The rapid and accurate determination of germ tube emergence site by Blumeria graminis conidia

The development of appressoria by germinating Blumeria graminis conidia depends on its germ tubes making contact with the host surface. Low angle, low temperature scanning electron microscopy showed that 80% or more of first-formed germ tubes of f. spp. hordei, tritici and avenae conidia emerged from close to the host leaf surface, and so made contact with it allowing them to become functional primary germ tubes. Light microscopy of f. sp.hordei confirmed this result and, in addition, showed that germ tubes frequently emerged close to, and contacted, various hydrophobic and hydrophilic artificial substrata. Geometric models of conidium-substratum interfaces were developed and a “surface point method” was derived to predict the frequency with which contact would result if germ tube emergence was a random phenomenon. However, observed contact frequencies were far higher (c. three to eight times) than predicted. Thus, the germ tube emergence site was determined as a response to substratum contact. In part, this appeared to be a non-specific response. Nevertheless, germ tube contact frequencies were greater on the curved surface of leaf epidermal cells than on planar surface, suggesting that specific recognition of leaf surface characteristics may promote directional emergence. The area of contact required to stimulate directional germ tube emergence was very small: contact with a microneedle tip or with a spiders’ suspension thread was sufficient for many conidia. Similarly, on leaves, the only contact is between the tips of a limited number of conidial wall projections and the edges of epicuticular leaf wax plates. Micromanipulation to roll conidia so that their original site of contact with a leaf was rotated away from it, led to the majority of first-formed germ tubes growing away from the leaf, i.e. emerging close to the site of original contact. The experiments indicated that the site of germ tube emergence is determined within 1 min of deposition. This implicated the release of conidial extracellular materials in recognition of the conidium-leaf surface contact site.     

Veterinary e-CPD: a new model for providing online continuing professional development for the veterinary profession

Continuing professional development (CPD) is widely recognized as an important element in effective lifelong learning for veterinary surgeons. Traditional methods of CPD do not suit all learners, as issues such as location, time, cost, and structure sometimes prevent individuals from completing the required number of CPD study hours per year. The rapid development of the Internet, and with it the increasing scope and sophistication of e-learning, provides new opportunities to address some of these constraints on the provision of CPD. This article describes one way in which e-learning has been deployed effectively to support veterinary surgeons in practice. Since 2003, a series of six-week e-CPD courses has been offered by the Royal Veterinary College (RVC) in an online format, with no face-to-face teaching component. Participants enrolled in courses from May 2006 to January 2007 were found to come from 23 different countries. Analysis of feedback forms indicates a general satisfaction with this new way of studying, with a significant majority of participants stating that they would wish to use this approach again in future. The feedback indicates that e-learning can offer an effective alternative to traditional face-to-face courses and that its popularity is likely to grow in future as veterinarians become increasing familiar with and confident about working online.     

Experimental evaluation of ophthalmic devices and solutions using rabbit models

OBJECTIVE: To analyze and compare the geometry of the anterior segment of rabbit and human eyes, with relevance for the evaluation of intraocular lenses, and to review rabbit models used in our laboratory for the evaluation of different ophthalmic devices and solutions. PROCEDURES: Fifteen rabbit and 15 human eyes (10 phakic and 5 pseudophakic/group) obtained postmortem were used. Anterior-posterior length, equatorial diameter, and white-to-white (corneal diameter) were measured with calipers. The eyes were then analyzed with a very high-frequency ultrasound (Artemis, Ultralink) for measurements of the anterior chamber depth, and anterior chamber and ciliary sulcus diameters. The capsular bag diameter was measured with calipers from a posterior view, and the diameter and thickness of the crystalline lenses were measured after their excision from the phakic eyes. RESULTS: Although the size of the rabbit eye is overall smaller than the size of the human eye, the dimensions of the anterior segment of rabbit eyes are generally larger. The differences between rabbit and human eyes were statistically significant (Wilcoxon rank sum test) in terms of anterior-posterior length, equatorial diameter, white-to-white measurements (P < 0.0001), anterior chamber diameter (P = 0.0004), ciliary sulcus diameter (P = 0.0012), and crystalline lens diameter and thickness (P = 0.0003). CONCLUSIONS: Experimental evaluation of design features of new phakic intraocular lenses in rabbit eyes may be inconclusive without adaptation of their size/design, contrary to the evaluation of new pseudophakic lenses by implantation in the capsular bag. The rabbit is a very valuable model for the experimental evaluation of different ophthalmic devices and solutions.     

