IPG (inositolphosphate glycan) as a cellular signal for TGF-β1 modulation of chondrocyte cell cycle

The knowledge of transforming growth factor (TGF)-β receptors has greatly progressed in the recent years. TGF-β receptors type I and II have been implicated in the modulation of cell proliferation, whereas type III (betaglycan) may act as a component presenting TGF-β to its signaling receptors. In addition, four other proteins that bind TGF-β1 or TGF-β2 have been recently identified in some cell lines, three being anchored to the membrane through a glycosylphosphatidylinositol (GPI). Despite this knowledge, the molecular mechanism of signal transduction through the TGF-β receptors remain an enigma. TGF-β family does not signal via any of the classical pathways. As GPI anchors of membrane proteins have been implicated in the transduction of some hormonal effects, we investigated the putative role of GPI in signaling the TGF-β effects on the proliferation of rabbit articular chondrocytes (RAC). We previously showed that TGF-β1 increased DNA replication rate of RAC, with a recruitment of cells in G2/M followed by a subsequent mitosis wave. Here, we find that the factor causes specific GPI hydrolysis, with correlated increase of inositolphosphate glycan (IPG). This effect was specifically inhibited by antibodies that bind TGF-β1. Using [³H]-inositol labeling and Triton X-114 extraction, we demonstrate that a hydrophobic material from the membrane is cleaved by treatment of cell cultures with phosphatidylinositol specific phospholipase C (PI-PLC) or by exposure to TGF-β, supporting that a PI-anchored molecule gives rise to IPG by TGF-β-induced hydrolysis. The biological relevance of this hydrolysis was demonstrated by the enhancing effect of purified IPG on the DNA synthesis rate, which mimicked the TGF-β action. These results demonstrate that IPG could be an early messenger in the cellular signaling that mediates the effect of TGF-β on RAC growth. © 1993 Wiley-Liss, Inc.     

Targeting of oleosins to the oil bodies of oilseed rape (Brassica napus L.)

Oleosins of Brassica napus L. (oilseed rape) synthesized by in-vitro translation were found to be very efficiently targeted to microsomal membranes but only poorly translocated to oil bodies or emulsified oil. The use of other bilayer membranes as controls showed that this interaction was specific. The rate of oleosin synthesis in the presence of microsomes was enhanced about threefold, indicative of the involvement of the signal-recognition particle in the targeting process. There is no evidence for the cleavage of the protein during targeting and the protein sequence reveals no consensus cleavage site for the signal peptide. Protection experiments using Proteinase K revealed that about 6 kDa of the protein is exposed on the cytoplasmic side of the ER but the remainder is protected. Carbonate (pH 11) washing of microsomal membranes after in-vitro translation confirmed that oleosins have a domain which remains inserted in the ER rather than the protein being transported completely into the lumen of the ER. These results indicate that oleosins are transported via the ER prior to their accumulation on oil bodies.     

Diol sulfonamides: A potent and novel class of inhibitors of human renin

The syntheses and pharmacological activity of a series of diol sulfonamides which function as inhibitors of human renin are described. The most potent compound in this series, compound 20 (SQ 33,800), is a subnanomolar inhibitor of human renin (IC₅₀ = 0.35 × 10⁻⁹ M).     

Smart hydrogels based on semi-interpenetrating polymeric networks of collagen-polyurethane-alginate for soft/hard tissue healing,drug delivery devices,and anticancer therapies

In this work, hydrogels based on semi-interpenetrating polymeric networks (semi-IPN) based on collagen-polyurethane-alginate were studied physicochemically and from different approaches for biomedical application. It was determined that the matrices in the hydrogel state are crosslinked by the formation of urea and amide bonds between the biopolymer chains and the polyurethane crosslinker. The increment in alginate content (0–40 wt%) significantly increases the swelling capacity, generating semi-crystalline granular structures with improved storage modulus and resistance to thermal, hydrolytic, and proteolytic degradation. The in vitro bioactivity results indicated that the composition of these novel hydrogels stimulates the metabolic activity of monocytes and fibroblasts, benefiting their proliferation; while in cancer cell lines, it was determined that the composition of these biomaterials decreases the metabolic activity of breast cancer cells after 48 h of stimulation, and for colon cancer cells their metabolic activity decreases after 72 h of contact for the hydrogel with 40 wt% alginate. The matrices show a behavior of multidose release of ketorolac, and a higher concentration of analgesic is released in the semi-IPN matrix. The inhibition capacity of Escherichia coli is higher if the polysaccharide concentration is low (10 wt%). The in vitro wound closure test (scratch test) results indicate that the hydrogel with 20 wt% alginate shows an improvement in wound closure at 15 days of contact. Finally, the bioactivity of mineralization was evaluated to demonstrate that these hydrogels can induce the formation of carbonated apatite on their surface. The engineered hydrogels show biomedical multifunctionality and they could be applied in soft and hard tissue healing strategies, anticancer therapies, and drug release devices.     

Forest resistance to drought in a humid tropical dipterocarp forest in the Western Ghats of India

Droughts are linked to tree die-offs in the biodiverse humid tropics. We assessed drought response of a Dipterocarp Forest and found a marginal decrease in tree survival, indicating drought resistance. Understory and emergent species were sensitive to drought. Urgent focus is needed to understand drought impacts and plant physiological responses in South Asian forests.     

Contribution of the different planktonic microbial assemblages to ETS activity in the Ligurian frontal area: north-west Mediterranean Sea

Spatial and size distribution of micro-organisms and their ETSactivity has been investigated in Ligurian Sea surface watersalong the Nice-Calvi transect across frontal areas from 18 to37 km offshore (TOMOFRONT 1 and 2 cruises, April 1988 and April-May1989 respectively). Aplastidic and plastidic nanoflagellatesand aplastidic picoflagellates were present in numbers closeto 0.25 x 10⁴ cells ml^–1, whereas plastidic picoflagellatesaccounted for about half this number. Correlations have beenevidenced between plastidic and aplastidic micro-organisms withinthe same size group, suggesting that they belong to a well-definedecosystem. The highest correlation between total ETS activityand abundance of the considered size groups was observed fornanoflagellates (r = 0.94, n = 22, and r = 0.90, n = 22 foraplastidic and plastidic cells respectively). The importanceof the role of nanoflagellates in surface waters, with respectto the overall ETS activity, was supported by results from sizefractionation which assigned to the 3–10 µm sizerange a 73.3% contribution to overall ETS activity. Resultsemphasize analysing global ETS activity of natural samples inorder to derive relationships between the different populationspresent in the sampled water. It is suggested that couplingflow cytometry to the ETS approach should be very helpful inthat respect.