bluuebunny/crossref_metadata_2025 huggingface dataset:
Biological effects of rat iso-atrial natriuretic peptide and brain natriuretic peptide are indistinguishable from each other
Authors: Wigle D. A. , Bennett B. M. , Jennings D. B. , Sarda I. R. , Flynn T. G. , Pang S. C.
Published: April 2011

Rat brain natriuretic peptide (rBNP) and iso-atrial natriuretic peptide (iso-rANP) were discovered independently by two research laboratories. They are considered to be members of the B-type natriuretic peptides. Except for the Gln/Leu substitution at position 44, the amino acid sequence of iso-rANP is identical with that of the C-terminal 45 amino acids of rat pro-BNP and with the 5-kDa cardiac peptide from rat atria. To determine whether this amino acid substitution can modify the known biological effects of rBNP and iso-rANP, the present investigation examined the cardiovascular and renal responses, vasorelaxant effect, receptor binding characteristics, and cyclic GMP production by the two peptides in relation to that of rat atrial natriuretic peptide (rANP). Results indicate that rBNP and iso-rANP are indistinguishable from each other in terms of these known biological activities of atrial natriuretic peptide. We therefore conclude that rBNP and iso-rANP are identical peptides and that the amino acid substitution at position 44 represents a polymorphic form of the rat B-type natriuretic peptide.Key words: atrial natriuretic peptide, brain natriuretic peptide, cardiovascular response, vasorelaxation, cyclic GMP, receptor binding.
Respiratory chain defect of myocardial mitochondria in idiopathic dilated cardiomyopathy of Doberman pinscher dogs
Authors: McCutcheon Laura Jill , Cory Colin Robert , Nowack Linda , Shen Hua , Mirsalami Medhi , Lahucky Rudolf , Kovac Lubomir , O'Grady Michael , Horne Rhonnie , O'Brien Peter James
Published: April 2011

Idiopathic dilated cardiomyopathy (IDCM) is a primary myocardial disease of unknown cause. We tested the hypothesis that IDCM was associated with a myocardial metabolic defect by determining a comprehensive biochemical profile of metabolite concentrations and enzyme activities for the major metabolic pathways of the myocardium. We used the Doberman pinscher breed as a naturally occurring canine model of IDCM and compared its myocardial profile with that of healthy adult mongrels. Compared with controls, myocardium in IDCM had markedly reduced mitochondrial electron transport activity and myoglobin concentration, in association with acidosis and energy depletion following anoxic challenge: 60% decreased NADH dehydrogenase and 50% decreased ATP synthetase activities; 90% decreased myoglobin concentration; and 30% reduced ATP and 50% increased lactate and proton concentrations. Sarcoplasmic reticulum Ca2+-transport ATPase was decreased by 42%. There was a 15% compensatory increase in fatty acid oxidation and Krebs cycle activity. Other biochemical changes were mild by comparison with the mitochondrial defects. We conclude that IDCM is associated with a marked impairment of mitochondrial production of ATP, arising from decreased activity of the mitochondrial electron transport system, including myoglobin. These changes may be secondary to an underlying genetic defect or may indicate a deficiency of the mitochondrial respiratory chain that predisposes this breed to heart failure.Key words: dilated cardiomyopathy, congestive heart failure, mitochondria, electron transport system, myoglobin, NADH dehydrogenase.
Adrenergic receptors (α1 and α2) modulate different potassium conductances in sympathetic preganglionic neurons
Authors: Inokuchi Hiroe , Yoshimura Megumu , Polosa Canio , Nishi Syogoro
Published: April 2011

Intracellular recordings were made from 168 sympathetic preganglionic neurons in the slice of the second or third thoracic spinal-cord segment of the adult cat to study the actions of noradrenaline on these neurons. Noradrenaline, applied by superfusion (0.5–50 μM), produced membrane depolarization in 73 neurons and membrane hyperpolarization in 39 neurons. In 26 neurons noradrenaline produced a biphasic response (depolarization–hyperpolarization or vice versa). The depolarization was blocked by prazosin, while the hyperpolarization was blocked by yohimbine. The noradrenaline-induced depolarization was associated with an increase in neuron input resistance, while the noradrenaline-induced hyperpolarization was associated with a decrease in neuron input resistance. Both responses decreased in amplitude with membrane hyperpolarization and were nullified at around the potassium equilibrium potential EK. The null potential of both responses became more and less negative with a decrease and an increase, respectively, in the extracellular potassium concentration. When the membrane potential was made more negative than EK, the noradrenaline-induced hyperpolarization reversed to depolarization in all cases, whereas in only 4 of 12 cases did the noradrenaline-induced depolarization reverse to hyperpolarization. These data suggest that the noradrenaline-induced depolarization is a result of a decrease, while the noradrenaline-induced hyperpolarization is a result of an increase in K+ conductance. Cobalt (2 mM), low calcium – high magnesium, and intracellular EGTA markedly reduced or abolished the noradrenaline-induced depolarization but had no significant effect on the noradrenaline-induced hyperpolarization. Barium (2 mM) depressed both responses. Tetraethylammonium (10–30 mM), 4-aminopyridine (3 mM), and cesium (2 mM) had no effect on either response. These data suggest that the noradrenaline-induced depolarization is a result of an inactivation of a background calcium-sensitive K+ conductance, while the noradrenaline-induced hyperpolarization is due to activation of a calcium-insensitive potassium conductance.Key words: K+ conductances, catecholamines, Ca2+ dependent, K+ current, spinal cord.
Changes in the glucose transporter of brain capillaries
Authors: Harik Sami I.
Published: April 2011

