bluuebunny/crossref_metadata_2025 huggingface dataset:
Avoidance and approach learning motivated by stimulation of identical hypothalamic loci
Authors: Brown George W. , Cohen Bertram D.
Published: December 2017

Cats with stimulating electrodes implanted in the lateral hypothalamus were subjected to two types of experimental procedures. In the first procedure the cats were given an opportunity to learn to avoid hypothalamic stimulation which produces a typical ‘hypothalamic rage’ response. The second procedure allows the same cats to learn to approach an area where the hypothalamic stimulus is administered. In both procedures, electrical stimulation was delivered through identical electrodes, yet each animal learned the appropriate avoidance or approach response, depending upon the experimental conditions. Therefore, lateral hypothalamic stimulation may act as an energizing, drive-arousing, operation to produce both avoidance and approach learning in cats.
Effects of altitude acclimatization on the equilibrium constant of rat oxymyoglobin
Authors: Strickland E. Hardin , Ackerman Eugene , Anthony Adam
Published: December 2017

After continually exposing rats to simulated altitudes of about 20,000 ft. for 2 months, studies were made of a possible adaptive shift in the oxymyoglobin equilibrium constant, K. The results indicated that cellular acclimatization does not involve changes in the value of K. The significance of this finding as it relates to the functional role of myoglobin during acclimatization is briefly discussed.
Buffer reflexes, tolerance to ganglioplegics and their relationship to enhanced pressor responsiveness
Authors: Page Irvine H. , McCubbin J. W.
Published: December 2017

Tetraethylammonium, hexamethonium, chlorisondamine or mecamylamine suppressed the dog's carotid occlusion reflex well before appearance of maximum augmentation of responses to pressor drugs. The reflex usually returned to near control values despite continued administration of ganglioplegics, while augmented responsiveness persisted or became more marked. An antipseudocholinesterase or prostigmine restored the suppressed reflex without loss of augmented responsiveness. Electroneurographic measurements of efferent spontaneous activity in postganglionic renal nerves revealed synaptic pathways resistant to blockade: a small amount of activity persisted during tolerance to ganglioplegics and showed reflex changes. Similar measurements of spontaneous and evoked potentials in the inferior cardiac nerve showed no synaptic activity during tolerance. Augmentation of response to pressor drugs by ganglioplegics does not depend wholly upon loss of compensatory reflexes; peripheral sensitization is probably another mechanism concerned. Maintenance of arterial pressure and persistence of cardiovascular reflexes during tolerance to ganglioplegics appear to depend upon transmission of a relatively few impulses over pathways resistant to blockade and upon peripheral sensitization to the presumably smaller amounts of norepinephrine released from nerve endings.
Effects of some physiologic substances on gastrointestinal propulsion in the rat
Authors: Lish Paul M. , Clark Byron B. , Robbins Sherman I.
Published: December 2017

The influence of some physiologic substances on the distribution of a dye following oral administration in the rat has been studied by a very sensitive and discriminative technique. Under certain conditions an agent may influence the rate of movement through one portion of the gastrointestinal tract while not affecting the transit through an adjacent segment. Propulsive motility was slowed following subcutaneous administration of l-epinephrine, l-norepinephrine, glucagon, 5-hydroxytryptamine, or 5-hydroxytryptophan. The characteristics of the inhibition produced by each agent were not the same. Insulin inhibited the motility of the gastrointestinal tract 15 minutes following subcutaneous administration, but 45 minutes after administration there was intense stimulation of propulsion. Ganglionic blockade eliminated the stimulating effect of insulin on the intestine but only partially reduced the stimulation of the stomach.
Acute unilateral ventricular failure in the isolated dog heart
Authors: Buckley N. M. , Zeig N. J.
Published: December 2017

Acute left ventricular failure was studied in the isolated dog heart exposed to elevated aortic resistance. Experiments in which only the left ventricle performed mechanical work established that progressive changes in distensibility and contractility occurred. When exposure to the elevated resistance was prolonged, the failure became hemodynamically irreversible and there was a loss of responsiveness to increases in filling pressure. Experiments in which both ventricles worked under separately controllable hemodynamic conditions established that acute failure did not develop in the adjacent right ventricle. The observations suggest that the unilateral ventricular failure involved a permanent alteration of the distensibility and contractility of the wall of the left ventricle as a result of a process which permitted the right ventricle to retain normal function.
Daily output of pancreatic juice and some dietary factors which influence it
Authors: Magee D. F. , Hong S. S.
Published: December 2017

Evidence is presented that the chronic pancreatic fistula dogs can be used effectively to study pancreatic physiology on a daily output basis. By increasing the amount of a mixed diet fed or by adding fat to the diet the volume and protease and lipase activities can be increased. Additions of cellulose, milk, casein hydrolysate were ineffective. On the basal mixed diet neither volume, amylase nor protease increased independently of each other. Changes in one enzyme activity without the other or in volume without enzymes were seen with supplements of essential amino acids or soy flour. The possible mechanism of these effects is discussed.
Enzyme patterns in cultured kidney cells
Authors: Burlington H.
Published: December 2017

The activity of a number of enzyme systems was compared in trypsinized suspensions of kidney cortex and primary cultures of the suspension grown as monolayers. Severe reduction in levels of acid and alkaline phosphatase, adenosine triphosphatase, succinic dehydrogenase and cytochrome oxidase was seen in the cultured cells. d-Amino oxidase and glucose-6-phosphatase were missing completely, along with the ability to accumulate para-aminohippuric acid. Aerobic glycolysis, on the other hand, suffered no reduction relative to the parent cells, while the activity of the initial reactions of the hexose monophosphate shunt was increased significantly above normal levels. Use of this preparation for study of development and regulation of cellular enzyme patterns seems justified.
Deposition and retention of fluoride and radiocalcium in the growing rat
Authors: Likins R. C. , Scow R. O. , Zipkin I. , Steere A. C.
Published: December 2017

Radiocalcium and fluoride were administered daily for 30 days to young rats. At 30 and 60 days, the tibia, femur, mandible, teeth and remaining skeleton were analyzed for Ca45 and F. The tibia was divided into several segments including the proximal epiphysis, the original diaphyseal segment, and those portions of the diaphysis added from 0 to 30 days and 30 to 60 days. Fluoride had no effect on the Ca45 or ash of bone but reduced Ca45 uptake by molar enamel. Ratios of F to Ca45 were dissimilar in the various tibial segments. Between 30 and 60 days essentially no Ca45 or F was lost from the skeleton, tibia or tibial segments excepting the 0–30-day proximal diaphyseal increment. Seventy per cent of the Ca45 and forty per cent of the F lost from this segment was found in the adjacent segment formed during the second 30-day period. These results suggest that much of the Ca45 and F released during remodeling of the ends of the growing bone did not enter the general circulation, but was deposited in the immediate vicinity.
Single proximal tubules of the Necturus kidney. III. Dependence of H2O movement on NaCl concentration
Authors: Windhager Erich E. , Whittembury Guillermo , Oken Donald E. , Schatzmann Hans J. , Solomon A. K.
Published: December 2017

Stopped flow microperfusion technique ( Am. J. Physiol. 195: 563, 1958) was used to study water movement across the proximal tubular wall of Necturus kidney. In 23 experiments, net water movement was measured from perfusion solutions containing 50, 62.5, 75 and 100 mEq. NaCl/1. which were made isosmotic with Necturus plasma by addition of mannitol. Water movement was shown to depend upon luminal NaCl concentration. Studies of the relationship between net solute flux and water flux demonstrated a linear relationship: net water flux (mµl/sec.) = 9.4 x net solute flux + 0.003. Net water flux is statistically zero when net solute flux is zero. Under these experimental conditions no force is important for water movement other than that arising from solute movement. It is concluded that net movement of Na has taken place up an electrochemical potential gradient, indicating active transport of this ion. Furthermore, movement of water from the tubule is considered to be passive since net water flux may be accounted for quantitatively in terms of osmotically induced forces arising from net solute movement.
Effects of ganglionic blockade and voluntary muscle paralysis on epinephrine blood pressure responses
Authors: Hilton James G. , Sekul Antonio A.
Published: December 2017

The blood pressure responses elicited by graded doses of epinephrine before and after voluntary muscle paralysis by curare have been studied in the dog anesthetized with sodium pentobarbital and pretreated with diphenhydramine and hexamethonium. These responses were compared before and after curare to determine the effects of voluntary muscle paralysis. The results were also compared with the earlier results of Hilton and Reid ( Am. J. Physiol. 186: 289, 1956) obtained in dogs under total spinal anesthesia. The comparisons showed that the actual rise in blood pressure and the duration of the rise in blood pressure were unaffected by the paralysis of the voluntary muscle. The maximum attainable blood pressure was lower following the curare. The amount of lowering in maximum was directly related to the effects of the curare upon the control blood pressure. The comparison of the blood pressure responses to epinephrine after diphenhydramine and hexamethonium with the blood pressure responses obtained from the same doses of epinephrine in unmedicated dogs showed that the diphenhydramine-hexamethonium potentiated the pressor responses. When the same comparison was made with responses in the dog under total spinal anesthesia there was no potentiation of the pressor responses. The results of these experiments seem to indicate that the potentiation of epinephrine pressor response varies with the degree of autonomic nervous activity, but not with voluntary muscle activity.
Effect of acceleration on cerebellar potentials in birds and its relation to sense of direction
Authors: Gualtierotti T. , Schreiber B. , Mainardi D. , Passerini D.
Published: December 2017

Rotatory and postrotatory cerebellar responses of homing and domestic pigeons and of migratory and sedentary doves have been studied by means of a centrifuge, the speed and plane of rotation of which could be changed at will. No appreciable differences have been found in the rotatory cerebellar responses in all the animals tested. Spindle-like postrotatory discharges, however, are a peculiar response of nearly all the homing pigeons and all the migratory doves tested; only 6–8% of the domestic pigeons and no sedentary doves showed similar afterdischarges. Of the hybrids, nearly half had the same postrotatory electrical activity in the cerebellum. The threshold value of centripetal acceleration to produce postrotatory discharges in homing and migratory birds has been found to be 0.004–0.005 g. Postrotatory responses show temporal summation; repetitive stimuli give more numerous and more ample afterdischarges. Nystagmus or, in general, contraction of the neck muscles, does not influence directly the cerebellar afterdischarges. The latter are present in curarized animals, which show no nystagmus and, in domestic pigeons, nystagmus is not accompanied by cerebellar afterdischarges. When coincident in time, however, nystagmus and cerebellar afterdischarges show at times a tendency to synchronization, through physiological factors, which are discussed. The threshold for afterdischarges has been found to be 1000 times higher than changes in possible geodetic forces involved in orientation. This seems to rule out the Ising hypothesis that geodetic forces may be responsible for direction in migration that, notwithstanding the existence of kinesthetic centers of higher sensitivity, is postulated in migratory animals.
Hyperpolarization of muscle by insulin in a glucose-free environment
Authors: Zierler Kenneth L.
Published: December 2017

In a glucose-free solution, insulin increased resting membrane potential of rat extensor digitorum longus muscle by as much as it had in the presence of glucose. Even in the absence of glucose there was probably net accumulation of potassium by muscle, but the increase in muscle potassium concentration was too small to have been the cause of the observed hyperpolarization. It is concluded that insulin hyperpolarizes muscle membrane, as a result of which potassium moves into muscle, and that the eventual effect of insulin on potassium movement can be independent of any effect insulin may also have on glucose uptake.
Vagal secretory nerves for pancreatic secretion in the rat
Authors: Lin T. M. , Alphin R. S.
Published: December 2017

Chronic pancreatic-fistula rats were given subcutaneously 0.25, 0.5, 1.0 and 2.0 u of insulin after a fast of 12–16 hours. The volume flow and the amylase output were both significantly increased at a dose of 0.5 u. Insulin at a total dose of 1.0 and 2.0 u increased the amylase output but had no significant effect on the volume flow. The effect of insulin on either volume flow or amylase output was abolished by vagotomy. Under repeated secretin injection and urethane anesthesia, weak faradic stimulation of the peripheral end of the vagus also significantly increased the amylase concentration as well as its output. These findings demonstrate that there are vagal ‘secretory’ fibers for pancreatic secretion in the rat.
Sodium exchange and distribution in the isolated heart of the normal dog
Authors: Conn Hadley L. , Wood John C.
Published: December 2017

Sodium exchange was studied in the isolated normal dog heart with the aid of a Na24 tracer technique. Transcellular sodium exchange was calculated to be 0.04 mEq/kg/beat. The results are consistent with the concept of sodium influx into the cell during the spike potential, relative membrane impermeability to sodium in the membrane resting state, and a membrane capacity of about 10 µf/cm2.
Plasma and erythrocyte Na, K, Cl and water in hypothermic and hyperthermic dogs
Authors: Spurr G. B. , Barlow George
Published: December 2017

Plasma and erythrocyte Na, K, Cl and water have been determined in hyperventilated dogs cooled to 25°C for periods up to 4 hours, in animals heated to either 41.5°C or 42.5°C for 1 hour and in hyperventilated-normothermic dogs. The induced respiratory alkalemia in both normothermic and hypothermic animals appeared to result in a shift of Na from plasma into red cells. Plasma K was reduced in both normothermic and hypothermic dogs, whereas a K elevation in erythrocytes occurred only in the normothermic animals following hyperventilation. Erythrocyte K remained unchanged in hypothermia. It seems, therefore, that the fall in plasma K which occurs in alkalemic normothermic dogs is due partially to a movement of K into red cells whereas, in hypothermia the K leaving extracellular fluid enters cells other than erythrocytes. The plasma and red cell electrolyte changes observed in the two hyperthermic groups of dogs were all in the direction of an increase. It is concluded that these changes were primarily the result of the increased body temperature and of consequent reductions in plasma and red cell water content, rather than the result of the blood pH changes associated with hyperthermia.
Fructose metabolism in the udders of dairy cows
Authors: Luick Jack R. , Kleiber Max , Lucas James M.
Published: December 2017

The metabolism of fructose by mammary tissue was studied by infusing U-C14 fructose into the one quarter of a lactating cow's udder. Comparison of specific activities of milk products isolated from the injected and uninjected quarters showed that fructose, unlike glucose, was not converted to lactose by mammary tissue. However, fructose was oxidized in the udder to metabolic intermediates which lead to the synthesis of milk protein, butterfat, citrate and CO2. It appeared that little fructose C14 was absorbed by mammary tissue. These results were discussed with regard to the known metabolic pathways of fructose metabolism. It is postulated that an active fructokinase enzyme system functions in mammary tissue and further, that the principal direction of metabolic reactions in the udder favors catabolism of hexose rather than its synthesis.
Adaptive increase in mammalian histidine decarboxylase activity in response to nonspecific stress
Authors: Schayer Richard W. , Ganley Oswald H.
Published: December 2017

Adaptive increase in histidine decarboxylase activity has been found to occur in all of the three species tested after a variety of stressful stimuli in rat skin following injection of polymyxin B, in mouse skin after burns, in lungs of mice injected with pertussis vaccine and in the skin of guinea pigs during the development of the tuberculin reaction. Mammalian histidine decarboxylase is one of the few enzymes which have been shown to increase in response to nonspecific stress; furthermore the conditions induced by these stressful stimuli have ‘histaminic’ implications. After a discussion of fallacies in earlier studies on the evaluation of the role of histamine, it is concluded that adaptive increase in histidine decarboxylase, attended by slow but increasing formation of histamine, must be seriously considered as an important causative mechanism in slowly developing inflammation.
Effects of membrane current on transmembrane potentials of cultured chick embryo heart cells
Authors: Crill W. E. , Rumery Ruth E. , Woodbury J. W.
Published: December 2017

Two to eleven days after myocardial cells were explanted to cultures from the ventricles of 4-day chick embryos two microelectrodes were inserted into a cell cluster. There was no detectable damage to the membrane. Current was passed through one electrode and the membrane potential was measured with the other. Since membrane current density is roughly uniform in nearly spherical cells, the membrane time constant could be directly estimated. The mean value of 17 measurements of the time constant was 35 ± 1 msec. As expected, strong depolarizing current stopped spontaneous contractions and weaker current increased the rate of contraction. Hyperpolarizing current decreased the rate. Break of a hyperpolarizing current nearly always initiated an action potential in both active and quiescent cells. On the basis of these preliminary results, voltage clamping at least of the plateau phase appears feasible in tissue cultures of myocardial cells.
Influence of blood volume restoration and tissue trauma on corticosteroid secretion in dogs
Authors: Walker William F. , Shoemaker William C. , Kaalstad Aud J. , Moore Francis D.
Published: December 2017

In this third paper the authors record the corticosteroid data derived from the animals reported in the previous studies. A total of 12 animals is described. Acute reduction in blood volume in dogs resulted in markedly increased concentrations of corticosteroids in the adrenal vein blood. In some instances, alteration in flow was so balanced that there was no increase in total secretion of corticosteroids; in others, the adrenal blood flow was such that the output total was increased. In dogs subjected to a more chronic shock challenge by prolonged bleeding, the concentration and output of corticosteroids varied considerably according to adrenal blood flow and the presence or absence of the ‘taking-up’ phenomena. Replacement of lost blood was accompanied by a reduction in concentration and, in some cases, total output of corticosteroids. Fracture of the femur in anesthetized dogs resulted in increased concentration of corticosteroids in the adrenal venous blood, seemingly unrelated to blood pressure changes. There was no sign of adrenocortical failure in any of these animals and in one case a low output of corticosteroids in response to hemorrhage did not appear to influence the resistance of the animal to hemorrhagic hypotension.
Regional tissue uptake of D2O in perfused organs: rat liver, dog heart and gastrocnemius
Authors: Thompson Alan M. , Cavert H. Mead , Lifson Nathan , Evans Robert L.
Published: December 2017

Regional tissue D2O concentrations were measured in the isolated dog heart, dog gastrocnemius and rat liver following relatively brief perfusions with D2O-labeled fluid. Results indicate heterogeneity of tissue concentrations in all three organs. A venous outflow concentration curve for the liver was reconstructed on the assumptions that each regional tissue sample represented an equally probable portion of a composite organ and that in each region D2O transport was flow-limited. The agreement between this curve and the observed outflow curve was sufficiently good to suggest that the discrepancies between the observed venous curve and that for the theoretical case of a completely flow-limited organ can be largely explained for the liver by macroscopic regional perfusion heterogeneity without invoking microscopic tissue transport limitation. In the case of the heart and the gastrocnemius, the observed macroscopic tissue heterogeneity was insufficient to account for the discrepancies between the respective venous outflow concentration curves and the theoretical case. However, in the heart, regions of low tissue concentration were apparently systematically missed in the sampling procedure. The actual heterogeneity in both organs was probably underestimated.
Sympathetic influences on circulation of the gastric mucosa of the rat
Authors: Arabehety Julian T. , Dolcini Horacio , Gray Seymour J.
Published: December 2017

A method is presented for quantitatively evaluating the gastric mucosal blood content in rats by densitometric measurement of the India ink content of the mucosa following the intra-aortic injection of India ink in the living animal. Animals injected after laparotomy alone showed a very sparse accumulation of India ink in the mucosa. Interruption of the sympathetic nerve supply to the stomach by splanchnic anesthesia or splanchnic section produced a marked filling of the mucosal capillary bed. The mucosal capillaries of the animals undergoing splanchnic section presented considerably more India ink than after splanchnic anesthesia. Rats injected after death presented the greatest amount of India ink in the mucosal capillaries. It is concluded that modification of the sympathetic innervation of the stomach in the rat leads to changes in the blood content of the mucosal capillaries.
Deposition and fate of cholesterol in ocular aortic implant and in the aorta in situ
Authors: Friedman Meyer , Byers Sanford O.
Published: December 2017

