bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential impairment of thermogenesis in the pigeon after chemical sympathectomy
Authors: Hohtola E. , Rintamäki H. , Hissa R.
Published: April 2011

A dose-controlled chemical sympathectomy with 6-hydroxydopamine (6-OHDA) did not disrupt thermostasis in the pigeon at +38 °C. At +6 °C, thermogenesis was impaired, but the lower body temperature and oxygen consumption were stable and vasoconstriction was normal. The stability may partly be explained by a massive release of adrenaline from the adrenals (50% in 20 min). Despite a deficit in heat production both after sympathectomy and after acute 6-OHDA, no change in muscle electrical activity was observed. Plasma free fatty acid (FFA) concentration was significantly elevated after sympathectomy, but no changes occurred in blood glucose or plasma lactate levels. The results indicate a major compensatory role for the adrenals in avian thermogenesis. They also suggest a sympathetically mediated auxiliary thermogenic mechanism independent of muscle electrical activity and coupled to FFA metabolism.
Epileptiform seizures in domestic fowl. VIII. Anticonvulsant activity of primidone and its metabolites, phenobarbital and phenylethylmalonamide
Authors: Johnson D. D. , Davis H. L. , Crawford R. D.
Published: April 2011

Primidone is an effective anticonvulsant against seizures induced in epileptic fowl by exposure to intermittent photic stimulation. Epileptic fowl metabolize primidone to phenobarbital. Pretreatment of epileptic fowl with SKF 525A to prevent the metabolism of primidone to phenobarbital indicated that primidone itself had anticonvulsant activity. Phenylethylmalonamide, a second metabolite of primidone, did not have anticonvulsant activity when administered at the same dose as primidone.
Tectospinal and tectoreticular cells: their distribution and afferent connections
Authors: Rose P. K. , Abrahams V. C.
Published: April 2011

Experiments on chloralose-anaesthetized cats have shown that cells in the superior colliculus may be antidromically activated either from the pontomedullary reticular formation or the ventral cervical spinal cord, or from both sites. In tests on 111 units this has provided a basis for differentiating between cells of origin of the tectospinal tract and the tectoreticular system within the superior colliculus. Tectospinal cells may be activated both by spinal and pontine stimulation; tectoreticular cells cannot be activated by spinal stimulation. Both tectoreticular and tectospinal cells respond to visual and muscle afferent stimulation. The afferent connections may be strongly inhibitory as afferent input to the superior colliculus often prevented subsequent antidromic invasion. This was more commonly seen in tectospinal cells than tectoreticular cells. The distribution of the two cell populations within the superior colliculus was also found to be dissimilar. Evidence has also been obtained to suggest that the tectoreticular system, in part, consists of collaterals of the tectospinal tract.
De novo formation of vascular receptors for bradykinin
Authors: Regoli D. , Marceau F. , Barabé J.
Published: April 2011

Two different types of receptors for bradykinin have been found in isolated veins of the rabbit. The first receptor is a stable component of the smooth muscle membrane and it is found in the jugular vein, while the second is generated de novo during incubation in vitro and it is present in the mesenteric vein. Actinomycin D and cycloheximide block the generation of receptors in the mesenteric vein, without exerting any action either on receptors for other agonists (e.g. substance P) in the same tissue, or on the other receptor for bradykinin in the jugular vein.
Hepatic parasympathetic neural effect on glucose balance in the intact liver
Authors: Lautt W. Wayne , Wong Chong
Published: April 2011

Sympathetic nerves to the intact liver of the cat were selectively destroyed by injection of 6-hydroxydopamine into the portal vein 1 week prior to the experiment. Glucose output was calculated from the product of the arterial–venous glucose difference and hepatic blood flow. Hepatic blood flow was monitored by an electromagnetic flowmeter using a hepatic venous long-circuit. Stimulation of the parasympathetic nerves isolated from around the common hepatic artery produced a rapid reduction in hepatic glucose output to one-quarter of control levels by 2 min and to zero by 10 min of nerve stimulation. The data show that hepatic glucose balance is readily influenced by the hepatic parasympathetic nerves.
Effects of 16,16-dimethyl prostaglandin E2 on ion transport by isolated rabbit gastric mucosa and rat intestinal epithelial cells
Authors: Tepperman Barry L. , Tepperman Fern S. , Fang Wan-Fen , Jacobson Eugene D.
Published: April 2011

The actions of 16,16-dimethyl prostaglandin E2 (dmPGE2) were investigated on ion transport in in vitro rabbit fundic mucosa and rat isolated jejunal cells. Addition of dmPGE2 (1.3 × 10−4 M) to the serosal side of the rabbit mucosa resulted in a significant decrease in the transmural potential difference (PD) and short circuit current (ISC). The transmembrane resistance (R) displayed a significant rise over control values. Furthermore, the net serosa to mucosa flux of chloride ion decreased while the net serosa to mucosa movement of sodium remained unchanged. In the rat intestinal cells, increasing the concentration of dmPGE2 from 10−10 to 10−4 M caused a fall in sodium efflux. These data indicate that dmPGE2 alters the rate of active transport of the predominant ion pump of the resting rabbit gastric mucosa and the rate of Na efflux from rat intestinal epithelial cells without apparently affecting the membrane permeability.
Transient potassium currents in slow muscle fibers
Authors: McLarnon James G.
Published: April 2011

