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Biomedical subjects

Y Kitamura

Publications and source records attributed to Y Kitamura.

At least 19 recordsLinked to original sources
PubMed1992

Localization and developmental expression of a novel protein kinase C delta gene.

The expression and localization of a novel protein kinase C delta (nPKC delta) mRNA were investigated using Northern blotting and in situ hybridization in the developmental process of mouse brain. In adult mice, nPKC delta was abundantly expressed in the thalamus, moderately in the pons and the cerebellum, but faintly in the cerebral cortex and the spinal cord. By in situ hybridization, the signals were observed specifically at the sensory and motor relay nuclei of the thalamus, the dorsal cochlear nuclei of the pons, and the molecular layer of the cerebellum. When developmental changes in the expression of nPKC delta gene were analyzed by in situ hybridization, it was not detectable in embryonic and neonatal brains, very weakly expressed in the thalamus in the first week, and highly expressed at two weeks of age. These results suggest that the gene expression of nPKC delta is strictly controlled by both the cell type and the developmental process.

Animals↗
PubMed1992

BALB/3T3 fibroblast-conditioned medium attracts cultured mast cells derived from W/W but not from mi/mi mutant mice, both of which are deficient in mast cells.

Proliferation of murine mast cells is induced by both T-cell-derived and fibroblast-derived growth factors. Because the most potent T-cell-derived mast cell growth factor, interleukin-3, promotes the migration of mast cells, we investigated whether fibroblast-derived growth factors had the chemoattractive activity as well. Conditioned medium (CM) of BALB/3T3 fibroblasts induced the migration of cultured mast cells (CMC) derived from normal (+/+) mice. BALB/3T3-CM contained the mast cell growth factor (MGF)/stem cell factor (SCF)/kit ligand (KL), which is the ligand for the receptor encoded by the W (c-kit) gene. CMC derived from the spleen of W/W mice lack the extracellular domain of the W (c-kit) receptor, and W/W CMC did not proliferate in response to BALB/3T3-CM. However, W/W CMC did migrate normally toward BALB/3T3-CM and, moreover, the antibody to the extracellular domain of the W (c-kit) receptor did not inhibit the chemoattractive activity of +/+ CMC toward BALB/3T3-CM. These results indicated that MGF/SCF/KL itself did not represent the major chemoattractive activity. On the other hand, BALB/3T3-CM induced neither proliferation nor migration of CMC derived from mi/mi mice. Both W/W and mi/mi mice are deficient in mast cells, but the present results suggest that the mechanism of the abnormality is different between W/W and mi/mi mice.

Animals↗
PubMed1992

Nonconservative recombination in Escherichia coli.

Homologous recombination between two duplex DNA molecules might result in two duplex DNA molecules (conservative) or, alternatively, it might result in only one recombinant duplex DNA molecule (nonconservative). Here we present evidence that the mode of homologous recombination is nonconservative in an Escherichia coli strain with an active RecF pathway (a recBC sbcBC mutant). We employed plasmid substrates that enable us to recover both recombination products. These plasmids carry two mutant alleles of neo gene in direct orientation, two drug-resistance marker genes, and two compatible replication origins. After their transfer to the cells followed by immediate selection for the recombination to neo+, we could recover only one recombination product. A double-strand break at the region of homology increased this nonconservative recombination. If a nonconservative exchange should leave an end, this end may stimulate another exchange. Such "successive half crossing-over events" can explain several recombination-related phenomena in E. coli, including the origin of plasmid linear multimers and of transcribable, nonreplicated recombination products, and also in yeast and mammalian cells.

Bacterial Proteins↗
PubMed1992

Nonrandom integration of retroviral DNA in vitro: effect of CpG methylation.

We have developed a PCR-based system that allows us to assess the relative frequency of use of specific bases as targets for the avian leukosis virus in vitro integration system. Using this system, we tested the effect of 5-methylation of cytosine in runs of CpG on the distribution of integration target sites. We found that the distribution of preferred integration sites was not uniform along the target DNA; rather, there was a distinct and reproducible pattern of frequently used sites. This pattern was independent of orientation of the integrated DNA, and of overall structure and sequence of the target and fragment amplified. Methylation did not inhibit integration into CpG dinucleotides; on the contrary, this modification created highly preferred targets within runs of alternating CpG. Finally, similar but not identical specificity was observed by using preintegration complexes in infected extracts or purified integrase and DNA as enzyme and substrate. Thus, most of the specificity observed is conferred by interaction of integrase and targets, although it may be modified by other viral and/or cellular components.

Animals↗
PubMed1992

Age-related changes in transmitter glutamate and NMDA receptor/channels in the brain of senescence-accelerated mouse.

The senescence-accelerated mouse (SAM-P/8) is known as a murine model of aging and memory dysfunction. In the hippocampus and cerebral cortex of P/8, the contents of glutamic acid and glutamine were significantly higher than those of normal strain R/1 during 2 and 14 months. High K(+)-evoked endogenous glutamic acid release from the slices of P/8 was increased in comparison with R/1 at 9 and 11 months. In addition, the Bmax of [3H]dizocilpine (MK-801, channel blocker for N-methyl-D-aspartic acid receptor/channel) binding in the cerebral cortex was age-dependently decreased in P/8 but not in R/1. These results suggest that synaptic dysfunctions in the glutamatergic system occur in the CNS of SAM-P/8.

Aging↗
PubMed1992

Necessity of extracellular domain of W (c-kit) receptors for attachment of murine cultured mast cells to fibroblasts.

The receptor encoded by the W (c-kit) locus (W receptor) is expressed on the surface of cultured mast cells (CMC) derived from normal (+/+) mice, whereas its ligand encoded by the Sl locus (Sl ligand) is expressed on the surface of fibroblast cell lines derived from murine embryos. Involvement of W receptors and Sl ligands in attachment of CMC to fibroblasts was investigated. CMC were cocultured with fibroblasts; nonattaching CMC were removed and the remaining CMC were counted. CMC derived from mice of the W/W genotype did not express the extracellular domain of W receptors, and attachment of W/W CMC to +/+ fibroblasts was significantly impaired. Fibroblasts derived from embryos of the Sl/Sl genotype did not express Sl ligands, and the attachment of +/+ CMC to Sl/Sl fibroblasts was also impaired. The Wv and W42 alleles are point mutations at the intracellular tyrosine kinase domain. Attachment of either Wv/Wv, W/Wv, or W/W42 CMC to +/+ fibroblasts was comparable with that of +/+ CMC. Moreover, the addition of monoclonal antibody against the extracellular domain of W receptors inhibited the attachment of +/+ CMC to +/+ fibroblasts. Thus, the extracellular domain of W receptors appeared to be necessary for attachment of CMC to fibroblasts.

Alleles↗
PubMed1992

Spatial expression of genes encoding c-kit receptors and their ligands in mouse cerebellum as revealed by in situ hybridization.

Expression of mRNA for c-kit receptors and their ligands was examined in the cerebellum of mice by in situ hybridization technique. The c-kit receptors were expressed in the molecular layer of the cerebellum and the ligands for the c-kit receptors were detected at the boundary of molecular and granular layers. The expression of the c-kit ligands was not detectable in the cerebellum of lurcher (Lc/+) mutant mice that lack Purkinje cells, indicating the cells expressing the c-kit ligands were Purkinje cells. The cells expressing c-kit receptors decreased but were present in the cerebellum of Lc/+ mice. The c-kit mRNA-positive cells appeared to represent basket cells and stellate cells from their appearance and location. Since neurons in the molecular layer construct suppressive neurojunctions with Purkinje cells, the present result suggests that c-kit receptors and their ligands may play an important role for the construction of their junctions.

