bluuebunny/crossref_metadata_2025 huggingface dataset:
Rates of insorption of sodium and potassium from stomachs of rats
Authors: Moll Johann C. , Code Charles F.
Published: December 2017

This study was undertaken to determine rates of insorption of radiosodium and radiopotassium from secreting and nonsecreting stomachs of rats. The methods employed have been described previously. Insorption of radiosodium from gastric contents to blood was always faster in nonsecreting than in acid-secreting stomachs. At the end of 15, 30, and 45 min the mean percentages insorbed from stomachs secreting acid were 1.6, 3.1, and 4.5, whereas from stomach not secreting acid the mean percentages were 5.8, 9.3 and 11.7, respectively. In contrast, the rate of insorption of radiopotassium was unaffected by presence or absence of acid. Its rate of insorption was uniformly low and about equal to the rate of insorption of radiosodium from the secreting stomach. The results demonstrate that the rat's stomach, like that of man and dog, offers a barrier to insorption of sodium which is more pronounced when acid is being secreted and that insorption of potassium, though slow, is unaffected by acid and most likely is independent of insorption of sodium.
Estimated regional blood flow by rubidium 86 distribution during arousal from hibernation
Authors: Bullard Robert W. , Funkhouser Gordon E.
Published: December 2017

The local organ or tissue blood flows during the process of arousal from hibernation have been estimated in the 13-lined ground squirrel by the Sapirstein method, which consists of the measurement of the regional distribution of injected rubidium 86. The studies demonstrated that during arousal there is a confinement of blood flow to the thoracic regions. After the heart rate has attained 100 beats/min, blood flow increases to the anterior portions of the animal. At the arousal level characterized by a heart rate of 200 beats/min, blood flow to anterior and thoracic tissue had attained levels almost equal to control flows. Posterior tissue flows were still much lower than control flows. The centralization of blood flow to thoracic and anterior tissues did not occur in the rat in the hypothermic state.
Rate of carbon clearance in three strains of germfree mice
Authors: Doll James P.
Published: December 2017

Three strains of germfree mice (ND-1, ND-2, C57), along with conventional controls, were compared in terms of their ability to rid the blood stream, via the reticuloendothelial system, of intravenously injected colloidal carbon. K values of ND-1 germfree mice were lower than values for their conventional controls, but there was no difference between ND-2 and C57 germfree and their controls. Germfree ND-1 mice had lower K values than germfree ND-2 or C57. Clearance rates were correlated to relative combined weights of liver and spleen. There was no significant difference in α values among these animals, indicating that although the liver + spleen weights of ND-1 were lower, these organs were not atrophied or nonfunctional. When the germfree mice with smaller liver + spleen weights were "conventionalized," relative liver + spleen weight increased as did their K values. No such increase was noted with conventionalized ND-2 mice. In other laboratories, ND-1 mice were found to be more susceptible to infectious agents than ND-2.
Temperature response of tube-fed rats
Authors: Hamilton C. L. , Brobeck John R.
Published: December 2017

Colonic temperatures of rats were recorded for periods of 3.5–5 hr after tube feeding at three ambient temperatures. At a neutral temperature (24 C) fall in body temperature was inversely related to calories intubated. In heat (32 C and 38 C) there was a direct relationship between calories intubated and body temperature. At 38 C mortality rate was a direct function of calories.
Effects of saturated and unsaturated fat feeding on experimental thromboatherosclerosis
Authors: Friedman Meyer , Byers Sanford O.
Published: December 2017

Intra-aortic insertion of magnesium-aluminum-zinc wire was used to induce experimental aortic thrombosclerosis in rabbits fed kennel chow and in rabbits fed chow supplemented with cholesterol, with and without additions of saturated or unsaturated fat. In the absence of cholesterol supplement, no spontaneous atherosclerosis developed and no excess lipid appeared in the thrombosclerotic plaque, regardless of supplementations with saturated or unsaturated fat. In the presence of cholesterol supplement, both spontaneous atherosclerosis and thromboatherosclerosis were noted. Additional supplementations with saturated or unsaturated fat did not ameliorate either lesion. Rabbits ingesting cholesterol plus unsaturated fat exhibited no less hypercholesteremia, spontaneous atherosclerosis, and thromboatherosclerosis than did rabbits on any other regimen. The results are discussed with reference to the effect of oral unsaturated fat on bile acid and cholesterol within the intestinal lumen.
Retention of potassium by mitochondria
Authors: Gamble James L.
Published: December 2017

Potassium of washed liver mitochondria behaves as though contained at a relatively fixed concentration, close to 90 mEq/ liter, in a compartment which includes approximately 1/3 the volume of centrifuged pellets. This compartment may be the membranous substance of the wall and cristae. With kidney mitochondria the amount retained in this way can be increased by 20–50% with initiation of respiration. This effect is inhibited by cyanide and by dinitrophenol; and it has appeared, in studies with radioactive potassium, to be an example of net uptake.
Effect of insulin on fatty acid transport and regional metabolism
Authors: Shoemaker William C. , Carruthers Peter J. , Elwyn David H. , Ashmore James
Published: December 2017

