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Biomedical subjects

E H Yap

Publications and source records attributed to E H Yap.

At least 73 records · Page 4Linked to original sources
PubMed1989

The determination of anti-Toxoplasma gondii antibodies in different IgG subclasses of human sera by the enzyme-linked immunosorbent assay (ELISA).

The level of activity of the 4 IgG subclasses in toxoplasmosis were determined in an ELISA employing commercially available monoclonal antibodies to the 4 subclasses. Forty-four sera positive by IgG-ELISA and 73 negative sera were tested for IgG subclass activity. IgG1 was found to be the predominant subclass while IgG3 and IgG4 were probably produced at low but significant levels in sera which were positive for IgG antibodies. The significance of the results were discussed.

Adult↗
PubMed1988

Serological evidence of hantavirus infection in laboratory rats and personnel.

Laboratory-acquired haemorrhagic fever with renal syndrome (HFRS) has been reported in many countries. A serological survey of laboratory white rats and of laboratory personnel for antibodies to hantaviruses was conducted in Singapore. Forty-four per cent (143/329) of rats were seropositive by the indirect immunofluorescent antibody test but none had hantaviral antigens in lung tissues. Two of 74 laboratory personnel were seropositive but neither had a history of clinical illness. The high seropositivity rate among laboratory rats led to their replacement with Hantaan virus-free strains. To eliminate the hazard of laboratory-acquired HFRS, regular serological screening of laboratory rats and replacement of infected animals with seronegative stocks should be implemented. High risk techniques with laboratory rats, which are likely to generate aerosols, should be performed in biological safety cabinets. Serological surveillance of laboratory personnel and reporting of suspected HFRS cases are useful in the early detection of hantavirus infection.

Animals↗
PubMed1988

Plasmid profiles compared with serotyping and pyocin typing for epidemiological surveillance of Pseudomonas aeruginosa.

The plasmid profiles of 112 clinical isolates of Pseudomonas aeruginosa were determined by two reproducible, rapid, plasmid screening methods. Plasmid DNA was present in 15% of isolates examined. Plasmids varied in size from 1.2 X 10(6) to 60.2 X 10(6) mol. wt. The dominant serotypes encountered were O:11 and O:4, which comprised 38% and 12% of strains, respectively. Four pyocin types (1, 10, 3 and 5) dominated (respective frequencies: 56, 15, 12 and 6%). Reproducibility of pyocin typing was distinctly inferior to both plasmid profiling and serotyping. Strains of identical serotypes could be further differentiated by dissimilar plasmid profiles. Serologically untypable or polyagglutinable strains were successfully characterised by plasmid profile patterns. Thus, plasmid profiling was shown to be a useful adjunct to serotyping for the epidemiological typing of P. aeruginosa.

Anti-Bacterial Agents↗
PubMed1987

Haemorrhagic fever with renal syndrome involving the liver.

A case of haemorrhagic fever with renal syndrome that originated in Malaysia is reported. The patient presented with clinical symptoms which were not typical of the disease as seen in endemic regions. Renal involvement, which is characteristic of haemorrhagic fever with renal syndrome, was mild, and the predominant symptom was a persistently marked elevation of serum transaminase levels that was suggestive of hepatitis. Liver involvement has not been described in the Asian form of haemorrhagic fever with renal syndrome. The patient developed a petechial skin rash and had severe thrombocytopenia. Serological confirmation of the diagnosis of haemorrhagic fever with renal syndrome was obtained by the demonstration of significant antibody rises to hantaviruses in the patient's acute- and convalescent-phase sera.

Adult↗
PubMed1987

Infections of forest rat filaria, Breinlia booliati, in neonate and juvenile laboratory white rats.

