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Biomedical subjects

A Nandy

Publications and source records attributed to A Nandy.

At least 37 records · Page 2Linked to original sources
PubMed1996

SCATPLOT: a computer program for determination of binding parameters of non-linear non-cooperative ligand-substrate interactions.

The importance of computer-assisted analysis of a non-linear binding phenomenon through Scatchard equation has been widely acknowledged. While several user-friendly softwares [LIGAND, SCTFIT, ALLFIT] are available for determining the binding parameters of nonlinear Scatchard phenomenon, there is no easily available software covering the class of phenomena described by the McGhee and von Hippel formalism [J. Mol. Biol. 86, 469-489 (1974)]. We report here user-friendly software, SCATPLOT, developed in Turbo BASIC, for the numerical estimation of binding parameters of a non-cooperative ligand-substrate interaction doing best fit to the experimental data on the basis of McGhee and von Hippel equation for a nonlinear Scatchard plot. A new parameter has also been incorporated to guide the process of least square analysis and subsequent determination of binding parameters.

Algorithms↗
PubMed1996

Two-dimensional graphical representation of DNA sequences and intron-exon discrimination in intron-rich sequences.

We have shown earlier that analysis of DNA sequences using a two-dimensional graphical representation provides considerable information on new global sequence patterns and homologies, repeated structures, relative base abundances, probable evolutionary paths and evolutionary divergence. We have also reported that at a more micro level the graphical representation reveals distinct differences in the features of intron and exon segments of eukaryotic sequences. In this paper, the distinguishing features of the intron and exon segments are exploited to show, through several examples of different gene structures, that an averaging procedure over the slopes of the representative maps provides an easy technique to differentiate between probable intron and exon regions. We thus expect that this method will enable a rapid search and preliminary indication of possible locations of protein coding regions in long eukaryotic sequences.

Animals↗
PubMed1995

Effects of two mutations detected in medium chain acyl-CoA dehydrogenase (MCAD)-deficient patients on folding, oligomer assembly, and stability of MCAD enzyme.

We have used expression of human medium chain acyl-CoA dehydrogenase (MCAD) in Escherichia coli as a model system for dissecting the molecular effects of two mutations detected in patients with MCAD deficiency. We demonstrate that the R28C mutation predominantly affects polypeptide folding. The amounts of active R28C mutant enzyme produced could be modulated between undetectable to 100% of the wild-type control by manipulating the level of available chaperonins and the growth temperature. For the prevalent K304E mutation, however, the amounts of active mutant enzyme could be modulated only in a range from undetectable to approximately 50% of the wild-type, and the assembled mutant enzyme displayed a decreased thermal stability. Two artificially constructed mutants (K304Q and K304E/D346K) yielded clearly higher amounts of active MCAD enzyme than the K304E mutant but were also responsive to chaperonin co-overexpression and growth at low temperature. The thermal stability profile of the K304E/D346K double mutant was shifted to even lower temperatures than that of the K304E mutant, whereas that of the K304Q mutant was closely similar to the wild-type. Taken together, the results show that the K304E mutation affects (i) polypeptide folding due to elimination of the positively charged lysine and (ii) oligomer assembly and stability due to replacement of lysine 304 with the negatively charged glutamic acid.

Acyl-CoA Dehydrogenase↗
PubMed1995

Subpopulations of T lymphocytes in the peripheral blood, dermal lesions and lymph nodes of post kala-azar dermal leishmaniasis patients.

Distribution of different subpopulations of T cells in the dermal lesions, lymph nodes and peripheral blood of post kala-azar dermal lesihmaniasis (PKADL) patients was studied by using appropriate phenotypic markers for CD2+, CD4+ and CD8+ cells. Histopathological studies of skin lesions showed marginal to massive infiltration of mononuclear cells depending upon the duration of illness and type of lesions. Thus, while the hypopigmented patches were represented by small focal collections of lymphocytes with scanty parasites in the dermis, these were replaced at the nodular stage with massive granulomas consisting of lymphocytes, plasma cells and histiocytes with numerous amastigotes. The involvement of CD4+ and CD8+ cell types in these lesions also showed a gradual change from the appearance of a few cells of both the phenotypes in early hypopigmented type to massive accumulation of cells, primarily of CD8+ phenotype, in the granuloma of nodular type. However, the observed preponderance of CD8+ cells at the lesion site of chronic PKADL patients is in contrast to their peripheral blood CD4+/CD8+ cell ratio (1.9:1) which remained within the normal limits. Similar studies of lymph nodes from PKADL patients with lymphadenopathy revealed infiltration of the cortical areas by T cells which were more of CD8+ than CD4+ phenotypes. All these results document the involvement of CD8+ cells in leishmanoid lesions. Thus, it is likely that these cells, in association with appropriate subpopulations of CD4+ cells, play a profound role in the evolution of dermal pathology in PKADL.

Adolescent↗
PubMed1995

Fulminating strongyloidiasis complicating Indian kala-azar.

