Selective Increase (selective + increase)

Distribution by Scientific Domains


Selected Abstracts


Insulin resistance in type 2 diabetes: role of fatty acids,

DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue S2 2002
Peter Arner
Abstract Insulin resistance is one of the key factors responsible for hyperglycaemia in type 2 diabetes and can result in a number of metabolic abnormalities associated with cardiovascular disease (insulin resistance syndrome), even in the absence of overt diabetes. The mechanisms involved in the development of insulin resistance are multifactorial and are only partly understood, but increased availability of free fatty acids (FFAs) is of particular importance for the liver and skeletal muscle. The role of FFAs in type 2 diabetes is most evident in obese patients who have several abnormalities in FFA metabolism. Because of a mass effect, the release of FFAs from the total adipose tissue depot to the blood stream is increased and the high concentration of circulating FFAs impairs muscle uptake of glucose by competitive inhibition. In upper-body obesity, which predisposes individuals to type 2 diabetes, the rate of lipolysis is accelerated in visceral adipose tissue. This results in a selective increase in FFA mobilisation to the portal vein, which connects visceral fat to the liver. A high ,portal' FFA concentration has undesirable effects on the liver, resulting in dyslipidaemia, hyperinsulinaemia, hyperglycaemia and hepatic insulin resistance. Recently, a new class of antidiabetic agents, the thiazolidinediones (TZDs) or ,glitazones' has been developed. A prominent effect of these agents is the lowering of circulating FFA levels and it is believed, but not yet proven, that this interaction with FFAs constitutes a major mechanism behind the glucose-lowering effect of the TZDs. Copyright © 2002 John Wiley & Sons, Ltd. [source]


Learning to filter out visual distractors

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2009
Viktor Gál
Abstract When learning to master a visual task in a cluttered natural environment, it is important to optimize the processing of task-relevant information and to efficiently filter out distractors. However, the mechanisms that suppress task-irrelevant information are not well understood. Here we show that training leads to a selective increase in motion coherence detection thresholds for task-irrelevant motion directions that interfered with the processing of task-relevant directions during training. Furthermore, using functional magnetic resonance imaging we found that training attenuated neural responses associated with the task-irrelevant direction compared with the task-relevant direction in the visual cortical areas involved in processing of visual motion. The strongest suppression of functional magnetic resonance imaging responses to task-irrelevant motion information was observed in human area MT+. These findings reveal that perceptual learning leads to the suppression and efficient filtering of task-irrelevant visual information. [source]


Selective activation of the ventrolateral prefrontal cortex in the human brain during active retrieval processing

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2001
Geneviève Cadoret
Abstract The present study examined the role of the prefrontal cortex in retrieval processing using functional magnetic resonance imaging in human subjects. Ten healthy subjects were scanned while they performed a task that required retrieval of specific aspects of visual information. In order to examine brain activity specifically associated with retrieval, we designed a task that had retrieval and control conditions that were perfectly matched in terms of depth of encoding, decision making and postretrieval monitoring and differed only in terms of whether retrieval was required. In the retrieval condition, based on an instructional cue, the subjects had to retrieve either the particular stimulus that was previously presented or its location. In the control condition, the cue did not instruct retrieval but shared with the instructional cues the function of alerting the subjects of the impending test phase. The comparison of activity between the retrieval and control conditions demonstrated a significant and selective increase in activity related to retrieval processes within the ventrolateral prefrontal cortical region, more specifically within area 47/12. These activity increases were bilateral but stronger in the right hemisphere. The present study by strictly controlling the level of encoding, postretrieval monitoring, and decision making has demonstrated a specific increase in the ventrolateral prefrontal region that could be clearly related to active retrieval processing, i.e. the active selection of particular stored visual representations. [source]


Nigrostriatal denervation does not affect glutamate transporter mRNA expression but subsequent levodopa treatment selectively increases GLT1 mRNA and protein expression in the rat striatum

