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Biomedical subjects

D Biswas

Publications and source records attributed to D Biswas.

At least 19 recordsLinked to original sources
PubMed2000

Arbitrary trajectory quantization method.

The arbitrary trajectory quantization method (ATQM) is a time dependent approach to quasiclassical quantization based on the approximate dual relationship that exists between the quantum energy spectra and classical periodic orbits. It has recently been shown however, that, for polygonal billiards, the periodicity criterion must be relaxed to include closed almost-periodic (CAP) orbit families in this relationship. In light of this result, we reinvestigate the ATQM and show that at finite energies, a smoothened quasiclassical kernel corresponds to the modified formula that includes CAP families while the delta function kernel corresponding to the periodic orbit formula is recovered as E-->infinity. Several clarifications are also provided.

Journal Article↗
PubMed2000

Recursive partitioning for prognostic grouping of patients with clinically localized prostate carcinoma.

BACKGROUND: Patients treated with radical prostatectomy for clinically localized prostate carcinoma present considerable heterogeneity in terms of disease free survival outcome. Multiple studies have attempted to create prognostic groupings of these patients in the perioperative phase, using information available regarding several clinicopathologic variables. Such groupings allow physicians to make early yet prudent decisions regarding adjuvant combination therapies. The current study presents results from a statistical analysis that enables the natural identification of such prognostic groups. METHODS: Examination of consecutive radical prostatectomy specimens was performed between January 1991 and December 1995 at Wayne State University, Harper Hospital, Detroit, Michigan. Disease free survival in a cohort of 485 of these men was analyzed using recursive partitioning and amalgamation technique. Clinicopathologic parameters evaluated included age, race, preoperative prostate specific antigen (PSA) level, clinical and pathologic stage, and Gleason grade of the fine-needle biopsy as well as the radical prostatectomy specimen. RESULTS: A binary decision tree representation was generated for classifying patients based on the clinicopathologic variables mentioned earlier. The worst prognosis was for patients with either advanced stage and a PSA level > 24.1 ng/mL or advanced stage, a PSA level </= 24.1 ng/mL, and age </= 65 years. This group had an estimated median disease free survival of only 10.3 months. Patients with lower pathologic stage, prostatectomy Gleason scores of </= 7, and a preoperative PSA level </= 22.7 ng/mL had the best prognosis. CONCLUSIONS: The recursive partitioning analyses allows easy characterization of a patient for prognosis shortly after radical prostatectomy. This will enable a physician to make more prudent decisions regarding whether to employ watchful waiting, proceed with accepted adjuvant therapy (radiotherapy or hormonal therapy), or refer patients to a research center that is able to administer experimental adjuvant therapy. [See editorial counterpoint on pages 232-3 and reply to counterpoint on pages 234-5, this issue.]

Adult↗
PubMed2000

Effect of Mg(2+) ion in protein secretion by magnesium-resistant strains of Pseudomonas aeruginosa and Vibrio parahaemolyticus isolated from the coastal water of Haldia port.

A rapidly growing industrial complex including oil refineries and chemical industries has developed around the coastal area of Haldia port in the district of Midnapore, West Bengal, India. The coastal water is highly polluted with industrial wastes along with petroleum hydrocarbons. The bacteria isolated from the different sites of the coastal waters were Escherichia coli, Alcaligenes, Acinetobacter, Klebsiella spp., Micrococcus spp., Vibrio spp., Pseudomonas aeruginosa and Vibrio parahaemolyticus. The salinity of the water during the time of collection of samples around the port area was 8. 2 ppt. Among the isolated organisms, only two isolates, P. aeruginosa and V. parahaemolyticus, showed growth at 300 mM Mg(2+) ion concentration. However, a 3 mM Mg(2+) concentration was detected in the coastal water whereas other metal ion concentrations were less than 3x10(-5) mM. Resistance to Mg(2+) (300 mM) was determined by a 5.5-kb plasmid. A large amount of a 40-kDa outer membrane protein, which was highly soluble in 1 M MgCl(2), was isolated from both V. parahaemolyticus and P. aeruginosa. The secretion of proteins in the culture supernatant of V. parahaemolyticus was highly increased when the cells were grown in the presence of 300 mM Mg(2+), whereas very low secretion was observed in the same concentration of Mg(2+) in the case of P. aeruginosa. Mg(2+) may act as a specific release factor in protein secretion by V. parahaemolyticus strains.

