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Biomedical subjects

J Menezes

Publications and source records attributed to J Menezes.

123 records · Page 7Linked to original sources
PubMed1975

Establishment and characterization of an Epstein-Barr virus (EBC)-negative lymphoblastoid B cell line (BJA-B) from an exceptional, EBV-genome-negative African Burkitt's lymphoma.

An Epstein-Barr virus (EBV)-negative lymphoblastoid cell line (LCL), BJA-B, was established from an African Burkitt's lymphoma (BL) which contained no detectable EBV DNA and did not express the EBV specified antigen EBNA, BJA-B cells grow in typically large, flat clumps. All carry surface-bound immunoglobulins, a B lymphocyte marker, and do not form rosettes with sheep erythrocytes. After infection of BJA-B cells by EBV the infected cells may produce either EBV-determined nuclear antigen (EBNA) or both EBNA and early antigen (EA), depending on the strain of EBV. The homogeneity of the BJA-B cell population with respect to immunological and isoenzyme markers and size suggests a clonal origin of the line. BJA-B is the first EBV-negative LCL established from an African Burkitt's lymphoma and demonstrates that an EBV-independent continuous B cell line can be established "in vitro" from other than leukemia or myeloma cells.

Antigens, Viral↗
PubMed1974

Infection of EBV-genome-negative and -positive human lymphoblastoid cell lines with biologically different preparations of EBV.

Epstein-Barr virus (EBV) derived from the B95-8 line has transforming activity for cord blood cells, whereas virus derived from the P3HR-1 line lacks such activity. When the two viral preparations were compared for their ability to infect the same EBV-genome-negative lymphoblastoid cell line, BJA-B, they induced approximately the same number of EBV-determined nuclear antigen (EBNA)-positive cells. EBNA is compatibile with continued cell proliferation. No early antigen (EA)-positive cells appeared in the B95-8 virus-infected cultures, whereas P3HR-1 virus-infected cells went on to express EA. EA signals the entry of the cell into the lytic cycle. No late viral antigen (VCA) appeared and, as a consequence, the P3HR-1 virus infection became abortive. In contrast, the EBNA-positive cells induced by the B95-8 virus continued to divide over several weeks. These findings show that different EBV isolates may differ in their biological activity, probably due to their having different degrees of viral dependence on restrictive host cell controls.

Antigens, Viral↗
PubMedDate not supplied

Purification of human respiratory syncytial virus: superiority of sucrose gradient over percoll, renografin, and metrizamide gradients.

A method was devised for producing and purifying human respiratory syncytial virus (HRSV) preparations with high titers. Previous attempts to obtain substantial amounts of purified human respiratory syncytial virus have been unsuccessful due to the extreme lability of this virus, its close association with the host cell membrane, and its tendency to aggregate during concentration procedures. We describe a comparative study of various purification media as well as a novel approach for obtaining high titers of HRSV. Virus was produced in HEp-2 cells grown on gelatin beads and concentrated either by precipitation with polyethylene glycol or by centrifugation over a sucrose cushion, the latter yielding 100% recovery. These procedures employed EDTA to disaggregate the virus and MgSO4 as a virus stabilizing agent. Attempts to purify HRSV over percoll, renografin and metrizamide gradients lead to loss of infectivity. Sucrose was found to represent the best purification medium with a yield of up to 60%.

Carcinoma↗
PubMedDate not supplied

Rosette formation by human lymphoid cells with monkey red blood cells.

The present paper describes a study on rosette formation by human lymphoid cells with monkey erythrocytes (MRBC) obtained from two species: African green monkey (Cercopithecus aethiops) and rhesus monkey (Macaca mulata). All the lymphocyte preparations obtained from peripheral blood, tonsils, thymocytes, bone-marrow and spleen biopsies formed rosettes in variable proportions with erythrocytes obtained from these two monkey species tested. Cells of established lymphoblastoid cell lines characterized as being of either B- or T-cell origin also formed rosettes with MRBC. Taken together, the data obtained suggest that the MRBC-rosette assay cannot be reliably used for identifying lymphocyte subpopulations presently known to us, thus largely contradicting the observations previously reported by others on the use of this assay. In addition, we found that the binding sites for MRBC on the above lymphoid cells are highly sensitive to trypsin treatment and can fully be regenerated within 14-15 h when these treated cells are cultured at 37 degrees.

Animals↗
PubMedDate not supplied

[Immunoglobulins and sheep red cell receptors in human lymphoblastoid cell lines simultaneously carrying Epstein-Barr virus and cytomegalovirus genomes].

In this communication we attempt to characterize the principal immunological properties of 3 human lymphoblastoid cell lines (LCL) established in our laboratory which carry both the EBV and CMV genomes. The data obtained suggests that two LCL are representative of B lymphocytes while the other LCL has a mixed cell population with the majority being of the B type. The reasons for this heterogeneity are discussed. It is suggested that CMV may also transform thymus-independent (B) lymphocytes.

Binding Sites, Antibody↗
PubMedDate not supplied

Retinoic acid and steroids inhibit Epstein-Barr virus-induced nuclear antigen, DNA synthesis and lymphocyte transformation.

Retinoic acid, dexamethasone and prednisolone were evaluated for their effects on Epstein-Barr virus (EBV)-induced nuclear antigen (EBNA), DNA synthesis and transformation of human thymus-independent, B lymphocytes. It was found that continuous treatment of target cells with these agents completely inhibited EBV-induced transformation events. However, discontinuous treatment of the virus-infected cultures with these agents resulted in the recovery of DNA synthesis, and the appearance of EBNA and transformation. When the cells were treated with these agents 8 days after the virus infection, the inhibitors had no effect. These results show that only continuous treatment with these agents inhibited EBV-mediated transformation; these inhibitors had no effect once the EBNA and EBV-induced DNA synthesis were initiated in target lymphocytes.

Antigens, Viral↗