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PubMedDate not supplied

[Experimental teratocarcinoma in mice: a model system for the study of the relationship between cellular surface antigens and embryonic differentiation].

Several cell lines (either of embryonal carcinoma or of differentiated cells derived from teratomas) have been established in vitro from transplantable testicular teratomas. Primitive cell lines, propagated in vitro as embryonal carcinoma have retained the ability of the original tumor to differentiate in vivo or in vitro into must embryonic cell types. Features of this model system for study of early embryogenesis are described. Emphasis is placed on the description of the cell surface antigens of several cell lines. Syngeneic antisera raised against two primitive lines (F9 and PCC4) and against a differentiated one (Endo) have allowed the detection of three groups of cell surface antigens, present on teratoma cells, tumor cells and embryonic cells. The F9 antigen appears to be specific to be specific of the very early steps of egg development (morula and blastocyst). After egg implantation, it keeps expressed on the cells of the male germ line. The PCC4 antigen has a similar cell type distribution but appears to be more specific of multipotential cells. The Endo antigen is essentially specific of endodermal derivatives. The F9 antigen is probably specified by the wild type allele (+ tl2) of the tl2 gene at the T-Locus of the mouse, a gene which plays some critical role in early development. The molecular structure of this antigen, as determined from immunoprecipitates is very similar to that of H-2 antigens. In addition, a cross-reacting material is found in Man, with a tissue distribution identical to that found in the mouse.

Alleles↗
PubMed1978

Asymmetric budding of viruses in epithelial monlayers: a model system for study of epithelial polarity.

Infection of two different lines of polarized epithelial cells grown as monolayers with several types of enveloped viruses results, for each virus type, in a characteristic asymmetric budding of virions. Influenza virus (WSN strain), simian virus 5, and Sendai virus bud exclusively from the free (apical) surface of the cells, while vesicular stomatitis virus acquires its envelope only from the basolateral plasma membrane. Because different viruses select specific domains of plasma membrane in the same cell type, virus-infected epithelial monolayers can provide an excellent model system for studies of the mechanisms that generate regional differences in the distribution of plasma membrane components of epithelial cells.

Cell Line↗
PubMed1988

Erythrocyte aging: a comparison of model systems for simulating cellular aging in vitro.

Senescent cell antigen (SCANT) is a "neo antigen" that appears on the surface of normal old cells and initiates IgG binding and cellular removal. To investigate the mechanism by which SCANT is generated from its parent molecule, band 3, we subjected intact human erythrocytes to treatments that have been reported to result in changes in band 3 and/or to mimick aging in vitro. The validity of these treatments as model systems for erythrocyte aging was evaluated using a "red cell aging panel" that provides a biochemical profile of a senescent red cell. Treatments were assessed for their ability to induce in vitro the following changes observed in normal erythrocytes aged in vivo: 1 increased breakdown of band 3 as detected by immunoblotting, 2 decrease in anion transport efficiency as detected with a sulfate self-exchange assay, 3 decrease in total glyceraldehyde 3-phosphate dehydrogenase activity with an increase in membrane-bound activity, and 4 increase in the binding of autologous IgG as detected with a protein A binding assay. Neither incubation with the free radical-generating xanthine oxidase/xanthine system, nor treatment with malondialdehyde, and end product of free radical-initiated lipid (per)oxidation, results in age-specific changes. Loading of the cells with calcium and oxidation with iodate results in increased breakdown of band 3, but does not lead to increased binding of autologous IgG. Only erythrocytes that have been stored for 3-4 weeks show the same structural and functional changes as observed during aging in vivo.

Anion Exchange Protein 1, Erythrocyte↗
PubMed2000

The role of oxygen and reduced oxygen species in nitric oxide-mediated cytotoxicity: studies in the yeast Saccharomyces cerevisiae model system.

The cytotoxicity of nitric oxide (NO) is well established, yet the mechanism(s) of its cytotoxicity is (are) still undefined and a matter of significant interest and speculation. Many of the previously proposed mechanisms for NO-mediated cytotoxicity involve interactions between NO and molecular oxygen (O(2)) and/or O(2)-derived species such as O(-)(2) and H(2)O(2). The yeast Saccharomyces cerevisiae represents a useful model system for evaluating the role of O(2) and O(2)-derived species in NO-mediated cytotoxicity. This study examines the contribution of O(2) and O(2)-derived species to NO-mediated cytotoxicity in the yeast S. cerevisiae. NO-mediated cytotoxicity was determined to be O(2)-dependent. However, this O(2) dependence was only minimally due to the generation of O(2)-derived species such as O(-)(2) and/or H(2)O(2).

Hydrogen Peroxide↗
PubMed1988

Radioimmunolocalization and selective delivery of radiation in a rat model system: comparison of intact and fragmented antibody.

Monoclonal antibody (MoAb) fragments are known to have advantages over intact immunoglobulins for radioimmunoscintigraphy. It is less clear whether they are as effective in the delivery of radioimmunotherapy. The imaging and dosimetric properties of an intact MoAb, K-1-21, reactive against human kappa light chains (LC) were compared with that of its F(ab')2 and Fab fragments using a normal rat model system. Two days after injection of 131I-K-1-21 into rats bearing antigen-sepharose implants, gamma camera images showed specific localization of the MoAb to the target (kappa LC) but not to the control (lambda LC) implant. Better images were obtained with K-1-21 F(ab')2 than with Fab or intact antibody. Mean kappa implant: blood ratios were 8.6 +/- 3.9 for Fab, 7.9 +/- 1.8 for F(ab')2 and 2.0 +/- 0.3 for intact K-1-21. The improvement associated with the use of 131I-K-1-21 fragments was, however, achieved at the expense of lower absolute values of activity at the target site. Thus the absorbed dose delivered to the implant by the intact K-1-21 was double that delivered with F(ab')2 and six times that delivered with Fab. As intact K-1-21 also delivered a greater radiation dose to normal tissues, F(ab')2 fragments may have the greatest overall advantages for therapy with radionuclide MoAb conjugates.

Animals↗
PubMed1999

Convenient synthesis of lactuloselysine and its use for LC-MS analysis in milk-like model systems.

The synthesis of the Amadori product lactuloselysine [N(epsilon)-(1-deoxy-D-lactulosyl-1)-L-lysine] was obtained starting from FMOC-lysine-OH (N(alpha)-9-fluorenylmethoxy-carbonyl-N(epsilon)H(2)-L-lysine-OH) and lactose. Compound identity was confirmed by MALDI-ToF, electrospray, and NMR analysis. A selective LC-MS procedure which allowed the detection of lactuloselysine up to 10 ng mL(-)(1) was set up and used to follow the formation of the compound in a lactose-lysine model system; quantification of this molecule after complete enzymatic hydrolysis of whey-proteins from milk samples was also performed.

Animals↗
PubMed2005

Inter- and intramolecular hydrogen bonding in phenol derivatives: a model system for poly-L-tyrosine.

The ultrafast dynamics of solutions of phenol and two phenol derivatives--hydroquinone (1,4-benzenediol) and pyrocatechol (1,2-benzenediol)--have been studied with Optically Heterodyne-Detected Optical Kerr-Effect (OHD-OKE) spectroscopy. The solvents, methanol and acetonitrile, were selected to provide strong and weak solvent-solute hydrogen-bonding interactions, respectively, while pyrocatechol features an intramolecular hydrogen bond. Together these provide a series of model systems for polypeptides such as polytyrosine, which facilitate the direct study of inter- and intramolecular hydrogen bonding. A broad contribution to the Raman spectral density of the methanol solutions at frequencies between 150 and 300 cm(-1) has been observed that is absent in acetonitrile. This contribution has been assigned to solvent-solute hydrogen-bond stretching vibrations. The OHD-OKE response of poly-L-tyrosine has been measured and was found to contain a similar contribution. Density functional theory geometry optimizations and normal mode calculations have been performed using the B3LYP hybrid functional and 6-311++G** basis set. These have yielded a complete assignment of the low-frequency Raman and far-infrared spectra of pyrocatechol for the first time, which has provided information on the nature of the intramolecular hydrogen bond of pyrocatechol.

