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Biomedical subjects

D R Hodgson

Publications and source records attributed to D R Hodgson.

At least 55 records · Page 3Linked to original sources
PubMed2000

Free-ligand accelerated dissociation of insulin-like growth factor 1 (IGF-1) from the type I IGF receptor is reduced by insulin-like growth factor binding protein 3.

Insulin-like growth factor binding proteins (IGFBP) can inhibit or accentuate the mitogenic activities of insulin-like growth factor 1 (IGF-1) depending upon the experimental model employed. Inhibitory effects may be attributed to sequestration of IGF-1 onto IGFBP rather than the type I IGF receptor. We have demonstrated that the presence of IGFBP in a simple equilibrium binding assay significantly reduces the total amount of IGF-1 bound to the type I IGF receptor and increases the IC(50) for IGF-1 binding. On the basis of such an experiment, performed at equilibrium, IGFBP should reduce the mitogenic activity of IGF-1. Recent work has demonstrated an inverse correlation between the dissociation rate of insulin-like molecules from their receptors and their mitogenic activity. It has also been suggested that the increased rate of dissociation of insulin and IGF-1 from their receptors at increased ligand concentrations serves as a 'dampening' mechanism to decrease mitogenic signalling. We have demonstrated increased rates of dissociation of IGF-1 from the type I IGF receptor with increasing concentrations of IGF-1. Furthermore, IGFBP-3 inhibits the acceleration of dissociation rates due to increased IGF-1 levels. Thus, under receptor saturating conditions IGFBP-3 may act to increase mitogenesis by increasing the residence time of individual molecules of IGF-1 upon the type I IGF receptor.

3T3 Cells↗
PubMed2000

Prevalence and clinical importance of heart murmurs in racehorses.

OBJECTIVE: To determine the prevalence of various types of heart murmurs in Thoroughbred racehorses and assess their association with performance by echocardiography and review of the horses' race records for the preceding 2 years. DESIGN: Clinical and retrospective study. ANIMALS: 846 Thoroughbred racehorses. PROCEDURE: Cardiac auscultations were performed by 3 individuals; for 30 horses, Doppler echocardiographic examinations were also performed. Statistical analyses of race records for 753 horses were performed to assess association of heart murmurs with performance. RESULTS: Heart murmurs were detected by cardiac auscultation in 686 of 846 (81.1%) horses. Systolic murmurs over the heart base were most common; 365 (43.1%) horses had systolic murmurs that were loudest over the pulmonary valve area, and 232 (27.4%) horses had systolic murmurs that were loudest over the aortic valve area. Systolic murmurs over the tricuspid valve area were detected in 241 (28.5%) horses, whereas systolic murmurs over the mitral valve area were detected in only 32 (3.8%) horses. Diastolic murmurs were much less common than systolic murmurs. Review of race records did not reveal a significant association between murmurs and performance. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that heart murmurs are a common finding in racehorses; most of these heart murmurs do not appear to be clinically important.

Age Factors↗
PubMed2000

Comparison of some responses to exercise on the track and the treadmill in French trotters: determination of the optimal treadmill incline.

The purpose of this study was to determine the optimal treadmill slope for trotters to produce the same heart rate and blood lactate responses as on the track during a standardized exercise test. Nine 2-year-old French trotters performed exercise tests on a training track and on a treadmill set at an incline of 0, 2 or 4%. For all horses, track testing was performed on day 1 and then on the treadmill according to a Latin-square design. The track test utilized three steps each of 3 min at speeds of 470, 530, 590 m/min and the same speeds were used on the treadmill. Derived physiological variables such as the speed at a HR of 200 bpm (V(200)) and the speed inducing blood lactate concentrations of 4 mmol/L (V(4)) were calculated. There were significant differences for V(200)and V(4)(P<0.05) between the track and the treadmill data when the treadmill was set at inclines of 0 and 4%, but no significant differences with the treadmill set at a 2% incline. The optimal treadmill incline to reproduce similar responses to those on the track was determined by regression analysis, and was found to be 2.4% for the two most often utilized derived physiological variables, V(4)and V(200).

Animals↗
PubMed2000

Surgical treatment of tarsometatarsal joint luxation in a miniature horse foal.

A 2-week-old Miniature Horse foal was referred for evaluation and treatment of a luxated right tarsometatarsal joint. Treatment consisted of closed reduction and internal fixation using two partially threaded Steinmann pins placed in normograde fashion through the tuber calcis into the proximal third metatarsus. Traumatic luxation has been reported to occur in the tarsocrural, proximal intertarsal and tarsometatarsal joints within the equine tarsus. Treatment for luxation of the distal intertarsal joint has not been documented. The treatment method most commonly suggested for tarsal luxation is closed reduction and cast immobilisation. Internal fixation using lag screws and plating has also been described. A combination of internal fixation and external coaptation is thought to achieve maximal stability and allow faster convalescence in cases of tarsal luxation. This case report describes for the first time a technique using two Steinmann pins to achieve successful internal fixation of a traumatic tarsometatarsal joint luxation in a 2-week-old Miniature Horse foal.

Animals↗
PubMed2000

Ventral midline caesarean section for dystocia secondary to failure to dilate the cervix in three alpacas.

Three alpacas that presented with dystocia characterised by failure of the cervix to dilate, underwent caesarean section. Surgery on each animal was performed through a ventral midline incision under general anaesthesia. Two live crias were delivered and one cria was dead at delivery. All three alpacas had retained foetal membranes for a period of 12 h to 4 d and one developed uterine prolapse, which was replaced using sedation and epidural anaesthesia. There were no complications associated with the surgical procedure and all three alpacas went on to have confirmed pregnancies. Caesarean section through a ventral midline incision should be considered an alternative for treatment of difficult dystocias in alpacas.

Animals↗
PubMed2000

Changes in cardiac dimensions and indices of cardiac function during deconditioning in horses.

OBJECTIVE: To investigate the effects of deconditioning on cardiac dimensions and indices of cardiac function in horses. ANIMALS: Thirteen 3-to 4-year-old Standardbred geldings. PROCEDURE: All horses had echocardiographic measurements performed at the conclusion of 9 months of intense training and at weeks 1.5, 4, 8, and 12 of deconditioning. Direct echocardiographic measurements included interventricular septal thickness, left ventricular internal dimensions, left ventricular freewall thickness, left atrial dimension, aortic diameter, diameter of the pulmonary artery, slopes of the mitral valve, heart rate, preejection period, and ejection time. Derived indices of cardiac function included fractional shortening, fractional area change, and cardiac output. RESULTS: Cardiac dimensions did not change significantly for the first 4 weeks of deconditioning but decreased significantly by week 8 and continued to decrease until week 12. Indices of cardiac function increased significantly during the first 10 days of deconditioning, remaining stable until week 4 of deconditioning. After week 4, indices of cardiac function decreased significantly until week 12. CONCLUSIONS AND CLINICAL RELEVANCE: Deconditioning resulted in a general reduction in cardiac dimensions and indices of cardiac function over 12 weeks. However, results of the study reported here indicate that following an intense period of training, cardiac function may be maintained during the first 4 weeks of deconditioning. Results indicate that trained horses may rest for up to 4 weeks without a substantial reduction in cardiac capacity as reflected by echocardiographic indices.

Animals↗
PubMed2000

Evidence for surfactant contributing to the gastric mucosal barrier of the horse.

This study was undertaken to determine the hydrophobicity of the luminal surface of the equine stomach and to elucidate the ultrastructure of the lining imparting that property. Gastric and duodenal mucosal samples from 5 horses were collected immediately after euthanasia and subjected to surface contact angle measurement using a goniometer. Gastric mucosal samples from 4 horses and a foal were examined by electron microscopy following a fixation procedure known to preserve phospholipids and oligolamellar structures. Contact angles for the equine gastric glandular mucosal surface (mean +/- s.e. 78.0 +/- 11.0 degrees) were greater than for the duodenum (33.4 +/- 8.7 degrees), (P = 0.003). The contact angles for gastric squamous tissue (50.4 +/- 4.5 degrees) tended to be greater than for duodenum (P = 0.15). Electron microscopy revealed the existence of surfactant as abundant osmiophilic phospholipid material within both squamous and glandular gastric mucosae. These results indicate the hydrophobic nature of the equine gastric mucosae. We propose that the water-repellent nature of the stomach contributes to the 'gastric mucosal barrier' and is imparted by surface-active phospholipid adsorbed to the surface. Phospholipids may also be utilised as a physical barrier to back-diffusion of acid by lining intracellular canaliculi and oxyntic ducts where other defence mechanisms are absent.

