bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of phenylbutazone on the intestinal mucosa of the horse: a morphological, ultrastructural and biochemical study
Authors: MESCHTER CAROL L. , GILBERT M. , KROOK L. , MAYLIN G. , CORRADINO ROBERT 
Published: April 2010

SummaryPhenylbutazone, a non‐steroidal anti‐inflammatory drug known to produce intestinal erosions, was administered intravenously (13.46 mg/kg bodyweight) to 12 horses which were killed after 24, 48, 72 and 96 h. Eight untreated horses served as controls. Annular erosions in the duodenum and mucosal necrosis in the colon were seen after 48 h which progressed in severity. The erosions were characterised by sloughing of the surface epithelium, subepithelial cleft and bleb formation, necrosis of thelamina propria, degeneration of the walls of subsurface capillaries and microthrombosis. Large numbers of neutrophils with abundant fibrin and cellular debris were present at the erosion sites. Ultrastructurally, there was swelling of the endothelium of capillaries and small vessels, and of pericyte and smooth muscle cytoplasm in arterioles. In capillaries and post capillary venules, the endothelium ranged from swollen to lysed and necrotic. Extensive extravasation of erythrocytes and oedema were seen. These lesions were not seen in the control horses. Phenylbutazone produces a microvascular injury associated with the formation of duodenal and colonic erosions in horses. The duodenal and colonic mucosa were assayed at 48 and 96 h for prostacyclin and PGE2. There was no statistically significant difference between prostaglandin levels in the mucosa of control and treated horses. It was concluded that there was no correlation between mucosal prostaglandin levels and intestinal erosions after 48 h.
Haemodynamic effects of small volume hypertonic saline in experimentally induced haemorrhagic shock
Authors: SCHMALL L. M. , MUIR W. W. , ROBERTSON J. T. 
Published: April 2010

SummaryA comparison of the haemodynamic benefits of small volume hypertonic saline (2,400 mOsm/litre) versus isotonic saline (300 mOsm/litre) was conducted in 12 adult horses using a haemorrhagic shock model. The horses were anaesthetised and intravascular catheters placed for the measurement of haemodynamic data. Mean systemic arterial pressure was then reduced to 50 to 60 mmHg by controlled haemorrhage and maintained at that level for 40 mins. Cardiac output, stroke volume, mean systemic arterial pressure, plasma volume and urine production decreased significantly following blood loss. Hypertonic or isotonic saline was administered randomly by intravenous infusion and haemodynamic data recorded for a 2 h period. Treatment with hypertonic saline produced rapid elevations in cardiac output, stroke volume, mean systemic and pulmonary arterial pressures, cardiac contractility and urine output, and was accompanied by expansion of the plasma volume. The changes in cardiac output and stroke volume were maintained for the duration of the recording period, whereas increases in mean systemic arterial pressure were not as remarkable. Infusion of isotonic saline caused only transient increases in cardiac output and mean systemic and pulmonary arterial pressure, and cardiac output; urine output and plasma volume did not change. This study indicates that hypertonic saline produces haemodynamic improvements in experimentally induced haemorrhagic shock in horses.
Haematological, serum electrolyte and blood gas effects of small volume hypertonic saline in experimentally induced haemorrhagic shock
Authors: SCHMALL L. M. , MUIR W. W. , ROBERTSON J. T. 
Published: April 2010

SummaryThe effects of treatment with small volume hypertonic (2400 mOsm/litre) and isotonic (300 mOsm/litre) saline on serum electrolyte and biochemical concentrations, haemograms and blood gases were evaluated in 12 horses using a haemorrhagic shock model. Intravascular catheters were placed surgically for sample collection prior to anaesthesia. Controlled haemorrhage was initiated and continued until mean systemic pressure reached 50 to 60 mmHg. Hypertonic or isotonic saline (2 litres) was administered by intravenous infusion and data collected for 2 h. Following haemorrhage, packed cell volume (PCV), haemoglobin, blood glucose concentrations and erythrocyte numbers increased whereas plasma total protein and albumin concentrations decreased. Infusion of hypertonic saline resulted in a further decrease in total protein and albumin concentrations. Glucose concentrations and other haematological variables were unaffected. Isotonic saline administration did not affect electrolyte, total protein or albumin concentrations. Concentrations of sodium and chloride were unaffected by hypotension but increased significantly following hypertonic saline treatment, exceeding normal values during the immediate post treatment period. Serum osmolality increased concurrently. No significant changes in arterial and venous blood gas values were observed with haemorrhage or isotonic saline treatment. A transient decrease in arterial and venous blood pH and a sustained decrease in venous bicarbonate and base excess concentrations occurred following hypertonic saline administration. No significant increases in any serum biochemical concentrations occurred during hypotension or following infusion of either isotonic or hypertonic saline. These results demonstrate that small volume hypertonic saline can be administered safely to horses without producing extreme changes in electrolyte concentrations, blood gases or haematological parameters.
Atelectasis causes gas exchange impairment in the anaesthetised horse
Authors: NYMAN G. , FUNKQUIST B. , KVART C. , FROSTELL C. , TOKICS L. , STRANDBERG Å. , LUNDQUIST H. , LUNDH B. , BRISMAR B. , HEDENSTIERNA G. 
Published: April 2010

