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Biomedical subjects

R K Chan

Publications and source records attributed to R K Chan.

At least 55 records · Page 3Linked to original sources
PubMed1995

PCR as a confirmatory test for human immunodeficiency virus type 1 infection in individuals with indeterminate western blot (immunoblot) profiles.

A combination of two PCR systems which amplify human immunodeficiency virus type 1 (HIV-1) gag and pol DNA was used to elucidate the HIV-1 infection status of a group of individuals screening positive for anti-HIV but having indeterminate Western blot (immunoblot) profiles. The results obtained suggest PCR could be used to resolve such cases.

Blotting, Western↗
PubMed1995

Prevalence of sexually transmitted diseases among commercial sex workers in Singapore from 1977 to 1993: the effects of screening measures.

This paper discusses the trend of sexually transmitted diseases (STDs) among commercial sex workers in Singapore. Various STD control measures were introduced in Singapore since 1976 to control STDs among commercial sex workers. Under a Medical Surveillance Scheme introduced in 1976, all commercial sex workers were encouraged to undergo regular STD screening and received treatment when found to be infected. As a result, the infection rates of various STDs among commercial sex workers have declined over the years. The infection rate for gonorrhoea has declined from 9% in 1977 to 1.7% in 1993. The chlamydia infection rate declined from 8% in 1992 to 4% in 1993. The human immunodeficiency virus (HIV) infection rate among commercial sex workers under the Medical Scheme was less than 0.1%. The STD infection rate of commercial sex workers who did not participate in the Medical Scheme was much higher than those enrolled in the Medical Scheme. Our findings indicated the effectiveness of the Medical Scheme in controlling STDs among commercial sex workers.

Chlamydia Infections↗
PubMed1995

Comparing the efficacy of pefloxacin and ciprofloxacin in the treatment of acute uncomplicated gonococcal urethritis in males.

The aim of this study was to compare the efficacy of single-dose pefloxacin 400 mg and ciprofloxacin 250 mg in the treatment of acute uncomplicated gonococcal urethritis in males. One hundred and twenty male patients with uncomplicated gonococcal urethritis were assigned alternately to receive single oral doses of either pefloxacin 400 mg or ciprofloxacin 250 mg. Forty-one out of 43 patients (95.3%) of the pefloxacin group and 46 of 47 (97.9%) of the ciprofloxacin group were cured of gonorrhoeae. The rates of post-gonococcal urethritis were 57.7% and 53.3% in the pefloxacin and ciprofloxacin groups respectively. There was a high incidence of penicillinase-producing gonococci (34.2%). High level resistance to pefloxacin (minimum inhibitory concentration [MIC] >1.0 mg/l) resulting in clinical failure on 400 mg stat dose was noted in 1 isolate. It also showed decreased susceptibility to ciprofloxacin (MIC 0.25 mg/l). Another isolate showed high-level resistance (MIC 0.06 mg/l) to ciprofloxacin 250 mg stat dose with concomitant decreased susceptibility to pefloxacin (MIC >1.0 mg/l). Ciprofloxacin 250 mg stat dose is still useful for the treatment of uncomplicated gonococcal urethritis in males. The cure rate of 95.3% with pefloxacin at 400 mg stat dose is acceptable, but needs to be monitored with caution. The emergence of a more resistant strain of Neisseria gonorrhoeae to fluoroquinolones calls for vigilance in the monitoring of antimicrobial susceptibility.

Acute Disease↗
PubMed1995

Dual therapy with doxycycline and ketoprofen compared to doxycycline in the treatment of uncomplicated non-gonococcal urethritis.

