bluuebunny/crossref_metadata_2025_split huggingface dataset:
UNUSUAL EFFECT OF SOME α‐MERCAPTOACRYLIC ACIDS ON METABOLISM OF ZINC IN THE RAT
Authors: Prakash N. J. , Schechter Paul J. , Giroux Eugene , Sjoerdsma Albert 
Published: June 2007

SUMMARY1. Gavage of rats with β‐aryl derivatives of α‐mercaptoacrylic acid resulted in pronounced and sustained elevation of serum zinc concentration. Greater than ten‐fold increases above normal zinc levels were attained 2–8 h after doses of 50 mg/kg of the phenyl and furan derivatives.2. These compounds were rapidly absorbed from the rat gastrointestinal tract and could be detected in serum for several days after a single dose. The return of serum zinc concentration to the normal level paralleled clearance of the mercaptoacrylic acid from plasma.3. Close to 100% of the zinc and of the α‐mercapto‐β‐(2‐furan)acrylic acid (MFA) in serum 4 h after administration of the compound were bound to serum macromolecules.4. MFA decreased excretion of endogenous zinc; it altered neither the gastrointestinal absorption of zinc nor serum concentrations of copper, albumin and total protein.5. These compounds appear to mobilize zinc from tissue stores and retard zinc clearance from plasma.
FORMATION OF A TERNARY COMPLEX WITH SERUM ALBUMIN: AN EXPLANATION FOR THE EFFECT OF α‐MERCAPTO‐β‐(2‐FURAN) ACRYLIC ACID ON RAT PLASMA ZINC CLEARANCE
Authors: Giroux Eugene , Prakash N. J. , Schechter Paul J. 
Published: June 2007

SUMMARY1. Four, six and eight hours after gavage of rats with α‐mercapto‐β‐(2‐furan) acrylic acid (MFA) (25 mg/kg) serum zinc concentration was increased ten‐fold over control levels and a mean molar ratio of 1 albumin:0.4 zinc:0.8 MFA was found for seventeen sera.2. At pH 7.5 a maximum of 1 mole of MFA could be bound per mole of metal‐free bovine serum albumin.3. In the presence of zinc ion, albumin‐zinc‐MFA complexes formed, since for each mole of albumin‐zinc complex an additional mole of MFA could be bound to albumin. Complexes up to a molar stoichiometry of 1 albumin:2 zinc:3 MFA were prepared.4. MFA stabilized the albumin‐zinc complex against dissociation.5. Formation of similar complexes in vivo may account for the markedly delayed clearance of plasma zinc seen in rats administered β‐aryl derivatives of α‐mercaptoacrylic acid.
THE PARTICIPATION OF ENTERIC INHIBITORY NERVES IN ACCOMMODATION OF THE INTESTINE TO DISTENSION
Authors: Furness J. B. , Costa M. 
Published: June 2007

SUMMARY1. The amounts by which various weights distended isolated segments from the distal colons of guinea‐pigs were measured.2. Tetrodotoxin substantially reduced the distensibility of the intestine, but bretylium, guanethidine, hyoscine and methysergide had no significant effect.3. It is concluded that a local reflex involving enteric inhibitory nerves causes an accommodation of the intestine to stretch.
BLOCKADE BY PHENTOLAMINE OF THE POTENTIATION OF HISTAMINE‐INDUCED VASOCONSTRICTION CAUSED BY SEROTONIN AND METHYSERGIDE IN THE RABBIT EAR ARTERY
Authors: Carroll P. R. , Morgans D. , Glover W. E. 
Published: June 2007

