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Biomedical subjects

M Yu

Publications and source records attributed to M Yu.

At least 433 records · Page 24Linked to original sources
PubMed1979

Decreased production of transforming virus and altered antigenic behaviour in cultured avian sarcoma cells.

Tumours induced in chickens by inoculation of avian sarcoma viruses are frequently capable of undergoing spontaneous regression. It is only those tumour cells which have been derived from progressively growing neoplasms that are able to produce transforming progeny virus in vitro and to shed into the culture medium antigens which are specifically reactive with the peripheral lymphocytes of sarcoma-bearing hosts. Following multiple passages and extended growth in culture, however, the ability of these tumour cell fluids to stimulate the lymphocytes of sensitized hosts diminishes in concert with the declining capacity of these cells to continue to synthesize fully transforming progeny virus. In certain instances, however, aged tumour cells are able to synthesize particles which contain the enzyme RNA-dependent DNA polymerase yet lack detectable envelope glycoprotein.

Animals↗
PubMed1979

Non-specific effects of avian retrovirus co-incubation on lymphocyte function: abrogation of antigen- and mitogen-induced proliferative responsiveness.

Peripheral blood lymphocytes from chickens bearing tumours induced by avian retroviruses can be stimulated to divide by group-specific antigens present in supernatant fluids of avian retrovirus-infected but not normal chicken embryo fibroblast (CEF) cells. Centrifugation studies revealed that the relevant antigenic activity is non-virion in nature. Indeed, the presence of avian retrovirus particles was found to be inhibitory to the capacity of sensitized lymphocytes to be stimulated in this antigen-driven blastogenesis assay. Similar results were obtained in lymphocyte mitogenesis experiments in which any of peripheral chicken lymphocytes or mouse splenic, lymph node or thymic lymphocytes were co-incubated with either concanavalin A or phytohaemagglutinin in the presence of numerous types of virus particles. This inhibitory effect was not due to infection of lymphocytes by the viruses tested, and was obtained in the case of lymphocyte-virus combinations for which the cells lacked the surface receptors required for viral entry. Virus could be added to lymphocyte cultures as late as 26 h after co-incubation with mitogen, and still inhibit the usual mitogenic response. In addition, co-addition of virus to lymphocytes in the presence of concanavalin A was found to block the capping of ligand-bound receptors which normally ensues. Pre-added virus did not, however, affect the ability of lectins to bind to cells.

Alpharetrovirus↗
PubMed1978

Adrenal and plasma corticosterone of hepatectomized rats: responses during hepatic restoration.

Adrenal and plasma corticosterone concentrations of partially (70%) hepatectomized male rats were examined during the course of liver restoration. Following hepatectomy, 33% of the liver mass observed in the sham operated group was present on day ), with approximately 50, 70, 75 and 82% present on days 2, 3, 4 and 7, respectively. Total restoration was noted by day 14. Plasma proteins abruptly decreased after hepatectomy and then gradually increased as liver mass was restored. The weights of both adrenal glands of hepatectomized animals were increased markedly on days 1 to 3, while adrenal corticosterone concentrations and production were elevated on day 2. Plasma corticosterone levels increased significantly following hepatectomy and remained elevated for 4 days, whereas only on the first day after surgery were the adrenal and plasma corticosterone levels elevated in the sham operated group. These data suggest that, despite the loss of liver mass and hence the apparent loss of delta 4-steroid hydrogenase activity, the adrenal glands do not decrease but actually increase their secretion during the first few days after hepatectomy.

Adrenal Glands↗
PubMed1978

[Immunological and structural properties of Rous sarcoma virus-transformed and tumor cells].

We compared the capacity of both normal and Rous sarcoma virus (RSV)-transformed chicken embryo fibroblast (CEF) cells as well as Rous sarcoma (RS) tumor cells to serve as targets in anti-tumor immunity assays. These studies showed that sera from tumor-bearing donors were able to stain transformed CEF more efficiently than RS cells as detected by immunofluorescence. In contrast, antiserum against the major viral glycoprotein, gp 85, stained a higher percentage of RS than transformed cells. Normal CEF cells, which served as controls, were essentially non-reactive with the immune system as judged by this type of assay. We observed that RS cells are considerably larger and contain far higher levels of protein than either normal or transformed CEF. Scanning electron microscopy revealed both the RS cells and transformed CEF to be rich in surface ruffles, blebs and microvilli as distinguished from the flattened, fusiform appearance of normal CEF cells.

Animals↗
PubMed1977

Cellular and humoral anti-tumor immune responsiveness in chickens bearing tumors induced by avian sarcoma virus.

