bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical activity of mammalian heart muscle: variable onset, species differences, and the effect of caffeine
Authors: Bodem R , Sonnenblick EH
Published: December 2017

The time course of the ability to shorten during contraction was measured using velocity of shortening of the contractile element corrected for length after quick releases to constant loads, in isolated papillary muscles of the cat, rabbit, dog, and rat. The ratios of time-to-peak shortening ability at preload (TTPA), to time-to-peak active force (TPF), were 0.30, 0.36, 0.32, and 0.70 in the cat, dog, rat and rabbit, respectively. When the pacing rate was increased from 12 to 60/min, peak force was augmented in the cat (36%) and rabbit (108%), while TPF decreased in the cat (by 30%) but not in the rabbit. Various inotropic interventions did not alter the ratio of TTPA/TPF in any species. However, caffeine (10mM) increased this ratio to that normally found in the rabbit, in which it was not altered. Afterloaded force-peak velocity relations of the cat, dog, and rat were curvilinear, but in the rabbit in the control state, and in the cat and dog in the presence of caffeine, these relationships tended to be linear. The differences in the time course of the ability to shorten among these mammalian species may be related to differences in excitation-contraction coupling.
Influence of pituitary growth hormone on DNA synthesis in rat tissues
Authors: Goldspink DF , Goldberg AL
Published: December 2017

DNA synthesis was compared in seven tissues of hypophysectomized rats and normally growing controls. Liver, heart, kidney, and three skeletal muscles of hypophysectomized rats incorporated[3H]thymidine into DNA more slowly than tissues of normal rats, measured either in intact rats or upon in vitro incubation of tissue slices. However, removal of the pituitary did not alter incorporation into DNA of brain. Administration of ovine growth hormone to hypophysectomized rats stimulated total body growth and increased incorporation into DNA of diaphragm within 6h. The response of liver to growth hormone was less marked and slower in onset than that of diaphragm. Incubation of diaphragm in vitro with growth hormone, however, did not affect [3H]thymidine incorporation. Hypophysectomy reduced incorporation into nuclear DNA of liver, kidney, and muscle, but did not suppress incorporation into mitochondrial DNA. These results suggest that growth hormone only affects synthesis of nuclear DNA. Autoradiographic studies indicate that DNA synthesis is stimulated in distinct cell types in the different organs, including hepatocytes in liver, epithelia of renal tubules, and fibroblasts within muscle.
Transmural coronary venous O2 saturations in normal and isolated hearts
Authors: Monroe RG , Gamble WJ , LaFarge CG , Benoualid H , Weisul J
Published: December 2017

Blood O2 saturations were measured by microscopic oximetry in the small coronary veins of wither open-chest or isolated and blood-perfused dog hearts. Subendocardial saturations (average 34%) were significantly lower than subepicardial (average 52%) in isolated hearts contracting isovolumically at systolic and coronary perfusion pressures of 100 mmHg. Saturations of botb regions fell and were not significantly different from each other (both averaged 16%) with partial coronary occlusion. When MVo2 was increased by calcium infusion, subendocardial saturations fell sharply to about 2% and were significantly, lower than subepicardial (average 10%). Conversely, when MVo2 was decreased by ventricular decompression, saturations rose equally in subendocardium (average 40%) and subepicardium (average 45%) (not significant). These data illustrate the efficacy of cascular autoregulation in isolated hearts. In open-chest dogs, as in isolated hearts with partial coronary occlusion, subendocardial (average 20%) saturations were not significantly diffenent from each other and ranged from 0 to 70%, suggesting the possibility of significant differences either in regional coronary flow or MVo2, or both, in closely adjacent areas throughout the myocardium.
Effect of dietary D-penicillamine on metabolism of copper in the rat
Authors: Owen CA  , Randall RV , Goldstein NP
Published: December 2017

When normal rats were put on a diet containing d-penicillamine equivalent to a dosage of about 1.75 g/day in a 70-kg man, there was a prompt, marked decrease in biliary excretion of copper and of radiocopper after its intravenous administration. Urinary copper increased as tissue copper levels decreased; this decrease was most pronounced in bone marrow, kidney, lung, and spleen. Plasma copper increased and p-phenylendiamine oxidase activity increased. Fecal copper decreased modestly, which was probably attributable to decreases in food intake and biliary copper. Copper-toxic rats, already hypercupriuric, excreted more urinary copper when given d-penicillamine.
Endotoxin-induced prostaglandin E and F release in dogs
Authors: Anderson FL , Jubiz W , Tsagaris TJ , Kuida H
Published: December 2017

Prostaglandin E and F (PGE and PGF) levels in sequential blood samples obtained simultaneously from the renal and portal veins and aorta during endotoxin shock in dogs were determined by radioimmunoassay. Four groups of dogs were studied. In five control dogs in which no endotoxin was given, PGE and PGF levels did not change significantly at 0, 15, 30, 60, and 90 min. In eight dogs given endotoxin alone, PGE and PGF levels did not change in the aorta. In samples taken from the portal vein there was a significant rise in PGE and PGF 15 min after endotoxin, whereas renal vein PGE and PGF did not become significantly elevated until 60 and 90 min after endotoxin. In six dogs pretreated with acetylsalicylic acid and six dogs pretreated with indomethacin, PGE and PGF levels did not change after endotoxin. Indomethacin modified the delayed hemodynamic effects of endotoxin whereas acetylsalicylic acid did not. Neither drug blocked the immediate hemodynamic effects of endotoxin. Endotoxin-induced PGE and PGF release is probably due to increased synthesis. The mechanism whereby synthesis is stimulated and the extent to which vasomotor tone is influenced by PGE and PGF during endotoxin shock cannot be determined from our data.
Ba++ on the resting frog stomach: effects on electrical and secretory parameters
Authors: Rangachari PK
Published: December 2017

