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Biomedical subjects

Y Miyagi

Publications and source records attributed to Y Miyagi.

At least 127 records · Page 7Linked to original sources
PubMed1995

Resting load regulates vascular sensitivity by a cytosolic Ca(2+)-insensitive mechanism.

The cellular mechanism underlying the regulation of the contraction of vascular smooth muscles by resting load is unknown. To determine the effects of changes in the resting load on vascular sensitivity to high K+ and to 9,11-dideoxy-11 alpha, 9 alpha-epoxy-methanoprostaglandin F2 alpha (U-46619), the force and cytosolic calcium concentration ([Ca2+]i) of arterial strips were recorded at resting loads of 200 (optimal load), 50, and 10 mg. A decrease in the resting load elicited a small decrease in the basal [Ca2+]i level without affecting the extent of maximal [Ca2+]i elevation induced by either stimulus. Through a decrease in the resting load, the concentration-response curves for the force development of high K+ or of U-46619 shifted to the right, whereas those for [Ca2+]i did not. We conclude that the basal [Ca2+]i level and the force development, but not the agonist-induced [Ca2+]i signals, of vascular smooth muscles depend on the resting load. We response that the resting load regulates the sensitivity of vascular smooth muscles, irrespective of types of stimuli, through a [Ca2+]i-insensitive mechanism.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1995

s-Myc acts as a transcriptional activator and its sequence-specific DNA binding is required for induction of programmed cell death in glioma cells.

We previously reported that s-Myc expression effectively induces programmed cell death (PCD) by apoptosis in glioma cells that express only mutated p53. To determine the molecular mechanism of s-Myc-induced PCD, we examined the correlation between transcriptional activation of s-Myc and its ability to induce PCD. Using a reporter plasmid having an upstream promoter region containing four repeats of the hexanucleotide CACGTG, we found that s-Myc can activate transcription of a reporter gene from this plasmid. Two mutated forms of s-Myc protein, s-MycCKII and s-MycmBR, were created. While s-MycCKII whose casein kinase (CK) II cognate sequence was restored in the internal acidic domain activated transcription as efficiently as wild-type s-Myc and induced PCD in glioma cells, s-MycmBR having a mutated basic region unable to bind the CACGTG motif did not. These findings suggest that transactivation activity of s-Myc through sequence-specific DNA binding may be indispensable for induction of PCD but that lack of a CK-II cognate sequence in the internal acidic domain may have little effect on these functions of s-Myc.

Journal Article↗
PubMed1995

Abundant expression of translation initiation factor EIF-4E in post-meiotic germ cells of the rat testis.

BACKGROUND: Eukaryotic translation initiation factor EIF-4E is a key component in the regulation of translational efficiency of MRNAs and its increased expression may accelerate cell growth and division. EIF-4E has the potential to transform rat embryo fibroblast cells by cooperation with v-Myc or adenovirus E1A. Our previous study showed that a variety of tumor cells examined exhibited elevated levels of eIF-4E gene expression. Thus it is thought that overexpression of EIF-4E can result in aberrant growth and cell transformation. EXPERIMENTAL DESIGN: To characterize rat EIF-4E, a clone containing rat eIF-4E cDNA was isolated from a rat testis cDNA library by screening with a synthetic probe prepared by the reverse transcription-polymerase chain reaction (RT-PCR) method. Based on the conserved nucleotide sequences between mouse and human eIF-4E cDNA, two oligonucleotide primers for RT-PCR were synthesized chemically. The cloned cDNA was sequenced and used as a probe for analysis of the expression level of eIF-4E mRNA in normal, differentiated rat tissues by Northern blot analysis. In situ hybridization analysis with digoxigenin-labeled antisense eIF-4E RNA as a probe was carried out to identify the eIF-4E-expressing sites in rat tissues. In addition, to analyse the phosphorylation level of EIF-4E, the proteins were fractionated from rat tissues by affinity column chromatography followed by isoelectric focusing (IEF)-gel electrophoresis. RESULTS: The nucleotide sequence of the eIF-4E cDNA is highly conserved in human, rat, and mouse. Extraordinarily elevated expression, more than 50-fold compared with that in the adult rat prostate, of eIF-4E was observed in testicular germ cells of rats of reproductive age, which was much greater than that in any tumor cell lines examined so far. The amount of EIF-4E fractionated from the adult rat testis was approximately 10 times higher than that from the adult rat liver. At least half of the purified testicular EIF-4E proteins were phosphorylated, a ratio similar to that in other rat tissues such as liver. In situ hybridization analysis demonstrated that elevated expression of eIF-4E mRNA was mainly observed in post-meiotic germ cells. CONCLUSIONS: Full activity of EIF-4E in translation requires the phosphorylation of the protein on a specific serine residue. Thus the elevated level of EIF-4E observed in the adult rat testis should be reflected in increase of the functional activity of EIF-4E. Based on the results of in situ hybridization analysis and characterization of EIF-4E, it was concluded that abundant EIF-4E in the testis may play an important role in spermatogenesis through translational regulation of stage-specific mRNAs during germ cell development.

