Characterisation, genomic organisation, expression and function of the mEphA1 receptor Tyrosine Kinase

The Eph receptor tyrosine kinases and their ephrin ligands are cell surface molecules with a wide range of biological functions. Specifically, the Eph/ephrin receptor-ligand family influences cell behaviour during both embryogenesis and adult life, principally through modification of cytoskeletal organisation and cell adhesion. EphA1 (previously referred to as eph) was isolated during a search for novel tyrosine kinases with oncogenic potential. The murine homologue of hEphA1, formerly Esk and now mEphA1, was cloned by reverse transcriptase PCR using degenerate oligonucleotide primers and RNA prepared from embryonic stem cells in culture. Northern blot analysis revealed expression in day 12 mouse embryo, and adult mouse thymus, liver, kidney, lung and placenta. The work in this thesis investigates the expression and function of EphA1 in mutant mouse and other animal models. This has been achieved by a number of different techniques including:- (1) the classical techniques of molecular biology; (2) a search for the zebrafish homologue of mEphA1; (3) generation and phenotypic analysis of the hPLAP EphA1 reporter knockout mouse and (4) generation of the EphA1 conditional knockout mouse. The chromosomal localisation and Southern blotting of genomic digests confirmed that Esk (mEphA1) is the murine homologue of eph (hEphA1). The binding of soluble mEphA1 to a panel of ephrin ligands analysed by surface plasmon resonance (BIACore), and the binding of various ephrin-Fc molecules to cell surface expressed EphA1, confirmed that EphA1 is the cognate receptor for the ephrin-A1 ligand. The mEphA1 genomic sequence was isolated, sequenced and the exon-intron boundaries mapped. Interestingly, Exon 3, which includes the ligand binding domain, is split into two smaller exons (Exon 3a and Exon 3b). This pattern was also found in hEphA1; however, it is a novel finding compared with the other Ephs, and the reason underlying this difference remains speculative. In situ hybridisation analysis confirmed epithelial expression of mEphA1 in the basal layer of the epidermis, developing hair follicles, thymic epithelial cells and adult kidney. At the commencement of the zebrafish (ZF) library screening project in 1997, it seemed likely that there was an ZF orthologue of EphA1. However, over 50 clones were isolated by degenerate PCR of zebrafish cDNA and genomic libraries, and although some of the sequences had homology to known Ephs, none matched EphA1. The ZF genome has now been sequenced completely [http://wwwmap.tuebingen.mpg.de/ ; http://zfin.org/] and has confirmed that there is indeed no zebrafish orthologue of EphA1. The hPLAP EphA1 reporter knockout mouse was generated with the technical assistance of Dr Graham Kay (Queensland Transgenic Laboratory). The homozygous null mice have a kinky tail in two separate embryonic stem cell lines with a high degree of penetrance. A proportion of female null mice display the imperforate vagina phenotype. The null mice are otherwise grossly normal, with equal sex ratios and normal growth, health and life expectancy. The microscopic examination of haematoxylin and eosin stained sections of all the major organs revealed no histological abnormalities. The expression of hPLAP, (hence mEphA1), analysed in frozen sections confirmed the previous work which defined the epithelial expression of mEphA1 to the basal epidermis and hair follicle. There was also previously undescribed hPLAP (mEphA1) expression in the uterus, vagina and small intestine. The EphA1 conditional knockout mouse was also generated with the assistance of the Queensland Transgenic Facility. The homozygous null mice were grossly normal with equal sex ratio and normal health and life expectancy. The kinky tail phenotype was observed infrequently and has not yet been fully characterised in these mice. Similarly the imperforate vagina phenotype has not been observed in this strain of mice. This strain of genetically modified EphA1 knockout mice can be mated with various strains of Cre-deleter mice to achieve tissue specific silencing of EphA1 and consequently allow more precise analysis of EphA1 function. In summary, the studies described in this thesis have confirmed the importance of the Eph/ephrin receptor-ligands in both embryonic development and the maintenance of adult tissues, and have generated several new findings which add to our knowledge of the biology of EphA1. The generation of the hPLAP EphA1 reporter mice and EphA1 conditional knockout mice has provided us with very useful tools. These knockout mice will allow further analysis of the role of EphA1 in mouse models of human diseases, including skin and colon cancer, severe sepsis and post-traumatic injury

