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Biomedical subjects

F Merino

Publications and source records attributed to F Merino.

At least 73 records · Page 4Linked to original sources
PubMed1982

Chediak-Higashi syndrome: description of a cluster in a Venezuelan-Andean isolated region.

Fourteen cases of the Chediak-Higashi syndrome found in twelve non-related families living in a defined geographical area not larger than 200 km2 of the Tachira State, Venezuela (population of around 72,000 inhabitants) were diagnosed between 1967 and 1974. The patients were pre-school or nursing age children except one eleven year old female. Six of the patients were male. All showed the same typical somatic characteristics of this syndrome. Four cases were 2 pairs of brothers. Consanguinity of the parents was seen in only two families, even though the majority of them come from the same restricted geographic zone (Pregonero). Since this anomaly is supposedly produced by a rare recessive autosomal gene, the existence of its high frequency in a small Venezuelan region may be explained through the "founder effect" in a population with a high inbreeding coefficient.

Chediak-Higashi Syndrome↗
PubMed1981

Reduced humoral and cellular cytotoxic sensitivity in histocompatibility variants of the YAC (Moloney) lymphoma.

Previously we have reported that two sublines of the YAC lymphoma selected for reduced expression of H-2a and Moloney-virus determined cell-surface (MCSA) antigens are, in contrast to YAC, allotransplantable in H-2-incompatible recipients, and resistant to rejection by preimmunized semisyngeneic hosts. A third YAC variant with reduced MCSA but unchanged H-2-antigen expression, was not allotransplantable and showed only a slight decrease in its immunosensitivity in preimmunized semisyngeneic hosts in vivo. This suggested that H-2-antigen expression may be more important than MCSA expression for recognition and rejection by semisyngeneic mice. We have not tested the sublines expressing low H-2a for their in vitro sensitivity to humoral and cell-mediated lysis. - The variants were more resistant than YAC to complement lysis by anti-H-2a , anit-MCSA, anti-Thy 1.2 and antispecies sera. Absorption tests with antispecies serum indicated that the decreased cytolytic sensitivity of the variants was not related to the concentration of the relevant antigens, which was similar to that of the original YAC tumor. As expected from the low amount of H-2a the variants showed a decreased sensitivity to the killing effect of allogeneic cytotoxic T lymphocytes (CTL). They were also lysed to a lesser extent than YAC by semisyngeneic CTL, probably directed against virally determined antigens. However, they were also less sensitive to lysis by natural killer (NK) cells, although NK lysis is probably unrelated to MHC expression. In conclusion, our selection for reduced H-2-expression appears to have resulted in the isolation of variants with a generally increased resistance to various humoral and cell-mediated lytic functions.

Animals↗
PubMed1981

Detection of cell-surface antigens in murine tumors by a protein A immunofluorescence test.

The detection of antibodies to H-2 and species cell-surface antigens, on suspensions of leukemia and MC-induced sarcomas by an assay using fluorescein-labelled protein A from Staphylococcus aureus is described. The presence of 'foreign' H-2 allospecificities on MC-induced sarcoma cells were detected. Antibodies to leukemia and MC sarcoma cells showed a high degree of cross-reactivity in their reaction with different MC-induced sarcomas and with leukemia cells.

Animals↗
PubMed1979

The effect of peritoneal macrophages from mice injected with Leishmania braziliensis on the in vitro growth of tumor cells.

Leishmania braziliensis reportedly is capable of producing a reduction in the growth of solid and ascites murine leukemia and lymphomas. The possibility that the inhibitory effect on the ascites tumor was produced by the activation of the macrophage peritoneal cell population was explored. It was observed that adherent cells from the peritoneal cavity of L. braziliensis injected mice caused a marked inhibitory effect on the in vitro growth of the 6C3HED lymphoma and EL-4 leukemia cells. This effect was dependent on the degree of the macrophage activation, was not produced by supernatants from cultures of activated macrophages, and it seems that contact cell between target and effector cells is necessary. In addition to being cytostatic, this effect was also cytotoxic. The L. braziliensis activated macrophages were also capable of suppressing the multiplication of normal cells induced by mitogen, but this was not observed if the cells were already undergoing multiplication. A similar cytostatic effect on the tumor cells was observed to be produced by the peritoneal non-adherent cell population of the L. braziliensis injected mice.

Animals↗
PubMed1979

Alien H-2 allospecificities in murine chemically-induced tumors.

Sera from C3H/HeHa mice immunized with syngeneic methylcholanthrene-induced sarcoma react with allogeneic thymus, lymphoma and leukemia cells. The presence on leukemia and lymphoma cells of H-2 specificities expressed on normal cells of other H-2 haplotypes from the one in which the tumor originates is described. It was observed that the reaction of antisera to H-2 specificities with lymphoma cells was blocked by anti-MCA sarcoma sera. The cross-reactivity between MC sarcomas, thymus, leukemia and lymphoma cells is considered to be due to antibodies against these "alien" allospecificities.

Animals↗
PubMed1977

In vitro infection of murine macrophage by Leishmania brasiliensis. Mechanism of penetration.

The in vitro infection of peritoneal murine macrophages by a cultured pathogenic strain of Leishmania brasiliensis was studied. By phase contrast and light microscopy it could be observed that L. brasiliensis is rapidly endocytosed by the macrophages and localized in the cytoplasm in a vacuole inside which it multiplies. By phase contrast and electron microscopy it was observed that L. brasiliensis enters the macrophage by the anterior end through which it first attaches to the cell membrane. This penetration involves invagination of the cell membrane around the entering flagellum and parasite body. A mechanism of entry involving and active participation of the parasite membrane through receptor sites and membrane activity by the microfilament system is presented.

Animals↗
PubMed1977

Immunological studies in onchocercosis patients.

The immunological profile of onchocercosis patients from an endemic region in Venezuela was studied. The sample was made up of patients suffering from onchocercosis and undergoing treatment, persons previously treated and apparently cured of the disease, and a group of apparently healthy individuals from the same area. The results obtained indicate that during the course of the disease the immunological apparatus suffers only slight modifications since no great variations were found in the immunoglobulin levels, the third component of the complement, the reactivity to DNCB, or the response of peripheral blood lymphocytes to mitogens. When under treatment, the levels of serum IgG and IgM are increased and there is a decrease in C3 levels. The slight modifications found can be attributed to the low severity of the disease as only one patient of those studied presented clinical manifestations ascribable to the disease (onchocercoma).

Adolescent↗