The role of the cysteine-rich region of the β2 integrin subunit in the leukocyte function-associated antigen-1 (LFA-1, αLβ2, CD11a/CD18) heterodimer formation and ligand binding

The cysteine-rich region (CRR) of the β2 integrin subunit was replaced by that of β1 to give the chimera β2NV1. β2NV1 can combine with αL to form a variant leukocyte-function-associated antigen (LFA)-1 on COS cell surface, suggesting that the specificity of the β2 interaction with αL does not lie in the CRR. Unlike those expressing wild-type LFA-1, COS cells expressing αLβ2NV1 are constitutively active in intercellular adhesion molecule (ICAM)-1 adhesion. These results suggest that activation of LFA-1 involves the release of an intramolecular constraint, which is maintained, in part, by the authentic β2 CRR.     

An “orientation sphere” visualization for examining animal head movements

1. Animal behavior is elicited, in part, in response to external conditions, but understanding how animals perceive the environment and make the decisions that bring about these behavioral responses is challenging.
2. Animal heads often move during specific behaviors and, additionally, typically have sensory systems (notably vision, smell, and hearing) sampling in defined arcs (normally to the front of their heads). As such, head‐mounted electronic sensors consisting of accelerometers and magnetometers, which can be used to determine the movement and directionality of animal heads (where head “movement” is defined here as changes in heading [azimuth] and/or pitch [elevation angle]), can potentially provide information both on behaviors in general and also clarify which parts of the environment the animals might be prioritizing (“environmental framing”).
3. We propose a new approach to visualize the data of such head‐mounted tags that combines the instantaneous outputs of head heading and pitch in a single intuitive spherical plot. This sphere has magnetic heading denoted by “longitude” position and head pitch by “latitude” on this “orientation sphere” (O‐sphere).
4. We construct the O‐sphere for the head rotations of a number of vertebrates with contrasting body shape and ecology (oryx, sheep, tortoises, and turtles), illustrating various behaviors, including foraging, walking, and environmental scanning. We also propose correcting head orientations for body orientations to highlight specific heading‐independent head rotation, and propose the derivation of O‐sphere‐metrics, such as angular speed across the sphere. This should help identify the functions of various head behaviors.
5. Visualizations of the O‐sphere provide an intuitive representation of animal behavior manifest via head orientation and rotation. This has ramifications for quantifying and understanding behaviors ranging from navigation through vigilance to feeding and, when used in tandem with body movement, should provide an important link between perception of the environment and response to it in free‐ranging animals.

     

The cucumber mosaic virus 1a protein regulates interactions between the 2b protein and ARGONAUTE 1 while maintaining the silencing suppressor activity of the 2b protein

The cucumber mosaic virus (CMV) 2b viral suppressor of RNA silencing (VSR) is a potent counter-defense and pathogenicity factor that inhibits antiviral silencing by titration of short double-stranded RNAs. It also disrupts microRNA-mediated regulation of host gene expression by binding ARGONAUTE 1 (AGO1). But in Arabidopsis thaliana complete inhibition of AGO1 is counterproductive to CMV since this triggers another layer of antiviral silencing mediated by AGO2, de-represses strong resistance against aphids (the insect vectors of CMV), and exacerbates symptoms. Using confocal laser scanning microscopy, bimolecular fluorescence complementation, and co-immunoprecipitation assays we found that the CMV 1a protein, a component of the viral replicase complex, regulates the 2b-AGO1 interaction. By binding 2b protein molecules and sequestering them in P-bodies, the 1a protein limits the proportion of 2b protein molecules available to bind AGO1, which ameliorates 2b-induced disease symptoms, and moderates induction of resistance to CMV and to its aphid vector. However, the 1a protein-2b protein interaction does not inhibit the ability of the 2b protein to inhibit silencing of reporter gene expression in agroinfiltration assays. The interaction between the CMV 1a and 2b proteins represents a novel regulatory system in which specific functions of a VSR are selectively modulated by another viral protein. The finding also provides a mechanism that explains how CMV, and possibly other viruses, modulates symptom induction and manipulates host-vector interactions.     

Partial deficiency of hypoxanthine-guanine phosphoribosyltransferase with reduced affinity for PP-ribose-P in four related males with gout

Summary A family is described in which four affected males, spanning two generations, have hyperuricemia and gout accompanied by hematuria but are without severe neurologic involvement. The affected males were found to have markedly reduced levels of erythrocytic hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity; these were 5–12% with hypoxanthine and 0.5–3% with guanine as compared to controls. Erythrocytic adenine phosphoribosyltransferase (APRT) was approximately three-fold elevated in the affected individuals.The residual HGPRT activity in affected males enabled characterization of some of the properties of this mutation. The apparent Michaelis constants (km) for both hypoxanthine and guanine were essentially unchanged, whereas the km for PP-ribose-P was approximately 10–20-fold elevated for all four affected males. The enzyme was more sensitive to product inhibition by IMP and GMP than controls, and exhibited greater thermal lability at 65°C than found with control lysates.     

Thermal sensitivity of scope for activity in Pagothenia borchgrevinki, a cryopelagic Antarctic nototheniid fish

The thermal sensitivity of scope for activity was studied in the Antarctic nototheniid fish Pagothenia borchgrevinki. The scope for activity of P. borchgrevinki at 0°C was 189 mg O₂ kg⁻¹ h⁻¹ (factorial scope 6.8) which is similar to that of temperate and tropical species at their environmental temperatures, providing no evidence for metabolic cold adaptation of maximum activity. The scope for activity increased to a maximum value of 266 mg O₂ kg⁻¹ h⁻¹ (factorial scope 8.3) at 3°C and then decreased from 3 to 6°C. The thermal sensitivity of critical swimming speed was also investigated and followed a similar pattern to aerobic scope for activity, suggesting oxygen limitation of aerobic performance. Oxygen consumption rates and ventilation frequencies were monitored for 24 h after the swimming challenge and the recovery of both parameters to resting levels was rapid and independent of temperature.