Atypical scrapie in a Swiss goat and implications for transmissible spongiform encephalopathy surveillance.

Different types of transmissible spongiform encephalopathies (TSEs) affect sheep and goats. In addition to the classical form of scrapie, both species are susceptible to experimental infections with the bovine spongiform encephalopathy (BSE) agent, and in recent years atypical scrapie cases have been reported in sheep from different European countries. Atypical scrapie in sheep is characterized by distinct histopathologic lesions and molecular characteristics of the abnormal scrapie prion protein (PrP(sc)). Characteristics of atypical scrapie have not yet been described in detail in goats. A goat presenting features of atypical scrapie was identified in Switzerland. Although there was no difference between the molecular characteristics of PrP(sc) in this animal and those of atypical scrapie in sheep, differences in the distribution of histopathologic lesions and PrP(sc) deposition were observed. In particular the cerebellar cortex, a major site of PrP(sc) deposition in atypical scrapie in sheep, was found to be virtually unaffected in this goat. In contrast, severe lesions and PrP(sc) deposition were detected in more rostral brain structures, such as thalamus and midbrain. Two TSE screening tests and PrP(sc) immunohistochemistry were either negative or barely positive when applied to cerebellum and obex tissues, the target samples for TSE surveillance in sheep and goats. These findings suggest that such cases may have been missed in the past and could be overlooked in the future if sampling and testing procedures are not adapted. The epidemiological and veterinary public health implications of these atypical cases, however, are not yet known.     

Jekyll and Hyde in the microbial world

Fungi are nonmotile organisms that obtain carbon from compounds in their immediate surroundings. Confronted with nutrient limitation, the yeast Saccharomyces cerevisiae undergoes a dimorphic transition, switching from spherical cells to filaments of adherent, elongated cells that can invade the substratum. A complex web of sensing mechanisms and cooperation among signaling networks (including a mitogen-activated protein kinase cascade, cyclic adenosine monophosphate-dependent protein kinase, and 5'-adenosine monophosphate-activated protein kinase) elicits the appropriate changes in physiology, cell cycle progression, cell polarity, and gene expression to achieve this differentiation. Highly related signaling processes control filamentation and virulence of many human fungal pathogens.     

Oscillatory zoning in plagioclase feldspar

A kinetic mathematical model of crystal growth from the melt is used to describe quantitatively the phenomenon of oscillatory zoning in plagioclase feldspar. In this model, the functional dependence of crystal growth rate on both melt and crystal surface composition and the transport of material within the melt are explicitly considered. Oscillatory zoning is found to develop for a wide variety of such functional dependence and to be sensitive to the initial composition of the melt.     

Subdiffraction multicolor imaging of the nuclear periphery with 3D structured illumination microscopy

Fluorescence light microscopy allows multicolor visualization of cellular components with high specificity, but its utility has until recently been constrained by the intrinsic limit of spatial resolution. We applied three-dimensional structured illumination microscopy (3D-SIM) to circumvent this limit and to study the mammalian nucleus. By simultaneously imaging chromatin, nuclear lamina, and the nuclear pore complex (NPC), we observed several features that escape detection by conventional microscopy. We could resolve single NPCs that colocalized with channels in the lamin network and peripheral heterochromatin. We could differentially localize distinct NPC components and detect double-layered invaginations of the nuclear envelope in prophase as previously seen only by electron microscopy. Multicolor 3D-SIM opens new and facile possibilities to analyze subcellular structures beyond the diffraction limit of the emitted light.     

Shifts in rhizosphere microbial communities and enzyme activity of Poa alpina across an alpine chronosequence

