Aurelio Bairati

Presence of a smooth muscle system in aortic valve leaflets

SummaryThe location and the spatial arrangement of smooth muscle cells in aortic valves have been assessed by a systematic analysis of serial semithin sections of plastic embedded porcine and human aortic leaflets, combined with an electron microscope study.The investigation showed that smooth muscle cells, either single and arranged in thin bundles, and other cell types such as myofibroblasts are constantly present in the aortic valve leaflets. In addition, it was possible to devise a model of the three dimensional, specific organization of the smooth muscle bundles which can be interpreted as an intrinsic muscle system of the leaflets. As the muscular elements might play an active role in the normal functioning of the valve, their presence should be taken into account in designing (bio) prosthetic leaflets and in the evaluation of valve pathology.

Struttura ed ultrastruttura dell'apparato genitale maschile di Drosophila melanogaster Meig.

SummaryThe structure of the testes of Drosophila melanogaster Meig. was re-examined by means of phase contrast and polarized light microscopy; the ultrastructure was investigated by electron microscopy. Testes from adult virgins of wild strain “Varese” were studied, but some observations were made also on the testes of different aged insects, of some insects examined at different times during and after mating, and on testes from sterile mutant strains.The results are summarized in the following points: 1) The testis is made up of an external wall and of an internal germinal tissue. The wall appears to be composed of two overlapping layers of very flattened cells: pigmented cells and muscle cells. 2) The ultrastructure of the muscle cells gives rise to some interesting considerations arising out of the fact that there are two kinds of filaments, but without any evident transverse band organization. 3) The testis falls into three different portions according to the organisation of the germinal tissue: the apical portion (spermatogonial zone), the middle portion (spermagenetic zone) and the terminal portion (spermatic zone). 4) The germinal tissue is made up of germinal cells and interstitial cells. The germinal cells occur in groups consisting of a fixed number of elements in a syncytial state: these groups are enveloped by interstitial cells forming the cyst. The cysts can be considered as the supracellular unit of germinal tissue.The results are discussed in relation to numerous problems, such as: the existence and meaning of the syncytial state of the germinal cells; the existence of a functional cycle of the interstitial cells associated with the maturation of germinal elements; the phagocytic and mechanical functions of terminal epithelium; the existence of various movements of germinal tissue elements along the length of the testis from the apical zone to the terminal one.The paper ends with a discussion on functional aspects of the male reproductive organs.

The ultrastructure of the byssal apparatus of Mytilus galloprovincialis

SummaryThe ultrastructure of the byssus of Mytilus galloprovincialis was analysed by transmission electron microscopy in thin sections of either embedded or frozen samples. All parts of the byssus (stem core laminae, stem outer laminae, threads proximal and distal parts) appear to be formed by the same basic filamentous components organized in different ways at the submicroscopic level and embedded in a variable quantity of matrix. The filaments appear to consist of a central electron-lucent zone (3 nm in diameter), surrounded by an electron-dense rim (total diameter 7 nm). The matrix has a granular or microfilamentous structure. The stem and the threads differ greatly in their submicroscopic organization, but their basic constituents (filaments and matrix) are similar. Peculiar filamentous banded elements (FBE) were found mainly in the stem outer laminae. A relation between the ultrastructure and mechanical properties of the different parts of the byssus was established. The presence of collagen is discussed; since no morphological evidence of any of the known forms of collagen organization was revealed by electron microscopy, it is suggested that byssus collagen may be localized in the matrix and in the FBE.

Calorimetric, biochemical and morphological investigations to validate a restoration method of fire injured ancient parchment

Abstract Differential scanning calorimetry, thermogravimetry, biochemical tests, morphological investigations, via electron, polarizing and phase contrast microscopy have been used to validate the effects of a restoration method for fire injured ancient parchment codices, requiring parchment softening, regeneration, stretching and drying. The results allowed understanding of modifications induced by the heat, namely collagen denaturation, and those by the restoring process on heat damaged ancient parchments.

L'ultrastruttura dell'organo dell'emolinfa nella larva di Drosophila melanogaster

SummaryThe structures formerly described as “blood-forming organs” or “lymph glands” in Drosophila melanogaster were re-examined by means of phase contrast, polarized light, and electron microscopy. As a result, the term “haemolymph organ” is suggested as more appropriate for these peculiar organs. Haemolymph organs of second and third instar larvae, and first stage (white) pupae from a wild strain (Varese) were studied; the methods are described in detail.The haemolymph organ consists of two voluminous anterior lobes and several smaller posterior ones that are ovoid or tubular in shape. The anterior lobes comprise an outer capsule containing some muscle cells, a supporting stroma, and various kinds of cells. The stroma appears to consist of lamellated material of scleroprotein nature similar to that described in other organs of numerous insect species. This material must be considered as a component of the connective tissue characteristic of insect organs.The cells are isolated or organized in groups of various sizes. The following types can be distinguished: rounded cells that are poorly differentiated, polygonal cells with well developed cytoplasm rich in organelles, polygonal cells with clear cytoplasm, and cells that appear to be intermediate form of the types mentioned above.The morphological data presented confirm that the haemolymph organ produces and releases into the haemolymph various types of cells; of these the polygonal cells have a phagocytic and excretory function while only hypotheses can be presented at present concerning the role of the rounded cells. In addition the presence of polygonal cells with clear cytoplasm, showing signs of secretory activity, suggest that the haemolymph organ is involved in the production of substances constituting the fluid fraction of the haemolymph.

