Exercise does not affect stiffness and mineralisation of third metacarpal condylar subarticular calcified tissues in 2 year old thoroughbred racehorses.

Impact exercise has a profound effect in increasing volumetric density of epiphyseal bone, as clearly shown in 2 year old thoroughbred racehorses from which we derived the tissue studied in the present investigation. Here, we asked the question whether the fabric-level properties of the mineralised tissues immediately below hyaline articular cartilage which transmit the extra loads are themselves altered in consequence. We therefore studied the nanoindentation elastic modulus and its relationship to the concentration of mineral determined by quantitative backscattered electron imaging in the heavily loaded palmar medial and lateral condyles of the distal third metacarpal bone (Mc3) of 4 untrained and 4 trained 2-year old Thoroughbred racehorses. We found no difference between trained and untrained horses in either subchondral bone or calcified cartilage in the mean stiffness or mineral content or their correlation. Thus neither articular calcified cartilage nor the immediately adjacent subchondral bone were affected by exercise, even though they transmitted the higher load associated with athletic training through to the deeper bone, which itself responded floridly to exercise. Under the circumstances of this experiment and at least in the very small regions studied, therefore, the structure of these two tissues was apparently optimised to function.

Prevalence of serotype specific antibody to equine encephalosis virus in Thoroughbred yearlings in South Africa (1999-2004).

Cohorts of yearlings were sampled over a period of 6 years in a retrospective serological survey to establish the annual prevalence of serotype specific antibody to equine encephalosis virus on Thoroughbred stud farms distributed within defined geographical regions of South Africa. Seasonal seroprevalence varied between 3.6% and 34.7%, revealing both single and multiple serotype infections in an individual yearling. During the course of this study serotypes 1 and 6 were most frequently and extensively identified while the remaining serotypes 2, 3, 4, 5 and 7 were all identified as sporadic and localized infections affecting only individual horses. This study of the seasonal prevalence of equine encephalosis virus has a corollary and serves as a useful model in the seasonal incidence of the serotypes of African horse sickness and bluetongue in regions where the respective diseases are endemic.

Monte Carlo simulations of electron scattering in bone.

Relative changes in the mineralization level within bone can be studied using backscattered electron (BSE) imaging in a scanning electron microscope (SEM). We calculated the size and shape of the volume element studied, choosing conditions which are typical for practical experimental work with polymethylmethacrylate (PMMA)-embedded bone. Absolutely flat surfaces of embedded bone blocks cannot be generated, and a further aim was to examine the effect of the surface topography on the detected BSE signal level. For normal beam incidence, 20 kV, and modeling an annular detector by collecting BSE with take-off angles of between 45 degrees and 75 degrees to the flat sample surface, it was found that the collectable BSE signal intensity peaks for electrons which leave the specimen surface at a radial distance of approximately 1 micron from the beam impact point. The layered structure of the bone generates topographic relief on polishing. Modeling this by a sinusoidal profile of wavelength 5.0 and amplitude 0.5 micron and again for 20 kV, it was found that the signal derived from the troughs is reduced by 14.4% and that from the crests is increased by 17.2%. The two effects may add constructively to generate the frequently observed strong contrast correlating with the distribution of bone lamellae. No net change in mineral packing density would be expected from a change in collagen orientation, and the lamellar contrast observed in practice can be explained solely by the topographic contrast.

A model of temperature transients in dental implants.

Dental implants provide a continuous interface between the oral environment and the deep core structures of the jaws. Implants and trans-mucosal superstructures are primarily metal and heat conduction occurs readily. A hypothetical heat conduction model is investigated to determine the ranges of temperature gradients that might occur in implants. This model showed that a 60 degrees C heat source will cause a heat front of > or = 47 degrees C to advance > 3 mm down an implant within one second. Oral temperature transients may be a factor in implant pathology.

A group-specific, indirect sandwich ELISA for the detection of equine encephalosis virus antigen.

A polyclonal antibody-based, group-specific, indirect, sandwich ELISA (S-ELISA) for the detection of equine encephalosis virus (EEV) antigen was developed. Purified EEV particles were titrated in the S-ELISA and the limit of detection was determined to be approximately 9.0 ng of antigen/ml (0.45 ng/well). Positive S-ELISA reactions were recorded with seven serologically distinct EEV serotypes. No cross-reactions were recorded with other arboviruses including African horse sickness virus (AHSV) serotypes 1-9, bluetongue serotypes 1-24, epizootic haemorrhagic disease serotypes 1-8 and isolate 318, and selected isolates of Palyam, Eubenangee, Corriparta, Warrego, Akabane and bovine ephemeral fever viruses. The assay proved to be sensitive and specific for the rapid detection of EEV in cell cultures and in homogenated suckling mouse brain (MB). The data generated in this study suggest that the ELISA will be valuable for epidemiological studies of EE and will assist in making a reliable differential diagnosis between EEV and AHSV infections.

The variation in the size and shape of the human speech pattern with incisor-tooth relation.

A mandibular kinesiograph was used to monitor the movement of the lower incisors of young dentate adults reading a standard text. An interface to a microcomputer which recorded and analysed these movements. As the tracings accumulated on the computer monitor, a characteristic pattern was produced. The dimensions of this speech pattern, or envelope of movement, were measured and correlated with the subject's sex and incisor classification. Four distinct patterns were found and these correlated well with incisor classification. Small differences were noted in the dimensions of the speech envelope between men and women, but these were not significant.

Lateral transmission of equine arteritis virus among Lipizzaner stallions in South Africa.

REASONS FOR PERFORMING STUDY: A serological study conducted in 1995 revealed that 7 stallions at the Lipizzaner Centre, Gauteng, South Africa, were seropositive for antibody to equine arteritis virus (EAV). A Lipizzaner stallion imported into South Africa from Yugoslavia in 1981 had previously (1988) been confirmed to be an EAV carrier. Despite being placed under life-long breeding quarantine, EAV had been transmitted between stallions at the Lipizzaner Centre. OBJECTIVES: To investigate the phylogenetic relationships between the strain of EAV shed in the semen of the original carrier stallion and strains recovered from the semen of 5 other stallions; and to investigate the means whereby lateral transmission of EAV occurred among 7 in-contact, nonbreeding stallions at the Centre. METHODS: EAV was isolated from semen collected from the seropositive stallions using RK-13 cells. Viral RNA was reverse transcribed and amplified by polymerase chain reaction using ORF 5-specific primers, subjected to sequence and phylogenetic analysis. RESULTS: Phylogenetic analysis of strains of EAV recovered from the semen of 6 persistently infected stallions confirmed that all viruses were closely related and probably derived from a common ancestor, i.e. the stallion imported from Yugoslavia. Lateral transmission subsequently occurred among 7 in-contact, nonbreeding stallions at the Centre. It is speculated that these stallions may have been exposed to virus from bedding or fomites contaminated with semen. CONCLUSIONS: These data confirm that lateral transmission of EAV can occur from shedding stallions to susceptible, in-contact horses, including other stallions, which may become persistently infected with the virus. POTENTIAL RELEVANCE: The findings are consistent with lateral spread of a single, unique strain of EAV among a group; and suggest that transmission of EAV may be initiated by infection of one or more stallions with virus on bedding or other fomites contaminated with EAV- infected semen.

West Nile virus infection of Thoroughbred horses in South Africa (2000-2001).

REASONS FOR PERFORMING STUDY: West Nile virus (WNV) infection is endemic in southern Africa. With the recent emergence of WNV infection of horses in Europe and the USA the present study was performed to estimate the risk of seroconversion to WNV in a cohort of 488 young Thoroughbred (TB) horses. OBJECTIVES: To estimate the risk of seroconversion to WNV among a cohort of South African TB yearlings sold at the 2001 National Yearling Sales (NYS) and to determine whether the risk varied geographically. Two horses were also infected with a recent South African isolate of WNV to evaluate its virulence in horses. METHODS: Serum samples were collected from the cohort of 488 TB yearlings at the 2001 NYS. Serum samples that were collected from the same horses at the time that they were identified were sourced from our serum bank. Sera from 243 of the dams that were collected at the time that the foals were identified were also sourced from our serum bank. These sera were subjected to serum neutralisation (SN) tests for antibody to WNV. RESULTS: Approximately 11% of yearlings seroconverted to WNV on paired serum samples collected from each animal approximately 12 months apart. Studfarms with WNV-seropositive yearlings were widely distributed throughout South Africa and SN tests on sera from their dams indicated that exposure to WNV was even more prevalent (75%) in this population. Neurological disease was not described in any of the horses included in this study and 2 horses inoculated with a recent lineage 2 South African isolate of WNV showed no clinical signs of disease after infection and virus was not detected in their blood. CONCLUSIONS: Infection of horses with WNV is common in South Africa, but infection is not associated with neurological disease. POTENTIAL RELEVANCE: In contrast to recent reports from Europe, North Africa, Asia and North America, the results of our field and experimental studies indicated that exposure of horses to the endemic southern African strains of WNV was not associated with neurological disease.

Monte Carlo simulation of electron backscattering from compounds with low mean atomic number.

This paper reports a Monte Carlo simulation where a single atom scattering model is adopted. The element taking part in each electron-atom interaction is selected on the basis of its contribution either to the total elastic cross section or to the electron's mean free path. Both Rutherford and Mott scattering are considered, with the continuous slowing down process of Bethe used to calculate the energy loss to the system. The backscattered electron coefficients show good agreement with experimental results from a large group of low atomic number materials when using a model which selects the scattering atom by its contribution to the whole compound calculated from its atomic fraction of the total elastic cross-section.

