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PubMed1985

Altered skin elastic fibers in hypothyroid myxedema and pretibial myxedema.

Elastic fibers account for 2% of dermal volume and are responsible for normal skin resiliency. We investigated a disorder of the dermal elastic component as the mechanism for the decreased elasticity of skin in myxedema. Skin biopsy specimens were obtained from patients with thyroid diseases and normal subjects matched for age, sex, and biopsy location. Elastic fiber concentration, determined by computerized morphometric analysis of Verhoeff-van Gieson-stained sections, was significantly lower than normal in hypothyroid and pretibial myxedema. The decreased elastin concentration was not a consequence of the glycosaminoglycan infiltration. Ultrastructural studies of myxedematous skin showed wide variability of elastic fiber diameter and decreased microfibrils. Myxedema (hypothyroid and pretibial) is consistently associated with quantitative and qualitative defects of dermal elastic fibers.

Adult↗

PubMed1979

[Arterial subendothelial structures: anatomy, biochemistry, functions].

This review summarizes the main structural and biochemical features of the fibrillar constituents of the subendothelial layers of the arterial wall. Several constituents are directly identified by various histochemical methods and electron-microscopic studies. (1) The microfibrils (MF), stained by tannic acid, cationic stains such as ruthenium red, and various peroxidase-labeled lectins are mostly found in association with elastin within the internal elastic lamina (IEL). They have been characterized by chemical analysis as acidic glycoproteins, hydrolyzed by a variety of proteases, but resistant to collagenases. The endothelial cells seem to participate in their biosynthesis. (2) Elastin (El), which is the main constituent of the IEL, forms a wide, concentric, electron-lucent, tannic-acid-stainable zone. Fibrous El results from the association of tropoelastin (or proelastin) molecules by intermolecular cross-linkage. During the elastigenesis, this cross-linkage occurs directly between tropoelastin molecules which have been previously sterically oriented by the MF probably synthetized by the same cells (smooth muscle cells and possibly endothelial cells). (3) Interstitial collagen forms sparse fibers characterized by their cross-striation (with a periodicity of 640 A). They are relatively resistant to most proteolytic enzymes, except collagenases. They result from the intermolecular cross-linkage of rigid molecules, resulting themselves from the intramolecular cross-linkage of three helical alpha chains as a triple helix. The interstitial subendothelial collagen has been identified by indirect immunofluorescence as a type III collagen. The same technique has also been used to detect type IV collagen and fibronectin. This glycoprotein could play a role in the attachment of the endothelial cells to the fibrillar network of the subendothelium, despite an affinity which is greater toward denatured collagen than toward native collagen. One of the most important functions of the subendothelium is its role in thrombogenesis, in which both MF and collagen are involved. In type III collagen, this property is linked to the preservation of an ordered structure in which a 9-amino acids fragment, localized in the central part of each chain, could bear an adhesion site.

Animals↗

PubMed1985

Ultrastructural aspects of rat tail tendon sheaths.

An investigation was carried out on the sheaths which envelop rat tail tendons. The samples were processed for observation by light and electron microscopy. In the case of electron microscopy, thin sections of specimens embedded in epoxy resin and replicas of freeze etched samples were used. On the basis of histological and ultrastructural observations, four distinct connective tissue sheaths have been detected. The paratendineum is a thick fibrous sheath that covers externally the four groups of tendons arranged around the vertebrae of the tail; the epitendineum is a distinct fibrous sheath surrounding each tendon group; the peritendineum is composed of concentric cellular laminae enveloping each tendon; lastly, the endotendineum is made up of one cellular lamella which adheres to the fibres of the tendon, projecting trabeculae between the individual tendon fascicles. In the para- and epitendineum, thick bundles of collagen fibrils, running parallel to the fibres of the tendon, were visible. The collagen fibrils had a wide variability of diameters (from 35 to 220 nm) and, when examined in replica, their microfibrillar arrangement appeared to be straight. In the peri- and endotendineum, thin bundles of collagen fibrils were visible between the cellular laminae, parallel to the main axis of the tendon. Among these collagen bundles, elastic fibres and numerous glycoproteins containing microfibril-like filaments were visible. The collagen fibrils were small and of uniform diameter (50 nm) and, when observed on replica, showed a helicoidal microfibrillar arrangement. The cell layers of the peri- and endotendineum were made up of flattened fibroblasts which were connected by specialised junctions and which contained numerous micropinocytotic vesicles. A thin layer of granular electron-dense material, with ultrastructural characteristics similar to those of a basement membrane, was visible on the surface of the most external cellular layer of the peritendineum and on the outer surface of the cellular lamella of the endotendineum. Due to their morphological characteristics it is supposed that the four tendon sheaths are involved in different and special functions. Moreover, collagen Type I and collagen Type III, demonstrated by means of immunofluorescence techniques in previous investigations, show respectively a close similarity in distribution to the thick collagen fibrils, with a straight microfibrillar arrangement, of the two external sheaths, and to the thin collagen fibrils, with a helicoidal microfibrillar arrangement, of the two internal sheaths.

Animals↗

PubMed1977

[Isolation of structural glycoproteins from human placenta].

Microfibrils about 100 A wide are isolated by mechanical procedures (sieving and ultrasonic disintegration from villosities of human placenta. Amino acid and carbohydrate compositions seem to be related to structural glycoproteins described before in connective tissues.

Amino Acids↗

PubMed1979

Development of Bruch's membrane in the chick: an electron microscopic study.

The development of fibrous connective tissue in Bruch's membrane within the choroid of chronologically staged chick embryos was observed by means of transmission electron microscopy. The appearance of these connective tissue elements follows an orderly developmental sequence. The first component of Bruch's membrane to appear is a continuous basal lamina at the basal surface of the presumptive retinal pigment epithelium (RPE) at 21/2 days. Microfibrils and associated amorphous material are present in the adjacent connective tissue space. A discontinuous inner collagenous layer is observed at the basal aspect of the RPE during the fourth day. A definitive elastic layer is present during the ninth day and becomes more apparent following subsequent stages of development. An outer collagenous layer begins development during the tenth and twelfth days. Collagenous fibrils average 37 nm in diameter and display axial periodicity measuring 46 nm between major periods. These measurements increase with age as do the number of collagenous fibrils. Only isolated patches of basal lamina are observed in association with the choriocapillary endothelium by the twentieth day.

Animals↗

PubMed1973

Acute leukemic cells. Qualitative and quantitative electron microscopy.

Quantitative and qualitative electron microscopic studies were performed on the leukemic cells of 3 patients with stem cell leukemia, 6 patients with acute lymphoblastic leukemia, 7 patients with acute monoblastic leukemia, 3 patients with acute myeloblastic leukemia and 7 patients with acute monomyeloblastic leukemia. Significant quantitative differences were noted between some of the leukemic cells in heterochromatin:euchromatin ratios, cell size, granules per cell, amount of endoplasmic reticulum and the number of polyribosomes. Qualitative abnormalities which were found in some cells of all the leukemic groups were observed. These abnormalities included nuclear pockets, deep nuclear indentations (usually not the stem cell), nucleosomes, dilated perinuclear spaces, centrioles located in nuclear pockets (not in the stem cell or lymphoblast), accumulation of microfibrils (greatest in the monoblast and myeloblast), disrupted mitochondria with virus-like particles (none in stem cells), smaller granules and mitochondrial DNA, glycogen, and myelin whorls. The presence of the smaller granules in disrupted mitochondria and the resulting clear areas is probably related to the deranged carbohydrate metabolism of these cells. The presence of virus-like particles within mitochondria may be extremely important, but requires much more investigation. Some of the above findings may offer clues to further investigation of the acute leukemic cell.

Acute Disease↗

PubMed1979

Long-term observation of arachnoid villi after subarachnoid hemorrhage: an electron microscopic study in dogs.

The sequential electron microscopic examinations were carried out on arachnoid villi of the dog after subarachnoid hemorrhage (SAH). A few days after SAH, red blood cells were accumulated and degenerated in the villi. 10 days after SAH, remarkable phagocytosis and micropinocytosis were observed in the arachnoid villi, which may suggest increased metabolic activity of the arachnoid cells. 30 days after SAH, increased cellularity in the arachnoid villi developed and intercellular spaces became very narrow. 90 days after SAH, the arachnoid villi demonstrated many cytoplasmic filaments and hemidesmosome-like structures in the arachnoid cells, as well as narrowed intercellular space and increased cellularity. Microfibrils increased and structures resembling basal laminae were observed in the stromas. These morphological alterations may have a relation to the disturbance of absorption of cerebrospinal fluid.

Animals↗

PubMedDate not supplied

[Two possible mechanisms for forming supramolecular structures of the collagen type].

Comparative electron microscopic investigation of submolecular structure formation of native collagen molecules and denaturated collagen peptides in tropocollagen and gelatin gels was carried out. Submolecular terminal structures were similar. Fibrils exist with cross striation region of 64--70 nm. In spite of this the intermediate steps in the formation of both structures differ. In case of collagen the bundle of parallel microfibrils forms the thick fibrils. In case of gelatin the aggregates of spherical anisotropic particles form the fibrils of gelatin gels.

Chemical Phenomena↗

PubMed1979

[Electron microscopic study of the process of the removal of autogenous blood erythocytes beyond the limits of the subdural space].

