PubMed Health⌕ Search

Biomedical subjects

S Colucci

Publications and source records attributed to S Colucci.

47 records · Page 3Linked to original sources
PubMed1990

Cytosolic free calcium dependent regulation of osteoclast bone resorbing activity.

Osteoclasts are sensitive to KCl-induced depolarization and to increased extracellular calcium concentration, and respond to these treatments with cytosolic calcium increase. In this study we evaluated the possibility that these experimental conditions could affect osteoclast bone resorption. We found that, incubating osteoclasts with 3H-proline previously labeled bone particles the resorbing activity was inhibited by both depolarization and extracellular calcium concentration increase. The released radioactivity was, in fact, 48% and 52% respectively compared to the untreated cultures. These data demonstrated that cytosolic calcium increase is one of the messengers of the pathway that inhibits, in this condition, bone resorption. Furthermore, as in parathyroid cells, extracellular calcium acts with a negative direct feedback mechanism that controls osteoclast activity.

Animals↗
PubMed1990

Osteoblast-osteoclast interaction in bone resorption. Preliminary results.

Osteoclastic bone resorption has been evaluated in vitro by release of tritiated collagen fragments from 3H-proline prelabeled bone particles incubated for 48 hours in presence of avian isolated osteoclasts. Cells were co-incubated with periosteum-free chick calvarial fragments by interposition of 0.4 micron millipore membrane transwells, in presence or absence of 10(-8) M 1.34 bovine parathyroid hormone (PTH). Results demonstrated that i) calvaria exert a stimulating effect over osteoclastic bone resorption which was 1.8 fold enhanced with respect to controls (p less than 0.001). ii) the stimulating effect is exerted by calvarium-derived soluble molecules capable of crossing the 0.4 micron millipore membrane interposed between calvarial fragments and osteoclasts, iii) in this experimental system no further enhancement of calvarial stimulating effect is operated by PTH treatment.

Animals↗
PubMed1989

Carbon tetrachloride-induced experimental cirrhosis in the rat: a reappraisal of the model.

The goal of this study was to evaluate the presence of extrahepatic damage and the uniformity and reversibility of the histological findings in CCl4-induced liver cirrhosis in the rat. To verify these findings rats were sacrificed 2 and 10 weeks after a treatment consisting of ten intragastric doses of CCl4, administered weekly. All treated rats developed an irreversible micronodular cirrhosis with no damage to the brain, kidney and pancreas. Moreover, rats sacrificed 2 weeks after the last CCl4 dose showed a number of functional alterations usually observed in man. In particular, low branched chain/aromatic amino acids (BCAA/AAA) plasma ratio, high ammonia, low zinc and high insulin with normal blood glucose were obtained.

Amino Acids↗
PubMed1989

Voltage dependent calcium channel expression in isolated osteoclasts.

In this study the expression of voltage-dependent calcium channels on osteoclast plasma membrane has been investigated. We found that osteoclasts were sensitive to KCl-induced depolarization. In this circumstance a 4 fold transient cytosolic calcium concentration ([Ca2+]i) increase was observed. This increase was dose-dependent. Its half maximal effect was achieved at 30 mM KCl. Voltage sensitive calcium channels in osteoclasts were inhibited by specific antagonists. Nicardipine, a dihydropyridine derivative, was the most effective, inducing complete block of the channels at 10(-6) M. Verapamil (phenylalkylamine) and diltiazem (benzodiazepine) were less effective. These results are consistent with the presence, on the osteoclast membrane, of L-type voltage-sensitive calcium channels.

Animals↗
PubMed1989

Regulation of podosomes by intracellular pH in avian osteoclasts.

The effects of changes in intracellular pH (pH1) on the organization of the clear zone of isolated avian osteoclasts in culture were studied. The distribution of podosomes, the close contact areas that mediate the adhesion of osteoclasts to the substrate, was investigated by decoration of microfilaments with fluorescent phalloidin. Intracellular acidification by butyric acid induces significant increase of podosome formation at the level of the clear zone compared to controls. Conversely, alkalinization by HCO3- reduces the percentage of osteoclasts with podosomes. A role of pH1 on the adhesion of the osteoclasts to the substrate is hypothesized.

Animals↗
PubMed1989

Immunolocalization of beta 3 subunit of integrins in osteoclast membrane.

Utilizing isolated and cultured osteoclasts it has been possible to establish that they adhere to the substrate through specialized close contact areas, the podosomes, that in fully spread osteoclasts in vitro or in vivo are located within the clear zone. The cytochemical organization of podosomes has further been investigated in order to elucidate their possible involvement in the control of substrate recognition, that precedes bone resorption. An immunofluorescence investigation, performed utilizing human osteoclasts, shows that the beta 2 integrin subunit that in human monocytes is expressed and located in podosomes is absent in human osteoclasts, while the beta 3 subunit of the vitronectin receptor is expressed by osteoclasts, but not by other monocyte-derived cells and colocalizes with vinculin around the actin core of the podosome. The beta 1 subunit of the fibronectin receptors is also found, but with a diffuse pattern, in the osteoclast membrane. These results indicate that podosomes, while present in different cell types, may have in the osteoclast an unique cytochemical organization related to the peculiar function of this cell.

Bone Resorption↗
PubMed1989

Podosome expression in osteoclasts: influence of high extracellular calcium concentration.

In this study the effect of high extracellular calcium concentration has been evaluated, by immunofluorescence, on podosome expression in chicken osteoclasts. Cells were cultured in presence of 0.2 and 4 mM calcium for 90 minutes and microfilaments were detected, after fixation and permeabilization, by decoration with rodhamine conjugated phalloidin. Results showed that increased extracellular calcium concentration induces the inhibition of podosome expression indicating that these close-contact areas are capable of calcium-mediated regulation.

Animals↗
PubMed1989

Intracellular acidification induces decrease of cytosolic calcium in isolated osteoclasts.

In this study the effects of changes in intracellular pH on cytosolic Ca2+ were examined in single isolated osteoclasts. Alkalinization, performed by incubation in HCO3 containing buffer, induced increases in [Ca2+]. Conversely acidification, obtained by incubation in Na-butyrate-containing buffer induced a rapid and sustained decrease of [Ca2+]. The decrease of [Ca2+], during acidification with Na-butyrate was inhibited by VO4, an inhibitor of the Ca2+-ATPase. All these pieces of information indicate that changes in pH1 can modulate osteoclast activity together with modifications of [Ca2+], probably acting as intracellular signals.

Animals↗
PubMedDate not supplied

Normal EOG values in intraretinal metastasis from cutaneous melanoma: a case report.

PURPOSE: The electro-oculogram (EOG) is a powerful test to diagnose primary and metastatic choroidal tumors. While in benign tumors light-peak to dark-trough ratio values are in the range of normal subjects, these values appear highly altered in eyes affected by malignant choroidal tumors. Here we report a clinical case of a patient with intraretinal metastasis from cutaneous melanoma; notwithstanding the malignancy of the tumor, the EOG doesn't present alterations. METHODS AND RESULTS: Standard electro-oculographic recordings were performed before and after local excision of the tumor: recordings from the normal eye were taken as control. The EOG values were always normal in both eyes. Histological sections showed no evident change in the cell population of the retinal pigment epithelium (RPE) and Bruch's membrane. CONCLUSION: Our results suggest that the presence of an intact RPE is a crucial requirement to obtain a normal EOG.

Adult↗
PubMedDate not supplied

HGF and M-CSF modulate adhesion of MDA-231 breast cancer cell by increasing osteopontin secretion.

Recent studies reported an increased expression of osteopontin (OPN) in metastatic breast cancer cells, but the mechanisms modulating OPN production and the interaction of the cells with the secreted protein are far from clear. In this work, we utilized as an experimental system the cell line MDA-231 and we showed that HGF and M-CSF significantly enhance their adhesion onto OPN. Furthermore, in the presence of HGF and M-CSF, MDA-231 cells can adhere when plated onto BSA via increased OPN secretion. Moreover HGF and M-CSF induce de novo synthesis of OPN. In conclusion, these data suggest that HGF and M-CSF stimulate OPN production by MDA-231 cells, and that OPN is subsequently used as a substrate for cell adhesion.

Blotting, Western↗