Learning chronobiology by improving Wikipedia.

Although chronobiology is of growing interest to scientists, physicians, and the general public, access to recent discoveries and historical perspectives is limited. Wikipedia is an online, user-written encyclopedia that could enhance public access to current understanding in chronobiology. However, Wikipedia is lacking important information and is not universally trusted. Here, 46 students in a university course edited Wikipedia to enhance public access to important discoveries in chronobiology. Students worked for an average of 9 h each to evaluate the primary literature and available Wikipedia information, nominated sites for editing, and, after voting, edited the 15 Wikipedia pages they determined to be highest priorities. This assignment (http://www.nslc.wustl.edu/courses/Bio4030/wikipedia_project.html) was easy to implement, required relatively short time commitments from the professor and students, and had measurable impacts on Wikipedia and the students. Students created 3 new Wikipedia sites, edited 12 additional sites, and cited 347 peer-reviewed articles. The targeted sites all became top hits in online search engines. Because their writing was and will be read by a worldwide audience, students found the experience rewarding. Students reported significantly increased comfort with reading, critiquing, and summarizing primary literature and benefited from seeing their work edited by other scientists and editors of Wikipedia. We conclude that, in a short project, students can assist in making chronobiology widely accessible and learn from the editorial process.

Activation induces rapid and profound alterations in the trafficking of T cells.

Activation and differentiation of lymphocytes have profound effects on their trafficking. Whereas naive T cells recirculate through lymphoid organs, activated cells localize predominantly in other compartments. Here, we report that changes in migratory properties of T cells occur immediately upon activation via the TCR. One hour stimulation is enough to target T cells into lung and liver following i.v. injection. The high localization within lung and liver and the lack of recirculation through lymphoid tissues are key features of activated lymphocytes. the source, in vitro as well as in vivo activated lymphocytes show this behavior, which is not caused by increased cell size. Accumulation in the lung requires protein synthesis and is partly mediated by LFA-1, in contrast to the acquisition of liver "homing" properties. Intravital microscopy reveals firm adhesion of activated cells within periportal sinusoids of the liver. Selective homing to other organs, such as skin or mucosa, was not observed, regardless of the cell's origin. These data indicate that activation quickly switches the trafficking program of lymphocytes from recirculation to sequestration; it is tempting to speculate that especially the induced trapping in the liver has a distinct role in limiting systemic T cell responses.

Dissemination capacity of murine lymphoma cells is not dependent on efficient homing.

The extravasation of normal lymphocytes from blood into tissues is controlled by adhesion molecules ("homing receptors") that mediate their interaction with endothelial cells. It is an intriguing question whether malignant cells use the same pathways for hematogenous dissemination and whether these molecules are involved in the organ-specific formation of metastasis. To analyze the migration behavior of lymphoma cells in vivo, we here used several lines and sublines which exhibit differential expression of the lymph node homing receptor L-selectin and the mucosa-specific integrin alpha4beta7. We demonstrate that the ability of the various types of cells tested to accumulate in lymph nodes within the first 24 hr after intravenous (i.v.) injection is negligible, independent of their homing receptor expression profile. Our data indicate that lymphoma cells have, in comparison with naive lymphocytes, an impaired capacity to extravasate via high endothelial venules (HEV). Instead they predominantly accumulate in lung and liver, similar to activated lymphocyte populations. Nevertheless, most of the lymphoma lines tested readily form lymph node metastases in vivo. In addition, blockade of L-selectin by continual treatment with an anti-L-selectin antibody did not prevent metastatic growth of TK-1 cells in peripheral lymph nodes. We conclude that the expression of homing receptors and a high extravasation efficiency of neoplastic cells is not a prerequisite for their dissemination into lymphatic tissue.

Choroidal neovascularization secondary to Candida albicans chorioretinitis.

