Stress response inside perturbed particle assemblies

The effect of structural disorder on the stress response inside three dimensional particle assemblies is studied using computer simulations of frictionless sphere packings. Upon applying a localised, perturbative force within the packings, the resulting {\it Green's} function response is mapped inside the different assemblies, thus providing an explicit view as to how the imposed perturbation is transmitted through the packing. In weakly disordered arrays, the resulting transmission of forces is of the double-peak variety, but with peak widths scaling linearly with distance from the source of the perturbation. This behaviour is consistent with an anisotropic elasticity response profile. Increasing the disorder distorts the response function until a single-peak response is obtained for fully disordered packings consistent with an isotropic description.Comment: 8 pages, 7 figure captions To appear in Granular Matte

Adipocytes cause leukemia cell resistance to daunorubicin via oxidative stress response.

Adipocytes promote cancer progression and impair treatment, and have been shown to protect acute lymphoblastic leukemia (ALL) cells from chemotherapies. Here we investigate whether this protection is mediated by changes in oxidative stress. Co-culture experiments showed that adipocytes protect ALL cells from oxidative stress induced by drugs or irradiation. We demonstrated that ALL cells induce intracellular ROS and an oxidative stress response in adipocytes. This adipocyte oxidative stress response leads to the secretion of soluble factors which protect ALL cells from daunorubicin (DNR). Collectively, our investigation shows that ALL cells elicit an oxidative stress response in adipocytes, leading to adipocyte protection of ALL cells against DNR

Development of catecholamine and cortisol stress responses in zebrafish.

Both adrenal catecholamines and steroids are known to be involved in the stress response, immune function, blood pressure and energy homeostasis. The response to stress is characterized by the activation of the hypothalamus-pituitary-adrenal (HPA) axis and the sympathetic-adrenomedullary system, though the correlation with activation and development is not well understood. We evaluated the stress response of both cortisol and catecholamines during development in zebrafish. Zebrafish at two different stages of development were stressed in one of two different ways and cortisol and catecholamine were measured. Cortisol was measured by enzyme immune assay and catecholamine was measured by ELISA. Our results show that stress responses are delayed until after the synthesis of both cortisol and catecholamines. These observations suggest that the development of HPA axis may be required for the acquisition of the stress response for cortisol and catecholamines

The Effects of Epigenetics on Stress Response

Despite the vast amount of resources at the disposal of humanity today, the intricacies of human biology are often a mystery. The chemical and biological products of the human genome have been well studied and documented, but many of the chemical and neurological pathways are missing quite a few details. The human stress response is one of the most primal and valuable functions of this code that developed as a self- preservation mechanism (Hans, 1975) to naturally increase the odds of procreation. However, this function is prone to overload, particularly in individuals with certain epigenetic traits instilled by early life events, or even events taking place before their life began. Left unchecked, this overclocked stress response can lead to irate outward behavior with no known cause, and even worse, no known treatments. These irate behaviors can be seen on the experimental level; mice who are not adequately groomed by their mothers expressed an increase glucorticoid receptor (GR) response than mice with adequate grooming (Radtke et al., 2011). In human studies, these GR reactions are responsible for a myriad of mental disorders including suicidal tendencies, psychopathy, and increased aggression. Gene therapy is possible for these epigenetic factors, opening up new possibilities for treatment of mental disorders

The effect of a trapping procedure on the stress response of wild rainbow trout

Fish traps are a common research and management tool in which fish are subjected to procedures that elicit a stress response in other contexts. The effects of trapping on the stress response of sexually mature, wild rainbow trout Oncorhynchus mykiss were investigated during their upstream spawning migration by measuring concentrations of plasma cortisol, lactate, and glucose. Males had significantly lower basal plasma cortisol concentrations (6.1 ± 0.8 ng/mL [mean ± SE]) than females (21.4 ± 5.9 ng/mL). Similarly, the plasma cortisol response in males was significantly lower than that in females for all experiments. Fish working the barrier before entering the trap had increased concentrations of plasma cortisol. Confinement in the trap also induced a stress response. Plasma cortisol concentrations increased to 185.1 ± 40.9 ng/mL in males and 549.1 ± 60.1 ng/mL in females after confinement for 1 h. After processing, the magnitude of the stress response and the relative duration of recovery was less in fish that were confined longer in the trap. However, resting cortisol concentrations in females were not reached after 40 h of recovery in either group. Recovery to resting concentrations of plasma lactate occurred within 15 h after processing. In contrast, concentrations of plasma glucose remained significantly elevated at 40 h after processing. Postspawning fish had significantly lower plasma concentrations of cortisol, glucose, and lactate following application of an extreme stressor compared with prespawning fish. Based on the results of this study, we conclude that the trapping procedure induces a severe and prolonged stress response in wild rainbow trout

Work-Related Stress, Physio-Pathological Mechanisms, and the Influence of Environmental Genetic Factors

Work-related stress is a growing health problem in modern society. The stress response is characterized by numerous neurochemicals, neuroendocrine and immune modifications that involve various neurological systems and circuits, and regulation of the gene expression of the different receptors. In this regard, a lot of research has focused the attention on the role played by the environment in influencing gene expression, which in turn can control the stress response. In particular, genetic factors can moderate the sensitivities of specific types of neural cells or circuits mediating the imprinting of the environment on different biological systems. In this current review, we wish to analyze systematic reviews and recent experimental research on the physio-pathological mechanisms that underline stress-related responses. In particular, we analyze the relationship between genetic and epigenetic factors in the stress response

MiRNA-34 and stress response

Psychiatric disorders are known to result from a strong interaction between genetic predisposition and environmental factors, mainly exposure to stressful events. Environmental events can modulate genes expression, possibly via epigenetic mechanisms, and affect onset/expression of a disease [1]. Epigenetic mechanisms include, among others, post-transcriptional regulation by non-coding RNAs such as microRNAs (miRNAs). MiRNAs are small non-coding RNAs predicted to regulate hundreds of targets and to be engaged in every biological process [2]. Thanks to their ability to fine-tune gene expression, miRNAs can control gene expression patterns favoring organism’s adaptation to internal and environmental (external) factors [3], such as stressful events

Environmental stress responses in Lactococcus lactis

Bacteria can encounter a variety of physical conditions during their life. Bacterial cells are able to survive these (often adverse) conditions by the induction of specific or general protection mechanisms. The lactic acid bacterium Lactococcus lactis is widely used for the production of cheese. Before and during this process as well as in its natural habitats, it is subjected to several stressful conditions. Such conditions include oxidation, heating and cooling, acid, high osmolarity/dehydration and starvation. In many environments combinations of these parameters occur. Understanding the stress response behaviour of L. lactis is important to optimize its application in industrial fermentations and is of fundamental interest as L. lactis is a non-differentiating Gram-positive bacterium. The stress response mechanisms of L. lactis have drawn increasing attention in recent years. The presence in L. lactis of a number of the conserved systems (e.g. the heat shock proteins) has been confirmed. Some of the regulatory mechanisms responding to an environmental stress condition are related to those found in other Gram-positive bacteria. Other stress response systems are conserved at the protein level but are under control of mechanisms unique for L. lactis. In a number of cases exposure to a single type of stress provides resistance to other adverse conditions. The unravelling of the underlying regulatory systems gives insight into the development of such cross resistance. Taken together, L. lactis has a unique set of stress response mechanisms, most of which have been identified on the basis of homology with proteins known from other bacteria. A number of the regulatory elements may provide attractive tools for the development of food grade inducible gene expression systems. Here an overview of the growth limits of L. lactis and the molecular characterization of its stress resistance mechanisms is presented.

From the stress response function (back) to the sandpile `dip'

We relate the pressure `dip' observed at the bottom of a sandpile prepared by successive avalanches to the stress profile obtained on sheared granular layers in response to a localized vertical overload. We show that, within a simple anisotropic elastic analysis, the skewness and the tilt of the response profile caused by shearing provide a qualitative agreement with the sandpile dip effect. We conclude that the texture anisotropy produced by the avalanches is in essence similar to that induced by a simple shearing -- albeit tilted by the angle of repose of the pile. This work also shows that this response function technique could be very well adapted to probe the texture of static granular packing.Comment: 8 pages, 8 figures, accepted version to appear in Eur. Phys. J.