Biomedical subjects

S Biswas

Publications and source records attributed to S Biswas.

At least 91 records · Page 5Linked to original sources

PubMed2000

Effect of cationic amino acid, L-lysine and its polymers on the growth and secretion of hybridoma cell line OKT-3.

Apart from their pivotal roles in anabolic protein synthesis, cationic amino acids, particularly, L-lysine HCl and its oligomers, up to molecular weight 1000, showed a remarkable property of cellular growth stimulation both in vitro and in vivo. L- and D-Lysine HCl, at a maximal stimulatory concentration of 7 microg/mL of added load of the amino acid, supported a characteristic time-scaled cellular expansion in vitro, and L-lysine-mediated cell expansion in batch cultures always showed a stimulation index (S.I.) ranging up to approximately 35, compared with the matched control populations. Variable S.I. was possibly due to factors such as seeding density, type of media additives, number of passages the cells have undergone before being stimulated, etc. Beyond and before maximal stimulatory concentration of the amino acid, there is a sharp decline in the cellular growth-promoting activity of monomeric L-lysine HCl in vitro, thereby showing a clear concentration window for maximum cellular growth promotion. While the essential amino acid does not have any dedicated cell surface receptor, the monomeric and oligomeric amino acid molecule(s) possibly mediates the serum-derived growth factor-receptor binding on the cell membrane by having two cationic charge centres at two ends of the molecule. Beyond a cutoff molecular weight of 1000, oligomeric lysines did not show any positive effects on either cell division and secretion.

Animals↗

PubMed2000

Metalloprotease activity in a small heat shock protein of the human malaria parasite Plasmodium vivax.

The malaria parasite affects millions of people each year, lives and multiplies in two different hosts, and synthesizes a large number of proteases and heat shock proteins (HSPs) for its survival. We describe here the characterization of a metalloprotease activity which resides in the small HSP (PVHSP28) of the common but noncultivable human malaria parasite Plasmodium vivax. The protein is expressed by erythrocytic stages of the parasite. It is expressed as a approximately 55-kDa polypeptide which is then processed to the 28-kDa mature protein. The latter was found to be an active protease in gelatin zymography. This protease showed its optimal activity at 37 degrees C (pH 7.6). It also retained its proteolytic activity at higher temperatures of up to 55 degrees C. The enzyme belongs to the metalloprotease class, as its proteolytic activity was most effectively blocked by 1,10-phenanthroline and was restored to a maximal level by the addition of zinc metal ions. Inhibitors for the cysteine, serine, and aspartate classes of proteases were ineffective against this enzyme. A homology search indicates that PVHSP28 probably belongs to a new class of HSPs which possess the metalloprotease signature sequence.

Amino Acid Sequence↗

PubMed2000

Graft failure in human donor corneas due to transmission of herpes simplex virus.

AIM: To report the clinical consequences of contamination of human donor corneas by herpes simplex virus (HSV) in organ culture. METHODS: Two patients without previous history of ocular HSV infection underwent penetrating keratoplasty (PK), one for keratoconus and the other for Fuchs' endothelial dystrophy. One patient suffered primary graft failure while the other developed a persistent epithelial defect, ultimately resulting in graft failure. Viral culture of swabs taken from both corneas during the early postoperative period was undertaken. The failed donor corneas were examined histopathologically by immunohistochemistry (IHC) for HSV-1 antigens, transmission electron microscopy (TEM), and by polymerase chain reaction (PCR) for HSV DNA. Both failed corneas were replaced within 6 weeks of the initial surgery. The records of the fellow donor corneas were also examined for evidence of infection. RESULTS: HSV was cultured from both corneas during the early postoperative period. Histology of both donor corneas demonstrated a thickened corneal stroma with widespread necrosis of keratocytes and loss of endothelial cells. IHC showed keratocytes positive with antibodies to HSV-1 antigens. TEM demonstrated HSV-like viral particles within degenerating keratocytes. PCR performed on the failed corneal grafts was positive for HSV-1 DNA, whereas PCR performed on the excised host corneal buttons was negative in both patients. Records of the fellow donor corneas showed that one cornea was successfully transplanted into another recipient after 18 days in organ culture, whilst the other was discarded because of extensive endothelial cell necrosis noted after 15 days in organ culture. CONCLUSION: HSV within a donor cornea may cause endothelial destruction in organ culture and both primary graft failure and ulcerative keratitis after transplantation. Endothelial necrosis of a donor cornea in culture also raises the possibility of HSV infection within the fellow cornea.

