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Biomedical subjects

F Merino

Publications and source records attributed to F Merino.

At least 55 records · Page 3Linked to original sources
PubMed1985

Chédiak-Higashi syndrome in a Venezuelan black child.

One case of Chédiak-Higashi syndrome (CHS) in a black male child, born to a consanguineous couple from a rural village in the State of Falcón, is described. At birth the child had marked skin depigmentation and ash-gray hair. A few months later he developed an almost normal black skin color. The diagnosis of CHS was established by the presence of large peroxidase-positive granules in his leukocytes. Neutrophils showed decreased chemotaxis and lack of digestive capacity against Candida albicans. Unusual features included extreme rarity of CHS in blacks, progressive repigmentation of the skin, and an early benign evolution. A high consanguinity index in the village from which this patient originated raised the possibility of the presence of a new cluster of this disease in Venezuela.

Black or African American↗
PubMed1985

The storage pool deficiency in platelets from humans with the Chédiak-Higashi syndrome: study of six patients.

Functional and biochemical studies of platelets from human Chédiak-Higashi syndrome (CHS) are scarce and/or incomplete. In the present report, the aggregation response to a variety of inducers of platelet aggregation, the content of the dense granule constituents ATP, ADP, serotonin and calcium, the secretion of ATP, ADP, and calcium induced by thrombin, the total content of magnesium, the incorporation of 14C-adenine in the cytoplasmic pool of adenine nucleotides, as well as the content of intracellular cyclic-AMP, have been quantitated in six patients with CHS. Furthermore, data is presented on the kinetics of uptake of radiolabelled serotonin and its storage in human CHS platelets. An abnormal aggregation behaviour was found in all patients. However, the response of CHS platelets to the different inducers studied did not show a uniform pattern. The total content and the maximal amounts of the dense granule constituents secretable by thrombin were greatly decreased in all six patients. Total magnesium content was similar to that of normal platelets. The ATP/ADP ratio was higher than in controls. Uptake of radiolabelled serotonin by CHS platelets closely followed the uptake by normal platelets; during the first 2-3 min, however, incorporation of the amine by CHS platelets came rapidly to a plateau which contrasts with the steady, linear increase in uptake found in controls. CHS platelets loaded with radiolabelled serotonin and gel-filtered, showed a spontaneous release of radioactivity not observed in normal platelets under the same conditions. The cyclic-AMP content of CHS platelets was similar to that of normals. In contrast to platelets from patients with storage pool disease, the secretable calcium from CHS platelets represents a 67% of total platelet calcium (61% in normals), suggesting that the absolute values for the non-secretable portion in CHS platelets must be very low. The results reported confirm the existence of a true storage pool deficiency of the dense granule constituents as a common defect in CHS platelets. The variety of responses among patients, to the different aggregatory stimuli studied, can not be solely ascribed to the storage pool deficiency described.

Adenine Nucleotides↗
PubMed1984

Natural antibodies to human T-cell leukemia/lymphoma virus in healthy Venezuelan populations.

Serum samples of 769 healthy Venezuelan donors were assayed for natural antibodies to HTLV-I by the ELISA technique. Specific HTLV-I antibody prevalence was 6.8% but varied from 1% in Caracas to 13.7% in the Amazonas region and the State of Zulia. Adults infected with Trypanosoma cruzi had the highest HTLV-I antibody prevalence of 15%. Areas of high antibody prevalence were correlated most strongly with the presence of arthropod-borne diseases and to a lesser extent with socio-economic factors. Genetic factors were not correlated with antibody prevalence. Antibodies were seen in children as young as 3 years of age in the most endemic areas. Antibody titers increased with age, suggesting continuous exposure to the virus. The data provide clues for elucidation of the geographic variation in HTLV-I antibody prevalence seen Venezuela and other HTLV-I endemic areas. In addition, they further confirm the Caribbean region as being endemic for HTLV-I and extend this region to inland areas of South America.

Adolescent↗
PubMed1984

Functions of neutrophils in endemic Chediak-Higashi syndrome.

Endemic Chediak-Higashi Syndrome occurs in a restricted geographic area (Pregonero, State of Táchira, Venezuela). Neutrophils from these patients were unable to digest Candida albicans in vitro, but showed normal or increased metabolic activities. This finding supports the view that the endemic syndrome is bona fide Chediak-Higashi Syndrome.

Chediak-Higashi Syndrome↗
PubMed1984

T-cell-dependent hybrid resistance against a natural killer-resistant Moloney virus-induced lymphoma (YWA): in vitro generation of cytotoxic lymphocytes.

A Moloney leukemia virus-induced lymphoma of the A.SW strain, YWA, was used to generate cytotoxic cells in vitro. Cocultivation of spleen cells from in vivo primed syngeneic and semisyngeneic mice with X-irradiated YWA tumor cells for 5 days resulted in a strong killing activity against YWA. The cytotoxicity was H-2 restricted and mediated by Thy-1.2-positive lymphocytes. F1 hybrids with variable degrees of natural resistance to the YWA tumor in vivo all generated cytotoxic cells after secondary stimulation in vitro but showed differences in optimal responder:stimulator requirements.

Animals↗
PubMed1984

Heterophile antibodies in sera of patients with Chediak-Higashi syndrome.

