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Biomedical subjects

H M Clayton

Publications and source records attributed to H M Clayton.

17 recordsLinked to original sources
PubMed1991

Advances in motion analysis.

Time magnification in motion photography allows the observation of events in the stride cycle that normally are beyond the resolution of the human eye. Quantitative analysis goes a stage further by measuring the stride in terms of timing, distance, and angular variables. Motion analysis is a good technique for detecting left-right asymmetries of gait, and the nature of the asymmetries has some value in locating the site of a lameness. Repeated analyses of the same horse allow an objective assessment of the effects of local anesthesia, surgical treatment, or medication. It is anticipated that this will be one of the most useful clinical applications of motion analysis in the clinical setting. This article reviews the hardware and software available for cinematographic and videographic gait analysis. Manual digitization is tedious and time consuming, but these drawbacks are partially overcome by semi-automated systems, which use point prediction to estimate the location of the markers. Fully automated systems rely on the use of contrasting markers attached to the horse's skin overlying the anatomic landmarks. In some joints, skin motion relative to the underlying bones is sufficient to introduce significant errors in joint angle calculations unless appropriate correction algorithms are applied.

Animals↗
PubMed1989

Kinematics of the cervical spine of the adult horse.

At least three types of movement, dorsoventral flexion and extension, axial rotation and lateral bending, were shown to occur at each of the intervertebral joints in the cervical spine. Between the first two cervical vertebrae the mean axial rotation was 107.5 degrees, which was 73 per cent of the total axial rotation of the cervical spine. The atlantooccipital joint rotated through a mean of 27 degrees, whereas the remaining cervical joints each had less than 3 degrees of rotatory movement. Dorsoventral flexion and extension were maximal at the atlantooccipital joint, which had an amplitude of 86.4 degrees and accounted for 32 per cent of the total dorsoventral movement of the cervical spine. Lateral bending was relatively more uniform along the length of the neck, with mean values ranging from 25 to 45 degrees for each joint except that between the first two cervical vertebrae, which had a mean of only 3.9 degrees of lateral bending.

Analysis of Variance↗
PubMed1989

Cervical spinal kinematics: a comparison between foals and adult horses.

A photographic method was used to measure axial rotation, dorsoventral flexion and extension and lateral bending at each intervertebral joint complex from the occiput to the first thoracic vertebra in spinal segments from 19 foals under 12 months of age and 14 horses over three years of age. Comparisons between the two groups showed that there was a general reduction in cervical spinal mobility with age. For the three types of movement at the eight joints tested, adults' mobility exceeded that of foals in only three cases (axial rotation and lateral bending at the A-O joint, and lateral bending at C7-T1). These differences were not significant (P greater than 0.05). In the remaining 21 cases the amplitude of movement was greater in the foals, the differences being significant (P less than 0.05) in 16 cases. With regard to overall mobility of the cervical spine the foals exceeded the adults by 17.3 per cent for axial rotation, 22.0 per cent for dorsoventral flexion and extension and 18.7 per cent for lateral bending.

Aging↗
PubMed1989

Kinematic analysis of cutting horses working a mechanical flag.

High-speed cinematography was used to record the movements of 12 cutting horses performing a standard test with a mechanical flag. Based on their previous competitive performances, horses were classified into 2 groups: group 1, composed of 5 moderately successful or average performers that had won less than $35,000 in purse money; and group 2, composed of 7 highly successful or elite performances that had amassed greater than $35,000 in competition earnings. Analysis of the results indicated that, compared with horses of the average group, the elite horses had faster reaction times in response to the start and cessation of flag movement (P less than 0.01), and were positioned closer to the flag during all stages of the trial (P less than 0.05). Discriminant analysis was used to construct a mathematical formula that could be used to classify an individual horse into 1 of the 2 alternative groups, based on the set of measurements. Two predictor variables were selected that described the maximal distance between the horse and the flag during the run and the part of the body that was moved first in response to the initial flag movement. The accuracy of the predicted group membership, compared with the actual group membership, was 100%.

Animals↗
PubMed1986

Ascarids. Recent advances.

P. equorum is a common and ubiquitous parasite that persists for many years in stables and on pasture in spite of good hygiene and anthelmintic control programs. Foals are usually infected early in life. During the migratory phase of the infection, clinical signs include coughing and a nasal discharge followed by depression and unthriftiness as the worms mature in the gut. Some foals die as a result of intestinal impaction or rupture. Patency is established around 3 months of age, and fecal egg counts may rise to very high levels. From 6 months of age onwards, the ascarid burden diminishes as the foals become immune. Patent infections are seldom found in mature horses and, when present, they tend to be of low magnitude. Preventive measures are aimed at treating foals frequently enough to prevent the development of a large mass of ascarids in the intestine. This is achieved by a 6-weekly dosing regimen using an anthelmintic with proven and reliable efficacy against P. equorum.

