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Scanning electron microscope findings of solar elastosis were compared with those of normal dermis in specimens digested by hyaluronidase and by autoclaving. Solar elastosis showed amorphous masses and broad fibres with irregular shapes and sizes in specimens digested by hyaluronidase, while it showed only fibrous structures in those after autoclaving. It is suggested that the origin of solar elastosis is elastic tissue.
Exposure to solar UV radiation (UVR) leads to changes in the extracellular matrix of the dermis, which is largely composed of collagen and elastin. Collagen and elastin proteins and their corresponding mRNA were assessed in dorsal skins of hairless mice exposed to 0.64 J/cm2 UVR (295-400 nm), 5 days per week, over a 12 week period. A 48% increase in skin-fold thickness was accompanied by increased elastic tissue deposition and more compressed collagen bundles as assessed histologically. Collagen I mRNA levels were similar to those in control skins at 1, 2, 3 and 6 weeks of UVR and less than control levels at 9 and 12 weeks. Collagen III mRNA levels were elevated after 1 week of UVR, remained elevated for a further 2 weeks and then returned to control levels at weeks 6, 9 and 12 when changes are occurring in collagen I transcripts. There was no evidence of corresponding changes in collagen I and III protein levels assessed using electrophoretic techniques. These results suggest that damage to the extracellular matrix, consequent on UVR, is associated with some pretranslational events. Elastin mRNA levels were unaffected by UVR, suggesting that elastic tissue hyperplasia is a posttranscriptional phenomenon.
On examination in the electron microscope elastic tissue is seen to consist of an amorphous component surrounded by microfibrillar components. The exact relationship between these components is unknown, although during development the microfibrils appear before the amorphous material. In this report we summarize our recent observations on the microfibrillar material. At high magnification the microfibrils are seen to have a poorly staining central core around the periphery of which are arranged more densely staining filaments which appear to wind around the microfibrils in a spiral fashion. Careful measurements of microfibrillar diameters from the aorta of four large species show that there are significant differences in the mean diameter and population distributions with species. The mean diameter of the microfibrils changes with age during fetal and postnatal development. The results of immunoelectronmicroscopic localization of an antibody to a microfibrillar component are reported and the possible roles of microfibrils in elastic tissue formation are examined.
The question as to whether the incudo-malleolar joint (IMJ) is mobile or immobile at moderate sound pressure levels (SPLs) is addressed. Referring to the mechanical properties of elastic tissue, we suggest that the IMJ is mobile at any SPL. In order to test this hypothesis, we investigated the dynamics of the IMJ in nine temporal bones by means of laser scanning doppler vibrometry. The dynamic behavior of both ossicles, malleus and incus is described by three degrees of freedom, and transfer functions (TFs) are shown for each motion component [corrected]. We show that there is indeed relative motion between the malleus and the incus. This transmission loss affects the middle ear TF and results in a frequency dependent sound transmission loss. Some characteristics of our results are in agreement with middle ear TFs described in the literature. The increasing transmission loss towards higher frequencies is caused by relative motion between malleus and incus at the IMJ. The concept that the IMJ is functionally mobile is consistent with the physical properties of elastic tissues which most likely define the mechanics of this joint. Since the IMJ is indeed mobile at moderate sound intensities and audible frequencies the theory of the lever ratio being responsible for the characteristics of the middle ear TF must be reconsidered.
Laser holographic interferometry is based on the superimposition of the holograms of different motional states of an object on a single holographic storing medium. Using a combination of holographic interferometry and endoscopic imaging, we tried to detect areas of focally disturbed tissue elasticity in gastric cancer preparations. By connecting a mobile electronic speckle pattern interferometry (ESPI) camera system (light source: double frequency Nd:YAG laser, lambda = 532 nm) to different types of endoscopes, ex vivo experiments were performed on ten formalin fixed human stomachs, nine containing adenocarcinomas and one with a gastric lymphoma. Linking the endoscopic ESPI camera complex to a fast image processing system, the method of double pulse exposure image subtraction was applied at a video frame rate of 12.5 Hz. Speckle correlation patterns and corresponding phase difference distributions resulting from gastric wall deformation by gentle touch with a guide wire were analyzed. Tumor-free gastric areas showed high-contrast concentric fringes around the point of stimulation. In contrast, fringe patterns and filtered phase difference distributions corresponding to the areas of malignancy in all the cases were characterized by largely parallel lines, indicating that stimulation of rigid tumor tissue primarily led to tilting. Our ex vivo investigations of malignant gastric tumors show that the application of dynamic holographic endoscopy makes it possible to distinguish areas of malignancy from surrounding healthy tissue based on the differences in tissue elasticity.
