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Biomedical subjects

K Kamata

Publications and source records attributed to K Kamata.

At least 289 records · Page 16Linked to original sources
PubMed1984

Long-term amphetamine treatment attenuates or reverses the depression of neuronal activity produced by dopamine agonists in the ventral tegmental area.

Neuronal activity was recorded from the ventral tegmental area (VTA) of immobilized, locally anesthetized rats on the day immediately following long-term treatment (twice daily for 6 consecutive days) with saline, 1.0 or 5.0 mg/kg d-amphetamine (d-AMPH). Each rat was challenged intravenously with d-AMPH (beginning with 0.0625 mg/kg) or with 0.005 mg/kg apomorphine. Treatment with d-AMPH significantly reduced the ability of this drug to inhibit VTA activity. In fact, nearly half of the neurons in the high-dose treatment group were excited by d-AMPH, whereas only 20% of control neurons showed this response. Moreover, apomorphine routinely accelerated firing rate in the VTA following treatment with 5.0 mg/kg d-AMPH but this response was never observed in control neurons, not even in those that were excited by d-AMPH. Thus, tolerance appears to develop to the ability of dopamine agonists to inhibit VTA activity and this effect may be mediated, at least in part, by a subsensitivity of inhibitory dopamine autoreceptors.

Action Potentials↗
PubMed1984

Effect of mizoribine on lupus nephropathy of New Zealand black/white F1 hybrid mice.

Therapeutic trials with mizoribine (MZR), an imidazole nucleoside immunosuppressant, on experimental lupus nephropathy of NZB/W F1 mice resulted in the following. The MZR treatment, 20 mg per kilogram of body weight every other day, starting at 14 weeks of age, caused a significantly prolonged survival time of mice with a mean life span of 54.3 +/- 4.2 weeks, compared with the untreated controls, who had a mean survival time of 38.1 +/- 2.9 weeks (P less than 0.01). In addition, MZR suppressed the elevation of serum anti-DNA antibody titers, the spontaneous development of splenomegaly, and the histological development and progression of glomerulonephritis observed in untreated animals. Although no definite explanation is available at present to explain how MZR caused decreased anti-DNA antibody production and delay in the development of glomerulonephritis in these animals, it is suggested that it acts by directly suppressing the hyperfunctioning B cells of lupus mice. MZR may prove to be a promising immunosuppressant for the treatment of human lupus, in view of its lesser side effects such as bone marrow suppression or hepatotoxicity.

Animals↗
PubMed1984

A dissecting aneurysm of the vertebral artery.

A rare case of dissecting aneurysm of the vertebral artery evidenced by ischemic attacks is reported. The aneurysm was treated by proximal ligation of the artery. There have been no repeated ischemic attacks and bleeding for 20 months. Analysis of 51 cases of vertebral artery aneurysm failed to disclose any comparable case. A review of the literature also revealed that clinically diagnosed dissecting aneurysms of the vertebrobasilar system have been reported rarely. Most of these cases were found at autopsy.

Aortic Dissection↗
PubMed1984

Derangement of humoral immune system in nondialyzed uremic patients.

To evaluate the humoral immune system in patients with chronic renal failure, a cytological approach was taken. The uremic lymphocytes and their subsets in the peripheral blood were quantitated and their functions studied. In order to exclude the possible effects of extra-uremic factors, the lymphocytes were obtained from the uremic patients with serum creatinine levels of 8 mg/dl or more, and who had been submitted neither to blood transfusions nor dialysis therapy. Absolute numbers of PBL, T cells, B cells, null cells and double marker cells were decreased in uremic patients compared to healthy controls (p less than 0.001), although the percentages of each cell subset of the patients were the same as with the healthy controls. In vitro plaque forming cell responses and DNA synthesis by uremic lymphocytes, stimulated with pokeweed mitogen, were significantly lower than those of the healthy controls. These data point to B lymphocyte as well as T lymphocyte dysfunction in uremia, which may be causally related to the uremic state itself.

Adult↗
PubMed1983

Dopaminergic and neostriatal neurons: dose-dependent changes in sensitivity to amphetamine following long-term treatment.

