Learning-set formation by mink, ferrets, skunks, and cats

The ability of mink, fer rets, skunks, and cats to learn to dis criminate between objects was com pared. Performance of mink and fer rets was similar to that reported for primates. This observation suggests that there is considerable overlap among mammals in ability to form learning sets.     

Cooperative control of potassium accumulation by ouabain in vascular smooth muscle

The effects of ouabain on potassium accumulation were studied in the dog carotid artery. It was confirmed that vascular smooth muscle lost potassium in the presence of ouabain greater than 10(-9) molar. This effect could be reversed by systematically increasing potassium in the external medium. The action of ouabain on ion accumulation was represented quantitatively with the application of a recent biophysical approach.     

Hemoglobin Kinetics of the Galapagos Rift Vent Tube Worm Riftia pachyptila Jones (Pogonophora; Vestimentifera)

Kinetics of the reactions of Riftia pachyptila hemoglobin with oxygen were followed spectrophotometrically by stopped-flow and laser flash photolysis techniques. The rate of oxygen dissociation increases eightfold over the range of 5 degrees to 20 degrees C (k = 2.2 sec(-1)at 10 degrees C). Oxygen recombination after flash photolysis was biphasic. The rates of both slow and fast phases of the reaction were independent of temperature from 0 degrees to 20 degrees C(k'fast = 7 x 10(6); k'slow = 1 x 16(6) liter mole (-1) sec(-1)). As the oxygen affinity is relatively temperature independent, analysis in terms of the two-state model of cooperativity requires that the conformational equilibrium constant L decrease by about 50-fold between 3 degrees and 15 degrees C.     

Cladosporium Avr2 inhibits tomato Rcr3 protease required for Cf-2-dependent disease resistance

How plants recognize pathogens and activate defense is still mysterious. Direct interaction between pathogen avirulence (Avr) proteins and plant disease resistance proteins is the exception rather than the rule. During infection, Cladosporium fulvum secretes Avr2 protein into the apoplast of tomato leaves and, in the presence of the extracellular leucine-rich repeat receptor-like Cf-2 protein, triggers a hypersensitive response (HR) that also requires the extracellular tomato cysteine protease Rcr3. We show here that Avr2 binds and inhibits Rcr3 and propose that the Rcr3-Avr2 complex enables the Cf-2 protein to activate an HR.     

Nanoparticle superlattice engineering with DNA

A current limitation in nanoparticle superlattice engineering is that the identities of the particles being assembled often determine the structures that can be synthesized. Therefore, specific crystallographic symmetries or lattice parameters can only be achieved using specific nanoparticles as building blocks (and vice versa). We present six design rules that can be used to deliberately prepare nine distinct colloidal crystal structures, with control over lattice parameters on the 25- to 150-nanometer length scale. These design rules outline a strategy to independently adjust each of the relevant crystallographic parameters, including particle size (5 to 60 nanometers), periodicity, and interparticle distance. As such, this work represents an advance in synthesizing tailorable macroscale architectures comprising nanoscale materials in a predictable fashion.     

Local macrophage proliferation, rather than recruitment from the blood, is a signature of TH2 inflammation

A defining feature of inflammation is the accumulation of innate immune cells in the tissue that are thought to be recruited from the blood. We reveal that a distinct process exists in which tissue macrophages undergo rapid in situ proliferation in order to increase population density. This inflammatory mechanism occurred during T helper 2 (T(H)2)-related pathologies under the control of the archetypal T(H)2 cytokine interleukin-4 (IL-4) and was a fundamental component of T(H)2 inflammation because exogenous IL-4 was sufficient to drive accumulation of tissue macrophages through self-renewal. Thus, expansion of innate cells necessary for pathogen control or wound repair can occur without recruitment of potentially tissue-destructive inflammatory cells.     

Evidence for antibody-catalyzed ozone formation in bacterial killing and inflammation

Recently, we showed that antibodies catalyze the generation of hydrogen peroxide (H2O2) from singlet molecular oxygen (1O2*) and water. Here, we show that this process can lead to efficient killing of bacteria, regardless of the antigen specificity of the antibody. H2O2 production by antibodies alone was found to be not sufficient for bacterial killing. Our studies suggested that the antibody-catalyzed water-oxidation pathway produced an additional molecular species with a chemical signature similar to that of ozone. This species is also generated during the oxidative burst of activated human neutrophils and during inflammation. These observations suggest that alternative pathways may exist for biological killing of bacteria that are mediated by potent oxidants previously unknown to biology.     

Partial control of an ion-molecule reaction by selection of the internal motion of the polyatomic reagent ion

The ion-molecule reaction NH(3)(+) + ND(3) has been studied at various collision energies (1 to 5 electron volts in the center of mass) with preparation of the NH(3)(+) reagent in two nearly isoenergetic vibrational states. One state corresponds to pure out-of-plane bending of the planar NH(3)(+) ion (0.60 electron volts), whereas the other state is a combination of in-plane and out-of-plane motion (0.63 electron volts). The product branching ratios differ markedly for these two vibrational-state preparations. The differences in reactivity suggest that the in-plane totally symmetric stretching mode is essentially inactive in controlling the branching ratio of this reaction.     

Sex pheromones in snakes

The majority of pheromones identified to date are insect pheromones, which are volatile in nature. Identification of nonvolatile pheromones have been relatively rare, especially in vertebrates. Male and female garter snakes use pheromones to mediate sexual behavior. The female sex attractiveness pheromone of the Canadian red-sided garter snake, Thamnophis sirtalis parietalis, consists of a novel series of nonvolatile saturated and monounsaturated long-chain methyl ketones, whereas the male sex recognition pheromone contains squalene. These compounds were isolated, identified, and partially synthesized, and field tests show them to be biologically active.     

Strange magnetism and the anapole structure of the proton

The violation of mirror symmetry in the weak force provides a powerful tool to study the internal structure of the proton. Experimental results have been obtained that address the role of strange quarks in generating nuclear magnetism. The measurement reported here provides an unambiguous constraint on strange quark contributions to the proton's magnetic moment through the electron-proton weak interaction. We also report evidence for the existence of a parity-violating electromagnetic effect known as the anapole moment of the proton. The proton's anapole moment is not yet well understood theoretically, but it could have important implications for precision weak interaction studies in atomic systems such as cesium.