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PubMed1995

[Trabecular meshwork and elastin].

Evidence that elastic fibers with elastin exists in the trabecular meshwork (TM) and play an important role in aqueous outflow resistance is presented. The elastic fibers consist of abundant microfibrillar components containing glycoproteins and amorphous components containing elastin. If TM tissues are digested with elastase, the cells composing trabecular sheets and Schlemm's canal are separated with a decrease of elastin and come in contact with each other with reproduction of elastin. When the anterior segments of eyes are perfused with elastase, the intraocular pressure drops with a decrease of outflow resistance. A large quantity of elastin exists in fine fibrils lying underneath the trabecular wall of Schlemm's canal in primary open angle glaucoma (POAG) eyes, in pseudoexfoliation (PE) materials of PE glaucoma eyes and in basement membrane and fine fibril-like materials of steroid glaucoma eyes. In congenital and juvenile glaucoma eyes, however, instead of elastin, fibronectin localizes in basement membrane and fine fibril-like materials. When TM tissues respond to steroid hormone, the tissues synthesize and secret microfibrils and elastin, components of the elastic fibers. Elastin gene expresses in human TM. Orally administered elastase is transferred in aqueous humor and digests elastin in TM. Therefore it is possible that such a drug decreases the outflow resistance of glaucoma eyes.

Animals↗
PubMed1995

Ultrastructure of elastin.

Almost all structural studies on elastin have been done in higher vertebrates, in which it is organized as an extracellular network of branched fibres which vary from fractions f microns to several microns in diameter. By conventional electron microscopy, elastin appears amorphous. By both freeze-fracture and negative staining on cryosections, it can be resolved as beaded filaments 5 nm in diameter forming a 3D meshwork that, upon stretching, becomes oriented in the direction of the force applied. This filamentous aggregation of elastin molecules is confirmed in vitro by the observation that its soluble precursor, tropoelastin, shows a strong tendency to associate into short 5 nm-thick filaments that, with time, become longer and aggregate into bundles of various dimensions. If chemically fixed and embedded, these aggregates appear amorphous and identical to natural elastin fibres. The tendency of tropoelastin to aggregate into 4-5 nm-thick beaded filaments, which then associate into 12 nm-thick filaments forming a 3D network, has been observed by atomic force microscopy for recombinant human tropoelastin. Therefore, the amorphous structure of elastin seems to be a technical artefact. Apart from elastin-associated microfibrils, which are always present at the periphery of growing elastic fibres and probably have a role more complex than being a scaffold for tropoelastin aggregation in vivo, the elastic fibres seem to be composed of several matrix constituents, which are different in different organs and change with age and in pathological conditions. This is demonstrated by immunocytochemical studies on ultrathin sections.

Animals↗
PubMed1996

Effect of poly(vinylsulfonate) on murine AA amyloid: a high-resolution ultrastructural study.

In experimental murine inflammation-associated amyloidosis (AA amyloidosis), an interaction between heparan sulfate and serum amyloid A (SAA), the AA precursor, has been demonstrated and is believed to play an important role in AA amyloidogenesis. Poly(vinylsulfonate) sodium salt (PVS) can arrest AA amyloid induction and cause established amyloid deposits to regress. PVS is thought to have this property by virtue of limited anionic structural similarities it has to heparan sulfate. In the present study, a comparison has been made of the in situ light microscopic and high-resolution ultrastructure of amyloid deposits before and after PVS treatment. As shown recently in situ, AA fibrils from untreated mice are composed of an outer layer of heparan sulfate proteoglycan and a 1- to 2-nm filament network of AA protein. This layer encloses a microfibril-like structure composed of chondroitin sulfate proteoglycan wound around a core of amyloid P component. After treatment with PVS, both the heparan sulfate proteoglycan and the AA filament network are lost from the fibrils, and the more central portion disintegrates into the chondroitin sulfate proteoglycan with associated amyloid P subunits. These findings add further support to the concept that heparan sulfate proteoglycan is important in amyloid fibril structure, and interference with its binding interactions with the amyloid filament protein provides a point of therapeutic attack.

Amyloidosis↗
PubMed1995

Ultrastructural Localization of elastin-like immunoreactivity in the extracellular matrix around human small lymphatic vessels.

The distribution of elastin-like immunoreactivity around small lymphatic vessels was investigated in three different human tissues (skin, heart and dental pulp) using high resolution immunocytochemistry. Quantitative assessment of the immunogold reaction was performed with an image analysis system. Intense and moderate elastin-immuno-reactivity was detected in the extracellular matrix around small lymphatic vessels of the skin and heart, respectively. By contrast, absence of immunostaining was observed around lymphatic vessels in the dental pulp. Although the staining was mostly detectable on the non-fibrillar amorphous component of the extracellular matrix, some microfibrils were also immunostained in close proximity to the lymphatic vessel wall. These findings support the concept that small lymphatic vessels may be heterogeneous with respect to the composition of the extracellular matrix around their wall. The observation that it is possible to observe small lymphatic vessels displaying low or no elastin-immunoreactivity in the adjoining matrix militates against the hypothesis that elastic fibers play a pivotal role in the mechanisms that regulate the function of small lymphatic vessels.

Elastin↗
PubMed1996

Generalized acquired cutis laxa associated with coeliac disease: evidence of immunoglobulin A deposits on the dermal elastic fibres.

Acquired cutis laxa (ACL) is an uncommon elastolytic disorder of unknown aetiology. In rare instances, ACL has been reported in association with autoimmune diseases and dermal deposit of immunoglobulins, suggesting that destruction of elastic tissue may be immunologically mediated. We report a 35-year-old man with generalized acquired cutis laxa (GACL) associated with a persistent papular erythematous eruption that histopathologically showed some resemblance to dermatitis herpetiformis. A marked reduction and degeneration of dermal elastic fibres was noted in biopsies from loose-hanging skin. Direct immunofluorescence from non-inflammatory loose skin revealed granular immunoglobulin A (IgA) deposits at the basement membrane zone and fibrillar IgA deposits in the dermal papillae. IgA deposits were also observed on the elastic fibres of the reticular dermis. Electron microscopy of skin from the submammary fold revealed fragmented elastic fibres, partial absence of peripheral microfibrils and abundant neutrophils, some of which were degranulated and adjacent to elastic fibres. Immunoelectron microscopy of an erythematous papule revealed IgA deposits around dermal elastic fibres. Antigliadin, antireticulin and antiendomysium antibodies were present. Jejunal biopsies showed a gluten-sensitive enteropathy. A possible IgA-mediated immune mechanism for the development of GACL in our patient is suggested.

Adult↗
PubMed1995

A syndrome of fibrosing pleuritis, pericarditis, and synovitis with infantile contractures of fingers and toes in 2 sisters: "familial fibrosing serositis".

We describe a family in which 2 sisters born to consanguineous parents developed childhood onset fibrosing pleuritis in association with constrictive pericarditis and bilateral deforming arthropathy of large and small joints of upper and lower extremities including flexion contractures of several fingers (camptodactyly) and toes. One patient also had mitral value prolapse. Histopathological examination of the synovium and pericardium revealed fibrosis, and ultrastructural study of synovium showed abundant inter and intracellular mesh of 9 nm microfibrils. We describe this distinct clinicopathological entity with pleiotropic manifestations, the common features of which appears to be the fibrosis of serous membranes. Therefore, the term "familial fibrosing serositis" is proposed for this entity.

Adolescent↗
PubMed1996

CD97 is a processed, seven-transmembrane, heterodimeric receptor associated with inflammation.

CD97 is a receptor that spans the membrane seven times, a defining feature of G protein-coupled receptors. CD97 is predominantly expressed in leukocytes, but the function and accurate protein structure of this receptor have not been described. We show here that CD97 has the novel property among G protein-coupled receptors characterized to date of being processed intracellularly in either the endoplasmic reticulum or early Golgi from a proprotein into a noncovalently associated two-subunit structure that becomes expressed on the cell surface and is composed of a large extracellular protein (CD97alpha) and a seven-membrane spanning protein (CD97beta). CD97beta is part of an evolutionarily conserved subfamily of four proteins, including two Caenorhabditis elegans proteins of as yet unknown function, which is distinct from but most closely related to the glucagon receptor family. CD97alpha exists in three alternatively spliced isoforms that contain between three and five epidermal growth factor (EGF)-like repeats that are related to the calcium binding EGF-like repeats in the microfibril protein fibrillin. Leukocytes strongly positive for CD97 are concentrated at sites of inflammation relative to CD97 expression in normal lymphoid tissues. Soluble CD97alpha was found in body fluids from inflamed tissues, suggesting that a functional consequence of the CD97 heterodimeric structure is the stable existence of CD97alpha in a cellfree form. CD97 appears to be a multifunctional protein that may play a signal transduction role associated with the establishment or development of an inflammatory process.

