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S Das

Publications and source records attributed to S Das.

At least 217 records · Page 12Linked to original sources
PubMed2000

SALP16, a gene induced in Ixodes scapularis salivary glands during tick feeding.

Guinea pigs infested with Ixodes scapularis acquire antibody-mediated resistance to tick bites, a phenomenon known as tick-immunity. An I. scapularis salivary gland cDNA expression library was therefore probed with sera from tick-immune guinea pigs to identify antigens that elicit humoral responses in the host. Sera from sensitized guinea pigs strongly recognized 3 of 4,500 library clones in an initial screening. The open reading frames of all 3 clones encoded a putative 16.4-kD acidic protein, designated Salp16, with an N-terminal signal sequence and signal peptidase cleavage sites specific for secretory proteins. The salp16 mRNA and Salp16 protein were detected in the salivary glands of engorged, but not unfed, nymphal and adult ticks, and Salp16 was also found in the saliva of engorged ticks. Immunization with recombinant Salp16 induced high antibody titers in guinea pigs, but did not elicit tick-immunity. Salp16 is the first feeding inducible gene that has been cloned from L. scapularis. Molecular characterization of I. scapularis salivary antigens that are induced upon tick feeding should help to facilitate our understanding of tick-host interactions.

Amino Acid Sequence↗
PubMed2000

Loss of nuclear p16 protein expression is not associated with promoter methylation but defines a subgroup of aggressive endometrial carcinomas with poor prognosis.

The p16INK4aa (CDKN2) tumor suppressor gene is altered in several tumor types, but the frequency and mechanism of inactivation are largely unknown for endometrial carcinomas. We therefore wanted to assess the pattern and prognostic impact of p16 protein expression and promoter region methylation in a population-based series of 316 endometrial carcinoma patients with long-term and complete follow-up. Nuclear staining of p16 protein was related to clinicopathological variables, tumor markers, patient survival, and the presence of promoter region methylation. Absent/minimal nuclear staining for p16 protein was found in 14% of the tumors. Methylation of the p16 promoter region was found in only one tumor (0.7%) in a subset of 138 cases studied. This tumor lacked nuclear p16 protein expression as well. Loss of nuclear p16 staining was significantly associated with increased age, high FIGO (International Federation of Gynecology and Obstetrics) stage, serous papillary or clear cell histological types, high histological grade, aneuploidy, low estradiol and progesterone receptor concentrations, high expression of Ki-67, high intratumor microvessel density, and strong nuclear p53 protein expression. The 5-year survival was 47% for patients with absent/minimal nuclear p16 expression (n = 39) compared with 81% for patients with moderate/high nuclear p16 expression (n = 247; P < 0.0001). In Cox proportional hazards regression analysis, nuclear p16 expression showed an independent prognostic impact in addition to FIGO stage, age, Ki-67 expression, and microvessel density, with an adjusted hazard ratio of 2.9 (95% confidence interval, 1.3-6.5). The other variables lost their prognostic impact when nuclear p16 staining was added to the Cox model. In conclusion, loss of nuclear p16 protein expression was associated with aggressive endometrial carcinomas and high proliferative activity (Ki-67) and was found to represent a strong and independent prognostic indicator. Methylation of the promoter region seems to be an uncommon mechanism of p16 inactivation in endometrial carcinoma.

Aged↗
PubMed2000

Centronuclear myopathy--morphological relation to developing human skeletal muscle: a clinicopathological evaluation.

Centronuclear myopathy (CNM), an uncommon condition, is one of the congenital myopathies. It is believed to arise as a result of maturational arrest, with persistence of myotubes postnatally. However, denervation being the basic disease process and its possible influence on central nervous system causing defect in nuclear migration has also been postulated. Keeping in view these existing controversies, we have studied 17 cases of CNM (neonatal - 1, childhood - 13, adulthood - 3) during the last twelve and a half years. Diagnosis was based on histological and enzyme histochemical findings of muscle biopsy along with clinical data. Ultrastructural characterstics of muscle have been studied in 10 cases. The affected muscle fibres showed a central nucleus (40-99%) with perinuclear halo. Type I fibre predominance with hypoplasia was consistently seen. Fibre type disproportion was noticed in 7 cases. The neonatal form revealed dense oxidative enzyme reaction product in the centre. The morphological features of CNM were compared with foetal skeletal muscles obtained at gestational ages ranging from 9 weeks - 36 weeks (n = 18). In the severe neonatal form th myofibres resembled the foetal myotubes. In the less severe childhood and adult form of CNM, aberrant organization of cytoskeletal network might have played a pathogenetic role in causing the disease.

Adolescent↗
PubMed2000

Primary angiitis of CNS : neuropathological study of three autopsied cases with brief review of literature.

Primary angiitis of CNS(PACNS) or granulomatous angiitis of CNS is a rare inflammatory disease of small blood vessels mostly confined to the CNS. The clinical and pathological features of 3 autopsied cases are described. Clinically all the three PACNS patients were young males, age ranging from 19 to 31 years. All presented with varied neurological manifestations. There was no evidence of systemic disease in any of the cases. The ESR was normal and CSF analysis showed chronic meningitic pattern. The cerebral angiogram in one case was normal and the CT scan done in another case showed multiple intracerebral haematoma due to vasculitis. Brain biopsy was not done. Diagnosis was made at post-mortem examination. Histology showed characteristic but variable degree of granulomatous and non-granulomatous angiitis of small vessels. Venulitis with parenchymal haemorrhages was the predominant feature and in one case phlebitis with thrombosis was noted. Since the disease responds to steroids and immunosuppressive therapy, establishing antemortem diagnosis is important. In view of the association of angiitis of CNS with bacteria and viral infections, their role in the evolution of the disease needs to be investigated.

Adolescent↗
PubMed2000

Methylation of hMLH1 in a population-based series of endometrial carcinomas.

Microsatellite instability (MSI) is a characteristic feature of hereditary nonpolyposis colorectal cancer and is also observed in sporadic colorectal and endometrial cancers. Alterations in the mismatch repair genes hMLH1 and hMSH2 are important for the development of MSI. It has recently been demonstrated that hypermethylation of the hMLH1 promoter region is associated with MSI and appears to be a common mechanism for gene inactivation. For endometrial carcinoma, however, previous studies have been relatively small and have not been population based. We therefore wanted to assess the frequency and prognostic significance of hypermethylation of the hMLH1 and hMSH2 genes in conjunction with hMLH1 protein expression in a prospective and population-based series of endometrial carcinoma patients with known MSI status and complete follow-up. A total of 138 patients were studied, and methylation of hMLH1 was found in 23% of tumors with conclusive results, whereas methylation of hMSH2 was seen in only 1% of tumors. Methylation of hMLH1 was significantly correlated with MSI (P < 0.001). Loss of nuclear staining of hMLH1 protein was seen in 14% of the cases and was significantly correlated with hMLH1 methylation and MSI (P < 0.001). Normal expression of hMLH1 was seen in all of the unmethylated tumors (100%). Of the 14 MSI-positive tumors that were also methylated, all but 1 (93%) showed a loss of nuclear expression of hMLH1. None of the tumors with loss of hMLH1 expression or hMLH1 methylation were aneuploid (P for both < or = 0.05), and loss of hMLH1 expression and hMLH1 methylation was significantly correlated with lack of p53 overexpression (P for both < or = 0.05). Nuclear hMLH1 staining and hMLH1 methylation did not significantly influence survival. In conclusion, hMLH1 methylation was common and was significantly correlated with loss of hMLH1 protein expression, MSI, diploid tumors, and lack of p53 overexpression. In contrast, hMSH2 methylation was infrequent in this prospective and population-based series of endometrial carcinomas.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Loss of estrogen receptor (ER) expression in endometrial tumors is not associated with de novo methylation of the 5' end of the ER gene.

Normal endometrium, an estrogen-responsive tissue, expresses the estrogen receptor (ER) alpha gene. Loss of ER expression, the basis for which is currently unknown, is often seen in advanced stage, poor prognosis endometrial tumors. The ER gene undergoes de novo methylation with high frequency in a wide variety of human tumors, including ER-negative breast cancers. In this study, we used several bisulfite-based detection methods to assess whether loss of ER positivity in endometrial tumors is associated with aberrant methylation of the ER gene. Although extensive methylation of a 600-bp region at the 5' end of the gene was seen in two endometrial carcinoma cell lines, none of the 55 CpGs in this region was methylated in 25 of 26 ER-deficient endometrial carcinomas.

Adult↗
PubMed2000

In situ analysis of tissue factor-dependent thrombin generation in human atherosclerotic vessels.

Tissue factor (TF) is expressed in human atherosclerotic plaques where it may contribute to the thrombogenicity of the lesions and their progression toward unstable syndromes and acute myocardial infarction. In this study we tested the hypothesis that thrombin generation takes place in the lesion. Localisation of TF, factor VII (FVII), factor X/Xa (FX/Xa), thrombin, thrombin receptor PAR-1 and FXa receptor EPR-1 was done by immunostaining, ligand binding, or immunogold electron microscopy. Quantitation of TF antigen was done using a modified ELISA on fixed tissue sections. The amount of antigen was correlated with the pattern and intensity of immunostaining as detected on consecutive sections using confocal microscopy. TF-dependent generation of FXa on cryosections was used to assess the functional activity of TF. Active thrombin was detected using hirudin as a specific probe, followed by anti-hirudin IgG. Our light microscopy and immunogold electron microscopy results showed that the factors involved in TF-dependent coagulation are localised in atherosclerotic plaques in close proximity and colocalise with active thrombin and fibrin deposits. We have detected 3 to 7-fold increase of TF antigen and TF-dependent FXa generation in atherosclerotic vessels as compared with controls. Hirudin binding proved that active thrombin is present within the lesions. In conclusion, our data show that active coagulation factors are generated within atherosclerotic lesions and co-localise with their cellular receptors. These findings may suggest possible roles of the TF-dependent coagulation pathway in the intramural fibrin deposition and the progression of the atherosclerotic lesions.

