Morphology,shape variation and movement of skeletal elements in starfish (Asterias rubens)

Starfish (order: Asteroidea) possess a complex endoskeleton composed of thousands of calcareous ossicles. These ossicles are embedded in a body wall mostly consisting of a complex collagen fiber array. The combination of soft and hard tissue provides a challenge for detailed morphological and histological studies. As a consequence, very little is known about the general biomechanics of echinoderm endoskeletons and the possible role of ossicle shape in enabling or limiting skeletal movements. In this study, we used high‐resolution X‐ray microscopy to investigate individual ossicle shape in unprecedented detail. Our results show the variation of ossicle shape within ossicles of marginal, reticular and carinal type. Based on these results we propose an additional classification to categorize ossicles not only by shape but also by function into ‘connecting’ and ‘node’ ossicles. We also used soft tissue staining with phosphotungstic acid successfully and were able to visualize the ossicle ultrastructure at 2‐μm resolution. We also identified two new joint types in the aboral skeleton (groove‐on‐groove joint) and between adambulacral ossicles (ball‐and‐socket joint). To demonstrate the possibilities of micro‐computed tomographic methods in analyzing the biomechanics of echinoderm skeletons we exemplarily quantified changes in ossicle orientation for a bent ray for ambulacral ossicles. This study provides a first step for future biomechanical studies focusing on the interaction of ossicles and soft tissues during ray movements.     

Scleral Ossicles of Teleostei: Evolutionary and Developmental Trends

Scleral ossicles are bones within the sclera of the eye. A total of 547 teleost species (744 specimens) from 36 orders and 163 families were investigated with respect to scleral ossicle presence/absence and number. This is the first extensive investigation into the distribution of scleral ossicles in living teleosts. Derived orders were found to have the most variable scleral ossicle numbers (zero, one, or two per eye), while more basal groups tend to have no ossicles. Whereas more data on the activity level of individual families and on family‐level interrelationships is needed, significant findings were nevertheless made. Ninety‐four percent of the families investigated have a consistent ossicle number, indicating that family level is a reliable predictor of scleral ossicle presence/absence. In a subgroup analysis of 28 families, additional trends were observed with regard to activity level, namely that 80% of the families that are described as sluggish have no scleral ossicles while 100% of those that are very active have two ossicles per eye. In addition, fish that inhabit deep sea environments are the most likely ones to lack scleral ossicles. The analysis also supports the hypothesis that scleral ossicle number declined from the basal condition of four elements per eye seen in Cheirolepis to no ossicles in the eye, early in teleost evolution. At least 24 evolutionary steps are needed to account for the scleral ossicle distribution seen in teleost orders today. This study describes the variation of scleral ossicles in the most diverse group of vertebrates, Teleostei, and provides the first step in understanding the evolvability of these elements in bony fishes. Anat Rec, 291:161–168, 2008. © 2008 Wiley‐Liss, Inc.     

Ectopic ossicles associated with metacercariae of Apophallus brevis (Trematoda) in yellow perch, Perca ftavescens (Teleostei): development and identification of hone and chondroid bone

This paper describes the development and tissues in mineralized ossicles in the musculature of Perca flavescens infected with metacercariae of the trematode Apophallus brevis. Analysis involved light microscopy, transmission and scanning electron microscopy, X-ray scanning electron microprobe analysis, and tetracycline labelling. Two to 14 days post-infection, fibroblast-like host cells stream towards the parasite cyst forming a fusiform cellular capsule. By 14 days post-infection the capsule differentiates into an inner hypertrophied layer, an extensive middle layer of fibroblast-like cells, and a thin outer layer of flattened fibroblast-like cells forming a fibrous sheath at the capsule/muscle interface. From 21–35 days post-infection, a bony tissue is deposited periosteally in an equatorial ring around the cyst. With time, additional tissue is secreted over the ring increasing its thickness and advancing the matrix front towards the poles of the ossicle. Plump osteoblast-like cells cover the developing ossicle and may become trapped within the matrix in lacunae encapsulated by collagen. By 63 days post-infection, medium-sized ossicles are morphologically similar to large cysts from perch captured in the wild; ovoid with two polarized canals, but lacking acellular or lamellar bone-like tissue. Mineralized ossicles contain calcium, phosphorus and oxygen. Large ossicles retrieved from perch given multiple doses of tetracycline revealed discrete fluorescent bands, indicative of incremental growth. Fully developed ossicles are composed of two skeletal tissues, an inner region of chondroid bone and an outer region of acellular, lamellar bone.     