PURPOSE: To study the clinical histories and courses of six patients with choroidal neovascularization secondary to endogenous Candida albicans chorioretinitis. METHODS: The medical records, fundus photographs, and fluorescein angiograms of six patients who developed C. albicans chorioretinitis secondary to candidemia and who subsequently developed choroidal neovascularization in one or both eyes were reviewed. RESULTS: The six patients ranged in age from 18 to 79 years. Four were women and two men; all but one showed evidence of bilateral chorioretinal scarring secondary to C. albicans chorioretinitis. All patients had been treated successfully with systemic antifungal therapy (amphotericin B). Two weeks to two years after the chorioretinitis, choroidal neovascularization developed in one eye (four cases) or both eyes (two cases). The neovascularization on initial examination was subfoveal in four eyes, extrafoveal in three eyes, and juxtafoveal in one eye. Laser photocoagulation was used in four of the eight involved eyes. In these cases, the active choroidal neovascularization was brought under control. In one eye, the patient had submacular surgery for excision of the choroidal neovascular membrane. Final visual acuities ranged from 20/20 to 20/200 in treated eyes and from 20/50 to 20/400 in untreated eyes. CONCLUSION: Choroidal neovascularization is a potential cause of late visual loss in patients who have had C. albicans sepsis and endogenous C. albicans chorioretinitis. Eyes that have chorioretinal scarring from C. albicans chorioretinitis should be watched for the development of choroidal neovascularization. Laser photocoagulation or perhaps surgical excision of the neovascular complex may be of benefit in selected cases.

Vitrectomy for vitreomacular traction syndrome with macular detachment.

PURPOSE: To describe the clinical characteristics of the vitreomacular traction syndrome with macular detachment and to report our surgical experience with this condition. METHODS: A retrospective chart and photographic review was performed on nine patients (nine eyes) who had a symptomatic decrease in visual acuity from a macular traction retinal detachment caused by vitreomacular traction syndrome. Vitrectomy was performed in each eye to reattach the retina. RESULTS: Intraoperative observation confirmed partial posterior vitreous separation with adherence of the posterior hyaloid to the detached retina and separation of the posterior hyaloid from the attached retina. After surgery the macula was reattached in seven eyes (78%). Visual acuity was improved in four eyes, stable in four eyes, and worse in one eye. CONCLUSION: Macular detachment may occur secondary to vitreomacular traction syndrome. Although the retina may be reattached surgically in these cases, visual improvement may be limited by chronic detachment, premacular fibrosis, cystoid macular edema, or macular schisis.

Therapeutic effects of antibodies against adhesion molecules in murine collagen type II-induced arthritis.

Adhesion molecules play important roles in immune reactions and inflammatory processes and may constitute attractive targets for immunomodulatory approaches. In this study, blocking mAbs against a series of adhesion molecules were tested for their therapeutic effect on developing arthritis in a mouse model. MAbs were given for a period of 4 weeks at the time of exspected incidence of visible disease symptoms, i.e. 4 weeks after priming with collagen type II. A significant reduction of incidence down to values of 13% and 29% of the controls was obtained with mAbs against CD44 and alpha 4-integrin, respectively, during an observation time of 13 weeks. MAbs against CD4 and LFA-1 resulted only in weaker, non-significant effects or a delay in the incidence. MAbs against other molecules including L-selectin, ICAM-1 or VCAM-1 were not effective. The development of antibodies against collagen type II, collagen type I, proteoglycans and the immunogen, bovine collagen type II was affected by mAb treatment to a different extent. In this case, the anti CD4 mAb was the most effective, followed by the anti alpha 4-antibodies in most cases, whereas anti CD44 showed less clear effects on the development of humoral responses. In a skin delayed type hypersensitivity model analyzed for comparison, mAbs against LFA-1/ICAM-1 and alpha 4-integrin showed the largest effects on ear swelling. These data show that mAbs against several adhesion molecules are able to block selectively distinct aspects of immune reactions, and that CD44 and alpha 4-integrins could be promising targets for an immunotherapy of rheumatoid arthritis with receptor-interfering agents.

Role of alpha 4-integrins in lymphocyte homing to mucosal tissues in vivo.

