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Biomedical subjects

A Srivastava

Publications and source records attributed to A Srivastava.

At least 19 recordsLinked to original sources
PubMed1999

Human fibroblast growth factor receptor 1 is a co-receptor for infection by adeno-associated virus 2.

Adeno-associated virus 2 (AAV)-based vectors have gained attention as a potentially useful alternative to the more commonly used retroviral and adenoviral vectors for human gene therapy. Although AAV uses the ubiquitously expressed cell surface heparan sulfate proteoglycan (HSPG) as a receptor, the transduction efficiency of AAV vectors varies greatly in different cells and tissues in vitro and in vivo. We demonstrate here that cell surface expression of HSPG alone is insufficient for AAV infection, and that AAV also requires human fibroblast growth factor receptor 1 (FGFR1) as a co-receptor for successful viral entry into the host cell. We document that cells that do not express either HSPG or FGFR1 fail to bind AAV and, consequently, are resistant to infection by AAV. These non-permissive cells are successfully transduced by AAV vectors after stable transfections with cDNAs encoding the murine HSPG and the human FGFR1. Furthermore, AAV infection of permissive cells, known to express both FGFR1 and the epidermal growth factor receptor, is abrogated by treatment of cells with basic fibroblast growth factor, but not with epidermal growth factor. The identification of FGFR1 as a co-receptor for AAV should provide new insights not only into its role in the life cycle of AAV, but also in the optimal use of AAV vectors in human gene therapy.

3T3 Cells↗
PubMed1998

Prognostic significance of p53 protein overexpression in betel- and tobacco-related oral oncogenesis.

We have previously reported overexpression of p53 protein in tobacco-related oral dysplasia and squamous cell carcinoma (SCC) in the Indian population. A follow-up study was carried out to determine the prognostic significance of an accumulation of p53 protein during oral tumorigenesis. One hundred and two of 145 (70%) of oral SCCs and 39/75 (52%) of oral dysplasias showed overexpression of p53 protein, while only 3 of 107 (3%) normal oral tissues showed a detectable level of the protein. Follow-up studies of these patients suggest that an accumulation of p53 protein may be involved in the early phases of oral SCC development and indicate the predisposition of a particular premalignant lesion towards malignancy. In patients with premalignant lesions, the median transition time (premalignancy to malignancy) was significantly shorter in p53 positive cases than in p53 negative cases (p = 0.013). Among the oral cancer patients, univariate analysis showed that alteration in p53 expression was associated with significantly decreased disease-free survival. The p53 positive cases showed decreased median disease-free survival time (no recurrence/metastasis) compared with the p53 negative cases (p = 0.013), indicating that p53 accumulation may serve as a prognostic indicator in oral cancer patients.

Adult↗
PubMed1998

Action of the allelochemical, fischerellin A, on photosystem II.

The cyanobacterium, Fischerella muscicola, produces a secondary metabolite named fischerellin A (FS) that strongly inhibits the growth of cyanobacteria and other photosynthetic organisms. The compound exhibits a unique structure and is composed of two cyclic amines and a C15 substituent that contains a double bond in the (Z) configuration and two triple bonds [L. Hagmann, F. Jüttner, Tetrahedron Lett., 37 (1996) 6539-6542]. The site of FS action is located in photosystem II (PSII). The chlorophyll fluorescence induction transient and O2 evolution methods have been used to determine the site of action of FS in PSII. FS affects the fluorescence transients, as well as O2 evolution by the cyanobacterium, Anabaena P9. The green alga, Chlamydomonas reinhardtii, and higher plants were also affected by FS in a concentration- and time-dependent fashion. FS acts at several sites which appear with increasing half-time of interaction in the following sequence: (1) effect on the rate constant of QA- reoxidation; (2) primary photochemistry trapping; (3) inactivation of PSII reaction center; and (4) segregation of individual units from grouped units. FS does not affect the photosynthetic activity of purple bacteria, Rhodospirillum rubrum.

Chlorophyta↗
PubMed1998

Quantification of busulfan in plasma by gas chromatography-mass spectrometry following derivatization with tetrafluorothiophenol.

A specific and highly sensitive method has been developed for the determination of busulfan in plasma by gas chromatography-mass spectrometry using a deuterium-labeled busulfan (busulfan-d8) as internal standard. Plasma containing busulfan and busulfan-d8 were extracted with ethyl acetate and derivatized with 2,3,5,6-tetrafluorothiophenol prior to the monitoring of specific ions. The limit of quantification of the assay was 20 ng/ml and the calibration curve was linear over the range of 10 to 2000 ng/ml of derivatized busulfan. This method was in good agreement with the GC-MS assay using derivatization with sodium iodide and measuring diiodobutane. In addition, a pharmacokinetic study of busulfan was conducted in six children. The apparent oral clearance was 5.7+/-1.9 ml/kg/min and the volume of distribution was 1.0+/-0.4 l/kg and were similar to those previously reported in pediatric patients.

Alkylating Agents↗
PubMed1998

22-Mb integrated physical and genetic map based on YAC/STS content spanning the interval DXS1125-DXS95 in human Xq12-q21.31.

A YAC/STS map has been assembled spanning 22 Mb across Xq12-q21.31, between markers DXS1125 and DXS95. In addition to the landmark loci for the X-inactivation center XIST and the ATRX, ATP7A, phosphoglycerate kinase, POU3F4, and choroideremia genes, the candidate disease gene regions for torsion dystonia 3 and two X-linked mental retardation syndromes are included. Also, the human voltage-dependent anion channel gene (HVDAC1) has been placed near DXS986. The current map incorporates 211 YACs from five different libraries, formatted with 185 STSs that comprise 26 genetic linkage markers, 60 newly-developed YAC-end STSs, and eight ESTs. The multiple clone coverage and average resolution of one STS per 120 kb provide resources for disease gene searches and are facilitating complete sequencing of the region.

Base Sequence↗
PubMed1998

Cell surface expression of 70 kDa heat shock protein in human oral dysplasia and squamous cell carcinoma: correlation with clinicopathological features.

To understand the role of 70 kDa heat shock protein (HSP70) in the pathogenesis of oral cancer, its expression was studied in human normal, premalignant and malignant oral mucosa. Cell surface expression of HSP70 was assessed in oral tissue specimens by flow cytometric analysis using a mouse monoclonal antibody against HSP70. A significant increase in cell surface expression of HSP70 was observed as the tissue progressed from normal to dysplasia towards carcinoma. Correlation of HSP70 expression with clinicopathological features showed a positive association with the severity of dysplasia. Among the oral tumours assessed, a significantly positive association was observed between HSP70 expression and dedifferentiation of oral squamous cell carcinomas (SCCs). Poorly differentiated tumours showed significantly higher levels of HSP70 expression on the surface of tumour cells, compared with well differentiated carcinomas (P < 0.05). Cell surface expression of HSP70 was observed to be significantly higher in clinically advanced stage tumours (T3/T4), compared with T1/T2 stage tumours (P < 0.05). The variation in cell surface expression of HSP70 in normal, dysplastic and malignant oral lesions suggests that it is differentially expressed during oral tumorigenesis and may play a specific role in the pathogenesis of oral cancer.

Carcinoma, Squamous Cell↗
PubMed1998

Expression of 70-kDa heat shock protein in oral lesions: marker of biological stress or pathogenicity.

We showed differential expression of HSP70 during oral tumorigenesis. The precise functional role of HSP70 overexpression in the pathogenesis of betel and tobacco related oral cancer remains to be determined. To evaluate the utility of HSP70 as an indicator of the biological stress experienced by tumour cells or the malignant potential of oral epithelial lesions and predicting clinical outcome, its expression was assessed in different stages of oral carcinogenesis by immunohistochemical analysis and correlated with clinicopathological parameters. Overexpression of HSP70 protein was observed in 38 of 64 (59%) dysplastic lesions and 92 of 125 (74%) oral squamous cell carcinomas (SCCs) which included 76 of 105 cases (72%) of primary oral SCCs and 16 of 20 (80%) of recurrent oral SCCs. A significant correlation of HSP70 expression was observed with severity of dysplasia (P = 0.0006767), poor histological differentiation of primary tumours (P = 0.0184348), increase primary tumour size (P = 0.0221103) and consumption of betel and tobacco (P < 0.01). Follow-up studies showed that in patients with premalignant lesions the median transition time (premalignancy to malignancy) was significantly shorter in HSP70 overexpressing cases than those showing basal level of HSP70 (P = 0.012). Oral cancer patients with elevated levels of HSP70 showed decreased median disease-free survival time (no recurrence/metastasis) than those showing basal HSP70 immunoreactivity (P = 0.0246). The results suggest that HSP70 expression may not be a mere marker of biological stress but may also be implicated in the pathogenesis of oral cancer.

Areca↗
PubMed1998

Management of haemophilia in the developing world.

The problems with management of haemophilia in developing countries are poor awareness, inadequate diagnostic facilities and scarce factor concentrates for therapy. The priorities in establishing services for haemophilia include training care providers, setting up care centres, initiating a registry, educating affected people and their families about the condition, providing low-cost factor concentrates, improving social awareness and developing a comprehensive care team. A coagulation laboratory capable of reliably performing clotting times with correction studies using normal pooled, FVIII and FIX deficient patient plasma and factor assay is most essential for diagnosis. More advanced centralized laboratories are also needed. Molecular biology techniques for mutation detection and gene tracking should be established in each country for accurate carrier detection and antenatal diagnosis. Different models of haemophilia care exists. In India, there is no support from the government. Services, including import of factor concentrates, are organized by the Haemophilia Federation of India, with support from other institutions. Haemophilia is managed with minimal replacement therapy (about 2000 i.u./PWH/year). In Malaysia, where the system is fully supported by the government, facilities are available at all public hospitals and moderate levels of factor concentrates are available 'on-demand' (about 11,000 i.u./PWH/year) at the hospitals. Haemophilia care in South Africa is provided through major public hospitals. Intermediate purity factor concentrates are locally produced (about 12,000 i.u./PWH/year) at low cost. The combined experience in the developing world in providing haemophilia services should be used to define standards for care and set achievable goals.

Developing Countries↗
PubMed1998

Factor concentrates for haemophilia in the developing world.

The success in the management of haemophilia in the last two decades has been predominantly due to the availability of sufficient quantities of safe factor concentrates. Unfortunately, the prohibitive cost of these products has prevented this benefit from being available to the vast majority (approximately 80%) of haemophiliacs living in the developing world. A few developing countries have established facilities for the production of low- to intermediate-purity factor concentrates locally. The infrastructure required to achieve this can be very basic. The experience in South Africa, Thailand, Cuba and Brazil, described herein, shows that this approach provides factor concentrates which are very economical in comparison with more purified commercial products. This has had a major impact on the quality of haemophilia care in these countries. Wide availability of low-cost factor concentrates has made these products accessible to a large number of haemophiliacs and even made home therapy possible. The effort to provide these products results in improvement of the blood transfusion services. This, in turn, contributes to better facilities for patients with other transfusion-dependent diseases and society in general. Installation of small plasma fractionation plants is also a viable option. This not only allows processing of large pools of plasma for greater quantities of factor concentrates but also provides albumin and immunoglobulin. The revenue generated from the sale of the other products has been used to improve and subsidize haemophilia care. It is concluded that local production of intermediate purity factor concentrates in developing countries is absolutely necessary. A well organized transfusion service is required to collect adequate quantities of plasma for fractionation.

Blood Coagulation Factors↗
PubMed1998

Pth1/Vam3p is the syntaxin homolog at the vacuolar membrane of Saccharomyces cerevisiae required for the delivery of vacuolar hydrolases.

The PEP12 homolog Pth1p (Pep twelve homolog 1) is predicted to be similar in size to Pep12p, the endosomal syntaxin homolog that mediates docking of Golgi-derived transport vesicles and, like other members of the syntaxin family, is predicted to be a cytoplasmically oriented, integral membrane protein with a C-terminal transmembrane domain. Kinetic analyses indicate that deltapth1/vam3 mutants fail to process the soluble vacuolar hydrolase precursors and that PrA, PrB and most of CpY accumulate within the cell in their Golgi-modified P2 precursor forms. This is in contrast to a pep12 mutant in which P2CpY is secreted from the cell. Furthermore, pep12 is epistatic to pth1/vam3 with respect to the CpY secretion phenotype. Alkaline phosphatase, a vacuolar membrane hydrolase, accumulates in its precursor form in the deltapth1/vam3 mutant. Maturation of pro-aminopeptidase I, a hydrolase precursor delivered directly to the vacuole from the cytoplasm, is also blocked in the deltapth1/vam3 mutant. Subcellular fractionation localizes Pth1/Vam3p to vacuolar membranes. Based on these data, we propose that Pth1/Vam3p is the vacuolar syntaxin/t-SNARE homolog that participates in docking of transport vesicles at the vacuolar membrane and that the function of Pth1/Vam3p impinges on at least three routes of protein delivery to the yeast vacuole.

