Effect of alpha-helical-CRF[9-41] on feeding in goldfish: involvement of cortisol and catecholamines

The anoretic effect of corticotropin-releasing factor (CRF) was not dependent on adrenal activation in goldfish (Carassius auratus). Moreover, an interaction between CRF and the hypothalamic catecholaminergic system in the central regulation of food intake was observed. The intracerebroventricular (icv) administration of CRF increased cortisol levels and reduced food intake and hypothalamic norepinephrine and dopamine content at 2 hr postinjection, with these effects reversed by alpha-helical CRF[9-41] pretreatment. The anoretic effect of CRF was independent of the circulating cortisol increase, because it was only evoked after icv injections but not after intraperitoneal (ip) administration. Furthermore, the increase in plasma cortisol levels induced by ip administration of this steroid did not modify feeding.     

Role of the alpha 1-, and alpha 2- and beta-adrenoceptors of the median preoptic area on the water intake, renal excretion, and arterial pressure induced by ANG II

The present experiments were conducted to investigate the role of the alpha 1-, alpha 2- and beta-adrenergic receptors of the median preoptic area (MnPO) on the water intake and urinary electrolyte excretion, elicited by central injections of angiotensin II (ANG II). Prazosin (an alpha 1-adrenergic receptor antagonist) and yohimbine (an alpha 2-adrenergic receptor antagonist) antagonized the water ingestion, Na+, K+, and urine excretion induced by ANG II. Administration of propranolol, a beta-adrenergic receptor antagonist increased the Na+, K+, and urine excretion induced by ANG II. Previous treatment with prazosin and yohimbine reduced the pressor responses to ANG II. These results suggest that the adrenergic neurotransmission in the MnPO may actively participate in ANG II-induced dipsogenesis, natriuresis, kaliuresis, diuresis and pressor responses in a process that involves alpha 1-, alpha 2-, and beta-adrenoceptors.     

Effects of intrathecal alpha1- and alpha2-noradrenergic agonists and norepinephrine on locomotion in chronic spinal cats

Noradrenergic drugs, acting on alpha adrenoceptors, have been found to play an important role in the initiation and modulation of locomotor pattern in adult cats after spinal cord transection. There are at least two subtypes of alpha adrenoceptors, alpha1 and alpha2 adrenoceptors. The aim of this study was to investigate the effects of selective alpha1 and alpha2 agonists in the initiation and modulation of locomotion in adult chronic cats in the early and late stages after complete transection at T13. Five cats, chronically implanted with an intrathecal cannula and electromyographic (EMG) electrodes were used in this study. Noradrenergic drugs including alpha2 agonists (clonidine, tizanidine, and oxymetazoline) and an antagonist, yohimbine, one alpha1 agonist (methoxamine), and a blocker, prazosin, as well as norepinephrine were injected intrathecally. EMG activity synchronized to video images of the hindlimbs were recorded before and after each drug injection. The results show differential effects of alpha1 and alpha2 agonists in the initiation of locomotion in early spinal cats (i.e., in the first week or so when there is no spontaneous locomotion) and in the modulation of locomotion and cutaneous reflexes in the late-spinal cats (i.e., when cats have recovered spontaneous locomotion). In early spinal cats, all three alpha2 agonists were found to initiate locomotion, although their action had a different time course. The alpha1 agonist methoxamine induced bouts of nice locomotor activity in three spinal cats some hours after injection but only induced sustained locomotion in one cat in which the effects were blocked by the alpha1 antagonist prazosin. In late spinal cats, although alpha2 agonists markedly increased the cycle duration and flexor muscle burst duration and decreased the weight support or extensor activity (effects blocked by an alpha2 antagonist, yohimbine), alpha1 agonist increased the weight support and primarily the extensor activity of the hindlimbs without markedly changing the timing of the step cycle. Although alpha2 agonists, especially clonidine, markedly reduced the cutaneous excitability and augmented the foot drag, the alpha1 agonist was found to increase the cutaneous reflex excitability. This is in line with previously reported differential effects of activation of the two receptors on motoneuron excitability and reflex transmission. Noradrenaline, the neurotransmitter itself, increased the cycle duration and at the same time retained the cutaneous excitability, thus exerting both alpha1 and alpha2 effects. This work therefore suggests that different subclasses of noradrenergic drugs could be used to more specifically target aspects of locomotor deficits in patients after spinal injury or diseases.     

Norepinephrine-induced contraction of isolated rabbit bronchial artery: role of alpha 1- and alpha 2-adrenoceptor activation

The contractile effect of norepinephrine (NE) on isolated rabbit bronchial artery rings (150-300 microns in diameter) and the role of alpha 1- and alpha 2-adrenoceptors (AR) on smooth muscle and endothelium were studied. In intact arteries, NE increased tension in a dose-dependent manner, and the sensitivity for NE was further increased in the absence of endothelium. In intact but not in endothelium-denuded arteries, the response to NE was increased in the presence of both indomethacin (Indo; cyclooxygenase inhibitor) and NG-nitro-L-arginine methyl ester [L-NAME; nitric oxide (NO) synthase inhibitor], indicating that two endothelium-derived factors, NO and a prostanoid, modulate the NE-induced contraction. The alpha 1-AR antagonist prazosin shifted the NE dose-response curve to the right, and phenylephrine (alpha 1-AR agonist) induced a dose-dependent contraction that was potentiated by L-NAME or removal of the endothelium. The sensitivity to NE was increased slightly by the alpha 2-AR antagonists yohimbine and idazoxan, and this effect was abolished by Indo or removal of the endothelium. Similarly, contractions induced by UK-14304 (alpha 2-AR agonist) were potentiated by Indo or removal of the endothelium. These results suggest that NE-induced contraction is mediated through activation of alpha 1- and alpha 2-ARs on both smooth muscle and endothelium. Activation of the alpha 1- and alpha 2-ARs on the smooth muscle causes contraction, whereas activation of the endothelial alpha 1- and alpha 2-ARs induces relaxation through release of NO (alpha 1-ARs) and a prostanoid (alpha 2-ARs).     

Effect of sodium naproxen on inflammatory response induced by anterior chamber paracentesis in the rabbit

This study evaluated the effect of sodium naproxen (a reversible competitive inhibitor of cyclo-oxygenase) and phenylephrine (a mydriatic alpha-adrenergic agent) eye drops in maintaining atropine mydriasis in the rabbit after paracentesis. Moreover, to assess the influence of these treatments on vascular and cellular inflammatory responses in the rabbit eye, several biochemical parameters were considered. Anterior chamber paracentesis significantly reduced atropine-induced mydriasis and a parallel elevation of proteins, polymorphonuclear leucocytes (PMNs), prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) levels in the secondary aqueous humour (obtained 120 min later) was observed. A significant increase in PMNs in the aqueous humour and a parallel increase in myeloperoxidase activity, a measure of PMN infiltration, in the iris-ciliary body were detected. Atropine-induced mydriasis was maintained in rabbits treated with either sodium naproxen or phenylephrine eye drops. However, only in the former group were the inflammatory parameters significantly reduced, with the exception of aqueous LTB4 levels. The inhibition of the protein influx in the aqueous humour and of the miosis produced by sodium naproxen can be related to the high drug levels in the aqueous humour that were effective in inhibiting the cyclo-oxygenase pathway of arachidonic acid metabolism, whereas the effects on PMN infiltration appear to be independent of significant release of the potent chemotactic agent LTB4, synthesized via the 5-lipoxygenase pathway.     

Effects of helical structures formed by the binding arms of DNAzymes and their substrates on catalytic activity

As a part of our efforts to clarify structure-function relationships in reactions catalyzed by deoxyribozymes (DNAzymes), which were recently selected in vitro , we synthesized various chimeras and analyzed the kinetics of the corresponding cleavage reactions. We focused on the binding arms and generated helices composed of binding arms and substrates that consisted of RNA and RNA, of RNA and DNA or of DNA and DNA. As expected for the rate limiting chemical cleavage step in reactions catalyzed by DNAzymes, a linear relationship between log( k cat) and pH was observed. In all cases examined, introduction of DNA into the binding helix enhanced the rate of chemical cleavage. Comparison of CD spectra of DNAzyme. substrate complexes suggested that higher levels of B-form-like helix were associated with higher rates of cleavage of the substrate within the complex. To our surprise, the enhancement of catalytic activity that followed introduction of DNA into the binding helix (enhancement by the presence of more B-form-like helix) was very similar to that observed in the case of the hammerhead ribozymes that we had investigated previously. These data, together with other observations, strongly suggest that the reaction mechanism of metal-ion-dependent DNAzymes is almost identical to that of hammerhead ribozymes.     

