JW Mak | International Medical University (original) (raw)

Papers by JW Mak

The dynamics ofthe transmission of subperiodic Brugia malayi in a typical endemic area in Malaysi... more The dynamics ofthe transmission of subperiodic Brugia malayi in a typical endemic area in Malaysia was studied over a period of 4 years. Mass chemotherapeutic control with diethylcarbamazine citrate was found to be inefficient, new cases being detected even after the fifth treatment cycle of 6 mg/kg x 6 days per cycle. This is in marked contrast to the situation in periodic B. malayi areas where mass treatment efficiently controlled the infection. The disparity in results in these two areas is attributed to zoonotic transmission of subperiodic B. malayi from non-human primates where a mean infection rate of 76.39r was found.

Southeast Asian Journal of Tropical Medicine and Public Health, 1981

Nasopharyngeal carcinoma (NPC) is a type of epithelial neoplasms arising from the nasopharynx. Th... more Nasopharyngeal carcinoma (NPC) is a type of epithelial neoplasms arising from the nasopharynx. The disease is frequently encountered in southern China, Taiwan and Hong Kong. Algae are known to be a potential source of bioactive compounds with antiproliferative activity on cancer cells. The objective of this study was to screen extracts of microalgae from the University of Malaya Algae Culture Collection (UMACC) for antiproliferative activity against NPC cell lines. Solvent and aqueous extracts of 19 microalgae from the UMACC were screened for antiproliferative activity on four NPC cell lines, namely CNE1, HONE1, TWO1 and TWO4. The methanol extracts from two microalgae, namely Ankistrodesmus convolutus UMACC 101 and Synechococcus elongatus UMACC 105 showed antiproliferative activity on the NPC cell lines, with IC50 values ranging from 95.7 to 98.0ptg/mL. The methanol extract from Synechococcus elongatus was subjected to fractionation by column and thin layer chromatography (TLC) using a combination of hexane and acetone at different ratios. Fraction 7' obtained from the pooled eluents of 6:4, 5:5, 4:5 and 3:7 hexane-acetone was the most active, with IC50 values of 10.2 and 4.8 ptg/mL on CNE1 and TWO4 cells respectively. The cytotoxic effect of Fraction 7'was evident against CNE1 and TWO4 cells after 24 and 48h respectively at 30.0 ptg/mL. The mechanism of action of Fraction 7' could be through induction of apoptosis as indicated by the increased percentage of cells in the Sub-GO phase in cell cycle analysis by flow cytometry. The active compound in Fraction 7' could be a derivative product of chlorophyll a, as indicated by the blackish green spot after separation by TLC. Further studies are warranted to elucidate the structure of the active principle in Fraction 7'.

Annals of Tropical Medicine & Parasitology, 1986

Field observations were made on Coquillettidia crassipes during a study of Mansonia in a swamp fo... more Field observations were made on Coquillettidia crassipes during a study of Mansonia in a swamp forest ecotype in Tanjong Karang. There was an increase in abundance in July consistent with the increase in abundance of Mansonia and an increase in rainfall. The biting cycle showed a dramatic early peak during the period 1900-2000 hours. The probability of daily survival through one day for the first three gonotrophic cycles was 0•770, 0•722 and 0•759. Two of the 54 Cq. crassipes dissected were infective, with two and 25 L3 larvae of Brugia. Both subperiodic B. malayi and B. pahangi developed into L3 larvae in laboratory bred Cq. crassipes. The index of experimental infection was higher for B. pahangi. Mansonia bonneae and Ma. uniformis showed higher indices of experimental infection than Cq. crassipes for subperiodic B. malayi. It is concluded that in an endemic area with a high density of Cq. crassipes it could act as a secondary vector ofBrugian filariasis.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 1980

Seventy-eight microfilaraemic patients with Wuchereria bancrofti and Brugia malayi infections wer... more Seventy-eight microfilaraemic patients with Wuchereria bancrofti and Brugia malayi infections were treated with various oral levamisole hydrochloride total dosage regimes of 150 to 3,150 mg and total diethvlcarbamazine citrate (DE0 of 36 _.._~. s and 126 mg per kg bodyweight. Sign&cant'microtiicidal and probable macrofilaricidal effects were seen at total levamisole hydrochloride dosages of 300 to 3,150 mg and the DEC dosages. The ootimum dosage regime with levamisole hydrochoride recommended for treatment of microfilaraemic natients is 100 mg; initiallv followed bv 100 mg twi'ce daily for 10 da@. This hosage regime was as effective as a total oral dosage of DEC at 126 mg per kg bodyweight. Side reactions were dose-dependent, mild and transient, with fever being the most common. One patient developed fits after 150 mg levemisole hydrochloride. The pathophysiology of these side reactions is discussed and it is recommended that levamisole hydrochloride, as a probable alternative for the treatment of patent and occult filariasis, should be used only under close medical supervision.

