摘要:

SUMMARYIn developing numerical methods for the solution of computational problems of an involved and pragmatic nature, as occur for example in stereology, the approach should be first to classify the distinct types of numerical problems which arise. If available, appropriate results from numerical analysis can then be used to develop stable numerical processes for their solution. In fact, many of the results relating to the construction of basic numerical methods, such as spectral methods for the stable differentiation of experimental data and product integration methods for the evaluation of integrals with oscillatory and singular integrands, have been resolved. Thus, we are now in a position to apply the above approach to the more complex computational problems which arise in stereology.Many of these problems belong to one of the following two classes: (i) the solution of integral equations of Abel type; and (ii) the solution of some numerical differentiation problem.In Part I of this paper, we illustrate the generality in stereology of the Abel type integral equation and numerical differentiation formulations. As well, we derive the specific properties required in Part II which is mainly concerned with the construction of stable computational methods for (i). Included among these properties are the explicit inversion formulae which are known for general Abel type integral equations. It is these inversion formulae which we use to construct stable computational methods.Often, when estimates for linear properties of the solutions of (i) and (ii) are required, the numerical solution of (i) and (ii) can be circumvented by estimating the linear properties directly from the given observational data. In deriving such estimates, use of the properties of the Abel type integral equation and differentiation formulations plays an essential role. Because of the close connection between such estimation problems and (i) and (ii), the estimation of linear properties from truncated observational data is also examined in Part I.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04045.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYAs mentioned in Part I of this paper, Part II is mainly concerned with the construction of stable computational methods for the solution of integral equations of Abel type which occur in stereology. However, in order to develop a rationale for the types of methods which we shall propose, it is first necessary to review the different types of methods which have been suggested to date in the stereological literature. This is done in section 2. From the review, we conclude that the construction of stable methods can be based on the use of spectral differentiation and product integration to evaluate appropriate inversion formulae, when they are known. Using the Random Spheres Model as exemplification, we examine the nature of such methods in section 3. The potential of the proposed methods is illustrated in section 4 by examining the reliability of the random spheres approximation—an unsolved problem in stereology proposed by Moran (1972). We conclude from this examination that the random spheres approximation is quite reliable for particles which approximate sphere

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04046.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04047.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYA method is reported for preparing, examining and analysing frozen hydrated tissue sections using transmission electron microscopy and X‐ray microanalysis. Use of this method permits localization and measurement of water soluble or diffusible elements within the hydrated cell matrix. Since any change in total fresh weight of the specimen will affect the concentration of all components, great care has been taken to demonstrate that the mass neither increases nor decreases and to ensure that the tissue remains frozen‐hydrated. Criteria for assessing whether or not the tissue remains frozen‐hydrated are reported.After quench freezing, 1–2 μm thick sections of mouse liver were cut at 193°K and picked up on a specially designed annular specimen holder covered with an aluminium coated nylon film. Using a transfer device which prevents contamination of the tissue sections while maintaining them at a low temperature (below 143°K), the sections are transferred either to the vacuum evaporator cold stage or the scanning microscope cold stage. The tissue sections may be coated with an aluminium layer to improve electrical and thermal conductivity. The specimens are examined in the scanning transmission imaging mode and analysed using an energy dispersive X‐ray analyser. Concentration of intra‐nuclear and intracytoplasmic K, P, S and Cl are reported for mouse hepatocytes as ratios of the characteristic radiation to the continuum radiation used as a measure of mass. Ratios for all four elements were higher in the nucleus than the cytoplasm. Examples are given of this method as applied to plant and

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04048.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04049.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYA marine unicellular organism, human trophoblast tissue and cultured trophoblast cells of human origin have been satisfactorily preserved for electron microscopy without resort to washing either before dehydration or between different stages of fixation.The time required to fix and dehydrate a specimen using this method is 55 min.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04050.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYA computer‐aided graphical analysis system is presented which can be used to quantify several types of information from micrographs of cross‐sectioned peripheral nerves. A simple input consisting of eight points, corresponding to two diameters of each axon and two for each axon plus myelin, is used to compute statistical and numerical estimates of these diameters, the myelin thickness being expressed as a function of axon diameter, and both the spatial position and distribution of nerve fibres within the bundle. The computer programs presented and summarized here describe the procedure for digitizing the input data and the subsequent computations for editing and analysis. The general applicability of this approach for automated analyses of other anatomical areas is also presen

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04051.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYFluctuating concentrations of calcium in the blood supplying the avian shell gland are not reflected at tissue level. Analyses of oviducal mucosa throughout the laying cycle show that the concentration of calcium remains relatively unaltered even at peak activity thereby implying a rapid transfer process. These experiments describe the use of potassium pyroantimonate as a localizing agent. The precipitate produced by injecting the latter via the aorta was identified as calcium pyroantimonate by electron diffraction and the efficiency of the precipitant estimated by neutron activation analysis of eggshells present in the shell gland at the time of operation. Results indicate that calcium is transferred across the surface epithelial cells of the shell gland (tubular and pouch regions). Its localization in the former is taken as an indication of the involvement of this region in the production of the mammillary mantle.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04052.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe advantages of using image‐intensifiers and other image pickup systems as an aid to the observation of the image in the electron microscope have been known for many years, and a review of a number of the systems employed so far is presented here. The additional advantages to be gained by the use of a sensitive TV pickup tube in conjunction with a storage tube are discussed, with particular reference to a proposed system for use with a high voltage, high resolution, electron microscope. It is shown that the prime limitation to the signal‐to‐noise ratio obtainable in the image pickup‐display chain is due to the noise in the electron microscope signal itself, and that with the proposed pickup and storage tube arrangement a field of 800 by 600 picture points, with adequate signal‐to‐noise ratio, should be obtainable for a current density of 10−9A/m2in the image plane of the microscope if an integration period of abou

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04053.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYA method is described using simple apparatus for separating and concentrating nematode larvae from host faecal material and a recommended procedure is given for processing the helminths for transmission electron microscopical examination.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1975.tb04054.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY