In vivo function of regulatory DNA sequence elements of a major histocompatibility complex class I gene.

Major histocompatibility complex class I genes are expressed in nearly all somatic tissues, although their level of expression varies. By analysis of a set of promoter deletion mutants introduced into transgenic mice, a complex regulatory element, consisting of overlapping enhancer and silencer activities, is demonstrated to function as a tissue-specific regulator of class I expression. The enhancer activity predominates in lymphoid tissues but not in nonlymphoid tissues. In contrast to the tissue-specific functions of the complex regulatory element, a second novel silencer element is shown to function in both lymphoid and nonlymphoid tissues. The complement of DNA-binding factors in different cell lines is shown to correlate with the levels of class I expression.     

Exposure of Fischerella [Mastigocladus] to high and low temperature extremes: strain evaluation for a thermal mitigation process

In conjunction with a proposed algal cultivation scheme utilizing thermal effluent, twelve Fischerella strains were tested for tolerance to temperatures above and below their growth range. Exposure to 65 °C or 70 °C for 30 min caused bleaching and death of most or all cells. Effects of 60 °C exposure for periods of up to 2 h ranged from undetectable to severe for the various strains. Chlorophyll a content typically decreased 21–22% immediately following 60 °C or 65 °C (1 h) exposure. However, the 60 °C-shocked cultures regained normal Chl a content after 24 h at 45 °C, whereas Chl a in 65 °C-shocked cultures immediately lost visible autofluorescence and was later degraded. Exposure to 15 °C virtually stopped growth of all strains during a 48 h exposure period. Most strains grew as rapidly as 45 °C controls when restored to 45 °C, while a few strains recovered more slowly. Comparison with dark-incubated controls indicated that photooxidative damage did not occur during cold shock. Certain strains exhibited relatively rapid recovery from both heat and cold exposure, thus meeting the temperature tolerance criteria for the proposed algal cultivation process.     

Characterization of AmphiF-spondin reveals the modular evolution of chordate F-spondin genes

The F-spondin genes are a family of extracellular matrix molecules united by two conserved domains, FS1 and FS2, at the amino terminus plus a variable number of thrombospondin repeats at the carboxy terminus. Currently, characterized members include a single gene in Drosophila and multiple genes in vertebrates. The vertebrate genes are expressed in the midline of the developing embryo, primarily in the floor plate of the neural tube. To investigate the evolution of chordate F-spondin genes, I have used the basal position in chordate phylogeny of the acraniate amphioxus. A single F-spondin-related gene, named AmphiF-spondin, was isolated from amphioxus. Based on molecular phylogenetics, AmphiF-spondin is closely related to a particular subgroup of vertebrate F-spondin genes that encode six thrombospondin repeats. However, unlike these genes, expression of AmphiF-spondin is not confined to the midline but is found through most of the central nervous system. Additionally, AmphiF-spondin has lost three thrombospondin repeats and gained two fibronectin type III repeats, one of which has strong identity to a fibronectin type III repeat from Deleted in Colorectal Cancer (DCC). Taken together, these results suggest a complex evolutionary history for chordate F-spondin genes that includes (1) domain loss, (2) domain gain by tandem duplication and divergence of existing domains, and (3) gain of heterologous domains by exon shuffling.      

Scheduling parallel applications in distributed networks

Prophet is a run-time scheduling system designed to support the efficient execution of parallel applications written in the Mentat programming language (Grimshaw, 1993). Prior results demonstrated that SPMD applications could be scheduled automatically in an Ethernet-based local-area workstation network with good performance (Weissman and Grimshaw, 1994 and 1995). This paper describes our recent efforts to extend Prophet along several dimensions: improved overhead control, greater resource sharing, greater resource heterogeneity, wide-area scheduling, and new application types. We show that both SPMD and task parallel applications can be scheduled effectively in a shared heterogeneous LAN environment containing ethernet and ATM networks by exploiting the application structure and dynamic run-time information. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nucleotide sequence of the gene for the major structural protein of SV40 virus.

We have determined the sequence of the portion of Simian Virus 40 (SV40) that codes for the major structural protein of the virus. The gene contains 361 codons. Synonym codons for an amino acid are not used randomly. The dinucleotide CG occurs only once and there is 2 to 1 preference for uridylic acid in the third position of codons.