The effect of repeated freeze‐thaw cycles on human muscle tissue visualized by postmortem computed tomography (PMCT)

The aim of this study was to determine whether effects of repetitive freeze‐thaw cycles, with various thawing temperatures, on human muscle tissue can be quantified using postmortem computed tomography (PMCT) technology. An additional objective was to determine the preferred thawing temperature for muscle tissue in this study. Human cadaver upper extremities were divided into two different thawing temperature groups and underwent a series of four freeze‐thaw cycles in total. Axial CT scans were performed after each cycle. CT attenuation (in Hounsfield units, HU) was measured in four muscles of the upper extremities. HU values changed significantly with the introduction of each subsequent freeze‐thaw cycle. Moreover, the changes in HU values were different for each thawing group. There was a significant increase of HU values in both groups between t₀ and t₁. Unfrozen tissue showed large variation of HU values in all samples. It was possible to distinguish between samples thawed at different thawing temperatures based on their respective HU values. It is advisable to keep the number of freeze‐thaw cycles to just one, if the human cadaveric tissue is to be used for educational purposes. The preferred thawing temperature in this study is 2°C. Clin. Anat. 30:799–804, 2017. © 2017Wiley Periodicals, Inc.     

Sound‐generating and ‐detecting motor system in catfish: Design of swimbladder muscles in doradids and pimelodids

Catfishes have evolved a diversity of swimbladder muscles serving in the generation of different sounds and probably other acoustic functions. In order to find out if anatomical and acoustical differences are parallelled by fine structural differences, I examined the sonic muscles of the doradid Platydoras and the pimelodid Pimelodus by gross dissections and ultrastructural methods. In Platydoras, the sound‐generating (drumming) muscle (DM) inserts on a dorsal bony plate that vibrates the swimbladder. In pimelodids, the large DM attaches directly on the ventral surface of the swimbladder, whereas the small tensor tripodis muscle (TT) inserts on the rostral surface near the tripus, the most caudal Weberian ossicle. Fibers of all three muscles possess an extensive development of sarcoplasmatic reticulum (SR) in association with very thin myofibrils (MF) but differed widely in their arrangement. In Platydoras, ribbons of MFs are arranged radially around a central core. Mitochondria were found within the core and the peripheral sarcoplasm. Pimelodus does not have a differentiated core and the cross‐sectional area of DM‐MFs is about 15% larger as determined by stereological measurements. The TT possesses shorter sarcomeres and more mitochondria than DMs, which were primarily found between MFs. This suggests faster contraction properties and greater resistence to fatigue compared with sonic muscles. Data indicate that the higher amount of DM‐myofibrils in pimelodids might result in stronger muscle contractions and, presumably, in higher sound intensities. The fine structure of the TT reveals that contractions most likely prevent transmission of swimbladder vibrations to the inner ear via the Weberian ossicles during vocalization. Anat Rec 263:297–306, 2001. © 2001 Wiley‐Liss, Inc.     

Immunohistochemical assessment of collagen types I, III, IV and VI in biopsy samples of the bovine uterine wall collected during the oestrous cycle

Uterine biopsies were collected at cycle days 1 (oestrous), 8, 15 and 19 in six cows. Unfixed cryostat sections were used to immunolocalise collagen types I, III, IV and VI by an indirect FITC method. Collagen I was sparsely found in the endometrium where it formed a fine meshwork of thin fibres directly below the surface epithelium, clearly visible only at cycle days 8 and 15. Collagen III formed the bulk of connective tissue fibres and was arranged in fine aggregates within the superficial endometrial stroma, while in the deeper areas it consisted of many thick fibre bundles. Collagen IV was found in basement membranes underlying all endometrial epithelia. Furthermore, it surrounded smooth muscle cells of blood vessels. A few single fibrils also stained positively within the endometrial stroma, more numerous at cycle days 1 and 19 as compared to days 8 and 15. Collagen VI formed a mesh of fine and pericellularly situated fibrils within the endometrial stroma. The contribution of the collagen types studied to the connective tissue of caruncles, blood vessels, lymph follicles, and myometrium is also reported. The results of the present study indicate that the connective tissue of the bovine uterine wall is composed of different collagen types, which exhibit a characteristic distribution pattern each. The day of cycle may influence amounts and organisation of collagen types I and IV as demonstrated here at the light-microscopical level.     

