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Biomedical subjects

M R Abedi

Publications and source records attributed to M R Abedi.

15 recordsLinked to original sources
PubMed1998

Transdominant genetic analysis of a growth control pathway.

Genetic selections that use proteinaceous transdominant inhibitors encoded by DNA libraries to cause mutant phenocopies may facilitate genetic analysis in traditionally nongenetic organisms. We performed a selection for random short peptides and larger protein fragments (collectively termed "perturbagens") that inhibit the yeast pheromone response pathway. Peptide and protein fragment perturbagens that permit cell division in the presence of pheromone were recovered. Two perturbagens were derived from proteins required for pheromone response, and an additional two were derived from proteins that may negatively influence the pheromone response pathway. Furthermore, three known components of the pathway were identified as probable perturbagen targets based on physical interaction assays. Thus, by selection for transdominant inhibitors of pheromone response, multiple pathway components were identified either directly as gene fragments or indirectly as the likely targets of specific perturbagens. These results, combined with the results of previous work [Holzmayer, T. A., Pestov, D. G. & Roninson, I. B. (1992) Nucl. Acids. Res. 20, 711-717; Whiteway, M., Dignard, D. & Thomas, D. Y. (1992) Proc. Natl. Acad. Sci. USA 89, 9410-9414; and Gudkov, A. V., Kazarov, A. R., Thimmapaya, R., Axenovich, S. A., Mazo, I. A. & Roninson, I. B. (1994) Proc. Natl. Acad. Sci. USA 91, 3744-3748], suggest that transdominant genetic analysis of the type described here will be broadly applicable.

Cell Cycle↗
PubMed1998

Green fluorescent protein as a scaffold for intracellular presentation of peptides.

Peptide aptamers provide probes for biological processes and adjuncts for development of novel pharmaceutical molecules. Such aptamers are analogous to compounds derived from combinatorial chemical libraries which have specific binding or inhibitory activities. Much as it is generally difficult to determine the composition of combinatorial chemical libraries in a quantitative manner, determining the quality and characteristics of peptide libraries displayed in vivo is problematical. To help address these issues we have adapted green fluorescent protein (GFP) as a scaffold for display of conformationally constrained peptides. The GFP-peptide libraries permit analysis of library diversity and expression levels in cells and allow enrichment of the libraries for sequences with predetermined characteristics, such as high expression of correctly folded protein, by selection for high fluorescence.

Amino Acid Sequence↗
PubMed1997

Preventive effect of IgG from EBV-seropositive donors on the development of human lympho-proliferative disease in SCID mice.

The effect of weekly treatments with various gammaglobulin preparations on the development of human B-cell tumors was studied in severe combined immunodeficient (SCID) mice. SCID mice were injected i.p. with human peripheral blood mononuclear cells (PBMCs) from an Epstein-Barr virus (EBV)-seropositive healthy blood donor. Repopulated SCID mice were divided into 7 treatment groups receiving either PBS, 2 commercial gammaglobulin preparations, purified IgG prepared from pooled plasma from EBV-seronegative or -seropositive blood donors, a rabbit anti-serum against EBV envelope glycoprotein gp340 or interferon (IFN)-alpha. All treatments started 1 day after injection of PBMC and continued for 8 weeks. In the PBS-treated control group, 85% of mice developed tumors in the abdominal cavity, mostly with liver metastasis within 150 days. Tumor formation was prevented by treatment with the 2 commercial gammaglobulin preparations as well as by purified IgG from EBV-seropositive donors. In contrast, purified IgG from EBV-seronegative donors, rabbit anti-gp340 anti-serum or IFN-alpha had no effect. Our results indicate that the effect of gammaglobulin is due to the presence of specific antibodies against EBV antigens. Further experiments showed that both the time of onset and the duration of treatment, as well as the dose of Ig, are important factors for prevention of tumor formation. Studies aiming at identification of target antigens for antibodies which prevent lymphoma development may be clinically relevant for prevention and possibly treatment of lympho-proliferative disease in severely immuno-compromised patients.

Abdominal Neoplasms↗
PubMed1997

Gap junctions promote the bystander effect of herpes simplex virus thymidine kinase in vivo.

Transfer of the herpes simplex thymidine kinase gene (HSVtk) into tumor cells followed by the administration of ganciclovir (GCV) provides a potential strategy for the treatment of some malignancies. During GCV treatment, not only the cells that express the HSVtk gene are killed but also frequently neighboring tumor cells that are not genetically altered. This has been called the "bystander effect." Although the mechanism of the bystander effect in vivo remains elusive, our results suggest that gap junction formation between neighboring cells is an important contributing factor. The C6 rat glioma cell line, which exhibits a low level of intercellular communication by gap junctions and connexin43 (Cx43)-transfected clones of this cell line forming gap junctions from a moderate level (Cx43-12 and Cx43-14) to a high level (Cx43-13), were transduced with HSVtk. Transduced and nontransduced cells were mixed in various concentrations and then cultured in vitro or injected s.c. into C.B-17/SCID-beige mice followed by i.p. injections of GCV. Cx43-transfected clones showed a significant increase of the bystander effect compared with the less coupled C6 parental cell line. In 11 of 12 mice injected with cells of Cx43-transfected clones, no tumors were seen at the inoculation site when a mixture of 50% HSVtk-negative and HSVtk-positive cells was used. Moreover, in mice injected with cells of clone Cx43-13, which exhibits the highest intercellular communication, tumors were frequently undetectable at the inoculation site when using mixtures of 75% HSVtk-negative and 25% HSVtk-positive cells, and even mixtures containing 5% HSVtk-positive cells of Cx43-transfected clones showed tumor size reduction. All animals in control groups (n = 26) developed large tumors at every injection site. These results demonstrate that gap junctions are an important component in mediating the bystander effect in vivo.

Animals↗
PubMed1996

Suicide gene therapy for plasma cell tumors.

Suicide gene therapy for plasma cell tumors was attempted in severe combined immunodeficient (SCID) mice injected with human myeloma cell lines. Initially, a ganciclovir-induced bystander effect was observed in vitro using myeloma cells transduced with a herpes simplex thymidine kinase (HSVtk) gene. Transduced cells injected subcutaneously (SC) into SCID mice could be eradicated by the administration of ganciclovir (GCV). Furthermore, an in vivo bystander effect was noticed when mice received mixtures of HSVtk-positive and nontransduced cells. Unexpectedly, a "distant bystander" effect was observed as tumors in regions inoculated with only nontransduced cells were significantly smaller and had increased frequency of apoptotic figures and decreased mitotic frequency in GCV-treated mice transplanted with HSVtk-positive cells at a different region compared with control mice.

Animals↗
PubMed1996

Reduction in serum levels of antimitochondrial (M2) antibodies following immunoglobulin therapy in severe combined immunodeficient (SCID) mice reconstituted with lymphocytes from patients with primary biliary cirrhosis (PBC).

The effect of gammaglobulin treatment on autoantibody production was investigated in SCID mice reconstituted with human peripheral blood mononuclear cells (PBMC) obtained from patients with PBC. All reconstituted mice displayed the presence of human antimitochondrial antibodies (alpha M2Ab) of both IgG and IgM types before treatment with human immunoglobulin. Two weeks after i.p. injection of 20 x 10(6) PBMC into SCID mice, i.p. treatment with various preparations of human immunoglobulin was initiated. In control animals treated with saline, serum levels of human alpha M2Ab of the IgG type increased with time, peaking around 4 weeks after reconstitution. In contrast, human IgG autoantibodies rapidly decreased in all animals treated with human IgG. Treatment with a human IgM preparation had no effect on serum levels of alpha M2Ab of the IgG type. The results may suggest that the pronounced reduction of specific IgG autoantibodies was due to an increased catabolism of human IgG, including the autoantibodies, in the gammaglobulin-treated mice. Although the production of human alpha M2Ab in reconstituted mice could be easily shown, PBC-specific liver lesions or bile duct destruction were not observed, irrespective of treatment protocol.

Animals↗
PubMed1995

Retroviral-mediated gene transfer into human bone marrow stromal cells: studies of efficiency and in vivo survival in SCID mice.

