Morphological and ultrastructural study of the ventral nerve cord in Branchiobdella pentodonta Whitman (Annelida, Oligochaeta).

The ventral nerve cord of Branchiobdella pentodonta consists of paired ganglia containing three different types of neurons, a central neuropil showing characteristic synapses and of an intersegmental apparatus made up of two large lateral connectives and a smaller ventral one. Some remarkable differences exist between the ventral nerve cord and that found in other oligochaetes; these include the presence of a large dorsal blood vessel, two dorsal muscular cells per metamere, and supportive glial cells ventral to the neuropil which have long transverse processes coming into contact with the segmental nerves.

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.

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.

Morphological and ultrastructural aspects of Branchiobdella pentodonta Whit. (Annelida, Oligochaeta) suckers.

The muscular system in the posterior sucker of Branchiobdella pentodonta Whit. has circular, longitudinal and radial fibers. In the anterior sucker, which has circular and longitudinal fibers, the muscle system is scarce. Concentric fibers are found around the mouth. In both suckers the glandular element form voluminous complexes secreting mucus for attachment to the substrate. Suckers show neuromuscular junctions and three distinct types of neuroglandular junctions: one with typical neurosecretory granules, one with larger neurosecretory granules produced by cells located at the origin of the segmental nerves, and one with presynaptic vesicles. The second type is peculiar to the posterior sucker. A comparison is made between suckers of Branchiobdella and those of leeches.

Ultrastructure of the paraphysis in Bufo bufo larvae.

A study of the ultrastructure and function of the paraphysis in Bufo bufo larvae was carried out. The structure is a tubular-ramified gland made up of numerous tubules with monolayered epithelial walls surrounded by connective tissue and sinusoids. The epithelial cells secrete glycoprotein to contribute to production of the cephalorachidian fluid. The role of the paraphysis in the transport of fluids and electrolytes from the blood to the cephalorachidian fluid in regulation of ionic and osmotic homeostasis is discussed.

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.

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.

Ultracytochemical localization of guanylate cyclase after stimulation with natriuretic peptides in frog choroid plexus.

The ultracytochemical localization of particulate guanylate cyclase (GC) has been studied in Rana esculenta choroid plexus after activation with rat atrial natriuretic peptide (ANP), porcine brain natriuretic peptide (BNP) and porcine C-type natriuretic peptide (CNP). This study shows that the three peptides are activators of GC in the choroid plexus as demonstrated by the presence of reaction products at the level of the epithelium and sinusoids. In the apical zone of the epithelial cells predominantly BNP seems to activate GC, while ANP and CNP activate GC mainly at the level of the lateral surfaces. Moreover, ANP stimulates the enzyme along the basal membrane of the epithelial cells as well as the membranes of the endothelium of the sinusoids. In the presence of CNP, enzyme stimulation can also be found at the level of the endocellular membranes. These results confirm that the choroid plexus is an organ with receptors for the natriuretic peptides which are involved in the processes of osmoregulation and the control of cerebrospinal fluid production.

Ultrastructural analysis and cytochemical localization of atrial natriuretic peptide-stimulated guanylate cyclase in internal gills of Bufo bufo tadpoles.

In this study on the internal gills of the larvae of Bufo bufo we examined the ultrastructural features and, using cytochemical methods, showed the localization of guanylate cyclase in the presence of atrial natriuretic peptide. The gill apparatus consists of a series of arches each with a dorsal part or gill rakers with filtering and glandular functions. In the epithelium, cells were found that contain granular secretions similar to those atrial natriuretic factor-immunoreactive granules of larval Bufo arenarum gill rakers. The ventral portion of the gill arches is made up of gill tufts with a respiratory function. The cytochemical localization of the guanylate cyclase in the presence of exogenous atrial natriuretic peptide demonstrates that the internal gills of the larvae are an important target organ for the peptide and therefore, it is proposed that, at this level, the atrial natriuretic peptide carries out an important osmoregulatory role.

The fine structure of the myoneural junctions in the body wall muscles in Branchiobdella pentodonta Whit. (Annelida, Oligochaeta).

The ultrastructure of the myoneural junctions in the body wall muscles has been studied in Branchiobdella pentodonta Whit. A single junctional type has been found. Within the terminal axon there are two types of vesicles, which differ in number, size and electron opacity. The junctional gap contains the basement membrane. The post-junctional membrane displays concave patches on which slender projections arising from the outer lamina of the sarcolemma extend into the junctional gap. These concave patches overlie a cytoplasmic lamina made up of electron dense material.

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.

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.