The kinetics of Breinlia booliati infection in 3 inbred rat strains (Lewis, Wistar and Sprague Dawley) were investigated. One group of rats was infected as neonates (less than 24 hours of age) with third-stage larvae of B. booliati and the other group was infected as juveniles (4 weeks of age). The results showed that infection in the neonates were significantly different from the infection in the juveniles. The 60 rats infected as neonates, when necropsied between 8 to 10 months postinfection, yielded adult worms. The 2 neonatal infection groups of Lewis and Wistar strains showed highest susceptibility to the infections. The mean prepatent period was 85 days. Ninety to 95% of the infected rats were patent with microfilaraemia and a large percentage (33 to 47%) of them had high microfilaraemia counts exceeding 3000 mff/20 mm3 of blood and larger sizes (mean 157.11 mm for female adult worms and 61.88 mm for male adult worms. The adult worms were distributed equally in both the pleural (57%) and peritoneal cavity (43%). In most aspects, the neonatal infection group of the Sprague-Dawley strain was intermediate in susceptibility between the 2 neonatal infection groups of the Lewis and Wistar strains and the 3 juvenile infection groups. In contrast to neonatal infection groups, the 3 juvenile infection groups exhibited low infection rates (37%, 58% and 47% for the Lewis, Wistar and Sprague Dawley strains respectively), longer prepatent periods (mean 101 days), lower recovery rates (2 to 4%), lower adult worm loads (mean 0.4 to 0.8 female worms, and 0.2 to 0.8 male worms per rat), and smaller sizes (mean 141.24 mm for female adult worms and 53.75 mm for male adult worms). Forty-four to 57% of these infected rats harboured either single male or single female adult worms in the body cavity. Most (92%) of the adult worms recovered from the juvenile infection groups resided in the pleural cavity and the remaining 8% were recovered from the peritoneal cavity. Microfilaraemia could be detected in only 3/20 Lewis rats, 5/20 Wistar rats and 5/20 Sprague Dawley rats. The mean peak microfilaraemia of the 3 pooled juvenile infection groups was 632 mff/20 mm3 of blood, ranging from 7 mff/20 mm3 to 1856 mmf/20 mm3. Our results indicate that the susceptibility to B. booliati infection in white rats is both genetic and age-associated. The responses of the 2 distinct infection groups to B. booliati infections are discussed.

Animals↗
PubMed1987

Haemorrhagic fever with renal syndrome: clinical, virological and epidemiological perspectives.

Haemorrhagic fever with renal syndrome (HFRS) is caused by a group of RNA viruses within the family of Bunyaviridae known as hantaviruses. The classical, severe form of HFRS is characterized by fever, headache, abdominal and lumbar pain, proteinuria, haemorrhagic phenomena, shock and renal failure. The disease is associated with the prototype Hantaan virus and occurs in rural areas of Korea and China with Apodemus mice as reservoir hosts. A clinically less severe form of HFRS, which is caused by Seoul virus, occurs in urban areas with the house rat Rattus novegicus as the main reservoir host. The disease in nonendemic areas may be atypical and patients with symptoms the hepatitis and minimal renal involvement have been observed in Malaysia. Outbreaks of HFRS in humans involving infected laboratory rat colonies have occurred in several medical centres in various countries. Hantaviruses cause a chronic, asymptomatic infection in rodents which excrete the virus in their lungs, saliva and urine. Man becomes infected mainly by inhalation of infected droplets from healthy rodent carriers. Seroepidemiological studies using mainly the indirect immunoflourescent antibody test of sera from humans and rats showed that hantaviruses have a worldwide distribution.

Animals↗
PubMed1984

Studies on filariasis in Singapore: immunodiagnosis using indirect immunofluorescence.

Filarial antibodies were detected by the indirect fluorescent antibody (IFA) technique using sonicated microfilariae of Brugia malayi as antigen. Of the 324 sera of patients with clinical symptoms suggestive of filarial infection, 90 (28%) had detectable antibodies with titres ranging from 1 : 4 to 1 : 4096. Forty-six percent of patients with eosinophilic lung were positive with titres ranging from 1 : 4 to 1 : 1024. Highest rates of positives were seen in Indians (48%) with lower rates in Malays (36%) and Chinese (15%).

Animals↗
PubMed1982

Melanization and encapsulation in Aedes aegypti and Aedes togoi in response to parasitization by a filarioid nematode (Breinlia booliati).

