Interaction of tralomethrin,tralocythrin, and related pyrethroids in Na+ channels of insect and mammalian neuronal cells

The neurotoxic activity of the tetrahalogenated pyrethroids, tralomethrin and tralocythrin, which are dibromo adducts of deltamethrin and RU 24501, respectively, and RU 27218, which is a dichloro adduct of RU 24501, have been studied on two different excitable membranes using in vitro methods: insect axonal membranes and mammalian neuroblastoma cells in culture. The results show that molecules whose chrysanthemic acid chain at C₃ is saturated by halogen addition have intrinsic toxicity on the sodium channels of nerve membranes. They increase the amplitude of negative after-potential, depolarize the cockroach axonal membrane, and stabilize an open conformation of voltage-dependent Na⁺ channels in mouse neuroblastoma cells, thereby producing a massive uptakeof Na⁺ by the cells. All effects were observed in the absence of metabolic transformation of the compounds tested. In light of these experiments, it is concluded that tralomethrin and tralocythrin cannot be considered as propyrethroids.     

Development and evaluation of a real-time quantitative PCR assay for Culicoides imicola, one of the main vectors of bluetongue (BT) and African horse sickness (AHS) in Africa and Europe

The current microscopy method for identifying the Culicoides imicola Kieffer, 1913 species can be time and labour intensive. There is a need for the development of a rapid and quantitative tool to quantify the biting midges C. imicola ss in light trap catches. A reproducible and sensitive real-time polymerase chain reaction method that targets the internal transcribed spacer (ITS-1) of ribosomal DNA of C. imicola ss species was developed. This real-time PCR assay was first performed on 10-fold serial dilutions of purified plasmid DNA containing specific C. imicola ss ITS-1. It was then possible to construct standard curves with a high correlation coefficient (r2=0.99) in the range of 10(-2)-10(-8) ng of purified DNA. The performances of this PCR were evaluated in comparison with morphological determination on Culicoides trapped along the Mediterranean coastal mainland France. ROC statistical analysis was carried out using morphology as gold standard and the area under the ROC curve had a satisfactory value of 0.9752. The results indicated that this real-time PCR assay holds promise for monitoring C. imicola ss population in both surveillance and research programmes because of its good specificity (92%) and sensitivity (95%).     

Effect of intravenous lidocaine on heart rate, systolic arterial blood pressure and cough responses to endotracheal intubation in propofol-anaesthetized dogs

OBJECTIVE: To evaluate the effect of intravenous lidocaine on coughing and variations in heart rate (HR) and systolic arterial pressure (SAP) at endotracheal intubation in propofol-anaesthetized dogs. STUDY DESIGN: Prospective, randomized, blinded clinical study. ANIMALS: Eighty dogs, ASA grades I/II. METHODS: Dogs were randomly assigned to one of two treatments, with dogs in the lidocaine group receiving 1 mg kg(-1) lidocaine intravenously and those in the saline group receiving 0.05 mL kg(-1) saline intravenously before induction of anaesthesia with up to 6.5 mg kg(-1) propofol intravenously. An electrocardiogram was recorded continuously. Heart rate was calculated and SAP (using Doppler ultrasonic flow detection) was recorded at the following time points: pre-treatment, following lidocaine or saline administration, before and after intubation. The occurrence, number and strength of coughs were recorded. Systolic arterial pressure and HR were compared using one-sample t-tests to examine whether SAP and HR changed with test drug administration or following intubation. The number of coughs was compared between groups using t-tests. A cross tabulation and chi-square or Fisher's exact test was used to compare proportions of dogs that coughed and intensity of coughing in each group. The level of significance was set at p < 0.05. RESULTS: Heart rate did not change in either group. Systolic arterial blood pressure increased following intubation in both the lidocaine (p = 0.003) and saline groups (p = 0.001). There was no difference in the increase in SAP or in the number or intensity of coughs at intubation between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Intravenous lidocaine had no effect on the occurrence or intensity of coughing or on changes in SAP at endotracheal intubation in dogs anaesthetized with propofol. The use of 1 mg kg(-1) lidocaine intravenously before intubation in dogs to attenuate cough and the pressor response was not supported.     

Comparison of ultrasonic Doppler flow monitor,oscillometric, and direct arterial blood pressure measurements in ill dogs

Objective – To compare blood pressure measurements obtained via ultrasonic Doppler flow monitor (DOP) and 2 oscillometric noninvasive blood pressure monitors (CAR and PAS) to invasive blood pressure (IBP) in hospitalized, conscious dogs with a range of blood pressures. Design – Prospective clinical study. Setting – University teaching hospital. Animals – Eleven client‐owned dogs aged between 4 months and 11.5 years (median 6 y), and weighing between 5.8 and 37.5 kg (median 30.2 kg). Interventions – Blood pressure measurement. Measurements and Main Results – Three consecutive measurements of systolic, diastolic, and mean arterial pressure (MAP) were recorded for each of the 3 indirect devices (only systolic for DOP), along with concurrent IBP measurements. The data were categorized into 3 groups: hypotensive (direct MAP<80 mm Hg), normotensive (80 mm Hg≤direct MAP≥100 mm Hg), and hypertensive (direct MAP>100 mm Hg). Each indirect method was compared with the corresponding direct arterial pressure using the Bland‐Altman method. Within the hypotensive group, each indirect method overestimated the corresponding IBP. Within the normotensive group all indirect systolic measurements and the PAS diastolic measurements underestimated the corresponding IBP. The remaining indirect measurements overestimated the corresponding IBP. Within the hypertensive group, DOP and CAR systolic measurements underestimated the corresponding IBP, and the remaining indirect measurements overestimated the corresponding IBP. In hypertensive dogs oscillometric systolic measurements were more accurate than MAP. In hypotensive dogs MAP measurements were more accurate than systolic measurements. All indirect measurements were most accurate in hypertensive dogs. Conclusions – The noninvasive blood pressure monitors in our study did not meet the validation standards set in human medicine. However, CAR diastolic and MAP measurements within the normotensive group, CAR MAP measurements within the hypertensive group, and PAS diastolic measurements in all groups were close to these standards. All indirect measurements showed greater bias during hypotension. Precision was poorer for all indirect systolic measurements than for MAP.     

