Search PubMed⌕ Search

Biomedical subjects

K Shimada

Publications and source records attributed to K Shimada.

At least 1,243 records · Page 69Linked to original sources
PubMed1987

Response of the flagellar rotary motor to abrupt changes in extracellular pH.

Cells of a motile Streptococcus were starved, tethered to a quartz coverslip, energized with a potassium diffusion potential, and exposed to sudden decrements in external pH generated by flash photolysis of 2-hydroxyphenyl-1-(2-nitro)phenyl phosphate. The rotation rate of the cells increased following the flash but only after a brief time lag. Lags of the order of 0.1 second were observed in a dilute buffer (0.05 mM), confirming results obtained earlier. These lags were longer when the buffer was prepared in D2O. However, lags as short as 0.01 second were found in more concentrated buffers (1 and 3 mM). In this case, there was no deuterium solvent isotope effect. These differences arise from the extra time required for diffusion of protons from a dilute medium into the cell wall, which has a large buffering capacity. The short lags observed in concentrated media could be inherent to the flagellar motor, but the possibility that they are due to buffered diffusion through the cell wall or to elastic filtering by the tether has not been ruled out.

Cell Movement↗
PubMed1987

Tissue-specific and developmental expression of human transthyretin gene in transgenic mice.

To analyze the regulation of transthyretin gene expression we have produced transgenic mice by microinjecting cloned human transthyretin genes into fertilized eggs of C57BL/6 mice. The 7.6-kilobase (kb) human transthyretin gene containing about 500 base pairs (bp) in the upstream region was used for microinjection. Seven out of nine transgenic mice had detectable amounts of human transthyretin in serum when analyzed by enzyme-linked immunosorbent assay. Transthyretin mRNA was detected in liver and yolk sac but not in other tissues including brain. The amount of mRNA was variable among transgenic mice and was about one-tenth of mouse endogenous transthyretin mRNA. Human and mouse transthyretin mRNAs were detected in liver of fetus and yolk sac at 13 days of gestation and unlike yolk sac the level of mRNA in liver increased gradually during development and reached the maximum at around 17 days of gestation. Human transthyretin was associated with mouse transthyretin to form tetramers as judged from the dilution curve of enzyme-linked immunosorbent assay and the spur formation in Ouchterlony assay.

Animals↗
PubMed1987

Subendothelial extracellular-matrix heparan sulfate proteoglycan-degrading activity of human monocyte macrophages.

At the early stage of atherogenesis, circulating monocyte macrophages appear to adhere to the endothelial cell surface and migrate subendothelially to become foam cells. The mechanism of these macrophage-endothelial cell interactions was investigated. Adherent macrophages isolated from human blood were plated on [35S]O4-prelabeled extracellular matrix-coated dishes prepared from cultured porcine aortic endothelial cells. During incubation for 2-3 days at pH 7.4 either in the presence or absence of serum, macrophages solubilized the labeled extracellular matrix to a lower molecular weight component (Kav approximately equal to 0.5) than the materials (Kav = 0) released into the medium containing no cells. The degrading activity was not stored intracellularly but instead was found pericellularly, requiring continuous cell-matrix contact. Heparin (10 micrograms/ml) inhibited this degrading activity of macrophages. Degradation products were precipitated with cetylpyridinium chloride and were resistant to further digestion with alkali, pronase, or chondroitinase ABC, but were converted to further lower molecular weight fragments (Kav = 0.84) after nitrous acid digestion or heparitinase treatment. The intact glycosaminoglycan side chains determined by subjecting the extracellular matrix to cleavage with alkali or pronase were larger (Kav congruent to 0.20) than those of degradation products released by macrophages. These results suggest that the attachment and subsequent invasion of endothelial cells by monocyte macrophages may involve the production of extracellular-matrix heparan sulfate proteoglycan-degrading activity by these cells.

Animals↗
PubMed1987

Interrelationship between arginine vasotocin, prostaglandin, and uterine contractility in the control of oviposition in the hen (Gallus domesticus).

Uterine electromyographic activity (EMG), plasma concentrations of prostaglandin (PG) F and E, and arginine vasotocin (AVT) were simultaneously measured in relation to PGE2-induced premature oviposition and to indomethacin-blocked oviposition in chickens. The administration of indomethacin (5 mg, im) 3 hr before the predicted time of oviposition delayed egg lay by 8-14 hr, whereas control hens laid eggs at the predicted time. In indomethacin-treated hens increases in uterine EMG activity and plasma concentrations of PGF, PGE, and AVT were not observed at the expected time of oviposition, whereas a marked increase in plasma PGF and AVT occurred during spontaneous oviposition. The intrauterine administration of PGE2 (1 microgram) 3 hr before predicted oviposition induced premature egg lay within 5 min. Premature oviposition was accompanied by significant elevations in both uterine EMG activity and plasma levels of AVT. Changes in plasma levels of PGF and PGE were not observed. When premature oviposition was induced, significant increases in EMG activity and plasma concentrations of PGF and AVT were observed at the expected time of oviposition in the absence of an egg in the uterus. The administration of PGE2 at the predicted time of oviposition in hens pretreated with indomethacin induced oviposition which was accompanied by a significant increase in plasma AVT levels. The results suggest that AVT release is stimulated by uterine contractility in chickens.

Animals↗
PubMed1987

Prealbumin gene expression during mouse development studied by in situ hybridization.

