The effectiveness of ovarian cancer screening. A decision analysis model

OBJECTIVE: To estimate the effectiveness of ovarian cancer screening with CA 125 and transvaginal sonography. DESIGN: Decision analysis was used to examine the no-screen compared with the screen strategy. SETTING: Estimates of cancer incidence, survival, and life expectancy were derived from population-based data and clinical series. SUBJECTS: A cohort of 40-year-old women of all races and residing in the United States. INTERVENTIONS: A one-time screening intervention. The criterion standard for diagnosis of ovarian cancer was evaluation with exploratory laparotomy. MAIN OUTCOME MEASURE: Average years of life expectancy gained by women in the screened group. RESULTS: Screening for ovarian cancer with a combination of CA 125 and transvaginal sonography increases the average life expectancy in the population by less than 1 day. CONCLUSIONS: Given the limited effect on overall life expectancy, it is unlikely that mass screening for ovarian cancer with CA 125 and transvaginal sonography would be an effective health policy.     

Evidence for a catabolic role of glucagon during an amino acid load

Despite the strong association between protein catabolic conditions and hyperglucagonemia, and enhanced glucagon secretion by amino acids (AA), glucagon's effects on protein metabolism remain less clear than on glucose metabolism. To clearly define glucagon's catabolic effect on protein metabolism during AA load, we studied the effects of glucagon on circulating AA and protein dynamics in six healthy subjects. Five protocols were performed in each subject using somatostatin to inhibit the secretion of insulin, glucagon, and growth hormone (GH) and selectively replacing these hormones in different protocols. Total AA concentration was the highest when glucagon, insulin, and GH were low. Selective increase of glucagon levels prevented this increment in AA. Addition of high levels of insulin and GH to high glucagon had no effect on total AA levels, although branched chain AA levels declined. Glucagon mostly decreased glucogenic AA and enhanced glucose production. Endogenous leucine flux, reflecting proteolysis, decreased while leucine oxidation increased in protocols where AA were infused and these changes were unaffected by the hormones. Nonoxidative leucine flux reflecting protein synthesis was stimulated by AA, but high glucagon attenuated this effect. Addition of GH and insulin partially reversed the inhibitory effect of glucagon on protein synthesis. We conclude that glucagon is the pivotal hormone in amino acid disposal during an AA load and, by reducing the availability of AA, glucagon inhibits protein synthesis stimulated by AA. These data provide further support for a catabolic role of glucagon at physiological concentrations.     

A theoretical study of light emission from nanoscale silicon

In comparing our calculated exciton energies with those obtained from pseudopotential calculations (Ref. 27) and from a previous tight binding calculation (Ref. 30), we stated that the differences between the three semi-empirical calculations arise because of different treatment of the nanocrystal surfaces. This appears not to be correct. Subsequent calculations with variable Si-H parameters have shown that the band gap is actually rather insensitive to the actual value of these. Instead, the important feature appears to be the overall quality of the bulk band structure parameterization. References 27 and 30 use more extensive and higher quality empirical parameterizations for bulk Si than the sp³s∗ model used by us. Repeating our time dependent calculations with an improved sp³d⁵ parameterization results in similar values to those of Refs. 27 and 30 for the exciton energies.¹ The agreement of the sp³s∗ values with experimental photoluminescence energies (Fig. 7) cannot, therefore, be regarded as well understood at this time.^1,2     

Experience with the antibiotic resistance analysis and DNA fingerprinting in tracking faecal pollution at two lake beaches.

Posting or closing of swimming beaches because of faecal contamination is a widespread problem reported in many locations. In a risk-based approach to this problem, the risk to swimmers' health is assessed by field monitoring of indicator bacteria and the associated risks are managed by source controls and other remedial measures. In risk assessment, great advances have been made in recent years with the introduction of microbial source tracking (MST) techniques. Two such techniques, antibiotic resistance analysis and DNA fingerprinting, were applied in a study of causes of faecal contamination at two lake beaches in Toronto, Ontario. Both methods identified bird faeces as the dominant sources of E. coli. Coping with this type of pollution presents a major environmental challenge.     

Electrodeposited polytyramine as an immobilisation matrix for enzyme biosensors

The application of an electrodeposited polytyramine film as an immobilisation matrix for the construction of enzyme biosensors is described. Glucose oxidase (used as a model enzyme) is covalently attached to free amine groups on the polytyramine film using the coupling reagents 1-ethyl-3(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide. The resultant recognition interface consisted of multilayers of GOx immobilised onto the polymer surface. This method of constructing enzyme biosensors is shown to produce a highly reproducible and stable device. The biosensor showed no loss in electrode response after four months of dry storage and exhibited only minor loss in response after 20 days of repeated use. The resultant biosensor had a linear range of 0.1-28 mM glucose and a detection limit of 0.01 mM.