The eye of the magellanic penguin (Spheniscus magellanicus): Structure of the anterior segment

We undertook a light and scanning electron microscopic study of the eye in the Magellanic penguin (Spheniscus magellanicus). The anatomical peculiarities of the eyeball shape in Sphenisciformes have been previously described by others; here, we show that they are accompanied by several modifications in the organization of the anterior segment of the eye. The main change was found in the portion of opaque sclera extending from the cornea to the anterior border of the scleral ossicles, which was much broader than in other avian eyes. This scleral region was made of a very dense fibrous tissue and was as difficult to cut as the ossicles. The corneoscleral boundary was also different from that of other birds, since the aqueous humor channel and the pectinate ligament were located 1.0–1.5 mm posterior to the cornea. The osseous ring was formed by 13 bones, including three pairs of over-and underplates. There was a single ciliary muscle, with meridionally oriented striated fibers. They were inserted on a circumference along the boundary between the fibrous sclera and the ossicles, far away from the wall of the aqueous humor channel. On their posterior end, the muscle fibers formed a tendinous structure attached to the inner surface of the sclera and to the outer surface of the ciliary body. Only short zonular fibrils were observed. These anatomical features are probably relevant for the adaptation of penguin eyes to vision on land and in the aquatic environment.     

Ectopic ossicles associated with metacercariae of Apophallus brevis (Trematoda) in yellow perch,Perca ftavescens (Teleostei): development and identification of hone and chondroid bone

This paper describes the development and tissues in mineralized ossicles in the musculature of Perca flavescens infected with metacercariae of the trematode Apophallus brevis. Analysis involved light microscopy, transmission and scanning electron microscopy, X-ray scanning electron microprobe analysis, and tetracycline labelling. Two to 14 days post-infection, fibroblast-like host cells stream towards the parasite cyst forming a fusiform cellular capsule. By 14 days post-infection the capsule differentiates into an inner hypertrophied layer, an extensive middle layer of fibroblast-like cells, and a thin outer layer of flattened fibroblast-like cells forming a fibrous sheath at the capsule/muscle interface. From 21–35 days post-infection, a bony tissue is deposited periosteally in an equatorial ring around the cyst. With time, additional tissue is secreted over the ring increasing its thickness and advancing the matrix front towards the poles of the ossicle. Plump osteoblast-like cells cover the developing ossicle and may become trapped within the matrix in lacunae encapsulated by collagen. By 63 days post-infection, medium-sized ossicles are morphologically similar to large cysts from perch captured in the wild; ovoid with two polarized canals, but lacking acellular or lamellar bone-like tissue. Mineralized ossicles contain calcium, phosphorus and oxygen. Large ossicles retrieved from perch given multiple doses of tetracycline revealed discrete fluorescent bands, indicative of incremental growth. Fully developed ossicles are composed of two skeletal tissues, an inner region of chondroid bone and an outer region of acellular, lamellar bone.     

Identification of collagen, elastic, elaunin and oxytalan fibres in ganglia of the myenteric plexus of the human oesophagus

Summary The connective tissue associated with the myenteric plexus of the human oesophagus was studied by light and electron microscopy. Collagen fibres were identified by picrosirius staining with polarization microscopy and from their fine structural morphology. A capsule of connective tissue invests the ganglia while septa of connective tissue separate groups of ganglion neurons, surrounding each individual ganglion neuron and each nerve bundle. Collagen fibrils surround the ganglia, each ganglion neuron and each nerve bundle. The fibrils are disposed in various orientatons forming networks. Elastic, elaunin and oxytalan fibres were identified by their staining characteristics and fine structural morphology. The bulk of the ganglion sheath consists of coarse elastic fibres and elaunin fibres. Elaunin and oxytalan fibres form the intraganglionic network. Oxytalan, elaunin and elastic fibres appear to be located in areas related to different stresses and deformation to which the ganglia of the myenteric plexus are exposed during the contraction of the esophageal wall. The ganglia of the myenteric plexus of the human oesophagus show structural organisation of the connective tissue component similar to that seen in sympathetic and parasympathetic ganglia.     

