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Biomedical subjects

R Nagarajan

Publications and source records attributed to R Nagarajan.

At least 19 recordsLinked to original sources
PubMed2006

Acetylcholinesterase activities in marine snail (Cronia contracta) as a biomarker of neurotoxic contaminants along the Goa coast, West coast of India.

The measurement of acetylcholinesterase (AChE) activity is used worldwide as a biomarker of environmental contamination due to neurotoxic substances. In the present study the AChE activities was measured in marine snails (Cronia contracta) collected seasonally from six sampling sites (viz. Arambol, Anjuna, Dona Paula, Vasco, Velsao and Palolem) along the Goa coast during the pre-monsoon (April, 2004), monsoon (September, 2004) and post-monsoon (November, 2004) periods. The AChE activities in C. contracta showed wide variation along the Goa coast. It was found to be quite high at the reference site, Palolem (23.97, 21.72 and 24.85) throughout the sampling period (April-November, 2004). The AChE activities in C. contracta decreased significantly at Vasco (44.6-52.4% reduction) followed by Dona Paula (24.9-36.2% reduction), Velasao (10.8-35.9% reduction), Arambol (12.6-37.3% reduction) and Anjuna (0-12.7% reduction). Such a significant variation of AChE activities in the marine snail along the Goa coast can be attributed to neurotoxic substances prevalent in those regions. The high concentration of different neurotoxic metals (lead, cadmium, copper, manganese and iron) and petroleum hydrocarbons in the tissues of the marine snails at Dona Paula, Vasco and Velsao clearly substantiate reduction of AChE activities in C. contracta. The in vitro studies on the inhibition of AChE by different metals and PHC indicated that lead, cadmium and copper are the most predominant inhibitor. Based on the AChE activities in C. contracta the sampling sites along the Goa coast can be classified into three major clusters such as highly contaminated sites (Dona Paula, Vasco and Velsao), moderately contaminated sites (Arambol, Anjuna) and least contaminated site (Palolem).

Acetylcholinesterase↗
PubMed2004

Function and quality-of-life of survivors of pelvic and lower extremity osteosarcoma and Ewing's sarcoma: the Childhood Cancer Survivor Study.

Limb-sparing surgeries have been performed more frequently than amputation based on the belief that limb-sparing surgeries provide improved function and quality-of-life (QOL). However, this has not been extensively studied in the paediatric population, which has unique characteristics that have implications for function and QOL. Using the Childhood Cancer Survivor Study, 528 adult long-term survivors of pediatric lower extremity bone tumours, diagnosed between 1970 and 1986, were contacted and completed questionnaries assessing function and QOL. Survivors were an average of 21 years from diagnosis with an average age of 35 years. Overall they reported excellent function and QOL. Compared to those who had a limb-sparing procedure, amputees were not more likely to have lower function and QOL scores and self-perception of disability included general health status, lower educational attainment, older age and female gender. Findings from this study suggest that, over time, amputees do as well as those who underwent limb-sparing surgeries between 1970 and 1986. However, female gender, lower educational attainment and older current age appear to influence function, QOL and disability.

Adolescent↗
PubMed2003

Amine-templated linear vanadium sulfates with different chain structures.

Amine-templated vanadium sulfates of the formula [HN(CH(2))(6)NH][(V(IV)O)(2)(OH)(2)(SO(4))(2)].H(2)O, I, [H(3)N(CH(2))(2)NH(3)][V(III)(OH)(SO(4))(2)].H(2)O, II, and [H(2)N(CH(2))(4)NH(2)][(V(IV)O)(H(2)O)(SO(4))(2)], III, have been prepared under hydrothermal conditions. These vanadium sulfates add to the new emerging family of organically templated metal sulfates. Compound I has a linear chain structure consisting of V(2)O(8) square-pyramid dimers connected by corner-sharing SO(4) tetrahedra, creating four-membered rings along the chain. Both II and III possess simple linear chain topologies formed by VO(6) octahedra and SO(4) tetrahedra, with II having the tancoite chain structure. Compound I crystallizes in the triclinic space group P1 (No. 2) with a = 7.4852(4) A, b = 9.5373(5) A, c = 11.9177(6) A, alpha = 77.22 degrees, beta = 76.47(2) degrees, gamma = 80.86 degrees, Z = 2. Compound II: monoclinic, space group P2(1)/c (No. 14), a = 6.942(2) A, b = 10.317(3) A, c = 15.102(6) A, beta = 90.64(4) degrees, Z = 4. Compound III: triclinic, space group P1 (No. 2) with a = 6.2558(10) A, b = 7.0663(14) A, c = 15.592(4) A, alpha = 90.46(2) degrees, beta = 90.47(2) degrees, gamma = 115.68(2) degrees, Z = 2. Magnetic susceptibility measurements reveal weak antiferromagnetic interactions in I and III and ferromagnetic interactions in II.

