Modulation of the activity of RNase E in vitro by RNA sequences and secondary structures 5' to cleavage sites

The endoribonuclease RNase E is believed to initiate the degradation of many mRNAs in Escherichia coli, yet the mechanism by which it recognizes cleavage sites is poorly understood. We have prepared derivatives of the mRNA encoding ribosomal protein S20 which contain a single major RNase E cleavage site at residues 300/301 preceded by variable 5' extensions. Three of these RNAs are cleaved in vitro with significantly reduced efficiencies relative to the intact S20 mRNA by both crude RNase E and pure Rne protein (endonuclease component of RNase E). In all three substrates as well as in the full-length mRNA the major cleavage site itself remains single-stranded. One such substrate (t84D) contains a 5' stem-loop structure characterized by three noncanonical A-G pairs. Removal or denaturation of the stem restores efficient cleavage at the major RNase E site. The other two contain single-stranded 5'-termini but apparently lack cleavage sites near the termini. Our data show that sensitivity to RNase E can be influenced by distant structural motifs in the RNA and also suggest a model in which the initial recognition and cleavage of a substrate near its 5' end facilitates sequential cleavages at more distal sites. The model implies that RNase E contains at least a dimer of the Rne subunit and that the products of the first cleavage are retained by Rne prior to the second cleavage.     

Radiofrequency catheter ablation of sustained monomorphic ventricular tachycardia in hypertrophic cardiomyopathy

INTRODUCTION: Incessant monomorphic ventricular tachycardia (VT) with a right bundle branch block morphology and a northwest axis is a rare arrhythmic complication in a patient with hypertrophic cardiomyopathy and apical left ventricular aneurysm. METHODS AND RESULTS: The origin of this VT was localized using the following criteria: the presence of entrainment without fusion, equal intervals from the stimulus to the beginning of the QRS complex and from the electrogram to the QRS complex during VT, and the first postpacing interval identical to the tachycardia cycle length. Radiofrequency energy applied to the septoapical part of the apical left ventricular aneurysm terminated the tachycardia within 2 seconds. CONCLUSION: Using criteria to guide radiofrequency (RF) ablation of VT in patients with coronary artery disease, an incessant monomorphic VT in a patient with hypertrophic cardiomyopathy was successfully ablated.     

Treatment of l(2)mbn Drosophila tumorous blood cells with the steroid hormone ecdysone amplifies the inducibility of antimicrobial peptide gene expression

Insects rely on both humoral and cellular mechanisms to defend themselves against microbial infections. The humoral response involves synthesis of a battery of potent antimicrobial peptides by the fat body and, to a lesser extent, by blood cells. The cellular response on the other hand consists of phagocytosis of small microorganisms and melanization and encapsulation of larger parasites. The l(2)mbn cell line, established from tumorous larval hemocytes, represents a system of choice to dissect the molecular events controlling cellular immunity. We report here that l(2)mbn cells can be efficiently induced to differentiate in adherent, macrophage-like cells by treatment with 20-hydroxyecdysone. Ecdysone treatment increases both the phagocytic capacity of l(2)mbn cells and their competence to express antimicrobial genes in response to immune challenge. We also report that expression of several regulatory molecules thought to be involved in the immune response is up-regulated by ecdysone in l(2)mbn cells.     

Molecular pathology of breast cancer and its application to clinical management

Breast cancer is a major cause of morbidity and mortality in women in many parts of the world. Breast carcinomas are heterogenous in their biological and clinical behaviour and a greater understanding of how they develop and progress could lead to more directed forms of screening and therapy. It is important to determine the molecular mechanisms underlying the natural history of breast cancer. Developments in the techniques for molecular analysis have meant that they can now be applied to a large range of clinical material such as cytological preparations and fixed, embedded material, so increasing the potential for relating any molecular alterations to clinical behaviour and response to therapy. In this review we consider recent developments in three areas of importance to breast cancer; genetic analysis-oncogenes, tumour suppressor genes, loss of heterozygosity, microsatellite instability, familial breast cancer; steroid receptors, oestrogen regulated proteins, epidermal growth factor receptor, growth factors particularly transforming growth factor beta; and cell adhesion, invasion and metastasis-E-cadherin, integrins, proteases. These are discussed in relation to potential for screening, prognosis and treatment.     

Development and validation of a Structured Telephone Interview for Dementia Assessment (STIDA): the NIMH Genetics Initiative

Eating disorders are an increasing problem for society and the medical professions. The dental practitioner has an important role both in identifying the illnesses and in minimising its affects on the dentition. This paper highlights the features of the most common eating disorders and discusses the possible role of the dental profession in the long-term care of patients suffering from the problem.     

Membrane fusion induced by the HIV type 1 fusion peptide: modulation by factors affecting glycoprotein 41 activity and potential anti-HIV compounds

Peptides representing a sequence of 23 amino acid residues at the N terminus of human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp41 bind and subsequently induce fusion of large unilamellar vesicles (LUV), an activity presumably related to gp41 function in viral infection. These in vitro effects can be modulated by several factors that are known to affect HIV-1 infectivity and gp41-mediated virus-cell fusion. Peptide-induced membrane fusion but not peptide binding can be inhibited by two factors known to block gp41 activity: a polar amino acid substitution V --> E in position 2 and the presence of the N-terminal hexapeptide of gp41 in addition to the parent sequence. Whereas inclusion of the alternative gp120 receptor galactosylceramide in membranes has virtually no effect, membrane cholesterol stimulates fusion activity. In view of its putative physiological relevance, we have used the fusion activity of the peptides as a tool to evaluate the inhibitory effect of antivirals that might target this sequence. We describe three dissimilar effects: Amphotericin B inhibits in a cholesterol-independent way peptide-induced fusion but not binding, human serum albumin inhibits binding and consequently fusion, and dextran sulfate (M(r) 5000) does not affect either binding or fusion.     

Couvelaire uterus

Uteroplacental apoplexy is a rare but nonfatal complication of severe forms of placental abruption. It occurs when vascular damage within the placenta causes hemorrhaging that progresses to and infiltrates the wall of the uterus. It is a syndrome that can only be diagnosed by direct visualization or biopsy (or both). For this reason, its occurrence is perhaps underreported and underestimated in the literature. The subject of this report is a 24-year-old pregnant woman who had a placental abruption an in whom classic uteroplacental apoplexy was diagnosed at the time of her cesarean section.     

Risk factors for adverse drug reactions during thiacetazone treatment of pulmonary tuberculosis in human immunodeficiency virus infected adults

It is well established that many continuously distributed traits have a heritable component. However, it is often difficult to communicate to the general public the meaning of quantitative estimates of heritability. To address this problem, the present paper introduces a heuristic for communicating heritability to nonscientific audiences. This heuristic involves adopting an extremely simplified model of inheritance and artificially (and somewhat arbitrarily) defining a cutoffs of "low environmental risk" and "affectation status." Using body weight and obesity as an example, we present a table which gives estimates of the proportion of obese persons who are "genetically obese" assuming varying levels of "environmental risk" for obesity and relative body weight scores for defining obesity. The resulting statistic may prove useful for lay audiences in understanding a heritability estimate.