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Biomedical subjects

R J Thomas

Publications and source records attributed to R J Thomas.

At least 19 recordsLinked to original sources
PubMed2000

Methylation of exon 2 of p16 is associated with late stage oesophageal cancer.

Methylation of the p16 gene was studied in 16 oesophageal tumours. Five (31%) of the tumours were found to be methylated in exon 1 and eight (50%) were methylated in exon 2. The loss of p16 protein correlated with methylation of exon 1 (P = 0.005). However, methylation of exon 2, but not exon 1, was found to be associated with late stage tumours (P = 0.01). We conclude that the methylation of exon 2 of p16 may have effects on the progression of oesophageal tumours that are independent of the expression of the p16 protein.

Adenocarcinoma↗
PubMed1999

Lipopolysaccharide-induced priming of the human neutrophil is not associated with a change in phosphotyrosine phosphatase activity.

The activation of the neutrophil respiratory burst is a two-step process involving an initial 'priming' phase followed by a 'triggering' event. The biochemical mechanisms which underlie these events are yet to be fully elucidated, but the evidence suggests a crucial role for stimulus-induced tyrosine phosphorylation. The enhanced tyrosine phosphorylation observed upon triggering primed cells may reflect an increase in tyrosine kinase activity or a reduction in the levels of the opposing phosphotyrosine phosphatases (PTPases). We have investigated the latter by examining the possibility that lipopolysaccharide (LPS)-induced priming of the neutrophil respiratory burst involves the suppression of cellular PTPase activity. Purified human neutrophils were incubated for 60 min with and without LPS. Priming of the respiratory burst was confirmed by fMet-Leu-Phe-induced cytochrome c reduction. The level of PTPase activity was assessed by dephosphorylation of [32P]RR-src peptide as substrate. Pretreatment of human neutrophils with 200 ng/ml LPS induced a 2.9 +/- 0.3 (mean +/- SEM, n = 3, P = 0.022) fold increase in the fMet-Leu-Phe-triggered respiratory burst. In the same cells, LPS did not induce a significant change in the total cellular PTPase activity (1.02 +/- 0.02-fold, mean +/- SEM, n = 3, P = 0.63). Similarly, stimulation of neutrophils with fMet-Leu-Phe or phorbol myristate acetate did not significantly affect the cellular PTPase activity (P = 0.94 and 0.68, respectively). Our results suggest that suppression of PTPase activity is not the mechanism underlying the priming and/or triggering of the neutrophil respiratory burst.

Dose-Response Relationship, Drug↗
PubMed1999

Localization of RANKL (receptor activator of NF kappa B ligand) mRNA and protein in skeletal and extraskeletal tissues.

RANKL (receptor activator of NFkappaB ligand) is a membrane-associated osteoblastic molecule, and along with macrophage-colony-stimulating factor, is crucial for osteoclast formation. RANKL is known to be strongly expressed in osteoblasts and lymphoid tissues. We have sought to determine the skeletal and extraskeletal sites of production of RANKL mRNA and protein using the techniques of in situ hybridization and immunohistochemistry. Expression of RANKL mRNA and protein were determined in the developmental progression of endochondral bone formation in mouse, intramembranous bone formation in a rabbit model (mRNA only), in human giant cell tumors of bone, and at extraskeletal sites in the mouse. RANKL mRNA was expressed in prehypertrophic and hypertrophic chondrocytes at day E15 embryonic mouse long bone, and its expression was maintained at these sites throughout development. In newborn and adult mice, high levels of RANKL mRNA were expressed in mesenchymal cells of the periosteum and in mature osteoblasts, while megakaryocytes within the marrow microenvironment expressed RANKL mRNA from 1 week of age. Immunohistochemical analysis revealed a similar localization pattern of RANKL protein at the sites described. In the intramembranous bone formation model, RANKL mRNA was expressed in mesenchymal cells and in actively synthesizing osteoblasts, but not in flattened lining osteoblasts or late osteocytes. Expression of RANKL mRNA and protein in osteoclasts was variable with those within resorption lacunae showing the strongest signal/staining. Likewise, expression varied in osteoclasts from giant cell tumor of bone with a minority of tartrate-resistant acid phosphatase-positive multinucleated cells having no detectable RANKL mRNA or protein. In extraskeletal tissues, RANKL mRNA and protein were detected in the brain, heart, kidney, skeletal muscle, and skin throughout mouse development, suggesting the possibility of several other functions of the molecule. RANKL was also developmentally regulated, as evidenced by its expression in the intestine, liver, and lung at E15 and newborn mouse but not in the adult.

