摘要:

SUMMARYAn improved version of the tandem‐scanning reflected‐light microscope (Petranet al., 1968) has been studied with respect to its applicability to the study of mammalian mineralized tissues. It was found to have important advantages compared with other light microscopic methods, since it allowed microscopic structures to be seen at considerable depths within intact specimens. It has a small depth of focus and gives high contrast for features such as osteocyte lacunae and canaliculi in bone, and prism boundaries in dental ena

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04703.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYThe tritium content of nervous tissue sections is calculated from grain‐density of autoradiographs without loss in anatomical information. The calculation is not based on determination of (expected) grain numbers but on photometric measurements (SKphot), interpreted as the result of the function of exposure time (T) and incorporated activity (β): SKphot =f (T, β).As experimental radiation standards homologous material (optic nerve preparations) with different activities determined by liquid scintillation counting has been used. Exposure times between 12 h and 28 weeks for these preparations with known radioactivities yielded a set of curves (nomogram) relating photometric values to exposure times. At any given exposure time the knowledge of photometric readings and related radioactivities within that set of curves enabled the development of a function covering all photometer readings within the range of the nomogram. Thus, any photometric reading could be correlated to the corresponding radioactivity.Such a function has been applied for the transformation of photometric values obtained from particular brain‐section areas exposed for 16 weeks. Since the results are given in Bq, they may be related and, if necessary, corrected to results obtained by other tritium detection methods.Terminology used in the text: experimental radiation source = experimental standards prepared from optic nerve sections; standard radiation source = polymer reference s

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04704.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYA new method for measuring refractive‐index gradients in rotation‐symmetric objects is described. Interference micrographs of intact objects, with the symmetry axis perpendicular to the optical axis of the microscope, are used to obtain a phase‐shift profile, which is converted into a refractive‐index profile by a computer program. The conversion calculations are based on iterative approximations of the gradient slope in a number of presumed shells in the object. The method is fast, convenient and yields highly accurate results even when only a small number of phase shift values can be obtained. The new method is especially advantageous for analysing many invertebrate eyes but it can also be used for measuring manufactured graded‐index optic

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04705.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYA survey will be given of the theoretical and practical progress that has been made thus far in the field of high‐resolution image computations especially with respect to computational speed and memory requirements. Attention is paid to some problems that have not completely been solved yet and some future prospects are outline

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04706.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYIn stereological studies analysis of sampling variances is used for optimizing the sampling design. In organs with a heterogeneous distribution of the phase of interest the analysis of sampling variances can be undertaken only if the observed variance between sections is distributed into the fraction which is due to random variation and the fraction which is due to the heterogeneity. In the present example (pancreatic islet volume estimated by light microscopic point‐counting) the density of islets showed a linear increase along the axis of the organ. By analysis of sampling variances it was calculated that the most efficient number of sections (cut perpendicular to the organ) was considerably lower when the isolated contribution from the random variation was considered.The total islet volume was obtained by the product of the fractional islet volume and the pancreatic weight. Analysis of sampling variances of thetotalislet volume was performed by including the variance contribution from the individual pancreatic weights to the variance of the group mean total islet volume. Due to a negative correlation between the fractional volume and organ weight the total islet volume in the group of animals was more precisely estimated than the fractional islet volume.The methods used for dealing with the heterogeneity of the organ and for estimating sampling variances of total structural quantities generalize to a large number of stereological studies in biolog

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04707.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYSpherical particles are embedded in an opaque matrix. Circular profiles with radiiX1,…,Xnare then observed from a cross‐section. To estimate the distribution of the particle sizes a two‐stage method is proposed. The probability density of the profile radii is statistically estimated by a smooth, piecewise quartic polynomial, and then an inversion formula is used. The method has some advantages over existing techniques in that the estimate is continuous, is quite straightforward computationally and it involves a less subjective choice of statistical parameters. In the case of several types of distributions, the procedure performed well for simulated

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04708.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYMica is proposed as a convenient substrate for SEM specimens. Mechanically, mica is rigid and can be cut, punched and cleaved into suitable sizes. Compared to glass substrates, mica seems to be more charge ‘resistant’ when irradiated with the same beam density in the microsc

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04709.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYEpoxy‐embedded biological material, sectioned for conventional or high‐voltage electron microscopy, can be visualized within the section with good contrast and detail by phase‐contrast or dark‐field light microscopy. The (phase) contrast of such material is not substantially influenced by the type of embedding resin or section support substrate. It is, however, influenced by the type of fixation, by heavy metal (uranyl and lead) staining and by the section thickness. After screening ultrathin and semithin sections for content with the light microscope, one need stain and examine only those grids containing sections of interest. This approach eliminates the need to screen sections with the electron microscope and, in some cases, the need to stain non‐useful sections. This time‐saving procedure is particularly useful for studies requiring ultrastructural examination of a selected area or structure which is large enough to be visualized with the light microscope but which comprises only a small volume of the embedd

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04710.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYThe paper describes a new polymerization system for embedding soft tissues in glycol methacrylate (GMA). The polymerization of GMA is initiated by means of a barbituric acid derivative in combination with chloride ions and dibenzoyl peroxide. The catalyst system contains no aromatic amines which constitutes a toxicological advantage over the commonly employed system of peroxide/aromatic amine. Clear blocks are obtained from which 1–2 μm sections are easy to cut. In combination with an appropriate softener, polyethylene glycol400, serial sectioning may be practis

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04711.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SUMMARYA stereographic‐based method, utilizing both tilt and rotation, is demonstrated, whereby the underlying crystallography of three‐dimensional planes and directions on fine grained and highly deformed metallic specimens can be determined in a scanning electron microscope (SEM). It requires the recording of two micrographs of the same area (or three‐dimensional object) at different orientations, obtained by tilting and rotating the specimen holder. By measuring the projected lengths and angles of lines with respect to the tilt axis on both micrographs, the interangles between directions can be found, and eventually the crystallographic planes and directions can be ident

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1983.tb04712.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY