Browsing by Author "Lal, AV"

Now showing 1 - 12 of 12
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    1,25-dihydroxyvitamin D-3 receptor is upregulated in aortic smooth muscle cells during hypervitaminosis D
    (LIFE SCIENCES, 2002)
    Several studies have demonstrated that excess of vitamin D-3 is toxic particularly to vascular tissues. A notable pathological feature is arterial calcification. The nature of the toxic metabolite in hypervitaminosis D and the pathogenesis of arterial calcification are not clearly understood. The present study was undertaken to explore whether arterial calcification is a sequel of increased calcium uptake by arterial smooth muscle mediated by up regulation of vitamin D receptor in the cells in response to elevated circulating levels of vitamin D-3 in serum. The experimental study was performed in 20 New Zealand white female rabbits aged 6 months. Animals in the test group were injected 10,000 IU of cholecalciferol intramuscularly twice a week for one month. Six control animals were given intra-muscular injections of plain cottonseed oil. Animals were sacrificed and aortas were examined for pathological lesions, 1,25-dihyroxyvitamin D-3 (1,25(OH)(2) D-3) receptor levels and Ca-45 uptake in smooth muscle cells. Serum samples collected at intervals were assayed for levels of 25-OH-D-3 and calcium. The results showed that in animals given injections of cholecalciferol, serum levels of 25-OH-D-3 Were elevated. In four of these animals calcification and aneurysmal changes were seen in the aorta. Histological lesions comprised of fragmentation of elastic fibers as well as extensive loss of elastic layers. 1,25(OH)(2) D-3 receptor levels were up regulated and Ca-45 uptake enhanced in aortas of animals which were given excessive vitamin D-3. The evidences gathered suggest that excess vitamin D is arteriotoxic and that the vitamin induces arterial calcification through up regulation of 1,25(OH)(2)D-3 receptor and increased calcium uptake in smooth muscle cells of the arteries. (C) 2002 Elsevier Science Inc. All rights reserved.
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    An improved method for isolation of anti-viper venom antibodies from chicken egg yolk
    (JOURNAL OF BIOCHEMICAL AND BIOPHYSICAL METHODS, 2002)
    The production of antibodies and its purification from mammalian blood has been found low yielding and laborious. Therefore, anti snake venom antibodies for therapeutic use is obtained mostly as polyvalent whole serum or partially purified polyvalent immunoglobulin. The side effects of anti snake venom (ASV) therapy are mainly serum sickness and renal failure, which may be reduced by using sufficiently Pure antibodies. Therefore, we have standardized a simple method for production If purified antivenom. Here, we present the development of polyclonal antibodies against viper venom in liens and its isolation from the c,, yolk of immunized birds. We have modified the reported methods of purification of immunoglobulin from egg yolk, and thus yielded 90% purity of the protein. The modified method involves only two steps, such as removal of lipids from the diluted egg yolk by a freeze-thaw cycle and centrifugation, followed by gel filtration on Biogel P-150. The advantages are that the process is very simple, and from one egg, 100+/-20 mg of pure immunoglobulin is obtained. The antibodies are present in the egg for up to 100 days after the immunization. Thus, using small amounts of venom, a large quantity of the immunoglobulin is obtained in a sufficiently pure form. The antigen binding ability of the pure antibody is found good by the Ouchterlony's double diffusion experiment. (C) 22002 Published by Elsevier Science B.V.
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    Comparative evaluation of absorbable hemostats: advantages of fibrin-based sheets
    (BIOMATERIALS, 2004)
    Bioactive hemostats and wound dressings consist of either inherently active materials or act as delivery vehicles which contain such materials. Fibrin is a natural hemostat and scaffold, guiding the direction of wound contraction and closure. In order to improve the ease of application of liquid fibrin glue, we have made a freeze-dried form of polymerized fibrin that supports hemostasis and wound healing. The bleeding from the middle ear artery of rabbits was found to be arrested instantaneously on application of fibrin sheets, even when the animal was heparinized systemically. As the fibrin sheet was found to be fragile, gelatin was incorporated to the sheet and thus the mechanical stability was improved without compromising the hemostatic effect. The efficacy of the fabricated fibrin and fibrin-gelatin sheets to seal traumatized rat liver was compared with commercially available hemostats, Abgel (cross-linked gelatin) and Surgicel (cross-linked cellulose). Tissue compatibility of all the hemostats was studied by analyzing the liver tissue 15 days after application. While the hemostatic effect was best with fibrin and fibrin-gelatin sheets, both Surgicel and Abgel were not capable of arresting the bleeding quickly. Gross analysis of tissue on the 15th day of application, visibly, Abgel was not only degraded but resulted in severe adhesions of internal organs and histologically capsule formation around the implant was evident. Though Surgicel was also seen as cream soft material on the site of application that joined two pieces of liver, there was no adhesion of other internal organs and histologically, immune reaction and foreign-body-type giant cells were present in large amounts. Fibrin was not found grossly on application site whereas fibrin-gelatin was seen as a small white spot. Granulation tissue formation and cell migration into the fibrin-based sheets were evident, and therefore, fibrin-based sheets are not only efficient hemostats but showed optimum degradation and wound healing. (C) 2004 Elsevier Ltd. All rights reserved.
