Intermediate filament proteins and epithelial differentiation in the embryonic ovary of the rat

Abstract. The development and sexual differentiation of gonads in female rat embryos and fetuses between the ages of 11 and 17 days was studied by immunocytochemical analysis of intermediate filament proteins and laminin by light and electron microscopy. In the 11-day-old pregonadal embryo, the surface epithelial cells in the ventral cortex of the mesonephros contained desmin but not cytokeratin or vimentin. The development of the gonad began on the following day by proliferative growth of the mesonephric surface cells, which like the subepithelial cells soon expressed vimentin in addition to desmin. The differentiation continued by formation of separate epithelial cell clusters, which joined into cords, irregular in shape and size. Desmin disappeared from the cord cells and cytokeratins appeared while vimentin remained in all somatic cell types. Desmin was especially abundant in some stromal cells adjacent to the epithelial tissues. After the segration of the basic ovarian tissues, vimentin and desmin decreased and cytokeratins appeared in the surface epithelial cells. New changes in cytokeratin expression appeared with the differentiation of the embryonic cords in a sex-specific manner with gradual decrease of reactivity for cytokeratin 18. No immunoreaction to the neurofilament proteins was found at the present ages, and the germ cells were negative for intermediate filaments. The results show that desmin is expressed in several primitive ovarian and mesonephric cells even though they are not myogenic. The sexual differences emerge after the incipient formation of the genetically female gonad, as different organization of the internal epithelial tissue with different timing of changes in intermediate filament proteins when compared with the male gonad.     

Basement membrane and epithelial features of fetal-type Leydig cells in rat and human testis

The basement membranes of developing Leydig cells in fetal and newborn testis of rat were studied by ultrastructural and immunocytochemical methods. Fetal-type Leydig cells in prenatal rats were organized in irregularly outlined groups in the interstitium and were extensively surrounded by ultrastructurally identifiable basement membranes and immunocytochemically localized laminin and collagen type IV. Prenatal Leydig cell precursors had small patches of laminin and collagen type IV on their surfaces, which indicated that changes in extracellular matrix took place during their differentiation to mature fetal-type Leydig cells. Additionally, ultrastructural evidence was obtained for a basement membrane surrounding the fetal human Leydig cells similar to that in fetal rats. Soon after birth the rat fetal-type cells gathered into distinct clusters surrounded by delicate envelope cells and a discontinuous basement membrane. Basement-membrane structures, laminin, and collagen type IV were observed between the clustered cells as well. The basement membranes covering large cell surface areas of the fetal-type Leydig cells in fetal and newborn rats differed from those of the adult-type cells, which, according to our earlier study, are covered only by small patches of basement membrane. The difference between the basement membranes of the fetal- and adult-type rat Leydig cells further supports the concept of two different Leydig cell populations. The earlier findings of the epithelial nature of the Leydig cells agree with the observation of basement membranes in the Leydig cells.     

Application of the Red List Index as an indicator of habitat change

For the first time ever, the International Union for Conservation of Nature Red List Index for habitat types was calculated for an entire country, Finland. The RLIs were based on species threat assessments from 2000 and 2010 and included habitat definitions for all 10,131 species of 12 organism groups. The RLIs were bootstrapped to track statistically significant changes. The RLI changes of species grouped by habitats were negative for all habitat types except for forests and rural biotopes which showed a stable trend. Trends of beetles and true bugs were positive in rural and forest habitats. Other 16 observed trends of species group and habitat combinations were negative. Several trends observed were in accordance with studies focusing on particular taxa and habitats, and drivers for their change. This study demonstrates the usefulness of the RLI as a tool for observing habitat change based on species threat assessment data.     

Infrared Thermography and Ultrasonography to Indirectly Monitor the Influence of Liner Type and Overmilking on Teat Tissue Recovery

Eight Danish Holstein cows were milked with a 1-mm thick specially designed soft liner on their right rear teat and a standard liner mounted under extra high tension on their left rear teat. Four of the animals were overmilked for 5 min. Rear teats were subjected to ultrasound examination on the first day and to infrared thermography on the second day. Teats were submersed in ethanol 20 min post-milking on the second day. Ultrasonography measurements showed that teat canal length increased by 30–41% during milking. Twenty minutes after milking, teats milked with modified standard liners still had elongated teat canals while teats milked with the soft liner were normalized. Overmilking tended to increase teat wall thickness. Approximately 80% of variability in teat canal length, from before teat preparation to after milking, could be explained by changes during teat preparation. Thermography indicated a general drop in teat temperature during teat preparation. Teat temperature increased during milking and continued to increase until the ethanol challenge induced a significant drop. Temperatures approached pre-challenge rather than pre-milking temperatures within 10 minutes after challenge. Teat temperatures were dependent on type of liner. Mid-teat temperatures post-challenge relative to pre-teat preparation were dependent on overmilking. Thermography and ultrasound were considered useful methods to indirectly and non invasively evaluate teat tissue integrity.     