Lymphocyte recirculation through different organs is thought to be regulated by adhesion molecules ("homing receptors") recognizing tissue-specific vascular addressins on endothelium. Here we show that the alpha 4/beta 7-integrin has a key role in the migration of mouse lymphocytes to mucosal sites. Homing to Peyer's patches but not to peripheral lymph nodes is inhibited by Fab fragments of mAb PS/2 against the alpha 4-integrin chain, by mAb DATK32 recognizing a combinatorial epitope on the alpha 4/beta 7-integrin, and by mAb FIB30 against the beta 7-chain. The Abs significantly reduce homing of lymphocytes to the intestine, as well. The migration of immunoblasts to gut and gut-associated lymphoid tissue also involves the alpha 4/beta 7-integrin heterodimer. Another anti-alpha 4 Ab, R1-2, which blocks lymphocyte binding to Peyer's patches in the Stamper-Woodruff frozen section assay and lymphocyte adhesion to VCAM-1 and fibronectin, has only minor effects on lymphocyte traffic in vivo. Anti-VCAM-1 Ab as well as the fibronectin peptide CS-1 are without influence on the migration to Peyer's patches or intestine, in contrast to Ab against the mucosal addressin MAdCAM-1. Thus, homing to gut-associated sites is regulated by the alpha 4/beta 7-integrin heterodimer interacting with the vascular addressin, MAdCAM-1, and not with fibronectin or VCAM-1 as counterstructures. Inhibition of homing to Peyer's patches and intestine by the anti-integrin Abs studied was only partial. L-selectin also participates in the homing of small lymphocytes to mucosal sites, especially Peyer's patches, but does not contribute substantially to the localization of blasts into the intestinal wall. The results support a major, but not exclusive role of the alpha 4/beta 7-integrin in lymphocyte traffic to mucosal sites.

Integrins and L-selectin in lymphocyte-endothelium interactions and homing into gut-associated tissue.

The selective entry of subpopulations and distinct differentiation stages of lymphocytes into different tissues is thought to be mediated by interaction of endothelial ligands with adhesion molecules on lymphocytes. L-selectin has been considered as a peripheral lymph node-specific homing receptor and alpha 4-integrins have been supposed to mediate entry into mucosa-associated lymphoid tissue. In vivo homing studies show that the specificity is not so clear-cut. The MEL-14 antibody indeed blocks almost completely lymphocyte homing into peripheral lymph nodes. However, entry into Peyer's patches and even the intestine itself is also affected. Thus, L-selectin plays a broader part as previously thought. Some antibodies against the alpha 4 and beta 1-integrin chain inhibit selectively lymphocyte homing to Peyer's patches by 50-70%. alpha 4-integrins therefore seem to be important for homing into mucosa-associated tissue, although a considerable fraction of cells does not require this molecule (or this epitope) for recognition of Peyer's patch endothelium. In vitro and in vivo data indicate that neither VCAM-1 nor fibronectin play a role for homing into Peyer's patches; most likely a further ligand recognized by distinct epitopes of alpha 4 is used for recognition of Peyer's patch HEV. A combination of the mAbs MEL-14 and PS/2.3 blocks nearly completely the localization in Peyer's patches. Beside alpha 4-integrins, the beta 2-integrin LFA-1 has been shown to be involved in lymphocyte recirculation. Also combinations of antibodies against LFA-1 and L-selectin as well as of anti LFA-1 with anti alpha 4 show synergistic effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphocyte activation and regulation of three adhesion molecules with supposed function in homing: LECAM-1 (MEL-14 antigen), LPAM-1/2 (alpha 4-integrin) and CD44 (Pgp-1).

Directed migration of lymphocytes from blood into lymph nodes and gut-associated lymphatic tissue, also referred to as homing, is subject to change following activation. Lymphocyte migration into lymphoid organs in vivo and binding to high endothelial venules in vitro is largely suppressed after short-term stimulation with phorbol esters. The observed functional alterations were correlated with changes in the expression of three putative homing receptors, LECAM-1 (MEL-14 antigen), LPAM-1/2 (alpha 4-integrin) and the murine CD44 (Pgp-1, H-CAM, Hermes-antigen equivalent) upon different modes of cellular activation. Expression of LECAM-1 (gp90 MEL-14), a lymphocyte adhesion molecule implicated in targeting extravasation into lymph nodes, was found to be lost almost completely within minutes after protein kinase C activation. LECAM-1 re-expression occurred within less than 24 h. Rapid loss of LECAM-1 was also observed after calcium ionophores whereas anti-CD3 or concanavalin A elicited a gradual and heterogeneous loss of LECAM-1 becoming detectable after several hours only. A number of cytokines tested were not able to induce alterations in LECAM-1 expression. In contrast, expression of LPAM-1/2 (alpha 4-integrin) and CD44 (Pgp-1, H-CAM), two adhesion molecules supposed to direct extravasation into Peyer's patches, remained stable for hours after every stimulus tested; CD44 expression gradually increased 24 h after mitogenic activation, whereas a small reduction only was observed for the expression of the alpha 4-chain under certain conditions. Thus, reduced extravasation of lymphocytes into Peyer's patches after activation is not due to a decline in the surface density of LPAM-1/2 alpha-chain or CD44 whereas alterations in migration into lymph nodes parallel the expression of LECAM-1.

Homing receptors reexamined: mouse LECAM-1 (MEL-14 antigen) is involved in lymphocyte migration into gut-associated lymphoid tissue.

Specific recognition molecules ("homing receptors") on lymphocytes are thought to direct selective entry of cells into different organs. The lectin-related cell adhesion molecule LECAM-1 has previously been supposed to mediate lymphocyte entry into peripheral lymph nodes and, partially, mesenteric nodes but not into Peyer's patches. Here we present evidence that in vivo the molecule is also implicated in homing of mouse lymphocytes to Peyer's patches and may have a more general role as homing receptor for high endothelial venules-bearing lymphoid tissue, but not for most non-lymphoid tissue.

Intraocular tumor from disseminated histoplasmosis.

We identified and treated a solid, growing fungal tumor mass in a patient with disseminated histoplasmosis. Although the most commonly reported intraocular lesions from disseminated histoplasmosis are areas of inactive chorioretinal scars or areas of localized subretinal neovascular membrane formation, a focus of active fungal growth needs to be ruled out in all such cases. When a solid tumor mass is identified, the most effective way of preserving vision is with systemic antifungal therapy.

Evidence for an accessory role of LFA-1 in lymphocyte-high endothelium interaction during homing.

In a variety of lymphocyte interactions, lymphocyte function-associated antigen-1 (LFA-1) plays an important role as an accessory mechanism mediating cell adhesion. We tested the possibility that LFA-1 could also be involved in the specific binding of lymphocytes to high endothelial venules (HEV) during homing. Antibodies against LFA-1 but not against various other cell surface molecules (except the putative gp90 homing receptor defined by the MEL-14 antibody) were found to inhibit in vitro adherence of lymphocytes to HEV in frozen sections of lymph nodes. Binding of T cell lines to HEV was also inhibited by anti-LFA-1 antibody. Using sublines selected for differential expression of the MEL-14 antigen, MEL-14 high cells (which bind well to HEV) were less susceptible to inhibition by anti-LFA-1 than poor binders with low levels of the homing receptor, supporting the model of LFA-1 being an accessory mechanism strengthening weak interactions between cells. Parallel results were found in vivo where anti-LFA-1 antibodies reduced the migration of normal lymphocytes into lymph nodes and Peyer's patches by 40 to 60%. Localization in the lung, especially of activated lymphocytes, was also impaired, although to a lesser extent. These findings suggest that LFA-1 plays an accessory role in cellular interactions relevant for lymphocyte migration.

Regulation of lymphocyte homing. I. Alterations in homing receptor expression and organ-specific high endothelial venule binding of lymphocytes upon activation.

