Stimulus-response function at several levels of background luminance,in the cat visual areas 17 and 18

Summary Stimulus-response curves of simple cells of the visual cortex were obtained by using 500-msec stationary stimuli. Background influence on single unit responses was studied. The contrast sensitivity of simple cells increases as a function of background luminance. The resolution power of these cortical cells for detecting differences in stimulus contrast decreases at background levels above 0.09 cd/m².This investigation was supported by a grant from the Consiglio Nazionale delle Ricerche, Rome (Italy).     

一种改进的Knockout抠图方法

通过对Knockout算法的研究分析,针对其在实际应用中需要用户大量的交互工作以及因模型简单造成的抠图不精确问题,提出了一种改进算法。该算法用区域生长方法将用户输入的前、背景线段生长聚合成前、背景区域;然后用轮廓查找方法找到两个区域的轮廓作为Trimap的前、背景轮廓线;最后使用优化颜色样本的方法对每个未知像素点的样本进行优化,提高抠图的精确度。实验结果表明,改进后的算法需要用户较少的工作量,能够得到传统Knockout算法更好的抠图效果。     

Sustained and transient cortical neurones in area 18 of the cat

Summary The majority of the simple cells in area 18 of the cat's visual cortex gave pure transient responses to flashing slits of light. A few simple cells gave sustained responses to stationary slits of light. All of the complex cells encountered gave transient responses.     

Effect of infection of mice with Friend leukemia complex viruses on background antibody-forming cell production in vitro

Friend leukemia complex (FLC), and Rowson-Parr virus (RPV) infections of donor mice depress the production of background antibody-forming cells by splenocytes cultured in the absence of specific antigenic stimulation.     

An improved thioflavine S method for staining neurofibrillary tangles and senile plaques in Alzheimer's disease.

Large differences are usually observed when standard staining methods for a number of pathological lesions in neurodegenerative disorders are compared. With the modified thioflavine S method presented here (easy and cheap to perform), the morphological appearance of the stained neurofibrillary tangles (NFT) and senile plaques (SP) is greatly improved. Furthermore, the intense contrast between stained lesions and background obtained with this technique permits an accurate automatic quantification of NFT and SP using a computer-assisted image analysis system.     

An improved thioflavine S method for staining neurofibrillary tangles and senile plaques in Alzheimer's disease

Large differences are usually observed when standard staining methods for a number of pathological lesions in neurodegenerative disorders are compared. With the modified thioflavine S method presented here (easy and cheap to perform), the morphological appearance of the stained neurofibrillary tangles (NFT) and senile plaques (SP) is greatly improved. Furthermore, the intense contrast between stained lesions and background obtained with this technique permits an accurate automatic quantification of NFT and SP using a computer-assisted image analysis system.     

人结肠癌CW-2干细胞获取方法研究

目的运用3种不同的方法分离纯化人结肠癌CW-2干细胞,并对其分离纯化效率进行比较,探讨获得癌干细胞的有效方法。方法采用单纯无血清悬浮培养、无血清悬浮培养联合化疗药物、流式细胞分选技术分别富集人结肠癌细胞株CW-2干细胞;然后运用流式细胞术、NOD—SCID小鼠致瘤实验和Transwell侵袭实验分析比较3种方法的富集效率。结果无血清悬浮培养细胞．无血清悬浮培养联合化疗药物处理细胞和流式细胞仪分选技术分选后细胞中具有结肠癌干细胞特性的CD44＋EPCAM_细胞分别为（59．39±4．55）％、（74.36±6．78）％、（86．43±8．43）％;3群细胞的成瘤能力和侵袭能力都存在显著统计学差异（P值〈0．05）：流式细胞分选技术分选后细胞〉无血清悬浮培养联合化疗药物处理细胞〉单纯无血清悬浮培养细胞。结论流式细胞分选技术富集癌干细胞的能力强于单纯无血清悬浮培养和无血清悬浮培养联合化疗药物,无血清悬浮培养联合化疗药物又强于单纯无血清悬浮培养。     

Dexamethasone enhances CTLA-4 expression during T cell activation

T cell activation is enhanced by the costimulatory interaction of B7 on antigen-presenting cells and CD28 on T cells, resulting in long-term T cell proliferation, differentiation and production of large amounts of cytokines, such as interleukin (IL)-2. CTLA-4 is a co-stimulation receptor that shares 31% homology with CD28 and binds B7 family members with higher affinity. CTLA-4 is transiently expressed intracellularly and on the cell surface following activation of T cells. We have studied the kinetics of CTLA-4 expression and the effects of dexamethasone on CTLA-4 expression during T cell activation in cultures of mouse spleen cells stimulated by a mixture of immobilized anti-CD3 and anti-CD28 monoclonal antibodies (anti-CD3/CD28 mAb) or concanavalin A (ConA). CTLA-4 expression peaked on day 2 and returned to background levels after 7 days. Dexamethasone was found to potentiate CTLA-4 expression in a dose-dependent manner with an EC₅₀ effective concentration 50%) of about 10⁻⁸ M. In contrast, other immunosuppressive agents, such as rapamycin or cyclosporin A had no or an inhibitory effect on CTLA-4 expression, respectively. Dexamethasone also stimulated CD28 expression, but inhibited IL-2R expression during anti-CD3/CD28 mAb-induced mouse splenic T cell activation. Western blot analyses of lysates of activated mouse T cells showed that dexamethasone increased CTLA-4 protein levels twofold during anti-CD3/CD28 mAb-induced activation. Dexamethasone also enhanced CTLA-4 messenger RNA twofold as quantified by ribonuclease protection assay. The effects of dexamethasone on CTLA-4 expression were glucocorticoid-specific and completely inhibited by the glucocorticoid receptor antagonist mifepristone (RU486), indicating that the effect of dexamethasone on CTLA-4 expression is mediated through the glucocorticoid receptor. In conclusion, the immunosuppressive agent dexamethasone actually stimulates CTLA-4 expression, which is involved in downregulation of T cell activation. Received 19 May 1999; received after revision 13 July 1999; accepted 13 July 1999     