Adult↗

PubMed2000

Protein A-activated rat splenic lymphocyte proliferation involves tyrosine kinase-phospholipase C-protein kinase C pathway.

Protein A (PA) of Staphylococcus aureus was long been known for its affinity towards the Fc domain of immunoglobulin G. It is now well established that PA is a potent biological response modifier showing simultaneously antitumor, antitoxic, and anticarcinogenic properties. This bacterial protein was also observed to stimulate production of cytokines. But the molecular mechanism(s) of immunocyte activation by PA still remained essentially unknown. In this report, we demonstrate a hitherto undescribed role of PA as a signal inducer in rat splenic lymphocytes. Our studies describe that PA induces transition of G0/G1 to S and G2/M phases of cell cycle, thus ultimately stimulating splenic lymphocyte proliferation. It has also been revealed that PA binds to rat splenic lymphocytes in a dose dependent manner and stimulates proliferation via tyrosine kinase-phospholipase C (PLC)-Ca2+-dependent protein kinase C (PKC) pathway. These observations will be of valid help in correlating the immunostimulatory activities of PA with the molecular mechanism(s) of its action.

Animals↗

PubMed2000

Recent trends in leprosy in a large district of West Bengal, India, revealed by a modified leprosy elimination campaign (MLEC), 1998.

A Modified Leprosy Elimination Campaign (MLEC) in September 1998 in the District of Midnapore, West Bengal, covered a population of 8.1 million people and detected 8181 new cases. Available data from 7328 cases were studied to observe the trend for leprosy in this area. Data are presented on sex and age distribution, classification and the proportions of multibacillary (MB), paucibacillary (PB) and single skin lesion (SSL) cases discovered in a period of only 8 days. The large numbers of people examined in this district and the high total of new cases revealed are in keeping with experience in other parts of the State and in other parts of India. However, many cases were found in endemic areas and these will receive special attention in a second MLEC, planned for January 2000.

Adolescent↗

PubMed2000

Community studies on prevalence of HBsAg in two urban populations of southern India.

OBJECTIVE: To find out prevalence of HBsAg in general population, especially in under-five children. SETTING: Bangalore and Rajahmundry towns in southern India. METHODS: Localities were chosen as the sampling units in each town. About 10-20 households were randomly selected from each locality. Only the youngest but apparently healthy person present in the household was interviewed for age, sex and history of jaundice any time in life. Mothers were interviewed to collect data for children below 15 years of age. Blood samples were collected from these persons on filter paper strips (18-mm diameter disc, Whatman filter paper No. 3) by finger prick method. The samples were tested for HBsAg by Micro ELISA (Ortho-Clinical Diagnostics). RESULTS: Overall, 3.3% (95% CI, 2.0-4.5) of 737 persons in Rajahmundry and 4.2% (95% CI, 2.8-5.5) of 816 persons in Bangalore were found carriers of HBsAg. Age-specific or sex specific carrier rates were similar in Rajahmundry as well as in Bangalore. Most of the carriers (96%) denied having jaundice ever in life. CONCLUSIONS: The results from this community based study are in agreement with the historical data from hospital based studies that about 3-5% of persons may be carriers of HBsAg and that the pool of chronic carriers of hepatitis B virus in India is built up in childhood and is then maintained in older children and adults. The results highlight the need of completing hepatitis B immunization during the infancy.

Adolescent↗

PubMed2000

Genetic characterization of gram-positive homologs of the XerCD site-specific recombinases.

