Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Seeded aggregation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38Linked to original sources
PubMed2005

In vitro antimicrobial activity of Fill Canal, Sealapex, Mineral Trioxide Aggregate, Portland cement and EndoRez.

AIM: To determine in vitro the antimicrobial activity of Fill Canal, Sealapex, Mineral Trioxide Aggregate (MTA), Portland cement and EndoRez on various species of microorganisms. METHODOLOGY: The diffusion method on Müller-Hinton agar (MH) was employed. A base layer was made using MH agar and five wells were made by removing agar at equidistant points. Sealers were placed into the wells immediately after manipulation. The microorganisms Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Micrococcus luteus ATCC 9341, Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis ATCC 12228, Pseudomonas aeruginosa ATCC 27853 and Candida albicans ATCC 10231 were seeded by pour plate. The plates were kept at room temperature for 2 h for prediffusion and then incubated at 37 degrees C for 24 h. Aliquots of 10 mL of 0.05% triphenyltetrazolium chloride gel were added for optimization and the zones of inhibition were measured. RESULTS: Sealapex and Fill Canal demonstrated antimicrobial activity for all strains. For MTA and Portland cement, only E. coli was not inhibited. No antimicrobial activity was detected for EndoRez. CONCLUSIONS: In this laboratory study, Fill Canal, Sealapex, MTA and Portland cement presented antimicrobial activity whilst EndoRez did not.

Aluminum Compounds↗
PubMed2006

Spatiotemporal clustering and association of Ephestia kuehniella (Lepidoptera: Pyralidae) and two of its parasitoids in bulk-stored wheat.

To assess the spatiotemporal distribution of insects in a flat storage containing wheat (Triticumn spp.), probe traps were suspended in the wheat bulk and inspected for captured insects at 15-d intervals, from June 2001 to August 2002. The grain bulk was 1 m in height, and traps were placed at the upper and the lower 0.5 m of the bulk. During the entire trapping period, 17 insect taxa were recorded. The most abundant species were Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) and its larval parasitoids Harbobracon hebetor (Say) (Hymenoptera: Braconidae) and Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae). Most individuals were found in the upper bulk part. The highest E. kuehniella trap catches were found between August and November 2001 and during June and July 2002. Of the two parasitoids, H. hebetor was more abundant than V. canescens, with the exception of winter and early spring, when both species occurred at low numbers, especially H. hebetor. Spatial analysis by distance indices (SADIE) spatiotemporal analysis showed significant clustering of species, especially during summer and autumn. Early in the season and during spring 2002, at low host numbers, V. canescens occupied the locations where E. kuehniella mainly aggregated, but with the increase of E. kuehniella population, H. hebetor occupied these host groups and replaced V canescens. Although the two parasitoids competed for the same host species, both species coexisted in the storage facility during the entire trapping period.

Animals↗
PubMed2005

Chitosan particles agglomerated scaffolds for cartilage and osteochondral tissue engineering approaches with adipose tissue derived stem cells.

It is well accepted that natural tissue regeneration is unlikely to occur if the cells are not supplied with an extracellular matrix (ECM) substitute. With this goal, several different methodologies have been used to produce a variety of 3D scaffolds as artificial ECM substitutes suitable for bone and cartilage tissue engineering. Furthermore, osteochondral tissue engineering presents new challenges since the combination of scaffolding and co-culture requirements from both bone and cartilage applications is required in order to achieve a successful osteochondral construct. In this paper, an innovative processing route based on a chitosan particles aggregation methodology for the production of cartilage and osteochondral tissue engineering scaffolds is reported. An extensive characterization is presented including a morphological evaluation using Micro-Computed Tomography (microCT) and 3D virtual models built with an image processing software. Mechanical and water uptake characterizations were also carried out, evidencing the potential of the developed scaffolds for the proposed applications. Cytotoxicity tests show that the developed chitosan particles agglomerated scaffolds do not exert toxic effects on cells. Furthermore, osteochondral bilayered scaffolds could also be developed. Preliminary seeding of mesenchymal stem cells isolated from human adipose tissue was performed aiming at developing solutions for chondrogenic and osteogenic differentiation for osteochondral tissue engineering applications.

