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Query: UMLS:C0344329 (collapse)
 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To understand the role of microtubules in growth cone turning, we observed fluorescently labeled microtubules in neurons as they encountered a substrate boundary. Neurons growing on a laminin-rich substrate avoided growing onto collagen type IV. Turning growth cones assumed heterogeneous morphologies and behaviors that depended primarily in their extent of adhesion to the substrate. We grouped these behaviors into three categories-sidestepping, motility, and growth-mediated reorientation. In sidestepping and motility-mediated reorientation, the growth cone and parts of the axon were not well attached to the substrate so the acquisition of an adherent lamella caused the entire growth cone to move away from the border and consequently reoriented the axon. In these cases, since the motility of the growth cone dominates its reorientation, the microtubules were passive, and reorientation occurred without significant axon growth. In growth-mediated reorientation, the growth cone and axon were attached to the substrate. In this case, microtubules reoriented within the growth cone to stabilize a lamella. Bundling of the reoriented microtubules was followed by growth cone collapse to form new axon, and further, polarized lamellipodial extension. These observations indicate that when the growth cone remains adherent to the substrate during turning, the reorientation and bundling of microtubules is an important, early step in growth cone turning.
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PMID:The role of microtubules in growth cone turning at substrate boundaries. 782 10

The aim of this study was to expose the inflated 3-D structure of lung elastin. Formic acid digestion followed by freeze-drying unveiled the lamellar framework. The 3-D structure of elastin was well preserved within the alveolar septa and ducts, as demonstrated by scanning electron microscopy/stereo-pair photography. Elastin fibers are seen in the alveolar septa, which are continuous with the lamellae. The removal of collagen fibers and cells by formic acid was visualised as a function of time: The optimum was 48 hours. Transverse sections still retained some collagen fibrils and partially digested cells in addition to elastin as shown by transmission electron microscopy (TEM). Formic acid digestion followed by critical point drying caused damage to the lamellar structures and they appeared to collapse. Sodium hydroxide digestion combined with freeze-drying did not preserve the 3-D lamellar structure of elastin, but converted it into flat ribbonlike bands. The main structures remaining following alkali treatment were identified by TEM as collagen fibrils well preserved in their original locations.
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PMID:Three-dimensional structure of lung elastin demonstrated by scanning electron microscopy/stereo-pair images. 784 31

We have studied asteroid bodies (ABs) of multinucleated giant cells (MGCs) in a series of sarcoid and foreign body granulomas with a standard streptavidin-biotin peroxidase technique, using commercial antibodies against collagen, vimentin and tubulin on routinely processed tissue as well as, in one case, on fresh frozen sections (FS). Our findings clearly indicate that ABs are products of the microtubule (MT) system and lack collagen. The tubulin in them stains in fresh FS but is "masked" in formalin-fixed tissue. It can be fully "unmasked" by dephosphorylation and partially by trypsinization. Compared to single microtubule organizing centers (MTOCs) in mononuclear cells serving as internal controls, ABs are obvious replicas of centrosome-nucleated MT assemblies from which they differ principally by the disproportionate size of their components and by the invariable vacuolation of the surrounding cytoplasm. Relying on bits of relevant information gleaned from the literature, our observations support the following preliminary conclusions: 1) spokes are massive bundles of MTs rich in tyrosinated alpha-tubulin coassembled in phosphorylated linkages with yet unidentified microtubule associated proteins (MAPs) and probably microfilament proteins; cores are masses of pericentriolar material including amorphous tubulins, MAPs, phosphoproteins and phospholipids; 2) their size, at least in some ABs, appears to indicate the presence of overlapping centrosome-nucleated MTOCs which in monocyte-derived MGCs are known to be multiple; 3) the cytoplasmic vacuolations around them reflect a collapse and retraction of intermediate filaments (IFs), indicating substantial ongoing MT depolymerization with disruption of MT-IF interactions; 4) ABs are products of unusual MTOC dynamics characterized by simultaneous MT assembly and depolymerization; such a phenomenon, termed "microtubule catastrophe", has been recognized in vitro with centrosome-nucleated MT assemblies under conditions of low tubulin concentrations.
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PMID:Asteroid bodies: products of unusual microtubule dynamics in monocyte-derived giant cells. An immunohistochemical study. 789 35

