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Biomedical subjects

S G Williams

Publications and source records attributed to S G Williams.

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

Peak exercise cardiac power output; a direct indicator of cardiac function strongly predictive of prognosis in chronic heart failure.

OBJECTIVES: This study assessed the prognostic value of peak cardiac power output, measured non-invasively during maximal cardiopulmonary exercise testing, against other exercise-derived haemodynamic variables in patients with chronic congestive heart failure. METHOD AND RESULTS: Two hundred and nineteen unselected, consecutive patients with congestive heart failure (166 men, mean (+/-SD) age of 56+/-13 years) who underwent maximal symptom limited cardiopulmonary treadmill exercise testing with non-invasive estimation of cardiac output using carbon dioxide re-breathing techniques, were followed-up for a mean period of 4.64 (4.47--4.82, 95% CI) years. Cardiac power output was calculated from the product of cardiac output and mean arterial blood pressure. All cause mortality was 12.3% (27 deaths). Peak and resting cardiac power output, peak mean arterial blood pressure, peak and resting cardiac output and peak VO(2)were all predictive of outcome on univariate analyses. Peak cardiac power output, either entered continuously or categorically with a cut-off value of 1.96 watts, was the only independent predictor of mortality (P=0.0004 for values < or >1.96 watts and P=0.001 for continuous values) using multivariate analysis. A relative risk ratio of 5.08 (1.94-13.3, 95% CI) was obtained for a cardiac power output <1.96 watts. CONCLUSION: Peak cardiac power output is an independent predictor of mortality that can be measured non-invasively using cardiopulmonary exercise testing. It can give further prognostic power to a peak VO(2)in the assessment of patients with congestive heart failure.

Adult↗
PubMed2001

Assessment of adenosine, arbutamine and dobutamine as pharmacological stress agents during (99m)Tc-tetrofosmin SPECT imaging: a randomized study.

We evaluated the use of adenosine, dobutamine and arbutamine with (99m)Tc-tetrofosmin myocardial perfusion imaging. Forty patients under investigation for suspected coronary artery disease were recruited. Each had a resting scan and two separate stress scans on different days, in a randomized cross-over study. Resultant images were blindly reported in 13 segments per scan as normal, reversible or fixed defects. A score was given (0-3) for segmental defect severity. Haemodynamic responses were as expected for each agent. Subjective side effect scores did not differ overall between agents. Adenosine caused a significantly higher incidence of abnormal taste (54%) than dobutamine and arbutamine (both 23%) and a lower incidence of palpitations (25% vs 69% and 54%, respectively), all P<0.05. Arbutamine caused significantly more chest pain than adenosine (77% vs 46%) though less flushing (35% vs 68%), both P<0.05. Comparison of the results obtained showed highly significant levels of segmental agreement for visual and semi-quantitative analysis between adenosine and arbutamine, kappa value and correlation coefficient of 0.78 and 0.86, respectively, dobutamine and adenosine 0.69 and 0.78, and arbutamine and dobutamine 0.75 and 0.78, all P<0.0001. Adenosine, arbutamine and dobutamine differ in their haemodynamic response and side effect profile but provide highly comparable results during (99m)Tc SPECT imaging.

Adenosine↗
PubMed2001

Differences in gene expression in muscle-invasive bladder cancer: a comparison of Italian and American patients.

OBJECTIVE: To seek differences in gene expression in the primary muscle-invasive bladder cancers of two cohorts of patients having different survival rates. An Italian group treated by transurethral resection of the bladder tumor (TURBT) and neo-adjuvant chemotherapy using methotrexate, vinblastine, adriamycin and cisplatin (M-VAC) followed by TURBT, partial cystectomy or radical cystectomy (75% 3-year survival) was compared to an American cohort treated by radical cystectomy (51% 3-year survival). METHODS: Immunohistochemistry was used to examine the protein expression levels of three genes that act at the G1/S cell cycle checkpoint, p53, p21/waf-1/cip1 (a downstream effector gene in the p53 pathway) and Rb, plus a major inhibitor of apoptosis, Bcl-2. RESULTS: For the bladder cancers of the Italian patient cohort, there was a significantly higher rate of p53 immunopositivity (93 vs. 63%, p = 0.002) and a significantly lower rate of Rb loss (25 vs. 54%, p = 0.009). In bivariate analysis, 72% of Italian tumors were immunopositive for both p53 and p21 (p53+/p21+) vs. 49% for the American tumors. The subset of Italian patients with p53+/p21+ tumors were more frequently disease-free (stage pT0) following chemotherapy and were less likely to fail therapy than those with p53+/p21- tumors (p = 0.0357). Loss of Rb staining was associated with a decreased 5-year survival in the Italian, but not in the American patients. CONCLUSIONS: (1) Significant differences in the expression of the p53, p21 and Rb genes were found between the 2 groups of patients. (2) Italian patients with p53+/p21+ tumors had significantly lower recurrence rates after TURBT and chemotherapy than those having p53+/p21- tumors. (3) Absence of p21 immunopositivity in the Italian tumors may identify alterations in the p53 pathway that predict poor outcome.

