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Biomedical subjects

C C Lau

Publications and source records attributed to C C Lau.

At least 37 records · Page 2Linked to original sources
PubMed1996

Accuracy and efficiency of X-ray requests initiated by triage nurses in an accident and emergency department.

A study was carried out from 1 March 1995 to 31 March 1995 in the Accident & Emergency department, Pamela Youde Nethersole Eastern Hospital, Hong Kong. The aim was to assess the feasibility of requesting X-rays by triage nurses based on a pre-set protocol prior to patients being seen by a doctor. Judgement of the attending physician was used as the gold standard by which to judge the need for radiographs requested by the triage nurse. In addition, the senior medical officer or consultant would judge whether the triage nurse had applied the protocol correctly. A total of 934 patients were included in the study and 883 (94.54%) patients had X-rays requested by the triage nurse. Only 5.44% of the radiographs requested by nurses were considered to haven been unnecessary by the doctor. There was no statistically significant difference in agreement for the child and adult groups. In 917 (98%) of cases, nurses had adhered to the protocol. A saving of an average of 18.59 minutes of total service time was obtained during the study. Requesting of X-ray by triage nurse was feasible

Adult↗
PubMed1996

Effect of hearing aid experience on preferred insertion gain selection.

The effect of hearing aid experience (measured as years of hearing aid use and user insertion gain at octave frequencies from 250 Hz to 4000 Hz) on the selection of preferred insertion gain under six listening conditions and one vocalization condition was examined. Thirteen experienced hearing aid users selected their preferred insertion gain in each test condition using a modified simplex procedure. The results showed that for the listening conditions, preferred insertion gain was highly correlated with the subjects' hearing loss from 500 Hz to 2000 Hz. Hearing aid experience did not correlate at all with preferred insertion gain. On the other hand, user insertion gain at 250 Hz and 500 Hz correlated highly with preferred insertion gain selected during vocalization. Years of hearing aid use did not correlate with preferred insertion gain selection. These results suggest that user insertion gain can affect preferred insertion gain selection only when the test conditions are identical to those that the hearing aid wearers experience in everyday lives. In typical laboratory conditions, preferred insertion gain is likely determined by the stimulus characteristics and subjective preference.

Adult↗
PubMed1995

Evidence for a multifocal origin of papillary serous carcinoma of the peritoneum.

Histopathological evidence suggests that papillary serous carcinoma of the peritoneum (PSCP) may be multifocal in origin. Utilizing a PCR based method to detect tandem repeat polymorphisms in formalin fixed tissue, loss of heterozygosity at eight loci on chromosomes 1, 3, 4, and 17 was studied in six cases of PSCP. Loss of heterozygosity was assessed at between 5 and 11 tumor sites/patient. Allelic losses at 4 loci (1q32-qter, 3p14.3-21.1, 17q12, 17q21.3-23) were noted. Three cases demonstrated a different pattern of allelic loss at various anatomic sites within the same patient. In an additional case, a mutation of the p53 gene, detected by quantitative PCR followed by single-strand conformation polymorphism analysis, was detected in only 2 of 5 tumor sites. The pattern of allelic loss and the mutational pattern of the p53 gene varied at tumor sites within the same patient in 4 of 6 cases of PSCP. These findings are consistent with histopathological evidence that PSCP is multifocal in origin.

Base Sequence↗
PubMed1994

Molecular cloning of differentially expressed genes in human epithelial ovarian cancer.

A DNA-fingerprinting approach has been adapted to detect differentially expressed genes in human ovarian carcinoma. This method is based on the use of arbitrary primers to generate fingerprints from total RNA isolated from normal ovarian epithelial cells and ovarian carcinoma cells by polymerase chain reaction (PCR). Using this method, we cloned two cDNA fragments (DOC-1 and DOC-2) which were present in normal ovarian surface epithelial cells but consistently absent in all of the ovarian cancer cell lines from the differential display. In addition, we also identified a cDNA fragment (LF4.0) which is overexpressed in most of the tumor cell lines and tumor tissues in comparison to the normal ovarian surface epithelial cells. The differential expression of the genes in the tumor cell lines as well as in the tumor tissues was also confirmed by Northern analysis. The clone DOC-2, which is a 800-bp cDNA fragment, has one open reading frame suggesting that the gene may be translated. Assuming that this frame is the sense strand, we generated both sense and antisense riboprobe for in situ mRNA hybridization. Only the antisense DOC-2 riboprobe revealed a hybridization signal which was restricted to the human surface ovarian epithelium. The potential functional roles of these genes is now under investigation.