Bacterial Proteins↗
PubMed2000

Semiclassical inequivalence of polygonalized billiards

Polygonalization of any smooth billiard boundary can be carried out in several ways. We show here that the semiclassical description depends on the polygonalization process and the results can be inequivalent. We also establish that generalized tangent polygons are closest to the corresponding smooth billiard and for de Broglie wavelengths larger than the average length of the edges, the two are semiclassically equivalent.

Journal Article↗
PubMed2000

Closed almost-periodic orbits in semiclassical quantization of generic polygons

Periodic orbits are the central ingredients of modern semiclassical theories and corrections to these are generally nonclassical in origin. We show here that, for the class of generic polygonal billiards, the corrections are predominantly classical in origin owing to the contributions from closed almost-periodic (CAP) orbit families. Furthermore, CAP orbit families outnumber periodic families but have comparable weights. They are hence indispensable for semiclassical quantization.

Journal Article↗
PubMed2000

Escape from noisy intermittent repellers

Intermittent or marginally stable repellers are commonly associated with a power law decay in the survival fraction. We demonstrate how the presence of weak additive noise alters the spectrum of the Perron-Frobenius operator significantly, giving rise to exponential decays even in systems that are otherwise regular. Implications for ballistic transport in marginally stable miscrostructures are also discussed.

Journal Article↗
PubMed2000

Uptake pathways of clinical and healthy animal isolates of Campylobacter jejuni into INT-407 cells.

Campylobacter jejuni isolates obtained from human and animal sources showed different invasion levels into human embryonic intestinal (INT-407) cells. There was no significant relation between the degree of invasion and cytotoxins production. The depolymerization of both microfilaments by cytochalasin-D and microtubules by colchicine, demecolcine and nocodazole or stabilization of microtubules by paclitaxel reduced the invasiveness of C. jejuni, although microfilament depolymerization showed greater inhibition than microtubule depolymerization. Interference with receptor-mediated endocytosis by G-strophanthin and monodansylcadaverine and inhibition of endosome acidification by monensin reduced the number of viable intracellular C. jejuni cells. Furthermore inhibition of only host protein kinases by staurosporine, but not phosphoinositide 3-kinase by wortmannin or protein kinase-C by calphostin-C, significantly reduced invasion of epithelial cells by C. jejuni. These data suggest that the internalization mechanism triggered by C. jejuni is strikingly different from the microfilament-dependent invasion mechanism exhibited by many of the well-studied enteric bacteria such as enteroinvasive strains of Escherichia coli, Salmonella typhimurium, Shigella flexneri, Yersinia enterocolitica and Yersinia pseudotuberculosis.

Actin Cytoskeleton↗
PubMed2000

Virulent resurgence of malaria in Calcutta, West Bengal.

The reasons of virulent resurgence of malaria and the measures adopted for its control in a metropolitan city by Calcutta Municipal Corporation is discussed in detail along with proper references. Publicity compaign, especially among school students, has been stressed.

Animals↗
PubMed1999

Adhesion and invasion of a mutant Shigella flexneri to an eukaryotic cell line in absence of the 220-kb virulence plasmid.

A Shigella flexneri strain, cured of the large 220-kb virulence plasmid, expresses adhering and invading ability in confluent monolayers of HeLa cells similar to its parent strain. Invasion by both the parent and the cured strains resulted in alteration of the monomeric actin (G) in the total actin pool of HeLa cells. Other indicators of invasive characteristics of virulent Shigella strains such as production of keratoconjunctivitis in guinea pig eye in vivo, Congo red binding and expression of contact hemolysin however, indicated loss of invasive properties in the plasmid cured strain. Further, pretreatment of bacterial cells with para-bromophenacyl bromide (p-BPB), a specific chemical inhibitor of phospholipase A, adversely affected adhesion to and invasion of HeLa cells in vitro, irrespective of the presence of the 220-kb plasmid indicating the possible involvement of the enzyme phospholipase A in the invasion process. Adherence of both the strains to guinea pig colonic epithelial cells (CECs) in vitro was reduced significantly on pretreatment of bacteria or CECs with p-BPB. Expression of exocellular enzymes viz. protease, elastase, phospholipase A and phospholipase C were not related to the large plasmid.

