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L M Yu

Publications and source records attributed to L M Yu.

59 records · Page 4Linked to original sources
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Variable number of tandem repeat (VNTR) polymorphism at locus D17S5 (YNZ22) in four ethnically defined human populations.

We have analyzed the hypervariable locus D17S5 in four well-defined human populations (Kachari of Northeast India; Dogrib Indian of Canada; New Guinea Highlander of Papua New Guinea; and a relatively homogeneous Caucasian population of North German extraction) using both Southern blot analysis and the polymerase chain reaction (PCR) technique to: (1) compare the efficiency and limitation of Southern blotting versus PCR-based techniques in genotyping variable number of tandem repeat loci, and (2) provide allele frequency data at this locus in these four anthropologically defined populations. Preferential PCR amplification of smaller alleles associated with D17S5 was corrected by lowering the DNA template concentration to 200 ng, and by reducing the extension time to 2 min. A perfect correspondence was observed between the results from Southern blot and PCR analysis in all but one sample. A very large allele, of approximately 24 to 25 repeat units, detected by Southern blotting, could not be amplified by PCR, resulting in an incorrect genotyping rate of less than 0.5%. Considering the grave consequences of mistyping in forensic and paternity testing, it is suggested that heterozygous controls consisting of large and small alleles should be employed in each PCR experiment, and PCR-generated homozygotes should be confirmed by Southern blotting. Significant variation in the number and frequency of alleles at this locus was observed in the four examined populations. A total of 15 different alleles were detected. The average heterozygosity varied from 54% in the Dogrib to 89% in the Kachari. No heterozygote deficiency was observed at this locus in any of the examined populations.

Asian People↗
PubMedDate not supplied

Invasion and growth of Plasmodium falciparum is inhibited in fractionated thalassaemic erythrocytes.

Epidemiological and clinical studies have indicated that the thalassaemias may confer protection against malaria. The study reported here investigated this protective effect in vitro, using a new approach which controls for the potential effect of red cell size and age on the virulence of the parasite. A Percoll density gradient method was used to separate alpha- and beta-thalassaemic trait, haemoglobin H and normal red blood cells (RBC) into fractions of different density. Correlations between RBC density, age and size in fractions of all genotypes were established using red cell creatine as an index of cell age. The development of Plasmodium falciparum over 3 erythrocytic cycles (144 h) in whole blood as well as fractionated samples was monitored by slide microscopy and flow cytometry. A significantly reduced rate of parasite invasion and growth was demonstrated in RBC from all thalassaemic genotypes tested. Poor reinvasion rates were noted in the second and third cycles. Increased duration of culture and red cell age also had a greater negative impact on parasite growth in thalassaemic RBC. This poor growth rate was also associated with the arrest of parasite growth at the schizont stage (schizont maturation arrest) and the accumulation of abnormal, trophozoite/schizont stage parasites in the older thalassaemic RBC fractions. These findings suggest a defect in the number and viability of merozoites generated by parasites growing in thalassaemic RBC. Age related factors such as oxidant stress may play a key role in mediating this kind of protective mechanism and deserve further investigation.

Animals↗
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An embryonal carcinoma multiple phenotype locus maps to the proximal position of the mouse X chromosome.

A mutant embryonal carcinoma cell line, NR1-6, was established subsequent to retroviral insertion. The insertion was shown to be causative for a number of aberrant properties associated with the mutant cells. Analysis of >17 kb of the insertion site flanking region failed to reveal any homology between this locus and any reported sequence with the exception of one EST of unknown function and a few repetitive elements including B1 element and a CA dinucleotide repeat. CA repeats occur commonly in the mouse genome and usually show size variation. In this study, we mapped this multiphenotype locus using CA repeat polymorphism and Jackson Laboratory's interspecific backcross panels. The locus maps to the proximal end of the X chromosome between MGI offsets 1.5 and 4.5 and has been designated DXUalb1. There are several interesting candidate genes within this region. Analyses of their expression pattern may lead us to a better understanding of the molecular regulation of the variant mutant phenotypes.

Animals↗