Detection of Ureaplasma diversum in the upper airways of Australian feedlot cattle

Bovine respiratory disease (BRD) exerts a major impact on the beef cattle industry nationally and worldwide, with a range of aetiological factors impacting its pathogenesis. Previous research has focussed on an increasing number of bacteria and viruses that have been shown to play a role in eliciting disease. Recently, additional agents have been emerging as potential contributors to BRD, including the opportunistic pathogen Ureaplasma diversum. To determine if U. diversum was present in Australian feedlot cattle and if that presence was linked to BRD, nasal swabs were collected from a cohort of 34 hospital pen animals and compared to 216 apparently healthy animals sampled contemporaneously at feedlot induction and again after 14 days on feed at an Australian feedlot. All samples were subjected to a de novo polymerase chain reaction (PCR) assay targeting U. diversum in combination with other BRD agents. U. diversum was detected at a low prevalence in cattle at induction (Day 0: 6.9%, Day 14: 9.7%), but in a significantly greater proportion of cattle sampled from the hospital pen (58.8%). When considering the presence of other BRD-associated agents, co-detection of U. diversum and Mycoplasma bovis was most common in hospital pen animals receiving treatment for BRD. These findings suggest that U. diversum may be an opportunistic pathogen involved in the aetiology of BRD in Australian feedlot cattle, in combination with other agents, with further studies are warranted to identify if a causal relationship exists.

Efficiency-corrected PCR quantification for identification of prevalence and load of respiratory disease-causing agents in feedlot cattle

Bovine respiratory disease (BRD) is the most prevalent disease in feedlot cattle worldwide with Bovine alphaherpesvirus 1 (BoAHV1), Histophilus somni, Mannheimia haemolytica, Mycoplasma bovis, Pasteurella multocida and Trueperella pyogenes accepted to be common etiological agents associated with BRD. Although these agents are common in the upper and lower airways in clinical BRD cases, some also exist as normal flora suggesting their presence in the upper airways alone is not necessarily informative with respect to disease status or risk. To determine the relationship between presence, load and disease status, we investigated the relationship between load in the upper airways at induction and active BRD cases in feedlot cattle using efficiency-corrected PCR quantification. By this approach, we were able to accurately determine the prevalence and load of the key BRD agents in the upper respiratory tract showing that cattle in the hospital pen had a higher prevalence, and load, of these agents both singly and in combination compared to cattle sampled at feedlot induction. A combination of agents was the most accurate indicator of BRD risk with cattle with four or more agents detected in the upper airway more likely to be undergoing treatment for BRD than non-BRD ailments. In addition, M. bovis was rarely detected at feedlot induction but was identified at high prevalence in cattle in the hospital pen. These findings present a potential new technological approach for the investigation, analysis and identification of BRD-associated viral and bacterial agents for Australian feedlot systems as well as for BRD disease management and treatment.

Producer practices and attitudes: Non-replacement male calf management in the Australian dairy industry

Currently, there is no standardized rearing method or production guidelines for non-replacement male dairy calves that maximizes their economic viability. Producers have highlighted the need to match consumer expectations, but even with broadscale welfare improvement across the dairy industry, challenges remain at providing reliable and valuable pathways for non-replacement male dairy calves for beef production. A key consumer concern has been the use of on-farm euthanasia. Euthanasia has been a catalyst for change in the industry from a human and animal welfare perspective. The practice of euthanasia can lead to a decline in personnel wellbeing. To investigate the relationship between on-farm management practices of non-replacement male dairy calves and producer perceptions of their value proposition, an online questionnaire was provided to Australian dairy producers between June and October 2021. The aim was to identify supply-chain profitability of non-replacement male calves and investigate the attitudes and effects of euthanasia on producer wellbeing as part of managing these calves. A total of 127 useable responses were obtained, and a Bayesian network (BN) was utilized to model the interdependencies between management practices and wellbeing among participants. The results indicated that in general, dairy producers desired high welfare standards in their enterprises with regard to non-replacement male calves as well as expressed a desire to meet industry and consumers' expectations. In line with anecdotal reports of a reduction in practice, euthanasia was not identified as common practice in this group; however, producers were still accessing early-life markets for non-replacement male calves with operational requirements and environmental factors influencing their decisions. Producers expressed dissatisfaction with market access for their calves, as well as the lack of suitability of Australian beef grading standards for dairy-bred carcasses. Australian dairy managers and owners identified that euthanasia influenced employee wellbeing; however, they did not acknowledge euthanasia had an effect on their own wellbeing. Overall, the findings of this study indicate that all non-replacement male calf breeds had the potential to access profitable markets, and avoidance of euthanasia is a strong driver of change among dairy beef production systems in Australia.

Meta-Analysis of qPCR for Bovine Respiratory Disease Based on MIQE Guidelines

Qualitative and quantitative PCR-based tests are widely used in both diagnostics and research to assess the prevalence of disease-causing pathogens in veterinary medicine. The efficacy of these tests, usually measured in terms of sensitivity and specificity, is critical in confirming or excluding a clinical diagnosis. We undertook a meta-analysis to assess the inherent value of published PCR diagnostic approaches used to confirm and quantify bacteria and viruses associated with bovine respiratory disease (BRD) in cattle. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A thorough search of nine electronic databases (Web of Science, EBSCOhost, Cambridge journals online, ProQuest, PubMed, Sage journals online, ScienceDirect, Wiley online library and MEDLINE) was undertaken to find studies that had reported on the use of PCR and/or qPCR for the detection and/or quantification of BRD associated organisms. All studies meeting the inclusion criteria for reporting quantitative PCR for identification of BRD associated microorganisms were included in the analysis. Studies were then assessed on the applications of the Minimum Information for Publication of Quantitative Real-Time PCR Experiment (MIQE) and PCR primer/probe sequences were extracted and tested for in silico specificity using a high level of stringency. Fourteen full-text articles were included in this study. Of these, 79% of the analysed articles did not report the application of the MIQE guidelines in their study. High stringency in silico testing of 144 previously published PCR primer/probe sequences found many to have questionable specificity. This review identified a high occurrence of primer/probe sequences with a variable in silico specificity such that this may have implications for the accuracy of reporting. Although this analysis was only applied to one specific disease state, identification of animals suspected to be suffering from bovine respiratory disease, there appears to be more broadly a need for veterinary diagnostic studies to adopt international best practice for reporting of quantitative PCR diagnostic data to be both accurate and comparable between studies and methodologies.

Relative perceptions of prevalence, impact and importance of photosensitisation in Australian livestock: A survey of veterinarians, livestock traders and livestock producers

AIMS

To investigate the relative differences in the perceptions and awareness of outbreaks of photosensitisation in Australian livestock stakeholders, including veterinarians, livestock traders and producers.

METHODS

A questionnaire was developed and circulated to livestock veterinarians, producers and traders in Australia via email addresses obtained from public access sources. The questionnaire was designed to evaluate participants' awareness and perception of health, welfare, and production issues associated with outbreaks of photosensitisation and towards the incidence and importance of photosensitisation in livestock.

RESULTS

One hundred and twenty-eight online responses were received in total. Nearly half of the respondents (49.0%) indicated they would encounter 1-3 outbreaks annually. The majority of veterinarian and livestock producers stated that outbreaks of photosensitisation were common and economically important, with cattle and sheep being equally considered as susceptible species to this condition, and secondary (hepatogeneous) photosensitisation is the most common type.

CONCLUSION

This survey confirms the anecdotal evidence that photosensitisation in livestock in Australia is commonly encountered by veterinarians and livestock producers. However, there is no industry-wide common acceptance of the issue, broader opinions should be canvassed when considering impacts on stakeholders regarding photosensitisation outbreaks in livestock in Australia or abroad in the future.

Barriers to Utilizing Non-replacement Male Calves in the Australian Dairy Industry: A Qualitative Study

Male non-replacement calves in dairy systems represent an underutilized economic resource for dairy producers worldwide. Despite this, increasing the practice of rearing non-replacement male calves has significant barriers both in on-farm adoption and practice. Poor neonatal rearing practices, higher levels of morbidity and mortality, and disaggregated production pathways with multiple points of handling, have all been described as barriers to adoption of surplus calf production. To identify the critical decision-determining challenges associated with broader adoption of raising non-replacement stock, and to investigate the whole-of-value chain issues faced by dairy producers to rear non-replacement male calves, we undertook a series of semi-structured interviews with Australian dairy producers to interrogate their key challenges. To achieve this, a constructivist grounded theory approach was used to inform the process of analysis of in-depth interviews with Australian dairy producers regarding their current practices and perceptions. Five major themes emerged from these conversations that were key barriers to on-farm non-replacement calf rearing in the producer group participants. These were: impacts of drought on cost and availability of feed for these calves and the whole herd; the management requirements of non-replacement male calves as an additional workload to that of their current operation; their attitudes and current practices to and surrounding euthanasia; perceived ease of supply-chain access for these calves, and their perceptions of the economic value of dairy-beef product as a return on investment. Understanding the barriers to adoption of non-replacement calf rearing, and addressing the value proposition for dairy beef, can assist increased uptake of non-replacement calf rearing. These findings will allow development of strategies to address these barriers, and extension of viable management strategies to increase adoption of profitable business practices surrounding non-replacement male calf production.

Genotypic identification of Panicum spp. in New South Wales, Australia using DNA barcoding

Australia has over 30 Panicum spp. (panic grass) including several non-native species that cause crop and pasture loss and hepatogenous photosensitisation in livestock. It is critical to correctly identify them at the species level to facilitate the development of appropriate management strategies for efficacious control of Panicum grasses in crops, fallows and pastures. Currently, identification of Panicum spp. relies on morphological examination of the reproductive structures, but this approach is only useful for flowering specimens and requires significant taxonomic expertise. To overcome this limitation, we used multi-locus DNA barcoding for the identification of ten selected Panicum spp. found in Australia. With the exception of P. buncei, other native Australian Panicum were genetically separated at the species level and distinguished from non-native species. One nuclear (ITS) and two chloroplast regions (matK and trnL intron-trnF) were identified with varying facility for DNA barcode separation of the Panicum species. Concatenation of sequences from ITS, matK and trnL intron-trnF regions provided clear separation of eight regionally collected species, with a maximum intraspecific distance of 0.22% and minimum interspecific distance of 0.33%. Two of three non-native Panicum species exhibited a smaller genome size compared to native species evaluated, and we speculate that this may be associated with biological advantages impacting invasion of non-native Panicum species in novel locations. We conclude that multi-locus DNA barcoding, in combination with traditional taxonomic identification, provides an accurate and cost-effective adjunctive tool for further distinguishing Panicum spp. at the species level.

Efficiency Correction Is Required for Accurate Quantitative PCR Analysis and Reporting

BACKGROUND

Quantitative PCR (qPCR) aims to measure the DNA or RNA concentration in diagnostic and biological samples based on the quantification cycle (Cq) value observed in the amplification curves. Results of qPCR experiments are regularly calculated as if all assays are 100% efficient or reported as just Cq, ΔCq, or ΔΔCq values.

CONTENTS

When the reaction shows specific amplification, it should be deemed to be positive, regardless of the observed Cq. Because the Cq is highly dependent on amplification efficiency that can vary among targets and samples, accurate calculation of the target quantity and relative gene expression requires that the actual amplification efficiency be taken into account in the analysis and reports. PCR efficiency is frequently derived from standard curves, but this approach is affected by dilution errors and hampered by properties of the standard and the diluent. These factors affect accurate quantification of clinical and biological samples used in diagnostic applications and collected in challenging conditions. PCR efficiencies determined from individual amplification curves avoid these confounders. To obtain unbiased efficiency-corrected results, we recommend absolute quantification with a single undiluted calibrator with a known target concentration and efficiency values derived from the amplification curves of the calibrator and the unknown samples.

SUMMARY

For meaningful diagnostics or biological interpretation, the reported results of qPCR experiments should be efficiency corrected. To avoid ambiguity, the Minimal Information for Publications on Quantitative Real-Time PCR Experiments (MIQE) guidelines checklist should be extended to require the methods that were used (1) to determine the PCR efficiency and (2) to calculate the reported target quantity and relative gene expression value.

Liveweight and carcass characteristics of White Dorper and Crossbred lambs grazing lucerne, subterranean clover, biserrula or a choice of subterranean clover plus biserrula in southern Australia

Context Biserrula (Biserrula pelecinus L.) is a relatively new legume species in Australia that has been shown to maintain higher quality forage late in the season than subterranean clover (Trifolium subterraneum L.). Aim This study investigated the suitability of lucerne (Medicago sativa L.), subterranean clover and biserrula, or a choice of both biserrula and subterranean clover, for finishing White Dorper and White Suffolk × Merino lambs during spring. Methods An experiment was established near Wagga Wagga, NSW, in 2013 in a randomised complete block design with three replicates and four pasture treatments grazed by lambs during late spring and early summer. Liveweight, carcass weight and GR fat depth of White Dorper and White Suffolk × Merino lambs grazing lucerne, subterranean clover, biserrula or a choice of subterranean clover plus biserrula were compared. Key results Lambs grazing lucerne had significantly (P < 0.05) higher final liveweight, carcass weight and GR fat depth than lambs grazing other pasture treatments. After 61 days of grazing, mean liveweight of lambs grazing lucerne, subterranean clover and subterranean clover plus biserrula was higher than of lambs grazing biserrula monoculture. In vitro digestible organic matter digestibility and crude protein content indicated that lambs grazing biserrula should have achieved growth rates at least as high as lambs grazing subterranean clover. Sheep genotype and pasture type affected final liveweight. Final liveweight was higher for White Dorper lambs when grazing the subterranean clover plus biserrula treatment than the subterranean clover monoculture (45.6 vs 44.5 kg; P < 0.05) but was similar for White Suffolk × Merino lambs grazing these treatments (47.3 vs 47.2 kg; P > 0.05). Conclusions Provision of a companion species or mixture of species when lambs graze biserrula during late spring to summer appears to offer benefits for lamb growth rate over this period.

