M.K Thakur - Academia.edu (original) (raw)

Papers by M.K Thakur

International Journal of Biological Macromolecules, 2015

Recently, biorenewable polymers from different natural resources have attracted a greater attenti... more Recently, biorenewable polymers from different natural resources have attracted a greater attention of the research community for different applications starting from biomedical to automotive. Lignin is the second most abundant non-food biomass next to cellulose in the category of biorenewable polymers and is abundantly available as byproduct of several industries involved in paper making, ethanol production, etc. The development of various green materials from lignin, which is most often considered as waste, is therefore of prime interest from environmental and economic points of view. Over the last few years, little studies have been made into the use of lignin as an indispensable component in the hydrogels. This article provides an overview of the research work carried out in the last few years on lignin based hydrogels. This article comprehensively reviews the potential efficacy of lignin in biopolymer based green hydrogels with particular emphasis on synthesis, characterization and applications. In this article, several examples of hydrogels synthesized using different types of lignin are discussed to illustrate the state of the art in the use of lignin.

ACS Sustainable Chemistry & Engineering, 2014

Chitosan is among one of the most important and most studied natural polymers. The cationic natur... more Chitosan is among one of the most important and most studied natural polymers. The cationic nature of chitosan makes it a polymer of high importance from environmental and biomedical point of views among the other natural polysaccharides. However, it also suffers from a few disadvantages and requires further development to achieve the targeted results and desired range of efficiency. To overcome some of the disadvantages of the pristine chitosan, it is most imperative to functionalize it with suitable functional groups. Therefore, it is highly desired to understand the chemistry of the reactions used to alter the surface characteristics of chitosan. Among various techniques presently being used to tailor the surface characteristics of chitosan, graft copolymerization is of the utmost importance. The aim of the present perspective is to describe the recent advances in the graft copolymerization of chitosan with particular emphasis on atom transfer radical polymerization (ATRP). This perspective describes the synthesis, characterization, and multifunctional applications of different types of chitosan-based copolymers.

ACS Sustainable Chemistry & Engineering, 2014

Rising environmental concerns and depletion of petrochemical resources has resulted in an increas... more Rising environmental concerns and depletion of petrochemical resources has resulted in an increased interest in biorenewable polymer-based environmentally friendly materials. Among biorenewable polymers, lignin is the second most abundant and fascinating natural polymer next to cellulose. Lignin is one of the three major components found in the cell walls of natural lignocellulosic materials. Lignin is widely available as a major byproduct of a number of industries involved in retrieving the polysaccharide components of plants for industrial applications, such as in paper making, ethanol production from biomass, etc. The impressive properties of lignin, such as its high abundance, low weight, environmentally friendliness and its antioxidant, antimicrobial, and biodegradable nature, along with its CO 2 neutrality and reinforcing capability, make it an ideal candidate for the development of novel polymer composite materials. Considerable efforts are now being made to effectively utilize waste lignin as one of the components in polymer matrices for high performance composite applications. This article is intended to summarize the recent advances and issues involving the use of lignin in the development of new polymer composite materials. In this review, we have made an attempt to classify different types of lignin-reinforced polymer composites starting from synthetic to biodegradable polymer matrices and highlight recent advances in multifunctional applications of lignin. The structural features and functions of the lignin/polymer composite systems are discussed in each section. The current research trends in lignin-based materials for engineering applications, including strategies for modification of lignin, fabrication of thermoset/thermoplastic/biodegradable/rubber/foam composites, and the use of lignin as a compatibilizer are presented. This study will increase the interest of researchers all around the globe in lignin-based polymer composites and the development of new ideas in this field.

Qualitative Research, 2010

Carol Grbich's Qualitative Data Analysis: An Introduction is a well written, practical guide for ... more Carol Grbich's Qualitative Data Analysis: An Introduction is a well written, practical guide for students and researchers alike, regardless of the reader's level of qualitative research expertise. Unlike many of its predecessors, which tend to provide practical computer-based guides and/or descriptions of the various analytical approaches to analysis, this book provides a detailed guide through the design, analysis and write up stages of a qualitative research project. The book is split into five sections which correspond to the main stages of the research process. This includes an overview of epistemological and general approaches to design and analysis in Part 1 to a discussion of specific analytical approaches including phenomenology and more recent ethnographical approaches in Part 2. The most substantial section of the text is dedicated to data analysis techniques including conventional approaches such as discourse analysis to more novel methods of visual interpretation. The final two chapters are of particular use to student researchers as they provide a detailed guide to writing up research findings and presenting different forms of data as well as providing a brief overview of the qualitative computing programmes currently available. Grbich begins her text with a guide through the history, characteristics and ongoing debates surrounding key epistemological positions including: positivism/empiricism; critical emancipatory; constructivism/interpretivism; postmodern and poststructuralist epistemologies. This first chapter provides a clear and user-friendly introduction to the main features of each position, whilst also presenting different methodological options available to researchers when adopting a specific epistemology. Dispersed within discussions of author/ researcher standpoint are useful practical tips on displaying qualitative data, such as the use of hyperlinks and footnotes to highlight potential researcher bias and data sources. 129

Neurochemistry International, 2007

Estrogen actions are mainly mediated by estrogen receptor (ER)a and ERb which in turn are regulat... more Estrogen actions are mainly mediated by estrogen receptor (ER)a and ERb which in turn are regulated by several factors including age, sex and gonadal steroid hormones 17b-estradiol and testosterone. In the present study, we have used nuclear runoff assay to examine the effect of these factors on the rate of transcription of ERa and ERb of mouse cerebral cortex. The runoff assay result was further corroborated with the measurement of steady state level of ERa and ERb mRNA by semiquantitative RT-PCR method. Our results reveal that ERa transcription rate decreases in old mice of both sexes, whereas ERb transcription rate decreases only in old females when compared to their adult counterparts. 17b-Estradiol supplementation reduces the transcription rate of ERa and ERb in all groups except in adult male while testosterone treatment down regulates the transcription rate of ERa and ERb in all groups. The semiquantitative RT-PCR analysis reveals that the level of ERa mRNA decreases in old male but shows no effect in old female as compared to adult counterpart. In contrast, ERb transcript level decreases in old mice of both sexes. Furthermore, ERa mRNA level is higher in adult female than in adult male but no sex-dependent difference is seen in ERb mRNA level. Supplementation of 17b-estradiol shows no significant alteration but testosterone reduces the ERa level in male mice, while 17b-estradiol and testosterone down regulate the ERa level in female mice of both ages. In case of ERb, 17b-estradiol decreases the transcript level in all groups except adult male while testosterone treatment results in the down regulation of transcript level in all groups. Thus these findings suggest differential effects of age, sex, 17b-estradiol and testosterone supplementation on the transcription of mouse ER genes which may account for differences in the protein levels of ERa and ERb and their functions in the brain.

Neurochemical Research, 2006

The brain undergoes many structural and functional changes during aging. Some of these changes ar... more The brain undergoes many structural and functional changes during aging. Some of these changes are regulated by estrogens which act mainly through their intracellular receptors, estrogen receptor ERa and ERb. The expression of these receptors is regulated by several factors including their own ligand estrogen, and others such as growth hormone and thyroid hormone. The levels of these factors decrease during aging which in turn influence estrogen signaling leading to alterations in brain functions. In the present paper, we review the effects of aging on brain structure and function, and estrogen action and signaling during brain aging. The findings suggest key role of estrogen in the maintenance of brain functions during aging.

Neurobiology of Aging, 2006

Estrogen receptor (ER), which mediates the multiple effects of estrogen in brain, is regulated by... more Estrogen receptor (ER), which mediates the multiple effects of estrogen in brain, is regulated by several factors including its own ligand. In the present study, we have examined the effect of age, sex and gonadal steroids (estrogen and testosterone) on the level of ER␣ and ER␤ in the cerebral cortex of AKR mice. Adult and old mice of both sexes were divided into four groups: intact, gonadectomized, 17␤-estradiol treated and testosterone treated. Western blot analysis showed higher level of ER␣ and ER␤ in the cerebral cortex of adult female than male mice. ER␤ level decreased significantly with advancing age in both sexes, whereas 17␤-estradiol supplementation decreased ER␣ level in old male and increased in old female, it also increased ER␤ level in old male and adult female. On the other hand, testosterone treatment decreased ER␣ level significantly in old female and ER␤ level in adult female but increased ER␤ level in male mice of both ages. Thus, these findings showed that the expression of ER␣ and ER␤ protein is differentially influenced by age, sex and gonadal steroids in the mouse cerebral cortex, suggesting differences in ER-mediated brain functions.

Molecular Biotechnology, 2010

Escherichia coli is one of the most common and widely used prokaryotic hosts for the expression o... more Escherichia coli is one of the most common and widely used prokaryotic hosts for the expression of recombinant proteins. The overexpression of recombinant proteins occasionally increases bacterial growth but sometimes reduces it and becomes lethal to the host cells. Here, we report the overexpression of mouse ER-β and its domains in the prokaryotic expression system and its opposite effect on the growth characteristics of E. coli. ER-β protein was immunologically detected as a 53 kDa his-tag protein in the pellet of the bacterial lysate. Its overexpression, as reflected by the total protein content and expression pattern, resulted in the decrease of bacterial growth. However, the overexpression of ER-β transactivation domain (TAD) using pIVEX and ligand binding domain (LBD) using pRSETA in E. coli BL21 (DE3) show opposite pattern. TAD was immunologically detected as 20 kDa and LBD as 22 kDa protein in the supernatant of the bacterial lysate and their overexpression increased the bacterial growth.

Molecular Biology Reports, 1989

The in vitro acetylation of HMG proteins was studied using liver slices of young (18-week) and ol... more The in vitro acetylation of HMG proteins was studied using liver slices of young (18-week) and old (138-week) male rats. Acetylation of total HMG proteins is lower in old age. The incorporation of (14C) acetate into individual HMG proteins varies remarkably with advancing age. Whereas acetylation of high mol. wt. proteins (HMG 1 and 2) is higher, that of low mol. wt. proteins (HMG 14 and 17) is lower in the liver of young rats as compared to the old ones. Spermine stimulates the acetylation of HMG 1 and 14 in young and HMG 1, 2 and 14 in old age. It inhibits the acetylation of HMG 17 in both ages. Dexamethasone decreases the level of incorporation of (14C) into HMG 1 and 17 in young and HMG 14 and 17 in old rats. On the other hand, it stimulates the acetylation of HMG 14 by two-fold in young and that of HMG 1 and 2 by more than three-fold in old rats. Such alteration in the acetylation of HMG proteins may account for age-related changes in the structure and function of chromatin.

Mechanisms of Ageing and Development, 1993

Considerable amount of data has accumulated during the past few years showing several changes in ... more Considerable amount of data has accumulated during the past few years showing several changes in gene expression as a function of age. However, the basic mechanism of aging still remains poorly understood. In this review, we have mainly analysed the data pertaining to the hypothesis that aging is associated with genetic instability and have attempted further to highlight the gaps that need to be bridged in order to have a clear picture of the aging phenomenon. Extensive investigations employing new and novel approaches are needed in future to elucidate the intricately interwoven patterns of molecular control that underlie the various aspects of gene expression during aging.

Journal of Molecular Neuroscience, 2010

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulatio... more Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid beta peptides, which are produced by the proteolytic cleavage of amyloid precursor protein (APP). As the incidence of AD is higher in females and sex steroids are implicated in this disease, we have examined the effect of sex steroids (testosterone and 17β-estradiol) on the expression of APP mRNA and protein in the cerebral cortex of adult and old mice of both sexes. Northern blot analysis detected APP mRNA as a single 3.5-kb band and its level is increased in old as compared to adult. Following gonadectomy, its level was upregulated in female mice but downregulated in male mice. Supplementation with testosterone or estradiol decreased its levels in female mice of both ages. Testosterone supplementation increased the mRNA levels in both adult and old male mice. Estrogen supplementation decreased its level in adult but increased in old male mice. Western blot analysis detected APP specific bands ranging from 95 to 125 kD. The level of 95 kDa band representing APP695 protein showed difference in levels with age or hormone treatment. These results provide evidence for increase in APP mRNA level in the cerebral cortex of old mice and its regulation by sex steroids during aging.

International Journal of Polymeric Materials and Polymeric Biomaterials, 2013

ABSTRACT In view of recent technological significance of green cellulosic polymers in environment... more ABSTRACT In view of recent technological significance of green cellulosic polymers in environmentally friendly materials, the present study is an attempt to synthesize Saccaharum cilliare-graft-poly (ethyl acrylate) (Saccaharum cilliare-g-PEA) copolymers via pressure-induced free-radical polymerization. The effect of pressure, time, ratio of monomer, solvent, and initiator concentrations were determined to get the premier percentage of grafting. It has been observed from this study that the physicochemical and thermal properties of the grafted cellulosic polymers have increased to a considerable extent and can be a potential material for a number of applications.

International Journal of Polymer Analysis and Characterization, 2012

The increasing demand for green, environmentally friendly materials has resulted in new natural f... more The increasing demand for green, environmentally friendly materials has resulted in new natural fiber–based materials as replacements for nondegradable materials derived from petroleum resources that are currently being used for a number of applications. Hence, this study deals with long fiber–reinforced green polymer composites fabricated using the compression molding technique. Initially, green composites were produced with long fibers using 10,

International Journal of Polymer Analysis and Characterization, 2013

ABSTRACT Increasing environmental concerns and depletion of petroleum resources has forced resear... more ABSTRACT Increasing environmental concerns and depletion of petroleum resources has forced researchers around the globe to find new green materials. In the present research work, a particular interest was focused on the effective use of lignocellulosic natural fibers as reinforcement using polymer resin as a novel matrix. Green composites were prepared using the compression molding technique with different fiber contents. The physicomechanical and thermal characteristics of the different composite samples were investigated as a function of fiber contents. The results obtained suggest that the properties of the polymer matrix are positively affected by the incorporation of natural cellulosic fibers.

Clinical and Experimental Pharmacology and Physiology, 2007

1. For animals of all ages, during activation of skeletal muscles and the subsequent contraction,... more 1. For animals of all ages, during activation of skeletal muscles and the subsequent contraction, the balance between the force developed by the muscle and the external load determines whether the muscle shortens, remains at fixed length (isometric) or is lengthened. With maximum activation, the force developed is least during shortening, intermediate when muscle length is fixed and greatest during lengthening contractions. During lengthening contractions, when force is high, muscles may be injured by the contractions. 2. 'Frailty' and 'failure to thrive' are most frequently observed in elderly, physically inactive people. A 'frail' person is defined as one of small stature, with muscles that are atrophied, weak and easily fatigued. The condition of 'failure to thrive' is typified by a lack of response to well-designed programmes of nutrition and physical activity. 3. With ageing, skeletal muscle atrophy in humans appears to be inevitable. A gradual loss of muscle fibres begins at approximately 50 years of age and continues such that by 80 years of age, approximately 50% of the fibres are lost from the limb muscles that have been studied. For both humans and rats, the observation that the timing and magnitude of the loss of motor units is similar to that for muscle fibres suggests that the mechanism responsible for the loss of fibres and the loss of whole motor units is the same. The degree of atrophy of the fibres that remain is largely dependent on the habitual level of physical activity of the individual. 4. 'Master athletes' maintain a high level of fitness throughout their lifespan. Even among master athletes, performance of marathon runners and weight lifters declines after approximately 40 years of age, with peak levels of performance decreased by approximately 50% by 80 years of age. The success of the master athletes and of previously sedentary elderly who undertake well-designed, carefully administered training programmes provide dramatic evidence that age-associated atrophy, weakness and fatigability can be slowed, but not halted.

