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Biomedical subjects

R Jayasekara

Publications and source records attributed to R Jayasekara.

12 recordsLinked to original sources
PubMed2004

Application of a quartz crystal microbalance to evaluate biodegradability of starch by Bacillus subtilis.

Biodegradation of solution-cast starch films by Bacillus subtilis was monitored using a quartz crystal microbalance (QCM). A starch film was formed on the crystal by solution casting and exposed to the Bacillus subtilis culture in a bioreactor. The high sensitivity of the QCM could monitor small weight changes of the starch films on the crystal in the initial stages of biodegradation by secreted exo-enzymes of the bacterium. The feasibility of this approach as a means of quantification and characterisation of biodegradability of different polymeric materials by selected organisms is discussed.

Bacillus subtilis↗
PubMed1996

Genetic variation in Sri Lanka.

A population genetic study was designed to analyze genetic composition and population structure of the five main population groups (Sinhalese, Tamils, Moors, Burghers, and Malays) of Sri Lanka. Twentyseven polymorphic and three monomorphic loci were examined in all five populations. Several genetic markers, including subtype variation of HP, TF, PI, GC, ORM, and PGM1, were analyzed for the first time and helped to clarify the range of genetic variation for Sri Lankan populations. Many genetic systems (Rh, JK, ACP, ESD, HP, C3, TF, and GC) showed a high level of variation among the populations of Sri Lanka. However, at the individual level the Burgher population (a hybrid group between the Dutch and Portuguese and the local Sinhalese) showed European features, but its gene frequencies were either intermediate to its parental populations or more similar to the local Sinhalese. In the F statistic analysis all populations showed positive FIS values, ranging from 0.0305 in the Burghers to 0.1084 in the Malays; however, for a large number of loci the FIS values for the Burghers were negative, indicating the possible hybrid nature of this population. In genetic affinity studies the Burghers, Moors, and Malays showed a greater degree of isolation, but compared with the possible populations of their origin, the five populations of Sri Lanka tended to show some degree of affinity to each other. Our analysis therefore suggests that there is little evidence of disruptive selection; however, restricted gene flow favors the change of allele frequency toward the local Sinhalese and Tamil populations.

Ethnicity↗
PubMed1996

Population genetic study of three VNTR loci (D2S44, D7S22, and D12S11) in five ethnically defined populations of the Indian subcontinent.

Using RFLP (restriction fragment length polymorphism) analysis, we have characterized the genotypic variation of three VNTR (variable number of tandem repeat) loci (D2S44, D7S22, and D12S11) with probes YNH24, g3, and MS43a, respectively, for 288 individuals from 5 genetically well-defined ethnic groups (Brahmins, Maratha, Gujarati Patel, Sinhalese, and Moors) of the Indian subcontinent. The distributions of VNTR alleles at the binned level were examined among the five populations, and the genetic affinities obtained using the VNTR data were compared with serogenetic data on 22 blood group and protein loci previously reported from our laboratory. For classical genetic markers the Sinhalese show slight affinity with the populations of western India. However, the genetic affinity results considerably parallel the results for VNTR loci and 25 combined VNTR/blood group/protein loci, suggesting that the Sinhalese show the least affinity with the populations of western India. These results confirm the findings of a recent study of genetic relationships of the populations of Sri Lanka based on admixture analysis. The concerns regarding whether or not the pattern of genetic variation of VNTR loci at the bin level can be studied using classical population principles are addressed.

Ethnicity↗
PubMed1994

Distribution of group specific component (GC) and transferrin (TF) subtypes in populations of Sri Lanka.

A random sample of 503 individuals from five endogamous groups of Sri Lanka was studied for the genetic polymorphism of the group specific component (GC) and transferrin (TF) using isoelectric focusing. Both systems showed statistically significant heterogeneity among the five main populations of the island. The GC allele frequencies of Malays are significantly different from those of the other four populations (Sinhalese, Tamils, Moors and Burghers). However, the TF system shows less variation, since only the Moors show a significant heterogeneity compared to Tamils and Burghers. The frequencies found in the present study are very different from those reported for the populations of the Indian mainland.

Alleles↗
PubMed1994

Skeletal fluorosis with neurological complications.

A case of skeletal fluorosis with spinal cord compression from Kekirawa following consumption of water with high fluoride content for about 20 years is described. The observations of other workers (4,5) and the present case report show that more extensive field studies among vulnerable populations is indicated in this region. The need to search for a cost effective method of defluoridation of water is stressed.

Adult↗
PubMed1993

Genetic polymorphism of orosomucoid (ORM) in populations of the United Kingdom, Indian subcontinent, and Cambodia.

The genetic variation of the human serum orosomucoid (ORM) was investigated by isoelectric focusing (IEF) followed by immunofixation in 15 different populations from East Midlands (United Kingdom), India, Sri Lanka, and Cambodia. Statistically significant differences were observed between various Asiatic and British populations, however differences within Asiatic and European populations were minor. The distribution of ORM1 alleles in populations investigated to date suggests an interesting east-west geographical cline. There is a suggestion that present day wide polymorphism at the ORM1 locus may be influenced by selection.

Alleles↗
PubMed1993

Deletion screening of Sri Lankan Duchenne muscular dystrophy patients using the polymerase chain reaction.

Duchenne muscular dystrophy (DMD) is an X-chromosome-linked myopathy caused by a defect in the DMD gene. Intragenic deletions appear to be the most common gene defect leading to DMD, and the deletion frequency has been estimated to be 66%. Results of this study using a group of 24 DMD patients of Sri Lankan origin employing the technique of multiplex DNA amplification using the polymerase chain reaction indicated a deletion frequency of 62.5%. Eighty per cent of these deletions were localized in a region of the DMD gene regarded as a 'hot spot' for DMD deletions. Our results are in agreement with the results of other studies carried out on Caucasian populations.

Gene Amplification↗
PubMed1992

Screening for Turner syndrome: how useful is the buccal smear test?

The buccal smear test was used to screen for Turner syndrome in a sample of girls with severe short stature who did not have any other clinical features of that condition. The majority of the girls did not show X chromatin bodies in the buccal mucosal cells. None of those who qualified for chromosomal analysis showed an XO chromosomal pattern either. We conclude that reliability of the buccal smear test as a screening method for Turner syndrome remains doubtful.

Cheek↗