摘要:

The nature and mechanisms of septohippocampal transmission have been elucidated by taking advantage of an in situ preparation in experiments with Sprague–Dawley rats under urethane. Both extracellular field potentials and intracellular recordings were made in CA1–3 regions of the hippocampus; and the hippocampal commissure and medial septum stimulated to evoke synaptic activity. Using muscarinic and nicotinic agonists and antagonists it was shown that both acetylcholine and medial septal activity can increase the excitability of pyramidal cells, mainly through muscarinic receptors. The effect of septal stimulation was enhanced by local application of physostigmine and reduced by intraventricular injections of hemicholinium. It was also shown that acetylcholine, when applied in the stratum pyramidale, can reduce the voltage and conductance changes observed during evoked inhibitory postsynaptic potentials (IPSP) without affecting the action of γ-aminobutyric acid on membrane conductance and voltage. It is therefore proposed that acetylcholine can reduce evoked IPSPs through presynaptic inhibition. Evidence is also presented that medial septal stimulation can reduce the efficacy of evoked IPSPs. These observations provide further support for the existence of a cholinergic septohippocampal pathway.

ISSN:0008-4212    

DOI:10.1139/y85-138

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

This study reports the effectsin vitroandin vivoofL-canavanine (LCN), an amino acid found in commonly consumed legumes, on immune function in normal and autoimmune mice.L-Canavanine in high doses effectively blocks all DNA synthesisin vitrowithin 24 h. At lower doses, LCN affects B-cell function of autoimmune New Zealand Black/New Zealand White (NZB/NZW)F1mice, inhibiting [3H]thymidine incorporation in response to B-cell mitogens, and pokeweed-induced intracytoplasmic immunoglobulin synthesis. LCN stimulates intracytoplasmic immunoglobulin (IgG > IgM). T-cell functions such as lymphoproliferation in response to concanavalin A or phytohemagglutinin and T-cell cytotoxicity are not affected. Suppression of the lipopolysaccharide response by LCN is removed by the addition of fresh B cells. Addition of the amino acid to mouse diet resulted in a decrease in the life-span of the autoimmune NZB and (NZB × NZW)F1mice and abolished the protective effect of male sex on their survival. The decrease in survival in LCN-treated autoimmune mice correlated with an increase in spontaneous immnunoglobulin-secreting cells (IgG > IgM) and antinuclear and double-stranded DNA antibodies. The histopathological analyses revealed increased glomerular damage and immunoglobulin deposition in the kidneys of the LCN-treated autoimmune and normal (DBA/2) mice. Ten percent of normal mice developed high titers of autoantibodies after 24 weeks of the diet. These data suggest a dietary amino acid,L-canavanine, affects B-cell function resulting in autoimmune phenomena and providing a new animal model of autoimmunity, a diet-induced systemic lupus erythematosus.

ISSN:0008-4212    

DOI:10.1139/y85-139

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Aortas from four sheep and three fetal lambs were fixed at physiological pressure in 10% neutral buffered formalin. The regions with branches were serially sectioned in either cross or longitudinal section at 7-μm intervals and stained for elastin with Gomori–aldehyde–fuchsin. A large model of one aortointercostal junction was made from Plexiglas to show that bundles of elastin appeared to be continuous from the aorta into the branch. These bundles were then studied from large photomicrographs of the other junctions. At the intercostals and lumbars, the elastin lamellae ran continuously from the outer third of the media into the branch. There was often an added "pad" of elastin and other acellular material on the flow divider (distal lip). The large muscular branches which arose from the abdominal aorta have much less elastin than the intercostals. In them the aortic elastin appears to merge into a raphe on the proximal and lateral sides of the junction, with a very abrupt transition. A "tongue" of muscle from the branch often penetrated into the media of the aorta distally. Occasionally a small acellular cap was seen on the apex of the flow divider. There were few significant differences between the lambs and the sheep, probably because embryologically the arteries develop very early. The proximal and distal lips of all junctions were easily distinguished from each other, and the small and large branches were also different. We suspect these regions may respond differently to pressure, but we did not test this hypothesis.