Brain capillary endothelium has a high density of the GLUT-1 facilitative glucose transporter protein. This is reasonable in view of the brain's high metabolic rate for glucose and its isolation behind unique capillaries with blood – brain barrier properties. Thus, the brain endothelium, which constitutes less than 0.1% of the brain weight, has to transport glucose for the much larger mass of surrounding neurons and glia. I describe here the changes that occur in the density of glucose transporters in brain capillaries of subjects with Alzheimer disease, where there is a decreased cerebral metabolic rate for glucose, and in a novel clinical entity characterized by defective glucose transport at the blood – brain barrier. In subjects with Alzheimer disease, cerebral microvessels showed a marked decrease in the density of the glucose transporter when compared with age-matched controls, but there was no change in the density of glucose transporters in erythrocyte membranes. Thus, I believe that the decreased density of glucose transporters in the brains of subjects with Alzheimer disease is the result rather than the cause of the disease. In contradistinction, the primary defect in glucose transport at the blood – brain barrier in subjects with the recently described entity is associated with decreased density of GLUT-1 in erythrocyte membranes.Key words: brain microvessels, capillary endothelium, blood – brain barrier, glucose transporter, Alzheimer disease, hypoglycorrhachia.
Glycolytic and oxidative metabolic contributions to potassium ion transport in rat cerebral cortex
Authors: Rosenthal Myron , Sick Thomas J.
Published: April 2011

Putative roles of glycolytic and oxidative metabolism in the removal of potassium ion from the extracellular space were examined in rat cerebral cortex. In response to direct electrical stimulation of the cerebral surface, the activity of extracellular potassium ion [Formula: see text] transiently increased. Inhibition of glycolysis with iodoacetate prolonged the time required for dissipation of the elevated [Formula: see text]. This slowing was most evident in the early period after stimulation, when [Formula: see text] was relatively high. Levels of high-energy intermediates were unchanged by iodoacetate. In contrast, severe hypoxemia was without effect during the early phase of K+ removal but hypoxemia slowed the later restoration of the [Formula: see text] baseline. These data demonstrate that the rapid removal of potassium ion from the extracellular space following intense neuronal activity is aided by the Embden–Myerhoff metabolic pathways and perhaps by direct coupling of ATP produced by glycolysis. We suggest that removal of potassium ion from the brain extracellular space depends on two ATP pools, one derived from oxidative phosphorylation, the other from glycolysis. The glycolytic ATP pool may be most involved in the early and rapid phase of potassium clearance; the oxidative ATP pool may be more associated with the second and slower phase of [Formula: see text] clearance, and with the maintenance of the [Formula: see text] baseline under 'resting' conditions.Key words: potassium, glycolysis, oxidative phosphorylation, hypoxemia, iodoacetate.
Relationships between ions and energy metabolism: cerebral calcium movements during ischaemia and subsequent recovery
Authors: Erecińska Maria , Silver Ian A.
Published: April 2011

Intra- and extra-cellular concentrations of calcium were measured in hippocampal neurones of areas CA1 and CA3 during 8 min ischaemia and short-term (up to 60 min) recovery. During an ischaemic insult, [Ca2+]i increased progressively and [Ca2+]e decreased. There were large interneuronal differences, although, in general, rises in [Ca2+]i were much larger in area CA1 than in CA3. Restitution of blood flow was followed by movements of calcium in the directions opposite to those seen during ischaemia: [Ca2+] in the extracellular space gradually rose whereas that inside neurones fell. Within 30 – 60 min, calcium balance was restored to the original pre-ischaemic level. It is postulated that (i) large increases in [Ca2+]i in cerebral neurones during ischaemia are related to the high density of pathways on neurones that allow calcium entry; (ii) differences in the amount of calcium accumulated during periods of oxygen deprivation between neurones of the CA1 and CA3 regions are linked to the level of glutamatergic input (and hence excitatory synapses) that the two areas receive; (iii) restitution of blood flow and consequent rapid restoration of ATP synthesis permit reactivation of calcium-eliminating mechanisms. These latter involve especially sequestration by the mitochondria and extrusion by the plasma membrane Ca pump, which restore the low cytoplasmic [Ca2+].Key words: brain ischemia, calcium homeostasis, microelectrodes.
Pharmacological properties of excitatory amino acid induced changes in extracellular calcium concentration in rat hippocampal slices
Authors: Arens J. , Stabel J. , Heinemann U.
Published: April 2011

