摘要:

SynopsisThe same typo of mitotic aberration can be induced by substances of dissimilar chemical constitution. Conversely, in the presence of certain compounds almost every conceivable kind of abnormality of division can be observed. Nevertheless, certain substances in high dilution exert a highly specific action on dividing cells, without appreciably injuring “resting” cells.The phases of mitosis are characterized by fluctuations in the water content of definite regions of the cell. Furthermore, hypotonicity and hypertonicity of the surrounding medium can cause derangements of all phases of mitosis. It is therefore suggested that mitotic aberrations are explicable as the result of chemical and physical reactions bringing about alterations in the normal distribution and interchange of water amongst the protein molecules of different parts of the cell at various stages of division. This conception does not invalidate the probability that in certain instances specific chemical reactions are involved which determine precisely the type of mitotic aberration that will oc

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1953.tb02343.x

出版商:Blackwell Publishing Ltd    

年代:1953

数据来源: WILEY

摘要:

SynopsisThe paper describes the technique for using the microscope in the region 2,000Å. to 1,000Å. and the instrument for doing this. The experimental work shows that if the instrument is mounted in a chamber containing nitrogen instead ofin vacuothe technique is greatly facilitated. Reflecting objectives of the Schwarzschild type and a refracting type monochromat (made in fluorite) have been used in this work. Photomicrographs taken with the instrument are included in the pape

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1953.tb02344.x

出版商:Blackwell Publishing Ltd    

年代:1953

数据来源: WILEY

摘要:

SynopsisThe vector method developed in previous papers of this series has been applied to certain problems in negative phase contrast. Unlike positive phase contrast, increasing the absorption of the phase plate increases the range of phase change in the object over which contrast remains unreversed (i.e. bright). As absorption approaches 100 p.c., conditions change over smoothly to central dark‐ground illumination, in which all object details appear brighter than the background. In negative phase contrast it is preferable to have the retardation ψ produced by a phase plate greater than 90°, whereas in positive phase contrast ψ should be less than 90°. Maximum sensitivity occurs when ψ = 90°, in each case. The characteristic of the phase plate needed to give maximum contrast for a given phase detail are di

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1953.tb02345.x

出版商:Blackwell Publishing Ltd    

年代:1953

数据来源: WILEY

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1953.tb02346.x

出版商:Blackwell Publishing Ltd    

年代:1953

数据来源: WILEY

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1953.tb02347.x

出版商:Blackwell Publishing Ltd    

年代:1953

数据来源: WILEY

摘要:

Œstrogens and Neoplasia. H. Burrowsand E. S. Horning(with contributions by W. C. J. Rossand C. W. Shoppee)

ISSN:0368-3974    

DOI:10.1111/j.1365-2818.1953.tb02348.x

出版商:Blackwell Publishing Ltd    

年代:1953

数据来源: WILEY