Interventions for preventing eating disorders in children and adolescents.

BACKGROUND: Eating disorders represent an extremely difficult condition to treat and patients consume an enormous amount of mental health energy and resources. Being young, female, and dieting are some of the few identified risk factors that have been reliably linked to the development of eating disorders, and several prevention eating disorder prevention programs have been developed and trialed with children and adolescents. The purpose of this systematic review is to evaluate the effectiveness of eating disorder prevention programs for children and adolescents both in the general population and those determined to be at risk. OBJECTIVES: 1. To determine if eating disorder prevention programs are effective in promoting healthy eating attitudes and behaviours in children and adolescents; 2. To determine if eating disorder prevention programs are effective in promoting psychological factors that protect children and adolescents from developing eating disorders; 3. To determine if eating disorder prevention programs are effective in promoting satisfactory physical health in children and adolescents; 4. To determine if eating disorder prevention programs have a long-term, sustainable, and positive impact on the mental and physical health of children and adolescents; and, 5. To determine the safety of eating disorder prevention programs in terms of possible harmful consequences on the mental or physical health of children and adolescents. SEARCH STRATEGY: Relevant trials are identified through searching the Cochrane Controlled Trial Register (CCTR) and relevant biomedical and social science databases. All terms necessary to detect prevention programs and the participant groups are used. A strategy to locate randomised controlled trials is used. Other sources of information are the bibliographies of systematic and non-systematic reviews and reference lists from articles identified through the search strategy. In order to identify unpublished studies, experts in the field are contacted by letter and/or electronic mail. SELECTION CRITERIA: Randomised controlled trials (RCT) with a major focus on eating disorder prevention programs for children and adolescents, where there is no known DSM-IV diagnosis of an eating disorder, are eligible for inclusion in the review. Trials must include a control group and at least one objective outcome measure (eg. BMI) or a standardised psychological measure used with the intervention and control group, pre- and post-intervention. DATA COLLECTION AND ANALYSIS: A total of 1379 titles have been identified through the search to date. 13 studies were located that reported use of a randomised controlled trial methodology and were critically appraised by two independent reviewers. Five (5) studies were excluded as data were not reported in a useable form or useable data could not be obtained from the trial authors, one dissertation could not be obtained, one study had no "true" no-treatment or usual treatment control group, and one study did not use a pre-test outcome measure. Eight (8) studies met the selection criteria outlined above. MAIN RESULTS: Only one of eight pooled comparisons of two or more studies using similar outcome measures and similar intervention types demonstrated the statistically significant effect of a particular type of eating disorder prevention program for children and adolescents. Combined data from two eating disorder prevention programs based on a media literacy and advocacy approach indicate a reduction in the internalisation or acceptance of societal ideals relating to appearance at a 3- to 6-month follow-up (Kusel, unpublished; Neumark-Sztainer2000) [SMD -0.28, -0.51 to -0.05, 95% CI]. However, there is insufficient evidence to conclude that this approach also demonstrated a significant impact on awareness of societal standards relating to appearance. There is insufficient evidence to support the effect of four programs designed to address eating attitudes and behaviours and other adolescent issues on body weight, eating disorder symptoms, associated eating disorder psychopathology or general psychological and physical well-being in the general sample or those classified as being at high risk for eating disorder (Buddeberg-F 1998; Killen 1993/1996; Santonastaso 1999; Zanetti 1999). Given only one program used a psychoeducation approach to prevent bulimia nervosa (Jerome, unpublished) and only one program adopted a focus on self-esteem (O'Dea 2000), the effect of these approaches could not be evaluated via meta-analyses. In relation to potential harmful effects, there is not sufficient evidence to suggest that harm resulted from any of the prevention programs included in the review. REVIEWER'S CONCLUSIONS: The one significant pooled effect in the current review does not allow for any firm conclusions to be made about the impact of prevention programs for eating disorders in children and adolescents, although none of the pooled comparisons indicated evidence of harm. From a clinical perspective, the development and refinement of prevention programs is complicated by a lack of knowledge about risk factors associated with eating disorders and the need to strike a balance between delivering preventive interventions for eating disorders and considering the potential to cause harm. From a research perspective, the idea of "thresholds" for identifying young people at risk of developing eating disorders has been raised, and denial of concern or denial of illness represents a further issue complicating early identification in relation to eating disorder symptomatology. Longer-term effects of the intervention approaches will need to be monitored across development in order to demonstrate a decline in the incidence of eating disorders and associated risk factors.

