Changes in plasma glucagon and insulin associated with fasting in sea bass (Dicentrarchus labrax)

Juvenile sea bass (Dicentrarchus labrax) were fasted for 22 days and changes in plasma insulin, glucagon and glucose levels, as well as glycogen and protein content in liver and muscle were analyzed. Glucagon increased initially on the 4th day of fasting. The glucagon/insulin ratio (G/I) increased from a value of 0.11±0.02 (24h of fasting) to 0.21±0.05 (4th day of fasting). Thereafter, both glucagon and insulin levels decreased and remained at low concentrations until the 22nd day of fasting. Plasma glucose levels fell at the beginning of fasting, stabilized between the 4th and 8th day, and gradually declined during the rest of the experiment. There was a body weight loss of 15% and a significant decrease in both the hepatosomatic index and mesenteric fat. The decrease in the percentage of muscle proteins was not significant, while liver glycogen content showed a sharp decline.     

Composition and biological activity of essential oils from Labiatae against Nezara viridula (Hemiptera: Pentatomidae) soybean pest

BACKGROUND: Plant essential oils have been recognised as an important natural source of insecticide. This study analysed the chemical constituents and bioactivity of essential oils that were isolated via hydrodistillation from Origanum vulgare L. (oregano) and Thymus vulgaris L. (thyme) against eggs, second instar and adults of Nezara viridula (L.). RESULTS: The major component of oregano was p‐cymene, and, for thyme, thymol. The ovicidal activity was tested by topical application; the essential oil from thyme was more effective. The fumigant activity was evaluated in an enclosed chamber; the LC₅₀ values for oregano were 26.8 and 285.6 µg mL^?1 for nymphs and adults respectively; for thyme they were 8.9 µg mL^?1 for nymphs and 219.2 µg mL^?1 for adults. To evaluate contact activity, a glass vial bioassay was used; the LC₅₀ values for oregano were 1.7 and 169.2 µg cm^?2 for nymphs and adults respectively; for thyme they were 3.5 and 48.8 µg cm^?2 respectively. The LT₅₀ analyses for contact and fumigant bioassays indicated that thyme was more toxic for nymphs and adults than oregano. Both oils produced repellency on nymphs and adults. CONCLUSION: These results showed that the essential oils from O. vulgare and T. vulgaris could be applicable to the management of N. viridula. Copyright © 2011 Society of Chemical Industry     

Nitrogen Mobility at the Sediment-Water Interface of Lake Maracaibo,Venezuela

Nitrogen is one of the two most important elements in the metabolism of aquatic ecosystems. At low concentrations it can limit primary productivity and when present at very high concentrations it can participate in the eutrophication process of these environments. The mechanism of nitrogen transport in sediments is almost unknown, nevertheless it is of vital importance for establishing mass balances in aquatic systems. In the study presented here, we assessed the nitrogen flux in sediments of the central part of tropical Lake Maracaibo, Venezuela, in particular with regard to dissolved oxygen concentrations. Experiments were performed under laboratoryconditions in a batch system, and at varying dissolved oxygenregimes (aerobic and anaerobic). Every two days, during 3 months,overlying water samples were taken to analyze nitrite, nitrate,ammonium and Kjeldahl total nitrogen. Average release rates oftotal nitrogen were 0.86 in aerobic, and 1.06 mmol N m^-2 d^-1 in anaerobic systems corresponding to 41.7% of total N input to the lake. The behavior of nitrogen was strongly influenced by nitrate concentrations under aerobic conditions, and by organic nitrogen under anaerobic conditions during the course of the experiment. A major trend for the release of organic nitrogen during anaerobic conditions, and of nitrate, during aerobic conditions, was observed. Also fluxes of NO₃ ^-, NH₄ ⁺, organic N and Total N across the sediment-water interface were measured. In anaerobic conditions, which are predominant in the hypolimnetic cone of LakeMaracaibo, denitrification was estimated to be 0.02 mmol N m^-2 d^-1, which corresponds to 1.89% of the total N released from sediments.This is to our knowledge the first study of nitrogen fluxes insediments from Lake Maracaibo. The laboratory data presented herereflects conditions in the lake when major nutrients accumulation occurs.     

