1,720,961 research outputs found
Effect of DL-penicillamine on the aorta of growing chickens. Ultrastructural and biochemical studies
No full textThe effect of DL-penicillamine on the architecture of the aortic wall of growing chickens was studied, with particular attention to elastin and collagen. Penicillamine was added to the diet (0.2% and 0.4%, in the presence or not of 10 mg/kg CuSO4 and 100 mg/kg vitamin B6) from hatching, for periods from 7 days up to 2 months. The same regions of the thoracic aortas were examined and compared in all the different experimental conditions. The results showed that penicillamine induced relevant modifications in the process of elastin fibrogenesis. The alterations consisted of an increase of elastin in the extracellular space, associated with an increase in the number of elastin fibers per unit area, and a decrease of the mean profile area of the fibers. Interestingly, penicillamine induced the formation of numerous bundles of microfibrils associated or not with elastin fibers. After prolonged treatment, elastin tended to diminish and the fibers tended to fuse into polymorphic syncytia. Collagen fibrils were larger, showed more heterogeneous cross diameters, were less numerous, and were more spread out within the tissue. All the other components of the aortic wall appeared not to be altered by the chemical. Penicillamine did not modify the copper content of chick aortas, whereas it induced a 40-50% reduction of the activity of both salt and 4 M urea-soluble peptidyl lysyl oxidases in the same tissue. These data may help in understanding some of the pathologic manifestations in human beings during penicillamine treatment
Lysyl oxidase activity and elastin/glycosaminoglycan interactions in growing chick and rat aortas
No full textHydrophobic tropoelastin molecules aggregate in vitro in physiological conditions and form fibers very similar to natural ones (Bressan, G.M., I. Pasquali Ronchetti, C. Fornieri, F. Mattioli, I. Castellani, and D. Volpin, 1986, J. Ultrastruct. Molec. Struct. Res., 94:209-216). Similar hydrophobic interactions might be operative in in vivo fibrogenesis. Data are presented suggesting that matrix glycosaminoglycans (GAGs) prevent spontaneous tropoelastin aggregation in vivo, at least up to the deamination of lysine residues on tropoelastin by matrix lysyl oxidase. Lysyl oxidase inhibitors beta-aminopropionitrile, aminoacetonitrile, semicarbazide, and isonicotinic acid hydrazide were given to newborn rats, and the ultrastructural alterations of the aortic elastic fibers were analyzed and compared with the exent of the enzyme inhibition. When inhibition was >65% all chemicals induced alterations of elastic fibers in the form of lateral aggregates of elastin, which were always permeated by cytochemically and immunologically recognizable GAGs. The number and size of the abnormal elastin/GAGs aggregates were proportional to the extent of lysyl oxidase inhibition. The phenomenon was independent of the animal species. All data suggest that, upon inhibition of lysyl oxidase, matrix GAGs remain among elastin molecules during fibrogenesis by binding to positively charged amino groups on elastin. Newly synthesized and secreted tropoelastin has the highest number of free epsilon amino groups, and, therefore, the highest capability of binding to GAGs. These polyanions, by virtue of their great hydration and dispersing power, could prevent random spontaneous aggregation of hydrophobic tropoelastin in the extracellular space
Postnatal transformations of alveolar surfactant in the rabbit: changes in pool size, pool morphology and isoforms of the 32-38 kDa apolipoprotein.