Homologs of the XerCD enzymes, which in Escherichia coli have been shown to be responsible for resolving chromosomal multimers prior to chromosome segregation, were identified in the genomes of Staphylococcus aureus and Streptococcus pneumoniae. Phylogenetic and conservation pattern analysis suggests that the S. aureus gene products are orthologs of XerC and D. A S. aureus xerC null mutant displayed in vitro characteristics consistent with the segregation defect reported for E. coli xer mutants, and was found to be attenuated in a murine infection model. Strikingly, the S. aureus xerD gene appears to be absolutely required for viability, and may therefore be the first example of an essential gene of the lambda integrase family. In contrast, phylogenetic and conservation pattern analysis show that the S. pneumoniae gene products are more closely related to phage integrases than to XerCD. S. pneumoniae xer1, 2 and 3 null mutants were each found to be attenuated in a murine infection model, suggesting that they may control processes which affect virulence.

Alleles↗

PubMed2000

Serological investigation of malaria outbreak in Thar desert of Rajasthan.

A serological investigation by a repeat cross-sectional survey was conducted in Thar desert (Rajasthan) during and after one year of malaria outbreak to determine malaria endemicity using ELISA as a tool. The assay was based on indirect ELISA to measure antibody levels against a nonapeptide R1 (EENVEHDA-cys) derived from Pf 155/Resa and Plasmodium falciparum crude antigen. Finger prick blood samples were collected from individuals belonging to all age groups. Sera were tested at already standardized optimum dilution to detect antigen specific immunoglobulin isotype. The mean ELISA O.D. values 0.153 for anti R1 peptide and 0.162 for anti Pf antigen reflected the seronegative profile, when the focal malaria outbreak occurred in 1994. A substantial increase in antibody levels was detected in individuals after one year showing mean ELISA values for anti-R1 and anti-Pf antigens as 0.52 and 0.58 and seropositivity as 75.2% and 52% respectively. Data obtained from the present study indicate that serological survey could be done to assess the situation in case of reappearing or disappearing status of malaria in a defined population.

Animals↗

PubMed2000

Pulmonary histopathology and alteration in cellular pattern of bronchoalveolar lavage fluid in experimental silicosis.

Pathogenesis of silicosis is still being evaluated. Cellular and histopathological changes in lung following acute and chronic exposure of quartz in rats have been investigated. Inbred wistar rats were given single intratracheal injection of quartz (10 mg in 0.05 ml saline) in groups of acute model, and inhalation of quartz (40 mg/m3 with air flow 5 l/hr in a simulation chamber, 6 hr/day) in groups of chronic model. The control groups were exposed to vehicles only. Rats were sacrificed on day 3, 5 and 7 of intratracheal injection and after 2, 4 and 8 weeks of inhalation. Total and differential cell counts (TC and DC) were performed in bronchoalveolar lavage fluid (BALF). Histopathology was done in the lungs. There was significant (P < 0.001) increase in TC and significant (P < 0.001) changes in percentage of inflammatory cell counts on DC in the BALF of silicotic rats. Histopathology showed progressive inflammatory and fibrotic response in quartz exposed lungs in both acute and chronic models. The results indicate duration dependent inflammatory changes in lungs of both the models. Changes in cell counts precede the histopathological changes and may serve as early biological marker for detection of silicosis.

Acute Disease↗

PubMed1999

Prevention of cytotoxic effects of arsenic by short-term dietary supplementation with selenium in mice in vivo.

Interaction between selenium and arsenic has been used to protect against the genotoxic effects of sodium arsenite through dietary intervention by an equivalent amount (1/10 LD50) of sodium selenite. The two salts were administered by gavaging to laboratory bred Swiss albino mice sequentially and in combination. Cytogenetic endpoints, including chromosomal aberrations (CA) and damaged cells (DC) were recorded 24 h after exposure from chromosome spreads in bone marrow cells. Administration of sodium selenite 1 h before sodium arsenite reduced the clastogenic effects of the latter significantly. The protection was less when the salts were given together and negative when arsenite was given before selenite. Histological changes were recorded. Such reduction of arsenic toxicity through dietary intervention by selenium is of significance in protecting against the widespread toxicity observed in human populations exposed to arsenic through drinking water from contaminated deep tubewells in West Bengal and Bangladesh.

