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Biomedical subjects

M Sawada

Publications and source records attributed to M Sawada.

At least 469 records · Page 26Linked to original sources
PubMed1985

Influences of pressure-injected cyclic AMP on the membrane current and characteristics of an identified neuron of Aplysia kurodai.

The ionic mechanism of the effect of intracellularly injected adenosine 3',5'-cyclic monophosphate (cAMP) on the membrane of identified neuron L5 of Aplysia kurodai was investigated with conventional voltage-clamp and ion-substitution techniques. The intracellular elevation of cAMP caused an inward current (IcAMP), which was not accompanied by a significant change in membrane conductance at potentials more hyperpolarized than -60 mV. The current increased over the voltage range (-50 to -30 mV) associated with a conductance decrease and decreased at potentials more hyperpolarized than -60 mV. Elevated intracellular cAMP was found to enhance a region of negative slope resistance in steady-state I-V relations. Duration of the IcAMP was greatly prolonged by bath-applied isobutylmethylxanthine (50 microM), but imidazole (10 mM) had an opposite effect on the IcAMP. Tolbutamide (5 mM), a protein kinase inhibitor, reduced the IcAMP. The current was not affected by the presence of bath-applied TTX (50 microM), ouabain (50 microM), or triaminopyrimidine (5 mM). Reduction of [Na+]0 reversibly decreased the IcAMP. Li+ could largely substitute for Na+. Alterations of [K+]0, and bath application of 4-AP (5 mM) and TEA (30 mM) did not affect the IcAMP. In the presence of Na+, Cl-, and divalent cations such as Ca2+ and Ba2+ inhibited the IcAMP. These results suggest that fast elevation of intracellular cAMP induces a TTX-resistant slow Na+ inward current, and the current might be due to activation of cAMP-dependent protein kinase.

1-Methyl-3-isobutylxanthine↗
PubMed1985

Mechanisms of interleukin-2-mediated signaling and role of calcium in T cell mitogenesis.

In T lymphocytes stimulated by concanavalin A (Con A), interleukin 2 (IL-2) acts on the late G1 stage of the cell cycle. Ca2+ uptake by T cells was not enhanced with the stimulation of Con A (initiation) or IL-2 (late G1 stage), but Ca2+ requirement was observed at the two stages. These results indicate that the enhancement of Ca2+ uptake is not necessary, but intracellular Ca2+ may act as an important messenger in T cell mitogenesis.

Biological Transport, Active↗
PubMed1985

[Effects of long-term high doses of sex steroid hormones on human endometrial adenocarcinoma transplanted into nude mice].

To clarify the minute reactions of endometrial adenocarcinoma to sex steroid hormones, especially gestagen, an in vivo model (AD-30) transplanted into nude mice was established. The AD-30, well differentiated papillo-tubular type, was given 500 micrograms/kg/day of estradiol benzoate (E2) for 50 days or 0.1-100mg/kg/day of medroxyprogesterone acetate (MPA) for 120 days. Thereafter sequential histopathological changes, tumor growth curve and volume doubling time (VDT) were investigated as compared to the castrated control group. Histopathological changes: Following E2 administration, the cells increased in number and were packed in the tubular glands, and following a large dose of MPA, while secretory producing fluid was accumulated in the lumen, cells were shrunk, damaged and finally necrosed, but almost un affected cells were also observed. Tumor growth curve and VDT: E2 somewhat lifted the curve and shortened the VDT to 184 hr (control: 250 hr), while MPA produced various curves, some were diminished, some suppressed and others equal to the control group-with additional secretory fluid. Also MPA elongated the VDT to 412 hr.

Adenocarcinoma, Papillary↗
PubMed1984

Immunosuppressive acidic protein in patients with gynecologic cancer.

Immunosuppressive acidic protein (IAP) was determined in sera of patients with gynecologic tumors using the single radial immunodiffusion method. The normal limit of IAP of 490 micrograms/ml was derived from the mean value + 2 SD of IAP in 150 healthy females. Among 141 patients with gynecologic cancers, serum IAP was elevated in 87 patients (62%). Among 190 patients with benign tumors (98 uterine myoma, 92 benign ovarian tumors) serum IAP was elevated in 14 patients (7%). Elevated levels of IAP were recognized in 43% of 77 patients with cervical cancer, in 55% of 11 endometrial cancer patients, and in 91% of 53 ovarian cancer patients. The frequency of elevated levels showed a tendency to increase with advancing stage of disease. In ovarian cancer elevation of IAP was observed even in early stages. All of 13 patients with recurrent cervical cancer had elevated IAP while only 6 of 35 (17%) previously treated patients without evidence of recurrence had elevated IAP. Immunosuppressive acidic protein determinations may be useful in monitoring the recurrence of cervical cancer. The measurement of serum IAP as a marker for gynecologic cancer is recommended as an addition to diagnostic procedures.

