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Biomedical subjects

H Ikeda

Publications and source records attributed to H Ikeda.

At least 595 records · Page 33Linked to original sources
PubMed1995

Impairment of adenylyl cyclase signal transduction in mecobalamin-deficient rats.

This study examined alterations in the beta-adrenoceptor-G5-adenylyl cyclase system in cerebral cortex membranes from vitamin B12-deficient rats fed a diet lacking vitamin B12 (mecobalamin) for 15 weeks. Basal, 5(7)-guanylylimidodiphosphate (GppNHp)-, isoproterenol-, and forskolin-stimulated adenylyl cyclase activities were significantly reduced in mecobalamin-deficient rats compared with those in control rats. However, no significant differences were observed in the amount and function of G5- estimated by immunoblotting and guanine nucleotide photoaffinity labeling, respectively, or in the densities and the dissociation constants of beta-adrenoceptors, estimated by [125I] pindolol binding, between control and the deficient rats. These results indicate that vitamin B12 deficiency results in the impairment of the coupling among the beta-adrenoceptor, G5- and the catalytic subunit of adenylyl cyclase, and in dysfunction of the catalytic subunit of the enzyme, suggesting that vitamin B12 participates in the regulation of neuronal adenylyl cyclase signal transduction.

Adenylyl Cyclase Inhibitors↗
PubMed1995

A hotspot of spontaneous and UV-induced illegitimate recombination during formation of lambda bio transducing phage.

To study the mechanism of spontaneous and UV-induced illegitimate recombination, we examined the formation of the lambda bio specialized transducing phage in Escherichia coli. Because most lambda bio transducing phages have double defects in the red and gam genes and have the capacity to form a plaque on an E. coli P2 lysogen (Spi- phenotype), we selected lambda bio transducing phage by their Spi- phenotype, rather than using the bio marker. We determined sequences of recombination junctions of lambda bio transducing phages isolated with or without UV irradiation and deduced sequences of parental recombination sites. The recombination sites were widely distributed on E. coli bio and lambda DNAs, except for a hotspot which accounts for 57% of UV-induced lambda bio transducing phages and 77% of spontaneously induced lambda bio transducing phages. The hotspot sites on E. coli and lambda DNAs shared a short homology of 9 bp. In addition, we detected direct repeat sequences of 8 bp within and near both the bio and lambda hotspots. A recA mutation did not affect the frequency of the recombination at the hotspot, indicating that this recombination is not a variant of recA-dependent homologous recombination. We discuss a model in which the short homology as well as the direct repeats play essential roles in illegitimate recombination at the hotspot.

Bacteriophage lambda↗
PubMed1995

Increased soluble form of P-selectin in patients with unstable angina.

BACKGROUND: P-selectin in platelets and endothelial cells mediates adhesive interaction with leukocytes to form thrombi. The purpose of the present study was to investigate the plasma levels of P-selectin in patients with unstable angina and in those with stable effort angina of different pathophysiologies. METHODS AND RESULTS: Plasma P-selectin levels were determined by a monoclonal antibody-based enzyme immunoassay on plasma samples taken from 12 patients with unstable angina, 11 patients with stable effort angina, and 15 healthy volunteers. Patients with unstable angina had angina at rest associated with ECG changes. In patients with unstable angina, plasma P-selectin levels within 1 hour (361 +/- 90 ng/mL) and at 3 hours (282 +/- 56 ng/mL) after angina were significantly (P < .05) higher than those in volunteers (177 +/- 31 ng/mL). Plasma P-selectin levels at 5 hours after attack (242 +/- 46 ng/mL) did not differ from those in volunteers. Although patients with stable effort angina developed angina with ST-segment depressions by treadmill exercise, their plasma P-selectin levels did not change (before, 178 +/- 45; immediately after, 186 +/- 36; and 1 hour after the exercise, 179 +/- 34 ng/mL). CONCLUSIONS: Plasma P-selectin levels after angina increased significantly in patients with unstable angina but did not in patients with stable effort angina. These findings may contribute to understanding of the pathophysiology of the acute coronary syndrome of unstable angina.

Aged↗
PubMed1995

Cell-free transmission of Fv-4 resistance gene product controlling Friend leukemia virus-induced leukemogenesis: a unique mechanism for interference with viral infection.

