Defoliation induces root exudation and triggers positive rhizospheric feedbacks in a temperate grassland

The facilitating effect of the exudation of carbon (C) compounds from roots on rhizospheric processes has been shown in controlled experiments; however, it still remains unclear how important this pathway of C from plants to the soil may be in energy and nutrient processes in grazed grasslands under natural conditions. Root exudation may be a particularly important C pathway in grazed grasslands and help promote positive feedbacks between large herbivores and plants. In this study we performed a ¹³C pulse-chase experiment on plots that were clipped or left unclipped in a mesic grassland in Yellowstone National Park. The dominant grass species in the plots was Poa pratensis and it was used to measure the effect of defoliation on root C exudation, the rhizospheric microbial community, and feedbacks on plant nutrient uptake over a time period of 24–72 h. Defoliation stimulated C exudation from roots by 1.5-fold, which concomitantly increased rhizospheric microbial biomass by the same factor. The facilitating effects of defoliation on rhizospheric processes resulted in positive feedback on soil inorganic N pools and leaf N content, which increased by 1.2- and 1.5-fold respectively. Changes in soil inorganic N pools during the experiment indicated that the effect of the C flush on the rhizospheric decomposer community of defoliated plants resulted in a 5-fold increase in rhizospheric daily net N mineralization rate. These findings demonstrate that in a natural grassland community defoliation-induced stimulation of C exudation stimulates rhizospheric N-mineralization which ultimately benefits defoliated plants. The results also indicate the important role that short-term root–rhizospheric microbe interactions play in the C and N processes in grazed grasslands.     

A common fold mediates vertebrate defense and bacterial attack

Proteins containing membrane attack complex/perforin (MACPF) domains play important roles in vertebrate immunity, embryonic development, and neural-cell migration. In vertebrates, the ninth component of complement and perforin form oligomeric pores that lyse bacteria and kill virus-infected cells, respectively. However, the mechanism of MACPF function is unknown. We determined the crystal structure of a bacterial MACPF protein, Plu-MACPF from Photorhabdus luminescens, to 2.0 angstrom resolution. The MACPF domain reveals structural similarity with poreforming cholesterol-dependent cytolysins (CDCs) from Gram-positive bacteria. This suggests that lytic MACPF proteins may use a CDC-like mechanism to form pores and disrupt cell membranes. Sequence similarity between bacterial and vertebrate MACPF domains suggests that the fold of the CDCs, a family of proteins important for bacterial pathogenesis, is probably used by vertebrates for defense against infection.     

Detection of Neospora caninum tachyzoites in cerebrospinal fluid of a dog following prednisone and cyclosporine therapy

Abstract: A 9‐year‐old female spayed Shetland Sheepdog was presented to the Kansas State University Veterinary Medical Teaching Hospital for evaluation following a 3‐week history of left rear limb lameness that had progressed to generalized ataxia. Multifocal or diffuse brain lesions were suspected based on physical examination findings. Cerebrospinal fluid (CSF) contained 52 nucleated cells/μL composed of mixed inflammatory cells. Treatment with prednisone and cyclosporine was initiated based on a presumptive diagnosis of granulomatous meningoencephalitis. Thirteen days later the dog was nonambulatory and mentally obtunded. Repeat CSF analysis revealed 298 nucleated cells/μL with 61% eosinophils. Rare protozoal tachyzoites consistent with Neospora caninum, Toxoplasma gondii, or Sarcocystis spp. were found extracellularly and within macrophages and an eosinophil. Despite cessation of prednisone and cyclosporine therapy and provision of supportive care, the dog died 6 days later. Examination of brain tissue sections revealed multifocally extensive, necrotizing, histiocytic, and lymphoplasmacytic meningoencephalitis with numerous protozoal zoites and cysts. Immunohistochemical analysis of brain tissue using a monoclonal antibody specific for N. caninum confirmed the diagnosis of neosporosis. Similar but less severe lesions were noted in the spinal cord, although organisms were not found. This case emphasizes the value of repeated CSF analysis when therapy is ineffective and the importance of excluding infectious causes of meningoencephalitis before commencement of immunosuppressive therapy.     

