Pathway of ultrasound waves in the equine third metacarpal bone

The velocity of ultrasound waves through bone has been used widely as a non-invasive method for assessing bone quality. Accurate measurement of velocity depends on accurate assessment of the distance travelled by the sound wave. It has been argued that the sonic pathway is deflected around the marrow cavity and so does not follow a straight line through the bone; therefore, correction factors have been developed to account for the extra distance travelled. This hypothesis was examined in vitro using sections from the equine third metacarpal bone. Two 1 MHz transducers used with the transmitting transducer energized by a 600 V electrical spike generator produced a 0.1 μs pulse width and the received signal was recorded on a delayed time-base oscilloscope, from which the velocity was calculated. Two distinct peaks were apparent in the received signal, corresponding to a direct cortical transmission wave and a direct medullary transmission wave. This observation was confirmed quantitatively using models of the third metacarpal made from homogeneous materials that allow accurate determination of the transit times of each component of the signal. Perspex was used to mimic cortical bone, with water as the mimic for the contents of the medullary canal; these materials were chosen because they have transmission velocities similar to the materials they were mimicing. The results confirmed that the pathway went straight through the bone with a time lag in the medullary wave due to the slower transmission velocity of the marrow. To ensure that the cortical wave is always received, transducers larger than the medullary width should always be used.     

Cell proliferation patterns during development of the equine placenta

Placentation involves considerable growth and reorganization of both maternal and fetal tissues. In this investigation, immunohistochemical localization of the proliferation marker Ki-67 antigen was used to monitor cell division during placentation in mares. Endometrial biopsies were obtained from eight mares between day 14 and day 26 of pregnancy and from eight anoestrous mares that had been treated with various combinations of progesterone and oestrogen. Samples of endometrium and fetal membranes were obtained from 19 mares carrying normal horse conceptuses between day 30 and day 250 of gestation and from three failing extraspecific donkey-in-horse pregnancies. Proliferation in the superficial strata of the endometrium was increased by day 18 of gestation and this effect could be mimicked by supplementing with oestradiol benzoate during the last 6 days of a prolonged period (18-36 days) of progesterone administration. Fetal chorionic girdle cells were proliferating vigorously at days 30-32 of gestation, but stopped dividing after they invaded the endometrium, while the trophoblast cells of the allantochorion showed an increase in mitotic activity after day 38. The luminal epithelium of the endometrium started to proliferate only after the primary villi of the true epitheliochorial placenta had been formed, and during days 58-70 this effect was seen only in the pregnant horn in which placentation was further advanced. During the second half of gestation, most of the mitotic activity was confined to the periphery of the microcotyledons which were still growing. In the donkey-in-horse pregnancies, proliferation rates of the maternal and fetal epithelial at day 70 of gestation were markedly reduced in areas of heavy endometrial lymphocyte infiltration and poor placentation. These results provide a basis for further studies on factors that influence invasive and non-invasive placentation.     

Using partial least squares regression as a predictive tool in describing equine third metacarpal bone shape

Population variance in bone shape is an important consideration when applying the results of subject-specific computational models to a population. In this letter, we demonstrate the ability of partial least squares regression to provide an improved shape prediction of the equine third metacarpal epiphysis, using two easily obtained measurements.     

Cell proliferation patterns in the equine endometrium throughout the non-pregnant reproductive cycle.

Immunohistochemical detection of the proliferation marker Ki-67 antigen was used to monitor mitotic activity in the endometrium of mares. The monoclonal antibody MIB1 was validated for use on equine tissues by demonstrating its reaction with activated peripheral blood lymphocytes, and endometrial biopsies were recovered from 26 non-pregnant mares at selected stages during the reproductive cycle. The proportion of positively stained nuclei was counted in five random areas on each histological section to determine the percentage and type of proliferating cells. Multiplication rates in the types of cell found in the superficial strata, comprising the luminal epithelium, the epithelium of the gland necks and the stromal cells of the stratum compactum, were greatest during oestrus, presumably under the influence of oestrogens secreted by the growing ovarian follicles. In contrast, the mitotic activity in the cells of the deeper secretory portions of the endometrial glands was restricted to a brief phase between day 3 and day 7 of dioestrus, most likely as a delayed response to the decreasing oestrogen concentrations after ovulation. Some of the degenerate glands in subfertile mares did not follow this pattern of increased epithelial proliferation at that stage. After day 7 of dioestrus, the proliferation rates of cells in the endometrium decreased to basal values and remained low for as long as progesterone concentrations remained evaluated, even during prolonged dioestrus. The technique enabled characterization of normal cell proliferation patterns in the endometrium of mares and it will be a useful tool in the future for monitoring the endometrial responses of reproductively healthy and subfertile mares.     