Ba++ added to the nutrient solution bathing the resting frog stomach increased resistance, decreased the PD, and stimulated acid secretion. Under short-circuit conditions, the increase in H+-secretory rate was accompanied by a decrease in short-circuit current (I-sc). These changes were reversed by NaSCN (10 mM), suggesting that Ba++ had not impaired the current-generating mechanism per se. Histamine-induced acid secretion was associated with an increase in net Cl- flux, particularly in the N yields S flux (JNS). Ba++ increased acid secretion with no increase in JNS and a decrease in net Cl- flux. The effects of Ba++ were amplified by low-Cl- solutions. Histamine, in the presence of Ba++ and low-Cl- solutions, increased acid secretion and transmucosal resistance, suggesting the operation of a neutral pump in the secretion of HCl. It is concluded that Ba++ limits Cl- entry and also acts as a secretagogue.
Postnatal development of adenylate cyclase in rat salivary glands: patterns of hormonal sensitivity
Authors: Grand RJ , Chong DA , Ryan SJ
Published: December 2017

In order to compare the known morphological changes which occur during the postnatal development of the salivary glands in the rat with alterations in membrane function, we measured adenylate cyclase activity and its responses to sodium fluoride (NaF), norepinephrine, and isoproterenol in salivary gland membranes at various times after birth. In the parotid gland, basal enzyme activity did not change significantly during postnatal life, but fluoride-stimulated activity rose on day 15; A similar marked rise in activity stimulated by norepinephrine (0.02 mM) and isoproterenol (0.03 mM) was noted simultaneously. In the submandibular gland, basal adenylate cyclase activity was higher just after birth than at 25 days of life or in maturity. Fluoride-stimulated activity was 7 times higher than basal activity on day 1, greater than 10 times higher on day 25, and 30 times greater in the adult. The gland was as responsive to norepinephrine and isoproterenol on day 5 as it was on day 25 or in the mature animal, showing a two- to threefold increase over the basal enzyme value at each time point studied. Residual phosphodiesterase activity in the membranes was always negligible. The data demonstrate a time-dependent developmental change in the responsiveness of the parotid gland to norepinephrine and isoproterenol, which corresponds to the time when morphological maturation normally occurs. By contrast, in the submandibular gland, membrane-bound adenylate cyclase is fully developed at the time of birth.
Metabolic responses to varying restrictions of coronary blood flow in swine
Authors: Liedtke AJ , Hughes HC , Neely
Published: December 2017

An in situ working swine heart preparation is described in which total coronary perfusion was controlled. At normal rates of coronary flow, oxygen, glucose, and fatty acid utilization were stable for at least a 60-min perfusion period. With a 50% reduction in coronary flow, oxygen and glucose consumption were reduced during 30 min of perfusion and fatty acid extraction was lower at the end of 30 min. Glycogen utilization was increased, but tissue levels of creatine phosphate, ATP, and lactate were similar to those in hearts receiving normal flow. With a 60% reduction in coronary flow, uptake of oxygen, glucose, and fatty acids were further decreased. Tissue levels of high-energy phosphates and glycogen were decreased and ADP, AMP, and lactate increased. Mechanical performance progressively deteriorated in these hearts, and ventricular fibrillation developed after about 20 min (19.8 plus or minus 3.0 min). The data indicate that this preparation is suitable for the study of myocardial metabolism during mild and severe ischemia and may be useful for the evaluation of pharmacological interventions designed for the treatment of myocardial ischemia.
Nonsustained pulmonary vasoconstriction during acute hypoxia in anesthetized dogs
Authors: Tucker A , Reeves JT
Published: December 2017

The objectives of this study were to describe in greater detail the initial rise and spontaneous decline in acute hypoxic pulmonary vasoconstriction and to investigate a number of mechanisms that could have caused this secondary vasodilation. With the onset of isocapnic hypoxia (Pao2 of 28, 44, or 56 mmHg), pulmonary vascular resistances increased to maximum values at 3 min and then spontaneously declined toward control values. Pulmonary perfusion pressures rose to maxima at approximately 4 min and then also declined. During severe hypoxic exposures (Pao2 of 30-37 mmHg) this secondary vasodilation was found not to be due to beta-adrenergic-induced vasodilation, withdrawal of alpha-adrenergic-induced vasoconstriction, vasodilation caused by a sustained increase in pulmonary blood flow, fatigue of the vascular smooth muscle contractile mechanism, or release of vasodilatory prostaglandins. It is suggested that the decline in hypoxic pulmonary vasoconstriction may be due to an exhaustion of a chemical mediator, release of a pulmonary vasodilator agent, or myogenic stress relaxation.
Effects of ouabain and amiloride on Na pathways in turtle bladders
Authors: Wilczewski T , Brodsky WA
Published: December 2017

