Higher myocardial strain rates duringisovolumic relaxation phase than duringejection characterize acutely ischemic myocardium

AbstractObjectivesThe aim of this study was to define an index that can differentiate normal from ischemic myocardial segments that exhibit postsystolic shortening (PSS).BackgroundIdentification of ischemia based on the reduction of regional systolic function is sometimes challenging because other factors such as normal nonuniformity in contraction between segments, tethering effect, pharmacologic agents, or alterations in loading conditions can also cause reduction in regional systolic deformation. The PSS (contraction after the end of systole) is a sensitive marker of ischemia; however, inconsistent patterns have also been observed in presumed normal myocardium.MethodsTwenty-eight open-chest pigs underwent echocardiographic study before and during acute myocardial ischemia induced by coronary artery occlusion. Ultrasound-derived myocardial longitudinal strain rates were calculated during systole (SSR), isovolumic relaxation (IVRSR), and rapid filling (ESR) phases in both ischemic and normal myocardium. Systolic strain (ϵsys) and postsystolic strain (ϵps) were calculated by integrating systolic and postsystolic strain rates, respectively.ResultsDuring ischemia, SSR, ESR, and ϵsys in ischemic segments were significantly lower (in magnitude) than in nonischemic segments or at baseline. However, some overlap occurred between ischemic and normal values for all three parameters. At baseline, 18 of 28 animals had negative IVRSR (i.e., PSS) in at least one segment. During coronary artery occlusion, IVRSR became negative and larger in magnitude than SSR in all ischemic segments. The IVRSR/SSR and ϵps best differentiated ischemic from nonischemic segments.ConclusionsIn the presence of reduced regional systolic deformation, a higher rate of PSS than systolic shortening identifies acutely ischemic myocardium

Intracardiac measurement of pre-ejection myocardial velocities estimates the transmural extent of viable myocardium early after reperfusion in acute myocardial infarction

AbstractOBJECTIVESWe hypothesized that wall motion velocity during pre-ejection is proportional to the regional content of viable myocardium after reperfusion for acute myocardial infarction (AMI).BACKGROUNDPre-ejection wall motion consists of short and fast inward and outward movement towards and away from the center of the left ventricle (LV) and is altered during regional ischemia. This short-lived event can be accurately quantified by Doppler myocardial imaging (DMI).METHODSFourteen open-chest pigs underwent 60 to 120 min of left anterior descending coronary artery occlusion followed by 30 min of reperfusion. The DMI data were collected using a phased-array intracardiac catheter (LV cavity) from ischemic and nonischemic myocardium encompassed within a plane passing through two epicardial bead markers. Peak tissue velocities during isovolumic contraction (IVC) (peak positive and peak negative), ejection (S) and early filling (E) were measured. The cardiac specimen was sliced through the epicardial markers in a plane approximating the ultrasound imaging plane. The transmural extent of necrosis (TEN) (%) was measured by triphenyltetrazolium chloride staining.RESULTSDuring ischemia, positive IVC velocity was zero in ischemic walls with TEN >20%. At reperfusion, positive IVC velocity correlated better with TEN (r = −0.94, p < 0.0001) than it did S (r = −0.70, p < 0.01) and E (r = −0.81, p < 0.01). Differential IVC (the difference between peak positive and peak negative velocity) highly correlated with TEN, during ischemia (r = −0.78, p < 0.001) and during reperfusion (r = −0.93, p < 0.0001).CONCLUSIONSPre-ejection tissue velocity, as measured by intracardiac ultrasound, allows rapid estimation of the transmural extent of viable myocardium after reperfusion for AMI

Sonoporation: Mechanical DNA Delivery by Ultrasonic Cavitation

Development of nonviral gene transfer methods would be a valuable addition to the gene-therapy armamentarium, particularly for localized targeting of specific tissue volumes. Ultrasound can produce a variety of nonthermal bioeffects via acoustic cavitation including DNA delivery. Cavitation bubbles may induce cell death or transient membrane permeabilization (sonoporation) on a single cell level, as well as microvascular hemorrhage and disruption of tissue structure. Application of sonoporation for gene delivery to cells requires control of cavitation activity. Many studies have been performed using in vitro exposure systems, for which cavitation is virtually ubiquitous. In vivo, cavitation initiation and control is more difficult, but can be enhanced by cavitation nucleation agents, such as an ultrasound contrast agent. Sonoporation and ultrasonically enhanced gene delivery has been reported for a wide range of conditions including low frequency sonication (kilohertz frequencies), lithotripter shockwaves, HIFU, and evendiagnostic ultrasound (megahertz frequencies). In vitro, a variety of cell lines has been successfully transfected, with concomitant cell killing. In vivo, initial applications have been to cancer gene therapy, for which cell killing can be a useful simultaneous treatment, and to cardiovascular disease. The use of ultrasound for nonviral gene delivery has been demonstrated for a robust array of in vitro and mammalian systems, which provides a fundamental basis and strong promise for development of new gene therapy methods for clinical medicine.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45550/1/11188_2004_Article_457016.pd