We have studied extracellular ionic changes induced by iontophoretic application of excitatory amino acids in rat hippocampal slices. In contrast to kinetics of changes in [Ca2+]o, kinetics of changes in [K+]o, [Na+]o, [Cl−]o as well as in extracellular space size were comparable for different glutamate receptor agonists. Thus, α-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA), quisqualate (quis), and kainate caused reductions in [Ca2+]o followed by an increase of [Ca2+]o above baseline, whereas glutamate, aspartate, N-methyl-D-aspartate (NMDA), and DL-homocysteic acid caused only reductions in [Ca2+]o. After blocking the NMDA receptors with ketamine and 2-amino-5-phosphonovaleric acid (2-APV), glutamate-induced decreases in [Ca2+]o were followed by an overshoot. Reductions of the transmembrane Na+gradient by lowering [Na+]o, blocking of the Na+–K+ ATPase by lowering [K+]o, and application of ouabain blocked the overshoots after quis application, whereas vanadate, a blocker of the Ca2+–Mg2+ ATPase, had no effects. Lithium enhanced the reductions in [Ca2+]o and blocked the overshoots. Amiloride also reduced the overshoots. All organic Ca2+ entry blockers diminished reductions of [Ca2+]o but increased the overshoots. Inorganic Ca2+ antagonists had variable effects. Ni2+ had similar effects as the organic Ca2+ entry blockers while Cd2+ reduced both the [Ca2+]o decreases as well as the subsequent overshoots. Co2+ had initially a similar action as Ni2+. With prolonged application, [Ca2+]o decreases became augmented and, during wash, overshoots could no longer be elicited. We suggest that the overshoots in [Ca2+]o are due to a combined effect of extracellular space shrinkage and activation of the Na+/Ca2+ exchanger. This would imply that NMDA receptor activation blocks extrusion of Ca2+ from the cells. We tested the hypothesis that quis-induced intracellular Ca2+ release and extrusion of Ca2+ from the cells contributed to the overshoots. Dantrolene was without effect on the quis-induced signals, while ryanodine reduced the overshoots. Caffeine on the other hand diminished the [Ca2+]o decreases with no effects on the overshoots. To test for possible second messenger routes by which NMDA receptor activation might slow Ca2+ extrusion from cells, we investigated the effects of arachidonic acid and N-monomethyl-D-arginine on the quis-induced signals. While these agents reduced decreases in [Ca2+]o, they had no clear effects on the overshoots. Thus a possible route by which NMDA receptor activation may affect Ca2+ extrusion from cells has still to be elucidated.Key words: glutamate, quisqualate, N-methyl-D-aspartate, Ca2+ concentration, hippocampus, rat.
Astrocytes, as well as neurons, express a diversity of ion channels
Authors: Sontheimer H.
Published: April 2011

The electrophysiologist's view of brain astrocytes has changed markedly in recent years. In the past astrocytes were viewed as passive, K+ selective cells, but it is now evident that they are capable of expressing voltage- and ligand-activated channels previously thought to be restricted to neurons. The functional importance of most of these ion channels is not understood at present. However, from studies of astrocytes cultured from different species and brain regions, we learned that like their neuronal counterparts astrocytes are a heterogeneous group of brain cells showing similar heterogeneity in their ion-channel expression. Not only are subpopulations of astrocytes within areas of the brain equipped with specific sets of ion channels but, furthermore, regional heterogeneity is apparent. In addition, astrocyte ion channel expression is dynamic and changes during development. Some ion channels are only expressed postnatally, yet others appear to be expressed only during certain stages of development. Interestingly, the expression of some astrocyte channels, including Na+, Ca2+, and some K+ channels, appears to be controlled by neurons via mechanisms that are presently unknown. Some studies suggest roles for astrocyte channels in basic cell processes such as cell proliferation. Thus, although the role of some astrocyte channels remains unclear, our understanding of astrocyte physiology is starting to take shape and points towards roles of ion channels not involved in electrogenesis.Key words: astrocyte, ion channel, development, review, transmitter receptor.
Alkaline extracellular pH shifts generated by two transmitter-dependent mechanisms
Authors: Chesler M. , Chen J. C. T.
Published: April 2011

Recent studies of the effect of γ-aminobutyric acid (GABA) on brain extracellular pH are reviewed. Experiments were performed on isolated turtle cerebellum, using double-barrelled pH-sensitive microelectrodes. Superfusion of GABA (1 mM) caused a rapid extracellular alkaline shift accompanied by a rise in extracellular K+. Washout of GABA was often associated with an acid rebound, concomitant with an undershoot of extracellular K+. The GABA-evoked alkaline shift was blocked by picrotoxin and mimicked by the GABA-A agonists isoguvacine and muscimol. The response persisted in the nominal absence of extracellular calcium, but it was reversibly abolished in nominally bicarbonate free media. In contrast, extracellular alkaline shifts evoked by repetitive stimulation of the parallel fibers were amplified in bicarbonate-free media and were insensitive to picrotoxin. These results indicate the existence of separate, transmitter-dependent mechanisms of extracellular alkalinization: (i) a GABA-A receptor mediated process, most likely associated with efflux of bicarbonate ions across GABA-A anion channels and (ii) a bicarbonate-independent process associated with excitatory synaptic transmission.Key words: GABA, bicarbonate, extracellular pH, alkaline shift.
Extracellular K+, pH, and volume changes in spinal cord of adult rats and during postnatal development
Authors: Syková E. , Jendelová P. , Svoboda J. , Chvátal A.
Published: April 2011