Renal fibrosis in mice treated with human recombinant transforming growth factor-beta2.

BACKGROUND: The biologic responses to transforming growth factor-beta (TGF-beta) suggest many potential therapeutic applications; however, in the only clinical trial to examine the effect of the systemic administration of a TGF-beta isoform, patients experienced significant but reversible declines in renal function. We studied the effects of administering human recombinant TGF-beta2 to adult mice. METHODS: The effect of daily administration of TGF-beta2 on tissue vasoconstriction, tissue levels of endothelin and angiotensin II, tissue hypoxia, and renal fibrosis were examined. RESULTS: Daily administration of TGF-beta2 at 10 or 100 microg/kg caused apparent tissue vasoconstriction that was visualized by vascular casting, with the largest impact seen in the kidney. Tissue levels of endothelin 1 and angiotensin II were significantly elevated in kidneys of treated mice, as was urinary thromboxane beta2. Renal fibrosis was observed in the cortical tubular interstitium and vasculature, particularly at the cortical-medullary junction and medullary vasa recta; however, glomerular sclerosis was not observed. Fibrosis was correlated to focal tissue hypoxia as determined by immunohistochemical detection of tissue bound pimondazole. CONCLUSION: We conclude that there are significant histopathologic consequences, focused in the kidney, resulting from the daily administration of high doses of human recombinant TGF-beta2, and we propose that selective vascular constriction with consequent tissue hypoxia is a contributing factor.

Recombinant human antithrombin III improves survival and attenuates inflammatory responses in baboons lethally challenged with Escherichia coli.

Plasma-derived antithrombin III (ATIII) prevents the lethal effects of Escherichia coli infusion in baboons, but the mechanisms behind this effect are not clear. In the present study, we evaluated the effects of recombinant human ATIII (rhATIII) on the clinical course and the inflammatory cytokine and coagulation responses in baboons challenged with lethal dose of E coli. Animals in the treatment group (n = 5) received high doses of rhATIII starting 1 hour before an E coli challenge. Those in the control group were administered saline. Survival was significantly improved in the treatment group (P =.002). Both groups had similar hemodynamic responses to E coli challenge but different coagulation and inflammatory responses. The rhATIII group had an accelerated increase of thrombin-ATIII complexes and significantly less fibrinogen consumption compared to controls. In addition, the rhATIII group had much less severe thrombotic pathology on autopsy and virtually no fibrinolytic response to E coli challenge. Furthermore, the rhATIII group had a significantly attenuated inflammatory response as evidenced by marked reduction of the release of various cytokines. We conclude that the early administration of high doses of rhATIII improves the outcome in baboons lethally challenged with E coli, probably due to the combined anticoagulation and anti-inflammatory effects of this therapy. (Blood. 2000;95:1117-1123)

Acute and chronic renal effects of recombinant human TGF-beta2 in the rat.

The expression of transforming growth factor-beta (TGF-beta) correlates with the incidence of renal glomerular and interstitial injury, however, nothing is known of the effect of these proteins on renal hemodynamics. This study examines the renal hemodynamic and morphologic effects of recombinant human TGF-beta2 in normal male Sprague Dawley rats. Acute infusion of TGF-beta (1.2 microg/kg per min) induced no hemodynamic changes, except for a modest though significant fall in mean arterial pressure. Administering TGF-beta2 at varying doses (20, 100, and 400 microg/kg) for 9 wk caused modest increases in systolic BP and proteinuria and minimal tubular interstitial fibrosis, however, renal hemodynamic end points were not significantly altered. TGF-beta2 (800 microg/kg) was also administered to volume-depleted rats for 7 consecutive days. In contrast to the findings in volume-replete animals, administration of TGF-beta2 to volume-depleted rats caused a marked reduction in GFR and medullary blood flow. Histologic fibrosis of the medullary vasa recta and cortical interstitium was seen, but glomeruli were unaffected. Thus, acute and short-term chronic TGF-beta2 administration did not induce major renal changes in the volume-replete state, however, TGF-beta2 combined with volume depletion caused medullary hypoperfusion and reduced GFR.

TGF-beta in the central nervous system: potential roles in ischemic injury and neurodegenerative diseases.

