Shrub-interspace dynamics alter relationships between microbial community composition and belowground ecosystem characteristics

In desert ecosystems, belowground characteristics are influenced chiefly by the formation and persistence of “shrub-islands of fertility” in contrast to barren plant interspaces. If soil microbial communities are exclusively compared between these two biogeochemically distinct soil types, the impact of characteristics altered by shrub species, especially soil C and N, are likely to be overemphasized and overshadow the role of other characteristics in structuring microbial composition. To determine how belowground characteristics influence microbial community composition, and if the relative importance of these characteristics shifts across the landscape (i.e., between and within shrub and interspace soils), changes in microbial communities across a 3000-year cold desert chronosequence were related to 27 belowground characteristics in surface and subsurface soils. When shrub and interspace communities in surface and subsurface soils were combined across the entire chronosequence, communities differed and were primarily influenced by soil C, NO₃⁻ concentrations, bulk density, pH, and root presence. Within shrub soils, microbial communities were shrub species-specific, especially in surface soils, highlighting differences in soil characteristics created by specific shrub species and/or similarity in stresses structuring shrub species and microbial communities alike. Microbial communities in shrub soils were not influenced by soil C, but by NO₃⁻ and NH₄⁺ concentrations, pH, and silt in surface soils; and Cl, P, soil N, and NO₃⁻ concentrations in subsurface soils. Interspace soil communities were distinct across the chronosequence at both depths and were strongly influenced by dune development. Interspace communities were primarily associated with soil stresses (i.e., high B and Cl concentrations), which decreased with dune development. The distribution of Gram-positive bacteria, Actinobacteria, and fungi highlighted community differences between and within shrub and interspace soils, while Gram-negative bacteria were common in all soils across the chronosequence. Of the 27 belowground characteristics investigated, 13 separated shrub from interspace communities, and of those, only five emerged as factors influencing community composition within shrub and interspace soils. As dunes develop across this cold desert chronosequence, microbial community composition was not regulated primarily by soil C, but by N and P availability and soil stresses in shrub soils, and exclusively by soil stresses in interspace soils.     

Development and evaluation of a noninvasive marker cluster technique to assess three-dimensional kinematics of the distal portion of the forelimb in horses

OBJECTIVE: To develop and evaluate a marker cluster set for measuring sagittal and extrasagittal movement of joints in the distal portion of the forelimb in ponies. ANIMALS: 4 ponies. PROCEDURES: 5 infrared cameras were positioned on a concrete walkway in a frontal-sagittal arc and calibrated. Four segments were defined: hoof, middle phalanx, proximal phalanx, and metacarpus. Rigid clusters with 4 retroreflective markers were placed on each segment. A static trial was recorded with additional anatomic markers on the medial and lateral joint lines. Those anatomic markers were removed, and kinematic data were recorded at 240 Hz during walking. An ensemble mean was computed from the 4 ponies from 5 replicates of the walks. Joint kinematic variables were calculated by use of the calibrated anatomical system technique. The design and error dispersion of each marker were evaluated. RESULTS: Marker clusters were quasiplanar, but variation in orientation error was reduced because the mean radii were > 10 times the largest error dispersion values. Measurements of sagittal rotations of the distal interphalangeal, proximal interphalangeal, and metacarpophalangeal joints were similar to measurements obtained with bone-fixed triads, but larger discrepancies between the 2 methods were found for extrasagittal rotations. CONCLUSIONS AND CLINICAL RELEVANCE: Development of noninvasive methods for quantifying data pertaining to 3-dimensional motion in horses is important for advancement of clinical analysis. The technique used in the study enabled identification of flexion-extension motions with an acceptable degree of accuracy. Appropriate correction algorithms and improvements to the technique may enable future quantification of extrasagittal motions.     

Partitioning and inhibition of lipid oxidation in mechanically separated turkey by components of cranberry press cake

Extracts from cranberry press cakes were prepared either using ethanol or an ethyl acetate-acetone mixture. The press cake extracts were compared with extracts from cranberry juice powder (CJP), prepared using chloroform:methanol (1:1), for their ability to inhibit lipid oxidation in mechanically separated turkey (MST). Because of the susceptibility of muscle membrane lipids to oxidation, the ability of quercetin in the extracts to partition between the aqueous and the membrane phases was studied. Membrane suspensions were prepared from MST. Partitioning of quercetin was quantified using high-performance liquid chromatography. Oxidation was studied by measuring thiobarbituric acid reactive substances and lipid peroxides. The effectiveness of the extracts to inhibit lipid oxidation was CJP extract > ethyl acetate extract of press cake > or = ethanol extract of press cake. The amount of quercetin in the extracts and the amount of quercetin that partitioned into the membranes followed the same order. However, the total phenolic content of the extracts did not follow the same order as that of inhibitory power. The phenolic content of the extracts decreased, ethyl acetate extract > ethanol extract of press cake > or = chloroform extract of CJP. Irrespective of the extraction method, around 78% quercetin from the extracts partitioned into the membranes. It could be concluded that increasing the amount of quercetin in the press cake extracts increases the ability of the extracts to inhibit lipid oxidation in MST. Hence, a proper choice of solvents and extraction method, which would increase the amount of quercetin in the press cake extracts, might increase the antioxidant potential of the extracts and hence their economic value.     

