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Biomedical subjects

G Srivastava

Publications and source records attributed to G Srivastava.

At least 73 records · Page 4Linked to original sources
PubMed1996

Accumulation of p53 protein in inverted transitional cell papilloma of the urinary bladder.

Aims-To study the possible accumulation of p53 protein in inverted papilloma of the urinary bladder.Methods-Formalin fixed, paraffin wax embedded sections from 14 cases of inverted papilloma of the urinary bladder were studied retrospectively. Accumulation of p53 was detected by immunohistochemistry using a mouse monoclonal antibody directed against p53. p53 protein reactivity was scored as follows: 0 = 10%; 1 = 10% to <30%; 2 = 30% to <50%; and 3 = >50% of cells p53 positive.Results-The 14 sections were scored as follows: 3 in four cases; 2 in four cases; 1 in one case; and 0 in five cases. Overall, nine (64%) of the 14 cases were positive for p53 protein.Conclusions-The accumulation of p53 protein in inverted papilloma of the urinary bladder suggests that p53 may have has an important role in the neoplastic process of this tumour. However, the benign nature of inverted papillomas suggests that p53 protein accumulation is not related to tumour invasiveness and metastasis. p53 reactivity cannot be used as a marker of malignancy for urothelial neoplasia. Further studies are required to determine the role of p53 protein in the oncogenesis of urothelial neoplasms.

Journal Article↗
PubMed1996

Gene expression of the receptor for growth-hormone-releasing hormone is physiologically regulated by glucocorticoids and estrogen.

We investigated the effects of glucocorticoids and estrogen on the gene expression of growth hormone (GH) and the receptor for growth-hormone-releasing hormone (GHRH) by measuring the mRNA levels of GH and GHRH receptor in pituitary tissues of Sprague-Dawley rats using Northern blot hybridization and specific cDNA probes. Male rats, 6 weeks of age, were either adrenalectomized (or sham-operated) or treated with varying doses of dexamethasone (40, 200, 500 or 1,000 micrograms/kg/day, i.p.) for 3 days. Female rats, 4 weeks of age, were oophorectomized or sham-operated, and treated with 17 beta-estradiol benzoate 25 micrograms/kg/day (or vehicle) s.c. for 5 days starting 10 days after oophorectomy. Adrenalectomy was associated with a reduction in weight gain and decreased GHRH receptor mRNA levels (p < 0.05 and p < 0.0001 versus sham-operated, respectively). Dexamethasone treatment, however, was associated with a dose-dependent reduction in weight gain (p < 0.0001) but dose-dependent increases in GHRH receptor mRNA and GH mRNA levels (p < 0.0001 and p < 0.05, respectively). In the female rats, weight gain was increased by oophorectomy (p < 0.005 vs. sham-operated) and decreased by estrogen treatment (p < 0.05 vs. vehicle-treated). Pituitary GHRH receptor mRNA levels were also increased by oophorectomy (p < 0.05) and decreased by estrogen (p < 0.005). GH mRNA levels were unchanged by oophorectomy but decreased after estrogen treatment (p < 0.05). In conclusion, our findings suggest that endogenous glucocorticoids and estrogen are physiological regulators of pituitary GHRH receptor gene expression. Glucocorticoids and estrogen also regulate GH secretion via effects on GH gene expression. Changes in GHRH receptor and GH mRNA levels cannot explain the growth retardation in dexamethasone-treated rats.

Animals↗
PubMed1996

Gene expression of hypothalamic somatostatin, growth hormone releasing factor, and their pituitary receptors in hypothyroidism.

Thyroid hormones are important to growth in mammals and have been shown to rapidly stimulate the rate of GH gene transcription. In this study, we investigated whether thyroid hormones modulate GH secretion through their effects on the gene expression of GRF, somatostatin (SS), GRF receptor, and receptor subtype 2 for SS (SSTR2). Male adult Sprague-Dawley rats were rendered hypothyroid with a single injection of propylthiouracil followed by methimazole in drinking water (0.02%) for 1 day to 12 weeks. Total RNA extracted from the anterior pituitary and hypothalamus was analyzed by Northern hybridization. GH messenger RNA (mRNA) level in the anterior pituitary was significantly reduced in the hypothyroid animals (P < 0.0001 vs. controls for all treatment duration > or = 1 week). An increase in hypothalamic GRF mRNA level, by 2- and 4-fold, respectively, was seen after 3 and 12 weeks of antithyroid treatment (both P < 0.001 vs. controls). Hypothalamic GRF content, studied in 12-week hypothyroid rats only, was decreased compared with controls (P < 0.05). A reduction in pituitary GRF receptor mRNA level was observed after 1 week of antithyroid treatment (P < 0.01 after 1 week, P < 0.001 after 3 weeks). Total hypothalamic SS content and SS mRNA level in hypothalamic fragments consisting predominantly of the paraventricular and periventricular nuclei became significantly decreased (P < 0.05 and P < 0.005 respectively) after 12-weeks of antithyroid treatment. The reduction in SS gene expression in the periventricular nuclei was confirmed by in situ hybridization. No significant change in the mRNA level of pituitary SSTR2 was observed up to 12 weeks of antithyroid treatment. In conclusion, we have demonstrated a reduction in the gene expression of GRF receptor and SS in the hypothyroid rat. Our results suggest that the changes in hypothalamic GRF and SS gene expression in hypothyroid rats may be compensatory in nature and are likely to be secondary to the reduction in GH synthesis and secretion in these animals. The reduction in basal and GRF-stimulated GH secretion in hypothyroidism can be explained by the observed reduction in GH and GRF receptor gene expression.

Animals↗
PubMed1996

Detection of Epstein-Barr virus-infected mucosal lymphocytes in nasal polyps.

Primary nasal lymphomas of T or NK cell origin are known to be associated with Epstein-Barr virus (EBV). However, it is not known whether EBV is normally present in nasal mucosa as distinct to nasopharyngeal tissue. This study investigates the prevalence of EBV infection in 13 cases of nasal polyps. EBV DNA was detected in 2 of 13 (15%) by Southern blot hybridization and in 9 of 13 (69%) by polymerase chain reaction. In situ hybridization for EBV-encoded small nuclear RNAs (EBER) was positive in 11 of 13 (85%) cases; the virus was present in stromal lymphocytes only and not in the epithelial cells. Immunohistochemistry for EBV proteins in 7 cases revealed EBV nuclear antigen (EBNA)-2, latent membrane protein (LMP)-1, and ZEBRA (the switch protein encoded by gene BZLF1) expression in rare isolated stromal lymphocytes in 3 cases. Double immunostaining in 1 case showed that the LMP-1+ cells were B or T cells. Immunohistochemistry for EBV lytic proteins showed very rare viral capsid antigen (VCA)+ and membrane antigen (MA)+ cells in 1 case and very rare diffuse early antigen (EA-D)+ and VCA+ cells in 1 other case. The expression of ZEBRA, EA-D, VCA, and MA suggested a disruption of latency in very rare stromal lymphocytes leading to a productive cycle. Although the incidence of EBV positivity in nasal polyps in our population is high (85%), very low numbers of EBV+ cells are found in each case. Nevertheless, they indicate that nasal mucosa could be one of the sites of EBV persistence through a low level of infection of the resident lymphocytes and thereby provide a possible setting for the emergence of virally associated tumors in this site.

Adult↗
PubMed1995

Absence of Epstein-Barr virus in penile carcinoma. A study of 42 cases using in situ hybridization.

