bluuebunny/crossref_metadata_2025 huggingface dataset:
α1a-Adrenergic receptor mediated positive chronotropic effect in right atria isolated from rats
Authors: Williamson Anthony P. , Seifen Ernst , Lindemann Jon P. , Kennedy Richard H.
Published: April 2011

Experiments in right atria isolated from adult male rats were designed to determine which of the α1-adrenergic receptor (α1-AR) subtypes are involved in the positive chronotropic effect of phenylephrine, an α1-AR agonist. Chloroethylclonidine (CEC), an irreversible α1b-, α1c-, and α1d-AR antagonist, did not alter the efficacy or potency of phenylephrine; however, CEC did elicit a concentration-dependent negative chronotropic effect and reduce the absolute maximum spontaneous rate observed in the presence of phenylephrine. WB4101, a competitive α1a- and α1c-AR-selective antagonist, did not alter basal spontaneous rate or the efficacy of phenylephrine, but it did produce a significant rightward shift of the phenylephrine concentration–response curve. Phenoxybenzamine, an irreversible nonselective α-AR antagonist, elicited a concentration-dependent negative chronotropic effect, a significant rightward shift of the phenylephrine concentration–response curve, and a reduction in the efficacy of phenylephrine. The chronotropic action of the β-adrenergic agonist isoproterenol was not affected by CEC, WB4101, or phenoxybenzamine. These data suggest that the positive chronotropic effect of α1-adrenergic agonists in rat right atria is mediated via stimulation of α1a-ARs.Key words: α1-adrenergic receptor subtypes, chloroethylclonidine, WB4101, phenylephrine, right atria (rat).
Aging and immune response to exercise
Authors: Shinkai Shoji , Konishi Masamitsu , Shephard Roy J
Published: April 2011

Human immune function undergoes adverse changes with aging. The T cells, which have a central role in cellular immunity, show the largest age-related differences in distribution and function, with thymus involution as the apparent underlying cause. The immune responses to acute exercise and training have not been studied extensively in the elderly. The natural killer (NK) cell response to a single exercise challenge is normal in older individuals, but immediately after exercise the elderly subjects manifest less suppression of phytohemagglutinin (PHA)-induced lymphocyte proliferation than younger individuals. In contrast, a strenuous exercise seems to induce a more sustained postexercise suppression of cellular immunity in older individuals than in their young peers. A few cross-sectional comparisons of immune status between physically fit elderly individuals and young sedentary controls suggest that habitual physical activity may enhance NK cell activity, checking certain aspects of the age-related decline in T cell function, such as reduced mitogenesis in response to plant lectins and decreases in the production of certain types of cytokine. The clinical implications, however, remain to be clarified by future study.Key words: immune senescence, innate immunity, adaptive immunity.
Radical species in inflammation and overtraining
Authors: Tiidus Peter M
Published: April 2011

Reactive oxygen species can be important in the initiation of exercise-induced muscle damage and in the initiation and propagation of the subsequent acute muscle inflammatory response. Oxygen radicals generated via the neutrophil respiratory burst are vital in clearing away muscle tissue that has been damaged by exercise and they may also be responsible for propagation of further damage. Intervention by antioxidants to limit the postexercise inflammatory response and its potential to impair optimal muscle function are of interest to serious and recreational sports participants. Although antioxidants have the potential to limit muscle oxidative stress during the postexercise period, direct evidence for their role in this is limited. It is likely that short-term training can protect muscle from subsequent exercise-induced damage and inflammation without necessarily improving muscle antioxidant status. Although muscle antioxidant status may be enhanced by longer term training, diet, or antioxidant administration, the significance of antioxidants in limiting muscle damage during the acute inflammatory response needs to be more clearly defined. It may even be counterproductive to limit neutrophil function during the inflammatory response, since this may inhibit subsequent muscle repair.Key words: inflammation, muscle, exercise, oxygen radicals, antioxidants.
The cytokine response to strenuous exercise
Authors: Pedersen Bente Klarlund , Ostrowski Kenneth , Rohde Thomas , Bruunsgaard Helle
Published: April 2011

Strenuous exercise is accompanied by an increase in circulating proinflammatory and inflammation responsive cytokines, having some similarities with the response to sepsis and trauma. The sequential release of tumour necrosis factor-alpha, interleukin (IL)1beta, IL-6, and IL-1 receptor antagonist (IL-1ra) in the blood is comparable to that observed in relation to bacterial diseases. Eccentric exercise is associated with an increase in serum IL-6 concentrations and is significantly correlated with the concentration of creatine kinase (CK) in the following days, whereas no changes are found after the concentric exercise; this demonstrates a close association between exercise-induced muscle damage and increased serum levels of IL-6. The time course of cytokine production, the close association with muscle damage, and the finding of mRNA-IL-6 in skeletal muscle biopsies after intense exercise all support the idea that during eccentric exercise myofibers are mechanically damaged and that this process stimulates the local production of inflammatory cytokines. It remains to be shown whether systemic endotoxemia during exercise is also a cause of elevated levels of cytokines in the plasma. The present review also discusses the possible roles of protein breakdown, delayed onset muscle soreness, and clinical implications of the acute-phase response following exercise.Key words: exercise, sport, trauma, sepsis, cytokines, interleukin, muscle.
Tachykinins mediate noncholinergic excitatory neural responses in the circular muscle of rat proximal colon
Authors: Serio R , Mulè F , Bonvissuto F , Postorino A
Published: April 2011

