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Biomedical subjects

K Katayama

Publications and source records attributed to K Katayama.

At least 91 records · Page 5Linked to original sources
PubMed2000

beta-blockers reduce the incidence of cardiac events in post-myocardial infarction patients.

The capacity of beta-blockers to prevent cardiac events in post-myocardial infarction (MI) patients was investigated. Among 1,483 study participants, a beta-blocker was included in the therapeutic regimens of 833 (beta-blocker group) and was omitted from the regimens of 650 (control group). The incidence of cardiac events (recurrent MI, sudden death and death by congestive heart failure) during a follow up period of 17.4 +/- 20.9 months was retrospectively compared between the two groups. Cardiac events occurred in 27 (3.2%) members of the beta-blocker group and in 44 (6.8%) controls, which represents a significant decline in the incidence of cardiac events among patients administered beta-blockers (p < 0.01, odds ratio 0.46, 95 % confidence intervals 0.28-0.75). Subgroup and multivariate analyses showed beta-blockers to be as efficacious in Japanese post-MI patients as was previously shown in Western patients. While these findings are compelling, it is clear that confirmation in a large, multicenter, placebo - controlled, randomized clinical trial, analogous to those that have been carried out in Western countries, is necessary.

Adrenergic beta-Antagonists↗
PubMed2000

Teratologic studies on rat perinates and offspring from dams treated with ethylnitrosourea (ENU).

Ethylnitrosourea (ENU), a well known DNA alkylating agent, induces anomalies in the central nervous system (CNS), craniofacial tissues, limbs and male reproductive organs. Recently we clarified that excess cell death caused by apoptosis occurred in these organs and tissues of rat fetuses from dams treated with ENU at day 13 of gestation (GD13). In this study, we examined fetuses at GD21 and offspring at 10 weeks of age after ENU administration to pregnant rats at GD13 in order to clarify the relationship between ENU-induced apoptosis in the fetal tissues and teratogenicity of ENU. Severe intrauterine growth retardation was observed in the ENU group, and the body weight of the offspring in the ENU group was significantly lower than that of the control group throughout the experiment. In addition, a high incidence of microencephaly, ectrodactyly and curved caudal vertebrae was observed in the offspring from dams treated with ENU at GD13. Judging from the results of our previous and present studies, it was strongly suggested that ENU-induced apoptosis in rat fetal tissues may play an important role in the induction of anomalies in the corresponding tissues.

Abnormalities, Drug-Induced↗
PubMed2000

Indirect evidence of TTV replication in bone marrow cells, but not in hepatocytes, of a subacute hepatitis/aplastic anemia patient.

The presence of a new DNA virus (TTV) has been reported in sera from patients with posttransfusion hepatitis of unknown etiology. The precise replication site of TTV, however, has not been established. In this study, the presence of TTV in liver autopsy material, and in bone marrow biopsy and autopsy samples taken from a subacute hepatitis/aplastic anemia patient was determined by PCR and Southern blot analyses. Liver cells were found to contain only TTV DNA and not mRNA. Bone marrow material, especially that taken at biopsy, contained high levels of TTV DNA. It is suggested that the TTV replication site was in the bone marrow rather than in the liver, and that TTV infection was the cause of this patient's aplastic anemia. The precise etiological association of TTV with hepatitis remains to be established.

Adult↗
PubMed2000

Evaluation of portosystemic collaterals by SPECT imaging after endoscopic variceal sclerotherapy: usefulness for predicting recurrence.