Surface roughness of preparations for backscattered electron-scanning electron microscopy: the image differences and their Monte Carlo simulation.

Patterns and levels of mineralisation in the biological hard tissues have been studied using the backscattered electron (BSE) mode in the scanning electron microscope (SEM). To prevent gross topographic detail overwhelming changes in signal from composition, samples are embedded in polymethylmethacrylate (PMMA) and a flat block surface produced by polishing or micromilling. This study was undertaken to establish the degree of residual topography achieved in these finishing processes. A sample of human rib was embedded in PMMA and prepared, as for examination in the SEM, by polishing on graded abrasives and pre- and, finally, ultramilling. After each preparation step, the block face was imaged using a confocal reflection microscope surface mapping facility. The recorded topographies were used in a Monte Carlo simulation to model the surface interface and thus, for each of the sample preparation techniques, to calculate predicted variations in BSE signal. The latter were compared with experimental data derived under standard operating conditions in the SEM. Micromilling produced block faces with typical peak-trough relief of 80 nm, while hand polishing left occasional scratches 1.5 microns deep with a general undulation of 150-250 nm. Monte Carlo simulations of a rough surface of bone using these data predicted that additional contrast levels of 5% could be expected from micromilled surfaces and > 10% for hand polished samples of bone. Thus, micromilling is the best preparation method for bone, since this tissue develops a collagen orientation-related relief on polishing, which may be largely responsible for the (incorrect) supposition that lamellation in bone is related to changes in net degree of mineralisation.

Correlative light and backscattered electron microscopy of bone--part II: automated image analysis.

Detailed studies of biological phenomena often involve multiple microscopy and imaging modes and media. For bone biology, various forms of light and electron microscopy are used to study the microscopic structure of bone. Integrating information from the different sources is necessary to understand how different aspects of the bone structure interact. To accomplish this, methods were developed to prepare and image thin sections for correlative light microscopy (LM) and backscattered electron imaging in the scanning electron microscope (BSE-SEM). Images of the same fields of view may then be analyzed for degrees of relationships between specimen features not observed by LM or SEM alone. These methods are applied here to study possible associations between the degree of bone mineralization and pattern of collagen fiber orientation in the mid-shaft of the human femur. The "relational images" obtained allow us to examine the relationship between these two variables, both objectively and quantitatively.

Light collection efficiency and light transport in backscattered electron scintillator detectors in scanning electron microscopy.

Experimentally, scintillator detectors used in scanning electron microscopy (SEM) to record backscattered electrons (BSE) show a noticeable difference in detection efficiency in different parts of their active zones due to light losses transport in the optical part of the detector. A model is proposed that calculates the local efficiency of the active parts of scintillator detectors of arbitrary shapes. The results of these calculations for various designs are presented.

The size of occlusal rest seats prepared for removable partial dentures.

OBJECTIVE: The aim of this study was to test whether rest seats cut by a group of general dental practitioners for a removable partial denture differed in size and shape from those prepared by either a group of postgraduate students or their academic teachers. METHOD: The occlusal surfaces of a number of plastic teeth were scanned by a laser profilometer. Each tooth was then placed in a set of articulated phantom head dental arches. 30 dental practitioners, 16 postgraduates and 11 dental academics were asked to cut a rest seat preparation in the mesial marginal ridge suitable for the construction of a removable chromium cobalt partial denture. The tooth was removed from the models, rescanned, and this data converted to grey level images for measurement of the width, length and area of each rest seat. Depth was calculated as the difference between the pre and post preparation scanned profiles. RESULTS: There was a wide variation in the size of the individual rest seat preparations. There was no significant difference between the measured parameters from the images of the preparations made by academic staff and postgraduate students. The two sets of data were therefore combined. The length, width and area of the rest seats prepared by the staff and postgraduate group were significantly greater than those cut by the dental practitioner group. However, there was no significant difference in the depths measured. The outline form of the rests prepared by the dental practitioners was often round with sharply defined margins contrasting with the smooth triangular preparation the staff and postgraduates prepared. CONCLUSION: A 'refresher' in tooth modification for GDPs designing partial dentures would improve the long term success of the prosthesis.

The classification of seven serotypes of equine encephalosis virus and the prevalence of homologous antibody in horses in South Africa.

Selected isolates of equine encephalosis virus were shown to have comparable viral protein profiles and to represent seven distinct serotypes, based on cross-neutralization tests. Serotype-specific virus-neutralizing antibody in serum samples from horses confirmed the widespread occurrence of infection. The distribution and prevalence of individual serotypes however, varied considerably. Localised foci with an increased seasonal seroconversion in groups of horses to a specific serotype and the detection of an ongoing low level of infection from other serotypes within the population, confirmed the independent persistence of the viruses in a maintenance cycle. The identification of donors with antibody resulting from infection with multiple serotypes indicated a low level of cross-protection in horses to natural reinfection.

