Biomedical subjects
Publications and source records attributed to Seema Singh.
India is a country in transition, and so is its science. Scientific institutions, researchers, regulatory agencies, and government policies are in a state of flux as changes are instigated to overcome the bureaucracy and inertia that are characteristic of a populous developing nation.
Long-range hydrophobic interactions operating underwater are important in the mediation of many natural and synthetic phenomena, such as protein folding, adhesion and colloid stability. Here we show that rough hydrophobic surfaces can experience attractive forces over distances more than 30 times greater than any reported previously, owing to the spontaneous evaporation of the intervening, confined water. Our finding highlights the importance of surface roughness in the interaction of extended structures in water, which has so far been largely overlooked.
Amphiphilic phospholipids were used to direct the formation of biocompatible, uniform silica nanostructures in the presence of Saccharomyces cerevisiae and bacterial cell lines. The cell surfaces organize multilayered phospholipid vesicles that interface coherently with the silica host and help relieve drying stresses that develop with conventional templates. These host structures maintain cell accessibility, addressability, and viability in the absence of buffer or an external fluidic architecture. The cell surfaces are accessible and can be used to localize added proteins, plasmids, and nanocrystals. Prolonged cell viability combined with reporter protein expression enabled stand-alone cell-based sensing.
Ethanolic extract of H. rhamnoides L. leaf (HL-EOH), water and ethanolic extract of H. rhamnoides fruit (HF-W and HF-EOH), and H. rhamnoides flavone from fruit (HR-flavone) were evaluated against percutaneously administered sulphur mustard (SM), a chemical warfare agent. The animals administered with SM (9.7, 19.3 and 38.7 mg/kg) died at various days depending upon the dose and there was a significant reduction in the body weight. The H. rhamnoides extracts (1 g/kg; 3 doses; po) significantly protected the lethality, with a protective index of 2.4, 1.7, 1.7 and 2.2 for HL-EOH, HF-W, HF-EOH and HR-flavone respectively. Reduced glutathione (GSH) and oxidized glutalthione (GSSG) levels were reduced, and malondialdehyde (MDA) was elevated after percutaneous administration of SM. Oral administration of HL-EOH and HR-flavone significantly protected the body weight loss. Recovery in the levels of GSH, GSSG and MDA were also observed following oral administration of HL-EOH and HR-flavone. All the extracts were non-toxic and the LD50 was more than 5 g/kg. The present study shows that percutaneous administration of SM induces oxidative stress and ethanolic extract of leaf of H. rhamnoides and H. rhamnoides flavone from fruit can significantly protect it.
Neutron reflectivity (NR) is used to probe the solid, liquid, vapor interface of a porous superhydrophobic (SH) surface submerged in water. A low-temperature, low-pressure technique was used to prepare a rough, highly porous organosilica aerogel-like film. UV/ozone treatments were used to control the surface coverage of hydrophobic organic ligands on the silica framework, allowing the contact angle with water to be continuously varied over the range of 160 degrees (superhydrophobic) to <10 degrees (hydrophilic). NR shows that the superhydrophobic nature of the surface prevents infiltration of water into the porous film. Atomic force microscopy and density functional theory simulations are used in combination to interpret the NR results and help establish the location, width, and nature of the SH film-water interface.
BACKGROUND: In our part of the world, the majority of the patients with breast cancer present with locally advanced disease and require neo-adjuvant chemotherapy as the primary treatment modality. It is essential to monitor the response to chemotherapy in these patients. Clinical examination as the sole criterion of response assessment is entirely subjective and fallacious. Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) are expensive. The role of Doppler ultrasonography as an imaging modality for this purpose is therefore being evaluated. METHODS: A prospective study was undertaken of 25 cases of locally advanced breast carcinoma (LABC) and Color Doppler sonography was used for the sequential assessment of chemotherapeutic response. The response assessed on the basis of clinical examination and Color Doppler was compared with the histological response. The parameters assessed on color Doppler were a change in the number of flow signals, maximum flow velocity (Vmax), pulsatility index (PI) and resistivity index (RI). Responses were analysed statistically using the Pearson correlation coefficient and Kappa statistics (kappa). The sensitivity, specificity, positive predictive & negative predictive values for predicting complete histological response were calculated. RESULTS: Color Doppler showed a sensitivity of 88.88 % for predicting complete histological response. The negative predictive value of color Doppler was 92.3 %. A significant correlation was obtained between color Doppler and histopathological response. CONCLUSIONS: Color Doppler was found to be an objective and effective tool or modality compared with clinical evaluation in sequential response assessment, especially for predicting complete histological response.
