Canada’s Commercial Seal Hunt

Like efforts to end the commercial hunting of whales, the campaign to stop the slaughter of seals in Canada has become a major focus for animal and environment protection groups and governments the world over. For decades the face of the harp seal pup has been a symbol—to many, the symbol—of environment and animal advocacy. But as much as the campaign to save the seals has become an icon for those who would protect wildlife, the campaign to continue the hunt has become a focus for those who would block the progress of the animal protection and environmental movements

Microbial In Vitro Model of Root Surface Caries

Root surface caries is an economically important disease in Western industrialised nations and appears likely to become more so in future due to demographic changes and improvements in oral hygiene. There are a variety of model systems which have been used to study root surface caries including; in situ studies, experimental laboratory animals, the use of pure acids in vitro and the use of bacterial cultures in vitro. However the published data fail to present a clear and definitive picture of the role that different bacterial species play or of the biochemical stages in the demineralisation of root surfaces by bacteria. Therefore it was decided to develop a novel in vitro model to study this problem. The first system investigated was the Millicell-HA tissue culture insert (Millipore, U.K.), which consisted of a polystyrene cylinder sealed at one end with a 0.45mum pore-size membrane filter. These units are relatively cheap, easy to handle, provide a stable surface to support bacteria and also keep the bacteria separate from their broth supply to facilitate collection of samples for analysis. In chapter 3 a series of experiments is described in which three bacterial species - Streptococcus mutans, Lactobacillus casei and Actinomyces viscosus - were selected for study on the basis of previous scientific reports. Relatively reproducible films of the three test species were cultured in Millicell- HA inserts, with no significant differences between the retrievable viable counts of each species whether as pure or mixed cultures. Furthermore scanning electron micrographs confirmed that both S. mutans and A, viscosus could be cultured as healthy biofilms in the inserts, although technical difficulties precluded this conclusion for L. casei. Moreover there appeared to be a maximum attainable population density of approximately 108 c.f u./cm2, which was independent of the initial inoculum density. However, when the incubation period was extended it was found that S. mutam passed from the Millicell-HA inserts into the nutrient broth phase by day 4 of incubation, although the population densities of both L. casei and A. viscosus remained stable for 14 days. It was therefore decided to discontinue work on the Millicell-HA model system. The second system investigated was the Ultrafree-CL ultrafiltration unit (Millipore, U.K.), which is structurally similar to the Millicell-HA insert but available with smaller diameter pores. Chapter 4 characterised the properties of the model, which included the following; (i) reproducible films of the three test species could be grown as pure or mixed cultures with no significant differences between the final viable counts and (ii) S. mutans was retained by the filter membrane with a pore size of 0.22mum for around 7 - 8 days and for at least 21 days by a 0.1 mum pore size. Since transverse sections of S. mutans films in Ultrafree-CL units with 0.22mum pores showed bacteria invading the membrane filter structure it is likely that this is the route of spread. Populations of L. casei remained stable within the Ultrafree-CL units for up to 21 days, whilst A. viscosus viable counts tended to decline between days 6 and 21 days. Furthermore there appeared to be a maximum population density of approximately 107 c.f.u/cm2, which was independent of the viable counts in the initial inoculum. However, when the films were cultured with sucrose solution or distilled water instead of Todd Hewitt broth (T.H.B.) there were substantial decreases in viable counts, although these could be reversed by returning the films to T.H.B. This suggested that transfer from sucrose back to T.H.B. could allow one film to be used for a series of studies with few adverse effects on the overall viable counts. In chapter 5, preliminary experiments are described which sought to determine whether the test bacterial species could cause demineralisation of root surfaces or hydroxyapatite powder within the Ultrafree-CL model system. The data indicated that they did indeed cause calcium release from mineral, with the rank order of S mutans ~ L casei > A. viscosus, whilst lactate was usually the predominant anion. These results concur in general with the available literature. However, there was substantial variation in both the acid anion production and calcium release data between repeat experiments which indicated that modifications to the model system may be required before it can be successfully employed for demineralisation experiments. In chapter 6 a range of modifications to the Ultrafree-CL system are described which would help to reduce the variation to acceptable levels and allow the model to be employed to investigate root surface caries further

Trajan Places: Establishing Identity and Context for the Bosham and Hawkshaw Heads

Two damaged, weathered marble portraits, both discovered in the 1780s at opposite ends of Roman Britain, one at Bosham in West Sussex, the other at Hawkshaw in Peeblesshire, are here re-examined and identified as portraits of the emperor Trajan. The Bosham head is interpreted as a post-mortem image of the deified Trajan set up at the margins of Chichester Harbour, probably during the visit to Britain by the emperor Hadrian in the early a.d. 120s. The Hawkshaw portrait of Trajan appears to have been refashioned from a likeness of Domitian and may originally have been part of a monument created to celebrate and commemorate the total conquest of Britain, in the early a.d. 80s, which was decapitated and buried during a period of unrest on the northern frontier

‘Sons of athelings given to the earth’: Infant Mortality within Anglo-Saxon Mortuary Geography

FOR 20 OR MORE YEARS early Anglo-Saxon archaeologists have believed children are underrepresented in the cemetery evidence. They conclude that excavation misses small bones, that previous attitudes to reporting overlook the very young, or that infants and children were buried elsewhere. This is all well and good, but we must be careful of oversimplifying compound social and cultural responses to childhood and infant mortality. Previous approaches have offered methodological quandaries in the face of this under-representation. However, proportionally more infants were placed in large cemeteries and sometimes in specific zones. This trend is statistically significant and is therefore unlikely to result entirely from preservation or excavation problems. Early medieval cemeteries were part of regional mortuary geographies and provided places to stage events that promoted social cohesion across kinship systems extending over tribal territories. This paper argues that patterns in early Anglo-Saxon infant burial were the result of female mobility. Many women probably travelled locally to marry in a union which reinforced existing social networks. For an expectant mother, however, the safest place to give birth was with experience women in her maternal home. Infant identities were affected by personal and legal association with their mother’s parental kindred, so when an infant died in childbirth or months and years later, it was their mother’s identity which dictated burial location. As a result, cemeteries central to tribal identities became places to bury the sons and daughters of a regional tribal aristocracy

The Pseudomonas Quinolone Signal (PQS) Balances Life and Death in Pseudomonas aeruginosa Populations

When environmental conditions deteriorate and become inhospitable, generic survival strategies for populations of bacteria may be to enter a dormant state that slows down metabolism, to develop a general tolerance to hostile parameters that characterize the habitat, and to impose a regime to eliminate damaged members. Here, we provide evidence that the pseudomonas quinolone signal (PQS) mediates induction of all of these phenotypes. For individual cells, PQS, an interbacterial signaling molecule of Pseudomonas aeruginosa, has both deleterious and beneficial activities: on the one hand, it acts as a pro-oxidant and sensitizes the bacteria towards oxidative and other stresses and, on the other, it efficiently induces a protective anti-oxidative stress response. We propose that this dual function fragments populations into less and more stress tolerant members which respond differentially to developing stresses in deteriorating habitats. This suggests that a little poison may be generically beneficial to populations, in promoting survival of the fittest, and in contributing to bacterial multi-cellular behavior. It further identifies PQS as an essential mediator of the shaping of the population structure of Pseudomonas and of its response to and survival in hostile environmental conditions