Protein-free small nuclear RNAs catalyze a two-step splicing reaction

Pre-mRNA splicing is a crucial step in eukaryotic gene expression and is carried out by a highly complex ribonucleoprotein assembly, the spliceosome. Many fundamental aspects of spliceosomal function, including the identity of catalytic domains, remain unknown. We show that a base-paired complex of U6 and U2 small nuclear RNAs, in the absence of the ≈200 other spliceosomal components, performs a two-step reaction with two short RNA oligonucleotides as substrates that results in the formation of a linear RNA product containing portions of both oligonucleotides. This reaction, which is chemically identical to splicing, is dependent on and occurs in proximity of sequences known to be critical for splicing in vivo. These results prove that the complex formed by U6 and U2 RNAs is a ribozyme and can potentially carry out RNA-based catalysis in the spliceosome.     

Phase I trial of fludarabine, bortezomib and rituximab for relapsed and refractory indolent and mantle cell non-Hodgkin lymphoma

Based on the hypothesis that bortezomib may potentiate fludarabine activity by inhibiting DNA repair, we designed a phase I trial using this combination with rituximab in patients with relapsed and refractory indolent and mantle cell non-Hodgkin lymphoma. Twenty-four patients were enrolled. Non-Hodgkin lymphoma subtypes included 12 patients with follicular lymphoma, four with marginal zone lymphoma, three with lymphoplasmacytic lymphoma, three with mantle cell lymphoma and two with small lymphocytic/chronic lymphocytic leukaemia. Fludarabine and bortezomib were escalated in cohorts of three patients. Rituximab was added to the maximum tolerated dose of fludarabine and bortezomib and added significant dose-limiting myelosuppression. The maximum tolerated dose was fludarabine 25 mg/m² on days 1–3, bortezomib 1·3 mg/m² on days 1, 4, 8, 11, with rituximab 375 mg/m² on day 1 administered every 21 d. Clinical responses were observed in 11 patients, five of whom were refractory to their most recent treatment regimen. Six additional patients had stable disease for a median of 10 months (range 4–30+). Cumulative myelosuppression and neuropathy was observed. The combination of fludarabine, bortezomib, and rituximab appears to be an active regimen with manageable toxicity for relapsed NHL.     

Prevalence of patients continuing to smoke after vascular interventions

INTRODUCTION: Smoking is one of the most important risk factors for the development and progression of atherosclerosis. Smoking cessation is an obligatory element in the management of vascular problems and in patients scheduled for vascular interventions. The aim of this study was to assess the prevalence of patients smoking before and after vascular surgical procedures and to evaluate the requirements for inpatient programs for smoking cessation and nicotine replacement therapy. METHODS: 500 patients admitted for vascular interventions were included in this prospective study. Smoking status was evaluated both objectively and subjectively. All patients underwent measurements of exhaled breath carbon monoxide to quantify nicotine dependency and all answered a standardized Fagerstr?m questionnaire both on admission and after surgery to identify current smokers. RESULTS: Of 500 vascular patients included in the study, only 70 (14 %) never had smoked, 243 (49 %) had given up smoking before admission and 161 (32 %) were current smokers. Of the current smokers, 64 (40 %) did not smoke during hospitalization but 97 (60 %) continued to smoke in hospital. Of these 97 patients, 78 (80 %) were men and 19 women; their mean age was 61 +/- 4 years (range 40-84). Four patients had surgery for infrarenal aortic aneurysm, 40 underwent carotid endarterectomy and 53 had peripheral arterial occlusive disease (PAD). There was no difference between abstinent patients and continuing smokers in previous cigarette consumption or Fagerstr?m score, a predictor for long-term smoking behavior. Patients with carotid artery stenosis were significantly more abstinent while hospitalized (P = 0.006); patients with PAD, however, were more likely to continue smoking as inpatients (P = 0.004). Sixty-five percent of continuing smokers stated that they would stop smoking in hospital if counseling and nicotine replacement therapy were provided. With regard to their predominant location of atherosclerosis, patients with PAD were less willing than those with carotid stenosis to abstain from smoking while hospitalized (53 % vs 88 %, respectively; P < 0.001). CONCLUSION: A substantial proportion of patients admitted for vascular surgery are smokers. More than half of these continue to smoke in the hospital, an environment where smoking is prohibited by law. Counseling, nicotine replacement therapy and smoking-cessation programs are urgently needed for vascular surgical inpatients.     