Factors affecting porcine sperm mediated gene transfer

“Sperm mediated gene transfer” (SMGT) is based on the ability of sperm cells to bind exogenous DNA. The main objective of this study was to improve the production of transgenic pigs by SMGT. Taking into account that there is a lack of repeatability in studies of SMGT and that the mechanism of binding and internalization of exogenous DNA is a question that has not been solved, different factors involved in the production of transgenic animals by SMGT method were evaluated. Here we set out to: (1) evaluate the sperm capacity to bind exogenous DNA after DMSO treatment; (2) determine the location of the transgene–spermatozoa interaction; and (3) evaluate the efficiency of production of transgenic piglets by deep intrauterine artificial insemination (AI) with sperm incubated with DNA. The percentage of DNA binding was higher than 30% after 2 h of co-culture, but it was not affected by sperm treatment with DMSO (0.3% or 3%). The integrity of the sperm plasma membrane plays a critical role in DNA interaction, and altered plasma membranes facilitate interactions with exogenous DNA. DNA bound mainly to spermatozoa with reduced viability. DNA molecules were found to be mainly associated to the post-acrosomal region (61.9%). After deep intrauterine AI a total of 29 piglets were obtained, but none of them integrated the transgene. In conclusion, although it has been confirmed that DNA can associate with boar spermatozoa, the efficiency of producing transgenic pigs by AI was not confirmed by the present experiments, mainly due to a reduced DNA binding to functional spermatozoa.     

Plasma concentrations resulting from florfenicol preparations given to pigs in their drinking water

Florfenicol administered through the drinking water has been recommended as a metaphylactic antibacterial drug to control outbreaks of respiratory diseases in pigs caused by strains of Actinobacillus pleuropneumoniae and Pasteurella multocida, yet it is difficult to pinpoint in practice when the drug is given metaphylactically or therapeutically. Further, pigs are likely to reject florfenicol-medicated water, and plasma concentrations of the drug are likely to be marginal for diseases caused by Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus. The reported minimal inhibitory concentration (MIC) values for these organisms show a breakpoint of 2 to 3 μg/mL. An experiment was conducted during September and October 2009. One hundred twenty healthy crossbred pigs (Landrace-Yorkshire), weighing 23 ± 6.2 kg, were used in this trial. They were randomly assigned to 5 groups, with 3 replicates of 8 animals/group. Two commercial preparations of florfenicol were administered through the drinking water at 2 concentrations (0.01 and 0.015%). Water intake was measured before and after medication, and plasma concentrations of florfenicol were determined by HPLC. Considerable rejection of florfenicol-medicated water was observed. However, plasma florfenicol concentrations were of a range sufficient for a methaphylaxis approach to preventing disease by bacteria, with MIC breakpoints of ≤ 0.25 μg/mL. Decreased efficacy as a metaphylactic medication should be expected for bacteria with MIC >0.25 μg/mL, considering the reported existence of bacteria resistant to florfenicol and the natural resistance of Streptococcus suis or E. coli to this drug.     

Natural progression of Bovine Leukemia Virus infection in Argentinean dairy cattle

We describe the progression of Bovine Leukemia Virus (BLV) infection from birth until the first lactation in 61 animals from a typical large dairy herd of Argentina, with more than 85% of prevalence. The purpose was to identify potential points to effectively break the BLV cycle of transmission in our dairy productive system. We detected early infection in 11.47% of newborn calves by nested PCR. From birth to 12 months, no evidence of new infections was observed. After 12 months of age, the detection of new reactors increased slowly with time, from 15.09% at 15 months to 24% at 27 months. After that, the number of reactors increased rapidly up to 40% and 60.76% at 30 and 36 months, respectively. This last 9-month period coincided with parturition and the entry into the milking herd. Real-time PCR showed that more than 75% of adult animals had low peripheral-blood proviral load. Complementary, all infected animals showed low levels of provirus in milk and colostrum. The most important finding was that even when management procedures to prevent BLV iatrogenic transmission were followed, no significant change was observed in the prevalence after three years, strongly suggesting that other way/s of transmission play a key role under natural conditions. This study showed an interesting baseline to draw an alternative approach based on selective segregation according to the peripheral-blood proviral load as a potential indicator of risk transmission, and as an alternative to classical control measures.     

Effects of different variables on whole blood cholinesterase analysis in dogs.

The influence of several variables such as sample and reagent storage, anticoagulants, reaction temperature, pH, and substrate concentration on whole blood cholinesterase determination was studied. Storage of nondiluted whole blood samples at room temperature or under refrigeration (4 C) was adequate for short-term storage (3 days to 2 weeks). However, freezing would be more appropriate for long-term storage (> or = 1 month), and successive thawing and freezing did not produce any loss of cholinesterase activity. All reagents (2,2'-dithiodipyridine as chromophore and acetylthiocholine and butyrylthiocholine as substrates) were stable for 3 months when frozen. Heparin and ethylenediaminetetraacetic acid were the most suitable anticoagulants for whole blood acetylcholinesterase and butyrylcholinesterase determination, because citrate yielded lower acetylcholinesterase values and fluoride inhibited butyrylcholinesterase. Increases in reaction temperature and pH yielded higher cholinesterase values but also increased nonenzymatic substrate hydrolysis. Higher cholinesterase and nonenzymatic substrate hydrolysis values were obtained as higher substrate concentrations were used.     

Serum and Tissue Steroid Hormone Levels in Canine Mammary Tumours: Clinical and Prognostic Implications

Hormonal dependency of canine mammary tumours (CMT) has been studied over the last few decades. However, studies assessing the prognostic and predictive potential of serum and/or tissue steroid hormone levels are still scarce in CMT. To the best of our knowledge, this is the first report relating serum and tissue levels of steroid hormones and prognosis in dogs. Serum and tumour tissue from 45 female dogs with spontaneous CMT were included in the study. Moreover, serum and normal mammary tissue from 13 healthy female dogs were also included as controls. Steroid hormones were determined by competitive enzyme immunoassay. Overall, levels of steroid hormones in serum and tissue homogenates were significantly different between malignant and benign mammary tumours (p < 0.01), except for progesterone (P4) serum levels that revealed no statistical differences between groups. In malignant tumours, oestrone sulphate (SO4E1), dehydroepiandrosterone (DHEA), androstenedione (A4), testosterone (T) and P4 elevated tissue concentrations were significantly associated with tumour relapse and/or distant metastasis during follow‐up. A significant association was found between elevated tissue SO4E1 (p = 0.003), 17β‐oestradiol (E2) (p = 0.036), DHEA (p = 0.022), A4 (p = 0.001) and P4 (p = 0.013) concentrations and shorter disease‐free survival and overall survival in female dogs with malignant mammary tumours. The high levels of tissue steroids found in cases of poor prognosis open the possibility of additional new therapeutic approaches. Future clinical trials will be needed to clarify the usefulness of targeting steroid hormones in the treatment of this neoplastic disease.     

Oomycete species associated with Theobroma cacao crops in Colombia

The study of oomycetes associated with crops is highly important due to the economic losses they might cause. In cacao, the genus Phytophthora has been extensively studied, but little is known about other genera and species of oomycetes associated with this plant. This study aimed to determine the oomycetes’ diversity present in Colombian cacao crops. A total of 146 isolates were obtained from diseased plants and soil in 11 departments. Analysis of internal transcribed spacer (ITS) and cytochrome oxidase subunit I (coxI) sequences was performed along with the assessment of morphological characteristics. Nine species were identified, distributed in four genera: Phytophthora (P. palmivora, 54%; P. nicotianae, 1%), Phytopythium (Phy. chamaehyphon, 15%; Phy. cucurbitacearum, 9%; Phy. vexans, 7%; Phy. helicoides, 1%), Globisporangium (G. splendens, 3%), and Pythium (Py. delicense, 1%; Py. inflatum,1%). Additionally, an unidentified and possibly new species of Phytophthora (5%) and three unidentified species of Phytopythium (3%) were found. This is the first report of Globisporangium, Phytopythium, and Pythium in cacao crops of Colombia and the first report of the species Phy. chamaehyphon in the country. Interestingly, some isolates of Phytopythium spp. were isolated from necrotic leaves and vascular section of stems, which may suggest a role in cacao diseases traditionally associated with Phytophthora. Also, it is proposed that the new species of Phytophthora may be contributing significantly to black pod disease in Colombian cacao crops, and we highlight that the study of P. palmivora is urgent because of its distribution all over the country.