Computed Tomography Coronary Angiography Possibilities in “High Risk” Plaque Identification in Patients with non-ST-Elevation Acute Coronary Syndrome: Comparison with Intravascular Ultrasound

Aim To evaluate structural characteristics of atherosclerotic plaques (ASP) by coronary computed tomography arteriography (CCTA) and intravascular ultrasound (IVUS).Material and methods This study included 37 patients with acute coronary syndrome (ACS). 64-detector-row CCTA, coronarography, and grayscale IVUS were performed prior to coronary stenting. The ASP length and burden, remodeling index (RI), and known CT signs of unstable ASP (presence of dot calcification, positive remodeling of the artery in the ASP area, irregular plaque contour, presence of a peripheral high-density ring and a low-density patch in the ASP). The ASP type and signs of rupture or thrombosis were determined by IVUS.Results The IVUS study revealed 45 unstable ASP (UASP), including 25 UASP with rupture and 20 thin-cap fibroatheromas (TCFA), and 13 stable ASP (SASP). No significant differences were found between distribution of TCFA and ASP with rupture among symptom-associated plaques (SAP, n=28) and non-symptom-associated plaques (NSAP, n=30). They were found in 82.1 and 73.3 % of cases, respectively (p>0.05), which indicated generalization of the ASP destabilization process in the coronary circulation. However, the incidence of mural thrombus was higher for SAP (53.5 and 16.6 % of ASP, respectively; p<0.001). There was no difference between UASP and SASP in the incidence of qualitative ASP characteristics or in values of quantitative ASP characteristics, including known signs of instability, except for the irregular contour, which was observed in 92.9 % of UASP and 46.1 % of SASP (p=0.0007), and patches with X-ray density ≤46 HU, which were detected in 83.3 % of UASP and 46.1 % of SASP (р=0.01). The presence of these CT criteria 11- and 7-fold increased the likelihood of unstable ASP (odd ratio (OR), 11.1 at 95 % confidence interval (CI), from 2.24 to 55.33 and OR, 7.0 at 95 % CI, from 5.63 to 8.37 for the former and the latter criterion, respectively).Conclusion According to IVUS data, two X-ray signs are most characteristic for UASP, the irregular contour and a patch with X-ray density ≤46 HU. The presence of these signs 11- and 7-fold, respectively, increases the likelihood of unstable ASP.

Allometric equations for the invasive vine air potato (Dioscorea bulbifera) in its exotic range in Florida

Nondestructive means for estimating air potato (also known as air yam; Dioscorea bulbifera L.) biomass will help gauge its management efficacy over time. We developed allometric equations to estimate total and fractional biomass components and densities of aerial bulbils and underground tubers of field-grown D. bulbifera in Florida. We selected four naturally infested sites representing its southern, central, and northern distribution in Florida and measured three independent variables (vine densities, stem diameters, and top heights) of 84 (21 site−1) discrete D. bulbifera patches during late October to early December of 2012. We destructively harvested D. bulbifera biomass, sorted by tubers, stems, leaves, and bulbils; counted units of bulbils and underground tubers (dependent variables); and dried to a constant weight. Mean percentages of tuber, stem, leaf, and bulbil fractions in total biomass were 42.0, 15.6, 26.0, and 16.4, respectively. We developed a parameterized multiplicative prediction model and regression equation for each dependent variable. Slopes of relationships among independent and dependent variables varied by biomass and density (bulbil and tuber) of plant components. Multiplied values of independent variables: all three for total, tuber, stem, and leaf biomass; two (vine base diameter*patch height) for bulbil biomass; two (vine density*patch height) for bulbil density; and only one (stem density) for tuber density provided best (R2-based) prediction values. These models will provide nondestructive methods for estimating biomass components and density of vegetative propagules of naturally growing D. bulbifera. Models are critical for understanding the performance of D. bulbifera in its exotic range, estimating biomass to project control costs, and comparing biomass components and bulbil/tuber densities during pre- and postmanagement periods to gauge control efficacy.

Fragment shape and size, landscape permeability and fragmentation level as predictors of primate occupancy in a region of Brazilian Cerrado

Human activities result in the formation of a mosaic of forest patches within a non-habitat matrix. The response of the local biodiversity to changes in land-use may occur at different scales. It is important to evaluate the effects of the attributes of both the patches and the surrounding landscape on the occupancy of forest patches by animal populations. Here, we assessed the predictive potential of local (basal area, tree density), patch (size, shape) and landscape scale (total area of forest, number of patches, matrix permeability, patch proximity) variables on the occupancy of forest patches by the syntopic primates Alouatta caraya, Sapajus libidinosus and Callithrix penicillata in the city of Goiânia in the Cerrado region of central Brazil. We used playback to survey primate populations in 22 focal patches and assessed the landscape within a 1000 m buffer zone around each site. In A. caraya, occupancy was influenced by the shape of the focal patches, the amount of forest and fragmentation level of the landscape. Focal patch size and the permeability of the matrix were the principal determinants of the occupancy of S. libidinosus. None of the predictors influenced patch occupancy in C. penicillata, and the structure of the vegetation did not influence occupancy in any of the species. The preservation of as many forest patches as possible, both large and small, as well as gallery forests, and the enhancement of matrix permeability will be essential for the long-term conservation of the syntopic primates of the Cerrado of central Brazil.

