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Biomedical subjects

K Seto

Publications and source records attributed to K Seto.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1988

Electrophysiology of neurones projections from the rat A1 noradrenergic region to the medial preoptic/anterior hypothalamic area: lack of effect of the oestrous cycle on their excitability.

The neuronal excitability of presumed A1 noradrenergic neurones in the ventrolateral medulla (VLM) which directly project to the medial preoptic/anterior hypothalamic area was analysed in pro-oestrous and metoestrous female rats under urethane anaesthesia. No significant difference was detected between the two groups for the antidromic activation threshold, absolute refractory period, frequency of successful antidromic propagation into the somatodendritic membrane, duration of post-stimulus inhibition, or spontaneous firing rate of these neurones. These results do not support the idea that the neuronal somata of A1 noradrenergic neurones in the VLM show a pro-oestrous increase in excitability during the oestrous cycle, although limitations of the methodology employed do not completely rule out this possibility.

Animals↗
PubMed1988

[Basic and clinical studies on patients who have undergone autologous or allogeneic bone marrow transplantation].

Bone marrow transplantation (BMT) is now increasingly applied not only to hematologic disorders such as leukemias and aplastic anemia but also to some of solid tumors. We experienced ten cases of bone marrow harvest and six cases of autologous or allogeneic BMT during the period from June, 1986 to August, 1987. For autologous BMT cases, bone marrow cells were harvested and cryopreserved at -196 degrees C in liquid nitrogen tank and colony forming assays were examined to ascertain the colony forming ability of harvested bone marrow stem cells. Recovery of colony forming ability after cryopreservation in colony forming unit in culture and burst forming unit in erythrocyte is about 63 to 73% and well preserved. Among 6 cases undergone BMT, five cases are patients with advanced solid tumors including breast cancer, seminoma, lung cancer, malignant lymphoma and brain tumor and these 5 cases have undergone autologous BMT. Conditioning regimen for each cancer in autologous BMT differs based upon conventional chemotherapy regimen and two to four fold dose of conventionally used chemotherapy regimen were administered and after two or three days of high dose chemotherapy, cryopreserved bone marrow cells were thawed and infused. Peripheral white blood cells and platelets were recovered to more than 1000/microliters and 5 x 10(4)/microliters, respectively, within 21 days after bone marrow cell infusion. Disappearance or decrease in tumor size was observed in all cases except brain tumor even though those cases were advanced ones. After autologous BMT, recurrence occurred within three to five months in three cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Lateral hypothalamic region excites the activity of vasopressin neurons in the supraoptic nucleus through subfornical organ neurons.

In urethane-anesthetized male rats, microinjection of angiotensin II into the lateral hypothalamic area excited the activity of about half (N = 7) of subfornical organ neurons (N = 15) antidromically identified as projecting to the hypothalamic supraoptic nucleus. Microinjection of angiotensin II also excited the activity of approximately one-quarter (N = 8) of putative vasopressin-secreting neurons (N = 28) in the hypothalamic supraoptic nucleus and these excitatory responses of putative vasopressin-secreting neurons were blocked (N = 3) or attenuated (N = 3) by pretreatment with the angiotensin II antagonist saralasin, but not by isotonic saline (N = 2), in the subfornical organ.

Action Potentials↗
PubMed1987

Subfornical organ neurons act to enhance the activity of paraventricular vasopressin neurons in response to intravenous angiotensin II.

The effects of pretreatment of the angiotensin II (ANGII) antagonist, saralasin (Sar), in the subfornical organ (SFO) on intravenous ANGII-induced responses of the activity of phasically firing paraventricular nucleus (PVN) neurons (n = 23) antidromically identified as projecting to the posterior pituitary were examined in urethane-anesthetized rats. The activity of the majority (n = 18) of identified PVN neurons was excited by intravenously administered ANGII, whereas the remaining neurons (n = 5) were not affected. The excitatory responses (n = 13) to ANGII were prevented by pretreatment with Sar, but not by isotonic saline (n = 3), in the SFO. These results suggest that ANGII-sensitive SFO neurons may act to enhance the excitability of putative vasopressin (VP)-secreting neurons in the PVN in response to circulating ANGII.

Action Potentials↗
PubMed1987

Influence of microinjection of glucagon into ventromedial hypothalamus on acetate metabolism in liver slices of rabbit.

Glucagon was injected directly into the ventromedial hypothalamic nuclei (VMH) of rabbits, and changes in hepatic acetate metabolism were studied. The injection of 3 ng glucagon into the VMH of intact rabbits increased the rates of 14C transfer from 14C-1-acetate into CO2, glucose and ketone bodies but decreased those into cholesterol ester, triglyceride, free cholesterol, free fatty acids and phospholipids. However, after glucagon injection into the VMH of rabbits with VMH lesions and the parietal cortex of intact rabbits, hepatic acetate metabolism did not differ from that of the control rabbits, which received saline injection into the same brain regions. These observations support the hypothesis that the VMH are parts of a glucagon-sensitive brain regulator system in the hepatic acetate metabolism.

Acetates↗
PubMed1987

Influence of electrical stimulation of the limbic structure on glucagon level in rabbit's plasma.

Amygdala (AMYG) stimulation caused marked increase in the circulating level of glucagon and these stimulatory effects were abolished by lesions of stria terminalis (ST). Stimulation of dorsal hippocampus (DHPC), on the other hand, greatly decreased the glucagon level and lesions of dorsal fornix (DFX) abolished these stimulatory effects. These results suggested that the reciprocal influence of AMYG and DHPC on plasma level of glucagon played some role in the regulation of glucagon release and these limbic structure had hypothalamic-mediated effects on glucagon release.

Amygdala↗