Assessing genetic diversity of wild southeastern North American <Emphasis Type="Italic">Vaccinium</Emphasis> species using microsatellite markers

Wild species representatives from Northwestern, Central and Southern Florida, and neighboring U.S. states were collected in multiple United States Department of Agriculture (USDA) exploration expeditions and are being preserved at the USDA, Agricultural Research Service, National Clonal Germplasm Repository in Corvallis, Oregon. Germplasm from these southeastern regions of North America is particularly vulnerable to loss in the wild due to encroachment of human development in key habitats and biotic and abiotic stresses from climate change. Fourteen simple sequence repeats (SSRs), previously developed from the highbush blueberry (Vaccinium corymbosum) cultivar ‘Bluecrop’, were used to estimate genetic diversity and genetic differentiation of 67 diploid individuals from three species, including 19 V. elliottii, 12 V. fuscatum, and 35 V. darrowii accessions collected throughout the species’ ranges. Results from our analyses indicated that the samples from each species could be reliably resolved using genetic distance measures with ordination and neighbor joining approaches. In addition, we estimated admixture among these species by using Bayesian assignment tests, and were able to identify a mis-labeled accession of V. darrowii ‘Johnblue’, two mis-classified accessions (CVAC 735.001 and CVAC 1223.001), and four accessions of previously undescribed hybrid origin (CVAC 734.001, CVAC 1721.001, CVAC 1741.001, and Florida 4B CVAC 1790). Allele composition at the 14 SSRs confirmed that Florida 4B CVAC 1790, the donor of low chilling for the southern highbush blueberry, was the critical parent of US 74. Genetic diversity assessment and identification of these wild accessions are crucial for optimal germplasm management and expand opportunities to utilize natural variation in breeding programs.     

Yield response of two potato culivars to supplemental irrigation and N fertilization in New Brunswick

Nitrogen and water are important factors influencing potato production, and crop response to these two factors may vary with cultivars. The yield response of two potato cultivars (Russet Burbank and Shepody) to six rates of N fertilization (0-250 kg N ha^-1) with and without supplemental irrigation was studied at four onfarm sites in each of three years, 1995 to 1997, in the upper St-John River Valley of New Brunswick, Canada. On average, irrigation increased total yield from 31.9t ha^-1 without irrigation to 38.41 ha^-1 with irrigation and marketable yield from 25.61 ha^-1 without irrigation to 30.71 ha^-1 with irrigation. Potato yields were increased by irrigation at nine out of the 12 sites, and the irrigation response was similar for both cultivars. Nitrogen fertilization significantly increased both total and marketable yields at all sites except one. The yield response to N fertilization was greater with irrigation. The N fertilization rate (Nmax) required to reach maximum total and marketable yield, however, was similar with and without irrigation. A large variation in Nmax was observed among sites. With irrigation Nmax varied between 158 and 233 kgN ha^-1 for total yield, and between 151 and 250 kg N ha^-1 for marketable yield. There was no interaction between N fertilization and potato cultivar for both total and marketable yields. The two cultivars had similar total yields (35 t ha^-1). Shepody, however, had a greater marketable yield (28.9 t ha^-1) than Russet Burbank (27.4 t ha^-1). Our results indicate that the response to two of the most significant factors of potato production, irrigation and N fertilization, varies greatly with sites and climatic conditions, and that field specific recommendations are required for the optimum management of N and irrigation.     

Immunohistochemical and PCR studies of wild fish for Tetracapsula bryosalmonae (PKX), the causative organism of proliferative kidney disease

Tetracapsula bryosalmonae, previously referred to as PKX, causes proliferative kidney disease (PKD) in salmonids and is an economically important myxozoan pathogen in salmonid culture. A variety of molecular and immunological tools have been developed to detect the parasite. To determine the specificity of four monoclonal antibodies (MAbs) raised against T. bryosalmonae, archive material of fish infected with various myxosporean species was obtained and immunostained. Wild fish were also collected from enzootic waters and examined for T. bryosalmonae infection using immunohistochemistry and the polymerase chain reaction (PCR). Three of the MAb probes appear to be specific for T. bryosalmonae while only two of the five sets of primers tested appeared to specifically amplify T. bryosalmonae DNA. The results of the immunostaining and the PCR demonstrate that T. bryosalmonae occurs in the tubules of grayling Thymallus thymallus L., brown trout, Salmo trutta L. and Atlantic salmon, Salmo salar L. outside of the PKD season (June‐September) in the UK. This confirms the results of previous studies that these species are the preferred fish hosts for the parasite in the UK.     

Primary hyperaldosteronism in two cats.

A condition of primary hyperaldosteronism resulting from an adrenal tumor in two cats is presented and was characterized by hypertension, hypokalemia, inappropriate kaliuresis, low normal plasma renin activity, and markedly increased serum aldosterone concentration. One of the two cats underwent a laparotomy, and in this case hypertension and hypokalemia resolved following the removal of an adrenal tumor.     

Atrazine intoxication in cattle,confirmed by gas chromatography–mass spectrometry

Ten of 40 cows died within 48 h of gaining access to a barn in which various chemicals were stored. Some of the surviving cows exhibited drooling, muscle tremors, and agitation. Postmortem examinations of 2 cows were performed in the field, and revealed nonspecific, moderate-to-severe pulmonary congestion. Liver and rumen contents, each from a different cow, were analyzed using a qualitative, multi-residue GC-MS method validated for the detection of pesticides and other chemical analytes. Using this method, extracts from the liver and rumen content samples were compared to atrazine (neat standard) and matrix-matched, control samples fortified with atrazine. GC-MS analysis detected atrazine at 215 m/z (NIST match >97%) with a retention time of ~13 min in liver and rumen content samples from our case. Detection of atrazine in the samples from the cows in this herd, combined with the clinical history, indicate that atrazine toxicity was the likely cause of clinical signs and death observed in this herd.