The removal of metallic single-walled carbon nanotubes using an aqueous two-phase system.

Here we report our findings on the removal of metallic single-walled carbon nanotubes using an aqueous two-phase system. The aqueous two-phase system contained as received carbon nanotubes, polyethylene glycol, dextran, N-methylpyrrolidone, cetyltrimethylammonium bromide, and water which phase separated into top and bottom phases. The top phase was dominated by polyethylene glycol whereas the bottom phase was dominated by dextran. The dextran-rich phase contained more semiconducting species while metallic species was more abundant in the polyethylene glycol rich-phase. It was found via Fourier-Transform Infrared Spectroscopy that cetyltrimethylammonium bromide only present in the dextran-rich phase. A selectivity mechanism is tentatively proposed and discussed.

Bacterial diversity on different surfaces in urban freshwater.

Microbial loads in freshwater systems have important implications in biogeochemical cycling in urban environments. Immersed surfaces in freshwaters provide surfaces for bacterial attachment and growth. Microorganisms that adhere initially to these surfaces play a critical role in biofilm formation and sustenance. Currently, there is little understanding on the type of organisms that initially adhere to different surfaces in urban canals. In this study, water from an urban stormwater canal was employed to allow bacteria to attach to different surfaces in a flowcell apparatus and understand the differences and changes in bacterial community structure. Bacterial communities were highly diverse on different surfaces as indicated by Jaccard's indices of 0.14-0.56. Bacteria on aluminium were the most diverse and on Plexiglas the least. Bacterial communities were highly dynamic in the early attachment phase and it changed by 59% between 3 and 6 h on aluminium. Specificity of attachment to surfaces was observed for some bacteria. Judicious use of materials in urban aquatic environment would help mitigate microbial load in urban waters.

LARG at chromosome 11q23 has functional characteristics of a tumor suppressor in human breast and colorectal cancer.

Deletion of 11q23-q24 is frequent in a diverse variety of malignancies, including breast and colorectal carcinoma, implicating the presence of a tumor suppressor gene at that chromosomal region. We examined a 6-Mb region on 11q23 by high-resolution deletion mapping, using both loss of heterozygosity analysis and customized microarray comparative genomic hybridization. LARG (leukemia-associated Rho guanine-nucleotide exchange factor) (also called ARHGEF12), identified from the analysed region, is frequently underexpressed in breast and colorectal carcinomas with a reduced expression observed in all breast cancer cell lines (n=11), in 12 of 38 (32%) primary breast cancers, 5 of 10 (50%) colorectal cell lines and in 20 of 37 (54%) primary colorectal cancers. Underexpression of the LARG transcript was significantly associated with genomic loss (P=0.00334). Hypermethylation of the LARG promoter was not detected in either breast or colorectal cancer, and treatment of four breast and four colorectal cancer cell lines with 5-aza-2'-deoxycytidine and/or trichostatin A did not result in a reactivation of LARG. Enforced expression of LARG in breast and colorectal cancer cells by stable transfection resulted in reduced cell proliferation and colony formation, as well as in a markedly slower cell migration rate in colorectal cancer cells, providing functional evidence for LARG as a candidate tumor suppressor gene.

Angiotensin receptor antagonist vs. angiotensin-converting enzyme inhibitor in Asian subjects with type 2 diabetes and albuminuria - a randomized crossover study.

BACKGROUND: Subjects with type 2 diabetes mellitus (T2DM) and albuminuria are at risk for progressive diabetic nephropathy. The relative blood pressure lowering and antialbuminuric efficacy of angiotensin receptor antagonist (ARB) vs. angiotensin-converting enzyme (ACE) inhibitor has not been well studied. METHODS: Forty-one ARB- and ACE inhibitor-naive T2DM subjects with albuminuria (>30 mg/g creatinine) were given either 50 mg of losartan (ARB) or 20 mg of quinapril (ACE inhibitor) (50% maximum dose) for 4 weeks, with a 4-week wash-out period in-between interventions in a crossover fashion. The order of intervention was randomized. The primary endpoint was the reduction of blood pressure and albuminuria. Secondary endpoint was changes in plasma transforming growth factor beta (TGF-beta). RESULTS: Among the 41 subjects, 66% were male. The mean age (s.d.) was 52 (10) years, and duration of diabetes was 8 (14) years. Blood pressure reduction (though not statistically significant) was similar on both interventions [systolic: losartan 3 (15) vs. quinapril 2 (13) mmHg, p = 0.52; diastolic: losartan 1 (9) vs. quinapril 2 (8) mmHg, p = 0.55]. However, amelioration of albuminuria [mean (s.e.)] was significantly greater with losartan [losartan vs. quinapril: -93 (82) vs. -49 (65) mg/g, p = 0.02]. There was no change in plasma TGF-beta levels [mean (s.d.)] on either treatment, losartan [before 12.1 (8.9) vs. after 11.9 (9.6) ng/ml, p = 0.68] and quinapril [11.1 (7.9) vs. 11.1 (7.8) ng/ml, p = 0.87). CONCLUSION: In Asian subjects with T2DM and albuminuria, 4 weeks of losartan therapy at 50 mg daily appeared to have greater antialbuminuric effect than 20 mg of quinapril.