Aortic implants were placed in the anterior eye chamber of 30 rabbits subsequently fed excess cholesterol and cottonseed oil. After 3 months of such feeding, seven of these animals were sacrificed, and their implants and also segments of their own aorta were analyzed for cholesterol. Two more groups of these rabbits were sacrificed 2 and 3 months, respectively, after their return to a cholesterol-free diet. It was observed that the aortic implant gained almost twice as much cholesterol as the host's own aorta at the end of the cholesterol feeding period. This difference became even greater in animals that were sacrificed 2 months after cessation of excess cholesterol feeding, but still hypercholesteremic. However, the ocular implants of rabbits examined 3 months after cessation of cholesterol feeding were observed to have lost almost all of their cholesterol, whereas the animal's own aorta continued to exhibit an unchanged excess of cholesterol. The findings suggest that the ocular aortic implant differs markedly from the aorta in situ in regard to its penetration and retention of cholesterol.
Hormonal and metabolic influences on intracellular peptidase activity
Authors: Rose Herbert G. , Robertson Mary C. , Schwartz Theodore B.
Published: December 2017

A procedure which permits the estimation of intracellular peptidase activity of surviving rat diaphragm has been evaluated following changes in the hormonal and metabolic environment. It was found that leucine aminopeptidase (LAP) activity fluctuated with the seasons, rising during the summer and decreasing to low levels during the winter. LAP activity was significantly increased after acute and chronic fasting, cortisone administration and triiodothyronine administration. Conversely, LAP activity was reduced following adrenalectomy or thyroidectomy. The ‘stress’ of saline injection did not provoke significant changes in aminopeptidase activity and attempts to induce enzyme adaptation by injection of peptide substrate were unsuccessful. These data are consistent with the view that intracellular peptidases perform an important regulatory function in the control of protein metabolism. The possibility has been raised that the changes noted may be the result of varying degrees of intracellular exposure of substrate to enzyme.
Contralateral renal function after unilateral renal vein ligation
Authors: Perlmutt Joseph H.
Published: December 2017

The effect of increased pressure in one kidney, produced by ligation of its vein, on contralateral renal function was investigated in eight anesthetized dogs. Kidney function was determined under the same experimental conditions in five dogs, but without renal vein ligation. For the latter group, renal function, on the average, remained reasonably stable. After left renal vein ligation, findings for the right kidney were as follows: a) decreased urine flow, amounting maximally to 9.5–41.4% of control flows; b) slight increase of questionable significance in creatinine clearance; c) inconstant changes in PAH clearance; d) increase in urine osmolality to hypertonic values; e) decrease in solute-free water clearance; f) slight rise of questionable significance in total solute clearance; and g) either no change or inconstant changes in excretion rates Na+ and K+. The data indicate that the oliguria resulted solely from increased renal tubular reabsorption of water, suggesting liberation of antidiuretic hormone as the possible mechanism. Direct nervous influences on tubular reabsorption of water cannot, however, be presently ruled out.
Effect of carbonic anhydrase on CO2 tension of urine and plasma during respiratory acidosis
Authors: Kaim John T. , Brodsky William A.
Published: December 2017

Urine-plasma gradients of pCO2 were found in 20 dogs under conditions of respiratory acidosis induced by inhalation of 15–20% CO2. CO2 tension of plasma varied from 100 to 120 mm Hg in some dogs and from 170 to 190 mm Hg in others, while that of urine varied from 100 to 250 mm Hg. In 25% of periods, pCO2 of urine was less than that of plasma by 10–35 mm Hg In 40% of the periods, pCO2 of urine exceeded that of plasma by 10–35 mm Hg. Injection of carbonic anhydrase in amounts of 60,000–100,000 Brinkman u failed to obliterate gradients of pCO2 in acidic urine, even though abundant quantities of enzyme were detected in urine. On the other hand, carbonic anhydrase did obliterate pCO2 gradients between alkaline urine and plasma. Tonometric determinations of α and pKa were made on several specimens of urine and of plasma, especially those wherein pCO2 of urine was less than that of plasma. This made it possible to estimate the pCO2 of biological fluids to within 2–3% of the true value. The usual magnitude of urine-plasma difference of pCO2 was of the order of 15–20%. Therefore, we inferred that gradients of pCO2 between acidic urine and plasma are not experimental artifacts. Relationships between mechanisms of urinary acidification and urine-plasma gradients of pCO2 are discussed.
Regulation of contractile force during ventricular arrhythmias
Authors: Siebens Arthur A. , Hoffman Brian F. , Cranefield Paul F. , Brooks Chandler McC.
Published: December 2017

Causes of fluctuations in ventricular pressure during arrhythmias were studied in anesthetized dogs. Excitability and contractility were measured throughout the cardiac cycle and their relationship to the problem was assessed. The strength of premature contractions was found to vary inversely with prematurity. Weakness of premature beats could not be ascribed to subnormal excitability nor to insufficient ventricular filling. Contractility was virtually zero at the end of the total refractory period, increased progressively thereafter and was fully restored only at the very end of the cardiac cycle. Sensitivity of contractile force to increments in ventricular filling paralleled the return of contractility. The strength of the postcompensatory contraction was always enhanced, this potentiation increasing as a linear function of the extrasystole's prematurity. Postextrasystolic potentiation was attributed to the extrasystole itself rather than to the pause which follows it or to increases in ventricular filling and distention. It was therefore concluded that pressure fluctuations during ventricular arrhythmias are not due to subnormal excitability and would occur independently of variations in ventricular filling.
Relationship between antithrombin and thrombin levels in plasma and serum
Authors: Monkhouse Frank C.
Published: December 2017

