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Biomedical subjects

R Chan

Publications and source records attributed to R Chan.

At least 109 records · Page 6Linked to original sources
PubMed1995

Correlation between steady-state plasma concentration of antituberculous drugs and age, inclusion of rifampicin in the treatment regimen, adverse drug reactions and other clinical parameters.

A regional hospital in Hong Kong examined the correlation between plasma concentrations of rifampicin, pyrazinamide, isoniazid and its metabolite hydrazine and age, inclusion of rifampicin in the treatment regimen, adverse drug reactions and other clinical parameters. One hundred eighty subjects with tuberculosis were admitted consecutively to the medical wards of the Prince of Wales Hospital over a one and a half year period. Elderly patients > 65 years were randomized into one of two treatments with and without rifampicin in addition to isoniazid, pyrazinamide and ethambutol; younger patients received all four drugs. Plasma antituberculous drug concentrations were determined using high performance liquid chromatography. Elderly patients taking rifampicin had a higher mean steady-state concentration of isoniazid, together with a higher incidence of adverse effects compared with those not taking rifampicin. No age related differences were observed for the other drugs. For the whole group, higher mean concentrations of hydrazine, rifampicin and pyrazinamide were associated with a higher incidence of adverse effects and the presence of coexisting diseases. It is concluded that in sick elderly patients with coexisting diseases, use of rifampicin in the antituberculous regimen should be accompanied by close monitoring for side effects, and that there may be an indication for use of lower dosages of antituberculous drugs in such patients.

Adult↗
PubMed1994

A 92 kDa gelatinase (MMP-9) cleavage site in native type V collagen.

Native type V collagen molecules resist mammalian collagenase but are cleaved by certain gelatinases. We report a prominent site of cleavage within the collagen type V molecules by 92 kDa gelatinase (MMP-9). The enzyme was purified from conditioned medium of a rabbit synovial cell line (HIG-82). It cleaved native type V collagen from bovine bone in solution at two molecular sites, one near the amino-terminus, the other producing a 3/5 C-terminal fragment. Amino-terminal sequence analysis of the individual alpha chains from this latter fragment showed that MMP-9 had cleaved between residues Gly439-Val in both alpha 1(V) and alpha (XI) and between residues Gly445-Leu in the alpha 2(V) chain. These sites are close to the previously reported trypsin-cleavage site. The findings imply that gelatinases may be necessary for initiating or completing degradation of type I/type V copolymeric fibrils for growth and remodeling of extracellular collagen.

Amino Acid Sequence↗
PubMed1993

Interactions of temperature and steroids on larval growth, development, and metamorphosis in a toad (Bufo boreas).

The effects of temperature and steroids [testosterone (T), estradiol (E2), and corticosterone (B)] on premetamorphic growth and development were investigated in the toad (Bufo boreas). The effects of steroids were both temperature and age dependent. In the first experiment, steroids (1.1-1.4 microM) were administered by dissolving them in the water beginning 1 day after hatching at 22 degrees C or 27 degrees C. At 22 degrees C, B inhibited growth (P < 0.001) but had no significant effect on development. Forelegs never emerged in B-treated animals and all died before complete tail resorption. Discontinuation of B treatment allowed normal growth and metamorphosis, but the resulting post-metamorphic animals were significantly shorter (snout-vent length, P < 0.001) than after other treatments. At 22 degrees C, T and E2 had no effect on larval growth and development or size at metamorphosis (P > 0.05), but T induced early foreleg emergence (FLE) (P < 0.005). At 27 degrees C, B was fatal after 2 weeks of treatment, and T and E2 inhibited growth (P < 0.001) and development (P < 0.001), but did not affect time to FLE. In a second experiment at 27 degrees C, treatment with 1.1 microM B starting 15 days after hatching induced early metamorphic events (P < 0.001), such as tail resorption and emergence of the left foreleg (but not the right), but jaw and head restructuring failed to occur. All B-treated animals died before complete tail resorption. In a third experiment, 0.275 and 1.11 microM B, starting at day 43 (stage 43), induced early FLE (P < 0.05) and decreased snout-vent length at tail resorption (P < 0.005) without a dose effect. A higher dose of B (4.44 microM) decreased snout-vent length at tail resorption and time to FLE (P < 0.05) but did not affect body weight at metamorphosis (P > 0.05). Animals in this experiment survived to complete tail resorption and transformed normally. The actions of B in these experiments closely resemble those observed with administration of thyroid hormones, suggesting that steroids may interact with endogenous thyroid hormones.

Animals↗
PubMed1993

Endocarditis caused by Brucella melitensis.

OBJECTIVE: To describe the management of an uncommon but serious infection in Australia. CLINICAL FEATURES: A 25-year-old woman developed endocarditis after residence in Turkey and consumption of goat dairy products. Brucella melitensis was isolated from blood cultures. INTERVENTION AND OUTCOME: The valve remained infected after prolonged intravenous administration of trimethoprim-sulfamethoxazole, gentamicin and rifampicin. Uncontrolled sepsis and worsening haemodynamic function necessitated valve replacement. To date the patient remains well while taking trimethoprim-sulfamethoxazole and rifampicin. CONCLUSION: Endocarditis due to Brucella spp. is uncommon in Australia. This infection is difficult to cure with antimicrobial therapy alone and early surgical intervention is advisable.

Adult↗
PubMed1993

Left ventricular false aneurysm complicating mitral valve repair.

Left ventricular false aneurysm is a rare complication of mitral valve replacement or myocardial infarction. A case of left ventricular false aneurysm complicating mitral valve repair is presented. The patient was clinically asymptomatic, and the diagnosis was made on postoperative transesophageal echocardiography. The patient subsequently underwent successful mitral valve replacement and false aneurysm repair.

Aged↗
PubMed1993

Radioimmunoassay of ganirelix in plasma or serum.

A procedure for the radioimmunoassay (RIA) of ganirelix in plasma or serum at concentrations as low as 0.050 ng/ml is described. Antiserum was produced by coupling the N-terminus glycyl analog of ganirelix to BSA by a carbodiimide reaction and immunizing rabbits with this conjugate. The antiserum did not crossreact with LHRH or with various ganirelix peptide fragments. For RIA, 125I labeled ganirelix was used as the tracer and a double antibody procedure was used to separate the free and bound fractions. No purification of the analyte was required prior to RIA. Accuracy of the method was assessed by adding known quantities of ganirelix to ganirelix-free plasma and determining the ratio of measured to added analyte. Linear regression analysis for the concentration range 0.050-50.0 ng/ml yielded a regression equation of y = 0.97x + 0.18, r = 0.999, where x is the amount added and y is the amount measured. Additional validation was obtained from an in vivo study in which [3H]-ganirelix was administered to monkeys and plasma clearance profiles were determined by RIA and an HPLC-radiochemical method. The results were in agreement within experimental error of the two methods. Linear regression analysis of the comparative data gave the equation y = 0.92x + 33.7, r = 0.980, where x is the amount measured by RIA and y is the amount measured by HPLC-radiochemical analysis.

Amino Acid Sequence↗
PubMed1993

Reperfusion injury, stunning and myocardial viability.

Recent experimental data suggest that current thrombolytic strategies may not yet have achieved their full potential for myocardial salvage. In fact, reperfusion may result in microvascular and myocardial cellular injuries. These may translate into transient loss of contractile function ('myocardial stunning'), and possibly contribute to the ultimate extent of myocardial necrosis. A number of imaging modalities are now available to detect the presence and amount of these dysfunctional but viable myocardial segments. Myocardial reperfusion experiments using animal models have studied possible mechanisms responsible for reperfusion injury. These may help in the search for novel pharmacological and other adjunctive approaches which may overcome potential adverse effects of reperfusion.

Animals↗
PubMed1993

Laparoscopic suture technique after common bile duct exploration.

Performing both laparoscopic cholecystectomy and choledocholithotomy during the same operative procedure for both suspected and unsuspected stones is an attractive alternative to preoperative endoscopic retrograde cholangiopancreatography and stone removal or to conversion of the laparoscopic procedure to open common duct exploration. During laparoscopic exploration, intracorporeal suture and knot-tying may be tedious. We thus developed a technique of suture of the choledochus that avoids the use of knots and avoids placing metal clips in contact with the common bile duct. This technique was accurate, fast, and easily controlled in eight of 21 patients, and no major complications or mortality occurred.

Cholecystectomy, Laparoscopic↗
PubMed1992

Hepatitis C viremia in patients with hepatitis C virus infection.

Sera from 103 patients were tested for hepatitis C virus RNA by nested polymerase chain reaction assay. Using primers from the highly conserved 5'-untranslated region, we detected hepatitis C virus RNA in 67 (88.2%) of 76 patients positive for antibody to hepatitis C virus by both second-generation and neutralization enzyme immunoassays. Hepatitis C virus RNA was detected in 93% of patients who had been infected for 10 yr or less and in 89% of those who had been infected for longer than 10 yr. Hepatitis C virus RNA was detected in all patients with chronic hepatitis, active cirrhosis or hepatocellular carcinoma and in 50% of those with nonspecific reactive hepatitis or inactive cirrhosis. Hepatitis C virus RNA was not detected in sera from 22 patients negative for antibody to hepatitis C virus or in 5 patients positive for antibody to hepatitis C virus by second-generation but not by neutralization enzyme immunoassay. Using primers from the less conserved nonstructural region 4, we detected hepatitis C virus RNA at a lower frequency, in 66% of patients who were positive for antibody to hepatitis C virus by both second-generation and neutralization enzyme immunoassays. The detection rate was higher in patients with frequent parenteral exposure. Our study showed that hepatitis C viremia can be detected in most patients with hepatitis C virus infection, including those with long-standing infection or advanced liver disease.

