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At least 631 records · Page 35Linked to original sources
PubMed1992

Thrombogenicity and procoagulant activity of human mesothelial cells.

Cell seeding may decrease the thrombogenicity of implanted vascular grafts, but its application is hampered by the limited availability of autologous endothelial cells. We studied the interaction of alternate cells, human peritoneal mesothelial cells, with whole blood in a flow chamber. When citrated blood was perfused over mesothelial cells, platelet adhesion was seen on the intercellular matrix but not on the cells themselves. Perfusions with blood anticoagulated with low-molecular-weight heparin resulted in fibrin formation at the surface of mesothelial cells but not at the surface of human umbilical venous endothelial cells. At shear rates of 200 sec-1 fibrin deposition on the mesothelial cell surface increased during the first 5 minutes to 5.7 +/- 1.06 micrograms fibrin per square centimeter, whereafter these values stabilized. The procoagulant activity of cultured mesothelial cells was higher than that of peritoneal membrane studied ex vivo. However, cultured mesothelial cells incubated with polyclonal antibodies against tissue factor showed a significant decrease in procoagulant activity. We conclude that human peritoneal mesothelial cells may be used for cell seeding procedures, provided that their tissue factor expression can be controlled.

Blood Coagulation Factors↗
PubMed2002

Aggregation of immobilized activated sludge cells into aerobically grown microbial granules for the aerobic biodegradation of phenol.

AIMS: The aim of this study is to evaluate the utility of aerobically grown microbial granules for the biological treatment of phenol-containing wastewater. METHODS AND RESULTS: A column-type sequential aerobic sludge blanket reactor was inoculated with activated sludge and fed with phenol as the sole carbon source, at a rate of 1.5 g phenol l-1 d-1. Aerobically grown microbial granules first appeared on day 9 of reactor operation and quickly grew to displace the seed flocs as the dominant form of biomass in the reactor. These granules were compact and regular in appearance, and consisted of bacterial rods and cocci and fungi embedded in an extracellular polymeric matrix. The granules had a mean size of 0.52 mm, a sludge volume index of 40 ml g-1 and a specific oxygen utilization rate of 110 mg oxygen g VSS-1 h-1 (VSS stands for volatile suspended solids). Specific phenol degradation rates increased with phenol concentration from 0 to 500 mg phenol l-1, peaked at 1.4 g phenol g VSS-1 d-1, and declined with further increases in phenol concentration as substrate inhibition effects became important. CONCLUSIONS: Aerobically grown microbial granules were successfully cultivated in a reactor maintained at a loading rate of 1.5 g phenol l-1 d-1. The granules exhibited a high tolerance towards phenol. Significant rates of phenol degradation were attained at phenol concentrations as high as 2 g l-1. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to demonstrate the ability of aerobically grown microbial granules to degrade phenol. These granules appear to represent an excellent immobilization strategy for microorganisms to biologically remove phenol and other toxic chemicals in high-strength industrial wastewaters.

Aerobiosis↗
PubMed2006

Human alveolar bone cells interact with ProRoot and tooth-colored MTA.

The cellular response to mineral trioxide aggregate (MTA) is important for the repair and regeneration of periradicular tissues. The purpose of this study was to analyze the response of human alveolar bone cells to MTA. A human alveolar bone chip was obtained from an oral surgical procedure and explant cultures harvested after 3 to 4 weeks of outgrowth in alpha-minimum essential medium supplemented with fetal calf serum. Cells in early passage were seeded onto preset ProRoot (gray) MTA, tooth-colored (white) MTA, and MTA prepared with local anesthetic solution. Scanning electron microscopy showed cells were attached and spread out onto MTA within 24 hours, and proliferated to form a matrix-like layer within 7 days. Cell attachment and cell-surface interactions with the gray and white MTA, and with the MTA prepared with local anesthetic were comparably propagated for 14 days. The surgically derived human alveolar bone cells provided a clinically relevant model that demonstrated the capacity of both ProRoot and tooth-colored MTA to support cell attachment, proliferation, and matrix formation.

Aluminum Compounds↗
PubMed1977

A simple procedure for the isolation of L-fucose-binding lectins from Ulex europaeus and Lotus tetragonolobus.

L-Fucose-binding lectins from Ulex europeaus and Lotus tetragonolobus were isolated by affinity chromatography on columns of L-fucose-Sepharose 6B. L-Fucose was coupled to Sepharose 6B after divinyl sulfone-activation of the gel to give an affinity adsorbent capable of binding more than 1.2 mg of Ulex lextin/ml of gel, which could then be eluted with 0.1M or 0.05M L-fucose. Analysis of the isolated lectins by hemagglutination assay, by gel filtration, and polyacrylamide disc-electrophoresis revealed the presence of isolectins, or aggregated species, or both. The apparent mol. wt. of the major lectin fraction from Lotus was 35000 when determined on Sephadex G-200 or Ultrogel AcA 34. In contrast, the apparent mol. wt. of the major lectin fraction from Ulex was 68 000 when chromatographed on Sephadex G-200 and 45 000 when chromatographed on Ultrogel AcA 34. The yields of lectins were 4.5 mg/100 g of Ulex seeds and 394 mg/100 g of Lotus seeds.

ABO Blood-Group System↗
PubMed1996

Selective inhibition of Abeta fibril formation.

We describe here an inhibitor of in vitro fibril formation, hexadecyl-N-methylpiperidinium (HMP) bromide, which is selective for the Alzheimer's disease peptide Abeta. At 10 microM, its IC50 for inhibiting Abeta aggregation at pH 5.8, HMP bromide does not inhibit fibril formation by other amyloidogenic polypeptides nor does it affect the folding stability of the beta-sheet-rich immunoglobulin VL domain REI. In addition, small structural modifications of HMP bromide reduce or eliminate its ability to inhibit pH 5.8 aggregation of Abeta. These indications of specificity, plus the ability of the molecule to inhibit A beta aggregation at concentrations almost an order of magnitude below its critical micelle concentration, suggest a mechanism of inhibition other than micellar solubilization of Abeta. HMP bromide is required in approximately a 1:1 stoichiometry for effective inhibition at pH 5.8. Although stoichiometric amounts of HMP bromide with respect to total Abeta inhibit Abeta fibril formation at pH 7.4, the molecule is incapable, at lower concentrations, of blocking the seeding of fibril formation by small amounts of added Abeta fibrils. The results suggest the existence of a binding surface on A beta capable of binding amphipathic molecules such as HMP bromide and which, when occupied, precludes assembly of A beta into amyloid fibrils. Molecules that bind to this site with high specificity may prove to be useful therapeutic agents for preventing or retarding the cerebral amyloid plaque formation implicated in Alzheimer's disease pathology.

Alzheimer Disease↗
PubMed1977

Biological investigations of higher and lower plants aboard Soyuz 19.

Biological investigations carried out aboard Soyuz 19 consisted of three independent complex experiments. All biological materials aboard the spacecraft were kept in "Biocat" thermostats which maintained the required temperature. The objective of the experiment "Genetic investigations" was to determine the effect of space flight factors on the heredity of lower (Chlamydomonas reinhardi Dang) and higher (Crepis capillaris (L) Wallr and Arabidopsis thaliana (L) Heynh) plants, and on the radiosensitivity of plant seeds and the radiation effect of prior gamma-irradiation. The space flight factors decreased the survival of Chlamydomonas cells and A. thaliana plants of the first generation. They decreased the germination of seeds, increased the rate of chlorophyll mutations and embryonal lethals, produced no effect on the rate of visible mutations in unicellular algae, increased the rate of chromosome aberrations in root meristem cells C. capillaris, induced disturbances in mitosis of unicellular algae and modified the effect of prior gamma-irradiation. The experiment "Growth of micro-organisms" was conducted with a culture of Proteus vulgaris in a growth chamber. After return to the laboratory the experimental and control variants were studied for twenty-two tests. The control and experimental material differed in the average cell size, biomass distribution, the character of haemotaxis, the rate of cell migration over the substratum surface, dehydrogenase activity, ribosomal aggregation, and ultrastructural peculiarities of cells. The experiment "Embryological investigations" was carried out to study the effect of space flight factors on embryogenesis of the bony fish Brachyodanio rerio. No abnormalities were noted in the course or rate of the development of spawn cultivated in a special thermostat.

Animals↗
PubMed1999

Crystallization during volume reduction of solutions with a composition corresponding to that in the collecting duct: the influence of hydroxyapatite seed crystals and urinary macromolecules.

To examine the effect of hydroxyapatite (HAP) seed crystals and urinary macromolecules on the crystallization under conditions similar to those in the collecting duct, we evaporated 100 ml samples of salt solutions with an ion composition assumed to correspond to that in the collecting duct without and with HAP seed crystals. The crystallization in seeded solutions was assessed both with and without dialysed urine (dU). After evaporation the number and volume of crystals were recorded in a Coulter Multisizer and the crystal morphology examined with scanning electron microscopy (SEM) and X-ray crystallography. Addition of HAP crystals was apparently followed by an approximately 15-20% increase in heterogeneous nucleation of calcium oxalate (CaOx). In these experiments SEM and X-ray crystallography showed a high percentage of CaOx in the precipitate. In samples reduced to 40-69 ml, addition of dU to the collecting duct solution containing HAP seed resulted in a greater mean (SD) number of crystals; 3895 (1841) in samples with dU and 1785 (583) in samples without. This was mainly explained by an increased mean (SD) number of small crystals. The mean crystal volume was 17.8 (1.1) and 34.3 (9.1) in samples reduced to 40 69 ml with and without dU, respectively. This might reflect the inhibitory effect of dU on the growth and/or aggregation of the CaOx-CaP precipitate or a promoted nucleation resulting in a large number of small crystals. It is concluded that calcium phosphate formed above the collecting duct might induce heterogeneous nucleation of CaOx at lower levels of the renal collecting system, and that urinary macromolecules are powerful modifiers of these processes.

Calcium Oxalate↗
PubMed1998

A nucleated assembly mechanism of Alzheimer paired helical filaments.

Alzheimer's disease is characterized by two types of fibrous aggregates in the affected brains, the amyloid fibers (consisting of the Abeta-peptide, generating the amyloid plaques), and paired helical filaments (PHFs; made up of tau protein, forming the neurofibrillary tangles). Hence, tau protein, a highly soluble protein that normally stabilizes microtubules, becomes aggregated into insoluble fibers that obstruct the cytoplasm of neurons and cause a loss of microtubule stability. We have developed recently a rapid assay for monitoring PHF assembly and show here that PHFs arise from a nucleated assembly mechanism. The PHF nucleus comprises about 8-14 tau monomers. A prerequisite for nucleation is the dimerization of tau because tau dimers act as effective building blocks. PHF assembly can be seeded by preformed filaments (made either in vitro or isolated from Alzheimer brain tissue). These results suggest that dimerization and nucleation are the rate-limiting steps for PHF formation in vivo.

Alzheimer Disease↗
PubMed2000

Adhesion of human osteoblasts on root-end filling materials.

Adhesion of human osteoblasts to root-end filling materials (mineral trioxide aggregate (MTA), IRM, composite, and amalgam) was observed by scanning electron microscopy. Root-end filling materials were inserted into 96-well flat-bottomed plates and condensed to disks of approximately 1 mm thick and the same diameter as the wells. After the disks were set, they were placed in the bottom of Nunc four-well culture plates at one disk per well. Then human osteoblasts were seeded into the wells at 1.5 x 10(5) cells per well. After 1 day in culture the disks of root-end filling materials along with cells grown on their surface were examined with a scanning electron microscopy. Results showed that osteoblasts attached and spread on MTA and composite by forming a monolayer. Osteoblasts also attached on amalgam, but with few cells spreading. In the presence of IRM, osteoblasts appeared rounded with no spreading. These results indicate that osteoblasts have a favorable response to MTA and composite resin compared with IRM and amalgam.

Aluminum Compounds↗
PubMed2006

Exogenous induction of cerebral beta-amyloidogenesis is governed by agent and host.

