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Biomedical subjects

C Chan

Publications and source records attributed to C Chan.

At least 73 records · Page 4Linked to original sources

Ophthalmomyiasis and nasal myiasis in New Zealand: a case series.

We report three cases of ophthalmomyiasis in New Zealand, due to the larvae of Oestrus ovis. All three patients reported eye injury caused by a fly. The larvae were removed from the conjunctival sac without difficulty under local anaesthesia. Presenting ocular symptoms of foreign body sensation, irritation, redness and photophobia all resolved swiftly. Topical antibiotic and steroid eye drops were administered. All three patients also developed nasal symptoms such as sneezing, nasal discharge and epistaxis. Otolaryngology follow-up demonstrated nasal myiasis in two patients which was treated with nasal decongestants. In addition, all three patients were treated with ivermectin (Mectizan).

Adolescent↗

Measurement of biodegradable substances using the salt-tolerant yeast Arxula adeninivorans for a microbial sensor immobilized with poly(carbamoyl)sulfonate (PCS). Part II: Application of the novel biosensor to real samples from coastal and island regions.

A microbial sensor for rapid measurement of the amount of biodegradable substances based on the salt-tolerant yeast Arxula adeninivorans LS3 has been developed especially for coastal and island regions. Our parameter, the so-called sensorBOD, that is available after only a few minutes, agrees with the 5-day value for the biochemical oxygen demand (BOD5) very well. We have employed the Arxula sensor in the short-time estimation and supervision of the BOD of both domestic and industrial wastewater with high salinity. The novel sensor makes it possible to monitor the different types of wastewater rapidly without pretreatment, and it can be used for an active process control of sewage treatment works. Compared to a commercially available sensor, the novel sensor achieves better agreement between sensorBOD and BOD5 measurements with salt containing samples.

Ascomycota↗

Screening for trisomy 18 by fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A at 10-14 weeks of gestation.

In a study of 50 cases of trisomy 18 compared with 947 controls we have found the median multiple of the median (MoM) of maternal serum free beta human chorionic gonadotrophin to be significantly decreased (0.281 MoM) in samples collected between the 10th and 14th week of gestation. Similarly, maternal serum pregnancy associated plasma protein A (PAPP-A) levels are also decreased (0.177 MoM), whilst the median nuchal translucency is significantly higher (3.272 MoM). Free beta-hCG MoM was less than the 5th centile of normal in 64 per cent of cases of trisomy 18 and for PAPP-A was less than the 5th centile in 78 per cent of cases. Also, in 78 per cent of cases the nuchal translucency was above the 95th centile. When combined together in a multivariate algorithm with maternal age, we predict that 89 per cent of cases of trisomy 18 could be detected at a 1 per cent false-positive rate. We conclude that specific trisomy 18 risks should be part of developing risk algorithms combining maternal serum biochemistry and nuchal translucency for use in first trimester screening alongside those for trisomy 21.

Adolescent↗

Immobiline-based two-dimensional gel electrophoresis: an optimised protocol for resolution of human colonic mucosal proteins.

An optimised protocol for the production of two-dimensional protein patterns of human colonic mucosal cells using immobilised pH gradients in the first dimension is presented. We tested a wide variety of solubilising agents and electrophoretic parameters, separately and in combination. Protein solubilisation was found to be best using a lysis solution containing 9 M urea, 2% Triton X-100, 2% 2-mercaptoethanol, 0.8% Pharmalyte pH 3-10 and 8 mM phenylmethylsulfonyl fluoride (PMSF). Horizontal streaking of basic proteins in the first dimension was virtually eliminated by a combination of washing Immobiline strips in 100 mM asorbic acid, pH 4.5, for 24 h before use and isoelectric focusing samples at 40 degrees C. The presence of 2% glycerol in the first dimension resulted in tighter resolution throughout the entire pH range. The use of these conditions may prove to have broad applicability to the generation of optimally resolved Immobiline-based two-dimensional protein patterns of many other tissues.

