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Biomedical subjects

K Seto

Publications and source records attributed to K Seto.

At least 127 records · Page 7Linked to original sources
PubMed1989

Excitatory influence of the accessory olfactory bulb on tuberoinfundibular arcuate neurons of female mice and its modulation by oestrogen.

The role of the accessory olfactory bulb in conveying pheromonal information to tuberoinfundibular arcuate neurons was examined electrophysiologically in chloral hydrate-anaesthetized, oestrogen (0.5 micrograms in silastic capsules)-treated and untreated ovariectomized Balb/c female mice. Electrical stimulation of the accessory olfactory bulb orthodromically excited part of tuberoinfundibular neurons which were antidromically stimulated from the median eminence and histologically verified as being located within the arcuate nucleus. No inhibitions followed accessory bulb stimulation. The excitatory response to accessory bulb stimulation was reversibly blocked by the local anaesthetic lignocaine infused into the amygdala. The percentage of tuberoinfundibular arcuate neurons responding to accessory bulb stimulation was significantly higher in oestrogen-treated than in untreated animals. There was no difference between the two groups for the antidromic activation threshold, spontaneous firing rate, absolute refractory period or frequency of successful antidromic propagation into the soma of tuberoinfundibular arcuate neurons. In oestrogen-treated preparations, tuberoinfundibular arcuate neurons responsive and unresponsive to accessory bulb stimulation could be distinguished by the frequency of successful antidromic propagation into the soma. These studies demonstrate that olfactory relay neurons in the accessory olfactory bulb act to enhance the activity of a subpopulation of tuberoinfundibular arcuate neurons via the amygdala and that this neural transmission is modulated by oestrogen.

Action Potentials↗
PubMed1989

Influence of microinjection of glucagon into the amygdala on hepatic acetate metabolism in rabbits.

Glucagon was injected directly into the medial amygdala (AMYG) of rabbits, and changes in hepatic acetate metabolism were studied. The injection of 3 ng glucagon into the AMYG of intact rabbits increased the rates of 14C transfer from 14C-1-acetate into CO2, glucose, ketone bodies, cholesterol ester, free fatty acids and phospholipids but decreased those of 14C transfer into triglyceride. However, the glucagon injection into the AMYG of rabbits with lesions of stria terminals or into the parietal cortex of intact rabbits had no effects on the hepatic acetate metabolism. These observations support the hypothesis that the AMYG is a part of the glucagon-sensitive brain regulator system in the hepatic acetate metabolism.

Acetates↗
PubMed1989

Influence of electrical stimulation of the limbic structure on adrenocortical steroidogenesis in hypophysectomized rats.

The effects of electrical stimulation of the medial amygdala (AMYG) and dorsal hippocampus (DHPC) on the rates of 14C transfer from 14C-1-acetate into adrenocortical steroids in adrenal slices of hypophysectomized rats were investigated. The 14C transfer rates into corticosterone were increased by stimulation of the AMYG and DHPC. The 14C transfer rates into cortisol were increased by the AMYG stimulation but were not altered by the DHPC stimulation. From these results, it might be suggested that these limbic structures were involved in the regulation of adrenocortical steroidogenesis without participation of the pituitary.

Adrenal Cortex Hormones↗
PubMed1989

Preparation of Mycoplasma hyopneumoniae antigen for the enzyme-linked immunosorbent assay.

Methods of preparation of Mycoplasma hyopneumoniae antigens for the enzyme-linked immunosorbent assay to detect specific antibody, and properties of the antigens, are described. The reactivity and specificity of antigen prepared by Sephacryl S-300 column chromatography after treatment of M. hyopneumoniae cells with Tween 20 (S-300 antigen) were superior to those of antigen prepared by Sephadex G-25 column chromatography after treatment with Tween 20, or to lipid antigen. There were no differences among strains MI-3, J and VPP11 of M. hyopneumoniae. The S-300 antigen did not show cross-reactivity against porcine hyperimmune sera produced by M. hyorhinis, M. hyosynoviae, M. hyopharyngis, M. flocculare and Acholeplasma granularum. Antibody was first detected in sera of pigs inoculated intranasally with M. hyopneumoniae at two to four weeks after inoculation and seven to eight weeks after pigs were contact-exposed to the same mycoplasma.

Animals↗
PubMed1989

[A molecular basis for multidrug resistance and reversal of the resistance].

Multidrug-resistance is frequently characterized by enhanced drug efflux resulting from a membrane glycoprotein of 170,000 daltons (P-glycoprotein). Analysis of cloned cDNAs for the human MDR 1 gene, whose product is the P-glycoprotein, indicates that P-glycoprotein is an energy-dependent drug-efflux system for cytotoxic hydrophobic anticancer drugs. We have demonstrated that a photoanalog of a reversing agent, SDB-ethylenediamine, specifically binds to P-glycoprotein. The binding site on P-glycoprotein seems to be identical with that of anticancer agents and other reversing agents. On the other hand, the radioactive photoactive dihydropyridine calcium channel blocker, [3H] azidopine, photolabels P-glycoprotein in membrane vesicles from multidrug-resistant cells. This photolabeling is almost completely inhibited by excess dihydropyridine analogs that reverse or lower drug-resistance. In contrast, the labeling is not significantly inhibited by analogs that do not reverse resistance. These results suggest that it may be possible to quickly screen for dihydropyridine analogs that reverse multidrug resistance by measuring the inhibition of [3H] azidopine labeling of P-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1989

[Bone scintigraphy in evaluation of the effect of renal transplantation in patients with renal osteodystrophy].

Bone scintigraphy before and after renal transplantation was studied in 14 patients with renal osteodystrophy. The radionuclide distribution patterns visualized on the images before transplantation were classified into two groups; one group with markedly increased tracer uptake throughout the whole skeleton, especially in the skull, another group with prominent tracer uptake in the soft tissues. These abnormal tracer accumulations improved after renal transplantation. Bone scintigraphy before and after renal transplantation provides useful information concerning the follow-up of patients with renal osteodystrophy.

Adult↗
PubMed1989

An immunological study of tricalcium phosphate supplied by three different manufacturers.

Antigenicity of tricalcium phosphate (TCP) ceramics which were supplied by two Japanese manufacturers and a manufacturer of United States was studied by means of delayed skin reactions in guinea pigs. Skin reactions were elicited 13 days after being immunized by intradermal injection of the ceramics into the dorsal flanks of guinea pigs. After 24 and 48 hr, these reactions were assessed by measuring the diameter of the erythema, the degree of hemorrhaging and its induration. Antigenicity was not detected in the TCP obtained from the Asahi Optical Co., Ltd. and the Kyocera Corporation by means of skin reactions. In contrast, TCP from Miter, Inc. (Synthograft) raised a delayed type hypersensitivity (DTH) 24 hr after antigen elicitation. The reaction appeared to be based on tuberculin type and Jones-Mote type of reactions. Arthus reactions were not observed in either the normal groups or groups immunized with TCP.

Animals↗
PubMed1989

[Bone scintigraphy in evaluation of the effect of renal transplantation in the patients with renal osteodystrophy].

Bone scintigraphy before and after renal transplantation was studied in 10 patients with renal osteodystrophy. The hemodialyses, which resulted in renal osteodystrophy, were maintained for years in all cases before renal transplantation. The radionuclide distribution patterns visualized on the images before transplantation were classified into two groups, that is, one group with markedly increased tracer uptake throughout the whole skeleton, especially in the skull, another group with prominent tracer uptake in the soft tissues. These abnormal increased tracer accumulation improved after renal transplantation. Bone scintigraphy before and after renal transplantation brings about a useful information concerning the follow-up of the patients with renal osteodystrophy.

Adult↗
PubMed1988

Involvement of the septum in the regulation of paraventricular vasopressin neurons by the subfornical organ in the rat.

Extracellular recordings were obtained from 58 phasically active neurosecretory neurons in the hypothalamic paraventricular nucleus (PVN) of urethane-anesthetized male rats. Of these PVN neurons, 39 exhibited an increase and 11 displayed a reduction in ongoing activity following electrical stimulation of the subfornical organ (SFO), while the remaining neurons were unresponsive. Microinjection of the local anesthetic lidocaine into the medial septum reversibly abolished the SFO stimulus-evoked reduction in 7 out of 9 PVN neurons tested, whereas similar injection was without effect on the stimulus-evoked increase in 18 out of 20 PVN neurons tested. These results suggest that the SFO efferents through the medial septum to the PVN exert a predominantly inhibitory influence on the excitability of putative vasopressin (VP)-secreting neurons in the PVN.