Adolescent↗
PubMed1984

Polarization fluoroimmunoassay of biopterin and neopterin in human urine.

A polarization fluoroimmunoassay has been developed for the routine determination of biopterin and neopterin levels in human urine. The method employs fluorescein-labeled biopterin and neopterin. The assay is fast (incubation time: 2 min) and no separation step is required prior to measurement of fluorescence polarization. Linearity, recovery and precision were satisfactory. Estimations of biopterin and neopterin levels in human urine samples closely correlated with those obtained by radioimmunoassay.

Animals↗
PubMed1984

Ionic mechanism of a hyperpolarizing glutamate effect on two identified neurons in the buccal ganglion of Aplysia.

The ionic mechanism of a membrane effect of L-glutamate on two identified neurons in the buccal ganglion of Aplysia kurodai was investigated with conventional microelectrode techniques and glutamate iontophoresis. Bath-applied and iontophoresed glutamate hyperpolarized the membrane and increased the membrane conductance. The hyperpolarizing glutamate response decreased in amplitude and finally reversed its polarity by conditioning hyperpolarization. The reversal potential of the hyperpolarizing glutamate response was close to the ECl (-60 mV). The reversal potential changed by 22.4 mV when the external chloride concentration was altered by a factor of 5. The relationship between the iontophoretically applied current and the membrane conductance changes was suggestive of two glutamate molecules reacting with a single receptor site. The hyperpolarizing glutamate response was essentially unaffected by 2-amino-4-phosphonobutyric acid (2-APB), L-proline, and quinuclidinyl benzilate (QNB). It was concluded that the hyperpolarizing glutamate response was generated by an activation of Cl- conductance.

Animals↗
PubMed1984

Organization of ribosomal RNA genes in Mycoplasma capricolum.

DNA segments carrying rRNA genes of Mycoplasma capricolum have been cloned and characterized by restriction endonuclease mapping, DNA-RNA hybridization and nucleotide sequencing. The M. capricolum genome has two sets of rRNA gene clusters, where the arrangement is in the order of (5')16S-23S-5S(3'). The spacer region between 16S and 23S rDNA is extremely rich in AT and does not carry any tRNA genes.

Base Sequence↗
PubMed1984

Radioimmunoassay for neopterin in body fluids and tissues.

Specific antibodies against D-erythroneopterin have been prepared in rabbits using a conjugate of D-erythroneopterin to bovine serum albumin (D-erythroneopterinylcaproyl-bovine serum albumin). The antiserum distinguished D-erythroneopterin from other pteridines, i.e., three stereoisomers of neopterin, L-erythrobiopterin, folic acid, xanthopterin, and four other synthetic pteridines. Using this specific antiserum, a radioimmunoassay for D-erythroneopterin has been developed to measure the neopterin concentrations in urine and tissues. The conjugate of D-erythroneopterin with tyramine (NP-Tyra) was synthesized and labeled with 125I as the labeled ligand NP-[125I]tyra for the radioimmunoassay. The minimal detectable amount of neopterin was about 0.1 pmol. The concentration of total neopterin (neopterin, 7,8-dihydroneopterin, quinonoid dihydroneopterin, and tetrahydroneopterin) in the biological samples was obtained by iodine oxidation under acidic conditions prior to the radioimmunoassay, and that of neopterin plus 7,8-dihydroneopterin by oxidation under alkaline conditions. Total neopterin values in human urine obtained by this new radioimmunoassay showed a good agreement with those obtained by high-performance liquid chromatography with fluorescence detection. With rat tissue samples which contained very low concentrations of neopterin as compared to biopterin, biopterin was simultaneously determined by our previously reported radioimmunoassay, and neopterin values were corrected for the cross-reactivity (0.1%). The neopterin concentrations obtained by this method agreed with the values obtained by the radioimmunoassays for neopterin and biopterin after their separation by high-performance liquid chromatography. This very small amount of neopterin, as compared with biopterin, in rat tissues could not be determined by high-performance liquid chromatography-fluorometry alone due to the masking of the neopterin peak by a large biopterin peak.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Primary mutagenicity screening of food additives currently used in Japan.

Salmonella/microsome tests (Ames tests) and chromosomal aberration tests in vitro using a Chinese hamster fibroblast cell line were carried out on 190 synthetic food additives and 52 food additives derived from natural sources, all of which are currently used in Japan. Fourteen out of 200 tested in the Ames assay showed positive effects and 54 out of 242 were positive in the chromosome test. Three additives (erythorbic acid, chlorine dioxide and beet red) were positive only in the Ames test, although their mutagenic potentials were relatively weak, while 43 additives were positive only in the chromosome test. Eleven additives (calcium hypochlorite, cinnamic aldehyde, L-cysteine monohydrochloride, Food Green No. 3 (Fast Green FCF), hydrogen peroxide, potassium bromate, sodium chlorite, sodium hypochlorite, sodium nitrite, cacao pigment and caramel) were positive in both the Ames test and the chromosome test. The usefulness of such primary screening tests combining two different genetic end-points, gene mutation and chromosomal aberration, and some correlation between mutagenicity and carcinogenicity of food additives are discussed.

Animals↗
PubMed1984

Effects of U.V. radiation on the lifespan of the rotifer Asplanchna brightwelli.

Groups of rotifers of the species Asplanchna brightwelli were exposed to U.V. irradiation at dosages ranging from 50 to 4800 J/m2. The lifespan of the rotifers was significantly reduced by exposure to U.V. in the range of 200 to 4800 J/m2. A logarithmic decline in lifespan was seen as the U.V. dose increased. Rotifers were most sensitive to U.V. exposure during the prereproductive stage at the beginning of their lifecycle. Exposure of rotifers to visible light following U.V. radiation provided no evidence that photoreactivation could influence lifespan in this species.

Aging↗
PubMed1984

A study of dietary restriction and lifespan in the rotifer Asplanchna brightwelli monitored by chronic neutral red exposure.

The rotifer Asplanchna brightwelli could be exposed to concentrations of neutral red at 0.1 to 0.75 microgram/ml for two consecutive generations with no adverse effect on the lifespan or fecundity of either generation. Chronic exposure to higher concentrations of neutral red caused reductions in both lifespan and fecundity of the rotifers. Because neutral red stains the Paramecium which serve as a food source for the rotifers, the extent of red coloration in each rotifer's gut gave an approximation of how much food that rotifer had consumed. The Paramecium concentration had to be reduced to 100 per ml before pale gut coloration provided clear evidence of reduced food intake or dietary restriction. The group of rotifers with reduced food intake had a significantly longer lifespan than any other group. Their lifespan was 14.2% longer than that of control rotifers.

Aging↗
PubMed1984

The effect of light, dark or altered circadian cycle on the lifespan of the rotifer Asplanchna brightwelli.

Rotifers were maintained in various light conditions for at least 20 generations. In the first set of experiments lifespan and fecundity data were compared for groups of rotifers maintained under LL (continuous light), DD (continuous dark) or LD 12:12 (control, 12 hr. light 12 hr. dark). The mean lifespan of the rotifers cultured in DD conditions was significantly increased as compared to the LL or LD 12:12 groups but there were no fecundity differences. There was no alteration in lifespan or fecundity of the LL group as compared to the LD 12:12 control. In a second set of experiments, an LD 6:18 cycle was imposed to determine whether a shift in the circadian cycle would influence lifespan. Rotifers exposed to the LD 6:18 cycle and to the DD conditions showed an 18% and 22% increase in mean lifespan respectively. The results are interpreted to demonstrate that lifespan is influenced by the circadian cycle.

Animals↗
PubMed1984

Vitamin E extends lifespan in the short-lived rotifer Asplanchna brightwelli.

Supplementation with vitamin E at a concentration of 25 micrograms/ml significantly increased the mean lifespan of the rotifer Asplanchna brightwelli. Of the three life stages, the prereproductive, reproductive and postreproductive, only the prereproductive stage was significantly extended by vitamin E supplementation. Vitamin E supplemented rotifers were larger than control rotifers in their early stages of life, but both groups attained the same size by the end of their lifespan.

Animals↗
PubMed1984

Effects of 5-hydroxytryptamine on membrane potential, contractility, accumulation of cyclic AMP, and Ca2+ movements in anterior aorta and ventricle of Aplysia.

Effects of 5-hydroxytryptamine (serotonin; 5-HT) on the anterior aorta and ventricle muscle of the marine gastropod Aplysia are characterized. Bath-applied 5-HT depolarizes muscle fibers and causes tension increases in both the anterior aorta and ventricle above ca. 10(-9) M. Iontophoretically applied 5-HT caused localized depolarizations of anterior aorta muscle fibers. 5-HT increases the levels of adenosine-3',5'-cyclic monophosphate (cAMP) markedly in the anterior aorta of A. kurodai and A. californica and in the ventricle of A. kurodai. Effects of 5-HT on the contractility of and cAMP synthesis in the anterior aorta and ventricle are both blocked by methysergide. 5-HT and cAMP analogs stimulate 45Ca2+ efflux from the ventricle, implying that the effects of cAMP on contractility involve intracellular Ca2+ movements.

Animals↗