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N Dhingra

Publications and source records attributed to N Dhingra.

At least 19 recordsLinked to original sources
PubMed2000

The importance of homologous recombination in the generation of large deletions in hybrid plasmids in Amycolatopsis mediterranei.

The cloning vector pRL60 was developed previously as a tool for genetic manipulations in Amycolatopsis mediterranei, which produces the commercially and medicinally important antibiotic rifamycin. Here, a method based on intraplasmid recombinations is described for the construction of smaller plasmids in A. mediterranei, which also helped in delimiting the origin of replication (pA-rep) of the parent plasmid. The strategy involved the cloning of a selectable marker, erythromycin resistance gene (ermE), onto plasmids pULAM2 and pULVK2A (derivatives of pRL1), followed by selection of the hybrid or concatemeric plasmids pRL50 and pRL80 (with large homologous repeats) in Escherichia coli GM2163. These hybrid plasmids were then transferred to A. mediterranei DSM 40773 by electroporation, with selection in the presence of different antibiotics. During the process of transformation and selection in A. mediterranei, pRL50 and pRL80 underwent intraplasmid recombinations, yielding derivatives that retained a common region essential for maintenance and replication, as well as the selected resistance genes. This approach produced several smaller plasmids designated pRL51, pRL52, pRL53, pRL60, pRL81, and pRL82. These plasmids, isolated from A. mediterranei DSM 40773, could be transferred to different Amycolatopsis strains at transformation efficiencies ranging from 0.7 x 10(2) to 4 x 10(4) transformants/microg DNA. The electroporation parameters under which maximum transformation efficiencies were obtained varied from strain to strain. Since the isolation of plasmid DNA from Amycolatopsis strains were extremely difficult, a convenient and rapid method of direct transfer of plasmid DNA, i.e., electroduction, was also developed in which the above-described shuttle plasmids were transferred directly from A. mediterranei to E. coli. In addition, the sequence of the minimal (pA-rep, approximately 1.0 kb) of plasmid pRL51 was determined. The nucleotide base sequence of the pA-rep region did not have any clear similarity to the DNA or amino acid sequences in various databases, suggesting that it is unique.

Actinomycetales↗
PubMed2000

Regulation and manipulation of the gene clusters encoding type-I PKSs.

Modular polyketide synthases are large, multifunctional enzyme complexes that are involved in the biosynthesis of important polyketides. Recent studies have revolutionized our understanding of the linear organization of polyketide-synthase-gene clusters. They have provided crucial information on the initiation, elongation and termination of polyketide chains, and thus a rational basis for the generation of novel compounds. Combinatorial libraries have helped this field to move from a random approach to a more empirical phase. The large number of diverse analogs of antibiotics that are presently produced demonstrate the enormous potential of combinatorial biosynthesis.

Combinatorial Chemistry Techniques↗
PubMed2000

Efficacy of fluconazole and liposome entrapped fluconazole for C. albicans induced experimental mycotic endophthalmitis in rabbit eyes.

PURPOSE: To study the efficacy of intravitreally injected plain and liposome encapsulated fluconazole in the doses of 100 and 200 microg in Candidal endophthalmitis in rabbit eyes. METHOD: Endophthalmitis was induced by injecting Candida albicans (1000 CFU/0.1 ml). Seventy two hours after inoculation, plain and liposome encapsulated fluconazole (REVs) were injected. At day 16 sterility was studied using vitreous culture. RESULTS: In the 100 & 200 microg plain fluconazole group, vitreous sterility was seen in 62.5% and 75%, respectively. In the liposome entrapped fluconazole a culture sterility of 25% and 50% for 100 microg and 200 microg, respectively, was seen. CONCLUSION: Plain fluconazole in the dose of 100 and 200 microg was equally effective against Candidal endophthalmitis in rabbits, but a failure of 25-37.5% of the eyes to respond, discourages one from using fluconazole as a sole therapy. Liposome entrapped fluconazole was found to be inferior to plain fluconazole in this model.

Animals↗
PubMed2000

Audit of small-incision cataract surgery using an anterior chamber maintainer.

PURPOSE: To assess the results of small-incision cataract surgery with intraocular lens implantation using an anterior chamber maintainer (ACM) performed between March 1997 and December 1998. METHOD: A retrospective audit was performed of all 300 consecutive patients who underwent extracapsular cataract extraction using a 6 mm scleral tunnel incision, anterior chamber maintainer and manual fragmentation of the nucleus. RESULTS: Ninety per cent of patients had a gain in visual acuity at the end of 3 months. The rate of posterior capsule opacification was comparable to the results of the National Cataract Surgery Survey (RCO 1993), i.e. 13%, but the rate of corneal endothelial decompensation and endophthalmitis was marginally higher. CONCLUSION: Appropriate selection of cases, meticulous wound closure and subconjunctival antibiotics at the end of surgery make this an acceptable alternative small-incision closed-system low-cost procedure where phacoemulsification is not available.