Journal Article↗
PubMed2003

Analysis of uterine contractions: a dynamical approach.

The development of suitable techniques for quantifying mechanical and electrophysiological aspects of uterine contractions has been an active area of research. The uterus is a physiological system consisting of a large number of interacting muscle cells. The activity of these cells evolves with time, a trait characteristic of a dynamical system. While such complex physiological systems are non-linear by their very nature, whether this non-linearity is exhibited in the external recording is far from trivial. Traditional techniques such as spectral analysis have been used in the past, but these techniques implicitly assume that the process generating the contractions is linear and hence may be biased. In this tutorial review, a systematic approach using a hierarchy of surrogate algorithms is used to determine the nature of the process generating the contractions produced during labor. The results reveal that uterine contractions are probably generated by non-linear processes. The contraction segments were obtained through simultaneous recordings of the electrical and magnetic signals corresponding to the electrophysiological activity of the uterus and then analyzed. The electrical activity was recorded by placement of non-invasive electrodes onto the maternal abdomen and magnetic activity was recorded non-invasively using a superconducting quantum interference device (SQUID).

Algorithms↗
PubMed2003

Studies on Merops orientalis Latham 1801 with special reference to its population in Mayiladuthurai, Tamil Nadu.

Role of habitat-structure and climatic factors in the population dynamics of the small green bee-eater Merops orientalis was evaluated in three habitats viz., agricultural lands, river banks and human habitations during 1991-1993. The river banks supported relatively high population of bee-eaters (157/Km2) followed by the agricultural lands (101/Km2) and human habitations (58/Km2). Bee-eater populations showed year-wise variations in river banks and human habitations having high values during 1992 (123/Km2) and 1993 (43/Km2) respectively. Agricultural lands showed a significantly low mean density in 1991 than other years. Seasonal variations in the bee-eater densities among the habitats were also recorded. Vegetation structure, food (insects) availability, climatic conditions and human disturbance were the casual factors for variations in bee-eater populations.

Animals↗
PubMed2002

Oystercatchers use colour preference to achieve longer-term optimality.

The optimal diet model entails that foragers look beyond the individual prey encounter, to at least the level of intake rate across a bout of foraging, but optimization over a longer time remains controversial. In this paper, we show how oystercatchers increase their intake over the longer term using mussel colour as a cue. Wintering oystercatchers Haematopus ostralegus feed extensively on mussels Mytilus edulis in the estuaries of southern Britain. They show a marked preference for brown-shelled mussels over the commoner black-shelled morph, and we show that this enables them to maximize their rate of energy gain over a longer period than a single foraging bout. The brown and black mussels did not differ in ventral thickness and energy content, which are the main criteria for mussel selection and most important for short-term optimization. The brown mussels contained significantly less moisture, so by selecting them, oystercatchers could pack more mussel flesh into their limited oesophageal storage capacity. This enables them to increase their overall consumption during a feeding bout and increases their long-run energy gain rate, to an extent that is large enough to be significant for survival, especially during the short exposure of the mussel beds in winter.

Animals↗
PubMed2001

Identification of genes induced in peripheral nerve after injury. Expression profiling and novel gene discovery.

Peripheral nerve injury results in axonal degeneration and in phenotypic changes of the surrounding Schwann cells, whose presence is critical for nerve regeneration. To identify genes induced after nerve injury in Schwann cells, we developed a strategy that included differential screening of a subtractive library enriched for cDNAs expressed in injured nerve, sequence analysis, and expression profiling. By using real time quantitative reverse transcriptase-polymerase chain reaction, we found that injury-induced genes could be categorized into four temporal expression patterns. Among the clones we identified were a number that were homologous only to expressed sequence tags in the data base. These were stratified based on their expression profile, presence of identifiable sequence motifs, homologies to other proteins, and evolutionary conservation. We chose one representative gene, nin283, to analyze in detail. The nin283 gene encodes a 227-residue protein containing both a zinc finger and a RING finger motif. nin283 is highly expressed in the central nervous system, particularly in the developing cortical plate in embryos. It is also expressed in peripheral ganglia and is induced by nerve growth factor in PC12 cells. Subcellular localization analysis demonstrated that Nin283 is located in the endosome/lysosome compartment, suggesting that it may participate in ubiquitin-mediated protein modification.

Amino Acid Motifs↗
PubMed2001

Paris-Trousseau syndrome platelets in a child with Jacobsen's syndrome.

