A national survey of anthelmintic resistance in ascarid and strongylid nematodes in Australian Thoroughbred horses

This study quantified the extent of anthelmintic resistance (AR) in ascarid and strongylid nematodes against commonly used anthelmintics in Australian Thoroughbred horses. Faecal egg count reduction tests (FECRTs, n = 86) and egg reappearance period (ERP) tests were conducted on 22 farms across Australia. Faecal egg counts (FECs) were determined using the modified McMaster technique, and percent faecal egg count reduction (%FECR) was calculated using the Bayesian hierarchical model and hybrid Frequentist/Bayesian analysis method. The results were interpreted using old (published in 1992) and new (2023) research guidelines of the World Association for the Advancement of Veterinary Parasitology (WAAVP). The species composition of strongylid nematodes was detected utilising a DNA-metabarcoding method using pre- and post-treatment samples. Resistance was observed in strongylid nematodes to commonly used single-active and combination anthelmintics, including ivermectin (IVM %FECR range: 82%-92%; 95% lower credible interval (LCI) range: 80%-90%), abamectin (ABM: 73%-92%; 65%-88%), moxidectin (MOX: 89%-91%; 84%-89%), oxfendazole (OFZ: 0%-56%; 0%-31%) and its combination with pyrantel (OFZ + PYR: 0%-82%; 0%-78%). Resistance in Parascaris spp. was observed to IVM (10%-43%; 0%-36%), ABM (0%; 0%) and MOX (0%; 0%). When the new thresholds recommended by the WAAVP were used, AR was detected in six additional FECRTs for strongylids and three more tests for Parascaris spp., introducing resistance to OFZ and OFZ + PYR in the latter. Shortened ERPs (4-6 weeks) of strongylids were observed in 31 FECRTs in which AR was not detected at 2 weeks post-treatment for all the anthelmintics tested. Among cyathostomins, Cylicocyclus nassatus, Cylicostephanus longibursatus and Coronocyclus coronatus were the most prevalent species at 2 weeks post-treatment, whereas the main species appearing at five weeks following treatments with macrocyclic lactones were Cylicocyclus nassatus, Cylicostephanus longibursatus and Cylicocyclus ashworthi. After treatment with OFZ + PYR, the latter three, plus Coronocyclus coronatus and Cyathostomum catinatum, were detected at 5 weeks post-treatment. Overall, the study highlights the prevalence of AR in both ascarids and strongylid nematodes against commonly used anthelmintic products to control worms in Australian horses. The results indicate that ML combination products provided acceptable efficacy at 2 weeks. However, ERP calculations suggest that products work less effectively than previously measured. It is suggested to regularly monitor the efficacy of the anthelmintics and consider changing the worm control practices to better manage worms and AR in Australian horses.

Worm control practices used by Thoroughbred horse managers in Australia: A national survey

This study assessed worm control practices used by Australian Thoroughbred farm managers with an online questionnaire survey. The questionnaire comprised 52 questions (close-ended: 44; open-ended: 8) about farm demography and general husbandry practices, farm managers' knowledge of gastrointestinal nematodes (GIN) and their importance, diagnosis, worm control strategies and anthelmintics, anthelmintic resistance (AR) and grazing management. Following the pilot survey, the link for the questionnaire survey was sent to all (n = 657) registered members of the Thoroughbred Breeders Australia on 12th April 2020. The response rate for the questionnaire was 18.5% (122 of 675). The farm managers reported a good understanding of GIN and their importance in different age groups of horses as most respondents (70% of 122) perceived worm-related illness to be more important in young (i.e., foals, weanlings and yearlings) than adult (> 3 years old) horses. Although most respondents (93%, 113 of 122) used anthelmintics prophylactically to control GIN, only 15% (18 of 122) observed worm-related illness in their horses. Just under 40% of respondents were performing faecal egg counts, with less than 20% using the results of faecal egg counts to guide deworming decisions. The interval-based deworming strategy was the most common method (≥55% of 122 respondents) to control GIN in all age groups of horses. Macrocyclic lactones were the first choice of anthelmintics for all age groups of horses. Although the majority of respondents (88%, 107 of 122) perceived resistance in GIN against commonly used anthelmintics as an important issue in managing worms in horses, only 29% assessed the efficacy of anthelmintics and 91% (111 of 122) were unaware of AR on their properties. Grazing management practices, such as manure removal, were more frequently performed on smaller paddocks (<0.20 ha: 58%) than on larger paddocks (>0.20 ha: 18%). Multiple correspondence analyses showed that the likelihood of suboptimal worm control practices on small farms (n = ≤50 horses) was greater than that of medium (n = 51-100) and large (n = >100) farms. This study provides insights into the demography of Thoroughbred farms in Australia, husbandry practices used by stud managers and their knowledge about worms, control options and AR concerns, thereby paving the way for taking any initiatives to address the problem of AR in GIN of Australian Thoroughbred horses.

Understanding temporal and spatial distribution of intestinal nematodes of horses using faecal egg counts and DNA metabarcoding

This study reports the spatial and temporal distribution of ascarid and strongylid nematodes in Thoroughbred horses by age category across different climatic zones in Australia over an 18-month period. Faecal samples (n = 2046) from individual horses were analysed using the modified McMaster technique for faecal egg counts (FECs). Strongylids were identified using PCR-directed next-generation sequencing of the second internal transcribed spacer (ITS-2) of the nuclear ribosomal DNA. Yearlings had the highest prevalence (82%) of strongyle eggs followed by weanlings (79%), foals (58%), wet mares (49%) and dry mares (46%). For Parascaris spp., foals had the highest prevalence (35%) followed by weanlings (21%) and yearlings (10%). The highest mean FECs for Parascaris spp. were observed in foals (525 eggs per gram [EPG] of faeces) while those for strongyles were in yearlings (962 EPG). Among horses that were classified as adults at the time of sampling, 77% (860 of 1119) of mares were low (i.e., <250 EPG) strongyle egg-shedders. Mean strongyle FEC counts were highest in the Mediterranean (818 EPG) followed by summer (599 EPG), winter (442 EPG), and non-seasonal (413 EPG) rainfall zones. Twenty-six nematode species were detected, with Cylicostephanus longibursatus (26.5%), Cylicocyclus nassatus (23.7%) and Coronocyclus coronatus (20.5%) being the most frequently detected species. Their richness and relative abundance varied with horse age, season and climatic zone. In addition, Strongylus equinus and Triodontophorus spp. (T. brevicauda and T. serratus) were also detected. This comprehensive study elucidates spatial (climatic zone) and temporal (i.e., seasonal) trends in prevalence and burdens of intestinal nematodes in Australian horses using non-invasive conventional and molecular methods. The information presented in this study is crucial for developing integrated management strategies to control horse parasites in farmed horses.

Assessment of worm control practices recommended by equine veterinarians in Australia

This study aimed to assess Australian veterinarians' knowledge, perceptions and treatment strategies for worm control in horses with an online questionnaire. The questionnaire comprised 64 questions covering various aspects of: (i) veterinary practice; (ii) the veterinarian's knowledge of gastrointestinal nematodes (GINs) and the importance of parasites in different age groups of horses; (iii) the diagnosis and control of worms; (iv) anthelmintics and anthelmintic resistance (AR); (v) grazing management; and (vi) the means of communication and the discussion between veterinarians and their clients regarding worm control. Following a pilot survey, a link for the questionnaire survey was sent to all (n = 1,148) registered members of Equine Veterinarians Australia in April 2020. The response rate for the questionnaire was 10% (118 of 1,148). The findings of this study illustrate veterinarians' good understanding of aspects of equine parasites, including control. However, respondents mainly recommended frequent, interval-based prophylactic deworming in young horses, and only 40% (96 of 239) diagnosed GIN infections based on faecal egg count (FEC) results in all age groups of horses. Furthermore, only 27% (88 of 330) of the respondents made deworming decisions based on FECs. Most of the respondents recommended macrocyclic lactones (MLs) for all age groups of horses (71%, 481 of 677), and the most frequently used method to calculate the dose of anthelmintics was by estimating the weight of animals visually (53%, 63 of 118). Although the majority of respondents (97%, 115 of 118) perceived AR to be a critical issue in managing worms in horses, 58% (67 of 118) of them were unaware of the status of AR on their clients' properties. Forty-two percent (50 of 118) of the respondents perceived the presence of AR in worms, including pinworms (16%), strongylins (15%), species of Draschia and Habronema (6%), Strongyloides westeri (2%) and tapeworms (1%). Twenty-seven percent (32 of 118) of the respondents rarely discussed equine worm control practices with their clients. This study provides insights into the perception and worm control practices recommended by Australian veterinarians to manage equine parasites. The findings highlight the importance of continued education and awareness of AR, and the use of non-chemical methods as well as consideration of the legislation of prescription-only use of anthelmintics based on FECs to achieve sustainable control of GINs in Australian horses.

Prevalence and diversity of ascarid and strongylid nematodes in Australian Thoroughbred horses using next-generation sequencing and bioinformatic tools

The study presents the results of a cross-sectional survey to describe the epidemiology of ascarid and strongylid nematodes in horses, the impact of diverse climatic conditions on parasite diversity and the levels of faecal egg shedding in different age groups of managed Thoroughbred horses. Individual faecal samples (n = 1377) collected from 62 Thoroughbred farms across four climatic zones in Australia were analysed using the modified McMaster technique for faecal egg counts (FECs) and strongylid nematodes were identified utilising PCR-directed next-generation sequencing (NGS) of the second internal transcribed spacer of the nuclear ribosomal DNA (ITS-2). Across all age groups, the prevalence of ascarid and strongylid nematodes was 12% (95% confidence interval 10-14%) and 72% (70-74%), respectively. Based on strongylid FECs, yearlings had the highest prevalence (89%) followed by weanlings (83%), foals (79%), wet mares (61%), dry mares (59%) and stallions (54%). However, for Parascaris spp., foals had the highest prevalence (46%) followed by weanlings (32%) and yearlings (13%). The highest mean FECs for Parascaris spp. were observed in foals (418 eggs per gram [EPG] of faeces) while those for strongylids were in yearlings (1002 EPG). Of the adult horses (mares and stallions), 67% (489 of 729) and 11% (77 of 729) were low (i.e., ≤250 EPG) and moderate (i.e., 251-500 EPG) strongylid egg-shedders, respectively. Strongylid egg shedding varied across climatic zones, with the highest mean FECs in the summer rainfall (723 EPG) followed by non-seasonal rainfall (629 EPG), winter rainfall (613 EPG), and Mediterranean (606 EPG) rainfall zones. Twenty-three nematode species were detected using NGS, with Cylicostephanus longibursatus (28%), Cylicocyclus nassatus (23%) and Coronocyclus coronatus (23%), being the most abundant species. Three species of Strongylus (i.e., S. vulgaris, S. equinus and S. edentatus) were also detected. The nemabiome composition, species richness and relative abundance varied within horse age and between climatic zones. These empirical findings provide a comprehensive understanding of the prevalence of parasites within horse populations and the multifaceted factors that influence their occurrence, thereby allowing for the formulation of tailored strategies aimed at parasite control in domestic horses.

Egg reappearance periods of anthelmintics against equine cyathostomins: The state of play revisited

Cyathostomins are the most common and highly prevalent parasites of horses worldwide. Historically, the control of cyathostomins has mainly relied on the routine use of anthelmintic products. Increasing reports on anthelmintic resistance (AR) in cyathostomins are concerning. A potential method proposed for detecting emerging AR in cyathostomins has been estimating the egg reappearance period (ERP). This paper reviews the data available for the ERP of cyathostomins against the three major classes of anthelmintics, macrocyclic lactones, tetrahydropyrimidines, and benzimidazoles. Published peer-reviewed original research articles were obtained from three databases (PubMed, CAB Direct and Web of Science) and were evaluated for their inclusion in a systematic review. Subsets of articles were then subjected to a review of ERP data. A total of 54 (of 134) studies published between 1972 and 2022 met the criteria for inclusion in the systematic review. Until the beginning of 2022, there was no agreed definition of the ERP; eight definitions of ERP were identified in the literature, complicating the comparison between studies. Additionally, potential risk factors for the shortening of the ERP, including previous anthelmintic use and climate, were frequently not described. Reports of shortened ERP for moxidectin and ivermectin are frequent: 20 studies that used comparable ERP definitions reported shortened moxidectin and ivermectin ERPs of 35 and 28 days, respectively. It is unclear whether the ERPs of these anthelmintics reduced to such levels are due to the development of AR or some biological factors related to horses, cyathostomin species, and/or the environment. The ERPs for other anthelmintics, such as fenbendazole and pyrantel, were frequently not reported due to established resistance against these drugs. Future research in horses is required to understand the mechanism(s) behind the shortening of ERP for cyathostomins. Based on this systematic review, we propose recommendations for future ERP studies.

Cyathostomin resistance to moxidectin and combinations of anthelmintics in Australian horses

Background

Cyathostomins are the most important and common parasitic nematodes of horses, with > 50 species known to occur worldwide. The frequent and indiscriminate use of anthelmintics has resulted in the development of anthelmintic resistance (AR) in horse nematodes. In this study we assessed the efficacy of commonly used anthelmintics against cyathostomins in Australian thoroughbred horses.

Methods

Two drug efficacy trials per farm were conducted on two thoroughbred horse farms in the state of Victoria, Australia. In the first trial, the horses on Farm A were treated with single and combinations of anthelmintics, including oxfendazole (OFZ), abamectin (ABM), abamectin and morantel (ABM + MOR), moxidectin (MOX) and oxfendazole and pyrantel (OFZ + PYR), at the recommended doses, whereas the horses on Farm B only received MOX, at the recommended dose. The faecal egg count reduction test (FECRT) was used to determine the efficacy and egg reappearance period (ERP) of anthelmintics. Based on the results of the first trial, the efficacies of MOX and a combination of ABM + MOR were reassessed to confirm their activities against cyathostomins.

Results

Of the five anthelmintic products tested on Farm A, resistance against OFZ, ABM and OFZ + PYR was found, with efficacies of − 41% (− 195% lower confidence limit [LCL]), 73% (60% LCL) and 82% (66% LCL) at 2 weeks post-treatment, respectively. The FECRT showed high efficacies of MOX and ABM + MOR (100%) at 2 week post-treatment and shortened ERPs for these anthelmintics (ABM + MOR: 4 weeks; MOX: 5 weeks). Resistance to MOX was found on Farm B, with a reduced efficacy of 90% (70% LCL) and 89% (82% LCL) at 2 weeks post-treatment in trials one and two, respectively.

