Biomedical subjects

Satish Kumar

Publications and source records attributed to Satish Kumar.

At least 37 records · Page 2Linked to original sources

PubMed2005

Dispersion of nitric acid-treated SWNTs in organic solvents and solvent mixtures.

The dispersion of pristine and nitric acid-treated single-wall carbon nanotubes (SWNTs) has been studied in organic solvents and solvent mixtures using optical absorption, as a function of settling time. The extinction coefficients of both the pristine and acid-treated tubes at 500-nm wavelength was measured to be 25.5 (mg/L)(-1) cm(-1) in various solvents. The dispersibility of nitric acid-treated tubes increased with the solvent's hydrogen-bonding ability and reached 27 mg/L in ethanol and 35 mg/L in water. Nitric acid-treated tubes could also be dispersed in butanol/toluene and xylene/ethanol mixtures, which are known to be poor solvents for the pristine SWNTs.

Journal Article↗

PubMed2005

Effect of buffalo seminal plasma heparin binding protein (HBP) on freezability and in vitro fertility of buffalo cauda spermatozoa.

The study was conducted to assess the effect of heparin binding seminal plasma proteins (HBP) on freezability and in vitro fertilizing ability of buffalo cauda epididymal spermatozoa. Spermatozoal motility, viability and acrosomal integrity at prefreeze and post-thaw stages were studied. The in vitro fertilizing ability of spermatozoa was assessed by the application of two tests, i.e. bovine cervical mucus penetration test (BCMPT) and hypo-osmotic sperm swelling test (HOST). HBP isolated from buffalo seminal plasma and maintained in the laboratory were used for the study. Twelve pairs of epididymis from adult buffaloes slaughtered at the local abattoir were used for the study. The results indicated that HBP addition improved the progressive motility, BCMPT and HOST response at prefreeze level. HBP at a concentration of 40 microg/ml showed better results than HBP at a concentration of 80 microg/ml. However, subjecting the HBP treated spermatozoa to cryopreservation resulted in significant reduction of motility, viability, acrosomal integrity and response to BCMPT and HOST in the HBP treated groups when compared to those in control group. The deleterious effect of HBP was found to be concentration dependent with the higher concentration causing higher post-thaw damage.

Acrosome↗

PubMed2005

Nonlinear evolution of thin liquid films dewetting near soft elastomeric layers.

The nonlinear evolution of thin liquid films dewetting near soft elastomeric layers is examined in this work. Evolution equations are derived by applying the lubrication approximation and assuming that van der Waals forces in the liquid cause the dewetting and that the solid can be described as a linear viscoelastic material. Two cases are examined: (i) a liquid layer resting on an elastomer bounded from below by a rigid substrate, and (ii) an elastomer overlying a thin liquid film bounded from below by a rigid substrate. Linear stability analysis is carried out to obtain asymptotic relations which are then compared against solutions of the full characteristic equations. In the liquid-on-solid case, numerical solutions of the evolution equations show that van der Waals forces cause thinning of the liquid film and thickening of the elastomeric solid beneath film depressions. Inclusion of a short-range repulsive force suggests that regular patterns may form in which ridges of fluid rest on depressions in the solid. In the solid-on-liquid case, the van der Waals forces cause the solid layer to break up before the liquid film can dewet. The results presented here support the idea that the dewetting of thin liquid films might be exploited to create topographically patterned surfaces on soft polymeric solids.

Journal Article↗

PubMed2005

Brownian dynamics simulations of polyelectrolyte adsorption in shear flow.

Brownian dynamics simulations are used to study the adsorption of an isolated polyelectrolyte molecule onto an oppositely charged flat surface in the absence and the presence of an imposed shear flow. The polyelectrolyte is modeled as a freely jointed bead-rod chain where excluded volume interactions are incorporated by using a hard-sphere potential. The total charge along the backbone is distributed uniformly among all the beads, and the beads are allowed to interact with one another and the charged surface through screened Coulombic interactions. The simulations are performed by placing the molecule a fixed distance above the surface, and the adsorption behavior is then studied as a function of screening length. In the absence of an imposed flow, the chain is found to lie flat and extended on the adsorbing surface in the limit of weak screening, whereas in the limit of strong screening it desorbs from the surface and attains free-solution behavior. For intermediate screening, only a small portion of the chain adsorbs and it becomes highly extended in the direction normal to the surface. An imposed shear flow tends to orient the chain in the direction of flow and also leads to increased contact of the chain with the surface.

