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Biomedical subjects

T A Uchida

Publications and source records attributed to T A Uchida.

At least 19 recordsLinked to original sources
PubMed1991

Ultrastructural changes of the midgut epithelial cells in feeding and moulting nymphs of the tick Haemaphysalis longicornis.

The midgut epithelial cells in nymphs fed on laboratory rabbits were examined during feeding and after detachment. The midgut epithelium at the unfed stage consisted of digestive cells of lower activity, containing such nutritive substances as protein, lipid and glycogen. As feeding proceeded, the cells became active in intracellular digestion. At the middle of the feeding stage, the spent digestive cells derived from the active digestive cells began to be replaced by the new digestive cells of lower activity. After detachment, the pinocytotic activity of the above cells increased greatly, and the digestive activity increased to some extent. As a result, many large endosomes were formed by fusion of numerous pinosomes. Thereafter, endosomes decreased in size as digestion proceeded and there was an increase of haematin granules. On day 7 after detachment, the new digestive cells of lower activity, belonging to the 'nutritional reserve' type, appeared adjacent to the spent digestive cells which had almost exhausted all endosomes, and these new cells had completely replaced the spent cells by day 3 after moulting.

Animals↗
PubMed1989

Physiological phases of nymphal molting defined by mobility, body weight decrease, and excretion in Haemaphysalis longicornis (Acari: Ixodidae).

Based on the rate of body weight decrease, the nymphal premolting period in Haemaphysalis longicornis Neumann was divided into three phases: a period of rapid weight decrease following detachment, a period of slight decrease, and another period of relatively rapid decrease before molting. Phase 1 was characterized by increased guanine excretion and mobility. The rate of weight decrease during phase 1 was greater in males than in females. During the premolting period, excreta consisted only of guanine and were devoid of hematin. In phases 2 and 3, neither excretion nor mobility was observed. Twenty-eight percent of the females and 40% of the males did not undergo phase 3. Adult body weight decreased rapidly until about day 5 after molting, after which weight was maintained until the end of the experiment. Guanine was excreted in large quantities just after molting and in small amounts for 4 d thereafter. Hematin excretion followed guanine excretion and was concentrated in a 3-d period starting 4 d after molting. The beginning of hematin excretion coincided approximately with the point at which body weight was maintained at a constant state. There were no quantitative differences per unit of body weight between the sexes with the exception of the rate of body weight loss during nymphal phase 1.

Animals↗
PubMed1988

Formation of the microtubule bundle and helical shaping of the spermatid in the common finch, Lonchura striata var. domestica.

Spermiogenesis in the common finch with special reference to the role of microtubules constituting the microtubule bundle was examined. Microtubules first appear in a loosely grouped cluster which helically surrounds the spherical nucleus. Concurrently with the formation of a single helical bundle of microtubules, the nucleus first assumes a helical shape. With a change in microtubular array, the ridge surface of the nuclear helix becomes flattened and depressed; the gyres of the nuclear helix increase in number. During helical shaping of the acrosome, the microtubule bundle is closely associated with the posterior one gyre of the acrosomal helix with the same pitch as in the nuclear helix. At the completion of acrosomal shaping, the microtubule bundle is separated from the acrosome by the Sertoli cell process. The microtubule bundle completely disappears in the mature spermatid. It is suggested that microtubules play an important role in helical shaping of the acrosome and nucleus.

Acrosome↗
PubMed1987

Effects of temperature on development and growth in the tick, Haemaphysalis longicornis.

As a part of ecological studies on Haemaphysalis longicornis, the effects of controlled temperatures (12, 15, 20, 25 and 30 degrees C; approximately 100% RH) on development and growth of the tick were investigated and the critical low temperature for each stage in the life cycle was estimated. As the temperature became low, the periods of preoviposition, oviposition, egg hatching (incubation) and moulting were prolonged. At 12 degrees C, however, oviposition, egg hatching and moulting of the larva and nymph did not occur. The critical low temperatures for oviposition, egg hatching (developmental zero) and larval and nymphal moulting, which were calculated theoretically from the regression equations, were 11.1, 12.2, 10.2 and 11.8 degrees C, respectively. The temperature also affected the egg productivity and hatch-ratio. The number of deposited eggs per mg of body weight decreased markedly at 15 degrees C, and the hatch-ratio was lowered with dropped temperatures.

