Niche Expansion and Contraction in a Variable Environment

When food is abundant, sparrows are found in great variety ofhabitats and appear to specialize on particularly profitabletypes of seeds. However, during periods of food scarcity, eachsparrow species occupies a very narrow range of habitats butconsumes a great variety of seeds within each occupied habitat.As a result, average dietary overlap may underestimate the potentialfor competition for food within habitats during periods of foodshortage whereas average habitat overlap overestimates the potentialfor competition since each species occupies a different habitatduring periods of food shortage.     

Plasma Equine γ-Globulin in Tolerant Adult Dogs given Anti-lymphocyte Globulin

THIS report describes a positive correlation between sequential serum concentrations of EγG and the dosage schedule of equine anti-dog-lymphocyte globulin (EADLG) in dogs in which tolerance was induced by pretreatment with ultra-centrifuged EγG (tolerogen). This was in marked contrast to results in dogs which were not pretreated with tolerogen.     

Characterization and Quantitation of Membrane Antigens of New World Leishmania Species by Using Monoclonal Antibodies in Western Blot and Flow Microfluorometric Assays1

ABSTRACT. Membrane-specific monoclonal antibodies generated against promastigotes of New World Leishmania species were used in Western blot, ELISA, and flow microfluorometric assays to characterize their antigen specificity and to determine the external surface distribution of the reactive epitopes. Three major membrane antigens of molecular weight 72 KD, 55 KD, and 42 KD were identified as well as a dominant antigen that migrated as a broad band on SDS-PAGE, corresponding to a molecular weight of 10–15 KD. By dot-ELISA this antigen was also found to be excreted by promastigotes into their culture medium. One minor membrane antigen of 25 KD and a triplet component of 66, 58, and 56 KD were also identified. While assays performed on air-dried promastigotes revealed the almost ubiquitous presence of the 72 KD and 55 KD antigens, indirect immunofluorescent staining of live promastigotes followed by flow cytometric analysis revealed that these antigens had no external exposure. Antibodies binding the 55 KD component were also reactive toward purified mammalian tubulin. The remaining antigens had a variable distribution on the eight isolates utilized, and these quantitative differences could be used to distinguish isolates of the Leishmania mexicana complex from those belonging to the Leishmania braziliensis complex.     

Glycolate Metabolism in Eurasian Watermilfoil (Myriophyllum spicatum)

The metabolism of glycolate by Eurasian watermilfoil (Myriophyllum spicatum L.), a submersed angiosperm, was studied by feeding radioactive glycolate and glyoxylate and by analysis of glycolate and glycolic acid oxidase. Evidence for operation of the glycolate pathway is given. Glycolic acid oxidase occurs at levels comparable to amounts in species showing photorespiration. This species has a high affinity for CO₂ and a possible mechanism for it is described.