Acrylamides↗

Conjunctival rotation autograft for pterygium. An alternative to conjunctival autografting.

OBJECTIVE: To determine the safety and efficacy of conjunctival rotation autografting (CRA) as an alternative to conventional conjunctival autograft after pterygium excision. DESIGN: Prospective noncomparative case series. PARTICIPANTS: Consecutive patients seen at the Pterygium Clinic of the Singapore National Eye Centre who were thought to be unsuitable for conventional conjunctival autografting underwent a modified surgical procedure, which the authors describe as CRA. There were 51 rotation autografts performed on 45 eyes of 43 patients. INTERVENTION: In this procedure, the underlying fibrovascular pterygium tissue was removed and the original epithelium (with minimal subepithelial tissue included) replaced over the bare sclera with a 180 degrees rotation. Surgeries were performed by one surgeon (DT) from April 1995 to May 1996. MAIN OUTCOME MEASURE: Pterygium recurrence and complications of CRA were measured. RESULTS: The mean follow-up time was 12 months (range, 2-22 months). There were 46 primary and 5 recurrent pterygia. The indications for CRA were combined cataract and pterygium surgery (39.2%), double pterygia (31.4%), the need to preserve the superior conjunctiva (21.6%), and superior conjunctival scarring (7.8%). There were two recurrences (4% recurrence rate), one occurring at 4 months and the other occurring at 7 months after surgery. No significant complications were encountered. However, 50% of the grafts remained mildly injected for more than 3 months, and some remained injected for up to 13 months after surgery (average of 4 months). Pigmentary changes were also noted in six grafts (12%). CONCLUSION: Conjunctival rotation autografting is a useful technique of conjunctival grafting in cases in which it is not possible or desirable to use the superior conjunctiva as a donor source.

Adult↗

Measurement of biodegradable substances using the salt-tolerant yeast Arxula adeninivorans for a microbial sensor immobilized with poly(carbamoyl) sulfonate (PCS) Part I: Construction and characterization of the microbial sensor.

A microbial biosensor based on the yeast Arxula adeninivorans LS3 has been developed for measurement of biodegradable substances. Arxula is immobilized in the hydrogel poly(carbamoyl) sulfonate (PCS). The immobilized yeast membrane is placed in front of an oxygen electrode with -600 mV versus Ag/AgCl. Arxula is salt tolerant; it can give a stable signal up to 2.5 M NaCl in sample (120 mM in measuring cell). The sensor's measurements are highly correlated to BOD5 measurements. It has a very high stability which can last for 40 day without any decrease in signal. The linear range of the sensor is up to a corresponding BOD value of 550 mg/l.

Biodegradation, Environmental↗

Management of allogeneic bone marrow transplant recipients at risk for cytomegalovirus disease using a surveillance bronchoscopy and prolonged pre-emptive ganciclovir therapy.

BACKGROUND: Patients undergoing allogeneic bone marrow transplant (BMT) are considered to be at increased risk of cytomegalovirus (CMV) disease if they and/or their donor are CMV seropositive pre-transplant. Although several pre-emptive strategies have been shown to be effective in preventing early CMV disease, the ability of pre-emptive strategies using prolonged ganciclovir therapy to reduce the incidence of late-onset CMV infection, disease and mortality has not been fully evaluated. OBJECTIVE: To assess the efficacy of 18 weeks of pre-emptive ganciclovir therapy in preventing late-onset (> 100 days post-transplant) CMV disease when administered to asymptomatic BMT patients found to have CMV in bronchoalveolar lavage (BAL) fluid obtained during a surveillance bronchoscopy approximately 35 days post-transplant. To determine whether or not survival of BMT recipients is influenced by pre-transplant donor and recipient CMV serostatus in the context of this pre-emptive ganciclovir strategy. STUDY DESIGN: Consecutive patients undergoing allogeneic BMT were assessed for their risk of developing CMV disease based on their pre-transplant CMV serostatus and that of their donor. Patients who were CMV seropositive and/or received marrow from a CMV seropositive donor underwent a surveillance bronchoscopy and BAL approximately 35 days post-transplant. Patients with positive BAL fluid for CMV received pre-emptive ganciclovir therapy for 18 weeks at decreasing dose levels. Patients considered to be at low risk for the development of CMV disease (donor and recipient CMV seronegative) were followed without intervention. RESULTS: Of 98 consecutive patients, 55 were considered to be at risk for CMV disease and underwent a surveillance bronchoscopy. Sixteen (29%) patients had a positive BAL fluid for CMV and were started on pre-emptive ganciclovir therapy. Two patients progressed and died with CMV-related pneumonia. One additional patient developed CMV-related enteritis on day 42 post-transplant and recovered with continuing ganciclovir treatment. Of the 39 patients with a negative BAL fluid for CMV, one developed a fatal CMV pneumonia 150 days post-transplant and two additional patients developed gastrointestinal CMV disease 28 and 57 days post-BMT, respectively. None of the patients in the low risk group developed CMV disease. CONCLUSIONS: The strategy utilizing a surveillance bronchoscopy for CMV and initiating prolonged (18 weeks) pre-emptive ganciclovir therapy for patients with a positive BAL fluid for CMV resulted in a low incidence of CMV-related post-transplant complications. After a minimum follow-up of 16 months, late CMV reactivations (occurring > 100 days post-transplant) were not observed in the group of individuals pre-emptively treated with ganciclovir. This observation suggests that prolonged therapy with a reduced dose of ganciclovir may be important in the prevention of CMV reactivation. The CMV serostatus of donors and recipients prior to BMT did not correlate with survival.

Adult↗

Atovaquone suspension compared with aerosolized pentamidine for prevention of Pneumocystis carinii pneumonia in human immunodeficiency virus-infected subjects intolerant of trimethoprim or sulfonamides.

Atovaquone suspensions (750 mg and 1500 mg once a day) were compared with aerosolized pentamidine (300 mg once a month) for the prevention of Pneumocystis carinii pneumonia (PCP) in subjects with human immunodeficiency virus (HIV) infection who were intolerant to trimethoprim or sulfonamides (or both). Median time using the assigned therapy was 6.6 months, and the median follow-up was 11.3 months. Intent-to-treat analyses (n=549) showed no statistically significant differences among subjects with regard to the incidence of PCP (26%, 22%, and 17%, respectively) or mortality (20%, 13%, and 18%, respectively). The incidence of treatment-limiting adverse events with atovaquone was significantly higher (P<.01). There was, however, no significant difference in the time using therapy. Incidences of PCP and death were higher in subjects receiving 750 mg of atovaquone than in subjects receiving 1500 mg. Atovaquone suspension at 1500 mg once a day has an efficacy similar to that of aerosolized pentamidine for prevention of PCP in HIV-infected subjects and is a safe, effective alternative in those who are intolerant to trimethoprim or sulfonamides.

AIDS-Related Opportunistic Infections↗

Evidence of clonal dissemination of multidrug-resistant Streptococcus pneumoniae in Hong Kong.

The relationship between the phenotypic and genotypic characteristics of 105 penicillin-intermediate or -resistant Streptococcus pneumoniae isolates saved during 1994 to 1997 at the Prince of Wales Hospital and Pamela Youde Nethersole Eastern Hospital, Hong Kong, was studied. The pbp genes for penicillin-binding proteins 1a, 2b, and 2x for each isolate were amplified by PCR, and the products were digested with restriction enzymes HinfI and AluI. A combination of the pulsed-field gel electrophoresis (PFGE) profiles, pbp fingerprints, and phenotypic characteristics of capsular types and antibiograms enabled these isolates to be divided into four major groups. Seventy-four percent (78 of 105) of the strains, belonging to serotypes 23F, 19F, and 14, showed indistinguishable pbp fingerprint patterns (group A1, 1-1-1, 1-1-1), with PFGE patterns belonging to group A and its subtypes, suggesting that these strains were closely related. Eighty-three percent (65 of 78) of these isolates were also resistant to tetracycline, erythromycin, chloramphenicol, and trimethoprim. The type 23F isolates were indistinguishable from representative strains of the Spanish 23F clone by these molecular methods, indicating that these strains may be variants of the Spanish 23F clone. Serotype 6B accounted for 19% (20 of 105) of the isolates with reduced penicillin susceptibility and was made up of variants belonging to four different pbp fingerprint groups with the PFGE pattern group B, the predominant group being indistinguishable from that of the Spanish 6B clone. Other PFGE and fingerprint groups were mainly obtained from penicillin-susceptible strains of various serotypes. The results suggest that the rapid emergence of drug-resistant S. pneumoniae in Hong Kong has been due to the rapid dissemination of several successful clones.

