Fibrous framework of human skeletal muscles, fasciae and tendons

By means of scanning and transmissive electron microscopy, the construction of the fibrous framework of the human skeletal muscles, fasciae and tendons has been investigated and its morphofunctional analysis has been performed. The fibrous framework of the endomysium is presented as a complexly organized system of anastomosing fibers of the connective tissue, forming a net-like construction. The fibrous structures of the framework are united into a whole construction by connecting fibers and fibrils. Different types of structural interconnection of collagenous fibers with sarcolemma are revealed. The structure of the fibrous framework both in different muscles and within one muscle has certain peculiarities. The main constructive element of the fascial fibrous framework make large anastomosing collagenous fibers, their architectonics is stabilized by connective fibers and fibrils. The construction of the tendinous fibrous framework is characterized by a pronounced anisotropia of the largest collagenous fibers and a developed network of connective structures both on the surface and inside the collagenous fibers. Structural mechanisms, interconnecting muscles and tendons, are demonstrated. Presence of anastomoses between the fibrils in the composition of the collagenous fibers in the fascia and Achilles tendon are stated. Together with the peculiarities existing, the general principle of the structural organization of the fibrous framework of the muscle system is the net-like constructure dependent on presence of anastomoses and elements of the connective system between the fibrous structures. Depending on the organ's function, the construction of the network acquires certain specific morphological forms.     

Collagen of slow twitch and fast twitch muscle fibres in different types of rat skeletal muscle

The appearance of collagen around individual fast twitch (FT) and slow twitch (ST) muscle fibres was investigated in skeletal muscles with different contractile properties using endurance trained and untrained rats as experimental animals. The collagenous connective tissue was analyzed by measuring hydroxyproline biochemically and by staining collagenous material histochemically in M. soleus (MS), M. rectus femoris (MRF), and M. gastrocnemius (MG). The concentration of hydroxyproline in the ST fibres dissected from MS (2.72 +/- 0.35 micrograms X mg-1 d.w.) was significantly higher than that of the FT fibres dissected from MRF (1.52 +/- 0.33 micrograms X mg-1 d.w.). Similarly, the concentration of hydroxyproline was higher in ST (2.54 +/- 0.51 micrograms X mg-1 d.w.) than in FT fibres (1.60 +/- 0.43 micrograms X mg-1 d.w.), when the fibres were dissected from the same muscle, MG. Histochemical staining of collagenous material agreed with the biochemical evidence that MS and the slow twitch area of MG are more collagenous than MRF and the fast twitch area of MG both at the level of perimysium and endomysium. The variables were not affected by endurance training. When discussing the role of collagen in the function of skeletal muscle it is suggested that the different functional demands of different skeletal muscles are also reflected in the structure of intramuscular connective tissue, even at the level of endomysial collagen. It is supposed that the known differences in the elastic properties of fast tetanic muscle compared to slow tonic muscle as, e.g., the higher compliance of fast muscle could at least partly be explained in terms of the amount, type, and structure of intramuscular collagen.     

Structural and functional organization of the suprapatella in two cercopithecines

Gross and microscopic study of Cercopithecus aethiops pygerythrus and Papio cyanocephalus anubis shows that these cercopithecines have a quadriceps tendon the distal portion of which consists mostly of dense collagenous bundles with scattered fine elastic fibres most of which lie in the loose connective tissue planes within and around the tendon and around blood vessels. A distinct fibrovesicular structure, the suprapatella, lies within the tendon of the vastus intermedius above the pony patella. Histologically, this structure is characterised by interwoven bundles of collagenous fibres, among which are enmeshed large cells containing prominent nuclei surrounded by large clear spaces. It is postulated that this structure facilitates hyperfluxion of the knee during the initial phases of springing and jumping.     

Ultrastructural organization of the basic substance of human dermis]

The data on ultrastructural organization of the ground substance in the human dermis obtained electron histochemically are represented. Five types of ruthenium positive structures of polysaccharide origin are detected: retinal structure (I), amorfous substance (II), membranes of collagen fibrils (III) and elastic fibres (V), fine ruthenium positive streakness of collagen fibrils (IV). These structures, except fine streakness, form a united polysaccharide system of the dermis participating in maintenance of structural-functional integrity of the connective tissue (collagen-elastic) carcass of the dermis. Two mechanisms, interconnected and oppositely directed, perform this function: the buffer mechanism preventing the connective tissue fibers and collagen fibrils to approach each other, and the binding mechanism preventing the fibrils and fibers to dissociate. The reticular structure performs mainly this function at the level of fibers, and the amorphous substance does it at the level of fibrils.     