Carotid Artery Diseases↗
PubMed2000

Facial nerve neurinoma presenting as middle cranial fossa and cerebellopontine angle mass: a case report.

Facial nerve neurinomas are rare. The tumours arising from the geniculate ganglion may grow anteriorly and superiorly and present as a mass in the middle cranial fossa. Only a few cases of facial nerve neurinomas presenting as middle cranial fossa mass have so far been reported. These tumours present with either long standing or intermittent facial palsy along with cerebellopontine angle syndrome.

Adult↗
PubMed2000

Etiology based prevalence of Budd-Chiari syndrome in eastern India.

BACKGROUND: Diagnosis of Budd-Chiari syndrome (BCS) is often missed unless its possibility has been kept in mind. Obstruction of inferior vena cava (IVC) is reportedly the most frequent cause of BCS in Afro-Asian variety. AIM: An attempt was made to classify BCS (in an eastern Indian population) etiopathologically. PATIENTS AND METHODS: Thirty consecutive cases of BCS presenting over a period of five years were included. Following a thorough physical examination, necessary investigations (including coagulation profile, ultrasonography (with Doppler study) of hepatobiliary tract, hepatic vein and IVC angiography (n = 22) and liver biopsy (n = 26, including autopsy in two cases) were performed. RESULTS: Mean age at presentation was 32.7 +/- 10.36 years (range 12-60 years) with M:F = 21:9. Clinical presentations included, hepatomegaly in 28 (93.3%), ascites in 27 (90%), splenomegaly in 15 (50%), pain in abdomen in 26 (86.6%), jaundice in 10 (33.3%), back veins in 20 (66.6%) and gastrointestinal bleeding in three (10%) cases. Amongst the total of 30 patients, four, six and 20 cases presented as fulminant, acute and chronic BCS respectively. Twenty four cases of BCS could be diagnosed by ultrasonography alone, while the remainder required angiography for diagnosis. IVC and hepatic vein angiography revealed membranous obstruction in nine, partial stricture of IVC in six, and IVC and/or hepatic vein block in others. The etiopathological nature in 30 cases were as follows: idiopathic membranous obstruction in nine (30%), hepatocellular carcinoma in six (20%), idiopathic stricture in six (20%) cases and one case (3.3%) each of the following: cholangiocarcinoma, renal cell carcinoma, chronic pancreatitis, hydatid cyst in liver, protein S deficiency, oral contraceptive use, nephrotic syndrome (with antithrombin III deficiency), polycythemia rubra vera and chronic lymphatic leukemia. CONCLUSION: Idiopathic membranous obstruction and stricture of IVC are the commonest cause of BCS in the eastern part of India. Hepatocellular carcinoma is also a common cause, presenting in the fulminant form. Ultrasonography may be a helpful screening test for BCS, but IVC and hepatic vein catheterisation is essential for a complete work up of these patients.

Adolescent↗
PubMed2000

Laparoscopic surgeries for the bladder.

Various reparative, reconstructive, extirpative, and miscellaneous surgeries of the bladder with laparoscopic techniques are in the process of evolution. Our increasing expertise enhanced by improved instrumentation make these procedures feasible and encourage us to venture into this relatively less explored arena of laparoscopic urology.

Humans↗
PubMed1999

Roles of aromatic residues in high interfacial activity of Naja naja atra phospholipase A2.

Acidic phospholipase A2 (PLA2) from the venom of Chinese cobra (Naja naja atra) has high activity on zwitterionic membranes and contains six aromatic residues, including Tyr-3, Trp-18, Trp-19, Trp-61, Phe-64, and Tyr-110, on its putative interfacial binding surface. To assess the roles of these aromatic residues in the interfacial catalysis of N. n. atra PLA2, we mutated them to Ala and measured the effects on its interfacial catalysis. Enzymatic activities of the mutants toward various vesicle substrates and human neutrophils indicate that all but Trp-18 make significant contributions to interfacial catalysis. Among these aromatic residues, Trp-19, Trp-61, and Phe-64 play the most important roles. Binding affinities of the mutants for phospholipid-coated beads and their monolayer penetration indicate that Trp-19, Trp-61, and Phe-64 are critically involved in interfacial binding of N. n. atra PLA2 and penetrate into the membrane during the interfacial catalysis of N. n. atra PLA2. Further thermodynamic analysis suggests that the side chain of Phe-64 is fully inserted into the hydrophobic core of membrane whereas those of Trp-19 and Trp-61 are located in the membrane-water interface. Together, these results show that all three types of aromatic residues can play important roles in interfacial binding of PLA2 depending on their location and side-chain orientation. They also indicate that these aromatic side chains interact with membranes in distinct modes because of their different intrinsic preference for different parts of membranes.