In a Na-rich bathing system, addition of amiloride to the mucosal fluid of turtle bladders produces decreased in the transepithelial potential difference (PD), short-circuiting current (I-sc), and conductance. Removal of amiloride results in complete reversal of these changes; and this reversibility is incomplete in amiloride-blocked bladders exposed to ouabain. In a Na-free bathing system, step increased in mucosal [Na] evoke rapid initial spikes in PD, Isc, and conductance, the magnitudes of which are independent of prior ouabain treatment. After these spikes, PD and Isc in the ouabain-treated bladder rapidly decay, while conductance remains unchanged and high. This unchanging conductance, plus the fact that ouabain inhibits half the microsomal (Na plus K). ATPase of this tissue within 1 min, suggests that ouabain inhibits Na pumping without changing tissue conductance. The delayed decrease in conductance (beginning 30 min after ouabain addition), a nonspecific and secondary effect of ouabain, is due to a concomitant collapse of the intercellular channels.
Restitution of blood volume after hemorrhage: mathematical description
Authors: Pirkle JC  , Gann DS
Published: December 2017

An analytical model was developed to simulate the restitution of blood volume after hemorrhage. This model was used to test two previously proposed hypotheses for the restoration of plasma oncotic pressure required for full restitution of blood volume: increased lymphatic flow or decreased trans-capillary leakage of albumin. Neither hypothesis could account for the temporal and quantitative features of experimentally observed restitution of blood volume. An alternate hypothesis, that restitution of blood volume results from a fluid shift from intracellular-extracellular fluid shift occurs in dogs treated with high doses of cortisol analog. Thus the results of the simulation support the hypothesis that full restitution of blood volume requires an intracellular-extracellular fluid shift. This fluid shift may be mediated by high circulating levels of cortisol secondary to hemorrhage.
Citric, orotic, and other organic acids in rats injected with active or inactive urease
Authors: Prior RL , Zimber A , Visek WJ
Published: December 2017

Male rats were fed laboratory chow or a purified L-amino acid diet containing 11.2 or 5.6 g arginine/kg. Hyperammonemia was produced by injection of crystalline jackbean urease. Control animals were injected with saline or inactivated urease. Rats injected with 55 U urease activity/kg body wt (an LD50 dose) exhibited acute signs of hyperammonemia and elevated orotate and citrate in their urine. Plasma glucose, lactate, citrate, and alpha-ketoglutarate concentrations were also markedly elevated. Three injections of active urease (10 U/kg body wt) given at intervals of about 10 h produced hyperammonemia, which persisted for 25 h after the first injection. Blood glucose and ammonia concentrations were increased 2.6- and 22-fold, respectively, when compared with controls. Total urinary citrate excretion for 25 h was 371 mueq for active urease-injected rats compared with 62 mueq for rats injected with inactivated urease. Rats fed a purified amino acid diet containing 5.6 g arginine/kg excreted greater quantities of urea, citrate, and orotic acid than rats fed 11.2 g arginine/kg of diet. Injection of active urease increased citrate excretion by rats fed either concentration of dietary arginine. Changes produced with active urease were not observed if inactivated urease was injected.
Acute effects of lithium on the renal concentrating mechanism in a primate
Authors: Webb RK , Woodhall PB , Tisher CC , Robinson RR
Published: December 2017

Although chronic lithium therapy has been associated with a defect in the urinary concentrating mechanism, short-term renal effects of lithium have received little attention in the intact animal. Solute-free water reabsorption (T-cH2O) and free water clearance (CH2O) were measured in primates of the genus Galago under control conditions and while animals were receiving either 0.5 mmol/kg-h or 1.0 mmol/kg-h lithium chloride (135 mM) intravenously. CH2O was unchanged by lithium infusion (P greater than 0.10), whereas T-cH2O was significantly depressed at all levels of osmolal clearance (P smaller than 0.01). Spontaneous recovery of near-normal T-cH2O was documented in two animals within 1 wk following acute lithium infusion. In addition it was observed that lithium-induced depression of T-cH2O could be partially prevented by pretreatment with intravenous amiloride. These results suggest that alterations in the renal concentrating mechanism can occur rapidly following the onset of lithium administration. They also imply that impairment of the renal concentrating mechanism by lithium is due at least in part to antagonism of the action of vasopressin on the collecting duct.
Release of cyclic AMP by toad urinary bladder
Authors: Urakabe S , Handler JS , Orloff J
Published: December 2017

Cyclic AMP accumulates in the Ringer solution bathing the toad urinary bladder in vitro. At least 4 times more cyclic AMP is released into the solution bathing the serosal surface than into the solution bathing the mucosal surface. Most of the cyclic AMP originates in the epithelial cells rather than the stroma. Vasopressin increased the content of cyclic AMP in the epithelial cells and increases the amount of cyclic AMP in the Ringer solution. Since there is not an increase in medium cyclic AMP when cell cyclic AMP levels are increased by theophylline, it is suggested that theophylline may reduce the permeability of the cell membrane to cyclic AMP. Finally, it is demonstrated that 10 mM NaF increase the amount of cyclic AMP in the epithelial cells and in the solution bathing the bladder, but block the effect of vasopressin on water permeability, presumably at a step subsequent to the formation of cyclic AMP.
Ileal HCO3 secretion: relationship to Na and Cl transport and effect of theophylline
Authors: Sheerin HE , Field M
Published: December 2017

