Biomedical subjects

S Sawada

Publications and source records attributed to S Sawada.

At least 109 records · Page 6Linked to original sources

PubMed1999

Identification by subtractive hybridization of a novel insertion sequence specific for virulent strains of Porphyromonas gingivalis.

Subtractive hybridization was employed to isolate specific genes from virulent Porphyromonas gingivalis strains that are possibly related to abscess formation. The genomic DNA from the virulent strain P. gingivalis W83 was subtracted with DNA from the avirulent strain ATCC 33277. Three clones unique to strain W83 were isolated and sequenced. The cloned DNA fragments were 885, 369, and 132 bp and had slight homology with only Bacillus stearothermophilus IS5377, which is a putative transposase. The regions flanking the cloned DNA fragments were isolated and sequenced, and the gene structure around the clones was revealed. These three clones were located side-by-side in a gene reported as an outer membrane protein. The three clones interrupt the open reading frame of the outer membrane protein gene. This inserted DNA, consisting of three isolated clones, was designated IS1598, which was 1,396 bp (i.e., a 1,158-bp open reading frame) in length and was flanked by 16-bp terminal inverted repeats and a 9-bp duplicated target sequence. IS1598 was detected in P. gingivalis W83, W50, and FDC 381 by Southern hybridization. All three P. gingivalis strains have been shown to possess abscess-forming ability in animal models. However, IS1598 was not detected in avirulent strains of P. gingivalis, including ATCC 33277. The IS1598 may interrupt the synthesis of the outer membrane protein, resulting in changes in the structure of the bacterial outer membrane. The IS1598 isolated in this study is a novel insertion element which might be a specific marker for virulent P. gingivalis strains.

Amino Acid Sequence↗

PubMed1999

The regulation of CD4 and CD8 coreceptor gene expression during T cell development.

The two major subsets of T lymphocytes in the peripheral immune system, the helper and cytotoxic T cells, are defined by their expression of either the CD4 or the CD8 glycoproteins, respectively. Expression of these molecules, which serve as coreceptors by interacting specifically with either MHC class II or class I molecules, also defines discrete stages of T cell development within the thymus. Thus, CD4+ and CD8+ single-positive (SP) thymocytes arise from common progenitor double positive (DP) cells that express both CD4 and CD8, during a process known as positive selection. The molecular mechanisms underlying the developmental choice toward the helper or cytotoxic lineage remain poorly understood. Because regulation of coreceptor gene expression appears to be coupled to the phenotypic choice of the differentiating T cell, it is likely that shared signaling pathways direct CD4 and CD8 transcription and the development of an uncommited DP thymocyte toward either the helper or cytotoxic lineage. Therefore, an understanding of how CD4 and CD8 expression is regulated will not only provide insights into transcriptional control mechanisms in T cells, but may also result in the identification of molecular factors that are involved in lineage choices during T cell development. In this review, we summarize recent progress that has been made toward an understanding of how CD4 and CD8 gene expression is regulated.

Animals↗

PubMed1999

Cell cycle and LET dependence for radiation-induced mutation: a possible mechanism for reversed dose-rate effect.

A previous study of the mutagenic action of 252Cf radiation in mouse L5178Y cells showed that the mutation frequency was higher when the dose was chronic rather than acute, which was in sharp contrast to the effects reported for gamma-rays (Nakamura and Sawada, 1988). A subsequent study using synchronized cells revealed that the cells at the G2/M stage were uniquely sensitive to mutation induction by 252Cf radiation but not to gamma-rays (Tauchi et al., 1993). A long phase cell population was first subjected to conditioning gamma or 252Cf radiation doses at different dose-rates. The cell cycle distribution of these cells was then observed, and they were then exposed to 252Cf radiation, and the mutation rate was determined. The G2/M fraction increased by 3- to 4-fold when the conditioning doses (2 Gy of gamma or 1 Gy of 252Cf radiation) were delivered chronically over 10 h, but only slightly when the same doses were delivered over a 1 h period or less. Subsequent 252Cf irradiation gave higher mutation frequencies in the cells pre-irradiated with gamma-rays over a protracted period of time than in those exposed with the higher dose-rate gamma-rays. These results suggest that the radiation-induced G2 block could be at least partly (but not totally) responsible for this reverse dose-rate effect (Tauchi et al. 1996). Possible factors which cause the hyper-sensitivity of G2/M cells to mutation induction by neutrons will be discussed.

