Search PubMed⌕ Search

Biomedical subjects

T Imoto

Publications and source records attributed to T Imoto.

227 records · Page 13Linked to original sources
PubMedDate not supplied

Severe endurance training fails to change myosin heavy-chain distribution of diaphragm.

Histochemical analysis by Green et al. (1989) revealed that severe endurance training caused a transformation from type IIA to type IIB fibres in the costal diaphragm region of the rat. With the use of the electrophoretic method, in the current study, it was re-examined whether such a change was brought about in this respiration muscle. The animals were capable of running for 240 min/day at 40 m/min during the final phase of a 16-week training program. Four heavy-chain (HC) isoforms were separated by a single percentage polyacrylamide gel electrophoresis of extracts from muscles. Densitometric analysis of these HC isoforms revealed that exercise training failed to change the relative distribution of any HC isoforms in the diaphragm.

Animals↗
PubMedDate not supplied

Construction of a plasmid vector for the regulatable high level expression of eukaryotic genes in Escherichia coli: an application to overproduction of chicken lysozyme.

A novel expression vector pKP1500 for synthesizing unfused protein in Escherichia coli was constructed. pKP1500 perserves the tac promoter, the lacZ SD sequence, unique restriction sites (EcoRI, SmaI, BamHI, SalI, PstI and HindIII) and the rrnB terminators of pKK223-3, but the replication origin is replaced with that of pUC9. Construction of this plasmid is based upon the observation that the copy number control of pUC9 is temperature dependent. At 28 degrees C, the copy number of pKP1500 is less than 25 per chromosome, approximately the same copy number as that of pKK223-3, which contains the replication origin of pBR322, whereas at 42 degrees C, the copy number increases about 10 times and reaches up to 230 copies per chromosome. The main advantage of this system is that the temperature-dependent copy control and regulatable expression of the tac promoter make cells carrying pKP1500 derivatives stable against selective pressure by detrimental overproduction of foreign proteins at a low temperature and permits high expression of cloned DNAs at a high temperature. When chicken lysozyme cDNA carrying the initiation codon (ATG) immediately upstream from the Lys1 codon was inserted downstream from the tac promoter and the SD sequence, the pKP1500 derivative produced lysozyme at about 25% of the total cellular proteins. This value is more than 10 times higher than that obtained with the pKK223-3 derivative carrying the same lysozyme cDNA. By comparison, the expression of eukaryotic genes from the tac promoter reported by others has usually been less than a few % of the total cellular protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Point mutation of alanine (31) to valine prohibits the folding of reduced lysozyme by sulfhydryl-disulfide interchange.

In the preceding paper in this issue, we described the overproduction of one mutant chicken lysozyme in Escherichia coli. Since this lysozyme contained two amino acid substitutions (Ala31----Val and Asn106----Ser) in addition to an extra methionine residue at the NH2-terminus, the substituted amino acid residues were converted back to the original ones by means of oligonucleotide-directed site-specific mutagenesis and in vitro recombination. Thus, four kinds of chicken lysozyme [Met-1Val31Ser106-, Met-1Ser106-, Met-1Val31- and Met-1 (wild type)] were expressed in E. coli. From the results of folding experiments of the reduced lysozymes by sulfhydryl-disulfide interchange at pH 8.0 and 38 degrees C, followed by the specific activity measurements of the folded enzymes, the following conclusions can be drawn: (i) an extra methionine residue at the NH2-terminus reduces the folding rate but does not affect the lysozyme activity of the folded enzyme; (ii) the substitution of Asn106 by Ser decreases the activity to 58% of that of intact native lysozyme without changing the folding rate; and (iii) the substitution of Ala31 Val prohibits the correct folding of lysozyme. Since the wild type enzyme (Met-1-lysozyme) was activated in vitro without loss of specific activity, the systems described in this study (mutagenesis, overproduction, purification and folding of inactive mutant lysozymes) may be useful in the study of folding pathways, expression of biological activity and stability of lysozyme.

Alanine↗
PubMedDate not supplied

Alkalinizing water-soluble local anesthetic solutions by addition of cyclodextrin.

