Biological Models (biological + models)

Distribution by Scientific Domains

Selected Abstracts

Enhanced amygdala and medial prefrontal activation during nonconscious processing of fear in posttraumatic stress disorder: An fMRI study

Richard A. Bryant
Abstract Biological models of posttraumatic stress disorder (PTSD) suggest that patients will display heightened amygdala but decreased medial prefrontal activity during processing of fear stimuli. However, a rapid and automatic alerting mechanism for responding to nonconscious signals of fear suggests that PTSD may display heightened rather than decreased MPFC under nonconscious processing of fear stimuli. This study used functional magnetic resonance imaging to examine blood oxygenation level-dependent signal changes during nonconscious presentation (16.7 ms, masked) of fearful and neutral faces in 15 participants with PTSD and 15 age and sex-matched healthy control participants. Results indicate that PTSD participants display increased amygdala and MPFC activity during nonconscious processing of fearful faces. These data extend existing models by suggesting that the impaired MPFC activation in PTSD may be limited to conscious fear processing. Hum Brain Mapp, 2008. © 2007 Wiley-Liss, Inc. [source]

Glutamylated tubulin: Diversity of expression and distribution of isoforms

CYTOSKELETON, Issue 1 2003
Marie-Louise Kann
Abstract Glutamylation of , and , tubulin isotypes is a major posttranslational modification giving rise to diversified isoforms occurring mainly in neurotubules, centrioles, and axonemes. Monoglutamylated tubulin isoforms can be differentially recognized by two mAbs, B3 and GT335, which both recognize either polyglutamylated isoforms. In the present study, immunoelectron microscopy and immunofluorescence analyses were performed with these two mAbs to determine the expression and distribution of glutamylated tubulin isoforms in selected biological models whose tubulin isotypes are characterized. In mouse spermatozoa, microtubules of the flagellum contain polyglutamylated isoforms except in the tip where only monoglutamylated isoforms are detected. In spermatids, only a subset of manchette microtubules contain monoglutamylated tubulin isoforms. Cytoplasmic microtubules of Sertoli cells are monoglutamylated. Mitotic and meiotic spindles of germ cells are monoglutamylated whereas the HeLa cell mitotic spindle is polyglutamylated. Three models of axonemes are demonstrated as a function of the degree and extent of tubulin glutamylation. In lung ciliated cells, axonemes are uniformly polyglutamylated. In sea urchin sperm and Chlamydomonas, flagellar microtubules are polyglutamylated in their proximal part and monoglutamylated in their distal part. In Paramecium, cilia are bi- or monoglutamylated only at their base. In all cells, centrioles or basal bodies are polyglutamylated. These new data emphasize the importance of glutamylation in all types of microtubules and strengthen the hypothesis of its role in the regulation of the intracellular traffic and flagellar motility. Cell Motil. Cytoskeleton 55:14,25, 2003. © 2003 Wiley-Liss, Inc. [source]

Toxicity Evaluation for Safe Use of Nanomaterials: Recent Achievements and Technical Challenges

Saber M. Hussain
Abstract Recent developments in the field of nanotechnology involving the synthesis of novel nanomaterials (NM) have attracted the attention of numerous scientists owing to the possibility of degradative perturbations in human health. This Review evaluates previous investigations related to NM toxicity studies using biological models and describes the limitations that often prevent toxicologists from identifying whether NM pose a real hazard to human health. One major limitation to assess toxicity is the characterization of the NM prior to and after exposure to living cells or animals. The most relevant physicochemical characteristics of NM are: size, surface chemistry, crystallinity, morphology, solubility, aggregation tendency, homogeneity of dispersions, and turbidity. All of these properties need to be assessed in order to determine their contribution to toxicity. Due to the lack of appropriate methods to determine the physicochemical nature of nanoparticles in biological systems, the exact nature of NM toxicity is not fully described or understood at this time. This Review emphasizes the need for state-of-the-art physicochemical characterization, the determination of appropriate exposure protocols and reliable methods for assessing NM internalization and their kinetics in living organisms. Once these issues are addressed, optimal experimental conditions could be established in order to identify if NM pose a threat to human health. Multidisciplinary research between materials scientists and life scientists should overcome these limitations in identifying the true hazards of NM. [source]

Urethral ,recurrence' found 14 years after radical cystectomy

Abstract We report a case of transitional cell urethral cancer diagnosed 14 years after radical cystectomy. Traditionally, in the postcystectomy setting, these cancers have been referred to as ,recurrences'. We review the biological models for the oncogenesis of these cancers and propose that they are typically a result of a field cancerization effect, rather than being derived from the same clone responsible for the original urothelial tumor. [source]

Systems biology approaches for toxicology,

William Slikker Jr
Abstract Systems biology/toxicology involves the iterative and integrative study of perturbations by chemicals and other stressors of gene and protein expression that are linked firmly to toxicological outcome. In this review, the value of systems biology to enhance the understanding of complex biological processes such as neurodegeneration in the developing brain is explored. Exposure of the developing mammal to NMDA (N -methyl- d -aspartate) receptor antagonists perturbs the endogenous NMDA receptor system and results in enhanced neuronal cell death. It is proposed that continuous blockade of NMDA receptors in the developing brain by NMDA antagonists such as ketamine (a dissociative anesthetic) causes a compensatory up-regulation of NMDA receptors, which makes the neurons bearing these receptors subsequently more vulnerable (e.g. after ketamine washout), to the excitotoxic effects of endogenous glutamate: the up-regulation of NMDA receptors allows for the accumulation of toxic levels of intracellular Ca2+ under normal physiological conditions. Systems biology, as applied to toxicology, provides a framework in which information can be arranged in the form of a biological model. In our ketamine model, for example, blockade of NMDA receptor up-regulation by the co-administration of antisense oligonucleotides that specifically target NMDA receptor NR1 subunit mRNA, dramatically diminishes ketamine-induced cell death. Preliminary gene expression data support the role of apoptosis as a mode of action of ketamine-induced neurotoxicity. In addition, ketamine-induced cell death is also prevented by the inhibition of NF- ,B translocation into the nucleus. This process is known to respond to changes in the redox state of the cytoplasm and has been shown to respond to NMDA-induced cellular stress. Although comprehensive gene expression/proteomic studies and mathematical modeling remain to be carried out, biological models have been established in an iterative manner to allow for the confirmation of biological pathways underlying NMDA antagonist-induced cell death in the developing nonhuman primate and rodent. Published in 2007 John Wiley & Sons, Ltd. [source]

Mathematical and biological models of blood coagulation.

A rebuttal

Photoreactivity of the Nonsteroidal Anti-inflammatory 2-Arylpropionic Acids with Photosensitizing Side Effects,

Francisco Boscá
ABSTRACT The photoreactivity of the nonsteroidal anti-inflammatory 2-arylpropionic acids benoxaprofen, carprofen, naproxen, ketoprofen, tiaprofenic acid, and suprofen is reviewed with special emphasis on fundamental photophysical and photochemical properties. The absorption and emission properties of the excited states of these drugs as well as their main photodegradation routes are summarized. The photochemical mechanisms are discussed on the basis of product studies and detection of short-lived intermediates by means of laser flash photolysis. After dealing with the unimolecular processes, attention is focused on the photosensitized reactions of key biomolecules, such as lipids, proteins or nucleic acids. Finally, a short section on the photobiological effects on simple biological models is also included. Although some earlier citations are included, the literature coverage is in general limited to the last decade. [source]

ORIGINAL ARTICLE: Urocortin Increases IL-4 and IL-10 Secretion and Reverses LPS-induced TNF-, Release from Human Trophoblast Primary Cells

Michela Torricelli
Problem, As urocortin (Ucn) is a placental peptide belonging to the corticotrophin-releasing hormone (CRH) family that modulates immune function in other biological models, this study evaluated Ucn effects on cytokines secretion from cultured human trophoblast cells. Method of study, Placentas were collected from normal term pregnancies after elective caesarean section, and primary trophoblast culture was prepared followed by the treatment of Ucn and/or CRH selective antagonists, antalarmin and astressin 2b. The anti-inflammatory cytokines IL-4 and IL-10 and the pro-inflammatory cytokine TNF-, were measured by ELISA. Results, Urocortin treatment induced a significant and dose-dependent increase of IL-4 and IL-10, whereas it did not affect TNF-, secretion. When incubated in the presence of LPS, Ucn reversed LPS-induced TNF-, release from cultured trophoblast cells, an effect that was blocked by the CRH-R2 selective antagonist, astressin 2b. Conclusion, Urocortin stimulates IL-4 and IL-10 secretion and reverses LPS-induced TNF-, release from trophoblast cells through action on CRH-R2 receptors, suggesting that this peptide may play a possible role as an anti-inflammatory agent. [source]

Model-free feedback design for a mixed cancer therapy

S. Chareyron
Abstract In this article, a model-free feedback control design is proposed for the drug administration in mixed cancer therapy. This strategy is very attractive because of the important issue of parameter uncertainties unavoidable when dealing with biological models. The proposed feedback scheme use past measurements to update an on-line simplified model. The control design is then based on model predictive control in which a suitable switching is performed between two different cost functions. The effectiveness of the proposed model-free control strategy is validated using a recently developed model (unknown to the controller) governing the cancer growth on a cells population level under combined immune and chemotherapy and using real human data. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

Prediction of ice content in biological model solutions when frozen under high pressure

B. Guignon
Abstract High pressure is, at least, as effective as cryoprotective agents (CPAs) and are used for decreasing both homogenous nucleation and freezing temperatures. This fact gives rise to a great variety of possible cryopreservation processes under high pressure. They have not been optimized yet, since they are relatively recent and are mainly based on the pressure,temperature phase diagram of pure water. Very few phase diagrams of biological material are available under pressure. This is owing to the lack of suitable equipment and to the difficulties encountered in carrying out the measurements. Different aqueous solutions of salt and CPAs as biological models are studied in the range of 0°C down to -35°C, 0.1 up to 250 MPa, and 0,20% w/w total solute concentration. The phase transition curves of glycerol and of sodium chloride with either glycerol or sucrose in aqueous solutions are determined in a high hydrostatic pressure vessel. The experimental phase diagrams of binary solutions were well described by a third-degree polynomial equation. It was also shown that Robinson and Stokes' equation at high pressure succeeds in predicting the phase diagrams of both binary and ternary solutions. The solute cryoconcentration and the ice content were calculated as a function of temperature and pressure conditions during the freezing of a binary solution. This information should provide a basis upon which high-pressure cryopreservation processes may be performed and the damages derived from ice formation evaluated. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]