The use of computed tomography-guided stereotactic techniques in the treatment of brain stem abscesses

A case of a brain stem abscess that was successfully treated using CT guided stereotaxy together with antibiotic therapy is presented. The literature is reviewed and the role of stereotaxy in the treatment of brain stem abscess is discussed.     

Reference values for 75 g oral glucose tolerance test in pregnancy

A 75 g oral glucose tolerance test was performed in 212 pregnant women with no predisposing factors suggesting glucose intolerance to establish the normal pattern of glucose metabolism in pregnancy. Reference values for the test were established for the middle of pregnancy (14-20 weeks, n = 43) and late pregnancy (28-37 weeks, n = 168). One woman was excluded because she had diabetes that required treatment with insulin. There were statistically significant differences between the two groups for samples taken both one and two hours after the glucose load. Reference ranges for the interpretation of the glucose tolerance test in pregnancy should therefore take account of the period of gestation. Arbitrary upper limits of normal (represented by the 97.5 centile) two hours after a 75 g oral glucose load are proposed at 7.5 and 9.6 mmol/l for the second and third trimesters, respectively.     

Recommended relative potency factors for 2,3,4,7,8-pentachlorodibenzofuran: the impact of different dose metrics.

The recent National Toxicology Program (NTP) cancer bioassays for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,4,7,8-pentachlorodibenzofuran (4-PeCDF) permit a reevaluation of the current TEF value of 4-PeCDF. The data also allow for the derivation of relative potency factors (RPFs) for cancer, which are based not only on administered dose but also on potentially more informative dose metrics, such as liver concentration, area under the liver concentration curve, and lifetime average body burden. Our analyses of these data indicate that chi-squared tests of observed versus predicted liver tumor incidence for 4-PeCDF reject the current TEF value of 0.5 value as too high. 4-PeCDF RPFs were derived using estimation methods that either did or did not assume parallelism of the 4-PeCDF and TCDD dose-response curves. The resulting parallelism-based RPFs for administered dose, liver concentration at terminal sacrifice, liver concentration AUC, and lifetime average body burden are 0.26, 0.014, 0.021, and 0.036, respectively. The administered dose RPF estimate is approximately one-half the current TEF value of 0.5. However, the use of administered dose fails to take into account pharmacokinetic differences between congeners and the generally acknowledged belief that body burden or some other measure of cumulative dose is more appropriate for estimating the health risk posed by persistent chemicals. The other three dose metrics do account for these important factors, and the corresponding RPFs are at least 10-fold lower than the current TEF for 4-PeCDF. In summary, our analyses support an administered dose TEF no greater than 0.25 and one in the 0.05-0.1 range for internal dose metrics such as lifetime average liver concentration or body burden.     

Toxicity of the blue-green alga (cyanobacterium) Microcystis aeruginosa in drinking water to growing pigs,as an animal model for human injury and risk assessment

Hepatotoxins from blue-green algae are increasingly recognized as a potential hazard in drinking water supplies. The clinical consequences of ingestion include acute or chronic liver injury, with the possibility of enhanced susceptibility to, and growth of, liver tumors. To establish guidelines for water safety requires the demonstration of dose-dependent effects of toxicity and experimental determination of maximum “no-adverse-effect levels.” This paper describes the use of growing pigs as a model for human injury resulting from Microcystis toxins in drinking water. Risk assessment calculations using a series of safety factors are carried out, resulting in a guideline level after incorporating an additional safety factor for tumor promotion of approximately 1.0 μg toxins/L. With the Microcystis used for this trial, that concentration corresponds to 5000 cells/mL. © 1994 by John Wiley & Sons, Inc..