JOURNAL OF NEUROCHEMISTRY, Issue 4 2001
J.-C. Liévens
There is growing evidence that the loss of the nigrostriatal dopaminergic neurones induces an overactivity of the corticostriatal glutamatergic pathway which seems to be central to the physiopathology of parkinsonism. Moreover, glutamatergic mechanisms involving NMDA receptors have been shown to interfere with the therapeutical action of levodopa. Given the key role played by uptake processes in glutamate neurotransmission, this study examined the effects of nigrostriatal deafferentation and of levodopa treatment on the striatal expression of the glutamate transporters GLT1, GLAST and EAAC1 in the rat. No significant changes in striatal mRNA levels of these transporters were detected after either levodopa treatment (100 mg/kg; i.p., twice a day for 21 days) or unilateral lesion of the nigrostriatal pathway by intranigral 6-hydroxydopamine injection. In contrast, animals with the lesion subsequently treated with levodopa showed a selective increase (36%) in GLT1 mRNA levels in the denervated striatum versus controls. These animals also showed increased GLT1 protein expression, as assessed by immunostaining and western blotting. These data provide the first evidence that levodopa therapy may interfere with striatal glutamate transmission through change in expression of the primarily glial glutamate transporter GLT1. We further suggest that levodopa-induced GLT1 overexpression may represent a compensatory mechanism preventing neurotoxic accumulation of endogenous glutamate. [source]


Long-Term Modulation By Postnatal Oxytocin of the ,2 -Adrenoceptor Agonist Binding Sites in Central Autonomic Regions and the Role of Prenatal Stress

JOURNAL OF NEUROENDOCRINOLOGY, Issue 3 2004
Z. Díaz-Cabiale
Abstract The aim of this work was to evaluate whether oxytocin administered in male rats subcutaneously early in life in the absence or presence of food restriction during pregnancy has life-long effects on the ,2 -agonist binding sites in the nucleus of the solitarii tract (NTS), in the hypothalamus and the amygdala, as evaluated by quantitative receptor autoradiography. Maternal food restriction alone increased the affinity of the ,2 -agonist [3H]UK14.304 binding sites exclusively in the NTS. In offspring from ad libitum fed dams, oxytocin treatment significantly increased the density of ,2 -agonist binding sites in the NTS and in the hypothalamus. The Kd value of the ,2 -agonist binding sites in the hypothalamus of these rats, but not in the other regions studied, was also significantly increased. In offspring from food-restricted dams, oxytocin treatment produced a significant increase of the Bmax values in the hypothalamus and the amygdala and the Kd value of the ,2 -agonist binding sites in the NTS of these rats also was selectively and significantly increased. These results suggest that a postnatal, oxytocin-induced increase of regional ,2 -adrenoceptor function can be seen in adulthood by a persistent, regionally selective increase in the density of central ,2 -adrenoceptor agonist binding sites, in the absence of an affinity change in the NTS. Such a regional increase of ,2 -adrenoceptor signalling in adulthood may contribute to the anti-stress action of postnatal oxytocin. By contrast, after prenatal stress, the potential increase in ,2 -adrenoceptor signalling takes place via selective increases of density with no changes of affinity of the ,2 -agonist binding sites in the hypothalamus and the amygdala. [source]


Altered Motor Cortex Excitability to Magnetic Stimulation in Alcohol Withdrawal Syndrome

ALCOHOLISM, Issue 4 2010
Raffaele Nardone
Background:, Alcohol addiction is a complex brain disease caused by alterations in crucial neurotransmitter systems, including gamma-aminobutyric acid (GABA) and glutamate. These disturbances could be revealed by changes in cortical excitability parameters, as assessed by transcranial magnetic stimulation (TMS). This study was aimed to further investigate the complex pathophysiology of alcohol withdrawal syndrome (AWS). Methods:, Motor cortex excitability was examined in 13 subjects with AWS in a mild predelirial state, in 12 chronic alcoholics and in 15 age-matched control subjects, using a range of TMS protocols. Central motor conduction time, resting and active motor threshold, duration of the cortical silent period, short latency intracortical inhibition (SICI), and intracortical facilitation (ICF) to paired TMS were examined. Results:, Intracortical facilitation was significantly increased in the AWS patients when compared with the chronic alcoholics and the control subjects. The other TMS parameters did not differ significantly from the controls. Administration of a single oral dose of the glutamatergic antagonist riluzole in a subgroup of 8 patients significantly reduced ICF; motor threshold and SICI were not affected by riluzole. Conclusion:, Transcranial magnetic stimulation shows a selective increase in intracortical facilitation after ethanol withdrawal. Our findings support the theory that altered glutamatergic receptor function plays an important role in the pathogenesis of human alcohol withdrawal. This study provides further physiological evidence that antiglutamatergic approaches represent an efficacious alternative for treating alcohol withdrawal symptoms. [source]