The effects of insulin on organ or regional free fatty acid (FFA) movements were measured in the unanesthetized dog. Using chronic indwelling catheters in the portal vein, hepatic vein, and splenic artery together with hepatic blood flow measurement by a modified Bromsulphalein method, the net rate of hepatic FFA uptake or output was calculated. Similarly, the rate of FFA metabolism by the nonhepatic splanchnic area was approximated. There was a marked increase in the rate of FFA uptake by the liver after insulin and a lesser uptake by the nonhepatic splanchnic area. The rate of omental FFA output or uptake was obtained by collecting the omental efflux with a system of catheters and snares into graduate cylinders over time periods. The omental FFA output was calculated as the product of the omental venous-arterial concentration difference and the omental blood flow. The omentum took up FFA in the period immediately after insulin but later on released them. The hindquarters also showed a decreased FFA output after insulin administration.
Factors affecting liver uptake of serum free stearic acid-1-C14
Authors: Trout David L. , Estes E. Harvey
Published: December 2017

Hepatic extraction of intravenously injected albumin-bound stearic acid-1-C14 was studied in anesthetized rats. Hepatic C14 contents were nearly maximal within 4 min and, in young fed females, represented 47% of the injected label. By this time, about 98% of the stearate-1-C14 in the livers of all groups had been esterified and appeared chiefly in the phospholipids. Livers of large fed rats (500–600 g) and of 2-day fasted animals represented a smaller portion of body weight and acquired a lesser fraction of the injected stearate-1-C14 than did those of young fed controls. Subcutaneous epinephrine also reduced hepatic C14 incorporation. A single feeding of fasted rats with glucose or olive oil had no significant effect on C14 distribution. Contrary to inferences from several recent studies, there was no consistent relationship between serum free fatty acid level and the fraction of injected stearate-1-C14 appearing in the livers.
Effects of metabolic disturbances on potential difference across intestinal wall of rat
Authors: Sawada Masashi , Asano Tomoaki
Published: December 2017

The potential difference across the wall of the small intestine was determined in vitro under a variety of conditions using rats. When the normal Ringer's containing 200 mg/100 ml glucose was applied on both sides of the wall, the potential difference attained 5–9 mv, the serosal side being positive. The potential difference was temperature dependent, becoming reduced at low temperature, the temperature coefficient being 1.7 between 40 and 34 C. The potential difference was inhibited with 0.1 mm monoiodoacetic acid, 1 mm sodium azide, 0.1 mm dinitrophenol, and 50 µm ouabain applied on the mucosal side. Withdrawal and restitution of 200 mg/100 ml glucose on the mucosal side induced a rapid decline and recovery of the potential difference. The lowered potential difference was partially recovered by 200 mg/100 ml galactose but not by sorbitol.
Inactivity of cerebrospinal fluid in regulation of blood glucose concentration
Authors: Sloviter Henry A. , Sakata Kazuki
Published: December 2017

Experiments in dogs and rabbits have shown that increasing or decreasing the concentration of glucose in cerebrospinal fluid has no significant effect on the blood glucose concentration. The presence of 2-deoxy-d-glucose or d-ribose in spinal fluid also does not influence blood glucose concentration although these substances have a marked effect when given intravenously. The injection of insulin into the spinal fluid does not affect blood glucose concentration except that if a large amount is injected, then blood glucose concentration decreases as a result of the absorption of insulin from the spinal fluid into the systemic circulation.
In vitro antifibrinolytic activity of various compounds
Authors: Barr Fred S. , Brent B. J. , Holtman D. Frank
Published: December 2017

Adrenochrome monosemicarbazone, vitamin C, nicotinic acid, epsilon aminocaproic acid, 4-aminobutyric acid, sodium salicylate, and adrenochrome isonicotinic acid hydrazone were tested for antifibrinolytic activity in vitro. Adrenochrome monosemicarbazone, epsilon aminocaproic acid, 4-aminobutyric acid, and adrenochrome isonicotinic acid hydrazone were found to exert an antifibrinolytic effect. Vitamin C was considered to have minimal effect and nicotinic acid and sodium salicylate were ineffective.
Statistics of spontaneous electrical activity of supra- and ectosylvian gyri of the dog
Authors: Tunturi Archie R.
Published: December 2017

The standard deviations of the spontaneous electrical activity (SEA) of the suprasylvian gyrus (SSG) ranged between 57–131 µv and for the middle ectosylvian (MES) gyrus, 88–175 µv. Correlation coefficients, r, served to distinguish three regions of the SSG. The rostral showed low correlation with the middle, high correlation with the caudal, and low to negative correlation with the MES. The middle showed moderate correlation with the MES, and the caudal showed zero to negative correlation with the MES. Within the SSG, correlation was low and in the MES high, for spacings of 2 mm. Cocaine applied to both areas sharpened the boundaries at the sulci, reduced standard deviations, did not affect the correlation between the caudal SSG and the MES area, and increased r between all locations in the MES but not in the SSG. Cocaine on the SSG had no effect on the mean and standard deviation of the evoked potential in the MES, but decreased r of the SEA significantly.
Diastolic pressure and peripheral resistance during stellate ganglion stimulation
Authors: Freis Edward D. , Cohn Jay N. , Liptak Thomas E. , Kovach Aristide G. B.
Published: December 2017

The mechanism of the diastolic pressure elevation occurring during left stellate ganglion stimulation was investigated. The cardiac output rose considerably, the heart rate remained essentially unchanged, and the total peripheral resistance fell moderately. The diastolic rise appeared to be due to increased blood flow rather than to any active changes in resistance vessels.
Effect of vasopressin and dehydration on protein-bound sulfhydryl and disulfide groups in renal cells
Authors: Molina G. , Farah A. , Kruse R.
Published: December 2017

