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Biomedical subjects

S Nakai

Publications and source records attributed to S Nakai.

At least 91 records · Page 5Linked to original sources
PubMed1997

Improving the thermostability of Bacillus stearothermophilus neutral protease by introducing proline into the active site helix.

A proline residue was introduced into the N-terminus (Ile140 and Asp141), the middle (Leu147) and the C-terminus (Asp153) of the active site helix of Bacillus stearothermophilus neutral protease for comparing the effects on the thermostability. Introduction of a proline residue into the N-terminus at sites 140 and 141 increased the half-survival temperature (HST) by 7.5 and 2.8 degrees C, respectively, from 68.3 degrees C of the wild-type enzyme. A proline residue at Leu147 decreased the HST by 10.2 degrees C, while no change was observed by introducing a proline residue in the C-terminus. These results were coincidental with the CD data which indicated increases in Tm values of 4.4 and 2.3 degrees C for I140P and D141P, respectively. Susceptibility to alpha-chymotrypsin hydrolysis markedly decreased in mutants I140P and D141P, while increasing in L147P. Molecular modeling suggested that glycine residues on the N-terminus side of proline residues in I140P and D141P relaxed the possible strain caused by proline introduction. The thermostability can, therefore, be explained based on changes in the molecular rigidity.

Amino Acid Sequence↗
PubMed1997

Relationship between aerobic power, blood volume, and thermoregulatory responses to exercise-heat stress.

To clarify the relationship between aerobic power (VO2max), blood volume (BV), and thermoregulatory responses to exercise-heat stress, we analyzed the cross-sectional relationship between the resting BV, plasma volume (PV), erythrocyte volume (EV), VO2max, forearm blood flow (FBF), and sweating responses during exercise in a hot environment (31 degrees C, 50% relative humidity). Twelve college-aged male subjects with a mean maximal oxygen uptake of 48 (range 42-59) mL.kg-1.min-1, a mean PV of 54 (range 42-72) mL.kg-1, a mean EV of 31 (range 23-43) mL.kg-1, and a mean BV of 85 (range 67-115) mL.kg-1 (measured by the Evans Blue dye dilution method) performed three sessions of 20-min cycle exercise at two levels of intensity (40% and 60% VO2max). The BV, PV and EV correlated positively with peak FBF (r = 0.596-0.711, P < 0.05), the increase of FBF in response to a unit rise in esophageal temperature (Tes; peak delta FBF/peak delta Tes) (r = 0.592-0.656, P < 0.05) and with total sweat loss (TSL) (r = 0.599-0.634, P < 0.05) during the exercise. The VO2max correlated with TSL during exercise at 40% VO2max (r = 0.578, P < 0.05), but not with peak FBF and peak delta FBF/peak delta Tes. The VO2max per lean body mass also showed a significant positive correlation with BV (r = 0.769, P < 0.01), PV (r = 0.706, P < 0.05), and with EV (r = 0.841, P < 0.001). The peak delta FBF/peak delta Tes was correlated positively with peak FBF (r = 0.597-0.830, P < 0.05-0.01) and negatively with peak Tes (r = 0.641-0.769, P < 0.05-0.01) during the exercise at the two levels. However, the chest sweat rate (CSR), TSL, and the increase of CSR in response to a unit rise in Tes (peak delta CSR/peak delta Tes) showed no correlation with peak Tes during the exercise at the two levels. These findings suggest that 1) heat dissipation responses during exercise were related more to blood volume than aerobic power and 2) skin blood flow was related more to body temperature than sweating responses during exercise under mild heat stress.

Adolescent↗
PubMed1997

New method to calculate creatinine generation rate using pre- and postdialysis creatinine concentrations.

The creatinine (Cr) generation rate reflects the muscle mass, a possible indicator of protein nutritional status. Thus, in this study, we developed equations for calculating the Cr generation rate. Depner and Daugirdas recently developed a method for determining the protein catabolic rate (PCR) from the pre- and postdialysis blood urea nitrogen concentrations. We modified their method to develop equations for calculating the total Cr generation rate from the measured predialysis Cr concentration and estimated postrebound concentration. The total Cr generation rate is defined as the sum of the intrinsic Cr generation rate and the extrinsic Cr generation rate (i.e., the generation rate of Cr derived from food). In the present study, the postrebound Cr concentration was estimated on the basis of postdialysis Cr concentration and the K/V for Cr. The intrinsic Cr generation rate was obtained by subtracting the extrinsic Cr generation rate, which was estimated on the basis of the PCR, from the total Cr generation rate calculated. The intrinsic Cr generation rate determined with this method was virtually the same as that obtained using the postrebound Cr concentration, the concentration immediately before the next hemodialysis (HD) session, and the PCR. The intrinsic Cr generation rate determined with the present method did not vary with changes in the HD prescription (i.e., with an increase in blood flow rate, a prolongation of the HD duration time, or a change in dialyzer membrane area). The present study also indicated that the intrinsic Cr generation rate decreased with age in both males and females.

Adult↗
PubMed1997

Aspirin plus either dipyridamole or ticlopidine is effective in preventing recurrent myocardial infarction. Secondary Prevention Group.

The efficacy of combining antiplatelet agents with low doses of aspirin to prevent cardiac events in patients with myocardial infarction was examined. A total of 1,083 patients with prior myocardial infarction were randomly divided into those who were (618) and were not (465) treated with antiplatelet agents, and observed for 12.5 +/- 18.5 months. Those treated with antiplatelet agents included 113 patients treated with aspirin (50 mg) plus dipyridamole (150 mg/day), 253 treated with aspirin (50 mg) plus ticlopidine (200 mg/day), and 252 treated with only 1 of the 3 antiplatelet agents. Cardiac events, including fatal or nonfatal recurrent myocardial infarction, death by congestive heart failure, and sudden death, occurred in 34 patients (7.3%) in the nontreatment group and in 19 patients (3.1%; p < 0.01) in the treatment group; odds ratio 0.40, 95% confidence interval 0.23-0.71. There were only 2 cardiac events (1.8%) in the aspirin + dipyridamole group (p < 0.05 vs nontreatment group: odds ratio 0.28: 0.08-1.03), and 5 such events (2.0%) in the aspirin + ticlopidine group (p < 0.01; odds ratio 0.28: 0.11-0.69). Subgroup analysis to exclude differences in the patients' background confirmed the efficacy of these antiplatelet agents. We conclude that combined treatment with low doses of aspirin plus either dipyridamole or ticlopidine is effective in preventing cardiac events in patients who have had prior myocardial infarction.

Aged↗
PubMed1997

Increased coronary vasomotor tone in acute myocardial infarction patients with spontaneous coronary recanalization.

To clarify the role of coronary spasm or dynamic coronary obstruction in the development of acute myocardial infarction (AMI) with spontaneous recanalization (SR), symptoms in 296 patients with AMI admitted within 24 h after the onset of chest pain were analyzed just before and after onset, and coronary angiograms were analyzed soon after onset. Patients were divided into 3 groups according to the initial angiographic findings in the infarct-related coronary artery (IRCA): group 1 comprised 172 patients with total occlusion (TIMI O); group 2 comprised 57 patients with subtotal occlusion (TIMI 1,2); and group 3 comprised 67 patients with SR (TIMI 3). The incidence of SR was 20.3% at 0-4 h after onset, 22.2% at 4-6 h, 19.7% at 6-12 h, 24.0% at 12-24 h, and 36.0% at 24 h or later. The incidence of SR did not increase significantly as time elapsed. The incidence of angina at rest and variable-threshold angina before the onset of infarction was only 16.2% in group 1, but was significantly higher in groups 2 (64.3%) and 3 (61.9%). The incidence of intermittent chest pain at onset in group 1 (8.4%) was significantly lower than in groups 2 (54.5%) and 3 (38.8%). Vasodilation of the proximal normal segment adjacent to the stenotic site of the IRCA induced by intracoronary nitroglycerin was significantly higher in groups 2 (11.7 +/- 1.2%) and 3 (20.7 +/- 2.6%) than in group 1 (4.0 +/- 0.6%). These results suggest that coronary spasm or dynamic obstruction may be involved in the pathogenesis of thrombus formation or coronary obstruction causing AMI in many Japanese patients.

Adult↗
PubMed1997

Effects of misclassification and temporal change of response in food frequency on risk ratio.

Misclassification and temporal changes of food consumption frequencies were estimated under the statistical models with some assumptions, and their effects on risk ratios were evaluated. Food frequencies of 27 items in 214 subjects were doubly measured by a questionnaire with 2 weeks interval, and those in 326 subjects were measured in 1989, 1993 and 1994. Median of probabilities of misclassification in responses among 27 food items was estimated to be 0.12. Medians of proportions of persons whose responses in 1989 were different from those after 5 years, were calculated to be 35% with misclassification and 27% without misclassification. For the true risk ratio of 3, medians of the risk ratios of dietary habits during 5 years, based on food frequencies measured at 1989, were observed to be 2.2 in case of responses with misclassification, and 1.7 in case of responses with misclassification and temporal changes. These suggested that the risk ratios of food frequencies would be seriously affected by misclassification and temporal changes in responses.

Adult↗
PubMed1997

[Response rates and non-response bias in a health-related mailed survey].

