Ultrastructure and behavior of actin cytoskeleton during cell wall formation in the fission yeast Schizosaccharomyces pombe

Fluorescence microscopy has shown that F-actin of the fission yeast Schizosaccharomyces pombe forms patch, cable and ring structures. To study the relationship between cell wall formation and the actin cytoskeleton, the process of cell wall regeneration from the protoplast was investigated by transmission electron microscopy (TEM), immunoelectron microscopy (IEM) and three-dimensional reconstruction analysis. During cell wall regeneration from the protoplast, localization of F-actin patches was similar to that of the newly synthesized cell wall materials, as shown by confocal laser scanning microscopy (CLSM). In serial sectioned TEM images, filasomes were spherical, 100-300 nm in diameter and consisted of a single microvesicle (35-70 nm diameter) surrounded by fine filaments. Filasomes were adjacent to the newly formed glucan fibrils in single, cluster or rosary forms. By IEM analysis, we found that colloidal gold particles indicating actin molecules were present in the filamentous area of filasomes. Three-dimensional reconstruction images of serial sections clarified that the distribution of filasomes corresponded to the distribution of F-actin patches revealed by CLSM. Thus, a filasome is one of the F-actin patch structures appearing in the cytoplasm at the site of the initial formation of the cell wall and it may play an important role in this action.     

Cell wall formation in regenerating protoplasts of Schizosaccharomyces pombe: study by high resolution, low voltage scanning electron microscopy

The ultrastructure of regenerating cell wall in Schizosaccharomyces pombe protoplasts was studied with a high resolution, low voltage scanning electron microscope (LVSEM). In contrast to the transmission electron microscopy, the LVSEM images give three-dimensional information on the cell wall regeneration in yeast protoplasts. We found that, after only a few minutes of incubation, the protoplasts began to show protuberances in a unipolar manner, and a fibrilar network was formed asymmetrically which covered the whole surface of the protoplasts after 5 hr. The network consisted of microfibrils about 8 to 10 nm wide, forming flat and wavy bundles of various widths and lengths, up to about 200 nm wide and 1 micron long, mainly made of yeast glucan. Free ends of microfibrils were seldom found. Interfibrillar spaces were progressively filled with granular particles and finally the complete cell wall was formed after 12 hr. The fibrillar network was destroyed by the digestion with beta (1----3)-glucanase. When protoplasts were regenerating in the presence of aculeacin A, the fibrillar networks were not formed, resulting in incomplete cell wall formation. These observations suggest that beta-glucan is the main component of the microfibrils and that it plays an important role in the formation of the cell wall in S. pombe.     

Abnormal formation of the glucan network from regenerating protoplasts in Schizosaccharomyces pombe cps8 actin point mutant

To study the close relationship between the actin cytoskeleton and cell wall formation, the process of cell wall formation in reverting protoplasts of the fission yeast, Schizosaccharomyces pombe, cps8 actin point mutant was investigated by ultra-high-resolution low-voltage scanning electron microscopy (UHR-LVSEM) and transmission electron microscopy (TEM). The protoplast of the cps8 mutant began to form a glucan network in a unipolar manner and to secrete alpha-galactomannan. The site of cell wall formation grew in a cylindrical shape in the wild-type protoplast. The alpha-galactomannan did not fill in the intrafibrillar spaces completely, however, and the fibrils were exposed on the cell surface. UHR-LVSEM images indicated that the glucan fibrils were thin and rope-shaped, forming a looser network than the wild-type. TEM images indicated the finest fibrils were approximately 1.5 nm in diameter, the same diameter as the wild-type. These results suggest that the cps8 mutant was insufficient in developing cross-linkage with the glucan fibrils up to the wide ribbon shape as found in the wild-type [Osumi M et al. (1989) J. Electron Microsc. 38: 457-468; Osumi M (1998) Micron 29: 207-233]. These findings appear to indicate that the actin cytoskeleton controls formation of the glucan network and secretion of beta-1,6-glucan, and confirm the close relationship of the actin cytoskeleton and glucan formation.     

In situ fault detection of wafer warpage in microlithography

Wafer warpage is common in microelectronics processing. Warped wafers can affect device performance, reliability and linewidth control in various processing steps. We proposed in this paper an in situ fault detection technique for wafer warpage in microlithography. Early detection will minimize cost and processing time. Based on first principle thermal modeling, we are able to detect warpage fault from available temperature measurements. Experimental results demonstrate the feasibility and repeatability of the approach. The proposed approach is applicable to other semiconductor substrates.     