Antidiuresis caused by the injection of vasopressin in rats can be correlated with a reduction in protein-bound sulfhydryl (PBSH) but not with changes in protein-bound disulfide (PBSS) in the cytoplasm of kidney tubular cells. During recovery from the effects of vasopressin PBSH increased while PBSS virtually disappeared. Amounts of vasopressin which were associated with a reduction in PBSH in the cytoplasm of renal cells produced a slight increase in liver cytoplasmic PBSH. Oxytocin did not produce these changes in PBSH in renal cells. Quantities of vasopressin as small as 0.1 milliunits given subcutaneously produced near maximal effects on PBSH. Dehydration produced effects similar to those observed with vasopressin injections and rehydration of dehydrated rats produced a recovery of PBSH and a temporary disappearance of PBSS. These results have been discussed and it is concluded that the PBSH changes observed cannot be produced by a stoichiometric binding with antidiuretic hormone. It is proposed that vasopressin, by reducing PBSH, produces some configurational changes in the membrane which might increase the permeability of these membranes to water and electrolytes.
Inhibitory synaptic potential of frog motor neurons
Authors: Kubota Kisou , Brookhart John M.
Published: December 2017

Using isolated frog spinal cords treated lightly with pentobarbital, intracellular recordings from motor neurons revealed hyperpolarization of the membrane following selected dorsal root stimulation. The response showed 5.0 msec latency, 6.4 msec rise time, and 16.9 msec time constant of decay. Its reversal potential was 7.6 mv more negative than resting membrane potential. Threshold of the membrane for spike generation increased corresponding to the time course of the hyperpolarization. Spike potential generation following excitatory synaptic activation (dorsal root, lateral column, and adjacent ventral root) was depressed during the hyperpolarizing potential. Therefore, this hyperpolarization can be designated as inhibitory synaptic potential (IPSP). Pentobarbital sensitivity suggests a polysynaptic pathway. Evidence is presented which suggests that the IPSP is initiated from terminals on the somatic portion of the membrane.
Changes in bone potassium in response to hypercapnia
Authors: Clancy Richard L. , Brown E. B.
Published: December 2017

Experiments were carried out on two groups of rats and one group of dogs for the purpose of determining the effect of hypercapnia on bone potassium. Rats that breathed 30% CO2 for 4 hr did not show a statistically significant change in the concentration of potassium in compact bone. Four hours of breathing 30% CO2 in dogs and 48 hr of 15% CO2 in rats, however, resulted in an increase in bone potassium. Changes in potassium in bone and interstitial fluid were in the same direction but the magnitude of change in interstitial fluid was not sufficient to account for the change in bone. All of the experiments indicate that bone does not contribute to the hyperkalemia associated with respiratory acidosis since bone apparently takes up potassium which is being transferred to the extracellular fluid from other sources.
Dose and time as variables in barbiturate action upon water ingestion
Authors: Schmidt H. , Dry L.
Published: December 2017

The effect of phenobarbital, amobarbital, and secobarbital upon the volume of water ingested by thirsty rats was investigated shortly after injection, 1 day later, and 2 days later. The first effect was the characteristic rise in water intake at low dosages, and a fall at higher dosages. Twenty-four hours later there is a fall at the lower dosages, and a rise at the higher quantities. Two days after injection, there was some quite slight residual effect of both amobarbital and secobarbital but equilibration was nearly complete. Phenobarbital demonstrates some depressant activity at this time. When phenobarbital is administered and water ingestion held at a constant level for 2 days, the depressant effect is still obtained. These data indicate that the barbiturates have sequential effects upon water ingestion which are to some large degree independent of water balance per se.
Quantitative measurements of acetoacetate metabolism and oxidation in sheep
Authors: Bergman E. N. , Kon K. , Katz M. L.
Published: December 2017

Ketosis was produced in sheep by intravenous infusions of large quantities of acetoacetic acid (AcAc). At the infusion rates employed less than 5% was excreted in the urine. Acetoacetic acid-3-C14 was administered also as a continuous infusion to both normal and ketotic sheep. Constant plasma concentrations and specific activities were obtained and with known C14 infusion rates, several parameters of AcAc metabolism were calculated. Mean endogenous AcAc turnover rates were about 0.04 g/hr kg3/4 (<1 g/sheep hr) but the maximal capacity of ketotic sheep to utilize AcAc was about 10-fold greater. In both normal and ketotic ewes, about one-half of the utilized AcAc was oxidized to CO2. The percentage of the total respired CO2 derived from AcAc metabolism increased from about 2% in normal ewes to over 30% during ketosis. The results indicate that the metabolism of ketone bodies by the normal ruminant is relatively insignificant but that, during ketosis, their contribution to the animal's total metabolism can be of major importance.
Acetate-1-C14 metabolism of white fat from hamsters in cold exposure and hibernation
Authors: Baumber Joan , Denyes Arliss
Published: December 2017

Incorporation of C14 from acetate-1-C14 into lipid and CO2 by epididymal fat from golden hamsters kept at room temperature, acclimated to 5 ± 1 C, in hibernation and arousing from hibernation, was measured in vitro at 37 C. Summer and winter series were compared. The C14O2 production by tissue from control and acclimated animals was similar but the C14O2 production of tissue from hibernating and arousing hamsters was significantly greater than that from acclimated animals. There was a large increase in the lipid-C14 of tissue from cold-acclimated animals and this increase persisted into hibernation but was slightly depressed in tissue from arousing animals. Many acclimated and all hibernating hamsters had involuted testes and a greater incorporation of C14 into lipid than those with noninvoluted testes. A greater percentage of hamsters hibernated in the cold room during the winter and at this time the incorporation of C14 into lipid by the fat pad was greater than in the summer.
Rate of protein extravasation in inflammation
Authors: Aschheim Emil
Published: December 2017