No full textTo clarify perinatal transformations of surfactant we performed lung lavage in term fetuses and in 0-24-h-old newborn rabbits. Lavage fluid was separated into three pools, namely lavage pellet, lavage supernatant and cells. We found that at birth the pellet contains 94.1 ± 1.4% (S.E.) saturated phosphatidylcholine, while the supernatant and cells contain traces of it. At birth the pellet contains secreted lamellar bodies while the supernatant lacks any recognizable structure. After birth, the alveolar saturated phosphatidylcholine level increases 5.1-times in 24 h, the proportions between pools reaching adult values in 90 min (pellet = 75.9 + 4.8%, supernatant = 22.7 ± 4.9%), and small vesicles appear in the supernatant, probably originating from the turnover of alveolar surfactant during breathing. The saturated phosphatidylcholine associated with cells remains unchanged. At birth, the 32-38 kDa surfactant apolipoprotein appears to be less extensively sialylated than in adult life. © 1988
Ultrastructure of elastin
No full textAlmost all structural studies on elastin have been done in higher vertebrates, in which it is organized as an extracellular network of branched fibres which vary from fractions f microns to several microns in diameter. By conventional electron microscopy, elastin appears amorphous. By both freeze-fracture and negative staining on cryosections, it can be resolved as beaded filaments 5 nm in diameter forming a 3D meshwork that, upon stretching, becomes oriented in the direction of the force applied. This filamentous aggregation of elastin molecules is confirmed in vitro by the observation that its soluble precursor, tropoelastin, shows a strong tendency to associate into short 5 nm-thick filaments that, with time, become longer and aggregate into bundles of various dimensions. If chemically fixed and embedded, these aggregates appear amorphous and identical to natural elastin fibres. The tendency of tropoelastin to aggregate into 4-5 nm-thick beaded filaments, which then associate into 12 nm-thick filaments forming a 3D network, has been observed by atomic force microscopy for recombinant human tropoelastin. Therefore, the amorphous structure of elastin seems to be a technical artefact. Apart from elastin-associated microfibrils, which are always present at the periphery of growing elastic fibres and probably have a role more complex than being a scaffold for tropoelastin aggregation in vivo, the elastic fibres seem to be composed of several matrix constituents, which are different in different organs and change with age and in pathological conditions. This is demonstrated by immunocytochemical studies on ultrathin sections
Aortic Elastin Abnormalities in Osteogenesis Imperfecta Type II
No full textSkin and aortic samples from two patients who died by lethal perinatal Osteogenesis Imperfecta (O. I.) were studied by optical and electron microscopy and compared with similar samples from two normal human fetuses and one newborn child. No significant abnormalities were observed in the dermis of O. I. patients apart from small differences in the diameter of reticular collagen fibrils. On the contrary, in the aortas of both patients collagen fibrils were significantly smaller than in the controls; moreover, elastin lamellae were deeply altered and consisted of roundish aggregates of elastin, massively permeated by cytochemically recognizable glycosaminoglycans. As identical features were described in experimental lathyrism by using inhibitors of the enzyme lysyl oxidase (Pasquali Ronchetti et al., 1984), the conclusion is reached that in the two cases of lethal perinatal O. I. examined, a severe lysyl oxidase deficiency could account for the observed ultrastructural abnormalities of elastin and that, besides defects of collagen type I, additional alterations of cellular metabolism might be responsible for the clinical heterogeneity of the diesease. © 1986, Gustav Fischer Verlag · Stuttgart · New York. All rights reserved
Dermal elastin and collagen in systemic sclerosis. Effect of D-penicillamine treatment
No full textSkin biopsies from 4 systemic sclerosis (SSc) patients, 6 SSc patients treated with D-penicillamine (from 8 to 60 months) and 4 normal subjects were analyzed by light and electron microscopy. By light microscopy, collagen bundles of SSc dermis were thicker and more compact than in age-matched controls; D-penicillamine treatment did not significantly modify their organization. On the contrary, a stereological analysis showed that the elastin volume density was higher in patients than in controls, and increased again after D-penicillamine treatment: moreover, the number of elastin fibers per unit area was significantly higher in the dermis of patients compared to controls, and became even higher after D-penicillamine treatment. The phenomena were evident in all strata of the dermis; however, the most significant increase of elastin in SSc patients compared to controls was in the superficial dermis, whereas after D-penicillamine treatment, all the strata of the dermis showed a significant increase in the percentage of elastin and in the number of elastin fibers per unit area compared to untreated patients and to controls. There were no relationships between elastin increase and time from the onset of SSc or time and dose of D-penicillamine treatment. At the ultrastructural level, collagen fibrils had rather heterogeneous diameters and formed more compact fibers, especially in the reticular and in the deep dermis of SSc patients compared to controls. After D-penicillamine, collagen fibril diameters in three of 5 patients examined were statistically wider and more heterogeneous than in controls and in untreated patients, whereas in the other 2 subjects both the mean diameter and the distribution of the class diameter were similar to both controls and untreated patients. This could suggest a specific individual reaction to the drug. Elastin fibers were smaller, more numerous and polymorphous in all patients compared to controls. After D-penicillamine, elastin fibers became even more numerous and smaller than in untreated patients. There was no correlation between the number and size of the elastin fibers and the time or dose of D-penicillamine. The internal organization of the elastin fibers was normal. These data indicate that the amount and distribution of collagen and elastin are altered in the dermis of SSc patients, and that D-penicillamine interferes with the deposition of both fibrous proteins in the dermal extracellular space
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