Transient changes in potassium conductance in chronically depolarized slow muscle fibers have been studied using a voltage clamp method. The transient behavior included current decays from initial to steady state for hyperpolarizing and depolarizing voltage clamp steps. A two-pulse voltage clamp sequence (conditioning step followed by test step) showed the initial potassium test current to depend sigmoidally on conditioning potential implicating the involvement of a membrane-bound charged group in regulating potassium current.
Characterization of the inotropic response induced by stimulation of β-adrenergic and H1 histaminergic receptors in guinea pig left atria
Authors: Tenner Jr. Thomas E. , McNeill John H.
Published: April 2011

The inotropic response induced by β-adrenergic and H1 histaminergic receptor stimulation was characterized in guinea pig left atria by obtaining dose–response relationships for isoproterenol and histamine under various experimental conditions. Conditions (hypothermia, high frequencies of stimulation, and large extracellular calcium concentrations) which enhanced the ability of cardiac muscle to develop force also increased the sensitivity of the left atrium to isoproterenol while decreasing its efficacy. On the other hand, conditions which enhanced the ability of cardiac muscle to develop force depressed the efficacy of histamine to such an extent that the sensitivity to histamine was also decreased. In addition, conditions which markedly depressed the ability of cardiac muscle to develop force also decreased the efficacy and sensitivity to histamine. The data indicate that while β-adrenoceptor stimulation results in an inotropic response under all conditions studied, stimulation of H1 histaminergic receptors results in an inotropic response only within a narrow range of experimental conditions.
Thyroxine levels in male and female white-tailed deer (Odocoileus virginianus)
Authors: Bubenik G. A. , Bubenik A. B.
Published: April 2011

Four major findings are described: (1) The episodic secretion of thyroxine in mature male white-tailed deer is most pronounced in the warmer months (June and September) and least demonstrated during the coldest months (November and January); (2) no clear annual rhythm of thyroxine was demonstrated in juvenile or mature male or mature barren female white-tailed deer. The monthly mean levels in mature males and females oscillate between 11 and 14 μg/100 ml throughout the year; (3) the seasonal levels of thyroxine in mature males are almost identical with the thyroxine levels of adult barren females; (4) the seasonal thyroxine levels of juvenile males are constantly higher than levels found in mature males. However, when these deer reach the age of 3 years, their thyroxine levels decrease to those of the adult.The collected data could serve as a tool of evaluation of population structure for wildlife management purposes.
The effect of iodine deficiency and propylthiouracil on the hypothalamo–pituitary–thyroid axis in the neonatal rat
Authors: Dussault J. H. , Walker P.
Published: April 2011

The effect of chronic propylthiouracil (PTU) and low iodide diet (LID) on the development of the hypothalamo–pituitary–thyroid axis in the rat has been studied. Pregnant and neonatal rats received 0.05% PTU in their drinking water or LID (distilled water and LID: Teklad Mills, Madison, Wisconsin). Control animals received tap water and Purina rat chow ad libitum. Hypothalamic thyrotropin-releasing hormone (TRH), pituitary and serum thyroid-stimulating hormone (THS), and serum thyroxine (T4) and triiodothyronine (T3) were measured by specific double-antibody radioimmunoassay. Both PTU- and LID-exposed animals had low hypothalamic TRH concentrations at 1 day and a rapid rise to peak levels of 2.4 ± 0.4 pg/μg protein (mean ± SEM) between 12 and 24 days in the PTU animals and 3.2 ± 0.4 pg/μg protein between 12 and 18 days in the LID rats. Hypothalamic TRH concentrations remained relatively stable in the PTU animals, whereas in the LID rats, after a brief but significant decline from 24 to 28 days, hypothalamic TRH concentrations rose to the highest values observed at 57 days (3.9 ± 0.5 pg/μg protein). Both groups of animals had elevated serum TSH levels at 1 day, with higher values seen in the PTU group (p < 0.01), and both showed a rapid rise at 12 days. Thereafter, serum TSH concentrations remained high in the PTU rats but declined to stable, albeit elevated, levels by 24 days (1260 ± 140 ng/ml) in the LID animals. Hypothyroidism was confirmed in the PTU animals by undetectable T4 and reduced T3 concentrations. In the LID rats, serum T4 concentrations rose from undetectable levels at 1 day to stable values by 32 days (2.18 ± 0.13 μg/dl). Serum T3 rose to peak values of 157.0 ± 6.9 ng/dl at 32 days and was elevated at all times after 12 days. These data suggest that chronic exposure to PTU or LID results in a marked derangement of the ontogenetic pattern of the hypothalamo–pituitary–thyroid axis. In addition, neonatal rats exposed to LID appear to respond appropriately by preferential T3 production.
Effect of porcine follicular fluid injection on FSH secretion in the immature female rat
Authors: Pomerantz David K.
Published: April 2011

Porcine ovarian follicular fluid (pFF) contains a substance capable of selectively suppressing FSH secretion in adult rats. The effectiveness of this material in prepubertal female rats was examined. Steroids were removed from pFF or pig serum by adsorption to charcoal. Twenty-four hours after sham or bilateral ovariectomy, at 17 days of age, the rats received an intraperitoneal injection of 0.4 ml charcoal-extracted pFF or serum. Eight hours after injection animals were killed by cervical dislocation and blood collected. Serum estrogen and FSH concentrations were estimated by radioimmunoassay. Ovariectomy reduced total serum estradiol from 181 ± 25 to 77 ± 18 pg/ml (mean ± SEM) and pFF had no effect on this response. Ovariectomy caused an increase of serum FSH from 1275 ± 239 to 2392 ± 122 ng FSH (RP – 1)/ml in control and gonadectomized rats, respectively. Post-ovariectomy hypersecretion of FSH was completely Mocked when animals were treated with pFF. in sham-ovariectomized animais pFF was unable to suppress FSH secretion. These results support the notion that the relatively high levels of FSH found in intact female rats of this age might be explained in part by a low responsiveness to the inhibin-like component of follicular fluid.
Enzymatic modifications of bovine adrenocortical angiotensin II receptors
Authors: Forget Gilles , Heisler Seymour
Published: April 2011

Several classes of proteolytic enzymes were used to gain an insight into the biochemical composition of the antiotensin II (ATII) receptor prepared from bovine adrenal cortices. Exposure of the receptor fractions to trypsin reduced their capacity to bind [3H]ATII. Phospholipases A2 and C similarly inhibited the [3H]ATII binding process, while phospholipase D had no effect. Binding was stimulated following addition of phosphatidylcholine but inhibited by lysophosphatidylcholine. Neuraminidase had no influence on [3H]ATII affinity for binding, while β-galactosidase reduced binding of the radioligand. Concanavalin A did not displace [3H]ATII bound to receptor fractions. Very little aminopeptidase activity was detected in the receptor fraction, relative to the homogenate. The data suggest that the ATII recognition sites contain protein moieties, while phospholipids may play an essential role in ATII binding. Galactose units may form a part of the ATII receptor not directly associated with the binding site. The peptidase studies indicate that ATII probably cannot be hydrolyzed to its des-Asp1 metabolite at or near the site of binding.
Neurotransmitter receptors on gill muscle fibers and the gill peripheral nerve plexus in Aplysia
Authors: Ruben P. C. , Swann J. W. , Carpenter D. O.
Published: April 2011

Isolated pinnules of the gill of Aplysia contract when dopamine (DA) is perfused through the bath. The contraction is not blocked by high-Mg2+ seawater, and reflects excitatory receptors for DA on the smooth muscle cells of the gill. The pinnule often shows irregular, spontaneous contractions which are blocked by high-Mg2+ seawater and 30 mM CoCl2. These contractions reflect spontaneous activity of a peripheral nerve plexus. No other transmitter was found to be directly excitatory on the muscle fibers, although there are inhibitory receptors for serotonin (5-HT). Tactile stimulation of the pinnule evoked a two-component contractile reflex contraction due to activation of the peripheral nerve plexus. Acetylcholine, octopamine, and 5-HT but not several other transmitters depressed these responses, presumably due to inhibitory receptors on the neurons of the peripheral plexus.
La S-adénosyl-L-homocystéine : 2. Anticonvulsivante
Authors: Fonlupt Pierre , Roche Maurice , Andre Annie-Claire , Cronenberger Lucien , Pacheco Henri
Published: April 2011

S-Adenosyl-L-homocysteine (SAH) decreases the epileptiform discharges induced by hippocampic stimulation. SAH reduces the pentetrazol convulsions, does not modify picrotoxine convulsions, and increases strychnine toxicity. These effects are not linked to γ-aminobutyric acid metabolism perturbation or to the concentration of some amino acids known for their action in synaptic transmission.
Rapid orthograde transport of 32P-labelled material in amphibian sensory axons: a multiwire proportional chamber study
Authors: Snyder R. E. , Nichols T. R. , Smith R. S.
Published: April 2011

A multiwire proportional chamber was used to follow the axonal transport of material labelled with [32P]orthophosphate in dorsal root ganglion (DRG) – sciatic nerve preparations of Xenopus laevis and Rana catesbiana. The DRG were exposed to label for a period of 4 h following which there was a period of continued delivery of labelled material to the nerve for up to 18 h. The front of the labelled material in the nerve moved at a velocity of 160–170 mm/24 h at room temperature (22.5–23.5 °C). Sectioning the nerve at a proximal position showed that labelled material behind the front moved at a similar rapid velocity. Experiments in which the nerve was sectioned showed that some of the rapidly transported label appeared to be deposited into a relatively stationary phase. Extrapolation of the results indicated that the delay between the presentation of the label to the DRG and the onset of the transport of labelled material in the nerve was 4–6 h. The rapid transport of the label was inhibited by vinblastine sulphate at concentrations of 130–950 μM. Most of the rapidly transported material was found to be in a chloroform–methanol extractable form. In conclusion, 32P labels materials whose transport dynamics are very similar to those observed when [35S]methionine is used as the precursor.
Changes in extracellular Ca2+ and K+ activity accompanying hippocampal discharges
Authors: Krnjević K. , Morris M. E. , Reiffenstein R. J.
Published: April 2011