Using the sucrose-gap technique, we attempted to assess a role for tachykinins (TKs) in mediating noncholinergic excitatory junction potential (EJP) and contraction, in the circular muscle of rat proximal colon. Excitatory responses were evoked by submaximal electrical field stimulation (EFS) in the presence of atropine (1 µM), guanethidine (1 µM), indomethacin (10 µM), and Nomega -nitro-L-arginine methyl ester (L-NAME) (100 µM). The NK1 receptor antagonist, SR 140,333 (up to 3 µM) or the NK2 receptor antagonists, SR 48,968 and MEN 10,627 (up to 5 µM) produced a partial inhibition of the excitatory responses to EFS. The co-administration of the selective NK1 and NK2 receptor antagonists produced additive effects on the responses to EFS. Selective NK1 receptor agonist, [Sar9, Met (O2)11]-substance P, induced depolarization and contraction, antagonized by SR 140,333, but not by NK2 receptor antagonists. NK2 receptor agonist, [ betaAla8]-neurokinin A (4-10), also produced electrical and mechanical excitatory effects that were antagonized by SR 48,968 or MEN 10,627, but not by the NK1 receptor antagonist. Our results provide evidence that, in circular muscle of rat colon, endogenous tachykinins are the main excitatory transmitters for nonadrenergic, noncholinergic (NANC) excitation and their action is mediated by both NK1 and NK2 receptors.Key words: NK1 receptor, NK2 receptor, nonadrenergic, noncholinergic (NANC) excitatory junction potential, intestine.
Minoxidil accelerates heart failure development in rats with ascending aortic constriction
Authors: Turcani Marian , Jacob Ruthard
Published: April 2011

To test the ability of the heart to express characteristic geometric features of concentric and eccentric hypertrophy concurrently, constriction of the ascending aorta was performed in 4-week-old rats. Simultaneously, these rats were treated with an arteriolar dilator minoxidil. An examination 6 weeks after induction of the hemodynamic overload revealed no signs of congestion in systemic or pulmonary circulation in rats with aortic constriction or minoxidil-treated sham-operated rats. The magnitude of hemodynamic overload caused by aortic constriction or minoxidil treatment could be considered as equivalent, because the same enlargement of left ventricular pressure-volume area was necessary to compensate for either pressure or volume overload. Myocardial contractility decreased in rats with aortic constriction, and the compensation was achieved wholly by the marked concentric hypertrophy. Volume overload in minoxidil-treated rats was compensated partially by the eccentric hypertrophy and partially by the increased myocardial contractility. In contrast, increased lung weight and pleural effusion were found in all minoxidil-treated rats with aortic constriction. Unfavorable changes in left ventricular mass and geometry, relatively high chamber stiffness, and depressed ventricular and myocardial function were responsible for the massive pulmonary congestion.Key words: cardiac hypertrophy, heart failure, pressure overload, volume overload, minoxidil.
Long-term supplementation of culture medium with essential fatty acids alters α-linolenic acid uptake in Caco-2 clone TC7
Authors: Tranchant T , Besson P , Hoinard C , Pinault M , Alessandri J M , Delarue J , Couet C , Goré J
Published: April 2011

We investigated the influence of four different culture media: 20% fetal bovine serum (FBS), 5% FBS, 5% FBS supplemented with 10 mg·L-1 linoleic acid (18:2(n-6)) or alpha-linolenic acid (18:3(n-3)) on alpha-linolenic acid apical uptake in clone TC7 of human intestinal Caco-2 cell line. Neither cellular viability nor cell monolayer integrity and permeability were altered by the four culture conditions. Our results show that the different culture media led to changes in alpha-linolenic acid maximal rate of uptake (Vmax) but did not alter the apparent transport constant (Km). Reducing FBS concentration from 20% to 5% increased significantly the rate of alpha-linolenic acid uptake, which was further increased by supplementation of the medium with 18:2(n-6) or 18:3(n-3). Supplementation with essential fatty acids led to a marked enrichment of brush-border membrane phospholipids in polyunsaturated fatty acids of the corresponding series and decreased significantly the levels of monounsaturated fatty acids. Saturated fatty acids, unsaturation index, and cholesterol / fatty acid ratios were unchanged. No clear relation could be established between the changes in membrane lipid composition and the alterations of alpha-linolenic acid uptake. These results indicate a weak influence of membrane lipid composition in the modulation of the uptake. Therefore, the increase of uptake following long-term supplementation of TC7 cells with essential fatty acids could be attributed to an increase of the expression of membrane protein(s) involved in the apical uptake of long-chain fatty acids. This remains to be established.Key words: fatty acid intestinal absorption, Caco-2 cells, membrane fatty acid transport protein, membrane phospholipid fatty acid composition.
L-type Ca2+ currents in ventricular myocytes from neonatal and adult rats
Authors: Katsube Yasuhiro , Yokoshiki Hisashi , Nguyen Lam , Yamamoto Masao , Sperelakis Nicholas
Published: April 2011

