Influence of low temperature on phosphatase in roots of Verbascum thapsus,a biennial weed

The temperature peak (15 °C) of acid and alkaline phosphatase in this study coincides with a peak in alpha-amylase as seen in an earlier study of roots of Verbascum thapsus. It is speculated that one of the results of higher phosphatase activities may be increased amount of orthophosphate which can be utilized in phosphorylation of soluble carbohydrates which in turn are in greater supply due to the higher activities of the starch-degrading enzymes.A second peak in activities of acid and alkaline phosphatase was seen in plants which were returned to the greenhouse following cold treatment. This increase in enzymatic activities is also similar to increases in activities of three starch degrading enzymes studied earlier. Alkaline phosphatase showed greater activities than did acid phosphatase at lower temperatures (10 and 4 °C) and under greenhouse conditions following cold treatment.     

The polyadenylated RNA of zoospores and growth phase cells of the aquatic fungus,Blastocladiella

The stored poly(A) + RNA from zoospores of the aquatic fungus Blastocladiella emersonii represents 2.5% of the total RNA and has a model MW of 425,000 daltons and an average poly(A) isostich of 32 bases. The poly(A) + RNA also represents 2.5% of the total RNA from early growth phase cells and has a modal MW of 360,000 daltons and an average poly(A) isostich of 38 bases. The poly(A) + RNA from spores and 2-hr plants contains a structure resistant to RNases T₁, T₂, and A, which can be labeled with ³²PO₄ and which will bind to DBAE-cellulose. These characteristics strongly suggest that both the zoospore poly(A) + RNA and the 2-hr cell poly(A) + RNA are capped at the 5′ end; and, hence, it is unlikely that capping is involved in the control of protein synthesis during germination.Approximately 80% of the poly(A) + RNA of the spore is located in the membrane-enclosed ribosomal nuclear cap, and more than 90% of the poly(A) + RNA within the cap is found in the 80S monoribosome and heavier fractions.Synthesis of new poly(A) + RNA occurs very early during zoospore germination, and the labeled poly(A) + RNA rapidly enters the newly organized polysomes. The labeling data for early germination also suggest that cytoplasmic polyadenylation occurs.     

Repetitive DNA in Cichorieae (Compositae)

Thermally denatured DNA of 11 species of Cichorieae (Compositae) was allowed to renature at 69° C in 0.8 M Na⁺. Two distinct fractions of repetitive DNA (fast: 10⁵ repetitions, intermediate: 10³ repetitions) were found in all species. The remaining (slow) fraction comprises 26 to 58% of the genome. The relative amounts of fast and intermediate fractions maintain constant proportions to the slow fraction except for saltatory changes, especially halvings in species with reduced genome sizes.     

A Model of Functional Epistasis and Linkage Disequilibrium in Populations with Overlapping Generations

A model of functional epistasis is proposed in which it is assumed that coupling and repulsion genotypes differ in metabolic efficiency and thus in development time and net fecundity. The implications of this model are investigated for iteroparous populations with fluctuating rates of increase. It is found that the fluctuations in rate of increase can lead to large fluctuations in gamete frequency and D, the coefficient of linkage disequilibrium, but that D will almost always have a value of zero at some point during the populations' demographic cycle. Some of the model populations would be expected to be in a state of linkage disequilibrium only fleetingly: others would exhibit D-cycles interpretable as random fluctuation. Implications of the model for interpretations of existing data on linkage disequilibrium among enzyme loci in Drosophila are discussed.     

Intramolecular determination of primary kinetic isotope effects in hydroxylations catalyzed by cytochrome P-450

Isotope effects for hydroxylation reactions catalyzed by cytochrome P-450 have usually been measured by comparing the overall reaction velocities of deuterated and nondeuterated substrates. Since the rate-limiting step is probably not the single reaction involving covalent bond cleavage, such an approach does not yield information about the primary isotope effect. We measured the primary kinetic isotope effect for benzylic hydroxylation by a method utilizing intramolecular competition, using the symmetrical substrate 1,3-diphenylpropane-1,1-d₂. These experiments yield a value of $\text{k}{}_{\mathrm{<mtext>H</mtext>}}\text{k}{}_{\mathrm{D}}\text{= 11}$, a larger effect than has previously been reported for benzylic hydroxylations.     

Mapping of nucleoside phosphorylase (Np-1) and esterase 10 (Es-10) on mouse chromosome 14

A method for detecting two alleles at Np-1 (nucleoside phosphorylase) and three alleles at Es-10 (esterase 10) from mouse blood by cellulose acetate electrophoresis is described. The allelic constitution at these loci for 44 inbred strains and stocks was determined. The location of Np-1 on chromosome 14 was established by backcross experiments in which alleles at Np-1 and Robertsonian translocations were segregating. Es-10 was shown to be linked to Np-1, and the following genetic map of Chr 14 was constructed: centromere-(8.9±4.0 cM)-[Np-1, Wc]-(10.2±1.9 cM)-Es-10-(15.5±3.7 cM)-s. The homologous human loci, NP and ES-D, are not linked.This work was supported by Contract E(11-1)-3267 with the Energy Research and Development Administration, by Contracts NO1-ES4-2156 and NO1-ES4-2159 with the National Institute of Environmental Health Sciences, and by Grants GM 19656 and GM 20919 from the National Institute of General Medical Sciences. D. A. K. was a participant in the 1975 Summer Program for College, Graduate, and Medical Students, which was supported, in part, by the Clark Foundation. The Jackson Laboratory is fully accredited by the American Association for Accreditation of Laboratory Animal Care.