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PubMed1993

Endothelial cell connecting filaments anchor endothelial cells to the subjacent elastic lamina in the developing aortic intima of the mouse.

The ultrastructural association of endothelial cells with the subjacent elastic lamina was investigated in the developing mouse aorta by electron microscopy. In the 5-day postnatal aorta, extensive filament bundles extend along the subendothelial matrix connecting the endothelial cells to the underlying elastic lamina. The connecting filaments form lateral associations with the abluminal surface of the endothelial cells in regions of membrane occupied by membrane-associated dense plaques. On the intracellular face of each plaque, the termini of stress fibers penetrate and anchor to the cell membrane in alignment with the extracellular connecting filaments. Both the stress fibers and the connecting filaments are oriented parallel to the longitudinal axis of the vessel. High magnification electron micrographs of individual endothelial cell connecting filaments reveal features similar to those of elastin-associated microfibrils. Each connecting filament consists of a 9-10 nm linear core with an electron-lucent center and peripheral spike-like projections. From the filaments, small thread-like extensions span laterally, linking the filaments into a loose bundle and anchoring them to the endothelial cell membrane and the surface of the elastic lamina. The filaments also appear heavily coated with electron-dense material; often with some degree of periodicity along the filament length. During development, the number of endothelial cell connecting filaments decreases as the elastic lamina expands and the subendothelial matrix is reduced. In the aortic intima of mature mice, the elastic lamina is closely apposed to the abluminal surface of the endothelial cell and no connecting filaments are seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Actin Cytoskeleton↗
PubMed1983

The taenia of the rabbit colon, an elastic visceral muscle.

The longitudinal musculature (taeniae) of the rabbit proximal colon was studied by phase contrast and electron microscopy. The taenia coli of the rabbit has several structural features which are not found in other visceral muscles of this or other species, and which, on the other hand, are common in certain vascular muscles. Among the characteristics of taenia coli are: highly corrugated muscle cell profiles (even when the muscle is fixed in a resting condition), very high surface-to-volume ratio (1 micron m2/0.5 micron m3), large percentage volume of the extracellular space (about 40%), absence of intramuscular septa, and very large number of elastic fibres, which run mainly longitudinally in broad meshworks parallel to the serosal surface. Several points of contact between elastic fibres and muscle cell membrane occur at all levels along the length of the cells, often involving 11-nm microfibrils; these contacts, and others involving collagen fibrils, are regarded as cell-to-stroma junctions. The taenia coli is virtually devoid of intramuscular blood vessels, including capillaries. The possibility that the lack of capillaries is related to the abundance of elastic material is discussed.

Animals↗
PubMed1975

[Cardiac glomus tumor. Light- and electron microscopic investigations (author's transl)].

A cardiac glomus tumor, first described by Masson, was observed in a 28 year old woman who presented symptoms of cardiac dysfunction. Electron microscopic studies disclose a wide range of differentiation of glomus cells from smooth muscle cells to epitheloid cells. The common feature of both cell types include cytoplasmic microfibrils, fusiform condensations and small vesicles. The endothelial cells also show some structural similarities to these glomus cells. The histogenesis of this cardiac tumor is discussed on the basis of its ultrastructure and its uncommon localization. It is concluded that cardiac glomus tumors arise from primitive mesenchymal cells.

Adult↗
PubMed1988

Mucochondroid (mucous connective) tissues in the heads of teleosts.

