Impact of Non-Native Birds on Native Ecosystems: A Global Analysis

Introduction and naturalization of non-native species is one of the most important threats to global biodiversity. Birds have been widely introduced worldwide, but their impacts on populations, communities, and ecosystems have not received as much attention as those of other groups. This work is a global synthesis of the impact of nonnative birds on native ecosystems to determine (1) what groups, impacts, and locations have been best studied; (2) which taxonomic groups and which impacts have greatest effects on ecosystems, (3) how important are bird impacts at the community and ecosystem levels, and (4) what are the known benefits of nonnative birds to natural ecosystems. We conducted an extensive literature search that yielded 148 articles covering 39 species belonging to 18 families -18% of all known naturalized species. Studies were classified according to where they were conducted: Africa, Asia, Australasia, Europe, North America, South America, Islands of the Indian, of the Pacific, and of the Atlantic Ocean. Seven types of impact on native ecosystems were evaluated: competition, disease transmission, chemical, physical, or structural impact on ecosystem, grazing/ herbivory/ browsing, hybridization, predation, and interaction with other non-native species. Hybridization and disease transmission were the most important impacts, affecting the population and community levels. Ecosystem-level impacts, such as structural and chemical impacts were detected. Seven species were found to have positive impacts aside from negative ones. We provide suggestions for future studies focused on mechanisms of impact, regions, and understudied taxonomic groups.     

Separate Intramolecular Targets for Protein Kinase A Control N-Methyl-d-aspartate Receptor Gating and Ca2+ Permeability

Protein kinase A (PKA) enhances synaptic plasticity in the central nervous system by increasing NMDA receptor current amplitude and Ca²⁺ flux in an isoform-dependent yet poorly understood manner. PKA phosphorylates multiple residues on GluN1, GluN2A, and GluN2B subunits in vivo, but the functional significance of this multiplicity is unknown. We examined gating and permeation properties of recombinant NMDA receptor isoforms and of receptors with altered C-terminal domain (CTDs) prior to and after pharmacological inhibition of PKA. We found that PKA inhibition decreased GluN1/GluN2B but not GluN1/GluN2A gating; this effect was due to slower rates for receptor activation and resensitization and was mediated exclusively by the GluN2B CTD. In contrast, PKA inhibition reduced NMDA receptor-relative Ca²⁺ permeability (P_Ca/P_Na) regardless of the GluN2 isoform and required the GluN1 CTD; this effect was due primarily to decreased unitary Ca²⁺ conductance, because neither Na⁺ conductance nor Ca²⁺-dependent block was altered substantially. Finally, we show that both the gating and permeation effects can be reproduced by changing the phosphorylation state of a single residue: GluN2B Ser-1166 and GluN1 Ser-897, respectively. We conclude that PKA effects on NMDA receptor gating and Ca²⁺ permeability rely on distinct phosphorylation sites located on the CTD of GluN2B and GluN1 subunits. This separate control of NMDA receptor properties by PKA may account for the specific effects of PKA on plasticity during synaptic development and may lead to drugs targeted to alter NMDA receptor gating or Ca²⁺ permeability.     

Enterobacteriaceae, coliforms, faecal coliforms and salmonellas in raw ewes' milk

Thirty-nine samples of freshly drawn ewes' milk collected at 13 farms, and 120 samples of raw ewes' milk collected on arrival at a dairy were examined. Farm samples had geometric mean counts of 4.4 X 10(2) Enterobacteriaceae/ml, 3.9 X 10(2) coliforms/ml and 2.0 X 10(2) faecal coliforms/ml, whereas the respective mean counts were 6.2 X 10(3)/ml, 5.4 X 10(3)/ml and 1.3 X 10(3)/ml for dairy samples. Salmonellas were not detected by enrichment procedures in any of the 159 samples examined. Escherichia coli (47.5% strains), Enterobacter cloacae (17.7%), Ent. agglomerans (11.3%), Hafnia alvei (6.5%) and Klebsiella oxytoca (6.0%) were the predominant species in 434 Enterobacteriaceae strains isolated from farm samples. Levels and species of Enterobacteriaceae found in the present work in raw ewes' milk imply a considerable risk of early blowing in cheese-making from unpasteurized milk.     

Possible role of cytokinins in cereals with regard to the resistance to obligate fungus parasites

The cultivars of barley and wheat resistant to mildew had a higher level of free zeatin and its derivatives during the whole ontogeny than the susceptible cultivars. The effect of exogenous application of cytokinins on the growth ofErysiphe graminis DC. was different. Kinetin and benzylaminopurine showed only a slight inhibitory effect. Zeatin and its derivatives completely inhibited growth of this fungus. Presented at the International Symposium “Plant Growth Regulators” held on June 18-22 1984 at Liblice, Czechoslovakia.     