Interrelationships among Na, Cl, and HCO3 transport processes were examined in short-circuited rabbit ileal mucosa. As serosal (HCO3) was increased from 10 to 50 mM (pH from 7.1 to 7.8), net Na absorption decreased from 4.6 to 0.3 mueq/h-cm2, net Cl flux changed from absorption of 0.9 to secretion of 0.9 and a net HCO3 secretion of 3.0 developed. A similar change in net Cl flux was also observed when serosal Pco2 was altered at constant (HCO3). In Cl-free SO4-Ringer, serosal alkalinization produced net HCO3 secretion which was not significantly less than that observed in Cl-containing Ringer. Theophylline caused secretory changes in net Na and Cl fluxes at both 10 and 50 mM serosal (HCO3). Theophylline did not alter net HCO3 flux in Cl-Ringer but increased net HCO3 flux in SO4-Ringer. Total dc conductance was decreased by both serosal alkalinization and theophylline. Shortcircuit current was consistently increased by theophylline but not by serosal alkalinization. The results indicate that ileal ion transport is regulated in part by serosal pH and/or (HCO3) and that resulting changes in Cl and HCO3 transport are coupled one-for-one with changes in Na transport. Furthermore, HCO3 secretion does not require the presence of Cl in the bathing medium.
Tetany: quantitative interrelationships between calcium and alkalosis
Authors: Edmondson JW , Brashear RE , Li TK
Published: December 2017

Tetany occurs with hypocalcemia and alkalosis or both. The interrelationship of calcium and acid-base balance necessary for inducing tetany, the role of the central nervous system, and the rate of development of hypocalcemia have been investigated. Tetany occurred in less than 50 percent of one group of dogs made alkalotic by hyperventilation or made hypocalcemic by infusion of ethylene glycol-bis(beta-amino ethyl ether) N, N'-tetraacetate. In contrast, hypocalcemia combined with hypocapnic alkalosis always produced tetany. Slowly evolving hypocalcemia was achieved inanother group of dogs by thyroparathyroidectomy, and tetany was induced postoperatively by hypocapnic alkalosis. An identical relationship between serum calcium ion concentration and arterial pH or CO2 tension was found in both groups. Tetany could not be related to the cerebrospinal fluid (CSF) calcium ion content in either group. Hypocalcemia and alkalosis are therefore coparticipants in the development of tetany and are independent of the rate of development of hypocalcemia and of CSF calcium ion concentration. The importance of alkalosis in tetany with hypoparathyroidism is emphasized.
Distribution of H+ and HCO3 minus between CSF and blood during metabolic acidosis in dogs
Authors: Pavlin EG , Hornbein TF
Published: December 2017

To determine whether the regulation of brain extracellular fluid acid-base balance is by active ion transport or passive distribution, changes in cisternal and lumbar cerebrospinal fluid (CSF) (H+) and (HCO3 minus) were assessed in five dogs with normal acid-base status and in six dogs during metabolic acidosis. Both groups were mechanically ventilated to maintain a constant PaCO2. The pH, PCO2, (HCO3 minus), and (lactate) in CSF and arterial plasma and the CSF/plasma DC potential difference were determined at intervals, and the electrochemical potential differnces (mu) for H+ and HCO3 minus were calculated. Following control measurements at pHa equal to 7.40, metabolic acidosis was induced by infusion of 0.6 N HCl. Measurements were made 0, 3, 4.5, and 6 h thereafter and at 0, 3, and 6 h in the control series. A steady state for ion distribution was reached by 4.5 h. In the control series at 6 h the values of mu for H+ and HCO3 minus were within minus 0.2 and +0.5 mV of initial values at the cistern and +0.1 and +0.9 mV at the lumbar site. During metabolic acidosis, the 6-h values at the cistern returned to 0.0 and +0.7 mV of control for muH+ and muHCO3 minus while lumbar values returned to +0.5 and minus 0.4 mV. The closeness of these 6-h values of mu to control is compatible with passive distribution of H+ and HCO3 minus between CSF and blood.
Distribution of H+ and HCO3 minus between CSF and blood during metabolic alkalosis in dogs
Authors: Pavlin EG , Hornbein ttf
Published: December 2017

In anesthetized, paralyzed dogs ventilated to maintain a normal PaCO2, metabolic alkalosis was induced and held constant over 6 h by infusion of sodium bicarbonate. Determination of pH, PCO2, (HCO3 minus), and (lactate) in cisternal and lumbar cerebrospinal fluid (CSF) and in arterial plasma together with measurement of the CSF/plasma DC potential differences permitted calculation of the electrochemical potential difference (mu) for H+ and HCO3 minus; measurements were made prior to induction of metabolic alkalosis at pHa equal to 7.40, as soon after induction as stable arterial values were achieved and 3, 4.5, and 6 h thereafter. A steady state for ion distribution was reached by 4.5 h. Values of mu for H+ and HCO3 minus returned to +0.1 and +0.9 mV of control at 6 h for cisternal CSF and +0.6 and minus 0.4 mV for lumbar CSF. This return of muH+ and muHCO3 minus close to control in the steady state is compatible with passive distribution of these ions between brain extracellular fluid and blood.
Effects of flow rate and potassium intake on distal tubular potassium transfer
Authors: Khuri RN , Strieder WN , Giebisch G
Published: December 2017

Potassium transport was studied across proximal and distal tubular epithelium in rats on a normal, low- and high-potassium intake during progressive loading with isotonic saline (150 mM) or a moderately hypersomotic urea (200 mM) sodium chloride (100 mM) solution. Free-flow micropuncture and recollection techniques were used during the development of diruesis and tubular fluid (TF) analyzed for inulin-14C, potassium (K) and sodium (Na). Tubular puncture sites were localized by neoprene filling and microdissection. During the large increase in tubular flow rates (10 times): 1) fractional potassium reabsorption fell along the proximal tubule, 2) TFk along the distal tubule remained constant and independent of flow rate in control and high-k rats; thus, net potassium secretion increased in proportion to and was limited by flow rate. 3) In low-K rats TF k fell; with increasing flow rates distal K secretion was not effectively stimulated. 4) Distal tubular sodium reabsorption increased in all animals with flow rate, but tubular Na-K exchange ratios varied greatly. It is suggested that whenever sodium delivery stimulates distal tubular potassium secretion it does so by 1) increasing volume distal tubular potasssium secretion and by 2) augmenting the transepithelial electrical potential difference (lumen negative).
Afferent aortic nerve fibers with their pathways in cardiac sympathetic nerves
Authors: Uchida Y
Published: December 2017

