Poly(A) sequences were demonstrated in the RNA of encephalomyocarditis (EMC) virus by affinity chromatography on poly(U)-Sepharose, treatment with RNases, and determination of the ability of the RNA ...to prime for reverse transcription. The size of the poly(A) sequences was estimated as 10-20 nucleotides in length by determination of the fraction resistant to pancreatic RNases plus T1 RNases, followed by analysis of electrophoretic mobility on polyacrylamide gels and of the AMP-to-adenosine ratio after alkaline hydrolysis. The poly(A) sequences are located at the 3' end of the RNA as shown by mild digestion by snake venom phosphodiesterase.
Polyadenylation of cytoplasmic RNAs was investigated in L cells infected with encephalomyocarditis virus. During the early stage of infection, the mean size of newly made poly(A) chains attached to ...cell mRNAs decreased gradually, in parallel with the shut-off of RNA synthesis. Later on, poly(A) segments, an average of 50 nucleotides long, were associated with viral RNA isolated either from polysomes or whole cytoplasm. These segments seemed to be processed differently in the course of time, and RNA molecules containing short poly(A) tracts (less than 20 bases) were incorporated into the virions.
Plasmids were constructed whereby the expression of a reporter gene, either the cDNA corresponding to the secreted form of human alkaline phosphatase (SEAP) or the herpes simplex virus type 1 (HSV1) ...thymidine kinase (tk) gene, was rendered dependent upon the expression of the human immunodeficiency virus type 1 (HIV1) tat and rev proteins. The SEAP or tk genes were placed between HIV1 splice donor and acceptor sites. One SEAP construct carried a series of alternating splice donor and acceptor sites. In all cases, the rev response element mapped within an intron. Despite such mimicry of the HIV1 genome, residual expression of the reporter gene in the absence of tat and rev was observed. These results, as well as non-specific T-cell recruitment, suggest limits to the specificity of using HIV-activated toxic gene expression to kill HIVinfected cells.
Nous avons construit des plasmides porteurs de gènes rapporteurs, soit l'ADNc correspondant à la phosphatase alcaline humaine sous sa forme sécrétée (SEAP), soit le gène codant pour la thymidinekinase (tk) du virus herpès simplex type 1 (HSV1) dont l'expression est sous la dépendance des protéines tat et rev du virus de l'immunodéficience humaine de type 1 (VIH1).
Les gènes SEAP et tk sont placés entre les sites donneurs et accepteurs d'épissage du virus VIH1. Dans un plasmide, le gène SEAP est placé entre des sites d'épissage donneurs et accepteurs alternatifs. Dans toutes les constructions, l'élément de réponse à la protéine rev (RRE) est introduit dans un intron. Malgré une telle organisation mimant celle du génome du VIH, une expression résiduelle des gènes rapporteurs en l'absence des protéines tat et rev est observée. Ces résultats, ainsi que le recrutement non spécifique des cellules T, montrent les limites de l'utilisation d'un gène toxique dont l'expression est activée par les protéines de régulation du VIH pour détruire les cellules qu'il infecte.
Single stranded DNA (ss-DNA) isolated from nuclear DNA of human rhabdomyosarcoma (RD line) cells amounts to 2% of total DNA. As compared with native double-stranded DNA (ds-DNA), ss-DNA has a lower ...mean sedimentation coefficient, higher buoyant density, contains fewer repeated DNA sequences and a greater proportion of it can be hybridized to human RNAs (up to 35% and less than 8% for ds-DNA). The hybridization kinetics determined by S1 nuclease digestion and verified by other methods (hydroxylapatite chromatography, density gradient centrifugation and thermal melting) indicate that ss-DNA corresponds to a great number and variety of transcripts. These data are discussed as evidence for DNA strand dissociation in the course of gene activity.
The aim of this retrospective multicenter study was to determine present characteristics of infectious endocarditis complicated by abscess and to identifying predictive factors of mortality. The ...files of 233 patients with infectious endocarditis complicated by perivalvular abscesses between January 1989 and December 1993 were analysed. Two hundred and thirteen patients underwent medico-surgical treatment (175 aortic and 38 mitral abscesses) and 20 patients underwent medical treatment alone (17 aortic and 3 mitral abscesses). The abscess was observed on native valves in 156 cases and valve prostheses in 77 cases. The causative organism was identified in 69% of cases : the commonest organism was the staphylococcus. The diagnostic sensitivity of transthoracic and transoesophageal echocardiography was 36 and 80% respectively. The operative mortality at one month was 16%. Patients over 65 years of age, staphylococcal infection, renal failure and fistulisation of the abscess, were identified as independent predictive factors of mortality at one month. The survival rate three months after surgery was 75 +/- 10% and 59 +/- 11% at 27 months. An age over 65, staphylococcal infection, uncontrolled infection, circumferential abscess and fistulisation were independent predictive factors of global mortality (the first month and after). The mortality rate in unoperated patients was 40%: cardiac failure and fistulisation of the abscess detected by echocardiography were predictive factors of mortality on univariate analysis.
Mycotic aneurysms of the extracranial carotid arteries are rare. A new case of mycotic aneurysm of the bifurcation of the carotid artery secondary to acute bacterial endocarditis affecting the aortic ...valve is reported. Simultaneous treatment of the two lesions was instituted. The twenty six cases of mycotic aneurysm of the extracranial carotid arteries previously described in the literature are reviewed by the authors.
