PubMed Health⌕ Search

Biomedical subjects

M Yu

Publications and source records attributed to M Yu.

At least 415 records · Page 23Linked to original sources
PubMed1988

Influenza surveillance in Singapore: 1972-86.

Prospective laboratory surveillance of influenza viruses has been carried out since 1973 in Singapore. The results indicate that antigenic shift variants caused epidemics at various times of the year over this period, whereas drift variants were associated with a regular increase in incidence during the second and fourth calendar quarters. Outbreaks due to influenza A virus occurred every year and to influenza B virus at intervals of 16-24 months. Between outbreaks, viruses belonging to either of the two types could be detected during most months, and certain variants appeared several months before the outbreaks they subsequently caused. The factors that contribute to the seasonal pattern are at present unknown.

Adolescent↗
PubMed1988

[Two cases of adrenal myelolipoma].

Myelolipoma of the adrenal gland is a benign oligosymptomatic tumor composed of various proportions of fat and bone marrow elements. We report two operated cases found incidentally in a 76-year-old man and 49-year-old man.

Adrenal Gland Neoplasms↗
PubMed1987

Effect of morpholinyladriamycin analogs and adriamycin on the activities of DNA polymerase alpha and RNA polymerase II of chicken leukemia cells.

The new adriamycin (ADR) derivatives, 3'-deamino-3'-(4"-morpholinyl)adriamycin (MRA) and 3'-deamino-3'-(3"-cyano-4"-morpholinyl)-adriamycin (MRA-CN), were studied, in comparison with ADR, for their inhibitory effects on DNA and RNA syntheses in vitro using isolated DNA and RNA polymerases from both Escherichia coli and chicken (myeloblastosis) leukemia cells. Under standard assay conditions, MRA and ADR demonstrated a similar inhibitory effect on the enzymes, whereas MRA-CN showed a slightly greater inhibitory activity than ADR or MRA at low drug concentrations, but with the inhibitory effect plateauing when drug concentration reached 10 microM. Both the A and B forms of the MRA-CN diastereoisomers were effective as inhibitors. Kinetic studies of the inhibition showed that unlike ADR, MRA-CN inhibition of DNA or RNA synthesis could not be reversed by increasing DNA-template concentration in the reaction mixture. Whereas ADR or MRA relaxed completely 1 microgram of pBR322 supercoiled DNA at a drug concentration of 15 microM, MRA-CN, at 60 microM, produced a mixture of intermediate relaxation forms of the DNA. A complete relaxation was achieved at 300 microM MRA-CN. Both DNA relaxation and fluorescence spectroscopic studies indicated that DNA-drug interactions occurred in the following order: ADR (or MRA) greater than MRA-CN greater than N-trifluoroacetyl-ADR-14-O-hemiadipate (a DNA-nonbinding anthracycline).

Animals↗
PubMed1986

Site and stage specific action of endogenous nuclease and micrococcal nuclease on histone genes of sea urchin embryos.

The early histone genes of sea urchin embryos are expressed exclusively during cleavage stages of embryogenesis. The chromatin containing these genes was examined by nuclease sensitivity. An endogenous nuclease active during cleavage, produces 1300-bp segments containing early histone genes. The cutting sites have been mapped; there are very sensitive sites close to the cap site for H1, H2A, H2B, and H4. Chromatin obtained from embryos of later stages, when the genes are not expressed, do not display this pattern of nuclease sensitivity. Micrococcal nuclease produces nucleosomes that contain histone genes when used with nuclei from later stages, but not with nuclei from cleavage stages.

Animals↗
PubMed1984

Hypoxic and nycthemeral responses by the adrenal cortex of partially hepatectomized rats.

Adrenocortical nycthemeral (day-night alteration) and hypoxic stress responses of rats were evaluated 48 h following 70% hepatectomy. Morning plasma and adrenal corticosterone concentrations of hepatectomized (H) rats at 0800 hours were significantly higher than those of sham (S) operated animals. Although both groups showed significant nocturnal elevations in these parameters at 2000 hours, the nocturnal rises in plasma corticosterone levels were 75% and 223% in H and S rats, respectively, yet the absolute steroid levels did not differ between the groups. The hypothalamic-pituitary-adrenocortical (HPA) response of H animals to hypoxia was assessed by measuring plasma corticosterone levels at various times before, during and after exposure to 10% O2 at ground level. Curvilinear analysis of the plasma steroid levels revealed a significantly slower corticosterone rise during the hypoxic phase in H than S animals, as well as a much slower return to baseline levels after the hypoxic stimulus was terminated. The latter indicates a decreased hepatic capacity to inactivate steroids in H animals, while the sluggish activation of the HPA system by hypoxia may be due to altered neuroendocrine control resulting from prior exposure of feedback sites to elevated basal plasma corticosterone levels.

Adrenal Cortex↗
PubMed1983

Adoptive transfer of delayed wattle reactivity in chickens with a dialyzable leukocyte extract containing transfer factor.