Cellular and Molecular Neurobiology, 2010

The allelic variant of apolipoprotein (Apo) E4 is a known risk factor for the development of most... more The allelic variant of apolipoprotein (Apo) E4 is a known risk factor for the development of most common late onset form of Alzheimer's disease (AD). As aging is associated with reduced circulating level of gonadal steroid hormones, hormone replacement therapies have been used for the possible treatment of AD. Both estrogen and testosterone have beneficial effects on brain due to interaction with apoE, but the underlying mechanism is still not clear. In this article, we report the effects of gonadectomy and hormone supplementation on apoE protein level in male and female mouse cerebral cortex during normal aging. We could not get any effect of gonadectomy and estradiol or testosterone treatment in adult and old mice of either sex. This suggests that during normal aging apoE protein level is not affected due to steroid hormone withdrawal or supplementation in the mouse cerebral cortex.

Cellular and Molecular Neurobiology, 2010

Following binding to cognate ligand, estrogen receptor (ER) b interacts with specific responsive ... more Following binding to cognate ligand, estrogen receptor (ER) b interacts with specific responsive elements of the target genes and recruits a host of nuclear proteins for hormone dependent gene regulation. However, it is poorly known which proteins interact with ER b in mouse brain and whether their interaction and expression change with age. In this report, we have used his-tag mouse ER b for interaction with nuclear proteins of cerebral cortex of young (6 ± 1 weeks), adult (25 ± 2 weeks), and old (70 ± 5 weeks) female mice. We have identified estrogen receptor-associated protein (ERAP) 140 as one of the interacting proteins and studied its interaction by pull down immunoblotting, far-Western blotting and immunoprecipitation, and expression by western blotting. The data show that ERAP 140 interacts with ER b and its interaction decreases but its expression increases with age in mouse cerebral cortex, suggesting its role in estrogen-mediated brain functions during aging.

Carbohydrate Polymers, 2014

Research highlights Interest in natural cellulosic polymers is increasing rapidly New frontie... more Research highlights Interest in natural cellulosic polymers is increasing rapidly New frontiers and potential applications of natural cellulose polymers highlighted Processing, surface modifications and different characterizations of natural cellulose polymers Focus on sustainability and future perspectives of natural cellulose polymers/ composites.

Carbohydrate Polymers, 2013

Cellulose is the most abundant natural polysaccharide polymer, which is used as such or its deriv... more Cellulose is the most abundant natural polysaccharide polymer, which is used as such or its derivatives in a number of advanced applications, such as in paper, packaging, biosorption, and biomedical. In present communication, in an effort to develop a proficient way to rapidly synthesize poly(methyl acrylate)-graftcellulose (PMA-g-cellulose) copolymers, rapid graft copolymerization synthesis was carried out under microwave conditions using ferrous ammonium sulfate-potassium per sulfate (FAS-KPS) as redox initiator. Different reaction parameters such as microwave radiation power, ratio of monomer, solvent and initiator concentrations were optimized to get the highest percentage of grafting. Grafting percentage was found to increase with increase in microwave power up to 70%, and maximum 36.73% grafting was obtained after optimization of all parameters. Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA/DTA/DTG) analysis were used to confirm the graft copolymerization of poly(methyl acrylate) (PMA) onto the mercerized cellulose. The grafted cellulosic polymers were subsequently subjected to the evaluation of different physico-chemical properties in order to access their application in everyday life, in a direction toward green environment. The grafted copolymers demonstrated increased chemical resistance, and higher thermal stability.

Carbohydrate Polymers, 2013

Cellulose, a linear polysaccharide polymer with numerous glucose monosaccharide units is of enorm... more Cellulose, a linear polysaccharide polymer with numerous glucose monosaccharide units is of enormous interest because of its applications in biosorption, biomedical, packaging, biofiltration and biocomposites. In this study, cellulose-graft-poly(butyl acrylate) copolymers were synthesized under microwave conditions. Effects of microwave radiation doses and different reaction parameters were optimized to get the optimum percentage of grafting. The dependence of optimum conditions for better physico-chemical properties of the cellulosic polymers was also determined. Fourier transform infrared spectroscopy (FT-IR) analysis was used to authenticate the chemical reaction taking place between cellulosic polymers and monomer. The thermogravimetric behavior of the raw and grafted cellulosic polymers was characterized by thermogravimetric analysis (TGA). The surface structure of the raw and grafted cellulosic polymers was analyzed through scanning electron microscopy (SEM). The graft copolymers have been found to be more moisture resistant and also showed better chemical and thermal resistance.

