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Biomedical subjects

Y Chiba

Publications and source records attributed to Y Chiba.

At least 91 records · Page 5Linked to original sources
PubMed1999

Polio surveillance in Lao PDR: a two-year experience of active case search, 1994-96.

The underdeveloped health infrastructure and limited epidemiological data on polio are major obstacles to the establishment of the acute flaccid paralysis (AFP) surveillance system in Lao People's Democratic Republic (Lao PDR). We initiated a nationwide active case search for case investigations at the community level in March 1994 to support the development of the AFP surveillance system. We identified 164 polio cases that occurred between 1979 and 1993 in 511 villages, indicating that wild poliovirus had circulated extensively during that period. Of these, only 59 (36 per cent) had visited health facilities, and polio was diagnosed in 15 (9 per cent). As national immunization days (NIDs) progressed, the number of polio cases decreased to an undetectable level after 1994. The active case search was useful for educating the local staff about AFP and the components of a surveillance system, and as an adjunct to national AFP surveillance programme in the country as it approaches the goal of polio eradication.

Age Distribution↗
PubMed1999

timrit Lengthens circadian period in a temperature-dependent manner through suppression of PERIOD protein cycling and nuclear localization.

A fundamental feature of circadian clocks is temperature compensation of period. The free-running period of ritsu (timrit) (a novel allele of timeless [tim]) mutants is drastically lengthened in a temperature-dependent manner. PER and TIM protein levels become lower in timrit mutants as temperature becomes higher. This mutation reduces per mRNA but not tim mRNA abundance. PER constitutively driven by the rhodopsin1 promoter is lowered in rit mutants, indicating that timrit mainly affects the per feedback loop at a posttranscriptional level. An excess of per+ gene dosage can ameliorate all rit phenotypes, including the weak nuclear localization of PER, suggesting that timrit affects circadian rhythms by reducing PER abundance and its subsequent transportation into nuclei as temperature increases.

Animals↗
PubMed1999

[Probable involvement of the augmented agonist-induced Ca2+ sensitization of airway smooth muscle contraction in the pathogenesis of airway hyperresponsiveness].

Nonspecific airway hyperresponsiveness (AHR) is a common feature of allergic bronchial asthmatics, but the underlying mechanism (s) of AHR have yet to be elucidated. The importance of AHR in the pathogenesis of asthma has been suggested by its relevance to the severity of this disease. There is thus a need to understand the underlying mechanisms of AHR for the sake of asthma therapy. In the present minireview, we discussed the involvement of the augmented agonist-induced Ca2+ sensitization of airway smooth muscle contraction in the pathogenesis of AHR. Treatment with acetylcholine (ACh) of a beta-escin-permeabilized intrapulmonary bronchial smooth muscle of the rat induced a stronger contractile force even when the Ca2+ concentration was clamped at 1 microM. The ACh-induced Ca2+ sensitization of myofilaments was found to be significantly greater in antigen-induced airway hyperresponsive rats than in control rats. The ACh-induced Ca2+ sensitization was completely blocked by treatment with Clostridium botulinum C3 exoenzyme, an inactivator of the Rho family proteins. Moreover, the protein level of RhoA in the intrapulmonary bronchi was demonstrated to be significantly increased in the airway hyperresponsive rats. Thus, the increased airway smooth muscle contractility observed in asthmatics may be related to the augmented agonist-induced, Rho-mediated Ca2+ sensitization of myofilaments.

Acetylcholine↗
PubMed1999

Bone marrow aplasia with prominent atypical plasmacytic proliferation preceding acute lymphoblastic leukemia.

