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Biomedical subjects

T Hibi

Publications and source records attributed to T Hibi.

At least 37 records · Page 2Linked to original sources
PubMed1993

Use of adenosine (5')polyphospho(5')pyridoxals to study the substrate-binding region of glutathione synthetase from Escherichia coli B.

Adenosine(5')polyphospho(5')pyridoxals (APn-PLs, n = 2, 3, 4) were examined for affinity labeling of glutathione synthetase (EC 6.3.2.3) from Escherichia coli B. When the enzyme was incubated with an APn-PL or pyridoxal phosphate in the presence of Mg2+ and then reduced with sodium borohydride, it was most rapidly inactivated by AP4-PL. AP4-PL had a high affinity to the enzyme. The dissociation constant of AP4-PL in the inactivation process was 23 microM. The enzyme was almost completely protected from inactivation by addition of either ATP or gamma-glutamylcysteine. Complete inactivation corresponded to the incorporation of 1 mol of AP4-PL/mol of subunit of the tetrameric enzyme. Proteolytic digestion and sequence analysis of the AP4-PL-labeled enzyme revealed that only Lys-18 was modified. In contrast, the less efficient AP3-PL was found attached to Lys-17, Lys-18, Lys-144, and Lys-148. In the three-dimensional structure of the enzyme, Lys-18 is located close to the putative gamma-glutamylcysteine-binding site, but Lys-17, Lys-144, and Lys-148 are in the mouth of the inner-solvent region, at the bottom of which is the active-site cleft. Furthermore, difference Fourier analysis with the AP4-PL-soaked crystal of the enzyme showed that the adenosine moiety of the bound AP4-PL was in the crevice, which is the ATP-binding site of the enzyme. These results demonstrate the bivalent binding of AP4-PL lying across the gamma-glutamylcysteine- and ATP-binding sites.

Adenine Nucleotides↗
PubMed1993

Sequence variation, differential expression and chromosomal location of rice chitinase genes.

Rice chitinases are encoded by a small multigene family. To clarify the overall organization of rice chitinase genes, we have isolated and characterized the genes Cht-1, Cht-2 and Cht-3. Although all the three genes encode class I chitinase, the nucleotide sequences of the coding regions of Cht-1 and Cht-3 are very similar (90%), while that of Cht-2 is clearly more divergent (78%). Only Cht-2 has a 130 bp intron and encodes a C-terminal peptide sequence similar to that known to function as a vacuolar targeting signal. In 5' flanking regions of Cht-1 and Cht-3, but not of Cht-2, conserved sequences (GGCCGGCYGCCCYAG) were found. Related sequences were found also in the 5' flanking regions of another chitinase gene and a beta-glucanase gene which has also been reported to be stress-induced in rice. RNA blot hybridization analysis demonstrated that the stress-induced expression patterns of the Cht-1 and Cht-3 genes are similar, but quite different from that of Cht-2. However, all three genes are active in unstressed roots. By restriction fragment length polymorphism (RFLP) linkage analysis, Cht-1 and Cht-3 were mapped onto chromosome 6 and shown to be closely linked (0.8 cM). Cht-2 was mapped onto chromosome 5. All these features suggest that the expression patterns of rice class I chitinase genes may be correlated with their levels of sequence divergence and their chromosomal location.

Amino Acid Sequence↗
PubMed1993

Fatal herpes simplex hepatitis type 2 in a post-thymectomized adult.

The authors report an unusual case of herpes simplex type 2 (HSV) hepatitis which presented as part of a systemic HSV infection accompanied by disseminated intravascular coagulation (DIC). The patient was a 49-year-old Japanese male who three months prior to admission underwent surgical resection of his thymus for an invasive thymoma. Postoperatively, he received a course of chemotherapy which included prednisone, cyclophosphamide, vincristine, and pinorubicin. After discharge from the hospital, he was put on a maintenance dosage of prednisone and cyclophosphamide. Two weeks prior to this admission, the patient developed rhinorrhea, chills and general fatigue. Routine follow-up laboratory tests revealed markedly elevated liver enzymes which led to his immediate hospitalization. The tentative diagnosis on admission was fulminant hepatitis with DIC. The patient's condition steadily worsened during his hospitalization and acyclovir was initiated on the 4th hospital day due to the possibility of HSV hepatitis. He died on the same day. Histopathology performed on the liver at autopsy revealed hepatic inclusion bodies of HSV with positive immunohistochemical detection of the HSV type 2 antigen. Our case is the first report of HSV hepatitis associated with the removal of the thymus secondary to thymoma. It supports previous observations of disseminated HSV infection being prevalent in those patients with disorders of cell mediated immunity.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Analysis of genes within the HLA region affecting susceptibility to ulcerative colitis.

To clarify the molecular relationship between HLA loci and ulcerative colitis (UC) in Japanese patients, we performed HLA-DP genotyping by the PCR-RFLP method and studied tumor necrosis factor beta-chain genetic polymorphism by Southern hybridization, in addition to conventional serologic typing. Significant increase was observed in Bw52, DPw9 (DPB1*0901), and DR2 (DRB1*1502) in Japanese patients with UC. Linkage analysis indicated that A24-Bw52-DR2-DPw9 alleles constitute a common haplotype in Japanese UC patients. Among the patients not carrying Bw52, B13 was significantly increased and B44 was relatively increased. These Bw52, B13, and B44 alleles share the unique amino acids, serine and aspartic acid at positions 67 and 77, respectively. These positions are in the second hypervariable region of the alpha 1-domain of the HLA-B13, B44, Bw52, and B49 antigens (B49 is quite rare in the Japanese population). The inflammatory region in UC patients was found to vary depending on their HLA-B alleles. These results suggest that the HLA-B locus itself plays an important role in the susceptibility to Japanese UC.

Adult↗
PubMed1993

Changes of proliferative activity and phenotypes in spontaneous differentiation of a colon cancer cell line.

We examined the alterations of proliferative activity and c-myc expression of a colon cancer cell line (Caco-2) during its spontaneous differentiation. Caco-2 cells were cultured in various types of media and the degree of differentiation was monitored in terms of dome formation in cell monolayers and expression of alkaline phosphatase (ALP) activity. In Caco-2 cells cultured with Eagle's minimum essential medium (EMEM) containing 10% fetal calf serum (FCS), dome formation was demonstrated and ALP activity was markedly increased after the cells reached confluence. Five-fold reduction of c-myc mRNA and a marked decrease in S-phase cells were observed in the differentiated cells. These changes were not induced in FCS-free EMEM. The addition of insulin and transferrin to FCS-free EMEM did not induce cell differentiation or reduction of c-myc mRNA expression. When Caco-2 cells were cultured with three different serum-free media, the induction of dome formation and the increase of ALP activity were observed to varying degrees. Expression of c-myc mRNA in the cells cultured with one serum-free medium decreased to a level similar to that in fully differentiated cells cultured with EMEM containing 10% FCS. These results suggest that a spontaneous switch from a proliferative state with high c-myc expression to differentiated phenotype occurs after cells reach confluence and depends on the culture conditions.

Cell Differentiation↗
PubMed1993

Interleukin 2 and interferon-gamma augment anticolon antibody dependent cellular cytotoxicity in ulcerative colitis.

In vitro effects of cytokines and therapeutic drugs on antibody dependent cellular cytotoxicity (ADCC) mediated by anticolon antibody were investigated in serum samples from patients with ulcerative colitis. A 51Cr release assay was used to examine ADCC activity with the colon cancer cell line, colo 205, as the target and peripheral blood mononuclear cells as the effector. High ADCC activity was shown in 13 of 32 (41%) patients with ulcerative colitis. This ADCC activity was inhibited by protein A treatment of the serum samples. Interleukin 2 (IL2) activated effector cells could enhance ADCC activity, but interferon-gamma (IFN-gamma) or tumour necrosis factor-alpha (TNF-alpha) had no effect on the cytotoxic activity of effector cells. Treatment of target cells with IFN-gamma increased the vulnerability of these cells to ADCC with a large increase of intercellular adhesion molecule-1 (ICAM-1) expression on their surface. Monoclonal antibodies to ICAM-1 inhibited this IFN-gamma enhanced ADCC activity. Interestingly, prednisolone (PSL) reduced ADCC activity, but sulphasalazine (SASP) or 5-aminosalicylic acid (5-ASA) did not. These results suggest that IL2 and IFN-gamma could enhance colonic epithelial cell injury mediated by the ADCC mechanism in ulcerative colitis and that ADCC enhanced by cytokines is restored by PSL treatment.