International Journal of Biological Macromolecules, 2015

Recently, biorenewable polymers from different natural resources have attracted a greater attenti... more Recently, biorenewable polymers from different natural resources have attracted a greater attention of the research community for different applications starting from biomedical to automotive. Lignin is the second most abundant non-food biomass next to cellulose in the category of biorenewable polymers and is abundantly available as byproduct of several industries involved in paper making, ethanol production, etc. The development of various green materials from lignin, which is most often considered as waste, is therefore of prime interest from environmental and economic points of view. Over the last few years, little studies have been made into the use of lignin as an indispensable component in the hydrogels. This article provides an overview of the research work carried out in the last few years on lignin based hydrogels. This article comprehensively reviews the potential efficacy of lignin in biopolymer based green hydrogels with particular emphasis on synthesis, characterization and applications. In this article, several examples of hydrogels synthesized using different types of lignin are discussed to illustrate the state of the art in the use of lignin.

ACS Sustainable Chemistry & Engineering, 2014

Chitosan is among one of the most important and most studied natural polymers. The cationic natur... more Chitosan is among one of the most important and most studied natural polymers. The cationic nature of chitosan makes it a polymer of high importance from environmental and biomedical point of views among the other natural polysaccharides. However, it also suffers from a few disadvantages and requires further development to achieve the targeted results and desired range of efficiency. To overcome some of the disadvantages of the pristine chitosan, it is most imperative to functionalize it with suitable functional groups. Therefore, it is highly desired to understand the chemistry of the reactions used to alter the surface characteristics of chitosan. Among various techniques presently being used to tailor the surface characteristics of chitosan, graft copolymerization is of the utmost importance. The aim of the present perspective is to describe the recent advances in the graft copolymerization of chitosan with particular emphasis on atom transfer radical polymerization (ATRP). This perspective describes the synthesis, characterization, and multifunctional applications of different types of chitosan-based copolymers.

ACS Sustainable Chemistry & Engineering, 2014

Rising environmental concerns and depletion of petrochemical resources has resulted in an increas... more Rising environmental concerns and depletion of petrochemical resources has resulted in an increased interest in biorenewable polymer-based environmentally friendly materials. Among biorenewable polymers, lignin is the second most abundant and fascinating natural polymer next to cellulose. Lignin is one of the three major components found in the cell walls of natural lignocellulosic materials. Lignin is widely available as a major byproduct of a number of industries involved in retrieving the polysaccharide components of plants for industrial applications, such as in paper making, ethanol production from biomass, etc. The impressive properties of lignin, such as its high abundance, low weight, environmentally friendliness and its antioxidant, antimicrobial, and biodegradable nature, along with its CO 2 neutrality and reinforcing capability, make it an ideal candidate for the development of novel polymer composite materials. Considerable efforts are now being made to effectively utilize waste lignin as one of the components in polymer matrices for high performance composite applications. This article is intended to summarize the recent advances and issues involving the use of lignin in the development of new polymer composite materials. In this review, we have made an attempt to classify different types of lignin-reinforced polymer composites starting from synthetic to biodegradable polymer matrices and highlight recent advances in multifunctional applications of lignin. The structural features and functions of the lignin/polymer composite systems are discussed in each section. The current research trends in lignin-based materials for engineering applications, including strategies for modification of lignin, fabrication of thermoset/thermoplastic/biodegradable/rubber/foam composites, and the use of lignin as a compatibilizer are presented. This study will increase the interest of researchers all around the globe in lignin-based polymer composites and the development of new ideas in this field.

Qualitative Research, 2010

Carol Grbich's Qualitative Data Analysis: An Introduction is a well written, practical guide for ... more Carol Grbich's Qualitative Data Analysis: An Introduction is a well written, practical guide for students and researchers alike, regardless of the reader's level of qualitative research expertise. Unlike many of its predecessors, which tend to provide practical computer-based guides and/or descriptions of the various analytical approaches to analysis, this book provides a detailed guide through the design, analysis and write up stages of a qualitative research project. The book is split into five sections which correspond to the main stages of the research process. This includes an overview of epistemological and general approaches to design and analysis in Part 1 to a discussion of specific analytical approaches including phenomenology and more recent ethnographical approaches in Part 2. The most substantial section of the text is dedicated to data analysis techniques including conventional approaches such as discourse analysis to more novel methods of visual interpretation. The final two chapters are of particular use to student researchers as they provide a detailed guide to writing up research findings and presenting different forms of data as well as providing a brief overview of the qualitative computing programmes currently available. Grbich begins her text with a guide through the history, characteristics and ongoing debates surrounding key epistemological positions including: positivism/empiricism; critical emancipatory; constructivism/interpretivism; postmodern and poststructuralist epistemologies. This first chapter provides a clear and user-friendly introduction to the main features of each position, whilst also presenting different methodological options available to researchers when adopting a specific epistemology. Dispersed within discussions of author/ researcher standpoint are useful practical tips on displaying qualitative data, such as the use of hyperlinks and footnotes to highlight potential researcher bias and data sources. 129

