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Biomedical subjects

B K Tan

Publications and source records attributed to B K Tan.

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

Flavonol-cinnamate cycloadducts and diamide derivatives from Aglaia laxiflora.

Leaf extracts of the Malaysian plant Aglaia laxiflora provided two cytotoxic compounds, a new rocaglaol rhamnoside (1), a known rocaglaol (2), new (but inactive) flavonol-cinnamaminopyrrolidine adducts (3-6), and their probable biosynthetic precursors (7 and trimethoxyflavonol). All structures were elucidated primarily by 2D NMR spectroscopy. The structure and stereochemistry of aglaxiflorin A (3) were confirmed by single-crystal X-ray crystallography.

Animals↗
PubMed2000

Navigating the internet maze.

The 'internet-driven information age' is a term in common usage, implying that everyone can access all the information they need, when they need it. The purpose of this brief paper is to outline some web sources that highlight the possibilities and potential for accessing web-based knowledge. From this the clinician will be encouraged to follow leads along the labyrinth of links to a greater appreciation of how this resource can be used to shape their practice. Examples of web links are provided for: search engines; library-based sources, including medical databases and electronic journals; evidence-based practice databases, mail-groups; electronic conferences; research centres; and general health sources. Importantly, this review does not aspire to be all-inclusive, for the web changes, chameleon-like, to the seasons. The web is here to stay. It will provide the framework for much education and will guide clients to a greater appreciation of their disease or disability than ever before. It may ultimately be the tool through which health fund agents will promote best practice, including self-help to clients, and therefore direct discriminating individuals to select health practitioners who have been endorsed by professional and fund agencies as providing a contemporary service which conforms to evidence-based practice.

Humans↗
PubMed2000

Proliferative potential in nasopharyngeal carcinoma: correlations with metallothionein expression and tissue zinc levels.

Metallothionein (MT) is a cysteine-rich protein with pleiotropic functions and a high binding affinity for heavy metals. The present study was designed to examine the relationship between MT expression and tissue zinc levels in conjunction with cell proliferation in nasopharyngeal cancer (NPC). Proliferative activity in NPC was quantified by Ki67 immunolabelling and MT expression was determined by immunohistochemistry. Total zinc and subcellular zinc fractions were analysed by flame atomic absorption spectrometry. MT immunostaining was observed in the nuclei of NPC cells, with the percentage MT immunopositivity ranging from 3.0 to 59.7%. Thirteen tumours displayed weak MT staining and the remaining 11 showed moderate to strong immunostaining. There was a significant positive correlation between MT and Ki67 positivity (P = 0.0127). Tissue zinc levels were higher in NPC as compared with benign nasopharyngeal tissues (4.800 +/- 0.4610 versus 2.889 +/- 0.4045 microgram/g dry wt tissue, respectively; P = 0.0122). Nuclear zinc levels in NPC were significantly higher than levels in membrane and cytosolic fractions (mean zinc levels 1.4840 +/- 0.1489, 0.6286 +/- 0.0789 and 0.3014 +/- 0.0250 microgram/mg protein, respectively). A linear relationship was also observed between nuclear zinc levels and MT immunostaining (P = 0.0024) as well as with Ki67 immunopositivity (P = 0.0123). Our results show that MT and zinc are correlated with proliferative activity in NPC, providing further insights into the biology of this enigmatic and aggressive tumour.

Carcinoma↗
PubMed2000

Anatomic basis of safe percutaneous subclavian venous catheterization.

BACKGROUND: The technique of percutaneous catheterization of the subclavian vein by the infraclavicular approach is dependent on the location of the subclavian vein in relation to the clavicle. The purpose of this study was to analyze the anatomic relationship between these two structures and how it is influenced by changes in shoulder positioning. METHODS: Dissections of the infraclavicular region were performed in seven fresh cadavers and linear measurements made to determine the extent of overlap between the vein and the clavicle in different shoulder positions. RESULTS: When the shoulder was in neutral position, the subclavian vein was overlapped by the medial third or more of the clavicle and this segment of bone was able to serve as a landmark for the vein. However, shoulder elevation displaced the clavicle cephalad and reduced the degree of overlap. Mild shoulder retraction increased the area of contact between the vein and the undersurface of the clavicle, whereas protraction lifted the clavicle off the vein. CONCLUSION: Infraclavicular subclavian venipuncture should be performed with shoulders in a neutral position and also in slight retraction. An appreciation of the anatomic relationship between the clavicle and the subclavian vein is the key to successful execution of this technique.

Adult↗
PubMed2000

Extended lower trapezius island myocutaneous flap: a fasciomyocutaneous flap based on the dorsal scapular artery.

The lower trapezius island myocutaneous flap is a useful flap in head and neck reconstruction. It is thin and pliable and can reach defects in most areas of the head and neck. Its usefulness in head and neck reconstruction has often been limited or discouraged by reports of significant failure rates. In this study, the vascular anatomy and clinical use of the extended lower trapezius myocutaneous flap based solely on the dorsal scapular artery system are elucidated, and experience gained performing 20 flaps over the past 5 years by using the extended lower trapezius myocutaneous flap is reported. The vascular anatomy of the dorsal scapular artery system is reviewed in 13 fresh cadaveric dissections by using methylene blue, latex injection studies, and radiologic examination.

Aged↗
PubMed2000

The lateral forearm flap as a modification of the lateral arm flap: vascular anatomy and clinical implications.

The forearm extension of the lateral arm flap was introduced on the basis of the vascular territory of the posterior radial collateral artery extending beyond the elbow into the forearm. However, there is controversy as to whether the posterior radial collateral artery extends as a single trunk below the elbow or if it terminates more proximally with only a rich vascular plexus extending beyond the elbow. The purpose of this study was to revisit the artery's anatomy in the region of the elbow and to study its distribution in the forearm. Using latex and barium-gelatin injections of the posterior radial collateral artery in ten cadaveric upper limbs, it was observed that terminal branching of the artery occurred 4.5 cm proximal to the lateral epicondyle of the humerus. Distal to the epicondyle, the terminal branches of the posterior radial collateral artery were seen to fan out as finely arborized branches supplying the lateral forearm skin. No single, constant vascular trunk to the forearm skin could be identified. Furthermore, in its distribution toward the periphery, the terminal branches of the posterior radial collateral artery took an increasingly superficial course. Proximal to the epicondyle, the vessels lay deep within the subcutaneous fat, whereas distal to the epicondyle, they were very close to skin. These findings suggest that lateral forearm skin cannot be islanded without risk of vascular disruption and that the distally sited flap should include skin proximal to the epicondyle for safety.

Cadaver↗
PubMed2000

Effects of an ethanolic extract of Gynura procumbens on serum glucose, cholesterol and triglyceride levels in normal and streptozotocin-induced diabetic rats.

AIM OF STUDY: The aim was to demonstrate the effects of the leaves of Gynura procumbens (Lour.) Merr. on blood sugar and lipid levels in experimental animals. METHODOLOGY: We obtained an ethanolic extract of the leaves of G. procumbens and monitored the effects of an oral administration of (i) different single doses of the extract on oral glucose tolerance in streptozotocin-induced diabetic and normal rats and (ii) fourteen doses over 7 days on serum cholesterol and triglyceride levels in streptozotocin-induced diabetic rats. Metformin and glibenclamide were used as positive control drugs. RESULTS: The extract, at single doses of 50, 150 and 300 mg/kg orally, significantly suppressed the elevated serum glucose levels in diabetic rats; 150 mg/kg was found to be the optimum hypoglycaemic dose. The extract however did not significantly suppress the elevated serum glucose levels in normal rats, unlike glibenclamide. Metformin, but not glibenclamide, improved glucose tolerance in the diabetic rats. When the optimum dose was given to diabetic rats for 7 days, the extract significantly reduced serum cholesterol and triglyceride levels in these rats. CONCLUSION: These results indicate that the leaves of G. procumbens may have biguanide-like activity.

Administration, Oral↗
PubMed2000

Salvia miltiorrhiza and ischemic diseases.

The demonstration of beneficial effects of salvia miltiorrhiza (DanShen) on ischemic diseases has revolutionized the management of angina pectoris, myocardial infarction (MI) or stroke in Chinese society. Experimental studies have shown that DanShen dilated coronary arteries, increased coronary blood flow, and scavenged free radicals in ischemic diseases, so that it reduced the cellular damage from ischemia and improved heart functions. Clinical trials also indicated that DanShen was an effective medicine for angina pectoris, MI, and stroke. This review will focus on DanShen's effects in angina pectoris, MI and stroke.

Angina Pectoris↗
PubMed2000

Anti-diabetic property of ethanolic extract of Andrographis paniculata in streptozotocin-diabetic rats.

AIM: To investigate the anti-diabetic effect of a crude ethanolic extract of Andrographis paniculata in normal and streptozotocin (STZ)-induced diabetic rats. METHODS & RESULTS: Oral administration of the extract at different doses (0.1, 0.2, and 0.4 g/body weight) significantly reduced the fasting serum glucose level in STZ-diabetic rats compared to the vehicle (distilled water), but not in normal rats. This effect was dose-dependent. A similar result was seen with metformin (0.5 g/body weight). In the glucose tolerance test, an oral administration of the extract at the same doses suppressed the elevated glucose level in normal and diabetic rats, as did metformin. The effects were also dose-respondent. In the long-term experiment, the extract (0.4 g/body weight), metformin (0.5 g/body weight), and vehicle were given twice daily to diabetic rats for 14 d. On d 15, fasting serum glucose levels were found to be significantly lower in the extract- and metformin-treated groups (P < 0.001) than in the vehicle-treated group. The mean food and water intakes over 14 days were significantly lower in the extract-treated group (P < 0.05, P < 0.01, respectively) and also in the metformin-treated group (both P < 0.001) when compared to the vehicle-treated group. No significant change in insulin level was observed among the 3 groups of diabetic rats. The extract, like metformin, maintained the leptin levels after 14-d treatment, whereas this level was significantly decreased (P < 0.05) in the vehicle-treated group. The activity of hepatic glucose-6-phosphatase (G-6-Pase) was significantly reduced by the extract as well as by metformin (both P < 0.05). No significant difference in hepatic glycogen stores was noted among the 3 groups. The extract caused 49.8% reduction of fasting serum triglyceride levels, compared to 27.7% with metformin. However, neither the extract nor metformin significantly affected serum cholesterol level. CONCLUSION: The ethanolic extract of A paniculata possesses antidiabetic property. Its antidiabetic effect may be attributed at least in part to increased glucose metabolism. Its hypotriglyceridemic effect is also beneficial in the diabetic state.

Animals↗
PubMed1999

Lipid peroxidative stress and antioxidative enzymes in brains of milk-supplemented rats.

Skim milk cultured with lactic acid bacteria has been previously reported to reduce lipid peroxidation in rat livers. In this study, the effects of skim milk and cultured milk supplementation on peroxidative stress in brains of weanling rats were investigated. We observed a reduction of brain thiobarbituric acid reacting substances (TBARS) concentration in milk-supplemented animals as compared with controls. In brains of control rats, the superoxide dismutase (SOD) enzyme levels were significantly higher than those from the milk-supplemented animals. In addition, SOD activity in control animal brains had a positive correlation with the TBARS concentration. There was no significant differences in the brain glutathione-S-transferase (GST) levels of all the three groups of animals. The results suggest that milk supplementation may be beneficial in reducing peroxidative stress in the developing rat brain.

Animals↗
PubMed1999

The onset of atherosclerotic lesion formation in hypercholesterolemic rabbits is delayed by iron depletion.

The theory that iron may play a significant role in atherogenesis by promoting the formation of free radicals is controversial. Previous results using the new technique of nuclear microscopy showed a seven-fold increase in iron concentrations within newly formed atherosclerotic lesions in hypercholesterolemic rabbits compared to healthy artery tissue. In a follow-up time sequence study described here, we show that iron accumulation occurs at the onset of lesion formation. In addition, weekly bleeding decreases the iron uptake into the artery wall and delays the onset of atherogenesis. These results provide direct evidence for a key role of iron in initiating atherogenesis.

Animals↗
PubMed1999

Effects of 14-deoxyandrographolide and 14-deoxy-11,12-didehydroandrographolide on nitric oxide production in cultured human endothelial cells.