Base Sequence↗
PubMed1993

Molecular genetic evidence of a unifocal origin for human serous ovarian carcinomas.

The hypothesis that ovarian cancer is multifocal in origin was examined using molecular genetic techniques. Patterns of allelic deletion on chromosome 17 were studied in 16 informative cases of Stage III serous epithelial ovarian carcinoma. DNA was extracted from specimens collected from the omentum and both ovaries, and the specific alleles and chromosomal loci involved in the deletion were identified and compared. In all cases, the patterns of allelic deletion were identical for the tumors that had been collected from different sites in the same patients. In addition, 4 of the 16 cases were heterozygous for the hypoxanthine phosphoribosyl transferase (HPRT) gene on the X-chromosome and were examined for methylation status. In all 4, the same parental allele of the HPRT gene was methylated in tumor cells collected from both ovarian and omental sites, suggesting that the patterns of inactivation of the X-chromosome are identical. This pattern of allelic deletion and HPRT-gene methylation in tumor samples collected from different sites implies that ovarian carcinomas have a unifocal origin.

Alleles↗
PubMed1992

Systemic lupus erythematosus valve disease by transesophageal echocardiography and the role of antiphospholipid antibodies.

OBJECTIVES: The aims of this study were to better characterize valve disease in systemic lupus erythematosus and to determine its association with antiphospholipid antibodies. BACKGROUND: Estimates of the prevalence of valve disease in systemic lupus erythematosus have been higher in autopsy series than in clinical studies using transthoracic echocardiography. Antiphospholipid antibodies have been suggested to be a primary pathogenetic factor. METHODS: Transesophageal echocardiography was performed on 1) 54 patients with lupus erythematosus, 22 of them with (group I) and 32 without (group II) antiphospholipid antibody; 2) on 10 patients with antiphospholipid syndrome (group III); and 3) on 35 normal subjects (group IV). RESULTS: Patients in groups I and III had similar types and concentrations of antibodies. Leaflet thickening was found in 50% of group I, 47% of group II, 10% of group III and 9% of group IV patients (group I or II vs. group III or IV, p < 0.03). Leaflet thickening in patients with lupus erythematosus was diffuse; it usually involved the mitral and aortic valves and was associated with valve regurgitation (73%) or valve masses (50%). Valve masses were observed in 41% of group I, 25% of group II, 10% of group III and in none of group IV patients (group I or II vs. group IV, p < 0.002). Most valve masses in patients with lupus erythematosus were located near the base on the atrial side of the mitral valve or on the vessel side of the aortic valve, had variable size (0.2 to 0.85 cm2), shape and echodensity. Valve regurgitation was observed in 64% of group I, 59% of group II, 10% of group III and 20% of group IV patients (group I or II vs. group III or IV, p < 0.006). Moderate or severe regurgitant lesions were noted in 27% of group I and 25% of group II patients. CONCLUSIONS: Lupus erythematosus valve disease is frequent (74%) regardless of the presence or absence of antiphospholipid antibodies. Therefore antiphospholipid antibodies may not be a primary pathogenetic factor. The characteristic appearance of leaflet thickening and masses in patients with lupus erythematosus may be unique.

Adult↗
PubMed1992

Unifocal origin of advanced human epithelial ovarian cancers.

Ovarian cancers are often diagnosed at a late stage, after the cancer cells have spread to extraovarian sites. Failure to diagnose these tumors earlier may reflect the lack of symptoms and the need for a sensitive, reliable screening test. Alternatively, this can be explained by the hypothesis that some of the extraovarian tumor implants do not represent metastatic spread from the primary cancer but instead are multiple primary tumors developing simultaneously in the peritoneal epithelium. If this is the case, some patients with advanced ovarian cancer may never have had a stage I disease, making early detection theoretically impossible. In this study, we examined the mutational pattern of the p53 gene in 9 patients with epithelial ovarian cancers using tissue collected from different sites within the same patient. In all 9 cases, the mutational pattern of the p53 gene was identical in cancer cells from different sites within the same patient, strongly suggesting that these ovarian tumors were of unifocal origin and that cancer tissues collected from different sites are derived from a single origin.

