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Biomedical subjects

M Chandrasekaran

Publications and source records attributed to M Chandrasekaran.

12 recordsLinked to original sources
PubMed2007

Compressive properties and degradability of poly(epsilon-caprolatone)/hydroxyapatite composites under accelerated hydrolytic degradation.

Hydroxyapatite (HA) was incorporated as filler into polycaprolactone (PCL) matrix to improve the bioactivity as well as the compressive properties of the polymer composites that can be typically used in tissue engineering scaffolds. The compressive properties of five PCL/HA composites of different compositions were investigated in conjunction with the study of their rate of degradation. As PCL has a slow degradation rate, the experiment was conducted in a concentrated 5M sodium hydroxide medium to accelerate the degradation process. The compressive strength and modulus of all PCL/HA compositions were observed to decrease as the degradation experiment progressed, with samples having high HA content degraded most significantly as compared with samples with lower HA content. Pure PCL samples, however, were found to retain their mechanical properties comparatively well in the same degradation experiments. Although the addition of HA as filler into the PCL matrix was shown to have improved mechanical properties and bioactivity initially, these results do raise concerns of material properties being compromise during hydrolytic degradation.

Biocompatible Materials↗
PubMed2006

Evaluation of bone mineral density in thyrotoxicosis.

INTRODUCTION: This project aimed to study the incidence and profile of bone involvement in thyrotoxicosis patients by dual energy X-ray absorptiometry (DEXA) scan and the effect of treatment on the bone mineral density (BMD). METHODS: A total of 50 young patients with a mean age of 29.4 years, diagnosed to have thyrotoxicosis clinically and proven by thyroid function tests, were included in this prospective three-year study conducted at the Madras Medical College and Government General Hospital in Chennai, India. Patients were enrolled if they had bone pain or had elevation of serum alkaline phosphatase. All these patients had a baseline BMD measurement by DEXA scans in the region of the lumbar vertebrae before treatment and the T-score was computed. All other secondary causes of low BMD, like primary hyperparathyroidism, long-term steroid intake, vitamin D deficiency, was ruled out. After definitive management of hyperthyroidism by anti-thyroid drugs and surgery, all the patients with bone involvement had a repeat DEXA scan after one year and the T-score was computed. RESULTS: Out of 50 patients, 46 had bone involvement (92 percent). Based on the World Health Organisation classification, 16 (32 percent) had osteopenia and 30 patients (60 percent) had osteoporosis. After control of thyrotoxicosis, the mean bone mass increased from 0.729 g/sq cm to 0.773 g/sq cm, a statistically significant increase of 0.044 g/sq cm (p-value is less than 0.001) after one year, compared to age- and sex-matched controls. The mean percentage of the bone mass compared to the peak BMD increased from 70.2 percent to 74.2 percent after treatment, an increase of four percent (p-value is less than 0.001). The mean percentage of the bone mass compared to the age-matched BMD increased from 71.2 percent to 75.2 percent after treatment, an increase of four percent (p-value is less than 0.001), all of which were statistically significant. CONCLUSION: Metabolic bone disease should be looked for in all thyrotoxic patients, especially patients complaining of bone pain and those with elevated bone enzymes. DEXA scans offer a convenient, reliable and noninvasive modality for diagnosis and monitoring therapy.

Absorptiometry, Photon↗
PubMed2005

Effect of seaweed extracts on the growth and biochemical constituents of Vigna sinensis.

The effect of seaweed liquid fertilizers (SLF) of Sargassum wightii and Caulerpa chemnitzia on growth and biochemical constituents of Vigna sinensis was studied. The seeds soaked with aqueous extract of seaweeds performed better when compared to the water soaked controls. Hundred per cent germination was recorded both in aqueous extract soaked and water soaked treatments. The low concentration (20%) of aqueous extracts of S. wightii and C. chemnitzia promoted the seedling growth including the parameters of shoot length (15.87, 14.13 cm/seedling), root length (6.42, 5.38 cm/seedling), fresh weight (4.017, 4.012 g/seedling) and dry weight (0.878, 0.865 g/seedling), chlorophyll (1.599, 1.491 mg g-1 fr. wt.), carotenoids (0.899, 0.875 mg g-1 fr. wt.), protein content of shoot (3.956, 3.474 mg g-1 fr. wt.) and root (2.926, 2.890 mg g-1 fr. wt.), amino acid content of shoot (1.447, 1.429 mg g-1 fr. wt.) and root (0.698, 0.680 mg g-1 fr. wt.), reducing sugar content of shoot (6.426, 6.233 mg g-1 fr. wt.) and root (5.118, 5.103 mg g-1 fr. wt.), total sugar content of shoot (11.846, 11.350 mg g-1 fr. wt.) and root (10.368, 10.102 mg g-1 fr. wt.), alpha-amylase (1.927, 1.819 microg min-1 mg-1 protein) and beta-amylase (1.730, 1.617 microg min-1 mg-1 protein) activities in V. sinensis. Among the two seaweeds tested, S. wightii exhibited better responses.

Amino Acids↗
PubMed2004

Antibacterial and antifungal activity of Syzygium jambolanum seeds.

The water and methanolic extracts of Syzygium jambolanum seeds were examined for antibacterial and antifungal activity in vitro using the disc diffusion method, minimum inhibitory concentration, minimum bactericidal concentration and minimum fungicidal concentration. Activity against gram positive bacteria (Bacillus subtilis, Staphylococcus aureus), gram negative bacteria (Salmonella typhimurium, Pseudomonas aeruginosa, Klebsiella pneumoniae and Escherichia coli) and fungal strains (Candida albicans, Cryptococcus neoformans, Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Rhizopus sp., Trichophyton rubrum, Trichophyton mentagrophytes and Microsporum gypseum) is discussed.

