Immunodetection of Leishmania Infantum in the Subungual Area of Dogs with Visceral Leishmaniasis

Onychogryphosis is one of the main clinical findings in dogs with visceral leishmaniasis (VL); however, research focusing on the subungual area of infected dogs is scarce. This study aims to assess the subungual area of dogs with VL that presented or not onychogryphosis by means of histopathological analyses and immunohistochemical studies (parasite burden). The third digit of the thoracic and pelvic limbs of Leishmania infantum naturally infected dogs was collected regardless of sex, breed or age. The animals were split into two groups, dogs with onychogryphosis (G1; n=7) and without onychogryphosis (G2; n=9). The digits were evaluated in four areas (dorsal epidermis/dermis, ventral epidermis/dermis, dorsal matrix/dermis and ventral matrix/dermis). All lesions observed (mononuclear inflammatory infiltrate, vacuolar degeneration of basal keratinocytes, dermoepidermal clefting and pigmentary incontinence) were present in both groups, being more severe in the digits of G1 group. Immunostaining of the amastigote forms of Leishmania infantum were observed in the different areas of the digit, with statistical difference between the dorsal epidermis/dermis area and the dorsal matrix/dermis of G1 group. In conclusion, the main histopathological alteration of the digit of dogs with VL is mononuclear inflammatory infiltrate and parasite burden, especially in cutaneous tissue adjacent to the nail matrix. This aspect can influence the onychogryphosis development, due to the presence of the parasite and by inflammatory mediators released in the nail microenvironment.

Cell–cell and cell–extracellular matrix adhesions cooperate to organize actomyosin networks and maintain force transmission during dorsal closure

Tissue morphogenesis relies on the coordinated action of actin networks, cell–cell adhesions, and cell–extracellular matrix (ECM) adhesions. Such coordination can be achieved through cross-talk between cell–cell and cell–ECM adhesions. Drosophila dorsal closure (DC), a morphogenetic process in which an extraembryonic tissue called the amnioserosa contracts and ingresses to close a discontinuity in the dorsal epidermis of the embryo, requires both cell–cell and cell–ECM adhesions. However, whether the functions of these two types of adhesions are coordinated during DC is not known. Here we analyzed possible interdependence between cell–cell and cell–ECM adhesions during DC and its effect on the actomyosin network. We find that loss of cell–ECM adhesion results in aberrant distributions of cadherin-mediated adhesions and actin networks in the amnioserosa and subsequent disruption of myosin recruitment and dynamics. Moreover, loss of cell–cell adhesion caused up-regulation of cell–ECM adhesion, leading to reduced cell deformation and force transmission across amnioserosa cells. Our results show how interdependence between cell–cell and cell–ECM adhesions is important in regulating cell behaviors, force generation, and force transmission critical for tissue morphogenesis.

New interpretation of the wings of the pterosaur Rhamphorhynchus muensteri based on the Zittel and Marsh specimens

The Zittel wing of Rhamphorhynchus muensteri is reinterpreted as preserving negative impressions of closely spaced broad flat actinofibrils that were replaced by calcite but were prepared away by the specimen’s finder. The Marsh specimen preserves positive impressions of the dorsal and ventral surfaces of the wing, which show that the skin was smooth with fine wrinkles and that actinofibrils were not on the wing surface. Based on comparisons of those specimens, the dactylopatagium consisted of dorsal and ventral skins of epidermis and dermis surrounding a common hypodermis core, and keratinous actinofibrils developed in place within the dorsal epidermis adjacent to a layer of linear collagen fibers in the dorsal dermis. The actinofibrils and linear collagen fibers together formed the main functional structure of the dactylopatagium. That structure made the dactylopatagium somewhat stiff and essentially inextensible so that it folded up along discrete fold lines that probably were genetically determined. A pneumatic retrophalangeal wedge behind the antebrachium through at least wing phalanx 3 streamlined the transition between the thick wing spar and thin patagium.

Studies in the genus Riccia (Marchantiales) from southern Africa. 25. A new species in subgenus Ricciella, section Ricciella

Riccia sibayenii Perold is a new species, recently collected in Mpumalanga, near Sibayeni and has been named for this town, which is close to the Mozambique border and is in the summer rainfall area. R. sibayenii is distinguished by lime- green, medium-sized to quite large thalli with a chlorophyllose dorsal epidermis, air pores that soon enlarge and lead into mostly 6-sided air chambers below; ventrally with a thin median layer of storage tissue; ventral scales absent and the rhizoids all smooth. The spores are winged and polar, the distal face completely or incompletely reticulate and the proxi­mal face ornamented with fine to coarse, sometimes spinose granules.

ribbon encodes a novel BTB/POZ protein required for directed cell migration in Drosophila melanogaster

During development, directed cell migration is crucial for achieving proper shape and function of organs. One well-studied example is the embryonic development of the larval tracheal system of Drosophila, in which at least four signaling pathways coordinate cell migration to form an elaborate branched network essential for oxygen delivery throughout the larva. FGF signaling is required for guided migration of all tracheal branches, whereas the DPP, EGF receptor, and Wingless/WNT signaling pathways each mediate the formation of specific subsets of branches. Here, we characterize ribbon, which encodes a BTB/POZ-containing protein required for specific tracheal branch migration. In ribbon mutant tracheae, the dorsal trunk fails to form, and ventral branches are stunted; however, directed migrations of the dorsal and visceral branches are largely unaffected. The dorsal trunk also fails to form when FGF or Wingless/WNT signaling is lost, and we show that ribbon functions downstream of, or parallel to, these pathways to promote anterior-posterior migration. Directed cell migration of the salivary gland and dorsal epidermis are also affected in ribbon mutants, suggesting that conserved mechanisms may be employed to orient cell migrations in multiple tissues during development.

Investigation of leading edge formation at the interface of amnioserosa and dorsal ectoderm in theDrosophilaembryo

The leading edge (LE) is a single row of cells in the Drosophila embryonic epidermis that marks the boundary between two fields of cells: the amnioserosa and the dorsal ectoderm. LE cells play a crucial role in the morphogenetic process of dorsal closure and eventually form the dorsal midline of the embryo. Mutations that block LE differentiation result in a failure of dorsal closure and embryonic lethality. How LE cells are specified remains unclear. To explore whether LE cells are specified in response to early dorsoventral patterning information or whether they arise secondarily, we have altered the extent of amnioserosa and dorsal ectoderm genetically, and assayed LE cell fate. We did not observe an expansion of LE fate in dorsalized or ventralized mutants. Furthermore, we observed that the LE fate arises as a single row of cells, wherever amnioserosa tissue and dorsal epidermis are physically juxtaposed. Taken together our data indicate that LE formation is a secondary consequence of early zygotic dorsal patterning signals. In particular, proper LE specification requires the function of genes such as u-shaped and hindsight, which are direct transcriptional targets of the early Decapentaplegic/Screw patterning gradient, to establish a competency zone from which LE arises. We propose that subsequent inductive signaling between amnioserosa and dorsal ectoderm restricts the formation of LE to a single row of cells.