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Biomedical subjects

K Hiwatashi

Publications and source records attributed to K Hiwatashi.

At least 19 recordsLinked to original sources
PubMed1992

Stable and unstable transformation by microinjection of macronucleoplasm in Paramecium.

Transformation by microinjection of macronucleoplasm in Paramecium caudatum was investigated. Macronucleoplasm with three genetic markers (behavior, trichocyst, and mating type) was injected into the macronucleus. To facilitate microinjection, in most cases, paramecia were immobilized in a gelatin (7.5%) solution. The injected cells began to express a dominant gene (cnrA+ or cnrB+) of the donor 9-24 hr after injection. Expression did not require cell division suggesting injected macronucleoplasm was capable of expressing a phenotype. The amount of injected macronucleoplasm appears to correlate with the frequency of successful expression but not to correlate with the time required for expression. After a number of fissions, the injected cells produced clones which had cells expressing the phenotype of the donor. This suggests that injected macronucleoplasm was replicated and expressed in the recipient cell lines. The transformed clones were classified into two groups. In one group, transformation was stable. All cell lines derived from the injected cells expressed a phenotype similar to the heterozygote of donor and recipient cells. In the other group, transformation was unstable. During the first five to seven fissions after injection, at each division, cells produced one daughter cell which later reverted to the recipient phenotype. After this unstable period, cells no longer produced the recipient phenotype but produced the donor phenotype exclusively. Donor and recipient phenotypes were, thus, segregated in different cell lines. Observation of genetic markers and analysis by computer simulation shed light on the mode of transmission of injected macronucleoplasm. In stable transformation, injected macronucleoplasm appears to be distributed equally to daughter cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Intracellular positional control of survival or degeneration of nuclei during conjugation in Paramecium caudatum.

The survival or degeneration of nuclei produced after meiosis in Paramecium caudatum depends upon their position in the cytoplasm. The surviving nucleus lies in the paroral region, which is the region around the cytostome. In this study, this was confirmed by quantitative measurements of the location of surviving nuclei in both stained and living conjugating cells. Observation of nuclear behaviour in living cells shows that there is an active mechanism for localizing one of the four meiotic products into the paroral region after the second meiotic division. When this mechanism is inhibited by vinblastine, none of the four nuclei gets into the paroral region and all of them become pycnotic, before degenerating. The results show that migration into the paroral region is essential for survival of the nucleus and that microtubules are involved in this nuclear migration.

Animals↗
PubMed1978

Control of lower-esophageal-sphincter contractile activity by motilin in conscious dogs.

The effect of synthetic motilin on contractile activity in the lower esophageal sphincter (LES) and the stomach has been studied in 5 healthy dogs by means of chronically implanted strain gage force transducers. Motilin produced strong contractions in the LES and the stomach simultaneously after intravenous doses ranging from 0.3 to 2.7 microgram/kg hr, which were similar to the naturally occurring interdigestive contractions in the LES and the stomach. However, these contractions could be induced only in the interdigestive state; infusion of motilin into dogs in the digestive state brought about no significant effect on either the LES or the stomach. Motilin-induced contractions in the LES and the stomach were instantly abolished by ingestion of food. It is considered that the contractions induced by motilin are identical with the naturally occurring interdigestive contractions in the LES and these contractions are the most orad component of the interdigestive cyclic recurring caudad-moving bands of strong contractions in the dogs.

Animals↗
PubMed1978

Mutants of sexual maturity in Paramecium caudatum selected by erythromycin resistance.

Cells of Paramecium caudatum, syngen 3 usually become sexually mature about 50 fissions after conjugation. In order to study the genetic mechanisms that control fission-department expression of maturity, an attempt was made to obtain early mature mutants by treatment with N-methyl-N'-nitro-N-nitrosoguanidine. A new cytoplasmic marker, erythromycin resistance, was used to eliminate nonconjugant and macronuclear regeneration clones. Twenty early mature clones were obtained from five different mutagenized cultures. Three of them were genetically analyzed by crosses to wild-type stocks. The results show all three mutants to be controlled by incompletely dominant genes, i.e., the homozygotes became mature 20-25 fissions and the heterozygotes 15 fissions earlier than the wild-type clones. At least two different loci are suggested for the early maturity.

Animals↗
PubMed1977

[The motility of the lower esophageal sphincter (author's transl)].

