bluuebunny/crossref_metadata_2025 huggingface dataset:
Hepatic Capacitance Vessel Responses to Bilateral Carotid Occlusion in Anesthetized Cats
Authors: Lautt W. W. , Greenway C. V.
Published: April 2011

Hepatic volume was recorded by a plethysmographic technique in cats anesthetized with pentobarbital; the hepatic artery and portal vein remained intact. The mean change in hepatic blood volume during bilateral carotid occlusion was less than 2% and there was no significant difference between responses in innervated and denervated livers. These results, together with other reports in the literature, support the conclusion that capacitance vessel responses, a redistribution of blood volume, a change in cardiac output, and release of catecholamines from the adrenal medullae do not occur in arterial baroreceptor reflex responses.
Plasma Volume and Total Erythrocyte Volume in the Molybdenotic Rabbit
Authors: Robinson G. A. , Warren D. V.
Published: April 2011

Total erythrocyte volumes (51Cr label) of rabbits fed toxic quantities of sodium molybdate decreased relative to control values but plasma volumes (125I-albumin label) increased such that the blood volumes of molybdenotic rabbits were restored to levels which may have been expected had these rabbits grown normally. With severe losses in body weight in molybdenotic rabbits, the use of packed cell volumes and body weight values together as a substitute for total erythrocyte volumes led to errors reaching a 25% overestimate for control and a 20% underestimate for test groups in repeat studies. The F cells ratio was unchanged in chronic molybdate poisoning indicating that no redistribution of erythrocytes and plasma had occurred in the vascular system. Mean F cells ratio for 51 test and control rabbits was 0.746 ± 0.009 (S.E.M.).
Correlation Between Changes in the Endogenous Energy Stores and Myocardial Function due to Hypoxia in the Isolated Perfused Rat Heart
Authors: Dhalla N. S. , Yates J. C. , Walz D. A. , McDonald V. A. , Olson R. E.
Published: April 2011

On perfusing the isolated rat heart for 7 min with substrate-free hypoxic medium, the contractile force, rate of change of contractile force, time to peak tension, and heart rate declined whereas resting tension increased. The coronary flow and the pH of the perfusate reached maximum and minimum values, respectively, within 2 min of hypoxia whereas the optical density of the perfusate at 260 mμ increased progressively over the 7 min of perfusion with hypoxic medium. The levels of glycogen, creatine phosphate, and ATP declined whereas the concentrations of lactate, ADP, AMP, creatine, and Pi increased during the 1st min of hypoxia at which time the contractile force and heart rate decreased by about 20% of the control values. During the 1st min of hypoxia the diminution in phosphate potential and creatine phosphate/Pi ratio was found to be of greater magnitude than that in the contractile force. Between 2 and 7 min of perfusion with hypoxic medium a marked reduction in contractile force occurred without appreciable changes in the coronary flow, the phosphate potential, the levels of ADP and AMP, and creatine phosphate/Pi ratio. No change in myocardial lipids occurred under the present experimental conditions whereas changes in the electrical activity, time for half relaxation, norepinephrine stores, and mitochondrial structure lagged behind the changes in the high energy phosphate stores due to hypoxia. Although a clear relation between changes in the cardiac function and any one biochemical parameter throughout the period of hypoxia is not apparent from this study, the onset of failure of the hypoxic heart to generate contractility may be considered due to an insufficiency in the process of energy generation. The complete inability of the hypoxic heart to develop contractile force may be due to abnormalities in the processes of energy utilization subserving the mechanisms for the maintenance of ionic gradient and excitation–contraction coupling.
Decreased Airway Conductance with Nebulization of Water: Its Response to Epinephrine, Atropine, and N-Acetylcysteine
Authors: Melville G. Norris , Ward E. E. , Morris D.
Published: April 2011

The effect of administering a mucolytic (N-acetylcysteine) and a sympathomimetic (epinephrine) drug by inhalation, and a parasympatholytic (atropine) drug by intraperitoneal injection on the prevention or reversal of the decrease in specific airway conductance (S.G.aw), which is induced in rats by nebulization of distilled water or tap water, was assessed. N-Acetylcysteine or epinephrine administered to the breathing medium of nebulized distilled or tap water for the duration of the experiment did not prevent any decrease in S.G.aw. Administration of N-acetylcysteine in aerosol, after the animals had already been exposed for 12 min to either of the nebulized media, did not reverse decreases in S.G.aw. Epinephrine administered in aerosol after exposure to nebulized distilled or tap water for 12 min caused an insignificant increase in S.G.aw. Atropine administered either throughout the experiment or after 12 min exposure to either of the breathing media prevented or reversed decreases in S.G.aw, respectively. It is suggested that the decreased S.G.aw in rats caused by nebulization of distilled or tap water could be prevented and reversed by parasympatholytic therapy.
Some Effects of Blood Sera on the Glycogenic Effects of Insulin on Muscle
Authors: Merrilees Margaret A. , Coddling Judith A. , Davidson J. K. , Haist R. E.
Published: April 2011

Fresh rabbit serum inhibited basal glycogen deposition in mouse hemidiaphragms and reduced the glycogenic effect of 0.3 mU/ml insulin. This inhibitory effect was abolished by adrenalectomy. Dialysis of serum from fasting rabbit, dog, or man increased glycogen deposition in mouse hemidiaphragms in the presence or absence of insulin. This enhancing effect was due largely to enhancement of insulin action since most of it could be removed by addition of insulin antiserum. Insulin was added to fresh rabbit serum, dialyzed rabbit serum, and basal salts – gelatin solution and the immunoreactive insulin levels of the sera were measured before and after hemidiaphragms were incubated in them. Similar results were obtained for fresh and dialyzed sera, yet glycogen deposition was greater in hemidiaphragms incubated in dialyzed sera than in fresh sera or basal salts – gelatin solution. The enhanced effect was not due to differences in insulin removal. This was demonstrated also for dialyzed serum from depancreatized dogs. The presence in sera of factors affecting insulin action may introduce errors in biological assays. Standards must be made up in solutions resembling as closely as possible the unknown solution but lacking the substance under test.
Factors Involved in the Loss of Spontaneous Contractile and Electrical Activity in Clusters of Cultured Cardiac Cells
Authors: Schanne O. F.
Published: April 2011

Beating cell clusters were obtained by trypsinization from hearts of newborn rats. Spontaneous activity ceased after several weeks while the cultures were still proliferating. Experiments were performed to identify the physiological determinant causing cessation of spontaneous activity. (a) Cell clusters having lost their spontaneous activity responded to extracellular stimulation. (b) Reduction of [K]o by 50% increased the number of beating cell clusters by 40%; doubling [K]o reduced the number of beating cell clusters by 49%. (c) Cell clusters which were in the process of losing their ability to contract spontaneously needed a progressively increasing temperature to induce spontaneous activity. These results suggest (1) that the pacemaker mechanism fails first when a cell cluster loses its spontaneous activity and (2) that shortly before the cluster fails to contract spontaneously, it requires more energy to maintain pacemaker activity because of possible structural membrane changes or changes in the enzyme pattern of the cells.
Some Cardiorespiratory Effects of Histamine, 5-Hydroxytryptamine, and Compound 48/80 in the Calf
Authors: Lewis A. J. , Eyre P.
Published: April 2011

The cardiorespiratory responses to histamine, 5-hydroxytryptamine, and compound 48/80 have been examined in the calf. The simultaneous measurement of whole blood histamine and plasma 5-hydroxytryptamine during compound 48/80 infusion showed significantly elevated levels that followed a biphasic pattern. However, mast cell changes in the sites examined were minimal and there was no significant difference in histamine concentrations in tissues examined. Marked systemic effects were observed and included an initial rise in femoral arterial blood pressure which was later followed by a terminal hypotension and death. Pulmonary arterial blood pressure and venous pressure were both elevated and dyspnoeic respiration was also evident. A combination of mepyramine and methysergide inhibited the toxicity of compound 48/80 which suggested that histamine and 5-hydroxytryptamine played a major role in the toxic response to this substance in the calf.
Natriuresis after Preoptic Lesions in Rats
Authors: Keeler R.
Published: April 2011

Bilateral lesions in the preoptic area of the rat hypothalamus were followed by an increased renal excretion of sodium. This natriuretic response usually lasted several hours and in some animals the peak rate of excretion was as much as 100 times the control rate.The response was not prevented by large doses of desoxycorticosterone acetate, removal of the thyroid and thyroid 'C' cells, or administration of the autonomic blocking agents phenoxybenzamine, α-methyltyrosine, reserpine, or atropine.In animals in which clearance measurements were made, the lesions did not have a statistically significant effect on filtration rate, renal plasma flow, filtration fraction, mean systemic arterial pressure, or the excretion of potassium.
Effects of Ions, Ouabain, Epinephrine, and Tetrodotoxin on Glucose Metabolism and on Contractility in the Perfused Guinea Pig Heart
Authors: Benmouyal E.
Published: April 2011

In the perfused guinea pig heart, the rate of glucose-U-14C oxidation to 14CO2 was directly related to the external ratio [Ca2+]/[Na+]2. The metabolic stimulatory effects of ouabain were concentration-dependent, and those brought about by epinephrine were not prevented by the presence of ouabain or added Ca2+. The increased glucose utilization produced by ouabain or Ca2+ was reduced by tetrodotoxin (TTX), whereas that produced by epinephrine or reduced extracellular Na+ (100 mM) was not. It was also found that TTX inhibited the positive inotropic effects of Ca2+ and ouabain, but did not reduce the contractile force during perfusion in presence of epinephrine or at 100 mM Na+. It is concluded that (a) ouabain (or Ca2+) and epinephrine, producing additive effects, have different modes of action; (b) TTX and ouabain (or Ca2+) have antagonistic effects, probably resulting from their opposite action on calcium movements.
Effects of Rare Earths and Yttrium on Striated Muscle and the Neuromuscular Junction
Authors: Bowen John M.
Published: April 2011

Effects of several rare earths and yttrium on isolated frog sartorius muscles were investigated. Lanthanum (La), praseodymium, neodymium (Nd), samarium, gadolinium, dysprosium, erbium, thulium, ytterbium, and yttrium (Y) inhibited twitch tension of indirectly stimulated preparations. Concentrations required to reduce twitch tension to 50% of control tension in 15 min ranged between 0.52 mM and 1.10 mM (Ringer solution; pH 6.0). Similar concentrations (La, Nd, and Y) also inhibited twitch tension of directly stimulated, curarized preparations. A relationship between effect on twitch tension and atomic number was not found. La (0.3 mM) and Y (0.3 mM) reduced the amplitude, but did not appear to alter the time course, of extracellularly recorded end-plate potentials (E.P.P.'s). Amplitudes of intracellularly recorded E.P.P.'s were reduced by La (0.0125–0.05 mM) and Y (0.0125 and 0.025 mM). Effect on quantal contents of E.P.P.'s indicated that the principal action of both agents was an inhibition of transmitter release. La (0.025 and 0.05 mM) and Y (0.05 mM) significantly increased the frequency of miniature end-plate potentials. It is concluded that the prejunctional membrane does not differentiate significantly between the action of the trivalent rare earth ion lanthanum and the action of the trivalent rare-earth-like ion yttrium.
Analysis of Cannabis Smoke Obtained under Different Combustion Conditions
Authors: Fehr K. O'Brien , Kalant H.
Published: April 2011

The recovery of cannabinoids was investigated by combustion of marihuana cigarettes in a specially constructed smoking machine, with air flow parameters varying within potential human physiological limits. Combustion temperature was found to be about 600°. Percentage recovery of tetrahydrocannabinol in the smoke increased slightly but significantly with increasing air flow rate, but was unaffected by continuous versus intermittent flow. Maximum recovery after complete combustion was about 60%, with negligible change in cannabinoid ratios. Synthetic tetrahydrocannabinol applied to tobacco or alfalfa cigarettes was less completely recovered. Total dry residue (tar content) of the cannabis smoke was somewhat greater than that of tobacco smoke.
The Effect of Furosemide on the Intrarenal Blood Flow Distribution in the Dog
Authors: Carrière Serge , Desrosiers Michel , Friborg Jacques , Brunette Michèle Gagnan
Published: April 2011

Furosemide (40 μg/min) was perfused directly into the renal artery of dogs in whom the femoral blood pressure was reduced (80 mm Hg) by aortic clamping above the renal arteries. This maneuver, which does not influence the intrarenal blood flow distribution, produced significant decreases of the urine volume, natriuresis, Ccreat, and CPAH, and prevented the marked diuresis normally produced by furosemide. Therefore the chances that systemic physiological changes occurred, secondary to large fluid movements, were minimized. In those conditions, however, furosemide produced a significant increase of the urine output and sodium excretion in the experimental kidney whereas Ccreat and CPAH were not affected. The outer cortical blood flow rate (ml/100 g-min) was modified neither by aortic constriction (562 ± 68 versus 569 ± 83) nor by the subsequent administration of furosemide (424 ± 70). The blood flow rate of the outer medulla in these three conditions remained unchanged (147 ± 52 versus 171 ± 44 versus 159 ± 54). The initial distribution of the radioactivity in each compartment remained comparable in the three conditions. In parallel with the results from the krypton-85 disappearance curves, the autoradiograms, silicone rubber casts, and EPAH did not suggest any change in the renal blood flow distribution secondary to furosemide administration.
Effects of Perfusate on Cation Transport by Slices from the Isolated Perfused Rat Liver
Authors: Nestruck A. C. , Furneaux R. W.
Published: April 2011

Isolated livers from fed rats were perfused for 1 h with a basic Krebs–Ringer bicarbonate buffer solution containing albumin and glucose and added (1) α-ketoglutarate, (2) pyruvate, fumarate, and glutamate, or (3) washed red blood cells. Perfusate flow rate, [Formula: see text], [Formula: see text], and pH changes across the liver, and glucose efflux in the perfusate, were measured during perfusion. Rewarmed slices of liver taken at the beginning of perfusion were found to be able to reverse a cation shift imposed by cold incubation. Slices of liver taken after 1 h of perfusion were not able to effect this cation shift unless red blood cells were included in the perfusate. It is proposed that noncellular perfusates containing metabolic substrates are not ideal for isolated rat liver perfusion studies as evidenced in the altered membrane transport capacity of slices after perfusion.
Action of Some Centrally Active Drugs and Heavy Metals on In Vitro Oxidation of Dopamine by Rat Brain Tissue
Authors: Bhatnagar S. P.
Published: April 2011

The effect of chlorpromazine, amitryptyline, amphetamine, diphenhydramine, and iproniazid on the in vitro oxidation of dopamine to melanin by rat brain mitochondrial preparation was investigated. Chlorpromazine and amitryptyline very markedly inhibited the oxidation (ED50 60 and 180 μM, respectively) while iproniazid was ineffective. Other drugs were moderately active. The reaction was enzyme catalyzed and could not be ascribed to the anionic component. Chronic administration of chlorpromazine and amitryptyline (19 and 9.5 mg/kg, i.p.) produced a biphasic response characterized by stimulation of melanogenesis during the first 2–3 weeks followed by inhibition. On the other hand, physostigmine and choline markedly stimulated the oxidation process. The chronic ingestion of heavy metals; mercury, lead, and cadmium, up to toxic levels had no effect on the in vitro oxidation of dopamine.
Failure of Acetylcholine to Stimulate Pancreatic Acinar Secretion In Vitro
Authors: Haig T. H. Brian , Lamb Jonathan D.
Published: April 2011

The acinar secretory response of dog, rat, and pigeon pancreas to acetylcholine, methacholine, and pancreozymin has been measured in vitro. Dose–response curves fail to show evidence of cholinergic mediated secretion in tissue preparations that respond vigorously to pancreozymin. Prolonged incubation with acetylcholine leads to an augmented accumulation of enzyme in the medium, that may be better explained by altered cell membrane permeability than on the basis of active secretion. These results suggest that acetylcholine may not be a chemical mediator of pancreatic acinar secretion which would favor the concept that parasympathetic stimulation of acinar secretion is indirect.
The Effect of Sodium and Potassium on Calcium Uptake by Frog Skeletal Muscle Mitochondria and Vesicles
Authors: Batra Satish
Published: April 2011

Calcium uptake by mitochondria of frog skeletal muscle increased when K replaced Na or sucrose in the medium. There was no difference in passive binding of Ca and the amount of ATP split when K replaced Na. Ca uptake was increased by substituting K for Na in the medium and was maximal in a medium containing 100 mM K and no Na. Azide and dinitrophenol (DNP) inhibited K-stimulated Ca uptake completely. Inhibition by these agents in Na medium was relatively small. Ca uptake by vesicles was little affected by changing from Na to K medium, by azide, or by DNP. Ageing reduced Ca uptake in both fractions and stimulation by K of mitochondrial Ca uptake nearly disappeared after 4 h of storage (at 4 °C). Since Ca was taken up to the same extent in Na or sucrose medium, it is concluded that Ca uptake by mitochondria is stimulated by K rather than inhibited by Na.
Build-Up of Calcium Content and Contractile Force in the Rabbit Heart
Authors: Saari Jack T. , Johnson John A.
Published: April 2011

Build-up of whole heart calcium content and contractile force was studied in the isolated, perfused rabbit heart during uptake of calcium ion. Calcium content increased in one exponential phase (rate constant 0.119 s−1) from a constant unexchangeable pre-build-up value. Contractile force increased in one exponential phase (rate constant 0.084 s−1) from its resting value. The rate constants for calcium content and contractile force build-up did not differ significantly. A difference in the above build-up rate constants from those of calcium and force decay observed in prior work in the same preparation was presumed due to dependence of capillary permeability on calcium concentration.
The Function of the Basal Filaments in the Parietal Layer of Bowman's Capsule
Authors: Webber W. A. , Wong W. T.
Published: April 2011

A number of cell types in the nephron have been known for some time to contain basally located filaments demonstrable by a variety of both light and electron microscopic techniques.]t has been proposed that these filaments may provide a contractile mechanism which would have implications for the control of renal function. One site in which these filaments have been observed is in the parietal layer of Bowman's capsule. The present study was designed to see if contraction of this layer of cells could be demonstrated and if so whether the basal filaments appeared to play a role in the process. Renal cortical tissue was fixed both in vivo and in vitro in the presence and absence of histamine, adrenaline, and acetylcholine and examined by conventional electron microscopic techniques. Basal folding of the cell membrane was observed particularly in the adrenaline-treated tissue and was interpreted as reflecting a conformational change in the cell such as might be expected with contraction. The relationship of this folding, however, to the arrangement of the basal filaments was such as to suggest that contraction of the filaments was not responsible for the folding observed. Alternative roles for the fibrils either as a structural framework or as a component in an attachment mechanism of the cells to the underlying basement membrane were therefore proposed.
Vitamin A Content of Livers and Kidneys from Dogs Fed DDT
Authors: Ottoboni Alice , Bissell Glenn D. , Loon Albert J. Van
Published: April 2011

The livers and kidneys from adult beagle dogs chronically exposed to 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and from their F1 weanling progeny were analyzed for vitamin A content. The dogs, subjects of a multigeneration study of the effects of DDT on canine reproduction, were fed diets which were optimum for growth and reproduction. The DDT feeding levels were 0, 1, 5, and 10 mg technical DDT/kg body weight per day. The effect of DDT in reducing vitamin A levels in liver and kidney that has been demonstrated in other species was not manifest in adult or weanling dogs in this study.Interference by p,p′-DDT, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (p,p′-DDD), 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p′-DDE), and 1-chloro-2,2-bis(p-chlorophenyl-ethylene (p,p′-DDMU) in the analysis for vitamin A in liver and kidney tissue was investigated and found to be of no practical importance in the present study.
The Effect of Loading with Hypertonic Saline on Dogs Deprived of Carotid Sinuses
Authors: Passmore John C. , Ederstrom H. E.
Published: April 2011

The effects of chronic carotid sinus extirpation on water and electrolyte regulation were studied following rapid loading with hypertonic sodium chloride to give 22.4 mequiv/kg. Under sodium pentobarbital the following parameters were measured at intervals for 5 h: blood pressure; hematocrit; urine Na, K, and urine volume. Hypertonic infusions in control dogs resulted in prolonged diuresis and natriuresis. In dogs without carotid sinuses, diuresis and natriuresis were larger than in controls initially, but declined in 20–40 min. Kaliuresis was slight in all groups. Results indicated that the carotid sinus or associated structures may be involved in the overall regulation of water and electrolyte balance.
On the Mechanism of Adenyl Cyclase Inhibition by Adenosine
Authors: McKenzie S. G. , Bär H. P.
Published: April 2011

Adenosine inhibited basal and fluoride- or hormone-stimulated adenyl cyclase activities from various sources. Inhibition was usually noted at 0.01 mM adenosine and was 40–75% at 1 mM. The effect appeared to be rapid and reversible, but it was not competitive with respect to ATP, as determined with enzyme from rat brain. Stimulated adenyl cyclase activities from rat fat cells and Ehrlich ascites cells were proportionately more inhibited than basal activity indicating the possibility of multiple sites for inhibitory action by adenosine. The effect of adenosine on adenyl cyclase and other enzymes of the cyclic AMP pathway may be of pharmacological or physiological significance in certain tissues.
Macromolecules May Inhibit Diffusion of Hemoglobin from Lysing Erythrocytes by Exclusion of Solvent
Authors: Seeman P.
Published: April 2011

An interpretation is provided for the phenomenon of macromolecule inhibition of hemoglobin release from hemolyzing erythrocytes. High concentrations of macromolecules, which are extensively hydrated, remove solvent volume accessible to the diffusing hemoglobin, thus retarding the diffusion. This explanation considerably alters previous interpretations of the mechanism of immune lysis of cells.
Oscillations of Intramuscular pH in Perfused Rat Heart
Authors: Dhalla Naranjan S. , Yates John C. , Kleinberg Israel
Published: April 2011

The intramuscular pH of the isolated perfused rat heart fluctuated between 7.11 and 7.14 during each contraction–relaxation cycle; the pH began to decline prior to the onset of cardiac contraction. The observed pH oscillations are independent of the mechanical activity and seem to reflect cyclic fluctuations in heart metabolism during the process of "excitation – metabolic stimulation" in the cardiac muscle.
Serum Enzyme Changes in Untrained Subjects Following a Prolonged March
Authors: Shapiro Y. , Magazanik A. , Sohar E. , Reich C. B.
Published: April 2011

The relationship between maximal aerobic capacity [Formula: see text] and blood enzyme level changes during long marching was studied in two groups of healthy untrained volunteers aged 18–19, who covered 110 km in 2 days. Group A (nine subjects) walked at a uniform rate of 6 km/h, while group B (17 subjects) walked at either 4, 5, or 6 km/h, according to whether their [Formula: see text] was, respectively, low, moderate, or high. In group A there were striking elevations in the activities of muscle enzymes, e.g. creatine phosphokinase, glutamic–oxaloacetic transaminase, and aldolase, at the end of the march, while the elevations in group B were moderate at most. A classification of the subjects in group A according to their maximal oxygen consumption showed that the highest enzyme elevation appeared in the subjects with the lowest [Formula: see text] and moderate elevation in those with high [Formula: see text]. In group B, whose subjects were prefitted to exercise intensity according to each subject's [Formula: see text], no enzymatic differences between the subgroups appeared. These findings suggest that enzyme elevations are primarily related to the intensity of the effort with respect to the [Formula: see text] of the individual and not to its duration. Adjusting work intensity to the level of [Formula: see text] should minimize muscle enzyme leakage and muscular changes.
Restoration of the Ability of Frog Skeletal Muscle to Develop Potassium Contractures in Calcium-Deficient Media
Authors: Foulks J. G. , Miller J. A. D. , Perry Florence A.
Published: April 2011

A number of agents were tested for their ability to restore potassium (K) contractures in calcium-free media. Effective agents included caffeine, chloroform, more polar permeant anions (e.g. nitrate and perchlorate) in place of external chloride, as well as divalent cations, e.g. Mg2+. The presence of sufficient EGTA to preclude significant increases in [Ca]0 did not affect the extent of K contracture restoration produced by these agents. The loss of K contracture capacity in calcium-free media, and its restoration by effective agents, appear to be related to the disproportionate effect of these procedures on the relation between log [K]0 and the potential-dependent processes which regulate contractile function.
The Effects of Anorexic Doses of dextro-Amphetamine on the Ventromedial-Hypothalamic Hyperphagic Rat
Authors: Wishart Thomas B. , Walls Elwood K.
Published: April 2011

Rats were made hyperphagic by the production of electrolytic lesions in the ventromedial hypothalamus. Following a recovery period during which a rapid weight gain was observed, d-amphetamine was administered intraperitoneally in various dosages, and food intakes, water intakes, and body weight changes were measured after a 3 h feeding period. A dosage of 0.2 mg/kg d-amphetamine had no observable effect. Increasing the dosage to 0.5 or 1.0 mg/kg, however, significantly depressed food and water intakes, and resulted in reduced weight gains in control and experimental animals. Furthermore, the dose–response curves for both experimental and control groups were similar, indicating that d-amphetamine has the same effect in the hyperphagic rat as in the control. It is concluded that amphetamine anorexia is not mediated by the ventromedial hypothalamus.
Renin Activity in Canine Acute Hepatic Necrosis and Chronic Toxic Hepatitis
Authors: Tapia Hugo R. , Kuster Gustavo G. R. , Woods John E. , Strong Cameron G.
Published: April 2011

Hepatic metabolism of renin activity in dogs was investigated in seven normal animals, twelve with acute hepatic allograft rejection, and five with chronic toxic hepatitis. Renin activity (P.R.A.) was measured by radioimmunoassay in hepatic arterial, portal venous, and hepatic venous plasma. In normal dogs the P.R.A. gradient through the hepatic circulation was significant (P < 0.03). Such a gradient was not observed in decompensated acute allograft rejection, and there was also a significant increase of P.R.A. in the inflow and outflow tracts. Fractional hepatic renin extraction (normal, 36.7%) decreased significantly (P < 0.04) to −2.9%. The data in dogs with compensated chronic toxic hepatitis did not differ from normal. A significant difference between portal venous P.R.A. (8.69 ± 1.51 ng/ml/h) and hepatic artery P.R.A. (5.67 ± 1.91) was found. This difference suggests a splanchnic source of renin, confirming previous reports from this and other laboratories.
Sodium and Water Transport Across the Jejunum of Fasted Rats
Authors: Beck Ivan T. , Dinda P. K.
Published: April 2011

The effect of 72 h fasting on the transmural electrical potential difference (P.D.), the unidirectional fluxes, and the net flux of sodium and the net transport of fluid across the jejunum of rats was investigated. Everted jejunal segments were incubated in 12 ml of Krebs–Ringer bicarbonate solution containing 5.55 mM glucose on either side for 1 h at 37 °C. Seventy-two hours fasting caused a 63% increase in the transmural P.D., a 60% increase in the flux of Na from the mucosal to the serosal side, and a 48% increase in the flux of Na from the serosal to the mucosal side. The net mucosal to serosal Na flux increased by 97%. There was also a 41% increase in fluid transport across the intestine of fasted rats. The concomitant increase in sodium and fluid transport and in transmural P.D. is consistent with the current hypotheses of fluid and sodium transport.
Vascular Resistance and Na+–K+ Gradients in the Perfused Rat-Tail Artery
Authors: Friedman S. M. , Nakashima M. , Palatý V. , Walters B. K.
Published: April 2011

The changes in the resistance of the perfused ventral rat-tail artery resulting from exposure of the tissue to ouabain-containing and/or K+-free physiological salt solution were studied. In each case, there was an increase in the vascular resistance which was not sustained. The response of the arterial wall to the above stimuli was abolished in the absence of external Ca2+. In contrast to the delayed response of the wall to either ouabain-containing or K+-free solution, an almost instantaneous rise in the resistance was observed if the two stimuli were combined, though the rate of loss of the tissue K+ was not accelerated significantly under these experimental conditions. The tension developed in K+-free solution was relieved almost instantaneously upon readmittance of external potassium.
Bile Acid Metabolism in Mammals. V. Studies on the Sex Difference in the Response of the Isolated Perfused Rat Liver to Chenodeoxycholic Acid
Authors: Yousef I. M. , Magnusson R. , Price V. M. , Fisher M. M.
Published: April 2011

The hepatic metabolism of chenodeoxycholic acid (CDCA) was studied using the isolated perfused rat liver technique. In 12 perfusions, six male and six female, 30 μmol of CDCA were added to the perfusion medium, and in 12 other perfusions, also six of each sex, 1 μmol of CDCA was added to the perfusion medium. The CDCA was added after 2 h of base-line perfusion and the bile acids of liver, plasma, and bile were analyzed by combined thin-layer and gas chromatography. In the 2 h of perfusion prior to the addition of exogenous CDCA there were sex differences in the kinetics of bile acid secretion in the bile and in the bile acid composition of that bile. Following the addition of CDCA to the perfusion medium the female liver was found to take up more CDCA from the perfusion medium, to store more CDCA, and to convert less CDCA to β-muricholic acid. It was documented that the toxicity of CDCA for the isolated perfused liver of the female rat is not due to α- or β-muricholic acid, the end products of CDCA metabolism in the rat. The relatively greater capacity of the male liver to convert potentially toxic CDCA to nontoxic β-muricholic acid may explain, at least in part, the observed sex difference in CDCA hepatotoxicity.
Phenobarbital Metabolism in Ethanol-Intoxicated Rats
Authors: Coldwell B. B. , Paul C. J. , Thomas B. H.
Published: April 2011

The effects of an acute dose of ethanol on the metabolism of 14C-phenobarbital was studied in the rat. The ethanol-treated rats had higher blood and tissue levels of radioactivity than control animals for 10–12 h following oral administration of the drugs. No redistribution of radioactivity between blood and tissues was observed. Only unchanged phenobarbital was found in the brain, and only traces of phenobarbital metabolites were detected in the blood and liver. Ethanol inhibited the excretion of radioactivity during the first 12 h after dosing. This was due to reduced excretion of p-hydroxyphenobarbital. It is concluded that ethanol inhibits the hydroxylation of phenobarbital in the rat.
Effets de la Chlorpromazine à Faible Dose sur le Syndrome d'Hyperactivité Induit par Stimulation Electrique de l'Aire Tegmentale Ventrale du Mesencephale chez le Rat
Authors: Miliaressis Theris E.
Published: April 2011

Eight rats with electrodes in ventral tegmental area of mesencephalon (VTA) were used and the effects of a weak dose of chlorpromazine (CPZ) was studied on self stimulation and exploratory activity. The effects of CPZ were also studied on exploratory activity normally induced by electrical stimulation of the VTA. CPZ at 1 mg/kg inhibits self stimulation partially while inducing a hyperactive syndrome identical to that obtained by intracranial stimulation; however, this syndrome instead of increasing, disappears under the joint action of CPZ and intracranial stimulation. This suggests that this phenomenon is due to anxiolytic properties of CPZ. If so, it is suggested that stimulation of VTA causes a state of dissatisfaction. Finally, the compatibility of this hypothesis is discussed with relation to the existence of self stimulation in this area.
Central Nervous System Interaction of Pyrazole and Ethanol in the Rat
Authors: LeBlanc A. E. , Kalant H.
Published: April 2011

The degree of impairment of a motor performance test under the influence of alcohol (1.4–2.0 g/kg) was increased progressively by increasing doses of pyrazole (0–3.5 mmol/kg), which had no discernible effect of their own. Blood alcohol concentrations were not affected by pyrazole at the times of testing, indicating that the interaction was at the level of the central nervous system.
Supplemental Copper and Selenium For Calves: Effects Upon Ceruloplasmin Activity and Liver Copper Concentration
Authors: Amer M. A. , St-Laurent G. J. , Brisson G. J.
Published: April 2011

