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排序方式: 共有379条查询结果,搜索用时 15 毫秒
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F. P. Kolb K. B. Irwin J. R. Bloedel V. Bracha 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1997,114(2):255-270
Temporary inactivation of the cerebellar interposed nuclei was used to assess the role of the intermediate cerebellum in
the performance of forelimb cutaneo-muscular reflexes in the cat. The following types of reflexive responses were evaluated:
the classically conditioned and unconditioned forelimb withdrawal responses and the forelimb tactile placing, hopping and
magnet responses. The experiments tested the hypothesis that the intermediate cerebellum is involved in the performance of
all the above forelimb reflexes. The forelimb withdrawal reflex was classically conditioned in a newly developed paradigm
in which animals were first operantly conditioned to stand on four elevated platforms. Trained animals were microinjected
with a γ-aminobutyric acid (GABA) agonist, muscimol, in the interposed nuclei, and the effects of inactivation of the intermediate
cerebellar output on the forelimb reflexes were examined. The main findings of these experiments are that unilateral muscimol
inactivation of the interposed nuclei in the cat abolished the expression of the classically conditioned limb flexion reflex,
suppressed the performance of the unconditioned withdrawal reflex and, in parallel, downregulated the tactile placing, hopping
and magnet postural responses in the ipsilateral forelimb. These observations are inconsistent with concepts indicating exclusive
involvement of the intermediate cerebellum in the classically conditioned reflexes elicited by aversive stimuli. On the contrary,
they support the hypothesis of a more global involvement of this structure in learned and unlearned defensive flexion reflexes
and in automatic postural response systems.
Received: 29 July 1996 / Accepted: 26 September 1996 相似文献
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Zhang X Zhang Z Alexander D Bracha R Mirelman D Stanley SL 《Infection and immunity》2004,72(2):678-683
Entamoeba histolytica trophozoites produce amoebapores, a family of small amphipathic peptides capable of insertion into bacterial or eukaryotic membranes and causing cellular lysis. Recently, E. histolytica trophozoites that are totally deficient in the production of amoebapore-A were created through a gene silencing mechanism (R. Bracha, Y. Nuchamowitz, and D. Mirelman, Eukaryot. Cell 2:295-305, 2003). Here we tested the virulence of amoebapore A(-) trophozoites in models of the two major forms of amebic disease: amebic liver abscess and amebic colitis. We demonstrate that amoebapore expression is required for full virulence in the SCID mouse model of amebic liver abscess, but E. histolytica trophozoites that do not express amoebapore-A can still cause inflammation and tissue damage in infected human colonic xenografts. These data are consistent with the concept that tissue damage may proceed by different mechanisms in amebic liver abscess compared to amebic colitis. 相似文献
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Shimansky Y Wang JJ Bauer RA Bracha V Bloedel JR 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2004,155(2):156-172
Although the cerebellum has been shown to be critical for the acquisition and retention of adaptive modifications in certain reflex behaviors, this structures role in the learning of motor skills required to execute complex voluntary goal-directed movements still is unclear. This study explores this issue by analyzing the effects of inactivating the interposed and dentate cerebellar nuclei on the adaptation required to compensate for an external elastic load applied during a reaching movement. We show that cats with these nuclei inactivated can adapt to predictable perturbations of the forelimb during a goal-directed reach by including a compensatory component in the motor plan prior to movement initiation. In contrast, when comparable compensatory modifications must be triggered on-line because the perturbations are applied in randomized trials (i.e., unpredictably), such adaptive responses cannot be executed or reacquired after the interposed and dentate nuclei are inactivated. These findings provide the first demonstration of the condition-dependent nature of the cerebellums contribution to the learning of a specific volitional task. 相似文献
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Yui K Goto K Ikemoto S Ishiguro T Angrist B Duncan GE Sheitman BB Lieberman JA Bracha SH Ali SF 《Molecular psychiatry》1999,4(6):512-523
A number of consistent clinical observations provide direction for the hypothesis that pathological sensitization of neuronal systems may be an important factor for relapse or the onset of stimulant-induced psychosis (eg, methamphetamine or amphetamine psychosis, cocaine psychosis and phencyclidine psychosis) and schizophrenia. First, psychotic symptoms can be produced in normal subjects by stimulants. Secondly, a large portion of schizophrenic patients exhibit exacerbation of psychotic symptoms in response to stimulants at doses which would not be psychotogenic in normal subjects. Lastly, the ability of stress to precipitate the onset and relapse of schizophrenia is well documented. In this regard, acute responses to stimulants provide useful information for relapse prediction of schizophrenia and substance abuse. This paper addresses the nature and role of pathological sensitization in relapse of stimulant- and phencyclidine-induced psychosis and schizophrenia, and its relation to pathophysiology of schizophrenia. 相似文献
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Subtle signs of prenatal maldevelopment of the hand ectoderm in schizophrenia: a preliminary monozygotic twin study 总被引:2,自引:0,他引:2
H S Bracha E F Torrey L B Bigelow J B Lohr B B Linington 《Neuropsychopharmacology》1991,30(7):719-725
Genes that predispose to psychosis may act by making individuals more vulnerable to the disruptive effects of various prenatal insults. Fetal organogenesis is mostly completed in the first prenatal trimester. The second trimester is a critical period of massive neuronal migration from the periventricular germinal matrix to the cortex. A peripheral appendage developing simultaneously with this neural migration to the cortex is the distal upper limb. The ectodermal cells of the fetal upper limb migrate to form the hand skin during the fourth and fifth months of gestation (first two-thirds of the second prenatal trimester). Discrepancies in hand morphology between two identical (monozygotic [MZ]) co-twins may be temporal markers, that is, the "fossilized" evidence of various ischemic and other nongenetic insults that may have affected one fetus more than his MZ co-twin during that early part of the second trimester. In twins, prenatal insults (e.g., ischemia) frequently do not affect both co-twins to the same extent, so we examined seven putative markers of prenatal injury to the hand in 24 MZ twin pairs discordant for schizophrenia or delusional disorder. Compared with well co-twins, the affected co-twins had significantly higher total scores of fourth- and fifth-month dysmorphological hand anomalies. 相似文献
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