A two-year-old boy presented with pancytopenia. Bone marrow examination revealed an aplastic marrow with prominent immature plasma cell proliferation, which mimicked plasma cell leukemia. Immunohistochemistry, however, revealed a polyclonal population consistent with a reactive process, excluding plasma cell neoplasia. Administration of granulocyte-colony stimulating factor resulted in recovery of normal hematopoiesis with resolution of plasmacytosis. Seven months later, the patient had an elevated white blood cell count and bone marrow findings diagnostic of acute lymphoblastic leukemia. To the best of our knowledge this is the first reported case of bone marrow aplasia with prominent polyclonal plasmacytosis presenting as a prodrome of acute lymphoblastic leukemia in childhood.

Anemia, Aplastic↗
PubMed1999

Enhanced Ca2+ sensitization of the bronchial smooth muscle contraction in antigen-induced airway hyperresponsive rats.

To investigate the alteration in acetylcholine (ACh)-induced increase in Ca2+ sensitization of bronchial smooth muscle contraction concurrent with the airway hyperresponsiveness (AHR), the ACh-induced increases in cytosolic Ca2+ ([Ca2+]) level and contractile response were simultaneously determined by using Fura-2 loaded bronchial smooth muscle. The left main bronchi were isolated from AHR rats which were sensitized and repeatedly challenged with DNP-Ascaris antigen. The tissue ring preparations were incubated in loading solution containing 10 microM Fura-2AM for 3 hr at room temperature. Then the isometrical contraction and [Ca2+]i (F340/F380) were monitored. Although the ACh (10(-3) M)-induced contractile response in AHR group (322 +/- 60 % of 60 mM K+ induced contraction) was significantly greater than that in control animals (173 +/- 15 %, p<0.05), the ACh (10(-3) M)-induced increase in [Ca2+]i was without significant difference between the two groups (128 +/- 15 and 171 +/- 29% of 60 mM K+ -induced increase in [Ca2+]i, respectively). These findings suggest that an augmentation of ACh-induced Ca2+ sensitization may occur in bronchial smooth muscle of the rats with antigen-induced AHR.

Acetylcholine↗
PubMed1999

Changes of angiogenesis and tumor cell apoptosis during colorectal carcinogenesis.

Activation of the angiogenic process occurs during tumorigenesis, as does disturbance of cell proliferation and apoptosis. Seeking a potential correlation, we investigated tumor cell apoptosis, proliferation, and angiogenesis in the adenoma-carcinoma sequence of colorectal carcinogenesis using an in situ apoptosis detection kit and MIB-1 and anti-CD34 antibodies in 27 adenomas with low dysplasia, 17 adenomas with high dysplasia, and 26 carcinomas in adenoma, as well as assessed p53 and bcl-2 expressions. The results showed that the potential for apoptosis was augmented, paralleling the increment of proliferation, in adenomas with low dysplasia but diminished when adenomas progressed from low dysplasia to high dysplasia and cancer. A gradual increment of microvessel density was observed during the progression with an increase during transition from low dysplasia to high dysplasia and cancer. Correlation coefficient test showed an inverse correlation between apoptotic index and microvessel density when all of the lesions were taken into account. No apparent impact of aberrant p53 on angiogenesis or bcl-2 on apoptosis was observed in this study. These results suggest that the angiogenesis initiates during transition from low dysplasia to high dysplasia and cancer, which may, in turn, contribute to the reduction of tumor cell apoptosis during colorectal carcinogenesis.

Adenocarcinoma↗
PubMed1998

Production of human compatible high mannose-type (Man5GlcNAc2) sugar chains in Saccharomyces cerevisiae.

A yeast mutant capable of producing Man5GlcNAc2 human compatible sugar chains on glycoproteins was constructed. An expression vector for alpha-1,2-mannosidase with the "HDEL" endoplasmic reticulum retention/retrieval tag was designed and expressed in Saccharomyces cerevisiae. An in vitro alpha-1,2-mannosidase assay and Western blot analysis showed that it was successfully localized in the endoplasmic reticulum. A triple mutant yeast lacking three glycosyltransferase activities was then transformed with an alpha-1, 2-mannosidase expression vector. The oligosaccharide structures of carboxypeptidase Y as well as cell surface glycoproteins were analyzed, and the recombinant yeast was shown to produce a series of high mannose-type sugar chains including Man5GlcNAc2. This is the first report of a recombinant S. cerevisiae able to produce Man5GlcNAc2-oligosaccharides, the intermediate for hybrid-type and complex-type sugar chains.