Animals↗
PubMed2000

Superficial digital flexor tendonitis in the horse.

The superficial digital flexor tendon (SDFT) is an elastic structure that during maximal exercise appears to operate close to its functional limits. The biomechanical and biochemical responses to exercise, injury, and healing are still poorly understood but ongoing research is providing valuable new information which is addressed in this review. It appears that the SDFT matures early, after which time it has limited ability to adapt to stress and undergoes progressive degeneration. Focal hypocellularity, collagen fibril degeneration, selective fibril loading and alterations in the noncollagenous matrix occur primarily within the central core region of the midmetacarpal segment. Current treatment strategies have had equivocal results in returning animals to optimal athletic activity. To date it would seem that progressive rehabilitation programmes coupled with regular ultrasonographic evaluations are a cost-effective and comparable strategy when compared to surgical treatment methods. Recent interest in pharmacological modulation of intrinsic healing of collagenous structures has led to the investigation of various growth factors as potential therapeutic aids in the healing of tendon injuries. However, one of the major goals in tendon research, and one which holds the most optimism for success in the immediate future, is the prevention of tendon injuries.

Animals↗
PubMed1999

Impact of injuries and disease on a cohort of two- and three-year-old thoroughbreds in training.

A prospective study of injuries and disease in a cohort of Australian thoroughbreds in training was conducted with the participation of 24 trainers. From the horses catalogued at a major yearling sale in 1995, 169 were enrolled in the study and followed through their two- and three-year-old racing seasons. The principal aim was to quantify the time lost in training as a result of the various categories of injuries and disease, recorded as either days of modified training, or weeks rested at pasture. Shin soreness was the most common condition in two-year-olds (affecting 42 per cent of the horses that had entered training), followed by fetlock problems (25 per cent), and coughs and nasal discharge (16 per cent). Lameness, excluding lacerations and traumatic injuries, was the most common reason for lost training days (56.2 per cent of total days modified) and for resting horses at pasture (81.2 per cent of total weeks rested for injury or disease). Of the individual categories of injury or disease, lacerations and traumatic injuries, coughs and nasal discharge, shin soreness, carpal problems and fetlock problems were the most important causes of modified training days. In terms of weeks rested at pasture, fetlock problems, shin soreness, carpal problems, and coughs and nasal discharge had the greatest impact. Major injury was uncommon in young horses in training, but there was a high incidence of relatively low-grade injuries and disease during the training of two-year-olds.

Animal Husbandry↗
PubMed1999

Plasma cortisol and beta-endorphin concentrations in trained and over-trained standardbred racehorses.

The effects of training and over-training on plasma cortisol and beta-endorphin (betaEP) concentrations at rest and after standardised exercise tests and the cortisol responses to adrenocorticotropin (ACTH) administration were investigated in standardbred horses. Twelve horses were divided randomly into control and over-trained (OT) groups after 17 weeks slow- and moderate-intensity treadmill training. The standardised treadmill exercise test consisted of 2 min at velocities corresponding to 30, 50, 70 and 100% of maximum O2 consumption. Over-training, defined as a significant decrease in body weight and treadmill run-time-to-fatigue in an incremental velocity test, occurred in the OT group after 32 weeks of training exercise. Peak cortisol concentrations after exercise decreased significantly in the OT group from 320+/-15.6 at week 8 to 245+/-17.0 nmol l(-1) at week 32, and mean cortisol concentrations over a 120-min period after exercise decreased from 258+/-11.7 to 192+/-16.6 nmol l(-1) (P<0.05). Mean and total cortisol and betaEP concentrations in resting horses were not significantly different after over-training. Peak cortisol concentrations after adrenocorticotropin (ACTH) administration were not significantly different in the over-trained group. Dysfunction of the hypothalamo-pituitary-adrenocortical axis occurs in over-trained horses, but this adaptation is not associated with a change in the adrenocortical responsiveness to ACTH.