Postnatal changes in the slow Ca2+ current (ICa(L)) were investigated in freshly isolated ventricular myocytes from neonatal (1-7 days old) and adult (2-4 months old) rats, using whole-cell voltage clamp and single-channel recordings. The membrane capacitance (mean ± SEM) averaged 23.2 ± 0.5 pF in neonates (n = 163) and 140 ± 4.1 pF in adults (n = 143). ICa(L) was measured as the peak inward current at a test potential of +10 mV (or +20 mV) by applying a 300-ms pulse from a holding potential of -40 mV; 1.8 mM Ca2+ was used as charge carrier. The basal ICa(L) density was 6.7 ± 0.2 pA/pF in neonatal and 7.8 ± 0.2 pA/pF in adult cells (p < 0.05). The time course of inactivation of the fast component (at +10 ms) was significantly longer in the neonatal (10.7 ± 1.4 ms) than in the adult (6.6 ± 0.4 ms) cells (p < 0.05). Ryanodine (10 muM) significantly increased this value to 18.0 ± 1.9 in neonate (n = 8) and to 17.7 ± 2.0 in adult (n = 9). For steady-state inactivation, the half-inactivation potential (Vh) was not changed in either group. For steady-state activation, Vh was 5.1 mV in the neonatal (n = 6) and -7.9 mV in the adult cells (n = 7). Single-channel recordings revealed that long openings (mode-2 behavior) were occasionally observed in the neonatal cells (11 events from 1080 traces / 11 cells), but not in the adult cells (400 traces / 4 cells). Slope conductance was 24 pS in both the neonatal and adult cells. Results in rat ventricular myocytes suggest the following: (i) the peak Ca2+ current density is already well developed in the neonatal period (being about 85% of the adult value); (ii) the fast component of inactivation is slower in neonates than in adults; and (iii) naturally occurring long openings are occasionally observed in the neonatal stage but not in the adult. Thus, the L-type Ca2+ channels of the neonate were slightly lower in density, were inactivated more slowly, and occasionally exhibited mode-2 behavior as compared with those of the adult.Key words: Ca2+ channels; neonatal heart cells; whole-cell voltage clamp; single-channel recordings; long openings of Ca2+ channels.
Inhibition of airway hyperreactivity, edema, and lung cell infiltration by compound U-83836E in sensitized guinea pigs
Authors: Carvalho Celso , Jancar Sonia , Sirois Pierre
Published: April 2011

Sensitized guinea pigs were used to assess the effect of treatment with the compound U-83836E ((-)-2-[[4-(2,6-di-1-pyrrolidinyl-4-pyrimidinyl)-1-piperazinyl]methyl]-3,4-dihydro-2,5,7,8-tetramethyl-2H-1-benzopyran-h-6-ol, dihydrochloride) on the antigen-induced late-phase (16 h) airway hyperreactivity, increase in inflammatory cell number, edema, and release of inflammatory mediators in the bronchoalveolar lavage (BAL) fluid. After antigen challenge, an increase of the in vitro reactivity of the trachea and upper bronchi to acetylcholine and histamine and an increase in the number of leukocytes in the BAL fluid, mainly eosinophils and mononuclear cells, were observed. The concentrations of proteins, histamine, and PGE2 in the BAL fluid were also significantly increased by 53, 57, and 216%, respectively, after antigen challenge. Treatment with U-83836E (10 mg/kg) given i.p. 17 and 3 h before and 6 h after antigen challenge inhibited by approximately 80% the total cell number in the airways and the BAL fluid protein content. Moreover, this treatment totally inhibited airway hyperreactivity. Histamine and PGE2 levels in the BAL fluid were not significantly affected by U-83836E treatment. These results indicate that U-83836E is effective against some of the characteristic features of asthma in ovalbumin-sensitized guinea pigs.Key words: U-83836E, aminochroman, hyperreactivity, lung inflammation, edema.
Respiratory effects of pressor and depressor agents in conscious rats
Authors: Walker Julia KL , Jennings Donald B
Published: April 2011

We hypothesized that the respiratory baroreflex in conscious rats is either more transient, or has a higher pressure threshold than in other species. To characterize the effect of arterial pressure changes on respiration in conscious rats, ventilation (V) was measured by the plethysmographic technique during injections, or infusions, of pressor and depressor agents. Bolus injections of angiotensin II (Ang II) or arginine vasopressin (AVP), transiently increased mean arterial pressure (MAP; mean ± SE) 43 ± 6 and 28 ± 5 mmHg (1 mmHg = 133.3 Pa), respectively, and immediately reduced tidal volume (Vt) and, in the case of AVP, V. In contrast, by 10 min of a sustained elevation of MAP (40 ± 3 mmHg) with infusion of Ang II, Vt, f, and V were not different from control levels. Bolus injection of sodium nitroprusside (SNP) to lower MAP (-28 ± 3 mmHg) immediately increased breathing frequency (f) and V, whereas sustained infusion of SNP to lower MAP (-21 ± 3 mmHg) did not change f or V at 10 and 20 min. In conscious rats, both injection and infusion of the pressor agent PE (+40 to 50 mmHg) stimulated f and V; this contrasted with anesthetized rats where PE inhibited f and V, as reported by others. In conscious rats, respiratory responses associated with baroreflexes adapt rapidly and, in the case of PE, can be overridden by some other mechanism.Key words: angiotensin II, arginine vasopressin, baroreceptor reflex, phenylephrine, sodium nitroprusside.
Neurotransmission in the medulla mediating insular cortical and lateral hypothalamic sympathetic responses
Authors: Butcher Kenneth S , Cechetto David F
Published: April 2011