Breast vibro-acoustography: initial results show promise

INTRODUCTION: Vibro-acoustography (VA) is a recently developed imaging modality that is sensitive to the dynamic characteristics of tissue. It detects low-frequency harmonic vibrations in tissue that are induced by the radiation force of ultrasound. Here, we have investigated applications of VA for in vivo breast imaging. METHODS: A recently developed combined mammography-VA system for in vivo breast imaging was tested on female volunteers, aged 25 years or older, with suspected breast lesions on their clinical examination. After mammography, a set of VA scans was acquired by the experimental device. In a masked assessment, VA images were evaluated independently by 3 reviewers who identified mass lesions and calcifications. The diagnostic accuracy of this imaging method was determined by comparing the reviewers' responses with clinical data. RESULTS: We collected images from 57 participants: 7 were used for training and 48 for evaluation of diagnostic accuracy (images from 2 participants were excluded because of unexpected imaging artifacts). In total, 16 malignant and 32 benign lesions were examined. Specificity for diagnostic accuracy was 94% or higher for all 3 reviewers, but sensitivity varied (69% to 100%). All reviewers were able to detect 97% of masses, but sensitivity for detection of calcification was lower (≤ 72% for all reviewers). CONCLUSIONS: VA can be used to detect various breast abnormalities, including calcifications and benign and malignant masses, with relatively high specificity. VA technology may lead to a new clinical tool for breast imaging applications

The human body at cellular resolution: the NIH Human Biomolecular Atlas Program

Abstract: Transformative technologies are enabling the construction of three-dimensional maps of tissues with unprecedented spatial and molecular resolution. Over the next seven years, the NIH Common Fund Human Biomolecular Atlas Program (HuBMAP) intends to develop a widely accessible framework for comprehensively mapping the human body at single-cell resolution by supporting technology development, data acquisition, and detailed spatial mapping. HuBMAP will integrate its efforts with other funding agencies, programs, consortia, and the biomedical research community at large towards the shared vision of a comprehensive, accessible three-dimensional molecular and cellular atlas of the human body, in health and under various disease conditions

Changing Bee and Hoverfly Pollinator Assemblages along an Urban-Rural Gradient

The potential for reduced pollination ecosystem service due to global declines of bees and other pollinators is cause for considerable concern. Habitat degradation, destruction and fragmentation due to agricultural intensification have historically been the main causes of this pollinator decline. However, despite increasing and accelerating levels of global urbanization, very little research has investigated the effects of urbanization on pollinator assemblages. We assessed changes in the diversity, abundance and species composition of bee and hoverfly pollinator assemblages in urban, suburban, and rural sites across a UK city.Bees and hoverflies were trapped and netted at 24 sites of similar habitat character (churchyards and cemeteries) that varied in position along a gradient of urbanization. Local habitat quality (altitude, shelter from wind, diversity and abundance of flowers), and the broader-scale degree of urbanization (e.g. percentage of built landscape and gardens within 100 m, 250 m, 500 m, 1 km, and 2.5 km of the site) were assessed for each study site. The diversity and abundance of pollinators were both significantly negatively associated with higher levels of urbanization. Assemblage composition changed along the urbanization gradient with some species positively associated with urban and suburban land-use, but more species negatively so. Pollinator assemblages were positively affected by good site habitat quality, in particular the availability of flowering plants.Our results show that urban areas can support diverse pollinator assemblages, but that this capacity is strongly affected by local habitat quality. Nonetheless, in both urban and suburban areas of the city the assemblages had fewer individuals and lower diversity than similar rural habitats. The unique development histories of different urban areas, and the difficulty of assessing mobile pollinator assemblages in just part of their range, mean that complementary studies in different cities and urban habitats are required to discover if these findings are more widely applicable