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Biomedical subjects

S Gangopadhyay

Publications and source records attributed to S Gangopadhyay.

At least 19 recordsLinked to original sources
PubMed2005

Dorsal plating of unstable distal radius fractures using a bio-absorbable plating system and bone substitute.

This study reports the results of open reduction and internal fixation of 26 unstable, intraarticular, dorsally displaced fractures of the distal radius using a bio-absorbable dorsal distal radius (Reunite) plate and calcium phosphate (Biobon) bone substitute. The bio-absorbable plate has the advantage of being low profile, easily contourable and angularly stable. In the majority of cases, this plate produces functional results comparable with metal plates. The Gartland and Werley score was excellent or good in 21 patients. The theoretical advantage over metal plates is in eliminating the need to remove the plate and hence the need for a second operation if implant-related extensor tenosynovitis occurs. Inflammatory tissue reaction to the degradation products of the plate is a potential concern, although the co-polymer ratio used in this plate appears to have reduced the severity of this reaction, which was seen in two patients in this series. The reduction was lost in five patients with severe dorsal comminution. Following this experience, we do not recommend this plating system for fractures with a metaphyseal gap of greater than 7 mm following reduction.

Absorbable Implants↗
PubMed2003

A comparative study between longitudinal and "T" incisions for dorsal plating of the distal radius.

A retrospective review of 24 patients with dorsal incisions for open reduction and internal fixation of Frykman VII/VIII distal radius fractures using a dorsal plate was performed. Half of them had a longitudinal incision while the other half had a T-shaped incision. No difference in the healing properties or wound morbidity could be demonstrated between the two groups. However, the T incision provided improved exposure of the distal radius and patient satisfaction with its cosmetic result was superior. The horizontal limb was well camouflaged within the transverse skin crease on the dorsal aspect of the wrist. The vertical limb did not extend into the dorsum of the hand and could, therefore, be hidden by appropriate clothing.

Absorbable Implants↗
PubMed1999

Kinetics of template-directed pyrophosphate-linked dideoxyguanylate synthesis as a function of 2-MeImpdG and poly(C) concentration: insights into the mechanism.

Aqueous solutions of deoxyguanosine 5'-monophosphate 2-methylimidazolide, 2-MeImpdG, yield primarily deoxyguanosine 5'-monophosphate, 5'dGMP, and pyrophosphate-linked dideoxyguanylate, dG5'ppdG, abbreviated G2p (see Chart 1). The initial rate of G2p formation, d[G2p]/dt in M h-1, determined at 23 degrees C, pH 7.8, 1.0 M NaCl and 0.2 M Mg2+ by timed high-performance liquid chromatography (HPLC) analysis, exhibits a second-order dependence on 2-MeImpdG concentration, [G]o, indicating a bimolecular mechanism of dimerization in the range 0.02 M < or = [G]o < or = 0.09 M. In the presence of polycytidylate, poly(C), G2p synthesis is accelerated and oligodeoxyguanylate products are formed by incorporation of 2-MeImpdG molecules. The kinetics of G2p formation as a function of both monomer and polymer concentration, expressed in C equivalents, were also determined under the above conditions and exhibited a complex behavior. Specifically, at a constant [poly(C)], values of d[G2p]/dt typically increased with [G]o with a parabolic upward curvature. At a constant [G]o, values of d[G2p]/dt increase with [poly(C)], but level off at the higher poly(C) concentrations. As [G]o increases this saturation occurs at a higher poly(C) concentration, a result opposite to expectation for a simple complexation of two reacting monomers with the catalyst prior to reaction. Nevertheless, these results are shown to be quantitatively consistent with a template-directed (TD) mechanism of dimerization where poly(C) acts as the template to bind 2-MeImpdG in a cooperative manner and lead, for the first time, to the formulation of principles that govern template-directed chemistry. Analysis of the kinetic data via a proposed TD cooperative model provides association constants for the affinity between polymer and monomer and the intrinsic reactivity of 2-MeImpdG toward pyrophosphate synthesis. To the best of our knowledge, poly(C)/2-MeImpdG is the first system that could serve as a textbook example of a TD reaction under conditions such that the template is fully saturated by monomers and under conditions that it is not.