Antithrombin levels were measured following the addition of varying amounts of thrombin to defibrinated plasma and following the intravenous injection of thrombin into rats. In the in vitro studies the decrease in antithrombin was proportional to the thrombin added. The addition of 30–40 u of thrombin to 1 ml of plasma caused a 50% decrease in antithrombin. Similar results were obtained in the in vivo studies. Six-hundred units of thrombin injected into heparinized rats caused a 40% reduction in plasma antithrombin. Thrombin generation in samples of recalcified plasma was measured according to the method of Pitney and Dacey ( J. Clin. Path. 6:9, 1953) and the values compared with changes in antithrombin. The amount of thrombin generated when full strength plasma was recalcified was only a fraction of the amount potentially available according to estimations by the two-stage method. When plasma was diluted with one to two volumes of saline before activation the amount of thrombin generated was increased two- to threefold. The antithrombin level of the serum from the diluted samples was correspondingly decreased.
Generation of proteolytic activity during activation of prothrombin
Authors: Landaburu Ricardo H. , Seegers Walter H.
Published: December 2017

In the activation of purified prothrombin with thrombin, with platelet factor 3, or in 25% sodium citrate solution the free thrombin activity which develops is greater at all times when measured by hydrolysis of p-toluenesulfonyl-arginine-methyl ester than when measured by the clotting of fibrinogen. Since the esterase activity appears before clotting power and remains after clotting power is lost, the clotting property must arise from a dissociable complex arising from the unit that has the esterase function. It is postulated that "clotting thrombin" may be a dimer of the lowest subunit of prothrombin required to have the proteolytic enzyme. The latter could have an important function in our physiology quite apart from the clotting of blood.
Effects of estrogen on blood volume and hemoglobin in immature pullets
Authors: Campbell E. A.
Published: December 2017

Blood volume was determined on immature Leghorn pullets 14–16 weeks of age, before and after administration of 18 mg of estradiol benzoate over a period of 14 days. Results show that estrogen increases plasma volume and it is suggested that this mechanism is also responsible for the marked fall in hemoglobin/100 ml of blood which occurs when pullets come into lay.
Buffer function of the nerves arising at the thyrocarotid arterial junction in the dog
Authors: Gann Donald S. , Bartter Frederic C.
Published: December 2017

The carotid arteries were constricted in normal dogs, while arterial, atrial and venous pressures were recorded. Carotid constriction above the thyroid arteries but below the carotid sinuses produced less reflex rise in peripheral arterial pressure than constriction below the thyroid arteries, despite equal falls in intracarotid pressure. The difference was abolished by bilateral denervation of the thyrocarotid arterial junctions, but not by vagotomy. Mild, persistent hypertension followed chronic thyrocarotid arterial junction denervation. Carotid constriction also produced reflex increase in right atrial pulse pressure; this was abolished by denervation of both carotid sinuses and thyrocarotid arterial junctions. The data suggest that the thyrocarotid arterial junction is an important buffer area in the dog.
Effect of anodal and cathodal pulses applied during action potential at a single Ranvier node
Authors: Ooyama Hiroshi , Wright Ernest B.
Published: December 2017

An anodal pulse applied during the falling phase of an action potential, if weak, produces a slight enhancement of negativity of the falling phase, but if increased in amplitude produces a split of the action potential into an early and "delayed" response and finally, complete abolition of the falling phase. If the pulse amplitude is increased still more after abolition, a second response is elicited. The latency to this second response following abolition is shorter than the latency to the delayed response, and further increase of the applied pulse amplitude cannot abolish this second response. To obtain abolition of the delayed response it is necessary to apply a considerably stronger anodal pulse near the peak of the spike than later during the falling phase. The reverse is true to obtain the second response. The anodal pulse sufficient to produce anode break excitation during the action potential and elicit the second response is ineffective applied to a resting node membrane. It is postulated that: a) due to an effect of the action potential itself the membrane is being actively depolarized during the early falling phase of the spike and b) the excitability of the node membrane is actually retained both during and following an action potential in the so-called refractory period but requires "resetting" by a positive pulse in order for re-excitation to take place.
Transport of vitamin A in vitro across normal isolated rat intestine and intestine subjected to ‘partial’ resection
Authors: Loran M. R. , Althausen T. L.
Published: December 2017

The transport of vitamin A across normal and resected intestine was studied in vitro by the method of Darlington and Quastel. The results showed that under aerobic conditions the rate of transport of vitamin A across normal and resected intestine was identical. In contrast, under anaerobic conditions transport was reduced 50% for resected intestine and totally inhibited for control intestine. These results were duplicated under aerobic conditions when 2, 4, dinitrophenol was added to the mucosal solution. Thus for the control intestine, transport is entirely dependent on DNP-sensitive phosphorylation mechanisms which require a wetting agent (polyoxyethylene sorbitan monooleate, ‘Tween 80’) as a solubilizer on the serosal side for the transport of vitamin A across the intestine. The DNP-insensitive mechanisms responsible for 50% of the total transport across the resected intestine were inhibited by iodoacetic acid and sodium fluoride. Chromatographic analysis of intestinal homogenates and mucosal solution at the end of the perfusion demonstrated that vitamin A palmitate is converted to the alcohol either in the lumen or on the surface of the epithelial cells and is then re-esterified in the intestinal mucosa. Transport of this vitamin is via ‘active’ energy-requiring mechanisms. In the normal intestine energy is supplied by oxidative phosphorylation, and in the resected intestine by oxidative as well as anaerobic glycolytic phosphorylation.
Soluble sulfhydryl changes in dietary and environmental stress
Authors: Register U. D. , La Sorsa A. M. , Katsuyama D. M. , Smith H. M.
Published: December 2017

The protein sulfhydryl (PSH) and nonprotein sulfhydryl (NPSH) interrelationships in liver were studied in rats fed stock, protein-free and methionine-deficient diets, and then exposed to cold stress. In stress, the NPSH levels decreased in the stock fed animals, but significantly increased in the dietary deficiency states. Contrariwise, the PSH levels were, in all cases, significantly increased in stress. The major NPSH changes were confined to glutathione. The point is made that these results are analogous to the nitrogen balance phenomena found in the well nourished and the malnourished animal in stress. NPSH formation during recovery from a protein-deficient diet overshoots previous levels by about 35%.
Intracellular and external recording from frog ventricular fibers during hypertonic perfusion
Authors: Sperelakis Nick , Hoshiko T. , Keller R. F. , Berne Robert M.
Published: December 2017

Isolated frog hearts perfused with hypertonic solutions passed through three reversible stages: I) altered spontaneous waveforms; II) absence of spontaneous activity but responsive to stimulation; III) nonresponsive. The following patterns of action potentials were observed with intracellular recording during stage I: 1) the plateaus gradually disappeared leaving short-duration spikes. 2) These spikes often occurred as high-frequency bursts usually accompanied by sustained contractions. Quiescent cells were often located adjacent to active ones, and many fibers fired at frequencies lower than that of the ECG. 3) Often a ‘slow wave’ gradually differentiated from the plateau and resulted in separation of a fast initial spike from a later slow wave. These observations suggest fiber-to-fiber junctional transmission rather than conduction within a syncytium. Hypertonic solutions may: a) depress fiber-to-fiber transmission, b) alter the time courses of the Na and K conductances and c) directly depress the contractile mechanism.
Hemorrhagic shock of germfree rats
Authors: McNulty W. P. , Linares Rafael
Published: December 2017

Germfree and ordinary laboratory rats of the same strain, half of each sort treated with oral aureomycin for 3 days prior to shock, were subjected to hemorrhagic shock. At the level and duration of hypotension selected, the procedure was highly lethal for all four groups. The single survivor was not a germfree rat. No evidence was found for protection against fatal outcome by either germfree status or treatment with aureomycin, and the gross pathological changes seen at autopsy following death from shock were essentially similar in all groups. The volumes of blood shed, the times spontaneous uptake of blood began, and the volumes of uptake did not differ significantly among the groups. It is concluded that bacteria and bacterial products are not essential for the development of irreversibility in hemorrhagic shock as customarily produced in rats.
Movement of electrolytes across the wall of the urinary bladder in dogs
Authors: Rapoport A. , Nicholson T. F. , Yendt E. R.
Published: December 2017

The transfer of certain electrolytes (Na+, K+, Cl–, H+) through the wall of the isolated urinary bladder has been studied in the dog. When test solutions are introduced into the bladder, changes in the concentration of these ions occur in the direction of their concentration gradient with plasma. The magnitude of these changes depends chiefly upon the magnitude of the concentration gradient but is influenced, as well, by the time the solution is allowed to remain in the bladder, by the pH of the solution and probably by its volume. By the use of Na22 it has been shown that sodium moves through the bladder wall in both directions at the same time. The movement of electrolytes into and out of the bladder appears to be passive. It is reaffirmed that the urinary bladder is not an impermeable reservoir and that, in some circumstances, the composition of bladder urine need not be identical with that of the urine as it leaves the kidney.
Hematological changes in deer mice acclimated at different ambient temperatures
Authors: Sealander John A.
Published: December 2017

Deer mice ( Peromyscus maniculatus and Peromyscus leucopus) were acclimated at temperatures of 5° ±0.5°C and 30°±0.5°C for various intervals with periods at 20°±0.5°C preceding the cold and warm acclimation periods. Hemoglobin concentrations, hematocrits and erythrocyte diameters were measured on a group of nonsplenectomized mice and on another group of splenectomized mice which were subjected to similar temperature conditions. It was found that there were significant increases in hemoglobin and hematocrit values with acclimation at 5°C, which were more marked in the splenectomized mice. Differences in hemoglobin concentrations and hematocrits were significant between 5° and 30°C, but differences were not as apparent between mice at 30°C and those exposed at 20°C. There were no significant changes in erythrocyte diameters, although the mean corpuscular hemoglobin concentration was significantly lower in all of the splenectomized mice as opposed to the nonsplenectomized ones. It is suggested that splenectomy in some way enhances erythopoiesis in response to low temperature since there was no significant difference in hematocrits of nonsplenectomized and splenectomized mice exposed at 20°C prior to cold acclimation.
Responses of cerebral cortex to diffuse monocular and binocular stimulation
Authors: Burns B. Delisle , Heron W. , Grafstein Bernice
Published: December 2017

