Binding of Radioactively Labelled Concanavalin A and Wheat Germ Agglutinin to Normal and Virus-transformed Cells

VARIOUS substances isolated from plants cause animal cells to clump. Several of these lectins¹ preferentially agglutinate cells which have been transformed spontaneously or by chemicals or viruses^2–7. The best known lectins of this class are concanavalin A (Con A) isolated from jack beans⁸ and wheat germ agglutinin⁴, which seem to bind to carbohydrate groups on the cell surface. The determinants recognized by the lectins seem to be N-acetyl-D-glucosamine for WGA⁴ and probably α-methyl-D-glucopyranoside for Con A⁶.     

Production of a stream shredder, Peltoperla maria (Plecoptera: Peltoperlidae) in disturbed and undisturbed hardwood catchments

SUMMARY. (1) The average benthic density of Peltoperla maria in an undisturbed southern Appalachian stream was more than twice that of a nearby stream draining a previously clear-cul catchment in its tenth year of natural secondary succession.
(2) Peltoperla production estimates, using three methods, do not show a significant difference in production between streams draining the two catchments. We attribute these results to quicker growth and slightly higher densities of larger nymphs in the disturbed stream. Production estimates for the disturbed stream ranged from 498 to 560 mg (ash free dry weight) m⁻²y⁻¹ while those for the undisturbed stream were 41–4–515 mg m⁻² y⁻¹.
(3) Our results reinforce the view that conclusions based solely upon numerical densities may lead to erroneus interpretations about the roles organisms play in ecosystems.
(4) Annual frass production by this shredder is about 20 times (10 g m⁻² y⁻¹) the secondary production of P. maria.     

Phenylalanine ammonia-lyase activity in callus cultures of Pinus elliotii

Phenylalanine ammonia-lyase (PAL) activity increased 8- to 12-fold in pine (Pinus elliotii Engelm.) callus tissue within 2 days after subculturing on fresh medium. Factors such as increasing the sucrose content of the media, imposing additional tissue in jury or subculturing more frequently did not cause additional stimulation of PAL activity. The rapid increase in PAL activity appeared to be due to enzyme activation, since cycloheximide did not appreciably reduce the stimulation of PAL activity. The subsequent loss of increased PAL activity with age was reduced by cycloheximide and a cool growth environment.     

Multiple determinants influence root colonization and induction of induced systemic resistance by Pseudomonas chlororaphis O6

Colonization of the roots of tobacco by Pseudomonas chlororaphis O6 induces systemic resistance to the soft-rot pathogen, Erwinia carotovora ssp. carotovara SCC1. A screen of the transposon mutants of P. chlororaphis O6 showed mutants with about a fivefold reduction in ability to induce systemic resistance to the soft-rot disease. These mutations disrupted genes involved in diverse functions: a methyl-accepting chemotaxis protein, biosynthesis of purines, phospholipase C, transport of branched-chain amino acids and an ABC transporter. Additional mutations were detected in the intergenic spacer regions between genes encoding a GGDEF protein and fumarate dehydratase, and in genes of unknown function. The mutants in the ABC transporters did not display reduced root colonization. However, the other mutants had up to 100-fold reduced colonization levels. Generally the production of metabolites important for interactions in the rhizosphere, phenazines and siderophores, was not altered by the mutations. A reduced induction of systemic resistance by a purine biosynthesis mutant with a disrupted purM gene correlated with poor growth rate, lesser production of phenazines and siderophore and low levels of root colonization. These studies showed that multiple determinants are involved in the induction of systemic resistance, with there being a requirement for strong root colonization.     

Acanthamoeba comandoni and A. astronyxis: Taxonomic Characteristics of Mitotic Nuclei, "Centrosomes" and Cysts

SYNOPSIS. A new strain (F-111) of Acanthamoeba comandoni was isolated from Turtle Pond, Boston, Mass. Comparative studies of A. comandoni Pussard, 1964 and A. astronyxis Ray & Hayes, 1954 indicated that the 2 species are distinct, and that the 2 names are valid and not synonymous as proposed by various investigators. An astral or brush-pile “centrosomal body” was present near the nucleus of interphase stages of both species. During mitosis, bipolar “centrosomal bodies” were detected in A. comandoni but not in A. astronyxis. Cysts of both species were spherical and had stellate or rayed endocysts. The rays in cysts of A. comandoni extended outward and upward at different angles, and all of them were not visible in the same optical plane. In A. astronyxis, the rays extended outward from the central cyst mass, and all of them were visible in the same optical plane.     

Environmental Pollution: Leaf Cuticular Patterns in Trifolium pratense L.

Red clover populations collected from the polluted environmentsof Memphis, Nashville, and Knoxville (Tennessee) showed decreasedfloral production, low stomatal frequency, high trichome density,and longer trichomes. The results for plant population collectedfrom a less polluted, rural Reelfoot Lake area were quite theopposite. Subsidiary cell complex remained the same in all thepopulations, while stomatal size range showed little variation.