Biomedical subjects

Y Kikuchi

Publications and source records attributed to Y Kikuchi.

At least 343 records · Page 19Linked to original sources

PubMed1995

A high dose of the STM1 gene suppresses the temperature sensitivity of the tom1 and htr1 mutants in Saccharomyces cerevisiae.

A new gene (STM1; suppressor of tom1) of Saccharomyces cerevisiae was isolated by the ability to suppress the temperature sensitivity of a tom1 mutant, by increasing its gene dosage. The gene could also suppress the temperature sensitivity of the htr1 disruptant (Kikuchi et al. (1994) Mol. Gen. Genet. 245, 107-116) and was physically mapped in the region near PEP3 on chromosome XII R. The predicted gene product (29,999 Da) is basic and partially homologous to various histone H1. The level of the gene expression increased 2-fold when exposed to mating pheromone.

Amino Acid Sequence↗

PubMed1995

Production of a chimeric fibroin light-chain polypeptide in a fibroin secretion-deficient naked pupa mutant of the silkworm Bombyx mori.

The allelic Nd-s and Nd-sD mutations of the silkworm Bombyx mori are mapped to the same locus as that of the fibroin light (L)-chain gene (Fib-L). The silkworm carrying the homozygous Nd-s or Nd-sD mutation secretes less than 0.3% of the normal level of fibroin and produces a thin cocoon (naked pupa). In this study, cDNA sequences of the Nd-s and Nd-sD L-chains were compared with the cDNA and genomic sequences of the L-chain of the B. mori J-139 strain, a normal-level producer of fibroin. The two mutant cDNA sequences are almost identical except for one base change in the coding region. The N-terminal half of the L-chain encoded by exons I to III is identical between the mutants and J-139, but the rest of the molecule is completely different. The C-terminal half of the Nd-sD mutant L-chain is encoded by two exons, IV' and V', which are brought into proximity with the exon III by recombination between sequences in the third intron and in the far downstream region with concomitant loss of a region containing exons IV to VII. Sequences corresponding to exons IV' and V' are present about 10 kb downstream of the L-chain gene in the J-139 genome. Their homologous sequences have not been found in the DNA and protein databases. The chimeric L-chain molecule of about 27 kDa is present in posterior silk glands of Nd-s and Nd-sD strains without disulfide-bonding to the fibroin heavy (H-) chain, as revealed by Western blotting with the antibody specific to the C-terminal half of the mutant L-chain.

Amino Acid Sequence↗

PubMed1995

Nitric oxide as a retrograde messenger in the nucleus tractus solitarii of rats during hypoxia.

1. We examined the role of nitric oxide (NO) in respiratory regulation in the nucleus tractus solitarii (NTS), where L-glutamate release associated with peripheral chemoreceptor activation modulates the hypoxic ventilatory response. 2. Experiments were performed in unanaesthetized freely moving rats. First, the effects on the hypoxic ventilatory response of sodium nitroprusside (SNP, a NO donor) or NG-monomethyl-L-arginine (L-NMMA, a NO synthase inhibitor), microinjected into the NTS, were investigated. Second, using in vivo microdialysis, changes in extracellular L-glutamate during hypoxia were examined in the presence of L-NMMA. Third, the effect of L-NMMA on ventilatory augmentation by exogenous L-glutamate was examined. Furthermore, we measured extracellular L-citrulline concentration changes during hypoxia in the NTS to assess NO formation indirectly and also examined the effect of MK-801 (an NMDA receptor antagonist) on L-citrulline levels during hypoxia. 3. SNP increased ventilation during both normoxia and hypoxia. L-NMMA did not alter ventilation or L-glutamate levels during normoxia but significantly attenuated the hypoxic ventilatory response and the increase in L-glutamate during hypoxia. The inhibition by L-NMMA was blocked by L-arginine. The ventilatory augmentation by exogenous L-glutamate was attenuated by L-NMMA. L-Citrulline increased during hypoxia, and this increase was inhibited by MK-801. 4. We provide the first in vivo evidence that, in the NTS, NO works as a retrograde messenger in an L-glutamate-releasing positive feedback system contributing to the augmentation of ventilation during hypoxia.

Animals↗

PubMed1995

Diverse incidences of individual oligopeptides (dipeptidic to hexapeptidic) in proteins of human, bakers' yeast, and Escherichia coli origin registered in the Swiss-Prot data base.

