Occurrence of grapevine leafroll-associated virus complex in Napa Valley

Grapevine leafroll disease (GLD) is caused by a complex of several virus species (grapevine leafroll-associated viruses, GLRaV) in the family Closteroviridae. Because of its increasing importance, it is critical to determine which species of GLRaV is predominant in each region where this disease is occurring. A structured sampling design, utilizing a combination of RT-PCR based testing and sequencing methods, was used to survey GLRaVs in Napa Valley (California, USA) vineyards (n = 36). Of the 216 samples tested for GLRaV-1, -2, -3, -4, -5, and -9, 62% (n = 134) were GLRaV positive. Of the positives, 81% (n = 109) were single infections with GLRaV-3, followed by GLRaV-2 (4%, n = 5), while the remaining samples (15%, n = 20) were mixed infections of GLRaV-3 with GLRaV-1, 2, 4, or 9. Additionally, 468 samples were tested for genetic variants of GLRaV-3, and of the 65% (n = 306) of samples positive for GLRaV-3, 22% were infected with multiple GLRaV-3 variants. Phylogenetic analysis utilizing sequence data from the single infection GLRaV-3 samples produced seven well-supported GLRaV-3 variants, of which three represented 71% of all GLRaV-3 positive samples in Napa Valley. Furthermore, two novel variants, which grouped with a divergent isolate from New Zealand (NZ-1), were identified, and these variants comprised 6% of all positive GLRaV-3 samples. Spatial analyses showed that GLRaV-3a, 3b, and 3c were not homogeneously distributed across Napa Valley. Overall, 86% of all blocks (n = 31) were positive for GLRaVs and 90% of positive blocks (n = 28) had two or more GLRaV-3 variants, suggesting complex disease dynamics that might include multiple insect-mediated introduction events.     

Rapid UPLC-MS/MS method for routine analysis of plasma pristanic, phytanic, and very long chain fatty acid markers of peroxisomal disorders

Quantification of pristanic acid, phytanic acid, and very long chain fatty acids (i.e., hexacosanoic, tetracosanoic, and docosanoic acids) in plasma is the primary method for investigateing a multitude of peroxisomal disorders (PDs). Typically based on GC-MS, existing methods are time-consuming and laborious. In this paper, we present a rapid and specific liquid chromatography tandem mass spectrometric method based on derivatization with 4-[2-(N,N-dimethylamino)ethylaminosulfonyl]-7-(2-aminoethylamino)-2,1,3-benzoxadiazole (DAABD-AE). Derivatization was undertaken to improve the poor mass spectrometric properties of these fatty acids. Analytes in plasma (20 mul) were hydrolyzed, extracted, and derivatized with DAABD-AE in approximately 2 h. Derivatives were separated on a reverse-phase column and detected by positive-ion electrospray ionization tandem mass spectrometry with a 5 min injection-to-injection time. Calibration plots were linear over ranges that cover physiological and pathological concentrations. Intraday (n = 12) and interday (n = 10) variations at low and high concentrations were less than 9.2%. Reference intervals in normal plasma (n = 250) were established for each compound and were in agreement with the literature. Using specimens from patients with established diagnosis (n = 20), various PDs were reliably detected. In conclusion, this method allows for the detection of at least nine PDs in a 5 min analytical run. Furthermore, this derivatization approach is potentially applicable to other disease markers carrying the carboxylic group.     

Toxoplasma gondii stimulates the release of 13- and 9-hydroxyoctadecadienoic acids by human platelets.

We have recently demonstrated a novel cytotoxic effect of human platelets against Toxoplasma gondii and a role for thromboxane (TX) in this process (Yong et al., 1991). We now report on the spectrum of lipid mediators released by human platelets after interaction with T. gondii. In addition to TXB2, human platelets after incubation with T. gondii for 90 min released 12-hydroxyheptadecatrienoic acid (12-HHT), 12-hydroxyeicosatetraenoic acid (12-HETE), and an unidentified peak (UVmax 234 nm) as determined by reverse-phase high-performance liquid chromatography. Thermospray-liquid chromatography/mass spectrometry analysis and straight-phase HPLC identified the unknown peak as a mixture of 13-hydroxyoctadecadienoic acid (HODE) and 9-HODE. Radiolabeling studies with [14C]linoleic acid indicated that the platelets were the cellular source of the octadecanoids with 13-HODE (87.7%) greater than 9-HODE (12.3%). Inhibitor studies with indomethacin indicated that 13-HODE was a lipoxygenase product and 9-HODE was a cyclooxygenase product of linoleic acid. Thus, Toxoplasma-stimulated platelets release oxygenated products of both arachidonic acid and linoleic acid which may be important in the host response to T. gondii infection.     

