bluuebunny/crossref_metadata_2025 huggingface dataset:
The interaction of glutamic and aspartic acids with excitatory amino acid receptors in the mammalian central nervous system
Authors: McLennan H. , Wheal H. V.
Published: April 2011

Firing rates of single thalamic neurones of the cat and the rat have been measured as functions of the currents used to apply glutamic and aspartic acids electrophoretically. Hill plots of the data suggest that three amino acid molecules are probably required to activate an excitatory receptor.
Species differences in the reactivation of organophosphate-inhibited plasma esterases by diacetymonoxime
Authors: Ecobichon D. J.
Published: April 2011

A study was conducted to assess whether the protection afforded to organophosphate-poisoned animals by diacetylmonoxime (DAM) was correlated with the reactivation of non-essential aliesterases (AliE). In vitro, the DAM-catalyzed reactivation of plasma AliE and cholinesterases (ΨChE) of rat, rabbit and guinea pig inhibited by 10−5 M diisopropylphosphorofluoridate (DFP) and O,O-dimethyl-2,2-dichlorovinyl phosphate (DDVP) was investigated. Marked reactivation of the rat plasma enzymes was achieved with 10 mM DAM. Higher concentrations (30 mM) were necessary for the slow reactivation of rabbit and guinea pig plasma AliE. Reactivation of the ΨChE of these species was comparatively slow. Reactivation of DDVP-inhibited esterases proceeded in all species at a more rapid rate than those inhibited by DFP. The dependence of ΨChE reactivation upon concomitant more rapid reactivation of AliE by DAM was demonstrated using Sephadex fractionated AliE and ΨChE but only a marked effect was observed with the rat, suggesting that the plasma AliE of this species is functionally different.The in vitro observations were confirmed by in vivo studies in rats and rabbits. DAM (50 or 150 mg/kg), administered to atropinized rats 15 min before a lethal dose of DFP, protected the animals. Few severe toxic signs were observed and reactivation of both plasma AliE and ΨChE occurred. In contrast, DAM protected the rabbit against a lethal dose of DFP but only reactivation of the erythrocyte acetylcholinesterase was observed.
Dexclamol, a candidate for neuroleptanalgesia
Authors: Jaramillo J.
Published: April 2011

Dexclamol, a potent neuroleptic, was found to potentiate the anesthetic actions of halothane when given at relatively small doses to albino rats. This effect was further enhanced by the addition of phenoperidine, a potent analgesic, at doses that per se did not influence the effects of halothane. Droperidol was used as a standard. In potentiating the effects of halothane, dexclamol behaved both qualitatively and quantitatively in a manner similar to droperidol. Dexclamol, however, was approximately 37 times less potent than droperidol in antagonizing the vasopressor effects of epinephrine.
Is cyclic guanosine monophosphate the internal 'second messenger' for cholinergic actions on central neurons?
Authors: Krnjević K. , Puil E. , Werman R.
Published: April 2011

The most consistent effects produced by intracellular injections of guanosine 3′,5′-cyclic monophosphate (cGMP) (but not 5′-guanosine 5′-monophosphate in spinal motoneurons of cats are a rise in membrane conductance, acceleration in time course of spike potentials, and accentuation of the post-spike hyperpolarization. Associated changes in resting potential are smaller, less constant, and more often in the depolarizing than hyperpolarizing direction. cGMP tends to increase electrical excitability but reduces excitatory post-synaptic potential amplitudes. Most of the effects of intracellular cGMP are quite different from, or indeed opposite to, those of either extra- or intracellular applications of acetylcholine and therefore not consistent with the proposal that cGMP is the internal mediator of muscarinic actions.
Cardiac responsiveness to β-adrenergic stimulation in experimental anemia
Authors: Biro G. P. , Foëx P. , Clarke T. N. S. , Prys-Roberts C.
Published: April 2011

Cardiac reactivity of β-adrenergic stimulation was assessed by isoproterenol dose–response curves (dose range 0.025–0.4 μg/kg) before and 1 h after the rapid induction of anemia in dogs anesthetized with halothane:N2O:O2. Anemai (hematocrit = 16 ± 4%) was induced by an isovolumic exchange transfusion with Dextran 70, and was followed by significant increments in cardiac output (+57 ± 9%), max dP/dt of the left ventricle (+37 ± 7%), and in peak acceleration of blood flow in the ascending aorta (+46 ± 13%). Anemia was associated with a significant reduction of the chronotropic responses to all but the lowest dose of isoproterenol. The simultaneously determined inotropic responses (max dP/dt) where the same before and after the induction of anemia. The responses in terms of peak acceleration of aortic blood flow tended to be greater in the anemic than in the control phase, at all dose levels used. These findings indicate that in rapidly induced experimental anemia the heart is capable of responding to marked degrees of β-adrenergic stimulation, representing a more than twofold increase in the dP/dt.
Preparation and characterization of adrenocortical plasma membrane angiotensin II receptors
Authors: Forget Gilles , Heisler Seymour
Published: April 2011

A bovine adrenocortical particulate fraction prepared by zonal ultracentrifugation and banding between ρ20 1.08 and 1.101 in a linear sucrose gradient bound 7.3 times more [3H]angiotensin II (ATII) per milligram protein than the original homogenate. Enzyme marker and electron microscope studies indicated that this fraction was largely devoid of mitochondria while being enriched in smooth membranes of predominantly plasmalemmal origin. The binding of labeled ATII was maximal after 10 min incubation (22 °C) and remained at equilibrium for at least 20 min thereafter. [3H]ATII binding was completely inhibited by saturating concentrations of nonradioactive ATII. The high-affinity binding site in the preparation had a specific binding capacity of 2.38 pmol∙mg−1, with an equilibrium constant of 2.36 × 108 M−1. Inhibition–displacement studies with unlabeled ATI, ATII, ATII fragments, analogs, and antagonists show that the receptor fraction has the highest affinity for the intact native octapeptide. ACTH and bradykinin had no specific effects on [3H]ATII binding. The current study suggests that the receptor fraction may be of use in a highly sensitive ATII radioligand assay.
The contribution of the extrahepatic bile ducts to bile formation
Authors: Strasberg S. M. , Petrunka C. N. , Ilson R. G.
Published: April 2011

This study was performed to determine the contribution of the extrahepatic bile ducts to bile flow in the rhesus monkey. Bile flow from the two sides of the liver was divided. The major extrahepatic bile ducts remained connected to one side of the liver only. Bile flow, and the concentrations of [14C]erythritol, bicarbonate, bile acid, and bilirubin in bile samples from the two sides of the liver, in the fed state were measured and compared. An estimate of the net flow from the extrahepatic ducts was obtained from the [14C]erythritol concentrations on the two sides of the liver and the bile flow rate on the side with the extrahepatic ducts. The [14C]erythritol bile–plasma ratio was significantly lower in bile collected from the side with the extrahepatic bile ducts, than in bile from the other side of the liver. About 10% of total hepatic bile flow originated in the extrahepatic bile ducts, in the fed state. The bicarbonate-[14C]erythritol concentration ratio was significantly higher in bile from the side with the extrahepatic bile ducts. Bicarbonate – bile acid, and bicarbonate–bilirubin concentration ratios were also significantly higher in bile from the side of the liver with the extrahepatic ducts. The extrahepatic bile ducts have a physiologically significant role in the secretion of bile water. Bicarbonate is secreted in association with water in the extrahepatic ducts.
Patterns of gastric electrical and motor activity in miniature pigs
Authors: Rozé Claude , Couturier Daniel , Debray Charles
Published: April 2011

Gastric myoelectrical and mechanical activity was recorded in miniature pigs using chronically implanted electrodes and strain gauge force transducers. Semiautomated methods were devised to obtain quantitative evaluations of the electrical and mechanical parameters measured in fasted and fed animals. The patterns of gastric myoelectrical activity in pigs were, on the whole, similar to the patterns described in dogs, including regular cyclic control activity and spike response activity associated with muscle contraction. However, several points were peculiar to the species studied: conduction velocity of pacesetter potentials increased only moderately in the antrum; tachygastria never occurred in the experiments; in response to a standard meal, the frequency of pacesetter potentials gradually increased; mechanical activity proceeded at its maximal force immediately after feeding and for a long period; no evidence of 'migrating electrical complexes' was found in the stomach during fasting. The 40-min period following administration of a test meal appeared especially suitable for pharmacological or physiological experiments in which inhibitory factors are to be tested on the stomach.
Lack of release of ACTH from the denervated rat pars intermedia in vivo
Authors: Kraicer Jacob
Published: April 2011

The purpose of this study was to ascertain whether the pars intermedia of the rat adenohypophysis, isolated from direct innervation via the infundibular stem, could maintain adrenal cortical weight and plasma corticosterone levels. We compared the adrenal cortical response of rats 40 days after either complete hypophysectomy, hypophysectomy with reinsertion of only the pars distalis, or hypophysectomy with reinsertion of only the nervosa-intermedia. Adrenal weight and plasma corticosterone levels were partially maintained in the group with reinserted pars distalis. These parameters were not different from the complete hypophysectomy group in the animals with reinserted nervosa-intermedia. Thus, the pars intermedia, with its nerve supply disrupted, cannot maintain adrenal cortical function.
Vasopressin contamination as a cause of some apparent renal actions of prolactin
Authors: Keeler R. , Wilson N.
Published: April 2011

The injection or infusion of NIAMDD prolactin (NIH P-S-10) into unanesthetized rats resulted in water and electrolyte retention with a large increase in urine osmolality but no effect on glomerular filtration rate. Since these effects on urine output were also observed in homozygous Brattleboro rats, the antidiuretic activity could not have been caused by the release of endogenous antidiuretic hormone.Radioimmunoassay of NIH prolactin showed that it was contaminated with vasopressin (20 ng/mg of prolactin). By comparison, Sigma prolactin had no observed effect on urine excretion and contained very little vasopressin (2.5 ng/mg).It is concluded that some of the renal effects of prolactin that have been reported in the literature may have been caused by the contaminating vasopressin.
Endorphin activity in anterior, intermediate, and posterior pituitary
Authors: LaBella F. , Downey G. , Queen G. , Pinsky C.
Published: April 2011

The content of endogenous morphine-like substance in bovine pituitary and brain was determined by an opiate radioreceptor assay. The intermediate lobe was most concentrated in activity and the brain least concentrated. Most of the endorphin is obtained in a 120 000 g-min fraction from pituitary or brain homogenates.
A Markov chain characterization of human neutrophil locomotion under neutral and chemotactic conditions
Authors: Boyarsky Abraham , Noble Peter B.
Published: April 2011

The locomotion of human neutrophils is modelled by a continuous-time Markov chain model consisting of five states: state 0, where the cell is stationary, and four motile states whose directions are defined by the four quadrants of a Cartesian plane. In this paper, the Markov property is verified experimentally in special cases. Further experimental evidence for the model is provided by the waiting-time distributions in each of the five states, which are well approximated by exponential distributions. Using the steady-state distribution of the Markov chain as a measure of the ultimate motion of the cells, it is possible to detect the effect of known chemotactic agents upon neutrophil locomotion. Other useful parameters describing neutrophil locomotion are presented.
The development of the hypothalamo–pituitary axis in the neonatal rat: pituitary and serum prolactin concentrations
Authors: Dussault J. H. , Walker P. , Dubois J. D.
Published: April 2011

Using highly specific double-antibody radioimmunoassay techniques, we have measured pituitary and serum prolactin (PRL) concentrations in neonatal rats from birth to 60 d. Pituitary PRL concentration was low at birth in both sexes and peak prepuberal values were attained at 25–28 d. Following this time, pituitary PRL concentrations in females were significantly higher than those observed in males (p < 0.01). Serum PRL concentrations were low at birth in both sexes and remained low until 15 d, when they rose to peak values just before puberty. There were no significant sex differences with respect to serum PRL concentrations. These data indicate that hypothalamic control of PRL secretion develops during the neonatal period of the rat. The relationship of this developmental process in the neonatal rat as a possible model for the study of the midgestational hypothalamic maturation of the human fetus is discussed.
Fate of orally dosed linamarin in the rat
Authors: Barrett M. D. , Hill D. C. , Alexander J. C. , Zitnak A.
Published: April 2011

Wistar rats, about 100 g in weight, were dosed by stomach tube with 30 mg of pure linamarin. No intact linamarin was identified in the feces or blood but 5.65 mg was excreted in the urine along with 0.823 mg of thiocyanate ion. A 50-mg dose of linamarin was lethal to 7 of 10 rats receiving this dose.
Fiberoptic ear densitometer for measurement of cardiac output
Authors: Sekelj P. , Retfalvi S. , Lavoie A.
Published: April 2011

This study presents theory, operation, and evaluation of a new earpiece method for measurement of cardiac output using the multichannel fiberoptic system recently described. The system includes an earpiece of simple design and small size suitable for applications in all subjects regardless of their age or size. The method requires no withdrawal and analysis of blood samples for calibration. Compared with earlier techniques the present method, based on measurements in three distinct absorption bands in the infrared, provides an increase in accuracy of the estimations.This accuracy was tested in children undergoing routine cardiac catheterization. Comparisons were made in 39 instances (25 subjects) between simultaneously carried out determinations by the earpiece and cuvette densitometer methods. The agreement was good (r = 0.97, p < 0.001), with a standard deviation of the differences of 0.479 ℓ/min, or 10.2% of the mean values derived from the cuvette curves. The regression equation describing the values derived from ear curves in terms of values from the cuvette curves differed only slightly from unity (Y = 0.167 + 0.985X).The usefulness of the fiberoptic earpiece technique both in clinical investigations and cardiovascular diagnosis was demonstrated.
A free-running endogenous rhythm of the resting heart rate in man
Authors: Doust John W. Lovett
Published: April 2011

A sine-wave oscillating rhythm of the heart rate is reported in 24 out of 31 resting healthy subjects. Identification of these free-running cycles was by spectral analysis of minute-by-minute recordings of electrocardiograms, and in a few cases by inspection of cardiotachometer records. The periodicity of this rhythm was circa 10 min and was intermediate in frequency between the rapid fluctuations with frequencies of 15, 30, and 60 s and those of a frequency recurrent every 90 min already described in the literature. Our cycles were independent of age and sex.
Nonshivering thermogenesis in the rat. II. Measurements of blood flow with microspheres point to brown adipose tissue as the dominant site of the calorigenesis induced by noradrenaline
Authors: Foster David O. , Frydman M. Lorraine
Published: April 2011

Cardiac output (CO) and the fractional distribution (FD) of γ-labeled plastic microspheres (15 ± 5 μm) injected into the left ventricle were used to calculate blood flow to organs and tissues of barbital-sedated warm-acclimated (WA) or cold-acclimated (CA) white rats at rest and then during their maximal calorigenic response to infused noradrenaline (NA). Flow to the major masses of brown adipose tissue (BAT) increased in WA rats from a mean of 0.81 ml/min (0.92% of CO) at rest to 13.5 ml/min (11.4% of CO) during calorigenesis; it increased in CA rats from 2.3 ml/min (2.6% of CO) to 57.2 ml/min (33.5% of CO). Flow to skeletal muscle increased in WA rats from 12.0 ml/min at rest to 15.1 ml/min during calorigenesis; it increased in CA rats from 9.9 ml/min to 14.5 ml/min. Flow to heart and to muscles involved in respiratory movements was two to five times greater during calorigenesis. Flow to most other tissues and organs increased or decreased by less than 40%.Arteriovenous differences in blood oxygen [Formula: see text] across interscapular BAT (IBAT) during rest and during calorigenesis together with measurements of blood flow established that IBAT alone accounted for 14% of the extra O2 used by CA rats during NA-induced calorigenesis. If during calorigenesis other masses of BAT have an [Formula: see text] as great as that for IBAT, the major masses of BAT together would account for 60% of the calorigenic response of the CA rat. In contrast, even if the skeletal muscle of the CA rat used all the O2 in the blood flowing through it during calorigenesis, it could not have been responsible for more than 12% of the calorigenic response.The rat, long considered to exemplify major participation of skeletal muscle in nonshivering thermogenesis (NST), now becomes just one of a growing list of species for which there is explicit or circumstantial evidence that NST occurs principally in BAT. It thus becomes reasonable to propose as a general principle that BAT is the primary anatomical site of the NST that is characteristic of many small mammals: CA adults, newborns, and hibernators alike.
Baclofen: effects on amino acid release
Authors: Potashner S. J.
Published: April 2011

This study investigated the effects of the antispastic drug β-(p-chlorophenyl)-γ-amino-butyric acid (Baclofen) on the release of amino acids from slices of guinea pig cerebral cortex. Electrical stimulation of slices evoked the release of endogenous14C-labelled glutamate, aspartate, γ-aminobutyric acid (GABA), alanine, and threonine–serine–glutamine (labelled via metabolism of D-[U-14C]glucose), and of exogenous glutamate, aspartate, GABA, and α-aminoisobutyrate. The releases of endogenous14C-labelled glutamate, aspartate, and GABA were three to seven times larger than those of other amino acids. Baclofen (4 μM) inhibited the evoked release of endogenous 14C-labelled glutamate and aspartate by nearly 60%, that of endogenous14C-labelled threonine–serine–glutamine and alanine by 14–19%, but had no effect on that of endogenous14C-labelled GABA. The drug inhibited the evoked release of the exogenous amino acids by 25–32%. Baclofen doubled the incorporation of 14C from D-[U-14C]glucose into endogenous alanine but was without effect on either the incorporation of 14C into the other endogenous amino acids or the turnover of any of the endogenous14C-labelled amino acids. Because endogenous14C-labelled glutamate, aspartate, and GABA are probably released from nerve terminals, Baclofen selectively suppresses the release of excitatory amino acids from nerve terminals. Similarly, depression of the release of excitatory transmitter (presumably glutamate) from primary afferent terminals in the spinal cord may at least partly explain the antispastic action of Baclofen.
Excitation and inhibition of neurons in the trigeminal nucleus caudalis following periaqueductal gray stimulation
Authors: Andersen R. K. , Lund J. P. , Puil E.
Published: April 2011

Electrical stimulation (3–4 shocks, 300 Hz, 30–150 μA) of the periaqueductal gray matter (CG) or dorsal raphé nucleus (DR) of decerebrate cats reduced or abolished the jaw-opening reflex response evoked by stimulation of either the tooth pulp or infraorbital nerve. In addition, CG or DR stimulation inhibited the response of 12 out of 16 trigeminal nucleus caudalis neurons to activation of their sensory afferent inputs. Ten other neurons recorded in the same sites, and often at the same time, but which did not respond to the sensory inputs utilized, were excited by identical stimuli to CG or DR. This excitatory response was blocked by intravenously administered naloxone (0.1–0.2 mg/kg). It is suggested that those neurons which are excited by CG and DR stimulation may be interneurons involved in pre- and post-synaptic inhibition of sensory transmission during stimulus-produced or narcotic analgesia.
Effects of brain monoamine depletion on chlorpromazine-induced hypothermia in rabbits
Authors: Lin M. T.
Published: April 2011

The thermal responses of three groups of control, 6-hydroxydopamine (6-OHDA) treated and 5,7-dihydroxytryptamine (5,7-DHT) treated rabbits to the administration of chlorpromazine (CPZ) were assessed at three different ambient temperatures (Ta: 2, 22, and 32 °C). Depleting catecholamines (CA) in brain with 6-OHDA produced a decrease in metabolic rate, in respiratory evaporative heat loss, and in ear blood flow at both Ta's of 2 and 22 °C, while depleting 5-hydroxytryptamine (5-HT) contents in brain with 5,7-DHT produced the opposite responses at the same Ta's. However, these amine-depleted animals maintained their rectal temperatures within normal limits over a wide range of Ta's tested. Furthermore, intraperitoneal administration of CPZ produced hypothermia at both Ta's of 2 and 22 °C. The major cause of the CPZ-induced hypothermia was an inhibition of metabolic heat production at Ta of 2 °C. At Ta of 22 °C, the CPZ-induced hypothermia was due to both a decrease in heat production and an increase in ear blood flow. However, CPZ hypothermia was attenuated in the CA-depleted animals, but was potentiated in the 5-HT-depleted animals. The data indicate that brain monoamines are involved in the central mechanisms of CPZ-induced hypothermia.
Inhibition of passive lung anaphylaxis in the rat by AY-25,674
Authors: Greenberg R. , Martel R. R. , Smorong K.
Published: April 2011

The antiallergic properties of AY-25,674 were studied in a model of passive lung anaphylaxis. AY-25,674 caused a dose-related inhibition of antigen-induced bronchoconstriction in the passively sensitized rat. AY-25,674 was found to be twice as potent as disodium cromoglycate (DSCG) when injected intravenously. The oral administration of AY-25,674 also effectively inhibited antigen-induced bronchoconstriction. A tachyphylactic effect of repeated administration was found when the rats were pretreated with a large dose of AY-25,674. The compound did not significantly antagonize the bronchoconstriction produced by 5-hydroxytryptamine. These results indicate that AY-25,674 is an orally effective antianaphylactic compound with a mode of action similar to that of DSCG in preventing allergic mediator release.
Phosphate-induced renal calcification in the rat
Authors: Hitchman A. J. , Hasany S. A. , Hitchman A. , Harrison J. E. , Tam C.
Published: April 2011

