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Biomedical subjects

P Ramesh

Publications and source records attributed to P Ramesh.

35 records · Page 2Linked to original sources
PubMed2001

Electrochemical and spectroscopic characterization of quinone functionalized exfoliated graphite.

Natural graphite was exfoliated by thermal decomposition of graphite-bisulfate intercalation compound. Oxidative/reductive pre-treatment of exfoliated graphite was subsequently carried out to introduce various functional groups on the graphite surface. The resulting material was covalently modified with redox active quinones. The covalent modification was effected through oxygen containing functional groups formed on the graphite surface. The modified exfoliated graphite was characterized by infra-red (FTIR) and X-ray photoelectron spectroscopy (XPS). Electrochemical characterization of the pressed pellets of the modified graphite showed that the modification occurred at the edge sites. These electrodes were found to be very stable and the surface renewal was simply accomplished by polishing the surface using SiC emery sheets. Application of the benzoquinone modified electrode for the electrocatalysis of ascorbic acid oxidation was demonstrated.

Journal Article↗
PubMed2001

A comparative evaluation of coefficient of friction and mechanical properties of commercially available Foley catheters.

Three commercially available urinary catheters were evaluated for their coefficient of friction and mechanical properties, which are two important parameters as far as the intended use is considered. The apparent coefficient of friction was measured from the slope of the force versus normal load graph using an in-house fabricated setup. The mechanical properties like ultimate tensile strength, elongation at break and modulus were evaluated before and after aging in synthetic urine. The swelling behavior of the catheter samples was studied in toluene and found to correlate well with the mechanical properties.

Catheters, Indwelling↗
PubMed2000

A binderless, bulk-modified, renewable surface amperometric sensor for NADH and ethanol.

Graphite particles are exfoliated and subsequently functionalized with toluidine blue. The resulting covalently modified graphite particles are restacked without any binder to form a surface-renewable, bulk-modified electrode. Electrocatalytic oxidation of NADH and its application in the amperometric biosensing of ethanol using alcohol dehydrogenase enzyme have been demonstrated with this material.

Alcohol Dehydrogenase↗
PubMed2000

Assessment of in vivo chromosomal aberrations--potency of zinc mercapto benzo thiazole.

Chromosomal aberrations are microscopically visible changes in the chromosome structure. The double-stranded breaks are the ultimate DNA lesions for chromosomal aberrations. The purpose of the present study was to evaluate the induction of chromosomal aberrations by the rubber accelerator zinc mercapto benzo thiazole (ZMBT). The experiment was designed with five groups, each composed of four Swiss albino mice. The first three groups received ZMBT at 1920, 960, and 480 microg/20 g animal. The remaining two groups were the vehicle (cotton seed oil) and positive (methyl methane sulphonate) controls. Animals were given a single dose of test and control samples by IP injection. Colchicine (20 microg/animal) was administered 90 minutes before sacrificing the animals. All the animals were sacrificed at the end of 36 h by cervical dislocation. Bone marrow preparations were made, stained with Giemsa stain, and examined for chromosomal abnormalities. The results indicated a lack of incidence of chromosomal abnormalities in the test and control groups. However, significant chromosomal abnormalities such as gaps, breaks, and translocations were observed in the positive control group. Hence, the study concluded that ZMBT at different concentrations fails to induce structural chromosomal aberrations in bone marrow cells.

Animals↗
PubMed1999

Tensile set behavior of Foley catheter balloons.

The removal of indwelling urinary balloon catheters from patients is usually associated with many problems. The problems such as balloon deflation failure; encrustations on balloons, eyes, and lumen; and catheter associated infections are widely discussed in the literature. The tensile set exhibited by the catheter balloon material could also play a role and further complicate the removal process. This article addresses this issue by comparing the tensile set behavior of the balloon material from three commercially available Foley catheters. The balloon materials were subjected to aging in synthetic urine at 37 degrees C for 28 days to simulate clinical conditions. The deflation time of catheter balloons aged in similar conditions were also measured. It was found that different brands of catheters exhibited statistically significant differences in their properties. The tensile set data of the aged samples could be correlated with the deflation time of the balloons. The clinical significance of the tensile set is also highlighted.

Biocompatible Materials↗
PubMed1999

Microbial transformation of delta 9(15)-africanene.

Incubation of delta 9(15)-africanene with fungi Aspergillus niger and Rhizopus oryzae for 8 days yielded two oxidized derivatives, 10 alpha-hydroxy-delta 9(15)-africanene and 9 alpha,15-epoxyafricanane. The structure of the two products were assigned by interpretation of their spectral data.