Fv-4 is a mouse gene that dominantly confers resistance to infection by ecotropic murine leukemia virus (MuLV). We previously demonstrated that mixed radiation bone marrow chimeras containing Fv-4r-bearing BALB/c-Fv-4Wr (C4W) bone marrow and Fv-4r-bearing C3H/He (C3H) bone marrow grafted into C3H recipient mice (C4W+C3H-->C3H) were resistant to Friend leukemia virus (FLV)-induced leukemogenesis, even when they contained as high as 70% C3H-derived cells. This indicates that FLV-sensitive C3H-derived cells are rendered refractory to infection and/or transformation with FLV when they coexist in mice with Fv-4r-bearing cells. To investigate the mechanism of Fv-4 resistance to FLV-induced leukemogenesis, we first examined the expression of Fv-4r env antigen in the peripheral blood mononuclear cells (PBMC) of these chimeras. The Fv-4r env antigen was present not only on C4W-derived cells, but also on Fv-4r-bearing C3H-derived cells in C4W+C3H-->C3H mixed bone marrow chimeras. The Fv-4r env antigen that binds to the cells surface of C3H cells was found in sera from normal C4W mice, C4W-->C3H chimeras, and C4W+C3H-->C3H mixed chimeras. The serum Fv-4r env antigen binds to ecotropic MuLV receptors, shown by specific binding to transfectant mink cells expressing ecotropic MuLV receptor, but not to parental mink cells. To determine whether the binding of Fv-4r env antigen to the putative MuLV receptors would block FLV infection, C3H thymocytes or spleen cells that had been preincubated with C4W serum were mixed with FLV and the subsequent production of MuLV specific antigens was examined. C3H thymocytes or spleen cells treated with C4W serum became refractory to binding by FLV. These results provide evidence that the Fv-4r env antigen is released from C4W-derived cells in vivo and binds to cells expressing surface receptors for ecotropic MuLV, thereby protecting them from infection with FLV. The implication of these findings for gene therapy of retrovirus-induced disease such as acquired immune deficiency syndrome (AIDS) is discussed.

Animals↗
PubMed1995

Growth response of acute myeloblastic leukemia cells to recombinant human thrombopoietin.

Thrombopoietin (TPO) is a newly identified hematopoietic growth factor that stimulates both megakaryopoiesis and thrombopoiesis through its interaction with a specific cell surface receptor encoded by the c-mpl proto-oncogene. In an effort to investigate the effect of TPO on human myeloid leukemia cells, the expression of c-mpl and the proliferative response to recombinant human (rh) TPO were investigated in a series of patients with acute myeloblastic leukemia (AML). Of 50 cases of AML, the c-mpl mRNA was detectable by means of Northern blot analysis in 26 cases, and the in vitro treatment with rhTPO led to proliferation of AML cells in 22 cases. The c-mpl expression and proliferative response to rhTPO was observed in all subtypes of AML and did not correlate with French-American-British classification, whereas all cases of M7-type AML cells expressed c-mpl and proliferated in response to rhTPO. Furthermore, rhTPO-induced proliferation of AML cells was augmented with the addition of interleukin-3 (IL-3), IL-6, stem cell factor, or granulocyte-macrophage colony-stimulating factor. These results suggested that c-mpl may be functional in terms of supporting proliferation of various types of AML cells and that TPO may contribute, at least in part, to abnormal growth of the cells, especially in combination with other hematopoietic growth factors.

Acute Disease↗
PubMed1995

Cytokine-producing mammary carcinomas in transgenic rats carrying the pX gene of human T-lymphotropic virus type I.

In two lines of transgenic rats (pX rats) from WKAH and F344 strains and carrying the human T-lymphotropic virus type I pX gene, undifferentiated mammary carcinomas developed predominantly in females starting at about 5 months of age, and there was massive infiltration of granulocytes in the tumor tissue. The incidence of the tumor reached about 40% when the rats were 12 months old. mRNAs of both pX and host genes Gro and MIP-2, which are granulocyte chemoattractants of the interleukin 8 family, were highly expressed in the tumor tissue. Since expression and point mutation of several oncogenes and the antioncogene were not demonstrated, hitherto unidentified novel oncogenic pathways may be transactivated by the pX transgene in these pX rats.

