Biomedical subjects

Katsuhiro Tamura

Publications and source records attributed to Katsuhiro Tamura.

5 recordsLinked to original sources

PubMed2005

High-pressure acceleration of the growth kinetics of glucose isomerase crystals.

The growth and dissolution rates of glucose isomerase crystals ({1 0 1} face) were measured in situ at 0.1 and 100 MPa. From these data, we determined that the solubilities at 25 degrees C were C(e) = 3.1 +/- 0.9 and 2.6 +/- 0.5 mg mL(-1) at 0.1 and 100 MPa, respectively. At the same supersaturation of sigma = 2.5 (sigma identical with ln(C/C(e)), C = the concentration of glucose isomerase, C(e) = the solubility) and temperature (T = 25 degrees C), the growth rate under 100 MPa was 7.6 times larger than that under 0.1 MPa. This result shows, for the first time, a kinetic acceleration of the growth rates of protein crystals with increasing pressure. The growth rates vs sigma data fitted well with a two-dimensional nucleation growth model of a polynucleation type. The fitting results indicate that the acceleration is mainly due to the decrease in the molecular surface energy of the glucose isomerase crystal with pressure.

Aldose-Ketose Isomerases↗

PubMed2005

Effect of high-pressure gas on yeast growth.

Microcalorimetry is a useful tool for monitoring the growth behavior of microorganisms. In this study, microcalorimetry was used to investigate the effects of nitrogen, air, oxygen, nitrous oxide, argon, and krypton at high pressure on the growth of the yeast Saccharomyces cerevisiae. Growth thermograms (metabolic heat vs. incubation time) were generated to estimate metabolic activity under compressed gases and to determine the 50% inhibitory pressure (IP(50)) and minimum inhibitory pressure (MIP), which are regarded as indices of the toxicity of compressed gases. Based on MIP values, the most toxic to the least toxic gases were found to be: O(2) > N(2)O > air > Kr > N(2) > Ar.

Air Pressure↗

PubMed2004

Bioassay of various pesticides by microcalorimetry measuring the metabolic heat of yeast.

Using a microcalorimeter, the heat evolved during incubation of yeast cultures at 30 degrees C was detected in the form of a growth thermogram (metabolic heat-incubation time curve). The correlation between the growth thermograms and the growth curves obtained by colony counting or from the turbidity measurements of the cultures was very good. In this study, the effects of 12 pesticides that are used widely on golf courses on the growth thermograms of yeast were investigated and the inhibitory action of the pesticides on the growth of yeast was quantitatively evaluated using a microcalorimeter (Biothermo Analyzer). The growth thermograms were applied to estimate the microbial activity of yeast in the presence of pesticide and to determine the 50% inhibitory concentration (K) and minimum inhibitory concentration (MIC), which can be regarded as good indexes of the toxic potency of pesticides. It was found that the addition of TPN, captan, thiuram and copper oxide to the yeast cultures clearly induced inhibitory action on the growth of yeast cells. On the other hand, the other 8 pesticides, iprodione, isoprothiorane, chloroneb, pencycuron, metalaxyl, toleclofos-methyl, flutolanil, and mepronil did not affect the growth over the concentration range up to 30 mg/l.

Biological Assay↗

PubMed2002

Protein crystallization under high pressure.

Pressure is expected to be an important parameter to control protein crystallization, since hydrostatic pressure affects the whole system uniformly and can be changed very rapidly. So far, a lot of studies on protein crystallization have been done. Solubility of protein depends on pressure. For instance, the solubility of tetragonal lysozyme crystal increased with increasing pressure, while that of orthorhombic crystal decreased. The solubility of subtilisin increased with increasing pressure. Crystal growth rates of protein also depend on pressure. The growth rate of glucose isomerase was significantly enhanced with increasing pressure. The growth rate of tetragonal lysozyme crystal and subtilisin decreased with increasing pressure. To study the effects of pressure on the crystallization more precisely and systematically, hen egg white lysozyme is the most suitable protein at this stage, since a lot of data can be used. We focused on growth kinetics under high pressure, since extensive studies on growth kinetics have already been done at atmospheric pressure, and almost all of them have explained the growth mechanisms well. The growth rates of tetragonal lysozyme decreased with pressure under the same supersaturation. This means that the surface growth kinetics significantly depends on pressure. By analyzing the dependence of supersaturation on growth rate, it was found that the increase in average ledge surface energy of the two-dimensional nuclei with pressure explained the decrease in growth rate. At this stage, it is not clear whether the increase in surface energy with increasing pressure is the main reason or not. Fundamental studies on protein crystallization under high pressure will be useful for high pressure crystallography and high pressure protein science.

Animals↗

PubMed1999

Oral UFT (uracil plus futrafur) for neoadjuvant chemotherapy of gastric cancer.

BACKGROUND: Neoadjuvant chemotherapy has become one of the topics of interest in chemotherapy of gastric cancer; the present study assessed the clinical benefits of neoadjuvant chemotherapy with oral uracil and futrafur (UFT) for gastric cancer.METHODS: Between 1991 and 1997, 82 patients with gastric cancer (36 with early and 46 with advanced cancers) received UFT at 300-600 mg/day orally for 1-6 weeks before surgery. Objective responses, histological effects, and postsurgical survival rates were assessed.RESULTS: In 69 of the 82 patients, the objective responses of the primary lesions were assessed by endoscopy or upper gastrointestinal series examination, and 2 complete responses (CR)s, 25 partial responses (PRs), and 42 no changes (NCs) were seen (39.1% response). Histological effects were evaluated in 82 patients, and 2 grade 3, 11 grade 2, 11 grade 1b, 27 grade 1a, and 31 grade 0 effects were seen. A longer period of UFT administration was associated with a CR or PR. However, the objective responses did not correlate with the histological effects. All the patients underwent gastrectomy, and during the median follow-up period of 41 months, 3-year survival rates were 97.1% for pTNM stage 1, 75% for stage 2, 86.7% for stage 3, and 41.6% for stage 4. The survival rates of stage 3 and stage 4 patients were higher than those of the historical controls in our department. However, CR or PR did not correlate with the improvement in survival. Side effects before surgery were not serious; they included slight myelotoxicity, liver dysfunction, and anorexia; however, 3 patients (3.7%) had suture insufficiency, 3 patients (3.7%) had methicillin-resistant Staphylococcus aureus (MRSA) enteritis, and 7 patients (8.5%) had liver dysfunction.CONCLUSIONS: Preoperative chemotherapy for gastric cancer with oral UFT was safe and resulted in a good local response (macro- and microscopically) which may indicate the possibility of improved survival with neoadjuvant chemotherapy with UFT. Furthermore, preoperative chemotherapy with oral UFT is easy and patients can receive this treatment on an outpatient basis.

Journal Article↗