Adult↗
PubMed2000

Intravitreal pharmacokinetics of plain and liposome-entrapped fluconazole in rabbit eyes.

The objective of our experiment was to study the pharmacokinetics of plain and liposome-encapsulated fluconazole after an intravitreal injection (100 microg/0.1 ml) in rabbit eyes. Equal concentrations of plain and liposome-entrapped fluconazole were injected intravitreally into albino rabbits through the pars plana after intravenous pentobarbitone anesthesia. The rabbits were sacrificed at various time intervals, and the concentration of fluconazole in vitreous, retina-choroid, aqueous humor and cornea was estimated using High Performance Liquid Chromatography (HPLC). Plain fluconazole showed a rapid vitreal clearance and a short half-life (3.08 hr), whereas liposome-entrapped fluconazole showed a longer half-life (23.40 hr). The terminal elimination constant (Ke) of the liposome-loaded drug from the vitreous was seven times less than the plain drug. In the plain fluconazole group, at 1 hr, a high concentration of the drug was found in the retina. To conclude, the elimination of fluconazole was primarily transretinal and was very rapid. Liposome encapsulation significantly increased the half-life of fluconazole in the vitreous cavity.

Animals↗
PubMed1998

Development of an improved cloning vector and transformation system in Amycolatopsis mediterranei (Nocardia mediterranei).

A versatile plasmid cloning vector pRL60 carrying kanamycin/neomycin resistance (km/neo), erythromycin resistance (ermE) and alpha-amylase (alpha-amy) marker genes that replicates in various Amycolatopsis mediterranei strains and Escherichia coli has been constructed. This cloning vector has been derived from a hybrid plasmid pRL50, which was developed by cloning ermE from pIJ4026 into a pRL1 derivative pULAM2. While cloning ermE into the BamHI site of pULAM2, only a hybrid plasmid pRL50 with an additional copy of pULAM2 was selected. Thus pRL50 (18.7 kb) contained two copies each of the km/neo, alpha-amy, and one copy of ermE. When pRL50 was transformed into A. mediterranei DSM 40773 through electroporation and selected under erythromycin resistance, the plasmid underwent a spontaneous deletion of 8.5 kb fragment resulting in the formation of plasmid pRL60. pRL60 (10.2 kb) is a shuttle vector between A. mediterranei and E. coli with three marker genes: km/neo, ermE and alpha-amy. ermE is expressed in A. mediterranei thus allowing good selection of transformants. The alpha-amy gene of pRL60 is also expressed in A. mediterranei DSM 40773 and its activity can be easily detected on starch containing medium after iodine staining. Most critical parameters evaluated for electrotransformation using pRL60 in A. mediterranei were growth phase, electrical field strength, pulse length, pretreatment of mycelia with lysozyme and use of salt free water. At optimized parameters, a transformation efficiency of 4.0 x 10(4) transformants/microg DNA was reproducibly achieved for A. mediterranei DSM 40773. pRL60 could also be transformed into A. mediterranei DSM 43304, DSM 46095, MTCC-17 and in mutants F1/24 and T-195, (derived from an industrial strain of A. mediterranei N813). The alpha-amy of pRL60 conferred an amylolytic phenotype to all these strains. With the development of pRL60 and a reproducible transformation protocol, the application of recombinant DNA techniques to these industrial microorganisms has now become feasible.

Actinobacteria↗
PubMed1998

Process indicators for malaria control.

Malaria Control efforts are existing in India since antiquity. Organised malaria control interventions were initiated in 1953 by launching of National Malaria Control Programme (NMCP) which was soon converted to eradication in 1958. The initial success achieved was short-lived as malaria resurged in sixties. In 1977, Modified Plan of Operations was launched and the malaria decreased to 2-3 million cases in 1984 and was maintained at the same level. In 1994, after large scale epidemics were experienced, deaths due to malaria increased. WHO recommended a process-based approach to malaria control involving community with decentralized planning in the Global Malaria Control Strategy. Decentralised requires redefining the role and responsibilities at each level of implementation. To facilitate this and monitor the implementation of malaria control detailed process indicators have been developed.

Humans↗
PubMed1998

Some aspects of changing behaviour of malaria vectors in tribal areas of India.

