Plasmodium Sporozoite Interactions with Macrophages In Vitro: a Videomicroscopic Analysis

ABSTRACT. Studies of in vitro interactions between Plasmodium berghei sporozoites and peritoneal macrophages from mice and rats were performed. A videomicroscopic analysis was made of interactions observed by phase-contrast microscopy. Our results showed a diversity of dynamic interactions between sporozoites and macrophages that included no interaction, surface interaction without sporozoite interiorization, active sporozoite penetration, active penetration with subsequent sporozoite escape, macrophage destruction, and the formation of "tethers" or web-like structures by sporozoites that had actively invaded macrophages. Sporozoites are thus clearly capable of actively invading host macrophages and are not restricted to being phagocytosed for interiorization. The formation of "tethers" by the moving sporozoite might function in vivo by anchoring the sporozoite to the cells lining the lumen of the liver sinusoid. Active sporozoite motility appears to be a functional phenomenon involved in sporozoite invasion of host liver cells.     

Novel,panzootic and hybrid genotypes of amphibian chytridiomycosis associated with the bullfrog trade

Global amphibian declines are linked with the presence of specific, highly virulent genotypes of the emerging fungal disease chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd) known as the global panzootic lineage (Bd‐GPL). The global trade in amphibians for human consumption is suspected to have facilitated emergence of the disease, but evidence to support this is largely lacking. Here, we investigated the role the Lithobates catesbeianus (North American bullfrog) trade in spreading Bd genotypes by comparing strains associated with L. catesbeianus to a global panel using 36 sequenced loci from multiple chromosomal regions. Most bullfrogs were infected with Bd‐GPL genotypes, but we also detected novel, highly divergent Bd genotypes (Bd‐Brazil) from a live bullfrog in a US market and from native Brazilian anurans in the Atlantic Forest where bullfrogs are widely farmed. Sexual reproduction was also detected for the first time in Bd in the form of a hybrid genotype between the Bd‐GPL and Bd‐Brazil lineages in the Atlantic Forest. Despite the demonstration that ribosomal RNA types in Bd fail to undergo concerted evolution (over 20 sequence types may be found in a single strain), the Bd‐GPL and Bd‐Brazil lineages form largely separate clusters of related internal transcribed spacer (ITS) RNA sequences. Using ITS sequences, we then demonstrate the presence of Bd‐Brazil in Japan, primarily on invasive L. catesbeianus. The finding that Bd is capable of sexual reproduction between panzootic and endemic genotypes emphasizes the risk of international wildlife trade as a source of additional Bd epizootics owing to hybridization.     

Diversity of mitochondrial DNA of the endangered white-clawed crayfish (Austropotamobius italicus) in the Po River catchment

1. The strong contraction of the European populations of white‐clawed crayfish has stimulated research of its population genetics. As part of a conservation project to introduce and improve Italian populations of Austropotamobius italicus, the genetic diversity of 16 populations from 10 tributaries of the Po River drainage was evaluated by sequencing a 494 bp length of cytochrome oxidase subunit I (COI mtDNA). 2. The evolutionary tree topologies and the parsimony network of 26 haplotypes separated into two clusters, on the basis of high average genetic distance (6.51 ± 0.42%). This finding indicated the presence of distinct evolutionary lineages, other than different allopatric sources. 3. An ancestral haplotype (Nav) was identified and 13 haplotypes, found mainly as singletons, were independently connected to Nav by short branches with one mutation site. Unimodal mismatch distribution and the goodness‐of‐fit of the observed data reflected a model of sudden population expansion, after the last glacial bottleneck event. 4. A general moderate level of genetic variability (h = 0.22–0.7 and π = 0.045–0.27%) was highlighted within A. italicus populations inhabiting Alpine and Apennine tributaries of the Po River. Analysis of molecular variance (amova ) revealed significant genetic structuring across all hierarchical levels, indicating that a major proportion of genetic variance is structured among localities within drainages. Multiple adjacent localities, strictly connected by the Po River, shared the two most frequent haplotypes (Nav and Laz), while remote populations, far from the Po River inflow, move towards a mtDNA fixation. 5. The results of this study indicate that distinct populations should be treated as separate entities for management. The key implication of the data is that ad hoc measures for successful programmes of recovery and management strategies for A. italicus conservation, such as the phylogeographic study of haplotype distribution at a local scale and the genetic variability of populations used as stock breeders, should be considered.     

South African Museums and the Creation of a New National Identity

Museums are important sites of national cultural production, collective memory making, and the construction of national narratives. Contemporary South Africa is a particularly interesting place to study these processes. With the demise of apartheid, South Africa faces the difficult challenge of creating a new national identity that incorporates an examination of past oppression yet leaves the way open for building a national identity that incorporates all its diverse groups. The museums reviewed below, the Robben Island Prison Museum, the District Six Museum in Capetown, and the Kwa Muhle local history museum in Durban all make important contributions to this process.     

Interaction Between TRPC Channel Subunits in Endothelial Cells

Transient Receptor Potential Canonical (TRPC) proteins have been identified in mammals as a family of plasma membrane calcium-permeable channels activated by different kinds of stimuli in several cell types. We have studied TRPC subunit expression in bovine aortic endothelial (BAE-1) cells, where stimulation with basic fibroblast growth factor (bFGF), a potent angiogenetic factor, induces calcium entry carried at least partially by TRPC1 channels. By means of a RT-PCR approach, we have found that, in addition to TRPC1, only TRPC4 is expressed, both at the mRNA and protein level, as confirmed by immunoblotting and immunocytochemical analysis. Because functional TRPC channels are formed by assembly of four subunits in either homo- or heterotetrameric structures, we have carried out immunoprecipitation experiments and showed that TRPC1 and TRPC4 interact to form heteromers in these cells, independently from culture conditions (high or low percent of fetal calf serum, stimulation with bFGF). Moreover, the data show that TRPC subunits are not tyrosine-phosphorylated after bFGF stimulation and they do not co-immunoprecipitate with the type 1 FGF receptor. These results suggest that BAE-1 cells are a suitable model to study function and regulation of endogenous TRPC1/TRPC4 heteromers.     

Effect of Lithium on Rearing Activity in Rats

EVEN though the use of lithium salts is well established in the clinical treatment of manic states¹ and to a lesser extent in the prophylactic treatment of recurrent depression², there have been few reports of their effects on animal behaviour in laboratory conditions. One reason may lie in Schou's doubts³ as to whether lithium salts have any effects on behaviour outside the clinical context. This view was based on unpublished findings of I. M. Nielson, A. Amdisen, D. R. Maxwell and Schou himself and on the hypothesis that lithium serves to correct a specific biochemical or physiological imbalance characteristic of recurrent affective disorders⁴.