Ectopic pairing and evolution of 5S ribosomal RNA genes in the chromosomes of Drosophila funebris

5S ribosomal RNA from Drosophila melanogaster labeled with ¹²⁵I was used to locate the 5S rRNA genes in chromosomes of D. funebris by means of in situ hybridization. Silver grains were observed at three distinct sites, one of which was a recognized reverse repeat. Only one half of the reverse repeat, however, hybridizes with 5S rRNA and the significance of this phenomenon is discussed. A case of ectopic pairing between two different 5S sites in the genome is reported, and the significance of ectopic pairing is considered.The author was a Predoctoral Fellow supported by Grant GM 1974 from the National Institute of General Medical Sciences, National Institutes of Health.Contribution from Oak Ridge National Laboratory, operated by the Union Carbide Corporation for the U.S. Energy Research and Development Administration.     

Mechanism of the thrombin-mediated burst in oxygen consumption by human platelets.

We present evidence that added thrombin stimulates release of endogenous arachidonic acid by suspensions of human platelets. We also show that added arachidonic acid causes a burst in O2 consumption that mimics one of the well described effects of thrombin on these cells. Further, added aspirin, a known inhibitor of the burst in O2 consumption caused by thrombin, also blunted the stimulatory effect of arachidonate on O2 consumption, and eicosatetraynoate, a known inhibitor of arachidonate oxygenation, blunted the burst in O2 consumption initiated by both thrombin and arachidonate. We conclude that rapid oxygenation of endogenously released arachidonic acid accounts for the thrombin-mediated burst in oxygen consumption by platelets.     

The phosphorylation of rabbit skeletal muscle glycogen synthase by glycogen synthase kinase-2 and adenosine-3':5'-monophosphate-dependent protein kinase.

Purified glycogen synthase is contaminated with traces of two protein kinases that can phosphorylate the enzyme. One is protein kinase dependent on adenosine 3':5'-monophosphate (cyclic AMP) and the second is an activity termed glycogen synthase kinase-2 [Nimmo, H.G. and Cohen P, (1974)]. Glycogen synthase kinase-2 has been found to be localized relatively specifically in the protein-glycogen complex. It has been purified 4000-fold by two procedures, both of which involve disruption of the complex, followed by the DEAE-cellulose and phosphocellulose chromatographies. However the salt concentration at which glycogen synthase kinase-2 is eluted from DEAE-cellulose depends on the method that is used to disrupt the complex. The results indicate that glycogen synthase kinase-2 is firmly attached to a protein component of the complex. The isolation procedures separate glycogen synthase kinase-2 from phosphorylase kinase, cyclic AMP-dependent protein kinase and other glycogen-metabolising enzymes. Glycogen synthase kinase-2 is the major phosvitin kinase in skeletal muscle, although glycogen synthase is a six to eight-fold better substrate than phosvitin under the standard assay conditions. Phosphorylase kinase and phosphorylase b are not substrates for glycogen synthase kinase 2. Following incubation with cyclic-AMP-dependent protein kinase, cyclic AMP and Mg-ATP, the phosphorylation of glycogen synthase reaches a plateau at 1.0 molecules of phosphate incorporated per subunit and the activity ratio measured in the absence and presence of glucose 6-phosphate falls from 0.8 to a plateau of 0.18. The Ka for glucose 6-phosphate of this phosphorylated species, termed glycogen synthase b1, is the 0.6 mM. Following incubation with glycogen synthase kinase-2 and Mg-ATP, the phosphorylation reaches a plateau of 0.92 molecules of phosphate incorporated per subunit and the activity ratio decreases to a plateau of 0.08. The Ka for glucose 6-phosphate of this phosphorylated species, termed glycogen synthetase b2, is 4 mM. In the presence of both cyclic-AMP-dependent protein kinase and glycogen synthase kinase-2, the phosphorylation of glycogen synthase reaches a plateau when 1.95 molecules of phoshophate have been incorporated per subunit. The activity ratio is 0.01 and the Ka for glucose 6-phosphate is 10 mM. The results indicate that glycogen synthase can be regulated by two distinct phosphorylation-dephosphorylation cycles. The implication of these findings for the regulation of glycogen synthase in vivo are discussed.     

Intracellular cAMP levels in normal rat mammary gland and adenocarcinoma. In vivo vs in vitro.

Intracellular cAMP levels determined by radioimmunoassay technique were compared in normal rat mammary gland and DMBA-induced mammary adenocarcinoma as well as in epithelial cells derived from these tissues and grown in monolayer cultures. It was found that cAMP levels were higher in mammary tumors (0.643 p mole/mg wet weight) than in normal gland (0.158 p mole/mg). In contrast, cAMP levels in cultured adenocarcinoma cells were lower than those in normal mammary epithelial cells. The apparent contradiction may be a consequence of the fact that $\text{in vivo}$ cAMP values represent the average value of the composite cell types and not the epithelial components in question.     

The permeability of liposomes to nonelectrolytes. II. The effect of nystatin and gramicidin A.

The process of selective permeation of nonelectrolytes across liposomes of different lipid composition and amount of cholesterol has been studied. The extent of the selectivity for diffusion within the membranes has been found to be related to the physical state of the hydrocarbon chains. It has been also found that incorporation of cholesterol into egg-lecithin membranes decreases the overall permeability by affecting the dehydration step more than the subsequent diffusion of the solute. The incorpporation into liposomes of the antibiotics nystatin and gramicidin A produces changes in the selective permeation of nonelectrolytes that are consistent with the formation by these molecules of aqueous pores of fixed dimensions. Finally, comparisons are made between the process of permeation in biological membranes and in liposomes with and without antibiotics.     

Migration inhibitory activity in serum and cell supernatants in patients with Sezary syndrome.

The abnormal lymphocytes from patients with the Sezary syndrome produce macrophage migration inhibitory factors (MIF) both in vitro and in vivo. Five of six individuals studied had significant serum MIF activity and one had borderline activity. In contrast, in this study 47 normal individuals and 9 of 10 patients with extensive skin disease other than that of the Sezary syndrome had no such activity. Since the neoplastic T cells in patients with the Sezary syndrome localize in the skin, their production of chemical mediators in that site may be responsible for the generalized exfoliative erythroderma seen in that disease.     

Species specificity and intraspecific variation in the chemical profiles of Heliconius butterflies across a large geographic range

In many animals, mate choice is important for the maintenance of reproductive isolation between species. Traits important for mate choice and behavioral isolation are predicted to be under strong stabilizing selection within species; however, such traits can also exhibit variation at the population level driven by neutral and adaptive evolutionary processes. Here, we describe patterns of divergence among androconial and genital chemical profiles at inter‐ and intraspecific levels in mimetic Heliconius butterflies. Most variation in chemical bouquets was found between species, but there were also quantitative differences at the population level. We found a strong correlation between interspecific chemical and genetic divergence, but this correlation varied in intraspecific comparisons. We identified “indicator” compounds characteristic of particular species that included compounds already known to elicit a behavioral response, suggesting an approach for identification of candidate compounds for future behavioral studies in novel systems. Overall, the strong signal of species identity suggests a role for these compounds in species recognition, but with additional potentially neutral variation at the population level.