Browsing by Author "Umashankar, PR"

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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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    A method for arterial blood pressure measurement in conscious restrained rabbits
    (INDIAN VETERINARY JOURNAL, 1998) Umashankar, PR; Lal, GAV
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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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    Anaesthetic regimen for coronary stenting in porcine model
    (INDIAN VETERINARY JOURNAL, 2006) Harikrishnan, VS; Shenoy, SJ; Umashankar, PR
    Coronary stent is one of the medical devices that is used in the treatment of localized atherosclerotic plaques in coronary artery. A suitable animal model is an essential step involved in stabilizing the safety and efficacy of implants. Swine is the animal model of choice for cardiovascular implantables (Francis et al., 1986; Martin et al., 1995 and Hughes, 1986), and is used as the animal model for coronary stent evaluation (Schulz et al., 2000). Since the normal porcine coronary artery is hypersensitive to surgical manipulations and anaesthetics (Michael et al., 1986), swine is prone to cardiac fibrillations and dysrhythmias. Halothane sensitizes the myocardium to endogenous catacholamines such as adrenaline, which can produce cardiac arrhythmias (Paddleford, 1984). An anesthetic technique found effective in performing coronary stenting with good results in 32 pigs is discussed in this article.
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    An automated data acquisition system for capturing physiological parameters during animal trials of artificial heart valves
    (International journal of Biomedical Engineering and Technology, 2012-10) Sujesh, S; Rajeev, A; Shenoy Sachin, J; Umashankar, PR; Muraleedharan, CV
    Animal trials form an important phase of any medical device development, especially in the context of implantable devices like artificial heart valves. Monitoring and recording parameters such as physiological pressures and Electrocardiogram (ECG) is essential for assessing the performance of the valve. A dedicated automated data acquisition system was developed for capturing these vital characteristics during implantation, immediately post operative and prior to the explantation of the device. The hardware was designed around the PXI (Pci eXtension for Instrumentation) modular data acquisition chassis and the software was developed using LabVIEW (both National Instruments, USA). A set of transducers was identified, validated and incorporated into the system for converting physical signals to analogue electrical signals. The system was employed in more than fifteen animal experiments and found to be extremely useful for automated data capturing. It provided valuable sets of additional data for many specific studies like analysis of valve sounds, which would not have been possible if the conventional approach to animal experiments and data collection was used. A well planned strategy for collecting maximum useful data from animal experiments goes well along with the reduction alternative of the 3R strategies of replacement, reduction and refinement of animal experiments.
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    Bone growth response with porous hydroxyapatite granules in a critical sized lapine tibial-defect model
    (Bulletin of Materials Science., 2002) John, A; Abiraman, S; Varma, HK; Kumar, TV; Umashankar, PR
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    Cerebral protection for the preclinical evaluation of a vascular graft in sheep carotid artery model
    (SCANDINAVIAN JOURNAL OF LABORATORY ANIMAL SCIENCE, 2015) Harikrishnan, VS; Umashankar, PR
    A protocol for cerebral protection without systemic hypothermia to aid the safe, smooth and fast recovery of sheep used for the preclinical evaluation of a, prosthetic vascular graft in the carotid artery is presented in this study. Ten adult Ramnad white sheep (33.8 +/- 3.2 kg) were green grass deprived and anticoagulated from 5 days prior to surgery with aspirin 150 mg and clopidogrel 75 mg till the end of the study. After anesthetic premedication and endotracheal intubation, the animals were ventilated at the rate of 12 breaths/min and tidal volume of 12 ml/kg. Ten minutes prior to carotid artery clamping (right unilateral internal carotid artery) which was performed after heparinisation, pharmacologic mitigation was done for cerebral protection with a total dose of thiopentone 50 mg (2.5%), 8 mg dexamethasone, 100 mg hydrocortisone and 15 ml (7.5% w/v) sodium bicarbonate as i/v bolus and 250 ml dextran 40 (10% w/v) at 40 ml/hour as i/v drip. Mean values of arterial pressure and heart rate were 94 +/- 16 mmHg and 88 +/- 11 min(-1) respectively, over the entire intra operative period. A moderate alkalosis which occurred in all animals under anaesthesia was postulated to supplement cerebral protection and was corrected by reducing the respiratory rate and tidal volume to 10 breaths/min and 10ml/kg respectively. Significant variation in pH (p<0.05) was observed at 90, 120, 150 and 180 minutes after induction of anaesthesia. Significant variation in MAP (p<0.05) was observed at 180 minutes after premedication, which was related to alkalosis and resultant hypokalemia and was effectively corrected with 31 +/- 7 meq potassium chloride (40 meq in 500 ml ringer lactate). The total procedure lasted 126 +/- 18 minutes and total unilateral right carotid arterial clamping time was 36.7 +/- 6.5 minutes. 28 +/- 5 minutes after spontaneous respiration, the animals were extubated and moved to the postoperative cage. Three doses of nadroparine 3800 IU s/c at 12 hour intervals were given postoperatively. All animals were free from any neurological deficits, which showed the effectiveness of the perioperative protocol encompassing the cerebral protective medication.
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    Cerebral protection for the preclinical evaluation of a vascular graft in sheep carotid artery model.
    (Scandinavian Journal of Laboratory Animal Science, 2016-08) Harikrishnan, VS; Umashankar, PR
    A protocol for cerebral protection without systemic hypothermia to aid the safe, smooth and fast recovery of sheep used for the preclinical evaluation of a prosthetic vascular graft in the carotid artery is presented in this study. Ten adult Ramnad white sheep (33.8± 3.2 kg) were green grass deprived and anticoagulated from 5 days prior to surgery with aspirin 150 mg and clopidogrel 75 mg till the end of the study. Aft er anesthetic premedication and endotracheal intubation, the animals were ventilated at the rate of 12 breaths/min and tidal volume of 12 ml/ kg. Ten minutes prior to carotid artery clamping (right unilateral internal carotid artery) which was performed aft er heparinisation, pharmacologic mitigation was done for cerebral protection with a total dose of thiopentone 50 mg (2.5%), 8 mg dexamethasone, 100 mg hydrocortisone and 15 ml (7.5% w/v) sodium bicarbonate as i/v bolus and 250 ml dextran 40 (10% w/v) at 40 ml/hour as i/v drip. Mean values of arterial pressure and heart rate were 94±16 mmHg and 88±11 min-1 respectively, over the entire intra operative period. A moderate alkalosis which occurred in all animals under anaesthesia was postulated to supplement cerebral protection and was corrected by reducing the respiratory rate and tidal volume to 10 breaths/min and 10ml/kg respectively. Signifi cant variation in pH (p<0.05) was observed at 90, 120, 150 and 180 minutes aft er induction of anaesthesia. Signifi cant variation in MAP (p<0.05) was observed at 180 minutes aft er premedication, which was related to alkalosis and resultant hypokalemia and was eff ectively corrected with 31±7 meq potassium chloride (40 meq in 500 ml ringer lactate). Th e total procedure lasted 126±18 minutes and total unilateral right carotid arterial clamping time was 36.7±6.5 minutes. 28±5 minutes aft er spontaneous respiration, the animals were extubated and moved to the postoperative cage. Th ree doses of nadroparine 3800 IU s/c at 12 hour intervals were given postoperatively. All animals were free from any neurological defi cits, which showed the eff ectiveness of the perioperative protocol encompassing the cerebral protective medication
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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 decellularised animal tissue for cardiovascular application ( Project - 8016 )
    (SCTIMST, 2011-12-31) Umashankar, PR; Anil S, Das; Krishna Manohar, SR; Muraleedharan, CV; Nagesh, DS; Maya, Nandakumar; Binoy, VS
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    Effect of blood flow on drug release from DES: An experimental study
    (INTERNATIONAL JOURNAL OF CARDIOLOGY, 2009) Umashankar, PR; Hari, PR; Sreenivasan, K
    DES has made stenting a successful treatment modality. Still problems exists such as late thrombosis and continued neo-intimal proliferation. Blood flow affects the drug retained in the stent and subsequently on the time frame of vascular healing. To find out drug release kinetics from DES implanted in two different flow conditions, DES were implanted in porcine carotid artery and coronary artery. The drug release kinetics was found out by estimating the drug retained in the stent at different time periods. Through this study it is shown that DES in the coronary artery has a T1/2 of 24 days compared to 2 days in the carotid artery. The difference in T1/2 is attributed to the difference in flow as estimated using Hagen - Poiseuille equation. Evaluation of DES through heterotopic implantation may yield false results due to flow discrepancy. Moreover flow conditions should also be considered while designing the drug matrix to have optimum clinical efficacy. (C) 2007 Elsevier Ireland Ltd. All rights reserved.
