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Biomedical subjects

C Nishimura

Publications and source records attributed to C Nishimura.

At least 127 records · Page 7Linked to original sources
PubMed1984

Activation of distinct T cell subsets involved in IgM antibody response of mice by pertussis toxin from Bordetella pertussis strain Maeno.

T cell activation mechanisms in the spleen induced by pertussis toxin (PT) were investigated. The degree of T cell activation was judged from results of helper activity assessed by measuring the in vitro antitrinitrophenyl (TNP) IgM antibody response. When mice were injected intraperitoneally with 4 X 10(5) sheep erythrocytes (SRBC) and concomitantly given an intravenous injection with 10 micrograms of PT 4 days previously, significant generation of nonspecific helper T cells was observed unless primed T cells were stimulated in vitro with TNP-SRBC. Stimulation with TNP-SRBC resulted in marked suppression of helper activity because it induced generation of suppressor T cells specific for the carrier antigen.

Adjuvants, Immunologic↗
PubMed1984

Cell cycle requisite for vesicular stomatitis virus replication in T lymphocytes activated with concanavalin A.

The relationship between the development of virus plaque forming cells (V-PFC) and the blastogenic response of T cells activated with concanavalin A (Con A) was investigated in connection with the cell cycle using a modified virus plaque assay (VPA) which facilitated the quantitative detection of T lymphoblasts with low susceptibility to infection by vesicular stomatitis virus (vsv). The generation of V-PFC markedly decreased when DNA synthesis inhibitors such as thymidine, hydroxyurea and cytosine arabinoside (Ara C) were added to spleen cell cultures stimulated with Con A, while the addition of a mitotic inhibitor, Colcemid, to the cultures caused only partial reduction of V-PFC development. These results indicate that the S to G2 phases of the first cell cycle are essential for vsv-replication or V-PFC development in Con A activated T cells. However, vsv-replication in the activated T cells does not depend on the initial G1 phase during the blastogenic response since the morphological blast formation of activated T cells is not suppressed by treatment with DNA synthesis inhibitors.

Animals↗
PubMed1983

Taurine biosynthesis in frog retina: effects of light and dark adaptations.

The retinal uptake and metabolism of cysteine, a precursor for taurine biosynthesis, were analysed using the bull frog. The [14C] cysteine uptake into isolated retina had some specific properties: It was rather temperature independent, required Na ions, was inhibited by ouabain but not by dinitrophenol, and exhibited saturation kinetics composed of two components. When retinal homogenate was incubated with 12-30 microM of L-[U-14C]cysteine, the accumulation of labeled alanine, cysteine sulfinic acid (CSA), cysteic acid (CA), hypotaurine, and taurine was detected. The metabolic conversions of [14C] cysteine to labeled alanine, hypotaurine, and taurine were linear over 90 minutes. Prolonged light adaptation (3 weeks) induced a significant reduction in the formation of labeled CA, CSA, hypotaurine, and taurine from [14C] cysteine. On the other hand, it was found that in dark-adapted retinae, the formation of labeled taurine from [14C] cysteine increased significantly in spite of the reduction in the formation of labeled CA. These results indicate that biosynthetic pathways exist for taurine from cysteine in frog retina, and that these metabolic pathways are involved in the regulation of retinal taurine content under continuous visual adaptation.

Adaptation, Physiological↗
PubMed1983

High frequency detection of different T-cell subsets in mice by a modified virus plaque assay.

Different T-cell subsets participating in immune responses were detected at a high frequency by a modified virus plaque assay (VPA). By using the modified VPA, different activated T-cell subsets generated in primary immune responses, helper and suppressor T cells participating in antibody formation, and effector T cells involved in the delayed-type hypersensitivity (DTH) reaction were enumerated directly without in vitro antigen stimulation. The frequency of detection in immune systems used was 7.5-17.7 V-PFC/10(3) spleen cells. Although neither helper T cells for antibody formation nor effector T cells for DTH reaction were detected as V-PFC at a high frequency by the original VPA, it was also found in secondary immune response that Lyt 1 positive, antigen-specific helper and effector T-cell subsets, and cyclophosphamide (CY)-resistant precursors were enumerated at a high frequency by the modified VPA when the received in vitro antigen stimulation, and that the proliferative stage of these cells was critical for the development of V-PFC.

