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PubMed1995

Morphology and morphogenesis of hepatitis E virus (strain 87A).

The morphology and morphogenesis of isolated hepatitis E virus (HEV, strain 87A) were observed by electron microscopy (EM) and immune electron microscopy (IEM). Progressively developing local vesicles, virions accumulation in crystalline arrays and viroplasmic focus were seen in cytoplasm of infected cells. Replication and assembly of the new generation viruses were closely associated with rough endoplasmic reticulum (RER), inclusion body (IB) and microfibrils. Condensation and margination of chromatin, dispersion of nucleolar material, nuclear membrane alteration and masses of threads, granular material, and fibrillar component of the nucleus were frequently found. These changes revealed that this strain virus was confirmed as a RNA virus. The shape of the virus particles appeared approximately spherical whether the specimens were from the tissue culture crude suspension or purified highly concentrated preparations. The size of the virion was about 30 nm in diameter. The viral particles appeared unsmooth and irregular in outline. The spike-like structures may be occasionally observed on the surface of some viral capsides. The diameter of the strain 87 A virus is larger than the picornavirus and smaller than the calicivirus. This strain virus is different from classical calicivirus in without the cup-shaped surface depressions. The new genus, heparnavirus genus of caliciviridae family should be proposed for HEV.

Hepatitis E virus↗
PubMed1995

Thrombospondin modulates human breast adenocarcinoma cell adhesion to human vascular endothelial cells.

Thrombospondin (TSP), a M(r) 450,000 cytoadhesive glycoprotein, has been shown to potentiate tumor cell metastasis in mice by a mechanism that involves the hemostatic system of the host. In this study, the potential involvement of TSP in the interaction of human mammary adenocarcinoma MCF-7 cells with human umbilical vein endothelial cells (HUVECs) in culture was investigated. Using an ELISA, preconfluent HUVECs synthesized 100-fold more TSP than did MCF-7 cells during 24 h of culture (20 versus 0.2 microgram/10(6) cells). Confocal microscopy localized TSP within intercellular junctions between aggregated MCF-7 cells in suspension. On adherent cells, TSP exhibited a patchy distribution both on the cell surface and in the cytosol. In HUVECs, TSP strongly stained the perinuclear space and was also found in association with cytoskeletal microfibrils. Flow cytometric analysis indicated the presence of a large number of unoccupied receptors for TSP on MCF-7 cells. Binding studies using [125I]TSP demonstrated the presence of 1.6 x 10(6) sites/cell with an apparent Kd of 28 nM. Attachment of radiolabeled MCF-7 cells to a TSP-coated substrate and to HUVEC monolayers was inhibited in the presence of a polyclonal antibody to TSP (10 micrograms/ml) or increasing concentrations (1-10 micrograms/ml) of soluble TSP. Neither nonimmune IgG nor the cell adhesion peptide Gly-Arg-Gly-Asp-Ser (100 micrograms/ml) inhibited these interactions. Inhibition was also observed with heparin (10 micrograms/ml), suggesting the participation of TSP heparin-binding domain(s) and heparin-like molecules. In the presence of an excess of soluble TSP or anti-TSP antibody, MCF-7 cells did not form aggregates in suspension and preformed aggregates were readily dissociated by the addition of soluble TSP. These results indicate that mammary adenocarcinoma cells use TSP to form aggregates and to attach to human endothelial cells. These interactions may have physiological implications during the hematogenous spread of tumor cells.

Adenocarcinoma↗
PubMed1994

Differential allelic expression of a fibrillin gene (FBN1) in patients with Marfan syndrome.

Marfan syndrome is a connective-tissue disorder affecting cardiovascular, skeletal, and ocular systems. The major Marfan locus has been identified as the FBN1 gene on chromosome 15; this codes for the extracellular-matrix protein fibrillin, a 350-kD constituent of the 8-10-nm elastin-associated microfibrils. We identified five MFS patients who were heterozygous for an RsaI restriction-site dimorphism in the 3' UTR of the FBN1 gene. This expressed variation was used to distinguish the mRNA output from each of the two FBN1 alleles in fibroblast cultures from these five patients. Three of the patients were shown to produce < 5% of the normal level of FBN1 transcripts from one of their alleles. This null-allele phenotype was not observed in 10 nonmarfanoid fibroblast cell lines.

Adult↗
PubMed1994

Toxocara canis (Nematoda, Ascarididae): ultrastructure of the rachis and the ovarian wall.

