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.

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.

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.

Granulocytic-macrophagic and macrophagic colony stimulating factors elicit colonies of mast cells in mouse bone marrow agar culture. An electron microscope study

Granulocytic-macrophagic colony stimulating factor (GM-CSF) and macrophagic colony stimulating factor (M-CSF or CSF-1) stimulate bone marrow cells of mouse to produce in semisolid agar colonies in which mononuclear cells were reported to be macrophages. We verified in such colonies the ultrastructure of the mononuclear cells which had cytoplasmic granules of the mast cells and lacked lysosomes, therefore we considered them as mast cells. However, the granules content did not reach the degree of condensation typically found in granules of mouse peritoneal mature mast cells. The mast cells of colonies obtained in agar can be mast cells arrested at some point in the maturative process, mast cells of a yet unrecognized type or cells with mast cells ultrastructural features which behave as precursors for cells of myeloid lineage.

[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.

Ultrastructural study of the decapitated sperm defect in an infertile man

An infertile man presented a spermiogram in which 100% of the spermatozoa displayed separation of head from tail at the level of the proximal centriole. Most tails were normally structured and ended anteriorly with the proximal centriole covered by a continuous plasma membrane. In a small percentage of tails a rudimentary connecting piece was surrounded by a minute cytoplasmic mass and the middle piece was missing, whereas the chromatoid body and the spindle-shaped body were still present. Finally, a few tails had a large cytoplasmic mass surrounding either regular connecting and middle pieces or a rudimentary connecting piece continuous with the main piece. Tails of the first type had good forward motility, although the pattern of movement appeared altered. The other types were immotile or motile but without forward progression. In the loose heads the implantation fossa had failed to differentiate. The separation of heads from tails appeared to be the result of a specific morphogenetic defect and took place at different stages of spermatid differentiation, giving rise to the structurally different types of tails.