The cytoskeleton of chondrocytes of Sepia officinalis (Mollusca, Cephalopoda): an immunocytochemical study

Our previous electron microscope study showed that chondrocytes from cephalopod cartilage possess a highly developed cytoskeleton and numerous cytoplasmic processes that ramify extensively through the tissue. We have now carried out a light microscope immunocytochemical study of chondrocytes from the orbital cartilage of Sepia officinalis to obtain indications as to the nature of the cytoskeletal components. We found clear positivity to antibodies against mammalian tubulin, vimentin, GFAP, and actin, but not keratin. The simultaneous presence of several cytoskeletal components is consistent with the hypothesis that cephalopod chondrocytes have the characteristics of both chondrocytes and osteocytes of vertebrates, which endow the tissue as a whole with some of the properties of vertebrate bone. We confirm, therefore, the presence in molluscs of the ubiquitous cytoskeletal proteins of metazoan cells that have remained highly conserved throughout phylogenetic evolution.

Immunocytochemical localization of protein p27BBP in human skin and invertebrate (Sepia officinalis) integument

The protein p27BBP (alias eIF6) occurs in yeast and mammalian epithelial cells. It is essential for ribosome genesis and has also been implicated in the functionality of integrins and intermediate filaments. By immunoblot, we show that homogenized integument from Sepia officinalis (Cephalopoda, Mollusca) contains a protein with immunological properties that closely resemble those of p27BBP. We also demonstrate, by immunogold electron microscopy with an indirect immunoreaction technique on ultrathin sections of human skin and Sepia integument, that p27BBP is constantly present in both species in epithelial cells, fibroblasts, and muscle fibers. It is found in the vicinity of intermediate filaments, in nucleoli, along the internal wall of the nuclear membrane, and in association with desmosomes and hemidesmosomes and occasionally occurs extracellularly. Thus, the structure and function of p27BBP seem to have been highly conserved throughout evolution; the protein appears to be essential in eukaryotic cells in which it interacts with several ultrastructural components of diverse function.

Collagen fibrils of an invertebrate (Sepia officinalis) are heterotypic: immunocytochemical demonstration

Collagen fibrils from the dermis of Sepia officinalis were processed for immunoelectron microscopy to reveal reactions to antibodies against mammalian types I, III, and V, teleost type I and cephalopod type I-like collagens, by single and double immunogold localization. The fibrils were observed: (a) in suspensions of prepared fibrils, (b) in ultrathin sections of embedded fibril preparations, and (c) in ultrathin sections of dermal tissue. Some samples were subjected to acetic acid or urea dissociation. It was found that collagen fibrils from Sepia dermis are heterotypic in that they are composed of type I-like and type V collagens. Type I-like collagen epitopes were present mainly at the periphery of the fibrils; type V collagen epitopes were present throughout the fibrils. This is the first demonstration that collagen fibrils from an invertebrate are heterotypic, suggesting that heterotypy may be an intrinsic characteristic of the fibrils of fibrillar collagens, independent of evolutionary or taxonomic status.

An ultrastructural study of connective tissue in mollusc integument III. Cephalopoda

We studied structure and ultrastructure of the subepidermal connective tissue (SEC) of the integument of three cephalopods (Sepia officinalis, Octopus vulgaris and Loligo pealii). In all species, three distinct regions of the SEC were recognised: (a) an outer zone (OZ) that included the dermal-epidermal junction, and consisted of a thin layer of connective tissue containing muscles, (b) an extensive middle zone (MZ) containing a compact network of collagen fibres and numerous cells, (c) an inner zone (IZ) of loose connective tissue that merged with muscular fascia. This arrangement differs from that in bivalves and gastropods and recalls vertebrate integument. The dermal-epidermal junction of cephalopods differed from that of bivalves, gastropods and mammals in that the epidermal cells did not possess hemidesmosomes, and their intermediate filaments terminated directly in the plasmamembrane. The thick (120-500 nm) basal membrane (BM) had a superficial zone containing a regular array of granules; a lamina densa composed of a compact network of small filaments and granules; and an IZ distinguished by expansions of granular material protruding into underlying structures. Collagen fibres contained fibroblast-derived cytoplasmic thread, running through their centres and were surrounded by granular material that joins them to adjacent fibres. The collagen fibrils were of medium diameter (30-80 nm) had the typical ultrastructure of fibrillar collagens, and were surrounded by abundant interfibrillar material. The hypodermis was loose, with a network of small bundles of collagen fibrils. Cephalopod integument appears to represent a major evolutionary step distinguishing this class of molluscs.

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.

