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Biomedical subjects

H Akahori

Publications and source records attributed to H Akahori.

33 records · Page 2Linked to original sources
PubMed1994

Effect of recombinant human granulocyte colony-stimulating factor on efficacy of radiation therapy in tumor-bearing rats.

The effect of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on radiation-induced neutropenia and on growth of transplanted tumors treated by irradiation was investigated using tumor-bearing rats as a model for radiation therapy. In a preliminary study using normal rats, neutropenia induced by upper hemi-body irradiation at 3 Gy/day 5 times a week for 3 weeks was prevented by consecutive subcutaneous injections of rhG-CSF at 100 micrograms/kg/day. Rats bearing Walker-256, a mammary tumor, were scheduled to receive upper hemibody irradiation at 3 Gy/day for 15 times in 3 weeks if white blood cell (WBC) counts were maintained above 3,000/microliters. In control tumor-bearing rats not receiving rhG-CSF, irradiation was often withheld because of the decrease in WBC counts below 3,000/microliters. In contrast, a decrease in WBC counts below 3,000/microliters was rarely found in tumor-bearing rats injected daily with rhG-CSF. The average number of radiation treatments in control rats and rats treated with rhG-CSF was about 8 and 14, respectively, out of the scheduled 15 treatments in 3 weeks. Treatment with rhG-CSF made it possible to complete the radiation therapy regimen and thus inhibit the growth of the transplanted tumor more effectively. These results suggest that rhG-CSF may be useful to ensure radiation therapy on schedule in cancer patients.

Animals↗
PubMed1991

Pentamer arrangements in fragments of human rotavirus inner capsids observed by low dose electron microscopy.

Fragments of disrupted capsids were frequently seen in purified preparations of human rotavirus inner capsids by negative staining method in electron microscopy. The ultrastructures of these fragments were analyzed in comparison with the T = 13L model. Well-resolved pentamers were rarely seen in the fragments on observation at the standard electron doses, but were frequently seen at low electron doses, which meant a better preservation of the steric structure of capsid fragments in the latter case. Thus advantages of low dose electron microscopy have been shown in observation of capsid fragments.

Capsid↗
PubMed1990

The finest ultrastructural details of the inner layer of rotavirus revealed by minimal electron doses.

The inner layer of human and calf rotavirus ultrastructure was analyzed using minimal doses in transmission electron microscopy. The morphological unit of spontaneously disrupted virions has the aspect of a flower-like structure, and its petals are hexagonally arranged and have a central pin hole. The similar flower appearance can be observed in complete virions and in rotavirus tube structures produced in aged samples of rotavirus kept for more than a year.

Animals↗
PubMed1989

Influence of aging on the histamine release and membrane fluidity of rat peritoneal mast cells.

The maturational changes in the degree of homologous passive cutaneous anaphylaxis (PCA) and the histamine release from peritoneal mast cells induced by several secretagogues were studied using Wistar rats (4-40 weeks old). Although the increase in vascular permeability of the rat skin induced by intradermal injection of histamine did not change significantly from one maturation period to the next, 6- to 8-weeks old rats were both the most susceptible to PCA reactions and the most responsive to histamine-releasing stimuli. Among rats in this age group (6-8 weeks), the fluidity of the resting cell membrane and the extent of membrane fluidity increase in response to compound 48/80 were greatest. Analysis of the lipid composition of mast cells indicated that the ratio of cholesterol to phospholipids was lowest at the age of 6-8 weeks. From the present study, we concluded that the maturational changes in the extent of histamine release seem to be related to membrane fluidity, which has a profile similar to that of maturation.

Aging↗
PubMed1987

[Ultrastructure of spermatozoa of rats (Rattus norvegicus). Use of 3 technics in transmission electron microscopy].

Ultrastructures spermatozoa taken from the seminiferous tubules of rat testes (Rattus norvegicus) were observed under transmission electron microscopy, using the techniques of ultrathin sections, microspreading specimens and replicas. The heads of isolated spermatozoa were of homogeneously high electron density, and had a slightly curved end; in longitudinal sections these zones were composed of a compact homogeneous DNA, covered by a nuclear envelop, cell membrane and small amounts of acrosomal material. The middle piece contained the modified centrioles in the junction zone and flagella microtubules. In transverse sections as well as in replicas, this region consisted of 10 pairs of microtubules and 9 dense fibers surrounded circularly by the mitochondria (mitochondrial sheath).

Animals↗
PubMed1986

Influence of histamine and related compounds on the hypnotic effect of thiopental in mice.