Activity-related transient changes in extracellular K+ concentration ([K+]e), extracellular pH (pHe), and extracellular volume (EC volume) were studied by means of ion-selective microelectrodes in the adult rat spinal cord in vivo and in neonatal rat spinal cords isolated from pups 3 – 14 days of age. Repetitive electrical nerve stimulation (10 – 100 Hz) in adults elicited increases in [K+]e by about 2.0 – 3.5 mM, followed by a poststimulation K+ undershoot and triphasic alkaline – acid – alkaline changes in pHe. In 3- to 6-day-old pups, the [K+]e increased by as much as 6.5 mM at a stimulation frequency of 10 Hz, and this was accompanied by an alkaline shift. Increases in [K+]e as large as 1.3 – 2.5 mM accompanied by an alkaline shift were evoked by a single electrical stimulus. Stimulation in 10- to 13-day-old pups produced smaller [K+]e change and an acid shift, which was preceded by a small initial alkaline shift, as in adult rats. We conclude that glial cells buffer the activity-related [K+]e increase and alkaline pHe shifts. Mg2+ blocked the alkaline but not the acid shift. Acetazolamide had no effect on the alkaline shift but blocked the acid shift. The alkaline shift was enhanced and the acid shift blocked by Ba2+, amiloride, 4-acetamido-4′-isothiocyanotostiibene-2,2′-disulfonic acid (SITS), and 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS). Activity-related acid shifts therefore have a complex mechanism, which includes Na+/H+ exchange, Cl−/HCO3− exchange, or Na+/Cl−/H+/HCO3− antiport, Na+–HCO3− cotransport, and H+ efflux through voltage-sensitive H+ channels. Application of GABA evoked an alkaline shift in the pHe baseline, which was blocked by picrotoxin. The activation of GABA-gated Cl− channels, which induces a passive net efflux of bicarbonate, can therefore lead to an alkaline shift in pHe. The poststimulation alkaline shifts were blocked by ouabain and reflect coupled clearance of K+ and H+ by active transport processes. The EC volume in the adult rat occupies about 20–25% of the tissue; in neonatal cord, 28–40%. Electrical or adequate stimulation-evoked ionic changes in adult rats were accompanied by shrinkage of the extracellular space by 20–50%. We conclude that the size of the EC volume is altered during stimulation of an afferent input, central nervous system development, and peripheral or central injury.Key words: astrocytes, extracellular K+, extracellular pH, extracellular volume, development, neuroglia, spinal cord, rat.
Active skeletal muscle metabolism and tension production: the influence of biopsies
Authors: Graham T. E. , Wolfe B. , Barclay J. K.
Published: April 2011

The influence of repeated sampling by the biopsy technique on skeletal muscle's metabolic and force-output responses was studied using the in situ canine gastrocnemius preparation. The left muscle was stimulated (8 V, 0.2 ms) for 1 h at 3 Hz. In the biopsy series (n = 9) muscle samples were taken at rest, and at 0.5, 2, 5, 15, 30, 45, and 60 min of stimulation. In the control series (n = 8) the left and right muscles were quick-frozen in N2 immediately after the 60 min of stimulation. The two series were not different in blood flow, [Formula: see text], arterial or venous [H+], muscle glycogen, or lactate release throughout the 60 min of activity. The lactate release was transient and was associated with an accumulation of intramuscular lactate and a period of rapid glycogenolysis. The biopsy series had a modest but significantly (p < 0.05) higher muscle lactate concentration both at rest and at the end of the contractions. The biopsy series also had less (p < 0.05) tension development throughout the hour; however, the O2 cost per unit of tension development was not different between groups, nor was the rate of tension decline over time different. This together with the similarities in perfusion, carbohydrate use, and lactate metabolism suggests that repeated biopsies had minimal impact on the muscle. The technique allows the collection of data over time; this improves the detail of experiments and means that fewer animals are required for a study.Key words: glycolysis, lactate, hydrogen ion, fatigue, muscle glycogen.
Steroidogenic enzyme activities in rat polycystic ovaries
Authors: Cooke Gerard M. , Brawer James R. , Farookhi Riaz
Published: April 2011

Ovaries containing multiple follicular cysts occur in a variety of anovulatory conditions. A macrocystic condition occurs spontaneously in rats following a single injection of estradiol valerate. The ovaries are small, and exhibit scant stromal tissue, few healthy follicles, and numerous large cystic and precystic follicles. We have also generated a microcystic condition by means of subcutaneous estradiol-containing silastic implants. These ovaries are large, and exhibit a stroma of hypertrophied lipid-filled cells, and numerous small cysts encircled by hypertrophied thecal cells. The macrocystic condition is associated with a uniformly attenuated plasma luteinizing hormone (LH) pattern, whereas large LH episodes characterize the microcystic condition. The marked dissimilarities between these two methods suggest that there may be corresponding differences in ovarian steroidogenic activity. We have measured the activity of enzymes involved in progestin and androgen biosynthesis in the two types of multicystic ovaries before and after LH – human chorionic gonadotropin (hCG) stimulation. Control ovaries were obtained at late proestrus from age-matched cycling animals. Radiometric enzyme assays for 3β-hydroxysteroid dehydrogenase (3β-HSD), 20α-hydroxysteroid dehydrogenase (20α-HSD), C17,20-lyase (lyase), and aromatase were conducted on the microsomal fraction of ovarian homogenates. 3β-HSD activity was reduced by > 50% in both types of cystic ovaries compared with controls. There was a slight elevation in the 3β-HSD activity of macrocystic ovaries in response to hCG. 20α-HSD activity was similar in controls and macrocystic ovaries but significantly lower (< 20% of control) in the microcystic ovaries. Lyase and aromatase activities were undetectable in cystic ovaries. Although these results are consistent with the morphology and plasma LH patterns characterizing the macrocystic condition, the microcystic ovary presents an unexpected paradox. These results underscore the complexity and multidimensional nature of cystic ovarian disease.Key words: steroidogenic activity, ovary, polycystic.
Effect of carbonic anhydrase III inhibition on substrate utilization and fatigue in rat soleus
Authors: Côté Claude , Riverin Hélène , Barras Marie-Josée , Tremblay Roland R. , Frémont Pierre , Frenette Jérôme
Published: April 2011