The Transforming Growth Factor-betas (TGF-beta) are a group of multifunctional proteins whose cellular sites of production and action are widely distributed throughout the body, including the central nervous system (CNS). Within the CNS, various isoforms of TGF-beta are produced by both glial and neural cells. When evaluated in either cell culture or in vivo models, the various isoforms of TGF-beta have been shown to have potent effects on the proliferation, function, or survival of both neurons and all three glial cell types, astrocytes, microglia and oligodendrocytes. TGF-beta has also been shown to play a role in several forms of acute CNS pathology including ischemia, excitotoxicity and several forms of neurodegenerative diseases including multiple sclerosis, Parkinson's disease, AIDS dementia and Alzheimer's disease.

Recombinant human thyrotropin stimulates thyroid function and radioactive iodine uptake in the rhesus monkey.

The administration of bovine TSH to stimulate thyroid radioactive iodine uptake to detect functioning thyroid tissue in man after surgery for thyroid cancer is rarely, if ever, used, due to allergic reactions and/or the development of TSH antibodies. Human (h) TSH would be far less likely to induce allergic reactions or TSH antibodies. Recombinant hTSH (rec-hTSH) was produced by a line of Chinese hamster ovary cells that had been transfected with cDNA for the two subunit proteins that comprise hTSH. The present study was carried out to determine the half-life of rec-hTSH in the monkey and its ability to stimulate thyroid function. The half-life of rec-hTSH after iv administration was approximately 63 min for the rapid phase and 326 min for the slow phase. After three daily im injections of 2 U rec-hTSH to two monkeys, serum T4 concentrations increased several-fold, and serum T3 increased 2-3 times above basal values. The 6 and 20 h thyroid 123I uptakes doubled after rec-hTSH administration. These results demonstrate the biological efficacy of rec-hTSH administered to the monkey and strongly suggest that rec-hTSH will be effective in stimulating thyroid function in man.

Differences in the biological activities of transforming growth factor-beta and platelet-derived growth factor in vivo.

Transforming growth factor-beta 1 (TGF-beta 1 and recombinant platelet-derived growth factor-BB (rPDGF-BB) promoted an extensive, dose-dependent development of fibrous connective tissue when continuously delivered for 8 days by mini-osmotic pumps implanted subcutaneously in adult guinea pigs. Biochemical analyses demonstrated that TGF-beta 1 and rPDGF-BB stimulated dose-dependent increases in the dry weight, and protein, DNA, collagen, and glycosaminoglycan (GAG) contents of the fibrous connective tissue capsule that enveloped the pumps. The GAG/DNA mass ratio was markedly elevated by TGF-beta 1, but the collagen/DNA, protein/DNA, and collagen/protein ratios were not significantly increased. In contrast, rPDGF-BB generally decreased these mass ratios. Histological analyses suggested that this was due to the fact that rPDGF-BB induced a very cellular response with a marked influx of neutrophils and fibroblasts. TGF-beta 1 induced significantly less cellular response, which consisted primarily fibroblasts and macrophages. These results indicated that rPDGF-BB and TGF-beta 1 induced connective tissue deposition in vivo in a dose-dependent fashion, although the cellular nature of the responses as well as the structural composition of the extracellular matrices were clearly distinguishable between the two growth factors.

Biological activity and metabolic clearance of a recombinant human thyrotropin produced in Chinese hamster ovary cells.

The presence and specific structures of the oligosaccharides on TSH have been shown to be important for its production and bioactivity. Since the carbohydrate structure of a protein reflects the glycosylation apparatus of the host cells in which the protein is expressed, we examined the biological activity and metabolic clearance of a preparation of purified recombinant human (rh) TSH derived from a stable transfectant of Chinese hamster ovary cells. Carbohydrate compositional analysis of this rTSH showed it to be more highly sialylated than a nonrecombinant, cadaver-derived pituitary hTSH. In addition, no N-acetyl galactosamine was detectable in rhTSH, which implies the absence of terminal sulfate moieties, both of which are present in pituitary-derived TSH. The immunologic activity and porcine TSH receptor-binding activity of the preparation of rhTSH were 3- to 4-fold lower than those of a standard pituitary hTSH. The rhTSH showed a maximum stimulatory activity similar to that of pituitary hTSH in two different in vitro bioassays. However, rhTSH elicited about 3-fold and 5-fold less cAMP than pituitary TSH after stimulation of adenylyl cyclase in bovine thyroid membranes and the rat FRTL-5 cell line, respectively. Removal of sialic acid did not alter the immunologic activity of rhTSH. However, the potencies of rhTSH in receptor-binding, adenylyl cyclase, and FRTL-5 assays were increased 2.4-, 2.6- and 26.7-fold, respectively after sialic acid removal. These data suggest that the in vitro biological activity of rhTSH is influenced by its highly sialylated oligosaccharide chains. The rhTSH had a 2-fold lower metabolic clearance rate than pituitary TSH, resulting in a greater than 10-fold higher serum concentration of rhTSH at 3 h as compared to pituitary hTSH. After sialic acid removal, the rhTSH was cleared faster (7.5-fold) than pituitary hTSH, showing that its longer plasma half-life was due to its higher sialylation. Biologically active rhTSH should be of clinical value in the diagnosis and treatment of patients with thyroid cancer and as a pure hTSH reference preparation.

Inhibition of connective tissue formation in dermal wounds covered with synthetic, moisture vapor-permeable dressings and its reversal by transforming growth factor-beta.

An investigation of synthetic, adherent, moisture vapor-permeable dressings (SAM) on dermal wounds healing by secondary intent has yielded the novel observation that SAM dressings severely inhibited the deposition of granulation tissue and subsequent collagenous tissue when compared with air-exposed wounds in mouse and guinea pig systems. Repair tissue was quantitated histomorphometrically in full-thickness wounds covered with SAM or left air-exposed for periods up to 3 weeks. Early in healing, mouse wounds left open to the atmosphere formed a scab which overlay a large volume of granulation tissue derived from two sources, one lateral, and the other deep and centrally located. In contrast, SAM-covered wounds contained only a small amount of granulation tissue which was derived solely from lateral sources. Granulation tissue was replaced by fibrous connective tissue over time, and this was always less in SAM-covered wounds. Deposition of large amounts of connective tissue in air-exposed wounds was associated with significant polymorphonuclear and mononuclear cell infiltrates, while the lack of granulation tissue formation in SAM-covered sites was associated with reduced inflammation. Dressing-induced inhibition of connective tissue could be partially reversed by treatment with transforming growth factor-beta form 1 or 2. Deposition of granulation tissue in large lenticular wounds in guinea pig skin, but not in 6-mm punch wounds, was also inhibited when the wounds were covered with SAM, and the morphology of air-exposed and SAM-covered wounds was similar to that in mice. SAM-covered wounds in mice and guinea pigs may be useful as models of chronic non-healing wounds.

Transforming growth factors-beta 1 and beta 2 induce synthesis and accumulation of hyaluronate and chondroitin sulfate in vivo.

Subcutaneous implantation in rats of partially purified transforming growth factor-beta (TGF-beta) derived from bovine bone induced extensive development of connective tissue with associated edema. Subcutaneous injection of pure TGF-beta 1 or TGF-beta 2 also induced connective tissue deposition in mice and guinea pigs. Sustained release of TGF-beta 1 from mini-osmotic pumps implanted subcutaneously in mature guinea pigs promoted connective tissue deposition that encapsulated the pumps. Biochemical analyses of the connective tissue capsule demonstrated that TGF-beta 1 induced a dose-dependent accumulation of glycosaminoglycans (GAGs). The GAG/DNA ratio also increased as a function of the rate of TGF-beta 1 released, suggesting that the factor increased production of GAGs per cell. Cellulose acetate gel electrophoresis of the GAGs and hydrolysis with specific glycosidases revealed that the majority of GAGs consisted of hyaluronate and chondroitin sulfate. These results demonstrate that TGF-beta 1 and TGF-beta 2 stimulate the production of not only collagenous extracellular matrix components, but also dramatically increase the in vivo synthesis of hyaluronate and chondroitin sulfate.

Matrix-driven cell size change modulates aortic endothelial cell proliferation and sheet migration.

Current hypotheses suggest that the extracellular matrix modulates cellular function in physiologic homeostasis and during injury and repair and that selected cellular functions are cell and nuclear size dependent. For elucidation of the role of extracellular matrix-driven cell size changes in the modulation of endothelial cell proliferation and sheet migration an in vitro model system was used that allows for the culture of bovine aortic endothelial cells (BAEC) on various purified extracellular matrix components. BAEC exhibited distinct patterns in rates of attachment, spreading, migration, and proliferation when cultured on the selected extracellular matrix components laminin, types I and III collagen, type IV collagen, and fibronectin. In addition, there was a correlation between cell and nuclear size (on the various matrices tested) and rates of cell attachment and spreading. In contrast, an inverse correlation was noted between cell and nuclear size (on the various matrices tested) and proliferation and sheet migration. These data demonstrate that endothelial cells respond to matrix components in specific but complex fashions, mediated, in part, by changes in cell and nuclear size.