Blind trading: A literature review of research addressing the welfare of Ball pythons in the exotic pet trade

Extensive numbers of Ball pythons are caught, bred, traded and subsequently kept in captivity across the world as part of the exotic pet industry. Despite their widespread availability as pets, relatively little is known about the potential welfare challenges affecting them. We reviewed the literature for research focused on the health and welfare of Ball pythons in the international pet trade. From a total of 88 articles returned from the search criteria, our analysis showed that very few actually focused on trade (10%) or animal welfare (17%). Instead, the majority (64%) of articles focused on veterinary science. There was a considerable bias towards physical health, with most studies neglecting the four other domains of animal welfare (behaviour, nutrition, environment and mental health). Furthermore, very few studies considered Ball pythons prior to resulting pet ownership, during wild capture and transportation or captive breeding operations. Our review demonstrates that our current understanding of welfare for Ball pythons traded as exotic pets is limited. We recommend that future research should focus on aspects of the industry that are currently overlooked, including the potential consequences of genetic selection during captive-breeding and the conditions provided for snakes prior to and during international transportation

Predictors and prognosis of population-based subjective cognitive decline: longitudinal evidence from the Caerphilly Prospective Study (CaPS)

Objectives: To understand associations between the subjective experience of cognitive decline and objective cognition. This subjective experience is often conceptualised as an early step towards neurodegeneration, but this has not been scrutinised at the population level. An alternative explanation is poor meta-cognition, the extreme of which is seen in functional cognitive disorder (FCD). Design: Prospective cohort (Caerphilly Prospective Study). Setting: Population-based, South Wales, UK. Participants: This men-only study began in 1979; 1225 men participated at an average age of 73 in 2002–2004, including assessments of simple subjective cognitive decline (sSCD, defined as a subjective report of worsening memory or concentration). Dementia outcomes were followed up to 2012–2014. Data on non-completers was additionally obtained from death certificates and local health records. Primary and secondary outcome measures: The primary outcome measure was incident dementia over 10 years. Secondary outcome measures included prospective change in objective cognition and cross-sectional cognitive internal inconsistency (the existence of a cognitive ability at some times, and its absence at other times, with no intervening explanatory factors except for focus of attention). Results: sSCD was common (30%) and only weakly associated with prior objective cognitive decline (sensitivity 36% (95% CI 30 to 42) and specificity 72% (95% CI 68 to 75)). Independent predictors of sSCD were older age, poor sleep quality and higher trait anxiety. Those with sSCD did not have excess cognitive internal inconsistency, but results suggested a mild attentional deficit. sSCD did not predict objective cognitive change (linear regression coefficient −0.01 (95% CI −0.13 to 0.15)) nor dementia (odds ratio 1.35 (0.61 to 2.99)) 10 years later. Conclusions: sSCD is weakly associated with prior objective cognitive decline and does not predict future cognition. Prior sleep difficulties and anxiety were the most robust predictors of sSCD. sSCD in the absence of objective decline appears to be a highly prevalent example of poor meta-cognition (ie, poor self-awareness of cognitive performance), which could be a driver for later FCD