Animals↗
PubMed1992

Maintenance by androgen and thyroid hormone of androgen-induced convoluted tubular cells in mouse submandibular glands.

Injection of 5 alpha-dihydrotestosterone (DHT) into castrated adult female mice stimulated the proliferation of a small proportion of the convoluted tubular cells in the submandibular glands. We investigated the effects of DHT and thyroxine (T4) on the maintenance of these proliferated convoluted tubular cells. For this, castrated adult female mice that had been treated daily with DHT for 3 days and then once with [3H]thymidine, received a first series of daily injections of DHT for various periods or T4 for 10 days, and then a second series of injections of treatment with DHT or T4, or no further treatment. The second series of treatments with DHT or T4 maintained the percentages of 3H-labeled convoluted tubular cells at similar or slightly lower levels than those at the end of the first series of treatments. In mice that did not receive the second series of treatments, the percentages of 3H-labeled convoluted tubular cells decreased markedly, becoming significantly lower than those at the end of the second series of treatment with DHT or T4. We also examined the effect of DHT on the proliferation of convoluted tubular cells of castrated adult female mice that had received 10 daily injections of DHT and then no treatment for 28 days. In these mice, the cells did not proliferate markedly on stimulation with DHT. These results suggest that androgen and thyroid hormone maintain convoluted tubular cells that have proliferated in response to androgen, and that the convoluted tubular cells may become unresponsive to androgen in terms of proliferation after their exposure to androgen.

Animals↗
PubMed1992

Magnetic resonance imaging detection of aortic and pulmonary artery wall thickening in the acute stage of Takayasu arteritis. Improvement of clinical and radiologic findings after steroid therapy.

OBJECTIVE: Early diagnosis of Takayasu arteritis in the acute stage (prepulseless stage) is extremely difficult. Identification of a useful approach to detecting the initial changes of arteritis is therefore desirable. METHODS: Careful clinical examination of a young woman with persistent fever and dry cough revealed faintly audible bruits at the cervical, supraclavicular, and abdominal regions. Aortographic features suggested thickening of the wall of the descending thoracic aorta. Magnetic resonance imaging (MRI) of this area was diagnostic. RESULTS: MRI demonstrated involvement of the ascending aorta and right main pulmonary artery. Steroid therapy (prednisolone 60 mg/day) induced dramatic clinical and radiologic improvement in 2 months. CONCLUSION: This is the first report of MRI-documented reduction in the thickness of the walls of both the aorta and the pulmonary artery following steroid therapy.

Acute Disease↗
PubMed1992

Localization of mRNA for c-kit receptor and its ligand in the brain of adult rats: an analysis using in situ hybridization histochemistry.

Localization of mRNA for the c-kit receptor and its ligand (Sl factor) in the brain of adult rats was studied using in situ hybridization histochemistry. The mRNA for the c-kit receptor was detected in the forebrain, the lower brain stem and the cerebellum. In the forebrain, the c-kit mRNA signals were detected in the olfactory bulb, the caudate-putamen, throughout the superficial cortex, the accumbens nucleus, the nucleus of vertical limb diagonal band, the bed nucleus of anterior commissure, Ammon's horn, the entopeduncular nucleus, the subthalamic nucleus, the dorsal raphe nucleus, the parasubiculum, the presubiculum, the ventricular nucleus of lateral lemniscus, and the entorhinal cortex. In the lower brain stem, the signals were detected in the inferior colliculus, the spinal vestibular nucleus, the spinal tract nucleus of trigeminal nerve, and the pyramidal tract. In the cerebellum, the signals were detected in the molecular layer of the cortex and cerebellar nuclei. By contrast, the signals of mRNA for Sl factor were detected in the forebrain and the cerebellum. In the forebrain, the signals were detected in the olfactory bulb, the endopiriform nucleus, the septohippocampal nucleus, the habenular nuclei, and most of the thalamic nuclei. In the cerebellum, the signals were detected in Purkinje cells. Several pairs of structures were found in which mRNA of either the c-kit receptor or the Sl factor was expressed and between which the synaptic connection had been reported, suggesting that the interaction between the c-kit receptor and the Sl factor may play some roles in the development of such synaptic connections.