Conclusions

This study provides the first evidence of MOX- and multidrug-resistant (ABM and combinations of anthelmintics) cyathostomins in Australia and indicates the need for continuous surveillance of the efficacy of currently effective anthelmintics and large-scale investigations to assess the ERP for various anthelmintics.

Graphical Abstract

Comparisons of PNEC derivation logic flows under example regulatory schemes and implications for ecoTTC

Derivation of Predicted No Effect Concentrations (PNECs) for aquatic systems is the primary deterministic form of hazard extrapolation used in environmental risk assessment. Depending on the data availability, different regulatory jurisdictions apply application factors (AFs) to the most sensitive measured endpoint to derive the PNEC for a chemical. To assess differences in estimated PNEC values, two PNEC determination methodologies were applied to a curated public database using the EnviroTox Platform (www.EnviroToxdatabase.org). PNECs were derived for 3647 compounds using derivation procedures based on example US EPA and a modified European Union chemical registration procedure to allow for comparisons. Ranked probability distributions of PNEC values were developed and 5th percentile values were calculated for the entire dataset and scenarios where full acute or full chronic data sets were available. The lowest PNEC values indicated categorization based on chemical attributes and modes of action would lead to improved extrapolations. Full acute or chronic datasets gave measurably higher 5th percentile PNEC values. Algae were under-represented in available ecotoxicity data but drove PNECs disproportionately. Including algal inhibition studies will be important in understanding chemical hazards. The PNEC derivation logic flows are embedded in the EnviroTox Platform providing transparent and consistent PNEC derivations and PNEC distribution calculations.

Comparative studies on faecal egg counting techniques used for the detection of gastrointestinal parasites of equines: A systematic review

Faecal egg counting techniques (FECT) form the cornerstone for the detection of gastrointestinal parasites in equines. For this purpose, several flotation, centrifugation, image- and artificial intelligence-based techniques are used, with varying levels of performance. This review aimed to critically appraise the literature on the assessment and comparison of various coprological techniques and/or modifications of these techniques used for equines and to identify the knowledge gaps and future research directions. We searched three databases for published scientific studies on the assessment and comparison of FECT in equines and included 27 studies in the final synthesis. Overall, the performance parameters of McMaster (81.5%), Mini-FLOTAC® (33.3%) and simple flotation (25.5%) techniques were assessed in most of the studies, with 77.8% of them comparing the performance of at least two or three methods. The detection of strongyle, Parascaris spp. and cestode eggs was assessed for various FECT in 70.4%, 18.5% and 18.5% studies, respectively. A sugar-based flotation solution with a specific gravity of ≥1.2 was found to be the optimal flotation solution for parasitic eggs in the majority of FECT. No uniform or standardised protocol was followed for the comparison of various FECT, and the tested sample size (i.e. equine population and faecal samples) also varied substantially across all studies. To the best of our knowledge, this is the first systematic review to evaluate studies on the comparison of FECT in equines and it highlights important knowledge gaps in the evaluation and comparison of such techniques.

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An assessment of studies on the comparison of faecal egg counting in equine parasitology was undertaken.

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A consensus on the methodology and performance parameters for faecal egg counting techniques is required.

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Technical and biological sources of variability in faecal egg counts should be considered.

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Minimum analytical and diagnostic performance parameters should be assessed.

Systematic review of gastrointestinal nematodes of horses from Australia

Background

Equine gastrointestinal nematodes (GINs) have been the subject of intermittent studies in Australia over the past few decades. However, comprehensive information on the epidemiology of equine GINs, the efficacy of available anthelmintic drugs and the prevalence of anthelmintic resistance (AR) in Australasia is lacking. Herein, we have systematically reviewed existing knowledge on the horse GINs recorded in Australia, and main aspects of their pathogeneses, epidemiology, diagnoses, treatment and control.

Methods

Six electronic databases were searched for publications on GINs of Australian horses that met our inclusion criteria for the systematic review. Subsets of publications were subjected to review epidemiology, diagnoses, pathogeneses, treatment and control of GINs of horses from Australia.

Results

A total of 51 articles published between 1950 to 2018 were included. The main GINs reported in Australian horses were cyathostomins (at least 28 species), Draschia megastoma, Habronema muscae, H. majus, Oxyuris equi, Parascaris equorum, Strongyloides westeri and Trichostrongylus axei across different climatic regions of Queensland, New South Wales, Victoria, and Western Australia. Nematodes are diagnosed based on the traditional McMaster egg counting technique, though molecular markers to characterise common GINs of equines were characterised in 1990s. The use of anthelmintic drugs remains the most widely-used strategy for controlling equine GIN parasites in Australia; however, the threshold of faecal egg count that should trigger treatment in horses, remains controversial. Furthermore, anthelmintic resistance within GIN population of horses is becoming a common problem in Australia.