Animals↗

PubMed1999

[Mutagenicity study of gadobenate dimeglumine formulation (E7155) (3)--Micronucleus test in rat bone marrow cells].

The mutagenic potential of gadobenate dimeglumine formulation (E7155) was studied by the micronucleus test in rats. Single intraperitoneal injection of E7155 to Sprague Dawley rats at the dose of 5295.2 mg/kg (5 mmol/kg) did not induce any statistically significant increase in the frequency of micronucleate cells in the bone marrow sampled after 18, 42 and 66 hr from time of administration.

Animals↗

PubMed1999

[Mutagenicity study of gadobenate dimeglumine formulation (E7155) (2)--Chromosome aberration test with human lymphocytes in culture].

The mutagenic potential of gadobenate dimeglumine formulation (E7155) was studied by the chromosome aberration test in cultured human lymphocytes. Human lymphocytes were exposed to E7155 at 0.078-10 mM both in the presence and absence of S9 mix derived from rat livers. Three dose levels (2.5-10 mM) were selected for the metaphase analysis. E7155 induced no increase in the incidence of aberrant cells or polyploid cells in any treatments both in the presence and absence of metabolic activation. Thus, it is concluded that E7155 has shown no evidence of clastogenic or polyploidy-inducing activity under these experimental conditions.

Animals↗

PubMed1999

A novel mutation in the vasopressin V2 receptor gene in a woman with congenital nephrogenic diabetes insipidus.

A 56-year-old Japanese woman with congenital nephrogenic diabetes insipidus (CNDI) is reported. She was diagnosed with CNDI accompanied by advanced gastric cancer. After total gastrectomy, approximately 500 ml fluid per hour was necessary to prevent dehydration. Urinary volume was decreased by administration of hydrochlorothiazide. We detected a novel mutation in the vasopressin V2 receptor gene of her chromosomal DNA. A substitution from G to A was found at the 631 nucleotide position, altering codon 12 from glycine (GGG) to glutamic acid (GAG) in the first extracellular domain. This missense mutation appeared to be the cause of her resistance to arginine vasopressin.

Amino Acid Sequence↗

PubMed1999

Sickness absence due to mental disorders in Japanese workforce.

This study was conducted to elucidate sickness absence due to mental disorders in Japanese companies. Data on sickness absence taken for seven consecutive days or more at eight companies (total number of employees: 44,816) was used for the analysis. Diagnosis of mental disorders was based on medical certificates prepared by physicians. The frequency of absence due to all diseases and mental disorders was 3.0% and 0.3%, respectively. The proportion of frequency absence due to mental disorders compared to that for all diseases was 9.4%. Figures for absence prevalence were almost the same as those for frequency absence. The average length of absence due to mental disorders and non-mental disorders was 119.5 days and 47.3 days, respectively. Rate of absence days due to mental disorders compared to that for all diseases was 21.0%. Percent of sickness absenteeism was 0.4%. In one company, the proportion of frequency absence and rate of absence days due to mental disorders compared to those for all diseases had an increasing tendency over the last six years.

Absenteeism↗

PubMed1999

Saline-jet aspiration thrombectomy catheter. Clinical results in patients with venous thrombosis.

