladder wall was highly permeable to urea and less to NaCl while it was not to sucrose. When various sucrose solutions were introduced, the fluid volume within the gall bladder varied as a function of the existing osmotic pressure gradient, indicating that the gall bladder under some conditions resembles an osmometer. The gall bladder wall was able to absorb chloride against a tenfold concentration gradient. However, this ability to absorb chloride was abolished in presence of 10–2 m monoiodoacetic acid, but not in presence of 2,4-DNP, NaF, or KCN, suggesting that the chloride absorption is carried out by glycolytic energy. Since the gall bladder bile, as well as the hepatic bile, was isosmotic with plasma, it is concluded that the primary event of concentrating bile within the gall bladder is the active absorption of NaCl accompanied by water.
Effects of ouabain and calcium on potassium balance of isolated guinea pig ventricle
Authors: Kahn J. B. , Eakin Edwin , Levi Don E.
Published: December 2017

Isolated guinea pig ventricles were perfused as follows: A—45 min with normal Krebs-Ringer solution containing tracer amounts of K42 (NKR*); B—15 min with NKR*, 15 min with KR* in which half the calcium was replaced with sodium (Ca/2-KR*), 15 min with NKR*; C—15 min with NKR*, 15 min with Ca/2-KR*, 15 min with Ca/2-KR* + 10–6 m ouabain; D—15 min with NKR*, 15 min with NKR* + 3.4 x 10–4 m pentobarbital (PB), 15 min with NKR* + PB + ouabain. K influx, net K loss, contraction height, and flow rate were determined, and K efflux was calculated. Decreasing the external calcium concentration ([Ca]e) decreased K efflux with no effect on K influx; restoring [Ca]e increased K efflux without affecting influx. Ouabain decreased K influx more than it decreased K efflux. If [Ca]e was constant, reducing the contraction height with PB did not affect K movements. These findings are consistent with the hypotheses that: 1) calcium and potassium can compete for fixed intracellular anionic binding sites and 2) calcium and ouabain produce their effects on K movements by different means.
Unequal right and left ventricular ejection with ectopic beats
Authors: Levy Jay M. , Mesel Emmanuel , Rudolph Abraham M.
Published: December 2017

Simultaneous right and left ventricular stroke volumes were measured with electromagnetic flow probes in open-chest, anesthetized dogs. Atrial ectopic beats with normal ventricular depolarization produced differences between right and left ventricular stroke output, although the right and left ventricular pressures were proportionately reduced to an equal extent. This imbalance in volume ejected was a result of the differences in diastolic level, related to peak systolic pressure, in the aorta compared with pulmonary artery. With ventricular ectopic beats, the stimulated ventricle failed to develop the same percentage of control pressure as did the contralateral ventricle. The difference between aortic and pulmonary flow was thus less marked with right ventricular ectopic beats, and exaggerated with left ventricular ectopic beats.
Effects of electrolytes on contractility of artery segments in vitro
Authors: Hinke J. A. M. , Wilson M. L.
Published: December 2017

A 3-cm length of the ventral rat tail artery was excised and mounted in a way that permitted fluid under pressure to flow through its lumen. Muscle activity of the wall was associated with narrowing of the segment and reduction in flow rate at a given intraluminal pressure. The contractility to natural vasopressor agents was studied in normal Krebs solution, in high [K+]0 solutions, and in low [Na+]0 Krebs solutions. Identical responses were produced with 0.1 µg/ml epinephrine, 0.5 µg/ml norepinephrine, 0.4 µg/ml angiotensin II, and 2.5 mU/ml Pitressin, in normal Krebs solution. High [K+]0 Krebs solutions alone constricted the arterial segment and low [Na+]0 Krebs solutions alone distended (relaxed) the arterial segment. High [K+]0 solutions potentiated the response to all four vasopressor agents. In low [Na+]0 sucrose-Krebs, the constrictor response was unaltered for norepinephrine and epinephrine but was reduced for angiotensin II and Pitressin. In low [Na+]0 Li+-Krebs and choline+-Krebs, the constrictor response to norepinephrine was potentiated.
Stop-flow analysis of creatinine excretion in the dog
Authors: Swanson Robert E. , Hakim Ali A.
Published: December 2017