Locomotory aspects of squid mantle structure

Morphological aspects of squid ( Loligo, Lolliguncula ) mantle relevant to locomotory function were studied. Methods used included polarized light microscopy of frozen sections of untreated tissue taken from animals immediately after death and electron microscopy.
The mantle consists of circular and radial muscles arranged in alternating rings along the whole length of the mantle. The muscle is obliquely striated. Connective tissue fibres are found in the body of the muscle and in the outer and inner tunics. The outer tunic consists of layers of large collagenous fibres. The fibres run in superimposed right- and left-handed helical courses that lie at an angle of 27° to the long axis of the animal. The tunics and the intramuscular connective fibres are thought to resist length changes in the mantle while permitting the changes in girth required for the jet power stroke. Both the intramuscular and the tunic fibre systems may provide elastic energy for the return phase of the jet cycle. Tunic fibres appear to be a geodesic tensile reinforcing system ensuring smooth shape changes in the mantle.     

Studies on the ultrastructure of the lymph nodes

Summary The reticular network of the lymph nodes has been studied with a variety of methods aimed to elucidate its chemical composition, submicroscopic structure and relationship with the cells.To study the chemical composition, the reticular network has first been isolated by means of sonic disruption and differential centrifugation, avoiding the use of enzymes or chemical extractions. The material prepared in this way has been studied with the polarized light and electron microscopes and has been subjected to X-ray diffraction and chemical analysis, including chromatographic separation of the collagenous proteins.The results of this work show that the reticular network of lymph nodes has a chemical composition similar to that of loose connective tissues: the fibrils are made of collagenous proteins and the concept of reticulin as a chemical or morphological entity does not appear to be justified.In addition the structure of the reticular network and its relationships with the different cells have been studied with the electron microscope on ultrathin sections of lymph nodes from dogs, cats, rabbits and rats: the reticular fibres appeared to be made of bundles of collagen fibrils with the typical banded structure; the fibres have close contacts with the reticular cells and also with the lymphoid elements of the nodes.In conclusion no elements exist that point towards some specific properties of the reticular connective tissue: the reticular network of the lymph nodes appears not to be basically different from the usual loose connective tissue from which it is distinct only because it harbours a considerable number of immunologically competent cells of the lymphoid series; functional interrelationships between the reticular and lymphoid cells in the nodes are, of course, not excluded.To Prof. F. E. Lehmann on his sixtieth birth day.Supported by a grant of C.N.R.     

Distribution and organization of the elastic system fibres in healthy human gingiva

Summary The ultrastructural distribution and organization of the elastic system fibres, i.e. oxytalan, elaunin and elastic fibres, were studied by transmission electron microscopy and by an immunohistochemical method for the detection of elastin in healthy human gingiva. The morphological distribution of these fibres was characterized by the presence of oxytalan, elaunin and elastic fibres, respectively, in the upper, medium, and deep layers of gingival connective tissue. Anti-elastin antibody reacted with microfibrils and amorphous material of the elastic system fibres throughout the gingival connective tissue. These findings were interpreted as indicating that the microfibrils were associated with small amounts of elastin at their surface.     

The giant neurone system in ophiuroids

Summary The morphology of the circumoral nerve ring of an ophiuroid, Ophiura texturata, is described. Particular attention is given to a system of fibres which are giant by echinoderm standards, and which occur both in the ectoneural and hyponeural parts of the nerve ring. The giant fibres in the ectoneural tissue do not show the complicated pattern of distribution present in the segmental ganglia of the radial nerves. The main areas of neuropil in the ectoneural tissue are associated with small axon bundles which leave the nerve ring to innervate the gut and disc. The hyponeural tissue is exclusively motor and is involved in the innervation of the main radial and inter-radial muscles of the disc. Branches of the motor nerves are also associated with juxtaligamental tissue, the secretory products from which are thought to influence the plasticity of collagenous connective tissue. The structure of the circumoral nerve ring suggests that it serves as a functional connection between the nerve cords in adjacent radii. The ultrastructural evidence does not support the view that the circumoral nerve ring represents a central nervous system.     