SummaryThe anatomical basis of gas exchange impairment in the anaesthetised horse was studied by computerised tomography (CT; three Shetland ponies) and morphological analysis (one pony and three horses). By means of CT, densities were seen in dependent lung regions early during anaesthesia, both with spontaneous breathing and with mechanical ventilation. The densities remained for some time where they had initially been created when the animal was turned from dorsal to sternal recumbency. Deep insufflation of the lungs reduced the dense area. Gas exchange was impaired roughly in proportion to the dense area. On histological analysis, the densities were atelectatic and congested with blood. Gravimetry showed no more extravascular water per unit lung tissue in the atelectatic than in the ‘normal’ regions, and the blood content was increased only slightly. It is concluded that the horse develops atelectasis in dependent lung regions early during anaesthesia in dorsal recumbency, and that atelectasis is the most likely explanation for the large shunt and impaired arterial oxygenation regularly seen during anaesthesia.
Doxapram infusion during halothane anaesthesia in ponies
Authors: TAYLOR POLLY M. 
Published: April 2010

SummaryDoxapram, 0.05 mg/kg bodyweight/min, was infused during the second hour of 2 h halothane anaesthesia in six ponies. Two of the ponies were anaesthetised on a second occasion as controls and given 5 per cent dextrose in place of the doxapram. Respiratory depression typical of halothane anaesthesia in ponies developed in the first hour of anaesthesia and continued during the second hour in the control animals. During doxapram infusion arterial carbon dioxide tension decreased and pH increased. Arterial blood pressure increased but there was no change in pulse rate, the electrocardiogram or arterial oxygen tension. Anaesthesia lightened during doxapram infusion necessitating an increase in the vapouriser setting in order to prevent arousal. Recovery from anaesthesia appeared unaffected by the doxapram infusion.
The influence of photoperiod on gonadotrophin‐releasing hormone stimulated luteinising hormone release in the anoestrous mare
Authors: NEQUIN LYNN G. , KING SHERYL S. , MATT KATHLENE S. , JURAK RITA C. 
Published: April 2010

SummaryThe transition from anoestrus to oestrus in mares is controlled by photoperiod. The present study examined whether additional daylength would accelerate the mares' response to gonadotrophin‐releasing‐hormone (GnRH). Nine anoestrous mares were placed under ambient or artificial long lighting on 7th January. The four month experimental period was divided into a three‐day sequence which was repeated at 21 day intervals. Ovaries were palpated rectally on Day 1; saline was injected (1 ml intravenously [iv]) on Day 2; GnRH was administered (0.59 μg/kg bodyweight iv) on Day 3. Blood was taken at −60, 0, 15, 30, 60 and 120 mins relative to saline or GnRH treatment. Serum luteinising hormone (LH) was determined by a homologous equine radioimmunoassay (RIA). Several criteria were employed to define a positive response to GnRH and the results were analysed by Fisher's exact probability test. Treatment with artificial light allowed a response to GnRH within six weeks whereas the mares in ambient lighting took 12 weeks to respond to GnRH. The advancement in the time of response to GnRH under the long photoperiod could be related to changes in pituitary LH content, accelerated follicular activity or alterations in other brain‐pituitary hormone levels.
Cardiopulmonary effects of epidurally administered xylazine in the horse
Authors: LEBLANC P. H. , EBERHART SUSAN W. 
Published: April 2010

