Influence and modelling of urban runoff on the peak flows in rivers.

Surface waters and urban drainage systems are usually studied separately. However there are important interactions between both systems. Urban drainage systems can have an important impact on the surface waters, mainly at combined sewer overflows.

Science-policy interfacing in support of the Water Framework Directive implementation.

Many current water-related RTD projects have established operational links with practitioners, which allow the needs of policy makers to be taken into account. However, RTD results are not easily available to water policy implementers and research scientists may lack insight in the needs of policy makers and implementers (i.e.

Advection-dispersion modelling tools: what about numerical dispersion?

In general the transport of dissolved substances and fine suspended particles is governed by the one-dimensional advection-dispersion equation. In order to model the transport of dissolved substances and fine suspended particles, the advection-dispersion equation is incorporated into commonly used urban drainage modelling tools such as InfoWorks CS (Wallingford Software, United Kingdom) and MOUSE (DHI Software, Denmark). Two examples show the use of InfoWorks CS and MOUSE using standard model settings.

Solids separation efficiency of combined sewer overflows.

The removal of sewer solids at combined sewer overflow locations depends on the flow patterns inside the overflow structure on the one hand and on the sediment characteristics on the other hand. Flow conditions can be described by the residence time distribution; sewer sediments can be characterised by their settling velocity distribution. The combination of both distributions leads to a dimensionless efficiency curve, which gives the removal efficiency as a function of the Hazen number.

Design rules and impact assessment for source control measures based on continuous long-term simulations.

In recent years, more emphasis has been put on source control measures in order to reduce the peak runoff from urban areas during wet weather conditions. This involves the construction of upstream storage and infiltration facilities and rainwater tanks for reuse in households and the revaluation of ditches. Because of the long emptying times of source control facilities, a long antecedent period of rainfall influences the design.

100 years of Belgian rainfall: are there trends?

In 1999 the digitisation of old rainfall records of measurements at Uccle (Belgium) was completed, which resulted in a unique rainfall series of 100 years (period 1898-1997). This is an ideal opportunity to search for trends in the rainfall over the last century. Large variations in rainfall probability over the century have been observed.

Bone resorption and response to calcium-regulating hormones in the absence of tissue or urokinase plasminogen activator or of their type 1 inhibitor.

Plasminogen activators (PA) are implicated in cell migration and tissue remodeling, two components of the bone resorption processes. Using mice with inactivated tissue PA (tPA), urokinase PA (uPA), or type 1 PA inhibitor (PAI-1) genes, we evaluated whether these processes, or their stimulation by parathyroid hormone (PTH) or 1,25-dihydroxyvitamin (1,25[OH]2D3) are dependent on these genes. Two culture models were used, one involving 19-day fetal calvariae, to evaluate the direct resorptive activity of osteoclasis, and the other involving 45Ca-labeled 17-day fetal metatarsals, in which this activity depends on preliminary (pre)osteoclast migration.

Relationship of the plasminogen activator/plasmin cascade to osteoclast invasion and mineral resorption in explanted fetal metatarsal bones.

An attempt was made to establish whether the activation of plasminogen into plasmin is necessary either for the preparatory phases to bone resorption, involving the recruitment of osteoclast precursors, their migration toward mineralized surfaces, and their final differentiation, or for the subsequent osteoclastic resorption phase. 45Ca-labeled fetal (17 day) mouse metatarsals were cultured under conditions in which they pursue their modeling for a few days. In this model, the resorption phase, monitored by the release of 45Ca into the medium, is entirely dependent on the preparatory phases affecting osteoclast precursors.

(Pro)collagenase (matrix metalloproteinase-1) is present in rodent osteoclasts and in the underlying bone-resorbing compartment.

Osteoclasts resorb the extracellular matrix of bone by secreting enzymes and acid into a sealed-off compartment that they form upon attachment to the bone surface. Although the lysosomal cysteine proteinases can degrade collagen after the demineralization of bone at low pH, several lines of evidence suggest that collagenase (matrix metalloproteinase-1, EC 3.4.

Degradation of collagen in the bone-resorbing compartment underlying the osteoclast involves both cysteine-proteinases and matrix metalloproteinases.

The site of action of cysteine-proteinases (CPs) and matrix metalloproteinases (MMPs) in the degradation of bone collagen by osteoclasts was investigated by evaluating the effects of the CP-inhibitor trans-epoxy-succinyl-L-leucylamido (4-guanidino)-butane (E-64) and the MMP-inhibitor N-(3-N-benzyloxycarbonyl amino-1-R-carboxypropyl)-L-leucyl-O-methyl-L-tyrosine N-methylamide (Cl-1) in an in vitro model system of PTH-stimulated mouse calvaria. In the presence of each of the two inhibitors a large area of collagen free of mineral crystallites was seen adjacent to the ruffled border of the osteoclasts. Following a culture period of 24 h this area proved to be about 10 times larger in inhibitor-treated explants than in controls.

