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S Rajagopalan

Publications and source records attributed to S Rajagopalan.

At least 19 recordsLinked to original sources
PubMed1992

Clinical and histopathologic changes in the host cornea after epikeratoplasty for keratoconus.

Five consecutive patients underwent epikeratoplasty for keratoconus. Postoperatively, four patients had poor visual acuity (average, 20/200) secondary to folds in Descemet's membrane and interface scarring. Two underwent penetrating keratoplasty eight months later. Histopathologic examination of the host corneas and the overlying lenticules disclosed epithelial irregularity and subepithelial fibrosis. The host corneas showed folds in Descemet's membrane and focal posterior stromal fibrosis. Electron microscopy disclosed breaks in Bowman's membrane with irregular collagen, posterior aggregates of amorphous material, and focal endothelial degeneration. The fifth patient had graft ulceration and vascularization that required removal of the lenticule. She underwent a penetrating keratoplasty five months later and histopathologic examination demonstrated persistent folds in Descemet's membrane. Immunostaining of specimens from three cases disclosed a reduced expression of sulfated epitopes of keratan sulfate and an increase in sulfated dermatan sulfate in the lenticule and host corneal tissues. These alterations in stromal proteoglycans are characteristic of stromal scars and keratoconus and provide evidence of pathologic processes in the graft tissue. Because of potential complications, epikeratoplasty should be considered only for those patients who are unsuitable candidates for contact lenses or penetrating keratoplasty.

Adult↗
PubMed1992

The same gamma-glutamyl transpeptidase RNA species is expressed in fetal liver, hepatic carcinomas, and rasT24-transformed rat liver epithelial cells.

In rats, gamma-glutamyl transpeptidase (gamma GT) exists as a single-copy gene, and three distinct species of RNA (types I, II, and III) that differ in their 5' untranslated regions have been identified. To compare steady-state levels of these gamma GT RNAs in rat tissues, hepatic carcinomas, and cultured cells, we used RNA dot-blot hybridization and a reverse transcriptase-polymerase chain reaction (RT-PCR) technique with oligonucleotides specifically designed for each type of RNA. Fetal liver, hepatic carcinomas, rasT24-transformed rat liver epithelial (RLE) cells and pancreas make only type III RNA. Liver and untransformed RLE cells do not make detectable levels of gamma GT RNA. We found that both fetal and adult kidneys synthesize all three types of RNA, indicating that increases in gamma GT RNA known to occur after birth do not result from recruitment of additional RNA species. When we increased the sensitivity of the assay approximately 1000 fold by sequencing the RT-PCR product directly after an additional round of amplification, we found that very low levels of types I and II RNA were present in fetal liver, rasT24-transformed RLE cells, and pancreas, and that adult liver and untransformed RLE cells synthesized very low levels of all three RNA species. Rat-1 fibroblasts did not make levels of gamma GT RNA detectable by this method. These results demonstrate that different gamma GT RNA species are regulated differently during development and neoplastic transformation and that there is a commitment in some cell types to very-low-level expression of gamma GT RNAs.

Animals↗
PubMed1992

Pathogenic autoantibody-inducing gamma/delta T helper cells from patients with lupus nephritis express unusual T cell receptors.

In previous work, we found that only 59 (15%) of 396 "autoreactive" T cell clones derived from five patients with lupus nephritis had the ability to selectively augment the production of pathogenic anti-DNA autoantibodies and the majority (49/59) of those autoimmune T helper (Th) clones were CD4+. Surprisingly, 7 of those Th clones were CD4-/CD8- and gamma/delta TCR+, capable of augmenting the production of pathogenic anti-DNA autoantibodies up to 125-fold. The gamma/delta Th clones responded in a MHC-nonrestricted manner to some endogenous autoantigen associated with heat shock proteins (HSP60) on the lupus B cells. The gamma/delta TCR genes expressed by 4 of these Th clones were amplified and sequenced here. Three of the 4 Th clones, each from a different lupus patient, expressed a gene from the V gamma 1 subgroup. Moreover, 2 of the Th clones expressed V delta 5, and the others V delta 1 or V delta 3. These TCRs are rarely expressed by peripheral blood gamma/delta T cells of normal adult humans. The predominant gamma/delta T cells in human peripheral blood express V gamma 2 (V gamma 9) and V delta 2 TCR genes, including HSP-responsive T cells. None of the lupus Th clones expressed this combination of TCR genes. In addition, some of these pathogenic autoantibody-inducing Th clones from the lupus patients had limited diversity and few N-nucleotide additions in their gamma/delta TCR junctional regions (CDR3), thus resembling fetal gamma/delta thymocytes early in ontogeny.

