Search PubMed⌕ Search

Biomedical subjects

M Koyama

Publications and source records attributed to M Koyama.

At least 91 records · Page 5Linked to original sources
PubMed1998

Effect of site directed mutagenesis in the CMGCC region of the alpha-subunit on immunoreactive human thyrotropin.

The cDNA of the common alpha-subunit of human glycoprotein hormone was mutated by site directed mutagenesis in the CMGCC region composed of cysteine-methionine-glycine-cysteine-cysteine (position 28-32). The cDNA of wild-type human thyrotropin (hTSH) beta-subunit and that of wild-type or mutant common alpha-subunits were co-transfected into COS-I cells. The concentration of hTSH determined by two immunoradiometric assay systems was detectable in culture media of COS-I cells transfected with wild-type (CMGCC) and a mutant (CRGCC) alpha-subunits but not four other mutants (YMGCC) (CMRCC) (CMACC) (CMDCC). The present data with the other studies on wild-type or mutant glycoprotein hormones support our hypothesis that an amino acid motif of "C-X-G-X-C" in the common alpha-(CMGCC in human) and beta-(CAGYC in human) subunits play an important role in biosynthesis of glycoprotein hormones in all species.

Amino Acid Substitution↗
PubMed1998

Mean regional cerebral blood flow images of normal subjects using technetium-99m-HMPAO by automated image registration.

UNLABELLED: The purpose of this study was twofold: to calculate relative uptake values for 99mTc-HMPAO in various regions of the normal brain after alignment and registration to a standard shape and size, and to validate the automated image registration (AIR) program for SPECT-to-SPECT transformation. METHODS: Thirty subjects took part in this study. Technetium-99m-HMPAO brain SPECT and x-ray-CT scans were acquired. SPECT images were normalized to an average activity of 100 counts/pixel. Intersubject accuracy was evaluated on brain images of 17 normal subjects (mean age = 64.9 +/- 8.7 yr). These images were aligned and registered to a standard size and shape with the help of AIR. Realigned images were overlaid on reference images to determine the overlap areas. Intrasubject accuracy was evaluated by realigning 20 degree rotated brain images with an index calculated as: overlap area/(overlap area + nonoverlap area). Anatomical variability between realigned target and reference images was evaluated by measurements on corresponding x-ray-CT scans, realigned using transformations that were established by the SPECT images. Realigned brain SPECT images of 30 normal subjects (mean age = 50.7 +/- 18.7 yr), including those subjects examined in the accuracy validation study, were used to generate mean and s.d. images. Images based on the mean value of each voxel (n = 30) were compared with other mean images prepared by the human brain atlas (HBA) standardization technique on a voxel-by-voxel basis to generate T maps. RESULTS: Accuracy indices were 0.98 +/- 0.006 and 0.99 +/- 0.002 for the intersubject and intrasubject evaluations, respectively. The maximum anatomical variability was 4.7 mm after realignment. Paired Student's t-test comparisons of mean HBA and AIR images revealed statistically significant differences for the deep white matter, pons and occipito-temporal regions. These differences could be explained by variation in the population being studied and the protocol for data handling by AIR and HBA. CONCLUSION: AIR aligns and registers brain SPECT images with acceptable accuracy, without the necessity of MRI or x-ray-CT scans.

Brain↗
PubMed1998

[Endoscopic pointing device for virtual bronchoscopy].

Virtual bronchoscopy is useful for understanding the morphology of tracheobronchial space. Because it is difficult to operate the system, we developed a new pointing device simulating the grip of a flexible bronchofiberscope. With this device, it was possible to simulate the handling of a bronchofiberscope (in or out, clockwise or counterclockwise rotation, arbitrary angle of view). We conclude this type of pointing device could prove to be a useful tool in endoscopic simulation.

Bronchoscopy↗
PubMed1997

Parallel-up structure evidences the molecular directionality during biosynthesis of bacterial cellulose.

The "parallel-up" packing in cellulose Ialpha and Ibeta unit cells was experimentally demonstrated by a combination of direct-staining the reducing ends of cellulose chains and microdiffraction-tilting electron crystallographic analysis. Microdiffraction investigation of nascent bacterial cellulose microfibrils showed that the reducing end of the growing cellulose chains points away from the bacterium, and this provides direct evidence that polymerization by the cellulose synthase takes place at the nonreducing end of the growing cellulose chains. This mechanism is likely to be valid also for a number of processive glycosyltransferases such as chitin synthases, hyaluronan synthases, and proteins involved in the synthesis of nodulation factor backbones.

Bacteria↗
PubMed1997

Chymase is activated in the hamster heart following ventricular fibrosis during the chronic stage of hypertension.

Chronic pressure overload induces cardiac tissue remodeling. Chymase is known to regulate matrix metabolism and angiotensin II formation. In the present study, we investigated the pathophysiological functions of chymase in the pressure-overloaded hamster heart induced by a two-kidney, one-clip (2K1C) hypertension procedure. Fibrosis and apoptosis were observed in the pressure-overloaded hearts of 2K1C hamsters 32 weeks after clipping, but these histological changes were not detected at 16 weeks. Heart chymase-like activity of 2K1C hamsters at 32 weeks increased 5.2-fold compared with that at 16 weeks, while angiotensin-converting enzyme was not activated. Chymase might be involved in cardiac tissue remodeling during the chronic stage of hypertension.

Animals↗
PubMed1997

Biparental alleles of HLA-G are co-dominantly expressed in the placenta.

HLA-G is the only major histocompatibility complex molecule expressed in the human placenta and thus has been considered to be necessary for maintenance of pregnancy. We investigated whether HLA-G expression is regulated in a parent-of-origin allele-specific manner. Of six first trimester and three third trimester placentas, three first trimester and two third trimester placentas showed heterozygosity at the PstI polymorphic site in the 3'-untraslated region. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed biallelic expression of HLA-G in all the informative cases, indicating that HLA-G is not imprinted during the gestational period, at least at the transcriptional level. As HLA-G has been postulated to be polymorphic not only at the DNA sequence level but also at the peptide level, co-dominant expression of the gene suggests that each parental allele is involved in the allogenic response during pregnancy.

Alleles↗
PubMed1997

A method for the quantification of benzodiazepine receptors by using 123I-iomazenil and SPECT with one scan and one blood sampling.

Iodine-123-iomazenil (Iomazenil) is a ligand of central type benzodiazepine receptors for single photon emission computed tomography (SPECT). Previously we reported a simple, table look-up method for quantification of its binding potential (BP) by using two SPECT scans and calibrated standard input function with one blood sampling. This method is based on a two-compartment model (K1: influx rate constant; k2: efflux rate constant; Vd (= K1/k2): the total distribution volume corresponding BP), and requires two SPECT scans for calculating both K1 and Vd values. If the K1 value in the two-compartment model can be assumed to be constant, the radioactivity of one SPECT scan at 180 min after injection can be considered to tabulate as a function of Vd for a given K1 value and a given input function, and a table look-up procedure provides the corresponding Vd value. The purpose of this study was to develop a simple, autoradiographic method for quantification of BP by using one SPECT scan and calibrated standard input function with one blood sampling. SPECT studies were performed on 14 patients. A dynamic SPECT scan was initiated following an intravenous bolus injection of Iomazenil. A static SPECT scan was performed at 180 min after the injection. Frequent blood sampling from the brachial artery was performed on all subjects to determine the arterial input function. Simulation studies revealed that errors in calculated Vd values were around +/-10-15% for varied K1 values. A good correlation was observed between total distribution volume values calculated by three-compartment model analysis and those calculated by the present method (r = 0.90), supporting the validity of this method. The present method is simple and applicable for clinical use, and will be able to provide images of BP.

Adult↗
PubMed1997

Spool-like stent for the open sternum after cardiac operations.

Severe edematous heart after a cardiac operation is impossible to treat if there is compression of the heart due to the sternum. In these patients delayed sternal closure may be a useful procedure until the heart decreases in size. We devised a spool-like stent for the open sternum to maintain the optimal cardiac space for the severely edematous heart and to fix the chest wall to allow for management while the sternum is open.

Cardiac Surgical Procedures↗
PubMed1997

Expression of prostaglandin EP2 receptor mRNA in the rat spinal cord.

RT-PCR and an in situ hybridization analyses demonstrated expression of prostaglandin EP2 receptor mRNA in the subfield of the dorsal horn of the rat spinal cord. The intensive signals from the cells labeled with digoxigenin-11-dUTP were scattered through this region and they corresponded to neurons. EP2 receptor-mediated signal transduction is expected to play roles in modulating some neuronal functions such as transmission of nociceptive reaction or motor reflex.

Animals↗
PubMed1997

A molecular basis for species differences in Thy-1 expression patterns.

Thy-1 is a membrane glycoprotein that displays species-specific differences in its pattern of expression. Although it is expressed on thymocytes and splenocytes in mice, it is only expressed on thymocytes in rats. Based on previous studies suggesting that the third intron of the mouse Thy-1 gene is required for its expression in thymocytes, in vivo footprinting analysis was performed on the third introns of both the mouse and rat Thy-1 genes, and led to the identification of homologous 36 bp "footprinted" regions. The mouse 36 bp region was found to be capable of specifically binding an Ets-1-like nuclear factor present in both mouse thymocytes and splenocytes. In contrast, the homologous 36 bp region of the rat which differs from the mouse 36 bp region by three nucleotides resulting in the loss of the Ets-1 binding site, is unable to bind a similar Ets-1-like factor present in rat thymocytes. Instead, this region of the rat third intron binds another nuclear factor which is present in rat thymocytes but not splenocytes. These observations suggest that the differential expression of the mouse and rat Thy-1 genes in thymocytes and splenocytes is the result of differential expression of nuclear factors that bind to this 36 bp region.

Animals↗
PubMed1997

The influence of peri-operative blood transfusion during radical hysterectomy on the prognosis of uterine cervical cancer.

To evaluate the clinical implications of peri-operative transfusion in the surgical treatment of uterine cervical cancer, a detailed analysis of the cumulative survival rate was performed using clinical data from 145 patients with FIGO stage Ib cervical cancer of the squamous cell type acquired between 1982 and 1989 at the Center for Adult Diseases. The cumulative survival rate was statistically analyzed using the Kaplan Meier method. Of the 145 patients with stage Ib cancer, 103 were considered to have undergone complete excision and received no further treatment post-operatively, and 42 were considered to have undergone incomplete excision because of the involvement of lymph nodes or the lymphovascular space. Of the 79 patients in the former group who received peri-operative transfusion, 69 received less than seven units (1400 mL) and 10 received more than eight units (1600 mL). The cumulative 5-year survival rate was 100% in the 24 patients who received no transfusions, 91.7% in those who received less than 1400 mL, and 90.0% in those who received more than 1600 mL. Similarly, of the 42 patients in the incomplete excision group, nine did not receive any peri-operative transfusion, 27 received less than 1400 mL, and six received more than 1600 mL. The 5-year survival rate in these groups was 88.9, 77.8 and 50.0%, respectively. The survival rate of our patients with stage Ib cervical cancer without peri-operative transfusion was significantly higher than that of those with transfusion, regardless of post-operative irradiation therapy status, indicating that peri-operative transfusion has an adverse influence on the prognosis in cervical cancer.

Adult↗
PubMed1997

High-density lipoproteins from probucol-treated patients have increased capacity to promote cholesterol efflux from mouse peritoneal macrophages loaded with acetylated low-density lipoproteins.

To elucidate the anti-atherogenic effect of probucol, high-density lipoprotein (HDL) was isolated from probucol-treated patients (n = 14) and compared with that from control subjects (n = 12). The HDL obtained from probucol-treated patients was low in cholesteryl ester (CE) in comparison with that from control subjects (21.3 +/- 3.9 mol per cent vs. 27.6 +/- 3.2 mol% of total lipids. P < 0.001), and the peak diameters of patients' HDL were significantly smaller than those of control subjects on 4-30% non-denaturing polyacrylamide gradient gel electrophoresis (10.6 +/- 0.6 nm vs. 12.1 +/- 0.4 nm, P < 0.001). These data may be explained by the increased cholesteryl ester transfer protein (CETP) activities of probucol-treated patients (129 +/- 12% of control subjects, P < 0.001). The in vitro ability of HDL to remove CE from lipid-laden macrophages induced by incubation with acetylated low-density lipoprotein (Ac-LDL) was studied. The small and CE-poor HDL obtained from probucol-treated patients had a greater capacity to promote CE efflux from macrophages than did control HDL (59.8 +/- 6.9% vs. 44.2 +/- 5.4%, P < 0.01). Furthermore, the ability of HDL to promote cholesterol efflux correlated negatively with the CE content and particle diameter of HDL (r = -0.561 and r = -0.583 respectively; P < 0.01). When the inhibitory effect of HDL on the incorporation of [14C]-oleate into cellular cholesteryl ester was compared, the HDL from patients and control subjects inhibited CE formation to a similar extent. The enhanced ability of probucol-treated patients' HDL may, therefore, be involved in the acceleration of hydrolysis of the CE pool in macrophages. Taken together, we conclude that CETP plays a crucial role in making HDL more active in its anti-atherogenic function by reducing CE and making HDL smaller, and that probucol may enhance reverse cholesterol transport by activating CE transfer in vivo. The current study demonstrated, for the first time, that HDL modified by enhanced CETP activity in vivo is potentially anti-atherogenic.

