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Biomedical subjects

P F Lai

Publications and source records attributed to P F Lai.

12 recordsLinked to original sources
PubMed2003

Urethritis in men at the Genito-Urinary Medicine Clinic Kuala Lumpur Hospital.

The clinical features and aetiology of 100 consecutive symptomatic heterosexual male patients with urethritis were studied from March 1994 to August 1994 in the Genito-Urinary Medicine (GUM) Clinic, Kuala Lumpur Hospital. Gonococcal urethritis (GU) was found to be more common (53%) than non-gonococcal urethritis(47%). All patients with GU confirmed microbiologically had clinically evident urethral discharge. Almost half (41%) of the patients with GU developed post-gonococcal urethritis (PGU). The most common organism isolated in PGU was Ureaplasma urealyticum (37%) whilst only 4% had both Chlamydia trachomatis and Ureaplasma urealyticum. Of the 47% of patients with non-gonococcal urethritis (NGU), 50% had no microorganism isolated, 32% had Ureaplasma urealyticum, 7% Chlamydia trachomatis and 11% both Chlamydia trachomatis and Ureaplasma urealyticum.

Adult↗
PubMed2001

Negative staining permits 4.0 A resolution with low-dose electron diffraction of catalase crystals.

Low-dose electron diffraction of thin single crystals of catalase that are negatively stained with the light-atom compound, dipotassium glucose-1,6-diphosphate, reveals Bragg reflections extending to 4.0A (= 0.40 nm). Under the same conditions, negative staining with the traditional heavy-metal salt, ammonium molybdate, also gives diffraction spots extending to 4.0 A. These results establish that negative staining of protein crystals preserves periodic structural information into the high-resolution range, unlike the widely accepted current belief that this methodology can give a resolution limited to only 20-25 A.

Catalase↗
PubMed2000

Molecular phylogeographic studies on Paragonimus westermani in Asia.

The lung fluke, Paragonimus westermani (Kerbert, 1878), is widely distributed in Asia, and exhibits much variation in its biological properties. Previous phylogenetic studies using DNA sequences have demonstrated that samples from north-east Asia form a tight group distinct from samples from south Asia (Philippines, Thailand, Malaysia). Among countries from the latter region, considerable molecular diversity was observed. This was investigated further using additional DNA sequences (partial mitochondrial cytochrome c oxidase subunit 1 (COI) and the second internal transcribed spacer of the nuclear ribosomal gene repeat (ITS2)) from additional samples of P. westermani. Phylogenies inferred from these again found three or four groups within P. westermani, depending on the method of analysis. Populations of P. westermani from north-east Asia use snail hosts of the family Pleuroceridae and differ in other biological properties from populations in south Asia (that use snail hosts of the family Thiaridae). It is considered that the populations we sampled can be divided into two species, one in north-east Asia and the other in south Asia.

Animals↗
PubMed1996

The spectrum of cavernous sinus and orbital venous thrombosis: a case and a review.

Orbital venous pathologies encompass a broad range of entities including tumors, shunts, congenital anomalies, aneurysms, and obstructive lesions. Patients may present with a variety of clinical findings which may include a combination of tumefaction, vascular engorgement, orbital pulsation, and exophthalmos, depending on the relationship between the lesion and the vascular system. Clinical findings may be unreliable in excluding serious underlying disorders, and so an extensive clinical and radiologic evaluation is necessary. This article presents a rare case of spontaneous aseptic cavernous sinus-superior ophthalmic vein thrombosis in a woman on hormone replacement therapy, and illustrates the multidisciplinary approach in diagnosis and management. The literature on issues surrounding this case is reviewed.

Case Reports↗
PubMed1996

Serological evidence of schistosomiasis in the Malaysian police field force.

A total of 1131 Police Field Force personnel were screened serologically for schistosomiasis in Malaysia. A total of 150 (13.3%) were tested positive or borderline. Stool samples from 75 of these cases were however all negative for schistosome eggs. This survey suggests that Police Field Force personnel may be agents for propagating the schistosome life cycle in Malaysia.

Animals↗
PubMed1995

Effects of mutations in cAMP-dependent protein kinase on chloride efflux in Caco-2 human colonic carcinoma cells.

In order to evaluate the importance of cAMP and cAMP-dependent protein kinase (cAMPdPK) in the regulation of chloride efflux via the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel, Caco-2, human colonic carcinoma cells were transfected with an expression vector encoding a mutant form of regulatory subunit of cAMPdPK under control of the mouse metallothionein 1 promoter. Four stable transformants were isolated that expressed the mutant subunit in a Zn(2+)-inducible manner and exhibited Zn(2+)-inducible inhibition of cAMPdPK activity. The parental and transformed Caco-2 cells were examined for their abilities to regulate chloride efflux in response to various secretagogues using a radioactive iodide-efflux assay. In the transformants, induction of the protein kinase mutation with ZnSO4 markedly decreased chloride efflux in response to forskolin, the 8-(4-chlorophenylthio) analog of cAMP, vasoactive intestinal polypeptide, prostaglandin E2 and isoproterenol, whereas Zn(2+)-treated parental cells remained responsive to these secretagogues. Treatment with carbachol, calcium ionophores or phorbol ester did not acutely affect chloride efflux. Together, these studies indicate that cAMP and cAMPdPK are essential components of secretagogue-regulated chloride channel activity in the Caco-2 cell line. In whole cell patch clamp recordings, induction of the cAMPdPK mutation inhibited anionic conductances indicative of the CFTR chloride channel, whereas purified catalytic subunit of cAMPdPK, added intracellularly, reversed the inhibition. These latter results demonstrate that the CFTR chloride channels in the protein kinase-defective transformants are normal and that the protein kinase mutation specifically affects their regulation, presumably by direct phosphorylation.

Carbachol↗
PubMed1989

Malaysian schistosomiasis: description of a population at risk.

A stable population at risk of Malaysian schistosomiasis was studied. Census results indicated that approximately one-fourth of the inhabitants used a stream where Schistosoma malayensis-infected snails were present as their principal source of water for bathing, drinking, and household tasks. The general population also contacted this stream when fording it or while fishing. Serological surveys using enzyme-linked immunosorbent assay (ELISA) and the circumoval precipitin (COP) test revealed six (9%) and three (4%) positives, respectively, among 67 persons examined. No schistosome ova were found in a general survey of 56 persons which included five ELISA positive and two COP test positive patients. ELISA and COP test prevalences among those dependent on the foci of transmission for water, 13 and 7% respectively, were only slightly higher than prevalences among the remainder of the population, 8 and 4% respectively. These results indicate that even among a stable population at risk of Malaysian schistosomiasis the prevalence is low. Our findings support the hypothesis that S. malayensis is a zoonotic infection in man and that it is unlikely to become a significant public health problem.

Adolescent↗
PubMed1975

Experimental infection of Rattus sabanus and Rattus muelleri with subperiodic Brugia malayi.

R. sabanus and R. muelleri are very common in the lowland forests of Malaysia. In nature they are infected with Breinlia sp. and D. ramachandrani. In an attempt to determine whether they are also susceptible to subperiodic B. malayi and thereby being potential reservoirs of infection of the disease, 24 R. muelleri and 17 R. sabanus were experimentally infected with the parasite. Results show that although they can support the full development of the parasite, they are poor hosts. This confirms the observation that in Malaysia natural infection of Rattus spp. with the parasite has not been seen. These rats therefore are probably not important in the zoonotic transmission of subperiodic B. malayi in Malaysia.

Animals↗