Sub-cellular damage by copper in the cnidarian Zoanthus robustus.

Sessile organisms may experience chronic exposure to copper that is released into the marine environment from antifoulants and stormwater runoff. We have identified the site of damage caused by copper to the symbiotic cnidarian, Zoanthus robustus (Anthozoa, Hexacorallia). External changes to the zoanthids were apparent when compared with controls. The normally flexible bodies contracted and became rigid. Histological examination of the zoanthid tissue revealed that copper had caused sub-cellular changes to proteins within the extracellular matrix (ECM) of the tubular body. Collagen in the ECM and the internal septa increased in thickness to five and seven times that of controls respectively. The epithelium, which stained for elastin, was also twice as thick and tough to cut, but exposure to copper did not change the total amount of desmosine which is found only in elastin. We conclude that copper stimulated collagen synthesis in the ECM and also caused cross-linking of existing proteins. However, there was no expulsion of the symbiotic algae (Symbiodinium sp.) and no effect on algal pigments or respiration (44, 66 and 110 microg Cu L(-1)). A decrease in net photosynthesis was observed only at the highest copper concentration (156 microg Cu L(-1)). These results show that cnidarians may be more susceptible to damage by copper than their symbiotic algae.

Field-induced phase transitions and reversible field-induced inversion of chirality in tilted smectic phases of bent-core mesogens.

Three homologous achiral five-ring bent-core mesogens are presented where 4-chlororesorcinol is the central core and the aromatic rings are linked by ester groups. These compounds form smectic phases with a tilted arrangement of the molecules (tilt angle approximately 45 degrees). On cooling the isotropic liquid this phase adopts a fan-like texture which shows for two homologues at relatively high electric fields ( 25-35 V microm(-1)) an antiferroelectric electro-optical response based on the collective rotation of the molecules around their long axes. At lower temperature the application of a sufficiently high electric field leads to a continuous transition into a non-birefringent texture which exhibits randomly distributed domains of opposite handedness. These domains can be reversibly switched into a state of opposite chirality by reversal of the field polarity. This switching is bistable and shows a current response typical for a ferroelectric ground state. The possible mechanism of the field-induced phase transition, of the ferroelectric switching and of the field-induced inversion of the chirality is discussed on the base of XRD, 13C- and 1H-NMR investigations, dielectric and electro-optical measurements.

Decorin affects endothelial cells by Akt-dependent and -independent pathways.

Decorin, a small multifunctional proteoglycan, has been shown to be causally involved in the formation of capillary-like structures and a decrease in apoptosis. Here we investigated signal transduction pathways mediating effects of decorin on endothelial cells (ECs). Addition of decorin led to a fourfold increase in phosphorylation of Akt/protein kinase B on Thr307 and a l.4-fold increase on Ser473 after 10 min, but this phosphorylation could not be blocked by preincubation with Ly29400 (10 micro M). Six hours after the addition of decorin, the synthesis of p21 and p27, two inhibitors of cyclin-dependent kinases, started and increased up to 18 h, while synthesis of cyclin A peaked at 12 h and decreased after 24 h below base level. Induction of dominan-negative Akt by a replication-deficient adenovirus blocked p21 and cyclin A synthesis, but had no effect on p27. Dominant-negative Akt also blocked the antiapoptotic effect of decorin on ECs, but induction of dominant-positive Akt could not rescue the cells from apoptosis. Thus, the matrix proteoglycan decorin is a signaling molecule in ECs that affects cell survival by Akt-dependent and -independent pathways.

Four-helix bundle topology re-engineered: monomeric Rop protein variants with different loop arrangements.

We converted the small homodimeric four-helix bundle repressor of primer protein (Rop) into a monomeric four-helix bundle by introduction of connecting loops. Both left- and right-handed four-helix bundles were produced. The left-handed bundles were more stable and were used to introduce biologically interesting peptides in one of the loops.

Experimental evidence for an achiral orthogonal biaxial smectic phase without in-plane order exhibiting antiferroelectric switching behavior.

We report unambiguous experimental evidence for an achiral orthogonal biaxial smectic-A phase which exhibits antiferroelectric switching behavior. The evidence is based on x-ray-diffraction measurements, texture observation, and the results of dielectric and electro-optical measurements.

Proteoglycans of the extracellular matrix and growth control.

Regulated cell growth results from the biological balance between soluble growth-regulating factors, their receptors and the elicited signal cascade on the one hand side and from extracellular macromolecular components and their interplay with membrane receptors on the other side. Proteoglycans have recently been recognized not only to play a part in providing shape and biomechanical strength of organs and tissues, but also to exhibit direct and indirect cell signalling properties. In this review, we discuss the direct growth-regulating role of proteoglycans with special emphasis on the lectican family and on the family of small proteoglycans with leucine-rich repeats (SLRPs). Indirect actions of proteoglycans by modulation of growth factor activities and growth factor distribution are exemplified by discussing the TGF-beta-binding properties of SLRPs and the interactions of core proteins of matrix proteoglycans with other growth factors. It is emphasized that the modulatory role of proteoglycans on cell proliferation cannot be separated from their participation in tissue organization in general, thereby explaining the diverse and sometimes contradictory reports on the effects of proteoglycans on cell proliferation and differentiation.

The small proteoglycans decorin and biglycan in human articular cartilage of late-stage osteoarthritis.

