摘要:

SUMMARYTheoretical results are given for the evaluation of the mass thickness of unstained and stained biological sections based on the scattering contrast model for in‐focus electron microscope images. Densitometer measurements on photographic images enable the scattered electron intensity (I) and the incident electron intensity (I0) to be determined, and it is shown that the ratioI/I0can be related to the mass thickness ρtof a particular region of the specimen byI/I0= exp (−Spρt). The parameterSpis given for a range of incident electron energies (E0= 20–100 keV) and objective aperture sizes (semi‐angle α subtended at the specimen 5–15 mrad). Experimental results on thin stained sections ofBacillus subtilisforE0= 40–100 keV and α = 3.8–17.5 mrad demonstrate the internal consistency of the theoretical curves for the calculation of mass thickness of both the embedding medium and the biological material. The sensitivity of this method for the determination of mass thickness depends onE0and α; variations in mass thickness of ±2 mg m−2can be determined forE0= 40 keV and α = 5 mrad, becoming less sensitive asE0and α are increased, so that forE= 80 keV and α = 10 mrad the sensitivity is reduced to ±5 mg m−2. This means that density variations of ±40 and 100 kg m−3, respectively, can be determined in sectioned biological material. Because of the requirement of a linear relation between log (I/I0) and ρt, the theoretical calculations are limited to a maximum mass thickness of 200 mg m−2or a section thickness of about 200 nm for material of density 1000 kg m−3.These calculations are relevant to applications in microbiol

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01127.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYAliquots of lymphocyte cell suspensions were pretreated according to the following three schedules before freeze fracturing: (a) prefixed with 2% glutaraldehyde before infiltration with 25% glyercol in medium RPMI‐1640; (b) frozen in medium RPMI‐1640 without additional pretreatment; and (c) frozen after pretreatment with 25% glycerol in medium RPMI‐1640. The diameters of the fractured nuclear pore complexes of cells prefixed with glutaraldehyde were normally distributed within the range 70–120 nm (median 90 nm). The nuclear envelopes of 66–75% of cells processed through schedules b and c, which omitted glutaraldehyde fixation, had 70–120 nm diameter pores, while the remainder had pores with diameters in the range 120–175 nm. The large pores were structurally similar to the smaller pores except for their dimensions. These results indicate that glutaraldehyde gives rise to shrinkage of the larger pores to the minimum, smaller, diameter. Apparent orifices of at least 30 nm diameter were sometimes observed at the centres of these large pore complexes. We propose that the variation in pore diameters may indicate opening and closure of this orifice, and that the widely reported ‘central granule’ of the nuclear pore complex corresponds with the orifice in a clo

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01128.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYA method is described by which frozen hydrated bovine muscle is prepared for the transmission electron microscope. The importance of maintaining specimen temperatures at −110°C (163°K), or below, during the preparation of frozen thin sections and during specimen transfer and microscopical observations is emphasized and documented.Electron micrographs of a section of muscle were followed through three levels of dehydration. Electron micrographs of frozen hydrated muscle were compared with micrographs of fixed and embedded muscle. In general, the micromorphology of muscle prepared by the two methods was found to be quite simi

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01129.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYA method of cell surface mapping has been developed on spermatozoa. Concanavalin A binding sites have been simultaneously revealed both by peroxidase DAB reaction and by iron dextran coupling. The areas are examined in scanning and transmission electron microscopes and submitted to electron probe X‐ray microanalysi

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01130.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYThe present study was designed to investigate the cellular uptake of technetium‐99m (99mTc) and chromium‐51 (51Cr) by autoradiographic methods and to compare these data to those obtained by gamma scintillation counting. HeLa cells, a fibrosarcoma of murine origin (Sarcoma I) and human peripheral blood lymphocytes were labelled with either99mTc‐sodium pertechnetate or51Cr‐sodium chromate. Cells were non‐uniformly labelled with both radionuclides. Nevertheless, uptake as determined by both autoradiography and gamma scintillation counting revealed that each cell type had a characteristic labelling pattern which appeared to have a relationship to cell surface area. This was determined to be linear for99mTc when counts per minute were plotted as a function of area (μm2). Grains were randomly scattered over the entire cell surface and occasionally tracks could be seen as a trail radiating out from the periphery. HeLa cells had the largest surface area, the highest grain counts and the greatest uptake of both99mTc and51Cr as determined by gamma counting. Lymphocytes had the smallest surface area, the lowest grain counts and the least uptake. Both radionuclides are non‐specific cell labels which are taken up independently of mitosis and protein synthesis. The favourable chemical properties of99mTc‐sodium pertechnetate have led to its use as a label for a wide variety of inorganic and organic compounds which are employed as radiopharmaceuticals. Autoradiographic methods could be useful in determining the cellular localization of these compounds, as well as any protein molecule with which pertechnetate forms chelates. Although the 6 h half life of99mTc limits its use to short term experiments, it does permit brief exposure times prior

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01131.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYThe Hitachi H500 transmission electron microscope has been modified in order that both the top and side entry specimen stages may be fitted simultaneously. This made possible top entry multi‐specimen operation up to a maximum magnification of × 100,000 and a resolution of 1.8 nm, combined with the normal side entry stage facilities of ±60° tilt, 0.45 nm resolution and × 400,000 magnific

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01132.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYA semi‐automatic device is described for the coating of slides with nuclear emulsions for autoradiography. The design embodies a metal heatsink for warming the emulsion, and an elevating gantry which withdraws coated slides at a controlled constant spee

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01133.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYX‐ray microanalysis of phosphorus, transition elements and heavy metals in biological tissue is frequently carried out on thin sections of specimens embedded in epoxy resin. A logical choice for the quantitive microprobe analysis of these specimens is a standard, consisting of a homogeneous solution of the elements of interest in the epoxy resin. Four kinds of compounds were found suitable for this purpose: (1) phenyl compounds containing group Vb elements, (2) cyclopentadienyl‐derivatives, (3) a pentanedione derivative (acetylacetonate) and (4) complexes of metals with dialkyldithiocarbamates. In the latter case, the standard also contains sulphur. Standards for P, Sb (1) Mn, Fe (2) Ni (3) Cu, Zn, Cd, Hg, Pb, Bi (4) were prepared in Epon 812 or Spurr epoxy resin. The compounds were mixed with the resin (without accelerator) to which some propylene oxide may be added, and dissolved immediately or after short heating. The maximal concentration of metal was in the order of magnitude of several promilles to 1%. Solubility in the Spurr resin was better than in Epon 812. After addition of the accelerator, polymerization was carried out as usual. The compounds used are commercially available at low cost or can be easily prepa

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01134.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYReticulin has been classically identified by virtue of its argyrophilia, as observed by light microscopy. The similarity between reticulin and collagen has been a matter for considerable discussion. This paper describes the application of a silver‐staining procedure which demonstrates the fine structure of these fibres when studied by electron microscopy, giving a direct indication of the morphological identity of the argyrophilic structures, i.e. reticulin, with collagen. Beef lymph node tissue was used for this stud

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01135.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYCircumstantial evidence suggests that sodium cacodylate may be a far greater health hazard than has been generally assumed. Until further information is available, electron microscopists should see that extreme care is exercised during the preparation of cacodylate buffers by their staff.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01136.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY