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N M Desai

Publications and source records attributed to N M Desai.

18 recordsLinked to original sources
PubMed1998

Utility of adenoviral-mediated Fas ligand gene transfer to modulate islet allograft survival.

BACKGROUND: One of the best-defined mechanisms for the induction of apoptosis involves signaling via the cell surface molecule Fas, after binding of Fas ligand. Expression of Fas ligand is tightly regulated, being expressed primarily by T cells after activation, where it serves as a self-regulatory mechanism for immune responses. Fas ligand has also been found to be expressed constitutively at sites of immune privilege such as the testes and the anterior chamber of the eye. Recently, co-transplantation of Fas ligand-transfected myoblasts in association with islet cell allografts was shown to prolong islet allograft survival but only rarely led to indefinite graft survival. Graft rejection was associated with loss of Fas ligand on the myoblasts, suggesting that direct expression of the transgene on the islets might be more effective. METHODS: A replication-defective adenoviral construct containing murine Fas ligand (Ad/MFL) was prepared by homologous recombination. NIH 3T3 cells, rodent splenocytes, and murine islets were infected with Ad/MFL and examined in vitro for functional murine Fas ligand expression. Survival of Ad/MFL-infected islets was subsequently evaluated in vivo in both syngeneic and allogeneic islet transplantation models. RESULTS: Cell lines and islet allografts transfected with Ad/MFL expressed a functional Fas ligand, capable of inducing apoptosis (confirmed by three distinct assays for DNA fragmentation) in Fas+ targets, but not in Fas- controls. Furthermore, Ad/MFL was able to modify allogeneic immune responses in vitro, as addition of this virus, but not a control adenovirus, significantly reduced proliferation in a mixed lymphocyte reaction. Surprisingly, however, transplantation of islet allografts transfected with Ad/MFL resulted in long-term allograft survival in only 1 of 30 recipients. Moreover, adenoviral-mediated Fas ligand gene transfer was complicated by transient, dose-dependent islet dysfunction, perhaps contributing to the lack of long-term engraftment. CONCLUSION: These data suggest that adenoviral-mediated Fas ligand expression may impair normal islet function in vivo, and indicate that alternative strategies for Fas ligand transgene delivery may be required in this setting.

Adenoviridae↗
PubMed1994

Genetically engineered grafts to study xenoimmunity: a role for indirect antigen presentation in the destruction of major histocompatibility complex antigen deficient xenografts.

BACKGROUND: The genetic engineering of xenogeneic donor species for transplantation may provide a means of attenuating the potent immune response elicited by tissues from foreign species. Because of their well-established role in allograft rejection, a logical target for genetic manipulation is the genes encoded by the major histocompatibility complex (MHC). In the current study we examined whether skin, heart, or pancreatic islet xenografts harvested from lines of transgenic mice rendered deficient in MHC antigen expression by gene disruption would exhibit a survival benefit when transplanted to xenogeneic rat recipients. In addition, we characterized the in vitro response of rat T cells to normal and MHC-deficient mouse cells. METHODS: Skin, heart, and pancreatic islet grafts were harvested from control C57Bl/6 and each of three lines of mice deficient in MHC antigen expression. MHC-deficient lines included (1) mice selectively lacking MHC class I antigens (CID), produced by disruption of the beta-2 microglobulin gene; (2) mice lacking MHC class II expression (CIID), produced by targeting the I-A beta-chain gene; and (3) mice devoid of both class I and class II molecules (CI,IID). RESULTS: In contrast to the prolonged survival that has been observed for certain allografts deficient in MHC antigen expression, we did not detect significant extension of survival in the case of xenografts. Using in vitro assays of T-cell function, we demonstrated that rats that rejected grafts lacking MHC expression evidenced sensitization of T cells specific for graft antigens presented by rat antigen-presenting cells. CONCLUSIONS: The strategies of gene targeting of donor species to produce less immunogenic xenografts may be hampered by the presence of a strong response through the indirect pathway of immunity. Immune intervention directed at the indirect antigen presentation pathway may be of benefit in xenotransplantation.

Animals↗
PubMed1993

Allograft rejection by T cell receptor transgenic mice.

