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Biomedical subjects

M Takata

Publications and source records attributed to M Takata.

At least 73 records · Page 4Linked to original sources
PubMed2000

Mutant DnaA proteins defective in duplex opening of oriC, the origin of chromosomal DNA replication in Escherichia coli.

We characterized three mutant DnaA proteins with an amino acid substitution of R334H, R342H and E361G that renders chromosomal replication cold (20 degrees C) sensitive. Each mutant DnaA protein was highly purified from overproducers, and replication activities were assayed in in vitro oriC replication systems. At 30 degrees C, all three mutant proteins exhibited specific activity similar to that seen with the wild-type protein, whereas at 20 degrees C, there was much less activity in a replication system using a crude replicative extract. Regarding the affinity for ATP, the dissociation rate of bound ATP and binding to oriC DNA, the three mutant DnaA proteins showed a capacity indistinguishable from that of the wild-type DnaA protein. Activity for oriC DNA unwinding of the two mutant DnaA proteins, R334H and R342H, was more sensitive to low temperature than that of the wild-type DnaA protein. We propose that R334H and R342H have a defect in their potential to unwind oriC DNA at low temperatures, the result being the cold-sensitive phenotype in oriC DNA replication. The two amino acid residues of DnaA protein, located in a motif homologous to that of NtrC protein, may play a role in the formation of the open complex. The E361 residue may be related to interaction with another protein present in a crude cell extract.

Adenosine Triphosphate↗
PubMed2000

Clinicopathologic analysis of stage II-III hepatocellular carcinoma showing early massive recurrence after liver resection.

BACKGROUND AND AIMS: Prognosis after hepatectomy for hepatocellular carcinoma (HCC) has been improved by progress in the evaluation of hepatic functional reserve, surgical techniques and perioperative management. However, even when curative resection is performed at a relatively early stage, a considerable number of patients develop early intrahepatic and/or extrahepatic recurrence postoperatively. This study analyzed the clinicopathologic features of HCC with early recurrence. METHODS: We reviewed records of 513 consecutive patients who had undergone liver resection for HCC. There were 48 deaths within a year after surgery from recurrence, including 21 patients with stage II or III HCC (group I). Clinicopathologic parameters of group I patients were compared with those of 188 patients (group II) who developed recurrence following resection of stage II or III HCC and died more than 1 year after surgery. RESULTS: On univariate analysis, age, tumor diameter (phi), alpha-fetoprotein (AFP):phi and protein induced by vitamin K absence or antagonist II (PIVKA-II):phi were significantly greater in group I than in group II. Macroscopic portal vein invasion, microscopic vascular invasion, intrahepatic metastasis, poor differentiation, pleomorphism, sarcomatous change, vascular lake, and angiographic condensed pooling were more frequently observed in group I than group II. Five independent determinants were selected by multivariate analysis: AFP:phi, histologic pleomorphism, sarcomatous change, vascular lake and angiographic condensed pooling. CONCLUSIONS: Highly malignant HCC with extremely poor prognosis exhibits peculiar clinicopathologic characteristics, particularly histologic immaturity, and can be predicted by preoperative indicators such as markedly elevated tumor marker concentrations and condensed pooling on angiography.

Aged↗
PubMed2000

GnRH agonist-suppressed expression of nitric oxide synthases and generation of peroxynitrite in adenomyosis.

Because overproduction of nitric oxide (NO) and peroxynitrite is known to cause tissue injury, the expression of NO synthases (NOS) and generation of peroxynitrite were investigated in adenomyosis. Immunoreactivities to endothelial and inducible NOS demonstrated phase-dependent changes in normal endometrium, and in eutopic endometrium of adenomyosis. However, NOS were expressed throughout the menstrual cycle in ectopic endometrium from the majority of patients with adenomyosis. Nitrotyrosine, a footprint of peroxynitrite, was detected concomitantly with NOS protein. This suggested that high doses of NO and superoxide are produced in the ectopic endometrium, presumably by stimulation with bioactive molecules such as cytokines and growth factors. The expression of NOS and generation of peroxynitrite were markedly reduced by administration of gonadotrophin-releasing hormone agonists (GnRHa). The suppression of serum concentrations of nitrite/nitrate, stable metabolites of NO, by long-term administration of GnRHa was also demonstrated. The suppression of synthesis of NO and/or peroxynitrite may be part of both the therapeutic and adverse effects of GnRHa therapy.

Adult↗
PubMed2000

What patients can survive disease free after complete resection for hepatocellular carcinoma?: A multivariate analysis.

BACKGROUND: Although there have been extensive studies to determine risk factors affecting survival after resection for hepatocellular carcinoma (HCC), we still do not know which patients can survive disease free after curative resection. This study was undertaken to determine independent risk factors affecting the length of disease-free survival. METHODS: 171 patients, who survived disease free more than 1 year after curative resection, were divided into four groups according to the disease-free period: Group I (n = 96) for the patients with intrahepatic recurrence between 1 and 3 postoperative years, Group II(n = 27) for those between 3 and 5 years, Group III (n = 40) for those between 5 and 10 years and Group IV (n = 8) for those without recurrence within 10 years. The 37 variables (host factors, tumor factors, non-tumor liver factors, surgical factors) were compared among the four groups. Activity of hepatitis and hepatic fibrosis was scored by the Histological Activity Index (HAI). In a multivariate study, possible prognostic variables with a statistical difference in the disease-free survival rate among each category were preliminarily selected from the 37 variables and the independent variables were finally selected using a proportional hazard analysis. RESULTS: The patients' age, indocyanine green retention rate, microscopic tumor capsular invasion and portal invasion, cell differentiation, extent of hepatectomy, aggressiveness of chronic hepatitis and inflammatory activity assessed by HAI score were significantly different among the four groups. In the multivariate analysis, the following variables were selected as the independent determinants favorable for achieving a longer disease-free period: younger age, lower indocyanine green retention rate, solitary HCC with expansive growth, no microscopic portal invasion and lower activity of co-existing hepatitis. CONCLUSIONS: The importance of inflammatory activity in addition to aging, hepatic reserve and tumor characteristics was confirmed as a risk factor for recurrence by multivariate analysis. To achieve better disease-free survival, not only early detection but also suppression of co-existing hepatitis is necessary.

Aged↗
PubMed2000

The Rad51 paralog Rad51B promotes homologous recombinational repair.

The highly conserved Saccharomyces cerevisiae Rad51 protein plays a central role in both mitotic and meiotic homologous DNA recombination. Seven members of the Rad51 family have been identified in vertebrate cells, including Rad51, Dmc1, and five Rad51-related proteins referred to as Rad51 paralogs, which share 20 to 30% sequence identity with Rad51. In chicken B lymphocyte DT40 cells, we generated a mutant with RAD51B/RAD51L1, a member of the Rad51 family, knocked out. RAD51B(-/-) cells are viable, although spontaneous chromosomal aberrations kill about 20% of the cells in each cell cycle. Rad51B deficiency impairs homologous recombinational repair (HRR), as measured by targeted integration, sister chromatid exchange, and intragenic recombination at the immunoglobulin locus. RAD51B(-/-) cells are quite sensitive to the cross-linking agents cisplatin and mitomycin C and mildly sensitive to gamma-rays. The formation of damage-induced Rad51 nuclear foci is much reduced in RAD51B(-/-) cells, suggesting that Rad51B promotes the assembly of Rad51 nucleoprotein filaments during HRR. These findings show that Rad51B is important for repairing various types of DNA lesions and maintaining chromosome integrity.

Amino Acid Sequence↗
PubMed2000

Renal structural properties in prehypertensive Dahl salt-sensitive rats.

In 10- to 12-week-old Dahl salt-sensitive (DS) and salt-resistant (DR) rats fed a 0.3% salt diet (n=10 in each group), flow-pressure and pressure-glomerular filtration rate (F-P and P-GFR, respectively) relationships were established for maximally vasodilated perfused kidneys. From these relationships, 3 indices of vascular structural properties were estimated: slope of F-P (minimal renal vascular resistance reflecting overall luminal dimensions of preglomerular and postglomerular vasculature), slope of P-GFR (glomerular filtration capability against pressure), and threshold pressure for beginning filtration at P-GFR (preglomerular-to-postglomerular vascular resistance ratio). Thereafter, maximal renal vascular resistance was determined to assess wall-to-lumen ratios of the resistance vessels in half of each group. In the remainder, the kidneys were perfusion-fixed for histological analysis. Mean arterial pressure did not differ between the DS and DR rats. There were no significant differences in the slopes of F-P between the 2 groups. In contrast, the slope of P-GFR was significantly lower (33%) in DS rats than in DR rats, although the DS kidneys began filtering at a threshold pressure similar to that of the DR kidneys. Thus, in DS rats, there were no abnormalities in luminal dimensions at preglomerular and postglomerular vascular segments, but the kidney filtration capacity decreased at any given increase in pressure. Maximal vascular resistance was greater in DS than in DR rats, a finding compatible with the histological appearance, which showed vascular hypertrophy with little, if any, vascular narrowing in the interlobular arteries of DS rats. In conclusion, hypertrophic remodeling without vascular narrowing at preglomerular resistance vessels and structural defects in filtering at the glomeruli could occur in prehypertensive DS rats.

Animals↗
PubMed2000

Tumor-like splenic extramedullary hematopoiesis in a patient with myelofibrosis.

A 61-year-old woman, who was diagnosed in 1982 as having polycythemia vera, was admitted to our hospital in July 1998 because of a splenic tumor in an enlarged spleen due to myelofibrosis. As it was difficult to identify the etiology of the splenic tumor, partial splenectomy was carried out. The resected tumor proved to be an extremely proliferative lesion as the result of extramedullary hematopoiesis. Since it is difficult to diagnose the etiology of splenic tumor, the collection and analysis of reports of relevant cases may well facilitate diagnosis.

Diagnosis, Differential↗
PubMed2000

[Nevoid basal cell carcinoma syndrome].

The nevoid basal cell carcinoma syndrome is an autosomal dominant disorder characterized by multiple cutaneous basal cell carcinomas, jaw keratocysts and a variety of other tumours, and developmental abnormalities. Recently, this syndrome was shown to result from germ line mutations in human patched(PTC) gene, which encodes a membrane receptor and functions as an important developmental regulator and a tumour suppressor. Haploinsufficiency for the PTC locus is likely to give rise to developmental abnormalities characterized by symmetrical defects and malformed spine and ribs. Postnatal loss of the normal PTC allele leads to multiple basal cell carcinomas and other cancers. PTC mutations and loss of the remaining wild-type allele have also been identified in sporadic basal cell carcinomas and meduloblastomas.

Animals↗
PubMed1999

Mre11 is essential for the maintenance of chromosomal DNA in vertebrate cells.

Yeast Mre11 functions with Rad50 and Xrs2 in a complex that has pivotal roles in homologous recombination (HR) and non-homologous end-joining (NHEJ) DNA double-strand break (DSB) repair pathways. Vertebrate Mre11 is essential. Conditionally, MRE11 null chicken DT40 cells accumulate chromosome breaks and die upon Mre11 repression, showing frequent centrosome amplification. Mre11 deficiency also causes increased radiosensitivity and strongly reduced targeted integration frequencies. Mre11 is, therefore, crucial for HR and essential in mitosis through its role in chromosome maintenance by recombinational repair. Surprisingly perhaps, given the role of Mre11 in yeast NHEJ, disruption of NHEJ by deletion of KU70 greatly exacerbates the effects of MRE11 deficiency, revealing a significant Mre11-independent component of metazoan NHEJ.

Animals↗
PubMed1999

Requirement for Akt (protein kinase B) in insulin-induced activation of glycogen synthase and phosphorylation of 4E-BP1 (PHAS-1).

The roles of Akt (protein kinase B) and the atypical lambda isoform of protein kinase C (PKClambda), both of which act downstream of phosphoinositide 3-kinase, in the activation of glycogen synthase and phosphorylation of 4E-BP1 (PHAS-1) in response to insulin were investigated. A mutant Akt (Akt-AA) in which the phosphorylation sites targeted by growth factors are replaced by alanine was shown to inhibit insulin-induced activation of both Akt and glycogen synthase in L6 myotubes. Expression of a mutant Akt in which Lys179 in the kinase domain was replaced by aspartate also inhibited insulin-induced activation of glycogen synthase but had no effect on insulin activation of endogenous Akt. A kinase-defective mutant of PKClambda (lambdaDeltaNKD), which prevents insulin-induced activation of PKClambda, did not affect the activation of glycogen synthase by insulin. Insulin-induced phosphorylation of 4E-BP1 was inhibited by Akt-AA in Chinese hamster ovary cells. However, lambdaDeltaNKD had no effect on 4E-BP1 phosphorylation induced by insulin. These data suggest that Akt, but not PKClambda, is required for insulin activation of glycogen synthase and for insulin-induced phosphorylation of 4E-BP1.

