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Biomedical subjects

Y Hotta

Publications and source records attributed to Y Hotta.

At least 181 records · Page 10Linked to original sources
PubMed1989

Ornithine aminotransferase distribution in ocular tissues and retinas of cat and mouse.

Ornithine aminotransferase (OAT), a mitochondrial matrix enzyme, is genetically deficient in patients with gyrate atrophy of the choroid and retina. Histologically defined micro-samples (10 ng-6.8 micrograms dry weight) were dissected out from freeze-dried tissue sections of eyeballs of cat and mouse, and the OAT activities were determined by a newly developed microassay method in the ocular tissues and retinal layers. Very high specific activities of OAT, expressed on a dry weight basis, were found in the feline ocular tissues of ectodermal origin, that is, neuroretina, retinal pigment epithelium, ciliary processes and epithelium of iris. In cat and mouse retinas, high OAT activities were distributed in the inner retina with an activity peak in the inner plexiform and ganglion cell layers. Very low activity was present in the outer nuclear layer. The inner segments of photoreceptor cells, which are very rich in mitochondria, contained the highest OAT activity. In contrast, the outer segments of photoreceptor cells contained the low activity resulting from contamination by small pieces of inner segments.

Animals↗
PubMed1989

Gene transfer and expression of human ornithine aminotransferase.

A generalized deficiency in the mitochondrial enzyme, ornithine aminotransferase (OAT), is present in the hereditary blinding disease, gyrate atrophy (GA). Because the OAT gene is a multi-gene family, and the native OAT enzyme is an oligomer, it would be important to identify the gene locus actually responsible for the OAT activity and affected in GA. A mammalian expression clone containing a previously characterized human OAT cDNA (pHOAT), corresponding to the OAT gene on chromosome 10, was prepared (pcDHOAT), transfected, and tested for expression in NIH3T3 cells and OAT(-) Chinese hamster ovary (CHO) cells. Incorporation of pcDHOAT and synthesis of human OAT mRNAs and active enzyme were demonstrated in both cell types, confirming the completeness of the coding sequence of pHOAT. The results indicated that the chromosome 10 gene corresponding to the cDNA is the functional gene fully capable of expressing the active oligomeric enzyme by itself and is, therefore, consistent with being the site of the molecular defect in GA.

Animals↗
PubMed1989

Ultrastructural studies on a cadmium-storing cell in rat pancreatic tissues following cadmium chloride administration.

A new type of cell was found in the pancreatic connective tissues of rats following cadmium chloride administration. The cells contained several lipid droplets that were strongly electron-dense after the treatment with oxine, which made cadmium-oxine deposits. This suggested that the lipid droplets stored cadmium or related substances. These cells were named "cadmium-storing cells." Cadmium-storing cells are subdivided into two cell types according to their origins, "fibroblast type" and "pericyte type." The structure and function of the cadmium-storing cell were described and discussed.

Animals↗
PubMed1989

Inheritance of ornithine aminotransferase gene, mRNA, and enzyme defect in a family with gyrate atrophy of the choroid and retina.

We studied the human ornithine aminotransferase (OAT) gene, mRNA, and enzyme activity in fibroblasts from a family with gyrate atrophy (G.A.) of the choroid and retina, using a normal human OAT cDNA as a probe. The family consists of an affected patient, who is heterozygous for a partial deletion of the functional OAT gene and whose cells produce no mRNA, and of his father, mother, two sons, and a daughter. Southern blot analysis of the OAT gene showed the partial deletion in the patient and in his father and daughter and in one son. Northern blot analysis revealed no OAT mRNA in the patient and approximately 50% of the normal level of OAT mRNA in the father, mother, two sons, and daughter. Assay showed that the OAT activity in these individuals mirrored the OAT mRNA levels. The results indicate that an active allele of the OAT gene expresses 50% of the total normal OAT mRNA and activity and that both alleles of the gene are inactive in the patient in this pedigree, a situation resulting in a complete absence of the OAT mRNA, in accordance with the autosomal recessive mechanism of this disease; they also indicate a 50% decrease of OAT mRNA and enzyme activity in obligate heterozygous carriers carrying one defective allele and that these defects are stably inherited.

Alleles↗
PubMed1988

Structure of retinular cells in a Drosophila melanogaster visual mutant, rdgA, at early stages of degeneration.

A Drosophila visual mutant rdgA has photoreceptive cells which degenerate gradually after eclosion. Fine structure of the retinular cells of rdgAKS60 and rdgAKO14 was studied during early stages of degeneration to determine the initial morphological defects. The retinular cells of these two alleles showed the following structural abnormality within 1 day after eclosion: (1) rhabdomeres were small and irregular in shape; (2) cisternae of the rough endoplasmic reticulum were more numerous than those in normal retinular cells; (3) submicrovillar cisternae were absent; and (4) lysosomes were fewer than normal. Three-dimensional reconstruction of serial sections of the ommatidia showed that the degeneration of mutant rhabdomeres proceeds more rapidly in regions remote from the nuclei. These results suggest that the process of turnover of rhabdomeric microvilli is abnormal in rdgA. We also confirmed an increase of lysosomes and destruction of cellular organelles, as reported by previous investigators at more advanced stages of degeneration.

Animals↗
PubMed1988

The effect of temperature on recombination activity in testes of rodents.

An extractable enzyme system capable of catalyzing recombination in vitro was described in murine spermatocytes [Hotta et al. (1985) Chromosoma 93, 140-151]. The system is specific to meiosis, its activity increasing 400-fold between the premeiotic S-phase and mid-pachytene. The present study examines the effect of temperature on this system since the elevation of testicular temperature is one of the major factors causing impairment of testicular function. A strong depression of in vitro recombination activity occurred immediately after raising the testicular temperature in vivo by translocating the testes into the abdominal cavity (cryptorchid). The in vitro study also showed that the extract from spermatocytes preferred lower temperatures (30-32 degrees C) than somatic cells (37 degrees C) for maximal activity of recombination. These results suggest that the strong depression of recombination activity may be an important factor which causes degeneration of testes by heat.

Animals↗
PubMed1988

Membrane-associated phospholipase C of Drosophila retina.

Phospholipase C activities against phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol have been examined using head homogenate of Drosophila visual mutants. In many mutants the enzyme activities were found to be reduced. The activities against both phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol were always affected in parallel among the mutants, while the activities of other enzymes related to phosphatidylinositol metabolism, such as diacylglycerol kinase, were not. The enzyme was concluded to be membrane-associated and was activated maximally at low Ca2+ concentration (10(-7) M), when phosphatidylinositol 4,5-bisphosphate was used as a substrate, while the activity obtained with phosphatidylinositol increased with the Ca2+ concentration up to 10(-4) M. The effects of pH on these two enzyme activities differed to some extent.

Animals↗
PubMed1988

Identification of calcium binding proteins in two-dimensional gel electrophoretic pattern of Drosophila thorax and their distribution in two types of muscles.

Ten Drosophila thorax proteins (six myosin light chains and four proteins called a, b, c, d) were found to have high affinities with Ca2+. This was proved after subjecting the total Drosophila thorax proteins to two-dimensional (2D) transblot, followed by 45Ca2+ autoradiography. Three proteins (a, c, d) showed Ca2+ dependent electrophoretic mobility changes. To know their tissue-specific localization, fibrillar and tubular type muscle fibers were individually dissected from freeze-dried flies and separately subjected to 2D gel electrophoresis. Fibrillar type muscle had protein b and a small amount of protein a. Tubular type muscle had proteins c, d and a very large amount of protein a. Protein d was characterized to be calmodulin.

Animals↗
PubMed1988

Expression defect of ornithine aminotransferase gene in gyrate atrophy.

A generalized deficiency in the mitochondrial enzyme, ornithine aminotransferase (OAT: EC 2.6.1.13), is the hallmark of gyrate atrophy (GA), a hereditary degenerative disease of the choroid and retina of the eye that leads to blindness. A human OAT cDNA, previously constructed and characterized in our laboratory, and anti-human OAT antibody were used as probes to examine the OAT gene, mRNA and protein of GA patients. A blot analysis of the genomic DNAs, RNAs and proteins of 14 GA patients identified a case with a partial heterozygous deletion of the functional OAT gene located on chromosome 10, no detectable OAT mRNA, and a barely detectable level of OAT antibody-reactive protein. The rest of the cases showed grossly normal OAT gene, mRNA, and variably reduced levels of OAT protein. A restriction fragment length polymorphism (RFLP) was identified in the functional OAT gene sequence with EcoRI which may be useful for prenatal diagnosis of GA. RFLPs were also identified in the OAT-related gene sequences located on the X chromosome with Hind III and Pst I which may potentially show linkage to X-linked retinitis pigmentosa locus. The finding of an OAT gene, mRNA, and protein defect in a GA case constitutes the first real demonstration of the molecular genetic defect of OAT in GA.

Choroid↗
PubMed1987

Quantitative tissue isolation from Drosophila freeze-dried in acetone.

Freeze-drying procedures were developed to enable collection of tissues from Drosophila flies. The flies were frozen in acetone at -86 or -94 degrees C, and dehydrated therein. After drying, many tissues could be easily taken in entirety and free of neighbouring tissues without action of degradative enzymes. Seven polypeptide species specific to retina, and nine specific to cornea, were identified on two-dimensional electrophoretograms. Phospholipids of the dried tissues could be studied by t.l.c., and phosphatidic acid of the fly head was found to occur predominantly in the retina. Activity of three enzymes in the dried tissues could be assayed. The results of protein, phospholipid and enzyme analyses were corroborated by analyses by 'genetic dissection' using an eyeless mutant line.

Acetone↗
PubMed1987

Two cases of NADH-coenzyme Q reductase deficiency: relationship to MELAS syndrome.

Muscle biopsy specimens from two patients with MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes) were studied biochemically. 14CO2 production rates from (1-14C)pyruvate, (U-14C)malate, and (1-14C)2-ketoglutarate were all decreased in intact mitochondria in both patients. Rotenone-sensitive NADH cytochrome c reductase activities were decreased to 8% (patient 1) and 6% (patient 2) of control values; succinate cytochrome c reductase and cytochrome c oxidase values were within normal limits. These results indicate that both patients have a defect of NADH-CoQ reductase of the respiratory chain and that MELAS can be brought about by a defect of NADH-CoQ reductase.

Acidosis, Lactic↗