The distribution and structure of mucochondroid tissues in the heads of teleosts has been studied in 56 species from 26 families. The tissues could also be called mucous connective tissue and have previously been known as basophilic gelatinous tissue. They are a heterogeneous group of tissues that contain fibroblasts (type example--the subcutaneous mucochondroid of the Cobitidae) or hyaline cells (type example--the mucochondroid around the medulla oblongata and spinal cord of Rasbora heteromorpha), embedded in a pale-staining matrix in which there are variable numbers of collagen fibres and blood vessels. Mucochondroid tissue is especially common beneath the skin, in labial folds, around olfactory and accessory olfactory sacs, in opercular valves and beneath the sensory epithelia of the stato-acoustic organ. The histochemistry of several mucochondroid tissues has been studied in Misgurnus anguillicaudatus, Acanthopsis choirorhynchus, Gnathonemus petersi and Cyclopterus lumpus. They have widely different amounts and types of glycoproteins, glycosaminoglycans and connective tissue fibres. The ultrastructure of subcutaneous mucochondroid is described in Acanthophthalmus semicinctus. Its cells contain little rough endoplasmic reticulum and a small Golgi apparatus, but numerous plasmalemmal vesicles, especially in the cell processes. The matrix contains 23-35 nm diameter granules, collagen and 11-12 nm diameter microfibrils. The similarities between mucochondroid and hyaline cell chondroid (cartilage) at the ultrastructural level, are more obvious than their differences.

Animals↗
PubMed1987

The structural relationship between mesangial cells and basement membrane of the renal glomerulus.

It has been shown by many studies that mesangial cell contraction exerts considerable influences on glomerular filtration dynamics. However, experimental findings about the geometrical changes within the glomerular tuft going along with mesangial cell contractions are lacking. This study analyzes the geometry of mesangial cells and their relationship to glomerular capillaries, especially to the glomerular basement membrane (GBM). By applying a new staining technique of unosmicated specimens for TEM, the cellular outlines of glomerular cells (mesangial, endothelial and epithelial) and the distribution of extracellular matrices can be more easily studied than in conventionally osmicated specimens. It became obvious that mesangial cells and the GBM are extensively connected with each other, either by direct attachments or indirectly by microfibrils. These connections are especially prominent at mesangial angles, i.e. at sites where the GBM deviates from its pericapillary course and covers the mesangium. Thereby, the GBM is not only coupled to the mesangium but--via mesangial cell processes--also to the GBM at the opposing mesangial angle. It seems possible that contraction of mesangial cells can bring the GBM from opposing mesangial angles closer together. Therefore we conclude that the GBM and the contractile mesangial cells together establish a biomechanical unit capable of developing wall tension in glomerular capillaries and of changing the geometry of glomerular capillaries following mesangial contraction or relaxation.

Animals↗
PubMed1989

Fetal membranes and placenta of the African green monkey (Cercopithecus aethiops).

This study examined developmental changes in fetal membranes and placenta of Cercopithecus aethiops from a Carnegie developmental stage 12 embryo to near-term fetuses. Ultrastructurally, yolk sac cells (endoderm and mesothelium) were similar to comparable stages in other primates. Endodermal cells had few apical microvilli, abundant rough-endoplasmic reticulum, electron dense mitochondria and dense bodies. In contrast, mesothelial cells were squamous with numerous microvilli, small mitochondria and a few short strands of rough endoplasmic reticulum. Amnion cells early in gestation were squamous with few microvilli, large glycogen deposits and poorly developed cytoplasmic components. Tight junctions and desmosomes held adjacent cells together. The basal surface was smooth and the basal lamina was distinct. As development proceeded the amniotic cells became cuboidal and possessed numerous microvilli. Cytoplasmic organelles were better developed and glycogen deposits increased by mid-gestation. A thick layer of microfibrils and collagen fibers was prominent below the basal lamina. Near-term, the glycogen had virtually disappeared and the amount of lipid droplets increased. Basal infoldings and podocytic processes and the extracellular matrix had increased. The smooth chorion consisted of pseudostratified columnar cells. Cells had short microvilli, numerous granules and vesicles of variable size and electron density in early gestation. With increasing age, amounts of granules and vesicles decreased, as the endoplasmic reticulum became prominent. The chorionic trophoblast was a continuous layer in mid-pregnancy and its cells had well-developed organelles and inclusions. Late in gestation, the trophoblastic layer became discontinuous and wide intercellular spaces and channels were present. In the placenta, the trophoblastic elements showed features characteristic of primate placenta.

Amnion↗
PubMed1991

Pentosome--a new connective tissue component--is a subunit of amyloid P.

