摘要:

SUMMARYThe starting point is the problem of finding the percentageq2of paired nuclei in liver cells, when the percentagep2of twin cuts in slices is known. The general solution for unequal spheres becomes most simple for equal spheres and leads to an extrapolation for endless straight chains of equal spheres, at first for closed and then for open series with constant intervals. Three total sums of endless series of fractions are a welcome mathematical extra.The microscopist will prefer instructions which are generalized from counts in final rows of spheres. With them he can analyse the composition of a mixture of limited chains, with different numbers of spheres.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1972.tb01058.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYQuantitative Polarographic studies of the reaction between methylmercuric iodide and variously reduced wool keratin indicate that reaction occurs specifically with the thiol groups from cystine. Since loss of protein from fibres is negligible, this organomercurial is preferred as a selective amino acid label in electron microscope studies. Similar reactions of wool with parachloromercuribenzoate (PCMB) result in extensive structural modifications.The mercury mercaptides were shown to be thermally unstable in the electron beam and cooling of the specimen between — 140°C and — 88°C coupled with low beam intensities was found necessary to study the original distribution of the mercurials in the samples. Since a direct relationship between the electron scattering sites of the mercurial and cystine within the keratin was established, it has been possible to demonstrateunambiguouslyfor the first time that:(a) There exists a radial distribution of cystine within cuticular cells. Indeed a new sulphur‐rich component at the outer edge of the ‘a’ layer in peripheral cuticular cells has been identified.(b) Para‐cortical cells of intact keratin contain a higher proportion of cystine than ortho‐type cells.(c) A dense concentration of cystine labelled by the electron scattering centres (mercurials) corresponds closely to an intermicrofibrillar‐matrix system in the cortex.Furthermore, a method has been devised for determining the cystine content of the exocuticle using data obtained from ele

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1972.tb01059.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYA method is described whereby steric configurations and surface contours may be produced in schematic form from serial light or electron micrographs. The resultant illustration, similar to those used by cartographers, is easily prepared and obviates the necessity of publishing large numbers of half‐tone micrographs to substantiate the analysi

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1972.tb01060.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe paper describes the use of a double refracting interference microscope with variable amount and direction of wavefront shear for the study of synthetic polymer fibres. General theoretical aspects of the field of the differential interference contrast method, and practical problems related to the application of this method in fibre examination are discussed. Some improvements in the micro‐interferometric measurement of the birefringence and refractive indices of fibres are suggested. Advantages of the developed double refracting interference microscope with variable wavefront shear are discussed from the point of view of fibre microscopy, and illustrated by photomicrograph

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1972.tb01061.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYRoots grown in glycerol and frozen‐etched show fracture faces of the tonoplast covered with particles having a density distribution on face A different from that on face B. In contrast, roots prefixed in glutaraldehyde prior to freezing show tonoplasts either with particle populations comparable to those in frozen living cells, particles interspersed with plaques, plaques only, or surfaces devoid of both particles and plaques. Membranes with plaques are the most frequently found. Plaques occur as slightly raised structures and with approximately equal frequency on faces A and B of the tonoplast. Other membranes of the cell seldom show plaques and resemble those of unfixed roots. Plaques occur independently of the concentration of glutaraldehyde or glycerol, the stage at which buffer is added during the schedule, and whether fixation is simultaneous with glycerination or followed by glycerination. It is argued that plaques are the result of contamination during etching rather than being due to an alteration in the plane of fracturing. It would appear that prefixation enhances the formation of plaques by altering the properties of the tonoplast so that the membrane acts as a site for the selective condensation of contaminant materia

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1972.tb01062.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYA study has been made of the initial stages of decomposition of a supersaturated solid solution of a cobalt alloy containing 7·5 atomic percent titanium. It is shown that the initial precipitation of Co‐Ti is periodic (along) and that spacings and sizes measured by field‐ion microscopy agree well with those measured by transmission electron microscopy and from ‘sidebands’ on X‐ray diffraction photographs. The experimental conditions under which contrast between the precipitate and matrix may be obtained are

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1972.tb01063.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYSeveral techniques and procedures of negative staining are described and compared from the point of view of both ‘drying’ and ‘specific staining’ artefacts. These are shown on examples from several virus species. The ‘drying artefacts’ can be prevented using the freeze‐drying technique or reduced using ‘paper‐filtration’, ‘pseudoreplication’ or the Kleinschmidt techniques. The ‘specific staining’ artefacts can be avoided by using another stain which does not affect the structure under study. Different ways are shown to stain the surface or the

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1972.tb01064.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYMethods are described for the estimation of the dry specific gravities (SG) of specimens in thin sections, especially for the comparison of one group with another and for the quantification of electron stains. Variations in section thickness are overcome by using the naked supporting film as a base‐line, and relating the SG of the specimen to that of the resin, which acts as a standard. Section thicknesses may also be estimated by using similar methods. The optical densities of their images are compared with those of standards; knowledge of the SG of the resin allows one to calculate its thicknes

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1972.tb01065.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYElectronic devices for the control of culture environmental temperature and for a more flexible operation of the cine camera are described with circuit diagrams. The advantage(s) and limitations of each device are discussed.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1972.tb01066.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYConstruction and use are described for a stand to enable either or both microscopes to be rotated while examining pairs of specimens through a comparison eyepiece. The device facilitates accurate orientation of the images, enabling rapid and critical detection of similarities or differences between them.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1972.tb01067.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY