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Biomedical subjects

K Suga

Publications and source records attributed to K Suga.

279 records · Page 16Linked to original sources
PubMedDate not supplied

Cancer-preventive effects of drinking green tea among a Japanese population.

BACKGROUND: Laboratory studies have revealed the cancer preventive effects of green tea, so the association between green tea consumption and cancer was examined in a human population. METHODS: The association between green tea consumption and cancer incidence was studied in our prospective cohort study of a Japanese population. We surveyed 8,552 individuals over 40 years of age living in a town in Saitama prefecture on their living habits, including daily consumption of green tea. During the 9 years of follow-up study (71,248.5 person-years), we identified a total of 384 cases of cancer in all sites. RESULTS: We found a negative association between green tea consumption and cancer incidence, especially among females drinking more than 10 cups a day. The slowdown in increase of cancer incidence with age observed among females who consumed more than 10 cups a day is consistent with the finding that increased consumption of green tea is associated with later onset of cancer. Age-standardized average annual incidence rate was significantly lower among females who consumed large amounts of green tea. Relative risk (RR) of cancer incidence was also lower among both females (RR = 0.57, 95% CI = 0.33-0.98) and males (RR = 0.68, 95% CI = 0.39-1.21) in groups with the highest consumption, although the preventive effects did not achieve statistical significance among males, even when stratified by smoking and adjusted for alcohol and dietary variables. CONCLUSION: Our epidemiological study showed that green tea has a potentially preventive effect against cancer among humans.

Adult↗
PubMedDate not supplied

Muscle pathology in Marinesco-Sjogren syndrome: a unique ultrastructural feature.

The light- and electron-microscopical findings in the skeletal muscle of a patient with Marinesco-Sjogren syndrome (MSS) are presented. Muscle biopsy specimens showed myopathy with slightly dystrophic changes including variation in fiber size, muscle fiber necrosis, regeneration and rimmed vacuole formation. Fiber type analysis with myosin ATPase staining showed a mild increase in type 2C fibers. Electron microscopy revealed autophagic vacuoles with numerous myeloid bodies, and a unique dense membranous structure associated with nuclei. We consider that this unique membranous structure is an important feature in the muscle pathology of MSS.

Biopsy↗
PubMedDate not supplied

Fluorescence polarization study of a salt bridge between a single chain Fv and its antigen ribonuclease A.

The interaction between a single chain Fv (sFv) of the monoclonal antibody 3A21 and its antigen, bovine pancreatic ribonuclease A (RNase A), was studied by site-directed mutagenesis of the hypervariable regions and fluorescence polarization analysis. The affinity constants of wild-type sFv and a mutant sFv D31A (Asp31 of heavy chain was replaced by Ala) for RNase A were found to be 2.7 x 10(7) and 4.7 x 10(6) M(-1) in PBS at pH 7.2 and 37 degrees C, respectively. Whereas the affinity constant of D31A is not affected by NaCl concentration, that of wild-type sFv is almost the same as that of D31A in the presence of more than 1 M NaCl. These results demonstrate that Asp31 of the heavy chain interacts electrostatically with a positively charged amino acid residue of RNase A.

Animals↗
PubMedDate not supplied

Amplified gene location in chromosomal DNA affected recombinant protein production and stability of amplified genes.

Previously, we established an easy and quick construction method for obtaining a stable and highly productive gene-amplified recombinant Chinese hamster ovary (CHO) cell line. With a gradual increase in methotrexate (MTX) concentration, gene-amplified cell pools had high and stable specific growth and production rates. Moreover, the phenotype of gene-amplified cells seemed to be affected by the location of the amplified gene in chromosomal DNA. We suspected that various kinds of gene-amplified cells might appear during the long-term selection to construct gene-amplified cell pools. To clarify the behavior of gene-amplified cell pools during a stepwise increase of MTX concentration, we isolated gene-amplified clones derived from gene-amplified cell pools. We compared the characteristics of isolated clones, such as the productivity of recombinant protein, stability of amplified genes, and the location of amplified genes. As a result, telomere-type clones, in which the amplified gene was located near the telomeric region, were found to be more stable and productive than other types of clones. Telomere-type clones had over 100 copies of amplified genes in the chromosomal DNA. In contrast, a large number of other types of clones had less than 10 copies of amplified genes. During long-term cultivation in the absence of MTX, in other types of clones, amplified genes rapidly decreased in the chromosomal DNA.

Animals↗
PubMedDate not supplied

Optimization of rice alpha-amylase production using temperature-sensitive mutants of Saccharomyces cerevisiae for the PHO regulatory system.

