Movement of Bactericera cockerelli (Heteroptera: Psyllidae) in relation to potato canopy structure, and effects on potato tuber weights

With the threat of new plant diseases on the increase, plant disease epidemiology requires research on pathogen vector movement. Here, releases were performed in planted potato fields of different ages and canopy structures, located in the Texas Panhandle, to evaluate the range of movement of the potato psyllid Bactericera cockerelli (Sulc.). This insect is a known causative agent of psyllid yellows disease, and is a vector of the reported etiological agents of zebra chip disease of potato, 'Candidatus Liberibacter solanacearum/psyllaurous'. Based on collections of B. cockerelli immatures along transects 9 m long radiating in four cardinal directions from release points, adult females dispersed considerable distances, regardless of plant age or canopy structure. Immature abundance declined along transects and were well described by linear and nonlinear models, but abundance patterns did not differ among the different planting dates and canopy structures. However, unequal immature abundance was detected among the four cardinal directions, with more immatures generally collected along transects to the north and west of release points, opposite of prevailing winds in the area at the time of release. Plots where B. cockerelli were released had significantly lower mean potato tuber weights than control plots with no B. cockerelli. However, few plots with B. cockerelli released in them had declining trends in tuber weights with increasing distance from release points.     

The effect of wild radish floral morphology on pollination efficiency by four taxa of pollinators

The effects of floral morphology on rates of pollen removal and deposition by different pollinators in generalist plant species are not well known. We studied pollination dynamics in wild radish, Raphanus raphanistrum, a plant visited by four groups of pollinators: honey bees, small native bees, butterflies, and syrphyd flies. The effects of anther position and other factors on pollen removal during single visits by all four pollinator taxa were measured. Flowers with high anther exsertion (i.e., anthers placed higher above the opening of the corolla tube) tended to have the highest numbers of pollen grains removed, but this effect was strongest for honey bees and butterflies. For all pollinator taxa, pollen removal increased with the number of pollen grains available on a flower and whowed a positive, decelerating relationship with the duration of the visit. The effects of stigma position and other factors on pollen deposition during single visits by honey bees and butterflies were also studied. The nectar-feeding butterflies had a higher pollination efficiency (percentage of pollen grains removed from anthers that were subsequently deposited on a stigma) than the nectar- and pollen-feeding honey bees. Flowers with intermediate stigma exsertion had the highest numbers of pollen grains deposited on their stigmas by butterflies, but stigma exsertion had no effect on deposition by honey bees. For both butterflies and honey bees, pollen deposition on the recipient flower increased with the amount of pollen removed from the donor flower, and there was a positive, decelerating relationship between deposition and time spent at the flower; these results are analogous to those for pollen removal. The effects of anther and stigma exsertion on pollen removal and denosition did not fit predictions based on patterns of floral correlations, but results for morphology, pollen availability, time spent per visit, and pollinator efficiency are in broad agreement with previous studies, suggesting the possible emergence of some general rules of pollen transfer.     

Inhibition of translation by UAUUUAU and UAUUUUUAU motifs of the AU-rich RNA instability element in the HPV-1 late 3' untranslated region

The human papillomavirus type 1 (HPV-1) late mRNAs contain a 57-nucleotide adenosine- and uridine-rich RNA instability element termed h1ARE in their late 3' untranslated regions. Here we show that five sequence motifs in the h1ARE (named I-V) affect the mRNA half-life in an additive manner. The minimal inhibitory sequence in motifs I and II was mapped to UAUUUAU, and the minimal inhibitory sequence in motifs III-V was mapped to UAUUUUUAU. We also provide evidence that the same motifs in the AU-RNA instability element inhibit mRNA translation, an effect that was entirely dependent on the presence of a poly(A) tail on the mRNA. Additional experiments demonstrated that the h1ARE interacted directly with the poly(A)-binding protein, suggesting that the h1ARE inhibits translation by interfering with the function of the poly(A)-binding protein.     

