Enhancing chlamydospore production in Duddingtonia flagrans on solid substrate: The impact of mannitol and varied cultivation conditions.

Duddingtonia flagrans is a nematophagous fungus which has shown promising results as a non-chemical parasitic control tool. The fungus disrupts the parasite's life cycle by trapping larvae in the environment through the networks generated from chlamydospores, thus preventing the reinfection of animals. One barrier to the development of a commercial product using this tool is the need to increase chlamydospore production in the laboratory for its administration to livestock. The purpose of this study was to evaluate the addition of mannitol to an enriched culture medium and the effect of adverse cultivation conditions on chlamydospore production. D. flagrans was cultivated on Petri dishes with corn agar for 4 weeks at 27 °C and 70% relative humidity (RH). Four groups were then formed, all with Sabouraud agar as a base, to which different growth inducers were added: GSA (glucose Sabouraud agar), GSA-MI (glucose Sabouraud agar + meso inositol), GSA-E (enriched glucose Sabouraud agar), and AE-M (enriched agar + mannitol). After 4 weeks, chlamydospores were recovered by washing the surface of each plate with distilled water and then quantified. The medium that yielded the highest amount of chlamydospores was subjected to different cultivation conditions: NC (normal conditions): 70% RH and 27 °C, AC (adverse conditions) 1: 20% RH and 40 °C, CA2: 60% RH and 27 °C, and CA3: 55% RH and 24 °C. It was determined that mannitol increases chlamydospore production (65x106 chlamydospores/plate), and when reducing humidity by 10% under cultivation conditions it resulted in an approximately 10% increase in chlamydospore production compared to the control group. These results suggest that the addition of polyols, as well as its cultivation under certain environmental conditions, can improve chlamydospore production on a laboratory scale.

Extraction of chlorophyll a from Tetradesmus obliquus-a method upgrade.

Nowadays, the use of algae is prevalent for both industrial and agricultural purposes. The determination of chlorophyll (Chl) content is a commonly used method for estimating the phytoplankton abundance in different water bodies or biomass density of algal cultures. The aim of the present work is to optimise the efficiency of the Chl extraction from the green alga Tetradesmus obliquus using methanol as extracting solvent. The extraction efficiency was estimated by measuring the Chl a concentration of the extracts using fluorescence spectroscopy. To increase the extraction yield, glass fibre filters with algal cells on top were treated with 10% (v/v) formalin prior to the extraction. We found that this pretreatment significantly enhanced the extraction yield of Chl without its chemical decomposition. We also found that the optimal cell concentration for Chl determination ranged from 1.44 × 104 to 3.60 × 105 cells/mL and the extraction efficiency was lower when the cell density of the culture was out of this range. These results highlight the importance of the optimization of the pigment extraction for the studied algal species.

Pharmacokinetic-pharmacodynamic assessment of the ivermectin and abamectin nematodicidal interaction in cattle.

In a context of nematodicidal resistance, anthelmintic combinations have emerged as a reliable pharmacological strategy to control gastrointestinal nematodes in grazing systems of livestock production. The current work evaluated the potential drug-drug interactions following the coadministration of two macrocyclic lactones (ML) ivermectin (IVM) and abamectin (ABM) to parasitized cattle using a pharmacokinetic/pharmacodynamic (PK/PD) approach. The kinetic behavior of both compounds administered either separately or coadministered was assessed and the therapeutic response of the combination was evaluated under different resistance scenarios. In the pharmacological trial, calves received a single subcutaneous (s.c.) injection of IVM (100 µg/Kg); a single s.c. injection of ABM (100 µg/Kg) or IVM + ABM (50 µg/Kg each) administered in different injection sites to reach a final ML dose of 100 µg/Kg (Farm 1). Plasma samples were taken from those animals up to 20 days post-treatment. IVM and ABM plasma concentrations were quantified by HPLC. A parasitological trial was carried out in three farms with different status of nematodes resistance to IVM. Experimental animals received IVM (200 µg/Kg), ABM (200 µg/Kg) or IVM + ABM (100 µg/Kg each) in Farm 2, and IVM + ABM (200 µg/Kg each) in Farms 3 and 4. The anthelmintic efficacy was determined by fecal egg count reduction test (FECRT). PK analysis showed similar trends for IVM kinetic behavior after coadministration with ABM. Conversely, the ABM elimination half-life was prolonged and the systemic exposure during the elimination phase was increased in the presence of IVM. Although IVM alone failed to control Cooperia spp., the combination IVM + ABM was the only treatment that achieved an efficacy higher than 95% against resistant Cooperia spp. in all farms. In fact, when Cooperia spp. was the main genus within the nematode population and Haemonchus spp. was susceptible or slightly resistant to ML (Farms 2 and 4), the total FECR for the combination IVM + ABM was higher than 90%. Instead, when the predominant nematode genus was a highly resistant Haemonchus spp. (Farm 3), the total FECR after the combined treatment was as low as the single treatments. Therefore, the rational use of these pharmacological tools should be mainly based on the knowledge of the epidemiology and the nematode susceptibility status in each cattle farm.

Impact on beef cattle productivity of infection with anthelmintic-resistant nematodes.

ABSTRACTAims: The main goal of the current study was to evaluate, on a commercial beef cattle farm, the impact of infection with gastrointestinal nematodes resistant to both ivermectin (IVM) and moxidectin (MXD) on the productivity of calves.Methods: Male Aberdeen Angus calves, aged 9-11 months, with faecal nematode egg counts (FEC) ≥200 epg and body weight ≥190 kg, were allocated to two herds. Herd A (n = 90) grazed a maize-winter forage crop rotation and Herd B (n = 90) grazed a 2-year-old Agropyrum pasture. On Day 0 in each herd, calves were randomly allocated into five groups (n = 18), which were treated with 0.2 mg/kg IVM; 0.2 mg/kg MXD; 3.75 mg/kg ricobendazole (RBZ), both IVM and RBZ, or remained untreated. Faecal samples collected on Days -1 and 19 were used to determine the percentage reduction in FEC, and genera of the nematodes were determined by the identification of the third-stage larvae recovered from faecal cultures. Total weight gain was determined from body weights recorded on Days -1 and 91.Results: Overall mean reduction in FEC was 42% for IVM, 67% for MXD, 97% for RBZ and 99% for IVM + RBZ. The reduction in FEC for Cooperia spp. was ≤78% for IVM and MXD, and for Haemonchus spp. was 0 and 36% for IVM and MXD, respectively, confirming the presence of parasites resistant to both anthelmintics. Only IVM + RBZ treatment resulted in 100% efficacy against Haemonchus spp. The overall estimated mean total weight gain for calves treated with IVM was 15.7 (95% CI = 11.9-19.7) kg and for calves treated with IVM + RBZ was 28.8 (95% CI = 25-32.5) kg (p < 0.001). Mean total weight gain for calves treated with MXD was 23.5 (95% CI = 19.7-27.2) kg.Conclusions and clinical relevance: In calves naturally infected with resistant nematodes, under the production system assessed here, weight gains were lower in calves treated with anthelmintics that were moderately or highly ineffective compared to those treated with highly effective anthelmintics. These results demonstrate to farmers and veterinarians the importance of a sustainable and effective nematode control under field conditions.

Pharmaco-parasitological evaluation of the ricobendazole plus levamisole nematodicidal combination in cattle.

