Phenotypic and histological expression of different genetic backgrounds in interactions between lettuce, wild Lactuca spp., L. sativa × L. serriola hybrids and Bremia lactucae

Phenotypic and histological responses of cultivated lettuce (Lactuca sativa) and wild relatives L. saligna, L.␣virosa as well as interspecific crosses derived from L. sativa × L. serriola to two races of Bremia lactucae (CS2, CS9) were investigated. With the exception of L. sativa genotypes, all accessions and hybrids expressed incomplete or complete resistance to both pathogen races, with slight differences at seedling and adult plant stages, respectively. Histological features of the interactions (development of pathogen infection structures and host hypersensitive response to attempted infection) were studied on leaf discs 48 h after inoculation. Interactions with similar phenotypic expression of resistance were characterized by significant variation in rate of development of pathogen infection structures and hypersensitive reactions. Differences found within eight Lactuca spp. accessions and hybrids challenged by two distinct pathogen races are interpreted and discussed.     

Evaluation of brush cytology in the diagnosis of chronic intranasal disease in cats

Brush cytology was used as a diagnostic aid in 85 cats affected with chronic intranasal disease. Fifty-three of these cases, sampled over a five-year period, were included in this study, while the other cases were excluded due to poor cellularity of the cytological samples (nine cases) or a lack of histological or follow-up data (23 cases). Thirty-six brush samples were classified by cytology as inflammatory. Subsequent histological examination revealed a false negative diagnosis of neoplasia in six cats, two of which had malignant tumours (one adenocarcinoma and one lymphoma), the remaining four having benign tumours (two adenomas and two osteochondromas). Seventeen samples were classified by brush cytology as neoplastic. This was confirmed in 16 of these cases by histology or follow-up (nine epithelial malignant tumours, six lymphomas and one osteosarcoma). In the remaining case, a false positive diagnosis of lymphoma was made. The procedure had an overall 86.8 per cent (46/53) agreement between the diagnosis of inflammatory conditions versus neoplasia, with a sensitivity of 72.7 per cent, a specificity of 96.8 per cent, a predictive value of a positive test of 94.1 per cent and a predictive value of a negative test of 83.3 per cent.     

Effects of the needle bladder rust (Chrysomyxa rhododendri) on Norway spruce: implications for subalpine forests

Norway spruce trees in the subalpine forests of the European Alps are frequently attacked by the needle rust Chrysomyxa rhododendri. The obligate parasite undergoes a complex life cycle with a host shift between rhododendrons (Rhododendron sp.) and Norway spruce [Picea abies (L.) Karsten] and causes a yellowing and defoliation of the current-year needles in summer. Infected trees show several anatomical, morphological and physiological modifications, including a decrease in pigment content and net photosynthesis of infected needles, lower biomass production and reduced radial and height growth. The consequences are diminished timber yield and cripple growth. Because of repeated heavy infections in recent years, forest managers report increasing difficulties in both natural regeneration and afforestation at high elevation sites, where rhododendrons occur. This review gives a summary of the present knowledge about the effects of C. rhododendri infections on Norway spruce, including so far unpublished findings and with particular attention to the phenomena of resistant trees. Implications for subalpine forests and counter strategies are discussed.     

Uniaxial compression of rotationally symmetric Norway spruce samples: surface deformation and size effect

The influence of size on strength is well known for various materials and testing methods, but not enough data and knowledge of the effect on wood under compressive strength can be found. Therefore, the deformation and compressive strength of hyperboloid Norway spruce samples were tested for different dimensions. To determine the influence of size on the strength, three different approaches were used: “weakest link theory”, “size effect law” and “multifractal scaling law”. Of the three scaling theories, the “size effect law” and the “weakest link theory” predicted the effect well. Additionally, to determine the surface deformation of various samples, DIC3D was used on the largest sample geometry. The experiments show the existence of a possible size effect during compression, while digital image correlation illustrates the expected differences in deformation due to the shape and dependence of the strain distribution on the structure of wood. Additional experiments are proposed to further verify the observed effects and expand the knowledge of the size effect.     

Stem cell depletion through epidermal deletion of Rac1

Mammalian epidermis is maintained by self-renewal of stem cells, but the underlying mechanisms are unknown. Deletion of Rac1, a Rho guanosine triphosphatase, in adult mouse epidermis stimulated stem cells to divide and undergo terminal differentiation, leading to failure to maintain the interfollicular epidermis, hair follicles, and sebaceous glands. Rac1 exerts its effects in the epidermis by negatively regulating c-Myc through p21-activated kinase 2 (PAK2) phosphorylation. We conclude that a pleiotropic regulator of cell adhesion and the cytoskeleton plays a critical role in controlling exit from the stem cell niche and propose that Rac and Myc represent a global stem cell regulatory axis.     

Macrophakia in three cats

This report describes three cases of bilateral macrophakia in 3-, 5-, and 9-year-old cats, respectively. All cats were presented because of visual deficits. Ophthalmic examination revealed macrophakia (the vitreous was replaced by the lens) and retinal changes (tapetal hyper-reflectivity, attenuation of retinal vessels, and retinal folds) in all cats. In addition, bilateral subconjunctival orbital fat prolapse in one cat and microphthalmos in another cat were present. To confirm the ophthalmologic diagnosis of macrophakia, gross pathology examination in one cat and ultrasound examination in another cat were performed.     

Gastrointestinal stromal tumors in equids.

Eleven gastrointestinal neoplasms from 10 aged horses and 1 pony were examined grossly, his tologically, immunohistochemically, and (in two cases) ultrastructurally. Clinical signs were associated with two neoplasms, and the other nine tumors were incidental findings at laparotomy or necropsy. The neoplasms were solitary (9/11) or multifocal (2/11), well demarcated, serosal or mural masses of stomach (1), jejunum (1), ileum (3), cecum (5), and/or colon (2). Microscopic examination revealed discrete spindle cells arranged in compact patterns with fascicles and whorls or cribriform pattern with fascicles and rare palisades, often with a myxoid interstitial matrix. Three tumors infiltrated between the muscularis interna and the muscularis externa at the myenteric plexi. All neoplasms were vimentin positive, 3/11 were S-100 positive, 2/11 were muscle actin positive, and no neoplasm was positive for glial fibrillary acid protein, desmin, factor VIII, chromogranin, or neuron-specific enolase. Of the two tumors studied ultrastructurally, one contained an admixture of smooth muscle cells and cells resembling Schwann cells, and the second was populated by homogeneous fusiform mesenchymal cells separated by homogeneous matrix. Gastrointestinal stromal tumors (GIST) have been recognized in humans, more recently in dogs and nonhuman primates, and now in equids. Most of these tumors are comprised of a loosely arranged network of spindled cells separated by myxoid matrix. GIST may be composed of myogenic, neurogenic, combined myogenic and neurogenic, and undifferentiated mesenchymal cells.