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PubMed1995

Lipolysis-induced partitioning of free fatty acids to lipoproteins: effect on the biological properties of free fatty acids.

Free fatty acids (FFA) released during the lipolysis of triglyceride (TG)-rich lipoproteins in vivo are generally believed to be bound to serum albumin. When hypertriglyceridemic (HTG) sera were lipolyzed in vitro by purified bovine milk lipoprotein lipase (LpL), there was an 11- to 18-fold increase in serum FFA levels, and a major portion (> 80%) of the FFA in serum was partitioned to lipoprotein fractions. The greatest portion (33%) of FFA in lipolyzed HTG serum was associated with newly formed flocculent remnants that banded just below low density lipoproteins (LDL) in the density gradient tube. Very low density lipoprotein (VLDL), LDL, and high density lipoprotein (HDL) fractions in lipolyzed HTG serum contained 18- to 29-times more FFA molecules than those in prelipolysis serum. Analysis of the fatty acyl chain composition of FFA in lipolyzed HTG serum showed that the extent of partitioning of saturated FFA into the lipoprotein fractions relative to that of polyunsaturated FFA was about 4.5- to 11-times greater than that partitioned into the free protein fraction; most (84%) of FFA partitioned into flocculent remnants were saturated fatty acids. In vivo lipolysis of TG-rich lipoproteins in HTG subjects, induced by heparinization, resulted in only a small (2.8-fold) increase in serum FFA and little or no increase in the partitioning of FFA to lipoproteins. However, in vitro incubation of the postheparin serum at 37 degrees C for 90 min resulted in a 2.9- to 6.8-fold increase in the serum FFA level and the partitioning of > 66% of total serum FFA into lipoprotein fractions. Studies of the interaction of various plasma fractions from control and in vitro lipolyzed HTG serum with cultured mouse peritoneal macrophages (MPM) showed that FFA partitioned to lipoprotein fractions were highly cytotoxic to cultured MPM, whereas FFA partitioned to albumin at a 10 x greater concentration were not cytotoxic. The cytotoxic potencies of FFA bound to lipoproteins and albumin were further compared after in vitro incorporation of FFA (oleic acids) into LDL and to albumin. FFA bound to LDL but not to albumin were cytotoxic to cultured MPM; the cytotoxicity of FFA bound to LDL was more closely related to the FFA to LDL-cholesterol molar ratio than to the total FFA concentration in the culture dish. The ability of FFA bound to LDL and albumin to induce foam cell formation was studied in THP-1 monocyte-derived macrophages, which were less susceptible to cytotoxicity produced by FFA bound to LDL than MPM.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1997

Ultrastructural investigation of calcification and ossification in experimental fracture healing with special reference to osteogenic role of fibroblasts.

OBJECTIVE: To investigate ultrastructurally the process of calcification and ossification in experimental fracture healing. METHODS: A standardized fracture of the radius was made in rabbits. Undecalcified callus tissues from different fracture regions were subjected to ultrastructural observation under transmission electron microscope. RESULTS: In the mitochondria and membrane-bound vesicles of the fibroblasts, osteoblasts and chondrocytes, high electron density calcium granules were seen. These granules provided raw materials for the deposition of calcium salt crystals. Around these cells, round, oval or irregularly shaped matrix vesicles could also be discerned, and they became calcified and formed flocculent calcospherules. Then in the Type I collagen fibrils around the fibroblasts and osteoblasts, and in the Type II collagen fibrils around the chondrocytes, calcium salt crystals also appeared. Innumerable flocculent calcospherules and calcified collagen fibrils coalesced together, expanded and finally turned into pieces of bone tissues. The fibroblasts also possessed the indispensable prerequisites for calcification and ossification in fracture healing. They either transformed into osteocytes or degenerated, perished and eventually were replaced by bone tissues. CONCLUSIONS: Sequence of events taking place in calcification and ossification in experimental fracture healing was depicted. Calcification of matrix vesicles and collagen fibrils triggered these processes. Evidence of osteogenic role played by fibroblasts was provided.

Animals↗

PubMed1998

Functional and structural successions in arbitrary samples of heterotrophic bacteria during aerobic treatments of lignite-carbonization wastewater in in situ enclosures.

In situ mesocosm experiments were performed in Lake Schwelvollert (located in the district of Weissenfels, Saxony-Anhalt, Germany), an anaerobic lignite-carbonization effluent lake containing phenolic compounds and their autoxidation products (anthropogenic humic matter). In the aeration enclosure, the anaerobic Schwelvollert wastewater was aerated and in the flocculation enclosure, it was flocculated to precipitate the oxygen-trapping anthropogenic humic matter to enhance the input of oxygen by diffusion. To gain an insight into the metabolic state of the aerobic heterotrophic microbiota during the treatments, arbitrary samples of bacterial isolates were taken from a general agar medium and tested for their abilities to cleave predominant phenolic contaminants by a procedure called the isolate sample assay. In this way, successions of degradation potentials were observed in both mesocosms, with degradation abilities for meta- and para-alkylated phenols appearing before degradation abilities for ortho-substituted phenols as a common phenomenon. To examine the structure of samples, the respective isolates were characterized using the Biolog GN MicroPlate system, the random amplified polymorphic DNA nucleic acid (RAPD) fingerprinting technique, and amplified ribosomal DNA restriction analysis (ARDRA). Although similar functional patterns occurred in both mesocosms, the compositions and diversities of the respective bacterial communities varied significantly, even at different depths from the same enclosure, with members of the Pseudomonas RNA group I being predominant.

Aerobiosis↗

PubMed1998

Characterization of the Prk1 protein kinase from Schizosaccharomyces pombe.

We report the isolation and characterization of a protein kinase from the fission yeast Schizosaccharomyces pombe. The proposed Prk1 protein contains 352 amino acids and has significant homology to the Ume5p kinase (also known as Srb10p, Ssn3p and Are1p) of the budding yeast Saccharomyces cerevisiae, a cyclin-dependent kinase involved in regulating the transcription of a diverse set of genes. Disruption of the prk1 gene increases flocculation but does not appear to have any other significant effect on cell behaviour. This defect can be overcome by expressing the UME5 gene, indicating that Prk1 is the fission yeast homologue of Ume5p.

Amino Acid Sequence↗

PubMed1996

Two case reports of neurological disease in coal mine preparation plant workers.

Of 60 cases of neurotoxicity related to occupational exposures of workers at plants producing acrylamide monomers, cases involving neurotoxicity related to jobs using polymers with acrylamide monomer contamination have not been widely reported. In 1992, two patients were referred to the Division of Occupational and Environmental Health, Department of Family and Community Health, Marshall University School of Medicine, in Huntington, West Virginia for evaluation. The patients had worked in different coal preparation plants in southern West Virginia for over 10 years and had exposure to an acrylamide polymer flocculent contaminated with acrylamide monomer. Both patients had no instruction on proper use of, or the dangers of, acrylamide and were not given adequate safety equipment. Patient A developed Parkinsonism and Patient B peripheral neuropathies with a neurogenic bladder. These two case reports highlight the need to reemphasize the basic tenets of occupational health and safety. Many chemicals are being introduced into mining operations and awareness of potential toxic exposures and new diseases not previously reported in the mining industry must become part of the surveillance system by mine management and labor safety committees. Further studies on the extent of acrylamide neurotoxicity in the mining industry is encouraged.

Acrylamides↗

PubMed2001

On-line size measurement of yeast aggregates using image analysis.

Alcohol fermentation productivity can be strongly improved using a flocculation-based yeast recycle. However, the efficiency of the biomass retention system depends strongly on the yeast particle size. Accordingly, the monitoring and control of yeast floc diameter are of primary importance. The on-line measurement of mean floc diameter has been achieved using on-line image analysis, based on the evaluation of image texture. The texture analysis method consisted in the building of a co-occurrence matrix from which the so-called "Energy parameter" was extracted. While image texture is usually used for classification purposes, it has been used here as a quantitative descriptor: a correlation has been found between this statistical image feature and off-line manual floc-size determinations. In the floc-size range investigated (X 0.5-4.3 mm), the evaluated mean diameter was in good agreement with the actual particle size, with a determination coefficient equal to 0.980. In contrast with manual measurements, slow and tedious, this method gave the value of the mean particle diameter in real-time, without sampling. This novel tool has been used to investigate the behavior of yeast aggregates as a function of fermentation conditions. While biomass concentration was kept constant, step increases of the feed rate led to a decrease of the mean floc diameter. Image analysis showed that the particle-size reduction could occur within a few minutes after modification of the medium dilution rate, demonstrating the disruptive effect of the CO(2) efflux. The kinetic of aggregate formation was dependent on the gas-phase composition. Instead of recycling fermentation gas, sparging the fermentor with nitrogen, to reduce dissolved CO(2) concentration, increased the rate of floc-size growth.

Automation↗

PubMed2004

Physicochemical surface properties of brewing yeast influencing their immobilization onto spent grains in a continuous reactor.

Immobilization of brewing yeast onto a cellulose-based carrier obtained from spent grains, a brewing byproduct, by acid/base treatment has been studied in a continuously operating bubble-column reactor. The aim of this work was to study the mechanisms of brewing yeast immobilization onto spent grain particles through the information on physicochemical surface properties of brewing yeast and spent grain particles. Three mechanisms of brewing yeast immobilization onto spent grains carrier were proposed: cell-carrier adhesion, cell-cell attachment, and cell adsorption (accumulation) inside natural shelters (carrier's surface roughness). The possibility of stable cell-carrier adhesion regarding the free energy of interaction was proved and the relative importance of long-range forces (Derjaguin-Landau-Verwey-Overbeek theory) and interfacial free energies was discussed. As for the cell-cell attachment leading to a multilayer yeast immobilization, a physicochemical interaction through localized hydrophobic regions on cell surface was hypothesized. However, neither flocculation nor chain formation mechanism can be excluded so far. The adsorption of brewing yeast inside sufficiently large crevices (pores) was documented with photomicrographs. A positive effect of higher dilution rate and increased hydrophobicity of base-treated spent grains on the yeast immobilization rate has also been found.

Cell Adhesion↗

PubMed1987

Effect of liposomes on suspension stability.

The effect of positively charged liposomes on the stability of negatively charged indomethacin particle suspensions was investigated by adsorption, microelectrophoresis, sedimentation volume, and redispersibility. It was found that flocculation occurred in the neighborhood of the zero point of charge of the liposome:indomethacin suspensions. This resulted from the operation of van der Waals attraction under the condition of nil electrostatic repulsion. Correlation among the results of adsorption, microelectrophoresis, sedimentation volume, and redispersibility was good. The mixing effect of the suspension was examined by microelectrophoresis and confirmed by sedimentation volume and redispersibility. Results indicate that there was no difference between the method of dilution of the liposome:indomethacin concentrated suspension after mixing and the method of dilution of liposomes prior to mixing with the indomethacin suspension. This was due to interaction depending on the charge density of the particles.

Adsorption↗

PubMed1994

Another brick in the wall? Recent developments concerning the yeast cell envelope.

To a yeast, the cell wall is an important living organelle performing a number of vital functions, including osmotic and physical protection, selective permeability barrier, immobilized enzyme support and cell-cell recognition and adhesion. Our basic model of wall structure involves attachment of secreted mannoproteins to a fibrillar inner layer of beta-glucan. Recent work has emphasised the importance of chitin in lateral walls, examined the mechanisms of attachment of mannoproteins to the various cell wall glucan fractions and elucidated the pathway of beta-glucan synthesis, by means of resistance to glucan-binding killer toxins. The conventional view of wall structure has been challenged by the discovery of a class of GPI-anchored, serine/threonine-rich wall-proteins. It has been suggested, that these proteins are anchored in the plasma membrane, spanning the wall with extended O-glycosylated structures and protruding out into the medium. Examination of these proteins shows a diversity of structures, sizes and behaviour that makes it improbable that these represent a new class of wall proteins. The possible roles of one of these proteins associated with flocculation, Flo1p, are discussed.

Cell Wall↗

PubMed2002

The effect of molecular weight of nonadsorbing polymer on the structure of depletion-induced flocs.

This work explores the structural compactness of depletion-induced particle flocs with respect to the molecular weight of nonadsorbing polymer flocculants. Small-angle static light scattering was used to monitor the structural characteristics of the flocs, which were formed by the addition of nonadsorbing poly(acrylic acids) to a stable colloidal polystyrene latex dispersion. It was found that the floc mass fractal dimension, considered to be a measure of structural compactness, was dependent upon both the molecular weight and the concentration of the polyacid. In particular, reducing the molecular weight of the polymer at a fixed polyacid concentration resulted in higher mass fractal dimensions, despite the highly polydisperse nature of the polymer samples. This structural behavior was attributed to the lower particle sticking efficiencies upon collision. This reduced sticking ability is the result of the shallowing in the secondary potential energy well with decreasing polymer chain length, which was directly supported by atomic force microscopy data. Our results suggest that the formation of a shallower attraction well with a lower molecular weight nonadsorbing polymer is the result of the insufficiency of the increased osmotic pressure to counter-balance the short-ranged nature of the depletion interaction.

Acrylic Resins↗

PubMed2002

Long anchor using Flo1 protein enhances reactivity of cell surface-displayed glucoamylase to polymer substrates.

We investigated the influence of anchor length on the reactivity to polymer substrate of enzyme displayed on yeast cell surfaces. Using various lengths [42, 102, 146, 318, 428, and 1,326 amino acids (aa)] of the C-terminal region of the Saccharomyces cerevisiae Flo1 protein (Flo1p), which plays a major role in yeast flocculation, six display systems with various anchor lengths were constructed. In these systems, the target protein was displayed on the yeast cell surface under the control of the 5'-upstream region of the isocitrate lyase gene of Candida tropicalis ( UPR-ICL). Cell-surface display of Rhizopus oryzae glucoamylase by these systems was induced and confirmed in all systems by immunofluorescence microscopy and immunoblotting. Flow-cytometer measurement of the fluorescence intensity of immunofluorescence-labeled yeast cells displaying glucoamylase indicated that glucoamylase displayed with longer anchors, especially those of 428 and 1,326 aa in length, had higher reactivity to antibodies. The reactivity of starch to displayed glucoamylase, which was evaluated by plate assay, increased with anchor length, as did the cell growth-rate in starch-containing medium. These results indicate that cell-surface display systems using 428- and 1,326-aa length anchors of Flo1p are effective for the display of enzymes on the outer surface of yeast cells.

Cloning, Molecular↗

PubMed1980

Quantitative determination of rheumatoid factor by an enzyme-labeled immunoassay.

The presence and quantity of rheumatoid factor (RF) in human serum were determined by an indirect enzyme-linked immunoabsorbent assay (ELISA). A human rheumatoid factor control serum, standardized against the WHO reference rheumatoid arthritis serum preparation, was used to derive a standard curve in each assay. The results of unknowns were estimated from the standard curve and reported in International Units (IU) per milliliter (ml). The ELISA assay was compared with the bentonite flocculation test. The overall coefficient of correlation between the two assays was 87%; it was 93.3% for patients with rheumatoid arthritis but only 67.5% for patients with undiagnosed conditions. The error of the ELISA assay (coefficient of variation) was generally less than 10% at both high and low concentrations of rheumatoid factor. The quantitative reproducible nature of the assay allows the detection of small variations of rheumatoid factor level and could be useful in the serial evaluation of patients.

Animals↗

PubMed1993

An immunosensor for syphilis screening based on surface plasmon resonance.

In this paper the development of a surface plasmon resonance (SPR) immunosensor for syphilis screening is described. This immunosensor is based on the detection of antibodies in serum against the causative organism Treponema pallidum. In order to achieve selectivity a recombinant Treponema pallidum membrane protein A (TmpA) was used. This antigen can react with antibodies to T. pallidum, present in serum of syphilitic patients. Reproducible results have been obtained, using a 'sandwich SPR' method: binding of a sandwich antibody to the treponemal antibody after serum incubation was measured in real time while the binding was taking place. The SPR results obtained from ten blind-coded sera corresponded well with classical syphilis tests (Treponema pallidum haemagglutination assay (TPHA), fluorescent treponemal antibody-absorbed test (FTA-ABS), venereal diseases research laboratory flocculation test (VDRL) and TmpA-based enzyme-linked immunosorbent assay (TmpA-ELISA)). Preliminary experiments showed that direct measurement of serum (in the 'one step SPR') is not yet possible, probably as a result of non-uniformity of serum samples. The application of latex beads is considered to solve this problem.

Antibodies, Bacterial↗

PubMed2004

Adsorbent supplemented biological treatment of pre-treated landfill leachate by fed-batch operation.

Biological treatment of landfill leachate usually results in low COD removals because of high chemical oxygen demand (COD), high ammonium-N content and presence of toxic compounds. Coagulation-flocculation with lime addition and air stripping of ammonia were used as pre-treatment in this study in order to improve biological treatability of the leachate. Pre-treated leachate was subjected to adsorbent supplemented biological treatment in an aeration tank operated in fed-batch mode. COD and NH(4)-N removal performances of powdered activated carbon (PAC) and powdered zeolite (PZ) were compared during biological treatment. Adsorbent concentrations varied between 0 and 5 gl(-1). Percent COD and ammonium-N removals increased with increasing adsorbent concentrations. Percent COD removals with PAC addition were significantly higher than those obtained with the zeolite. However, zeolite performed better than the PAC in ammonium-N removal from the leachate. Nearly 87% and 77% COD removals were achieved with PAC and zeolite concentrations of 2 gl(-1), respectively. Ammonium-N removals were 30% and 40% with PAC and zeolite concentrations of 5 gl(-1), respectively at the end of 30 h of fed-batch operation.

Adsorption↗

PubMed2005

Comparison of a static gravity screen-roll press combination separator to a PAM-assisted gravity belt thickener system for swine waste slurry solids separation.

Liquid effluent resulting from solids separation from raw swine slurry (RS) using a static gravity screen-roll press separator (SE) and a polyacrylamide (PAM) flocculant-assisted gravity belt thickener system (BE1 and 2, with BE2 designating an added belt thickening of SE) were compared. Effluent pH was 7.6-7.7. Dissolved oxygen was less than 0.01 mg/l in RS and SE and 0.50 mg/l in BE1 and 2. Solids dry weight and total phosphorus concentrations were reduced significantly (p0.05) in SE (17-27%) and in BE1 and 2 (92-96%), relative to RS. Phosphorus concentration reductions were higher than those previously found. Settleable and suspended solids, total nitrogen and chemical oxygen demand were significantly reduced in BE1 and 2 (63-99%). No significant differences (p>0.05) were found between BE1 and 2. Results indicated that the gravity belt thickener system was more efficient at solids separation than the screen-roll press system.

Acrylic Resins↗

PubMed2004

Effect of pH on the aggregation of a gray humic acid in colloidal and solid states.