A new minute connective tissue structure, referred to as "pentosome", has been investigated by electron microscopy and its nature has been examined by immunoperoxidase tests. Pentosomes are 3.5-nm wide, particulate structures that have been observed in the posterior chamber of the eye, the connective tissue spaces of the mouse foot-pad and the matrix of the mouse EHS tumor. They are usually found in the vicinity of microfibrils whether they are free or associated with elastic fibers. They tend to be organized into groups forming a three-dimensional semi-crystalline lattice at 10-nm intervals, but are connected by fine filaments. At high magnification, pentosomes appear as hollow structures composed of two parallel pentagons, which respectively measure 2.7 and 3.5 nm, and are held together by a cross-bar. A series of immunoperoxidase tests has only shown antigenicity against a serum protein, the amyloid P component. However, pentosomes are only about one-third the size of the 8.5-nm wide, disk-like segments of the amyloid P molecule. Since they could be subunits of these molecules, such subunits were prepared and compared with pentosomes; they appeared to be identical. It is concluded that the pentosomes found in connective tissue are AP subunits.

Animals↗
PubMed1994

Investigation of the early mineralisation on collagen in dentine of rat incisors by quantitative electron spectroscopic diffraction (ESD).

The earliest crystallites in dentine appear as chains of "dots" in ultra-thin sections viewed by transmission electron microscopy. These dots rapidly coalesce along the longitudinal directions of the collagen microfibrils to form needle-like structures that coalesce preferentially in lateral directions to form ribbon-like or plate-like crystallites. This morphological interpretation is supported by line-scans of the corresponding zero-loss filtered electron spectroscopic diffraction patterns, which demonstrate the crystalline structure of the dentine mineral (apatite). The intensity ratio of the Debye-Scherrer rings of the characteristic Bragg-reflections (002 to 300, together with 1 or 2 unresolved reflections) shows a maximum in the region of early chain-like and needle-like crystallites, decreasing with maturation of the dentine mineral to the ribbon-plate-like crystallites. Detailed investigations using line-scans of the zero-loss filtered electron spectroscopic diffraction patterns through the dentine zone show that the intensity ratio found near the mineralisation front is repeated 3-5 times at distances of about 10-20 microns. This may represent a circadian pattern of mineralisation corresponding to light microscopically visible incremental lines in dentine.

Animals↗
PubMed1993

Collagen fibrillogenesis in a three-dimensional fibroblast cell culture system.

The purpose of this study was to follow collagen fibril formation in a newly developed three dimensional cell culture system. Human neonatal foreskin fibroblasts were grown on a nylon mesh in Dulbecco's Modified Eagles Medium (DMEM) supplemented with 10% fetal calf serum and antibiotics. Fibrillogenesis was initiated by the addition of 50 micrograms/ml ascorbate to confluent cultures. Sample meshes were processed for electron microscopy or immuno-electron microscopy. Fibrils approximately 20-30 nm in diameter, with 67 nm periodicity, were first detected five days after the addition of ascorbate. As cultures progressed, cells organized into parallel layers between which collagen fibers continued to form and increase in diameter. By day 50, fiber diameter ranged from 30 to 80 nm and large bundles were seen. No collagen fibril formation occurred in control cultures to which no ascorbate was added. However, large amounts of microfibrils were observed. Antibodies against the aminopropeptide of type I procollagen were found to bind to fibrils with diameters less than 34 nm while antibodies against the aminopropeptide of type III collagen bound primarily to fibers which ranged from 35-54 nm in diameter. We believe that this system, which morphologically resembles a normal dermis, will serve as an excellent model for the study of collagen fibrillogenesis.

Cells, Cultured↗
PubMed1992

Increase in types IV and VI collagen in cherry haemangiomas.

The capillaries in cherry haemangiomas show perivascular hyalinized sheaths. In order to clarify the nature of this sheath material, the extracellular matrix of cherry haemangiomas from 20 normal volunteers (age range 30-64 years) was investigated using immunohistochemical and electronmicroscopical methods. Antibodies against collagen types III, IV and VI and laminin were used. Hyaluronic acid was visualized using the hyaluronic acid binding region of the cartilage proteoglycan as ligand. Electronmicroscopically, the sheaths contained multilaminated basement membrane-like material, collagen fibres 20-25 nm thick with a periodicity of 67 nm and broad-banded aggregates with a periodicity of 100 nm (zebra bodies or fibrous long-spacing fibres). Immunohistochemically, type IV collagen was stained throughout the whole sheath material. Staining for laminin was more confined to the endothelial side of the sheath. Intense staining for type III collagen and hyaluronic acid was found in the connective tissue of the subpapillary layer and between the cherry haemangioma capillaries. Much weaker staining for type III collagen and no staining for hyaluronic acid were found invariably in an area 4-10 microns thick directly around the capillaries. Both sheath material and intercapillary connective tissue of the haemangiomas showed pronounced staining for collagen type VI. Immunogold staining revealed that type VI collagen was localized to microfibrils 5-6 nm thick and to the broad-banded aggregates with 100 nm periodicity. These findings further underline the assumption that the broad-banded aggregates consist of type VI collagen.

Adult↗
PubMed1987

Stabilization of chitin synthetase and purification of chitosomes from several mycelial Mucorales.

Stability of chitin synthetase in cell-free extracts from mycelial fungi was markedly improved by the presence of sucrose in the homogenization media. Breakage of mycelium in sucrose-containing buffer yielded enzyme preparations from which chitosomal chitin synthetase could be purified by a procedure involving ammonium sulfate precipitation, gel filtration and centrifugation in sucrose density gradients. Purified chitosomes catalyzed the synthesis of chitin microfibrils in vitro upon incubation with substrate and activators. Chitosomal chitin synthetase from the filamentous form of M. rouxii was similar to the enzyme from yeast cells, except for the poorer stability and diminished sensitivity to GlcNAc activation of the former.

Centrifugation, Density Gradient↗
PubMed1979

Septal ultrastructure in Sirobasidium magnum and its taxonomic implications.

The parenthesomes of Sirobasidium magnum (Sirobasidiaceae) are composed of arrays of ampulliform vesicles from whose bases microfibrils connect to bands of striated material in the dolipore orifices. This septal morphology and the associated character of a yeast haplophase are comparable to that found in species of the Tremellaceae and Filobasidiaceae. The similarity of these basic characteristics in these three families supports their separation into the suborder Tremellineae (species of the Tremellales with regular dolipore/parenthesome septa and mycelial monokaryons are grouped in the suborder Exidiineae).

Basidiomycota↗
PubMed1981

The basement membrane complex of the human corneal epithelium.

The present report reviews the fine structure of the basement membrane zone or complex in the normal human cornea and describes its alterations in cases of early and acute keratoconus. In normal human cornea the basement membrane zone is formed by a basal lamina (with a lamina lucida and a lamina densa), "special fibrils", collagen fibrils and assemblies of filaments. These components are less evident in the central region of the cornea than in its periphery. In early stages of keratoconus the basement membrane zone is thickened and the lamina densa displays an irregular course. In acute keratoconus, the basement membrane zone is also thickened and includes a large number of "special fibrils" as well as bundles of "microfibrils" (oxytalan fibers). The conclusion that the basement membrane complex of the corneal epithelium is equivalent to the epidermal-dermal junction of the skin is discussed.

Adult↗
PubMed1979

[Synthesis of elastoidic fibers in the organ culture of human dermis (author's transl)].

Organ cultures of human dermal excisions placed on the chorioallantoic membrane (CAM) of incubated chick eggs showed that a elastoidic fiber type could be achieved under experimental conditions within 5 h. The stages leading up to fiber formation could very well be produced by fibrocytes as well as by the splitting of collagen fibrils. The microfibrils (lacking a periodicity and with a diameter of 60-100 A) are characterized by a strong capacity to bind carbohydrate-proteinrich complexes (proteoglycans and glycoproteins). These then aggregate to elastoidic fibers. The amorphous fiber center remains strongly attractive for binding cations. This fiber type is then compared to the (elastoidic) fibers present in senile Elastosis and Pseudoxanthoma elasticum. Finally, the possibility of using CAM-cultures as experimental means for simulating such diseases is discussed.