SUMMARY1. In subconstrictor doses, both serotonin and methysergide potentiated the vasoconstrictor responses to histamine in the isolated artery of the rabbit ear.2. In the presence of phentolamine (5 μg/ml) the potentiating actions of serotonin and methysergide were significantly reduced.3. This blocking action of phentolamine could be overcome by increasing the concentration of serotonin or by washing the preparation.4. In arteries taken from rabbits pretreated with reserpine, serotonin still potentiated the response to histamine and phentolamine still blocked this potentiation.5. The concentration of phentolamine required to block potentiation also blocked the direct constrictor response to serotonin. It did, however, produce a significantly greater blockade of the vasoconstrictor response to noradrenaline.6. The results indicate that the action of phentolamine in blocking the vascular potentiation produced by serotonin and methysergide is not due to a blockade of α‐receptors.
SYMPATHETIC CARDIOVASCULAR REFLEX INITIATED BY BRADYKININ‐INDUCED STIMULATION OF CARDIAC PAIN RECEPTORS IN THE DOG
Authors: Staszewska‐Barczak Janina , Dusting G. J. 
Published: June 2007

SUMMARY1. Bradykinin (0.02–5 μg) applied to the epicardium of the left ventricle in the open‐chest, anaesthetized dog, elicits dose‐related reflex pressor effects and acceleration of the heart rate.2. Bradykinin‐induced reflex tachycardia was suppressed after the blockade of β‐adrenoceptors with propranolol, whereas reflex pressor responses were prevented by blocking the α‐adrenoceptor sites with phenoxybenzamine.3. Vagotomy and atropine treatment did not affect reflex hypertension and tachycardia to epicardial bradykinin.4. After spinal section at C1, the pressor responses to epicardial bradykinin were significantly reduced, but still present in all but one experiment. A small acceleration of the heart occurred in two out of five spinal dogs with intact vagi and was absent in three vagotomized spinal dogs.5. The results indicate the reflex activation of the sympathetic outflow to the heart and blood vessels, mediated mainly at a supraspinal level as a predominant mechanism for the cardiovascular response initiated by bradykinin‐induced stimulation of cardiac pain receptors.
THE INFLUENCE OF ALTERATIONS IN THE CARDIAC LOADING CONDITIONS ON INDICES OF MYOCARDIAL CONTRACTILITY IN THE ANAESTHETIZED DOG
Authors: Angus J. A. , Richmond D. R. , Cobbin L. B. , Goodman A. H. 
Published: June 2007

SUMMARY1. An online analogue computer was used to measure myocardial contractility as the ratio dP/dt/IIT where dP/dt is maximum rate of change of left ventricular pressure and IIT is integrated isometric tension.2. In the open thorax anaesthetized dog, max (dP/dt) and dP/dt/IIT were compared during alterations in preload, by partial vena caval occlusion, and changes in after‐load obtained by acetylcholine injections and by partial occlusion of the descending thoracic aorta.3. A fall in preload lowered max (dP/dt) but did not alter dP/dt/IIT A rise and fall in afterload produced respectively an increase and decrease in max (dP/dt) but dp/dt/IIT was unaltered.4. From expanded time base recordings, the time from the start of aortic flow (EM flowmeter) to max (dP/dt) was measured to indicate the relationship between valve opening and rnax (dP/dt). At low preload or elevated afterload the aortic valve opened well after max (dP/dt) had been reached. When the afterload fell, max (dP/dt) occurred after the opening of the aortic valve.5. Positive inotropic stimulation following intravenous isoprenaline caused a marked elevation in dP/dt/IIT. However, the rise in max (dP/dt) was attenuated in comparison to dP/dt/IIT by a marked fall in afterload and thus early opening of the aortic valve.6. It is concluded that max (dP/dt) is very sensitive to alterations in preload or afterload but the index——‐dP/dt/IIT is normalized so that changes in end diastolic fibre length do not alter this index. When the afterload falls max (dP/dt) is no longer determined in the isovolumic phase of contraction so that magnitude of rnax (dP/dt) is reduced. However, it is an empirical finding that IIT also falls so that the ratio is unaltered. dP/dt/IIT is a useful index of myocardial contractility that is insensitive to changes in preload or afterload.
THE EFFECT OF APOMORPHINE AND CLONIDINE ON LOCOMOTOR ACTIVITY IN MICE AFTER LONG TERM TREATMENT WITH HALOPERIDOL
Authors: Dunstan Robin , Jackson D. M. 
Published: June 2007

