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PubMed1991

IgA-binding structures in dermatitis herpetiformis skin are independent of elastic-microfibrillar bundles.

Dermatitis herpetiformis (DH) is characterized in part by the presence of granular deposits of IgA in the papillary dermis just beneath the dermal-epidermal junction. The nature of the structures to which IgA binds in DH skin, however, has not been clearly demonstrated. Previous immunoelectron-microscopy studies using the peroxidase-antiperoxidase technique have concluded that the IgA may bind to abnormal elastic microfibrillar bundles. Recently, antibodies have been developed against a major component of the elastic microfibril bundles, fibrillin. In addition, another dermal matrix protein, hexabrachion, has been characterized and found in normal human skin in a distribution similar to the IgA deposits of DH. Utilizing antibodies against fibrillin, hexabrachion, and human IgA and immunoelectronmicroscopy with immunogold staining techniques, we have examined the skin from patients with DH in order to localize the IgA deposits. Normal-appearing skin from five patients with DH exhibited electron-dense patches within the dermis, which were not seen in skin from normal subjects. These structures were sometimes adjacent to the basement membrane zone, but appeared amorphous and without a well-defined fibrillar structure. The electron-dense patches were labeled with anti-human IgA, but not with antibodies to fibrillin or hexabrachion. The anti-IgA antibody did not label the normal basement membrane. These studies confirm the presence of abnormal electron-dense, amorphous structures in the skin of patients with DH. Due to this lack of association with the elastic microfibril bundles and the lack of labeling with antibodies against fibrillin, we suggest that these deposits are distinct from the microfibrillar bundles of elastic tissue and may represent IgA bound to degraded basement membrane or isolated dermal deposits of IgA.

Actin Cytoskeleton↗
PubMed1976

Ultrastructure of the microvasculature in skin affected by systemic scleroderma.

The microvasculature of the upper dermis in cases of systemic scleroderma was examined with an electron microscope. Microvessels in clinically uninvolved skin areas showed nearly normal structure. On the other hand, in moderately involved skin, enlargement of the vascular lumen, endothelial swelling, increase in the pinocytotic vesicle and microvilli and reduplication of the basal lamina were observed. Along with these, Ruthenium red-positive granules, microfibrils and fine collagen fibrils were perivasculary increased. Markedly involved skin revealed a degenerative change in the endothelial cells with interendothelial gap; in the perivascular region the number of microfibrils and Ruthenium red-positive granules decreased, and were replaced by increased collagen fibrils.

Adult↗
PubMed1998

Elastic fibers in dermis of juvenile elastoma.

To explore the ultrastructure of elastic fibers in juvenile elastoma, three patients (two without osteopoikilosis and one under examination of bones and joints) were studied by routine electron microscopy. In addition to normal elastic fibers, all the patients also exhibited alterations in elastic fibers. The altered ultrastructures showed lucent, homogenous matrix without peripheral microfibrils. The homogenous matrix were seen in various extensions from the small protrusions of the normal elastic fibers to the complete replacement of the entire fibers. Collagen fibrils occasionally showed twisted figures. Normal shapes of dermal glycosaminoglycans were increased in number. It seems likely that the lucent, homogenous matrix without peripheral microfibrils are the characteristic changes of elastic fibers in juvenile elastoma. The alteration could be nevoid in nature.

Actin Cytoskeleton↗
PubMed1976

Ultrastructure and chemical analysis of the cell wall of Pythium debaryanum.

The ultrastructure and component polysaccharides of the cell wall of Pythium debaryanum IFO-5919 were investigated. From results obtained by means of acid, alkali, Schweitzer reagent and beta-1, 3-glucanase treatments and electron microscopy, it was concluded that 1) the acid-extracted fraction was a 1,3-linked branched glucan, 2) the alkali-extranded fraction was a mixture of 1,3-, 1,6-, and 1,3,6-linked highly branched two glucans, 3) the Schweitzer reagent-extracted fraction was a beta-1, 4-linked glucan, 4) the cell wall was constructed from two types of cullulosic microfibrils, as a frame and as a finer network, and amorphous beta-1, 3-glucan including beta-1, 6-linkage, 5) cellulosic microfibrils were covered by matrix material consisting of a mixture of amorphous beta-1, 3-linked and beta-1, 6-linked branching glucans.

Cell Wall↗
PubMed1980

Ultrastructure of transplant glomerulopathy.

