The ultrastructure of the androgenic gland in Porcellio scaber Latr. (terrestrial isopods)

Summary This paper presents the normal ultrastructural features of the androgenic gland in Porcellio scaber. It describes the changes in the organelles of its cells through the course of the secretory cycle, which terminates with the regression and destruction of these holocrine glandular cells. As products of this activity, the electron-opaque bodies (granules, lysosomes, agglomerates) and clear substances accumulate in the cytoplasm. With the destruction of the cell membrane, the entire cell content passes into the spaces of the haemocoele. The morphological modifications of the mitochondria and rough endoplasmic reticulum are the most striking changes.

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Résumé Les auteurs présentent, dans ce travail, les aspects ultrastructuraux normaux de la glande androgène chez l'oniscoïde Porcellio scaber. On montre, par des phases successives, les modifications morpho-fonctionnelles des organites cellulaires jusqu'à la fin du cycle sécrétoire, qui finit par la dégradation et la destruction des cellules glandulaires, dont la fonction est de type holocrin. Comme produits de cette activité, des corps éléctrono-opaques (grains, agglomerats, lysosomes) et des substances claires apparaissent dans le cytoplasme. Par la destruction de la membrane plasmique, tout le contenu cellulaire est éliminé dans les espaces haemocoeliens, soit par écoulement soit par fragments. Le RE et le chondriome subissent les modifications les plus spectaculaires.

     

Immunosedimentation analysis of proteins

After performing experiments with protein sedimentation the ultracentrifuge test-tube was attached to the inferior opening of the channel in the agar block with a vertical gradient of saccharose concentration. The liquid with protein zones was removed from the test-tube to the channel, forcing a 60% solution of saccharose beneath the lower layers in the test-tube. Horizontal electrophoresis was performed so that the protein zones penetrated the width of the channel walls. A piece of agar gel was cut out from the walls along the whole height of the channel. That piece was placed on the slide and embedded with a mixture of agar and antiserum. Immunoelectrophoresis was made according to Lowrell. The method permits obtaining for the first time continuous sedimentograms during immunodevelopment of the protein zones derived on ultracentrifugation.     

Visual exploration and object recognition by lattice deformation

Mechanisms of explicit object recognition are often difficult to investigate and require stimuli with controlled features whose expression can be manipulated in a precise quantitative fashion. Here, we developed a novel method (called "Dots"), for generating visual stimuli, which is based on the progressive deformation of a regular lattice of dots, driven by local contour information from images of objects. By applying progressively larger deformation to the lattice, the latter conveys progressively more information about the target object. Stimuli generated with the presented method enable a precise control of object-related information content while preserving low-level image statistics, globally, and affecting them only little, locally. We show that such stimuli are useful for investigating object recognition under a naturalistic setting--free visual exploration--enabling a clear dissociation between object detection and explicit recognition. Using the introduced stimuli, we show that top-down modulation induced by previous exposure to target objects can greatly influence perceptual decisions, lowering perceptual thresholds not only for object recognition but also for object detection (visual hysteresis). Visual hysteresis is target-specific, its expression and magnitude depending on the identity of individual objects. Relying on the particular features of dot stimuli and on eye-tracking measurements, we further demonstrate that top-down processes guide visual exploration, controlling how visual information is integrated by successive fixations. Prior knowledge about objects can guide saccades/fixations to sample locations that are supposed to be highly informative, even when the actual information is missing from those locations in the stimulus. The duration of individual fixations is modulated by the novelty and difficulty of the stimulus, likely reflecting cognitive demand.     

Ena/VASP is required for endothelial barrier function in vivo

Enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) proteins are key actin regulators that localize at regions of dynamic actin remodeling, including cellular protrusions and cell–cell and cell–matrix junctions. Several studies have suggested that Ena/VASP proteins are involved in the formation and function of cellular junctions. Here, we establish the importance of Ena/VASP in endothelial junctions in vivo by analysis of Ena/VASP-deficient animals. In the absence of Ena/VASP, the vasculature exhibits patterning defects and lacks structural integrity, leading to edema, hemorrhaging, and late stage embryonic lethality. In endothelial cells, we find that Ena/VASP activity is required for normal F-actin content, actomyosin contractility, and proper response to shear stress. These findings demonstrate that Ena/VASP is critical for actin cytoskeleton remodeling events involved in the maintenance of functional endothelia.     

Obstructive hypertrophic cardiomyopathy is associated with reduced expression of vinculin in the intercalated disc

Mutations in the cardiac-specific insert of vinculin, metavinculin, rarely cause hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). Subsequently, a missense mutation in the ubiquitously expressed vinculin was discovered in a patient with obstructive HCM. Microscopic examination of both myectomy specimens from patients bearing genetic defects in metavinculin and vinculin showed a marked reduction of vinculin/metavinculin expression in the intercalated disc, but normal expression in the Z-disc. Given that distinct functional domains were altered by the metavinculin and vinculin mutations, we hypothesized that the intercalated disc-specific reduction of vinculin may stem from left ventricular tract obstruction in general rather than rarely observed perturbations in VCL-encoded vinculin. To test this hypothesis, we examined the localization of vinculin/metavinculin in hypertrophied human heart tissue from patients with cardiovascular conditions associated with obstruction and hemodynamic overload using an immunohistochemistry approach. Tissue specimens derived from patients with obstructive HCM and aortic stenosis (AS) showed a universal defect of vinculin/metavinculin expression in the intercalated disc but preserved expression in the cardiac Z-disc, whereas tissue specimens derived from patients with either DCM, hypertensive heart disease (HTN), or pulmonary hypertension (PHTN) exhibited normal expression of vinculin/metavinculin in both the Z- and the intercalated disc despite being associated with hypertrophy. Results of this study suggest that cardiac hypertrophy may be associated with different expression of the marker vinculin/metavinculin depending on the underlying pathophysiology; hemodynamic overload may not affect the localization whereas obstructive disease substantially reduces the expression of vinculin preferentially in the intercalated disc.     