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    Effect of chronic inflammation and immune response on regeneration induced by decellularised bovine pericardium
    (JBMR Part A, 2016-08) Umashankar, PR; Arun, T; Kumari, TV
    Decellularised tissue produces a variety of host responses ranging from constructive remodeling to scarring on account of its differences in the source of tissue, processing or sterilization methods. In this study, in vivo regeneration induced by decellularised bovine pericardium with or without mild glutaraldehyde crosslinking was studied in relation to its immune and inflammatory response using rat abdominal regeneration model. Mild glutaraldehyde crosslinking was done to subdue inflammatory and immune response without compromising host cell incorporation and graft remodeling. Evaluations were done at both 21 and 90 days. Un-crosslinked decellularised bovine pericardium showed more intense macrophage response predominantly of M2 phenotype at 90 days indicating chronic inflammatory response compared to mildly crosslinked group. This group also showed significant increase in plasma cell and lymphocyte count indicating immune stimulation. Lymphocyte transformation test detected presence of bovine pericardial antigen sensitized lymphocytes at both periods in un-crosslinked group. Lymphocytes from mildly crosslinked group failed to respond in this test at both periods. Significantly higher antibody response was also noted at both periods in un-crosslinked group. However, abdominal wall regeneration was observed only in animals implanted with un-crosslinked decellularised bovine pericardium at 90 days. From the above findings, it is inferred that un-crosslinked decellularised bovine pericardium produced significant chronic inflammatory response at 90 days and stimulated both humoral and cell mediated immune response in comparison to mildly crosslinked decellularised bovine pericardium. Yet this group produced skeletal muscle formation within graft at 90 days.
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    Effect of chronic inflammation and immune response on regeneration induced by decellularized bovine pericardium
    (JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A, 2013) Umashankar, PR; Arun, T; Kumary, TV
    Decellularised tissue produces a variety of host responses ranging from constructive remodeling to scarring on account of its differences in the source of tissue, processing or sterilization methods. In this study, in vivo regeneration induced by decellularised bovine pericardium with or without mild glutaraldehyde crosslinking was studied in relation to its immune and inflammatory response using rat abdominal regeneration model. Mild glutaraldehyde crosslinking was done to subdue inflammatory and immune response without compromising host cell incorporation and graft remodeling. Evaluations were done at both 21 and 90 days. Un-crosslinked decellularised bovine pericardium showed more intense macrophage response predominantly of M2 phenotype at 90 days indicating chronic inflammatory response compared to mildly crosslinked group. This group also showed significant increase in plasma cell and lymphocyte count indicating immune stimulation. Lymphocyte transformation test detected presence of bovine pericardial antigen sensitized lymphocytes at both periods in un-crosslinked group. Lymphocytes from mildly crosslinked group failed to respond in this test at both periods. Significantly higher antibody response was also noted at both periods in un-crosslinked group. However, abdominal wall regeneration was observed only in animals implanted with un-crosslinked decellularised bovine pericardium at 90 days. From the above findings, it is inferred that un-crosslinked decellularised bovine pericardium produced significant chronic inflammatory response at 90 days and stimulated both humoral and cell mediated immune response in comparison to mildly crosslinked decellularised bovine pericardium. Yet this group produced skeletal muscle formation within graft at 90 days. (c) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
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    Evaluation of an in situ forming hydrogel wound dressing based on oxidized alginate and gelatin
    (BIOMATERIALS, 2005)
