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Biomedical subjects

K Hosaka

Publications and source records attributed to K Hosaka.

At least 109 records · Page 6Linked to original sources
PubMed1985

Structural and functional adaptation of the pulpal nerve fibers in the rat incisor.

Special fine structure of the pulpal nerve fibers adapted to the continuously growing incisor was studied on 20 rats (25-d-old-males) electron microscopically and was compared with that of the molars of limited growth. The incisal pulp was innervated by 2 kinds of the nerve fibers derived from the cervical sympathetic and the trigeminal ganglia: polyaxonal unmyelinated and monoaxonal myelinated. In the apical pulp, however, the pulpal nerve fibers were unmyelinated, showing 3 different profiles in the fine structure: 1. polyaxonal, 2. polyaxonal with dial plate-like profile and 3. monoaxonal. The monoaxonal unmyelinated fiber reflected the transverse profile of the unmyelinated part of the myelinated axon derived from the trigeminal ganglion. It can be concluded that the pulpal nerve fibers derived from the trigeminal ganglion maintain the immatured nature in the apical proliferating pulp to adapt to the continuous growth of the incisor.

Animals↗
PubMed1984

Partial purification and properties of phosphatidate phosphatase in Saccharomyces cerevisiae.

Using an aqueous dispersion of [32P]phosphatidate as substrate we detected phosphatidate phosphatase (EC 3.1.3.4) activity in a cell-free extract of the yeast, Saccharomyces cerevisiae. The activity was found in both the membrane and the soluble fractions. The enzyme was purified from the soluble fraction about 600-fold. The purification procedure involved (NH4)2SO4 fractionation, poly(ethylene glycol) 6000 fractionation and column chromatography on DEAE-Sepharose, Sephadex G-100 and Blue-Sepharose. The purified enzyme almost absolutely required Mg2+ for activity. The molecular weight of the enzyme was estimated by analytical gel filtration on Sephadex G-100 to be approx. 75000. The enzyme was highly specific for phosphatidate. The apparent Km for phosphatidate was approx. 0.05 mM. The optimum pH was between 7.0 and 8.0.

Hydrogen-Ion Concentration↗
PubMed1984

Regulatory role of phosphatidate phosphatase in triacylglycerol synthesis of Saccharomyces cerevisiae.

The regulatory mechanism of triacylglycerol synthesis in Saccharomyces cerevisiae was studied. The triacylglycerol content increased markedly during the entry of cells into the stationary growth phase, whereas the content of phospholipids remained unchanged. Pulse-labeling experiments to measure [14C]acetate incorporation into triacylglycerol revealed that the synthesis of triacylglycerol increased in the stationary growth phase. An increase in fatty acid synthesis was observed only in the later stage of the stationary growth phase and thus does not seem to be the principal causative factor for the triacylglycerol accumulation. Among various triacylglycerol-synthetic enzymes tested, the increase in the phosphatidate phosphatase (EC 3.1.3.4) activity was most closely correlated with the accumulation of triacylglycerol in the stationary phase. Our results show that phosphatidate phosphatase plays an important role in the regulation of triacylglycerol synthesis in S. cerevisiae.

Acetates↗
PubMed1984

Toxicology of mabuterol.

The acute, subacute and chronic toxicity of dl-1- (4-amino-3-chloro-5-trifluoromethyl-phenyl)-2-tert.-butyl-amino-ethanol hydrochloride (mabuterol), a new beta 2-selective adrenoceptor stimulant, was studied in mouse, rat, rabbit and dog. The acute oral LD50 was between 199.9 and 319.3 mg/kg in all four species used and did not differ significantly between the sexes. Intravenous LD50 was between 18.3 and 51.1 mg/kg (four species), i.p. between 60 and 78.3 mg/kg and s.c. between 113 and 125.7 mg/kg (mouse and rat only). In subacute and chronic studies in Wistar rats, mabuterol was dosed by gavage at 0, 10, 20, 40, 80 and 120 mg/kg for 1 month, and 0, 1, 2.5, 10 and 40 mg/kg for 3 (interim) and 6 months or in food at 0, 2.5, 10 and 40 mg/kg for 6 (interim) and 12 months. Beagle dogs were dosed by gelatine capsule with 0, 0.05, 0.5, 5 and 50 (25) mg/kg for 6 (interim) and 24 months. In rats, 1 and 2.5 mg/kg were well tolerated. At 10 mg/kg and above, irritability and hypersalivation were seen dependent on dose. Two males and one female given 120 mg/kg died from the test substance. In dogs, 0.05, 0.5 and 5 mg/kg were well tolerated. 50 mg/kg caused vomiting, diarrhoea, tonic-clonic convulsions and increased salivation. One male had to be killed because of severe convulsions. At term, 3 of 56 female rats of the one-year study had benign mesovarian leiomyomas. No other substance-related changes were discovered but all findings belonged to the spontaneous pathology of rat and dog, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗
PubMed1984

Motor innervation of the mole and shrew snout muscles by means of horseradish peroxidase technique.