Urinary excretion patterns of creatinine and inulin under stop-flow conditions in male mongrel dogs were compared. Evidence for a weak creatinine secretory mechanism at the proximal tubule level include the following: 1) Exogenous creatinine in the stop-flow samples appears prior to inulin when both are injected midway during a 10-min ureteral clamping period. 2) The ratio of creatinine/inulin U/P values (creatinine clearance ratio) shows a peak and a distribution coextensive with PAH/inulin clearance ratios. 3) Self-depression of the peak stop-flow creatinine clearance ratio was obtained at high plasma creatinine concentrations. 4) High plasma p-aminohippuric acid levels depressed the free-flow and peak stop-flow creatinine clearance ratios and, conversely, high plasma creatinine concentration depressed free-flow and peak stop-flow PAH clearance ratios (competitive inhibition). 5) Probenecid reduced free-flow and peak stop-flow creatinine clearance ratios (creatinine secretory mechanism blocked). The mean free-flow creatinine/inulin clearance ratios in 44 clearance periods was 1.2±0.1 (sd), compared to the peak stop-flow ratio of 1.8±0.4 (sd) (N = 20) at plasma creatinine concentrations less than 20 mg/100 ml.
Stimulus of leucine incorporation into perfused liver protein by insulin
Authors: Penhos J. C. , Krahl M. E.
Published: December 2017

Livers from 24-hr fasting sham-operated or partially pancreatectomized rats were perfused at 38 C with heparinized blood from normal 24-hr fasting rats. Leucine-1-C14, 1.6 x 105 counts/min per ml, and glucose to make the initial total concentration 2 mg/ml were added to the blood. Incorporation of leucine-1-C14 into protein proceeded linearly for 2 hr, then at a decreased rate. The leucine-1-C14 incorporated into protein over the initial 2-hr perfusion period decreased progressively as the time after partial pancreatectomy of the liver donors increased, up to 6 months. Insulin, 0.01 unit/ml, added to the perfusing blood stimulated leucine incorporation into protein of livers from rats partially pancreatectomized 3 months before (mean terminal blood sugar 160 mg/100 ml) but not into that of livers from the 6-month series (mean terminal blood sugar 315 mg/100 ml). No significant effect of insulin was obtained in any of the sham-operated groups. It is concluded that insulin added in vitro can stimulate incorporation of leucine into protein in livers from mildly diabetic, but not severely diabetic, rats.
Quantitative aspects of glucose metabolism in pregnant and nonpregnant sheep
Authors: Bergman E. N.
Published: December 2017

Labeled glucose was infused into four groups of ewes: nonpregnant fed; nonpregnant fasted; twin-pregnant fed; and twin-pregnant hypoglycemic and ketonemic. Mean glucose pool sizes were 157 and 127 mg/kg in nonpregnant and pregnant ewes, respectively, with decreased values in both fasting and hypoglycemia. Nonpregnant animals had glucose turnover rates averaging 4.0 g/hr (0.22 g/hr·kg3/4) when fed and only 2.7 g/hr (0.15 g/hr·kg3/4) after fasting. These values were only 60–80% of that of pregnant sheep, implying that glucose utilization due to twin-pregnancy was 20–40% of the total. The mean glucose space was about 27% of the body weight, indicating predominantly extracellular distribution of glucose even in hypoglycemia. In all animals about 8–10% of the exhaled CO2 was found to be derived from glucose oxidation and about one-third of the total glucose turnover was used for CO2 production. Comparisons of these data to values obtained from other mammals indicated further that there is a lower rate of glucose oxidation and metabolism in ruminants.
Prepyriform electrical activity after 250 r whole-body X irradiation in rats
Authors: Rosenthal Fred , Timiras Paola S.
Published: December 2017

Evoked and spontaneous electrical activity was recorded from the prepyriform cortex of rats with permanently implanted electrodes. Evoked responses were obtained by lateral olfactory tract stimulation. Measurements of the electrical activity were made daily for 10 days before and after 250 r of whole-body X irradiation. Radiation did not significantly alter spontaneous activity. On the other hand, irradiation produced a decrease in the latency of the evoked response and a reduction in the average voltage of the response to a test stimulus given 12–24 msec after a conditioning stimulus. The results were interpreted in terms of an increase in conduction velocity in the olfactory tract axons and a reduction of the action of prepyriform inhibitory elements after irradiation.
Effects of cyanide at different concentrations on single nerve fibers
Authors: Schoepfle Gordon M.
Published: December 2017

