bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of the disappearance curves of 133Xe and 85Kr for the measurement of the intrarenal distribution of blood flow
Authors: Carrière Serge
Published: April 2011

Krypton-85 and xenon-133 disappearance curves which are used to measure the intrarenal distribution of blood flow have been compared in two groups of animals under normal conditions. The blood flow rates (ml/100 g per min), percentage of initial radioactivity, and regional blood flow (ml/100 g kidney tissue) of the cortex calculated from the krypton-85 decay curves were found to be more elevated than those obtained from the xenon-133 curves. The same conclusions can be drawn from the results obtained for the outer medulla with the exception that the percentage of initial radioactivity was not different when calculated with either method. Among other considerations, the fact that the tissue to blood partition coefficient of krypton is not influenced by the hematocrit and that this radioisotope may be used for the preparation of the autoradiograms leads to the conclusion that it is preferable to use krypton-85 rather than xenon-133 for the measurement of intrarenal distribution of blood flow in animal experimentation.
Supersensitivity of the Isolated Rat Heart after Chemical Sympathectomy with 6-Hydroxydopamine
Authors: Nadeau R. A. , Champlain J. De , Tremblay G. M.
Published: April 2011

Presynaptic supersensitivity was demonstrated in isolated rat atria and perfused hearts 2 h after an intravenous injection of 6-hydroxydopamine (6-OH-DA), 100 mg/kg. This coincided with a maximum depletion of cardiac endogenous noradrenaline, a disappearance of the fluorescence of terminal adrenergic nerve fibers in the atrial myocardium, and an abolished chronotropic response to tyramine. The chronotropic response to dopamine was also significantly diminished. Maximal supersensitivity to the chronotropic effect of noradrenaline was observed 72 h after the injection of 6-OH-DA. Two weeks after the administration of 6-OH-DA, supersensitivity to noradrenaline was less marked, and the response to tyramine was restored. These changes corresponded to an increasing noradrenaline content in the heart and to the reappearance of histofluorescent fibers in the atria.
The Effect of Temperature on Sodium Movements in Rat Uteri and a Model for Control of their Ion Content
Authors: Daniel E. E. , Robinson Kathleen
Published: April 2011

The uptake and efflux of 22Na was studied in isolated rat uterine horns (both fresh and Na-rich) at 5, 15, 25, and 37 °C. Reduction of temperature from 37 °C to 25 or to 15 °C reduced 22Na uptake into, and efflux from, both the extracellular space and cells to the degree expected of a diffusion-controlled process (Q10 < 2). Reduction of the temperature to 5 °C during uptake into Na-rich horns revealed that a substantial fraction of cellular sodium became less exchangeable. At 5 °C, 22Na efflux was also markedly reduced, more than from ouabain or ATP depletion. Analysis of this change by curve-peeling and by reducing the temperature at various stages of efflux suggested that the main cause was a shift of 22Na from the larger, faster cellular fraction (No. 2) to the slower cellular fraction (No. 3). Bound 22Na was also markedly increased. The rate coefficients from curve-peeling for both cellular fractions were decreased. Radioactivity still in fraction 2 at 5 °C emerged at a rate of about half that at 15 °C. However, an overall coefficient for efflux of 22Na which would have emerged in fraction 2 at 15 or 25 °C showed that the Q10 for 22Na efflux between 5 and 15 °C was about 15. Tissues did not swell when they gained sodium at 5 °C. The effects of ouabain to increase 22Na influx and 42K efflux were eliminated at 5 °C. The effects of ATP depletion by iodoacetate and dinitrophenol to decrease 22Na efflux and to increase 22Na uptake, K loss, and swelling were reduced at 5 °C. Prior ATP depletion altered but did not prevent the marked reduction of efflux by cooling to 5 °C. Efflux of lithium, but not of potassium, was markedly slowed at 5 °C. K-free solutions still increased 22Na uptake at 5 °C. A model involving pinocytotic vesicles to explain these and earlier results was postulated.
The Action of Diazoxide on Isolated Vascular Smooth Muscle Electrophysiology and Contraction
Authors: Rhodes H. James , Sutter M. C.
Published: April 2011

Diazoxide inhibits spontaneous motility and contractile responses to noradrenaline, serotonin, or procaine in isolated rabbit anterior mesenteric vein (A.M.V.). Diazoxide fails to inhibit noradrenaline-induced contractions in ouabain-depolarized isolated A.M.V. Sucrose gap recordings show that spontaneous electrical activity in A.M.V., in guinea pig taenia coli, and in estrogen-dominated rabbit uterus is inhibited by diazoxide. The addition of extra calcium failed to overcome the inhibitory effect of diazoxide on smooth muscle contraction except when tissues were depolarized and calcium itself was the contractile agonist. It is suggested that diazoxide ordinarily inhibits contraction in vascular smooth muscle by acting on a membrane-potential-dependent component of excitation–contraction coupling. An additional mechanism of action of diazoxide, which is nonmembrane-potential-dependent, can be unmasked in depolarized A.M.V. where diazoxide can antagonize calcium-induced contractions.
Effects of Sex Hormones on the Renal Pressor System
Authors: Nasjletti Alberto , Matsunaga Masato , Masson Georges M. C.
Published: April 2011

The effects of sex and sex hormones on angiotensinogen, renin activity, and renin concentration in plasma and on renal renin were investigated in rats. During estrus there was a significant increase in angiotensinogen, which was suppressed by ovariectomy. In males, castration had no effect. Administration of stilbestrol caused a rapid increase in angiotensinogen. Renal renin and plasma renin concentration decreased while plasma renin activity remained near normal levels. Following addition of a constant dose of rat renin, plasma from estrogen-treated rats released angiotensin at a faster rate than normal plasma; this increased reactivity is attributed to the high substrate concentration and not to the lack of an inhibitor, to the presence of an activator, or of a more reactive substrate. These changes were not modified by progesterone or testosterone. Progesterone alone caused a significant increase in renal renin. Estrogens did not elicit hypertension nor modify a preexisting renal hypertension. These observations support the hypothesis that the primary effect of estrogens is an increased angiotensinogen formation, and that the resulting enhancement in plasma reactivity to renin causes an increase in angiotensin which acts as a negative feedback on renin production.
The Effects of Cold and Prostaglandin E1 on Lipid Mobilization in the Chicken
Authors: Wagner W. D. , Peterson R. A. , Cenedella R. J.
Published: April 2011

Plasma free fatty acid (FFA) levels and the effects of prostaglandin E1 (PGE1) were studied in cold-acclimated and cold-exposed chickens and compared to controls. Chickens cold-acclimated at 4–7 or 8–11 °C for 4 weeks had significantly elevated plasma FFA when compared to the controls at 19–21 °C. Although PGE1 had no effect on the basal level of FFA of controls, a significantly lower plasma FFA was seen after injection of either 10 or 30 μg PGE1/kg in cold-acclimated chickens. Chickens cold-exposed to 2–3 °C for 4 h demonstrated significant elevations of plasma FFA when compared to controls. Only 30 μg PGE1/kg significantly depressed the plasma FFA in the cold-exposed birds. No inhibition of basal FFA release was seen in control animals. From these experiments, it is concluded that chickens mobilize FFA extensively under cold-exposure and that this stimulated lipolysis is inhibited by PGE1.
Effects of Bilateral Vagotomy on Renal Function in the Rat
Authors: Mercer Paul F.
Published: April 2011

Renal function was studied in rats before and after section of the vagus nerves at the level of the common carotid arteries. In the control group of rats, sodium output and volume rate of urine flow increased following vagal section but glomerular filtration rate did not change. This response was not altered in other rats by desoxycorticosterone acetate, vasopressin, or renal nerve section. This response was similar to that seen in rats in which both common carotid arteries had been occluded. The natriuresis following bilateral vagotomy did not occur in rats in which the blood pressure was prevented from rising by means of aortic constriction. It is concluded that a natriuresis does occur following bilateral vagotomy. This natriuresis may be a result of the effect of arterial blood pressure following the vagotomy.
A Simple Quantitative Procedure for the Partition of Free and Esterified FattyAcids from Fecal Lipids
Authors: Hamilton R. M. G. , McDonald B. E.
Published: April 2011

A procedure is presented for the partition of dietary and fecal lipids into free fatty acids (FFA), esterified fatty acids (EFA), and nonsaponifiable (NSF) fractions. The method permits quantitation of the lipid fractions and subsequent determination of the fatty acid composition of the FFA and EFA fraction by gas–liquid chromatography (g.l.c). Petroleum ether soluble lipids of acidified (HCl–ethanol) lyophilized feces and feed were partitioned into FFA and an esterified fatty acid plus nonsaponifiable fraction using a 0.05 N KOH – 60% ethanol partitioning solvent. The latter fraction was saponified and partitioned into EFA and NSF. Total recoveries of 93–100% were obtained with the method for lipid mixtures of known composition, dietary fats except coconut oil (88%), and fecal lipids. Separation of the lipids into individual fractions by this method was shown to be essentially complete by thin-layer chromatography and g.l.c. analysis.
Effect of Phenylephrine on Cardiac Contractility and Adenyl Cyclase Activity
Authors: Benfey B. G. , Carolin T.
Published: April 2011

Both phenylephrine and noradrenaline increased the force of contraction of isolated preparations of rabbit and chicken heart. Noradrenaline increased the rate of formation of cyclic 3′,5′-AMP in homogenate of rabbit or chicken heart, but phenylephrine did not. These results demonstrate that sympathomimetic amines can increase cardiac contractility without increasing the activity of adenyl cyclase.
Resolution of Two Components in the Upstroke of the Action Potential in Atrioventricular Fibers of the Rabbit Heart
Authors: Ceretti E. Ruiz de , Zumino A. Ponce , Parisii I. M.
Published: April 2011

A preparation is described which allows recording of unaltered intracellular potentials from different regions of the perfused heart (atrium, interventricular septum, and atrioventricular junction). Two components were identified in the upstroke of action potentials from nodal (A.V.) cells. In low sodium medium, a time lag between the two components becomes evident. Amplitude and slope of the first one decrease and the characteristics of the second one remain unaltered. It is concluded that the first component is sodium-dependent, while another not yet identified ion determines the second component.
Effect of External Potassium Concentration on Caffeine Contractures in Frog Toe Muscle
Authors: Foulks J. G. , Perry Florence A. , Sanders H. D.
Published: April 2011

Increased [K]0 sufficient to produce submaximum depolarization contractures of frog toe muscle enhanced the tension produced during subsequent caffeine contractures, but caffeine-contracture tension was depressed after an increase in [K]0 sufficient to produce maximum or near-maximum depolarization contractures.Reduced external concentration of divalent cations often augmented caffeine-contracture tension at normal [K]0 but did not do so after [K]0 was increased to levels which produce maximum K contractures. Increased [Mg]0 or [Ca]0 had little direct effect on caffeine contractures but shifted the effect of [K]0 on caffeine contractures toward higher [K]0 in accordance with the shift in [K]0 required to produce depolarization contractures. Replacement of external chloride with acetate, which shifts the relation between [K]0 and depolarization-contracture tension toward lower [K]0, produced a similar shift in the effect of [K]0 on caffeine contractures. Maximum depolarization contractures relaxed rapidly when superimposed on submaximum caffeine contractures, often to a level of residual tension which was less than that developed by the initial caffeine contracture. This effect was particularly marked in media containing acetate in place of chloride.
Biochemical and Morphological Parameters of Taurolithocholate-Induced Cholestasis
Authors: Priestly Brian G. , Côté Michel G. , Plaa Gabriel L.
Published: April 2011

Intravenous injection of sodium taurolithocholate (NaTL) into rats produces a dose-related cholestatic response. A dose of 100 mg/kg was chosen to study the temporal effects on bile flow, serum bilirubin (SB) concentrations, serum transaminase (SGPT) activity, and serum alkaline phosphatase (SAP) activity. Cessation of bile flow after NaTL injection or bile duct ligation (B.D.L.) was accompanied by progressive elevations of SB and SGPT; after NaTL, these parameters reached maximal values at a time when bile flow was returning to normal. Changes in SAP were similar in both NaTL-treated and B.D.L. groups. Elevation of SGPT and SB was also seen when a combination of NaTL and taurocholic acid (TC) was injected, although cholestasis was not produced. TC alone produced similar changes. NaTL injection produced changes in hepatic ultrastructure, of which the most marked were dilatation of biliary canaliculi and the endoplasmic reticulum. The disruption was marked at 12 h and was reversed at 24 h. This correlated with changes in SGPT and microsomal function as measured by zoxazolamine paralysis time. TC also produced elevation of SGPT in the isolated perfused rat liver. The above changes are consistent with obstruction of the biliary tract by NaTL precipitation. However, the data also indicate that a combination of NaTL and TC can elicit hepatocyte disturbances without causing a diminution in bile flow.
Analysis of Heparin – Azure A Metachromasy in Agarose Gel
Authors: Wollin A. , Jaques L. B.
Published: April 2011

The effect of changes in pH, temperature, salt, and ethanol concentrations on the metachromatic heparin – azure A complex was studied in solution and in agarose gel photometrically. Salt, ethanol, and low pH inhibit the heparin – azure A interaction. With low salt concentration the inhibition is greater in aqueous solution than in agarose gel. Increasing ethanol concentrations interfere stepwise, with a plateau between 40–80% ethanol. Visual estimates of metachromasy do not coincide with the photometric measurements. Increase in temperature decreases the heparin – azure A complex in agarose. The responses to the parameter changes are similar in both media, with differences attributable to the different physical states.
The Pressor and Myotropic Effects and the Antagonistic Properties of Several Analogues of Angiotensin II
Authors: Regoli D. , Park W. K.
Published: April 2011

The substitution of an unnatural amino acid, 1-aminocyclopentanecarboxylic acid (Acpc), for each of the eight amino acids of angiotensin (AT) has been used to study the relationship between chemical structure and biological activities of angiotensin. The pressor and the myotropic activities of the various ATII derivatives have been tested on the rat blood pressure and on three isolated organs: rat isolated colon, rat stomach strip, and rabbit isolated kidney.The results indicate that 6-His and 8-Phe are essential for the activities of angiotensin II. Moreover, (8-Acpc)-ATII, but not (6-Acpc)-ATII, antagonizes the pressor and myotropic effects of ATII and ATI. αE and pD2 of all analogues have been estimated on the isolated rat stomach strip to evaluate intrinsic activity and affinity for the receptors. (1-, (2-, (3-, (4-, and (5-Acpc)-ATII have the same intrinsic activities as ATII, while those of (6-, (7-, and (8-Acpc)-ATII are much lower.Analogues of ATII substituted in position 8 antagonize specifically the myotropic and pressor effects of ATII and ATI. On the contrary, the effects of other smooth muscle stimulating agents (acetylcholine, 5-hydroxytryptamine, bradykinin, and vasopressin) are not modified.Log dose response curves of ATII and ATI are shifted to the right in the presence of antagonists, but remain parallel. The antagonism is rapidly reversible and may be competitive.
Events Occurring in the Region of the Threshold for Potassium-Induced Contractures of Frog Skeletal Muscle. Changes in Elasticity and Oxygen Consumption
Authors: Vos E. C. , Frank G. B.
Published: April 2011

Small bundles of fibers of the semitendinosus of Rana pipiens were subjected to rapid stretches in normal Ringer solution and solutions containing potassium in concentrations just below the mechanical threshold for tension development. The resistance to stretch (R.T.S.) increased with increasing [K+]0. The increase in R.T.S. was dependent on the duration of exposure; the maximum occurred after about 30 s while longer exposures led to a decrease in the R.T.S. The maximum increase in the R.T.S. varied from two to six times the normal R.T.S. The increase in the R.T.S was hyperbolically related to [K+]0. An attempt was made to correlate the mechanical activation and the increase in respiration in muscles exposed to elevated [K+]0 (Solandt effect) by continuously measuring the oxygen consumption [Formula: see text] of toe muscles. Following exposure to an elevated [K+]0 just below the mechanical threshold, the [Formula: see text] started to increase after about 30 s and took 2–3 min to reach a new steady level. The results suggest that: (a) a low level of activation of the contractile elements occurs just below the mechanical threshold for tension development, (b) the excitation–contraction coupling process of frog striated muscle is one of continuous change, i.e. without a sharply defined threshold, and (c) the Solandt effect is probably the expression of a continuous relaxation-type process.
Seasonal Variations of the Immune Response of Ground Squirrels Kept at 22–24 °C
Authors: Sidky Y. A. , Hayward J. S. , Ruth R. F.
Published: April 2011

