Sex differences in ischemic heart disease and heart failure biomarkers

Since 1984, each year, more women than men die of ischemic heart disease (IHD) and heart failure (HF), yet more men are diagnosed. Because biomarker assessment is often the first diagnostic employed in such patients, understanding biomarker differences in men vs. women may improve female morbidity and mortality rates.Some key examples of cardiac biomarker utility based on sex include contemporary use of “unisex” troponin reference intervals under-diagnosing myocardial necrosis in women; greater use of hsCRP in the setting of acute coronary syndrome (ACS) could lead to better stratification in women; and greater use of BNP with sex-specific thresholds in ACS could also lead to more timely risk stratification in women.Accurate diagnosis, appropriate risk management, and monitoring are key in the prevention and treatment of cardiovascular diseases; however, the assessment tools used must also be useful or at least assessed for utility in both sexes. In other words, going forward, we need to evaluate sex-specific reference intervals or cutoffs for laboratory tests used to assess cardiovascular disease to help close the diagnostic gap between men and women.     

Antisera to scrapie-associated fibril protein and prion protein decorate scrapie-associated fibrils.

Scrapie-associated fibrils (SAF) are an infection-specific structure observed in the unconventional-agent diseases. Polyclonal antisera raised to scrapie proteins were used to test the antigenic relationship between purified fibrils and SAF isolated from non-protease-treated synaptosomal-mitochondrial preparations. The experimental design utilized fibrils from scrapie strain 263K-infected hamsters, scrapie strain 139A-infected mice, and scrapie strain ME7-infected mice. Preparations were examined by negative-stain immune electron microscopy and Western blot analysis of the polypeptides. Fibrils and polypeptides from each preparation reacted with a rabbit antiserum raised to each of the following: hamster 263K prion protein (PrP 27-30), hamster 263K SAF protein, and mouse ME7 SAF protein. Immune electron microscopy and Western blot analysis revealed similar antigenic relationships among the three scrapie antisera. Thus, fibrils and polypeptides can be considered to be the same in each preparation. No reactivity of the fibrils was observed with antisera raised to Alzheimer neurofibrillary tangles or a synthetic peptide of cerebrovascular amyloid. Thus, the fibrils observed in purified preparations share structural and antigenic similarities plus biochemically related peptides with SAF present in non-protease-treated preparations.     

Insights into the function of the zinc hydroxide-Thr199-Glu106 hydrogen bonding network in carbonic anhydrases

The exact functional role of the zinc hydroxide (water)-Thr199-Glu106 hydrogen bond network in the carbonic anhydrases is unknown. However, from the results of molecular dynamics simulations (MD) we are able to better define its function. From computer graphics analysis and MD simulations on the zinc hydroxide form of human carbonic anhydrase II we find that this interaction forces the hydroxide hydrogen atom to be in a "down" position relative to the deep water-binding pocket. From previous work we have found that this pocket is a high-affinity binding site for CO2. We also note that during the timescale of our simulation (126 ps) the hydrogen bonds between the hydroxide hydrogen atom and Thr199 and the one between Thr199 and Glu106 are not fluxional. We propose that the role of the zinc hydroxide (water)-Thr199-Glu106 hydrogen bond network is to lock the hydrogen atom in the down position in order to expose the CO2 molecule bound in the deep water pocket to a lone pair of the hydroxide oxygen atom. This would allow for the rapid reaction of the CO2 molecule around the zinc ion. Furthermore, if the hydroxide hydrogen atom were not locked in the down position the binding of CO2 to the deep water pocket could be interfered with by the unrestrained hydroxide hydrogen atom (e.g. the N-Zn-O-H torsion could undergo rotational transitions that would partially block the deep water pocket). In summary, the roles we ascribe to this hydrogen bonding network are (1) to allow for facile access of CO2 to the deep water pocket and (2) to allow for maximal exposure of a hydroxide oxygen lone pair to the CO2 carbon atom.     

Analysis of polypeptide disposition in human erythrocyte membranes employing membrane inversion

High resolution segregation of erythrocyte membrane polypeptides achieved by isoelectric focusing in 8 M urea was employed in conjunction with surface-restricted radioiodination to analyze the disposition of polypeptides within the human erythrocyte membrane. Several membrane polypeptides showed significant uptake of radioiodine, with the principal labeled component migrating between pH values of 3.0 and 3.5. Two approaches were taken in examining membrane polypeptide disposition on both faces of the erythrocyte membrane. Saturation labeling of the outer face of the membrane with one iodine isotope followed by cell lysis and re-iodination with a second iodine isotope did not prove feasible and another procedure based on surface iodination with ¹²⁵I, formation of sealed inside-out vesicles and re-iodination with ¹³¹I was adopted. Studies of sialic acid release from the membrane surface and trypsin cleavage of radioiodinated peptides indicated that selectively labeled, sealed inside-out vesicles had been formed. The ratio of ¹²⁵I to ¹³¹I in membrane polypeptides separated by isoelectric focusing confirmed the existence of externally disposed, internally disposed and spanning proteins.