Response of an insect herbivore to host plants grown in carbon dioxide enriched atmospheres

Rising atmospheric carbon dioxide concentration is expected to increase plant productivity, but little evidence is available regarding effects on insect feeding or growth. Larvae of the soybean looper, a noctuid moth, were fed leaves of soybean plants grown under three carbon dioxide regimes (350, 500 and 650 l·l^-1). Larvae fed at increasingly higher rates on plants from elevated carbon dioxide atmospheres: 30% greater on leaves from the 650 l·l^-1 treatment than on leaves from the 350 l·l^-1 treatment. When variation in larval feeding was related to the leaf content of nitrogen and water, there was no significant remaining effect of carbon dioxide treatment. The principal effect on herbivores of increasing the carbon supply of leaves appeared to be reduction of leaf nutrient concentration. This study suggests that feeding by herbivores on the leaves of C₃ plants may increase as the level of atmospheric carbon dioxide rises.     

The two-dimensional polypeptide profile of terminally non-dividing human diploid cells

We have used high resolution two-dimensional polyacrylamide gel electrophoresis (PAGE) to compare the polypeptides synthesized by normal human diploid fibroblasts cells which have significant proliferative capacity with those of cells which are terminally non-dividing. Normal cells that are terminally non-dividing (i.e., have no remaining proliferative potential) synthesize two polypeptides that are not detected in young cells which are either actively proliferating or growth arrested by incubation in medium containing a low concentration of serum (0.3%) for 72 h. Continued maintenance of young cells in the growth-arrested state ultimately leads to the detectable synthesis of one of the polypeptides synthesized by terminally non-dividing cells. Some preliminary biochemical properties of these two polypeptides are examined.     

ATP analog specificity of cAMP-dependent protein kinase, cGMP-dependent protein kinase, and phosphorylase kinase

The ATP analog specificities of the homogeneous cGMP-dependent protein kinase and the catalytic subunit of cAMP-dependent protein kinase have been compared by the ability of 27 analogs to compete with ATP in the protein kinase reaction. Although the data suggest general similarities between the ATP sites of the two homologous cyclic-nucleotide-dependent protein kinases, specific differences especially in the adenine binding pocket are indicated. These differences in affinity suggest potentially useful ATP analog inhibitors of each kinase. For example, apparent autophosphorylation of the purified regulatory subunit of the cAMP-dependent protein kinase is blocked by nebularin triphosphate, suggesting that the phosphorylation is catalyzed by trace contamination of cGMP-dependent protein kinase. Some of the ATP analogs have also been tested using phosphorylase b kinase in order to compare this enzyme with the cyclic-nucleotide-dependent enzymes. All three protein kinases have high specificity for the purine moiety of ATP, and lower specificity for the ribose or triphosphate. The similarity between the ATP site of phosphorylase b kinase to that of the cyclic-nucleotide-dependent protein kinases suggests that it is related to them. The ATP analog specificities of enzymes examined in this study are different from those reported for several unrelated ATP-utilizing enzymes.     

Herbivory on Diplacus aurantiacus shrubs in sun and shade

This study tested the hypothesis that carbon allocation to the production of leaf antiherbivore chemicals reflects the intensity of herbivory and interacts with resource allocation to photosynthesis. The amount of herbivory by Euphydryas chalcedona butterfly larvae was measured on Diplacus aurantiacus shrubs growing in different daily solar irradiance regimes. The amount of herbivory sustained by plants was directly related to the degree of solar irradiance the shrubs received and to characteristics which vary with light intensity, e.g. leaf specific weight, but not to leaf resin or nitrogen content. Carbon allocation to the defense of leaf area was marginally related to the light regime, but was not directly related to photosynthetic income.     

Phosphorylation of mammalian myosin light chain kinases by the catalytic subunit of cyclic AMP-dependent protein kinase and by cyclic GMP-dependent protein kinase

The phosphorylation of the calmodulin-dependent enzyme myosin light chain kinase, purified from bovine tracheal smooth muscle and human blood platelets, by the catalytic subunit of cAMP-dependent protein kinase and by cGMP-dependent protein kinase was investigated. When myosin light chain kinase which has calmodulin bound is phosphorylated by the catalytic subunit of cAMP-dependent protein kinase, 1 mol of phosphate is incorporated per mol of tracheal myosin light chain kinase or platelet myosin light chain kinase, with no effect on the catalytic activity. Phosphorylation when calmodulin is not bound results in the incorporation of 2 mol of phosphate and significantly decreases the activity. The decrease in myosin light chain kinase activity is due to a 5 to 7-fold increase in the amount of calmodulin required for half-maximal activation of both tracheal and platelet myosin light chain kinase. In contrast to the results with the catalytic subunit of cAMP-dependent protein kinase, cGMP-dependent protein kinase cannot phosphorylate tracheal myosin light chain kinase in the presence of bound calmodulin. When calmodulin is not bound to tracheal myosin light chain kinase, cGMP-dependent protein kinase phosphorylates only one site, and this phosphorylation has no effect on myosin light chain kinase activity. On the other hand, cGMP-dependent protein kinase incorporates phosphate into two sites in platelet myosin light chain kinase when calmodulin is not bound. The sites phosphorylated by the two cyclic nucleotide-dependent protein kinases were compared by two-dimensional peptide mapping following extensive tryptic digestion of the phosphorylated myosin light chain kinases. With respect to the tracheal myosin light chain kinase, the single site phosphorylated by cGMP-dependent protein kinase when calmodulin is not bound appears to be the same site phosphorylated in the tracheal enzyme by the catalytic subunit of cAMP-dependent protein kinase when calmodulin is bound. With respect to the platelet myosin light chain kinase, the additional site that was phosphorylated by cGMP-dependent protein kinase when calmodulin was not bound was different from that phosphorylated by the catalytic subunit of cAMP-dependent protein kinase.     

Behavioral and ecological interactions of foraging mice (Peromyscus melanotis) with overwintering monarch butterflies (Danaus plexippus) in México

Summary Mice (Peromyscus melanotis) immigrate extensively to overwintering colonies of monarch butterflies (Danaus plexippus) in México. There they feed on both live and dead butterflies that accumulate on the ground and in low vegetation. Through a series of feeding experiments, we examined the potential impact of mouse predation on these colonies, as well as how this predation was influenced by the accessibility and the degree of desiccation of the monarchs. Mice attacked on average 39.9 wet (freshlykilled) butterflies per night. We estimated that a population of mice (75–105 individuals) could kill approximately 0.40–0.57 million butterflies in a 1 ha colony (4–5.7% of the colony) over the 135-day overwintering season. In feeding experiments, mice fed disproportionately on: 1) wet (hydrated) monarchs close to the ground versus those perched higher; 2) wet monarchs, when both wet and dry (desiccated) monarchs were on the ground; and 3) wet monarchs on stakes versus dry monarchs on the ground. Mice commonly ate the entire abdomen of dry monarchs, whereas they fed selectively on the abdomen of wet monarchs by discarding the bitter, cardenolide-laden cuticle and eating the internal tissues. These results suggest that the monarchs' state of desiccation is more important than their accessibility in determining the feeding preferences of these mice. However, the monarchs' strong tendency to crawl up vegetation does appear to reduce their risk to mouse predation.     

A genetic linkage map of 27 loci from PND to FY on the short arm of human chromosome I.

A genetic linkage map of 27 loci on the short arm of human chromosome 1 has been developed by analysis of the 40 families in the Centre d'Etude du Polymorphisme Humain (CEPH) reference panel. Probes that recognize 14 novel RFLPs at loci designated D1S9-D1S22 were isolated from a flow-sorted chromosome 1 library. A linkage map of chromosome 1p was constructed from the genotypic data at these 14 loci, RFLPs at eight cloned genes (PND, ALPL, FUCA1, SRC2, MYCL, GLUT, TSHB, and NGFB), two previously identified RFLPs (D1S2 and D1S57), two blood group antigens (RH and FY), and the isozyme PGM1. All 27 loci form a continuous linkage group, from FY to PND, of 102 cM in males and 230 cM in females. This map provides a basis for highly informative multipoint mapping studies for most of the short arm of chromosome 1.     

Enhancement of 2- and 16 alpha-estradiol hydroxylation in MCF-7 human breast cancer cells by 2,3,7,8-tetrachlorodibenzo-P-dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin exhibits antiestrogenic activity and induces cytochromes P-450 in estrogen-dependent MCF-7 human breast-cancer cells. To determine whether induction of 2- or 16 alpha-hydroxylation of 17 beta-estradiol has a role in this antiestrogenic activity, MCF-7 cells which were exposed to this xenobiotic for 72 hrs were incubated with either [2-3H] or [16 alpha-3H] 17 beta-estradiol and the extent of tritiated H2O formation, indicative of site-specific hydroxylation, was determined. 2,3,7,8-Tetrachlorodibenzo-p-dioxin-treated MCF-7 cultures showed an 8-fold increase in 2-hydroxylation and a 2-fold increase in 16 alpha-hydroxylation. These results support the suggestion that increased hydroxylation of 17 beta-estradiol may have a role in the antiestrogenic activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin in MCF-7 cells.     

Three new species and a new combination in Arracacia Bancroft (Umbelliferae/Apiaceae)

Three species ofArracacia—A. hintonii, A. colombiana, andA. tillettii—from Mexico, Colombia, and Venezuela, respectively, are described as new, andCoulterophytum brevipes Coulter & Rose is transferred toArracacia asA. quadrifida, nom. nov. and comb. nov.