Dual ecosystem services of syrphid flies (Diptera: Syrphidae): pollinators and biological control agents

With increasing worldwide pressure on bee pollinator populations and an increase in insecticide resistance amongst pest insects, there is a growing need for diversification of pollinator and pest control systems. Syrphid flies (Diptera: Syrphidae) contribute ecosystem services to agroecosystems through their supporting roles as crop pollinators and predators of pests. Adult syrphids are important pollinators with high floral visitation rates and pollen carrying capacity, while predatory syrphid larvae are natural biological control agents, reducing aphid populations in both field and laboratory conditions. The present challenge is to determine whether syrphid flies have the potential for application as pollinators and in integrated pest management schemes as biological control agents. Currently, there are gaps in research that are hindering the use of syrphids as dual service providers. Such gaps include a lack of knowledge of syrphid floral preferences, the role and viability of adult syrphids as pollinators in natural and agro‐ecological pollinator networks, and the predatory efficiency of larvae in field and glasshouse conditions. By reviewing relevant literature, we demonstrate syrphid flies have the potential to be used as pollinators and biological control agents. © 2020 Society of Chemical Industry     

Cardiopulmonary effects of pleural insufflation with CO2 during two-lung ventilation in dorsally recumbent anesthetized horses

Objective

To record the cardiopulmonary effects of pleural CO₂ positive pressure insufflation in anesthetized horses.

A review of student evaluation of teaching: applications to veterinary medical education

Student evaluation of teaching is ubiquitous to teaching in colleges and universities around the world. Since the implementation of student evaluations in the 1970s in the US, considerable research has been devoted to their appropriate use as a means of judging the effectiveness of teaching. The present article aims to (1) examine the evidence for the reliability, validity, and utility of student ratings; (2) provide seven guidelines for ways to identify effective instruction, given that the purpose of student evaluation is to assess effective teaching; and (3) conclude with recommendations for the integration of student ratings into the continuous evaluation of veterinary medical education.     

Evaluation of Culicoides insignis (Diptera: Ceratopogonidae) as a vector of bluetongue virus.

Based upon epidemiological evidence, Culicoides insignis Lutz is a probable biological vector of bluetongue viruses (BTV) in South Florida, the Caribbean Region and Central America. The vector potential of this species for BTV was evaluated in the laboratory in a series of experiments using insects caught in the field. Although there was great variation in the percentage of flies that fed from any one catch, it was demonstrated that C. insignis became infected after membrane feeding on a mixture of blood and virus. The infection rates ranged from 20 to 62.5%. Following intrathoracic inoculation, BTV replicated to high titres in C. insignis. Such flies were also shown to be capable of transmitting BTV to susceptible sheep and embryonated chicken eggs. This series of experiments provides the first conclusive evidence that C. insignis is a biological vector of bluetongue virus. This is the first proven vector of BTV in the neotropics.     

Effects of meperidine or saline on thermal, mechanical and electrical nociceptive thresholds in cats

ObjectiveTo measure cutaneous electrical nociceptive thresholds in relation to known thermal and mechanical stimulation for nociceptive threshold detection in cats.Study designProspective, blinded, randomized cross-over study with 1-week washout interval.AnimalsEight adult cats [bodyweight 5.1 ± 1.8 kg (mean + SD)].MethodsMechanical nociceptive thresholds were tested using a step-wise manual inflation of a modified blood pressure bladder attached to the cat’s thoracic limb. Thermal nociceptive thresholds were measured by increasing the temperature of a probe placed on the thorax. The electrical nociceptive threshold was tested using an escalating current from a constant current generator passed between electrodes placed on the thoracic region. A positive response (threshold) was recorded when cats displayed any or all of the following behaviors: leg shake, head turn, avoidance, or vocalization. Four baseline readings were performed before intramuscular injection of meperidine (5 mg kg⁻¹) or an equal volume of saline. Threshold recordings with each modality were made at 15, 30, 45, 60, 90, and 120 minutes post-injection. Data were analyzed using anova and paired t-tests (significance at p < 0.05).ResultsThere were no significant changes in thermal, mechanical, or electrical thresholds after saline. Thermal thresholds increased at 15–60 minutes (p < 0.01) and mechanical threshold increased at 30 and 45 minutes after meperidine (p < 0.05). Maximum thermal threshold was +4.1 ± 0.3 °C above baseline at 15 minutes while maximum mechanical threshold was 296 ± 265 mmHg above baseline at 30 minutes after meperidine. Electrical thresholds following meperidine were not significantly different than baseline (p > 0.05). Thermal and electrical thresholds after meperidine were significantly higher than saline at 30 and 45 minutes (p < 0.05), and at 120 minutes (p < 0.05), respectively. Mechanical thresholds were significantly higher than saline treatment at 30 minutes (p ≤ 0.05).Conclusion and clinical relevanceElectrical stimulation did not detect meperidine analgesia whereas both thermal and mechanical thresholds changed after meperidine administration in cats.