PubMed Health⌕ Search

Biomedical subjects

S M Tan

Publications and source records attributed to S M Tan.

32 records · Page 2Linked to original sources
PubMed1998

cDNA cloning reveals two mouse beta5 integrin transcripts distinct in cytoplasmic domains as a result of alternative splicing.

The integrin beta5 subunit has only been found to form a heterodimer with subunit alphav which acts as a vitronectin receptor. Integrin alphavbeta5 has been implicated in cell migration and growth factor-induced angiogenesis. In the present study, a mouse liver cDNA library was screened using a human beta5 cDNA fragment obtained by reverse transcriptase PCR (RT-PCR). Three of the clones (MB5, MB15 and MB17) overlapped to give an open reading frame, called beta5A, which is homologous to the human beta5 subunit. The sequence of another clone (MB26), called beta5B, was identical with beta5A, except for a deletion of 29 bp near the 3' end of the open reading frame. The 29 bp deletion resulted in an open-reading-frame shift and a completely different C-terminal sequence in beta5B. beta5A and beta5B were shown, by RT-PCR, to be co-expressed in most mouse tissues tested, although beta5B mRNA was detected at much lower levels than beta5A. beta5A and beta5B mRNAs were also detected in the mouse monocytic cell line, J774, and in isolated mouse peritoneal macrophages. Adhesion of peritoneal macrophages has been shown to up-regulate the expression of both beta5A and beta5B mRNAs. The 29 bp sequence begins with a putative intron-splicing donor site (GTGAT...). A 3' fragment of the mouse integrin beta5 gene was cloned by PCR and sequenced showing that the 29 bp sequence was also immediately followed by an intron. Therefore, the 29 bp sequence was apparently expressed as part of the beta5A mRNA but was spliced out as part of the downstream intron in beta5B. Since the cytoplasmic domains of the integrin beta subunits are important in cytoskeleton attachment and signalling, the two alternatively spliced beta5 isoforms may have distinct roles in cell adhesion and other cellular functions.

Alternative Splicing↗
PubMed1998

Ureteroscopic lithoclast lithotripsy: a cost-effective option.

Seventy-four consecutive cases of ureteral stones listed for ureteroscopic lithotripsy were studied prospectively. In all cases, the Wolf 7.5F or 9F ureteroscope was used in conjunction with the Swiss Lithoclast system. Dormia baskets were employed on four occasions to prevent forward propulsion of fragments. Ureteroscopic access to the stones was successful in 70 patients (95%). Lithoclast lithotripsy was successfully applied in 68 patients (92%), with complete fragmentation noted in 62 patients (91%), one requiring two sessions. The 6-week stone-free rate was 96% for these patients. Five patients with partial fragmentation had successful adjuvant SWL. The overall successful fragmentation rate was thus 84% (62 of 74) and 91% (67 of 74) in combination with adjuvant SWL. Cost analysis indicated a three-fold advantage for the Lithoclast over Candela lasertripsy. Ureteroscopic Lithoclast lithotripsy is a cost-effective treatment modality for ureteral stones.

Adult↗
PubMed1998

Non-operative treatment of breast abscesses.

BACKGROUND: Breast abscesses are conventionally treated by incision and drainage. This often requires general anaesthesia and a hospital stay. Non-operative treatment by needle aspiration and oral antibiotics is reported as a viable alternative. METHODS: All patients who presented with breast abscesses and who were assessed by one surgeon between November 1995 and January 1997 were managed using a conservative approach and they are the subjects of this study. RESULTS: Twenty-one consecutive patients were seen over a period of 26 months. All had non-lactational breast abscesses. Nineteen patients were successfully treated by needle aspiration and antibiotics while two patients required incision and drainage. The mean size of the aspirated abscesses was 3.5 cm (range 1-15 cm) and required an average of 2.4 aspirations (range 1-5). Of those treated by aspiration, three patients developed recurrent abscesses, two of which were successfully managed by repeat aspiration while one patient eventually required surgery. CONCLUSIONS: The majority of non-lactational breast abscesses seen in clinical practice can be treated without surgery by a combination of needle aspiration and antibiotics.

Abscess↗
PubMed1997

Purification and binding properties of a human ficolin-like protein.

Ficolin was initially identified from porcine uterus as a TGF-beta 1 binding protein and is considered to have an overall structure similar to that of the complement protein C1q and the collectins. Recent studies have shown that human ficolin is synthesized mainly by monocytes in peripheral blood and that it could potentially bind to sugar structures on microorganisms. The aim of the present investigations was to isolate ficolin from human plasma by affinity chromatography on immobilized sugars. A human serum protein was identified in the GlcNAc eluate from GlcNAc-Sepharose which migrated as a polypeptide of approx. 40 kDa on SDS-PAGE under reducing conditions and was, after further purification by FPLC on a mono-Q column, shown to have an identical N-terminal sequence, over the first 14 residues, to P35, a plasma protein having similar sequence and domain organisation to ficolin. This protein, named the ficolin-like protein, was shown to be sensitive to collagenase and similar to P35 in that it was also disulphide-linked into an oligomer of approx. 320 kDa. However, unlike P35, its binding to GlcNAc was independent of Ca2+. Gel-filtration studies showed that this ficolin-like protein also had a molecular weight of approx. 320 kDa under non-dissociating conditions. During the course of this study this ficolin-like protein was found to simply bind to CNBr-activated Sepharose which had been inactivated with Tris, and from which it could be eluted with GlcNAc. This ficolin-like protein was also shown to bind to GlcNAc, but not to mannose and maltose. The functional significance of the unusual binding property of this ficolin-like protein is not clear, but it has facilitated the development of a simple method for its purification.

Acetylglucosamine↗
PubMed1997

Duodeno-ureteric fistula secondary to chronic duodenal ulceration.

Renoalimentary fistulae are rare. When they occur, they are usually between the right renal pelvis and the duodenum. The primary pathology often resides in the kidney, and nephrectomy is often necessary in the management of such fistulae. We describe a case of an elderly man who presented with non-specific abdominal pains. He had a history of peptic ulcer which was treated with H2 antagonist. He was well for the past few years until recently when he experienced upper abdominal pains. Subsequent investigations showed a duodeno-ureteric fistula secondary to a chronic duodenal ulcer. The kidney was normal. Polya gastrectomy was performed and the patient recovered with complete resolution of his symptoms.

Chronic Disease↗
PubMed1996

Improvements on the purification of mannan-binding lectin and demonstration of its Ca(2+)-independent association with a C1s-like serine protease.

Mannan-binding lectin (MBL), previously called 'mannan-binding protein' or MBP, is a plasma C-type lectin which, upon binding to carbohydrate structures on micro-organisms, activates the classical pathway of complement. Purification of MBL relies on its Ca(2+)-dependent affinity for carbohydrate, but existing methods are susceptible to contamination by anti-carbohydrate antibodies. In the present study a sequential-sugar-elution method has been developed which can achieve a preparation of virtually pure MBL and its associated serine protease (MBL-associated serine protease, MASP) by two steps of affinity chromatography. In further separation of MASP from MBL, it was found that activated MASP was associated with MBL independent of Ca2+. Since MBL was found to bind to underivatized Sepharose 4B, the MBL-MASP complex was purified using Sepharose 4B and protease inhibitors were included to purify the complex with MASP in its proenzyme form. Analysis of thus-purified MBL-MASP complex by gel filtration on a Sephacryl S-300 column at pH 7.8 showed that the proenzyme MASP was also associated with MBL independently of Ca2+, but that the complex could be disrupted at a low pH (5.0). Therefore the mechanism of MBL-MASP-mediated complement activation appears to be significantly different from the C1-mediated classical pathway.

Calcium↗
PubMed1996

Primary amyloidosis of the bladder: a case report.

An otherwise healthy elderly lady who presented with gross haematuria was found to have a papillary lesion in her bladder. Histological examination of the lesion showed amyloid deposits. Investigations for systemic amyloidosis were all negative. Primary amyloidosis of the bladder is a rare clinicopathological condition with only 57 documented cases in the medical literature. It often mimics bladder carcinoma in presentation and cystoscopic appearance. Amyloid deposits in the bladder may be primary (organ-limited amyloidosis) or part of systemic amyloidosis. Exclusion of systemic amyloidosis is important for management and prognosis. Localised primary lesions are best treated with transurethral resection and recurrences are uncommon. Diffuse involvement of the bladder is difficult to manage and may require urinary diversion. We report the first case of primary amyloidosis of the bladder in Singapore.

Amyloidosis↗
PubMed1995

Laparoscopic varicocelectomy: technique and results.