Amino Acid Sequence↗
PubMed1998

Platelet-derived endothelial cell growth factor/thymidine phosphorylase expression correlated with tumor angiogenesis and macrophage infiltration in colorectal cancer.

To clarify whether platelet-derived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/TP) expression in both tumor cells and stromal cells has independent or synergistic effects on tumor angiogenesis and progression and to explore a possible regulator for PD-ECGF/TP expression, immunohistochemical staining was conducted on 148 specimens of colorectal cancer. The microvessel count was significantly correlated with the extent of PD-ECGF/TP expression. Macrophage infiltration in tumors with positive TP was significantly higher than in tumors with negative TP (P < 0.001). The Cox model showed that PD-ECGF/TP expression was an independent prognostic factor, although the microvessel count had a stronger value in determining the patient prognosis.

Adenocarcinoma↗
PubMed1998

In vivo observations of the intramural arterioles and venules in beating canine hearts.

1. To evaluate the effects of cardiac contraction on intramyocardial (midwall) microvessels, we measured the phasic diameter change of left ventricular intramural arterioles and venules using a novel needle-probe videomicroscope with a CCD camera and compared it with the diameter change in subepicardial and subendocardial vessels. 2. The phasic diameter of the intramural arterioles decreased from 130 +/- 79 ìm in end-diastole to 118 +/- 72 micron (mean +/- S.D.) in end-systole by cardiac contraction (10 +/- 6 %, P < 0.001, n = 21). 3. The phasic diameter in the intramural venules was almost unchanged from end-diastole to end-systole (85 +/- 44 vs. 86 +/- 42 micron, respectively, 2 +/- 6 %, n. s., n = 14). 4. Compared with intramural vessels, the diameters of subendocardial arterioles and venules decreased by a similar extent (arterioles: 10 +/- 8 %, P < 0. 001; venules: 12 +/- 10 %, P < 0.001) from end-diastole to end-systole, respectively, whereas the diameter of the subepicardial arterioles changed little during the cardiac cycle, and subepicardial venule diameter increased by 9 +/- 8 % (P < 0.01) from end-diastole to end-systole. These findings are consistent with our previous report. 5. We suggest that the almost uniform distribution of the cardiac contractility effect and arteriolar transmural pressure between the subendocardium and the midmyocardium, which together constitute the systolic vascular compressive force, accounts for the similarity in the arteriolar diameter changes in both myocardial layers. The smaller intravascular pressure drop from deep to superficial myocardium relative to the larger intramyocardial pressure drop explains the difference in the phasic venular diameter changes across the myocardium.

Animals↗
PubMed1998

Alternatively spliced forms of cyclin D1 modulate entry into the cell cycle in an inverse manner.

Alternative splicing of cyclin D1 gene mRNA has recently been demonstrated. The novel transcript shows no splicing at the downstream exon 4 boundary and encodes a protein with an altered carboxyl-terminal domain that is a cyclin D1 variant; exon 5 is not included in the coding sequence which terminates downstream of exon 4. We here produced cells that exogenously express each form of cyclin D1 and analysed their cell cycle regulation. We found that (1) alternative splicing forms of cyclin D1 modulated entry into the cell cycle in an inverse manner; (2) both splicing forms suppressed cell growth; and (3) cells overexpressing form [a] were inhibited from entry into and completion of the S phase, although form [b]-expressing cells showed no reduction of G1- to S transition. We also found that overexpression of either cyclin D1 form upregulated Rb gene products, suggesting that this upregulation may be one of the causes of growth suppression in cyclin D1 overexpressing cells.

Alternative Splicing↗
PubMed1998

Relationship between flushing pressure and nitric oxide production in preserved lungs.