Carbonic anhydrase III (CA III; EC 4.2.1.1) is the most abundant cytosolic enzyme in type I skeletal muscle fibers. We have previously shown that inhibiting the CA III activity of type I muscle can influence fatigability. Our goal was to test the hypothesis that the influence on fatigability of CA III inhibition is linked to an increased utilization of carbohydrates. Rat soleus muscles were incubated in vitro in a physiological solution with or without CA inhibitor (methazolamide, 1 mM) and submitted to a fatigue protocol. When the bathing solution contained glucose, the muscles incubated with methazolamide maintained a higher level of tension production than control muscles for the first 55–60 min of the test compared with 35–40 min when glucose was not added. Measurement of muscle glycogen content revealed that muscles incubated with CA inhibitor were utilizing their glycogen at a higher rate than control muscles over the first 45 min of the fatigue protocol. When glycolysis was inhibited with sodium iodoacetate, fatigability was not influenced by the addition of a CA inhibitor. These results further support the existence of a link between CA III activity and energy metabolism in type I skeletal muscle fibers.Key words: muscle fatigue, sulfonamide, glycolysis, glycogenolysis, soleus muscle, glycogen, phosphorylase.
Reevaluation of the balloon in gastrointestinal manometry
Authors: Wilkes Peter R. H. , Hoskin Robert W. , Semlacher Eric A. , MacCannell Keith L. , Tyberg John V.
Published: April 2011

Although the flow-through catheter (FTC) system has been useful and satisfactorily accurate for gastrointestinal manometry, we hypothesized that a cylindrical, liquid-filled balloon would also accurately reflect stress imposed by a sphincter. Latex balloons were fitted over the side ports of a closed-end catheter. The responses of the balloon and FTC system were compared in a cylindrical chamber commonly identified as a Starling resistor. Independent, constant-pressure sources were used to control both the inwardly directed "contact pressure" of the Starling resistor (Ps) and the intraluminal fluid pressure (Plum). The balloon transducers responded linearly and accurately (slope = 1) to changes in both Ps and Plum within the test range (0–200 mmHg, 0–26.7 kPa). When either Plum or Ps was held constant and the other changed, the balloon transducers always accurately measured the higher of the two pressures. Although the performance of the FTC system was improved after the Starling resistor was lubricated, the FTC system sometimes responded inaccurately to changes in Ps. The ability of the balloon transducers to measure the contractions of the lower esophageal sphincter and of the esophagus was demonstrated. We conclude that the balloon transducer can measure sphincter pressure accurately and suggest that, in certain circumstances, it might be advantageous relative to the FTC system.Key words: balloon manometry, flow-through catheter system, Starling resistor, lower esophageal sphincter, contact pressure.
Hyperplastic effects of aerosolized sodium metabisulfite on rat airway mucus-secretory epithelial cells
Authors: Pon Douglas J. , Staden Carlo J. van , Boulet Louise , Rodger Ian W.
Published: April 2011

The ability of aerosolized sodium metabisulfite to induce hypertrophic and hyperplastic changes in rat airway secretory epithelial cells was investigated. A 10% solution of sodium metabisulfite was aerosolized into a Plexiglas exposure chamber, using an ultrasonic humidifier. The level of SO2 gas generated by this apparatus was measured to be 500 ppm. Measured levels of neutral and acidic mucous glycoproteins in extracts from tracheal and lung tissue were used as indices of hypertrophic (increases in mucus content per cell) and hyperplastic (increased numbers of cells containing mucus per gram of tissue) changes occurring in mucus-secreting cells of the airways. Exposing rats to sodium metabisulfite for 3 weeks resulted in profound increases in total neutral mucous glycoproteins found in tracheal and lung tissue (6.2-fold and 10.1-fold, respectively), compared with the H2O-treated counterparts. Total acidic mucous glycoproteins were significantly elevated in lung tissue only (13.5-fold). In addition, neutral and acidic mucous glycoproteins were elevated 20-fold and 9-fold, respectively, in bronchoalveolar lavage samples prepared from sodium metabisulfite exposed animals. These results indicate that aerosolized sodium metabisulfite may be a useful agent for developing small animal models of mucus hypersecretion.Key words: mucus, hypertrophy, hyperplasia, secretion, airway, epithelia.
Cardiovascular and single-unit responses to subfornical organ stimulation are abolished by pentobarbital anesthesia
Authors: Ferguson Alastair V. , Loucks Craig
Published: April 2011

The nature of reflex cardiovascular responses to electrical stimulation in the central nervous system has been suggested to be influenced by anesthetic. We report here that pressor responses to subfornical organ stimulation observed in urethane-anesthetized rats (n = 4) are absent, or reversed in animals under pentobarbital anesthesia (n = 5; Student's t test, p < 0.01, compared with urethane anesthesia. Single-unit recordings from identified hypothalamic neurons (n = 60) showed that the activation of these cells, by subfornical organ efferents, with systemic angiotensin observed in urethane-anesthetized animals (29 of 39 cells tested), was not observed under pentobarbital anesthesia (2 of 21 cells tested). Bicuculline treatment of pentobarbital-anesthetized rats (n = 5) restores small pressor responses to subfornical organ stimulation (t test, p < 0.05), suggesting that potentiated GABA inhibition underlies this modified state under pentobarbital anesthesia.Key words: subfornical organ, urethane, pentobarbital, cardiovascular, vasopressin, oxytocin.
Brown adipose tissue thermogenesis evoked by medial preoptic stimulation is mediated via the ventromedial hypothalamic nucleus
Authors: Thornhill J. , Jugnauth A. , Halvorson I.
Published: April 2011

