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Biomedical subjects

C S Loh

Publications and source records attributed to C S Loh.

At least 37 records · Page 2Linked to original sources
PubMed2001

The effects of treating lower urinary tract symptoms on sexual function.

We prospectively evaluated the effect of the treatment of lower urinary tract symptoms (LUTS) on sexual function. The patients were assessed by using the International Index of Erectile Function (IIEF-15) inventory at baseline and three months after medical (alpha-blockers) or surgical treatment (transurethral resection of the prostate, TURP). Following treatment, there were improvement in erectile function and intercourse satisfaction while orgasmic, overall satisfaction and sexual drive were relatively unchanged in the medication group. Patients who had surgical treatment suffered retrograde ejaculation, dissatisfaction in sexual intercourse and overall sexual satisfaction compared to patients who were on alpha-blockers.

Adrenergic alpha-Antagonists↗
PubMed2000

The psychological effects of treatments for lower urinary tract symptoms.

OBJECTIVE: To assess and evaluate the level of depression, anxiety and psychiatric status in patients with lower urinary tract symptoms (LUTS) before and after treatment by surgery or drugs. PATIENTS AND METHODS: The study included 123 patients (mean age 64.6 years, SD 7. 95) with LUTS who were treated medically (with alpha-blockers, i.e. terazosin, prazosin, doxazosin and alfuzosin), and 52 patients (mean age 69.6 years, SD 7.94) with LUTS and confirmed to have benign prostatic hyperplasia (BPH) who underwent transurethral resection of the prostate (TURP). Both groups were assessed at baseline and 3 months after treatment using standardized questionnaires (the Beck Depression Inventory, the State-Trait Anxiety Inventory and the General Health Questionnaire-12). RESULTS: Patients before TURP were significantly more depressed, worried and psychiatrically morbid than were those before medical treatment. Three months after medical and surgical treatment, there was significantly less depression, anxiety and psychiatric morbidity in the TURP than in the medication group. CONCLUSIONS: TURP is a better treatment than medication for minimising anxiety, depression and psychiatric morbidity after treatment in patients with LUTS, but causes greater psychological stress before treatment.

Adrenergic alpha-Antagonists↗
PubMed2000

The quality of life outcome following treatment for lower urinary tract symptoms.

This study aims to assess the impact of medical and surgical treatment on treating lower urinary tract symptoms (LUTS) on pain, prostatic symptoms, disease-specific quality of life and health-related quality of life. Patients scheduled for medical (alpha-blockers) and surgical treatment (transurethral resection of the prostate, TURP) were recruited in the study. The patients were assessed using the Visual Analogue Scale (VAS), Present Pain Intensity (PPI), International Prostate Symptom Score (I-PSS) and Health-Related Quality of Life (HRQOL) at 3-month, 6-month and 12-month (baseline). Before treatment, most of the patients with LUTS had severe pain, LUTS and deterioration of health-related quality of life. Following treatment, both medical and surgical treatment improved their pain, LUTS and health-related quality of life. Both treatments are effective in relieving the symptoms of pain, LUTS and health-related quality of life.

Aged↗
PubMed2000

Traditional Chinese medicines as immunosuppressive agents.

INTRODUCTION: Traditional Chinese Medicines (TCM) have been used for centuries in China to treat various immune-mediated disorders. METHODS: This review focuses on the clinical and experimental studies that have been performed with TCM as immunosuppressive agents for the treatment of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), atopic eczema and solid organ transplantation. RESULTS: The "thunder god" vine, Tripterygium wilfordii Hook F (TWHf), has been extensively used in China to treat SLE and RA. TWHf not only inhibited mitogen-stimulated lymphoproliferation, but its active derivatives have also been shown to inhibit production of proinflammatory cytokines by monocytes and lymphocytes, as well as prostaglandin E2 production via the cyclooxygenase, COX-2, pathway, a potential mechanism of action in patients with RA. Demethylzelasteral (TZ-93), a triterpenoid isolated from the root cortex of TWHf, the plant alkaloid berbamine, and the hydrophobic extract of a Chinese herbal decoction, CMX-13, were all shown to be active in prolonging allograft survival in experimental animal models of heart, skin and single lung transplants, respectively. There are few well-designed randomised placebo-controlled clinical trials demonstrating the efficacy of TCM in various diseases. Zemaphyte, a decoction of 10 herbs, has been shown to be efficacious in the treatment of atopic dermatitis in both children and adults in two randomised double-blind placebo-controlled trials. CONCLUSION: There is both laboratory and clinical evidence that the derivatives of many of these herbs may have significant beneficial immunosuppressive effects, however, concerns of toxicity must also be addressed, as exact dosing of the active derivatives is difficult to achieve with the current prescriptions of TCM.

Arthritis, Rheumatoid↗
PubMed1999

Immunoassay for wheat processing quality: utilization of a sandwich assay incorporating an immobilized single-chain fragment.

A single-chain fragment (scFv) was engineered from a monoclonal antibody to high molecular weight glutenin subunits (HMW-GS), wheat flour polypeptides that play a major role in determining the mixing- and extension strength-related properties of dough and its subsequent baking performance. The scFv was expressed in a thioredoxin mutant Escherichia coli strain that allows disulfide bond formation in the cytoplasm and incorporated into a diagnostic test for wheat quality. Although the scFv lacks the more highly conserved antibody constant regions usually involved with immobilization, it was able to be directly immobilized to a polystyrene microwell solid phase without chemical or covalent modification of the protein or solid phase and utilized as a capture antibody in a double-antibody (two-site) immunoassay. In the sandwich assay, increasing HMW-GS concentrations produced increasing assay color, and highly significant correlations were obtained between optical densities obtained in the ELISA using the scFv and the content of large glutenin polymers in flours as well as measures of dough strength as measured by resistance to dough extension in rheological testing. The assay using the scFv was able to be carried out at lower flour sample extract dilutions than that required for a similar assay utilizing a monoclonal capture antibody. This research shows that engineered antibody fragments can be utilized to provide superior assay performance in two-site ELISAs over monoclonal antibodies and is the first application of an engineered antibody to the analysis of food processing quality.

Antibodies, Monoclonal↗
PubMed1998

Synergism in replication of cymbidium mosaic potexvirus (CymMV) and odontoglossum ringspot tobamovirus (ORSV) RNA in orchid protoplasts.

An in vitro orchid protoplast isolation method to study replication kinetics of CymMV and ORSV was developed. This method allows the isolation of viable and raphid-free petal protoplasts from an orchid hybrid, Dendrobium Sonia (Dendrobium Caesar x Dendrobium Tomie Drake). The optimum field strength for both viral RNA to achieve good efficiency of electroporation was 750 V/cm and the optimum viral RNA concentration required was 1 microgram and 4 micrograms per 2 x 10(6) protoplasts for CymMV and ORSV, respectively. Autoradiographs of Northern blots depicting the viral genomic and subgenomic RNA in the extracts, referred to as the "Replication Footprint Profiles" (RFP) of specific CymMV/ORSV virus were prepared at different time intervals. Viral RNA synthesis reached a maximum at 18 h for CymMV and 24 h for ORSV. When CymMV and ORSV viral RNA were electroporated into the protoplasts simultaneously, detection signals of both the positive and negative strand viral RNA increased as compared to the singly infected protoplasts. Thus, synergism in replication of CymMV and ORSV was observed in orchid protoplasts.

Electroporation↗
PubMed1998

Quantitative studies of the kinetics of 5-aminolaevulinic acid-induced fluorescence in bladder transitional cell carcinoma.

Photodynamic therapy is a potential treatment for superficial bladder cancer that utilizes photosensitizer drugs, which are activated by light to cause tissue destruction. However, first-generation photosensitizers cause prolonged phototoxicity, have poor tumour specificity and can accumulate within detrusor muscle, resulting in permanent loss of bladder capacity following treatment. A newer drug, called 5-aminolaevulinic acid (ALA), generates a sensitizer called protoporphyrin IX (PpIX) in situ and has been shown, qualitatively, to be more tumour specific. The fluorescence kinetics of ALA-induced PpIX was investigated in patient biopsies of bladder tumour, normal urothelium and detrusor muscle, both in vitro after incubation of specimens in ALA-rich culture medium for various times and in vivo after instillation of intravesical ALA before endoscopic resection. The fluorescence in tumour tissue was twice that of normal urothelium in vitro and up to tenfold in vivo. There was little ALA-induced fluorescence in detrusor muscle, both in vitro and in vivo. Most importantly, no patients experienced phototoxicity or other adverse events following intravesical instillation of ALA.

Administration, Intravesical↗
PubMed1997

Photodynamic therapy of bladder cancer cell lines.

OBJECTIVE: To determine the effect of photodynamic therapy mediated by 5-aminolevulinic acid (ALA) on a range of bladder cancer cell lines, including a squamous cancer cell line and a multi-drug resistant cell line. MATERIALS AND METHODS: Experiments were performed on cells growing in culture: the cell lines studied were the transitional cell cancer lines RT112, T24 and EJ138, the squamous cancer cell line, SCaBER, and the multi-drug resistant transitional cancer cell line, MGH-U1(R), together with its non-resistant parent line, MGH-U1. The kinetics of the ALA-mediated generation of fluorescent photosensitizer were determined using flow cytometry. Photodynamic therapy was performed by incubating cells in ALA followed by exposure to various doses of white light. RESULTS: The response of the various transitional cancer cell lines to photodynamic therapy depended on dose. The squamous cell line was relatively resistant to photodynamic therapy. There was some cross-resistance of the MGH-U1(R) cell line to photodynamic therapy, although the mechanism of cross-resistance appeared not to be necessarily a property of the drug-resistant phenotype. CONCLUSION: This study suggests that ALA-mediated photodynamic therapy may be effective in transitional cell carcinoma of the bladder. Based on these findings, this therapeutic method should be further evaluated clinically.

Aminolevulinic Acid↗
PubMed1996

The complete sequence of a Singapore isolate of odontoglossum ringspot virus and comparison with other tobamoviruses.

The complete sequence of a Singapore isolate of odontoglossum ringspot virus (ORSV-S1) comprises 6609 nucleotides (nt) and four open reading frames (ORFs 1 to 4). The 126/183-kDa RNA-dependent RNA polymerase (RdRp), 33-kDa movement protein (MP) and 18-kDa coat protein (CP) cistrons are located at nt 63-3401/4901, 4807-5718, and 5721-6197 on the genome, respectively. The 5' UTR contains three copies of an 8-base direct repeat and (CAA)n motifs. Characteristic tRNA-like structure and three consecutive homologous regions were present in the 3' UTR. The genomic RNA and MP of ORSV-S1 are one of the longest among all members of the TOV group. Phylogenetic analysis of all four genes indicates evolutionary divergence, but within each gene there are some degrees of evolutionary convergence. The conserved amino acid sequences in the MP can be used for the classification of tobamoviruses.

Amino Acid Sequence↗
PubMed1996

The value of exfoliative urine cytology in combination with flexible cystoscopy in the diagnosis of recurrent transitional cell carcinoma of the urinary bladder.

