5 NEW high yield topics for the upcoming examinations-30-10-14 1)JAK 2 MUTATION 2)Drug resistance 3)Conjucated vaccines 4) M. catarrhalis 5) Single- photon emission computed tomography (SPECT) and positron emission tomography (PET). 1)JAK 2 MUTATION *Janus kinase 2 (commonly called JAK2) is a non receptor tyroisine kinase. It is a member of the janus kinase family . Mutations in JAK2 have been implicated in polycythemia vera, essential thrombocythemia, and myelofibrosis This mutation, (V617F) a change of valine tophenylalanine at the 617 position, appears to render hematopoietic cells more sensitive to growth factors such aserythropoietin and thrombopoietin. The Janus family of protein tyrosine kinases (JAK) have four JAK kinases, JAK1, JAK2, JAK3, and Tyk2. Mutations of JAK3 result in a disorder identical to X-SCID. JAK2 (AI-2010***) is located on the short arm of chromosome 9 2)Drug resistance * Ampicillin resistance is common in E. faecium. The mechanism of ampicillin resistance in E. faecium is related to a penicillin-binding protein (PBP) designated PBP5, which is the target of -lactam antibiotics. * Two common mechanisms of high-level ampicillin resistance (MIC, >64 g/mL) in clinical strains are (1) mutations in the PBP5-encoding gene that further decrease the affinity of PBP5 for ampicillin and (2) hyperproduction of PBP5. * Vancomycin resistance (particularly in E. faecium) - mechanism involves the replacement of the last d-alanine residue of peptidoglycan precursors with d-lactate or d-serine, with consequent high- and low-level resistance, respectively. Vancomycin-resistant organisms also produce enzymes that destroy the D-alanine–D-alanine-ending precursors. * Enteritis necroticans-most commonly involves the jejunum, whereas necrotizing enterocolitis affects the ileum and frequently the ileocecal valve. 3)Conjucate vaccines Key advantages of conjugate vaccines compared with polysaccharide vaccines include: • Improved immune and memory response, • Longer lasting protection, • The protection of infants and toddlers, • Their effect on bacterial carriage, • The creation of herd immunity. 4) M. catarrhalis * It is a gram-negative coccus with side-by-side kidney or bean configuration . * It is also called as Micrococcus catarrhalis, Neisseria catarrhalis, and Branhamella catarrhalis.It grow well on blood or chocolate agar. M. catarrhalis is the second most common bacterial cause of COPD exacerbations (after H. influenzae). 5) Single- photon emission computed tomography (SPECT) and positron emission tomography (PET). * SPECT perfusion tracers are thallium-201 (201Tl) and technetium-99m (99mTc) labeled isonitriles. * 99mTc isonitriles have higher photon energies and shorter physical half-lives than 201Tl, permitting injection of higher doses with less radiation exposure * The FDA-approved PET tracers are rubidium-82 (82Rb) and 13N ammonia (13NH3) * PET has the ability to quantify myocardial blood flow and flow reserve in absolute terms.
Posted on: Thu, 30 Oct 2014 10:57:35 +0000