Infestation in the dog by the paralysis tick, Ixodes holocyclus — 4. Cardiovascular effects

To determine the extent and significance of changes in heart rate and rhythm noticed previously in dogs paralysed with Ixodes holocyclus, two studies were undertaken. In one the electrocardiogram was recorded at stages throughout the disease and the traces analysed for changes, while in the second a detailed study of the effect of Ixodes holocyclus on the cardiovascular system was undertaken. The electrocardiographic changes were extremely variable between stages and between dogs. Generally, if a dysrhythmia occurred in stages 1, 2 or 3 it tended to be sinus tachycardia, ventricular tachycardia or sinus arrest. In stage 4 sinus arrest, sinus bradycardia, or sinus or ventricular tachycardia were the prominent dysrhythmias, whereas in stage 5 sinus bradycardia predominated. Cardiovascular measurements indicated an increase in peripheral vascular resistance leading to a significant elevation in mean arterial pressure at all stages of the disease. Cardiac output was decreased significantly only at stage 2, although it was below the control measurements at all stages. Pulmonary arterial pressure was significantly elevated at stages 2, 3 and 4 due most probably to an increase in pulmonary vascular resistance. Myocardial contractility was not significantly changed throughout the disease. The changes observed in the electrocardiogram and the cardiovascular system in stages 1, 2 and 3 are unlikely to be due to hypoxia and could represent dysfunction of the autonomic nervous system. During stages 4 and 5 oxygen levels were below normal and the bradycardia seen terminally is almost certainly due to hypoxaemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Angiotensin Converting Enzyme in Bovine Ovarian Follicular Fluid and its Relationship with Oestradiol and Progesterone

The purpose of the present study was to identify angiotensin converting enzyme (ACE) in bovine ovarian follicular fluid and to relate the ACE activity to the phase of the oestrous cycle, pregnancy, and the follicular fluid concentrations of oestradiol and progesterone. The ACE activity was similar to that found in bovine serum and was completely inhibited by the specific ACE inhibitor captopril. The 50% inhibitory concentration (IC₅₀) was 1.4 × 10^?8 mol/l (range 0.8 × 10^?8 to 5.0 × 10^?8 mol/l; n=6), which is similar to that found in bovine and human serum. The ACE activity did not differ in the pre‐ovulatory and luteal phase, pregnancy or cystic follicles. It correlated with the follicular fluid concentration of progesterone in cycling cows (ρ=0.476; p < 0.005; n=36), but did not correlate with the diameter of the follicles, the follicular fluid concentration of oestradiol or the ratio between the oestradiol and progesterone concentrations. The demonstration of ACE in bovine ovarian follicular fluid provides further evidence for the presence of a local renin–angiotensin system in the bovine ovary.     

Levator Nasolabials Muscle Transposition to Prevent an Orosinus Fistula after Tooth Extraction in Horses

The ventral part of the levator nasolabialis muscle was transposed to the alveolar defect after sinusotomy and tooth extraction in five normal horses and six horses with a tooth root abscess and sinusitis. In the normal horses at weeks 6, 10, 14 and 18, the transposed muscles remained viable and were incorporated into the recipient sites, and orosinus fistulae did not form. Histologically, there was a progressive transition from muscle to fibrous tissue. There was no facial deformity or loss of nasal function at the donor site. A localized abscess was associated with incomplete removal of tooth root fragments in one horse. After 1 year or more, five horses treated for dental disease had complete resolution of clinical signs. One horse continued to have intermittent mild nasal discharge.     

Assessing the Status of Rotifer Mass Cultures

Rotifers are widely used as live larval feed in aquaculture. The stability of rotifer mass cultures, however, remains a critical unresolved problem. It would be useful to develop indicators that can assess the status of rotifer mass cultures and serve as an early warning of trouble. Indicators should be sensitive, easy to measure and have quick response time. Two indicators have been developed that fulfill these criteria: swimming activity and egg ratio (eggs per female). A swimming activity test is described based on the measurement of rotifer swimming over a grid. Results are obtained in minutes and are sensitive indicators of pH, un-ionized ammonia, starvation and temperature stress in the mass culture. For un-ionized ammonia, swimming activity is about nine times more sensitive than an LC₅₀ test, and maximum response occurs within ten minutes. Egg ratio is also a sensitive indicator of physiological stress, but there is a 18-24 h time lag between exposure to stress and a change in egg ratio. Egg ratios during log phase of population growth ranged from 0.5-1.2 and 0.13-0.5 during stationary phase. When egg ratio fell below approximately 0.13, rotifer populations declined. Monitoring of swimming activity and egg ratios should make it easier for aquaculturists to keep their rotifer cultures productive and stable.     

Effects of polyethylene colour and thickness on grass silage quality

The aim of the investigation was to determine the influence of variations in thickness and colour of agricultural plastic film on silage preservation conditions and grass silage quality. For this purpose, 30 cylindrical plastic containers (mini‐silos; 0·3 m³) were filled with chopped grass and covered with five films of different thickness and colour: 90 μm, white; 125 μm, green; 150 μm, black; 200 μm, green and 200 μm, white. Four replications of each film type were placed in the open air. Two replications were housed indoors and exposed to an ‘artificial sky’ in a test apparatus. The surface temperature of the films was found to be strongly dependent on film thickness and colour. Results of the chemical analysis of silages did not reveal any significant influence of the films. This was also the case when restricting the analysis to the uppermost silage layer. The results showed that under the conditions of this experiment, well preserved forage can be produced with films of differing colour, as well as of lesser thickness.     

Reproductive performance of immobilized cryopreserved bovine semen used for timed artificial insemination

The SpermVital^® technology comprises embedding of spermatozoa within an alginate gel to facilitate release of sperm cells over a prolonged period in utero after AI. The aim of this study was to examine whether the survival time of spermatozoa is extended when applying this immobilization technology in combination with cryopreservation. Sperm cell survival (acrosome and plasma membrane integrity) was studied in vitro for 48 hr at physiological temperature. One dose of SpermVital^® (SV) semen was compared with single doses of Biladyl^® (B) processed semen as well as double doses of B (B double). B double was obtained by adding a second B dose the following day, thereby mimicking double AI. Furthermore, reproductive performance applying single early timed AI (TAI) with SV following oestrus synchronization was studied in a field trial. Double insemination (TAI on two consecutive days) with B semen served as control. Number of acrosome‐intact live sperm cells decreased over time in vitro for all treatments (p < .05). There was no difference between SV sperm cell survival and B double after 24 hr (p > .05). However, after 48 hr, SV sperm cell survival was higher than B double (p < .05). Moreover, multivariate analysis showed that the outcome of single early TAI with SV was not significantly different from B double (p > .05). Likelihood of pregnancy and calving in the heifer group was higher than in the cow group (p < .05). These results imply that spermatozoa immobilized in alginate gel have prolonged survival.