The oogonia and oocytes in the ovaries of Toxocara canis are joined to a cytoplasmic process called the rachis. The rachis is a much branched cytoplasmic mass without cell components in the germinal zone. At the end of the germinal zone and in the growth zone the cytoplasmic mass is formed into a central axial cylinder, containing small dense granules, lipid drops and glycogen. Throughout the growth zone shell granules similar to those present in the oocytes are also present in the rachis. Anterior to the opening of the ovaries into the oviduct the rachis disappears. The ovarian wall is composed of epithelial cells, adjoining the basal lamina. They are characterized by the presence of large numbers of mitochondria, especially in the germinal zone. The epithelial cells in the growth zone also contain rough endoplasmic reticulum, ribosomes and bundles of microfibrils. A dense tubular material occurs between the basal membrane of the epithelial cells and the basal lamina as well as in the wall intercellular spaces in the ovarian growth zone. Multivesicular labyrinth-like formations can also be observed in the epithelial intercellular spaces in the central portion of the T. canis ovary.

Animals↗
PubMed1994

Lectin electron microscopic histochemistry of the pseudoexfoliative material in the skin.

PURPOSE: To investigate the hypothesis that pseudoexfoliation (PSX) syndrome is a systemic disorder, the authors studied the composition of glycoconjugates in the intraocular and extraocular PSX material at the electron microscopic level, using a panel of lectins as cytochemical probes. METHODS: The authors examined 8 lid skins, 11 trabecular tissues, and 3 cataractous lenses from human eyes with PSX syndrome. Tissues were processed for electron microscopical histochemistry and stained with PNA, RCA120, DBA, SBA, ConA, WGA, UEA-I, and Lotus, with an indirect lectin-colloidal gold technique. RESULTS: Both the intraocular and extraocular PSX materials manifested almost identical reactivity to lectins, which indicated that glycoconjugates in the PSX material contained with sugar residues of galactose (PNA, RCA120), alpha-mannose (ConA), and N-acetyl-D-glucosamine (WGA). On the other hand, it was indicated that sugar residues of N-acetyl-D-galactosamine (DBA, SBA) and fucose (UEA-I, Lotus) were absent. Granular inclusions and microfibrils in the capsule and ocular zonules were stained similarly and weakly. CONCLUSIONS: The intraocular and extraocular PSX materials contained the same sugar residues of glycoconjugates, which suggested that those materials had the same nature. This study, the first documentation of lectin-binding sites on the extraocular PSX material, supported the hypothesis of PSX syndrome as a systemic disorder.

Exfoliation Syndrome↗
PubMed1994

Calcium binding, hydroxylation, and glycosylation of the precursor epidermal growth factor-like domains of fibrillin-1, the Marfan gene protein.

The extracellular matrix protein fibrillin-1 is a major component of elastic microfibrils, which are complex assemblies of several proteins and are found in most connective tissues, frequently associated with elastin. Fibrillin-1 contains 43 precursor epidermal growth factor-like (pEGF) domains that have a consensus sequence for calcium binding. The calcium binding potential of a fibrillin-1 pepsin fragment (PF2) was quantitatively analyzed using microvolume equilibrium dialysis. Peptide sequence data and pepsin fragment size determination indicate that PF2 contains seven pEGF domains, each with the calcium binding consensus sequence. Scatchard plot analysis of the calcium binding data shows that PF2 has six to seven high affinity binding sites with a Kd = 250 microM at pH 7.5. There is a second overlapping consensus sequence in the pEGF domains for beta-hydroxylation of a specific Asp/Asn residue. Five partially hydroxylated Asn residues have been identified by protein sequence analysis of fibrillin-1 fragments. This is the first demonstration of this modification in a connective tissue protein. The calcium binding consensus sequence also contains a conserved Ser residue with an apparently novel modification, which causes the Ser residue to behave like an Asp residue during protein sequencing. Marfan syndrome, a heritable disorder of connective tissue, is known to be associated with mutations in the FBN1 gene. Most of these mutations have been found in pEGF domains, frequently substituting Cys for another amino acid, destroying the pEGF motif secondary structure along with its calcium binding potential. Other mutations cause the substitution of single amino acids in the calcium binding consensus sequence, which could affect calcium binding but also the hydroxylation of Asp/Asn residues or the modification of Ser residues.

Amino Acid Sequence↗
PubMed1976

[Vascular subendothehlium: structure and functions (author's transl)].