Radioalbumin was used to study the course of the inflammatory reaction induced in rats by the topical application of xylene. The water content of normal skin was found to amount to 57.49% (sd = 3.6) of its weight, and to increase continuously throughout the duration of the inflammatory reaction. The intravascular volume of the normal skin amounts to 3.63% of its weight, corresponding to 0.0237 ml plasma/g normal skin. One minute after the application of xylene, blood plasma begins to leak out of the vessels at the rate of 0.0468 ml plasma/min g normal skin. The rate of protein extravasation does not remain constant, but increases linearly with time for the next 3.5 min, when it reaches a maximum. This relation is interpreted as resulting from the continuous application of a constant phlogogenic stress on the system. After the peak is reached, the rate of protein extravasation decreases exponentially with time, with a time constant equal to –0.2236 min–1 (t1/2 = 3.1 min). The kinetics of this phase of the reaction is thought to result from a number of parallel exponential processes.
Sodium, potassium, and chloride in frog stomach muscle
Authors: Armstrong William McD.
Published: December 2017

In freshly excised stomach muscles of Rana temporaria total Na was found to be 40.2 ± 6.1 mEq/kg wet wt. Total K was 66.5 ± 4.8 and total Cl was 33.9 ± 3.9 mEq/kg. Total water content was 805 ± 16 g/kg and inulin space was 341 ± 52 ml/kg. The average intrafiber concentrations calculated from these data were 10 mEq Na, 141.5 mEq K, and 18 mEq Cl/ liter fiber water. In muscles immersed overnight at 5 C in Ringer's solutions containing various amounts of KCl, total muscle Cl was a direct linear function of external KCl. When the external KCl concentration was less than 20 mm/liter, muscle K decreased on immersion. Increasing the external KCl from 20 to 40 mm/liter resulted in a sharp increase in muscle K. Further increasing external KCl from 40 to 80 mm/liter had relatively little effect on total muscle K. The Na content of these muscles was in all cases greater than that of freshly excised muscles. Muscles immersed overnight in the cold in K-free solutions gained Na and lost K. On reimmersion at room temperature in solutions containing KCl there was a net loss of Na from and a net gain of K by the fibers. The amount of K taken up was a function of the external KCl concentration. Na loss and K accumulation were inhibited by ouabain and by iodoacetate.
Effect of a myocardial volume overload on lactate transport in skeletal muscle sarcolemmal vesicles
Authors: Aschenbach William G. , Brower Gregory L. , Talmadge Robert J. , Dobson John L. , Gladden L. Bruce
Published: December 2017

This study sought to determine the effect of a myocardial volume overload (MVO) on sarcolemmal (SL) lactate (La−) transport and the aerobic profile of skeletal muscle. SL vesicles were obtained from female rats 10 wk after either a MVO was induced by creation of an infrarenal fistula ( n = 10), or sham surgeries were performed ( n = 11). Influx of14C-labeled L(+)-La−was measured at various unlabeled La−concentrations under zero- trans conditions. La−transport kinetics were determined using a Michaelis-Menten equation with an added linear component to discriminate between carrier-mediated and diffusional transport. Although heart and lung weights were significantly increased ( P < 0.0001) in the MVO group, left ventricular function was only modestly altered ( P < 0.05). A significant reduction in type I myosin heavy chain (MHC) in the soleus and a strong trend ( P = 0.06) for a reduced type IIx MHC in the plantaris were observed in MVO rats, but no differences in citrate synthase activity or monocarboxylate transporter proteins (MCT)-1 expression were noted in any muscle. Carrier-mediated La−influx into SL vesicles was similar between sham and MVO ( Km= 12 ± 1 and 18 ± 3 mM; apparent Vmax= 772 ± 99 and 827 ± 80 nmol · mg−1· min−1, respectively). Total influx at 100 mM was lower in MVO, and this was due to a 30% reduction in membrane diffusion. In conclusion, a 10-wk MVO did not alter MCT-mediated La−transport or protein expression but was associated with modest changes in myofibrillar proteins and impaired SL diffusive properties.
Role of calcium channels and adenylate cyclase in the PACAP-induced adrenal catecholamine secretion
Authors: Fukushima Yasuo , Nagayama Takahiro , Kawashima Hisako , Hikichi Hirohiko , Yoshida Makoto , Suzuki-Kusaba Mizue , Hisa Hiroaki , Kimura Tomohiko , Satoh Susumu
Published: December 2017

We elucidated the functional contribution of voltage-dependent calcium channels (VDCCs) and adenylate cyclase to epinephrine (Epi) and norepinephrine (NE) secretion induced by pituitary adenylate cyclase-activating polypeptide (PACAP) in the isolated perfused rat adrenal gland. PACAP increased Epi and NE output, which was inhibited by perfusion with calcium-free solution or by nifedipine, an L-type VDCC blocker. However, the PACAP-induced responses were resistant to ω-conotoxin GVIA, an N-type VDCC blocker, or ω-conotoxin MVIIC, a P/Q-type VDCC blocker. MDL-12330A, an adenylate cyclase inhibitor, inhibited the PACAP-induced increase in Epi, but not NE, output. Treatment with nifedipine and MDL-12330A caused additive inhibition of the PACAP-induced catecholamine responses. These results suggest that opening of L-type VDCCs is responsible for adrenal catecholamine secretion induced by PACAP and that activation of adenylate cyclase is involved in the PACAP-induced Epi, but not NE, secretion. These pathways may act independently of each other.
Cardiovascular effects of vasopressin following V1 receptor blockade compared to effects of nitroglycerin
Authors: Cooke C. R. , Wall B. M. , Huch K. M. , Mangold T.
Published: December 2017