Changes in lower esophageal sphincter (LES) motility have been mainly studied by intraluminal manometry. However, it is not suitable for continuous measurement of LES pressure. With extraluminal force transducers developed and constracted in our laboratory, we measured changes in contractile activity of the LES. Three anesthetized mongrel dogs were used for preliminary experiment. A transducer was sutured on the serosal surface of the LES immediately inferior to the phrenoesophageal membrane. A catheter with a side hole was simultaneously passed into the stomach through a mouth so that the side hole was anchored at the highest pressure zone of the gastroesophageal junction. It was found that dose-related changes in motor activity of the LES to pentagastrin were obtained by both methods. This result indicate changes obtained by transducers represent those in intraluminal pressure measured manometory. Transducers were chronically implanted on the LES and the gastric body and antrum to record changes in contractile activity in conscious state. It was found that a group of contractions lasting for 25 +/- 2.5 min occurred at regular intervals of quiescence until next meal. Furthermore, these motor increase precisely coincided with the interdigestive contractions of the stomach.

Animals↗
PubMed1976

Mating-reactive membrane vesicles from cilia of Paramecium caudatum.

Membrane vesicles with a high mating reactivity were obtained from cilia of Paramecium caudatum by treatment with a solution containing 2 M urea and 0.1 mM Na2-EDTA. All processes of conjugation were induced in cells of the complementary mating type by approximately 10 mug/ml proteins of the vesicles. Electron microscope observation showed that the membrane vesicles have a diameter of 100-150 nm. Electrophoretic analysis on SDS polyacrylamide gel revealed no significant difference in polypeptide patterns of the particles from the two complementary mating types.

Animals↗
PubMed1976

Hemorrhagic diathesis in Weber-Christian disease.

A case of a 21-year-old woman with Weber-Christian disease, associated with consumption coagulopathy and adequately controlled over the past year or more by corticosteroid and heparin therapy, has been described. Through the study on this case, it was concluded that a hemorrhagic diathesis complicating Weber-Christian disease, at least in advanced cases, was characterized by consumption coagulopathy associated with enhanced blood coagulability which arises from hyperlipemia due to abnormal lipid metabolism and further, that the consumption coagulopathy was modified by diminished synthesis of clotting factors and activation of the fibrinolytic system due to the secondary hepatic impairment. It might also be likely that systemic vascular changes contribute to the activation of the clotting system as a trigger of clotting factor consumption. The complex pathophysiology of a hemorrhagic diathesis in this disease seemed to be brought about by a complex combination of such a variety of factors. In addition, decreased erythrocyte sedimentation rate observed characteristically during hemorrhage might probably have a direct correlation with hypofibrinogenemia due to consumption coagulopathy in advanced cases.

Adult↗
PubMed1976

Motilin-induced mechanical activity in the canine alimentary tract.

Gastrointestinal contractile activity from the lower esophageal sphincter to the terminal ileum in the conscious dogs was continuously recorded on a multi-channel polygraph for several weeks by means of chronically implanted strain gage force transducers. It was found that the 24-hour gastrointestinal motor activity consisted of the two different major patterns; the digestive and interdigestive patterns. The interdigestive motor activity was characterized by a cyclic recurring, caudad-moving band of strong contractions interrupted by long lasting motor quiescence. When one band of strong contractions reached the distal ileum, another developed in the LES, stomach and duodenum again and propagated in a caudad-direction. Such recycling episodes repeatedly occurred until the next meal. After ingestion of food, gastrointestinal motor activity was continous and such characteristic interdigestive patterns were not observed. Synthetic motilin, 0.1-2.7 mug/kg/hr, was assayed for its motor stimulating activity in the both states. In the digestive state, an i.v. infusion of motlin had no influence upon the motor activity even if the dose was increased up to 6.0 mug/kg/hr. On the other hand, when motilin was infused during the interdigestive state, it induced a pattern precisely like the naturally-occurring interdigestive contractions. Not only the naturally-occurring contractions but also motilin-induced contractions were strongly inhibited by the ingestion of food or an i.v. infusion of pentagastrin (0.2-1.8 mug/kg/hr). Duodenal acidification (0.1 N HC1, 3-16 ml/kg/hr) in the interdigestive state disturbed or inhibited the regular cycle of the natural contractions but was counteracted by exogenous i.v. infusion of motilin. These findings strongly suggest the view that the interdigestive gastrointestinal motor activity is at least in part regulated by circulating motilin concentration in the blood, however, its cyclic recurring, caudad propagating mechanism may be controlled in part by the nervous system. Motilin is the only substance known to be active during the interdigestive state and therefore may be called the interdigestive hormone.

Animals↗