Thirty-one specimens of tissue were obtained from 15 renal allografts 3-96 months after transplantation and studied by light, electron and in some cases also by immunofluorescence microscopy. All patients had a degree of renal insufficiency and almost all had proteinuria and moderate hypertension; nephrotic syndrome was present in one and hematuria in two. On histological examination one patient showed cellular proliferation suggestive of glomerulonephritis (recurrent or de novo) and another patient had numerous crescents. The most frequent glomerular lesion was widening of the lamina rara interna with subendothelial accumulation of finely granular material, formation of new subendothelial basement membrane and deposition of microfibrils and fine filaments. The mesangial changes were mainly those of mesangiolysis and mesangial sclerosis with deposition of mesangial matrix and microfibrils, but little cellular proliferation. Fragmented red blood cells were seen in nearly half of the patients. In another seven patients the lesion resembled focal segmental glomerulosclerosis. This combination of changes termed transplant glomerulopathy leads to diffuse glomerular sclerosis. Arterial intimal thickening and occasionally also thrombosis produced ischaemic changes in the kidney and in the glomeruli and contributed significantly to the process of transplant rejection.

Arteries↗
PubMed1983

Bidirectional shadowing in freeze-etching.

Bidirectional shadowing in freeze-etching may be achieved by firing an electron-beam shadowing source, rotating the specimen stage through a desired angle, and re-firing the shadowing source. It is demonstrated that portrait shadow-casting, which permits information to be drawn from much of the specimen region lying within primary shadows, can be readily achieved using a 90 degree specimen rotation. With 180 degree specimen rotation, particle-size analysis is feasible. Particle-height analysis is demonstrated using membrane-associated particles as an example. Data from suitable sets of micrographs can also be used for the estimation of particle-width exaggeration due to the accumulation of the shadowing-metal cap. Fibre-width analysis, using the linear regression method, is demonstrated by a study of native cellulosic microfibrils. Mean microfibril widths were found to be 5.5-7.0 nm.

Cell Membrane↗
PubMedDate not supplied

Ultrastructural aspects of the demolition of human hair in vitro by Chrysosporium tropicum Carmichael.

The pattern of invasion of human hair in vitro by a non-dermatophytic fungus, Chrysosporium tropicum, was studied by transmission and scanning electron microscopy. The components of the hair were attacked in sequence, depending on their level of keratinization, i.e. their content of cystine. In the cuticle, the sequence of digestion was as follows: intercellular material, cytoplasmic membrane, endocuticle, exocuticle, layer A, and a thinner layer below the inner cytoplasmic membrane of the cuticle cells. In the cortex, the order was: cementing material, plasmalemma, intermacrofibrillar material, microfibrils and matrix of the microfibrils. At the same time a different mode of attack was radial penetration of the various layers without regard to degree of keratinization. This occurred by means of perforating hyphae originating in the cuticle from structures similar to appressoria. With both modes of attack, the process showed all the characteristics of enzymatic digestion rather than physical breakdown. Ch. tropicum thus demonstrated important physiological parallels with dermatophytes in its demolition of hair in vitro. This could be of interest in predicting its ability to infect in vivo.

Chrysosporium↗
PubMed1982

Ultrastructural study on the release reaction of the platelet. Release I.

The ultrastructural changes of human or rabbit platelets in response to release inducers I were studied by using isolated cells from the respective platelet rich plasma. The changes of platelets were more dynamic in ADP than those in epinephrine and endotoxin though common changes occurred in all cases. In the platelets on release reaction, there were well preserved alpha-granules and the disappearance of very dense granules accompanied by simultaneous appearance of round vesicles. The contraction wave of the microtubules rarely occurred and the microfibrils increased in amount in the cytoplasm of platelets. The canalicular system in response to ADP alone is morphologically interpreted as the open canalicular system. On the other hand, epinephrine and endotoxin did not cause obvious morphological changes of the open canalicular system. When the contents of very dense granules alone were discharged leaving the round vesicles behind in the release I, it seems likely that the microfibrils play a more important role than the microtubules. Furthermore, the author suggests that the dense tubular system or third canalicular system may play an essential role for the release I as a secretory pathway in place of the open canalicular system.

Adenosine Diphosphate↗
PubMed1982

Ultrastructural study on the release reaction of the platelet. Release II.