Amino Acid Sequence↗
PubMed1999

Breast cancer cells interact with osteoblasts to support osteoclast formation.

Breast cancers commonly cause osteolytic metastases in bone, a process that is dependent upon osteoclast-mediated bone resorption. Recently the osteoclast differentiation factor (ODF), better termed RANKL (receptor activator of NF-kappaB ligand), expressed by osteoblasts has been cloned as well as its cognate signaling receptor, receptor activator of NFkappaB (RANK), and a secreted decoy receptor osteoprotegerin (OPG) that limits RANKL's biological action. We determined that the breast cancer cell lines MDA-MB-231, MCF-7, and T47D as well as primary breast cancers do not express RANKL but express OPG and RANK. MCF-7, MDA-MB-231, and T47D cells did not act as surrogate osteoblasts to support osteoclast formation in coculture experiments, a result consistent with the fact that they do not express RANKL. When MCF-7 cells overexpressing PTH-related protein (PTHrP) were added to cocultures of murine osteoblasts and hematopoietic cells, osteoclast formation resulted without the addition of any osteotropic agents; cocultures with MCF-7 or MCF-7 cells transfected with pcDNAIneo required exogenous agents for osteoclast formation. When MCF-7 cells overexpressing PTHrP were cultured with murine osteoblasts, osteoblastic RANKL messenger RNA (mRNA) levels were enhanced and osteoblastic OPG mRNA levels diminished; MCF-7 parental cells had no effect on RANKL or OPG mRNA levels when cultured with osteoblastic cells. Using a murine model of breast cancer metastasis to bone, we established that MCF-7 cells that overexpress PTHrP caused significantly more bone metastases, which were associated with increased osteoclast formation, elevated plasma PTHrP concentrations and hypercalcaemia compared with parental or empty vector controls.

Animals↗
PubMed1999

Spectrally resolved white-light interferometry for measurement of ocular dispersion.

Spectrally resolved white-light interferometry was used to measure the wavelength dependence of refractive index (i.e., dispersion) for various ocular components. Verification of the technique's efficacy was substantiated by accurate measurement of the dispersive properties of water and fused silica, which have both been well-characterized in the past by single-wavelength measurement of the refractive index. The dispersion of bovine and rabbit aqueous and vitreous humors was measured from 400 to 1100 nm. In addition, the dispersion was measured from 400 to 700 nm for aqueous and vitreous humors extracted from goat and rhesus monkey eyes. An unsuccessful attempt was also made to use the technique for dispersion measurement of bovine cornea and lens. The principles of white-light interferometry, including image analysis, measurement accuracy, and limitations of the technique, are discussed. In addition, alternate techniques and previous measurements of ocular dispersion are reviewed.

Animals↗
PubMed1998

Gene organization and alternative splicing of human prohormone convertase PC8.

The mammalian Ca2+-dependent serine protease prohormone convertase PC8 is expressed ubiquitously, being transcribed as 3.5, 4.3 and 6.0 kb mRNA isoforms in various tissues. To determine the origin of these various mRNA isoforms we report the characterization of the human PC8 gene, which has been previously localized to chromosome 11q23-24. Consisting of 16 exons, the human PC8 gene spans approx. 27 kb. A comparison of the position of intron-exon junctions of the human PC8 gene with the gene structures of previously reported prohormone convertase genes demonstrated a divergence of the human PC8 from the highly conserved nature of the gene organization of this enzyme family. The nucleotide sequence of the 5'-flanking region of the human PC8 is reported and possesses putative promoter elements characteristic of a GC-rich promoter. Further supporting the potential role of a GC-rich promoter element, multiple transcriptional initiation sites within a 200 bp region were demonstrated. We propose that the various mRNA isoforms of PC8 result from the inclusion of intronic sequences within transcripts.

Alternative Splicing↗
PubMed1998

Colorectal cancer: a survey of community beliefs and behaviours in Victoria.

OBJECTIVE: To document self-reported beliefs and behaviours in relation to colorectal cancer (CRC) and screening for CRC. DATA COLLECTION: A stratified random sample was selected from the telephone directory, and structured telephone interviews were conducted using a computer-assisted telephone interviewing system. PARTICIPANTS: 500 men and 500 women aged 40-60 years, 70% randomly selected from the Melbourne metropolitan area and 30% from rural Victoria. The response rate to the initial telephone invitation of 1569 eligible people was 63.7%. OUTCOME MEASURES: Awareness of and experience with CRC; knowledge of CRC risk, risk reduction behaviour, and screening tests for CRC; willingness to have screening tests for CRC; and test preferences. RESULTS: The people surveyed were relatively unaware of their personal risk of CRC, despite 61% (95% CI, 57%-65%) knowing someone who had CRC. Although 51% (95% CI, 48%-54%) could not name any CRC screening test, 68% (95% CI, 65%-71%) knew of the value of a high fibre diet in prevention. However, 67% (95% CI, 64%-70%) thought it was unlikely they would have a screening test for CRC in the next two years, but 64% (95% CI, 61%-67%) considered that some person could influence their decision to have a test, 60% (95% CI, 56%-64%) stating that they would be influenced by a doctor. Faecal occult blood testing and sigmoidoscopy were equally acceptable. In general, women were more knowledgeable than men. There were no systematic age or urban/rural differences. CONCLUSIONS: There is a variable understanding of CRC in the community. Although prevention is well understood, this is not true of screening. General practitioners are likely to be influential in the uptake of any screening programs.

Adult↗
PubMed1998

Increased levels of phosphatidylinositol 3-kinase activity in colorectal tumors.

BACKGROUND: Phosphatidylinositol 3-kinase (PI 3-kinase), an enzyme that phosphorylates inositol phospholipids at the D-3 position of the inositol ring, has been implicated in the signaling pathways regulating cell growth by virtue of its activation in response to various mitogenic stimuli. In spite of the considerable attention PI 3-kinase has received with regard to its possible role in the mitogenic pathways in hematopoietic malignancies, there are few reports of investigations into PI 3-kinase activity in solid tumors. METHODS: Colorectal tumor tissue and normal-appearing colonic mucosa from the same patients were homogenized and solubilized and adjusted to equal protein levels. PI 3-kinase then was immunoprecipitated from 200 microg of the solubilized tissue using a polyclonal antibody to the p85 subunit of PI 3-kinase. PI 3-kinase activity was assessed using phosphatidylinositol as the substrate and the assay product analyzed by thin-layer chromatography. Phosphorylation of phosphatidylinositol in the D-3 position was confirmed by high performance liquid chromatography analysis of deacylated and deglycerated products. RESULTS: Thirty-two of the 37 tumors tested (86%) demonstrated increased PI 3-kinase activity compared with normal-appearing mucosa from the same patients (overall mean increase+/-standard error of the mean=3.8+/-0.6-fold; P < 0.05, Student's t test for paired data). The frequency and extent of increased PI 3-kinase enzyme activity in tumors did not correlate with clinical parameters or the presence of oncogenic ras mutations. CONCLUSIONS: In this study colorectal tumors exhibited enhanced PI 3-kinase activity compared with normal colonic mucosa, raising the possibility that PI 3-kinase may be a potential target for new strategies for the treatment of colorectal carcinoma.