Studies to more clearly determine the mechanisms associated with arginine vasopressin (AVP)-induced vasodilation were performed in normal subjects and in quadriplegic subjects with impaired efferent sympathetic responses. Studies to compare the effects of AVP with the hemodynamic effects of nitroglycerin, an agent that primarily affects venous capacitance vessels, were also performed in normal subjects. Incremental infusions of AVP following V1-receptor blockade resulted in equivalent reductions in systemic vascular resistance (SVRI) in normal and in quadriplegic subjects. However, there were major differences in the effect on mean arterial pressure (MAP), which was reduced in quadriplegic subjects but did not change in normal subjects. This difference in MAP can be attributed to a difference in the magnitude of increase in cardiac output (CI), which was twofold greater in normal than in quadriplegic subjects. These observations are consistent with AVP-induced vasodilation of arterial resistance vessels with reflex sympathetic enhancement of CI and are clearly different from the hemodynamic effects of nitroglycerin, i.e., reductions in MAP, CI, and indexes of cardiac preload, with only minor changes in SVRI.
Effects of hypotension and fluid depletion on central angiotensin-induced thirst and salt appetite
Authors: Thunhorst Robert L. , Johnson Alan Kim
Published: December 2017

We examined the effects of hypotension and fluid depletion on water and sodium ingestion in rats in response to intracerebroventricular infusions of ANG II. Hypotension was produced by intravenous infusion of the vasodilator drug minoxidil (25 μg · kg−1 · min−1) concurrently with the angiotensin-converting enzyme inhibitor captopril (0.33 mg/min) to prevent endogenous ANG II formation. Hypotension increased water intake in response to intracerebroventricular ANG II (30 ng/h) but not intake of 0.3 M NaCl solution and caused significant urinary retention of water and sodium. Acute fluid depletion was produced by subcutaneous injections of furosemide (10 mg/kg body wt) either alone or with captopril (100 mg/kg body wt sc) before intracerebroventricular ANG II (15 or 30 ng/h) administration. Fluid depletion increased water intake in response to the highest dose of intracerebroventricular ANG II but did not affect saline intake. In the presence of captopril, fluid depletion increased intakes of both water and saline in response to both doses of intracerebroventricular ANG II. Because captopril administration causes hypotension in fluid-depleted animals, the results of the two experiments suggest that hypotension in fluid-replete animals preferentially increases water intake in response to intracerebroventricular ANG II and in fluid-depleted animals increases both salt and water intake in response to intracerebroventricular ANG II.
Antagonism of adenosine A1 receptors in the NTS does not affect the chemoreflex in awake rats
Authors: de Paula Patrícia M. , Machado Benedito H.
Published: December 2017

The possible involvement of adenosine A1 receptors in neurotransmission of the sympathoexcitatory component of the chemoreflex in the nucleus tractus solitarii (NTS) of awake rats was evaluated. Unilateral microinjection of increasing doses of adenosine (0.01, 0.06, 0.12, 1.25, 2.5, and 5.0 nmol/50 nl) into the lateral aspect of the commissural NTS produced a long-lasting increase in baseline mean arterial pressure (MAP) and no changes in baseline heart rate (HR). Microinjection of adenosine at 1.25 nmol/50 nl (ED50) into the NTS ( n = 9) produced a significant increase in baseline MAP (119 ± 3, 122 ± 4, and 117 ± 4 mmHg at 30 s, 1 min, and 2 min, respectively) compared with control (102 ± 3 mmHg) but no significant changes after previous microinjection of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), an adenosine A1 receptor antagonist (107 ± 3, 107 ± 3, and 106 ± 3 mmHg at 30 s, 1 min, and 2 min, respectively) compared with control (102 ± 3 mmHg). Microinjection of adenosine before and after DPCPX into the same site of the lateral commissural NTS produced no changes in baseline HR. In another group of rats ( n = 8), microinjection of DPCPX (0.285 nmol/50 nl) into lateral and midline aspects of the commissural NTS produced no significant changes in pressor (+46 ± 4 vs. +47 ± 2 mmHg) or bradycardic responses (−216 ± 9 vs. −226 ± 12 beats/min) to chemoreflex activation with intravenous potassium cyanide compared with control responses. These data show that microinjection of adenosine into the NTS produced a small and long-lasting pressor response by activating A1 receptors and that blockade of these receptors produced no changes in cardiovascular responses to chemoreflex activation. We conclude that adenosine A1 receptors are not involved in processing of the chemoreflex afferents at the NTS level.
Short-term mild hyperglycemia enhances insulin-stimulated glucose disposal in lactating goats
Authors: Lemosquet Sophie , Debras Elisabeth , Balage Michèle , Hocquette Jean François , Rulquin Henri , Grizard Jean
Published: December 2017

This work was designed to study the effect of a 3-day mild hyperglycemia (5.3 vs. 3.3 mM) on the regulation of glucose metabolism in lactating goats. Glucose was intravenously infused at variable rates simultaneously with a constant potassium-amino acid infusion. Diet plus substrate infusion maintained net energy but not protein supply. Milk yield did not change. Skeletal muscle glucose transporter (GLUT-4) was analyzed before and after hyperglycemia. In addition, the acute effect of medium and high insulin doses on glucose turnover was measured in vivo during euglycemic and hyperglycemic hyperinsulinemic clamps under potassium and amino acid replacement. Hyperglycemia reduced the endogenous glucose appearance but increased glucose disposal. It decreased the total membrane-associated GLUT-4 protein in skeletal muscle. In contrast, it improved the acute insulin-stimulated glucose disposal. Both the level and duration (3 days) of hyperglycemia contributed to this improvement. We conclude that short-term mild hyperglycemia has similar effects in lactating goats as those already observed in nonlactating rodents or humans.
Effect of acute exercise and prolonged training on insulin response to intravenous glucose in vivo in rat
Authors: James D. E. , Burleigh K. M. , Kraegen E. W. , Chisholm D. J.
Published: December 2017

