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Biomedical subjects

R M Nagy

Publications and source records attributed to R M Nagy.

At least 19 recordsLinked to original sources
PubMed2000

Nonpeptide alpha(v)beta(3) antagonists. 1. Transformation of a potent, integrin-selective alpha(IIb)beta(3) antagonist into a potent alpha(v)beta(3) antagonist.

Modification of the potent fibrinogen receptor (alpha(IIb)beta(3)) antagonist 1 generated compounds with high affinity for the vitronectin receptor alpha(v)beta(3). Sequential modification of the basic N-terminus of 1 led to the identification of the 5,6,7, 8-tetrahydro[1,8]naphthyridine moiety (THN) as a lipophilic, moderately basic N-terminus that provides molecules with excellent potency and selectivity for the integrin receptor alpha(v)beta(3). The THN-containing analogue 5 is a potent inhibitor of bone resorption in vitro and in vivo. In addition, the identification of a novel, nonpeptide radioligand with high affinity to alpha(v)beta(3) is also reported.

Animals↗
PubMed1999

Stable association of PYK2 and p130(Cas) in osteoclasts and their co-localization in the sealing zone.

Bone resorption is initiated by osteoclast attachment to the mineralized matrix, cytoskeletal reorganization, cellular polarization, and the formation of the sealing zone. The present study examines the interaction between PYK2 and p130(Cas) (Crk-associated substrate), suggested to be part of the signaling pathway initiated by osteoclast adhesion. Using murine osteoclast-like cells (OCLs) and their mononuclear precursors (pOCs), generated in a co-culture of bone marrow and osteoblastic MB1.8 cells, we show that: 1) p130(Cas) is tyrosine-phosphorylated upon adhesion of pOCs to vitronectin or ligation of beta3 integrins; 2) p130(Cas) colocalizes with PYK2 and the cytoskeletal proteins F-actin, vinculin, and paxillin in the podosomal-rich ring-like structures of OCLs plated on glass and in the sealing zone in actively resorbing OCLs on bone; 3) p130(Cas) and PYK2 form a stable complex in pOCs, independent of tyrosine phosphorylation of either molecule, and this complex is present in Src (-/-) OCLs, in which neither protein is phosphorylated or associated with the osteoclast adhesion structure; 4) the association of p130(Cas) and PYK2 is mediated by the SH3 domain of p130(Cas) and the C-terminal domain of PYK2. These findings suggest that p130(Cas) and its association with PYK2 may play an important role in the adhesion-dependent signaling that leads to cytoskeletal reorganization and formation of the sealing zone during osteoclast activation.

Animals↗
PubMed1998

PYK2 in osteoclasts is an adhesion kinase, localized in the sealing zone, activated by ligation of alpha(v)beta3 integrin, and phosphorylated by src kinase.

Osteoclast activation is initiated by adhesion to the bone surface, followed by cytoskeletal rearrangement, the formation of the sealing zone, and a polarized ruffled membrane. This study shows that PYK2/CAKbeta/RAFTK, a cytoplasmic kinase related to the focal adhesion kinase, is highly expressed in rat osteoclasts in vivo. Using murine osteoclast-like cells (OCLs) or their mononuclear precursors (pOCs), generated in a coculture of bone marrow and osteoblastic MB1.8 cells, we show: (a) tyrosine phosphorylation of PYK2 upon ligation of beta3 integrins or adhesion of pOCs to serum, vitronectin, osteopontin, or fibronectin but not to laminin or collagen; (b) coimmunoprecipitation of PYK2 and c-Src from OCLs; (c) PYK2 binding to the SH2 domains of Src; (d) marked reduction in tyrosine phosphorylation and kinase activity of PYK2 in OCLs derived from Src (-/-) mice, which do not form actin rings and do not resorb bone; (e) PYK2 phosphorylation by exogeneous c-Src; (f) translocation of PYK2 to the Triton X-100 insoluble cytoskeletal fraction upon adhesion; (g) localization of PYK2 in podosomes and the ring-like structures in OCLs plated on glass and in the sealing zone in OCLs plated on bone; and (h) activation of PYK2, in the presence of MB1.8 cells, parallels the formation of sealing zones and pit resorption in vitro and is reduced by echistatin or calcitonin and cytochalasin D. Taken together, these findings suggest that Src-dependent tyrosine phosphorylation of PYK2 is involved in the adhesion-induced formation of the sealing zone, required for osteoclastic bone resorption.

Animals↗
PubMed1995

Isolation and characterization of highly enriched, prefusion mouse osteoclastic cells.

This study describes the isolation and characterization of highly enriched mammalian osteoclast precursors, released by the "disintegrin" echistatin, from an osteoclast formation culture. Incubation of a 6-day coculture of mouse bone marrow cells and mouse osteoblastic cells (MB1.8) with echistatin (30 nM), an RGD-containing snake venom, for 20 min yielded an 88-95% pure population of tartrate-resistant acid phosphatase-positive cells, 1.5 x 10(5) cells per 150 cm2 culture dish. These cells were mostly mononucleated and based on the following characteristics are considered to be prefusion osteoclasts (pOC cells): (i) presence of calcitonin (CT) receptors documented by 125I-sCT autoradiography and cAMP generation in response to salmon calcitonin; (ii) expression of mRNAs for alpha v beta 3 integrin, osteopontin, 92-kDa type IV collagenase (matrix metalloproteinase 9), carbonic anhydrase II, OC-2 (an "osteoclastic" cysteine proteinase), and protein tyrosine phosphatase epsilon; and (iii) high level expression of pp60c-src protein. The pOC cells resorb bone (form "pits" on bone slices) but only in the presence of osteoblastic MB1.8 cells and 1,25(OH)2D3. Resorption was inhibited by CT. In conclusion, we describe a rapid, reproducible procedure to isolate virtually pure mammalian prefusion osteoclasts, which should help in the study of osteoclast formation, composition, and function.