Effects of glycosaminoglycans on the glomerular changes induced by Adriamycin

BACKGROUND: A model of moderate acute necrotizing pancreatitis is essential for the study of the pathophysiology of the disease and novel therapies. We tried to establish a model of bile salt-induced acute necrotizing pancreatitis in rats. METHODS: Acute pancreatitis was induced by retrograde infusion of bile salt into the cannulated pancreatobiliary duct. Twenty-six rats wee divided into 3 groups. Group I (n = 8) received 0.2 ml of glycodeoxycholic acid (GDOC) 10 mmol/l; group II (n = 10) 0.2 ml of 2.5% sodium taurodeoxycholate (NaTDC); group III (n = 8) the mixture of 0.2 ml GDOC 10 mmol/l and 10 U enterokinase. Serum levels of amylase and lipase, hematocrit, mean arterial pressure and heart rate were determined at baseline and 5 hours later. Then the pancreas was removed for histopathology and grading (0-3; absent-severe) with regard to leukocyte infiltration, edema, necrosis, hemorrhage and acinar cell vacuolization. RESULTS: Serum levels of amylase and lipase increased significantly in 5 hours in all the groups. Serum amylase levels were significantly lower in group III than in group II. No significant difference of serum lipase was found among the groups. Group II had the highest scores of necrosis and acinar cell vacuolization, whereas group III had the highest scores of leukocyte infiltration and edema. The degree of necrosis was significantly more severe in group II than in group I. The hematocrit increased significantly in 5 hours in groups I and II. The mean arterial pressure in 5 hours decreased significantly in group I. There was no significant difference of the changes of heart rate in 5 hours among 3 groups. CONCLUSIONS: Intraductal infusion of NaTDC was a good method to induce moderate acute necrotizing pancreatitis in rats. GDOC caused mild pancreatitis, and pancreatic injury was aggravated when enterokinase was added. The severity of pancreatic histopathology was not correlated with the changes of serum levels of pancreatic enzymes, hematocrit or mean arterial pressure at the early stage of pancreatitis.     

Exogenous NPY modulation of cardiac autonomic reflexes and its pressor effect in the conscious rabbit

1. Neuropeptide Y (NPY) may inhibit sympathetic and vagal transmission via presynaptic Y2 receptors and cause vasoconstriction via postsynaptic Y1 receptors. We examined the effects of NPY and related peptides on cardiovascular parameters and autonomic reflexes in the conscious rabbit. Further, the postjunctional effects of NPY and related peptides were assessed on acetylcholine (ACh) and isoprenaline agonist dose-chronotropic response curves. 2. In conscious rabbits the cardiac baroreceptor-heart rate reflex (baroreflex), Bezold-Jarisch like and nasopharyngeal reflexes were assessed in control, propranolol-treated or methscopolamine-treated (baroreflex only) groups, before and 30 min after i.v. administration of NPY (10 microg kg[-1] + 5 microg kg[-1] min[-1]) or vehicle (saline, 10 ml h[-1]). The effects of equivalent pressor doses of [Leu31, Pro34]NPY or methoxamine on the baroreflex were also examined. In separate animals, dose-heart rate (HR) response curves to isoprenaline or ACh were constructed before and 15 min after administration of NPY, [Leu31,Pro34]NPY (ACh only) or [Leu31,Pro34]NpY + sodium nitroprusside (ACh only). 3. Administration of NPY-receptor agonists caused sustained bradycardia (in the absence of methscopolamine) and rightward shifts of the barocurves in all 3 groups. The range of sympathetically-mediated tachycardia was significantly decreased by NPY or [Leu31,Pro34]NPY in the methscopolamine-treated group. However, these changes in the baroreflex were no different from those elicted by equipressor doses of methoxamine. There was no vagal inhibition by any NPY-receptor agonist in all three autonomic reflexes examined. ACh or isoprenaline dose-HR response curves were not affected by NPY peptide administration. 4. We conclude that in the conscious rabbit, at a single dose that elicits a significant pressor response, exogenous NPY has no direct effect on modulation of cardiac and autonomic reflexes. Non-specific effects of exogenous NPY on the baroreflex may be fully explained by its pressor action. There was no effect of NPY on postjunctional ACh or isoprenaline agonist dose-response curves. Therefore, it is unlikely that endogenous NPY has a functional role in directly modulating cardiac autonomic neurotransmission in the rabbit.     

Alterations of the Frank orthogonal scalar leads induced by anaphylactic shock in the rabbit

The anaphylactic shock of the rabbit is characterized by an acute right ventricular overload, accompanied by severe alterations of cardiac electrogenesis. During shock, the mean QRS vector, as measured from the algebraic sum of the Q, R, and S deflections on the three leads, shifts to the right, inferiorly and anteriorly. An injury current quickly appears. The TQ vector points away from the right ventricle. A progressive depolarization on the right ventricular wall is displayed by suction electrodes and the suppression of right ventricular hypertension by a cross circulation produces an almost immediate disappearance of the injury current. The geneses of these electrical alterations are briefly discussed. The possibility of an anaphylactic reaction at the level of the coronary arterial wall, previously mentioned in the literature, seems unlikely. The role of the haemodynamic changes and of the increased right ventricular blood pool is thought to be predominant.     

Anatomical partitioning and nerve branching patterns in the adult rabbit masseter

We examined responses of preterm infants to swaddling after a heel lance. Fifteen preterm infants from two postconceptional age (PCA) groups (Group 1: n = 7, PCA < 31 wk; Group 2: n = 8, PCA > or = 31 wk) were observed for 30 minutes during blood sampling followed by routine care; blood sampling followed by swaddling; and no blood sampling and routine care. In both groups, blood sampling resulted in concurrent increases in heart rate and state of arousal, in negative facial displays, and in reductions in blood oxygensaturation. After the blood was drawn, infants less than 31 weeks PCA exhibited an immediate and spontaneous return to behavioral patterns similar to those observed during the no-blood-sample condition, regardless of treatment condition. Infants 31 weeks PCA or older exhibited protracted behavioral disturbance that was significantly reduced by the use of swaddling. We discuss the significance of these findings.     

Effects of leptin on corticotropin-releasing factor (CRF) synthesis and CRF neuron activation in the paraventricular hypothalamic nucleus of obese (ob/ob) mice

The effects of leptin on the levels of CRF messenger RNA (mRNA) in the paraventricular hypothalamic nucleus (PVN), on the activation of the PVN CRF cells, and on the plasma levels of corticosterone were investigated in lean (+/?) and obese (ob/ob) C57BL/6J male mice. Murine leptin was s.c. infused using osmotic minipumps. The treatment period extended to 7 days, and the daily dose of leptin delivered was 100 microg/kg. The mice were killed either in a fed state or following 24 h of total food deprivation. The starvation paradigm was employed to enhance the activity of the hypothalamic-pituitary-adrenal axis in obese mice. In situ hybridization histochemistry was performed to determine the PVN levels of CRF mRNA and the arcuate nucleus levels of neuropeptide Y mRNA. The activity of the PVN CRF cells was estimated from the number of PVN cells colocalizing CRF mRNA and the protein Fos. Leptin led to a reduction in body weight gain and fat deposition. These effects were seen in both +/? and ob/ob mice and were observed to be particularly striking in obese mutants, in which leptin also caused an important reduction in food intake. Leptin also was found to affect plasma levels of corticosterone. It lowered the high corticosterone levels of obese mutants, an effect that appeared more evident in food-deprived than in fed mice. Finally, leptin prevented the induction of CRF synthesis in the PVN and the activation of the PVN CRF neurons observed in food-deprived ob/ob mice and hindered the elevation of arcuate nucleus neuropeptide Y synthesis in ob/ob mice. Together these results suggest a role for leptin in the excessive response of the hypophysiotropic CRF system of the ob/ob mouse.     

Effects of ketamine on the peripheral autonomic nervous system of the rat

It has been demonstrated that activated C3 products might bind to lymphocyte C3 receptors and inhibit subsequent complement-dependent lymphocyte rosette formation. Sera from patients with various types of chronic glomerulonephritis (GN) have been tested in a complement-dependent rosette inhibition assay using normal donors' lymphocytes as reacting cells. Control subjects consisted of healthy donors and patients with miscellaneous renal and general diseases. Most sera of membranoproliferative GN and of systemic lupus erythematosus, and two-thirds sera of focal glomerolosclerosis patients, significantly inhibited rosette formation. Only 15-40 percent sera of patients with other types of GN were inhibitory. Serum inhibiting activity usually correlated with low serum C3 level (P less than 0.0005), although inhibition could be observed with normal serum C3. However, no correlation was found between a patient's own complement-dependent lymphocyte rosette count and his serum inhibitory activity. These results extend previous findings and suggest that the complement-dependent rosette inhibition assay can be used routinely to detect serum activated complement components either free or bound to immune complexes.     

Peripheral autonomic mechanisms and Pavlovian conditioning in the rabbit (Oryctolagus cuniculus).

Three experiments examined the effects of peripheral administration of 0–50 mg/kg atropine methyl nitrate and 6-hydroxydopamine hydrobromide on differential classical conditioning of eye-blink (EB) and heart rate (HR) responses in 102 New Zealand albino rabbits. Atropine decreased HR CR magnitude and increased baseline HR, although the latter declined somewhat over the 1st few sessions of the experiment. As baseline HR declined, EB CRs increased in Ss treated with atropine. However, the acquisition of the EB response was impaired in these Ss compared with Ss treated with saline. The administration of 6-hydroxydopamine produced an impairment of the HR response early and late during acquisition but had no effect on EB conditioning. Control experiments suggested that the impairments produced by methyl atropine were not due to general somatomotor deficits or to a differential sensitivity to the electric shock UCS. The conditioning data are consistent with B. C. Lacey and J. I. Lacey's (1974) peripheral afferent feedback hypothesis of autonomic-somatic relations. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nicotinic cholinergic influences in pancreatic secretion induced by intraduodenal alkaline and acid solutions in the rabbit

1. The effect of hexamethonium on the exocrine pancreatic response to intraduodenal acidification and alkalinization, and the secretin and VIP release after these stimuli, was studied. 2. The hydroelectrolyte secretion after hydrochloric acid and sodium carbonate perfusion was reduced by hexamethonium treated (322 +/- 44% of maximum response in flow rate to sodium carbonate perfusion in untreated animals vs 140 +/- 12% in pretreated animals, and 252 +/- 19% of maximum response in flow rate to HCl in untreated animals vs 166 +/- 11% in pretreated animals). 3. However, hexamethonium has no effect on secretin plasma levels after either intraduodenal acidification or alkalinization. 4. On the contrary, the ganglion blocker significantly (P < 0.01) reduced plasma VIP levels in response to intraduodenal HCl (maximum response 320 +/- 74% in untreated vs 184 +/- 44% in hexamethonium-treated animals). 5. Plasma VIP levels showed a similar increase in both untreated (maximum response: 151 +/- 12%) and ganglion blocked animals (170 +/- 26%) in response to sodium carbonate. 6. These data suggest the existence of complex neural mechanisms in the exocrine pancreatic response to intraduodenal stimuli, these mechanisms being different depending on the intraduodenal stimulus.     

Effects of cadmium and lead on adrenergic neuromuscular transmission in the rabbit

The effects of inorganic lead (PbCl2) and cadmium (DdCl2) on the pressor response of rabbit saphenous arteries produced by sympathetic nerve stimulation were examined. A 1- to 3-cm length of artery was removed, placed in a bath containing mammalian Ringer solution, and perfused with the same solution at a constant rate sufficient to maintain a 40-60 mmHg perfusion pressure. Increases in perfusion pressure resulting from electrical stimulation -f periarterial nerve endings were reduced or completely blocked by the addition of 5-20 muM lead or cadmium to the bathing solution for a period of 15-30 min. Responses to norepinephrine or to direct electrical stimulation of the muscle remained relatively unaffected. During lead or cadmium blockade, the response to nerve stimulation could be restored by a fourfold increase in calcium concentration. It is concluded that lead and cadmium reduce the response to sympathetic nerve stimulation primarily through an effect on presynaptic nerve terminals.     

Effects of timolol and betaxolol on choroidal blood flow in the rabbit

Endothelium-dependent hyperpolarization of vascular smooth muscle cells (VSMCs) plays a crucial role in regulating vascular tone, especially in resistance vessels. It has been proposed that metabolites of arachidonic acid (AA), formed by cytochrome P-450 monooxygenase (P450), are endothelium-derived hyperpolarizing factors (EDHFs). These metabolites have been reported to mediate dilation to endogenous vasoactive compounds, such as bradykinin and acetylcholine. However, it is not known whether these metabolites of AA contribute to dilation of human resistance vessels. This is important since it has been proposed that EDHF serves as a compensatory mechanism to maintain dilation in disease states. Therefore, we studied the effect of AA on vessel diameter and VSMC membrane potential in isolated human coronary microvessels. Arterioles (81+/-5 microm, n=70) were dissected from right atrial appendages at the time of cardiac surgery and cannulated at a distending pressure of 60 mm Hg and zero flow. Changes in internal diameter were recorded with videomicroscopy. Some vessels were impaled with glass microelectrodes to measure membrane potential of VSMCs while internal diameters were simultaneously recorded. After constriction (47+/-2%) with endothelin-1, AA (10(-10)to 10(-5)mol/L) induced substantial dilation of human coronary microvessels, which was abolished by removal of the endothelium. Treatment with 17-octadecynoic acid (17-ODYA, 10(-5) mol/L; a P450 inhibitor) attenuated maximal dilation to AA (49+/-9% versus 91+/-4% [control]; P<0.05 versus control), whereas indomethacin (INDO, 10(-5) mol/L; a cyclooxygenase inhibitor) and N omega-nitro-L-arginine methyl ester (L-NAME, 10(-4) mol/L; a NO synthase inhibitor) were without effect. Both 17-ODYA and miconazole (10(-5) mol/L, a chemically distinct P450 inhibitor) further reduced the dilation to AA in the presence of INDO. The presence of 40 mmol/L KCl or charybdotoxin (10(-8) mol/L, a blocker of large-conductance Ca2+-activated K+ channels) impaired dilation to AA (19+/-9% [KCI] versus 76+/-5% [control] and 47+/-6% [charybdotoxin] versus 91+/-3% [control]; P<0.05 for both). After depolarization with endothelin-1 (-26+/-1 mV from -48+/-3 mV [before endothelin]), AA (10(-5)mol/L) in the presence of INDO and L-NAME induced hyperpolarization of VSMCs (-57+/-5 mV). In the presence of 17-ODYA together with INDO and L-NAME, endothelin produced similar depolarization (-26+/-2 mV from - 48+/- 3 mV), but hyperpolarization to AA was reduced (-33+/-2 mV; P<0.05 versus absence of 17-ODYA). AA metabolites formed primarily by P450 produce potent endothelium-dependent dilation of human coronary arterioles via opening of Ca2+-activated K+ channels and hyperpolarization of VSMCs. These findings support an important role for P450 metabolites in the regulation of human coronary arteriolar tone.     

Study of the polymorphism of ovine alpha s1- and alpha s2-caseins by capillary electrophoresis

Polymorphism of ovine alpha s-caseins was studied by capillary electrophoresis at pH 3.0 +/- 0.1. Individual caseins (CN) were selected according to their genetic variants, as determined by PAGE and isoelectric focusing. The ovine caseins, containing different genetic variants of alpha s1-CN and alpha s2-CN, were fractionated by cation-exchange FPLC. The alpha s1-CN variants A, B and C, and the fast moving alpha s2-CN variant were identified by a capillary electrophoresis method. The fast moving alpha s2-CN variant, so-called for its behaviour in PAGE, also had a faster electrophoretic mobility than the common alpha s2-CN when analysed by the present technique. The capillary electrophoresis method gave excellent, rapid, automated separation of alpha s1-CN and alpha s2-CN variants and was suitable for screening studies.