Effects of an experimental acid pulse on invertebrates in a high altitude Sierra Nevada stream

The effects of pulsed acidification on invertebrate densities and drift, and water chemistry, in a high altitude Sierra Nevada stream were measured using artificial stream channels. Water was diverted from the Marble Fork of the Kaweah River, California, U.S.A., through twelve replicate channels; however, low flow in the summer of 1985 eliminated all but four of these channels. Channels were stocked with natural substrates and organisms from the Marble Fork of the Kaweah River. After a three week acclimation period, we simulated a low pH rain event by adding acid (H₂SO₄ and HNO₃) to two of the channels, reducing pH to 5.0 for 6 hours. The other two channels acted as controls (pH 6.4). During acid additions, Baetis spp. drift in acidified channels was ca. 7 times higher than in control channels (F = 39.02, p < 0.025; data fourth root transformed, ANOVA), and the percentage of drifting baetids that was dead was significantly higher in acidified than control channels (46% vs. 0%, F = 29.86, p < 0.05; arcsine square root transformed data, ANOVA). Other taxa showed no significant drift responses, and benthic densities of all taxa showed no effects two days after acidification, probably owing to rapid recolonization by invertebrate drift in influent waters. Stream chemistry data are presented; heavy metal concentrations did not significantly increase in the 2 m stream channels.     

Glycoprotein B Cleavage Is Important for Murid Herpesvirus 4 To Infect Myeloid Cells

Glycoprotein B (gB) is a conserved herpesvirus virion component implicated in membrane fusion. As with many—but not all—herpesviruses, the gB of murid herpesvirus 4 (MuHV-4) is cleaved into disulfide-linked subunits, apparently by furin. Preventing gB cleavage for some herpesviruses causes minor infection deficits in vitro, but what the cleavage contributes to host colonization has been unclear. To address this, we mutated the furin cleavage site (R-R-K-R) of the MuHV-4 gB. Abolishing gB cleavage did not affect its expression levels, glycosylation, or antigenic conformation. In vitro, mutant viruses entered fibroblasts and epithelial cells normally but had a significant entry deficit in myeloid cells such as macrophages and bone marrow-derived dendritic cells. The deficit in myeloid cells was not due to reduced virion binding or endocytosis, suggesting that gB cleavage promotes infection at a postendocytic entry step, presumably viral membrane fusion. In vivo, viruses lacking gB cleavage showed reduced lytic spread in the lungs. Alveolar epithelial cell infection was normal, but alveolar macrophage infection was significantly reduced. Normal long-term latency in lymphoid tissue was established nonetheless.     

Identification of two distinct microtubule binding domains on recombinant rat MAP 1B.

A set of partially overlapping cDNA clones covering 9 kb of continuous sequence encoding the high molecular weight microtubule-associated protein (MAP) 1B, was isolated from a rat brain library in lambda gt11. The protein encoded was immunoreactive with monoclonal antibodies raised against calf MAP 1B, rat MAP 1X, and rat MAP 5, as shown by immunoblotting. Using Northern blot analysis, it was shown that the level of MAP 1B mRNA increased dramatically upon nerve growth factor-induced PC12 cell differentiation. The expression of polypeptides encoded by cDNA constructs, in conjunction with microtubule binding assays, revealed two separate microtubule binding domains, corresponding to sequences at the 5' and 3' end of the mRNA. As shown by DNA sequencing, the binding domain encoded by 5' terminal sequences consisted of the basic repeat motif KKEE(I/V), previously identified in mouse MAP 1B (Noble, M., S. A. Lewis, N. J. Cowan, J. Cell Biol. 109, 3367-3376 (1989)). The second binding domain, too, was found to be basic, but without any apparent repeat structure. It is concluded that single proteolytically unprocessed MAP 1B molecules would have the potential to function as microtubule cross-linkers.     

Comparison of the effects of IL-1 alpha and TNF-alpha on phagocyte accumulation and murine antibacterial immunity

IL-1 and TNF both are reported to increase host antibacterial resistance. To directly compare their effects on tissue phagocyte accumulation and antibacterial activity, we infused recombinant human IL-1 alpha and TNF-alpha into C3H/HeJ mice. Although IL-1, at a dose of 1 microgram/day, did not significantly elevate blood neutrophil concentrations, it increased the number of PMNs within the spleen three to fourfold within 2 days. Similar neutrophil accumulation also occurred in the lungs, bone marrow, and liver of treated animals without detectable changes in macrophage numbers. IL-1 also increased myelopoiesis in the spleen by Days 3-4 of infusions. The capacity of splenocytes from IL-1-treated animals to kill Listeria monocytogenes in vitro and to suppress listeria proliferation in vivo after the intravenous infusion of bacteria both rose in parallel with PMN accumulation. Comparable doses of TNF also enhanced listeria killing in vivo but in contrast to IL-1, it significantly depressed peripheral blood neutrophil counts, and inhibited splenic neutrophil accumulation and in vitro listericidal activity in listeria-infected mice. Our results suggest that IL-1 enhances host resistance to infection by increasing tissue neutrophil accumulation while TNF protects by a different mechanism, despite a net inhibitory effect on neutrophil accumulation.     

Persistent Popular Images of Pastoralists

Pastoralists have long been recurrent figures in visual images and other representations of Africa and Africans. Whether seen in positive or negative terms, pastoralists have provided means for thinking about and imaging cultural difference and identity, with considerable continuity in representational forms and themes. As popular visual media proliferated and changed over the past two centuries--from postcards, trade cards, and live shows to Hollywood films and video games--African pastoralists have continued to appear in each new form, often replicating the types and stereotypes of Euroamerican understandings even as they register new and varied circumstances. The proliferation and reverberation of similar images through diverse visual media is one way these images have come to seem "natural" and to develop such remarkable persistence [Kratz 2002]. Using cases drawn from eastern and southern Africa, this collection of articles considers the multifaceted processes of representation involved in imaging African pastoralists. It invites attention to how such representations are produced in diverse visual media and through interconnections among visual and verbal media, examining the range of actors, interactions, and mediations involved in crafting representations of African pastoralists at different times and in different places.     

Blue Light Overrides Repression of Asexual Sporulation by Mating Type Genes in the Basidiomycete Coprinus cinereus

Monokaryotic mycelia of the homobasidiomycete Coprinus cinereus form asexual spores (oidia) constitutively in abundant numbers. Mycelia with mutations in both mating type loci (Amut Bmut homokaryons) also produce copious oidia but only when exposed to blue light. We used such an Amut Bmut homokaryon to define environmental and inherent factors that influence the light-induced oidiation process. We show that the Amut function causes repression of oidiation in the dark and that light overrides this effect. Similarly, compatible genes from different haplotypes of the A mating type locus repress sporulation in the dark and not in the light. Compatible products of the B mating type locus reduce the outcome of light on A-mediated repression but the mutated B function present in the Amut Bmut homokaryons is not effective. In dikaryons, the coordinated regulation of asexual sporulation by compatible A and B mating type genes results in moderate oidia production in light. Copyright 1998 Academic Press.