University of Colombo

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Browsing University of Colombo by Author "CHANDRASEKHARAN, NV"

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    Cloning and characterization of repetitive deoxyribonucleic acid sequences from DIROFILARIA REPENS and the gene for actin from SETARIA DIGITATA
    (University of Colombo: UC(MED)., 1994) CHANDRASEKHARAN, NV
    A repetitive DNA element from the genome of the filarial nematode Dirofilaria repens has been cloned and sequenced. The 176-base pair repeating units are arranged in direct tandem and are clustered in the parasite genome. The repeats are present in about 15,000 copies per haploid genome and constitute approximately 3 percent of the parasite genome. All repeats appear to belong to a single family although some elements have diverged significantly. The cloned repetitive sequence hybridized only to D. repens DNA and was sensitive enough to detect 250 to 500pg of D. repens DNA, a single microfilariae in infected blood samples, and a single third stage larva in mosquitoes. The high specificity and sensitivity of the cloned fragment makes it ideal as a diagnostic probe for detecting D. repens in both the host and the vector. A recombinant clone containing the entire Setaria digitat actin gene together with its 5' and 3' untranslated regions has been fully sequenced and characterized. The coding region was interrupted by five short introns ranging in size from 81 to 194 base pairs. The sequences around the 5' and 3' spice junctions were found to be fairly conserved and to closely resemble splice junctions of eukaryotes including those of parasitic nematodes. The coding nucleic acid sequence predicts a protein of 376 amino acids. Based on the N-terminal amino acid residues, S. digitata actin closely resembles vertebrate cytoplasmic y actin. The other isotype specific amino acid residues are characteristic of both muscle and cytoplasmic actins though the overall data when applied quantitatively indicate Setaria actin to resemble vertebrate cytoplasmic actins ( Beta or Gama). Setaria actin showed a high degree of homology to actins isolated from many other organisms from a wide range of taxonomic groups. The overall G+C content of the gene together with its 5' and 3' flanking regions was 39 percent while the coding region had a G+C content of 45 percent. The introns were unusually A+T rich (86 percent) while the 5' and 3' untranslated regions had an A+T content of 64 percent. A marked bias was not observed in codon utilization. Overall there was a 60 percent preference for A or T in the third position and a 40 percent preference for G or C. Analysis of the 5' untranslated region revealed a potential TATA box and a CAAT box while a putative polyadenylation signal was identified in the 3' untranstated region. The gene appears to be single copy and Nothern blot analysis showed it to be transcriptionally active producing a RNA species of around 1300 nucleotides.
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    Evaluation of an analytical technique for the estimation of glycosylated hemoglobin and plasma proteins and the establishment of clinical norms for Sri Lanka
    (University of Colombo: UC(MED)., 1984) CHANDRASEKHARAN, NV
    The relative importance of the measurement of glycosylated hemoglobin as an objective and quantitative index reflecting blood glucose levels of diabetics is well established. Similarly glycosylated plasma proteins could be used as an index of short term glycaemic control. Since no previous investigations have been carried out in Sri Lanka on glycosylated haemoglobin and plasma proteins, a suitable technique has been evaluated for the assay and the clinical norms established. The colorimetric method meets many of the criteria for an ideal laboratory test. It proves to be the most suitable method for the measurement of glycosylated haemoglobin and plasma proteins as a routine assay in general and regional hospitals in Sri Lanka.