Experiments were designed to determine if a functional ventromedial hypothalamic nucleus was required for the activation of brown adipose tissue thermogenesis evoked by medial preoptic stimulation. Male, urethane-anesthetized Long–Evans rats, maintained at 37 °C, had temperatures (thermistor probes for gastrocnemius, Tm; intrascapular brown adipose tissue, 7IBAT; colonic, Tc; and tail, Tt), gastrocnemius electromyogram activity (via stainless steel recording electrodes), and systemic blood pressure and heart rate (via a femoral arterial catheter) measured before and after a series of unilateral medial preoptic electrical stimulations (monophasic 0.5-ms pulses of 300 μA at 50 Hz for 30 s). Measurements were made (i) after an initial control medial preoptic electrical stimulation, (ii) after medial preoptic stimulation was applied 1 min following an intracranial injection of 300 nL of sterile saline or buffered 2% Lidocaine into the ipsilateral posterior hypothalamic nucleus or the ipsilateral ventromedial hypothalamic nucleus, and (iii) after recovery medial preoptic stimulation 45 min after Lidocaine was injected into the ventromedial hypothalamic nucleus. TIBAT and blood pressure rose significantly (p < 0.05) above the corresponding prestimulation control values with all protocols, except when Lidocaine was injected into the ventromedial hypothalamic nucleus prior to medial preoptic stimulation. Shivering (electromyogram) activity was not evoked following medial preoptic stimulation and Tm and Tt did not significantly change from the corresponding prestimulation values. A recovery medial preoptic stimulation 45 min after Lidocaine treatment of the ventromedial hypothalamic nucleus again evoked significant increases in TIBAT above the core temperature, similar to the rise in TIBAT seen after the first control medial preoptic stimulation. Pretreatment with Lidocaine into the posterior hypothalamic nucleus before medial preoptic stimulation caused no suppression of blood pressure compared with treatments after the control medial preoptic stimulation; however, TIBAT was reduced (p < 0.05) from the marked rise in TIBAT seen after the control stimulation. Results indicate that a functional ventromedial hypothalamic nucleus is required for medial preoptic stimulation to activate brown adipose tissue thermogenesis.Key words: brown adipose tissue thermogenesis, medial preoptic stimulation, thermoregulation, heat production.
Ultrastructure of interstitial cells of Cajal in the canine distal esophagus
Authors: Berezin I. , Daniel E. E. , Huizinga J. D.
Published: April 2011

The ultrastructure of canine distal esophagus was studied focusing on interstitial cells of Cajal (ICC) and their relationships to nerves and muscle. The distal esophagus consisted of two muscle layers composed of intertwining skeletal and smooth muscle bundles. The ICC formed an interconnecting network and were an integral part of these structures. The ICC communicated with one another and with adjacent smooth muscle cells through numerous gap junctions. The morphology of individual ICC resembled that observed in other gut regions. All interstitial cells were densely innervated. The highest density of ICC, just proximal to the lower esophageal sphincter, coincided with the previously reported highest incidence of occurrence of electrical slow wave type action potentials. Examination of a large number of structural associations of ICC led us to conclude that in the distal esophagus, two networks of ICC and nerves exist, one associated with the inner muscle layer, another associated with the outer muscle layer. These networks are not sheet-like structures, such as the network of ICC in the myenteric plexus or deep muscular plexus of the small intestine, but are three dimensional and are interspersed throughout both muscle layers. The networks do not extend into Auerbach's plexus. The main branches of the networks run along the long axis of the esophagus and seem ideally suited to facilitate communication in this direction. These observations suggest that esophageal interstitial cells are structurally organized in such a manner that they may play a role in pacemaking and neural control of esophageal motility.Key words: interstitial cells of Cajal, enteric nervous system, esophagus, ultrastructure, pacemaking.
Signal transduction events involved in bombesin-stimulated gastrin release from human G cells in culture
Authors: Buchan Alison M. J. , Meloche R. Mark
Published: April 2011

The mechanism of action of bombesin on human antral gastrin cells in culture was evaluated by modulating internal and external calcium levels and intracellular enzyme activities. Increasing extracellular calcium increased basal gastrin release and had an additive effect on bombesin-stimulated gastrin release. Removing extracellular calcium had no effect on bombesin-stimulated gastrin release. Inhibiting the activities of phospholipase C by neomycin and protein kinase C by staurosporine had no effect on basal release but decreased bombesin-stimulated gastrin release by up to 50%. Chelating intracellular calcium with BAPTA-AM also decreased bombesin-stimulated release by up to 50%. Increasing intracellular calcium levels with thapsigargin did not alter basal gastrin release and had no effect on bombesin-stimulated release. The preparation utilized was a mixed, primary cell culture. To demonstrate direct activation of gastrin cells, alterations in internal calcium levels were monitored by dual-excitation microfluorometry of fura 2-AM loaded cells. The individual cells were subsequently identified by immunocytochemistry, confirming that bombesin directly increases calcium levels in the G cells. The data indicated that bombesin acting directly on the G cells activated both arms of the phosphoinositol signalling pathway and that both activities were required for optimal gastrin release.Key words: gastrin, bombesin, intracellular calcium, protein kinase C, cultured cells.
Neurogenically evoked cerebral artery constriction is mediated by neuropeptide Y
Authors: Laher Ismail , Germann Peter , Bevan John A.
Published: April 2011

