Biomedical subjects

A G Heath

Publications and source records attributed to A G Heath.

13 recordsLinked to original sources

PubMed2003

The effect of mercury on the feeding behavior of fathead minnows (Pimephales promelas).

Fathead minnows (Pimephales promelas) were exposed to mercury (1.69, 6.79, and 13. 57 microg/L HgCl(2), 10 days exposure), and afterward their foraging ability was tested in a vegetated habitat for 7 days. Among the foraging metrics used were foraging efficiency, capture speed, and the ability to learn and retain information regarding habitat characteristics. In addition to behavioral tests, muscle tissue acetylcholinesterase activity and brain levels of several neurotransmitters were investigated. Comparisons with control fish and fish from the two highest exposure groups revealed consistent performance deficits in foraging efficiency and capture speed. However, no treatment effects on learning were detected, nor were differences in neurotransmitter levels detected. In determining the underlying proximate cause of the foraging deficits, it is believed that the greater pause time exhibited by treatment fish while foraging was the main cause of treatment differences. In the future, behavioral studies will continue to allow toxicity testing of environmentally relevant variables such as those used by behavioral ecologists.

Acetylcholinesterase↗

PubMed1997

Physiological responses of fathead minnow larvae to rice pesticides.

Newly hatched fathead minnow (Pimephales promelas) larvae were exposed for 4 days to two pesticides and ambient receiving waters to simulate conditions in the Sacramento River, California, during the striped bass spawning season which coincides with pesticide use in adjacent rice culture. Carbofuran and molinate were tested at two concentrations: a higher level approximating one-half the LC50 and a level much lower that is similar to that seen in the receiving waters of Colusa Basin Drain. Physiological measurements were made immediately after the exposures and again after a 10-day recovery period in noncontaminated waters. These included growth rate, swimming capacity, response to a mild electric shock, upper and lower lethal temperatures, and activity of acetylcholinesterase in whole-body homogenates. The higher concentrations of carbofuran and molinate caused reductions in swimming capacity, an increased sensitivity to the electric shock, and a reduction in upper lethal temperature. Acetylcholinesterase was reduced in those larvae exposed to the higher levels of carbofuran. In general, the lower levels of pesticide exposure caused no measureable effects nor did exposure to water from Colusa Basin Drain.

Acetylcholinesterase↗

PubMed1997

Secondary stress responses to acute handling in striped bass (Morone saxatilis) and hybrid striped bass (Morone chrysops x Morone saxatilis).

OBJECTIVE: To test the hypothesis that, compared with pure striped bass, hybrid striped bass have reduced secondary physiologic responses to handling stress. A secondary objective was to determine whether not feeding fish for a 3-day period affected responses. ANIMALS: Hatchery-reared adult striped bass (Morone saxatilis) and adult hybrids of striped bass with white bass (M chrysops), with mean length of 27.9 cm and mean weight of 487 g. PROCEDURE: Fed and 3-day nonfed fish, in groups of 6, were held in dip nets above water for 3 minutes. Severity of response to handling was determined by measuring plasma glucose and chloride and blood lactic acid, sodium, and potassium concentrations. Terminal samples were taken from fish before handling (control), immediately after handling, and after 12, 24, and 48 hours of recovery. RESULTS: Striped bass were hyperglycemic and lactacidemic after stress and for 12 to 48 hours afterward, whereas glucose and lactic acid values in hybrids were essentially unchanged. Blood sodium and chloride concentrations of hybrids decreased after stress, then returned to control values within 24 hours. Striped bass, however, had a greater decrease in values for these electrolytes and failed to recover in 48 hours. Blood potassium concentration remained unchanged in all test groups. Nonfeeding for 3 days before handling did not appear to affect stress response in striped bass or hybrids. CONCLUSIONS AND CLINICAL RELEVANCE: Striped bass have an appreciably greater response to acute handling stresses, such as those that may be experienced in hatcheries and experimental laboratories, than do hybrid bass. Thus, pure striped bass require more care in handling. The usual practice of not feeding before handling does not affect physiologic responses.

Analysis of Variance↗

PubMed1993

Sublethal effects of three pesticides on Japanese medaka.

One- to 2-day-old medaka (Oryzias latipes) larvae were exposed for 4 days to the rice field pesticides methyl parathion, molinate, carbofuran and a mixture of all three. Pesticide concentrations were one-half the 96 h LC50 ("high concentration") and levels approximating those measured in receiving waters from rice field runoff ("low concentration"). Maximum swimming speed, spontaneous muscular activity, acetylcholinesterase activity, dry weight, RNA:DNA ratio, and five morphometric variables were determined at the end of the exposures. Larvae were retained for an additional 10 days in non-contaminated water, and the same measurements taken to investigate residual effects. Results are compared to a parallel study on striped bass larvae to evaluate the suitability of this species as a surrogate for the bass in toxicological studies involving sublethal exposures. There was no relationship between mortality rate and pesticide exposure either during the exposures or during the ten day subsequent period. Only the high concentration of carbofuran caused an impairment of swimming performance. Spontaneous activity was stimulated in the high concentration of molinate and the combined pesticides groups. Acetylcholinesterase was severely inhibited in parathion and molinate, and this persisted in some cases after 10 days in non-contaminated water. The pesticides had little effect on growth rate except for molinate which acted as a stimulant. Combining the three pesticides caused a less than additive effect. Except for decreases in acetylcholinesterase, the sublethal effects of the pesticides tested at the very low concentrations used were subtle. Apparently, larvae of this species are less sensitive to these pesticides than are striped bass larvae.

Animals↗

PubMed1987

Comparison of in vivo energy metabolism in the brain of rainbow trout, Salmo gairdneri and bullhead catfish, Ictalurus nebulosus during anoxia.

1. Rainbow trout and bullhead catfish (Ictalurus nebulosus) were exposed to anoxic water inside a plastic tube until death (12 min for trout; 62 min for catfish). Immediately upon death, the brain was removed and analyzed for metabolites, high energy phosphate compounds, and metabolic fuel while the blood was analyzed for metabolites. 2. Control bullhead brains had higher concentrations of glycogen, ATP, creatine phosphate (CrP), and glucose than control trout. 3. After anoxia bullheads showed a significant decrease in ATP, CrP, and glycogen while lactate more than doubled in concentration. 4. After anoxia trout showed a doubling in brain lactate and a decline in glycogen, but no decline in ATP or CrP. There were no changes in brain glucose, ketone bodies, or alternative anaerobic end-products in either species although an elevation in blood isobutyrate was noted. 5. Brain death in the catfish may be due to depletion of fuel for anaerobiosis and a subsequent loss of ATP. In the trout there may be other causes such as a greater permeability of its neuronal membranes and alterations in intracellular free calcium stores.

Adenosine Triphosphate↗

PubMed1984

Ventilatory changes in the golden hamster, Mesocricetus auratus, compared with the laboratory rat, Rattus norvegicus, during hypercapnia and/or hypoxia.

Tidal volume, respiratory frequency, and minute volume were measured with total body plethysmography. Both hypercapnic (0-7% CO2) and hypoxic (13-21% O2) gas mixtures caused "dose" related hyperventilation in the hamsters. However, there was no synergism between combined stimuli. Rats exhibited greater hyperventilation than the hamsters during hypercapnic + hypoxic and hypercapnic exposures. Hamsters responded more than the rats to hypoxia alone. Greater blood buffering capacity of hamsters is a possible explanation for the species differences in ventilatory sensitivity.

Animals↗

PubMed1979