Previous evidence has shown sympathetic nerve responses to insular cortical (IC) stimulation are mediated by synapses within the lateral hypothalamic area (LHA) and ventrolateral medulla (VLM). The present study was aimed at determining the neurotransmitter(s) and receptor(s) involved at the synapse in the VLM. Twenty male Wistar rats were instrumented for renal nerve, arterial pressure, and heart rate recording. The IC or the LHA was stimulated with a bipolar electrode (200-1000 µA; 2 ms; 0.8 Hz) to elicit sympathetic nerve responses. Antagonists were then pressure-injected into the VLM (300 nL). Bilateral and unilateral kynurenate (25 mM) resulted in 100% block of IC- and LHA-stimulated sympathetic nerve responses. Bilateral injection of the non-NMDA (N-methyl-D-aspartate) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 200 µM) also resulted in up to 100% block of IC and LHA sympathetic responses. In addition, unilateral injections of CNQX were made in two animals, resulting in 100 and 83% block of LHA sympathetic responses. Bilateral injection of the NMDA receptor antagonist DL-2-amino-5-phosphonopentanoic acid (AP5; 200µM) did not affect the response to IC or LHA stimulation. Kynurenate, CNQX, and AP5 all resulted in an elevation of baseline sympathetic nerve activity and a pressor response. Kynurenate resulted in a 263 ± 79% increase in baseline activity, while CNQX and AP5 resulted in 83 ± 19% and 91 ± 21% increases, respectively. Bilateral injections of antagonists for GABAA (bicuculline; 0.1 µM), acetylcholine (atropine; 0.1 µM) and catecholaminergic alpha and beta receptors (phentolamine and propranolol: 0.1 µM) had no effect on LHA sympathetic responses. Thus, sympathetic responses originating in the IC and LHA are mediated by a non-NMDA receptors in the VLM, which are likely AMPA receptors.Key words: insular cortex, ventrolateral medulla, glutamate, sympathetic activity.
Differential susceptibilities of isolated hamster lung cell types to amiodarone toxicity
Authors: Bolt M W , Racz W J , Brien J F , Bray T M , Massey T E
Published: April 2011

Treatment of cardiac dysrhythmias with the iodinated benzofuran derivative amiodarone (AM) is limited by pulmonary toxicity. The susceptibilities of different lung cell types of male Golden Syrian hamsters to AM-induced cytotoxicity were investigated in vitro. Bronchoalveolar lavage and protease digestion to release cells, followed by centrifugal elutriation and density gradient centrifugation, resulted in preparations enriched with alveolar macrophages (98%), alveolar type II cells (75-85%), and nonciliated bronchiolar epithelial (Clara) cells (35-50%). Alveolar type II cell and Clara cell preparations demonstrated decreased viability (by 0.5% trypan blue dye exclusion) when incubated with 50 µM AM for 36 h, and all AM-treated cell preparations demonstrated decreased viability when incubated with 100 or 200 µM AM. Based on a viability index ((viability of AM-treated cells ÷ viability of controls) × 100%), the Clara cell fraction was significantly (p < 0.05) more susceptible than all of the other cell types to 50 µM AM. However, AM cytotoxicity was greatest (p < 0.05) in alveolar macrophages following incubation with 100 or 200 µM AM. There was no difference between any of the enriched cell preparations in the amount of drug accumulated following 24 h of incubation with 50 µM AM, whereas alveolar macrophages accumulated the most drug during incubation with 100 µM AM. Thus, the most susceptible cell type was dependent on AM concentration. AM-induced cytotoxicity in specific cell types may initiate processes leading to inflammation and pulmonary fibrosis.Key words: amiodarone, susceptibility, alveolar macrophage, accumulation.
Respiratory, cardiovascular, and metabolic adjustments to hypoxemia during sleep in piglets
Authors: Côté Aurore , Porras Hernan
Published: April 2011

The influence of sleep on ventilation, metabolic rate, cardiovascular function, and regional distribution of blood flow during hypoxemia (PaO2 of 45-50 mmHg (1 mmHg = 133.3 Pa)) was studied in piglets at 6 ± 1 and 34 ± 5 days (mean ± SD). Measurement of ventilation and metabolic rate was done in a metabolic chamber, and blood flow was measured using the microsphere technique. A subgroup of animals was instrumented for cardiac output measurement (dye-dilution technique) and continuous monitoring of the hemoglobin saturation in oxygen (SaO2) We found that although sleep did not influence the metabolic and cardiac output response to hypoxemia, it affected the ventilatory response as well as the brain and the respiratory muscle blood flows. During active sleep in the older animals, the ventilatory response to hypoxemia was smaller than in the other two states; marked drops in SaO2 occurred with changes in the breathing pattern; and that state was associated with the highest rate of brain blood flow. As well, age affected the ventilatory and metabolic response, but not the cardiovascular response to hypoxemia. The age-dependent ventilatory changes with hypoxemia (smaller ventilatory response in the young than in the older animals) were related to the different levels of oxygen consumption. In summary, active sleep was responsible for all the sleep-dependent changes in the response to a moderate degree of hypoxemia.Key words: breathing pattern, metabolic rate, blood flow, microspheres, maturation.
Ca2+-independent synergistic augmentation of O2- production by FMLP and PMA in HL-60 cells
Authors: Tsukii Katsuyoshi , Nakahata Norimichi , Tsurufuji Susumu , Ohizumi Yasushi
Published: April 2011