Ground squirrels (Citellus richardsoni) were kept at 22–24 °C for 13 months beginning in May 1969. These squirrels did not enter deep hibernation. The primary immune response measured as the serum antibody titer and the number of plaque-forming cells in the spleen decreased to a minimum in Janaury 1970 and recovered during the following spring. It is suggested that the poor immunological response of deep hibernation represents two influences, a primary circennial depression and a secondary exaggeration of this associated with deep hibernation per se.
Biochemical Basis of Heart Function. V. Effect of Starvation on Storage, Transport, and Synthesis of Cardiac Norepinephrine in Rats
Authors: Balasubramanian V. , Dhalla Naranjan S.
Published: April 2011

Starvation of rats was observed to increase the concentration of endogenous norepinephrine in both normal and adrenalectomized animals. Refeeding the starved animals restored the cardiac level of norepinephrine toward the control value. The proportion of norepinephrine decreased in the granular fraction and increased in the soluble fraction of the heart in fasted rats. Although the plasma level of norepinephrine in starved rats was higher than the control, no appreciable difference in the abilities of the hearts from these animals to accumulate 3H-norepinephrine was observed. The uptake of 14C-tyrosine by the hearts of starved animals was comparable to that by the control rats; however, the rate of synthesis of 14C-catecholamines in the hearts of starved rats was significantly decreased. Tyramine treatment was found to lower the cardiac norepinephrine content in the starved rats to the same extent as in the control. On the other hand, exposure of the rats to cold reduced the cardiac norepinephrine to a lesser degree in the starved animals in comparison to the control. It is suggested that starvation may decrease the proportion of norepinephrine which is available for release from the storage granules and thus reduces the influence of sympathetic activity in the heart.
Isoprenaline-induced Relaxation of Smooth Muscle not due to Electrogenic Sodium Pumping
Authors: Bose Deepak , Innes Ian R.
Published: April 2011

Ouabain or replacement of NaCl by LiCl abolishes the relaxation due to addition of KCl to sodium-rich cat carotid artery strips kept in a K+-free medium. Neither treatment antagonizes the relaxation due to β-adrenoceptor stimulation by l-isoprenaline. Unlike KCl-induced relaxation, the relaxation induced by l-isoprenaline is not due to stimulation of an electrogenic sodium pump.
Biochemical Basis of Heart Function. VI. Influence of Cations on Norepinephrine Transport, Storage, and Synthesis in the Isolated Perfused Rat Heart
Authors: Balasubramanian V. , Dhalla Naranjan S.
Published: April 2011

The effects of Ca2+ (0–5 mM), Mg2+ (0–16 mM), K+ (0–20 mM), and Na+ (0–145 mM) on the uptake, subcellular distribution, and release of exogenously given 3H-norepinephrine were investigated in the isolated perfused rat heart. The uptake of 14C-tyrosine, the synthesis of 14C-catecholamines, and the endogenous levels of norepinephrine were also determined under these experimental conditions. The uptake of 3H-norepinephrine was markedly decreased on perfusing the hearts with media containing low concentrations of Na+. Addition of Ca2+ to the perfusion medium containing Na+ increased the uptake of 3H-norepinephrine while Mg2+ or K+ had no effect. Increasing the concentration of Na+ from 0 to 145 mM in the perfusion medium increased the 3H-label in the granular fraction and decreased it in the soluble fraction whereas Ca2+, Mg2+, or K+ did not show any action. The spontaneous release of 3H-label was not influenced by the presence or absence of Ca2+, Mg2+, or K+ in the medium. On the other hand, the absence of Na+ was found to accelerate the spontaneous release of 3H-label and this effect was further enhanced when Ca2+ was also omitted from the perfusion medium. Increasing the concentrations of Ca2+ or Na+ in the perfusion medium decreased the rate of synthesis of 14C-catecholamincs from 14C-tyrosine whereas Mg2+ and K+ showed no effect. Absence of Na+, but not of K+, Ca2+, or Mg2+, resulted in a decrease in the endogenous level of norepinephrine. The amount of newly synthesized 14C-catecholamines in the perfusate was more on perfusing the hearts with Ca2+-free or Na+-free medium. These results are consistent with the view that Na+ is required for storage as well as uptake of norepinephrine in the adrenergic nerve terminals in the heart. Ca2+ appears necessary for the optimal uptake of norepinephrine due to Na+ and has been shown to inhibit the spontaneous release of norepinephrine due to Na+ lack. In addition, Na+ and Ca2+ reduce the rate of synthesis of catecholamines in the adrenergic nerve endings in the heart.
Absorption of Retinol and Retinyl Esters via Lymph and the Portal Vein in the Rat
Authors: Yeung D. L. , Veen-Baigent M. J.
Published: April 2011

3H-11,12-retinyl acetate (3H-RA) was administered orally at various dose levels to normal and vitamin A deficient male Wistar rats. While the greater proportion of the vitamin was absorbed as retinyl ester (RE), a small but measurable amount of retinol (ROH) consistently appeared in plasma and liver within 1 h after dosing. Comparison of the specific activities (S.A.) of plasma and liver ROH and RE indicated that ROH had been absorbed as such. Furthermore, labelled ROH was detected in the lymph of thoracic duct cannulated rats within 30 min after dosing. The S.A. of the recovered ROH was very similar to that of the administered 3H-RA. The presence of labelled ROH and RE in plasma of cannulated rats suggested simultaneous absorption via the portal vein. The ability of the portal vein to absorb these two forms of the vitamin was confirmed in thoracic duct ligated rats. Quantitative estimates of ROH and RE over the two routes of absorption could not be made from the present data.Thus a small amount of ingested vitamin A is consistently absorbed as ROH as a normal event during absorption. The possible physiological significance of these observations is discussed.
Effect of Starvation on Pituitary and Serum Follicle-Stimulating Hormone and Luteinizing Hormone Following Ovariectomy in the Rat
Authors: Ibrahim E. A. , Howland B. E.
Published: April 2011

The concentration of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in serum and pituitary glands was studied in intact female rats and rats that were ovariectomized on day 0 of the experiment and then starved or fed for 2, 4, 7, or 9 days. Ovariectomy resulted in enhanced rates of synthesis and release of FSH and LH as indicated by the significant (P < 0.01) rises in the concentration of both hormones in the pituitary gland and serum.Starvation resulted in a decrease in body and pituitary weight. The concentration of FSH and LH in pituitary glands of starved rats was higher (P < 0.05) than that in fed rats on days 7 and 9. The concentration of FSH and LH in serum of starved rats was increased after ovariectomy but the levels on days 7 and 9 were lower than those of fed rats.These results suggest that the synthesis of FSH and LH was enhanced in both starved and fed rats following ovariectomy while the rate of release of both hormones was decreased at 7 and 9 days of starvation in comparison with rats fed ad libitum.
Hormonal Release by Dispersed Pituitary Cells
Authors: Kudo Catherine F. , Rubinstein David , McKenzie J. Maxwell , Beck John C.
Published: April 2011

Dispersed anterior pituitary cells were prepared by treatment of hog pituitaries with collagenase. The cell yield based on DNA recovered in intact cells after collagenase treatment was 5–10%. Ninety percent of the cells appeared intact by phase contrast microscopy. The three major cell types were identifiable by Mallory-Heidenhain staining. The dispersed cells incorporated glucose carbon into CO2 and leucine into protein more rapidly than corresponding slices. Increasing the glucose concentration of the medium caused a progressive rise in cellular growth hormone (GH) content and in leucine incorporation into protein. The dispersed cells were capable of releasing immunoreactive GH and bioassayable thyroid-stimulating hormone (TSH). Crude acid extracts of stalk-median eminence had variable effects on the release of these hormones. Some extracts enhanced GH release while having a minimal effect on TSH release; others had the reverse effect. Stimulation of adenyl cyclase activity paralleled TSH release, but not GH release. In addition, during short incubations dibutyryl cyclic AMP and inhibitors of phosphodiesterase activity had no effect on GH release, but enhanced TSH release. Other cyclic nucleotides did not stimulate the release of either hormone. Prostaglandin E1 stimulated GH and TSH release as well as adenyl cyclase activity. These results suggest that the mechanisms controlling GH and TSH release differ, and that cyclic AMP may not be involved in GH release.
Quantitative Aspects of the Urinary and Fecal Excretion of Radioactive Metabolites of Vitamin A in the Rat
Authors: Varma R. N. , Beaton G. H.
Published: April 2011

Urinary and fecal excretion of radioactive metabolites has been followed for 8 days (12 days in one group) in groups of rats having different initial body stores of vitamin A and given a single oral dose of 11,12-3H-retinyl acetate in oil. During the collections animals were fed a vitamin A deficient diet except for one group which was given laboratory chow throughout. At the end of the collection period animals were killed for determination of liver, kidney, and plasma vitamin A and radioactivity. Specific activities were similar in the three tissues; total liver vitamin A contents ranged from undetectable to 7700 μg. Excretion of fecal and urinary radioactivity was high initially but fell to apparently stable levels by day 8. When the combined urinary and fecal excretion was expressed in terms of the liver vitamin A equivalent (ELV), there was a gradual increase in excretion rate with the logarithm of liver vitamin A up to 150–300 μg/g liver; thereafter the rate of excretion increased more rapidly with liver stores to the highest level studied, 500–550 μg/g. In the initial phase the ELV values were 4–10 μg/day, rising to 22–24 μg/day in the second phase. These studies suggest that (a) a portion of newly absorbed vitamin A is metabolized before mixing with general body pools and probably without greatly altering the metabolism of endogenous vitamin A, (b) after equilibration of body pools, urinary excretion of radioactivity should be a useful index in experimental studies of factors affecting vitamin A metabolism, and (c) chemical determination of urinary metabolites of vitamin A is a potential index of vitamin A nutritional status.
Human Skeletal Muscle Phosphorylase Activities with Exercise and Training
Authors: Taylor A. W. , Booth M. A. , Rao S.
Published: April 2011

Fifteen healthy male subjects classified as sedentary (7) or active (8), exercised to exhaustion on a bicycle ergometer at a work load requiring 70% of their maximal aerobic capacity. Biopsy samples of the vastus lateral is muscle were taken at rest, at the time of fatigue, and after a 10 min recovery. Training increased [Formula: see text], [Formula: see text], work time to fatigue, skeletal muscle glycogen levels, and phosphorylase a activity (P < 0.01). An exhaustive submaximal exercise reduced the glycogen levels of the trained group to values similar to the fatigue levels of the nontrained subjects: the higher the initial glycogen levels, the longer the subjects were able to exercise before the onset of fatigue. Skeletal muscle phosphorylase a activities decreased with exercise to fatigue in all groups whereas phosphorylase b activities were maintained. Training had no effect on resting phosphorylase b activity.
Aortic Reactivity of Rats with Genetic and Experimental Renal Hypertension
Authors: Field F. P. , Janis R. A. , Triggle D. J.
Published: April 2011

The isometric tensions produced by low concentrations of norepinephrine (1 × 10−10 and 3 × 10−10M) or potassium (10 mM) were greater in aortic rings from mature rats with hypertension produced by bilateral renal encapsulation and from rats with genetic hypertension than from Car-worth normotensive Wistar rats. This hyper-reactivity was not associated with a hypersensitivity to low calcium concentrations in the presence of 80 mM KCl. Similarly the loss of maximum response to KCl with time in calcium-free solution was the same for aortic smooth muscle from normotensive and hypertensive rats. However, the rate of relaxation after 80 mM KCl was washed from the bath with normal Krebs solution was much faster for aortic smooth muscle from normotensive than from hypertensive animals. Spontaneous contractions were observed in aortic rings obtained from eight of 12 renal hypertensive rats but were not observed in rings from either spontaneously hypertensive or normotensive rats. An elevated thyroid activity was not associated with the increase in systolic blood pressure to 185 mm Hg in the renal encapsulated rats. The results suggest that the hypersensitivity to norepinephrine of the aortic smooth muscle is due to an altered cell membrane rather than a specific alteration of the adrenergic α-receptors.
Calcium Inward Currents in Insect Muscle Fibers
Authors: Washio H.
Published: April 2011

The membrane current in a locust muscle fiber was characterized by an early but slow inward current followed by a small late outward current in a solution containing Ca and tetraethylammonium (TEA). The maximum inward current decreased with decreasing Ca concentration, almost disappearing upon complete removal of Ca. The inward current has so far not been found in the standard saline. The results indicate that the inward currents are carried by Ca ions.
Vitamin A Status and Hepatic Drug Metabolism in the Rat
Authors: Becking G. C.
Published: April 2011

The effect of vitamin A status on hepatic drug metabolism was studied in rats. Animals were fed diets with and without vitamin A for 20 and 25 days. Weight gains of control and deficient animals were not significantly different, whereas liver vitamin A levels had decreased to less than 10% of control animals after 20 days and were essentially zero after eating the deficient diet for 25 days. Aniline metabolism in vitro and aminopyrine metabolism in vitro and in vivo were significantly lower in male weanling rats fed a vitamin A deficient diet for 20 days. No alteration in in vitro p-nitrobenzoic acid metabolism was noted after 25 days on the test. Vitamin A deficiency did not alter microsomal protein levels or cytochrome c reductase activity but deficient animals did have a lower microsomal cytochrome P-450 content. Hepatic enzyme activities and cytochrome P-450 levels were restored to values approaching those found in control animals by feeding vitamin A deficient rats the vitamin A containing diet for 21 days. Liver vitamin A levels were markedly increased after re-feeding studies but were still significantly lower than control animals.
Effect of Aminotriazole on Isopropanol- and Acetone-Induced Potentiation of CCl4 Hepatotoxicity
Authors: Traiger George J. , Plaa Gabriel L.
Published: April 2011

The effect of aminotriazole on (1) isopropanol- and acetone-induced potentiation of CCl4 hepatotoxicity, and (2) the in vivo metabolism of isopropanol and acetone was studied in rats. Aminotriazole plus isopropanol, 18 h prior to a challenging dose of CCl4, reduced the isopropanol-enhanced response of CCl4; serum glutamic–pyruvic transaminase (SGPT) activities were less than those found for isopropanol plus CCl4. Hepatic triglyceride content also reflected reduced hepatotoxicity. Aminotriazole pretreatment did not produce any change in the rate of isopropanol elimination nor was the rise and subsequent decline in the blood concentrations of the derived acetone altered. An 18 h pretreatment with acetone enhanced CCl4 hepatotoxicity. Aminotriazole, 15 min prior to acetone, diminished the enhanced response of CCl4 to acetone (reduced SGPT activities and hepatic triglyceride content). Aminotriazole had no effect on acetone elimination from the blood 1, 4, and 8 h after the oral administration of acetone. Aniline hydroxylase activity was increased 17 h after the administration of isopropanol. The data are consistent with the hypothesis that isopropanol augments CCl4 hepatotoxicity by affecting the microsomal drug-metabolizing enzyme system.
Magnesium: Electroencephalographic and Behavioral Effects in Cats
Authors: Heavner James E. , Jong Rudolph H. de
Published: April 2011

Magnesium sulfate was given intravenously to eight cats with recording electrodes permanently implanted in the brain. The MgSO4 caused marked behavioral changes; yet, brief amplitude depression aside, cortical and subcortical electrical activity remained unchanged. Small doses of MgSO4 (25 mg/kg) caused retching only; larger doses (50 and 75 mg/kg) produced muscle paralysis and respiratory depression. Even so, there were no electroencephalographic signs of sedation or narcosis. Any anesthetic or analgesic action of magnesium is overshadowed by its neuromuscular blocking effect.
Myocardium–Blood Gradients of Lactate and Pyruvate in the Dog
Authors: Chiong Miguel A.
Published: April 2011

Myocardium – coronary sinus blood gradients (M/CS) of lactate and pyruvate were determined in 24 open-chest dogs under conditions of normoxia, hyperoxia, and hypoxia, in the presence and absence of carbon dioxide. Four groups of experiments were carried out according to the gas mixture used during a control and an experimental period: group Co, 20% O2 in nitrogen; group H1, 20% O2 in nitrogen and 6% O2 in nitrogen; group H2, 20% O2 plus 5% CO2 and 6% O2 plus 5% CO2; and group H3, 95% O2 plus 5% CO2 and 6% O2 plus 5% CO2. Normal myocardial lactate extraction and high M/CS ratios for lactate were present during ventilation with 20% O2 (group Co and control period of group H1). When 5% CO2 was added to the inspired gas (control period of group H2), much higher M/CS ratios were observed due to elevation of myocardial concentrations of lactate although blood levels and myocardial extraction remained unchanged. Ventilation with 95% O2 plus 5% CO2 (control period of group H3) was associated only with decreased lactate blood levels, and consequently higher M/CS ratios than in group Co. Acute hypoxia (group H1) caused a marked increase in blood and myocardial lactate levels with a fall in extraction and M/CS ratios (group H1). In the presence of 5% CO2 (group H2), hypoxia was associated with a smaller rise in blood lactate levels than that seen in group H1, myocardial lactate concentration failed to rise above the high prehypoxic control levels, and the M/CS ratio fell although a significant gradient persisted during hypoxia. Group H3, ventilated with 95% O2 plus 5% CO2 during the control period and exposed to 5% CO2 during hypoxia, showed moderate increase in blood and myocardial lactate levels and abolition of the M/CS gradient during O2 lack. The changes in blood and myocardial pyruvate observed in this study were similar to the described changes for lactate. These results show (1) that myocardium – coronary sinus blood gradients of lactate and pyruvate are present in the dog heart under these experimental conditions; (2) that these gradients may be influenced by ventilation with gas mixtures containing 5% CO2, by hyperoxia and hypoxia; and (3) that an active transport mechanism in the myocardium may be responsible for the uptake of these compounds against a concentration gradient.
The Accumulation of Hemicholinium by Tissues that Transport Choline
Authors: Collier B.
Published: April 2011

Cat superior cervical ganglia accumulated 14C-hemicholinium (HC-3), but the amount of drug taken up was not changed by nerve stimulation; accumulated HC-3 was not released by subsequent nerve stimulation. Choline and HC-3 were accumulated by a crude preparation of synaptosomes; the uptake of choline was blocked by HC-3, but the uptake of HC-3 was not blocked by choline. Choline, but not HC-3, was transported by red blood cells. It is concluded that HC-3 is not transported by the choline transport mechanism, and that in concentrations that are usually used in pharmacological experiments, HC-3 appears not to act as, or to form, a false cholinergic transmitter.
Some Effects of Caffeine and Quinidine on Sarcoplasmic Reticulum of Skeletal and Cardiac Muscle
Authors: Thorpe William R.
Published: April 2011

Sarcoplasmic reticulum (SR) was prepared from the gastrocnemius muscle and the heart of freshly killed rabbits. It was found that the skeletal SR actively bound significantly more calcium than did the cardiac SR under the same experimental conditions. The effect of caffeine and quinidine on the release of calcium actively bound by both cardiac and skeletal SR was studied. Quinidine (10−3 M) released 4.1% of the calcium bound by skeletal SR and 27.7% of that bound by cardiac SR. Similarly, caffeine (20 mM) released 10.5% and 34.3% of the calcium bound by skeletal and cardiac SR, respectively. It is suggested that both caffeine and quinidine could produce contracture of skeletal muscle by acting on the SR and that caffeine could stimulate myocardial contractility through its action on the cardiac SR. However, it is unlikely that quinidine exerts its negative inotropic effect on the heart through its calcium releasing action on the cardiac SR.
Effect of Diazoxide on Aortic Reactivity to Calcium in Spontaneously Hypertensive Rats
Authors: Janis R. A. , Triggle D. J.
Published: April 2011

Diazoxide (10−4M) reduced the maximum response to noradrenaline of aortic strips from normotensive and spontaneously hypertensive rats (S.H.R.). The extent of this inhibition was the same for aortae from both types of rat and was greater than the depression of maximum response to KCl. The percent reduction of maximum response to noradrenaline after exposure of aortae to calcium-free solution for various times was the same for tissues from normotensive and hypertensive rats. When calcium was added to calcium-free solution containing either noradrenaline or KCl, a greater inhibition of contraction of aortae from S.H.R. than from normotensive rats was produced by diazoxide. Under the special conditions of the latter experiments, these results are consistent with the hypothesis that vascular smooth muscle of normotensive and S.H.R. differ in their reaction with diazoxide, and that this agent could exert its antihypertensive effect at a site that is not specifically related to adrenergic α-receptors.
The Relationship of Membrane ATPase Activity to Ouabain-Insensitive Sodium Transport in Human Red Cells
Authors: Smith E. K. M. , Welt L. G.
Published: April 2011

A component of active sodium efflux has been described by Hoffman and Kregenow (1966, Ann. N.Y. Acad. Sci. 137, 566–567) which is not inhibited by ouabain but is inhibited by ethacrynic acid. This has been called "Pump II" and these authors have produced evidence suggesting that the process does not require adenosine triphosphate (ATP) for its energy supply. Studies of membrane adenosine triphosphatase (ATPase) from human erythrocytes have therefore been carried out to determine if any component of this enzyme behaved in a qualitatively similar way to that of "Pump II." Our results have shown that ethacrynic acid behaved like a nonspecific sulfhydryl-reacting substance with no discrete inhibitory properties. Two analogues of ethacrynic acid, which did not have any sulfhydryl-reacting properties, could also inhibit "Pump II" but did not inhibit membrane ATPase.It is concluded that there is no direct qualitative correlation between "Pump II" and membrane ATPase in the human red cell. This supports the view that "Pump II" functions independently of the activity of membrane ATPase. Whether "Pump II" is an active transport system or part of a cation exchange diffusion mechanism, it is unlikely that ATP or membrane ATPase are concerned in its function.
Chronic Propranolol Treatment in Young Spontaneously Hypertensive and Normotensive Rats
Authors: Vávra I. , Tom H. , Greselin E.
Published: April 2011

Oral treatment with propranolol, 1 or 5 mg/kg per day, was started in young spontaneously hypertensive rats (S.H.R.) 1 week after weaning and continued for 12 weeks. The same doses were administered to age-matched normotensive rats. Propranolol was admixed to a standard laboratory diet in concentrations calculated on the basis of average food consumption. Blood pressure was measured by an indirect method.As compared to control S.H.R., a significantly lower blood pressure was recorded in S.H.R. treated with propranolol, 1 mg/kg, at week 10 and 12 of the treatment and in those treated with 5 mg/kg at weeks 6–12. The heart rate was not consistently affected.The blood pressure of control and treated normotensive rats did not differ significantly with the exception of an elevated blood pressure in both dosage groups at the first reading.The growth of rats was not impaired by propranolol and no morphological organ changes related to the treatment could be detected at the end of the experiment.
Effect of Different Anions on 22Na Permeability of Liposomes
Authors: Singer M. A.
Published: April 2011

The 22Na efflux from phosphatidylcholine liposomes was measured in the presence of different anions. Only salicylate significantly increases sodium permeability. Although this anion adsorbs onto the liposomal surface creating a negative zeta potential, evidence is presented that this is not the sole mechanism underlying the enhanced cation permeability. It is proposed that salicylate also alters the dipole potential at the membrane–solution interface.
Inhibition of Cortical Neurones by Imidazole and Some Derivatives
Authors: Godfraind J. M. , Krnjević K. , Maretić H. , Pumain R.
Published: April 2011

Systematic tests of imidazole and 15 derivatives, applied by microiontophoresis in anesthetized cats, showed a high inhibitory potency of imidazole-4-acetic and imidazole-4-propionic acids and also of their amyl and propyl esters; but imidazole 4-carboxylic and 1-methylimidazole-4-acetic acids were largely inactive. This order of potency is very different from the relative potencies of imidazole derivatives in facilitating cyclic nucleotide phosphodiesterase activity. It is therefore unlikely that their inhibitory action is simply related to changes in cellular levels of cyclic AMP. The characteristics of this action, including lack of antagonism by bicuculline, are consistent with the possibility that it is mediated by γ-aminobutyric acid receptors.
Drug-Induced Porphyrin Biosynthesis—VIII. Investigation of the Importance of an Allyl Group for Activity in Substituted Acetamides
Authors: Marks G. S. , Krupa V. , Roomi M. W.
Published: April 2011

Allylisopropylacetamide (AIA) was found to be considerably more potent than propylisopropylacetamide (PIA) in inducing hepatic δ-aminolevulinic acid (ALA) synthetase activity and hepatic porphyrin accumulation in the 17-day-old chick embryo, chickens, and mice of the CBA/J strain. AIA and PIA were shown to be approximately equipotent in inducing ALA synthetase activity and porphyrin accumulation in chick embryo liver cell culture. It is likely that the unusual responsiveness of chick embryo liver cell culture to PIA is not due to species or developmental differences but to the large amount of PIA available to the cultured liver cells.
Fever in Newborn Lambs
Authors: Pittman Q. J. , Cooper K. E. , Veale W. L. , Petten G. R. Van
Published: April 2011

An initial injection of intravenous bacterial pyrogen in newborn lambs failed to produce fever, but did cause the typical fall in the number of circulating blood leucocytes. A second challenge of bacterial pyrogen in 60-h-old lambs caused fever. Other lambs also 60 h old, not previously injected with pyrogen, did not respond to a similar challenge. Thus, sensitization to bacterial pyrogen is necessary for development of fever in response to injection of bacterial pyrogen.
Exocytosis (Secretory Granule Extrusion) Induced by Injection of Calcium into Mast Cells
Authors: Kanno T. , Cochrane D. E. , Douglas W. W.
Published: April 2011

Injection of Ca (but not Mg or K) through micropipettes placed within rat peritoneal mast cells elicited extrusion of secretory granules. The result is considered direct support for the view that a rise in the intracellular concentration of Ca ions suffices to induce exocytosis and accounts for the general requirement for Ca in stimulus–secretion coupling.
Tongue Activity During Respiration, Jaw Opening, and Swallowing in Cat
Authors: Lowe Alan A. , Sessle Barry J.
Published: April 2011

Some of the factors involved in the control of tongue position have been investigated. The electromyographic activity reported here provides evidence that genioglossus, the protrusive muscle of the tongue, is under the control of physiological processes associated with respiration, jaw movements, and swallowing. Additional studies are in progress to define further the neutral mechanisms underlying these effects.