In situ measurement of misalignment errors in free-space opticalinterconnects

A nonobtrusive technique for measuring misalignment errors in multistage free-space optical interconnects is proposed. The technique makes use of dedicated microoptics to relay higher order dedicated alignment beams generated by an optical power supply onto alignment detectors located on the periphery of a smart pixel chip. An implementation of this technique for measuring lateral (x-y) misalignment error in a multistage optical backplane demonstrator is then presented. Performance parameters are analyzed and future directions such as photonic extensions to electronic boundary scan standards are suggested     

In situ optical diagnostics of growing surfaces in the process of nanoheterostructure fabrication

It is demonstrated that in situ reflectance and reflectance-anisotropy measurements can be used as efficient real-time monitoring tools for all stages of the growth of heterostructures with ultrathin (few-monolayer) GaAs and AlAs layers. Changes in the layer composition at normal GaAs/AlAs interfaces in the active region of resonant-tunneling diode structures are detected with a thickness resolution on the order of one monolayer. Resonant-tunneling diodes with a peak-to-valley ratio of 3.3 and peak current density of 6.6 × 10⁴ A/cm² are fabricated.     

In situ study of the formation of silicide phases in amorphous Co-Si mixed layers

We investigate Co silicide phase formation when extra Si is added within an as deposited 50 nm Co film. The addition of Si is investigated for both the Co/SiO₂ and Co/Si(1 0 0) system. A series of 10 Co-Si mixed films with a Si content varying from 21 to 59 at.% was prepared and investigated during annealing with in situ X-ray diffraction. The oxide system is used as reference system to identify phases that initially crystallize in an amorphous mixture of a given composition. Multiple phases can nucleate, and the temperature of crystallization depends on the Co-Si atomic ratio. Upon heating of the Co(Si)/Si system, the first reaction is a similar crystallization reaction of the Co(Si) mixture. Once the first phase is formed, one has the normal system of a silicide phase in contact with an unlimited amount of Si from the substrate, and the sequential phase formation towards CoSi₂ is established. For deposited layers of composition ranging from 48%Si to 52%Si, the CoSi is the first phase to form and increasing the amount of Si leads to a remarkable improvement of the thermal stability of CoSi on Si(1 0 0). CoSi₂ nucleation was extensively delayed by 150 °C compared to the reaction observed from a pure Co film on Si(1 0 0). Electron backscatter diffraction measurements reveal that in this range, the gradual Si increase systematically leads to bigger CoSi grains (up to 20 μm). This shows that the grain size of the CoSi precursor strongly affects the nucleation of the following CoSi₂ phase. Laser-light scattering measurements suggest that adding more than 42%Si reduces the roughness of the CoSi₂ layer.     

In situ off-axis electron holography of metal-oxide hetero-interfaces in oxygen atmosphere

Off-axis electron holography has been extended to in situ observations in gas atmospheres. The Yttria-stabilized zirconia (YSZ)-Pt hetero-interface was characterized by electron holography at high temperature in a vacuum and in an oxygen atmosphere. Analysis of the phase shift profiles revealed high mobility of anions in the oxide in the vicinity of the interface in the oxygen atmosphere. This would compensate for any increase in the number of oxygen vacancies in YSZ through the metal interface.     

透射电镜原位研究Ni纳米晶粒成核生长

离子注入能够精确地控制能量和剂量 ,能够注入几乎所有的元素 ,甚至同位素 ,而且注入离子形成的纳米晶粒镶嵌在衬底里 ,使得形成的纳米颗粒得到了很好的保护。近年来 ,离子注入绝缘衬底材料形成量子点结构成为研究的热点。随着离子注入技术和工艺的不断改善 ,该方法在工业应用中成本越来越低 ,相信会在今后的材料制备中得到更广泛的应用。本研究在法国核谱质谱中心 (ＣＮＳＮＭ)的离子注入机和透射电镜联机装置上进行[1] ,衬底材料是用电子束蒸发沉积而形成的非晶ＳｉＯ2 薄膜 ,厚度在 90～ 10 0ｎｍ。选取适当的注入能量使注入离子的投影射…     

In situ optical monitoring of the movpe growth of ZnSe on GaAs

In situ optical reflection measurement was employed to study surface processes during the MOVPE growth of ZnSe films under an alternate supply of diethylzinc (DEZn) and dimethylselenide (DMSe) using H₂ and/or N₂ as carrier gases. We have found that the time-dependent reflection signal exhibits a unique saw-toothed pattern during the DEZn supply, which is attributed to the adsorption and structural change of the DEZn. In contrast, the influence of DMSe on the time-dependent signal appears to be rather marginal. A growth mechanism is proposed based on these experimental results, through which the important role of ambient hydrogen is discussed.     

铝合金塑性变形的原位背散射电子衍射研究

利用扫描电镜中的拉伸台和原位背散射电子衍射(EBSD)研究了Al-Zn-Mg合金在单轴拉伸过程中塑性变形的显微结构演化规律.结果表明,晶粒的取向在塑性变形过程中会发生明显的转动行为.晶粒具有相同或相近的取向,其转动会沿近似的趋势进行.〈101〉取向附近的晶粒其取向转动按照Sachs模型进行,向〈001〉-〈111〉连线方向转动；〈001〉-〈111〉连线附近的晶粒其取向转动按照Taylor模型向〈111〉方向转动,或按照Sachs模型向〈001〉-〈111〉方向转动.取向转动可以导致Schmid因子的增大或减小.实验结果说明,晶粒取向的转动行为受邻近晶粒的取向、变形行为影响.     

Actin ring formation around the cell nucleus of long-neck yeast

The unique long-neck yeast Fellomyces fuzhouensis has F-actin cables and cortical patches. Here, we describe a new F-actin structure present in fungi, a perinuclear F-actin collar ring around the cell nucleus. This F-actin structure can be visualized by fluorescent microscopic imaging of rhodamine-phalloidin-stained F-actin in cells treated with the mitotic drug isopropyl N-(3-chlorophenyl) carbamate or the microtubule inhibitor thiabendazol or when cells were grown in cut dried radish medium or yeast extract pepton dextrose (YEPD) medium. In contrast, these structures were absent in cells treated with Latrunculin A. The hypothetical functions of the F-actin ring are discussed.     

In situ high temperature TEM observation of interaction between multi-walled carbon nanotube and in situ deposited gold nano-particles

Interaction between multi-walled carbon nanotubes (MWNTs) and deposited gold nano-particles has been dynamically observed in a 200 kV transmission electron microscope (TEM) using a specimen heating holder. Gold particles with diameters of several tens of microns were mixed with MWNTs to mount on the heating element of a specimen heating holder. The gold particles were instantaneously heated to 1373 K to deposit gold nano-particles on the MWNTs from a very short distance. The MWNTs were then heated to 1073 K to observe interaction between the deposited gold nano-particles and MWNTs. Some gold nano-particles drilled through the wall of the MWNT and entered the capillary space of the MWNTs. To characterize the mechanism of the transition of the gold nano-particles into the capillary space of the MWNT, high resolution TEM observation of the deformed wall of MWNT was also carried out.     

应用电镜及电镜原位杂交法观察和分析SARS-CoV在人体细胞内的定位

本文通过电镜及电镜原位杂交方法,观察和分析SARS患者外周血淋巴细胞和SARS尸体解剖肺组织内的SARS CoV病毒颗粒的分布,并对SARS CoV病毒颗粒进行定性鉴定。在SARS患者外周血淋巴细胞和Ⅱ型肺泡上皮细胞内均发现了SARS CoV病毒样颗粒,直径大小80～120nm,圆形或椭圆     

文昌鱼表皮中酚氧化酶的超微结构定位

文昌鱼是从无脊椎动物到脊椎动物的过渡类型,在进化上占有极重要的地位。本文以L－多巴为底物,显示酚氧化酶（PO）存在于文昌鱼体表上皮细胞的胞质中,PO颗粒呈圆形均质状,直径在420－700nm之间,电子密度较高,其外无膜包被。苯硫尿（PTU）抑制酚氧化酶反应,指出该反应为PO的特异性反应,而不是底物的自氧化或其它假阳性反应。     

In situ FTIR and surface analysis of the reaction of trimethylgallium and ammonia

Using a combination of in situ FTIR spectroscopy and detailed surface analysis, we find that TMGa decomposes at the same rate in either hydrogen or nitrogen forT < 300° C. Although ammonia does not decompose under these conditions, mixing TMGa with ammonia increases the rate of methane formation. Reacting perdeutroammonia with TMGa shows that hydrogen from the ammonia is incorporated into the product methane (whereas deuterium in the gas phase is not incorporated into the gaseous product). TMGa and ND₃ do react; however, nitrogen incorporation in the growing film is temperature dependent. Further, although the decomposition of TMGa occurs in the gas phase, the last steps of the decomposition/reaction occur on the substrate surface.