Timed environmental exposure indicates sample stability for reliable noninvasive measurement of fecal cortisol metabolite concentrations in sheep

The use of noninvasive techniques to evaluate stress responses in animals has become an increasingly popular method of animal welfare assessment in both production animals and wildlife. In particular, using fecal samples to measure fecal cortisol metabolites (FCMs) as a quantitative measure has proven ideal as samples can be collected remote to the animal after defecation without the need for invasive procedures. Colorimetric enzyme immunoassays (EIAs) have been shown to have a high level of selectivity and sensitivity for FCM concentration analysis, equivalent to the traditionally used radioimmunoassay. Regardless of the assay system used, species- and sample-specific validation must be undertaken to ensure the reliability of results, particularly where sampling is undertaken in a novel species or where environmental conditions might impact FCM stability in the fecal sample. To determine the limit of environmental exposure acceptable for analysis of FCM concentrations in ovine scat samples collected from a paddock under conditions of stable heat and humidity, this study quantified FCMs in ovine feces shortly after defecation (2-7 h) and after timed environmental exposure (1-9 d). Samples were determined to show stable FCM concentrations for up to 5 d by this analysis. Understanding the impacts of environmental exposure, and therefore the viability of remote fecal collection methods for quantitative analysis of FCM by EIA, is important to assess the utility of noninvasive measures of endocrine status in animals where the exact timing of defecation may not be known.

PGRMC1 effects on metabolism, genomic mutation and CpG methylation imply crucial roles in animal biology and disease

Background

Progesterone receptor membrane component 1 (PGRMC1) is often elevated in cancers, and exists in alternative states of phosphorylation. A motif centered on PGRMC1 Y180 was evolutionarily acquired concurrently with the embryological gastrulation organizer that orchestrates vertebrate tissue differentiation.

Results

Here, we show that mutagenic manipulation of PGRMC1 phosphorylation alters cell metabolism, genomic stability, and CpG methylation. Each of several mutants elicited distinct patterns of genomic CpG methylation. Mutation of S57A/Y180/S181A led to increased net hypermethylation, reminiscent of embryonic stem cells. Pathways enrichment analysis suggested modulation of processes related to animal cell differentiation status and tissue identity, as well as cell cycle control and ATM/ATR DNA damage repair regulation. We detected different genomic mutation rates in culture.

Conclusions

A companion manuscript shows that these cell states dramatically affect protein abundances, cell and mitochondrial morphology, and glycolytic metabolism. We propose that PGRMC1 phosphorylation status modulates cellular plasticity mechanisms relevant to early embryological tissue differentiation.

Treatment with potassium bromide mitigates ataxia and reduces tremor in lambs with perennial ryegrass toxicosis

Aims: To assess the use of potassium bromide (KBr) as a therapeutic intervention for perennial ryegrass toxicosis (PRGT) in lambs fed ryegrass seed containing lolitrem B. Methods: Male lambs aged 10-12 months (n = 43) were assigned to receive ryegrass seed containing lolitrem B, at a dose of 0.16 mg/kg/day (Groups 2, 3 and 4), or lucerne chaff and molasses (Groups 1 and 5). Lambs in Groups 2 and 3 were observed for clinical signs and gait changes until defined signs of PGRT were observed, when they were transferred, with lambs in Group 1, to the Testing phase of the trial. Lambs in Group 3 were then treated with a single oral dose of 300 mg/kg bromide. Lambs in Groups 4 and 5 received KBr daily from the start of the trial (540 mg/kg bromide over 3 days then 20 mg/kg daily) and were transferred to the Testing phase after 18 days. Clinical examination and gait assessment, and surface electromyography of the triceps muscle, measuring root-mean-square (RMS) voltages, were carried out on Days 0, 1 and 2 of the Testing phase followed by necropsy, histopathology, measurement of concentrations of bromide in serum and CSF and faecal cortisol metabolites (FCM). Results: In Group 3 lambs, mean composite gait scores decreased between Testing phase Day 0 and Days 1 and 2 (p < 0.001), but increased in lambs in Group 2 between Day 0 and Day 2 (p = 0.015). Scores for lambs in Group 3 on Day 2 were lower than for lambs in Group 2 (p < 0.001). Mean RMS voltages on Day 2 were higher in lambs in Group 2 than Group 3 (p = 0.045). Mean concentrations of bromide in serum were >800 µg/mL in lambs in Groups 3 and 4 on Day 2. Concentrations of FCM were higher in lambs from Group 2 than in Groups 1 or 5, but were similar in Groups 2, 3 and 4. Histopathological findings in the cerebellum of lambs from Groups 2, 3 and 4 were similar, showing pyknosis of neurons within the granular layer of the cerebellum and Purkinje neuron proximal axonal spheroid formation. Conclusions and clinical relevance: A single oral dose of 300 mg/kg bromide in lambs with neurological signs of PRGT resulted in reduced composite gait scores and reduced RMS voltages, indicating a significant improvement in clinical signs of ataxia, movement disorder and muscle tremor associated with the neurotoxic effects of lolitrem B.