Distribution and chemical fractionation of some heavy metals in bottom sediments of Lake Nasser

Distribution and phase association of Cd, Cr, Cu, Fe, Mn, Ni,Pb, Zn and organic matter in Nile sediments taken from LakeNasser (Aswan, Egypt) were investigated. The sediment sampleswere subjected to selective chemical extraction proceduresdesigned to fractionate the particulate heavy metals into sixfractions: (A) ammonium acetate-extractable metals; (B) sodiumacetate-extractable metals; (C) acid oxalate-extractablemetals; (D) hydroxylamine HCl-extractable metals; (E) aquaregia-extractable metals and (F) total metals (HF/HCl/HNO₃destruction). Exchangeable metals which can be extracted byammonium acetate solution are generally considered readilybioavailable as they are weakly bound and may equilibrateeasily with the aqueous phases. In the present study very smallconcentrations of all heavy metals considered were found inthis phase. Between this phase and the metal phases which arenot bioavailable (those exist in highly resistant phases) thereexist several geochemical phases (fractions B, C & D) that maypotentially release their associated metals under changingenvironmental conditions, such as pH and redox potential in thewater sediment interface. This revised version was published online in July 2006 with corrections to the Cover Date.     

Glucagon-stimulated calcium efflux in the isolated perfused rat liver is dependent on cellular redox potential

In the absence of any exogenous substrates, glucagon (1 X 10(-9) M) stimulated 45Ca2+ efflux from perfused livers derived from fed rats but not in livers of 24-h-fasted animals. In livers of 24-h-fasted animals perfused under conditions which would decrease cellular NAD(P)H/NAD(P)+ ratio (pyruvate (2.0 mM) or acetoacetate (10.0 mM], glucagon (1 X 10(-9) M) did not stimulate 45Ca2+ efflux. Similarly, in livers of 24-h-fasted animals perfused with substrates which increase cellular NAD(P)H content (lactate (2.0 mM) or beta-hydroxybutyrate (10.0 mM], glucagon (1 X 10(-9) M) did not increase 45Ca2+ efflux. Glucagon (1 X 10(-9) M) elicited an increase in 45Ca2+ efflux from livers of 24-h-fasted animals, only when the livers were perfused with [lactate]/[pyruvate] and [beta-hydroxybutyrate]/[acetoacetate] ratios similar to those reported for livers of fed rats. Stimulation of 45Ca2+ efflux elicited by either 8-CPT-cAMP, a cAMP analog, or high glucagon concentrations (1 X 10(-8) M) was not affected whether livers were perfused with pyruvate (2.0 mM) or lactate (2.0 mM). Administration of isobutylmethylxanthine (50 microM) alone, or glucagon (1 X 10(-9) M) in the presence of isobutylmethylxanthine (50 microM) stimulated 45Ca2+ efflux from livers of 24-h-fasted animals perfused with pyruvate (2.0 mM) but not from livers perfused with lactate (2.0 mM). The ability of glucagon (1 X 10(-9) M) to elevate tissue cAMP levels was also regulated by the oxidation-reduction state of the livers. The data indicate that glucagon-stimulated 45Ca2+ efflux from perfused livers is mediated via cAMP and is dependent on the oxidation-reduction state of the livers.     