Colorectal Neoplasms↗
PubMed1998

Varied presentations of unilateral lung hypoplasia and agenesis: a report of four cases.

Unilateral lung hypoplasia or agenesis can be asymptomatic or present with recurrent respiratory symptoms. The latter may be amenable to surgical treatment in selected cases. Of four children in this report, two are being managed without surgery. A third was relieved of his symptoms by pneumonectomy. The fourth presented with acute foreign-body inhalation into the healthy right main bronchus, and coexistent left pulmonary agenesis was discovered at bronchoscopy. Bronchoscopy and computed tomography were found to be the most useful investigations in management.

Child, Preschool↗
PubMed1998

Asymptomatic sexually transmitted disease prevalence in four military populations: application of DNA amplification assays for Chlamydia and gonorrhea screening.

The prevalence of asymptomatic chlamydial and gonococcal infections in male and female military populations was determined using urine-based ligase chain reaction DNA amplification assays (DAAs). Cross-sectional surveys in four military settings revealed an overall prevalence of asymptomatic chlamydial infection of 4.2% (56/1338). This included 3.4% (21/618) of Western Pacific shipboard US Marine Corps enlisted men; 5.2% (21/406) of male marines shore-based in Okinawa, Japan; 2.7% (5/183) of female enlisted US Navy subtender personnel in dry dock; and 6.9% (9/131) of shore-based female naval personnel in San Diego. No gonococcal infections were detected. All subjects were treated within 2 weeks of screening; none of them had progressed to symptomatic disease. General population-based screening for asymptomatic sexually transmitted diseases, and in particular chlamydial infection, can be successfully implemented using urine-based DAA tests. Benefits are maximized in a population in which compliance for follow-up therapy is high.

Adult↗
PubMed1998

Seven-year change in graded exercise treadmill test performance in young adults in the CARDIA study. Cardiovascular Risk Factors in Young Adults.

PURPOSE: Most studies of physical fitness change have been relatively small, not population-based, and lacking in women and nonwhites. The purpose of this analysis was to evaluate the 7-yr change in physical fitness in a biracial (black and white) population of young men and women. METHODS: We evaluated change in exercise treadmill test performance in a biracial (black and white) population of 1,962 young adults, ages 18-30 yr at baseline, who completed symptom-limited graded exercise treadmill tests at the baseline (1985-1986) and year 7 (1992-1993) examinations of the CARDIA study. RESULTS: Mean test duration decreased 58 s (9.5%) over 7 yr (black men, 13.6% decrease, white men, 7.4%; black women, 11.1%; white women, 7.0%). Mean time to heart rate 130 (WL130), a measure of submaximal performance, decreased 31 s (11.3%) (black men, 16.9%; white men, 10.0%; black women, 12.3%; white women, 6.1%). Baseline body mass index (BMI) and physical activity were not statistically significant predictors of test duration change in any race-gender group, but change in BMI and activity were. Seven-year weight gain >20 lbs (31% of cohort) was associated with a large decrease in fitness (18.5% decrease in mean duration, 21.8% decrease in WL130). CONCLUSION: These data suggest that fitness declines during young adulthood in blacks and whites and that fitness changes are related to changes in weight and physical activity.

Adult↗
PubMed1998

Rising incidence of oesophageal adenocarcinoma in men in Australia.

Adenocarcinomas of the oesophagus and of the gastric cardia have been reported to be increasing in incidence in many countries, while the incidence of squamous cell carcinoma of the oesophagus is stable and non-cardia gastric cancers are decreasing in incidence. Age-standardized incidence rates for the years 1982-1993 for oesophageal adenocarcinoma and non-adenocarcinoma, and gastric cardia and non-cardia cancers were calculated based on state cancer registry incidence data. Time trends in the age-standardized rates were assessed using linear regression. A consistent increasing trend in the incidence of oesophageal adenocarcinoma in men was seen in all states of Australia and was statistically significant in all states except South Australia. There were no consistent nationwide trends in the incidence of oesophageal adenocarcinoma in women, although a trend towards an increase in the incidence of this cancer reached statistical significance (P < 0.05) in three states (New South Wales, Victoria, Queensland). There were no important trends in the incidence of oesophageal non-adenocarcinoma in either men or women. There were no consistent nationwide changes in the incidence of gastric cardia cancer in either men or women, although this cancer was significantly increasing in Tasmania in both men and women. The incidence of cancer of the stomach not arising at the gastric cardia was significantly decreasing in men in all states and was also decreasing in women in all states, although in women this decrease was statistically significant only in New South Wales, Victoria and Western Australia. There has been a dramatic increase in the incidence of oesophageal adenocarcinoma in men in Australia. The incidence of this cancer in men is now approximately equal with that of non-adenocarcinoma of the oesophagus. The incidence of non-cardia stomach cancer continues to fall.

Adenocarcinoma↗
PubMed1998

Community (mis)understanding of colorectal cancer treatment.

BACKGROUND: A study was undertaken to assess community understanding of colorectal cancer symptoms and colorectal cancer treatment. METHODS: A computer-assisted telephone survey was undertaken to interview 1000 men and women aged 40-60 years. RESULTS: Overall there was a considerable lack of information in the community about colorectal cancer symptoms and treatment. Men were less knowledgeable than women, and 28% of men were unable to name any symptoms of bowel cancer. Although surgery was mentioned by 53% of the sample, a third could not name any treatments. Most responses to questions about the effects of treatment related to chemotherapy-related disturbances and the possibility of having a colostomy bag postoperatively. CONCLUSIONS: There is inaccurate information in the community about colorectal cancer symptoms and treatment. This may inhibit involvement in screening programmes or delay presentation for therapy, as a result of undue concern about the prospects of treatment.

Adult↗
PubMed1998

Parathyroid hormone-related protein (PTHrP) mRNA splicing and parathyroid hormone/PTHrP receptor mRNA expression in human placenta and fetal membranes.

During human pregnancy, parathyroid hormone-related protein (PTHrP) and parathyroid hormone (PTH)/PTHrP receptor are produced by the uterus, placenta, fetal membranes (amnion and chorion) and developing fetus. PTHrP alternative 3' mRNA splicing results in transcripts which encode three PTHrP isoforms and have been identified in amnion. Uteroplacental PTHrP expression is greatest in amnion and increases dramatically during late pregnancy. The aims of this study were to determine PTH/PTHrP receptor mRNA expression at preterm and term gestations and to determine 3' alternative splicing patterns in placenta, amnion and choriodecidua at preterm and term gestations. Using semiquantitative reverse transcription-polymerase chain reaction, PTHrP and PTH/PTHrP receptor transcripts were identified in preterm (n=5) and term (n=7) gestational tissues. PTH/PTHrP receptor mRNA expression did not differ between tissue types or change with advancing gestation. In contrast, PTHrP expression in the same tissues increased with advancing gestation and was significantly greater in amnion than in placenta and choriodecidua. Thus PTHrP, although produced predominantly in amnion, may act in amnion and other tissues including placenta, choriodecidua and myometrium. In amnion over placenta, transcripts encoding PTHrP 1-139 and 1-173 were detected in some preterm and all term samples and those encoding PTHrP 1-141 were detected in all samples. Similar results were obtained for reflected amnion. In placenta and choriodecidua, PTHrP 1-139 and 1-173 transcripts were undetectable or of low abundance. PTHrP 1-141 transcripts were detected in some placenta and choriodecidua samples. In summary, transcripts encoding PTHrP 1-141 appeared to be more abundantly expressed than those encoding PTHrP 1-139 or 1-173. However, the up-regulation of PTHrP expression in amnion at term may involve each of the alternative 3' mRNA splicing pathways since transcripts for each isoform appeared to be more consistently expressed at term.

Alternative Splicing↗