The aim of this study was to see if differences in proficiency exist between advanced-and novice-level horseback riders with regard to head movement and EMG activity. Three advanced-and three novice horseback riders rode a horse at a walk, sitting trot and canter whilst their head acceleration and the EMG activity of their rectus abdominis muscle (M. rectus abdominis), erector spinae muscle (M. erector spinae) and abductor magnus muscle (M. adductor magnus) were recorded simultaneously. All results were conducted with Frequency Analysis by the Maximum Entropy Method. At walk, the novice rider showed a frequency distribution dispersion (P<0.1) of the head in the proximal-distal direction which was not observed in the advanced rider, but no distinct primary factors were observed in the muscular discharge frequency distributions-perhaps due to the novice rider's level which was not completely inexperienced. At a sitting trot, unstable movements of the novice rider's upper body were observed in the cranial-caudal direction (P<0.05), mirroring the horse's violent rocking movements. The electromyogram frequency distributions at this gait suggest that the novice rider was unable to balance the erector spinae and rectus abdominis muscles, and therefore unable to cope with the unstable movement. It also suggests that there was instantaneous muscular activity of the adductor magnus muscle in order to stabilize the ill-balanced body. At a canter, there were no significant differences in the dispersion of acceleration frequency distribution or in the electromyogram frequency distribution, but although there were no "significant" differences, the results obtained from the advanced rider at this gait showed a dispersion of acceleration frequency distribution that was slightly greater than that of the novice rider. This situation was only observed at a canter. In conclusion, differences exist in the degree of difficulty of coordination between horse and rider according to the gait. In addition, from the results of this study, we can clearly see that differences also exist in the rider's own skill and ability to "maintain posture".
The social organization of three populations of 2 species of zebras in Kenya and its relationship to their communication behaviour were studied. Grant's zebras (Equus burchelli bohmi) (GTZ) inhabiting a dry savanna area had a harem-type social organization. Grevy's zebras (Equus grevyi) inhabiting a dry savanna area with many bushes, formed a territorial society (GYZ-1). Grevy's zebras (GYZ-2) inhabiting the same area as GTZ, created groups of a few to 20 males and females, bachelor groups and solitary males in the rainy season, and formed large groups of over 100 males and females in the dry season. The GTZ displayed three types of scent-marking, but GYZ-1 showed seven types, and GYZ-2 four types. In the GTZ the frequency of scent-marking with the urine of males on the urine of females (FUU) in the rainy season, and in the GYZ-1 the frequency of scent-marking with the faeces of males on his own faeces (MFF) during both seasons, were each significantly higher than other types of scent-marking in the respective groups. In the GYZ-2 male/female mixed groups, the frequency of FUU was significantly higher during the rainy season than during the dry season. The frequency of mutual grooming and mutual chin-resting in the GTZ was each significantly higher than that in the GYZ-1 or GYZ-2. Mutual chin-resting was occasionally observed in the GYZ-2. Neither mutual grooming nor mutual chin-resting was observed in the GYZ-1. These results suggest that the type and frequency of communication behaviour differs depending on the type of social organization in Equus species.
In order to determine the exon-intron structure and the nucleic acid sequences of the equine genomic cytochrome P450 steroid 17α-hydroxylase/17,20-lyase gene (CYP17), inter-exonal PCR amplifications were performed with equine genomic DNA as a template. The amino acid coding region of the equine CYP17 gene was consisted of 8 exons and 7 introns, and the total 6217 base pairs of nucleotide sequence was determined. The numbers of exons and introns were identical to the human CYP17. It was suggested that the equine CYP17 gene exists as a single locus gene in a genome alike in case of humans, by accordance of the overlapping part of PCR clones include one or more introns. In the intron C of the equine CYP17 gene, two nucleotide sequences of 72 base-pairs homologous to 70 base-pairs core motif of the mammalian-wide interspersed repeats (MIRs) were tandemly repeated with Hind III restriction site between them.
Adult BALB/c mice were inoculated intranasally with African horsesickness virus serotype 4 (AHSV-4), the attenuated-vaccine strain. The 4-week-old mice died after developing nervous signs at 7 to 8 days post infection (p.i). Lesions, such as perivascular accumulation of lymphocytes and necrosis of neurons, were found only in the brains of virus-infected mice, but not in those of controls. Brains, red blood cells (RBC) and white blood cells (WBC) were collected from two mice each day p.i for virus isolation and RT-PCR. Virus could be isolated from brains collected at 2 to 7 days p.i of infection mice and only one of WBC sample collected on 7 day p.i, but no virus was isolated from any RBC samples. In contrast, RT-PCR products were visible in agarose gel electrophoresis stained with ethidium bromide from RBC and WBC samples collected at days 1 to 7 p.i, and from brain samples collected at days 2 to 7 p.i. The amplified PCR products were increased with days p.i when using extracted RNAs from brain samples, but the quantity of the PCR products was relatively constant with the RBC and WBC samples. It was shown that mice were susceptible to AHSV.