Historical and Life History Factors in the Biogeography of Mayflies

SYNOPSIS. Cladistic analysis of mayflies suggests that dispersalwas very asymmetrical after the new land connection betweenNorth and South America. Twenty-one genera apparently movedfrom South to North and Central America, but there is good evidencefor only one North American genus moving into the south. Testablepredictions are possible once the boreal (Laurasian) or austral(Gondwanian) designations are made. For example, Paracloeodes,a genus of austral origin, was predicted to be found in SouthAmerica, and in North America in warm rivers north and eastof its known distribution. These predictions have been confirmed.Other characteristics of tropical mayflies, such as length oflarval period and emergence and mating patterns, may be usedto predict habitats and characteristics of present North Americangenera. Merger events and consequent dispersal of organismshave profound influences on distributional patterns, and fromsuch information, biologically useful generalities can be made.     

Effect of concanavalin a on ganglioside metabolism of human lymphocytes

The effect of Con-A on the incorporation of radioactivity from [¹⁴C]-glucosamine into gangliosides of human lymphocytes was investigated. Compared with non-stimulated lymphocytes there was increased incorporation into gangliosides and total lipids within the first 24 hours of exposure to Con-A. Ganglioside synthesis also occurred in later time intervals within the 96 hour incubation period. GM3 accounted for 80% of the labeled ganglioside in Con-A stimulated cells at all times studied. Thus ganglioside synthesis is not only associated with cellular division, but also occurs within a few hours of lymphocyte activation representing an extremely early prereplicative event.     

Haemorrheological response to plasma exchange in Raynaud's syndrome.

Eight patients with Raynaud''s syndrome were treated by weekly plasma exchange for four weeks using a Haemonetics Model 30 Blood Processor. The mean whole-blood viscosity at a shear rate of 0.77/s was significantly lower after treatment, and the mean index of red-cell deformability was significantly improved. In four patients studied serially the mean percentage fall in whole-blood viscosity after a single plasma exchange was 49% at 0.77/s but only 14% at 91/s. All patients noticed symptomatic improvement including healing of ischaemic digital ulcers. In six patients the number of digital arterial segments containing detectable blood flow was measured by directional Doppler; in all six the number increased. It is concluded that plasma exchange is an effective means of haemorrheological treatment and may be beneficial in patients with digital ischaemia.     

Elementary steps of the (Na+ + K+)-ATPase mechanism, studied with formycin nucleotides.

1. Formycin triphosphate (FTP), a fluorescent analogue of ATP, is a substrate for (Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3), with properties similar to those of ATP. 2. FTP and formycin diphosphate (FDP) bind to the enzyme with high affinity and, on binding, the nucleotide fluorescence is enhanced 3-4-fold. It is therefore possible, with a stopped-flow fluorimeter, to measure the rates of binding and release of FTP and FDP under conditions in which turnover does not occur. 3. When the enzyme-FTP complex is exposed to conditions permitting turnover (Mg2+, Na+ +/- K+), changes in fluorescence occur which can be explained by supposing that they reflect the interconversion of states with or without bound nucleotides. A rapid fall in fluorescence, that we attribute to the rapid release of FDP from newly phosphorylated enzyme, is followed by a steady state in which low fluorescence suggests that little nucleotide is bound. Eventually, exhaustion of FTP allows rebinding of FDP to the enzyme, which is signalled by a rise in fluorescence. 4. The estimated rate of FDP release from newly formed phosphoenzyme is unaffected by the presence of K+ (0-2 mM) or the concentration of FTP (1-20 micron). 5. Experiments with [gamma-32P]FTP show that about 1 mol of 32P is incorporated per mol of enzyme. The rate of phosphorylation of the enzyme by [gamma-32P]FTP has been measured with a rapid-mixing-and-quenching apparatus. 6. Kinetic data from the fluorescence and phosphorylation experiments show that the behaviour of the enzyme, at least at the low nucleotide concentrations employed, is consistent with the Albers-Post model, and is difficult to reconcile with models in which K+ acts at or before the step in which FDP is released during turnover.     

The binding of lectins to components of plasma membranes from porcine submaxillary lymph node lymphocytes

By sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis the plasma membranes from porcine lymphocytes contain at least 30--35 glycopolypeptides and one or more glycolipids to which one or more of 12 purified lectins bind. The specificities of binding generally followed the same pattern as those of the reaction of the lectin with intact pig lymphocytes. Some lectins (e.g., the isolectin pair, Agaricus bisporus lectins A and B and a group consisting of the Lens culinaris A and B isolectins and the closely related Pisum sativum lectins) bind to almost identical populations of plasma membrane components and compete with each other for all their binding sites. Others (e.g., Concanavalin A and the Lens culinaris-Pisum sativum group and a group consisting of phytohemagglutinin-L, Ricinus communis lectin-60 and Ricinus communis lectin-120 bind in a cross reactive manner to some common binding moieties but, in addition, to certain nonshared ones. Still others (e.g., soybean agglutinin, peanut agglutinin and wheat germ agglutinin) do not share any common binding moieties with the other lectins. The amount of lectin binding and the number of membrane components to which a lectin binds is directly related to the Ka of binding of the lectin to the intact lymphocyte. Those with high Ka (Cocanavalin A Lens culinaris lectins, Pisum sativum lectins, phytohemagglutinin-L), bind to 20-30 different components giving very complex binding patterns while those with lower Ka (Agaricus bisporus lectins, wheat germ agglutinin, peanut agglutinin, and soybean agglutinin) bind to 8--13 components with easily distinguishable patterns. Soybean agglutinin binds almost exclusively to a glycolipid fraction while for the others one or more glycopolypeptides served as the major lectin-binding molecule. The Ricinus lectins, two lymphocyte toxins, bind to essentially every plasma membrane component to which the mitogen phytohemagglutinin-L binds, in fact competing for most of those plasma membrane moieties which bind phytohemagglutinin-L.     

Late Devonian benthic marine communities of the central Appalachian Allegheny Front

Four benthic marine communities occur in the clastic facies of the prograding Upper Frasnian-Lower Famennian (Upper Devonian) Foreknobs Formation in the Central Appalachians along the Allegheny Front in Maryland, West Virginia, and Virginia. Deep-water, rapidly prograding environments were inhabited by the Ambocoelia-Chonetes Community, dominated by an epifauna of unattached brachiopods. Offshore bar environments were inhabited by the Cyrtospirifer-Camarotoechia Community, exhibiting adaptations to shallow-water, high-energy conditions and probably lowered salinities. Shallow-water, sublittoral environments were inhabited by the Atrypa-Cypricardella Community, a community in which existed a variety of life habitats and a diverse epifaunal and infaunal association of brachiopods and bivalve molluscs. The Leptodesma-Tylothyris Community flourished in nearshore bar-protected environments in the southern region of the study area, whereas in the north the Cyrtospirifer-Camarotoechia Community inhabited nearshore environments in conjunction with the onshore development of a large fluviodeltaic system.     

Fatty Acid and Chlorophyll Levels of Coastal Bermudagrass during the Day and during Maturation

Lipids were extracted from fresh, field-grown coastal bermudagrass (Cynodon dactylon (L.) Pers.) and the fatty acids determined by gas chromatography. Total fatty acid levels (dry weight basis) increased during the day and reached a single maximum at sunset in 2-week-old grass; whereas, in older grass, the fluctuations in fatty acid levels showed two maxima. The first maximum occurred 4 h after sunrise and the second maximum occurred at sunset. Total fatty acid levels, based on dry weight, decreased during the first 6 weeks of growth and changed very little after an additional 4 weeks' growth in bermudagrass leaf blades. Chlorophyll levels (dry weight basis) continuously decreased during the entire growth period (10 weeks). Chlorophyll alb ratios increased at sunset in 2- and 6-week-old grass, but this ratio did not change during the day in subsequent growth stages. The results of these experiments show that stages of maturity affected fatty acid fluctuations during the day as well as total fatty acid and chlorophyll levels in Coastal bermudagrass leaf blades. Chlorophyll alb ratios varied independently of fatty acid levels.     

A Cannibal in the National Museum: The Early Career of Franz Boas in America

Franz Boas spent several weeks at Fort Rupert, British Columbia, at the end of 1894, when he saw the Kwakiutl hamatsa ritual in situ for the first time. Soon after his return east Boas posed for a series of photographs in the U.S. National Museum for a diorama of the hamatsa dance. These photographs, now published for the first time, are a sharp reminder of Boas' constant (and sometimes forced) collaboration with the limited number of anthropological institutions in America at the end of the century, and of his personal difficulties in establishing himself professionally in America.     

Messenger RNA metabolism of animal cells: possible involvement of untranslated sequences and mRNA-associated proteins

The past several years have seen a virtual revolution in the study of eukaryotic mRNA. Among the notable recent achievements are the positive identification of mRNA precursors in HnRNA, the enumeration of the DNA sequences from which mRNA is transcribed, and the finding that mRNA in cultured cells is much more stable than was previously believed. One of most far-reaching discoveries has been the finding that mRNA in eukaryotes contains poly A. This discovery, aside from providing a powerful tool for mRNA isolation, has generated a large body of research into the properties and metabolism of poly A itself. In addition, the finding of a poly A-associated protein has given a renewed stimulus to the study of proteins associated with mRNA. This review is devoted to a discussion of these and related achievements, and some of their implications