14-deoxyandrographolide (DA) and 14-deoxy-11,12-didehydroandrographolide (DDA) are two diterpenoids isolated from A. paniculata, a popular folk medicine used as an antihypertensive drug in Malaysia. We have previously reported that DDA exhibited a greater hypotensive effect in anaesthetized rats and a vasorelaxant activity in isolated rat aorta, compared with DA. Their vasorelaxant activities were mediated through the activation of the enzymes, nitric oxide synthase (NOS) and guanylyl cyclase. The present study demonstrated that both DA and DDA stimulated nitric oxide (NO) release from human endothelial cells. DDA compared with DA caused a greater production of NO; this is in line with the finding of the earlier study that the vasorelaxant effect of DDA was more dependent on endothelium than DA.

Antihypertensive Agents↗
PubMed1999

Prefabrication of jejunum for challenging reconstruction of cervical esophagus.

A significant benefit exists for a jejunal replacement of the cervical esophagus, if indicated. The absence of available recipient vessels may impede free tissue transfer. If vascular induction between a vascular carrier and the selected jejunal segment is done as a kind of flap prefabrication, the jejunal interposition flap can be used without the need for complex microsurgery.

Adult↗
PubMed1999

Tissue microangiography using a simplified barium sulphate cadaver injection technique.

This study investigated the application of soft tissue X-ray imaging as a method of studying vascular anatomy in injected cadaveric specimens. The arterial system of the anatomical region of interest was perfused with a barium sulphate-gelatin suspension. After curing, the tissues were removed by meticulous dissection and examined using the soft tissue X-ray imaging system. This technique of microangiography was able to demonstrate the entire arterial system of the perfused specimen. This simplified technique shows great potential in the study of vascular anatomy of flaps.

Angiography↗
PubMed1999

Combined third and fourth toe transplantation.

Multiple toe transplantation has been established as an effective technique for restoring prehensile ability in the metacarpal hand. The combined third and fourth toe transplant is a new toe transplant that has been developed for bilateral metacarpal hand reconstruction. Since 1991, the combined third and fourth toe transplant was added to the armamentarium of toe transplants for metacarpal hands, although its role in metacarpal hand reconstruction has not been described previously. This article introduces the indications for combined third and fourth toe transplant, outlines relevant vascular anatomy, and discusses technical considerations pertaining to toe harvest and transplantation.

Adult↗
PubMed1999

Strategies in multiple toe transplantation for bilateral type II metacarpal hand reconstruction.

Multiple toe transplantation has been established as an effective means of restoring prehensile function in the metacarpal hand. The attainable outcome, however, must be weighed against potential donor site morbidity. Restoration of prehensile function in bilateral type II metacarpal hands can be achieved by reconstructing three opposable digits in the dominant hand and two opposable digits in the nondominant hand. This article outlines the strategy for optimizing functional outcome and discusses the rationale behind toe selection to reduce donor morbidity.

Adult↗
PubMed1999

A review of mandibular fractures in a craniomaxillofacial trauma centre.

This report is a retrospective review of 74 cases of mandibular fractures managed in a craniomaxillofacial trauma centre between January 1994 and May 1998. Demographic data revealed that 85% of the patient population were male, with a mean age of 27.5 years. The commonest causes of injury were motor vehicle accidents (48.6%), followed by assault (16.2%) and accidental falls (17.6%). In 25 patients (33.8%) the fractures were single. Of these, fractures of the condylar region were the most common (8 patients). The remaining patients sustained fractures in two or more anatomic sites. There were other associated facial fractures in 45.9% of patients. Trauma to other systems was present in 37.8%, with orthopaedic and neurosurgical injuries being the most common. Surgical management in the form of open reduction and internal fixation was carried out in 61 patients (82.4%). Maxillo-mandibular fixation was used as an adjunct to maintain occlusion and bony reduction in unstable and comminuted fractures (15 patients, 20.3%), and as the primary mode of treatment in patients with stable, undisplaced fractures, particularly condylar fractures, in which the pretraumatic occlusal relationship was not disrupted (9 patients, 12.2%). A successful outcome was defined as a stable and healed fracture, with restoration of functional occlusion, facial symmetry and facial aesthetics. Complications observed included temporomandibular joint dysfunction (10.8%), malocclusion (9.5%), infection (8.1%), implant exposure (5.4%), and non-union or delayed union (4.1%).

Accidents, Traffic↗