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Biomedical subjects

K Seto

Publications and source records attributed to K Seto.

At least 181 records · Page 10Linked to original sources
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↗
PubMed1984

The action of the A1 noradrenergic region on phasically firing neurons in the rat paraventricular nucleus.

Electrical stimulation of the rat A1 noradrenergic region produced orthodromic inhibition (34%), excitation (23%) or excitation-inhibition sequence (25%) of the spontaneous activity of phasically firing units in the paraventricular nucleus of the hypothalamus (PVH). Excitatory responses could be distinguished into two types on the basis of their latency and duration. Both the primary and post-excitatory inhibitory responses were significantly attenuated by intravenous injection of propranolol, a beta-adrenoceptor antagonist, whereas neither type of excitatory response was affected.

Animals↗
PubMed1984

Influence of lesions in the limbic-hypothalamic system on metabolic response of acetate to daily repeated immobilization stress.

The effects of lesions in the basal medial hypothalamus and limbic structure on the acetate metabolic responses to daily repeated exposure to immobilization stress in the liver of rabbits have been investigated. The experimental results were as follows: (1) The acetate metabolic response to the 1st exposure to immobilization stress (exposure on the 1st day) were considerably altered by lesions in the periventricular arcuate nucleus (ARC) ventromedial hypothalamus (VMH), stria terminalis (ST) and dorsal fornix (FX). (2) The acetate metabolic responses to immobilization stress were completely abolished by seven times repetition of immobilization stress in the rabbits with lesions in ARC, VMH and FX; they were similar to sham-operated groups. (3) In rabbits with ST lesions, the acetate metabolic responses to the 7th exposure (exposure on the 7th day) to immobilization stress were exactly the same as those after the 1st exposure of immobilization stress, but these metabolic responses were completely abolished by the seven times repetition of exposure in the sham-operated animals. (4) These results suggest that firstly, the ARC, VMH, amygdala(AMYG)-ST system and dorsal hippocampus(HPC)-FX system are involved in the acetate metabolic responses to the 1st exposure of immobilization stress, and secondly, that only the AMYG-ST is involved in the disappearance process of acetate metabolic responses to immobilization stress by the daily repetition of immobilization stress.

Acetates↗
PubMed1984

Influence of lesions in the limbic-hypothalamic system on metabolic response of acetate to daily repeated heat exposure in rabbit.

The effects of lesions in the basal medial hypothalamus and limbic structure on the acetate metabolic responses to daily repeated heat exposure in the liver of rabbits have been investigated. The results obtained were summarized as follows: (1) THe acetate metabolic responses to the 1st heat exposure (heat exposure on the 1st day) were altered by the lesions in the periventricular arcuate nucleus (ARC), ventromedial hypothalamus (VMH), stria terminalis (ST) and dorsal fornix (FX). (2) The acetate metabolic responses to heat exposure were completely abolished by the ten times repetition of heat exposure in the rabbits with lesions in ARC or VMH. They were similar to sham-operated animals. (3) The acetate metabolic responses to heat exposure remained even after the ten times repetition of heat exposure in the rabbits with lesions in ST and FX indicating the differences from sham-operated animals. (4) From these results, it might be suggested that the basal medial hypothalamus and limbic structure participated in the mechanism of acetate metabolic response to the 1st heat exposure, but only these limbic structure played some roles in the complete disappearance process of acetate metabolic responses to heat exposure by the ten times repetition of heat exposure.

Acetates↗
PubMed1984

Influence of lesions in the limbic-hypothalamic system on insulin responses to daily repeated cold exposures in rabbits.

The effects of lesions in the basal medial hypothalamus and limbic structures on the responses in plasma levels of insulin and glucose to daily repeated cold exposure in rabbits have been investigated. The results obtained were summarized as follows: (1) The 1st cold exposure (cold exposure on the 1st day) decreased insulin levels and increased glucose levels, and these responses of insulin and glucose to cold exposure gradually decreased and then completely abolished by daily repetition of exposures in intact rabbits and each sham-operated group. (2) The lesions of periventricular arcuate nucleus (ARC), stria terminalis (ST) and dorsal fornix (FX) had no effects on the insulin responses to the 1st cold exposure, but the rates of insulin responses to the 1st cold exposure were decreased by the lesions of ventromedial hypothalamus (VMH). (3) The ARC lesions had no effects on the glucose responses to the 1st cold exposure, but the glucose responses to the 1st cold exposure were abolished by VMH lesions and were altered by lesions of ST and FX. (4) The insulin responses to cold exposure were abolished by daily repetition of exposures in rabbits with ARC lesions as same in the cases of sham-operated animals, but the insulin responses to cold exposure persisted even after daily repetition of exposures in rabbits with lesions of VMH, ST and FX different from sham-operated animals. (5) The glucose responses to cold exposure were abolished by daily repetition of exposures in rabbits with lesions of ARC and ST as same as in the cases of sham-operated animals, but the glucose responses to cold exposure persisted even after daily repetition of exposures in rabbits with FX lesions different from sham-operated animals.

Animals↗