Electrophoretic and immunochemical study of collagens from Sepia officinalis cartilage

Electrophoretic and Western blot studies were conducted on collagen fractions extracted from Sepia officinalis (cuttlefish) cartilage using a modified salt precipitation method developed for the isolation of vertebrate collagens. The antibodies used had been raised in rabbit against the following types of collagen: Sepia I-like; fish I; human I; chicken I, II, and IX; rat V; and calf IX and XI. The main finding was that various types of collagen are present in Sepia cartilage, as they are in vertebrate hyaline cartilage. However, the main component of Sepia cartilage is a heterochain collagen similar to vertebrate type I, and this is associated with minor forms similar to type V/XI and type IX. The cephalopod type I-like heterochain collagen can be considered a first step toward the evolutionary development of a collagen analogous to the typical collagen of vertebrate cartilage (type II homochain). The type V/XI collagen present in molluscs, and indeed all phyla from the Porifera upwards, may represent an ancestral collagen molecule conserved relatively unchanged throughout evolution. Type IX-like collagen seems to be essential for the formation of cartilaginous tissue.

An ultrastructural study of connective tissue in mollusc integument: II. Gastropoda

We studied the ultrastructure of the subepidermal connective tissue (SEC) in different zones of the integument in terrestrial, marine and freshwater gastropods (eight species). In all cases, the SEC was a layer of loose connective tissue between the basal membrane (BM) of the epidermis and the connective tissue of the deeper muscle layers. It was of monotonous structure and not differentiated into layers such as are found in mammalian dermis. The extracellular matrix (ECM) consisted of a network of collagen fibrils of variable diameter, with abundant anchoring devices and proteoglycans. In six species, variables quantities of haemocyanin were present within haemocoelic sinuses present in the SEC. The thickness and density of the BM varied from species to species, as well as within species in the various zones of integument. The ultrastructure of the lamina densa (LD) was indistinguishable from that of BM in bivalves and similar to that in mammals, although basotubules and double pegs were absent. An irregularly spaced lamina lucida was usually present and was often shot thorough with filaments and small protrusions of the LD that connected with epithelial plasma membrane or with hemidesmosomes. A lamina fibroreticularis was not present. LD protrusions characterize the connection between BM and the ECM of SEC. In the terrestrial gastropods, a spongy matrix with ultrastructure closely similar to LD occupied large tracts of the SEC. In the mantle region of Arion rufus, the integumental SEC contained large cavities filled with spherical concretions, probably representing rudiments of a shell. In the mantle where the integument contained abundant muscle fibres, the BM was thick and directly connected to the ECM of the SEC which consisted of compact laminae of collagen fibrils with abundant anchoring devices. Along the edge of the foot of Patella ulyssiponensis, the SEC contained a layer of paramyosinic muscle fibres adhering to the epidermis. No differences or gradations in integumental SEC structure could be related to the phylogenetic position of the species examined.

An ultrastructural study of connective tissue in mollusc integument: I. Bivalvia

The ultrastructure of the subepidermal connective tissue (SEC) in different areas of the integument of the bivalves Callista chione, Pecten jacobaeus, Mytilus galloprovincialis and Ostrea edulis was studied by transmission electron microscopy. The main organisation of the SEC was broadly similar in all species: the SEC was connected to the epidermis by a basement membrane and merged directly with the deeper connective tissue surrounding muscles. The SEC was not differentiated into layers like the papillary and reticular dermis of mammals, however, the architecture, thickness and shape of the basement membrane varied from species to species, as well as within species (in the foot, central or marginal zones of the mantle). The ultrastructure of the lamina densa was broadly similar to that in mammals: although basotubules and double pegs were absent, proteoglycans and rod-like units homologous to 'double tracks' were always abundant. A zone similar to the lamina lucida was irregularly present and was shot thorough with small protrusions of the lamina densa that connected with the epithelial hemidesmosomes or focal adhesions. Nevertheless zones were observed where the lamina densa fuse directly to the epithelial plasmamembrane. This variability of connection may be related to the various types of epidermal cell. A lamina fibroreticularis was not recognized since anchoring fibrils and microfibrils were not present; lamina densa protrusions into the extracellular matrix (ECM) of SEC characterize the connection between basement membrane and SEC. Collagen fibrils were small and of constant diameter and were never organised into fibres. Anchoring devices - similar to the anchoring plaques of mammalian dermis - were abundant and scattered between SEC collagen fibrils. The orange-pink pigmentation of C. chione seems due to electron-dense granules embedded within the connective ECM.