Protein aggregation is an established pathogenic mechanism in Alzheimer's disease, but little is known about the initiation of this process in vivo. Intracerebral injection of dilute, amyloid-beta (Abeta)-containing brain extracts from humans with Alzheimer's disease or beta-amyloid precursor protein (APP) transgenic mice induced cerebral beta-amyloidosis and associated pathology in APP transgenic mice in a time- and concentration-dependent manner. The seeding activity of brain extracts was reduced or abolished by Abeta immunodepletion, protein denaturation, or by Abeta immunization of the host. The phenotype of the exogenously induced amyloidosis depended on both the host and the source of the agent, suggesting the existence of polymorphic Abeta strains with varying biological activities reminiscent of prion strains.

Aged↗
PubMed2006

Overexpression of the RADICAL-INDUCED CELL DEATH1 (RCD1) gene of Arabidopsis causes weak rcd1 phenotype with compromised oxidative-stress responses.

rcd1 is a mutant of Arabidopsis thaliana that is more resistant to methyl viologen, but more sensitive to ozone than the wild type. rcd1-2 is caused by a single nucleotide substitution that results in a premature stop codon at Trp-332. The rcd1-2 mRNA level does not change significantly with the mutation. Since overexpression of rcd1-1 cDNA has been shown to bring about an rcd1-like phenotype, we created and examined the overexpression lines of RCD1 by the use of the cauliflower mosaic virus 35S promoter. The transgenic lines exhibited a weak rcd1-like phenotype, although no resistance to methyl viologen was observed. Further, they fully complemented the aberrant rcd1-2 phenotype. Subcellular localization of RCD1 was examined by transiently expressing green fluorescent protein (GFP) fused with RCD1 in onion epidermal cells. GFP signals are observed as aggregated foci in the inner nuclear matrix-like region.

Arabidopsis↗
PubMed1997

Accumulation of a lectin-like breakdown product of beta-conglutin catabolism in cotyledons of germinating Lupinus albus L. seeds.

During germination of Lupinus albus seeds, a 20-kDa polypeptide accumulates in the cotyledons of 4-d-old plants (Ferreira et al., 1995b, J Exp Bot 46: 211-219). Immunological, polypeptide cleavage with cyanogen bromide and amino acid sequencing experiments indicate that the 20-k-Da polypeptide and ubiquitin are structurally unrelated. However, there is a strong sequence homology between the 20-kDa polypeptide and the vicilin-like storage proteins from pea and soybean. Our results indicate that the 20-kDa polypeptide is an intermediate breakdown products of beta-conglutin catabolism, the vicilin-like storage protein from L. albus, and that its interaction with anti-ubiquitin antibodies results from the recognition of the antibodies by the 20-kDa polypeptide rather than by the opposite. Besides rabbit anti-ubiquitin antibodies, the 20-kDa polypeptide interacts with a variety of glycoproteins, including immunoglobulin G from several animal species, peroxidase and alkaline phosphatase, suggesting that it possess a lectin-type activity. Its activity is resistant to sodium dodecyl sulfate or methanol treatments, boiling and autoclaving. Purification of the 20-kDa polypeptide and immunological studies with anti-20-kDa-polypeptide antibodies showed that the non-glycosylated polypeptide is part of a glycoprotein with an estimated molecular mass of 210 kDa, composed of several types of structurally related subunit with molecular masses ranging from 14 to 50 kDa. Purified native protein containing the 20-kDa polypeptide self-aggregates in a calcium-dependent manner as reported for some glycosylated lectins. The possible physiological function of the 20-kDa polypeptide is discussed.

Amino Acid Sequence↗
PubMed2005

Growth model for arc-deposited fullerene-like CNx nanoparticles.

Multiwall CNx nanotubes, nanoonions, and amorphous nanoballs were formed by carbon DC arc evaporation in a nitrogen atmosphere. The samples were investigated by conventional and high-resolution transmission electron microscopy. We propose a fragment-by-fragment growth mechanism for the formation of the nanoparticles. Accordingly, particles and aggregates of particles form in the vacuum ambient by the collisions between atomic species and small fragments. This growth model is supported by the discontinuous inner shells and disordered surface layers composed from graphene fragments. Image simulations confirm the detectability of dangling and back-folding surface layers in the experimental images. Further, the simulated images also confirm that the growth of nanoonions starts from a single fullerene-like seed. The amorphous nanoballs form when ordering of the building blocks during growth is hindered by the cross-linking nitrogen bonds.