The axonal transport method of the horseradish peroxidase (HRP) was used for defining the anatomical background of the snout movements in 54 Japanese shrew-moles, Urotrichus talpoides, 4 Temminck's moles, Mogera wogura, and 21 big-clawed shrews, Sorex unguiculatus. Either snout muscle or proximal stump of the facial nerve on one side was exposed to HRP. The results obtained from this experimental study were as follows: HRP-containing cells were found either ipsilaterally or bilaterally in the facial motor nucleus in both the moles and shrews. The HRP-containing cells were grouped into 4 subnuclei: ventrolateral, ventromedial, dorsal and accessory. In case of the snout muscle being exposed to the HRP were the HRP-containing cells found in the ventral groups. A HRP-positive fiber bundle was found at the genu of the facial motor root extending toward the median raphe, when the proximal stump of the facial nerve was exposed to the HRP.

Animals↗
PubMed1983

An enzymic cycling method for the determination of free fatty acids with acyl-CoA synthetase and acyl-CoA hydrolase.

A method for measuring free fatty acids by enzymic cycling is described. Free fatty acids are converted to acyl-CoAs by acyl-CoA synthetase, then the acyl-CoAs are hydrolyzed back to the free fatty acids by acyl-CoA hydrolase in a cyclic fashion. The amounts of AMP produced during this cyclic reaction are determined from the absorbance at 340 nm in the presence of AMP deaminase and glutamate dehydrogenase. This method is sensitive to as low as 0.1 nmol of free fatty acids, and the standard curve is linear up to 1.0 nmol. This method shows a broad specificity for long-chain fatty acids (C12--C20) and the recoveries of fatty acids added to bacterial cell-free extracts are more than 90%.

AMP Deaminase↗
PubMed1982

Regulation of the phosphatidylethanolamine methylation pathway in Saccharomyces cerevisiae.

1. Phosphatidyl-N-methylethanolamine methyltransferase mutants of Saccharomyces cerevisiae were isolated. Genetic analysis showed that phosphatidylethanolamine methyltransferase and phosphatidyl-N-methylethanolamine methyltransferase are coded for by separate genes. Phosphatidyl-N-methylethanolamine methyltransferase activity and phosphatidyl-N,N-dimethylethanolamine methyltransferase activity appeared to be catalyzed by the same enzyme. 2. Phosphatidyl-N-methylethanolamine methyltransferase was found to be repressed by myo-inositol and choline. Both myo-inositol and choline at concentrations of 10 micrograms/ml were required for repression. The decreased enzyme level was restored by the removal of myo-inositol or choline or both. 3. Both myo-inositol and choline were required for the maximum repression of phosphatidylethanolamine methyltransferase in wild-type cells. In contrast, choline was not required for the repression of the enzyme in mutant strain 172. This was due to a single nuclear gene mutation in the genome of strain 172. 4. The activity of the phosphatidylethanolamine methylation pathway in cells decreased with time on incubation of cells with myo-inositol and choline, myo-Inositol could not be replaced by other structurally related compounds, such as scyllo-inositol or mannitol. 5. The physiological significance of the repression of the phosphatidylethanolamine methylation pathway is discussed with respect to the mechanism for maintaining the contents of phosphatidylethanolamine and phosphatidylcholine at normal levels.

Choline↗
PubMed1981

A new colorimetric method for the determination of free fatty acids with acyl-CoA synthetase and acyl-CoA oxidase.

A rapid and sensitive spectrophotometric assay for free fatty acids using acyl-CoA synthetase and acyl-CoA oxidase is described. It is sensitive to as low as 5 nmol of free fatty acids, and the standard curve is linear up to 100 nmol. The assay consists of the measurement of H2O2 produced from free fatty acids by acyl-CoA synthetase and acyl-CoA oxidase. The quantity of H2O2 is determined by the absorbance at 550 nm in the presence of catalase and 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AHMT). This method shows a broad specificity to long-chain fatty acids and the recoveries of added fatty acids (C12-C18) are more than 90%. The presence or absence of serum components or Escherichia coli cell-free extracts has no significant effect on the recovery of added palmitic acid.

Acyl-CoA Oxidase↗
PubMed1981

Induction of choline transport and its role in the stimulation of the incorporation of choline into phosphatidylcholine by polyamines in a polyamine auxotroph of Saccharomyces cerevisiae.

1. A mutant of Saccharomyces cerevisiae, defective in ornithine decarboxylase, was isolated. A prolonged culture of the mutant in a polyamine-free medium resulted in a great decrease in the polyamine content and in cessation of growth. The addition of polyamines to the culture induced the growth after a lag period of 5--6.5 h. The growth rate in the presence of polyamine was comparable to that of the wild-type strain. The effectiveness of polyamines was as follows: spermidine greater than putrescine approximately equal to spermine. 2. Phosphatidylcholine-synthesizing activity during the lag phase of growth was determined by measuring the rate of incorporation of [14C]choline into phosphatidylcholine. The incorporation rate was markedly increased with time by polyamine prior to the initiation of cell division. Polyamines were effective in the following order: spermidine greater than putrescine approximately equal to spermine. Experiments with methylglyoxal bis(guanylhydrazone), an inhibitor of S-adenosylmethionine decarboxylase, showed that putrescine stimulates cell growth and choline incorporation into phosphatidylcholine after it has been converted into spermidine in the cell. 3. The induction of the choline transport system was shown to be responsible for the increase in the rate of incorporation of [14C]choline into phosphatidylcholine effected by polyamines. A low concentration of cycloheximide completely prevented the induction of choline transport by polyamines. The levels of the CDP-choline pathway enzymes such as choline kinase, cholinephosphate cytidyltransferase and cholinephosphotransferase were not significantly changed.

Biological Transport↗