Animals↗
PubMed1986

An anatomical and endoscopic study of the nasopharynx and larynx of the donkey (Equus asinus).

Using histological techniques, anatomical dissection, fibre optic endoscopy and radiography, the nasopharynx and larynx of the donkey were examined and described. Compared with horses, donkeys have a much deeper pharyngeal recess extending 4.0-6.0 cm caudally from a constricted orifice, through which it communicates with the nasopharynx. Movements of the membranous lining of the recess reflect pressure changes in the upper airways. A shallow, thumb shaped depression on the rostral face of each vocal fold corresponds in position to the lateral ventricle in the horse. In the donkey, large paired laryngeal saccules, interposed between the thyroarytenoideus muscle and the thyroid cartilage, open into the laryngeal cavity through small circular orifices near the rostroventral extremity of the vestibular folds. The large thyroarytenoideus muscle is subdivided into vestibular and vocal parts, which are thought to control the expression of secretion from the laryngeal saccules. The unusual characteristics of vocalisation in the donkey may be related to the shape and orientation of the resonance chambers of the upper airways. In comparison with the horse, the asinine nasopharynx is markedly constricted in its middle part and the laryngeal airway has a more acute angulation relative to the nasopharynx. Vocalisation in the donkey was observed to have an inspiratory and an expiratory component.

Animals↗
PubMed1979

Equine parasite control using pyrantel embonate.

Over a period of several years the use of pyrantel embonate in the control of helminth infections on three equine establishments was monitored by the examination of faecal samples collected immediately before each anthelmintic treatment. With a monthly interval between treatments for three years the faecal egg output of the horses remained at a very low level. One one establishment this was maintained when the treatment interval was extended to one-and-a-half months after treating monthly for two years. If a treatment interval of one-and-a-half months was used continuously for a number of years there was a cumulative effect, and the benefits, in terms of reduced faecal egg output of the horses, were more apparent during the second year of the control programme.

Animals↗
PubMed1979

Lungworm: (Dictyocaulus arnfieldi) infection in donkeys.

The clinical, parasitological and pathological findings in a group of six donkeys naturally infected with D arnfieldi larvae are described. One animal had to be sacrificed at an early date because it developed pneumonia. The remaining five were unthrifty, showed mild clinical respiratory signs and had heavy strongyle infections. They had varying numbers of adult worms in the airways of the lungs and eggs were found coiled up in the smaller bronchi where they had apparently lead to an obstruction to airflow in that segment. The most striking gross pathological changes were circular discrete areas of over-inflation surrounding such bronchi. Histologically the infected bronchi exhibited a marked bronchiolitis with goblet cell hyperplasia and a mainly lymphoid inflammatory infiltrate. These areas also showed a localised bronchiolitus and overinflated alveolar tissue although true emphysema was not present. It is postulated that the parasite is well-adapted to its host and is able to survive for long periods within the lung without causing a debilitating amount of damage to the host. The immunological aspects of the infection are discussed briefly.

Animals↗
PubMed1979

Efficacy of mebendazole against Dictyocaulus arnfieldi in the donkey.

In a controlled trial in naturally infected donkeys the efficacy of mebendazole against Dictyocaulus arnfieldi infection was evaluated. A powder formulation of mebendazole given orally at a dosage rate of 4.3 to 5.7 mg per kg per day for five days had no apparent effect on existing lungworm burdens. However a paste formulation of mebendazole given orally at a higher dosage rate of 15.2 to 20.0 mg per kg per day for five days was 75 to 100 per cent effective in the removal of lungworms from individual animals.

Animals↗
PubMed1979

The development of immunity to Parascaris equorum infection in the foal.

Following infection with 8000 Parascaris equorum eggs in two- to four-week-old foals reared under worm-free conditions a high percentage of the infective dose completed its tissue migration and returned to the small intestine. Patent infections were establisehd between 81 and 104 days after infection and high faecal egg counts were recorded. A group of six- to 12-month-old foals, which had been either reared under worm-free conditions or exposed to natural ascarid and strongyle infections on pasture, received a similar infection of 8000 P equorum eggs. Compared with the younger foals there was a marked reduction in the number of larvae reaching the small intestine. Also, patent infections were established less frequently (50 per cent of cases) and, when present, the faecal egg counts remained low.

Animals↗
PubMed1977

Experimental Parascaris equorum infection of foals.

Six worm-free pony foals, two to four months old, were infected with parascaris equorum eggs using three different dosage regimes and killed at either 40 or 95-100 days after infection. Coughing and a circulating eosinophilia were features of large infections from which only a small number of worms developed to maturity. In small infections a high percentage of the parasites matured in the small intestine and this was associated with unthriftiness. Pre-patent periods of 80 and 83 days were recorded.

Animals↗