Spectroscopic and Mechanistic Studies of Heterodimetallic Forms of Metallo-β-lactamase NDM-1

In an effort to characterize the roles of each metal ion in metallo-β-lactamase NDM-1, heterodimetallic analogues (CoCo-, ZnCo-, and CoCd-) of the enzyme were generated and characterized. UV–vis, 1H NMR, EPR, and EXAFS spectroscopies were used to confirm the fidelity of the metal substitutions, including the presence of a homogeneous, heterodimetallic cluster, with a single-atom bridge. This marks the first preparation of a metallo-β-lactamase selectively substituted with a paramagnetic metal ion, Co(II), either in the Zn1 (CoCd-NDM-1) or in the Zn2 site (ZnCo-NDM-1), as well as both (CoCo-NDM-1). We then used these metal-substituted forms of the enzyme to probe the reaction mechanism, using steady-state and stopped-flow kinetics, stopped-flow fluorescence, and rapid-freeze-quench EPR. Both metal sites show significant effects on the kinetic constants, and both paramagnetic variants (CoCd- and ZnCo-NDM-1) showed significant structural changes on reaction with substrate. These changes are discussed in terms of a minimal kinetic mechanism that incorporates all of the data

Strategies and Methods for Research on Sex Differences in Brain and Behavior

Female and male brains differ. Differences begin early during development due to a combination of genetic and hormonal events and continue throughout the lifespan of an individual. Although researchers from a myriad of disciplines are beginning to appreciate the importance of considering sex differences in the design and interpretation of their studies, this is an area that is full of potential pitfalls.A female’s reproductive status and ovarian cycle have to be taken into account when studying sex differences in health and disease susceptibility, in the pharmacological effects of drugs, and in the study of brain and behavior. To investigate sex differences in brain and behavior there is a logical series of questions that should be answered in a comprehensive investigation of any trait. First, it is important to determine that there is a sex differencein the trait in intact males and females, taking into consideration the reproductive cycle of the female. Then, one must consider whether the sex difference is attributable to the actions of gonadal steroids at the time of testing and/or is sexually differentiated permanently by the action of gonadal steroids during development. To answer these questions requires knowledge of how to assess and/or manipulate the hormonal condition of the subjects in the experiment appropriately. This article describes methods and procedures to assist scientists new to the field in designing and conducting experiments to investigate sex differences in research involving both laboratory animals and humans.NIMHPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49483/2/Becker et al Strategies sex differences Endo 2005.pd

Criteria for the selective use of chest computed tomography in blunt trauma patients

Item does not contain fulltextPURPOSE: The purpose of this study was to derive parameters that predict which high-energy blunt trauma patients should undergo computed tomography (CT) for detection of chest injury. METHODS: This observational study prospectively included consecutive patients (>or=16 years old) who underwent multidetector CT of the chest after a high-energy mechanism of blunt trauma in one trauma centre. RESULTS: We included 1,047 patients (median age, 37; 70% male), of whom 508 had chest injuries identified by CT. Using logistic regression, we identified nine predictors of chest injury presence on CT (age >or=55 years, abnormal chest physical examination, altered sensorium, abnormal thoracic spine physical examination, abnormal chest conventional radiography (CR), abnormal thoracic spine CR, abnormal pelvic CR or abdominal ultrasound, base excess or=1 positive predictors, 484 had injury on CT (95% of all 508 patients with injury). Of all 192 patients with no positive predictor, 24 (13%) had chest injury, of whom 4 (2%) had injuries that were considered clinically relevant. CONCLUSION: Omission of CT in patients without any positive predictor could reduce imaging frequency by 18%, while most clinically relevant chest injuries remain adequately detected.1 april 201

Evidence for Burgers' equation describing the untwisting of scroll rings

We study the dynamics of rotating scroll waves in three-dimensional excitable systems. Experiments are carried out with the 1,4-cyclohexanedione Belousov-Zhabotinsky reaction and wave patterns are measured using optical tomography. We create twisted scroll rings for which the rotation phase varies along their circular rotation backbone and measure the untwisting dynamics of the collapsing structures. Experimental data reveal the formation of an asymmetric, plateau-like phase profile with a growing region of leading phase and a shrinking region of lagging phase. The experimental data support a quantitative description in terms of a nonlinear diffusion equation

Racial and Ethnic Differences in Treatment and Outcomes of Severe Aortic Stenosis: A Review.

Aortic stenosis (AS) is among the most common valvular heart diseases encountered in the United States. In this review the authors examine differences between racial and ethnic groups in the epidemiology and management of severe AS, explore potential explanations for these findings, and discuss the implications for improving the delivery of care to racially and ethnically diverse populations. Underrepresented racial and ethnic groups experience a paradoxically lower prevalence or incidence of AS relative to white subjects, despite having a higher prevalence of traditional risk factors. Historically, UREGs with severe AS have had lower rates of both surgical and transcatheter aortic valve replacement and experienced more post-surgical complications, including, bleeding, worsening heart failure, and rehospitalization. Last, UREGs with severe AS have an increased risk for morbidity and mortality relative to white patients. To date much of the research on AS has examined black-white differences, so there is a need to understand how other racial and ethnic groups with severe AS are diagnosed and treated, with examination of their resulting outcomes. Overall, racial and ethnic disparities in health care access and care delivery are a public health concern given the changing demographics of the U.S. population. These differences in AS management and outcomes highlight the need for additional research into contributing factors and appropriate interventions to address the lower rates of aortic valve replacement and higher morbidity and mortality among UREGs