Neurochemistry International, 2007

Estrogen actions are mainly mediated by estrogen receptor (ER)a and ERb which in turn are regulat... more Estrogen actions are mainly mediated by estrogen receptor (ER)a and ERb which in turn are regulated by several factors including age, sex and gonadal steroid hormones 17b-estradiol and testosterone. In the present study, we have used nuclear runoff assay to examine the effect of these factors on the rate of transcription of ERa and ERb of mouse cerebral cortex. The runoff assay result was further corroborated with the measurement of steady state level of ERa and ERb mRNA by semiquantitative RT-PCR method. Our results reveal that ERa transcription rate decreases in old mice of both sexes, whereas ERb transcription rate decreases only in old females when compared to their adult counterparts. 17b-Estradiol supplementation reduces the transcription rate of ERa and ERb in all groups except in adult male while testosterone treatment down regulates the transcription rate of ERa and ERb in all groups. The semiquantitative RT-PCR analysis reveals that the level of ERa mRNA decreases in old male but shows no effect in old female as compared to adult counterpart. In contrast, ERb transcript level decreases in old mice of both sexes. Furthermore, ERa mRNA level is higher in adult female than in adult male but no sex-dependent difference is seen in ERb mRNA level. Supplementation of 17b-estradiol shows no significant alteration but testosterone reduces the ERa level in male mice, while 17b-estradiol and testosterone down regulate the ERa level in female mice of both ages. In case of ERb, 17b-estradiol decreases the transcript level in all groups except adult male while testosterone treatment results in the down regulation of transcript level in all groups. Thus these findings suggest differential effects of age, sex, 17b-estradiol and testosterone supplementation on the transcription of mouse ER genes which may account for differences in the protein levels of ERa and ERb and their functions in the brain.

Neurochemical Research, 2006

The brain undergoes many structural and functional changes during aging. Some of these changes ar... more The brain undergoes many structural and functional changes during aging. Some of these changes are regulated by estrogens which act mainly through their intracellular receptors, estrogen receptor ERa and ERb. The expression of these receptors is regulated by several factors including their own ligand estrogen, and others such as growth hormone and thyroid hormone. The levels of these factors decrease during aging which in turn influence estrogen signaling leading to alterations in brain functions. In the present paper, we review the effects of aging on brain structure and function, and estrogen action and signaling during brain aging. The findings suggest key role of estrogen in the maintenance of brain functions during aging.

Neurobiology of Aging, 2006

Estrogen receptor (ER), which mediates the multiple effects of estrogen in brain, is regulated by... more Estrogen receptor (ER), which mediates the multiple effects of estrogen in brain, is regulated by several factors including its own ligand. In the present study, we have examined the effect of age, sex and gonadal steroids (estrogen and testosterone) on the level of ER␣ and ER␤ in the cerebral cortex of AKR mice. Adult and old mice of both sexes were divided into four groups: intact, gonadectomized, 17␤-estradiol treated and testosterone treated. Western blot analysis showed higher level of ER␣ and ER␤ in the cerebral cortex of adult female than male mice. ER␤ level decreased significantly with advancing age in both sexes, whereas 17␤-estradiol supplementation decreased ER␣ level in old male and increased in old female, it also increased ER␤ level in old male and adult female. On the other hand, testosterone treatment decreased ER␣ level significantly in old female and ER␤ level in adult female but increased ER␤ level in male mice of both ages. Thus, these findings showed that the expression of ER␣ and ER␤ protein is differentially influenced by age, sex and gonadal steroids in the mouse cerebral cortex, suggesting differences in ER-mediated brain functions.

Molecular Biotechnology, 2010

Escherichia coli is one of the most common and widely used prokaryotic hosts for the expression o... more Escherichia coli is one of the most common and widely used prokaryotic hosts for the expression of recombinant proteins. The overexpression of recombinant proteins occasionally increases bacterial growth but sometimes reduces it and becomes lethal to the host cells. Here, we report the overexpression of mouse ER-β and its domains in the prokaryotic expression system and its opposite effect on the growth characteristics of E. coli. ER-β protein was immunologically detected as a 53 kDa his-tag protein in the pellet of the bacterial lysate. Its overexpression, as reflected by the total protein content and expression pattern, resulted in the decrease of bacterial growth. However, the overexpression of ER-β transactivation domain (TAD) using pIVEX and ligand binding domain (LBD) using pRSETA in E. coli BL21 (DE3) show opposite pattern. TAD was immunologically detected as 20 kDa and LBD as 22 kDa protein in the supernatant of the bacterial lysate and their overexpression increased the bacterial growth.

Molecular Biology Reports, 1989

The in vitro acetylation of HMG proteins was studied using liver slices of young (18-week) and ol... more The in vitro acetylation of HMG proteins was studied using liver slices of young (18-week) and old (138-week) male rats. Acetylation of total HMG proteins is lower in old age. The incorporation of (14C) acetate into individual HMG proteins varies remarkably with advancing age. Whereas acetylation of high mol. wt. proteins (HMG 1 and 2) is higher, that of low mol. wt. proteins (HMG 14 and 17) is lower in the liver of young rats as compared to the old ones. Spermine stimulates the acetylation of HMG 1 and 14 in young and HMG 1, 2 and 14 in old age. It inhibits the acetylation of HMG 17 in both ages. Dexamethasone decreases the level of incorporation of (14C) into HMG 1 and 17 in young and HMG 14 and 17 in old rats. On the other hand, it stimulates the acetylation of HMG 14 by two-fold in young and that of HMG 1 and 2 by more than three-fold in old rats. Such alteration in the acetylation of HMG proteins may account for age-related changes in the structure and function of chromatin.

