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R C Ko

Publications and source records attributed to R C Ko.

At least 55 records · Page 3Linked to original sources
PubMed1986

Isolation of specific antigens from Angiostrongylus cantonensis. 2. By affinity chromatography.

The crude adult worm extract of Angiostrongylus cantonensis was subjected to a series of affinity chromatography for selective removal of host antigens as well as cross-reactive components with other helminths. The purified fraction designated as AC(p) with molecular weights ranging from 10,000-42,000 was found to contain antigenic components specific to A. cantonensis as determined by immunoelectrophoresis and enzyme-linked immunosorbent assay.

Angiostrongylus↗
PubMed1986

Surface antigens of Angiostrongylus cantonensis developing in permissive and non-permissive hosts.

The immunofluorescent antibody test and immunocytochemical method were employed to study the surface antigens of Angiostrongylus cantonensis obtained from infected rats, mice and guinea pigs. Positive results with intense fluorescence and brownish peroxidase staining were observed on the cuticular surface of A. cantonensis recovered from rats 22 days (late cerebral phase) and 34 days (lung phase) post-infection when tested with antisera against host (normal rat serum) antigens as well as crude extracts of A. cantonensis. However, host antigens were not observed on the surface of the nematode recovered from the brain of mice and guinea pigs 15 days post-infection.

Angiostrongylus↗
PubMed1986

Further observations on the first documented outbreak of trichinosis in Hong Kong.

The first documented report of human trichinosis in Hong Kong is described comprising an outbreak amongst 20 Gurkha soldiers following a barbecue. The cardinal clinical features were fever, myalgia and facial oedema and the most useful laboratory tests were eosinophilia and elevated levels of creatinine phosphokinase. Gastrointestinal symptoms were uncommon. Seven patients who developed electrocardiographic abnormalities are the subject of an ongoing study. Four patients had psychiatric manifestations. Splinter haemorrhages, hypocalcaemia and evidence of renal dysfunction were absent. The parasite was recovered from 13 of patients and the diagnosis confirmed serologically in all. The value of the enzyme-linked immunosorbent assay (ELISA) for IgM and IgE antibodies is emphasized in that it is 100% specific and sensitive. Thiabendazole alone was used in treatment and all patients recovered.

Adolescent↗
PubMed1985

Isolation of specific antigens from Angiostrongylus cantonensis. 1. Preparative flatbed isoelectric focusing.

Electrophoresis on SDS gel and analytical isoelectric focusing showed that a crude extract of Angiostrongylus cantonensis consisted of at least 40 protein components with molecular weights ranging from 13 000-70 000 and isoelectric points of pI values ranging from 3.7-10.0. Crossed-immunoelectrophoresis with a hyperimmune antiserum to A. cantonensis showed at least 40 different antigenic components in the crude worm extract which were cross-reactive with those of Ascaris suum, Metastrongylus apri and Toxocara canis. Using preparative isoelectric focusing, the somatic worm preparation was divided into 13 equal fractions, of which 3, 4 and 5, with pI values of 3.7, 4.0 and 4.45 respectively, were later shown by immunoelectrophoretic techniques and enzyme-linked immunosorbent assay to contain antigens specific to A. cantonensis.

Angiostrongylus↗
PubMed1983

Study of acute trichinosis in Ghurkas: specificity and sensitivity of enzyme-linked immunosorbent assays for IgM and IgE antibodies to Trichinella larval antigens in diagnosis.

The enzyme-linked immunosorbent assay (ELISA) was successfully applied to detect IgE antibodies against parasitic antigens by using an additional antibody layer to attain an amplification effect. The sera of 18 Gurkha patients with clinical manifestations of acute trichinosis and 35 Chinese with other parasitic infections were tested for antibodies to Trichinella spiralis by IgE-, IgM- and IgG-ELISA, IgG-radioimmunoassay (RIA) and indirect haemagglutination test (IHA). ELISAs for detection of IgE and IgM antibodies provided a 100% specific and sensitive diagnosis. Although IHA, IgG-RIA and IgG-ELISA detected antibodies in 94% of patients, non-specific reactions were also observed in the two last named methods. Muscle biopsies were positive in only 56% of patients.