Animals↗
PubMed1987

Changes in progesterone concentrations in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus.

In the Japanese long-fingered bat, when compared with the baseline values during non-pregnancy in the autumn, plasma progesterone concentrations were not significantly elevated during the delayed implantation stage that begins before the bats enter hibernation. However, progesterone concentrations were significantly lower during the delayed development stage that occurs during hibernation and rose significantly during the rapid embryogenesis that occurs after arousal from hibernation in the spring. Changes in the corpus luteum volume corresponded closely with those of plasma progesterone values. Maintenance of gravid females at 25 degrees C for 2 weeks in winter resulted in significant increases in the plasma progesterone concentration and the corpus luteum volume.

Animals↗
PubMed1987

Sperm-epithelium relationships in relation to the time of insemination in little brown bats (Myotis lucifugus).

Copulation lasted for up to 46 min in little brown bats. Spermatozoa were stored in both the uterus and the utero-tubal junction, although intimate relationships between spermatozoa and the epithelium were particularly evident in the utero-tubal junction, and were established at the beginning of the period of sperm storage. Polymorphonuclear leucocytes were present in all uteri irrespective of whether or not they had been inseminated but were not generally present in the utero-tubal junction or oviduct. Engulfment of spermatozoa by the epithelial cells of the utero-tubal junction and by polymorphonuclear leucocytes in the uterine glands was evident soon after copulation. It is suggested that this may effect the removal of defective spermatozoa and allow luminal spermatozoa access to the spatially restricted storage sites. Uninseminated female bats attempted to elicit copulation from torpid males, and were also observed adjacent to copulating pairs. Female bats also uttered copulation calls.

Animals↗
PubMed1985

Prolonged survival of the Graafian follicle and fertilization in the Japanese greater horseshoe bat, Rhinolophus ferrumequinum nippon.

After the mating season of the Japanese greater horseshoe bat in mid- or late October, only the right ovary maintained a single Graafian follicle throughout hibernation until early April. During this time the ovum was in prophase of meiosis I (resting stage) with many large lipid droplets as a nutrient source. In synchrony with stigma formation, there was resumption of meiotic activity, separation of the cumulus oophorus from the granulosa layer and dispersion of the follicle cells just before ovulation in spring. The block to polyspermy seemed to reside in the zona pellucida, because no spermatozoa could be detected in the perivitelline space of the 6 fertilized ova examined, although a second spermatozoon was recognized in the zona pellucida of 3 ova.

Animals↗
PubMed1985

Ultrastructural observations of the intra-erythrocytic merozoite in Theileria sergenti.

The intra-erythrocytic merozoite of Theileria sergenti was 2.2 to 2.4 micron long; several mitochondria and a large nucleus lay at the anterior and posterior part of the cell, respectively, and free ribosomes were evenly scattered in the cytoplasm. A micropore located at the antero-ventral side of the protozoon was framed by the local thickening of the plasma membrane with high electron-density, nearby a large food vacuole containing erythrocytic matrix-like substances. The highly developed rough endoplasmic reticulum was abundant around the vacuole. On the other hand, the erythrocytes including many strongly basophilic stipplings seem to be the erythrocytes with a large quantity of highly electron dense granules. Uneven-surfaced reticulocytes with a certain amount of fine granules through-out the cytoplasm possessed some pinosomes, a considerable number of degenerating mitochondria and smooth endoplasmic reticulum.

Animals↗
PubMed1984

Sperm invasion of the oviducal mucosa, fibroblastic phagocytosis and endometrial sloughing in the Japanese greater horseshoe bat, Rhinolophus ferrumequinum nippon.

In the Japanese greater horseshoe bat, Rhinolophus ferrumequinum nippon, a vast number of spermatozoa invade the oviducal epithelial cells of the caudal isthmus and become concentrated in the endometrial lamina propria of the bicornuate horns. They are subsequently phagocytised and digested by fibroblasts. Then, finally, they become deposited in the uterine lumen together with a large quantity of secretory material from the endometrial connective tissue which, prior to this event, undergoes a massive infiltration by polymorphonuclear leucocytes.