Broad‐scale vegetation‐environment relationships in Eurasian high‐latitude areas

Question: How is tundra vegetation related to climatic, soil chemical, geological variables and grazing across a very large section of the Eurasian arctic area? We were particularly interested in broad‐scale vegetation‐environment relationships and how well do the patterns conform to climate‐vegetation schemes. Material and Methods: We sampled vegetation in 1132 plots from 16 sites from different parts of the Eurasian tundra. Clustering and ordination techniques were used for analysing compositional patterns. Vegetation‐environment relationships were analysed by fitting of environmental vectors and smooth surfaces onto non‐metric multidimensional scaling scattergrams. Results: Dominant vegetation differentiation was associated with a complex set of environmental variables. A general trend differentiated cold and continental areas from relatively warm and weakly continental areas, and several soil chemical and physical variables were associated with this broad‐scaled differentiation. Especially soil chemical variables related to soil acidity (pH, Ca) showed linear relationships with the dominant vegetation gradient. This was closely related to increasing cryoperturbation, decreasing precipitation and cooler conditions. Remarkable differences among relatively adjacent sites suggest that local factors such as geological properties and lemming grazing may strongly drive vegetation differentiation. Conclusions: Vegetation differentiation in tundra areas conforms to a major ecocline underlain by a complex set of environmental gradients, where precipitation, thermal conditions and soil chemical and physical processes are coupled. However, local factors such as bedrock conditions and lemming grazing may cause marked deviations from the general climate‐vegetation models. Overall, soil chemical factors (pH, Ca) turned out to have linear relationship with the broad‐scale differentiation of arctic vegetation.     

Microfragmentation concept explains non-positive environmental heterogeneity–diversity relationships

Although recent studies have revealed that the relationship between diversity and environmental heterogeneity is not always positive, as classical niche theory predicts, scientists have had difficulty interpreting these results from an ecological perspective. We propose a new concept—microfragmentation—to explain how small-scale heterogeneity can have neutral or even negative effect on species diversity. We define microfragmentation as a community level process of splitting habitat into a more heterogeneous environment that can have non-positive effects on the diversity through habitat loss and subsequent isolation. We provide support for the microfragmentation concept with results from spatially explicit heterogeneity–diversity model simulations, in which varying sets of species (with different ratios of specialist and generalist species) were modeled at different levels of configurational heterogeneity (meaning that only the habitat structure was changed, not its composition). Our results indicate that environmental heterogeneity can affect community diversity in the same way as fragmentation at the landscape level. Although generalist species might not be seriously affected by microfragmentation, the persistence of specialist species can be seriously disturbed by small-scale patchiness. The microfragmentation concept provides new insight into community level diversity dynamics and can influence conservation and management strategies.     

Visual Interactions Conform to Pattern Decorrelation in Multiple Cortical Areas

Neural responses to visual stimuli are strongest in the classical receptive field, but they are also modulated by stimuli in a much wider region. In the primary visual cortex, physiological data and models suggest that such contextual modulation is mediated by recurrent interactions between cortical areas. Outside the primary visual cortex, imaging data has shown qualitatively similar interactions. However, whether the mechanisms underlying these effects are similar in different areas has remained unclear. Here, we found that the blood oxygenation level dependent (BOLD) signal spreads over considerable cortical distances in the primary visual cortex, further than the classical receptive field. This indicates that the synaptic activity induced by a given stimulus occurs in a surprisingly extensive network. Correspondingly, we found suppressive and facilitative interactions far from the maximum retinotopic response. Next, we characterized the relationship between contextual modulation and correlation between two spatial activation patterns. Regardless of the functional area or retinotopic eccentricity, higher correlation between the center and surround response patterns was associated with stronger suppressive interaction. In individual voxels, suppressive interaction was predominant when the center and surround stimuli produced BOLD signals with the same sign. Facilitative interaction dominated in the voxels with opposite BOLD signal signs. Our data was in unison with recently published cortical decorrelation model, and was validated against alternative models, separately in different eccentricities and functional areas. Our study provides evidence that spatial interactions among neural populations involve decorrelation of macroscopic neural activation patterns, and suggests that the basic design of the cerebral cortex houses a robust decorrelation mechanism for afferent synaptic input.