Delayed wattle reactions (DWR) to tuberculin, diphtheria toxoid (DT), and keyhole limpet hemocyanin (KLH) were transferred to chickens with dialyzable leukocyte extracts (DLE) prepared from splenic leukocytes of chickens sensitized and reactive by DWR to the tuberculin, DT, or KLH. A DLE prepared from chickens unsensitized and unreactive to tuberculin by DWR failed to transfer DWR to tuberculin in recipients. Only chickens injected with DLE from tuberculin sensitized and reactive chickens exhibited significant (P less than .01) DWR to tuberculin. Chickens that received DLE prepared from DT sensitized and reactive chickens exhibited significant (P less than .01) DWR to DT but not to KLH. Further, DWR to both DT and KLH was transferred with DLE prepared from chickens sensitized to both antigens. Adoptive transfer of DWR to KLH in comparison to DT was more successful. Finally, the serial transfer of DWR to KLH (P less than .05) but not to DT (P greater than .05) was accomplished using DLE prepared from chickens that previously were recipients of DLE prepared from chickens sensitized to KLH and DT. Results indicate that DLE prepared from chickens contain transfer factor (TF) responsible for adoptive transfer of DWR to tuberculin, DT, and KLH.

Animals↗
PubMed1983

Activation of nonspecific killer cells by interleukin 2-containing supernatants.

In the absence of specific antigen stimulation, nonspecific killer cells were induced by culturing C57BL/6 lymph node or spleen cells with interleukin 2-containing supernatants. These supernatants were obtained from stimulation of either rat spleen cells with concanavalin A or a variant of the T cell lymphoma, EL4 (H-2b) with phorbol myristic acetate. The ability of the EL4 supernatant to induce nonspecific killer cells was abrogated by absorption with an interleukin 2-dependent T cell line or by concanavalin A-stimulated spleen cell blasts, but not by lipopolysaccharide-stimulated spleen cell blasts or by a non-interleukin 2-producing EL4 line. Partially purified interleukin 2 from EL4 supernatants could also support nonspecific killer cell induction. The induction of cytolytic cells by interleukin 2 is sensitive to gamma-irradiation and has a D omicron of 120 rad. The nonspecific killer cells induced are likely cytotoxic T lymphocytes; the majority of the precursor and effector cells bear the Thy-1 alloantigen marker. These nonspecific killer cells killed a broad spectrum of target cells, including concanavalin A- and lipopolysaccharide-induced splenic blasts of syngeneic or allogeneic mice, a syngeneic tumor, and a cloned allogeneic cytotoxic T cell line. The frequency of precursors for nonspecific killer cells in C57BL/6 lymph node and spleen cells are 1/7000 and 1/12,000, respectively. Clonal analyses revealed that these nonspecific killers exhibit heterogeneity with respect to their target cell specificities. The induction of nonspecific killers by interleukin 2-containing supernatants is partially dependent on nylon wool-adherent cells; in antigen-stimulated cultures the most specific killer cells were obtained from cultures in which nylon wool-nonadherent lymph node responder cells were stimulated with nylon wool-nonadherent allogeneic splenic stimulator cells that were treated with anti-Thy-1 antibody and complement. The relevance of these findings with respect to the frequencies and fine specificities of cytotoxic T lymphocytes generated in interleukin 2-supplemented cultures is discussed.

Animals↗
PubMed1982

Field trials with an oil emulsion infectious bursal disease vaccine in broiler breeder pullets.

Two independent field trials were undertaken with commercial broiler companies in separate sections of Alabama in order to test the efficacy of an experimental commercially prepared oil emulsion infectious bursal disease (IBD) vaccine in broiler breeder pullets. The IBD vaccine was tested both for safety and the production of neutralizing antibodies in pullets and their progeny as well as its ability to prevent early field exposure to virulent IBD virus (IBDV) in broiler progeny that may lead to immunosuppression resulting in poor performance. The following was demonstrated in both trials: 1) the IBD vaccine had no adverse effect on breeder performance, 2) the IBD antibody titers in breeders peaked at 10 weeks postvaccination (PV) and remained about 1.5 to 4 times higher than nonvaccinated breeders through 25 weeks (PV), 3) 1-day IBDV maternal titers in broilers were related to the parental titers, 4) the IBD vaccination in pullets prevented early infection to field IBDV in progeny as determined by antibody titers and various performance parameters.

Animals↗
PubMed1982

Immune selection of tumor cell variants in chickens bearing tumors induced by avian sarcoma virus.

We have compared avian sarcoma cells, cultured from tumors at various stages of growth, in terms of their ability to synthesize infectious progeny virus and to express antigens that are reactive with the sensitized lymphocytes of tumor-bearing hosts. Cell-mediated immunity in chickens bearing tumors induced by avian sarcoma viruses was monitored by each of a target cell cytotoxicity test and an antigen-driven lymphocyte stimulation assay. Our results show that it is only those tumor cells which have been derived from progressively growing neoplasms that are able to synthesize infectious progeny virus and to specifically interact with the sensitized lymphocytes of tumor-bearing hosts. In contrast, cells from regressing tumors do not express relevant antigens to the same extent as do progressors, and they synthesize noninfectious particles only. Experiments on cellular outgrowths, derived from the plating at limited dilution of progressively growing tumor cells, revealed that such producers of defective virus are present at the earliest stages of tumor growth. Both these cells and regressing tumor cells are poorly stained (about 10%) in indirect immunofluorescence tests by antiserum against viral envelope glycoprotein, whereas tumor cells from progressing neoplasms react well (about 60 to 85%). These results suggest that tumor cells which are found in regressing neoplasms are selected out by a functional immune response directed against cells which are efficient producers of progeny virus.

Animals↗
PubMed1982

Pathology services in Singapore.

The provision of an adequate Pathology Service is essential for the rational diagnosis, management and control of diseases. In Singapore such a need has long been recognised, and the service has made substantial progress since it started.

Hospital Departments↗