Oligopeptidic permutations of the 20 amino acid residues give rise to proteins of diverse functions. Our long-term goal is to produce a lexicon of oligopeptides, classifying them into at least five categories: (i) ubiquitous, (ii) function specific, (iii) group specific, (iv) species specific, and (v) nonexistent. To begin with, we report on the varying frequencies of individual oligopeptides (dipeptidic to hexapeptidic in length) found among 2862 human proteins, 1942 Saccharomyces cerevisiae proteins, and 2672 Escherichia coli proteins registered in the Swiss-Prot data base (version 29.0, released in June 1994). At all lengths (dipeptides to hexapeptides), homooligopeptides were very prominent among the most frequently occurring varieties in proteins of human and bakers' yeast origins. However, this was not the case with E. coli. While all of the expected 20(3) varieties of tripeptides were found among human proteins, three tripeptides (Cys-Cys-Trp, Trp-Trp-Cys, and Trp-Trp-His) were missing from the bakers' yeast proteins. Three tripeptides (Cys-Ile-Trp, Cys-Met-Tyr, and Cys-Trp-Trp) were also absent from E. coli proteins. Inasmuch as the Swiss-Prot data base already contained 67% of the expected total of 4000 E. coli proteins, it is virtually certain that 96,000 varieties of hexapeptides containing at least one or another of the three missing tripeptides noted above shall be nonexistent in E. coli. Furthermore, the observation of missing tripeptides in the bakers' yeast proteins suggests that nonexistent hexapeptides shall be highly phylum specific. Because of the sample size, only a small fraction of the 20(6) varieties of hexapeptides were expected to be encountered in the present survey. Indeed, only 1.2-1.5% of the possible hexapeptides were found, and the average copy number of observed hexapeptides varied between 1.06 and 1.25. Nevertheless, 33 varieties of hexapeptides occurred in 102-169 copies among human proteins. Furthermore, 15 of the 33 varieties contained such rarely used residues as Tyr, His, Cys, and Trp.

Amino Acid Sequence↗

PubMed1995

Possible function of Ah receptor nuclear translocator (Arnt) homodimer in transcriptional regulation.

Arnt (Ah receptor nuclear translocator) is a member of a transcription factor family having characteristic motifs designated bHLH (basic helix-loop-helix) and PAS and was originally found as a factor forming a complex with Ah receptor (AhR) to bind the specific xenobiotic responsive element (XRE) sequence for induction of drug-metabolizing P4501A1. We have examined interaction of Arnt with other PAS proteins--Drosophila Per, Sim, and AhR--by the coimmunoprecipitation method. Arnt formed a homodimer with itself as well as heterodimers with the others by means of the PAS and HLH domains in a cooperative way. The Arnt homodimer binds the sequence of adenovirus major late promoter (MLP) with the E box core sequence CACGTG, suggesting that the CAC half of the XRE, CACGCN(A/T), recognized by the AhR-Arnt heterodimer is a target for Arnt. Cotransfection experiments using CV-1 cells with an Arnt expression plasmid and a MLP chloramphenicol acetyltransferase (CAT) reporter plasmid revealed that Arnt markedly activated CAT expression, indicative of a newly discovered regulatory role of Arnt.

Amino Acid Sequence↗

PubMed1995

Early detection of Knudson's two-hits in preneoplastic renal cells of the Eker rat model by the laser microdissection procedure.

Hereditary renal cell carcinomas invariably develop by the age of 1 year in Eker rats. At the histological level, renal cell carcinomas develop through multiple stages from early preneoplastic lesions (e.g., phenotypically altered tubules) to adenomas. We previously reported that ionizing radiation induces additional tumors (large adenomas and carcinomas) in a linear dose-response relationship and that loss of heterozygosity (LOH) at chromosome 10, where the predisposing tuberous sclerosis (Tsc2) gene is localized, was found in the renal cell carcinomas which developed from hybrid F1 rats carrying the Eker mutation, indicating that in heterozygotes two events (one inherited, one somatic) are necessary to produce at least large adenomas and carcinomas. This study was designed to examine LOH in the earliest preneoplastic lesions, using a laser microdissection procedure. We could accurately dissect single altered renal tubules out of freeze-dried sections and clearly detected LOH in 4 of 19 altered tubules (21%). This is the first demonstration of LOH in single renal tubules. Our present results support the theory of a second, somatic mutation (second hit) as rate-limiting step of renal carcinogenesis in the Eker rat model of dominantly inherited cancer and the tumor suppressor nature of the Tsc2 gene function.