Physical training causes hypoinsulinemia and enhanced insulin sensitivity. Insulin sensitivity is also enhanced by a single bout of exercise. However, changes in beta-cell responsiveness with acute exercise are ill defined. To clarify these relationships intravenous glucose tolerance tests were performed in 1) physically trained rats (3 different levels), 48 h after the last bout of exercise; 2) untrained rats, 0.5, 4, and 24 h after a single bout of exercise; or 3) sedentary control rats. The total area under the glucose-stimulated insulin response curve (GSIR) was negatively correlated with total distance run during training (r = -0.45, P less than 0.05), whereas glucose tolerance was improved (P less than 0.005 vs. controls) with intensive training. GSIR was suppressed by 38% (P less than 0.01 vs. controls) 0.5 h after a single bout of exercise. This effect persisted for 4 h but was not present after 24 h. These results indicate that a single bout of exercise induces suppression of GSIR which lasts less than 24 h. In contrast, physical training induces prolonged suppression (for at least 48 h) of GSIR, proportional to the intensity of training, and improved glucose tolerance.
Effects of unilateral hypoxia on neuroepithelial bodies in rabbit lungs
Authors: Lauweryns J. M. , de Bock V. , Guelinckx P. , Decramer M.
Published: December 2017

The present study was undertaken to investigate the influence of regional (unilateral) alveolar hypoxia on the intrapulmonary neuroepithelial bodies (NEB), which contain bioactive substances and are distinctly innervated. Eight (4-wk-old) rabbits were subjected to unilateral hypoxia. The animals were anesthetized by an intramuscular injection of Hypnorm and breathed spontaneously during the experiment. The right lung received a hypoxic gas mixture (10% O2-90% N2) and the left lung a hyperoxic mixture. Blood gas measurements indicated that no systemic hypoxemia or acidosis occurred under these conditions. Lung samples were examined by electron microscopy to determine morphometrically the extent of a secretory exocytosis at the basal cell pole of the NEB and by a microspectrographical analysis of the formaldehyde-induced fluorescence to quantify the NEB serotonin content. After 20 min of unilateral hypoxia the NEB in the right hypoxic lung exhibited an increased exocytosis and a lower serotonin content in comparison with the left hyperoxic lung NEB. These results indicate that NEB react to regional alveolar hypoxia by secreting serotonin and/or peptides to the surrounding lung tissue (blood vessels, smooth muscle, nerve endings, etc.).
Fast vs. slow exhalation before O2 inhalation alters subsequent phase III slope
Authors: Hurst T. S. , Graham B. L. , Cotton D. J.
Published: December 2017

We studied 10 symptom-free lifetime non-smokers and 17 smokers all with normal pulmonary function studies. All subjects performed single-breath N2 washout tests by either exhaling slowly (“slow maneuver”) from end inspiration (EI) to residual volume (RV) or exhaling maximally (“fast maneuver”) from EI to RV. After either maneuver, subjects then slowly inhaled 100% O2 to total lung capacity (TLC) and without breath holding, exhaled slowly back to RV. In the nonsmokers seated upright phase III slope of single-breath N2 test (delta N2/l) was lower (P less than 0.01) for the fast vs. the slow maneuver, but this difference disappeared when the subjects repeated the maneuvers in the supine position. In contrast, delta N2/l was higher for the fast vs. the slow maneuver (P less than 0.01) in smokers seated upright. For the slow maneuver, delta N2/l was similar between smokers and nonsmokers but for the fast maneuvers delta N2/l was higher in smokers than nonsmokers (P less than 0.01). We suggest that the fast exhalation to RV decreases delta N2/l in normal subjects by decreasing apex-to-base differences in regional ratio of RV to TLC (RV/TLC) but increases delta N2/l in smokers, because regional RV/TLC increases distal to sites of small airways obstruction when the expiratory flow rate is increased.
Effect of endotoxin on lung fluid balance in unanesthetized sheep
Authors: Gabel J. C. , Hansen T. N. , Drake R. E.
Published: December 2017

We used a gravimetric technique to test for increased pulmonary capillary permeability after Escherichia coli endotoxin infusion in unanesthetized sheep. The sheep were chronically prepared with cannulas placed into the left atrium and pulmonary artery 1–2 wk before the experiments. We estimated pulmonary capillary pressure (Pc) as the average of pulmonary arterial and left atrial pressures, and used the modified method of Pierce to estimate the ratio of extravascular fluid weight (EVF) to blood-free dry weight. In 15 sheep we inflated a left atrial balloon to raise Pc to -10.7, 5, 10, or 15 mmHg above plasma oncotic pressure (IIc) for 3 h, then measured EVF. EVF averaged 4.0 +/- 0.2 (base line), 4.3 +/- 0.1, 4.5 +/- 0.1, and 5.1 +/- 0.5 (SD), respectively, for the four levels of Pc - IIc. We gave seven additional sheep 1 microgram/kg of E. coli endotoxin (0127:B8) and measured EVF after 3 h of stable Pc. Endotoxin increased Pc in each sheep. EVF was higher than control for the endotoxin sheep with Pc - IIc greater than -1. This finding is consistent with an increase in pulmonary capillary permeability caused by endotoxin. However, EVF was not elevated in the endotoxin sheep with Pc - IIc less than 1 mmHg. This shows that the increased permeability was insufficient to cause edema unless Pc was elevated. Thus endotoxin may cause edema by two mechanisms, 1) an increase in capillary permeability, and 2) an increase in Pc.
Laryngoscopic endotracheal intubation of rats for inhalation anesthesia
Authors: Schaefer C. F. , Brackett D. J. , Downs P. , Tompkins P. , Wilson M. F.
Published: December 2017

