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Biomedical subjects

S Chan

Publications and source records attributed to S Chan.

At least 217 records · Page 12Linked to original sources
PubMed1987

c-myc oncogene expression in colorectal cancer.

The pattern of c-myc gene organization and expression has been examined in resected colonic tumors and in the adjacent normal colon from 15 patients undergoing radical surgery. DNA hybridization showed no evidence of gene amplification or rearrangement. Transcripts of the c-myc messenger ribonucleic acid (mRNA) were elevated up to 32-fold in 12 of 15 tumors. The gene product, p62c-myc, was detected by both immunoblotting and immunohistology using a monoclonal antibody raised against a synthetic peptide immunogen. There was close correlation between c-myc mRNA copy number and p62c-myc abundance. Three well differentiated tumors contained high levels of transcript and protein, whereas four poorly differentiated tumors had the lowest levels. The assay of oncogene products may provide new biologically relevant tumor markers for determining prognosis and guiding treatment.

Aged↗
PubMed1987

Soluble minerals in chemical evolution. II. Characterization of the adsorption of 5'-AMP and 5'-CMP on a variety of soluble mineral salts.

The adsorption of 5'-AMP and 5'-CMP was studied in saturated solutions of several soluble mineral salts (NaCl, Na2SO4, MgCl2 X 6H2O, MgSO4 X 7H2O, CaCl2 X 2H2O, CaSO4 X 2H2O, SrCl2 X 6H2O, SrSO4, and ZnSO4 X 7H2O) as a function of pH, ionic strength, and surface area of the solid salt. The adsorption shows a pH dependence; this can be correlated with the charge on the nucleotide molecule which is determined by the state of protonation of the N-1 nitrogen of 5'-AMP or N-3 nitrogen of 5'-CMP and the phosphate oxygens. The adsorption which results from the binding between the nucleotide molecule and the salt surface is proposed as being due to electrostatic forces. It was concluded that the adsorption was reversible in nature. The adsorption shows a strong dependence upon ionic strength and decreases with increasing ionic strength. Surface area is shown to be an important factor in evaluating and comparing the magnitude of adsorption of nucleotides onto various mineral salts. The implications of the results of the study are discussed in terms of the importance of soluble mineral salts as adsorption sites in the characterization of the adsorption reactions of an adsorbed template in biogeochemical cycles.

Adenosine Monophosphate↗
PubMed1987

Publication bias and clinical trials.

A study was performed to evaluate the extent to which the medical literature may be misleading as a result of selective publication of randomized clinical trials (RCTs) with results showing a statistically significant treatment effect. Three hundred eighteen authors of published trials were asked whether they had participated in any unpublished RCTs. The 156 respondents reported 271 unpublished and 1041 published trials. Of the 178 completed unpublished RCTs with a trend specified, 26 (14%) favored the new therapy compared to 423 of 767 (55%) published reports (p less than 0.001). For trials that were completed but not published, the major reasons for nonpublication were "negative" results and lack of interest. From the data provided, it appears that nonpublication was primarily a result of failure to write up and submit the trial results rather than rejection of submitted manuscripts. The results of this study imply the existence of a publication bias of importance both to meta-analysis and the interpretation of statistically significant positive trials.

Clinical Trials as Topic↗
PubMed1987

A novel tumour marker related to the c-myc oncogene product.

We have studied the utility of the c-myc oncogene product as tumour marker using a set of monoclonal antibodies raised against synthetic peptides constructed from sequence data of the human c-myc oncoprotein. One antibody, Myc1-9E10, raised against the C-terminal 32 amino acids, has been shown to detect specifically the 62 kDa c-myc gene product in tumour cells. Immunoblotting of sera and urine with this antibody consistently revealed a single 40 kDa band (p40). Quantitative analysis using dilution dot immunoblotting demonstrated a considerable increase in the titre of p40 in the sera of 51 patients with a wide range of advanced solid tumours when compared with 17 healthy controls and 50 patients with non-malignant diseases. Serial measurement of the p40 titre in 12 patients with resected colorectal carcinoma shows a gradual return to normal with a half-life of 7 days. Our data suggests that p40 may be a useful new marker for monitoring tumour activity.

Biomarkers, Tumor↗
PubMed1987

Free drug monitoring.

The principles, technique of measurement, and clinical significance of free drugs are reviewed. Albumin, alpha-1-acid glycoprotein, and lipoprotein are the main drug-binding proteins in blood. Variations of the concentrations of these proteins owing to disease would result in changes in the free drug levels. These levels may be determined by equilibrium dialysis, ultrafiltration, and other techniques.

Blood Proteins↗
PubMed1987

The potential of oncogene products as tumour markers.

This paper discusses the possibilities of using the altered expression of oncogenes and their products in neoplastic tissues as markers for the diagnosis, prognosis and monitoring of human malignant disease. Results from our studies of the c-myc oncogene and its product in human solid tumours, using DNA and RNA hybridization and a set of monoclonal antibodies (MCAs) raised against synthetic peptides, are presented. These illustrate three important principles. Firstly, the level of expression of the gene correlates closely with histological grading. Secondly, the increased expression of an oncogene in a tumour can be used as a marker for imaging with radiolabelled MCA. Thirdly, the detection of a 40,000 dalton serum protein, which is immunologically related to the p62c-myc oncoprotein, and its quantitative analysis in patients with cancer and normal controls, suggests that oncogene-related serum proteins may provide novel markers for monitoring tumour activity. These data support the view that the detailed analysis of oncogene expression has the potential to predict a tumour's behaviour and response to different therapeutic modalities.

Antibodies, Monoclonal↗
PubMed1986

Trazodone: a simple, clean extraction and rapid quantification by high pressure liquid chromatography.

We have developed an HPLC technique which is precise, rapid and reliable. Sample preparation involves simple alkaline extraction into an organic solvent mixture. Trazodone elutes at 3.2 min in this reverse phase system. There is no requirement for elevated column temperature. The method is linear to 3000 ng/ml. The availability of a technique which is transferrable to the clinical laboratory may help to define the proper role of therapeutic monitoring of trazodone.

Chlordiazepoxide↗
PubMed1986

Erythrocytic sedimentation rate as a measure of clinical activity in inflammatory bowel disease.

To assess the reliability of the erythrocytic sedimentation rate (ESR) as a measure of clinical activity in inflammatory bowel disease, we analyzed the correlations of ESR with a global assessment of clinical activity in 77 patients with varying extents of Crohn's disease and ulcerative colitis. Analysis of all 141 ESR determinations in all 77 patients showed a highly significant correlation between mean ESR and clinical activity score (r = 0.54, p less than 0.001). Analysis of 133 ESR determinations in these 77 patients when their disease activity was either mild, moderate, or severe showed some significant differences among certain disease categories. The highest mean ESRs were in patients with the most extensive colon involvement (Crohn's colitis 40.7 +/- 3.3, universal ulcerative colitis 31.0 +/- 3.9), whereas the lowest mean ESRs were in patients with the most limited disease (ulcerative proctitis and proctosigmoiditis 19.2 +/- 2.1). The rate of increase in ESR with progressively increasing clinical activity from mild to moderate was the same in all disease categories, with the exception of Crohn's disease limited to the small bowel (ileitis or jejunoileitis), in which the ESR was relatively unchanged in a small sample of patients. By the time clinical activity became severe, however, patients in all disease categories manifested similarly high ESRs, with the exception of ulcerative proctitis in which the ESR remained low in the single patient tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Sedimentation↗
PubMed1985

Soluble minerals in chemical evolution. I. Adsorption of 5'-AMP on CaSO4--a model system.