Animals↗
PubMed1995

Platelet-activating factor mediates the ozone-induced increase in airway microvascular leakage in guinea pigs.

In the present study, we asked whether platelet-activating factor (PAF) mediates the ozone-induced increase in airway microvascular leakage. To answer this question, we examined the effect of a PAF receptor antagonist on the ozone-induced increase in airway microvascular leakage quantified by the extravasation of Evans blue dye in the guinea pig trachea and main bronchi. Guinea pigs were pretreated with the PAF receptor antagonist, E6123 ((S)-(+)-6-(2-chlorophenyl)-3-cyclopropane-carbonyl-8,11-dimethyl-2,3,4, 5- tetrahydro-8H-pyrido[4',3':4,5]thieno[3,2- f][1,2,4]triazolo[4,3-a][1,4]diazepine) (0.01, 0.1 and 1.0 mg/kg i.v.) and then exposed to 3 ppm ozone for 30 min. The PAF receptor antagonist significantly reduced the ozone-induced increase in microvascular leakage in a dose-dependent manner in both the trachea and main bronchi. Our results indicate that PAF mediates the ozone-induced increase in airway microvascular leakage. We therefore suggest that PAF may be involved in ozone-induced airway inflammation.

Animals↗
PubMed1995

Enhancement of Escherichia coli H(+)-ATPase caused by binding of monoclonal antibodies is attributed to structural changes of Leu-456 and Ser-440 in the alpha subunit.

Five monoclonal antibodies against the alpha subunit of F1-ATPase from Escherichia coli alpha 104, alpha 105, alpha 107, alpha 109, and alpha 110 were prepared. The monoclonal antibodies alpha 104 and alpha 110 enhanced the F1-ATPase activity maximally to 1.6- and 1.7-fold that of the wild-type, respectively, while alpha 105 did not. Both antibodies bound to a peptide corresponding to the region between residues 354 and 513. Mutations in this region which caused reduced binding of the alpha subunit to the antibodies were identified at residues Ser-440, Leu-456, Leu-471, Leu-482, Met-483, and Ser-506 for alpha 104 and residues Ser-440, Leu-456, Leu-471, Asp-476, Leu-482, Met-483, and Ser-506 for alpha 110. These residues are possibly involved in the epitopes for the antibodies and are located close together on the surface of the alpha subunit. Among the mutations, Leu-456 to Pro and Ser-440 to Pro mutations caused increase of the F1-ATPase activity up to 1.9 and 1.2 times that of the wild-type, respectively, while Leu-471 to Pro mutation caused a defect in assembly of the F1-ATPase on the membrane. The other mutations caused no significant change in ATPase activity. These results suggested that Ser-440 and Leu-456 have an important role in regulating catalysis by the F1-ATPase, but that the neighboring residue Leu-471 has an important role in assembly of the F1-ATPase complex. It was also suggested that binding of the monoclonal antibodies alpha 104 and alpha 110 to residues Ser-440 and Leu-456 caused local conformational changes, leading to enhancing effects on F1-ATPase activity similar to the Ser-440 to Pro and Leu-456 to Pro mutations.

Animals↗
PubMed1995

Polyunsaturated fatty acid regulation of lipogenic enzyme gene expression in liver of genetically obese rat.

The polyunsaturated fatty acid regulation of lipogenic enzyme gene expression in genetically obese rats (Wistar fatty, non-insulin-dependent diabetes mellitus) has been investigated. The hepatic mRNA concentrations and activities of lipogenic enzymes in the fatty and lean rat were greatly increased by feeding a hydrogenated fat diet to fasted rats, and also reached similar maximum levels with similar time courses. By feeding a corn oil diet, however, the increases were markedly reduced in the lean rats, but were not significantly reduced in the fatty rats. Consequently, when the animals were fed corn oil, the mRNA concentrations and activities in the fatty rats were higher than those in the lean. Thus, it appeared that the higher gene expression in the fatty rats can be ascribed to the defects of polyunsaturated fatty acid suppression. On the other hand, insulin binding to receptors in the liver was reduced by the corn oil diet in the lean rats but was not reduced in the fatty rats (although the insulin binding level was lower in the Wistar fatty rats than in the lean). Changes in the insulin receptor autophosphorylation and kinase activity toward exogenous substrate were similar to the insulin binding. It is suggested that the polyunsaturated fatty acids may not suppress insulin binding activity to receptors in the livers of the fatty rats, probably due to down regulation by hyperinsulinemia. The defects of polyunsaturated fatty acid suppression of lipogenic enzyme gene expression may be one of the factors of obesity.