SummaryThis study was designed to determine whether the epidural administration of an alpha2agonist, xylazine, would produce measurable changes in arterial blood pressure, electrocardiographic (ECG) activity and arterial blood gas values in horses. Six horses were given each of four treatments: epidural xylazine, intravenous xylazine, epidural lidocaine and epidural saline. A carotid artery catheter was used to measure arterial blood pressure and to collect samples for blood gas analysis before treatment and at intervals post treatment. Heart rate, arterial pressures, ECG activity and respiratory rate were recorded at the same intervals. No significant changes were recorded between time intervals or between individual treatments. It was concluded that this method of xylazine administration to horses produced potent caudal analgesia without measurable cardiopulmonary effects.
An investigation of the second heart sound in the normal horse
Authors: WELKER F. H. , MUIR W. W. 
Published: April 2010

SummaryThe second heart sound was evaluated in conscious, normal horses using intracardiac and external sound detection devices and echocardiography. The second heart sound (S2) in the normal horse is single or split by a narrow interval, not usually detected by external phonocardiographic evaluation. Splitting of S2 was classified as normal (aortic [A2] preceding pulmonic [P2] components) in 66.7 per cent and reversed (P2 preceding A2) in 33.3 per cent of the horses studied. Normal splitting appears to result from lower impedance of the pulmonary vasculature delaying the onset of P2. Reverse splitting appears to result from a delay in A2 resulting from prolongation of PEP and LVET. There does not appear to be variation in splitting of S2 due to respiration based on the cases in which this was measured.
Effects of time of insemination relative to ovulation on pregnancy rate and embryonic‐loss rate in mares
Authors: WOODS JEANINE , BERGFELT D. R. , GINTHER O. J. 
Published: April 2010

SummaryThe effects of pre‐ovulatory and post ovulatory insemination on pregnancy rate and embryonic‐loss rate were studied in 268 mares in two experiments. Within each experiment mares were randomised within replicates as follows: to be inseminated on the day the pre‐ovulatory follicle reached 35 mm (pre‐ovulatory group), to be inseminated on the day of ovulation (Day 0 group), and to be inseminated on the day after ovulation (Day 1 group). Ultrasonic pregnancy diagnoses were performed on Days 11, 12, 13 and 14 (Experiment 1) and Days 11, 12, 13, 14, 15, 20 and 40 (Experiment 2). Combined for the two experiments, pregnancy rates were different (P<0.01) among the three groups. For Experiment 2, pregnancy rate within the pre‐ovulatory group was lower (P<0.05) for insemination 4 days or more before ovulation than for up to 3 days before ovulation. Pregnancy rate was lower (P<0.05) for the Day 0 group than for the pre‐ovulatory group inseminated up to 3 days before ovulation. In Experiment 2, ovulation was detected by examinations every 6 h; pregnancy rate was greater (P<0.05) for mares inseminated 0 to 6 h after ovulation than for mares inseminated at 18 to 24 h. No pregnancies occurred when mares were inseminated 30 h or more after ovulation. The mean day of first detection of the embryonic vesicle was different (P<0.0001) among the three groups. Diameter of embryonic vesicle averaged over Days 11 to 15 also differed (P<0.0001) among groups. The rate of embryonic loss (Experiment 2) between day of first detection of the conceptus and Day 40 was greater (P<0.05) for the Day 0 group than for the pre‐ovulatory group. Insemination up to 12 h post ovulation resulted in pregnancy rates equivalent to those for pre‐ovulatory insemination. Thereafter, the pregnancy rates diminished with no pregnancies occurring after 30 h. Embryonic vesicles were smaller and embryonic‐loss rate was greater for mares inseminated after ovulation.
Inflammatory components in uterine fluid from mares with experimentally induced bacterial endometritis
Authors: PYCOCK J. F. , ALLEN W. E. 
Published: April 2010

SummaryExudate and uterine flushings were collected at either 30, 60, 120 or 240 mins after intrauterine infusions ofStreptococcus zooepidemicusin genitally normal mares during oestrus. Uteri were also flushed without prior induction of endometritis. Protein concentrations in exudate and flushings increased with time and exudate pH decreased with time; the pH of flushings did not alter. Lysozyme and lactate dehydrogenase were present in flushings from non‐infected uteri, but concentrations increased with time after infection. Immunoreactive prostaglandin E2 was undetectable before infection, but concentrations rose after infection. No neutrophils were present in non‐infected flushings but, by 30 mins, there were significant (P<0.01) neutrophil numbers in exudate and flushings; thereafter numbers increased, particularly in exudate. Acute endometritis resembled acute inflammation at other sites in the horse and a significant response had occurred by 30 mins after experimental infection.
The effects of copper supplementation on the prevalence of cartilage lesions in foals
Authors: KNIGHT DEBRA A. , WEISBRODE S. E. , SCHMALL L. M. , REED S. M. , GABEL A. A. , BRAMLAGE L. R. , TYZNIK W. I. 
Published: April 2010

SummaryThe potential role of dietary copper in the development of cartilage defects in foals was investigated. Twenty‐one mares were fed rations containing 13 ppm copper (CuC, control) or 32 ppm copper (CuS, supplemented) during the last three to six months of gestation and first three months of lactation. Their foals were fed pelleted concentrate containing 15 or 55 ppm Cu and were destroyed at 90 (5 CuC and 5 CuS foals) or 180 (6 CuC and 5 CuS foals) days. Focal cartilage lesions were found at multiple sites on necropsy. In foals killed at 90 days, there were over twice (9 versus 4) as many lesions of osteochondrosis and more than four times (9 versus 2) as many articular lesions of osteophyte formation or thinning in CuC foals compared with CuS foals. These differences were due predominantly to a higher number of lesions in one CuC foal. Two 90‐day CuC foals had osteochondrosis of articular‐epiphyseal (A‐E) complex, one with thickenings and separation from subchondral bone and one with subchondral fibrosis. One 90‐day CuS foal had a cartilage thickening of the A‐E complex in the tibiotarsal joint with separation from subchondral bone. In foals killed at 180 days, there were seven times more articular lesions (21 versus 3) of osteophyte formation or thinning, nearly twice as many lesions of osteochondrosis (13 versus 7) in the physis and over five times as many involving the A‐E complex (11 versus 2) in six CuC foals compared with five CuS foals. Thirteen lesions of osteochondrosis in the A‐E complex had separation of the thickened cartilage from the subchondral bone, with nine exhibiting subchondral fibrosis. These were observed in 180‐day CuC foals only. Lesions of osteochondrosis with separation of cartilage from subchondral bone were not observed in CuS foals. Supplementation of dietary copper to mares during late stage pregnancy and to their foals from 90 to 180 days of age appears to reduce the prevalence and severity of osteochondrosis and other developmental cartilage lesions in the foals, compared with foals and their dams fed slightly above National Research Council recommended levels.
Hordenine: pharmacology, pharmacokinetics and behavioural effects in the horse
Authors: FRANK M. , WECKMAN T. J. , WOOD T. , WOODS W. E. , TAI CHEN L. , CHANG SHIH‐LING , EWING A. , BLAKE J. W. , TOBIN T. 
Published: April 2010

SummaryHordenine is an alkaloid occurring naturally in grains, sprouting barley, and certain grasses. It is occasionally found in post race urine samples, and therefore we investigated its pharmacological actions in the horse. Hordenine (2.0 mg/kg bodyweight [bwt]) was administered by rapid intravenous (iv) injection to 10 horses. Typically, dosed horses showed a flehmen response and defecated within 60 secs. All horses showed substantial respiratory distress. Respiratory rates increased about 250 per cent and heart rates were approximately double that of resting values. All animals broke out in a sweat shortly after iv injection, but basal body temperature was not affected. These effects were transient, and the animals appeared normal within 30 mins of dosing. Treated horses were tested in a variable interval responding apparatus 30 mins after dosing and no residual stimulation or depressant effects of hordenine were apparent. Animals dosed orally with 2.0 mg/kg bwt of hordenine showed no changes in heart rate, respiratory rate, basal body temperature or behaviour. After iv injection of hordenine, (2.0 mg/kg bwt) plasma reached a maximum value of about 1.0 μg/ml, and declined thereafter in a biexponential fashion. Kinetics of plasma concentration satisfied the concept of a two compartment open system, with an α‐phase half‐life of about 3 mins, and a ß‐phase half‐life of about 35 mins. Total urinary concentrations of hordenine (free and conjugated) peaked at about 400 μg/ml, and then declined exponentially to background levels by 24 h after dosing. Oral administration of hordenine (2.0 mg/kg bwt) showed peak plasma levels of about 0.15 μg/ml 1 h after dosing, followed by a slow multi‐exponential decline in blood levels of the drug. Total urinary concentrations of hordenine (free and conjugated) peaked at about 200 μg/ml, remained at this level for about 8 h, and then declined to background levels. Plasma levels of hordenine were reflected by a kinetic model which assumed very slow absorption of hordenine from the gastrointestinal tract and no effect on behaviour, heart rate or respiratory rate were noted after oral administration. Because of the low plasma levels, it would appear to be particularly difficult to obtain a pharmacological effect of hordenine after oral administration.
The distribution of ventilation‐perfusion ratios in the lungs of a dysmature foal
Authors: STEWART JENNIFER H. , ROSE R. J. , YOUNG I. H. , COSTAS L. 
Published: April 2010

