Biomedical subjects

K Miki

Publications and source records attributed to K Miki.

At least 235 records · Page 13Linked to original sources

PubMed1994

Preliminary X-ray crystallographic studies of photosynthetic reaction center from a thermophilic sulfur bacterium, Chromatium tepidum.

A membrane protein complex, photosynthetic reaction center purified from the thermophilic purple sulfur bacterium, Chromatium tepidum has been crystallized from a phosphate buffer containing a detergent, n-octyl-beta-D-glucopyranoside and a precipitant, polyethylene glycol 4000. The crystals diffracted X-rays beyond 3A resolution with synchrotron radiation and are suitable for high-resolution X-ray crystallographic studies. The crystals belong to the orthorhombic space group P2(1)2(1)2(1) with unit-cell dimensions of a = 136A, b = 197A, and c = 82A. Assuming that they contain one reaction center complex in the asymmetric unit, VM was calculated to be 4.3 A3/Da, which agrees with the values obtained in the membrane protein complexes.

Chromatium↗

PubMed1994

Possible role of Helicobacter pylori infection in early gastric cancer development.

BACKGROUND: Gastric cancer is the most frequently diagnosed malignancy in Japan. The possible relationship between Helicobacter pylori infection and gastric cancer in Japan was evaluated. METHODS: H. pylori infection was identified by the presence of anti-H. pylori IgG. The frequency of H. pylori infection was compared in 213 patients with gastric cancer and the same number of asymptomatic control subjects matched for age and sex. RESULTS: The presence of IgG antibody to H. pylori was significantly more prevalent (P < 0.001) in those with gastric cancer compared with asymptomatic control subjects (88.2% versus 74.6%). H. pylori positive rates were significantly greater in patients with the intestinal type (90.4%, P < 0.001) and diffuse type (86.4%, P < 0.05) of gastric cancer than in control subjects. Ninety-three percent of the patients with early gastric cancer tested positive for H. pylori (P < 0.001 compared with control subjects), whereas no significant difference was observed between those with advanced gastric cancer and control subjects. The intestinal type of early gastric cancer showed only the significantly increased frequency of high titer (optical density > 1.50) of H. pylori IgG antibody (P < 0.001) compared with control subjects without cancer. CONCLUSIONS: These results suggest that H. pylori infection may be associated with the development of early gastric cancer in Japan.

Adult↗

PubMed1994

Serum pepsinogen as a new marker for gastric carcinoma among young adults. Research Group on Prevention of Gastric Carcinoma among Young Adults.

BACKGROUND: Gastric carcinoma is relatively uncommon in Japan among persons younger than 40 years of age, but its prognosis is not favorable and it affects young adults in their most productive years. This study was performed to evaluate the validity of serum pepsinogen as a new marker for gastric carcinoma among Japanese younger than 40 years of age. METHODS: Data and sera were collected from the patients (108 patients younger than 40 years of age with gastric carcinoma from nine hospitals in the Kanto-Shin'etsu area in Japan) and from the control subjects (108 hospital control subjects and 108 screening control subjects) whose sex and age (within 4 years) were matched. Pepsinogen I and pepsinogen II values were measured and compared between patients and control subjects by paired t test. Sensitivities and specificities when criteria were defined by pepsinogen I, pepsinogen II, and pepsinogen I/II ratio were calculated. RESULTS: The pepsinogen I and pepsinogen II levels among patients were higher and the pepsinogen I/II ratio among patients was lower than among control subjects. When a pepsinogen II level higher than 14.8 ng/ml was considered positive, the test showed high sensitivity (83.3% for total gastric carcinoma and 85.0% for early gastric carcinoma) and high specificity (76.9% for hospital control subjects and 75.0% for screening control subjects). Similar degrees of sensitivity and specificity were obtained with the pepsinogen I/II ratio. CONCLUSIONS: These results suggest that a high pepsinogen II level combined with a low pepsinogen I/II ratio may be a useful screening test for gastric carcinoma in a young population at high risk for gastric carcinoma. This impression should be confirmed by a more extensive field trial to determine whether performance of these assays promotes early diagnosis of gastric carcinoma.

Adolescent↗

PubMed1994

Structural similarity of cytochrome c2 from Rhodopseudomonas viridis to mitochondrial cytochromes c revealed by its crystal structure at 2.7 A resolution.