The goals of the current study were to evaluate the potential pharmacokinetic (PK) interactions and the clinical efficacy occurring after the subcutaneous (s.c.) administration of ricobendazole (RBZ) and levamisole (LEV) given both separately and co-administered to calves naturally infected with susceptible gastrointestinal nematodes. The clinical efficacy was shown in two seasons, winter and spring, with predominance of different nematode populations. Groups of 15 calves were treated with RBZ alone, LEV alone and RBZ + LEV combination, and an untreated group was kept as a Control. RBZ and LEV plasma concentrations were quantified by HPLC. The clinical efficacy was determined by the faecal egg count reduction test. RBZ and LEV have similar plasma persistence, being detected in plasma over 24 hr post-treatment. No PK interactions were observed after the combined treatment, with similar PK parameters (p > .05) obtained for the single-drug and the combination-based strategy. In winter, the observed clinical efficacies were 96%, 99% and 100% for groups treated with RBZ, LEV and RBZ + LEV, respectively; however, in spring, the efficacies were 95%, 93% and 96% for the same groups. Remarkably, the combination was the only treatment that achieved 100% clinical efficacy against both Haemonchus spp and Ostertagia spp in winter; but the increased presence of Ostertagia spp. in spring (28% in untreated group) determined a tendency to reduced efficacies compared to winter time (only 10% of Ostertagia spp. in untreated group), even for the combined treatment. Overall, in a scenario where the nematode population is susceptible, the RBZ + LEV treatment may be a valid combination in cattle to delay the development of resistance, especially in winter when this combination achieved 100% of efficacy. Thus, selection of anthelmintic resistance will never occur. In fact, this is one of the greatest challenges for the whole cattle production system: to be one step ahead of anthelmintic resistance.

An attempt to replace an ivermectin-resistant Cooperia spp. population by a susceptible one on grazing pastures based on epidemiological principles and refugia management.

The maintenance of anthelmintic-susceptible parasite refugia to delay the onset of anthelmintic resistance is an almost impossible effort in many grazing livestock production countries given that current refugia consist of already resistant parasites. Rather, efforts could be focused on replacing the resistant parasite refugia by susceptible parasite ones and implementing sustainable parasite control measures from then on. To this purpose, a trial was conducted to attempt to establish a new population of ivermectin-susceptible Cooperia sp. on a beef cattle farm with proven problems of ivermectin-resistant Cooperia. During two consecutive years, 82 (Year 1) and 100 (Year 2) recently weaned and parasite-free heifers were inoculated with 40,000 or 30,000 susceptible Cooperia L3, respectively, at a time when levels of resistant parasite refugia were normally low. The animals were subsequently allowed to graze on the problem pastures during autumn until the end of spring. Levels of parasitism in the animals and on pasture were monitored monthly and animals were treated with levamisole when needed. The combination of parasitological monitoring and local epidemiological knowledge was essential to determine when treatments were to be administered. No clinical signs of gastrointestinal parasitosis in the herd were observed throughout the study and unnecessary treatments were avoided. Faecal egg counts reduction tests (FECRT) and controlled efficacy tests (CET) employing worm counts were carried out at different times throughout the study to determine the clinical efficacy (FECRT) and the absolute efficacy (CET) of ivermectin, respectively. The clinical efficacy of ivermectin increased from an initial 73% to 99.4%, while the absolute efficacy increased from 54.1% to 87.5% after just two animal production cycles. The switch from a resistant parasite population to a susceptible one requires knowledge of parasitological epidemiology, especially in relation to seasonal variations of parasite populations in both the host and in refugia.

Chemical probes for water-oxidation: synthetic manganese complexes in photoactivation of water splitting complex and as exogenous electron donors to photosystem II.

Photoactivation of the water splitting enzyme was performed with 13 different synthetic manganese complexes and characterized by oxygen evolution yield, thermoluminescence and chlorophyll fluorescence induction kinetics. The efficiency of different compounds in photoactivation correlated with the rate of linear electron transport in the presence of these compounds. The organic ligands, associated with the manganese ions, do not prevent the photoactivation of the water splitting complex (WOC). Photoactivation with different manganese complexes depended on the number of the Mn-ions in the complex, their valence state and the nature of their donor atoms. The most efficient restorations were achieved by using tetrameric complexes having a dimer+dimer structure, complexes containing Mn(II) ions, and having 4-6 oxygen and 0-2 nitrogen atoms as donor atoms. Further, the effectiveness of photoactivation depended largely on the structure of the complexes. Our data support the notion that WOC in intact thylakoids requires the cooperation and well determined arrangement of all four manganese ions, and argue against the hypothesis that two manganese ions are sufficient for water splitting. Photoactivation by some complexes led to anomalous flash-oxygen patterns, which are explained by a modified/perturbed water splitting complex.

Comparative EPR and thermoluminescence study of anoxic photoinhibition in Photosystem II particles.

Photosystem II particles were exposed to 800 W m(-2) white light at 20 °C under anoxic conditions. The Fo level of fluorescence was considerably enhanced indicating formation of stable-reduced forms of the primary quinone electron acceptor, QA. The Fm level of fluorescence declined only a little. The g=1.9 and g=1.82 EPR forms characteristic of the bicarbonate-bound and bicarbonate-depleted semiquinone-iron complex, QA (-)Fe(2+), respectively, exhibited differential sensitivity against photoinhibition. The large g=1.9 signal was rapidly diminished but the small g=1.82 signal decreased more slowly. The S2-state multiline signal, the oxygen evolution and photooxidation of the high potential form of cytochrome b-559 were inhibited approximately with the same kinetics as the g=1.9 signal. The low potential form of oxidized cytochrome b-559 and Signal IIslow arising from TyrD (+) decreased considerably slower than the g=1.9 semiquinone-iron signal. The high potential form of oxidized cytochrome b-559 was diminished faster than the low potential form. Photoinhibition of the g=1.9 and g=1.82 forms of QA was accompanied with the appearance and gradual saturation of the spin-polarized triplet signal of P 680. The amplitude of the radical signal from photoreducible pheophytin remained constant during the 3 hour illumination period. In the thermoluminescence glow curves of particles the Q band (S2QA (-) charge recombination) was almost completely abolished. To the contrary, the C band (TyrD (+)QA (-) charge recombination) increased a little upon illumination. The EPR and thermoluminescence observations suggest that the Photosystem II reaction centers can be classified into two groups with different susceptibility against photoinhibition.

[Treatment of malignant occlusions of bile ducts by one-step technique using metallic endoprostheses. A multicenter study of 50 cases]. / Trattamento delle occlusioni maligne delle vie biliari mediante endoprotesi metalliche con tecnica "one-step". Studio policentrico di 50 casi.

Long-term patency and ease of insertion of self-expandable metallic stents seem to overcome the disadvantages of plastic stents, changing the therapeutic approach to unresectable biliary tree malignancies. Their high cost is the main problem of metallic stents and reducing hospitalization time is a real opportunity to overcome this problem. Self-expandable stents could be the turning point to reduce overall costs. Fifty patients with malignant biliary tree obstruction (Zubrod performance status < 3) were treated with percutaneous placement of 58 Wallstent endoprostheses by the one-step technique. All patients had undergone thorough diagnostic exams - i.e., US, CT, PTC, ERCP with biopsy or brushing. Two major complications occurred in this series: a iatrogenic pseudoaneurysm requiring selective catheterization and embolization with Gianturco coils and a hepatic abscess six months after stent placement. Late stent occlusion occurred in six patients (12%) and was resolved by balloon dilatations. All patients were followed-up with clinical examinations, US and laboratory tests until death; median survival after stent placement was 122 days (range: 70 to 510 days). Average hospitalization time was 7 days with an acceptable cost reduction.

Participation of the g = 1.9 and g = 1.82 EPR forms of the semiquinone-iron complex, QA-.Fe2+ of photosystem II in the generation of the Q and C thermoluminescence bands, respectively.

Following illumination at 200 K, the charge recombination reactions and the origin of the thermoluminescence (TL) bands appearing at about 0 degree C (Q band) and +50 degrees C (C band) in the glow curve were investigated by comparative TL and EPR measurements in DCMU-treated photosystem II particles. Decay half-time measurements carried out at -25 degrees C and +25 degrees C, respectively, suggest that the S2 state (multi-line signal) undergoes charge recombination with the g = 1.9 form of the semiquinone-iron complex, QA-.Fe2+, resulting in the appearance of the Q band, and that the g = 1.82 form of QA-.Fe2+ back-reacts with the oxidized tyrosine, YD+ (Signal IIs), accounting for the generation of the C band.