Adipose Tissue↗
PubMed1994

Clusterin expression in differentiating smooth muscle cells.

Clusterin is a heterodimeric glycoprotein, expressed by various cell types and shown to have activity in cell-cell adhesion. Cultured porcine smooth muscle cells (SMC) undergo morphological and phenotypic modulation associated with a change from a substrate-attached monolayer culture to a nodular culture in which most of the cells are present in multicellular aggregations (nodules). During that transition from monolayer to nodular cell culture (> 8 days) the expression of an mRNA and protein with significant homology to rat and human clusterin is increased. Clusterin expression continues in the nodular cell cultures and it is secreted at 0.3 micrograms/ml/24 h as a protein with an apparent molecular mass = 80 kDa. In the presence of beta-mercaptoethanol the molecular mass is approximately 40 kDa. SMC clusterin expression is regulated by culture conditions that also affect culture morphology. SMC cultures seeded on a preformed extracellular matrix composed of Matrigel form nodules within 24 h and cultures seeded on a collagen gel form nodules in 48-72 h. We establish here that Matrigel contains clusterin and propose that endogenous clusterin supports the rapid formation of nodules. The collagen gel does not contain clusterin but facilitates clusterin expression by smooth muscle cells. Nodule formation in SMC cultures growing on collagen gel is inhibited by the addition of anticlusterin antibody to SMC growing on collagen gels and the antibody effect is eliminated by preincubation with purified plasma clusterin. These results demonstrate differential expression of SMC clusterin and suggest that clusterin has a functional role in SMC modulation.

Animals↗
PubMed2002

Exogenous induction of cerebral beta-amyloidosis in betaAPP-transgenic mice.

A key commonality of most age-related neurodegenerative diseases is the accumulation of aggregation-prone proteins in the brain. Except for the prionoses, the initiation and propagation of these proteopathies in vivo remains poorly understood. In a previous study, we found that the deposition of the amyloidogenic peptide Abeta can be induced by injection of dilute extracts of Alzheimeric neocortex into the brains of Tg2576 transgenic mice overexpressing the human beta-amyloid precursor protein. The present study was undertaken to assess the pathology after long-term (12 months) incubation, and to clarify the distinctive anatomical distribution of seeded Abeta-immunoreactivity. All mice were injected at 3 months of age; 5 months later, as expected, Abeta deposits were concentrated mostly in the injected hemisphere. After 12 months, abundant, transgene-derived Abeta deposits were present bilaterally in the forebrain, but plaque load was still clearly greater in the extract-injected hemisphere. There was also evidence of tau hyperphosphorylation in axons of the corpus callosum that had been injured by the injection, most prominently in transgenic mice, but also, to a lesser degree, in non-transgenic mice. Five months following injection of AD-extract, an isolated cluster of Abeta-immunoreactive microglia was sometimes evident in the ipsilateral entorhinal cortex; the strong innervation of the hippocampus by entorhinal cortical neurons suggests the possible spread of seeded pathology from the injection site via neuronal transport mechanisms. Finally, using India Ink to map the local dispersion of injectate, we found that Abeta induction is especially potent in places where the injectate is sequestered. The AD-seeding model can illuminate the emergence and spread of cerebral beta-amyloidosis and tau hyperphosphorylation, and thus could enhance our understanding of AD and its pathogenic commonalties with other cerebral proteopathies.

Amyloid beta-Protein Precursor↗
PubMed2004

Spatial structure and genetic diversity of two tropical tree species with contrasting breeding systems and different ploidy levels.