Infection with Strongyloides stercoralis in an immunocompetent host usually remains unrecognized. Sometimes, however, it may cause serious problems in the immunocompromised host due to its enhanced invasiveness. We present here details of three kala-azar patients with fulminating strongyloidiasis manifested by acute diarrhoea with blood and mucus, severe dehydration, cough and dyspnoea with low peripheral blood eosinophils and filariform larvae of S. stercoralis in faeces. No larvae could be detected in the sputum in spite of radiological evidence of infiltration. The impact of albendazole was dramatic with a disappearance of parasites from the faeces and of pulmonary infiltration and an increase in blood eosinophil count. It is emphasized that S. stercoralis infection in kala-azar patients should be considered a serious infection and treated accordingly.

Adolescent↗
PubMed1995

Pathogenicity of Artyfechinostomum oraoni in naturally infected pigs.

In an attempt to establish the diarrhoeogenic potential of the newly identified Artyfechinostomum oraoni, which was associated with human diarrhoea in a tribal community near Calcutta, India, two naturally infected domestic pigs of the locality were followed in captivity. Both pigs developed fatal diarrhoea after 5 months. The autopsy revealed a massive infection with the echinostome on a haemorrhagic and oedematous mucosa of the jejunum and duodenum extending up to pyloric end of the stomach. It is suggested that similar pathology might also be operating in the infected man.

Animals↗
PubMed1995

Studies on the life cycle of Artyfechinostomum oraoni Bandyopadhyay, Manna & Nandy 1989: embryogenesis & development in the intermediate host.

A study was undertaken to elucidate the life cycle of the parasite A.oraoni, isolated from man. For the purpose, operculated eggs were isolated from faeces of oraon tribals belonging to the village Bandipore, district North 24-Parganas of West Bengal province of India. The purified eggs were incubated at different temperatures, salinity and pH. Larvae (miracidia) could be observed to develop between the 7th and 8th day of incubation at a temperature range between 22 degrees-30 degrees C. While the optimum pH was observed to be neutral, larval development did not take place at salinity beyond 0.8 per cent. To identify the correct intermediate host, all available species of snails from the study village were colonised and infected with the laboratory hatched miracidia from human derived operculated eggs. It was observed that of all the snails infected, only Lymnaea supported the development of rediae from miracidia, which could be observed on the 32nd post infection day. Considering the results of the experimental study, it was hypothesised that Lymnaea spp. of snails under natural condition also, might act as the first intermediate host for A. oraoni.

Animals↗
PubMed1994

Characterization of wild-type human medium-chain acyl-CoA dehydrogenase (MCAD) and mutant enzymes present in MCAD-deficient patients by two-dimensional gel electrophoresis: evidence for post-translational modification of the enzyme.

Two-dimensional gel electrophoresis was used to study and compare wild-type medium-chain acyl-CoA dehydrogenase (MCAD; EC 1.3.99.3) and mis-sense mutant enzyme found in patients with MCAD deficiency. By comparing the patterns for wild-type and mutant MCAD expressed in Escherichia coli or in eukaryotic COS-7 cells we demonstrate that variants with point mutations changing the net charge of the protein can be readily resolved from the wild-type protein. After expression of the cDNA in eukaryotic cells two spots representing mature MCAD can be distinguished, one with an isoelectric point (pI) corresponding to that obtained for the mature protein expressed in E. coli and another one shifted to lower pI. This demonstrates that MCAD protein is partially modified after transport into the mitochondria and removal of the transit peptide. The observed pI shift would be compatible with phosphorylation of one aspartic acid residue per monomer. Comparison of pulse labeling and steady-state amounts of MCAD protein in overexpressing COS-7 cells confirms that K304E MCAD is synthesized and transported into mitochondria in amounts similar to the wild-type protein, but is degraded much more readily. For wild-type MCAD, the spot representing the nonmodified form predominates after pulse labeling while that representing the modified form is relatively stronger in steady state, demonstrating that the modification occurs in mitochondria after the transit peptide has been removed. For K304E mutant MCAD, the nonmodified spot is relatively stronger both in pulse labeling and in steady state, indicating that either the efficiency of modification or the stability of the modified form is affected by the K304E mutation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acyl-CoA Dehydrogenase↗
PubMed1994

Recent investigations into global characteristics of long DNA sequences.

The sequencing of very large genes comprising tens and hundreds of thousands of bases raises important questions of how the data are to be viewed and analysed and what new information and rules on genome characterisation and organisation may exist in nature. Representation of such gene sequences require more compact techniques than the widely used letter-series method; several graphical techniques have been proposed that partially meet this need and reveal new patterns in sequence composition in conserved genes. Investigations using Chaos techniques have displayed self-similarities in the graphical representation of several classes of gene sequences that point to a fractal nature embedded in the sequence organisation in a scale-independent manner. Scale invariance is also seen in studies that have revealed unexpected correlations in gene sequences that imply that a nucleotide at any position influences nucleotides thousands of base positions away. These observations have given rise to a new way of looking at long gene sequences, but questions on the origin of such patterns and correlations and their implications in gene sequences and evolution remain to be resolved. This review provides a brief overview of the recent papers covering the techniques and the issues raised in these investigations on the global characteristics of long DNA sequences.