Estrogens are a known risk factor for breast cancer. Studies indicate that initiation of breast cancer may occur by metabolism of estrogens to form abnormally high levels of catechol estrogen-3,4-quinones, which can then react with DNA to form depurinating adducts and, subsequently, induce mutations that lead to cancer. Among the key enzymes metabolizing estrogens are two activating enzymes: cytochrome P450 (CYP)19 (aromatase), which converts androgens to estrogens, and CYP1B1, which converts estrogens predominantly to the 4-catechol estrogens that are further oxidized to catechol estrogen-3,4-quinones. Formation of the quinones is prevented by methylation of the 4-catechol estrogens by the enzyme, catechol-O-methyltransferase (COMT). In addition, catechol estrogen quinones can be reduced back to catechol estrogens by NADPH quinone oxidoreductase 1 (NQO1) and/or are coupled with glutathione, preventing reaction with DNA. Thus, COMT and NQO1 are key deactivating enzymes. In this initial study, we examined whether the expression of these four critical estrogen activating/deactivating enzymes is altered in breast cancer. Control breast tissue was obtained from four women who underwent reduction mammoplasty. Breast tissues from five women with breast carcinoma, who underwent mastectomy, were used as cases. The level of expression of CYP19, CYP1B1, COMT and NQO1 mRNAs was quantified from total RNA using a real time RT-PCR method in an ABI PRISM 7700 sequence detection system. The control breast tissues showed lower expression of the activating enzymes, CYP19 and CYP1B1, and higher expression of the deactivating enzymes, COMT and NQO1, compared to the cases. In the cases, the reverse pattern was observed: greater expression of activating enzymes and lower expression of deactivating enzymes. Thus, in women with breast cancer, estrogen metabolism may be related to altered expression of multiple genes. These unbalances appear to be instrumental in causing excessive formation of catechol estrogen quinones that, by reacting with DNA, initiate the series of events leading to breast cancer.
BACKGROUND: Vascular access is judged on its ability to provide good dialysis adequacy, its durability and complication rates. Formation of a functional arteriovenous fistula is desirable but difficult to achieve in a significant proportion of patients. We report the large-scale use of Tesio-Caths, a twin-line single-lumen central venous catheter, to maximize dialysis adequacy where formation of an arteriovenous fistula was not possible. METHODS: All patients who had Tesio-Caths inserted between 1 January 1999 and 1 October 2002 were studied. RESULTS: Six hundred and twenty-three Tesio-Caths were inserted from 1 January 1999 to 1 October 2002 in 435 patients, generating 7464 patient months of follow-up. Five hundred and ninety-four out of 623 (95.3%) Tesio-Caths were immediately functional. Mean dialysis adequacy measured by single-pool Kt/V was 1.5+/-0.3 for all Tesio-Caths for the entire period of study, with 68% of Tesio-Caths delivering a Kt/V >1.4. Cumulative functional Tesio-Cath survival to final failure was 77.8 and 44% at 1 and 3 years, respectively. Cumulative patient survival was 84.7, 71.4 and 63% at 1, 2 and 3 years, respectively. Access-related infection accounted for 0.28 admissions/1000 catheter days, and the death rate from access-related sepsis was 9.6 deaths/1000 patient years at risk. The admission rate for access dysfunction was 0.33/1000 patient years at risk. CONCLUSION: Tesio-Caths provide good dialysis adequacy for patients in whom an arteriovenous fistula cannot be formed. Patient and functional access survival for this group was comparable with current European data irrespective of vascular access type. Complication rates were acceptably low.
BACKGROUND: Indo-Asian and Afro-Caribbean patients have higher rates of renal failure and requirement for renal replacement therapy than the general population in the UK. Despite this, information regarding survival on dialysis is limited. METHODS: The incident hemodialysis population of a large west London renal service was reviewed from 1996 to 2001 (N = 465). RESULTS: The cohort's ethnic background was Indo-Asian (30.8%), Caucasian (49%), Afro-Caribbean (18.3%), and other (1.9%). Indo-Asians and Afro-Caribbeans were younger than Caucasian patients, with a higher rate of diabetes mellitus. Survival on hemodialysis for Indo-Asians was 97.5% and 81.6% at 1 and 3 years, respectively, compared with 92.7% and 75.2% for Caucasians, and 97.5% and 85.3% for Afro-Caribbeans (P = nonsignificant). Dialysis adequacy was observed to be associated with survival. Patients with mean single pool Kt/V of over 1.4 had survival of 90.6% and 74.8% at 2 and 5 years, respectively, compared with 74.0% and 42.9% for those with Kt/V less than 1.4 (P < 0.001). There were significantly more patients in the Indo-Asian cohort with a mean Kt/V of 1.4 or over (87.4%) compared with Caucasians (57.6%) and Afro-Caribbeans (52.4%), and the benefit of higher Kt/V was seen in all ethnic groups. In a multivariate analysis of factors including Kt/V over 1.4, age, diabetic status, gender, and ethnicity, Indo-Asian or Afro-Caribbean ethnicity did not confer a survival disadvantage. The strongest predictors of survival were age and dialysis adequacy. CONCLUSION: Indo-Asian and Afro-Caribbean hemodialysis patients have survival comparable to Caucasians despite a higher burden of diabetes.
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A 27-year-old woman developed recurrent hydatid of liver. CT scan showed unilocular cysts in segments IV and VII. Intraoperatively, there was a fistulous communication between the gall bladder and the cyst in segment IV. Partial pericystectomy along with cholecystectomy was done for the segment IV cyst; percutaneous aspiration, instillation and re-aspiration using hypertonic saline was done for the cyst in segment VII. This was followed by albendazole treatment.