SUMMARY1. Mice were given haloperidol (approximately 3 mg.kg−1 day−1) or vehicle for 21 days and then withdrawn from the drug. All tests were performed 4 days after withdrawal.2. Haloperidol treated mice (premedicated with reserpine plus a‐methyl‐p‐tyrosine) displayed an increased locomotor response to apomorphine and to apomorphine plus clonidine, but neither haloperidol‐ or vehicle‐treated animals revealed any stimulant response to clonidine.3. In mice which had not been pretreated with reserpine plus a‐methyl‐p‐tyrosine, clonidine produced a significant stimulation of locomotor activity in animals withdrawn from haloperidol but not in those withdrawn from the vehicle. Phen‐oxybenzamine blocked the locomotor stimulant difference between these two groups, but did not completely antagonize the stimulant effect of clonidine in mice withdrawn from haloperidol. Pimozide was largely effective in blocking the clonidine‐induced stimulation. Co‐administration of phenoxybenzamine and pimozide was completely effective in blocking the stimulant effect of clonidine in mice withdrawn from haloperidol.4. The evidence for a change in catecholamine receptor sensitivity was supported by the increased stimulant effect of dexamphetamine in the haloperidol‐treated, compared to the vehicle‐treated animals.5. The data suggest that there is a change in the functional responsiveness of both adrenergic and dopaminergic receptors after withdrawal from long term haloperidol treatment.
A COMPARISON OF THE CARDIAC ACTIONS OF DOPAMINE AND NORADRENALINE IN ANAESTHETIZED DOGS AND GUINEA‐PIG ATRIA
Authors: Einstein Rosemarie , Barrett A. M. 
Published: June 2007

SUMMARY1. The positive chronotropic and inotropic actions of dopamine and noradrena‐line have been compared in anaesthetized dogs and isolated guinea‐pig atria.2. Inotropic activity was measured with a strain‐gauge arch in vagotomized dogs or estimated from max (dp/dt) in dogs with denervated hearts.3. The effects of propranolol and haloperidol on the concentration‐response curves to both amines were studied in isolated atria.4. In anaesthetized vagotomized dogs noradrenaline was more potent than dopamine but dopamine appeared to have a selective inotropic action, less apparent with noradrenaline. In denervated hearts, doses of noradrenaline and dopamine which caused similar increases in max (dp/dt) also caused similar increases in heart rate.5. In isolated atrial preparations, concentrations of dopamine and noradrenaline which produced similar increases in force of contraction also had similar chronotropic effects.6. Propranolol produced a shift to the right of the concentration‐response curves to both dopamine and noradrenaline but the antagonism of noradrenaline was quantitatively greater. Haloperidol had no effect in concentrations below those found to cause general tissue depression.7. It is concluded that neither dopamine nor noradrenaline show any real difference in their relative inotropic and chronotropic activities in the absence of autonomic innervation.
THE INTERACTION OF FRUCTOSE, DEXTROSE AND ETHANOL ON HUMAN PERFORMANCE
Authors: Franks H. M. , Hagedorn H. , Hensley V. R. , Hensley W. J. , Starmer G. A. 
Published: June 2007

SUMMARY1. The effects of orally administered fructose (1.2 g.kg−1) and dextrose (1.2 g.kg−1) on the performance decrement induced by ethanol (1.0 g.kg−1) in a series of perceptual, cognitive and motor tests were studied in twelve healthy, paid University student volunteers using a double‐blind cross‐over design. Ethanol was consumed at a constant rate over 20 min and the hexoses or placebo were given approximately 40 min later.2. The peak blood ethanol concentration was attained earlier when the subjects also received either hexose than after placebo but although its rate of fall was unaffected, significantly lower ethanol concentrations were encountered in the hexose‐treated groups in the latter part of the experiment.3. In general, the subjects were impaired to a slightly lesser degree when they received a combination of hexose and ethanol than after ethanol alone. There were no differences between the effects of fructose and dextrose.4. The results do not support contentions that fructose is able to accelerate a return to sobriety and observed differences between hexose and placebo‐treated groups were attributed to an effect on the absorption of ethanol rather than its metabolism.
THE EFFECTS OF SOME BRONCHODILATOR AND ANTI‐INFLAMMATORY DRUGS ON PROSTAGLANDIN F2a‐INDUCED CONTRACTION OF GUINEA‐PIG ISOLATED TRACHEA
Authors: McIntyre Heather J. , Temple Diana M. 
Published: June 2007