PURPOSE: To evaluate hydraulic thrombectomy using a saline-jet aspiration thrombectomy catheter in the treatment of venous thrombosis. MATERIAL AND METHODS: Ten patients underwent 12 hydraulic thrombectomy procedures using 2.7 or 4.0 mm catheters. The site of the thrombus was either central, peripheral or in portal veins. The age of the thrombi was between 2 and 60 days (mean 19.7 days). The efficacy of hydraulic thrombectomy was evaluated based on the aspirated thrombus ratio (ATR), i.e. the volume of the thrombus aspirated divided by the volume of the thrombus before thrombectomy. ATR was estimated by comparing the angiograms of the lesion before and after thrombectomy. RESULTS: Soft thrombi were usually rapidly removed. ATR was >2/3 in 3, 2/3-1/3 in 2, 1/3-0 in 4, and 0 in 1 patient. The activation time of the injector was 23-224 s (mean 102 s) and the volume of aspirated blood was 30-680 ml (mean 250 ml). Compensatory infusion of saline was performed for blood loss, and 400 ml of packed red blood cells was transfused in 1 patient. No complications of the hydraulic thrombectomy were observed. Thrombolysis or additional treatment were performed in 9 patients. CONCLUSION: Hydraulic thrombectomy using this catheter can contribute to the treatment of venous thrombosis.

Equipment Design↗

PubMed1999

Damage to DNA purified from the radioresistant prokaryote, Deinococcus radiodurans, by acid heating.

Using a highly radioresistant bacterium, Deinococcus radiodurans, the mechanism of degradation of the purified DNA molecules by heating was examined under acidic conditions. Setting the treatment temperature at 55ûC with a duration of 0 to 20 min and adjusting the pH of the cell suspension to 3, 5 or 7, cell viabilities after the treatment were compared. The survival rate decreased in proportion to the reduction of pH. DNA purified from D. radiodurans was then damaged by irradiation with gamma-rays at 0.22 kGy or 1 kGy. It was considered that the radioresistance of D. radiodurans was due to its high repair capability, rather than any specificity of DNA structure. Purified D. radiodurans DNA was resistant to heating up to 90ûC at neutral pH. However, marked DNA damage occurred when it was heated at pH values below 5.0. Then, DNA labeled with [3H]adenine was examined. Treatment at lower pH and higher temperature resulted in release of more adenine base, i.e., the purine ring, from the DNA molecules. Therefore, we assumed that the decrease in survival of D. radiodurans in vivo and damage to its DNA in vitro by acid heating were due to the release of adenine and guanine from the DNA, i.e., depurination.

Acids↗

PubMed1999

Sensitivity of shuttle vector plasmid pZ189 DNA to carbon ion beams.

The sensitivity of shuttle vector plasmid pZ189 DNA to carbon ion beams was studied under dry conditions. This plasmid contains the supF gene that can be used in mutagenesis analysis. The survival curve of the plasmid had both a shoulder and exponential parts, and showed a D10 value of about 17 kGy for both Escherichia coli wild-type and DNA repair-deficient mutant (UV-sensitive) strains. Therefore, it was assumed that the excision repair system was not effective for repairing DNA lesions induced by irradiation with carbon ion beams.

Carbon↗

PubMed1999

[Prospective study on the relationship between physical fitness and all-cause mortality in Japanese men].

This study was conducted to examine the relationship between physical fitness and all-cause mortality in Japanese men. We evaluated the physical fitness and risk for all-cause mortality of 9,986 Japanese men who were given a submaximal exercise test and a medical examination between 1982 and 1984. Physical fitness was measured using a bicycle ergometer test, and maximal oxygen uptake was estimated. The average follow-up time was 14 years, for total of 139,836 person-years of observation. There were 247 deaths during the observation period. The relative risk and 95% confidence intervals (95% CI) for all-cause mortality were obtained using the Cox proportional hazards model. Following age adjustment, and using the lowest physical fitness (quintile I) group as a reference, the hazard ratios for quintiles II through V were, 0.54 (0.39-0.77), 0.66 (0.47-0.94), 0.58 (0.39-0.86), and 0.46 (0.27-0.78), respectively. After being adjusted for age, body mass index, hypertension, and urinary protein, the hazard ratios were, 0.52 (0.37-0.73), 0.60 (0.42-0.87), 0.50 (0.33-0.75), and 0.39 (0.22-0.67), respectively. The results presented here support the hypothesis that a low level of physical fitness in an important risk factor for all-cause mortality in Japanese men.

Adult↗

PubMed1999

Preliminary investigation of resistance of plasmid DNA to neon ion beams using transformation into recipient Escherichia coli cells.

The sensitivity of the vector plasmid pKmK8 DNA to neon ion beams was studied under dry conditions. This plasmid contains the cloning vector pJKKmf(-) and a 3.6 kbp segment encoding the Escherichia coli crp gene that can be used in mutagenesis analysis. The survival curve of the plasmid indicated an exponential profile and a D10 value of about 16 kGy in the E. coli wild-type strain for DNA repair capability. This was similar to the D10 value for the shuttle vector plasmid pZ189 DNA. Therefore, it was assumed that the excision repair system in E. coli was not effective for repairing DNA lesions induced by irradiation with heavy ion beams.

DNA Damage↗

PubMed1999

Phylogenetic characterization of Centipeda periodontii, Selenomonas sputigena and Selenomonas species by 16S rRNA gene sequence analysis.

The nearly complete 16S rRNA gene sequences for oral Gram-negative anaerobic motile bacteria, Centipeda periodontii, Selenomonas sputigena and Selenomonas species (formerly S. sputigena type strain), were determined in order to unveil their relationship to other oral motile bacteria. To determine the phylogenetic characterization of these bacteria, their 16S rRNA gene sequences were obtained and compared with those from the ribosomal sequence databases previously reported. The 16S rRNA gene sequences of these bacteria were similar to those of Selenomonas ruminantium and Schwartzia succinivorans isolated from rumens, and to Pectinatus cerevisiiphilus isolated from spoiled beer. Among oral bacteria, the nucleotide sequence analysis of these bacteria revealed high nucleotide similarity to Veillonella species, whereas low similarity to oral motile bacteria such as Campylobacter species. Phylogenetic analysis clearly confirmed that C. periodontii and two Selenomonas species were classified as relatives of a group besides Selenomonas, Schwartzia, and Pectinatus species, and not as close relatives to oral motile bacteria, such as Campylobacter species. These results suggest that such oral Gram-negative anaerobic motile bacteria are close relatives of oral bacteria.

Phylogeny↗

PubMed1999

The effects of angiotensin metabolites on the regulation of coagulation and fibrinolysis in cultured rat aortic endothelial cells.

Not only angiotensin II (Ang II) but also other angiotensin metabolites such as angiotensin I (Ang I), angiotensin III (Ang III), angiotensin IV, or angiotensin 1-7 have recently been reported to have various activities. Few data, however, are available on the regulation of thrombus formation. In this study, we investigated the effects of angiotensin metabolites on the mRNA expression of tissue factor (TF), tissue factor pathway inhibitor (TFPI), plasminogen activator inhibitor-1 (PAI-1), and tissue type plasminogen activator (TPA) in cultured rat aortic endothelial cells. None of the used angiotensin metabolites altered TFPI or TPA mRNA expression levels. Ang I, Ang II, and Ang III made TF and PAI-1 mRNA inductions which were inhibited by an selective antagonist of angiotensin II type 1 receptors. These metabolites made TF predominant to TFPI or PAI-1 to TPA, and could render endothelial cells thrombogenic.

Angiotensin I↗

PubMed1998

A short-term assessment of tumor-promotion activity in the livers of rats treated with two genotoxic methylating agents: dimethylnitrosamine and methylnitrosourea.

Induction of replicative DNA synthesis (RDS) and mitoinhibitory effects were studied in the hepatocytes of F344 rats exposed in vivo to the methylating agents dimethylnitrosamine (DMN, hepatocarcinogen) and methylnitrosourea (MNU, non-hepatocarcinogen). Cytotoxicity and chromosome aberrations (CA) in rat liver were also investigated to clarify the cause of changes in RDS and mitoinhibitory effects, respectively. The animals were killed at different intervals (up to 14 days) after a single oral dose, or 1 day after 7 or 14 days of repeated oral doses. The hepatocytes were isolated and cultured with Williams' medium E to assess their RDS, mitoinhibitory effects and CA. Mitoinhibitory effects were investigated by monitoring their effect on epidermal growth factor-induced replicative DNA synthesis (EGF-induced RDS) in rat hepatocytes. Hepatotoxic effects were assessed by measuring aspartate transaminase and alanine transaminase in the plasma and by histopathological examination. In the single-dose study, DMN (20 mg/kg body weight (bw)) induced both RDS and hepatotoxicity. MNU (50 mg/kg bw) induced RDS without causing hepatotoxicity, and thus was classified as a mitogen. In the repeated-dose study, DMN (4 mg/kg bw) induced both RDS and hepatotoxicity, but MNU (10 mg/kg bw) induced neither. Both inhibition of EGF-induced RDS and induction of CA were observed in the hepatocytes of rats treated with DMN, but were not observed with MNU in both single and repeated dose studies. The mitoinhibitory effect of DMN persisted for 14 days after the single dose and time dependently increased for 14 days after repeated administration. This mitoinhibitory effect correlated positively with CA. The mitoinhibitory effect was thought to be attributable to the DNA-damaging effect that induces CA. We concluded that the differences which we found in this study between DMN and MNU contribute to the differences in their hepatocarcinogenicity. Our findings suggested that both cell proliferative and mitoinhibitory properties play an important role in tumor promotion, and measuring them may provide an ancillary index that is useful in predicting hepatocarcinogenicity.

Alanine Transaminase↗

PubMed1998

Disturbed CD4+ T cell homeostasis and in vitro HIV-1 susceptibility in transgenic mice expressing T cell line-tropic HIV-1 receptors.

T cell line-tropic (T-tropic) HIV type 1 strains enter cells by interacting with the cell-surface molecules CD4 and CXCR4. We have generated transgenic mice predominantly expressing human CD4 and CXCR4 on their CD4-positive T lymphocytes (CD4+ T cells). Their primary thymocytes are susceptible to T-tropic but not to macrophage-tropic HIV-1 infection in vitro, albeit with a viral antigen production less efficient than human peripheral blood mononuclear cells. Interestingly, even without HIV infection, transgenic mice display a CD4+ T cell depletion profile of peripheral blood reminiscent of that seen in AIDS patients. We demonstrate that CD4+ T cell trafficking in transgenic mice is biased toward bone marrow essentially due to CXCR4 overexpression, resulting in the severe loss of CD4+ T cells from circulating blood. Our data suggest that CXCR4 plays an important role in lymphocyte trafficking through tissues, especially between peripheral blood and bone marrow, participating in the regulation of lymphocyte homeostasis in these compartments. Based on these findings, we propose a hypothetical model in which the dual function of CXCR4 in HIV-1 infection and in lymphocyte trafficking may cooperatively induce progressive HIV-1 infection and CD4+ T cell decline in patients.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Assessment of diagnostic performance of quantitative flow measurements in normal subjects and patients with angiographically documented coronary artery disease by means of nitrogen-13 ammonia and positron emission tomography.

