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Biomedical subjects

R J Rose

Publications and source records attributed to R J Rose.

At least 73 records · Page 4Linked to original sources
PubMed1999

Factors associated with time until first race and career duration for Thoroughbred racehorses.

OBJECTIVE: To determine whether sex or foaling period were associated with time to first race start and whether sex, age at time of first race start, or inter-race period were associated with career duration for Thoroughbred racehorses in Australia. ANIMALS: 553 Thoroughbred racehorses. PROCEDURE: Race records through to the end of the 6-year-old racing season were obtained for each horse. Product-limit survival analysis was used to determine whether sex or foaling period was associated with time to first race start and whether sex or age at first race was associated with career duration. A Cox proportional hazards model was used to determine whether sex, age at first possible race, age at first race, or inter-race period was associated with time to first race start or career duration. RESULTS: 472 horses (85.4%) raced. Time to first race start was not associated with sex or foaling period. However, males, who had their first race at a younger age and a greater mean number of rest days between races, had longer careers. The hazard ratio for career duration of males versus females, controlling for age at time of first race and inter-race period (0.27), confirmed that males had a higher probability of a long racing career. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that for Thoroughbred racehorses, sex and time of birth during the foaling season were not associated with time to first race. Male Thoroughbred racehorses that were raced less intensively or raced at a younger age were more likely to have long racing careers.

Age Factors↗
PubMed1998

Skeletal muscle adaptations to prolonged training, overtraining and detraining in horses.

Thirteen standard-bred horses were trained intensively for 34 weeks and detrained for 6 weeks to study skeletal muscle adaptations to prolonged training, overtraining and detraining. Training included endurance (phase 1, 7 weeks), high-intensity (phase 2, 9 weeks) and overload training (OLT) (phase 3, 18 weeks). During phase 3, horses were divided into two groups, OLT and control (C), with OLT horses performing greater intensities and durations of exercise than C horses. Overtraining was evident in OLT horses after week 31 and was defined as a significant reduction in treadmill run time in response to a standardised exercise test (P<0.05). Relationships between peripheral (skeletal muscle) and whole body (maximum O2 uptake, V.O2, max, treadmill run time) adaptations to training were determined. Prolonged training resulted in significant adaptations in morphological characteristics of skeletal muscle but the adaptations were limited and largely completed by 16 weeks of training. Fibre area increased in all fibres while the number of capillaries per fibre increased and the diffusional index (area per capillary) decreased. Mitochondrial volume density continued to increase throughout 34 weeks of training and paralleled increases in V.O2,max and treadmill run time. Significant correlations were noted between mitochondrial volume and V.O2,max (R=0.71), run time and V.O2,max (R=0.83) and mitochondrial volume and run time (R=0.57). We conclude that many of adaptive responses of muscle fibre area and capillarity occur in the initial training period but that markers of oxidative capacity of muscle indicate progressive increases in aerobic capacity with increases in training load. The lack of differences between C and OLT groups indicated that there may be an upper limit to the ability of training stimulus to evoke skeletal muscle adaptive responses. There was no effect of overtraining or detraining on any of the adaptive responses measured.

Adaptation, Physiological↗
PubMed1998

Induced diarrhoea in horses. Part 1: Fluid and electrolyte balance.

Sodium, potassium and water balance, and measurements of acid-base status, haematocrit, packed cell volume and plasma total protein, were studied in four adult standardbred geldings following castor oil induced diarrhoea. Castor oil (2 mL kg-1) administration resulted in signs consistent with mild to moderate acute colitis. The total (combined faecal and urinary losses) losses of sodium and potassium ions were 2169 and 2864 mmol, respectively. Faeces constituted the major route for sodium loss, while urine was the major route for potassium loss at all times. Faecal dry matter potassium concentration did not vary significantly at any stage. Faecal dry matter sodium concentration increased significantly, coinciding with the onset of clinical diarrhoea. Faecal water loss increased significantly from 2.15 +/- 0.44 mL kg-1 h-1 to 5.15 +/- 0.92 mL kg-1 h-1 while clinical diarrhoea was observed. While plasma volume (PV) did not vary significantly in this study, there was a trend for PV to decrease while horses were clinically dehydrated.