ISSN:0008-4212    

DOI:10.1139/y85-140

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Mongrel dogs were fitted with indwelling hepatic portal catheters. After recovery from surgery, experiments were conducted in fasting, unrestrained, fully conscious, normal dogs which were accustomed to handling and withdrawal of blood samples.L-Tryptophan, a specific serotonin precursor, was injected into a saphenous vein, 10 μM/kg body weight, dissolved in saline. Plasma serotonin, dopamine, norepinephrine, and epinephrine were determined by radioenzymatic assays in blood samples withdrawn at frequent intervals for 2 h, simultaneously from the indwelling catheter and from a catheter temporarily inserted into a saphenous vein other than the one used for the injection of tryptophan. The injection of the amino acid caused a significant elevation of the concentration of platelet-free serotonin within 60 min and this was accompanied by a reduction in the concentration of the catecholamines, dopamine, norepinephrine, and epinephrine. The changes occurred only in the portal circulation and were not detected in peripheral blood samples. The results of these experiments indicate the existence of a cause and effect related interdependence between the splanchnic serotonergic and adrenergic systems in that the tryptophan-stimulated increase in serotonergic activity resulted in a concomitant reduction in gut adrenergic activity.

ISSN:0008-4212    

DOI:10.1139/y85-141

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The adrenergic receptors of porcine coronary arteries were investigated in helically cut strips of small (≤0.5 mm outer-diameter (od), medium (0.8–1.2 mm od), large (1.5–2.5 mm od), and very large (>4 mm od) coronary arteries. Both the beta1agonist dobutamine and the beta2agonist terbutaline relaxed coronary arteries partially contracted by 25 mMof KCl. Dobutamine contracted small coronary arteries at 10−5 Mconcentrations, then relaxed them at 10−4 M. The beta1-adrenoceptor antagonist metoprolol contracted coronary arteries relaxed by either dobutamine or terbutaline, but the beta2antagonist H35/25 did so only in high and probably nonselective concentrations. Alpha1-adrenoreceptor stimulating concentrations of phenylephrine did not contract any of the arteries. Metoprolol and high concentrations of H35/25 further contracted large coronary arteries partially contracted by 25 mMpotassium. These contractions were blocked by verapamil and papaverine but not by atropine, phentolamine, yohimbine, mepyramine, or methysergide. This seems to indicate that beta-adrenergic receptors in porcine coronary arteries are beta1-receptors, or closely resemble beta1-receptors. They differ from many other beta1-receptors, however, in that they are stimulated by terbutaline. Alpha1adrenoreceptors seem not to be present in these porcine coronary arteries to a significant extent. Metoprolol and high concentrations of H35/25 have a direct contractile effect in large porcine coronary artery that is not mediated by alpha-adrenergic, muscarinic, histaminergic, or serotonergic receptors but requires verapamil-sensitive calcium.

ISSN:0008-4212    

DOI:10.1139/y85-142

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

To determine the alterations in cellular function which may contribute to the chronic predisposition of neuronal tissue to epileptiform activity, the membrane properties and inhibitory processes of hippocampal CA1 pyramidal cells were investigated usingin vitroslices prepared from commissural-kindled rats. No changes were observed in resting membrane potential, input resistance, spike amplitude, and membrane time constant of "kindled" CA1 pyramidal neurons when compared with controls. There were also no differences between control and kindled preparations in the amplitude of recurrent inhibitory postsynaptic potentials (IPSP) and in the duration of inhibition produced by either alvear (Alv) or stratum radiatum (SR) stimulation. Irrespective of group, repetitive stimulation of the Alv reduced the amplitude of the recurrent IPSP but failed to induce seizurelike activity. On the other hand, repetitive stimulation of SR frequently produced a neuronal burst discharge even though the duration and to some extent the amplitude of orthodromic inhibition was increased. On the basis of these data, it may be suggested that chronic changes in CA1 pyramidal cell membrane properties and transient reductions of inhibitory processes do not underlie the enhanced sensitivity of these neurons to seizure activity associated with kindling.