Mechanisms of Ageing and Development, 1993

Considerable amount of data has accumulated during the past few years showing several changes in ... more Considerable amount of data has accumulated during the past few years showing several changes in gene expression as a function of age. However, the basic mechanism of aging still remains poorly understood. In this review, we have mainly analysed the data pertaining to the hypothesis that aging is associated with genetic instability and have attempted further to highlight the gaps that need to be bridged in order to have a clear picture of the aging phenomenon. Extensive investigations employing new and novel approaches are needed in future to elucidate the intricately interwoven patterns of molecular control that underlie the various aspects of gene expression during aging.

Journal of Molecular Neuroscience, 2010

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulatio... more Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid beta peptides, which are produced by the proteolytic cleavage of amyloid precursor protein (APP). As the incidence of AD is higher in females and sex steroids are implicated in this disease, we have examined the effect of sex steroids (testosterone and 17β-estradiol) on the expression of APP mRNA and protein in the cerebral cortex of adult and old mice of both sexes. Northern blot analysis detected APP mRNA as a single 3.5-kb band and its level is increased in old as compared to adult. Following gonadectomy, its level was upregulated in female mice but downregulated in male mice. Supplementation with testosterone or estradiol decreased its levels in female mice of both ages. Testosterone supplementation increased the mRNA levels in both adult and old male mice. Estrogen supplementation decreased its level in adult but increased in old male mice. Western blot analysis detected APP specific bands ranging from 95 to 125 kD. The level of 95 kDa band representing APP695 protein showed difference in levels with age or hormone treatment. These results provide evidence for increase in APP mRNA level in the cerebral cortex of old mice and its regulation by sex steroids during aging.

International Journal of Polymeric Materials and Polymeric Biomaterials, 2013

ABSTRACT In view of recent technological significance of green cellulosic polymers in environment... more ABSTRACT In view of recent technological significance of green cellulosic polymers in environmentally friendly materials, the present study is an attempt to synthesize Saccaharum cilliare-graft-poly (ethyl acrylate) (Saccaharum cilliare-g-PEA) copolymers via pressure-induced free-radical polymerization. The effect of pressure, time, ratio of monomer, solvent, and initiator concentrations were determined to get the premier percentage of grafting. It has been observed from this study that the physicochemical and thermal properties of the grafted cellulosic polymers have increased to a considerable extent and can be a potential material for a number of applications.

International Journal of Polymer Analysis and Characterization, 2012

The increasing demand for green, environmentally friendly materials has resulted in new natural f... more The increasing demand for green, environmentally friendly materials has resulted in new natural fiber–based materials as replacements for nondegradable materials derived from petroleum resources that are currently being used for a number of applications. Hence, this study deals with long fiber–reinforced green polymer composites fabricated using the compression molding technique. Initially, green composites were produced with long fibers using 10,

International Journal of Polymer Analysis and Characterization, 2013

ABSTRACT Increasing environmental concerns and depletion of petroleum resources has forced resear... more ABSTRACT Increasing environmental concerns and depletion of petroleum resources has forced researchers around the globe to find new green materials. In the present research work, a particular interest was focused on the effective use of lignocellulosic natural fibers as reinforcement using polymer resin as a novel matrix. Green composites were prepared using the compression molding technique with different fiber contents. The physicomechanical and thermal characteristics of the different composite samples were investigated as a function of fiber contents. The results obtained suggest that the properties of the polymer matrix are positively affected by the incorporation of natural cellulosic fibers.

Clinical and Experimental Pharmacology and Physiology, 2007

1. For animals of all ages, during activation of skeletal muscles and the subsequent contraction,... more 1. For animals of all ages, during activation of skeletal muscles and the subsequent contraction, the balance between the force developed by the muscle and the external load determines whether the muscle shortens, remains at fixed length (isometric) or is lengthened. With maximum activation, the force developed is least during shortening, intermediate when muscle length is fixed and greatest during lengthening contractions. During lengthening contractions, when force is high, muscles may be injured by the contractions. 2. 'Frailty' and 'failure to thrive' are most frequently observed in elderly, physically inactive people. A 'frail' person is defined as one of small stature, with muscles that are atrophied, weak and easily fatigued. The condition of 'failure to thrive' is typified by a lack of response to well-designed programmes of nutrition and physical activity. 3. With ageing, skeletal muscle atrophy in humans appears to be inevitable. A gradual loss of muscle fibres begins at approximately 50 years of age and continues such that by 80 years of age, approximately 50% of the fibres are lost from the limb muscles that have been studied. For both humans and rats, the observation that the timing and magnitude of the loss of motor units is similar to that for muscle fibres suggests that the mechanism responsible for the loss of fibres and the loss of whole motor units is the same. The degree of atrophy of the fibres that remain is largely dependent on the habitual level of physical activity of the individual. 4. 'Master athletes' maintain a high level of fitness throughout their lifespan. Even among master athletes, performance of marathon runners and weight lifters declines after approximately 40 years of age, with peak levels of performance decreased by approximately 50% by 80 years of age. The success of the master athletes and of previously sedentary elderly who undertake well-designed, carefully administered training programmes provide dramatic evidence that age-associated atrophy, weakness and fatigability can be slowed, but not halted.