Fullerenes↗
PubMed1990

Mechanism of freeze-thaw damage to liver alcohol dehydrogenase and protection by cryoprotectants and amino acids.

Multiple freeze-thaw (FT) cycles, with complete melting between cycles, resulted in an exponential decline in liver alcohol dehydrogenase (LADH) enzyme activity. The reduction in activity of LADH as a result of FT damage was proportional to the decrease in the intensity of the tryptophan fluorescence of the enzyme. Treatment with urea resulted in a similar relationship between tryptophan fluorescence intensity and inactivation. Evidence from fluorescence and activity studies from the same sample, as well as gel electrophoresis, indicates that damage to LADH from a FT cycle, resulting in inactivation, is likely an unfolding of the enzyme rather than separation of subunits or aggregation of enzymes at the enzyme concentrations and cooling rates used. A nonexponential decline in enzyme activity, as a function of the number of FT cycles, can be achieved if complete melting between cycles is not allowed or if the samples are stored at +4 degrees C for 24 hr following the last FT cycle, prior to assay. In the latter case, a partial recovery in enzyme activity is seen. "Seeding," while lowering the enzyme activity, is desirable to achieve consistent results without the artifacts that are introduced if not used. Amino acids were tested for their effectiveness as cryoprotectants. From the results of this study, the mean fractional area loss of amino acid residues upon incorporation in globular proteins (f) is inversely proportional to the FT protection by these free amino acids. Thus, amino acid residues which tend to be found at the surface of proteins (e.g., glutamate) improve the FT survival of LADH, when added as the free amino acid, while those amino acids which are found in the interior of proteins (e.g., valine, leucine) sensitize LADH to FT damage. The pattern of protection ("fingerprint") of LADH by various amino acids is different from that of living cells. Furthermore, unlike the case with cells, glutamine and DMSO do not act independently when protecting LADH.

Alcohol Dehydrogenase↗
PubMed1990

Calcium phosphate cements: study of the beta-tricalcium phosphate--dicalcium phosphate--calcite cements.

The setting and strengthening properties of beta-tricalcium phosphate (beta-TCP)--dicalcium phosphate dihydrate (DCPD)--calcite blends upon admixture with water were investigated at 25 and 37 degrees C. Setting was accelerated by seeding the system with hydroxyapatite (HAp), and strengthening improved when the solids were mixed with a solution saturated with DCPD and HAp. The relationship strength versus ageing time in wet conditions was correlated with mineralogical changes of the material. X-Ray diffraction, thermal analysis and scanning electron microscopy observations showed that DCPD and calcite react together to form small HAp crystals acting as bridges between the beta-TCP aggregates present in the paste. Both gaseous CO2 released by the reaction of calcite and the conversion of lower (DCPD, calcite) to higher-density phases (HAp) contributed to increase the porosity of the material. Nevertheless, quite acceptable diametral strengths (around 1.5 MPa) could be achieved, despite the high porosity of the hardened product (up to 54 vol%). After exhaustion of DCPD, calcite can react with beta-TCP to form further HAp, but this process is detrimental to the strength of the material. Both the mineralogical transformations, and the strengthening of the material were accelerated considerably upon increasing the ageing temperature.

Adhesives↗
PubMed1996

Recovery of endothelial cells and prostanoid production in endothelial cell-seeded grafts.