A single exposure to the tremorgenic mycotoxin lolitrem B inhibits voluntary motor activity and spatial orientation but not spatial learning or memory in mice

The indole diterpenoid toxin lolitrem B is a tremorgenic agent found in the common grass species, perennial ryegrass (Lolium perenne). The toxin is produced by a symbiotic fungus Epichloë festucae (var. lolii) and ingestion of infested grass with sufficient toxin levels causes a movement disorder in grazing herbivores known as 'ryegrass staggers'. Beside ataxia, lolitrem B intoxicated animals frequently show indicators of cognitive dysfunction or exhibition of erratic and unpredictable behaviours during handling. Evidence from field cases in livestock and controlled feeding studies in horses have indicated that intoxication with lolitrem B may affect higher cortical or subcortical functioning. In order to define the role of lolitrem B in voluntary motor control, spatial learning and memory under controlled conditions, mice were exposed to a known dose of purified lolitrem B toxin and tremor, coordination, voluntary motor activity and spatial learning and memory assessed. Motor activity, coordination and spatial memory were compared to tremor intensity using a novel quantitative piezo-electronic tremor analysis. Peak tremor was observed as frequencies between 15 and 25Hz compared to normal movement at approximately 1.4-10Hz. A single exposure to a known tremorgenic dose of lolitrem B (2 mg/kg IP) induced measureable tremor for up to 72 h in some animals. Initially, intoxication with lolitrem B significantly decreased voluntary movement. By 25 h post exposure a return to normal voluntary movement was observed in this group, despite continuing evidence of tremor. This effect was not observed in animals exposed to the short-acting tremorgenic toxin paxilline. Lolitrem B intoxicated mice demonstrated a random search pattern and delayed latency to escape a 3 h post intoxication, however by 27 h post exposure latency to escape matched controls and mice had returned to normal searching behavior indicating normal spatial learning and memory. Together these data indicate that the tremor exhibited by lolitrem B intoxicated mice does not directly impair spatial learning and memory but that exposure does reduce voluntary motor activity in intoxicated animals. Management of acutely affected livestock suffering toxicosis should be considered in the context of their ability to spatially orientate with severe toxicity.

Chemometric analysis of Amaranthus retroflexus in relation to livestock toxicity in southern Australia

Amaranthus retroflexus L., an introduced invasive weed in southern Australia, has been associated with acute renal failure and/or mortality in a number of livestock species. While its leaves, flowers and stems are generally reported to contain high levels of nitrogen, few studies have fully characterised the chemical composition of A. retroflexus foliage with respect to mammalian toxicity. We performed extensive metabolic profiling of stems, leaves, roots and inflorescence tissues of A. retroflexus collected from three spatially and/or temporally distinct toxicity outbreaks, and report on the 1) composition of primary and secondary metabolites in methanolic extracts of A. retroflexus tissues using HPLC and HPLC-MS QToF and 2) chemometric analysis of A. retroflexus extracts in relation to the associated toxin(s). All tissues of A. retroflexus possessed an abundance of N-containing metabolites, particularly quaternary ammonium compounds which were identified as betaines, two of which (valine betaine and isoleucine betaine) are rarely encountered in plants. Cytotoxicity to murine fibroblasts was highest in extracts of leaf tissue and was associated with a single, a small modified peptide with high similarity to N-acetyl-L-α-aspartyl-L-alanyl-L-α-aspartyl-L-α-glutamyl-O-(carboxymethyl)-L-tyrosyl-L-leucinamide, a synthetic phosphotyrosyl mimic involved in cell signaling processes. One possible mode of action leading to acute renal failure in grazing livestock by a modified peptide such as this is proposed.

The aetiology, prevalence and morbidity of outbreaks of photosensitisation in livestock: A review

BACKGROUND

Photosensitisation is a clinical condition occurring in both humans and animals that causes significant injury to affected individuals. In livestock, outbreaks of photosensitisation caused by ingestion of toxic plants are relatively common and can be associated with significant economic loss.

OBJECTIVES

The agents that are most commonly implicated in outbreaks of photosensitisation have not been formally investigated on a global scale. To address this question, a systematic review of the literature was undertaken to determine the most common causative agents implicated in outbreaks of photosensitisation in livestock in Australia and globally, as well as the prevalence and morbidity of such outbreaks.

METHODS

A systematic database search was conducted to identify peer-reviewed case reports of photosensitisation in livestock published worldwide between 1900 and April 2018. Only case reports with a full abstract in English were included. Non peer-reviewed reports from Australia were also investigated. Case reports were then sorted by plant and animal species, type of photosensitisation by diagnosis, location, morbidity and mortality rate and tabulated for further analysis.

RESULTS

One hundred and sixty-six reports qualified for inclusion in this study. Outbreaks were reported in 20 countries. Australia (20), Brazil (20) and the United States (11) showed the highest number of peer-reviewed photosensitisation case reports from this analysis. Hepatogenous (Type III) photosensitisation was the most frequently reported diagnosis (68.5%) and resulted in higher morbidity. Panicum spp., Brachiaria spp. and Tribulus terrestris were identified as the most common causes of hepatogenous photosensitisation globally.

CONCLUSIONS

Hepatogenous photosensitisation in livestock represents a significant risk to livestock production, particularly in Australia, Brazil, and the United States. Management of toxic pastures and common pasture weeds may reduce the economic impact of photosensitisation both at a national and global level.

Development of a model for investigation of perennial ryegrass toxicosis in sheep

AIMS To develop a clinical model of perennial ryegrass toxicosis (PRGT) based on feeding a known dose of lolitrem B and ergotamine, and to produce a consistent clinical presentation for assessment of disease pathophysiology, neurological changes and neurohistopathology. METHODS Male lambs, aged between 10-12 months, were randomly assigned to either Treatment (n=9) or Control (n=9) groups. Lambs in the Treatment group received feed containing a novel endophyte-infested perennial ryegrass seed, commencing on Day 0 of the Feeding phase with a low induction dose, then increasing after 3 days to provide 0.16 mg/kg live bodywight (LBW)/day of lolitrem B and 0.054 mg/kg LBW/day ergotamine. Lambs were examined daily and when defined signs of PRGT were observed they were transferred to the Testing phase. Neurological examinations, assessment of gait, surface electromyography (EMG) and mechanosensory nociceptive threshold testing were carried out and blood samples collected during both phases of the trial, with a full necropsy, histopathological examination and measurement of faecal cortisol metabolites (FCM) performed on Day 2 of the Testing phase. RESULTS Typical clinical signs of PRGT, including ataxia of vestibulocerebellar origin leading to stumbling, were observed in all Treatment lambs. The median interval from the start of the Feeding phase to entry into the Testing phase was 21 (min 18, max 34) days. Histopathological characterisation of neurological lesions included the presence of Purkinje cell vacuolation, pyknotic granular layer neurons and proximal axonal Purkinje cell spheroids. Lesions were most apparent within the vestibulocerebellum. Mean root-mean-square voltages from triceps EMG increased in Treatment lambs between Feeding phase Day 0 and Testing phase Day 2 (p<0.001). Daily water intake during the Testing phase for the Treatment group was less than in Control group lambs (p=0.002), and concentrations of FCM at necropsy were higher in Treatment compared to Control lambs (p=0.02). CONCLUSIONS AND CLINICAL RELEVANCE Lolitrem B and ergotamine dosing in feed on a live weight basis combined with neurological/gait assessment provides an effective model for investigation of PRGT and potential therapeutics. Assessment of gait changes using defined criteria and RMS voltages from EMG appear to be useful tools for the assessment of the severity of neurological changes.

Acute-onset high-morbidity primary photosensitisation in sheep associated with consumption of the Casbah and Mauro cultivars of the pasture legume Biserrula

Background

Primary photosensitisation (PS) subsequent to ingestion of the pasture legume Biserrula pelecinus L. (biserrula) has recently been confirmed in grazing livestock. Given the potential utility of this pasture species in challenging climates, a grazing trial was undertaken to examine if both varieties ‘Casbah’ and ‘Mauro’ were able to cause photosensitisation in livestock, and if this could be mitigated by grazing in winter, or in combination with other common pasture species.

Results

A controlled grazing trial was undertaken in winter in Australia with plots containing a dominant pasture of Biserrula pelecinus L. cv. ‘Casbah’ or ‘Mauro’, or mixed biserrula/perennial ryegrass populations. A photosensitisation grading system was established. 167 prime meat ewe lambs were introduced to the plots and monitored twice daily. Mild clinical signs were observed at 72 h on pasture. All animals were removed from biserrula dominant stands at this point. Four animals grazing ‘Casbah’ dominant pasture rapidly proceeded to severe photosensitisation in the following 12 h. Animals remaining on mixed biserrula/ryegrass stands did not exhibit severe PS but showed an 89% incidence of mild to moderate photosensitisation over the following 14 days. Animals on mixed lucerne showed significantly lower PS score than animals grazing biserrula varieties of any composition. The trial was halted at 14 days as only plots with low biserrula proportion still contained unaffected animals.

Necropsy revealed severe multifocal erythematous ulcerations and alopecia of the ear pinnae, severe bilateral periorbital and conjunctival oedema and variably severe subcutaneous facial oedema. No evidence of hepatopathy was present. A diagnosis of acute unseasonal primary photosensitisation caused by biserrula ingestion with no other underlying pathology was confirmed.

Conclusions

We report an unseasonal outbreak of acute photosensitisation in sheep grazing Biserrula pelecinus L cvs.’Casbah’ and ‘Mauro’ with exceedingly high morbidity. A grading system is also proposed as a tool for objective and consistent clinical appraisal of future PS outbreaks. This finding expands our definition of seasonal and temporal risk periods for biserrula photosensitisation, and is the first to identify that both commercial cultivars of biserrula can cause primary photosensitisation in sheep.

An outbreak of primary photosensitisation in lambs secondary to consumption of Biserrula pelecinus (biserrula)

CASE REPORT

An outbreak of photosensitisation affecting approximately 25% of a flock of 120 meat lambs that was grazing a monoculture of the pasture legume Biserrula pelecinus var. Casbah (biserrula) was investigated. Blood samples were taken from sheep with moderate to severe clinical signs, and from apparently normal animals, for a complete blood count and biochemistry; 5 affected animals were subjected to a full necropsy. Histopathological investigation showed lesions consistent with photosensitisation of the exposed unpigmented skin of the face and ears. No histopathological or clinical pathological abnormalities suggestive of a hepatopathy were detected in any of the cases, indicating that the lesions observed in this flock were caused by a primary photosensitising agent present in B. pelecinus.

CONCLUSION

This is the first confirmation that photosensitisation caused by ingestion of biserrula is caused by a primary photosensitising agent.

Acute renal failure associated with Amaranthus species ingestion by lambs

CASE REPORT

This report documents an outbreak of acute renal failure in a flock of 9-month-old White Suffolk-cross ewe lambs. The mortality rate was moderate but the morbidity was high. The lambs had grazed a wheat stubble paddock in which there were several weed species, including Amaranthus spp.

CLINICAL SIGNIFICANCE

Renal failure in livestock has been reported internationally following the ingestion of Amaranthus spp. and although it has previously been suspected in Australia no cases have been documented. It is important for Australian veterinarians and farmers to realise the toxic potential of this group of plants.

Super pharmacological levels of calcitriol (1,25-(OH)2D3) inhibits mineral deposition and decreases cell proliferation in a strain dependent manner in chicken mesenchymal stem cells undergoing osteogenic differentiation in vitro

The biologically active form of vitamin D₃, calcitriol (1,25-(OH)₂D₃), plays a key role in mineral homeostasis and bone formation and dietary vitamin D₃ deficiency is a major cause of bone disorders in poultry. Supplementary dietary cholecalciferol (25-hydroxyvitamin D, 25-OH), the precursor of calcitriol, is commonly employed to combat this problem; however, dosage must be carefully determined as excess dietary vitamin D can cause toxicity resulting in a decrease in bone calcification, hypercalcinemia and renal failure. Despite much research on the therapeutic administration of dietary vitamin D in humans, the relative sensitivity of avian species to exogenous vitamin D has not been well defined. In order to determine the effects of exogenous 1,25-(OH)₂D₃ during avian osteogenesis, chicken bone marrow-derived mesenchymal stem cells (BM-MSCs) were exposed to varying doses of 1,25-(OH)₂D₃ during in vitro osteogenic differentiation and examined for markers of early proliferation and osteogenic induction. Similar to humans and other mammals, poultry BM-MSCs were found to be highly sensitive to exogenous 1,25-(OH)₂D₃ with super pharmacological levels exerting significant inhibition of mineralization and loss of cell proliferation in vitro. Strain related differences were apparent, with BM-MCSs derived from layers strains showing a higher level of sensitivity to 1,25-(OH)₂D₃ than those from broilers. These data suggest that understanding species and strain specific sensitivities to 1,25-(OH)₂D₃ is important for optimizing bone health in the poultry industry and that use of avian BM-MSCs are a useful tool for examining underlying effects of genetic variation in poultry.

Complex Membrane Channel Blockade: A Unifying Hypothesis for the Prodromal and Acute Neuropsychiatric Sequelae Resulting from Exposure to the Antimalarial Drug Mefloquine

The alkaloid toxin quinine and its derivative compounds have been used for many centuries as effective medications for the prevention and treatment of malaria. More recently, synthetic derivatives, such as the quinoline derivative mefloquine (bis(trifluoromethyl)-(2-piperidyl)-4-quinolinemethanol), have been widely used to combat disease caused by chloroquine-resistant strains of the malaria parasite, Plasmodium falciparum. However, the parent compound quinine, as well as its more recent counterparts, suffers from an incidence of adverse neuropsychiatric side effects ranging from mild mood disturbances and anxiety to hallucinations, seizures, and psychosis. This review considers how the pharmacology, cellular neurobiology, and membrane channel kinetics of mefloquine could lead to the significant and sometimes life-threatening neurotoxicity associated with mefloquine exposure. A key role for mefloquine blockade of ATP-sensitive potassium channels and connexins in the substantia nigra is considered as a unifying hypothesis for the pathogenesis of severe neuropsychiatric events after mefloquine exposure in humans.

Evidence of dehydration and electrolyte disturbances in cases of perennial ryegrass toxicosis in Australian sheep

CASE REPORT

Perennial ryegrass toxicosis (PRGT) is a common disease entity in Australia, presenting as an association of clinical signs including alterations in normal behavioural, ataxia ('staggers'), ill thrift and gastrointestinal dysfunction ('scours'). Clinical signs can range in severity from mild (gait abnormalities and failure to thrive) to severe (seizures, lateral recumbency and death). Presentation across the flock is usually highly variable. PRGT is caused by toxins produced by the endophytic fungus Neotyphodium lolii, a symbiont of perennial ryegrass that is present in pastures across the temperate regions of Australia and Tasmania. A particular feature of PRGT in Australia is the occasional occurrence of large-scale sheep losses, suggesting other factors are influencing mortality rates compared with other PRGT risk zones such as North America and New Zealand. During 2011, producers in the state of Victoria experienced a mild outbreak of PRGT that affected large numbers of animals but with limited mortalities. Clinical samples taken from affected sheep showed a high incidence of dehydration and electrolyte abnormalities.

CONCLUSION

We speculate that changes in hydration status may be a contributory aetiological factor in those years in which high numbers of deaths are associated with PRGT outbreaks in Australia.

The transcription factor Foxg1 regulates telencephalic progenitor proliferation cell autonomously, in part by controlling Pax6 expression levels

Background

The transcription factor Foxg1 is an important regulator of telencephalic cell cycles. Its inactivation causes premature lengthening of telencephalic progenitor cell cycles and increased neurogenic divisions, leading to severe hypoplasia of the telencephalon. These proliferation defects could be a secondary consequence of the loss of Foxg1 caused by the abnormal expression of several morphogens (Fibroblast growth factor 8, bone morphogenetic proteins) in the telencephalon of Foxg1 null mutants. Here we investigated whether Foxg1 has a cell autonomous role in the regulation of telencephalic progenitor proliferation. We analysed Foxg1^+/+↔Foxg1^-/- chimeras, in which mutant telencephalic cells have the potential to interact with, and to have any cell non-autonomous defects rescued by, normal wild-type cells.

Results

Our analysis showed that the Foxg1^-/- cells are under-represented in the chimeric telencephalon and the proportion of them in S-phase is significantly smaller than that of their wild-type neighbours, indicating that their under-representation is caused by a cell autonomous reduction in their proliferation. We then analysed the expression of the cell-cycle regulator Pax6 and found that it is cell-autonomously downregulated in Foxg1^-/- dorsal telencephalic cells. We went on to show that the introduction into Foxg1^-/- embryos of a transgene designed to reverse Pax6 expression defects resulted in a partial rescue of the telencephalic progenitor proliferation defects.

Conclusions

We conclude that Foxg1 exerts control over telencephalic progenitor proliferation by cell autonomous mechanisms that include the regulation of Pax6, which itself is known to regulate proliferation cell autonomously in a regional manner.

Novel lines of Pax6-/- embryonic stem cells exhibit reduced neurogenic capacity without loss of viability

Background

Embryonic stem (ES) cells can differentiate into all cell types and have been used extensively to study factors affecting neuronal differentiation. ES cells containing mutations in known genes have the potential to provide useful in vitro models for the study of gene function during neuronal differentiation. Recently, mouse ES cell lines lacking the neurogenic transcription factor Pax6 were reported; neurons derived from these Pax6^-/- ES cells died rapidly after neuronal differentiation in vitro.

Results

Here we report the derivation of new lines of Pax6^-/- ES cells and the assessment of their ability to survive and differentiate both in vitro and in vivo. Neurons derived from our new Pax6^-/- lines were viable and continued to elaborate processes in culture under conditions that resulted in the death of neurons derived from previously reported Pax6^-/- ES cell lines. The new lines of Pax6^-/-ES cells showed reduced neurogenic potential, mimicking the effects of loss of Pax6 in vivo. We used our new lines to generate Pax6^-/- ↔ Pax6^+/+ chimeras in which the mutant cells survived and displayed the same phenotypes as Pax6^-/- cells in Pax6^-/- ↔ Pax6^+/+ chimeras made by embryo aggregation.

Conclusions

We suggest that loss of Pax6 from ES cells reduces their neurogenic capacity but does not necessarily result in the death of derived neurons. We offer these new lines as additional tools for those interested in the generation of chimeras and the analysis of in vitro ES cell models of Pax6 function during neuronal differentiation, embryonic and postnatal development.

Controlled overexpression of Pax6 in vivo negatively autoregulates the Pax6 locus, causing cell-autonomous defects of late cortical progenitor proliferation with little effect on cortical arealization

Levels of expression of the transcription factor Pax6 vary throughout corticogenesis in a rostro-lateral(high) to caudo-medial(low) gradient across the cortical proliferative zone. Previous loss-of-function studies have indicated that Pax6 is required for normal cortical progenitor proliferation, neuronal differentiation, cortical lamination and cortical arealization, but whether and how its level of expression affects its function is unclear. We studied the developing cortex of PAX77 YAC transgenic mice carrying several copies of the human PAX6 locus with its full complement of regulatory regions. We found that PAX77 embryos express Pax6 in a normal spatial pattern, with levels up to three times higher than wild type. By crossing PAX77 mice with a new YAC transgenic line that reports Pax6 expression (DTy54), we showed that increased expression is limited by negative autoregulation. Increased expression reduces proliferation of late cortical progenitors specifically, and analysis of PAX77<---->wild-type chimeras indicates that the defect is cell autonomous. We analyzed cortical arealization in PAX77 mice and found that, whereas the loss of Pax6 shifts caudal cortical areas rostrally, Pax6 overexpression at levels predicted to shift rostral areas caudally has very little effect. These findings indicate that Pax6 levels are stabilized by autoregulation, that the proliferation of cortical progenitors is sensitive to altered Pax6 levels and that cortical arealization is not.

Penetrance of eye defects in mice heterozygous for mutation of Gli3 is enhanced by heterozygous mutation of Pax6

BACKGROUND

Knowledge of the consequences of heterozygous mutations of developmentally important genes is important for understanding human genetic disorders. The Gli3 gene encodes a zinc finger transcription factor and homozygous loss-of-function mutations of Gli3 are lethal. Humans heterozygous for mutations in this gene suffer Greig cephalopolysyndactyly or Pallister-Hall syndromes, in which limb defects are prominent, and mice heterozygous for similar mutations have extra digits. Here we examined whether eye development, which is abnormal in mice lacking functional Gli3, is defective in Gli3+/- mice.

RESULTS

We showed that Gli3 is expressed in the developing eye but that Gli3+/- mice have only very subtle eye defects. We then generated mice compound heterozygous for mutations in both Gli3 and Pax6, which encodes another developmentally important transcription factor known to be crucial for eye development. Pax6+/-; Gli3+/- eyes were compared to the eyes of wild-type, Pax6+/- or Gli3+/- siblings. They exhibited a range of abnormalities of the retina, iris, lens and cornea that was more extensive than in single Gli3+/- or Pax6+/- mutants or than would be predicted by addition of their phenotypes.

CONCLUSION

These findings indicate that heterozygous mutations of Gli3 can impact on eye development. The importance of a normal Gli3 gene dosage becomes greater in the absence of a normal Pax6 gene dosage, suggesting that the two genes co-operate during eye morphogenesis.

Pax6 controls cerebral cortical cell number by regulating exit from the cell cycle and specifies cortical cell identity by a cell autonomous mechanism

Many cerebral cortical neurons and glia are produced by apical progenitors dividing at the ventricular surface of the embryonic dorsal telencephalon. Other neurons are produced by basal progenitor cells, which are derived from apical progenitors, dividing away from the ventricular surface. The transcription factor Pax6 is expressed in apical progenitors and is downregulated in basal progenitors, which upregulate the transcription factor Tbr2. Here we show that Pax6^−/− cells are under-represented in the cortex of Pax6^+/+↔Pax6^−/− chimeras early in corticogenesis, indicating that Pax6 is required for the production of normal numbers of cortical cells. We provide evidence that this underproduction is attributable to an early depletion of the progenitor pool caused by greater than normal proportions of newly divided cells exiting the cell cycle. We show that most progenitor cells dividing away from the ventricular surface in Pax6^−/− embryos fail to express the transcription factor Tbr2 and that Pax6 is required cell autonomously for Tbr2 expression in the developing cortex of Pax6^+/+↔Pax6^−/− chimeras. Transcription factors normally expressed ventrally in the telencephalic ganglionic eminences (Mash1, Dlx2 and Gsh2) are upregulated cell autonomously in mutant cells in the developing cortex of Pax6^+/+↔Pax6^−/− chimeras; Nkx2.1, which is expressed only in the medial ganglionic eminence, is not. These data indicate that early functions of Pax6 in developing cortical cells are to repress expression of transcription factors normally found in the lateral ganglionic eminence, to prevent precocious differentiation and depletion of the progenitor pool, and to induce normal development of cortical basal progenitor cells.

Identification and characterization of a novel transcript down-regulated in Dlx1/Dlx2 and up-regulated in Pax6 mutant telencephalon

By using a custom-made array containing cDNAs preferentially expressed in the mouse embryonic telencephalon (Porteus et al. [1992] Brain Res Mol Brain Res 12:7-22; and Alessandro Bulfone, unpublished data), we studied the gene expression profile of the Dlx1/Dlx2(-/-) subpallium and Pax6(-/-) pallium. We identified a transcript corresponding to Unigene Cluster Mm.94021 and rat Evf-1, which is down-regulated in the Dlx1/Dlx2(-/-) subpallium and up-regulated in the Pax6(-/-) pallium. Here, we report the expression pattern of this transcript, designated mouse Evf1 (mEvf1), in the prenatal forebrain of wild-type, Dlx1/Dlx2(-/-) and Pax6(-/-) mice using RNA in situ hybridization and reverse transcriptase-polymerase chain reaction. In the wild-type forebrain mEvf1 expression is restricted to the ventral thalamus, hypothalamus, and subpallial telencephalon (caudal, lateral, and medial ganglionic eminences and septal primordia), whereas it is down-regulated in the Dlx1/Dlx2(-/-) subpallium (mainly in caudal, lateral, and medial ganglionic eminences), and up-regulated in the Pax6(-/-) lateral and ventral pallium at embryonic day 12.5 and in the dorsal, lateral, and ventral pallium at embryonic day 14.5.

Shrinkage stresses in bone cement

Shrinkage of bone cement is reported primarily as a consequence of polymerisation, however thermal shrinkage also occurs as a result of its exothermic reaction. It is proposed that the latter effect is important, since it occurs late in the curing cycle at a time when the cement has attained its mechanical properties as a solid, and that residual stresses result. Observations from experiments and literature reports suggest that residual stresses may be sufficient to initiate cracks at the interface between hip replacement stems and cement.A theoretical model has been developed to calculate interference stresses, using thick-walled cylinder theory, on the basis of thermal and total shrinkages. Thermal shrinkage values were calculated using the coefficient of linear thermal expansion of bone cement, while total shrinkages were measured. Moduli of elasticity values were measured for acrylic bone cements ranging from 2.1 to 2.7GPa, as were Poisson's ratio values ranging from 0.38 to 0.46. Theoretical calculation of stresses in a cement mantle, based on assumptions of thermal shrinkage alone, predicted circumferential stresses of 8.4-25.2MPa for cement curing temperatures in the range 60-140 degrees C. It is concluded that cracks observed around hip prosthesis stems in laboratory specimens of bone cement are due to shrinkage and that residual stresses are sufficient to cause crack initiation prior to functional loading.

Mouse models of telencephalic development

As the telencephalon first emerges from anterior neuroectoderm, signalling molecules and transcription factors combine to specify the identity and fate of cells in each of its regions. Studies of both naturally occurring and transgenic mutant mice have identified many genes that contribute to this process. The development of telencephalon and its regions is specified by signalling molecules produced at sites both surrounding and within the telencephalon. Different parts of the telencephalon express different combinations of transcription factors that control processes including proliferation, cell fate determination and migration in order to create the unique phenotype of each region.

The roles of Pax6 in the cornea, retina, and olfactory epithelium of the developing mouse embryo

The roles of Pax6 were investigated in the murine eye and the olfactory epithelium by analysing gene expression and distribution of Pax6(-/-) cells in Pax6(+/+) <--> Pax6(-/-) chimeras. It was found that between embryonic days E10.5 and E16.5 Pax6 is autonomously required for cells to contribute fully not only to the corneal epithelium, where Pax6 is expressed at high levels, but also to the to the corneal stroma and endothelium, where the protein is detected at very low levels. Pax6(-/-) cells contributed only poorly to the neural retina, forming small clumps of cells that were normally restricted to the ganglion cell layer at E16.5. Pax6(-/-) cells in the retinal pigment epithelium could express Trp2, a component of the pigmentation pathway, at E14.5 and a small number went on to differentiate and produce pigment at E16.5. The segregation and near-exclusion of mutant cells from the nasal epithelium mirrored the behaviour of mutant cells in other developmental contexts, particularly the lens, suggesting that common primary defects may be responsible for diverse Pax6-related phenotypes.