Surface potentials and single unit potentials in the cat's cerebral cortex have been recorded in response to diffuse visual stimulation. Surface responses produced by stimulation of the contralateral eye are larger in amplitude than those produced by stimulation of the ipsilateral eye, while those produced by binocular stimulation are larger still. The amplitude of the surface responses increases to a maximum with increasing intensity of stimulation. For any given single cell, there is a constant ratio between the average number of unit discharges in response to contralateral, ipsilateral and binocular stimulation. At different stimulus intensities this ratio is constant, although the absolute numbers of discharges may be different. It has been possible to divide the cells into functional groups according to a) which eye produces the larger number of discharges, i.e. which eye is ‘dominant’ and b) whether binocular stimulation produces more, fewer, or as many discharges as stimulation of the dominant eye alone. All the functionally different types of neurones may be found in all the cellular layers of the cortex. The latency of the unit responses is shorter with binocular than with monocular stimulation, and is shorter when brighter stimuli are used.
Relation of hepatic ketogenesis to radiation-induced decrease in fasting ketonemia
Authors: Ontko Joseph A.
Published: December 2017

Male, weanling rats were exposed to 500 r of whole-body x-irradiation and then fasted. Control rats were concurrently fasted. Ketonemia, ketonuria, hepatic glycogen, ketogenesis by liver slices and fatty acid oxidase activity of liver mitochondria were measured. A radiation-induced decrease in fasting ketonemia was observed. This decrease was mainly in the ß-hydroxybutyric acid fraction. Ketonuria was similar in both control and irradiated lots the 1st postirradiation day and lower in the irradiated lot during the 2nd day. Decreased ketonemia in the irradiated rats, which exhibited diuresis, was thus apparently not due to increased urinary excretion of ketone bodies. Ketogenesis by liver slices from irradiated rats was depressed. This indicated that an antiketogenic process contributed to the radiation-induced decrease in fasting ketonemia. Fatty acid oxidase activity of liver mitochondria isolated from control and irradiated rats was similar. Thus, rate-limiting fatty acid oxidizing enzymes were not altered by radiation under these conditions. This illustrates an apparent modifying effect of other cellular fractions on fatty acid oxidation in mitochondria.
Specificity of sugar transport by the intestine of the hamster
Authors: Wilson T. Hastings , Landau Bernard R.
Published: December 2017

The specificity of the sugar transport system of the hamster small intestine was tested with 20 sugars and sugar derivatives not previously tested in this system. The absorption of sugars across the intestinal wall against a concentration gradient was tested with the everted sac technique in vitro. 3-Deoxyglucose, 4-0-methylgalactose, 6-deoxy-6-fluoroglucose and α-methylglucoside were transported while a variety of other sugars were not. From the data derived from the study of a total of 49 sugars tested in this system, certain generalizations are made as to the structural limitations of the sugar-absorbing capacity of the hamster intestine.
Relative influence of respiratory and metabolic acid-base changes on renal acid excretion
Authors: Simmons Daniel H. , Assali Nicholas A. , Avedon Melvin
Published: December 2017

Arterial pH of anesthetized dogs was maintained constant for 90 minutes during continuous infusion of 0.15 m HCl or NaHCO3 (0.3 cc/kg/min.) by adjusting alveolar ventilation with a respiration pump. This resulted in simultaneous metabolic acidosis and respiratory alkalosis (acid infusion) or metabolic alkalosis and respiratory acidosis (base infusion) equal in degree with respect to their effect on blood pH. Since urine pH dropped and renal acid excretion increased during metabolic acidosis and respiratory alkalosis, while pH rose and acid excretion decreased during metabolic alkalosis and respiratory acidosis, metabolic acid-base disturbances appear to exert more influence on renal acid excretion than do respiratory disturbances comparable in terms of their effect on pH. This difference in response was shown not to be due to a time lag in renal response to respiratory disturbances, nor could it be explained by effects on urine flow, renal hemodynamics or renal handling of sodium.
Prolonged response of skeletal muscle in the absence of penetrating anions
Authors: Falk Gertrude , Landa Jorge F.
Published: December 2017

Replacement of Ringer's chloride by a variety of nonpenetrating anions results in prolonged electrical and mechanical responses of muscle to stimulation. The ‘negative after-potential’ is characterized by a slowly increasing secondary depolarization which reaches a stable plateau lasting as long as 2 minutes. After-discharge frequently occurs during early depolarization. In most fibers repolarization is relatively abrupt, but in some, slow oscillations resembling relaxation oscillations arise following the plateau, grow gradually in amplitude and, only when they are of sufficient amplitude, does the membrane repolarize. Prolonged depolarization can still be produced when the spike has failed. At times, fibers may respond with short-duration action potentials, but may be primed to give prolonged responses by previous stimuli or by increase of external potassium. Addition of chloride has no effect below a critical concentration. Reduction of sodium to 25% of normal does not change plateau level or duration. Duration of the plateau phase is decreased by potassium.