An enhancer that directs lineage-specific expression of CD8 in positively selected thymocytes and mature T cells

Positive selection of CD4+CD8+ T cells to the CD4+CD8- helper and CD4- CD8+ cytotoxic lineages is a multistep process that involves complex regulation of coreceptor gene expression. By analyzing expression of a reporter gene in transgenic mice, we have identified a DNA segment, located between the murine CD8beta and CD8alpha genes, that has enhancer activity restricted to CD8 lineage cells. Remarkably, this enhancer functions in thymocytes undergoing positive selection to the CD4-CD8+ phenotype but not in immature double-positive thymocytes. The enhancer also functions in gut intraepithelial lymphocytes that express CD8alpha but not CD8beta, suggesting that it is specific for CD8alpha expression. The tight correlation between activation of this enhancer and the final step in positive selection has important implications for understanding the mechanism of lineage commitment in thymocytes.     

Mutation of the htrB gene in a virulent Salmonella typhimurium strain by intergeneric transduction: strain construction and phenotypic characterization

The htrB gene product of Haemophilus influenzae contributes to the toxicity of the lipooligosaccharide. The htrB gene encodes a 2-keto-3-deoxyoctulosonic acid-dependent acyltransferase which is responsible for myristic acid substitutions at the hydroxy moiety of lipid A beta-hydroxymyristic acid. Mass spectroscopic analysis has demonstrated that lipid A from an H. influenzae htrB mutant is predominantly tetraacyl and similar in structure to lipid IV(A), which has been shown to be nontoxic in animal models. We sought to construct a Salmonella typhimurium htrB mutant in order to investigate the contribution of htrB to virulence in a well-defined murine typhoid model of animal pathogenesis. To this end, an r- m+ galE mutS recD strain of S. typhimurium was constructed (MGS-7) and used in inter- and intrastrain transduction experiments with both coliphage P1 and Salmonella phage P22. The Escherichia coli htrB gene containing a mini-Tn10 insertion was transduced from E. coli MLK217 into S. typhimurium MGS-7 via phage P1 and subsequently via phage P22 into the virulent Salmonella strain SL1344. All S. typhimurium transductants showed phenotypes similar to those described for the E. coli htrB mutant. Mass spectrometric analysis of the crude lipid A fraction from the lipopolysaccharide of the S. typhimurium htrB mutant strain showed that for the dominant hexaacyl form, a lauric acid moiety was lost at one position on the lipid A and a palmitic acid moiety was added at another position; for the less abundant heptaacyl species, the lauric acid was replaced with palmitoleic acid.     

Formal Techniques for Protocol Specification and Verification

Certain formal approaches, such as transition techniques and reachability analysis, show promising results when applied to protocol specification and verification.     

Effects of density and format on letter discrimination by beginning readers with different learning styles.

Investigated the processing requirements in letter discrimination for 40 1st graders with reflective-impulsive and field-dependent-field-independent learning styles. Field dependence was measured by the Children's Embedded Figures Test, and impulsivity was measured by the Matching Familiar Figures Test. The discrimination task, presented in vertical and horizontal formats and in high- and low-density arrangements, consisted of matching each of 12 letterlike symbols with 1 of its 12 transformations. Results support all a priori hypotheses: (a) Impulsivity-reflectivity was related only to number of errors and latency. (b) Field dependency-independency was unrelated to latency but interacted with contextual arrangements. Field dependents made more errors than field independents on high-density and horizontal presentations. Interpretations are made in terms of the feature analysis processes employed by beginning readers with different learning styles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On wear as a mechanism of granule attrition

Mechanisms of granule or agglomerate attrition are studied in the light of the principles of fracture mechanics. Fracture properties are measured for agglomerated systems including both glass beads bound by polymeric binders and pesticide products. In the present work, the sizes of typical granules are less than the critical specimen sizes capable of gross fracture, as calculated from fracture theory. This implies that the mode of granule attrition is primarily one of erosion of abrasive wear and not gross fracture. Previous abrasive wear research is reviewed, with the aim of establishing the dependence of agglomerate bar wear on material properties. Idealized bar agglomerates are studied, as they allow convenient characterization of the dependence of granule erosion on material properties. Bar wear rates are foud to parallel results from the ceramics wear literature. In particular, wear rate is found to have a similar but somewhat different dependence on fracture toughness than the work of Mullier et al.⁴, where both fluid-bed granule erosion rate and wear of bar agglomerates were found proportional to 1/K_c.     

Broad-Band Personal Computer LAN's

Broad-band technology provides several advantages for personal computer local area networks (PC LAN's) including mature readily available transmission technology, large total bandwidth, support for multiple services, and cost-effective expansion from very small to very large systems. This paper presents an overview of basic broad-band technology, hardware, software, and protocols needed for PC LAN's. Gateways and network management are also considered. Recent PC LAN products are compared, with a more detailed case study of the PC LAN developed by IBM and Sytek.     

Manpower needs for radiation oncology: a preliminary report of the ASTRO Human Resources Committee. American Society for Therapeutic Radiology and Oncology

In summary, the ASTRO Committee on Human Resources believes that there is ample evidence for the existence of an oversupply of radiation oncologists in the United States at the present time. It believes that this oversupply has already affected the specialty in a variety of ways that are difficult to measure, for example, increased competition, conflicts between radiation oncology groups, conflicts between the private sector and academics, and increased costs, and that it is beginning to have a significant effect on the job market. This oversupply came about because of the rapid expansion in medical school enrollment in the 1970s. This led to an increased number of graduates available for enrollment into specialty residencies, one of which was radiation oncology. The actual number of radiation oncology residency positions offered has not changed significantly since 1972. However, only about half of the residency positions were filled in the early years. Since 1986, virtually all radiation oncology training positions in the United States have been filled, and this has led to a significantly greater number of radiation oncologists entering the field than have left the field through death or retirement. Preliminary data suggest that a shift to a managed care system would result in decreased demand for radiation oncology services, and that would increase the manpower problem for our specialty.