Base Sequence↗
PubMed1992

Panstromal Schnyder's corneal dystrophy. Ultrastructural and histochemical studies.

BACKGROUND: A large cohort comprising four kindreds of patients with Schnyder's dystrophy has been identified in central Massachusetts. All patients were Swede-Finn with ancestry from the southwest Finnish coast on the Bay of Bothnia. METHODS: Of 60 members of this cohort examined by one of the authors (JSW), 18 had evidence of Schnyder's dystrophy. One female with Schnyder's dystrophy from each of three kindreds underwent penetrating keratoplasty for decreased visual acuity. We examined 4 corneal buttons from these unrelated women, aged 47, 63, and 72 years. RESULTS: The fluorescent probe filipin revealed that the majority of the lipid deposits were rich in unesterified cholesterol. Electron microscopy demonstrated abnormal accumulation of lipid and dissolved cholesterol in the epithelium, Bowman's layer, and throughout the stroma. Examination of the kindreds reflected the variable expression of crystals, which were present only in two patients, the 47-year-old and 63-year-old women. CONCLUSION: Ultrastructural and histochemical studies showed the panstromal localization of lipid in Schnyder's corneal dystrophy in three patients with Schnyder's dystrophy who underwent penetrating keratoplasty.

Aged↗
PubMed1992

Pleomorphic xanthoastrocytoma of the brain: MR findings in six patients.

OBJECTIVE: Pleomorphic xanthoastrocytoma is a rare, usually benign brain tumor. This pleomorphic supratentorial tumor involves the leptomeninges and superficial cortex in young patients with seizures. The MR imaging features of this distinct tumor have not been reported. We describe the MR imaging findings in six patients with pathologically proved pleomorphic xanthoastrocytoma. MATERIALS AND METHODS: We retrospectively reviewed the MR images of six patients with pathologically proved pleomorphic xanthoastrocytoma. MR images were reviewed by two neuroradiologists. The pathologic slides of the tumors were reviewed by two neuropathologists. We also analyzed the patients' clinical features. RESULTS: Most of the tumors were cortical based and isointense with gray matter on T1-weighted images and mildly hyperintense on T2-weighted images. All the masses enhanced with contrast material. Cystic components and gyriform and leptomeningeal enhancement were seen occasionally. The tumors occurred in the temporal lobes in four of the six patients. Three patients had seizures, and the other three had headaches. CONCLUSION: Pleomorphic xanthoastrocytoma is a rare, usually benign, cortical-based mass that often enhances intensely with contrast material. The most common location is in the temporal lobes. Seizures and headaches are common clinical features. Familiarity with this lesion is important in the differential diagnosis of enhancing cortical-based masses.

Adolescent↗
PubMed1992

Retinoblastoma: messenger RNA for interphotoreceptor retinoid binding protein.

Surgically excised retinoblastomas from 14 patients (age range nine months to two years) were assessed by immunocytochemistry for the expression of photoreceptor-specific proteins and neuronal and glial cell markers. Adjacent tissues were examined for messenger RNA expression of interphotoreceptor retinoid-binding protein (IRBP) using Northern blots. For immunocytochemical stains (ABC method), monoclonal and polyclonal antibodies included S-Ag, rhodopsin, neuron specific enolase (NSE), glial fibrillary acidic protein (GFAP), IRBP, neural adhesion molecule (N-CAM), and rod and cone specific transducin (TR alpha and TC alpha). Histopathology revealed mostly poorly differentiated tumors with necrosis and lack of Flexner-Wintersteiner rosettes. Immunocytochemical staining showed focal IRBP expression in one of the tumors and S-antigen in two cases. Immunoreactivity with rhodopsin was negative. N-CAM, a neural adhesive protein which appears to be involved in the regulation of adhesive interaction during neuronal differentiation, was positive except in two cases. All tumors showed immunoreactivity with NSE, whereas GFAP staining was limited to the perivascular glial tissue confirming the essential neuronal nature of retinoblastoma cells. TC alpha was detected in all tumors and TR alpha in one case. Messenger RNA for IRBP was detected in tumors in which IRBP immunoreactivity could not be detected.

