bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Pentobarbital on the Electrical and Mechanical Properties of Frog and Snake Twitch Muscle Fibers
Authors: Foulks J. G. , Perry Florence A. , Sanders H. D. , Washio H.
Published: April 2011

Pentobarbital (0.4–1.2 mM) produces marked enhancement of twitch tension in frog skeletal muscle. Latency is reduced and the rate of tension development is increased. In ordinary media, the agent impairs K contractures but this depressant effect can be eliminated by using a high calcium medium containing acetate in place of chloride. In such solutions, pentobarbital reduces the [K]0 necessary for K contractures. In snake twitch fibers depolarized by means of a voltage clamp, pentobarbital shifted the relation between membrane potential and contracture tension to a more negative level of potential. High concentrations of pentobarbital have a depolarizing effect which is greatly accentuated in a medium containing no permeant anion. The drug reduces the rate and extent of the depolarization produced by elevation of [K]0, and increases membrane resistance. These observations indicate that pentobarbital reduces the potassium permeability of the surface membrane of twitch muscle fibers.
On the Mechanism of Isosmotic Transport Across the Small Intestine. The Composition of the Absorbate Transported from a Mucosal Solution made Hypertonic by the Addition of Mannitol
Authors: Dinda P. K. , Beck Marjorie , Beck I. T.
Published: April 2011

Experiments were performed to investigate the mechanism by which the fluid transported across the small intestine becomes isosmotic with the mucosal solution when the latter is made hypertonic by the addition of a poorly absorbed substance. The mid small intestine of the hamster was isolated and everted. The mucosal surface of the control preparation was bathed with an isotonic Krebs–Ringer bicarbonate solution containing 10 mM glucose (KRBSG) (292 mOsmol/kg). The mucosal surface of the experimental preparations was bathed with one of the hypertonic solutions. These hypertonic solutions were prepared by the addition of 1, 50, 100, or 150 mM mannitol to KRBSG. No bathing solution was placed on the serosal side of these preparations, so that the fluid transported across the intestine, undiluted by a bathing solution (absorbate), could be collected on the serosal side. Results show that the absorbate was always isosmotic with the mucosal solution. In the experimental preparations, as compared to the absorption of other solutes, mannitol was poorly absorbed, even though its concentration in the absorbate sometimes reached 35% of its concentration in the mucosal solution. The small amount of mannitol found in the absorbate was never sufficient to render the absorbates isosmotic with hypertonic mucosal solutions. The absorbate became isosmotic with the mucosal solution due to an increased concentration of other solutes transported from the mucosal side. Increasing the osmolality of the mucosal solution progressively from 292 to 442 mOsmol/kg caused a linear increase in the concentration of Na, K, glucose, and mannitol in the absorbate, but, except for mannitol, the net amount of these substances transported (per gram dry tissue) to the serosal side decreased linearly. The transport of fluid also decreased. Our data further indicate that the ratio of fluid and solute transport progressively decreased with the increase in osmolality of the mucosal solution. Therefore, it appears that when the mucosal solution is made hypertonic by the addition of a poorly absorbed substance, the absorbate becomes isosmotic with the hypertonic mucosal solution by means of a greater diminution of fluid transport than of solute transport.
Studies on the Conversion of Proinsulin to Insulin in the Isolated Islets of Langerhans in the Rat
Authors: Sun A. M. , Lin B. J. , Haist R. E.
Published: April 2011

A time course study on proinsulin and insulin biosynthesis was carried out, and the results showed that proinsulin was synthesized in the microsomes and that conversion of proinsulin took place in the granule fraction (Golgi complex and granules) in isolated rat islets. When the granule fraction was incubated with exogenous 3H-labelled proinsulin for 1.5 h, no conversion of labelled proinsulin was observed. Nevertheless pulse-chase experiments showed that endogenous 3H-labelled proinsulin was converted to insulin in the granule fraction. Granular membrane and granular medium were prepared according to the method of Viverós. When endogenous 3H-labelled proinsulin was incubated with these fractions the conversion of labelled proinsulin was found only in the presence of the granular membrane fraction. The percentages of proinsulin and insulin in the total of proinsulin plus insulin changed from 80.6% and 19.4% before the incubation to 65.0% and 35.0% after the incubation. The conversion of exogenous 3H-labelled proinsulin was also found only in the presence of granular membrane. These results suggest that the granular membrane is not permeable to proinsulin and the conversion enzyme probably is bound to the membrane within the Golgi elements and/or granules.
Effects of Isoproterenol, Diazoxide, Ethacrynic Acid, and Furosemide on Skeletal Muscle Vascular Resistance
Authors: Larochelle P. , Mikulic E. , Ogilvie R. I.
Published: April 2011

The vasodilator properties of isoproterenol, diazoxide, ethacrynic acid, and furosemide were compared in the isolated canine gracilis muscle perfused with arterial blood at a constant rate. Isoproterenol was the most potent agent with a steep vasodilator response to 10−8–10−6 M infusions and a maximal decrease in perfusion pressure of 45.5 ± 2.9% at the 10−6 M concentration. The dose – vasodilator responses for diazoxide and ethacrynic acid were parallel to that for isoproterenol but shifted three log doses to the right. The dose–response for furosemide was almost flat with a maximal vasodilator response of 15.5 ± 2.3% at the 10−2 M concentration. The maximal effect of isoproterenol was noted within 5 min of starting the infusion whereas for diazoxide and furosemide it was noted after 10 min and for ethacrynic acid after 20 min. The mean ratio of venous to arterial resistance was unaltered during isoproterenol infusions, decreased with 10−3 M diazoxide, and increased with 10−3 M ethacrynic acid; however, none of these changes were statistically significant. Capillary hydrostatic pressure was significantly decreased only with higher concentrations of isoproterenol and diazoxide, an average of 6 mm Hg with 10−7 M isoproterenol, 8 mm Hg with 10−6 M isoproterenol, and 9 mm Hg with 10−3 M diazoxide. No significant changes in capillary pressure were noted during infusion of ethacrynic acid or furosemide. The results clearly differentiate these agents on the basis of potency, onset, and characteristics of vasodilator effect on sequential segments of a skeletal muscle vascular bed.
Effect of Salicylate on the Fate of Bishydroxycoumarin in the Rat
Authors: Thomas B. H. , Coldwell B. B. , Buttar H. S. , Zeitz W.
Published: April 2011