The field entomological studies and surveys carried out in 72 tribal districts out of 100 in seven penninsular States namely, Andhra Pradesh, Bihar, Gujarat, Madhya Pradesh, Maharashtra, Orissa and Rajasthan indicated that in most of the areas the vector mosquitoes encountered during the present study were almost the same as recorded by the earlier workers except that Anopheles fluviatilis James, 1902 was recorded in the areas of district Raipur, Durg, Bilaspur, Raigarh, Shahdol, Rajnandgaon, Barwani and Janjgir of Madhya Pradesh, and Sundergarh of Orissa during the present survey. This vector was not recorded in earlier studies by other workers. An. culicifacies Giles, 1901 was not found in present survey in East Godavari and Vishakhapatnam of Andhra Pradesh and Ganjam and Koraput of Orissa where this mosquito was found in collections earlier. Similarly, An. fluviatilis was not encountered during the present field study in Bhilwara of Rajasthan, Phulbani and Kalahandi of Orissa, Thane, Nanded and Nasik of Maharashtra and Bharuch of Gujarat state. During this study An. fluviatilis was noted to be mostly endophilic whereas earlier workers noted this mosquito to be exophilic in a large number of districts. The majority of the tribal districts seem to be under the influence of two malaria vectors, An. culicifacies and An. fluviatilis and these tribal districts are maintaining a high malaria endemicity with predominance of Plasmodium falciparum infection. In the present study, the transmission seasons were noted to be longer than recorded earlier in the districts of Andhra Pradesh, Gujarat, Rajasthan and Orissa. In the remaining states it is almost similar as recorded earlier.

Animals↗
PubMed1997

Dietary and nutritional abnormalities in alcoholic liver disease: a comparison with chronic alcoholics without liver disease.

OBJECTIVE: To document the profile and role of malnutrition in alcoholic hepatitis, compared with chronic alcoholics and nonalcoholic chronic liver disease. METHODS: To this end, we studied 67 patients with alcoholic liver disease (ALD) (group I), 52 chronic alcoholics without histological evidence of liver disease (group II), 44 nonalcoholic cirrhotics (group III), and 52 healthy controls (group IV). Alcoholic and nonalcoholic calories were calculated and percentage dietary and nutritional deficiencies computed. Anthropometric indices, nitrogen balance, and immune status of the patients were assessed. RESULTS: Alcohol constituted about 48% of daily caloric intake in patients with ALD. The percentage mean intake of carbohydrate, protein, and energy was decreased in all three study groups compared with controls. The deficiencies were more pronounced in patients with severe than with moderate ALD. These deficiencies were more severe in the group III patients. Whereas body fat stores were maintained in groups I and II, reduction in lean body mass and serum transferrin was significant in patients in groups I and III. In group II patients compared to group I patients, the body mass index (19.9 +/- 4.0 vs. 22.3 +/- 3.4) and triceps skinfold thickness (6.1 +/- 4.8 vs. 10.2 +/- 5.6 mm) were significantly lower. CONCLUSIONS: 1) protein energy malnutrition is common in both alcoholic and nonalcoholic cirrhotics, but is more pronounced in the latter; 2) the degree and profile of malnutrition in chronic alcoholics and in alcoholic cirrhotics are comparable; 3) based on our results, we hypothesize that malnutrition may not play a primary role in the pathogenesis of ALD.

Adult↗
PubMed1996

Engineering antibiotic producers to overcome the limitations of classical strain improvement programs.

Improvement of the antibiotic yield of industrial strains is invariably the main target of industry-oriented research. The approaches used in the past were rational selection, extensive mutagenesis, and biochemical screening. These approaches have their limitations, which are likely to be overcome by the judicious application of recombinant DNA techniques. Efficient cloning vectors and transformation systems have now become available even for antibiotic producers that were previously difficult to manipulate genetically. The genes responsible for antibiotic biosynthesis can now be easily isolated and manipulated. In the first half of this review article, the limitations of classical strain improvement programs and the development of recombinant DNA techniques for cloning and analyzing genes responsible for antibiotic biosynthesis are discussed. The second half of this article addresses some of the major achievements, including the development of genetically engineered microbes, especially with reference to beta-lactams, anthracyclines, and rifamycins.

Anthracyclines↗
PubMed1994

Erythrocyte T-activation: clinical importance & recognition by a simple routine technique.

Erythrocyte T-activation is reported in association with bacterial infections. Although it is an unfrequent phenomenon, it has been reported in cases of septicaemia and necrotizing enterocolitis. It is important to recognize these cases as, transfusion of blood & blood products and lead to haemolytic--transfusion reactions. Here we report a case of T-activation detected during routine immunohaematological procedure in the blood transfusion laboratory. This also emphasizes the role of a routine, cost-effective test to diagnose cases of T-activation.

Antigens, Tumor-Associated, Carbohydrate↗