Gray humic acids have a marked colloidal character, a large number of surface functional groups, and are subject to aggregation phenomena. They are able to complex soluble pollutants, and initiate flocculation processes as a function of environmental conditions. The aim of this work is to study the aggregation of a gray humic acid, which is stable in colloidal dispersion, by means of photon correlation spectroscopy, and molecular modeling. The effect of this aggregation in the solid state is also studied by means of N2 (to 77 K) and CO2 (to 273 K) adsorption isotherms, as well as FT-IR absorption. The variation of the colloid's zeta potential and size, with pH, reflects the ionization of the carboxylic and phenolic acidic groups, and a linear dependence of size on zeta potential. The decrease in the size of the colloids seems to be more affected by the ionization of the phenolic acid groups, than by that of the carboxylic acid groups, which is likely because in the case of the ionized carboxylic groups the humic colloids are still capable of generating H-bonds. In the solid state, aggregation effects are illustrated by a decrease in surface area, and a disappearance of certain micropores, with increasing pH. These features are likely due to an inhibition of aggregation in the colloidal state as a consequence of the increase in charge that results from ionization of the acidic groups, and also to an increased hindrance to H-bond formation, due to the loss of protons during the above-mentioned ionization process.

Adsorption↗

PubMed2005

Appropriate combination of physico-chemical methods (coagulation/flocculation and ozonation) for the efficient treatment of landfill leachates.

An integrated technique consisted of ozonation and coagulation/flocculation processes was studied, aiming to provide an efficient method for the treatment of stabilized/biologically pre-treated leachates, in order to reduce the organic pollutants' content to concentration values lower than the corresponding limits, imposed by the legislation. Leachates were collected from a municipal landfill site; samples containing around 1000 mg l(-1) COD and BOD(5)/COD ratio about 0.17 were treated by using two different processes or combinations between them, i.e. ozonation, coagulation-flocculation, ozonation followed by coagulation/flocculation and coagulation/flocculation followed by ozonation. The application of single ozonation resulted to the efficient removal of color and organic loading, due to the respective oxidation, induced by ozonation; however, COD values lower than 200 mg l(-1) could be only achieved after prolonged reaction times and for high ozone production rates. The coagulation of leachate samples was studied by the addition of ferric chloride or poly-aluminum chloride agents at various dosages. Maximum COD removal rates (up to 72%) were achieved by the addition of 7 mM Fe, or of 11 mM Al respectively. However, final COD values higher than 200 mg l(-1) were obtained indicating the requirement of an additional treatment step. Pre-ozonation followed by coagulation/flocculation was not found to be an efficient treatment approach for this aim, but coagulation/flocculation followed by ozonation, was proved to be an efficient process for the reduction of COD to lower than 180 mg l(-1).

Chemistry, Physical↗

PubMed2005

An experimental investigation of the stability of ethylcellulose latex: correlation between zeta potential and sedimentation.

This paper aims at explaining the experimental observations of the stability and redispersibility of an aqueous ethylcellulose latex through the electrokinetic characterization of the particles. The surface charge and the electrical double layer thickness play an essential role in the stability of the system, hence the need for a full characterization of the polymeric particles. The effect of both pH and ionic strength of the dispersion medium were investigated. It was found that at acid pH values the latex displays "delayed" or "hindered" sedimentation: in such conditions, the electrophoretic mobility and zeta potential are rather low, indicating a small electrokinetic charge on the particles. At alkaline pH, when the dissociation of ionizable surface groups must be complete, the zeta potential is high and negative. The electrostatic repulsion between polymer particles is responsible for the low sedimentation volume and poor redispersibility of the latex. The effect of NaCl and CaCl(2) concentration on both the zeta potential and stability of the latexes was also investigated: it was found that CaCl(2) has the greatest influence, yielding flocculated, easily re-dispersible systems when its concentration in the dispersion medium is high enough. There qualitative observations were ascertained by means of calculations of the potential energy of interaction between particles. In the case of NaCl solutions, a high and relatively wide potential energy barrier was predicted, that may prevent the particle aggregation. Above 5mM NaCl a shallow minimum in the potential energy curves must lead to the formation of aggregates. Similar results were found with CaCl(2) solutions, although in this case the secondary minima are deeper and appear at lower concentrations.

Calcium Chloride↗