The relation between plasma copper, ceruloplasmin concentration, and copper oxidase activity in postnatal calves fed supplemental amounts of copper (100 and 200 p.p.m.) and selenium (0.7 p.p.m.) singly or in combination was studied. Thirty-six 3-day-old calves were assigned at random to six dietary treatments (2 × 3 factorial) with six calves in each treatment. Blood samples were collected biweekly for a period of 56 days.A significant (P = 0.01) positive linear correlation was obtained between plasma copper (μg/100 ml) and p-polyphenylenediamine oxidase activity (expressed as absorbance at 552 mμ). Considerable changes in plasma copper were observed as the level of copper or copper plus selenium in the diet was elevated. Copper or copper plus selenium supplementation did not have any significant effect on the amount of copper in the albumin fraction of plasma and ceruloplasmin activity was completely absent.
Renal Vascular Resistance and Aortic Pressure as Determinants of Sodium Reabsorption
Authors: Zweig S. M. , Daugharty T. M. , Earley L. E.
Published: April 2011

During induced renal vasodilatation, angiotensin and norepinephrine result in an increased excretion of sodium (UNaV), which has been attributed to transmission of elevated aortic pressure (PA) to peritubular capillaries and not to direct effects of the drugs on sodium reabsorption. The importance of PA, intrarenal hemodynamics, and other possible effects of angiotensin and norepinephrine was examined in anesthetized dogs in which one kidney was vasodilated by denervation or acetylcholine, and the opposite kidney served as control. During elevation of aortic pressure, following bilateral carotid occlusion and vagotomy (B.C.O. and V), infusion of angiotensin and norepinephrine, increased UNaV occurred on only the vasodilated side. Changes in UNaV on both sides are related inversely to renal vascular resistance (R.V.R.) before elevation PA, but not to changes in R.V.R., glomerular filtration rate (G.F.R.), or filtration fraction following elevation of PA. When renal perfusion pressure was controlled during aortic constriction, persistent increases in UNaV and urine flow rate were abolished during infusion of norepinephrine and after B.C.O. and V, and markedly reduced during infusion of angiotensin. These effects could not be attributed to changes in intrarenal hemodynamics. Thus increased sodium and water excretion following infusion of norepinephrine and angiotensin, and B.C.O. and V, can be largely attributed to an interplay of increased renal perfusion pressure and reduced preset renal vascular resistance.
Application of Drug–Receptor Theories to Angiotensin
Authors: Rioux F. , Park W. K. , Regoli D.
Published: April 2011

The myotropic action of angiotensin II has been studied on two smooth muscle preparations: the strip of rat stomach and of rabbit thoracic aorta. Contractions evoked by angiotensin are not modified by atropine, methysergide, and diphenhydramine on the rat stomach or by phentolamine, methysergide, and diphenhydramine on the rabbit aorta. It appears that angiotensin acts directly on specific receptors and not through release of acetylcholine on the stomach or of noradrenaline on the aorta. Interference by intramural prostaglandins is excluded because angiotensin is equally active on tissues pretreated or not with indomethacin.Dose–response curves obtained with angiotensin on the two tissues are close to the theoretical curves predicted by the mass–action law. The relations stimulus effect is linear, indicating that the extent of the contraction is proportional to the number of receptors occupied by the agonist. No threshold phenomenon or spare receptor capacity could be demonstrated in either tissue. It is therefore concluded that the interaction of angiotensin with its specific receptors in the two smooth muscle preparations can be analyzed quantitatively with the occupation theory by applying the concepts of affinity and intrinsic activity as defined by Ariens in 1964. (Molecular pharmacology. Vol. 1. The mode of action of biologically active compounds. Academic Press, New York.)
The Effect of 18-Hydroxycorticosterone on the Salt-Secreting Gland of the Duck (Anas platyrhynchos)
Authors: Lanthier André , Sandor Thomas
Published: April 2011

The intravenous infusion of 18-hydroxycorticosterone in a normal adult unanesthetized duck produced an important and significant increase in the volume and on the total output of sodium by the salt gland.
Relationship of In Vitro Binding of Digoxin to its Intestinal Absorption in Rats
Authors: Thompson W. Grant
Published: April 2011

Digoxin is bound in aqueous solution to cholestyramine and various commercially available antacids. However, chronic ingestion of cholestyramine and an antacid in rats does not interfere with the intestinal absorption of digoxin.
Fractionation Studies on Plasma of Normals and Patients with Laron Dwarfism and Hypopituitary Gigantism
Authors: Bala R. M. , Beck J. C.
Published: April 2011

The molecular size of immunoreactive human growth hormone (IR-HGH) in serum and the relationship of IR-HGH to sulfation factor (SF) require further investigation. Sera obtained from normal volunteers, patients with Laron-type dwarfism, and hypopituitary patients with gigantism were fractionated on large columns of Sephadex. The IR-HGH in normal serum was found in a molecular size range similar to extracted pituitary HGH (epHGH), as well as in a larger and a smaller molecular size. Laron dwarf plasma had a similar molecular size IR-HGH distribution when compared with normal serum. Sera from hypopituitary patients with gigantism showed an increased relative amount of small IR-HGH compared with normal serum. SF activity was recovered in normal serum but not in other sera fractions. SF activity appeared mainly in the molecular size range less than 17 000 and another peak was noted in the molecular size area greater than 55 000.This study further supports the existence of IR-HGH in a large and a small molecular size in normal serum. IR-HGH in Laron dwarf serum appears similar in molecular size to normal serum IR-HGH. The relative increase in small IR-HGH in hypopituitary patients with gigantism requires further investigation. SF activity appears in a molecular size different from epHGH in normal serum, the main peak being in a smaller molecular size area, with a lesser peak in a larger size area.
The Effect of Nicotine on Ascorbic Acid Retention by Guinea Pigs
Authors: Keith M. O. , Pelletier O.
Published: April 2011