Adenocarcinoma↗
PubMed1992

Intraperitoneal radioimmunotherapy of refractory ovarian carcinoma utilizing iodine-131-labeled monoclonal antibody OC125.

Refractory epithelial ovarian cancer is generally confined to the peritoneal cavity and is thus amenable to intraperitoneal (ip) therapy. Radiolabeled monoclonal antibodies raised to tumor-associated antigens offer the promise of selective tumor irradiation while reducing toxicity to normal tissues. We have conducted a phase I therapeutic trial to examine the feasibility of ip radioimmunotherapy utilizing escalating doses of 131I-labeled OC125 F(ab')2. Twenty-nine patients were each treated with a single dose of radiolabeled antibody. Twenty-eight patients were evaluable for dose-related toxicity. The toxicities most frequently observed were hematologic and gastrointestinal. Hematologic toxicity was noted in 5/14 (36%) patients receiving 18-87 mCi and in 12/14 (71%) receiving 100-144 mCi (P = 0.018). The median white blood cell nadir of 2-3K/microliters (range, 1.4-3.5K/microliters occurred at a median of 4.5 weeks and the median platelet nadir of 41K/microliters (range, 20-78K/microliters) at a median of 6.5 weeks. Mild gastrointestinal toxicity was observed in 4/14 patients (28%) at doses less than 100 mCi whereas at doses greater than or equal to 100 mCi, 11/14 (79%) patients developed nausea, vomiting, or chronic ileus (P = 0.021). This toxicity occurred most frequently in patients with protracted urinary 131I excretion. We conclude that 131I-labeled OC125 can be safely administered ip. Hematologic and gastrointestinal toxicity is predictable and related to the dose and rate of clearance of isotope.

Animals↗
PubMed1992

Analysis of cytotoxicity of 131I-labelled OC125 F(ab')2 on human epithelial ovarian cancer cell lines.

Monoclonal antibody (mAb) OC125 detects the cell surface-antigen CA125, which is expressed in more than 80% of epithelial ovarian cancers but not in normal adult ovaries. Its high specificity and binding affinity makes OC125 a potential candidate for use in radioimmunotherapy (RIT) in patients with recurrent ovarian cancer. Initial biodistribution studies using radiolabelled specific mAbs have demonstrated significant increase in tumor uptake of dose as compared to radiolabelled irrelevant antibody. We report here an isodose comparison of the cytotoxicity of 131I-labelled OC125 F(ab')2, 131I-labelled nonspecific protein and external beam irradiation using a cesium-137 gamma source. Enhancement of cytotoxity due to the specific binding of the mAb could only be observed when a critical activity of 131I localized at the cell membrane. At a specific activity labelling of less than 4.1 mCi/mg, the antigen specificity of OC125 does not contribute to cell kill. Using a specific activity of 10.2 mCi/mg, the relative biological effectiveness of 131I-labelled OC125 (F(ab')2 was increased by a factor of 5 compared with external-beam X-ray therapy, and the specificity of mAb OC125 was found to enhance the cytotoxicity of the radioimmunoconjugate (RIC) by a factor of 2.7. This low value is in accordance with previously reported theoretical calculations for long range, low-LET isotopes and may be one of the reasons why RIT using 131I has severe limitations. In conclusion, it is necessary to maximize the specific activity of RICs with low-LET isotopes such as iodine-131 in order to maximize the ratio of the dose delivered specifically by membrane-bound mAb versus free-floating nonspecific protein.

Adenocarcinoma↗
PubMed1991

Effect of differentiation agents on expression of CA 125, alkaline phosphatase, and cytokeratins in human ovarian adenocarcinoma cells (OVCA 433).

A number of chemical agents have been found to influence the proliferation, morphology, enzymatic activity, and antigen expression of neoplastic cells toward a more differentiated phenotype. We studied the effects of differentiating agents retinoic acid, sodium butyrate, and dibutyryl cyclic AMP on the expression of the tumor-associated antigen CA 125 and several biochemical markers of differentiation in cultured OVCA 433 ovarian cancer cells. Treatment of OVCA 433 cells with these agents for 96 hr reduced cellular proliferation and altered cellular morphology. Quantitation of cell surface CA 125 using flow cytometry revealed that CA 125 expression was reduced by 35-50%. The amount of CA 125 antigen shed into the culture media was reduced to a similar degree. In addition, differentiation inducers markedly enhanced cellular alkaline phosphatase activity and induced the expression of a 65-67-kDa cytokeratin. These findings provide support for the induction of a more differentiated phenotype by these agents.