Relative roles of collagenase and lysosomal cysteine-proteinases in bone resorption.

Both lysosomal cysteine-proteinases and collagenase appear to be necessary for the resorption of actively growing, immature woven bone, but their relative roles are not yet clearly elucidated. The present evidence indicates that, during bone resorption, the osteoclast first solubilizes the mineral by a secretion of acid and then removes the exposed demineralized collagen by the action of secreted lysosomal collagenolytic cysteine-proteinases. Collagenase in bone seems to be mainly a product of osteoblasts and related cells, not osteoclasts.

Collagenolytic cysteine proteinases of bone tissue. Cathepsin B, (pro)cathepsin L and a cathepsin L-like 70 kDa proteinase.

The aim of the work was to identify and characterize the cysteine proteinases of bone tissue, as these enzymes appear necessary for bone resorption. Three cysteine-dependent proteolytic activities were separated from a homogenate of mouse calvaria by a fractionation procedure involving (NH4)2SO4 precipitation, gel filtration and ion-exchange chromatography. The first two are typical cathepsins B and L with respect to (1) their reactivity with anti-(cathepsin B) and anti-(cathepsin L) antibodies respectively, (2) their relative rate constants for inhibition by benzyloxycarbonyl-Phe-Phe-CHN2 and L-3-carboxy-trans-2,3-epoxypropionyl-L-leucylamido-(4-guanid ino)butane and (3) their enzymic properties, such as the higher activities of cathepsin L against collagen and gelatin as compared with cathepsin B, and the fact that benzyloxycarbonyl-Arg-Arg 4-methoxy-2-naphthylamide is hydrolysed only by cathepsin B.

Tissue and urokinase plasminogen activators in bone tissue and their regulation by parathyroid hormone.

The identification of the plasminogen activator (PA) types present in bone and the regulation of their activity by parathyroid hormone (PTH) were investigated in cultures of fetal mouse calvariae with the use of either a chromogenic substrate or a zymographic assay. PA was detected essentially in the tissue extracts of the explanted bones, with only 1-2% of the total activity released in the surrounding culture media. From their electrophoretic behavior compared to PAs of other mouse tissues and from their response to a specific antibody raised against the tissue type PA (tPA), two major molecular species, of 70 and 48 kD were identified as tPA and urokinase (uPA), respectively, a third minor species of 105 kD being likely to correspond to complexes between tPA and an inhibitor; the culture fluids, moreover, contained enzymatically active degradation products of uPA of 42 and 29 kD.

Production of gelatin-degrading matrix metalloproteinases ('type IV collagenases') and inhibitors by articular chondrocytes during their dedifferentiation by serial subcultures and under stimulation by interleukin-1 and tumor necrosis factor alpha.

The gelatin-degrading matrix metalloproteinase (MMP) activities and their inhibitors produced by rabbit articular chondrocytes have been characterized by gel substrate analysis ('zymography') after electrophoresis on non-reducing sodium dodecyl sulfate-polyacrylamide gels containing gelatin. Differentiated chondrocytes in confluent primary culture produced constitutively only one gelatinase which presented the main characteristics of proMMP-2 ('72 kDa type IV procollagenase'). It had an apparent Mr of 66,000 (unreduced), which was partially or totally converted to 61,000 by, respectively, trypsin or APMA treatment; exogenous TIMP (tissue inhibitor or metalloproteinases) inhibited the conversion triggered by APMA but not that induced by trypsin.

Modulation by interleukin 1 and tumor necrosis factor alpha of production of collagenase, tissue inhibitor of metalloproteinases and collagen types in differentiated and dedifferentiated articular chondrocytes.

The actions of interleukin 1 (IL1) and tumor necrosis factor alpha (TNF alpha) on several parameters of the collagen metabolism of rabbit articular chondrocytes were studied by comparing the responses of either differentiated chondrocytes in primoculture or dedifferentiated cells in late passage culture to human recombinant (hr) IL1 alpha, hr-TNF alpha and cytokine-enriched fractions of rabbit macrophage-conditioned media. In response to IL1 or TNF alpha, differentiated chondrocytes (i.e.

Production of collagens, collagenase and collagenase inhibitor during the dedifferentiation of articular chondrocytes by serial subcultures.

