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排序方式: 共有476条查询结果,搜索用时 15 毫秒
81.
82.
Developmental progression to early adult binge drinking and marijuana use from worsening versus stable trajectories of adolescent attention deficit/hyperactivity disorder and delinquency
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83.
Anger‐irritability as a mediator of attention deficit hyperactivity disorder risk for adolescent alcohol use and the contribution of coping skills
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84.
We present a model preparation, the crayfish, to investigate chronic stimulation effects in muscle fiber type and neuronal conversion from fast to slow. The results show a presynaptic alteration in transmitter release after 1 week of stimulation at 5 Hz for a 2-h daily regime. With the same stimulation paradigm, the muscle proteins displayed on a polyacrylamide gel only start to show changes after 3 weeks. The original phasic motoneurons within 1 week display an enhanced ability to resist synaptic depression, as do tonic motoneurons. The results show that identified phasic motoneurons and muscle fibers in the crayfish can be transformed to a toniclike state, and that the nerve terminals convert prior to the muscle fibers. Electrophysiological clinical measures indicating a change in transmitter release properties may not necessarily mean that the muscle fibers have fully adapted for long-lasting effects. This preparation allows stimulation conditions to be examined with ease. © 1998 John Wiley & Sons, Inc. Muscle Nerve 21:921–931, 1998. 相似文献
85.
Rebecca L. Cunningham Amy L. Herbert Breanne L. Harty Sarah D. Ackerman Kelly R. Monk 《Neural development》2018,13(1):17
Background
In the peripheral nervous system (PNS), specialized glial cells called Schwann cells produce myelin, a lipid-rich insulating sheath that surrounds axons and promotes rapid action potential propagation. During development, Schwann cells must undergo extensive cytoskeletal rearrangements in order to become mature, myelinating Schwann cells. The intracellular mechanisms that drive Schwann cell development, myelination, and accompanying cell shape changes are poorly understood.Methods
Through a forward genetic screen in zebrafish, we identified a mutation in the atypical guanine nucleotide exchange factor, dock1, that results in decreased myelination of peripheral axons. Rescue experiments and complementation tests with newly engineered alleles confirmed that mutations in dock1 cause defects in myelination of the PNS. Whole mount in situ hybridization, transmission electron microscopy, and live imaging were used to fully define mutant phenotypes.Results
We show that Schwann cells in dock1 mutants can appropriately migrate and are not decreased in number, but exhibit delayed radial sorting and decreased myelination during early stages of development.Conclusions
Together, our results demonstrate that mutations in dock1 result in defects in Schwann cell development and myelination. Specifically, loss of dock1 delays radial sorting and myelination of peripheral axons in zebrafish.86.
Harty SC Whaley JE Halperin JM Ranaldi R 《Pharmacology, biochemistry, and behavior》2011,98(3):337-340
Heroin addicts display poorer impulse control than non-addicts, however it is not known if high impulsivity is a function of chronic heroin intake or a pre-disposing vulnerability for heroin addiction. Using animal models, relatively few studies have examined changes in impulsive choice as a function of chronic drug. The objective of this study was to measure alterations in impulsive choice through a delay discounting paradigm, as a function of chronic heroin administration. Animals were trained on a series of delay discounting sessions. Each session contained 5 blocks of trials. Blocks started with 2 forced, followed by 6 free choice trials. Pressing one lever resulted in the delivery of a small immediate (1 food pellet) reward and another lever in a large delayed (5 pellets) reward. Sessions consisted of the 3 ascending delay sequences in seconds. On the terminal sequence (0, 10, 20, 40, and 60 s) animals exhibited a reversal of reward choice pattern of responding that allowed for the calculation of an indifference point (IP). After animals showed stable IPs they were treated with either heroin or saline for 12 days. Three days after the last injection animals were again placed in operant chambers and experienced the terminal delay discounting sequence at which time IPs were reassessed. Heroin-treated animals exhibited significant progressive increases in locomotor activity. Groups did not differ in IPs or performance across delay conditions during either before or after chronic treatment periods. These results indicate that chronic heroin intake does not impact later impulsive responding for natural (food) reward. 相似文献
87.
88.
The virion protein 40 (VP40) and nucleoprotein (NP) of Ebola (EBOV) and Marburg viruses (MARV) play key roles during virion assembly and egress. The ability to detect interactions between VP40-VP40, VP40-NP, and NP-NP and follow these complexes as they traffic through mammalian cells would enhance our understanding of the molecular events leading to filovirus assembly and budding, and provide new insights into filovirus replication and pathogenesis. Here, we successfully employed a bimolecular complementation (BiMC) approach to visualize interactions between EBOV and MARV VP40-VP40, NP-NP, and VP40-NP proteins and localize these protein complexes in mammalian cells using confocal microscopy. We demonstrate that VP40-VP40 complexes localized predominantly at the plasma membrane, whereas VP40-NP and NP-NP complexes displayed a more dispersed pattern throughout the cytoplasm. As expected based on previous findings, efficient interactions between EBOV or MARV VP40-VP40 proteins were independent of L-domains PTAPPEY and PPPY, respectively. In contrast, the formation of EBOV or MARV VP40-VP40 complexes was dependent on the previously characterized LPLGVA and LPLGIM motifs of EBOV and MARV VP40 proteins, respectively, indicating that these motifs are important for VP40 oligomerization and subsequent budding. These results highlight the feasibility and usefulness of the BiMC approach as a strategy to further characterize both filovirus protein interactions as well as filovirus-host interactions in real time in the natural environment of the cell. 相似文献
89.
Aberrant contraction of antigen-specific CD4 T cells after infection in the absence of gamma interferon or its receptor
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Several lines of evidence from different model systems suggest that gamma interferon (IFN-gamma) is an important regulator of T-cell contraction after antigen (Ag)-driven expansion. To specifically investigate the role of IFN-gamma in regulating the contraction of Ag-specific CD4 T cells, we infected IFN-gamma-/- and IFN-gammaR1-/- mice with attenuated Listeria monocytogenes and monitored the numbers of Ag-specific CD4 T cells during the expansion, contraction, and memory phases of the immune response to infection. In the absence of IFN-gamma or the ligand-binding portion of its receptor, Ag-specific CD4 T cells exhibited normal expansion in numbers, but in both strains of deficient mice there was very little decrease in the number of Ag-specific CD4 T cells even at time points later than day 90 after infection. This significant delay in contraction was not due to prolonged infection, since mice treated with antibiotics to conclusively eliminate infection exhibited the same defect in contraction. In addition to altering the number of Ag-specific CD4 T cells, the absence of IFN-gamma signaling also changed the phenotype of cells generated after infection. IFN-gammaR1-/- Ag-specific CD4 T cells reacquired expression of CD127 more quickly than wild-type cells, and more IFN-gammaR1-/- CD4 T cells were capable of producing both IFN-gamma and interleukin 2 following Ag stimulation. From these data we conclude that IFN-gamma regulates the contraction, phenotype, and function of Ag-specific CD4 T cells generated after infection. 相似文献
90.
Hartyánszky I Ablonczy L Bodor E Hartyánszky I Bodor G Mihályi S Sápi E Héthársi B Szatmári A 《Orvosi hetilap》2008,149(22):1035-1037
7-year-old boy, who underwent aortic valve replacement two years previously, suffered from idiopathic dilated cardiomyopathy. Because of poor condition (NYHA-IV), heart transplantation was performed on 18th October 2007. It was the first pediatric heart transplantation in Hungary. It was an uneventful early postoperative period, 6 months after the operation he is doing well, no biopsy-proven and tissue Doppler echocardiography (TDI-derived velocities measurement) rejection was detected. The immunosuppression was based on triple-drug therapy (tacrolimus+mycophenolate mofetil+corticosteroid) with use of induction therapy with interleukin-2 receptor blocker (basiliximab). 相似文献