The crystal structure of cytochrome c2 from Rhodopseudomonas viridis has been refined using molecular dynamics and restrained least-squares methods to a crystallographic R-factor of 0.216 at 2.7 A resolution. A structural comparison between Rps. viridis cytochrome c2 and the other bacterial cytochromes c2 or mitochondrial cytochromes c indicates that the overall protein foldings are very similar to each other with the exception of the surface loop and terminal region of the polypeptide chain. However, the position and hydrogen-bond pattern of the evolutionarily conserved water molecule buried within the heme binding pocket in Rps. viridis cytochrome c2 are common to those in the mitochondrial cytochromes c. This fact indicates that Rps. viridis cytochrome c2 is structurally more similar to mitochondrial cytochromes c than to the other bacterial cytochromes c2.

Crystallography, X-Ray↗

PubMed1994

Application of an automatic molecular-replacement procedure to crystal structure analysis of cytochrome c2 from Rhodopseudomonas viridis.

An automatic molecular-replacement procedure has been applied to solve the crystal structure of cytochrome c(2) from Rhodopseudomonas viridis. The structure was solved on the basis of the structure of tuna cytochrome c as a search model using an automatic processing program system, AUTOMR. The refinements by molecular dynamics and restrained least-squares methods result in a current crystallographic R factor of 0.219 for diffraction data at 3 A resolution.

Journal Article↗

PubMed1994

Suppression of neointimal smooth muscle cell accumulation in vivo by antisense cdc2 and cdk2 oligonucleotides in rat carotid artery.

Deendothelializing balloon injury of rat carotid artery results in progressive intimal smooth muscle cell accumulation and luminal stenosis over 14 days after injury. We have found transient rises (approximately 3-fold maximal increases over the uninjured control value) of the kinase activities of both cdc2 and cdk2, key molecules for cell cycle progression, in the injured carotid artery along with the development of intimal proliferation. The topical application of the antisense, but not the sense, cdc2 and cdk2 phosphorothioate oligodeoxynucleotides dissolved in F127 pluronic gel around the freshly injured artery resulted in reductions of the intimal smooth muscle cell accumulation by 47% and 55% respectively, as estimated by an intimal to medial cross-sectional area ratio, with concomitant decreases in cdc2 and cdk2 kinase activities. These results indicate that both cdc2 and cdk2 kinases are involved in intimal smooth muscle cell accumulation after balloon angioplasty and suggest a potential usefulness of the antisense cdc2 and cdk2 oligonucleotide therapy for arterial stenosis.

Angioplasty, Balloon↗

PubMed1994

Effect of omeprazole on secretion, synthesis and the gene expression of pepsinogen in the guinea pig stomach mucosa.

The effects of omeprazole, a proton pump inhibitor, on gene expression, protein synthesis, intracellular storage and secretion of pepsinogen in guinea pig stomach were investigated. After treatment with omeprazole for five days, acid and pepsinogen secretion into the gastric lumen was significantly reduced. Concomitant with this, there was an increase in intracellular pepsinogen as demonstrated by increased pepsin activity in the gastric mucosa, more intense immunohistochemical staining by antibodies specific for pepsinogen and accumulation of secretory granules in the cells producing pepsinogen. In these cells, the amount of pepsinogen mRNA was reduced as revealed by Northern blotting and in situ hybridization. Ultrastructurally the endoplasmic reticulum of these cells was poorly developed, the findings being consistent with a reduction in protein synthesis. It appears that omeprazole inhibits the secretion of pepsinogen, increasing the intracellular store and leading to the reduction in gene expression probably by a feedback mechanism and consequent reduction in pepsinogen synthesis. Since these changes were most evident in the acid-secreting fundic gland mucosa, as compared with other mucosae secreting only pepsinogen, namely pyloric and duodenal mucosa, it appears probable that these changes are linked with omeprazole-induced reduction in the acid secretion.

Animals↗

PubMed1994

Enhancement by tocoretinate of epidermal growth factor-induced DNA synthesis in human intestinal epithelial cells.

Tocoretinate (TR) is a hybrid compound composed of alpha-tocopherol esterified with retinoic acid. The present study was conducted to clarify whether or not TR affects DNA synthesis in a human intestinal cell line, FHs 74 Int. In these cells, addition of 10% serum resulted in an approximately 10-fold increase in DNA synthesis as assessed by [3H]thymidine incorporation. Epidermal growth factor (EGF) augmented DNA synthesis three- to fourfold. When EGF was added together with insulin-like growth factor-I (IGF-I), which had only a small effect by itself, a combination of these growth factors reproduced the effect of serum. In quiescent FHs 74 Int cells, TR had no effect on DNA synthesis by itself. However, when quiescent cells were pretreated with TR for 24 hr, DNA synthesis induced by EGF was markedly enhanced. Thus, in TR-pretreated cells, EGF stimulated DNA synthesis to the same extent as 10% serum. The effect of TR was dose-dependent and the maximal effect was obtained by 10(-7) M TR. Pretreatment with TR enhanced the effect of EGF on DNA synthesis but did not change the dose-response relationship for EGF-mediated DNA synthesis. All-trans-retinoic acid had similar stimulatory effect on EGF-induced DNA synthesis. When the medium was changed during the treatment with TR, the effect of TR on DNA synthesis was reduced. In addition, pretreatment with TR resulted in release of immunoreactive IGF-I into medium. Finally, the effect of TR was attenuated by an addition of antibody against IGF-I.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Line↗

PubMed1994

Fetal rat glandular stomach epithelial cells differentiate into surface mucous cells which express cathepsin E in the absence of mesenchymal cells in primary culture.

It is well established that the differentiation of glandular stomach epithelial cells is affected by many factors including epithelial-mesenchymal interactions. To clarify the control mechanism of their differentiation, we developed a primary culture system for fetal rat glandular stomach epithelial cells, and examined their differentiation in the absence of mesenchyme. Pure glandular stomach epithelial tissues obtained from 16.5-day fetal rats proliferated rapidly, increasing their number about 20 times in the first 7 days. The epithelial nature of the cells was confirmed by the presence of cytokeratin in the cells. Glandular stomach epithelial cells formed simple cuboidal/squamous epithelia with many mucous granules in their cytoplasm, and exhibited epithelial polarity with microvilli on the luminal surface, basal lamina-like material on the basal surface, and junctional complexes in the apical region. Biochemical analysis showed that the cells expressed acid protease activity in culture. Previous studies showed that glandular stomach epithelial cells specifically expressed two types of acid proteases: pepsinogens in chief and mucous neck cells, and cathepsin E in surface mucous cells. Immunohistochemical studies using specific antibodies showed that the cultured cells expressed cathepsin E but not pepsinogens, and the result was confirmed by zymogram and Western blotting analysis. We thus concluded that fetal rat glandular stomach epithelial cells differentiated into surface mucous cells that expressed cathepsin E in primary culture in the absence of mesenchyme.

Animals↗

PubMed1994

Analysis of AP-1 function in cellular transformation pathways.

To understand the role of endogenous AP-1 activity in cellular transformation induced by oncogenes, we have made use of a fos mutant (supfos-1) and a jun mutant (supjun-1), either of which can function as a transdominant inhibitor of AP-1-mediated transcriptional regulation. Chicken embryo fibroblasts (CEF) infected with a series of transforming retroviruses were doubly infected with retrovirus carrying supfos-1 or supjun-1, and suppression of cellular transformation was monitored in terms of reversion to normal cellular morphology or acquisition of anchorage-dependent growth. Cellular transformation induced by several exogenously expressed transforming genes of the fos or jun family was efficiently suppressed, as expected. CEF transformed by v-src, v-yes, v-fps, c-Ha-ras, and N-terminally truncated c-raf were also induced to revert to the normal phenotype by these transdominant mutants, suggesting that functional transcription factor AP-1 activity is essential for the cellular transformation induced by these oncogenes. The suppression is not attributable to nonspecific inhibition of cellular proliferation, because CEF transformed by v-ros or v-myc were not induced to revert to the normal phenotype. We next analyzed changes in all known components of chicken AP-1 induced by v-src, c-Ha-ras, or activated c-raf transformation. The levels of both Fra-2 and c-Jun expression were elevated two- to fourfold, and hyperphosphorylation of Fra-2 was also observed. We further showed that Fra-2-c-Jun heterodimer is mainly responsible for the elevated AP-1 DNA-binding activity in these transformed cells, and we propose that this heterodimer play a crucial role in the transformation induced by these oncogenes.

Animals↗

PubMed1994

Changes in muscle sympathetic nerve activity and renal function during positive-pressure breathing in humans.

The possibility that the decreased urinary flow during continuous positive-pressure breathing (CPPB) may be a consequence of a reflex mediated via the cardiopulmonary baroreceptors to increase neurohumoral secretion or to change the sympathetic outflow was assessed. Muscle sympathetic nerve activity (MSNA) on the right peroneal nerve, vasoactive hormones, and renal and cardiovascular responses were measured during CPPB (+12 mmHg) in 10 male subjects (22.0 +/- 0.6 yr, 66.8 +/- 1.5 kg body wt). The experiments consisted of a 1-h control, 1 h with CPPB (experimental) or without CPPB (a time control), and a 1-h recovery period. Two blood samples were taken during each period for measurements of arginine vasopressin (AVP), plasma aldosterone (PAldo), plasma renin activity (PRA), norepinephrine, and atrial natriuretic peptide (ANP), and urine was collected hourly for the measurement of urine volume and electrolytes and clearances. MSNA rapidly increased (P < 0.05) at the onset of CPPB, continued to increase during exposure, and rapidly returned to the normal level at recovery. The MSNA changes coincided with increased plasma NE and were concurrent with a reduced (P < 0.05) urine output associated with a reduction of both free water and osmolal clearances, Na+ and osmolal excretions, and creatinine clearance (glomerular filtration rate). AVP and PRA increased (P < 0.05), whereas PAldo and ANP were unchanged. The results are consistent with the concept that increased sympathetic outflow may play a role in the reduction of urinary output and Na+ excretion during unloading of the cardiopulmonary receptors.

Adult↗

PubMed1994

Effect of water temperature on diuresis-natriuresis: AVP, ANP, and urodilatin during immersion in men.

Effects of water temperature on diuresis, natriuresis, and associated endocrine responses during head-out immersion were studied in eight men (23.4 +/- 0.3 yr) during four 5-h experimental conditions: air control at 28 degrees C and immersion at 34.5 degrees C [thermoneutral (Tnt)], 36 degrees C [above Tnt (aTnt)], and 32 degrees C [below Tnt (bTnt)]. Esophageal temperature decreased by approximately 0.4 degrees C in bTnt and increased by approximately 0.5 degrees C in aTnt. Cardiac output increased by approximately 80% in aTnt and approximately 40% in bTnt while thoracic impedance, an index of central blood pooling, decreased by 7.5 omega in bTnt (NS vs. Tnt) and 8.8 omega in aTnt (P < 0.05 vs. Tnt and bTnt). Total peripheral resistance decreased at all temperatures (50% in aTnt, 20% in bTnt). Urine flow and Na+ excretion increased by sixfold in bTnt and Tnt but by only threefold in aTnt. Creatinine clearance was unchanged while osmolal clearance (but not free water clearance) increased two-fold with all immersions. Plasma atrial natriuretic peptide (ANP), urinary urodilatin, and urinary guanosine 3',5'-cyclic monophosphate increased while plasma renin activity, aldosterone, and arginine vasopressin (AVP) decreased similarly at all temperatures. bTnt did not potentiate diuresis by selective attenuation of AVP. The overall natriuretic response exhibited a higher correlation with urodilatin (r = 0.45, P < 0.001) than with ANP (r = 0.26, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Drug absorption from large intestine: physicochemical factors governing drug absorption.

Profiles of absorption versus drug molecular weight and absorption versus drug lipophilicity were investigated in both the small and large intestines of rats by an in situ loop method. The absorption-molecular weight profiles examined using different-sized polyethylene glycols (PEGs) were different between the small and large intestines; the large-intestinal absorption of PEGs with molecular weights larger than 300 was poor, while PEGs with molecular weights up to 600 were relatively well absorbed in the small intestine. It is suggested that the paracellular route for drug penetration in the large intestine is restricted more than in the small intestine. The absorption-lipophilicity profiles were also examined in various regions (loops of 6 cm) of rat intestine using three acylsalicylic acids, acetyl-, propionyl- and butyrylsalicylic acids. The absorption rates of the acylsalicylic acids were different in the intestinal regions: the jejunum > the ileum > the colon > the rectum. In each region, the absorption rate increased with the drug lipophilicity. However, it was shown that the absorption rates in the small intestine tended to reach a ceiling at the high lipophilicity. To confirm this tendency, the absorption rates of acetaminophen and indomethacin were compared in the four intestinal regions. The absorption rates of highly lipophilic indomethacin were similar in the large and small intestines, while intermediately lipophilic acetaminophen was more rapidly absorbed in the small intestine than in the large intestine. A thicker unstirred water layer adjacent to the small-intestinal mucosa would be one of the factors which cause such varying absorption-lipophilicity profiles.