Primary stroke center: basic components and recommendations

Stroke is the leading cause of disability and the third leading cause of death in the United States. The brain attack coalition (BAC), whose members belong to several professional medical societies, formed a working group to explore the factors and elements that are associated with better clinical outcome after acute stroke. In the year 2000, the BAC published the recommendations for primary stroke centers (PSC). The primary goals for the PSC are to improve and to standardize stroke care. Convinced by the compelling data on the PSC, the Joint Commission on Accreditation of Healthcare Organization adopted the BAC recommendations and started certifying hospitals as designated PSCs. Many hospitals are already certified and numerous others are currently seeking certification. The BAC is now working on the recommendations for a comprehensive stroke center. The nihilism which dominated the stroke field has finally been replaced by remarkable progress and better understanding of stroke and stroke treatment.     

Anatomy and pathology of the eye: role of MR imaging and CT

Since the development of CT and MR imaging, significant progress has been made in ophthalmic imaging. As the technology advanced and MR imaging units improved their ability in term of spatial resolution, the role of MR imaging in ophthalmic imaging has increased accordingly. This article considers the role of MR and CT imaging in the diagnosis of selected pathologies of the eye.     

High prevalence of HIV infection associated with incarceration among community-based injecting drug users in Tehran, Iran

OBJECTIVES: To determine the prevalence and correlates of HIV-1 infection among community-based injecting drug users (IDUs) in Tehran, Iran. METHODS: In October 2004, 213 IDUs were recruited from a drop-in center and its neighboring parks and streets in Tehran. Participants were interviewed using a structured questionnaire regarding their sociodemographics and HIV risk characteristics, and specimens of oral mucosal transudate were collected and tested for HIV-1 antibodies. Data were analyzed using chi and multiple logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI). RESULTS: The prevalence of HIV-1 infection was 23.2% (48 of 207) among male injecting drug users. In the multivariable analysis, a history of shared drug injection inside prison (OR, 2.45; 95% CI, 1.01-5.97) and that of multiple incarcerations (OR, 3.13; 95% CI, 1.08-9.09) were associated with significantly higher prevalence of HIV-1 infection. CONCLUSIONS: The prevalence of HIV-1 infection has reached an alarming level among IDUs in Tehran, with incarceration-related exposures revealed to be the main correlates of HIV-1 infection. Urgent and comprehensive harm reduction programs for drug users in prison and those in the community in Tehran are of prime importance to prevent further transmission of HIV infection.     

Molecular Dynamics Simulation of Chemokine Receptors in Lipid Bilayer: A Case Study on C–C Chemokine Receptor Type 2

Chemokine receptors belong to the membrane proteins that are included in many physiological phenomena. However, the mechanism of their action is unknown at the atomistic level in different aspects. In this study, a computational pipeline is exploited to investigate the molecular basis of how the structure of C–C chemokine receptor type 2, a prototypical chemokine receptor, is affected by lipid bilayer and an antagonist (INCB3344). This study includes homology modeling, molecular dynamics simulation in lipid bilayer, and docking. A detailed mechanism of INCB3344 has been described. Tyr 49, Trp 98, Tyr 120, His 121, and Glu 291 are proved to play important roles in binding. Integrating results obtained in this study and experimental data help us to suggest a two‐step ligand‐binding mechanism. The N‐terminus of protein first sticks out from the extracellular domain suitable for the contact with the antagonist. Binding of ligand to this segment leads to the geometrical changes to facilitate the ligand interactions with extracellular loop 2 of C–C chemokine receptor type 2. Finally, the interactions occurring between extracellular loop 2 and ligand induce conformational changes in C–C chemokine receptor type 2 structure. These changes bring the ligand closer to the binding pocket, allowing the interaction between INCB3344 and the residues of active site.