Regulation of branched-chain amino acid biosynthesis in Streptomyces fradiae,a producer of tylosin

Synthesis of threonine dehydratase in Streptomyces fradiae was positively influenced by valine and negatively by isoleucine. However, these two amino acids had no effect on the activity of this enzyme. Synthesis of threonine dehydratase in -aminobutyrate resistant mutants of S. fradiae was pronouncedly less sensitive to the positive effect of valine and this change in regulation led to valine overproduction. Synthesis of acetohydroxy acid synthase is regulated in a similar manner to that of threonine dehydratase, however a lower level of expression was detected in -aminobutyrate resistant mutants. And again, no effect of branched-chain amino acids on acetohydroxy acid synthase activity was observed. It follows that in S. fradiae synthesis of threonine dehydratase is the main regulatory mechanism governing production and the mutual ratio of synthesized valine and isoleucine.Abbreviations -AB -aminobutyrate - AHAS acetohydroxy acid synthase - -KB -ketobutyrate - MNNG N-methyl-N-nitro-N-nitrosoguanidine - TD threonine dehydratase - Trans. B. transaminase of branched-chain amino acids - VDH valine dehydrogenase     

Purification of phosphate-dependent glutaminase from isolated mitochondria of Ehrlich ascites-tumour cells.

Phosphate-dependent glutaminase was purified to homogeneity from isolated mitochondria of Ehrlich ascites-tumour cells. The enzyme had an Mr of 135,000 as judged by chromatography on Sephacryl S-300. SDS/polyacrylamide-gel electrophoresis displayed two protein bands, with Mr values of 64,000 and 56,000. Two major immunoreactive peptides of Mr values of 65,000 and 57,000 were found by immunoblot analysis using anti-(rat kidney glutaminase) antibodies. The concentration-dependences for both glutamine and phosphate were sigmoidal, with S0.5 values of 7.6 mM and 48 mM, and Hill coefficients of 1.5 and 1.6, respectively. The glutaminase pH optimum was 9. The activation energy of the enzymic reaction was 58 kJ/mol. The enzyme showed a high specificity towards glutamine. A possible explanation for the different kinetic behaviour found for purified enzyme and for isolated mitochondria [Kovacević (1974) Cancer Res. 34, 3403-3407] should be that a conformational change occurs when the enzyme is extracted from the mitochondrial inner membrane.     

Metabolism of l-threonine and fatty acids and tylosin biosynthesis in Streptomyces fradiae

Abstract In Streptomyces fradiae l -threonine is catabolized by threonine dehydratase or threonine aldolase to 2-ketobutyrate or acetaldehyde and glycine, respectively. Threonine dehydratase synthesis is repressed and its activity is inhibited by NH₄⁺ ions. Threonine aldolase is not repressed by NH₄⁺ ions and its activity is slightly stimulated by these ions. The addition of threonine to the medium increased pronouncedly the fraction of non-branched fatty acids with an even carbon number under conditions when threonine dehydratase was repressed and inhibited. The results indicate that threonine serves as a source of propionyl-CoA and 2-methylbutyryl-CoA and also of acetyl-CoA required for tylosin and fatty acid biosynthesis.     

Intestinal parasites in the Camiri, Gutierrez and Boyuibe areas, Santa Cruz Department, Bolivia

A parasitological study was carried out on 381 apparently healthy subjects from Camiri, Boyuibe, Gutierrez. Intestinal parasites and non-pathogenic protozoa were present in 78.7% of the population sampled; multiple infections were observed in 67.7% of the parasitized individuals. The protozoon most commonly found was Entamoeba coli (in 40.7% of specimens), followed by Giardia intestinalis (30.7%), Iodamoeba bütschlii (10%), Chilomastix mesnili (8.7%). Other protozoon parasites also present were Enteromonas hominis (3.4%), Retortamonas intestinalis (2.4%), Cryptosporidium (2.1%), Endolimax nana (2.1%), Balantidium coli (1.8%) and Pentatrichomonas hominis (0.8%). The helminths observed were hookworms (28.6%), Trichuris trichiura (19.7%), Ascaris lumbricoides (9.7%), Hymenolepis nana (8.7%), Trichostrongylus (5.5%), Strongyloides stercoralis (1.8%), Taenia (5 cases) and Enterobius (6 cases). Prevalence for nematodes is probably underestimated in the 3-9 years age group because of a mebendazole treatment given 5 weeks before the survey, under a Program of P D C of the Ministry of Health. The sample from Camiri was found to be the most parasitized (84.1%). An extraordinarily high infection rate was found in two urban institutions, as well as in Itanambicua, a rural community close to Camiri. No significant differences were observed in parasitic prevalence between rural and urban environments. Exposure to contamination with human and animal faeces, overcrowding and poor sanitation habits are some of the factors responsible for the parasitic situation evidenced.     

A quantitative study of enterotoxin production by sheep milk staphylococci

Of 124 staphylococcal strains isolated from sheep milk, 78 produced enterotoxin A, B, C, or D when evaluated by an enzyme-linked immunosorbent assay. Enterotoxins A and D, elaborated by 44 and 43 strains, respectively, showed the highest incidence. Enterotoxin production by coagulase-negative strains (one Staphylococcus cohnii, three S. epidermidis, five S. haemolyticus, and four S. xylosus) was detected. Linear and logarithmic-logarithmic regressions of optical density on enterotoxin concentration yielded the best-fitting equations for enterotoxin quantitation. A significantly higher incidence of enterotoxin producers and significantly higher levels of enterotoxins produced were recorded for coagulase-positive, thermostable nuclease-positive, hemolysis-positive, or mannitol-positive strains. Mannitol utilization was the best test for discriminating between enterotoxigenic and nonenterotoxigenic staphylococci.