The expression of plasminogen activator system in a rat model of periodontal wound healing

Background: The plasminogen activator system has been proposed to play a role in proteolytic degradation of extracellular matrices in tissue remodeling, including wound healing. The aim of this study was to elucidate the presence of components of the plasminogen activator system during different stages of periodontal wound healing. Methods: Periodontal wounds were created around the molars of adult rats and healing was followed for 28 days. Immunohistochemical analyses of the healing tissues and an analysis of the periodontal wound healing fluid by ELISA were carried out for the detection of tissue-type plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), and 2 plasminogen activator inhibitors (PAI-1 and PAI-2). Results: During the early stages (days 1 to 3) of periodontal wound healing, PAI-1 and PAI-2 were found to be closely associated with the deposition of a fibrin clot in the gingival sulcus. These components were strongly associated with the infiltrating inflammatory cells around the fibrin clot. During days 3 to 7, u-PA, PAI-1, and PAI-2 were associated with cells (particularly monocytes/macrophages, fibroblasts, and endothelial cells) in the newly formed granulation tissue. During days 7 to 14, a new attachment apparatus was formed during which PAI-1, PAI-2, and u-PA were localized in both periodontal ligament fibroblasts (PDL) and epithelial cells at sites where these cells were attaching to the root surface. In the periodontal wound healing fluid, the concentration for t-PA increased and peaked during the first week. PAI-2 had a similar expression to t-PA, but at a lower level over the entire wound-healing period. Conclusions: These findings indicate that the plasminogen activator system is involved in the entire process of periodontal wound healing, in particular with the formation of fibrin matrix on the root surface and its replacement by granulation tissue, as well as the subsequent formation of the attachment of soft tissue to the root surface during the later stages of wound repair.

A formal representation of assumptions in process modelling

In this work, we present a systematic approach to the representation of modelling assumptions. Modelling assumptions form the fundamental basis for the mathematical description of a process system. These assumptions can be translated into either additional mathematical relationships or constraints between model variables, equations, balance volumes or parameters. In order to analyse the effect of modelling assumptions in a formal, rigorous way, a syntax of modelling assumptions has been defined. The smallest indivisible syntactical element, the so called assumption atom has been identified as a triplet. With this syntax a modelling assumption can be described as an elementary assumption, i.e. an assumption consisting of only an assumption atom or a composite assumption consisting of a conjunction of elementary assumptions. The above syntax of modelling assumptions enables us to represent modelling assumptions as transformations acting on the set of model equations. The notion of syntactical correctness and semantical consistency of sets of modelling assumptions is defined and necessary conditions for checking them are given. These transformations can be used in several ways and their implications can be analysed by formal methods. The modelling assumptions define model hierarchies. That is, a series of model families each belonging to a particular equivalence class. These model equivalence classes can be related to primal assumptions regarding the definition of mass, energy and momentum balance volumes and to secondary and tiertinary assumptions regarding the presence or absence and the form of mechanisms within the system. Within equivalence classes, there are many model members, these being related to algebraic model transformations for the particular model. We show how these model hierarchies are driven by the underlying assumption structure and indicate some implications on system dynamics and complexity issues. (C) 2001 Elsevier Science Ltd. All rights reserved.

Microbiology and application of the anaerobic ammonium oxidation ('anammox') process

Ten years ago, an anaerobic ammonium oxidation ('anammox') process was discovered in a denitrifying pilot plant reactor. From this system, a highly enriched microbial community was obtained, dominated by a single deep-branching planctomycete, Candidatus Brocadia anammoxidans. Phylogenetic inventories of different wastewater treatment plants with anammox activity have suggested that at least two genera in Planctomycetales can catalyse the anammox process. Electron microscopy of the ultrastructure of B. anammoxidans has shown that several membrane-bounded compartments are present inside the cytoplasm. Hydroxylamine oxidoreductase, a key anammox enzyme, is found exclusively inside one of these compartments, tentatively named the 'anammoxosome'.

An ESR study on gamma-irradiated poly(vinyl alcohol)

The formation of radicals in poly(vinyl alcohol), PVA, powder irradiated at 77 K by gamma -rays and the transformations of these radicals during photolysis with visible wavelengths and on thermal annealing have been studied. After irradiation a four-line ESR spectrum was observed. It was assigned to a triplet of the C-alpha-radical (38%), with a splitting of 3.27 mT, superimposed on a doublet (62%) with a splitting of 2.7 mT. The doublet appears to be composed of two radicals, one of which is photo-bleachable (58%) and the other which is not photo-bleachable (42%). This suggests that the latter radical is a neutral radical. The photo-bleachable component of the doublet has been assigned to a carbonyl anion radical. but the second doublet due to a neutral radical is unassigned. The total G-value for formation of radicals at 77 K was found to be 2.41 +/- 0.03. Upon illumination with visible light, the anion radicals were removed and the doublet components or the spectrum diminished in intensity, while the three-line spectrum of the C-alpha-radical became more clearly visible. This transition was due to the photo-detachment of electrons from traps which were proposed to be located on carbonyl groups in the polymer resulting from incomplete hydrolysis of the vinyl acetate. The photo-decay of the anion radicals could be satisfactorily described by a two-stage process. The first stage comprised the decay of approximately 80% of the anion radicals present, while the second stage was associated with the decay of the remaining 20%. Subsequent thermal annealing of a photolysed sample to 290 K led to a change in the shape of the spectrum to form a more clearly defined triplet, As the doublet of the neutral radical decays on thermal annealing between 150 and 250K, the C-alpha-radical is formed. (C) 2001 Elsevier Science Ltd. All rights reserved.

Solid state F-19 NMR determination of new structure formation in FEP following radiolysis at 300 and 363 K

The radiation chemistry of FEP copolymer with a mole fraction TFE of 0.90 has been studied using Co-60 gamma -radiation at temperatures of 300 and 363 K. New structure formation in the copolymers was analysed by solid state F-19 NMR. New chain scission products were the principal new structures found. The G-value for the formation of new -CF3 groups was 2.2 and 2.1 for the radiolysis of FEP at 300 and 363 K, respectively, and the G-value for the loss of original -CF3 groups was G(-CF3) = 1.0 and 0.9 at these two temperatures, respectively. There was a nett loss of -CF- groups on irradiation, with G(-CF) of 1.3 and 0.9 at 300 and 363 K, respectively. (C) 2001 Elsevier Science Ltd. All rights reserved.

Formation of cumulenes, triple-bonded, and related compounds by flash vacuum thermolysis of five-membered heterocycles

Flash vacuum thermolysis of a large variety of heterocyclic compounds is a useful means of production of ketenes, ketenimines, thioketenes, allenes, iminopropadienones, bis(imino)propadienes, iminopropadienethiones, carbodiimides, isothiocyanates, acetylenes, fulminic acid, nitrile imines and nitrile ylides, nitriles, cyanamides, cyanates, and other compounds, often in preparatively useful yields.

Process mineralogy of fluorosilicate minerals in OK Tedi ores

The impact of fluorine in copper flotation was relatively unknown until the introduction of skarn ores in the Ok Tedi concentrator. Fluorine in the copper concentrates reports to the gas phase during the smelting stage and forms a corrosive H2SO4-HCl-HF acid brine mixture which must be neutralised. This work was aimed at studying the mineralogy of the fluorosilicate minerals contained in the various oretypes present in the Ok Tedi porphyry copper deposit. The electron microprobe was used to analyse for fluorine and hence identify the fluorosilicate minerals in each oretype. This study revealed talc, phlogopite, biotite, clays, amphiboles, fluoroapatite and titanite to be the sources of fluorine in the orebody. Laboratory and plant investigations were conducted to study the flotation response of these minerals. Chemical assaying of the products of these tests was done to determine the bulk assay of fluorine, Using Rietveld analysis, quantitative estimates of the fluorosilicate minerals in these products were generated. Marrying of the bulk assay with the respective mineralogical assay enabled the understanding of the flotation behavior of fluorine and it's associated mineralogy. Talc and phlogopite were found to be the causes of the fluorine problem at Ok Tedi. (C) 2001 Elsevier Science Ltd. All rights reserved.

An empirical framework for studying desistance as a process

Recent reviews of the desistance literature have advocated studying desistance as a process, yet current empirical methods continue to measure desistance as a discrete state. In this paper, we propose a framework for empirical research that recognizes desistance as a developmental process. This approach focuses on changes in the offending rare rather than on offending itself We describe a statistical model to implement this approach and provide an empirical example. We conclude with several suggestions for future research endeavors that arise from our conceptualization of desistance.