Staging of regeneration process of an arm of the feather star Oxycomanthus japonicus focusing on the oral‐aboral boundary

Crinoids have strong regenerative capability and rapidly restore their lost body parts such as arms. We observed the regeneration process of arms of the feather star (stalkless crinoid), Oxycomanthus japonicus, and divided the process into 10 stages. We clarify the position at which the oral and aboral epidermis adhere in wound closure and track the oral‐aboral boundary in the regenerate during the entire process of regeneration. We suggest that the concepts of distalization and intercalation, which are proposed to understand animal regeneration integrally, are also applicable to arm regeneration of the feather star. In addition, we clarify that pinnules, appendages extending from the sides of an arm, start to grow in the oral region of the regenerating arm even though a complete pinnule has an oral‐aboral axis. The mode of morphogenesis of pinnules in arm regeneration suggests that the oral region functions as the primary patterning tissue for pinnules. Developmental Dynamics 239:2947–2961, 2010. © 2010 Wiley‐Liss, Inc.     

Freehand three‐dimensional ultrasound to assess semitendinosus muscle morphology

In several neurological disorders and muscle injuries, morphological changes of the m. semitendinosus (ST) are presumed to contribute to movement limitations around the knee. Freehand three‐dimensional (3D) ultrasound (US), using position tracking of two‐dimensional US images to reconstruct a 3D voxel array, can be used to assess muscle morphology in vivo. The aims of this study were: (i) to introduce a newly developed 3D US protocol for ST; and (ii) provide a first comparison of morphological characteristics determined by 3D US with those measured on dissected cadaveric muscles. Morphological characteristics of ST (e.g. muscle belly length, tendon length, fascicle length and whole muscle volume, and volumes of both compartments) were assessed in six cadavers using a 3D US protocol. Subsequently, ST muscles were removed from the body to measure the same morphological characteristics. Mean differences between morphological characteristics measured by 3D US and after dissection were smaller than 10%. Intra‐class correlation coefficients (ICCs) were higher than 0.75 for all variables except for the lengths of proximal fascicles (ICC = 0.58). Measurement of the volume of proximal compartment by 3D US was not feasible, due to low US image quality proximally. We conclude that the presented 3D US protocol allows for reasonably accurate measurements of key morphological characteristics of ST muscle.     

Atrioventricular valves of the mouse: III. Collagenous skeleton and myotendinous junction

Background: The leaflet tissue of the mouse atrioventricular (AV) valves contains a system of wavy collagen bundles that organize like tendons, orientate along lines of tension, and constitute an essential component of the valve tissue. The organization of these bundles is different in the two AV valves, reflecting differences in the anatomy of the entire valvular complex. Further insights into this kind of organization are needed to gain a complete understanding of the functional anatomy of the mouse AV valves. Methods: The endocardial covering of the mouse AV valves (from 21 days to 1 year of age) was eliminated by the sonication or the maceration method. This allowed us to study in situ the organization of the collagenous valve skeleton, as well as the structure of the myotendinous junction. Results: The leaflets of the two AV valves are formed by a fibrous layer (on the ventricular side) and a spongy layer (on the atrial side). The fibrosa is formed by undulating collagen bundles that organize and orientate differently on the right and left sides. The spongiosa is formed, on both sides, by a loose network of thin collagen fibers with no apparent orientation. Myocardial cells in the papillary muscles of the tricuspid valve are elongated and show cone-shaped tips. Collagen fibers attach to the myocyte surface. Collagen struts and thin septa can also be recognized. On the other hand, the collagenous components of the mitral leaflets attach tangentially to the mitral papillary muscles. On the two sides, the myocytes appear to be ensheathed in a layer of collagenous tissue. The sheaths are formed by circularly arranged fibers and appear to be tightly interconnected. Conclusions: The differences in the collagenous organization between the two AV valves reflect differences in the gross anatomy of the valves. The attachment of collagen to the papillary myocytes in the tricuspid valve resembles that of a typical myotendinous junction. However, the collagenmuscle junction in the mitral valve is more similar to the structure of a pennate muscle. The collagen matrix of the heart has been divided into endomysial, perimysial, and epimysial components. The presence of sheaths housing individual myocytes and capillaries, struts, and thin septa, corresponds to the endomysium. The absence of perimysial septa, which aggregate myocytes into groups, is striking, but this may just be a species difference. The appropriateness of the term epimysium, as applied to the heart, is discussed. © 1995 Wiley-Liss, Inc.     