BACKGROUND AND OBJECTIVES: The use of sodium bicarbonate for alkalinization of local anesthetics to improve their efficacy has some disadvantages including decreased stability of the solutions. The present study was performed to evaluate usefulness of cyclodextrins (CDs) in improving the solubility and stability of local anesthetic solutions at near physiologic pH without precipitation. METHODS: Solubility of local anesthetics with or without CDs in physiologic saline was investigated by monitoring cloudiness or precipitate formation visually and by recording absorbance at 620 nm. Interaction of anesthetic and CD was also studied spectrophotometrically using spectral change of the drugs associated with the inclusion complex formation. RESULTS: Cyclodextrins improved the solubility and stability of the four local anesthetics studied (dibucaine, tetracaine, bupivacaine, and lidocaine). In the neutral pH region, the effects of the CDs were more significant with dibucaine and tetracaine, which are more hydrophobic than the other two. A type of effective CD was different for each anesthetic depending partly on the tendency to form inclusion complex with local anesthetic. The local anesthetic solutions solubilized by CDs were found to remain clear for more than 72 hours without any visible precipitation or turbidity at neutral pHs. CONCLUSIONS: The improved solubility of local anesthetics by adding CD may be caused by inclusion complex formation of CD with local anesthetics. This new preparation for the alkalinized water-soluble anesthetic solutions may be useful for practical application in the clinical setting, although this awaits further study.

Anesthetics, Local↗
PubMedDate not supplied

Inhibitory effect of gymnemic acid on intestinal absorption of oleic acid in rats.

Gymnemic acid, a mixture of triterpene glycosides extracted from the leaves of Gymnema sylvestre, is known to inhibit the intestinal absorption of glucose in human and rats. This work examined the effect of gymnemic acid on oleic acid absorption by the method of intestinal perfusion in rats. The results showed the following. (i) Gymnemic acid potently inhibited the absorption of oleic acid in intestine. (ii) This inhibition was dose dependent and reversible. (iii) The extent of inhibition and the recovery progress were extremely similar to that of glucose absorption. (iv) Taurocholate did not affect the inhibitory effect of gymnemic acid on oleic acid absorption, but lowering its concentration facilitated the recovery from the inhibition. (v) The absorption of oleic acid was not affected by other glycosides such as phloridzin, stevioside, and glycyrrhizin. These new findings are important for understanding the roles of gymnemic acid in therapy of diabetes mellitus and obesity.

Animals↗
PubMedDate not supplied

The clinical picture of Meniere's disease in the light of glycerin and urea tests.

A mathematical-statistical analysis of the role of glycerin and urea tests in patients with Meniere's disease is presented. Using the quantification method for multidimensional qualitative data, 13 variables were analysed. The younger the patient the stronger was the correlation between age and positive glycerin and urea tests. At ages over 50 years, no correlation to positive test results was found. The longer the duration of disease, the stronger was the correlation between this duration and a positive urea test. The glycerin test showed no correlation to the duration of the disease. Hearing losses of 40-69 dB were correlated both to a positive glycerin test and to a positive urea test. Greater hearing losses were correlated only to a positive glycerin test. Hearing losses of less than 39 dB were not correlated to positive results of either the glycerin or the urea test. Directional preponderance in the caloric test showed a correlation to a positive urea test. On the basis of these results a hypothesis has been formulated to explain how glycerin and urea might affect the internal ear.

Adult↗
PubMedDate not supplied

The role of the endolymphatic sac in statoconial formation and degradation.

In the present investigation we studied the morphology o the endolymphatic sac in guinea pig fetuses (age 20-, 30-, 45-, 60-days-old and newborns). Twenty-day and 30-days-old guinea pig fetuses often displayed small prismatic or hexagonally shaped granules, presumably representing miniature otoconia. The granules appeared freely in the lumen of the endolymphatic sac as well as incorporated in the cytoplasm of the freely floating cells or macrophages. The origin of these "sac otoconia' as well as the possible role of the endolymphatic sac in statoconis turnover and metabolism is discussed.

Animals↗
PubMedDate not supplied

Meniere's disease in Uppsala and Osaka. A comparative study.

A total of 100 patients with Meniere's disease, 50 at the University Hospital of Uppsala and 50 at the Osaka City University Hospital, were submitted to a test battery using the same methods, and the results obtained at the two hospitals were compared. Briefly the findings were as follows. There was no significant difference in age at examination or in the duration of illness. No significant difference was detected with regard to a) the average hearing loss or the types of audiogram, b) the incidence of spontaneous or positional nystagmus, or c) caloric and optokinetic test results. A linear correlation was found between caloric responses and pure tone audiograms in both the Uppsala and Osaka patients.

Audiometry, Pure-Tone↗