摘要:

SUMMARYTechniques were tested to ascertain the best method for preparing the surfaces of delicate plant cuticles for microscopic examination at magnifications not exceeding 10,000. Using scanning electron microscopy, comparative examinations were made of cuticles of fresh material, ambient dried, freeze dried, critical point dried, and frozen material kept at low temperature. Micrographs were compared with material examined using light microscopy which acted as a control at low magnification. Cuticles of the leaves of runner bean, Coleus and the petals of Nicotiana, showed best surface preservation and least wrinkling when frozen, held at low temperature, and examined on a cryostage.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04166.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYVascular reactions to fixation with a 2·5% w/v glutaraldehyde fixative were studied in a constant flow perfusion system on isolated rabbit intestines and hind limb preparations. Reactions induced by the fixative were compared to reactions induced by noradrenaline in each single preparation. Changes in vascular resistance were assessed from continuous recordings of arterial and venous pressures and perfusion flow. Changes in vascular filtration and macro‐molecular permeability during fixation were approximated from recordings of flow and measurements of concentrations of dextran in the perfusate at the arterial inlet and at the venous outlet.Our results indicate that the vascular bed of the preparations studied can be reliably fixed in a high resistance state of smooth muscle activity induced by noradrenaline as well as in a low resistance state in the absence of noradrenaline, provided that hydrodynamic parameters are strictly controlled. The vascular filtration decreases during fixation. In optimally perfused preparations 5–10 min are required to fully saturate the binding capacity of the tissue for glutaraldehyde.Data on viscosity and colloid osmotic pressure of Tyrode solution containing dextran T‐70 in various concentrations, and of various aldehyde‐containing fixatives in 0·1 M sodium phosphate buffer with and without dextran added,

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04167.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYPhysiological effects of the polymeric cryoprotectant dextran on an ion‐transporting epithelium were investigated. In the isolated rabbit pancreas, dextran caused inhibition of fluid secretion and an increase of the concentrations of Na+, K+and Cl−in the secreted fluid. Dextran did not affect the basal or pancreozymin‐stimulated enzyme secretion. These effects of dextran can partially be explained by the fact that it is osmotically active and does not permeate through the epithelium. The effect of dextran on water transport can be compensated by lowering the ion concentrations in the solvent of the cryoprotectant. It is concluded that in cryoprotected ion‐transporting epithelia the absolute ion concentration values obtained by X‐ray microanalysis of frozen‐hydrated specimens may not be completely correct, but that valid conclusions about intracellular ion distribution may sti

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04168.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYA modification of the conventional method for the staining of ultrathin sections resulted in an increase in contrast of ultrastructural detail in tissues. Tissues embedded in Spurr's low viscosity embedding medium were stained with freshly centrifuged Reynolds' lead citrate for 1–5 min, rinsed in double distilled water and dried prior to staining with a saturated solution of uranyl acetate for 40 min, and freshly centrifuged Reynolds' lead citrate for 20 min.Sections treated by this procedure showed enhanced staining of cellular organelles and cytoplasmic matrix. This procedure is recommended for tissues with poor staining qualities resulting from either prolonged fixation or from inadequacies in the buffer or embedding medium use

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04169.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYThe quantitative characterization of the arrangement of microstructural features is important for understanding the properties or function of materials or tissues. In this paper, the well‐known analysis of nearest neighbour distances is modified in order to separate clusters from a background of randomly disposed features and to characterize significant parameters of such sets. In addition, simple procedures are indicated to detect and to characterize regular arrangements, and computer simulated examples are used to demonstrate the efficiency of the suggested algorithms. Each step of the procedures can be used for three‐dimensional arrangements as w

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04170.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYA simple procedure is described for the reproducible and convenient assembly of stereo micrographs, particularly as transparencies, with the help of an apparatus developed for this purpose. Technical features and applications are discussed.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04171.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYA method utilizing polyethylene glycol (PEG) as an extractable embedment for electron microscopy is described. Tissues are fixed according to conventional protocols, embedded in PEG, and sectioned. Sections (ranging from 100 to 500 nm in thickness) are mounted on grids, divested of their PEG matrix, critical‐point‐dried, and examined stereoscopically. This method greatly facilitates studies on the three‐dimensional organization of cytoskeletal and cytoplasmic contractile systems in both muscle and nonmuscle

