Multiplication noise in the human visual system at threshold

Several kinds of light used in vision experiments produce photon statistics that are distinctly non-Poisson. Representative examples are light from a cathode-ray tube and an image-intensifier device. For the class of vision experiments in which the photon statistics play an important role, excess fluctuations produced by such light sources can alter the observed results and obscure the visual mechanisms being studied. They must therefore be accounted for in a proper way. We use the results of a Hecht-Shlaer-Pirenne type experiment, carried out with modulated Poisson light, to illustrate the point. Sensitivity and modulation depth, as well as sensitivity and reliability, are shown to be traded against each other. Finally, we demonstrate that number-state light, which is comprised of photons of an ideal kind, provides the ultimate tool for extracting information about the intrinsic noise distribution in the visual system at threshold. The state of the art in producing such light is discussed.This work was carried out at Columbia University and was supported by the National Science Foundation and the National Institutes of Health     

The effects of adrenalectomy on the sexual behaviour of castrated and intact BDF1 mice

Two experiments investigate the effects of adrenalectomy on the capacity of male mice of the BDF₁ genotype (C57B1/6Fa♀×DBA/2♂) to retain sexual behaviour following castration. Adrenalectomy is without effect and it is suggested that androgens can play no part in the maintenance of sexual behaviour in these castrates.     

The contributions of genotype and sex to variation in mating behaviour between geographical subspecies of the bank vole (Clethrionomys glareolus scheber)

The sexual behaviour of bank voles from the mainland of Great Britain, and from the island of Skomer, differs in a number of respects. Voles from the mainland population show in general greater sexual activity. These variations may be understood as adaptations to ecological differences, particularly in population density. The reciprocal hybrids resemble the mainland population in a number of aspects of their mating behaviour. The possible evolutionary importance of this dominance is discussed. The behaviour of the bank vole is put into the perspective of generalizations made about other mammals. The separate influence of the male and of the female on quantitative variation between the two forms was investigated by studying mating between members of different populations. Some aspects of mating behaviour are shown to be due primarily to the male, others primarily to the female and others to the particular combinations involved. This situation is discussed in relation to the separate action of natural selection on members of each sex.     

Inhibition of mitochondrial-specific protein symthesis in human lymphocytes and platelets is dependent upon the stage of cellular differentiation

Small lymphocytes differentiate into functionally active blast cells in vitro upon stimulation with such mitogens as phytohemagglutinin and sodium periodate. If stimulated lymphocytes are subsequently treated with the nucleic acid intercalating dye ethidium bromide, electron-dense complexes containing nucleic acid are formed in mitochondria, protein synthesis in mitochondria is inhibited, and lymphoblast division ceases. Formation of complexes and the development of morphologically abnormal mitochondria provide ultrastructural evidence of mitochondrial protein inhibition and serve as markers for mitogen-responsive lymphocytes. The formation of these abnormalities in all mitochondria of treated megakaryocytes and 22% of mitochondria in platelets indicates that platelets contain functional nucleic acid and that the induced structural changes may be occurring in a less-differentiated (i.e., younger) subpopulation of circulating platelets.