BACKGROUND: The relationship between Epstein-Barr virus (EBV) and carcinomas of the lower female genital tract has been the focus of some studies in recent years. However, the association between EBV and penile carcinoma never has been investigated. The aim of this study was to identify the possible role of EBV in penile carcinoma of Chinese patients. METHODS: Formalin fixed, paraffin embedded tissue of 42 cases of penile carcinoma (including 7 verrucous, 14 well differentiated, 15 moderately differentiated, and 6 poorly differentiated squamous cell carcinomas), 6 penile warts, and 9 normal penile samples were analyzed for EBV using in situ hybridization for EBV-encoded RNA (EBER). RESULTS: Epstein-Barr virus was only found in a few lymphocytes adjacent to the tumor epithelium in 12% (5 cases) of penile carcinoma. Conversely, the tumor cells, penile warts, and normal penile tissue were negative for EBV. CONCLUSIONS: The results suggest that EBV does not play a major role in the etiology of penile carcinoma.

Adult↗
PubMed1995

Epstein-Barr virus is localized in the tumour cells of nasal lymphomas of NK, T or B cell type.

Seven cases of nasal lymphoma were studied to identify the lineage of Epstein-Barr virus (EBV)+ cells using dual-labelling methods. Five cases were phenotypically and genotypically of natural killer cell (NK) type with germ-line configuration of T-cell receptor (TcR) beta-chain gene and immunoglobulin heavy-chain joining region (IgJH) gene, with one case each of T- and B-cell type showing rearranged TcR beta or IgJH and lambda-light chain genes respectively. EBV genome was clonal in all these cases except in the B-cell case where its clonality was undeterminable. Using in situ hybridization (ISH) for EBV-encoded small nuclear RNA 1 and 2 (EBER), signal was detected in 45% to 88% of nucleated cells in the tumours. Immunostaining for EBV latent membrane protein-I (LMP) also revealed numerous LMP+ cells in 3/5 NK-type cases and the T- and B-cell cases. Using ISH for EBER combined with immunostaining for CD markers and double immunohistochemistry for LMP and CD markers, the predominant lineage of the EBV+ cells was identified as: CD2+CD3-CD19-CD20- CD45R0 +/- CD56+CD68- in the NK-type cases, CD2+CD3 +/- CD19-CD20- CD45R0+CD56-CD68- in the T-cell case and CD20+CD45R0-CD68- in the B-cell case, in agreement with the genotype and phenotype of each tumour. These results show that, in EBV+ nasal lymphomas of NK, T- or B-cell lineage, EBV was consistently associated with the tumour-cell population and support the view that EBV serves a promoting role in the pathogenesis of different types of EBV+ nasal lymphoma.

Adult↗
PubMed1995

Evidence for lytic infection by Epstein-Barr virus in mucosal lymphocytes instead of nasopharyngeal epithelial cells in normal individuals.

Normal nasopharyngeal tissues from 23 individuals who died of causes unrelated to the upper respiratory system and had no evidence of Epstein-Barr virus (EBV)-related diseases were studied using in situ hybridisation (ISH) and immunohistochemistry for the detection of EBV RNA and expression of EBV proteins, respectively. ISH using 35S-labelled riboprobe for EBV EBER RNA showed occasional to a few EBER+ lymphocytes in the stroma of nasopharyngeal mucosa in 14/16 cases with available paraffin-embedded tissues. In addition, very rare intraepithelial EBER+ lymphocytes were also detected in 3/16 cases. However, in none of these cases was EBER detected in the epithelial cells. Similar results were obtained using a nonradioactive ISH method for EBER (Dako). In 3/23 cases, immunostaining using monoclonal antibodies for EBV proteins on cryostat sections showed occasional cells in the stroma expressing EBV nuclear antigen 2 (EBNA2), latent membrane protein-1 (LMP), and switch protein encoded by BZLF1 gene (ZEBRA) in two cases and only very rare LMP+ and ZEBRA+ cells in one other case. Double immunostaining combining alkaline phosphatase anti-alkaline phosphatase (APAAP) for CD markers and indirect immunofluorescence for LMP showed that the LMP+ cells were either CD19+ or less frequently CD3+, but none were CD68+. These results show that both B and T lymphocytes harbouring EBV can be found in the normal nasopharyngeal tissues. Interestingly, EBV proteins associated with lytic viral replication--diffuse early antigen (EA-D), viral capsid antigen (VCA), or membrane antigen (MA)--were also detected in rare cells in the stroma in one case, and in another case only one MA+ cell was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Expression of p53 and its relationship with human papillomavirus in penile carcinomas.

We studied p53 over-expression in a series of 42 primary penile carcinomas (seven verrucous carcinomas, 14 well-differentiated, 15 moderately-differentiated and six poorly-differentiated squamous cell carcinomas) from Chinese patients using the p53 protein specific mouse monoclonal antibody DO-7 on paraffin sections. p53 protein was detected in 40% (17 cases) of the tumours. The p53 staining was not observed in the penile warts (n = 6) and verrucous carcinomas (n = 7). Positive p53 staining was identified only in the less differentiated tumour cells in the periphery of the tumour cell nests in all the cases. The non-invasive dysplastic epithelium next to the tumours could also be positive for p53 protein (three out of 10 cases in which the dysplastic epithelium adjacent to the tumour was adequately sampled). Furthermore, 100% of the human papillomavirus (HPV)-positive cases showed positive p53 staining. It is concluded that p53 over-expression is present in penile squamous cell carcinomas and adjacent non-invasive tumour cells. An inverse correlation between HPV and p53 gene mutation is not observed in penile cancers.

Adult↗
PubMed1995

Absence of Epstein-Barr virus in oesophageal squamous cell carcinoma.

Aim-To identify the possible role of Epstein-Barr virus (EBV), in Chinese patients, in the pathogenesis of oesophageal squamous cell carcinoma.Methods-Formalin fixed, paraffin wax embedded tissues from 74 cases of oesophageal squamous cell carcinoma (28 with well differentiated, 27 with moderately differentiated and 18 with poorly differentiated carcinomas) were analysed for EBV using in situ hybridisation for EBV encoded small RNAs.Results-EBV was detected in only a few lymphocytes adjacent to the tumour epithelia in 14 (19%) cases of oesophageal carcinoma. The adjacent, non-pathological oesophageal tissue was EBV negative.Conclusions-EBV does not play a major role in the aetiology of oesophageal squamous cell carcinoma.

Journal Article↗
PubMed1994

Overexpression and point mutations of p53 tumor suppressor gene in hepatocellular carcinomas in Hong Kong Chinese people.

BACKGROUND: Gene deletion, point mutations, and abnormalities in expression of the tumor suppressor gene p53 in hepatocellular carcinoma have been reported to occur with varying frequency in different geographic regions. METHODS: To assess the expression and point mutation of the p53 gene, 31 patients with hepatocellular carcinomas were examined using Northern blotting, immunohistochemical methods, and DNA sequencing. All patients were Chinese, and 90.3% were positive for hepatitis B surface antigen (HBsAg). RESULTS: p53 transcript or protein was found in 14 (48.4%) of the 31 patients. Detectable p53 mRNA transcripts were found in 10 patients, and p53 protein was detected in 8 patients. In most cases of patients who had detectable p53 mRNA transcripts, the transcripts in the tumors were exhibited at a higher level than they were in the corresponding nontumorous livers. No p53 protein was detected in the nontumorous livers in all 31 patients. Six (23.1%) of the 26 tumors sequenced showed point mutation scattered in exons 5-9. Of these, only two were at codon-249, and the nature of these two mutations was G-to-T transversions. All but one of the six patients with point mutations had overexpression of the gene. CONCLUSIONS: Our results show that scattered point mutations are not uncommon in hepatocellular carcinomas in patients from Hong Kong. The distribution pattern of the mutations seems to have no particular correlation with HBsAg status despite a high prevalence rate of HBsAg positivity in our patients. Consistent with a low aflatoxin exposure, aflatoxin-related specific mutation at codon-249 is much less related to the pathogenesis of hepatocellular carcinoma in Hong Kong Chinese people than in other regions with a high-aflatoxin exposure.