OBJECTIVE: To determine the safety and efficacy of laparoscopic varicocelectomy in the treatment of symptomatic varicocele. PATIENTS AND METHODS: Indications for surgery were subfertility in 98 patients and pain in nine. All varicoceles were confirmed on Doppler ultrasound. Seventy-two per cent of the patients had left-sided varicoceles and bilateral varicoceles were seen in 27%. A three-puncture technique was used with carbon dioxide insufflation. The spermatic vessels were individually identified and clips were used to ligate the veins. The spermatic artery was preserved in all cases. The operation was performed on a day surgery basis with an average operative time of 61.4 min (56.6 min for unilateral and 75.8 min for bilateral varicocelectomy). RESULTS: Morbidity was low, with pneumoscrotum in two patients and wound infection in two others. Sixty-one patients for whom pre- and post-operative seminal analyses were available showed improvement in sperm count and motility, with a concomitant fall in the percentage of abnormal sperm forms. CONCLUSION: Laparoscopic varicocelectomy is safe and effective, causing minimal discomfort and allowing patients an early return to activity.

Adult↗
PubMed1995

Surgical treatment of symptomatic accessory navicular.

The accessory navicular is a known cause of foot pain. When symptomatic and conservative measures have failed, surgical intervention may be required. Simple excision of the ossicle or the Kidner procedure with transplantation of tibialis posterior tendon to the undersurface of the navicular bone may be done. Eighteen patients with symptomatic accessory navicular were reviewed at the Singapore General Hospital, Department of Orthopaedic Surgery 'O' Unit. All 18 patients had foot pain and restriction of activities. Thirteen noticed a prominence on the medial side of the affected foot and 7 had difficulty with shoe fitting. Nine underwent simple excision of the ossicle while the other 9 had the Kidner procedure done. The average follow-up period was 3.1 years. Both the simple excision and the Kidner procedure were equally successful in relieving symptoms in 15 out of the 18 cases. The Kidner procedure did not confer any particular advantage over simple excision.

Adolescent↗
PubMed1995

Traumatic bronchial rupture--a case report.

Traumatic bronchial rupture is a rarity. Its incidence is about 1.5% to 3% in most series of blunt chest trauma. We report a patient who presented after a road traffic accident with an apparently persistent pneumothorax which failed to respond to emergency treatment. This was later discovered to be due to a traumatic bronchial rupture. It is difficult to diagnose traumatic bronchial rupture, the main reason being that it is often not considered by doctors caring for the patient with blunt chest trauma in the Accident and Emergency Department. Failure to recognise this condition contributes to its high mortality. The authors would like to recommend that emergency bronchoscopy be carried out in patients with blunt chest trauma to exclude this potentially treatable condition. This is especially so if there are suggestive clinical features, such as the presence of extensive and spreading subcutaneous emphysema, pneumomediastinum, pneumothorax, haemoptysis, fractures of the first two ribs and respiratory distress. A history of massive blunt force to the chest wall as a mechanism of injury should also prompt the trauma team to consider the need for emergency bronchoscopy.

Accidents, Traffic↗
PubMed1992

A new technique for detecting oxytocinase activity in electrophoresis gels.

A sensitive staining method for the detection of oxytocinase (EC 3.4.11.3) activity in electrophoresis gels has been described. The method is based on the enzymatic release of p-nitroaniline (PNA) from two specific synthetic oxytocinase substrates, S-benzyl-L-cysteine-p-nitroanilide (BCN) and L-leucine-p-nitroanilide (LN), respectively. The PNA is then diazotized with sodium nitrite and subsequently coupled to a chromogen, N-(1-naphthyl)-ethylenediamine dihydrochloride (NED) to produce a deep pink/magenta colored azo-dye at the site of oxytocinase activity.

Aniline Compounds↗
PubMed1985

Prostaglandins, not cyclic GMP, inhibit oxytocinase isoenzymes from human amniotic fluid in vitro.

Two isoenzymes of oxytocinase (EC 3.4.11.3) activity were fractionated from human amniotic fluid samples between the 14th and 22nd weeks of gestation by Ultrogel acrylamide-agarose gel filtration and partially characterized. The isoenzymes were competitively inhibited by PGE1, PGE2 and PGF2 alpha more at pH 6.2 than at pH 6.8, whereas cyclic GMP (cGMP) and its 8-bromo derivative had no effect at either pH. The implications of these findings are discussed and it is suggested that since the activity of amniotic fluid oxytocinases is very low or minimal at or near term, inhibition of these by prostaglandins may not have physiological significance in the initiation of human parturition.

Aminopeptidases↗
PubMed1985

Repair of severe tissue loss and deformity of maxillofacial area.

Our experience in the management of 125 patients with massive facial defects since 1975 is detailed. The defects were closed in one of four principal ways (or a combination thereof): (1) free flap, (2) musculocutaneous flap, (3) forehead flap, and (4) dorsal tube flap. The surgical details and indications for each of these are outlined and examples given.

Adolescent↗