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Isolation, cell culture and immunocytochemical characterization of oviduct epithelial cells of the cow.

Incubation of cow oviducts flushed with 0.1 mg collagenase/ml, for 90 min helped to dislodge large numbers of ciliated and secretory cells. About 90-95% of the isolated epithelial cells were viable. The epithelial cells suspended in DMEM:F-12 + 10% serum attached to the plastic culture dish in 18-20 h after seeding. The ciliated cells which attached to the plastic dish lost their cilia after 4-5 days in culture. The attached cells, which proliferated to form a confluent monolayer 8-10 days after seeding in a 35-mm dish, could be subcultured at least 3 successive times. Some cell aggregates which did not attach to the culture dish proliferated into floating balls of cells. The ciliated cells in the unattached floating colonies maintained the ciliary movement for 9-10 days in the same culture medium. The primary cultures of the ciliated and the secretory cells maintained most of the histoarchitecture observed in intact epithelium. The secretory cells maintained their secretory activity of specific proteins in culture as indicated by immunocytology. The cultured cells contained keratin, a specific cytoskeletal component of epithelial cells.

Animals↗

[Proliferation of myeloid precursor cells in a microagar culture system].

A microagar-culture system for the in vitro study of myelopoiesis committed stem cells has been reported. Stimulation was induced by a commercially available conditioned medium obtained from culture of histiocytoma cells. The effect of different concentrations of conditioned medium and a linear relation between the seeded cells and the formed colonies has been established. The granulocytic-monocytic character of cell aggregates has been shown by morphologic studies. Further possibilities for the use of the described method have been briefly discussed.

Agar↗

Interaction of amelogenin with hydroxyapatite crystals: an adherence effect through amelogenin molecular self-association.

At the secretory stage of tooth enamel formation the majority of the organic matrix is composed of amelogenin proteins that are believed to provide the scaffolding for the initial carbonated hydroxyapatite crystals to grow. The primary objective of this study was to investigate the interaction between amelogenins and growing apatite crystals. Two in vitro strategies were used: first, we examined the influence of amelogenins as compared to two other macromolecules, on the kinetics of seeded growth of apatite crystals; second, using transmission electron micrographs of the crystal powders, based on a particle size distribution study, we evaluated the effect of the macromolecules on the aggregation of growing apatite crystals. Two recombinant amelogenins (rM179, rM166), the synthetic leucine-rich amelogenin polypeptide (LRAP), poly(L-proline), and phosvitin were used. It was shown that the rM179 amelogenin had some inhibitory effect on the kinetics of calcium hydroxyapatite seeded growth. The inhibitory effect, however, was not as destructive as that of other macromolecules tested. The degree of inhibition of the macromolecules was in the order of phosvitin > LRAP > poly(L-proline) > rM179 > rM166. Analysis of particle size distribution of apatite crystal aggregates indicated that the full-length amelogenin protein (rM179) caused aggregation of the growing apatite crystals more effectively than other macromolecules. We propose that during the formation of hydroxyapatite crystal clusters, the growing apatite crystals adhere to each other through the molecular self-association of interacting amelogenin molecules. The biological implications of this adherence effect with respect to enamel biomineralization are discussed.

Amelogenin↗

Rapid hepatocyte spheroid formation: optimization and long-term function in perfused microcapsules.

Enhancement of cell-cell interactions and, hence, long-term function in liver support systems can be effected by controlling the diameters of hepatocyte aggregates or spheroids. In this study, primary rat hepatocytes were induced to rapidly form spheroids using an intermittent settling and agitation protocol. The cells were seeded into albumin coated flasks at densities ranging from 80,000 to 520,000 cells/cm2. Hepatocytes were resuspended for 15 sec at 20-min intervals by placing the flasks on a timer controlled linear shaker. At time points ranging from 8 to 24 hr, hepatocyte aggregates were imaged via light microscopy. Mean spheroid diameter and shape factor were determined using computer analysis of captured images. Spheroid diameter could be controlled within the range of 60 to 240 microns. For long-term evaluation, spheroids were microencapsulated and cultured for 21 days under perfusion conditions. Encapsulated spheroids secreted albumin at rates comparable to collagen sandwich control cultures for at least 14 days, with peak rates (approximately 80 microns/day/10(6) cells) exhibited after culture medium changes. The results show that controlled, high efficiency hepatocyte aggregation can be accomplished in as little as 8 hr, and that the encapsulated spheroids exhibit long-term in vitro function.