Amino Acid Sequence↗
PubMed1998

Adeno-associated virus type 2-mediated gene transfer: role of epidermal growth factor receptor protein tyrosine kinase in transgene expression.

Adeno-associated virus type 2 (AAV), a single-stranded, DNA-containing, nonpathogenic human parvovirus, has gained attention as a potentially useful vector for human gene therapy. However, the transduction efficiency of AAV vectors varies greatly in different cells and tissues in vitro and in vivo. We have recently documented that a cellular tyrosine phosphoprotein, designated the single-stranded D-sequence-binding protein (ssD-BP), plays an important role in AAV-mediated transgene expression (K. Y. Qing et al., Proc. Natl. Acad. Sci. USA 94:10879-10884, 1997) and that a strong correlation exists between the phosphorylation state of the ssD-BP and AAV transduction efficiency in vitro as well as in vivo (K. Y. Qing et al., J. Virol. 72:1593-1599, 1998). In this report, we document that treatment of cells with specific inhibitors of the epidermal growth factor receptor protein tyrosine kinase (EGF-R PTK) activity, such as tyrphostin, leads to significant augmentation of AAV transduction efficiency, and phosphorylation of the ssD-BP is mediated by the EGF-R PTK. Treatment of cells with EGF results in phosphorylation of the ssD-BP, whereas treatment with tyrphostin causes dephosphorylation of the ssD-BP and consequently leads to increased expression of the transgene. Furthermore, AAV transduction efficiency inversely correlates with expression of the EGF-R in different cell types, and stable transfection of the EGF-R cDNA causes phosphorylation of the ssD-BP, leading to significant inhibition in AAV-mediated transgene expression which can be overcome by the tyrphostin treatment. These data suggest that the PTK activity of the EGF-R is a crucial determinant in the life cycle of AAV and that further studies on the interaction between the EGF-R and the ssD-BP may yield new insights not only into its role in the host cell but also in the successful use of AAV vectors in human gene therapy.

Cell Line↗
PubMed1998

Adeno-associated virus type 2-mediated gene transfer: correlation of tyrosine phosphorylation of the cellular single-stranded D sequence-binding protein with transgene expression in human cells in vitro and murine tissues in vivo.

Although the adeno-associated virus type 2 (AAV)-based vector system has gained attention as a potentially useful alternative to the more commonly used retroviral and adenoviral vectors for human gene therapy, the single-stranded nature of the viral genome, and consequently the rate-limiting second-strand viral DNA synthesis, significantly affect its transduction efficiency. We have identified a cellular tyrosine phosphoprotein, designated the single-stranded D sequence-binding protein (ssD-BP), which interacts specifically with the D sequence at the 3' end of the AAV genome and may prevent viral second-strand DNA synthesis in HeLa cells (K. Y. Qing et al., Proc. Natl. Acad. Sci. USA 94:10879-10884, 1997). In the present studies, we examined whether the phosphorylation state of the ssD-BP correlates with the ability of AAV to transduce various established and primary cells in vitro and murine tissues in vivo. The efficiencies of transduction of established human cells by a recombinant AAV vector containing the beta-galactosidase reporter gene were 293 > KB > HeLa, which did not correlate with the levels of AAV infectivity. However, the amounts of dephosphorylated ssD-BP which interacted with the minus-strand D probe were also as follows: 293 > KB > HeLa. Predominantly the phosphorylated form of the ssD-BP was detected in cells of the K562 line, a human erythroleukemia cell line, and in CD34+ primary human hematopoietic progenitor cells; consequently, the efficiencies of AAV-mediated transgene expression were significantly lower in these cells. Murine Sca-1+ lin- primary hematopoietic stem/progenitor cells contained predominantly the dephosphorylated form of the ssD-BP, and these cells could be efficiently transduced by AAV vectors. Dephosphorylation of the ssD-BP also correlated with expression of the adenovirus E4orf6 protein, known to induce AAV gene expression. A deletion mutation in the E4orf6 gene resulted in a failure to catalyze dephosphorylation of the ssD-BP. Extracts prepared from mouse brain, heart, liver, lung, and skeletal-muscle tissues, all of which are known to be highly permissive for AAV-mediated transgene expression, contained predominantly the dephosphorylated form of the ssD-BP. Thus, the efficiency of transduction by AAV vectors correlates well with the extent of the dephosphorylation state of the ssD-BP in vitro as well as in vivo. These data suggest that further studies on the cellular gene that encodes the ssD-BP may promote the successful use of AAV vectors in human gene therapy.

Animals↗
PubMed1998

Rescue and autonomous replication of adeno-associated virus type 2 genomes containing Rep-binding site mutations in the viral p5 promoter.

The Rep proteins encoded by the adeno-associated virus type 2 (AAV) play a crucial role in the rescue, replication, and integration of the viral genome. In the absence of a helper virus, little expression of the AAV Rep proteins occurs, and the AAV genome fails to undergo DNA replication. Since previous studies have established that expression of the Rep78 and Rep68 proteins from the viral p5 promoter is controlled by the Rep-binding site (RBS) and the YY1 factor-binding site (YBS), we constructed a number of recombinant AAV plasmids containing mutations and/or deletions of the RBS and the YBS in the p5 promoter. These plasmids were transfected in HeLa or 293 cells and analyzed for the potential to undergo AAV DNA rescue and replication. Our studies revealed that (i) a low-level rescue and autonomous replication of the wild-type AAV genome occurred in 293 but not in HeLa cells; (ii) mutations in the RBS resulted in augmented expression from the p5 promoter, leading to more efficient rescue and/or replication of the AAV genome in 293 but not in HeLa cells; (iii) little rescue and/or replication occurred from plasmids containing mutations in the YBS alone in the absence of coinfection with adenovirus; (iv) expression of the adenovirus E1A gene products was insufficient to mediate rescue and/or replication of the AAV genome in HeLa cells; (v) autonomously replicated AAV genomes in 293 cells were successfully encapsidated in mature progeny virions that were biologically active in secondary infection of HeLa cells in the presence of adenovirus; and (vi) stable transfection of recombinant AAV plasmids containing a gene for resistance to neomycin significantly affected stable integration only in 293 cells, presumably because rescue and autonomous replication of the AAV genome from these plasmids occurred in 293 cells but not in HeLa or KB cells. These data suggest that in the absence of adenovirus, the AAV Rep protein-RBS interaction plays a dominant role in down-regulating viral gene expression from the p5 promoter and that perturbation in this interaction is sufficient to confer autonomous replication competence to AAV in 293 cells.

DNA Helicases↗
PubMed1998

Recombinant human parvovirus B19 vectors: erythroid cell-specific delivery and expression of transduced genes.

A novel packaging strategy combining the salient features of two human parvoviruses, namely the pathogenic parvovirus B19 and the nonpathogenic adeno-associated virus type 2 (AAV), was developed to achieve erythroid cell-specific delivery as well as expression of the transduced gene. The development of such a chimeric vector system was accomplished by packaging heterologous DNA sequences cloned within the inverted terminal repeats of AAV and subsequently packaging the DNA inside the capsid structure of B19 virus. Recombinant B19 virus particles were assembled, as evidenced by electron microscopy as well as DNA slot blot analyses. The hybrid vector failed to transduce nonerythroid human cells, such as 293 cells, as expected. However, MB-02 cells, a human megakaryocytic leukemia cell line which can be infected by B19 virus following erythroid differentiation with erythropoietin (N. C. Munshi, S. Z. Zhou, M. J. Woody, D. A. Morgan, and A. Srivastava, J. Virol. 67:562-566, 1993) but lacks the putative receptor for AAV (S. Ponnazhagan, X.-S. Wang, M. J. Woody, F. Luo, L. Y. Kang, M. L. Nallari, N. C. Munshi, S. Z. Zhou, and A. Srivastava, J. Gen. Virol. 77:1111-1122, 1996), were readily transduced by this vector. The hybrid vector was also found to specifically target the erythroid population in primary human bone marrow cells as well as more immature hematopoietic progenitor cells following erythroid differentiation, as evidenced by selective expression of the transduced gene in these target cells. Preincubation with anticapsid antibodies against B19 virus, but not anticapsid antibodies against AAV, inhibited transduction of primary human erythroid cells. The efficiency of transduction of primary human erythroid cells by the recombinant B19 virus vector was significantly higher than that by the recombinant AAV vector. Further development of the AAV-B19 virus hybrid vector system should prove beneficial in gene therapy protocols aimed at the correction of inherited and acquired human diseases affecting cells of erythroid lineage.

Bone Marrow Cells↗