Adrenal Glands↗
PubMed1999

Bone marrow response to large volume blood collection in the horse.

Evaluation of erythropoietic regeneration in horses is difficult unless serial bone marrow aspirates are performed. To investigate the acute and chronic erythropoietic regenerative response of equine bone marrow following acute removal or loss of blood, sequential bone marrow aspirates over 4 weeks were taken from the sternum of five horses from which 20 ml kg(-1)of blood had been removed. We found that the total number of erythroid cells counted (expressed as a percentage of the total number of erythroid and myeloid cells counted) expanded initially by 13.7 per cent within 3 days after blood removal, the erythroid response peaking by 9 days with a further 13.5 per cent increase. This peak coincided with the lowest M:E ratio. Concomitantly, a shift from proliferative phase cells to maturing phase cells occurred, which appeared to persist beyond 31 days post collection. Thus, we found that the equine bone marrow mounted a regenerative erythropoietic response more slowly than previously determined and, also, regeneration of the erythroid compartment was incomplete 31 days after blood removal of this magnitude.

Animals↗
PubMed1999

The synovial response to exogenous phospholipid (synovial surfactant) injected into the equine radiocarpal joint compared with that to prilocaine, hyaluronan and propylene glycol.

AIMS: To determine the effects of the intra-articular injection of surface-active phospholipid in a propylene glycol carrier on synovial fluid composition and joint function of horses, and to compare these effects with those observed after the intra-articular administration of prilocaine, hyaluronan and propylene glycol alone. METHODS: Twenty-four horses were randomly allocated to four treatment groups: Group 1 100 mg of surface-active phospholipid in 1 ml of propylene glycol; Group 2 1 ml of propylene glycol; Group 3 10 ml of prilocaine; Group 4 2 ml of hyaluronan. Left radiocarpal joints were injected with the treatments and the right radiocarpal joints were injected with volume-matched saline as controls. Examinations for lameness, arthrocenteses and synovial fluid analyses were performed before and at 1, 3 and 7 days after injection. RESULTS: No horses became lame but treated joints temporarily developed mild to moderate effusions. Synovial fluid analyses indicated significantly greater inflammation in treated compared to control joints and this difference was greatest 24 hours after injection. There were no differences between the four treatments based on synovial fluid analysis except for neutrophil counts and alkaline phosphatase activities, which were significantly higher in prilocaine-treated joints. CONCLUSION: In horses, the intra-articular injection of surface-active phospholipid in a propylene glycol carrier induces clinically insignificant, temporary abnormalities in synovial fluid. Surface-active phospholipid was no more injurious to the synovium than prilocaine or hyaluronan. None of the agents used in this experiment caused lameness when injected into the joints of horses. RELEVANCE: This dose and formulation appear suitable for use in future experiments investigating the efficacy of surface-active phospholipid in the treatment or prevention of osteoarthritis in horses.

Journal Article↗
PubMed1999

Treatment of progressive ethmoidal haematoma using intralesional injections of formalin in three horses.

Three Thoroughbred horses with unilateral progressive ethmoid haematomas were treated using intralesional injections of 10% formalin (4% formaldehyde solution). Injections were performed in the standing sedated horse through the nasal passages under endoscopic guidance and, when the ethmoid haematoma involved the paranasal sinuses, through holes trephined into the affected sinus. Regression of the lesions occurred in all cases after repeated injections. This technique appears to be a safe and effective treatment for progressive ethmoid haematomas in the horse.

Animals↗
PubMed1999

Ultrastructure of the hydrophobic gastric surfactant barrier in the dog.