A typical example of rational system synthesis for bioproduction by the cultivation of microorganisms harboring a recombinant plasmid was studied. First, two temperature-controllable expression systems for a foreign gene in Saccharomyces cerevisiae were constructed. The promoter of the PHO84 gene, which encodes an inorganic phosphate (Pi) transporter of S. cerevisiae and is controlled by Pi concentration through the PHO regulatory system, was used. And two temperature-sensitive mutants of S. cerevisiae for the PHO regulatory system were used as the host with rice alpha-amylase expression vector. One was temperature-sensitive pho81 mutant, SH3337, and the other was temperature-sensitive pho80 mutant, YKU107. When the strain SH3337 is cultivated at a lower temperature, the rice alpha-amylase gene connected downstream of the PHO84 promoter is expressed, but at a higher temperature, it is not. Conversely, with the strain YKU107, the transcription of the rice alpha-amylase gene is induced at a higher temperature and repressed at a lower one. The optimal cultivation temperature strategies for maximum production of rice alpha-amylase in batch cultures of these two recombinant strains were then determined by the Maximum Principle using the relationships of the specific growth and specific production rates to the cultivation temperature. The optimal strategies were easy to realize and were shown to be effective for maximum product. Finally, under these maximum alpha-amylase production strategies, the alpha-amylase activities and alpha-amylase yields in terms of glucose consumption for these recombinant strains were calculated on the basis of experimental data and compared for various operation times. The study demonstrates how a foreign gene expression system can be synthesized using a temperature-sensitive mutant with a given objective and under given constraints.

Biotechnology↗
PubMedDate not supplied

Clinical study of varicocele by sequential scrotal scintigraphy.

Sequential scrotal scintigraphy was used to study testicular blood flow in 122 patients with clinically diagnosed varicocele. The sensitivity of scrotal scintigraphy was 91.7% on the whole sequential images. The late-phase image was superior in sensitivity to that of the early-phase images. The difference in time between the arrival of radioactivity in the iliac artery and in the pampiniform plexus grew shorter with increasing grade of varicocele. Time-activity curves were classified into four patterns. One type (Type 3), which was more frequently observed in grade II and grade III varicocele than grade I varicocele, showed a decreased arterial perfusion of the left side lesion. It is concluded that scintigraphic analysis using both sequential images and time-activity curves is not only highly representative of the grade of clinically palpable varicocele, but also provides a better understanding of local hemodynamics in the scrotum.

Adolescent↗
PubMedDate not supplied

Long-term culture of glutamine synthetase-transfected HepG2 cells in circulatory flow bioreactor for development of a bioartificial liver.

Glutamine synthetase (GS) is involved in an accessory pathway of ammonia removal in mammals. To develop a bioartificial liver with a human cell line, GS gene was transfected into HepG2 cells, which had no ammonia removal activity. After culturing in the presence of methionine sulfoximine (MSX), a GS inhibitor, we obtained a MSX-resistant HepG2 subline (GS-HepG2), which had amplified GS gene; ammonia removal activity was estimated to be 1/7 of that of rat primary culture hepatocytes. The cells were cultured in a circulatory flow bioreactor for 109 days, while they multiplied from 5 x 10(7) to 4 x 10(9) cells. Three days after inoculation, the ammonia level of the culture medium was lowered to a level maintained thereafter, suggesting that using recombinant cell lines for bioartificial livers enables long-term repeated treatment for hepatic failure patient. Judging from the rate of decrease in the amount of the added ammonia, the ammonia removal capability of 4 x 10(9) GS-HepG2 cells was almost equivalent to 5 x 10(8) porcine hepatocytes inoculated into the circulatory flow bioreactor. Apart from their ammonia removal activity, GS-HepG2 cells eliminated human tumor necrosis factor-alpha (TNF-alpha). Cytokine removal therefore promises to be another useful property of bioreactor cells.

Air Movements↗
PubMedDate not supplied

An attempt to add biological functions by genetic engineering in order to produce high-performance bioreactor cells for hybrid artificial liver: transfection of glutamine synthetase into Chinese hamster ovary (CHO) cell.

In the course of immortalization, hepatocyte cell lines lose their original differentiated functions, such as ammonia removal and urea formation, drug metabolism, serum protein synthesis, etc. (Enosawa et al., Cell Transplant. 5:S39-S40; 1996). With the aim of adding lost or deficient functions and producing cell lines for the bioreactor of a hybrid artificial liver, rat glutamine synthetase (GS) gene was transfected into Chinese hamster ovary (CHO) cells, because it is able to lower the ammonia level. The GS gene-inserted pSV2 plasmid was transfected into the CHO-K1 line by electroporation. Transfected CHO (GS-CHO) cells were cultured in a glutamine-free medium containing ammonia, glutamic acid, and the GS inhibitor methionine sulfoximine (MSX). The MSX concentration was increased stepwise from 25 mumol/L to 1600 mumol/L to amplify the GS gene. In several GS-CHO sublines resistant to 300-1600 mumol/L of MSX, the specific activities of GS were increased from 0.2 x 10(4) to 1.7-2.9 x 10(4) unit/10(6) cells. When the amplified GS-CHO cells were cultured in the ammonia-containing medium, a slow but steady decrease of the ammonia level was observed when the level was high. Finally, the prospect of genetically modulated cells for bioreactors in the hybrid artificial liver is discussed.

Ammonia↗