Carboxylation of epoxides to beta-keto acids in cell extracts of Xanthobacter strain Py2

A novel enzymatic reaction involved in the metabolism of aliphatic epoxides by Xanthobacter strain Py2 is described. Cell extracts catalyzed the CO2-dependent carboxylation of propylene oxide (epoxypropane) to form acetoacetate and beta-hydroxybutyrate. The time courses of acetoacetate and beta-hydroxybutyrate formaton indicate that acetoacetate is the primary product of propylene oxide carboxylation and that beta-hydroxybutyrate is a secondary product formed by the reduction of acetoacetate. Analogous C5 carboxylation products were identified with 1,2-epoxybutane as the substrate. In the absence of CO2, propylene oxide and 1,2-epoxybutane were isomerized to form acetone and methyl ethyl ketone, respectively, as dead-end products. The carboxylation of short-chain epoxides to beta-keto acids is proposed to serve as the physiological reaction for the metabolism of aliphatic epoxides in Xanthobacter strain Py2.     

Health and education: alternative courses for the development of nursing personnel

The disposition behavior of trientine, a selective copper-chelating drug for Wilson's disease, and its metabolites in normal patients with Wilson's disease and rats were studied. A high concentration of metabolites appeared in blood samples of patients and rats in the early stage after administration of trientine. Furthermore, large amount of trientine metabolites were excreted into the urine of patients. These results suggest that trientine is remarkably subjected to a first-pass effect. The drug concentration area under the curve (AUC) of the unchanged form and the metabolites of trientine in patients was not dependent on the administered dosage. It seems that the absorption process is an important factor for the disposition behavior of trientine, we have also investigated the uptake characteristics of trientine by rat intestinal brush-border membrane vesicles. The uptake characteristics of trientine were similar to the physiological polyamines, spermine and spermidine. The uptake rate of trientine was dose-dependently inhibited by spermine and spermidine. Moreover, spermine competitively inhibited the uptake of trientine with a Ki value of 18.6 muM. This value is very close to the Km value for spermine (30.4 muM). These data suggested that the uptake mechanism of trientine in rat small intestinal brush-border membrane vesicles was almost identical to that of spermine and spermidine, and that the physiological polyamines seem to have the ability to inhibit the absorption of trientine from the gastrointestinal tract.     

Biomechanical regularities in the distribution of tension in various topographic zones of the eyelids in children in health and myopia of different degree

The authors assessed the method for life-time study of the biomechanical characteristics of ocular tissues in 281 children (562 eyes) aged 7 to 14 years. The method for assessing the biomechanics of the eyelids is described. In detail. The rates of propagation of acoustic waves in normal tissue and in 1.0 to 6.0 diopters myopia are presented. A correlation has been revealed between the increase of the velocity of acoustic surface waves, propagating in the horizontal direction in the internal segment of the orbital area of the upper eyelids, and the value of clinical refraction in myopia. The authors consider clinical signs of myopia-screwing up one's eyes and a wider lid slit-from a biomechanical viewpoint.     

Site-directed mutagenesis of recombinant human beta 2-glycoprotein I identifies a cluster of lysine residues that are critical for phospholipid binding and anti-cardiolipin antibody activity

beta2-Glycoprotein I (beta2GPI) is a phospholipid-binding serum protein with anticoagulant properties. It plays a vital role in the binding of anti-cardiolipin Abs purified from patients with autoimmune disease when assayed in a cardiolipin (CL) ELISA. Based on a three-dimensional model of beta2GPI, electrostatic calculations, and earlier peptide studies, a highly positively charged amino acid sequence, Lys282-Asn-Lys-Glu-Lys-Lys287, located in the fifth domain of beta2GPI, has been predicted to be the phospholipid binding site. We tested this hypothesis by site-directed mutagenesis of residues in the predicted phospholipid binding site and by assessing the mutants for phospholipid binding and anti-beta2GPI activity. A single amino acid change from Lys286 to Glu significantly decreased the binding of beta2GPI to CL. Double and triple mutants 2k (from Lys286, 287 to Glu286, 287), 2ka (from Lys284, 287 to Glu284, 287), and 3k (from Lys284, 286, 287 to Glu284, 286, 287) possessed no binding of Ab to beta2GPI in a CL ELISA, as well as no inhibitory activity on the binding of iodinated native beta2GPI to CL. These results indicate that the residues Lys284, Lys286, and Lys287 in the fifth domain of beta2GPI are critical for its binding to anionic phospholipids and its subsequent capture for binding of anti-beta2GPI Abs.     

Lessons learned from the DIASTAT vascular access graft

In male Syrian hamsters, short days induce regression of the reproductive system, but eventually spontaneous recrudescence occurs ensuing from refractoriness to the inhibitory photoperiod. Although the photoperiod of 12 L:12 D (12 h light:12 h dark) may act like a short day by inducing the testicular cycle outlined above, it may fail to evoke the increase of circulating concentrations of prolactin that accompanies testicular recrudescence. This photoperiod may fail to induce photorefractoriness, as indicated by the prolonged low concentrations of prolactin in the blood. Herein, hamsters were exposed to either 8 L:16 D or 12 L:12 D from weaning and by 28 weeks exposure to either photoperiod, the hamsters had large testes following recrudescence from a photoperiod induced-regression). Transfer to 8 L:16 D from 12 L:12 D at 28 weeks resulted in a second testicular regression and recrudescence. In a second experiment, the testes of hamsters moved to 8 L:16 D from 12 L:12 D after 29 weeks exposure to the latter photoperiod similarly regressed and then regrew. Serum concentrations of prolactin decreased in these males after transfer to the shorter daylength but also decreased in hamsters kept under 12 L:12 D both groups were usually below those of hamsters moved to 14 L:10 D. These results show that exposure for 28 or 29 weeks to 12 L:12 D was insufficient to induce photorefractoriness, despite the recrudescence of the testes following involution.     

Meeting a person with AIDS in the classroom: an evaluation

Meeting a person with AIDS in the classroom was evaluated to determine if it had an impact on students' perceived susceptibility to HIV infection and attitudes toward persons with AIDS. The meeting was incorporated into the Grade 9 AIDS education program of a school district in Nova Scotia. Four schools participated in this study. Two schools were randomly assigned to the treatment group, which met the person with AIDS, and the remaining two schools formed the comparison group. Measures of the two attitudinal variables were collected using a self-report questionnaire that was administered both prior to and two weeks after the educational intervention. Meeting a person with AIDS in the classroom had no measurable impact on students perceived susceptibility to HIV infection nor on their attitudes toward persons with AIDS. Suggestions for using the educational intervention more effectively and for further research are made.