SUMMARY1. The bronchodilator drugs isoprenaline, salbutamol, theophylline and prostaglandin E1 (PGE1) relaxed the guinea‐pig isolated tracheal chain preparation dose‐dependently and their potencies were compared by EC50 values.2. The non‐steroid anti‐inflammatory drugs flufenamate, mefenamate and phenylbutazone also relaxed the preparation dose‐dependently, but were less potent than the sympathomimetic drugs and PGE1.3. The contractile response to a submaximal concentration of prostaglandin F2a (PGF2a) was antagonized by flufenamate, mefenamate, phenylbutazone, aspirin, theophylline, isoprenaline, salbutamol and PGE1, at concentrations similar to or less than the clinical peak plasma levels in man. A relatively higher concentration of indomethacin was required.4. The antagonism was relatively specific for PGF2a in the case of the fenamates, which did not cause comparable reductions in responses to equi‐effective concentrations of histamine and carbachol. The other anti‐inflammatory drugs, theophylline and the sympathomimetic drugs were less or non‐specific.5. The nature of the shifts in the log dose‐response curve for PGF2a caused by increasing concentration levels of flufenamate indicates a dual competitive/non‐competitive type of antagonism.
COUNTERCURRENT EXCHANGE OF EIIGHLY DIFFUSIBLE TRACERS IN SKELETAL MUSCLE: ITS ABSENCE IN THE LUNG
Authors: Smiley M. , Lawson M. , Garlick D. 
Published: June 2007

SUMMARY1. Multi‐exponential rates of desaturation of highly diffusible tracers were observed in vascular washout of skeletal muscle. This led to the hypothesis of counter‐current exchange of such solutes between pre‐ and postcapillary vessels which are closely apposed in skeletal muscle. By contrast, in the lung pre‐ and postcapillary vessels are separated by alveolar tissue.2. The ‘indicator diffusion’ method was used in studies on both organs. A vascular reference tracer and a highly diffusible tracer (125I‐iodoantipyrine, 3HOH, 14CO2) were rapidly injected intra‐arterially. Venous samples were collected to determine tracer concentrations. From the venous concentrations of the reference and diffusible tracers extraction of the diffusible tracer into the tissue could be determined.3. In the lung the diffusible tracers conformed to theoretical predictions. High extractions of diffusible tracers into lung tissue occurred in early venous samples. The values declined in subsequent samples as a result of significant tissue concentrations of the diffusible tracers.4. At low flows in skeletal muscle precession frequently occurred of the diffusible tracer ahead of the reference tracer. Extractions of diffusible tracers were low in early samples and subsequently increased to a maximum. At high flows these effects were considerably less. These features are characteristic of countercurrent exchange.5. In vivo in resting muscle, pre‐ to postcapillary shunting of O2 and of CO2 in the reverse direction would become cyclical. The hypoxaemia and hypercarbia would dilate precapillary vessels leading to increased flow thus reducing diffusional shunting of the respiratory gases. The resultant rise in oxygen tension would allow vascular constriction reducing flow and increasing shunting. This is consistent with vasomotion. In exercising muscle the marked increase in flow would minimize this shunting.
CHRONOPHARMACOLOGY OF STRYCHNINE AND ALLYLGLYCINE IN THE MOUSE
Authors: Piepho R. W. , Friedman A. H. 
Published: June 2007

