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Biomedical subjects

H S Yong

Publications and source records attributed to H S Yong.

At least 19 recordsLinked to original sources
PubMed2001

Karyotype comparison and phylogenetic relationships of Pipistrellus-like bats (Vespertilionidae; Chiroptera; Mammalia).

Detailed karyotype descriptions of 20 Pipistrellus-like bat species belonging to the family Vespertilionidae are presented. For the first time, chromosomal complements of four species, i.e. Pipistrellus stenopterus (2n = 32), P. javanicus (2n = 34), Hypsugo eisentrauti (2n = 42) and H. crassulus (2n = 30) are reported. A Pipistrellus kuhlii-like species from Madagascar represents a separate species distinguished from the European Pipistrellus kuhlii (2n = 44) by a diploid chromosome number of 42. Banded karyotypes are presented for the first time for Scotozous dormeri, Hypsugo capensis, Hesperoptenus blanfordi, Tylonycteris pachypus and robustula. Chromosomal evolution in the family Vespertilionidae is characterized by the conservation of entire chromosomal arms and reductions in diploid chromosome number via Robertsonian fusions. Less frequently, centric fissions, para- and pericentric inversions and centromere shifts were found to have occurred. In several cases a certain type of chromosomal change predominates in a karyotype. Examples of this are the acquisition of interstitial heterochromatic bands in Tylonycteris robustula, and centric shifts in P. javanicus, H. eisentrauti and Hesp. blanfordi. The species examined here belong to three tribes, i.e. Pipistrellini, Vespertilionini and Eptesicini, which are distinguished by chromosomal characteristics. According to our results, the species Pipistrellus (Neoromicia) capensis belongs to the Vespertilionini and not to the Pipistrellini. We therefore propose to elevate the subgenus Neoromicia to generic rank.

Animals↗
PubMed2000

Phylogenetic relationships, character evolution, and biogeography of the subfamily Lygosominae (Reptilia: Scincidae) inferred from mitochondrial DNA sequences.

Phylogenetic relationships among the lygosomine skinks were inferred from 1249 base positions of mitochondrial DNA sequences of 12S and 16S rRNA genes. The monophyly of this subfamily was confirmed and the presence of five distinct infrasubfamilial lineages detected. Of these, the Sphenomorphus group appears to have diverged first, followed by the Lygosoma and Egernia groups in order, leaving the Eugongylus and Mabuya groups as sister groups. Our results did not support monophyly of the Mabuya group sensu lato (i.e., an assemblage of the Lygosoma, Egernia, and Mabuya groups), for which a number of morphological and karyological studies demonstrated a considerable similarity. Our results also contradict the previous hypothesis, formulated on the basis of morphological and immunological data, which argued for the sister relationship between the Egernia and the Eugongylus groups. Morphological and karyological characters used to define the Mabuya group (sensu lato) may actually represent plesiomorphic states. The phylogenetic diversity of lygosomine skinks in the Australian region appears to have increased through multiple colonizations from Southeast Asia.

Animals↗
PubMed1999

Strain differences in Blastocystis isolates as detected by a single set of polymerase chain reaction primers.

A total of 20 isolates of Blastocystis were characterized using a single set of polymerase chain reaction (PCR) primers. The amplification product revealed five types of pattern. All four isolates from Singapore yielded PCR products quite different from those of the local isolates. However, most of the local isolates showed a major product at either 280 or 500 bp, or both. We also suspected that the amplification product detected at 280 bp might be an indicator of the pathogenicity of this parasite. One isolate (M12) obtained from a monkey showed patterns similar to those of human isolates (10203 and KP1) and probably belongs to the same strain. The results indicate that the intraspecific or interstrain variations in these 20 Blastocystis isolates belong to 5 different patterns. The differences among isolates of the same strain revealed by the presence or absence of certain amplification products showed further intrastrain variations in this parasite.

Animals↗
PubMed1997

Detection of circulating antigens of Parastrongylus cantonensis in human sera by dot-blot ELISA and sandwich ELISA using monoclonal antibody.