Conclusions

Although GINs infecting Australian horses have been the subject of occasional studies over the past few decades, the effective control of GIN infections is hampered by a generalised lack of knowledge in various disciplines of equine parasitology. Therefore, coordinated and focused research is required to fill our knowledge gaps in these areas to maximise equine health and minimise economic losses associated with the parasitic infections in Australia.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3445-4) contains supplementary material, which is available to authorized users.

Mode of Action (MOA) Assignment Classifications for Ecotoxicology: An Evaluation of Approaches

The mode of toxic action (MOA) is recognized as a key determinant of chemical toxicity and as an alternative to chemical class-based predictive toxicity modeling. However, MOA classification has never been standardized in ecotoxicology, and a comprehensive comparison of classification tools and approaches has never been reported. Here we critically evaluate three MOA classification methodologies using an aquatic toxicity data set of 3448 chemicals, compare the approaches, and assess utility and limitations in screening and early tier assessments. The comparisons focused on three commonly used tools: Verhaar prediction of toxicity MOA, the U.S. Environmental Protection Agency (EPA) ASsessment Tool for Evaluating Risk (ASTER) QSAR (quantitative structure activity relationship) application, and the EPA Mode of Action and Toxicity (MOAtox) database. Of the 3448 MOAs predicted using the Verhaar scheme, 1165 were classified by ASTER, and 802 were available in MOAtox. Of the subset of 432 chemicals with MOA assignments for each of the three schemes, 42% had complete concordance in MOA classification, and there was no agreement for 7% of the chemicals. The research shows the potential for large differences in MOA classification between the five broad groups of the Verhaar scheme and the more mechanism-based assignments of ASTER and MOAtox. Harmonization of classification schemes is needed to use MOA classification in chemical hazard and risk assessment more broadly.

Altering student responses through changes in teacher verbal behavior

Two experiments were conducted in a junior-high special-education class of eight pupils in an inner-city school. In the first experiment, the teacher doubled the number of words used by the pupils in answering questions by altering the type of questions asked. In the second experiment, the number of words used by students and the percentage of answers given in complete sentences, increased from less than 5% to approximately 90% when the teacher instructed the pupils to answer in complete sentences and asked another pupil to answer using a sentence if the first one did not do so. In both experiments, a brief return to baseline conditions brought a return to low levels of verbal responding. An analysis of which pupils were called on by the teacher, teacher praise, and in the second experiment the types of questions asked, indicated that these variables were not responsible for the increases in verbal responding.

Pre-operative embolisation of metastatic paraganglioma of the thoracic spine

We report a 46-year-old male with metastatic functioning paraganglioma of the thoracic spine. Thoracic spine functioning paragangliomas are rare and we describe the benefits of embolisation of the lesion prior to surgical decompression.

Severe persistent sciatic pain and weakness due to a gluteal artery pseudoaneurysm as a complication of bone marrow biopsy

Complications of bone marrow trephine are thought to be uncommon. Herein, we present a case of severe debilitating sciatic nerve palsy secondary to a gluteal artery pseudoaneurysm following bone marrow biopsy. The pseudoaneurysm was treated successfully by percutaneous embolization; however, the patient remains significantly impaired with persistent painless foot drop.

High biochemical selectivity of tadalafil, sildenafil and vardenafil for human phosphodiesterase 5A1 (PDE5) over PDE11A4 suggests the absence of PDE11A4 cross-reaction in patients

The physiological role of phosphodiesterase (PDE)11 is unknown and its biochemical characteristics are poorly understood. We have expressed human His-tagged PDE11A4 and purified the enzyme to apparent homogeneity. PDE11A4 displays K(m) values of 0.97 microM for cGMP and 2.4 microM for cAMP, and maximal velocities were 4- to 10-fold higher for cAMP than for cGMP. Given the homology between PDE11 and PDE5, we have compared the biochemical potencies of tadalafil (Cialis, Lilly-ICOS), vardenafil (Levitra, Bayer-GSK), and sildenafil (Viagra, Pfizer Inc.) for PDE11A4 and PDE5A1. PDE5A1/PDE11A4 selectivities are 40-, 9300-, and 1000-fold for tadalafil, vardenafil, and sildenafil, respectively. This suggests that none of these three compounds is likely to crossreact with PDE11A4 in patients.