Animals↗
PubMed1995

High dose rate brachytherapy for carcinoma of the uterine cervix: comparison of two different fractionation regimens.

PURPOSE: There is no consensus as to the best dose-fractionation regimen in high dose rate (HDR) brachytherapy for cervix cancer. Since 1983, two fractionation regimens have been used in different time periods at National Cancer Center Hospital, and their treatment results have been compared in terms of 5-year survival, local control, and complication rate to find the better therapeutic regimen. METHODS AND MATERIALS: From November 1983 to October 1990, 130 patients with uterine cervix carcinoma were treated with HDR intracavitary brachytherapy using a remote afterloading system. There were 21 Stage Ib patients, 5 Stage IIa, 29 Stage IIb, 2 Stage IIIa, 68 Stage IIIb, and 5 Stage IVa. The median age was 64 years. The median follow-up time was 50 months. Radiotherapy consisted of external beam irradiation to the pelvis (mean dose of 50 Gy), combined with HDR brachytherapy (mean dose of 20 Gy to point A) given 5 Gy per session twice weekly (group A: 54 patients) or 6 Gy once weekly (group B: 76 patients). RESULTS: The overall 5-year survival was 52% in group A and 72% in group B. Local recurrence rate was 11%, and distant failure rate was 21%, with no difference between the two groups. The complication rate was significantly lower in group B (37%) than in group A (55%). Multivariate analysis has shown that factors affecting survival were stage, brachytherapy dose, and local control status. No factor was predictive of local control, but the external beam radiation dose significantly influenced the risk of complications. CONCLUSION: The once-weekly HDR intracavitary applications combined with properly adjusted external beam pelvic irradiation is a safe and effective treatment for patients with uterine cervix cancer.

Adenocarcinoma↗
PubMed1995

Characterization of cDNA encoding mouse homolog of fission yeast dhp1+ gene: structural and functional conservation.

The dhp1+ gene of Schizosaccharomyces pombe is a homolog of Saccharomyces cerevisiae HKE1/RAT1/TAP1 gene that is involved in RNA metabolism such as RNA trafficking and RNA synthesis. dhp1+ is also related to S. cerevisiae DST2 (SEP1) that encodes a DNA strand exchange protein required for sporulation and homologous recombination in S.cerevisiae. We isolated several clones of Dhm1, a mouse homolog of dhp1+, from mouse spermatocyte cDNA library and determined its nucleotide sequence. The Dhm1 gene consists of an open reading frame predicting a protein with 947 amino acids and molecular weight of 107,955. Northern blot analysis revealed that Dhm1 is transcribed at high level in testis, liver and kidney. The predicted product of Dhm1 (Dhm1p) has a significant homology with Dhp1p, Hke1p/Rat1p/Tap1p and Dst2p. In particular, Dhm1p, Dhp1p and Hke1p/Rat1p/Tap1p share strong similarity at the two regions of their N- and C-terminal parts. The Dhm1 gene on a multicopy plasmid rescued the temperature-sensitivity of dhp1ts and lethality of dhp1 null mutation, suggesting that Dhm1 is a mouse homolog of S.pombe dhp1+ and functions similarly in mouse as dhp1+.

Amino Acid Sequence↗
PubMed1995

Constitutively activating mutations of c-kit receptor tyrosine kinase confer factor-independent growth and tumorigenicity of factor-dependent hematopoietic cell lines.

The c-kit receptor tyrosine kinase (KIT) is activated upon ligand binding, thereby leading to a variety of signaling events that play a fundamental role in hematopoiesis. In addition to ligand-dependent activation, we have previously shown that KIT is constitutively activated in a ligand-independent manner by two point mutations, Val-559-->Gly (G559) mutation in the juxtamembrane domain and Asp-814-->Val (V814) mutation in the phosphotransferase domain. To investigate the biochemical consequence and biologic significance of these mutations, retroviral vectors encoding KITG559 or KITV814 were introduced into murine pro-B-type Ba/F3 cells and myeloid FDC-P1 cells, both of which require interleukin-3 (IL-3) for their growth and survival. In the cells, KITG559 or KITV814 were found to be constitutively phophorylated on tyrosine in the absence of stem cell factor (SCF) that is a ligand for KIT. Chemical cross-linking analysis showed that a substantial fraction of the phosphorylated KITG559 underwent dimerization even in the absence of SCF, whereas the phosphorylated KITV814 did not, suggesting the distinct mechanisms underlying constitutive activation of KIT by G559 and V814 mutations. Furthermore, the cells expressing either KITG559 or KITV814 were found to show a factor-independent growth, whereas the cells expressing wild-type KIT (KITWT) proliferated in response to SCF as well as IL-3. Moreover, subcutaneous injection of Ba/F3 cells expressing KITG559 or KITV814 into nude mice resulted in production of large tumors at all sites of the injection within 2 weeks, and all nude mice quickly succumbed to leukemia and died. These results suggest that, although the mechanisms underlying constitutive activation of KITG559 or KITV814 may be different, both of the activating mutations have a function to induce a factor-independent and tumorigenic phenotype. Also, the data of this study raise the possibility that the constitutively activating mutations of c-kit may play a causal role in development of hematologic malignancies.

Amino Acid Sequence↗
PubMed1995

Differences in the antigens recognized by cytolytic T cells on two successive metastases of a melanoma patient are consistent with immune selection.

We have studied the patterns of antigens recognized by autologous cytolytic T lymphocytes (CTL) on two melanoma cell lines derived from metastases that were removed from patient LB33 at several years distance. Cell line LB33-MEL.A was obtained after surgery in 1988. A large number of CTL clones directed against LB33-MEL.A was obtained with blood lymphocytes collected from the patient in 1990. In vitro selection of melanoma cells that were resistant to these CTL clones indicated that at least five different antigens were recognized on LB33-MEL.A by autologous CTL. Four of these antigens were found to be presented by HLA-A28, B13, B44 and Cw6, respectively. The patient remained disease-free until 1993 when a metastasis was detected and was used to obtain cell line LB33-MEL.B. This cell line proved resistant to lysis by all the CTL clones directed against the LB33-MEL.A cells and showed no expression of HLA class I molecules except for HLA-A24. Using LB33-MEL.B cells to stimulate blood lymphocytes collected from the patient in 1994 we derived CTL clones that lysed these cells. All these CTL clones recognized a new antigen presented by HLA-A24. These results suggest that in patient LB33 the melanoma cells may have lost the expression of several HLA molecules under the selective pressure of an anti-tumor CTL response.

Adult↗
PubMed1995

AO-128, alpha-glucosidase inhibitor: antiobesity and antidiabetic actions in genetically obese-diabetic rats, Wistar fatty.

Antiobesity and antidiabetic actions of the alpha-glucosidase inhibitor AO-128 were examined using genetically obese-diabetic rats, Wistar fatty. Ten-week-old, male fatty rats were kept on CE-2 diet containing 10 or 25 ppm of AO-128 for 4 weeks. The average drug intake was calculated to be 0.74 or 1.78 mg/kg/day from the average food intake, respectively. The intestinal maltase and sucrase activities were decreased by AO-128 in a dose-related fashion. Food intake of fatty rats treated with AO-128 was decreased throughout the experiment. This decrease in food intake could hardly be explained only by diarrhea which occurred for the first 5 days of the administration of AO-128. AO-128 normalized hyperglycemia and markedly reduced hypertriglyceridemia and hyperinsulinemia in fatty rats. In addition, AO-128 decreased body weight gain, food efficiency, epididymal adipose tissue weight, carcass weight, and body fat deposition. These findings indicate that AO-128 may be useful for treating human obesity and diabetes.

Animals↗
PubMed1995

A rat model of HTLV-I infection: development of chronic progressive myeloneuropathy in seropositive WKAH rats and related apoptosis.