Interaction between muscles and fascia in the mystacial pad of whisking rodents

In whisking rodents, the mystacial pad is supplied with vibrissae and contains a collagenous skeleton that is a part of the snout fascia. The collagenous skeleton is composed of three interconnected layers: superficial, deep spongy mesh and subcapsular fibrous mat. We found that the first two layers contain diverse fascial structures, such as sheets of subcutaneous connective tissue, tendons, ligaments and follicular capsules which transmit muscle efforts to vibrissae and are thus involved in whisking. Subcapsular fibrous mat is built of oriented rostro-caudal wavy fibrils. It maintains spatial arrangement of whisker follicles, provides a quick response to deformation and connects entire mystacial pad to the skull. To move vibrissae, the forces of intrinsic muscles are applied directly to the capsules of the vibrissa follicles, whereas the forces of extrinsic muscles are applied to other parts of the collagenous skeleton, which transmit the forces to the capsules. According to the spatial distribution and anchoring sites of the muscles and fascia, extrinsic muscles provide vibrissa protraction or retraction by pulling the superficial layer of the collagenous skeleton rostral or caudal, respectively. Vibrissae can be also retracted when the efforts of extrinsic muscles are applied to the subcapsular fibrous mat. When the muscles relax, fascial structures return the vibrissae to their resting position. The deep spongy layer encompasses vibrissal follicles providing a uniform distribution of stresses and strains during whisking. In the mystacial pad, fascia is a dominant type of tissue that maintains the integrity of the vibrissa motor plant, translates muscular momentum to the vibrissae, and plays a role in vibrissae movements.     

Towards understanding the dose and timing effect of hydrocortisone treatment on the scleral ossicle system within the chicken eye

Previous work, almost four decades ago, showed that hydrocortisone (HC) treatment reduces the number of skeletogenic condensations that give rise to the scleral ossicles in the chicken eye. The scleral ossicles are a ring of overlapping intramembranous bones, the sclerotic ring, and are present in most reptiles, including birds. The scleral condensations that give rise to the scleral ossicles are induced by a series of overlying thickenings (or papillae) of the conjunctival epithelium. Here, we further explore the effects of altering the dosage and timing of HC treatment on the morphology and number of skeletogenic condensations and conjunctival papillae. We show that high doses can completely obliterate the entire sclerotic ring. Significantly, the reduction in papillae number we observed was less extreme than that of the scleral condensations, indicating that additional factors contribute to the observed skeletogenic condensation loss. Via immunohistochemical analyses, we show that HC treatment alters the spatial expression pattern of several extracellular matrix components (tenascin‐C, decorin and procollagen I) and also alters the vasculature network within the sclera. This research provides important insights into understanding the role of the scleral tissue components in ossicle development within the vertebrate eye.     

PDGFRα signalling promotes fibrogenic responses in collagen‐producing cells in Duchenne muscular dystrophy

Fibrosis is a characteristic of Duchenne muscular dystrophy (DMD), yet the cellular and molecular mechanisms responsible for DMD fibrosis are poorly understood. Utilizing the Collagen1a1‐GFP transgene to identify cells producing Collagen‐I matrix in wild‐type mice exposed to toxic injury or those mutated at the dystrophin gene locus (mdx) as a model of DMD, we studied mechanisms of skeletal muscle injury/repair and fibrosis. PDGFRα is restricted to Sca1+, CD45? mesenchymal progenitors. Fate‐mapping experiments using inducible CreER/LoxP somatic recombination indicate that these progenitors expand in injury or DMD to become PDGFRα+, Col1a1‐GFP+ matrix‐forming fibroblasts, whereas muscle fibres do not become fibroblasts but are an important source of the PDGFRα ligand, PDGF‐AA. While in toxin injury/repair of muscle PDGFRα, signalling is transiently up‐regulated during the regenerative phase in the DMD model and in human DMD it is chronically overactivated. Conditional expression of the constitutively active PDGFRα D842V mutation in Collagen‐I+ fibroblasts, during injury/repair, hindered the repair phase and instead promoted fibrosis. In DMD, treatment of mdx mice with crenolanib, a highly selective PDGFRα/β tyrosine kinase inhibitor, reduced fibrosis, improved muscle strength, and was associated with decreased activity of Src, a downstream effector of PDGFRα signalling. These observations are consistent with a model in which PDGFRα activation of mesenchymal progenitors normally regulates repair of the injured muscle, but in DMD persistent and excessive activation of this pathway directly drives fibrosis and hinders repair. The PDGFRα pathway is a potential new target for treatment of progressive DMD. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Fast low‐angle shot diffusion tensor imaging with stimulated echo encoding in the muscle of rabbit shank

