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Biomedical subjects

M Niimi

Publications and source records attributed to M Niimi.

At least 163 records · Page 9Linked to original sources
PubMed1988

Macroconidial development and germination in Trichophyton mentagrophytes.

Trichophyton Mentagrophytes was investigated for macroconidial development with particular emphasis on the conidial ageing by light and scanning electron microscopy. Macroconidial germination was also studied under various conditions. Sabouraud glucose agar supplemented with 3% NaCl was used to enhance production of macroconidia. After a long-term cultivation macroconidial compartments changed to spherical thick-walled structure. Some 12-month-old macroconidia were still capable of germination. A wide range of temperature (15-37 degrees C), and inoculum of less than 1 X 10(5) conidia per ml of rich media were appropriate for macroconidial germination. The germination process of macroconidia was highly tolerant to NaCl. A small fraction of the conidia were able to germinate even in distilled water without activation. Effect of freeze-thaw or ultraviolet irradiation on macroconidial germination was determined.

Sodium Chloride↗
PubMed1988

Physiological role of growth hormone (GH)-releasing factor and somatostatin in the dynamics of GH secretion in adult male rat.

To investigate the physiological role of GRF and somatostatin (SRIF) in GH secretion in adult male rats, we prepared in vitro models using the perifusion system of cultured rat anterior pituitary cells exposed to various combinations of human GRF-(1-44)NH2 (hGRF) and SRIF. We studied the following three models on GRF secretion: 1) pulsatile GRF secreted at 1-h intervals, 2) pulsatile GRF secreted at 3-h intervals, and 3) GRF continuously secreted. When 5-min pulses of 20 nM GRF were delivered at 1-h intervals, the responses to GRF gradually declined. The addition of continuous 20 nM SRIF with short pauses prevented this attenuated response and produced high peaks of GH at 3-h intervals. When 5-min pulses of 20 nM GRF were delivered at 3-h intervals, three high peaks of GH were observed regardless of the addition of SRIF. Pretreatment with GRF pulses enhanced the peaks of GH during SRIF pauses. When 20 nM GRF was continuously delivered, a rapid attenuated response to GRF was observed. Although the addition of continuous 20 nM SRIF with short pauses produced three small peaks of GH, these results were caused by the post-SRIF rebound release. These observations suggest that preexposure to prolonged SRIF can prevent an attenuated response to repeated GRF pulses, and that pretreatment with GRF pulses enhances post-SRIF rebound release.

Animals↗
PubMed1988

Respiration of medically important Candida species and Saccharomyces cerevisiae in relation to glucose effect.

Strains of medically important Candida species (C. albicans, C. tropicalis, C. parapsilosis and C. [Torulopsis] glabrata) and Saccharomyces cerevisiae were examined for a glucose effect on respiratory activity. Reduced O2-consuming ability and a relative decrease in cytochrome type c, as determined by polarography and spectrophotometry, respectively, were observed in glucose-grown S. cerevisiae cells in contrast with acetate- or ethanol-grown cells. In glucose-grown cells of C. glabrata, O2 consumption was also reduced without any change in the cytochrome pattern compared to acetate-grown cells, while no such decrease was detected in any of the other strains of Candida species tested. These results suggest that the medically important Candida species, except for C. glabrata, can be categorized as members of the glucose-insensitive yeast type with respect to respiration.

Candida↗
PubMed1986

Regulation of mannitol catabolism in Candida albicans: evidence for cyclic AMP-independent glucose effect.

Candida albicans was examined for a glucose effect and showed typical diauxic growth on a mixture of glucose and mannitol, in which mannitol utilization occurred only after exhaustion of glucose. The activity of NAD-linked mannitol dehydrogenase was very low while glucose was present in the medium, but started to increase after consumption of glucose. This increase in activity was fully prevented by trichodermin, an inhibitor of protein synthesis. The uptake of mannitol was detected in the cells grown on mannitol, but not in those grown on glucose with or without mannitol. Mannitol uptake by mannitol-grown cells was not affected by the presence of glucose (0.2 g l-1). These findings indicate that in C. albicans glucose represses the inducible syntheses of mannitol dehydrogenase and a mannitol transport system, and that the involvement of inducer exclusion in this effect is unlikely. Fructose, and to lesser extents galactose, mannose and sucrose, also exhibited similar effects on mannitol metabolism. No correlation was found between the intracellular cyclic AMP levels and the glucose effect.

Candida albicans↗
PubMed1985

Effects of age on GH responses to growth hormone-releasing factor in rats.

This paper aims to investigate the growth hormone (GH) responses to the growth hormone releasing factor-44 (GRF-44) in young and adult rats in vitro and in vivo. Male Wistar rats aged 28 days and 6 months were used. In pentobarbital anesthetized young rats, an intravenous administration of GRF-44 at a dose of 25 ng/100 g b.w. resulted in an 11.4 fold rise in the serum GH level at 5 min after GRF-44 injection. On the other hand, in adult rats the same dose of GRF-44 did not elicit a significant rise in the serum GH level. However, GH secretion in response to GRF-44 at a dose of 250 ng/100 g b.w. was not attenuated in adult rats. Isolated pituitary cells obtained from young and adult rats were incubated for 3 days. The addition of GRF-44 at a concentration of 5 ng/ml to the cultured pituitary cells from young rats caused a 3.2 fold increase in GH content in the medium. On the other hand, the same dose of GRF-44 added to the cultured pituitary cells from adult rats resulted in only a 2.3 fold increase in GH content. These data indicate that the sensitivity of somatotrophs to GRF may be diminished with age.

Aging↗
PubMed1985

Plasma concentration of prolactin during four-day osmotic pump infusion of thyrotropin-releasing hormone and vasoactive intestinal polypeptide in rats.

Pituitary prolactin (PRL) responses to 4-day continuous infusion of thyrotropin-releasing hormone (TRH) and vasoactive intestinal polypeptide (VIP) were investigated in unanesthetized male rats using Alzet osmotic minipumps. The TRH dose infused was 3.6 micrograms/day and the VIP dose was 32.8 micrograms/day. Infusion of TRH with osmotic pumps elevated the plasma PRL level compared to controls over the 4-day infusion period. However, mean levels of PRL tended to decrease during the 4-day infusion. On the other hand, continuous VIP infusion elicited a significant continuous PRL release over the 4-day infusion period. Thus, it may be said that the PRL responses to infused TRH and VIP were maintained during the 4-day infusion.

Animals↗
PubMed1985

Germ tube-forming cells of Candida albicans are more susceptible to clotrimazole-induced killing than yeast cells.

Yeast and germ tube-forming cells of Candida albicans were compared with respect to their susceptibility to killing induced by the imidazole antifungal clotrimazole. Cultures consisting largely of germ tube-forming cells or exclusively yeast cells were prepared by incubating cells of a germ tube-proficient strain in a proline-containing phosphate buffer at 37 degrees C or 25 degrees C, respectively. When treated with clotrimazole at 37 degrees C, the cultures of germ tube cells lost colony-forming ability much more rapidly than those of yeast cells. However, this difference was diminished in the cells preincubated at 37 degrees C but prevented from forming germ tubes by 5 mM cysteine, a suppressor of germ tube formation. In another C. albicans isolate showing a very poor capacity to form germ tubes at 37 degrees C, such a difference in killing rate was much smaller than that for the germ tube-proficient strain. Furthermore, when an isogenic pair of strains, one proficient and the other deficient in germ tube formation, were compared with each other, germ tube-forming cultures of the former were found to be more sensitive than yeast cell cultures of the latter. It is inferred from these results that the germ tube-forming cell of C. albicans is more sensitive to clotrimazole-induced killing than the yeast cell.

Candida albicans↗
PubMed1984

Corticotropin releasing factor (CRF)-like immunoreactivity in the hypothalamus and posterior pituitary of the goat, bovine, rat, monkey and human.

Goat hypothalamic extract prepared by HCl extraction and chromatographed on a Sephadex G-50 column showed two immunoreactive CRF peaks. Most of the immunoreactivity coeluted with synthetic ovine CRF, and a small peak eluted near the void volume. Bovine, monkey, rat and human hypothalamic extracts prepared by acid-acetone or acid-methanol extraction showed three immunoreactive peaks. Most of the immunoreactivity coeluted with ovine CRF, and other smaller peaks eluted near the void volume and slightly before arginine vasopressin. Goat hypothalamic extract showed the highest cross-reactivity with anti-ovine CRF serum, followed by bovine hypothalamic extract. Less cross-reactivity was found in human, rat and monkey hypothalamic extracts. CRF immunoreactivity in goat hypothalamic extract coeluted with ovine CRF on reversed phase high performance liquid chromatography (HPLC) and main CRF immunoreactivity in human and rat hypothalamic extracts eluted slightly later than ovine CRF. These results suggest that there is a heterogeneity among the CRF molecules in these species and that goat CRF may be more similar to that of sheep CRF and the amino acid sequence or molecular weight of other animals CRF may be different from that of sheep CRF. The monkey posterior pituitary and rat neurointermediate lobe showed similar elution patterns of CRF immunoreactivity to their hypothalamic extracts on Sephadex gel filtration and HPLC. These results indicate that the posterior pituitary contains a similar CRF to hypothalamic CRF.

Animals↗
PubMed1983

The laminar arrangement of limbic thalamocortical neurons in the lateropulvinar nuclei of the cat thalamus.

The topical organization of limbic cortical projections of the lateropulvinar nuclei of the thalamus in the cat was studied with the horseradish peroxidase (HRP) technique. The dorsal margins of the dorsal lateral, medial pulvinar and lateral pulvinar nuclei project to the postsubicular and presubicular areas (presubiculum in a wide sense), the most dorsal parts of these nuclei projecting to the retrosplenial area, and the dorsal parts to the cingular area. These three zones of limbic thalamocortical neurons in the lateropulvinar nuclei are arranged in lamination from the surface inward, and may be called presubicular, retrosplenial and cingular zones.

Animals↗
PubMed1983

Production of contiguously arranged chlamydospores in Candida albicans.

Contiguous arrangements of two to three chlamydospores occurred in a clinical isolate of Candida albicans. Time-lapse photography showed that the terminal cell of a cell chain was first transformed into a chlamydospore and such transformation proceeded centripetally to the next cell in the chain. Ultrathin sections revealed that the outermost layer of the three-layered chlamydospore wall was continuous throughout the interconnected spores, with the other layers surrounding each spore separately. Chlamydospore chains were common in this organism.

Candida albicans↗
PubMed1983

Effects of thyrotropin-releasing hormone on catecholamine concentration in various structures of the rat brain.

In an attempt to identify the site of TRH-action in the central nervous system (CNS), we have measured catecholamine levels in discrete brain regions of rats after an intravenous administration of TRH or a long-term intraventricular administration of TRH using Alzet's osmotic minipump. An intravenous administration of 50 micrograms TRH caused a rapid increase in dopamine (DA) concentration in the septal nucleus and then returned to the basal level at 30 min after injection. The concentration of DA in the septal nucleus after the long-term TRH intraventricular administration was also significantly higher than that in the controls. These results indicate that a long-term intraventricular administration of TRH as well as a bolus intravenous injection of TRH may affect the release or metabolism of DA in the septal nucleus.

Animals↗