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Biomedical subjects

S Koul

Publications and source records attributed to S Koul.

At least 19 recordsLinked to original sources
PubMed2006

Methane and nitrous oxide emission from bovine manure management practices in India.

We report seasonal variation in CH(4) and N(2)O emission rate from solid storage of bovine manure in Delhi as well as emission factors and emission inventory from manure management systems in India. Emission flux observed in the year 2002-2003 was 4.29+/-1, 4.84+/-2.44 and 12.92+/-4.25 mg CH(4)kg(-1)dung day(-1), as well as 31.29+/-4.93, 72.11+/-16.22 and 6.39+/-1.76 microgN(2)O kg(-1)dung day(-1) in winter, summer and rainy seasons, respectively. CH(4) emission factors varied from 0.8 to 3.3 kg hd(-1)year(-1) for bovines and were lower than IPCC-1996 default values. N(2)O emission factors varied from 3 to 11.7 mg hd(-1)year(-1) from solid storage of manure. Inventory estimates were found to about 698+/-27 Gg CH(4) from all manure management systems and 2.3+/-0.46 tons of N(2)O from solid storage of manure for the year 2000.

Air Pollutants↗
PubMed2004

Characterization of aerosols from biomass burning--a case study from Mizoram (Northeast), India.

Physical and optical properties of biomass burning aerosols in Northeastern region, India analyzed based on measurements made during February 2002. Large spatial extent of Northeastern Region moist tropical to moist sub-tropical forests in India have high frequency of burning in annual dry seasons. Characterization of resultant trace gases and aerosols from biomass burning is important for the atmospheric radiative process. Aerosol optical depth (AOD) observed to be high during burning period compared to pre- and post-burning days. Peak period of biomass burning is highly correlated with measured AOD and total columnar water vapor. Size distribution of aerosols showed bimodal size distribution during burning day and unimodal size distribution during pre- and post-burning days. Size distribution retrievals from biomass burning aerosols show dominance of accumulation mode particles. Weighted mean radius is high (0.22 microm) during burning period. Columnar content of aerosols observed to be high during burning period in addition to the drastic reduction of visibility. During the burning day Anderson sampler measurements showed dominance of accumulation mode particles. The diurnal averaged values of surface shortwave aerosol radiative forcing af biomass burning aerosols varies from -59 to -87 Wm(-2) on different days. Measured and modeled solar irradiances are also discussed in the paper.

Air Pollutants↗
PubMed2003

Kinetic resolution of 1-chloro-3-(1-naphthyloxy)-2-propanol, an intermediate in the synthesis of beta-adrenergic receptor blockers.

(R)- and (S)-1-chloro-3-(1-naphthyloxy)-2-propanol are intermediates in the synthesis of beta-adrenergic blocking agents and antihypertensive drugs such as propranolol and nadoxolol. Herein, improvement in the preparation of racemic 1-chloro-3-(1-naphthyloxy)-2-propanol generated from 1-naphthol and epichlorohydrin are reported. In addition, kinetic resolution studies have been conducted to obtain both (R) and (S)-1-chloro-3-(1-naphthyloxy)-2-propanol. These compounds were obtained in highly optically pure form by the stereoselective hydrolysis of its acyl derivatives using whole cell preparations containing enzymes from native sources. The results were compared with those obtained using commercial lipases.

Acylation↗
PubMed2003

In vitro cytotoxic elemanolides from Vernonia lasiopus.

Two new elemanolides, epivernodalol and lasiopulide, were isolated after chromatographic separation of the alcoholic extract of the dried aerial parts of the Vernonia lasiopus. These elemanolides are new C-10 epimers of the sesquiterpene lactones vernodalol and demethylacroylated vernodalol isolated from other species of Vernonia. Both elemanolides showed in vitro cytotoxicity against human cancer cell lines in culture. This is the first report of isolation and cytotoxic activity of the two elemanolides from V. lasiopus.

Antineoplastic Agents, Phytogenic↗
PubMed2002

Benzophenanthridine alkaloids from Corydalis flabellata.

Four new alkaloids, characterized as 6-(2-hydroxyethyl)-5,6-dihydrosanguinarine (1), 6-acetonyl-5,6-dihydrosanguinarine (2), N-methyl-2,3,7,8-tetramethoxy-5,6-dihydrobenzophenanthridine-6-ethanoic acid (3), N-methyl-2,3,7,8-tetramethoxy-6-oxo-5,6-dihydrobenzophenanthridine (4), together with oxosanguinarine (5), spallidamine (6), 6-acetonyl-5,6-dihydrochelerythrine (7), 6-oxochelerythrine (8) and sanguidimerine (9) were isolated from the roots of Corydalis flabellata.