Alternative Splicing↗
PubMedDate not supplied

[The comparative structural-functional characteristics of the cytoskeleton of animals and higher plants].

The peculiarities of structure, location and dynamics of microtubules (Mts) and microfilaments (Mfs) in cells of animals and of higher plants (growing by elongation and apical growth) are discussed. It is shown that in animal cells Mt-skeleton located mainly in the depths of the cytoplasm is responsible for directed intracellular movement and characteristic position of cell components. Animal Mf-skeleton forming a dense network is most often aggregated at the cell periphery. Its primary function is the shaping and locomotion of the cell. In contrast, one of the most characteristic features of the cytoskeleton in the elongating plant cells is the presence of only cortical Mts closely linked to the plasmalemma. Higher plant Mt-skeleton is involved primarily in the orientation of newly depositing cellulosic cell wall microfibrils and thus it controls the direction of cell growth which determines the cell shape. It also mediates (by means of preprophase Mt-band) the orientation of cytokinesis. Thus in plants the principal role of the Mt-skeleton is the control of morphogenesis. Far less important is supporting function of plant Mts. The nuclear envelope is main Mt organizing center in plant cells. Unlike Mts, plant Mf-skeleton is concentrated in the cell depths and is the involved in the intracellular transport and characteristic positioning of the cell components. Apically growing cells such as root hairs typically contain deeply distributed Mts in addition to cortical ones. The former may participate in the transfer of nucleus and/or plastids.

Animals↗
PubMed1996

[Pathology of aortic dissection].

Aortic dissection is not a popular disease but it should be listed in the disease to be excluded especially in acute emergent cases, because of its serious and protean clinical manifestations. While DeBakey classification was used over 30 years. Stanford classification is now widely accepted for its clinical availabilities. The features of the aortic dissection are 1) presence of the intimal tear at the proximal end in almost all cases, 2) its frequent location in the ascending aorta and aortic segment just distal to the left subclavian artery, and 3) the dissected plane at the outer media or medial-adventitial border. Systemic hypertension is frequently noticed in cases with aortic dissection. These features suggest hemodynamic effect as a pathogenic factor in addition to mural fragility of the aorta. Aortic dissection is frequently encountered in Marfan syndrome and other heritable diseases of connective tissue. Concerning Marfan syndrome, mutation of fibrillin gene was confirmed. Fibrillin is a microfibril consisting of glycoprotein closely bound to elastin. Therefore, traditional "cystic medial necrosis" which was referred as a principal morphological change corresponding to aortic dissection is now thought to be a secondary change to the aortic injuries occurred in the aortic wall.

Aortic Dissection↗
PubMedDate not supplied

[Allergy and histamine release (author's transl)].

Histamine is released from mastocytes and basophils polymorphonuclears. This occurs particularly in reaginic type of allergy. The different phases of the reaginic process has been studied: IgE bridgings with antigens, cell membrane activation, cytoplasmic biochemical reactions involving cyclic AMP and GMP leading to microtubules activities, contraction of microfibrils and degranulation. Calcium and magnesium contribute to the regulation of histamine release. Histamine releases could also be seen in non reaginic type of immuns allergic reactions by way of direct or indirect activation of complements, by stimulation of PAF, etc...Finally, quite a few substances could also provoke histamine release of non immunologic type (physical agents, snake and bee venoms chemical substances in micro or macromollecular forms used in therapeutics...). Their mechanisms of action are various; yet in a way, they present similaritis with immunoallergic reactions. In practice, it is often difficult to assert the allergic nature of a histaminic reaction. Immunologic evidences should be cautioniously searched before any conclusion.

Basophils↗
PubMed1997

The HNK-1 epitope and the elastic fiber system of the human ciliary body. An immunoelectron microscopic study.