The ultrastructural changes of the platelets stimulated by release inducers II such as thrombin, collagen, and latex particles were studied to compare the differences in morphology of release I and II. The characteristics of platelets in response to thrombin were the decrease in number of alpha-granules and marked dilation of the open canalicular system containing fibrin preceded by the disappearance of very dense granules. In the platelets in response to collagen or latex, the release of alpha-granules was initiated after taking the particles into the open canalicular system. In all of the cases, the amount of microfibrils was seen in the cytoplasm, while contraction wave of the microtubules was rare in the cytoplasm during the release and uptake of particles. Accordingly, the release of very dense granules seems to be followed by that of alpha-granules. It is suggested that the microfibrils play a more important role than the microtubules in the release II as well as release I. Furthermore, the contents of alpha-granules may be discharged via the open canalicular system on the release II by thrombin, collagen or latex particles.

Blood Platelets↗
PubMed1987

Flow loaded canine carotid artery. II. Ultrastructural changes in the subendothelial layer.

To study the subendothelial layer of the flow loaded arteries, blood flow changes were produced by constructing an arterio-venous shunt between the common carotid artery and the external jugular vein using eleven adult beagle dogs. One week after operation, the subendothelial layer of the flow loaded canine carotid arteries was observed with a transmission electron microscope. In the arteries loaded by highly elevated blood flow, the subendothelial layer showed thick subendothelial space (300 to 500 nm) with multilayered basement membrane. The microfilaments and microfibrils increased significantly. There were no collagen fibers. Spindle to cylindrical elastic fibers appeared in the luminal margin of the internal elastic lamina. On the other hand, in the control arteries, the subendothelial layer was thin (about 50 nm) with scanty basement-membrane-like material. There were a few microfilaments and microfibrils, but no collagen fibers. The luminal margin of the internal elastic lamina was smooth. It is suggested that these are the wall shear stress dependent subendothelial changes, which would be partly due to the increased protein synthesis by the endothelial cells stimulated by the wall shear stress and be partly due to the wall shear dependent mechanical stress transmitted from the endothelial surface.

Animals↗
PubMed2005

The morphogenesis of lobed plant cells in the mesophyll and epidermis: organization and distinct roles of cortical microtubules and actin filaments.

The morphogenesis of lobed plant cells has been considered to be controlled by microtubule (MT) and/or actin filament (AF) organization. In this article, a comprehensive mechanism is proposed, in which distinct roles are played by these cytoskeletal components. First, cortical MT bundles and, in the case of pavement cells, radial MT arrays combined with MT bundles determine the deposition of local cell wall thickenings, the cellulose microfibrils of which copy the orientation of underlying MTs. Cell growth is thus locally prevented and, consequently, lobes and constrictions are formed. Arch-like tangential expansion is locally imposed at the external periclinal wall of pavement cells by the radial arrangement of cellulose microfibrils at every wall thickening. Whenever further elongation of the original cell lobes occurs, AF patches assemble at the tips of growing lobes. Intercellular space formation is promoted or prevented by the opposite or alternate, respectively, arrangement of cortical MT arrays between neighboring cells. The genes that are possibly involved in the molecular regulation of the above morphogenetic procedure by MT and AF array organization are reviewed.

Actin Cytoskeleton↗
PubMed1975

[Ultrastructure of the genus Enteromonas da Fonseca (Zoomastigophorea) and revision of the order of Diplomonadida Wenyon].

Fine structure of 2 species of Enteromonas, one from the intestine of the salamander, Triturus vulgairs, and another from the feces of domestic rabbit, Oryctolagus cuniculi, is described. The pyriform cell has an anteriorly located nucleus. The 4 flagella originate from an area near the anterior end of the nucleus. The recurrent flagellum (R) is lodged in a ventral depression or cytostome. The kinetosomes, arranged into 2 pairs, anterior (no. 1, no. 2) and posterior ("3, R), are interconnected by microfibrils. One microtubular fiber, connected to kinetosome "1, is situated near the anterior surface of the nucleus. Another, subnuclear, microtubular fiber is homologous to the "crossed" fiber found in Diplozoa. The cytostome is bordered by 2 lips: the preeminent left lip is equipped with several rows of microtubules, while the right lip contains only a thin microtubular fiber associated with microfibrils. The cytostome occupies 2/3 of the ventral surface. The recurrent flagellum passos over the anterior surface of the cell and then comes to lie in the cytostome. The bacteria are phagocytosed in the bottom part of the cytostome between the 2 distended lips. They are digested in numerous vacuoles. The undigested residual bodies are evacuated by a rupture of the cell membrane. The ergastoplasm is concentrated near the cell periphery. Mitochondria and the Golgi apparatus are absent. In the cyst stage, the multinucleate cell is enclosed in a microfibrillar membrane; the axonemes lie free in the cytoplasm. Diplomonad forms of Enteromonas resembling Hexamita are numerous, except that the cytostome is different in these 2 genera. In such forms, the arrangement of the 2 individuals often has binary axial symmetry, but on occasion they are associated in a more anarchic fashion. The mastigont of Enteromonas is organized like that of a single zooid of a diplozoon. It is possible that the genus Enteromonas is ancestral to Diplomonadida and that the diplomonad state, transitory in Enteromonas, became permanently established in Diplomonadida. Enteromonas appears to be more primitive than the other genera of Diplomonadida. Thus we propose 2 suborders: Enteromonadina, subord. nov. with the genus Enteromonas, and Diplomonadina Wenyon, emend., with the genera Trepomonas, Trigonomonas, Hexamita, Spironucleus, Octomitus, Giardia. The arrangement of the kinetosomes and the existence of a cytostome are the principal characters common to Enteromonas and Retortamonadida, while their "accessory" fibers are not homologous. A more complete study of division of the 2 zooflagellate orders is necessary for the presentation of a more detailed evolutionary scheme of these groups.

