PubMed Health⌕ Search

Biomedical subjects

S Karmarkar

Publications and source records attributed to S Karmarkar.

18 recordsLinked to original sources
PubMed2006

Gel permeation chromatography of dextrans in parenteral solutions: calibration procedure development and method validation.

We describe development and validation of a gel permeation chromatographic (GPC) method for dextrans in parenteral solutions. The GPC method was adopted from USP monographs on Dextran 40 and Dextran 70 raw materials. The method was optimized with a mobile phase flow rate of 1 mL/min and column temperature of 40 degrees C, to sharpen dextran and dextrose peaks. An easy-to-use, curve-fitting program capable of non-linear regression was developed in-house, using Microsoft Excel and its Solver add-in to successfully meet the GPC calibration requirements for dextrans and dextrose, i.e., the experimental molecular weights within 100+/-5% of the known molecular weights for dextrans and molecular weight of dextrose within 180+/-2 Da. The GPC method was validated in terms of its stability indicating nature, robustness (column temperature of 40+/-3 degrees C), accuracy (lack of effects of pH and concentration of dextrans or matrix components), and precision (repeatability and intermediate). Molecular weight distribution of dextrans were unchanged when the dextran containing test solutions were subjected to forced degradation using heat, light (daylight and UV light), extreme alkaline conditions or oxidative conditions. The method was capable of detecting changes in molecular weight distribution caused by degradation under extreme acidic conditions and heat, thereby confirming the stability indicating nature of the method. The concentration of Dextran 40 and Dextran 70 (75-125% of the nominal assay concentration), matrix components (108-111% of their nominal concentrations), and solution pH (pH 3-7 for Dextran 40 solutions and pH 4-7 for Dextran 70 solutions) did not affect the measured molecular weight distribution of Dextran 40 or Dextran 70. The method was precise with %R.S.D. of less than 1% for M (W) values of Dextran 40 or Dextran 70.

Chromatography, Gel↗
PubMed2004

Validated ion-exclusion chromatographic method for citrate and acetate in medical fluids.

In this paper we describe the development and validation of a solid-phase extraction procedure, followed by ion-exclusion chromatographic determination of citrate and acetate in medical fluids. The medical fluids contained trace levels of non-polar compounds, which were not of interest for the purposes of assay requirements, but due to their strong affinity towards the ion-exclusion chromatography column necessitated a 180-min long runtime to elute. The developed SPE procedure, based on trapping the hydrophobic compounds, on a reversed-phase material, while allowing analytes of interest elute off unretained, shortened the runtime to 35 min. The procedure is simple since it has only two steps, conditioning of the SPE cartridge with acetonitrile and treating the sample. The SPE procedure followed by ion-exclusion chromatographic determination was successfully validated per the International Conference on Harmonization (ICH) guidelines in terms of specificity, accuracy as recovery versus untreated sample, precision, range, linearity of response, ruggedness, stability of treated samples, and robustness. The validation data showed that the method is specific, accurate, precise, rugged, and robust. The validated method has been routinely used in the manufacturing environment.

Acetates↗
PubMed2001

QSAR study on binding affinity of PATs (rodenticides) to the [3H]-mepyramine-labelled H1 receptor in rat and guinea pig brain.

The binding of a series of PAT analogues (rodenticides) to the [3H]-mepyramine-labelled H1 receptor in rat and guinea pig brain was investigated topologically using negentropy (N), molecular redundancy (MRI), first-order molecular connectivity (1chi(v)), Wiener (W), and Szeged (Sz) indices. Multiple regression analyses showed that MRI provided excellent results upon introduction of indicator parameters. Predictive ability of the proposed models was discussed using cross-validation parameters.

Animals↗
PubMed2000

A comparative QSAR study using Wiener, Szeged, and molecular connectivity indices

In this study we have investigated the relative correlation potential of Wiener (W), Szeged (Sz), and molecular connectivity indices (0chiR, 1chiR and 2chiR) in developing quantitative structure-activity relationships, QSAR; log P values of benzoic acid and its nuclear-substituted derivatives were used for this purpose. The statistical analyses for univariate and multivariate correlations had indicated that both W and Sz are closely related to the connectivity indices (mchiR) and that the W, the Sz, and the 1chiR indices have similar modeling potentials. 1chiR gives slightly better results than both W and Sz. Other connectivity indices 0chiR and 2chiR correlate poorly with log P.

Journal Article↗
PubMed1998

Presacral teratoma presenting with congenital urinary ascites.

Congenital teratomas occur most frequently in the sacrococcygeal region. Most grown into a large perineo-sacral swelling that is conspicuous externally. Infrequently, the neoplasm is contained almost entirely within the pelvis in the presacral space. Congenital urinary ascites is observed in patients with obstructive uropathy; posterior urethral valves in a newborn is one of the most prominent causes of urinary ascites. We report a case of presacral teratoma leading to rupture of the urinary bladder due to outflow obstruction and causing urinary ascites. The ascites was drained, the bladder was repaired, and the teratoma was successfully excised. A review of the literature did not reveal any similar case.

Ascites↗
PubMed1997

Papillomatosis of the gallbladder in metachromatic leukodystrophy.

A 2-year-old boy who presented with a cystic gallbladder mass was found histologically to have metachromatic leukodystrophy. Diffuse hyperplasia of the gallbladder mucosa, multiple tendrillar fronds extending into the lumen, extensive papillomatosis, and the presence of large numbers of macrophages bearing metachromatic material confirmed the diagnosis. The child developed progressive degeneration of the central nervous system, refractory bronchopneumonia, and generalized muscular atrophy. A computed tomographic scan of the brain demonstrated hypodense areas of white matter suggestive of demyelination. This report describes the rare association of gallbladder papillomatosis with a storage disorder and reviews the relevant literature.

Child, Preschool↗
PubMed1996

Vestibular schwannoma and the only hearing ear.

With the recent advances in the management of vestibular schwannomas, it is possible not only to save the facial nerve function but also preserve hearing in a small percentage of cases. Difficulties arise while managing patients with vestibular schwannoma in their only hearing ear. In this article we summarize our experience in managing seven of these patients. We recommended a watch and wait policy with a regular follow-up with audiometric testing and gadolinium-enhanced magnetic resonance imaging (MRI). Gamma knife radiosurgery is advised in cases with deterioration of hearing or increase in tumour size. Surgery is usually avoided unless there are brainstem compression symptoms.

Adult↗
PubMed1996

Congenital cholesteatomas of the middle ear: a different experience.

A retrospective analysis is presented of 44 cases of congenital cholesteatoma of the middle ear. Twenty-one patients had cholesteatoma localized to the posterosuperior mesotympanum in complete contrast to the commonly reported anterosuperior location seen in only two cases. The remaining 21 patients had cholesteatoma involving either the entire mesotympanum or epitympanum or both. The posteriorly located congenital cholesteatomas might represent a completely different entity and originate from the trapped epithelial cell rests in the posterior mesotympanum during the development of temporal bone. All but one patient were treated by using a closed tympanoplasty. Eight patients underwent a single-stage surgery. A preplanned second-stage procedure was performed in 33 patients, and three are awaiting their second stage. Residual disease was seen in 19 (57%) patients undergoing second-stage surgery. No patient has had recurrent disease so far. Thirty-eight (85%) patients had a preoperative air-bone gap of > or = 30 dB. Of the 33 patients considered for hearing results, 16 (48%) had a postoperative gap within 10 db.

Adolescent↗
PubMed1996

Blastopathies--symmetrical conjoined twins.

Conjoined twins are one of the rarest blastopathies, challenging the medical profession. The incidence in India is reported to be 1:60,000 pregnancies. This report records two cases of female conjoined twins. The sharing of various organs and complex cardiac anomalies encountered were very fascinating. Omphalopagus conjoined twins had only three lower extremeties, a common gastro-intestinal tract beyond the terminal ileum, crossed ectopia, hypoplastic kidneys and bicornuate uterus. The heart showed dextrocardia, A.S.D. and V.S.D. No attempt was made for surgical separation in this case. The second case was a thoracopagus, with the heart showing V.S.D., cor triatrium dexter with a posterior venous chamber. Surgical separation was attempted, but was unsuccessful. Both cases showed a single fused liver. The need for antenatal diagnosis and successful separation with good pre- and post-operative management is stressed.

Female↗
PubMed1995

Surgical treatment of cholesteatoma in children.

Treating cholesteatoma in children is still controversial. This article reviews 93 cases of pediatric cholesteatoma operated on from 1983 to 1991 in the Gruppo Otologico, Placenza, Italy, and details the results in 83 children who underwent the intact canal wall technique. During second-stage surgery, residual cholesteatoma was detected in 38% of patients. Recurrent cholesteatoma was detected in 10% of patients treated with the intact canal wall technique. Residual cholesteatoma was seen in the middle ear cleft in 63%, in the epitympanum in 26%, and in the mastoid in 11% of cases. Social hearing level (< 25 dB) was achieved in 85% of cases with suprastructure, whereas only 53% of patients without suprastructure had these levels. In the treatment of cholesteatoma in children by use of the intact canal wall technique, a preplanned second-look operation is mandatory to eradicate the disease.

Adolescent↗
PubMed1995

Hearing preservation in vestibular schwannoma surgery: fact or fantasy?

This study reviews 57 papers dealing with the issue of hearing preservation in vestibular schwannoma surgery published in otolaryngologic and neurosurgical literature between the years 1977 and 1994. The authors', in this review, have made an attempt to verify whether the claims of hearing preservation are real, whether there is a price to be paid in terms of morbidity and whether there are univocal criteria for reporting results. The review shows that there is a wide disarray in reporting hearing results and the claims of hearing preservation are often unreal and misleading. On retabulating the results of a few series according to the minimal prerequisites for normal hearing (PTA < or = 30 dB and SDS > or = 70 per cent) and according to other various commonly reported criteria, it became evident that rates of hearing preservation differed a lot depending upon criteria. While any measurable hearing could be preserved in many cases, only a few had normal hearing preserved.

Audiometry, Pure-Tone↗
PubMed1995

Canal wall down mastoidectomy: causes of failure, pitfalls and their management.

Managing patients with failed canal wall down mastoidectomy, requires a meticulous approach to control the disease and restore hearing. The present article reviews the causes of failure of the primary procedure and pitfalls encountered in 105 patients referred to our centre for revision canal wall down mastoidectomy. At post-revision surgery there were no cases with residual or recurrent cholesteatoma. The failures in our revision procedure were due to tympanic membrane perforation which occurred in five per cent (n = 4) and intermittent otorrhoea in two per cent (n = 2). A dry cavity with adequate middle ear space allowed for optimum audiological function even in revision canal wall down procedures.

Adolescent↗
PubMed1995

Intratemporal hemangiomas involving the facial nerve: diagnosis and management.

Intratemporal vascular tumors involving the facial nerve are rare benign lesions. Because of their variable clinical features, they are often misdiagnosed preoperatively. This study presents a series of 21 patients with such lesions managed from 1977 to 1994. Facial nerve dysfunction was the most common complaint, present in 60% of the cases, followed by hearing loss, present in 40% of cases. High-resolution computed tomography, magnetic resonance imaging with gadolinium, and a high index of clinical suspicion is required for preoperative diagnosis of these lesions. Early surgical resection of these tumors permits acceptable return of facial nerve function in many patients.

Journal Article↗
PubMed1995

An easy, cost-effective and time-conserving method of studying the vascular anatomy of the base of the skull.

In this work we present a simple, rapid, cost-effective and time-conserving method of studying the vascular anatomy of the base of the skull. This method is based on the injection of the arteries and veins with an appropriate coloring solution that possesses the property of rapid solidification. This technique of preparation of the coloring solution and the method of injection is described in detail. The advantages and disadvantages of this technique are also discussed.

Journal Article↗
PubMed1995

Cholesteatoma surgery: the individualized technique.

A retrospective analysis of 433 cholesteatoma cases, surgically treated at the Gruppo Otologico, Piacenza, Italy, over a 7-year period, is reported. The purpose of this study was to delineate actual indications for individualizing open and closed procedures and to compare their results as regards residual or recurrent disease and hearing. The total incidences of residual and recurrent cholesteatoma in the open cavity procedures were 10% and 2.38%, respectively, while the closed procedures showed higher incidences of residual and recurrent cholesteatoma: 31.22% and 11.16%, respectively. The problem of a persistently discharging cavity was encountered in only 1 case of an open procedure, while 2 patients had persistent otorrhea among the closed cavity cases. The hearing results, although slightly better in the closed procedures, were not significantly different from those in the open procedures.

Adolescent↗
PubMedDate not supplied

A novel PI index and its applications to QSPR/QSAR studies.

A novel topological index, PI (Padmakar-Ivan index), is derived in this paper. The index is very simple to calculate and has disseminating power similar to that of the Wiener (W) and the Szeged (Sz) indices. The comprehensive studies show that the proposed PI index correlates highly with W and Sz as well as with physicochemical properties and biological activities of a large number of diversified and complex compounds. The proposed PI index promises to be a useful parameter in the QSPR/QSAR studies. The stability of each model is demonstrated by applying cross-validation test. Furthermore, more favorable comparison with other representative indices such as the Randic index is also made in order to establish the predictive ability of the PI index. The results have shown that in several cases the PI index gave better results.

Alkanes↗
PubMedDate not supplied

Proximal jejunal obstruction due to eosinophilic gastroenteritis.

Eosinophilic enteritis or gastroenteritis is a rare disease characterised by tissue eosinophilia which can affect different layers of bowel wall. It can affect any area of gastrointestinal tract from the esophagus to the rectum, although stomach and small intestine are sites most frequently reported. It is important to recognize this disease early and institute the necessary treatment. An eight year old girl presented with acute intestinal obstruction. Exploration revealed a structure of proximal jejunum. Histopathology demonstrated eosinophilic jejunitis. The case is reported owing to this rarity and relevant literature is reviewed.

Acute Disease↗