E. Don Stevens

The effect of exercise on the distribution of blood to various organs in rainbow trout

Abstract 1. 1. Hemoglobin and plasma protein concentration were measured. A hemoconcentration occurred during exercise which was due to the osmotic shift of water from blood into muscle rather than to the addition of cells to blood. 2. 2. The effect of exercise on the distribution of blood to various organs was studied by using a radioisotope which stayed within the vascular compartment. 3. 3. The blood volume in white muscle, red muscle, gill, liver and kidney did not change as a result of exercise. There was a slight increase in gut blood volume and a slight decrease in spleen blood volume after exercise. 4. 4. Lateral red muscle contained 2·6 times as much blood as white muscle.

Factors affecting arterial pressures and blood flow from the heart in intact, unrestrained lingcod, Ophiodon elongatus

Abstract 1. 1. Increases in temperature resulted in large increases in heart rate but caused little change in stroke volume. Injections of atropine into the pericardial cavity caused an increase in heart rate, a decrease in stroke volume but little change in cardiac output. 2. 2. Injections of adrenaline into the dorsal aorta resulted in a rise in dorsal aortic blood pressure and a fall in heart rate and cardiac output. In the atropinized fish, adrenaline injections into the dorsal aorta caused a rise in dorsal aortic blood pressure, a fall in cardiac output but no change in heart rate. Blockade of α-adrenergic receptors with phenoxybenzamine abolished the circulatory changes associated with adrenaline injections. Addition of adrenaline to the water in which the fish was situated resulted in an increase in cardiac output and stroke volume, with little change in heart rate. 3. 3. Cardiovascular changes associated with swimming were similar to those that occurred when the animal was disturbed. There was a bradycardia, with little change in stroke volume. In the atropinized fish, exercise was associated with an increase in cardiac output and stroke volume with little change in heart rate.

Effects of Suture Type and Patterns on Surgical Wound Healing in Rainbow Trout

Abstract In two separate experiments we investigated the effects of different types of suture material and patterns on wound healing in rainbow trout Oncorhynchus mykiss with and without transmitter implants. We used absorbable and nonabsorbable monofilament and braided silk sutures in simple interrupted and vertical mattress patterns to close 3-cm incisions on rainbow trout. Braided silk sutures and vertical mattress suture patterns caused significantly more tissue inflammation (P < 0.05) as shown by macroscopic analysis. However, there were no significant differences in the histology or strength of the wounds related to the type of suture material or the type of suture pattern used. Dummy radio transmitters compounded the inflammatory effect silk had on healing incisions compared with inflammation without transmitters.

Brain and muscle temperatures in ocean caught and captive skipjack tuna

Abstract 1. 1. Red muscle, white muscle, and brain temperatures were measured in skipjack tuna ( Katsuwonus pelamis ). 2. 2. Red muscle temperature was 9·1°C above an ambient water temperature of 25·6°C. Excess red muscle temperature decreased after capture, and stayed lowered while in captivity. 3. 3. Prolonged strenuous exercise of captive tuna resulted in an increase in their body temperature, but not to the level observed in ocean-caught fish. 4. 4. Brain temperature was 4·5°C above an ambient water temperature of 25·6°C. 5. 5. We believe that skipjack tuna regulate their body temperature over an ambient temperature range of about 25–34°C.

Effects of different surgical techniques: Suture material and location of incision site on the behaviour of rainbow trout (Oncorhynchus mykiss)

We examined the effects of midline and off midline incision locations, and incisions closed with monofilament or silk suture on spontaneous swimming behaviour in fish. Each fish had a dummy transmitter surgically implanted into its peritoneal cavity. The behaviour of fish in each treatment was estimated using three different measures: the number of C‐turns performed, the number of sprints performed, and the total distance travelled. There were no significant differences (p > 0.05) among treatments with respect to the number of C‐turns or sprints made. Fish closed with monofilament with an off midline incision travelled significantly less distance (p = 0.014) than fish closed with monofilament and a midline incision, but neither treatment was significantly different from control fish. The three measures of behaviour: C‐turns, sprints and distance travelled, were not affected either by the amount of inflammation at the incision site or by the amount of inflammation at the entry and exit points of the sutures, regardless of the treatment. The surgical techniques tested had little effect on fish behaviour post surgery, regardless of inflammation levels. It seems that behaviour of fish may not be affected by surgery, but further testing examining more subtle behaviours will have to be performed.

Muscle temperature in free-swimming giant Atlantic bluefin tuna (Thunnus thynnus L.)

