1,355 research outputs found
Changes in Purkinje cell firing and gene expression precede behavioral pathology in a mouse model of SCA2.
Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominantly inherited disorder, which is caused by a pathological expansion of a polyglutamine (polyQ) tract in the coding region of the ATXN2 gene. Like other ataxias, SCA2 most overtly affects Purkinje cells (PCs) in the cerebellum. Using a transgenic mouse model expressing a full-length ATXN2(Q127)-complementary DNA under control of the Pcp2 promoter (a PC-specific promoter), we examined the time course of behavioral, morphologic, biochemical and physiological changes with particular attention to PC firing in the cerebellar slice. Although motor performance began to deteriorate at 8 weeks of age, reductions in PC number were not seen until after 12 weeks. Decreases in the PC firing frequency first showed at 6 weeks and paralleled deterioration of motor performance with progression of disease. Transcription changes in several PC-specific genes such as Calb1 and Pcp2 mirrored the time course of changes in PC physiology with calbindin-28 K changes showing the first small, but significant decreases at 4 weeks. These results emphasize that in this model of SCA2, physiological and behavioral phenotypes precede morphological changes by several weeks and provide a rationale for future studies examining the effects of restoration of firing frequency on motor function and prevention of future loss of PCs
Finite-temperature behavior of the Bose polaron
We consider a mobile impurity immersed in a Bose gas at finite temperature.
Using perturbation theory valid for weak coupling between the impurity and the
bosons, we derive analytical results for the energy and damping of the impurity
for low and high temperatures, as well as for temperatures close to the
critical temperature for Bose-Einstein condensation. These results show
that the properties of the impurity vary strongly with temperature. In
particular, the energy exhibits a non-monotonic behavior close to , and
the damping rises sharply close to . We argue that this behaviour is
generic for impurities immersed in an environment undergoing a phase transition
that breaks a continuous symmetry. Finally, we discuss how these effects can be
detected experimentally.Comment: 10 pages and 6 figure
Mutagenesis of Trichoderma reesei endoglucanase I: impact of expression host on activity and stability at elevated temperatures.
BackgroundTrichoderma reesei is a key cellulase source for economically saccharifying cellulosic biomass for the production of biofuels. Lignocellulose hydrolysis at temperatures above the optimum temperature of T. reesei cellulases (~50Ā°C) could provide many significant advantages, including reduced viscosity at high-solids loadings, lower risk of microbial contamination during saccharification, greater compatibility with high-temperature biomass pretreatment, and faster rates of hydrolysis. These potential advantages motivate efforts to engineer T. reesei cellulases that can hydrolyze lignocellulose at temperatures ranging from 60-70Ā°C.ResultsA B-factor guided approach for improving thermostability was used to engineer variants of endoglucanase I (Cel7B) from T. reesei (TrEGI) that are able to hydrolyze cellulosic substrates more rapidly than the recombinant wild-type TrEGI at temperatures ranging from 50-70Ā°C. When expressed in T. reesei, TrEGI variant G230A/D113S/D115T (G230A/D113S/D115T Tr_TrEGI) had a higher apparent melting temperature (3Ā°C increase in Tm) and improved half-life at 60Ā°C (t1/2ā=ā161Ā hr) than the recombinant (T. reesei host) wild-type TrEGI (t1/2 = 74Ā hr at 60Ā°C, Tr_TrEGI). Furthermore, G230A/D113S/D115T Tr_TrEGI showed 2-fold improved activity compared to Tr_TrEGI at 65Ā°C on solid cellulosic substrates, and was as efficient in hydrolyzing cellulose at 60Ā°C as Tr_TrEGI was at 50Ā°C. The activities and stabilities of the recombinant TrEGI enzymes followed similar trends but differed significantly in magnitude depending on the expression host (Escherichia coli cell-free, Saccharomyces cerevisiae, Neurospora crassa, or T. reesei). Compared to N.crassa-expressed TrEGI, S. cerevisiae-expressed TrEGI showed inferior activity and stability, which was attributed to the lack of cyclization of the N-terminal glutamine in Sc_TrEGI and not to differences in glycosylation. N-terminal pyroglutamate formation in TrEGI expressed in S. cerevisiae was found to be essential in elevating its activity and stability to levels similar to the T. reesei or N. crassa-expressed enzyme, highlighting the importance of this ubiquitous modification in GH7 enzymes.ConclusionStructure-guided evolution of T. reesei EGI was used to engineer enzymes with increased thermal stability and activity on solid cellulosic substrates. Production of TrEGI enzymes in four hosts highlighted the impact of the expression host and the role of N-terminal pyroglutamate formation on the activity and stability of TrEGI enzymes
Anesthetic Management of a Patient with Ebstein's Anomaly for Obstructed Inguinal Hernia
Ebsteinās anomaly is a rare congenital heart disease constituting less than 1% of patients with congenital heart diseases. It has diverse presentations, severity, and consequently, the management too. These patients are at increased risk of developing ventricular and supraventricular tachycardias, congestive heart failure, and even death. Here, we report a case of a 32-year old man with Ebsteinās anomaly, who had successfully undergone emergency open inguinal hernioplasty under nerve blocks
Trion resonance in polariton-electron scattering
Strong interactions between charges and light-matter coupled quasiparticles
offer an intriguing prospect with applications from optoelectronics to
light-induced superconductivity. Here, we investigate how the interactions
between electrons and exciton-polaritons in a two-dimensional semiconductor
microcavity can be resonantly enhanced due to a strong coupling to a trion,
i.e., an electron-exciton bound state. We develop a microscopic theory that
uses a strongly screened interaction between charges to enable the summation of
all possible diagrams in the polariton-electron scattering process. The
position and magnitude of the resonance is found to vary depending on the
values of the light-matter coupling and detuning, thus indicating a large
degree of tunability. We furthermore derive an analytic approximation of the
interaction strength based on universal lowenergy scattering theory. This is
found to match extremely well with our full calculation, indicating that the
trion resonance is near universal, depending more on the strength of the
light-matter coupling relative to the trion binding energy rather than on the
details of the electronic interactions. Thus, we expect the trion resonance in
polariton-electron scattering to appear in a broad range of microcavity systems
with few semiconductor layers, such as doped monolayer MoSe2 where such
resonances have recently been observed experimentally [Sidler et al., Nature
Physics 13, 255 (2017)].Comment: 13 pages and 8 figure
MARKETING OF GREEN PRODUCTS AND ITS UNDERLYING PRACTICES
According to the American marketing Association green marketing is the marketing of products that are presumed to be environmentally safe. Every company has its own favorite marketing mix. Companies that develop new and improved products and services with environment inputs in mind give themselves access to new markets, increase their profit sustainability, and enjoy a competitive advantage over the companies which are not concerned for the environment. This study discusses the manufacturers green marketing practices and analyze the respondentsā views about Green Marketing Practices. The researcher has selected 149 units, as samples selected through Proportionate Stratified Random sampling method. The researcher uses the interview schedule instrument to collect the data from the respondents. The main objectives of the study is consists, to know the awareness level of respondents about green marketing practices and which factor more accounted to adopt green marketing practices into their business. Therefore, to know the perception level on the green marketing practices; There are 30 statements observed by the researcher which are relevant and accounted for green marketing practices. The factor analysis technique applied for the purpose of extracting the latent factors accounted for green marketing practices. From the results of factor analysis, ābusiness ethicsā factor is high loading factor to influence the sampled respondents to adopt green marketing practices. Another thing should be noted that most of the respondents in the study very aware of green marketing and its practices. Finally the researcher offers suggestion for improvement of green marketing practices
Identification of a repetitive sequence belonging to a PPE gene of Mycobacterium tuberculosis and its use in diagnosis of tuberculosis
A repetitive sequence specific to Mycobacterium tuberculosis was isolated from a gt11 library of M. tuberculosis by DNA-DNA hybridization using genomic DNA of M. tuberculosis as probe followed by subtractive hybridization with a cocktail of other mycobacterial DNA. This led to identification of CD192, a 1291 bp fragment of M. tuberculosis containing repetitive sequences, which produced positive hybridization signals with M. tuberculosis DNA within 30 min. Nucleotide sequencing revealed the presence of several direct and inverted repeats within the 1291 bp fragment that belonged to a PPE family gene (Rv0355) of M. tuberculosis. The use of CD192 as a DNA probe for the identification of M. tuberculosis in culture and clinical samples was investigated. The 1291 bp sequence was present in M. tuberculosis, Mycobacterium bovis and M. bovis BCG, but was not present in many of the other mycobacterial strains tested, including M. tuberculosis H37Ra. More than 300 clinical isolates of M. tuberculosis were probed with CD192, and the presence of the 1291 bp sequence was observed in all the clinical strains, including those lacking IS6110. The sequence displayed RFLP among the clinical isolates. A PCR assay was developed which detected M. tuberculosis with 100 % specificity from specimens of sputum, cerebrospinal fluid and pleural effusion from clinically diagnosed cases of tuberculosis
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