Animals↗
PubMed1982

Inhibition of macrophage function by 2-chloroadenosine.

The inhibitory action of 2-chloroadenosine (2-CA) on murine macrophages was investigated by means of concanavalin A (Con A)-induced T-cell proliferative response and of in vitro antibody response to sheep red blood cells (SRBC). The viability of peritoneal exudate cells (PEC) markedly decreased when treated with 0.1 mM 2-CA at 37 degrees C for 2 hr before cell cultures. Morphological changes were also observed in PEC treated with 2-CA. When spleen cells were treated with 2-CA or macrophages were depleted from the spleen cells, Con A-induced proliferative responses were markedly reduced unless normal spleen adherent cells (SAC) were added back to the cultures. However, reduced response could not be restored to the control level by the addition of 2-CA-treated SAC. AntiSRBC antibody response was also suppressed by pretreatment of spleen cells with 2-CA when adenosine was not present during the period of the treatment. Therefore, 2-CA is a useful cytotoxic agent for inhibiting the accessory functions of macrophages.

2-Chloroadenosine↗
PubMed1981

Alteration of GABA system in frog retina following short light and dark adaptations - a quantitative comparison with retinal taurine.

Effect of short light and dark adaptations on retinal GABA and taurine was studied using bull frog (Rana catesbiana). The retinal GABA was increased significantly in light-adapted state, and this increase was accompanied by the increases of L-glutamate decarboxylase (GAD) activity and [3H]-GABA release. The activation of retinal GABA-transaminase succinic semialdehyde dehydrogenase (GABA-T:SSADH) was also observed after a lag period of several hours. Under the same experimental conditions, however, no significant changes were noted in retinal taurine content and cysteine sulfinate decarboxylase (CSD) activity. These findings suggest that a short light adaptation induces differential effects on retinal GABA and taurine, and the activation of GABAergic neurons in the retina may be involved in the process of short light adaptation.

Adaptation, Ocular↗
PubMed1981

Alteration of metabolism of retinal taurine following prolonged light and dark adaptation: a quantitative comparison with gamma-aminobutyric acid (GABA).

Alteration of metabolism of taurine in prolonged light- and dark-adapted frog retinae were studied in comparison with that of gamma-aminobutyric acid (GABA) and the following results were obtained. (1) Statistically significant alterations in retinal taurine, an increase in dark-adapted, and a decrease in light-adapted states, respectively, occurred when frogs were adapted continuously to light or dark for more than 3 weeks. Under the same experimental conditions, no alteration in retinal GABA was noted. (2) At 3 weeks and thereafter, a significant increase of retinal cysteine sulfinic acid decarboxylase (CSD; EC 4.1.1.12) activity, an enzyme involved in the biosynthetic pathway of taurine, also occurred in the dark, whereas the activity in the light-adapted retina was reduced. On the other hand, the retinal activity of L-glutamate decarboxylase (GAD; EC 1.1.1.15), the rate-limiting enzyme of GABA biosynthesis, was not altered in dark- as well as light-adapted state. Similarly, retinal GABA-transaminase (GABA-T; EC 2.6.1.19)-succinic semialdehyde dehydrogenase (SSADH; EC 1.2.1.16) was unaltered. (3) These alterations in retinal taurine were, however, unaccompanied by any changes in factors related to transmitter actions such as evoked release, high affinity uptake, and specific binding to synaptic membranes. The above results suggest that, different from GABA as a potent candidate for inhibitory neurotransmitter, retinal taurine may act as neuromodulator and/or may play an important role as a basic factor for maintaining cellular integrity under certain pathophysiological conditions.

4-Aminobutyrate Transaminase↗
PubMed1981

Process of cap formation of messenger RNA by vaccinia virus particles carrying an organized enzymes system.