Antibodies, Monoclonal↗
PubMed1991

Eye pathology associated with measles encephalitis in hamsters.

Measles encephalitis was produced in 41 hamsters by intracerebral injection of the hamster-neuroadapted Mantooth HBS viral strain. Group I (n = 10) included 2-day old (newborn) hamsters, each inoculated with 0.02 ml of 1:20 diluted virus. This group was sacrificed 4 days postinoculation (DPI). Group II (n = 31) included 25-day old hamsters, each inoculated with 0.03 ml of 1:10 diluted virus. This group was sacrificed 6, 13, 17, and 31 DPI. Clinical and histological evidence of measles encephalitis was present in all infected hamsters. Retinal lesions varied with the age of the animals at the time of inoculation. Retinal folds were observed in the 2-day old group and represented one form of retinal dysplasia. In the 25-day old group, however, earliest retinal involvement was in the form of hemorrhages, followed by focal retinitis in animals sacrificed 6-17 DPI. Measles keratitis was noted only in animals sacrificed 6 DPI. In 25-day old hamsters, measles keratitis and retinal hemorrhages represented the acute manifestations, whereas retinitis occurred later. However, ocular involvement did not correlate with the degree of severity of measles encephalitis.

Animals↗
PubMed1990

Cloning and analysis of the rat gamma-glutamyltransferase gene.

We have isolated and characterized a complete structural gene encoding the enzyme gamma-glutamyltransferase ((5-glutamyl)-peptide:amino acid 5-glutamyltransferase; EC 2.3.2.2). The gene contains 8 exons and spans approximately 12 kilobases. Ras-transformed rat liver epithelial cells and rat kidney express RNAs which differ in length by approximately 0.3 kilobase pair. Comparison of the genomic sequence with kidney gamma GT cDNA sequence indicates that the first exon is noncoding, and nuclease protection and primer extension data have identified a potential kidney transcription start site (defined as +1) for this exon. The site is not associated with a TATA box, but there are two CCAAT boxes (-136 and -599) and two sites (-101 and -746) containing the consensus sequences to which the transcription factor SP1 is known to bind. There is also a sequence at -453 (TGTGGTTG) that is highly homologous to the core sequence (TGTGG(T)3-5G) of SV40 and polyoma viral enhancers.

Base Sequence↗
PubMed1990

DNA interstrand cross-link and free radical formation in a human multidrug-resistant cell line from mitomycin C and its analogues.

A subline of the human breast tumor cell line (MCF-7), selected for resistance to Adriamycin and having the multidrug resistance phenotype, also developed significant cross-resistance to mitomycin C and its two analogues, BMY 25282 and BMY 25067. Because mitomycin C and the analogues contain both quinone and aziridine moieties, the mechanism of tumor cell kill is thought to involve alkylation and cross-linking of DNA molecules, hence they are not expected to show cross-resistance to cells selected for resistance to a DNA intercalator. Studies to understand this novel observation show that the resistant MCF-7 cells form significantly less hydroxyl radical and DNA cross-linking in the presence of mitomycin C and BMY 25282 than the sensitive cells. Although BMY 25067 formed less free radicals in the resistant cells, similar to the other two drugs, the formation of DNA cross-links was identical in both cell lines, indicating a somewhat different mechanism of tumor cell kill by this analogue. DNA cross-link formation increased slightly with time in the sensitive cells while there was a small decrease in the resistant cells. This difference in the formation of toxic intermediates appeared to result from enhanced detoxification of reactive species (hydrogen peroxide and alkylating intermediates) as a result of significantly higher glutathione peroxidase (14-fold) and glutathione S-transferase (44-fold) activities in the resistant cell line. These events, i.e., free radical formation and DNA alkylation, showed a good correlation with the cytotoxicity in drug-sensitive cells, indicating that both mechanisms contribute to cell killing of human breast tumor cells.

Alkylating Agents↗
PubMed1990

Analysis of the rearrangements associated with carcinogen-induced activation of the hamster thymidine kinase gene.

We have previously shown that chemical carcinogen treatment of RJK92 hamster cells activates the quiescent thymidine kinase (TK) gene and that 20% of the TK+ variants have a rearrangement in the region 5' to the TK gene (Barr et al. (1986) Mol. Cell. Biol. 6, 3023-3033). After cloning the wild type 5' region to obtain detailed mapping data and hybridization probes, we localized the rearrangement breakpoints by Southern blot analysis to a 1.5 kb region 6 kb 5' to the origin of transcription. This analysis also demonstrated that the rearrangements consist at least partly of a deletion of wild type sequences 5' to this breakpoint region. The region near the transcription origin in the rearranged TK genes has a DNase I-sensitive chromatin conformation and a DNase I hypersensitive site as well as the previously described domain of demethylation (Ibid.). Though this domain of demethylation extends into the breakpoint region, the rearranged region is not associated with DNase I sensitivity nor hypersensitive sites. The rearrangement also does not detectably alter the growth-related regulation of TK activity in these cells.

Animals↗
PubMed1990

Pathogenic anti-DNA autoantibody-inducing T helper cell lines from patients with active lupus nephritis: isolation of CD4-8- T helper cell lines that express the gamma delta T-cell antigen receptor.

The antigen responsible for autoimmunization in systemic lupus erythematosus is unknown. In spite of this obstacle, we show that T helper (Th) cell lines that are functionally relevant to this disease can be established in vitro. We derived a total of 396 interleukin 2-dependent T-cell lines from the in vivo activated T cells of five patients with lupus nephritis. Only 59 (approximately 15%) of these lines had the ability to selectively augment the production of pathogenic anti-DNA autoantibodies that were IgG in class, cationic in charge, specific for native DNA, and clonally restricted in spectrotype. Forty-nine of these autoantibody-inducing Th lines were CD4+ and expressed the alpha beta T-cell receptor (TCR). The other 10 were CD4-8- (double negative), 3 expressing the alpha beta TCR and 7 expressing the gamma delta TCR. All of the autoantibody-inducing Th lines responded to some endogenous antigen presented by autologous B cells. The autoreactive responses of the CD4+ Th lines were restricted to HLA class II antigens, whereas those of the double-negative cells were not. Endogenous heat shock or stress proteins of the HSP60 family that were expressed by the lupus patients' B cells were involved in stimulating an autoreactive proliferation of the gamma delta Th cells. These studies demonstrate a novel helper activity of certain gamma delta T cells in a spontaneous autoimmune response.

Antibodies, Monoclonal↗
PubMed1989

Free-radical formation by mitomycin C and its novel analogs in cardiac microsomes and the perfused rat heart.

Using a spin-trapping technique, we have examined free-radical formation by mitomycin C and its analogs, BMY 25282 and BMY 25067, in rat cardiac microsomes and isolated perfused rat hearts. All three drugs stimulated 2--4-fold OH radical formation in cardiac microsomes which was inhibited by SOD and catalase. Superoxide anion radical was also detected in the presence of diethylenetetraaminopentaacetic acid. Addition of DMSO yielded methyl radicals, thus indicating the production of free OH under these conditions. Similar stimulation of OH formation (2--3-fold) in the perfusates from rat hearts was detected with all three drugs. Perfusion with catalase (550 U/ml) completely suppressed the OH signal both in the presence and absence of the drugs, thus suggesting the intermediacy of hydrogen peroxide. However, BMY 25067-induced OH formation was more sensitive to inhibition by superoxide dismutase (SOD) and the iron chelator ICRF-187. Perfusion with DMSO produced methyl radicals at the expense of OH in the presence of all three drugs. SOD and catalase inhibited DMPO-OH signals, indicating that most of the OH formation was extracellular in this setting. While mitomycin C and BMY 25067 (up to 10 microM) did not affect the heart rate, perfusion with 10 microM BMY 25282 caused acute arrhythmia and cardiac standstill within 20 min. An initial surge in OH formation (2-fold) accompanied this cardiotoxic effect. Both the arrhythmia and the free radical signal were partially blocked by SOD, catalase and ICRF-187, indicating that iron-dependent oxygen radical formation from BMY-25282 (and possibly other compounds) is involved, in part, in inducing toxic manifestations in the rat heart and possibly in clinic.

Animals↗
PubMed1989

Adriamycin activation and oxygen free radical formation in human breast tumor cells: protective role of glutathione peroxidase in adriamycin resistance.

Previous studies with Adriamycin-sensitive and -resistant (ADRR) MCF-7 human breast tumor cell lines indicated that Adriamycin formed significantly less hydroxyl radical (.OH) as the result of enhanced detoxification of reactive oxygen intermediates in the ADRR cell line. In order to further define the sites of drug activation and the role of detoxification mechanisms in free radical levels, subcellular fractions were isolated from these two cell lines and free radical formation in the presence of Adriamycin was examined by using electron spin resonance spectroscopy. Studies reported here show that considerable NADPH-cytochrome P-450 reductase and NADH dehydrogenase activities were present in microsomes and mitochondria, respectively, and in nuclei obtained from these cells, and the relative activity of NADH dehydrogenase was 2-fold higher in the mitochondrial fraction of ADRR cells compared to the mitochondrial fraction from the parental wild type cells. In the presence of Adriamycin and a reducing cofactor (NADPH or NADH), Adriamycin semiquinone free radical, superoxide anion, and .OH were detected in all these fractions. Although only a small difference in the relative amount of oxy radical formation was detected in tumor microsomes, both mitochondria and nuclei of ADRR cells showed an overall 2-fold decreased formation of oxy radicals. The formation of the free radicals was significantly inhibited by superoxide dismutase, catalase, and dimethyl sulfoxide, indicating that free .OH generation was both superoxide and hydrogen peroxide dependent. The addition of purified glutathione peroxidase likewise inhibited .OH formation in a dose-dependent fashion. Similarly, when the lysate from ADRR cells, which contains 12- to 14-fold more glutathione peroxidase than Adriamycin-sensitive cells, was added to reaction mixtures containing Adriamycin-sensitive cells and Adriamycin, the .OH formation was diminished. Decreased free radical formation in nuclei and mitochondria, as a result of detoxification of hydrogen peroxide by glutathione peroxidase, may be significant in the protection of ADRR cells from Adriamycin-induced cell killing.

Biotransformation↗
PubMed1988

Adriamycin-induced free radical formation in the perfused rat heart: implications for cardiotoxicity.

Adriamycin is an anthracycline drug with a wide spectrum of clinical antineoplastic activity. However, the usefulness of the drug is limited by its dose-dependent cardiotoxicity. Adriamycin-stimulated free radical formation has been suggested as one of the mechanisms for its cardiotoxic effects. In order to evaluate this underlying mechanism, we have perfused rat hearts with Adriamycin, using a modified Langendorf technique, and the free radicals formed were analyzed by electron spin resonance spectroscopy using spin-trapping techniques. Our studies show that Adriamycin stimulated the formation of .OH in the heart, and the maximum .OH was formed with 1 microM of the drug. The addition of superoxide dismutase (600 units/ml) inhibited the hydroxyl radical formation by 2- to 3-fold, while catalase (550 units/ml) abolished it completely, showing the intermediacy of superoxide and H2O2. Furthermore, ICRF-187, an iron chelator and a cytotoxic drug, was also an effective inhibitor of .OH formation in the rat heart. The heart rate was not significantly modified by all the above experiments. This study demonstrates that Adriamycin stimulates the formation of .OH in the isolated rat heart and suggests that this mechanism may be significant in Adriamycin-induced cardiotoxicity.

Animals↗
PubMed1988

Retinal insulin receptors: localization using a polyclonal anti-insulin receptor antibody.

Although retinal insulin receptors have recently been described biochemically, the location of these receptors within the retina is unknown. The study presented here used a polyclonal anti-insulin receptor antibody (B10), immunofluorescence and immunoelectron microscopy to determine the location of insulin receptors in bovine, monkey and human retina. It was found that antibody immunofluorescence formed discrete bands localized predominantly to photoreceptor and neuronal cell bodies. In addition to the strong association with neuronal perikarya, a lower level of antibody binding was observed in photoreceptor outer segments. In human retina, some of the antibody immunofluorescence also had a pattern that suggested B10 binding to glial-like cells.

Animals↗