Sera of 6 patients with Chediak-Higashi syndrome and sera of their mothers were studied for heterophile antibodies. Sera of 5 patients as well as 5 sera of their mothers contained antibodies against trypsinized bovine erythrocytes, tissue sediments of guinea pig kidney or high molecular weight glycoprotein (HMWGP) of bovine erythrocyte stromata. The antibodies combining with HMWGP in enzyme immunoassay belonged to IgM and IgG classes. Although none of the sera had significant titer of agglutinins against sheep erythrocytes, on the basis of absorption and inhibition studies, these antibodies seemed to belong to the Hanganutziu-Deicher group of antibodies.

Animals↗
PubMed1984

Natural killer activity in experimental cutaneous leishmaniasis.

Studies were performed to determine the role of natural killer (NK) cell cytotoxicity in experimental cutaneous leishmaniasis. Analysis of a possible correlation between in vitro NK cell activity and in vivo susceptibility to Leishmania mexicana infection showed that there is no relationship between the degree of NK reactivity to YAC-1 lymphoma cells and in vivo leishmania growth. It was also observed that spleen lymphoid cells from mice with high NK activity did not cause an increase in isotope release by the macrophage permanent cell line J774G8-1 previously infected with the parasite and supporting its growth. Mice infected with L. mexicana manifested an increased NK activity to YAC-1 cells but not to leishmania-infected J774G8-1 tumor macrophages. The lack of effect of NK cell activity is discussed with regard to the role of NK cells in immune mechanisms to intracellular parasites.

Animals↗
PubMed1983

Elevated antibody titers to Epstein-Barr virus and low natural killer cell activity in patients with Chediak-Higashi syndrome.

Four Venezuelan patients with the autosomal recessive Chediak-Higashi syndrome (CHS) were studied. The results confirm the severe reduction in natural killer (NK) cell activity, as previously described and showed also a decline in the activity of cells involved in antibody-dependent cellular cytotoxicity (ADCC). No defect was found in the production of immunoglobulins and of specific antibodies to measles, varicella, herpes simplex, and cytomegalo viruses. Two of the patients had extremely high antibody titers to the Epstein-Barr virus (EBV) specific viral capsid antigen (VCA), to the restricted (R) component of the EBV-induced early antigen complex, and to the EBV-associated nuclear antigen (EBNA). These two patients had enlarged livers, spleens, and lymph nodes indicative of the lymphoproliferative phase. The other two patients were initially negative for all EBV-associated antibodies but seroconverted subsequently and, in the course of a year, also developed high antibody titers to VCA and R. In one of these patients the primary infection was accompanied by moderate signs of infectious mononucleosis (IM) followed after more than 6 months by persistent hepatosplenomegaly. The other patient also developed signs of a lymphoproliferative syndrome with hepatosplenomegaly and jaundice and died 8 months later. Such high anti-R titers are seen frequently in Burkitt's lymphoma, but rarely in other conditions. It is likely that the high antibody titers reflect an increased production of VCA and R due to defective NK and ADCC cell activities so that productively infected B lymphocytes are no longer eliminated before they have synthesized maximal amounts of antigens. The high anti-EBNA titers suggest normal T lymphocyte function. The possibility that the accelerated, lymphoma-like phase of the CHS involves EBV-transformed cells is discussed.

Adult↗
PubMed1983

Lymphocyte subsets in Chediak-Higashi patients.

Peripheral blood lymphocyte subsets were studied in 6 Chediak-Higashi patients and 12 family members. The lymphocyte subsets were characterized by monoclonal antibody reagents and fluorescence flow-cytometry. An increase in OKT8 (suppressor/cytotoxic) and a decrease in OKT4 (helper) cell populations was observed in all patients studied. No correlation was seen between the clinical status (presence or absence of the lymphoproliferative phase) and the percentage of the lymphocyte subsets. The patient's mothers also had an increased percentage of OKT8-positive cells. The significance of these findings is discussed regarding the patients clinical course.

Adolescent↗
PubMed1983

Effect of a purified excreted factor from Leishmania brasiliensis on macrophage activity.

The effect of a purified glycoprotein excreted to the culture medium by Leishmania brasiliensis on the endocytic and degradative capacity of macrophages was studied. It was demonstrated that 125I-albumin incorporation as well as its intracellular fate by mouse peritoneal or tumor J774-G8 macrophages was greatly reduced when they were treated with excreted factor (EF). EF appears to alter also membrane properties in addition to its intracellular effect. The results are discussed in relation to the Leishmania survival mechanism inside the host macrophages and its pathogenicity.

Animals↗
PubMed1982

Role of H-2 antigens in the host response to methylcholanthrene-induced tumors.

H-2 loss variant sublines of a sarcoma (M-AS), induced by methylcholanthrene in an (A x A.SW)F1 mouse, were used to study the role of the MHC products in the recognition of MC-TSTA. The two reciprocal variant sublines (M-A and M-S) were found to express the TSTA of the original tumor as shown by cross-reactions in graft rejection experiments performed in (A x A.SW)F1 mice. In the A/Sn and A.SW mice the presence of the reciprocal parental H-2 antigens on the immunizing cells decreased the response against the tumor antigens. An admixture of lymphocytes derived from hyperimmune mice inhibited the outgrowth of the tumor cells. The growth inhibition was mediated by T cells and was H-2 restricted. Cells derived from hyperimmune immunization but had no effect on the reciprocal variant subline.

Animals↗