Albumins↗

Simplified isolation and spheroidal aggregate culture of rat hepatocytes.

AIM:To explore a simplified method for isolation of hepatocytes and establish a method of primary hepatocyte culture with more aggregates and longer persisence.METHODS: Wistar rat hepatocytes were isolated by a single extracorporeal two-step perfusion method, and the cells were seeded on poly-HEMA coated flasks and cultured with hormonally defined medium and gentle shaking at regular intervals.RESULTS: The total yield of isolating hepatocytes amounted to 10(8) cells for each rat liver with the viability of more than 90% in all isolations. Under the nonadherent environments, the cells were found to attach to each other and form multicellular aggregates rapidly, and the aggregates became spheroidal shape after two days in culture. The morphologic characteristics and albumin synthetic unction of the multicellular spheroidal aggregates can be maintained for one month.CONCLUSION: The simple and reliable isolation as well as large scale and longer time culture of hepatocytes can be used for experiments in liver cell transplantation and bioartificial liver support system.

Journal Article↗

Suppression of DTT-induced aggregation of abrin by alphaA- and alphaB-crystallins: a model aggregation assay for alpha-crystallin chaperone activity in vitro.

The eye lens small heat shock proteins (sHSP), alphaA- and alphaB-crystallins, have been shown to function like molecular chaperones, both in vitro and in vivo. It is essential to assess the protective effect of alphaA- and alphaB-crystallins under native conditions to extrapolate the results to in vivo conditions. Insulin and alpha-lactalbumin have widely been used to investigate the chaperone mechanism of alpha-crystallin under native conditions. Due to its smaller size, insulin B-chain may not represent the binding of putative physiological substrate proteins. As it stands, the aggregation of alpha-lactalbumin and binding of alpha-crystallin to it varies under different experimental conditions. Abrin, a ribosome inactivating protein isolated from the seeds of Abrus precatorius, consists of a 30 kDa A-chain and a lectin-like B-chain of 33 kDa joined by a single disulfide bond. Reduction of the disulfide link between the two chains of abrin leads to the aggregation of the B-chain. In this study, we demonstrate that dithiothreitol (DTT)-induced aggregation of abrin B-chain could be monitored by light scattering similar to that of insulin. Moreso, this process could be suppressed by recombinant human alphaA- and alphaB-crystallins in a concentration dependent manner, notably by binding to aggregation prone abrin B-chain. SDS-PAGE and HPLC gel filtration analysis indicate that there is a soluble complex formation between alpha-crystallin and abrin B-chain. Interestingly, in contrast to insulin, there is no significant difference between alphaA- and alphaB-crystallin in suppressing the aggregation of abrin B-chain at two different temperatures (25 and 37 degrees C). HSP26, an another small heat shock/alpha-crystallin family protein, was also able to prevent the DTT-induced aggregation of abrin. These results suggest that due to relatively larger size of its B-chain (33 kDa), compared to insulin B-chain (about 3 kDa), abrin may serve as a better model substrate for in vitro chaperone studies of alpha-crystallin and as well as other sHSP.

Abrin↗

Aggregation of puroindoline in phospholipid monolayers spread at the air-liquid interface.