Animals↗

PubMed1995

The SMS1 gene encoding a serine-rich transmembrane protein suppresses the temperature sensitivity of the htr1 disruptant in Saccharomyces cerevisiae.

A new gene (SMS1; serine-rich multi-copy suppressor) of Saccharomyces cerevisiae was isolated by the ability to suppress the temperature sensitivity of the htr1 disruptant (Kikuchi et al. (1994) Mol. Gen. Genetics, in press) by increasing its gene dosage. The predicted gene product contains a serine-rich domain followed by a putative transmembrane region. The SMS1 gene was physically and genetically mapped in the region near cdc3 on chromosome XII R.

Amino Acid Sequence↗

PubMed1995

Correlation between expression of sialosyl-T antigen and survival in patients with gastric cancer.

Intestinal metaplasia of the gastric mucosa is an important lesion in the pathogenesis of gastric cancer. The expression of a mucin-associated antigen, sialosyl-T antigen, in the tissue of gastric cancer was investigated immunohistochemically to assess its biological role. Sialosyl-T antigen, detected by the monoclonal antibody TKH2, was present in 30 (23.6 per cent) of 127 lesions, and expressed sporadically in intestinal metaplasia. Patients negative for sialosyl-T had a significantly better 5-year survival than those who were positive (70.4 per cent versus 47.2 per cent). Grading by sialosyl-T antigen expression and the DNA ploidy pattern had a predictive value for prognosis in patients with gastric cancer. The biological role of sialosyl-T antigen is not clear but the mucin alteration reflects upon the biological behaviour of gastric cancer.

Follow-Up Studies↗

PubMed1995

Molecular genetic basis of renal carcinogenesis in the Eker rat model of tuberous sclerosis (Tsc2).

We have recently identified on rat chromosome 10q a germline mutation in the tuberous sclerosis gene (Tsc2), the gene predisposing to renal carcinoma (RC) in the Eker rat. The homozygous mutant condition is lethal at around the 13th day of fetal life. In heterozygotes, RCs invariably develop in the first year of life. Histologically, RCs develop through multiple stages from early preneoplastic lesions (i.e., phenotypically altered tubules) to adenomas. The wild-type allele mutation has been found even in the earliest preneoplastic lesions, fitting Knudson's two-hit hypothesis and supporting the hypothesis that Tsc2 is a tumor suppressor gene. In this study, homozygous deletion of the Ink4 homologue on rat chromosome 5q was observed in 14 of 24 (58%) RC-derived cell lines. This may represent involvement of a second tumor suppressor gene, contributing to tumor progression. Considering previous results of studies of homozygous deletion of the Ifn alpha gene in five of 24 cases (21%) and the Ifn beta gene in one of 24 cases (4%), the order of the genes may be Ink4-Ifn alpha-Ifn beta. Microsatellite instability was not observed in 26 Eker rat tumors.

Amino Acid Sequence↗

PubMed1995

An ovarian tumor of probable Wolffian origin with hormonal function.

In 1973, the histopathologic features of nine neoplasms with a distinctive appearance were reported under the term "female adnexal tumor of probable Wolffian origin." Although to date more than 40 cases of this disease have been reported in the literature, there have been only a few reports that the tumors might be endocrinologically active. We report on a hormonally active tumor of this type.

Estradiol↗

PubMed1995

Complete inhibition of human ovarian cancer xenografts in nude mice by suramin and cis-diamminedichloroplatinum(II).

In this study, we have determined the adjuvant effects of suramin to cis-diamminedichloroplatinum(II) (CDDP) on human ovarian cancer (KF) cell growth in vitro and in vivo. Suramin inhibited the ovarian cancer cell proliferation in vitro in a dose-dependent manner between 10 and 80 microM, showing the IC50 of 29 microM. From analysis of flow cytometry (FCM), suramin seemed to be a blocker of G2-M phase of the cell cycle. From the results of the isobologram, suramin appeared to have additive and somewhat synergistic effects on antitumor activity of CDDP. When 5 x 10(5) KF cells were inoculated sc into the right flank of nude mice, 8 of 10 mice formed solid tumor at 4 weeks. When 2 mg/kg CDDP was administered ip every week, the 80% tumor formation was prolonged to 10 weeks. Treatment with 5 and 10 mg/kg suramin decreased the formation rate of palpable tumor to 50 and 30%, respectively. When CDDP was followed by 5 or 10 mg/kg suramin, the tumor formation rate was 20 or 0%. On the other hand, if suramin was followed by CDDP, the tumor formation was not observed in any mouse during the experimental period. These results suggest that suramin may provide a new strategy for treatment of refractory ovarian carcinoma.