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04172.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYFractal properties and the concept of fractal dimension has been studied. Emphasis is given to the applicability in structure analysis. Comparison between different measurement procedures, analyses of mathematically defined lines and surfaces as well as measurements on real surfaces have been performed. The stereological consequences have been considered.A restrictive use of the fractal analysis results as an indicator of size, shape and self‐similarity is recommended. If results obtained by quantitative microscopy at different magnification‐resolution levels are to be compared, fractal analysis may be of advantage. The actual choice of resolution should yet be determined from the physical relevance of the geometrical deta

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04173.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYThe aim of the present investigation was to study the extent to which lipids are extracted from biological membranes during dehydration and embedding procedures carried out at high or low temperatures. Cells ofAcholeplasma laidlawiiwere used as experimental material, since the lipids of this bacterium easily can be radioactively labelled without labelling the rest of the cell, and the lipids are almost entirely located in the cytoplasmic membrane. The cells were fixed at 277 K with glutaraldehyde, sequentially with this reagent and osmium tetroxide, or with glutaraldehyde, osmium tetroxide and uranyl acetate in that order. Loss of lipid during these procedures was negligible.When cells fixed with glutaraldehyde and osmium tetroxide were dehydrated with ethanol at room temperature and embedded in Epon at 333 K, i.e. subjected to a conventional treatment, about 90% of the lipid content of the cells was extracted. The loss was reduced toc.20% when treatment with uranyl acetate was included in the procedure and the non‐polar methacrylate resin Lowicryl HM20 was substituted for Epon. When cells fixed with glutaraldehyde and osmium tetroxide were dehydrated with ethanol at 238 K and embedded in Lowicryl HM20 at room temperature, practically no lipid was extracted. Substitution of the polar methacrylate‐acrylate resin Lowicryl K4M for Lowicryl HM20 resulted in the loss of about half of the lipid content of the cells. The use of ethanediol as dehydrating agent instead of ethanol did not diminish the extraction. Cells fixed solely with glutaraldehyde lost about half of their lipid content, even when both dehydration and embedding was performed at 238 K.The lipid material extracted from glutaraldehyde‐fixed cells contained slightly more saturated fatty acids than that remaining in the cells. The reverse was true for osmium tetroxide‐fixed cells. With respect to lipid species, the extractions were generally rather uns

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04174.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYThree types of cationic reagent—cellulosic anion exchangers, cationic phthalocyanin dyes and detergents—formed insoluble complexes with the polyanions heparin, chondroitin‐4‐sulphate, hyaluronate, alginate and DNA. Dissociation of their complexes by MgCl2was a critical phenomenon, occurring at a sharply defined concentration, the critical electrolyte concentration (CEC), in water and in water‐organic‐solvent mixtures. CECs of polysulphates were always higher than those of polycarboxylates or polyphosphates, especially in the presence of dimethyl sulphoxide or ethanol. The latter effect should improve biochemical fractionations and differential histochemical staining of polyanions.A general theoretical framework is proposed. Complex formation is promoted by electrostatic attractions, and results in a loss of polymer mixing energy. Electrolytes suppress the electrostatic interaction, thus preventing complex formation. More efficient suppression of the electrostatic interaction is required in a ‘worsening’ solvent, i.e. where a rise in CEC occurs. Plots of CEC against solvent composition are interpreted on these bases. Available data on electrolyte solutions account for specific ionic effects.The dissociation of phthalocyanin dye micelles in aqueous dimethyl sulphoxide, etc, was studied spectroscopically. The results support and extend the conclusions derived from the insoluble anion‐exchange celluloses.The general concepts serve as a bridge between biochemical and histochemical fractionations (i.e. specific staini

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04175.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY