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PubMed1995

The effect of topical oestradiol on skin collagen of postmenopausal women.

OBJECTIVE: To examine the effect of topical oestradiol on skin collagen and elastin. SUBJECTS: Twelve postmenopausal women, aged 52 to 76 years. INTERVENTIONS: Topical oestradiol treatment on the skin of lower abdomen and the vehicle only on the contralateral site; once a day for three months. MAIN OUTCOME MEASURES: The content of skin hydroxyproline; the levels of the carboxyterminal propeptide of human type I procollagen (PICP) and of the aminoterminal propeptide of human type III procollagen (PIIINP). The number and the quality of collagen and elastic microfibrils. RESULTS: The amount of hydroxyproline in the skin significantly (P = 0.012) increased from 11.8 to 16.3 micrograms (38%) during oestradiol treatment. After treatment, the PICP level in the blister fluid was significantly (P = 0.024) higher on the treated site than on the control site. Also the level of PIIINP increased, but the change was not statistically significant. Electron microscopy showed morphologic improvement of elastic and collagen fibres, while the number of oxytalan and elaunin fibres was unchanged in light microscopy. CONCLUSIONS: Topical oestradiol treatment increases the amount of skin collagen. The increase in the level of PICP and PIIINP in skin blister fluid indicates that oestradiol treatment stimulates collagen synthesis. Furthermore, our results show that topical ostradiol treatment has a greater influence on the amount than on the quality of skin collagen. On the contrary, in elastic tissue the oestradiol treatment will only result in morphologic improvement.

Administration, Topical↗
PubMed1990

5-Hydroxytryptamine and arachidonic acid metabolites modulate extensive platelet activation induced by collagen in cats in vivo.

1. The pathways contributing to the platelet adhesion/aggregation reaction elicited by collagen microfibrils, administered to cats in vivo, were analysed. 2. The intra-aortic infusion of collagen (100 micrograms kg-1 in 1 min) caused an extensive activation of platelets, as evidenced by the time-dependent drop of free platelet numbers in whole blood, and the increases of 5-hydroxyindoles (5-HI), 5-hydroxytryptamine (5-HT) and thromboxane B2 (TXB2) levels in plasma, prepared from effluent venous blood sampled from the inferior caval vein. 3. 5-HT2 receptor blockade with ketanserin (0.63 mg kg-1 i.v., 10 min) and cyclo-oxygenase inhibition with aspirin (10 mg kg-1 i.v., 10 min) slightly attenuated the peak reduction of free platelets in whole blood in response to collagen without affecting changes in plasma 5-HI. Aspirin, but not ketanserin, reduced the collagen-induced changes in plasma TXB2, prostaglandin E2 (PGE2) and 6K-PGF1 alpha. 4. Dual TXA2 synthetase inhibition/TXA2-prostaglandin endoperoxide receptor antagonism with ridogrel (5 mg kg-1 i.v., 10 min) halved the drop in free platelets, reduced the release of platelet 5-HI, inhibited the increase in plasma TXB2 and elevated that of 6K-PGF1 alpha and PGE2 in response to collagen. 5. Combined treatment with ketanserin and aspirin reduced the collagen-induced drop of free platelets and the release of platelet 5-HI to a similar extent as ridogrel alone; plasma prostanoids were affected as with aspirin alone. 6. Combined administration of ketanserin and ridogrel virtually eliminated the collagen-induced platelet adhesion/aggregation response and release of 5-HI; prostanoids were affected as with ridogrel alone. 6. Combined administration of ketanserin and ridogrel virtually eliminated the collagen-induced platelet adhesion/aggregation response and release of 5-HI; prostanoids were affected as with ridogrel alone. 7. The results indicate that the interplay between 5-HT and arachidonic acid metabolites is causally involved in the platelet reaction to activation induced by collagen in cats in vivo.

Animals↗
PubMedDate not supplied

The platelet response to hypotonic shock. Its value as an indicator of platelet viability after storage.