PURPOSE: To localize at the electron microscopic level the cell adhesion-related HNK-1 carbohydrate epitope in the inner connective tissue layer (ICTL) of the human ciliary body. METHODS: Seven specimens representing the pars plicata (age range, 12 to 86 years) and three specimens representing the pars plana (age range, 29 to 71 years) of the ciliary body were sampled at death from eight normal human eyes. Three additional specimens from the pars plicata were taken from three eyes with exfoliation syndrome (age range, 78 to 81 years). All specimens were embedded in LR white resin and studied by postembedding immunogold labeling using two monoclonal antibodies (mAbs) HNK-1 and NC-1 in detecting the HNK-1 epitope. RESULTS: In the ICTL of the pars plicata and the pars plana, mAbs HNK-1 and NC-1 constantly bound to the surface of fibroblast-like cells present in the subepithelial connective tissue matrix. The immunoreaction was localized along the cell membrane, both around the cell body and around its long, slender cytoplasmic processes. Long microfibrillar bundles, which consisted of approximately 10-nm thick microfibrils in close association with these subepithelial matrix cells and elastic fibers, were also labeled. The periphery of elastic fibers was likewise immunolabeled for the HNK-1 epitope. The reaction pattern was essentially the same, regardless of age and presence or absence of exfoliation syndrome. CONCLUSIONS: At the ultrastructural level, the HNK-1 epitope in the ICTL is a common denominator to the subepithelial matrix cells, microfibrillar bundles, and elastic fibers. This suggests that the subepithelial matrix cells secrete this epitope, and that molecules hearing it may be involved in joining these connective tissue elements that structurally stabilize the ciliary body.

Adolescent↗
PubMed1997

Vortex keratopathy in a patient with multiple myeloma.

PURPOSE: We report a 52-year-old woman with vortex keratopathy (cornea verticillata) of unknown cause in whom multiple myeloma was found 18 months later. METHODS: Surgical biopsy of conjunctival crystalline deposits, which were stained immunohistologically and analyzed ultrastructurally, as well as hematologic workup for multiple myeloma, were performed. RESULTS: Light microscopy of conjunctival deposits revealed plasmacytoid infiltrates in the conjunctiva, which stained monoclonally for immunoglobulin G (IgG)-kappa light chains. Transmission electron microscopy showed intracellular hexagonal crystalline structures and extracellular microfibrils. Hematologic tests confirmed the diagnosis of multiple myeloma. CONCLUSION: Multiple myeloma is one of the many causes of vortex keratopathy.

Antineoplastic Agents↗
PubMed1998

A comparative histologic study of the fibrillin microfibrillar system in the lens capsule of normal subjects and subjects with Marfan syndrome.

PURPOSE: To gain a better understanding of the pathogenesis of ectopia lentis and myopia in Marfan syndrome, studies were performed to determine the distribution and structure of fibrillin microfibrils in the lens capsule of normal subjects and of subjects with Marfan syndrome. METHODS: Frozen sections and/or flat mounts of lens capsules were prepared from six autopsy eyes, nine surgical capsulotomy specimens obtained at the time of cataract extraction, and five capsules from patients with Marfan syndrome obtained at intracapsular lens extraction. Avidin-biotin-peroxidase complex (ABC) immunoperoxidase or immunofluorescence staining with monoclonal antifibrillin antibody was used to localize fibrillin in lens capsules. Image analysis was also performed to compare the amount of fibrillin expression in normal and Marfan syndrome capsules. RESULTS: Based on fibrillin staining patterns, we identified three distinct zones in the equatorial and periequatorial regions of the normal lens capsule. Zone I, a 0.75-mm-wide peripheral ring of the anterior capsule, contained radial bundles of fibrillin fibers. In Zone II, a 1-mm-wide meshwork of fibrillin-rich fibers encircled the equator and served as an insertion platform for zonular fibers. Zone III was composed of radial, 0.1-mm-wide bands arranged in a periodic fashion in the most peripheral part of the posterior capsule. Fibrillin fibers were abnormal and disrupted in all three zones in patients with Marfan syndrome. The amount of fibrillin staining per unit area was significantly reduced in Marfan capsules compared with normal capsules (16-26% versus 49-56% per unit area, respectively; P < 0.001). CONCLUSIONS: Fibrillin was a major constituent of the peripheral and equatorial areas of the lens capsule. Zonular fibers, also rich in fibrillin, insert into the equatorial region, primarily in Zone II. Possibly, fibrillin played a role in the ability of the lens to change its configuration during accommodation. The observed qualitative and quantitative abnormalities in fibrillin expression in the lens capsule of patients with Marfan syndrome supported a causal relationship to lens abnormalities in these patients.

Actin Cytoskeleton↗
PubMed1996

Distribution of proteoglycans in the trabecular tissue of eyes with neovascular glaucoma.