In seropositive HTLV-I carrier rats of the WKAH strain inoculated with 2 x 10(7) MT-2 cells at 3-6 months of age, chronic progressive myeloneuropathy, tentatively designated as HTLV-I-associated myelopathy (HAM) rat disease, occurred when the rats were 19-23 months old. Clinical and pathological findings were basically identical to those of seronegative HAM rats of the same strain neonatally inoculated with MT-2 cells. It appears that a high dose of MT-2 cells (10(8) cells) is more effective for the induction and acceleration of HAM rat disease. Seronegative and seropositive carriers of other strains (F344, ACI, and LEW), WKAH rats inoculated with HUT-78 (a human T cell line without HTLV-I infection), and untreated WKAH rats at comparable ages did not develop HAM rat disease, thereby indicating that development of this disease is caused by HTLV-I infection and is under strict genetic restriction of the host strain. Chronological examination of HAM rat disease induced by 10(7) MT-2 inoculation into newborn rats showed that the spinal cord lesion began to develop by 12 months of age. T cells were absent in the affected spinal cord throughout the disease process. There was morphological evidence of apoptotic death of oligodendrocytes in the affected spinal cord. Apoptosis was also confirmed by the specific nick end labeling of the nuclear fragmentation in situ, and the apoptotic oligodendrocytes confined to the demyelinating foci, and the number of apoptotic cells positively correlated with severity of the spinal cord lesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Brain tissue identification based on myosin heavy chain isoforms.

Non-muscle tissues contain 3 myosin heavy chain (MHC) isoforms; MIIA, MIIB1 and MIIB2. MIIA is a non-muscle type isoform distributed in all non-muscle tissues and smooth-muscle, while MIIB1 and MIIB2 are brain-type isoforms distributed mainly in neuronal tissues. The ratio of MIIA and MIIB (A/B ratio) differs between tissues, suggesting that this ratio may be a useful marker for tissue identification. To apply the A/B ratio for tissue identification in forensic practice, we developed a highly sensitive ELISA for quantification of each MHC isoform. At least 100 pg of both MHC isoforms could be detected by the present method. Analysis of the A/B ratio of the cerebrum, cerebellum, liver, kidney, spleen and andrenal gland by the present method indicated that the A/B ratio of the brain tissue (< 0.5) was quite different from other tissues (> 3.0). The A/B ratio could be determined from at least 8 micrograms of fresh tissue sample and 0.1 mg of dried tissue sample stored for 1 month at room temperature. Therefore, the A/B ratio seems to be an excellent marker for identification of the brain tissue.

Adrenal Glands↗
PubMed1995

Hyperresponse in calcium-induced insulin release from electrically permeabilized pancreatic islets of diabetics GK rats and its defective augmentation by glucose.

In spontaneously diabetic GK rats, insulin secretion from pancreatic beta cells in response to glucose is selectively impaired, probably due to deficient intracellular metabolism of glucose and impaired closure of KATP channels during glucose stimulation. By using electrically permeabilized islets of GK rats, we explored the functional modulations in exocytotic steps distal to the rise in [Ca2+]i in the diabetic condition. At 30 nmol/l Ca2+ (basal conditions) insulin release was similar between GK and non-diabetic control Wistar rats. In response to 3.0 mumol/l Ca2+ (maximum stimulatory conditions), insulin release was significantly augmented in permeabilized GK islets (p < 0.01). Raising glucose concentrations from 2.8 to 16.7 mmol/l further augmented insulin release induced by 3.0 mumol/l Ca2+ from permeabilized control islets (p < 0.001), but had no effect on that from permeabilized GK islets. The stimulatory effect of glucose on insulin release from permeabilized control islets was partly inhibited by 2,4-dinitrophenol, an inhibitor of mitochondrial oxidative phosphorylation (p < 0.01). The hyperresponse to Ca2+ in GK islets may play a physiologically compensatory role on the putative functional impairment both in [Ca2+]i rise and energy state in response to glucose in diabetic beta cells, and may explain the relative preservation of insulin release induced by non-glucose depolarizing stimuli, such as arginine, from pancreatic islets in non-insulin-dependent diabetes mellitus.

2,4-Dinitrophenol↗