Gene Expression Regulation, Neoplastic↗
PubMed2001

Molecular markers for diagnosis, staging, and prognosis of bladder cancer.

Conventional histopathologic evaluation of bladder cancer, encompassing tumor grade and stage, is inadequate to accurately predict the behavior of most bladder tumors. Intense research efforts are under way to identify and characterize various bladder cancers and their true biological potential more effectively. The need to predict which superficial tumors will recur or progress--and which invasive tumors will metastasize--has led to the identification of a variety of potential prognostic markers for patients with bladder cancer. The molecular changes that occur in transitional cell carcinoma of the bladder are numerous and can be categorized into (1) chromosomal alterations, leading to carcinogenesis; (2) loss of cell-cycle regulation, accounting for cellular proliferation; and (3) growth control events such as angiogenesis, resulting in metastasis. It is becoming apparent that the accumulation of genetic and molecular changes ultimately determines a tumor's phenotype and subsequent clinical behavior. The potential clinical application of new diagnostic techniques (ie, loss-of-heterozygosity analysis to identify tumor suppressor genes) and older, well-established, techniques (ie, immunohistochemistry) combined with improvements in the use of automated and standardized systems are areas of active investigation.

Biomarkers, Tumor↗
PubMed2000

Phase I/II study of paclitaxel, carboplatin, and methotrexate in advanced transitional cell carcinoma: a well-tolerated regimen with activity independent of p53 mutation.

OBJECTIVES: To evaluate the feasibility and activity of paclitaxel, carboplatin, and methotrexate in advanced transitional cell carcinoma (TCC) of the urothelium and to relate the activity of this combination to the mutational status of p53. METHODS: In the Phase I portion, paclitaxel 200 mg/m(2) (3-hour infusion), carboplatin dosed to an area under the curve (AUC) of 6 mg/mL. min, and methotrexate 10 mg/m(2), increasing in 10-mg/m(2) increments, were administered on day 1 and every 21 days thereafter with granulocyte colony-stimulating factor (G-CSF) and leucovorin support. Subsequently, a Phase II study was initiated in which the carboplatin dose was lowered to an AUC of 5 to allow treatment without G-CSF. p53 expression was evaluated using immunohistochemistry. RESULTS: Thirty-three patients were accrued. Median age was 66 years. No dose-limiting toxicities were seen in the Phase I portion despite escalation of the methotrexate to 60 mg/m(2). Principal toxicities were myelosuppression and neuropathy. The overall response rate (Phase I and II) was 56% (95% confidence interval 38% to 74%). Median survival was 15.5 months; 88% of patients overexpressed p53 at the primary site. CONCLUSIONS: Paclitaxel, carboplatin, and methotrexate were well tolerated and active in advanced TCC. The high response rate to this regimen despite frequent p53 mutation is consistent with the p53-independent mechanism of paclitaxel. Whether this regimen is superior to methotrexate/vinblastine/doxorubicin/cisplatin, other paclitaxel-based regimens, or to paclitaxel alone will require comparative trials.

Aged↗
PubMed2000

Risk of influenza A (H5N1) infection among health care workers exposed to patients with influenza A (H5N1), Hong Kong.

The first outbreak of avian influenza A (H5N1) occurred among humans in Hong Kong in 1997. To estimate the risk of person-to-person transmission, a retrospective cohort study was conducted to compare the prevalence of H5N1 antibody among health care workers (HCWs) exposed to H5N1 case-patients with the prevalence among nonexposed HCWs. Information on H5N1 case-patient and poultry exposures and blood samples for H5N1-specific antibody testing were collected. Eight (3.7%) of 217 exposed and 2 (0.7%) of 309 nonexposed HCWs were H5N1 seropositive (P=.01). The difference remained significant after controlling for poultry exposure (P=.01). This study presents the first epidemiologic evidence that H5N1 viruses were transmitted from patients to HCWs. Human-to-human transmission of avian influenza may increase the chances for the emergence of a novel influenza virus with pandemic potential.

Adult↗
PubMed1999

Percutaneous endoscopic gastrostomy feeding in patients with cystic fibrosis.

BACKGROUND: Malnutrition is a common management problem in patients with cystic fibrosis (CF). Various approaches to supplemental nutrition by both parenteral and enteral routes have been used. AIM: To analyse the efficacy and acceptability of supplemental overnight feeding using a percutaneous endoscopic gastrostomy (PEG) in patients with CF. PATIENTS: 53 patients with CF (43 adults; age >17 years) with severe pulmonary disease. METHODS: The technical success and complications of PEG insertion were documented together with changes in nutritional and pulmonary status of the cohort. RESULTS: PEG tubes were successfully inserted in all patients, with immediate complications (respiratory depression) in two (4%) and late complications in 13 (25%). Feeding was well tolerated by 50/51 (98%) of the cohort during a mean (SEM) follow up of 14.5 (2.1) months. The adult cohort had a significant increase in weight and body mass index at six months which was maintained at 12 months. Serum albumin concentration remained stable at six months but had fallen by 12 months, although the differences were not statistically significant. These results were reflected in the paediatric cohort. Pulmonary function in those followed up for one year had apparently stabilised, but the number of admissions to hospital over the year before and the year after PEG did not change. Half of the cohort were accepted for heart-lung/lung transplantation, the improvement in nutritional status being a prerequisite for this. CONCLUSION: Supplemental PEG tube feeding is well tolerated and results in a significant improvement in nutritional status and an apparent stabilisation of pulmonary function in severely malnourished CF patients with advanced pulmonary disease

Adolescent↗
PubMed1998

Repressor titration: a novel system for selection and stable maintenance of recombinant plasmids.

The propagation of recombinant plasmids in bacterial hosts, particularly in Escherichia coli, is essential for the amplification and manipulation of cloned DNA and the production of recombinant proteins. The isolation of bacterial transformants and subsequent stable plasmid maintenance have traditionally been accomplished using plasmid-borne selectable marker genes. Here we describe a novel system that employs plasmid-mediated repressor titration to activate a chromosomal selectable marker, removing the requirement for a plasmid-borne marker gene. A modified E.coli host strain containing a conditionally essential chromosomal gene (kan) under the control of the lac operator/promoter, lac O/P, has been constructed. In the absence of an inducer (allolactose or IPTG) this strain, DH1 lackan , cannot grow on kanamycin-containing media due to the repression of kan expression by LacI protein binding to lac O/P. Transformation with a high copy-number plasmid containing the lac operator, lac O, effectively induces kan expression by titrating LacI from the operator. This strain thus allows the selection of plasmids without antibiotic resistance genes (they need only contain lac O and an origin of replication) which have clear advantages for use as gene therapy vectors. Regulation in the same way of an essential, endogenous bacterial gene will allow the production of recombinant therapeutics devoid of residual antibiotic contamination.

Amino Acid Sequence↗
PubMed1998

Characterisation of a binding-protein-dependent, active transport system for short-chain amides and urea in the methylotrophic bacterium Methylophilus methylotrophus.

Three genes (fmdCAB) encoding an outer-membrane porin for short-chain amides and urea, formamidase, and a putative regulatory protein in Methylophilus methylotrophus have previously been cloned and characterised. Three genes have now been identified downstream of fmdB, viz fmdD encoding a hydrophilic protein containing an N-terminal signal sequence, and fmdEF encoding hydrophobic transmembrane proteins. The derived amino acid sequence of mature FmdD (predicted molecular mass 41,870 Da) was similar to the cytoplasmic, amide-binding protein (AmiC) from Pseudomonas aeruginosa and to several periplasmic, solute-binding proteins from other bacteria. Mature FmdD was purified and shown to be a monomer (40-45 kDa) with the predicted N-terminal amino acid sequence (ADYPTA-). Equilibrium dialysis showed that the purified protein bound short-chain amides and urea with high affinity (Kd 7.2 microM for [14C]urea). SDS/PAGE and western blotting using antiserum to mature FmdD showed it was induced by short-chain amides and urea, and repressed by excess ammonia. The derived amino acid sequences of FmdE (32,822 Da) and FmdF (incomplete; >25,435 Da) were similar to the transmembrane proteins BraD/LivH and BraE/LivM, respectively, in various leucine/isoleucine/valine transport systems. Uptake of [14C]urea by washed cells was inhibited by the uncoupling agent carbonyl cyanide p-trifluoromethoxyphenylhydrazone and unlabelled formamide. It is concluded that FmdDEF comprise part of a high-affinity, binding-protein-dependent active-transport system for short-chain amides and urea in M. methylotrophus.

Amides↗