Alkaloids↗
PubMed2001

Mapping the sites of putative tumor suppressor genes at 6p25 and 6p21.3 in cervical carcinoma: occurrence of allelic deletions in precancerous lesions.

Allelic deletions on the short arm of chromosome 6 (6p) are one of the common, possibly early, genetic changes that occur in the pathogenesis of cervical carcinoma (CC). Previous loss of heterozygosity (LOH) studies in CC identified a number of critical regions of deletions on 6p. However, the precise location of minimally deleted regions and their role in precancerous lesions have not been well characterized. To address these questions, we first performed a detailed LOH analysis on 6p in 59 cases of invasive CC. The pattern of LOH identified two minimal regions of deletions, one spanning a 5 cM genetic distance at 6p25 and a second site of 10.3 cM deletion mapping to 6p21.3. The 6p21.3 minimal deletion spans HLA class I genes. To understand the role of 6p genetic alterations in the development of CC, we also investigated 12 high-grade and 4 low-grade cases of cervical intraepithelial neoplasia (CIN) for LOH after laser microdissection. The high-grade CINs exhibited 91.7% LOH, and low-grade CINs had 50% LOH. These findings implicate the presence of at least two tumor suppressor genes on 6p relevant to CC and suggest that these genetic alterations occur very early in CC development. This study should therefore facilitate the identification of tumor suppressor genes on 6p and may identify which CINs are at high risk of progressing to invasive CC.

Chromosome Mapping↗
PubMed2001

Purification and characterisation of an ester hydrolase from a strain of Arthrobacter species: its application in asymmetrisation of 2-benzyl-1,3-propanediol acylates.

An ester hydrolase (ABL) has been isolated from a strain of Arthrobacter species (RRLJ-1/95) maintained in the culture collection of this laboratory. The purified enzyme has a specific activity of 1700 U/mg protein and is found to be composed of a single subunit (Mr 32,000), exhibiting both lipase and esterase activities shown by hydrolysis of triglycerides and p-nitrophenyl acetate respectively. Potential application of the enzyme concerns the asymmetrisation of prochiral 2-benzyl-1,3-propanediol esters besides enantioselective hydrolysis of alkyl esters of unsubstituted and substituted 1-phenyl ethanols.

Arthrobacter↗
PubMed2000

Koelpinin-A, B and C--three triterpenoids from Koelpinia linearis.

Three new triterpenoids, designated as koelpinin-A, B and C and characterised as 28-nor-lup-12,17-dien-3 beta,16 alpha-diol,3 beta-acetoxy-28-nor-lup-12,17-dien-16 alpha-ol and 28-nor-lup-12,17-dien-3 beta-ol-16-one, respectively, together with 30-nor-lup-3 beta-ol-20-one, taraxeryl acetate and germanicol, were isolated, from the aerial parts of Koelpinia linearis. 13C-NMR shifts were assigned after performing APT and DEPT experiments.

Models, Molecular↗
PubMed2000

Structure-activity relationship of piperine and its synthetic analogues for their inhibitory potentials of rat hepatic microsomal constitutive and inducible cytochrome P450 activities.

Inhibitors of drug metabolism have important implications in pharmaco-toxicology and agriculture. We have reported earlier that piperine, a major alkaloid of black and long peppers inhibits both constitutive and inducible cytochrome P450 (CYP)-dependent drug metabolising enzymes. In the present study, an attempt has been made to prepare several novel synthetic analogues so as to relate various modifications in the parent molecule to the inhibition of CYP activities. Two types of mono-oxygenase reactions arylhydrocarbon hydroxylase (AHH) and 7-methoxycoumarin-O-demethylase (MOCD) have been studied. Inhibition studies were investigated in rat microsomal fraction prepared from untreated, 3MC- and PB- treated rat liver in vitro. Modifications were introduced into the piperine molecule: (i) in the phenyl nucleus, (ii) in the side chain and (iii) in the basic moiety. Thus, 38 compounds have been subjected to such studies, and simultaneously an attempt has also been made to arrive at the structure-activity relationship of synthetic analogues. In general, most of the inhibitory potential of the parent molecule is lost with modification in either of the three components of piperine. Saturation of the side chain resulted in significantly enhanced inhibition of CYP while modifications in the phenyl and basic moieties in few analogues offered maximal selectivity in inhibiting either constitutive or inducible CYP activities. Thus few novel analogues as CYP inactivators have been synthesized which may have important consequences in pharmacokinetics and bioavailability of drugs.

Alkaloids↗
PubMed1999

Oxalate: from crystal formation to crystal retention.

Idiopathic calcium oxalate stone formation is a multifactorial disease. It is therefore unlikely that a single underlying condition will be responsible for entire spectrum of the disease; however, it appears that one important factor in the pathogenesis is an abnormality in oxalate metabolism. Whatever the cause, two critical parameters for stone formation are crystal formation and crystal retention in the renal tubules. Although crystal formination and role of oxalate in crystal formation have been evaluated extensively, it is only recently that crystal retention has been addressed. Previous studies from our laboratories demonstrated that oxalate exposure to renal epithelial cells in culture resulted in initiation of a program of events including DNA synthesis and cell death. The present studies evaluated effects of oxalate on cell proliferation and damage to distal tubular (Madin-Darby canine kidney cells) and proximal (LLC-PK1 cells) cells. Effects of oxalate exposure on calcium oxalate monohydrate (COM) crystal adherence to these cells were also evaluated. Results presented herein demonstrate that proximal tubular cells are more sensitive to oxalate than distal tubular cells. Furthermore, oxalate exposure to proximal tubular cells resulted in reinitiation of DNA synthesis, whereas no such effect was observed in distal tubular cells. Higher levels of oxalate (> 1 mM) resulted in cell loss of both proximal and distal tubular cells, as observed by crystal violet staining. Despite these differences, oxalate exposure to both proximal and distal tubular cells resulted in increased COM crystal adherence. Thus, oxalate exposure may promote crystal adherence to renal epithelial cells either secondarily to cell death and proliferation or by a yet unidentified mechanism. These studies provide the first direct evidence for the role of oxalate in promoting COM crystal retention by the urothelium.

Animals↗
PubMed1995

Identification of differentially expressed Leishmania donovani genes using arbitrarily primed polymerase chain reactions.

Arbitrarily primed polymerase chain reactions (AP-PCR) were used to amplify polymorphic DNA fragments from the genomes of a variety of geographic isolates of Leishmania donovani (Ld). From the latter, five polymorphic DNA fragments were cloned and sequence analysis identified 15 unique clones. Northern blot analysis showed that 13 of the 15 clones hybridized to transcribed RNAs isolated from Ld. Eight of these 13 AP-PCR clones specifically hybridized to Ld RNAs that were differentially expressed in promastigote and 'amastigote' cells. Comparative Northern analysis of four differentially expressed AP-PCR clones indicated that two clones, LdS-14-14 and LdI-9-7, were expressed in Ld and several other Leishmania species. However, RNAs corresponding to two other AP-PCR clones, LdE-6-1 and LdI-9-5, were detected only in members of the Ld complex, and not in L. major (Lm) or L. tropica (Lt). Comparative Southern blot analysis of the LdS-14-14 locus revealed numerous restriction-fragment length polymorphisms (RFLP) distinguishing Lm and Lt from the Ld isolates and L. infantum. However, the LdS-14-14 loci were mapped to similar-sized chromosomes observed among all Old World Leishmania species tested, indicating that localized nucleotide divergence, not chromosomal rearrangement, was responsible for altered Southern blot patterns. These results demonstrate that AP-PCR is a very useful method for identifying expressed gene sequences in organisms of relatively low-complexity genomes. Interestingly, the majority of these sequences identified in this study correspond to differentially expressed genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Identification of intra- and interspecific Leishmania genetic polymorphisms by arbitrary primed polymerase chain reactions and use of polymorphic DNA to identify differentially regulated genes.

Arbitrary primed polymerase chain reactions (AP-PCR) were used to amplify different polymorphic genomic DNA fragments from various Old World Leishmania species. Using four 10-mer AP primers, geographic isolates of L. donovani and various Old World species of Leishmania could be readily distinguished from one another by the pattern of amplified DNA products. Our studies confirmed two important characteristics of AP-PCR: its abilities to amplify a consistent pattern of DNA fragments from the genomes of different isolates of a single species and to identify genetic polymorphisms between the species isolates. We selected three polymorphic DNA fragments that differentiate L. donovani geographic isolates for further analysis. Sequence analysis of the clones derived from these three polymorphic fragments revealed eight unique sequences. Six of eight unique clones hybridized to distinct RNAs upon Northern-blot analysis. Three of these six clones hybridized to RNAs expressed differentially in in vitro grown L. donovani pro- and "amastigotes." One of the differentially expressed clones, LdE-6-1, exhibited restriction length polymorphisms that distinguished L. donovani from L. tropica and L. major. Comparative Northern blotting revealed that LdE-6-1 was differentially expressed in some members of the L. donovani species complex but not in L. major or L. tropica. These results demonstrate that AP-PCR can be used to generate products reflecting particular genes in organisms with low-complexity genomes.