N-Formyl-Met-Leu-Phe (FMLP) and phorbol 12-myristate 13-acetate (PMA) caused a synergistic augmentation of superoxide anion (O2-) production in neutrophil-like HL-60 cells differentiated with dibutyryl cAMP. The present study was undertaken to investigate the mechanism of the synergistic augmentation of O2- production. FMLP increased intracellular free Ca2+ concentration ([Ca2+]i), which was slightly suppressed by PMA and completely inhibited by an intracellular Ca2+ chelating agent, O,Oprime-bis(2-aminophenyl)ethyleneglycol-N,N,Nprime,Nprime-tetraacetic acid tetraacetoxymethyl ester (BAPTA-AM). Although FMLP-induced O2- production was inhibited by BAPTA-AM, a major part of the synergistic augmentation of O2- production by FMLP and PMA remained after BAPTA-AM treatment, suggesting that a Ca2+-independent mechanism might be involved in the augmentation. FMLP and PMA caused an activation of phospholipase D (PLD) almost additively in a Ca2+-sensitive manner. The synergistic activation of mitogen-activated protein kinase (MAPK) was evoked by combined addition of PMA and FMLP in a BAPTA-AM resistant manner. However, PD98059, a MAPK kinase inhibitor, did not affect the synergistic augmentation of O2- production, although it potently inhibited the synergistic augmentation of tyrosine phosphorylation of MAPK. Wortmannin, a phosphatidylinositol 3-kinase inhibitor, inhibited FMLP-induced O2- production, but it did not inhibit the synergistic augmentation of O2- production by PMA and FMLP. In contrast, staurosporine and GF109203X, protein kinase C inhibitors, reduced the synergistic augmentation induced by PMA and FMLP. In addition, pertussis toxin (PT) abolished the synergistic augmentation of O2- production. It is concluded that the synergistic augmentation of O2- production induced by PMA and FMLP is mediated through a PT-sensitive G protein and a protein kinase C in a Ca2+-independent manner.Key words: superoxide anion, phorbol 12-myristate 13-acetate, N-formyl-Met-Leu-Phe, intracellular Ca2+ ions ; protein kinase C.
Cold exposure and immune function
Authors: Shephard Roy J , Shek Pang N
Published: April 2011

The influence of cold exposure on immune function is reviewed. Data obtained mainly on small mammals suggest that the acute effect of severe chilling is a suppression of several cellular and humoral components of the immune response, including a decrease of lymphocyte proliferation, a down-regulation of the immune cascade, a reduction of natural killer (NK) cell count, cytolytic activity, activation of complement, and the induction of heat shock proteins. However, adaptation to a given cold stimulus appears to develop over the course of 2-3 weeks. Further work is needed to examine interactions between cold exposure and exercise, and to determine whether the disturbances of immune response are sufficient to impair immunosurveillance in human subjects.Key words: cytolic activity, heat shock proteins, hypothermia, infection, leukocytes.
The efficacy of diazepam in the treatment of acute iron overload in rats
Authors: Fassos Frank F , Berkovitch Matitiahu , Daneman Nicholas , Koren Lee , Cameron Ross , Klein Julia , Falcitelli Corrado , St. Louis Patrick , Daneman Richard , Koren Gideon
Published: April 2011

While conducting studies on the prevention of mortality from acute iron intoxication in rats, diazepam, given to prevent animal suffering, was observed to be associated with reduced mortality in a limited number of animals. The objective was to assess whether diazepam reduces mortality following acute iron intoxication in rats. Survival of rats was compared among groups receiving (i) orally 612 mg/kg iron alone (LD60), (ii) iron with a subcutaneous injection of 2.5 mg/kg diazepam (DZ), or (iii) iron, DZ with 800 mg/kg deferiprone intraperitoneal injections. The administration of DZ decreased mortality from 60 to 16% (p < 0.001). The addition of deferiprone to DZ resulted in zero mortality (p < 0.05 compared with the DZ group) over the study period. The administration of DZ was not associated with decreased iron absorption or increased urinary iron excretion, whereas the administration of deferiprone did result in urinary iron excretion. Microscopic examination suggests that diazepam administration may be associated with lower intracellular accumulation of iron. In conclusion, diazepam reduces mortality from iron overdose in rats through a yet unidentified mechanism, although the drug does not inhibit iron absorption or enhance urinary iron removal.Key words: iron overdose, diazepam, rats.
Sodium nitrite, a potent relaxant of rat stomach fundus: in vitro evidence
Authors: Ceregrzyn Michal , Ozaki Tsuyoshi , Kuwahara Atsukazu , Wiechetek Maria
Published: April 2011

The effects of sodium nitrite (0.1, 1, 10 mM) on mechanical activity of isolated rat stomach fundus muscle and the influence of guanylate cyclase activity inhibitor (methylene blue) and channel inhibitors (tetrodotoxin, charybdotoxin, apamin) were studied. Nitrite evoked dose-dependent relaxation in the longitudinal and circular muscle layers. The lowest effective concentration of sodium nitrite was 0.1 mM, which is comparable with the NOAEL (no observed adverse effect level). Tetrodotoxin (1 µM) markedly inhibited electrically induced contraction and rebound relaxation, but did not influence the nitrite-induced relaxation. Charybdotoxin (100 nM) decreased the relaxation evoked by 10 mM nitrite to 52.3 and 65.7% of control reaction in the circular and longitudinal muscle layer, respectively. Apamin (100 nM) did not influence the nitrite-induced relaxation. Methylene blue (10 µM) decreased relaxation induced by nitrite in the longitudinal and circular muscle layer, respectively, to 66.7 and 54.3% of the response to 1 mM nitrite alone. Relaxation induced by nitrite was decreased in the presence of L-cysteine (5 mM), and in the circular and longitudinal muscle layer reached 29.6 and 23.1%, respectively, of the response to 1 mM nitrite alone. We conclude that the relaxing effect of nitrite on gastric fundus results from its direct action on smooth muscle cells and probably the enteric nervous system is not involved in this action. The nitrite-elicited relaxation depends on activation of guanylate cyclase and high conductance Ca2+-activated potassium channels; however, activation of potassium channels might be a part of or might act in parallel with the mechanism involving the cyclic GMP system. Effects of nitrite observed in the presence of L-cysteine suggest that nitrosothiols are not responsible for nitrite-evoked activation of guanylate cyclase.Key words: nitrite, gastric motility, tetrodotoxin, methylene blue, charybdotoxin, L-cysteine.
Actions of excitatory amino acids on mesencephalic trigeminal neurons
Authors: Pelkey Kenneth A , Marshall Kenneth C
Published: April 2011

Mesencephalic trigeminal (MeV) neurons are primary sensory neurons of which the cell soma is located within the brainstem, and is associated with synaptic contacts. In previous studies it has been reported that these cells are resistant to kainic acid excitotoxicity, and have little or no responsiveness to exogenously applied glutamate or selective agonists. In an in vitro slice preparation with intracellular recording, we have found that these cells respond to pressure-applied glutamate, N-methyl-D-aspartic acid (NMDA), kainate (KA), and (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). The kainate and AMPA responses appear to be mediated by different receptors, at least in part, since they exhibit differing sensitivity to an AMPA receptor selective antagonist. The agonists generally evoke larger responses than glutamate and exhibit a long-duration desensitization requiring approximately 10 min for full recovery. Some cross-desensitization between the glutamate agonists is also observed. Mesencephalic trigeminal neurons exhibit high-frequency oscillatory activity during depolarizations that approach threshold potentials, and these could combine with transmitter-induced depolarizations to enhance the excitability of these cells. Previous reports of nonsensitivity to glutamate and to kainate excitotoxicity are attributable to relatively small responses, and to the desensitization expressed by these neurons.Key words: mesencephalic trigeminal neurons, glutamate, kainate, AMPA, oscillations, desensitization.
Effect of cicletanine on renal cGMP production
Authors: Valdivielso J M , Morales A I , Pérez-Barriocanal F , López-Novoa J M
Published: April 2011

The aim of the present study was to assess the effect of cicletanine on renal cGMP production. To do so we measured mean arterial pressure (MAP), creatinine clearance (CC), and urinary excretion of electrolytes and cGMP under basal conditions and after 6 h of cicletanine administration (10 and 15 mg/kg body weight by oral gavage) in conscious Wistar rats. Also, the in vitro effect of cicletanine was assessed by incubating renal slices and isolated rat glomeruli with two concentrations of cicletanine (0.1 and 1 mM) for different times (1, 2, 5, and 30 min) in the presence of 3-isobutyl-1-methylxanthine. Oral administration of cicletanine induced an increase in urinary flow (V) and the urinary excretion of electrolytes and cGMP, with no changes in CC. In addition, a significant decrease in MAP was observed, but only with the lower dose. Incubation with cicletanine did not induce significant changes in cGMP production in glomeruli or renal slices. These results show that cicletanine, administered in vivo at diuretic and antihypertensive doses, induces an increase in urinary cGMP excretion.Key words: cicletanine, cGMP, renal glomeruli.
Body fluid volume status and the renal response to atrial natriuretic peptide in rats
Authors: Honrath U , Chong C K , Sonnenberg H
Published: April 2011

The effect of altering the volumes of different body fluid compartments on the renal response to atrial natriuretic peptide (ANP) was studied in anesthetized rats before and during administration of the peptide at 170 ng/min. Four different groups were used. In the first (De), reduction of total body water content was induced by 48 h water deprivation. In the second (De+NaCl), an acute intravenous infusion after the same 48 h dehydration was used to restore the extracellular, but not the intracellular, fluid compartment. In the third (Eu+NaCl), euvolemic rats were infused with isotonic saline at the same rate as in group De+NaCl to expand both intravascular and interstitial components of extracellular fluid. In the fourth group (Eu+BSA) an infusion of hyperoncotic (6%) bovine serum albumin in isotonic saline was used to expand the intravascular volume while contracting the interstitial volume. Excretion of water and salt was predictably reduced in the De group compared with the others. This reduction was associated with increased tubular reabsorption, both upstream from the medullary collecting duct and in the duct itself. Administration of ANP did not significantly affect diuresis and saluresis, or tubular transport. By contrast, there were marked and similar diuretic and natriuretic responses to ANP in groups De+NaCl and Eu+NaCl, associated with transport inhibition primarily in the medullary collecting duct. Surprisingly, the rats infused with hyperoncotic solution (Eu+NaCl) also failed to show marked excretory or duct transport responses to ANP. According to the study design, the two nonresponding groups had, respectively, a decreased or a normal intracellular compartment, and a decreased or increased plasma volume. The common feature of both nonresponding groups was a decreased interstitial fluid compartment, whereas the two responding groups had normal or increased interstitial volume. We suggest, therefore, that a replete interstitial fluid compartment is essential for the renal response to ANP.Key words: water and sodium chloride excretion, collecting duct transport, plasma volume, interstitial fluid, intracellular compartment.
Isoform-specific protein kinase C activity at variable Ca2+ entry during coronary artery contraction by vasoactive eicosanoids
Authors: Kanashiro Celia A , Khalil Raouf A
Published: April 2011