Animals↗
PubMed1983

Metastatic choroidal melanoma. Hepatic binding protein reactivity toward a liver-metastasizing clone.

A clone of B16 malignant melanoma cells with a preference for metastasis to the liver was isolated and characterized. The parent tumor cells (F1) were injected in the tail vein of C57BL/6 mice, and the resultant liver colonizing cells were isolated and then subcultured for two to three weeks. The cells were then reinjected into the next series of mice. After five such passages, a clone (L4) of melanoma cells was obtained that metastasized almost exclusively to the liver. A hepatic binding protein (HBP) was isolated from rabbit liver that agglutinated neuraminidase-treated F1 and L4 malignant melanoma cells. Different agglutination titers found between the parent and liver-metastasizing clone demonstrated differences in cell-surface properties between the parent tumor and the liver-metastasizing clone. These results demonstrate that malignant melanoma cells can be selected for preferential liver metastasis and can be recognized and agglutinated by specific HBPs. Metastasis from human uveal malignant melanoma may occur by similar mechanisms.

Animals↗
PubMed1983

Metastatic uveal melanoma. Hepatic cell-surface enzymes, isoenzymes, and serum sialic acid levels in early metastatic disease.

Serum hepatic cell-surface enzymes, isoenzymes, and sialic acid levels may be useful adjuncts in detecting early metastatic disease and in evaluating the tumor burden of patients with uveal melanoma. Hepatic cell-surface enzyme concentrations were elevated in the serum of ten patients with uveal melanoma and liver metastasis and in five patients with other hepatobiliary disorders and in 75 control patients. Five patients in the metastatic group (50%) had serum gamma-glutamyl transpeptidase and 5'-nucleotide phosphodiesterase (5-NPD) bands known to be associated with either primary hepatic carcinoma or carcinoma metastatic to the liver. One patient with uveal melanoma without known metastasis had a positive 5-NPD pattern; metastatic disease was subsequently proved. Higher levels of sialic acid were found in the serum of patients with uveal melanoma and metastatic disease (4 mumole/mL) than in controls (2.4 mumole/mL).

Adult↗
PubMed1982

Epibulbar lesions simulating extraocular extension of uveal melanomas.

Twelve patients who were referred to the Oncology Service of Wills Eye Hospital, Philadelphia, with a pigmented epibulbar lesion that clinically resembled malignant melanoma of the choroid with extraocular extension were found to have other ophthalmic entities. The most common conditions that simulated extraocular extension of uveal melanoma were conjunctival malignant melanomas, which accounted for four of the 12 pseudomelanomas. Three of the 12 patients had staphylomas or scleral ectasis. Two of the 12 had subconjunctival hematomas. Senile scleral plaques, a presumed cellular blue nevus, and ocular melanocytosis accounted for the other three conditions. A thorough history, indirect ophthalmoscopy with scleral depression, ultrasonography, gonioscopy, and transillumination were helpful in distinguishing uveal malignant melanoma with extrascleral extension from other, often less serious, ophthalmic disorders.

Adult↗
PubMed1980

Cell-mediated immunity in herpes corneal stromal disease.

Regional draining lymph nodes (RDLN) from rabbits with herpes virus disciform keratitis (defined as corneal edema or corneal edema with concomitant epithelial lesions) were tested for general as well as specific immune cap-city. Although general RDLN immune capacity did not seem to be impaired, specific reactivity to herpes antigens was found only in those rabbits which presented with disciform keratitis and concomitant epithelial lesions; specific reactivity to herpes antigens was not found in those animals which presented with disciform edema alone. Additionally, the unilateral nature of the RDLN immune response during ocular infections of unequal severity was demonstrated.

Animals↗
PubMed1978

Scanning electron microscope study of herpes simplex virus experimental disciform keratitis.

Scanning electron microscopy of the endothelium of experimental disciform keratitis revealed corneal endothelial changes which distinguished disciform oedema from the more progressive stages of disciform keratitis. The endothelium of corneas with disciform oedema were wholly intact and characterised by subtle morphological alterations. In contrast, the more progressive stages of disciform keratitis were characterised by massive destruction and denudation of the endothelium. The significance of these observations is discussed.

Animals↗
PubMed1978

Scanning electron microscopic observation of two retinoblastoma cell lines.

Two continuous retinoblastoma cell lines were observed by scanning electron microscopy. Both cell lines spontaneously grow as a suspension of round cells in clusters, chains, and unique ring (rosette) formations. Scanning electron microscopy of suspension cells reveals some variation in the number and frequency of surface adornments such as blebs, lamellipodia, and microvilli. Although the cell lines are nonadherent to substratum and therefore assume a spherical form, highly villous cells are not characteristic of the entire cell populations. When WERI-Rb1 and Y79 are seeded onto a polyornithine-treated substrate, attachment and growth as adherent cultures are evident. With selective attachment on a positively charged substrate, we observe alteration of membrane architecture with the extension of cytoplasm and filopidia. In addition, WERI-Rb1 cell-to-substratum adhesion induces morphological changes suggestive of neuronal cell differentiation.

Cell Adhesion↗