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Biomedical subjects

Y Hotta

Publications and source records attributed to Y Hotta.

At least 253 records · Page 14Linked to original sources
PubMed1977

Biochemical analysis of meiosis in the male mouse. I. Separation of DNA labelling of specific spermatogenic stages.

Spermatogenic cells of the mouse have been separated by gravity sedimentation using a modification of a previously published method. Details are given for the collection of purified samples of specific meiotic stages and for the collection of labelled cell fractions following injection of 3H-thymidine. Suppression of semi-conservative meiotic DNA synthesis, essential to the biochemical analysis of pachytene DNA metabolism, has been achieved by in vivo administration of 1 M hydroxyurea.

Animals↗
PubMed1977

Biochemical analysis of meiosis in the male mouse. II. DNA metabolism at pachytene.

The DNA metabolism of mouse spermatogenic cells was investigated by intravenous administration of isotope and Staput fractionation of the cells. The pattern of metabolism is virtually identical with that observed in Lilium microsporocytes. A programmed single strand nicking of DNA occure at pachytene such that at least 50% of the DNA is in the form of 62S fragments. Repair replication of endogenously nicked sites is fully achieved during pachytene. The sites of nicking and repair are preferentially located in sequences that are repeated about 400 times. These results are considered as strong evidence for a universal pattern of meiotic prophase DNA metabolism which is associated with crossing-over.

Animals↗
PubMed1977

Biochemistry of meiosis.

The process of meiosis in Lilium falls into four physiological stages - prezygotene, zygotene, pachytene, and post-pachytene. Each of these stages has distinctive metabolic characteristics. Commitment to meiosis occurs during the prezygotene interval at about the time when S-phase replication is completed. The activities following commitment are essential to synapsis inasmuch as perturbations of cells during that interval have subsequent effects on synapsis and crossing over. Just before the initiation of synapsis, a distinctive lipoprotein complex appears in the nucleus. The complex most probably functions in the process of pairing. Zygotene is marked by the delayed replication of specific intercalary segments of chromosomal DNA (Z-DNA), the replication being a necessary condition for ongoing synapsis. The replication occurs in the lipoprotein complex in the presence of a reassociation protein (r-protein). Z-DNA segments would appear to have other meiotic functions inasmuch as the replicated segments remain unligated to the body of chromosomal DNA until the beginning of chromosome disjunction. The pachytene interval is marked by an activation of endonucleolytic activity. The enzyme produces single-stranded nicks in the DNA at specific loci. These loci consist of moderately repeated segments; about 100-200 base pairs long. Extracellular agents, such as radiation, cause random nicking regardless of the meiotic stage at which they are applied. Localized nicking and repair are thus unique features of meiosis. The temporal segregation of metabolic activities concerned with pairing and crossing over and their operation in special chromosome regions constitute the most prominent features of the biochemical events associated with meiosis.

Carrier Proteins↗
PubMed1977

Comparative light and electron microscopic study of the adrenal gland of the snake.

A new method employing both comparative light and electron microscopic observations on the study of identical cell elements was described. This method was characterized by the use of thick Epon-embedded sections (0.3-1.5 micron thick) for both light and electron microscopy. The use of a high voltage electron microscope of 1,000 kV accelerating potential made this study possible. Two types of chromaffin cells were distinguished in the adrenal gland of the snake, Elaphe quadrivirgata. Adrenaline storing (A) cells were found to be filled with slightly irregular, larger electron-dense granules, whereas noradrenaline-storing (NA) cells contained smaller granules with an electron-dense content. It was found that the chromaffin cells of the snake possess axon-like cytoplasmic processes.

Adrenal Glands↗
PubMed1976

Courtship in Drosophila mosaics: sex-specific foci for sequential action patterns.

Mosaic fate mapping is used to locate the foci determining sex-specific steps in the mating behavior of Drosophila. Male performance of following females and displaying wing vibration toward them requires that a focus inside the head be constituted of male tissue, regardless of the sex of the head sense organs, the legs, the wings, or the thoracic ganglion. For attempted copulation to occur, a second focus in the thoracic region must also be male. Courtship by males is induced by a posteriorly located focus in the female, but an anterior female focus determines receptivity to attempted copulation. The interplay of male and female foci in the complex behavioral sequence is delineated.

Animals↗