Animals↗
PubMed1992

Age-related changes in NMDA-induced [3H]acetylcholine release from brain slices of senescence-accelerated mouse.

From the brain slices of normal mice (ddY strain, subcloned from dd strain in National Institute of Health in Japan), N-methyl-D-aspartic acid (NMDA) at 0.01-1 mM evoked [3H]acetylcholine (ACh) release in a concentration dependent manner. [3H]ACh release evoked by 1 mM NMDA was significantly inhibited by 2-amino-5-phosphonovaleric acid (APV), phencyclidine (PCP) and 5-methyl-10,11-dihydroxy-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801). The effects of NMDA were not seen in the Ca2+ free medium and were inhibited by physiological concentration (0.83 mM) of Mg2+. NMDA seems to cause ACh release from nerve terminals through the receptor-ion channel mediated mechanism in the mouse brain. Based upon these results, we determined the activity of a high K(+)- or NMDA-evoked [3H]ACh release using prone/8 strain of senescence-accelerated mouse (SAM-P/8) (a murine model of accelerated aging and memory dysfunction) and SAM-resistance/1 strain (SAM-R/1) (normal aging mice as the control) and these release activities were compared between both strains and during aging. [3H]ACh release evoked by 30 mM KCl was significantly lower than that of age-matched SAM-R/1 at 9 and 12 months. NMDA evoked the [3H]ACh release at 2, 6, 10 and 14 months in R/1 mice. In SAM-P/8 mice the activity of NMDA-evoked release was seen at 2 months, but markedly decreased afterwards. Nonsignificant difference was observed on the uptake of [3H]choline and on the spontaneous release of [3H]ACh between SAM-P/8 and SAM-R/1 strains, and during aging.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1992

Glutamate inhibits adenylate cyclase activity in dispersed rat hippocampal cells directly via an N-methyl-D-aspartate-like metabotropic receptor.

Three major subtypes of glutamate receptors that are coupled to cation channels--N-methyl-D-aspartate (NMDA), kainate, and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors--are known as ionotropic receptors in the mammalian CNS. Recently, an additional subtype that is coupled to GTP binding proteins and stimulates (or inhibits) metabolism of phosphoinositides has been proposed as a metabotropic receptor. Incubation of dispersed hippocampal cells from adult rats with glutamate or NMDA decreased forskolin-stimulated cyclic AMP (cAMP) accumulation; half-maximal effects were obtained with 5.6 +/- 2.2 and 6.4 +/- 2.3 microM, respectively. Kainate and quisqualate were less potent. The effect of glutamate was antagonized by 2,3-diaminopropionate and 2-amino-5-phosphonovalerate, NMDA/glutamate receptor antagonists, but not by 0.5 microM Joro spider toxin, a specific blocker of the AMPA receptor. The inhibitory effect of glutamate on cAMP formation was not blocked by 2 microM tetrodotoxin or by the absence of Ca2+. In hippocampal membranes, glutamate, similar to carbachol, inhibited adenylate cyclase activity in a GTP-dependent manner. These findings suggest that the glutamate inhibition of adenylate cyclase is direct and is not due to a result of the release of other neurotransmitters. The effect of glutamate on cAMP accumulation was observed in an assay medium containing 0.7 mM MgCl2, which is known to inhibit both ionotropic NMDA receptor/channels in the hippocampus and metabotropic NMDA receptors in the cerebellum. The inhibitory effect of glutamate was abolished by pertussis toxin treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclase Inhibitors↗
PubMed1992

The pH dependent uptake of enoxacin by rat intestinal brush-border membrane vesicles.