OBJECTIVES: To confirm the hydrophobicity of the luminal surface of the canine stomach and to elucidate the ultrastructure of the lining imparting that property. DESIGN AND PROCEDURES: Gastric and duodenal mucosal samples from eight dogs were collected immediately after euthanasia and subjected to contact angle measurement using a goniometer. Other samples were examined by electron microscopy following a fixation procedure known to preserve phospholipids and oligolamellar structures. RESULTS: Contact angles for the canine gastric mucosal surface (85.1 +/- 5.5) were significantly greater (P < 0.0001) than for the duodenum (24.0 +/- 1.7). Electron microscopy revealed the existence of surfactant as abundant osmiophilic phospholipid material within the gastric and duodenal mucosae. CONCLUSION: We have confirmed the hydrophobic nature of the canine gastric mucosa whereas the luminal surface of the duodenum is hydrophilic. We propose that the water-repellent nature of the canine gastric lining contributes to the 'gastric mucosal barrier' and is imparted by an oligolamellar layer of surface-active phospholipid ('gastric surfactant') adsorbed to the surface. Both gastric and duodenal mucosae may also utilise phospholipids as an intercellular defense mechanism in the event that tight junctions are breached by acid. It is tempting to speculate that a deficiency of gastric phospholipids may predispose dogs to ulcers. Further, exogenous administration of phospholipids may be useful in preventing gastric ulceration.

Animals↗
PubMed1999

Equine castration: review of anatomy, approaches, techniques and complications in normal, cryptorchid and monorchid horses.

Complications associated with equine castration are the most common cause of malpractice claims against equine practitioners in North America. An understanding of the embryological development and surgical anatomy is essential to differentiate abnormal from normal structures and to minimise complications. Castration of the normal horse can be performed using sedation and regional anaesthesia while the horse is standing, or under general anaesthesia when it is recumbent. Castration of cryptorchid horses is best performed under general anaesthesia at a surgical facility. Techniques for castration include open, closed and half-closed techniques. Failure of left and right testicles to descend occurs with nearly equal frequency, however, the left testicle is found in the abdomen in 75% of cryptorchid horses compared to 42% of right testicles. Bilateral cryptorchid and monorchid horses are uncommon. Surgical approaches described for the castration of cryptorchid horses include an inguinal approach with or without retrieval of the scrotal ligament, a parainguinal approach, or less commonly a suprapubic paramedian or flank approach. Laparoscopic castration of cryptorchid horses has recently been described but the technique has limited application in practice at this time. A definitive diagnosis of monorchidism can only be made after surgical exploration of the abdomen, removal of the normal testis and hormonal testing. Hormonal assays reported to be useful include analysis of basal plasma or serum testosterone or oestrone sulphate concentrations, testosterone concentrations following hCG stimulation, and faecal oestrone sulphate concentrations. Reported complications of castration include postoperative swelling, excessive haemorrhage, eventration, funiculitis, peritonitis, hydrocele, penile damage and continued stallion-like behaviour.

Animals↗
PubMed1999

Nonsurgical management of type II fractures of the distal phalanx in 48 standardbred horses.

OBJECTIVE: To evaluate nonsurgical management of type II fractures of the distal phalanx in Standardbred horses. DESIGN: Retrospective study of 48 affected horses. RESULTS: Most fractures occurred on the lateral palmar process of the left forelimb or the medial palmar process of the right forelimb; 81% of horses were considered sound enough to return to training and 63% raced. Of those returning to racing, 41% competed in > 10 races, 37% in 2 to 10 races and 22% in only 1 race. There was no difference in performance before and after fracture. Twenty-four of 25 horses had a bar shoe fitted for > 50% of the treatment phase. Of those horses returning to training without a bar shoe, 89% refractured at the same site. Sixty percent of horses returning to training with a bar shoe raced successfully. The total convalescent time, the time rested in a box and the time spelled in a paddock were similar for horses returning to racing and those that did not. The age of the horse had no effect on the ability to return to racing. CONCLUSION: The prognosis for type II fractures of the distal phalanx is guarded. It is advisable to fit a bar shoe on the horse during convalescence. Horses returning to training and racing with a bar shoe appear less likely to refracture the distal phalanx. Those horses that return to racing can perform at a level similar to that prior to fracture.

Animals↗