Puroindolines, cationic and cystine-rich low molecular weight lipid binding proteins from wheat seeds, display unique foaming properties and antimicrobial activity. To unravel the mechanism involved in these properties, the interaction of puroindoline-a (PIN-a) with dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) monolayers was studied by coupling Langmuir-Blodgett and imaging techniques. Compression isotherms of PIN-a/phospholipid monolayers and adsorption of PIN-a to lipid monolayers showed that the protein interacted strongly with phospholipids, especially with the anionic DPPG. The electrostatic contribution led to the formation of a highly stable lipoprotein monolayer. Confocal laser scanning microscopy and atomic force microscopy showed that PIN-a was mainly inserted in the liquid-expanded phase of the DPPC, where it formed an aggregated protein network and induced the fusion of liquid-condensed domains. For DPPG, the protein partitioned in both the liquid-expanded and liquid-condensed phases, where it was aggregated. The extent of protein aggregation was related both to the physical state of phospholipids, i.e., condensed or expanded, and to the electrostatic interactions between lipids and PIN-a. Aggregation of PIN-a at air-liquid and lipid interfaces could account for the biological and technological properties of this wheat lipid binding protein.

1,2-Dipalmitoylphosphatidylcholine↗

Growing tissue-like constructs with Hep3B/HepG2 liver cells on PHBV microspheres of different sizes.

In this study, an oil-in-water emulsion solvent evaporation technique was used to fabricate poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV, 8% PHV), microspheres as scaffold, to guide liver cell growth. Human hepatoma cell lines, HepG2 and Hep3B, were cultured in vitro on both the microspheres and polymer films. SEM and optical microscope images showed that multilayer cells were formed among the microspheres to bridge them together and developed into cell-construct aggregates after 1 week of culture. MTT results showed that the cell proliferation on the microspheres was more than two times higher than that on the films after 12 days of culture. The cells seeded on microspheres secreted albumin 2-4 times more than that on the positive control after 1 week of culture, which indicated that this hepatic function was greatly improved by the aggregation of cells on microspheres. Although HepG2 failed to express P-450 activity, this hepatic function was preserved when Hep3B cultured on microspheres. All the results indicated that PHBV microspheres are appropriate scaffolds for liver tissue engineering.

Cell Culture Techniques↗

Properties of starch and dietary fibre in raw and processed quinoa (Chenopodium quinoa, Willd) seeds.

We investigated certain properties of starch in raw and in heat-treated samples of quinoa, properties that are of importance to the nutritional quality of an infant food currently being developed. Scanning electron microscopy of the starch in raw seeds showed polygonal granules (0.6 to 2.0 microns diameter) to be present both singly and as spherical aggregates. Thermograms (DSC) of the flours showed one transition phase for gelatinisation of the starch and another for the amylose-lipid complex. The gelatinisation temperature of the starch was 67 degrees C. Cooked samples manifested the highest degree of gelatinisation (97%), followed by the drum-dried (96%) and autoclaved (27%) samples. Separation of the starch on a SEPHAROSE CL-2B column showed the quinoa starch to be affected by the heat treatment, manifesting changes in the degree and extent of degradation. The amylograph viscosity of the quinoa flour showed no distinct peak for pasting, but the viscosity remained constant after gelatinisation. Cooking and autoclaving modified the viscosity of the paste. The drum-dried sample manifested a higher initial viscosity at 25 degrees C. The in vitro digestibility of raw quinoa starch determined by incubation for 60 min with alpha-amylase was 22%, while that of autoclaved, cooked and drum-dried samples was 32%, 45% and 73%, respectively. Saponins did not affect the digestibility of the starch, though they tended to increase the amylograph viscosity. The total dietary fibre content in the cooked sample (11.0%) was significantly lower than that in the autoclaved (13.2%), drum-dried (13.3%) or raw samples (13.3%), while the insoluble dietary fibre fraction in the samples did not change with heat treatment. However, as compared with that of raw quinoa, the soluble dietary fibre fraction was reduced significantly both by cooking (0.9%) and by autoclaving (1.0%).