Computer Simulation↗
PubMed2000

[Intervention in the process of work-health-disease based on the Betty Neuman's systems model].

This article proposes a referential landmark directed to the worker's area, attempting to answer theoretical and methodological needs in this field of action and professional intervention. The controversy of the relation work-health-disease and its implications to nursing are very challenging and, at the same time, quite intriguing as we seek for its interrelationships. Therefore, we intend to unfold them adopting the structural path of The Neuman Systems Model, systematizing a proposal of nursing action compromised with the relation work-health-disease. Also, we wish to investigate stress factors at work, environment and individual resources to deal with them, and the goals established to the interaction between nurse and worker. This interaction is seen as fundamental to the proposal of educational and/or assistencial actions to the worker's health. It is our intention to contribute with information and propositions to induce reflective thought and debate about the subject.

Humans↗
PubMed1988

Anti-fibrin monoclonal antibodies for radioimmunodetection: preliminary assessment in a rat model system.

The D Dimer (DD) site formed by linkage of D domains from adjacent fibrin (FN) molecules is unique to cross-linked FN and its degradation products and is not found in FN monomer or fibrinogen (FB). Thus monoclonal antibodies (MAb) reactive to DD should have a very suitable specificity for in vivo thrombus detection. Two anti-DD MAbs have been labelled with 131-I and assessed as scintigraphic agents in a normal rat model system. Each rat received 3 sc implants of antigen covalently coupled to Sepharose beads: 1) Human DD 2) Human FB 3) Glycine (GL) (control). Scintigraphic images taken 7 days after injection of 131-I anti DD MAb showed clear localisation of both anti-DD MAbs to the DD implant rather than to the FB or GL implants with no localisation in normal tissues. This was confirmed in biodistribution studies. Injection of anti-DD MAbs DD-3B6/22 and DD-IC3/108 resulted in DD: blood ratios of 10.4 +/- 0.6 and 4.9 +/- 0.3 respectively. These results suggest that anti-DD MAbs will have potential for thrombus radioimmunodetection.

Animals↗
PubMed1992

Modulatory influences of estrogen and progesterone on cervical dysplasia in mice model system.

The effectiveness of estrogen and progesterone on the different types of cervical dysplasia are poorly documented compared to their effects on the total process of cervical carcinogenesis. In the present study, an attempt has been made to evaluate the influences of estrogen and progesterone on the different types of cervical dysplasia which are believed to be the antecedents of cervical carcinoma induced by chemical carcinogen (20-Methy cholanthrene) in the mice model system. It was observed that moderate dysplasia is less aberrant than that of marked dysplasia which could not be modified by either of the hormones.

Animals↗
PubMedDate not supplied

[Electrogenic reactions in cytochrome bf-complexes in a model system].

By using the direct electrometric technique, the flash-induced generation of the difference in electrical potentials in hybrid proteoliposomes containing photosystem 1 and cytochrome bf complexes from cyanobacteria Synechocystis sp. PCC 6803 was studied. It was shown that the primary donor P700 in photosystem I and cytochrome f are predominantly localized near the outer surface of the proteoliposomal membrane, which made it possible to study for the first time electrogenic reactions of cytochrome bf complexes in a model system. In the presence of decyl plastoquinol and cytochrome c6, besides the fast electrogenic phase determined by the separation of charges in photosystem I, additional electrogenic phases in the submillisecond and millisecond ranges were observed. These phases were partially depressed in the presence of the inhibitor of the plastoquinone reductase site NQNO and fully disappeared after the addition of the inhibitor of the plastoquinol oxidase site stigmatellin. A possible mechanism of the electrogenic reactions in cytochrome bf complexes was considered.

Cyanobacteria↗
PubMed2006

Amphioxus and tunicates as evolutionary model systems.

One important question in evolutionary biology concerns the origin of vertebrates from invertebrates. The current consensus is that the proximate ancestor of vertebrates was an invertebrate chordate. Today, the invertebrate chordates comprise cephalochordates (amphioxus) and tunicates (each a subphylum in the phylum Chordata, which also includes the vertebrate subphylum). It was widely accepted that, within the chordates, tunicates represent the sister group of a clade of cephalochordates plus vertebrates. However, recent studies suggest that the evolutionary positions of tunicates and cephalochordates should be reversed, the implications of which are considered here. We also review the two major groups of invertebrate chordates and compare relative advantages (and disadvantages) of each as model systems for elucidating the origin of the vertebrates.

Animals↗
PubMed2006

C. elegans as a model system to study the function of the COG complex in animal development.

The conserved oligomeric Golgi (COG) complex is an octameric protein complex associated with the Golgi apparatus and is required for proper sorting and glycosylation of Golgi resident enzymes and secreted proteins. Although COG complex function has been extensively studied at the cellular and subcellular levels, its role in animal development mostly remains unknown. Recently, mutations in the components of the COG complex were found to cause abnormal gonad morphogenesis in Caenorhabditis elegans. In C. elegans, the COG complex acts in the glycosylation of an ADAM (a disintegrin and metalloprotease) family protein, MIG-17, which directs migration of gonadal distal tip cells to lead gonad morphogenesis. This is the first link between the COG complex and the function of an ADAM protease that is directly involved in organ morphogenesis, demonstrating the potential of C. elegans as a model system to study COG function in animal development.

Animals↗
PubMed2001

A normal ocular motor system model that simulates the dual-mode fast phases of latent/manifest latent nystagmus.

The fast phases of latent/manifest latent nystagmus (LMLN) may either cause the target image to fall within (foveating) or outside (defoveating) the foveal area. We previously verified that both types are generated by the same mechanism as voluntary saccades and propose a hypothetical, dual-mode mechanism (computer model) for LMLN that utilizes normal ocular-motor control functions. Fixation data recorded during the past 30 years from 97 subjects with LMLN using both infrared and magnetic search coil oculography were used as a basis for our simulations. The MATLAB/Simulink software was used to construct a robust, modular, ocular motor system model, capable of simulating LMLN. Fast-phase amplitude versus both peak velocity and duration of simulated saccades were equivalent to those of saccades in normal subjects. Based on our LMLN studies, we constructed a hypothetical model in which the slow-phase velocity acted to trigger the change between foveating and defoveating LMLN fast phases. Foveating fast phases were generated during lower slow-phase velocities whereas defoveating fast phases occurred during higher slow-phase velocities. The bidirectional model simulated Alexander's law behavior under all viewing and fixation conditions. Our ocular-motor model accurately simulates LMLN patient ocular motility data and provides a hypothetical explanation for the conditions that result in both foveating and defoveating fast phases. As is the case for normal physiological saccades, the position error determined the saccadic amplitudes for foveating fast phases. However, the final slow-phase velocity determined the amplitudes of defoveating fast phases. In addition, we suggest that individuals with LMLN use their fixation subsystem to further decrease the slow-phase velocity as the target image approaches the foveal center.

Adolescent↗
PubMed2003

Triazole fungicide degradation in peaches in the field and in model systems.

The degradation of five triazole fungicides (cyproconazole, hexaconazole, penconazole, propiconazole, tebuconazole) in peaches was evaluated in field studies to establish whether at the preharvest interval the residue levels were below the legal limit established in Italy. All fungicides, except propiconazole, showed higher residues than the legal limits because of their high stability. In fact, some did not decrease at all (cyproconazole, penconazole, tebuconazole), while others decreased only in part. The increasing weight of the fruit during growth was the main factor leading to an apparent decrease in pesticide levels on a weight for weight basis. The trials on model systems showed that co-distillation and sunlight photodegradation were the main mechanisms leading to a decrease in triazole levels. Although these fungicides are systemic, they did not enter the fruit and all residues were only present in the peel.