The influence of temperature and age on the T1 relaxation time of the equine distal limb

The extent of fat suppression using short tau inversion recovery (STIR) imaging is variable between horses. Our aim was to determine if patient's age and/or hoof temperature have an influence on the T(1) relaxation time of bone marrow in the equine distal limb, thereby affecting the suppression of fat signal. Magnetic resonance imaging was conducted on standing horses and cadaver samples using a low-field magnet (0.27 T). The hoof temperature was measured at the lateral side of the coronary band. A modified inversion recovery fast spin-echo (IR-FSE) sequence was used to measure the signal intensity for a range of inversion times (TIs) at six different regions of interest (ROI): (1) distal aspect of the proximal phalanx, (2) proximal aspect of the middle phalanx, (3) distal aspect of the middle phalanx, (4) navicular bone, (5) proximal aspect of the distal phalanx, and (6) distal aspect of the distal phalanx. The T(1) of the bone marrow in the equine distal limb was calculated from the results and was found to increase by 3.13 ± 0.08 (SE) ms/°C. There was no significant effect of age (2-16 years) but the T(1) values measured from the limbs of young (< 1 year) animals were considerably longer (32.6 ± 1.7 (SE) ms). Similar effects of temperature and age were found for all measured ROIs but there were significant differences in the mean values of T(1) , ranging from +7.7 (distal aspect of the distal phalanx) to -13.2 ms (distal aspect of the proximal phalanx).     

A B-cell targeting virus disrupts potentially protective genomic methylation patterns in lymphoid tissue by increasing global 5-hydroxymethylcytosine levels

The mechanisms by which viruses modulate the immune system include changes in host genomic methylation. 5-hydroxymethylcytosine (5hmC) is the catalytic product of the Tet (Ten-11 translocation) family of enzymes and may serve as an intermediate of DNA demethylation. Recent reports suggest that 5hmC may confer consequences on cellular events including the pathogenesis of disease; in order to explore this possibility further we investigated both 5-methylcytosine (5mC) and 5hmC levels in healthy and diseased chicken bursas of Fabricius. We discovered that embryonic B-cells have high 5mC content while 5hmC decreases during bursa development. We propose that a high 5mC level protects from the mutagenic activity of the B-cell antibody diversifying enzyme activation induced deaminase (AID). In support of this view, AID mRNA increases significantly within the developing bursa from embryonic to post hatch stages while mRNAs that encode Tet family members 1 and 2 reduce over the same period. Moreover, our data revealed that infectious bursal disease virus (IBDV) disrupts this genomic methylation pattern causing a global increase in 5hmC levels in a mechanism that may involve increased Tet 1 and 2 mRNAs. To our knowledge this is the first time that a viral infection has been observed to cause global increases in genomic 5hmC within infected host tissues, underlining a mechanism that may involve the induction of B-cell genomic instability and cell death to facilitate viral egress.     

Diffusion weighted magnetic resonance imaging is a feasible method for characterizing regional lymph nodes in canine patients with head and neck disease

In dogs diagnosed with solid tumors, regional lymph node involvement or evidence of distant metastasis can predict worse prognoses and significantly decreased survival. Lymph node size alone has been shown to be insufficient as a predictor for the accurate clinical staging of some canine neoplasia. However, certain regional lymph nodes (including those of the oral cavity) are difficult to access for routine tissue sampling. Diffusion weighted magnetic resonance imaging (MRI) has demonstrated the ability to differentiate metastatic from inflammatory/benign lymph nodes in clinical studies with human cancer patients through the calculation of quantitative values of diffusion termed apparent diffusion coefficients (ADC). The objective of this prospective, exploratory study was to evaluate diffusion‐weighted MRI and ADC as potential methods for detecting metastatic lymph nodes in dogs with naturally occurring disease. We hypothesized that diffusion‐weighted MRI would identify significantly different ADC values between benign and metastatic lymph nodes in a group of canine patients with head or neck disease. Our study population consisted of eight client‐owned canine patients, with a total of 20 lymph nodes evaluated (six metastatic, 14 benign). Our results demonstrated that two of four observers identified a significant difference between the mean ADC values of the benign and metastatic lymph nodes. When data from all four observers were pooled, the difference between the mean apparent diffusion coefficients values of the benign and metastatic lymph nodes did not reach significance (P‐value = 0.0566). Findings indicated that diffusion‐weighted MRI is a feasible method for further characterizing enlarged lymph nodes in dogs with head and neck disease, however measured ADC values did not differ for benign vs. metastatic lymph nodes in this small sample of dogs.     

