Relationship between domoic acid levels in the blue mussel (Mytilus edulis) and toxicity in mice.

Monitoring of eastern blue mussels (Mytilus edulis), contaminated with domoic acid, involved mouse bioassays and quantitative analysis using HPLC. Mice undergo a typical scratching syndrome at sublethal as well as lethal doses of domoic acid. The onset of scratching behaviour and time of death in mice were inversely related to the dosage of domoic acid. An LD50 (i.p.) of 3.6 mg domoic acid/kg mouse was calculated. Toxic mussels held in tanks and flushed with uncontaminated sea water showed a decline in domoic acid concentration in mussel tissue with time. In addition, domoic acid concentrations in mussels from two infected rivers declined to negligible levels in 40-50 days under normal environmental conditions. The bulk of domoic acid and toxicity was located in the hepatopancreas which also contained large amounts of chlorophyll-A, an algae biomass indicator, relative to control mussels. These results support the conclusion that domoic acid was the primary causative factor in the shellfish poisonings from Prince Edward Island mussels in late 1987.

Changes in the caecal flora associated with the onset of laminitis.

Caecal fluid samples collected 8 and 24 hours after carbohydrate overload were quantitatively compared to control samples in terms of aerobic and anaerobic bacteria. Concomitant increases in lactic acid-producing bacteria and decreases in Gram negative bacteria were substantiated during the onset of acute laminitis. Progressive decreases in caecal fluid pH were also quantitated. Although endotoxin assays of caecal fluid and blood were not done, the caecal flora changes suggest its presence during the onset of acute laminitis.

Measurement of specific laryngeal muscle function by ultrasound.

Ultrasonic dimension gauges were implanted in the crico-arytenoideus dorsalis muscle in a mature horse. Resting and contracted muscle length and average contraction rate were measured serially in the conscious state over a period of 25 days. Results suggest that specific laryngeal muscle function in the horse may be defined with this approach. Since man and horse are both known to suffer from laryngeal hemiplegia, this experimental preparation may help provide information of benefit to both species.

Systolic time intervals in induced atrial fibrillation in the dog: effects of ectopic ventricular activation.

Electrocardiogram, atrial electrogram, phonocardiogram, aortic pressure, and left ventricular pressure were recorded during periods of induced atrial fibrillation in dogs anesthetized with a combination of morphine sulfate and pentobarbital sodium. Data were accumulated by selecting 50 cardiac cycles which terminated in ectopic ventricular electrical complexes, and comparing systolic time intervals (STI) following these beats with STI Following 50 normal ventricular complexes. Ectopic ventricular activation prolonged left ventricular pre-ejection period and external isovolumic contraction time, and reduced duration of left ventricular ejection time. These events resemble changes in STI observed following induction of atrial fibrillation from a sinus rhythm, but they are of significantly greater magnitude than the effects of atrial fibrillation alone.

Recovery from anaesthesia in ponies: a comparative study of the effects of isoflurane, enflurane, methoxyflurane and halothane.

The duration and quality of recovery after separate 2 hour anaesthetic periods with equipotent alveolar concentrations of isoflurane, enflurane, halothane and methoxyflurane were evaluated in experimental ponies. Recovery was shortest after isoflurane anaesthesia, followed by enflurane, halothane and finally methoxyflurane, although standing was achieved more rapidly after enflurane than after isoflurane. This sequence of recovery times was compatible with the respective solubilities of the 4 agents. The smoothest recovery was obtained after isoflurane anaesthesia, followed by methoxyflurane, halothane and then enflurane. The isoflurane recovery was characterized by very quiet and prolonged sternal recumbency with excellent coordination upon standing. The chief difficulties with halothane recovery were shivering and delayed coordination upon standing. Enflurane anaesthesia was followed by a very brief period of sternal recumbency but there was considerable shivering and incoordination upon standing. This may have been due to central nervous stimulation during anaesthesia producing a residual excitatory effect. On the basis of this investigation, isoflurane was considered to be the most satisfactory volatile anaesthetic for the horse.

Anserine and carnosine in chicks (Gallus gallus) rat pups (Rattus rattus) and ducklings (Anas platyrhynchos): comparative ontogenetic observations.

1. Muscle and brain from developing chick embryos, as well as from day-old chicks, rats, and ducks were analyzed for the histidine-containing dipeptides, anserine and carnosine. 2. Anserine was found in the brain of all species studied, whereas in muscle, anserine was found only in chicks. 3. At 15 days, the muscle of developing chick embryo contained 41 +/- 9 mumoles/100 g anserine while carnosine was present at a level of less than 3 mumoles/100 g. 4. In day-old chicks the anserine level in muscle was 100 +/- 35 mumoles/100 g while the carnosine level was 22.5 +/- 1 mumoles/100 g. 5. These findings cast doubt on earlier hypotheses relating anserine and carnosine to muscle activity.

Systolic time intervals in domestic ponies: alterations in a case of coarctation of the aorta.

This report describes the measurement of systolic time intervals in a nine year old female domestic pony which was found at necropsy to show coarctation of the aorta and bilateral ventricular hypertrophy. Electrocardiogram, phonocardiogram and direct arterial blood pressure were recorded from the pony in a standing unmedicated state and systolic time intervals were measured from the resulting tracings. A prolongation of left ventricular ejection time and shortening of the pre-ejection period were observed in comparison to a group of normal ponies similarly examined. Such changes are consistent with outflow tract obstruction. The pony was also hypotensive and this condition was interpreted as a long-term compensation for the obstructive lesion. It is likely that the changes in systolic time intervals were at this stage predominantly affected by the hypotension. The report notes that the existence of such a case of spontaneous cardiovascular disease in the pony population might suggest the utility of the animal as a resource in comparative cardiovascular physiology and medicine.