Animals↗

PubMed1994

Regulated expression of an osteonectin variant in bovine aortic endothelial cells.

Using a mouse SPARC (Secreted Protein, Acidic and Rich in Cysteine) cDNA clone as the probe, three clones were isolated from a cDNA library of bovine aortic endothelial cells (BAEC). Inserted sequences in them were identical with that of bovine bone osteonectin except for the deletion of the TGC codon encoding Cys-193. Northern blot analysis and metabolic radio-labeling of BAEC showed that gene expression and synthesis of the osteonectin variant is stimulated by transforming growth factor (TGF) beta, a basic fibroblast growth factor (FGF), or a naturally occurring splicing variant of hepatocyte growth factor (varHGF).

Animals↗

PubMed1994

[Morphological change in the retina after injection of calcium and netilmicin sulfate in the rabbit vitreous body].

We reported previously selective damage of the outer segment of the photoreceptors and retinal pigment epithelium after intravitreal injection of netilmicin sulfate in the rabbit. The cellular damage was thought due to active damage of phospholipase C enzyme, preventing it from performing phospholipid inositol metabolism, and to the presence of calcium. Therefore we investigated the retinal damage following after intravitreal injection of calcium and netilmicin sulfate in the rabbit. Morphologically, the retina did not show any structural change after intravitreal injection of CaCl2 at any concentration. After an intravitreal injection of netilmicin sulfate mixed with CaCl2, the damage in the photoreceptor outer segment was reduced at a concentration of 200 micrograms/0.1 ml and in the retinal pigment epithelium at a concentration of 1,000 micrograms/0.1 ml. This showed that retinal damage due to netilmicin sulfate can be reduced by the addition of calcium.

Animals↗

PubMed1993

Effects of omeprazole on gastric mucosal growth and differentiation in developing rat.

The effects of omeprazole on developing rat stomach mucosa were investigated. Infant rats were given subcutaneous injections of either omeprazole (25 mg/kg body weight/day) or vehicle once a day from the day after birth. As a result, omeprazole caused an elevation of mucosal pH and suppressed an increase in mucosal pepsinogen and its mRNA levels during stomach development. Histologically, these changes were associated with a reduction in mature pepsinogen-producing cells throughout stomach mucosa. Omeprazole also caused a delay in the expression of cathepsin E in surface mucous cells and an increase in labeled cells with bromodeoxyuridine. Thus, the present results indicate that omeprazole induces an increase in mucosal cell proliferation and delays the differentiation of developing rat stomach mucosa. Since the observed changes were remarkable especially from days 15 to 21 after birth when significant development of acid secretion occurs, the effects of omeprazole appear to be related with the potent acid inhibitory effect of the reagent.

Aging↗

PubMed1993

Crystallization and preliminary X-ray diffraction studies of Bacillus stearothermophilus farnesyl diphosphate synthase expressed in Escherichia coli.

Thermostable farnesyl diphosphate synthase (EC 2.5.1.10) from Bacillus stearothermophilus, which was overexpressed in Escherichia coli, has been crystallized by the vapor-diffusion procedure. Tetragonal crystals were obtained using ammonium sulfate as a precipitant. The crystals diffracted X-rays to about 3 A resolution. The diffraction pattern indicated that the space group is I4(1)22 with unit-cell dimensions of a = b = 114 A and c = 247 A. It is thought that the asymmetric unit comprises two or three molecules of farnesyl diphosphate synthase.

Alkyl and Aryl Transferases↗

PubMed1993

Omeprazole, a proton pump inhibitor, reduces the secretion, synthesis and gene expression of pepsinogen in the rat stomach.

Omeprazole, a proton pump inhibitor, dose-dependently inhibited pepsinogen secretion as well as acid secretion in the rat glandular stomach. The reduction in the secretion was rapid and was followed by a decrease in the mRNA levels. The inhibitory effect of omeprazole on pepsinogen secretion and its effect on the mRNA level showed similar dose-response relationship, suggesting that pepsinogen secretion and the gene expression are regulated coordinately. Consistent with the reduction in the mRNA levels, protein synthesis was reduced. However, intracellular stores of pepsinogen increased in pepsinogen-producing cells, indicating that the inhibitory effect of omeprazole on pepsinogen secretion is greater than on its synthesis. Reducing the secretion, synthesis and gene expression of pepsinogen, omeprazole has a potent effect on pepsinogen-producing cells in vivo, as well as on parietal cells, in the rat glandular stomach.

Animals↗