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Biomedical subjects

E Zamir

Publications and source records attributed to E Zamir.

At least 19 recordsLinked to original sources
PubMed2001

Focal contacts as mechanosensors: externally applied local mechanical force induces growth of focal contacts by an mDia1-dependent and ROCK-independent mechanism.

The transition of cell-matrix adhesions from the initial punctate focal complexes into the mature elongated form, known as focal contacts, requires GTPase Rho activity. In particular, activation of myosin II-driven contractility by a Rho target known as Rho-associated kinase (ROCK) was shown to be essential for focal contact formation. To dissect the mechanism of Rho-dependent induction of focal contacts and to elucidate the role of cell contractility, we applied mechanical force to vinculin-containing dot-like adhesions at the cell edge using a micropipette. Local centripetal pulling led to local assembly and elongation of these structures and to their development into streak-like focal contacts, as revealed by the dynamics of green fluorescent protein-tagged vinculin or paxillin and interference reflection microscopy. Inhibition of Rho activity by C3 transferase suppressed this force-induced focal contact formation. However, constitutively active mutants of another Rho target, the formin homology protein mDia1 (Watanabe, N., T. Kato, A. Fujita, T. Ishizaki, and S. Narumiya. 1999. Nat. Cell Biol. 1:136-143), were sufficient to restore force-induced focal contact formation in C3 transferase-treated cells. Force-induced formation of the focal contacts still occurred in cells subjected to myosin II and ROCK inhibition. Thus, as long as mDia1 is active, external tension force bypasses the requirement for ROCK-mediated myosin II contractility in the induction of focal contacts. Our experiments show that integrin-containing focal complexes behave as individual mechanosensors exhibiting directional assembly in response to local force.

3T3 Cells↗
PubMed2001

Self-inflicted anterior scleritis.

PURPOSE: To describe and clinically characterize a syndrome of self-inflicted scleritis. STUDY DESIGN: Case reports and literature review. METHODS: Two patients had persistent scleritis at presentation. Both did not respond to prescribed therapy, including systemic corticosteroids and immunosuppression. The first had unexplained, diffuse anterior scleritis and persistent linear keratoconjunctival abrasions after a work-related injury. Several objective indicators pointed to concealed noncompliance with medications. The second patient was a medical assistant with diffuse, unilateral anterior scleritis and unexplained visual loss. Systemic work-up was negative. She had pharmacologic mydriasis and keratoconjunctival abrasions at presentation. RESULTS: Systemic therapy was stopped in both patients. The first patient, who was in the process of requesting permanent disability status, showed persistent inflammation on each follow-up visit. The second patient improved with no further therapy after she was confronted with objective indicators of a self-inflicted condition. CONCLUSIONS: Although the presentation of self-inflicted scleritis can be similar to that of idiopathic or autoimmune anterior scleritis, the former may show additional findings of traumatic conjunctival and corneal abrasions. Indicators of self-inflicted etiology, of which malingering is one such entity, include evidence of concealed noncompliance with prescribed treatments and lack of response to potent antiinflammatory and immunosuppressive agents. Correct diagnosis including early psychiatric evaluation in all such cases, may help prevent unnecessary treatment and unjustified work-related compensation.

Administration, Topical↗
PubMed2001

Rhabdomyomatous mesenchymal hamartoma of the eyelid: report of a case and literature review.

PURPOSE: To report a rare case of rhabdomyomatous mesenchymal hamartoma and to compare its features with those cases previously reported. DESIGN: Interventional case report and literature review. INTERVENTION: Complete ophthalmologic and systemic examinations followed by excisional biopsy and histopathologic examination. MAIN OUTCOME MEASURES: Clinical examination features and histopathologic findings. RESULTS: A 6-month-old Latino male presented with a congenital, elevated, smooth, flesh-colored right lower eyelid lesion. An ipsilateral right limbal dermoid and an upper eyelid coloboma were also present. Excisional biopsy of the eyelid lesion revealed randomly oriented mature striated muscle tissue with associated adipose tissue, blood vessels, pilosebaceous units, and peripheral nerves, findings consistent with rhabdomyomatous mesenchymal hamartoma. Of the 24 reported cases (including the current case), eight had associated congenital anomalies. CONCLUSIONS: Although rhabdomyomatous mesenchymal hamartomas are rare and benign, they may be associated with other congenital anomalies and anomaly syndromes. As a result, we recommend systemic evaluation of patients diagnosed with this entity.

Biopsy↗
PubMed2001

Proliferative activity and p53 expression in primary and recurrent pterygia.

PURPOSE: To assess p53 expression and proliferative activity in primary and recurrent pterygia from the same eyes. DESIGN: Retrospective comparative human tissue study. PARTICIPANTS: Tissue from excised primary pterygia that did not recur (group A, n = 10) was compared with tissue from primary pterygia that recurred (group B, n = 10) and to the recurrent pterygia tissue that was excised from subjects in group B (group C, n = 10). Ten normal conjunctivas served as controls (group D). METHODS: Sections from each pterygium were immunostained with the MIB-1 and bp53. 12 monoclonal antibodies that react with Ki-67 and p53 antigens, respectively. MAIN OUTCOME MEASURES: Proliferative activity was calculated as the mean of the MIB-1 positive cell count per eyepiece grid in high magnification (x40) (positive cell count/grid). Percentage of positive cells of all cells in the grid area was evaluated in the p53-stained sections. RESULTS: Proliferative activity was found in the epithelium overlying the pterygia and normal conjunctiva. The mean MIB-1 positive cell count/grid +/- standard error was 2.84 +/- 1.07, 1.74 +/- 0.82, 3.83 +/- 1.35, and 0.86 +/- 0.33 in groups A, B, C, and D, respectively (P = 0.17, Kruskal-Wallis). P53 staining was found in 50% of pterygia in groups A, B, and C; none of the normal conjunctival tissues showed p53 immunoreactivity. Four of five p53-positive tissues in group B were p53-negative in group C. In the p53-positive pterygia, less than 10% of cells were p53 positive. However, p53-positive pterygia had higher mean MIB-1 positive cell count/grid +/- standard error as compared with the p53-negative lesions, 4.56 +/- 0.94 vs 1.39 +/- 0.59 (P = 0.021, Mann-Whitney). CONCLUSIONS: p53 immunoreactivity and high proliferative activity in the epithelium overlying the pterygium are not associated with recurrence of pterygium.

Antibodies, Monoclonal↗
PubMed2001

Probing molecular processes in live cells by quantitative multidimensional microscopy.

Modern light microscopy has become a most powerful analytical tool for studying molecular processes in live cells. Recent advances in sample preparation, microscope design and image processing allow the generation of "multidimensional" data, simultaneously reporting the three-dimensional distribution and concentrations of several different molecules within cells and tissues at multiple time points with sub-micron spatial resolution and sub-second temporal resolution. Thus, molecular interactions and processes that were approached by biochemical analyses in vitro can now be directly monitored in live cells. Here, we address different aspects of multidimensional microscopy and, in particular, image quantification and the characterization of molecular dynamics, as applied to the study of cell adhesion.

Animals↗
PubMed2001

pp60(c-src) and related tyrosine kinases: a role in the assembly and reorganization of matrix adhesions.

Activation of tyrosine kinases during integrin-mediated cell-matrix adhesion is involved both in the regulation of focal contact assembly and in the initiation of signaling processes at the cell-matrix adhesive interface. In order to determine the role of pp60(c-src) and related kinases in these processes, we have compared the dynamic reorganization of phosphotyrosine, vinculin, focal adhesion kinase and tensin in cells with altered expression of Src-family kinases. Both null cells for pp60(c-src) and triple knockout cells for pp60(c-src), pp59(fyn), and pp62(c-yes) exhibited decreased phosphotyrosine levels in focal contacts when compared with wild-type cells. pp60(c-src)-null cells also exhibited faster assembly of cell-matrix adhesions and a more exuberant recruitment of FAK to these sites. Tensin, which normally segregates into fibrillar adhesions was localized in large focal contacts in the two mutant cell lines, suggesting involvement of pp60(c-src) in the segregation of focal contacts and fibrillar adhesions. Moreover, treatment of wild-type cells with tyrphostin AG1007, which inhibits both pp60(c-src) and FAK activity, induced accumulation of tensin in peripheral focal adhesions. These findings demonstrate that Src family kinases, and pp60(c-src) in particular, have a central role in regulating protein dynamics at cell-matrix interfaces, both during early stages of interaction and in mature focal contacts.

Animals↗
PubMed2001

Molecular complexity and dynamics of cell-matrix adhesions.

Currently >50 proteins have been reported to be associated with focal contacts and related ECM adhesions. Most of these contain multiple domains through which they can interact with different molecular partners, potentially forming a dense and heterogeneous protein network at the cytoplasmic faces of the adhesion site. The molecular and structural diversity of this 'submembrane plaque' is regulated by a wide variety of mechanisms, including competition between different partner proteins for the same binding sites, interactions triggered or suppressed by tyrosine phosphorylation, and conformational changes in component proteins, which can affect their reactivity. Indeed, integrin-mediated adhesions can undergo dynamic changes in structure and molecular properties from dot-like focal complexes to stress-fiber-associated focal contacts, which can further 'mature' to form fibronectin-bound fibrillar adhesions. These changes are driven by mechanical force generated by the actin- and myosin-containing contractile machinery of the cells, or by external forces applied to the cells, and regulated by matrix rigidity.