Forty-eight male guinea pigs on an ascorbic acid free diet received daily oral injections of 2 mg L-ascorbic acid/100 g body weight for 2 weeks. Simultaneous injections of nicotine were given subcutaneously at 0.66 mg per animal per day; during the second week a second nicotine dose was administered 3 h later. On an equal weight basis each injection was approximately double the nicotine intake of a smoker of 40 cigarettes per day. On the last day at 1 h after a dose of L-ascorbic acid-1-14C there was more radioactivity and ascorbic acid remaining in the gastrointestinal tract contents of nicotine-treated animals than in saline-injected control animals. There were lower concentrations of L-ascorbic acid-1-14C in adrenals, brain, kidneys, and liver of nicotine-injected animals 1 h after the dose but higher concentrations 3, 6, and 12 h after the dose when compared to saline-injected animals. At all times adrenal and liver total ascorbic acid concentrations were higher in nicotine-treated animals. Brain and kidney concentrations showed a similar trend. The results indicate that there was delayed absorption of ascorbic acid in the presence of nicotine. Possible mechanisms of this effect are considered.
Ouabain-Induced Seizures in Rats: Suppressive Effects of Taurine and γ-Aminobutyric acid
Authors: Izumi K. , Donaldson J. , Minnich J. L. , Barbeau A.
Published: April 2011

Investigations on the effects of taurine and of γ-aminobutyric acid (GABA) against ouabain-induced seizures in rats were conducted. Administration of taurine into the left lateral ventricle 10 min prior to ouabain showed a dose-dependent suppressive effect against the seizures induced by 5 μg of ouabain. All injection volumes were 50 μl. All of the animals receiving 9.5 × 10−2 M of taurine were completely protected from the seizure activity. The median effective dose (ED50) of taurine for protection against generalized clonic–tonic seizures was 2.8 × 10−2 M. Administration of GABA (9.5 × 10−1 M) under similar experimental conditions was only partially effective. A higher concentration of GABA (1.9 × 10−1 M) was required to completely abolish the seizure activity induced by the same ouabain injection (5 μg).
Differentiation of Pressor and Behavioral Effects of d-Amphetamine and 2,5-Dimethoxy-4-methylamphetamine (STP) by Cinanserin
Authors: Huang Jen-Tzaw , Ho Beng T.
Published: April 2011

Cinanserin was used to differentiate the effects of d-amphetamine and 2,5-dimethoxy-4-methyl-amphetamine (STP) on blood pressure and spontaneous locomotor activity in rats and mice. Cinanserin itself produced a decrease of blood pressure and spontaneous locomotor activity in the animals. A dose of 2 mg/kg of cinanserin blocked the increase of blood pressure caused by STP; however, it failed to affect the pressor action of d-amphetamine even when the dose was increased to 25 mg/kg. The increase of spontaneous locomotor activity induced by d-amphetamine was counteracted by cinanserin (10 mg/kg) but cinanserin (10 and 25 mg/kg) did not modify spontaneous locomotor activity produced by STP. The results showed that the pressor actions of STP and d-amphetamine, and most likely also their effects on spontaneous locomotor activity, were involved in different mechanisms.
Oxygen Consumption of Skeletal Muscles Relaxing Under Tension
Authors: McCarter Roger
Published: April 2011

The oxygen consumption of isolated frog sartorius muscles was measured in a moist chamber at 12 °C. The muscles were indirectly stimulated to perform two series of contractions: in the first of these the imposed loads re-extended the muscles in relaxation, whereas in the second series relaxation occurred without the external load. No difference in oxygen consumption was detected between the two series of experiments. In both, lightly loaded contractions resulted in less oxygen uptake than isometric contractions at the resting length and heavily loaded contractions resulted in a greater consumption than in the isometric case. It is concluded that, within the limitations of the technique used, there is no additional oxygen consumption associated with the persistence of tension in a muscle during relaxation.
In Vivo Disposal Kinetics of Blood Glucose Carbon to Hepatic and Non-hepatic Products in Normal and Diabetic Rats
Authors: Shipley R. A. , Gibbons A. P. , Chudzik E. B.
Published: April 2011

Individual rates of conversion of glucose (carbon) to a variety of products were determined separately for hepatic and non-hepatic tissue in fasted normal and diabetic rats. Because the method requires a sustained sojourn of 14C tracer in a conversion product, curves of accumulation of 14C during 6–8 h were obtained for each product. For non-hepatic tissue a satisfactory rise to a sustained level was observed for all products in normals and diabetics, but in the case of liver such behavior was observed only for glycogen in diabetics, neutral lipids in normals, and protein and phospholipids in both groups. For all measurable rates to products in both liver and non-hepatic tissue diabetes caused no reduction, but the associated rate constants and clearance constants were invariably impaired. Rates to non-hepatic products exceeded those to hepatic, save for glycogen in diabetics, however as ratios to recipient mass the hepatic rates were higher. An observed high rate to hepatic glycogen in diabetics accompanying a high glycogen content points to a relative depression of phosphorylase and/or activation of synthetase by hyperglycemia. It also argues against the presence of an on–off mechanism which would direct movement either to synthesis alone or degradation alone.