Daniela Vagnetti

Evidence of Batrachochytrium dendrobatidis Infection in Water Frogs of the Rana esculenta Complex in Central Italy

Batrachochytrium dendrobatidis (phylum Chytridiomycota, order Chytridiales) is the causative organism of chytridiomycosis in amphibians, a disease associated with their population decline worldwide. In this work, we report a cutaneous infection in water frogs of the Rana esculenta complex in agricultural areas of Umbria, central Italy. Histological, immunohistochemical, ultrastructural, and molecular analyses demonstrated for the first time the presence of the Batrachochytrium dendrobatidis in this complex; to date, no association between the presence of chytrid fungal infection and mortality has been found, to our knowledge. However, the presence of Batrachochytrium dendrobatidis infection in the water frogs of the Rana esculenta complex is of concern because the frogs could act as a reservoir species and contribute to the decline of less resistant species.

Ultrastructural aspects of mechano- and chemoreceptors in Branchiobdella pentodonta (annelida, oligochaeta)

The surface receptors in Branchiobdella pentodonta consist of “sense buttons” prevalent on the prostomium, isolated sense cells all along the body of the animal, and free nerve endings. The “sense buttons” are uni‐ and multiciliated neurosensitive elements and supporting cells together with mucus glandular processes and muscle fibers. In the neurosensitive elements the cilia are always surrounded by cytoplasmic extroversion. The cytoplasm of the apical zone has abundant small dense granules, mitochondria, bands of tonofilaments, and microtubules. The cilium of uniciliated elements originates from three short roots. The highly vacuolated support cells surround the neurosensitive elements, separating them from each other. The “sense buttons” appear to be mechanoreceptors and chemoreceptors, and the isolated sense cells tactile mechanoreceptors, as are the free nerve endings. The surface receptors are compared with those of other Oligochaeta and Hirudinea.

Morphological and Ultrastructural Study of Carpal Organ in Adult Female Wild Swine

The carpal organ of adult female wild swine is a sweat‐type gland which secretes an odorous substance. The gland consists of 5–7 lobes, each made up of lobules with convoluted glandular tubules. The gland secretion is transported in large excretory canals which empty from 5 to 7 clearly visible pores. An ultrastructural examination showed that the glandular tubules are made up of single‐layered epithelium with different types of cells. One type, with rather electron‐dense cytoplasm, is secretory cells full of granular material which empties into the tubule lumen. A second cell type has a glycogen‐rich, transparent cytoplasm. Its role appears to be secreting a watery, electrolyte‐containing liquid. In the intermediate zone of the tubules, there is a third type of cell with transparent cytoplasm. Its ultrastructural characteristics seem to indicate that its function is to reabsorb the excess watery component. In the wall of the glandular tubules, outside the epithelium, there are myoepithelial cells which facilitate the movement of the secretions toward the collector canal.

Epidermal cell migration during wound healing in Dugesia lugubris

SummaryThe epidermal cells that migrate over the surface during the wound closure stage of head regeneration in Dugesia lugubris s.l. were examined by scanning electron microscopy. The effect of cytochalasin B on epidermal cell migration was also examined. During the first few hours after decapitation epidermal cells at the edges of the wound showed significant changes of shape related to the process of migration that was accomplished approximately 10 h after wounding. Flattening of the marginal cells was associated with active epidermal spreading throughout the healing period. Suitable support for migrating cells appeared to be a rhabditic network attached to the wound tissue. Epidermal cell migration was inhibited by cytochalasin B. These results demonstrate that the basis for cell movement in planarians is similar to that of many other systems.

