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Biomedical subjects

A Nishi

Publications and source records attributed to A Nishi.

At least 19 recordsLinked to original sources
PubMed1995

Physarum polycephalum haemagglutinins: effect of nutrition on synthesis, and their possible role in nature.

The activity of haemagglutinins in plasmodia of Physarum polycephalum was measured under different culture conditions. The activity was markedly increased when the plasmodia were incubated in a non-nutrient salt medium. During starvation, significant amounts of haemagglutinins were found in the slime layer on the surface of the plasmodia. An increase in activity was not observed in the presence of actinomycin D or cycloheximide. Under starvation conditions, plasmodia are known to differentiate into either sclerotia (spherules) or fruiting bodies. Acceleration of haemagglutinin synthesis, however, was not always observed during spherulation and fruiting-body formation. Attempts to detect endogenous glycoconjugates that bind to the haemagglutinins were unsuccessful but we found that the haemagglutinins could bind to acidic polysaccharides produced by Escherichia coli K12. The bacterial glycoconjugates were purified and partially characterized. They contained N-acetylhexosamine residues which appeared to be important for binding with the haemagglutinins. It is possible that the haemagglutinins play a physiological role in the interaction with these organisms.

Animals↗
PubMed1995

Anti-neutrophil cytoplasmic antibody for proteinase 3 in a child with polyarteritis nodosa.

We report a case of a 15 year old boy with polyarteritis nodosa associated with antineutrophil cytoplasmic antibody (ANCA) against proteinase 3 (PR3). After months of steroid and immunosuppressant therapy, the symptoms subsided and the polyaneurysms almost disappeared. The levels of anti-PR3 antibody and of cytokines also decreased. The results indicate that ANCA is a good indicator of this disease activity, and may play some pathogenic role in the disease.

Adolescent↗
PubMed1995

Studies on metabolites of mycoparasitic fungi. II. Metabolites of Trichoderma koningii.

Four peptaibols, named trichokonins (TKs) V, VI, VII, and VIII, were isolated from the culture broth of Trichoderma koningii Oudemans. Primary structures of these peptaibols were elucidated by electrospray ionization mass spectrometry (ESI-MS), FAB-MS, and collision-induced dissociation (CID) techniques along with nuclear Overhauser enhancement spectroscopy (NOESY).

Alamethicin↗
PubMed1994

Change in growth kinetics of hybridoma cells entrapped in collagen gel affected by alkaline supply.

The growth yields for glucose and glutamine of murine hybridoma cells entrapped in collagen gel particles were examined during the growth phase. The immobilized hybridoma cells were cultivated in a fluidized bed fermenter where the medium was circulating to supply oxygen separately. Procedures to supply an alkaline solution for adjusting the pH level strongly affected the growth yields. A direct supply of the alkaline solution to the cultivation system reduced both the growth yields for glucose and glutamine, probably due to a local increase in pH level. On the other hand, when fresh medium in which the pH was adjusted to around 8.5 was added to the cultivation system, the growth yields were unchanged even at the same pH level as when direct alkaline supply was used. These results suggest that an indirect alkaline supply could be recommended to adjust the pH level when using medium-circulating-fermenters.

Animals↗
PubMed1994

Electrophoretic free mobility and viability of microbial cells: a preliminary study in preparation for space experiments.

Electrophoretic free mobilities (EFM) of four fungal spores and five bacterial cells were determined in 7 mM triethanolamine/acetate (TEA) buffer by means of microscopic electrophoresis (ME) and free flow electrophoresis (FFE). Spores of Aspergillus terreus, Penicillium citrinum, Gliocladium virens, and Rhizopus oryzae had similar EFM from 2.2 to 3.1 microns sec-1/V cm-1. The resolution of the spore mixture by FFE was therefore determined to be poor. Bacterial cells of Salmonella typhimurium LT2 mutants showed a distinctive EFM from 0 to 4.2 microns sec-1/V cm-1, which is a large enough difference to produce a clear separation of each mutant type from the mixture in FFE. The differences in the EFM of bacteria result from defective structures in the lipopolysaccharide of their outer membranes. The viability of bacteria in TEA buffer at 4 degrees C was investigated, and it was found to be stable for 14 days. This period is long enough to allow the performance of space experiments.

Aspergillus↗
PubMed1993

Dopamine regulation of renal Na+,K(+)-ATPase activity is lacking in Dahl salt-sensitive rats.