Acetophenones↗
PubMed1999

Prevalence of communicable disease among restaurant workers along a highway in Assam, India.

105 workers of 29 roadside restaurants along a highway in Assam were interviewed for their habits, educational status and were examined for their hygienic status and presence of communicable diseases (STDs,TB etc). Most of them were young, males with 40% literacy; more than half were unmarried. About 30% of them were alcoholic and smokers and 2.9% were addicted to cannabis. The hygienic conditions of the workers were poor. More than one third had sexual contact with multiple sex partners or commercial sex workers and 2% were engaged in homosexual activity. Most of them did not use condom. 25.7% of them had genital lesions suggestive of sexually transmitted disease, 11.8% showed gram negative diplococci in urethral smears and 5.1% were VDRL reactive. Skin infections followed by gastrointestinal disorders and respiratory tract infections were other prevalent problems. 70.6% were positive for intestinal parasites and 22.2% were sputum positive for acid fast bacilli. However all the collected blood samples were negative for HIV.

Adult↗
PubMed1997

The increasing burden of disease in Bangladeshi children due to Haemophilus influenzae type b meningitis.

A laboratory-based study of diagnosed bacterial meningitis in the national paediatric hospital identified 852 cases of meningitis in the 8-year period 1987-1994. There were 587 culture-positive cases, of which Haemophilus influenzae (47%) and Streptococcus pneumoniae (32%) accounted for 80%. H. influenzae showed a remarkable increase of 700% during the study period. Most of the H. influenzae cases (90%) occurred in the 1st 2 years of life. Analysis of culture-negative specimens by antigen detection in the last 2 years also revealed the predominance of H. influenzae (71.4%) and S. pneumoniae (22.4%). Typing of H. influenzae isolates during this time showed that 98% of the strains were type b. This retrospective hospital-based study indicated a pronounced increase in the incidence of H. influenzae meningitis and strongly supports the need for large-scale Hib vaccination for young children. However, such nationwide intervention will probably need to be based on a prospective on a prospective and population-based surveillance of H. influenzae infections.

Age Distribution↗
PubMed1997

Serotypes of Streptococcus pneumoniae causing invasive childhood infections in Bangladesh, 1992 to 1995.

One hundred sixty-five invasive Streptococcus pneumoniae strains were isolated from children under five at Dhaka Shishu (Children's) Hospital during the period 1992 to 1995. Ninety-four strains were from cerebrospinal fluid, and 71 were from blood. More than 91% of the strains were isolated from patients aged 24 months or less. Predominant serotypes were, in descending order 7F, 12F, 14, 15B, 18, 5, and 22A. These comprised 70% of all isolates. The marked differences in serotype distribution in different countries indicate the need for a sentinel surveillance study for the countries of South Asia, particularly Bangladesh, China, India, and Pakistan.

Bacterial Vaccines↗
PubMed1997

Human distomatosis due to Fasciola hepatica infection in Assam, India.

A seven year old girl in a rural area of Upper Assam was found to be infected with Fasciola hepatica. The girl gave history of eating watercress. Besides the presence of eggs in the stools, her liver was enlarged and tender. Liver function tests revealed hepato-biliary involvement with increase in serum AKP and ALT. Ultrasonography revealed presence of adult fluke in gall bladder, and a marginal thickening of gall bladder wall. However, the echo pattern of her liver parenchyma was normal. The case is reported for its public health significance and is a maiden report from north eastern India.

Child↗
PubMed1997

Isolation of a fluoroquinolone resistant Shigella dysenteriae 1 strain from Calcutta.

Fourteen strains of Shigella spp. were isolated from patients aged 5-12 yr, hospitalized with dysentery during 1995-1996. The strains isolated were Shigella dysenteriae 1, S. flexneri and S.sonnei. All but one of the 14 strains were sensitive to ciprofloxacin and norfloxacin. The MIC of both the fluoroquinolones was 15 micrograms/ml for the resistant S.dysenteriae 1 strain (NRM4). Therefore, the careful use of antimicrobials is required for therapy of Shigellosis.

Anti-Infective Agents↗