Two subendothelial structures, glomerular basement membrane and arterial subendothelium, were compared regarding their biochemistry and ultrastructure and their role in physiology and pathology. Filtration function of the glomerular basement membrane can be related to the presence of three layers which are superimposed on each other and which differ regarding the orientation and density of the microfibrils. The arterial subendothelium which is a mixture of amorphous material, microfibrilis, elastin and collagen, with a still unknown orientation of these components, limits the transport of many blood molecules and reinforces the endothelial barrier. A striking difference is observed in the thrombogenicity of these two structures, especially in their reactivity towards platelets. This can be related to the presence of collagen IV in the glomerular basement membrane and of collagen III in the arterial subendothelium: in both cases adhesion of platelets can be observed. The presence of platelet aggregates on the subendothelial surface may also be seen. This is probably due to the presence of collagen III which is known to be able to induce the platelet release reaction and thereby promotes aggregation.

Animals↗
PubMed1993

Analysis of early hard tissue formation in dentine by energy dispersive X-ray microanalysis and energy-filtering transmission electron microscopy.

Thin cryosections and sections of embedded tissue were prepared from dentine of cryofixed rat incisors. Energy dispersive X-ray microanalysis (EDX) and electron energy-loss spectroscopy (EELS) have been applied to study the calcium and phosphorus distribution in predentine of these incisors. A small enrichment of calcium and phosphorus was found in the predentine zone near the dentine border. Element distributions were correlated with analyses of the early crystal formation in dentine. These investigations were carried out by parallel applications of electron spectroscopic diffraction (ESD) and electron spectroscopic imaging (ESI) using zero-loss filtering. It was found that the earliest crystal formations already showed the lattice of the hexagonal mineral apatite. They form parallelly arranged chains of dots which coalesce rapidly to form "needle-like" crystallites along the collagen microfibrils.

Animals↗
PubMed1994

[Electron microscopic histochemical study in human trabecular meshwork--Second report: location of glycoconjugate residues using lectins].

The location of fourteen lectins in normal human trabecular meshworks were investigated with the electron microscope. The specimens were embedded in Lowicryl K4M at low temperature. Ultrathin sections were stained with biotin labeled lectins and colloidal gold labeled streptoavidin and observed with the electron microscope. ABA, ConA, DSA, PHA-E1, PHA-L4, WGA, LCA, and RCA120 were localized around fine fibrils underneath the endothelium of the trabecular wall of the Schlemm's canal (type I plaque) and collagenous fibers in the corneoscleral meshworks. ABA, ConA, and DSA were localized on the long-spacing collagens, basal membrane, microfibrils of elastic fiber (type II plaque), and fine granular (type III plaque). The present study indicated that extracellular matrices of normal human trabecular meshworks contained specific glycoconjugate residues.

Aged↗
PubMed1994

[Dexamethasone effects of protein synthesis on organ-cultured human trabecular meshwork--autoradiographical, biochemical, and immunohistochemical study].

The effect of dexamethasone (DEX) on organ-cultured human trabecular meshwork (HTM) was evaluated autoradiographically, biochemically, and immunohistochemically. The tissues were obtained from 11 normal postmortem individual eyes, aged 15-84 years. In 2 individuals, 2-week treatment of cultured HTM with DEX (1 x 10(-4) M, 1 x 10(-5) M, 1 x 10(-6) M) induced the expression of 35S-methionine-labelled cell proteins of 40, 55, and 66 kD which were not present in HTM cultures with out DEX treatment. In electron microscopic autoradiography of the same cases, trabecular cells containing numerous intracytoplasmic vacuoles were seen and silver grains were found on microfibrils in the intracytoplasmic vacuoles. In addition, in immunoblot analysis of anti-alpha elastin of the same cases, a 72 kD band representing elastin was seen and DEX treatment showed stronger reactivity than the control. In immuno-electron microscopy of the same cases, elastin was localized on the surface of trabecular cells containing numerous intracytoplasmic vacuoles. In the remaining 9 individuals, there were no significant differences between control and DEX treatment. The alterations in the proteins/glycoproteins and elastin produced by DEX observed in organ-cultured HTM may play a role in the reduction in aqueous outflow facility observed clinically in steroid glaucoma.

Aged↗
PubMed1994

[Lectin electron microscopic histochemistry of exfoliative material from capsular glaucoma].

