Immunogenicity of agarose-immobilized immune complexes

Summary A novel method is described for production of heterologous antisera to a specific tumor-associated murine antigen by immunization with agarose-trapped immune complexes.     

Determinants of woody cover in African savannas

Savannas are globally important ecosystems of great significance to human economies. In these biomes, which are characterized by the co-dominance of trees and grasses, woody cover is a chief determinant of ecosystem properties. The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover, but perceptions differ on which of these are the primary drivers of savanna structure. Here we show, using data from 854 sites across Africa, that maximum woody cover in savannas receiving a mean annual precipitation (MAP) of less than approximately 650 mm is constrained by, and increases linearly with, MAP. These arid and semi-arid savannas may be considered 'stable' systems in which water constrains woody cover and permits grasses to coexist, while fire, herbivory and soil properties interact to reduce woody cover below the MAP-controlled upper bound. Above a MAP of approximately 650 mm, savannas are 'unstable' systems in which MAP is sufficient for woody canopy closure, and disturbances (fire, herbivory) are required for the coexistence of trees and grass. These results provide insights into the nature of African savannas and suggest that future changes in precipitation may considerably affect their distribution and dynamics.     

Fractionation of mouse alpha-fetoprotein.

4 distinct alpha-fetoprotein (AFP) containing fractions were obtained upon ion-exchange chromatography of late-gestational fetal mouse extracts. Despite this chromatographic heterogeneity, the individual AFP isolates were antigenically indistinguishable.     

Listeriolysin O allows Listeria monocytogenes replication in macrophage vacuoles

Listeria monocytogenes is an intracellular bacterial pathogen that replicates rapidly in the cytosol of host cells during acute infection. Surprisingly, these bacteria were found to occupy vacuoles in liver granuloma macrophages during persistent infection of severe combined immunodeficient (SCID) mice. Here we show that L. monocytogenes can replicate in vacuoles within macrophages. In livers of SCID mice infected for 21 days, we observed bacteria in large LAMP1(+) compartments that we termed spacious Listeria-containing phagosomes (SLAPs). SLAPs were also observed in vitro, and were found to be non-acidic and non-degradative compartments that are generated in an autophagy-dependent manner. The replication rate of bacteria in SLAPs was found to be reduced compared to the rate of those in the cytosol. Listeriolysin O (LLO, encoded by hly), a pore-forming toxin essential for L. monocytogenes virulence, was necessary and sufficient for SLAP formation. A L. monocytogenes mutant with low LLO expression was impaired for phagosome escape but replicated slowly in SLAPs over a 72 h period. Therefore, our studies reveal a role for LLO in promoting L. monocytogenes replication in vacuoles and suggest a mechanism by which this pathogen can establish persistent infection in host macrophages.     

Population density, biomass, and age-class structure of an invasive clam Corbicula fluminea in rivers of the lower San Joaquin River watershed

Corbicula fluminea is well known as an invasive filter-feeding freshwater bivalve with a variety of effects on ecosystem processes. However, C. fluminea has been relatively unstudied in the rivers of the western United States. In June 2003, we sampled C. fluminea at 16 sites in the San Joaquin River watershed of California, which was invaded by C. fluminea in the 1940s. Corbicula fluminea was common in 2 tributaries to the San Joaquin River, reaching densities of 200 clams ? m –2 , but was rare in the San Joaquin River. Biomass followed a similar pattern. Clams of the same age were shorter in the San Joaquin River than in the tributaries. Distribution of clams was different in the 2 tributaries, but the causes of the difference are unknown. The low density and biomass of clams in the San Joaquin River was likely due to stressful habitat or to water quality, because food was abundant. The success of C. fluminea invasions and subsequent effects on trophic processes likely depends on multiple factors. As C. fluminea continues to expand its range around the world, questions regarding invasion success and effects on ecosystems will become important in a wide array of environmental settings.     

A road map for efficient and reliable human genome epidemiology

Networks of investigators have begun sharing best practices, tools and methods for analysis of associations between genetic variation and common diseases. A Network of Investigator Networks has been set up to drive the process, sponsored by the Human Genome Epidemiology Network. A workshop is planned to develop consensus guidelines for reporting results of genetic association studies. Published literature databases will be integrated, and unpublished data, including 'negative' studies, will be captured by online journals and through investigator networks. Systematic reviews will be expanded to include more meta-analyses of individual-level data and prospective meta-analyses. Field synopses will offer regularly updated overviews.     

The stoneflies (Plecoptera) of Louisiana

A list of species, illustrated keys to nymphs and adults, distribution, and biological notes are presented for 24 stonefly species occurring in Louisiana. Leuctra moha?, Pteronarcys dorsata, Helopicus subvarians, Paragnetina kansensis, Paragnetina immarginata, Phasganophora capitata, and Acroneuria evoluta are recorded only from the florida parishes east of the Mississippi River. Isoperla Coushatta, Isoperla mohri, Neoperla clymene, an undescribed Neoperla (Sp. A), Paragnetina fumosa, Acroneuria abnormis, Acroneuria arenosa, Perlinella drymo, and Perlesta placida are found both east and west of the Mississippi; and Allocapnia granulata, Allocapnia malverna, Amphinemoura nigritta, and three species of Taeniopteryx have been recorded only west of the Mississippi. Habitats are primarily sand-bottomed streams of pine-hardwood rolling hills, constituting a portion of the western Gulf Coastal Plain. Few stoneflies occur in streams of the Mississippi Alluvial Plain, the Alluvial Atchafalaya Basin, or the lowlands along the Red River.