Localization of prealbumin mRNA in tissues from mice at various stages of gestation was investigated using in situ hybridization procedures. Prealbumin mRNA was detected as early as the 10th day of gestation. It was specifically localized in endodermal cells of the visceral yolk sac, tela choroidea, and hepatocytes. In the adult mice, prealbumin mRNA was localized in the hepatocytes and choroid plexus epithelial cells. These observations indicate that synthesis of prealbumin mRNA is initiated in several different types of cells at early stages of fetal development.

Animals↗
PubMed1987

New derivatization method using ferrocene reagents for the determination of steroid glucuronides by high-performance liquid chromatography with electrochemical detection.

New derivatization methods using ferrocene reagents have been developed for the determination of steroid glucuronides by high-performance liquid chromatography with electrochemical detection. Condensation of glucuronides with 2-ferrocenylethylamine is effected in the presence of water-soluble carbodiimide and 1-hydroxybenzotriazole. The resulting amides show the satisfactory sensitivity at +0.45 V versus Ag/AgCl reference electrode, with a detection limit of 0.5 pmole. The present method is found to be applicable to the estimation of estrogen glucuronyltransferase activities and estrogen glucuronides in pregnancy urine.

Journal Article↗
PubMed1987

Prostaglandin levels in peripheral and follicular plasma, the isolated theca and granulosa layers of pre- and postovulatory follicles, and the myometrium and mucosa of the shell gland (uterus) during a midsequence-oviposition of the hen (Gallus domesticus).

Prostaglandins (PG) F and E were measured by radioimmunoassay in peripheral, uterine and follicular plasma and in the theca and granulosa layers of the five largest preovulatory and the three largest postovulatory follicles, and in the myometrium and mucosa. Plasma and tissues were collected 16, 12, 8 and 4 h before and immediately after a midsequence oviposition that was accompanied by the next ovulation. PGF concentrations in the peripheral and uterine plasma increased at oviposition with a concomitant, 16-fold increase in plasma PGF concentrations of the largest preovulatory (F1) follicle. There was a gradual increase in PGF concentrations in the theca layers during follicular maturation, with the large increases occurring 12 h before oviposition in most follicles. The highest and the second highest concentrations were observed at oviposition in the F1 and the largest postovulatory (R1) follicles. In contrast, there were no specific changes in PGF concentrations in the granulosa layers of the follicles in relation to oviposition or follicular maturation. PGE concentrations in the theca layers of the F2 and F1 follicles were greater than in other follicles, while concentrations in the granulosa layer of all the follicles remained low. PGF concentrations in the myometrium and mucosa increased 8 h before oviposition but abruptly decreased at oviposition. These results suggest that the primary source of the increase in plasma PGF at oviposition are the theca layers of the F1 and R1 follicles and that PGs may be involved in uterine contractions for oviposition and in the ovulation process.

Animals↗
PubMed1987

Effect of alternating current exposure on the resistivity of resting Escherichia coli B cells to crystal violet and other basic dyes.

Phosphate buffer suspensions of resting Escherichia coli B cells at pH 7.0 were anaerobically exposed to alternating current (a.c.) of 50 Hz at a current density of 600 +/- 60 mA/cm2 and 34 degrees +/- 3 degrees C. The minimum inhibitory concentrations of eight basic dyes: crystal violet, malachite green, brilliant green, fuchsin, methylene blue, toluidine blue, safranin and acriflavine for exposed cells were decreased to about the half values of those for unexposed ones when both cells were grown in the minimal medium including one of the dyes. The integrated viabilities of exposed cells tended to decline with increasing concentration of the dyes markedly more than those of unexposed ones, whereas the exposed cells took up the dyes less readily than the unexposed cells. These results suggested that a.c. exposure may serve as an agent which renders E. coli cells susceptible to the basic dyes.

Coloring Agents↗
PubMed1987

Molecular genetics of familial amyloidotic polyneuropathy.

We established a diagnosis of familial amyloidotic polyneuropathy (FAP) based on DNA and demonstrated a direct link between prealbumin gene mutation and FAP. The individuals with FAP, so far examined, were heterozygous for the prealbumin gene, carrying one normal and one mutant gene. To investigate the molecular pathogenesis of FAP, we isolated a normal prealbumin gene (7 kb in length) and also a mutant prealbumin gene associated with FAP. We compared their nucleotide sequences and found that they matched except for a single-base substitution present in the second exon. In an effort to construct mouse model systems for the FAP, we developed strains of transgenic mice carrying human mutant prealbumin genes.

Amyloidosis↗
PubMed1987

Changes in plasma concentrations of arginine vasotocin after intrauterine injections of prostaglandin F-2 alpha and acetylcholine at various times during the oviposition cycle of the domestic hen (Gallus domesticus).

Prostaglandin F-2 alpha (PGF-2 alpha, 1 microgram) and acetylcholine (10 mg) were injected into the uterus of chickens 23, 21, 16, 8 or 4 h before expected oviposition. Plasma concentrations of immunoreactive arginine vasotocin and PGF were measured in relation to the time of administration of PGF-2 alpha or acetylcholine or to the premature oviposition that was induced. PGF-2 alpha or acetylcholine administration caused premature oviposition and a marked increase in plasma arginine vasotocin levels only when an egg was present in the uterus. Changes in plasma PGF concentrations were not observed. After premature oviposition was induced, plasma values of PGF and arginine vasotocin increased at the expected time of oviposition. Manual stimulation of the uterus 4 h after oviposition also stimulated arginine vasotocin release. During spontaneous oviposition, a rise in plasma PGF concentration preceded increases in uterine contractility and plasma arginine vasotocin concentration. These results suggest that PGF may stimulate uterine contractility which in turn causes the release of arginine vasotocin to provide an additional contractile stimulus during oviposition.

Acetylcholine↗