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Reduced Responsiveness (reduced + responsiveness)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Effects of insulin resistance on endothelial function: possible mechanisms and clinical implications

DIABETES OBESITY & METABOLISM, Issue 10 2008
D Tousoulis
Insulin resistance (IR) is defined as a reduced responsiveness of peripheral tissues to the effects of the hormone, referring to abated ability of insulin in stimulating glucose uptake in peripheral tissues and in inhibiting hepatic glucose output. Insulin has both a vasodilatory effect, which is largely endothelium dependent through the release of nitric oxide, and a vasoconstrictory effect through the stimulation of the sympathetic nervous system and the release of endothelin-1. IR and endothelial dysfunction (ED) are not only linked by common pathogenetic mechanisms, involving deranged insulin signalling pathways, but also by other, indirect to the hormone's actions, mechanisms. Different treatment modalities have been proposed to affect positively both the metabolic effects of insulin and ED. Weight loss has been shown to improve sensitivity to insulin as a result of either altered diet or exercise. Exercise has favourable effects on endothelial function in normal states and in states of disease, in men and women, and throughout the age spectrum and, hence, in IR states. Metformin improves sensitivity to insulin and most likely affects positively ED. Studies have shown that inhibitors of the renin,angiotensin system alter IR favourably, while Angiotensin converting enzyme (ACE) inhibitors and Angiotensin receptor type II (ATII) inhibitors improve ED. Ongoing studies are expected to shed more light on the issue of whether treatment with the thiazolidinediones results in improvement of endothelial function, along with the accepted function of improving insulin sensitivity. Finally, improved endothelial function by such treatments is not in itself proof of reduced risk for atherosclerosis; this remains to be directly tested in clinical trials. [source]

Predator avoidance behaviour in wild and hatchery-reared brown trout: the role of experience and domestication

JOURNAL OF FISH BIOLOGY, Issue 6 2003
D. Álvarez
Juvenile brown trout Salmo trutta from natural populations reacted to the presence of piscivorous brown trout by increasing the use of refuges. In contrast, second-generation hatchery fish and the offspring of wild fish raised under hatchery conditions were insensitive to predation risk. The diel pattern of activity also differed between wild and hatchery brown trout. Second-generation hatchery fish were predominantly active during daytime regardless of risk levels. Wild fish, however, showed a shift towards nocturnal activity in the presence of predators. These findings emphasize the potential role of domestication in weakening behavioural defences. They support the idea that the behavioural divergence between wild and domesticated individuals can arise from a process of direct or indirect selection on reduced responsiveness to predation risk, or as a lack of previous experience with predators. [source]

Deviant Forms of Aggression in Glucocorticoid Hyporeactive Rats: A Model for ,Pathological' Aggression?

JOURNAL OF NEUROENDOCRINOLOGY, Issue 1 2001
J. Haller
Abstract Deviant forms of aggressiveness have been associated with low plasma glucocorticoid concentrations in humans. Here, we report data on the development of aggressive behaviour in rats in which glucocorticoid secretion was inhibited by adrenalectomy. Such rats were compared with both sham operated rats and adrenalectomized rats in which the fight-induced elevation of plasma glucocorticoids was mimicked by acute injections. Low and stable corticosterone plasma concentrations were maintained by subcutaneous glucocorticoid pellets in adrenalectomized rats. The development of aggressive behaviour was followed over three trials performed at 2-day intervals. Adrenalectomy lead to high aggressiveness already at the first encounter, a decreased threatening (attack signalling) behaviour and a change in attack targeting. While control rats targeted biting attacks towards less vulnerable dorsal parts of the opponent's body, adrenalectomized rats attacked the head frequently. Corticosterone injections that mimicked the fight induced adrenocortical reaction abolished this behavioural pattern. Thus, a reduced responsiveness of the adrenocortical system may be causally linked to deviant forms of aggression in rats. [source]

Over-expression of SOB5 suggests the involvement of a novel plant protein in cytokinin-mediated development

THE PLANT JOURNAL, Issue 5 2006
Jingyu Zhang
Summary Cytokinins are a class of phytohormones that play a critical role in plant growth and development. sob5-D, an activation-tagging mutant, shows phenotypes typical of transgenic plants expressing the Agrobacterium tumefaciens isopentenyltransferase (ipt) gene that encodes the enzyme catalyzing the first step of cytokinin biosynthesis. The sob5-D mutant phenotypes are caused by over-expression of a novel gene, SOB5. Sequence analysis places SOB5 in a previously uncharacterized family of plant-specific proteins. A translational fusion between SOB5 and the green fluorescent protein reporter was localized in the cytoplasm as well as associated with the plasma membrane when transiently expressed in onion epidermal cells. Analysis of transgenic plants harboring an SOB5:SOB5,, -glucuronidase (GUS) translational fusion under the control of the SOB5 promoter region showed GUS activity in vegetative tissues (hydathodes and trichomes of leaves, shoot meristems and roots) as well as in floral tissues (pistil tips, developing anthers and sepal vasculature). Cytokinin quantification analysis revealed that adult sob5-D plants accumulated higher levels of trans -zeatin riboside, trans -zeatin riboside monophosphate and isopentenyladenine 9-glucoside when compared to the wild-type. Consistent with this result, AtIPT3 and AtIPT7 were found to be up-regulated in a tissue-specific manner in sob5-D mutants. Physiological analysis of the sob5-D mutant demonstrated reduced responsiveness to exogenous cytokinin in both root-elongation and callus-formation assays. Taken together, our data suggest a role for the novel gene SOB5 in cytokinin-mediated plant development. [source]