Study of Earthquake Recurrence Intervals on the Wasatch Fault, Utah: Little Cottonwood Canyon Site

Detailed geologic mapping, topographic profiling, and trenching are being conducted at selected sites along the Wasatch fault zone to measure the cumulative fault displacements in Quaternary strata of various ages and to obtain data regarding the amount of displacement per surface faulting event and the number and recurrence of faulting events that produced the cumulative displacement. These data are used to estimate the frequency of occurrence and magnitude of earthquakes associated with surface faulting along individual segments of the Wasatch fault zone. Investigations have been completed at three sites, the Kaysville, Hobble Creek, and Little Cottonwood Canyon sites. The results of the investigations at the Kaysville and Hobble Creek sites are discussion in our previous reports, which are listed in Appendix A. Detailed geologic investigations were conducted at the Little Cottonwood Canyon site during June, July, and October, 1979. This report presents our findings, interpretations, and preliminary conclusions based on our field investigations at the Little Cottonwood Canyon site

A rock-surface microweathering index from Schmidt hammer R-values and its preliminary application to some common rock types in southern Norway

An index of the degree of rock-surface microweathering based on Schmidt hammer R-values is developed for use in the field without laboratory testing. A series of indices - I2 to In, where n is the number of successive blows with the hammer - is first proposed based on the assumption that the R-values derived from successive impacts on the same spot on a weathered rock surface converge on the value characteristic of an unweathered surface of the same lithology. Of these indices, the I5 index, which measures the difference between the mean R-value derived from first and fifth impacts as a proportion of the mean R-value from the fifth impact, is regarded as optimal: use of fewer impacts (e.g. in an I2 index) underestimates the degree of weathering whereas use of more impacts (e.g. in an I10 index) makes little difference and is therefore inefficient and may also induce an artificial weakening of the rock. Field tests of these indices on weathered glacially-scoured bedrock outcrops of nine common metamorphic and igneous rock types from southern Norway show, however, that even after ten impacts, successive R-values fail to approach the values characteristic of unweathered rock surfaces (e.g. bedrock from glacier forelands and road cuttings). An improved *I5 index is therefore preferred, in which the estimated true R-value of an unweathered rock surface is substituted. Weathered rock surfaces exposed to the atmosphere for ~10,000 years in southern Norway exhibit *I5 indices of 36-57%, values that reflect a similarly high degree of weathering irrespective of the rock type

An Upstream Open Reading Frame Controls Translation of var2csa, a Gene Implicated in Placental Malaria

Malaria, caused by the parasite Plasmodium falciparum, is responsible for substantial morbidity, mortality and economic losses in tropical regions of the world. Pregnant women are exceptionally vulnerable to severe consequences of the infection, due to the specific adhesion of parasite-infected erythrocytes in the placenta. This adhesion is mediated by a unique variant of PfEMP1, a parasite encoded, hyper-variable antigen placed on the surface of infected cells. This variant, called VAR2CSA, binds to chondroitin sulfate A on syncytiotrophoblasts in the intervillous space of placentas. VAR2CSA appears to only be expressed in the presence of a placenta, suggesting that its expression is actively repressed in men, children or non-pregnant women; however, the mechanism of repression is not understood. Using cultured parasite lines and reporter gene constructs, we show that the gene encoding VAR2CSA contains a small upstream open reading frame that acts to repress translation of the resulting mRNA, revealing a novel form of gene regulation in malaria parasites. The mechanism underlying this translational repression is reversible, allowing high levels of protein translation upon selection, thus potentially enabling parasites to upregulate expression of this variant antigen in the presence of the appropriate host tissue

Comparative Transcriptional and Genomic Analysis of Plasmodium falciparum Field Isolates

Mechanisms for differential regulation of gene expression may underlie much of the phenotypic variation and adaptability of malaria parasites. Here we describe transcriptional variation among culture-adapted field isolates of Plasmodium falciparum, the species responsible for most malarial disease. It was found that genes coding for parasite protein export into the red cell cytosol and onto its surface, and genes coding for sexual stage proteins involved in parasite transmission are up-regulated in field isolates compared with long-term laboratory isolates. Much of this variability was associated with the loss of small or large chromosomal segments, or other forms of gene copy number variation that are prevalent in the P. falciparum genome (copy number variants, CNVs). Expression levels of genes inside these segments were correlated to that of genes outside and adjacent to the segment boundaries, and this association declined with distance from the CNV boundary. This observation could not be explained by copy number variation in these adjacent genes. This suggests a local-acting regulatory role for CNVs in transcription of neighboring genes and helps explain the chromosomal clustering that we observed here. Transcriptional co-regulation of physical clusters of adaptive genes may provide a way for the parasite to readily adapt to its highly heterogeneous and strongly selective environment