Salicylate increased the rate of elimination of 14C-bishydroxycoumarin from the blood during the first 7 h after administration. A tissue distribution study showed most of the radioactivity to be found in liver, blood, lung, and kidney. Salicylate treatment increased the concentration of radioactivity in the liver and decreased it in blood, but had little effect in the other tissues. Biliary excretion of radioactivity was increased from 12.3 ± 2.7 to 29.3 ± 2.5% of the dose in the 0–6 h period by salicylate. Total urinary and fecal excretion was little affected. An in vitro plasma protein study showed that salicylate displaces bound bishydroxycoumarin. A similar effect was observed in vivo. It is concluded that salicylate increases the initial rate of bishydroxycoumarin elimination by displacing some of the bound drug from plasma proteins, thereby facilitating uptake into the liver where the drug is metabolized and excreted.
Sodium Retention Versus Renin–Angiotensin System In Experimental Renal Hypertension
Authors: Liard J. F.
Published: April 2011

The relative importance of sodium retention versus the renin–angiotensin pressor response in hypertension caused by constriction of one renal artery and contralateral nephrectomy in the rat was assessed. Attempts were made to lower the blood pressure by changing sodium balance while plasma renin activity was measured. Acute sodium depletion (furosemide) had no measurable effect on the pressure seemingly because activation of the renin–angiotensin system prevented a fall in pressure. However, the pressure decreased rapidly and markedly in response to sodium depletion when the renin-angiotensin system was suppressed by (a) removing the sole remaining kidney after the sodium depletion or (b) pretreating the animals with deoxycorticosterone and salt. These results emphasize the dual nature of the control of blood pressure by the kidney in experimental renal hypertension.
The Role of the Aortic Body Chemoreceptors in the Cardiac and Respiratory Responses to Acute Hypoxia in the Anesthetized Dog
Authors: Biro G. P. , Hatcher J. D. , Jennings D. B.
Published: April 2011

The participation of the aortic chemoreceptors in the reflex cardiac responses to acute hypoxia is suggested only by the indirect evidence of pharmacological stimulation of these receptors. In order to assess their role more directly, the response to a 15 min period of hypoxia was determined after surgical denervation of the aortic chemoreceptors (A.D.), and compared with the response of sham-operated (S.O.) dogs, anesthetized with morphine–pentobarbital. In the control period, while breathing room air, the cardiovascular and respiratory parameters measured in the A.D. animals were not different from those of the S.O. dogs. Hypoxia (partial pressure of oxygen approximately 30 mm Hg) in the S.O. dogs was associated with a statistically significant rise in the heart rate (+71 ± 7 min−1, mean ± S.E.M.) and of the cardiac output (+25 ± 10 ml kg−1 min−1). In the A.D. animals, the significantly smaller increment in heart rate (+29 ± 6 min−1) was associated with a fall of the cardiac output (−16 ± 12 ml kg−1 min−1). The hypoxia-induced changes in heart rate and cardiac output in the S.O. animals were different (p < 0.05) from those in the A.D. group. The minute volume of ventilation was significantly augmented in both groups, and to a comparable extent. These findings indicate that the aortic chemoreceptors play a significant role in the cardiac response to hypoxia, but they do not affect, to a significant extent, the respiratory response.
Interaction of Amantadine with Tyramine and Noradrenaline on the Cat Nictitating Membrane
Authors: Sinclair John G.
Published: April 2011

Amantadine has been postulated to enhance catecholamine (CA) transmission by blocking CA neuronal uptake or facilitating CA release. Drugs that block CA uptake enhance the effects of noradrenaline (NA) but antagonize the effects of tyramine on the cat nictitating membrane. Amantadine was found to enhance the response of NA to a limited extent but markedly enhanced the response to tyramine. Thus, amantadine does not appear to enhance CA transmission by blocking the uptake system.
Effect of Various Steroids on the Hepatic Glucuronidation and Biliary Excretion of Bilirubin
Authors: Solymoss B. , Zsigmond G.
Published: April 2011

In rats, treatment with spironolactone or pregnenolone-16α-carbonitrile (PCN) accelerates bile flow and enhances hepatic microsomal bilirubin–UDP glucuronyltransferase activity (EC 2.4.1.17) and the biliary transport maximum (Tm) of bilirubin. The distribution of ethylanthranilate azo-pigments in fractions separated by thin-layer chromatography also indicates increased glucuronidation of bilirubin. These findings explain the mechanism of enhanced serum bilirubin disappearance in rats treated with the steroids.
Relationship Between Aortic Reactivity and Blood Pressure of Renal Hypertensive, Hyperthyroid, and Hypothyroid Rats
Authors: Field F. P. , Janis R. A. , Triggle D. J.
Published: April 2011

The reactivity of aortic rings from normotensive rats and from young rats with hypertension induced by bilateral renal encapsulation was compared. Aortae of hypertensive rats (190–250 mm Hg) produced greater isometric tension in the presence of norepinephrine (0.1 × to 3 × 10−9 M), serotonin (0.03 × to 1 × 10−6 M), and KCl (2.5 × to 10 mM) than did those of normotensive rats. A relationship exists between systolic blood pressure and aortic responsiveness to norepinephrine and KCl. Aortae from rats with borderline hypertension (140–150 mm Hg) exhibited supersensitivity only to low doses of KCl (2.5 and 5 mM), although those from rats with moderate hypertension (160–170 mm Hg) exhibited increased responsiveness to low doses of both norepinephrine (0.1, 0.3, and 1 × 10−9 M) and KCl (2.5, 5, and 10 mM), and these responses tended to be less than those produced by aortae from rats with severe hypertension (190–250 mm Hg). Hyperthyroid and hypothyroid rats had significantly higher and lower systolic blood pressures, respectively, than euthyroid rats. Aortae from hyperthyroid and hypothyroid rats were supersensitive and subsensitive, respectively, to low doses of norepinephrine and KCl. The rate of relaxation of aortic segments, after 80 mM KCl was washed from the bath with normal Krebs solution, was studied; hyperthyroid and hypothyroid rats yielded segments whose rates of relaxation were slower and faster, respectively, than those of euthyroid rats. Similarly, the rate of relaxation of aortic smooth muscle from renal hypertensive rats was inversely related to aortic reactivity to low doses of KCl. The relationship between vascular reactivity, blood pressure, and thyroid state is discussed. The aorta of renal encapsulated rats appears to be a useful model for studying smooth muscle supersensitivity and changes of vascular sensitivity associated with hypertension.
The Role of Energy Metabolism in the Interaction between Amino Acid and Sugar Transport in the Small Intestine
Authors: Bihler I. , Sawh P. C.
Published: April 2011

The interaction between sugar and amino acid transport was studied in everted sacs of rat jejunum in vitro. The addition of the actively transported nonmetabolized sugars, D-galactose and α-methyl-D-glucoside, to the mucosal medium inhibited the active transport of cycloleucine (1-amino-cyclopentane-1-carboxylic acid). This effect was largely counteracted by the simultaneous presence of D-glucose in the serosal medium or of D-fructose. The results indicate that provision of substrates for energy metabolism relieves the inhibition of transport and supports the hypothesis that the interaction between the intestinal transport of sugar and of amino acid is at least in part due to competition for a limited supply of metabolic energy.
Response of the Rat Exocrine Pancreas to Secretin and Cholecystokinin-Pancreozymin
Authors: Shaw H. M. , Heath T. J. , Stark A. E.
Published: April 2011

In rats with chronic pancreatic fistulas, infusion of a preparation of Gastrointestinal Hormone Research Unit cholecystokinin-pancreozymin (CCK-PZ) resulted in significant increases in the flow of pancreatic juice and its content of bicarbonate. However, it could not be stated with certainty from the present data whether these increases were due to the CCK-PZ itself, the secretin contaminating the CCK-PZ preparation, or whether some interaction had taken place between the CCK-PZ and the contaminating secretin when the CCK-PZ preparation was administered. When this CCK-PZ was infused with submaximal doses of secretin, there resulted a greatly augmented pancreatic response to secretin. It must be the subject of further experimental study to determine whether a true interaction occurs between CCK-PZ and secretin in stimulating the flow and bicarbonate output of pancreatic juice, and whether in rats, during digestion, CCK-PZ plays an important role in augmenting the pancreatic response to secretin.
Evidence for K+ and Cl− Binding Inside Muscle from Diffusion Studies
Authors: Caillé J. P. , Hinke J. A. M.
Published: April 2011

Intrafiber diffusion of 42K+, 36Cl−, and 14C-sorbitol was measured along the longitudinal axis of a single muscle fiber which had been placed inside the lumen of a glass capillary at least 24 h beforehand. The mean diffusion coefficients (× 10−5 cm2/s) in myoplasm at 10 °C and at pH 7.5 were 0.728 ± 0.008, 0.683 ± 0.006, and 0.216 ± 0.005 for K+, Cl−, and sorbitol, respectively. The K+ coefficient decreased, the Cl− coefficient increased, and the sorbitol coefficient remained unchanged as the pH of the muscle-capillary preparation was increased. By applying Wang's theory to explain diffusion in polyelectrolyte solutions (1954), we have estimated the diffusible volume (1 − ϕ) and the binding fractions (ƒK and ƒCl) of K+ and Cl− in myoplasm. From pH 5.2 to 10, ƒK varied from 0 to 0.13 and ƒCl varied from 0.13 to 0. Analysis of this K+ diffusion data along with the Na+ diffusion data from an earlier study (Can. J. Physiol. Pharmacol. 50, 228–237, 1972) leads to the prediction that myoplasm at physiological pH has a minimum binding capacity for Na+ and K+ of about 70 mmol/kg dry weight and a selectivity of 3.3 for Na+ over K+. Estimations of the diffusible volume ranged from 0.7 to 0.8, indicating that probably all the intrafiber water (74–78% by weight) is being utilized in the diffusion process.
Biochemical Basis of Heart Function. X. Reduction in the Na+–K+-Stimulated ATPase Activity in Failing Rat Heart Due to Hypoxia
Authors: Balasubramanian V. , McNamara D. B. , Singh J. N. , Dhalla N. S.
Published: April 2011