Biopsy↗
PubMed1981

Host-parasite relationship of Angiostrongylus cantonensis. 2. Angiotropic behaviour and abnormal site development.

Migratory young fifth-stage Angiostrongylus cantonensis transplanted intracranially into recipient rats were found to reach the lungs 3-4 days later by randomly entering cerebral veins. However, worms which were transplanted close to extracranial veins such as the jugular and femoral veins, or into the pleural and peritoneal cavities failed to enter these blood vessels. Third-stage larvae were capable of infecting rats via skin wounds. Protease activity was not detected around young fifth and third-stage larvae incubated on gelatin films. The migratory young fifth-stage worms underwent a significant growth and completed development of their reproductive system during the first week after transplantation into pleural and peritoneal cavities and subcutaneous tissues where some survived for as long as 60 days. Oviposition also occurred in the pleural cavity.

Angiostrongylus↗
PubMed1980

Prevalence of Toxoplasma gondii antibodies in the Chinese population of Hong Kong.

Sera from 2,499 randomly selected Chinese inhabitants of Hong Kong were tested for the presence of Toxoplasma gondii antibodies using the indirect fluorescent antibody test. The over-all prevalence was 9.8%. The prevalence was significantly higher in the 10 to 19 and 30 to 39 year age group and the highest level of titres was found in the 20 to 29 group. There was no significant difference in prevalence between the male and female population and between the rural and city dwellers. The distinctly low prevalence of toxoplasmosis in Hong Kong can probably be attributed to the absence of cats in most domestic households and the preference of the people to eat well-cooked meat (commonly beef and pork).

Adolescent↗
PubMed1979

Changes in worm burden, haematological and serological response in rats after single and multiple Angiostrongylus cantonensis infections.

Thirteen groups of rats were first sensitized with single or double doses of 5--30 third-stage larvae of Angiostrongylus cantonensis, followed by a challenge infection with 100 larvae at various periods after the primary infection. Seven other groups of rats receiving only the sensitizing infection served as the controls. In all the sensitized rats, a significantly (p less than 0.05) smaller mean number of adult worms was found established in the challenge infection as compared to the control. The frequency of the sensitizing dose and timing of the challenge infection appeared to influence the intensity of the host's response. There was no conclusive evidence to indicate that the immune response could retard the growth, development, or sex ratios of the worms established in subsequent infections. A positive haemagglutinating antibody response was first observed in some rats as early as four weeks post-infection with 100 larvae when the worms began migrating from the brain to the lungs. The antibody response and eosinophilia were most pronounced during the oviposition of the female worms and hatching of first-stage-larvae. Changes in white blood cell, lymphocyte, and neutrophil counts were also followed in some groups.

Animals↗
PubMed1979

De novo purine ribonucleotide biosynthesis in adult Angiostrongylus cantonensis (Nematoda: Metastrongyloidea).

1. Radioactivity was found to be associated with purine ribonucleotides in extracts of gravid adult Angiostrongylus cantonensis from the lungs of rats when the parasite was incubated in a medium containing [14C]glycine. 2. The rate of incorporation was at least 0.2 pmole/min per mg of parasite and approximately equal amounts of adenine and guanine ribonucleotides were synthesized. 3. This is the first demonstration of the capacity for a mammalian parasitic helminth to synthesize purines de novo.

Adenine↗
PubMed1979

Host-parasite relationship of Angiostrongylus cantonensis. 1. Intracranial transplantation into various hosts.

Various stages of Angiostrongylus cantonensis recovered from the brain of experimentally infected mice were transplanted intracranially into rats. Third and fourth-stage worms recovered 2--7 days postinfection were able to develop normally after transplantation into recipient rats. The fifth-stage worm obtained 14--15 days postinfection would enter the brain tissue of rats but died shortly afterwards. However, the same stage of worms recovered from rats, after a similar transplantation, were found to develop normally in the recipient animal. Young fifth-stage worms, from the subarachnoid space of rats, which were ready for the pulmonary migration were also transplanted into rabbits but the worms failed to reach the lungs. In the control rat-to-rat transplantation, the worms successfully completed the pulmonary migration. The morphogenesis and initial growth rate of A. cantonensis were similar in both mice and rats but in the former host the worms started to grow at a markedly slower rate after the last moult and gradually degenerated.

Animals↗