At a constant pH of 9.0, with continuous perfusion of tris-buffered Ringer's solution, free of HCO3 and PO4, the time course of cyanide depression of frog single nerve-fiber spike height is independent of cyanide concentration within a range of 1 or 2–10 mm NaCN. Similar results are obtained during a transient period of increased rate of cyanide depression induced by forced feeding. Maximal limiting responses obtained during hyperpolarization are constant throughout the 1st hr of cyanide action. These data are taken to indicate that cyanide depresses the steady-state level of the sodium conductance h factor before it produces any appreciable change in the Na equilibrium potential as a result of interference with the metabolically linked Na-K exchange mechanism. It is concluded that cyanide blocks a chain of reactions at a link remote from the step directly concerned with maintenance of sodium conductance.
Sinus bradycardia during injections directly into the sinus node artery
Authors: James Thomas N. , Nadeau Reginald A.
Published: December 2017

In over 90% of 800 experiments in 75 dogs injection directly into the sinus node artery produced sinus bradycardia. Studies to explain this phenomenon included control of temperature, pH, osmolarity, oxygen, and ionic content of injecting solutions. Although unphysiologic variations of any of these are known to produce marked alterations in the sinus mechanism, sinus bradycardia from injection still occurred when they were controlled. Neurogenic mechanisms were excluded by bilateral cervical vagotomy, and by direct perfusion of the sinus node with atropine, hexamethonium, and trimethaphan. Because of the unique anatomic structure of the sinus node, which completely surrounds its nutrient artery, it is suggested that the sinus bradycardia may simply be the consequence of distending the sinus node artery. Implications concerning autoregulation of the normal heart rate are discussed.
Sodium space and acid secretion in frog gastric mucosa
Authors: Davenport Horace W.
Published: December 2017

Inulin, arabinose, mannitol, choline, and sodium, but not radioiodinated serum albumin (RISA), penetrate a space of about 320 ml/kg in gastric mucosa of Rana pipiens. Sixty-three to seventy-eight per cent of the space not penetrated by RISA is reached by the others from the serosal side. Sodium is quickly eluted from the mucosa by sodium-free solutions, only 2 mEq/kg remaining after 1 hr. When sodium is replaced by choline or mannitol the mucosa can still secrete acid. In sodium-free solutions containing mannitol at 200 mm the tissue loses potassium and its ability to secrete, but when [K] of bathing solution is increased tissue potassium rises and secretion is possible. Optimal external [K] is 36 mm. Sodium is not essential for acid secretion; it passes through the highly permeable basal membrane of the oxyntic cells into an intracellular space where its major function is osmotic. Potassium is the more important ion for acid secretion.
Maximum alkaline (bicarbonate) output of the dog pancreas
Authors: Baron J. H. , Perrier C. V. , Janowitz H. D. , Dreiling D. A.
Published: December 2017

By cannulation of the major pancreatic duct in six dogs with chronic Thomas type duodenal fistulas, dose-response curves have been obtained for the volume and bicarbonate output of pancreatic secretion stimulated by secretin (Vitrum). With single rapid intravenous injections (0.5–15 U/kg) or continuous intravenous infusions (1–16 U/min), increased doses of secretin produced increased volumes of pancreatic juice and bicarbonate outputs up to a maximum. This maximum alkaline output of the pancreas was reached at doses ranging from 7.5– 12.5 U/kg for single injections, and 4–16 U/min for infusions. In each dog supramaximum doses led to a fall in juice volume and bicarbonate output, unaccompanied by side effects. With supramaximum doses or intravenous infusions lasting longer than 30–90 min, bicarbonate concentration fell independently of juice volume. The chloride concentration consistently varied inversely with bicarbonate concentration. The sodium, potassium, and amylase concentrations were unaffected by rate of flow. Repeated measurements of basal secretion showed considerable variation. Coefficients of variation were low for repeated measurements of secretin-stimulated secretion, the most repeatable measurement being the maximum output of pancreatic juice in the first 15 min after a single injection which, in each of the six dogs, was almost identical to the plateau 15 min during infusion.
An attempt to demonstrate cerebral anoxia during hyperventilation of anesthetized dogs
Authors: Cain Stephen M.
Published: December 2017

Eight anesthetized, curarized dogs were ventilated to alveolar Pco2 of 40, 20, and 10 mm Hg. Blood samples were drawn from an artery and sagittal sinus and analyzed for Pco2, Po2, pH, hemoglobin saturation, lactic acid, and pyruvic acid. The vasoconstriction of the cerebral vessels was clearly demonstrated by the increased arteriovenous difference in hemoglobin saturation which increased on the average from 26% to 45% and to 48% during the two periods of hyperventilation. Sagittal sinus Po2 declined from 41 mm Hg during the control to 29 and to 25 mm Hg with hyperventilation. Calculation of the cerebral "excess lactate" production from the measurements of lactic and pyruvic acids showed no significant increase with hyperventilation. The conclusion was made, with reservation, that cerebral oxygenation during even severe hyperventilation was sufficient to maintain normal oxidative metabolism.
Alteration of peripheral nerve function in the rat after prolonged outdoor cold exposure
Authors: Miller L. Keith , Irving Laurence
Published: December 2017