Animals↗
PubMed1984

Development of the main and accessory placentae in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus.

The placentae of the Japanese long-fingered bat were characterized by their morphological and functional transition from the main placenta to the accessory placentae. The main placenta transformed from an endotheliodichorial to a haemodichorial (one layer of syncytiotrophoblast and one layer of cytotrophoblast cells) condition. Degeneration of the main placenta was accompanied by development of two accessory placentae. These developed on both sides (fetal side) of the main placenta, and subsequently converted from a haemodichorial (two layers of cytotrophoblast cells) to a haemomonochorial condition.

Animals↗
PubMed1984

Effects of elevated temperatures on the embryonic development and corpus luteum activity in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus.

Gravid female Japanese long-fingered bats were kept in captivity without hibernation at elevated temperatures (23-25 degrees C) in winter. The embryonic growth rate was accelerated and consequently parturition was advanced by a period equivalent to that of exclusion from hibernation as compared with that in the wild population. The corpus luteum became active, as indicated by an increase in the 'light' lutein cells in an experimental bat pregnant with a 15-mm embryo, but was less active (more 'dark' cells) in 2 hibernating control bats with an implanting blastocyst.

Animals↗
PubMed1983

Studies on the vaginal plug of the Japanese greater horseshoe bat, Rhinolophus ferrumequinum nippon.

The vaginal plug of the Japanese greater horseshoe bat is composed of an outer, thick, hard and homogeneous layer originating from the stratum disjunctum of the vaginal mucosa and a thin, soft and opaque central core containing accidentally trapped dead spermatozoa. The vaginal plug appeared to be expelled just before or after ovulation in spring. Immediately after copulation in autumn, uterine spermatozoa were dead but few leucocytes were present. As time passes after copulation, however, the infiltration of leucocytes into the uterus increased gradually, and extensive leucocytic phagocytosis of dead spermatozoa occurred during hibernation.

Animals↗
PubMed1983

Ultrastructural observations of delayed implantation in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus.

Embryonic development in Japanese long-fingered bats proceeded very slowly during and after the delayed implantation period (mid-October to mid-December). The primitive amniotic cavity and endoderm were formed before implantation. At the preimplantation stage (before hibernation) the corpus luteum cells appeared active, but became less active at the implantation stage (in hibernation). Activity was again apparent at the early placentation stage (after arousal).

Animals↗
PubMed1982

Changes in the morphology and behaviour of spermatozoa between copulation and fertilization in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus.

Live spermatozoa were first stored in the colliculus tubaricus of the uterotubal junction (UTJ) on both sides, Spermatozoa then ascended to the caudal isthmus just before ovulation. Spermatozoa with intact acrosomes in the caudal isthmus, which had their heads orientated towards the cephalic isthmus, were seen amongst groups of epithelial cilia in parallel to the epithelium; on the other hand, acrosome-less spermatozoa that were not attached to the epithelium were orientated irregularly in the lumen. A few acrosome-intact spermatozoa were found in the left ampulla at the time of ovulation of the single egg on the left side. Most of the spermatozoa failed to reach or survive in the ampulla of the right oviduct and leucocytic phagocytosis was restricted to this side.

Animals↗
PubMed1981

Ultrastructural observations of fertilization in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus.

Only a very few spermatozoa were found in the ampulla of the oviduct just after ovulation. The spermatozoa lost both the acrosome cap and the equatorial segment while passing between the cumulus cells surrounding an ampullar egg; many such spermatozoa were found in the perivitelline space. One spermatozoon was seen in contact with the plasma membrane of the ovum in the metaphase of the second meiotic division. Excess spermatozoa in the perivitelline space were phagocytosed by pseudopodial protrusions from the blastomere surface.

Animals↗
PubMed1981

Ultrastructural observations of ovulation in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus.

In the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus, ovulation occurred spontaneously with the disappearance of the granulosa layer and germinal epithelium at the apex of the stigma which was formed simultaneously with expulsion of the first polar body, and with the subsequent bleeding from the capillary lumina of the theca interna. After ovulation the rupture point was plugged by luteinizing granulosa cells and overgrown by newly regenerated cells of the tunica albuginea and germinal epithelium.

Animals↗