This study quantifies the influence of Poa alpina on the soil microbial community in primary succession of alpine ecosystems, and whether these effects are controlled by the successional stage. Four successional sites representative of four stages of grassland development (initial, 4 years (non-vegetated); pioneer, 20 years; transition, 75 years; mature, 9500 years old) on the Rotmoos glacier foreland, Austria, were sampled. The size, composition and activity of the microbial community in the rhizosphere and bulk soil were characterized using the chloroform-fumigation extraction procedure, phospholipid fatty acid (PLFA) analysis and measurements of the enzymes β-glucosidase, β-xylosidase, N-acetyl-β-glucosaminidase, leucine aminopeptidase, acid phosphatase and sulfatase. The interplay between the host plant and the successional stage was quantified using principal component (PCA) and multidimensional scaling analyses. Correlation analyses were applied to evaluate the relationship between soil factors (C_org, N_t, C/N ratio, pH, ammonium, phosphorus, potassium) and microbial properties in the bulk soil. In the pioneer stage microbial colonization of the rhizosphere of P. alpina was dependent on the reservoir of microbial species in the bulk soil. As a consequence, the rhizosphere and bulk soil were similar in microbial biomass (ninhydrin-reactive nitrogen (NHR-N)), community composition (PLFA), and enzyme activity. In the transition and mature grassland stage, more benign soil conditions stimulated microbial growth (NHR-N, total amount of PLFA, bacterial PLFA, Gram-positive bacteria, Gram-negative bacteria), and microbial diversity (Shannon index H) in the rhizosphere either directly or indirectly through enhanced carbon allocation. In the same period, the rhizosphere microflora shifted from a G⁻ to a more G⁺, and from a fungal to a more bacteria-dominated community. Rhizosphere β-xylosidase, N-acetyl-β-glucosaminidase, and sulfatase activity peaked in the mature grassland soil, whereas rhizosphere leucine aminopeptidase, β-glucosidase, and phosphatase activity were highest in the transition stage, probably because of enhanced carbon and nutrient allocation into the rhizosphere due to better growth conditions. Soil organic matter appeared to be the most important driver of microbial colonization in the bulk soil. The decrease in soil pH and soil C/N ratio mediated the shifts in the soil microbial community composition (bacPLFA, bacPLFA/fungPLFA, G⁻, G⁺/G⁻). The activities of β-glucosidase, β-xylosidase and phosphatase were related to soil ammonium and phosphorus, indicating that higher decomposition rates enhanced the nutrient availability in the bulk soil. We conclude that the major determinants of the microflora vary along the successional gradient: in the pioneer stage the rhizosphere microflora was primarily determined by the harsh soil environment; under more favourable environmental conditions, however, the host plant selected for a specific microbial community that was related to the dynamic interplay between soil properties and carbon supply.     

Teaching small animal reproduction via virtual patients

Virtual patients have become an interesting alternative in medical education. Due to increasing demands regarding theoretical and clinical teaching and to improve an interdisciplinary approach, a new blended learning concept including virtual patients was developed and implemented in the veterinary curriculum of the Freie Universität Berlin. In the presented project, three virtual patients from the field of canine reproduction were developed. They focus on pregnancy diagnosis with suspected luteal insufficiency, pyometra and benign prostatic hyperplasia, respectively. The results of an evaluation by veterinary students of the 7th semester showed a high acceptance of virtual patients in a blended learning reproduction module in the interdisciplinary lectures. Students especially preferred videos, such as video lectures, hands-on videos and animations as well as a glossary for background information, to successfully and autonomously work on a virtual case. The content covered by the new modules that were developed in the context of this project is part of a spiral curriculum; they will be revised and enhanced during the clinical year.     

Bovine viral diarrhea (BVD) eradication in Switzerland--experiences of the first two years

A national eradication programme was designed with the aim of achieving total freedom from bovine viral diarrhea virus (BVDV) infection in the Swiss cattle population. The eradication programme consisted of testing every Swiss bovine for antigen, culling virus-positive animals and applying movement restrictions. Starting in 2008, the campaign achieved the goal of reducing the proportion of newborn calves that were virus-positive from 1.8% to under 0.2% within two years (situation in September 2010). Both good data flow between the parties involved as well as speed and efficiency (e.g. concerning the application of tests, movement restrictions and slaughter) are central to the success of the programme. Since the beginning of the programme 2.85 million cattle have been tested for bovine viral diarrhea virus (BVDV). The BVD-prevalence in cattle at the individual and herd levels following the implementation of the eradication programme was assessed. Using data collected during this campaign a risk factor analysis was conducted in order to identify factors associated with the appearance of virus positive newborn calves in herds where BVD had not previously been detected; these risk factors would allow targeting of future surveillance. Herd size, early death rate (i.e. the number of animals that either die before 15 days of age or are stillborn per number of newborns per year), buying in stock, using communal summer grazing, production type, age structure and management strategy were factors associated with the appearance of new cases of infection. Testing of newborn calves for antigen will continue to be conducted until the end of 2011, this is combined with outbreak investigation of newly infected herds (consisting of re-testing dams of virus-positive calves and if necessary all cattle on or that recently left the farm). This process is done to identify infected animals that may have been missed during prior testing (false negatives), it also serves to identify other factors that may be responsible for the introduction of BVDV onto the farm. Since October 2009, testing of calves for antigen combined with outbreak investigation has led to the detection of 55 infected animals that had tested negative (presumably false negative) during previous rounds of testing.