Electrical characteristics of in vitro preparations of the ventral tail nerve were compared in rats exposed for 6 months to outdoor winter cold and control rats kept indoors at 24 C. Determinations of conduction velocity, excitability, and action potential height demonstrated changes in nerve function following outdoor cold exposure. Differences between nerves of outdoor and indoor rats were greatest at higher nerve temperatures (35 C), becoming less at lower temperatures, until no differences were present at 5 C. Conduction velocity showed the greatest changes with cold exposure. Excitability changes could only be demonstrated with stimulus durations less than .1 msec. No differences in absolutely refractory period were seen between cold-exposed and control rats. In general, changes that occurred with cold exposure resulted only in a decrease in the functions examined. The results show that changes in peripheral nerve function can occur in nonhibernating mammals following prolonged exposure to climatic cold, but that these changes are not necessarily of an adaptive nature.
Cryofibrinogen: formation and inhibition in heparinized plasma
Authors: Heinrich R. A. , Vonder E. C. , Climie A. R. W.
Published: December 2017

Cold precipitable proteins (cryoglobulins, cryofibrinogen, and heparin-precipitable fractions) have presented a considerable problem to the clinician in treatment of patients who are discovered to have such fractions and to the cardiac surgeon who is confronted with clogged filters in heart surgery with hypothermia. When heparin, 0.04 mg/ml blood, is added as an anticoagulant, fibrin threads or clots may be observed in the red cell mass. The plasma of such blood, when exposed to temperatures of 5 C for 16 hr will show two precipitable fractions, one of which is soluble at 37 C whereas the other is not. As the heparin concentration is increased, there is a serial disappearance of each fraction. The heat-soluble fraction is the last to disappear, and this occurs when the heparin concentration reaches 3.0 mg/ml blood. Normal blood similarly treated with sodium oxalate or sodium citrate shows no cold precipitation. Normal plasma, after addition of thrombin, shows both cold-precipitable fractions. Twelve patients who had varying amounts of cryofibrinogen were studied by employing a modification of the thromboplastin generation test. Eight of the twelve patients showed a hypercoagulable state.
Myocardial anaerobic metabolism in intact dogs
Authors: Neill William A. , Krasnow Norman , Levine Herbert J. , Gorlin Richard
Published: December 2017

Energy liberated from substrates of heart muscle metabolism appears as mechanical work and heat. External mechanical work and heat production of the left ventricle were compared with its oxygen consumption in intact dogs. Under control conditions, within the range of accuracy possible, the sum of work and heat was equal to energy from oxidative metabolism. Intravascular administration of cyanide increased heart work but reduced its rate of aerobic metabolism. During the cyanide effect, work plus heat exceeded the energy available from oxidative metabolism. The difference represents myocardial anaerobic metabolism. Since the energy of mechanical work output alone was greater than the myocardial aerobic energy source, a portion of the anaerobic energy liberated must have been converted to mechanical work.
Comparison of left ventricular volumes by dye dilution and angiographic methods in the dog
Authors: Hallermann Franz J. , Rastelli G. C. , Swan H. J. C.
Published: December 2017

In each of 12 mongrel dogs, data for end-diastolic volume, end-systolic volume, and stroke volume of the left ventricle were obtained by two independent methods: the indicator dilution method and a radiographic method. While the values for stroke volume showed good agreement between the two methods, a significant and directionally constant difference was found between values for end-diastolic volume and end-systolic volume calculated by the two different methods. This was observed in dogs with fast heart rates (exceeding 150 beats/min), as well as in dogs with heart rates of about 100 beats/min. The findings strongly suggest that a fundamental error is present in estimations of volume based on the washout of an indicator dye.
Vasodilation in skeletal muscle
Authors: Jones Richard D. , Berne Robert M.
Published: December 2017

Blood flow was studied in dog hind-limb muscle isolated except for femoral and sciatic nerves. At constant perfusion pressure, elevation of aortic pressure produced by blood transfusion or intravenous epinephrine administration elicited a three- to fourfold increase in blood flow in perfused muscle. The blood flow increase evoked by epinephrine could be prevented by maintaining aortic pressure at control levels by means of a pressure compensator. Carotid artery occlusion had little effect on muscle blood flow whereas release of carotid occlusion produced marked increases. Cold or procaine block of the femoral or sciatic nerves resulted in little change in blood flow, whereas nerve section distal to the block produced large transient increases in flow. It is concluded that muscle blood flow increase after aortic pressure elevation is the result of active vasodilation and that increase in muscle blood flow after nerve section is due to stimulation of vasodilator fibers or direct stimulation of vascular smooth muscle by pressure changes produced by the twitch contraction associated with nerve section.
Baroreceptor and chemoreceptor influences on sympathetic discharge to the heart
Authors: Downing S. Evans , Siegel John H.
Published: December 2017