SummaryThe distribution of ventilation‐perfusion (VA/Q) ratios, before and after 100 per cent oxygen, was studied in an induced‐premature foal at 4 h and again at eleven days of age, using the multiple inert gas elimination technique. The major finding was an absence of low VA/Q ratios when breathing air, indicating that low PaO2, in the neonatal period was totally attributable to the right‐to‐left shunt. At 4 h of age the PaO2 was 5.48 kPa and the right‐to‐left shunt represented 33.4 per cent of the cardiac output. At eleven days of age the PaO2 was 9.76 kPa and right‐to‐left shunt was 10.1 per cent of cardiac output. At both ages there was a separate high mode where ventilation was greatly in excess of blood flow but at neither age were units with low VA/Q ratios present. Oxygen breathing for 40 mins did not increase the right‐to‐left shunt, but at eleven days right‐to‐left shunt decreased when 100 per cent oxygen was administered.
Prolongation of xylazine/ketamine induced recumbency time with temazepam in horses
Authors: MATTHEWS NORA S. , DOLLARS N. S. , YOUNG D. B. , SHAWLEY R. V. 
Published: April 2010

SummaryShort term anaesthesia induced with xylazine and ketamine was compared to a combination of xylazine, ketamine and temazepam (a benzodiazepine) in six adult horses. Duration of recumbency was significantly prolonged when temazepam was administered with xylazine and ketamine. No significant differences in heart rate, respiratory rate, blood pressure or arterial pH, pCO2and pO2were seen between the xylazine and ketamine combination plus temazepam, and xylazine and ketamine combination only treated horses.
The action of low dose endotoxin on equine bowel motility
Authors: KING J. N. , GERRING E. L. 
Published: April 2010

SummaryPost operative ileus (POI) is a common and serious complication of colic surgery in the horse. There is a high correlation between the incidence of POI and the presence of ischaemic bowel, suggesting a role for endotoxin. 0.1μg/kg endotoxin was administered intravenously to six ponies with chronically implanted gastrointestinal electromechanical recording devices. It produced profound disruption of normal fasting bowel motility patterns, with an inhibition of gastric contraction amplitude and rate, left dorsal colon contraction product and small colon spike rate. In the small intestine an increase in abnormally arranged regular activity and a decrease in irregular activity was observed. There was no significant prolongation in stomach to anus transit time as assessed by the passage of plastic spheres. The bowel motility patterns induced by endotoxin could be mimicked by the intravenous infusion of PGE2and less potently by PGI2(prostacyclin), but not by PGF2α. This study provides evidence that systematic endotoxin present in clinical cases of colic may play a role in the pathogenesis of equine ileus. The acute effects of endotoxin on bowel motility appear to be mediated indirectly by prostaglandins, and the inhibitory effects may be mediated mainly by PGE2.
Effects of slow infusion of a low dosage of endotoxin on systemic haemodynamics in conscious horses
Authors: CLARK E. SUSAN , GANTLEY B. , MOORE J. N. 
Published: April 2010

SummaryThe effects of intravenous (iv) infusion of endotoxin for 60 mins at a cumulative dosage of 0.03 μg/kg bodyweight on systemic arterial, right atrial and pulmonary arterial pressures, heart rate, cardiac output, and derived pulmonary vascular resistance and total peripheral vascular resistance were compared to the effects of iv infusion of saline solution in four healthy horses. Heart rate was increased significantly after endotoxin infusion, although diastolic arterial pressure, systolic arterial pressure, electronically averaged arterial pressure, cardiac output, total peripheral resistance, and right atrial pressure did not change significantly. Average pulmonary arterial pressure was increased significantly by endotoxin infusion. This was accompanied by a trend toward increased diastolic pulmonary arterial pressure (P=0.1), systolic pulmonary arterial pressure (P=0.08) and pulmonary vascular resistance (P=0.07). These results suggest that low dosages of endotoxin produce pulmonary hypertension without causing hypotensive, hypodynamic shock.