SUMMARY1. The response of individually caged mice to the lethal actions of allylglycine and strychnine was evaluated in animals previously conditioned on an LD 12:12 (12 h light‐12 h darkness) schedule in a controlled environment.2. These convulsant agents were most toxic at 18.00 hours (during the light phase), and least toxic in the dark phase of the programmed lighting schedule. The relationship is considered of the circadian fluctuations in levels of inhibitory transmitter substances to the time‐linked action of convulsant agents.
EQUINE ANGIOTENSIN CONVERTING ENZYME: A ZINC METALLOENZYME
Authors: Fernley Ross T. 
Published: June 2007

SUMMARY1. Angiotensin I converting enzyme from horse plasma has been extensively purified and shown to be homogeneous by disc‐gel electrophoresis.2. The metal ion involved in the catalytic reaction of the enzyme has been identified for the first time as zinc by atomic absorption spectrometry.3. A number of other physicochemical properties of the enzyme are described and compared with results obtained by other investigators. The molecular weight was determined by gel filtration to be 113 000 daltons. The pH maximum was found to be 7.4. The chloride activation of the enzyme appears to act by facilitation of substrate binding to the enzyme.4. By use of enzyme inhibitors, tyrosine has been implicated as a functional residue at the active site of the enzyme.5. The enzyme shows a fairly high degree of specificity towards its substrates.
SPECIES DIFFERENCE IN THE β1/β2‐ADRENOCEPTOR SELECTIVITY OF SM220CL IN THE CAT AND GUINEA‐PIG
Authors: Bohmer K. , Raper C. 
Published: June 2007

SUMMARY1. The β‐receptor stimulant effects of Sm220Cl, dl‐N‐ (1,1‐dimethyl‐3‐phenylpropyl)‐2‐hydroxy‐2(3,4‐dihydroxy‐2‐methoxyphenyl)ethylamine, and (‐)‐isoprenaline have been compared in isolated atrial (β1) and tracheal (β2) preparations from guinea‐pigs and cats.2. The compounds were also tested for their ability to increase the heart rate (β1), reduce serotonin‐induced increases in pulmonary resistance (β2), and decrease soleus muscle contractility (β2) in vivo in the two species.3. In all experiments cumulative concentration or dose‐effect curves were established, EC50 or ED50 values obtained and molar activity‐ratios (Sm220Cl: (‐)‐isoprenaline) calculated.4. Calculated selectivity ratios [activity‐ratio (heart):activity‐ratio (bronchial smooth muscle)] from the in vitro experiments showed that Sm220Cl possessed β2‐receptor selectivity. This was more marked in guinea‐pig than in cat preparations.5. In the anaesthetized animals this species difference was more apparent; in cats Sm220Cl was non‐selective in its actions for β1‐ and β2‐receptor mediated responses, while marked β2‐receptor selectivity was obtained in the guinea‐pig.6. Since in both species the activity‐ratios for β2‐receptor mediated actions are similar, the differences in the β1/β2‐receptor selectivity of Sm220Cl are caused by the divergent cardiac effects produced by the drug.
CARDIAC ARREST TEMPERATURE: THE EFFECT OF ETHYL ALCOHOL AND CARBON DIOXIDE ON RATS, GUINEA‐PIGS AND ISOLATED RAT HEARTS
Authors: Duthie Ashley M. , White J. Forster 
Published: June 2007

SUMMARY1. Previous clinical and experimental reports have suggested that the systemic administration of ethyl alcohol permits lower body temperatures before the onset of hypothermic cardiac arrest.2. In the investigations described here, the effect of ethyl alcohol on the temperature at which cardiac arrest occurred in rats, guinea‐pigs and isolated rat hearts was studied. Comparison was also made of the difference between pulmonary ventilation with air and with 5% carbon dioxide in oxygen.3. The results demonstrated that both the administration of ethyl alcohol and ventilation with 5% carbogen reduced the cardiac arrest temperature of rats. Ethyl alcohol did not influence the cardiac arrest temperature of guinea‐pigs nor of isolated rat hearts.
THE EFFECTS OF SEROTONIN PRECURSORS ON THE PRESSOR RESPONSE TO INTRAVENOUS CLONIDINE IN CONSCIOUS RATS
Authors: Nolan P. L. 
Published: June 2007

SUMMARY1. The interaction of the biosynthetic precursors of serotonin with the a‐adrenoceptor‐mediated pressor response to intravenous clonidine was investigated in unanaesthetized rats.2. Pretreatment with 100 mg/kg of either L‐tryptophan or 5‐hydroxytryptophan (5‐HTP) reduced the magnitude of the pressor response elicited by intravenous clonidine (25 μg/kg) to 15% and 11%, respectively, of that observed in control rats.3. The depression by L‐tryptophan of the clonidine‐induced pressor response could be prevented by pretreatment with either the L‐aromatic amino acid de‐carboxylase inhibitor Rö‐4– 4602 or the serotonin antagonist methysergide.
CHOLIC ACID AND THE HEART: IN VITRO STUDIES OF THE EFFECT ON HEART RATE AND MYOCARDIAL CONTRACTILITY IN THE RAT
Authors: Joubert P. 
Published: June 2007

SUMMARY1. Cholic acid has a dose‐dependent negative chronotropic effect on isolated atria ofWistar rats.2. The positive inotropic effect of cholic acid is the result of a negative chronotropic effect and can be eliminated by electrical pacing.3. Cholic acid does not appear to exert its negative chronotropic effect through cholinoceptors and alterations in bath concentrations of calcium and potassium does not influence this effect significantly.4. Cholic acid is a functional antagonist of isoprenaline.5. It is suggested that cholic acid exerts its negative chronotropic effect by forming a monolayer on the surface of the cell membrane, thereby mechanically interfering with membrane function.
CARDIAC AND BRONCHIAL β‐ADRENOCEPTOR ANTAGONISTIC POTENCIES OF ATENOLOL, METOPROLOL, ACEBUTOLOL, PRACTOLOL, PROPRANOLOL AND PINDOLOL IN THE ANAESTHETIZED DOG
Authors: Harms Herman H. , Spoelstra Albert J. G. 
Published: June 2007

SUMMARY1. The β‐adrenoceptor antagonists atenolol, metoprolol, acebutolol, practolol, propranolol and pindolol have been tested for their ability to reduce isoprenaline‐induced bronchodilation and tachycardia in the anaesthetized dog.2. Atenolol, metoprolol, acebutolol and practolol all possessed a similar degree of cardioselectivity in this animal model.
INTRARENAL MECHANISM FOR RENAL VASOCONSTRICTION RESULTING FROM STIMULATION OF THE URETER IN THE DOG
Authors: Robie N. W. , McNay J. L. 
Published: June 2007

SUMMARY1. The mechanism responsible for ipsilateral renal vasoconstriction resulting from mechanical stimulation of the ureter was examined using the pharmacological antagonists saralasin, SQ20881, indomethacin, atropine and phentolamine.2. A segment of PE tubing was implanted in the left ureter, patency being well maintained. Three to four days later renal blood flow was measured bilaterally and antagonists administered intravenously.3. The mechanism responsible for vasoconstriction could not be attributed to either increased intrarenal noradrenaline or angiotensin, nor to a decreased activity of prostaglandins, kinins or acetylcholine.4. Histological and bacteriological examination also proved negative.5. Thus, additional evidence of an unidentified intrarenal mechanism causing vasoconstriction is presented.
PRESSOR ACTION OF PYRIDEVE‐2‐ALDOXIME IN MALATHION POISONING*
Authors: Chang P. , Ganendran A. 
Published: June 2007

SUMMARY1. Intravenous injections of pyridine‐2‐aldoxime (PAM) produced a marked, prolonged and dose‐related rise in blood pressure in anaesthetized cats treated with malathion (MT) and without malathion (NMT).2. The pressor effect of PAM was significantly reduced by phentolamine and phenoxygenzamine, but unaffected by hexamethonium.3. Pretreatment with guanethidine and reserpine almost completely abolished the pressor response to PAM.4. The results indicate that PAM has a potent sympathomimetic action which appears to be mediated through release of catecholamines from storage sites.