Dopamine is a natriuretic hormone that acts by inhibiting tubular Na+, K(+)-ATPase activity by activation of the dopamine-1 receptor (the thick ascending limb [TAL] of Henle) or by a synergistic effect of dopamine-1 and dopamine-2 receptors (the proximal tubule). The dopamine-1 receptor is coupled to adenylate cyclase. In this article we show that prehypertensive Dahl salt-sensitive (DS) rats have a blunted natriuretic response to dopamine determined during euvolemic conditions compared with Dahl salt-resistant (DR) rats. Furthermore, we have examined the renal tubular effects of dopamine in DS and DR rats. Basal Na+,K(+)-ATPase activity was similar in DS and DR rats. In proximal tubule, dopamine (10(-5) M) inhibited Na+,K(+)-ATPase activity in DR but not in DS rats. The dopamine-2 agonist LY171555 (10(-5) M) together with dibutyryl cyclic AMP (10(-6) M) inhibited proximal tubule Na+,K(+)-ATPase activity in both DS and DR rats. LY171555 alone had no effect. In TAL, the dopamine-1 agonist fenoldopam (10(-5) M) inhibited Na+,K(+)-ATPase activity in DR but not in DS rats. Dibutyryl cyclic AMP (10(-5) M) inhibited TAL Na+,K(+)-ATPase activity in both DS and DR rats. In cell suspensions from the cortex and the medulla, activation of the dopamine-1 receptor significantly increased cyclic AMP content in DR but not in DS rats. The results indicate that DS rats lack the capacity to inhibit tubular Na+,K(+)-ATPase activity because of a defective dopamine-1 receptor adenylate cyclase coupling. This defect may contribute to the impaired natriuretic capacity in DS rats.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1992

Isolation and partial characterization of haemagglutinins from plasmodia of Physarum polycephalum.

The soluble haemagglutinins produced by plasmodia of Physarum polycephalum were purified by chromatographic methods and resolved into haemagglutinins I and II. On SDS-PAGE, purified haemagglutinins I and II each gave a single band with an apparent molecular mass of 6 and 11 kDa, respectively. The results of gel-filtration chromatography suggested that both haemagglutinins were dimers of the respective subunits under non-denaturing conditions. Rabbit erythrocytes were preferentially agglutinated by both haemagglutinins. The human type A, B and O erythrocytes were agglutinated by haemagglutinin II to an equal degree but were not agglutinated by haemagglutinin I. Simple sugars failed to inhibit the activities of both haemagglutinins. The activities, however, were effectively inhibited by the addition of thyroglobulin. Other glycoproteins such as fetuin, orsomucoid and transferrin inhibited the activity of haemagglutinin I but not that of haemagglutinin II. These haemagglutinins were detected in a slime fraction obtained from the culture media of starved plasmodia, suggesting that they are released to the outside of the plasmalemma to become associated with the slime layer on the plasmodial surface.

Animals↗
PubMed1992

High salt diet down-regulates proximal tubule Na+, K(+)-ATPase activity in Dahl salt-resistant but not in Dahl salt-sensitive rats: evidence of defective dopamine regulation.

We examined the regulation of Na+,K(+)-ATPase activity in proximal tubule segments during a high salt diet in prehypertensive Dahl salt-sensitive and salt-resistant rats. Rats were placed on normal salt or high salt diets (0.9% saline as drinking water). During the normal salt diet, Na+,K(+)-ATPase activity was not different between Dahl salt-sensitive and salt-resistant rats. After 2 days and 10 days on a high salt diet, Na+,K(+)-ATPase activity in Dahl salt-resistant rats significantly decreased when compared to Dahl salt-resistant rats on a normal salt diet (P less than 0.01). The decreased Na+,K(+)-ATPase activity in Dahl salt-resistant rats during a high salt diet was reversed by treatment with an inhibitor of aromatic L-amino acid decarboxylase (dopamine synthesizing enzyme), benserazide. In contrast, Na+,K(+)-ATPase activity did not decrease during the high salt diet and benserazide had no effect on Na+,K(+)-ATPase activity in Dahl salt-sensitive rats. These results indicate that Dahl salt-sensitive rats do not have the capacity to down-regulate the proximal tubule Na+,K(+)-ATPase activity during a high salt diet. Indirect evidence suggests that the regulation of Na+,K(+)-ATPase activity by locally produced dopamine is absent in Dahl salt-sensitive rats.

Animals↗
PubMed1992

Adrenocorticoid regulation of Na+,K(+)-ATPase in adult rat kidney: effects on post-translational processing and mRNA abundance.

The mechanisms by which adreno-corticoid hormones regulate Na+,K(+)-ATPase in adult kidney were studied in adrenalectomized (Adx) rats. Five days after adrenalectomy, Na+,K(+)-ATPase activity was significantly reduced in the renal cortex homogenate (C = 13.0 +/- 0.8 vs. Adx = 7.1 +/- 0.7 mumol Pi mg-1 protein h-1) and in renal microsomes (C = 30.3 +/- 1.9 vs Adx = 14.6 +/- 1.3 mumol Pi mg-1 protein h-1). Glucocorticoid replacement treatment of adrenalectomized rats with betamethasone (20 micrograms kg-1 body wt twice daily for 5 days) effectively counteracted the observed reduction in Na+,K(+)-ATPase activity. In cortical homogenate the protein level of alpha 1 and beta 1 subunits measured in immunoblots was not significantly different in Adx and control rats, indicating that 5 days after adrenalectomy the alpha 1 and beta 1 subunits were present in renal cortical cells to almost normal extent but could not be assembled into a transmembrane functional unit. In support of this conclusion we found that the protein level of both the alpha 1 and beta 1 subunits was significantly lower (P less than 0.001 for both subunits) in microsomes from Adx than in control rats. The mRNA abundance for alpha 1 and beta 1 subunits were not lower in Adx as compared to control rats 1 and 5 days after surgery. However, if Adx rats were given a single dose of betamethasone (600 micrograms kg-1 body wt), a significant 2-fold increase in both alpha 1 and beta 1 mRNAs was observed (P less than 0.05 for both subunits).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗
PubMed1991

6-Hydroxymellein synthetase as a multifunctional enzyme complex in elicitor-treated carrot root extract.

Synthetic activity of a polyketide compound 6-hydroxymellein was induced in elicitor-treated carrot root tissues. The activity was significantly inhibited by an antiserum raised against the acyl carrier protein (ACP) of fatty acid synthetase, suggesting that the enzyme(s) for 6-hydroxymellein synthesis require(s) a functional unit similar to ACP. However, the synthetic activity was not stimulated by the addition of ACP purified from Escherichia coli and was not lost even after fractionation by gel-filtration chromatography. The active fraction obtained by gel-filtration (136 kDa) was subjected to immunoblot analysis, and a 128 kDa polypeptide in the fraction was found to cross-react with anti-ACP serum. These observations suggest that the biosynthesis of 6-hydroxymellein in carrot cells is catalyzed by an enzyme consisting of a single peptide chain.

Acyl Carrier Protein↗
PubMed1991

Abundance of Na(+)-K(+)-ATPase mRNA is regulated by glucocorticoid hormones in infant rat kidneys.

The administration of glucocorticoid hormone (GC) accelerates the postnatal maturation of renal Na(+)-K(+)-ATPase activity. This study examines the role of GC for the regulation of the Na(+)-K(+)-ATPase mRNA abundance in renal cortex during development. In 12- to 14-day-old rats an upsurge in serum GC concentration was accompanied by an increase in Na(+)-K(+)-ATPase activity and by an apparent increase in mRNA abundance. In 10-day-old rats injected with a single intraperitoneal dose of betamethasone (T) or diluent (C) the abundances of alpha 1- and beta-mRNAs were 1.8- to 2-fold higher in T than in C rats after 20 min. The mRNA abundance of both subunits was threefold higher after 1 h (P less than 0.01), and it was six- to sevenfold higher after 6 h (P less than 0.01). In any given sample there was a coordinate change in alpha 1- and beta-mRNAs relative to C rats. GC did not appear to induce the expression of any alternative catalytic subunit. The alpha 2-mRNA was not detectable in any experimental protocol. Furthermore, the ouabain inhibition of the Na(+)-K(+)-ATPase, partially purified from the renal cortex, was the same before and after GC. In adult rats injected with betamethasone neither the alpha 1- nor the beta-mRNA abundance was different at any time after injection from those in adult C rats. The rapid onset of the GC effect on mRNA abundance in infant rats suggests that the hormone directly activates the gene for Na(+)-K(+)-ATPase alpha 1-subunit, as well as beta-subunit in the developing kidney, and that GC thereby plays an important role for the postnatal maturation of the kidney.