The two oxpecker species reveal the role of movement rates and foraging intensity in species coexistence

The two Buphagus oxpecker species are specialized passerines that forage for ticks and other food particles on the body of ungulates in the African savannahs. One of their intriguing features is their ability to coexist despite sharing the same, specialized diet. Using co-occurrence data (photographs of giraffes with oxpeckers on them) and approximate Bayesian computing, we demonstrate that yellow-billed oxpeckers changed host faster than red-billed oxpeckers and appeared to displace red-billed oxpeckers from preferred giraffe body parts. Conversely, red-billed oxpeckers exhibited a fuller use of each host and displaced yellow-billed oxpeckers from distal giraffe body parts. These findings highlight that the partition of giraffe hosts in two separate niches was only part of the coexistence story in this species pair. More precisely, the oxpeckers shared the resource by exploiting it at different rates. They engaged in different trade-offs between giving-up density, patch discovery rate and competitor displacement ability. They illustrate the importance of the time frame of interactions.

Density dependence on multiple spatial scales maintains spatial variation in both abundance and traits

Population density affects fitness through various processes, such as mate finding and competition. The fitness of individuals in a population can in turn affect its density, making population density a key quantity linking ecological and evolutionary processes. Density effects are, however, rarely homogeneous. Different life-history processes can be affected by density over different spatial scales. In birds, for example, competition for food may depend on the number of birds nesting in the direct vicinity, while competition for nesting sites may occur over larger areas. Here we investigate how the effects of local density and of density in nearby patches can jointly affect the emergence of spatial variation in abundance as well as phenotypic diversification. We study a two-patch model that is described by coupled ordinary differential equations. The patches have no intrinsic differences: they both have the same fitness function that describes how an individual’s fitness depends on density in its own patch as well as the density in the other patch. We use a phase-space analysis, combined with a mathematical stability analysis to study the long-term behaviour of the system. Our results reveal that the mutual effect that the patches have on each other can lead to the emergence and long-term maintenance of a low and a high density patch. We then add traits and mutations to the model and show that different selection pressures in the high and low density patch can lead to diversification between these patches. Via eco-evolutionary feedbacks, this diversification can in turn lead to changes in the long-term population densities: under some parameter settings, both patches reach the same equilibrium density when mutations are absent, but different equilibrium densities when mutations are allowed. We thus show how, even in the absence of differences between patches, interactions between them can lead to differences in long-term population density, and potentially to trait diversification.

Hydrologic controls on aperiodic spatial organization of the ridge–slough patterned landscape

A century of hydrologic modification has altered the physical and biological drivers of landscape processes in the Everglades (Florida, USA). Restoring the ridge–slough patterned landscape, a dominant feature of the historical system, is a priority but requires an understanding of pattern genesis and degradation mechanisms. Physical experiments to evaluate alternative pattern formation mechanisms are limited by the long timescales of peat accumulation and loss, necessitating model-based comparisons, where support for a particular mechanism is based on model replication of extant patterning and trajectories of degradation. However, multiple mechanisms yield a central feature of ridge–slough patterning (patch elongation in the direction of historical flow), limiting the utility of that characteristic for discriminating among alternatives. Using data from vegetation maps, we investigated the statistical features of ridge–slough spatial patterning (ridge density, patch perimeter, elongation, patch size distributions, and spatial periodicity) to establish more rigorous criteria for evaluating model performance and to inform controls on pattern variation across the contemporary system. Mean water depth explained significant variation in ridge density, total perimeter, and length : width ratios, illustrating an important pattern response to existing hydrologic gradients. Two independent analyses (2-D periodograms and patch size distributions) provide strong evidence against regular patterning, with the landscape exhibiting neither a characteristic wavelength nor a characteristic patch size, both of which are expected under conditions that produce regular patterns. Rather, landscape properties suggest robust scale-free patterning, indicating genesis from the coupled effects of local facilitation and a global negative feedback operating uniformly at the landscape scale. Critically, this challenges widespread invocation of scale-dependent negative feedbacks for explaining ridge–slough pattern origins. These results help discern among genesis mechanisms and provide an improved statistical description of the landscape that can be used to compare among model outputs, as well as to assess the success of future restoration projects.