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Biomedical subjects

A K Nandi

Publications and source records attributed to A K Nandi.

9 recordsLinked to original sources
PubMed2001

Noninvasive fetal electrocardiogram extraction: blind separation versus adaptive noise cancellation.

The problem of the fetal electrocardiogram (FECG) extraction from maternal skin electrode measurements can be modeled from the perspective of blind source separation (BSS). Since no comparison between BSS techniques and other signal processing methods has been made, we compare a BSS procedure based on higher-order statistics and Widrow's multireference adaptive noise cancelling approach. As a best-case scenario for this latter method, optimal Wiener-Hopf solutions are considered. Both procedures are applied to real multichannel ECG recordings obtained from a pregnant woman. The experimental outcomes demonstrate the more robust performance of the blind technique and, in turn, verify the validity of the BSS model in this important biomedical application.

Abdomen↗
PubMed2000

A conserved function for Arabidopsis SUPERMAN in regulating floral-whorl cell proliferation in rice, a monocotyledonous plant.

Studies of floral organ development in two dicotyledonous plants, Arabidopsis thaliana and Antirrhinum majus, have shown that three sets of genes (A, B and C) can pattern sepals, petals, stamens and carpels [1] [2]. Mechanisms that define boundaries between these floral whorls are unclear, however. The Arabidopsis gene SUPERMAN (SUP), which encodes a putative transcription factor, maintains the boundary between stamens and carpels [3] [4] [5], possibly by regulating cell proliferation. By overexpressing SUP cDNA in rice, we examined whether its effects on whorl boundaries are conserved in a divergent monocotyledonous species. High-level ectopic SUP expression in transgenic rice resulted in juvenile death or dwarf plants with decreased axillary growth. Plants with lower levels of SUP RNA were vegetatively normal, but the flowers showed ubiquitous ventral carpel expansion. This was often coupled with reduced stamen number, or occurrence of third-whorl stamen-carpel mosaic organs. Additionally, proliferation of second-whorl ventral cells produced adventitious lodicules, and flowers lost the asymmetry that is normally inherent to this whorl. We predict that SUP is a conserved regulator of floral whorl boundaries and that it affects cell proliferation.

Arabidopsis↗
PubMed1997

Maternal and foetal ECG separation using blind source separation methods.

The separation of the maternal and foetal electrocardiograms (ECGs) from skin electrodes located on the mother's body may be modelled as a blind source separation (BSS) problem. This consists in the reconstruction of a set of unknown mutually independent source signals from the sole knowledge of another set of linear mixtures of the sources, where the mixture pattern is also unknown. Three BSS methods based on cumulants are considered: principal-component analysis (PCA), higher-order singular-value decomposition (HOSVD), and higher-order eigenvalue decomposition (HOEVD). All these methods are applied to the foetal-ECG extraction problem by using real ECG data. The last two methods appear to provide a more satisfactory separation than the first method, with HOEVD offering slightly better results.

Biomedical Engineering↗
PubMed1991

Generation of a nested series of interstitial deletions in yeast artificial chromosomes carrying human DNA.

We have generated a nested series of interstitial deletions in a fragment of human X chromosome-derived DNA cloned into a yeast artificial chromosome (YAC) vector. A yeast strain carrying the YAC was transformed with a linear recombination substrate containing at one end a sequence that is uniquely represented on the YAC and at the other end a truncated long interspersed repetitive element (LINE 1, or L1). Homologous recombination between the YAC and the input DNA resulted in a nested series of interstitial deletions, the largest of which was 500 kilobases. In combination with terminal deletions that can be generated through homologous recombination, the interstitial deletions are useful for mapping and studying gene structure-function relationships.

Chromosome Deletion↗
PubMed1990

Maternal mortality.

Maternal mortality in Chittaranjan Seva Sadan, Calcutta, in 1983, 1985 and 1986 was 2.45, 3.01 and 2.8 per thousand respectively. Abortion contributed a little in 1983 and 1985, whereas it was 15.7% in 1986. Haemorrhage was the commonest single cause of death in 1983 (28%) and 1985 (21.4%) as opposed to eclampsia in 1986 (28.9%). Infective hepatitis during pregnancy and labour was the commonest indirect cause of maternal mortality followed by anaemia. Usual difficulties like lack of antenatal care, multiparity, low socio-economical status, illiteracy, etc, in populated developing countries are responsible for this sad state of affairs in this country as well.

Female↗
PubMed1988

Regulated expression of genes inserted at the human chromosomal beta-globin locus by homologous recombination.

We have examined the effect of the site of integration on the expression of cloned genes introduced into cultured erythroid cells. Smithies et al. [Smithies, O., Gregg, R.G., Boggs, S.S., Koralewski, M.A. & Kucherlapati, R.S. (1985) Nature (London) 317, 230-234] reported the targeted integration of DNA into the human beta-globin locus on chromosome 11 in a mouse erythroleukemia-human cell hybrid. These hybrid cells can undergo erythroid differentiation leading to greatly increased mouse and human beta-globin synthesis. By transfection of these hybrid cells with a plasmid carrying a modified human beta-globin gene and a foreign gene composed of the coding sequence of the bacterial neomycin-resistance gene linked to simian virus 40 transcription signals (SVneo), cells were obtained in which the two genes are integrated at the beta-globin locus on human chromosome 11 or at random sites. When we examined the response of the integrated genes to cell differentiation, we found that the genes inserted at the beta-globin locus were induced during differentiation, whereas randomly positioned copies were not induced. Even the foreign SVneo gene was inducible when it had been integrated at the beta-globin locus. The results show that genes introduced at the beta-globin locus acquire some of the regulatory properties of globin genes during erythroid differentiation.

Animals↗