Rosalba Maria Farnesi

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.

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.

Morphology of excretory organs in branchiobdella pentodonta clitellata branchiobdellida

Abstract The nephridium of Branchiobdella pentodonta is composed of a richly ciliated nephrostome, a lacunar capsule whose cells are phagocytic, a long nephridial tubule and excretory canal both concerned with reabsorption, and a dorsally placed nephridial pore. In contrast to the nephridia of previously studied species of Oligochaeta and Hirudinea the nephridia of Branchiobdella are characterized by having only two pairs of nephridia: an anterior in the second, third and fourth segments of the trunk and a posterior in the eighth and ninth segments. Another characteristic of Branchiobdella pentodonta is that the excretory orgen has no vascular supply and therefore waste matter is excreted solely from the coelomic fluid.

CYTOCHEMICAL LOCALIZATION OF ADENYLATE CYCLASE IN THE LIMB BUDS OF BUFO BUFO

The importance of cyclic nucleotides in the regulation of the processes of differentiation and embryonic development is known. The possible role that cyclic adenosine monophosphate (cAMP) plays during the development of the posterior limb of Bufo bufo is studied by the cytochemical localization of adenylate cyclase (AC), an enzyme that catalyzes the synthesis of the cyclic nucleotide. The method is based on the reaction between the enzyme AC and its specific substrate AMP‐PNP (5′‐adenylylimidodiphosphate) in the presence of lead. The lead precipitates that form as secondary reaction products are evidence of enzymatic activity. Reaction products are present only at the epithelial level in the limb bud; initially, such products are visible only at the base of the bud, particularly on the epithelial fascia located at the boundary with the body. During successive elongation and toe formation, AC activity is only present on the cells of the proximal portion of each new segment. Enzymatic activity is never present in correspondence to the ectodermal apical crest. cAMP is probably not involved in the processes of cellular proliferation but, rather, in the processes of inducing differentiation of the internal mesenchymal cells. Microsc. Res. Tech. 40:446–454, 1998.

The frontal organ of a triclad flatworm, Dugesia lugubris

SummaryIn an examination of the ultrastructure of the anteromedian portion of the head of Dugesia lugubris we demonstrated a frontal glandulo-muscular organ which consists of a voluminous glandular complex with three types of secretory cells and a well-developed musculature derived from the sub-epidermal fibers. The presence of neurosecretory cells, free nerve endings and single axons with sensitive cilia at the apex is characteristic. The last of these ultrastructural observations, together with functional tests, lead us to believe that the frontal organ possesses a marked chemosensitivity. The nature and structure of this organ are compared with the glandulo-muscular organ described in other Tricladida paludicola, thus contributing toward their much-debated classification.