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Biomedical subjects

S T Chan

Publications and source records attributed to S T Chan.

At least 73 records · Page 4Linked to original sources
PubMed1994

A case of tetanus mimicking acute abdomen.

A 47-year-old man presented with backache and signs of acute abdomen. An exploratory laparotomy was performed. Post-operatively he developed hypoxaemia in the operating theatre and was brought to the Surgical Intensive Care Unit for ventilatory support and further investigations. History was then retaken and revealed a minor foot injury one month ago with subsequent development of muscle spasm and dysphagia. The diagnosis of tetanus was made. The patient was then treated with human antitetanus immune globulin and crystalline penicillin. Ventilatory support was continued, aided by infusion of morphine, diazepam and alcuronium. The recovery course was complicated by chest infection, urinary tract infection and sympathetic overactivity. He improved later and ventilatory support was discontinued three weeks after admission. He then made uneventful recovery and was discharged from the hospital forty days after admission.

Abdomen, Acute↗
PubMed1994

Abdominal trauma--a review.

Trauma is a leading cause of death in the 1-44 age group. In our study, the most common cause is road traffic accidents followed by stab wounds and falls from height. Blunt abdominal trauma accounted for 79% of the cases. The spleen and liver were the most common organs involved in blunt abdominal trauma. Clinical assessment of blunt abdominal trauma is unreliable. The diagnostic peritoneal lavage is a useful triage tool in the initial assessment.

Abdominal Injuries↗
PubMed1993

The in vitro metabolism of radioactive androstenedione and testosterone by the gonads of the protogynous Monopterus albus at different sexual phases: a time-course and seasonal study.

The seasonal gonadal steroidogenesis of Monopterus albus in relation to natural sex reversal was studied by in vitro time-course incubations. In vitro steroid metabolisms varied with the developmental stages of the gonad. In the female stage, the major products were either 3 beta-hydroxy-5 alpha-androstan-17-one or unidentified metabolites, depending on the season. In the males, 11-oxotestosterone was the major product during the prespawning, reproductively active period, while in other periods of the seasonal cycle, 5 alpha-reduced metabolites were more abundant. In the intersexes, the steroidogenic pattern changed from a female to a male pattern, i.e., the production of 11-oxotestosterone increased and that of the unidentified metabolites decreased.

Androstenedione↗
PubMed1993

Effects of LH and LHRH-analog on gonadal development and in vitro steroidogenesis in the protogynous Monopterus albus.

The effects of ovine luteinizing hormone (oLH) and a synthetic analog of luteinizing hormone releasing hormone, des-Gly10 [D-Ala6]-LHRH ethylamide acetate salt (LHRH-A), on gonadal development and on in vitro steroidogenesis in the female phase of the protogynous sex-reversing Monopterus albus were investigated at different periods of the seasonal cycle. At the postspawning stage, oLH induced a precocious sex reversal with marked proliferation of interstitial Leydig cells and development of spermatogonial cysts in the gonads, and enhanced in vitro production of unsaturated androgens. However, such oLH effects were insignificant in females during the early prespawning stage: some spermatogonial cysts appeared, but no proliferation of Leydig cells took place. During both the postspawning and early prespawning stages, LHRH-A stimulated growth of the oocytes with increased yolk content. Gonadal steroid metabolism by females at early prespawning stage was not affected by LHRH-A within the brief experimental period. In the postspawning period, LHRH-A caused a change in the in vitro steroidogenic profile from a postspawning pattern to that of a typical prespawning female pattern with increased production of estrogens and two unknown metabolites, and decreased production of 5 alpha-androstan-3 beta-OH-17-one.

Animals↗
PubMed1993

In vivo effects of oLH and LHRH-analog on sex reversal and plasma sex steroid profiles in the female Monopterus albus.

The effects of ovine-luteinizing hormone (oLH) or a synthetic analog of luteinizing hormone-releasing hormone, Des-Gly10[S-Ala6]-LHRH ethylamide acetate salt (LHRH-A), on the female phase of the protogynous Monopterus albus were investigated, and the plasma levels of androstenedione (Ad), testosterone (T), 11-oxotestosterone (KT), 11 beta-hydroxytestosterone (OHT), 17 beta-estradiol (E2) and progesterone were determined. In the postspawning stage, oLH induced precocious sex reversal in the gonad from female to male and increased plasma levels of Ad, T, KT and OHT. However, such oLH effects in M. albus females were slight at the early prespawning stage, and no significant signs of precocious sex reversal were found either in gonadal structure or in plasma hormones as those in postspawning treatment. After LHRH-A treatment of M. albus females in both postspawning and early prespawning stages, the gonadal structure remained "female type" with no sign of proliferation of either Leydig cells or male germ cells. The plasma levels of E2 were greatly increased after the treatment.

Animals↗
PubMed1993

Luteinizing hormone (LH) surge in patients using buserelin spray during ovarian stimulation for assisted reproduction.

The incidence of luteinizing hormone surge was studied in patients who were downregulated with a short protocol of gonadotrophin releasing hormone agonist before ovarian stimulation for assisted reproduction. Buserelin nasal spray 100 micrograms was given 5 times daily from day 2 of the cycle, followed by ovarian stimulation with human menopausal gonadotrophin and follicle stimulating hormone from day 3 onwards. Of the 159 cycles studied, luteinizing hormone surge was detected in 9 cycles (5.7%). The occurrence of LH surge was usually (67%) but not always associated with a fall in serum oestradiol level before administration of human chorionic gonadotrophin. None of the patients developed luteinizing hormone surge after day 10. Even in patients without luteinizing hormone surge the serum luteinizing hormone levels on the day of administration of hCG were significantly higher than those on day 2 before administration of buserelin. It is concluded that a short protocol with intranasal buserelin 500 micrograms per day is inadequate to suppress endogenous luteinizing hormone surge.

Administration, Intranasal↗
PubMed1993

Studies on the effect of lambdacyhalothrin on Anopheles maculatus Theobald and its response to residual spraying at Jeram Kedah, Negeri Sembilan, Malaysia.

A field trial was carried out to study the effect of lambdacyhalothrin on Anopheles maculatus in trap huts in Jeram Kedah, Negeri Sembilan, Malaysia. Two trap huts were built, of which one was sprayed with lambdacyhalothrin at a dosage of 25 mg ai/m2 and the other served as control. Eight collectors commenced collecting mosquitos from 1900 to 2400 hours, two each indoors and outdoors. Bioassay was also carried out in the treated and control huts to determine susceptibility of adult mosquitos to lambdacyhalothrin. In the treated hut more mosquitos were present during the pre- spraying period. Lambdacyhalothrin gave a mortality of 100% against An. maculatus for 8 months.

Animals↗
PubMed1993

A study of protein and glycoprotein syntheses in pre-implantation mouse embryos using mini-2D-electrophoresis, video densitometer scanning and computer-image analysis.

In the present study, proteins and glycoproteins of mouse embryos at 2-cell, morula and blastocyst stages were analyzed. The techniques of 35S-Met incorporation, ConA antiserum-precipitating ConA-binding proteins, mini-2D-electrophoresis, fluorography, video densitometer scanning and the computer-image system were used for analyses. Results of the investigations indicated that proteins and glycoproteins were synthesized by the embryos in a gradual increase manner from 2-cell to blastocyst. A relatively large amount of glycoproteins was synthesized during the morula and blastocyst stages. Two specific small glycoproteins respectively with molecular weights about 6500 and 9000 and PIs at 5.0 and 6.5 were apparently synthesized in the blastocyst but not in the 2-cell or the morula.

Animals↗
PubMed1992

Improved development of human embryos in vitro by a human oviductal cell co-culture system.

This study was undertaken to determine the effect of co-culture with human oviductal cells on human embryos. Spare embryos from gamete intra-Fallopian transfer (GIFT), pronuclear stage transfer (PROST) and in-vitro fertilization/embryo transfer (IVF/ET) programmes were either cultured in serum-supplemented Earle's balanced salt solution alone, or co-cultured in the same solution with oviductal cells from the pronuclear stage (day 1 post-insemination) or two- to four-cell stage (day 2 post-insemination). The co-cultured embryos appeared to have a higher developmental potential (higher rate of blastocyst formation and lower fragmentation rate), although there was no statistical difference in their rate of development, degree of fragmentation and stages attained, when compared with conventionally cultured embryos. The percentage of hatching blastocysts was significantly higher (P less than 0.05, Fisher's exact test) for embryos co-cultured from day 1 post-insemination (38%) than for embryos which had not been co-cultured (7%). The blastocyst hatching rate for embryos co-cultured from day 2 post-insemination was 15%. It was therefore concluded that co-culture of human embryos with oviductal cells could improve the development of the embryos in vitro. The degree of improvement was more pronounced when the co-culture started at an earlier stage.

