Search results for "Instability"

Tumor Hypoxia and Malignant Progression

2004

Publisher Summary This chapter discusses tumor hypoxia and malignant progression. Hypoxic (or anoxic) areas arise as a result of an imbalance between the supply and the consumption of oxygen. Whereas in normal tissues or organs the O2 supply matches the metabolic requirements, in locally advanced solid tumors the O2 consumption rate of neoplastic as well as stromal cells may outweigh an insufficient oxygen supply and result in the development of tissue areas with very low O2 levels. Major pathogenetic mechanisms involved in the emergence of hypoxia in solid tumors are (a) severe structural and functional abnormalities of the tumor microvessels (b) a deterioration of the diffusion geometry, …

Biological consequences of tumor hypoxia

2001

Growing evidence from experimental and clinical studies points to the fundamental, pathophysiologic role of hypoxia in solid tumors. Intratumoral hypoxia is a consequence of a structurally and functionally disturbed microcirculation, with deterioration of the diffusion geometry and of tumor-associated anemia. Hypoxia-induced changes of the proteome in the neoplastic and stroma cells may lead to neoplastic growth impairment through molecular mechanisms, resulting in cellular quiescence, differentiation, and apoptosis. Alternatively, hypoxia-induced proteome changes activating nonspecific stress response, anaerobic metabolism, angiogenesis, tissue remodeling, and change of cell contacts may p…

Physiological Mechanisms of Treatment Resistance

2009

It is generally accepted that tumor perfusion, microcirculation, characteristics of the interstitial space of tumors, oxygen (and nutrient) supply, tissue pH distribution and the bioenergetic status—factors that are usually closely linked and that define the so-called pathophysiological microenvironment—can markedly influence the therapeutic response of malignant tumors to sparsely ionizing radiation, chemotherapy, photodynamic therapy, hormonal therapy and immunotherapy. Besides more direct mechanisms involved in the development of acquired therapeutic resistance, there are in addition, obstacles in intratumor pharmacokinetics of antitumor agents due to delivery problems caused by an inade…

Genome structure reveals the diversity of mating mechanisms in Saccharomyces cerevisiae x Saccharomyces kudriavzevii hybrids, and the genomic instabi…

2020

Interspecific hybridization has played an important role in the evolution of eukaryotic organisms by favouring genetic interchange between divergent lineages to generate new phenotypic diversity involved in the adaptation to new environments. This way, hybridization between Saccharomyces species, involving the fusion between their metabolic capabilities, is a recurrent adaptive strategy in industrial environments. In the present study, whole-genome sequences of natural hybrids between Saccharomyces cerevisiae and Saccharomyces kudriavzevii were obtained to unveil the mechanisms involved in the origin and evolution of hybrids, as well as the ecological and geographic contexts in which sponta…

Patterns of genomic instability in gastric cancer: clinical implications and perspectives

2007

In gastric cancer (GC) the loss of genomic stability represents a key molecular step that occurs early in the carcinogenesis process and creates a permissive environment for the accumulation of genetic and epigenetic alterations in tumor suppressor genes and oncogenes. It is widely accepted that GC can follow at least two major genomic instability pathways, microsatellite instability (MSI) and chromosome instability (CIN). MSI is responsible for a well-defined subset of GCs. CIN represents a more common pathway comprising heterogeneous subsets of GC. In addition to MSI and CIN, the CpG islands methylator phenotype (CIMP) plays an important role in gastric carcinogenesis. CIMP may lead to th…

Differential diagnosis problems in a patient with dysphonia and chronic lymphocytic leukemia

2014

SUMMARY Dysphonia is frequently an expression of laryngitis, especially when it comes in the evolution of an immunosuppressed patient, as happens in chronic lymphoproliferation. But other causes of dysphonia should also not be forgotten, including the possibility of new malignancies, especially due to the fact that these patients have genomic instability that predisposes to appearance of a second or even a third cancer. We present the case of a patient who developed dysphonia during chronic lymphocytic leukemia evolution. Its etiology was a mediastinal compression through lymph nodes, not linked to leukemia, but produced by metastases of a bronchopulmonary cancer, appeared recently. Dysphon…

Pattern formation in 3-D numerical models of down-built diapirs initiated by a Rayleigh–Taylor instability

2015

Gesteigerte Expression des Tunnelproteins Connexin43 in der obstruierten Rattenblase - eine mögliche Ursache obstruktionsbedingter Blasenhyperaktivit…

2002

Fragestellung: Blasenhyperaktivitat ist ein haufiges und belastendes Symptom der Blasenauslassobstruktion und persistiert oft auch nach effektiver Deobstruierung. Gap junctions werden schon langer als mogliche Ursache von Blasenhyperaktivitat diskutiert. Wir untersuchten die regionale Verteilung des Gap-junction-Proteins Connexin43 in obstruierten und nicht obstruierten Rattenblasen. Material und Methode: Durch partielle Ligatur der Urethra wurde eine Obstruktion bei weiblichen Ratten erzeugt. Nach 6 Wochen wurden die Blasen entnommen und fur den molekularbiologischen Nachweis von Connexin43-mRNS durch kompetitive RT-PCR oder die immunhistochemische Detektion von Connexin43-Protein weiterve…

Hot cracking in Al–Mg–Si alloy laser welding – operating parameters and their effects

2005

Abstract Hot cracking is a phenomenon that frequently occurs in the laser welding of some “special” alloys, such as the aluminium–magnesium–silicon type. Each occurrence of this phenomenon needs to be studied in itself, taking into account not only the individual, but also the interactive, influences of the various parameters. The advantage of using laser beams in welding processes lies in the speeds that can be reached. The disadvantage, however, is that, owing to the high cooling rates characteristic of the interaction between the laser beam and the material, the welding speed itself becomes a cause of hot cracking. The aim of this paper is to see how this disadvantage may be eliminated. …

Electron-density critical points analysis and catastrophe theory to forecast structure instability in periodic solids

2018

The critical points analysis of electron density,i.e. ρ(x), fromab initiocalculations is used in combination with the catastrophe theory to show a correlation between ρ(x) topology and the appearance of instability that may lead to transformations of crystal structures, as a function of pressure/temperature. In particular, this study focuses on the evolution of coalescing non-degenerate critical points,i.e. such that ∇ρ(xc) = 0 and λ1, λ2, λ3≠ 0 [λ being the eigenvalues of the Hessian of ρ(x) atxc], towards degenerate critical points,i.e. ∇ρ(xc) = 0 and at least one λ equal to zero. The catastrophe theory formalism provides a mathematical tool to model ρ(x) in the neighbourhood ofxcand allo…