Animals↗
PubMed1987

The -SH and SS positive components in dermal connective tissues: a study by N-(7-dimethylamino-4-methyl-3-coumarinyl) maleimide (DACM) stain.

Although -SH and SS positive components in dermal connective tissue have been observed by N-(7-dimethylamino-4-methyl-3-coumarinyl) maleimide (DACM) stain, their nature is as yet unknown. In our study, we stained several organs such as human skin, rabbit aorta, auricle, and trachea using DACM stain, and studied the distribution of -SH groups and SS linkages among the elastic fibers in those organs. In the dermis of human skin, a moderately strong fluorescence by both -SH and SS stain was present all over the layer, especially in the lower half among collagen fibers in a fine linear or wavy pattern, and a fluorescence ascending vertically from the lower papillary dermis toward the epidermis was also observed. In rabbit aorta, a strong fluorescence by both -SH and SS stain was observed on well-developed elastic fibers. In the matrix of rabbit elastic cartilage, a strong reticular fluorescence by both -SH and SS stain was present. On the other hand, in rabbit hyaline cartilage, no -SH fluorescence was present on any components of the cartilage. However, though a diffuse moderate fluorescence for SS linkages was observed in the matrix, there was no reticular fluorescence such as that seen in the elastic cartilage. These results suggest that the -SH and SS components observed in the dermis by DACM stain are in fact elastic fibers, more precisely, "elastic tissue microfibrils".

Animals↗
PubMed1984

Morphological anomalies induced by Congo red in Aspergillus niger.

Aspergillus niger germ tubes were exposed for 6 h to 0.15 mg/ml of Congo red, a stain which prevents chitin microfibril assembly. The most evident alterations, detected under ultraviolet light and by transmission and scanning electron microscopy, concerned the hyphal tips which burst or, most frequently, expanded into bulges. In the latter structures, new hyphal tips appeared which, after giving rise to more or less developed hyphae, were themselves converted into new bulges. Therefore, segments derived from isotropic and polarized growth alternated in the organisms exposed to the dye. An interpretation of these abnormalities is advanced based upon the assumption that the maintainance of a regular gradient of wall viscosity in the hyphal extension zone depends primarily on the capability of glycan chains to form crystalline aggregates of increasing complexity.

Aspergillus niger↗
PubMed1994

Of mice and Marfan: genetic linkage analyses of the fibrillin genes, Fbn1 and Fbn2, in the mouse genome.

The fibrillin genes, FBN1 and FBN2, encode large extracellular matrix glycoproteins involved in the structure and function of microfibrils. Mutations in FBN1 are found in patients with Marfan syndrome, a heritable connective tissue disease that primarily affects the cardiovascular, ocular, and skeletal systems. We extended the studies of these genes by determining their chromosomal position in the mouse genome. Restriction fragment length polymorphisms (RFLPs) between the progenitors of an interspecific backcross involving AEJ/Gn and Mus spretus mice were used to establish the segregation patterns of the murine homologs, Fbn1 and Fbn2, in the backcross progeny. The results position Fbn1 between the B2m and Illa genes on mouse Chromosome (Chr) 2 and establish its candidacy for the Tight skin (Tsk) mutation. The results position Fbn2 between the D18Mit35 and Pdgfrb loci in the central region of mouse Chr 18. Fbn2 maps near three mutations [bouncy (bc), plucked (pk), and shaker with syndactyly (sy)] and may be a candidate for the pk mutation.

Animals↗
PubMed1980

Sclerema neonatorum. Light and electron microscopic studies.

Specimens from four cases of sclerema neonatorum were studied by light and electron microscopy. The connective tissue bands of the cutis and subcutis were thickened and alternated with loosely distributed bands in broad, distended areas of basal substance. Extensive areas areas filled with cross-banded structures were observed in the dermis. In the interlobular septa of the subcutaneous and perirenal fat splitting of fibers into microfibrils was visible. Changes in the capillaries and small blood vessels were also noted. Neither fat cells filled with rosettes of needle-like crystals, nor any inflammatory infiltrates of foreign body type giant cells were found in subcutaneous tissue.

Adipose Tissue↗