Molecular evolution of RNA in vitro

Experimental studies of RNA evolution in vitro are reviewed in the context of Eigen's 1971 theory and its subsequent extensions. Current research activity and future prospects for using automated molecular biology techniques for in vitro evolution experiments are surveyed.     

RE microfinance : New horizons for RE technologies in poverty alleviation projects

Innovative self-financing integrated development concepts enable even the world's poorest to finance their own development. Mass applications for PV (and alternative energy in general) offer ethical least-cost solutions to some of the most widespread problems facing mankind. T.E. Manning describes how PV technologies can be usefully incorporated without subsidy or paternalism in development projects.     

Reconstruction of mandibular discontinuity defects using autogenous grafting and a mandibular reconstruction plate: a prospective evaluation of nine consecutive cases

This article presents the clinical results of a prospective evaluation of nine cases of mandibular discontinuity that were reconstructed using autogenous grafting and a reconstruction plate. All patients were allowed to function immediately postsurgery. Acceptable esthetic and functional results were obtained with minimal donor and recipient site complications. All cases showed complete graft incorporation and restoration of osseous continuity.     

Error and the growth of technical understanding

Technical writers, for the most part, write user documentation of some kind. However, they also have skills that might enable them to also serve as user-advocates on product development teams and testers of prototype systems. In the computer hardware and software industry, they have the additional skills needed to develop online help tools, to design user interfaces, and to write system and error messages (J. Fisher, 1998). Fisher's recent survey of (Australian) technical communicators showed that some are employed in such tasks, but not widely so. She reports, for instance, that only 38% were consulted by developers about error messages, only 32% actually wrote error messages, and only 13% reported that they had some role in system testing (J. Fisher, 1998). A question emerges out of such results: is there really any necessary and supportive connection between the process of explaining a product to a user and the original process of developing that product? As technical writers looking to expand our roles [and salaries], we would like to say yes. But, in fairness, we have to admit our bias. We need to check such biases against other, independent evidence. The article interfaces this question with a parallel question in the philosophy of science: is there any connection between experimental test results used to “sell” a theory to a scientific audience and the original process of developing that theory?     

Using fluorescence-based human androgen receptor gene assay to analyze the clonality of microdissected dendritic cell tumors

The AGT1 permease is a alpha-glucoside-H+ symporter responsible for the active transport of maltose, trehalose, maltotriose, alpha-methylglucoside, melezitose and sucrose. In wild-type as well as in MAL constitutive strains, alpha-methylglucoside seemed to be the best inducer of transport activity, while trehalose had no inducing effect. Based on the initial rates of transport it seems that the sugar preferentially transported by this permease is trehalose, followed by sucrose.     

Effects of the E177K mutation in D-amino acid transaminase. Studies on an essential coenzyme anchoring group that contributes to stereochemical fidelity

D-Amino acid transaminase is a bacterial enzyme that uses pyridoxal phosphate (PLP) as a cofactor to catalyze the conversion of D-amino acids into their corresponding alpha-keto acids. This enzyme has already been established as a target for novel antibacterial agents through suicide inactivation by a number of compounds. To improve their potency and specificity, the detailed enzyme mechanism, especially the role of its PLP cofactor, is under investigation. Many PLP-dependent transaminases have a negatively charged amino acid residue forming a salt-bridge with the pyridine nitrogen of its cofactor that promotes its protonation to stabilize the formation of a ketimine intermediate, which is subsequently hydrolyzed in the normal transaminase reaction pathway. However, alanine racemase has a positively charged arginine held rigidly in place by an extensive hydrogen bond network that may destabilize the ketimine intermediate, and make it too short-lived for a transaminase type of hydrolysis to occur. To test this hypothesis, we changed Glu-177 into a titratable, positively charged lysine (E177K). The crystal structure of this mutant shows that the positive charge of the newly introduced lysine side chain points away from the nitrogen of the cofactor, which may be due to electrostatic repulsions not being overcome by a hydrogen bond network such as found in alanine racemase. This mutation makes the active site more accessible, as exemplified by both biochemical and crystallographic data: CD measurements indicated a change in the microenvironment of the protein, some SH groups become more easily titratable, and at pH 9.0 the PMP peak appeared around 315 nm rather than at 330 nm. The ability of this mutant to convert L-alanine into D-alanine increased about 10-fold compared to wild-type and to about the same extent as found with other active site mutants. On the other hand, the specific activity of the E177K mutant decreased more than 1000-fold compared to wild-type. Furthermore, titration with L-alanine resulted in the appearance of an enzyme-substrate quinonoid intermediate absorbing around 500 nm, which is not observed with usual substrates or with the wild-type enzyme in the presence of L-alanine. The results overall indicate the importance of charged amino acid side chains relative to the coenzyme to maintain high catalytic efficiency.     

Fetal assessment based on fetal biophysical profile scoring. VIII. The incidence of cerebral palsy in tested and untested perinates

OBJECTIVE: The intent of this comparative clinical study was fourfold: (1) to determine the incidence of cerebral palsy in a large obstetric population, (2) to compare the incidence of cerebral palsy in patients at high risk referred for and managed according to the fetal biophysical profile score result with the incidence among unreferred and untested patients, (3) to determine the relationship, if any, between the last fetal biophysical profile score and the incidence of cerebral palsy, and (4) to categorize cases of cerebral palsy according to the clinical parameters and the probable time and nature of the damaging insult. STUDY DESIGN: In this retrospective 5-year comparative study (1987 to 1991) the incidence of cerebral palsy was determined by analysis of International Classification of Diseases, Ninth Revision, -coded related medical services. The clinical records were then sought and reviewed in index cases and obstetric, neonatal, and postnatal clinical data were abstracted. Cross-correlation with partial registries was done to confirm completeness of capture of index cases. The population of referred high-risk patients who received serial fetal biophysical profile scoring and were managed according to test results was determined by review of a prospective computer-stored database and by review of patient log books. The population of untested patients was calculated as the residual of total cases minus tested cases. The rate of cerebral palsy for all patients and for the tested and untested population was calculated and compared. The tested and untested perinates were compared for birth age, weight, and assigned timing or etiology of cerebral palsy. In the tested population the distribution of test results by last recorded biophysical profile score was determined and the relationship between the last test result and cerebral palsy and predictive accuracy parameters of the fetal biophysical profile score were calculated. RESULTS: The incidence of cerebral palsy among the 84,947 live births was 3.68 per 1000 live births (313 cases). The rate of cerebral palsy in the 26,290 referred high-risk tested patients was 1.33 per 1000 (35 cases) compared with a rate of 4.74 per 1000 live births in the 58,657 untested mixed low-risk/high-risk patients (278 cases). These differences were highly significant. A significant declining trend in the annual incidence of cerebral palsy was observed in the total population and the untested population, whereas the rate in the tested population remained relatively constant over the 5-year study interval. The differences in the cerebral palsy rate between the tested and untested population were not related to differences in gestational age, birth weight, or assigned timing or etiology category. In the tested population the relationship between the incidence of cerebral palsy and the last test fetal biophysical profile score was inverse, exponential, and highly significant. CONCLUSIONS: Antepartum assessment by fetal biophysical profile scoring is associated with a significant reduction in the incidence of cerebral palsy compared with untested patients. The relationship between the last test score and the incidence of cerebral palsy is inverse and exponential, suggesting that antenatal asphyxia is an important and potentially avoidable cause of cerebral palsy.