The activities of the membrane bound enzyme Na+–K+-stimulated ATPase were studied in control and hypoxic isolated rat hearts. The control hearts were perfused with medium gassed with 95% O2 and 5% CO2, whereas hypoxia was induced by perfusing the hearts with medium gassed with 95% N2 and 5% CO2. The specific activity of the Na+–K+ ATPase was lower in the hypoxic hearts than in the control preparations. The enzyme activity of the hypoxic hearts was also lower when determined under different assay conditions obtained by changing the concentration of Na+, K+, H+, and MgATP in the incubation medium. The ouabain-induced inhibition of Na+–K+ ATPase activity in the hypoxic hearts was similar to that in the control. The depression in Na+–K+ ATPase activity due to hypoxia was reversible on perfusing the hypoxic heart with aerobic medium. The decreased Na+–K+ ATPase activity in the hypoxic heart preparations supports the concept of membrane abnormality associated with heart failure due to lack of oxygen. Since the depression in the activity of Na+–K+ ATPase in the hypoxic heart was markedly pronounced on omitting the substrate from the perfusion medium, it is likely that exogenous glucose plays an important role in maintaining the integrity of hypoxic heart membranes.
Evidence for an Angiotensinogen-Stimulating Factor after Nephrectomy
Authors: Hasegawa Hiroshi , Tateishi Hiroshi , Masson Georges M. C.
Published: April 2011

Plasma from nephrectomized rats contains an angiotensinogen-stimulating factor which is likely responsible for the rise in plasma angiotensinogen seen after nephrectomy. This factor is present in the γ-globulin fraction obtained by electrophoresis and ultracentrifugation.
Ouabain-Induced Seizures in Rats: Modification by Melatonin and Melanocyte-Stimulating Hormone
Authors: Izumi K. , Donaldson J. , Minnich J. , Barbeau A.
Published: April 2011

The effects of melatonin and synthetic alpha-melanocyte-stimulating hormone (MSH) on ouabain-induced seizures in experimental animals were determined. Fifteen micrograms of melatonin or ten micrograms of α-MSH (dissolved in 2% ethanol – 0.85% saline) were administered intraventricularly to young female rats. The administration of melatonin was found to provide a protective effect against the seizures. The maximum suppressive effect against ouabain seizures was obtained when melatonin was given 1 min prior to the injection of ouabain. In contrast, the injection of α-MSH aggravated seizure activity elicited by 3 μg of ouabain.During experiments designed to determine the regional distribution in the brain of intraventricularly administered 3H-melatonin, high accumulation of the radioactive compound was found in the medulla oblongata – pons, the hypothalamus, and the hippocampus. The lowest activity was in the cerebral cortex.
Metabolic, Ultrastructural, and Mechanical Changes in the Isolated Rat Heart Perfused with Aerobic Medium in the Absence or Presence of Glucose
Authors: Dhalla N. S. , Matoushek R. F. , Sun C. N. , Olson R. E.
Published: April 2011

On perfusing the isolated rat heart with substrate-free medium myocardial contractility was maintained for 30 min and thereafter declined towards zero in a subsequent period of 90 min. A slight decrease in heart rate was also apparent. In hearts deprived of the exogenous substrate, a marked reduction in the levels of glycogen, various glycolytic intermediates, triglycerides, high energy phosphate stores, and amino acids, which are most easily transaminated to Krebs cycle intermediates, was observed. Fluorescence due to reduced pyridine nucleotides, recorded from the surface of the heart, decreased during perfusion with substrate-free medium. Chemical analysis of substrate-depleted hearts also revealed a decrease in the concentrations of both NADH and NADPH. Perfusion of the heart with medium containing glucose for 2 h maintained myocardial contractility and slightly increased glycogen levels without appreciably affecting the slight decline in heart rate seen after perfusion with substrate-free medium. The presence of glucose in the perfusion medium partially prevented the changes in the levels of high energy phosphate stores, glycolytic intermediates, amino acids, triglycerides, and reduced pyridine nucleotides. Damage to the ultrastructure and swelling of mitochondria as seen on perfusing the hearts with substrate-free medium were also prevented partially by the presence of glucose in the perfusion medium. The ability of exogenous glucose to restore the contractile force and high energy phosphate stores towards the normal level declined over a 2 h period of preperfusion of the heart with substrate-free medium. The data support the general role of exogenous glucose in the maintainance of myocardial contractility fully and of metabolic and ultrastructure of the heart partially.
The Influence of Short Ether Anesthesia on Some Liver Enzyme Activities in the Rat
Authors: Katona E.
Published: April 2011

Rats were anesthetized by ether inhalation for 4–5 min and sacrificed 1–48 h after anesthesia. From their liver homogenates, the activities of nine enzymes were determined. Activities of urate oxidase and arylsulfatase-A did not change significantly but arylsulfatase-B was slightly decreased. Malate dehydrogenase, arylsulfatase-B, and thiamine pyrophosphatase reached their highest and "malic enzymes" their lowest activities at the same time, 5 h after anesthesia. Alkaline phosphatase first decreased, later increased. Acid phosphatase and glucose-6-phosphatase activities decreased following ether anesthesia. Thesechanges in the enzyme activities generally agree and partly explain previously reported effects of ether anesthesia observed in the serum.
Diffusion of CO2 and O2 Through the Walls of Plastic Syringes
Authors: Rosenberg Edith , Price Noble
Published: April 2011

