Search PubMed⌕ Search

Biomedical subjects

R Sharma

Publications and source records attributed to R Sharma.

At least 199 records · Page 11Linked to original sources
PubMed1998

Structure and Extent of Adsorbed Gelatin on Acrylic Latex and Polystyrene Colloidal Particles.

The extent and structure of the adsorbed layer of gelatin onto colloidal particles is measured using dynamic light scattering, small-angle neutron scattering, and dilution viscometry. Adsorption isotherms are measured using solution depletion of fluorescein-5-isothiocyanate tagged gelatin. The results show that the adsorbed gelatin layer at saturation on acrylic-based latex (pH 6.5, 0.01 M sodium acetate) has approximately twice the average density of the free gelatin in solution, while for the adsorption onto polystyrene latex (pH 8.7, deionized water), it has nearly the same average density. The energetics of gelatin affinity is calculated from the temperature dependence of the adsorption equilibrium constant. It was found that the enthalpy of adsorption of a net negatively charged gelatin onto a negatively charged surface is favorable. An additional, favorable entropy of adsorption is measured for the polystyrene latex, for which hydrophobic interactions are important. Selective, competitive adsorption of nonionic and anionic surfactants confirms the specific source of the adsorption interactions. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Development of a TEM to study in situ structural and chemical changes at an atomic level during gas-solid interactions at elevated temperatures.

A Philips (Eindhoven, The Netherlands) 430 (300 keV) high resolution transmission electron microscope has been modified for in situ study of gas-solid interactions at elevated temperatures. This microscope can be best described as a synthesis, processing, and characterization laboratory for nano-size materials. A differentially pumped environmental cell (E-cell), capable of handling up to 20 torr of gas pressure, is fitted in the objective lens pole-piece gap. Single-tilt or double-tilt heating holders can be used to heat the samples up to 1,300 degrees C and 850 degrees C, respectively. The system can handle any non-corrosive gases such as H2, O2, N2, NH3, CO, water vapor. Electron diffraction patterns are used to elucidate the reaction path and to identify stable and/or metastable phases formed. Time, temperature, and pressure resolved electron diffraction patterns can also be used to estimate the thermodynamical conditions for the onset of a reaction and the stability range of different phases observed during the process can also be determined. The high resolution imaging capabilities enable elucidation of the basic structural mechanisms involved at near atomic level. The TV rate camera/video recording system is used to measure the reaction rates (kinetics of the reaction). A post projector energy filter (Gatan Imaging Filter, GIF) is attached at the bottom of the microscope in order to filter the inelastic scattering from the gases/thick samples as well as to obtain energy filtered images (chemical maps). The GIF can also be used as a parallel electron energy loss spectrometer (PEELS) to obtain changes in the sample composition during the reactions. The changes in the near-edge structures of PEELS spectrum is used to monitor changes in bonding and/or chemical environment elements during reaction. The chemical maps obtained can also be used to identify preferred regions of gas reactions, e.g., grain boundaries or surfaces, etc. Various modifications of the microscope are described in detail, with suitable examples showing the performance.

Cerium↗
PubMed1998

Conformationally constrained analogues of diacylglycerol (DAG). 14. Dissection of the roles of the sn-1 and sn-2 carbonyls in DAG mimetics by isopharmacophore replacement.

The replacement of the sn-1 and sn-2 carbonyl esters in DAG-surrogate lactones by sulfonate esters showed that their isosteric properties in protein kinase C binding are controlled by the location of the hydrophobic alkyl chain on the molecule. The CO and SO2 groups appear to be true isosteres only when they are adjacent to the alkyl chain, which is presumed to insert normal to the lipid bilayer.

Diglycerides↗
PubMed1998

Total correction of tetralogy of Fallot in adults--surgical experience.

A total of 100 patients of tetralogy of Fallot aged 13 years and over were operated upon at the All India Institute of Medical Sciences, New Delhi, India between January 1991 and December 1996. There were 69 males (69%) and 31 females (31%). Age ranged from 13 years to 43 years (mean 19.66 years). Twenty % of patients had preoperative complications like haemoptysis, cerebrovascular accidents, brain abscess and infective endocarditis. Twenty-two patients had previous palliative shunts. Fifteen patients had coil embolisation of major collaterals prior to surgery. In hospital mortality rate was 4%. Follow-up ranged from 1 month to 5 years (mean 3.4 years). There was one late death due to infective endocarditis. Postoperatively 93.6% patients were in NYHA class I. Significant residual defects warranting re-operation were present in three patients. Total correction of tetralogy of Fallot in older patients can be performed with acceptable results.

Adolescent↗
PubMed1998

Nasoethmoid schwannoma with intracranial extension. Case report and review of literature.

Schwannomas are very rare in the nose and paranasal sinuses; their presence both intra-and extracranially is still rarer. Here we present a case of nasoethmoid schwannoma with intracranial extension into anterior cranial fossa. Clinical, radiological, pathological and operative findings are discussed and the literature is reviewed. We recommend bifrontal craniotomy for removal of intracranial and nasoethmoid extensions of this tumor.

Adult↗
PubMed1998

Spontaneous evacuation of cerebellar abscess through the middle ear. A case report.

Otogenic brain abscesses are a significant cause of mortality and morbidity in developing countries. Usually they occur either by distant thrombophlebitis of cerebral veins or by direct extension in an unsafe type of chronic suppurative otitis media. This case of cerebellar abscess was prepared for surgical excision, when sudden evacuation of pus through the left middle ear resolved the abscess and clinical features in the patient. No surgical intervention was required in this patient. The case under discussion is unique and unreported for its spontaneous evacuation through the middle ear.

Adolescent↗
PubMed1998

Juvenile (calcifying) aponeurotic fibroma of the neck.

A case of juvenile (calcifying) aponeurotic fibroma (JAF) arising in the neck of a 5-year-old female is presented. The lesion was misdiagnosed as fibrous hamartoma of infancy (FHI) on a superficial biopsy prior to total excision of the mass. Only one instance of JAF of the neck has previously been reported; the tumor is usually located in the distal extremities and often recurs following excision. FHI occurs most frequently at and about the axilla and shoulder, and does not recur in most instances.

Calcinosis↗
PubMed1998

Aneurysm of sinus of Valsalva dissecting into interventricular septum.

BACKGROUND: Dissection of interventricular septum by aneurysm of the sinus of Valsalva is extremely rare. We present our experience with the management of 10 patients with this condition. METHODS: Ten patients with aneurysm of the sinus of Valsalva dissecting into the interventricular septum were managed at All India Institute of Medical Sciences, New Delhi, between May 1987 and September 1996. Conduction abnormalities and aortic insufficiency dominated the clinical picture. Eight patients underwent surgical repair. Two patients refused operation, and only permanent pacemaker implantation was done for complete heart block in both these patients. RESULTS: There was no hospital mortality. Follow-up ranged from 1 to 9 years. There was one late death due to carcinoma of the larynx, and 1 patient required reoperation for persistent aortic insufficiency. All other patients who underwent operation are in New York Heart Association functional class I. CONCLUSIONS: We recommend surgical repair of this condition to deal with aortic regurgitation and to avoid the potential risk of rupture, thromboembolism, and infective endocarditis. However, surgical repair offers no guarantee against arrhythmias and conduction abnormalities.

Adolescent↗
PubMed1998

Surgical experience with intracardiac myxomas: long-term follow-up.

BACKGROUND: Myxomas are the most common benign intracardiac tumors. This report summarizes our 20-year experience with these tumors. METHODS: Sixty-six patients (25 male) with a median age of 39 years (range, 6 to 70 years) underwent surgical excision of primary or recurrent intracardiac myxomas during the years 1976 to 1996. Symptom duration ranged from 2 to 8 months. There were 55 left atrial myxomas, 10 right atrial myxomas, and 1 biatrial myxoma. Three of the patients were in one family. The surgical approach comprised complete wide excision. RESULTS: There were two early deaths. Late follow-up is 89% (57/64) complete. There was one late death, which was not due to a cardiac cause. Echocardiography at a mean follow-up of 66.9 months (range, 7 to 241 months) showed no recurrence of sporadic myxomas. However, 2 of the 3 patients with familial myxomas had recurrence. CONCLUSIONS: Surgical excision of atrial myxoma gives excellent short-term and long-term results leading to eventual cure of nonfamilial myxomas. However, familial myxomas retain a strong tendency to recur even 20 years after excision.

Adolescent↗
PubMed1998

Amylases synthesis in scutellum and aleurone layer of maize seeds.

The endosperm of germinating maize seeds contains four isozymes of alpha-amylases (alpha-amylase-1 to -4) and one isozyme of beta-amylase. The alpha-amylases were purified by affinity chromatography on amylose and separated by DEAE-cellulose chromatography, into two groups, namely alpha-amylases-1,2 and alpha-amylases-3,4; and beta-amylase was purified by precipitation as a glycogen-enzyme complex. The molecular weight of alpha-amylases-1 and -2 was 46 kD, alpha-amylases-3 was 44.5 kD and of alpha-amylases-4 was 47.5 kD. The molecular weight of beta-amylase was 56 kD. During seed germination increase in amylolytic activity in endosperm was mainly contributed by secretion of alpha-amylases from adjoining aleurone layer and scutellum. The synthesis and secretion of alpha-amylases was first initiated in the scutellum followed by aleurone layers. Exogeneous Ca2+ stimulated synthesis of alpha-amylases in both eleurone layer and scutellum. In contrast, though scutellum and aleurone layer synthesized beta-amylase but it was not secreted to the medium. These results suggest that during the early germination period, alpha-amylases secreted from scutellum mobilizes starch.

Amylases↗
PubMed1998

Differential expression and properties of phenylalanine ammonia-lyase isoforms in tomato leaves.

In tomato leaves, excision and light treatments increase phenylalanine ammonia-lyase activity, which is contributed by three PAL isoforms. These isoforms possessed similar native and subunit Mr, but were different in their pI, Km for Phe and optimal pH for activity. Also these were differentially induced and affected by metabolites belonging to particular branches of phenylpropanoid pathway.

Chromatography, Gel↗
PubMed1998

Role of long-persisting human hepatitis E virus antibodies in protection.

The role of long-persisting HEV antibodies in humans was investigated. A well-characterized human volunteer anti-HEV (IgG) after 4 years of the recovery of the disease was passively immunized (200 mg kg-1 body wt) intramuscularly into three rhesus monkeys (nos 7, 8 and 9), while two monkeys (nos 5 and 6) were injected with normal immunoglobulin preparation (negative for anti-HEV IgG). At 16 h later all the animals were challenged intravenously with live HEV, as 10% stool extract prepared from the volunteer (positive for HEV by solid-phase immune electron microscopy). It was seen that transaminases (ALT/AST) were elevated in immunized monkeys on day 49 (no. 8), 60 (no. 7) and 86 (no. 9) after the virus challenge. On serological examination, all immunized (nos 7, 8 and 9) and one unimmunized (no. 6) monkeys were found positive for HEV IgM on day 10 post-challenge, while monkey no. 5 was negative. Further, all the animals from the immunized and unimmunized group seroconverted to HEV-IgG when tested on days 25 and 55 post-challenge. This has clearly shown that there is no protection. Therefore, these long-persisting HEV antibodies alone in humans, may not be protective in passive immunization.

Alanine Transaminase↗
PubMed1998

Oxidation and Reduction of Small Palladium Particles on Silica.

: We have used the technique of in situ electron microscopy to study the oxidation and reduction of the palladium (Pd) catalysts. In this study, we have subjected a Pd catalyst to oxidation and reduction cycles and studied the changes in particle structure and morphology with in situ electron diffraction and imaging. The PdO particles can be reduced to Pd metal in situ at temperatures as low as 200 degreesC in an atmosphere of a few Torr of both H2 and O2. We also found that essentially the same reduction occurred in the vacuums of 10(-6) to 10(-7) Torr in two different electron microscopes. Our in situ reduction studies show that many of the oxide particles form voids when reduced to Pd metal. The decrease in volume that occurs during reduction is often accommodated by a combination of particle shrinkage and void formation. The production of voids does not seem to depend on either the reducing atmosphere or the rate of reduction, although the voids appear to be unstable above 500 degreesC.

Journal Article↗
PubMed1998

Plasmapheresis in the treatment of steroid-resistant focal segmental glomerulosclerosis in native kidneys.

A circulating glomerular capillary albumin permeability factor (P(alb)) has been implicated in the pathogenesis of focal segmental glomerulosclerosis (FSGS), which recurs in transplanted kidneys. Plasmapheresis for recurrent FSGS may reduce proteinuria and stabilize renal function if instituted early. We performed six plasmapheresis treatments over 2 weeks in eight patients with a history of steroid-resistant idiopathic FSGS in native kidneys for an average of 12 +/- 2.3 months to determine whether treatment would decrease proteinuria or stabilize renal function. P(alb) was measured before and after plasmapheresis, and patients were followed-up for a mean of 29 +/- 4 months after the development of clinical symptoms. Proteinuria decreased in two of eight treated patients, although only transiently in one of the two. P(alb) improved in one of the two responding patients. Both patients with an improvement in proteinuria had stable renal function at last follow-up. In six of eight patients, there was no improvement in proteinuria despite an improvement in P(alb) (P < 0.0001) after plasmapheresis. At last follow-up, renal function was stable in two of the six nonresponding patients, and four of the six had significant progression of renal disease or were receiving dialysis treatments. These studies suggest that plasmapheresis may diminish proteinuria and stabilize renal function in a small minority of patients with steroid-resistant idiopathic FSGS. However, the lack of a relationship between the removal of the circulating permeability factor and the development of remission in these patients suggests that local factors associated with advanced renal injury or systemic factors unrelated to glomerular permeability play a significant role in determining proteinuria at this late stage of the disease.

Adolescent↗
PubMed1998

Bowel care for individuals with spinal cord injury: comparison of four approaches.

The efficacies of four bowel care regimens (bisacodyl suppositories, glycerin suppositories, mineral oil enemas and docusate sodium mini-enemas) were compared in seven subjects with traumatic spinal cord injury. Efficacy was assessed in terms of colonic transit time, bowel evacuation time and subjective responses to a questionnaire. Both docusate sodium mini-enemas and mineral oil enemas decreased total and left-sided colonic transit time. However, docusate sodium mini-enemas were superior to mineral oil enemas in terms of the decrease in bowel evacuation time and symptom reduction. Results in this small group of subjects suggest that docusate sodium mini-enemas may have advantages in the management of bowel evacuation in individuals with spinal cord injury.

Adult↗