共查询到20条相似文献,搜索用时 31 毫秒
1.
Experiments on rat hippocampal slices were performed with testing of the synaptic connections of Schaffer collaterals and neurons in field CA1 to study the effects of interrupting low-frequency test stimulation (0.05 Hz) on the amplitude of population spikes. These studies demonstrated a correlation between the duration of pauses in stimulation (form 10 to 120 min) and increases in the amplitude of spikes (on average by 30–100% of baseline response magnitude). This deprivation potentiation was additive and could persist for long periods of time (testing was up to 1 h). Preliminary induction of long-term post-tetanic potentiation, which prevented the subsequent development of the late, but not the short-term phase, for 1–3 h, led to suppression of the development of deprivation potentiation after a 60-min pause in stimulation. Similar results were obtained in experiments using 20 M polymyxin B, which blocks protein kinase C and the PKC-dependent phase of long-term post-tetanic potentiation; this is evidence supporting the previously advanced hypothesis that the development of deprivation potentiation and the late, PKC-dependent phase of long-term post-tetanic potentiation share common mechanisms, associated with people phosphorylation. 相似文献
2.
3.
4.
The aim of the present work was to study the interaction between the optical properties of images of “ disappearing” optotypes
and their recognition thresholds. The “disappearing” optotypes were figures with complex outlines and had a unique property-they
were close to the threshold of recognition and observation, which increases the accuracy of measurement of visual acuity and
the subjects’ attention to them. The recognition distances of “disappearing” optotypes were measured. A relationship was found
between the recognition distance of “disappearing” optotypes and different optical density profiles on the one hand and the
spatial and spatial frequency characteristics of the stimuli on the other. The decisive factor determining the threshold of
recognition of optotypes in spatial frequency terms is its spatial frequency spectrum; that in spatial terms is the width
of the black/white pair or black-white triad in the complex outline. Regardless of the shape of the optotype, one of the most
important limiting factors was the concordance of this test with the scattering function of the subject’s eye optics.
__________
Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 91, No. 9, pp. 1080–1090, September, 2005. 相似文献
5.
6.
Previous research in cellular adhesion has focused primarily on studying isolated cells under conditions where cells do not interact with each other. However, in vivo cells form sheets where both cell–substratum and cell–cell interactions contribute to the overall adhesive behavior. Our understanding of how cell–cell and cell–substratum interactions affect the overall process of cell adhesion in these situations is limited. To address this problem, we developed a systematic approach to evaluate how cell–cell and cell–substratum interactions affect the critical shear stress for detachment for semiconfluent and confluent sheets of cells. Our studies were based on subjecting cultures of adherent cells to a defined hydrodynamic flow in a radial-flow chamber with a gap height of 140 m. Using phase-contrast microscope imaging and analysis we measured shear-dependent patterns of detachment as a function of the extent of cell confluency. Our results show that the critical shear stress for detachment is maximum at intermediate extents of confluency of 10%–40%. These results have important implications for sodding vascular grafts and tissue engineering. © 1999 Biomedical Engineering Society.
PAC99: 8718-h, 8719Rr 相似文献
7.
8.
9.
WANGHui-min YANYu-hua LIShi-pu 《中国生物医学工程学报(英文版)》2004,13(1):16-20
Porous biomaterials are widely used as bone replacement materials because of thers high biocompatibility and osteoconductivity property. Understanding of their porous structure (i. e. geometrical and topological characteristic) and studying how to the body fluid flow through them are essential to investigate thed egradation behaviour at the surface-liquid interface. This research develops a numerical model to simulate the porous structure of biomaterials based on the stochastic approach in pore size distribution and interconnectivity. 相似文献
10.
《中国生物医学工程学报(英文版)》1999,(4)
1.IntroductionInordertofindQutthebestwaytodiagnoseandtreatthecarcinomaofbreaSt,thestudyforpathology,andmorphometryorstereologyareverynecessary.ButthequantitativeanalysisoftheultrastructllreortheStere0l0gyaboutbreaStcarcinomahasnotyotbeenseenandnottobereported('x'x').Sowemeasured28morphologicalparametersofmit0chondrion,lysosome,roughendoplasmicreticulumandribosomeintencasesofscirrhouscarcinomaofbreastbystereologicmethods.Wehopedthatthisworkwouldpr0vides0mequantitativedaaforpathologyandearlydi… 相似文献
11.
A. I. Nikolaev 《Bulletin of experimental biology and medicine》1959,48(6):1518-1523
Summary The valency of antibodies was studied by the method of exhaustion of antisera against mono-and diazoproteins, and subsequent cross reactions both with the antibodies left over in the supernatant fluid of the serum and with the precipitating and nonprecipitating antibodies isolated from the precipitate.It was proved that the antibodies interact with the antigens as multivalent compounds.The valency determined with regard to the azoproteins is dependent upon the number of groups introduced.Thus, bivalent antibodies correspond to monoazoproteins and trivalent ones to diazoproteins.The valency of antibodies is, evidently, determined by the structural similarity of the heterologous and the immunizing antigens as well as by the less complete specific conformity between the individual structural peculiarities of the antigen and its antibody.From the Tashkent Pharmaceutical Institute (Director-Docent M. A. Azizov)Presented by Active Member AMN SSSR N. N. Zhukov-Verezhnikov 相似文献
12.
Nabel EG 《The New England journal of medicine》2006,355(22):2365-2367
13.
We describe a new case of semantic deficit in which nonliving categories are disproportionately impaired. PL, a woman affected by progressive degeneration of the left temporal lobe, was examined twice, at a distance of 1 year. The deficit was first apparent on naming and on a verbal semantic questionnaire, but a year later nonliving categories were disproportionately affected also on verbal comprehension (word/picture matching task). Body parts and musical instruments were also investigated: the former was the best preserved category, whereas the latter was the most severely affected. Considering all categories, functional and perceptual information was not differently affected, but there was a trend toward a worse score for nonliving category functional questions. Discussing the current hypotheses on the genesis of category dissociations, we conclude that nonliving categories might not be a true domain, and that their impairment could simply derive from the relative sparing of the domains of the living categories, for which separate cognitive and anatomical representations can be better postulated. Finally, we discuss the problems raised by published cases in an attempt to find a consistent anatomical substrate for category dissociations. 相似文献
14.
We studied the effect of terahertz radiation at atmospheric oxygen frequency 129 GHz on blood nitrite concentration in different
types of experimental stress against the background of administration of nonselective inhibitor of constitutive NO-synthases.
Normalizing effects of radiation on blood nitrite dynamics in animals with acute stress was shown after 15-min exposure and
in animals with chronic stress after 30-min exposure. No positive effect of terahertz radiation was observed on altered blood
nitrite concentration in male rats after preliminary administration of nonselective constitutive NO-synthase isoform inhibitor
L-NAME. 相似文献
15.
16.
17.
A. I. Karamyan Yu. A. Pankov A. L. Protsenko T. N. Sollertinskaya I. L. Kofman 《Neuroscience and behavioral physiology》1991,21(5):453-460
The role of -endorphin in the regulation of conditioned instrumental food-procuring reactions and more complex forms of nervous activity such as reflexes of choice of the side of reinforcement was studied in cats. It was established that the subcutaneous injection of small doses of -endorphin (10 g/kg, 15 ·10–6 g/kg) exerts a facilitatory nonspecialized effect on positive and negative food-procuring conditioned reflexes that has an overall adaptive character overall. The influence of the same doses of -endorphin on conditioned reflexes of choice is more complex in character, depending upon the initial level of conditioned reflex activity and on the typological features of the experimental animals. A possible mechanism of the influence of -endorphin on higher nervous activity is discUSSed.Deceased.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 76, No. 8, pp. 992–1000, August, 1990. 相似文献
18.
Belsky YP Ivanova AN Danilets MG Belska NV Ligatcheva AA Uchasova EG Reikhart DV 《Bulletin of experimental biology and medicine》2011,151(2):190-193
We compared the effects of NF-κB inhibitor aurothiomalate and voltaren on NO production by mouse macrophages in vitro, their ability to cause local edema at the site of injection, and their effect on carrageenan-induced inflammation. High
concentrations of aurothiomalate reduced NO production, while in low concentrations both aurothiomalate and voltaren stimulated
this process. When injected into mouse footpad, aurothiomalate in a dose >1 mM and voltaren in a dose >1.6 μM induce paw edema.
Both compounds suppressed carrageenan-induced inflammation, but the efficacy of aurothiomalate 2-fold exceeded that of voltaren. 相似文献
19.
YUDan-ni 《中国生物医学工程学报(英文版)》2000,(1)
INTRODUCTION In the treatmentof labial teeth by light-cure composite resin,before acid-etchingthe artificial grinding method isusually adopted to thin the enamel supperficial layerso as to enhance the acid-etching effect and to improve the fixation of… 相似文献
20.