PubMed Health⌕ Search

Biomedical subjects

E Canalis

Publications and source records attributed to E Canalis.

At least 19 recordsLinked to original sources
PubMed1997

Transforming growth factor beta1 inhibits collagenase 3 expression by transcriptional and post-transcriptional mechanisms in osteoblast cultures.

Transforming growth factor (TGF) beta1 is an autocrine regulator of bone cell function. We demonstrated that TGF beta1 enhances bone collagen synthesis, but its effects on collagen degradation are not well characterized. We tested the effects of TGF beta1 on rat collagenase 3 expression in cultures of osteoblast-enriched cells from fetal rat calvariae (Ob cells). Treatment with TGF beta1 at 0.4 nM decreased steady state collagenase mRNA levels after 2 to 24 h. This dose-dependent effect was observed at TGF beta1 concentrations of 4 pM to 1.2 nM, and was accompanied by decreased levels of immunoreactive procollagenase. The protein synthesis inhibitor cycloheximide increased collagenase transcripts, but did not prevent the effect of TGF beta1 on collagenase mRNA levels. TGF beta1 accelerated the decay of collagenase mRNA in transcriptionally arrested Ob cells. In addition, TGF beta1 decreased the levels of collagenase heterogeneous nuclear RNA and the rate of collagenase gene transcription in Ob cells. TGF beta1 enhanced the expression of tissue inhibitors of metalloproteinases (TIMP) 1 and 3 and caused a modest decrease of TIMP 2 mRNA levels. In conclusion, TGF beta1 decreases interstitial collagenase transcripts and protease levels in Ob cells by transcriptional and post-transcriptional mechanisms, and this effect may contribute to its actions on bone matrix.

Animals↗
PubMed1997

Surgical treatment of primary spontaneous pneumothorax with video-assisted thoracic surgery.

We report the results of our experience using video-assisted thoracoscopic surgery (VATS) to treat primary spontaneous pneumothorax (PSP) from January 1992 until December 1994 in a multicentered co-operative study. A total of 132 patients (110 males and 22 females, aged 13-38 yrs, mean age 26 yrs) were treated by VATS to deal with the PSP that they presented with. A standard VATS technique was used. Apical bullae were always removed, and mechanical pleural abrasion was performed, leaving a pleural drainage tube. In two cases (1.5%), a switch to thoracotomy was necessary. In eight cases (6%), air leakage persisted for 5 days after surgery, which resolved with pleural drainage. There were eight postoperative relapses (6%), which were treated with pleural drainage (n = 4), VATS (n = 3) or axillar thoracotomy (n = 1). The average postoperative stay was 5.6 days (range 2-15 days). We conclude that video-assisted thoracoscopic surgery is a viable alternative for the treatment of primary spontaneous pneumothorax. There is, however, a high relapse rate, and in a number of cases air leakage persists in the postoperative period.

Adolescent↗
PubMed1997

Regulation of collagenase-3 by bone morphogenetic protein-2 in bone cell cultures.

Bone morphogenetic protein-2 (BMP-2), a member of the transforming growth factor superfamily of peptides, induces ectopic bone formation in vivo. The actions of BMP-2 on osteoblastic cells include stimulation of collagen synthesis, but the role of BMP-2 on collagen degradation is not known. We examined whether BMP-2 affects the expression of collagenase-3, an enzyme that degrades type I collagen at neutral pH, and that of tissue inhibitors of matrix metalloproteinases (TIMPs) in primary osteoblast-enriched cells from 22-day-old fetal rat calvariae. BMP-2 suppressed collagenase messenger RNA (mRNA) and immunoreactive protein levels. BMP-2 did not affect collagenase mRNA stability, but it reduced collagenase heterogeneous nuclear RNA levels and decreased the rate of transcription of the collagenase gene. BMP-2 also stimulated TIMP 1 and TIMP 3 mRNA levels, but failed to alter TIMP 2 expression. In conclusion, our studies indicate that BMP-2 suppresses collagenase-3 gene transcription and stimulates TIMP 1 and TIMP 3 expression in osteoblasts. The regulation of collagenase and TIMPs by BMP-2 in osteoblasts may play a role in osteoinduction.

Animals↗
PubMed1996

Cortisol inhibits the synthesis of insulin-like growth factor-binding protein-5 in bone cell cultures by transcriptional mechanisms.

Glucocorticoids inhibit the synthesis of insulin-like growth factor-binding protein-5 (IGFBP-5) in osteoblasts, but the mechanisms involved are unknown. IGFBP-5 stimulates bone cell growth, and its inhibition by glucocorticoids may be relevant to the action of this binding protein on bone formation. We tested the effects of cortisol on IGFBP-5 expression in cultures of osteoblast-enriched cells from fetal rat calvariae (Ob cells). Cortisol decreased IGFBP-5 polypeptide levels in the extracellular matrix and caused a time- and dose-dependent decrease in IGFBP-5 mRNA. IGFBP-5 transcripts were markedly decreased by cycloheximide, and further suppressive effects of cortisol could not be determined. Cortisol did not modify the decay of IGFBP-5 mRNA in transcriptionally arrested Ob cells. Cortisol decreased IGFBP-5 hnRNA, the rate of IGFBP-5 transcription, and the activity of the murine IGFBP-5 promoter by 35% in transient transfection experiments. Deletion analysis showed that the region responsive to cortisol is from base pairs -70 to +22, and E-box-binding proteins or c-Myb-related nuclear factors may be involved in its regulation. In conclusion, cortisol inhibits IGFBP-5 transcription in Ob cells through the Myb-binding domain. This effect may be partly responsible for the effect of glucocorticoids on bone formation.

Animals↗
PubMed1996

Retinoic acid stimulates the transcription of insulin-like growth factor binding protein-6 in skeletal cells.

Retinoic acid has important actions on cell differentiation and osteoblastic function, and some of these actions may be mediated by changes in the insulin-like growth factor (IGF) axis. Skeletal cells synthesize IGF I and II and the six known IGF binding proteins (IGFBP). IGFBP-6 binds IGF II with high affinity and prevents IGF II-mediated effects. In fibroblasts, IGFBP-6 levels are regulated by retinoic acid, and we postulated that retinoic acid may regulate IGF II in bone by altering IGFBP-6 synthesis. We examined the effect of retinoic acid on IGFBP-6 expression in cultures of osteoblast-enriched cells from 22-day fetal rat calvariae (Ob cells). Retinoic acid caused a time- and dose-dependent increase in IGFBP-6 mRNA levels, as determined by Northern blot analysis. The effect was maximal after 48 h of treatment and observed with retinoic acid at concentrations of 10 nM to 1 microM. Retinoic acid increased IGFBP-6 polypeptide levels in the culture medium, as determined by Western immunoblot analysis. Cycloheximide at 3.6 microM slightly decreased IGFBP-6 transcripts but did not prevent the stimulatory effect of retinoic acid. The decay of IGFBP-6 mRNA in transcriptionally arrested Ob cells was similar in control and retinoic acid-treated cells, and retinoic acid increased the rates of IGFBP-6 transcription, as determined by nuclear run on assays. In conclusion, retinoic acid enhances IGFBP-6 expression in Ob cells by transcriptional mechanisms. Since IGFBP-6 prevents the effects of IGF II, increased synthesis of IGFBP-6 could mediate selected actions of retinoic acid in bone.

Animals↗
PubMed1996

The divalent strontium salt S12911 enhances bone cell replication and bone formation in vitro.

In this study, we have determined the effect of the divalent strontium salt S12911 on bone cell replication and bone formation in two culture systems. In the first series of experiments, half-calvariae of newborn rats were cultured with S12911 from 24 to 96 h and labeled with 3H-thymidine for the last 6 h of culture or treated with S12911 for 24 h and labeled for 24 h with 3H-proline 24-48 h after the removal of the agent. Calvariae were then processed for histomorphometry. S12911 at 10(-3) M increased the replication of preosteoblastic cells by 30-50% after 24 h and by 60% after 96 h of treatment. This effect was specific, since the number of labeled osteoblasts and of periosteal cells was not changed. A transient 24 h treatment with S12911 at 10(-3) M increased bone formation 24 and 48 h after the removal of the agent. 3H-proline labeled surfaces and bone formation rates were increased by 20%-35%. In the second series of experiments, sequential collagenase digestions were used to isolate cell populations enriched in fibroblasts or osteoblasts (Ob) from 22 day fetal rat calvariae. Treatment with S12911 at 10(-3) M for 24 h enhanced DNA synthesis by three- to fourfold in cell populations enriched in fibroblasts and preosteoblastic cells. The effect was less pronounced and inconsistent in Ob cells. S12911 at 10(-3) M for 24 h also increased collagen and non-collagen protein synthesis by 35% in Ob cells. These data indicate that the divalent strontium salt S12911 enhances bone cell replication and bone formation in vitro, an effect that may contribute to the previously reported effects of S12911 on trabecular bone mass in vivo.

Animals↗
PubMed1996

Expression and growth factor regulation of platelet-derived growth factor B transcripts in primary osteoblast cell cultures.

Platelet-derived growth factor (PDGF), an important bone cell mitogen, exists as a homo- or heterodimer product of the PDGF-A and -B genes. Normal unstimulated cells of the osteoblast lineage express the PDGF-A gene, but it is not known whether they express the PDGF-B gene. We examined the expression of PDGF-B messenger RNA (mRNA) levels in cultures of osteoblast-enriched cells from 22-day-old fetal rat calvariae (Ob cells) and determined whether they were modified by transforming growth factor-beta 1 (TGF beta 1), basic fibroblast growth factor (bFGF), insulin-like growth factor I (IGF-I), and PDGF-BB. Ob cells expressed PDGF-B transcripts of 3.5 kilo-bases, as determined by Northern blot analysis. Treatment of Ob cells with TGF beta 1 at 0.01-1.2 nM caused a dose-dependent increase in steady state PDGF-B mRNA, an effect that was initially observed after 2 h and was maximal after 6h. Cycloheximide induced PDGF-B transcripts and decreased the effect of TGF beta 1. TGF beta 1 did not modify the half-life of PDGF-B mRNA in transcriptionally arrested Ob cells and increased the rate of PDGF-B gene transcription in nuclear run-on assays. In contrast, treatment with PDGF-BB at 3.3 nM, bFGF at 6 nM, or IGF-I at 100 nM for 2-24 h did not modify PDGF-B mRNA levels in Ob cells. In conclusion, normal Ob cells express the PDGF-B gene, and TGF beta 1 induces its transcription, whereas bFGF, IGF-I, and PDGF-BB do not enhance the levels of PDGF-B mRNA. PDGF-BB may act not only as a systemic but also as a local regulator of bone cell function.

Animals↗
PubMed1996

Autocrine down-regulation of collagenase-3 in rat bone cell cultures by insulin-like growth factors.

Insulin-like growth factors (IGF)-I and -II are presumed to act as autocrine regulators of bone formation. Recently, we demonstrated that IGF-I and -II inhibit bone collagen degradation and collagenase-3 synthesis in osteoblast cultures. Therefore, we tested the autocrine role of IGFs in the endogenous expression of collagenase-3 in cultures of osteoblast-enriched cells from 22-day fetal rat calvariae (Ob cells). Steady-state messenger RNA (mRNA) levels were determined by Northern blot analysis and collagenase concentrations in the culture medium were determined by Western immunoblot. Basal level collagenase-3 transcripts decreased in Ob cell cultures, coinciding with an increase in IGF-I and -II protein levels. Removal of the conditioned medium modestly increased collagenase-3 mRNA levels and restored the ability of exogenously added IGF-I to repress collagenase-3 transcripts. IGF neutralizing antibodies and IGF binding proteins-2 and -3 in excess increased and sustained collagenase mRNA, heterogeneous nuclear RNA, and protease levels in Ob cell cultures. In conclusion, IGF-I and -II are autocrine repressors of collagenase-3 synthesis, and this effect may contribute to their actions on the maintenance of a normal bone collagen matrix.

Animals↗
PubMed1996

Transcriptional and posttranscriptional regulation of interstitial collagenase by platelet-derived growth factor BB in bone cell cultures.

Platelet-derived growth factor (PDGF), a bone cell mitogen, stimulates bone collagen degradation and does not enhance bone matrix apposition rates. The mechanism of the effect on collagen degradation is unknown, and it could involve changes in interstitial collagenase synthesis. We tested the effects of PDGF on interstitial collagenase expression in cultures of osteoblast-enriched cells from fetal rat calvariae (Ob cells). After 4-8 h of treatment, PDGF BB at 0.3 nM increased steady state collagenase messenger RNA (mRNA), whereas PDGF AA had no effect. The effect of PDGF BB on collagenase transcripts was dose dependent. PDGF BB increased the levels of immunoreactive collagenase after 6 h, whereas the levels were decreased after 16 h. Stimulation of collagenase mRNA by PDGF BB was dependent on de novo protein synthesis and activation of protein kinase C. PDGF BB prolonged the half-life of collagenase mRNA in transcriptionally arrested cells. PDGF BB initially increased and subsequently decreased the rate of collagenase gene transcription and the levels of collagenase heterogeneous nuclear RNA. In conclusion, PDGF BB regulates interstitial collagenase in Ob cells by transcriptional and posttranscriptional mechanisms, and this effect may contribute to its stimulatory actions on bone collagen degradation.

Animals↗
PubMed1996

Cortisol enhances the transcription of insulin-like growth factor-binding protein-6 in cultured osteoblasts.