Cellular and Molecular Neurobiology, 2010

The allelic variant of apolipoprotein (Apo) E4 is a known risk factor for the development of most... more The allelic variant of apolipoprotein (Apo) E4 is a known risk factor for the development of most common late onset form of Alzheimer's disease (AD). As aging is associated with reduced circulating level of gonadal steroid hormones, hormone replacement therapies have been used for the possible treatment of AD. Both estrogen and testosterone have beneficial effects on brain due to interaction with apoE, but the underlying mechanism is still not clear. In this article, we report the effects of gonadectomy and hormone supplementation on apoE protein level in male and female mouse cerebral cortex during normal aging. We could not get any effect of gonadectomy and estradiol or testosterone treatment in adult and old mice of either sex. This suggests that during normal aging apoE protein level is not affected due to steroid hormone withdrawal or supplementation in the mouse cerebral cortex.

Cellular and Molecular Neurobiology, 2010

Following binding to cognate ligand, estrogen receptor (ER) b interacts with specific responsive ... more Following binding to cognate ligand, estrogen receptor (ER) b interacts with specific responsive elements of the target genes and recruits a host of nuclear proteins for hormone dependent gene regulation. However, it is poorly known which proteins interact with ER b in mouse brain and whether their interaction and expression change with age. In this report, we have used his-tag mouse ER b for interaction with nuclear proteins of cerebral cortex of young (6 ± 1 weeks), adult (25 ± 2 weeks), and old (70 ± 5 weeks) female mice. We have identified estrogen receptor-associated protein (ERAP) 140 as one of the interacting proteins and studied its interaction by pull down immunoblotting, far-Western blotting and immunoprecipitation, and expression by western blotting. The data show that ERAP 140 interacts with ER b and its interaction decreases but its expression increases with age in mouse cerebral cortex, suggesting its role in estrogen-mediated brain functions during aging.

Carbohydrate Polymers, 2014

Research highlights Interest in natural cellulosic polymers is increasing rapidly New frontie... more Research highlights Interest in natural cellulosic polymers is increasing rapidly New frontiers and potential applications of natural cellulose polymers highlighted Processing, surface modifications and different characterizations of natural cellulose polymers Focus on sustainability and future perspectives of natural cellulose polymers/ composites.

Carbohydrate Polymers, 2013

Cellulose is the most abundant natural polysaccharide polymer, which is used as such or its deriv... more Cellulose is the most abundant natural polysaccharide polymer, which is used as such or its derivatives in a number of advanced applications, such as in paper, packaging, biosorption, and biomedical. In present communication, in an effort to develop a proficient way to rapidly synthesize poly(methyl acrylate)-graftcellulose (PMA-g-cellulose) copolymers, rapid graft copolymerization synthesis was carried out under microwave conditions using ferrous ammonium sulfate-potassium per sulfate (FAS-KPS) as redox initiator. Different reaction parameters such as microwave radiation power, ratio of monomer, solvent and initiator concentrations were optimized to get the highest percentage of grafting. Grafting percentage was found to increase with increase in microwave power up to 70%, and maximum 36.73% grafting was obtained after optimization of all parameters. Fourier transforms infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA/DTA/DTG) analysis were used to confirm the graft copolymerization of poly(methyl acrylate) (PMA) onto the mercerized cellulose. The grafted cellulosic polymers were subsequently subjected to the evaluation of different physico-chemical properties in order to access their application in everyday life, in a direction toward green environment. The grafted copolymers demonstrated increased chemical resistance, and higher thermal stability.

Carbohydrate Polymers, 2013

Cellulose, a linear polysaccharide polymer with numerous glucose monosaccharide units is of enorm... more Cellulose, a linear polysaccharide polymer with numerous glucose monosaccharide units is of enormous interest because of its applications in biosorption, biomedical, packaging, biofiltration and biocomposites. In this study, cellulose-graft-poly(butyl acrylate) copolymers were synthesized under microwave conditions. Effects of microwave radiation doses and different reaction parameters were optimized to get the optimum percentage of grafting. The dependence of optimum conditions for better physico-chemical properties of the cellulosic polymers was also determined. Fourier transform infrared spectroscopy (FT-IR) analysis was used to authenticate the chemical reaction taking place between cellulosic polymers and monomer. The thermogravimetric behavior of the raw and grafted cellulosic polymers was characterized by thermogravimetric analysis (TGA). The surface structure of the raw and grafted cellulosic polymers was analyzed through scanning electron microscopy (SEM). The graft copolymers have been found to be more moisture resistant and also showed better chemical and thermal resistance.