Multiscale approach to investigate the radiochemical degradation of epoxy resins under high-energy electron-beam irradiation

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2006
N. Longiéras
Abstract A multiscale investigation of the degradation mechanism of two epoxy systems exposed to electron-beam irradiation under a helium atmosphere was carried out with a variety of analytical methods, including high-resolution solution- and solid-state NMR spectroscopy, NMR relaxometry, infrared spectroscopy, sterical exclusion chromatography, and differential scanning calorimetry. As a first step, we studied a linear phenoxy polymer, poly(2-hydroxyether of bisphenol A), which provided a basis for the investigation of the degradation of a more complex, insoluble epoxy,amine network, diglycidyl ether of bisphenol A/triethylene tetramine. Among different structural modifications, the main degradation process was shown to produce in both cases a chain scission. For the phenoxy resin, the hydroxypropylidene moiety was identified as the fragile site leading to the formation of two phenolic chain ends and acetone and isopropyl alcohol as low-molecular-weight products. All methods, ranging from molecular to supramolecular scales, were shown to correlate both qualitatively and quantitatively. Experimental results obtained with diglycidyl ether of bisphenol A/triethylene tetramine evidenced a different degradation scheme occurring at the ethylene amine part and producing a dangling vinyl amine as the major degradation product. A selective increase in the molecular mobility at this site was confirmed by a two-dimensional, local-field wide-line separation experiment. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 865,887, 2006 [source]


Metastable and stable states of xanthan polyelectrolyte complexes studied by atomic force microscopy

BIOPOLYMERS, Issue 3 2004
Gjertrud Maurstad
Abstract The compaction of the semiflexible polysaccharide xanthan with selected multi- and polyvalent cations was studied. Polyelectrolyte complexes prepared at concentrations of 1,2 ,g/ml were observed by tapping mode atomic force microscopy. High-molecular-weight xanthan compacted with chitosan yields a blend of mainly toroidal and metastable structures and a small fraction of rod-like species. Polyelectrolyte complexes of xanthan with polyethylenimine and trivalent chromium yielded similar structures or alternatively less well packed species. Racquet-type morphologies were identified as kinetically trapped states occurring on the folding path toward the energetically stable state of the toroids. Thermal annealing yielded a shift of the distribution of xanthan,chitosan morphologies toward this stable state. Ensembles of toroidal and rod-like morphologies of the xanthan,chitosan structures, collected using an asphericity index, were analyzed. The mean height of the toroids increased upon heating, with a selective increase in the height range above 2 nm. It is suggested that the observed metastable structures are formed from the high-molecular-weight fraction of xanthan and that these are driven toward the toroidal state, being a low-energy state, following annealing. Considered a model system for condensation of semiflexible polymers, the compaction of xanthan by chitosan captures the system at various stages in the folding toward a low-energy state and thus allows experimental analyses of these intermediates and their evolution. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004 [source]


Parvalbumin-, calbindin-, and calretinin-immunoreactive hippocampal interneuron density in autism

