Biomedical subjects

E C Firth

Publications and source records attributed to E C Firth.

At least 55 records · Page 3Linked to original sources

PubMed1998

The effect of injectable barium selenate on the selenium status of horses on pasture.

AIM: To examine the effect of intramuscular barium selenate on the blood selenium concentration of horses with marginal selenium status. METHODS: Eighteen mares were assigned to one of six groups. The mares in groups 1-4 received barium selenate at 0.5, 0.75, 1.0 and 1.5 mg Se/kg, respectively, injected into the right pectoral muscle mass. The mares in group 5 received sodium selenate at 0.05 mg Se/kg orally at 8-week intervals. The mares in group 6 were left untreated. Blood samples were collected at 0, 1, 2, 5, 10, 30, 60, 90, 120, 180, 240, 300 and 360 days after the initial treatment for assay of whole blood and plasma selenium. Injection site reactions were recorded on each sampling date. RESULTS: Treatment with barium selenate at each dose rate significantly increased whole blood, plasma and blood cell selenium concentrations when compared to no treatment or oral treatment with sodium selenate, and maintained group mean whole blood selenium concentrations in the adequate range (>1600 nmol/l) until the end of the experimental period of 1 year. The severity of injection site reactions increased with dose rate but was considered acceptable alt the lower dose rates used. CONCLUSION: The injection of barium selenate placed aseptically at a deep intramuscular site was efficacious in correcting the selenium status of mares grazing pasture with a selenium content of 0.01-0.07 mg/kg DM. However, some swelling and fibrosis at the injection site was apparent at all dose rates used. CLINICAL RELEVANCE: There is currently no long-acting selenium supplementation product licensed in New Zealand for use in horses. Barium selenate promises to provide a useful method for selenium supplementation for horses, with an effective duration of at least 1 year following a single injection.

Journal Article↗

PubMed1998

Exercise-related alterations in crimp morphology in the central regions of superficial digital flexor tendons from young thoroughbreds: a controlled study.

Injury to the core of the mid-metacarpal region of the superficial digital flexor tendon in Thoroughbred racehorses is a very frequent but poorly understood condition. It has been suggested that subclinical changes induced by galloping exercise weaken the collagen in this region of the tendon, predisposing it to rupture. The longitudinally arranged collagen fibrils in tendon follow a planar waveform, termed the crimp. Fibril bundles with a smaller crimp angle fail at a lower level of strain than those with a larger crimp angle. This study tested the hypothesis that a specific 18 month exercise programme would result in significant reduction of collagen fibril crimp angle and period length in the core region of the superficial digital flexor tendon of young Thoroughbreds (21 +/- 1 months), compared to the normal change in these parameters with age. Central region crimp angle and length were significantly lower in exercised horses than in control horses (P < 0.05). The crimp angle was significantly lower in this central region than in the peripheral region of the tendon in 4 of the 5 exercised horses, as was the crimp length in 3 of the 4 horses. The crimp angle in the peripheral region was significantly greater in exercised horses than in the controls (P < 0.05), which may indicate functional adaptation due to differing mechanical environment between the 2 tendon regions. The results of this study supported previous evidence that galloping exercise modifies normal age-related changes in crimp morphology in the core of the superficial digital flexor tendon. Such changes are indicative of microtrauma and would be detrimental to tendon strength.

Aging↗

PubMed1998

Effect of copper supplementation on copper status of pregnant mares and foals.

Pregnant Thoroughbred mares (n = 21) were grazed on tall fescue pasture containing 4.4-8.6 mg Cu/kg dry matter (DM). Twelve mares were supplemented with approximately 0.5 mg Cu/kg liveweight (LW)/day as copper sulphate for the final 13-25 weeks gestation. Plasma copper concentration declined during the third trimester for all mares and was not affected by copper supplementation. Liver copper concentration of mares and foals was determined when the foals were 4-10-days-old. Copper supplementation of the mares tended to increase mare liver copper concentration (P<0.08) and increased foal liver copper concentration (P<0.01). There was a significant relationship between mare and foal liver copper concentration (P<0.001, r2 = 0.7). Increasing the copper intake of mares is effective in enhancing the copper status of foals.