Structure and function of the gnathosoma of the mange mite, Psoroptes ovis

Mites of the genus Psoroptes (Acari: Psoroptidae) are obligate, non-burrowing, astigmatid ectoparasites of mammals. A detailed understanding of the morphology of the gnathosoma is an important step towards elucidation of the feeding behaviour of this mite and, hence, the pathology of psoroptic mange. Scanning and transmission electron microscopy were used to examine Psoroptes ovis (Hering) (syn. P. cuniculi). The gnathosoma is composed of an infracapitulum (hypostome), which forms the floor of an extended U-shaped pre-oral trough, bounded by laterally compressed palps and enclosing paired chelicerae. Distally, each palp terminates in a flap-like process and four tapered terminal sensillae. The floor of the infracapitulum is interrupted along its length by a dorsally projecting ridge. At the distal end of the infracapitulum are paired, grooved pseudorutellae and, between them, paired, ungrooved lateral lips. Between the lateral lips is a grooved, elongate labium. Medially, a pair of finger-like projections emanates from the paraxial walls of the palps and project anteriorly. Each chelicera is made up of fixed and mobile digits, with a cheliceral membranous fold articulating the two. The distal ends of both digits are chelated. For much of its length, the mobile cheliceral digit appears to lie within a fold formed by the infracapitular ridge, thereby creating a central channel between the chelicerae. It is suggested that this arrangement of elements may facilitate a two-way flow of liquid, where saliva flows down a central salivary canal and spills out onto the host's skin over the labium at the point where the chelated tips of the chelicerae meet and abrade the skin. Liquid food may move along the grooves of the pseudorutellae and then be sucked up a food canal formed by the paraxial walls of the palps and the outer wall of the chelicerae.

Non-neoplastic demyelinating process mimicking a disseminated malignant brain tumour

Non-neoplastic demyelinating processes of the brain with ring enhancing lesions and mass effect on MRI imaging, mimicking malignant brain tumours, are rare phenomena. We document the case of a 32 year old male with clinical, radiological and initial histological findings, suggestive of a malignant brain tumour. Additional investigations confirmed the diagnosis of multiple sclerosis. This case is significant as the lesion could not be easily distinguished from a malignant brain tumour on imaging alone. Cases such as this illustrate the importance of considering a demyelinating process in the differential diagnosis of tumour-like brain lesions.

Methylphenidate sensitization is modulated by valproate

Repeated administration of the stimulant methylphenidate (MPD) produces sensitization to its own effects. Glutamate, dopamine, and GABA have been implicated in the underlying mechanism of sensitization to stimulants such as amphetamine and cocaine. We have investigated effects of the GABAergic agent sodium valproate (VAL) on the locomotor response to MPD. Activities of male Sprague-Dawley rats were continuously recorded by a computerized activity monitoring system for 15 days. We studied the dose effect of valproate 1) at 50, 100, and 200 mg/kg (i.p.) on motor activities, 2) on the acute response of motor activities to 2.5 mg/kg MPD, and 3) on behavioral sensitization to subsequent repeated injections of MPD. Valproate alone did not significantly affect motor activities. All three doses of valproate attenuated the acute locomotor effects of MPD, while only the 50 mg/kg dose blocked the development of sensitization to subsequent administration. Possible mechanisms involving substrates for the effect of GABA agonists on sensitization are discussed.

Valproate prevents the induction of sensitization to methylphenidate (ritalin) in rats

Repetitive exposure to methylphenidate (MPD) elicits sensitization to its locomotor effects. Drugs that affect the GABA system may modify adaptations to drug exposure. Therefore, we have examined the effect of sodium valproate, which enhances GABA function, on the development of sensitization to MPD using an automated, computerized animal activity monitoring system to record each rat's motor activities for 15 consecutive days. Rats were recorded before and after saline injection (Days 1-2) to provide baseline activity. Animals were then randomly assigned to the following three groups that received: (1) 2.5 mg/kg MPD (s.c.) for six consecutive days (Days 3-8), (2) a single dose of valproate (50 mg/kg; i.p.) 1 h prior to the first (Day 3) of six daily doses of MPD (2.5 mg/kg; s.c. ), or (3) five daily doses of valproate (50 mg/kg, i.p.) 1 h prior to MPD (2.5 mg/kg, s.c.) on Days 4-8. There was no drug treatment during the next 5 days (Days 9-13). All rats were then re-challenged with MPD (2.5 mg/kg, s.c.) on Day 14. Group 2 rats were also re-challenged with 50 mg/kg valproate followed by 2.5 mg/kg MPD 1 h later on Day 15. Administration of MPD alone produced a sensitized response. Multiple valproate injections prevented the induction of MPD-elicited sensitization in all four motor indices, while a single valproate injection prevented the induction of MPD-elicited sensitization in two of four motor indices studied. In conclusion, a single injection 50 mg/kg valproate given prior to any MPD treatment partially blocked the induction of MPD sensitization while repeated injections of valproate co-administered with MPD treatment completely prevented this effect.

Valproate modulates the expression of methylphenidate (ritalin) sensitization

Repeated administration of amphetamine, cocaine, and methylphenidate (MPD) has been reported to elicit behavioral sensitization to their locomotor and stereotypic effects in rodents. GABAergic drugs have been shown to inhibit behavioral effects of stimulants. The objective of the present study was to determine whether single or multiple administration of sodium valproate, a GABA agonist, would prevent the expression of sensitization to the locomotor effect of MPD once it has developed. Twenty-eight male Sprague-Dawley rats were randomized into three treatment groups: a control group received only 2.5 mg/kg MPD during the 14-day cycle, a group received a single 50 mg/kg valproate injection on Day 9, and a group received multiple 50 mg/kg valproate injection on Days 9-13. Rats were housed in test cages and behavioral activities were recorded for 14 consecutive days. All injections were given between 12:00 h and 14:00 h. Multiple injection of MPD elicited sensitization to its locomotor and stereotypic effects. Single administration of valproate did not block the expression of sensitization in the four locomotor indices measured. However, multiple administration of valproate prevented MPD sensitization to horizontal activity, total distance and number of stereotypic movements.

