The enzymological basis for resistance of herpesvirus DNA polymerase mutants to acyclovir: relationship to the structure of alpha-like DNA polymerases

Acyclovir (ACV), like many antiviral drugs, is a nucleoside analog. In vitro, ACV triphosphate inhibits herpesvirus DNA polymerase by means of binding, incorporation into primer/template, and dead-end complex formation in the presence of the next deoxynucleoside triphosphate. However, it is not known whether this mechanism operates in vivo. To address this and other questions, we analyzed eight mutant polymerases encoded by drug-resistant viruses, each altered in a region conserved among alpha-like DNA polymerases. We measured Km and kcat values for dGTP and ACV triphosphate incorporation and Ki values of ACV triphosphate for dGTP incorporation for each mutant. Certain mutants showed increased Km values for ACV triphosphate incorporation, suggesting a defect in inhibitor binding. Other mutants showed reduced kcat values for ACV triphosphate incorporation, suggesting a defect in incorporation of inhibitor into DNA, while the rest of the mutants exhibited both altered km and kcat values. In most cases, the fold increase in Ki of ACV triphosphate for dGTP incorporation relative to wild-type polymerase was similar to fold resistance conferred by the mutation in vivo; however, one mutation conferred a much greater increase in resistance than in Ki. The effects of mutations on enzyme kinetics could be explained by using a model of an alpha-like DNA polymerase active site bound to primer/template and inhibitor. The results have implications for mechanisms of action and resistance of antiviral nucleoside analogs in vivo, in particular for the importance of incorporation into DNA and for the functional roles of conserved regions of polymerases.     

Evaluation of enterolithiasis in equids: 900 cases (1973-1996)

In this study we investigated the effect of lesioning the noradrenergic systems on the behavioral effects of (5R, 10S)-(+)-5-Methyl-10,11-dihydro-5H-dibenzo [a, d] cyclohepten-5,10-imine hydrogen maleate--MK-801, in rats. The noradrenergic system was lesioned with N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride--DSP4 (60 mg/kg IP). MK-801 increased the locomotor activity and rearing. DSP4 significantly further increased the hyperlocomotor activity, circling (especially to the left side), sniffing, rolling, and falling that were induced by MK-801. These results showed that destruction of the noradrenergic system increased MK-801-hyperlocomotor activity, ataxia and stereotypy.     

A combined surgical and radiologic technique for creating a functional neo-endocervical canal in a case of partial congenital cervical atresia

OBJECTIVE: To recanalize the endocervical canal in a patient with partial congenital cervical atresia. DESIGN: Case report. SETTING: University hospital. PATIENT: A 16-year-old girl referred with a history of primary amenorrhea, polycystic ovaries, and intermittent abdominal pain. Physical examination revealed a normal vagina and external cervical os, but magnetic resonance imaging revealed a solid endocervical tract. INTERVENTION(S): At laparotomy the endometrial cavity was accessed transfundally and outlined by injection of water-soluble contrast. A trocar needle was guided transvaginally into the uterus, the tract was dilated, and a 12F stent was placed. Oral contraceptives (OCs) and antibiotics were continued postoperatively. MAIN OUTCOME MEASURE(S): Hysterosalpingography and clinical follow-up. RESULT(S): The operation and postoperative course were uneventful. Withdrawal bleeding occurred at 8 weeks, after discontinuation of the OCs, at which time the stent was expelled. Later follow-up revealed recurrent narrowing, and the stent was replaced for 14 more weeks. After stent removal, regular menses continued (7 months to date). CONCLUSION: In select cases of congenital cervical atresia, recanalization may be safely performed with the use of the combined surgical-radiologic technique described, with good short-term outcome.     

The evolutionary biology and population genetics underlying fungal strain typing

Strain typing of medically important fungi and fungal population genetics have been stimulated by new methods of tapping DNA variation. The aim of this contribution is to show how awareness of fungal population genetics can increase the utility of strain typing to better serve the interests of medical mycology. Knowing two basic features of fungal population biology, the mode of reproduction and genetic differentiation or isolation, can give medical mycologists information about the intraspecific groups that are worth identifying and the number and type of markers that would be needed to do so. The same evolutionary information can be just as valuable for the selection of fungi for development and testing of pharmaceuticals or vaccines. The many methods of analyzing DNA variation are evaluated in light of the need for polymorphic loci that are well characterized, simple, independent, and stable. Traditional population genetic and new phylogenetic methods for analyzing mode of reproduction, genetic differentiation, and isolation are reviewed. Strain typing and population genetic reports are examined for six medically important species: Coccidioides immitis, Histoplasma capsulatum, Candida albicans, Cryptococcus neoformans, Aspergillus fumigatus, and A. flavus. Research opportunities in the areas of genomics, correlation of clinical variation with genetic variation, amount of recombination, and standardization of approach are suggested.     

Transmission intergénérationnelle des troubles intériorisés: Modèles théoriques et recherches empiriques.

It is well recognised that mental health disorders in parents are associated with internalizing disorders in their children. For better understanding of the nature of this association, this article presents a critical analysis of 5 theoretical models and of major findings from empirical studies conducted on this question in the past 15 years. Several psychosocial characteristics are found to be more frequent in families of depressed or anxious parents and are associated to a higher prevalence of internalizing disorders in their children. Two hypotheses are drawn from these findings : (a) The presence of internalizing disorders in a parent may contribute to the emergence of other at-risk conditions associated with internalizing disorders in children; and (b) the presence of some psychosocial characteristics may exacerbate the influence of being exposed to parental anxiety or depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Durability of concrete containing a natural pozzolan as defined by a performance-based approach

This paper deals with the application of a performance-based approach on the durability of concrete made with an Algerian natural pozzolan. The evaluation of the durability of concrete was based on the comparison of durability indicators with a reference concrete usually found in Algeria. The properties measured included general indicators (water porosity, gas permeability, capillary absorption and Portlandite content) and specific indicators related to degradation phenomena that might occur in Algeria: corrosion induced by carbonation and chlorides, and chemical attacks by sulphates and acids. For the specific degradations, the indicators measured included carbonation depths, chloride diffusion coefficients, chloride permeability, expansion and sulphate profiles, and depth of leaching due to ammonium nitrate attack. The results showed that general durability indicators were almost equivalent for all the types of concrete tested, highlighting the importance of using specific indicators for each type of exposure. The results of specific indicators for corrosion and acid attacks showed that increasing the pozzolan content led to higher resistance of the concrete. Thus, it is possible to improve the durability of typical concretes currently made in Algeria by using local materials.     

Contributing Authors

Biography

Contributing Authors