Structural analysis of some soluble elastins by means of FT‐IR and 2D IR correlation spectroscopy

Fourier transform infrared (FT‐IR) spectroscopy combined with 2D correlation spectroscopy has been used to offer some information about stability and structure of some soluble elastins. Temperature has been chosen as the perturbation to monitor the infrared behavior of various soluble elastins, namely, α‐elastin p, α‐elastin, and k‐elastin. In the 3800–2700 cm^?1 region, the H‐containing groups were analyzed. The bonded hydroxyls are found to decrease prior to the NH‐related hydrogen bonds and also to the conformational reorganization of hydrocarbon chains. The transition temperatures were evaluated and they were found to agree with those obtained from DSC data. The FTIR spectra and their 2nd derivatives denote that α‐ elastins exhibited amide‐I, ‐II and ‐III bands at 1656, 1539 and 1236 cm^?1, respectively, while in k‐elastin these bands were found at 1652 cm^?1 for amide I, 1540 cm^?1 for amide II and 1248 cm^?1 for amide III. The macroscopic IR finger‐print method, which combines: general IR spectra, secondary derivative spectra, and 2D‐IR correlation spectra, is useful to discriminate different elastins. Thus using the differences of the position and intensity of the bands from “fingerprint region” of studied elastins, which include the peaks assigned to C?O, C? C groups from α‐helix, β‐turn, and the peaks assigned to the amide groups, it is possible to identify and discriminate elastins from each others. Furthermore, the pattern of 2D‐IR correlation spectra under thermal perturbation, allow their direct identification and discrimination. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 1072–1084, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Integration and scaling of UV-B radiation effects on plants: the relative sensitivity of growth forms and interspecies interactions

Aims The relative plant type sensitivity and selected community interactions under increased UV-B radiation where examined. Specifically, we investigated: (i) if there are differences among growth forms in regard to their sensitivity to UV-B radiation, (ii) if increased UV-B radiation influences the plant competitive balance in plant communities and (iii) the response mechanisms of the UV-B radiation-sensitive species that might increase their fitness.Methods To answer our research questions, we used a mechanistic model that, for the first time, integrated the effects of increased UV-B radiation from molecular level processes, whole plant growth and development, and community interactions.Important findings In the model simulations, species types exhibited different levels of sensitivity to increased UV-B radiation. Summer C₃ and C₄ annuals showed similar growth inhibition rates, while biennials and winter C₃ annuals were the most sensitive. Perennials exhibited inhibitions in growth only if increased UV-B radiation results in increases in metabolic rates. In communities, species sensitive to UV-B radiation may have a competitive disadvantage compared to resistant plant species. But, sensitive species may have a wide array of responses that can increase their fitness and reproductive success in the community, such as, increased secondary metabolites production, changes in timing of emergence and reproduction, and changes in seed size. While individual plants may exhibit significant inhibitions in growth and development, in communities, these inhibitions can be mitigated by small morphological and physiological adaptations. Infrequent or occasional increased UV-B radiation events should not have any lasting effect on the structure of the community, unless other environmental factors are perturbing the dynamic equilibrium.     

Genetic analysis of the subunit organization and function of the conserved oligomeric golgi (COG) complex: studies of COG5- and COG7-deficient mammalian cells

The conserved oligomeric Golgi (COG) complex is an eight-subunit (Cog1-8) peripheral Golgi protein involved in Golgi-associated membrane trafficking and glycoconjugate synthesis. We have analyzed the structure and function of COG using Cog1 or Cog2 null Chinese hamster ovary cell mutants, fibroblasts from a patient with Cog7-deficient congenital disorders of glycosylation, and stable Cog5-deficient HeLa cells generated by RNA interference. Although the dilation of some Golgi cisternae in Cog5-deficient cells resembled that observed in Cog1- or Cog2-deficient cells, their global glycosylation defects (less severe) and intracellular processing and function of low density lipoprotein receptors (essentially normal) differed from Cog1- and Cog2-deficient cells. Immunoblotting, gel filtration, and immunofluorescence microscopy analyses of the COG-deficient cells and cell extracts indicated that 1) Cog2-4 and Cog5-7 form stable subcomplexes, 2) Cog1 mediates Golgi association of a Cog2-4 plus Cog8 subcomplex, 3) Cog8 associates stably with both Cog5-7 and Cog1-4 subcomplexes, and thus 4) Cog8 helps assemble the Cog1-4 and Cog5-7 subcomplexes into the complete COG complex. This model of the subunit organization of COG is in excellent agreement with in vitro data presented in an accompanying paper (Ungar, D., Oka, T., Vasile, E., Krieger, M., and Hughson, F. M. (2005) J. Biol. Chem. 280, 32729-32735). Only one or two of the seven Cog1- or Cog2-dependent Golgi membrane proteins called GEARs are also sensitive to Cog5 or Cog7 deficiency, indicating that the COG subunits play distinctive roles in controlling Golgi structure and function.