Calorimetry, Differential Scanning↗

Lysis of tumor cells by natural killer cells in mice is impeded by platelets.

Natural killer (NK) cells provide effective antitumoral activity in the blood stream of mice, leading to reduced metastasis. There are, however, tumor cells that metastasize despite the presence of an intact NK system. The capability of tumor cells to induce platelet aggregation, on the other hand, correlates with their enhanced metastatic potential. A counteractive role of platelets for the NK function in metastasis has never been conceived. Here we demonstrate for the first time that platelets directly protect tumor cells from NK lysis in vitro as well as in vivo. Using three different tumor cell lines in a mouse model of experimental metastasis, tumor seeding in the target organs was reduced when the host was platelet depleted, but only if the tumor cells were NK sensitive. Aggregation of platelets around tumor cells also inhibited in vitro NK tumorilytic activity. This protection of tumor cells by platelets was mouse strain independent and was equally observed with platelets from beta2-microglobulin-deficient mice, excluding a NK inhibitory function of MHC class I on platelets. Thus, even if tumor cells are NK susceptible and cytotoxic NK cells threaten their survival in the blood, platelets are capable of protecting them from cytolysis, thereby promoting metastasis. Surface shielding by platelet aggregates seems to be the main mechanism of this protection.

Animals↗

GM1 ganglioside and the seeding of amyloid in Alzheimer's disease: endogenous seed for Alzheimer amyloid.

A fundamental question about the pathogenesis of Alzheimer's disease (AD) is how monomeric, nontoxic amyloid beta-protein (Abeta) is converted to its toxic aggregates in the brain. The author previously identified a unique Abeta species in the AD brain, which is characterized by its binding to GM1 ganglioside (GM1). On the basis of the molecular characteristics of GM1-bound Abeta (GAbeta), the author hypothesized that GM1 plays a critical role in the process. The author recently examined this possibility using a novel monoclonal antibody raised against purified GAbeta and validated that GAbeta is endogenously generated in the brain and accelerates Abeta assembly by acting as a seed. Furthermore, the author provided a possibility that aging and the expression of apolipoprotein E4 facilitate Abeta assembly in the brain through an increase in the GM1 content in the neuronal membranes, which likely induces GAbeta generation. The author's results imply a mechanism underlying the onset of AD and also provide a new insight into development of novel therapeutic strategy.

Aging↗

Surface Aggregation of Candida albicans on Glass in the Absence and Presence of Adhering Streptococcus gordonii in a Parallel-Plate Flow Chamber: A Surface Thermodynamical Analysis Based on Acid-Base Interactions.

Adhesive interactions between yeasts and bacteria are important in the maintenance of infectious mixed biofilms on natural and biomaterial surfaces in the human body. In this study, the extended DLVO (Derjaguin-Landau-Verwey-Overbeek) approach has been applied to explain adhesive interactions between C. albicans ATCC 10261 and S. gordonii NCTC 7869 adhering on glass. Contact angles with different liquids and the zeta potentials of both the yeasts and bacteria were determined and their adhesive interactions were measured in a parallel-plate flow chamber.Streptococci were first allowed to adhere to the bottom glass plate of the flow chamber to different seeding densities, and subsequently deposition of yeasts was monitored with an image analysis system, yielding the degree of initial surface aggregation of the adhering yeasts and their spatial arrangement in a stationary end point. Irrespective of growth temperature, the yeast cells appeared uncharged in TNMC buffer, but yeasts grown at 37 degrees C were intrinsically more hydrophilic and had an increased electron-donating character than cells grown at 30 degrees C. All yeasts showed surface aggregation due to attractive Lifshitz-van der Waals forces. In addition, acid-base interactions between yeasts, yeasts and the glass substratum, and yeasts and the streptococci were attractive for yeasts grown at 30 degrees C, but yeasts grown at 37 degrees C only had favorable acid-base interactions with the bacteria, explaining the positive relationship between the surface coverage of the glass by streptococci and the surface aggregation of the yeasts. Copyright 1999 Academic Press.