ACTA NEUROLOGICA SCANDINAVICA, Issue 2 2010
Y. A. Lawrence
Lawrence YA, Kemper TL, Bauman ML, Blatt GJ. Parvalbumin-, calbindin-, and calretinin-immunoreactive hippocampal interneuron density in autism. Acta Neurol Scand: 2010: 121: 99,108. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Background ,, There has been a long-standing interest in the possible role of the hippocampus in autism and both postmortem brain and neuroimaging studies have documented varying abnormalities in this limbic system structure. Aims ,, This study investigates the density of subsets of hippocampal interneurons, immunostained with the calcium binding proteins, calbindin (CB), calretinin (CR) and parvalbumin (PV) to determine whether specific subpopulations of interneurons are impacted in autism. Materials and methods ,, Unbiased stereological techniques were used to quantify the neuronal density of these immunoreactive subpopulations of gamma-aminobutyric acid-ergic (GABAergic) interneurons analyzed in the CA and subicular fields in postmortem brain material obtained from five autistic and five age-, gender- and postmortem interval-matched control cases. Results ,, Results indicate a selective increase in the density of CB-immunoreactive interneurons in the dentate gyrus, an increase in CR-immunoreactive interneurons in area CA1, and an increase in PV-immunoreactive interneurons in areas CA1 and CA3 in the hippocampus of individuals with autism when compared with controls. Discussion/conclusions ,, Although our sample size is small, these findings suggest that GABAergic interneurons may represent a vulnerable target in the brains of individuals with autism, potentially impacting upon their key role in learning and information processing. These preliminary findings further suggest the need for future more expanded studies in a larger number of postmortem brain samples from cases of autism and controls. [source]


Long-Term Modulation By Postnatal Oxytocin of the ,2 -Adrenoceptor Agonist Binding Sites in Central Autonomic Regions and the Role of Prenatal Stress

JOURNAL OF NEUROENDOCRINOLOGY, Issue 3 2004
Z. Díaz-Cabiale
Abstract The aim of this work was to evaluate whether oxytocin administered in male rats subcutaneously early in life in the absence or presence of food restriction during pregnancy has life-long effects on the ,2 -agonist binding sites in the nucleus of the solitarii tract (NTS), in the hypothalamus and the amygdala, as evaluated by quantitative receptor autoradiography. Maternal food restriction alone increased the affinity of the ,2 -agonist [3H]UK14.304 binding sites exclusively in the NTS. In offspring from ad libitum fed dams, oxytocin treatment significantly increased the density of ,2 -agonist binding sites in the NTS and in the hypothalamus. The Kd value of the ,2 -agonist binding sites in the hypothalamus of these rats, but not in the other regions studied, was also significantly increased. In offspring from food-restricted dams, oxytocin treatment produced a significant increase of the Bmax values in the hypothalamus and the amygdala and the Kd value of the ,2 -agonist binding sites in the NTS of these rats also was selectively and significantly increased. These results suggest that a postnatal, oxytocin-induced increase of regional ,2 -adrenoceptor function can be seen in adulthood by a persistent, regionally selective increase in the density of central ,2 -adrenoceptor agonist binding sites, in the absence of an affinity change in the NTS. Such a regional increase of ,2 -adrenoceptor signalling in adulthood may contribute to the anti-stress action of postnatal oxytocin. By contrast, after prenatal stress, the potential increase in ,2 -adrenoceptor signalling takes place via selective increases of density with no changes of affinity of the ,2 -agonist binding sites in the hypothalamus and the amygdala. [source]


Multiple sclerosis in the Faroe Islands.

ACTA NEUROLOGICA SCANDINAVICA, Issue 2 2010

Wallin MT, Heltberg A, Kurtzke JF. Multiple sclerosis in the Faroe Islands. 8. Notifiable diseases. Acta Neurol Scand: 2010: 122: 102,109. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Objective,,, To seek evidence for a possible infectious origin of the type 1 epidemic of multiple sclerosis (MS) in the Faroe Islands. This began in 1943 coincident with their British military occupation throughout World War II. Materials and methods,,, Data obtained from the Danish National Health Service were assessed for all notifiable diseases in the Faroe Islands reported from 1900 to 1977. Results,,, Among 38 disorders, selective increases were found for acute infectious gastroenteritis (AIGE) and paradysentery, with outbreaks in late 1940 and in 1943 shortly after the introduction and later marked influx, respectively, of British troops. Five other infections showed elevated numbers in 1941 and 1942. Conclusions,,, There is a temporal association of AIGE and paradysentery in the Faroe Islands with the first arrival and later marked augmentation of British forces stationed there during the war. Rises in the incidence of other diseases in 1941,1942 seem more likely a consequence of increased foreign commercial travel by Faroese at that time. [source]