We examined the proposal that neuropeptide Y (NPY) released from nerve endings constricts cerebral arteries. Neurogenic vasoconstriction of rabbit basilar arteries is of adrenergic origin but is resistant to blockade by classical α-adrenoceptor antagonists. Tetrodotoxin-sensitive contractions of the rabbit basilar artery were elicited by transmural stimulation of nerves. The contractions were inhibited by incubation of tissues with an antiserum to NPY (0.32 μL undiluted immune serum/mL); addition of prazosin (0.1 μM) did not further attenuate the nerve-mediated contraction. The antiserum to NPY also antagonized vasoconstriction due to exogenously administered NPY and was without effect on responses due to histamine or angiotensin. Our results indicate that neurogenic vasoconstriction of the rabbit basilar artery is largely due to the release of NPY and that it is unlikely that other vasoconstrictors contribute significantly to the increased tone.Key words: cerebral artery, nerves, neuropeptide Y, norepinephrine.
Atrial natriuretic factor, angiotensin II, and the slow component of renal autoregulation
Authors: Naguib Raouf E. , Contant Chantal , Cupples W. A.
Published: April 2011

Autoregulation of renal blood flow is highly efficient and is mediated partly by tubuloglomerular feedback (TGF), which couples regulation of blood flow to that of sodium excretion. Atrial natriuretic factor (ANF) dilates preglomerular resistance vessels, in which autoregulation occurs, and has been reported to inhibit TGF. This study addressed potential actions of ANF on the slow, TGF-mediated, component of autoregulation. Renal blood flow was measured by an electromagnetic flow probe in Sprague – Dawley rats anesthetized by halothane or isoflurane while renal perfusion pressure was manipulated by a servo-controlled clamp placed on the aorta between the renal arteries. Progressive reduction of perfusion pressure to 60 mmHg (1 mmHg = 133.3 Pa) induced resetting of autoregulation to operate at the reduced pressure and to defend lower renal blood flow. Infusion of ANF at a dose shown to reliably increase sodium excretion did not affect autoregulation or its resetting. Because resetting is angiotensin II dependent, the converting enzyme inhibitor Enalaprilat® was used to provide angiotensin II blockade. As expected, autoregulation did not reset to operate at reduced perfusion pressure. Again ANF was without effect. In a third experiment, relaxation of resistance was assessed in response to repeated steps of perfusion pressure between 65 and 75 mmHg. Time constants of constriction and dilatation were recovered by fitting to a single exponential before and during ANF infusion. Time constants ranged from 0.045 to 0.055 Hz, were consistent with operation of TGF, were not different for constriction or dilatation, and were unaltered by ANF; nor did ANF affect the magnitude of constriction or dilatation. Autoregulation compensated for ≈ 87% of the increase and ≈ 79% of the decrease in driving pressure during control. During ANF infusion it compensated for ≈ 98% of the increase and ≈ 82% of the decrease. The results indicate that, although ANF and angiotensin II act on the same resistance vessels, ANF does not attenuate angiotensin II dependent resetting of renal autoregulation; nor does ANF inhibit the slow component of renal autoregulation.Key words: resistance, tubuloglomerular feedback, time constant.
Effects of synthetic cyclic AMP analogs on amylase exocytosis from rat pancreatic acini
Authors: Schäfer Claus , Steffen Hanna , Printz Hartmut , Göke Burkhard
Published: April 2011

Diastereomers of adenosine 3′,5′-phosphorothioate activate cAMP-dependent protein kinases (cAMP-PK) in vitro. We found that these compounds are highly selective tools to monitor cAMP-dependent PKA activation and its effect on amylase exocytosis from pancreatic acini. In permeabilized rat acinar cells, (Sp)-cAMPS dose-dependently stimulated amylase secretion, while (Rp)-cAMPS inhibited (Sp)-cAMPS-induced amylase release. In intact rat acini, 8-Br-(Sp)-cAMPS reduced the secretory responses to secretin, vasoactive intestinal polypeptide (VIP), 8-Br-cAMP, and 8-Br-(Sp)-cAMPS, but not to cerulein. Another derivative, dibutyryl-(Rp)-cAMPS, induced a small inhibitory effect against 8-Br-(Sp)-cAMPS and VIP, which was overlapped by an unspecific stimulatory effect on amylase exocytosis induced by the degradation product butyrate. Furthermore, (Sp)-5,6-dichloro-1-β-D-ribofuranosylbenzimidazole-3′,5′-monophosphorothioate ((Sp)-5,6-DCl-cBIMPS), a specific cAMP-PK activator, induced a maximal induction of cAMP-PK activity, but its stimulation of amylase secretion was less than that by secretin. (Sp)-5,6-DCl-cBIMPS regulated the phosphorylation of several proteins, which were also affected by secretin. However, secretin had additional effects. Its action was most likely mediated by a dual effect on the cAMP and the calcium pathway. Our results indicate that the cAMP-dependent pathway is involved in amylase exocytosis from rat pancreatic acini.Key words: secretin, vasoactive intestinal polypeptide, (Rp)-cAMPS, (Sp)-cAMPS, 8-Br-(Rp)-cAMPS, 8-Br-(Sp)-cAMPS, dibutyryl-(Rp)-cAMPS, (Sp)-5,6-DCl-cBIMPS, cAMP-dependent protein kinases, pancreatic acini, amylase secretion.
A radioimmunoassay for oncorhynchid growth hormone targeted to the physiological range
Authors: Kieffer Timothy J. , Schieldrop Phil J. , McLean Ewen , Donaldson Edward M. , Brown John C.
Published: April 2011