Retroviral-mediated gene transfer into bone marrow cells is extensively used in gene therapy protocols. Cytokines are needed for stimulation, to achieve a high rate of gene transfer. However, the stromal cell compartment of bone marrow is characterized by rapid proliferation even without cytokines. In this study, human bone marrow stromal cells were isolated and subsequently infected with recombinant retrovirus in a cell-free supernatant. The LN retroviral vector used in this study carries the bacterial neomycin phosphotransferase gene (neoR). Transduction efficiency was significantly enhanced by repeated cycles of infection, with a maximum of 91% transduced cells by four rounds of infection. Presence of the neoR-gene was detected by PCR from all stromal cells selected by G418. After culture in vitro for 3 months, cells were still positive for PCR amplification of the neoR-gene. Transduced stromal cells were also injected into SCID mice to study their homing and survival ability in vivo.

Animals↗
PubMed1993

Gamma-globulin modulates growth of EBV-derived B-cell tumors in SCID mice reconstituted with human lymphocytes.

The effect of weekly gamma-globulin injection on the development of human B-cell tumors was studied in 120 mice with severe combined immunodeficiency (SCID). The mice were injected intraperitoneally (i.p.) with human peripheral mononuclear cells (PBMC) from 6 different Epstein-Barr virus (EBV)-seropositive donors. Animals repopulated with cells from 5 donors received gamma-globulin or saline for 20 weeks and were followed up to 24 weeks after reconstitution. A delay in the appearance of fata EBV-derived human B-cell tumors was noticed in the gamma-globulin-treated groups as compared to the controls. In a separate experiment, the effect of gamma-globulin treatment during the initial 4 weeks after reconstitution was compared to treatment from week 5 to week 8 as well as to a continuous 20-week treatment. The results from this experiment showed that B-cell tumor growth could be prevented just as efficiently when the animals were treated only during the first 4 weeks. In contrast, no preventive effect was seen when the first gamma-globulin dose was given at the beginning of week 5 after reconstitution. Our results indicate that gamma-globulin reduces the frequency of EBV-derived B-cell tumor development and suggest that SCID mice repopulated with human cells represent a useful in vivo model for evaluation of the prophylactic and/or therapeutic effects of immunomodulatory treatments in lympho-proliferative disorders associated with immunosuppression.

Animals↗
PubMed1992

Immunoglobulin production in severe combined immunodeficient (SCID) mice reconstituted with human peripheral blood mononuclear cells.

Immunodeficient C.B-17 scid/scid (SCID) mice were reconstituted with human peripheral blood mononuclear cells and analyzed for humoral immunity. The majority of adoptively transferred animals had serum levels of 1-4 mg/ml of human IgG 8-12 weeks after i.p. reconstitution with 20 x 10(6) PBMC, whereas the IgM and especially IgA concentrations were considerably lower. The half-lives of human IgG, IgM, and IgA in SCID mice were 12 days, 36, and 23 hours, respectively. Furthermore, IgA was rapidly secreted into bile indicating that the low IgA concentration was mainly caused by a high turnover rate. IgG subclass distribution in mouse serum was similar to that found in the donor serum. Irradiation with 3 Gy prior to adoptive transfer resulted in increased levels of human IgG early after reconstitution, whereas both IgM and IgA concentrations were impaired. A polyclonal serum Ig pattern was found 4 weeks after transfer of human cells later frequently followed by a predominance of oligoclonal bands. Unexpectedly, oligoclonal bands were also found using donors with a negative Epstein-Barr virus serology. Human cells were found to reside in the peritoneal cavity for several months. Within 2 weeks of reconstitution, human cells were also identified in lymphoid structures in the vicinity of the liver hilus with a later spread to other lymphoid organs. Homing of human cells to skin and gut was not seen.

Animals↗
PubMed1990

Development of IgA deficiency after bone marrow transplantation. The influence of acute and chronic graft-versus-host disease.

Serum IgA levels were monitored at 3, 6, 12, and 24 months after BMT in 131 allogeneic and 3 syngeneic bone marrow transplant recipients. In general, IgA levels were low during the first 6 months and did not return to normal levels until 1-2 years after transplantation. Children (less than 15 years) had lower IgA levels at 3 and 6 months post-BMT compared to the adults (P less than 0.05), but donor age had no influence on the recipient IgA levels after BMT. Patients receiving either methotrexate or cyclosporine alone for GVHD prophylaxis had markedly lower IgA levels compared to those given a combination of these two drugs or patients transplanted with T-cell-depleted marrow (P less than 0.001). Mean IgA levels in patients without or with grade I acute GVHD were within the normal range at 3, 6, 12, and 24 months after BMT (greater than 0.3 g/L), although approximately 20% of the patients in each group showed low IgA levels (less than or equal to 0.3 g/L) early after transplantation. Patients with grade II or III acute GVHD had significantly lower values from 3 months up to 2 years after transplantation (P less than 0.01). Patients with chronic GVHD had significantly lower IgA levels 1 and 2 years after BMT compared to patients without chronic GVHD (P less than 0.005). Severe acute GVHD, particularly when followed by chronic GVHD, seems to be the main reason for low IgA levels, while other factors such as CMV infection or donor status may also contribute to the development of IgA deficiency after BMT.

Acute Disease↗
PubMed1990

Markedly increased serum erythropoietin levels following conditioning for allogeneic bone marrow transplantation.

Serum erythropoietin (EPO) levels were measured by radioimmunoassay in 36 patients undergoing allogeneic bone marrow transplantation (BMT). Serum EPO levels before conditioning treatment for BMT were generally higher than the levels obtained from healthy controls (49 +/- 17 (SEM) and 17 +/- 0.6, respectively). One day prior to BMT, after conditioning by chemotherapy with or without total body irradiation, the mean EPO level was markedly elevated (218 +/- 23 U/l, p less than 0.001) and reached to its highest level at 1 week post-BMT (269 +/- 40 U/l). Although, the EPO levels were significantly lower at 1 month (98 +/- 24 U/l, p less than 0.001), they were still elevated up to 3 months post-BMT, after which they gradually normalized. Patients given methotrexate and cyclosporine for prophylaxis against graft-versus-host disease (GVHD) had significantly lower EPO levels during the first 3 months post-BMT than patients transplanted with T cell-depleted marrow (p less than 0.05). Patients with post-transplant nephrotoxicity had lower, though not statistically significant, EPO levels than patients with normal renal function (p = 0.07). Acute GVHD and number of blood transfusions had no influence on serum EPO levels after BMT.

Adolescent↗
PubMed1989

Serum IgE levels after bone marrow transplantation.

Total serum IgE levels were followed in 135 bone marrow transplant recipients in order to determine the clinical significance of post-transplant serum IgE monitoring. Patients with IgE levels less than 60 U/ml at the time of bone marrow transplantation (BMT) (59%) experienced at least one IgE peak. Patients with pretransplant IgE levels greater than or equal to 60 U/ml (16%) showed decreasing values following BMT. In 19% of patients, IgE levels were low and did not change up to 3 months after BMT. Increase in IgE levels coincided in time with engraftment (p less than 0.01) and acute graft-versus-host disease (GVHD) (p less than 0.01). Early IgE peaks were also seen in patients without GVHD. Maximal IgE values did not differ during grades II-IV GVHD compared with grades 0-1, but two or more peaks were more common in patients with grades II-IV (p less than 0.001). IgE peaks also appeared in patients receiving T cell-depleted marrow without GVHD. Syngeneic bone marrow recipients had high IgE levels after BMT. Two patients had increasing IgE values following reconditioning and retransplantation, but booster grafts had no effect on IgE levels. IgE levels were not changed during septicemia, herpes simplex virus or cytomegalovirus infections, and chronic GVHD. No linear correlation was found between serum IgE levels and CD4+/CD8+ ratios, percentages, or absolute numbers of either group of cells. It was concluded that serum IgE elevation is found in association with engraftment and acute GVHD, but is mainly caused by the conditioning treatment.

Acute Disease↗