Root Uptake and Xylem Translocation of Pesticides from Different Chemical Classes

A pressure-chamber technique was used to study the root uptake and xylem translocation of some fungicides, herbicides and an insecticide from different chemical classes in detopped soybean roots. Physiological parameters such as K⁺ leakage from roots, K⁺ concentrations in the xylem sap, and protein and ATP levels in the root cells were measured so as to evaluate any potential damage of this technique to the root system. HPLC was used to quantify the compounds in the xylem sap. The pressure-chamber technique has proved useful to study the root uptake and translocation of pesticides, does not damage the root system, and allows one to obtain appreciable volumes of xylem sap that can be analysed directly by HPLC, thus avoiding dependence on the availability of radio-labelled compounds. The concentration of each pesticide in the xylem sap showed a steady-state kinetic profile. Non-linear regression analysis was used to calculate the steady-state concentration and the time required to achieve 50% of the steady-state concentration (TSSC₅₀). TSSC₅₀ was well correlated with log K_ow; the more lipophilic the compound the more time was required to reach the steady-state concentration. The efficiency of translocation was assessed by the transpiration stream concentration factor (TSCF) and a non-linear relationship between TSCF and log K_ow was observed. The highest TSCF values were measured for those compounds with log K_ow values around 3, a lipophilicity value similar to that reported earlier in an analogous experiment with detopped soybean plants but slightly higher than that reported in earlier experiments with intact barley plants. Lower TSCF values were obtained with chemicals with log K_ow values below as well as above 3. © 1997 SCI.     

A DNA vaccine against dolphin morbillivirus is immunogenic in bottlenose dolphins

The immunization of exotic species presents considerable challenges. Nevertheless, for facilities like zoos, animal parks, government facilities and non-profit conservation groups, the protection of valuable and endangered species from infectious disease is a growing concern. The rationale for immunization in these species parallels that for human and companion animals; to decrease the incidence of disease. The U.S. Navy Marine Mammal Program, in collaboration with industry and academic partners, has developed and evaluated a DNA vaccine targeting a marine viral pathogen – dolphin morbillivirus (DMV). The DMV vaccine consists of the fusion (F) and hemagglutinin (H) genes of DMV. Vaccine constructs (pVR-DMV-F and pVR-DMV-H) were evaluated for expression in vitro and then for immunogenicity in mice. Injection protocols were designed for application in Atlantic bottlenose dolphins (Tursiops truncatus) to balance vaccine effectiveness with clinical utility. Six dolphins were inoculated, four animals received both pDMV-F and pDMV-H and two animals received a mock vaccine (vector alone). All animals received an inoculation week 0, followed by two booster injections weeks 8 and 14. Vaccine-specific immune responses were documented in all four vaccinated animals. To our knowledge, this is the first report of pathogen-specific immunogenicity to a DNA vaccine in an aquatic mammal species.     

EFFECTS OF TWO DIFFERENT ANESTHETIC PROTOCOLS ON CARDIAC FLOW MEASURED BY TWO DIMENSIONAL PHASE CONTRAST MAGNETIC RESONANCE IMAGING

Companion animals are routinely anesthetized or heavily sedated for cardiac MRI studies, however effects of varying anesthetic protocols on cardiac function measurements are incompletely understood. The purpose of this prospective study was to compare effects of two anesthetic protocols (Protocol A: Midazolam, fentanyl; Protocol B: Dexmedetomidine) on quantitative and qualitative blood flow values measured through the aortic, pulmonic, mitral, and tricuspid valves using two‐dimensional phase contrast magnetic resonance imaging (2D PC MRI) in healthy dogs. Mean flow per heartbeat values through the pulmonary artery (Qp) and aorta (Qs) were compared to right and left ventricular stroke volumes (RVSV, LVSV) measured using a reference standard of 2D Cine balanced steady‐state free precession MRI. Pulmonary to systemic flow ratio (Qp/Qs) was also calculated. Differences in flow and Qp/Qs values generated using 2D PC MRI did not differ between the two anesthetic protocols (P = 1). Mean differences between Qp and RVSV were 3.82 ml/beat (95% limits of agreement: 3.62, ?11.26) and 1.9 ml/beat (?7.86, 11.66) for anesthesia protocols A and B, respectively. Mean differences between Qs and LVSV were 1.65 ml/beat (?5.04, 8.34) and 0.03 ml/beat (?4.65, 4.72) for anesthesia protocols A and B, respectively. Mild tricuspid or mitral reflux was seen in 2/10 dogs using 2D PC MRI. No aortic or pulmonic insufficiency was observed. Findings from the current study indicated that these two anesthetic protocols yield similar functional measures of cardiac blood flow using 2D PC MRI in healthy dogs. Future studies in clinically affected patients are needed.     

Measuring lesion attributes and analysing their spatial patterns at the leaf scale using digital image analysis

Digital image analysis was used to quantify size, shape and relative positions of individual plant disease lesions to determine their spatial distribution pattern at the leaf scale. Rice brown spot was used as a necrotrophic pathogen causing numerous discrete lesions. A 50‐leaf subsample was selected from an existing data set of 350 images of leaves taken from the field, and analysed for disease severity using image analysis. Further measurements included size, shape and the relative positions of lesions for all leaves with severity > 8% (n = 25) and an additional 25‐leaf sample with severity <8%. A total of 3964 necrotic and/or halo areas were selected using a manually defined threshold in the computer program Assess . There were significant and positive associations (Pearson's r > 0.81; P < 0.001) between the size‐related measurements (lesion area, longest and shortest axis). Coalesced areas, formed by interconnection of lesions and associated haloes, and a high number of small lesions were found with an increase in severity, suggesting a secondary cycle and autoinfection process. Results from quadrat‐based (Poisson distribution and Spatial Analysis by Distance IndicEs) and distance‐based (point‐process Poisson) spatial methods were in good agreement and, together with a Taylor power law model, suggested a shift from random to predominantly aggregated patterns of lesions at severities approaching 10%. This framework, which is applicable to other foliar diseases, proved useful in providing quantitative knowledge of epidemic processes at the leaf scale. Finally, these results may be useful in improving simulation models and disease assessment methods.     

Titan's rotation reveals an internal ocean and changing zonal winds

Cassini radar observations of Saturn's moon Titan over several years show that its rotational period is changing and is different from its orbital period. The present-day rotation period difference from synchronous spin leads to a shift of approximately 0.36 degrees per year in apparent longitude and is consistent with seasonal exchange of angular momentum between the surface and Titan's dense superrotating atmosphere, but only if Titan's crust is decoupled from the core by an internal water ocean like that on Europa.     

Foetal pulmonary maturity in dogs: Estimated from bubble tests in amniotic fluid obtained via amniocentesis

The goal of this study was to evaluate the reliability of amniocentesis during late pregnancy to assess lung maturity in puppies using a bubble test as described by Gunston and Davey (South African Medical Journal, 54, 1978, 495). Thirty‐five bitches from eight different breeds were followed during late pregnancy before undergoing elective Caesarean (C)‐section on days 61–62 after ovulation. Bubble tests were performed the day before the C‐section (n = 11 bitches) and before the administration of aglepristone on amniotic fluid samples obtained via amniocentesis and were repeated the day of the surgery on amniotic fluid samples collected via puncture of the amniotic bags before they were opened (n = 35 bitches). No complications were observed following amniocenteses and the C‐sections. The mortality rate (2.3%) was similar to the result of other studies using the same protocol for an elective C‐section. Of the non‐contaminated samples collected the day of the C‐section, 89.6% were positive in the bubble test, which was consistent with observations of clinical maturity the day of the surgery and on the following days. In contrast, 70% of the samples collected the day before the C‐section (when progesterone concentrations were still high) were negative, suggesting that the puppies were still immature at this point in the pregnancy. Additionally, we observed a significant difference in the bubble test results before and 18 hr after the administration of aglepristone, suggesting that aglepristone may act as an inducer of the final maturation of the puppies by inactivating progesterone receptors and simulating a physiological decrease in progesterone. Finally, we confirmed the need to exclude all contaminated samples, which could lead to false‐negative results.