S. Ghosh

Bio: S. Ghosh is an academic researcher from University of Calcutta. The author has contributed to research in topics: Sister chromatid exchange & Pelletron. The author has an hindex of 10, co-authored 30 publications receiving 283 citations.

Zirconium. An abnormal trace element in biology.

Abstract: The action of Zirconium (Zr) on biological systems presents an enigma. It is ubiquitous, being present in nature in amounts higher than most trace elements. It is taken up by plants from soil and water and accumulated in certain tissues. The entry into animal systems in vivo is related to the mode of exposure and the concentration in the surrounding environment. Retention is initially in soft tissues and then slowly in the bone. The metal is able to cross the blood brain-barrier and is deposited in the brain and the placental barrier to enter milk. The daily human uptake has been known to be as high as 125 mg. The level of toxicity has been found to be moderately low, both in histological and cytological studies. The toxic effects induced by very high concentrations are nonspecific in nature. Despite the presence and retention in relatively high quantities in biological systems, Zr has not yet been associated with any specific metabolic function. Very little information is available about its interaction with the compounds of the genetical systems, such as nucleic acids. Apparently, the metal is neither an essential nor toxic element in the conventional sense. However, the increasing exposure to this element through its increasing use in new materials and following radioactive fallout, has increased the importance of the study of its effects on living organisms. The tetravalent nature of the ionic state and the high stability of the compounds formed are important factors that need to be considered, as also the accumulation of this element in the brain, reminiscent of the relationship between Al3+ and Alzheimer's disease.

Cytogenetic studies in human populations exposed to gas leak at Bhopal, India.

Abstract: Frequencies of chromosomal abnormalities, sister chromatid exchanges, and replicative index were assessed following peripheral lymphocyte culture in 129 individuals from Bhopal, India. Of these, 83 persons (40 male and 43 female) had been exposed directly to the methyl isocyanate (MIC) gas after the accident at the Union Carbide plant on December 2 and 3, 1984. The remaining 46 samples were taken from age-matched unexposed persons in the same city. Chromosome aberrations were recorded at first cycle metaphase (M1) and sister chromatid exchanges, at second cycle metaphase (M2), following standard schedule. The frequency of chromosomal aberrations was, in general, higher in individuals from the exposed populations, with the females showing a higher incidence. Nondisjunction of chromosomes or laggard was rare. The frequencies of sister chromatid exchanges and depression in mitotic and replicative indices could not be related to exposure or sex. The persistence of chromosomal abnormalities in the form of replicating minutes and exchange configurations, even 1114 days after exposure to the gas, may indicate a residual effect on T-cell precursors.

Stopping power of Mylar for heavy ions up to copper

Abstract: The stopping powers of Mylar for several heavy ions covering Z =11 to 29 in the energy range ∼0.3 to 2.3 MeV/n have been measured using the elastic recoil detection technique and twin detector system. The technique provided a unique method to generate a variety of variable energy ion species utilizing a fixed energy 140 MeV Ag 13+ primary beam from the Pelletron accelerator facility at Nuclear Science Center, New Delhi, India. Most of these measurements are new. The experimentally measured stopping power values have been compared with those calculated using LSS theory, Ziegler et al. formulation and Northcliffe and Schilling tabulations. Merits and demerits of these formulations are highlighted. Stopping power calculations using the Hubert et al. formulation have been extended successfully beyond its recommended range of validity, i.e. 2.5–500 MeV/n down to energies as low as 0.5 MeV/n.

Volatilization of mercury by resting mercury-resistant bacterial cells

Abstract: The mercuric ion reduction system encoded by the Hg2+ inducible mer operon confers bacterial resistance to mercuric ion. The mer A gene product which is a FAD-containing enzyme catalyzes the reduction of Hg2+ to volatile elemental mercury with the help of intracellular thiols and NADPH as a cofactor (Schottel 1974; Summers and Silver 1978; Fox and Walsh 1982; Misra 1992). Our earlier studies have shown that growing cells of different mercury-resistant bacteria reduce Hg2+ compounds to Hg(O) (Ray et al. 1989; Pahan et al. 1990a; Gachhui et al. 1989). We have also shown the effect of thiol compounds and flavins on mercury-degrading enzyme activities in mercury-resistant bacteria (Pahan et al. 1990b). Here we report that resting cells of mercury-resistant bacteria survive in a buffer system for several hours, synthesize inducible mercury-degrading enzymes and volatilize mercury from a mercury-containing buffer system. We know of no information regarding studies of mercury-degrading enzymes in resting mercury-resistant bacterial cells.

Studies of electronic sputtering of fullerene under swift heavy ion impact

Abstract: The present work reports the dependence of electronic sputtering on thickness of fullerene film. The energetic ions of 200 MeV Au15+ are taken from NSC Pelletron at New Delhi and the Tandem accelerator at Munich. On-line elastic recoil detection analysis (ERDA) with ΔE–E telescope detector is used to determine the electronic sputtering yield. We observed systematic decrease in sputtering yield of carbon with increase in film (C60/silicon) thickness.