The American Journal of Tropical Medicine and Hygiene, 1993

A clinical trial on the efficacy of a single oral dose of ivermectin at 20, 50, 100, and 200 micr... more A clinical trial on the efficacy of a single oral dose of ivermectin at 20, 50, 100, and 200 micrograms/kg was carried out in 40 subjects with subperiodic Brugia malayi microfilaremia. There was no significant difference in the clearance of microfilaremia in the four treatment groups, and the lowest geometric mean microfilarial count (GMC) achieved in the 40 subjects was 8.8/ml or 8.3% of the initial count (106.1/ml), at two weeks post-treatment. The GMC started to increase at one month post-treatment and by six months was 22.2% of the initial GMC. Only 27.5%, 23.1%, 15.0%, and 18.9% of subjects were amicrofilaremic at two, four, 12, and 24 weeks post-treatment, respectively. Mild fever in 35% of the subjects was the primary side reaction and was more common in those with microfilarial counts > or = 500/ml (85.7%) than in those with counts < 500/ml (32%). The clearance of B. malayi microfilaremia by ivermectin was less rapid than that reported for Wuchereria bancrofti. The smaller number of side reactions encountered in the present study compared with those reported for bancroftian filariasis is probably related to the lower microfilarial density in the present subjects. Since ivermectin at a single oral dose of 20-200 micrograms/kg can reduce the GMC to less than 10% at two weeks and maintain it below 25% of the initial level even at six months post-treatment, it is recommended that the drug be seriously evaluated for use in the control of brugian filariasis.

The American Journal of Tropical Medicine and Hygiene, 1988

Mass drug administration via 3 modes of delivery reduced the incidence and prevalence rates and i... more Mass drug administration via 3 modes of delivery reduced the incidence and prevalence rates and intensity of Brugia malayi infection in 3 rural villages in the Bengkoka Peninsula, Sabah, in 1982-1983. A dosage of 6 mg diethylcarbamazine citrate (DEC-C)/kg body weight was administered either daily or weekly (total of 6 doses, 36 mg/kg body weight), and impact on B. malayi cases were comparable in the 3 villages. A total of 384 people participated in the DEC-C regimens, and all pregnant women and children under 2 years were excluded from the study. Bekessy&amp;#39;s method of estimation of incidence and recovery rates was applied to data on B. malayi microfilaremia before drug administration. Treatment with DEC-C by any of the 3 modes of delivery drastically reduced the number of episodes of patent microfilaremia, incidence and prevalence, and median microfilarial density. Reduction was sustained for at least 18 to 24 months after treatment.

Annales de Parasitologie Humaine et Comparée, 1988

Comparaison de souches périodiques humaines de Brugia malayi, provenant d'Inde, Chine, Corée, Mal... more Comparaison de souches périodiques humaines de Brugia malayi, provenant d'Inde, Chine, Corée, Malaisie et Indonésie, par l'analyse morphologique des mâles. Les caractères clas siques (oesophage, papilles, spicules, etc.) sont semblables d'une région à l'autre. Par contre l'ornementation cuticulaire de la région postérieure du corps, formée par l'area rugosa et par un système de perles, réalise un appareil d'accouplement « antidérapant » qui montre des différences selon l'origine géographique. Une clé dichotomique basée sur ce caractère est proposée.

Acta tropica, Jan 21, 2015

Human toxocariasis which is caused mainly by the larvae of Toxocara canis and Toxocara cati, is a... more Human toxocariasis which is caused mainly by the larvae of Toxocara canis and Toxocara cati, is a worldwide zoonotic disease that can be a potentially serious human infection. The enzyme-linked immunosorbent assay (ELISA) using T. canis excretory-secretory (TES) antigens harvested from T. canis larvae is currently the serological test for confirming toxocariasis. An alternative to producing large amounts of Toxocara TES and improved diagnosis for toxocariasis is through the development of highly specific recombinant antigens such as the T. canis second stage larva excretory-secretory 30kDa protein (recTES-30). The aim of this study was to evaluate the sensitivity and specificity of a rapid diagnostic kit (RDT, named as iToxocara kit) in comparison to recTES-30 ELISA in Serendah Orang Asli village in Selangor, Malaysia. A total of 133 subjects were included in the study. The overall prevalence rates by ELISA and RDT were 29.3% and 33.1% respectively, with more positive cases detected...