The aim of this study was to compare a combination of doxycyline and ketoprofen, and doxycycline alone in treating non-gonococcal urethritis (NGU), with particular emphasis on reducing recurrent or persistent disease. Sixty-five men with first episode acute NGU were enrolled between November 1992 and November 1994. The men were randomly assigned to either the doxycycline plus ketoprofen group, group A (doxycycline 100 mg twice daily for 10 days plus ketoprofen 200 mg daily for 10 days, n = 34), or the doxycycline group, group B (100 mg twice daily for 10 days, n = 31). Out of the 65 patients studied, Chlamydia trachomatis was isolated from 9 patients (13.8%), Ureaplasma urealyticum from 6 patients (9.2%) and Mycoplasma hominis from 2 patients (3.1%). At 6 weeks in group A, 16 patients (47%) were cured, one patient had a recurrence (2.9%), and 4 patients had persistent infection (11.8%). Eleven patients defaulted follow-up (32.4%) and 2 patients were dropped from the trial. In contrast, for group B, 13 patients (42%) were cured, 5 patients (16%) had a recurrence, 2 patients (6.5%) had persistent infection and 3 patients (9.7%) were reinfected. Eight patients (25.8%) defaulted follow-up. At 12 weeks, for group A, 14 patients (41.2%) remained cured, one patient (2.9%) had a recurrence, 4 patients (11.8%) had persistent infection and one patient (2.9%) was reinfected. Twelve patients (35.3%) defaulted follow-up. For group B, 8 patients (25.8%) remained cured, 6 patients (19.4%) had recurrence, 2 patients (6.5%) had persistent infection and 5 patients (16.1%) were reinfected. Ten patients (32.2%) defaulted follow-up. There were no statistically significant differences between the two groups except for patients with recurrent NGU where the difference (1 versus 6 patients) was statistically significant (P = 0.019).

Anti-Bacterial Agents↗
PubMed1995

A comparative study of the Abbott and Murex enzyme immunoassay, and cell culture in the detection of cervical chlamydial infection in female sex workers in Singapore.

Endocervical smears from 200 female sex workers were tested for Chlamydia trachomatis infection using the Abbott and Murex enzyme immunoassay (EIA) kits and the standard cell culture technique to compare the performance of these tests. The Abbott test had a sensitivity, specificity, predictive value of a positive result (PVP) and predictive value of a negative result (PVN) of 83.3%, 97.8%, 78.9% and 98.3% respectively. The corresponding figures for the Murex system were 77.8%, 98.4%, 82.4% and 97.8%; and of the standard culture test were 55.6%, 100% and 95.8%. EIA tests were more sensitive but slightly less specific than cell culture in the detection of Chlamydia trachomatis cervical infection in female sex workers in Singapore.

Bacteriological Techniques↗
PubMed1995

Human immunodeficiency virus (HIV) antigen testing to detect HIV infection in female sex workers in Singapore.

Human immunodeficiency virus (HIV) infection is characterised by seroconversion after a ¿window¿ period of 2 to 3 months. After this period antibodies are usually detectable by screening tests (enzyme immunoassay or particle agglutination) confirmed by Western blot analysis. We studied 1000 newly enrolled female sex workers who had not been previously tested for HIV to assess the usefulness of HIV antigen testing to improve the efficacy of HIV infection detection. Blood was taken at enrollment for HIV antigen and HIV antibody testing. The Abbott HIVAG-1 test was used to detect antigen; antibody detection was by the Abbott recombinant HIV-1/HIV-2 3rd generation enzyme immunoassay (EIA) test, the Fujirebio Serodia-HIV particle agglutination (PA) test for screening, and the Diagnostic Biotechnology HIV Blot 2.2 Western blot (WB) test for antibody confirmation. Of the 1000 samples, 26 were positive for HIV antibody testing (26/26 for EIA, 25/25 for PA, 26/26 for WB), giving a prevalence rate of 2.6%, Of these 26 seropositive samples 1 was positive on HIV antigen testing. There were no samples which were antigen-positive and antibody-negative. HIV antigen testing does not add to increased efficacy of HIV detection among female sex workers in Singapore.

Blotting, Western↗
PubMed1995

Correlation between saliva and serum for human immunodeficiency virus 1 and 2 antibodies using a rapid test system.