East Coast fever immunisation field trial in crossbred dairy cattle in Hanang and Handeni districts in northern Tanzania

East Coast fever (ECF) causes considerable mortality and production losses in the Tanzania smallholder dairy sector and limits the introduction of improved dairy breeds in areas where the disease is present. The infection and treatment method (ITM) was adopted by smallholder dairy farms for ECF immunisation in Hanang and Handeni districts of Tanzania. This study recorded incidence rates for ECF and other tick-borne diseases (TBDs) for ECF-immunised and non-immunised cattle between 1997 and 2000. Approximately 80% of smallholder households from both sites (n?=?167) participated in this longitudinal study, with immunisations carried out at the request of the livestock owners. Efficacy of ITM for preventing ECF cases in these crossbred dairy cattle was estimated at 97.6%, while that for preventing ECF deaths was 97.9%. One percent of the cattle developed clinical ECF as a result of immunisation. Since ECF immunisation permits a reduction in acaricide use, an increase in other TBDs is a potential concern. Sixty-three percent of farmers continued to use the same acaricide after immunisation, with 80% of these reducing the frequency of applications. Overall, 78% of farmers increased the acaricide application interval after immunisation beyond that recommended by the manufacturer, resulting in annual savings in the region of USD 4.77 per animal. No statistical difference was observed between the immunised and non-immunised animals in the incidence of non-ECF TBDs. However, immunised animals that succumbed to these diseases showed fewer case fatalities. ITM would therefore appear to be a suitable method for ECF control in Tanzania's smallholder dairy sector.     

Proteomic profiling of plasma-derived small extracellular vesicles: a novel tool for understanding the systemic effects of tick burden in cattle

Cattle ticks pose a significant threat to the health and profitability of cattle herds globally. The investigation of factors leading to natural tick resistance in cattle is directed toward targeted breeding strategies that may combat cattle tick infestation on the genetic level. Exosomes (EXs), small extracellular vesicles (EVs) of 50 to 150 nm diameter, are released from all cell types into biofluids such as blood plasma and milk, have been successfully used in diagnostic and prognostic studies in humans, and can provide essential information regarding the overall health state of animals. Mass spectrometry (MS) is a highly sensitive proteomics application that can be used to identify proteins in a complex mixture and is particularly useful for biomarker development. In this proof of principle study, EXs were isolated from the blood plasma of cattle (Bos taurus) with high (HTR) and low tick resistance (LTR) (n = 3/group). Cattle were classified as HTR or LTR using a tick scoring system, and EXs isolated from the cattle blood plasma using an established protocol. EXs were subjected to MS analysis in data-dependent acquisition mode and protein search performed using Protein Pilot against the B. taurus proteome. A total of 490 unique proteins were identified across all samples. Of these, proteins present in all replicates from each group were selected for further analysis (HTR = 121; LTR = 130). Gene ontology analysis was performed using PANTHER GO online software tool. Proteins unique to HTR and LTR cattle were divided by protein class, of which 50% were associated with immunity/defense in the HTR group, whereas this protein class was not detected in EXs from LTR cattle. Similarly, unique proteins in HTR cattle were associated with B-cell activation, immunoglobins, immune response, and cellular iron ion homeostasis. In LTR cattle, unique exosomal proteins were associated with actin filament binding, purine nucleotide binding, plasma membrane protein complex, and carbohydrate derivative binding. This is the first study to demonstrate that MS analysis of EXs derived from the blood plasma of HTR and LTR cattle can be successfully applied to profile the systemic effects of tick burden.