Phosphorylation of phosphodiesterase-5 by cyclic nucleotide-dependent protein kinase alters its catalytic and allosteric cGMP-binding activities

In addition to its cGMP-selective catalytic site, cGMP-binding cGMP-specific phosphodiesterase (PDE5) contains two allosteric cGMP-binding sites and at least one phosphorylation site (Ser92) on each subunit [Thomas, M.K., Francis, S.H. & Corbin, J.D. (1990) J. Biol. Chem. 265, 14971-14978]. In the present study, prior incubation of recombinant bovine PDE5 with a phosphorylation reaction mixture [cGMP-dependent protein kinase (PKG) or catalytic subunit of cAMP-dependent protein kinase (PKA), MgATP, cGMP, 3-isobutyl-1-methylxanthine], shown earlier to produce Ser92 phosphorylation, caused a 50-70% increase in enzyme activity and also increased the affinity of cGMP binding to the allosteric cGMP-binding sites. Both effects were associated with increases in its phosphate content up to 0.6 mol per PDE5 subunit. Omission of any one of the preincubation components caused loss of stimulation of catalytic activity. Addition of the phosphorylation reaction mixture to a crude bovine lung extract, which contains PDE5, also produced a significant increase in cGMP PDE catalytic activity. The increase in recombinant PDE5 catalytic activity brought about by phosphorylation was time-dependent and was obtained with 0.2-0.5 microM PKG subunit, which is approximately the cellular level of this enzyme in vascular smooth muscle. Significantly greater stimulation was observed using cGMP substrate concentrations below the Km value for PDE5, although stimulation was also seen at high cGMP concentrations. Considerably higher concentration of the catalytic subunit of PKA than of PKG was required for activation. There was no detectable difference between phosphorylated and unphosphorylated PDE5 in median inhibitory concentration for the PDE5 inhibitors, sildenafil, or zaprinast 3-isobutyl-1-methylxanthine. Phosphorylation reduced the cGMP concentration required for half-maximum binding to the allosteric cGMP-binding sites from 0.13 to 0.03 microM. The mechanism by which phosphorylation of PDE5 by PKG could be involved in physiological negative-feedback regulation of cGMP levels is discussed.

Expression of an active, monomeric catalytic domain of the cGMP-binding cGMP-specific phosphodiesterase (PDE5)

Phosphodiesterases (PDEs) comprise a superfamily of phosphohydrolases that degrade 3',5'-cyclic nucleotides. All known mammalian PDEs are dimeric, but the functional significance of dimerization is unknown. A deletion mutant of cGMP-binding cGMP-specific PDE (PDE5), encoding the 357 carboxyl-terminal amino acids including the catalytic domain, has been generated, expressed, and purified. The K(m) of the catalytic fragment for cGMP (5.5 +/- 0. 51 microM) compares well with those of the native bovine lung PDE5 (5.6 microM) and full-length wild type recombinant PDE5 (2 +/- 0.4 microM). The catalytic fragment and full-length PDE5 have similar IC(50) values for the inhibitors 3-isobutyl-1-methylxanthine (20 microM) and sildenafil (Viagra(TM))(4 nM). Based on measured values for Stokes radius (29 A) and sedimentation coefficient (2.9 S), the PDE5 catalytic fragment has a calculated molecular mass of 35 kDa, which agrees well with that predicted by amino acid content (43.3 kDa) and with that estimated using SDS-polyacrylamide gel electrophoresis (39 kDa). The combined data indicate that the recombinant PDE5 catalytic fragment is monomeric, and retains the essential catalytic features of the dimeric, full-length enzyme. Therefore, the catalytic activity of PDE5 holoenzyme requires neither interaction between the catalytic and regulatory domains nor interactions between subunits of the dimer.