Journal Article↗

PubMed2005

A mouse gene encoding a novel member of the WD family of proteins is highly conserved and predominantly expressed in the testis (Wdr13).

Wdr13, a novel member of the WD family of proteins and the mouse homolog of WDR13 is localized to the locus XA1.1 and is predominantly expressed in the testis. The expression begins at the early stages of gonadal development and is maintained throughout the adult life with a predominant expression in the germ cells of adult testis. RNA in situ hybridization on the testis and brain sections indicated a cytoplasmic expression of the transcript. The alternatively spliced transcripts of the gene are generated by different methods and showed a differential pattern of expression, suggesting functional diversity. The expression of the gene in the unfertilized egg and in the neural stem cells indicated the functional significance of the gene from the early stages of development. The nuclear localization of the mouse WDR13 protein suggested a regulatory function. Evolutionary analysis of the gene indicated an extensive functional conservation across diverse species. Comparison of the genomic organization of the different homologs revealed a varied organization in the invertebrate homolog and the retention of the functionally significant introns in the same.

Alternative Splicing↗

PubMed2005

Serodiagnosis of childhood tuberculosis by ELISA.

OBJECTIVE: Diagnosis of childhood tuberculosis remains an enigma despite many recent technological developments. The present study has been taken up with the aim to assess the diagnostic potential of mycobacterium tuberculosis excretory-secretory ES-31 antigen and affinity purified anti ES-31 antibodies in the serodiagnosis of different spectrum of childhood tuberculosis. METHODS: Mycobacterium tuberculosis H37Ra excretory-secretory antigen (ES-31) and affinity purified goat anti ES-31 antibodies were used in stick penicillinase ELISA for IgG antibody detection and stick Sandwich penicillinase ELISA for detection of circulating free and immune complexed antigen in the sera of 230 children. RESULTS: Analysis of tubercular antibody, circulating free and immune complexed antigen (CIC-Ag) was done in both pulmonary and extrapulmonary form of childhood tuberculosis and overall sensitivity of 81.4% with a specificity of 93% was achieved for detection of antitubercular IgG antibodies. Of the five cases of pulmonary tuberculosis showing absence of IgG antibody, 3 showed the presence of CIC-Ag and one was found positive for both free and CIC-Ag. Similarly out of 8 cases of extrapulmonary childhood tuberculosis missed by IgG detection 5 were found to be positive for CIC-Ag and 1 showed the positive reaction for both free and immune complexed antigens. CONCLUSION: IgG antibody to excretory-secretory antigen ES-31 is found to be having good specificity with acceptable sensitivity in detecting different forms of childhood tuberculosis. Further detection of circulating free and/or immunecomplexed antigen can be used as an adjunct tool in the diagnosis of childhood tuberculosis.

Antibodies, Bacterial↗

PubMed2005

Asymmetric subsethood-product fuzzy neural inference system (ASuPFuNIS).

This paper presents an asymmetric subsethood-product fuzzy neural inference system (ASuPFuNIS) that directly extends the SuPFuNIS model by permitting signal and weight fuzzy sets to be modeled by asymmetric Gaussian membership functions. The asymmetric subsethood-product network admits both numeric as well as linguistic inputs. Input nodes, which act as tunable feature fuzzifiers, fuzzify numeric inputs with asymmetric Gaussian fuzzy sets; and linguistic inputs are presented as is. The antecedent and consequent labels of standard fuzzy if-then rules are represented as asymmetric Gaussian fuzzy connection weights of the network. The model uses mutual subsethood based activation spread and a product aggregation operator that works in conjunction with volume defuzzification in a gradient descent learning framework. Despite the increase in the number of free parameters, the proposed model performs better than SuPFuNIS, on various benchmarking problems, both in terms of the performance accuracy and architectural economy and compares excellently with other various existing models with a performance better than most of them.

Algorithms↗

PubMed2005

Catheter-directed thrombolysis for the management of postpartum deep venous thrombosis.

BACKGROUND: Catheter-directed thrombolysis that removes the thrombus and restores patency of the veins appears to be a safe and effective management of acute deep venous thrombosis (DVT). It has been shown to reduce long-term postthrombotic morbidity and improve the quality of life. Pregnancy and the postpartum period are generally considered as contraindications for thrombolysis. However, catheter-directed thrombolytic therapy of DVT may reduce long-term sequelae in these young patients by restoring the patency of veins. The purpose of this pilot study was to evaluate the efficacy of catheter-directed thrombolysis in treating acute symptomatic postpartum DVT. METHODS: Patients enrolled had symptomatic acute DVT (<3 weeks duration) within 42 days of childbirth. Thrombolysis was performed using a recombinant human tissue plasminogen activator, alteplase 5 mg i.v. bolus, followed by an infusion at 0.01 mg/kg/h for the next 20-24 hr. Unfractionated heparin 5000 IU bolus followed by 300 IU/kg/24 hr was infused concomitantly into an arm vein. Fibrinogen and cephotest were obtained every 6 hr and maintained at >1 g/l and between 50 and 70 s, respectively, by adjusting heparin and alteplase infusion. Venography was repeated after 20-24 hr and angioplasty (+/- stenting) was performed if stenosis was present. In case of partial thrombolysis infusion was continued for a maximum of 96 hr. Lysis was considered complete if there was less than 5% residual luminal area narrowing. The treatment was considered successful if there was complete or partial resolution of lower extremity pain and edema, and recanalization of vein with less than 30% residual luminal area narrowing. Following thrombolytic therapy, patients were fitted with graduated compression stockings, and anticoagulated with oral warfarin for 1 year (or lifelong in case of stent implantation). RESULTS: Five women with postpartum DVT (four iliofemoral DVTs, and one renal and ovarian vein thrombosis on the left side) had catheter-directed thrombolysis. The treatment was successful in all four cases of iliofemoral DVT and symptom relief was achieved in all five cases. However, despite partial thrombolysis and restoration of some flow in the patient with renal and ovarian vein thrombosis, the renography performed 1 month later showed absent left kidney function. CONCLUSION: Where expertise exists, endovascular therapy consisting of catheter-directed thrombolysis with angioplasty and stenting in selected cases could be considered as a primary therapeutic procedure in patients with acute postpartum DVT.

Adult↗

PubMed2005

Effectivity of crude versus purified mycobacterial secretory proteins as immunogen for optimum antibody production.

Monospecific antibodies have been successfully utilized in antigen detection, which is better indicator of active infection. Mycobacterium tuberculosis excretory secretory (M tb ES) antigens such as ES 31, ES 41 and ES 43 (31 kDa, 41 kDa and 43 kDa protein, respectively) have been shown to be present in Mycobacterium tuberculosis H37Ra culture filtrate and are of diagnostic interest. To study the immunogenic potential of crude versus purified antigen, goat was immunized with M tb detergent soluble sonicate (DSS) antigen as well as purified antigen fraction (ESAS 7) containing ES 31 antigen. Both anti-DSS IgG antibody and anti ESAS 7 IgG antibody were found to be reactive with ES 31 antigen upto 1 ng concentration of antibody by ELISA. Crude DSS antigen was found to be quite effective in producing high titre antibodies and showed further high reactivity with other ES antigens (ES 41 and ES 43) of diagnostic interest.

Animals↗

PubMed2005

Adjuvant hormonal therapy in early breast cancer.

For many years, tamoxifen has been the gold standard adjuvant hormonal therapy with the greatest impact in early breast cancer for both pre- and postmenopausal women. Tamoxifen-based adjuvant endocrine therapy and chemotherapy have together contributed substantially to the reduction in breast cancer mortality that has occurred in recent years. Over the past few years, the role of aromatase inhibitors has grown in prominence and they are now on the threshold of supplanting tamoxifen as the new gold standard adjuvant therapy for postmenopausal women with estrogen-receptor-positive disease. With extended use of oral antihormones such as tamoxifen, the role of ovarian suppression on the other hand has become less clear in the adjuvant setting. This article reviews the most important data regarding the various adjuvant hormonal treatments in the management of early breast cancer and will also give a brief overview of the role of these agents in the neoadjuvant setting.

Aromatase Inhibitors↗

PubMed2004

Electrophoresis of a bead-rod chain through a narrow slit: a Brownian dynamics study.

We use two-dimensional Brownian dynamics simulations to study the electrophoresis of a bead-rod chain through a narrow slit. A constant electric field is assumed to act inside and outside of the slit, and each bead on the chain is assigned a constant uniform charge. We calculate the dependence of the polymer transit velocity on chain length, slit dimensions (width-to-length ratio), and electric-field strength. For sufficiently narrow slits, the transit velocity increases nonlinearly with the applied field for low-field strengths, whereas it increases linearly for high-field strengths. In the low-field strength region and for sufficiently narrow slits, the transit velocity decreases rapidly for small chain lengths and then decreases slowly beyond a critical chain length. As the slit width increases, the transit velocity decreases with chain length in more continuous manner, and for sufficiently large slits the transit velocity becomes independent of chain length as expected. Distributions of the chain end-to-end distances and the translocation times depend strongly on the relative size of the chain to the slit. These results show the sensitivity of the transit velocity vs chain length relationship to the slit dimensions and applied electric-field strength, and suggest that there may be an optimal slit width for a given field strength and vice versa. The results may be useful for microfluidic separations and for understanding the motion of biological polymers through narrow constrictions.

Journal Article↗

PubMed2004

Renal effects of Tamm-Horsfall protein (uromodulin) deficiency in mice.

The Tamm-Horsfall protein (THP; uromodulin), the dominant protein in normal urine, is produced exclusively in the thick ascending limb of Henle's loop. THP mutations are associated with disease; however, the physiological role of THP remains obscure. We generated THP gene-deficient mice (THP -/-) and compared them with wild-type (WT) mice. THP -/- mice displayed anatomically normal kidneys. Steady-state electrolyte handling was not different between strains. Creatinine clearance was 63% lower in THP -/- than in WT mice (P < 0.05). Sucrose loading induced no changes between strains. However, water deprivation for 24 h decreased urine volume from 58 +/- 9 to 28 +/- 4 microl x g body wt(-1) x 24 h(-1) in WT mice (P < 0.05), whereas in THP -/- mice this decrease was less pronounced (57 +/- 4 to 41 +/- 5 microl x g body wt(-1) x 24 h(-1); P < 0.05), revealing significant interstrain difference (P < 0.05). We further used RT-PCR, Northern and Western blotting, and histochemistry to study renal transporters, channels, and regulatory systems under steady-state conditions. We found that major distal transporters were upregulated in THP -/- mice, whereas juxtaglomerular immunoreactive cyclooxygenase-2 (COX-2) and renin mRNA expression were both decreased in THP -/- compared with WT mice. These observations suggest that THP influences transporters in Henle's loop. The decreased COX-2 and renin levels may be related to an altered tubular salt load at the macula densa, whereas the increased expression of distal transporters may reflect compensatory mechanisms. Our data raise the hypothesis that THP plays an important regulatory role in the kidney.

Animals↗

PubMed2004

Observations of instability, hysteresis, and oscillation in low-Reynolds-number flow past polymer gels.

We perform a set of experiments to study the nonlinear nature of an instability that arises in low-Reynolds-number flow past polymer gels. A layer of a viscous liquid is placed on a polydimethylsiloxane (PDMS) gel in a parallel-plate rheometer which is operated in stress-controlled mode. As the shear stress on the top plate increases, the apparent viscosity stays relatively constant until a transition stress where it sharply increases. If the stress is held at a level slightly above the transition stress, the apparent viscosity oscillates with time. If the stress is increased to a value above the transition stress and then decreased back to zero, the apparent viscosity shows hysteretic behavior. If the stress is instead decreased to a constant value and held there, the apparent viscosity is different from its pretransition value and exhibits sustained oscillations. This can happen even if the stress is held at values below the transition stress. Our observations suggest that the instability studied here is subcritical and leads to a flow that is oscillatory and far from viscometric. The phenomena reported here may be useful in applications such as microfluidics, membrane separations, and polymer processing. They may also provide insight into the rheological behavior of complex fluids that undergo flow-induced gelation.

Cross-Linking Reagents↗

PubMed2004

Diminished band-gap transitions of single-walled carbon nanotubes in complexation with aromatic molecules.

The near-IR absorption spectrum of semiconducting single-walled carbon nanotubes is characterized by the transitions associated with the first (S11) and second (S22) pairs of van Hove singularities in the electronic density of states. We report that a significant effect on the transitions can be caused by non-covalent complexation of the nanotube with planar aromatic molecules such as pyrenes in solution, resulting in the absence of S11 and S22 bands in the near-IR absorption spectrum. Since the complexation is reversible, the characteristic absorption bands can be turned on and off with the complexation in a reversible fashion.

Journal Article↗

PubMed2004

Dewetting of thin liquid films near soft elastomeric layers.

Thin liquid film instabilities driven by van der Waals forces and in the proximity of soft elastomeric layers are considered in this work through two model problems: (i) a liquid film resting on an elastomeric layer and (ii) a liquid film bounded from one side by a rigid substrate and from the other side by an elastomeric layer. The elastomeric layers are modeled as linear viscoelastic solids, van der Waals forces are assumed to act only in the liquid, and lubrication theory and linear stability analysis are applied. For a liquid film resting on an elastomeric layer, substrate deformability has a destabilizing effect, as evidenced by an increase in the maximum growth rate and range of unstable wavenumbers. The destabilization worsens for thicker solid layers and is due to a lowering of the effective liquid-air interfacial tension. For an elastomeric layer resting on a liquid film, layer deformability has a stabilizing effect for thin layers but a destabilizing effect for thicker layers, with the former due to an enhancement and the latter due to a reduction of the effective solid-air interfacial tension. The results presented here suggest the possibility of exploiting the dewetting of thin liquid films to create topographically patterned surfaces on soft polymeric solids.

Journal Article↗

PubMed2004

Selective interactions of porphyrins with semiconducting single-walled carbon nanotubes.

A derivatized porphyrin with long alkyl chains, 5,10,15,20-tetrakis(hexadecyloxyphenyl)-21H,23H-porphine, is selective toward semiconducting single-walled carbon nanotubes (SWNTs) in presumably noncovalent interactions, resulting in significantly enriched semiconducting SWNTs in the solubilized sample and predominantly metallic SWNTs in the residual solid sample according to Raman, near-IR absorption, and bulk conductivity characterizations.

Journal Article↗

PubMed2004

Epidemiological study of measles in slum areas of Kolkata.

OBJECTIVE: An epidemiological study on measles was conducted among the under five children in slum areas of Kolkata to assess the incidence of measles. METHODS: 20 cluster sampling technique was followed and in each cluster 250 under five children were covered. Paramedical workers identified children of the target of age group who had history of measles in past one year and the medical officer confirmed the diagnosis following standard case definition. RESULTS: Incidence of measles was found as 5.76%. Incidence was equal in both the sex groups, but found more among infants. The incidence of measles gradually declined with the increase of age strengthening the view in favor of early immunization. Amongst the measles cases only 19.7% were immunized with measles vaccine. 100% of measles cases gave history of rash, 98.9% had history of fever, 82.8% reported that the rash started from face and progressed downwards to abdomen and leg. Cough, redness of eye and discoloration of skin were reported by 97.5%, 83.8% and 65.2% measles cases respectively. Only 16.9% and 8.6% children received Vitamin A oil before and after the illness respectively. 49% gave history of exposure to measles cases and 46.6% cases had measles within 2 weeks incubation period. CONCLUSION: The study highlighted the necessity of timely measles vaccine coverage, additional dose at a higher age and Vitamin A supplementation through IEC activities.

Age Distribution↗

PubMed2004

Use of multiple antigenic peptides related to antigenic determinants of infectious bursal disease virus (IBDV) for detection of anti-IBDV-specific antibody in ELISA--quantitative comparison with native antigen for their use in serodiagnosis.

Multiple antigenic peptides (MAPs) prepared for the predicted antigenic determinants on the VP2 protein of infectious bursal disease virus (IBDV) were used as antigens in enzyme-linked immunosorbent assay (ELISA)--an alternative to whole viral antigen to detect anti-IBDV antibodies in the chicken sera. Two MAPs were synthesized, which could specifically detect the anti-IBDV antibodies in serum samples by ELISA. The optimum quantity of MAP1 and MAP2 required to coat the wells of the ELISA plate was 5 ng/ml, whereas the amount of purified IBDV whole viral antigen was 500 ng/ml, indicating the high efficiency of MAPs. In this study, we mainly focused on the antigenicity of two eight-branched MAPs to detect anti-IBDV antibodies in ELISA, which would serve as safe, chemically defined, noninfectious alternative antigens to whole virus in serodiagnosis. The specificity and sensitivity of both MAP1 and MAP2 were found to be relatively better than the whole viral antigen.

Animals↗