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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ageing and degenerative changes of the human aorta are associated with medial thinning and a reduced dry weight content of elastin. The metabolic stability of cross-linked elastin was investigated by measuring the accumulation of D-aspartate with ageing in insoluble elastin isolated from human aorta. D-Aspartate accumulation in elastin was compared with D-aspartate accumulation in aortic collagen and an elastin bound glycoprotein fraction. The D-aspartate content of elastin, purified from infrarenal aorta; increased linearly with age from 3% of the total aspartate in youth to 13% in the mid 80s. In contrast the D-aspartate content of aortic collagen remained invariant (3-5% of the total aspartate) from youth to old age. The apparent first order rate constant for the racemization of L-aspartate in elastin was 1.14 x 10(-3). The D-aspartate content of the elastin bound glycoproteins increased by only a small amount, from 3% in the mid 30s to 6% in the mid 80s. These results argue for the metabolic stability of aortic elastin as compared with the fibrillar collagens of the human aorta. Both the rate of racemization and the specific accumulation of D-aspartate in elastin, but not collagen, indicates that mature cross-linked elastin is not synthesized in the adult aorta.
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PMID:On the accumulation of D-aspartate in elastin and other proteins of the ageing aorta. 146 64

The changes induced by ageing of the skin are particularly visible in photo-exposed areas, indicating the interaction between actinic factors and factors specific to the ageing process itself. The corresponding histological signs affect various structures: epidermis (thinning of the epidermis, reduced cell proliferation...), dermis-epidermis junction (disappearance of the microvilli with defective adhesion of the epidermis to the dermis), dermis (degeneration of elastin and collagen, which is photoinduced, and a moth-eaten appearance with loss of microfibrils as a result of time-related ageing), microcirculation (reduced vascularization, particularly visible in photo-exposed areas...) appendages.
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PMID:[Histologic signs of cutaneous aging]. 189 70

Despite an overall thinning of the epidermis and focal areas of cytologic atypia, there was no morphologic evidence that the protective function of this tissue was compromised by age. The characteristic morphologic markers associated with the keratinization process were not altered either in appearance or in amounts. A well-formed stratum corneum was present, suggestive that barrier ability is not compromised in senile skin. Whereas alterations in the aged epidermis are slight, the dermal-epidermal changes are marked and have greater physiologic consequences. The major change is a relatively flat dermal-epidermal junction because of retraction of the epidermal papillae as well as the microprojections of basal cells into the dermis. This flattening results in a more fragile tissue that is less resistant to shearing forces. Retraction of the epidermal downgrowths may also explain the loss in proliferative capacity associated with the aged epidermis. The major alterations in the aged dermis concern the architecture of the collagen and elastin networks. Both fibrous components appear more compact because of a decrease in the voids or spaces between the fibers; the spaces resulted from a loss of ground substance. Collagen bundles appear to unravel, and the individual elastic fibers show signs of elastolysis. The net effect of these fibrous rearrangements and alterations is a dermis that is less stretchable, less resilient, more lax, and prone to wrinkling.
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PMID:Morphology of aged skin. 264 2

Pectus excavatum is a common malformation in diseases of elastic tissue (Marfan, Ehlers-Danlos...). When observed apparently alone it may represent a minor form of dystrophy, implying the same risk of a cardiac lesion. Abnormalities of the thoracic skeleton and echocardiographic mitral valve prolapse is a well established association, suggesting a common disorder of connective tissue. However, there is no absolute proof that this is a statistically significant association. Histological connective tissue changes relating these two markers have yet to be found. Clinical and echocardiographic examinations and skin biopsies were performed in 17 patients with pectus excavatum. Mitral valve prolapse was detected in 65% of cases (associated in 1 out of 3 cases with tricuspid valve prolapse). In 53% of cases electron microscopy showed abnormal skin collagen and elastin. Collagen abnormalities were twice as common as those of elastin and could be associated. Mixed changes of thinning of elastin and collagen fibres of irregular calibre were particularly suggestive. Pectus excavatum would therefore seem to be the expression of a minor form of dystrophy of collagen and elastin tissues and a clinical marker of possible mitral valve prolapse.
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PMID:[Mitral valve prolapse and pectus excavatum. Expressions of connective tissue dystrophy?]. 309 Sep 60

Despite an overall thinning of the epidermis and focal areas of cytologic atypia, there was no morphologic evidence that the protective function of this tissue was compromised by age. The characteristic morphologic markers associated with the keratinization process were not altered either in appearance or in amounts. A well-formed stratum corneum was present, suggestive that barrier ability is not compromised in senile skin. Whereas alterations in the aged epidermis are slight, the dermal-epidermal changes are marked and have greater physiologic consequences. The major change is a relatively flat dermal-epidermal junction because of retraction of the epidermal papillae as well as the microprojections of basal cells into the dermis. This flattening results in a more fragile tissue less resistant to shearing forces. Retraction of the epidermal downgrowths may also explain the loss in proliferative capacity associated with the aged epidermis. The major alterations in the aged dermis concern the architecture of the collagen and elastin networks. Both fibrous components appear more compact because of a decrease in the voids or spaces between the fibers; the spaces resulted from a loss of ground substance. Collagen bundles appear to unravel, and the individual elastic fibers show signs of elastolysis. The net effect of these fibrous rearrangements and alterations is a dermis that is less stretchable, less resilient, more lax, and prone to wrinkling.
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PMID:Morphology of aged skin. 352 84