Animals↗

PubMed1995

Effect of leukocytes and platelets on blood flow through a parallel array of microchannels: micro- and macroflow relation and rheological measures of leukocyte and platelet activities.

The effect of leukocytes and platelets on the flow of blood through a parallel array of identical microchannels (equivalent diameter 6 microns, equivalent length 20 microns, number 2600) was examined by microscopy and total flow rate under constant suction (20 cm H2O). Fresh heparinized whole blood was used for the measurement with dilution by autologous plasma to give leukocyte counts 1200-1300/microliters or platelet counts 45,000-50,000/microliters. Despite the uniform flow conditions, cells treated with 1-10 nM FMLP or 0.1-1 microM ADP produced large temporal and spatial (channel to channel) variations in the flow by their transient blocking of the channels. The irregular flow was further accentuated by concomitant aggregation of erythrocytes. However, no fluctuations were observed in the total flow rate of blood, which decreased exponentially with time or with blood volume that had passed through the channels and approached a constant value despite a continual increase in erythrocyte aggregation. Furthermore, the flow curve pattern, i.e., an exponential approach to a steady state, appeared to be independent of both the structural details of the microchannels and the degree of blocking within the microchannels. This suggests that the total flow rate shows a statistical mechanical behavior, i.e., a relaxation process of a macrosystem composed of identical microscopic components that fluctuate independently of each other. Phenomenological parameters (rate constants of blocking and reopening of the microchannels) which can describe the observed flow curves depended on the stimulant does and also differed between different subjects, and hence appear to be useful as measures of leukocyte and platelet activities related to their rheology.

Blood Flow Velocity↗

PubMed1995

Prognostic factors associated with differentiated thyroid cancer.

A multivariate analysis was conducted on the survival data of 180 patients who underwent curative resection for differentiated thyroid cancer between 1966 and 1987, and the 10- and 20-year survival rates were found to be 80.6% and 73.1%, respectively. A survival analysis was also performed, testing the following factors: the patient's age at the time of diagnosis, tumor size, extraglandular extension, nodal status, distant metastases, operative procedure, sex, and histology. A univariate analysis found the initial six factors to be significant prognostic variables, but the latter two to be of no significance. On the other hand, the multivariate analysis showed that distant metastases, age, and tumor size were the most significant prognosticators. Thus, the age of the patient should be taken into consideration during the follow-up of treatment for differentiated thyroid cancer.

Adenocarcinoma, Follicular↗

PubMed1995

Venous invasion as a prognostic factor in colorectal cancer.

Venous invasion as a prognostic factor was evaluated in 124 patients with colorectal cancer. By classifying the patients as having either negative to mild invasion or moderate to marked invasion, a significant correlation was found between the degree of venous invasion and clinicopathological variables such as lymphatic invasion, lymph node metastasis, liver metastasis, and DNA ploidy. Significantly more favorable survival was seen in those with a lower degree of vascular invasion; however, of the six prognosticators analyzed by Cox's proportional hazard model, the only significant factors were depth of invasion and DNA ploidy. Although venous invasion showed no significance, it is still considered a valuable prognostic indicator that is easy and economical to perform.

Adenocarcinoma↗

PubMed1995

Renal carcinogenesis in the Eker rat.

The Eker rat hereditary renal carcinoma is an excellent example of a Mendelian dominant predisposition to a specific cancer in an experimental animal. We recently reported that a germline insertion in the rat homologue of the human tuberous sclerosis (TSC2) gene gives rise to the dominantly inherited cancer in the Eker rat model. The function of the TSC2/Tsc2 gene product (called "tuberine" in the human case) is not yet understood, although it contains a short amino acid sequence homologous to the ras family GTPase-activating proteins (GAP3). In the study, we isolated subtracted cDNA clones having increased expression in Eker renal carcinoma cells, using a modified representational difference analysis method to search for additional genes specifically involved in renal carcinogenesis. Here we identified four genes: the third component of the complement (C3) gene, the fos-related antigen I (fra-1) gene, an unknown gene (designated as being expressed in renal carcinoma: erc) and the calpactine I heavy-chain (Annexin II) gene.