The effect of mechanical and chemical stimulation on activity of afferent aortic nerve fibers with pathways in the cardiac sympathetic nerves has been examined. Action potentials were derived from the second or third thoracic communicating ramus of the left side of anesthetized dogs. Thirty myelinated and 19 unmyelinated fibers responded to tapping the ascending aorta, aortic arch, and descending aorta. Both groups of fibers also responded to a rise as well as to a fall in aortic pressure. Spontaneous discharge of myelinated fibers was related to aortic pressure pulse whereas that of unmyelinated fibers was related to respiration. Asphyxia caused excitation of unmyelinated fibers but not of myelinated fibers. Both groups of fibers responded to topical application of lactic acid. Mechanical and chemical stimulation of the aorta after vagotomy caused a rise in systemic blood pressure and extension of the limbs. The results indicate the existence of afferent aortic fibers in the cardiac sympathetic nerves that cause circulatory and somatic responses.
Concentration of urine by the hibernating marmot
Authors: Zatzman ML , South FE
Published: December 2017

Studies wer performed with marmots (Marmota flaviventris) of both sexes that had chronic arterial, venous, and bladder catheters. Urine collection was performed during hibernation and urine osmolalities (611.6 not equal to 166.1 SD) were found to be lower than those of aroused animals (1264 not equal to 472.9 SD), but hypertonic to plasma. Peak osmolality of meduallary slices was found to be in the range of osmotic pressures of urine obtained from hibernating or aroused animals. After single injections of a mixture of rho-aminohippurate and inulin, or during constant infusion of inulin, steady-state excretion by hibernators was not achieved for several days. Indirect evidence indicateds that the hibernating marmot is capable of PAH secretion.
Effects of thyroid hormone administration on skeletal muscle mitochondria
Authors: Winder WW , Baldwin KM , Terjung RL , Holloszy JO
Published: December 2017

The effects of thyroid hormone administration on the levels of a number of mitochondrial markers were measured in skeletal muscle and liver of normal rats. Injection of 18 mug of L-thyroxine (T4) per 100 g body wt every 4th day for 3 wk had no effect on the concentrations of cytochrome c, on citrate synthase activity, or on respiratory capacity of skeletal muscle. Injection of 200 mug of L-triiodothyronine (T3) daily for 5 days, or feeding 23 mg T4 and 7 mg T3/kg of diet for 2 wk, resulted in thyrotoxicosis and large increases in the activity of hepatic alpha-glycerophosphate dehydrogenase and other mitochondrial markers; however, the levels of activity of mitochondrial marker enzymes in gastrocnemius and quadriceps muscles were not significantly changed. Only when rats were fed 3 mg T4 and 1 mg T3/kg diet for a 6-wk period did we observe an increase in skeletal muscle mitochondrial markers. Thus, thyroxine treatment must be sufficiently prolonged if it is to be used as a tool for studying skeletal muscle mitochondrial biogenesis.
Metabolic adaptation of the chick embryo to chronic hypoxia
Authors: Beattie J , Smith AH
Published: December 2017

In a colony of white leghorn chickens maintained at 3,800 m successive generations exhibited an increasing hatchability of fertile eggs incubated at elevation of 3,100m. Embryonated eggs produced by the high-altitude-adapted line (WM) and by genetically similar but unselected stocks at sea level (D) were incubated at 3,100 m and at sea level, and the oxygen consumption was measured on individual eggs after the 17th day of incubation. At sea level, oxygen consumption rates of WM strain were less than that of SL stocks during late embryonic development. At 3,100 m, embryonic respriation of all strains was reduced, but to a much lesser degree in the high-altitude strain. It appears that a decreased metabolic activity of the late embryo coupled with a slower rate of embryonic developement is an important factor in the adaptation of the domestic fowl to high altitude.
Salicylate, tryptophan, and tyrosine hypothermia
Authors: Francesconi RP , Mager M
Published: December 2017

The intraperitoneal administration of sodium salicylate, L-tryptophan, and tyrosine resulted in significant hypothermia when rats were exposed to a 4degree C ambient temperature. Salicylate and tryptophan increased plasma levels of nonprotein-bound tryptophan while total and bound tryptophan were reduced in salicylate-treated rats.Tryptophan concentrations were unaffected by tyrosine administration. Concomitant with increases in free plasma tryptophan, there occurred significant rises in brain levels of tryptophan in both groups of rats, while brain tyrosine levels were increased in those rats receiving tyrosine. Similarly, significant increments in hypothalamic serotonin levels in rats receiving salicylate or L-tryptophan and increases in hypothalamic norepinephrine in tyrosine-treated rats seem to reflect the increased availability of tryptophan and tyrosine for monamine synthesis. However, alternative mechanisms of hypothermiaseem to be operative since oxygen consumption studies demonstrate dissimilar results for tryptophan and salicylate administration.
Myocardial performance during hemorrhagic shock in the pancreatectomized dog
Authors: Coleman B , Kallal JE , Feigen LP , Glaviano VV
Published: December 2017