Previous work indicate that glucocorticoids inhibit the synthesis of insulin-like growth factor I (IGF-I) and IGF-binding protein-3 (IG-FBP-3), -4, and -5, but not IGFBP-6, in osteoblast cultures. IGFBP-6 binds IGF-II with high affinity and prevents IGF-II-mediated effects. As IGF-II is present at high concentrations in bone, we postulate that glucocorticoids may regulate IGF-II by altering IGFBP-6 synthesis. We tested the expression of IGFBP-6 in cultures of osteoblast-enriched cells from 22-day-old fetal rat calvariae (Ob cells). Treatment of Ob cells with cortisol caused a time- and dose-dependent increase in IGFBP-6 messenger RNA levels, as determined by Northern blot analysis. The effect was maximal after 48 h of treatment and observed with cortisol concentrations of 10 nM to 1 microM. Treatment with cortisol also increased IGFBP-6 polypeptide levels in the medium, as determined by Western immunoblot analysis. Cycloheximide at 3.6 microM decreased IGFBP-6 transcripts and prevented the stimulatory effect of cortisol. Cortisol did not modify the decay of IGFBP-6 messenger RNA in transcriptionally arrested Ob cells. In addition, cortisol increased the rate of IGFBP-6 transcription, as determined by nuclear run-on assays. In conclusion, cortisol stimulates IGFBP-6 expression in Ob cells by transcriptional mechanisms. As IGFBP-6 binds to and prevents the effect of IGF-II, its increased synthesis could be relevant to the inhibitory actions of cortisol in bone.

Animals↗
PubMed1996

Transcriptional regulation of insulin-like growth factor-binding protein-5 by prostaglandin E2 in osteoblast cells.

Insulin-like growth factor (IGF)-binding protein-5 (IGFBP-5) is an autocrine and paracrine factor that modulates the effects of IGFs. We examined the mechanisms that regulate IGFBP-5 synthesis by PGE2 in osteoblast-enriched cells from fetal rat calvaria (Ob cells). PGE2 at 1 microM for 2-8 h increased IGFBP-5 heterogeneous nuclear RNA levels and did not change the half-life of IGFBP-5 messenger RNA in Ob cells, suggesting that PGE2 stimulates IGFBP-5 transcription. To analyze the elements responsible for this effect, regions of the mouse IGFBP-5 promoter from -2695 to +120 bp were ligated into pGL-2-basic and transiently transfected into Ob cells. PGE2 caused a time- and dose-dependent increase in IGFBP-5 promoter activity. Further analysis revealed two potential PGE2-responsive regions in the -2695 to -1470 and the -989 to -332 fragments. The effect of PGE2 on IGFBP-5 messenger RNA and heterogeneous nuclear RNA levels was mimicked by forskolin and inhibited by the PKA inhibitor H-89, suggesting that part of the PGE2 effect was mediated through a cAMP-dependent pathway. H-89 also blocked basal and PGE2-stimulated IGFBP-5 promoter activities. We conclude that PGE2 regulates IGFBP-5 synthesis in Ob cells by transcriptional mechanisms. PKA-dependent pathways account for part of the effect of PGE2 on IGFBP-5 expression. Deletion analysis of the IGFBP-5 promoter suggests the presence of two PGE2-responsive regions.

Animals↗
PubMed1996

Invited review of a workshop: anabolic hormones in bone: basic research and therapeutic potential.

Age-, postmenopause-, and disease-related conditions that result in low bone mass represent important public health issues. Maintenance of bone mass is a balance between bone resorption and formation and is influenced by diet, body composition, activity level, and the interactions between and among a large number of hormones, growth factors, and cytokines. Recent research has emphasized establishing a more complete understanding of the hormonal regulation of bone and developing anabolic agents with therapeutic potential for the treatment of low bone mass. The NIDDK at the NIH recently sponsored a Workshop, entitled Anabolic Hormones in Bone: Basic Research and Therapeutic Potential, that attempted to define the current state of the art knowledge of hormones, growth factors, and cytokines that affect bone mass, with particular emphasis on those that could potentially have a role as anabolic agents in bone. This review presents a condensed proceedings of that workshop along with a summary of the optimal requisites for the development of anabolic agents with therapeutic potential in bone.

Bone and Bones↗
PubMed1995

Cortisol increases interstitial collagenase expression in osteoblasts by post-transcriptional mechanisms.