Administration, Oral↗

PubMed1999

Antimalarial activity of 3-hydroxyalkyl-2-methylene-propionic acid derivatives.

Several Baylis-Hillman adducts and their derivatives were synthesized and evaluated as targeted potential anti-malarials. The compounds 4, 7 and 9 were found to have highest potency against P. falciparum in vitro. The in vivo test result of compound 4 and 9 against P. berghei demonstrated activity at 80 mg/Kg dose level.

Animals↗

PubMed1999

Protection against cytotoxic effects of arsenic by dietary supplementation with crude extract of Emblica officinalis fruit.

Dietary administration of a crude aqueous extract of Emblica officinalis Gaertn. fruit reduced significantly the cytotoxic effects of sodium arsenite administered orally. The crude extract (685 mg/kg bw) was given daily by gavaging to age and sex matched laboratory bread Swiss albino mice for 7 and 14 days, followed by a single dose of sodium arsenite (2.5 mg/kg bw = 1/10 of LD(50)). The animals were killed after 24 h and chromosome preparations made following a schedule of colchicine-fixative-air drying-Giemsa. The endpoints screened were chromosomal aberrations and damaged cells. The crude extract reduced arsenic damage bringing the cells almost to the normal level.

Animals↗

PubMed1999

Theoretical aspects of single pulse induced modulation of cell-cell interactions favoring iso-electrofusion.

A single pulse-mediated electrofusion of freely suspending widely separated cells could reduce steps in the protocol. Prediction of such electrofusion is still unsolved. In pre-pulse condition, quantitative estimation with three-layered model cell surface reveals electrostatic repulsion (due to negative surface charge) is the major hindrance to membrane-to-membrane contact. On theoretical grounds we predict that designed single high voltage pulsing on widely separated model cell surface can counteract the non-specific repulsive interaction and favor approach of two apposed membranes. But hydrodynamic modulation of pulse exposed cell surface interaction can hamper approach of membranes contact when cells are held at a gap of more than approximately 450 A.

Cell Adhesion↗

PubMed1999

Multiple-pulse-mediated electrofusion of intact erythrocyte onto human term placental amnion.

The creation of surface modified human term placental amnion by electrofusing human cells onto its surface has been thought of. A multiple-pulse electrofusion protocol with 10 square pulses of 10-micros pulse length, and electric field of 0.2 kV cm(-1), can make erythrocyte-amnion tissue electrofusion possible. The protocol devised merge the cell-tissue-adherence steps with fusogenic pulse. The finding opens up a new avenue of cell electrofusion onto human tissue with minimal procedural complexities.

Amnion↗

PubMed1999

Membrane microextension: a possible mechanism for establishing molecular contact in electrofusion.

True cell membrane contact is an essential condition for electro-pulsed cell fusion, but initial morphological perturbation leading to true contact is still not clear. Dielectrophoresis mediated compression and fusogenic pulse induced compaction of cells led to rapid merger of tight membranes, and deprived direct microscopic view of surface membrane perturbation. Freely suspending cells with large and different cell-cell gaps may proceed to electrofusion with perturbed membrane and initiates fusion events at different time. These pulsed exposed cells can be used for capturing changes in the membrane surface and early electrofusion events. Early stage of fusion of freely suspended intact human erythrocytes exposed to single exponential decay pulse was studied by scanning electron microscopy (SEM). Field pulse induces small membrane bumps. Interaction of bumps on adjacent membranes lead to true membrane contact and form bridges between the membranes as microextension, combining both membranes into a topologically single structure. Some fusion products showed expanded fusion zones, which suggest indication of open lumen at contact area.

Electricity↗

PubMed1999

Comparison of clastogenic effects of inorganic selenium salts in mice in vivo as related to concentrations and duration of exposure.