Myocardial performance was evaluated in nine pancreatectomized and 12 nonpancreatectomized dogs by measuring left ventricular pressure (LVP), maximal dP/dt (max dP/dt), left ventricular end-diastolic pressure (LVEDP), pulmonary arterial pressure (PAP), aortic pressure (AoP), and lead II of the electrocardiogram during standardized hemorrhagic shock. Cardiac output (CO) and hematocrit were determined before hemorrhage, after 4 h of oligemia, when postinfusion mean blood pressure declined to 60 mmHg. Left ventricular function curves were obtained, by varying preload, in control dogs and 2 h after reinfusion of the shed blood in those dogs subjected to shock. Both groups of dogs showed identical responses to the shock procedure. In the immediate postinfusion period, LVP, max dP/dt, LVEDP, and mean blood pressure returned to near-control values, while PAP was significantly elevated. The postinfusion decline (after 60-90 min) in AoP was accompanied by a similar reduction in LVEDP. Left ventricular performance in hemorrhagic shock did not differ significantly from that seen in control dogs. In addition, there was no electrocardiographic indication of myocardial ischemia. The data indicate that terminal hemorrhagic shock need not be accompanied by myocardial depression whether or not the pancreas is intact.
Magnesium effects in rabbit ventricle
Authors: Shine KI , Douglas AM
Published: December 2017

Ten to twenty millimoles per liter Mg did not affect 42-K exchange in control isolated blood-perfused rabbit septa, but abolished acetyl strophanthidin (ACS)-induced net 42-K loss (constant heart rate) without attenuating the mechanical response. In six septa ACS-induced net K loss was reduced from 159.3 plus or minus 45 to 43.5 plus or minus 35 mumol/kg tissue water (P smaller than 0.05) by increasing Mg from 1.0 to 20 mM without a change in inotropic response. Ten to twenty millimoles per liter Mg did not reverse ACS inhibition of 42-K5 tissue uptake. In eight septa 16 mM K doubled the efflux rate for 42-K in 1mM Mg. Twenty millimoles per liter Mg abolished this effect. Sixteen millimoles per liter K increase 42-K effluent counts by 99.5 plus or minus 18.5 percent of control in 1.0 mM Mg, but by 44.9 plus or minus 14.1 percent (P smaller than 0.001) in 20 mM Mg. Mg inhibited 42-K exchange at sites that became rate limiting after ACS treatment. These sites were activated by 16mM K. ACS inotrophy was not quantitatively related to net K loss. The Mg effect during digitalis exposure did not result from reversal of ACS inhibition of NA-K-ATPase activity but from a separate effect on K efflux.
Effect of angiotensin II and an angiotensin II inhibitor on renin secretion in the dog
Authors: McDonald KM , Taher S , Aisenbrey G , De Torrente A , Schrier RW
Published: December 2017

This study examined the effect of angiotensin II (AII) and (Sar-1Gly-8) AII, a competitive inhibitor of AII, on renin release in anesthetized dogs. An intravenous infusion of AII (25 ng/kg per min) raised BP 24 mmHg and lowered plasma renin activity (PRA) from 18.8 plus or minus 2.8 to 6.2 plus or minus 1. 3 ng/ml per h (P smaller than .001). When the intravenous infusion of AII inhibitor (1.0 mug/kg per min) was superimposed on the AII infusion, PRA rose from 6.5 plus or minus 22 to 12.3 plus or minus 3.6 ng/ml per h (P smaller than .02). Renal hemodynamics, BP, and urinary sodium excretion (UNaV) reverted toward pre-AII control values. A small dose of AII inhibitor (0.1 mu/kg per min) was then infused into one renal artery in animals receiving the constant intravenous infusion of AII. Renin secretion rate (RSR) increased significantly, not only in the infused kidney, but also in the contralateral kidney. In the latter there were no changes in renal hemodynamics or UNaV, and RSR was unimpaired by denervation of that kidney. The results suggest that the AII inhibitor blocks both the vascular and the renin-suppressing actions of AII and that the latter effect is more susceptible to inhibition.
Heart rate response to sympathetic stimulation before and after sodium pentobarbital
Authors: Cowan MJ , Scher AM , Hildebrandt J
Published: December 2017

Heart rate response to electrical stimulation of the right stellate ganglion of vagotomized cats was studied before and after the administration of sodium pentobarbital. The increase and decrease of heart rate with the initiation and cessation of sympathetic stimulation could be accurately described by separate exponential time functions. The time constants of rise and decline, the maximum steady-state heart rate, and the time between cessation of stimulation and initial decrease of heart rate (lag) were functions of the frequency and voltage of stimulation. The main effects of sodium pentobarbital were: 1) to prolong the rise of heart rate by 20-30 percent (P smaller than 0.0001),2) to prolong the decay of heart rate by 36-56 percent (P smaller than 0.005), and 3) to decrease the resting heart rate. The effects were observed 10 min after administration of the drug and lasted at least 4 h.
Ca++ and pancreatic amylase release
Authors: Williams JA , Chandler D
Published: December 2017

The effects of Ca'++ on release of amylase by mouse pancreas in vitri was studied.The cholinergic agonist bethanechol was depressed about 50% in O Ca'++ medium.When pancreatic fragments were superfused with O Ca'++ medium, bethanechol still produced a normal stimulation of amylase release after half of the total tissue Ca'++ was washed out. This Ca'++ loss included both extracellular and some intracellularCa'++. Uptake and equilibration of '45Ca'++ into pancreatic fragments was multiphasic, with total equilibration with stable Ca'++ still not reached after 3 h. Addition of bethanechol had no effect on the rate of '45Ca uptake and equilibration. '45Ca'++ efflux was not influenced by superfision in O Ca'++ medium, while thestimulation of '45Ca'++ efflux by bethanechol was enhanced. It is concluded that extracellular Ca'++ and/or Ca'++ influx is not of major importance in triggering pancreatic enzyme release, but that extracellular Ca'++ may regulate the release process thus accounting for the parallel changes in unstimulated and stimulated amylase release.
Escape from vasoconstriction in the gastric microcirculation
Authors: Guth Paul H. , Smith Esther
Published: December 2017

Escape of splanchnic resistance vessels from vasoconstriction due to adrenergic stimulation has been attributed to increasing submucosal blood flow due to dilation of submucosal arteriovenous anastomoses (shunts). This postulate, as applied to the rat gastric microcirculation, was studied by in vivo microscopy. Using an image-splitting TV microscope recording system, response of gastric submucosal arterioles (13–33 µm) to 3 min of left splanchnic nerve stimulation, norepinephrine superfusion, and vasopressin superfusion was measured. All stimuli produced initial vasoconstriction. Escape occurred in all rats with nerve stimulation and norepinephrine, but in only one of five with vasopressin. No shunts were seen. The study demonstrates that the gastric submucosal arterioles exhibit an escape phenomenon, suggesting that "autoregulatory escape" in other splanchnic beds also may be due to relaxation of constricted vessels and not to opening of shunts.
Influence of poststimulation potentiation and heart rate on the fetal lamb heart
Authors: Kirkpatrick SE , Naliboff J , Pitlick PT , Friedman WF
Published: December 2017

Isolated cardiac muscle techniques and studies of the chronically instrumented fetal lamb heart were employed to evaluate the ability of fetal myocardium to exhibit poststimulation potentiation. Isometric tension development and the response to paired electrical stimulation were significantly reduced in isolated fetal ventricular myocardium when compared to the adult (P less than 0.001). As in the adult, increasing stimulation frequency raised fetal isometric tension via an increase in the rate of rise of tension development in the presence of reduction in time-to-peak tension. In seven fetal lambs the left ventricle was chronically instrumented with endocardial ultrasonic crystals and a high-fidelity micromanometer. After a 2-wk recovery period, heart rate was increased by atrial pacing from an average control level of 150 to 300 beats/min. Left ventricular dP/dt increased progressively and then fell beyond a heart rate of 270/min. When comparable pre- and immediate postpacing beats were analyzed, a step-wise increase in the velocity of left ventricular shortening and the mean rate of circumferential fiber shortening was observed in association with an increase in the extent of shortening. Thus, increases in the frequency of contraction exert a significant positive inotropic effect on the fetal heart.
Adaptation to fasting in baboon. II. Regulation of lipolysis early and late in fasting
Authors: Koerker DJ , Goodner CJ , Chideckel EW , Ensinck JW
Published: December 2017

Regulation of lipolysis by the sympathetic nervous system, basal insulin, and glucagon was studied in fasted baboons. Beta-Adrenergic mechanisms were evaluated by blockade with propranolol after 24, 40, and 65 h of fasting. Inhibition of lipolysis decreased with increasing duration of fasting. Insulin concentrations were markedly reduced by propranolol at all stages of fasting, whereas glucose and glucagon concentrations were unchanged. The roles of insulin and glucagon were evaluated by a 2-h infusion of somatostatin after 18 and 65 h of fasting. At both times, insulin and glucagon concentrations were markedly reduced. At 18 h of fasting but not at 65 h, lipolysis doubled. At both times the plasma glucose concentration fell 15-30%. At 18 h, preventing the decrease in glucose with glucose infusion prevented the increase in lipolysis. These data suggest that a beta-adrenergic mechanism is largely responsible for regulation of lipolysis early in fasting and that insulin, glucagon, and beta-adrenergic mechanisms play no major part in the maintenance of the accelerated lipolysis later in fasting.
Effect of exercise on lipoprotein lipase activity in rat heart and skeletal muscle
Authors: Borensztajn J , Rone MS , Babirak SP , McGarr JA , Oscai LB
Published: December 2017

Lipoprotein lipase activity was measured in the three skeletal muscle fiber types of untrained rats and in those of rats subjected to a 12-wk program of treadmill running. Lipoprotein lipase activity in slow-twitch red fibers was approximately 14- to 20-fold higher (P less than 0.001) than that in fast-twitch white and approximately 2-fold higher (P less than 0.001) than that in fast-twitch red fibers in the untrained animals. These results suggest that, in sedentary animals, mainly slow-twitch red and fast-twitch red fibers are capable of taking up plasma triglyceride fatty acids. Regularly performed endurance exercise resulted in significant increase (2- to 4.5-fold) in lipoprotein lipase activity in the three muscle fiber types examined. The increase in lipoprotein lipase activity in response to treadmill running suggests that exercise increases the capacity of these fibers to take up and oxidize plasma triglyceride fatty acids. Cardiac muscle did not undergo an exercise-induced increase in the levels of activity of lipoprotein lipase similar to that seen in skeletal muscle.
Plasma amino acid levels and development of hepatic gluconeogenesis in the newborn rat
Authors: Girard  , Guillet I , Marty J , Marliss EB
Published: December 2017