Exfoliative material of capsular glaucoma was studied by electron microscopic lectin histochemistry using sixteen kinds of lectin; PNA, RCA60 and 120, ABA, DBA, SBA, ConA, LCA, WGA, DSA, PHA-E4 and L4, UEA-I, Lotus, MAM, and SSA. The results indicated that sugar residues in exfoliative material on the lens and trabecular meshwork have the same characteristics, i.e., they contain glycoconjugates with sugar residues of beta-galactosyl, alpha-mannosyl, N-acetyl-D-glucosaminyl, and terminal sialic acid. The lectin staining pattern of microfibrils in exfoliative material, radially oriented fibrils and linear densities in the lens capsule, and zonular lamella was also similar to that of exfoliative material, and suggested their close association with exfoliative material. These results also indicated that lectin can be employed in the detection and identification of exfoliative material in various tissues.

Aged↗
PubMed1994

Localization of elastin in the normal and glaucomatous human trabecular meshwork.

PURPOSE: The extracellular materials (ECMs) in the trabecular meshwork (TM) are thought to play a crucial role in aqueous outflow resistance. Immunohistochemical localization of elastin, one of the major ECMs in the normal and glaucomatous human TM, was examined ultrastructurally. METHODS: Eight normal eye bank eyes and 16 trabeculectomy specimens of primary open angle glaucoma (POAG, 11 eyes from 8 cases), congenital glaucoma (2 eyes from 1 case), and juvenile glaucoma (3 eyes from 2 cases) were embedded in Lowicryl K4M at low temperature. The distribution of elastin was studied by the protein A-gold technique. RESULTS: In normals, the gold particles indicating the antigenic sites for elastin existed mainly in the central amorphous element of the elastic-like fibers, and a few gold particles were observed within the area containing fine granular-like material and fine fibrillar-like material. No labeling was observed in cellular materials or other ECMs. In congenital and juvenile glaucoma, labeling was similar to that observed in normals. In POAG specimens compared to normals, there was an increased amount of elastin-bound immunogold particles along the inner canal endothelium. The increased gold particles, which did not have a fibrillar arrangement and were not enclosed by electron-dense microfibrils, were found within the area containing fine fibrillar-like material. However, labeling within the elastic-like fibers was similar to that observed in normals. CONCLUSIONS: Under electron microscopy, elastin could be localized in the normal and glaucomatous human TM. The results of this investigation suggest that elastin may play an important role in the etiology of POAG.

Adult↗
PubMed1994

Identification of defects in the fibrillin gene and protein in individuals with the Marfan syndrome and related disorders.

The Marfan syndrome is an autosomal dominant disorder with pleiotropic manifestations that involve the cardiovascular, ocular, and skeletal systems. Through a number of investigational approaches, the gene encoding for fibrillin, the FBN1 gene on chromosome 15, has been identified as the defective gene causing the Marfan syndrome. Fibrillin is the large glycoprotein with a repetitive domain structure and is a major protein component of microfibrils, a fibrillar system closely associated with elastin in connective tissue. Mutational analysis of defects in the FBN1 gene in patients with the Marfan syndrome has revealed that most mutations are private or unique in an affected individual or family. Analysis of fibrillin protein or gene defects in individuals with related phenotypes has revealed that a perinatal lethal syndrome, termed neonatal Marfan syndrome, is due to FBN1 gene mutations. In addition, fibroblast cell strains from a subset of patients with idiopathic scoliosis have fibrillin protein defects. Last, fibroblasts from calves affected with bovine Marfan syndrome display defects in the fibrillin protein. These studies have wide-ranging implications in the diagnosis, treatment, and prevention of Marfan syndrome and related disorders.

Animals↗
PubMed1994

Fibrillin and elastin networks in extrafusal tissue and muscle spindles of bovine extraocular muscles.

PURPOSE: Bovine extraocular rectus muscles were examined to map the distribution of elastin and fibrillin in extrafusal tissue and muscle spindles. METHODS: Immunohistochemical techniques and immunolocalization were employed to pin-point the placement of molecules relative to muscle fibers. RESULTS: Strands containing elastin and fibrillin surrounded all extrafusal fibers. They also covered the external surface of intrafusal fibers, more extensively at the equator than at the pole. Within strands elastin was placed in the center, whereas fibrillin was located in microfibrils on the periphery. CONCLUSIONS: The wide distribution in extrafusal tissue of elastin and fibrillin suggests that they are factors in determining the mechanical properties of extraocular muscles. Their placement in proximity to individual intrafusal fibers should affect the viscoelastic properties of these fibers and, thus, influence the dimensions of the afferent discharge.

