ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03141.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYFor many species of Oomycetes, the infection of host plants is initiated by motile biflagellate zoospores. In recent years, studies of these zoospores have utilized monoclonal antibodies directed towards a variety of zoospore components. Although only two species of fungi,Phytophthora cinnamomiandPythium aphanidermatum, have been used for immunization and initial screening, the reactions of these antibodies with over thirty species of fungi in the Peronosporales or Saprolegniales have now been determined. The present paper reviews the methods employed to produce the monoclonal antibodies and to use them to study the biology of the zoospores and the infection process.The lack of a cell wall means that fixation protocols for zoospores for immunization and screening must be chosen carefully so that cell‐surface or intracellular sites will be accessible to the antibodies. The inclusion of glutaraldehyde in the fixative helps keep the zoospore plasma membrane as intact as possible, and screening with cells fixed in the presence of glutaraldehyde selects for antibodies that bind to the surface of the zoospores. Five different patterns of labelling to the zoospore surface have been found. Other antibodies bind with three distinct patterns to the surface of zoospores and/or cysts.The use of formaldehyde alone in the fixative solution allows fragmentation of the plasma membrane and the exposure of intracellular components. InP. cinnamomiattempts to obtain antibodies directed against intracellular antigens were hampered by the presence of an immunologically dominant component that is stored in small vesicles in the zoospore cortex and secreted onto the surface of cysts. This problem was resolved by immunotolerizing mice neonatally before proceeding with immunization 2 months later. Antibodies directed towards a number of novel sites were obtained in this way.Monoclonal antibodies generated by these methods have been used to identify taxonomically specific spore components, to locate surface molecules that might be responsible for the induction of zoospore encystment and to characterize molecules involved in spore adhesion to potential host

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03142.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYThe interpretation of element concentration data for X‐ray microanalyses of biological tissues, which are subjected to some experimental treatment, can be complicated by changes in cell volume and total cell dry matter induced by the treatment. We have examined the manner in which such changes would affect the values measured in frozen‐dried cryosections of soft tissues, and how they may be taken into account in the interpretation of the results. The element content (mass per unit dry weight) measured by the peak‐to‐continuum or Hall method is independent of changes in cell volume, but is sensitive to a change in the local dry mass. Conversely, intracellular concentrations in terms of mass per unit volume, as determined by the peripheral or internal standard technique, are dependent on volume changes but independent of dry mass. The estimated dry weight fraction is affected by changes in both volume and dry mass. The results obtained from both quantification methods can therefore provide information on the combination of changes in cellular element levels, volume and total dry mass that may occur following the experimental treatment.In a study of the late effect of the drug cisplatin on electrolyte concentrations in kidney proximal tubules, both quantification methods have been used to obtain wet weight and dry weight concentrations. By applying the above considerations, the analytical results have been interpreted as a combination of changes in element levels and a shrinkage of the tubule cells. Cell shrinkage was confirmed by morphometric analysis of tubular cross

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03143.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYAn inexpensive device for reproducible freeze‐substitution is described. The equipment consists of a reciprocating shaker, holding vials of substitution fluid, mounted in the gas phase of a large liquid nitrogen refrigerator. The shaker temperature is controlled by a programable microprocesso

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03144.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYFreeze‐substitution in combination with confocal scanning laser microscopy provides a unique means by which the microstructure of undecalcified, and chemically untreated, polyps of scleractinian corals can be examined free of preparation artefacts. Mucocytes and intercellular spaces are particularly well preserved and the relationships of cell layers to each other and to the skeleton are undisturbed. Freeze‐substitution also permits X‐ray microanalysis of bulk samples and thin sections, a procedure which has hitherto been impossible to carry out on corals except on fixed tissue samples. Analyses indicated a high retention of Na+and Cl−in spaces thought to be filled with fluid similar in composition to sea water. This increases confidence in freeze‐substitution as a means of retaining diffusible ions. Zooxanthellae contained metal/Ca ratios within the range of those previously reported for extracted zooxanthellae. It is shown that the mucocytes contain very high concentrations of S, K, Ca and Sr which are specifically localized in mucous granules. The concentrations differ between, and are characteristic of, different epithelial cell layers. Remarkably good correspondence was obtained between the two entirely different X‐ray analytical methods. This is the first time such a comparision between methods has been made. It is suggested that the uptake of transepithelially transported Ca2+and Sr2+by mucocytes may be a means of regulating the deposition of these ions in t

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03145.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYTissue samples that have been stored for many years, in different media and under a variety of conditions, have been examined by modern techniques of immunoelectron microscopy, using antibodies against elastic tissue components. A range of post‐embedding restorative procedures has been identified, which will allow reliable immunolocalization of antibodies against the elastic tissue component of such specimens. These methods have been applied successfully to autopsy‐derived material, fixed in buffered formaldehyde, to archival material stored frozen at −70 or −20·C, to specimens fixed for electron microscopy and stored for many years in buffer, and even to archival material from formaldehyde‐fixed, paraffin‐embedded blocks, reprocessed for electron microscopic examination.The successful restorative methods included pre‐treatment of the sections with 6***M guanidine hydrochloride, or 1M Tris/saline, each containing 100 ***mM dithiothreitol (a reducing agent) followed by alkylation with 220 mM iodoacetamide. The application of these techniques allowed reliable study of elastic tissue antibody distributions in archival tissues that could not be obtained again, as well as comparative studies with tissues processed many ye

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03146.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYThe ALCHEMI method for locating the sites of foreign atoms within crystals is known to be sensitive to the delocalized emission of X‐rays. This can result in large errors in some cases through differences in delocalization for different excitations or by error amplification in the ratio method of analysis. An alternative approach to the analysis of ALCHEMI data, using multivariate statistical analysis, is extended to the case of multiple impurities. Initial results from zone‐axis channelling experiments for a Yb‐doped zirconolite (CaZrTi2O7) are shown to confirm the improved accuracy of this method, especially for axial orientations. Data were collected using a 400‐keV analytical electron microscope fitted with an intrinsic Ge X‐ray detector. The potential advantages for ALCHEMI analysis of Ge detectors are c

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03147.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYAn evaluation was made of an intrinsic germanium X‐ray detector fitted to a 400‐keV electron microscope. Its characteristics as a function of accelerating voltage, pulse processor settings and count rate were investigated. Comparisons are drawn between intrinsic Ge and Si(Li) detectors at both an experimental and theoretical level. The software requirements for the successful collection of spectra are discus

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03148.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYThe environmental scanning electron microscope (ESEM) allows the examination of specimens in a gaseous environment. It is based on an integration of efficient differential pumping with a new design of electron optics and detection systems. Backscattered, cathodoluminescence and X‐ray detectors can be designed to fit and to perform optimally in the ESEM. The secondary electron signal can be detected with the gaseous detector device, which is a new multipurpose detector. Insulating, uncoated, wet and generally both treated or untreated specimens can be studie

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03149.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SUMMARYThe use of electron microscopy (EM) to study microporous membranes is described. Application of EM to polymer membranes can be classified into two major areas: elucidation of membrane formation mechanisms (the effect of preparative parameters on morphology of the final membrane) and physical characterization of membranes.Conventional transmission and scanning electron microscopes have been used successfully to clarify details of membrane organization (structure) and formation mechanisms as well as supplying some information on the pores. However, neither transmission electron microscopy nor scanning electron microscopy could resolve the fine surface morphology of ultrafiltration membranes due to instrumentation limitations. The recent development of field‐emission scanning electron microscopy has opened new opportunities in membrane researc

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1991.tb03150.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY