784 research outputs found
Data driven generation of Purkinje cell spike train correlations to study input output relations in deep cerebellar nuclei neurons
Use of Granger causality analysis and artificial spike trains to examine pause coding in Purkinje cell spike activity related to rhythmic licking
Logarithmic rate dependence in deforming granular materials
Rate-independence for stresses within a granular material is a basic tenet of
many models for slow dense granular flows. By contrast, logarithmic rate
dependence of stresses is found in solid-on-solid friction, in geological
settings, and elsewhere. In this work, we show that logarithmic rate-dependence
occurs in granular materials for plastic (irreversible) deformations that occur
during shearing but not for elastic (reversible) deformations, such as those
that occur under moderate repetitive compression. Increasing the shearing rate,
\Omega, leads to an increase in the stress and the stress fluctuations that at
least qualitatively resemble what occurs due to an increase in the density.
Increases in \Omega also lead to qualitative changes in the distributions of
stress build-up and relaxation events. If shearing is stopped at t=0, stress
relaxations occur with \sigma(t)/ \sigma(t=0) \simeq A \log(t/t_0). This
collective relaxation of the stress network over logarithmically long times
provides a mechanism for rate-dependent strengthening.Comment: 4 pages, 5 figures. RevTeX
Characterization of an extracellular lipase and its chaperone from Ralstonia eutropha H16
Lipase enzymes catalyze the reversible hydrolysis of triacylglycerol to fatty acids and glycerol at the lipid–water interface. The metabolically versatile Ralstonia eutropha strain H16 is capable of utilizing various molecules containing long carbon chains such as plant oil, organic acids, or Tween as its sole carbon source for growth. Global gene expression analysis revealed an upregulation of two putative lipase genes during growth on trioleate. Through analysis of growth and activity using strains with gene deletions and complementations, the extracellular lipase (encoded by the lipA gene, locus tag H16_A1322) and lipase-specific chaperone (encoded by the lipB gene, locus tag H16_A1323) produced by R. eutropha H16 was identified. Increase in gene dosage of lipA not only resulted in an increase of the extracellular lipase activity, but also reduced the lag phase during growth on palm oil. LipA is a non-specific lipase that can completely hydrolyze triacylglycerol into its corresponding free fatty acids and glycerol. Although LipA is active over a temperature range from 10 °C to 70 °C, it exhibited optimal activity at 50 °C. While R. eutropha H16 prefers a growth pH of 6.8, its extracellular lipase LipA is most active between pH 7 and 8. Cofactors are not required for lipase activity; however, EDTA and EGTA inhibited LipA activity by 83 %. Metal ions Mg[superscript 2+], Ca[superscript 2+], and Mn[superscript 2+] were found to stimulate LipA activity and relieve chelator inhibition. Certain detergents are found to improve solubility of the lipid substrate or increase lipase-lipid aggregation, as a result SDS and Triton X-100 were able to increase lipase activity by 20 % to 500 %. R. eutropha extracellular LipA activity can be hyper-increased, making the overexpression strain a potential candidate for commercial lipase production or in fermentations using plant oils as the sole carbon source.Malaysia-MIT Biotechnology Partnership Programm
Aberrant epithelial GREM1 expression initiates colonic tumorigenesis from cells outside the stem cell niche
Hereditary mixed polyposis syndrome (HMPS) is characterized by the development of mixed-morphology colorectal tumors and is caused by a 40-kb genetic duplication that results in aberrant epithelial expression of the gene encoding mesenchymal bone morphogenetic protein antagonist, GREM1. Here we use HMPS tissue and a mouse model of the disease to show that epithelial GREM1 disrupts homeostatic intestinal morphogen gradients, altering cell fate that is normally determined by position along the vertical epithelial axis. This promotes the persistence and/or reacquisition of stem cell properties in Lgr5-negative progenitor cells that have exited the stem cell niche. These cells form ectopic crypts, proliferate, accumulate somatic mutations and can initiate intestinal neoplasia, indicating that the crypt base stem cell is not the sole cell of origin of colorectal cancer. Furthermore, we show that epithelial expression of GREM1 also occurs in traditional serrated adenomas, sporadic premalignant lesions with a hitherto unknown pathogenesis, and these lesions can be considered the sporadic equivalents of HMPS polyps
Roles of Molecular Layer Interneurons in Sensory Information Processing in Mouse Cerebellar Cortex Crus II In Vivo
Cerebellar cortical molecular layer interneurons (MLIs) play essential roles in sensory information processing by the cerebellar cortex. However, recent experimental and modeling results are questioning traditional roles for molecular layer inhibition in the cerebellum. receptors uncovered larger EPSCs in PCs whose time to peak, half-width and 10–90% rising time were also significantly slower than in MLIs. Biocytin labeling indicated that the MLIs (but not PCs) are dye-coupled.These findings indicate that tactile face stimulation evokes rapid excitation in MLIs and inhibition occurring at later latencies in PCs in mouse cerebellar cortex Crus II. These results support previous suggestions that the lack of parallel fiber driven PC activity is due to the effect of MLI inhibition
Dynamic cerebral autoregulation after intracerebral hemorrhage: A case-control study