In Aedes aegypti (Singapore strain), s refractory host, there was a marked progressive decline of developing larvae of Breinlia booliati during the incubation period. However, in Aedes togoi, a susceptible host, the filarial larvae developed normally and the number of larvae remained constant throughout the incubation period. Encapsulation and melanization of B. booliati larvae in Ae. aegypti and Ae. togoi were studied. Ae. togoi occasionally mounted a defence reaction to the infection. In Ae. aegypti, various stages of filarial larvae were frequently affected by the defence mechanisms of the host, and a relatively large number of melanized larvae were recovered in dissections throughout the incubation period. The process of melanization is described and the relationship between melanization and haemocytes of mosquitoes is discussed. Haemocytes of the mosquito host appeared to be involved in the encapsulation of filarial larvae, as evidenced by adherence of cells to the cuticle of the larvae and the formation of a translucent, gelatinous envelope which contained intact cells, necrotic cells, spaces and numerous whitish granules. The possible involvement of a humoral reaction in bringing about the degeneration and retardation of the filarial larvae is discussed.

Aedes↗
PubMed1980

Immunofluorescent studies in filariasis: antibody levels in rats infected with the Malayan forest filaria, Breinlia booliati.

Antibody levels were investigated in rats infected with Breinlia booliati using the indirect immunofluorescent antibody technique. Sonicated antigens were prepared from microfilariae and adult worms. Adult worm antigen was rather unsatisfactory. The sonicated microfilarial antigen was useful in detecting antibodies in various groups of rat sera. Very high antibody levels were seen in amicrofilaraemic rats harbouring unisexual infections or varying worm loads. The significance of these observations are discussed.

Animals↗
PubMed1980

Studies on human filariasis in Malaysia: the application of an indirect hemagglutination technique for immunodiagnosis.

The indirect hemagglutination (IHA) test done with turkey red cells was applied to 173 serum samples obtained from patients and persons exposed to Wuchereria bancrofti and Brugia malayi in endemic areas of Peninsular Malaysia. A crude extract of adult worms of the rat filaria, Breinlia booliati, was used as the antigen. When a titer of 1:16 was taken as negative, positive IHA test rates in sera from microfilaria-negative persons in endemic areas, microfilaremic cases, and patients with clinical filariasis were 13%, 75%, and 80%, respectively. Results of the IHA test correlated well with results obtained with the indirect fluorescent technique.

Antibodies↗
PubMed1979

Studies on human filariasis in Malaysia: immunoglobulin and complement levels in persons infected with Brugia malayi and Wuchereria bancrofti.

Levels of immunoglobulins G, A, M and E as well as complement components C3c and C4 have been determined in populations in various endemic areas in Peninsular Malaysia and also in filariasis patients. High immunoglobulin levels were seen. In the microfilarial-negative group IgG was 2009 mg% while IgE was 3967 I.U./ml. In the filariasis group, Wuchereria bancrofti patients had significantly higher levels of IgG, IgM and IgE, namely, 3314 mg%, 804 mg% and 18400 I.U./ml respectively. The significance of these levels is discussed.

Adolescent↗
PubMed1979

Studies on human filariasis in Malaysia: immunodiagnosis using indirect immunofluorescence.

The indirect immunofluorescence test using sonicated microfilariae of Brugia malayi has been evaluated on 173 sera from patients and persons exposed to Wuchereria bancrofti and B. malayi in endemic areas of Peninsular Malaysia. In the microfilaria-negative group, without signs and symptoms of filariasis 55/62 sera (89%) had titers of 1:16 and less. In the microfilaremic groups and in the amicrofilaremic cases with clinical filariasis, all the sera tested were positive, with the antibody titers ranging generally from 1:16 - 1:256. Cross-reaction tests were done on 16 samples of onchocerciasis sera from West Africa using sonicated antigen as well as antigen-coated CNB1-activated sepharose. Antibody titers were detected in all the sera. The usefulness of the sonicated microfilarial antigen in serodiagnosis of filariasis is discussed.

Adolescent↗