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Biomedical subjects

I Tasaki

Publications and source records attributed to I Tasaki.

At least 19 recordsLinked to original sources
PubMed1992

Rapid structural changes in nerve fibers evoked by electric current pulses.

Using the garfish olfactory nerve, the time-courses of lateral expansion (swelling) and birefringence changes in nerve fibers have been examined at the site of application of electric current pulses. The effects of various chemical agents on these non-electrical signs of rapid structural changes in the nerve fibers have been examined. These studies have shown that a pulse of outwardly-directed current through the superficial layer evokes a fast increase, followed by a slow, gradual increase, in the water-content of the nerve fibers. The full significance of these findings in studies of the process of nerve excitation is discussed.

Animals↗
PubMed1992

Heat production associated with a propagated impulse in bullfrog myelinated nerve fibers.

By using heat-sensors constructed with thin film of polyvinylidene fluoride, it was found possible to detect the heat generated by myelinated fibers in the bullfrog sciatic nerve in association with a propagated impulse. The quantity of heat generated (about 0.4 microcal/g at 4.5 degrees C) is roughly two orders of magnitude smaller than that observed in nerves containing only non-myelinated nerve fibers. The smallness of the heat observed is attributed to the localization of the heat sources at the nodes of Ranvier. The major portion of the heat generated is re-absorbed by the nerve.

Animals↗
PubMed1991

Demonstration of heat production associated with spreading depression in the amphibian retina.

Using thin film of synthetic pyroelectric material, polyvinylidene fluoride, sensitive heat-sensors were constructed for the purpose of detecting heat production associated with the phenomenon of spreading depression in isolated amphibian retinae. Measurements with these sensors revealed the existence of large heat production, which closely follows the electrical sign of spreading depression. Studies of the effects of chemical agents known to affect spreading depression have demonstrated the usefulness of heat measurements.

Animals↗
PubMed1991

Thermal and mechanical responses of the amphibian skin to nerve stimulation.

The isolated calf skin of the toad and bullfrog was found to generate a burst of heat in response to stimulation of the cutaneous nerve. The electric responses of the skin evoked by nerve stimulation invariably lagged behind the heat burst. The generation of a heat burst was followed by a slow mechanical response of the skin. Suppression of these responses by adrenergic blocking agents suggests that heat is produced at the junction between the gland cells and the sympathetic nerve fibers. Large mechanical changes in the skin were observed when noradrenaline was applied to the inner surface of the skin.

Animals↗
PubMed1991

Nitrogen and energy utilization in germ-free and conventional chicks at early stages of growth.

Influence of aging on N and ME utilization in germ-free and conventional (CV) chicks was investigated at Stage 1 (2 to 6 days old) and Stage 2 (10 to 14 days old). Chicks were fed diets for ad libitum consumption with protein concentrations of 116, 220, or 445 g/kg diet. The N utilization was not affected by the gut microflora at either stages, but it significantly decreased for chicks on the high-protein diet compared with those on the low-protein and adequate-protein diets. The ME values of diets were not influenced by treatments, except for the high-protein diet at Stage 1, in which ME was significantly reduced.

Animals↗
PubMed1990

Mechanical changes associated with synaptic transmission in the mammalian superior cervical ganglion.

Mechanical changes in the superior cervical ganglion (SCG) of the guinea pig, evoked by stimulating the pre- or postganglionic nerve, were determined by using a mechano-electric transducer. The mechanical change evoked by either one of these nerves was monophasic, an initial phase of rapid swelling (about 1 dyn/cm2) being followed by a slow relaxation. The mechanism of these mechanical changes was examined by treating the preparations with agents which are known to suppress or facilitate synaptic transmission in the SCG. Mechanical changes elicited by preganglionic nerve stimulation were suppressed by agents that reversibly block ganglionic transmission (Ca2(+)-free high Mg2+, d-tubocurarine, hexamethonium, TEA, TTX). On the other hand, agents which are known to facilitate synaptic transmission (high Ca2+) increased both the amplitude and the duration of swelling. In a Ba2(+)-containing medium, a large, long-lasting shrinkage of the ganglion was observed. It is suggested that the mechanical changes recorded in this study are associated with postsynaptic electro-genesis.