Adolescent↗
PubMed1993

Revaluation of endoscopic laser therapy for treatment of early cancer in the stomach.

The efficacy and safety of the endoscopic laser therapy for eradication of early cancer in the stomach was revaluated in fourty-eight patients. In 37 of the 42 patients (88%) treated with the laser therapy alone, the procedure was effective and the complete eradication was confirmed at the end of the follow-up period. In seven of fourteen patients with the incomplete treatment, residual cancer cells were successfully removed by repeated laser therapy. The endoscopic mucosal resection was effective in 21 of the 30 patients (70%) with the early gastric cancer. Interestingly, six of the eleven cases with incomplete treatment with the endoscopic mucosal resection underwent the laser therapy and the complete eradication was achieved in all patients. Although the endoscopic mucosal resection is now the main method for the endoscopic treatment of the early gastric cancer, these data favor offering the endoscopic laser therapy as the combined method with the mucosal resection therapy.

Adult↗
PubMed1992

Tissue-type plasminogen activator of colonic mucosa in ulcerative colitis. Evidence of endothelium-derived fibrinolytic activation.

Microvascular endothelial alterations are thought to be a crucial step for development of hemorrhagic changes in various pathological states. In this study, we determined the activity and amount of tissue-type plasminogen activator (t-PA) in the biopsy specimens from sigmoid colon of patients with ulcerative colitis to evaluate endothelial alterations and vascular changes of permeability. The results of this investigation revealed that mucosal amount of t-PA in the active stage of ulcerative colitis was two- to threefold higher than in healthy controls, while t-PA levels in plasma samples showed no remarkable differences among the groups. Increased t-PA activity appeared to correlate well to the degree of inflammation of colonic mucosa, and t-PA amount was still increased in the inactive stage. The present study indicates that t-PA determination in colonic biopsy specimens may be useful for the evaluation of clinical activity of ulcerative colitis in terms of the mucosal microvascular endothelial changes.

Adult↗
PubMed1992

Electrotransfection of protoplasts from tomato, wild tomato, barley and chrysanthemum with tobacco mosaic virus RNA.

Protoplasts isolated from tomato, wild tomato, barley and chrysanthemum were electrotransfected with tobacco mosaic virus (TMV) RNA under almost the same optimum electric conditions: five square DC pulses of 50 microseconds duration at 500 to 800 V/cm, with the protoplasts suspended at 2 x 10(5)/ml in 0.5 M-mannitol containing 100 microM-MgCl2 and 10 to 20 micrograms/ml TMV RNA. ELISAs of these transfected protoplasts showed that the yields and the growth curves of the virus were quite similar, indicating a lack of host specificity in the initially infected cells of these plants.

Chrysanthemum cinerariifolium↗
PubMed1992

Radiotherapy for pediatric brain stem glioma: radiation dose, response, and survival.

An analysis of 39 patients under 20 years of age with brain stem glioma treated with radiotherapy between 1977 and 1991 was undertaken. Twenty-eight (71.2%) of the patients responded well to initial radiotherapy, and 11 (28.8%) responded poorly. Median survival for the total patient population was 10 months. Response rates and median survivals were influenced by radiation dose: 45.5% and 9 months at doses less than 4499 cGy (n = 11), 83.3% and 13 months at doses between 4500 and 5499 cGy (n = 12), 66.7% and 11.5 months at doses between 5500 and 6499 cGy (n = 9), and 100% and 10 months at doses more than 6500 cGy (n = 7). Multivariate analysis revealed the response to initial radiotherapy was the only predictor of survival with radiation doses up to 6499 cGy. Four of the patients who responded well demonstrated radiological and/or histological calcification within or around the tumor at the time of clinical deterioration. Radiation injury was confirmed in two autopsy cases. The possibility that intratumoral radiation injury causes clinical deterioration is suggested.