BACKGROUND: Nitric oxide (NO) is considered to be one of the endogenous inhibitory factors of ischemic reperfusion injury. In this study, the NO-producing ability of the preserved lung, flushed at various pulmonary artery pressures (flushing pressure), was studied during reperfusion using an ex vivo rabbit lung perfusion model. METHODS: The lungs were flushed with 200 ml of preservation solution with flushing pressures adjusted to 15, 15, 20, and 25 mmHg for groups 1, 2, 3, and 4, respectively (n=5 in each group). In the control group (group 1), the heart-lung block was harvested after flushing and the lungs were assessed without preservation. In the other groups, the harvested blocks were preserved at 8 degrees C for 24 hr and reperfused with homologous blood for pulmonary functional assessment. Pulmonary function was assessed by measuring mean airway pressure, mean pulmonary arterial pressure, partial oxygen tension of pulmonary venous effluent blood, and pulmonary wet-dry weight ratio. The sequential changes in the concentration of NO-related substances (NO-RS) in the serum of reperfused blood were also measured by chemiluminescence. RESULTS: During reperfusion, biphasic increases in NO-RS were observed in all groups. In groups 3 and 4, the increases in NO-RS were significantly lower than those of groups 1 and 2, and pulmonary function deteriorated. CONCLUSION: These data suggest that in order to maintain the endogenous NO-producing ability of preserved lung, the flushing pressure must be less than 20 mmHg.

Animals↗
PubMed1998

Upregulation of NMDA receptor subunit proteins in the cerebral cortex during diazepam withdrawal.

The present study investigated the changes in NMDA receptor subunit proteins in diazepam-withdrawn rat cerebral cortex, using Western blotting analysis. The protein levels of the NR1 and NR2B, but not NR2A, subunits were significantly increased in diazepam-withdrawn rats compared to those in control rats. Therefore, an increase in the NR1 and NR2B subunit proteins may be responsible for both the previously observed upregulation of [3H]dizocilpine binding in the cerebral cortex and the appearance of diazepam withdrawal signs.

Animals↗
PubMed1998

Selective antitumor activity of MKT-077, a delocalized lipophilic cation, on normal cells and cancer cells in vitro.

BACKGROUND AND OBJECTIVES: 1-Ethyl-2-¿[3-ethyl-5-(3-methylbenzothiazolin-2-yliden)]-4-+ ++oxothiazolidin-2-ylidenemethyl¿pyridium chloride (MKT-077, formerly known as FJ776), a delocalized lipophilic cation, is known to accumulate in the mitochondria, according to the negative potential inside the mitochondria, and exert its cytotoxicity. METHODS: The single-cell suspensions of human cancer cell lines, human spleen cells, and fresh cancer specimens obtained from patients with gastric carcinoma were used for the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl-2H tetrazolium bromide (MTT) assay. RESULTS: The antitumor activity of MKT-077 was dose and concentration related, and 50% inhibitory concentrations (IC50) ranged from 1.7 to 14.3 microg/ml, with a mean +/- standard deviation (SD) of 8.4 +/- 4.6 microg/ml. The IC50 of fresh surgical spleen-cell specimens ranged from 0.34 microg/ml to >100 microg/ml in a 48 h incubation, with a mean +/- SD of 66.5 +/- 37.7 microg/ml. When the antitumor activity of MKT-077 was compared between gastric cancer cells and spleen cells obtained from the same patient, the concentration-dependent antitumor activity of this agent was obvious in the cancer cells, while no significant cytotoxicity was observed in the spleen cells. The fresh surgical specimens of gastric cancer showed higher sensitivity to MKT-077 than did spleen cells at a concentration of 30 microg/ml, with a statistically significant difference at P < 0.05. CONCLUSIONS: The selective antitumor activity of MKT-077 was confirmed using fresh surgical specimens and warrants further investigation.

Antineoplastic Agents↗