Studies were done to investigate nephrocalcinosis produced in weanling female Wistar rats fed pelleted, semisynthetic diets. The rats were fed diets varying in concentrations of Ca and P supplied as inorganic salts for periods of 4–6 weeks and results compared with control rats fed laboratory rodent chow for the same period of time. Measurement of renal Ca and P concentrations showed that nephrocalcinosis was produced by semisynthetic diets with inorganic phosphate concentrations as low as 0.5% on a weight basis; in contrast, rats fed regular laboratory chow (P = 0.72%) showed no evidence of nephrocalcinosis. The severity of the lesion was proportional to dietary phosphate concentrations from 0.5 to 1.0% but other dietary factors modified the severity of the lesion. With the lower dietary phosphate of 0.5%, increasing dietary Ca from 0.5 to 1.0% decreased the severity of the renal calcification. Decreasing protein concentrations from 25 to 15% casein increased the severity of the renal lesions. Other dietary factors also appear to modify the phosphate-induced nephrocalcinosis since no lesions occurred in rats on laboratory chow. It is suggested that the availability of dietary phosphate may be a factor. The phosphate in the semisynthetic diets was totally inorganic while the natural foods of laboratory chow contain, at least in part, organic phosphate.
Aryl hydrocarbon (benzo[a]pyrene) hydroxylase in rat mammary tissue during pregnancy and lactation
Authors: Fysh Jacquelene M. , Okey Allan B.
Published: April 2011

Rats are highly resistant to mammary tumour induction by polycyclic aromatic hydrocarbons during pregnancy and lactation. Since local changes in hydrocarbon metabolism in mammary tissue or altered hepatic metabolism might contribute to the resistance, aryl hydrocarbon hydroxylase (AHH) activity in microsomes from mammary tissue and liver was measured throughout the course of pregnancy and lactation in Sprague–Dawley rats. Basal constitutive AHH activity in mammary tissue and liver of untreated rats did not change significantly during pregnancy or lactation. In rats injected with beta-naphthoflavone (BNF), AHH activity in liver microsomes increased approximately 25-fold over basal levels and the degree of enzyme induction by BNF was relatively constant throughout pregnancy and lactation. In mammary tissue, however, the induction of AHH by BNF increased dramatically from about 10 times basal at the beginning of pregnancy to over 80 times basal on day 3 of lactation. The high inducibility of mammary AHH during late pregnancy and early lactation exists both when activity is expressed per unit microsomal protein or per unit tissue DNA. Increased inducibility of mammary AHH may contribute to the resistance rats show to hydrocarbon carcinogenesis during pregnancy and lactation. Since the activity of hepatic AHH does not change significantly during pregnancy or lactation, it seems unlikely that resistance is due to altered hepatic metabolism of the hydrocarbons. AHH activity can be associated both with 'metabolic activation' and 'detoxification' of aromatic hydrocarbons. The balance between local 'activation' and 'detoxification' of aromatic hydrocarbons by AHH in mammary tissue during different physiological states is important in determining susceptibility to carcinogenesis and requires further study.
Receptors for angiotensin: A critical analysis
Authors: Regoli D.
Published: April 2011

Angiotensin exerts numerous contractile and secretory effects by activating specific receptors. Recent pharmacological findings obtained with this peptide in various laboratories are analyzed, using the order of potency of agonists and the affinity of competitive antagonists as criteria for the classification of receptors for angiotensin in several systems. The analysis is restricted to experiments in which biological effects have been measured. Desensitization (the third criterion for classification of receptors) is discussed and a new protocol is proposed for its utilization.The analysis reveals that receptors for angiotensin in intestinal and vascular smooth muscles, in the heart, and in the vas deferens are all of the same type, while the receptors mediating the release of catecholamines from the adrenal medulla and those subserving the steroidogenic action on the adrenal cortex remain still unidentified.The recently proposed role of ATI as mediator of renin in the adrenal medulla is not substantiated by pharmacological findings with decapeptide antagonists. Moreover, the utilization of ATI as an agonist to determine the order of potency of angiotensins and the use of SQ 20881 as an inhibitor of the converting enzyme have shown serious limitations and should be reconsidered.The hypothetical role of ATIII as mediator of the renin–angiotensin system in the adrenal cortex, at least in other species than the rat, appears to be supported by the high affinity of heptapeptide antagonists for the adrenocortical receptor. However, these antagonists have generally been compared with [Sar1,Ala8]-ATII, a compound which is definitely inadequate for evaluating the affinities of octapeptides in the adrenal cortex. Therefore most of the data supporting the role of ATIII in this system have to be carefully reconsidered.Analogues of ATII are proposed for using as agonists and as antagonists instead of the natural angiotensins (for determining the order of potency of agonists) and instead of [Sar1,Ala8]-ATII (for measuring the affinities of competitive antagonists).
Interaction de la dimethyl prostaglandine E2 et de l'ethanol sur la secretion pancreatique du rat
Authors: Bourry J. , Demol P. , Sarles H.
Published: April 2011