Ultrastructure of the melanotic masses in two tumorous strains of Drosophila melanogaster (tuB3 and Freckled)

Abstract The ultrastructure of melanotic tumors of Drosophila melanogaster was studied in two different strains, tuB 3 and Freckled , and the following observations have been made: (1) tuB 3 strain: Melanotic masses in larvae and adults consist of fragments of the hemolymph organ, which are gradually encapsulated by very flattened hemolymph cells (“lamellocytes”). Gradual deposition of very fine electron-opaque material occurs at first in the intercellular spaces along the cell membranes, later within the cells, so that the latter become completely melanized. (2) Freckled strain: two kinds of cells undergo melanization, fat cells and pericardial cells. In the fat cells melanization is intracellular and begins at the pupal stage: a deposition of very finely granular electron-opaque material starts in the perinuclear zone. In adults, the cytoplasm and nucleus of fat cells are masked by a dense deposit of electron-opaque substance. The pericardial cells of adults become melanized, being filled with phagocytosis vacuoles and granules of dense electron-opaque material. Viruslike particles, found in melanizing cells of both strains, were very numerous and often almost geometrically arranged within both cytoplasm and nucleus of melanotic cells. Cytochemical investigations confirmed the melanic nature of the substances present in the masses; DOPA reaction did not provide any evidence for the cytoplasmic presence of enzymes involved in the synthesis of melanic products.

The ultrastructure of the byssal apparatus of a mussel. V. Localization of collagenic and elastic components in the threads

Ultrastructural and cytochemical studies have been carried out on the proximal part of byssus threads (TPP) in an attempt to localize collagenic and elastic components. The results show that TPP autoclaving followed by hot alkali treatment causes the extraction of about two-thirds of hydroxyproline and the parallel removal of most of the matrix, leaving filaments unaffected. Moreover the results of the staining reactions signaletic for elastic tissues indicate that TPP filaments contain glycoproteins with a reactivity similar to that of many invertebrate elastic tissues. On the basis of these morphological findings, it seems reasonable to suggest that collagen may be located in TPP matrix, while filaments could be responsible for the elastic properties.

Immunohistochemical study of subepidermal connective of molluscan integument

Sections of integument from gastropod, bivalve and cephalopod species were studied immunohistochemically to determine reactivity to antibody against the type I-like collagen from Sepia cartilage and antibodies against components of the extracellular matrix (ECM) of vertebrate connective tissue: type I, III, IV, V, and VI collagens, laminin, nidogen and heparan sulphate. All samples exhibited similar reactivities to the antibodies, although differences in the intensity and localization of the immunostaining were found that were clearly correlated with between-species differences in integumental ultrastructure. These findings indicate that the composition of the integumental ECM is similar in the three classes of molluscs examined and that several types of collagen are present. However molluscan subepidermal connective tissue differs from the ECM of vertebrate dermis: molluscan integumental ECM contains collagens similar to type I, V and VI collagens but has no type III-similar collagen. Furthermore molecules similar to the type IV collagen, laminin, nidogen and heparan sulphate of vertebrates were present ubiquitously in molluscan basement membrane, confirming the statement that the structure and composition of basement membrane have remained constant throughout the evolution of all animal phyla.

The head cartilage of cephalopods II. Ultrastructure of isolated native collagen fibrils and of polymeric aggregates obtained in Vitro: Comparison with the cartilage of mammals

Native collagen fibrils were isolated from cephalopod head cartilage and mammal hyaline cartilage. The analysis with TEM after positive and negative staining demonstrated that the fibrils have a periodic structure similar to that of fibrillar type I collagen of mammals. The banding pattern of polymeric forms (SLS, FLS) obtained in vitro from squid cartilage collagen was remarkably different from the analogous forms of mammal collagen types I and II.

The head cartilage of cephalopods. I. Architecture and ultrastructure of the extracellular matrix

The morphology of head cartilage of the cephalopods Sepia officinalis and Octopus vulgaris has been studied on samples fixed and embedded for light- and electron microscopy and on fresh frozen sections viewed by polarizing microscopy. The organization of extracellular matrix (ECM) varies in different regions of the head cartilage. Superficial zones are made up of densely packed collagenous laminae parallel to the cartilage surface, while radially arranged laminae form a deeper zone where territorial and interterritorial areas are present. A compact arrangement of banded collagen fibrils (10-25 nm in diameter) forms the laminae of the superficial zones and of the interterritorial areas; a loose three-dimensional network of fibrils (10-20 nm) with many proteoglycan aggregates forms the territorial areas. A pericellular matrix surrounds the bodies of extremely branched territorial chondrocytes. Peculiar anchoring devices (ADs) are dispersed with variable orientation within the ECM. A perichondrium is present, but often connectival and muscular bundles are fused with the superficial layers of cartilage. Some vessels were also observed within the superficial inner zone and clusters of hemocyanin molecules were demonstrated both in the ECM and in some cells. The cephalopod head cartilage seems to share some morphological characteristics with both hyaline cartilage and bone tissue of vertebrates.