Some husbandry factors influencing weaning stresses in piglets.

The post-weaning diarrhoea syndrome (PWDS) in piglets is multi-factorial in origin. Numerous managemental, environmental, housing, nutritional, immunological and physiological factors are discussed, being primary factors in the cause of the PWDS. Infectious agents especially Escherichia coli are often incriminated as causes of PWDS but are more likely to be opportunistic elements due to faulty management of stressed animals.

A comparative microbiological study of clinically healthy eyes and those affected by ophthalmia in cattle and the association of noctuid eye-frequenting moths.

The eyes of clinically healthy Simmentaler cattle and those affected by ophthalmia were sampled once a month over a continuous period of 12 months for bacterial, mycoplasmal and ureaplasmal infections. In total 478 eyes, representing from a clinical viewpoint 414 healthy and 64 affected eyes, were swabbed. Bacteria were isolated from 201 (48.6%) healthy eyes and 56 (87.5%) affected eyes. No bacteria were isolated from the remaining eyes. Eleven genera of bacteria were isolated from healthy eyes and 8 genera from affected eyes. The majority of isolates were classified in the genera Moraxella, Neisseria and Staphylococcus. Mycoplasmas were isolated from 247 (50.7%) healthy eyes and 27 (42.2%) affected eyes. No mycoplasmas were isolated from the remaining eyes. Ureaplasmas were not isolated from any animal. Eye-frequenting moths were collected on 3 occasions during the investigation and bacterial and mycoplasmal isolation techniques were performed on a total of 21 moths. Twelve different genera of bacteria, mostly Nocardia, Corynebacterium, Staphylococcus, Moraxella, and mycoplasmas were isolated from various eye-frequenting moths. Scanning electron microscopical studies of the proboscis of the moths showed it to contain various sensillae and short triangular denticles that could possibly cause damage to the mucous membranes of the eyes and predispose to ophthalmia in cattle.

A biometric guide to prosthetic tooth positioning investigated in subjects with Class II division 2 incisor relationships.

A biometric guide for positioning of the maxillary central incisors in complete dentures is the incisor-incisive papilla distance. This distance was compared in dentate subject with either Class I or Class II/2 incisor relations. Maxillary casts were orientated parallel to the occlusal plane on an xy table, connected to a movable vertical arm. The distance from the posterior edge of the papilla to the labial incisor surface was measured. Results showed a mean difference of 2 mm between the groups, significant at the P < or = 0.001 level, however this distance would not appear to invalidate the conventional biometric guideline of 10 mm.

A competitive ELISA for the detection of group-specific antibody to equine encephalosis virus.

A polyclonal antibody-based, group-specific, competitive ELISA (C-ELISA) for the detection of antibodies to equine encephalosis virus (EEV) was developed. The assay measures the competition between a specific guinea pig antiserum and a test serum, for a pre-titrated EEV antigen. The C-ELISA detected antibodies to the seven known EEV serotypes. Reference antisera raised against other arboviruses did not cross react with EEV antigen. Negative sera from horses in the United Kingdom were used to establish the baseline for a negative population. Negative and positive populations of South African horses, selected on the basis of virus neutralisation were assayed subsequently. Optimal test parameters, where sensitivity≅specificity≅100%, were calculated by two-graph receiver operator characteristic (TG-ROC) analysis to be at a cut-off value of 29.5% inhibition. Results show the EEV C-ELISA described to be sensitive, specific and reliable. Used in conjunction with ELISAs available for African horse sickness virus (AHSV), differential serological diagnosis between EEV and AHSV can be achieved.

Changes in bone mineral and matrix in response to a soft diet.

Alterations in the magnitude of habitual mechanical loads upon the skeleton may not only affect bone architecture, but also influence the nature of the bone matrix. We tested the hypothesis that changing the mechanical consistency of the diet affects both the mineral and non-mineralized moieties of bone matrix. Female rats were fed a soft diet (powdered chow as a paste), while control animals were fed the standard chow. After 8 or 20 wks, animals were killed. Cranial (mandible, maxilla, parietal, and frontal) bones and ulnae were analyzed for mineralization density by quantitative backscattered electron microscopy, and sulphated glycosaminoglycan levels with alcian blue staining were measured by microdensitometry. The soft diet group showed a significant increase in mineralization density distribution at almost all cranial sites and a reduction in alcian blue staining in alveolar bone. Altering the consistency of the diet significantly affects mineral concentration and glycosaminoglycan content of alveolar bone.