A dot-blot ELISA was compared with a previously performed sandwich ELISA for the detection of Parastrongylus cantonensis antigens in sera from patients. Using the same monoclonal antibody and the same sera, 6 of 10 sera (60%) from parastronglyiasis patients were positive in dot-blot ELISA, whereas with sandwich ELISA, 5 of the same patient sera (50%) were positive. The specificity in both assays was 100% using 50 sera from patients with other parasitic diseases; of these, 10 each were from patients with cysticercosis, filariasis, gnathostomiasis, malaria and toxocariasis. The control group consisted of 53 sera from normal health Thais and Malaysians. The sensitivity of the assays was, however, slightly better with dot-blot ELISA and because it is simple, quick and cost-effective, it may be a test of choice for specific diagnosis of human parastrongyliasis.

Angiostrongylus cantonensis↗
PubMed1997

Detection of circulating antigens of Parastrongylus cantonensis in human sera by sandwich ELISA with specific monoclonal antibody.

A specific monoclonal antibody (AW-3C2) as revealed by ELISA was produced against the adult worm antigens of Parastrongylus cantonensis and used in a sandwich ELISA for the detection of circulating antigens in the sera of parastrongyliasis patients and those with other parasitic diseases. A total of 60 sera was used in this study. Of these, 10 each were from patients with parastrongyliasis filariasis, gnathostomiasis, malaria and toxocariasis. The control group consisted of 53 serum samples from normal healthy Thais and Malaysians. The mean +/- optical density (OD) values for the normal Thai and Malaysian groups were 0.126 +/- 0.028 and 0.124 +/- 0.029, respectively. Mean OD values of parastrongyliasis patient group differed significantly from that of the normal groups as well as those of other parasitic infections. Using a cut-off point of mean OD +/- 3SD of the normal control groups as indicating a positive reading, the specificity of the assay with this monoclonal antibody was 100% while the sensitivity was 50%.

Angiostrongylus cantonensis↗
PubMed1996

Synlophe of Batrachonema synaptospicula (Nematoda:Amphibiophilidae) collected from Malaysian frogs.

The synlophe of Batrachonema synaptospicula Yuen, 1965 collected from Rana limnocharis Boie, 1835 of peninsular Malaysia was found to be identical morphologically to that in the specimens from Rana narina Stejneger, 1901 of Okinawa, and R. limnocharis of Taiwan. In the midbody, 20-22 ridges are present, and the ridges increase gradually in size and are oriented from right to left in the dorsal and left ventral fields, whereas the right ventral ridges are small and almost perpendicular to the body wall. The orientation of ridges from right to left is considered to be a key characteristic of the genus Batrachonema. Because Amphibiophilus ranae Wang et al., 1978 and Amphibiophilus sp. from R. limnocharis of south China are regarded to be conspecific with B. synaptospicula, this nematode is surmised to be distributed widely in southeast and east Asia.

Animals↗
PubMed1995

Detection of circulating antigens of Parastrongylus cantonensis in human sera by sandwich ELISA with specific monoclonal antibody.

A specific monoclonal antibody (AW-3C2) as revealed by ELISA was produced against the adult worm antigens of Parastrongylus cantonensis and used in a sandwich ELISA for the detection of circulating antigens in the sera of parastrongyliasis patients and those with other parasitic diseases. A total of 60 sera was used in this study. Of these, 10 each were from patients with parastrongyliasis, cysticercosis, filariasis, gnathostomiasis, malaria and toxocariasis. The control group consisted of 53 serum samples from normal healthy Thais and Malaysians. The mean +/- optical density (OD) values for the normal Thai and Malaysian groups were 0.126 +/- 0.028 and 0.124 +/- 0.029, respectively. The mean OD values of the parastrongyliasis patient group differed significantly from that of the normal groups as well as those of other parasitic infections. Using a cut-off point of OD +/- 3SD of the control groups as indicating a positive reading, the specificity of the assay with this monoclonal antibody was 100% while the sensitivity was 50%.

Adult↗
PubMed1993

Genetic aspects of lymphatic filariasis.

The genetics of human susceptibility to lymphatic filariasis, the genetic basis of filarial susceptibility in vector mosquitos, and the genetic constitution of human filarial parasites and their mosquito vectors are reviewed. It is evident that our present knowledge on the genetics of lymphatic filariasis is still very meagre. The need to study various genetic aspects of the disease is highlighted.

Animals↗
PubMed1992

Detection of circulating plasmodial antigens in human sera by sandwich ELISA with monoclonal antibodies.

Two monoclonal antibodies (MAbs), one produced against Plasmodium falciparum (PF-IG8) and the other against P. cynomolgi (PC-IE12) schizont antigens were used in a sandwich ELISA for the detection of circulating plasmodial antigens in sera of patients infected with either P. falciparum, P. vivax or P. malariae. The mean +/- SD optical density (OD) values for the normal control group using PF-108 and PC-1E12 were 0.351 +/- 0.036 and 0.205 +/- 0.044, respectively. Mean OD values for the three infected groups were found to be significantly higher than those of the normal control group for both MAbs. However, ELISA values for individual serum specimens did not correlate with the level of parasitemia in the infected blood. Using a cut-off point of mean OD +/- 3 SD of the normal control group as indicating a positive reading, the specificity of this assay with both MAbs was 100%. The sensitivity of the assay using PF-1G8 was 95% while that obtained with PC-1E12 was 98%.

Animals↗
PubMed1991

Long term maintenance of Toxoplasma gondii (Rh strain) in Vero cell line and use of harvested antigens for immunodiagnosis.

Thirty in vitro serial passages of Toxoplasman gondii cultures in Vero cell line performed once in every five days had a mean increase in parasite count of 74.4 +/- 14.8 times from that of initial counts. Long term cultures in Vero cell line did not alter the virulence of the parasite. The good correlation (r = 0.99) between the IFA titer and ELISA OD values using the parasite antigens from in vitro sources indicates that long term maintenance of T. gondii in culture does not affect significantly the ability to recognize antibodies to surface and soluble antigens. The results also show that soluble antigens containing host cells can be directly used for immunodiagnostic purposes without purification. The in vitro maintenance of T. gondii is safer and cheaper when compared to the in vivo method.

Animals↗
PubMed1990

Low allozyme variability in Bactrocera albistrigata (Insecta: Diptera: Tephritidae) from Peninsular Malaysia.

1. Population samples of Bactrocera albistrigata from Peninsular Malaysia were analyzed for 12 to 14 gene-enzyme systems comprising 15-18 loci. 2. Three loci, aMDH, PGD and PGM, were polymorphic. 3. Anodal malate dehydrogenase and phosphogluconate dehydrogenase were represented by two alleles each, while phosphoglucomutase was represented by three alleles. 4. Phosphoglucomutase had a higher heterozygosity than anodal malate dehydrogenase and phosphogluconate dehydrogenase. 5. B. albistrigata was characterized by low genetic variability, as measured by the proportion of polymorphic loci and heterozygosity.

Alleles↗
PubMed1989

In vitro activity of some monoclonal antibodies against Brugia malayi microfiliariae and infective larvae.

Two out of six monoclonals (McAbs) produced against subperiodic Brugia malayi infective larva (L3) antigens impaired B. malayi L3 motility independently of human buffy coat cells. Scanning electron microscopy studies showed damage to L3 surface and loss of regular cuticular annulations. The two McAbs (BML 1a and BM1 8b) did not affect B. malayi microfilaria (mf). They were IFAT-positive with B. malayi adult and L3 antigens; other McAbs which did not affect mf or L3 motility were IFAT-negative. All six McAbs did not promote cellular adherence of normal human buffy coat cells to mf or L3.

Animals↗
PubMed1988

Nematode isoenzyme studies and cytogenetics.

The current information on isoenzyme studies of nematode parasites was reviewed. The genetic heterogeneity as reviewed by these studies was highlighted. Application of isoenzyme studies and the role of biotechnological techniques in isoenzyme studies was discussed, and the status of cytogenetic studies on nematode parasites was presented.

Animals↗