Base Sequence↗
PubMed1991

Botulinum toxin in the treatment of facial dyskinesias.

Patients with hemifacial spasm (N = 25), blepharospasm (n = 8), and benign eyelid fasciculation (n = 2) were treated with botulinum toxin injections (PHLS, Porton Down, England). All patients reported substantial symptomatic relief. Marked improvement was seen in fifteen patients with hemifacial spasm and six patients with blepharospasm. Benign eyelid fasciculation was completely abolished. Beneficial effects was evident two to three days after injections, became maximum at one week, and remained effective for up to six months. Side effects were transitory and mild. They included periorbital edema, mild diplopia, ptosis and facial weakness. Only in two patients was ptosis unacceptable. Severity of side effects was dose-related. Reinjections had similar efficacy. Botulinum toxin therapy is a safe and effective treatment for these facial dyskinesias and should be considered a viable alternative to surgical procedures.

Adult↗
PubMed1991

Prognostic usefulness of cytogenetic analysis for haematological malignancies--two case reports on acute myeloid leukaemia.

Since the setup of marrow cytogenetic analysis at the National University Hospital (NUH) of Singapore in 1988, we have systematically examined all patients with haematological neoplasia for clonal abnormalities. In most patients, diagnosis was unequivocal on clinical and morphological grounds so that karyotyping was undertaken for prognostic purposes. Two patients are described who illustrate the prognostic implications of nonrandom chromosomal derangements. They highlight the increasing appreciation of the importance of cytogenetic analysis as an independent and reliable prognostic tool in the management of haematological malignancies.

Acute Disease↗
PubMed1990

Hospital formularies: need for continuous intervention.

The effects of introducing a hospital formulary alone and with active intervention were compared prospectively with regard to drug costs and the quality of prescribing. Intervention comprised feedback on prescribing habits, peer comparison, and information on drugs. Aspects of prescribing that were not subjected to intervention did not alter. In the year in which intervention occurred generic prescribing rose by 50%; inappropriate prescribing and overall use of third generation cephalosporins fell; and compliance with the recommended list of drugs was good. Overall, drug costs remained static, compared with a projected increase of 0.25 m pounds; in a comparative control hospital drug costs rose by 18%. During the next year, when no form of intervention took place, previous gains were eroded and drug costs rose. Continuous intervention, review, and feedback are required if a formulary is to continue to achieve its objectives.

Costs and Cost Analysis↗
PubMed1990

Common peroneal nerve dysfunction after high tibial osteotomy.

We assessed 16 patients before and after high tibial osteotomy by electrophysiological recordings, creatine phosphokinase levels, radiographs and intracompartmental pressure monitoring. We found mild electrophysiological abnormalities pre-operatively in 12 of the 16 patients, but postoperatively these had deteriorated in 11 of the 14 patients studied. Creatine phosphokinase levels, compartment pressure and radiological deformity were not predictive of the development of postoperative common peroneal nerve palsy. Patients who also had a proximal fibular osteotomy had greater electrical abnormalities postoperatively and two of them developed common peroneal palsies. Proximal fibular osteotomy appears to be a causative factor in the development of common peroneal nerve palsy; more work is needed on the blood supply of the nerve.

Adult↗
PubMed1990

Preparation of lipid emulsions by pressure extrusion.

Lipid emulsions consisting of a surface monolayer of phospholipid enclosing a core of neutral lipids have been prepared by repeated extrusion through polycarbonate filters of defined pore size. Particle size, as measured by photon correlation spectroscopy, decreases on successive passes through a 100 nm filter, reaching a near constant value (130-150 nm) after 4 passes. A corresponding decrease in the standard deviation of the particle size distribution occurs during this process. The recovery of lipids, especially of cholesterol and cholesterol ester, is improved if the emulsion is sonicated before extrusion through filters. [31P]-NMR and fluorescence techniques are used to confirm that the resulting structures are emulsions rather than lipid bilayers.

Cholesterol↗
PubMed1990

Human immunodeficiency virus infection in Singapore--the first 50 cases.

As at 31 May 1990, fifty Singaporeans with the Human Immunodeficiency Virus (HIV) infection had been detected. Of these, nineteen had the Acquired Immunodeficiency Syndrome (AIDS). The majority of infected persons had been infected through sexual contact (homosexual 52%; bisexual 24%; heterosexual 20%) with men and women from countries where HIV infection was prevalent. The majority of infected patients (88%) were in the age range 20-39 years. There was one case of blood transfusion-associated AIDS. There were no infected paediatric or haemophiliac cases or intravenous drug use in any of the patients. A spectrum of AIDS-related opportunistic infections and cancers was observed, and Pneumocystis carinii pneumonia was the most frequent presentation. Thirteen patients with AIDS had died and the median survival time was about seven months.

Acquired Immunodeficiency Syndrome↗