The thrombocytopenia in an infant with clinical features of Jacobsen's syndrome characterized by multiple congenital anomalies, cardiac defects, psychomotor retardation, and deletion of chromosome 11 at 11q23.3 has been evaluated. Study of his platelets in the electron microscope revealed giant alpha granules in his cells identical in appearance to those reported in the family with Paris-Trousseau syndrome. As a result, the Paris-Trousseau syndrome appears to be a variant of the Jacobsen syndrome, and the thrombocytopenia observed in all cases of chromosome 11q23.3 deletion due to dysmegakaryopoieses. Giant alpha granules are frequently observed in normal platelets during long-term storage and may form in Jacobsen and Paris-Trousseau platelets during prolonged residence in the bone marrow.

Abnormalities, Multiple↗
PubMed2001

EGR2 mutations in inherited neuropathies dominant-negatively inhibit myelin gene expression.

The identification of EGR2 mutations in patients with neuropathies and the phenotype Egr2/Krox20(-/-) have demonstrated that the Egr2 transcription factor is critical for peripheral nerve myelination. However, the mechanism by which these mutations cause disease remains unclear, as most patients present with disease in the heterozygous state, whereas Egr2(+/-) mice are phenotypically normal. To understand the effect of aberrant Egr2 activity on Schwann cell gene expression, we performed microarray expression profiling to identify genes regulated by Egr2 in Schwann cells. These include genes encoding myelin proteins and enzymes required for synthesis of normal myelin lipids. Using these newly identified targets, we have shown that neuropathy-associated EGR2 mutants dominant-negatively inhibit wild-type Egr2-mediated expression of essential myelin genes to levels sufficiently low to result in the abnormal myelination observed in these patients.

Animals↗
PubMed2001

Successful treatment of refractory Langerhans cell histiocytosis with unrelated cord blood transplantation.

A 2-month-old girl presented for treatment with a diffuse rash, interstitial pneumonia, otorrhea, and lymphadenopathy. Skin biopsy confirmed Langerhans cell histocytosis by electron microscopy. After receiving multiple courses of chemotherapy, only marginal improvement was achieved, with progressive marrow and liver involvement. The decision was made to pursue a human leukocyte antigen-identical unrelated cord blood transplantation. Two years after transplant, the bone marrow was clear of Langerhans cell histocytosis and 100% donor engraftment. The poor prognosis of patients with an inadequate response to therapy and the presence of organ dysfunction (marrow and liver) substantiated the decision to pursue an unrelated cord blood transplantation.

Bone Marrow↗
PubMed2000

Functional compensation by Egr4 in Egr1-dependent luteinizing hormone regulation and Leydig cell steroidogenesis.

The Egr family of zinc finger transcription factors, whose members are encoded by Egr1 (NGFI-A), Egr2 (Krox20), Egr3, and Egr4 (NGFI-C) regulate critical genetic programs involved in cellular growth, differentiation, and function. Egr1 regulates luteinizing hormone beta subunit (LHbeta) gene expression in the pituitary gland. Due to decreased levels of LHbeta, female Egr1-deficient mice are anovulatory, have low levels of progesterone, and are infertile. By contrast, male mutant mice show no identifiable defects in spermatogenesis, testosterone synthesis, or fertility. Here, we have shown that serum LH levels in male Egr1-deficient mice are adequate for maintenance of Leydig cell steroidogenesis and fertility because of partial functional redundancy with the closely related transcription factor Egr4. Egr4-Egr1 double mutant male mice had low steady-state levels of serum LH, physiologically low serum levels of testosterone, and atrophy of androgen-dependent organs that were not present in either Egr1- or Egr4-deficient males. In double mutant male mice, atrophic androgen-dependent organs and Leydig cell steroidogenesis were fully restored by administration of exogenous testosterone or human chorionic gonadotropin (an LH receptor agonist), respectively. Moreover, a normal distribution of gonadotropin-releasing hormone-containing neurons and normal innervation of the median eminence in the hypothalamus, as well as decreased levels of LH gene expression in Egr4-Egr1-relative to Egr1-deficient male mice, indicates a defect of LH regulation in pituitary gonadotropes. These results elucidate a novel level of redundancy between Egr4 and Egr1 in regulating LH production in male mice.

Animals↗
PubMed1999

Preparation and activity of some novel organo-metallic complexes against Helicobacter pylori.

Some novel organo-metallic complexes were prepared by complexing the antibiotics erythromycin (CAS 114-07-8), doxycycline (CAS 564-25-0), ciprofloxacin (CAS 85721-33-1) and amoxicillin (CAS 26787-78-0) with bismuth citrate and their antibacterial activity against Helicobacter pylori and other micro-organisms were investigated. Amoxicillin-bismuth citrate had the strongest activity against H. pylori with a lowest minimum inhibitory concentration of 0.007 mg/l. The complexes exhibited moderate activity against Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis and Bacillus subtilis. The findings suggest that the activity of these organo-metallic complexes might be specifically directed against H. pylori.

