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Biomedical subjects

K L Chan

Publications and source records attributed to K L Chan.

At least 37 records · Page 2Linked to original sources
PubMed2003

Anaesthetic management of a parturient with pulmonary stenosis and aortic incompetence for Caesarean section.

Anaesthetic management of Caesarean section in a parturient with severe pulmonary stenosis and aortic regurgitation is described. The valvular sequelae resulted from previous unsuccessful surgical correction (Ross procedure) of congenital aortic stenosis. This case demonstrates the importance of multi-disciplinary assessment and careful anaesthetic planning, to avoid deterioration in perioperative cardiac performance in parturients with complex valvular disease.

Adult↗
PubMed2003

EMLA cream versus dorsal penile nerve block for postcircumcision analgesia in children.

We conducted a prospective, randomized, double-blinded trial comparing preoperative application of EMLA cream and sodium chloride solution dorsal penile block (n = 31) with placebo cream and bupivacaine dorsal penile nerve block (n = 32) for postcircumcision analgesia. Pain was assessed using modified Children's Hospital of Eastern Ontario Pain Scale and the duration of block by the time to requirement of first dose of postoperative analgesic. There was no difference in Children's Hospital of Eastern Ontario Pain Scale between the two groups, but bupivacaine dorsal penile nerve block resulted in longer analgesia (P = 0.003). There were no local or systemic complications related to either technique, and there was a very small incidence of vomiting. We conclude that preoperative application of EMLA cream is an effective and simple method to produce postcircumcision analgesia with a very small incidence of adverse effects.

Acetaminophen↗
PubMed2002

Endotoxemia associated with intussusception and its diagnostic and surgical interventions.

To determine if and when intussusception results in endotoxemia and to evaluate whether diagnostic and surgical interventions of intussusception aggravate endotoxemia, intussusception was created in seven pigs during general anesthesia (ileocolic n = 3, ileo-ileocolic n = 2, ileocolic with silicone ring as leadpoint n = 1, ileoileal with silicone ring n = 1). After a period of observation and before progression to bowel gangrene, a diagnostic ultrasound study with a saline enema was undertaken, followed by a laparotomy and resection of the intussusception with a primary bowel anastomosis. Serial blood samples were obtained before and at regular intervals after: (1) formation of the intussusception; (2) the enema; and (3) resection for endotoxin measurement by limulus amebocyte lysate assay. The mean level of endotoxin increased from a pre-intussusception value of 0.750 EU/ml (range: 0.215-1.281) to a post-intussusception maximum of 1.482 EU/ml (0.997-2.882, P = 0.009), peaking mostly at 2 h after the intussusception. The mean pre-saline-enema level was 1.547 EU/ml (0.869-2.677) while the post-enema level was 1.41 EU/ml (0.84-2.468, P = 0.655). The mean pre-resection level was 1.470 EU/ml (0.784-2.468) while the post-resection maximum was (2.130 EU/ml) (0.850-4.381, P = 0.09). It is concluded that: (1) even in the absence of bowel gangrene intussusception results in significant endotoxemia within 2 h of its formation; (2) gentle saline enemas are not associated with endotoxemia; and (3) surgical resection results in a further upward surge of endotoxemia. These findings provide a scientific basis for improved understanding and management of intussusception.

Animals↗
PubMed2002

Factors affecting outcomes of prenatally-diagnosed tumours.

OBJECTIVE: The outcomes of prenatally-diagnosed tumours affect obstetrical management and parental decisions. The present study reviews the factors affecting outcomes for fetuses with prenatally-diagnosed tumours. METHODS: Medical records of all fetuses referred to our institutions with antenatally-diagnosed tumours were reviewed for the type and location of the tumours, results of treatment and/or causes of death. RESULTS: From January 1994 to May 2001, there were 15 fetuses with antenatally- diagnosed tumours: mesoblastic nephroma (MN) (n=2); neuroblastoma (NB) (n=2); cystic hygroma (CH) (n=3); intracranial germ cell tumour (IGCT) (n=2); sacrococcygeal teratoma (SCT) (n=3) and haemangioma (liver, n=2; limb, n=1). One mother had termination of pregnancy for her fetal SCT. Three mothers had Caesarean section for large fetal heads (CH, n=2; IGCT, n=1). Three fetuses died; two with IGCT and one with SCT, who died of heart failure. Two newborns with CH needed emergency intubation and, later, one of them had tracheostomy. One baby had cardiac failure resulting from a lower limb haemangioma and needed drug therapy. All solid tumours (MN, NB, SCT) of the live births had no recurrence after surgery with or without adjuvant chemotherapy. CONCLUSION: Prenatally-diagnosed tumours without any other associated abnormality cause morbidity and mortality because of their location and vascularity. Solid tumours are relatively benign.

Adult↗
PubMed2002

Revisiting ischemia and reperfusion injury as a possible cause of necrotizing enterocolitis: Role of nitric oxide and superoxide dismutase.

BACKGROUND/PURPOSE: The pathogenesis of necrotizing enterocolitis (NEC) is unknown. Ischemia and reperfusion (I/R) injury has been considered a major contributing factor. Nitric oxide (NO) and superoxide dismutases (SODs) have been shown to protect bowel from I/R injury. This study aims to assess (1) the ability of premature intestine to resist I/R injury compared with mature intestine and (2) the possible role of NO and SODs in modulating such response. METHODS: Intestines from 5 groups of rats (n = 6 for each study group) were studied: (1) premature, gestational age 20 days; (2) premature, gestational age 22 days; (3) full-term, newborn; (4) infant, day 15; (5) infant, day 30. EXPERIMENTS: (1) The degrees of I/R injury after 0, 30, 60, 90 and 120 minutes, respectively, of ischemia and 25 minutes of I/R were assessed histologically by a pathologist who was unaware of the operative details. (2) Tissue NO and copper levels were measured by electroparamagnetic resonance (EPR) study; and nitric oxide synthases, copper zinc (CuZn) SODs and manganese (Mn) SODs were examined immunohistochemically. (3) and (4) I/R injury was assessed in rats that had received intraperitoneal injections of L-arginine (NO donor) and L-NAME (NO antagonist), respectively. RESULTS: For premature (1,2), newborn (3) and mature (4,5) intestines, grades of injury at maximum I/R period studied (120 minutes of ischemia, 25 minutes of reperfusion) were 0, 0, and 3, respectively (P <.05); NO levels were 1 u +/- 1.5, 3 +/- 2.5, and 22 u +/- 3.5, respectively (P <.05); Cu levels were 150 u +/- 15, 200 u +/- 41 and 12 u +/- 2, respectively (P <.05); NOS in intestines were +, +, +++ and CuZnSODs were ++, +++, +, respectively; and MnSODs were +++, ++, -, respectively. No change in NO levels was detected in groups (1), (2), or (3) after L-arginine and L-NAME injections. CONCLUSIONS: Premature rat intestine is highly resistant to I/R injury, which may indicate that I/R alone, in the absence of other predisposing factors (eg, bacterial colonization) may not be sufficient in causing NEC. Nitric oxide does not have a protective role for immature and newborn intestines in I/R as in mature intestine. The high level of SODs of the immature and newborn intestine may play an important role in its high resistance to I/R injury.

Animals↗
PubMed2002

Portal venous velocity in the follow-up of patients with biliary atresia after Kasai portoenterostomy.

BACKGROUND/PURPOSE: Liver transplantation is the only therapeutic option for biliary atresia (BA) patients with failed Kasai portoenterostomy (PE). The indication for and timing of liver transplantation in these patients are important management issues. The aims of this study are to evaluate the relationship between portal venous velocity (PVV) and clinical and biochemical indicators of liver function in BA, and to examine the role of PVV in the postoperative surveillance of these patients. METHODS: Twenty-nine children (mean age, 8 years 4 months) who had PE for BA underwent Doppler ultrasonography to evaluate PVV. Using regression analysis, these findings were correlated with biochemical indicators of liver function. The Mann-Whitney test was used to detect any significant differences in PVV between the Child-Pugh A group and combined Child-Pugh B and C group patients. RESULTS: The mean +/- SD PVV for the Child-Pugh A group and the combined Child-Pugh B and C group was 17.1 cm/s +/- 8.9 cm/s and 10.2 cm/s +/- 3.3 cm/s, respectively, and this difference was statistically significant (P =.037). CONCLUSIONS: Doppler ultrasonography measurement of PVV provides adjunctive information to the clinical and biochemical assessment of the liver function status in BA. Its use in the postoperative surveillance of these patients is helpful in identifying the need for and in timing of liver transplantation.

Adolescent↗
PubMed2002

A study of gut immunity to enteral endotoxin in rats of different ages: a possible cause for necrotizing enterocolitis.