The literature contains conflicting reports about the potential value of the processed human umbilical vein graft as an arterial substitute. With a view to a better understanding of the ultimate fate of this device, a series of long-term implantation was undertaken with a nonhuman primate model. Dardik Biografts were implanted as an infrarenal aortic substitute in 13 monkeys. Nine were put to death following complications after post-operative periods ranging from 3 months to 3 years, while four animals remain alive. No calcification or lipid infiltration was found, presumably because the animals were healthy. The patency rate was poor because of complications associated with thrombotic deposits and thinning of the graft wall after implantation, which led to stenosis and fibrous hyperplasia along the anastomoses. The external polyester mesh was found to encourage external tissue proliferation, which could not prevent the graft from dilating since it contained neither elastin nor smooth muscle cells. Because the places where the graft had been damaged before or during processing were the sites of thrombotic accumulation and initial collagen degeneration, it is essential to use only defect-free material. As a consequence the long-term durability of this graft continues to be questioned.
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PMID:The fate of human umbilical vein grafts as an infrarenal aortic substitute in monkeys. 403 10

beta-Aminopropionitrile (beta APN), a peptide found in leguminous plants, is a multifunctional aminonitrile because it has some action on collagen, elastin, and nervous cells. Due to its action on the nervous system, it is very interesting to show its inhibitory effect on cultures of neurons. In the present study, we have demonstrated that beta APN can produce progressive degeneration of neurons and that this effect is dose-dependant. Neuronal cultures were prepared from 14-day-old rat embryos with a cell density of 10(4) cells/cm2 in the control plates. Progressive concentrations of beta APN (from 10(-7) M to 10(-3) M) were added and a 50 Inhibitory Dose (ID50) of 10(-5) M was found. At concentrations of 10(-5) M of beta APN, the neurons showed a loss of synapsis and thinning of neuronal prolongations. Based on the morphological changes observed, we think that beta APN may be used as a neurodegeneration model similar to that obtained with acrylamide, carbon disulfide, beta-beta'-iminodipropionitrile, or aluminum salts.
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PMID:In vitro neuronal changes induced by beta-aminopropionitrile. 765 35

Striae distensae are characterized by a thinning of connective tissue stroma to produce linear, atrophic-appearing skin. Excessive adrenocortical activity, genetic factors and inherited defects of connective tissues, etc. are important causative factors in the formation of striae distensae, but the basic aetiology is not known. Total RNA was extracted from skin biopsies of five patients with striae distensae. The expression of genes coding for types I and III procollagen, elastin, fibronectin and beta-actin were studied and compared with those of four sex- and age-matched healthy individuals. The percentages of types I and III procollagen mRNA were 9.9 +/- 2.9% (mean +/- s.d.) and 10.6 +/- 1.6%, respectively, of the corresponding controls. The value for fibronectin mRNA in striae distensae was 7.3 +/- 1.8% of the control. The steady-state ratio fibronectin/type I procollagen mRNAs was 0.12 +/- 0.01 in striae distensae and 0.18 +/- 0.01 in the control. These observations suggest that expression of collagens, elastin and fibronectin genes are apparently decreased, and that there is a marked alteration of fibroblast metabolism, in striae distensae.
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PMID:Decreased expression of collagen and fibronectin genes in striae distensae tissue. 795 66

Tissue expansion has become a method of choice for immediate or delayed breast reconstruction. The compatibility of radiotherapy and tissue expansion is a growing problem. We analyse a series of 50 breast reconstructions by expansion, 24 without radiotherapy and 26 with radiotherapy. For the 24 patients without radiotherapy, very satisfactory cosmetic results were obtained in 71% of cases with 21% of stage III-IV capsular contractures and 8% of failures. For the 26 patients with a history of radiotherapy, very satisfactory cosmetic results were obtained in 65% of cases with 20% of capsular contractures and 10% of failure. 20% of cases also required a myocutaneous flap to complete the reconstruction. The complications related to radiotherapy are due to radiation lesions of endovasculitis and destruction of the network of elastin fibres. They result in the impossibility of filling the expander, deformation of the thoracic cage, expansion without projection, thinning of the tissues over the prosthesis and necrosis and exposure requiring the use of a myocutaneous flap. In conclusion, signs of radiation dermatitis constitute a contraindication to tissue expansion, which is nevertheless possible, but with a higher risk of complications. Irradiation to an expansion prosthesis is associated with an unacceptable complication rate.
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PMID:[Forum on tissue expansion. Are tissue expansion and radiotherapy compatible? Apropos of a series of 50 consecutive breast reconstructions]. 829 88

Most computations of arterial mechanics treat the wall as a mechanically homogeneous body, but there are no data to support or refute this. To evaluate this assumption, experiments were performed that measured the deformation of 4 elastic lamellae located at 4 equidistant points across the thickness of the media. Data were obtained at 25-mm Hg pressure steps between 0 and 200 mm Hg. To satisfy the constraints of incompressibility in an isovolumetric cylinder, the innermost structures must undergo larger deformations than the outermost structures. This manifests as thinning of the wall. Therefore, each experiment was performed twice: once with a vessel segment in its normal cylindrical configuration, and again with a contiguous vessel segment turned inside-out to form an inverted cylinder. The deformations of individual lamellae obtained in normal and inverted vessel segments were averaged to determine their extensions independent of location. Results showed that the extensibilities of the lamellae were equal at all 4 anatomic locations across the media, suggesting equal stiffnesses of the lamellae. Other studies were performed to examine the distribution of the circumferential retractions of the lamellae that occurs when a vessel is extended longitudinally. Results showed that circumferential retraction also was distributed uniformly across the wall. These findings demonstrate that the elastic lamellae behave uniformly in both the circumferential and longitudinal directions at different locations across the wall thickness. Because of the interlocked structure of the elastin, muscle, and collagen in the media, these findings suggest that although the media is histologically heterogeneous, it acts mechanically as a homogeneous material.
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PMID:Distribution of lamellar deformations: implications for properties of the arterial media. 1008 91


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