Journal Article↗

Simulations as analytical tools to understand protein aggregation and predict amyloid conformation.

Computational tools are increasingly being applied to solve the protein aggregation problem, providing insight into amyloid structures and aggregation mechanisms. The paradigm of Abeta amyloid structure elucidation provides an example of an innovative experimental design and endeavor, echoing the computational testing of possible molecular associations, all reflected in the current Ma-Nussinov-Tycko model of the Abeta amyloid. Simulations have shown that dimer formation can lock some misfolded conformations, and catalyze the shift of the equilibrium away from the native state. In most cases, a stable amyloid seed requires at least two-layered beta-sheets with properly registered side-chains. Under kinetic control, the final protein aggregations are the outcome of maximizing the van der Waals interactions between side chains and backbone hydrogen bonds.

Amyloid↗

Morphological and behavioral characteristics of two rat tumor cell lines with different metastatic capacities.

The morphological characteristics of two rat tumor cell lines were studied by means of scanning electron microscopy. While the ASML-cells (Ascites, Solid, Metastases, Lung) when spread via the lymphatic vessels form metastases in the lung, the AS-cells (Ascites, Solid) do not form secondary tumors. The ASML-cells do not attach on glass or plastic but grow in suspension; AS-cells, can be cultivated as monolayers. The ASML-cells form loosely packed clusters when they are shaken in a gyratory shaker, AS-cells produce well organized aggregates in which the intercellular contacts are very intensive. When a mixture of cells from both lines is aggregated the two types sort out and the line-specific aggregate or cluster is formed without interaction between the two types. ASML-cells remain spherical when confronted with pieces of the aortic wall and there are no signs of reaction with the underlying endothelial cells. The endothelium is drastically altered when AS-cells are seeded on top of the aortic wall: the tumor cells flatten, penetrate the endothelial layer and induce the endothelial cells to retract. These phenomena can also be seen in confrontations with the mesothelium of the diaphragm. As also cells from aggregates or clusters behave as the single cells we conclude that the newly formed heterotypic contacts are favored over homotypic ones. In addition they have proved to be more intensive.

Animals↗

Fine-scale spatial genetic structure with nonuniform distribution of individuals.

This paper presents the first theoretical study of spatial genetic structure within nonuniformly distributed continuous plant populations. A novel individual-based model of isolation by distance was constructed to simulate genetic evolution within such populations. We found larger values of spatial genetic autocorrelations in highly clumped populations than in uniformly distributed populations. Most of this difference was caused by differences in mean dispersal distances, but aggregation probably also produced a slight increase in spatial genetic structure. Using an appropriate level of approximation of the continuous distribution of individuals in space, we assessed the potential effects of density, seed and pollen dispersal, generation overlapping, and overdominance selection at an independent locus, on fine-scale genetic structure, by varying them separately in a few particular cases with extreme clumping. When selfing was allowed, all these input variables influenced both aggregation and spatial genetic structure. Most variations in spatial genetic structure were closely linked to variations in clumping and/or local density. When selfing was not allowed, spatial genetic structure was lower in most cases.

Biological Evolution↗

Cell-cell and cell-matrix interactions differentially regulate the expression of hepatic and cytoskeletal genes in primary cultures of rat hepatocytes.