Adult↗
PubMed1997

Immunohistochemical assessment of proliferative activity in mammary adenomyoepithelioma.

AIMS: Two cases of adenomyoepithelioma of the breast were examined by immunohistochemistry to evaluate proliferative activity of epithelial and myoepithelial components. METHODS AND RESULTS: The tumours showed a bicellular pattern of gland-forming epithelial cells and proliferative myoepithelial cells with clear cytoplasm. They showed foci of monotonous growth of myoepithelial cells devoid of glands with low mitotic rate (1-2/10 high-power fields) and mild cytological atypia. Immunohistochemically, the glandular cells were positive for epithelial membrane antigen, cytokeratin (KL-1 and CAM5.2) and carcinoembryonic antigen, whereas tumour cells with clear cytoplasm were reactive with muscle-specific actin (MSA), alpha smooth muscle actin, vimentin, and S100 protein but negative for desmin. Proliferative activities assessed by MIB-1 (Ki-67)/MSA positive cell index were greater in myoepithelial cells in both cases (19.2% and 17.7%) as compared to those in epithelial cells (MIB-1/CAM5.2 index: 10.2% and 9.5%). CONCLUSIONS: These results might account for the previous findings that myoepithelial components predominate over the epithelial ones in an advanced stage of this tumour as well as in recurrent or metastatic lesions.

Aged↗
PubMed1997

CD79 alpha/CD79 beta heterodimers are expressed on pro-B cell surfaces without associated mu heavy chain.

During B cell development, the surface expression of CD79 alpha/CD79 beta heterodimers had been thought to begin in the pre-B cell stage where the heterodimers constitute pre-B cell receptors together with mu heavy and surrogate light chains. Thereafter, in mature B cells, CD79 alpha/CD79 beta associates with surface Ig to form B cell antigen receptors. In this study, we revealed by using newly established mAb that CD79 beta was expressed on the surface of pro-B cells which had not undergone the productive Ig gene rearrangement. Biochemical analysis showed that CD79 beta on pro-B cells existed either as monomers or as disulfide-linked heterodimers with CD79 alpha, non-covalently associated with four unidentified membrane molecules. Our finding that CD79 beta is expressed on earlier B-lineage cells than previously expected coincides with the recent study in which CD79 beta-deficient mice exhibit a blockade of B cell differentiation at the pro-B cell stage. Thus, it is speculated that the CD79 beta-containing complexes on pro-B cell surfaces may function to induce early B cell differentiation.

Animals↗
PubMed1997

Human decidual cell biosynthesis of leukemia inhibitory factor: regulation by decidual cytokines and steroid hormones.

The production of leukemia inhibitory factor (LIF) is suggested to be critical for the successful implantation of blastocysts into decidua, because LIF expression is essential for the implantation of mouse blastocytes. We investigated the regulation of LIF production by decidual cytokines and steroid hormones. Stimulation of decidual cells by interleukin-1, tumor necrosis factor alpha, or transforming growth factor beta augmented LIF production in a dose-dependent manner. Moreover, estradiol, a steroid hormone that increases during ovulation and early pregnancy, also enhanced LIF production in a dose-dependent manner. These responses were blocked by protein kinase C (PKC) inhibitor but not by other kinase inhibitors, suggesting an important role of PKC in decidual LIF production mediated by cytokines and estradiol. We also showed that stimulating decidual cells with LIF failed to stimulate DNA synthesis and prolactin production in these cells. In summary, LIF was mainly localized in the decidual glands and stroma, and its production was increased by cytokines and estradiol in a dose-dependent fashion; but stimulation of decidual cells by LIF did not influence their proliferation or their prolactin production.

Animals↗