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Biomedical subjects

M Mitra

Publications and source records attributed to M Mitra.

At least 19 recordsLinked to original sources
PubMed2005

Tear film lipid layer thickness and ocular comfort after meibomian therapy via latent heat with a novel device in normal subjects.

AIM: This study measures changes in tear film lipid layer thickness (LLT) and ocular comfort in normal subjects after 10 min use of a novel device, which delivers meibomian therapy with latent heat. The device is designed to promote the release of meibomian sebum into the tear film by delivering latent heat to the eyelids, thus thickening the lipid layer. Normal lid movements are maintained, facilitating resurfacing of the tear film. METHOD: A prospective, controlled, observer masked, single intervention trial in which 24 normal subjects were randomised into three groups. Group I underwent 10 min treatment with the activated device, Group II used the inactivated device for the same duration of time, and Group III had no intervention. The LLT of each subject was measured with a Keeler Tearscope prior and subsequent to the 10-min period. Subjective alteration in ocular comfort was also assessed. RESULTS: Seven of eight subjects (87.5%) in Group I exhibited an increase in LLT. The mean LLT in this group showed a statistically significant increase (left eyes 1.0 levels, P<0.001, right eyes 0.9 levels, P<0.003) compared to Groups II and III. Six of eight subjects (75%) using the activated device experienced subjective improvement in ocular comfort. CONCLUSION: Meibomian therapy with this device increases LLT in normal individuals. This implies a more stable tear film, reflected in subjective improvement in ocular comfort.

Adult↗
PubMed2004

Generation of digital time database from paper ECG records and Fourier transform-based analysis for disease identification.

ECG signals recorded on paper are transferred to the digital time database with the help of an automated data extraction system developed here. A flatbed scanner is used to form an image database of each 12-lead ECG signal. Those images are then fed into a Pentium PC having a system to extract pixel-to-pixel co-ordinate information to form a raw database with the help of some image processing techniques. These raw data are then ported to the regeneration domain of the system to check the captured pattern with the original wave shape. The sampling period of each ECG signal is computed after detection of QRS complex. Finally, discrete Fourier transform of the generated database is performed to observe the frequency response properties of every ECG signal. Some interesting amplitude properties of monopolar chest lead V4 and V6 are noticed which are stated.

Databases as Topic↗
PubMed2004

DNA sequence variation and haplotype structure of the ICAM1 and TNF genes in 12 ethnic groups of India reveal patterns of importance in designing association studies.

We have examined the patterns of DNA sequence variation in and around the genes coding for ICAM1 and TNF, which play functional and correlated roles in inflammatory processes and immune cell responses, in 12 diverse ethnic groups of India. We aimed to (a) quantify the nature and extent of the variation, and (b) analyse the observed patterns of variation in relation to population history and ethnic background. At the ICAM1 and TNF loci, respectively, the total numbers of SNPs that were detected were 28 and 12. Many of these SNPs are not shared across ethnic groups and are unreported in the dbSNP or TSC databases, including two fairly common non-synonymous SNPs at positions 13487 and 13542 in the ICAM1 gene. Conversely, the TNF-376A SNP that is reported to be associated with susceptibility to malaria was not found in our study populations, even though some of the populations inhabit malaria endemic areas. Wide between-population variation in the frequencies of shared SNPs and coefficients of linkage disequilibrium have been observed. These findings have profound implications in case-control association studies.

Chromosome Mapping↗
PubMed2003

An automated data extraction system from 12 lead ECG images.

A software based normalized ECG data acquisition system is developed for both normal and abnormal ECG records. This system can transfer wave data recorded on paper to the digital time database. A flatbed scanner is used to form an image database of each 12 lead ECG signal. These TIF formatted gray tone images are then converted into two tone binary images with the help of histogram analysis. Smearing runlength technique is used to remove the vertical and horizontal line segments of graphical papers. Thinning algorithm is applied to each image to obtain the skeleton (1 pixel representation) of each image, which is essential to avoid excess data points in the database. After extracting pixel to pixel co-ordinate information of images of each of the signal of 12 lead ECG records, the data are sorted to regenerate the signal. From standard deviation of the database a graphical analysis is performed to examine the consistency of our database.