ISSN:0008-4212    

DOI:10.1139/y85-143

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Single crab (Callinectes danae) fibers were equilibrated with isotonic, high KC1 solutions and were subsequently returned to the control saline. This caused marked swelling of the T tubules. Fibers treated with 100 mMKCl had a 2.5-mV residual depolarization, a 50% decrease in effective membrane resistance (Reff) and a 75% reduction in membrane time constant (τm). These fibers exhibited large increases in membrane conductance upon depolarization and were inexcitable; membrane depolarization with current pulses elicited no contraction. The effects of the KCl treatment on membrane properties were not reproduced by treatment with high potassium gluconate solutions, which did not cause tubular swelling. Tetrabutylammonium (10 mM) or Ba ions (10–20 mM), but not tetraethylammonium (40–100 mM), Sr ions (15–70 mM), or procaine (1–8 mM) reversed the effects of the KCl treatment onReff, τm, membrane excitability, and excitation–contraction coupling. The time course of the Ba effects was consistent with the suggestion that the KCl treatment increases the K conductance of the tubular membranes, which in turn prevents the activation of voltage-dependent Ca channels located in the membranes of the T system. This results in inhibition of the Ca-dependent electrogenesis and consequently, the absence of contraction upon depolarization of the plasma membrane.

ISSN:0008-4212    

DOI:10.1139/y85-144

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The change in plasma and blood cell pools ofL-glutamine during a single pass through the kidney was studied in dogs and rats. It was shown that the glutamine content of blood cells does not change following one passage through the renal vascular bed in normal or acidotic dogs. Furthermore, an infusion ofL-glutamine elevating by 10-fold the plasma concentration of this amino acid only minimally changed the blood cells' glutamine content. Therefore within the time frame of acute experiments, the dog blood cells can be assumed to be impermeable to glutaminein vivo. Accordingly, renal glutamine extraction can be measured using either whole blood or plasma arteriovenous difference in this species. However, the latter value is larger and therefore can be measured more accurately. In normal rats, no net renal glutamine extraction is measured. In contrast, a considerable renal glutamine uptake occurs in acidotic rats, 23% of the extracted glutamine coming from the blood cell pool. A load of glutaminein vivosignificantly elevates both the plasma and the blood cell concentration. It is concluded (i) that the renal extraction of glutamine is best estimated using plasma arteriovenous difference in the dog, especially when the renal extraction is small; (ii) that whole blood measurements should be obtained in the rat.

ISSN:0008-4212    

DOI:10.1139/y85-145

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

To examine the modulation of fetal systolic time intervals of the ovine fetus in relation to fetal maturation, heart rate, respiratory activity, and circadian rhythm, studies were carried out on 13 fetal–maternal sheep preparations. The data obtained showed that there was a significant correlation between the ejection time (ET) and the RR intervals of the electrocardiogram. The pre-ejection period (PEP) and PEP/ET increased in relation to the fetal maturation (38 ms and 0.25 at 120 days to 52 ms and 0.33 at 145 days of gestation, respectively). When the circadian rhythmicity was analyzed, a relative tachycardia was in evidence during the 21- to 03-h period but systolic time intervals remained unchanged. Except for some tachycardia and cardiac rhythm variability, respiratory activity also had no influence on the systolic time intervals.

ISSN:0008-4212    

DOI:10.1139/y85-146

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Effects of neonatal sympathectomy with antiserum to nerve growth factor or 6-hydroxydopamine on the acetylcholine sensitivity of the rat left atria were investigated. Sensitivities to acetylcholine of atria from immunologically and chemically sympathectomized rats were much higher than that of control at 4 weeks of age. These results suggest possible involvement of the sympathetic nervous system in regulation of cardiac cholinergic sensitivity.

ISSN:0008-4212    

DOI:10.1139/y85-147

出版商:NRC Research Press    

年代:1985

数据来源: NRC