Point-spread functions, line-spread functions, and edge-response functions associated with modulation transfer functions (MTFs) of the form exp[-(omega/omega(c))(n)] are tabulated for values of the MTF index (n) in the range from n = 1.0 to n = 2.0, in steps of 0.10. The MTFs are also tabulated in this range. Measurements of any one of these four image transfer functions which agree with the tabulated valves for a given set of MTF parameters (omega(c,)n) allow the other three functions to be estimated by using these tables.

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Rates of synthesis and turnover of nitrate reductase in Chlorella vulgaris have been estimated from density-labelling experiments. It is demonstrated that nitrate stimulates the rate of turnover of the enzyme. Upon transfer of Chlorella from ammonium to nitrate medium there is a rapid increase in nitrate reductase activity, only part of which is a consequence of increased de novo synthesis: there must also be considerable activation of existing enzyme. It is shown that, in the absence of nitrate, the enzyme is very stable in vivo. Upon transfer from nitrate to ammonium medium, synthesis of nitrate reductase is reduced below the limits of defection. These effects are separate from the reversible (ferricyanide-reactivatable) inactivation of the enzyme which is also observed.

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Bone marrow from an 81-year-old male with acquired idiopathic sideroblastic anemia was found to be mosaic for 45, X/46, XY cell lines. Analysis of ringed sideroblasts for the presence or absence of a quinicrine fluorescent Y body indicated that all sideroblastic cells had lost the Y chromosome. The demonstration that the ringed sideroblasts were cytogenetically abnormal in this patient provides evidence that the cytogenetic changes often found in patients with sideroblastic anemia may not be due to randomly acquired chromosome aberrations accompanying tissue aging unrelated to the disease process.