Cytochemical and biochemical observations on the alveolar guanylate cyclase of golden hamster lung

Particulate guanylate cyclase (GTP pyrophosphate-lyase (cyclizing] has been cytochemically evidentiated in the cells which make-up the lung air-blood barrier. The cytochemical procedure utilized demonstrates the presence of membrane-bound guanylate cyclase activity through precipitation of lead pyrophosphate in tissues incubated with GTP or with guanylyl imidodiphosphate. Electron microscopic examination reveals that guanylate cyclase (GC) is localized, as micropinocytic vesicles, within endothelial components of small blood vessels, in basal lamina and in the flat alveolar cells. The secretory alveolar cells also exhibit the positive GC reactivity in their peripheric cytoplasm and in their microvilli. The observations support that GC and cGMP are involved in cellular transport phenomena. The enzyme might play a role in the secretion process of surface active material. Positive staining has been found also in other types of cells, namely alveolar macrophages and fibroblasts. A biochemical evaluation of GC activity shows that about 30-40% of this activity is associated with the particulate fraction, which justifies its abundance in the cytochemical reports shown in the paper.

The body surface of Branchiobdella pentodonta whit. (annelida, oligochaeta) examined by scanning microscopy

The body of Branchiobdella pentodonta is uniformly covered with cuticular microvilli and abounds in sensory receptors. Muscle attachments are clearly visible both on the prostomium and trunk (11 segments). The mouth opening, oriented dorsally with respect to the adhesive sucker disk, possesses papillae with apical notches.

Response of guanylate cyclase to atrial natriuretic factor in epithelial cells of the frog choroid plexus.

This study shows that the choroid plexus of Rana esculenta contains a guanylate cyclase particulate (GCp), similar to that identified in Mammalia, that is quite sensitive to the atrial natriuretic factor (ANF). The cytochemical tests for GCp show that ANF increases the enzymatic reaction products. Deposits are observed on the apical portion, at the basal level and along the lateral edges of the epithelial cells, with the exclusion of some intercalary epithelial cells with reaction-lacking microvilli. In particular, ANF seems to intensely stimulate the GCp activity along the lateral membranes of the epithelial cells delimiting enlarged intercellular spaces, which are probably dilated for the transport of water and solutes. These data confirm the osmoregulatory role of the hormone and its control of cephalorachidian liquid composition.

Biochemical and cytochemical analyses of BNP-stimulated guanylate cyclase in frog choroid plexus

This study shows that in the choroid plexus of Rana esculenta particulate guanylate cyclase (GC) is appreciably stimulated by porcine brain natriuretic peptide (BNP). Ultracytochemical tests for GC show that BNP notably increases the enzymatic reaction product along the apical surfaces of the epithelial cells. It can therefore be hypothesized that the apical zone of the epithelial cells possess receptors which have a particular affinity for BNP produced in the central nervous system and dumped into the cerebrospinal fluid. These results, together with those of a previous study [32], confirm that the choroid plexus is an organ which has receptors for the natriuretic peptides which are involved in the processes of osmoregulation and the control of cerebrospinal fluid production.

Ultrastructural and cytochemical analysis for adenyl cyclase in frog choroid plexus

An ultrastructural and cytochemical analysis of the anterior choroid plexus in adult Rana esculenta was undertaken. The epithelial cells are implicated in the production of cephalorachidian liquid by transporting metabolites from the blood and by synthesizing and secreting activity. The epithelial cells are also capable of re-absorbing catabolites from the cephalorachidian liquid. The presence of adenylate cyclase, along the basal and lateral membranes in some epithelial cells and along the apical membranes of others, leads us to hypothesize that the epithelium of the plexus is made up of two cell types, one type with a secretory function and another type with an absorption function.

Ultrastructure of the mouth apparatus in Branchiobdella pentodonta (Annelida, Clitellata)

The mouth apparatus in Branchiobdella pentodonta was studied by electron microscopy. The opening is situated dorsal to the adhesive disk of the anterior sucker and is surrounded by a ring of 16 papillae. The papillae have mono‐layered epithelium, muscle fibers, glandular processes, and taste and olfactory organs like “sensitive buttons.” The oral cavity contains jaws with horny teeth and “sensitive buttons,” and is surrounded by a ring of circular muscle fibers that connect to the muscle fiber of the papillae. This apparatus shows some analogies to that of Hirudinea, such as the presence of sucker and jaws with horny teeth.