Osteonecrosis frequently occurs in patients being treated with steroids for conditions such as systemic lupus erythematosus and other collagen diseases and in renal transplant recipients. It remains an unsolved problem and can cause more disability than the underlying disease, particularly in young patients. In a series of eight young patients who received continuous corticosteroids and immunosuppressive agents, we attempted hip salvage in ten joints by implantation of a vascularised fibular graft into the necrotic femoral head. Follow-up ranged from 18 to 36 months. Joints which were operated on prior to articular surface collapse had complete restoration of normal function. In patients with more advanced lesions, surgery resulted in a painless hip, improved range of motion, and cessation of further progress of the disease. The preliminary data are considered encouraging enough to suggest that the vascularised fibular graft is an appropriate method for hip salvage in immunosuppressed patients with osteonecrosis of the femoral head.
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PMID:Osteonecrosis of the femoral head in immunosuppressed patients: hip salvaging with implantation of a vascularised fibular graft. 796 79

The formation of post-collapse fibrosis was investigated in lymphoid tissues of rats simultaneously treated with cyclophosphamide and betamethazone. Effectiveness of treatment was monitored by means of peripheral blood smears. Animals were sacrificed 1, 2, 3, 4, and 7 days after the last injection. Fragments of lymph nodes and thymus were studied by light and electron microscopy. Compared with untreated controls, lymphoid organs from treated animals revealed considerable reduction in the number of cells and condensation of the stroma. Picrosirius-red stained slides seen under polarized light revealed the condensed stroma to contain mainly collagens. Electron microscopy confirmed the presence of collapsed collagen fibrils in the absence of signs of functional activation of the connective tissue cells within the collapsed areas. This investigation shows that a pure form of collapse fibrosis can be observed in lymph nodes and thymus following sudden atrophy of lymphoid cells.
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PMID:Stromal collapse in acute atrophy of lymphoid organs. 798 77

Atomic force microscopy (AFM) was used in the examination of the early stages of acid treatment of dentin. Disks of highly polished dentin were initially examined under deionized water and following exposure to 0.025 M nitric acid for 20 s intervals from 0-100 s. Peritubular depth changes were linear (0.005 microns/s). The intertubular dentin surface initially moved at approximately 1/2 the peritubular rate and then reached a plateau as the demineralized collagen scaffold collapsed. There was no apparent difference in the tubule center-to-center distance during the treatment. Differences in the movement and morphology of the zones are of importance in dentin bonding applications relying on penetration of the demineralized dentin by adhesive monomers. The changes are probably related to the partial collapse of the collagen matrix. Alternatively, access to the apatite crystals and solubility may be higher in the peritubular zone. AFM appears to hold exceptional promise for the study of conditioning and priming agents for dentin bonding.
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PMID:Atomic force microscopy of acid effects on dentin. 798 59

Adult male rats were subjected to pyelonephritis by direct kidney intramedullary injection of 0.1 ml saline suspension of 10(5) E. coli. Animals were killed at intervals of 4, 10, 15, 30 and 60 days. Half of each kidney and bladder were cultured in proper bacteriologic media to demonstrate the existence of infection. The other halves were submitted to light microscopy and ultrastructural studies. Immunofluorescence methods were used for the study of connective matrix components, at the initial stage of the inflammatory process (4, 10 and 15 days). Infection was documented by bacteriologic, gross and microscopic findings in all groups following inoculation, and it lasted up to two months. Following the acute inflammatory reaction, fibronectin and type III collagen were deposited in the interstitium of kidneys. Small amounts of type I collagen were found later. Type IV collagen appeared in small quantities, associated with collapse of structures containing basement membranes. Fibronectin became concentrated in re-activated foci. The subsequent scarring and associated focal renal atrophy depended upon the extension of the acute lesion.
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PMID:Dynamics of connective matrix deposition in acute experimental E. coli pyelonephritis in rats. 808 88

