Long before Krever's report,blood scare had changed face of medicine

The disaster involving blood-borne pathogens and Canada''s blood system was in the spotlight in November with the release of the Krever inquiry report. Many physicians consider the report anticlimactic because action has already been taken on several fronts and the use of donated bloods has declined, but it will still have a far-reaching impact.     

A Boolean Model of the Gene Regulatory Network Underlying Mammalian Cortical Area Development

The cerebral cortex is divided into many functionally distinct areas. The emergence of these areas during neural development is dependent on the expression patterns of several genes. Along the anterior-posterior axis, gradients of Fgf8, Emx2, Pax6, Coup-tfi, and Sp8 play a particularly strong role in specifying areal identity. However, our understanding of the regulatory interactions between these genes that lead to their confinement to particular spatial patterns is currently qualitative and incomplete. We therefore used a computational model of the interactions between these five genes to determine which interactions, and combinations of interactions, occur in networks that reproduce the anterior-posterior expression patterns observed experimentally. The model treats expression levels as Boolean, reflecting the qualitative nature of the expression data currently available. We simulated gene expression patterns created by all possible networks containing the five genes of interest. We found that only of these networks were able to reproduce the experimentally observed expression patterns. These networks all lacked certain interactions and combinations of interactions including auto-regulation and inductive loops. Many higher order combinations of interactions also never appeared in networks that satisfied our criteria for good performance. While there was remarkable diversity in the structure of the networks that perform well, an analysis of the probability of each interaction gave an indication of which interactions are most likely to be present in the gene network regulating cortical area development. We found that in general, repressive interactions are much more likely than inductive ones, but that mutually repressive loops are not critical for correct network functioning. Overall, our model illuminates the design principles of the gene network regulating cortical area development, and makes novel predictions that can be tested experimentally.     

Effects of detergent on substrate binding and spin state of purified liver microsomal cytochrome P-450LM2 from phenobarbital-treated rabbits

Spectral changes accompanying the binding of the nonionic detergent n-octyl beta-D-glucopyranoside (n-octyl glucoside) to cytochrome P-450LM2 purified from liver microsomes of phenobarbital-treated rabbits have been compared to changes in catalytic activity obtained in a reconstituted system consisting of various levels of detergent, P-450LM2, and NADPH-cytochrome P-450 reductase. In the absence of substrate and reductase, addition of n-octyl glucoside to 2-3 mM resulted in a difference spectrum (detergent-bound minus detergent-free cytochrome) characterized by a small maximum at 390 nm and a minimum at 410 nm, suggestive of a slight stabilization of the high-spin (S = 5/2) state of the cytochrome. As the detergent concentration was increased to 4-8 mM (corresponding to maximal activity and pentameric or hexameric P-450), a new peak appeared at 427 nm while the minimum remained at 410 nm. Between 10 and 30 mM n-octyl glucoside (conditions which produced catalytically inactive and monomeric P-450) the minimum in the difference spectrum shifted to 390 nm and the maximum to 425 nm, characteristic of a shift in spin equilibrium toward low-spin (S = 1/2) cytochrome. At low and high detergent concentrations, substrate [d-benzphetamine with n-octyl glucoside or cyclohexane with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS)] was bound to P-450LM2 with formation of high-spin P-450, although the increase in high-spin cytochrome was less at high detergent levels than at low. The affinity of P-450 for substrate decreased by 2-3-fold at high detergent.(ABSTRACT TRUNCATED AT 250 WORDS)     

A rapid method for the purification of supercoiled PM2 DNA by affinity chromatography on H1 histone covalently coupled to agarose.

A simple and rapid method is described for the purification of supercoiled PM2 DNA by affinity chromatography on columns of H1 histone covalently coupled to agarose. The method does not require the use of intercalating agents or ultracentrifugation procedures. Under the conditions most appropriate for purification, elution is carried out in a single step with buffered 0.7 M NaCl after the sample has been loaded onto the column in buffered 0.2 M NaCl. The DNA eluted at the higher salt concentration consists of supercoiled closed circular DNA at greater than 90% purity independently of the ratio of supercoiled to nicked circular DNA in the input mixture.     

Different populations of pig epidermal cells: isolation and lipid composition.

Preparations representing populations of (a) basal and spinous cells, (b) granular cells, and (c) stratum corneum cells were obtained by successive treatments of epidermal slices from pig skin with dilute buffered trypsin solutions. Total lipids accounted for about 8% of the cell dry weight in each of the three populations. Phospholipids, which predominated in the basal and spinous cells, accounted for only 21% of the total lipids in the granular cells and less than 0.1% in the stratum corneum. The latter cells contained more cholesterol (23% of total lipid) than either the granular cells (18%) or the basal and spinous cells (8%). The proportion of ceramide was also much higher in the stratum corneum (17%) and granular cells (9%) than in the basal and spinous cells (1%). The relative amounts of glycosphingolipid (glucosylceramide) and cholesteryl sulfate in the total lipids of stratum corneum cells were less than half those in the granular cells and basal and spinous cells. A novel phospholipid was a major component (26% of total) of the phospholipids from granular cells. The compound, which was partially characterized, contained phosphorus, fatty acids, and glycerol (molar ratio 1:3:2) and appeared to be a neutral derivative of phosphatidic acid.     

Postcolonial Identities in Africa

Postcolonial Identities in Africa. Richard Werbner and Terence Ranger. eds. London: Zed Books, 1996. 292 pp.