Amino Acid Sequence↗
PubMed1994

Negative effects of wild-type p53 and s-Myc on cellular growth and tumorigenicity of glioma cells. Implication of the tumor suppressor genes for gene therapy.

Human (U251, U87, U343) and rat glioma cell lines (C6, 9L) were examined by the reverse transcriptase-polymerase chain reaction and subsequent nucleotide sequencing analysis to see whether they express wild type (wt)-p53 or mutated form (mut)-p53 messages. Results showed that U87, U343, and C6 cells expressed wt-p53 messages whereas U251 and 9L cells expressed mut-p53 messages. All these cell lines were transfected with wt-p53 cDNA or the s-myc gene linked to the mouse mammary tumor virus (MMTV) promoter. Of several G418-resistant clones obtained from each transfection, a few expressed the s-Myc or wt-p53 proteins. Independent of mutations in the intrinsic p53 gene, the cellular growth in vitro and tumorigenicity in nude mice of these clones were drastically suppressed, the extent of suppression being correlated with the expression level of the transfected gene. Flow-cytometric analysis demonstrated that both p53 and s-Myc arrested the cell cycle at the G1/S boundary. These data suggest that these genes having negative effects on tumor cell proliferation could be used in gene therapy of gliomas, which are caused by alteration of the p53 gene or by some other genetic change.

Animals↗
PubMed1994

Beneficial effects of smoking cessation on the short-term prognosis for variant angina--validation of the smoking status by urinary cotinine measurements.

To examine whether smoking cessation would improve the short-term prognosis for patients with variant angina, 37 smokers with variant angina who were discharged after the complete disappearance of angina by medical treatment with calcium blockers were advised to stop smoking and were followed-up for 1 year. Urinary cotinine radioimmunoassay was used to evaluate their current smoking status. Patients with a urinary cotinine concentration above 50 ng/ml were classified as current smokers. The prevalence of smokers was underestimated by self-reports (11% by self-reports vs. 35% by urinary cotinine measurements after 3 months; 17% by self-reports vs. 36% by urinary cotinine measurements after 1 year). The presence of angina during the first 3 months was significantly (P < 0.05) more prevalent in those who continued to smoke (8/13, 62%) than in those who succeeded in smoking cessation (5/24, 21%) when the current smoking status was determined by urinary cotinine measurements. Smoking cessation definitely improved the prognosis for variant angina even during a relatively short follow-up period.

Angina Pectoris, Variant↗
PubMed1994

Establishment and characterization of a malignant melanoma cell line (YP-MEL) derived from a patient with neurocutaneous melanosis.

A cell line, YP-MEL, was established from an intracranial malignant melanoma occurring in a neurocutaneous melanosis (NCMsis) patient. The established cell line was successfully cultured in serum-free medium with a doubling time of 41 h. The cells were refractile and small in size, with occasional pigmented giant cells. Histochemical and immunohistochemical features were compatible with common malignant melanoma and its cell line. Chromosome analysis revealed many supernumerary chromosomes and marker chromosomes including double minutes (DMs). When transplanted into nude mice, YP-MEL formed tumors histologically consistent with the original tumor. Addition of sera to the medium caused cellular spreading and elongation of cytoplasmic processes with an increase of melanin contents and tyrosinase activity. Because there was no melanoma cell line derived from a NCMsis patient, YP-MEL might be a beneficial tool for study on NCMsis.

Biopsy↗
PubMed1994

Establishment of three rat soft tissue tumor cell lines with different degrees of myogenic differentiation.

Soft tissue malignancies often show divergent differentiation, including myogenic lineage. Five rat tumors induced with 20-hydroxymethylcholanthrene (20-OH-MCA), were cultured in vitro, and three cell lines (YMC-1, YMC-2, YMC-3) were established from them. YMC-2 and -3 cells were spindle-shaped, and YMS-1 cells round and epithelioid. In confluency, YMC-3 cells formed myotubes. The nude mouse xenotransplants showed morphological features consistent with their myogenic phenotypes. Muscle-specific enzyme activities were highest in YMC-3 cells. These lines may be useful in the investigation of the myogenic differentiation of undifferentiated mesenchymal cells.

Animals↗
PubMed1994

cDNA cloning and mRNA expression of a serine proteinase inhibitor secreted by cancer cells: identification as placental protein 5 and tissue factor pathway inhibitor-2.

A serine proteinase inhibitor was purified from conditioned medium of the human glioblastoma cell line T98G. Analysis of its partial amino acid sequences indicated that this protein was identical to placental protein 5 (PP5), a placenta-derived glycoprotein with serine proteinase inhibitor activity, the amino acid sequence of which had been partially determined. cDNA cloning of PP5 demonstrated that it belonged to the Kunitz-type serine proteinase inhibitor family, having three putative Kunitz-type inhibitor domains, and that it was identical to a recently reported inhibitor, tissue factor pathway inhibitor-2 (TFPI-2) [Sprecher et al. (1994) Proc. Natl. Acad. Sci. USA 91, 3353-3357]. PP5/TFPI-2 transcripts were highly abundant in the full-term placenta and widely expressed in various adult human tissues, such as the liver, skeletal muscle, heart, kidney, and pancreas. Several ovarian carcinoma cells as well as T98G also contained significant amounts of the transcripts.

Amino Acid Sequence↗
PubMed1994

Chromophobe renal cell carcinoma: a report of two cases.

Chromophobe renal cell carcinoma (RCC) is a recently established subtype of RCC, which has rarely been reported in Japan. In this communication, the authors report two Japanese cases of chromophobe RCC together with the immunohistochemical findings. The tumors were composed of sheets and cribriform glands formed by tumor cells with cloudy and reticular cytoplasm. Ultrastructurally, the cytoplasm was filled with numerous microvesicles. The tumor cells were positive for cytokeratin, epithelial membrane antigen, and Tamm-Horsfall protein. Occasionally, LeuM1-positive cells were also noted. Vimentin was negative, unlike the usual RCC. Reactivity for peanut agglutinin was more frequent than that to Lotus tetragonolobus agglutinin. The results of this study suggest that the tumor cells possessed phenotypes similar to the distal nephron rather than to the proximal tubular cells.

Adult↗
PubMed1994

Modulation of tumor immunogenicity of rat glioma cells by s-Myc expression: eradication of rat gliomas in vivo.

The Myc family proteins represented by c-Myc are thought to play a crucial role in cellular proliferation, differentiation, transformation, and apoptosis. In this study, we demonstrated the novel role for a Myc family protein in elicitation of immunogenic phenotypes in tumor cells. Injection of rat 9L or C6 glioma cells, together with the s-myc gene linked to the cytomegalovirus promoter, completely prevented formation of both brain tumors and s.c. tumors derived from the parental glioma cells. However, introduction of the s-myc gene had no inhibitory effect on development of B104-derived neuroblastoma. In addition, unlike the s-myc gene, injection of the c-myc or wild type p53 (wt-p53) gene together with glioma cells did not modulate the tumor immunogenicity and resulted in formation of gliomas in the animals. These findings suggest that s-Myc expression may stimulate the presentation of a tumor antigen common to 9L and C6 cells to T lymphocytes and augment the activity of the host immune system, resulting in prevention of glioma formation in vivo. This success in tumor eradication indicates the possibility of application of the s-myc gene for gene therapy of human brain tumors.

Animals↗
PubMed1994

The s-Myc protein having the ability to induce apoptosis is selectively expressed in rat embryo chondrocytes.

Gene transfection experiments demonstrated that over-expression of the s-myc gene under the control of a human metallothionein promoter induced apoptosis in cells such as rat and human glioma cells. In contrast to c-Myc-mediated apoptosis requiring withdrawal of serum growth factors, s-myc expression induced apoptosis in glioma cells in the presence of 10% fetal calf serum. Whereas, s-Myc-mediated apoptosis was suppressed in proportion to the increase of bcl-2 expression as seen in c-Myc mediated apoptosis. The s-myc gene was expressed in rat embryo cells being committed to differentiate to hypertrophic chondrocytes which undergo programmed cell death. CAT assay demonstrated that in the NH2-terminal region, the s-Myc protein contains a domain structure required for expression of transactivation activity that is approximately six times higher than that of c-Myc. Therefore, these findings strongly suggest that s-Myc may play an important role in transcription regulation of a set of genes whose expression induces programmed cell death in vitro and in vivo.

3T3 Cells↗
PubMed1993

Structural analysis of an extremely long 5'-noncoding region of rat brain argininosuccinate lyase mRNA: presence of multiple B1 repeats and multiple upstream AUG codons, and a possibility of translational control.