Freshly isolated adult rat hepatocytes exhibit a flat, extended morphology when cultured on dried rat tail collagen in the presence of growth factors; they actively synthesize DNA and express high levels of cytoskeletal mRNAs and proteins (actin, tubulin, cytokeratins, vinculin, alpha-actinin, and desmoplakin), while exhibiting low levels of liver-specific mRNAs (albumin, alpha 1-inhibitor III, and alpha 1-antitrypsin) and limited synthesis and secretion of albumin. Hepatocytes cultured on hydrated gel matrix from the Engelbreth-Holm-Swarm (EHS) mouse tumor form small spherical aggregates and exhibit low DNA, cytoskeletal mRNA, and protein synthesis, while at the same time exhibiting elevated liver-specific mRNAs and albumin production; these cells, therefore, more nearly conform to the program of gene expression seen within the normal animal. Hepatocytes on hydrated rat tail collagen resemble those on dry collagen when cultured at low density, but at high density they form compact trabecular aggregates, synthesize negligible amounts of DNA, and maintain a pattern of gene expression resembling that of hepatocytes seeded on the EHS matrix. If cell morphology is compact, as on EHS or on hydrated rat tail collagen when densely populated, DNA synthesis and expression of cytoskeletal genes are low, while liver-specific mRNAs are abundant. When cells are extended the opposite is the case. Without the growth supplement DNA synthesis is low throughout but gene expression is little affected. These studies point to the importance of cell-cell and cell-matrix interactions in determining the differentiated phenotype of hepatocytes, and they reveal an inverse relationship between cytoskeletal and liver-specific protein expression.

Albumins↗

Metastatic adenocarcinoma involving a mesothelial/monocytic incidental cardiac excrescence (cardiac MICE)

Mesothelial/monocytic incidental cardiac excrescence (MICE) is a recently described, peculiar microscopic finding in the endocardium or pericardium. These lesions are characterized by a mixture of mesothelial cell clusters and histiocytes, aggregated by fibrin. They have been interpreted as reactive or even artifactual, and the importance of distinguishing these aggregations from metastatic carcinoma has been emphasized. We report a unique case of a MICE that was seeded by clusters of metastatic adenocarcinoma cells. The patient was a 38-year-old woman with no history of previous cardiac instrumentation who was found to have an adenocarcinoma of the right lung involving the hilus but apparently not invading the pericardium. At surgery, a small fragment of tissue was found floating in the pericardial cavity, and microscopic examination revealed a cluster of histiocytes, mesothelial cells and fibrin (components of usual, benign MICE) in which rare pleomorphic adenocarcinoma cells were scattered. Unlike the surrounding mesothelial cells and histiocytes, the pleomorphic cells stained for carcinoembryonic antigen, epithelial membrane antigen, and BerEP4 and focally produced intracellular mucin, confirming their malignant glandular nature. It is possible that the surrounding mesothelial cells, histiocytes, and fibrin were formed in response to invasion of the pericardial space by adenocarcinoma. This case indicates that not all lesions with the characteristic architecture of MICE can be dismissed as non-neoplastic without careful evaluation of both the cellular constituents and the clinical circumstances.

Adenocarcinoma↗

Biophysical characterization of longer forms of amyloid beta peptides: possible contribution to flocculent plaque formation.

Alzheimer's disease is characterized by amyloid deposits in the parenchyma and vasculature of the brain. The plaques are mainly composed of amyloid beta (Abeta) peptides ending in residues 40 and 42. Novel longer Abeta peptides were found in brain homogenates of mouse models of Alzheimer's disease and human brain tissue of patients carrying the familial amyloid precursor protein V717F mutation. The biophysical characteristics of these longer Abeta peptides and their role in plaque formation are not understood. We chose to focus our studies on Abeta peptides ending in residues Ile45, Val46 and Ile47 as these peptides were identified in human brain tissue. A combination of circular dichroism and electron microscopy was used to characterize the secondary and tertiary structures of these peptides. All three longer Abeta peptides consisted mainly of a beta-sheet secondary structure. Electron microscopy demonstrated that these beta-structured peptides formed predominantly amorphous aggregates, which convert to amyloid fibres over extended time periods. As these longer peptides may act as seeds for the nucleation of fibrils composed predominantly of shorter amyloid peptides, these interactions were studied. All peptides accelerated the random to beta-structural transitions and fibril formation of Abeta40 and 42.

Amyloid beta-Peptides↗