Animals↗
PubMed1990

Heat generation associated with synaptic transmission in the mammalian superior cervical ganglion.

By use of a thermal detector constructed with a thin polyvinylidene fluoride film (PVDF), heat production in the superior cervical ganglion (SCG) of the guinea pig was examined. A single electric shock applied to the preganglionic nerve evokes a temperature rise of approximately 1.5 x 10(-6) deg. The thermal responses summate when the preganglionic nerve is stimulated repetitively. The amplitude of the thermal response is increased when the preparation is treated with a high Ca2+ medium. Treatment with agents that block ganglionic transmission (high Mg2+, d-tubocurarine, hexamethonium, TTX) reversibly suppresses thermal response. It is thus concluded that the thermal responses described in this paper are generated by the physico-chemical events underlying postsynaptic electrogenesis in the SCG cells.

Animals↗
PubMed1990

Heat production associated with neuromuscular transmission in the toad nerve-muscle preparation.

The time course of the heat produced by the toad sartorius muscle in response to nerve stimulation was determined by using a new type of heat-sensor with a high time resolution. The records obtained showed the existence of a brief burst of large heat production prior to the onset of the muscle heat associated with contraction. This initial heat-burst was shown to be produced at the motor endplates. The implications of these findings are discussed.

Animals↗
PubMed1989

Responses of the pancreatic digestive enzyme secretion to amino acids, glucose and cholecystokinin in chicks.

1. Pancreatic secretion of digestive enzymes, amylase, trypsinogen and chymotrypsinogen, was studied in response to the wing vein injection of digestive end products, various single amino acids and glucose, with or without cholecystokinin (CCK) in chicks. 2. Among amino acids administered, only phenylalanine significantly (P less than 0.05) increased trypsinogen and chymotrypsinogen secretions, while other amino acids did not. 3. Simultaneous injection of single amino acids with CCK increased digestive enzyme secretion to various extents depending on the kind of amino acids whereas the injection of glucose with CCK did not affect when compared with that of CCK alone. 4. By varying doses, a synergetic action of CCK plus amino acid on the secretion of pancreatic digestive enzymes was observed at 0.5 mM for valine and 5 mM for arginine.

Amino Acids↗
PubMed1989

Rapid mechanical and thermal changes in the garfish olfactory nerve associated with a propagated impulse.

Mechanical and thermal changes associated with a propagated nerve impulse were determined using the garfish olfactory nerve. Production of an action potential was found to be accompanied by swelling of the nerve fibers. The swelling starts nearly at the onset of the action potential and reaches its peak at the peak of the action potential. There is a decrease in the length of the fibers while an impulse travels along the fibers. The time-course of the initial heat was determined at room temperature using heat-sensors with a response-time of 2-3 ms. Positive heat production was found to start and reach its peak nearly simultaneously with the action potential. The rise in temperature of the nerve was shown to be 23 (+/- 4) mu degrees C. In the range between 10 degrees and 20 degrees C, the temperature coefficient of heat production is negative, primarily due to prolongation of the period of positive heat production at low temperatures. The amount of heat absorbed during the negative phase varies widely between 45 and 85% of the heat evolved during the positive phase. It is suggested that both mechanical and thermal changes in the nerve fibers are associated with the release and re-binding of Ca-ions in the nerve associated with action potential production.

Action Potentials↗
PubMed1989

Influence of dietary non-protein energy intake on whole-body protein turnover in chicks.

1. Three experiments were conducted to investigate the influence of dietary energy intake on whole-body protein turnover in chicks. 2. In Expt 1 a semi-purified diet with various dietary metabolizable energy (ME) concentrations, 10.9, 12.6, 14.2 and 15.9 kJ/g, was fed ad lib. to young chicks. Whole-body fractional synthesis rate (FSR) was increased with each increment in dietary ME level from 12.6 to 15.9 kJ/g, and whole-body fractional degradation rate (FDR) showed a similar, though less sensitive, trend to that of FSR. 3. In Expts 2 and 3, chicks were given graded ME intakes of 84, 126, 167, 209 or 293 kJ/d with a fixed intake of dietary protein. FSR was increased when the energy intake was raised from 84 to 167 kJ/d, and above this level it was almost constant. Similar to the trend obtained with ad lib. feeding, the response of FDR to changes in dietary energy intake was less sensitive than that of FSR. 4. Total heat production was increased when dietary energy intake was increased from 84 to 167 kJ/d, and there was no further increase at 209 kJ/d. In contrast, the contribution of protein synthesis to total heat production was not affected by varying the dietary energy intake.

