Biomedical subjects
Publications and source records attributed to S Das.
As laparoscopic techniques develop, endoscopic lymph node dissection is becoming preferred as the minimally invasive technique for lymph node staging of pelvic malignancies. We developed an extraperitoneal laparoscopic approach to staging pelvic lymphadenectomy, and describe our technique, results and experience in our initial 9 patients.
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Multiple door interlock switches in commercial microwave ovens are designed to prevent accidental exposure and injury. We report a) heating rate (degree/sec) measurements in a phantom of the human upper extremity in a 2450 MHz microwave oven having interlock switches deliberately bypassed; b) skin temperature measurements on the upper extremity of a human volunteer similarly exposed; c) perception of warmth and pain experienced by the volunteer during exposure; d) thermographic camera recordings of the volunteer's skin; and e) finite element modeling of specific absorption rate (SAR) in the volunteer's hand. Moderately severe pain was experienced at the fingertips after 5 sec of exposure, consistent with the modeled SAR, measured heating rates, and published data on the temperature threshold for pain. We estimate that an additional 9 sec of exposure would be required to produce irreversible injury, consisting of focal thermal injury in the fingertips and possibly the thenar and hypothenar eminences.
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The lipopolysaccharide (LPS) was isolated from Pseudomonas syringae pv. coriandricola W-43 by hot phenol-water extraction. Rhamnose and 3-N-acetyl-3-deoxyfucose were found to be the major sugar constituents of the LPS together with N-acetylglucosamine, N-acetylgalactosamine, heptose, and 3-deoxy-D-manno-octulosonic acid (Kdo). The main fatty acids of lipid A of the LPS were 3-OH-C:10, C12:0, 2-OH-C12:0, and 3-OH-C12:0. The O-specific polysaccharide liberated from the LPS by mild-acid hydrolysis was purified by gel permeation chromatography. The compositional analysis of the O-specific polysaccharide revealed the presence of L-rhamnose and 3-N-acetyl-3-deoxy-D-fucose in a molar ratio of 4:1. The primary structure of the O-specific polysaccharide was established by methylation analysis together with 1H and 13C nuclear magnetic resonance spectroscopy, including two-dimensional shift-correlated and one-dimensional nuclear Overhauser effect spectroscopy. The polysaccharide moiety was found to consist of a tetrasaccharide rhamnan backbone, and 3-N-acetyl-3-deoxy-D-fucose constitutes the side chain of the branched pentasaccharide repeating unit of the polysaccharide.
We have purified, sequenced, and prepared a synthetic clone of a small (60-nucleotide) RNA molecule from the yeast Saccharomyces cerevisiae that had previously been isolated on the basis of its ability to selectively block the translation of poliovirus mRNA. RNA derived from the clone by transcription with T7 RNA polymerase appears to block translation initiation by internal ribosome entry (cap independent) but does not significantly affect cap-dependent translation. Deletion analysis of the poliovirus 5'-untranslated region (5'-UTR) has shown that yeast inhibitor RNA (I-RNA) requires internal ribosome entry site sequences to inhibit the translation of poliovirus RNA in vitro. Using a bicistronic RNA construct, we show that I-RNA preferentially inhibits translation by internal ribosome entry. Gel retardation and UV cross-linking studies demonstrate that I-RNA specifically binds proteins which interact with RNA secondary structures within the poliovirus 5'-UTR presumably involved in internal initiation. Specifically, purified I-RNA competes with virus RNA structures within the 5'-UTR which bind a cellular protein with an approximate molecular mass of 52 kDa. Finally, when transfected into HeLa cells, I-RNA efficiently inhibits the replication of poliovirus RNA presumably by inhibiting translation of the input virus RNA.
Ionomycin, which mobilizes Ca2+, and phorbol 12-myristate 13-acetate (PMA), which activates protein kinase C (PKC), were used to compare the effects/interactions of Ca2+ and PKC on luteinizing hormone (LH) secretion from pituitaries of intact male and acutely ovariectomized (72 h) rats. Quartered pituitaries from donor animals were perifused at 0.25 ml/min and sequential effluent fractions were collected every 10 min. Continuous administration (4 h) of 1 nmol of gonadotropin-releasing hormone (GnRH) resulted in an increase in LH secretion. Cycloheximide (5 mumol) dissociated the GnRH-stimulated LH responses into protein synthesis-independent and -dependent components. While ionomycin (10 mumol) stimulated LH secretion from pituitaries of both sexes by protein synthesis-independent mechanisms, PMA (1 mumol) and the inactive phorbol ester, 4 alpha-phorbol 12,13-didecanoate (PDD), were ineffective secretagogues. However, PMA (but not PDD) interacted synergistically with ionomycin and GnRH to augment LH secretion by protein synthesis-dependent mechanisms. These results suggest a similarity in the effects/interactions of Ca2+ and PKC in gonadotropes from male and ovariectomized rats. If the effects of PMA can be attributed to PKC activation, then it also appears that Ca2+ mobilization is necessary for the manifestation of PKC as a mediator of LH secretion from these gonadotropes. While PKC activity can be divorced from the protein synthesis-independent component of LH release (this component appears to be mediated by Ca2+ mobilization), the enzyme might be involved in amplifying the response to Ca2+ mobilization through synergistic protein synthesis-dependent mechanisms.
