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K Segawa

Publications and source records attributed to K Segawa.

At least 127 records · Page 7Linked to original sources
PubMed1988

Three-dimensional ultrastructure of the Golgi region of the formative chondrocyte in newborn rat mandibular condyle.

The three dimensional ultrastructure of Golgi region of formative chondrocytes from newborn rat mandibular condyle was examined by means of the method based on dilute osmium maceration with a high-resolution scanning electron microscope. The large area of formative chondrocytes was occupied by the cytoplasmic organelles related to matrix-synthesis such as Golgi apparatus, rough endoplasmic reticulum (RER) and mitochondria. The Golgi region of formative chondrocytes was composed of the limiting membranous structures such as some groups of the stacks of Golgi cisterns, vesicles, vacuoles, secretory granules, reticular constituents and small tabular or tubular RER. The Golgi cisterns were composed of both small tabular parts and rod-like parts arising from tabular parts. Small tabular parts were furthermore subdivided into three types of many, few and no penetrated ones. Reticular constituents were made up of limiting membrane visible as smooth image by scanning electron microscopy, therefore, are assumed to be one part of the GERL (Golgi apparatus-endoplasmic reticulum-lysosome).

Animals↗
PubMed1987

Differential effects of DNA tumor virus nuclear oncogene products on adipocyte differentiation.

We have introduced SV40 and polyoma large T antigen- and adenovirus-type 12 E1A genes into mouse 3T3-L1 preadipocyte cells to study the ability of various nuclear oncogene products to modulate cell differentiation. Clones expressing E1A products could differentiate into adipocytes faster than the control in spite of the absence of adipogenic inducers, as measured by the appearance of lipid droplets microscopically and by staining accumulated triglycerides with oil red O. However, clones expressing SV40 and polyoma large T antigens could not differentiate even if they were exposed to the inducers.

Adenoviridae↗
PubMed1987

Transformation of glial cells in mouse embryonic brain cells in vitro with simian virus 40.

Embryonic (E10) mouse cerebellum and spinal cord cells were cultured and infected with simian virus 40 (SV40). In all infected dishes, rapid proliferations (a dividing time less than 18 h) of non-neuronal cells were detected. Three populations of those cells, SVa, SVb and SVc, could be passaged more than 10 times. They had flat morphologies like young astrocytes and, indeed, showed immunoreactivities to glial fibrillary acidic protein (GFAP), a marker for the astrocyte. However, they had an ability to form colonies in a soft agarose medium. The large-T antigen could be detected in nuclei of the three cell populations by a fluorescent antibody test and immunoprecipitation. No transformation of neuronal cells was detected, nevertheless there were neuronal cells still possessing dividing capacities in the culture preparation.

Animals↗
PubMed1987

Peptic ulcer is prevalent among shift workers.

To elucidate sleep disturbances in the etiology of peptic ulcers, the prevalence of peptic ulcer disease was compared among shift workers and daytime workers. The subjects (N = 11,657) were employees of various institutions, such as factories, banks, or schools, and had undergone a mass x-ray examination of the upper gastrointestinal tract. With present shift workers (N = 2269), the prevalence of gastric ulcers was 2.38% (N = 54) and that of duodenal ulcers, 1.37% (N = 31). With the past shift workers (N = 2111), the prevalence of gastric ulcers was 1.52% (N = 32) and that of duodenal ulcers, 0.62% (N = 13). On the contrary, with the daytime workers (N = 6525) the prevalence of gastric ulcer was 1.03% (N = 67) and that of duodenal ulcer, 0.69% (N = 45). The working schedule for 752 examinees was unknown. The prevalence of gastric and duodenal ulcers was higher with shift workers than daytime workers. Thus, shift work involving sleep disturbances may play an important role in the development of peptic ulcers.

Adult↗
PubMed1987

Effect of omeprazole on gastric acid secretion in rat: evaluation of dose, duration of effect, and route of administration.

The effect of omeprazole on gastric acid output was studied in rats before and during stimulation by continuous administration of tetragastrin at 50 micrograms/kg-hour. From 5 to 20 mg/kg of omeprazole was given to animals intraperitoneally, perorally and intravenously from 2 to 24 hours before the gastric secretory study was started, and the respective effects on acid secretion were compared. In each administration group, 20 mg/kg of omeprazole was the most potent among the groups receiving 5, 10 or 20 mg/kg, when the drug was given 2 hours before the study. There were statistically significant differences between the control group given tetragastrin only and each of the groups given 20 mg/kg of omeprazole perorally, intraperitoneally and intravenously. There was no significant difference among the groups given 20 mg/kg of omeprazole intraperitoneally, intravenously and perorally. The effect of 20 mg/kg of omeprazole continued at least 24 hours after the agent was administered perorally.

Administration, Oral↗
PubMed1987

Multicopy plasmid with a structure related to the polyoma virus genome.

In a subclone derived from mouse L(tk-) cells, we found a plasmid present in a high copy number (greater than 5000 copies per cell) that was stably maintained extrachromosomally without any cytopathic effect to the host cells. This plasmid, termed L factor, has two forms: 5.3 and 5.5 kilobase pairs. DNA sequencing and restriction enzyme mapping showed that, although the structure contains DNA sequences common to polyoma virus, plasmid sequences belonging to the regulatory region (the enhancer region) and other regions are quite different from those in polyoma. In cells bearing the plasmid, we detected a low level of material that cross-reacts with antibody to polyoma tumor antigens, suggesting that the plasmids replicate and are maintained in the cells by a mechanism different from that functioning during propagation following infection of papovaviruses.

Animals↗
PubMed1987

Induction of c-Ha-ras transcription in rat cells by simian virus 40 large T antigen.

Rat 3Y1 cells expressing simian virus 40 large T antigen under the control of the mouse mammary tumor virus long terminal repeat were established. The amount of c-Ha-ras mRNA in those cells was elevated by about 20 times in parallel with large T antigen after exposure to dexamethasone for 48 h. In chloramphenicol acetyltransferase assays with a plasmid containing the c-Ha-ras-1 promoter the increase in c-Ha-ras mRNA was shown to occur at the transcriptional level.

Animals↗
PubMed1987

Endoscopic study of upper gastrointestinal tract in patients with alcohol dependence.

This study was designed to elucidate the long-term effect of excess alcohol intake on the upper gastrointestinal tract. The subjects of the study were patients with alcohol dependence (n = 91). All of the subjects had been hospitalized to overcome their alcohol dependence. They underwent endoscopic examination of upper gastrointestinal tract, whether they had symptoms and a personal history of digestive organs trouble or not. Gastric ulcer (n = 14), gastroduodenal ulcer (n = 3), duodenal ulcer (n = 2), gastritis erosiva (n = 23), resected stomach (n = 13), esophageal cancer (n = 1), esophageal varix (n = 8), and esophagitis (n = 1) were among the lesions found by the endoscopic examination. This study indicated a close association of chronic upper gastrointestinal lesion with long-term excessive intake of alcohol.

Adult↗
PubMed1987

Immune response to Toxoplasma gondii--analysis of suppressor T cells in a patient with symptomatic acute toxoplasmosis.

Unresponsiveness of antigen-dependent (Toxoplasma-specific and purified protein derivative of tuberculin [PPD]-specific) T-cell proliferative responses of peripheral blood leukocytes (PBL) was observed in a patient with symptomatic acute toxoplasmosis. The immunosuppression of T-cell responses was mediated by Leu 1+, Leu 2a+, and Leu 3a- suppressor T cells that were induced by Toxoplasma gondii antigen and suppressed both Toxoplasma-specific and PPD-specific PBL T-cell responses from a patient with chronic toxoplasmosis when PBL of these patients were mixed and cocultured in vitro. Participation of class II molecules of HLA in Toxoplasma-specific proliferative T-cell responses and activation of suppressor T cells was examined by using monoclonal antibodies specific for HLA-DR and HLA-DQ molecules. Anti-HLA-DQ monoclonal antibody released the suppressive activity, while anti-HLA-DR monoclonal antibody inhibited Toxoplasma-specific T-cell responses. Thus, the suppressive effect of PBL from a patient with acute toxoplasmosis on antigen-dependent PBL T-cell responses from a patient with chronic toxoplasmosis was mediated by HLA-DQ molecules. By contrast, Toxoplasma-specific T-cell responses were activated by HLA-DR molecules (presumably present on antigen-presenting cells).

Acute Disease↗
PubMed1987

Precise gastric secretory studies using a new fiber-gastroscope.

A system for the precise measurement of gastric secretion was devised using an endoscope produced specially for this purpose. Gastric juice was collected through the endoscope every 10 minutes before and after tetragastrin stimulation. Results were compared with those obtained by the conventional method using a nasogastric tube in the same patients (n = 24). The ratio of gastric secretory volume and acid output with the endoscopic method, to those with the conventional method ranged from 1.30 to 1.48. This difference was statistically significant (p less than 0.01). There was no significant difference in the acid concentration of gastric juice collected by the two methods. The coefficient of variation for the volume collected in six basal 10-minute fractions was significantly smaller in the endoscopic method. Gastric secretory studies can be performed by endoscopy with no more discomfort, and the result is more accurate than studies using a gastric tube. This precise method of gastric analysis should prove useful in investigating gastric physiology when accuracy and reliability are paramount.

Gastric Acidity Determination↗
PubMed1987

Age-related changes in the trabecular meshwork of the normal human eye.

Specimens from 17 human eyes, ranging in age from 3 to 80 years, were subjected to morphometric studies using light microscope, transmission electron microscope and scanning electron microscope, in order to clarify the age-related changes in the normal trabecular tissue. Statistical analyses showed that the cellularity in the various regions of the trabecular meshwork significantly declined with age. The spaces corresponding to the aqueous outflow pathway in each region of the meshwork also significantly decreased with age. On the other hand, extracellular materials significantly increased in amount with age in all regions of the trabecular meshwork. However, the decrease in the cellularity and the outflow pathway spaces did not show any statistically significant regional difference. These results suggest that general narrowing of the outflow pathway spaces due to the accumulation of extracellular materials with age is the cause of the increase in aqueous outflow resistance with age, and that each region of the trabecular meshwork is equally responsible for the increased resistance.

Adolescent↗
PubMed1986

Cooperation of mitogenic growth factors with polyoma virus middle T antigen in transformation of secondary cultured rat cells.

Platelet derived growth factor cooperated with middle T antigen in inducing growth in agarose medium of secondary cultured rat embryo cells transfected with a polyoma virus middle T antigen cDNA clone. In contrast, epidermal growth factor and a conditioned medium containing transforming growth factor did not stimulate the colony-forming efficiency of such cells in the agarose medium.

Animals↗
PubMed1986

The effect of viral transformation on prostaglandin production depends on cell type.

The role of prostaglandins in cellular differentiation and transformation has been widely studied. We have found previously that prostaglandin E2 production was greatly diminished in dog kidney cells (MDCK) after transformation by Harvey murine sarcoma virus. In the present study, we have shown that viral transformation can have differing effects in the ability to modify the production of prostaglandin in cultured cells. For example, the prostaglandin E2 production in rat kidney cells (NRK) is decreased after transformation by Rous sarcoma virus, while production in 3T3 cells is increased markedly after transformation by the same virus. Similarly, SV40 transformation increases prostaglandin E2 production of 3T3 cells and decreases the production in rat thyroid cells (FRTL). These results indicate that the biosynthetic pathway for prostaglandin production has varying susceptibility following viral transformation and the effect of transformation depends more on the type of cell than virus. Taking advantage of the well-defined transforming proteins encoded by polyomavirus, we have further studied the relationship between prostaglandin production in cells and the expression of T antigens in transformed cells. We showed that the expression of middle T antigen, which is associated with a protein kinase and is responsible for phenotype of transformed cells, is required for the change in prostaglandin production in cells. How these changes of prostaglandin production relate to the progression of viral transformation remains to be explored.

Animals↗