Comprehensive analysis of the overall codon usage patterns in equine infectious anemia virus

Background

Equine infectious anemia virus (EIAV) is an important animal model for understanding the relationship between viral persistence and the host immune response during lentiviral infections. Comparison and analysis of the codon usage model between EIAV and its hosts is important for the comprehension of viral evolution. In our study, the codon usage pattern of EIAV was analyzed from the available 29 full-length EIAV genomes through multivariate statistical methods.

Finding

Effective number of codons (ENC) suggests that the codon usage among EIAV strains is slightly biased. The ENC-plot analysis demonstrates that mutation pressure plays a substantial role in the codon usage pattern of EIAV, whereas other factors such as geographic distribution and host translation selection also take part in the process of EIAV evolution. Comparative analysis of codon adaptation index (CAI) values among EIAV and its hosts suggests that EIAV utilize the translational resources of horse more efficiently than that of donkey.

Conclusion

The codon usage bias in EIAV is slight and mutation pressure is the main factor that affects codon usage variation in EIAV. These results suggest that EIAV genomic biases are the result of the co-evolution of genome composition and the ability to evade the host’s immune response.

     

A kinematic and strain gauge study of the reciprocal apparatus in the equine hind limb.

Hind limb kinematics were recorded in five horses at walk and trot using an opto-electronic CODA-3 system. Simultaneously, in vivo strain in the completely tendinous peroneus tertius muscle was registered by implanted mercury-in-silastic strain gauges. The origin-insertion length patterns of the peroneus tertius were calculated from raw kinematic data and from data corrected for the error caused by skin displacement, and compared with the directly measured strain. The strain patterns calculated from externally measured kinematic data appeared to be in accordance with the directly measured strain gauge data. However, a correction for skin displacement is an obligatory prerequisite to obtain reliable results. The amplitudes of strain did not exceed 3% and appeared to be of about the same magnitude at both walk and trot.     

The effects of strain heterology on the epidemiology of equine influenza in a vaccinated population

We assess the effects of strain heterology (strains that are immunologically similar but not identical) on equine influenza in a vaccinated population. Using data relating to individual animals, for both homologous and heterologous vaccinees, we estimate distributions for the latent and infectious periods, quantify the risk of becoming infected in terms of the quantity of cross-reactive antibodies to a key surface protein of the virus (haemagglutinin) and estimate the probability of excreting virus (i.e. becoming infectious) given that infection has occurred. The data suggest that the infectious period, the risk of becoming infected (for a given vaccine-induced level of cross-reactive antibodies) and the probability of excreting virus are increased for heterologously vaccinated animals when compared with homologously vaccinated animals. The data are used to parameterize a modified susceptible, exposed, infectious and recovered/resistant (SEIR) model, which shows that these relatively small differences combine to have a large effect at the population level, where populations of heterologous vaccinees face a significantly increased risk of an epidemic occurring.     

Predisposition for venoconstriction in the equine laminar dermis: implications in equine laminitis.

Equine laminitis is a crippling condition associated with a variety of systemic diseases. Although it is apparent that the prodromal stages of laminitis involve microvascular dysfunction, little is known regarding the physiology of this vasculature. The aim of the present study was to determine the relative responses of equine laminar arteries and veins to the vasoconstrictor agonists phenylephrine (1 nM-10 microM), 5-HT (1 nM-10 microM), PGF2alpha (1 nM-100 microM), and endothelin-1 (1 pM-1 microM). We have determined that laminar veins were more sensitive, with respect to the concentration of agonist required to initiate a contractile response and to achieve EC(50), for all agonists tested. EC50 values, for veins and arteries, respectively, were 84+/-7 vs. 688+/-42 nM for phenylephrine, 35+/-6 vs. 224+/-13 nM for 5-HT, 496+/-43 nM vs. 3.0+/-0.6 microM for PGF2alpha, and 467+/-38 pM vs. 70.6+/-6.4 nM for endothelin-1. Moreover, when expressed as a percentage of the response to a depolarizing stimulus (80 mM potassium), the maximal contractile response of laminar veins exceeded that for the laminar arteries for each agonist. These results indicate that there may be a predisposition for venoconstriction within the vasculature of the equine digit. While this physiological predisposition for venoconstriction may be important in the regulation of blood flow during exercise, it also may help to explain why laminitis can result from a variety of pathological systemic conditions.     

Age-dependent epidemiological patterns and strain diversity in helminth parasites

Field studies of schistosomes and the major intestinal nematodes Trichuris trichiura and Ascaris lumbricoides repeatedly demonstrate that the intensity and prevalence of infection exhibit marked dependency on host age. Peak levels of infection typically occur in hosts aged between 10 and 14 yr in endemically infected communities. It has widely been assumed that the slow acquisition of resistance in adults is caused by repeated exposure to the same antigenic repertoire of a single parasite strain. Consequently, these empirical patterns have previously been taken to suggest that human immunity to helminth parasites confers poor protection against reinfection. Here, an alternative explanation is suggested on the basis of results from a simplified model of helminth transmission. It is proposed that the empirical observations can be attributed to the circulation of multiple helminth strains that each elicit highly protective immunity. If this hypothesis is correct, estimates of epidemiological parameters from field data and the potential for control of helminth diseases might require reevaluation.     

Semen quality of stallions challenged with the Kentucky 84 strain of equine arteritis virus

Equine arteritis virus (EAV) is the causal agent of equine viral arteritis (EVA), a respiratory and reproductive disease of equids. Some strains of EAV can cause fever, leukopenia, and dependent edema of the limbs, scrotum, and preputium in the acutely infected stallion. We hypothesized that fever and scrotal edema observed during the acute phase of the infection, but not the presence of EAV, have an adverse effect on semen quality. A group of seven stallions were intranasally inoculated with the Kentucky 84 (KY84) strain of EAV. Stallions were monitored for clinical signs of EVA until 42 days postinoculation (dpi). Semen was collected every other day for the first 15 days and 2 times a week up to 79 dpi. Additional samples were collected at 147, 149, and 151 dpi. Semen from each stallion was evaluated on the basis of motion characteristics, total number of spermatozoa, membrane integrity, and morphology. Virus infectivity titers were determined in RK-13 cells. Significant decreases in sperm quality were observed between 9 and 76 dpi. LOWESS (locally weighted scatterplot smoothing) curves for each horse were fit and integrated to quantify spermatozoa exposure to fever, virus, and edema over a period of 67 days before each ejaculation. Linear mixed models were then fit to isolate the effects of each factor on semen quality. Scrotal edema and fever were found to exert independent effects on all the semen quality parameters (P ≤ 0.002), whereas virus seems to exert little to no direct effect, as virus titers remained high long after semen quality returned to baseline.     

The postvaccinal reaction in hamadryas baboons to the administration of attenuated strain 15 of the Venezuelan equine encephalomyelitis virus

Immunization of Papio hamadryas with attenuated VEE virus (strain 15) causes seroconversion in 100% of animals. Postvaccinal reaction such as viremia and short-lasting fever occurs in response to the injection of 10(3) ImD50 in about 30% of animals. CNS lesion symptoms characterizing infection of Papio hamadryas with natural Trinidad strain do not occur in response to injection with attenuated strain.     

Functional Consequences of Iron Overload in Catecholaminergic Interactions: the Youdim Factor

The influence of postnatal iron overload upon implications of the functional and interactive role of dopaminergic and noradrenergic pathways that contribute to the expressions of movement disorder and psychotic behaviours in mice was studied in a series of experiments. (1) Postnatal iron overload at doses of 7.5 mg/kg (administered on Days 10–12 post partum) and above, invariably induced a behavioural syndrome consisting of an initial (1st 20–40 min of a 60-min test session) hypoactivity followed by a later (final 20 min of a 60-min test session) hyperactivity, when the mice were tested at adult ages (age 60 days or more). (2) Following postnatal iron overload, subchronic treatment with the neuroleptic compounds, clozapine and haloperidol, dose-dependently reversed the initial hypoactivity and later hyperactivity induced by the metal. Furthermore, DA D₂ receptor supersensitivity (as assessed using the apomorphine-induced behaviour test) was directly and positively correlated with iron concentrations in the basal ganglia. (3) Brain noradrenaline (NA) denervation, using the selective NA neurotoxin, DSP4, prior to administration of the selective DA neurotoxin, MPTP, exacerbated both the functional (hypokinesia) and neurochemical (DA depletion) effects of the latter neurotoxin. Treatment with L-Dopa restored motor activity only in the animals that had not undergone NA denervation. These findings suggest an essential neonatal iron overload, termed “the Youdim factor”, directing a DA–NA interactive component in co-morbid disorders of nigrostriatal-limbic brain regions. Special issue dedicated to Dr. Moussa Youdim.     