OBJECTIVE: To investigate the function and morphology of endothelial cell (EC) seeded grafts. DESIGN: Experimental, open study. CHIEF OUTCOME MEASURES: Endoluminal release of prostacyclin (6-Keto-PGF1 alpha) and thromboxane B2 (TxB2), patency, EC coverage and cell identity. MATERIALS: In 12 sheep, segments of both carotid arteries were excised. On one side a seeded and on the other an unseeded dacron graft were inserted. After 3 months the grafts were excised. In grafts and arteries, the endoluminal release of 6-keto-PGF1 alpha and TxB2 was determined in a perfusion system. Scanning electron microscopy (SEM) and light microscopy were used to determine the EC coverage and cell identity. RESULTS: Eight animals survived. Three seeded and two unseeded grafts were occluded. Prostacyclin release did not differ significantly between seeded and unseeded grafts and arteries, when the arteries were looked upon as one group. When the graft was compared with its corresponding artery, i.e. the artery it replaced, a significantly lower release was found in the unseeded group. Thromboxane release was undetectable in arteries but significantly higher in both graft groups. SEM revealed a cellular coverage of 75% in the seeded grafts and 50% in the unseeded (not significant). Light microscopy showed a patchy staining for Factor VIII-related antigen in some grafts in both groups. CONCLUSION: Prostacyclin release in unseeded and seeded dacron grafts did not differ 3 months after implantation in sheep, except when the graft was compared with its corresponding artery. The significance of this remains to be settled. Seeded grafts did not have a higher proportion of endothelial coverage than unseeded grafts.

6-Ketoprostaglandin F1 alpha↗
PubMed2002

Transplanted hematopoietic cells seed in clusters in recipient bone marrow in vivo.

The process of hematopoietic stem and progenitor cell (HSPC) seeding in recipient bone marrow (BM) early after transplantation is not fully characterized. In vivo tracking of HSPCs, labeled with PKH dyes, through an optical window surgically implanted on the mouse femur revealed that transplanted cells cluster in the recipient BM. Within the first day after intravenous injection, 86 +/- 6% of the cells seeded in clusters (p < 0.001 versus scattered cells) in the endosteal surfaces of the epiphyses. The primary clusters were formed by concomitant seeding of 6-10 cells over an area of approximately 70 microm, and secondarily injected cells did not join the already existing clusters but formed new clusters. Major antigen-disparate HSPCs participated in formation of the primary clusters, and T lymphocytes were also incorporated. After 4 to 5 days, some cellular clusters were observed in the more central regions of the BM, where the brightness of PKH fluorescence decreased, indicating cellular division. These later clusters were classified as secondary, assuming that the mechanisms of migration in the BM might be different from those of primary seeding. Some clusters remained in the periphery of the BM and retained bright fluorescence, indicating cellular quiescence. The number of brightly fluorescent cells in the clusters decreased exponentially to two to three cells after 24 days (p < 0.001). The data suggest that the hematopoietic niche is a functional unit of the BM stromal microenvironment that hosts seeding of a number of transplanted cells, which form a cluster. This may be the site where auxiliary non-HSPC cells, such as T lymphocytes, act in support of HSPC engraftment.

Animals↗
PubMed2001

Bone tissue engineering in a rotating bioreactor using a microcarrier matrix system.

A novel approach was utilized to grow in vitro mineralized bone tissue using lighter-than-water, polymeric scaffolds in a high aspect ratio rotating bioreactor. We have adapted polymer microencapsulation methods for the formation of hollow, lighter-than-water microcarriers of degradable poly(lactic-co-glycolic acid). Scaffolds were fabricated by sintering together lighter-than-water microcarriers from 500 to 860 microm in diameter to create a fully interconnected, three-dimensional network with an average pore size of 187 microm and aggregate density of 0.65 g/mL. Motion in the rotating bioreactor was characterized by numerical simulation and by direct measurement using an in situ particle tracking system. Scaffold constructs established a near circular trajectory in the fluid medium with a terminal velocity of 98 mm/s while avoiding collision with the bioreactor wall. Preliminary cell culture studies on these scaffolds show that osteoblast-like cells readily attached to microcarrier scaffolds using controlled seeding conditions with an average cell density of 6.5 x 10(4) cells/cm(2). The maximum shear stress imparted to attached cells was estimated to be 3.9 dynes/cm(2). In addition, cells cultured in vitro on these lighter-than-water scaffolds retained their osteoblastic phenotype and showed significant increases in alkaline phosphatase expression and alizarin red staining by day 7 as compared with statically cultured controls.

Alkaline Phosphatase↗