Biomedical subjects
Publications and source records attributed to S T Chan.
Four species of malaria parasites are known to infect humans. A fifth species, Plasmodium knowlesi, has been reported to infect humans in Malaysian Borneo. Here we report for the first time the incrimination of Anopheles latens as the vector of P. knowlesi among humans and monkeys in Sarawak, Malaysia.
A study was carried out from July 2001 until January 2003 in the Kinabatangan area of Sabah, part of Borneo island, where malaria used to be mesoendemic. Vector surveys determined that Plasmodium falciparum was the predominant species and Anopheles balabacensis the primary vector. Malaria cases have dropped drastically over the years but P. falciparum is still predominant. In the present study, Anopheles donaldi was the predominant species and was positive for sporozoites. Although An. balabacensis was present, none were infective. An. donaldi bite more outdoors than indoors and have a peak biting time from 18:00 to 19:00 h when most people are still out of their homes. An integrated malaria control programme along with area development has helped in the control of malaria and its vector.
Surveys were conducted in malaria-endemic villages in the southern province of Attapeu, Lao PDR during various seasons over a 3-year period. All-night mosquito landing collections, blood surveys and a case-control study were conducted. Plasmodium falciparum was the predominant species, and slide positivity rates were higher during the transition/dry season compared with the wet season. Anopheles dirus A was found to be the primary vector, and sporozoite rates were highest during the transition/dry season. Anopheles dirus was found to be endophagic and endophilic. Not using insecticide-treated bed nets, houses close to breeding sites and sleeping away from home were risk factors associated with malaria.
A study was conducted in four villages in Attapeu Province, Lao PDR in 2002 to determine malaria endemicity. The study villages were Mixay, Beng Phoukham, Phou Vong and Pier Geo. Mass blood surveys were conducted in May, August, and October. Finger prick blood was collected for thick and thin blood film as well as for dipstick. The slide positivity rate was highest in Phou Hom in October (41.7%). Plasmodium falciparum was the dominant species comprising more than 80% of the cases. As a whole, the distribution of malaria was similar among males and females. Children below 15 years accounted for a large percentage of the cases. The sensitivity of the optimal dipstick was 62.36 and the specificity was 61.7. Microscopy was taken as the gold standard. Anopheles dirus was found to be the main vector and the vectorial capacity correlated well with the cases.
A study was carried out in four malaria-endemic villages in Attapeu Province, in the southern region of Lao PDR. All-night human landing collections were carried out in May, August, and October 2002, to determine malaria vectors. At the same time, mass blood surveys were also carried out in the same villages. Anopheles dirus was the predominant species in three of the study villages. Sporozoites were found only in An. drius from Phou Hom. However, in Beng Phoukham, An. dirus was positive for oocysts. The distribution of malaria cases was highest in Phou Hom and this correlated well with the vectorial capacity of An. dirus. The risk for infection from An. dirus was also high, at 0.99.
A patient undergoing excision of phaeochromocytoma developed refractory hypotension which was complicated by significant intraoperative blood loss. Cardiovascular support with fluids, blood and noradrenaline failed to reverse the hypotension. Introduction of vasopressin successfully reversed the hypotension. The experience with this case suggests that vasopressin may be a useful adjunct in the treatment of catecholamine-resistant hypotension after phaeochromocytoma excision.
Phaeochromocytoma of the urinary bladder is rare. We report a case of a patient with undiagnosed bladder phaeochromocytoma who developed haemodynamic disturbances during routine diagnostic cystoscopy. The diagnosis was only confirmed postoperatively.
OBJECTIVE: To investigate the relationship between cytoplasmic fragmentation and caspase activity in the mouse embryo. DESIGN: Experimental laboratory study. SETTING: University gynacology unit. ANIMAL(S): One-cell zygote of mouse (MF1 x BALB/c). INTERVENTION(S): Mouse embryos were treated with caspase inhibitors: benzyloxycarbonyl-Val-Ala-Asp fluoromethylketone (z-VAD-fmk) and benzyloxycarbonyl-Asp-glu-Val-Asp-fluoromethyl ketone (Z-DEVD-fmk). MAIN OUTCOME MEASURE(S): Morphological development of the embryo, proportion of fragmented embryos, caspase-3-like activity, DNA breakage, and phosphatidylserine exposure in blastomeres. RESULT(S): The proportion of embryo reaching two-cell, three- to four-cell, and morula stage at 48, 72, and 96 hours after hCG administration, respectively, were comparable between the control embryos and those treated with either z-VAD-fmk or z-DEVD-fmk, at three concentrations (10 microM, 50 microM, and 200 microM). Although the inhibitors suppressed the caspase-3-like activity in the embryo fragment before compaction and decreased DNA breakages, there was no statistically significant difference in the percentage of fragmented embryo between the control and those treated with caspase inhibitors. The inhibitors did not affect the incidence of phosphatidylserine exposure in the blastomere of the treated embryos. CONCLUSION(S): Cytoplasmic fragmentation in precompaction mouse embryos is not a consequence of caspase-related apoptosis.
PURPOSE: To investigate the embryotrophic mechanisms of Vero and oviductal cells coculture. METHODS: Mouse embryos were cultured in Chatot, Ziomek, and Bavister medium (CZB), in modified CZB media (MM) with nutrient concentrations adjusted to that found in conditioned media after different periods of Vero cells or oviductal cells culture, in reconstituted medium (RM) containing the purified > 100-kDa components of Vero cell conditioned medium that had been reconstituted with CZB medium, and cocultured with Vero cells with an interposing membrane. RESULTS: The blastulation rate was not different among embryos cultured in different Vero-cell-derived MMs. Nine-hour Vero-cell-derived MM significantly increased the total cell number and hatching frequency of the embryos. There was no difference in these parameters with oviductal-cell-derived MMs. The RM of Vero cells did not possess embryotrophic activity. The presence of a porous membrane between Vero cells and embryos did not affect the embryotrophic activity of coculture. CONCLUSIONS: Vero cells, but not oviductal cells, improved mouse embryo development partly by modifying the energy substrate concentration in culture medium.
We hypothesized that transforming growth factor beta1 (TGFbeta(1)) and its receptors play a role in the interaction between the preimplantation embryo and the reproductive tract. To investigate this hypothesis, TGFbeta 1 mRNA in mouse embryos was quantified by competitive reverse transcription-polymerase chain reaction using an RNA mimic. TGFbeta 1 was first detected in the unfertilized oocyte, disappeared after fertilization and was expressed again at the 2-cell stage (4410 +/- 1330 transcripts/embryo). Its expression increased gradually, peaked at the 8-cell stage (58 600 +/- 17 300 transcripts/embryo) and declined rapidly after the morula stage reaching a concentration of 1520 +/- 546 transcripts/embryo at the blastocyst stage. The mRNA levels of TGFbeta 1 at the 8-cell and morula stages were significantly higher than that at other cell stages (P < 0.05). The expression of TGF receptors in embryos and in the reproductive tract was also investigated. Both TGFbeta(1) type I (ALK-5) and type II TGFbeta receptors were detected in embryos from 1-cell to blastocyst stage by immunohistochemistry. Northern hybridization and immunohistochemistry showed a constant expression of both TGFbeta receptors in the oviduct from day 1 to day 4 of pregnancy, whilst in the uterus there was a marked increase in the expression of TGFbeta type I receptor on day 3. Expression of TGFbeta type II receptor in the uterus remained unaltered throughout the study period. This study has shown that preimplantation mouse embryos produce TGFbeta(1) and that both the embryos and the reproductive tract are responsive to TGFbeta(1) in the preimplantation period.
The objectives of this study were to compare the mRNA expression patterns in early mouse embryos in different culture conditions by differential display reverse transcription-polymerase chain reaction (DDRT-PCR). Embryos developed in vivo, cultured in vitro, and cocultured with human oviductal epithelial cells were studied at the 2-cell, 4-cell, 8-cell/morula, and blastocyst stages. Messenger RNA profiles were displayed by DDRT-PCR using downstream T11VV (V = A, C, or G) and upstream decamer primers. Total cDNA banding patterns were highly conserved in the three groups studied. Some fragments are unique in different culture conditions. Thirteen out of the 40 selected differentially expressed clones were characterized. The DNA sequence analyses of these clones displayed high sequence homology with cDNA sequences in the mouse expressed sequence tag database. Using semiquantitative RT-PCR, we confirmed differential expression of these DD amplicons in the three groups of embryos. The temporal expression of some of the selected DD amplicons during preimplantation development were studied in the three groups of embryos. In conclusion, DDRT-PCR is an effective tool for contrasting gene expression patterns and characterizing mRNA transcripts in mouse embryo.
Mouse embryos at different stages of development were cocultured with human oviduct cells or cultured in the presence of oviduct-derived embryotrophic factor-1, -2, and -3 (ETF-1, -2, and -3) for various amounts of time within the preimplantation period. Cocultures that included the period from 48 to 72 h post-hCG stimulated cell division and increased the cell numbers in the inner cell mass (ICM) of the exposed blastocyst. Exposure of embryos to oviductal cells from 96 to 120 h post-hCG increased the cell number in the trophectoderm (TE), blastocyst size, hatching rate, attachment, and in vitro spreading of the blastocyst. ETF-1 and ETF-2 affected embryos between 48 and 72 h post-hCG by increasing the number of cells in the ICM. In contrast, ETF-3 had a more profound effect on embryos that were exposed from 96 to 120 h post-hCG, where it mostly affected the development of TE cells, leading to higher hatching rate. Human oviductal cells improved mouse embryo development partly by the production of high molecular weight embryotrophic factors. These factors had differential effects on mouse embryo development.
Because the transcription factor, nuclear factor (NF)-kappaB, plays a key role in cellular inflammatory and immune responses, components of the NF-kappaB-activating signaling pathways are frequently used as targets for anti-inflammatory agents. This study shows that 2-(3',4'-dihydroxyphenyl)-5-hydroxybenzo[b]furan (GF-015) and 2,3-di(3',4'-dihydroxy-transstyryl) pyridine (GF-90), two conjugated polyhydroxybenzene derivatives, inhibited a common step in NF-kappaB activation in human NCI-H292 epithelial cells by preventing tumor necrosis factor (TNF)-alpha- and 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced IkappaB kinase (IKK) complex activation. Both agents inhibited the TNF-alpha- or TPA-induced expression of cyclooxygenase (COX)-2 mRNA and protein, COX-2 promoter activity, and prostaglandin E2 (PGE2) production. Overexpression of wild-type NF-kappaB-inducing kinase, IKKalpha, and IKKbeta led, respectively, to 3.5-, 2.6-, and 2.6-fold increases in COX-2 promoter activity, and these effects were inhibited by both compounds. GF-015 and GF-90 also prevented the TNF-alpha- and TPA-induced activation of IKK and NF-kappaB-specific DNA-protein binding activity. These results suggest that the inhibitory effect of GF-015 and GF-90 on TNF-alpha-induced COX-2 protein expression was caused by suppression of IKK activity and NF-kappaB activation in the COX-2 promoter, resulting in attenuation of COX-2 gene expression and PGE2 production.
INTRODUCTION: Sonography has found a role in the evaluation of patients with abdominal injury. However, the accuracy of sonography as performed by non-radiologists remains controversial. This study aims to determine the accuracy of focused abdominal sonography for trauma when performed by surgeons. MATERIALS AND METHOD: Over a 1-year period, 48 patients with abdominal injury were initially evaluated for free intraperitoneal fluid by sonography. These tests were performed by 2 surgeons who had received instructions and performed a minimum of 30 examinations. Sonographic findings were then compared with other diagnostic modalities including computed tomography (CT) scan, diagnostic peritoneal lavage and exploratory laparotomy. RESULTS: The sensitivity, specificity, positive predictive value, negative predictive value and accuracy for sonography were found to be 0.86, 0.92, 0.89, 0.90 and 0.89, respectively. Although not specifically sought for, 2 cases of solid organ injury and 1 haemothorax, which were missed in initial examinations and X-rays, were detected on sonography. CONCLUSION: In conclusion, our initial experience suggests that local surgeons can perform a focused sonographic examination for trauma with acceptable accuracy. Although sonography lacks the sensitivity of diagnostic peritoneal lavage and the accuracy of CT scan, the diagnostic algorithm for abdominal trauma should include sonography as a screening test.
INTRODUCTION: This prospective, randomised, double-blind study was designed to assess if the addition of 50 mg tramadol to 30 mL 0.5% lignocaine would improve the efficacy of intravenous regional anaesthesia. MATERIALS AND METHODS: Fifty-four adult patients undergoing upper limb surgery were randomly allocated to receive either 30 mL 0.5% lignocaine and 1 mL normal saline (group A) or 30 mL 0.5% lignocaine and 50 mg tramadol (group B). They were then assessed for onset of sensory and motor block and the VbAS score for tourniquet pain. RESULTS: Although more patients in group B had a faster onset of sensory and motor block, this was not significantly different. Patients in group B had a significantly lower VbAS score 30 min after tourniquet inflation and after change over to the distal tourniquet (P < 0.05). There were no complaints of postoperative nausea and vomiting. Two patients in group B developed localised skin urticaria of the forearm which resolved with the release of the tourniquet. CONCLUSION: There is a positive trend that tramadol might improve the quality of intravenous regional anaesthesia.