Currently, human immunodeficiency virus (HIV) tests are almost totally serum based. In situations where blood is difficult or inconvenient to obtain, a substitute to venepuncture offers an attractive alternative. The prototype OraScreen saliva dipsticks were tested on 278 samples comprising 100 normals, 100 samples from persons attending a sexually transmitted disease clinic and 78 samples from persons confirmed to have HIV. The specificity and the sensitivity of the diagnostic test for saliva was 99.5% and 94.7% respectively, when compared to a routine solid-phase enzyme-linked immunosorbent assay (ELISA) test on serum samples and Western blot test when indicated. The prototype OraScreen dipstick test shows potential for saliva testing in situations where it would be inconvenient to use blood. Further evaluation of saliva testing is warranted on a large sample population with a low prevalence of HIV infection.

Adult↗
PubMed1995

Project youth inform--a school-based sexually transmitted disease/acquired immune deficiency syndrome education programme.

A pilot project, ¿Youth Inform¿ endorsed by the Ministry of Health and Ministry of Education, Singapore, was undertaken in 1992 for 2 years. It aims to enhance sexually transmitted disease (STDs)/human immunodeficiency virus (HIV) control in Singapore by providing structured information for young people between the ages of 16 to 20 years in Polytechnics, Junior Colleges, Centralised Institutes and Pre-University Centres. Project Youth Inform comprises 8 components. They include a focus group discussion, a training seminar for teachers, a lecture/slide presentation cum question-and-answer session, an educational booklet/bookmark, exhibitions, a video, provisions for anonymous questions, and an evaluation. The programme is conducted during school hours at the premises of the institutions and the attendance per session is between 150 to 350 students. A total of 152 sessions have been completed for all the schools. It is ongoing and is currently administered by the School Health Service and Training and Health Education Department. Feedback from principals, teachers and students was gathered formally through surveys and informally through interviews and observations. One thousand students were randomly selected for the survey to assess their responses towards the programme. Eighty-six percent reported that they found it educational and informative. Indicators found to have an influence on the effectiveness of the programme were timing, vocabulary used (medical terms) and integration of the programme into the school's curriculum. In conclusion, Project Youth Inform was on the whole positively received. However, it is essential to constantly accommodate and adapt to new facts and methods of teaching and maintain close coordination with the Ministries and the schools. An effective STD/acquired immune deficiency syndrome programme is an important step towards the prevention, management and control of the epidemic.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Antimicrobial therapy of non-viral sexually transmitted diseases--an update.

Azithromycin is an azalide antibiotic with important properties which allow it to be used as a single-dose treatment for genital Chlamydia trachomatic infections. A single 1 g dose is as effective as a standard seven-day course of doxycycline. Ofloxacin 400 mg bid for seven days is also effective against Chlamydia trachomatis. Both azithromycin 2 g and ofloxacin are also effective against uncomplicated gonorrhoea. Neisseria gonorrhoeae continues to be sensitive to third generation cephalosporins, e.g. ceftriaxone 125 mg. Oral single dose cephalosporins offer ease of administration and safety, e.g. cefixime (400 mg), cefuroxime axetil (1 g) and cefpodoxime proxetil (200 mg). The fluoroquinolones, e.g. ciprofloxacin (500 mg) and ofloxacin (400 mg), are being increasingly used as first-line medications, however, caution is recommended as the development of resistance is anticipated and already being detected in many areas. Syphilis continues to be sensitive to penicillin. This should be administered parenterally. Coexistent human immunodeficiency virus infection may make standard therapy inadequate, and closer follow-up is recommended. Therapy with non-penicillin antibiotics is still inadequately studied. Chancroid is treated with ceftriaxone, ciprofloxacin, azithromycin, or erythromycin. In some areas, resistance to tetracyclines and TMP-SMX has made these drugs ineffective as first-line treatments. Bacterial vaginosis is effectively treated with a single dose of metronidazole 1 g or 500 mg bid over seven days. Similar regimens are also effective against trichomoniasis. Vulvovaginal candidiasis can be treated with topical imidazole preparations or oral antifungal medications.