Adult↗
PubMed2002

Growth pattern of the Kamars--a primitive tribe of Chhattisgarh, India.

A cross sectional study of the physical growth status was made on 655 Kamar children (341 boys and 314 girls), aged 5 to 18 years, in the Raipur district of Chhattisgarh. The study aimed to find out the growth pattern of the Kamar children, which is considered to be a primitive tribe of Chhattisgarh, India and was compared with another Indian tribe and the official data for all India (ICMR). Anthropometric measurements included height, weight, sitting height, biacromial diameter, biilliocrystal diameter, upper arm circumference, calf circumference and measurements of the triceps and subscapular skinfolds. All anthropometric measurements except skinfold thickness exhibit uniform increase with age in both sexes. However, when height and weight of the Kamar boys and girls were compared with the data for other tribes and for all India, the Kamar children (both boys and girls) indicated lower weight and height and the difference showed to be significant, for almost all ages. Kamar boys showed higher anthropometric values than girls in almost all measurements except in biilliocrystal diameter and in measured skinfolds. Poor socio-economic status of this primitive tribe may be one of the reasons for this poor growth pattern. However, in-depth study is necessary in order to arrive at any basic conclusions and to recommend any policy and interventions.

Adolescent↗
PubMed2001

Rearrangement of nicotinic receptor alpha subunits during formation of the ligand binding sites.

Muscle nicotinic acetylcholine receptors (AChRs) are pentamers that contain two alpha subunits a beta, gamma (or epsilon), and delta subunit. In this paper, we have characterized subunit processing and folding events leading to formation of the two AChR ligand binding sites. alpha subunit residues, 187-199, which are part of overlapping ACh and alpha-bungarotoxin (Bgt) binding sites on AChRs, were assayed using a monoclonal antibody (mAb) specific for these residues. We found that this region was inaccessible to the mAb early during AChR assembly but became accessible as the first of two Bgt binding sites formed later during assembly, indicating that the region changes conformation as the Bgt binding site appears. Without previous reduction, 20% of the alpha subunits could be alkylated by bromoacetylcholine bromide as the first ACh binding site formed, which further indicated that the disulfide bond between cysteines 192 and 193 does not form until the first ACh binding site appears soon after Bgt binding site formation. When alpha subunits were mutated to add a glycosylation site at residue 187, the number of Bgt binding sites increased threefold, AChRs assembled more efficiently, and 2.5-fold more AChRs reached the cell surface. Our results indicate that binding site formation involves a rate-limiting rearrangement of the alpha subunit that exposes the 187-199 region to the endoplasmic reticulum lumen and determines when cysteines 192 and 193 disulfide bond.

Acetylcholine↗
PubMed2001

Genomic structures and population histories of linguistically distinct tribal groups of India.

There are various conflicting hypotheses regarding the origins of the tribal groups of India, who belong to three major language groups--Austro-Asiatic, Dravidian and Tibeto-Burman. To test some of the major hypotheses we designed a genetic study in which we sampled tribal populations belonging to all the three language groups. We used a set of autosomal DNA markers, mtDNA restriction-site polymorphisms (RSPs) and mtDNA hypervariable segment-1 (HVS-1) sequence polymorphisms in this study. Using the unlinked autosomal markers we found that there is a fair correspondence between linguistic and genomic affinities among the Indian tribal groups. We reconstructed mtDNA RSP haplotypes and found that there is extensive haplotype sharing among all tribal populations. However, there is very little sharing of mtDNA HVS-1 sequences across populations, and none across language groups. Haplogroup M is ubiquitous, and the subcluster U2i of haplogroup U occurs in a high frequency. Our analyses of haplogroup and HVS-1 sequence data provides evidence in support of the hypothesis that the Austro-Asiatic speakers are the most ancient inhabitants of India. Our data also support the earlier finding that some of the western Eurasian haplogroups found in India may have been present in India prior to the entry of Aryan speakers. However, we do not find compelling evidence to support the theory that haplogroup M was brought into India on an "out of Africa" wave of migration through a southern exit route from Ethiopia. On the contrary, our data raise the possibility that this haplogroup arose in India and was later carried to East Africa from India.