OBJECTIVE: To study the value of exfoliative urine cytology in predicting recurrent tumour in patients undergoing surveillance for transitional cell carcinoma (TCC) and to assess the suitability of these patients for flexible cystoscopy. PATIENTS AND METHODS: Specimens of early-morning and freshly voided urine were submitted 2 weeks before surveillance cystoscopy by 111 consecutive patients with known TCC. All patients then underwent cystoscopy under general anaesthesia. The urine specimens were analysed by two pathologists with no knowledge of the patients' history. Cytological findings were correlated with the findings of cystoscopy. RESULTS: Urine cytology predicted 82% of all recurrent tumours found subsequently at cystoscopy; 60% of patients with non-neoplastic pathology had normal cystoscopy. Only 51% of patients with positive urine cytology were shown to have recurrent TCC, but 87% of patients with negative cytology had no recurrent tumours. CONCLUSION: Urine cytology is a good adjunct to assessing the suitability of flexible cystoscopy in the follow-up of patients with transitional cell tumours.

Adult↗
PubMed1996

Mucosal ablation using photodynamic therapy for the treatment of dysplasia: an experimental study in the normal rat stomach.

Surgery is the only effective treatment for dysplasia in the gastrointestinal tract with considerable associated morbidity and mortality and is difficult to justify without confirmed malignancy. Photodynamic therapy (PDT) produces localised necrosis, which can be limited to the mucosa. This study examined the mechanical properties of the normal rat stomach after PDT. The aim of this study was to measure the bursting pressure of PDT lesions in the stomach and to assess gastric emptying after producing circumferential mucosal necrosis at the pylorus by PDT. Two photosensitising agents were used--5-aminolaevulinic acid (ALA), and aluminium disulphonated phthalocyanine (A1S2Pc). Normal rats were sensitised and PDT lesions created in the stomach with red light. The bursting pressure was measured and compared with that in thermal control lesions. In further experiments, circumferential mucosal necrosis was produced at the pylorus, and animals observed for subsequent eating and weight gain. It was found that gastric bursting pressure was reduced after thermal injury, but not at any time after PDT (with A1S2Pc, but not ALA, adhesive omental reinforcement was required to maintain the gastric wall strength at one week). For the pyloric lesions, gastric emptying was permanently impaired using A1S2Pc, but with low dose ALA (20 mg/kg) had returned to normal by three days. With ALA, but not A1S2Pc, necrosis could be limited to the mucosa. In conclusion, using ALA, selective ablation of the gastric mucosa is possible, which does not reduce the strength of the stomach and only temporarily delays gastric emptying. PDT is a promising technique for the circumferential ablation of dysplastic mucosa.

Aminolevulinic Acid↗
PubMed1994

Photodynamic therapy for villous adenomas of the colon and rectum.

Endoscopic thermal laser therapy of colorectal villous adenomas is associated with a high recurrence rate due to incomplete tumor ablation, as treatment over carries a risk of perforation. Photodynamic therapy has been shown to be a promising in the treatment of small malignant tumors, and may be useful for benign adenomas. Eight patients with nine colosigmoid villous adenomas measuring 1-5 cm in length were treated with photodynamic therapy using either haematoporphyrin derivative or Photofrin as photosensitizer and multiple (4-16) applications of interstitial photoirradiation with red light (630 nm, 100 mW x 500 s per application). All but one adenoma had previously been incompletely treated with Nd-YAG laser therapy. Some skin sensitivity to light was seen in one patient. Seven adenomas were eradicated (follow-up 9-56 months, median = 12) as judged by follow-up endoscopy and biopsy. No local complications were seen. Substantial necrosis was produced in the other two adenomas, but they were not completely destroyed, probably due to inadequate light. PDT holds promise in the non-surgical management of villous adenomas, particularly after initial tumour debulking with the Nd-YAG laser.

Adenoma, Villous↗
PubMed1993

Nucleotide sequence of a flower-specific MADS box cDNA clone from orchid.

An orchid (Aranda deborah) mature flower cDNA library was screened with an agamous cDNA probe from Arabidopsis. One positive clone for agamous gene was isolated, cloned and sequenced. This cDNA clone (om1) has a full length open reading frame of 750 bp corresponding to 250 amino acid residues. Comparison of om1 MADS box with that of its counterparts in tomato and Arabidopisis reveals significantly high homology (> 95%). Northern analysis indicated this gene is expressed in mature flowers and not in young developing inflorescences or young floral buds. In the mature flowers, it is only expressed in petals and weakly in sepals but not in the column (gynostemium).