The adsorption of 5'-AMP onto solid CaSO4 2H2O was studied in a saturated suspension as a function of pH and electrolyte concentration. The adsorption is pH-dependent and is directly correlated with the charge on the 5'-AMP molecule which is determined by the state of protonation of the N-1 nitrogen of the purine ring and the phosphate oxygens. It is proposed that the binding occurs between the nucleotide and the salt is electrostatic in nature. The adsorption decreases with increasing ionic strength of the solution which means that in a fluctuating environment of wetting and drying cycles, a biomolecule similar to 5'-AMP could be expected to desorb during the drying phase. The results indicate that CaSO4 2H2O can serve as a concentrating surface for biomolecules. The significance of this is discussed with regard to the possible role of soluble minerals and their surfaces in a geochemical model consistent with the evolution of the Earth and the origin of life.

Adenosine Monophosphate↗
PubMed1984

Complete env gene deletions of three replication-defective strains of Rous sarcoma virus and a model for the origin of their genetic structures.

Replication-defective deletion mutants of Rous sarcoma virus (RSV) have been described which transform cells in culture and elaborate envelope (-) defective particles. The env deletions of two clonal variants of the Bryan strain of RSV, RSV(-)3, and RSV(-)16, and of a replication-defective variant of Schmidt-Ruppin RSV (SRN8) were analyzed by fingerprinting oligonucleotides hybridized by a molecularly cloned env DNA probe that spans from near the 3' end of pol to the 3' end of env. It was observed that all three replication-defective RSV strains are essentially complete env deletions but retain the 3' end of pol. Based on a common pol-src junction oligonucleotide that may reflect a homologous sequence repeated at both ends of env in nondefective RSV, the env deletions of RSV(-)3 and 16 appear to be isogenic. The original deletion may have involved recombination between these sequences. The absence of this oligonucleotide in SRN8 indicates that the env deletion of SRN8 has different borders and represents an independent env deletion of nondefective RSV. All three defective RSVs have the genetic structure gag-pol-src. This genetic structure is consistent with the need for a complete gag to make a particle and with the assumption that an independent src gene rather than a gag- or gag-pol-src hybrid gene functions in transformation. It is suggested that a complete pol is not necessary for, but may assist, virus particle formation.

Avian Sarcoma Viruses↗
PubMed1982

Two types of cross-gender identity.

A revision of the typology of male cross-gender identity was carried out by means of formalized, easily replicable methods. The results suggest (1) that there are two discrete types of cross-gender identity, one heterosexual, the other homosexual; (2) that transvestism, and closely related conditions of cross-gender identity, occur exclusively or almost exclusively in heterosexuals; (3) that of the two types of transsexualism distinguished in this study, type A is, in heterosexuals, very rare or completely nonexistent; (4) that (in the course of time) transvestites or borderline transsexuals (defined below) may develop sustained cross-gender identity, as observed by Stoller (1971); (5) that although, according to Hoenig and Kenna (1974), transsexualism by itself is not an anomalous erotic preference, it is (virtually) always either preceded by transvestism or accompanied by homosexuality or cross-gender fetishism.

Adult↗
PubMed1981

Conservative parotidectomy by the peripheral approach.

A series of 30 consecutive conservative parotidectomies is reported with a detailed assessment of the extent and duration of facial nerve damage. There was one case of severe temporary facial nerve paralysis but no cases of permanent palsy. All operations were performed using the peripheral approach to the facial nerve and the technique employed is described.

Adult↗
PubMed1981

Identification of mitogen responding lymphocytes by fluorescence polarization.

Measurements of the intensity and polarization distributions of fluorescein fluorescence in human lymphocyte populations show changes within minutes after exposure of the cells to the mitogens phytohemagglutinin and Concanavalin A. The distributions of polarization, which before mitogen exposure show essentially a single peak, after exposure develop a second peak at a lower value of polarization. Simultaneously, the intensity distributions show a shift to higher levels of intensity. These shifts can be modeled on the basis of a subpopulation of lymphocytes responding to mitogen. Interpretation of the results is complicated by many factors that may influence the shape of the polarization distributions. In particular we show that the measurements are sensitive to the concentrations of phytohemagglutinin, Concanavalin A, Ca++, K+, fluorescein diacetate, the incubation time and the specific donor. Nevertheless, fluorescein fluorescence measurements provide a rapid and sensitive method for studying the physiology of lymphocytes and for identifying responding lymphocyte subpopulations.

Calcium↗