Vaccinia virus mRNAs carry the cap structure m7G5'pppAm- or m7G5'pppGm- at the 5'-terminus, which is synthesized by a series of RNA polymerase and capping enzymes contained in the virus particle. The process of the cap formation at the 5'-terminus of mRNA was studied using an in vitro system under similar conditions to those of vaccinia virus multiplication in its host cell. After adding a methyl-group donor, methyl-3H-S-adenosylmethionine, the oligonucleotides, which were the de novo synthesized 5'-terminal part of mRNA, were isolated from the RNA-synthesizing virion at appropriate time intervals, and were analysed. The 5'-5' confronting nucleotides with 2'-O-methylation, G5'pppAm and G5'pppGm, were found with the completed cap structure, m7G5'pppAm and m7G5'pppGm. The confronting nucleotides with only 7-methyl guanine as a methylated component, m7G5'pppA and m7G5'pppG, were not detected at any incubation time, and it was concluded that methylation at the 2'-position of the 5'-terminal purine nucleoside of mRNA precedes methylation of the 7-position of the blocking guanosine. This result is different from that obtained using the enzymes isolated from vaccinia virus (Moss et al., 1976) and also from the results obtained using other kinds of virus particles, which carry RNA polymerase and capping enzymes. These differences may be due to the specific organization of a series of capping enzymes and RNA polymerase in each virus particle.

Methylation↗
PubMed1981

Methylation of 5'-5' confronting dinucleotides by vaccinia associated enzyme system.

Methylation of a series of the 5'-5' confronting dinucleotides containing various number of phosphates was examined by the use of virion enzyme system of vaccinia virus. Methylation was absolutely dependent on the number of interposed phosphate groups between 5'-5' confronting dinucleotides, showing maximum efficiency in the 3 phosphate compound corresponding to the blocked 5'-terminus (cap) of an eukaryotic mRNA. Methylation, if any, occurred only at the 7-position of guanine residue, but not at the 2' position of ribose moiety.

Dinucleoside Phosphates↗
PubMed1978

Reversible inhibition of the induction of DNA polymerase of herpes simplex virus type 2 in HeLa cells.

The induction of DNA polymerase of herpes simplex virus type 2 in HeLa cells was inhibited by 2-mercapto-1-(beta-4-pyridethyl)benzimidazole added at an early time after infection. However, the inhibitory effect was easily released by removal of the inhibitor. Since the drug disorganizes nucleolar structure and prevents its function in HeLa cells in a reversible manner, it is possible that nucleoli are involved in the induction of DNA polymerase of this virus.

Benzimidazoles↗
PubMed1978

Serum carcinoembryonic antigens in patients with carcinoma of the cervix.

Serum levels of carcinoembryonic antigen (CEA) were measured by a radioimmunoassay technique. The mean CEA level for 80 controls was 2.03 ng/ml with a standard deviation of 0.49 ng/ml. Hence, the upper limit of normal for serum CEA levels was considered to be 3.01 ng/ml, ie, two standard deviations above the mean. Serum CEA levels were measured in 86 patients with cervical squamous cell carcinoma, Stages 0 through IV. Thirty-five of the 74 patients with invasive cervical carcinoma were CEA-positive (serum levels above normal); patients with cervical dysplasia or carcinoma in situ were all CEA-negative. Study of the distribution of these patients together with the extent of their disease leads to the following conclusions: a) determination of serum CEA levels cannot serve as a test for the early diagnosis of cervical cancer or precancerous lesions; b) in patients with clinical Stage I or II cervical cancer, an elevated serum CEA level indicates a greater likelihood of parametrial invasion or lymph node metastasis; c) in patients with treated carcinoma of the cervix, continued normal levels of serum CEA affirm continued absence of the disease, whereas development of an elevated level is highly suspicious of occult residual or recurrent cancer. The authors urge periodic determinations of serum CEA levels in patients with treated cervical cancer.

Adult↗