Intraventricular injection of histamine (Hi) significantly prolonged thiopental sleeping time at doses of 0.5 microgram or larger. Both 1-methylHi and imidazole-4-acetic acid, however, did not affect thiopental narcosis. Pretreatment with alpha-fluoromethylhistidine diminished the effect of Hi, while histidine, metoprine and quinacrine prolonged thiopental narcosis. Injection with 2-methylHi did not affect thiopental sleeping time, while as in the case of Hi, 4-methylHi augmented the thiopental effect. In addition, H2-receptor blocking agents such as cimetidine, ranitidine and famotidine clearly antagonized Hi-induced prolongation of thiopental narcosis, while pyrilamine and chlorpheniramine had no effect. These results indicate that Hi-induced prolongation of thiopental narcosis appears to be exerted via H2-receptors and is, in some way, related to the Hi content in the brain.

Animals↗
PubMed1986

[Ultrastructure of rotavirus].

The human rotavirus is an icosadeltahedral structure, with a characteristic pattern of a triangulation number (T) of 13 with a skew symmetry. The inner layer of the rotavirus has 132 morphological units, with 260 structural units of trimetric structure. It is possible that the outer layer is a smooth geodesic shell.

Capsid↗
PubMed1986

Comparative study of various H1-blockers on neuropharmacological and behavioral effects including 1-(2-ethoxyethyl)-2-(4-methyl-1-homopiperazinyl)benzimidazole difumarate (KB-2413), a new antiallergic agent.

In a conditioned avoidance response tested in rats, all of the H1-blockers employed caused a dose-related inhibition at doses 5-20 mg/kg (i.v.) except for ketotifen that elicited significant suppression even at a dose of 1 mg/kg. No inhibition was seen after administration of 1-(2-ethoxyethyl)-2-(4-methyl-1-homopiperazinyl)benzimidazole difumarate (KB-2413). ED50s were ranged from 4.1 to 7.4 mg/kg in diphenhydramine, pyrilamine and promethazine. In laminectomized rats, diphenhydramine, pyrilamine, promethazine and ketotifen suppressed the amplitudes of monosynaptic reflex potentials at doses higher than 2 mg/kg (i.v.). In the case of chlorpheniramine, significant inhibition was observed at a dose of 20 mg/kg. In a polysynaptic reflex, similar but less prominent inhibitions were affected by those drugs. However, KB-2413 did not influence spinal reflexes even at a dose of 20 mg/kg. In the rat phrenic nerve-diaphragm preparation, perfusion of H1-blockers at a concentration of 10(-5) M decreased the amplitudes of end-plate potentials except for chlorpheniramine and KB-2413. At 10(-4) M, all the test drugs caused significant inhibition. When the action potential of superior cervical ganglion was measured by the sucrose gap method, promethazine inhibited the action potential significantly at 10(-6) M, but the rest of the test drugs depressed the potentials at 10(-5) M. In spontaneous EEG, all H1-blockers caused a marked drowsy pattern at lower doses (2-5 mg/kg) except for chlorpheniramine, while in higher doses (10-20 mg/kg) epileptic signs in EEG with or without convulsive behavior were noticed. However, after KB-2413 (5-20 mg/kg) neither drowsy nor seizure pattern was observed, in EEG or behavior.

Action Potentials↗
PubMed1985

The effects of histamine and some related compounds on conditioned avoidance response in rats.

When histamine (Hi) and other agonists were applied intraventricularly, Hi caused a dose-dependent inhibition of the avoidance response in rats; its ED50 was 3.60 micrograms. 1-methylHi, 1-methylimidazole acetic acid and imidazole acetic acid which are major metabolites of Hi produced no inhibitory effect even at 50 micrograms. H1-agonists (2-methylHi and 2-thiazolylethylamine) also depressed the avoidance response; their dose-response lines run parallel to that of Hi. The depressant effects of H2-agonists (4-methylHi and dimaprit) were relatively weak; their dose-response lines were not parallel to that of Hi. When antagonists were pretreated intravenously, Hi action was clearly antagonized by diphehydramine and pyrilamine, but not by cimetidine or ranitidine. Intraventricular injection of Hi mixed with cimetidine or ranitidine did not change the effect induced by Hi alone. The avoidance response was not affected by noradrenaline, dopamine or 5-hydroxytryptamine. Although acetylcholine (ACh) suppressed the avoidance response dose-dependently, its effect was much weaker than that of Hi. Pretreatment with cholinergic blocking drugs (atropine and scopolamine) antagonized ACh action but not Hi action. From these results, it is assumed that the inhibitory effect of Hi on the avoidance response is preferentially linked to the H1-receptor. After intraventricular application of 3H-Hi, the highest radioactivity was determined in the hypothalamus.

Acetylcholine↗