Blastocyst↗
PubMed1992

Evaluation of carbon dioxide and 1-octen-3-ol as mosquito attractants.

CDC Light traps were used to study the attractant effect of CO2 and 1-octen-3-ol on trap catches of mosquito populations at three different locations in Malaysia. There was a significant increase in the number of mosquitos caught in traps baited with CO2 and CO2 with 1-octen-3-ol. The number of mosquitos caught in the CDC light trap and in the CDC light trap baited with 1-octen-3-ol alone were very few. 1-octen-3-ol and CO2 acted synergistically in attracting significantly greater numbers of Culex tritaeniorhynchus. However Anopheles sp. were not very attracted to light traps even with attractants added to them.

Animals↗
PubMed1991

Pre- and post-testing of students in surgery: do medical rotations help?

A prospective multiple choice question (MCQ) study developed to pre- and post-test fifth year medical students at the University of Queensland, was undertaken during 1990. We investigated whether there was a significant gain in their surgical knowledge base resulting from non-surgical rotations during the same year. We have previously reported a retrospective study suggesting that there was such a gain. Comparable clinical surgical pre- and post-tests were adapted from a fresh question bank, and were presented prospectively to four groups of fifth year medical students at the beginning and end of each 7 week General Surgical term. In contrast to our retrospective study, we found there was no significant increment in surgical knowledge using non-parametric Notched Box and Whisker Plot analysis of data. We conclude that this is either because students are compartmentalizing their factual knowledge base between one speciality and the next, or that indeed there is no benefit to Surgical knowledge base from prior non-surgical rotations. Assuming the former, a combined Medical and Surgical Objective Structured Clinical Examination (OSCE) at the end of the fourth year could serve to broaden the student's horizons and reduce factual dissociation during the fifth year.

Clinical Clerkship↗
PubMed1991

Capture-recapture studies with Anopheles maculatus Theobald (Diptera: Culicidae) the vector of malaria in peninsular Malaysia.

Mark-release-recapture experiments were undertaken in January 1989, in Pos Betau, Pahang, Malaysia, with the malaria vector Anopheles maculatus. On two consecutive nights, 121 and 175 blood-fed mosquitos were released. A mean recapture rate of 11.5% and survival rates of 0.699-0.705 with an estimated oviposition cycle period of 2.35 days were obtained from the releases. About 68% of all recaptures were taken within a distance of 0.5 km from their release points and the longest detected flight was 1.6 km. No heterogeneity was found between indoor and outdoor biters of An. maculatus.

Animals↗
PubMed1990

Differential evaluation of human sperm hypoosmotic swelling test and its relationship with the outcome of in-vitro fertilization of human oocytes.

The hypoosmotic swelling test is a simple laboratory test to measure the functional integrity of the human sperm membrane. Its in-vivo and in-vitro applicability needs to be evaluated before it can be accepted as a useful routine test for the fertilizing potential of human semen. We studied the standard semen analysis results and differential sperm tail swelling patterns of seminal and swim-up sperm after hypoosmotic treatment in 97 semen samples used for in-vitro fertilization of human oocytes. Semen samples were classified as infertile (0% fertilization rate; n = 27) or fertile (greater than 0% fertilization rate; n = 70) before statistical analyses. There was a significant difference (P less than 0.005) in percentage normal morphology of seminal sperm between the fertile and infertile semen samples. The percentage normal morphology of seminal sperm correlated (r = 0.4250; P less than 0.005) with the in-vitro fertilization rate of human oocytes and this parameter was selected by the multivariate stepwise discriminant analysis as the discriminator capable of predicting the in-vitro fertilization rate with 57.7% accuracy. The percentage total swelling of seminal and swim-up sperm after hypoosmotic treatment was not correlated with the in-vitro fertilization rate. The percentage swelling pattern g (the open type) of seminal sperm was also selected by the multivariate stepwise discriminant analysis as the discriminator to predict the in-vitro fertilization rate. This parameter correlated with the percentage normal morphology of seminal sperm (r = 0.3014; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Membrane↗
PubMed1990

Effectiveness of repellent/insecticidal bars against malaria and filariasis vectors in peninsular Malaysia.