Adolescent↗
PubMed1992

The mechanism of action of serum immunosuppressive factor in Crohn's disease: it blocks the growth of mitogen-stimulated lymphocytes in early G1 phase through an inhibition of transferrin receptor expression.

The presence of serum immunosuppressive factor has recently been reported in patients with Crohn's disease. We investigated the mechanism of action of this immunosuppressive factor in vitro. The factor in serum fraction from patients with Crohn's disease had an inhibitory activity on the proliferation of phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMCs) from healthy volunteers. The growth of tumor cell lines, however, was not inhibited by the factor. While the factor did not influence the production of interleukin 2 (IL2) or the expression of IL2 receptor of PHA-stimulated PBMCs, it inhibited the expression of transferrin receptor. The effect of the factor on cell cycle of PHA-stimulated PBMCs was examined by flow cytometry analysis. The factor kept the cells in quiescent G0/G1 phase and decreased the number of cells in S phase. Prostaglandin E2, an immunosuppressive substance, may not participate in the inhibitory action of the factor, since indomethacin did not affect the inhibitory activity of the factor. These results suggest that the immunosuppressive factor in serum from patients with Crohn's disease is unique in the mechanism of inhibitory action and further clarification of this factor might contribute to the development of a new diagnostic assay for Crohn's disease and the elucidation of the pathogenesis of this disease.

Cell Cycle↗
PubMed1992

[Inhibition of neovascularization and tumor growth by dexamethasone].

It has been proposed that angiogenesis inhibitors should be used for the treatment of diseases accompanied by an uncontrolled angiogenic response, particularly such disease occurring during progressive growth of solid tumors. In this study, the antiangiogenic effect of dexamethasone (DEX) was studied in a system using chorioallantoic membranes (CAM) of fertilized eggs and rabbit corneas. First, DEX was examined for its effect on embryonic angiogenesis using 4, 5 day old CAMs of chick embryos. After the shell and shell membrane was removed, an EV pellet with or without DEX was placed within a silicon ring. Two days later, the antiangiogenic response was evaluated by measuring the avascular zone of the CAM beneath the pellet. When the CAM showed an avascular zone of 3 mm or more in diameter, the response was scored as positive. DEX showed potent antiangiogenic activity and produced an avascular zone in 100% of CAMs at the highest dose tested. (250 ng/egg). Next, inhibitory effect of vascularization and tumor growth by local implant of DEX was observed in a rabbit cornea assay. An intra-corneal pocket extending to within 1 mm of the limbus was used to house a 1-mm3 piece of glioma. In the treatment group, DEX-containing EV pellet was inserted between the limbus and glioma. Ten days after the implantation of glioma and EV pellet, vascular response and tumor growth was evaluated. For morphologic studies, the excised corneas were fixed with formaldehyde fixative and sectioned for light microscopy.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[Effect of serum factors on the differentiation of a colon cancer cell line Caco-2].

A human colon cancer cell line Caco-2 undergoes spontaneous enterocytic differentiation under the standard culture condition. We examined the changes in the proliferative activity of Caco-2 cells during the differentiation, and the effect of serum factors on this spontaneous differentiation. Caco-2 cells cultured in FCS-containing media exhibited the differentiation phenotypes such as dome formation and increase of ALP activity after the 6th day of culture. Cell cycle analysis showed a marked decrease in S phase cell population during the cell differentiation. When Caco-2 cells were cultured in FCS free media, the cell population of S phase remained unchanged during culture period and the differentiation phenotypes were not induced. The addition of FCS to Caco-2 cell cultured in the absence of FCS resulted in the rapid induction of the differentiation phenotypes. These results suggest that differentiation of Caco-2 cells is closely related to the reduction of cell proliferation and requires some factors in FCS.

Animals↗