The nature of the platelet response to osmotic shock and its relationship to platelet viability were studied. Light absorbancy changes of human platelet concentrates exposed to hypotonic shock were measured in a spectrophotometer: a sudden drop of light absorbancy was followed by a reversal of light absorbancy towards normal (reversal reaction). It was confirmed that the reversal reaction is a complex phenomenon dependent on the integrity of biochemical and enzymatic functions of the platelets. It was suppressed by glycolytic inhibitors and by SH-blocking agents. Ouabain had no immediate effect, but with prolonged incubation it depressed the reaction. Suspension of the platelets in a protein-free medium caused a rapid loss of the reversal reaction. Disappearance of the marginal bundle of microtubules by exposure to colchicine did not change the reaction leading to the hypothesis that microfibrils rather than the microtubules may have been responsible for the reversal reaction. The conclusion was derived that the reversal reaction is due to cell volume contraction for which integrity of the platelet contractile protein and energy availability are essential. Platelet storage at 4 degrees C or at 22 degrees C caused a progressive depression of the reversal reaction which was more severe in platelets preserved at 4 C than in those preserved at 22 degrees C, and paralleled the loss of the platelet capacity to survive in vivo. Cryoprotective agents (DMSO, DMAC and glycerol) partially inhibited the reversal reaction. Freezing with these agents caused a more severe depression of the reaction. The least depression was observed with 5 per cent DMSO. The results demonstrated that the reversal reaction is a valid and accurate in vitro indicator of in vivo platelet viability when the results to be compared are limited to a single method of storage. Usefulness of the reversal reaction is reduced when results obtained with different methods of storage are compared.

Blood Platelets↗
PubMed2006

Chitosomes: past, present and future.

José Ruiz-Herrera's discovery that chitin microfibrils could be made by a fungal extract paved the way for elucidating the intracellular location of chitin synthetase. In collaboration with Charles Bracker, chitosomes were identified as the major reservoir of chitin synthetase in fungi. Unique in size, buoyant density, and membrane thickness, chitosomes were found in a wide range of fungi. Their reversible dissociation into 16S subunits is another unique property of chitosomes. These 16S subunits are the smallest molecular entities known to retain chitin synthetase activity. Further dissociation leads to complete loss of activity. From studies with secretory mutants, yeast researchers concluded that chitosomes were components of the endocytosis pathway. However, key structural and enzymatic characteristics argue in favor of the chitosome being poised for exocytotic delivery rather than endocytotic recycling. The chitosome represents the main vehicle for delivering chitin synthetase to the cell surface. An immediate challenge is to elucidate chitosome ontogeny and the role of proteins encoded by the reported chitin synthetase genes in the structure or function of chitosomes. The ultimate challenge would be to understand how the chitosome integrates with the cell surface to construct the organized microfibrillar skeleton of the fungal cell wall.

Chitin↗
PubMed1994

The biological degradation of cellulose.

Cellulolytic microorganisms play an important role in the biosphere by recycling cellulose, the most abundant carbohydrate produced by plants. Cellulose is a simple polymer, but it forms insoluble, crystalline microfibrils, which are highly resistant to enzymatic hydrolysis. All organisms known to degrade cellulose efficiently produce a battery of enzymes with different specificities, which act together in synergism. The study of cellulolytic enzymes at the molecular level has revealed some of the features that contribute to their activity. In spite of a considerable diversity, sequence comparisons show that the catalytic cores of cellulases belong to a restricted number of families. Within each family, available data suggest that the various enzymes share a common folding pattern, the same catalytic residues, and the same reaction mechanism, i.e. either single substitution with inversion of configuration or double substitution resulting in retention of the beta-configuration at the anomeric carbon. An increasing number of three-dimensional structures is becoming available for cellulases and xylanases belonging to different families, which will provide paradigms for molecular modeling of related enzymes. In addition to catalytic domains, many cellulolytic enzymes contain domains not involved in catalysis, but participating in substrate binding, multi-enzyme complex formation, or possibly attachment to the cell surface. Presumably, these domains assist in the degradation of crystalline cellulose by preventing the enzymes from being washed off from the surface of the substrate, by focusing hydrolysis on restricted areas in which the substrate is synergistically destabilized by multiple cutting events, and by facilitating recovery of the soluble degradation products by the cellulolytic organism. In most cellulolytic organisms, cellulase synthesis is repressed in the presence of easily metabolized, soluble carbon sources and induced in the presence of cellulose. Induction of cellulases appears to be effected by soluble products generated from cellulose by cellulolytic enzymes synthesized constitutively at a low level. These products are presumably converted into true inducers by transglycosylation reactions. Several applications of cellulases or hemicellulases are being developed for textile, food, and paper pulp processing. These applications are based on the modification of cellulose and hemicellulose by partial hydrolysis. Total hydrolysis of cellulose into glucose, which could be fermented into ethanol, isopropanol or butanol, is not yet economically feasible. However, the need to reduce emissions of greenhouse gases provides an added incentive for the development of processes generating fuels from cellulose, a major renewable carbon source.

Biodegradation, Environmental↗
PubMed1981

Juvenile elastoma (Weidman). An ultrastructural study.

Two cases of juvenile elastoma (nevus elasticus in disseminated tumors) were histologically and ultrastructurally investigated. The predominant components of this disseminated dysembryoplasia are abnormal elastic fibers. Both cases showed numerous large elastic fibers with an abundant background matrix. The elastic microfibrils were replaced by granular material. In one case, most of the abnormal elastic units remained isolated without forming elastic fibers.

Adult↗
PubMed1983

Colloid and elastic fibre: ultrastructural study on the histogenesis of colloid milium.

Tissues peripheral to well-developed papules of colloid milium were chosen for biopsy and electron microscopy examination. Evidence was presented that colloid is derived from elastic fibres through sequential degenerative change. In the upper to middle dermis of the peripheral tissue, a number of abnormal masses in the vicinity of small colloid depositions were observed. Ultrastructurally, those abnormal masses were degenerating elastic fibres in which "electron-dense layers" of normal elastic fibre increased in amount, although their electron density diminished. Electron-light layers were gradually diminished in quantity. Degenerated elastic fibres finally became granulo-fibrillar and were indistinguishable from colloid. Many fibrils which closely resembled 10 nm tubular microfibrils of normal elastic fibre were observed in the granulo-fibrillar substance. Since one stage of the degeneration of elastic fibre which eventually leads to the formation of colloid milium was very similar to that of actinic elastosis, a direct role of sunlight in the formation of colloid milium is suggested.

Aged↗
PubMed1984

An ultrastructural study of pretibial myxedema utilizing improved ruthenium red stain.

A case of pretibial myxedema associated with Graves' diseases has been studied by electron microscopy utilizing an improved ruthenium red stain. An organized network of microfibrils with knobs were found within the widened interfibrous spaces. This network was clearly demonstrated by the ruthenium red stain, but only a weak trace could be observed when conventional staining techniques were utilized. Knobs of the network seemed to be composed of ruthenium red-positive granules which surrounded normal fibers and granules of degrading collagen fibers. Many fibroblasts showed dilated rough endoplasmic reticulum containing much amorphous material which indicated a significant role of fibroblasts in the pathogenesis of this disease.

Aged↗
PubMed1985

Intimate structural association of amyloid and elastic fibers in systemic and cutaneous amyloidoses.

Elastic fibers were found in the amyloid islands of primary systemic amyloidosis, heredo-familial amyloid polyneuropathy, macular amyloidosis and amyloidosis cutis nodularis atrophicans. In macular amyloidosis, the elaunin fibers in amyloid islands were loosely arranged, waved and twisted. In systemic amyloidosis and amyloidosis cutis nodularis atrophicans, amyloid fibers did not deposit in homogeneous electron-lucent material of elastic fiber, but were located close to the elastic fiber where the peripheral microfibrils were present.

Amyloid↗
PubMed1985

Bullous congenital ichthyosiform erythroderma masquerading as dystrophic epidermolysis bullosa.

A black baby, born at full term of a normal healthy mother, showed multiple erosions and ulcers. No history of skin diseases was known in the family. A skin biopsy taken shortly after birth from an arm lesion showed subepidermal edema and cavity formation. Electron microscopy showed clumping of microfibrils and anchoring fibril-like fibers at the dermo-epidermal junction. In more severely affected areas, absence of anchoring fibrils and collagenolysis were found and the diagnosis of dystrophic epidermolysis bullosa was made. Two weeks later, the lesions healed without leaving scars and a second biopsy from the chest area revealed typical histopathology of epidermolytic hyperkeratosis.

Biopsy↗
PubMed1986

Marfan syndrome: demonstration of abnormal elastic fibers in skin.

The back skin of a 15-year-old girl with Marfan syndrome has been investigated using scanning (SEM) and transmission (TEM) electron microscopy. The SEM showed that admixed with normal-looking portions, there were abnormal portions of the elastic fibers which were composed of many unusual fine fibers (5-22 nm in diameter), and had a cobweb-like appearance. The TEM showed that these fine fibers were substructures of the amorphous material and were surrounded by microfibrils. It is suggested that the fine fibers could be abnormal elastic fibers resulting from the incomplete fusion of the elastic units.

Adolescent↗
PubMed1995

Ultrastructural effects of topical tretinoin on dermo-epidermal junction and papillary dermis in photodamaged skin. A controlled study.