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    Development of a fiber optic delivery system for the application of laser in vascular diseases
    (PROCEEDING OF THE FIRST REGIONAL CONFERENCE - IEEE ENGINEERING IN MEDICINE & BIOLOGY SOCIETY AND 14TH CONFERENCE OF THE BIOMEDICAL ENGINEERING SOCIETY OF INDIA, 1995) Ramachandran, T; Lal, AV; Mandalam, KR
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    Fibrinolysis inhibitors adversely affect remodeling of tissues sealed with fibrin glue
    (BIOMATERIALS, 2003)
    Experiments have been carried out to determine if aprotinin and epsilon-amino caproic acid increases the quality of Fibrin glue. A rat model was used for tissues such as liver and skin while rabbits were used for application of glue in dura mater. Apposition of all the tissues, glued with fibrin was found to be good and remnants of the polymerized fibrin were seen even on the seventh day of application, though inhibitors were not incorporated with the glue. In skin, excessive amounts of fibrin remained as a result of addition of aprotinin and epsilon-amino caproic acid, as compared to the glue applied without any inhibitor. After dural sealing, the wound repair and new bone formation at cramotomy site progressed well in the fibrin glue applied area as compared to the commercially available glue that contained aprotinin. The adhesive strength of the glue without or with fibrinolysis inhibitors was found to be similar, after 1 h grafts on rat back. The observations from this study suggests that the use of aprotinin with fibrin glue may not be required because, even liver tissue that is known to have high fibrinolytic activity was sealed and repaired well in the absence of plasminogen inhibitors. On the other hand, it was found that if inhibitors were added, nondegraded matrix remained in the tissue even after 15 days and affected migration of repair cells. Thus, the inhibition of fibrinolysis after fibrin glue application is found detrimental to wound healing. (C) 2002 Elsevier Science Ltd. All rights reserved.
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    Osteogenesis of a bioactive ceramic calcium phospho silicate composite system in goat femur defect.
    (International Journal of Applied Ceramic Technology., 2011) John, A; Mani, S; Sandeep, G; Babu, SS; Lal, AV; Varma, HK
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    Osteogenesis of a Bioactive Ceramic-Calcium Phosphosilicate Composite System in Goat Femur Defect
    (INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, 2011) John, A; Mani, S; Gopalakrishnan, S; Babu, S; Lal, AV; Varma, H
    In spite of the array of synthetic bone grafts available, the pursuit for an ideal graft continues. In view of this, a synthetic bioactive calcium phosphosilicate composite (HABGS) has been developed combining the properties of hydroxyapatite and silicate system. The in vivo performance of HABGS granules in goat femur defect stimulated a favorable environment for de novo bone formation with faster resorption. The ceramic composite is attractive for its low Si content together with its negligible levels at implanted sites and vital organs postimplantation. Herein, we propose the safety and efficacy of this composite as a promising bone substitute.
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    Pattern of cardiac fibrosis in rabbits periodically fed a magnesium-restricted diet and administered rare earth chloride through drinking water
    (BIOLOGICAL TRACE ELEMENT RESEARCH, 1998)
    It has been postulated that causation of the tropical cardiomyopathy endomyocardial fibrosis (EMF) is linked to magnesium (Mg) deficiency and cardiac toxicity of the rare earth element cerium (Ce). The aim of the present study was to define the myocardial lesions in rabbits that were fed on Mg-restricted diet (70-80 ppm) periodically and were provided drinking water contaminated with rare earth chloride (1 g/L). Forty New Zealand white rabbits were divided into four groups following a 2 x 2 factorial design. Two groups were periodically fed on Mg-restricted diet with one of them receiving water contaminated with rare earth chloride. The other two groups were continuously fed on Mg-sufficient diet (350-400 ppm) with one of them receiving water contaminated with rare earth chloride. AU animals were sacrificed at the end of 6 mo. Cardiac tissues were subjected to histology, elemental analysis (calcium [Ca], Mg, and Ce) and estimation of collagen content and collagen phenotypes. Histological lesions were compared with those of EMF in humans and those of acute Mg deficiency in animals. The results suggest that in rabbits, recurrent episodes of Mg deficiency lead to myocardial fibrosis similar to the pattern observed in human EMF.
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    Progesterone release from glutaraldehyde cross-linked casein microspheres: In vitro studies and in vivo response in rabbits
    (CONTRACEPTION, 2000)
    Microspheres of bovine milk protein casein loaded with progesterone were fabricated by glutaraldehyde cross-linking of an aqueous alkaline solution of the protein dispersed in a hexane and dichloromethane non-aqueous dispersion medium with an aliphatic polyurethane as the stabilizer. Microspheres were characterized for their surface morphology and internal structure using scanning electron microscopy. In vitro release studies in phosphate buffer at 37 degrees C demonstrated that the rate of release of the steroid from the microsphere matrix was a function of cross-linking density, particle size, and drug payload. Microsphere formulations released 50% to 60% of the incorporated steroid in about 30 days and, thereafter, attained a steady state. in the presence of a protein-digesting enzyme such as protease, complete release of the steroid was observed in about 4 days in vitro into phosphate buffer. Intramuscular injection of progesterone-loaded microspheres into rabbits showed a plasma concentration of 1 to 2 ng/mL up to 5 months without any significant burst effect, whereas the powdered steroid administered in saline demonstrated a large burst effect peaking over 20 ng/mL, and the plasma concentration was not sustained beyond 4 days. Data obtained suggest that casein microspheres would be promising as a biodegradable drug carrier for sustained delivery of steroids. (C) 2000 Elsevier Science Inc. All rights reserved.
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    Progesterone-loaded chitosan microspheres: a long acting biodegradable controlled delivery system
    (JOURNAL OF CONTROLLED RELEASE, 1998)
    Smooth, highly spherical, crosslinked chitosan microspheres in the size range of 45-300 mu m loaded with progesterone were prepared by glutaraldehyde crosslinking of an aqueous acetic acid dispersion of chitosan containing progesterone in a non-aqueous dispersion medium consisting of liquid paraffin and petroleum ether stabilized using sorbitan sesquioleate. Ln vitro release of the drug into phosphate buffer at 37 degrees C was determined as a function of crosslinking density of the microspheres and particle size. The extent of drug release had a remarkable dependence on the crosslinking density of the microspheres, the highly crosslinked spheres releasing only around 35% of the incorporated steroid in 40 days compared to 70% from spheres lightly crosslinked. Determination of the in vivo bioavailability of the steroid from microsphere formulation by intramuscular injection in rabbits showed that a plasma concentration of 1 to 2 ng/ml was maintained up to 5 months without a high 'burst effect'. Data obtained suggest that the crosslinked chitosan microspheres would be an interesting system for long term delivery of steroids, (C) 1998 Elsevier Science B.V.
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    Short term tissue response to carbon fibre: A preliminary in vitro and in vivo study
    (BULLETIN OF MATERIALS SCIENCE, 1998) Mohanty, M; Kumary, TV; Lal, AV; Sivakumar, R
    Carbon in the form of pyrolytic carbon coating is used in a number of implantable medical devices. Carbon-reinforced carbon composite and other forms of diamond-like carbon coatings are being evaluated for their many potential biomedical applications. There is also a possibility of using carbon in fibre form. Though the possibility of using the fibre form of carbon in skeletal and dental implants has been recognized, a detailed study of tissue reaction to carbon fibre has not been reported so far. In this paper, we describe in vitro and irt vivo evaluation of carbon fibre in bone and muscle. Good cell and tissue biocompatibility of the material was observed in bone and muscle. New bone was present in contact with the fibres. Results of this study indicate that carbon fibre has potential in non-load bearing applications, such as skeletal repair and as ligament prosthesis.
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    TNF-alpha depresses endocardial endothelial cell mediated proliferation of cardiac fibroblasts
    (JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY, 2005) Kuruvilla, L; Nair, RR; Lal, AV; Umashankar, PR; Kartha, CC