Bacterial Capsules↗

Results of surgical treatment (modified Sugiura-Futagawa operation) of portal hypertension associated to complete splenomesoportal thrombosis and cirrhosis.

BACKGROUND: Hemorrhagic portal hypertension, secondary to both intrahepatic and extrahepatic portal hypertension, is an uncommon entity. In this condition, the extrahepatic and the intrahepatic obstruction of the portal vein, due to chronic liver disease, produce a more severe form of hemorrhagic portal hypertension that is more difficult to control. The results of surgical treatment (modified Sugiura-Futagawa operation) in this subset of patients is analyzed. METHODS: Among 714 patients with a history of hemorrhagic portal hypertension, 14 cases were found with histologically proven liver cirrhosis and complete splenomesoportal thrombosis demonstrated by means of preoperative angiography. Patients with incomplete (partial) splenomesoportal thrombosis were excluded. There were nine males and 5 females with a mean age of 51 years. Alcoholic cirrhosis was demonstrated in 50% of the cases, post hepatitic cirrhosis in 28%, primary biliary cirrhosis in 7%, and cryptogenic cirrhosis in 14%. There were nine Child-Pugh A and 5 B cases. All cases were treated by means of our modified Sugiura-Futagawa procedure. RESULTS: Bleeding recurrence from esophagogastric varices was shown in one case, colonic varices in one case and hypertensive gastropathy in another of the survivors. Post operative encephalopathy was shown in 3 of the cases. The thirty-six month survival rate was 30% (Kaplan-Meier). CONCLUSIONS: The combination of intrahepatic plus extrahepatic portal hypertension has a worse prognosis. Treatment options are limited (sclerotherapy and/or devascularization), because shunt surgery, TIPS and liver transplantation have a very restricted role and postoperative outcome is poor.

Adolescent↗

Reoperations for bleeding portal hypertension. Surgical rescue of surgical failures.

BACKGROUND: Surgery for portal hypertension has a low rebleeding rate. Patients that rebleed can be grossly divided into those who die as a consequence of the episode, those who don't die but develop liver failure (remaining as Child-Pugh C) and those who, in spite of the bleeding episode, retain good liver function (Child-Pugh A or B). At our hospital, the latter group is considered for further surgical treatment. We report here the results of surgical rescue of surgical failures. METHODS: In a twenty year period, 36 patients (30 Child-Pugh A, 6 Child-Pugh B) were reoperated. The files of these patients were reviewed. RESULTS: Average age was 33 years. Cirrhosis was present in 31 cases. All patients were electively reoperated with portal blood flow preserving procedures. Operative mortality for the whole group was 12% and for the Child-Pugh A group 6.6%. Rebleeding was observed in 5.5%. Postoperative incapacitating encephalopathy was recorded in one case (2.7%). Good quality of life was recorded in 84% of the cases. Survival (Kaplan-Meier) was 78% at 6 months and 69% at 5 years. CONCLUSIONS: Surgical failures in low risk patients (Child-Pugh A or B) can be treated by means of surgery, and a low mortality, re-bleeding and encephalopathy rate can be expected. The performance of a portal blood flow preserving procedure is recommended.

Adolescent↗

A taxonomy of health networks and systems: bringing order out of chaos.