The present study has been carried out with the aim of contributing, by means of the Scanning Electron Microscope (SEM), to the understanding of morphological changes in human articular cartilage during osteoarthrosis. Fragments from the femoral head of 10 patients subjected to total hip joint prosthesis were cryofractured and then studied by SEM after treatment with current procedures. The images obtained were considered observing the division of cartilage into superficial, medium and deep layers. The superficial layer is the one which suffers most seriously during osteoarthrosis, but collagen alterations, as fibrillation, involve all the layers together. Moreover, the observation of deformed cellular lacunae in the deep layer suggests that a precocious functional collapse involves the whole thickness of the cartilage, probably due to a metabolic suffering.
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PMID:Human articular cartilage during osteoarthrosis: a study under the scanning electron microscope. 818 35

The dynamics of the transmyocardial coronary flow patterns during normal and ischemic conditions are complex and relatively inaccessible to measurements. Therefore, theoretical analyses are needed to help in understanding these phenomena. The proposed model employs compartmental division to three layers, each with four vessel-size compartments which are characterized by resistance and compliance. These compartments are subjected to the extravascular compressive pressure (ECP) generated by cardiac contraction, which by modifying the transmural pressure causes changes in cross-sectional area of the vessels in each compartment continuously determining the resistance and capacitance values. Autoregulation and collaterals are also included in order to simulate the flow patterns during regional ischemia. Using these features, the model predicts the typical out of phase arterial and venous flow patterns. Systolic collapse of the large intramyocardial veins during the normal cycle, as well as systolic arteriolar collapse during ischemia are predicted. The transmural flow during ischemia is characterized by alternating flows between the layers. The ECP is considered here is two ways: (a) as a function of left ventricle (LV) pressure, decreasing linearly from endocardium to epicardium and (b) as the interstitial fluid pressure, employing a multilayer muscle-collagen model of the LV. While both of these approaches can describe the dynamics of coronary flow under normal conditions, only the second approach predicts the large compressive effects due to high ECP obtained at very low cavity pressure, resulting from significant muscle shortening and radial collagen stretch. This approach, combining a detailed description of transmural coronary circulation interacting with the contracting myocardium agrees with many observations on the dynamics of coronary flow and suggests that the type of LV mechanical model is important for that interaction.
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PMID:Coronary flow patterns in normal and ischemic hearts: transmyocardial and artery to vein distribution. 821 27

A morphological study was conducted on disc material obtained during surgical discectomy in 20 patients. The series was divided into 4 groups. Group I: 3 patients who had never been operated on before; group II: 3 patients who had already been submitted to discectomy but at a level which differed from that of the disc examined; group III: 4 patients treated surgically for contralateral herniation; group IV: 10 patients with true recurrent disc herniation, that is, already submitted to surgery for the treatment of homolateral herniation of the same disc. All of the cases submitted to surgery had been operated on more than a year previously. Moreover, the disc material obtained during autopsy in a patient operated 15 years before for disc herniation was studied. A morphological study of the cases and the data reported in the literature reveals that the fibrocartilaginous tissue of recurrences differs from that of primary herniation because of the presence of large collagen bundles associated with fibrillar framework. This aspect suggests the hypothesis that is also supported by the autoptic material examined that recurrent disc herniation is formed by repair tissue that substitutes the part of the disc that is operated on, and that recurrent herniation is caused by mechanical collapse of the repair tissue. From a surgical point of view, a distinction may be made in terms of early recurrences, which appear within one year of surgery and are formed by disc tissue which is identical to that of primary herniation, and late recurrences, the subject of this morphological study.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Recurrent lumbar disc herniation: what recurs? (A morphological study of recurrent disc herniation). 824 33


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