Chancroid↗
PubMed1994

Spatially and temporally differentiated patterns of c-fos expression in brainstem catecholaminergic cell groups induced by cardiovascular challenges in the rat.

Brainstem catecholaminergic neurons have been implicated as mediating adaptive autonomic and neuroendocrine responses to cardiovascular challenges. To clarify the nature of this involvement, immuno- and hybridization histochemical methods were used to follow c-fos expression in these neurons in response to acute stimuli that differentially affect blood pressure and volume. From low basal levels, hypotensive hemorrhage (15%) provoked a progressive increase in the number and distribution of Fos-immunoreactive (ir) nuclei in the nucleus of the solitary tract (NTS), the A1 and C1 cell groups of the ventrolateral medulla, and in the pontine A5, locus coeruleus, and lateral parabrachial cell groups peaking at 2.0-2.5 hours after the challenge. Fos-ir ventrolateral medullary neurons, subsets of which were identified as projecting to the paraventricular hypothalamic nucleus or spinal cord, were predominantly aminergic, whereas most of those in the NTS were not. Infusion of an angiotensin II antagonist blunted hemorrhage-induced Fos expression in the area postrema, and attenuated that seen elsewhere in the medulla and pons. Nitroprusside-induced isovolemic hypotension yielded a pattern of c-fos induction similar to that seen following hemorrhage, except in the area postrema and the A1 cell group, where the response was muted or lacking. Phenylephrine-induced hypertension stimulated a restricted pattern of c-fos expression, largely limited to induced hypertension stimulated a restricted pattern of c-fos expression, largely limited to non-aminergic neurons, whose distribution in the NTS conformed to the termination patterns of primary baroreceptor afferents, and in the ventrolateral medulla overlapped in part with those of vagal cardiomotor and depressor neurons. These findings underscore the importance of brainstem catecholaminergic neurons in effecting integrated homeostatic responses to cardiovascular challenges and their ability to responding strategically to specific modalities of cardiovascular information. They also foster testable predictions as to effector neuron populations that might be recruited to respond to perturbations in individual circulatory parameters.

Angiotensin II↗
PubMed1994

Molecular cloning of differentially expressed genes in human epithelial ovarian cancer.

A DNA-fingerprinting approach has been adapted to detect differentially expressed genes in human ovarian carcinoma. This method is based on the use of arbitrary primers to generate fingerprints from total RNA isolated from normal ovarian epithelial cells and ovarian carcinoma cells by polymerase chain reaction (PCR). Using this method, we cloned two cDNA fragments (DOC-1 and DOC-2) which were present in normal ovarian surface epithelial cells but consistently absent in all of the ovarian cancer cell lines from the differential display. In addition, we also identified a cDNA fragment (LF4.0) which is overexpressed in most of the tumor cell lines and tumor tissues in comparison to the normal ovarian surface epithelial cells. The differential expression of the genes in the tumor cell lines as well as in the tumor tissues was also confirmed by Northern analysis. The clone DOC-2, which is a 800-bp cDNA fragment, has one open reading frame suggesting that the gene may be translated. Assuming that this frame is the sense strand, we generated both sense and antisense riboprobe for in situ mRNA hybridization. Only the antisense DOC-2 riboprobe revealed a hybridization signal which was restricted to the human surface ovarian epithelium. The potential functional roles of these genes is now under investigation.

Base Sequence↗
PubMed1994

Effects of [Sar1, Ile8]-angiotensin II on rostral ventrolateral medulla neurons and blood pressure in spontaneously hypertensive rats.