This study describes the development of an oncorhynchid growth hormone (GH) radioimmunoassay using recombinant chum salmon GH (rsGH) and a rabbit antiserum (TJK-1) raised against this recombinant material. The assay was designed to measure the wide range of circulating immunoreactive GH (IRGH) levels in Pacific salmonids, resulting in a standard curve capable of accurately determining plasma levels, of IRGH from 0.5 to 250 ng/mL without dilution. The assay ED50 and ED90 values averaged 13.1 and 0.5 ng/mL, respectively. This radioimmunoassay specifically recognizes oncorhynchid IRGH, showing no cross-reactivity with recombinant porcine and bovine GH, or natural chum salmon prolactin at concentrations up to 10 μg/mL. Curves approximately parallel to the standard curve were obtained with purified natural coho salmon GH and plasma from chinook salmon. Recovery of rsGH from plasma was complete over the full range of the standard curve. Intra- and inter-assay coefficients of variation were 6.0 and 12.9%, respectively. Plasma IRGH levels in fed coho salmon were 30.6 ± 5.3 ng/mL, while those in fish starved for 2 weeks were 132.9 ± 53.9 ng/mL. Starvation for an additional 4 weeks had no significant effect. Plasma IRGH levels in control rainbow trout injected with saline were significantly higher 45 min post-injection. In contrast, fish injected with recombinant porcine GH exhibited no elevation in IRGH. It is speculated that exogenous GH inhibits the production of endogenous GH.Key words: recombinant chum growth hormone, coho growth hormone, rainbow trout growth hormone, growth hormone treatment.
Studies on ethanol-induced subepithelial fluid accumulation and jejunal villus bleb formation. An in vitro video microscopic approach
Authors: Dinda P. K. , Buell M. G. , Morris O. , Beck I. T.
Published: April 2011

Jejunal intraluminal ethanol causes morphological and mucosal microvascular injury. The purpose of the present study was to understand the mechanism of the morphological alterations caused by ethanol without the influence of ethanol's effect on the microcirculation. Therefore, we have investigated the ethanol-induced morphological changes in the absence of blood flow (i.e., in the jejunum in vitro) and compared these changes with those reported to occur in the presence of microcirculation (i.e., in the jejunum in vivo). The mucosa of jejunal segments was exposed to a control solution and to solutions containing 0.8, 1.6, and 4.8% (w/v) ethanol, using a specially designed apparatus. The morphological response of the mucosa to these solutions was continuously examined employing a video microscopic technique, and the changes were morpho-metrically evaluated on subsequent playback of videotapes. Ethanol caused a concentration-dependent increase in the number of villi with subepithelial fluid accumulation, i.e., blebs, and a decrease in the height of the villus core (i.e., lamina propria). With 0.8 and 1.6% ethanol, the contracted core remained partially attached to the epithelium and the total villus height (villus core plus epithelial layer) decreased. With 4.8% ethanol, the villus core contraction was so rapid that the stroma fully separated from the epithelium. Thus, among other factors, the rapidity of the villus core contractions appears to play a role in the subepithelial bleb formation and in the appearance of the bleb. The ethanol-induced changes in vitro are similar to those reported to occur in the jejunum in vivo. Therefore, we conclude that the effect of ethanol on morphology is independent of its action on the microcirculation.Key words: video microscopy, villus contraction, villus core contraction, bleb formation, jejunal injury.
Methimazole protection of rats against gentamicin-induced nephrotoxicity
Authors: Elfarra Adnan A. , Duescher Renee J. , Sausen Peter J. , O'Hara Todd M. , Cooley A. James
Published: April 2011

Methimazole was previously shown to protect rats, mice, and (or) dogs against cisplatin-, cephaloridine-, 2-bromohydro-quinone-, and S-(1,2-dichlorovinyl)-L-cysteine-induced nephrotoxicity. In this study, methimazole effects on gentamicin (GM) induced nephrotoxicity were examined. Rats given GM (40 mg/kg) twice daily for 10 days exhibited higher blood urea nitrogen (BUN) concentrations and severe necrosis of virtually all proximal tubules compared with saline-treated controls. Rats cotreated with methimazole (20 mg/kg) exhibited minimal proximal tubular necrosis and were protected against GM-induced increase in BUN concentrations, despite having higher kidney GM concentrations. Rats given GM alone for 3 days exhibited no proximal tubular necrosis and no elevation of BUN values. However, these rats exhibited an increase in nonprotein disulfide concentrations and a decrease in renal protein thiol and protein disulfide concentrations, as opposed to rats given GM and methimazole. Together the results show that methimazole was an effective antagonist of GM-induced nephrotoxicity. Methimazole did not inhibit GM renal uptake but may protect against GM-induced nephrotoxicity by acting as an antioxidant within the kidneys.Key words: nephrotoxicity, gentamicin, methimazole, protein thiols, nonprotein thiols.
Regulation of myocardial lipoprotein lipase activity by diabetes and thyroid hormones
Authors: Liu Limin , Severson David L.
Published: April 2011

Administration of streptozotocin (100 mg/kg) to adult Sprague–Dawley rats reduced both functional (heparin releasable) lipoprotein lipase activity in perfused hearts and total and heparin-releasable lipoprotein lipase activity in isolated cardio-myocytes, and produced a hypothyroid state (decreased plasma levels of triiodothyronine and thyroxine). Administration of replacement doses of triiodothyronine (3 or 10 μg/kg for 3 days) to diabetic rats normalized heparin-releasable lipoprotein lipase activity in perfused hearts, but the depressed lipoprotein lipase activity in cardiomyocytes from diabetic hearts was unchanged by in vivo thyroid hormone treatment. However, hypothyroidism in thyroidectomized rats did not alter lipoprotein lipase activity in either perfused hearts or isolated cardiomyocytes. Therefore, thyroid hormones may interact with some other factor(s) in this acute, insulin-deficient model of diabetes to selectively regulate functional, heparin-releasable lipoprotein lipase activity in perfused hearts.Key words: diabetes, hypothyroidism, lipoprotein lipase, perfused hearts, cardiomyocytes.