A health-related mailed survey was conducted to investigate the effect of follow-up mailings to response rates. In addition, the answer distributions among early and late respondents were compared to check non-response bias. Approximately 3,000 persons aged 40-64 were randomized into two groups; a questionnaire with four pages (twenty-two questions) was assigned to the first group, and a questionnaire with eight pages (thirty-five questions) to the second group. Both questionnaires contained questions of current health status, health-related practice, smoking status, etc. Follow-up mailings were sent twice to non-respondents. Response rates were increased from 38% to 62% by the first follow-up mail, and to 71% by the second follow-up mail. Although the length of the questionnaire did not affect response rates, response rates among the older subjects was higher than the younger subjects. Positive response to current smoking status was 10% lower among early respondents than late respondents, collected after the second follow-up mailing, and response to regular participation in physical/medical checkup was 15% higher among early respondents, whereas there were few differences for answers to other questions. Odds ratios between current health status and several health-related questions may not be biased by late response. However, increased response rates are needed to prevent non-response bias, because there were some differences in responses from follow-up mailings.

Adult↗
PubMed1996

First evidence for accumulation of protein-bound and protein-free pyrraline in human uremic plasma by mass spectrometry.

Glucose-derived advanced glycation end products (AGEs) cross-link proteins and cause various biological tissue damage. One of them, pyrraline [epsilon-2-(formyl-5-hydroxymethyl-pyrrol-1-yl) -L-norleucine], has been demonstrated by utilizing antibody to accumulate in plasma and sclerosed matrix of diabetic individuals, suggesting responsibility for diabetic complications. To elucidate the involvement of pyrraline in uremia, we examined the pyrraline levels in patients with chronic renal failure by a mass spectrometric approach. Here we show that protein-free pyrraline as well as pyrraline with binding protein are significantly increased in non-diabetic uremic plasma compared to healthy subjects. Our results suggest that circulating pyrraline could be a substance contributing to complications in uremia.

Blood Proteins↗
PubMed1996

Protective effect of lysozyme-galactomannan or lysozyme-palmitic acid conjugates against Edwardsiella tarda infection in carp, Cyprinus carpio L.

The protective effect of lysozyme-galactomannan or lysozyme-palmitic acid conjugates orally administered to carp, Cyprinus carpio L. was investigated using a virulent strain of Gram-negative Edwardsiella tarda isolated from an infected fish. Lysozyme-galactomannan conjugate was prepared through controlled Maillard reaction. Lysozyme-palmitic acid conjugate was prepared through base-catalyzed ester exchange using N-hydroxysuccinimide ester of palmitic acid. The conjugates provided substantial protection to carp infected with a Gram-negative bacteria fish pathogen E. tarda NG 8104. Lytic activities of lysozyme conjugates with galactomannan and palmitic acid were about 80 and 71% of native lysozyme using Micrococcus lysodeikticus as a substrate. Feeding with lysozyme conjugates, for 8 days, significantly enhanced fish protection against E. tarda infection. The survival rate was 30% for lysozyme-galactomannan conjugate treated fish and 20% for lysozyme-palmitic acid conjugate treated fish after 6 days cultivation while all control fish died within 3 days. On the other hand, a recovery rate of 40% after 6 days was observed in the fish group that were fed lysozyme-palmitic acid conjugate 3 and 2 h before and after E. tarda challenge, respectively, and for 6 consecutive days. The results of this work show the possibility of utilizing lysozyme conjugates with galactomannan or palmitic acid as a therapeutic for infection in fish.

Animals↗
PubMed1996

The Mfd protein of Bacillus subtilis 168 is involved in both transcription-coupled DNA repair and DNA recombination.

Inactivation of Bacillus subtilis orf1177 in an otherwise Rec+ strain reduced genetic exchange and DNA repair. When the mutation was transferred into a set of recombination-deficient and repair-deficient strains, the DNA repair and recombination ability of the double or triple mutant strains was drastically reduced. B. subtilis Orf1177 protein shares substantial homology with the Escherichia coli Mdf, RecG and UvrB proteins. In vivo analysis of UV-induced mutations suggests that Orf1177 is necessary for strand-specific DNA repair, as is the case for the E. coli MFD protein. Therefore, orf1177 and Orf1177 were termed mfd gene and Mfd protein, respectively. The purified Mfd protein has a native molecular mass of 140 kDa (expected molecular mass 133 kDa). The Mfd protein is a sequence-independent DNA binding protein with weak ATPase activity. The Mfd protein was able to displace in vitro B. subtilis or E. coli RNA polymerase stalled at a lesion. Therefore, Mfd protein appears to target the transcribed strand for repair by recognizing a stalled RNA polymerase and dissociating it from the DNA. In addition, the strong recombination-deficient phenotype of mfd- rec- strains suggest that Mfd protein is involved in homologous DNA recombination.

Amino Acid Sequence↗
PubMed1996

Thymus-dependent effects of a traditional Chinese medicine, ren-shen-yang-rong-tang (Japanese name; Ninjin-youei-to), in autoimmune MRI/MP-lpr/lpr mice.

Autoimmune MRL/lpr mice were i.p. treated with 200 mg/kg Ren-shen-yang-rong-tang (Japanese name: Ninjin-youei-to, NYT), a traditional Chinese herbal medicine (Japanese name: Kampo), from 8 weeks of age every 3 days before the onset of autoimmune disease Compared to age-matched control MRL/lpr mice, the serum IL-6 concentration in NYT-treated mice was decreased, their serum IFN-gamma concentration was increased, and the proliferative responses of whole and enriched CD4+ cells in their spleen and lymph nodes stimulated with ConA in vitro were restored. FACS analysis revealed that the rate of decreased CD4+CD8+ T-cell population in the thymus was decreased in MRL/lpr mice but recovered by NYT treatment. Further, adult thymectomized (ATX) MRL/lpr mice were treated with 200 mg/kg NYT similarly. NYT treatment prolonged the survival of sham-operated MRL/lpr mice and ameliorated their proteinuria but did not improve such autoimmune manifestations in ATX-MRL/lpr mice. These findings suggest that NYT plays an important role in the abrogation of autoimmune-prone T cell differentiation and that the therapeutic effect of NYT is dependent on the thymus in MRL/lpr mice.

Animals↗
PubMed1996

Alteration of numerical chromosomal aberrations during progression of colorectal tumors revealed by a combined fluorescence in situ hybridization and DNA ploidy analysis of intratumoral heterogeneity.

To trace the sequence of numerical chromosomal aberrations during tumor progression of colorectal tumors, we studied intratumoral heterogeneity of chromosomal copy number by a combined fluorescence in situ hybridization (FISH) and ploidy analysis. We used six formalin-fixed paraffin-embedded tumors of which the mucosal lesions were preserved. Nuclear suspensions were made from the tumor tissues that were scraped from several small regions in 100 micron thick sections. Copy number of chromosomes 1, 7, 17, and 18 were examined by FISH with centromeric repetitive probes. DNA ploidy was monitored by cytofluorometry, and was correlated to the chromosomal copy number on the smear slides of identical nuclear suspension from each tumor portion. All the tumors examined included the DNA-diploid regions in the mucosa, where cancer cells commonly showed monosomy 18 and/or trisomy 7. These chromosomal changes may be quite common early events before the occurrence of DNA-aneuploidy in the development of colorectal tumors. Three out of the 6 tumors included near-tetraploid (3.6-4.1C) cells in deeper invasive regions. Chromosomal constitution of DNA-aneuploid cells was suggested to derive from that of DNA-diploid cells through ploidy duplication with or without additional loss or gain of chromosomes.

Centromere↗
PubMed1996

Alternate repetition of short fore- and backfiltrations reduces convective albumin loss.

An effective therapeutic means to remove relatively large polypeptide uremic toxins seems to be a hemofiltration (HF) or hemodiafiltration (HDF) employing a larger-pore membrane, that is, a protein-permeable membrane. With either method, however, a significant amount of albumin will be lost into the ultrafiltrate or dialysate. Now, repetition of alternate short fore- and backfiltrations may prevent the development of the ultrafiltration-induced higher albumin concentration on the membrane surface (protein concentration polarization), where a single forefiltration time is shorter than the time needed for completion of protein concentration polarization. Since the albumin concentration on the protein-permeable membrane surface will be one of the determinants of albumin loss by convection, such HDF treatment may reduce protein loss into the dialysate. To examine this assumption, we alternately repeated short and rapid fore- and backfiltrations (push/pull HDF) through a protein-permeable membrane, each less than 1 second in duration and at each filtration volume of 15 ml, where a pyrogen-free dialysate was supplied. The present results indicated that the albumin amount lost by push/pull HDF was approximately one-third of that by conventional HDF. Nevertheless, the reduction rates of beta 2-microglobulin and myoglobin were significantly greater by push/pull HDF than by conventional HDF.

Blood Proteins↗
PubMed1996

Advantage of monitoring skin vibration as an index of arteriovenous fistular blood flow.

Monitoring of the skin vibration is disturbed little by environmental noise. Therefore, the skin vibration is more relevant than bruit on the skin by means of monitoring the fistular blood flow. Frequency analysis of the skin vibration generated by an internal arteriovenous fistula indicated two peaks of power spectral density (PSD), one in the frequency range of 4-10 Hz and the other from 100-300 Hz. The analysis of the skin vibration generated by an external fistula, however, showed only one peak in the range of 4-10 Hz and a moderate flat PSD level in the range of 100-300 Hz. The PSD level in the range of 100-300 Hz decreased dramatically or disappeared when the fistular blood flow diminshed or ceased. Therefore, the optimal frequency for monitoring skin vibration may be the range of 100-300 Hz.

Arteriovenous Fistula↗