Chromatography, Gas↗
PubMed2000

Dictyostelium discoideum: a new host model system for intracellular pathogens of the genus Legionella.

The soil amoeba Dictyostelium discoideum is a haploid eukaryote that, upon starvation, aggregates and enters a developmental cycle to produce fruiting bodies. In this study, we infected single-cell stages of D. discoideum with different Legionella species. Intracellular growth of Legionella in this new host system was compared with their growth in the natural host Acanthamoeba castellanii. Transmission electron microscopy of infected D. discoideum cells revealed that legionellae reside within the phagosome. Using confocal microscopy, it was observed that replicating, intracellular, green fluorescent protein (GFP)-tagged legionellae rarely co-localized with fluorescent antibodies directed against the lysosomal protein DdLIMP of D. discoideum. This indicates that the bacteria inhibit the fusion of phagosomes and lysosomes in this particular host system. In addition, Legionella infection of D. discoideum inhibited the differentiation of the host into the multicellular fruiting stage. Co-culture studies with profilin-minus D. discoideum mutants and Legionella resulted in higher rates of infection when compared with infections of wild-type amoebae. Because the amoebae are amenable to genetic manipulation as a result of their haploid genome and because a number of cellular markers are available, we show for the first time that D. discoideum is a valuable model system for studying intracellular pathogenesis of microbial pathogens.

Acanthamoeba↗
PubMed2006

FAMS complex: a fully automated homology modeling system for protein complex structures.

The formation of a protein-protein complex is responsible for many biological functions; therefore, three-dimensional structures of protein complexes are essential for deeper understandings of protein functions and the mechanisms of diseases at the atomic level. However, compared with individual proteins, complex structures are difficult to solve experimentally because of technical limitations. Thus a method that can predict protein complex structures would be invaluable. In this study, we developed new software, FAMS Complex; a fully automated homology modeling system for protein complex structures consisting of two or more molecules. FAMS Complex requires only sequences and alignments of the target protein as input and constructs all molecules simultaneously and automatically. FAMS Complex is likely to become an essential tool for structure-based drug design, such as in silico screening to accelerate drug discovery before an experimental structure is solved. Moreover, in this post-genomic era when huge amounts of protein sequence information are available, a major goal is the determination of protein-protein interaction networks on a genomic scale. FAMS Complex will contribute to this goal, because its procedure is fully automated and so is suited for large-scale genome wide modeling.

Automation↗
PubMed1977

Cell line A549: a model system for the study of alveolar type II cell function.

Cell line A549, a continuously cultured line derived from a human pulmonary adenocarcinoma that has morphologic and biochemical features of the pulmonary alveolar type II cell, was studied with regard to saturated phosphatidylcholine synthesis and secretion. Evaluation of a number of culture media showed that those media that supported the most rapid rate of in vitro growth were least optimal for saturated phosphatidylcholine synthesis. Similarly, a labeled precursor (choline labeled with tritium) was most efficiently converted to saturated phosphatidylcholine when growth was slow or arrested, whereas during phases of active cellular proliferation a greater proportion was incorporated into unsaturated (structural) phosphatidylcholine. De novo synthesis of phosphatidylcholine was primarily via the cytidine diphosphate-choline pathway, because no incorporation of labeled methyl groups from S-adenosyl-L-methionine was observed. Cortisol stimulated tritium-labeled choline incorporation into saturated phosphatidylcholine in a manner that likely involed a steroid receptor system, whereas cortisone was inactive. The half-life of cellular saturated phosphatidylcholine was of the order of 100 hours and could be accounted for virtually entirely by release of this phospholipid into the medium unchanged. Both cholinergic and adrenergic agents in high doses modestly stimulated the release of pre-labeled saturated phosphatidylcholine from the cells, and the response to these secretagogues was significantly enhanced by cortisol. Cell line A 549 promises to be a useful model system for studies of the cellular events involved in pulmonary saturated phosphatidylcholine synthesis and secretion.

Cell Differentiation↗