Cell Adhesion↗
PubMed2000

Retinitis pigmentosa associated with Fuchs' heterochromic uveitis.

OBJECTIVE: To investigate whether the combination of Fuchs' heterochromic uveitis (FHU) and retinitis pigmentosa (RP) in the same patient is coincidental or represents a true association. METHODS: We have examined the frequency of FHU in 338 patients with RP and in 1984 patients who were seen in our primary care ophthalmic clinic because of reasons other than RP. RESULTS: Of 338 patients with RP, 4 (1.2%) had the typical findings of FHU. Three of them had Usher syndrome type II, and 1 had RP simplex. By contrast, only 1 patient in the control group had FHU (5%), and the difference in the frequency of FHU between the 2 groups was significant (P=.002, Fisher exact test). CONCLUSIONS: Fuchs' heterochromic uveitis is associated with RP. Since autoimmune phenomena have been previously described in patients with RP, it is conceivable that RP predisposes to the development of FHU. Arch Ophthalmol. 2000;118:800-802

Adolescent↗
PubMed2000

Dynamics and segregation of cell-matrix adhesions in cultured fibroblasts.

Here we use time-lapse microscopy to analyse cell-matrix adhesions in cells expressing one of two different cytoskeletal proteins, paxillin or tensin, tagged with green fluorescent protein (GFP). Use of GFP-paxillin to analyse focal contacts and GFP-tensin to study fibrillar adhesions reveals that both types of major adhesion are highly dynamic. Small focal contacts often translocate, by extending centripetally and contracting peripherally, at a mean rate of 19 micrometers per hour. Fibrillar adhesions arise from the medial ends of stationary focal contacts, contain alpha5beta1 integrin and tensin but not other focal-contact components, and associate with fibronectin fibrils. Fibrillar adhesions translocate centripetally at a mean rate of 18 micrometers per hour in an actomyosin-dependent manner. We propose a dynamic model for the regulation of cell-matrix adhesions and for transitions between focal contacts and fibrillar adhesions, with the ability of the matrix to deform functioning as a mechanical switch.

Actins↗
PubMed2000

Physical state of the extracellular matrix regulates the structure and molecular composition of cell-matrix adhesions.

This study establishes that the physical state of the extracellular matrix can regulate integrin-mediated cytoskeletal assembly and tyrosine phosphorylation to generate two distinct types of cell-matrix adhesions. In primary fibroblasts, alpha(5)beta(1) integrin associates mainly with fibronectin fibrils and forms adhesions structurally distinct from focal contacts, independent of actomyosin-mediated cell contractility. These "fibrillar adhesions" are enriched in tensin, but contain low levels of the typical focal contact components paxillin, vinculin, and tyrosine-phosphorylated proteins. However, when the fibronectin is covalently linked to the substrate, alpha(5)beta(1) integrin forms highly tyrosine-phosphorylated, "classical" focal contacts containing high levels of paxillin and vinculin. These experiments indicate that the physical state of the matrix, not just its molecular composition, is a critical factor in defining cytoskeletal organization and phosphorylation at adhesion sites. We propose that molecular organization of adhesion sites is controlled by at least two mechanisms: 1) specific integrins associate with their ligands in transmembrane complexes with appropriate cytoplasmic anchor proteins (e.g., fibronectin-alpha(5)beta(1) integrin-tensin complexes), and 2) physical properties (e.g., rigidity) of the extracellular matrix regulate local tension at adhesion sites and activate local tyrosine phosphorylation, recruiting a variety of plaque molecules to these sites. These mechanisms generate structurally and functionally distinct types of matrix adhesions in fibroblasts.

Cell Adhesion↗
PubMed1999

Laser pointer maculopathy.

PURPOSE: To report a case of macular damage from a laser pointer. METHOD: Case report. A 19-year-old woman had an acute reduction of visual acuity in the right eye after deliberately staring into a commercial class 2 laser pointer for approximately 10 seconds. RESULTS: The patient's best-corrected visual acuity was RE: 20/40, and she had two small pericentral scotomata, as well as a hypopigmented ring-shaped lesion in the fovea. Within 8 weeks, her visual acuity improved to 20/20 and visual field returned to normal, but a subjective relative decrease in brightness of objects viewed by the right eye was apparent. Retinal pigment epithelial abnormality persisted. CONCLUSIONS: Commercial laser pointers, commonly used for teaching and entertainment purposes, may cause notable macular damage if abused. Morphologically, this may manifest as foveal retinal pigment epithelial disturbance.

Acute Disease↗