Glucocorticoids regulate both bone formation and bone resorption. In osteoblasts, they inhibit type I collagen synthesis; however, there is limited information about their effects on interstitial collagenase, the enzyme that degrades type I collagen. We used primary cultures of osteoblast-enriched cells from fetal rat calvariae (Ob cells) to study the effects of cortisol on collagenase expression. Northern blot analysis showed that cortisol increased collagenase transcript levels in a dose- and time-dependent manner, which was paralleled by an increase in immunoreactive metalloproteinase in the culture medium. Cortisol increased the half-life of collagenase mRNA from 6 to 12 h in transcription-arrested Ob cells. In contrast, cortisol modestly decreased collagenase gene transcription after 24 h of treatment. The up-regulation of collagenase by cortisol is osteoblast-specific, since the glucocorticoid decreased phorbol 12-myristate 13-acetate-induced collagenase mRNA expression in rat fibroblasts, a result that agrees with other studies of collagenase gene regulation in fibroblastic cells. In conclusion, cortisol increases interstitial collagenase transcript levels by post-transcriptional mechanisms in osteoblastic cells. Our data demonstrate that glucocorticoids regulate collagenase gene expression in a novel tissue-specific manner, further highlighting the differences in gene regulation between osteoblastic and fibroblastic cells.

Animals↗
PubMed1995

Skeletal growth factors regulate the synthesis of insulin-like growth factor binding protein-5 in bone cell cultures.

Skeletal cells secrete insulin-like growth factors (IGFs) I and II and six known IGF binding proteins (IGFBPs). IGFBP-5 stimulates bone formation, and its synthesis correlates with changes in osteoblast cell growth. We tested the effects of basic fibroblast growth factor (bFGF), transforming growth factor beta 1 (TGF beta 1), and platelet-derived growth factor (PDGF) BB on IGFBP-5 expression in cultures of osteoblast-enriched cells from 22-day-old fetal rat calvariae (Ob cells). Treatment of Ob cells with bFGF, TGF beta 1, and PDGF BB caused a time- and dose-dependent decrease in IGFBP-5 mRNA levels and inhibited IGFBP-5 polypeptide levels in the extracellular matrix. The effects of bFGF, TGF beta 1, and PDGF BB on IGFBP-5 transcripts were independent of cell division and were observed in the presence and absence of hydroxyurea. bFGF, TGF beta 1, and PDGF BB did not modify the decay of IGFBP-5 mRNA in transcriptionally arrested Ob cells, and they inhibited IGFBP-5 heterogeneous nuclear RNA and the rate of IGFBP-5 transcription. In conclusion, bFGF, TGF beta 1, and PDGF BB inhibit IGFBP-5 expression in Ob cells independently of their mitogenic activity and through mechanisms that involve decreased transcription.

Animals↗
PubMed1995

Cortisol downregulates osteoblast alpha 1 (I) procollagen mRNA by transcriptional and posttranscriptional mechanisms.

Glucocorticoids decrease osteoblast proliferation and type I collagen production, and this may play a role in the development of glucocorticoid-induced osteoporosis. Osteoblast-enriched cultures derived from fetal rat calvaria were used to determine the mechanisms by which cortisol decreases alpha 1 (I) procollagen expression in bone cells. A 24 h treatment with cortisol decreased collagen synthesis in these cultures in a dose-dependent manner. Cortisol decreased alpha 1 (I) procollagen transcripts in a dose- and time-dependent manner as well. Repression of alpha 1 (I) procollagen transcripts was evident as early as 2 h of treatment and was maximal after 48 h of treatment. Nuclear run-off assays showed that cortisol downregulated transcription of the alpha 1 (I) procollagen gene. In addition, pretreatment with cortisol decreased the stability of alpha 1 (I) procollagen mRNA in transcription-arrested osteoblast cultures. The ability of cortisol to downregulate alpha 1 (I) procollagen transcripts was sensitive to cycloheximide treatment, suggesting that the gene is under "secondary control" by glucocorticoids. Since cortisol decreases alpha 1 (I) procollagen gene transcription in osteoblasts but does not affect alpha 1 (I) procollagen gene transcription in fibroblasts, we suggest that the mechanisms controlling glucocorticoid repression of collagen expression are cell-type specific.

Animals↗
PubMed1995

[Traumatic pulmonary pseudocysts].

Two cases of traumatic pulmonary pseudocysts in young patients are presented. Blunt chest injuries resulting from traffic accidents were the causes in both cases. Air cavities were seen on chest films 12 hours and one hour, respectively, after trauma. In both cases, self-limited hemoptysis preceded the appearance of an air-fluid level on X-rays. The diagnoses of pulmonary pseudocyst were made after excluding other possible cause and the outcomes were satisfactory after treatment of symptoms and associated lesions.

Accidents, Traffic↗