Immunohistochemical study of collagens of the extracellular matrix in cartilage of Sepia officinalis

We used various anti-collagen antibodies to perform indirect immunofluorescent staining of cartilage sections from cuttlefish (S. officinalis). On ultrathin sections and collagen fibril preparations from the same tissue, we performed immunostaining with colloidal gold. The extracellular matrix (ECM) of S. officinalis cartilage reacted intensely and homogeneously with an antibody directed against type I-like collagen isolated from the cartilage of cuttlefish and with anti-rat type V collagen antibody. A weak reaction was observed with anti-fish and anti-chicken type I collagen antibodies, while no reaction was observed with anti-rat type I and anti calf type II collagen antibodies. Anti-chicken type II, anti calf type IX and type XI collagen antibodies reacted weakly with ECM, while stained cell bodies and cell processes reacted more intensely. A similar pattern of reaction was observed on cartilage section and isolated collagen fibrils prepared for electron microscopy. These findings suggest that ECM of cuttlefish cartilage may be composed of molecules similar to the type I, type V, type IX and type XI collagen molecules of vertebrates. Cephalopods have evolved a cartilage of structure and macromolecular organisation similar to that of vertebrate cartilage. However, the main molecular components of S. officinalis cartilage--type I-like and type V collagens--differ from those of vertebrate cartilage. We suggest that this type I-like collagen can be considered an initial step toward the evolution of type II collagen typical of vertebrates.

Use of rotary shadowing electron microscopy to investigate the collagen fibrils in the extracellular matrix of cuttle-fish (Sepia officinalis) and chicken cartilage

Collagen fibrils isolated from sternal cartilage of chick embryo and chondrocranium of cuttle-fish (Sepia officinalis) were examined with the electron microscope after rotary showing. The aim was to determine whether collagen fibrils from S. officinalis cartilage contained collagen molecules similar to the type IX collagen of vertebrate cartilage. Cartilage from both sources presented a highly variable appearance and only occasionally did preparations contain fibrils having the structure described by Vaughan et al. (1988) for vertebrate cartilage. Subsequent electron microscope investigation of collagen samples during the various stages of fibril preparation showed that the method did not yield reproducible results, and that is altered the morphology of the isolated structures. It was not, therefore, possible to confirm the hypothesis that collagen molecules with a morphology similar to that type IX vertebrate collagen are a component of the extracellular matrix of cephalopod cartilage.

An ultrastructural study of the perichondrium in cartilages of the chick embryo

The ultrastructure of perichondrial tissue of cartilage rudiments (metatarsus, tibiotarsus and sternum) of the chick embryo at various stages of development (H.H. stages 28-45) was investigated by transmission electron microscopy. Previous microscopic and submicroscopic data were generally confirmed, but new findings indicated: (a) the existence of a temporary syncytial state of perichondroblasts during the earliest developmental stages, (b) the existence of a perichondrial cambial layer of stem cells, (c) involvement of perichondroblasts in the appositional growth of cartilage. Electron microscopy revealed clear temporal relations between cell differentiation, perichondrial growth and the structure and production of perichondrial ECM. In addition, the boundaries between cartilage and perichondrial tissue were demonstrated unambiguously. Perichondrial structure varied specifically with each cartilage segment; in particular the perichondrium in long bone rudiments (where ossification starts early) contrasted with that in the permanent cartilage medial process of the sternum.

A comparative study of perichondrial tissue in mammalian cartilages

The general organization, cellular and extracellular components, and structural variation of perichondrium have been studied in different mammalian cartilages by polarized light and transmission electron microscopy. The overall structure is that of a dense connective tissue composed of variable numbers of thin, stratified, closely-packed lamellae, themselves composed of closely-matted collagen fibres running in the plane of the cartilage surface, but oriented at various angles to each other. Variations mainly concern the arrangement of the fibre bundles in the transition zones between perichondrial and cartilage matrices, and between perichondrium and surrounding tissues. Perichondrial cells have the characteristics of fibrocytes. A cambial layer of undifferentiated stem cells was never observed. A layer of 'perichondrial lining cells' with distinctive ultrastructural characteristics was observed in some cartilage units, which separates the perichondrium from the surrounding loose connective tissue. The ultrastructural results demonstrate that the cartilage and perichondrial extracellular matrices are distinct, and what have been designated perichondrial 'transition' and 'proliferative' zones are in fact parts of the most superficial cartilage layer. Variations in perichondrial structure appear to correlate with diversity of cartilage function and we conclude that each cartilage unit plus perichondrium forms a tightly-integrated entity, best regarded as a unitary organ within the skeletal system.

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.

