K. Thomas Joseph

Influence of isoproterenol-induced myocardial infarction on certain glycohydrolases and cathepsins in rats

The changes in the activities of certain lysosomal hydrolases, viz., beta-glucuronidase, beta-N-acetylglucosaminidase, beta-galactosidase, beta-glucosidase, alpha-glucosidase, alpha-galactosidase, alpha-mannosidase, cathepsin B, cathepsin D, and collagenolytic cathepsin, in serum and heart of rats subject to myocardial infarction with isoproterenol, were studied during the periods of peak infarction and recovery. The activities of all the enzymes assayed exhibited a significant increase both in serum and in heart at peak infarction stage and these levels returned to normal during the stage of recovery and repair. The infiltration of inflammatory cells at the infarct regions and the altered lysosomal fragility are probably responsible for the increased activity of the enzymes studied. This may also bring about the catabolism of connective tissue constituents as reported in literature.

Grafting of butyl acrylate onto gelatin in a water-isopropanol medium

Abstract Graft copolymerization of butyl acrylate onto gelatin using potassium persulphate initiator was studied in a water-isopropanol medium. The crude graft copolymers were soxhlet extracted with acetone to remove the loosely bound ungrafted homopolymer. The influence of a number of experimental factors such as effect of time, monomer concentration, initiator concentration, backbone concentration and temperature on the graft copolymerization of gelatin were investigated.

Grafting of methyl methacrylate onto cellulose nitrate initiated by benzoyl peroxide

It has been observed that grafting of vinyl monomers onto cellulose nitrate in solution takes place using benzoyl peroxode. The graft copolymer was isolated from the unreacted backbone and homopolymer by selective solvent extraction. The effect of variables, such as the initiator concentration, the monomer concentration and the reaction time on the percent grafting and the grafting efficiency, were discussed. A probable mechanism for grafting of vinyl monomers to cellulose nitrate in solution has been proposed.

Graft copolymerization of 2-hydroxyethyl methacrylate and methyl methacrylate onto hide powder

Abstract Graft copolymerization of 2-hydroxyethyl methacrylate(HEMA) and mixtures of HEMA with methyl methacrylate (MMA) onto hide powder was attempted using ceric ammonium nitrate as initiator, with a view to optimize the conditions for graft copolymerization. Percent grafting and grafting efficiency were calculated for various variables such as monomer concentration, initator concentration and mole ratio of HEMA to MMA. R p , R g and R h (rates of polymerization, grafting and homopolymerization respectively) were also evaluated. It was observed that R p increased linearly with increasing concentration of MMA except at very low concentrations of the monomer. An explanation is given for the effect of variables on extent of grafting and grafting efficiency.

Grafting of Acrylonitrile onto Gelatin in Zinc Chloride Medium

Abstract Grafting of gelatin with acrylonitrile in zinc chloride medium has been studied using potassium persulfate as the initiator. The rate of grafting, grafting efficiency, and percentage of grafting are calculated. The grafting results are discussed in the light of the rate of grafting. The enhanced activity of the monomer is due to the formation of AN … ZnCl2 complexes.

Graft Copolymerization of Acrylic Monomers onto Biopolymers. Part I. Grafting of Poly(butyl Acrylate) onto Gelatin

Abstract Gelatin was graft copolymerized with poly(butyl acrylate) using potassium peroxy disulfate in aqueous medium. Effects of temperature, time, monomer concentration, and backbone concentration were studied. The percent grafting was found to increase initially and then decreased in all cases. Infrared, viscosity, and thermal analysis were carried out on the graft copolymers, and the mechanism of the graft copolymerization reaction was discussed.

Studies on the reactive groups of collagen. I. Acylation and guanidino group destruction

Abstract 1. 1. Collagen was benzoylated with benzoyl chloride or benzoic anhydride under several conditions. The maximum amount of benzoyl groups introduced was only 0.7 mmoles/g. collagen. 2. 2. It has been shown that the benzoyl groups are attached to the amino and guanidino groups of collagen. 3. 3. Methods for quantitative as well as for selective acetylation of collagen were developed. The quantitative acetylation of all the amino and hydroxyl groups of collagen was effected. The maximum amount of acetyl groups introduced was 2.1 mmoles/g. collagen. 4. 4. About 50% of the hydroxyl groups of collagen were acetylated selectively without materially affecting the amino groups by means of acetic anhydride in the presence of thiocyanic acid. 5. 5. All the free amino groups and only a small portion of the hydroxyl groups were involved in the acetylation of collagen with acetyl pyridinium chloride. 6. 6. The transesterification method for the quantitative estimation of total acetyl groups was standardized. 7. 7. About 70% of arginine and about 17% of histidine in collagen were destroyed by treatment with sodium hypobromite.

Thermal properties of polyurethanes cross-linked with chlorinated rubber graft copolymers

Abstract Polyurethane prepolymers, prepared from castor oil, propylene glycol (MW 2000) and toluene diisocyanate, have been cross-linked using a graft copolymer of chlorinated rubber (CR). The grafted chain is a terpolymer of n-butyl methacrylate (nBMA), ethyl acrylate (EA) and 2-hydroxyethyl methacrylate (HEMA). The glass transition temperature (T g ), thermal stability and degradation kinetics were evaluated for different urethane systems in which the proportion of graft copolymer and HEMA content (i.e. functionality) was varied. The broadening observed in the glass transition is assumed to be due to the effect of mixing of graft copolymer which functioned as a reactive diluent. The increase in T g is explained on the basis of total cross-link density and copolymer effect. In TGA, the major weight loss was observed in two stages in all the systems studied. Degradation was observed only above 225°C. The energy of activation (E) associated with the degradation of the networks was evaluated by expressions appropriate to degradation kinetics. The values of E so obtained are in good agreement with each other.

Influence of Monomer and Initiator Concentrations on the Simultaneous Grafting of Several Monomers onto Insoluble Collagen

Abstract Simultaneous grafting of 2-hydroxyethyl methacrylate and methyl methacrylate (3:1 and 3:2 mole ratios) onto insoluble collagen with ceric ammonium nitrate as initiator was attempted with a view to optimizing conditions for the preparation of hydrogels. The influence of monomer and initiator concentrations on the grafting reactions was investigated. The grafting results are discussed in the light of grafting efficiency and percentage of grafting. They were found to be lower when the 3:1 mole ratio of monomers was used.

Chemically Modified Natural Polymers as Biomaterials 1. Polysaccharide-Gelatin Conjugates

SummaryNatural biopolymers such as carboxymethyl cellulose and alginic acid which contain carboxyl functional groups were converted to the corresponding azides. These azides were then reacted by coupling-grafting method with the ε-amino groups of gelatin. Positive proof of grafting of these natural polymers to gelatin was obtained based on the results of nitrogen analysis and IR spectra. These derivatives were found to be of wide interest in the field of biomedical polymers.