Search PubMed⌕ Search

Biomedical subjects

M K Das

Publications and source records attributed to M K Das.

At least 127 records · Page 7Linked to original sources
PubMed1978

Proteolytic susceptibility and methionine modification of monodeamidated ribonuclease A.

The susceptibility of a monodeamidated RNAaseA (RNAaseAa1) towards carboxypeptidaseA , alpha-chymotrypsin and pepsin has been studied. Similar to RNAaseA, the C-terminal of RNAaseAa1 is not available for carboxypeptidaseA hydrolysis. The thermal stability of RNAaseAa1 as probed through chymotryptic digestion is found to be less than that of RNAaseA. Preliminary chromatographic analysis of the digested material, however, suggests that the nature of thermal transition might be the same in the two proteins. Pepsin inactivates RNAaseAa1 more slowly than does RNAaseA. Accordingly, less peptide bonds, almost half that of RNAaseA, are cleaved by pepsin in RNAaseAa1. The accumulation of RNAase-P type intermediates is not evident during peptic digestion of RNAaseAa1. Reaction with O-benzoquinone at low pH shows that methionines of the deamidated protein seem to have higher reactivities. These observations indicate a different structure for RNAaseAa1 at elevated temperature and low pH.

Carboxypeptidases↗
PubMed1977

Stabilisation of enzyme structures by inhibitors. A nuclear magnetic resonance study of the effect of phosphate on the acid unfolding of ribonuclease A.

The acid denaturation of bovine pancreatic ribonuclease A in the presence of 0.2M sodium dihydrogen phosphate has been studied by n.m.r. spectroscopy. Phenylalanine, tyrosine and methionine resonances serve as monitors of the unfolding process. It is shown that the inhibitor shifts the equilibrium towards the native structure at acid pH. Exchange broadening of the C-2 resonances of the active site histidines, 12 and 119, occurs in the presence of phosphate, suggesting an equilibrium between native and unfolded structures. Stabilisation of the partially unfolded protein is observed at pH 1.5, as evidenced by the lack of the histidine resonance due to random coil protein. A scheme of the equilibria relating the various states of the protein is proposed.

Animals↗
PubMedDate not supplied

A long-term follow-up of asymptomatic amicrofilaraemic individuals living in a filaria-endemic region of Orissa, India: infection and disease status.

A group of asymptomatic amicrofilaraemic individuals (endemic normals) aged > 12 years was identified in 2 filaria-endemic villages of Orissa, India in 1990 (Bajapur village, n = 40) and in 1994 (Olosingh village, n = 47). They were re-examined for microfilaraemia and disease status in the year 2000 after a 10-year and a 6-year period. Studies conducted at both villages yielded a similar pattern in the development of disease. Above 85% of the females remained normal, compared to 54% of males. Remaining individuals had acquired hydrocoele (males) and adenolymphangitis (both males and females). Only 1 individual converted to having asymptomatic microfilariae. No case of elephantiasis was observed. Results indicate that most females remained normal and males faced considerable risk of developing hydrocoele in these Wuchereria bancrofti-endemic areas.

Adolescent↗
PubMedDate not supplied

Age-dependent prevalence of asymptomatic amicrofilaraemic individuals in a Wuchereria bancrofti-endemic region of India.

The age-related prevalence of asymptomatic amicrofilaraemics, apparently uninfected individuals, was determined in a Wuchereria bancrofti-endemic region of Orissa, India during 2001. The prevalence of these uninfected individuals was highest in the younger age groups (aged < or = 15 years), decreased rapidly in those aged > 15 to 40 years, and then stabilized in those aged > 40 years.

Adolescent↗
PubMedDate not supplied

Green pupa (gp), a male lethal in culex quinquefasciatus.

An autosomal recessive mutant, green pupa (gp), in Culex quinquefasciatus has been isolated. The homozygous (gp/gp) females are viable whereas male homozygotes do not develop beyond the pupal stage. The behavior of this mutant character in pedigree studies has been reported.

Animals↗
PubMedDate not supplied

Haemodynamic advantage with single chamber rate responsive pacemakers over dual chamber pacemakers during exercise in chronotropic incompetence.

Sequential cardiac chamber activation and chronotropic response are amongst the important determinants of cardiac performance. This study compared VVIR mode with DDD and VVI mode to assess the contribution of these two factors in the determination of cardiac performance during exercise. Ten patients with a mean age of 68 +/- 5 years were studied during 1988-90, who had complete heart block and sinus node dysfunction with a mean LV ejection fraction of 51.5 +/- 6.25%. Five patients had DDD pacemakers and the rest had VVIR pacemakers. Patients were exercised first in VVI mode followed by either DDD or VVIR mode. Exercise duration, maximum rate pressure product, exercise capacity and cardiac output were measured with graded treadmill test in Bruce protocol. There was remarkable increase in the exercise duration (P < 0.001) and the maximum rate pressure product (P < 0.001) in patients with VVIR as compared to DDD and VVI mode. In DDD mode, as compared to VVI mode, this increase was less remarkable, though statistically significant (P < 0.005). Therefore, it is concluded that patients with chronotropic incompetence as well as complete heart block do better during dynamic exercise when they have VVIR mode compared to VVI or DDD mode.

Aged↗
PubMedDate not supplied

Mosquito fauna and breeding habitats of anophelines in Little Andaman Island, Andaman and Nicobar Islands, India.

A total of 37 species of mosquitoes belonging to nine genera--Anopheles, Aedes, Armigeres, Culex, Harpagomyia, Mansonia, Orthopodomyia, Toxorhynchites and Uranotaenia were collected from Little Andaman Island. Mosquitoes of nine Anopheles group of species--An. barbirostris, An. barbumbrosus, An. balabacensis, An. insulaeflorum, An. kochi, An. philippinensis, An. roperi, An. sundaicus and An. vagus were recorded. An. philippinensis was found to be the most predominant species. Species-specific breeding preference and association in various types of acquatic habitats have been reported. This is the first record of mosquito fauna of Little Andaman Island.

Animals↗
PubMedDate not supplied

Bioecology of An. philippinensis in Andaman group of islands.

Studies on bioecology of An. philippinensis a vector of malaria was carried out in eight islands of the Andaman group. It was found that An. philippinensis preferred to rest and bite outdoors. Maximum biting was observed during 1800 to 2100 hrs on both cattle and human bait. The maximum breeding of An. philippinensis was recorded in slow moving stream followed by ponds with vegetation. The breeding sites infested with Chara and Spirogyra algae were most favourable whereas, with Lemna and Oscillatoria were unfavourable for the proliferation of this species. The breeding association of An. philippinensis was found with other seven anopheline species in different breeding habitats.

Animals↗
PubMedDate not supplied

Evaluation of repellent action of Cymbopogan martinii martinii Stapf var sofia oil against Anopheles sundaicus in tribal villages of Car Nicobar Island, Andaman & Nicobar Islands, India.

A field study was carried out to evaluate the mosquito repellent action of Cymbopogan martinii martinii Stapf var sofia oil in tribal village of Car Nicobar Island. Results revealed that application of 1 ml of the oil provided 98.7% protection in indoor and 96.52% in outdoor conditions during 12 h period of observation from the bites of An. sundaicus. Cymbopogan martinii martinii Stapf var sofia oil is an indigenous product, its application is safe and can be widely used for protection from malaria.

Animals↗