UNLABELLED: Bleeding from esophageal varices is a major cause of morbidity and mortality in cirrhotic patients. Identification of patients at high risk for bleeding is particularly important. The aim of this study was to determine whether detection of portosystemic collaterals by SPECT could predict the outcome of endoscopic injection sclerotherapy of esophageal varices and be useful for selecting appropriate therapy. METHODS: Sixty-two patients with liver cirrhosis who were considered at high risk of bleeding were treated with endoscopic injection sclerotherapy. Endoscopy was performed every 3 mo after therapy or until bleeding occurred. Before and within 2 wk after therapy, tomographic images of intra-abdominal blood pool were constructed by SPECT. RESULTS: Before therapy, the following portosystemic collateral routes were observed: coronary veins in 53 (85.5%) of 62 patients, short gastric veins in 8 patients (12.9%), splenorenal shunts in 10 patients (16.1%), and paraumbilical veins in 6 patients (9.7%). Patients positive for imaging of coronary veins were divided into 3 groups on the basis of changes in images after therapy: complete responders (n = 17), whose coronary vein images disappeared completely; partial responders (n = 18), whose images became smaller; and nonresponders (n = 18), whose images did not change significantly before or after therapy. The rates of recurrence after endoscopic injection sclerotherapy until 6 mo in complete responders (4/17, 23.5%) and partial responders (7/18, 38.9%) were significantly less (P < 0.05) than that in nonresponders (11/13, 84.6%). The rate of recurrence of esophageal varices until 6 mo in nonresponders treated with additional submucosal injection sclerotherapy (1/5, 20.0%) was significantly less (P < 0.05) than that in nonresponders without additional submucosal injection sclerotherapy (11/13, 84.6%). CONCLUSION: Abdominal blood-pool SPECT, a noninvasive method, is useful for evaluating the therapeutic effectiveness of endoscopic sclerotherapy, for predicting the recurrence of varices, and for selecting appropriate management after sclerotherapy.

Collateral Circulation↗
PubMed2000

[Drug treatment for secondary prevention of myocardial infarction].

The effects of drug treatment on cardiac events for 11 years from January 1986 to December 1996 were investigated in 1,483 patients with myocardial infarction, 1,164 men and 319 women (mean age 60.1 +/- 11.2 years), followed up for 17.4 +/- 20.9 months. Seventy-one patients (4.8%, 33 cases per 1,000 person-year) had cardiac events (recurrent myocardial infarction, sudden death and death by congestive heart failure). Multivariate analysis showed treatment with cholesterol lowering agents and beta-blockers reduced cardiac events, whereas administration of antiarrhythmic agents increased cardiac events. Univariate analysis showed that the incidence of cardiac events was 2.2% in patients treated with cholesterol lowering agents but 6.2% in patients without treatment, showing a significant difference (p < 0.01). The incidence was 3.2% for patients treated with beta-blockers and 6.8% for those without (p < 0.01), showing that beta-blockers were also effective to reduce cardiac events. Antiplatelet agents were also effective (3.7% vs 7.1%, p < 0.01). Calcium antagonists, angiotensin converting enzyme inhibitors and warfarin were not effective. Nitrates (6.0% vs 3.1%, p < 0.01) and antiarrhythmic agents (13.7% vs 3.6%, p < 0.01) increased the incidence of cardiac events. A placebo-controlled, double blind, large clinical multicenter study is required to confirm these results.

Adrenergic beta-Antagonists↗
PubMed2000

Study on eight patients with malignant tumors after renal transplantation.

The high incidence of cancer after renal transplantation is now a critical concern since the graft survival rate has been improved extensively. We experienced 9 malignancies in 8 patients out of 168 recipients up to December 31, 1999 in our hospital, consisting of a case of gastric plasmacytoma and cases of cancer in the liver (2), thyroid (2), prostate (1), breast (1), sigmoid colon (1) and gall-bladder (1). Two patients were diagnosed as having tumors within 3 months after transplantation, suggesting post-transplant acceleration of growth of the latent tumors. The other patients were diagnosed at an average of 128 months, ranging from 84 to 263 months after transplant. Two patients died of gastro-intestinal bleeding and acute heart failure. Four patients died directly of progressive neoplasm within 3 months after diagnosis. These results suggest that the course of malignancies developing in post-transplant recipients is more aggressive than that expected in non-transplant patients, and it is very important to intensively follow long-term surviving cases to detect the malignant tumors as early as possible.

Adolescent↗
PubMed2000

Did ossification of the posterior longitudinal ligament of the spine evolve in the modern period? A paleopathologic study of ancient human skeletons in Japan.

OBJECTIVE: To investigate the historical origins of ligamentous ossifications of the spine in Japan. METHODS: We studied skeletons of Jomonese of the period 5000-2300 years BP, of Japanese of the 17th-19th century Edo Period, and of Ainu of the 18th-20th century in Japan with special emphasis on spinal ligament ossifications as in the posterior longitudinal ligament. A comparison to our previous study on ancient Chinese skeletons was done. RESULTS: Cervical ossification of the posterior longitudinal ligament (OPLL) was the only ossification that increased significantly in prevalence in people of the near-modern period in comparison to the Neolithic gathering-hunting people. CONCLUSION: Socioeconomic changes from a subsistence gathering-hunting economy to the near-modern livelihood depending on rice-eating and a diet high in vegetable protein are speculated to be responsible for the prevalence increase of cervical OPLL.

Adult↗
PubMed1999

Neuron-specific expression of reporter gene in transgenic mice carrying the 5'-upstream region of mouse P/Q-type Ca2+ channel alpha 1A subunit gene fused to E. coli lacZ reporter gene.

To dissect the molecular mechanisms underlying the neuron-specific expression of the P/Q type calcium channel alpha 1A subunit gene, transgenic mice carrying a 0.5-kb, 1.5-kb, 3.0-kb or 6.3-kb 5'-upstream region of the gene fused to Escherichia coli lacZ reporter gene were produced. In transgenic mice carrying the 1.5-kb, 3.0-kb or 6.3-kb 5'-upstream region, the reporter gene was exclusively expressed in the nervous system, although those with the 0.5-kb 5'-upstream region failed to show reporter expression. Histological examinations showed that the three 5'-upstream regions induced distinct expression patterns of the reporter gene in the CNS and adrenal medulla. The 1.5-kb 5'-upstream region drove reporter gene expression in the olfactory bulb, dorsal cortex and hippocampus, while the regulatory element for the expression in the amygdaloid nucleus, septum, habenula medial nucleus, choroid plexus, substantia nigra, inferior colliculus, pontine nucleus and cerebellum was located in the 5'-upstream sequence between 1.5 kb and 6.3 kb. In the cerebellum, the expression of the reporter gene was induced by the 3.0-kb region in granule cells, whereas it was induced by the 6.3-kb region in Purkinje cells. The expression of the reporter gene in chromaffin cells in the adrenal medulla was induced only by the 6.3-kb 5'-upstream region. These results suggest that the expression of the mouse P/Q-type Ca2+ channel alpha 1A subunit gene is regulated in a complex fashion by both positive and negative cis-regulatory elements.

5' Untranslated Regions↗
PubMed1999

Vasogenic edema on MELAS: a serial study with diffusion-weighted MR imaging.

The authors performed a serial study of a patient with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like syndrome (MELAS) who presented with diffusion-weighted MRI (DWI). DWI demonstrated a higher apparent diffusion coefficient in the lesion than in the control region during the acute stage of stroke. Vasogenic edema is present in stroke-like episodes in MELAS.

Blood-Brain Barrier↗
PubMed1999

Equilibrium in the hydrolysis and synthesis of cannabimimetic anandamide demonstrated by a purified enzyme.

Anandamide, an endogenous ligand for cannabinoid receptors, loses its biological activities when it is hydrolyzed to arachidonic acid and ethanolamine by anandamide amidohydrolase. We overexpressed a recombinant rat enzyme with a hexahistidine tag in a baculovirus-insect cell expression system, and purified the enzyme with the aid of a Ni-charged resin to a specific activity as high as 5.7 micromol/min/mg protein. The purified recombinant enzyme catalyzed not only the hydrolysis of anandamide and palmitoylethanolamide, but also their reverse synthetic reactions. In order to attain an equilibrium of the anandamide hydrolysis and its reverse reaction within 10 min, we utilized a large amount of the purified enzyme. The equilibrium constant ([arachidonic acid][ethanolamine])/([anandamide][water]) was calculated as 4x10(-3) (37 degrees C, pH 9.0). These experimental results with a purified enzyme preparation quantitatively confirmed the reversibility of the enzyme reaction previously observed with crude enzyme preparations.

Amidohydrolases↗
PubMed1999

A novel apoptotic cascade mediated by CDK4 in rat pheochromocytoma PC12 cells.

Apoptosis induced by serum withdrawal in pheochromocytoma PC12 cells is promoted by overexpression of cyclin-dependent kinase 4 (CDK4). We compared CDK4-promoted apoptosis with that induced by serum withdrawal alone in PC12 cells. Protein synthesis inhibitors did not prevent apoptosis in parental cells, but prevented the promotion of apoptosis by CDK4 overexpression. Nerve growth factor, basic-fibroblast growth factor, and Bcl-2 proteins protected both parental and CDK4-overexpressing cells from apoptosis. However, insulin-like growth factor-I and Bcl-X(L) protein only partially inhibited apoptosis in the CDK4-overexpressing cells. Bcl-2 or Bcl-X(L) had no significant effect on CDK4 kinase activity in both cell lines. These results suggest a novel CDK4-mediated apoptotic cascade which is normally restrained, but which is activated by CDK4 overexpression. This apoptotic cascade should eventually converge with the cascade induced by serum withdrawal in normal PC12 cells. We discuss the interactions among these apoptotic cascades and the points where anti-apoptotic agents act.

Animals↗
PubMed1999

Isolation and functional characterization of the 5'-upstream region of mouse P/Q-type Ca2+ channel alpha1A subunit gene.

The omega-agatoxin-IVA-sensitive P/Q-type Ca2+ channel is predominantly expressed in the nervous system. To dissect the molecular mechanisms underlying the neuron-specific expression of the P/Q-type channel, we have isolated and characterized the 5'-upstream region of the mouse alpha1A subunit gene. A transcription start site appeared to exist at -269 bp upstream from the start codon as found by 5' RACE analysis. The proximal promoter of the alpha1A subunit gene lacks a typical TATA box, but contains several transcription factor binding sequences, including two Sp1 sites. When linked to a placental alkaline phosphatase (PLAP) reporter gene to examine the promoter activity, the 6.3-kb (-6,273 to +269) 5'-upstream region, but not a smaller 3.0-kb construct (-3, 021 to +269), was able to drive the reporter gene in neuron-like PC12 cells. In contrast, neither of these constructs enhanced the PLAP expression in fibroblast NIH3T3 cells. The sequence between 6.3 and 3.0 kb of the 5'-upstream region did not show promoter activity in either of the cell lines, but enhanced TK promoter activity in PC12 cells, though not in NIH3T3 cells. These results suggest that neuron-specific elements of the alpha1A subunit gene are likely to be located in the distal upstream regions (-6,273 to -3,021) of the 5'-upstream sequence.

3T3 Cells↗
PubMed1999

DnrD cyclase involved in the biosynthesis of doxorubicin: purification and characterization of the recombinant enzyme.

Mutations in the Streptomyces peucetius dnrD gene block the ring cyclization leading from aklanonic acid methyl ester (AAME) to aklaviketone (AK), an intermediate in the biosynthetic pathway to daunorubicin (DNR) and doxorubicin. To investigate the role of DnrD in this transformation, its gene was overexpressed in Escherichia coli and the DnrD protein was purified to homogeneity and characterized. The enzyme was shown to catalyze the conversion of AAME to AK presumably via an intramolecular aldol condensation mechanism. In contrast to the analogous intramolecular aldol cyclization catalyzed by the TcmI protein from the tetracenomycin (TCM) C pathway in Streptomyces glaucescens, where a tricyclic anthraquinol carboxylic acid is converted to its fully aromatic tetracyclic form, the conversion catalyzed by DnrD occurs after anthraquinone formation and requires activation of a carboxylic acid group by esterification of aklanonic acid, the AAME precursor. Also, the cyclization is not coupled with a subsequent dehydration step that would result in an aromatic ring. As the substrates for the DnrD and TcmI enzymes are among the earliest isolable intermediates of aromatic polyketide biosynthesis, an understanding of the mechanism and active site topology of these proteins will allow one to determine the substrate and mechanistic parameters that are important for aromatic ring formation. In the future, these parameters may be able to be applied to some of the earlier polyketide cyclization processes that currently are difficult to study in vitro.

Base Sequence↗
PubMed1999

Species difference in simultaneous transport and metabolism of ethyl nicotinate in skin.

The objective of this research was to compare the characteristics of skin permeation and metabolism of ethyl nicotinate (EN) among humans and several animal models. In vitro simultaneous skin permeation and metabolism experiment of EN was done in side by side diffusion cells at 37 degrees C. An EN hydrolysis experiment was carried out using skin homogenate and kinetic parameters (Vmax and K(m)) were estimated by computer data-fitting to Michaelis-Menten equation. Both EN and a metabolite, nicotinic acid (NA), were detected in all receiver solutions in permeation studies and no significant chemical hydrolysis was found, indicating that enzymatic hydrolysis of EN occurred during the skin permeation process. Difference in total (EN + NA) flux, from EN-saturated solution, was less than double among various species. The ratio of NA flux to total flux was highest for rat (0.94) followed by hairless rat, mouse, human and hairless mouse (0.76, 0.23, 0.19 and 0.13), and thus a great species difference was found in skin esterase activity. Total flux increased linearly with increase in donor concentration for all species. For hairless rat, mouse and hairless mouse, NA fluxes increased with increase in EN donor concentration and reached a plateau, suggesting that metabolic saturation occurred in skin. Species difference in NA fluxes and EN donor concentration in which the NA flux reached a plateau were also found. In rats, kinetic parameters for EN hydrolysis using skin homogenate were significantly higher than those in mice. These results suggest that species difference in permeation profiles of EN might primarily reflect the difference in esterase activity. To predict skin permeability in human using an animal model, the species difference in skin metabolism should be taken into consideration.

Animals↗
PubMed1999

Enzymological and molecular biological studies on anandamide amidohydrolase.

Previously we suggested that anandamide amidohydrolase partially purified from porcine brain catalyzed the anandamide synthesis. The reversibility of the anandamide hydrolytic reaction was confirmed with a recombinant enzyme of rat liver. We also showed that the recombinant enzyme had a wide substrate specificity hydrolyzing primary amides and esters of fatty acids in addition to anandamide. When the organ distribution of anandamide amidohydrolase was examined with rats, a large amount of the enzyme was contained in small intestine as well as liver and brain. The intestinal hydrolase was masked by endogenous lipid inhibitors. The enzyme was also found in various eye tissues.

Amidohydrolases↗
PubMed1999

Slow evolutionary rate of GB virus C/hepatitis G virus.

With the aim of elucidating evolutionary features of GB virus C/hepatitis G virus (GBV-C/HGV), molecular evolutionary analyses were conducted using the entire coding region of this virus. In particular, the rate of nucleotide substitution for this virus was estimated to be less than 9.0 x 10(-6) per site per year, which was much slower than those for other RNA viruses. The phylogenetic tree reconstructed for GBV-C/HGV, by using GB virus A (GBV-A) as outgroup, indicated that there were three major clusters (the HG, GB, and Asian types) in GBV-C/HGV, and the divergence between the ancestor of GB- and Asian-type strains and that of HG-type strains first took place more than 7000-10,000 years ago. The slow evolutionary rate for GBV-C/HGV suggested that this virus cannot escape from the immune response of the host by means of producing escape mutants, implying that it may have evolved other systems for persistent infection.

Evolution, Molecular↗
PubMed1999

Perioperative blood transfusion as a prognostic indicator in patients with hepatocellular carcinoma.

We studied the relation of perioperative blood transfusion and the outcomes in 175 patients with hepatocellular carcinoma (HCC) who underwent hepatic resection from 1986 to 1994 in our hospital. Hepatectomy was performed in 23 (13.1%) patients with and 152 (86. 9%) without blood transfusions. The cumulative cancer-free survival rates for patients who had received blood transfusion was significantly lower than that for patients who had not received blood transfusions (p = 0.003). Further examinations revealed a significant difference in cancer-free survival rates for stage I-II patients (n = 75) of HCC (p = 0.02) but not for stage III-IV patients (n = 56) (p = 0.06). Cox regression analysis for recurrence revealed that blood transfusion was the most significant prognostic indicator (p = 0.001) for recurrence in stage I-II patients but not in stage III-IV patients (p = 0.99). These results suggest that a perioperative blood transfusion may be a significant prognostic indicator for patients with HCC who had underwent hepatectomy, especially in stage I-II patients of HCC.

Adult↗