The present detailed analysis of the sequence of the extremely long (967 bp) 5'-noncoding region of a rat brain argininosuccinate lyase cDNA clone, reveals several features of interest. Multiple copies of partial and inverted (antisense) B1 repeats and multiple upstream ATG codons are present in the region, which suggests a possibility of translational control of the argininosuccinate lyase gene expression in rat brain.

Amino Acid Sequence↗
PubMed1993

Transient terminal U wave inversion as a more specific marker for myocardial ischemia.

Transient U wave inversion can be caused either by regional myocardial ischemia or by an elevation of systemic blood pressure. The characteristics of U wave inversion during chest pain attacks in 21 patients with variant angina were compared with those observed in 38 patients with hypertension without apparent ischemic heart disease. Differentiation was possible according to the ECG phase in which U wave inversion appeared. U wave inversion was considered to be significant if there was a discrete negative deflection of more than 0.05 mV within the TP segment. U wave inversion proceeded to positive deflection of U wave in patients with hypertension without ischemic heart disease (initial U wave inversion). In contrast, inverted U wave occurred after positive U wave deflection during attacks in patients with variant angina (terminal U wave inversion). When cold pressor test was performed in patients with variant angina during treatment with calcium entry blockers, no patient had either anginal attacks or ischemic ST-segment deviation, but 9 of 21 patients (43%) had transient initial U wave inversion, which was followed by positive U wave deflection. U wave inversion can be classified as initial U wave inversion and terminal U wave inversion according to the phasic relationship to positive U wave deflection; the latter is observed in association with regional myocardial ischemia. The former seems to be related to elevated blood pressure rather than to myocardial ischemia.

Adult↗
PubMed1993

Intraventricular cavernous malformation associated with medullary venous malformation.

We reported a case of cavernous malformation (CM) associated with medullary venous malformation in the same area. The CM was located in the trigone of the lateral ventricle in the dominant hemisphere and drained into the longitudinal caudate vein of Schlesinger via deep medullary veins. By a transsylvian transventricular approach, the CM was totally removed with successful preservation of the medullary venous malformation. This approach is available for trigonal lesions, especially in cases with enlarged inferior horn. We stress that CM removal can be conducted with preservation of the adjacent medullary venous malformation.

Cerebral Veins↗
PubMed1993

Striatal glucose metabolism and [18F]fluorodopa uptake in a patient with tumor-induced hemiparkinsonism.

We studied a patient with a falx meningioma in the right supplementary motor area and a left-sided hemiparkinsonism that resolved after the tumor was removed. Because there was no evidence of distortion of the basal ganglia and midbrain by the tumor on neuroradiological examination, the possible mechanism of parkinsonism is an impairment of the basal ganglia output to the supplementary motor area. Positron emission tomography scans with 2-[18F]fluoro-2-doxy-D-glucose and 6-L-[18F]fluorodopa were performed to measure regional cerebral glucose metabolism and striatal dopamine metabolism, respectively. Regional cerebral glucose metabolism was decreased in the striatum of the side of the lesion, although dopamine metabolism was normal. These data suggest that the tumor may have impaired synaptic function of the striatum as a whole, giving rise to contralateral hemiparkinsonism without an impairment of the presynaptic dopaminergic nerve terminals in the striatum.

Blood Glucose↗
PubMed1993

Augmentation of smoking cessation education by urinary cotinine measurement.

Monitoring the current smoking status by an objective method may augment the effects of smoking cessation instruction. To quantitatively evaluate smoking status and its modification by smoking cessation instruction, urinary cotinine, a major metabolite of nicotine, was measured by radioimmunoassay in 64 patients with a smoking habit before and during smoking cessation instruction. Urinary cotinine levels were used to discriminate between smokers and nonsmokers (with 50 ng/ml used as a threshold). In 49 patients who claimed to have stopped smoking, urinary cotinine concentrations 1 month after instruction indicated that only 30 (61%) of them had actually stopped (before: 243 +/- 104, after: 1 +/- 3 ng/ml) (mean +/- standard deviation). In the remaining 15 patients who failed to stop smoking while reporting a reduction of cigarette consumption (before: 27 +/- 12, after: 7 +/- 5/day), there was no appreciable reduction in urinary cotinine levels (before: 298 +/- 140, after: 229 +/- 171 ng/ml). When the patients who had failed to stop smoking again received intensive smoking cessation instruction, the success rate increased from 47% (30/64) to 69% (44/64) (p < 0.05). Thus, urinary cotinine measurement may provide a useful and quantitative method for monitoring actual smoking habits and thus augment the efficacy of smoking cessation educational programs.

Cotinine↗