Animals↗
PubMed1993

Relationship between magnesium and elastic fibres.

The presence of magnesium was demonstrated by histochemical methods in elastic fibres from different locations. After pretreatment with elastase a positive reaction could no longer be detected. Microfibrils which enclose the elastin core of the elastic fibres gave no positive reaction. These results support the supposition of a close relationship between Mg and elastin. Determination of the Ca/Mg ratio by atomic absorption spectrometry in variants of fibrous connective tissue showed a decreasing Ca level with increasing elasticity. The Ca/Mg ratio in lattices containing rubber-like particles disclosed striking diminution of Ca. These data support the speculation that the antagonism of Mg to Ca plays a fundamental role in the maintenance of elasticity. The special interaction of the Mg2+ ion with water molecules is very probably a further prerequisite for elasticity in natural elastic materials.

Calcium↗
PubMed1993

[Histopathologic study of anterior capsule opacification in pseudophakic eyes].

We performed posterior chamber lens implantation (IOL) in three monkey eyes. All pseudophakic eyes developed a ring-shaped opacity, appearing on the IOL optics along the anterior capsule incision line. Transmission electron microscopic study revealed that the anterior capsule opacification was composed of proliferated cellular and extracellular components between the anterior capsule and the IOL optics. The proliferated cells looked like fibroblasts, but they were connected by desmosomes and covered by basal lamina. These histologic findings represented morphological features of epithelial cells, probably lens epithelial cells. Extracellular components consisted of collagen fibers, microfibrils, and basal lamina-like materials.

Animals↗
PubMed1993

[Experimental study on intratumoral injection with hydroxyapatite bioceramics and adriamycin in implanted hepatoma in mice].

Hydroxyapatite (HA) bioceramics is a biomaterial used in orthopedic area. We observed its anticancer effect in experimental hepatoma-22 (H22) in mice. BALB/c mice implanted with H22 were grouped into I, II, III and IV. Intratumoral injections were given as follows: (I) HA 0.1 g and ADM 0.1 mg n = 28; (II) HA 0.1 g n = 16; (III) ADM 0.1 mg n = 16; (IV) untreated n = 20. The tumor regression rates of the groups I, II and III were 65.9%, 41.9% and 51.1%, respectively. The mean survivals of groups I, II, III and IV were 32, 22, 26 and 18 days. Six mice of group I were alive more than 50 days before being killed, in which 4 tumor samples showed that no residual tumor cells could be seen under microscope. The possible mechanism of HA anti-cancer action is: (1) the dissolved matter of HA, glycoprotein and microfibril around the tumor cells may disturb the metabolism of cancer; (2) fibrocalcific process restricts the tumor growth; (3) immunoenhancement action (4) as a drug-release system HA is a hopeful agent of intratumoral injection for treatment of cancer.

Animals↗
PubMed1993

Extracellular matrix 4: the elastic fiber.

The elastic properties of many tissues such as the lung, dermis, and large blood vessels are due to the presence of elastic fibers in the extracellular space. These fibers have been shown by biochemical and ultrastructural analysis to be composed of two distinct components, a more abundant amorphous component and a 10-12 nm microfibrillar component, which is located primarily around the periphery of the amorphous component. The protein elastin makes up the highly insoluble amorphous component and is responsible for the elastic properties. Elastin is found throughout the vertebrate kingdom and possesses an unusual chemical composition rich in glycine, proline, and hydrophobic amino acids, consonant with its characteristic physical properties. The 72-kDa biosynthetic precursor, tropoelastin, is secreted into the extracellular space where it becomes highly cross-linked into a rubber-like network through the activity of the copper-requiring enzyme lysyl oxidase. Analysis of the elastin gene has demonstrated that hydrophobic and cross-linking domains are encoded in separate exons and that there is significant alternative splicing, resulting in multiple isoforms of tropoelastin. The elastin gene promoter contains many potential binding sites for various modulating factors indicative of a complex pattern of transcriptional regulation. The microfibrils contain several proteins, including fibrillin, and probably act as an organizing scaffold in the formation of the elastin network. There appears to be a fibrillin gene family in which each protein contains multiple repeats of a motif previously found in epidermal growth factor and a second motif observed in transforming growth factor beta 1-binding protein. Mutations in the fibrillin gene located on human chromosome 15 have been strongly implicated as the cause of the Marfan syndrome.

Amino Acid Sequence↗