Analyses of the spatial distribution pattern, spatial genetic structure and of genetic diversity were carried out in two tropical tree species with contrasting breeding systems and different ploidy levels using a 50-ha demographic plot in a lowland dipterocarp forest in Peninsular Malaysia. Shorea leprosula is a diploid and predominantly outcrossed species, whereas S. ovalis ssp. sericea is an autotetraploid species with apomictic mode of reproduction. Genetic diversity parameters estimated for S. leprosula using microsatellite were consistently higher than using allozyme. In comparisons with S. leprosula and other tropical tree species, S. ovalis ssp. sericea also displayed relatively high levels of genetic diversity. This might be explained by the lower pressure of genetic drift due to tetrasomic inheritance, and for autotetraploids each locus can accommodate up to four different alleles and this allows maintenance of more alleles at individual loci. The observed high levels of genetic diversity in S. ovalis ssp. sericea can also be due to a random retention of more heterogeneous individuals in the past, and the apomictic mode of reproduction might be an evolutionary strategy, which allows the species to maintain high levels of genetic diversity. The spatial distribution pattern analyses of both species showed significant levels of aggregation at small and medium but random distribution at the big diameter-class. The decrease in magnitude of spatial aggregation from small- to large-diameter classes might be due to compensatory mortality during recruitment and survival under competitive thinning process. Spatial genetic structure analyses for both species revealed significant spatial genetic structure for short distances in all the three diameter-classes. The magnitude of spatial genetic structure in both species was observed to be decreasing from smaller- to larger-diameter classes. The high spatial genetic structuring observed in S. ovalis ssp. sericea at the small-diameter class is due primarily to limited seed dispersal and apomictic mode of reproduction. The similar observation in S. leprosula, however, can be explained by limited seed and pollen dispersal, which supports further the fact that the species is pollinated by weak fliers, mainly of Thrips and Megalurothrips in the lowland dipterocarp forest.

Age Factors↗
PubMedDate not supplied

Galactosylated poly(vinylidene difluoride) hollow fiber bioreactor for hepatocyte culture.

To overcome the limitations of long-term expression of highly differentiated hepatocyte functions, we have developed a novel bioreactor in which hepatocytes are seeded in a ligand-immobilized hollow fiber cartridge. Galactosylated Pluronic polymer is immobilized on poly(vinylidene difluoride) (PVDF) hollow fiber surface through an adsorption scheme yielding a substrate with hepatocyte-specific ligand and a hydrophilic surface layer, which can resist nonspecific protein adsorption and facilitate cell binding to the galactose ligand. Interestingly, the galactosylated PVDF hollow fiber shows enhanced serum albumin diffusion across the membrane. Freshly isolated rat hepatocytes were seeded and cultured in the extralumenal space of the hollow fiber cartridge for 18 days in a continuously circulated system. Albumin secretion function of the seeded hepatocytes was monitored by analyzing circulating medium by enzyme-linked immunosorbent assay. Urea synthesis and P-450 function (7-ethoxycoumarin dealkylase activity) were measured periodically by doping the circulating medium with NH4Cl and 7-ethoxycoumarin, respectively. Hepatocytes cultured on galactosylated PVDF hollow fibers maintained better albumin secretion and P-450 functions than on unmodified and serum-coated PVDF hollow fibers when cultured in serum-containing medium. Morphological examination by scanning electron microscopy showed that hepatocytes cultured on galactosylated PVDF hollow fibers developed significant aggregation, in contrast to those cultured on unmodified PVDF fibers or on serum-coated PVDF fibers. Transmission electron microscopy images revealed that tight junctions and canaliculus-like structures formed in these aggregates. These results suggest the potential application of this galactosylated PVDF hollow fiber cartridge for the design of a bioartificial liver assist device.

Animals↗
PubMedDate not supplied

New graft materials and current approaches to an acceptable small diameter vascular graft.

Prosthetic graft material has not been successful for small artery bypass. Mechanical, cellular, and humoral factors have all been implicated as a cause of failure. In vitro, ex vivo, and in vivo methods have been developed to assess platelet and fibrinogen deposition, measure compliance, and study other factors theorized to relate to graft failure. Cell culture techniques have been used to determine the role of cellular mitogens. The goal of an arterial substitute that can maintain patency in a 3-4 mm diameter low-flow configuration and that is not associated with the development of anastomotic hyperplasia has yet to be reached. A variety of solutions are being researched. New nonthrombogenic polymers are being tested as are new coatings for standard materials. Endothelial cell seeding has been accomplished in animals and is being tried in human clinical studies. Problems and results of endothelial seeding trials are reviewed. Other biologic approaches include the in vitro construction of a blood vessel model using cell coculture techniques and the implantation of bioabsorbable prosthetics into animals. The role of pharmacologic agents in maintaining graft patency is addressed.

Animals↗
PubMed2005

Spontaneous formation of detergent micelles around the outer membrane protein OmpX.

The structure and flexibility of the outer membrane protein X (OmpX) in a water-detergent solution and in pure water are investigated by molecular dynamics simulations on the 100-ns timescale and compared with NMR data. The simulations allow for an unbiased determination of the structure of detergent micelles and the protein-detergent mixed micelle. The short-chain lipid dihexanoylphosphatidylcholine, as a detergent, aggregates into pure micelles of approximately 18 molecules, or alternatively, it binds to the protein surface. The detergent binds in the form of a monolayer ring around the hydrophobic beta-barrel of OmpX rather than in a micellar-like oblate; approximately 40 dihexanoylphosphatidylcholine lipids are sufficient for an effective suppression of water from the surface of the beta-barrel region. The phospholipids bind also on the extracellular, protruding beta-sheet. Here, polar interactions between charged amino acids and phosphatidylcholine headgroups act as condensation seed for detergent micelle formation. The polar protein surface remains accessible to water molecules. In total, approximately 90-100 detergent molecules associate within the protein-detergent mixed micelle, in agreement with experimental estimates. The simulation results indicate that OmpX is not a water pore and support the proposed role of the protruding beta-sheet as a "fishing rod".

Bacterial Outer Membrane Proteins↗
PubMedDate not supplied

[Role and importance of dietary polyunsaturated fatty acids in the prevention and therapy of atherosclerosis].

INTRODUCTION: Hyperlipoproteinemia is a key factor in development of atherosclerosis, whereas regression of atherosclerosis mostly depends on decreasing the plasma level of total and LDL-cholesterol. Many studies have reported the hypocholesterolemic effect of linolenic acid. TYPES OF POLYUNSATURATED FATTY ACIDS (PUFA): Linoleic and alpha-linolenic acids are essential fatty acids. The main sources of linoleic acid are vegetable seeds and of alpha-linolenic acid-green parts of plants. alpha-linolenic acid is converted to eicosapentaenoic and docosahexaenoic acid. Linoleic acid is converted into arachidonic acid competing with eicosapentaenoic acid in the starting point for synthesis of eicosanoids, which are strong regulators of cell functions and as such, very important in physiology and pathophysiology of cardiovascular system. Eicosanoids derived from eicosapentaneoic acid have different biological properties in regard to those derived from arachidonic acid, i.e. their global effects result in decreased vasoconstriction, platelet aggregation and leukocyte toxicity. ROLE AND SIGNIFICANT OF PUFA: The n-6 to n-3 ratio of polyunsaturated fatty acids in the food is very important, and an optimal ratio 4 to 1 in diet is a major issue. Traditional western diets present absolute or relative deficiency of n-3 polyunsaturated fatty acids, and a ratio 15-20 to 1. In our diet fish and fish oil are sources of eicosapentaenoic and docosahexaenoic acid. Refined and processed vegetable oils change the nature of polyunsaturated fatty acids and obtained derivates have atherogenic properties.

Arteriosclerosis↗
PubMedDate not supplied

Ultrastructure of Gentiana tibetica proembryogenic cells before and after cooling treatments.

The influence of increased concentrations of sucrose, 0.4 M sorbitol, DMSO and vitrification solution (PVS2) on the ultrastructure of non-frozen and frozen suspensions of Gentiana tibetica King ex Hook. F.tissue cells was investigated. Embryogenic aggregates were composed of three groups of cells of different size with various types of plastids. The ultrastructural changes resulting from increasing the sucrose concentration in the medium from 3 to 6 percent for 4 weeks and from treatment with 0.4 M sorbitol for 48 h were similar. Observations showed replacement of large vacuoles by numerous small ones, condensation of cytoplasm, accumulation of starch, and fragmentation of endoplasmic reticulum. Treatment with PVS2 led to degradation of starch, coalescence of amyloplasts and to shrinking of nucleoli from the third group of cells when originating from 6 percent sucrose medium. The mitochondria initially had various shapes, but after PVS2 treatment showed only spherical shapes with sparse cristae. After programmed freezing of tissue protected by sorbitol and DMSO, lethal damage was observed: membrane and nuclei degradation, and cell destruction. Reversible changes after freezing were observed in tissue pretreated with vitrification solution: dilation of cell membranes, mitochondria with electron-lucent vessels, aggregation of numerous vesicles, and degradation of starch in amyloplasts. In cells cooled by a vitrification method, cell organelles appeared normal as early as 5 h after thawing, and anomalies were not observed after 48 h of post-thawing culture.

Cell Culture Techniques↗
PubMed2006

Fine-scale genetic structure among genetic individuals of the clone-forming monotypic genus Echinosophora koreensis (Fabaceae).

BACKGROUND AND AIMS: For rare endemics or endangered plant species that reproduce both sexually and vegetatively it is critical to understand the extent of clonality because assessment of clonal extent and distribution has important ecological and evolutionary consequences with conservation implications. A survey was undertaken to understand clonal effects on fine-scale genetic structure (FSGS) in two populations (one from a disturbed and the other from an undisturbed locality) of Echinosophora koreensis, an endangered small shrub belonging to a monotypic genus in central Korea that reproduces both sexually and vegetatively via rhizomes. METHODS: Using inter-simple sequence repeats (ISSRs) as genetic markers, the spatial distribution of individuals was evaluated using Ripley's L(d)-statistics and quantified the spatial scale of clonal spread and spatial distribution of ISSR genotypes using spatial autocorrelation analysis techniques (join-count statistics and kinship coefficient, F(ij)) for total samples and samples excluding clones. KEY RESULTS: A high degree of differentiation between populations was observed (phi(ST(g)) = 0.184, P < 0.001). Ripley's L(d)-statistics revealed a near random distribution of individuals in a disturbed population, whereas significant aggregation of individuals was found in an undisturbed site. The join-count statistics revealed that most clones significantly aggregate at < or = 6-m interplant distance. The Sp statistic reflecting patterns of correlograms revealed a strong pattern of FSGS for all four data sets (Sp = 0.072-0.154), but these patterns were not significantly different from each other. At small interplant distances (< or = 2 m), however, jackknifed 95% CIs revealed that the total samples exhibited significantly higher F(ij) values than the same samples excluding clones. CONCLUSION: The strong FSGS from genets is consistent with two biological and ecological traits of E. koreensis: bee-pollination and limited seed dispersal. Furthermore, potential clone mates over repeated generations would contribute to the observed high F(ij) values among genets at short distance. To ensure long-term ex situ genetic variability of the endangered E. koreensis, individuals located at distances of 10-12 m should be collected across entire populations of E. koreensis.

Conservation of Natural Resources↗
PubMedDate not supplied

Effects of shear stress on metabolic function of the co-culture system of hepatocyte/nonparenchymal cells for a bioartificial liver.

To improve the culture conditions of hepatocytes for use as a bioartificial liver, the effects of shear flow on the co-culture system of hepatocytes/nonparenchymal cells (NPC) were investigated. A flow chamber with a collagen coated rectangular glass plate, where hepatocytes (5 x 10(4) cell/cm2) and NPC (2 x 10(5) cell/cm2) were seeded, was used to attain a shear stress of 4.7 dyne/cm2. Concentrations of ammonia and urea in the medium were measured daily during the 2 week experiment. The metabolic activity of hepatocytes in the homotypic culture were lower than those of the co-culture, especially when the cultivation time exceeded 1 week. In addition, the applied shear flow promoted activity of the co-culture system. An enhancement in the rates of ammonium removal and urea synthesis was obtained in the perfusion systems. Morphologic observation revealed that aggregates of hepatocytes formed abundantly in the perfusion system and hepatocytes developed a cuboid shape. This suggested that perfusion affected the function and morphology of hepatocytes in the co-culture system. Shear flow could induce cell-cell interactions and secretion of extracellular matrix through the activation of NPC.

Animals↗
PubMed1984

Platelet reactivity in vivo in dogs with arterial prostheses seeded with endothelial cells.

This study was designed to assess platelet activity in vivo with vascular prostheses seeded with endothelial cells to determine the time course for development of thromboresistance and to test the ability of prostheses to produce prostacyclin. Sixteen dogs were randomly allocated to receive seeded (experimental group) or unseeded (control group) velour Dacron aortic prostheses. Serial measurements of platelet survival were performed to assess platelet interaction with prostheses in vivo, and platelet serotonin was monitored as an index of platelet release in vivo. After placement of prostheses, dogs in the experimental group had rapid normalization of platelet survival, with most having normal platelet survival at 4 to 8 weeks after surgery. In contrast, most control animals had reduced platelet survival throughout the 12 week period of study. Significant differences between groups in mean platelet survival were noted at 8 weeks after surgery (p less than .005) and in mean platelet serotonin at 12 weeks after surgery (p less than .05). Luminal surface production of 6-keto-PGF1 alpha from seeded prostheses was similar to aortic production and significantly greater (p less than .05) than that of control prostheses. Gross thrombus was present on 6.0 +/- 3.4% of the prosthetic surface in experimental animals in comparison to 26.6 +/- 19.2% in controls (p less than .005). The results of these studies document accelerated nonreactivity with platelets of seeded prostheses due to rapid coverage with endothelium possessing a normal ability to produce prostacyclin.

Animals↗
PubMedDate not supplied

Contributions of intermolecular interactions between constitutive arabinoxylans to the flaxseeds mucilage properties.

The main fraction (about 75%) of the mucilage extracted from seeds of Linum usitatissimum which consists of arabino-xylans (AX) has been studied in dilute and semidilute regimes by SEC/MALLS analysis and rheology, respectively. It has been found that AX contains 3 populations of about 5 000 000 g mol(-1) (less than 10%), 1 000 000 g mol(-1) (about 40%), and 200 000 g mol(-1) (about 50%). We have also observed a great retention of polymer during the filtration procedure, which is much pronounced as the AX concentration increases. This evidences the presence of large aggregates in the solution. The retention can be greatly diminished if the filtration is conducted under higher temperature. Aggregation could result from the establishment of intermolecular associations via hydrogen bonds. This hypothesis seems to be confirmed by the two higher populations in molar masses which present a random coil conformation consistent with a low degree of branching. Rheological measurements, conducted at 20 g L(-1), have confirmed the association tendency leading to pseudo gels behavior. Viscoelastic properties have been evidenced by time-temperature master curves of dynamic spectra. Such master curves have also been established with addition of chaotropic (i.e., KSCN) and lyotropic (i.e., NaCl) salts. It has been shown that intermolecular associations are greatly diminished under chaotropic salts influence. This has been also confirmed by SEC/MALLS analysis. These results point out the role of hydrogen bonds in the organization of the AX system.

Flax↗
PubMed1991

Comparison of morphological and biochemical characteristics of cultured chondrocytes isolated from proliferative and hypertrophic zones of bovine growth plate cartilage.