Animals↗

PubMed1995

Effects of cisapride on gallbladder emptying and pancreatic polypeptide and cholecystokinin release in humans.

We investigated the effects of cisapride on gallbladder motility and on the release of pancreatic polypeptide and cholecystokinin in the fasting and postprandial states. Cisapride (7.5 mg) and/or a test meal was administered intraduodenally to seven healthy volunteers with or without atropine pretreatment (0.5 mg, i.m.). In the fasting state, cisapride increased gallbladder volume to 154% of the basal level, and significantly elevated plasma pancreatic polypeptide levels. The effects of cisapride were inhibited by atropine. In the postprandial state, integrated pancreatic polypeptide and cholecystokinin responses were increased by cisapride to 180% and 192%, respectively, of control values. Atropine inhibited the integrated gallbladder and pancreatic polypeptide response to about 60% of the control value, but did not affect the cholecystokinin response. These observations suggest that: (1) fasting gallbladder tone is influenced by cholinergic inhibitory mechanisms, (2) acetylcholine (ACh) is the final mediator for about 40% of the postprandial gallbladder emptying and pancreatic polypeptide response, and (3) coordination between the ACh-independent cholecystokinin response and ACh-dependent pancreatic polypeptide response may be important in the regulation of postprandial gallbladder emptying.

Adult↗

PubMed1995

Nitric oxide modulates pancreatic edema formation in rat caerulein-induced pancreatitis.

This study was designed to investigate the role of nitric oxide (NO) in the formation of pancreatic edema in caerulein-induced pancreatitis in rats. Pancreatitis was produced by two intraperitoneal injections of caerulein, and plasma amylase concentration, pancreatic edema index (pancreatic wet weight/body weight), and Evans blue extravasation (as a measure of vascular permeability) were evaluated 5 h after the first injection. Four doses (1, 2.5, 5, and 10 mg/kg) of NG-nitro-L-arginine (L-NNA), an NO synthase inhibitor, were subcutaneously administered at -0.5, 0.5, 1.5, 2.5, and 3.5 h after the first injection of caerulein. L-NNA significantly lowered the edema index, the wet/dry weight ratio of the pancreas, and Evans blue extravasation in the rats with pancreatitis. The maximal effect was obtained by L-NNA at a dose of 2.5 mg/kg; this inhibited the increase in pancreatic edema formation from the control value by 60%-70%. Intraperitoneal injections (20 mg/kg, five times) of L-arginine, a substrate for NO production, partly reversed the L-NNA-induced inhibition of pancreatic edema formation, but D-arginine, an enantiomer of L-arginine, did not show any effect. Plasma amylase concentrations were not significantly affected by any dose of L-NNA, nor were they affected by L- or D-arginine. These findings strongly suggest that endogenous NO plays an important role in the formation of pancreatic edema in caerulein-induced pancreatitis in rats, probably by increasing vascular permeability and protein extravasation.

Acute Disease↗

PubMed1995

Non-invasive monitoring of tissue response to radiotherapy by localised proton spin-lattice relaxation time in mice.

Proton spin-lattice relaxation time T1 of the localised tumour portion and its neighbouring portion of tumour-bearing mice legs is successively observed before and after radiotherapy by applying the previously proposed magnetic focusing method. Changes in T1 values are also compared with the histological radiation effects. For un-irradiated tumours, T1 increases gradually with tumour growth. T1 of the tumour portion shows significant decrease after radiotherapy. The decrease in the T1 values of the tumour clearly depends on the single radiation dose of 30, 45 and 60 Gy, respectively. A rapid decrease in the T1 values of the tumour occurs prior to the decrease in tumour volume. These decreases in the T1 values of the tumour after radiotherapy correspond positively to the increase of the histological radiation effects. After the reduction in the T1 values of the irradiated tumour portion, a successive increase in T1 values is observed and suggests local recurrence of the tumour. These results show that localised T1 relaxation time is a good reflection of the tissue response to radiotherapy.

Animals↗