The Southeast Asian journal of tropical medicine and public health, 1998

The Southeast Asian journal of tropical medicine and public health, 1996

The Aborigines or Orang Asli in Peninsular Malaysia who are still seminomadic are known to have a... more The Aborigines or Orang Asli in Peninsular Malaysia who are still seminomadic are known to have a close association with dogs. In this study, enzyme-linked immunosorbent assay (ELISA) was used to detect anti-Sarcoptes scabiei var canis antibodies in this community as a measure of exposure to the mite. Out of 312 Orang Asli tested, 24.7% were positive for polyvalent anti-Sarcoptes antibodies. No significant difference was found between the positive rates in males (26.1%) and females (23.6%). Only 1.9% were positive for IgA and none was positive for IgE anti-Sarcoptes antibodies. Since there were very few patients with clinical manifestation of scabies, there is a possibility that continuous exposure to the dogs mite confers cross-protective immunity in the community against human scabies.

The Southeast Asian journal of tropical medicine and public health, 1993

IMSEAR Digital Repository, ...

The Southeast Asian journal of tropical medicine and public health, 1980

Comparative studies of vector efficiency were done with the Liverpool and Malaysian strains of Ae... more Comparative studies of vector efficiency were done with the Liverpool and Malaysian strains of Aedes (Finlaya) togoi for subperiodic Brugia malayi and Brugia pahangi. The Malaysian strain of A. togoi was found to take in fewer microfilariae under the same experimental conditions than the Liverpool strain. Also, for various microfilarial densities in the host's peripheral blood, the Malaysian strain had less mean infective larvae per fed mosquito than the Liverpool strain. The microfilarial intake of A. togoi was not affected by the site of feeding on the host affected by the site of feeding on the host. Most of the mosquitoes took in fewer microfilariae than expected. It is concluded from these studies that the Malaysian strain of A. togoi is a susceptible and reasonably good vector for subperiodic B. malayi and B. pahangi. Further field studies should be carried out to determine its importance as a natural vector of Brugian filariasis.

The Southeast Asian journal of tropical medicine and public health, 1983

The Southeast Asian journal of tropical medicine and public health, 1984

A total of 37 species of mosquitoes from seven genera were collected in six villages in the Bengk... more A total of 37 species of mosquitoes from seven genera were collected in six villages in the Bengkoka Peninsula, Sabah State, during two visits in 1981 in connection with studies on malaria and filariasis. Fifty-five per cent of the total mosquitoes collected were Mansonia. An. collessi constituted a new record of the species from Sabah. An. balabacensis was found to be naturally infected with sporozoites. Ma. bonneae was found to be naturally infected with Brugia, probably B. malayi. Parous rates of An. balabacensis and Ma. bonneae were very high with consequent high probability of survival ideally suiting transmission of malaria and filariasis.

The Southeast Asian journal of tropical medicine and public health, 1981

The Southeast Asian journal of tropical medicine and public health, 1985

Toxoplasmosis was found not to be an important cause of intrauterine infection in Malaysia as the... more Toxoplasmosis was found not to be an important cause of intrauterine infection in Malaysia as the rate of toxoplasma-specific IgM in 1,060 congenitally defective Malaysian children, 0 to 4 months old (0.4%) was lower than that in 405 normal children of the same age group (2.0%). A total of 8.2 intra-uterine toxoplasmic infections per 1,000 live births was detected of which one-third (2.7 per 1,000 live births) was overt, manifesting symptoms more of liver damage, than eye or brain damage. A comparison was made with the rates in U.S.A. and Europe. The role of toxoplasmosis in abortion needs to be studied.

The Southeast Asian journal of tropical medicine and public health, 1992

In spite of more than 30 years of control activities, malaria continues to be the most important ... more In spite of more than 30 years of control activities, malaria continues to be the most important parasitic infection in Malaysia, accounting for 39,189 confirmed cases in 1991, giving an annual parasite incidence rate of 2.2 per 1,000 population. Some factors contributing to the continued transmission of malaria are the development of drug resistant Plasmodium falciparum, changes in vector behavior, and ecological changes due to socio-economic reasons. Malaria parasite rates are higher among the Aborigines, land scheme settlers and those in intimate contact with the jungle, like loggers. There has been no substantial change in the proportion of the three common malaria species responsible for infections, P. falciparum, P. vivax, P. malariae and mixed infections accounting for about 70%, 28%, 1% and 1%, respectively of all infections. Drug resistant P. falciparum is unevenly distributed in Malaysia, but based on clinical experience and in vitro drug sensitivity studies, chloroquine r...

The Southeast Asian journal of tropical medicine and public health, 1991

Thirty in vitro serial passages of Toxoplasman gondii cultures in Vero cell line performed once i... more 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.