Role of calcium in synaptosomal substrate oxidation

The effect of veratridine-mediated depolarization on rat brain synaptosomal respiration in the presence and absence of calcium was investigated. Studies on respiration were performed employing three different pretreatments of the synaptosomes which attempted to deplete endogenous substrates. First, synaptosomes were preincubated for 10 min in the absence of any substrates in medium either containing or devoid of calcium. Second, synaptosomes were preincubated for either 15 or 60-min periods in the presence and absence of calcium, and the incubation medium was changed by centrifugation and resuspension of synaptosomes in their respective media. Irrespective of the prior treatment, maximal stimulation of respiration (400-600%) during veratridine (100 microM) elicited depolarization was observed only when calcium was present in the incubation media. In incubations performed in the absence of calcium, veratridine addition either modestly stimulated (10- and 15-min preincubated synaptosomes) or did not affect (60-min preincubated synaptosomes) the rate of respiration. However, when calcium was added back to these incubations the rate of respiration in the presence of veratridine was stimulated by five- to six-fold. Similarly, the rates of 14CO2 production from [1-14C]- and [2-14C]pyruvate were increased by veratridine only when synaptosomes were incubated in calcium-replete medium. These data indicate that calcium plays an obligatory role in depolarization-elicited stimulation of synaptosomal oxidative processes.     

Effect of recombinant erythropoietin on ischemia–reperfusion-induced apoptosis in rat liver

Ischemia–reperfusion (I/R) cannot be avoided in liver transplantation procedures, and apoptosis is a central mechanism of cell death after liver reperfusion. Protective effect of recombinant erythropoietin (rhEPO) on liver apoptosis has not been clearly investigated. This work investigated intraportal (IP) rhEPO-protective effect in a rat model of hepatic I/R-induced apoptosis and its appropriated time and dose of administration. Eight groups were included (n = 10/group): sham-operated, I/R (45 min ischemia and 2 h reperfusion), preconditioned rhEPO I/R (24 h or 30 min before ischemia), and postconditioned rhEPO I/R (before reperfusion) using two different rhEPO doses (1,000 and 5,000 IU/kg). When compared with the sham-operated group, the I/R group showed significant increase of serum levels of aspartate and alanine aminotransferases (AST, ALT), hepatic caspase-9 activity(894.99 ± 176.90 relative fluorescence units (RFU)/mg/min versus 458.48 ± 82.96 RFU/mg/min), and Fas ligand (FasL) expression, histopathological damages, and significant decrease in the antiapoptotic Bcl-xL/apoptotic Bax ratio(0.38 ± 0.21 versus 3.35 ± 0.77) rhEPO-improved ALT and AST but failed to reduce FasL expression in all groups compared with the I/R group. Thirty minutes and 24 h preconditioning with rhEPO (1,000 IU/kg) increased Bcl-xL/Bax ratio and reduced caspase-9 activity, and the same effect was observed when higher dose was given 24 h before ischemia. Preconditioning was more effective than postconditioning in improving caspase-9 activity, and no dose-dependent effect was observed. In conclusion, single IP rhEPO injection 30 min before ischemia has an advantage over rhEPO postconditioning in improving post-hepatic I/R-induced apoptosis with no additional time- and dose-dependent effects which may provide potentially useful guide in liver transplantation procedures.     

Electrical characterization of phytoplankton suspensions using impedance spectroscopy

Journal of Applied Phycology - This study used impedance spectroscopy measurements to extract the electrical properties of phytoplankton cells in suspension. Experimental measurements were...     

Grapevine genotype susceptibility to Xylella fastidiosa does not predict vector transmission success

For vector-borne diseases, interactions between vector, host, and pathogen can influence patterns of disease spread. In particular, previous studies suggest that host genotype may influence disease dynamics because of differences in susceptibility to the pathogen and, therefore, subsequent vector transmission efficiency from these plants. We tested this hypothesis by using the pathogenic bacterium Xylella fastidiosa, the etiological agent of Pierce's disease in grapevines, and its leafhopper vector Homalodisca vitripennis (Germar). Pathogen infection level and transmission efficiency among several widely cultivated red and white wine, table, and raisin grape cultivars, were compared with the expectation that vector transmission rate would differ among cultivars, because of underlying differences in susceptibility to infection. The 14 grapevine genotypes evaluated showed significant differences among cultivars in the populations of X. fastidiosa that developed in petioles. 'Flame seedless' hosted the highest bacterial populations, between 1.81 and 2.05 times higher than the least susceptible 'Merlot', 'Crimson seedless', 'Grenache Noir', and 'Rubired'. Although the transmission rate of X. fastidiosa by H. vitripennis varied substantially (zero to 33%), it was not significantly different among cultivars. These results suggest that either the relationship between vine infection level and transmission is weaker than previously reported, or innate differences in vector preference among cultivars confounded any effects of vine susceptibility to infection.