The present study was an attempt to determine the influence of brain angiotensin II, the activity of which is known to be higher in spontaneously hypertensive rat, on the spontaneous activity of the cardiovascular neurons in the rostral ventrolateral medulla of the spontaneously hypertensive rat. Both the spontaneous activity of the spinal projecting rostral ventrolateral medulla cardiovascular neurons and the arterial blood pressure were simultaneously measured in the pentobarbital-anesthetized spontaneously hypertensive rat and its normotensive control, the Wistar Kyoto rat, following microinjection to rostral ventrolateral medulla of an angiotensin II antagonist, [Sar1, Ile8]-angiotensin II (sarile). A microinjection method was developed that enabled us to perform extracellular recording of the rostral ventrolateral medulla cardiovascular neurons during the microinjection of drug to the vicinity of the neuron. It was found that sarile reduced both the arterial blood pressure and firing rate of some rostral ventrolateral medulla cardiovascular neurons dose-dependently. The effects of sarile were significantly greater in spontaneously hypertensive rat than in the Wistar Kyoto rat. The present findings indicate that the rostral ventrolateral medulla cardiovascular neurons of spontaneously hypertensive rat exhibit an augmented sensitivity to endogenous brain angiotensin II. Such an increase in sensitivity to brain angiotensin II in the spontaneously hypertensive rat may contribute to the enhanced spontaneous activities of rostral ventrolateral medulla cardiovascular neurons, as in the sarile responsive single discharge units, even in the resting or prestimulation state. This interaction of brain angiotensin II and rostral ventrolateral medulla cardiovascular neurons is likely to be contributory to the genesis of hypertension in this strain of rats.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1994

Clinical implications of the morphological features of central pulmonary artery thromboemboli shown by transoesophageal echocardiography.

OBJECTIVES: To illustrate the use of transoesophageal echocardiography in the detection of the morphological features of central pulmonary artery thromboemboli and their clinical implications. DESIGN: Review of five cases of central pulmonary artery thromboemboli detected by transoesophageal echocardiography. SETTING: University teaching hospital. PATIENTS: Five patients (three men and two women) admitted under general medical units. RESULTS: Central pulmonary artery thromboemboli were detected by the use of transoesophageal echocardiography in all the patients presented. Presentations were acute, subacute, or chronic. The morphological features of the thromboemboli on transoesophageal echocardiography were used to correlate with the time course of the illness, and to guide treatment. Two patients received thrombolytic treatment, one patient was treated with anticoagulation alone, and two patients had inferior vena caval filters implanted. CONCLUSIONS: Transoesophageal echocardiography is an alternative diagnostic tool in the detection of central pulmonary artery thromboemboli. Morphological features of central pulmonary thromboemboli on echocardiography can provide useful information that may help to guide treatment.

Acute Disease↗
PubMed1994

Fatal haemoptysis in Salmonella typhimurium septicaemia--a cautionary tale.

Septicaemia and mycotic aneurysm may occur in a patient who is an enteric-carrier of Salmonella typhimurium. We report such a case of an elderly man who presented with chest pain and fatal massive haemoptysis from a likely mycotic thoracic aneurysm. This report underscores the importance of increased awareness of the disease which may allow more frequent and earlier diagnosis.

Aged↗
PubMed1993

Comparison of three dosing procedures for administration of bovine surfactant to neonates with respiratory distress syndrome.

A multicenter, randomized, double-blind, controlled trial compared three beractant (Survanta) administration procedures in the treatment of neonatal respiratory distress syndrome. Infants weighing > or = 600 gm with respiratory distress syndrome who required assisted ventilation were treated within 8 hours of birth with beractant administered intratracheally. Procedure A required administration in two fractional doses after removal of the infant from the ventilator. Procedure B required administration in two fractional doses through a neonatal suction valve and did not require removal of the infant from the ventilator, and procedure C required administration in four fractional doses during removal from the ventilator. Procedure C is the method used in all previous beractant studies. Of the 299 infants enrolled, 103 were randomly assigned to procedure A, 100 to procedure B, and 96 to procedure C. The results indicate no significant differences among the treatment groups in the clinical outcome measures of fractional inspired oxygen, mean airway pressure, and arterial-alveolar ratio of partial pressure of oxygen at 72 hours of life, or in the incidences of air leaks, pulmonary interstitial emphysema, or death through 72 hours of life. There were no significant differences in the lowest heart rates recorded during administration of doses, but there was less oxygen desaturation during administration of dose 1 with procedure B than with procedure A (p = 0.001), and more reflux of beractant after procedure B than after procedure C (p = 0.007). We conclude that the three procedures are equally effective and can be used to administer beractant safely and effectively. Procedure B has the advantage of allowing administration without interrupting mechanical ventilation.

Biological Products↗
PubMed1993

Nosocomial urinary tract infection: a microbiological study.

Nosocomial urinary tract infection (UTI) is an important cause of increased morbidity and mortality in hospitalised patients. The increasing use of broad spectrum antibiotics will result in changes in the microbiological and antibiotic sensitivity pattern of pathogens isolated from nosocomial UTI. We have endeavoured to study the bacteriological pattern of nosocomial UTI and the antibiotic sensitivity patterns of the pathogens concerned. Over a period of one year, a total of 541 patients with 656 episodes of nosocomial UTI were studied. A total of 748 organisms were isolated. The two main complicating factors in nosocomial UTI were urogenital instrumentation (70.4%) and diabetes mellitus (24.2%). Klebsiella species (spp) was the predominant organism isolated (25.0%) and was significantly associated with age and diabetes mellitus. Klebsiella spp in nosocomial UTI showed an overall increase in resistance to antibiotics and multiple antibiotic resistant strains were not uncommon. Escherichia coli was isolated in 17.7% of cases. Streptococcus faecalis was isolated in 10.6% of cases and was significantly associated with instrumentation. Pseudomonas spp was isolated in 8.6% of cases and was generally sensitive to ceftazidime and amikacin. It was associated with systemic malignancies and the use of immunosuppressants.

Adolescent↗
PubMed1993

A comparison of two immediate-early genes, c-fos and NGFI-B, as markers for functional activation in stress-related neuroendocrine circuitry.

The promoter regions of the rat corticotropin-releasing factor (CRF), oxytocin (OT), and vasopressin (AVP) genes contain sequences similar to the cis-acting response element identified for NGFI-B, an immediate-early gene structurally related to the steroid hormone receptor superfamily. Combined immuno- and hybridization histochemical approaches were used to determine whether challenges that influence the synthesis and secretion of CRF, OT, and/or AVP result in altered expression in neurosecretory neurons of NGFI-B and another immediate-early gene, c-fos, which is widely used as a marker for functionally activated neurons. NGFI-B mRNA was found to be expressed at constitutively high levels in the telencephalon, but not in the endocrine hypothalamus, of unperturbed controls; basal levels of c-fos expression were uniformly low throughout the CNS. NGFI-B and c-fos mRNAs, and Fos protein, were induced with a similar time course and in similar neuroendocrine cell types in response to acute hypotensive hemorrhage (15% reduction in blood volume), intravenous injection of interleukin-1 beta (IL-1 beta; 1.87 micrograms/kg), chronic salt loading (7 d maintenance on 2% saline), and acute bilateral adrenalectomy. c-fos mRNA and Fos protein were readily demonstrable in afferent pathways that have been implicated as mediating the neuroendocrine responses in the three stress paradigms; these include medullary catecholaminergic cell groups in response to IL-1 beta and hemorrhage, and cell groups lining the lamina terminalis in response to salt loading. Challenge-specific induction of NGFI-B expression was detectable in these extrahypothalamic cell groups, though with a lesser sensitivity than that required to reveal NGFI-B induction in the hypothalamus, or c-fos expression in these related afferents. These results establish NGFI-B as a useful adjunct to c-fos, for revealing synaptic and/or transcriptional activation in the magno- and parvocellular neurosecretory systems. Differences in the sensitivity of the two markers in revealing functionally related activation in extrahypothalamic regions speak to general issues concerning the use of immediate-early genes in mapping functional circuitry in the CNS.

Adrenalectomy↗