Amino Acid Sequence↗
PubMed1999

p16INK4a inactivation is not frequent in uncultured sporadic primary cutaneous melanoma.

In an attempt to examine whether the inactivation of p16INK4a is an important early event in the development of sporadic melanoma in vivo, we have systematically analysed 46 uncultured primary cutaneous melanomas. Loss of heterozygosity (LOH) of chromosome region 9p21-22 (where the p16INK4a resides) was detected in 11 tumours (24%) by PCR-based LOH analyses. Direct sequencing of all three exons of the p16INK4a gene in these 11 tumours revealed no somatic mutation although germline mutations which have not been reported previously as common polymorphisms were detected in two patients. Further sequencing analyses of the p16INK4a gene exon 2 in 19 additional tumours with no evidence of LOH on 9p21-22 identified only one heterozygous C- >T mutation at codon 81 altering a proline to a leucine. A sensitive methylation-specific PCR assay did not reveal de novo methylation of the 5'CpG island in exon 1 of the p16INK4a gene in any of the tumours showing 9p21-22 allelic loss or a heterozygous p16INK4a mutation. Complete loss of p16INK4a protein, most likely due to homozygous deletion of the p16INK4a gene, was observed in 6 (15%) out of 39 evaluable cases by immunohistochemical analyses on frozen sections using two different anti-p16INK4a antibodies. The results show that inactivation of p16INK4a is not as frequent in primary melanoma as has been reported in cell lines, and warrant further search for another tumour suppressor on 9p21-22. This study also emphasizes the importance of examining uncultured primary tumours rather than cell lines to define early events in tumorigenesis.

Chromosomes, Human, Pair 9↗
PubMed1999

Joint effects of HMG-CoA reductase inhibitors and eicosapentaenoic acids on serum lipid profile and plasma fatty acid concentrations in patients with hyperlipidemia.

HMG-CoA reductase inhibitors reduce serum total cholesterol concentrations and the risk of coronary heart disease in patients with hypercholesterolemia. Recently, it has been reported that patients with combined hyperlipidemia are also at risk of coronary heart disease. However, HMG-CoA reductase inhibitor therapy alone does not sufficiently reduce serum triglyceride concentrations. Epidemiological and clinical evidence has shown that fish oil can lower plasma lipid levels, especially triglycerides. Consequently, we investigated the effects of the combination of HMG-CoA reductase inhibitors and eicosapentaenoic acid, a major component of fish oil, on hyperlipidemia. We administered 900-1,800 mg/day of the ethyl ester of eicosapentaenoic acid to patients with hyperlipidemia who had been treated with HMG-CoA reductase inhibitors for 30 +/- 6 months (means +/- SE). Serum total cholesterol and triglyceride concentrations were significantly decreased 3 months after the administration of eicosapentaenoic acid (from 5.63 +/- 0.23 mmol/l to 5.02 +/- 0.20 mmol/l, P < 0.05; from 2.07 +/- 0.41 mmol/l to 1.08 +/- 0.17 mmol/l, P < 0.01, respectively). Serum high-density lipoprotein-cholesterol concentrations were significantly increased after the treatment (from 1.23 +/- 0.12 mmol/l to 1.34 +/- 0.13 mmol/l, P < 0.05). Plasma eicosapentaenoic acid concentrations and the ratio to arachidonic acid in plasma were also significantly increased 3 months after the treatment (from 101.9 +/- 8.1 mg/l to 181.8 +/- 23.9 mg/l, P < 0.001; from 0.640 +/- 0.075 to 1.211 +/- 0.170, P < 0.001, respectively). These results suggested that the combination therapy of HMG-CoA reductase inhibitors and eicosapentaenoic acid was effective for patients with hyperlipidemia.

Aged↗
PubMed1999

The effect of left-to-right shunting on coronary oxygenation during extracorporeal membrane oxygenation.