The mechanism of the intestinal transport of enoxacin, an orally active fluoroquinolone antibiotic, has been investigated using brush-border membrane vesicles isolated from rat small intestine. The initial rate and time-course of enoxacin uptake were considerably dependent upon the medium pH (pH 5.5 greater than pH 7.5) and upon the percent ionization of the carboxyl group (pKa 6.2, anionic charge), namely, the degree of uptake of cationic form was higher than that of the zwitterionic form. There was evidence of transport into the intravesicular space as shown by the effect of extravesicular medium osmolarity on enoxacin uptake at steady state (30 min). This transport across the brush-border membrane was stimulated by the valinomycin-induced K(+)-diffusion potential (interior negative) and an outward H(+)-diffusion potential. Furthermore, changing the pH of the medium from 5.5 to 7.5 significantly decreased the effect of valinomycin-induced K(+)-diffusion potential on the enoxacin uptake. These results suggest that the uptake behaviour of the cationic form of enoxacin plays an important role in the intestinal absorption process of enoxacin.

Animals↗
PubMed1992

Gynecomastia and ectopic human chorionic gonadotropin production by transitional cell carcinoma of the bladder.

We report a patient with gynecomastia and ectopic production of human chorionic gonadotropin (HCG) by a transitional cell carcinoma of the bladder. In the present case, serum HCG levels and gynecomastia paralleled the clinical course. On admission, the patient was suffering from invasive transitional cell carcinoma (grade 3) of the bladder with metastasis to the left inguinal lymph nodes, together with gynecomastia. The serum HCG level was also elevated. After anticancer chemotherapy, the apparent bladder lesion and gynecomastia disappeared, and the serum HCG level declined to within normal limits. About 2 months after discharge, when the patient suffered from recurrent invasive tumors of the bladder, gynecomastia reappeared and the serum HCG level again became elevated. beta-HCG was demonstrated in biopsy tissue using the immunoperoxidase technique. The presence of beta-HCG was always focally demonstrated and was shown to be localized in the cytoplasm of the tumor cells.

Carcinoma, Transitional Cell↗
PubMed1992

[Incidence of renal cell carcinoma in Chiba Prefecture, Japan; ten years experience].

Many reports about the increase of renal cell carcinoma patients have been published in Japan recently, however, the real fluctuations in the total number of patients in relation to the change of population have not been reported yet. Most of the patients with renal cell carcinoma in the last 10 years were examined in Chiba prefecture, which has a population of about five million and 25 active urological offices. Histologically confirmed cases were investigated by sending questionnaire letters. The items were as follows; sex, age, address, occupation, family history, past history, symptoms, examination methods that first detected the tumor, operation date, tumor diameter and clinical stage. Twenty two offices returned answers and 560 cases who lived in Chiba were found to have renal cell carcinoma from 1980 to 1989. Yearly incidence rates per 100,000 persons demonstrated a significant increase from 0.32 to 2.07. Small, asymptomatic and low stage cancers have been increasing rapidly, however, the rate of metastatic disease has not shown any decrease. The main cause of rapid increase seems to be attributed to progress in diagnostic methods and increase of early detection, but the possibility of an increase in some carcinogenic factors can not be ruled out.

Adult↗
PubMed1992

[Prognostic factors in patients with invasive differentiated thyroid carcinoma who underwent palliative resection].

In order to determine surgical strategy for locally advanced thyroid carcinoma, a multivariate analysis of prognostic factors was carried out with 70 patients of locally advanced thyroid carcinoma who underwent palliative surgery. Multivariate analysis was conducted by Cox's proportional hazard model. The patients have been followed up from 5 to 26 years. We have demonstrated the influence of age, sex, distant metastasis, pathological findings, numbers of adjacent organs, infiltrated, extent of resection, external irradiation and 131I therapy on survival. The result of this study showed that age had an impact on survival. The survival rate of the patients under 40 years was much better than that of the patients 40 years and over. The result implies that aggressive surgery and postoperative adjuvant therapy should be considered in the old patients, but not always be indication in the young patients.

Adenocarcinoma↗