Action Potentials↗
PubMed1988

The median preoptic nucleus participates in the control of paraventricular vasopressin neurons by the subfornical organ in the rat.

Extracellular single-unit activity was recorded from phasically firing neurohypophyseal neurons (n = 41) in the hypothalamic paraventricular nucleus (PVN) of urethane-anesthetized male rats. Electrical stimulation of the subfornical organ (SFO) produced orthodromic long-duration (n = 18) or short-duration (n = 10) excitation or inhibition (n = 8) of the activity of PVN neurons. The long-duration excitatory response of about half (n = 7) the neurons (n = 15) tested was reversibly abolished by microinjection of the local anesthetic lidocaine into the median preoptic nucleus (MnPO), whereas neither the short-duration excitatory (n = 7) nor inhibitory (n = 6) responses were affected. These results suggest that the SFO efferents through the MnPO to the PVN may transmit the neuromodulatory signals which evoke long-duration increases in the excitability of putative vasopressin (VP)-secreting neurons in the PVN.

Action Potentials↗
PubMed1988

Neurons in the lateral hypothalamic area and zona incerta with ascending projections to the subfornical organ area in the rat.

Sixteen neurons in the lateral hypothalamic area (LH) and 12 neurons in the zona incerta (ZI) were antidromically activated by electrical stimulation of the subfornical organ (SFO) area in urethane-anesthetized male rats. The activity of these LH and ZI units was examined for response to intracarotid injections of isotonic (0.15 M NaCl solution, 0.05 ml) or hypertonic (0.18 M or 0.3 M NaCl solution, 0.05 ml) saline. All the units did not change their activity to the injections of isotonic saline. Of these units, 9 LH and 5 ZI units displayed an increase and 2 LH and 3 ZI units exhibited a reduction in neuronal activity following the injections of hypertonic saline, while the remaining 5 LH and 3 ZI units were unresponsive. The present results suggest that the LH and ZI neurons with ascending projections to the SFO may carry the information from osmoreceptive elements for modulating the actions of the SFO.

Afferent Pathways↗
PubMed1988

Neurons in the nucleus of the solitary tract with ascending projections to the subfornical organ in the rat.

Thirty-one neurons in the region of the nucleus of the solitary tract (NTS) were antidromically activated by electrical stimulation of the subfornical organ (SFO) in male rats under urethane anesthesia. The activity of these identified neurons was tested for a response to activation of peripheral baroreceptors, achieved by rising arterial blood pressure with an intravenous administration of the alpha-agonist metaraminol. Of the neurons tested, 17 displayed an increase and 6 exhibited a reduction in neuronal firing that accompanied a 40- to 60-mmHg elevation in mean arterial pressure, while 8 were unresponsive. The results suggest that neurons projecting to the SFO in the region of the NTS may be important for carrying peripheral baroreceptor information to the SFO.

Action Potentials↗
PubMed1988

Lateral hypothalamic area and paraventricular nucleus connections with subfornical organ neurons: an electrophysiological study in the rat.

The neural pathways from the lateral hypothalamic area (LHA) to the hypothalamic paraventricular nucleus (PVN) mediated by subfornical organ (SFO) neurons were examined in urethane-anesthetized male rats in order to determine the excitability of vasopressin (VP)-secreting neurons in the PVN. Microinjection of angiotensin II (AII) into the LHA excited the activity of nearly half (n = 8) of the SFO neurons (n = 18) activated antidromically by electrical stimulation of the PVN. Microinjection of AII into the LHA also caused excitation of approximately one-quarter (n = 11) of putative VP-secreting neurons (n = 45) in the PVN while the excitatory responses of the putative VP-secreting neurons were blocked or attenuated by pretreatment with the AII antagonist, saralasin (Sar), in the SFO. Electrical stimulation of the LHA, on the other hand, produced excitation (n = 17) or inhibition (n = 14) of the putative VP-secreting neurons (n = 52) in the PVN. About half of the excitatory responses to LHA stimulation were blocked or attenuated by pretreatment with Sar in the SFO, whereas the inhibitory responses were not affected. These results show some possible connections between the LHA and PVN, and suggest that AII-sensitive LHA neurons with efferent projections to the SFO may act to enhance the excitability of putative VP-secreting neurons in the PVN via an excitatory influence on the AII-sensitive SFO neurons.