BACKGROUND/PURPOSE: Blood perfusion to the coronary artery (CA) during venoarterial (VA) extracorporeal membrane oxygenation (ECMO) was examined to determine whether it was receiving highly oxygenated ECMO blood or desaturated blood from the pulmonary circulation of diseased lungs. METHODS: In the first experiment, left ventricle output and oxygen saturation in the left ventricle (LV) and CA were measured in dogs placed on VA ECMO. In the second experiment, dogs with an artificial subclavian-pulmonary artery shunt were placed on VA ECMO at 100 mL/kg/min, and oxygen saturation was measured as the shunt flow increased. RESULTS: Without an artificial shunt, a substantial portion of coronary perfusion was found to be supplied by the left ventricle (54 + 30%), even at a high ECMO flow rate of 100 mL/kg/min and low LV output (22+/-17%) relative to ECMO flow. With a shunt, oxygen saturation in the CA was more than 95%, even when shunt flow was only 7.5% of ECMO flow and output from the left ventricle was less than 25% of the ECMO flow rate. CONCLUSIONS: These results suggest that an excessive "lung rest" strategy during VA ECMO may produce suboptimal coronary oxygenation possibly leading to myocardial damage. The presence of a small left-to-right shunt may prevent coronary hypoxia.

Animals↗
PubMed1999

Inhibition of styloglossus motoneurons during the palatally induced jaw-closing reflex.

The inhibition of hypoglossal motoneurons innervating the styloglossus muscle during transient jaw closing, the so-called jaw-closing reflex, was studied in cats. The application of diffuse pressure stimulation to the posterior palatal surface produced the jaw-closing reflex and inhibitory postsynaptic potentials in the styloglossus motoneurons, indicating that mechanosensory inputs from the posterior palatal mucosa sent inhibitory synaptic inputs to styloglossus motoneurons. We also demonstrated that, during the palatally induced jaw-closing reflex, the tongue extended at jaw closure and was still extended forward in the initial part of the opening phase. In all of 22 styloglossus motoneurons studied, the depression of firing was elicited after the onset of jaw closure. In 14 of 22 styloglossus motoneurons, the depression of firing was elicited in the closing phase, and in the remaining cells it was elicited in the occlusal phase. By increasing the intracellular concentration of chloride ions, the inhibitory postsynaptic potential elicited in the styloglossus motoneuron converted to a depolarizing potential. It is concluded that the inhibition of styloglossus motoneurons may be involved in the maintenance of tongue protrusions during the palatally induced jaw-closing reflex, and that inhibitory postsynaptic potentials evoked in the styloglossus motoneurons are partly due to a chloride-dependent inhibitory postsynaptic potential.

Animals↗
PubMed1999

Relation of plasma brain and atrial natriuretic peptides to left ventricular geometric patterns in essential hypertension.

We investigated whether plasma brain and atrial natriuretic peptide (BNP and ANP, respectively) levels could reflect left ventricular (LV) geometry and function in patients with mild to moderate essential hypertension. A positive correlation was found between LV mass index (LVMI) and plasma ANP levels in 84 untreated, hypertensive patients, but not between LVMI and plasma BNP levels. As compared with other geometric patterns, plasma BNP levels were increased in concentric hypertrophy, in which LVMI was increased and LV diastolic function was decreased. These data suggest that production of BNP was increased in hypertensive patients with concentric hypertrophy via LV overload or depression of diastolic function.

Adult↗
PubMed1999

Different platelet aggregability during mental stress in two stages of essential hypertension.

To determine whether platelet response to mental stress is altered in essential hypertension, platelet aggregability and plasma beta-thromboglobulin were determined in 24 patients with essential hypertension (11 patients with World Health Organization (WHO) stage I and 13 patients with stage II) and 14 normotensive controls before and after a 10-min arithmetic stress (serial subtraction of 7 from 1000). In normotensive subjects, arithmetic stress did not affect primary aggregations to 1.0 micromol/L adenosine diphosphate (ADP) and to 2.5 micromol/L 5-hydroxytryptamine (5-HT), ADP threshold for biphasic aggregation and plasma beta-thromboglobulin level. In hypertensive patients with WHO stage I, these parameters were similar to those in normotensives before arithmetic stress, but the arithmetic stress test significantly increased primary aggregation to reagents and beta-thromboglobulin level, and decreased threshold of ADP for biphasic aggregation. In WHO stage II patients, platelet aggregability to reagents and beta-thromboglobulin level were already enhanced as compared with WHO stage I patients and normotensive subjects before arithmetic stress. However, the stress-induced changes in platelet function were less pronounced in WHO stage II patients compared with stage I patients. In conclusion, platelet aggregability and proaggregatory effect of mental stress differed depending on the severity of hypertension in patients with essential hypertension; the transient activation of platelet function during stress with no enhancement under the resting condition in the early phase of hypertension and the continuous activation of platelet function in the advanced phase with hypertensive organ damage.

Adenosine Diphosphate↗