We examined the effects of daily topical application of 0.05% tretinoin cream on photodamaged Caucasian facial skin by electron microscopy. Specimens obtained pretreatment, after 6 and 12 months of tretinoin therapy (20 patients), and after 6 months of vehicle treatment (5 patients) were compared in a blinded fashion, with special attention to the dermoepidermal junction and papillary dermis. Baseline specimens disclosed various degrees of damage including reduplication of basal lamina, smudging and sparsity of collagen fibers, and nodular arrangement of degenerated microfibrils in the papillary dermis. No significant changes were observed at 6 months in the papillary dermis of either tretinoin-treated or vehicle-treated patients. After 12 months of tretinoin treatment, however, disorganized collagen fibers, which were conspicuous in 11 patients at baseline, were replaced by new well-organized collagen fibers in a wavy pattern in 6 patients. In addition, the amount of nodularly degenerated microfibrillar material decreased in 15 of 18 patients with this finding at baseline. In contrast, no significant change was noted in the number of anchoring fibrils per unit length of the lamina densa. These observations provide further evidence that topical treatment with 0.05% tretinoin produces papillary dermal reconstruction, for which more than 6 months of application were required.

Administration, Topical↗
PubMed1979

Amyloid-like green birefringence in cytoskeletal 10 nm filaments after staining with Congo red.

The commonly accepted markers for amyliod are a fibrillar ultrastructure and congophilia combined with green birefringence when viewed under polarized light. Although a number of cells have been implicated in amyloid formation the detailed events leading to accumulation of amyloid are still unknown. Previous studies have suggested that amyloid shares antigenic properties with cytoskeletal intermediate (10 nm) filaments and connective tissue microfibrils. In the present study we show that such filaments present in fibroblasts and lymphoid cells have an affinity for Congo red, exhibit the typical green birefringence and are ultrastructurally indistinguishable from amyloid fibrils. Intermediate filaments of cultured fibroblasts depleted of nutrient medium retained the Congo red birefringent property and typical ultrastructure despite cell damage. Our observations suggest that amyloid deposits may form locally through abnormal accumulation of bundles of cytoskeletal intermediate filaments under conditions characterized by increased cell proliferation and death.

Amyloid↗
PubMed1985

Genes for hair and avian keratins.

This paper briefly reviews the present level of understanding of the genes that code for hair keratins and the keratins of avian feather and scale. The emphasis to date has been on the structure of the genes, the derivation of amino acid sequences for several of the proteins from the coding sequences, and the organization of the different gene families within genomic DNA. Genomic sequences for the proteins of the three main gene families for wool keratin have been isolated from sheep genomic libraries and their detailed analysis by DNA sequencing is proceeding. Already, representative sequences for the genes of the microfibril (alpha-filament or IF) proteins and for the cysteine-rich and HGT matrix proteins are available. With these sequences as sources of probes, it is now possible to move from organizational and structural studies and undertake the study of the control of the expression of these genes either in wool (hair) follicles in vivo or after transfection with specific keratin genes of suitable epidermal cells in culture. Parallel with these studies is the investigation of the fate of trichohyalin droplets in the inner root sheath during its maturation, which is coordinated with keratinization in the hair itself. These unusual proteins and the changes they undergo suggest a highly specific function. The discovery of that function might come from the use of molecular cloning techniques especially for the synthesis of quantities of protein adequate for study. The avian keratins of feather and scale are coded for by a large family of evolutionarily related genes as shown in recent investigations of the DNA sequences. Again, derived protein sequences have provided a view of the feather and scale structures previously unavailable. Information on the fine structure of the genes is enabling the examination of their expression in vivo during embryonic development and the possible significance in this development of the histidine-rich ("fast") protein. The lack of any detectable transcripts from characterized feather keratin genes injected into Xenopus oocytes is presenting the possibility of testing for tissue-specific protein factors that might be responsible for the specific activation of keratin genes.

Animals↗
PubMed1985

Structure and macromolecular organization of type VI collagen.

Collagen VI is a large, disulfide-bonded protein complex which is widely distributed in connective tissue. The constituent polypeptide chains (Mr = 110,000-140,000) consist of collagenous and noncollagenous segments, are degraded to chains of about half the size when collagen VI is solubilized by pepsin, and assemble to a unique pattern of oligomers. As revealed by electron microscopy, the triple-stranded protomer consists of a triple helix 105 nm in length flanked on each side by globular domains of similar size (diameter about 7 nm). Protomers are assembled to dimers by an antiparallel staggered alignment of triple-helical segments. This leads to inner regions, 75 nm in length, of two slightly supercoiled triple helices flanked by globular domains. At both sides 30-nm-long outer triple-helical segments emerge that are terminated by globules. Tetramers are formed from laterally aligned dimers that cross with their outer triple-helical segments in a scissors-like fashion. The same structures, except with much smaller globular domains, are found in pepsin-treated collagen VI. Disulfide-linked collagen VI produced by cultured fibroblasts has a size similar to that of genuine collagen VI found in tissue extracts. Larger forms of collagen VI are assembled from tetramers by end-to-end aggregation which because of an overlap of the outer segments brings all globular domains close together. This arrangement predicts microfibrillar structures in tissues with a periodicity of 100-110 nm and a diameter of 5-10 nm. Structures consistent with this proposal were indeed found by immunoelectron microscopy of placenta and aorta using the ferritin technique. Large, lateral aggregates of collagen VI microfibrils may in addition exist in cell cultures and tissues ("zebra collagen," "Luse bodies") and are presumably maintained by contacts between globular domains.