Elucidation of reaction scheme describing malondialdehyde-acetaldehyde-protein adduct formation

Malondialdehyde and acetaldehyde react together with proteins and form hybrid protein conjugates designated as MAA adducts, which have been detected in livers of ethanol-fed animals. Our previous studies have shown that MAA adducts are comprised of two distinct products. One adduct is composed of two molecules of malondialdehyde and one molecule of acetaldehyde and was identified as the 4-methpl-1,4-dihydropyridine-3,5-dicarbaldehyde derivative of an amino group (MHHDC adduct). The other adduct is a 1:1 adduct of malondialdehyde and acetaldehyde and was identified as the 2-formyl-3-(alkylamino)butanal derivative of an amino group (FAAB adduct). In this study, information on the mechanism of MAA adduct formation was obtained, focusing on whether the FAAB adduct serves as a precursor for the MDHDC adduct. Upon the basis of chemical analysis and NMR spectroscopy, two initial reaction steps appear to be a prerequisite for MDHDC formation. One step involves the reaction of one molecule of malondialdehyde and one of acetaldehyde with an amino group of a protein to form the FAAB product, while the other step involves the generation of a malondialdehyde-enamine. It appears that generation of the MDHDC adduct requires the FAAB moiety to be transferred to the nitrogen of the MDA-enamine. For efficient reaction of FAAB with the enamine to take place, additional experiments indicated that these two intermediates likely must be in positions on the protein of close proximity to each other. Further studies showed that the incubation of liver proteins from ethanol-fed rats with MDA resulted in a marked generation of MDHDC adducts, indicating the presence of a pool of FAAB adducts in the liver of ethanol-fed animals. Overall, these findings show that MDHDC-protein adduct formation occurs via the reaction of the FAAB moiety with a malondialdehyde-enamine, and further suggest that a similar mechanism may be operative in vivo in the liver during prolonged ethanol consumption.

Dipeptidyl peptidase IV is a target for covalent adduct formation with the acyl glucuronide metabolite of the anti-inflammatory drug zomepirac

The nonsteroidal anti-inflammatory drug zomepirac (ZP) is metabolised to a chemically reactive acyl glucuronide conjugate (ZAG) which can form covalent adducts with proteins. In vivo, such adducts could initiate immune or toxic responses. In rats given ZP, the major band detected in liver homogenates by immunoblotting with a polyclonal ZP antiserum was at 110 kDa. This adduct was identified as ZP-modified dipeptidyl peptidase IV (DPP IV) by immunoblotting using the polyclonal ZP antiserum and monoclonal DPP IV antibodies OX-61 and 236.3. In vitro, ZAG, but not ZP itself, covalently modified recombinant human and rat DPP IV. Both monoclonal antibodies recognized DPP IV in livers from ZP- and vehicle-dosed rats. Confirmation that the 110 kDa bands which were immunoreactive with the ZP and DPP IV antibodies represented the same molecule was obtained from a rat liver extract reciprocally immunodepleted of antigens reactive with these two antibodies. Furthermore, immunoprecipitations with OX-61 antibody followed by immunolotting with ZP antiserum, and the reciprocal experiment, showed that both these antibodies recognised the same 110 kDa molecule in extracts of ZP-dosed rat liver. The results verify that DPP IV is one of the protein targets for covalent modification during hepatic transport and biliary excretion of ZAG in rats. (C) 2001 Elsevier Science Inc. All rights reserved.

Evidence for the presence of a widespread PCDD source in coastal sediments and soils from Queensland, Australia

Recent studies have demonstrated the occurrence of elevated levels of higher chlorinated PCDDs in the coastal environment of Queensland, Australia. This study presents new data for OCDD contamination and full PCDD/F profile analysis in the environment of Queensland. Marine sediments, irrigation drain sediments and topsoil were collected from sites that were expected to be influenced by specific land-use types. High OCDD concentrations were associated mainly with sediments collected near the mouth of rivers which drain into large catchments in the tropical and subtropical regions. Further, analysis of sediments from irrigation drains could be clearly differentiated on the basis of OCDD contamination, with high concentrations in samples from sugarcane drains collected from coastal regions, and low concentrations in drain sediments from drier inland cotton growing areas. PCDD/F congener-specific analysis demonstrated almost identical congener profiles in all samples collected along the coastline. This indicates the source to be widespread. Profiles were dominated by higher chlorinated PCDDs, in particular OCDD whereas 2,3,7,8-substituted PCDFs were below the limit of quantification in the majority of samples. The full PCDD/F profile analysis of samples strongly resemble those reported for lake sediments from Mississippi and kaolinite samples from Germany, Strong similarities to these samples with respect to congener profiles and isomer patterns may indicate the presence of a similar source and/or formation process that is yet unidentified. (C) 2001 Elsevier Science Ltd. All rights reserved.

Time-dependent master equation simulation of complex elementary reactions in combustion: Application to the reaction of (CH2)-C-1 with C2H2 from 300-2000 K

Computational simulations of the title reaction are presented, covering a temperature range from 300 to 2000 K. At lower temperatures we find that initial formation of the cyclopropene complex by addition of methylene to acetylene is irreversible, as is the stabilisation process via collisional energy transfer. Product branching between propargyl and the stable isomers is predicted at 300 K as a function of pressure for the first time. At intermediate temperatures (1200 K), complex temporal evolution involving multiple steady states begins to emerge. At high temperatures (2000 K) the timescale for subsequent unimolecular decay of thermalized intermediates begins to impinge on the timescale for reaction of methylene, such that the rate of formation of propargyl product does not admit a simple analysis in terms of a single time-independent rate constant until the methylene supply becomes depleted. Likewise, at the elevated temperatures the thermalized intermediates cannot be regarded as irreversible product channels. Our solution algorithm involves spectral propagation of a symmetrised version of the discretized master equation matrix, and is implemented in a high precision environment which makes hitherto unachievable low-temperature modelling a reality.

Photocatalytic degradation of the cyanotoxin cylindrospermopsin, using titanium dioxide and UV irradiation

Cylindrospermopsis raciborskii produces the cyanotoxin cylindrospermopsin, which is commonly found in SouthEast Queensland water reservoirs, and has been responsible for the closure of these reservoirs as a source of drinking water in recent times. Thus, alternative more effective treatment methods need to be investigated for the removal of toxins such as cylindrospermopsin. This study examined the effectiveness of two brands of titanium dioxide under UV photolysis for the degradation of cylindrospermopsin. Results indicate that titanium dioxide is an efficient photocatalyst for cylindrospermopsin degradation. The titanium dioxide (TiO2), brand Degussa P-25 was found to be more efficient than the alternate brand Hombikat UV-100. There was an influence from solution pH (4, 7, and 9) with both brands of titanium dioxide, with high pH resulting in the best degradation rate. Importantly, there was no adsorption of cylindrospermopsin to titanium dioxide particles as seen with other cyanotoxins, which would adversely influence the degradation rate. Degradation rates were not influenced by temperature (19-34 degreesC) when P-25 was the source of TiO2, some temperature influence was observed with UV-100. Dissolved organic carbon concentration will reduce the efficiency of titanium dioxide for cylindrospermopsin degradation, however the presence of other inorganic matter in natural waters greatly assists the photocatalytic process. With minimal potentially toxic by-product formation expected with this treatment, and the effective degradation of cylindrospermopsin, titanium dioxide UV photolysis is a promising speculative alternative water treatment method. (C) 2001 Elsevier Science Ltd. All rights reserved.

Human pigmentation genes: identification, structure and consequences of polymorphic variation

The synthesis of the visible pigment melanin by the melanocyte cell is the basis of the human pigmentary system, those genes directing the formation, transport and distribution of the specialised melanosome organelle in which melanin accumulates can legitimately be called pigmentation genes. The genes involved in this process have been identified through comparative genomic studies of mouse coat colour mutations and by the molecular characterisation of human hypopigmentary genetic diseases such as OCA1 and OCA2. The melanocyte responds to the peptide hormones a-MSH or ACTH through the MC1R G-protein coupled receptor to stimulate melanin production through induced maturation or switching of melanin type. The pheomelanosome, containing the key enzyme of the pathway tyrosinase, produces light red/yellowish melanin, whereas the eumelanosome produces darker melanins via induction of additional TYRP1, TYRP2, SILV enzymes, and the P-protein. Intramelanosomal pH governed by the P-protein may act as a critical determinant of tyrosinase enzyme activity to control the initial step in melanin synthesis or TYRP complex formation to facilitate melanogenesis and melanosomal maturation. The search for genetic variation in these candidate human pigmentation genes in various human populations has revealed high levels of polymorphism in the MC1R locus, with over 30 variant alleles so far identified. Functional correlation of MC1R alleles with skin and hair colour provides evidence that this receptor molecule is a principle component underlying normal human pigment variation. (C) 2001 Elsevier Science B.V. All rights reserved.