We have studied the action of 16,16-dimethyl prostaglandin E2 methyl ester (DiMePGE2) on pancreatic secretion in the unanesthetized rat with pancreatic and duodenal fistulae. DiMePGE2 inhibited volume, protein secretion, and bicarbonate output. The inhibition of protein concentration is dose related (ED50 = 5.35 μg/rat).DiMePGE2 was effective by the intraduodenal, intravenous, and intraperitoneal routes.Intraduodenal infusion of ethanol alone (2 mL 16% (v/v) in 1 h) strongly increased protein secretion (concentration, +30%; output, +69%). When 4 μg DiMePGE2 was injected intraperitoneally just before the ethanol infusion, the secretory effect of ethanol disappeared and the inhibition was similar to that observed with DiMePGE2 alone.
Effects of noradrenaline and metaraminol on isolated aortic strips and auricles obtained from untreated and reserpine-treated rabbits
Authors: Tayyaba Bushra , Qayum A. , Yusuf S. M.
Published: April 2011

The isolated aortic strips of the untreated rabbits responded to noradrenaline in concentrations ranging from 20 to 160 ng/mL, whereas similar preparations from reserpine-treated animals responded to lower concentrations (from 2.5 to 10 ng/mL) and larger effects were produced by concentrations ranging from 20 to 160 ng/mL. Comparatively stronger concentrations (from 0.4 to 1.6 μg/mL) of metaraminol were required to produce suitable contractile responses, which were not modified by reserpine pretreatment. On the isolated auricles obtained from untreated rabbits, noradrenaline was used in concentrations of 20 and 80 ng/mL, but these concentrations were reduced to 2.5 and 10 ng/mL in the case of tissues obtained from reserpinized rabbits. Comparatively stronger (0.2 and 0.8 μg/mL) concentrations of metaraminol were required to produce a stimulant effect on this preparation, and the sensitivity was not altered by reserpine pretreatment. These observations lead to the conclusions that though reserpine pretreatment produces a well-marked increase in the sensitivity of isolated rabbit aortic strips and auricles to noradrenaline, it does not modify the sensitivity of these preparations to metaraminol. Reserpine was used in 0.3 mg/kg doses injected subcutaneously for 3 successive days.
Activity of precentral neurons during torque-triggered hand movements in awake primates
Authors: Wong Y. C. , Kwan H. C. , Murphy J. T.
Published: April 2011

In monkeys performing a handle-repositioning task involving primarily wrist flexion–extension (F–E) movements after a torque perturbation was delivered to the handle, single units were recorded extracellularly in the contralateral precentral cortex. Precentral neurons were identified by passive somatosensory stimulation, and were classified into five somatotopically organized populations. Based on electromyographic recordings, it was observed that flexors and extensors about the wrist joint were specifically involved in the repositioning of the handle, while many other muscles which act at the wrist and other forelimb joints were involved in the task in a supportive role. In precentral cortex, all neuronal responses observed were temporally correlated to both the sensory stimuli and the motor responses. Visual stimuli, presented simultaneously with torque perturbations, did not affect the early portion of cortical responses to such torque perturbations. In each of the five somatotopically organized neuronal populations, task-related neurons as well as task-unrelated ones were observed. A significantly larger proportion of wrist (F–E) neurons was related to the task, as compared with the other, nonwrist (F–E) populations. The above findings were discussed in the context of a hypothesis for the function of precentral cortex during voluntary limb movement in awake primates. This hypothesis incorporates a relationship between activities of populations of precentral neurons, defined with respect to their responses to peripheral events at or about single joints, and movements about the same joint.
Tissue distribution of cold-induced thermogenesis in conscious warm- or cold-acclimated rats reevaluated from changes in tissue blood flow: The dominant role of brown adipose tissue in the replacement of shivering by nonshivering thermogenesis
Authors: Foster David O. , Frydman M. Lorraine
Published: April 2011

Radioactive microspheres (12–16 μm) were used to measure cardiac output (CO), its fractional distribution, and hence tissue blood flow in conscious, warm-acclimated (WA) or cold-acclimated (CA) white rats exposed to temperatures of 25, 21, 6, −6, and −19 °C, the objective being to assess the tissue distribution of cold-induced thermogenesis. Total oxygen consumption was also measured. CA rats at 25 °C (CA25) had elevated arteriovenous shunting and other signs of heat stress. CA21 proved more suitable controls for the CA group. The cold-induced changes in blood flow to total skeletal muscle not involved in respiratory movements (M) and to the major masses of brown adipose tissue (BAT) were quantitatively very different in the two acclimation groups: in WA25 and CA21 flows to M were 31 (0.24 CO) and 27 (0.17 CO) mL/min, respectively, while flows to BAT were 2.1 and 9.7 mL/min; in WA−19 and CA−19 flows to M were 62 (0.32 CO) and 35 (0.16 CO) mL/min, respectively, while flows to BAT were 25 and 56 mL/min. In contrast, the effects of cold exposure on flows to other tissues and organs were remarkably alike in the two acclimation groups: e.g., flows to heart, ribcage, and diaphragm increased about three times between 25 and −19 °C, flow to the skin fell about 50%, and flows to the hepatosplanchnic region and kidneys were little or not at all affected by cold exposure. Estimates of the contributions of different tissues and organs to cold-induced thermogenesis were made on the basis of the relative changes in blood flow. It is concluded that BAT is by far the dominant anatomical site of the increased heat production of cold-exposed CA rats, and that nonshivering thermogenesis in BAT supplements considerably the shivering thermogenesis of cold-exposed WA rats.
Action of oxytocin on mammary gland: Influence of hypotonicity
Authors: Ferrier B. M.
Published: April 2011

The enhancement of the response of an isolated strip of lactating mouse mammary gland to oxytocin, resulting from dilution of the Tyrode solution in which oxytocin is administered, is due to the effects of hypotonicity per se and not to changes in concentration of any of the ions in the bathing solution. Inhibition of membrane ATPase also causes an enhancement, which is probably due to activation of a secondary facilitating mechanism, rather than to enhancement of the entire train of oxytocin-induced reactions. A variety of conditions which alter the response to oxytocin have the same effect on the response to acetylcholine. Hypotonicity can therefore increase the sensitivity of this bioassay for oxytocin, but not its selectivity.
The time course of brain and blood catecholamines, catechol O-methyltransferase, and amino acids in rats convulsed by oxygen at high pressure
Authors: Banister E. W. , Singh A. K.
Published: April 2011

The time course of changes in blood and brain catecholamines, catechol (O-methyltransferase (COMT), ammonia, and amino acids leading to convulsion by high pressure oxygen breathing (OHP) in rats has been investigated. Brain catecholamines were suppressed by OHP. They changed in phase with brain COMT concentration and consequently were not due to the action of this degrading enzyme. Convulsive actions seem not to be influenced by brain catecholamine concentration. Blood adrenaline concentrations are, however, significantly elevated both prior to and during convulsions. In both brain and blood, ammonia concentration increases, glutamate decreases, and glutamine–aspargine increases. It is proposed that the efficacy of the glutamate–glutamine ammonia buffering system in blood and brain is important in the prevention of the onset of convulsions but that when brain γ-aminobutyric acid is depressed to critical levels, convulsions result.
Effet du benzoate d'oestradiol sur la fonction hépatique et sur le métabolisme du cholesterol et des acides biliaires chez la caille
Authors: Laugier Christian , Pageaux Jean-François , Duperray Bernard , Pacheco Henri , Brard Emile
Published: April 2011

Immature female quails were treated for 6 days with estradiol benzoate at daily 0.01-, 0.02-, 0.1-, and 1-mg dosages. At the end of treatment, bile outflow, biliary cholesterol (CST), and bile acid (BA) secretory rates and liver, bile, and serum CST and BA levels were determined. Some quails were used to measure the ratio (R) of the rates of intravenously injected [2-14C]acetate radioactivity incorporation in cholic (C) and chenodeoxycholic (CDC) acids excreted in bile. The oestrogenic treatments at doses greater than 0.01 mg/day caused a marked disturbance in hepatic function and in CST and BA metabolism: they induced an increase in relative liver weight, liver CST stores, serum CST, C, CDC, and SGOT levels and in choleresis (respectively up to 56, 57, 650, 6000, 700, 42, and 235%, increase at the daily 0.1-mg dosage) and they decreased bile total BA and CDC levels, bile and serum CDC to C level ratios, and R ratio (by 71, 82, 69, 84, and 58%, respectively). An increase in the bile salts independent fraction of bile was responsible for hypercholeresis, whether alone at low dosage or in conjunction with other factors at higher dosage. These results are compared with those obtained in mammals, particularly in the rat.
Structure–activity studies on the inhibition of γ-aminobutyric acid uptake in brain slices by compounds related to nipecotic acid
Authors: Wood J. D. , Tsui D. , Phillis J. W.
Published: April 2011

Various N-methyl derivatives of nipecotic acid and related compounds were tested as inhibitors of γ-aminobutyric acid (GABA) uptake into mini slices. N-Methylnipecotic acid, N,N-dimethyinipecotic acid, N-methylguvacine, and N-methylnicotinic acid were effective inhibitors. None of them, however, were as potent as nipecotic acid itself. All the effective inhibitors, including nipecotic acid, also inhibited the uptake of L-proline, but to a much lesser extent. Four of the test compounds produced a depressant action on cerebral cortical neurons, but even N-methylisoguvacine, the most potent in this respect, was considerably less active than GABA. None of the test compounds caused any clearly discernible changes in the gross behaviour or appearance of mice in the 1-h period following intramuscular injection. It was concluded that methylation of the N atom of nipecotic acid and its derivatives was unlikely to lead to the development of agents with greater experimental or therapeutic potential than that of nipecotic acid itself, if the action of the agent was dependent on its effects on GABA uptake.
Simultaneous measurement of cell loss and gastric potential difference in the rat: Effects of short-term fasting
Authors: Harding R. K. , Morris G. P. , Doan C.
Published: April 2011

These experiments utilized ex vivo gastric chamber preparations in both fed rats and rats fasted for 14–18 h. A new, simple technique is described for the quantification of cells in small volumes of fluid. The data indicate that exposure to solutions of 50 mM HCl was accompanied by greater cell loss in fasted vs. fed animals. The gastric potential differences of mucosae exposed to Ringer's mammalian saline, and subsequently to 50 mM HCl, were consistently at least 10 mV more negative in fasted animals.
The effect of ambient temperature on β-adrenergic responsiveness in rats
Authors: Barney C. C. , Katovich M. J. , Fregly M. J. , Tyler P. E. , Dasler A. R.
Published: April 2011

The responses of tail skin and colonic temperatures of female rats to ambient temperatures of 20, 22, 24, 26, 28, and 30 °C were measured. Within this range, colonic temperature was stable while tail skin temperature increased linearly with increasing ambient temperature. Administration of the β-adrenergic agonist, d,l-isoproterenol, at 10.0, 25.0, and 62.5 μg/kg, sc, at each ambient temperature was accompanied by increases in tail skin and colonic temperatures that were dependent on both the dose of isoproterenol administered and the ambient temperature. The integrated responses of tail skin temperature following administration of the three doses of isoproterenol were maximal at an ambient temperature of 26 °C while the integrated responses of colonic temperature were maximal at 30 °C. The results suggest that tests of β-adrenergic responsiveness using this technique should be performed at an ambient temperature of 26 °C for maximal sensitivity.
Uptake of liposome-entrapped mannitol by diaphragm
Authors: Nakatsu K. , Cameron D. A.
Published: April 2011

Tissue uptake of liposome-entrapped radioactive mannitol was examined in rats and mice after both intravenous and intraperitoneal injection. In accord with results from other laboratories, liver and spleen effectively accumulated liposomes. Diaphragm also took up significant amounts of label. In nearly all cases the radioactive content of perfused tissues was less than tissues which were not perfused but this was statistically significant in only a few comparisons.
Release of exogenous γ-[3H]aminobutyric acid during seizure activity in chronically denervated and normal cat cortex
Authors: Reiffenstein R. J.
Published: April 2011

The hypothesis that the seizure susceptibility of chronically denervated cortex is due to interruption of recurrent inhibitory pathways was tested by examining the release of 3H-labeled γ-aminobutyric acid ([3H]GABA) from chronic slabs and normal cortex of cats. Seizure activity was maintained throughout the test periods in both normal and chronically isolated cortex. When methacholine was used to evoke seizure activity, [3H]GABA release was depressed in both normal and epileptic cortex, suggesting that the mechanism of seizure genesis by cholinomimetics involves suppression of inhibitory neuron activity. Pentylenetetrazol-induced seizures evoked a small, equal increase in [3H]GABA efflux from epileptic and normal cortex. Continuous electrical stimulation evoked a large, and again equal increase in [3H]GABA release. Preseizure efflux of [3H]GABA was the same from chronic slabs and normal cortex in all experiments. Since the interruption of recurrent inhibitory pathways by chronic denervation would result in a decreased resting and seizure-evoked release of [3H]GABA, results obtained do not support the above-mentioned hypothesis.
Effect of somatostatin suppression of glucagon secretion on glucose production in sheep
Authors: Brockman Ronald P.
Published: April 2011

The effect of somatostatin (SRIF) on glucagon and insulin secretion was examined in fed and fasted sheep. This was related to changes in glucose production. Infusion of SRIF at 80 μg/h caused a marked reduction in plasma glucagon concentrations. However, the insulin response to SRIF infusion was not consistent; its concentrations decreased occasionally, but often did not change. The depression of glucagon was not associated with a significant reduction in blood glucose concentrations in either fed or fasted sheep, but was associated with a reduction in glucose production by 12–15%. The inhibitory effect of insulin on glucose production was not markedly increased by glucagon deficiency. Infusion of insulin at 1.17 U/h with SRIF decreased glucose production only an additional 10%. Thus, it appears that under basal conditions pancreatic hormonal influences on hepatic glucose production were relatively small in sheep. This implies that under normal conditions in sheep, substrate supply has a much greater impact on hepatic glucogenesis than do hormones.
Effect of alcohol on thermal balance of man in cold water
Authors: Fox G. R. , Hayward J. S. , Hobson G. N.
Published: April 2011

The effects of alcohol on core cooling rates (rectal and tympanic), skin temperatures, and metabolic rate were determined for 10 subjects rendered hypothermic by immersion for 45 min in 10 °C water. Experiments were duplicated with and without a 20-min period of exercise at the beginning of cold water immersion. Measurements were continued during rewarming in a hot bath. With blood alcohol concentrations averaging 82 mg 100 mL−1, core cooling rates and changes in skin temperatures were insignificantly different from controls, even if the exercise period was imposed. Alcohol reduced shivering metabolic rate by an overall mean of 13%, insufficient to affect cooling rate. Alcohol had no effect on metabolic rate during exercise. During rewarming by hot bath, the amount of 'afterdrop' and rate of increase in core temperature were unaffected by alcohol. It was concluded that alcohol in a moderate dosage does not influence the rate of progress into hypothermia or subsequent, efficient rewarming. This emphasizes that the high incidence of alcohol involvement in water-related fatalities is due to alcohol potentiation of accidents rather than any direct effects on cold water survival, although very high doses of alcohol leading to unconsciousness would increase rate of progress into hypothermia.
Actions of various gastrointestinal peptides on the isolated amphibian spinal cord
Authors: Phillis J. W. , Kirkpatrick J. R.
Published: April 2011

The effects of a number of peptides which are found in the gastrointestinal tract have been ascertained on the direct current recorded dorsal and ventral root responses of the isolated hemisected toad spinal cord. Motilin, substance P, bombesin, neurotensin, and thyrotropin-releasing hormone had potent depolarizing actions on dorsal root terminals and motoneurons. These substances evoked discernable effects at concentrations as low as 10−7 M, or even lower with motilin. The effects of motilin, neurotensin, and thyrotropin-releasing hormone were greatly reduced or abolished by perfusion of the preparation with tetrodotoxin. Adrenocorticotrophic hormone, secretin, and pancreozymin (cholecystokinin) also depolarized dorsal root terminals and motoneurons. The effects of secretin and cholecystokinin were not abolished by tetrodotoxin. Leu- and Met-enkephalin had weak hyperpolarizing actions on the dorsal and ventral root potentials of repetitively stimulated preparations. Gastrin, gastric inhibitory peptide, glucagon, and somatostatin had no apparent effects on the responses of the preparation. Angiotensin and vasopressin both had rather weak depolarizing effects on the dorsal and ventral roots.