<p>Abstract</p> <p>Background</p> <p>Dynamic cerebral autoregulation after intracerebral hemorrhage (ICH) remains poorly understood. We performed a case-control study to compare dynamic autoregulation between ICH patients and healthy controls.</p> <p>Methods</p> <p>Twenty-one patients (66 ± 15 years) with early (< 72 hours) lobar or basal ganglia ICH were prospectively studied and compared to twenty-three age-matched controls (65 ± 9 years). Continuous measures of mean flow velocity (MFV) in the middle cerebral artery and mean arterial blood pressure (MAP) were obtained over 5 min. Cerebrovascular resistance index (CVR<sub>i</sub>) was calculated as the ratio of MAP to MFV. Dynamic cerebral autoregulation was assessed using transfer function analysis of spontaneous MAP and MFV oscillations in the low (0.03-0.15 Hz) and high (0.15-0.5 Hz) frequency ranges.</p> <p>Results</p> <p>The ICH group demonstrated higher CVR<sub>i </sub>compared to controls (ipsilateral: 1.91 ± 1.01 mmHg·s·cm<sup>-1</sup>, <it>p </it>= 0.04; contralateral: 2.01 ± 1.24 mmHg·s·cm<sup>-1</sup>, <it>p </it>= 0.04; vs. control: 1.42 ± 0.45 mmHg·s·cm<sup>-1</sup>). The ICH group had higher gains than controls in the low (ipsilateral: 1.33 ± 0.58%/mmHg, <it>p </it>= 0.0005; contralateral: 1.47 ± 0.98%/mmHg, <it>p </it>= 0.004; vs. control: 0.82 ± 0.30%/mmHg) and high (ipsilateral: 2.11 ± 1.31%/mmHg, <it>p </it>< 0.0001; contralateral: 2.14 ± 1.49%/mmHg, <it>p </it>< 0.0001; vs. control: 0.66 ± 0.26%/mmHg) frequency ranges. The ICH group also had higher coherence in the contralateral hemisphere than the control (ICH contralateral: 0.53 ± 0.38, <it>p </it>= 0.02; vs. control: 0.38 ± 0.15) in the high frequency range.</p> <p>Conclusions</p> <p>Patients with ICH had higher gains in a wide range of frequency ranges compared to controls. These findings suggest that dynamic cerebral autoregulation may be less effective in the early days after ICH. Further study is needed to determine the relationship between hematoma size and severity of autoregulation impairment.</p
Episodic formation of cometary material in the outburst of a solar-like young star
Our Solar System originated in interstellar gas and dust; the latter is in
the form of amorphous silicate particles and carbonaceous dust. The composition
of cometary material shows that a significant fraction of the amorphous
silicates was transformed into crystalline form during the early evolution of
the protosolar nebula. How and when this transformation happened has been
controversial, with the main options being heating by the young Sun or shock
heating. Here we report mid-infrared features in the outburst spectrum of the
young solar-like star EX Lupi that were not present in quiescence. We attribute
them to crystalline forsterite; the crystals were produced via thermal
annealing in the surface layer of the inner disk by heat from the outburst, a
process that has hitherto not been considered. The observed lack of cold
crystals excludes shock heating at larger radii.Comment: 13 pages of PDF, including Supplementary Informatio
The role of cognitive dysfunction in the symptoms and remission from depression.
The disability and burden associated with major depression comes only in part from its affective symptoms; cognitive dysfunctions associated with depression also play a crucial role. Furthermore, these cognitive impairments during depression are manifold and multilevel affecting elementary and more complex cognitive processes equally. Several models from different directions tried to evaluate, conceptualize and understand the depth and magnitude of cognitive dysfunctions in depression and their bidirectional interactions with other types of depressive symptomatology including mood symptoms. In the current review, we briefly overview different types of cognitive symptoms and deficits related to major depression including hot and cold as well as trait- and state-like cognitive alterations and we also describe current knowledge related to the impact of cognitive impairments on the course and outcomes of depression including remission, residual symptoms, function, and response to treatment. We also emphasize shortcomings of currently available treatments for depression in sufficiently improving cognitive dysfunctions and point out the need for newer pharmacological approaches especially in cooperation with psychotherapeutic interventions
Long-term changes in habitat and trophic level of Southern Ocean squid in relation to environmental conditions
Long-term studies of pelagic nekton in the Southern Ocean and their responses to ongoing environmental change are rare. Using stable isotope ratios measured in squid beaks recovered from diet samples of wandering albatrosses Diomedea exulans, we assessed decadal variation (from 1976 to 2016) in the habitat (δ13C) and trophic level (δ15N) of five important Southern Ocean squid species in relation to indices of environmental conditions—Southern Oscillation Index (SOI) and Southern Annular Mode (SAM). Based on δ13C values, corrected for the Suess effect, habitat had changed over the last 50 years for Taonius sp. B (Voss), Gonatus antarcticus, Galiteuthis glacialis and Histioteuthis atlantica but not Moroteuthopsis longimana. By comparison, mean δ15N values were similar across decades for all five species, suggesting minimal changes in trophic levels. Both SAM and SOI have increased in strength and frequency over the study period but, of the five species, only in Taonius sp. B (Voss) did these indices correlate with, δ13C and δ15N values, indicating direct relationships between environmental conditions, habitat and trophic level. The five cephalopod species therefore changed their habitats with changing environmental conditions over the last 50 years but maintained similar trophic levels. Hence, cephalopods are likely to remain important prey for top predators in Southern Ocean food webs, despite ongoing climate change
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