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Biomedical subjects

K Seto

Publications and source records attributed to K Seto.

At least 109 records · Page 6Linked to original sources
PubMed1985

Subfornical organ neurons with efferent projections to the hypothalamic paraventricular nucleus: an electrophysiological study in the rat.

Seventeen neurons in the subfornical organ (SFO) were antidromically activated by electrical stimulation of the paraventricular nucleus (PVN) in the rat. The activity of all identified SFO neurons was excited by microiontophoretically (MIPh) applied angiotensin II (AII) and the effect of AII was blocked by MIPh-applied saralasin (Sar), an AII antagonist, but not by atropine (Atr), a muscarinic antagonist. In these identified SFO neurons, 9 were also excited and 8 were not affected by MIPh-applied acetylcholine (ACh) and the effect of ACh was attenuated by not only MIPh-applied Atr but also by Sar. These results suggest that there are specific AII- and both AII- and ACh-sensitive types of SFO neurons with efferent projections to the PVN.

Acetylcholine↗
PubMed1985

Electrophysiological evidence that circulating angiotensin II sensitive neurons in the subfornical organ alter the activity of hypothalamic paraventricular neurohypophyseal neurons in the rat.

Thirteen neurons in the subfornical organ (SFO) were antidromically activated by electrical stimulation of the paraventricular nucleus (PVN) in the rat. The activity of these identified SFO neurons was excited by intravenous injection of angiotensin II (AII). Electrical stimulation of the SFO produced orthodromic excitation (40%) and inhibition (40%) of the activity of putative vasopressin (VP)-secreting PVN neurons. These results suggest that circulating AII sensitive SFO neurons with efferent projections to the PVN have both excitatory and inhibitory influences on the activity of putative VP-secreting neurons in the PVN.

Angiotensin II↗
PubMed1985

Inputs from the A1 noradrenergic region to hypothalamic paraventricular neurons in the rat.

Electrical stimulation of the rat A1 noradrenergic region produced excitation (77%) of the activity of putative vasopressin (VP)-secreting neurons in the paraventricular nucleus (PVN) and produced excitation (4%), inhibition (26%) and excitation-inhibition (11%) of the activity of PVN neurons that were not antidromically identified by neurohypophysial stimulation. The excitatory response of putative VP-secreting neurons was blocked by microiontophoretically applied phentolamine, an alpha-adrenoceptor antagonist, but not by timolol, a beta-adrenoceptor antagonist. The inhibitory response of unidentified PVN neurons, on the other hand, was blocked by timolol, but not by phentolamine.

Adrenergic Fibers↗
PubMed1985

Noninvasive recording of His bundle electrograms using vectorial leads system.

His bundle electrograms were recorded in 8 rats by a signal averaging technique using the Takayasu vectorial lead system. Animals were anesthetized and placed in the prone position. The polarity of three orthogonal leads were: the X axis, from right to left; the Y axis, from top to bottom; the Z axis, from back to front. Potentials from the X, Y, and Z leads were amplified by 20,000 with high-pass 12 dB/octave filtering at 80 Hz, and signal averaging of 2000 beats was performed at a sampling interval of 100 microseconds. The His bundle potential could be clearly defined in all 8 rats. The mean amplitude of the His potential was larger in the X-axis (23.6 +/- 9.2 mu V) or the Y-axis (28.4 +/- 14.5 mu V) than the Z-axis lead (11.5 +/- 8.6 mu V). Directions of the His potential vectors were to the left in 5 of 8 rats (62.5%), to the caudal in 4 of 6 rats (66.7%), and to the dorsal site in 6 of 8 rats (75.0%). This vectorial lead system, devised in accordance with McFee and Johnston's theory on lead field, was useful for recording His bundle electrograms.

Animals↗
PubMed1985

Proteolytic activity of mycoplasmas and ureaplasmas isolated freshly from human saliva.

Mycoplasma and Ureaplasma strains freshly isolated from human saliva were examined for proteolytic activity. All the strains tested (101 strains of Mycoplasma salivarium, 97 strains of Mycoplasma orale, and 3 strains each of Mycoplasma hominis and Ureaplasma urealyticum) decomposed horse serum proteins, bovine albumin, and casein. Ten of the M. salivarium and 8 of the M. orale strains were tested for aminopeptidase activity as well, using L-leucine-p-nitroanilide as a substrate, and were shown to possess the activity. Thus proteolytic activity was suggested to be one of the biological characteristics of these two species. The level of both caseinolytic and aminopeptidase activity was significantly higher in M. salivarium than M. orale strains.

Aminopeptidases↗
PubMed1985

Response of phasically firing paraventricular neurons to A1 noradrenergic region stimulation and its attenuation by adrenoceptor antagonists.

In urethane-anesthetized rats electrical stimulation of the A1 noradrenergic region in the ventrolateral medulla produced excitatory (27%), excitatory-inhibitory (24%), or inhibitory (34%) responses of spontaneous activity of phasically firing units in the paraventricular nucleus (PVN) of the hypothalamus. The latency of excitatory responses was significantly shorter in those followed by inhibition, suggesting the existence of two distinct excitatory pathways. The latency of inhibitory responses, however, was not different between primary and postexcitatory inhibitory responses. Effects of alpha- and beta-adrenoceptor antagonists on responses of phasically firing PVN units to stimulation of the A1 region were tested. The excitatory responses that were not followed by inhibition were significantly attenuated by intraperitoneal phenoxybenzamine, whereas the other responses were not affected. Both primary and postexcitatory inhibitory responses were significantly attenuated by intravenous propranolol, whereas neither type of excitatory response was affected. These results suggest that the medullary (A1 region) inputs to phasically firing PVN units are mediated by alpha-adrenergic (excitatory), beta-adrenergic (inhibitory), and nonaminergic (excitatory) pathways.

Adrenergic alpha-Antagonists↗
PubMed1985

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

Insulin was injected directly into the ventromedial hypothalamic nuclei (VMH) of rabbits, and changes in hepatic acetate metabolism were studied. The injection of 50 microU insulin into the VMH of intact rabbits decreased the rates of 14C transfer from 14C-1-acetate into glucose and cholesterol ester in liver slices. But after insulin injection into the parietal cortex of intact rabbits and into the VMH of rabbits with VMH lesions, 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 an insulin-sensitive brain regulator system in the hepatic acetate metabolism.

Acetates↗
PubMed1985

Changes in pituitary-adrenal function under extreme cold in DHA-treated persistent estrous rats.

The plasma corticosterone levels and incorporation of 14C-l-acetate into corticosterone and cortisol were measured in dehydroepiandrosterone (DHA)-treated persistent estrous rats and control estrous cyclic rats exposed to cold (-5 degrees C) for 12 hrs. Cold exposure significantly facilitated incorporation of 14C-l-acetate into corticosterone and cortisol in both DHA-treated and control rats. However, the rates of increase of plasma corticosterone level and 14C-incorporation into corticosterone are 61% and 77% in controls, and 19% and 44% in DHA-treated rats, respectively. The activity of stress-induced pituitary-adrenal function showed masculine patterns in DHA-treated rats. The diurnal patterns of plasma corticosterone in DHA-treated rats are similar in controls. Plasma corticosterone levels in DHA-treated rats are evidently greater than those in controls. It is suggested that neonatal administration of DHA caused the changes not only in pituitary-gonadal system but also in pituitary-adrenal system.

Animals↗
PubMed1985

Influence of lesions in the limbic-hypothalamic system on metabolic response of pyruvate to daily repeated cold exposure in rabbits.

The effects of lesions of the limbic-hypothalamic structures on the pyruvate metabolic responses to daily repeated cold exposures in the liver of rabbits have been investigated. The experimental results were as follows: The metabolic pattern of pyruvate and the pyruvate metabolic responses to the 1st cold exposure (cold exposure on the 1st day) were altered by lesions of periventricular arcuate nucleus (ARC), ventromedial hypothalamus (VMH), stria terminalis (ST) and dorsal fornix (FX). The pyruvate metabolic responses to cold exposure were completely abolished by seven times repetition of daily cold exposures in rabbits with lesions of ARC, VMH and FX, as well as in each sham-operated group. In rabbits with ST lesions, the pyruvate metabolic responses to cold exposure remained even after the seven times repetition of daily cold exposures. From these results, it might be suggested that the ARC, VMH, amygdala (AMYG)-ST system and dorsal hippocampus (HPC)-FX system played a certain role in the metabolic regulation of pyruvate and in the mechanisms of pyruvate metabolic responses to the 1st cold exposure, but that only the AMYG-ST system participated in the process of pyruvate metabolic adaptation to daily repeated cold exposures.

Animals↗
PubMed1985

Influence of microinjection of insulin into amygdala on acetate metabolism in liver slices of rabbit.

Insulin was injected directly into the medial amygdala (AMYG) of rabbits, and changes in hepatic acetate metabolism were studied. The injection of 50 microU insulin into the AMYG decreased the rates of 14C transfer from 14C-1-acetate into CO2 and cholesterol ester, and increased those into free cholesterol and phospholipids. But after insulin injection into parietal cortex of intact rabbits and into the AMYG of rabbits with lesions of stria terminalis (ST), 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 AMYG is a part of insulin-sensitive brain regulator system in the hepatic acetate metabolism.

Acetates↗
PubMed1985

Influence of lesions in the limbic-hypothalamic system on metabolic responses of pyruvate to daily repeated heat exposures in rabbits.

The effects of lesions of the limbic-hypothalamic structures on the pyruvate metabolic responses to daily repeated heat exposures in the liver of rabbits have been investigated. The experimental results were as follows: 1. The pyruvate metabolic responses to the 1st heat exposure (heat exposure on the 1st day) were altered by lesions of periventricular arcuate nucleus (ARC), ventromedial hypothalamus (VMH), stria terminalis (ST) and dorsal fornix (FX). 2. The pyruvate metabolic responses to heat exposure were completely abolished by the ten times repetition of daily heat exposures in rabbits with lesions of ARC, VMH and ST, as same as in each sham-operated group. 3. In rabbits with FX lesions, the pyruvate metabolic responses to heat exposure remained even after the ten times repetition of daily heat exposures. 4. From these results, it might be suggested that ARC, VMH, amygdala (AMYG)-ST system and dorsal hippocampus (HPC)-FX system played a certain role in the mechanisms of pyruvate metabolic responses to the 1st heat exposure, but only the HPC-FX system participated in the process of pyruvate metabolic adaptation to daily repeated heat exposures.

Animals↗