Primary cultures of chondrocytes isolated from the proliferative and hypertrophic zones of bovine growth plate cartilage were established, and their morphological and biosynthetic characteristics were compared. High-cell-density monolayer cultures maintained a predominantly chondrocytic morphology, preserved their zone-specific collagen phenotype, and produced an abundant proteoglycan matrix. In contrast, monolayer cultures plated at low cell densities contained many cells with fibroblastic morphology and initiated the synthesis of type I collagen within 72 h following seeding. On a per cell basis, the proliferative zone chondrocytes displayed greater biosynthetic activity than chondrocytes from the hypertrophic region. Characterization of newly synthesized collagens showed that type II collagen was the major biosynthetic product of both types of cells. In contrast, type X collagen was synthesized exclusively by hypertrophic chondrocytes and represented about 20% of the total collagen produced by these cells. The type X collagen molecules synthesized by the hypertrophic cells contained disulfide bonds within their triple-helical domains and assembled into a high-Mr aggregate. When polymerase chain reaction (PCR) was employed to amplify type X collagen sequences from cDNA obtained by reverse transcription of mRNA from cultures of both types of chondrocytes, only the hypertrophic chondrocyte mRNA yielded PCR amplification products indicative of the presence of type X collagen transcripts.

Amino Acid Sequence↗
PubMed2005

Evaluation of polymer scaffolds to be used in a composite injectable system for intervertebral disc tissue engineering.

Adult porcine nucleus pulposus cells were seeded onto gelatin, demineralized bone matrix (DBM), and polylactide scaffolds and cultured in vitro. Cellular behavior in response to the scaffolds was analyzed using biochemical assays, histology, and real-time quantitative reverse transcriptase-polymerase chain reaction. Scanning electron microscopy showed pronounced differences in surface texture of the scaffolds. Nucleus pulposus cells attached and assumed an elongated fibroblast-like morphology on the gelatin and DBM scaffolds. The cells cultured on the gelatin and DBM were metabolically active and expressed types I and II collagen and aggrecan. Detached cellular aggregates with a rounded morphology were noted in the culture tubes containing the polylactide scaffolds. Both surface chemistry and texture likely had a role in causing differences in cellular behavior in response to scaffold material. Promising results were observed using the gelatin and demineralized bone scaffolds, but the behavior of cells cultured on these scaffolds will need to be characterized further. This initial research will be used to direct future work involved in developing this composite injectable tissue engineering system.

Animals↗
PubMed2002

Effects of free fatty acid on polymerization of islet amyloid polypeptide (IAPP) in vitro and on amyloid fibril formation in cultivated isolated islets of transgenic mice overexpressing human IAPP.

BACKGROUND: Islet amyloid polypeptide (IAPP) is deposited as amyloid in the islets of Langerhans in type 2 diabetes. The mechanism behind the formation of the cytotoxic fibrils is unknown. Islet amyloid develops in a mouse IAPP null mouse strain that expresses human IAPP (+hIAPP/-mIAPP) after 9 months on a high-fat diet. Herein we investigate the effect that individual free fatty acids (FFAs) exert on formation of amyloid-like fibrils from synthetic IAPP and the effects of FFAs on IAPP polymerization in +hIAPP/-mIAPP islets cultivated in vitro. MATERIALS AND METHODS: In the study myristic acid, palmitic acid, stearic acid, oleic acid, and linoleic acid were used together with albumin. Thioflavin T (Th T) assay was used for quantification of amyloid-like fibrils. Islets were isolated from the +hIAPP/-mIAPP transgenic strain and cultured in the presence of the FFAs for 2 days. Immuno-electron microscopy was used for evaluation. RESULTS: The Th T assay showed that all studied FFAs potentiated fibril formation but that myristic acid revealed the highest capacity. In some cells from cultured islets, intragranular aggregates were present. These aggregates had a filamentous appearance and labeled with antibodies against IAPP. In some cells cultured in the presence of linoleic acid, large amounts of intracellular amyloid were present. Earlier, this has not been observed after such a short incubation period. CONCLUSIONS: Our studies suggest that FFAs can potentiate amyloid formation in vitro, probably without being integrated in the fibril. Cultivation of +hIAPP/-mIAPP transgenic mouse islets with FFAs results in altered morphology of the secretory granules with appearance of IAPP- immunoreactive fibrillar material. We suggest that such fibrillar material may seed extracellular amyloid formation after exocytosis.

Amyloid↗