Baroreceptor and chemoreceptor influences in the regulation of sympathetic discharge to the heart were investigated, utilizing electroneurographic recordings from the left inferior cardiac nerve in the cat. Spontaneous discharge patterns exhibited phasic inhibition with the heartbeat and with inflation of the lungs. This was shown to be the consequence of baroreceptor and afferent vagal activity, respectively. Increasing blood pressure with epinephrine or angiotensin II caused marked inhibition of discharge which was abolished by baroreceptor deafferentation. No increase of cardiac sympathetic discharge occurred after the introduction of hypoxic blood into the isolated carotid sinus. Systemic hypoxia caused a marked increase in sympathetic discharge to the heart despite a large increase of systemic blood pressure. This response persisted after denervation of the peripheral chemoreceptors. A similar but less pronounced response to systemic hypercapnia was found. Systemic hypoxia frequently produced bradycardia which could be converted to tachycardia by atropine. This was associated with a large and continuous increase of cardiac sympathetic discharge to the heart. It is concluded that in systemic hypoxia both sympathetic and parasympathetic discharge to the heart is enhanced.
Mannitol diuresis in hemorrhagic hypotension
Authors: Peters G. , Brunner H.
Published: December 2017

In anesthetized dogs and cats bleeding to arterial pressures below 50 mm Hg did not cause anuria when infusions of hypertonic mannitol were given at 0.20–0.40 ml/kg·min. In animals infused with isotonic saline, urine flow stopped below 50 mm Hg, but could be re-established by infusion of hypertonic solutions of mannitol, sodium sulfate, or urea. In both groups urine flow finally stabilized at 5–40%, and GFR (CIn) at 2–14% of prehemorrhagic values. CCr(exog)/CIn fell to values below unity in hemorrhagic hypotension in most dogs. In most cats CCr(exog) /CIn was larger than 1.10, and was lowered in hemorrhagic hypotension.
Afterload as a primary determinant of ventricular performance
Authors: Sonnenblick Edmund H. , Downing S. Evans
Published: December 2017

The importance of aortic blood pressure as a determinant of left ventricular performance was systematically evaluated in the intact cat heart, and compared with the effects of afterloading on work performed by the isotonically contracting isolated cat papillary muscle. In the papillary muscle, at any one muscle length and state of contractility, work was determined by the afterload with which the muscle shortened. In the intact heart, blood pressure (BP) may be considered a gross approximation of the afterload encountered by the contracting ventricle. It was found that at any given initial left ventricular end-diastolic pressure (LVEDP), work performed was a function of the BP. At a constant BP, norepinephrine increased the work performed at any LVEDP by augmenting stroke volume. This work could be further increased by a concomitant increase of BP. Over a broad range, stroke volume was independent of the BP. The state of contractility of the myocardium sets the limits of work; however, work performance remains largely dependent on the BP (afterload). Thus, ventricular performance at a given constant inotropic state is the product of two largely independent variables, the preload (establishing initial muscle length) and the afterload.
Effect of selective embolization of various sized pulmonary arteries in dogs
Authors: Hyland John W. , Smith George T. , McGuire Lockhart B. , Harrison Donald C. , Haynes Florence W. , Dexter Lewis
Published: December 2017

Pulmonary embolism was produced in 30 closed-chest 8-kg dogs with polystyrene spheres, glass beads, or blood clots of precise graded size. The sizes matched selectively the internal diameter of pulmonary arteries from lobar branches (5–6 mm) down to atrial arteries (0.17 mm). Emboli were injected into the right atrium until the pressure in the pulmonary artery rose 5–10 mm Hg. The number of emboli of a given size required to produce this incipient pulmonary hypertension was compared with the number of vessels of that same size as determined from the literature as well as by postmortem injection with Schlesinger mass. The number of emboli bore a constant relation to the number of vessels of that same size. With each size, the majority of vessels had to be occluded before pulmonary hypertension appeared. This was true even in the absence of anesthesia. The results support the thesis that mechanical blockade rather than vasoconstriction is the mechanism by which pulmonary hypertension is produced by emboli occluding pulmonary arterial (as opposed to arteriolar) vessels.