Seeking serpents: ball python trade in Benin, West Africa

Ball pythons are traded as bushmeat, leather and belief-based medicine in West Africa, and specimens are exported in large numbers for the exotic pet trade. Here, we focused on understanding the purpose and socio-economic context of this trade in Benin through interviews with 44 actors involved in the trade of this species. We provided a snapshot of trade dynamics during a period when hunters are not predominantly actively involved in supplying eggs, neonates and gravid females for ranching and export as exotic pets. Our findings revealed that hunters and traders were largely focused on supplying the bushmeat and medicine markets in West Africa during this time. We estimated that the 21 collectors engaged in hunting in our study collectively hunt between 576 and 5,083 ball pythons from the wild each year. Collection rates reported by some suggests that they could earn more than 15,000 USD from ball python sales in bushmeat markets annually. Ball pythons hunted in Benin were mainly sold to local customers as “bushmeat” (53%) or for belief-based uses (39%) (including “fetish”, “medicinal products” and “voodoo”). However, cross-border trade with neighboring countries of Togo, Nigeria, and Ghana (or even further) also occurred. Although profitable for some, the scale of this practice, together with the widely reported decline in ball python populations in Benin, raises concern about the sustainability and long-term economic viability of this type of large-scale commercial wildlife trade in West Africa, especially as it occurs alongside extensive ranching practices to support the exotic pet trade

Dropping the Ball? The Welfare of Ball Pythons Traded in the EU and North America.

Ball pythons (family Pythonidae) remain a commonly exploited species, readily available for purchase in North America and Europe. We assessed the housing conditions of more than 5000 Ball pythons across six exotic pet expositions and 113 YouTube videos. We scored provisions for hygiene, mobility, shelter, substrate and water provision, based on the Royal Society for the Protection of Animals (RSPCA) minimum guidelines. We found most entities involved in this commercial enterprise are not providing housing conditions that meet the minimum welfare recommendations for Ball pythons, either publicly or privately. We found that breeders and vendors typically utilised small and highly restrictive enclosures, with dimensions that prevented occupants from extending their bodies to full and unrestricted natural length. Our study also highlights that most vendors are not providing adequate written husbandry guidance to potential consumers, either at exotic pet expositions, on their commercial website, or on associated social media pages. Furthermore, our study also indicates that most potential consumers may themselves be unable to recognise unsuitable housing conditions that do not meet minimum animal welfare standards for Ball pythons. We suggest that more consistent guidance, adherence to agree principles and more potent operating models that are formally incorporated into relevant legislation would greatly aid existing and future efforts to safeguard animal welfare in this regard

A preliminary assessment of bacteria in “ranched” ball pythons (Python regius), Togo, West Africa

Captive reptiles are routinely identified as reservoirs of pathogenic bacteria and reports of reptile-associated infections relating to some species are well documented (e.g., salmonellosis). Currently, relatively little is known about the epidemiology and bacteria of ball pythons. We carried out a survey of ball python farms in Togo, West Africa to assess the presence of any potentially pathogenic bacterial taxa that have been identified in recent scientific literature relating to this species. The presence of bacteria belonging to the genera Acinetobacter, Bacteroides, Citrobacter, Enterobacter, Lysobacter, Proteus, Pseudomonas, Staphylococcus, and Tsukamurella in oral and cloacal samples taken from five individual ball pythons is of potential concern for horizontal transmission given that pathogenic species belonging to these genera have been previously documented. The presence of bacteria belonging to the genera Clostridium, Escherichia, Moraxella, and Stenotrophomonas in the oral and rectal samples taken from five mice used to feed ball pythons suggests that they represent a potential reservoir of infection for wild caught ball pythons and their progeny. Furthermore, possible sources of environmental contamination include other captive amphibians, birds, reptiles and mammals, as well as free ranging birds and small mammals. Additional surveillance of ball pythons in the wild and in captivity at python farms in West Africa will shed light on whether or not this type of commercial activity is increasing pathogen exposure and lowering barriers to transmission. Meanwhile, as a precautionary measure, it is recommended that python farms should immediately establish biosecurity and disease surveillance practices to minimize potential horizontal and vertical bacterial transfer

Isotonic versus hypotonic solutions for maintenance intravenous fluid administration in children

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