In rats under urethane anaesthesia, changes in the extracellular activities of K+ and Ca2+ (aK and aCa) evoked by fimbrial or entorhinal stimulation and recorded in area CA3 with ion-selective microelectrodes are maximal in the pyramidal cell layers. With 10/s stimulation, aK increases by 6-9 mM whereas aCa falls by 0.5-1.0 mM. In contrast with the increase in aK, which is distributed over a wide range of depth, the reduction in aCa is particularly sharply limited to the level of pyramidal cell bodies. It is regularly associated with a negative afterpotential in the extracellular field, which presumably reflects a large postsynaptic Ca2+ inward current, apparently predominant in the cell bodies. Repetitive stimulation sometimes evokes spreading depressionlike swings in potential, which are seen only near the pyramidal stratum and are accompanied by massive increases in aK (to 30-40 mM) and falls in aCa (to < 0.1 mM). A large Ca2+ influx into pyramidal cells may be of significance for "plastic" aspects of hippocampal function and when excessive, as during repetitive convulsive activity, may be responsible for the necrosis of CA3 neurons.
Effects of histamine on rat isolated atria
Authors: Laher I. , McNeill J. H.
Published: April 2011

The effects of histamine were studied in atria obtained from untreated and reserpine-pretreated rats. At high doses, histamine caused a positive chronotropic response that was not antagonized by either promethazine or cimetidine. In the presence of propranolol or in atria from reserpine-pretreated rats histamine caused an atropine-sensitive negative chronotropic response. Large doses of histamine also caused a positive inotropic response in left atria that were antagonized by the β adrenoceptor antagonist propranolol. Reserpine pretreatment abolished the inotropic response of histamine in the rat heart. The results indicate that in large doses histamine causes an indirect stimulation of β adrenoceptors (right and left atrium) by releasing endogenous noradrenaline and of muscarinic receptors (right atrium) by releasing acetylcholine.
The effect of histamine and epinephrine on adenylate cyclase prepared from dog ventricle
Authors: Cros G. H. , Katz S. , McNeill J. H.
Published: April 2011

The possible presence of histamine H2 receptors in dog ventricle was investigated by determining the effect of histamine on adenylate cyclase prepared from that tissue. Epinephrine produced a dose-dependent increase in adenylate cyclase activity but histamine had no effect. Histamine H2 receptors probably do not exist in dog ventricle.
Electrophysiologic effects and electrolyte changes in total myocardial ischemia
Authors: Nguyen-Thi An , Ruiz-Ceretti Elena , Schanne Otto F.
Published: April 2011

The ventricular membrane potential was measured in the perfused rabbit heart under control conditions and during total cardiac ischemia produced by an arrest of the coronary perfusion. The steady-state inactivation characteristic of the sodium system and the sodium dependence of the upstroke velocity were determined by measurements of the maximum rate of rise ([Formula: see text]) as a function of the resting potential (RP) and the [Na]o to [Na]i ratio. The intracellular concentrations of sodium and potassium ([Na]i, [K]i) were estimated from measurements of the cellular electrolyte content, the total water content, and the volume of the extracellular space. Ischemia produced a net sodium gain of 58 mmol/kg dry weight and a slight loss of potassium. As a consequence, [Na]i increased and [K]i decreased. Under ischemia the resting potential was closer to the potassium equilibrium potential than in the controls. The changes in action potential configuration and plateau level suggested that ischemia inhibited the slow inward current. The [Formula: see text] decreased within 10 min of ischemia. Neither membrane depolarization nor a reduction in the sodium gradient could entirely explain the low [Formula: see text] of ischemic cells. It is concluded that the electrophysiologic effects of ischemia result from changes in ionic gradients and membrane electrical properties.
The Schild regression in the process of receptor classification
Authors: Kenakin Terry P.
Published: April 2011

The history and derivation of the Schild equation is reviewed as well as the conditions under which the intercept of a Schild regression (the pA2, an empirical quantity) can be considered to be an estimate of the equilibrium dissociation constant of the antagonist for the receptor (KB). This parameter is of value in the classification of receptors. To be considered competitive (and, therefore, to be described in molecular terms by a KB), an antagonist must produce parallel displacement of agonist concentration–response curves with no alteration in the maximal response and thereby yield unambiguous dose ratios of agonist which are independent of agonist concentration. These dose ratios (dr) then can be utilized in the Schild equation (log (dr − 1) = n ∙ log [B] − log KB, where [B] is the molar concentration of antagonist) in the form of a regression of log (dr − 1) on log [B]. If the regression is linear and has a slope of unity, the blockade is consistent with simple competitive antagonism and the intercept can be considered an estimate of the KB. Experimentally, the slope is a parameter critical to the assessment of competitivity. While a slope significantly different from unity may indicate that an antagonist is not competitive, it also may indicate that nonequilibrium conditions exist in the experimental procedures. The importance of uptake mechanisms for agonists, with regards to producing underestimations of antagonist potency, are reviewed along with a concise model by Furchgott which conveniently incorporates these concepts. The possible significance of Schild regression slopes < 1 and > 1 are discussed along with caveats regarding Schild regressions with slopes of unity but erroneous estimates at KB. Short discussions of the use of selective agonists, experiments in vivo, and the assessments of receptor differences from estimates of KB also are given.
Glucose utilization and nitrogen balance in the obese on a protein–lipid hypocaloric diet
Authors: Reid D. , Rasio E.
Published: April 2011

Glucose utilization and insulin and growth hormone responses were evaluated in eight obese women by three rapid intravenous glucose tolerance tests (IVGTT): during a control period, and after 1 and 3 weeks of a 750 kcal/day protein–lipid diet (1 kcal = 4.1855 kJ). Weight loss averaged 454 g/day during the 1st week and 238 g/day for the 2nd and 3rd weeks of the diet. Nitrogen balance was maintained in equilibrium. Plasma insulin concentrations fell by 50% within 1 week of dieting; growth hormone levels were not modified. The net rate of glucose disappearance dropped from 0.98 to 0.65 and 0.68%/min, the glucose pool from 16.2 to 13.3 and 13.4 g, and glucose utilization from 158 to 88 and 87 mg/min during the control period, and at 1 and 3 weeks of dieting, respectively. The insulinogenic index decreased from 0.41 to 0.24 to 0.16 with successive IVGTT's. The glucose volume of distribution was not modified with dieting. It is concluded that a hypocaloric protein–lipid diet induces (i) a carbohydrate intolerance not related to a negative nitrogen balance and (ii) a rapid initial weight loss which cannot be ascribed to a depletion of the glucose volume.
Glycogen and histological changes in muscle grafts of rats during fasting or exercise
Authors: Mong Franz S. F. , Poland James L. , Poland Jerry W.
Published: April 2011

The metabolic integrity of skeletal muscle grafts must be restored, along with histological regeneration, if muscle transplants are to be clinically acceptable. The purpose of the present study was to contrast glycogen changes in muscle grafts after exercise or fasting with those in normal muscles. The extensor digitorum longus (EDL) and soleus (SOL) muscles were switched to each other's muscle bed in one leg of male Sprague–Dawley rats. Fifty days later, some of the rats were fasted for 48 h and sacrificed either immediately or after 4 h of refeeding. Other rats were run on a treadmill for 30 min (1 mi/h (0.447 m/s)) and sacrificed either immediately or after 4 h of resting. Muscle grafts and contralateral normal muscles of these experimental, as well as control animals (neither exercised nor fasted), were removed for determination of glycogen concentration. The results show that glycogen in muscle grafts, as in normal muscles, decreases with exercise or fasting. After 4 h of rest or refeeding, glycogen is restored in both grafts and normal muscles. It is concluded, therefore, that muscle grafts are metabolically active and that their pattern of utilization and restoration of glycogen in response to physiological events, such as exercise or fasting, is similar to that of normal muscle.
The influence of voltage conditioning on chloride currents in amphibian muscle membrane: the sigmoid conductance–voltage relation extended into the outward current region
Authors: Vaughan Peter , Trotter Martin
Published: April 2011

Sartorius muscle fibres of Xenopus laevis were depolarized in solutions of high K+ content and then voltage clamped in solutions in which K+ was replaced by Rb+ and(or) tetraethylammonium ion (TEA+) at pH 9. A three-microelectrode clamp system was used in which the bath was held at virtual ground using an operational amplifier in a current meter configuration. The holding potential was set at zero membrane current potential (resting potential), close to −25 mV. A two-pulse paradigm was used to test the effects of conditioning the membrane at voltages away from the resting potential on initial currents at positive test potentials. In the absence of TEA+ rapidly rising outward currents were generated at positive test potentials, following hyperpolarizing conditioning. These currents inactivated in time and obscured predicted chloride currents. When TEA+ was added to the solution (60 mequiv./L) the currents at positive potentials rose more slowly and declined either very slowly or not at all. Projection of these current waveforms, by curve fitting, to the instant of potential change gave a sigmoid dependence of test current on conditioning voltage that was predicted from earlier results. Predictably there is a test voltage at which the initial current is independent of conditioning potential: from the data it appears that this is not necessarily the resting potential, but the cause of the shift is not clear. The results also indicated that there is a component of outward current that is very small, apparently earned by cations ("delayed rectifier current"), that does not inactivate, even at potentials more positive than the resting potential.
Cross-adaptive responses to different forms of leg training: skeletal muscle biochemistry and histochemistry
Authors: Daub W. D. , Green H. J. , Houston M. E. , Thomson J. A. , Fraser I. G. , Ranney D. A.
Published: April 2011

The influence of a program of high intensity training and of a combined program of high intensity training and prolonged submaximal training on adaptations to the vastus lateralis muscle was investigated in two groups of elite athletes. The high intensity training (HI) consisted of ice hockey practices and games over a 14-week period while the combined program (HI–LO) included the addition of supplementary sessions of cycling, three times per week, progressively increasing from 30 to 45 min per session and at an intensity of 70% [Formula: see text]. Determinations of enzyme activities representative of energy supplying pathways revealed no change in 3-hydroxyacl CoA dehydrogenase (HADH), total phosphorylase (PHOSP), phosphofructokinase (PFK), lactate dehydrogenase (LDH), and a 7% increase (p < 0.05) in succinate dehydrogenase (SDH). The addition of the supplementary program caused no further adaptation in the metabolic profile. Similarly, neither the HI nor the HI–LO program induced any alteration in the percentage fibre type (slow twitch (ST) vs. fast twitch (FT)) or the subtypes (FTa, FTb, FTc). Reductions in the size (p < 0.05) of ST fibres were noted for both the HI and the HI–LO training programs. In contrast, increases in capillarization (p < 0.05) were found for both the ST (23%) and FTa (32%) fibres for the HI–LO program whereas a reduction in capillarization (21%) occurred in the FTa fibres as a result of HI training only. It is concluded that metabolic differentiation does not appear to occur in a manner consistent with the conditions of energy expenditure at least for high intensity work.
Comparison of responses of helical strips of artery from anesthetized and untreated rats
Authors: Kassay-Farkas N. , Wyse D. G.
Published: April 2011