Animals↗
PubMed1996

Elastic fiber-associated proteins of skin in development and photoaging.

We sought to use antibodies against structural (tropoelastin fibrillin) and nonstructural (decay-accelerating factor [DAF], serum amyloid P -SAP- components of elastic fibers to characterize fiber structure in neonatal skin, normal adult skin and adult skin with solar elastosis from advanced photoaging. We found by immunohistochemistry and by western blotting that DAF, unlike SAP, is present on cutaneous elastic fibers in neonates and young children, suggesting that DAF may play an early, integral role in protecting elastic fibers from destruction by complement. The most superficial portion of oxytalan fibers stained with antibodies against fibrillin and DAF, while anti-tropoelastin stained only the deeper portion of oxytalan fibers. This suggests that deep oxytalan fibers are composed of both elastin and microfibrils, while the most superficial component is composed solely of microfibrillar proteins. Solar elastosis showed increased fibrillin, DAF, tropoelastin and SAP. Thus, solar elastosis is composed of both microfibrillar and elastin proteins.

Adult↗
PubMed1989

Ultrastructure of transport pathways in stressed synovium of the knee in anaesthetized rabbits.

1. The hydraulic conductance of the synovial lining of a rabbit knee increases greatly when intra-articular pressure (IAP) is raised above approximately 9 cmH2O (yield point). To investigate the cause, synovium was fixed in situ by perfusion at controlled IAP and prepared for transmission electron microscopy. Micrographs of synovium fixed below yield pressure (atmospheric pressure and 5 cmH2O IAP, ten joints) and above it (25 cmH2O IAP, five joints) were analysed by morphometry. 2. The discontinuous cellular lining consisted of fibroblast-like cells (67%) and macrophage-like cells (33%) separated by interstitium-filled gaps. Interstitium formed 26-36% of the surface below yield pressure. Depending on sample site the surface gaps averaged 1.9 +/- 0.2 to 2.4 +/- 0.2 microns wide below yield pressure (mean +/- S.E.M. throughout). Above yield pressure the mean gap width increased by 42-64% (P less than 0.05, analysis of variance). 3. The qualitative and quantitative composition of the lining varied with distance below the surface. In a plane 5 microns deep, the intercellular distances and interstitial area fraction were almost double those at the surface. Classic periodic collagen fibrils (diameter 50 +/- 3 nm) abounded at 5 microns depth whereas the surface interstitium was richer in Ruthenium Red-staining microfibrils (diameter 9.3 +/- 0.7 nm) associated with 93 nm period fibrous long-spacing bundles. 4. Averaging over all the tissue between the surface and the 5 microns deep plane, the mean interstitial volume fraction was 0.61 +/- 0.05 at 5 cmH2O and 0.67 +/- 0.02 at 25 cmH2O (n.s.). 5. Capillary fenestrae (8.5 +/- 1.1 per fenestrated profile) and intercellular junctions were unaltered at high IAP. The tortuosity of the capillary-to-joint cavity path was 1.50 +/- 0.01 below yield pressure and 1.86 +/- 0.24 at 25 cmH2O (n.s.). 6. Intra-articular tracers (ferrocyanide, ferritin and glycogen) permeated synovial interstitium without evidence of preferential pathways. Ferrocyanide delineated the capillary intercellular junction as a permeable channel. Ferritin and glycogen were phagocytosed by the macrophages. 7. In suprapatellar areolar synovium, the most extensive and most altered tissue, the ratio of interstitial area to path length increased maximally 4.1 times between 5 and 25 cmH2O IAP. This represents a substantial contribution to the physiologically estimated rise in interstitial conductance (14 x) but does not wholly explain it.

Animals↗
PubMed1967

Ultrastructure of thrombosthenin, the contractile protein of human blood platelets.

Partially purified thrombosthenin with adenosine triphosphatase activity similar to that of actomyosin was subjected to electron microscopy. More than 50 percent of the material consisted of fibrils 80 to 100 angstroms in width. Occasional fibrils suggested a periodic structure. The morphology of isolated thrombosthenin resembled that of microfibrils in the cytoplasm and pseudopods of intact platelets.

Blood Platelets↗