Rats were pretreated with saline, 1.0 or 5.0 mg/kg of (+)-amphetamine twice daily for 6 consecutive days. Single unit recording in the substantia nigra pars compacta (SNC) and the neostriatum, on the following day, revealed a differential shift in the intravenous dose of the drug required to produce at least a 50% change in neuronal activity (ED50) depending on the pretreatment dose. In the substantia nigra pars compacta, pretreatment with the small dose significantly reduced the ED50, compared to saline controls, whereas in rats pretreated with the large dose, the ED50 was significantly increased. In the neostriatum, control rats responded to increasing incremental doses of (+)-amphetamine with either an inhibition followed by an excitation, or an excitation. Following pretreatment with 1.0 mg/kg, neurons responded with either a depression or an excitation, whereas only amphetamine-induced excitations were recorded in the neostriatum following pretreatment with 5.0 mg/kg. The complex changes in firing rate produced by repeated exposure to amphetamine were dose-dependent in both sites and cannot be simply explained by a decrease in the sensitivity of dopamine neurons to this drug.

Action Potentials↗
PubMed1983

Immunosuppressive effect of bredinin on cell-mediated and humoral immune reactions in experimental animals.

Bredinin (BR), an imidazole nucleoside isolated from Eupenicillium brefeldianum was previously reported to prolong kidney allograft survival in dogs. The immunosuppressive effect of BR was studied in experimental animals. In beagles, in vitro responses of lymphocytes stimulated by mitogens or allogeneic cells were suppressed by in vitro BR treatment. BR, given in vivo, also showed an inhibitory action against development of delayed hypersensitivity reaction to tubercle bacilli in guinea pigs or against hemagglutinin production following booster SRBC injection in rabbits. Of note may be the fact that BR was found to have an immunosuppressive potency comparable to that of azathioprine and, in addition, to show a decreased hepatotoxicity compared with the latter.

Animals↗
PubMed1983

[Culture of mouse embryo for the toxicological evaluation of drugs in vitro. (2). Differential staining of sister chromatids of blastocyst cell].

A method for differential staining of sister chromatids of cell from mouse blastocyst was devised. Mouse embryo was cultured for 24 hr in BMOC-III medium from the 8 cell stage and then transferred into the medium containing 5-bromodeoxyuridine (BrdU) for a further 24 hr. At 4 hr prior to the termination of culture, colchicine was added to arrest the cell division in metaphase. Cells were fixed on a slide glass, air-dried, stained with Hoechst 33258, lighted with a mercury light, and stained with Giemsa. Basic conditions for the differential staining such as the concentration of BrdU and lighting were examined. When the mercury light (400 W) was used at 15 cm distance for 60-90 min, sister chromatids could be clearly differentiated with a BrdU concentration of 3-30 ng/ml. Under these concentrations of BrdU, the frequency of sister chromatid exchange (SCE) was almost the same as the control level. Thus the concentration could not affect the SCE frequency. This method can be used for the evaluation of drug toxicity of genetic or mutational effects on mammalian embryos.

Animals↗
PubMed1983

Immunosuppressive factors in uraemic sera are composed of both dialysable and non-dialysable components.

The immunosuppressive factors in uraemic sera were studied. Sera were obtained from 46 uraemic patients with a mean serum creatinine of 1.24 mM/1 +/- 0.36 (s.d.) prior to being introduced to dialysis therapy. Normal peripheral blood mononuclear cells, which were incubated in vitro with pokeweed mitogen (PWM) in the presence of 10% uraemic sera plus 10% pooled normal human serum sustaining the culture, showed decreased 3H-thymidine uptake compared to the control culture with normal sera. The immunosuppressive activity of uraemic sera was partially lost by in vitro dialysis, although a moderate degree of suppressive potency to the normal cells cultured with PWM remained in the dialysed uraemic sera. The remaining inhibitory activity in the dialysed sera was found to be unrelated to anti-lymphocyte antibodies.

Adult↗
PubMed1983

[Experimental study on the effect of acetylspiramycin on the fertilized ova].

Growth of fertilized mouse eggs treated with acetylspiramycin (ASPM) for 24 hours in their diplophase and octaplophase was observed morphologically. Changes in function of the fertilized cells in growth process were also examined, determining cell counts, mitotic index, and sister chromatid exchange as indices. These indices were all inhibited after treatment with ASPM. However, it seems that the effect was induced by H2SO4 which was used as solvent rather than by ASPM because growth inhibition and functional changes of cells were also caused by H2SO4. Therefore, it is thought that ASPM, at the concentration of 3-10 microgram/ml, has little effect on the development of fertilized eggs.

Animals↗