Pax6 regulates regional development and neuronal migration in the cerebral cortex

Mutations in the Pax6 gene disrupt telencephalic development, resulting in a thin cortical plate, expansion of proliferative layers, and the absence of the olfactory bulb. The primary defect in the neuronal cell population of the developing cerebral cortex was analysed by using mouse chimeras containing a mixture of wild-type and Pax6-deficient cells. The chimeric analysis shows that Pax6 influences cellular activity throughout corticogenesis. At early stages, Pax6-deficient and wildtype cells segregate into exclusive patches, indicating an inability of different cell genotypes to interact. At later stages, cells are sorted further based on telencephalic domains. Pax6-deficient cells are specifically reduced in the mediocaudal domain of the dorsal telencephalon, indicating a role in regionalization. In addition, Pax6 regulates the process of radial migration of neuronal precursors. Loss of Pax6 particularly affects movement of neuronal precursors at the subventricular zone/intermediate zone boundary at a transitional migratory phase essential for entry into the intermediate zone. We suggest that the primary role of Pax6 is the continual regulation of cell surface properties responsible for both cellular identity and radial migration, defects of which cause regional cell sorting and abnormalities of migration in chimeras.

Disruption of early events in thalamocortical tract formation in mice lacking the transcription factors Pax6 or Foxg1

Early events in the formation of the thalamocortical tract remain poorly understood. Recent work has suggested that thalamocortical axons follow a path pioneered by transient thalamic afferents originating from the medial part of the ventral telencephalon. We studied the development of these transient afferents and the thalamocortical tract in mutant mice lacking transcription factors normally expressed in the dorsal thalamus or ventral telencephalon. Pax6 is expressed in the dorsal thalamus, but not in the medial part of the ventral telencephalon, and the thalamocortical tract fails to form in Pax6(-/-) embryos. We found that transient thalamic afferents from the ventral telencephalon do not form in Pax6(-/-) embryos; this may contribute to the failure of their thalamocortical development. The distribution of Pax6(-/-) cells in Pax6(-/-)<--> Pax6(+/+) chimeras supports conclusions drawn from forebrain marker gene expression that Pax6 is not required for the normal development of the medial part of the ventral telencephalon but is required in the dorsal thalamus. Failure of the transient afferent pathway to develop is therefore likely a cell nonautonomous defect reflecting primary defects in the thalamus. We then examined the formation of thalamic afferents and efferents in Foxg1(-/-) embryos, which lack recognizable ventral telencephalic structures. In these embryos thalamic efferents navigate correctly through the thalamus but fail to turn laterally into the telencephalon, whereas other axons are able to cross the diencephalic/telencephalic boundary. Our results support a role for the ventral telencephalon in guiding the early development of the thalamocortical tract and identify a new role for the transcription factor Pax6 in regulating the ability of the thalamus to attract ventral telencephalic afferents.

Primary defects in the lens underlie complex anterior segment abnormalities of the Pax6 heterozygous eye

We describe lens defects in heterozygous small eye mice, and autonomous deficiencies of Pax6(+/-) cells in the developing lens of Pax6(+/+) <--> Pax6(+/-) chimeras. Two separate defects of the lens were identified by analyzing the distribution of heterozygous cells in chimeras: Pax6(+/-) cells are less readily incorporated into the lens placode than wild type, and those that are incorporated into the lens are not maintained efficiently in the proliferating lens epithelium. The lens of chimeric eyes is, therefore, predominantly wild type from embryonic day 16.5 onwards, whereas heterozygous cells contribute normally to all other eye tissues. Eye size and defects of the iris and cornea are corrected in fetal and adult chimeras with up to 80% mutant cells. Therefore, these aspects of the phenotype may be secondary consequences of primary defects in the lens, which has clinical relevance for the human aniridia (PAX6(+/-)) phenotype.

Genetic background effects on dental and other craniofacial abnormalities in homozygous small eye (Pax6Sey/Pax6Sey) mice

Small eye (Pax6Sey) is a semi-dominant mutation affecting development of the eyes, brain and nasal structures. The mutant phenotype arises from defects within the Pax6 gene and several mutant alleles have been identified. A previous study reported that Pax6Sey/Pax6Sey homozygotes, in a random-bred stock, had a median cartilaginous rod-like structure in the nasal region and 80% had supernumerary upper incisor teeth. In this study we show that supernumerary upper incisor teeth and a previously unreported nasal capsule-derived cartilaginous 'spur' occur in compound heterozygous Pax6Sey-Neu/Pax6Sey and homozygous Pax6Sey/Pax6Sey fetuses from several strains of mice. The frequencies of the abnormal phenotypes were not related to allele type but showed variable penetrance, which was dependent on genetic background. The median nasal cartilaginous rod-like structure was present in all homozygous small eye fetuses. The Pax6Sey/Pax6Sey homozygote may provide insight into the complex gene interactions involved in eye, nasal and craniofacial morphogenesis.

Multiple functions for Pax6 in mouse eye and nasal development

Mouse embryos, homozygous for the small eye (Sey) mutation die soon after birth with severe facial abnormalities that result from the failure of the eyes and nasal cavities to develop. Mutations in the Pax6 gene are responsible for the Sey phenotype. As a general disruption of eye and nasal development occurs in the homozygous Sey embryos, it is unclear, from the mutant phenotype alone, which tissues require functional Psx6. To examine the roles for Pax6 in eye and nasal development we produced chimeric mouse embryos composed of wild-type and Sey mutant cells. In these embryos we found that mutant cells were excluded from both the lens and nasal epithelium. Both of these tissues were smaller, and in some cases absent, in chimeras with high proportions of mutant cells. The morphology of the optic cup was also severely affected in these chimeras; mutant cells were excluded from the retinal pigmented epithelium and did not intermix with wild-type cells in other regions. The evidence shows that Pax6 has distinct roles in the nasal epithelium and the principal tissue components of the embryonic eye, acting directly and cell autonomously in the optic cup and lens. We suggest that Pax6 may promote cell surface changes in the optic cup and control the fate of the ectoderm from which the lens and nasal epithelia are derived.

Flow chart eases planning process for hospitals

If planning is the key word for hospitals in the next decade, how do their administrators get through the tedious tasks associated with formulating strategy, making purchases or changing directions for individual units? In the following article, the author suggests a methodology to streamline the process and put it in the hands of department managers.

The nurse manager and ethical choices

Ethical decision making on issues other than those in the clinical area are presenting a special challenge to today's nurse managers. This article discusses some of these issues and presents a model for use in analyzing them. Frequently used ethical principles are also included.