Drivers of density for the exploited giant clam Tridacna maxima: a meta‐analysis

Giant clam populations have been over‐exploited throughout their range over the past decades for their meat and shells. Tridacna maxima, commonly known as the ‘small giant clam’, has remained relatively untargeted by fishers in areas where larger species occur (e.g. Tridacna squamosa), and high densities of the species are still observed on some isolated and enclosed reefs of the Central Pacific. However, it is unclear whether reported discrepancies in densities worldwide reflect differences in fishing pressure only or a combination of differences in exploitation levels and environmental forcing. We reviewed T. maxima surveys throughout its range to (i) identify patterns of density at global scale, site scale (e.g. island) and intrasite scale; (ii) discuss the influence of sampling method on density estimates; and (iii) identify the primary drivers of giant clam density along gradients of human pressure and natural forcing. We found 59 studies that reported density estimates for 172 sites across 26 countries in the Indo‐Pacific and Red Sea. At intrasite scale, densities were strongly dependent on sampling protocols and surveyed habitats. At site scale, we found close links between T. maxima density and human population per reef area, suggesting that isolated reefs where exploitation only recently started may be more vulnerable to stock collapse in the future. Density patterns were also found to vary significantly depending on reef type (e.g. atoll, island, continental coastline). We discuss how natural processes and fishing pressure may control population dynamics and densities among sites, and make recommendations for future research.     

Effectiveness of native West African arbuscular mycorrhizal fungi in protecting vegetable crops against root-knot nematodes

Twenty strains of arbuscular mycorrhizal fungi (AMF), native to West Africa, and three commercial AMF, were evaluated for their protective effect against root-knot nematodes, Meloidogyne spp., in pots and field experiments in Benin. In pots, these strains were assessed in sterilized soil following inoculation of nematodes and in non-sterilized soil naturally infested with nematodes using tomato. The four strains showing greatest potential in suppressing nematode development were further assessed in the field with a relatively high natural infestation level of nematodes (155 per 100 cm³ soil) over a tomato–carrot double cropping. In the pot experiments, most native strains provided significant suppression of nematode multiplication and root galling, but in most cases the level of nematode control depends on either sterilized or non-sterilized soils. In the field experiments, application of AMF mostly resulted in significant suppression of nematode multiplication and root galling damage on both crops indicating that the AMF persists and remains protective against root-knot nematodes over two crop cycles. Field application of AMF increased tomato yields by 26% and carrot yields by over 300% compared with the non-AMF control treatments. This study demonstrates for the first time, the protective effect of indigenous West African AMF against root-knot nematodes on vegetables. The potential benefits of developing non-pesticide AMF-based pest management options for the intensive urban vegetable systems are evident.     

Comparison of different tube materials and use of Chinese finger trap or four friction suture technique for securing gastrostomy, jejunostomy, and thoracostomy tubes in dogs

Objective— To compare Chinese finger trap (CFT) and 4 friction suture (FFS) techniques to secure gastrostomy (GT), jejunostomy (JT), and thoracostomy (TT) tubes of different materials.
Study Design— Prospective experimental study.
Animals— Canine cadavers (n=20).
Methods— Randomly, GT (n=20), JT (20), and TT (20) were inserted using 2 different suture techniques (10 for each tube type) and either silicone or another material (10 for each type). Axial distraction was applied to each tube until failure. Force and displacement to failure and failure mode were recorded and compared between techniques and materials for GT, JT, and TT.
Results— CFT failed most commonly by suture breakage whereas FFS failed mainly by tube slippage ( P =.003). For GT, failure occurred more commonly by tube slippage (n=15; P <.001) whereas tube breakage was more common for JT (n=10; P <.001) and suture breakage for TT (n=14; P =.022). Silicone had higher force to failure than latex with GT, lower force to failure than red rubber with JT, and lower displacement to failure than polyvinylchloride with TT.
Conclusions— Different failure modes occurred for CFT (suture breakage) and FFS (tube slippage) and among different tube types (tube slippage with GT, tube breakage with JT, and suture breakage with TT). Based on study results, CFT is preferred to FFS for anchoring silicone GT and TT. Silicone GT, red rubber JT, and polyvinylchloride TT were more secure than latex GT, silicone JT, and silicone TT, respectively.
Clinical Relevance— CFT should be preferred over FFS based on force and displacement to failure, but tube type and tissue reaction could influence anchoring strength.