Anti-Bacterial Agents↗
PubMed1999

Infertility associated with incomplete spermatogenic arrest and oligozoospermia in Egr4-deficient mice.

Male fertility is complex and depends upon endocrine/paracrine regulatory mechanisms and morphogenetic processes occurring during testicular development, spermatogenesis (mitosis and meiosis) and spermiogenesis (spermatid maturation). Egr4 (NGFI-C, pAT133), a member of the Egr family of zinc-finger transcription factors, is thought to be involved in cellular growth and differentiation, but its specific function has been previously unknown. We derived Egr4 null mice through targeted mutagenesis and found that they were phenotypically normal with the exception that males, but not females, were infertile. Egr4 is expressed at low levels within male germ cells during meiosis and is critical for germ cell maturation during the early-mid pachytene stage. While most Egr4 null male germ cells undergo apoptosis during early-mid pachytene, some are capable of maturing beyond an apparent Egr4-dependent developmental restriction point. Consequently, a limited degree of spermiogenesis occurs but this is accompanied by markedly abnormal spermatozoon morphology and severe oligozoospermia. Egr4 appears to regulate critical genes involved in early stages of meiosis and has a singularly important role in male murine fertility. These data raise the possibility that Egr4 may contribute to some forms of human idiopathic male infertility.

Animals↗
PubMed1999

Optic disc size in ocular hypertension.

PURPOSE: To study the optic disc size in eyes with ocular hypertension (OHT) in comparison to primary open-angle glaucoma (POAG) and normals. METHODS: Optic disc photographs obtained with the Nidek 3dx NM camera were digitized (Nikon coolscan) and disc area calculated using Littmann correction in a randomly chosen eye of 28 OHT, 42 POAG and 30 normal subjects. OHT was defined as increased intraocular pressure with no disc or field changes suggestive of glaucoma with open angles. RESULTS: The optic disc area in OHT was 9.47 +/- 1.09 mm2; 12.27 +/- 2.87 mm2 in POAG; and 12.11 +/- 2.83 mm2 in normal individuals. CONCLUSION: Using magnification corrected morphometry and the criteria for OHT diagnosis, the optic disc area in OHT was significantly smaller (p < 0.0001) in POAG and normals.

Glaucoma, Open-Angle↗
PubMed1998

Biconical Bob Oscillatory Interfacial Rheometer.

This paper describes a biconical bob oscillatory interfacial rheometer designed to measure the dynamic viscoelastic response of a liquid-liquid interface subjected to a small amplitude oscillatory shear stress. This instrument is used to examine the rheological behavior of interfaces in the presence of surfactants, especially macromolecular types. Rheological parameters are calculated from a hydrodynamic analysis incorporating a linear viscoelastic interfacial rheological model. The general response of this instrument is compared with the oscillatory deep channel interfacial rheometer which is also capable of similar measurements. Measurements of interfacial viscoelasticity for the same liquid-liquid system with the two rheometers, the biconical bob and the deep channel rheometers, are shown to be comparable. This study demonstrates the intrinsic nature and, therefore, the instrument independence of these dynamic interfacial rheological properties. Accurate measurements of interfacial shear viscoelasticity can be carried out over a wide range of systems by combining measurements with the oscillatory interfacial rheometers. The limitations and regime of usefulness of these instruments are discussed. Copyright 1998 Academic Press.

Journal Article↗
PubMed1996

Comparison of Solubilization of Hydrocarbons in (PEO-PPO) Diblock versus (PEO-PPO-PEO) Triblock Copolymer Micelles

The solubilization of hydrocarbons by micelles formed of diblock and symmetric triblock copolymers in water are compared in the framework of a mean-field theory of solubilization. The block copolymers contain poly(ethylene oxide) as the hydrophilic block and poly(propylene oxide) as the hydrophobic block and are designated as EXPYEX or EWPZ (where E and P denote ethylene and propylene oxides and the subscripts denote the number of segments). In the presence of a variety of aromatic and aliphatic hydrocarbon solubilizates, the core radius, corona thickness, and aggregation number of the micelle and also the volume fraction of the hydrocarbon solubilized in the core are predicted. The calculations show that for identical molecular weights and block compositions, the diblock (E200P64) copolymer micelles have a much larger core radius, corona thickness, aggregation number, and volume fraction of the hydrocarbon solubilized in the core compared with the symmetric triblock (E100P64E100) copolymer micelles. In contrast, the diblock copolymer (E100P32), having the same block composition but half the molecular weight of the symmetric triblock copolymer (E100P64E100), gives rise to micelles having the same core radius, corona thickness, and volume fraction of the hydrocarbon solubilized as the micelles formed of the triblock copolymer, and an aggregation number twice that of the triblock copolymer micelle.

Journal Article↗