Anti-Bacterial Agents↗
PubMed2002

Friction and wear of hydroxyapatite reinforced high density polyethylene against the stainless steel counterface.

Hydroxyapatite (HA) reinforced high density polyethylene (HDPE) was invented as a biomaterial for skeletal applications. In this investigation, tribological properties (e.g. wear rate and coefficient of friction) of unfilled HDPE and HA/HDPE composites were evaluated against the duplex stainless steel in dry and lubricated conditions, with distilled water or aqueous solutions of proteins (egg albumen or glucose) being lubricants. Wear tests were conducted in a custom-built test rig for HDPE and HA/HDPE containing up to 40 vol % of HA. It was found that HA/HDPE composites had lower coefficients of friction than unfilled HDPE under certain conditions. HA/HDPE also exhibited less severe fatigue failure marks than HDPE. The degradation and fatigue failure of HDPE due to the presence of proteins were severe for low speed wear testing (100 rpm) as compared to high speed wear testing (200 rpm). This was due possibly to the high shear rate at the contact which could remove any degraded film instantaneously at high sliding speed, while with a low sliding speed the build-up of a degraded layer of protein could occur. The degraded protein layer would stay at the contact for a longer time and mechanical activation would induce adverse reactions, weakening the surface layer of HDPE. Both egg albumen and glucose were found to be corrosive to steel and adversely reactive for HDPE and HA/HDPE composites. The wear modes observed were similar to that of ultra-high molecular weight polyethylene. Specimens tested with egg albumen also displayed higher wear rates, which was again attributed to corrosion accelerated wear.

Journal Article↗
PubMed1998

Shape memory and superelastic alloys: the new medical materials with growing demand.

Shape memory and superelasticity are novel properties not exhibited by common materials. In recent years, these properties and the alloys exhibiting them have found widespread use as new medical materials, in devices such as diagnostic and therapeutic catheters of different kinds, stents, needle wire localisers, orthodontic arch wires, implantable drug delivery system etc. The reasons for this trend and the future potential of these materials in medical applications will be explained in this presentation.

Alloys↗
PubMed1993

Dyshormonogenetic goitre.

Thirty-seven patients with dyshormonogenetic goitre seen in the last five years are discussed. Males were as frequently affected as females. The peak incidence was in the second decade. The commonest presentation was a multinodular goitre with patent or subclinical hypothyroidism. Surgery was avoided except for gross disfigurement or presence of malignancy. Surgery done was near total thyroidectomy. All patients treated conservatively and those who were operated on have been advised life-long thyroxin therapy.

Adolescent↗
PubMed1992

Performance of a kinetic model for intracellular ice formation based on the extent of supercooling.

Cryomicroscopy was used to study the incidence of intracellular ice formation (IIF) in protoplasts isolated from rye (Secale cereale) leaves during subfreezing isothermal periods and in in vitro mature bovine oocytes during cooling at constant rates. IIF in protoplasts occurred at random times during isothermal periods, and the kinetics of IIF were faster as isothermal temperature decreased. Mean IIF times decreased from approximately 1700 s at -4.0 degrees C to less than 1 s at -18.5 degrees C. Total incidence of IIF after 200 s increased from 4% at -4.0 degrees C to near 100% at -15.5 degrees C. IIF behavior in protoplasts was qualitatively similar to that for Drosophila melanogaster embryos over the same temperature ranges (Myers et al., Cryobiology 26, 472-484, 1989), but the kinetics of IIF were about five times faster in protoplasts. IIF observations in linear cooling of bovine oocytes indicated a median IIF temperature of -11 degrees C at 16 degrees C/min and total incidences of 97%, 50%, and 19% at 16, 8, and 4 degrees C/min, respectively. A stochastic model of IIF was developed which preserved certain features of an earlier model (Pitt et al. Cryobiology 28, 72-86, 1991), namely Weibull behavior in IIF temperatures during rapid linear cooling, but with a departure from the concept of a supercooling tolerance. Instead, the new model uses the osmotic state of the cell, represented by the extent of supercooling, as the independent variable governing the kinetics of IIF. Two kinetic parameters are needed for the model: a scale factor tau 0 dictating the sensitivity to supercooling, and an exponent rho dictating the strength of time dependency. The model was fit to the data presented in this study as well as those from Myers et al. and Pitt et al. for D. melanogaster embryos with and without cryoprotectant, and from Toner et al. (Cryobiology 28, 55-71, 1991) for mouse oocytes. In protoplasts, D. melanogaster embryos, and mouse oocytes, the parameters were estimated from IIF times in the early stages of isothermal periods, while the osmotic state of the cell was relatively constant. In bovine oocytes, the parameters were estimated from linear cooling data. Without further calibration, the model was used to predict total IIF incidence under different cooling regimes. For protoplasts, D. melanogaster embryos, and bovine oocytes, the model's predictions were quite accurate compared to the actual data. In mouse oocytes, adjustment of the hydraulic permeability coefficient (Lp) at 0 degree C was required to yield realistic behavior.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Fish flesh agar medium--a suitable experimental medium for the detection of spoilage bacteria.

The spoilage characteristics of bacterial strains were studied by growing them at 28 +/- 2 degrees C in agar and broth media prepared with sterile fish and prawn flesh homogenates. The percentage of spoilers found among the bacterial isolates tested, as shown by odour production and halo zone formation, was independent of the source of flesh used. Indole and fluorescent pigment production were also observed in the broth. Pseudomonas, Vibrio and Acinetobacter exhibited faster growth in flesh media than in the usual artificial media. Decrease of protein and lipid concentration in the clear zone of agar media suggests the utilization of the available substrate by spoilage bacteria.

Acinetobacter↗