[Ultrastructural analysis of human ejaculate from infertile subjects]

It has been demonstrated that the semen of infertile patients contains at high percentage of abnormal forms and no clear answer has been so far provided to the questions of which malformations are compatible with male fertility, which malformations are responsible for the infertility and which is the percentage of defective cells that gives rise to infertility. In this study the eiaculates of 56 patients of suspected male infertility were used as material. The semen samples were fixed for 2 hr at room temperature in 4% glutaraldehyde in 0.05 M cacodilate buffer + 0.018% CaCl2 + 6.6% sucrose, post-fixed in 1.5% OsO4 in same buffer + 6.6% sucrose, dehydrated and embedded in Spurr. The samples were sectioned with Reichert OMu3 ultratome. The sections, contrasted with uranyl acetate and lead citrate, were examined in a Feol M T8 E.M. The varieties of sperm malformations are described and classificated into morphological categories based upon the type of alteration and the cellular portion in which the malformation appeared. From this research we have got the following conclusions: 1) an absolute correlation between microscopical, ultrastructural defects and functionality of spermatozoa does not exists; 2) the submicroscopic analysis contributes to a more accurate definition of the eiaculate; 3) the high variability of the ultrastructural defects needs that the submicroscopical analysis of the human semen must be supplemented by a quantitative evaluation.

Subcellular localization of serotonin-immunoreactivity in the pedal ganglion of Mytilus galloprovincialis (Mollusca, Bivalvia)

Serotonin has been localized in neurons of the pedal ganglion of Mytilus galloprovincialis by means of colloidal gold immunostaining. Ultrastructural quantitative analysis shows that gold particles are concentrated over perikarya and fibers containing a unique vesicle population. The vesicles are round or elliptical with a diameter ranging from 100 to 180 nm and have a dense core with areas of minor density. Their intense labelling suggests that they are the main cellular compartment where serotonin is stored.

Testicular biopsy of azoospermic men with vas deferens malformation using two different techniques

A morphological analysis was carried out on testicular biopsies of men with obstructive azoospermia as consequence of vas deferens malformations as compared with biopsies from fertile men. For each case the biopsies were processed with two different techniques: routine histological procedure, and semithin sections of specimens processed for electron microscopy. Four parameters were considered: tubular morphology, testicular biopsy score count (TBSC), tubular diameter, and germinal cell density. The data were quantified and analyzed by statistical tests. The biopsies of azoospermic men present a higher frequency of tubular sections with "tubular blockage," "sloughing" and cellular degeneration, lower values of TBSC, and lower germinal cell density. The results appear to be of relevant interest in relation to the existence of long-term testicular alteration following vasectomy.

The morphology of seminiferous tubules of human testicular biopsies. Analysis of the data obtained with two different techniques

Testicular biopsies of fertile men and of azoospermic patients for vas deferens agenesis were processed with two different techniques, i.e. routine histological procedure and semithin sections of electron microscopy preparations. Tubular morphology, testicular biopsy score count and tubular diameter were analyzed in comparison. The two techniques give rise to a different qualitative and quantitative evaluation of all tubular parameters considered. Otherwise they confirm the real existence of the so-called 'tubular blockage' situation with central tubular cellular mass and cell degeneration.

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.

Presence of a smooth muscle system in aortic valve leaflets

The 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.

[Ultrastructure of Sertoli cells of the human testis in agenesis of the vas deferens]

Ten testicular biopsies from adult males with agenesis of the vas deferens have been investigated with light and electron microscopy. The ultrastructural study of SERTOLI cells has demonstrated that: (a) the junctions between SERTOLI cells and between SERTOLI and germinal cells retain their normal ultrastructural features. (b) Lanthanum permeates SERTOLI cells tight junctions, but its diffusion towards the adluminal compartment is prevented. (c) SERTOLI cells present unusual amounts of cytoplasmic inclusions, especially lipofuscin granules. A relationship between these inclusions and phagocytosis has not been demonstrated. (d) "Dark" SERTOLI cells which show alterations of their typical junctional complex have been frequently observed, although their frequency varies among the different patients. The results are discussed in relation to diagnostic significance of the ultrastructural study of testicular biopsies.

[Cuticular collagen in Lumbricus sp. Ultrastructure of native fibrils and of precipitates obtained from acetic solutions]

The paper describes the techniques used to isolate the cuticular collagen fibrils of Lumbricus sp. As revealed by electron microscope examination the isolated fibrils, positively and negatively stained, are aperiodic and appear made up of bundles of filaments (30 A) with an helicoidal arrangement. A filamentous network has been precipitated from the acetic solutions of cuticular collagen. The network exhibits an electrondense cross-striation every 3 000 A.

The ultrastructure of the byssal apparatus of Mytilus galloprovincialis. IV. Observations by transmission electron microscopy

The 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.