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Biomedical subjects

Y Cho

Publications and source records attributed to Y Cho.

At least 181 records · Page 10Linked to original sources
PubMed1979

Entry of metastatic malignant cells into the circulation from a subcutaneously growing myelogenous tumor.

The initial stage of metastasis formation, i.e., the entry of metastatic cells from a malignant subcutaneously growing myelogenous tumor into the circulation, was observed by means of transmission electron microscopy and scanning electron microscopy in Long-Evans rats. The transmural passage of malignant cells occurred through the walls of intact venules within the tumor. The malignant cell penetrated the endothelial cell body by making a temporary migration pore. The migration pore closed after the malignant cell entered the vascular lumen. The endothelial vascular lining remained continuous. The entry of malignant cells into the circulation was not the result of the general invasive and destructive properties of malignant tumor cells, but the consequence of a specific action of the tumor cells on the abluminal plasma membrane of the endothelium.

Animals↗
PubMed1978

Applications of purification reactions for minimizing reaction-generated enzyme poisoning.

A mathematical model has been employed to examine the interplay of reaction and mass transfer in immobilized enzyme systems involving reaction-generated enzyme poisions. Deactivation rates can be significantly reduced in some cases by catalyzing a purification reaction in which the poison is transformed into an innocuous substance. This conclusion in illustrated experimentally for reaction-generated H2O2 in a continuous-flow stirred slurry reactor containing glucose oxidase immobilized on activated carbon.

Enzymes, Immobilized↗
PubMed1978

Destruction of circulating leukemia cells by phagocytosis in rats with myelogenous leukemia.

Acute myelogenous leukemia was induced in outbred Long-Evans rats by iv injections of leukemia cells from a subcutaneous tumor of Shay myelogenous leukemia. In rats with this leukemia the peripheral white blood cell (WBC) counts varied from 2.4 to 700 X 10(9)/liter. No differences were found in the bone marrow of the rats with the high WBC counts and that of rats with low WBC counts. This observation could explain the large variations in the number of circulating leukemia cells caused by differences in cell proliferation or delivery of cells into the circulation. Massive phagocytosis of leukemia cells occurred in animals with low WBC counts (less than 12 X 10(9)/liter) but not in animals with high WBC counts (greater than 150 X 10(9)/liter). This phagocytosis was directed against circulating leukemia cells. The main phagocytes were Kupffer's cells of the liver and macrophages of the spleen parenchyma. In addition, phagocytosis occurred in the spleens and bone marrow by intravascular macrophages, which were derived from extravascular sites. The endothelium of the postcapillary venules of the lymph nodes participated in the phagocytosis of circulating leukemia cells while continuing to be the locus of lymphocytic return from circulation to lymphatic parenchyma. The factors underlying the differences in macrophage activity between the rats with high and low WBC counts were unknown.

Animals↗
PubMed1976

The epizootiology of infectious bursal disease and prevention of it by immunization.

Transport of leftover feed from infectious disease (IBD) farms to susceptible flocks on clean premises is believed to have played an important role in the transmission of this disease to new farms and to new areas. Servicemen, caretakers, contaminated equipment and air were suspected in the spread of the disease, but these modes were not demonstrated. Litter, drinking water and samples of feed from feeders of IBD flocks were found to be infectious when added to rations of susceptible chickens but were not when added to drinking water. Infectious bursal agent (IBA) remained viable for at least 6 months in dry litter and in unused dry chicken houses for more than 1 year. IBA was found in circulating blood of infected chickens 36 hours after inoculation, but not after 72 hours. Liver, spleen, thymus, kidney, pancreas and intestines were infectious at 72 hours. Bursa and feces were infectious from 48 hours through 7 days after inoculation. Tests on 4 1/2 to 6-week-old birds from 10-12 farms of each of several broiler complexes in three southeastern states of the U.S. revealed IBA present on a high percentage of farms even though none had used vaccine. Vaccination with modified or unmodified IBA administered to millions of 4-10-day-old chicks gave good protection for the life of broilers and laying birds. Effect of IBD on development of immunity to other diseases will be discussed.

Animals↗
PubMed1975

Passage of red blood cells through the sinusoidal wall of the spleen.

The migration of blood cells across the wall of splenic sinusoids has been studied by means of serial sections in rats inoculated with murine erythroblastosis virus (MEV). The sinusoidal walls of the normal spleen have no permanent openings. In the normal spleen, mature red blood cells and blood cells in the latest stages of maturation can be seen in diapedesis. The predominant form of transmural migration is intercellular. In MEV-inoculated animals, in which there is a vigorous erythroblastic proliferation, large numbers of erythroblasts are in transmural passage. Serial sections show that these cells migrate through the cytoplasm of the endothelial lining cells. On the basis of these observations, it is suggested that the transcellular mode of migration may be related to the delivery of newly formed red blood cells into the circulation while the intercellular mode may be part of the mechanism by which the spleen controls the removal of red cells from the circulation.

Animals↗
PubMed1975

On the development of the lymphoid follicles of the bursa of Fabricius.

The structural features of the development of the bursa of Fabricius in white Leghorn chick embryos are depicted at carefully timed intervals during embryogenesis, with emphasis on the sequence of events between the ninth and twelfth days of incubation. The direction and character of the migration of lymphoid cell precursors and granulocytes from the intravascular space to intraepithelial sites, where the formation of the primitive lymphoepithelial nodule takes place, is demonstrated. The mechanism of the mode of migration of these cells through the stromal epithelial interface is described and illustrated with electron micrographs and their role in the development of the primitive lymphoid follicles is described and discussed.

Animals↗
PubMedDate not supplied

Disability status differentials across fifteen Asian and Pacific Islander groups and the effect of nativity and duration of residence in the U.S.

This study examines disparities in disability status across 15 Asian and Pacific Islander American (API) subpopulations and how nativity and duration in the U.S. influence these differences. Employing three disability questions (work limitations, mobility limitations, and self-care limitations) from the 1990 PUMS, the authors find substantial heterogeneity in disability status across API subgroups: while Japanese American adults have the most favorable outcomes, Other Southeast Asian adults (Laotians, Hmong, and Cambodians), followed by Vietnamese and Pacific Islander adults, suffer from a high risk of disabilities. Many of the disparities in disability status across API subpopulation adults are attributable to differentials in demographic characteristics and SES. The inclusion of an interaction term of age and nativity/duration of residence in the U.S. in multivariate regression analyses demonstrates that the effect of nativity/duration plays a different role across age, net of demographic, and SES risk factors. The overall findings are also consistent with previous studies on the relationship between immigrant health and nativity/duration. That is, immigrants with short duration in the U.S. have superior health status, measured by risk of disability, than longer-term immigrants and their U.S.-born counterparts.

Activities of Daily Living↗
PubMedDate not supplied

Behavior and muscle performance in heterothermic bats.

Body temperatures of winter-resident Korean bats typically range from 10 degrees to 40 degrees C between August and September and from 3 degrees to 15 degrees C between January and April. To learn how behavior and the motor systems of heterothermic bats respond to this body-temperature variation, we examined whole-organism performance and the temperature-dependence of contractile properties of flight muscle in Murina leucogaster ognevi. In winter and midspring, the lowest limits of body temperature were 8 degrees C for biting and crawling, 16 degrees C for visually observable shivering, 22 degrees C for wing flapping (without powered flight), and 28 degrees C for aerial flight. In summer, the lowest temperature limits changed little for biting and wing flapping, but the temperature limits increased about 3 degrees C for crawling, shivering, and flight. Maximum isometric tetanic tension of the isolated biceps brachii muscle was almost insensitive to tissue temperatures between 10 degrees and 40 degrees C, with an average temperature coefficient of 1.02 in summer and of 0.96 in winter. Rate of tetanic tension production between 10 degrees and 40 degrees C and shortening velocity and power between 15 degrees and 25 degrees C were temperature sensitive, with average temperature coefficients of 1.3-2.3. Seasonal differences in contractile properties within each temperature were not significant, except for maximum tetanic tension at 30 degrees - 40 degrees C. Thus, the motor system of the bats had functional capacity over the range of body temperature experienced in winter to summer. The temperature-dependence of behavior was consistent with muscle physiology. The defensive behaviors, like biting and crawling, observed at 8 degrees - 12 degrees C body temperature could be exerted by using temperature-independent tetanic tension, whereas activities, such as flight, that require power generation would be restricted to higher body temperatures by temperature-sensitive rate properties. Some rate processes appeared to be more temperature sensitive in summer than in winter.

Animals↗