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Biomedical subjects

I Tasaki

Publications and source records attributed to I Tasaki.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1988

Analysis of factors affecting year-round performance of Single Comb White Leghorn laying hens reared under an open-sided housing system.

Based upon a field survey, an analysis was made to clarify factors affecting year-round performance of laying hens reared within an open-sided housing system. Data were collected from flocks located in Kumagaya city (36 degrees N, Japan), where they were subjected to periodic seasonal changes in photoperiod and ambient temperature specific to that area. Monthly performance of Single Comb White Leghorn laying hens at 5 to 16 mo of age was recorded and analyzed in terms of month of hatch, ambient temperature, and age. Changes in egg production and daily egg mass coincided with those in natural daylength. Egg weight was significantly lower in June-hatched layers; egg mass was highest in May and lowest in December hatches. Feed, CP, and ME intakes showed opposite periodic changes to that of ambient temperature with various delay times: ME intake showed no delay, whereas feed and CP intakes had 18 and 29-day delays, respectively. By comparing the performances of April to June and September to November-hatched hens, it was found that natural photoperiod appeared to be more important than ambient temperature in egg production, and that the effect of natural photoperiod became small and insignificant as the bird aged. The effect of temperature on egg production rate was found to be dependent on age of laying hens, i.e., it was more evident in old birds, especially when birds were exposed to a cold climate. Apparent age-dependent changes in the periodic element of egg production rate as related to calendar month were also shown.

Animals↗
PubMed1988

A macromolecular approach to excitation phenomena: mechanical and thermal changes in nerve during excitation.

(1) Nerve fibers and cells were shown to swell when they develop action potentials. Both in the squid giant axon and in the garfish olfactory nerve, the peak of swelling coincides with the peak of the action potential recorded from the site of mechanical recording. Substitution of univalent cations for the bivalent cations (Ca) bound to multi-anion sites in the membrane macromolecules is considered to be at the base of the phenomenon of swelling. (2) Measurements of heat production by the garfish olfactory nerve indicate that the rate of temperature rise is maximal at the peak of the action potential. Since heat production lasts for the entire depolarizing phase of the action potential, the "condenser theory" of heat production is abandoned. Again, substitution of the bound bivalent cations in the membrane macromolecules with univalent cations is regarded as the origin of nerve heat. (3) The two stable states of the nerve membrane, which are readily demonstrable in TEA-treated or internally perfused squid giant axons, are shown to represent bivalent cation-rich and univalent cation-rich states of the nerve membrane. (4) A physicochemical theory is described that explains macromolecular transitions between two stable states. The mechanism of nerve excitation is explained on a physicochemical basis. (5) The importance of the role played by water molecules in the process of nerve excitation is emphasized.

Action Potentials↗
PubMed1987

Influence of the gut microflora on protein synthesis in tissues and in the whole body of chicks.

1. The influence of the gut microflora on protein synthesis in individual tissues and in the whole body of young chicks was investigated by the large-dose injection of [3H]phenylalanine. 2. Growth of germ-free chicks was significantly better than that of conventional controls. Wet weights of liver, spleen, duodenum, jejunum + ileum and caeca were heavier in conventional birds than in germ-free counterparts. 3. Fractional rates of protein synthesis were higher in jejunum + ileum and whole body of conventional birds than in those of germ-free birds. Amounts of protein synthesized were larger in liver, jejunum + ileum and caeca in the presence of the gut microflora. 4. When tissues were classified into gut + liver and the remainder of the carcass, in the presence of the gut microflora an enhanced protein synthesis in fractional and absolute rate was found in the gut + liver, which is in direct contact or in close association with micro-organisms, whereas virtually no effect of the gut micro-organisms was detected in the remainder of the carcass. 5. The contribution of protein synthesis of gut + liver to that of the whole body was larger in conventional chicks than in germ-free birds, whereas the reverse was true for the remainder of the carcass.

Animals↗
PubMed1987

Heat production associated with synaptic transmission in the bullfrog spinal cord.

By using heat detectors made with pyroelectric film, rapid heat production by the bullfrog spinal cord in response to dorsal root stimulation has been demonstrated. The heat production rises to its peak in about 100 ms after the arrival of afferent impulses and falls slowly with a time course comparable to that of the dorsal root potential. Stimulation of the ventral roots produces no detectable heat. The heat production was reversibly suppressed by immersion of the cord in a low Ca2+, high Mg2+ salt solution, indicating that the underlying exothermic process is associated with intraspinal synaptic transmission. The source of this 'synaptic heat' is located near the boundary between the dorsal column and the substantia gelatinosa in the vicinity of the stimulated dorsal roots.

Animals↗
PubMed1987

Rapid mechanical changes in the amphibian retina evoked by brief light pulses.

Dark-adapted retinae of the toad and bullfrog were found to respond to brief light stimuli with a succession of rapid mechanical changes. The latencies of the mechanical responses, as well as the effects of chemicals known to block the synapses on photoreceptor cells, indicate that the first mechanical response represents swelling of the photoreceptor cells. The first response is followed by mechanical changes in the postsynaptic elements. It is suggested that the observed response of the photoreceptor cells is a mechanical expression of the process underlying heat production by the cells.

Animals↗
PubMed1987

Effect of protein starvation on protein turnover in liver, oviduct and whole body of laying hens.

1. Whole body protein turnover rates in White Leghorn laying hens were reduced by protein starvation for 7 days, followed by complete restoration by protein repletion for 7 days. 2. Protein starvation considerably reduced fractional and absolute rates of protein synthesis both in the liver and, to a greater extent, in the oviduct. 3. It was suggested that a considerable portion of the reduced whole body protein synthesis could be accounted for by the reduced protein synthesis in these organs when laying hens were subjected to protein starvation.

Animals↗