Action Potentials↗
PubMed1988

Response of medial preoptic/anterior hypothalamic neurones to ventrolateral medulla stimulation and its attenuation by adrenoceptor antagonists.

Extracellular single-unit recordings were made from medial preoptic/anterior hypothalamic (MPOAH) neurones in urethane-anaesthetized female rats, and the responses of these neurones to electrical stimulation of the ventrolateral medulla (VLM) were investigated. Of 189 neurones tested, 20% were excited and 21% were inhibited following VLM stimulation. The latency of inhibitory responses showed a normal distribution and the mean latency was 47 ms, whereas the latency of excitatory responses showed a bimodal distribution with peaks in the ranges of 0-10 ms and 40-50 ms, respectively. Excitatory responses with latencies greater than 15 ms and inhibitory responses were significantly attenuated by intravenous injections of the alpha-adrenoceptor antagonist phenoxybenzamine but not the beta-adrenoceptor antagonist propranolol. In the light of these observations and the known anatomical and electrophysiological findings, it is suggested that A1 noradrenergic and/or C1 adrenergic inputs from the VLM to MPOAH neurones are, at least in part, mediated by alpha-adrenoceptors.

Animals↗
PubMed1988

Influence of microinjection of corticosterone into hippocampus on hepatic acetate metabolism in rabbits.

Corticosterone was injected directly into the hippocampus of rabbits, and changes in hepatic acetate metabolism were studied. The microinjection of corticosterone with seasame oil into hippocampus decreased the rates of 14C transfer from 14C-1-acetate into CO2 and free cholesterol, and increased 14C transfer into glucose, ketone bodies, triglyceride, free fatty acids and phospholipids. But after microinjection of corticosterone into the hippocampus of rabbits with lesions of dorsal fornix, hepatic acetate metabolism did not differ from that of control rabbits, which received injection of seasame oil into the same brain region. From these results it might be suggested that the hippocampus is a part of corticosterone-sensitive brain regulator system in the hepatic acetate metabolism.

Acetates↗
PubMed1988

Influence of electrical stimulation of the limbic structure on ovarian steroidogenesis in hypophysectomized and adrenalectomized rats.

The effects of electrical stimulation of the medial amygdala (AMYG) and dorsal hippocampus (DHPC) on the rates of 14C transfer from 14C-1-acetate into ovarian steroids in hypophysectomized and adrenalectomized rats (H-A rats) were investigated. The 14C transfer rates into estrogen were increased by stimulation of AMYG and DHPC. The 14C transfer rates into progesterone and 20 alpha-hydroxy-pregn-4-en-3-one (20 alpha-OH-P) were increased by the AMYG stimulation but decreased by the DHPC stimulation. From these results, it might be suggested that these limbic structures were involved in the regulation of ovarian steroidogenesis without participation of pituitary and adrenal.

17-alpha-Hydroxypregnenolone↗
PubMed1988

Influence of microinjection of corticosterone into ventromedial hypothalamus on hepatic acetate metabolism in rabbits.

Corticosterone was injected into the ventromedial hypothalamus (VMH) of rabbits, and changes in hepatic acetate metabolism were studied. The microinjection of corticosterone with seasame oil into the VMH of intact rabbits increased the rates of 14C transfer from 14C-1-acetate into CO2, glucose, ketone bodies, triglyceride, free cholesterol, free fatty acids and phospholipids but decreased those of 14C transfer into cholesterol ester. However, corticosterone injected into the VMH of rabbits with VMH lesions or the parietal cortex of intact rabbits was without effect on the hepatic acetate metabolism. From these results it might be suggested that the VMH is an integral part of the corticosterone-sensitive brain regulator system in the hepatic acetate metabolism.

Acetates↗