Amino Acid Sequence↗
PubMed1999

Evidence for nonlinear capacitance in biomembrane channel system.

The electrophysiological properties of voltage-dependent anion channels from mitochondrial membrane have been studied in a bilayer membrane system. It was observed that the probability of opening of the membrane channel depends on externally applied voltage and the plot is a bell-shaped curve symmetric around probability axis. A scheme of conformational energy levels under varying externally applied voltage was formulated. Assuming that the probability follows Boltzmann distribution, we arrive at an expression of change in energy containing a separate term identical to the energy of a capacitor. This fact indicates the possibility of existence of an added capacitance due to the channel protein. Further it was shown that the aforesaid channel capacitor could be a function of voltage leading to nonlinearity. We have offered a general method of calculating nonlinear capacitance from the experimental data on opening probability of a membrane channel. In case of voltage-dependent anion channel the voltage dependence of the capacitor has a power 0.786. The results have been interpreted in view of the structural organization of the channel protein in the membrane. Our hypothesis is that the phenomenon of capacitor behaviour is a general one for membrane channels.

Animals↗
PubMed1999

Amino acid substitution in alpha-helix 7 of Cry1Ac delta-endotoxin of Bacillus thuringiensis leads to enhanced toxicity to Helicoverpa armigera Hubner.

Insecticidal proteins or delta-endotoxins of Bacillus thuringiensis are highly toxic to a wide range of agronomically important pests. The toxins are formed of three structural domains. The N-terminal domain is a bundle of eight alpha-helices and is implicated in pore formation in insect midgut epithelial membranes. All the delta-endotoxins share a common hydrophobic motif of eight amino acids in alpha-helix 7. A similar motif is also present in fragment B of diphtheria toxin (DT). Site-directed mutagenesis of Cry1Ac delta-endotoxin of B. thuringiensis was carried out to substitute its hydrophobic motif with that of DT fragment B. The mutant toxin was shown to be more toxic to the larvae of Helicoverpa armigera (cotton bollworm) than the wild-type toxin. Voltage clamp analysis with planar lipid bilayers revealed that the mutant toxin opens larger ion channels and induces higher levels of conductance than the wild-type toxin.

Amino Acid Substitution↗
PubMed1999

In vivo endochondral bone formation using a bone morphogenetic protein 2 adenoviral vector.

Bone morphogenetic proteins (BMPs) are polypeptides that induce ectopic bone formation in standard rat in vivo assay systems. Previous studies have demonstrated the clinical utility of these proteins in spinal fusion, fracture healing, and prosthetic joint stabilization. Gene therapy is also a theoretically attractive technique to express BMPs clinically, since long-term, regulatable gene expression and systemic delivery with tissue-specific expression may be possible in future. This study was performed to determine whether an adenoviral vector containing the BMP-2 gene can be used to express BMP-2 in vitro and promote endochondral bone formation in vivo. In vitro, U87 MG cells transduced per cell with 20 MOI of an adenoviral construct containing the BMP-2 gene under the control of the universal CMV promoter (Ad-BMP-2) showed positive antibody staining for the BMP-2 protein at posttransfection day 2. The synthesis and secretion of active BMP-2 into the conditioned medium of Ad-BMP-2-transduced 293 cells were confirmed by Western blot analysis and the induction of alkaline phosphatase activity in a W-20 stromal cell assay. In vivo, Sprague-Dawley rats and athymic nude rats were injected with Ad-BMP-2 in the thigh musculature and were sacrificed on day 3, 6, 9, 12, 16, 21, 60, and 110 for histological analysis. The Sprague-Dawley rats showed evidence of acute inflammation, without ectopic bone formation, at the injection sites. In the athymic nude rats, BMP-2 gene therapy induced mesenchymal stem cell chemotaxis and proliferation, with subsequent differentiation to chondrocytes. The chondrocytes secreted a cartilaginous matrix, which then mineralized and was replaced by mature bone. This study demonstrates that a BMP-2 adenoviral vector can be utilized to produce BMP-2 by striated muscle cells in athymic nude rats, leading to endochondral bone formation. However, in immunocompetent animals the endochondral response is attenuated, secondary to the massive immune response elicited by the first-generation adenoviral construct.

Adenoviridae↗