Animals↗
PubMed1975

alpha1-Antitrypsin deficiency and skin abnormalities.

A 19-year-old Moroccan male was found to have total absence of serum alpha1-antitrypsin, a major inhibitor of elastase. This patient had chronic obstructive lung disease, hyperextensibility of the skin over the cheeks and wrists, and hyperlaxity of the hand joints. Microscopic sections of the skin revealed a thickened dermis with shortened and rarefied elastic fibers. Ultrastructural study showed collagen fibers with variable and irregular diameters. Elastic fibers were scarce and their relatively poor matrix was surrounded by numberous microfibrils. The outline of the fibers was irregular with deep recesses filled with microfibrils. The ergastoplasm of the fibroblasts was well developed. The differential diagnosis with other connective dystrophies showed the original characteristic of this case. Clinically and histopathologically, the skin abnormalities are probably related to the deficiency in elastase inhibitor.

Adult↗
PubMed1985

Calcification of non-collagenous matrix in human gingiva: a light and electron microscopic study.

Tissue samples obtained from human gingiva with soft tissue calcification were processed for light and transmission electron microscopy. The stroma in these specimens revealed numerous foci of calcification in a matrix that consisted of closely packed branching microfibrils, 12 nm in diameter and a maximum of 2.5 micron in length. Calcospherites, 0.25-1.11 micron in diameter, were present within the matrix. They were constructed of needle-like units shown by high resolution electron microscopy and energy dispersive X-ray microanalysis to be apatite. Larger calcified masses were composed of calcospherites which were fused together. Matrix vesicles or other forms of membraneous material could not be found. The relationship between the mineral and non-collagenous microfibrils may suggest a role for the latter in the onset of calcification in this ectopic site.

Amelogenesis Imperfecta↗
PubMed1991

Distribution of collagens type V and VI in the normal human alveolar mucosa: an immunoelectronmicroscopic study using ultrathin frozen sections.

The ultrastructural localization of collagens type V and VI in normal human gingival mucosa was investigated by immunoelectron microscopy. Twenty biopsies were fixed in dimethylsuberimidate and shock-frozen in slush nitrogen. Collagen type V was mainly located to meshworks of uniform nonstriated microfibrils of 12 to 20 nm width, which preferentially appeared in larger spaces between cross-striated major collagen fibrils. Occasionally single microfibrils of collagen type V fanned out from the ends of major collagen fibrils, which may indicate a role as a core fibril. Collagen type V was not found in the subepithelial basement membrane and the immediately adjacent stroma. Collagen type VI was detected in a loose reticular network of unbanded microfilaments that were morphologically distinguishable by knoblike protrusions every 100-110 nm. These microfilaments were found in the vicinity, but not as an intrinsic component, of the subepithelial basement membrane. Single filaments of collagen type VI filaments appeared to form bridges between neighboring cross-striated major collagen fibrils, suggesting an interconnecting role for this collagen type. The method presented appears to be excellently suited to study the normal and pathological supramolecular organization of the oral extracellular matrix.

Adolescent↗
PubMed1985

Twisted architectures in cell-free assembled collagen gels: study of collagen substrates used for cultures.