OBJECTIVE: To use existing theory and data for empirical development of a taxonomy that identifies clusters of organizations sharing common strategic/structural features. DATA SOURCES: Data from the 1994 and 1995 American Hospital Association Annual Surveys, which provide extensive data on hospital involvement in hospital-led health networks and systems. STUDY DESIGN: Theories of organization behavior and industrial organization economics were used to identify three strategic/structural dimensions: differentiation, which refers to the number of different products/services along a healthcare continuum; integration, which refers to mechanisms used to achieve unity of effort across organizational components; and centralization, which relates to the extent to which activities take place at centralized versus dispersed locations. These dimensions were applied to three components of the health service/product continuum: hospital services, physician arrangements, and provider-based insurance activities. DATA EXTRACTION METHODS: We identified 295 health systems and 274 health networks across the United States in 1994, and 297 health systems and 306 health networks in 1995 using AHA data. Empirical measures aggregated individual hospital data to the health network and system level. PRINCIPAL FINDINGS: We identified a reliable, internally valid, and stable four-cluster solution for health networks and a five-cluster solution for health systems. We found that differentiation and centralization were particularly important in distinguishing unique clusters of organizations. High differentiation typically occurred with low centralization, which suggests that a broader scope of activity is more difficult to centrally coordinate. Integration was also important, but we found that health networks and systems typically engaged in both ownership-based and contractual-based integration or they were not integrated at all. CONCLUSIONS: Overall, we were able to classify approximately 70 percent of hospital-led health networks and 90 percent of hospital-led health systems into well-defined organizational clusters. Given the widespread perception that organizational change in healthcare has been chaotic, our research suggests that important and meaningful similarities exist across many evolving organizations. The resulting taxonomy provides a new lexicon for researchers, policymakers, and healthcare executives for characterizing key strategic and structural features of evolving organizations. The taxonomy also provides a framework for future inquiry about the relationships between organizational strategy, structure, and performance, and for assessing policy issues, such as Medicare Provider Sponsored Organizations, antitrust, and insurance regulation.

American Hospital Association↗

QOL and outcomes research in prostate cancer patients with low socioeconomic status.

The VA Cancer of the Prostate Outcomes Study (VA CaPOS) is collecting quality-of-life (QOL) information from prostate cancer patients, spouses, and physicians at six VA medical centers. Currently, 601 men with prostate cancer are included in the study, most of whom are of low socioeconomic status and over half of whom are African-American. Quality-of-life responses were most favorable for newly diagnosed patients, intermediate for those with stable metastatic disease, and poorest for those with progressive metastatic disease. Patients could not provide reliable estimates of their own preferences for future QOL states but responded reliably to questions phrased as a comparison of the preferences of two hypothetical patients. High out-of-pocket costs for hormonal therapies, lack of health insurance, and a belief that the non-VA system offered poorer services were the most common reasons for patient transferral to the VA system. Satisfaction with medical care was generally high. While African-American patients were more likely to have advanced prostate cancer at diagnosis, after adjustment for differences in health literacy, race was no longer a significant predictor of advanced disease. The VA CaPOS provides useful information on health status and patient satisfaction of VA prostate cancer patients. Long-term evaluations are needed to detect clinically meaningful QOL information as the disease progresses.

Adult↗

Planning of skull base surgery in the virtual workbench: clinical experiences.

Based on the KRDL Virtual Workbench, we present a neurosurgical planning system called VIVIAN (Virtual Intracranial Visualization And Navigation). This VR environment allows for fast and intuitive interaction with three-dimensional multimodal (MRI, MRA, MRV, CT) patient specific data-sets. The user reaches behind a mirror into a 3D workspace where the 3D data is surrounded by interactive virtual tools-racks. Tumors, blood vessels, cranial nerves and surgically relevant parts of the brain are segmented by interactive control of density transfer-functions or by manual outlining and tracing tools. A neurosurgical procedure is planned by using various visualization and measurement tools and the system allows for the simulation of bone drilling and tissue removal. We have planned 16 cases which required tumor surgery at the cranial base. VIVIAN provided an efficient and comprehensive way to understand pre-operatively the complexity of anatomical and pathological relationships. The ideal craniotomy and the extent of the required skull base exposure could be specified accurately.