Amino Acid Sequence↗
PubMed1993

Endogenous porphyrin distribution induced by 5-aminolaevulinic acid in the tissue layers of the gastrointestinal tract.

The accumulation of endogenous porphyrins in rats following systemic administration of 5-aminolaevulinic acid (ALA) has been examined to assess the photosensitization characteristics of this technique for photodynamic therapy (PDT) and chemical extraction assays with fluorescence and absorbance detection of the porphyrin content have been carried out. We compared the results obtained using quantitative microfluorimetry on normal gastric and colonic tissues in rats at 0.5, 1, 2, 4 and 6 h and chemically induced duodenal tumours 2 and 4.5 h after intravenous administration of ALA at a dose of 200 mg kg-1. With chemical extraction followed by high performance liquid chromatography analysis, protoporphyrin IX (PpIX) was found to be the predominant porphyrin present, reaching peak levels of several microgrammes per gramme at 2-4 h in each type of tissue; a small amount of coproporphyrin was detected at 0.5 and 2 h in normal gastric mucosa and duodenal tumour respectively. Both the extraction assay and quantitative microfluorimetry showed that the porphyrin fluorescence builds up rapidly in the mucosal layers of the colon and stomach, reaching a maximum at 2 h, whereas lower fluorescence levels were found with a slower rate of accumulation in the corresponding muscularis layers. A significant PpIX content was found in the duodenal tumour, with a maximum of 7.1 micrograms g-1 4.5 h after ALA administration. We conclude that systemic administration of ALA can induce effective tissue sensitization with protoporphyrin IX and appears to be a promising technique for PDT.

Aminolevulinic Acid↗
PubMed1993

Oral versus intravenous administration of 5-aminolaevulinic acid for photodynamic therapy.

Endogenously synthesised protoporphyrin IX (PpIX) following the administration of 5-amino-laevulinic acid (ALA) is an effective photosensitiser for photodynamic therapy (PDT). Following intravenous administration, PpIX accumulates predominantly in mucosa of hollow viscera and on light exposure, mucosal ablation results with relative sparing of the submucosa and muscularis layers. Oral administration is effective with ALA in contrast to conventional exogenous photosensitisers such as haematoporphyrin derivative and phthalocyanines. Oral administration of ALA is also simpler, safer, cheaper and more acceptable to patients. We studied the porphyrin sensitisation kinetics profile in the stomach, colon and bladder in normal rats following enterally and parenterally administered ALA using microscopic fluorescence photometric studies of frozen tissue sections. Mucosal cells in all three organs exhibit higher fluorescence levels as compared with underlying smooth muscle following both intravenous and oral administration. Peak concentration were seen 4 h after sensitisation at the highest doses used (200 mg kg-1 i.v., 400 mg kg-1 oral), and slightly earlier with lower doses. The temporal kinetics of both routes of administration were similar although a higher oral dose was required to achieve the same tissue concentration of PpIX. The highest level of fluorescence was achieved in the gastric mucosa and in decreasing levels, colonic and bladder mucosa. A similar degree of mucosal selectivity was achieved in each organ with each route of administration but an oral dose in excess of 40 mg kg-1 was required to achieve measurable PpIX sensitisation. In a pilot clinical study, two patients with inoperable rectal adenocarcinomas were given 30 mg kg-1 and one patient with sigmoid colon carcinoma was given 60 mg kg-1 ALA orally. Serial biopsies of normal and tumour areas were taken over the subsequent 24 h. Fluorescence microscopy of these specimens showed maximum accumulation of PpIX 4 to 6 h after administration of 30 mg kg-1 ALA. There was greater PpIX accumulation in tumour than adjacent normal mucosa in two patients. Preferential PpIX accumulation in tumour was greater in the patient receiving 60 mg kg-1 ALA.

Adenocarcinoma↗