Endotracheal intubation of the rat under direct vision is described together with the details of procedures and apparatus for conducting inhalation anesthesia in this species. Our intubation method requires no special manufacture of equipment, because it employs the human laryngoscope equipped with an infant blade (size 0). Using inhalation anesthetics such as enflurane or halothane for induction, clear laryngoscopic visualization of the glottis is reliably obtained, allowing rapid and routine intubation of the rat in a highly predictable amount of time. In contrast, the injected anesthetics such as ketamine or pentobarbital sodium seem unsuited to laryngoscopic intubation as a result of problems of variable induction times, copious oral secretions, and strong pharyngeal-laryngeal reflexes.
Interrupter technique for measurement of respiratory mechanics in anesthetized cats
Authors: Gottfried S. B. , Rossi A. , Calverley P. M. , Zocchi L. , Milic-Emili J.
Published: December 2017

In six spontaneously breathing anesthetized cats (pentobarbital sodium, 35 mg/kg ip), airflow, changes in lung volume, and tracheal and esophageal pressures were measured. Airflow was interrupted by brief airway occlusions during relaxed expirations (elicited via the Breuer-Hering inflation reflex) and throughout spontaneous breaths. A plateau in tracheal pressure occurred throughout relaxed expirations and the latter part of spontaneous expirations indicating respiratory muscle relaxation. Measurement of tracheal pressure, immediately preceding airflow, and corresponding volume enabled determination of respiratory system elastance and flow resistance. These were partitioned into lung and chest wall components using esophageal pressure. Respiratory system elastance was constant over the tidal volume range, divided approximately equally between the lung and chest wall. While the passive pressure-flow relationship for the respiratory system was linear, those for the lung and chest wall were curvilinear. Volume dependence of chest wall flow resistance was demonstrated. During inspiratory interruptions, tracheal pressure increased progressively; initial tracheal pressure was estimated by backward extrapolation. Inspiratory flow resistance of the lung and total respiratory system were constant. Force-velocity properties of the contracting inspiratory muscles contributed little to overall active resistance.
Regulation of fatty acid biosynthesis in rats by physical training
Authors: Scorpio R. , Rigsby R. L. , Thomas D. R. , Gardner B. D.
Published: December 2017

Physical training in the form of long-term nonexhaustive daily exercise was studied as a means of regulating fatty acid biosynthesis. Male rats were required to swim for periods up to 90 min/day. The exercise was carried out 6 days/wk for approximately 11 wk. Hepatic fatty acid biosynthesis and acetyl-CoA carboxylase [acetyl-CoA: CO2 ligase (EC 6.4.1.2)] activities were compared with nonexercised rats. At the end of the training period the exercised rats had a lower rate of fatty acid biosynthesis activity and a lower rate of acetyl-CoA carboxylase activity. The difference in acetyl-CoA carboxylase activity was due to a change in maximal velocity with no significant change in the Michaelis constant for acetyl-CoA. Untrained rats were subjected to a single bout of exercise. They also exhibited lower rates of fatty acid biosynthesis and acetyl-CoA carboxylase activities compared with nonexercised rats. However, the lower rates of these enzyme activities were sustained longer in the physically trained rats compared with the exercised untrained rats after the cessation of exercise. These results implicate acetyl-CoA carboxylase as a control site in the regulation of hepatic fatty acid biosynthesis by both physical training and acute exercise in rats. Possible inhibitory mechanisms are discussed.
An evaluation of ventilation in dystrophic Syrian hamsters
Authors: Schlenker E. H.
Published: December 2017

Ventilatory responses of 10 control and 10 dystrophic male hamsters to air, hypercapnia, and hypoxia were evaluated at four ages (40, 70, 100, and 140 days). Tidal volume (VT), frequency (f), minute ventilation (VE) as well as inspiratory and expiratory time of awake animals were measured with a plethysmograph. There was a small increase of VT in both groups with age. Although there was no change of f in the control group with age, there was a progressive decrease in f (means +/- SE: 92 +/- 8, 97 +/- 9, 74.5 +/- 10, and 68 +/- 8 breaths/min) in the dystrophic group. Consequently VE on air decreased in the dystrophic group. Both groups showed similar responses to hypoxia (13 and 10% O2) and hypercapnia (3, 5, and 8% CO2) at 40 days. By 70 days the hypercapnic, but not hypoxic, response of the dystrophic animals was significantly decreased compared with that of the control group (at 8% CO2, VE = 47.4 +/- 4.1 vs. 75.7 +/- 7.6 ml/min, P less than 0.01). At both 100 and 140 days the response of the dystrophic group to CO2 was flat; i.e., the slope VE vs. fractional concentration of inspired CO2 was close to zero, and the hypoxic responses were greatly diminished. Because hamsters increase VE in response to CO2 primarily by increasing VT, the data suggest that dystrophic hamsters are unable to increase VT at a very early age, presumably due to muscle weakness. The normal response of hamsters to hypoxia, which is primarily to increase f, appears to be maintained for a longer time.
Effects of naloxone on the hering-breuer apnea in sleeping kittens
Authors: Chow C. M. , Read D. J.
Published: December 2017

The modulatory role of endogenous opiates on the Hering -Breuer inflation reflex was examined in 11 newborn kittens, aged 10–31 days, during active and quite sleep. The Hering -Breuer apnea duration was significantly shortened by naloxone (1 mg/kg, intraperitoneally; P less than 0.05). This effect was abolished by 100% O2 breathing. The duration of apnea, and its shortening by naloxone, did not differ significantly in the two sleep states. Hering -Breuer apnea is a result of the inspiratory inhibition and expiratory excitation of medullary neurons in response to lung stretch; the apnea is terminated by the opposing influences of chemoreceptors, which respond to hypercapnia and hypoxia. The results suggest that opioid influences on the Hering -Breuer reflex are due to an opioid modulation of the carotid body discharge in hypoxia, or of its central integration, and that sleep state is not implicated in such modulation in kittens.
Dynamic water vapor and temperature calibration system
Authors: Montague F. W. , Primiano F. P. , Saidel G. M.
Published: December 2017

The objective evaluation of thermal and humidification processes in the pulmonary system requires accurate dynamic measurements of temperature and water vapor concentration of a flowing gas mixture. The adequacy of instruments used for such measurements can only be determined by dynamic calibration techniques. We have developed a method of producing step changes in temperature and water vapor content of a gas mixture undergoing controlled steady flow. The system consists of two reservoirs and a slide valve that switches a test section between them. The inlet (usually a probe or catheter tip) of the device to be calibrated is positioned in the test section. The flow rate through the test section is minimally changed during the transition between gas from one reservoir to that of the other. The system has been used to analyze the response of a thermistor and a respiratory mass spectrometer to changes in gas temperature and water vapor.
Neurotransmitters and biphasic respiratory response to hypoxia
Authors: Long W. A. , Lawson E. E.
Published: December 2017

Recent work from this laboratory (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 55:483–488, 1983) has shown that the biphasic respiratory response to hypoxia in piglets is due to changing central neural respiratory output. To test the hypothesis that either adenosine or opiatelike neurotransmitters mediate the failure to sustain hyperpnea in response to hypoxia, 12 piglets were studied ata mean age of 2.9 +/- 0.4 days (range 2–6 days). Animals were anesthetized, paralyzed, and ventilatedusing a servo-controlled system that maintained end-tidal CO2 constant. Electrical activity of the phrenic nerve was recorded as the index of breathing. An initial experimental trial of 6 min ventilation with 15% O2 was performed in all 12 piglets. Thereafter all 12 piglets were treated with aminophylline (n = 6), naloxone (n = 3), or naltrexone (n = 3) and again subjected to 15% O2. During initial exposure to hypoxia there was an initial increase in phrenic activity that was not sustained. During recovery ventilation with 100% O2, phrenic activity transiently declined below the base-line level and then gradually returned. Subsequent intravenous administration of aminophylline, naloxone, or naltrexone caused base-line phrenic activity to increase. Thereafter repeat exposures to 15% O2 were carried out. During these posttreatment trials of hypoxia, phrenic activity further increased, but the hyperventilation was again not sustained. These findings suggest it is unlikely that either adenosine or mu-endorphin neurotransmitters are the primary mediators of the biphasic response to hypoxia in newborns.
Model analysis of tidal volume response to inspiratory elastic loads
Authors: Zin W. A. , Rossi A. , Zocchi L. , Milic-Emili J.
Published: December 2017

Based on experimental inspiratory driving pressure waveforms and active respiratory impedance data of anesthetized cats, we made model predictions of the factors that determine the immediate (first loaded breath) intrinsic (i.e., nonneural) tidal volume compensation to added inspiratory elastic loads. The time course of driving pressure (P) was given by P = atb, where a is the pressure at 1 s from onset of inspiration and represents the intensity of neuromuscular drive, t is time, and b is an index of the shape of the driving pressure wave. For a given active respiratory impedance, tidal volume compensation to added elastic loads decreases with increasing inspiratory duration and decreasing value of b but is independent of a. We have also assessed the validity of the “effective elastance” (Lynne-Davies et al., J. Appl. Physiol. 30: 512–516, 1971) as a predictor of tidal volume responses to elastic loads. In absence of vagal feedback, the effective elastance appears to be a reliable predictor, except for short inspiratory duration and a very high intrinsic resistance.
Lipoproteins, lipoprotein lipase, and glycogen after prolonged physical activity
Authors: Lithell H. , Schele R. , Vessby B. , Jacobs I.
Published: December 2017

The effect of strenuous exercise on lipoprotein level and composition as well as on lipoprotein lipase activity (LPLA) and glycogen stores in skeletal muscle was studied in 16 healthy young men after military field maneuvers. Body weight was reduced by 1 kg after the maneuvers and was gradually restored during a 5-day recovery phase. Glycogen levels were reduced by 50% and LPLA increased threefold immediately after the exercise, and neither were restored until 3–5 days of recovery. Serum triglycerides were decreased by about 50% after 1 day of recovery and the cholesterol concentration in high-density lipoproteins increased but only immediately after exercise. In contrast, the apolipoproteins A-I and A-II, the main protein constituents, were both decreased and remained so for 3–5 days. The results indicate that significant alterations of plasma lipoprotein level and composition as well as of muscle metabolism occur after prolonged physical exertion and that some changes are still evident after 5 days of recovery.