Molecular Basis of Gene-for-Gene Specificity in Bacterial Speck Disease of Tomato

Transient expression of the Pseudomonas syringae avirulence gene avrPto in plant cells resulted in a Pto-dependent necrosis. The AvrPto avirulence protein was observed to interact directly with the Pto resistance protein in the yeast two-hybrid system. Mutations in the Pto and avrPto genes which reduce in vivo activity had parallel effects on association in the two-hybrid assay. These data suggest that during infection the pathogen delivers AvrPto into the plant host cell and that resistance is specified by direct interaction of Pto with AvrPto.     

The content of total mercury and methylmercury in common carp from selected Czech ponds

The aim of the present study was to investigate concentrations of total mercury (THg) and methylmercury (MeHG) in the common carp from Czech ponds of Rožmberk, Spolsky, Nezmar, and Velky Bědny. Seven common carps (Cyprinus caprio) from each of the ponds were caught. Muscle tissue, the liver, and the soft and hard roe were used for the tests. Total mercury and methylmercury were found in all the muscle tissue samples examined. Detection limits for total mercury and methylmercury determination methods were 0.001 mg kg^–1 and 0.013 mg kg⁻¹ respectively. Methylmercury levels in the liver and gonads were below the method’s limits of detection. THg and MeHg concentrations in muscle tissues were 0.018–0.063 mg kg^–1 w.w. and 0.019–0.063 mg kg^–1 w.w. respectively. MeHg made up 90–100% of THg in muscle tissues. Total mercury and methylmercury concentrations were significantly (P < 0.05) higher in fish from the Spolsky pond than from the Nezmar pond. MeHg/THg ratios were significantly (P < 0.05) higher in fish from the Rožmberk, Spolsky and Nezmar ponds compared with fish from the Velky Bědny pond.     

Discontinuity in fish assemblages across an elevation gradient in a southern Appalachian watershed, USA

Abstract –  We examine patterns in fish species assemblages in the Toxaway and Horsepasture rivers, two high elevation streams in North Carolina, USA. This region is noted for extreme topographical relief, high cumulative annual rainfall and many rare and endemic plants and animals. The study area encompasses a portion of the Blue Ridge Escarpment and the associated Brevard Fault Zone. We hypothesise that major waterfalls and cascade complexes have acted to limit invasion and colonisation by fishes from downstream. This hypothesis is supported by longitudinal fish assemblage patterns in our study streams. Fish species richness in Toxaway River increased from 4 to 23 between Lake Toxaway and Lake Jocassee, a distance of 10 river km. We found similar discontinuities in neighbouring Horsepasture River and Bearwallow Creek. We found no instances of species replacement along this elevation gradient, and the trend in increased diversity downstream showed discontinuities coincident with sharp elevation breaks. With regard to theories posited to explain community formation in headwater stream fish communities (especially in those characterised by high topographical relief), we suggest coloniser 'access' may be more important than other factors including competitive interactions.     

Multiple viral plaques with sebaceous differentiation associated with an unclassified papillomavirus type in a cat

Abstract

CASE HISTORY AND CLINICAL FINDINGS

A 15-year-old neutered male domestic short-haired cat was presented due to multiple 0.5–2?cm-diameter crusting plaques in the left preauricular region, over the bridge of nose, and in the right periocular region. The plaques did not appear to cause discomfort.     

Participation of Opioid Peptides in Sucking‐induced Oxytocin and Prolactin Secretions in Lactating Goats

The role of opioid peptides in the secretion of oxytocin (OT) and prolactin (PRL) induced by sucking was studied in goats. Seven goats were isolated with their kids (four singletons and three twins) in individual corrals 3–4 weeks after parturition. On day 1 of the experiment, the kids were separated from the does for 7 h and were weighed before and 15 min after being reunited with their mothers to assess the amount of milk obtained by sucking. The does were blood‐sampled 10 min before and at the end of the sucking period. On day 2, a similar protocol was followed, but naloxone was given immediately after the first blood sample. On day 3, the protocol was repeated but saline vehicle was injected instead of naloxone. On day 5, the naloxone experiment was repeated as on day 2. Milk ejection was evaluated as the difference in the weight of the kids before and after sucking for 15 min, and the maternal serum levels of OT and PRL were measured by radioimmunoassay. A significant decrease in the weight gain of the kids was obtained when the mothers were treated with naloxone on day 2. Consistently, serum levels of OT and PRL induced by sucking were significantly reduced; indicating that sucking‐induced OT secretion for milk ejection in lactating goats is facilitated by opioid peptides. In a second experiment performed in the same animals 10 days later, the administration of OT, immediately after naloxone administration, prevented the decrease in the weight gain induced by naloxone, suggesting that the effect of the opioid antagonist on milk ejection in goats is a result of a reduced OT secretion. The results of this study confirm the importance of sucking‐induced OT secretion for milk ejection in lactating goats, and indicate that OT and PRL secretion are regulated by opioid peptides in this species.     

Copper Release, Speciation, and Toxicity Following Multiple Floodings of Copper Enriched Agriculture Soils: Implications in Everglades Restoration

This study characterizes the effects of water–soil flooding volume ratio and flooding time on copper (Cu) desorption and toxicity following multiple floodings of field-collected soils from agricultural sites acquired under the Comprehensive Everglades Restoration Plan (CERP) in south Florida. Soils from four field sites were flooded with three water–soil ratios (2, 4, and 6 [water] to 1 [soil]) and held for 14 days to characterize the effects of volume ratio and flooding duration on Cu desorption (volume ratio and flooding duration study). Desorption of Cu was also characterized by flooding soils four times from seven field sites with a volume ratio of 2 (water) to 1 (soil) (multiple flooding study). Acute toxicity tests were also conducted using overlying waters from the first flooding event to characterize the effects of Cu on the survival of fathead minnows (Pimephales promelas), cladocerans (Daphnia magna), amphipods (Hyalella azteca), midges (Chironomus tentans), duckweed (Lemna minor), and Florida apple snails (Pomacea paludosa). Acute tests were also conducted with D. magna exposed to overlying water from the second and third flooding events. Results indicate that dissolved Cu concentrations in overlying water increased with flooding duration and decreased with volume ratio. In the multiple flooding study, initial Cu concentrations in soils ranged from 5 to 223 mg/kg (dw) and were similar to Cu concentration after four flooding events, indicating retention of Cu in soils. Copper desorption was dependent on soil Cu content and soil characteristics. Total Cu concentration in overlying water (Cu_w) was a function of dissolved organic carbon (DOC), alkalinity, and soil Cu concentration (Cu_s): log(Cu_w)?=?1.2909?+?0.0279 (DOC)?+?0.0026 (Cu_s)???0.0038 (alkalinity). The model was validated and highly predictive. Most of the desorbed Cu in the water column complexed with organic matter in the soils and accounted for 99% of the total dissolved Cu. Although total dissolved Cu concentrations in overlying water did not significantly decrease with number of flooding events, concentrations of free Cu²⁺ increased with the number of flooding events, due to a decrease in DOC concentrations. The fraction of bioavailable Cu species (Cu²⁺, CuOH⁺, CuCO₃) was also less than 1% of the total Cu. Overlying water from the first flooding event was only acutely toxic to the Florida apple snail from one site. However, overlying water from the third flooding of six out of seven soils was acutely toxic to D. magna. The decrease in DOC concentrations and increase in bioavailable Cu²⁺ species may explain the changes in acute toxicity to D. magna. Results of this study reveal potential for high Cu bioavailability (Cu²⁺) and toxicity to aquatic biota overtime in inundated agricultural lands acquired under the CERP.     

Exercise-induced malignant hyperthermia in an English springer spaniel

An exercise-induced malignant hyperthermia-like syndrome developed in an English Springer Spaniel. Moderate exercise resulted in pronounced hyperlactacidemia, dyspnea, and hyperthermia. Before exercise, the dog had high activities of serum muscle enzymes, mild reticulocytosis, abnormally increased erythrocyte osmotic fragility, and a positive result from the caffeine-halothane contracture test. This report supports the hypothesis of a canine stress syndrome and indicates a role for exercise/challenge tests in diagnosis of malignant hyperthermia susceptibility.