Asymmetry of the mandibular condyle in Haida Indians

The condyles of 72 aged and sexed Haida Indians were measured for anteroposterior and mediolateral diameter and their approximate areas calculated. Dental wear was assessed for the same individuals. Asymmetry of condyle size did not appear to change with age. In a pair-wise analysis, no relationship was found between the largest of a pair of condyles and the most worn side of the dentition. The difference in size between each pair of condyles (normalized for individual size) was plotted as a histogram and found to have a normal distribution with a mean of 0 and no skewness. Condyle asymmetry does not appear to be related to differential chewing forces but more closely fits the model of fluctuating asymmetry.     

Stability of transgene methylation patterns in mice: Position effects,strain specificity and cellular mosaicism

The methylation status of a transgene, which carried the adenovirus type 2 E2A late promoter linked to the chloramphenicol acetyltransferase gene, was studied in three transgenic mouse lines (5–8, 7–1 and 8–1). These lines were analysed over a large number of offspring generations beyond the founder animal. In mating experiments, the influence of the parent-of-origin and strain-specific backgrounds on the transgene methylation patterns were assessed and found to have no effect on the pre-established methylation patterns in mouse lines 5–8 and 8–1. The founder animal 7–1 carried two groups of a total of ten transgenes, which were located on two different chromosomes. These arrays of transgenes could be segregated into separate mouse lines 7-1A and 7-1B. The transgenes of 7-1A animals exhibited cellular mosaic methylation, patterns that were demethylated in approximately 10% of the offspring in a mixed genetic background. Upon further transmission of these transgenes in a mixed genetic background, the grandparental methylation patterns were reestablished in most progeny. Mating to inbred DBA/2 mice resulted in maintenance of the demethylated pattern or in further demethylation of the transgenes in approximately 50% of the offspring. In contrast, an equal number of transgenic siblings from matings to C57BL/6 mice showed a return to the original methylation pattern. The mosaic methylation status of this locus was apparently controlled by mouse-strain-specific factors. The methylation patterns of the 7-1B transgenes were not cellular mosaic and remained stable in all offspring, as with lines 5–8 and 8–1. Hence, the strain-dependent and cellular mosaic transgene methylation patterns of 7-1A animals were probably a consequence of the chromosomal integration site of the transgenes (position effect).     

Subchondral bone failure in overload arthrosis: a scanning electron microscopic study in horses

Mechanical overload leads to a common arthrosis in the metacarpal condyle of the fetlock joint of racehorses. This is usually asymptomatic but severe forms can cause lameness. Subchondral bone failure is often present and the predictability of the site provided an opportunity to study of the progression of bone failure from microcracks to actual collapse of subchondral bone. Twenty-five fetlock condyles from racehorses with various stages of disease were selected. Stages ranged from mild through severe subchondral bone sclerosis, to the collapse of bone and indentation or loss of cartilage known as 'traumatic osteochondrosis'. Parasagittal slices were radiographed and examined with scanning electron microscopy. Fine matrix cracks were seen in the subchondral bone layer above the calcified cartilage and suggested loss of water or other non-collagenous components. The earliest microcracks appeared to develop in the sclerotic bone within 1-3 mm of the calcified cartilage layer and extend parallel to it in irregular branching lines. Longer cracks or microfractures appeared to develop gaps as fragmentation occurred along the margins. Occasional osteoclastic resorption sites along the fracture lines indicated activated remodeling may have caused previous weakening. In one sample, smoothly ground fragments were found in a fracture gap. Bone collapse occurred when there was compaction of the fragmented matrix along the microfracture. Bone collapse and fracture lines through the calcified cartilage were associated with indentation of articular cartilage at the site.     

Effects of chest wall on volume and strain patterns in canine lungs

Lobar functional residual capacity-to-total lung capacity ratios (FRC/TLC) and strains in five supine anesthetized dogs were determined from volumes and side lengths of tetrahedra formed by multiple intraparenchymal markers whose positions were determined roentgenographically. Strain is related to fractional changes in length of elements in a Cartesian coordinate system and was used to describe parenchymal distortion. Volumes and strain patterns were compared in three states: intact dogs, after transection of forelimb structures to relieve traction on the chest wall, and in dogs' excised lungs. Removing traction (NT) decreased the plethysmographically determined FRC and the upper-to-lower lobe ratio (UL/LL) for FRC/TLC. The ratio in the NT state was more like the ratio in the excised lungs (UL/LL approximately equal to 1) than in the intact dog (UL/LL greater than 1). Strain patterns were similar between the intact and the NT states, indicating no lobar shape change at FRC between these two states. Strain in the excised lungs differed greatly from strains in the intact and NT states. We conclude that forelimb traction alters volume distribution between lobes and that lung-chest wall interactions are important in determining volume and strain patterns.