Is venus concentrating interplanetary dust toward its orbital plane?

By use of observations of zodiacal light, the symmetry plane or plane of maximum density of interplanetary dust at elongations of 32 degrees to 50 degrees from the sun has been found to be closer to the orbital plane of Venus than to the invariable plane. This suggests that the plane of maximum density in this region is being gravitationally perturbed closer to the orbital plane of Venus.     

Bovine interleukin 2: regulatory mechanisms

A cDNA clone of the bovine interleukin-2 (IL-2) gene has been isolated and demonstrated to produce a functional bovine IL-2 protein when transfected into either CV-1 or COS-1 monkey cells. Homology comparisons of both the nucleotide and predicted amino acid sequences of bovine IL-2 with those of the human and mouse show extensive regions of sequence conservation between the species. The amino acid sequence of the mature bovine IL-2 protein shares about 60-63% homology with those of the human and mouse, but the 3' untranslated regions of the human and mouse gene share as much, if not greater, sequence homology with the 3' untranslated regions of the human and mouse genes. In particular, a tandemly repeated sequence (TATT), n, found in the 3' untranslated tail of the bovine IL-2 clone is also found in the 3' untranslated region of a large group of cytokine genes and other inducible genes of the lymphoid and immune response systems. This sequence may serve a specific regulatory function in the immune system.     

Quantification of the influence of surface structure on C--h bond activation by iridium and platinum

The trapping-mediated dissociative chemisorption of ethane on the closest packed Ir(111) surface has been investigated, and the activation energy and preexponential factor of the surface reaction rate coefficient have been measured. These results are compared to those of ethane activation on Pt(111) and on the missing row reconstructed Ir(110)-(1x2) and Pt(110)-(1x2) surfaces, allowing a quantitative determination of the effect surface structure has on the catalytic activation of C-H bonds. In the order Pt(111), Pt(110)-(1x2), Ir(111), and Ir(110)-(1x2), the activation energies for the dissociative chemisorption of ethane are 16.6, 10.5, 10.3, and 5.5 kilocalories per mole, demonstrating that the electronic and geometric effects are of approximately equal importance for ethane activation on these catalysts.     

Quantification of primary versus secondary C-h bond cleavage in alkane activation: propane on pt

The trapping-mediated dissociative chemisorption of three isotopes of propane (C(3)H(8), CH(3),CD(2)CH(3), and C(3)D(8)) has been investigated on the Pt(110)-(1 x 2) surface, and both the apparent activation energies and the preexponential factors of the surface reaction rate coefficients have been measured. In addition, the probabilities of primary and secondary C-H bond cleavage for alkane activation on a surface were evaluated. The activation energy for primary C-H bond cleavage was 425 calories per mole greater than that of secondary C-H bond cleavage, and the two true activation energies that embody the single measured activation energy were determined for each of the three isotopes. Secondary C-H bond cleavage is also preferred on entropic grounds, and the magnitude of the effect was quantified.     

B-cell function in canine X-linked severe combined immunodeficiency

Canine X-linked severe combined immunodeficiency (XSCID) is due to mutations in the common gamma (gammac) subunit of the IL-2, IL-4, IL-7, IL-9 and IL-15 receptors and has a similar clinical phenotype to human XSCID. We have previously shown that the block in T-cell development is more profound in XSCID dogs than in genetically engineered gamma c-deficient mice. In this study we evaluated the B-cell function in XSCID dogs. In contrast to the marked decrease in peripheral B-cells in gamma c-deficient mice, XSCID dogs have increased proportions and numbers of peripheral B-cells as observed in XSCID boys. Canine XSCID B-cells do not proliferate following stimulation with the T-cell-dependent B-cell mitogen, pokeweed mitogen (PWM); however, they proliferate normally in response to the T-cell-independent B-cell mitogen, formalin-fixed, heat-killed Staphylococcus aureus. Canine XSCID B-cells are capable of producing IgM but are incapable of normal class-switching to IgG antibody production as demonstrated by in vitro stimulation with PWM and immunization with the T-cell-dependent antigen, bacteriophage PhiX174. Similar results have been reported for XSCID boys. Thus, it appears that gamma c-dependent cytokines have differing roles in human and canine B-cell development than in the mouse making the XSCID dog a valuable model for studying the role of these cytokines in B-cell development and function.