The diffusion of O2 and CO2 through the walls of two types of plastic syringes was measured. When the syringes were filled with 16% O2, 5% CO2, and the balance N2, the average outward diffusion of CO2 was 0.076% per hour and the average inward diffusion of O2 was 0.06% per hour in room air at room temperature. When the syringes were surrounded by room air cooled in ice the average loss of CO2 was 0.137% per hour and the average increase in O2 content 0.10% per hour. From the measurements we conclude that diffusion of gases through the walls of disposable syringes cannot be responsible for the low [Formula: see text] values of "normal" arterial blood reported by clinical laboratories.
The Action of Prostaglandin E1 on Frog Skeletal Muscle
Authors: Marco L. A. , Coceani F.
Published: April 2011

The effects of prostaglandin E1 (PGE1) were investigated in frog semitendinosus and sartorius muscle preparations in vitro, PGE1 augmented and prolonged the twitch response, and the effect was equally developed in preparations stimulated through the nerve or directly. The threshold concentration was between 0.03 and 0.14 mM, and definite changes occurred with concentrations between 0.7 and 1.4 mM. Enhancement of twitch responses developed gradually, and a peak was reached within 5–20 min following PGE1 application. Prolonged exposure of the tissue to PGE1 showed that the twitch height increases first to a maximum and then declines to control values and below, despite the continuous presence of the compound in the bath. This decrease of twitch height was coupled with a progressive lengthening of the response. Twitch depression and prolongation were not reversible after transfer to normal Ringer but 2 mM caffeine consistently restored the depressed response to control levels, or above. PGE1, unlike caffeine, did not elicit sarcomeric oscillations. No substantial changes of membrane potentials at junctional or extrajunctional regions resulted from PGE1 treatment. It is concluded that PGE1 acts at a muscle site possibly by lowering the mechanical threshold of the contracting element.
Biochemical Effects of Oxygen at High Pressure in Rats
Authors: Banister E. W. , Davison A. J. , Bhakthan N. M. G. , Asmundson C.
Published: April 2011

Changes in brain and muscle lactate dehydrogenase, cytochrome oxidase, and NADH dehydrogenase (cytochrome c reductase) have been measured in rats convulsed by exposure to oxygen at high pressure 6 ATA (OHP). Blood glucose levels and some plasma and serum enzymes (lactate dehydrogenase, alkaline phosphatase, aspartate transaminase, and creatine kinase) were measured simultaneously. The lack of widespread inhibition of several markers for the glycolytic sequence, the Krebs cycle, or the cytochrome chain, together with elevated blood glucose levels in hyperoxia and increased blood alkaline phosphatase and lactate dehydrogenase in all hyperbaric conditions (and as well as oxygen), suggests tissue damage and a generalized etiology for the convulsive state.
Increased Renin Activity after Cold Storage of Human Plasma
Authors: Osmond D. H. , Ross L. J. , Scaiff K. D.
Published: April 2011

The velocity of angiotensin generation during incubation for 3 h at 37 °C increased up to 600% if plasma (EDTA) from normal men was first preincubated for 3 days at 4 °C. Longer preincubation (9–31 days) generally resulted in additional potentiation that continued to be expressed during incubation periods of 3–48 h at 37 °C. The effect is not abolished in the presence of up to 200 μg/ml of neomycin sulfate. Recovery of synthetic angiotensin I added to both cold-stored and control plasma is about 90% after 3 h of contact at 4 °C. The cause of potentiation has not been established, but possibilities under investigation include renin activation and preferential degradation of a renin inhibitor.
Effects of Anions on Frog Ventricle
Authors: Anderson Esther R. , Foulks J. G.
Published: April 2011

The effects of replacement of external chloride by other anions on the electrical and mechanical properties of frog ventricular muscle have been studied.The effects of methylsulfate were similar to those expected for replacement of a permeant anion with an impermeant anion. Increased twitch tension was largely dependent on action potential prolongation. Other anions of the sulfate–sulfonate series produced similar changes, but minor differences in their actions indicated that their effects could not be explained entirely by the elimination of chloride current.Acetate and its analogues produced dramatic changes in both the electrical and mechanical properties of frog heart. All caused a marked hyperpolarization of the resting membrane potential, accompanied by characteristic changes in the shape and duration of the repolarization phase of the action potential. Enhanced contractile performance was characterized by an increased rate of tension development and a slow onset of relaxation. These effects were equally prominent upon transfer to acetate Ringer's solution after previous equilibration to a medium containing methylsulfate in place of chloride. Although similar qualitatively, the members of this series of anions also displayed marked quantitative differences in the intensity and time course of their effects.
Diurnal Rhythm of Corticotropin-Releasing Factor Activity in the Pigeon Hypothalamus
Authors: Sato Takenori , George John C.
Published: April 2011

An attempt was made to detect diurnal periodicity in the hypothalamic content of corticotropin-releasing factor (CRF) activity in the normal pigeon (Columba livia) employing the intrapituitary microinjection method. It was found that CRF activity in the pigeon hypothalamus exhibits a typical diurnal rhythm, with its peak value at 6 a.m. and its trough at 8 p.m. under a lighting regimen of 12-h light and 12-h dark daily cycle. Moreover, this rhythm of CRF activity was shown to be well correlated with a diurnal rhythm of plasma corticosterone level with a definite phase shift. These findings support the concept that the diurnal periodicity of plasma corticosteroid level in the pigeon, originates in the cyclic phases of the releasing factor within the hypothalamus. The physiological significance of these findings is discussed with special reference to the hypothalamic regulation of adrenocorticotropin secretion in the pigeon.
Thermoregulation in Exercising White Rats
Authors: Myhre K. , Hellstrøm B.
Published: April 2011