A photoaffinity probe covalently modifies the catalytic site of the cGMP-binding cGMP-specific phosphodiesterase (PDE-5)

The cGMP-binding cGMP-specific phosphodiesterase (PDE-5) contains distinct catalytic and allosteric binding sites, and each is cGMP-specific. Cyclic nucleotide phosphodiesterase inhibitors, such as 3-isobutyl-1-methylxanthine (IBMX), are believed to compete with cyclic nucleotides at the catalytic sites of these enzymes, but the portion of PDE-5 that accounts for interaction of either of these inhibitors of the substrates themselves with the catalytic domain of the enzymes has not been identified. IBMX was derivatized to yield the photoaffinity probe 8([3-125I,-4-azido]-benzyl)-IBMX, which is referred to as 8(125IAB)-IBMX. This probe was incubated with partially purified recombinant bovine PDE-5. After UV irradiation and SDS-PAGE, a single radiolabeled band that coincided with the position of PDE-5 was visualized on the gel, and the photoaffinity labeling of PDE-5 was linear with increasing concentration of the 8(125IAB)-IBMX. Prominent Coomassie blue-stained bands other than PDE-5 were not labeled significantly. The photoaffinity labeling was progressively blocked by cGMP at concentrations higher than 10 microM, whereas cAMP or 5'-GMP exhibited only weak inhibitory effects. Other compounds that are believed to interact with the PDE-5 catalytic site, including IBMX, cIMP, and beta-phenyl-1,N2-etheno-cGMP (PET-cGMP), also inhibited the photoaffinity labeling in a concentration-dependent manner. The IC50 of PET-cGMP for inhibition of photoaffinity labeling was 10 microM, which compared favorably with an IC50 of 5 microM for inhibition of PDE-5 catalytic activity by this compound. It is concluded that the interaction of this photoaffinity probe with PDE-5 is highly specific for the catalytic site over the allosteric binding sites of PDE-5 and could prove useful in studies to map the catalytic site of PDE-5.

Ligand-induced conformational changes in cyclic nucleotide phosphodiesterases and cyclic nucleotide-dependent protein kinases

Three methods have been used to assess the conformational effects associated with ligand binding to two unrelated cyclic nucleotide receptor proteins: the cGMP-binding, cGMP-specific phosphodiesterase (cGB-PDE or PDE5A) and the cGMP-dependent protein kinase (PKG). The methods should be applicable to other proteins and to other types of modification such as phosphorylation. The procedures use either ion-exchange chromatography, size-exclusion chromatography, or native gel electrophoresis of these proteins in the absence and presence of regulatory ligands. Measurements from these respective approaches allow documentation of changes in the quaternary structure, surface electronegativity, and relative compactness (Stokes radius) of the protein molecule. The combined data allow the changes in protein conformation to be quantitated in terms of alterations in the axial ratio or length/width dimension of the molecule. The methods can be applied to partially purified proteins and to proteins that are available in limited quantities. Conformational changes due to stable modifications of proteins can be potentially examined in crude extracts of intact cells. Each of the methods can be tailored to optimize resolution of a particular protein under a variety of conditions. Activity measurements, Coomassie brilliant blue or silver staining of gels, radioautography, or Western blot analysis can be used for detection of the protein.

Nontarget Herbicide Losses from Application of Granular Ronstar to Container Nurseries

With empty containers, nontarget herbicide loss was 23 percent when the containers were spaced container to container. Spacing the containers on 20 (8 in) and 30 cm (12 in) centers resulted in nontarget losses of 51 and 80 percent loss respectively. Nontarget losses were similar when a dense canopy plant (Rhododendron × ‘Trouper’) and an open canopy plant (Berberis thunbergii ‘Crimson Pygmy’) were spaced container to container or on 20 (8 in) or 30 cm (12 in) spacings.

A comparison of injectable anesthetic combinations in horses

Six combinations of injectable anesthetic agents were administered to six adult horses in a Latin square design. The drug combinations were xylazine-ketamine, xylazine-butorphanol-ketamine, xylazine-tiletamine-zolazepam, xylazine-butorphanol-tiletamine-zolazepam, detomidine-ketamine, and detomidine-butorphanol-ketamine. Measured variables were heart rate, respiratory rate, systolic blood pressure, arterial pH (pHa), PaCO2, PaO2, recumbency time, and number of attempts necessary to stand. Quality of induction and recovery, muscle relaxation, and response to stimulus were evaluated subjectively. The horses required significantly more attempts to stand after administration of xylazine-tiletamine-zolazepam, xylazine-butorphanol-tiletamine-zolazepam, and detomidine-ketamine than after xylazine-ketamine, xylazine-butorphanol-ketamine, or detomidine-butorphanol-ketamine. Mean recumbency times varied from 23.0 minutes with xylazine-ketamine to 41.3 minutes with xylazine-butorphanol-tiletamine-zolazepam. There were significant differences in mean heart rates at minute 15, mean respiratory rates at minutes 5, 10 and 15, and mean systolic blood pressures at minute 10 of anesthesia. There were no significant differences in pHa, PaCO2 or PaO2.

Breastfeeding studies: culture, biomedicine, and methodology

The research and literature focusing on aspects of human lactation and infant feeding are dominated by a biomedical orientation. This paper posits that such a manner of delimiting the data to be acquired and analysed represents a peculiarly Western mode of thought. An overview and classification of the types of cultural studies on human lactation and infant feeding confirms the domination of a biomedical approach to the subject and allows the identification of areas which have received little attention. Thus many English language cultural studies of breastfeeding by employing this same methodology against different cultural backdrops offer little or no fresh knowledge or insight into that culture's view of breastfeeding.