Inorganic selenium compounds in the diet have been known to protect against cancer in laboratory animals, but were harmful in high concentrations. In the present work, the relative effects of two salts, sodium selenite and sodium selenate, administered to mice in vivo, in different concentrations and durations of exposure, were compared. Aqueous solutions of each salt (7, 14, 21 and 28 mg Kg-1 bw) were fed by gavaging to mice matched in age and sex. The animals were sacrificed at intervals of 6, 12, 18 and 24 h and chromosome preparations were made following the usual schedule of colchicine-hypotonic-fixative-airdrying-Giemsa staining. The endpoints screened were chromosomal aberrations (CA) and damaged cells (DC). Both salts affected chromosome structure and spindle formation, sodium selenite being more cytotoxic than sodium selenate. The frequencies of aberrations induced were directly proportional to the concentrations used and duration of exposure.

Analysis of Variance↗

PubMed1999

Low-dose midazolam infusion for oculoplastic surgery under local anesthesia.

PURPOSE: Oculoplastic surgery with infiltration of local anaesthesia at the operative site performed as a day-case procedure is both efficient and cost-effective. Patients considered unsuitable for this because of fear or apprehension may, however, benefit from per-operative conscious sedation. We sought to study the efficacy and safety of this using midazolam, a water-soluble benzodiazepine. METHOD: We have performed a controlled clinical trial comparing the effect of a low-dose intravenous infusion of midazolam (0.2 mg/ml of normal saline at a rate of 1 mg/h) with saline placebo on 48 subjects undergoing oculoplastic surgery with local anaesthesia. Patients were given pre- and post-operative questionnaires assessing, amongst other factors, anxiety levels, pain, degree of reported amnesia and psychomotor recovery. RESULTS: Using the low-dose midazolam infusion no adverse cardiorespiratory reactions occurred. Patients receiving midazolam reported remembering significantly less about their operation than controls (p = 0.04) and showed significantly lower state-anxiety after their operation than before (p < 0.02). This change was not noted in the placebo group. There was no significant difference in the psychomotor performance of patients given midazolam compared with controls 2 h after surgery. CONCLUSIONS: A low-dose continuous infusion of midazolam can be used to safely provide effective anxiolysis and conscious sedation with good psychomotor recovery during oculoplastic procedures in a day-case setting.

Adolescent↗

PubMed1999

Effect of pelvic endometrial implants on overall reproductive functions of female rats.

The effects of pelvic endometrial implants on the overall reproductive potential of female rats were investigated. After homologous transplantation in the peritoneum, the ectopic endometrium developed into highly vascularized nodes that gradually increased in mass until the 9th week postsurgery and then plateaued. In the presence of these implants, overall reproductive function was adversely affected. The effect was of greatest magnitude during 50-70 days posttransplantation. As compared with values in corresponding controls, ovulation was reduced by 43% (6 of 14) (p < 0.05), mating rate was reduced by 44% (12 of 27) (p < 0.025), and premature termination of pregnancy occurred in 34% (5 of 15) of rats. Wastage of pregnancy, which included complete termination or reduction of fetal number, occurred during the postimplantation course of gestation. Furthermore, 100% of the rats with transplants failed to respond to the copulomimetic stimulation for the induction of pseudopregnancy (p < 0.01, compared with corresponding controls). However, on exposure to vasectomized males, 46% (6 of 13) of these rats exhibited development of pseudopregnancy (p < 0.05, compared with corresponding group receiving copulomimetic stimulation). Increased rate of mating failure and differential pseudopregnancy rates after copulomimetic and natural cervical stimulation suggest that the rats with endometrial explants possibly had an absence or a short appearance of behavioral estrus. Hormonal assessment during the preovulatory phase showed a tendency toward lower mean levels of preovulatory estradiol and significantly lower LH (p < 0.01) and progesterone (p < 0.01) concentrations. The adversely affected reproductive functions may be a secondary consequence of these altered endocrine milieus.

Abortion, Spontaneous↗