Hypersensitive response of wheat to the Hessian fly

Hessian flyMayetiola destructor (Say) larvae are able to obtain food from their host plant without inflicting mechanical damage to the plant surface, apparently by secreting substances which elicit release of nutrients from plant cells surrounding the feeding site. Cells of fully susceptible plants retain their normal appearances, while in resistant plants extensive areas of cellular collapse occur. These responses indicate that hypersensitivity is the basis of wheat's resistance to the Hessian fly. The fly's feeding mechanism more closely resembles that of a pathogen than of a phytophagous insect; correspondingly, both the genetic relationship and resistance mechanism of the host plant to the parasite are of the sorts commonly associated with bacterial and fungal pathogens.     

Oxalate-stimulation of ATP-dependent Ca-uptake is diminished during smooth muscle subcellular fractionation

The ATP-dependent azide-insensitive Ca-uptake by the postnuclear supernatant from rat myometrium is stimulated more by 5 mM oxalate than by 25 mM phosphate. During subcellular fractionation, however, the percent recovery of the oxalate stimulated Ca-uptake diminishes more rapidly than that of the Ca-uptake without any added oxalate or phosphate. The percent recovery of the phosphate stimulated Ca-uptake also diminishes but not to as low levels as that of the oxalate stimulated Ca-uptake. The net result is higher stimulation of this uptake by 25 mM phosphate than by 5 mM oxalate in the various sucrose density gradient fractions. This discrepancy in percent recoveries presents a major concern about the use of oxalate or phosphate stimulated Ca-uptake as a marker for smooth muscle membranes.     

Peroxide resistance of ER Ca2+ pump in endothelium: implications to coronary artery function

We examined the effects of peroxide on the sarco(endo)plasmicreticulum Ca²⁺ (SERCA) pump in pigcoronary artery endothelium and smooth muscle at three organizationallevels: Ca²⁺ transport inpermeabilized cells, cytosolicCa²⁺ concentration in intactcells, and contractile function of artery rings. We monitored theATP-dependent, azide-insensitive, oxalate-stimulated ⁴⁵Ca²⁺uptake by saponin-permeabilized cultured cells. Low concentrations ofperoxide inhibited the uptake less effectively in endothelium than insmooth muscle whether we added the peroxide directly to theCa²⁺ uptake solution or treatedintact cells with peroxide and washed them before the permeabilization.An acylphosphate formation assay confirmed the greater resistance ofthe SERCA pump in endothelial cells than in smooth muscle cells.Pretreating smooth muscle cells with 300 µM peroxide inhibited (by 77 ± 2%) the cyclopiazonic acid (CPA)-induced increase in cytosolicCa²⁺ concentration in aCa²⁺-free solution, but it did notaffect the endothelial cells. Peroxide pretreatment inhibited theCPA-induced contraction in deendothelialized arteries with a 50%inhibitory concentration of 97 ± 13 µM, but up to 500 µMperoxide did not affect the endothelium-dependent, CPA-inducedrelaxation. Similarly, 500 µM peroxide inhibited the angiotensin-induced contractions in deendothelialized arteries by 93 ± 2%, but it inhibited the bradykinin-induced,endothelium-dependent relaxation by only 40 ± 13%. The greaterresistance of the endothelium to reactive oxygen may be importantduring ischemia-reperfusion or in the postinfection immune response.

     

Orientation-Based Control of Microfluidics

Most microfluidic chips utilize off-chip hardware (syringe pumps, computer-controlled solenoid valves, pressure regulators, etc.) to control fluid flow on-chip. This expensive, bulky, and power-consuming hardware severely limits the utility of microfluidic instruments in resource-limited or point-of-care contexts, where the cost, size, and power consumption of the instrument must be limited. In this work, we present a technique for on-chip fluid control that requires no off-chip hardware. We accomplish this by using inert compounds to change the density of one fluid in the chip. If one fluid is made 2% more dense than a second fluid, when the fluids flow together under laminar flow the interface between the fluids quickly reorients to be orthogonal to Earth’s gravitational force. If the channel containing the fluids then splits into two channels, the amount of each fluid flowing into each channel is precisely determined by the angle of the channels relative to gravity. Thus, any fluid can be routed in any direction and mixed in any desired ratio on-chip simply by holding the chip at a certain angle. This approach allows for sophisticated control of on-chip fluids with no off-chip control hardware, significantly reducing the cost of microfluidic instruments in point-of-care or resource-limited settings.     

Endothelin contraction in pig coronary: Receptor types and Ca2+-mobilization

Endothelin is one of the most potent vasoconstrictors known. It plays an important role in the regulation of vascular tone and in the development of many cardiovascular diseases. This study focuses on the receptor types and the Ca²⁺ mobilization responsible for endothelin-1 (ET-1) contraction in de-endothelialized pig coronary artery rings. ET-1 contracted the artery rings with an EC₅₀ = 6.5 ± 1 nM and a maximum contraction which was 98.6 ± 9% of the contraction produced by 60 mM KCl. BQ123 (5 µM), an ET_A antagonist, reversed 78 ± 3% of the ET-1 contraction (50 nM). IRL1620, a selective ET_B agonist, produced 23 ± 3% of the total ET-1 contraction with an EC₅₀ = 12.7 ± 2 nM. More than 85% of the contraction due to 100 nM IRL 1620 was inhibited by 200 nMBQ788, an ET_B antagonist. Therefore, approximately 80% of the ET-1 contraction in this artery occurred via ET_A receptors, and the other 20% was mediated by ET_B receptors. To assess the Ca²⁺ pools utilized during the ET-1 response, ET-1 contraction was also examined in medium containing an L-type Ca²⁺ channel blocker nitrendipine, and in Ca²⁺ free medium containing 0.2 mM EGTA. In Ca²⁺ containing medium the contraction elicited by ET-1 was 98.6 ± 9% of the KCl contraction, however, in the presence 10 µM nitrendipine the ET-1 induced contraction was 54 ± 7% of the KCl contraction, and in Ca²⁺-free medium it was 13 ± 2%. Similarly, the IRL 1620 contractions in Ca²⁺ containing medium, in the presence of nitrendipine and in Ca²⁺-free medium were 22.4 ± 3%, 12 ± 3% and 11 ± 2% of the KCl response respectively. Thus, both ET_A and ET_B contractions utilize extracellular Ca²⁺ pools via L-type Ca²⁺ channels and other undefined route(s), as well as intracellular Ca²⁺ pools. In the pig coronary artery smooth muscle, ET-1 contractions occur predominantly via ET_A receptors, with ET_B receptors using similar Ca²⁺ mobilization pathways, but the ET_B receptors appear to use the intracellular Ca²⁺ stores to a greater extent.     

Nucleotide sequence of psbQ gene for 16-kDa protein of oxygen-evolving complex from Arabidopsis thaliana and regulation of its expression.

The psbQ gene encoding a 16-kDa polypeptide of the oxygen-evolving complex of photosystem II has been isolated from Arabidopsis thaliana and characterized. The gene consists of a 28 nucleotide long leader sequence, two introns and three exons encoding a 223-amino-acid precursor polypeptide. The first 75 amino acids act as a transit peptide for the translocation of the polypeptide into the thylakoid lumen. Expression studies show that the gene is light-inducible and expresses only in green tissues with high steady-state mRNA levels in leaves. Using this gene as a probe, restriction fragment length polymorphism between two ecotypes, Columbia and Estland, has also been detected.