Search PubMed⌕ Search

Biomedical subjects

S T Chan

Publications and source records attributed to S T Chan.

At least 37 records · Page 2Linked to original sources
PubMed2000

A non-invasive isotope dilution technique for quantifying hepatic blood flow using radiolabelled red blood cells.

Clinically significant changes in hepatic haemodynamics accompany the development of portal hypertension, hepatocellular carcinoma, liver metastases and liver cirrhoses, and after major liver resection. Hepatic blood flow parameters, such as hepatic arterial flow (HAF), hepatic portal flow (HPF), total hepatic blood flow (THBF) and hepatic perfusion index (HPI), are useful adjuncts to the diagnosis of liver pathology, the evaluation of disease progress and prognostication. Here, we describe a non-invasive method that combines the measurement of these parameters in a single study in real time. Red blood cells from eight pigs were labelled with 99Tc(m) using an in-vitro method and re-injected into the pigs. Data acquisition over the heart, lungs, liver and kidneys was started immediately and a blood sample was obtained 15 min post-injection. Hepatic arterial flow was determined from the ratio of the maximum gradients between the integrated time-activity curve of the left ventricle and the first-pass time-activity curve of the liver before the peak of the kidneys time-activity curve. The hepatic perfusion index was determined by comparing the slope of the liver time-activity curve before and after the kidney peak. Hepatic portal flow was determined from the hepatic arterial flow and the hepatic perfusion index, and total hepatic blood flow was determined as the sum of arterial and portal flow. The results were compared against those obtained from a clearance method using 99Tc(m)-DISIDA. The average hepatic perfusion index was 0.38, and the average hepatic arterial flow and hepatic portal flow were 168.3 +/- 52.9 and 274.6 +/- 60.1 ml x min(-1) respectively. The average total hepatic blood flow was 442.8 +/- 53.5 ml x min(-1), while the total hepatic flow determined by 99Tc(m)-DISIDA clearance was 419.7 +/- 62.6 ml x min(-1). No significant difference in total hepatic blood flow was found between the two methods. The results of this study show that it is possible to obtain all hepatic haemodynamics data in a single study using a non-invasive method.

Animals↗
PubMed2000

Transurethral surgery and the adductor spasm.

INTRODUCTION: Transurethral surgery has become the dominant treatment for bladder and prostatic tumours. Regional anaesthesia is the favoured anaesthetic technique but adductor spasm leading to bladder wall perforation and increased morbidity is not uncommon. This review seeks to outline the cause, risk factors predisposing to this complication and the various techniques that have been adopted to eradicate it. METHODS: Literature search was performed from PubMed (1965 onwards). All studies related to obturator nerve stimulation or adductor spasm in transurethral surgery were short-listed. RESULTS: Various methods have been attempted. These ranged from local blockade of the obturator nerve, periprostatic and subvesical lignocaine infiltration, changing the site of the inactive electrode, reduction of the electrocoagulation voltage and general anaesthesia with muscle relaxants. CONCLUSIONS: Hitherto, local blockade of the obturator nerve, either by the direct method or "3-in-1" method is the most effective in preventing this complication. With the aid of a nerve stimulator, greater accuracy and use of smaller volumes of local anaesthetic will improve the safety of this block.

Female↗
PubMed1999

Separation of bovine serum albumin and its monoclonal antibody from their immunocomplexes by sodium dodecyl sulfate-capillary gel electrophoresis and its application in capillary electrophoresis-based immunoassay.

A non-competitive immunoassay was performed by sodium dodecyl sulfate-capillary gel electrophoresis with UV detection using bovine serum albumin (BSA) and monoclonal anti-BSA. BSA, anti-BSA and their immunocomplexes were well resolved under non-denaturing conditions. A linear calibration curve was obtained and can be used for the quantification of anti-BSA. The limit of detection of anti-BSA was 0.1 microM under the present conditions. Compared with capillary zone electrophoresis, we believed that this method has the potential to be used as a more general format for performing capillary electrophoresis-based immunoassay of medium- and large-sized analytes.

Antibodies, Monoclonal↗
PubMed1999

Use of capillary electrophoresis-based competitive immunoassay for a large molecule.

A systematic study on the optimization of capillary electrophoresis-based immunoassay (CEIA) was performed using bovine serum albumin (BSA) and monoclonal anti-BSA. The immunocomplex could not be resolved from free BSA or anti-BSA with UV detection. When fluorescein isothiocyanate-labeled BSA (FITC-BSA) was used as tracer, the free and bound FITC-BSA were well separated giving definite peaks with laser induced fluorescence detection. The factors affecting the separation of the free and bound FITC-BSA, including voltage, pH and ionic strength of the running buffer, were systematically analyzed. Competitive CEIAs were demonstrated in uncoated and coated capillaries with whole or Fab fragment of the antibody. The coefficient of variation for the quantification of BSA in coated capillary was less than that in uncoated capillary. This study demonstrated that competitive CEIA could be applied to quantify high-molecular-mass protein in biological fluids.

Antibodies, Monoclonal↗
PubMed1999

Relationship of thyroid blood flow to reproductive events in normal Chinese females.

The purpose of this study was to investigate the blood flow characteristics in the superior thyroid artery (STA) in normal females of prepubertal, reproductive, and postmenopausal age. The study was performed in 29 prepubertal girls, 27 females of reproductive age, and 26 postmenopausal women. The peak systolic velocity (PSV) and the pulsatility index (PI) of the STA were measured repeatedly during one menstrual cycle in females of reproductive age, and measured once in each prepubertal and postmenopausal subject. Different waveforms were observed in females of prepubertal, reproductive, and postmenopausal age. The PSV of the STA increased progressively in females from prepubertal to postmenopausal phases. The PI of the STA in all of the prepubertal girls was lower than that of adult females in different phases of the menstrual cycle. In adult females, the PI in the follicular phase was significantly higher than those in the ovulatory and luteal phases. In all of the postmenopausal women, the PI was comparable to that in older prepubertal subjects and in adult females during the ovulatory and luteal phases. The results suggest that oestrogen may affect thyroid blood flow during the normal menstrual cycle. Growth and progressive change of arterial structure are suggested to affect the thyroid blood flow in prepubertal and postmenopausal states.

Adult↗
PubMed1999

Bile duct injuries during laparoscopic cholecystectomy: a collective experience of four teaching hospitals and results of repair.

BACKGROUND: Laparoscopic cholecystectomy has been performed in Singapore since 1990 and, up until the end of 1997, a total of 4445 procedures had been performed in the four major teaching hospitals. Although bile duct injuries were thought to have increased following the introduction of laparoscopic cholecystectomy, there have been no reviews done on the incidence of these injuries in the Singapore context. METHODS: The present retrospective review aimed to audit the rate of bile duct injuries in the four major teaching hospitals in Singapore and to document the results of management of these injuries. RESULTS: Of the 4445 procedures performed, there were 19 (0.43%) cases of bile duct injuries. These involved the common hepatic duct (n = 8), common bile duct (n = 10), and the right hepatic duct (n = 1). The underlying gall bladder pathology included non-inflamed gall bladders (n = 10), acute cholecystitis (n = 4), Mirrizzi's syndrome (n = 3) and mucocele of the gall bladder (n = 2). Transection of the duct accounted for the majority of the injuries. Eleven bile duct injuries were identified at the time of operation. These were primarily repaired over a T tube (n = 4) or by a bilio-enteric bypass (n = 7). The remainder were diagnosed at a median of 7 days (range: 1-556 days) after surgery with a presentation of jaundice or pain. These were repaired by bilio-enteric anastomosis (n = 7) and closure over a T tube (n = 1). Three patients developed strictures subsequently, two following bilio-enteric repair after delayed diagnosis and one following immediate primary repair over a T tube. One patient developed intrahepatic stones and required a left lateral segmentectomy. CONCLUSIONS: The experience of a 0.43% bile duct injury rate is comparable to the best results from most large series in the West. Inflammation at Calot's triangle is an important associated factor for injury. Early recognition and prompt repair affords good results, and hepaticojejunostomy is recommended as the repair of choice.

Adult↗
PubMed1999

Splenic actinomycosis.

We report a rare case of abdominal actinomycosis occurring in the spleen and review the literature on abdominal actinomycosis.

Actinomycosis↗
PubMed1999

Use of EMLA cream or alfentanil for analgesia during ophthalmic nerve blocks.

This prospective double-blind study compared the effectiveness of EMLA with alfentanil and placebo in reducing the overall pain during ophthalmic nerve blocks. Seventy-five patients scheduled for cataract surgery were divided into three groups. Patients in the EMLA group had EMLA cream applied over skin areas corresponding to injection sites for retrobulbar and facial nerve blocks one hour before the nerve blocks, and placebo intravenous normal-saline injection 2 minutes before the first nerve block. The alfentanil group had placebo cream applied and intravenous alfentanil 10 micrograms.kg-1 while patients in the placebo group received placebo cream and intravenous normal-saline at similar time intervals prior to the nerve blocks. Patients then received facial nerve blocks and retrobulbar block by the same surgeon. Pain scores by patients and independent observers were significantly lower in the EMLA and alfentanil groups compared to placebo (P < 0.005) with no significant difference between the EMLA and alfentanil groups.

Aged↗
PubMed1998

Alteration of thyroid blood flow during the normal menstrual cycle in healthy Chinese women.

The purpose of this study was to investigate the relationship between thyroid activity and the menstrual cycle by measuring the Doppler parameters of the superior thyroid arteries in women of reproductive age. The study was performed in 27 healthy Chinese women aged between 19 and 28 y for one menstrual cycle, and 25 age-matched healthy Chinese men for 3 weeks for comparison. In women, the peak systolic velocity increased from the follicular phase to the luteal phase, and the pulsatility index decreased from the follicular phase to the ovulatory phase and increased slightly in the luteal phase. In men, alterations in the pattern of thyroid blood flow were not observed; however, the average values of Doppler parameters during the study period in women were similar to those in men. The gender difference in the pattern of flow characteristics in the superior thyroid artery suggests effects of estrogen on thyroid function.

Adolescent↗
PubMed1998

Preventable trauma deaths in Singapore.

BACKGROUND: This study was undertaken to determine the incidence of preventable trauma death at a non-designated trauma centre in Singapore. METHODS: A retrospective audit was carried out on all trauma deaths that occurred between January 1993 and December 1994 at the National University Hospital, Singapore. Of the 138 deaths, 38.4% (53/138) of patients were dead on arrival and were omitted from the study. Data from the remaining 85 deaths were summarized and presented before a multidisciplinary review board and injuries were scored according to the Abbreviated Injury Scale (AIS). RESULTS: Except for one patient, all deaths had an AIS score of 16 or greater. Sixty-one per cent (52/85) of deaths were the result of severe head injuries, and the rest had severe injuries in more than one body region. Following the guidelines of the Trauma Research and Education Foundation of San Diego, the incidence of 'not preventable', 'potentially preventable' and 'frankly preventable' deaths were 77.6, 15.3 and 7.1%, respectively. The most common errors in management were caused by delays in inter-departmental transfer (25.9%) and missed initial diagnosis (16.5%). After assessment by the Coroner's Office, autopsies were carried out in 60% of the cases and yielded information that altered the assessment of preventable deaths, particularly in the group with multiple injuries. CONCLUSIONS: The present study concludes that the preventable death rates in the National University Hospital are comparable to those in non-trauma designated centres elsewhere. There can only be a decrease in the preventable death rate if an improved system of pre-hospital trauma care, improved interdisciplinary communication, closer supervision of the initial attending physicians and stricter protocols on clinical monitoring are established.

Abbreviated Injury Scale↗
PubMed1998

Partial purification of embryotrophic factors from human oviductal cells.

Embryotrophic factors from human oviductal cells were partially purified by liquid chromatographic methods. The conditioned medium from human oviductal cell culture was fractionated successively by concanavalin A (Con-A) affinity chromatography, ion-exchange chromatography and gel filtration. The presence of the embryotrophic activity in the eluates was determined by the stimulatory effects on the development of mouse embryos in vitro. The fraction that did not bind to the lectin Con-A possessed no embryotrophic activity. Ion-exchange chromatography separated the glycoproteins that bound to Con-A into five fractions. Three of them significantly enhanced blastulation as well as conceptus formation. Gel filtration further separated these embryotrophic fractions into five fractions. Three of them with molecular weights of 154 +/- 1, 164 +/- 0.2 and 207 +/- 0.3 kDa significantly stimulated blastulation of mouse embryos. The results of this study demonstrated that several embryotrophic factors with different biochemical properties contributed to the embryotrophic effect of the human oviductal cell/mouse embryo co-culture system.

Animals↗
PubMed1998

Abdominal surgery in human immunodeficiency virus (HIV) infected patients--early local experience.

The prevalence of human immunodeficiency virus (HIV) infection is increasing in Singapore. The surgical experience, however, remains limited. A retrospective review of 13 HIV-positive patients requiring abdominal surgery within Singapore was done. There were 4 females and 9 males with age ranging from 21 to 44 years. Operations included appendicectomy, colectomy, splenectomy, intestinal bypass, gastrostomy and exploratory laparotomy. Pathologic findings directly related to HIV infection were found in two-fifths (5 out of 13) of these patients. A low CD4+ count or signs of full-blown acquired immunodeficiency syndrome (AIDS) were not associated with a higher likelihood of HIV-related pathology; neither did it preclude a successful outcome. There were 2 early postoperative deaths, both with HIV-related pathology. Five of our patients who survived their abdominal surgery died on follow-up with a median survival of 17 months. In patients with typical surgical problems, e.g. appendicitis and torsion of the ovary, early surgery allows for rapid recovery similar to normal surgical patients. Care of these patients is best provided by surgeons with experience and interest in this condition together with infectious diseases physicians. Even palliative surgery offers a respite from acute and often severe problems and improves the quality of life significantly. Two patients with AIDS presented with sepsis and diffuse abdominal tenderness. Subsequent laparotomy revealed only primary bacterial peritonitis. For patients with AIDS and non-localizing abdominal signs, alternative non-invasive diagnostic modalities such as computed tomographic (CT) scan should be considered.

Abdomen↗
PubMed1998

Ambulatory anorectal surgery--is it feasible locally?

Currently, anorectal procedures are done in an inpatient setting in most local hospitals. This study examines the feasibility of performing these procedures in an outpatient setting. Patients (age range 16 to 65 years) with anorectal complaints requiring surgery were randomized into 2 groups of 40 patients each. Procedures performed included haemorrhoidectomy, fistulotomy, lateral sphincterectomy, excision of rectal polyps and examination under anaesthesia. The first group was managed in the conventional inpatient setting with regional anaesthesia. The second group was done on an ambulatory basis with local anal block. Intravenous and oral ketorolac was used for postoperative pain control and patients were discharged about 4 hours postoperatively. No complications were noted in the second group while the first group had 2 cases of acute urine retention requiring temporary catheterisation and 2 cases of significant bleeding requiring hospitalisation. Pain and satisfaction scores for both groups were similar. Anorectal surgery can be performed in an outpatient setting locally with safety and efficacy. The cost savings can be significant.

Adolescent↗
PubMed1997

Transfection of rat brain cells by electroporation.

Genetic intervention is a powerful means for answering basic biological questions about molecular events taking place in brain cells underlying complex behaviors. Traditional transfection method has proved difficult to apply to neuronal cells. We therefore described an alternative procedure for introducing DNA into cultured rat brain cells by electroporation. The various parameters involving the voltage, capacitance and electroporation buffer are investigated. We found that this transfection procedure is simple, reproducible and applicable to rat brain cells in vitro.

Animals↗
PubMed1997

Effects of physical barriers in prevention of adhesions: an incisional hernia model in rats.

BACKGROUND: Adhesion formation between viscera and mesh is almost inevitable following incisional hernia repair with prosthetic mesh. Such adhesions may lead to intestinal obstruction and enterocutaneous fistulae formation and make further laparotomies extremely difficult. Sodium carboxymethylcellulose (SCMC) and Interceed TC7 (oxidized regenerated cellulose) as physical barriers have been shown to be effective in reducing postoperative adhesions. MATERIALS AND METHODS: To evaluate the effects of SCMC and Interceed TC7, we used an incisional hernia model in rats. A ventral abdominal defect (15 x 25 mm) was created in each of 36 male rats which were then divided into three equal groups. In Group I (control) the defect was repaired with polypropylene mesh (PPM) only; in Group II the defect was repaired after a layer of Interceed TC7 was laid over the viscera with Interceed TC7-covered PPM; in Group III the defect was repaired after a layer of SCMC was laid over the viscera with SCMC-coated PPM. Six of the animals from each group were sacrificed at Postoperative Day 7 and the adhesions were scored. The remaining 6 were sacrificed at Day 30 and histological evaluation was made in addition to the adhesion score. RESULTS: Animals in the SCMC-treated group developed significantly less adhesions (P = 0.0002) compared with control and Interceed TC7-treated groups. However, histological analysis revealed poor fibroblast proliferation with impaired wound healing in the SCMC group. CONCLUSION: SCMC prevented adhesion formation but seriously impaired wound healing, and Interceed TC7 was ineffective in preventing adhesion in this model.

Animals↗
PubMed1997

Expression of differential nitric oxide synthase isoforms in human normal gastric mucosa and gastric cancer tissue.

The present study investigated the expression and distribution of three isoforms of nitric oxide synthase (NOS) in different anatomical regions of the human stomach and in gastric neoplastic tissues by immunohistochemistry using specific antibodies. Intracellular localization of individual isoenzymes of NOS was detected in normal gastric mucosa. Gastric cancer tissues had a marked reduction of all three NOS isoforms expression. The expression of the endothelial NOS, neuronal NOS and inducible NOS in the tumor tissue was significantly lower than in normal gastric mucosa (P = 0.01, P = 0.02, P < 0.01, respectively). In the tumor tissue the expression of inducible NOS was significantly lower than the expression of both constitutive forms of NOS (P < 0.01). There was a tendency to higher expression of both constitutive forms of NOS in earlier stages T2 of the tumor compared to advanced T4 tumor. In contrast, the expression of inducible NOS was higher than in the advanced T4 tumor than in the earlier stages T2 of the tumor. The mapping of the expression of endothelial NOS, neuronal NOS and inducible NOS in human stomach showed higher expression of NOS isoforms in the distal third than in the proximal third of the stomach (P = 0.03, P = 0.04, P = 0.01, respectively). We conclude that there is greater expression of NOS in the stomach corpus and in antrum than in the proximal third of the normal human stomach mirroring the anatomical predilection of common pathological changes in this part of the human stomach. Furthermore, there was loss of the expression of individual isoenzymes in gastric neoplasms.

Adult↗