We have used a line of T cell receptor (TcR) transgenic mice, in which a significant portion of CD8+ T cells expresses a TcR that is specific for the minor histocompatibility antigen H-Y presented by the H-2Db Class I molecule, to examine the immune response to H-Y-incompatible skin or pancreatic islet allografts. Our results indicate that, in contrast to the conclusions of previous reports, pancreatic islet endocrine cells are invulnerable or only weakly vulnerable to an H-Y-directed immune response. An even more unexpected finding was that unlike normal female mice of the C57BL/6 background which consistently reject male skin within a few weeks, TcR transgene+ littermates reject male skin only infrequently. Our results are consistent with the conclusion that the inability of H-Y TcR females to reject male skin is due to a deficiency of cells with male-specific helper activity. Long-term acceptance of male grafts by H-Y TcR females leads to a state of T cell hyporesponsiveness to male skin grafts. In addition, T cells harvested from long-term skin acceptors were hyporesponsive to in vitro stimulation by a clonotype-specific monoclonal antibody. Transgenic mice with TcRs having antigenic specificity for defined transplantation antigens provide a unique model for study of the allograft response.

Animals↗
PubMed1993

Islet allograft, islet xenograft, and skin allograft survival in CD8+ T lymphocyte-deficient mice.

Despite extensive study, the immunologic mechanisms mediating allograft rejection have not been completely defined. In the current study, we evaluated the T cell subsets important in islet allograft, skin allograft, and islet xenograft rejection using a genetically engineered line of mice deficient in beta 2-microglobulin expression. Because these mice lack cell surface MHC class I expression, they are deficient in T cells of the CD8 subset (class I-restricted cytotoxic T cells). Pancreatic islet allografts transplanted to CD8+ T cell-deficient recipients showed prolonged survival compared with controls. No prolongation was observed in the survival of pancreatic islet xenografts or in the survival of skin allografts transplanted to the CD8+ T cell--deficient hosts. We conclude that CD8+ T cells play a prominent role in islet allograft, but not islet xenograft or skin allograft, rejection in mice.

Animals↗
PubMed1992

Indefinite survival of MHC class I-deficient murine pancreatic islet allografts.

To examine the immune response to class I-deficient allogeneic tissue, we used beta 2-microglobulin-deficient mice as graft donors. These mice lack cell surface class I major histocompatibility complex antigen expression. Pancreatic islet allografts from class I-deficient donors survived indefinitely in a majority of fully allogeneic BALB/c recipients. In contrast, host recognition of graft class I antigen was unnecessary for prompt destruction of skin allografts of for autoimmune damage of transplanted pancreatic islet grafts in nonobese diabetic mice. These studies provide evidence that intentional genetic elimination of immunologically relevant donor antigens may prove an effective strategy for preventing allograft rejection.

Animals↗
PubMed1989

Compensatory mutations demonstrate that P8 and P6 are RNA secondary structure elements important for processing of a group I intron.

Compensatory mutations have been constructed which demonstrate that P8 and P6, two of nine proposed base-pairing interactions characteristic of group I introns, exist within the folded structure of the Tetrahymena thermophila rRNA intervening sequence, and that these secondary structure elements are important for splicing in E. coli and self-splicing in vitro. Two-base mutations in the 5' and 3' segments of P8 are predicted to disrupt P8 and a strong splicing-defective phenotype is observed in each case. A compensatory four-base mutation in P8 is predicted to restore pairing, and results in the restoration of splicing activity to nearly wild type levels. Thus, we conclude that P8 exists and is essential for splicing. In contrast to the strong phenotypes generally exhibited by mutations which disrupt RNA secondary structure, a two-base mutation in L8, the loop between P8[5'] and P8[3'], results in only a slight decrease in splicing activity. We also tested P6, a pairing which is proposed to consist of only two base-pairs in this intron. A two-base mutation in P6[3'] reduces splicing activity to a greater extent than does a two-base mutation in P6[5']. Comparison of the activities of these mutants and a compensatory P6 four-base mutant support the existence of P6, and suggest that the P6 pairing may be particularly important in the exon ligation step of splicing.

Animals↗
PubMed1988

Polycyclic aromatic hydrocarbons in kajal and surma eye cosmetic preparations.

Levels of polycyclic aromatic hydrocarbons (PAH) were determined in Kajal and Surma eye cosmetic preparations. All the preparations showed the presence of the majority of priority PAH in varying levels. The median level of a total 18 identified PAH in kajal was 851.3 micrograms/g. The level of total PAH in black, whitish black and white surma preparations were 243.34, 230.60 and 45.40 micrograms/g respectively.

Asia↗
PubMed1987

Cloning and sequence of rat myoadenylate deaminase cDNA. Evidence for tissue-specific and developmental regulation.

Myoadenylate deaminase is the muscle-specific isoform of AMP deaminase (EC 3.5.4.6), an enzyme which plays a special role in energy metabolism in skeletal muscle. A 2.3-kilobase cDNA encoding this enzyme has been cloned from a lambda gt10 library prepared from rat skeletal muscle using oligonucleotide probes designed from AMP deaminase peptide sequences. This cDNA was sequenced, and the amino acid sequence of this isoform of AMP deaminase was deduced. Sequences homologous to this cDNA are identified in the genome of eukaryotes as diverse as yeast and man. Tissue-specific expression of a 2.5-kilobase AMP deaminase transcript is demonstrated, and the abundance of this transcript as well as the 80-kDa adult, muscle-specific peptide of AMP deaminase increase in parallel during postnatal skeletal muscle development. In the adult animal, the abundance of this transcript and AMP deaminase activity are differentially expressed in various skeletal muscle fiber types. We conclude that AMP deaminase sequences have been highly conserved during evolution, and in mammals there is developmental and tissue-specific control of expression of this gene.

AMP Deaminase↗
PubMed1987

Evidence for sequential expression of multiple AMP deaminase isoforms during skeletal muscle development.

AMP deaminase (myoadenylate deaminase; EC 3.5.4.6) is an integral part of the myofibril in skeletal muscle, and this enzyme plays an important role in energy metabolism in this tissue. We report here the identification of three AMP deaminase isoforms during skeletal muscle development in the rat. An embryonic isoform is expressed in the developing hindlimb of the rat between 7 and 14 days of gestation. This isoform is not unique to skeletal muscle or the embryo as it is also expressed in many nonmuscle tissues of the perinatal and adult rat. A perinatal isoform of AMP deaminase that is restricted to skeletal muscle is produced 4-6 days before birth and persists for 2-3 weeks of postnatal life. An adult, skeletal muscle-specific isoform of AMP deaminase appears at birth and reaches maximal levels after 3 weeks of postnatal development. We conclude from these studies there is a developmentally controlled program that leads to the sequential expression of AMP deaminase isoforms during the transition from embryonic to adult skeletal muscle.

AMP Deaminase↗
PubMedDate not supplied

Switching from depot antipsychotics to risperidone: results of a study of chronic schizophrenia. The Schizophrenia Treatment & Assessment Group.

Designed to provide information about patients with schizophrenia who switch from depot neuroleptics to the oral, atypical antipsychotic risperidone, this multicenter observational study enrolled patients who wished to stop the depot, had an unsatisfactory response, or experienced unacceptable side effects. Individuals remained on depot medication for 4 weeks and then received risperidone monotherapy for 3 months. Of the 143 patients who entered the study, 130 received risperidone, 109 completed the initial 16-week study, and 88 entered an optional 12-week follow-up. Symptoms and side effects did not change significantly during the depot phase (mean Positive and Negative Syndrome Scale [PANSS] score 72.2 at baseline, 71.6 at visit 2), but PANSS scores, global assessment of functioning, parkinsonism, and dyskinesia improved significantly during the risperidone phase (mean PANSS score decreased from 71.6 to 55.5 after 3 months). The number of contacts with healthcare professionals fell significantly during the risperidone phase; in addition, symptomatic improvements were maintained during follow-up, and movement disorders continued to decrease significantly. The investigators considered that 81% of patients had switched successfully. Patient acceptance of risperidone was significantly higher than for depot medication (83% vs 23%; P < .001), and 65% considered risperidone better than their previous treatment. Indications for depot medication should be reviewed, and patients may benefit from a switch to risperidone.

Administration, Oral↗