The neuroactive substances and associated muscle system in Rhipidocotyle campanula (Digenea,Bucephalidae) from the intestine of the pike Esox lucius

We report about the muscular system and the serotonergic and FMRFamidergic components of the nervous system of the Bucephalidae trematode, Rhipidocotyle campanula, an intestinal parasite of the pike. We use immunocytochemical methods and confocal scanning laser microscopy (CLSM). The musculature is identified by histochemical staining with fluorescently labeled phalloidin. The body wall musculature of R. campanula contains three layers of muscle fibres – the outer thin circular, intermediate longitudinal and inner diagonal muscle fibres running in two opposite directions. The digestive system of R. campanula possess of a well-developed musculature: radial, longitudinal and circular muscle elements are detected in the pharynx, circular and longitudinal muscle filaments seen in the oesophagus, and longitudinal and the circular muscle fibres were found in the intestinal wall. Specific staining indicating the presence of actin muscle filaments occurs in the cirrus sac localized in the posterior body region. The frontal region of anterior attachment organ, the rhynchus, in R. campanula is represented by radial muscle fibres. The posterior part of the rhynchus comprise of radial muscles forming the organ's wall, and several strong longitudinal muscle bundles. Serotonergic and FMRFamidergic structures are detected in the central and peripheral compartments of the nervous system of R. campanula, that is, in the paired brain ganglia, the brain commissure, the longitudinal nerve cords, and connective nerve commissures. The innervations of the rhynchus, pharynx, oesophagus and distal regions of the reproductive system by the serotonergic and FMRFamidergic nervous elements are revealed. We compare our findings obtained on R. campanula with related data for other trematodes.     

A Functional Study of Papillae and Pads in the Foot of Passerines, Parrots, and Owls

The pattern of pads, the morphology and microscopical anatomy of the papillae, the structure of dermis, and the attachment of the skin to the skeletal elements were studied in species representing Passeriformes, Psittaciformes, and Strigiformes. Functional observations were made while dissecting fresh material. The secondary insertion of the flexor muscles on the skin structures is discussed. The papillae in the pad of the passerine species is connected to a plate mainly composed of the horny cells of stratum corneum; only the top of the papillae are free to penetrate roughnesses in the bark of branches or twigs. The parrot has papillae free from one another and often supplied with Herbst corpuscles, indicating touch function. The owl has also free papillae, but these are supported by densely packed collagenous fibres in the dermis, forming a plate functionally comparable to the horny plate of the passerine. The pads and folds in the passerine are attached to the skeletal elements, both directly by collagenous fibre bundles and indirectly by the large scales on the dorsal side of the digit, which are firmly anchored to the phalanges. The pads in the parrot and the owl are directly attached by collagenous fibres to the skeletal elements. The structure of the pad and the papillae correlate with the habits: in the passerine, to jump and fly between branches; in the parrot, to move sluggishly on branches and manipulate food with the feet; and in the owl, to perch on branches and grasp prey.     

Electronmicroscopy of the buccal proper lamina in leukoplakia

The observations included the connective tissue laminae originating from samples of the buccal mucous membrane in leukoplakia. Following fixation and dehydration the materials were embedded in Epon 812, and the electronograms for the evaluation were obtained with the use of a Tesla BS 500 electron microscope. The macrophages were encountered close to the basal membrane in the proper lamina. The space between the basal cells and the macrophages was filled with the connective tissue matrix and numerous collagen fibres, as well as the fibroblast cells. Numerous mast cells, characterized by a specific activity, were noted. Additionally, the proper lamina contained few nerve fibres, usually nonmyelinated. The vascular bed was normal. The electronograms in leukoplakia revealed an active synthesis of the connective tissue matrix and collagen fibres. The marked activity of the mast cells was manifested by a high number of cells containing a relatively differentiated amount of granulation. This might be related to the chronic character of the disease. A significant activity of particular elements of the proper lamina, i.e. the cellular elements, collagen fibres and the connective tissue matrix appears to be characteristic of leukoplakia.     

Reticular meshwork of the spleen in rats studied by electron microscopy

The reticular meshwork of the rat spleen, which consists of both fibrous and cellular reticula, was investigated by transmission electron microscopy. The fibrous reticulum of the splenic pulp is composed of reticular fibers and basement membranes of the sinuses. These reticular fibers and basement membranes are continuous with each other. The reticular fibers are enfolded by reticular cells and are composed of two basic elements: 1) peripheral basal laminae of the reticular cells, and 2) central connective tissue spaces in which microfibrils, collagenous fibrils, elastic fibers, and unmyelinated adrenergic nerve fibers are present. The basement membranes of the sinuses are sandwiched between reticular cells and sinus endothelial cells and are composed of lamina-densalike material, microfibrils, collagenous fibrils, and elastic fibers. The presence of these connective tissue fibrous components indicates that there are connective tissue spaces in these basement membranes. The basement membrane is divided into three parts: the basal lamina of the reticular cell, the connective tissue space, and the basal lamina of the sinus endothelial cell. When the connective tissue space is very small or absent, the two basal laminae may fuse to form a single, thick basement membrane of the splenic sinus wall. The fibrous reticulum having these structures is responsible for support (collagenous fibrils) and rebounding (elastic fibers). The cells of the cellular reticulum--reticular cells and their cytoplasmic processes, which possess abundant contractile microfilaments, dense bodies, hemidesmosomes, basal laminae, and a well-developed, rough-surfaced endoplasmic reticulum, and Golgi complexes, which are characteristic of both fibroblasts and smooth muscle cells--are considered to be myofibroblasts. They may play roles in splenic contraction and in fibrogenesis of the fibrous reticulum. The contractile ability may be influenced by the unmyelinated adrenergic nerve fibers that pass through the reticular fibers. The three-dimensional reticular meshwork of the spleen consists of sustentacular fibrous reticulum and contractile myofibroblastic cellular reticulum. This meshwork not only supports the organ but also contributes to a contractile mechanism in circulation regulation, in collaboration with major contractile elements in the capsulo-trabecular system.     

Three-dimensional arrangement of dense connective tissue around the human major duodenal papilla. Including the ampullary region and the distal choledochal duct

Directionally arranged dense connective tissue fibres were investigated in 21 specimens of the major duodenal papilla. Specimens were examined using a stereoscope, polarization microscopy and serial histological sections at three different planes. Directionally arranged dense connective tissue fibres spread in a deltoid pattern from the orifice of the major duodenal papilla and its intraduodenal part to the circular duodenal musculature. Connective tissue fibres crossing at different angles form a texture from the orifice of the major duodenal papilla to the distal choledochal duct. The functional significance of the dense connective tissue fibres, e.g. for the muscular system in the investigated area, is discussed as well as possible reasons for gallstone impactions.     

Formation of the tectorial membrane of the cochlear canal during the embryogenesis of birds

By means of electron microscopy formation of the tectorial membrane of the cochlear canal and differentiation of the cells participating in the process (supporting cells of the basilar papilla and anterior homogeneous cells--AHC) have been studied in chick embryos. The AHC, to which the tectorial membrane is fixed, produce fine fibrillar material, included into the composition of the tectorial membrane. The cells mentioned form a number of cytoskeletal structures connected with the mechanical function of the tectorial membrane. Besides the network of the tonofilaments, gradually filling cytoplasm of the AHC, some peculiar attachings in the form of collagenous fibrillar bundles are revealed, they reach the AHC from the sublying connective tissue and have a direct contact with the basal membrane of the cells. The beginning of the tectorial membrane formation precedes the formation of the cytoskeletal structures. The latter appear only when the mass of the tectorial membrane, and hence, the mechanical loading on the AHC is great enough.     

STRUCTURAL BIOLOGY OF THE FIBRES OF THE COLLAGENOUS AND ELASTIC SYSTEMS

The different types of fibres of the collagenous and elastic systems can be demonstrated specifically in tissue sections by comparing the typical ultrastructural picture of each of the fibre types with studies using selective staining techniques for light microscopy. A practicalmodus operandi, which includes the recommended staining procedures and interpretation of the results, is presented. Micrographs and tables are provided to summarize the differential procedures. Reticulin fibres display a distinct argyrophilia when studied by means of silver impregnation techniques, and show up as a thin meshwork of weakly birefringent, greenish fibres when examined with the aid of the Picrosirius-polarization method. In addition, electron-microscopic studies showed that reticulin fibres are composed of a small number of thin collagen fibrils, contrasting with the very many thicker fibrils that could be localized ultrastructurally to the sites where non-argyrophilic, coarse collagen fibres had been characterized by the histochemical methods used. The three different fibre types of the elastic system belong to a continuous series: oxytalan—elaunin—elastic (all of the fibre types comprising collections of microfibrils with, in the given sequence, increasing amounts of elastin). The three distinct types of elastic system fibres have different staining characteristics and ultrastructural patterns. Ultrastructurally, a characteristic elastic fibre consists of two morphologically different components: a centrally located solid cylinder of amorphous and homogeneous elastin surrounded by tubular microfibrils. An oxytalan fibre is composed of a bundle of microfibrils, identical to the elastic fibre microfibrils, without amorphous material. In elaunin fibres, dispersed amorphous material (elastin) is intermingled among the microfibrils.     

Characterization of collagenous meshworks by volume exclusion of dextrans.

