Increased postnatal growth rates of offspring after antiestrogen treatment of rat dams during pregnancy.

The effects of administration of estradiol antiserum to pregnant rats on birth weight, subsequent growth velocity, carcass composition, and reproductive performance of their offspring were examined. Treated rats were injected i.p. with a potent antiestradiol serum on d 12 of gestation, whereas control rats received a similar injection of normal sheep serum. The pups from the treated rats were 12.2% heavier at birth than those from control rats (P less than .01) and had a greater postnatal growth rate (P less than .05). Chemical analysis of body composition at 56 d of age revealed that there was a tendency for female offspring from treated rats to exhibit carcass characteristics (such as increased percentage of body fat) that were more similar to those of normal male rats than to those of normal female rats. Neither onset of puberty nor reproductive performance was affected by the treatment. These results indicate that treatment of rats during pregnancy with antiestradiol may have potential as a technique for increasing postnatal growth rates.     

Significance for exercise capacity of some electrocardiographic findings in racehorses

Summary Various cardiorespiratory and metabolic indices were assessed during treadmill exercise in Thoroughbred and Standardbred racehorses with T wave changes in 4 or more leads on the electrocardiogram or second-degree atrio-ventricular (AV) block, and in horses that had no abnormalities on clinical examination, resting electrocardiography or upper respiratory tract endoscopy. No significant differences in heart rate, plasma lactate concentration, arterial blood gases, oxygen uptake, run time, peak velocity, or blood and red cell volumes were found between normal horses and horses with T wave changes or second-degree AV block. These results indicate that some electrocardiographic findings that are considered by some clinicians to indicate cardiac dysfunction, may have little effect on exercise capacity.     

Relationships between electrocardiographic findings, racing performance and training in Standardbred horses

SUMMARY The presence of abnormal T waves in three or more electrocardiographic leads has been used to diagnose the cause of poor race performance in horses. This study investigated the relationship between previous racing performance in Standardbred horses and T waves, and the effect of training on the T wave. Thirty-two horses were electrocardiographed in two Sydney racing stables. Sixteen horses (50%) had ECGs with three or more leads with abnormal T waves, and these horses had won more races, had a greater ratio of wins per start and a greater number of dollars earned per start than horses with less than three abnormal T waves (P < 0.05). Horses with abnormal T waves also had significantly faster racing times (P < 0.01). There were significant (P < 0.01) correlations between the number of abnormal T waves and both number of wins (R = 0.47) and dollars earned per start (R = 0.45). Fastest winning mile rate was also negatively correlated with number of leads with abnormal T waves (R =?0.52, P < 0.01). Twenty two horses were also electrocardiographed within seven days of good racing performance. The mean number of abnormal T waves was 2.7 ± 0.41, and the mean T wave amplitude in the four chest leads (CV, CR, CL, CF) was 0.9 ± 0.15 mV. Thirteen horses (59%) had abnormal T waves in three or more leads. The effect of training on the T wave was also investigated in nine previously untrained and unraced Standardbred racehorses. There were significant effects of training (P < 0.01) on the number of abnormal T waves and mean chest lead T wave amplitude. These increases occurred in the second phase of training during which faster exercise, race trials and racing were conducted. We concluded that abnormal T waves are a common finding in the race-fit Standardbred horse, and can be found in more than 50% of horses currently performing well in races. In addition, chest lead T waves become more positive after training.     

ULTRASONOGRAPHIC EVALUATION OF THE FETUS AND INTRAUTERINE ENVIRONMENT IN HEALTHY MARES DURING LATE GESTATION

Mares with uncomplicated pregnancies (n = 33) underwent transabdominal sonography to evaluate fetal well-being, obtain measurements of fetal size and characterize the intrauterine environment. Data from the last examination obtained prior to parturition were used for statistical analysis. All mares had one active fetus with good fetal tone. The maximal vertical depth of amniotic fluid (7.9 ± 3.5 cm) was less than allantoic (13.4 ± 4.4 cm) and fewer echogenic particles were detected in amniotic fluid. The maximal uteroplacental thickness was 1.38 ± 0.23 cm (retrospective) and 1.15 ±± 0.24 cm (propspective). In 3 mares small anechoic spaces were imaged between the uterus and placenta. Fetuses had a regular cardiac rhythm with a mean heart rate of 75 ± 7 beats/minute and breathing movements. The diameter of the fetal aorta (mean = 22.8 ± 2.15 mm) was significantly correlated with neonatal foal weight (P<0.0008, r = 0.72) and maternal prepartum weight (P<0.002, r = 0.86). This information of the normal intrauterine environment and fetal well-being can be used to develop a biophysical profile specific for the equine fetus.     

RADIATION EXPOSURE DURING EQUINE RADIOGRAPHY

All personnel present in the X-ray examination room during equine radiography were monitored using low energy direct reading ionization chambers (pockets dosimeters) worn outside the lead apron at neck level. The individuals' task and dosimeter readings were recorded after each examination. Average doses ranged from 0 to 6 mrad per study. The greatest exposures were associated with radiography of the shoulder and averaged less than 4 mrad. The individual extending the horse's limb was at greatest risk although the individual holding the horse's halter and the one making the X-ray exposure received similar exposures.
A survey of the overhead tube assembly used for some of the X-ray examinations also was performed. Meter readings obtained indicated an asymetric dose distribution around the tube assembly, with the highest dose occurring on the side to which the exposure cord was attached.
Although the exposures observed were within acceptable limits for occupational workers, we have altered our protocol and no longer radiograph the equine shoulder unless the horse is anesthetized. Continued use of the pocket dosimeters and maintenance of a case record of radiation exposure appears to make the technologists more aware of radiation hazards.     

Distribution of lymphoid leukosis virus and p27 group-specific antigen in tissues from laying hens

In order to gain insight into transmission and pathogenesis of infection, specimens from laying hens that had been naturally exposed to lymphoid leukosis virus (LLV) were tested for group-specific antigen (gsa) of the virus by immunofluorescence (IF), complement fixation (CF), and the enzyme-linked immunosorbant assay (ELISA). Electron microscopic examinations determined the distribution of C-type virus particles in tissues, and the phenotypic-mixing test served as a biological assay for exogenous LLV. The IF gsa was found in all organs tested, and fluorescence was usually found where virus particles were concentrated. In the oviduct and intestine, IF gsa was frequently at the border of the lumina and in the connective tissue associated with basal membranes of glands. In skin, the antigen was detected in smooth muscle, in feather pulp, and in basal epidermal cells of developing feathers. Results of various tests on Ottawa strains of chickens were usually in agreement. For example, among hens that shed gsa into egg albumen, only the viremic hens were consistently positive for IF gsa in both spleens and oviducts. Geometric mean CF titers of antigen were respectively five- and 23-fold higher in spleens and oviducts from viremic hens than in those from nonviremic hens. These findings suggest that the gsa was associated with exogenous virus infection. In Cornell S strain hens that had not been exposed to LLV, gsa was detected in splenic tissue by CF and ELISA but not by the IF test. This gsa was presumed to be of endogenous origin.