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An increasing flow of evidences collected on elementary forms of learning processes in selected animal models evidentiates some mechanisms which can represent the basic cellular principles underlying plastic changes: 1. 5HT and second messengers of nucleotide type (like cAMP) have a pivotal role in the learning process. 2. In almost all short-term learning processes the modifications are subserved by a mechanism of protein phosphorylation. 3. In various animal models the modulation of K+ and Ca2+ channels is the molecular mechanism for learning. Experiments performed in sensory T neuron of the leech indicate that the modulation of Na+/K+ electrogenic pump is one of the fundamental mechanism for learning. 4. In long-term plastic changes, the most important finding is that newly synthesized proteins are formed. 5. In addition to what has been observed in the Aplysia model, where changes in synaptic efficacy represent the basic principles of memory storage, in the leech it has been demonstrated that a molecular machinery present in a single neuron can adapt the activity of the cell to environmental stimuli.  相似文献   
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钢液和铁液的吸氮脱氮动力学研究   总被引:2,自引:0,他引:2  
研究了1600℃时钢液的吸氮和脱氮以及铁液的吸氮动力学,测定了相应的传质系数并与文献数据及理论计算值进行了比较。  相似文献   
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A sensitive and precise in vitro technique for detecting DNA strand discontinuities produced in vivo has been developed. The procedure, a form of runoff DNA synthesis on molecules released from lysed bacterial cells, mapped precisely the position of cleavage of the plasmid pMV158 leading strand origin in Streptococcus pneumoniae and the site of strand scission, nic, at the transfer origins of F and the F-like plasmid R1 in Escherichia coli. When high frequency of recombination strains of E. coli were examined, DNA strand discontinuities at the nic positions of the chromosomally integrated fertility factors were also observed. Detection of DNA strand scission at the nic position of F DNA in the high frequency of recombination strains, as well as in the episomal factors, was dependent on sexual expression from the transmissable element, but was independent of mating. These results imply that not only the transfer origins of extrachromosomal F and F-like fertility factors, but also the origins of stably integrated copies of these plasmids, are subject to an equilibrium of cleavage and ligation in vivo in the absence of DNA transfer.  相似文献   
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Human mono- and lymphocytes from peripheral blood and the monoblastoid cell line U-937 were used in this in vitro study of drug-induced lipidosis. Mono- and lymphocytes were exposed for 4 days to three different tricyclic antidepressants (TCAs), imipramine (25 microM), clomipramine (10 microM) and citalopram (80 microM). The lipophilic fluorophore Nile red, which stains intracellular lipid structures selectively, was used as a lipid probe. Fluorescence microscopy, spectrofluorimetry and flow cytometry were used to detect cellular lipidosis, as verified by electron microscopy. Our results demonstrate that imipramine, clomipramine and citalopram induce lipidosis in monocytes and U-937 cells, but not in lymphocytes. An accurate quantitation of induced intracellular lipidosis can be achieved by spectrofluorimetric and flow cytometric analysis.  相似文献   
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The clinical features and outcome of thyroid cancer in 61 pregnant women (mean age, 26.0 +/- 5.9 SD yr) and in 528 female, age-matched controls who were not pregnant (mean age, 26.3 +/- 5.9 SD yr) were compared. Median follow-up was 22.4 and 19.5 yr [P = not significant (NS)] in the two groups, respectively. The thyroid nodule was asymptomatic and discovered on routine examination more often in the pregnant women (74%) than in controls (43%, P < 0.001); other clinical and tumor features were similar in the two groups. Most of the pregnant women underwent thyroidectomy after delivery (77%) or during the second trimester of pregnancy (20%). Near-total thyroidectomy was done in 43 (73%) of the pregnant women and 265 (59%) of the controls (P = NS), and nearly the same proportion of both groups (30% and 25%, respectively) were treated with 131I postoperatively. Outcome in the pregnant women and controls, respectively, was: cancer recurrence 9 (15%) and 107 (23%, P = NS); distant recurrences 1 (2%) and 12 (3%, P = NS), and cancer deaths 0 and 6 (1.2%, P = NS). Outcomes were similar when surgery was done during or after pregnancy, despite a longer delay in treatment of the latter (1.1 +/- 1.0 vs. 16.1 +/- 19.7 months, P < 0.001). This study suggests that the prognosis of differentiated thyroid cancer is the same in pregnant women and nonpregnant women of the same age, and that the diagnosis and treatment of thyroid cancer occurring during pregnancy can be delayed until after delivery in most patients.  相似文献   
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The MMPI-2 was administered twice to college students under two formats: standard booklet administration and oral presentation, with the examiner reading the items to the students and recording their answers. The two types of administration were compared in a series of mixed-factor analyses of variance. No significant differences were found when comparing oral and booklet presentation for either men or women.  相似文献   
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