A region of the Herpesvirus saimiri genome required for oncogenicity

Herpesvirus saimiri naturally infects squirrel monkeys (Saimiri sciureus) without producing signs of disease; infection of other New World primates, however, results in a rapidly progressing, malignant, T-cell lymphoma. Results described in this report identify a region of the viral genome that is required for oncogenicity in owl monkeys (Aotus trivirgatus); this region is not required for replication of the virus. This is believed to be the first such genomic region identified in a herpesvirus system.     

Evolution of bunyaviruses by genome reassortment in dually infected mosquitoes (Aedes triseriatus)

Aedes triseriatus mosquitoes became dually infected after ingesting two mutants of LaCrosse (LAC) virus simultaneously or after ingesting, by interrupted feeding, the two viruses sequentially within a 2-day period. After 2 weeks of incubation, approximately 25 percent of the vectors contained new virus genotypes as the result of RNA segment reassortment. New viruses were transmitted when the mosquitoes fed on mice. Viruses ingested more than 2 days after the initial infecting virus did not cause superinfection of the mosquito vectors.     

African hot spot volcanism: small-scale convection in the upper mantle beneath cratons

Numerical models demonstrate that small-scale convection develops in the upper mantle beneath the transition of thick cratonic lithosphere and thin oceanic lithosphere. These models explain the location and geochemical characteristics of intraplate volcanos on the African and South American plates. They also explain the presence of relatively high seismic shear wave velocities (cold downwellings) in the mantle transition zone beneath the western margin of African cratons and the eastern margin of South American cratons. Small-scale, edge-driven convection is an alternative to plumes for explaining intraplate African and South American hot spot volcanism, and small-scale convection is consistent with mantle downwellings beneath the African and South American lithosphere.     

Profile. The risks--and rewards--of war zone research

Gulu, about 4 hours north of here by car, is in an "upcountry" region torn by armed conflict. So upcountry clinical researchers like Matthew Lukwiya, a native of the Gulu district, play a critical role--and win high praise from their colleagues.     

Human beta-adrenoceptors: relation of myocardial and lymphocyte beta-adrenoceptor density

In human right atria obtained from 21 patients during open-heart surgery, beta-adrenoceptor density [assessed by iodine-125-labeled (-)-cyanopindolol binding] and responsiveness (positive inotropic responses to isoprenaline) were linearly related to the beta-adrenoceptor density in the corresponding circulating lymphocytes. This direct relation of human myocardial and lymphocyte beta-adrenoceptor alterations, therefore, makes it possible to monitor drug- or disease-induced beta-adrenoceptor changes in tissues not easily accessible in humans.     

Characterization of T cell receptor gamma chain expression in a subset of murine thymocytes

While much information exists about the structure and function of the clonally distributed T cell receptor (TCR) alpha beta heterodimer, little is known about the gamma protein, the product of a third rearranging TCR gene. An antiserum to a carboxyl-terminal peptide common to several of the murine gamma chain constant regions and a monoclonal antibody to the murine T3 complex were used to identify products of this TCR gene family in a subpopulation of Lyt2-, L3T4- thymocytes. This subpopulation does not express TCR alpha or full-length TCR beta messenger RNA. The gamma chain is a 35-kilodalton (kD) protein that is disulfide-bonded to a 45-kD partner and is associated with the T3 complex. Analysis of the glycosylation pattern of this thymic gamma chain revealed that the major variable region gamma (V gamma) gene transcribed in activated peripheral T cells is absent from this subpopulation. The cells that bear this second T cell receptor may therefore represent a distinct lineage differentiating within the thymus.     

Earth's early atmosphere

Ideas about atmospheric composition and climate on the early Earth have evolved considerably over the last 30 years, but many uncertainties still remain. It is generally agreed that the atmosphere contained little or no free oxygen initially and that oxygen concentrations increased markedly near 2.0 billion years ago, but the precise timing of and reasons for its rise remain unexplained. Likewise, it is usually conceded that the atmospheric greenhouse effect must have been higher in the past to offset reduced solar luminosity, but the levels of atmospheric carbon dioxide and other greenhouse gases required remain speculative. A better understanding of past atmospheric evolution is important to understanding the evolution of life and to predicting whether Earth-like planets might exist elsewhere in the galaxy.     

A single receptor binds both insulin-like growth factor II and mannose-6-phosphate

Amino acid sequences deduced from rat complementary DNA clones encoding the insulin-like growth factor II (IGF-II) receptor closely resemble those of the bovine cation-independent mannose-6-phosphate receptor (Man-6-P receptorCI), suggesting they are identical structures. It is also shown that IGF-II receptors are adsorbed by immobilized pentamannosyl-6-phosphate and are specifically eluted with Man-6-P. Furthermore, Man-6-P specifically increases by about two times the apparent affinity of the purified rat placental receptor for 125I-labeled IGF-II. These results indicate that the type II IGF receptor contains cooperative, high-affinity binding sites for both IGF-II and Man-6-P-containing proteins.