In Vitro Effects of Agriculture Pollutants on Microcrustacean and Fish Acid Phosphatases

Chemical inputs from agricultural activities represent a threat to aquatic biota and its biochemical systems. Among these systems, acid phosphatases are involved in autophagic digestive processes, decomposing organic phosphates, signaling pathways, and other metabolic routes. In vitro tests are helpful to generate hypotheses about pollutant mechanisms of action through comparison of the toxicity effects of these compounds. In this work, we investigated the inhibitory effects of four organic pesticides and three metals on the acid phosphatases extracted from the freshwater microcrustacean Daphnia similis and the fish Metynnis argenteus. Our results demonstrated that only the metals have considerable inhibitory effects (50% or higher) on the enzyme activities. The calculated median effect concentrations (IC50) for the enzyme inhibition were 0.139 mM Hg²⁺ (fish enzyme), 0.652 mM Cu²⁺ (fish enzyme), and 1.974 mM Al³⁺ (Daphnia enzyme). Due to the relatively low value of the inhibition parameter for Hg²⁺, its inhibitory property could be used as a tool for Hg²⁺ detection in environmental samples. The enzyme activities obtained in the presence of the inhibitors are potential data as in vivo biomarkers for metals in both aquatic species.     

Partial external mitral annuloplasty in dogs with myxomatous mitral valve degeneration and congestive heart failure: Outcome in 9 cases

Objective

To report the outcome of partial external mitral annuloplasty in dogs with congestive heart failure (CHF) due to mitral regurgitation caused by myxomatous mitral valve degeneration (MMVD).

Animals, materials and methods

Nine client-owned dogs with CHF due to mitral regurgitation caused by MMVD. Surgery consisted of a double row of pledget-butressed continuous suture lines placed into the left ventricle parallel and just ventral to the atrioventricular groove between the subsinuosal branch of the left circumflex coronary artery and the paraconal branch of the left coronary artery.

Results

Two dogs died during surgery because of severe hemorrhage. Two dogs died 12 and 36 h after surgery because of acute myocardial infarction. Three dogs were euthanized 2 and 4 weeks after surgery because of progression of CHF, 1 was euthanized 30 days after surgery for non-cardiac disease, and 1 survived for 48 months. In the 5 dogs that survived to discharge there was no significant change in the left atrium to aortic ratio with surgery (3.6 ± 0.56 before surgery; 3.1 ± 0.4 after surgery; p = 0.182), and no significant change in mitral regurgitant fraction in 4 dogs in which this measurement was made (78.7 ± 2.0% before surgery; 68.7 ± 7.5% after surgery; p = 0.09).

Conclusions

Partial external mitral annuloplasty in dogs with CHF due to MMVD was associated with high perioperative mortality and most dogs that survived to discharge failed to show clinically relevant palliation from this procedure. Consequently, partial external mitral annuloplasty is not a viable option for dogs with mitral regurgitation due to MMVD that has progressed to the stage of CHF.     

C-Farm: A simple model to evaluate the carbon balance of soil profiles

Soil carbon cycling is an essential component of agroecosystems models. Simulating soil carbon (C_s) cycling has become an issue of societal importance for C_s storage can play a role reducing the rate of increase of atmospheric CO₂ concentration. To participate in carbon trading markets, growers have to evaluate their local, site-specific options to increase C_s or reduce C_s losses. This paper introduces C-Farm, a daily time step cropping systems model that allows calculating the Cs balance using a one-pool soil organic matter sub-module. In C-Farm the C_s turnover rate depends non-linearly on C_s and on environmental and management controls. Two long-term experiments were selected to evaluate C-Farm: a wheat-summer fallow 70+ years experiment at Pendleton, Oregon, and the continuous wheat experiment at the Rothamsted experiment station in the United Kingdom. C-Farm simulated well the long-term C_s evolution observed in these experiments. In addition, simulations performed in the dryland US Pacific Northwest show its applicability for assessing C_s storage rates in a region with large variation in precipitation. C-Farm can be easily customized to a large array of local conditions, providing robust estimates of short- and long-term on-farm carbon storage rates. The model is being further developed to provide estimates of nitrous oxide emission.     

Biosynthesis of the Torpedo californica acetylcholine receptor alpha subunit in yeast

Yeast cells were transformed with a plasmid containing complementary DNA encoding the alpha subunit of the Torpedo californica acetylcholine receptor. These cells synthesized a protein that had the expected molecular weight, antigenic specificity, and ligand-binding properties of the alpha subunit. The subunit was inserted into the yeast plasma membrane, demonstrating that yeast has the apparatus to express a membrane-bound receptor protein and to insert such a foreign protein into its plasma membrane. The alpha subunit constituted approximately 1 percent of the total yeast membrane. The alpha subunit constituted approximately 1 percent of the total yeast membrane proteins, and its density was about the same in the plasma membrane of yeast and in the receptor-rich electric organ of Electrophorus electricus. In view of the available technology for obtaining large quantities of yeast proteins, it may now be possible to obtain amplified amounts of interesting membrane-bound proteins for physical and biochemical studies.     

Presymptomatic detection of prions in blood

Prions are thought to be the proteinaceous infectious agents responsible for transmissible spongiform encephalopathies (TSEs). PrP(Sc), the main component of the infectious agent, is also the only validated surrogate marker for the disease, and its sensitive detection is critical for minimizing the spread of the disease. We detected PrP(Sc) biochemically in the blood of hamsters infected with scrapie during most of the presymptomatic phase of the disease. At early stages of the incubation period, PrP(Sc) detected in blood was likely to be from the peripheral replication of prions, whereas at the symptomatic phase, PrP(Sc) in blood was more likely to have leaked from the brain. The ability to detect prions biochemically in the blood of infected but not clinically sick animals offers a great promise for the noninvasive early diagnosis of TSEs.