DNA, Mitochondrial↗
PubMed2000

Fundamental patterns underlying gene expression profiles: simplicity from complexity.

Analysis of previously published sets of DNA microarray gene expression data by singular value decomposition has uncovered underlying patterns or "characteristic modes" in their temporal profiles. These patterns contribute unequally to the structure of the expression profiles. Moreover, the essential features of a given set of expression profiles are captured using just a small number of characteristic modes. This leads to the striking conclusion that the transcriptional response of a genome is orchestrated in a few fundamental patterns of gene expression change. These patterns are both simple and robust, dominating the alterations in expression of genes throughout the genome. Moreover, the characteristic modes of gene expression change in response to environmental perturbations are similar in such distant organisms as yeast and human cells. This analysis reveals simple regularities in the seemingly complex transcriptional transitions of diverse cells to new states, and these provide insights into the operation of the underlying genetic networks.

Cell Cycle Proteins↗
PubMed2000

A high yielding mutant of mycobacteriophage L1 and its application as a diagnostic tool.

L1 is a lysogenic phage of mycobacteria, which along with L5 and D29 constitute a closely linked family of homoimmune mycobacteriophages. These phages can be potentially used for genetic engineering of mycobacteria and diagnosis of mycobacterial infection. The effectiveness of such phage based systems depends on the efficiency with which they infect and grow within target cells. While working with phage L1c1ts which is a temperature sensitive mutant of phage L1, we observed that high yielding phage stocks were generated by repeated passage through the host, Mycobacterium smegmatis. A plaque purified mutant L1-P2, obtained from one such high yielding stock, when analyzed further was found to infect host cells with increased efficiency. The DNA obtained from L1-P2 was examined by restriction digestion, and it was observed that spontaneous loss of DNA fragment from the right arm, which encodes early regulatory factors, had occurred. It has been further demonstrated that the high yielding property of the mutant phage could be utilized to increase the sensitivity of mycobacteriophage-based detection systems.

Adsorption↗
PubMed2000

Purification and characterization of alpha-N-acetylgalactosaminidase from Clostridium perfringens.

alpha-N-Acetylgalactosaminidase from Clostridium perfringens is an exoglycosidase that degrades the human blood type A epitope. A highly purified preparation of alpha-N-acetylgalactosaminidase was obtained from C. perfringens by salt precipitation, gel filtration, ion-exchange chromatography, chromatofocusing, and high-pressure liquid chromatography. The final preparation was homogeneous by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with a molecular mass of 72.1 kDa. The enzyme was highly selective for terminal N-acetyl-alpha-D-galactosamine residues. No other substantial glycosidase activities, specifically neuraminidase, were detected. The pH optimum of the enzyme was between 6.5 and 7.0, and activity was unaffected by ionic strength. No protease activity was detected and enzyme activity was stable at 4 degrees C for 12 months. ELISA experiments demonstrated activity against blood type A epitope.

Chromatography, Gel↗
PubMed1999

Dimer dissociation and thermosensitivity kinetics of the Saccharomyces cerevisiae and human TATA binding proteins.

A kinetic analysis of dimer dissociation, TATA DNA binding, and thermal inactivation of the yeast Saccharomyces cerevisiae and human TATA binding proteins (TBP) was conducted. We find that yeast TBP dimers, like human TBP dimers, are slow to dissociate in vitro (t(1/2) approximately 20 min). Mild mutations in the crystallographic dimer interface accelerate the rate of dimer dissociation, whereas severe mutations prevent dimerization. In the presence of excess TATA DNA, which measures the entire active TBP population, dimer dissociation represents the rate-limiting step in DNA binding. These findings provide a biochemical extension to genetic studies demonstrating that TBP dimerization prevents unregulated gene expression in yeast [Jackson-Fisher, A. J., Chitikila, C., Mitra, M., and Pugh, B. F. (1999) Mol. Cell 3, 717-727]. In the presence of vast excesses of TBP over TATA DNA, which measures only a very small fraction of the total TBP, the monomer population in a monomer/dimer equilibrium binds DNA rapidly, which is consistent with a simultaneous binding and bending of the DNA. Under conditions where other studies failed to detect dimers, yeast TBP's DNA binding activity was extremely labile in the absence of TATA DNA, even at temperatures as low as 0 degrees C. Kinetic analyses of TBP instability in the absence of DNA at 30 degrees C revealed that even under fairly stabilizing solution conditions, TBP's DNA binding activity rapidly dissipated with t(1/2) values ranging from 6 to 26 min. TBP's stability appeared to vary with the square root of the TBP concentration, suggesting that TBP dimerization helps prevent TBP inactivation.

Cross-Linking Reagents↗
PubMed1999

A role for TBP dimerization in preventing unregulated gene expression.

The recruitment of the TATA box-binding protein (TBP) to promoters in vivo is often rate limiting in gene expression. We present evidence that TBP negatively autoregulates its accessibility to promoter DNA in yeast through dimerization. The crystal structure of TBP dimers was used to design point mutations in the dimer interface. These mutants are impaired for dimerization in vitro, and in vivo they generate large increases in activator-independent gene expression. Overexpression of wild-type TBP suppresses these mutants, possibly by heterodimerizing with them. In addition to loss of autorepression, dimerization-defective TBPs are rapidly degraded in vivo. Direct detection of TBP dimers in vivo was achieved through chemical cross-linking. Taken together, the data suggest that TBP dimerization prevents unregulated gene expression and its own degradation.

Amino Acid Substitution↗
PubMed1998

A second-generation screen of the human genome for susceptibility to insulin-dependent diabetes mellitus.

During the past decade, the genetics of type 1 (insulin-dependent) diabetes mellitus (IDDM) has been studied extensively and the disorder has become a paradigm for genetically complex diseases. Previous genome screens and studies focused on candidate genes have provided evidence for genetic linkage between polymorphic DNA markers and 15 putative IDDM susceptibility loci, designated IDDM1-IDDM15. We have carried out a second-generation screen of the genome for linkage and analysed the data by multipoint linkage methods. An initial panel of 212 affected sibpairs (ASPs) was genotyped for 438 markers spanning all autosomes, and an additional 467 ASPs were used for follow-up genotyping. Other than the well-established linkage with the HLA region at chromosome 6p21.3, there was only one region, located on chromosome 1q and not previously reported, where the log likelihood ratio (lod) was greater than 3. Lods between 1.0 and 1.8 were found in six other regions, three of which have been reported in other studies. Another reported region, on chromosome 6q and loosely linked to HLA, also had an elevated lod. Little or no support was found for most reported IDDM loci (lods were less than 1), despite larger sample sizes in the present study.

Chromosome Mapping↗
PubMed1997

Infantile spasms.

Explore the source record for details and available documents.

Epilepsy↗
PubMed1996

The activity of a blood type B specific exoglycosidase from Glycine max.

Soluble antigens, enzyme-linked immunosorbent assays (ELISA), and cell suspension assays were used to study the blood group B activity of Glycine max (soybean) alpha-D-galactosidase. The enzyme readily hydrolyzed the terminal alpha-D-galactosyl of the B antigen under a variety of conditions, converting it to H antigen. Conversion of the B antigen to H antigen produces blood type O which is universally transfusable. These preliminary studies are important in determining optimal conditions for enzymatic conversion of blood type B to O erythrocytes if efficient large-scale production of enzymatically converted, universally transfusable red blood cells is to be achieved.

ABO Blood-Group System↗