Vasoactive eicosanoids have been implicated in the pathogenesis of coronary vasospasms. The signaling mechanisms of eicosanoid-induced coronary vasoconstriction are unclear, and a role for protein kinase C (PKC) has been suggested. Activated PKC undergoes translocation to the surface membrane in the vicinity of Ca2+ channels; however, the effect of Ca2+ entry on the activity of the specific PKC isoforms in coronary smooth muscle is unknown. In the present study, 45Ca2+ influx and isometric contraction were measured in porcine coronary artery strips incubated at increasing extracellular calcium concentrations ([Ca2+]e) and stimulated with prostaglandin F2α (PGF2α) or the stable thromboxane A2 analog U46619, while in parallel, the cytosolic (C) and particulate (P) fractions were examined for PKC activity and reactivity with anti-PKC antibodies using Western blot analysis. At 0-300 µM [Ca2+]e, both PGF2α and U46619 (10-5 M) significantly increased PKC activity and contraction in the absence of a significant increase in 45Ca2+ influx. At 600 µM [Ca2+]e, PGF2α and U46619 increased P/C PKC activity ratio to a peak of 9.52 and 14.58, respectively, with a significant increase in 45Ca2+ influx and contraction. The 45Ca2+ influx - PKC activity - contraction relationship showed a 45Ca2+-influx threshold of ~7 µmol·kg-1·min-1 for maximal PKC activation by PGF2α and U46619. 45Ca2+ influx > 10 µmol·kg-1·min-1 was associated with further increases in contraction despite a significant decrease in PKC activity. Western blotting analysis revealed α-, δ-, ε-, and ζ-PKC in porcine coronary artery. In unstimulated tissues, α- and ε-PKC were mostly distributed in the cytosolic fraction. Significant eicosanoid-induced translocation of ε-PKC from the cytosolic to the particulate fraction was observed at 0 [Ca2+]e, while translocation of α-PKC was observed at 600 µM [Ca2+]e. Thus, a significant component of eicosanoid-induced coronary contraction is associated with significant PKC activity in the absence of significant increase in Ca2+ entry and may involve activation and translocation of the Ca2+-independent ε-PKC. An additional Ca2+-dependent component of eicosanoid-induced coronary contraction is associated with a peak PKC activity at submaximal Ca2+ entry and may involve activation and translocation of the Ca2+-dependent α-PKC. The results also suggest that a smaller PKC activity at supramaximal Ca2+ entry may be sufficient during eicosanoid-induced contraction of coronary smooth muscle.Key words: protein kinase C, isoform, calcium influx, eicosanoids, vascular smooth muscle, contraction.
Regulation of in vivo whole blood aggregation in rats by calcitonin gene related peptide
Authors: Booth Brian P , Fung Ho-Leung
Published: April 2011

The purpose of these experiments was to determine whether calcitonin gene related peptide (CGRP) mediates physiological control of platelet function in vivo. Rat blood pressure was continuously monitored via a femoral arterial cannula, and whole blood aggregation was assessed periodically ex vivo with an impedance aggregometer before and following a 1.4 nmol/kg bolus dose of CGRP8-37, a specific receptor antagonist of CGRP. Mean arterial blood pressure was not significantly affected by CGRP8-37 over a 30-min period (p > 0.05). However, whole blood aggregation increased by 38.4 ± 18.0% (p < 0.01) and 32.0 ± 11.2% (p < 0.05), at 5 and 15 min post CGRP8-37, respectively, when compared with control. Whole blood aggregation was not significantly different from control at 30 min (p > 0.05), suggesting a relatively short duration of action for in vivo CGRP8-37. These data suggest that CGRP contributes to the maintenance of hemostasis, and that this function may be more important than the better known vasodilatatory effects of this neuropeptide.Key words: hemostasis, calcitonin gene related peptide (CGRP), CGRP8-37, blood pressure, platelet aggregation.
Dose-dependent effects of nitric oxide synthase inhibition on systemic and renal hemodynamics in conscious lambs
Authors: Sener Alp , Smith Francine G
Published: April 2011

The present experiments were carried out to determine the role of nitric oxide in influencing systemic and renal hemodynamics in conscious young sheep. Parameters of cardiovascular function were measured before and for 4 h after intravenous injection of either L-NAME (NG-nitro-L-arginine methyl ester) or D-NAME (NG-nitro-D-arginine methyl ester) at doses of 10, 20, or 40 mg/kg in 13 conscious, chronically instrumented young sheep aged 43 ± 5 days. Blood pressure increased and heart rate decreased in a dose-dependent manner following administration of L-NAME. Renal vascular resistance was increased for 10 min following a dose of 10 mg/kg of L-NAME and for 120 min following a dose of 40 mg/kg of L-NAME. The renal vasodilatory response to close arterial injection of 1 µg/kg of acetylcholine was attenuated by L-NAME in a dose-dependent manner. These experiments provide the first information that under normal physiological conditions in conscious young animals, nitric oxide influences systemic and renal hemodynamics.Key words: renal vascular resistance, renal blood flow, maturation, sheep, vascular tone, nitric oxide, endothelial-derived relaxing factor, L-NAME (NG-nitro-L-arginine methyl ester).
Behavior of the hunting wasp Liris nigra V.d.L. (Hymenoptera, Larrinae) in particular or in unusual situations
Authors: Steiner André L.
Published: April 2011

On the average, a typical nesting cycle of this cricket-hunting wasp involves the following sequence of activities: nest digging—prey hunting and stinging (four stings are usually given)—malaxation of foreleg(s)—storage in nest—malaxation again, in nest—egg laying—nest closure.Many variations and unusual outcomes were observed, some mainly at particular stages of the life or nesting cycle of the wasp: nesting cycles with missing last stage(s) (early period of reproductive season and of daily cycle); abortive individual activities discontinued before completion (early stages of successive phases of nesting cycle); condensed nesting cycles, based on use of paralyzed crickets, nests of other Liris wasps (end of reproductive season).Other unusual behavior was observed in unusual situations or in case of interference. Various patchworks of response components were often performed, particularly in ambivalent or ambiguous contexts.Discussion of these unusual outcomes points to the possible importance of response, posture, and stimulus components or objects common to several nesting activities; of displacement activities; of changes in responsiveness of the wasp; and of stimulus situations that can vary in graded rather than discrete fashion.
Etude de trois populations de Viviparus malleatus (Reeve) (Gastropoda, Prosobranchia) de la région de Montréal. I. Croissance, fécondité, biomasse et production annuelle
Authors: Stańczykowska Anna , Magnin Etienne , Dumouchel André
Published: April 2011