Animals↗
PubMed1989

Utilization of dietary diammonium citrate by germ-free chicks.

This study was conducted to clarify the effect of the gut microflora on the utilization of dietary diammonium citrate in the chick. Germ-free and conventional Single Comb White Leghorn chicks were given a basal diet, which contained adequate amounts of all essential amino acids but none of the nonessential amino acids as nitrogen sources, or a diammonium citrate-supplemented diet. Irrespective of presence or absence of the gut microflora, values for body weight gain, feed efficiency, and protein and energy utilization were improved by supplementing the basal diet with diammonium citrate. This suggests that the gut microflora are not required for the chick to utilize diammonium citrate.

Amino Acids↗
PubMed1988

Large mechanical changes in the bullfrog olfactory bulb evoked by afferent fiber stimulation.

The isolated olfactory bulb of the bullfrog responds to olfactory nerve stimulation with large mechanical changes in the bulb. The sequence of these changes represents: (1) swelling of the bulb associated with action potential production in the secondary neurons; (2) shrinkage during powerful inhibition of the secondary neurons; and (3) swelling accompanied by repetitive firing of action potentials in the bulb. The effects of bicuculline and Cl-free Ringer on these mechanical changes were examined. The shrinkage of the bulb is closely related with the inhibitory postsynaptic potentials (IPSPs) in the mitral cells.

Action Potentials↗
PubMed1988

Energy cost of whole-body protein synthesis measured in vivo in chicks.

1. Energy cost of whole-body protein synthesis was measured in vivo in chicks by comparing the changes in protein synthesis and heat production after the administration of cycloheximide, an inhibitor of protein synthesis. 2. Incorporation of phenylalanine into whole-body protein fraction was promptly inhibited after the intravenous injection of cycloheximide, and the effect was sustained for at least 3 hr. 3. Both whole-body protein synthesis and total heat production were significantly reduced by the cycloheximide administration. 4. The energy cost of whole-body protein synthesis was calculated to be 5.35 kJ per g protein synthesis, and hence on a molar basis 7.52 ATPs are required per peptide bond synthesis.

Animals↗
PubMed1988

Effect of low ambient temperature on protein turnover and heat production in chicks.

1. Effect of low ambient temperature on protein turnover in the liver and whole body was investigated in chicks together with the contribution of protein synthesis to the total heat production. 2. Both protein synthesis and degradation in the whole body were increased, the latter to a larger extent, at low ambient temperature (LT, 22 degrees C) compared with adequate temperature (AT, 30 degrees C). Liver protein synthesis was not significantly altered by the temperature treatment. 3. The total heat production of LT group was as high as 160% of the AT group. 4. The increased heat production due to enhanced whole-body protein synthesis accounted for only 1.4% of the heat increment in thermogenesis at low ambient temperature, suggesting that protein synthesis would contribute little, if any, to cold-induced thermogenesis in chicks.

Acclimatization↗
PubMed1988

Influence of the gut microflora on fasting heat production in chicks.

1. The influence of the gut microflora on fasting heat production in chicks was investigated. 2. Single Comb White Leghorn chicks were fed on an adequate diet from 2 to 12 d of age and then fasted for 3 d. Fasting heat production was estimated from changes in body composition and energy content of droppings from days 1 to 3 of fasting. Measurements of body temperature and plasma thyroxine concentration were also made. 3. Body fat content was consistently higher in germ-free (GF) chicks than in conventional (CV) counterparts during the starvation period, whereas no difference was found in body protein content. The GF birds had a significantly higher body temperature than the CV controls with no change in plasma thyroxine concentration. 4. It was concluded that estimated fasting heat production of chicks was increased by the absence of the gut microflora.

Animals↗