The effects of two forms of elastase on the Young's Modulus of elastic tissue have been studied. The monomeric, calcium poor form of the enzyme lowers the value of the Young's Modulus before an appreciable amount of protein is taken into solution. The polymeric, calcium rich enzyme on the other hand degrades the protein before reduction in Young's Modulus occurs. On the basis of these observations, it is confirmed that the enzyme/substrate complex in elastolysis is formed by interaction through a co-ordinately bound calcium atom and that this atom can be derived either from the substrate, where it stabilises the molecule, or from the enzyme.
A 9 year old boy sought medical attention because of a cutaneous infiltrate of the nape that could not be diagnosed macroscopically. Microscopic examination showed it to be a fascicular fibroma of a special structure. The striking feature of the stroma was the distinct proliferation and degeneration of the elastic fibers. The alteraions of the elastic tissue are similar to those seen in elastofibroma dorsi. It is discussed if the lesion results from a hyperplasia of true elastic or/and pseudo-elastic fibers.
Uniaxial loading of human lens, zonules, ciliary muscle, and choroid shows a nonlinear relationship between stress and deformation of the specimen, and hysteresis on unloading. Spring constants, at 10% elongation, have been calculated for all specimens and for several combinations. Except for zonules they are significantly correlated with age. They will provide a basis for a model of accommodation. The mean force required for 10% elongation of the lens, at mean age 43, is about 22 x greater than for the zonules; and the mean elongation of the zonules is nearly 7 x that of the lens at a load of 0.01 N (approximately 1 g). Ranges of forces and pressures in the accommodated and nonaccommodated eye are estimated.
Little is known about intracranial venous pressure in hydrocephalus. Recently, we reported that naturally occurring hydrocephalus in Beagle dogs was associated with an elevation in cortical venous pressure. We proposed that the normal pathway for cerebrospinal fluid (CSF) absorption includes transcapillary or transvenular absorption of CSF from the interstitial space and that the increase in cortical venous pressure is an initial event resulting in decreased absorption and subsequent hydrocephalus. Further analysis, however, suggests that increased cortical venous pressure reflects the effect of the failure of transvillus absorption with increase in CSF pressure on the venous pressure gradient between ventricle and cortex. Normally, the cortical venous pressure is maintained above CSF pressure by the Starling resistor effect of the lateral lacunae. A similar mechanism is absent in the deep venous system, and thus the pressure in the deep veins is similar to that in the dural sinuses. Decreased CSF absorption causes an increase in CSF pressure followed by an increase in cortical venous pressure without a similar increase in periventricular venous pressure. The periventricular CSF to venous (transparenchymal) pressure (TPP) gradient increases. In contrast, cortical vein pressure remains greater than CSF pressure (negative TPP). The elevated periventricular TPP gradient causes ventricular dilatation and decreased periventricular cerebral blood flow (CBF), a condition that persists even if the CSF pressure returns to normal, particularly if tissue elastance is lessened by tissue damage. If deep CBF is to be maintained, periventricular venous pressure must increase. Since the veins are in a continuum, cortical venous pressure will further increase above the CSF pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
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Generalized elastolysis is a rare and unique systemic disorder of connective tissue in which the elastic fibers suddenly become fragmented, disorganized and fewer in number with the resultant production of such entities as cutis laxa, emphysema, aortic aneurysms and bowel diverticula appearing in the organ system involved, that is, skin, lung, vasculature or gastrointestinal tract. Presented here are three cases that, illustrate the typical features of this condition. In addition, 14 more cases were retrieved from the literature and the information reviewed. Various etiologic factors relating to the synthesis and degradation of elastic tissue are discussed in light of recent findings in the biochemistry of connective tissue.