Phenotypic modulation of endothelial cells by transforming growth factor-beta depends upon the composition and organization of the extracellular matrix.

Transforming growth factor beta (TGF-beta) is angiogenic in vivo. In vitro, endothelial cell proliferation is inhibited by TGF-beta. We have correlated this inhibitory effect with an increase in cellular fibronectin synthesis and deposition in a two-dimensional culture system using specific matrix coatings. The inhibitory effect was mimicked by addition of soluble fibronectin to cultures. In contrast, TGF-beta was found to elicit the formation of tube-like structures (mimicking angiogenesis) when microvascular endothelial cells were grown in three-dimensional collagen gels. In this culture system TGF-beta elicited rapid extensive formation of complex, branching, tube-like structures, while cell proliferation was not inhibited. These data confirm and support the hypothesis that TGF-beta is angiogenic and may exert some of its effects through modulation of matrix synthesis and are consistent with the hypothesis that the organization of the extracellular environment influences cellular responses to this "panregulin."

Aortic endothelial cell proteoheparan sulfate. II. Modulation by extracellular matrix.

The effects of extracellular matrix components on proteoheparan sulfate biosynthesis was studied for bovine aortic endothelial cells in tissue culture. When the cells were maintained on a variety of different purified components of the extracellular matrix, the cells expressed the same three species of proteoheparan sulfates as the cells cultured on tissue culture plastic (HS I, HS II, and HS III). However, the amounts of the three species recovered from the tissue culture medium were found to be dependent on the substrate on which the cells are grown as well as on other factors. In comparison with plastic, much less HS I was found in the medium of cells maintained on substrates containing diverse matrix molecules, whereas the amounts of HS II and HS III essentially remained the same. In contrast, when bovine aortic organ cultures were analyzed under pulsatile flow, marked differences in the profile of proteoheparan sulfate biosynthesis were observed: HS I was found exclusively associated with the plasma membrane of the endothelial cells; HS II was localized only to the subendothelial matrix; and HS III represented the only proteoheparan sulfate species in the medium. This distribution is consistent with polarized secretion and deposition into the subcellular matrix of HS III and retention of HS I in the plasma membrane in the organ culture situation, a biosynthetic phenotype which can only be approximated at best by maintaining the endothelial cells on a substrate other than plastic. When aortic media (devoid of endothelial cells) was placed in organ culture, no HS III could be detected, which suggested that the vascular endothelial cell is the major cell type responsible for its synthesis in organ culture. Thus, the extracellular matrix, depending upon its composition and organization, may play an important role in stabilizing cell polarity and thereby contribute to maintenance of the differentiated phenotype appropriate for the endothelial cell.

Retinol and extracellular collagen matrices modulate hepatic Ito cell collagen phenotype and cellular retinol binding protein levels.

The hepatic vitamin A-storing Ito cell has been implicated as a causative cell in hepatic fibrogenesis. Using a modification of a recent method (Friedman, S. L., Roll, F. J., Boyles, J., and Bissell, D. M. (1985) Proc. Natl. Acad. Sci. U. S. A. 82, 8681-8685), rat Ito cells were isolated and passaged in vitro on collagen-coated plastic dishes through cell generation 40-50. The collagen synthetic phenotype for Ito cells grown on various extracellular matrices was demonstrated by immunofluorescence and quantitated by competition enzyme-linked immunosorbent assays. When grown on a type I collagen matrix, Ito cells produced type IV greater than type III greater than type I collagen. When grown on a type IV collagen matrix, the cells produced relatively equal amounts of types I and III collagen. The absolute amounts of type I collagen produced were greater when cells were grown on type IV versus type I matrix. When 10(-5) M retinol was added to cell cultures, there was a uniform increase in type III collagen regardless of matrix type but a decrease in type I collagen when cells were grown on a type IV matrix and a large increase in type I collagen when cells were grown on a type I collagen matrix. The levels of cellular retinol binding protein, a key cytosolic retinol transport protein, were quantitated by high performance liquid chromatography and compared for cells grown on type I versus type IV collagen matrices. It was found that cells on a type I matrix contain 4.96 +/- 2.8 times more cellular retinol binding protein than do cells grown on a type IV matrix. In conclusion, Ito cell collagen synthesis may be altered by underlying extracellular matrix and exogenous retinol. This in vitro culture system should allow the study of regulatory factors and possible therapeutic anti-fibrogenic mediators.

Endothelial cell proliferation during angiogenesis. In vitro modulation by basement membrane components.

Modulation of the behavior of microvascular endothelial cells during angiogenesis has been observed to correlate with changes in the extracellular matrix. These reports prompted a comparison of the growth of microvascular endothelial cells on monolayers of various matrix components in vitro. Over a 5 day period, the proliferation of these cells was significantly greater on laminin than on either plasma fibronectin, the interstitial collagen types I and III, or on the basement membrane collagen type IV. Proliferation of the microvascular endothelial cells was compared with that of bovine aortic endothelial cells and bovine aortic smooth muscle cells on the same matrices. All three cell types grew significantly more rapidly on laminin than on fibronectin. The aortic endothelial cells differed from their microvascular counterparts in that the growth of these large vessel endothelial cells on the collagenous matrices (types I and III, or type IV) was not significantly different from that observed for laminin, but was greater than the relatively slow growth seen on plasma fibronectin. Further comparison of the growth of the microvascular endothelial cells on the two basement membrane components, laminin and type IV collagen, demonstrated that the growth of these cells on laminin can be modulated by the presence of type IV collagen. This was true either if the two matrices were combined as a mixed layer, or if the laminin was specifically bound to a layer of type IV collagen, more closely simulating the distribution of these molecules in a basement membrane. Examination by immunoperoxidase of in vivo model of neovascularization in the murine cornea revealed a temporally staggered appearance of basement membrane components. The appearance of laminin was found to occur throughout the newly formed vessels, as well as in individual cells at the migrating, proliferating tips. In contrast, the appearance of type IV collagen correlated with lumen formation and was not detected at the vessel tips. The results of this study suggest that the temporally ordered synthesis of specific matrix components plays a significant role in orchestrating the growth and differentiation of endothelial cells during the highly integrated set of responses known as angiogenesis.

Mechanisms of cytoskeletal regulation: modulation of aortic endothelial cell protein band 4.1 by the extracellular matrix.

The bovine aortic endothelial cell (BAEC) cytoskeleton is a complex structure modulated by many stimuli including release from contact inhibition and various components of the extracellular matrix (ECM). Transduction of information from the ECM to the cell nucleus proceeds via several complex pathways including the cytoskeleton. We have demonstrated the presence of an immunoreactive isoform of the human erythrocyte cytoskeletal protein band 4.1 (4.1) in BAEC. BAEC 4.1 is similar in molecular weight to the erythroid protein by immunoblot analyses and produces a similar pattern of cysteine specific cleavage products consistent with a cluster of cysteine residues previously described in the erythroid molecule. We have also examined the effects of defined ECM proteins on the distributions of cultured BAEC 4.1 and actin filaments (AF) at confluency and following release from contact inhibition. The distribution of 4.1 in BAEC on a plasma fibronectin substrate is complex, having partial codistribution with cytoplasmic AF and a unique perinuclear staining. In contrast, on a collagen type I/III substrate, 4.1 is localized, in part, to peripheral areas of cell-cell contact distinct from the dense peripheral band staining of AF. During migration on this substrate, 4.1 had a filamentous distribution having partial codistribution with AF. Indirect immunofluorescence staining of cross-sections of bovine calf aortae revealed a cortical staining pattern in the aortic endothelial cells with staining noted on the luminal and basolateral aspects of the cells. These data suggest that, in endothelial cells, protein 4.1 is a cortical membrane protein which may function to link actin filaments to other skeletal proteins such as spectrin. These findings also suggest an active role for protein 4.1 in cytoskeletal reorganization events which can occur in response to external stimuli, such as the extracellular matrix or contact with other cells.

Immunolocalization of type IV collagen and laminin in nonbasement membrane structures of murine corneal stroma. A light and electron microscopic study.

The extracellular matrix of adult vertebrate corneal stroma is composed primarily of the interstitial collagen type I and smaller amounts of types III and V collagen. These collagens are organized into overlapping lamellae of striated filaments. In addition to these lamellar structures, the corneal stroma also contains 100- to 250-nm bundles of nonstriated 8- to 11-nm microfibrils. By immunofluorescent localization and electron microscopic immunolocalization, these microfibril bundles in the mouse are associated with type III collagen, type IV collagen, and laminin. By immunologic and histochemical criteria, these bundles do not contain either type I collagen, type V collagen, elastin, or oxytalan microfibrils. The cellular source, composition, and possible functions of these microfibril bundles are discussed.