Upon activation, lymphocytes display profound alterations in their in vivo migration behavior. In an attempt to understand some of the cellular mechanisms responsible for this altered behavior, in vitro stimulated lymphocytes have been analyzed for their expression of a putative homing receptor (HOR) (defined by mAb MEL-14) and for their ability to bind to specialized lymphoid organ high endothelial venules (HEV) in vitro. The results indicate that signals related to lymphocyte activation induce complex alterations in HOR expression and organ-specificity of HEV-binding: 1) submitogenic stimuli induce an increase in MEL-14 antigen expression. This applies to almost all lymphocytes in autologous cultures, for the fraction of cells in periodate, LPS- or Con A-treated cultures not fully activated and for cultures stimulated with suboptimal doses of Con A. 2) Full blast transformation is associated with a decrease or complete loss of MEL-14 antigen expression on the majority of blasts in all activating systems used, but a subset of up to 30 to 40% of fully activated cells may nonetheless express very high levels of the MEL-14 antigen. 3) Functional assays reveal that Con A and periodate stimulation lead to a selective, nearly complete suppression of the lymphocytes binding to HEV of Peyer's patches, even under conditions where overall binding to peripheral node HEV is increased. This indicates a differential regulation of the two respective receptors, with the mucosa system-specific HOR being more prone to down-regulation during in vitro activation by these mitogens.

Homing receptor expression and migration of activated lymphocytes.

The experiments show that homing receptors are regulated in a complex fashion during initial cellular activation: Signals leading to blast formation induced either: --a decrease of homing receptor expression in the majority of blasts; --an increase of the Mel-14 expression in 20-40% of the blasts, and --a selective down-regulation in the capacity to bind to Peyer's patch HEV even under conditions, where binding to peripheral HEV is high. Submitogenic stimuli in partially activated cultures induce a rise in Mel-14 antigen expression and binding to peripheral node HEV, whereas Peyer's patch binding is unchanged or lowered. Thus, a selective and differential regulation of organ-specific homing receptors takes place under distinct activation conditions. The mucosal system-related receptor is more easily down-regulated upon activation. The in vivo homing experiments indicate that mitogen activation induces one dominant migratory phenotype. Alterations in homing receptor expression seem to be associated with changes in further cellular functions leading to reduced entry into lymphatic tissues and increased localization of these cells in lung or liver. The mechanisms regulating the differential expression of organ-specific homing receptors and additional homing-relevant properties of the cells are still unknown.

Contact interaction between lymphocytes is a general event following activation and is mediated by LFA-1.

When lymphocytes are activated in vitro, discrete cell-cell contacts are initiated which result in cluster formation. This contact interaction is found in syngeneic or allogeneic mixed leukocyte reactions as well as in mitogen-stimulated cultures (concanavalin A, periodate, lipopolysaccharide). T cells as well as B cells display the binding phenomenon. This activation-dependent lymphocyte-lymphocyte adhesion involves LFA-1, since monoclonal antibodies (including Fab fragments) against this molecule inhibit adhesion between clustering lymphocytes in a dose-dependent manner, whereas antibodies directed to several other cell surface antigens are inactive. Since a wide variety of functional interactions are inhibited by antibodies to LFA-1, it may be concluded that LFA-1-mediated cell contact is a discrete and essential step between a recognition event and the generation of functional activities by lymphocytes in general.

Lymphocytes express specific antigen-independent contact interaction sites upon activation.

Cell contact between lymphocytes can be observed in the form of clustering in autologous cultures of rat or mouse lymph node cells. Mutual binding takes place in the absence of adherent cells and is displayed by B cells as well as by T cells, with the exception of immature (Lyt 1,2+) T cells. Contact formation is related to activation of the lymphocytes since thymidine-incorporating cells as well as plaque-forming cells are concentrated in the cluster cell fraction and the formation of clusters is greatly increased by periodate stimulation. The interaction is selective with respect to cell type (cells of other tissue origin are not bound) and differentiation (only activated lymphocytes and some of several lymphoid cell lines are able to interact). The reaction is not genetically restricted, but takes place even between different (but related) species. Neither antigen nor MHC structures are involved in contact formation. Protease treatment abolishes the ability to form clusters, but one part of the interacting receptor/acceptor structures is apparently trypsin resistant. The interaction is dependent on the presence of magnesium, whereas calcium ions have no supporting effect. Involvement of the cytoskeleton is shown by a partial inhibition of the cluster formation by cytochalasin B and azide. No indication for a lectin nature of the binding structures could be found by carbohydrate inhibition studies. The relation of this interaction mechanism to other models of physical interaction in the immune system as well as its possible function for signal exchange and local recruitment of activated cells is discussed.