A comparison was made of the responses of helical strips of rat ventral tail artery from rats killed by cervical dislocation and rats subjected to poly-drug anesthesia. Anesthetized rats were premedicated with meperidine and atropine. Anesthesia was induced with thiopental and maintained with N2O. The animals were paralyzed with pancuronium and ventilated for 1 h. A mixture of fentanyl and droperidol was administered during anesthesia. Responses of arterial strips from these rats to norepinephrine, 5-hydroxytryptamine, vasopressin, and transmural electrical stimulation were identical with those of similar strips from control rats. Poly-drug anesthesia does not alter responses of isolated strips subsequently studied in vitro.
Intravenous infusion of nitroglycerin: effects upon cardiovascular dynamics and regional blood flow distribution in conscious dogs
Authors: Dumont Louis , Lamoureux Claudette , Lelorier Jacques , Stanley Paul , Chartrand Claude
Published: April 2011

We have studied both central and peripheral hemodynamic changes induced by infusion of nitroglycerin (55 μg/kg per minute) over a 15-min period in conscious dogs to clarify its mechanism of action. Dogs were prepared with an electromagnetic flow probe positioned at the root of the aorta, and microspheres (9 μm) were used to measure regional blood flow distribution before and after 15 min of infusion. Controlled hypotension (−15 to −20 mmHg (1 mmHg = 133.322 Pa)) was maintained throughout the infusion period and this hypotensive state was associated with a significant decrease in stroke volume (−30%), cardiac index (−20%), and left ventricular work (−43%). Regional blood flow studies showed that at the 15th min of infusion, nitroglycerin induced significant decrease in blood flow to all components of the myocardium (range −12 to −20%) while their vascular resistances were not affected significantly. Blood perfusion to liver (hepatic artery), spleen, and intestine was also modified significantly (−22, −18, and −16%, respectively) while their vascular resistances remained close to control values. By the time measurements were made, blood flow and vascular resistance of cerebral and renal tissues remained normal. For each organ studied, blood perfusion was uniform. These results indicate that nitroglycerin elicits both central and peripheral hemodynamic changes and that local reflex adjustments modify the vasodilator effect of the drug in most vascular beds that we have studied.
Vascular reactivity during the development of two-kidney, one-clip Goldblatt hypertension in conscious dogs
Authors: Greenberg Stan , McGowan Claude , Gaida Monica
Published: April 2011

This study evaluates the sequential changes in vascular reactivity in conscious dogs during the early and late phases of two-kidney, one-clip Goldblatt hypertension (2-KGH) produced by unilateral renal artery constriction (URAC). The in vivo responses to serotonin (5-HT), norepinephrine (NE), angiotensin II (Ang II), prostacyclin (PGI2), acetylcholine (ACH), and nitroglycerin (GTN) were reproducible and stable throughout the 32-day period of study in dogs subjected to sham URAC. The vascular responses to 5-HT, Ang II, and PGI2 were enhanced day 1 post-URAC, before mean arterial pressure (MAP), cardiac output (CO), or total peripheral resistance (TPR) increased. The magnitude of the enhanced reactivity progressed on days 4 and 32 post-URAC, as hypertension developed. The pressor responses to NE did not change from pre-URAC values until CO and MAP were elevated. The vasodepressor responses to ACH and GTN diminished over a 12-day period post-URAC, in parallel with the change in CO, but prior to any increase in TPR. These data suggest that in dogs with 2-KGH changes in vascular reactivity precede the development of the increased MAP and TPR of hypertension. The lack of uniformity of the onset of the reactivity changes to the different agonists suggests that both intrinsic factors and pressure changes modify the vascular wall in the early and later stages of 2-KGH.
The effects of thiosalicylic and hydroxyethylethylenediaminetriacetic acids on the absorption and excretion of 54Mn and 65Zn in the duodenally dosed sheep
Authors: Ivan M. , Veira D. M. , Hidiroglou M.
Published: April 2011

Nine sheep, each prepared with a single cannula in the ascending duodenum and a reentrant cannula in the terminal ileum were fed a purified diet deficient in manganese and zinc for a period of 1 month. The sheep were then divided into three equal groups and duodenally dosed with a mixture containing MnSO4, ZnSO4, 54Mn, 65Zn, and water (control), thiosalicylic acid (TSA), or hydroxyethylethylenediaminetriacetic acid (HEDTA). Blood and ileal digesta were sampled for 24 h and total urine and feces were collected for 14 days after dosing. Plasma uptake of 54Mn 1 h after dosing was more than threefold higher in the HEDTA-dosed sheep than in other sheep, indicating higher absorption of 54Mn. This was accompanied by a lower flow of 54Mn through the terminal ileum during the first 12 h after dosing. However, total 14-day urinary and fecal excretion of 54Mn and 65Zn were apparently higher in the HEDTA-dosed sheep than in other sheep, each approaching 100% of the dose. Excretion of 54Mn and 65Zn in TSA-dosed sheep was apparently higher than in control sheep. Plasma uptake 65Zn was higher in TSA-dosed sheep and lower in HEDTA-dosed sheep than in control sheep. However, total 14-day excretion of 65Zn in feces and urine was slightly higher in TSA-dosed than in control sheep. It was concluded that chelation of Mn and Zn with HEDTA or TSA would aggravate rather than alleviate a Mn or Zn deficiency in sheep.
Effects of reduced PO2 on rapid-drive-induced hyperpolarization of diastolic transmembrane potential in feline cardiac Purkinje strands
Authors: Benditt David G. , Scheinman Melvin M. , Snow Thomas R. , Strauss Harold C.
Published: April 2011

