Effect of temperature on drought resistance and growth of cotton plants

In cotton plants ( Gossypium hirsutum L. cv. B.J.A.) the temperature of the roots affected both root and shoot growth, as did the temperature of the shoot. Drought resistance increased when the temperature imposed on roots (27°C) was lower than that imposed on shoots (17°C); the result was a decrease in both transpiration and flow of root sap. Stomatal characteristics as measured by density, index and resistance, depended only on shoot temperature. Differences in drought resistance, depended only on shoot temperature. Differences in drought resistance seem to be a result of changes in transpiration flow modulated by the amount of absorbed water.     

SYNTHESIS OF RNA IN NEURONS OF THE HYPOGLOSSAL NERVE NUCLEUS, AFTER SECTION OF THE AXON, IN MICE

Synthesis of RNA in neurons of the hypoglossal nerve nucleus after axonal section was studied by means of [5-³H]uridine administration and radioautographic counting techniques in mice. The results of the experiments were evaluated by counts of silver grains over the nucleoplasm and cytoplasm of the neurons. RNA synthesis was greater in neurons after axonal section, and this increase was evident from 12 hr after the operation. The greatest increases in the operated side were observed in the 1st, 2nd and 3rd days after operation. In the 7th and 14th days RNA synthesis was still greater in the hypoglossal nucleus of the sectioned nerve but the difference in the control nucleus was not so striking. In the 30th day synthesis of RNA in left and right hypoglossal nuclei was comparable.     

Physiology of a choline-requiring strain of Torulopsis pintolopesii

Summary A choline-requiring strain of Torulopsis pintolopesii when growing on choline-methyl-¹⁴C or choline-methyl-³H excretes the radioactivity incorporated in the first 24–48 h of incubation up to ca. 85–95% of the radioactivity added at the beginning of the incubation. The addition of non-radioactive methionine did not interfere with the uptake and excretion of radioactivity from choline-Me-¹⁴C. Radioactive methyl group of methionine previously incorporated by growing cells of T. pintolopesii on varying concentrations of choline was not excreted in appreciable amounts. No evidence was obtained for the oxidation of choline to betaine, degradation to trimethylamine, or net incorporation of labelled choline into lecithin. The occurrence of a new pathway for the utilization of choline in yeasts is suggested. The requirement of choline by T. pintolopesii is explained tentatively by the formation and excretion of a compound containing the carbon and hydrogen atoms from the methyl groups of choline and whose chemical structure still under study, may comprise a heteroside containing mannitol as the polyhydroxylated moiety.     

A rapid posttranslational myristylation of a 68-kD protein in D. discoideum

Cells incubated with [3H]myristate were shown to rapidly and specifically acylate a 68-kD protein, p68, in a developmentally-regulated manner. The fatty acid incorporated into p68 was identified as myristate, and is linked to the protein via an amide bond, apparently to an NH2-terminal glycine. The acylation of p68 in D. discoideum displays some unusual properties. Unexpectedly, myristylation of p68 is a posttranslational event and occurs in the presence of inhibitors of protein synthesis. Another unusual finding was that although p68 is a stable protein, the acyl moiety is removed with a half time of approximately 15 min.     

Through-bond electron-transfer interaction in proteins

A model for the through-bond electronic interaction between electron donor and acceptor in proteins is developed. We use a one-electron Hamiltonian, write the Dyson's equation in site representation and solve it by using a Green's function formalism with some renormalization ideas. An expression for Tab which describes the exponential decay with distance bond per bond is obtained. Covalent, non-covalent and convergent pathways are considered and no periodic approximation is needed.