Animals↗
PubMed1994

A four-year follow-up study on the incidence of diabetic retinopathy in older onset diabetes mellitus.

Out of 369 diabetic patients with an age at onset of diabetes > or = 30 years previously studied, 325 (88%) were included in an ophthalmological follow-up examination 4 years later. In patients treated with oral drugs at baseline, the incidence of any type of retinopathy was 30.8% and of severe retinopathy 5.7%. All patients who developed severe retinopathy received insulin during the follow-up period. At baseline, duration of diabetes, diastolic blood pressure, and signs of nephropathy (p < 0.05 in all cases) as well as degree of metabolic control (p < 0.01) differed between patients who developed retinopathy and those who did not. At follow-up, there were no longer any differences regarding degree of metabolic control and diastolic blood pressure. In patients treated with insulin at baseline, the incidence of any type of retinopathy was 41.0% and of severe retinopathy 16.1%. At baseline, duration of diabetes (p < 0.01), degree of metabolic control, and insulin dosage (p < 0.05 in both cases) differed between patients who developed retinopathy and those who did not. At follow-up, there was no longer any difference in insulin dosage.

Adult↗
PubMed1993

Studies on experimental chlamydial mastitis in goat histoenzymology.

Two strains of Chlamydia psittaci (one isolated from aborted goat foetus and the other from brain of a buffalo calf that had died of meningoencephalitis) were injected intracisternally into six goats to produce experimental mastitis. Cryostat sections of 7-8 microns thickness, obtained from udder, teat, liver and kidney of infected and control animals were incubated for histoenzymic demonstration of alkaline-(AKPase), acid-(ACPase) and adenosine-tri-(ATPase) phosphatases; lactate-(LDH) and succinate-(SDH) dehydrogenases and for reduced nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-D). Results demonstrated that AKPase and NADPH-D declined while ACPase accumulated in acinar cells of udder while both NADPH-D and ACPase decreased in teat sinus epithelium. Hepatic canaliculi in perilobular areas of liver lobules registered complete absence of AKPase and ATPase. Hepatocytes and renal tubules accumulated LDH, SDH and NADPH-D. The interstitial connective tissue of udder and kidney presented higher levels of AKPase. Comparison of results with biochemical alterations in the level of these enzymes revealed striking discrepancies which seem to arise because of failure of biochemical procedures to discriminate between functional cells of tissue and inflammatory cells. The functional significance of histoenzymic alterations has been discussed.

Animals↗
PubMed1990

Intraocular levels of cefuroxime in uninflamed rabbit eyes.

Intraocular levels of cefuroxime following subconjunctival, intravitreal and combined intravitreal and intravenous administration were determined in uninflamed rabbit eyes. Intraocular levels of the antibiotic were assayed by a biological method. Penetration of cefuroxime into the vitreous following subconjunctival administration was poor. Subconjunctival administration produced higher levels of cefuroxime in the aqueous when compared to parenteral administration alone. Higher levels of cefuroxime were achieved both in the aqueous and in the vitreous after an intravitreal injection. Intravitreal injection of 100 and 1000 micrograms cefuroxime produced intravitreal levels close to the minimum inhibitory concentration (MIC) for most ocular pathogens up to 24 h after drug administration. Intravenous supplementation did neither enhance the intraocular levels nor did it delay the clearance of the intravitreally injected antibiotic. Mild histopathological changes were seen with equal frequency both in the control and the test eyes and are attributed to the sampling techniques. Electroretinography (ERG) showed no definite changes suggestive of retinal toxicity up to 55 days after intravitreal administration.

Animals↗
PubMed1990

Primary ascaridial perforations of small intestine and Meckel's diverticulum.

The clinical presentation of six cases with primary ascaridial perforations of the terminal ileum (4 cases) and Meckel's diverticulum (2 cases), without any associated underlying intestinal disease, is described. All the cases presented clinically as peritonitis and had worm masses in the intestinal lumen with maximal impaction in the terminal ileum. Ileal perforations were surgically closed in two layers after removal of the worms. Diverticulectomy after removal of the worms was performed for Meckelian diverticular perforations. Peritoneal toilet was done in all the cases. Pressure necrosis from the impacted worm masses probably resulted in these perforations.

Ascariasis↗