Transabdominal duplex Doppler ultrasonography (TDDU) is commonly used for measuring hepatic blood flow (HBF) in clinical practice. Flow velocity and the cross-sectional area (CSA) of vessels are obtained separately and used to compute blood flow. Respiration and changes in portal pressure are known to cause variations in the CSA of the portal vein, but the impact of these parameters on TDDU measurement of portal blood flow is unclear. Eight Yorkshire pigs (20.7-25.1 kg) were used for the study. TDDU determination of portal blood flow was carried out using CSA of the portal vein obtained at inspiration (maximal) and at expiration (minimal) for computation, and the differences obtained were compared. Determination of HBF was carried out simultaneously on the same animals using diisopropyliminodiacetic acid (DISIDA) clearance. A physiological increase in portal pressure was then created by 50% hepatectomy and TDDU measurement similarly carried out on the second postoperative day. Computing portal blood flow in the intact liver using maximal and minimal CSA gave rise to a mean difference of 7.0 ml kg(-1) min(-1) (P < 0.001). A significant correlation was obtained between HBF and portal flow computed from maximal CSA (Pearson's correlation = 0.85, P < 0.033). The respiratory index of the portal vein (maximal CSA/minimal CSA) decreased from 1.5 to 1.2 after hepatectomy, which also caused a 90% increase in portal pressure. Respiration and portal pressure thus significantly impact on TDDU determination of HBF, and in this porcine model, computation using maximal CS more accurately reflects HBF.
OBJECTIVE: To investigate the effect of human oviductal cell coculture on the incidence of apoptosis in mouse embryos. DESIGN: Experimental laboratory study. SETTING: University gynecology unit. PATIENT(S): Fallopian tubes were obtained from patients undergoing hysterectomy. INTERVENTION(S): Mouse embryos were cocultured with human oviductal cells. MAIN OUTCOME MEASURE(S): Blastocyst development, allocation of inner cell mass (ICM) and trophectoderm (TE) in blastocyst, and apoptosis in embryos. RESULT(S): Oviductal cells significantly enhanced the blastulation (38%) and hatching rate (22%) of the cocultured zygotes. The corresponding values in medium alone culture were 21% and 9%, respectively. The cocultured embryos also had higher blastomere count at blastocyst stage (P<0. 005). This was due to increase in both the cell count of ICM (P<0. 05) and TE (P<0.001). Coculture reduced the incidence of apoptosis in the cultured morula and blastocyst from 38% and 48% to 16% (P<0. 001) and 27% (P<0.05), respectively. The number of apoptotic blastomeres per morula (1.5 +/- 0.6; P<0.005) and blastocyst (2.3 +/- 0.7; P<0.005) after coculture was also significantly lower than that of the corresponding control (morula, 2.1 +/- 0.8; blastocyst, 3.5 +/- 1.1). CONCLUSION(S): Human oviductal cells improved mouse embryo development partly by decreasing the incidence of apoptosis.
BACKGROUND AND AIMS: Significant changes in hepatic haemodynamics occur after major hepatectomy, but the pathogenesis of this phenomenon is unclear. This study investigates the serum profile of prostaglandin and nitric oxide in the hepatic and systemic circulation before and after hepatectomy and the temporal relationship of these to changes in the hepatic blood flow. METHODS: Blood samples were collected from the internal jugular, portal and hepatic veins of six Yorkshire pigs (17-25 kg) before, immediately after and 48 h after partial hepatectomy. RESULTS: Serum levels of prostacyclin I2 (PGI2) and prostaglandin E2 (PGE2) from the systemic circulation, the portal circulation and from the hepatic veins were found to differ considerably even before hepatectomy. After the hepatectomy was performed, there was a significant rise in PGI2 levels in the systemic circulation (P=0.027). Hepatic blood flow and cardiac output were measured before hepatectomy, 24 and 48 h after hepatectomy in another six pigs. A significant increase in hepatic blood flow (P=0.029) occurred after the hepatectomy and this was accompanied by a concomitant increase in the cardiac output (P=0.042). The increase in PGI2 concentration in the systemic circulation after hepatectomy appears to accompany the development of hyperdynamic hepatic and systemic circulations. No significant change was found in circulating PGE2 levels in the systemic, portal and hepatic veins at the three collection intervals (i.e. pre, post and 48 h after hepatectomy). The PGE2 levels in the hepatic vein, however, were significantly higher from than in the portal vein (P=0.028). No significant changes were observed in the level of nitric oxide. CONCLUSION: This study demonstrates an increase in the total hepatic blood flow after hepatectomy together with a threefold increase in prostacyclin in the systemic circulation. The liver was identified as the main source of circulatory prostaglandin.