Base Sequence↗
PubMed1993

Co-overexpression of bacterial GroESL chaperonins partly overcomes non-productive folding and tetramer assembly of E. coli-expressed human medium-chain acyl-CoA dehydrogenase (MCAD) carrying the prevalent disease-causing K304E mutation.

The influence of co-overexpression of the bacterial chaperonins GroEL and GroES on solubility, tetramer formation and enzyme activity of three variants of heterologously-expressed human medium-chain acyl-CoA dehydrogenase (MCAD) was analysed in order to investigate the molecular mechanism underlying MCAD deficiency caused by the prevalent K304E mutation. Depending on which of the three amino acids--lysine (wild-type), glutamic acid (K304E) or glutamine (K304Q) are present at position 304 of the mature polypeptide, three different patterns were observed in our assay system: (i) solubility, tetramer formation and yield of enzyme activity of wild-type MCAD is largely independent of GroESL co-overexpression; (ii) the larger part of the K304Q mutant is insoluble without and solubility is enhanced with GroESL co-overexpression; solubility correlates with the amount of tetramer detected and the enzyme activity measured as observed for the wild-type protein. (iii) Solubility of the K304E mutant is in a similar fashion GroESL responsive as the K304Q mutant, but the amount of tetramer observed and the enzyme activity measured do not correlate with the amount of soluble K304E MCAD protein detected in Western blotting. In a first attempt to estimate the specific activity, we show that tetrameric K304E and K304Q mutant MCAD display a specific activity in the range of the wild-type enzyme. Taken together, our results strongly suggest, that the K304E mutation primarily impairs the rate of folding and subunit assembly. Based on the data presented, we propose that lysine-304 is important for the folding pathway and that an exchange of this amino acid both to glutamine or glutamic acid leads to an increased tendency to misfold/aggregate. Furthermore, exchange of lysine-304 with an amino acid with negative charge at position 304 (glutamic acid) but not with a neutral charge (glutamine) negatively affects conversion to active tetramers. A possible explanation for this latter effect--charge repulsion upon subunit docking--is discussed.

Acyl-CoA Dehydrogenase↗
PubMed1993

Sensitivity of non-cooperative binding parameters of ligand-DNA complex by computer analysis.

A simple user-friendly computer programme has been developed to operate on an IBM-PC compatible machine to aid in the process of curve fitting using the McGhee and von Hippel equation [J. Mol Biol, 86 (1974), 469-489] for the analysis of ligand-DNA interactions and the experimental data on berberine-calf thymus DNA and berberine-poly(dI-dC). poly(dI-dC) for non-cooperative binding. A sensitivity analysis on binding constant (K0) and the number of binding sites (N0) show that a small variation in the latter remarkably alters the fitting curve. At a level of 1% change in N0 from the best fit value, the standard deviation grows by almost 4%, while, on the other hand, a 1% change in K0 affects the same value only by less than 0.4%.

Berberine↗
PubMed1992

Ten years of kala-azar in west Bengal, Part I. Did post-kala-azar dermal leishmaniasis initiate the outbreak in 24-Parganas?

Following resurgence in Bihar of epidemic kala-azar, outbreaks of the disease were identified simultaneously in two separate foci about 500 km apart in West Bengal in 1980. While the outbreak in one of these foci, in northern West Bengal, was the result of a direct extension of the Bihar epidemic, the source of parasite in the other (in the village of Bandipur in the south of West Bengal) remained unknown until a case of nodulo-ulcerative post-kala-azar dermal leishmaniasis (PKDL) was located in the village. The continued presence of this case in the village from a time long before the outbreak aroused strong suspicion about its causal role. Laboratory-bred female Phlebotomus argentipes sandflies were allowed to feed on four cases of PKDL, including the case from Bandipur, to determine the transmission potential of these cases. Of a total of 400 flies in the experiment, 104 (26%) fed on the cases, and of these flies 44 died (31 within 48 hours of feeding). Of the surviving 60 flies, 32 developed promastigotes in the mid-gut. In view of the presence of the case of PKDL in the village prior to the outbreak and the availability of a susceptible human population and vectors, it is possible that the patient with PKDL was a source of Leishmania donovani parasites for the local focus. Furthermore, PKDL may act as a reservoir of parasites during inter-epidemic periods.

Animals↗
PubMed1991

Leishmanial blepharo-conjunctivitis.

We describe a case of blepharo-conjunctivitis due to Leishmania donovani in association with nodules of post kala azar dermal leishmaniasis (PKDL) on the chin. The diagnosis was confirmed by isolation of the parasite in culture. Direct implantation of the parasite by contaminated fingers from the chin nodules to the eye is suggested as the mode of spread. The role of cell-mediated immunity, (CMI) in restricting the skin lesions on the chin for 37 years at the same site, was suspected. This is only the second report of ocular involvement in L. donovani infection from India.

Agglutination Tests↗