    Wound dressings that can be formed in situ offer several advantages over the use of preformed dressings such as conformability without wrinkling or fluting in the wound bed, ease of application and improved patient compliance and comfort. Here we describe such an in situ forming hydrogel wound dressing from gelatin, oxidized alginate and borax. Periodate oxidized alginate rapidly cross-links proteins such as gelatin in the presence of borax to give in situ forming hydrogels that are both non-toxic and biodegradable. The composite matrix has the haemostatic effect of gelatin, the wound healing-promoting feature of alginate and the antiseptic property of borax to make it a potential wound dressing material. The hydrogel was found to have a fluid uptake of 90% of its weight which would prevent the wound bed from accumulation of exudates. The water vapour transmission rate (WVTR) of the hydrogel was found to be 2686 + 124 g/m(2)/day indicating that the hydrogel can maintain a moist environment over wound bed in moderate to heavily exuding wound which would enhance epithelial cell migration during the healing process. The wound healing efficacy of hydrogel was evaluated in experimental full thickness wounds using a rat model which demonstrated that within 2 weeks, the wound covered with gel was completely filled with new epithelium without any significant adverse reactions. These in situ forming hydrogels fulfil many critical elements desirable in a wound dressing material. (c) 2005 Elsevier Ltd. All rights reserved.
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    Fibrin glue as an osteoinductive protein in a mouse model
    (BIOMATERIALS, 2002)
    Fibrin sealant or fibrin glue (FG) has been found to be effective as a wound-healing substance in surgery. However, its role in bone fracture healing and osseous tissue response is not fully understood. This ambiguity questions the potential of FG as an inductive protein. The present study was undertaken to evaluate the osteoinductive property of FG when coated with calcium phosphate and glass ceramics and implanted in the extraskeletal site of male Swiss albino mice. Implant materials used for this study were hydroxyapatite (HA) porous granules (300-350 mum), bioactive glass system (BGS)-AW type and calcium phosphate calcium silicate system (HABGS) non-porous granules (300-350 mum). Uncoated granules (control) and coated granules with 2.5 mg FG and 5 mg FG were implanted in the quadriceps muscle of mice and sacrificed after 28 days. Histologically, HA, BGS and HABGS implanted animal groups showed good healing response. However, neo-osteogenesis was observed only in the BGS and HABGS granules impregnated with FG. Furthermore, bone formation was observed to be more conspicuous in 5 mg FG coated BGS and HABGS granules when compared with 2.5 mg FG coated BGS and HABGS granules. Fluorochrome labeling proved that mineralization had already started by day 15 with FG preadsorbed BGS and HABGS granules. On the contrary, the uncoated granules did not show any de novo bone formation. This experimental study provides an evidence of the positive role of FG as a potential osteoinductive biologic tissue adhesive. (C) 2002 Elsevier Science Ltd. All rights reserved.
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    Glutaraldehyde treatment elicits toxic response compared to decellularization in bovine pericardium.
    (Toxicology international, 2012)
    Glutaraldehyde-stabilized bovine pericardium is used for clinical application since 1970s because of its desirable features such as less immunogenicity and acceptable durability. However, a propensity for calcification is reported on account of glutaraldehyde treatment. In this study, commercially available glutaraldehyde cross-linked bovine pericardium was evaluated for its in vitro cytotoxic effect, macrophage activation, and in vivo toxic response in comparison to decellularized bovine pericardium. Glutaraldehyde-treated bovine pericardium and its extract were observed to be cytotoxic and it also caused significant inflammatory cytokine release from activated macrophages. Significant antibody response, calcification response, necrotic, and inflammatory response were noticed in glutaraldehyde-treated bovine pericardium in comparison to decellularized bovine pericardium in a rat subcutaneous implantation model. Glutaraldehyde-treated bovine pericardium also failed in acute systemic toxicity testing and intracutaneous irritation testing as per ISO 10993. With respect to healing and implant remodeling, total lack of host tissue incorporation and angiogenesis was noticed in glutaraldehyde-treated bovine pericardium compared to excellent host fibroblast incorporation and angiogenesis within the implant in decellularized bovine pericardium. In conclusion, using in vitro and in vivo techniques, this study has demonstrated that glutaraldehyde-treated bovine pericardium elicits toxic response compared to decellularized bovine pericardium which is not congenial for long-term implant performance.
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    In vitro and in vivo performance of a dual drug-eluting stent (DDES)
    (BIOMATERIALS, 2010) Huang, YY; Venkatraman, SS; Boey, FYC; Lahti, EM; Umashankar, PR; Mohanty, M; Arumugam, S; Khanolkar, L; Vaishnav, S
    This study reports on a dual drug-eluting stent (DDES) that has an anti-proliferative and an anti-thrombotic in a biodegradable polymer-coated onto a cobalt-chromium stent. The DDES was prepared by spray coating the bare metal stent with a biodegradable polymer loaded with sirolimus and triflusal, to treat against restenosis and thrombosis, respectively. The 2-layered dual-drug coated stent was characterized in vitro for surface properties before and after expansion, as well as for possible delamination by cross-sectioning the stent in vitro. The in vitro anti-platelet behavior of the triflusal-loaded films was investigated by using dynamic platelet adhesion measurements. Additionally, the in vitro degradation and release study of the films and the stents w/single sirolimus and dual sirolimus-triflusal in different formulations were examined. Finally, in vivo studies (in a porcine carotid artery model) were performed for acute thrombosis, inflammation and restenosis at 30 days. The in vitro results show DDES can sustain release both anti-proliferation drug (sirolimus) and anti-thrombosis drug (triflusal), two drugs were controlled in different rates to effectively reduce thrombosis and proliferation at the same time. In vivo results show a significant reduction in restenosis with dual-drug eluting stent compared with the controls (a bare metal stent, a sirolimus coated and a pure polymer-coated stent). The reduction in restenosis with a dual sirolimus-triflusal eluting stent is associated with an inhibition of inflammation, especially thrombus formation, suggesting that such dual-drug eluting stents have a role to play for the treatment of coronary artery disease. (C) 2010 Elsevier Ltd. All rights reserved.
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    Long duration anaesthesia for experimental surgical procedures in pigs.
    (INDIAN VETERINARY JOURNAL, 2006) Harikrishnan, VS; Umashankar, PR
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    Long-term healing of mildly cross-linked decellularised bovine pericardial aortic patch
    (JBMR-part B, 2016-08) Umashankar, PR; Sabareeswaran, A; Shenoy, SJ
    : Glutaraldehyde treated bovine pericardium is extensively used in cardiovascular surgery. However, frequent occurrence of failure modes, such as calcification and structural failure, has hard pressed the need for finding an alternate technology. Decellularized bovine pericardium is an emerging technology. Mildly cross-linked decellularized bovine pericardium promotes positive remodeling with insignificant calcification and acute inflammation. In the present study, mildly cross-linked decellularized bovine pericardium was evaluated as a cardiovascular patch by studying mechanical strength as well as graft remodeling, resistance to calcific degeneration and inflammatory response using long duration porcine aortic implantation. It was observed that decellularized bovine pericardium, although thinner and less elastic had equivalent tensile properties such as tensile strength and stiffness when compared to commercially available glutaraldehyde-treated bovine pericardium. It showed the potential for site appropriate remodeling evidenced by host cell incorporation, thinner neointima, graft degradation, and neocollagenisation making it suitable for vascular patch application, whereas glutaraldehyde-treated pericardium failed to integrate with host tissue through timely degradation and host cell incorporation or neocollagenization. Conversely, it elicited persistent acute inflammation and produced calcification. VC 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000–000, 2016.
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    Management of damaged lumbosacral plexus due to foetopelvic disproportion in a gilt
    (INDIAN VETERINARY JOURNAL, 2006) Shenoy, SNJ; Umashankar, PR; Lal, GAV