Hindlimb unweighting decreases endothelium-dependent dilation and eNOS expression in soleus not gastrocnemius.

We tested the hypothesis that hindlimb unweighting (HLU) decreases endothelium-dependent vasodilation and expression of endothelial nitric oxide synthase (eNOS) and superoxide dismutase-1 (SOD-1) in arteries of skeletal muscle with reduced blood flow during HLU. Sprague-Dawley rats (300-350 g) were exposed to HLU (n = 15) or control (n = 15) conditions for 14 days. ACh-induced dilation was assessed in muscle with reduced [soleus (Sol)] or unchanged [gastrocnemius (Gast)] blood flow during HLU. eNOS and SOD-1 expression were measured in feed arteries (FA) and in first-order (1A), second-order (2A), and third-order (3A) arterioles. Dilation to infusion of ACh in vivo was blunted in Sol but not Gast. In arteries of Sol muscle, HLU decreased eNOS mRNA and protein content. eNOS mRNA content was significantly less in Sol FA (35%), 1A arterioles (25%) and 2A arterioles (18%). eNOS protein content was less in Sol FA (64%) and 1A arterioles (65%) from HLU rats. In arteries of Gast, HLU did not decrease eNOS mRNA or protein. SOD-1 mRNA expression was less in Sol 2A arterioles (31%) and 3A arterioles (29%) of HLU rats. SOD-1 protein content was less in Sol FA (67%) but not arterioles. SOD-1 mRNA and protein content were not decreased in arteries from Gast. These data indicate that HLU decreases endothelium-dependent vasodilation, eNOS expression, and SOD-1 expression primarily in arteries of Sol muscle where blood flow is reduced during HLU.     

Genomic analysis of bacteriophages SP6 and K1-5, an estranged subgroup of the T7 supergroup

We have determined the genome sequences of two closely related lytic bacteriophages, SP6 and K1-5, which infect Salmonella typhimurium LT2 and Escherichia coli serotypes K1 and K5, respectively. The genome organization of these phages is almost identical with the notable exception of the tail fiber genes that confer the different host specificities. The two phages have diverged extensively at the nucleotide level but they are still more closely related to each other than either is to any other phage currently characterized. The SP6 and K1-5 genomes contain, respectively, 43,769 bp and 44,385 bp, with 174 bp and 234 bp direct terminal repeats. About half of the 105 putative open reading frames in the two genomes combined show no significant similarity to database proteins with a known or predicted function that is obviously beneficial for growth of a bacteriophage. The overall genome organization of SP6 and K1-5 is comparable to that of the T7 group of phages, although the specific order of genes coding for DNA metabolism functions has not been conserved. Low levels of nucleotide similarity between genomes in the T7 and SP6 groups suggest that they diverged a long time ago but, on the basis of this conservation of genome organization, they are expected to have retained similar developmental strategies.     

Target-derived and locally derived neurotrophins support retinal ganglion cell survival in the neonatal rat retina

Brain-derived neurotrophic factor (BDNF) and neurotrophin-4/5 (NT-4/5) protein and mRNA are found in the neonatal rat retina and also in target sites such as the superficial layers of the superior colliculus. Both neurotrophins support neonatal retinal ganglion cell survival in vitro. In vivo, injections of recombinant BDNF and NT-4/5 reduce naturally occurring cell death as well as death induced by removal of the contralateral superior colliculus. In the latter case, the peak of retinal ganglion cell death occurs about 24 h postlesion. We wished to determine: whether a similar time-course of degeneration occurs after selective removal of target cells or depletion of target-derived trophic factors, and whether ganglion cell viability also depends on intraretinally derived neurotrophins. Retinal ganglion cell death was measured 24 and 48 h following injections of kainic acid or a mixture of BDNF and NT-4/5 blocking antibodies into the superior colliculus and 24 h after intraocular injection of the same antibodies. Retinotectally projecting ganglion cells were identified by retrograde labeling with the nucleophilic dye diamidino yellow. We show that collicular injections of either kainic acid or BDNF and NT-4/5 blocking antibodies significantly increased retinal ganglion cell death in the neonatal rat 24 h postinjection, death rates returning to normal by 48 h. This increase in death was greatest following collicular injections; however, death was also significantly increased 24 h following intravitreal antibody injection. Thus retinal ganglion cell survival during postnatal development is not only dependent upon trophic factors produced by central targets but may also be influenced by local intraretinal neurotrophin release.     

SOD-1 expression in pig coronary arterioles is increased by exercise training

Coronary arterioles of exercise-trained (EX) pigs have enhanced nitric oxide (NO.)-dependent dilation. Evidence suggests that the biological half-life of NO. depends in part on the management of the superoxide anion. The purpose of this study was to test the hypothesis that expression of cytosolic copper/zinc-dependent superoxide dismutase (SOD)-1 is increased in coronary arterioles as a result of exercise training. Male Yucatan pigs either remained sedentary (SED, n = 4) or were EX (n = 4) on a motorized treadmill for 16-20 wk. Individual coronary arterioles ( approximately 100-microm unpressurized internal diameter) were dissected and frozen. Coronary arteriole SOD-1 protein (via immunoblots) increased as a result of exercise training (2.16 +/- 0.35 times SED levels) as did SOD-1 enzyme activity (measured via inhibition of pyrogallol autooxidation; approximately 75% increase vs. SED). In addition, SOD-1 mRNA levels (measured via RT-PCR) were higher in EX arterioles (1.68 +/- 0.16 times the SED levels). There were no effects of exercise training on the levels of SOD-2 (mitochondrial), catalase, or p67(phox) proteins. Thus chronic aerobic exercise training selectively increases the levels of SOD-1 mRNA, protein, and enzymatic activity in porcine coronary arterioles. Increased SOD-1 could contribute to the enhanced NO.-dependent dilation previously observed in EX porcine coronary arterioles by improving management of superoxide in the vascular cell environment, thus prolonging the biological half-life of NO.     

Synthesis and SAR of highly selective MMP-13 inhibitors

The structure-based design and synthesis of a series of novel biphenyl sulfonamide carboxylic acids as potent MMP-13 inhibitors with selectivity over MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-14, Aggrecanase 1, and TACE are described.     

Conformational stability of ferrocytochrome c. Electrostatic aspects of the oxidation by tris(1,10-phenanthroline)cobalt(III) at low ionic strength

At ionic strengths below 0.1 M the oxidation of horse ferrocytochrome c by tris(1,10-phenanthroline)cobalt (III) and tris(2,2'-bipyridine)cobalt(III) proceeds by a pathway which is independent of the transition metal complex concentration. Formation of an activated form of the protein appears to be rate limiting. The rate of oxidation decreases as the ionic strength increases. This dependence of the reaction rate on inert electrolyte concentration indicates that electrostatic association of anions under physiological ionic strength confers stability to the protein. The activated form of the protein, which reacts at least 10(4) times as fast as the predominant form, is thought to be a conformation of the reduced protein with an open heme crevice. Binding of the open form of ferrocytochrome c with the redox-inactive cationic transition metal complexes hexamminecobalt(III) and tris(1,10-phenanthroline)chromium(III) inhibits the oxidation by tris(1,10-phenanthroline)cobalt(III). Reactions of tris(1,10-phenanthroline)cobalt(III) with 4-carboxy-2,5-dinitrophenyllysine 13 and 72 ferrocytochromes c show no dependence on ionic strength. NMR studies at pH 7 demonstrate that ferricytochrome c is partly (15%) in the open conformation at low ionic strength. Furthermore, the interaction of redox-inert tris (1,10-phenanthroline)chromium(III) with ferricytochrome c under conditions identical to those of the kinetic studies demonstrates that the transition metal complex binds only to the open form of the protein. Titration with increasing amounts of tris(1,10-phenanthroline) chromium(III) shows changes in the NMR spectrum that are inconsistent with a single binding site.