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Biomedical subjects

T Taira

Publications and source records attributed to T Taira.

204 records · Page 12Linked to original sources
PubMedDate not supplied

Effect of beta-casomorphin on neonatal sleep in rats.

The effects of bovine beta-casomorphin(1-7) (Tyr-Pro-Phe-Pro-Gly-Pro-Ile) on neonatal sleep in rats were studied. The pups received intraperitoneal injections of beta-casomorphin(1-7) (1 mg, 5 mg, 10 mg, 50 mg, or 100 mg/kg) or a corresponding volume of sodium chloride. In any of the doses used, beta-casomorphin(1-7) had no effect on waking. Only 100 mg/kg caused significant changes in sleep: the percentage of quiet state of the total recording time (TRT) increased and the percentage of active sleep decreased. Beta-casomorphin(1-7) did not cause significant respiratory depression. Naloxone pretreatment (1 mg/kg IP) reversed the effects of beta-casomorphin(1-7) on sleep, a finding which suggests that opiate mu-receptors are involved in mediating the sleep effects of beta-casomorphin.

Amino Acid Sequence↗
PubMedDate not supplied

Effect of sex and age on brain monoamines and spatial learning in rats.

The concentrations of noradrenaline (NA), dopamine (DA), serotonin (5-HT), and their metabolites were measured in the prefrontal cortex, caudate-putamen, and hippocampus in young (3 months) and aged (27-31 months) Wistar rats of both sexes. Age-related changes were found in prefrontal NA and HVA/DA ratio, striatal DA and DOPAC/DA ratio, and striatal and hippocampal 5-HT and 5-HIAA/5-HT ratio. Age and sex dependent changes were found in striatal DA and DOPAC/DA ratio, and hippocampal MHPG-SO4/NA ratio. The aged rats were tested in spatial discrimination and reversal tasks in a T maze. The effects of alpha 2-agonist medetomidine (3 micrograms/kg) on the task performance were assessed in relation to individual variation in monoamine metabolism. Medetomidine impaired spatial discrimination learning of the aged rats by interacting with the hippocampal 5-HT turnover. Medetomidine improved reversal learning through an interaction with the striatal DA turnover and reduced the number of perseverative errors after reversal, mainly due to its interaction with the prefrontal NA turnover. It is concluded that the memory enhancing effect of drugs acting through the brain monoamine systems is highly dependent on the stage of degeneration of these systems that show considerable individual variation in aged animals.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

Effect of postnatal exposure to GABA agonist muscimol on age-related changes in hypothalamic noradrenaline concentration in rats.

Concentrations of cortical and hypothalamic monoamines and their metabolites after postnatal administration of the GABAA agonist muscimol or ethanol were studied in 37- and 120-day-old rats to clarify the role of GABAergic mechanisms in the development of central monoaminergic neurons. In control rats the hypothalamic noradrenaline (NA) concentration tended to be higher in 120-day-old rats when compared to 37-day-old controls, whereas in muscimol-treated rats the hypothalamic NA concentration was decreased as a function of age. Concentrations of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were increased in the hypothalamus as a function of age regardless of postnatal treatment. In the cerebral cortex there was an age-dependent increase in the concentrations of NA, serotonin (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA), as well as a decrease in the concentration of homovanillic acid (HVA) and 5-HIAA/5-HT and HVA/DA ratios in all rats. Thus, the drug treatments did not alter the course of development of cortical monoamine levels. These data suggest that postnatal exposure to the GABA agonist muscimol disturbs specifically the development of hypothalamic NA system in rats.

Aging↗
PubMedDate not supplied

Intracellular calcium suppresses mechano-electrical transduction current in chick cochlear hair cells.

Intracellular calcium concentration ([Ca2+]i) was elevated by photolysis of the caged calcium compound, Nitr-5, and by use of the intrapipette perfusion technique in hair cells dissociated from the chick cochlea. An increase in [Ca2+]i induced an outward-going current at a membrane potential of -40 mV, as recorded with an intracellular medium of 160 mM KCl. This current was carried by the Ca2+-activated K+ current. In contrast, an increase of [Ca2+]i induced an inward-going current at -50 mV with a 160 mM CsCl-based intracellular medium. This inward-going current was carried by the Ca2+-activated non-selective cation current. The amplitude of the mechano-electrical transduction current was suppressed by the increase of [Ca2+]i, achieved both by photolysis and by use of the intrapipette perfusion method.

Animals↗
PubMedDate not supplied

A new bioprosthetic cardiac valve with reduced calcification.

A bioprosthetic cardiac valve cross-linked with a glycerol polyglycidyl ether polyepoxy compound (PC) was developed in order to reduce calcification and degeneration, which often occurs in bioprosthetic cardiac valves. Aortic valves harvested from dogs were treated with PC (PC valve). Right ventricle (RV)-pulmonary artery (PA) bypasses were placed in 12 dogs with PC-valved conduits, and the main PA was ligated. X-ray right ventriculography at 36 days (1 dog) and 37 days (1 dog) revealed an excellent open/close performance of the PC valve, and there was no visible thrombus in the valve. In our basic study, PC treated collagen gel disks implanted in the subcutaneous layer of growing rats showed remarkably less calcium deposition than did those treated with glutaraldehyde (GA). Biologic materials cross-linked with PC maintain their pliability, and become more hydrophilic and more hydrated than those cross-linked with GA. The hydrophilicity and hydration provide sufficient antithrombogenicity and a suitable environment for metabolism in the tissue fluid which contains oxygen, nutritive substances, and electrolytes, leading to inhibition of material degeneration. Therefore, PC valves are expected to show good valve function, sufficient antithrombogenicity, and excellent durability with less calcification, when compared to GA treated valves.

Animals↗