The internal plate of the dura mater and arachnoidea of the dob brain was studied by electron microscopy after introducing 0.3--0.5 ml of the autogenous blood into the subdural space. The arachnoidea of the excretory channels and structural elements of the internal plate of the dura mater (cells of the internal covering layer, the collagen fibril and microfibril layer, the wall of the blood capillaries of the internal capillary network) involve the morphological substratum of the liquor-blood barrier-I between the liquor and blood of the blood capillaries of the internal capillary network of the dura mater. It was established that red cells of the subdural space penetrate the thickness of the dura mater, where they concentrate around blood capillaries of the internal capillary network, rather than penetrate into the arachnoidea.

Animals↗

PubMed1979

[Maturing of fibrils and intraosseous osteogenesis as a basis for the development of lamellae and the osteon structure].

We investigated in continuation of lightmicroscopical (phasecontrast, polarized light) and statistical studies concerning the formation of lamellae and osteons electromicroscopical the nature of fibrils in different areas of the cross section of the metacarpus from a cattle fetus of 520 mm SSL. During the maturation of fibrils in a subperiostal trabecal the diameter of fibrils increased (465 to 470 A). The period (316 or 536 A) contains primarily only a broad band and a small interband. Subsequently the interband increased (221 or 215 A), but the band decreased (324 or 271 A). In the centre of trabeculae the fibrils formate microlamellae. The fibrils split later on in the medial part of the cross section in microfibrils with irregular oreintation and appear lightmicroscopical as intermediate tissue (blasse Mittellinie). At the same time new fibrils are synthesized around the osteocytes and their canaliculi. As the result of a kind of remodeling the fibrils arrange in a parallel order forming packages which appear lightmicroscopical as fibrous felts. These fibrous felts exhibits partly an periodical arrangement with a small band (164 A) and a wide interband (287 A). In a following stage in the fibrous felts lamellae are developed, the length of which increased around the medullary cavity. Firstly after the development of lamellae the definite bone fibrils are reconstituted (diameter: 530 A; band: 348 A; interband: 212 A). Apparently the osteocytes are responsible for these procedures in a stage specific synthetic and lytic activity. The modification of the nature of fibrils results probably after the dissolving of the structural glycoproteins, which stabilize the tropocollagen molecules. A reconstitution of the structural glycoproteins after formation of the lamellae induce the reconstitution of bone specific collagenfibrils. The regulating mechanism for the codification of these structural development are unknown.

Animals↗

PubMed1975

[The biomechanics of hyaline cartilage under distension stress].

UNLABELLED: The mechanical properties of costal cartilage specimens from cattle were tested under periodical compressive loads. The specimens were put between the compression plates of an electronic materials testing machine and were exposed to defined deformations and deformation rates. On the basis of these induced periodical deformation-time curves as input functions we obtained force-time curves as output functions. RESULTS: (1) The cyclic force-time curves generated by deformation-time input functions with constant amplitudes initially showed a general decrease of force peaks until a force-time curve with constant amplitudes gradually arose. (2) If periodically loaded after a constant deformation had taken place the force peaks increased, at first pronouncedly but later diminishing. We named this the 'peak increase phenomenon'. (3) The mechanorheological curves of hyaline cartilage can be explained approximately by the viscoelastic behaviour of microfibrils in a parallel arrangement with the elastoviscous properties of cartilaginous ground substance.

Animals↗

PubMed1979

Ultrastructural observations on collagen and proteoglycans in the annulus fibrosus of the intervertebral disc.

Replicas of freeze-fractured collagen fibrils of peripheral and central parts of the annulus fibrosus of bovine intervertebral discs show microfibrils which run either arranged in parallel or in a helix with an inclination-angle ranging from 4 degrees to 8 degrees. According to results of freeze-fracutred tissues, thin sections of specimens treated with 4M guanidinium chloride show collagen fibrils with a parallel or a slightly wavy microfibrillar packing. Thin sections of specimens treated with alcian blue diluted in MgCl2 critical electrolyte solutions reveal interfibrillar proteoglycan particles with a filamentous shape in the peripheral zones of the annulus fibrosus and a predominant leaf-like appearance in the inner ones. These observations are discussed with reference to previous data concerning the variation in composition from the peripheral to the inner parts of the annulus fibrosus.

Animals↗

PubMed1979

Ultrastructure of the cyst of Hymenolepis diminuta larvae.

Electron microscopical studies of the cyst of 1-month-old H. diminuta larvae revealed considerable thickening of the superficial syncytium of tegument and formation of a large number of cavities and canals. The cytoplasm of the tegument is filled with microtubules produced by cytons of parenchymal layer which are analogs of tonofibrils. These peculiarities, together with numerous processes of the external fibrous layer, are regarded as adaptative to the changes of the hydrostatic pressure of the hemocoel of the intermediate host. The superficial syncytium is covered with microvilli and keeps polycellular cytoplasmatic bonds with cytons, which ensures energetic and plastic requirements for the stabilization of the hypertrophied syncytium and its physiological regeneration. Accumulations of fibres identical with those of the connective tissue were found in the cytons of the tegument. The cyst parenchyma consists mostly of cells with widened canals of granular endoplasmic reticulum associated with the microfibrils and production of fibrous filaments. The internal fibrous layer is produced by typical fibroblasts. The tegument of the cercomer is thinner and is considered to be less differentiated.

Animals↗

PubMed1979

Long spacing collagen in dermal disorders.

Electron microscopic studies of biopsy material from the vulva of six patients with lichen sclerosus et atrophicus and two patients with condyloma latum, and from the skin of the back and shoulder of one patient with scleromyxoedema and the forearm of one patient with macular amyloidosis revealed the presence of long spacing collagen (LSC) of one patient with macular amyloidosis revealed the presence of long spacing collagen (LSC) intermingled with an increased amount of ground substance and extracellular microfibrils. The presence of LSC in condyloma latum is believed not to have been reported previously. The LSC displayed an axial periodicity varying from 1000 to 2000 A. Our studies support the contention that the appearance of LSC is not specific of any disorder, and the formation of LSC is associated with the presence of increased amounts of glycosaminoglycan-rich ground substance and the abundance of microfilaments in the extracellular space.

Amyloidosis↗

PubMed1977

Histologic and ultrastructural features of primary and secondary endocardial fibroelastosis.

The average size of elastic fibers in thickened left ventricular endocardium was much larger in four patients with congenital endocardial fibroelastosis (EFE) than in six patients with acquired EFE (secondary to ischemic heart disease in two patients, to prosthetic cardiac valves in three, and to irradiation of the chest in one). Both components of normal elastic tissue (central, amorphous cores, and peripheral microfibrils) were present in endocardial elastic fibers of each patient. Ultrastructural identification of elastic fibers was greatly facilitated by staining with silver tetraphenylporphin sulfonate.

Adult↗

PubMed1976

Ultrastructure of localized myxedema.

Five biopsies from three patients with localized myxedema were studied by electron microscopy. The dermis showed an overwhelming accumulation of microfibrils with knobs (acid glycosaminoglycans) and an amorphous material containing glycoprotein. Furthermore, evidence of degradation without new formation of collagen fibrils was found. Considerable numbers of mast cells with various types of granules, fibroblasts with dilated granular endoplasmic reticulum, and macrophages were seen in the mucinous areas.

Adult↗

PubMed1984

Ultrastructural findings in the skin lesions of patients with anetoderma.

Eight biopsy specimens from the skin lesions of five patients with anetoderma were studied for their ultrastructural findings. In all of them, normal elastic fibers were absent and a few very thin, irregular elastic fibers with a more or less complete loss of the amorphous substance and a relative conservation of the microfibrils were observed. The collagen fibers were normal. Inflammation composed of macrophages and lymphocytes, with some plasma cells, was a prominent finding. It is suggested that anetoderma and acquired cutis laxa are part of the same spectrum of elastolytic disease.

Adolescent↗

PubMed1984

The effect of agarose and dexamethasone on the nature and production of extracellular matrix components by elastic cartilage chondrocytes.

Chondrocytes isolated enzymatically from rabbit ear cartilage, were cultivated in vitro in the presence of 2% agarose or 0.1 mumol/l dexamethasone. Freshly-isolated chondrocytes suspended in either Eagle's medium or 2% agarose were auto-transplanted intramuscularly. Samples were then examined by light microscopy and transmission electron microscopy. The cells cultivated in vitro rapidly formed confluent multiple overlapping layers filled with a loose matrix consisting of single collagen fibres, proteoglycans and scarce elastic fibres. The number and maturity of the elastic fibres increased substantially after dexamethasone was added. The chondrocytes in intramuscular transplants produced a larger amount of intercellular matrix with many elastic fibres than those cultured in vitro. Addition of agarose to in vitro and in vivo systems selectively suppressed the elastin production but did not diminish the production of elastic fibre microfibrils and other matrix components. This made cultures and transplants of elastic chondrocytes resemble rather hyaline cartilage than the original tissue. It seems that the lack of elastin in the matrix does not result simply from inhibition of elastin secretion or increased elastolysis. It may be related to a reversible change of genetic expression of elastic cartilage chondrocytes under the influence of agarose.

Animals↗