Resistance to quinclorac and ALS-inhibitor herbicides in Galium spurium is conferred by two distinct genes

Classical Mendelian experiments were conducted to determine the genetics and inheritance of quinclorac and acetolactate synthase (ALS)‐inhibitor resistance in a biotype of Galium spurium. Plants were screened with the formulated product of either quinclorac or the ALS‐inhibitor, thifensulfuron, at the field dose of 125 or 6 g active ingredient (a.i.) ha^?1 respectively. Segregation in the F₂ generation indicated that quinclorac resistance was a single, recessive nuclear trait, based on a 1 : 3 segregation ratio [resistant : susceptible (R : S)]. Resistance to ALS inhibitors was due to a single, dominant nuclear trait, segregating in the F₂ generation in a 3 : 1 ratio (R : S). The genetic models were confirmed by herbicide screens of F₁ and backcrosses between the F₁ and the S parent. F₂ plants that survived quinclorac treatment set seed and the resulting F₃ progeny were screened with either herbicide. Quinclorac‐treated F₃ plants segregated in a 1 : 0 ratio (R : S), hence F₂ progenitors were homozygous for quinclorac resistance. In contrast, F₃ progeny segregated into three ratios: 1 : 0, 3 : 1 and 0 : 1 (R : S) in response to ALS‐inhibitor treatment. This segregation pattern indicates that their F₂ parents were either homozygous or heterozygous for ALS‐inhibitor resistance. Therefore, there were clearly two distinct resistance mechanisms encoded by two genes that were not tightly linked as demonstrated by segregation patterns of the F₃.     

Lack of clinical efficacy of a phosphodiesterase-4 inhibitor for treatment of heaves in horses

Phosphodiesterase-4 (PDE 4) enzyme inhibitors have been shown to have anti-inflammatory properties in various animal disease processes and therefore could be effective drugs for the treatment of equine airway diseases. The purpose of this study was to evaluate the efficacy and adverse effects of the PDE 4 inhibitor L-826,141 in horses with heaves. In a blinded parallel design, horses with heaves exposed daily to moldy hay were given a placebo for 14 days and then administered either L-826,141 (n = 6; loading dose of 1 mg/kg IV followed by 0.5 mg/kg IV q48h) or dexamethasone (n = 6; 0.04 mg/kg IV q24h) from days 15 to 29 (study 1). Pulmonary function and bronchoalveolar (BAL) cytology were evaluated weekly from baseline (day 0) to 29 days. In study 2, horses were treated with L-826,141 (1.0 mg/kg IV q24h) for 8 days. Although ex vivo lipopolysaccharide-induced tumor necrosis factor (TNF)-alpha and LTB4 production by fresh blood were inhibited up to 90% after repeated administrations of L-826,141, this treatment failed to improve lung function. In contrast, dexamethasone (positive control) treatment resulted in significant improvement in lung mechanics and airway function in all horses. Neither drug had a significant effect on BAL total cell counts and differential cytology. Administration of the PDE 4 inhibitor L-826,141 for up to 14 days to horses with heaves was not associated with an improvement in airway function or inflammation. These findings suggest that the PDE 4 enzyme is not a key mediator of lung inflammation in heaves.     

The equine immune response to Streptococcus equi subspecies zooepidemicus during uterine infection

The purpose of this study was to describe strain-specific immune responses to Streptococcus equi subspecies zooepidemicus (S. zooepidemicus) during uterine infection in horses. Five isolates of S. zooepidemicus were differentiated into four strains antigenically by bactericidal testing in blood of 12 horses, and genetically by pulsed-field gel electrophoresis. Eight healthy mares were then divided into two groups, each inoculated with one strain intrauterinely on three successive oestrous cycles followed by a second strain for three successive cycles, first and second strains being reversed for each group. Immune responses to both strains were assessed by bactericidal testing and immunoblotting over eight cycles. Both techniques indicated that immune responses to each strain arose at different times. Immunoblots showed greater binding to the first inoculated strain than to the second (P < 0.05). These data confirm that immune responses to S. zooepidemicus during uterine infection are partly strain-specific.     

Assessing disease risk at the wildlife–livestock interface: A study of Sierra Nevada bighorn sheep

Despite evidence that domestic sheep diseases threaten the persistence of bighorn sheep populations, the economic consequences of restricting domestic sheep grazing has polarized the debate, with some arguing that disease risk posed by domestic sheep has been exaggerated and grazing restrictions should be eased. We constructed a model to assess how different management strategies (grazing allotment closures, grazing time reductions, and reduced probability of stray domestic sheep) affect the risk of respiratory disease transmission from domestic sheep to endangered Sierra Nevada bighorn sheep, and to predict population-level impacts of an outbreak. Even when management strategies reduced risk of interspecies contact to less than 2% per year, our model predicted a 50% probability of a catastrophic respiratory disease outbreak during the next 10 bighorn sheep generations. If an outbreak occurs in the near future, the model predicts that the smallest Sierra Nevada bighorn sheep population would have a 33% probability of quasi-extinction. To eliminate all risk of contact and potential disease transmission, domestic sheep cannot be grazed on allotments that overlap with areas utilized by Sierra Nevada bighorn sheep. Where wildlife and domestic animal populations share limited habitat, and there is documented evidence of a substantial disease threat and extinction risk, stakeholders must recognize that the only way to eliminate contact and risk of disease transmission is to give priority to one species or the other. If conservation is the priority, difficult decisions will need to be made to balance trade-offs between economic livelihoods and species conservation.     

MCPA (4-Chloro-2-ethylphenoxyacetate) resistance in hemp-nettle (Galeopsis tetrahit L.)

The physiological basis for MCPA resistance in a hemp-nettle (Galeopsis tetrahit L.) biotype, obtained from a MCPA-resistant field population, was investigated. Dose-response studies revealed that the resistance factor for MCPA, based on GR50 comparisons of total dry weight of resistant (R) and susceptible (S) plants, was 3.3. Resistance factors for fluroxypyr, dicamba, 2,4-D, glyphosate, and chlorsulfuron were 8.2, 1.7, 1.6, 0.7, and 0.6, respectively. MCPA resistance was not due to differences in absorption, because both R and S biotypes absorbed 54% of applied [14C]MCPA 72 h after treatment. However, R plants exported less (45 vs 58% S) recovered 14C out of treated leaves to the apical meristem (6 vs 13% S) and root (32 vs 38% S). In both biotypes, approximately 20% of the 14C recovered in planta was detected as MCPA metabolites. However, less of the 14C recovered in the roots of R plants was MCPA. Therefore, two different mechanisms protect R hemp-nettle from MCPA phytotoxicity: a lower rate of MCPA translocation and a higher rate of MCPA metabolism in the roots. In support of these results, genetic studies indicated that the inheritance of MCPA resistance is governed by at least two nuclear genes with additive effects.     

Peptides enhance magnesium signature in calcite: insights into origins of vital effects

Studies relating the magnesium (Mg) content of calcified skeletons to temperature often report unexplained deviations from the signature expected for inorganically grown calcite. These "vital effects" are believed to have biological origins, but mechanistic bases for measured offsets remain unclear. We show that a simple hydrophilic peptide, with the same carboxyl-rich character as that of macromolecules isolated from sites of calcification, increases calcite Mg content by up to 3 mole percent. Comparisons to previous studies correlating Mg content of carbonate minerals with temperature show that the Mg enhancement due to peptides results in offsets equivalent to 7 degrees to 14 degrees C. The insights also provide a physical basis for anecdotal evidence that organic chemistry modulates the mineralization of inorganic carbonates and suggest an approach to tuning impurity levels in controlled materials synthesis.