Analysis of Variance↗

PubMed1998

Effect of copper supplementation on the copper status of pasture-fed young Thoroughbreds.

The effect of copper supplementation of pasture fed mares and foals on the copper status of the foals, in terms of plasma, soft tissue and bone copper concentrations and caeruloplasmin activity, was investigated. Twenty-one Thoroughbred foals from either control mares (n = 9), or copper-supplemented mares (n = 12) were divided randomly into control (pasture only, n = 10) or supplemented (pasture and oral copper sulphate, n = 11) groups. The pasture diet was grazed by all animals, and contained 4.4-8.6 mg Cu/kg dry matter (DM). The copper supplement for the mares contained copper sulphate equivalent to 0.5 mg Cu/kg liveweight (LW)/day. This daily dose was converted to allow administration as a thrice weekly dose (i.e. multiplied by 7/3) which was given for 13-25 weeks prior to foaling. The supplemented foals, also dosed 3 times a week, received 0.2 mg Cu/kg LW/day at age 21 days, which was increased to 0.5 mg Cu/kg LW/day at 49 days and was continued at this level until euthanasia at 150 days. Foal plasma copper concentration and caeruloplasmin activity increased from birth to 21 days post partum and then plateaued at a concentration similar to the mare, but the rise in these indices was not affected by copper supplementation of the mare or foal. Copper supplementation of the foal increased foal liver copper concentration at 150 days (P<0.03). Copper intake of diets containing approximately 8-28 mg Cu/kg DM is well reflected by liver copper concentration, but is poorly reflected by bone, other soft tissue copper concentrations and circulating copper status indices.

Administration, Oral↗

PubMed1998

Effect of copper supplementation on the evidence of developmental orthopaedic disease in pasture-fed New Zealand Thoroughbreds.

The effect of copper status on the evidence of bone and cartilage lesions was investigated in 21 Thoroughbred foals. The foals and their dams were grazed on pasture containing 4.4-8.6 mg Cu/kg dry matter (DM). Four treatment groups were created by randomly allocating mares and their foals to either copper supplemented (0.5 mg Cu/kg liveweight (LW)/day), or control (pasture only) groups. This experimental design allowed the effect of copper supplementation of mare and foal to be examined independently. Parameters of bone and cartilage development were assessed in the foals both in vivo, and at post mortem at approximately age 150 days. Mare copper supplementation significantly (P<0.01) decreased radiographic indices of physitis in the distal third metatarsal bone of the foals at 150 days, and the prevalence of articular cartilage lesions (P<0.05). Articular cartilage lesions were minor in all foals, with no evidence of clinical developmental orthopaedic disease (DOD) in vivo, with the exception of minor radiographic changes assessed at post mortem. Copper supplementation of the foal had no effect on any of the bone and cartilage parameters. Copper supplementation of the mares did not abolish DOD in the growing foals, emphasising the probable multifactorial nature of this condition. However, mare supplementation may be a useful treatment regime on a farm where the incidence and severity of DOD are of concern.

Analysis of Variance↗

PubMed1998

Effects of training on collagen fibril populations in the suspensory ligament and deep digital flexor tendon of young thoroughbreds.

OBJECTIVE: To determine the effect of a specific galloping exercise regimen on collagen fibril mass-average diameters (MAD) in the deep digital flexor tendon (DDFT) and suspensory ligament (SL) of young Thoroughbreds. ANIMALS: 12 Thoroughbred fillies, 21 +/- 1 (mean +/- SD) months old. PROCEDURE: 6 horses underwent a specific 18-month treadmill training program involving galloping exercise. The remaining 6 horses served as controls, undertaking low-volume walking exercise over the same period. Sections were excised from the midpoint of the DDFT and SL, and small strips were dissected from central and peripheral locations for each structure. Fibril diameters were measured from micrographs of transverse ultrathin sections, using a computerized image analysis program. An MAD value was calculated for the central and peripheral regions of the DDFT and SL for each horse. Values for both regions were compared between exercised and control horses. RESULTS: The MAD did not change significantly with exercise for either the DDFT or the SL. CONCLUSION: Loading of the DDFT as a result of this exercise regimen was not sufficient to stimulate collagen fibril hypertrophy, in keeping with current data that indicate this tendon, compared with the SL and superficial digital flexor tendon (SDFT), is subjected to low loads. Microtrauma, in terms of reduction in fibril MAD, may have occurred in the SL at a site different from that sampled. Another possibility is that, between the trot and the gallop, loading of the SL does not increase to the same extent as that of the SDFT.

Animals↗

PubMed1997

Exercise modifies the age-related change in crimp pattern in the core region of the equine superficial digital flexor tendon.

One of the current concepts with regard to equine superficial digital flexor tendonitis is that cumulative subclinical microscopic damage weakens the structure, predisposing the tendon to partial or complete rupture. This microtrauma is likely to affect the waveform or crimp of the collagen fibrils, which are the units of tensile strength. Collagen fibril crimp morphology characteristics were determined in superficial digital flexor tendons of 18 horses presented for necropsy. Horses were separated into exercised (n = 9) and non-exercised groups (n = 9), based on recent function. Five of the eight exercised horses below the age of 10 years showed a significantly lower crimp angle in the central region of the tendon in comparison with the periphery. Three of those five animals also showed a significantly lower crimp period length in the centre. No non-exercised horses in this age group showed such regional differences. Horses classified as non-exercised may have Horses classified as non-exercised may have undergone competitive galloping activity at an earlier age, implying that changes in central region crimp morphology did not occur at that time, or had reverted to normal values in the intervening period. A lower crimp angle in the core region in comparison with the periphery is abnormal in animals younger than 10 years, on the basis of previous data obtained from wild horses. It is hypothesised that imposed exercise regimens involving galloping modify the normal age-related reduction of crimp angle in the tendon core, probably as a result of the increased number of rapid high-strain cycles experienced by the collagen fibrils.

Journal Article↗

PubMed1997

Liver biopsy techniques for adult horses and neonatal foals to assess copper status.

OBJECTIVE: To evaluate standing, percutaneous, ultrasound-guided, transthoracic liver biopsy in mares, and transabdominal laparoscopically-guided, liver biopsy under general anaesthesia in foals, as techniques for obtaining tissue for assessment of copper status. The techniques were evaluated with respect to ease of use and effect on the animal. PROCEDURE: Twenty of 24 Thoroughbred mares and 21 of their foals were biopsied. The animals were part of a larger study of the effect of copper supplementation on copper status and the prevalence of developmental orthopaedic disease. Livers were also collected from unrelated horses and sampled to investigate the variability in the distribution of copper in liver tissue. RESULT: The biopsy technique caused no lasting effect on the mares, but there was an increased risk of viscus penetration associated with taking multiple biopsy cores. The use of ultrasonography to scan the target area for the liver identified four cases that were not appropriate candidates for liver biopsy, because of large intestine being located in the biopsy area. In the foals there were no serious postoperative adverse effects, nor was there any evidence of problems caused by the procedure when the abdomen was examined post-mortem at 5 months of age. In livers collected to investigate the variability of copper concentration, copper appeared to be relatively evenly distributed through the liver. CONCLUSION: Standing, percutaneous, ultrasound-guided, transthoracic liver biopsy in mares, and transabdominal, laparoscopically-guided, liver biopsy under general anaesthesia in foals are convenient procedures for obtaining liver tissue for assessing copper status in horses. The use of ultrasound to identify liver tissue is recommended, especially in older mares.

Animals↗

PubMed1997

Age-related differences in collagen crimp patterns in the superficial digital flexor tendon core region of untrained horses.

OBJECTIVE: To measure collagen fibril crimp angles and lengths as well as collagen fibril mass-average diameters in central and peripheral regions of the superficial digital flexor tendon of wild horses, to ascertain any age-related changes in either region in the absence of imposed galloping exercise. DESIGN: Measurements from a random cull of wild horses. SAMPLE POPULATION: Superficial digital flexor tendon samples were taken from 23 wild horses ranging in age from two to ten years. PROCEDURE: Horses were divided into 'young' (< 5 years, n = 10), 'middle-aged' (5 to < 10 years, n = 9) and 'old' groups (10+ years, n = 4) and the mean crimp angle, mean crimp length and collagen fibril mass-average diameter calculated for the central region, and for the peripheral region of each group. Differences between groups and regions were analysed using two-tailed t tests. RESULTS: The crimp angle for the central region was found to decrease with age, so that in old horses it was smaller than that for the tendon periphery (P, 0.05). The crimp angle for the latter region did not alter significantly with age. Crimp period lengths and collagen fibril mass-average diameters did not show significant changes with age in either region. CONCLUSIONS: Reduction of the crimp angle in the core of the superficial digital flexor tendon occurs normally with age, as tendons of older animals would have undergone a higher number of loading cycles. It is possible that athletic training increases the frequency and/or the magnitude of high loading cycles experienced by the tendon, and may accelerate and worsen the normal load-related ageing process in the superficial digital flexor tendons of young performance horses, particularly in the central regions where lesions usually occur.

Aging↗

PubMed1997

Comparison of collagen fibril populations in the superficial digital flexor tendons of exercised and nonexercised thoroughbreds.

This study was undertaken to test the hypothesis that collagen fibrils, the submicroscopic units of strength in tendon, would hypertrophy in response to a specific defined training programme. Fibril diameters were measured in central and peripheral regions of superficial digital flexor tendon (SDFT) samples from five 18-month-old horses which underwent a subsequent 18 month training programme and 6 age- and sex-matched controls. Central region fibrils from the trained horses had a mass-average diameter (MAD) of 105.3 nm, which was significantly lower (P < 0.01) than that of 131.7 nm for the same region in the control horses. This reduction in fibril diameter in the region of tendon which is predisposed to injury was interpreted as evidence of microtrauma, as it implies the region is weakened by the training regimen. Repeated episodes of microtrauma may accumulate and eventually result in degenerative lesions and clinical tendonitis.

Aging↗

PubMed1997

An age-related study of morphology and cross-link composition of collagen fibrils in the digital flexor tendons of young thoroughbred horses.

The superficial digital flexor tendon is the most commonly injured tendon in the racing Thoroughbred. Despite the clinical significance of this structure, only limited data exist regarding normal age-related morphology of the tensile units, the collagen fibrils. The age at which these collagen fibrils become mature in composition and structure may be of importance. Consequently, the association of age and collagen fibril crosslink composition, diameter distribution and crimp morphology in the superficial and deep digital flexor tendons of Thoroughbreds up to and including three years of age has been studied. Replacement of immature crosslinks, peaking of the collagen fibril mass-average diameter and collagen fibril index, and stabilization of collagen crimp morphology changes supported the hypothesis that both digital flexor tendons become mature in structure by two years of age.

Aging↗

PubMed1996

Pharmacokinetic interactions between repeated dose phenylbutazone and gentamicin in the horse.

