Biomedical subjects

Dipankar Ghosh

Publications and source records attributed to Dipankar Ghosh.

6 recordsLinked to original sources

PubMed2006

Amperometric detection of pesticides using polymer electrodes.

The real time monitoring of some organophosphorus based pesticides is of great concern to environmentalists because the widespread use of pesticides is causing severe health hazards to all living beings and also hampering our ecological balance. The traditional methods of measurement of pesticide residues are time consuming, need sample pre-treatment, and lack desired specificity and accuracy. We have developed an amperometric biosensor for indirect measurement of the pesticide concentration precisely in ppb level. The method is based on the action of two enzymes namely acetylcholine esterase and choline oxidase which are uniquely immobilized in a polymeric porous network directly on the working electrode of a screen-printed sensor. Polyacrylamide matrix has been prepared by copolymerisation of acrylamide and N,N'-methylenebisacrylamide using Potassium peroxodisulphate (K2S2O8) as initiator. A linear relationship was obtained between the range of 0 to 10 ppb.

Acetylcholinesterase↗

PubMed2006

Extraction and monitoring of phytoecdysteroids through HPLC.

The size of the phytoecdysteroids family is rapidly growing. Recent data shows over 250 ecdysteroid analogs have been identified so far in plants. It is theorized that there are over 1000 possible structures, which might occur in nature, but it is a fact that ecdysteroids usually occur in plants as a complex cocktail of structurally different compounds. Among these compounds, the major component is usually the common ecdysteroid-like 20-hydroxyecdysone. Ecdysteroids are polar steroids, almost sugar-like in their solubility properties. Extraction and purification of ecdysteroids (polyhydroxy steroids) is complicated by their polar nature and poor crystallizing properties. These properties make them difficult to separate from other polar plant constituents. Besides, this plant extract is very often processed by multistep procedures to isolate the major and minor ecdysteroids from the new or existing sources. A simplified scheme consisting of a few extraction steps for the purification of ecdysteroid from plants is in great demand. A quantitative approach through high-performance liquid chromatography has been initiated for developing an easy method for the extraction of ecdysteroids from Ipomoea hederacea (kaladana) seeds.

Chromatography, High Pressure Liquid↗

PubMed2003

Protection against enteric salmonellosis in transgenic mice expressing a human intestinal defensin.

Genetically encoded antibiotic peptides are evolutionarily ancient and widespread effector molecules of immune defence. Mammalian defensins, one subset of such peptides, have been implicated in the antimicrobial defence capacity of phagocytic leukocytes and various epithelial cells, but direct evidence of the magnitude of their in vivo effects have not been clearly demonstrated. Paneth cells, specialized epithelia of the small intestinal crypt, secrete abundant alpha-defensins and other antimicrobial polypeptides including human defensin 5 (HD-5; also known as DEFA5). Although antibiotic activity of HD-5 has been demonstrated in vitro, functional studies of HD-5 biology have been limited by the lack of in vivo models. To study the in vivo role of HD-5, we developed a transgenic mouse model using a 2.9-kilobase HD-5 minigene containing two HD-5 exons and 1.4 kilobases of 5'-flanking sequence. Here we show that HD-5 expression in these mice is specific to Paneth cells and reflects endogenous enteric defensin gene expression. The storage and processing of transgenic HD-5 also matches that observed in humans. HD-5 transgenic mice were markedly resistant to oral challenge with virulent Salmonella typhimurium. These findings provide support for a critical in vivo role of epithelial-derived defensins in mammalian host defence.

Animals↗

PubMed2003

Efficient utilization of medical practice resources: a framework and case analysis.

In the present environment of cost containment, physicians need to better understand their practice cost of providing patient care. The objectives of this study are to provide a control framework to help physicians assess the effectiveness of resource utilization of their practices and to discuss a case illustrating the application of this framework at a practice clinic.

Accounting↗

PubMed2002

Paneth cell trypsin is the processing enzyme for human defensin-5.

The antimicrobial peptide human alpha-defensin 5 (HD5) is expressed in Paneth cells, secretory epithelial cells in the small intestine. Unlike other characterized defensins, HD5 is stored in secretory vesicles as a propeptide. The storage quantities of HD5 are approximately 90 450 microg per cm2 of mucosal surface area, which is sufficient to generate microbicidal concentrations in the intestinal lumen. HD5 peptides isolated from the intestinal lumen are proteolytically processed forms--HD5(56-94) and HD5(63-94)--that are cleaved at the Arg55-Ala56 and Arg62-Thr63 sites, respectively. We show here that a specific pattern of trypsin isozymes is expressed in Paneth cells, that trypsin colocalizes with HD5 and that this protease can efficiently cleave HD5 propeptide to forms identical to those isolated in vivo. By acting as a prodefensin convertase in human Paneth cells, trypsin is involved in the regulation of innate immunity in the small intestine.

Amino Acid Sequence↗

PubMed2002

Amperometric biosensors for detection of the prostate cancer marker (PSA).

Prostate specific antigen (PSA) has been identified as the most reliable clinical tool for diagnosing and monitoring prostate cancer (CAP). Since, there is no curative therapy available for prostate cancer, detecting the disease at the early stage is the best hope of increasing mortality rate. There are some procedures available for the detection of prostate cancer e.g. Tandem-R PSA, Hybritech Inc. (USA), IMx-PSA Abbott Laboratories (USA). However, these are time consuming and costly. We have developed a very simple and cost effective technique for identification and monitoring of prostate cancer using amperometric immunosensor. PSA is a glycoprotein with 93% peptide and 7% sugar content and isoelectric pH of 6.9. It may exist in the human serum as free (f-PSA) and complex (PSA-ACT) forms. Normally if the total PSA (t-PSA) level is more than 10 ng/ml, CAP is suspected. This paper presents an amperometric detection procedure for t-PSA using three electrode system in which working electrode (WE) is made of hydroxyethyl cellulose (HEC) and rhodinised carbon. The method used is rapid, very easy to use and involves low cost compared with other procedures. The electrochemical response was directly observed due to enzymatic reaction via a sandwich immunoassay on the WE. Monoclonal capture antibody (Mab) to PSA was immobilised on the WE and the other Mab labelled by the enzyme marker, horseradish peroxidase (HRP), was used as a tracer antibody.

Biomarkers↗