In the past, spin‐echo (SE) echo planar imaging(EPI)‐based diffusion tensor imaging (DTI) has been widely used to study the fiber structure of skeletal muscles in vivo. However, this sequence has several shortcomings when measuring restricted diffusion in small animals, such as its sensitivity to susceptibility‐related distortions and a relatively short applicable diffusion time. To address these limitations, in the current work, a stimulated echo acquisition mode (STEAM) MRI technique, in combination with fast low‐angle shot (FLASH) readout (turbo‐STEAM MRI), was implemented and adjusted for DTI in skeletal muscles. Signal preparation using stimulated echoes enables longer effective diffusion times, and thus the detection of restricted diffusion within muscular tissue with intracellular distances up to 100 µm. Furthermore, it has a reduced penalty for fast T₂ muscle signal decay, but at the expense of 50% signal loss compared with a SE preparation. Turbo‐STEAM MRI facilitates high‐resolution DTI of skeletal muscle without introducing susceptibility‐related distortions. To demonstrate its applicability, we carried out rabbit in vivo measurements on a human whole‐body 3 T scanner. DTI parameters of the shank muscles were extracted, including the apparent diffusion coefficient, fractional anisotropy, eigenvalues and eigenvectors. Eigenvectors were used to calculate maps of structural parameters, such as the planar index and the polar coordinates θ and ? of the largest eigenvector. These parameters were compared between three muscles. θ and ? showed clear differences between the three muscles, reflecting different pennation angles of the underlying fiber structures. Fiber tractography was performed to visualize and analyze the architecture of skeletal pennate muscles. Optimization of tracking parameters and utilization of T₂‐weighted images for improved muscle boundary detection enabled the determination of additional parameters, such as the mean fiber length. The presented results support the applicability of turbo‐STEAM MRI as a promising method for quantitative DTI analysis and fiber tractography in skeletal muscles. Copyright © 2013 John Wiley & Sons, Ltd.     

The pectoral fin muscles of the coelacanth Latimeria chalumnae: Functional and evolutionary implications for the fin‐to‐limb transition and subsequent evolution of tetrapods

To investigate the morphology and evolutionary origin of muscles in vertebrate limbs, we conducted anatomical dissections, computed tomography and kinematic analyses on the pectoral fin of the African coelacanth, Latimeria chalumnae. We discovered nine antagonistic pairs of pronators and supinators that are anatomically and functionally distinct from the abductor and adductor superficiales and profundi. In particular, the first pronator and supinator pair represents mono‐ and biarticular muscles; a portion of the muscle fibers is attached to ridges on the humerus and is separated into two monoarticular muscles, whereas, as a biarticular muscle, the main body is inserted into the radius by crossing two joints from the shoulder girdle. This pair, consisting of a pronator and supinator, constitutes a muscle arrangement equivalent to two human antagonistic pairs of monoarticular muscles and one antagonistic pair of biarticular muscles in the stylopod between the shoulder and elbow joints. Our recent kinesiological and biomechanical engineering studies on human limbs have demonstrated that two antagonistic pairs of monoarticular muscles and one antagonistic pair of biarticular muscles in the stylopod (1) coordinately control output force and force direction at the wrist and ankle and (2) achieve a contact task to carry out weight‐bearing motion and maintain stable posture. Therefore, along with dissections of the pectoral fins in two lungfish species, Neoceratodus forsteri and Protopterus aethiopicus, we discuss the functional and evolutionary implications for the fin‐to‐limb transition and subsequent evolution of tetrapods. Anat Rec, 299:1203–1223, 2016. © 2016 Wiley Periodicals, Inc.     

Vitamin D sclerosis in rats.

The early fine structural changes in the arteries of rats induced by excess vitamin D3 perorally or parenterally were essentially similar, except the latter had a more prominent toxic effect to the vascular wall. The ultrastructural features, incidental to calcification, included the appearance of increased ground substance with a separation of collagenous and elastic fibrils, and degenerative changes in smooth muscle cells. Atherosclerosis was greatly accelerated at the sites of vascular injury when cholesterol, cholic acid and thiouracil were added to the basal diet. Calcification was initially observed in relation to elastic fibrils or degenerated cells in the upper and middle layers of the arteries, although there were few such deposits in the thickened intima of the coronary arteries. Calcium deposition could not be a direct effect of hypercalcemia, but the functional activity of smooth muscle cells did seem to promote the mineralization of calcium and phosphate. Furthermore, vitamin D-induced sclerosis did not prevent intimal thickening of the arteries when vitamin D3 was withdrawn.