PURPOSE: Immature gut immunity can be a predisposing factor for necrotizing enterocolitis (NEC). The gut active immunity and innate defense to the Escherichia coli endotoxin lipopolysaccharide (LPS) in immature and mature rats were studied. METHODS: LPS, started at a dose of 10 mg/kg, was instilled into the stomachs of fetal, newborn, 1-month and 3-month-old rats. Boost doses and normal saline control instillations were given on day 14. Rats that died after instillation had detailed postmortem examinations. For survivors, a group of 6 immunized and 6 controls were killed on day 7 for the collection of serum, spleens, mesenteric lymph nodes, and small intestines. Lymphocytes (10(6)) prepared from each tissue sample of individual group were cultured for 5 days. Serum and supernatant were analyzed for IgA and anti-E coli IgA levels. RESULTS: All control rats survived. The doses of LPS given were 10, 5, 2.5, and 1.25 mg/kg. All fetal rats died after LPS instillation. Half-lethal dose for newborns was 2.5 mg/kg. One-month and 3-month-old rats survived all doses of LPS. The cause of death was endotoxemia. The serum IgA and total supernatant anti- E coli IgA levels of rats of all ages studied showed no significant difference. CONCLUSION: The poor innate gut defense, not so much the active immunity, may provide an explanation for the susceptibility of the premature babies and newborn infants to the development of NEC.

Animals↗
PubMed2002

Surgical complications and outcome of pediatric liver transplantation in Hong Kong.

PURPOSE: The aim of this study was to analyze the early and late results of pediatric liver transplantation, with particular reference to complications that required surgical or radiologic intervention. METHODS: The records and code sheets of children who underwent liver transplantation in the authors' institution between September 1993 and December 2001 were reviewed. RESULTS: Twenty-nine children (16 boys and 13 girls) underwent 31 liver transplantations (23 living donor, 8 cadaveric donor) during the study period. The ages of the children ranged from 4 months to 132 months (median, 16 months). Eighteen children had complications that required surgical or radiologic interventional procedures. Complications included, among others, hepatic vein thrombosis (n = 1, 3%), hepatic vein stenosis (n = 2, 7%), portal vein thrombosis (n = 2, 7%), biliary stricture (n = 3, 10%), bile leakage (n = 2, 7%), hepatic artery pseudoaneurysm (n = 1, 3%), jejuno-jejunostomy leakage (n = 1, 3%), graft hepatitis (n = 1, 3%), and posttransplant lymphoproliferative disorder (n = 2, 7%). In addition, 6 children (21%) suffered from intraabdominal bleeding from a variety of causes. After appropriate interventions, at a median follow-up of 38 months (range, 1 to 96 months), patient and graft survival rates were 79% and 74%, respectively. The retransplantation rate was only 7%. There was no incidence of hepatic artery thrombosis. All living donors remain alive and well. CONCLUSIONS: Complications are inevitable in pediatric liver transplantation. However, with timely recognition and active intervention, a good outcome can be achieved.

Child↗
PubMed2002

Transcript levels of the eukaryotic translation initiation factor 5A gene peak at early G(1) phase of the cell cycle in the dinoflagellate Crypthecodinium cohnii.

A cDNA encoding a eukaryotic translation initiation factor 5A (eIF-5A) homolog in heterotrophic dinoflagellate Crypthecodinium cohnii (CceIF-5A) was isolated through random sequencing of a cDNA library. The predicted amino acid sequence possesses the 12 strictly conserved amino acids around lysine 52 (equivalent to lysine 50 or 51 in other eukaryotes). A single 1.2-kb band was detected in Northern blot analysis. In synchronized C. cohnii cells, the transcript level peaked at early G(1) and decreased dramatically on the entry to S phase. Although this has not been previously reported, studies of budding yeast (Saccharomyces cerevisiae) and certain mammalian cell types suggest a role for eIF-5A in the G(1)/S transition of the eukaryotic cell cycle. Phylogenetic trees constructed with 26 other published eIF-5A sequences suggest that CceIF-5A, while falling within the eukaryotic branches, forms a lineage separate from those of the plants, animals, and archaebacteria. The posttranslational modification of eIF-5A by a transfer of a 4-aminobutyl moiety from spermidine to conserved lysine 50 or 51, forming amino acid hypusine, is the only demonstrated specific function of polyamines in cell proliferation. It has been suggested that polyamines stimulate population growth of bloom-forming dinoflagellates in the sea. We demonstrate here putrescine-stimulated cell proliferation. Furthermore, ornithine decarboxylase inhibitor D-difluoromethylornithine and the specific hypusination inhibitor N-guanyl-1,7-diaminoheptane exhibited inhibitory effects in two species of dinoflagellates. The possible links of polyamines and saxitoxin synthesis to the arginine cycle are also discussed.

Animals↗
PubMed2002

Personality of males charged with outrage of modesty.

Outrage of modesty (OOM) is considered a serious crime in Singapore and offenders are often charged with a period of imprisonment with or without a fine and caning. Previous studies have indicated that non-violent sexual offenders tend to have a socially inhibited personality. No published study has yet been conducted to investigate the personality of OOM offenders. The purpose of the current study was to assess the personality of males charged with outrage of modesty and compare them to a group of males charged with theft using the 16 Personality Factors questionnaire (16PF; Cattell, Eber, and Tatsuoka, 1970). Participants were selected over a two-year study period from a cohort of prisoners serving sentence at Changi Prison. A total of 30 OOM and 22 theft offenders completed the 16PF. All OOM subjects had been charged for molesting an adult female. Unexpectedly, planned comparisons revealed that OOM subjects had marginally higher scores on Factor H (boldness) compared to theft subjects. Exploratory analyses revealed no other significant differences between OOM and theft subjects. Implications of findings and limitations of the study are discussed.

Adult↗
PubMed2002

Paediatric hepatoblastoma and hepatocellular carcinoma: retrospective study.

OBJECTIVES: To compare and contrast clinical characteristics and outcomes of hepatoblastoma or hepatocellular carcinoma in paediatric patients. DESIGN: Retrospective study. SETTING: University teaching hospital, Hong Kong. PATIENTS AND METHODS: Medical records of 22 paediatric patients with hepatoblastoma (n=11) or hepatocellular carcinoma (n=11) admitted to Queen Mary Hospital between 1989 and 2000 were reviewed. Data gathered included demographic data, results of liver function tests, hepatitis A, B, and C titres, and alpha-foetoprotein levels, and imaging studies including chest X-ray, ultrasound study, computed tomography scan, and magnetic resonance imaging/hepatic angiogram for tumour staging and resectability. RESULTS: The mean age of patients with hepatoblastoma was 18 months (range, 5 months to 3 years), while that of patients with hepatocellular carcinoma was 10.2 years (range, 2 to 16 years). Females predominated in the hepatoblastoma group (female:male, 8:3) and males in the hepatocellular carcinoma group (male:female, 10:1). None of the patients with hepatoblastoma were hepatitis B surface antigen positive, in contrast to 64% of the hepatocellular carcinoma group. Only 45% of the hepatocellular carcinomas were resectable at presentation and this figure remained unchanged following chemotherapy. A total of 91% of hepatoblastomas were resectable, four at presentation, and a further six after chemotherapy. Tumour rupture was more common in patients with hepatoblastoma than in those with hepatocellular carcinoma (36% versus 9% of cases, respectively). Mortality rates were considerably higher among the hepatocellular carcinoma group than the hepatoblastoma group in this series. CONCLUSION: Childhood hepatoblastoma and hepatocellular carcinoma differ with respect to age and tumour stage at presentation, hepatatis B surface antigen status, tendency to rupture, chemosensitivity, and prognosis.

Carcinoma, Hepatocellular↗
PubMed2001

Inhibin binding sites and proteins in pituitary, gonadal, adrenal and bone cells.

Activin signals via complexes of type I (50-55 kDa) and II (70-75 kDa) activin receptors, but the mechanism of inhibin action is unclear. Proposed models range from an anti-activin action at the type II activin receptor to independent actions involving putative inhibin receptors. Two membrane-embedded proteoglycans, betaglycan and p120, have recently been implicated in inhibin binding, but neither appears to be a signalling receptor. The present studies on primary cultures of rat pituitary and adrenal cells, and several murine and human cell lines were undertaken to characterise inhibin binding to its physiological targets. High affinity binding of inhibin to the primary cultures and several of the cell lines, like that previously described for ovine pituitary cells, was saturable and reversible. Scatchard analysis revealed two classes of binding sites (K(d) of 40-400 and 500-5000 pM, respectively). Affinity labelling identified [125I]inhibin binding proteins with apparent molecular weights of 41, 74, 114 and >170 kDa in all cell types that displayed high affinity, high capacity binding of inhibin. Additional labelling of a 124 kDa species was evident in gonadal TM3 and TM4 cell lines. In several cases, activin (> or =20 nM) competed poorly or not at all for binding to these proteins. The 74, 114 and >170 kDa inhibin binding proteins in TM3 and TM4 cells were immunoprecipitated by an anti-betaglycan antiserum. These three proteins correspond in size to the activin receptor type II and the core protein and glycosylated forms of betaglycan, respectively, that have been proposed to mediate anti-activin actions of inhibin, but the identity of the 74 kDa species is yet to be confirmed. Studies of [125I]inhibin binding kinetics and competition for affinity labelling of individual binding proteins in several cell lines suggest these three species and the 41 and 124 kDa proteins form a high affinity inhibin binding complex. In summary, common patterns of inhibin binding and affinity labelling were observed in inhibin target cells. Novel inhibin binding proteins of around 41 and 124 kDa were implicated in the high affinity binding of inhibin to cells from several sources.

Activin Receptors↗