Cultivation of arterial endothelial cells from human umbilical cord

We have developed a simple method for the isolation of endothelial cells from human umbilical artery. The method provides a sufficient number of cells to be of experimental value. The presence of factor VIII antigen specific for endothelium has been demonstrated by immunofluorescence as well as by the peroxidase-antiperoxidase immune complex method.     

Effect of infection of mice with Friend leukemia complex viruses on background antibody-forming cell production in vitro

Summary Friend leukemia complex (FLC) and Rowson-Parr virus (RPV) infections of donor mice depress the production of background antibody-forming cells by splenocytes cultured in the absence of specific antigenic stimulation.Supported in part by a grant from the Italian Research Council (Progetto finalizzato virus, CT 77.00248.84).     

Pigment distribution in cyanobacteria: An in vivo microspectroscopic investigation

Summary In vivo microspectroscopy represents an effective and reliable technique to study pigment composition and distribution. In contrast to traditional extractive techniques, it preserves the integrity of biological specimens, without modifying the nature of the pigments. The spectroscopic apparatus we used is very simple and consists of a common microscope equipped with a monochromator, a photomultiplier, and two pinhole diaphragms. Absorption spectra obtained by means of this apparatus on different species of cyanobacteria are presented.     

Mitogenicity of autolysates of Trypanosoma congolense

Autolysates of Trypanosoma congolense, in subcytotoxic amounts, were found to be highly mitogenic in vitro for the spleen cells of normal mice. Significant amounts of [3H]-thymidine were also incorporated by the responding spleen cells of nu/nu (athymic) mice. In contrast, the spleen cells of cyclophosphamide-treated mice were unresponsive. The findings suggest that a potent B-cell-mitogen is generated by the autolysing T. congolense organism.     

A simple technique for scintillation counting of cell preparations on coverslips

Summary A simple, rapid and versatile technique for scintillation counting of cells on coverslips is described. The cells are conserved for subsequent staining and autoradiography so that other data can be collected from the same specimen.The financial support of the North West Cancer Research Fund (U.K.) and the skilled photographic assistance of Mr I. Miller are gratefully acknowledged.     

Anchorage-dependent culture of line 10 guinea-pig hepatoma cells

Summary A simple method for the anchorage-dependent culture of line 10 guinea-pig hepatoma cells is described.     

Beziehung zwischen Nebenniere und aktivem Kationentransport

Summary The active sodium transport through the membrane of coldstored red cells of adrenalectomised rats is significantly decreased, whereas the rate of active exchange of potassium is not influenced by adrenalectomy. Cardiac glycosides likewise slow down only the active sodium exchange in the blood of both the normal and adrenalectomised animals in contrast to their action on human red cells.     

Some observations on the Rohon-Beard cell perikaryon.

During the hatching period, the Rohon-Beard cells of Salmo gairdneri showed definite structural maturity of their perikarya, which is in contrast to the amphibian species investigated, where neuronal maturation of the Rohon-Beard cells is finished only in later -- posthatching -- developmental stages.     

Measurement of the biliary tree volume in the rat under Tm-conditions

Summary Biliary tree capacities determined under Tm-conditions using³⁵S-sulfobromophthalein sodium,^35S-sulfobromophthalein glutathione, and¹⁴C-taurocholate sodium as markers exceeded markedly the biliary volumes reported until now. This may have been caused at least partly by a more homogenous distribution of the marker substance throughout the liver parenchyma in contrast to simple bolus injection studies.     

A pragmatic account of mechanistic artifact explanation

A mechanistic artifact explanation is an explanation that accounts for an artifact behavior by describing the underlying mechanism. The article shows that there are different kinds of mechanistic artifact explanation: top-down and bottom-up explanation, and I also distinguish between less and more inclusive top-down explanations. To illustrate these different kinds of explanation, the behavior of a simple, fictional artifact is explained in different ways. I defend that which explanation is ideal, depends on pragmatic factors (e.g., the background knowledge of the explainee and the specific goal for which the explanation will be used). For each kind of explanation, the situations, goals and interests for which it is most appropriate are specified, resulting in a pragmatic theory of mechanistic artifact explanation. This theory is compared to Jeroen de Ridder’s account of the pragmatics of mechanistic artifact explanation.     

Some observations on the Rohon-Beard cell perikaryon

Summary During the hatching period, the Rohon-Beard cells of Salmo gairdneri showed definite structural maturity of their perikarya, which is in contrast to the amphibian species investigated, where neuronal maturation of the Rohon-Beard cells is finished only in later — posthatching — developmental stages.