Field tests were conducted to compare the degree of protection from bites of Mansonia species and Anopheles maculatus by applying two repellent/insecticidal bars, MOSBAR and MOSKIL, to exposed arms and legs. Human test subjects were exposed to natural populations of mosquitos for an 8-hour night time period while using the repellent/insecticidal bars. MOSBAR gave good protection against the bites of Mansonia and An. maculatus. MOSKIL was effective against An. maculatus but not against Mansonia. High mortality was observed among the mosquitos collected from human test subjects treated with the repellent/insecticidal bars. Use of MOSBAR in terms of cost-effectiveness and safety by field and health workers entering into malaria and filariasis endemic areas is discussed.

Animals↗
PubMed1989

Predictive value of sperm morphology and movement characteristics in the outcome of in vitro fertilization of human oocytes.

One hundred fourteen semen samples from Chinese males were analyzed for routine semen parameters including the semen volume, sperm count, percentage motility, and percentage normal morphology. Of these 114 samples, 54 also had movement characteristics of seminal and swim-up sperm evaluated by the computer image analyzer system (Cellsoft; Cryo Resources Co., New York). All semen samples were subjected to the swim-up procedure to harvest the motile sperm before inseminations of human oocytes. Fertilization was considered to have occurred when at least one oocyte was observed with two or more pronuclei. Semen samples were classified as infertile (0% fertilization rate; N = 32) or fertile (greater than 0% fertilization rate; N = 82) before statistical analyses. There was a significant difference (P less than 0.005) in percentage normal morphology of seminal sperm between the fertile (mean +/- SE; 67.3 +/- 1.2%) and the infertile (59.3 +/- 2.2%) samples. The percentage normal morphology of seminal sperm correlated (r = 0.3049; P less than 0.002) with the fertilization rate and this parameter was selected by the multivariate stepwise discriminant analysis as the discriminator capable of predicting the fertilization rate with 57.9% accuracy. Statistical analyses of samples where sperm movement was also evaluated demonstrated that there was significant differences (P less than 0.01) between the fertile (N = 38) and the infertile (N = 16) samples in percentage normal morphology of seminal sperm (67.8 +/- 1.8% vs 56.2 +/- 2.6%) and curvilinear velocity of swim-up sperm (89.2 +/- 3.5 vs 68.2 +/- 7.2 microns/sec).(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1989

Efficacy of the urinary hemagglutination test (Higonavis) and enzyme immunoassay (Ovustick) in detection of the spontaneous luteinizing hormone surge in an in vitro fertilization/gamete intrafallopian transfer (IVF/GIFT) program.

Fifty-eight treatment cycles in an in vitro fertilization/gamete intrafallopian transfer (IVF/GIFT) program were studied to compare the efficacy of two urinary methods, hemagglutination test (Higonavis) and enzyme immunoassay (Ovustick), in detection of spontaneous luteinizing hormone (LH) surge. If an isolated rise in urinary LH level was taken as indicative of LH surge, the false-positive rate was 36.7% for Higonavis and 10.2% for Ovustick. The difference was statistically significant (P less than 0.001). If only a sustained rise in urinary LH was taken to indicate LH surge, the false-positive rate was 6.1% for Higonavis and 0% for Ovustick. In the seven cycles with a spontaneous plasma LH surge, there was a positive correlation between the plasma LH levels and the two urinary assay methods in six cycles (85.7%). Compared to plasma LH, there was a mean delay of 17.4 hr by the Higonavis test and 15.6 hr by the Ovustick test. If a sustained rise in urinary LH levels was taken as indicative of LH surge, both methods are quite accurate but the Ovustick appeared to be more specific.

Evaluation Studies as Topic↗