Colonic temperatures (TC), heart rates (HR), back skin and tail skin temperatures (TST) were measured in six warm acclimated (+24 °C) male albino rats running on a treadmill at three different work loads (HR ranging from 400 beats/min to 500 beats/min). Ambient temperatures (TA) ranged from about +8 °C to about +30 °C. TC increased immediately upon onset of work. Exercising in a cold environment ultimately made the rats hypothermic and in a warm environment hyperthermic. Within the limits set by the external thermal stress the rats controlled TC independently of the work intensity.High trunk skin temperatures were recorded in all experiments. Exercise in cold and cool environments produced tail skin vasoconstriction. In the 21 °C environment half of the rats produced tail skin vasodilation. In the 28 °C environment most experiments produced this effect. Cessation of work was accompanied by prompt vasoconstriction. The results indicated that exercise time before tail vasodilation was affected by exercise as well as by the tail skin temperature prior to vasodilation.
Characteristics of Skeletal Muscle Fiber Types in the Miniature Pig and the Effect of Training
Authors: Fitts R. H. , Nagle F. J. , Cassens R. G.
Published: April 2011

The fiber types present in miniature pig skeletal muscle were determined with enzyme histochemical techniques. Three distinct fiber types were found: a fast white fiber, a fast intermediate fiber, and a slow red fiber. The fiber types found in miniature pig (large mammal) skeletal muscle were different from those in rat (rodent) skeletal muscle where the fiber types are classified as fast white, slow intermediate, and fast red. The fiber type distribution in miniature pig skeletal muscle was not altered by either an endurance or sprint running program, despite physiologically measurable training effects. It is concluded that enzyme histochemistry is a good qualitative tool for assessing the fiber types present in a muscle but lacks the sensitivity to measure or quantitate changes due to training.
Mechanoreceptor and Photoreceptor Tonic Integration in the Crayfish
Authors: Galeano C. , Beliveau S.
Published: April 2011

The activity of the caudal photoreceptor of crayfish was studied in: (1) intact tail ganglion, (2) partially isolated, and (3) totally isolated ganglion preparations. Statistical analysis of the photoreceptor activity included average frequency, average interval, variance, standard deviation, coefficient of variation, interval histograms, auto-expectation density, and cross-expectation density. Results showed that the average influence of the mechanoreceptor synapses on the photoreceptors during a period of several seconds was inhibitory, strong on the contralateral and weak on the ipsilateral side.
Effect of Sulfonylureas on the Secretion of Pancreatic Immunoreactive Glucagon and Enteric Glucagon-like Immunoreactivity
Authors: Crockford P. M. , Powell P. , Addah S. A.
Published: April 2011

The influence of two sulfonylureas, tolbutamide and glibenclamide, on the secretion of rat pancreatic immunoreactive insulin (IRI), glucagon (IRG), and intestinal glucagon-like immunoreactivity (GLI) was studied in vitro. Both hypoglycemic agents induced significant IRI release but had no effect on the secretion of IRG or GLI. These studies suggest that the sulfonylureas do not influence the altered IRG and GLI metabolism reported in diabetes mellitus but exert their major effect through the stimulation of IRI release.
Blockade of Cardiac Histamine Receptors by Promethazine
Authors: McNeill John H. , Verma Subhash C.
Published: April 2011

The inotropic and chronotropic effects of histamine on the isolated perfused guinea pig heart were antagonized by promethazine over a concentration range 4 × 10−6 – 16 × 10−6 M. Promethazine (4 × 10−6 M) decreased the ability of histamine (1 μg) to elevate cardiac cyclic AMP. A higher dose of histamine could not overcome the promethazine blockade. Promethazine (4 × 10− 6 M) did not block the inotropic effect of noradrenaline. Higher concentrations of promethazine, particularly 16 × 10−6 M did decrease the noradrenaline response. The data indicate that promethazine can interact with cardiac histamine receptors but the interaction is either noncompetitive or competitive non-equilibrium in nature.
Renal Sodium- and Potassium-Activated Adenosine Triphosphatase Deficiency During Post-obstructive Diuresis in the Rat
Authors: Wilson D. R. , Knox W. , Hall E. , Sen A. K.
Published: April 2011

Renal function studies and tissue enzyme analysis were carried out in rats with bilateral ureteral ligation (24 h) and after relief of obstruction at intervals of 2 h, 24 h, 3 days, and 7 days. A persistent decrease in glomerular filtration rate and in tubular reabsorption of sodium, solute, and water was noted at each interval after relief of obstruction. Renal sodium- and potassium-activated adenosine triphosphatase (Na–K-ATPase) activity was unchanged in kidneys obstructed for 24 h, but enzyme activity was decreased in the outer medulla of the kidney and, less often, in the renal cortex, at each interval studied during the post-obstructive period. Magnesium-dependent adenosine triphosphatase (Mg-ATPase) activity was not changed in any of the groups. In the post-obstructive kidney (24 h, 3 days, and 7 days) there was a significant correlation between the decrease in outer medullary Na–K-ATPase activity and the changes in filtered sodium load, tubular reabsorption of sodium, and urine osmolality. A deficiency of renal Na–K-ATPase could be important in the pathogenesis of post-obstructive natriuresis and diuresis.
Determination of the Therapeutic Mean Effective Doses of Several Anti-inflammatory Agents in Adjuvant Arthritic Rats
Authors: Martel R. R. , Klicius J. , Herr F.
Published: April 2011

The large variation in the severity of the arthritic response of the adjuvant-injected rat often makes it impossible to obtain statistically manageable dose–response curves with anti-inflammatory drugs. Consequently, the relative potency of anti-inflammatory drugs generally was not established. In the present study, with a modification of the therapeutic test, reliable dose–response curves were obtained with seven anti-inflammatory drugs. With this method the "therapeutic" mean effective dose (ED50) and relative potency were calculated by probit analysis. Charles River rats were injected in the left hind paw with adjuvant. On day 14, rats with an injected paw volume of 4–6 ml that increased by at least 0.5 ml between days 10 and 14 were selected for drug treatment. Groups of 6–12 rats with a mean injected paw volume of 5–5.5 ml were formed. Dosing with compounds was started on day 14 and continued daily until day 22 (nine injections). Ninety-four percent of the arthritic control rats showed a further increase in injected paw size between days 14 and 22 (mean, 1.06 ± 0.12 ml) whereas rats dosed with anti-inflammatory compounds showed a dose-related decrease in paw size during the same period. A decrease of 0.5 ml or more between days 14 and 22 was considered to be a therapeutic effect, smaller decreases were taken as no effect. The oral ED50's in milligrams per kilogram were indomethacin, 0.22 ± 0.05; prednisolone, 3.49 ± 1.0; hydrocortisone, 12.4 ± 3.0; phenylbutazone, 13.27 ± 2.7; mefenamic acid 20.10 ± 5.8; aminopyrine, 129.95 ± 25.3; and aspirin, 279.0 ± 24.6. Except for aspirin, the relative potency of the compounds studied by this therapeutic test (chronic) was comparable to that reported for the acute carrageenin assay. Aspirin appears to be markedly less active in chronic inflammation than in acute. This finding is consistent with both experimental and clinical observations.
Stimulation of Nerve Fiber Growth from Cultured Sympathetic Explants
Authors: Recklies Anneliese D. , Rathbone Michel P. , Hall Ross H.
Published: April 2011

Both N6,O2′-dibutyryl adenosine-3′,5′-cyclic monophosphate (DBcAMP) and prostaglandin E1 (PGE1) stimulate maturation and differentiation of neuroblastoma cells in tissue culture. This effect is potentiated by several phosphodiesterase inhibitors. DBcAMP and adenosine-3′,5′-cyclic monophosphate (cAMP) have also been reported to mimic the effects of nerve growth factor (NGF) on dorsal root ganglia but not on sympathetic ganglia in stimulating neurite outgrowth.We found that prostaglandins E1 and E2 as well as cAMP and DBcAMP elicit neurite outgrowth from chick embryo sympathetic ganglia incubated in microtest tissue culture plates with a liquid medium. The effects of DBcAMP were also evoked by the addition of sodium butyrate to the culture medium. When these compounds were used in the presence of 4 mM theophylline the neurite growth barely exceeded that observed in control cultures. Theophylline also reduced the amount of nerve fiber growth obtained in the presence of NGF. Thus it seems likely that theophylline acts on nerve fiber growth in a manner different from its known action on intracellular cAMP levels.The amount of neurite outgrowth caused by all compounds tested was always significantly less than that in response to NGF. The morphology of the neurite growth in response to PGE1, PGE2, cAMP, DBcAMP, and sodium butyrate was different than that observed with neurites growing in the presence of NGF. It is possible that the former compounds act on some non-neuronal components of the sympathetic explants, whereas NGF acts on the neuronal cells directly.
Influences from Upper Respiratory Tract on Caudal Brainstem Neurones of Cat
Authors: Sessle Barry J. , Greenwood L. Frances , Kenny David J.
Published: April 2011

During microelectrode penetrations of the solitary tract nucleus and adjacent reticular formation, single neurones were located that discharged in a rhythm that was linked with respiration but that persisted after muscle paralysis. Many of these neurones could be activated from the vagus or upper respiratory tract areas. Some had no demonstrated excitatory input, yet their rhythmic activity could be abolished only by stimulation of nerves innervating the upper respiratory tract. This stimulation also abolished respiration. Such findings emphasize the significance of upper respiratory tract feedback in normal respiratory function and possibly in abnormal conditions such as the 'sudden infant death syndrome.'
Acetylcholine Sensitivity of Hippocampal Formation Neurons
Authors: Bland B. H. , Kostopoulos G. K. , Phillis J. W.
Published: April 2011

Microiontophoretic application of acetylcholine to neurons in the CA1 pyramidal and dentate granule layers of the rabbit hippocampus revealed differences both in the number of cells excited and the nature of the excitation in the two populations of neurons. A smaller percentage (35.7%) of CA1 pyramidal neurons were found to be excited by acetylcholine, compared with the percentage (92.3%) of dentate granule cells excited. Excitation of CA1 pyramidal cells was slow in onset and antagonized by atropine. Excitation of dentate granule cells was rapid in onset and atropine did not specifically antagonize the action of acetylcholine on these cells.
Effects of Vitamin A on Blood Coagulation and Clot-Lysis Times
Authors: Woodward Bill , March B. E.
Published: April 2011

The effects of dietary excess of vitamin A on one-stage prothrombin time and on one-stage euglobulin-lysis time were studied in Single Comb White Leghorn, New Hampshire, and Black Australorp chicks. Prothrombin time was increased by the feeding of 100 000 and 200 000 I.U. of vitamin A per kilogram of diet to the Black Australorp chicks but it was not increased when these amounts of vitamin A were fed to either the White Leghorn or the New Hampshire chicks. The prolongation of prothrombin time was reversed within 16 h by injection of menadione. Vitamin A at 100 000 and 200 000 I.U./kg of diet decreased euglobulin-lysis times in chicks of all three breeds but increased the concentration of fibrinogen in the plasma. The effect of excess vitamin A on euglobulin-lysis time was not associated with induced vitamin K deficiency. The decreased euglobulin-lysis time resulting from intake of excess vitamin A persisted for 6 weeks subsequent to the feeding of moderate amounts of vitamin A.
Physical Factors Influencing Fluid Reabsorption from Henle's Loop
Authors: Baines A. D. , Wu C. K.
Published: April 2011

Our objective was to produce reductions in the luminal volume of Henle's loop and increases in linear flow velocity through the loop. We did this in a recollection micropuncture study by collecting fluid with and without suction from early distal tubules. With suction, transit time of fast green dye through the loop decreased by 34%, calculated loop volume decreased by 28%, and fractional water reabsorption fell from 73.6 to 70.3% (p < 0.025) in water diuretic rats. Absolute water reabsorption did not decrease significantly. In urea–saline diuretic rats transit time decreased 25%, calculated loop volume decreased 22%, fractional reabsorption fell from 59.0 to 51.7% (p < 0.001), and absolute reabsorption decreased by 2.3 nl/min(p < 0.025). Single nephron glomerular filtration rate, distal tubular sodium concentration, and osmolality were unaffected. The less pronounced effect of collection with suction in water diuretic rats may be related to the lower medullary fluid osmolality, which was 338 ± 9(S.E.)mOsmol/kg as compared to497 ± 35 in urea–saline diuretic rats. Collecting fluid with suction from late proximal tubules did not alter glomerular filtration rate or fractional water reabsorption. Stumpe et al. ((1970) J. Clin. Invest. 49, 1200–1212) noted an inverse correlation between fluid reabsorption from Henle's loop and flow velocity in rats with hypertension or congestive heart failure. One can reproduce this correlation by artificially altering the transmural pressure gradient in the loop.
The Inhibitory Effects of Prostaglandin E1 on Guinea-Pig Ureter
Authors: Johns A. , Wooster M. J.
Published: April 2011

Prostaglandin E1 (PGE1) hyperpolarized the smooth muscle cells of guinea-pig ureter in normal Krebs solution and was without effect on ureters depolarized in KCl Krebs. PGE1 inhibited both electrically induced contractions and K+-induced contractures of the ureters. Conditions that favored greater tension development by the ureters, namely, high [K+] or high [Ca2+] reduced the inhibitory effects of PGE1 on the K+-induced contractures. Depolarization of guinea-pig ureter with KCl Krebs led to an increase in radio-calcium content of the tissue over a 30 min loading period. This increase in the tissue's radio-calcium content was further increased by PGE1 but not by theophylline. PGE1 was found to have no effect on either total calcium content or the calcium efflux from the tissue. It is suggested that PGE1 exerts its inhibitory action by increasing calcium sequestration at the inner surface of the cell membrane.
Magnesium Binding in the Digesta of the Chicken
Authors: Guenter W. , Sell J. L.
Published: April 2011

Two experiments involving laying hens and mature roosters were carried out to determine the effect of pH on the ultrafilterable fraction of Mg((Mg)u) present in the digesta along the gastrointestinal tract. Concurrently, the approximate molecular weight of the (Mg)u was determined. The average pH's for laying hens were: crop 4.88, proventriculus 5.27, ventriculus 4.77, duodenum 5.57, jejunum 6.15, ileum 7.82, and colon 6.65. Similar pH values were obtained for mature roosters. The (Mg)u fraction decreased significantly in the ileum where the pH was greater than 7.00. However, treating the ileal digesta with an acid pH buffer released about 70% of the nonfilterable Mg. The molecular weight of the (Mg)u was found to be less than 700, suggesting that the Mg was present in digesta as an inorganic salt or as an organic complex of low molecular weight.
Phosphate Uptake into Organic Compounds in Skeletal Muscle
Authors: Dunkley C. R. , Manery J. F.
Published: April 2011

Isolated intact frog muscles were incubated in 32P-labelled Ringer's solution for various periods of time (30 s – 20 h). Labelled compounds were isolated from TCA, methanol–chloroform–water, and water extracts of muscle. Hexosephosphates, phosphocreatine, phosphoenolphyruvate, α-glycerol phosphate, adenosine triphosphate, and inorganic phosphate were identified after 30 s, and 4 h incubation. Much more labelling was found after 20 h. The incorporation of 32P in 30 s into organic phosphate compounds, such as α-glycerol phosphate and ATP, showed that immediate esterification of Pi occurred on, or just inside, the sarcolemma.
Destinée des deux plus gros follicules des ovaires de brebis à la suite de la destruction du plus gros follicule et/ou de l'enlèvement du corps jaune à deux moments du cycle
Authors: Bhérer Jacques , DuFour Jacques , Matton Pierre
Published: April 2011

Marking of the largest (F1) and the second largest (F2) follicles of the ovaries of the sheep with India ink has allowed us to observe the fate of these follicles after different treatments.All the F1 and F2 follicles of the controls marked on the 10th day of the cycle became atretic, but when the marking was done on the 14th day, only the F1 (of the marked follicles) ovulated. Destruction of the F1 with or without removal of the corpora lutea allowed some of the F2 to ovulate, whereas only removal of the corpora lutea decreased the number of F1 ovulating. It thus appears that the fate of the F1 is related to the time of the cycle and that the F1 could have an inhibitory effect on the ovulation of the F2. Removal of the corpora lutea also induced the development of several cystic follicles and decreased the total ovulation rate.