Animals↗
PubMed1999

Novel steroid constituents of the soft coral Sinularia dissecta.

Chemical examination of the soft coral Sinularia dissecta furnished five steroids (1-5), which include four new polyhydroxy steroids (2-5). The structures of new compounds have been established by the study of their spectral data. Steroid 5 was a novel polyoxygenated epoxy steroid.

Animals↗
PubMed1998

MEICPS: substitution mutations to engineer intracellular protein stability.

UNLABELLED: In MEICPS, results from earlier analyses are utilized to suggest possible substitution point mutations to engineer intracellular stability using a given sequence or structure of the protein. AVAILABILITY: From bvbreddy@ccmb.ap.nic.in. This program needs data from other software, PSA and SSTRUC, available from sali@tamika.rockefeller.edu and tom@cryst.bioc.cam.ac.uk, respectively. CONTACT: bvbreddy@ccmb.ap.nic.in

Computational Biology↗
PubMed1997

Surgical treatment of acquired ventricular septal defects in the elderly.

OBJECTIVE: As the population continues to age, older patients are being referred for repair of acquired ventricular septal defect (VSD) following myocardial infarction (MI). The purpose of this study was to assess the effect of age (> or = 70 years) on operative risk and long term survival following repair of an acquired VSD. METHODS: Between January 1972 and December 1995, 179 patients have undergone repair of acquired VSDs following MI in our unit. There were 118 males and 61 females (age range 43-80 years) of whom 60 were aged 70 years or above. RESULTS: The overall early mortality was 27%. On univariate analysis risk factors for early death included shorter time from both MI and detection of murmur to operation (P < 0.01, P = 0.04), site of MI (P < 0.01), higher NYHA class (P < 0.01), lower preoperative blood pressure (P < 0.01) and longer cardiopulmonary bypass and cross clamp times (P < 0.01, P = 0.03). Non significant variables included age, sex, concomitant CABG and preoperative renal function. Early mortality was 28.6% (34/119) in patients under 70 and 25.0% (15/60) in those over 70. This difference was not significant. The only significant differences between the age groups were sex distribution (females > males, P < 0.01), in the older group, and shorter time from both MI and detection of murmur to operation (P = 0.04, P = 0.02). Cardiopulmonary bypass was the only statistically significant variable on multivariate analysis (P = 0.01). CONCLUSIONS: There was no significant difference in early mortality between the two age groups. As shorter times from both MI and detection of murmur to operation adversely affect early mortality, age over 70 years should not be used to determine suitability for surgery.

Adult↗
PubMed1996

Open-access echocardiography to general practitioners for suspected heart failure.

Echocardiography is now considered to be the key investigation when heart failure is suspected, and should improve clinical management. An open-access echocardiography service was piloted to 24 general practitioners and the service was audited after 250 cases. The impact on clinical management was assessed by reviewing general practice notes 2 months after the echocardiogram. Significant impairment of left ventricular function was found in 49 patients (20%). Out of these subjects, 38 had been started on an ACE inhibitor. Twenty patients were considered to have a significant valve lesion by echocritiera, of whom 14 had been referred for a cardiological opinion. The provision of an open-access echocardiography service was popular with general practitioners and the information resulted in appropriate management decisions being made.

Adolescent↗
PubMed1992

Structural analysis of human anti-mouse H-2E xenorecognition: T cell receptor bias and impaired CD4 interaction contribute to weak xenoresponses.

T lymphocyte responses to the MHC of an evolutionarily distant species are known to be weak compared with responses against allogeneic MHC products within a species. This fact was used to examine the regions of human MHC class II molecules required for the stimulation of strong primary immune responses against MHC alloantigens. A panel of mouse DAP.3 transfectants expressing the products of wild-type and recombinant DR1/H-2Ek MHC class II genes paired to either DR alpha or H-2E alpha genes was generated, and tested as stimulator cells for purified human T cells. A strong proliferative response to DAP.3 transfectants expressing allogeneic HLA-DR molecules was seen. In contrast, weak or absent responses were recorded against DAP.3 cells expressing H-2E molecules. Substitution of the DR1 beta chain with H-2E beta k led to a dramatic loss of recognition; alpha chain substitution had a less marked effect. Furthermore, replacement of the beta 2 domain of DR1 with H-2E sequence caused 90% inhibition, whereas introduction of the beta 2 domain of DR1 into H-2Ek led to a 10-fold increase in T cell response. These results are most readily explained if the beta 2 domain contributes to the interaction site for the CD4 molecule. Substitution of either half of the beta 1 domain led to a marked loss of response. This was more impressive following substitution of the TCR-contacting alpha-helical region of the domain.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