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Five cases of adenoid cystic carcinoma of minor salivary glands were studied. The mucoid material in the characteristic cystlike space of this neoplasm was distaseresistant periodic acid-Schiff (PAS)--positive, alcain blue-positive, toluidine blue-positive, and mucicarmine-positive. Verhoeff-Van Gieson's method and Weighert's method did not reveal elastic tissue in the cystlike spaces. Mallory's method revealed that a central core in cystlike spaces was similar in stainability to collagen. Wilder's method did not reveal reticular fibers in these spaces. Electron microscopy revealed three readily recognizable zones: a juxtacellular zone of a network of replicated basal lamina, and intermediate zone of stellate granules of mucoid material, and a central core of densely packed aperiodic filaments or collagen fibrils. The histogenesis of cystlike spaces and their realtionship with biologic behaviors of the neoplasm were discussed.
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Over the last decade, a considerable amount of new information has emerged describing the protein components of elastic fibers. It is now evident that elastic fibers are complex extracellular matrix polymers, composed of at least 19 different proteins that comprise both the microfibrillar and the amorphous components of elastic fibers. Mutations in three of the genes encoding the most abundant of these elastic fiber proteins result in a broad spectrum of elastic tissue phenotypes, ranging from skeletal and skin abnormalities to vascular and ocular defects. The following disorders will be discussed in this review: supravalvular aortic stenosis; Williams-Beuren syndrome; cutis laxa; Marfan syndrome; ectopia lentis; familial thoracic aortic aneurysms and dissections; MASS syndrome; isolated skeletal features of Marfan syndrome; Shprintzen-Goldberg syndrome; and congenital contractural arachnodactyly.
The fibrinolytic system is known to play an important role in the protection of lung architecture and function. This study investigated the effects on lungs of inhibiting the fibrinolytic system using tranexamic acid (TXA). Thirty cats were used, 15 experimental and 15 control. TXA was administered intravenously to the experimental animals for 3 h at 200 mg/kg (acute) and 7 days at 100 mg/kg (chronic). Blood samples were obtained from the carotid artery. The acute dose cats were sacrificed at 3 h and 24 h and the chronic dose cats at 8 days. Samples of inflated and fixed lung were examined morphologically and their collagen contents were determined. Fibrinolytic activity in blood samples was determined by fibrinogen degradation products levels, fibrin plate lytic area diameter, and the euglobulin lysis time. Hyperemia, lung interstitial oedema, haemorrhaging, inflammatory cell infiltration, pneumocyte type II cell proliferation, thrombosis and emphysema-related changes, characterized by enlargement of air spaces accompanied by destruction of alveolar walls, were observed in experimental cats group. None of these alterations except hyperemia and lung interstitial oedema were observed in two control animals. Electron microscopy results revealed oedema fluid in the interstitium, proliferation of pneumocyte type II cells, thickening of the alveolar septa and presence of marked amounts of collagen. Vacuoles were seen in the capillary endothelial cells. Elastic tissue was observed as elastic masses and partly disrupted, although elastic fibers were not prominent in all parts of the interstitium. Collagen content in the chronic dose experimental group was significantly higher than in all control and acute dose experimental groups. The inhibition of fibrinolytic system appears to have caused the emphysematous alterations, alveolar wall destruction and collagen accumulation possibly by causing microthromboses leading to mechanical blockage-ischemic changes, or by causing secondary fibrinolysis as a result of fibrin degradation products affecting local plasminogen activators and proteases. An injury-repair process also appears to have occurred.
BACKGROUND: Fibrel is a medical implant device that has demonstrated use in the correction of cutaneous depressions from acne scars and wrinkles. OBJECTIVE: Mechanisms of actions have been proposed that have theorized the production of new collagen over time as a result of the Fibrel implant. The present study utilized human volunteers to study the histologic response of Fibrel over time. METHODS: Fibrel was injected into tattoo sites behind the ears of human volunteers; skin biopsies were taken at various time intervals and studied histologically by a clinical pathologist. RESULTS: An overall increase over time was noted with regard to production of collagen and inflammatory response. No change in elastic tissue was found. CONCLUSIONS: Fibrel does promote new collagen synthesis and inflammatory response and thus is useful to correct cutaneous depressions via soft tissue augmentation.
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