Redefining the role of syndecans in C. elegans biology

Cytosolic calcium is an important factor during fertilization, development and differentiation. Hence, the control of cytosolic calcium levels has been studied extensively for several decades. Numerous calcium channels have been identified and their mechanism of action elucidated. However, the mode of calcium channel regulation remains elusive. Here we discuss our recent findings regarding the role of syndecans in the regulation of cytosolic calcium levels. Syndecans are transmembrane proteoglycans present in both vertebrates and invertebrates that interact with extracellular ligands resulting in the activation of several downstream signaling pathways. We identified a previously unappreciated role of syndecans in cytosolic calcium regulation in mammals that is conserved in C. elegans. We concluded that calcium regulation is the basic, evolutionarily conserved role for syndecans, which enables them to be integral for multiple cellular functions.

Proteoglycans in basement membranes

Previous studies have shown that sulphated proteoglycans are integral components of basement membranes. We have used mouse parietal yolk sac cells as a model system for our studies. These cells produce several basement membrane components, including a heparan sulphate proteoglycan and a chondroitin sulphate proteoglycan. The structure of the heparan sulphate proteoglycan has been described previously. The chondroitin sulphate proteoglycan has an Mr of 200 000-300 000 and contains 10-20 chondroitin sulphate chains (Mr = 14 000-16 000), attached to a core protein that on polyacrylamide gel electrophoresis appears as a doublet (with Mr = 34 000 and 27 000). Further structural analysis suggests that the majority of the polysaccharide chains are clustered around one segment of the core protein. The polysaccharide chains carry sulphate residues predominantly attached to C-4 of the galactosamine unit. More than 60% of the uronic acid residues are of the glucuronic configuration, the rest being iduronic acid. The parietal yolk sac cells secrete about equal amounts of the two proteoglycans into the culture medium, whereas heparan sulphate proteoglycan is the predominant proteoglycan found in the extracellular matrix of these cells. This proteoglycan appears to be anchored in the matrix by interactions involving the core protein rather than the polysaccharide chains.

Intercountry Adoption in New Zealand - A Child Rights Perspective

In 1996, the Adoption Amendment Bill (No 2) was introduced into Parliament. The aim of the Bill was to implement in New Zealand the Hague Convention on Protection of Children and Co-operation in Respect of Intercountry Adoption. New Zealand's accession to the Hague Convention would provide significantly improved protection for some children who come to New Zealand as a result of intercountry adoption. This article provides information on intercountry adoption in New Zealand, the background to the Bill, and concludes that the Bill, if passed in its current form, would fail to provide protection for the majority of children who come to New Zealand as a result of intercountry adoption, and would not fulfil New Zealand's obligations concerning adoption under the United Nations Convention on the Rights of the Child.

Long-term treatment with lipoteichoic acid from Streptococcus faecalis affects differentiation and expression and cellular distribution of beta 1 integrins in human urothelial cells

Gram-positive bacteria are recognized pathogens in urinary tract infections. Cellular mechanisms triggered by lipoteichoic acids (LTs), cell well components of gram-positive bacteria, have not been completely defined. We have postulated that infection-induced altered function of progenitors of urothelial cells residing in the basal layer is likely to have long lasting effects on the architecture and function of the urothelium. Our recent studies in vitro showed that treatment of poorly differentiated urothelial cells of basal type with LT from Streptococcus faecalis (LT-2) stimulated rapid proliferation of a subpopulation of progenitors of urothelial cells, supporting this possibility (Elgavish et al., 1996, J. Cell. Physiol., 169:42-51). The hypothesis underlying the present studies was that, following LT-triggered increase in proliferation of progenitors, the rate of differentiation of the resulting progeny was also stimulated. We proposed that this mechanism may allow rapid removal of cells from the injured area and replacement by cells that have not been exposed to infection. To simulate in vitro conditions in the basal layer that inhibit terminal differentiation, cells grew on fibronectin or collagen-coated substrate, in medium containing low Ca2+ (0.2 mM) and low levels of growth factors (0.005% bovine pituitary extract [BPE]). During the last 3 days in culture, cells grew in the same low Ca2+ (0.2 mM) medium, but without BPE, with or without LT-2. In a positive control group, cells grew during their last 3 days in culture in medium without BPE and LT-2 but in which levels levels of Ca2+ were higher (2 mM), a condition known to stimulate differentiation in other cell types. Several lines of evidence supported the possibility that long-term treatment with LT-2 stimulated progression of large colonies (i.e., the progeny resulting from LT-triggered proliferation) to a more differentiated state: (1) the rate of their differentiation, determined by criterion of intense cytokeratin 8 expression, was increased; (2) steady-state level of beta mRNA and expression of beta 1 subunit of integrins at the protein level were inhibited; (3) in contrast to large colonies in control cultures, the entire population of LT-2-treated large colonies contained beta 1 integrins distributed at cell-cell contacts. Raising extracellular Ca2+ concentration to 2 mM induced similar effects, suggesting that LT-2 may act by stimulating an increase in intracellular levels of Ca2+. However, further studies will be needed to elucidate the molecular mechanisms underlying the stimulatory effect of LT-2 on proliferation of progenitors of urothelial cells in the basal layer of the urothelium and subsequent differentiation of their progeny. We propose that these processes may have a causative role in the pathological changes that occur in the aftermath of chronic or recurrent suburothelial infection in the urinary bladder.

Stage-specific remodeling of the mammary gland basement membrane during lactogenic development

Several in vitro studies have highlighted the importance of extracellular matrix proteoglycans as regulators of mammary epithelial cell differentiation. In this study monospecific antibodies to heparan (HS) and chondroitin/dermatan sulfate (CS/DS) proteoglycans were used to determine their possible significance in vivo. Immunohistochemical studies of proteoglycan distribution in virgin, pregnant, and lactating tissue demonstrated that heparan sulfate proteoglycan was found in the epithelial cell basement membrane at all stages of development. This was also true for CS/DS proteoglycans, but the relative proportions of CS and DS were strikingly modulated during lactogenesis. Notably DS glycosaminoglycans were the dominant components of the basement membrane in lactating tissue but CS glycosaminoglycans were the major proteoglycans of pregnant tissue. The possible significance of these results for gene expression in the gland is discussed.