OBJECTIVE: Disturbances in proteoglycan metabolism of hyaline cartilage play an essential role in the pathology of degenerative joint disease. We investigated the relation between transcript expression, protein synthesis and the ultrastructural localization of the matrix-organizing proteoglycans decorin and biglycan within intra- and extracellular compartments of late-stage osteoarthritic human articular cartilage. METHODS: Human cartilage samples of a macroscopically intact area, the adjoining area and an area of the main defect from knee joints of 10 patients with late stage osteoarthritis were investigated. In situ hybridization and immunogold histochemistry were carried out separately and in combination at the light and electron microscopic level. RESULTS: Ultrastructurally, three main chondrocyte types were identified. The highest levels of mRNA of decorin and biglycan were produced by elongated secretory type 2 cells, already known to synthesize type I collagen. Cells with high levels of mRNA also translated the corresponding proteins to be found in the extracellular compartment. The highest production rate of decorin and biglycan was seen in the tissue area adjoining the main defect. CONCLUSION: The results indicate that at late stages of osteoarthritis the levels of transcription and translation for decorin and biglycan are up-regulated, probably in an effort to compensate for the general proteoglycan loss, characteristic of this disease stage.

Decorin-mediated signal transduction in endothelial cells. Involvement of Akt/protein kinase B in up-regulation of p21(WAF1/CIP1) but not p27(KIP1).

Endothelial cells undergoing angiogenesis express decorin, a small multifunctional proteoglycan. We have shown that decorin is causally involved in the formation of capillary-like structures and a decrease in apoptosis in endothelial cells cultured in a collagen lattice. Here we investigate signal transduction pathways mediating the effects of decorin. Reverse transcription-polymerase chain reaction demonstrated that p21 and p27, two inhibitors of cyclin-dependent kinases, were up-regulated by decorin induction. Decorin also increased protein levels of p21 and caused its translocation into the nucleus. p21 synthesis started 6 h after decorin addition and reached a plateau after 18 h, while cyclin A, which was also induced, peaked at 12 h and declined below basal levels within 24 h. These effects were mediated by the Akt/protein kinase B pathway. Akt phosphorylation at Thr-308 increased 4-fold and at Ser-473 1.4-fold within 10 min after decorin addition. Overexpression of dominant negative Akt inhibited the decorin-mediated induction of p21 and cyclin A, but had no effect on p27. These results show that decorin is a signaling molecule in sprouting endothelial cells where it acts via different pathways, one of them involving Akt/protein kinase B.

Expression of decorin and biglycan in rat gastric tissue: effects of ulceration and basic fibroblast growth factor.

BACKGROUND: The small chondroitin/dermatan sulphate proteoglycans decorin and biglycan participate in organizing the network of collagen fibrils and interact with non-collagenous matrix proteins. In addition, via interactions with cytokines they are directly or indirectly involved in signalling, growth and cell differentiation. We aimed to analyse their expression in normal gastric tissue and during gastric ulcer healing. METHODS: Proteoglycan expression was studied by immunohistochemistry and in situ hybridization in acetic acid-induced gastric ulcers in rat during early phases and during chronic ulceration. The effects of treatment with an acid stable mutein of FGF-2 (bFGF) were also studied. RESULTS: In normal gastric tissue, both proteoglycans were most strongly expressed in the submucosal layer. However, some epithelial cells were positive for biglycan and, surprisingly, also for decorin. In the early phase after ulcer induction exclusively decorin became induced in the muscularis mucosae, while biglycan became detectable in this layer only after 2 weeks. There was no up-regulation of either proteoglycan in other layers, nor could an effect of FGF-2 treatment be seen. CONCLUSIONS: The expression of decorin could be observed for the first time in epithelial cells. Decorin, but not biglycan, appears as an early phase reactant in the muscularis mucosae in accordance with its putative role during angiogenesis and the prevention of apoptosis.

Small proteoglycans in human diabetic nephropathy: discrepancy between glomerular expression and protein accumulation of decorin, biglycan, lumican, and fibromodulin.

Small leucine-rich proteoglycans (SLRPs), for example, decorin, biglycan, fibromodulin, and lumican, are extracellular matrix organizers and binding partners of TGF-b. Decorin is also involved in growth control and angiogenesis. Hence, these proteoglycans are likely of importance in the pathogenesis of diabetic glomerulosclerosis. In normal kidney, SLRPs were preferentially expressed in the tubulointerstitium. Weak expression occurred in the mesangial matrix. Biglycan was expressed by glomerular endothelial cells and, together with fibromodulin, by distal tubular cells and in collecting ducts. In all stages of diabetic nephropathy, there was a marked up-regulation of the proteoglycans in tubulointerstitium and glomeruli. Decorin and lumican became expressed in tubuli. However, in glomeruli, overexpression was not mirrored by local proteoglycan accumulation except in advanced nephropathy. In severe glomerulosclerosis, increased decorin concentrations were found in plasma and urine, and urinary TGF-b/decorin complexes could be demonstrated indirectly. The failure to detect an increased glomerular proteoglycan quantity during the development of nephropathy could be explained by assuming that they are secreted into the mesangial matrix, but cleared via the vasculature or the urinary tract, in part as complexes with TGF-b. They could thereby counteract the vicious circle being characterized by increased TGF-b production and increased matrix deposition in diabetic nephropathy.