Adult↗
PubMed1994

Epstein-Barr virus (EBV)-related lymphoproliferative disorder with subsequent EBV-negative T-cell lymphoma.

A 58-year-old Chinese man presented initially with generalized lymphadenopathy, and lymph-node biopsy showed disturbed architecture with preponderance of large B-blasts mixed with numerous CD8+ T lymphocytes, consistent with an acute Epstein-Barr virus (EBV) infection. Immunohistological and gene rearrangement studies confirmed the absence of clonal T or B cells. Polyclonal EBV with lytic infection was detected by Southern blot hybridization (SoBH). Expression of EBV proteins (EBNA2, LMP and ZEBRA) was detected in a proportion of cells by immunostaining. EBV-lytic proteins EA-D, VCA, MA were also detected in rare scattered cells. Double immunostaining showed that the LMP-positive cells were of B and of T phenotype: 73% CD19+, 26% CD2+, 23% CD3+, 8% CD4+, 17% CD8+. After biopsy, there was spontaneous regression of lymph-node enlargement, but lymphadenopathy recurred 8 months later, and the second lymph-node biopsy showed T-cell lymphoma, confirmed by detection of clonally rearranged T-cell-receptor beta-chain gene. However, EBV genome could not be detected in the second biopsy by SoBH, in situ hybridization for EBV-encoded EBER RNA, and immunostaining for EBNA2, LMP and ZEBRA was also negative. This case is of special interest because an EBV-negative T-cell lymphoma developed shortly after an acute episode of EBV-related lymphoproliferation, even though many EBV-positive T cells were detected during the acute episode. EBV was apparently not a direct cause of the lymphoma, but the close temporal association of the 2 lesions supports the hypothesis that EBV can act as a co-factor in lymphomagenesis.

Gene Rearrangement↗
PubMed1994

The pili of Pseudomonas aeruginosa strains PAK and PAO bind specifically to the carbohydrate sequence beta GalNAc(1-4)beta Gal found in glycosphingolipids asialo-GM1 and asialo-GM2.

Pseudomonas aeruginosa employs pili to mediate adherence to epithelial cell surfaces. The pilus adhesin of P. aeruginosa strains PAK and PAO has been shown to bind to the glycolipid asialo-GM1 (Lee et al., 1994--accompanying article). PAK and PAO pili were examined for their abilities to bind to the synthetic beta GalNAc(1-4)beta Gal (a minimal structural carbohydrate receptor sequence of asialo-GM1 and asialo-GM2 proposed by Krivan et al., 1988a) using solid-phase binding assays. Both pili specifically bound to beta GalNAc(1-4)beta Gal. The binding of beta GalNAc(1-4)beta Gal-Biotin to the immobilized PAK and PAO pili was inhibited by corresponding free pili. The receptor binding domain of the PAK pilus resides in the C-terminal disulphide-looped region (residues 128-144) of the pilin structural subunit (Irvin et al., 1989). Biotinylated synthetic peptides corresponding the C-terminal residues 128-144 of P. aeruginosa PAK and PAO pilin molecules were shown to bind to the beta GalNAc(1-4)beta Gal-(bovine serum albumin (BSA)). The binding of biotinylated peptides to beta GalNAc(1-4)beta GAL-BSA was inhibited by PAK pili, Ac-KCTSDQDEQFIPKGCSK-OH (AcPAK(128-144)ox-OH) and Ac-ACKSTQDPMFTPKGCDN-OH (AcPAO(128-144)ox-OH) peptides. (In these peptides Ac denotes N alpha-acetylation of the N-terminus, -OH means a peptide with a free alpha-carboxyl group at the C-terminus and the 'ox' denotes the oxidation of the sulphhydryl groups of Cys-129 and Cys-142.) Both acetylated peptides were also able to inhibit the binding of beta GalNAc(1-4)beta Gal-biotin to the corresponding BSA-Peptide(128-144)ox-OH conjugates.(ABSTRACT TRUNCATED AT 250 WORDS)

Adhesins, Bacterial↗
PubMed1994

Epstein-Barr virus associated aplastic anaemia and hepatitis.

We report a Chinese girl with Epstein-Barr virus (EBV) associated aplastic anaemia and hepatitis. Epstein-Barr virus genome was demonstrated in her bone marrow cells and EBV-specific serology suggested reactivation of EBV infection. She was initially treated with anti-thymocyte globulin (ATG) and methylprednisolone but with no haematologic response, and liver function continued to deteriorate. She was then treated with acyclovir. Her aplastic anaemia improved and hepatitis resolved, and there was eradication of EBV genome from her bone marrow cells.

Acyclovir↗
PubMed1994

Fimbria-mediated adherence of Candida albicans to glycosphingolipid receptors on human buccal epithelial cells.

Candida albicans is an opportunist fungal pathogen that has the ability to adhere to host cell surface receptors via a number of adhesins. Yu et al. (L. Yu, K. K. Lee, K. Ens, P. C. Doig, M. R. Carpenter, W. Staddon, R. S. Hodges, W. Paranchych, and R. T. Irvin, Infect. Immun. 62:2834-2842, 1994) described the purification and initial characterization of a fimbrial adhesin from C. albicans. In this paper, we show that C. albicans fimbriae also bind to asialo-GM1 [gangliotetraosylceramide: beta Gal(1-3)beta GalNAc(1-4) beta Gal(1-4)beta Glc(1-1)Cer] immobilized on microtiter plates in a saturable and concentration-dependent manner. C. albicans fimbrial binding to exfoliated human buccal epithelial cells (BECs) was inhibited by asialo-GM1 in in vitro binding assays. The fimbriae interact with the glycosphingolipid receptors via the carbohydrate portion of the receptors, since fimbriae were observed to bind to synthetic beta GalNAc(1-4)beta Gal-protein conjugates and the disaccharide was able to inhibit binding of fimbriae to BECs in in vitro binding assays. We conclude from these results that the C. albicans yeast form expresses a fimbrial adhesin that binds to glycosphingolipids displayed on the surface of human BECs.

Candida albicans↗
PubMed1994

Lack of correlation between expression of Epstein-Barr virus (EBV) latent membrane protein and bcl-2 oncoprotein in vivo.

AIMS: To evaluate whether there is any correlation between the expression of Epstein-Barr virus (EBV) latent membrane protein (LMP) and oncoprotein bcl-2 in the lymph node biopsy specimens of a Chinese patient with EBV-related reactive lymphoproliferation who later developed T cell lymphoma after a short period of time. METHODS: Immunohistochemistry, with a standard alkaline phosphatase antialkaline phosphatase (APAAP) method and New Fuchsin as a chromogen, was used for single staining of bcl-2 or LMP. Double immunostaining combining APAAP and indirect immunofluorescence was performed for dual labelling of LMP and bcl-2. RESULTS: bcl-2 was expressed in 10-30% of cells in the first lymph node biopsy specimen (EBV-associated lymphoproliferative disorder) and 30-50% of cells in the second lymph node biopsy specimen (T cell lymphoma). LMP was expressed in the first biopsy specimen but not in the second. Double immunostaining results showed that around 78% of LMP positive cells were bcl-2 negative and 94% bcl-2 positive cells were LMP negative. Among the very small fraction of LMP and bcl-2 double positive cells, the intensity of bcl-2 staining was heterogeneous and was not always stronger than that observed in LMP negative bcl-2 positive cells. CONCLUSIONS: The expression of bcl-2 protein is independent of LMP protein status in vivo. Several mechanisms may be involved in EBV associated lymphomagenesis, and bcl-2 induction may occur independently of LMP expression.

Fluorescent Antibody Technique↗