OBJECTIVES: Regional myocardial blood flow (MBF) and flow reserve measurements using nitrogen-13 (N-13) ammonia positron emission tomography (PET) were compared with quantitative coronary angiography to determine their utility in the detection of significant coronary artery disease (CAD). BACKGROUND: Dynamic PET protocols using N-13 ammonia allow regional quantification of MBF and flow reserve. To establish the diagnostic performance of this method, the sensitivity and specificity must be known for varying decision thresholds. METHODS: MBF and flow reserve for three coronary territories were determined in 20 normal subjects and 31 patients with angiographically documented CAD by means of dynamic PET and a three-compartment model for N-13 ammonia kinetics. Ten normal subjects defined the normal mean and SD of MBF and flow reserve, and 10 normal subjects were compared with patients. PET flow obtained in the territory with the most severe stenosis in each patient was correlated with the angiographic assessment of the stenosis (severity > or = 50%, > or = 70%, > or = 90%). Receiver operating characteristic (ROC) curve analysis was performed for 1.5, 2.0, 2.5, 3.0 and 4.0 SD of flow abnormalities. RESULTS: MBF and flow reserve values from the normal subjects and from territories with documented stenoses > or = 50% were significantly different (p < 0.05). A significant difference was found between normal subjects and angiographically normal territories of patients with CAD. High diagnostic accuracy and sensitivity, with moderately high specificity, were demonstrated for detection of all stenoses. CONCLUSIONS: Quantification of myocardial perfusion using dynamic PET and N-13 ammonia provides a high performance level for the detection and localization of CAD. The specificity of dynamic PET was excellent in patients with a low likelihood of CAD, whereas an abnormal flow reserve in angiographically normal territories was postulated to represent early functional abnormalities of vascular reactivity.

Adult↗

PubMed1998

Effect of antisense oligonucleotides against cholesteryl ester transfer protein on the development of atherosclerosis in cholesterol-fed rabbits.

Cholesteryl ester transfer protein (CETP) is the enzyme that facilitates the transfer of cholesteryl ester from high density lipoprotein (HDL) to apolipoprotein B (apoB)-containing lipoproteins. However, the exact role of CETP in the development of atherosclerosis has not been determined. In the present study, we examined the effect of the suppression of increased plasma CETP by intravenous injection with antisense oligodeoxynucleotides (ODNs) against CETP targeted to the liver on the development of atherosclerosis in rabbits fed a cholesterol diet. The ODNs against rabbit CETP were coupled to asialoglycoprotein (ASOR) carrier molecules, which serve as an important method to regulate liver gene expression. Twenty-two male Japanese White rabbits were used in the experiment. Eighteen animals were fed a standard rabbit chow supplemented with 0.3% cholesterol throughout the experiment for 16 weeks. At 8 weeks, they were divided into three groups (six animals in each group), among which the plasma total and HDL cholesterol concentrations did not significantly change. The control group received nothing, the sense group were injected with the sense ODNs complex, and the antisense group were injected with the antisense ODNs complex, respectively, for subsequent 8 weeks. ASOR. poly(L-lysine) ODNs complex were injected via the ear veins twice a week. Four animals were fed a standard rabbit diet for 16 weeks. The total cholesterol concentrations and the CETP mass in the animals injected with antisense ODNs were all significantly decreased in 12 and 16 weeks compared with those injected with sense ODNs and the control animals. The HDL cholesterol concentrations measured by the precipitation assay did not significantly change among the groups fed a cholesterol diet, and triglyceride concentrations did not significantly change in the four groups. However, at the end of the study, when the HDL cholesterol concentrations were measured after the isolation by ultracentrifugation and a column chromotography, they were significantly higher in the animals injected with antisense ODNs than in the animals injected with sense ODNs and in the control animals. A reduction of CETP mRNA and an increase of LDL receptor mRNA in the liver were observed in the animals injected with antisense ODNs compared with those injected with sense ODNs and the control animals. Aortic cholesterol contents and the aortic percentage lesion to total surface area were significantly lower in the animals injected with antisense ODNs than in the animals injected with sense ODNs and in the control animals. These findings showed for the first time that suppression of increased plasma CETP by the injection with antisense ODNs against CETP coupled to ASOR carrier molecules targeted to the liver could thus inhibit the atherosclerosis possibly by decreasing the plasma LDL + very low density lipoprotein (VLDL) cholesterol in cholesterol-fed rabbits.

Animals↗