Computer Simulation↗

An interface for precise and comfortable 3D work with volumetric medical datasets.

We have developed a 3D/2D paradigm of interaction that combines manipulation of precise 3D volumetric data with unambiguous widget interaction. Precise 3D interaction is ensured by a combination of resting the lower arms on an armrest and pivoting the hands around the wrist. Unambiguous 2D interaction is achieved by providing passive haptic feedback by means of a virtual control panel whose position coincides with the physical surfaces encasing the system. We have tested this interface with a neurosurgical planning application that has been clinically used for 17 skull-base cases at two local hospitals.

Computer Simulation↗

The role of pancreaticoduodenectomy in the treatment of severe chronic pancreatitis.

Chronic pancreatitis remains a debilitating disease with few definitive options for treatment. The purpose of this study was to evaluate the benefit of pancreaticoduodenectomy in the treatment of chronic pancreatitis. The results were evaluated by standard descriptive statistics. In a retrospective study, we reviewed the patients at a single institution undergoing pancreaticoduodenectomy between 1994 and 1997 for complications of chronic pancreatitis. Patients were evaluated for preoperative indication for surgery and perioperative morbidity and mortality, as well as long-term results. Thirty-two patients underwent pancreaticoduodenectomy for chronic pancreatitis; 56 per cent (18) underwent pylorus-preserving and 44 per cent (14) underwent classic pancreaticoduodenectomy. The mean age of these patients was 56+/-14.7 years (range, 23-79). All patients underwent preoperative CT scan and endoscopic retrograde cholangiopancreatography. The preoperative indication for surgery in 81 per cent (26) of these patients was intractable pain in the setting of a nondilated pancreatic duct. The other 19 per cent were treated for biliary/pancreatic duct stricture and pancreatic head fibrosis (mass suspicious of malignancy). Fifty-three per cent of the patients had a history of previous abdominal surgery. There were no perioperative deaths. The mean postoperative stay was 12.2+/-7.4 days. The postoperative morbidity rate was 31 per cent (10), consisting of 25 per cent with delayed gastric emptying, 3 per cent with pneumonia, and 3 per cent with wound infections. There was no occurrence of pancreatic fistulas. With a mean follow-up of 40 months (range, 10-52 months), 85 per cent reported a significant improvement in pain with 71 per cent being pain free and not requiring narcotics. Twenty per cent developed new-onset diabetes. The overall event survival rate at 5 years was 97 per cent. Thus, in a selected group of patients with severe chronic pancreatitis, resection of the head of the pancreas achieved relief of symptoms and was a safe and effective treatment for chronic pancreatitis.

Adult↗

Sequencing regular and labeled oligonucleotides using enzymatic digestion and ionspray mass spectrometry.

A method using a combination of enzymatic digestion and ionspray mass spectrometry (MS) was developed for sequencing oligodeoxynucleotides (ODNs) containing more than 20 bases. Phosphodiesterase (PDE) digestion of ODNs produced truncated ODNs whose molecular weights (MWs) were determined by ionspray MS. It was demonstrated that reconstruction of MW spectra over a large MW range produced easy-to-read sequence ladders similar to those obtained using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Sample and enzyme cleanup, digestion control, and MW reconstruction were found to be crucial factors. For regular ODNs, both 5'- and 3'-PDE digestions are needed for complete sequencing. Late in the time course of PDE digestions, 5'-nucleoside monophosphates were found to produce artifactual peaks in the reconstructed MW spectra, and a table correlating base compositions and MS ions was compiled to handle such situations. For labeled ODNs, it is necessary to use collision-induced dissociation-tandem mass spectrometry (CID-MS/MS) for complete sequence determination. Sequencing of regular 22-mer and labeled 18-mer ODNs was demonstrated in this work.

Animals↗