Factors associated with whole carcass condemnation rates in provincially-inspected abattoirs in Ontario 2001-2007: implications for food animal syndromic surveillance

Background  

Ontario provincial abattoirs have the potential to be important sources of syndromic surveillance data for emerging diseases of concern to animal health, public health and food safety. The objectives of this study were to: (1) describe provincially inspected abattoirs processing cattle in Ontario in terms of the number of abattoirs, the number of weeks abattoirs process cattle, geographical distribution, types of whole carcass condemnations reported, and the distance animals are shipped for slaughter; and (2) identify various seasonal, secular, disease and non-disease factors that might bias the results of quantitative methods, such as cluster detection methods, used for food animal syndromic surveillance.     

Peripheral NK1.1 NKT cells are mature and functionally distinct from their thymic counterparts

One interesting aspect of NKT cell development is that although they are thymus dependent, the pivotal transition from NK1.1(-) to NK1.1(+) can often take place after immature NK1.1(-) NKT cells are exported to the periphery. NK1.1(-) NKT cells in general are regarded as immature precursors of NK1.1(+) NKT cells, meaning that peripheral NK1.1(-) NKT cells are regarded as a transient, semimature population of recent thymic emigrant NKT cells. In this study, we report the unexpected finding that most NK1.1(-) NKT cells in the periphery of naive mice are actually part of a stable, mature and functionally distinct NKT cell population. Using adult thymectomy, we show that the size of the peripheral NK1.1(-) NKT cell pool is maintained independently of thymic export and is not the result of NK1.1 down-regulation by mature cells. We also demonstrate that most peripheral NK1.1(-) NKT cells are functionally distinct from their immature thymic counterparts, and from NK1.1(+) NKT cells in the periphery. We conclude that the vast majority of peripheral NK1.1(-) NKT cells are part of a previously unrecognized, mature NKT cell subset.     

Infrared spectroscopy and differential scanning calorimetry studies of binary combinations of cis-6-octadecenoic acid and octadecanoic acid

Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) studies are reported for combinations of cis-6-octadecenoic acid (also termed petroselinic acid, PSA) and octadecanoic acid (also termed stearic acid, SA) across a wide range of binary mole ratio combinations. The data are then used to plot the phase diagram which is found to be montotectic with the PSA reducing the melting temperature of SA at all compositions. The relevance of these experiments to stratum corneum (SC) biophysical behavior, particularly the influence and potential mechanisms of PSA on dermal permeation, is discussed. The potential role of cis-6-octadecenoic acid as a permeation enhancer is discussed in the context of these studies of its interaction with saturated fatty acids.     

pH reduction as a trigger for dissociation of herpes simplex virus type 1 scaffolds

Assembly of the infectious herpes simplex virus type 1 virion is a complex, multistage process that begins with the production of a procapsid, which is formed by the condensation of capsid shell proteins around an internal scaffold fashioned from multiple copies of the scaffolding protein, pre-VP22a. The ability of pre-VP22a to interact with itself is an essential feature of this process. However, this self-interaction must subsequently be reversed to allow the scaffolding proteins to exit from the capsid to make room for the viral genome to be packaged. The nature of the process by which dissociation of the scaffold is accomplished is unknown. Therefore, to investigate this process, the properties of isolated scaffold particles were investigated. Electron microscopy and gradient sedimentation studies showed that the particles could be dissociated by low concentrations of chaotropic agents and by moderate reductions in pH (from 7.2 to 5.5). Fluorescence spectroscopy and circular dichroism analyses revealed that there was relatively little change in tertiary and secondary structures under these conditions, indicating that major structural transformations are not required for the dissociation process. We suggest the possibility that dissociation of the scaffold may be triggered by a reduction in pH brought about by the entry of the viral DNA into the capsid.     

Iota-carrageenan: molecular structure and packing of polysaccharide double helices in oriented fibres of divalent cation salts

The Ca²⁺ and Sr²⁺ salts of i-carrageenan have isomorphous crystal structures with trigonal unit cells of dimensions a = b = 1.373 nm, c = 1.328 nm, γ = 120 °. Two kinds of fibre diffraction pattern were found for the Mg²⁺ salt: one resembling the Ca²⁺ and Sr²⁺ patterns and one with additional layer lines interleaved midway between those in the usual kind of pattern. Specimens of this second type convert to the first type on storage at 92% relative humidity. These Mg²⁺i-carrageenate diffraction patterns provide direct evidence for the double-helical nature of the carrageenan molecule.A molecular model has been derived that consists of two, identical, righthanded, 3-fold helical polysaccharide chains of pitch 2.656 nm. One chain is translated axially 1.32 nm relative to the other.A packing arrangement with up-pointing and down-pointing double helices distributed randomly among the molecular sites explains the presence of both Bragg reflections and layer line streaks. The space group of our statistical crystal structure is P3₂12. The divalent cations were found by Fourier difference syntheses to be at ($\text{2}\text{3}$, $\text{1}\text{3}$, $\text{1}\text{6}$) and symmetry-related positions. The co-ordination of each cation to sulphate groups on two different helices leads to a continuous set of cation-sulphate-cation-… interactions that accounts for the high crystallinity of these salts.The structure of the Ca²⁺ salt has been refined by constrained linked-atom least-squares methods. The structural isomorphism of the Sr²⁺ salt was confirmed by an independent refinement.     