Using standard microelectrode techniques, we evaluated effects of diminished oxygen tension on the magnitude and time course of frequency dependent changes in maximum diastolic transmembrane potential (MDP) and on alteration of action potential duration (APD) in feline Purkinje fibers. MDP was recorded continuously during a control period (cycle length (CL) = 1000 ms), during a 5-min period of rapid drive (CL = 400 ms) and following return to pacing CL = 1000 ms. Rapid drive resulted in hyperpolarization of MDP from control value; and after return to pacing CL = 1000 ms, MDP gradually depolarized, eventually attaining a steady state value within ± 0.5 mV of the control value. The difference between hyperpolarized MDP value and final steady-state value was designated VH, and the decline of MDP towards steady-state value approximated an exponential function (time constant = τVH). Exposure to reduced [Formula: see text] (75 ± 2.1 mmHg vs. control 473 ± 39.1 mmHg) (1 mmHg = 133.322 Pa) resulted in reduction in the magnitude of VH (6.2 ± 3.43 mV vs. 7.8 ± 2.73 mV, mean ± SD, p < 0.005) and shortening of APD within 0–24 min, while measurable prolongation of τVH (75 ± 18.5 vs. 54 ± 9.0 s, p < 0.005) began at 25–49 min following onset of reduced [Formula: see text]. These observations suggest that rate-related changes of MDP in cardiac tisues are oxygen dependent, and they support previously reported analagous observations in nerve which suggested that frequency dependent potential changes may in part reflect alterations of electrogenic Na-K pump activity.
Interaction of excitatory and inhibitory inputs to motoneurons in man
Authors: Bawa Parveen
Published: April 2011

Two separate paradigms were used to study the interaction of excitatory and inhibitory inputs to the motoneuron pools of lower leg muscles in human subjects. During inhibition of tibialis anterior muscle from Ia soleus afferents, the probability of firing of the higher threshold unit decreased more than that of the lower threshold unit in 14 out of 18 pairs. When soleus motor units were recruited by tendon vibration reflex and the subject voluntarily inhibited one unit, the higher threshold unit was silenced first in 55 pairs, whereas the lower threshold unit ceased firing first in 29 pairs, and 16 showed inconsistencies. It is concluded that although under standard conditions there is orderly derecruitment of units which is the reverse of recruitment, vibration of the intact human tendon brings about synaptic effects in the spinal cord which affect the normal patterns of recruitment and derecruitment of motor units.
Subendocardial verses transmural myocardial infarction: relationship to the collateral circulation in canine and porcine hearts
Authors: Warltier David C. , Zyvoloski Mark G. , Gross Garrktt J. , Brooks Harold L.
Published: April 2011

In the present study, the relationship between transmural perfusion gradients and myocardial infarct size and distribution in canine and porcine hearts was characterized. Anesthetized pigs (N = 6) and dogs (N = 7) underwent a 2-h occlusion and 5-h reperfusion of the distal third of the left anterior descending coronary artery. The area at risk for infarction and ultimate infarct size were determined by fluorescein dye infused intracoronary and nitro blue tetrazolium stain, respectively. Myocardial perfusion within normal, ischemic, and infarcted regions was determined by the radioactive microsphere technique in each species. In dogs, infarction was subendocardial and comprised 29.9 ± 5.5% of the area at risk, while in pigs infarction was transmural and comprised 50.1 ± 4.2% (p < 0.05). Collateral perfusion of the subendocardium of infarcted regions in pig and dog hearts was similar (0.05 mL∙min−1∙g−1), while flow to the subepicardium was significantly (p < 0.05) higher in dogs than in pigs (0.25 versus 0.05 mL∙min−1∙g−1). The data demonstrate that species differences in myocardial infarct size and shape are related to differences in coronary collateral blood flow. The smaller subendocardial infarction in dog hearts is related to a relatively high subepicardial perfusion and transmural infarction in pig hearts owing to the lack of collateral perfusion in subepicardium as well as subendocardium.
Acid phosphatase and protease activities in immobilized rat skeletal muscles
Authors: Witzmann Frank A. , Troup John P. , Fitts Robert H.
Published: April 2011

The effect of hind-limb immobilization on selected lysosomal enzyme activities was studied in rat hind-limb muscles composed primarily of type I, IIA, or IIB fibers. Following immobilization, acid protease and acid phosphatase both exhibited significant (P < 0.05) increases in their activity per unit weight in all three fiber types. Acid phosphatase activity increased at day 14 of immobilization in the three muscles and returned to control levels by day 21. Acid protease activity also changed biphasically, displaying a higher and earlier rise than acid phosphatase. The pattern of change in acid protease, but not acid phosphatase, closely parallels observed muscle wasting. The present data therefore demonstrate enhanced proteolytic capacity of all three fiber types early during muscular atrophy. In addition, the data suggest a dependence of basal hydrolytic and proteolytic activities and their adaptive response to immobilization on muscle fiber composition.
Nutrient control of brain neurotransmitter synthesis and function
Authors: Anderson G. Harvey , Johnston Janice L.
Published: April 2011

The significance of normal variations in dietary and plasma nutrient content to brain metabolism and function began to receive examination in the past decade. It is now clear that the brain is much more sensitive to variations in nutrient supply than previously thought. Indeed, it seems likely that the diet-induced plasma fluctuations in nutrients, either as a result of their cofactor roles or as neurotransmitter precursors, are important components of feedback systems assisting the brain in controlling many of its functions. This discovery has suggested new approaches to understanding mechanisms controlling brain function and to treatment of diseases of the brain.
Acute effects of amiodarone in the isolated dog heart
Authors: Kobayashi Miyoharu , Godin Diane , Nadeau Réginald
Published: April 2011

Direct injection of amiodarone (10–1000 μg) into the sinus node artery of the isolated blood-perfused dog atrium produced dose-dependent negative inotropic and chronotropic responses that were unaffected by atropine. Intraarterial amiodarone also had a negative inotropic action on isolated left ventricular muscle preparations electrically paced at 1.5 to 2.0 Hz. A continuous infusion of 100 μg/min of amiodarone significantly suppressed the positive chronotropic effect of norepinephrine whether expressed in percent change or in absolute values; its positive inotropic effect expressed in percent change was not suppressed but rather enhanced by amiodarone. Calcium chloride induced positive chronotropic and inotropic effects expressed in percent change were, respectively, slightly suppressed and enhanced by amiodarone. Intravenous injection of amiodarone (5 mg/kg) decreased the heart rate and blood pressure of the support dog and produced a negative inotropic response in the isolated left ventricular muscle preparation perfused with arterial blood from the support dog. These results suggest first, that amiodarone has direct negative inotropic and chronotropic effects that are not mediated by cholinergic mechanisms and second, that it has a depressive action on norepinephrine and calcium-induced positive chronotropic effects and an enhancing action on their positive inotropic effects.
The fate of orally administered [4-l4C]phenytoin in two healthy male volunteers
Authors: Kadar D. , Fecycz T. D. , Kalow W.
Published: April 2011

A recovery study was conducted to determine whether phenytoin (DPH), like the barbiturates, is metabolized via the recently discovered N-glucosidation pathway. Virtually 100% of the ingested 14C-labelled doses in two subjects could be accounted for in the excreta within 5 days, with 35% in feces and 65% in urine. Radioactivity in the urine was entirely due to free and conjugated 5-(4-hydroxy-phenyl)-5-phenylhydantoin (p-HPPH) and the dihydrodiol, and that in the feces mostly due to the unmetabolized drug. There was no indication of phenytoin N-glucoside being excreted in either the urine or feces of either subject, although one of the subjects was known to possess a particularly strong N-glucosidation capacity for barbiturates. The other subject was a poor metabolizer of debrisoquine and sparteine. Nevertheless, the DPH disappearance from serum and the DPH metabolite excretion in urine were virtually alike in these two subjects, indicating that the debrisoquine 4-hydroxylating and DPH hydroxylating capacities may be separable entities.
Changes in cerebrospinal fluid and plasma vasopressin in the febrile sheep
Authors: Kasting Norman W. , Carr Daniel B. , Martin Joseph B. , Blume Howard , Bergland Richard
Published: April 2011

Plasma and cerebrospinal fluid (CSF) concentrations of vasopressin (AVP) were measured in conscious sheep during fever induced by iv endotoxin. Body temperature and blood pressure were also measured. AVP concentrations increased in both CSF and plasma although increases were not parallel. AVP concentrations in CSF were significantly correlated to increases in body temperature whereas plasma AVP concentrations were not. Neither CSF nor plasma AVP concentrations were correlated with changes in blood pressure. These data indicate that there may be independent regulation of AVP release into plasma and CSF compartments and supports the idea that AVP may have several physiological functions to perform during fever.
Receptor and postreceptor insulin resistance induced by in vivo hyperinsuiinemia
Authors: Martin C. , Desai K. S. , Steiner G.
Published: April 2011

We examined the effects of inducing hyperinsuiinemia in vivo in rats on the insulin receptors of, and the glucose oxidation by their adipocytes. Hyperinsulinemia was induced over a 2-week period by injecting NPH insulin subcutaneously. This was given in doses that were gradually increased to a final dose of 6 units/day. Profound hypoglycemia was avoided by providing supplemental sucrose to both the insulin-treated and control rats. The insulin concentration was eight times greater in the insulin-treated rats. However, they were not grossly obese and their adipocytes were not enlarged. The adipocytes of the hyperinsulinemic rats had a 25% lower maximal insulin binding capacity and were resistant to the effects of insulin on glucose oxidation. We felt that the hyperinsuiinemia was sufficient so that, despite their somewhat lower insulin binding capacity, these adipocytes would not bind less insulin in vivo than would adipocytes from control rats. Hence, we postulated that, this massive hyperinsulinemia not only down regulated the insulin receptor, but also led to a postreceptor resistance. This notion was supported by two lines of in vitro data. First, even at maximally effective medium concentrations of insulin, the maximum rate of glucose oxidation by the adipocytes from hyperinsulinemic rats reached a plateau which was less than that reached by cells from controls. Second, when this in vitro glucose oxidation was related not merely to the medium insulin concentration, but to the amount of insulin bound to adipocytes, the response of the hyperinsulinemic rats' cells was always lower than control. These changes occurred in the absence of any difference in fat cell size. Thus, in vivo hyperinsulinemia led to insulin resistance in adipocytes. This was associated both with down regulation of the insulin receptors and with a postreceptor defect.