Animals↗
PubMed1989

Derailment product in NADPH-dependent synthesis of a dihydroisocoumarin 6-hydroxymellein by elicitor-treated carrot cell extracts.

Synthetic activity of 6-hydroxymellein, the immediate precursor of carrot phytoalexin 6-methoxymellein, from acetyl-CoA and malonyl-CoA was induced in carrot cell extracts when the root disks were treated with CuCl2 or oligogalacturonide elicitor. These elicitors showed specific inducing activity of phytoalexin production and did not affect fatty acid synthesis in carrot tissues which may share some common properties with 6-hydroxymellein biosynthesis. 6-Hydroxymellein production was an NADPH-dependent process and, in the absence of the reagent, triacetic acid lactone was produced as a derailment product of the reaction process. This finding suggested that the reduction of the double bond at the 3,4-position of the phytoalexin takes place during the elongation of the poly(oxomethylene) chain. This NADPH-dependent reduction seems to occur at the triacetate stage before the condensation of the third malonyl-CoA as the conversion of carbonyl to hydroxyl group.

Fatty Acids↗
PubMed1988

Carrot phytoalexin alters the membrane permeability of Candida albicans and multilamellar liposomes.

The biochemical basis for the antimicrobial effect of the carrot phytoalexin 6-methoxymellein (6-MM) was examined. At fungistatic concentrations 6-MM retarded the ability of Candida albicans to incorporate radioactive thymidine, uridine and leucine into biopolymers. When C. albicans was incubated with 6-MM, 260-nm-absorbing materials and 3H-labelled compounds leaked from the cells. The inhibitory effects of 6-MM on cell growth and membrane functions were, however, reduced as the concentration of divalent metal cations added to the medium was increased. 6-MM interacted with multilamellar liposomes constituted from phosphatidylcholine, cholesterol and dicetyl phosphate, or from phosphatidylcholine only, resulting in the release of glucose trapped in these liposomes. These results suggest that 6-MM exerts its toxic effects on susceptible cells as a result of its interaction with their membranes and disturbance of membrane-associated functions.

Candida albicans↗
PubMed1985

[3H]5-hydroxytryptamine binding to reconstituted fraction with sulphatides, phosphatidylserine and phosphatidylinositol.

As a first step toward the examination of the involvement of sulphatides, phosphatidylserine and phosphatidylinositol in 5-HT receptor mechanisms, we performed [3H]5-HT binding experiments on the various reconstituted fractions with these acidic lipids. A binding assay of [3H]5-HT to these fractions was carried out by Sephadex LH20 column chromatography. Among various reconstituted fractions, only the reconstitution system with the three acidic lipids exhibited a saturable [3H]5-HT binding capacity, whereas no binding was seen with [3H]-spiperone. When the binding of [3H]5-HT to this fraction was plotted as a function of the ligand concentration, a multiple binding mode with three classes of binding components (or sites) was observed. Furthermore, the double reciprocal plot indicated that this reconstitution system had three apparent KD values of 4.7, 15 and 59 nM. The displacement studies with various compounds indicated that only a few 5-HT agonists (5-methoxytryptamine and tryptamine) and neurotransmitters (DA and ACh) inhibited the [3H]5-HT binding to this fraction, but 5-HT antagonists, LSD analogues and neuroleptics had no effect. Moreover, GTP, GDP and Gpp(NH)p clearly inhibited the [3H]5-HT binding in spite of their weak potencies, while GMP did not have any effect.

Animals↗
PubMed1984

Differentiation response of Physarum polycephalum to macrocysts at various times in nuclear cycle.

Macrocyst (spherule) formation was induced in synchronized suspension cultures of microplasmodia of Physarum polycephalum under conditions where DNA synthesis was inhibited. Plasmodia in early G2 phase of nuclear cycle were able to differentiate to spherules in the presence of an inhibitor of DNA synthesis, whereas those in late G2 phase required another round of DNA replication before they could enter into the spherulation process. These facts suggest that commitment to DNA synthesis occurred about halfway through G2 phase. The idea was also supported by the results of autoradiographic study in which spherulating plasmodia were fed with radioactive thymidine and labelled plasmodia were scored at the terminal differentiation stage.

Aphidicolin↗