Animals↗
PubMed1998

Induced diarrhoea in horses. Part 2: Response to administration of an oral rehydration solution.

Hydration status, electrolyte balance and acid-base balance were studied in four adult standardbred geldings with castor oil-induced diarrhoea. The horses received an oral rehydration solution (ORS) at a point when signs consistent with mild decreases in effective circulating fluid volume were first detected. Within 1.5 h of ORS administration, all horses exhibited a significant metabolic acidosis. At this time, mean values for venous blood pH, [HCO3], and standard base excess were 7.264 +/- 0.011, 17.7 +/- 0.3 mmol L-1, and -8.2 +/- 0.4 mmol L-1, respectively. Throughout the duration of the study, plasma volume did not change significantly, despite a decreasing trend, which tended to recover towards normal values 8 h after administration of the ORS. Signs of abdominal discomfort were observed in all horses following the last of three doses of ORS (8-10 L) administered at 30 min intervals. Faecal fluid sodium concentration increased significantly with diarrhoea, and reached values fourfold those in normal horses, while faecal dry matter sodium concentration increased exponentially following the onset of clinical signs. Despite this increase in sodium concentration, faecal fluid remained hypotonic at all stages. Our findings suggest that, while ORS can help restore systemic fluid balance, several factors influence their effectiveness. Two likely factors identified in this study were the ionic composition of the ORS as well as the rate of administration. We concluded that the electrolyte composition of current ORS may not be ideal to treat diarrhoea in horses and that administration of 8-10 of ORS every 30 min via nasogastric tube may result in too rapid small intestinal transit to allow sufficient time for absorption.

Acidosis↗
PubMed1998

Effects of two large doses of equine recombinant growth hormone on clinical, haematological and serum biochemical variables in adult horses.

OBJECTIVE: To evaluate the clinical, haematological, and serum biochemical effects of two large doses of recombinant equine growth hormone. DESIGN: Duplicated Latin square. SAMPLE POPULATION: Three Thoroughbred and three Standardbred mares aged between 12 and 17 years. PROCEDURE: Two horses were randomly assigned into one of three groups. On each of three successive days, each horse pair received one of two dosages of growth hormone or a saline placebo so that by the end of the experiment all three horse pairs had received both dosages and the saline placebo. Dose rates selected were 50 micrograms/kg, and 100 micrograms/kg. A clinical examination was performed and a venous blood sample drawn for a complete blood count and serum biochemical analysis before administration of growth hormone and at 1, 2, 3, 4, 6, 8 and 24 h after injection. Data were analysed by a repeated measures analysis of variance assessing the effects of dose and time. RESULTS: There was an effect of time on a number of clinical, haematological, and serum biochemical variables. There were significant effects of growth hormone on heart rate and serum glucose concentration but values for both variables remained within the reference range. CONCLUSION: The results of the present study suggest that equine recombinant growth hormone has a wide margin of safety and show that the single administration of up to five times the recommended dose rate has no significant effects on clinical, haematological, or serum biochemical variables.

Animals↗
PubMed1998

Flat, hurdle and steeple racing: risk factors for musculoskeletal injury.

A retrospective case-control study was conducted to identify and quantify risk factors for serious musculoskeletal injury sustained at 4 Australian metropolitan racetracks. During the period of study (August 1988-July 1995) there were 196 cases from flat racing, 52 cases from hurdle racing and 53 cases from steeplechases. The incidences of fatal musculoskeletal injuries per start for flat, hurdle and steeple races were 0.06, 0.63 and 1.43% respectively. Logistic regression identified harder track surfaces, horses being older than age 3 years, one racecourse (Flemington) and jumping races as significant risk factors which increased the risk of musculoskeletal breakdown. The incidence of fatal musculoskeletal injuries for flat races at the 4 study tracks was similar to that reported in the UK but less than the USA. Death rates for hurdle and steeple races in the study population were higher than in the UK. Strategies to reduce the incidence of serious musculoskeletal injuries may include avoidance of excessively hard track surfaces through closer regulation of track moisture content; implementation of more rigorous prerace lameness examinations of horses, particularly older horses; and altering the design and number of jumps in hurdle and steeple races. The quantification of risk, as we have reported here, is the first step towards addressing the causes of musculoskeletal breakdown and should help in applying a reasoned approach to intervention measures that may be effective in reducing racing injuries.

Analysis of Variance↗
PubMed1998

A developmental behavior-genetic perspective on alcoholism risk.

Although behavioral problems associated with abuse of alcohol emerge during late adolescence and adulthood, some behavioral characteristics indicative of an increased risk of alcoholism may already be obvious during early childhood. Studies in several countries have demonstrated that children with high levels of novelty-seeking behavior and low levels of harm-avoidance behavior are more likely to develop alcohol-related problems during adolescence. Moreover, as early as age 3, children at high risk of future alcoholism because of a family history are more active, more impatient, and more aggressive than matched controls of low-risk children. Causal influences on the initiation of drinking must be distinguished from those that affect patterns of consumption once drinking is initiated. Studies of adolescent twins have demonstrated that initiation of drinking is primarily influenced by the drinking status of parents, siblings, and friends and by socioregional differences in the environments within which adolescent twins reside. The influence of genetic factors is negligible. Conversely, once initiated, differences in frequency and quantity of drinking are strongly influenced by genetic factors. However, these influences, too, are modulated by sibling and peer effects and by regional environmental variation.

Alcoholism↗
PubMed1998

Effects of concentrated electrolytes administered via a paste on fluid, electrolyte, and acid base balance in horses.

OBJECTIVES: To test effectiveness of an electrolyte paste in correcting fluid, electrolyte and acid base alterations in response to furosemide administration. ANIMALS: 6 Standardbreds. PROCEDURES: Horses received electrolyte paste or water only (control). The paste was given orally 3 hours after furosemide administration (1 mg/kg of body weight, IM). Water was given ad libitum soon after the paste and 3 hours after furosemide administration to treated and control groups, respectively. Paste Na+, K+, and Cl- composition was approximately 2,220, 620, and 2,840 mmol, respectively. The PCV and plasma concentrations of total protein ([TP]), [Na+], [K+], [Cl-]), and bicarbonate ([HCO3-]) were determined, and urinary fluid and electrolyte excretion, fecal water, and body weight changes were measured. RESULTS: At the end of a 6-hour period, the paste-treated group had higher water consumption, which resulted in lower plasma [TP]; net electrolyte losses also were substantially less. With paste administration, [Na+] was approximately 2 mmol/L above a prefurosemide value of 137.3 mmol/L; control horses had values similar to the prefurosemide value. Plasma [Cl-] remained at the prefurosemide value, but values in control horses decreased by 7 mmol/L with water consumption. Plasma [K+] remained approximately 0.8 mmol/L below prefurosemide values in both groups. Venous [HCO3-] returned to prefurosemide values after paste administration, but alkalosis persisted in control horses after consumption of water only. Body weight loss was less after paste administration. CONCLUSIONS: Administration of electrolyte paste is advantageous over water alone in restoring fluid, electrolyte, and acid base balance after fluid and electrolyte loss attributable to furosemide administration.

Administration, Oral↗
PubMed1997

Risk factors associated with musculoskeletal injuries in Australian thoroughbred racehorses.

Risk factors for musculoskeletal injury in racing Thoroughbreds were investigated in a case-control study conducted at racetracks administered by the Australian Jockey Club. Univariable analysis of 137 cases from the official Veterinary Surgeon's reports and an equal number of randomly selected controls from the Australian Race Results identified field size, barrier position and class of race as being significantly associated with breakdown (P < 0.05). Multiple logistic regression was then used to investigate the effect of each putative risk factor whilst controlling for all others. Horses at greater risk were older, started from a wider barrier position, ran at the same distance as their previous race and raced in the highest class of race. There was no significant difference between tracks or significant association with track condition. The incidence of fatalities in the study population was less than that reported in the UK and USA.

Animals↗
PubMed1997

Cyclic AMP-mediated regulation of vascular smooth muscle cell cyclic AMP phosphodiesterase activity.

1. Rat cultured aortic vascular smooth muscle cells (VSMC) express both cyclic GMP-inhibited cyclic AMP phosphodiesterase (PDE3) and Ro 20-1724-inhibited cyclic AMP phosphodiesterase (PDE4) activities. By utilizing either cilostamide, a PDE3-selective inhibitor, or Ro 20-1724, a PDE4-selective inhibitor, PDE3 and PDE4 activities were shown to account for 15% and 55% of total VSMC cyclic AMP phosphodiesterase (PDE) activity. 2. Treatment of VSMC with either forskolin or 8-bromo-cyclic AMP caused significant concentration- and time-dependent increases in total cellular cyclic AMP PDE activity. Using cilostamide or Ro 20-1724, we demonstrated that both PDE3 and PDE4 activities were increased following forskolin or 8-bromo-cyclic AMP treatment, with a relatively larger effect observed on PDE3 activity. The increase in cyclic AMP PDE activity induced by forskolin or 8-bromo-cyclic AMP was inhibited by actinomycin D or cycloheximide, demonstrating that new mRNA synthesis and protein synthesis were required. An analogue of forskolin which does not activate adenylyl cyclase (1,9-dideoxyforskolin) or an analogue of cyclic GMP (8-bromo-cyclic GMP) did not affect total cyclic AMP PDE activity. 3. Incubation of VSMC with 8-bromo-cyclic AMP for 16 h caused a marked rightward shift in the concentration-response curves for both isoprenaline- and forskolin-mediated activation of adenylyl cyclase. A role for up-regulated cyclic AMP PDE activity in this reduced potency is supported by our observation that cyclic AMP PDE inhibitors (IBMX, cilostamide or Ro 20-1724) partially normalized the effects of isoprenaline or forskolin in treated cells to those in untreated cells. 4. We conclude that VSMC cyclic AMP PDE activity is increased following long-term elevation of cyclic AMP and that increases in PDE3 and PDE4 activities account for more than 70% of this effect. Furthermore, we conclude that increases in cyclic AMP PDE activity contribute to the reduced potency of isoprenaline or forskolin in treated VSMC. These results have implications for long-term use of cyclic AMP PDE inhibitors as therapeutic agents.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1997

Postmortem lesions in the intercarpal ligaments of the equine midcarpal joint.

OBJECTIVE: To determine the frequency of damage to the medial palmar intercarpal ligament (MPICL), and the range of sizes of the dorsomedial intercarpal ligament (DMICL) of the midcarpal joint in horses with no history of carpal joint disease. MATERIALS AND METHODS: Cadaver limbs were collected from 72 horses with no history of carpal joint disease. One hundred and forty-two midcarpal joints were dissected and the MPICL and DMICL were examined. Measurements were made with a digital micrometer. RESULTS: MPICL tearing was present in 88 of 96 joints from horses 2 years and older. Tears were predominantly of the dorsolateral bundle and complete rupture of the dorsolateral and dorsomedial bundles was not observed. Tearing was not present in foals less than 4 months of age and the severity of tearing increased significantly with age (P < 0.0001). Severity of tearing was significantly greater in racing Standardbreds than racing Thoroughbreds (P < 0.01), but there was no significant difference between racing and non-racing horses. The lateromedial thickness of the DMICL ranged from 0.4 mm to 2.6 mm in horses 2 years and older. Lateromedial thickness increased significantly with age, and was significantly greater in racing Standardbreds than racing Thoroughbreds (P < 0.01). There was no significant difference between racing and nonracing horses. CONCLUSIONS: Damage confined to the dorsolateral bundle of the MPICL is a common finding in horses over 1 year of age and is probably of little clinical significance. Complete rupture of both dorsolateral and dorsomedial bundles is uncommon in horses with no history of midcarpal joint disease. Variation in size of the DMICL is observed in horses of all ages, but is most marked in 2-year-old horses.

Aging↗
PubMed1997

Cardiorespiratory responses to exercise in horses with different grades of idiopathic laryngeal hemiplegia.

The relationship between different grades of laryngeal function, as assessed by endoscopy at rest, and the measurements of indices of gas exchange and exercise capacity was assessed during a standardised treadmill exercise test in 149 horses. Horses with abnormalities other than idiopathic laryngeal hemiplegia (ILH) were excluded from the study and laryngeal function was graded according to an established system. There were no significant differences in age, weight, maximum oxygen uptake, maximum carbon dioxide production, maximum respiratory exchange ratio, maximum oxygen pulse and run time between the grades. Blood lactate concentration at 10 m/s was greater (P < 0.01) in horses with grade 5 laryngeal function than other grades. Minimum PaO2 (P < 0.001) and SaO2 (P < 0.01) were lower and maximum PaCO2 (P < 0.001), higher in horses with grades 4 and 5 laryngeal function than other grades. Horses with grade 4 function had a lower minimum CaO2 (P < 0.01) than horses with other grades. Minimum PAO2 decreased from grades 1 and 2 to grades 4 and 5 (P < 0.05). The minimum alveolar ventilation was lower (P < 0.05) in horses with grades 4 and 5 laryngeal function compared to other grades. The results of this study indicate that endoscopic assessment of laryngeal function at rest, using a simple grading system, provides an indication of dynamic changes in ventilation and the effects on blood gases during exercise. From the data, we suggest that horses that have some movement of the left arytenoid cartilage but are unable to achieve full abduction have similar ventilatory effects and blood gas responses during maximal exercise to those with complete paralysis. Some horses with grade 3 laryngeal function had blood gas results similar to those of horses with grades 4 and 5 laryngeal function, indicating that discrepancies may occur between the resting assessment and laryngeal function during strenuous exercise.

Animals↗
PubMed1997

Effects of training on the development of exercise-induced arterial hypoxemia in horses.

OBJECTIVES: To compare the development of exercise-induced arterial hypoxemia in horses before and after training, and to determine whether increases in maximum oxygen uptake (VO2max) following training results in a greater degree of exercise-induced arterial hypoxemia. ANIMALS: 13 three- to five-year-old. Standardbred geldings without clinical signs of respiratory or cardiovascular disorders. PROCEDURE: Horses were rested for 4 months prior to commencing a 16-week training program. Arterial blood was collected from the transverse facial artery during standardized exercise tests performed before and after 8 and 16 weeks of training. Variables measured during exercise tests included arterial blood gas tensions and VO2max. Training and testing was performed on a treadmill set at a 10% slope. RESULTS: Minimum arterial partial pressures of oxygen (PaO2) during exercise decreased from 83.3 +/- 1.5 mm of Hg before training to 77.8 +/- 1.0 mm of Hg after 16 weeks of training. Maximum arterial oxygen content increased from 239.2 +/- 3.1 to 257.9 +/- 3.8 ml/L, which resulted from an increase in hemoglobin concentration. The VO2max increased by 19% following training. Minimum values of PaO2 and arterial oxygen saturation were significantly correlated with VO2max when data from each stage of training were pooled. Calculated values for minimum alveolar oxygen tension decreased after 8 weeks of training, and alveolar ventilation increased at the end of training. Alveolar-arterial oxygen tension of difference increased by 4 mm of Hg following training. CONCLUSIONS: In trained horses, an increase in VO2max is associated with a decrease in minimum PaO2, during intense exercise and is mostly attributable to an increase in the alveolar-arterial oxygen tension difference. Therefore, interpretation of blood gas data from exercising horses should take into consideration VO2max.

Animals↗
PubMed1997

A review of orthodontic appliance problems in general dental practice.

Patients will often visit their general dental practitioner when experiencing problems with orthodontic appliances, even if they were referred to a specialist for treatment. Reassurance may be all that is necessary, but simple intervention may allow the treatment to continue with a minimum of interruption. This article is an overview of the common orthodontic appliance problems that may be encountered and provides practical advice on how to deal with them.

Equipment Failure↗