Adenocarcinoma↗
PubMed1990

Cochlear implant in Hong Kong Cantonese.

Cochlear implant surgery was performed in four Cantonese-speaking postlingually deaf Chinese adults, using the House/3M single channel device. This article outlines the methodology, including preoperative assessment and postoperative rehabilitation; and explains the necessary modifications in speech and audiologic work-up in Cantonese-speaking patients. Salient features of Cantonese phonetics, especially its tonal characteristics, are described. The findings of the study are presented. The results of the cochlear implant would suggest a performance superior to that of the hearing aid. Furthermore, the cochlear implant is able to detect tonal cues. This quality of the cochlear implant may prove to be a valuable asset to a tonal language-speaking cochlear implantee.

Adult↗
PubMed1990

Minimal change glomerulopathy in two patients after thymectomy.

Two myasthenia gravis patients developed nephrotic syndrome due to minimal change glomerulopathy 3 to 14 years after thymectomy for malignant thymoma. Impaired cellular and humoral immunity has been documented in patients with thymoma and persists after thymectomy. The occurrence of minimal change disease lends support to the hypothesis that the glomerulopathy is secondary to T-cell dysfunction, resulting in production of a lymphokine which increases glomerular basement membrane permeability.

Adult↗
PubMed1988

Superior vena cava syndrome: a rare presenting feature of acute myeloid leukemia.

The mediastinum is seldom involved by granulocytic sarcoma and superior vena cava (SVC) obstruction is an even rarer presentation. Some radiologists advocate to treat SVC obstruction as a semimedical emergency regardless of the underlying pathology. This policy has been criticized. We describe a patient with severe SVC obstruction preceding the development of frank acute myeloblastic leukemia and granulocytic sarcoma in breasts. Review of the literature yields 11 patients with prominent mediastinal granulocytic sarcoma complicating myeloid leukemia; 3 of them presented with superior vena cava syndrome.

Adult↗
PubMed1988

Material for Cantonese speech audiometry constructed by appropriate phonetic principles.

Cantonese is the common Chinese dialect spoken by the citizens in Hong Kong. It is difficult to construct a material for speech audiometry in the Chinese language in view of 3 facts: (1) all words are monosyllabic, (2) the language is tonal and (3) there are many homophones. Since well-documented Cantonese speech audiometry is not available, an attempt is made in this pilot study to construct short word lists which are equal in phonemic distribution.

Audiometry, Speech↗
PubMed1988

Middle ear diseases in cleft palate patients in Singapore.

A preliminary prospective study of the correlation between middle ear diseases and cleft palate was started in February 1987. Eighty three patients from the Plastic Surgical Department of the Singapore General Hospital have been screened. Three quarters of the ears screened were normal. Middle ear effusion was the commonest disease especially in younger children found in eighteen of thirty four abnormal ears; all these patients benefited from myringotomy and insertion of a ventilating tube. Other types of middle ear disease included adhesive otitis media, perforation of the eardrum, attic retraction and cholesteatoma; these were found predominantly in older patients. The incidence of middle ear disease was 23% in Chinese patients with cleft palate as compared with up to 90% in Caucasian patients.

Adolescent↗
PubMed1987

Transfection with plasmid pSV2gptEJ induces chromosome rearrangements in CHEF cells.

In previous cytogenetic studies, trisomy for 3q was found to be the most frequent chromosome change associated with induced tumorigenicity by a variety of agents in Chinese hamster cells. Here we describe similar chromosome changes in 11 lines of CHEF/18 cells transfected with the mutant c-Ha-ras containing plasmid pSV2gptEJ. All 11 lines contained the transfected EJ gene and expressed increased levels of p21, the EJ gene product. Ten of the 11 lines were tumorigenic and all but 2 of these were trisomic for all or part of 3q. One line remained diploid and was nontumorigenic despite expressing elevated p21. Two tumorigenic lines from "hit-and-run" transfection with pSV2gpt were shown to express only control levels of p21, but they were trisomic for 3q. These results show that increased p21 expression is neither necessary nor sufficient for inducing tumorigenicity of CHEF cells. We propose that tumorigenicity in the transfected CHEF/18 cells of this study was induced by chromosome rearrangements, especially trisomy for 3q, that occurred at increased frequencies following transfection with pSV2gptEJ.

Animals↗