Reprecipitated fibrils from collagen solutions assemble into aggregates often showing a remarkable twisted structure. We first observed these aggregates in collagen gels prepared to facilitate culture of epithelial cells. We verified that these structures form in the absence of cells and correspond to a process of self-assembly. Studies on reconstructed fibrils of collagen are generally based on the examination of thin specimens mounted onto coated grids prepared for electron microscopy. We rather applied the classical methods of fixation, embedding and ultramicrotomy, which allowed us to analyze the structure of these aggregates, several microns in diameter. Our gels were prepared from 2.5 mg/ml tropocollagen solutions usually chosen for cell and organ cultures. The time required to obtain twisted architectures, in these aggregates, depends on temperature and the presence of factors such as fetal calf serum proteins. Twist is observed at two different levels of organization. Microfibrils are gathered into twisted bundles which condense into cross-striated fibrils. These fibrils themselves aggregate and show a mutual twist whose orientation is left-handed as is the twist observed within each microfibril bundle. Several models of these architectures are presented. Planar twist, cylindrical twist and toroidal twist are described and their relation to the structure of certain liquid crystals is considered. Examples of orthogonal packing also have been observed. These structures obtained in vitro are very close to patterns already described in vivo in numerous collagen matrices.

Animals↗
PubMed2002

Origin of the biomechanical properties of wood related to the fine structure of the multi-layered cell wall.

In this study, a basic model is introduced to describe the biomechanical properties of the wood from the viewpoint of the composite structure of its cell wall. First, the mechanical interaction between the cellulose microfibril (CMF) as a bundle framework and the lignin-hemicellulose as a matrix (MT) skeleton in the secondary wall is formulated based on "the two phase approximation." Thereafter, the origins of (1) tree growth stress, (2) shrinkage or swelling anisotropy of the wood, and (3) moisture dependency of the Young's modulus of wood along the grain were simulated using the newly introduced model. Through the model formulation; (1) the behavior of the cellulose microfibril (CMF) and the matrix substance (MT) during cell wall maturation was estimated; (2) the moisture reactivity of each cell wall constituent was investigated; and (3) a realistic model of the fine composite structure of the matured cell wall was proposed. Thus, it is expected that the fine structure and internal property of each cell wall constituent can be estimated through the analyses of the macroscopic behaviors of wood based on the two phase approximation.

Anisotropy↗
PubMed1984

Specific phases of root hair attachment in the Rhizobium trifolii-clover symbiosis.

The time course and orientation of attachment of Rhizobium trifolii 0403 to white clover root hairs was examined in slide cultures by light and electron microscopy. Inocula were grown for 5 days on defined BIII agar medium and represented the large subpopulation of fully encapsulated single cells which uniformly bind the clover lectin trifoliin A. When 10(7) cells or more were added per seedling, bacteria attached within minutes, forming randomly oriented clumps at the root hair tips. Several hours later, single cells attached polarly to the sides of the root hair. This sequence of attachment to clover root hairs was selective for R. trifolii at inoculum sizes of 10(7) to 4 X 10(8) per seedling, specifically inhibited if 2-deoxy-D-glucose, a hapten for trifoliin A, was present in the inoculum, and not observed when 4 X 10(8) cells were added to alfalfa seedling roots or to large clover root cell wall fragments which lacked trifoliin A but still had trifoliin A receptors. Once attached, R. trifolii 0403 became progressively less detachable with 2-deoxy-D-glucose. At smaller inoculum sizes (10(5) to 10(6) cells per seedling), there was no immediate clumping of R. trifolii at clover root hair tips, although polar binding of bacteria along the root hair surface was observed after 4 h. The interface between polarly attached bacteria and the root hair cell wall was shown to contain trifoliin A by immunofluorescence microscopy. Also, this interface was shown by transmission electron microscopy to contain electron-dense granules of host origin. Scanning electron microscopy revealed an accumulation of extracellular microfibrils associated with the lateral and polar surfaces of the attached bacteria, detectable after 12 h of incubation with seedling roots. At this same time, there was a significant reduction in the effectiveness of 2-deoxy-D-glucose in dislodging bacteria already attached to root hairs and an increase in firm attachment of bacteria to the root hair surface, which withstood the hydrodynamic shear forces of high-speed vortexing. These results are interpreted as a sequence of phases in attachment, beginning with specific reversible interactions between bacterial and plant surfaces (phase I attachment), followed by production of extracellular microfibrils which firmly anchor the bacterium to the root hair (phase 2 adhesion). Thus, attachment of R. trifolii to clover root hairs is a specific process requiring more than just the inherent adhesiveness of the bacteria to the plant cell wall.(ABSTRACT TRUNCATED AT 400 WORDS)

Microscopy, Phase-Contrast↗