Computer Simulation↗
PubMed1999

Relative reactivity of ribosyl 2'-OH vs. 3'-OH in concentrated aqueous solutions of phosphoimidazolide activated nucleotides.

Phosphoimidazolide activated ribomononucleotides (*pN, see structure) are useful substrates for the non-enzymatic synthesis of oligonucleotides. In the presence of metal ions, aqueous solutions of *pN yield primarily the two internucleotide-linked (pN2' pN and pN3' pN) and the pyrophosphate-linked (N5' ppN) dimers. Small amounts of cyclic dimers and higher oligomers are also produced. In this study the relative reactivity of 2'-OH vs. 3'-OH was determined from the ratio of the yields of pN2' pN vs. pN3' pN. Experiments were performed at 23 degrees C in the range 7.2 < or = pH < or = 8.4 with substrates that differ in nucleobase (guanosine (G), cytidine (C), uridine (U), and adenosine (A)) and leaving group (imidazole (Im), 2-methylimidazole (2-MeIm) and 2,4-dimethylimidazole (2,4-diMeIm)). Two metal ions (Mg2+ or Mn2+) were employed as catalysts. The conditions used here, i.e. a substrate concentration in the range 0.1 M to 1.0 M and metal ion concentration in the range 0.05 M to 0.2 M, favor base-stacking interactions. The ratio pN2' pN: pN3' pN = 2'-5': 3'-5' was found independent of nucleobase and typically varied between 2 to 3 indicating that the 2'-OH is about 2 to 3 times more reactive than the 3'-OH. *pN with Im, compared to 2-MeIm and 2,4-diMeIm leaving group, produce lower yields of internucleotide linked dimers, and a higher pN2' pN: pN3' pN ratio. Trends in the data, observed with all three leaving groups, suggest an increase in pN2' pN: pN3' pN ratio with decreasing substrate concentration (up to 5.47 with 0.051 M ImpG). The observations are in accord with earlier studies reporting a relative reactivity 2'-5': 3'-5' = 6 to 9 obtained with Im as the leaving group, in dilute nucleotide solutions and under conditions that disfavor stacking. It is speculated that the concentration induced change in the relative reactivity is the result of self-association via base-stacking that enhances selectively the proximity of the 3'-OH of one molecule to the reactive P-N bond of an other molecule. The implication of these conclusions for oligomerization/ligation reactions is discussed.

Hydrogen-Ion Concentration↗
PubMed1996

Cyclophosphamide in the treatment of toxic epidermal necrolysis.

A patient with non-small cell lung carcinoma and recent radiotherapy for brain metastases developed toxic epidermal necrolysis (TEN) shortly after therapy with phenytoin was initiated for a seizure. Exfoliation progressed to involve 90% of her body surface despite treatment with high-dose corticosteroids for 5 days, but sloughing and systemic toxicity ceased within 2 days of initiating therapy with intravenous cyclophosphamide (300 mg/day). Reepithelialization rapidly followed. This experience and the reports of others suggest that intravenous cyclophosphamide is helpful in the treatment of TEN.

Adult↗
PubMed1996

A longitudinal study of biological changes with age among the Brahmins of Calcutta.

In this paper, the individual biological sequence of change with age in a sample taken in metropolitan city, Calcutta, West Bengal, is discussed. The study comprises a few anthropometric measurements (stature, weight, biacromial breadth, nasal length, nasal breadth, upper facial height) taken on the same population at an interval of five years (first in the year 1982 and again in the year 1987). The study reveals that the amount of increment or decrement of some characters (the above mentioned traits) are different for different chronological age; and these differences can only be identified with the help of a longitudinal study which is free from the effect of secular change in the younger generations.

Adult↗
PubMed1989

Subsidy policies with capital accumulation: maintaining employment levels.

The authors study a dual economy model of growth and unemployment in the presence of Harris-Todaro type labor migration. The model is a discrete time model of economic growth with a given population but endogenous migration of labor. The economy tries to reach development in the quickest possible time while not allowing unemployment to rise above a socially acceptable level. The authors also characterize situations under which maximizing the accumulation of capital in each period is optimal and study how particular taxes and subsidies affect unemployment and capital accumulation. Finally, they show that a higher initial capital stock does not necessarily mean a quicker attainment of self- sustained full employment.

Commerce↗