The abdominal compartment syndrome

Abstract: : In two patients, a man aged 67 and a woman aged 80, an abdominal compartment syndrome was diagnosed. The man had been treated surgically for an abdominal aortic aneurysm; he recovered after re-operation. The woman had been treated by sigmoidectomy because of ileus. A Bogota bag and a vacuum-assisted wound-closure system were applied to the abdominal wound. Her condition deteriorated, an intestinal perforation became apparent, of which she did not recover and died. An abdominal compartment syndrome should always be kept in mind when a patient at risk presents with increased intra-abdominal pressure and at least one of the following symptoms: oliguria, decreased cardiac output, increased pulmonary-artery pressure, hypotension and acidosis. Measurement of the bladder pressure remains the method of choice to establish the abdominal pressure level. However, there is a lack of correlation between the measured pressure and the clinical condition of the patient. Therefore, the combination of clinical findings and the observed trend in serial measurements of the bladder pressure is preferred to a single pressure measurement.

Effects of alloying elements on the corrosion behavior and biocompatibility of biodegradable magnesium alloys: a review

Abstract: Magnesium (Mg) based alloys have been extensively considered for their use as biodegradable implant materials. However, controlling their corrosion rate in the physiological environment of the human body is still a significant challenge. One of the most effective approaches to address this challenge is to carefully select alloying compositions with enhanced corrosion resistance and mechanical properties when designing the Mg alloys. This paper comprehensively reviews research progress on the development of Mg alloys as biodegradable implant materials, highlighting the effects of alloying elements including aluminum (Al), calcium (Ca), lithium (Li), manganese (Mn), zinc (Zn), zirconium (Zr), strontium (Sr) and rare earth elements (REEs) on the corrosion resistance and biocompatibility of Mg alloys, from the viewpoint of the design and utilization of Mg biomaterials. The REEs covered in this review include cerium (Ce), erbium (Er), lanthanum (La), gadolinium (Gd), neodymium (Nd) and yttrium (Y). The effects of alloying elements on the microstructure, corrosion behavior and biocompatibility of Mg alloys have been critically summarized based on specific aspects of the physiological environment, namely the electrochemical effect and the biological behavior.

Mechanisms of nickel toxicity in microorganisms

Abstract: Nickel has long been known to be an important human toxicant, including having the ability to form carcinomas, but until recently nickel was believed to be an issue only to microorganisms living in nickel-rich serpentine soils or areas contaminated by industrial pollution. This assumption was overturned by the discovery of a nickel defense system (RcnR/RcnA) found in microorganisms that live in a wide range of environmental niches, suggesting that nickel homeostasis is a general biological concern. To date, the mechanisms of nickel toxicity in microorganisms and higher eukaryotes are poorly understood. In this review, we summarize nickel homeostasis processes used by microorganisms and highlight in vivo and in vitro effects of exposure to elevated concentrations of nickel. On the basis of this evidence we propose four mechanisms of nickel toxicity: (1) nickel replaces the essential metal of metalloproteins, (2) nickel binds to catalytic residues of non-metalloenzymes; (3) nickel binds outside the catalytic site of an enzyme to inhibit allosterically and (4) nickel indirectly causes oxidative stress.

Ion beam induced surface and interface engineering

Abstract: The injection of material into a target specimen in the form of an accelerated ion beam offers a most valuable tool for altering its physical, chemical, structural, surface and interface properties in a controlled manner and tailoring new materials for basic and applied research for science and technology. The present review describes experimental, theoretical and recent aspects of ion beam modifications at various solids, thin films, and multilayered systems covering wider energy ranges including the older basic concepts which are now of interest. These results reveal that the ion–solid interaction physics provides a unique way for controlling the produced defects of the desired type at a desired location. These interests have been stimulated by the possibilities of synthesizing novel materials with potential applications in the field of thin films, surfaces and interface science. Many applications of ion induced engineering are being developed for various sciences of high technological interest for future aspects.

In vivo biodistribution and accumulation of 89Zr in mice.

Abstract: Introduction The present investigation focuses on the chemical and biological fate of 89 Zr in mice. Electrophoreses of 89 Zr solvated or chelated in different conditions are here presented. The biological fate of mice injected with [ 89 Zr]Zr-oxalate, [ 89 Zr]Zr-chloride, [ 89 Zr]Zr-phosphate, [ 89 Zr]Zr-desferrioxamine and [ 89 Zr]Zr-citrate is studied with the biodistribution, the clearances and positron emission tomography images. A special focus is also given regarding the quality of 89 Zr bone accumulation. Methods Electrophoreses were carried out on chromatography paper and read by gamma counting. Then, the solutions were intravenously injected in mice, imaged at different time points and sacrificed. The bones, the epiphysis and the marrow substance were separated and evaluated with gamma counts. Results The clearances of [ 89 Zr]Zr-chloride and [ 89 Zr]Zr-oxalate reached 20% of injected dose (ID) after 6 days whereas [ 89 Zr]Zr-phosphate was only 5% of ID. [ 89 Zr]Zr-citrate and [ 89 Zr]Zr-DFO were noticeably excreted after the first day postinjection (p.i.). [ 89 Zr]Zr-chloride and [ 89 Zr]Zr-oxalate resulted in a respective bone uptake of ∼15% ID/g and∼20% ID/g at 8 h p.i. with minor losses after 6 days. [ 89 Zr]Zr-citrate bone uptake was also observed, but [ 89 Zr]Zr-phosphate was absorbed in high amounts in the liver and the spleen. The marrow cells were insignificantly radioactive in comparison to the calcified tissues. Conclusion Despite the complexity of Zr coordination, the electrophoretic analyses provided detailed evidences of Zr charges either as salts or as complexes. This study also shows that weakly chelated, 89 Zr is a bone seeker and has a strong affinity for phosphate.