We investigated histo-chemically the composition and distribution of proteoglycans in the trabecular tissue of eyes with neovascular glaucoma. Cupromeronic blue in combination with a series of enzyme digestions and nitrous acid treatment were used. The spaces between the trabecular beams were lined by a single layer of vascular endothelium and were filled with red blood cells. A basal lamina and microfibrils were detected just beneath the newly formed vascular endothelial cells. Chondroitin-sulfate- and dermatan-sulfate-type proteoglycans were present in association with collagen fibrils in the extracellular matrix. Heparan-sulfate-type proteoglycans were present in association with the basal lamina of both the vascular endothelial cells and the trabecular cells. It is unlikely that these abnormalities in the type or distribution of proteoglycans in the trabecular meshwork have a major role in the pathogenesis of glaucoma.

Adult↗
PubMed1976

[The development of arterial thrombi].

The factors involved in arterial thrombosis include the endothelial and subendothelial cells of the arterial wall, platelets and other blood cells, plasma factors and blood flow. An arterial thrombus arises from an interaction between platelets and the subendothelium (basement membrane and microfibrils) which has been shown by recent experiments to have a thrombogenic propensity. The particular structure of the subendothelium and its glycoprotein membrane receptors for platelets is implicated on thrombogenesis which requires the intervention of von Willebrand's factor; the well-known role of collagen is also important. An arterial thrombosis may evolve into a mural thrombus or may spread or form an embolus.

Arterial Occlusive Diseases↗
PubMed1997

[Marfan's syndrome. Cardiovascular manifestations and therapeutic indications].

Marfan's syndrome is a disease of collagen microfibrils, the essential composition of which, fibrillin, is defective. The coding gene of this large protein has been localised on chromosome 15 and partially cloned. Its mutation is transmitted in the autosomal dominant mode. It is common, affects many organs, especially those rich in collagen. They include the skeleton, the eye and cardiovascular system. The prognosis of these patients depends on the degree of cardiovascular involvement; the aorta is the principal site of the lesions, particularly the aortic root which tends to develop aneurysmal dilatation, then dissection, the main cause of premature death of these patients. Mitral valve prolapse giving rise to mitral regurgitation may also be observed. Much progress has been made is recent years in the management of Marfan's syndrome, especially in ultrasound follow-up of the aortic root and the definition of risk factors for dissection. In parallel, advances have been made in the treatment, both medical with the use of betablockers to try to slow progression to aneurysm, and surgical, in replacement of the aorta and aortic valve in time and under optimal conditions. Life expectancy is thereby significantly increased. Similar progress has been made to allow these patients to have a pregnancy, classically thought to carry a high risk of maternal death.

Adrenergic beta-Antagonists↗
PubMed1997

[Fibrillary glomerulopathy].

The authors present an account on contemporary knowledge of the diagnosis and differential diagnosis of fibrillar glomerulopathies. The latter are characterized by extracellular localized microfibrils and microtubules resp. in the glomeruli of the kidneys, their diameter being 8-60 nm. They are divided into amyloid and non-amyloid types. The others are classified according to the immunofluorescent finding into immunoglobulin positive and negative ones. The differential diagnosis is important in particular in immunoglobulin positive ones as they are present in serious diseases such as cryoglobulinaemia, monoclonal gammapathy, systemic lupus erythematosus and immunotactoid glomerulopathy.

Adult↗
PubMed1998

Increased expression of fibrillin-1 in human corneas with bullous keratopathy.

PURPOSE: To characterize the expression of fibrillins, microfibril components, in human corneas with pseudophakic/aphakic (PBK/ABK) bullous keratopathy. METHODS: Normal and PBK/ABK corneas were stained by immunofluorescence for fibrillin-1 and -2. The expression of fibrillin-1 messenger RNA (mRNA) was studied by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and Southern analysis. RESULTS: Only fibrillin-1 was detected in normal and diseased corneas. As described previously, in normal corneas, it was found in the limbal stroma and basement membrane (BM) and in the peripheral corneal epithelial BM for a short distance near the limbus. Central corneal BM, stroma, and Descemet's membrane were negative. All PBK/ABK corneas were positive for fibrillin-1, which was detected in fibrillar deposits at the endothelial face of Descemet's membrane, in the epithelial BM, subepithelial fibrosis areas, and posterior collagenous layer. By RT-PCR, low levels of fibrillin-1 mRNA were detected in normal corneas, and they increased significantly in PBK/ABK corneas. CONCLUSION: The deposition of fibrillin-1, together with tenascin-C, in PBK/ABK corneas may be part of an abnormal fibrotic/wound-healing process that occurs during the development of postsurgical corneal edema with the formation of bullae and posterior collagenous layer.

Actin Cytoskeleton↗