A discrete slug population model determined by egg production

Slugs are significant pests in agriculture (as well as a nuisance to gardeners), and it is therefore important to understand their population dynamics for the construction of efficient and effective control measures. Differential equation models of slug populations require the inclusion of large (variable) temporal delays, and strong seasonal forcing results in a non-autonomous system. This renders such models open to only a limited amount of rigorous analysis. In this paper, we derive a novel batch model based purely upon the quantity of eggs produced at different times of the year. This model is open to considerable reduction; from the resulting two variable discrete-time system it is possible to reconstruct the dynamics of the full population across the year and give conditions for extinction or global stability and persistence. Furthermore, the steady state temporal population distribution displays qualitatively different behavior with only small changes in the survival probability of slugs. The model demonstrates how small variations in the favorability of different years may result in widely different slug population fluctuations between consecutive years, and is in good agreement with field data

Using lamb sales data to investigate associations between implementation of disease preventive practices and sheep flock performance

Although the UK is the largest lamb meat producer in Europe, there are limited data available on sheep flock performance and on how sheep farmers manage their flocks. The aims of this study were to gather evidence on the types of disease control practices implemented in sheep flocks, and to explore husbandry factors associated with flock productivity. A questionnaire focusing on farm characteristics, general husbandry and flock health management was carried out in 648 farms located in the UK over summer 2016. Abattoir sales data (lamb sales over 12 months) was compared with the number of breeding ewes on farm to estimate flock productivity (number of lambs sold for meat per 100 ewes per farm per year). Results of a multivariable linear regression model, conducted on 615 farms with complete data, indicated that farms vaccinating ewes against abortion and clostridial agents and administering a group 4/5 anthelmintic to ewes (as recommended by the Sustainable Control of Parasites in Sheep Initiative) during quarantining had a greater flock productivity than farms not implementing these actions (

Sheep scab in Northern Ireland: its distribution, costs and farmer knowledge about prevention and control

Sheep scab (psoroptic mange), which is endemic in the United Kingdom (UK) flock, has a significant, negative impact on sheep welfare. Nothing has previously been published about the distribution of sheep scab in Northern Ireland (NI), nor about Northern Irish farmers’ knowledge and behaviours relating to the disease, its treatment, prevention and control. Between March and June 2021 an online questionnaire on the disease was completed by sheep farmers in NI. Forty-four respondents out of a total of 122 valid returns (36%) indicated that they had at least one outbreak of sheep scab in their flock within the previous five years. These flocks were spread throughout NI and included flocks grazing on common land. Farmers reporting sheep scab in their flock considered movements of sheep between flocks to be the main cause of flock infestation. Respondents demonstrated knowledge gaps in relation to the parasite biology, disease transmission, prevention and treatment options, as well as a lack of awareness of some of the relevant industry guidelines. We highlight that some farmers rely on clinical signs alone to rule out the possibility that newly purchased sheep are infested with sheep scab before mixing them with their flock. This activity poses a high risk for the introduction of sheep scab into previously uninfested flocks. The inadequacy of some farmers’ quarantine rules, or their inability to follow them, was also reported by farmers as being the cause of their flock infestation. Sheep scab outbreaks were shown to result in significant financial cost, with some farmers reporting their most recent outbreak had cost over £2500 ($3329). The paper also highlights that in addition to the animal health and welfare impact and financial cost, sheep scab was reported to have a social cost: 94 respondents (79%) agreed that a sheep scab outbreak caused emotional stress to affected farmers. These findings have provided evidence of the widespread nature of sheep scab in the NI flock, and of the knowledge gaps and behaviours which need to be addressed to improve sheep scab control. This will require a combination of focused research, knowledge exchange between farmers, advisors, policy makers and regulators, and co-developed disease control plans at a flock and national level

Cognitive performance in light current users and ex-users of ecstasy (MDMA) and controls

Previous research has shown that heavy users of ecstasy may suffer impaired cognitive functioning, and the present study set out to investigate whether such impairment might also be found in light users or ex-users of ecstasy. Sixty subjects, comprising 20 current light users, 20 ex-users, and 20 non-users of ecstasy, were tested on an extensive battery of cognitive tests. Current light users of ecstasy achieved significantly lower scores on the overall cognitive test battery than did the non-users (p=0.011), though there were no significant differences on any individual subtests. However, the scores obtained by the ex-users of ecstasy did not differ significantly from those of the non-users. It was concluded that current light users of ecstasy show a small but significant cognitive impairment, but that no such impairment is detectable in ex-users who had abstained from the drug for at least 6 months

Sleep-wake sensitive mechanisms of adenosine release in the basal forebrain of rodents : an in vitro study

Adenosine acting in the basal forebrain is a key mediator of sleep homeostasis. Extracellular adenosine concentrations increase during wakefulness, especially during prolonged wakefulness and lead to increased sleep pressure and subsequent rebound sleep. The release of endogenous adenosine during the sleep-wake cycle has mainly been studied in vivo with microdialysis techniques. The biochemical changes that accompany sleep-wake status may be preserved in vitro. We have therefore used adenosine-sensitive biosensors in slices of the basal forebrain (BFB) to study both depolarization-evoked adenosine release and the steady state adenosine tone in rats, mice and hamsters. Adenosine release was evoked by high K+, AMPA, NMDA and mGlu receptor agonists, but not by other transmitters associated with wakefulness such as orexin, histamine or neurotensin. Evoked and basal adenosine release in the BFB in vitro exhibited three key features: the magnitude of each varied systematically with the diurnal time at which the animal was sacrificed; sleep deprivation prior to sacrifice greatly increased both evoked adenosine release and the basal tone; and the enhancement of evoked adenosine release and basal tone resulting from sleep deprivation was reversed by the inducible nitric oxide synthase (iNOS) inhibitor, 1400 W. These data indicate that characteristics of adenosine release recorded in the BFB in vitro reflect those that have been linked in vivo to the homeostatic control of sleep. Our results provide methodologically independent support for a key role for induction of iNOS as a trigger for enhanced adenosine release following sleep deprivation and suggest that this induction may constitute a biochemical memory of this state

Stabilisation of β-Catenin Downstream of T Cell Receptor Signalling

The role of TCF/β-catenin signalling in T cell development is well established, but important roles in mature T cells have only recently come to light.Here we have investigated the signalling pathways that are involved in the regulation of β-catenin in primary human T cells. We demonstrate that β-catenin expression is upregulated rapidly after T cell receptor (TCR) stimulation and that this involves protein stabilisation rather than an increase in mRNA levels. Similar to events in Wnt signalling, the increase in β-catenin coincides with an inhibition of GSK3, the kinase that is required for β-catenin degradation. β-catenin stabilisation in T cells can also be induced by the activation of PKC with phorbol esters and is blocked by inhibitors of phosphatidylinositol 3-kinase (PI3K) and phospholipase C (PKC). Upon TCR signalling, β-catenin accumulates in the nucleus and, parallel to this, the ratio of TCF1 isoforms is shifted in favour of the longer β-catenin binding isoforms. However, phosphorylated β-catenin, which is believed to be inactive, can also be detected and the expression of Wnt target genes Axin2 and dickkopf is down regulated.These data show that in mature human T cells, TCR signalling via PI3K and PKC can result in the stabilisation of β-catenin, allowing β-catenin to migrate to the nucleus. They further highlight important differences between β-catenin activities in TCR and Wnt signalling