In the search for chemopreventive agents for cancer many natural products have been identified. Among them extensive experimental studies have been made on protease inhibitors which not only occur naturally in many plant products, but have also been synthesized in the laboratory. Many of these studies revealed the fact that protease inhibitors are able to prevent carcinogenesis and tumour promotion. A review of the reports available to date suggests that protease inhibitors are potential chemopreventive agents although their biological role and mechanism of action are not very clear.
A review of current literature reveals that the relationships between vitamin E and cancer is not yet fully understood though many experimental and clinical studies have shown that vitamin E can protect against carcinogenesis and tumour growth. This vitamin also appears to reduce toxicity of several anticancer therapies. Such effects are probably due to the antioxidant property and immunomodulatory function of vitamin E. The findings of different groups suggest that this vitamin may be helpful as a cancer chemopreventive agent.
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As early as 1860, innovative research defined the neural and vascular phenomena which generate male sexual tumescence. Sophisticated animal experiments provided important data about enhanced arterial inflow and occlusion of venous outflow which cause and maintain erection of the penis. On the basis of these observations, various treatment strategies for impotence, like sclerotherapy or surgical ligation to improve penile venous occlusion, have been attempted since 1873. In this historical review, I assert that contemporary theories of the role of penile venous occlusion during tumescence reiterate ideas proposed more than a century ago.
Patients with malignant bone tumours often come at a very late stage of disease to Medical Colleges. Because of their high mortality rate, accurate & quick diagnosis of these lesions become essential, inspite of clinical, radiological and histopathological assessments. A simple, inexpensive, safe & least traumatic technique-fine needle aspiration cytology (FNAC) in diagnosis of 55 malignant bone tumours was carried out. Specific tumour types metastatic tumour (12), Giant cell tumour (12), Ewing's sarcoma (10), Osteosarcoma (7), Multiple myeloma (7), Chordoma (3), Chondrosarcoma (3) and Fibrosarcoma (1) could be ascertained in 87.2% whereas malignant tumour was suggested in 94.5% (52 cases).
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Hypotensive effect of the extract of leaves of C. colebrookianum was investigated. An extremely bitter fraction was isolated, which gave positive test for alkaloids. The fraction produced fall of blood pressure in a dose dependent manner. The fall of blood pressure was blocked by atropine. Hypertensive effects of adrenaline and noradrenaline were slightly antagonised by the alkaloidal extract.
Intra-tumour and inter-tumour heterogeneity in the cytokinetic organization was studied in 235 primary human brain tumours. DNA index (DI; relative tumour cell DNA content) and proliferating fraction (%PF; a measure of proliferative status) were analyzed in tumour biopsy by flow cytometry using a DNA specific fluorochrome (DAPI) and internal standards (chicken erythrocytes, CE). Incidence of micronuclei was studied in tumour biopsy tissue as well as in explants maintained in organ culture. Clonal diversity (implied by the presence of multiple peaks in the DNA histograms) was highest among medulloblastomas (44%) followed by gliomas (19%) and meningiomas (14%). Nearly 85 per cent of the malignant gliomas analyzed (histological grade III/IV) exhibited a great deal of regional variation in the proliferative status as well as micronuclei frequency as compared to meningiomas. Inter-tumoural variations in the DNA content was highest among gliomas (0.9 < DI < 3.6) and lowest among schwannomas (1.7 < DI < 2.2). Similarly, the distribution of %PF values was also broader (10-49%) in gliomas as compared to the other primary brain tumours (5-36%). Analysis of tumours taking both DI and %PF values improved the ability to discern histologically graded low and high tumours. Analysis of clonal diversity and spatial heterogeneity in the cytokinetic parameters could complement the clinicopathological findings in assessing the biological behaviour of human brain tumours, facilitating the prognostification and design of otpimal treatment regimen.
Fibroblast cultures from 12 unrelated patients with classical Menkes disease were analyzed for mutations in the MNK gene, by reverse transcription-PCR (RT-PCR) and chemical cleavage mismatch detection. Mutations were observed in 10 patients, and in each case a different mutation was present. All of the mutations would be predicted to have adverse effects on protein expression. Mutations that resulted in splicing abnormalities, detected by RT-PCR alone, were observed in six patients and included two splice-site changes, a nonsense mutation, a missense mutation, a small duplication, and a small deletion. Chemical cleavage analysis of the remaining six patients revealed the presence of one nonsense mutation, two adjacent 5-bp deletions, and one missense mutation. A valine/leucine polymorphism was also observed. These findings, combined with the prior observation of deletions in 15%-20% of Menkes patients, suggest that Southern blot hybridization and RT-PCR will identify mutations in the majority of patients.
We examine the functioning of isolated rat liver gap junction protein after reconstituting into unilamellar liposomes with the help of fluorescence-efflux assay. Monitoring of the dequenching of a fluorescence marker 5, (6) CF due to its efflux from proteoliposomes into extra-liposomal space via its passage through reconstituted gap junctional channels has been performed. The efflux of dye from intra-liposomal to extra-liposomal compartment (both final release or Feq and initial rate or IR) was found dependent on gap junction concentrations. The opening and closing of reconstituted gap junctional channels were found influenced by pH and osmolarity of the extra-liposomal solution.