Search

A series of wetting tests on unsaturated compacted GMZ07 sodium bentonite, taken from the Gaomiaozi area, Inner Mongolia, China, was performed to investigate the swelling characteristics of the GMZ07 sodium bentonite at temperatures of 5, 20, 60 and 75 °C. The influences of temperature and initial dry density on swelling deformation and swelling pressure were studied by performing a series of constant-stress and constant-volume tests under the wetting condition. The test results showed that the swelling deformation and swelling pressure due to saturation decreased slightly with increasing temperature. A linear relationship was present between the vertical pressure and corresponding saturated void ratio in the semi-logarithmic coordinate at a given temperature; this line is referred to as a state line. Swelling or collapse due to saturation was found to be dependent on the relative location of the initial state between the state line and initial state. The void ratios after saturation at different initial dry densities were close at the same temperature and vertical pressure. [ABSTRACT FROM AUTHOR]

Background: Most migraineurs develop cutaneous allodynia (CA) during migraine, and the underlying mechanism of CA in migraine is thought to be sensitization of the third-order trigeminovascular neurons in the posterior thalamic nuclei. This study aimed to investigate whether the ascending/descending pathway associated with the thalamus is disturbed in migraineurs with CA (MWCA) using effective connectivity analysis of resting-state functional magnetic resonance imaging. Methods: Thirty four migraineurs without aura (14 MWCA and 20 migraineurs without CA (MWoCA)) and 25 matched healthy controls (HC) were recruited in the study. The effective connectivity pathways associated with the posterior thalamus (PTH) were investigated using the Granger causality analysis. We chose bilateral PTH as two individual seeds, and compared MWCA with MWoCA and HC, respectively. Spearman correlation analysis was performed to test the correlation between the abnormal effective connectivity and the allodynia severity of MWCA. Results: Compared with MWoCA, MWCA showed decreased inflows from the left limbic regions and dorsal medial prefrontal cortex (dmPFC) to the ipsilateral PTH, as well as increased inflow from the right ventral medial prefrontal cortex (vmPFC) to the ipsilateral PTH; no significantly different outflows from the bilateral PTH to other regions were found. Compared with HC, MWCA showed increased outflows from the left PTH to the bilateral vmPFC, decreased outflows from the right PTH to the bilateral temporoparietal areas, decreased inflow from the left parietooccipital area to the ipsilateral PTH, and increased inflows from the right dorsolateral prefrontal cortex and the bilateral temporoparietal areas to the right PTH. Correlation analyses revealed that the disturbed connectivities between PTH and cuneus, as well as PTH and middle frontal gyrus were associated with the allodynia severity of MWCA. Conclusions: MWCA demonstrated disrupted effective connection pathways between the PTH and other cortical or subcortical regions that participated in multi-dimentional pain processing. Our findings highlight the dysfunctional ascending and descending pain network at the thalamic-level and may help to illuminate the possible pathophysiologic mechanisms of CA. [ABSTRACT FROM AUTHOR]

Objective Cutaneous allodynia (CA) is a characteristic of central sensitization, predicting migraine progression, and poor response to therapy. The present study aimed to find out the cerebral functional alterations related to the establishment of central sensitization in migraineurs using functional magnetic resonance imaging (fMRI). Design The experiment was performed in 15 migraineurs with Cutaneous allodynia (MWCA) and 19 patients without Cutaneous allodynia (MWoCA) in the interictal phase, and 20 matched healthy controls. Blood oxygen level dependent-fMRI was applied in all subjects when they were given transcutaneous electrical nerve stimulation at the left medial forearm, achieving to a predetermined level of pain sensation (i.e., visual analogue scale [VAS] = 40). Contrast images were then produced to determine whether this disorders present functional changes in the brain during pain processing. Results Demographic and headache characteristics were balanced between groups. The contrast images of both migraine groups comparing to healthy controls exhibited weaker activation of various brain regions (e.g., cerebellum and insulae), which might be relevant to the pathophysiological procedure of migraine. The direct comparison between the two migraine groups revealed that activation in the dorsal pons and contralateral (right) inferior parietal lobule of MWCA subjects were significantly lower than it in MWoCA ones. Conclusions The interictal dysfunction of pain processing pathway may be responsible for (at least relevant to) central sensitization in migraine patients, via abnormal modulations of nociceptive transmission. [ABSTRACT FROM AUTHOR]