Muscle temperature was measured by telemetry in giant Atlantic bluefin tuna whilst the tuna were free-swimming in large pounds. Muscle temperature tended to remain steady at about 24 degrees C; water temperature ranged from 9 to 17 degrees C. Muscle temperature was much less variable than stomach temperature in these fish. Muscle temperature varied less than 3 degrees C whereas stomach temperature varied by as much as 14 degrees C.

Hydrodynamics of water flow in front of and through the gills of skipjack tuna

Abstract 1. 1. The structure of the gills of skipjack tuna ( Katsuwonus pelamis ) is reviewed and the pattern of water flow in front of, and through, the gills is described. The tuna system is attractive for analysis of this type because water flow is continuous rather than pulsatile and the gill system is more rigid than that of other fish. In addition, oxygen uptake rates are the extreme case (i.e. highest values) for water-breathers. 2. 2. Flow into the slits between the gill bars is rectilinear and nearly uniform, and therefore irrigation at the gill sieve should be nearly uniform. 3. 3. Reynolds numbers are so low that turbulent flow is unlikely and entrance effects are negligible.

The capacity of mdx mouse diaphragm muscle to do oscillatory work

Mdx mice were used as a model for Duchenne muscular dystrophy; both lack dystrophin. It was hypothesized that the mdx condition would have a marked effect on the ability of diaphragm muscle from mdx mice to do active net work and generate power. This hypothesis was tested using the work‐loop technique. Specific twitch force, specific tetanic force and maximum power were all significantly less in diaphragm strips from mdx mice than those from control mice. In all preparations muscle length at which maximum power was achieved (Lw) was about 8% less than that at which maximum tetanic force was achieved (L0), both in mdx and control muscle. The isometric force‐length curve for mdx muscle was steeper on both sides of the plateau. Similarly, the curve relating net work per cycle to muscle length was steeper for mdx muscle on both sides of the plateau. Maximum power of mdx muscle was achieved at a lower strain than for control muscle; maximum power occurred at a strain of 10.2% for mdx and 14.7% for control. Further increases in strain caused a marked decrease of power production in mdx muscle, whereas they caused a smaller decrease in control muscle. In summary, at muscle lengths longer than Lw and at high strains, performance of mdx muscle was compromised relative to that of control muscle. Work and power were compromised more than isometric force.

A Novel Behavioral Fish Model of Nociception for Testing Analgesics

Pain is a major symptom in many medical conditions, and often interferes significantly with a persons quality of life. Although a priority topic in medical research for many years, there are still few analgesic drugs approved for clinical use. One reason is the lack of appropriate animal models that faithfully represent relevant hallmarks associated with human pain. Here we propose zebrafish (Danio rerio) as a novel short-term behavioral model of nociception, and analyse its sensitivity and robustness. Firstly, we injected two different doses of acetic acid as the noxious stimulus. We studied individual locomotor responses of fish to a threshold level of nociception using two recording systems: a video tracking system and an electric biosensor (the MOBS system). We showed that an injection dose of 10% acetic acid resulted in a change in behavior that could be used to study nociception. Secondly, we validated our behavioral model by investigating the effect of the analgesic morphine. In time-course studies, first we looked at the dose-response relationship of morphine and then tested whether the effect of morphine could be modulated by naloxone, an opioid antagonist. Our results suggest that a change in behavioral responses of zebrafish to acetic acid is a reasonable model to test analgesics. The response scales with stimulus intensity, is attenuated by morphine, and the analgesic effect of morphine is blocked with naloxone. The change in behavior of zebrafish associated with the noxious stimulus can be monitored with an electric biosensor that measures changes in water impedance.

Wound Healing in Rainbow Trout following Surgical Site Preparation with a Povidone–Iodine Antiseptic

Abstract We investigated the effects of preparing surgical incision sites with a topical antiseptic on wound healing and hematological response in rainbow trout Oncorhynchus mykiss. A povidone–iodine solution was applied both pre- and postsurgery to the incision sites on treated fish. Three-centimeter incisions in both treated (N = 9) and control (nontreated, N = 9) fish were closed with four nonabsorbable sutures sewn in a simple interrupted pattern. During the 42-d period of wound healing, there were no statistically significant changes in total erythrocyte counts (1.28 × 106/mm3 ± 0.05 SE), in percentage of dividing erythrocytes (0.76% ± 0.07 SE), or in differential leukocyte counts. Postmortem, pathogenic bacterial infections in the kidney or spleen were not detected in any of the fish. There was no histological difference between control and treated incisions to show either beneficial or adverse tissue reactions to the topical antiseptic treatments. Blinded histological analysis revealed both treated...