A systematic comparison was undertaken of the respective abilities of normal chicken embryo fibroblast (CEF) cells, Rous sarcoma virus (RSV)- transformed CEF cells, avian Rous sarcoma (RS) tumor cells and murine RS cells to serve as targets and antigen donors in various assays for the detection of cellular and humoral anti-tumor immunity in chickens bearing tumors induced by Rous sarcoma virus. As measured by a cytotoxicity procedure, avian and murine RS cells were more susceptible to the killing effects of sensitized lymphocytes than were transformed CEF which in turn were more reactive than normal CEF. In contrast, sera from tumor-bearing animals were able to stain by indirect immunofluorescence only the avian RS and transformed CEF cell types. Extracts of both transformed CEF cells and avian RS cells but not normal CEF were equally effective as inhibitors of migration of peritoneal exudate cells derived from tumor-bearing animals. Transformed CEF were found to produce far higher quantities of transforming virus progeny than avian RS cells, although the latter were apparently albe to synthesize defective viral particles. These data indicate the significant variations which may occur under experimental conditions, depending on the types of assays and target cells employed.

Animals↗
PubMed1976

Adrenocortical responses of rats to acute hypoxic and hypercapnic stresses after treatment with aminergic agents.

Monoaminergic influences on the regulation of the hypothalamo-hypophyseal-adrenocortical (HHA) system during acute stresses (hypoxia and hypercapnia) were investigated in male rats. Plasma corticosterone levels were used to assess HHA activity, and the alterations in monoaminergic activity were induced by pretreating the animals with various pharmacologic agents (reserpine, alpha MT, FLA-63, pCPA, L-Dopa, pargyline, Lilly 110140, phentolamine and propranolol). Dexamethasone-treated rats were utilized to assess the site at which these monoaminergic substances acted. The latter experiments showed that these agents did not have a marked effect directly on the adrenal cortex and thus the site(s) of action was at the level of the anterior pituitary and/or above. Altering the serotoninergic system did not appreciably influence the HHA response to hypoxia and hypercapnia, whereas increasing the activity of the adrenergic system partially prevented the rise usually observed in plasma corticosterone levels during these stresses. These data suggest that different aminergic pathways may be utilized for different stresses.

Adrenal Cortex↗
PubMed1975

Immunodeficiency to hepatitis B virus infection and genetic susceptibility to development of hepatocellular carcinoma.

The high frequency of hepatitis B antigen (HBsAg) in hepatocellular carcinoma (HCC) patients has led to the hypothesis that immunoresponsiveness to hepatitis B virus (HBV) may be deficient in some patients, and that the immune response deficiency may have a genetic basis. Radioelectrocomplexing (REC), a radioimmunoassay in gel based on the principle of counterimmunoelectrophoresis (CIE), has been used to identify four HBV immune status subgroups: 1) HBsAg +ve/HBsAb +ve; 2) HBsAg +ve/HBsAb -ve; 3) HBsAb -ve/HBsAb +ve; 4) HBsAg -ve/HBsAb -ve/HBsAb -ve. These subgroups comprise 2, 6, 70, and 22 percent, respectively, among blood donors, and 32, 19, 23, and 26 percent, respectively, among HCC patients. Although the HBV exposure rates in the two groups were similar, the immune complexemic rates and HBs antigenemic rates were significantly higher in HBB patients than in the blood donors. It is proposed that the failure of termination of HBV infection revealed by these high rates reflects an immunodeficiency state characterized by an inability to produce high-avidity HBsAb. The immunodeficiency might have a primary genetic basis, or it might be secondary to the immunodepressive effects of concurrent viral or parasitic infections.

Antigen-Antibody Reactions↗
PubMed1975

Optimal statistical design of radioimmunoassays and competitive protein-binding assays.

The statistical analysis of radioimmunoassay and competitive protein binding assay data is complex. Because the response variable (percent counts) is not lineraly related to log dose, a logit transformation of the response variable usually is performed to permit linear regression analysis. This transformation induces marked heterogeneity of variance, so that iterative weighted regression programs have been used to achieve the best standard curve and the most precise dose estimates of unknowns. In this study several parameters of assay design are investigated in order to establish those designs yielding antigen concentration estimates of highest precision as well as estimates of comparable precision by either simple linear regression analysis or by the more complex weighted regression technique. Unknown estimates of highest precision are obtained when 1) the present counts of the standard doses covers a range of approximately 80 percent to 20 percent, 2) the number of standard dose levels is eight or more, 3) the number of replicates at each dose level is two or more, and 4) the percent counts of the unknowns also are within the range 80 percent ot 20 percent. Under these conditions, also, simple linear regression yields unknown estimates of comparable precision to weighted regression and therefore may be safely used.

Antigens↗
PubMed1973

Chronic liver disease: differences in autoimmune serological reactions between Australians and Asians.

A total of 164 patients from Australia, Ceylon, India, Singapore, and Thailand were studied for the prevalence of autoantibodies associated with "idiopathic" chronic liver disease-namely, antinuclear antibody, smooth muscle antibody, and mitochondrial antibody. The prevalence of these autoantibodies was high among patients from Australia (55%), but was low among patients from Ceylon (14%), India (11%), Singapore (0%), and Thailand (8%). There are variations in types of hepatitis and cirrhosis between races, and this applies particularly to the type associated with autoimmune markers. This may be related to genetic differences that have evolved between peoples of European and Asian descent.

Antibodies, Antinuclear↗