Rabbit articular chondrocytes were cultured in monolayer and the progressive loss of their differentiated phenotype was monitored from passage to passage. The cell densities achieved in confluent cultures decreased abruptly between the primoculture and the second or third subculture, and more slowly thereafter, reflecting parallel morphological changes. The synthesis of collagen (but not that of other proteins) decreased sharply, and a smaller proportion of collagen was incorporated into the matrix.

Direct extraction and assay of collagenase from human osteoarthritic articular cartilage.

A method has been developed for the direct extraction of collagenase from small quantities (5 mg) of human osteoarthritic articular cartilage. The enzyme, which was not detected in normal cartilage, was entirely in a latent form and demonstrated typical properties of mammalian collagenase after activation by trypsin.

The enzymatic evaluation of procollagenase and collagenase inhibitors in crude biological media.

The validity of the enzymatic assay of procollagenase within crude biological media containing also the collagenase inhibitor TIMP (tissue inhibitor of metalloproteinases) as well as other (pro)metalloproteinases and sometimes, metalloproteinase-TIMP complexes, has been reevaluated. To be enzymatically assayed, procollagenase has to be activated. The standard activation procedures by either trypsin or 4-aminophenylmercuric acetate (APMA) both allow an optimal recovery of collagenase from procollagenase when the media do not contain free TIMP.

Bone-resorbing agents affect the production and distribution of procollagenase as well as the activity of collagenase in bone tissue.

The participation of collagenase in bone resorption has been investigated by assaying the procollagenase extracted from fetal mouse calvaria cultured under a variety of conditions, and by evaluating its ability to degrade bone collagen. Procollagenase was found in two separate pools, one requiring demineralization for its extraction, the other not. Culturing the bones with PTH, 1,25-dihydroxyvitamin D3, prostaglandin E2, interleukin-1, tumor necrosis factor-alpha, catabolin, retinoic acid, or endotoxin (but not with heparin) induced resorption, enhanced lysosomal enzyme release, and markedly increased the procollagenase content of the second pool.

Cellular biology and biochemical mechanism of bone resorption. A review of recent developments on the formation, activation, and mode of action of osteoclasts.

The newest knowledge on the osteoclast allows us to consider bone resorption in a global perspective, as the resultant of three successive steps that may each be individually regulated by physiopathologic or pharmacologic agents. The first involves the formation of osteoclast progenitors in hematopoietic tissues followed by their vascular dissemination and the generation of resting preosteoclasts and osteoclasts in bone. The second consists in the activation of osteoclasts at the contact of mineralized bone.

The effects of inhibitors of cysteine-proteinases and collagenase on the resorptive activity of isolated osteoclasts.

The effects of specific inhibitors of cysteine-proteinases ((Z-Phe-Ala-CHN2: benzyloxycarbonyl-phenyl-alanyl alanyl diazomethane and E-64: trans-epoxy-succinyl-L-leucylamido(4-guanidino)-butane) and collagenase and collagenase ((Cl-1: N-(3-N-benzyloxycarbonyl amino-1-R-carboxypropyl)-L-leucyl-O-methyl-L-tyrosine N-methylamide) have been tested on the osteoclastic resorption of dentine. Chick osteoclasts were cultured in the presence or absence of 12.5 microM Z-Phe-Ala-CHN2, 40 or 60 microM E-64, or 40 or 100 microM Cl-1 for 1 or 2 days.

Direct extraction and assay of bone tissue collagenase and its relation to parathyroid-hormone-induced bone resorption.

A method has been developed for the quantitative extraction of collagenase from as little as one 19-day-fetal-mouse calvarium. About 20-40 munits of collagenase are extracted per mg of tissue, all in a latent form that, after proper activation, shows the typical properties of mammalian collagenase. Culturing the calvaria for 2 days with parathyroid hormone (PTH) increases their procollagenase content up to 3-fold and induces bone resorption.

Inhibition of bone resorption in culture by (+)-catechin.

A pretreatment with (+)-catechin renders embryonic mouse calvaria in culture resistant to the action of bone resorbing agents, either parathyroid hormone (PTH), prostaglandin E2 or retinoic acid, and inhibits in a parallel way the enhanced excretion of N-acetyl-beta-glucosaminidase, a reference lysosomal enzyme, induced by these agents; it has, however, no effect on the small spontaneous leakage of lactate dehydrogenase from the explants. Moreover, the resorption induced in calvaria by a pretreatment with PTH or retinoic acid is inhibited by a further culture with catechin. This inhibition of bone resorption is discussed in relation with the collagen-stabilizing properties of (+)-catechin.