Total gastrectomy for gastric cancer: the rationale for J-pouch reservoir.

This prospective study examines the results of total gastrectomy in 56 consecutive patients (38 males and 18 females) and compares Hunt-Limo-Basto J-pouch reconstruction (23 patients) with simple oesophago-jejunostomy (33 patients). There was no difference in morbidity and mortality between the two groups, which are fairly well-matched proportionately in age, concomitant disease and stage of disease. There was, however, a male predominance in the non-pouch group. Anastomotic leak occurred in only one patient with gastric reconstruction while one duodenal stump leak developed in the non-pouch patient. Construction of the stapled J-pouch extended the operation by a mean time of 14 min. The only advantage of the J-pouch is that it facilitates introduction of a larger diameter stapler for oesophago-jejunostomy. The nutritional benefit remains uncertain.

Surgical considerations in the Hartmann's procedure.

BACKGROUND: The present study examines the surgical outcome of the Hartmann's and Hartmann-type procedures, the problems with the remnant rectal stump and the issues related to the colorectal anastomosis as well as the differences in patient outcome. METHODS: One hundred and five consecutive patients (mean age 66) were evaluated. Surgical morbidity and mortality were analysed with regard to the colorectal pathology and the type of rectal stump remnant. The surviving patients were reviewed according to whether they had second-stage anastomosis. RESULTS: In 65% of cases there were obstructed or perforated malignancies and in 16% complicated diverticular diseases. The peri-operative mortality and morbidity were 11.4% and 24%, respectively. Seventy-two patients had intraperitoneal rectal stumps and stump blowout occurred in three intraperitoneal and one extraperitoneal remnant stumps. Local tumour recurrence (four) and diversion proctitis (three) were diagnosed in the rectal stump among asymptomatic patients. When the second-stage reversal of Hartmann's procedure was considered (35 cases), twice as many were performed for diverticular and other benign conditions as for tumour cases. CONCLUSIONS: Although there is a good anatomical basis for advocating extraperitoneal rather than intraperitoneal stumps, in practice the stump blowout rate is not statistically significant (3% vs 4.1%). However, the chances of regaining normal rectal function are much better for benign disease (68% vs 32%--Fisher's exact test, P = 0.004). Complications from second-stage re-anastomosis are not determined by timing of the closure, provided the septic episode has subsided.

Laparoscopic Nissen fundoplication for hiatus hernia: a case report.

Laparoscopic Nissen fundoplication has rapidly become an established technique in the management of severe or complicated reflux oesophagitis. We describe our initial experience with laparoscopic Nissen fundoplication in a 54-year-old man with intractable severe haemorrhagic oesophagitis and a large sliding hiatus hernia. The Rossetti modification of Nissen fundoplication was used as this is a surgical procedure eminently suited for the laparoscopic approach since minimal dissection is needed. The operative time taken was 260 minutes, there was minimal blood loss, minimal postoperative analgesia requirement and early return of bowel function.

Incidental cholecystectomy--an old problem reconsidered.

This paper reexamines the issues and indications for incidental cholecystectomy when gallstones are present during laparotomy for an unrelated condition. Seventy-nine such patients were studied between 1988 and 1993--66 had incidental cholecystectomy (both elective and emergency) while asymptomatic gallstones were left alone in 13 patients for various reasons. There was little morbidity and no mortality arising directly from biliary surgery. Interestingly, four bile cultures from the asymptomatic gallbladders grew bacteria and this could explain why patients may develop severe disease postoperatively if their gallbladders were left alone. The added cholecystectomy resulted in an acceptable extension of 22 to 23 minutes in the operative time without compromising the patients' safety.

Endoscopic oesophagectomy--a case report.

Endoscopic oesophagectomy was first successfully performed in Singapore for a 64-year-old Chinese patient who had a 6 cm mid-oesophageal tumour. The postoperative recovery was very remarkable. He was extubated at the end of the surgical procedure, stayed in the intensive care unit for only one day and was quite mobile by the end of the week. The surgical techniques are described in this case-report.

Evaluation of non-surgical treatment of benign oesophageal stricture.

Benign oesophageal stricture is a disabling problem associated with oesophageal surgery, injection sclerotherapy and patients with reflux problems. Fortunately, mechanical dilatation has emerged as an effective treatment of choice. In recent years, balloon dilatation appears to have gained popularity because of its efficacy and safety. This study of 43 patients compares manual dilatation with balloon dilatation. Twenty-one patients underwent manual dilatation with either Eder-Puestow or Gum Elastic dilators. There were 4 failures which were then treated successfully with balloon dilatation. Two other patients developed perforation and needed emergency surgery. Nine patients required 3 or more graduated dilatations within one month. Another group of 22 patients were treated successfully by balloon dilatation without any complications. Ten patients developed recurrent dysphagia and needed another repeat dilatation after an interval averaging 4.5 months. The results show quite conclusively that balloon dilatation is superior to manual dilatation.

Emergency surgery for bleeding oesophageal varices.

PURPOSE OF STUDY--This case-series reviews patients who underwent emergency transgastric ligation or oesophageal transection for uncontrolled bleeding oesophageal varices despite initial conservative therapy with vasoactive drugs, balloon tamponade and injection sclerotherapy. The study seeks to identify factors determining outcome of surgery and the problems of transection surgery following endoscopic sclerotherapy. SELECTION OF STUDY SUBJECTS--One hundred and ninety-eight patients (median age 54.6 years) were treated for bleeding varices between 1981 and 1991. Of these, 36 (18%) required emergency surgery and they formed the cohort under study. OBSERVATIONAL METHODS AND MAIN FINDINGS--Twenty-three patients underwent transabdominal oesophageal devascularisation and oesophageal transection while 13 had transgastric ligation. Nine patients were graded Child-Pugh's A, 20 Child-Pugh's B and 7 Child-Pugh's C-mortality was 11%, 25% and 100% respectively. Of all the risk factors, the Child-Pugh's grade was the single most important factor determining outcome (Chi-square test; 2 degrees of freedom, p < 0.0005). The data also showed that patients who were transfused less than 3 litres of blood had a mortality of 18% compared to 55% for those requiring 3 or more liters (Fisher's exact test p = 0.0155). There was no difference in mortality between transgastric ligation and oesophageal transection when patients were evaluated according to the Child-Pugh's grade. The results indicate that oesophageal transection is to be recommended for better control of bleeding (0% vs 23% post procedure) but conversely is associated with higher anastomotic leakage rate (8.7% vs 0%). PRINCIPAL CONCLUSIONS--We conclude that the decision to operate on bleeding variceal patients should be made early as procrastination is detrimental to their surgical outcome. In view of the extremely poor results with Child-Pugh's C patients, emergency surgery is best offered to the Child's A and B cases.

Colonic anastomosis with sutureless biofragmentable rings.

PURPOSE OF STUDY--To evaluate the safety and applicability of a biofragmentable anastomotic ring (VALTRAC BAR) in an Asian population and report on its performance as an alternative to sutures and stapling devices. SELECTION OF STUDY SUBJECTS--A consecutive series of 20 patients undergoing colonic surgery over a 7-month period from October 1992 to April 1993. OBSERVATIONAL METHODS AND MAIN FINDINGS--A protocol was drawn up for prospective record of data from 11 male and 9 female patients (age 34 years to 83 years). Information was collected regarding length of operation (average 3 hours), actual anastomotic time (average 13.5 minutes) and problems or complications associated with the Valtrac device during surgery (none). Postoperatively, the cases were carefully documented for intestinal obstruction from faecal impaction due to Valtrac fragments (none), the timing of bowel movements (majority 4th day, range 1-7 days), and awareness of passing fragments (none). There were no mortality and no anastomotic leakage though two patients developed wound infection. PRINCIPAL CONCLUSIONS--This preliminary study confirms that the biofragmentable anastomotic ring is a simple, rapid and efficacious method of bowel anastomosis comparable to existing procedures. It has the distinct advantage of being uniformly reproducible.

Percutaneous biliary drainage into the jejunum via a tube gastrostomy in patients with complete biliary obstruction: a report of two cases.

In recent years, percutaneous gastrostomy has been used to return bile draining from percutaneous transhepatic drainage catheters in patients with complete biliary obstruction that could not be bypassed surgically or stented either percutaneously or endoscopically. We report our initial experience with two patients in whom the combined percutaneous and endoscopic technique was used to divert the bile back into the jejunum.

Gastritis polyposus et cystica--an unusual case without exophytic growth and antecedent surgery.

Gastritis polyposus et cystica is usually an exophytic growth developing at the gastroenterostomy site. This is a case-report of a patient without any antecedent surgery or obvious lesion though the computed tomographic scan showed an interacting 'gyral' form of enhancement which has not been reported. This X-ray image correlated with the hypertrophic mucosa fold and cystic changes and may help towards pre-operative diagnosis, thereby avoiding unnecessary surgery.

Breast carcinoma-in-situ: an emerging problem in Singapore.

Breast carcinoma-in-situ constitutes 4.1% of 707 breast cancers diagnosed between 1988 and 1990. Among these 30 patients, intraductal carcinoma-in-situ (DCIS) outnumbers lobular carcinoma-in-situ (LCIS) by 9-fold. They are mostly symptomatic - 87% present as breast lumps and/or nipple discharge, with 52% of lumps exceeding 2cm size. Three patients were detected by screening mammography and it is expected that more breast carcinoma-in-situ will be detected through mammographic screening. Two-thirds of the patients had mastectomy while the rest had lesser procedures. The different surgical procedures and adjuvant therapy instituted for the patients are reflections of the differing opinions regarding optimum therapy for carcinoma-in-situ and the differing rationale for DCIS and LCIS lesions.

Relative risks of complications in giant and nongiant gastric ulcers.

There are two divergent views regarding giant gastric ulcers. Traditionally, they have been regarded as a virulent disease prone to massive hemorrhage, intractability, and perforation. Recently, an entirely opposing viewpoint has developed that considers them no different from ordinary gastric ulcers. In this study between 1984 and 1989, 62 patients with giant ulcers (greater than or equal to 3 cm) were compared with 476 benign gastric ulcer patients to evaluate their relative risks of ulcer complications. The results showed that giant ulcers are more prone to severe hemorrhage (44% versus 27%; chi 2 test: p less than 0.009) but not more prone to free perforation. Penetration into contiguous organs occurred more frequently with giant gastric ulcers (45% versus 10%; chi 2 test: p less than 0.0001). The risk of the presence of microscopic malignancy in the macroscopically benign-looking giant ulcer is significantly greater than in the nongiant type (13% versus 3%; Fisher's exact test: p = 0.0013). The data showed that patients with giant gastric ulcers are more at risk for the development of life-threatening complications and, hence, more likely to require surgery.

Clinical and social problems in young women with breast carcinoma.

Studies have noted that Asian women tend to have invasive breast cancer at a younger age compared with their Western counterparts. This is a rising trend among women in Singapore. This study compares 46 women less than or equal to 35 years with 313 women greater than 35 years who were treated in a teaching hospital between January 1983 and December 1989. Despite better education, the younger women (less than or equal to 35 years) were no different from their older counterparts in delaying medical consultation for more than 3 months after self-detection (39 vs 38.6%) though a higher percentage of older women procrastinated for over a year (16.6 vs 6.5%). As a result, 28% of younger women and 21.6% of older women presented with late disease (TNM Stage III and IV). Primary healthcare physicians contributed towards further delay among 65% of women less than or equal to 35 years. They were more suspicious when breast lumps were detected in women greater than 35 years and only 8% had delayed referrals. Failure in advising early biopsy added further delay (greater than 3 months) in 27.6% of younger patients whereas it was seldom delayed for the other older group (0.3%). Eight patients less than or equal to 35 years were initially reluctant to undergo definitive surgery. These cumulative delays resulted in progression of disease in seven patients of the 11 patients whose therapy was delayed more than 6 months.

Computed tomography for oesophageal carcinoma: its value to the surgeon.

Between January 1988 and June 1991, 75 patients with carcinoma of the oesophagus or gastro-oesophageal junction were evaluated by computed tomography (CT). Fifty of these patients underwent operation, allowing 48 cases to have a detailed surgical and pathological verification of CT features. For thoracic oesophageal tumours the accuracy of CT was 59% for fat plane status, 86% for aortic contact, 81% for tracheobronchial tree compression and 66% for direct local invasion. CT was 69% accurate for identifying lymph nodes, of which only 38% contained metastatic deposits. For gastro-oesophageal junction tumours, CT was 74% accurate for fat plane status and 90% accurate for direct local invasion. Accuracy for detecting lymph node involvement was 63%, metastatic tumour being present in 91% of these nodes. By pathological staging, only 15% of all resections could be considered potentially curative. The value of CT was found to be in predicting a palliative or curative resection, and in warning the surgeon about possible infiltration of specific mediastinal or abdominal structures that would be encountered during operative dissection.

Thyroid papillary carcinoma with unusual breast metastasis.

Breast metastasis from thyroid carcinoma is a rare occurrence. We report a case of immunohistologically proven breast metastasis from a thyroid papillary carcinoma. The association of primary breast carcinoma and thyroid carcinoma is noted and the usefulness of immunohistological techniques emphasised especially when histological assessment is difficult.