The volumes from which 3H-labelled dextrans are excluded by dermal collagenous fibres were calculated by dilution of dextran probes. Five dextrans, of average Stokes' radii 1.72, 2.53, 3.92, 4.54 and 14.24nm, were investigated at concentrations between 0.1 and 3% (w/w). The excluded volume was dependent on dextran concentration only for the two smaller probes. The largest dextran was shown not to bind to the fibres. A plot of the square root of excluded volume against Stokes' radius was linear for the four smallest dextrans, corresponding to the predictions of Ogston's [(1958) Trans. Faraday Soc. 54, 1754--1757] rod-and-sphere model of fibrous exclusion, and suggesting that dextrans of Stokes' radius between 1.72 and 4.54 nm were excluded by a cylindrical solid fibre of radius 2.90 +/- 0.72 nm. Larger molecules were excluded by a structure of much greater size, since the volume exclusion for the largest dextran was only slightly greater than that of the dextran less than one-third its radius. The excluded volume of 3H2O fell slightly below the line describing the dextran data, indicating that water had access to most of the volume not occupied by the collagenous fibres.     

Connective tissue structures of human skeletal muscle and their significance in the biomechanics of the body

By means of light optic and electron microscopy (SAM, TAM) histoconstruction of the connective tissue structures of the human skeletal muscles have been investigated and its analysis has been performed from biomechanical point of view. Fibrillar elements of the connective tissue are demonstrated to play an important role in structural adaptation of the skeletal muscle, as the organ, performing certain mechanical functions. The data obtained makes it possible to formulate the state, that the fibrillar network of the connective tissue is a polyfunctional system, that ensures integration of the structural elements of the muscle, transmission of mechanical strains, is the carcass of the organ and participates in formation of its buffer and amortizational mechanisms. The integration mechanisms of the main functional elements of the muscle belly, tendons and fascia to a great extent are of a unification character.     

SR-G-AB显示胶原、网状纤维和粘液的复合染色法

在组织细胞的染色中,为了证明双重纤维和粘液物质,通过分别选用和组合的天狼星红(Sirius)苦味酸、Comori和阿尔辛蓝(Alcian blue)醋酸染色试剂,已能够显示鼠肺组织中胶原纤维呈红色,网状纤维呈黑色,粘液物质呈绿蓝色,背景呈黄色。对比清晰,色彩鲜艳,是较为理想的复合染色方法。     

Submicroscopic structure of collagen--a basis for the interpretation of corresponding polarization-optical and histochemical findings]

In view of new possibilities of acquiring relatively quantitative information about the molecular structure of collagenous fibres in histological section with the help of polarization and histochemical methods a survey is given of the most important aspects of the molecular structure of collagen in connection with the formation of "cross-links", giving due attention to the role of functional groups. These create the basis for interpreting morphological findings covering free amino-groups of lysin and hydroxylysin, guanidine groups of arginine and carboxyl groups of glutamic acid and asparaginic acid, gained by adding phenol or toluidine blue to collagenous fibres and by performing path difference measurements. References made to the applicability of this polarization-histochemical method in clinical research and diagnostics, in gathering reproducible data on processes of development or growth and aging and pathological changes in collagen are intended to encourage wide use of this examination technique in practice.     

Architecture and functional aspects of the distal airways of Antarctic seals with different habits,the Weddell Seal (Leptonychotes weddellii) and the Crabeater Seal (Lobodon carcinophagus)

Summary The lung of the deep diving Weddell Seal is characterized by an unusually well developed periacinar dense collagenous connective tissue, and a thick coat of smooth musculature particularly in the distal bronchioli. Both, collagen and smooth musculature appear to be functionally interrelated, the first serving presumably as site of origin or attachment for the latter. The orientation of the bronchiolar smooth muscle cells is complex: there exists a basic pattern of two crisscrossing helical bundles that wind in opposite direction. In addition, longitudinal bundles are frequent both at the inside and the outside of the muscular coat. Furthermore, more or less complete ringshaped bundles occur as well as groups of muscle fibres running radially into the collagenous tissue of the surroundings of a bronchiolus. This complex architecture presumably allows active adjustment to various physiological needs of the Weddell Seal including as extremes both closing and widening of the bronchiolar lumen. Isometric contractions of the smooth musculature may stiffen the wall of the distal airways while diving. In the Crabeater Seal which dives for shorter durations and by far less deeply than the Weddell Seal, both periacinar collagen and bronchiolar smooth musculature are of similar arrangement, however, occur in considerably reduced amounts. A rich supply of autonomie nerve fibres with abundant varicosities controls the smooth muscle cells, which are interconnected by gap junctions and receive their innervation par distance (visceral type of smooth musculature). The majority of varicosities contains small clear vesicles, as is typical for cholinergic nerves, suggesting a strong parasympathetic influence. Other varicosities are presumably of peptidergic type. Mast cells and epithelial endocrine cells may exert additional influence on the musculature.