This study examined the pharmacokinetics of steady-state phenylbutazone and single bolus intravenous gentamicin when administered together in the horse. The trial design was completed as a cross-over with seven thoroughbred horses. In the first phase each horse received 2.2 mg/kg gentamicin intravenously. After a 2-week washout, each horse received 4.4 mg/kg phenylbutazone intravenously every 24 h for 5 days. On the fourth day each horse received gentamicin as before. Plasma was harvested for gentamicin concentration determination by fluorescence polarization immunoassay and for phenylbutazone concentration determination by high-performance liquid chromatography. All gentamicin data were best approximated by a two-compartment open model using sequential, weighted non-linear regression. Pharmacokinetic parameters were calculated using model-dependent formulae. Phenylbutazone data were analysed by non-compartmental methods. Phenylbutazone induced a 49% increase in the rate of gentamicin return to the central compartment from peripheral tissues (k21) (P < 0.05) and there was a trend to a 24% increase in k12 (P = 0.052). The gentamicin elimination half-life was decreased 23% and the Vd(urea) was reduced by 26%. No induction by gentamicin of changes in phenylbutazone pharmacokinetics were detected. In summary, phenylbutazone induced changes to the rate and extent of distribution and elimination of gentamicin. Therefore, care should be exercised in the use of aminoglycosides in equine patients concurrently maintained on phenylbutazone.

Animals↗

PubMed1996

Collagen fibril diameter distributions in ligaments and tendons of the carpal region of the horse.

Since horses bred for the racing industry are subject to rigorous training procedures there is a real need to understand how the stresses experienced by their tendons and ligaments in vivo relate to the major load-bearing elements-the collagen fibrils. Consequently, an age-related study has been made of the collagen fibril diameter distributions of nine ligaments in and around the equine carpus. This is the first stage of a larger study aimed at understanding the ultrastructural changes that occur as a result of exercise. Most of the ligaments showed a bimodal diameter distribution at maturity, and decreased diameters at old age as the fibrils break down. The scaphocapitate ligament, however, was unique in that the constituent fibrils were small, almost invariant in diameter with age, and had a unimodal distribution of sizes. The mechanical attributes of these tissues, as deduced from a theoretical analysis of the diameter distributions, are consistent with observation.

Aging↗

PubMed1995

The disposition of gentamicin in equine plasma, synovial fluid and lymph.

Plasma (P), synovial fluid (SF) and lymph (L) concentrations of gentamicin were studied in two trials. A lymph vessel in the hindlimb was cannulated. The day after surgery (trial A), P and L samples were collected for 12 h after intravenous injection of gentamicin sulphate at 2.2 mg/kg dose rate. Approximately 48 h after surgery (trial B), the fetlock joint of the cannulated hindlimb was catheterized and P, SF and L samples collected for 12 h after a similar intravenous injection. The kinetic parameters were similar to those in other reports and did not differ between trials (P < 0.05). The P, L and SF disposition profiles were similar. The 95% confidence interval for P & L concentrations overlapped 2-3 h after injection. Thereafter, parallelism between L and P concentrations was observed, but L concentrations were on average 60% higher than P concentrations, and elimination from L was slower than from P. The mean L/SF and P/SF ratios were 1.54 +/- 0.2 and 1.25 +/- 0.2, 2-4 h after injection. Gentamicin elimination from SF appeared to be slower than from L and P. Lymph cannulation is a viable technique for antibiotic disposition studies. A sample of any of the fluids 3 h after injection was representative of the others. While SF concentrations were of limited value for predicting tissue fluid (L) concentrations 3-8 after injection, P concentrations were a useful index.

Animals↗

PubMed1995

The dose-related effects of phenylbutazone and a methylprednisolone acetate formulation (Depo-Medrol) on cultured explants of equine carpal articular cartilage.

The dose-related effects of phenylbutazone and Depo-Medrol on chondrocyte viability and chondrocyte-mediated synthesis and depletion of proteoglycans were investigated using cultured explants of equine middle carpal joint articular cartilage. Explants from 12 horses (941 x 3 mm diameter) were cultured for a total of 5 days, which included 3 days' exposure to either phenylbutazone (0, 2, 20, 200 or 2000 micrograms/mL) or Depo-Medrol (0, 20, 200 or 2000 micrograms/mL). For each explant, amino sugar content was used as a measure of proteoglycan content, 35S incorporation as a measure of the rate of proteoglycan synthesis and the number of pyknotic nuclei as a measure of cell death. During culture, control explants remained metabolically active and viable but suffered a net loss of proteoglycans. Proteoglycan loss was reduced by the presence of either phenylbutazone or Depo-Medrol. This effect was significant at clinically relevant concentrations of phenylbutazone (2-20 micrograms/mL), but not Depo-Medrol (20-200 micrograms/mL). Depo-Medrol caused a dose-dependent suppression of proteoglycan synthesis at all concentrations, but chondrocyte viability was affected only at the 2000 micrograms/mL dose. Phenylbutazone affected proteoglycan synthesis and cell viability only at the 2000 micrograms/mL concentration. At all concentrations, the anticatabolic effects of each drug influenced the proteoglycan content of the explants far more than did any antianabolic or cytotoxic drug effect. The results suggest that the therapeutic potential of both phenylbutazone and Depo-Medrol may not be restricted to their anti-inflammatory effects on the soft tissues of the joint.

Animals↗

PubMed1995

Transphyseal vessel involvement in repair of metaphyseal retained cartilage.

A foal with retained cartilage in the distal metaphysis of the right and left radii and third metacarpal bones had abnormal physeal vasculature. In areas where cartilage was retained, vessels crossed the physis, and branched at the physeal-metaphyseal junction or at the site of retained cartilage. Vessels appeared to be involved in re-initiation of endochondral ossification and in the repair reponse to the presence of retained cartilage. In areas where the physis was radiographically and histologically normal, no vessels crossed the physis. A function of transphyseal vessels may be as a reserve blood supply in areas of metaphyseal abnormality, at a stage of maturity when metaphyseal vessels are not well developed.

Animals↗

PubMed1994

Changes in plasma cortisol concentrations before, during and after analgesia, anaesthesia and anaesthesia plus ovariohysterectomy in bitches.

Plasma cortisol concentrations were determined before, during and after analgesia, anaesthesia and anaesthesia plus ovariohysterectomy in six New Zealand border collie cross bitches. The treatments were: control, analgesia with butorphanol, anaesthesia with thiopentone sodium, halothane and oxygen and anaesthesia plus surgery. In addition, each bitch was given an ACTH challenge. All the bitches showed transient increases in plasma cortisol concentrations and the integrated cortisol responses (calculated as the area under the cortisol curve above the pre-treatment concentration) for 6.25 hours after treatment increased in the order: control, anaesthesia, analgesia, surgery. The control group had increased cortisol concentrations attributable to the excitement from handling. The plasma cortisol concentrations of the group subjected to surgery were greater than the other groups for at least 6.25 hours, with an approximately four-fold increase above pre-treatment values, but they had returned to pre-treatment levels after 24 hours.

Analgesia↗

PubMed1994

The relationship between intra-articular and juxta-articular intraosseous pressures in the metatarsophalangeal region of the pony.

Eight metatarsophalangeal (fetlock) joints were studied in anaesthetized young ponies. Pressure measurements were made in the joint and at various sites in the marrow cavity of the third metatarsal bone with simultaneous measurement of systemic arterial and venous blood pressures. Fetlock joint flexion was always associated with a statistically significant initial decrease in intra-articular pressure (p < 0.05) followed by a marked increase in pressure (p < 0.05). Subsequent extension was accompanied by a similar pressure pattern, although there appeared to be a hysteretic relationship. Fetlock joint distension induced by incremental injection of saline caused a stepwise increase in the intra-articular pressure. Both joint flexion and effusion were associated with an increased intraosseous pressure within the third metatarsal bone. This effect was most pronounced at the distal end of the bone, probably through partial obstruction of the vessels draining the epiphysis and metaphysis.

Animals↗