Ecological and biological similarities and differences were observed in these three populations. These variations may partially be explained by the physical and chemical characteristics of the waters in which the specimens were collected. They may also be due to trophic relations which will be described in another paper.
The physiology of diapause in Diacyclops navus Herrick (Crustacea, Copepoda)
Authors: Watson Nelson H. F. , Smallman B. N.
Published: April 2011

Physiological parameters for the developmental arrest in the fourth copepodite instar of cyclopid copepods were determined to examine the assumption that this arrest corresponds to diapause in insects. In the initial "refractory" phase of arrest, the oxygen consumption was reduced to less than 0.01 μl per individual per hour. Tolerance to cyanide was increased to 2 × 10−3M; and survival time in anaerobic water was increased to a median value of 235 h at 15 °C. In the later "competent" phase of arrest, when individuals become capable of resuming development, oxygen consumption increased to 0.06 μl per individual per hour in fed animals; tolerance to cyanide remained about the same; and survival time in anaerobic water was reduced to a median value of 113 hours at 15 °C. These data are compared with those for fourth copepodites induced to develop directly (without arrest), and for adults. The results, coupled with the authors' previous evidence for the photoperiodic induction and termination of the arrest, justify extending the term "diapause" to cyclopid copepods.
Body mass, energetic constraints, and duck nesting ecology
Authors: Shutler Dave , Gloutney Mark L , Clark Robert G
Published: April 2011

Body size can impose tighter energetic constraints on smaller than on larger species. Accordingly, we tested whether smaller duck species were more inclined than larger species to save on metabolic costs by using nest sites that received more solar radiation (insolation) and experienced higher temperatures, and by initiating nests during warmer seasons. We also tested whether smaller duck species nested closer to food (wetlands) than did larger species, to save energy during incubation or on foraging trips. Because nest sites receiving less insolation may also be less concealed, we made an additional prediction that nest-predation rates would be higher for smaller than for larger species. Tests were also conducted intraspecifically. Over 8 years, variables used for testing these predictions were quantified at nests representing six species and 838 individuals. Body masses of 189 females from these nests were also obtained. Predictions that body size would affect nest concealment, nest-initiation date, and distance from water were supported by the results of interspecific tests. Additional support for the prediction that smaller species would nest later in the year was obtained from the literature. The prediction that species using less nest concealment would also have higher predation rates was not supported. Intraspecific variation in body mass was not a good predictor of either nest concealment, distance to water, or susceptibility to predation. Overall, our results reveal important influences of body size on duck nesting ecology.
Sperm-cell ultrastructure of North American sturgeons. I. The Atlantic sturgeon (Acipenser oxyrhynchus)
Authors: DiLauro Martin N , Kaboord Wayne , Walsh Rosemary A , Krise William F , Hendrix Michael A
Published: April 2011

Atlantic sturgeon (Acipenser oxyrhynchus) and lake sturgeon (Acipenser fulvescens) sperm-cell morphologies were examined using scanning electron microscopy. Major differences were found in four of nine metrics, all in the head region of the cell. Atlantic sturgeon sperm cells were much shorter than those of lake sturgeon. Anterior head width exceeded posterior head width, in contrast to the arrangement in lake sturgeon sperm cells. Lake sturgeon sperm cells are nearer in size to those of other sturgeons than are Atlantic sturgeon sperm cells. Comparisons were made with sperm-cell structures known from other sturgeon species, including the Russian sturgeon (Acipenser gueldenstaedti colchicus), stellate sturgeon (Acipenser stellatus), Chinese sturgeon (Acipenser sinensis), and white sturgeon (Acipenser transmontanus). Variation in cell morphology may indicate evolutionary relationships. In addition, the fine structure of Atlantic sturgeon sperm cells was examined using transmission electron microscopy and selected metrics are described. The cell possesses a distinct acrosome, a midpiece, and a single flagellum. A comparison is made with ultrastructural details of the sperm cells of stellate and white sturgeons. Similarities among these species include radial symmetry about the longitudinal axis, an elongate shape, a distinct acrosome, and the presence of endonuclear canals. Noteworthy differences include a smaller total length and width than stellate and white sturgeon sperm cells. The main sperm-cell body is approximately 4 µm long and the flagellum about 37 µm long, resulting in a total cell length of about 41 µm. Also, the Atlantic sturgeon sperm cell possesses only two membraned endonuclear canals, in contrast to the arrangement in white and stellate sturgeons, where three such organelles are found. A structural connection of unknown function between the nuclear fossa and proximal centriole is also present in the Atlantic sturgeon sperm cell. Sperm-cell nuclei of white and stellate sturgeons are elongate trapezoids, with the anterior end narrower, whereas in Atlantic sturgeon the anterior portion of the trapezoid is wider than the posterior. Structural similarities between species may indicate a commonality of ancestral and evolutionary relationships that may have taxonomic implications. Ultrastructure suggests a closer evolutionary relationship between the white and stellate sturgeon than between either of these species and the Atlantic sturgeon. The present findings may be used by biologists studying the reproductive physiology, forensics, taxonomy, and genetics of sturgeons.