The metabolism of endogenous and exogenous amino acids has been characterized during a 16-h fast after birth in the rat. Eighteen of 22 amino acids showed a decrease in plasma concentration up to 16 h, the most profound and sustained changes affecting those quantitatively important in gluconeogenesis. The hepatic accumulation of injected [14C]aminoisobutyric acid showed a progressive rise after birth. The in vivo conversion of 14C-labeled lactate, alanine, serine, and glutamine to [14C]glucose increased for 6 h, but all except glutamine showed a decline by 16 h. The in vitro conversion of several gluconeogenic substrates (10mM), however, increased with time in each instance. These data confirm that the capacity for hepatic gluconeogenesis and maintenance of blood glucose concentration appears immediately after birth. Nevertheless, profound hypoglycemia recurs at 16 h and responds only minimally and transiently to exogenous gluconeogenic substrate loads. In contrast, the fed newborn maintains normoglycemia, higher endogenous amino acid levels, and the capacity for substrate conversion at this time. The mechanism for stimulation of hepatic gluconeogenic pathways thus is present in both fasted and fed neonatal rats. However, owing to insufficient energy sources to sustain gluconeogenesis and to inadequate gluconeogenic substrate, the rat is unable to maintain normoglycemia if fasted 16 h.
Dispersed rat parotid acinar cells. II. Characterization of adrenergic receptors
Authors: Mangos JA , McSherry NR , Barber T , Arvanitakis SN , Wagner V
Published: December 2017

The in vitro characterization of adrenergic receptors in isolated rat parotid acinar cells was accomplished through investigations of the transmembrane influxes of K and of the secretion of amylase in response to interactions of the cells with selected agonists and antagonists. Interaction of epinephrine (EPI) at concentrations of 10(-3)-10(-9) M with the alpha-adrenergic receptors resulted in rapid efflux of K from the cells. This effect was inhibited by phentolamine but not by propranolol or atropine. The process of secretion of amylase by these cells involved the activation of the beta-adrenergic receptors by the adrenergic agonists DL-isoproterenol (IPR) and EPI at similar to above concentrations. The interaction of these agonists with the beta receptors was inhibited by propranolol but not by phentolamine or atropine. Dibutyryl clclic AMP stimulated secretion of amylase at concentrations of 10(-8) M. A progressive increase in the secretory response of the cells was observed with increases in the dibutyryl cyclic AMP concentrations up to 10(-5) M. This effect was not inhibited by propranolol. This study demonstrates that dispersed rat parotid acinar cells have functionally intact adrenergic receptors and could be used as experimental tools for the studies of receptor physiology and pharmacology as well as other aspects of secretion at the cellular level.
Tubular organization and vascular-tubular relations in the dog kidney
Authors: Beeuwkes R , Bonventre JV
Published: December 2017

Tubular organization and vascular-tubular relations were studied by double injection in canine kidneys. Blood vessels were injected via the artery after perfusion fixation. Tubules were injected by micropipettes inserted into the urinary spaces of selected glomeruli in cleared slices. One hundred proximal convoluted tubules, 16 Henle loops, and 5 distal convoluted tubules were defined. Only subcapsular proximal convolutions were perfused by efferent vessels arising from the same glomerulus (43 of 55). In midcortex, proximal convolutions were generally perfused over less than half their length by the parent efferent (21 of 31). Here tubules entirely perfused by the parent efferent were rare (2 of 31). No inner cortical proximal convolutions were perfused by the efferent from the same glomerulus (0 of 14). Henle's loops were found to be perfused by the efferents of many glomeruli regardless of the cortical position of the parent glomerulus. Distal convolutions shared the perfusion of proximal convolutions of the same glomerulus. Thus, each nephron is apparently functionally dependent on efferent blood from glomeruli of many other nephrons. New synoptic diagrams of canine renal organization are presented.
Effect of beta-adrenergic blockade and inhibitors of angiotensin II and prostaglandins on renal autoregulation
Authors: Anderson RJ , Taher MS , Cronin RE , McDonald KM , Schrier RW
Published: December 2017

The role of the renin-angiotensin system and prostaglandins in renal autoregulation was investigated in dog kidneys in situ. Renal autoregulation during decreases in renal arterial pressure (RAP) was examined in animals pretreated with a competitive antagonist of angiotensin ii, [1-sarcosine, 8-glycine] angiotensin II, or one of two chemically dissimilar inhibitors of prostaglandin synthetase, indomethacin and meclofenamate. Because of recent evidence suggesting a role for an intrarenal beta receptor in regulating renin release, renal autoregulation was also examined in animals treated with the beta-adrenergic blocking agent propranolol. In all groups of animals constancy of glomerular filtration rate (GFR) and renal blood flow (RBF) was observed after substantial decreases in RAP to a range of 70-90 mmHg. These studies therefore do not provide evidence in support of a role for angiotensin II, prostaglandins, or an intrarenal beta receptor as mediators of the renal autoregulation of GFR or total RBF.
Pressure-flow and volume-flow relationships of the systemic circulation of the dog
Authors: Green JF
Published: December 2017

Mean systemic pressure-flow (Ps-Q) and volume-flow (V-Q) relationships of the systemic vascular bed were determined in two groups of dogs anesthetized with sodium pentobarbital (group I) and with methoxyflurane (group II). All blood returning to the heart (Q) was removed from the right atrial appendage and passed through a Starling resistor, a pump, a flowmeter , and then returned directly into the pulmonary artery. Ps was estimated from plateau values of right atrial pressure obtained during stop-flow procedures. Both the Ps-Q and V-Q relationships were nonlinear. This nonlinearity may be attributed to a redistribution of blood flow between systemic vascular compartments of unequal time constants. With group II, the Ps-Q and V-Q curves were shifted markedly to the right along the Ps and V axes, respectively. Evidence is presented which suggests that this shift was due to an effective back pressure other than right atrial pressure produced by a hepatic waterfall. The beta-adrenergic antagonist practolol increased the effective back pressure and augmented the shift in the Ps-Q and V-Q curves.