The Product of the Herpes Simplex Virus Type 1 UL25 Gene Is Required for Encapsidation but Not for Cleavage of Replicated Viral DNA

The herpes simplex virus type 1 (HSV-1) UL25 gene contains a 580-amino-acid open reading frame that codes for an essential protein. Previous studies have shown that the UL25 gene product is a virion component (M. A. Ali et al., Virology 216:278–283, 1996) involved in virus penetration and capsid assembly (C. Addison et al., Virology 138:246–259, 1984). In this study, we describe the isolation of a UL25 mutant (KUL25NS) that was constructed by insertion of an in-frame stop codon in the UL25 open reading frame and propagated on a complementing cell line. Although the mutant was capable of synthesis of viral DNA, it did not form plaques or produce infectious virus in noncomplementing cells. Antibodies specific for the UL25 protein were used to demonstrate that KUL25NS-infected Vero cells did not express the UL25 protein. Western immunoblotting showed that the UL25 protein was associated with purified, wild-type HSV A, B, and C capsids. Transmission electron microscopy indicated that the nucleus of Vero cells infected with KUL25NS contained large numbers of both A and B capsids but no C capsids. Analysis of infected cells by sucrose gradient sedimentation analysis confirmed that the ratio of A to B capsids was elevated in KUL25NS-infected Vero cells. Following restriction enzyme digestion, specific terminal fragments were observed in DNA isolated from KUL25NS-infected Vero cells, indicating that the UL25 gene was not required for cleavage of replicated viral DNA. The latter result was confirmed by pulsed-field gel electrophoresis (PFGE), which showed the presence of genome-size viral DNA in KUL25NS-infected Vero cells. DNase I treatment prior to PFGE demonstrated that monomeric HSV DNA was not packaged in the absence of the UL25 protein. Our results indicate that the product of the UL25 gene is required for packaging but not cleavage of replicated viral DNA.     

Seasonal energetics of northern phocid seals

The metabolic rate of harp (Pagophilus groenlandicus), harbor (Phoca vitulina), and ringed seals (Pusa hispida) was measured at various temperatures in air and water to estimate basal metabolic rates (BMRs) in these species. The basal rate and body composition of three harp seals were also measured throughout the year to examine the extent to which they vary seasonally. Marine mammalian carnivores generally have BMRs that are over three times the rates expected from body mass in mammals generally, both as a response to a cold-water distribution and to carnivorous food habits with the basal rates of terrestrial carnivores averaging about 1.8 times the mean of mammals. Phocid seals, however, have basal rates of metabolism that are 30% lower than other marine carnivores. Captive seals undergo profound changes in body mass and food consumption throughout the year, and after accounting for changes in body mass, the lowest rate of food intake occurs in summer. Contrary to earlier observations, harp seals also have lower basal rates during summer than during winter, but the variation in BMR, relative to mass expectations, was not associated with changes in the size of fat deposits. The summer reduction in energy expenditure and food consumption correlated with a reduction in BMR. That is, changes in BMR account for a significant portion of the seasonal variation in energy expenditure in the harp seal. Changes in body mass of harp seals throughout the year were due not only to changes in the size of body fat deposits, but also to changes in lean body mass. These results suggest that bioenergetics models used to predict prey consumption by seals should include time-variant energy requirements.     

Food habits, energetics, and the reproduction of marsupials

Basal rate of metabolism in marsupials and in eutherian mammals is principally correlated with body mass, food habits and activity. Feeding on fruit, the leaves of woody plants, or invertebrates is associated with low basal rates, especially at large masses, in both groups of mammals. These foods lead to low basal rates because they are seasonally unavailable, are indigestible, or need to be detoxified. The depression in basal rate associated with frugivory and folivory is increased when coupled with sedentary, arboreal habits in both marsupials and eutherians. In contrast, eutherians that feed on vertebrates or herbs generally have high basal rates, while marsupials that eat these foods do not have high basal rates. These foods permit high basal rates, which are exploited by eutherians because high basal rates in these mammals lead to high rates of reproduction. Marsupials have, at best, a limited correlation of reproduction with rate of metabolism, so that feeding on vertebrates or herbs does not lead to high basal rates in these mammals. This difference between marsupials and eutherians in the coupling of reproduction to energetics has at least two ecological consequences. 1) Marsupials generally do not tolerate cold-temperate environments because they do not accelerate growth and development to complete reproduction within a short spring and summer. 2) Marsupials coexist with ecologically similar eutherians as long as marsupials have food habits that are correlated with low rates of metabolism in eutherians (i.e. they feed on fruit, the leaves of woody plants, or invertebrates), but they tend to be displaced by eutherians when marsupials have food habits that are associated with high rates of metabolism in eutherians (i.e. when they feed on vertebrates and, probably, herbs).     

Analysis of factors that influence energy expenditure in honeyeaters (Meliphagidae)

The energy expenditure of the tūī (Prosthemadera novaeseelandiae), a meliphagid endemic to New Zealand, was measured and compared with 20 species of honeyeaters (family Meliphagidae) to determine whether its expenditure is influenced either by life in a moist, temperate climate or an island residence. Body mass in the honeyeaters accounted for 91.5% of the variation in basal rate. The combination of body mass, climate and the maximal limit to an altitudinal distribution explained 98.6% of the variation in basal rate with tropical, low-altitude species having the highest mass-independent rate. The basal rates of meliphagids in tropical highlands are similar to those in temperate lowlands, which may reflect similar food supplies. The tūī mass-independent expenditure appears to reflect an active lifestyle in a temperate climate with no evidence that an island residence influenced its rate, whereas sedentary birds on New Zealand have responded to island life with a depressed basal rate. An effective analysis of the variation in energy expenditure requires the inclusion of the ecological and behavioural characteristics that distinguish species.