Lavern J. Weber

Changes in Avoidance Response Time of Juvenile Chinook Salmon Exposed to Multiple Acute Handling Stresses

Abstract A simple behavioral test was devised to determine the effects of multiple acute stresses on the avoidance response time of fish. Groups of freshwater-adapted juvenile chinook salmon Oncorhynchus tshawytscha were exposed to a sudden overhead light and the time it took each fish to reach cover was noted. Tests were done on fish stressed one, two, or three times with 3 h between stresses, and on fish 1, 3, 6, and 24 h after each level of stress; unstressed fish served as controls. All unstressed fish reached cover within 15 s. Stressed fish took longer to reach cover (often several minutes), with the greatest delay in response occurring immediately after the stress. There was a gradual decrease in response time with recovery from the stresses. Exposure to two or three consecutive stresses increased the delay in response time over that offish exposed to a single stress, indicating that the effects of the stresses were cumulative.

Toxic response as a quantitative function of body size

Abstract Lethal response (96-hr) studies were conducted exposing mature male guppies (Poecilia reticulata) in lots representing different weight classes to ambient concentrations of six discrete toxicants: dieldrin, potassium pentachlorophenate, potassium cyanide, and copper, zinc, and nickel chlorides. Linear regressions with high correlation coefficients were defined for each toxicant by the equation, Y = a − b log ( M W h ) , where Y = % mortality as probits, M = mean toxicant concentration, W = weight of each lot, and h = an exponent of weight. The computed value of h was 0.81 for dieldrin, 0.72 for pentachlorophenate, cyanide, and copper, 0.67 for nickel, and 0.30 for zinc. Additional lethal response studies were conducted exposing mature females of different size, juveniles of different size, and newborn guppies of similar size to dieldrin. The dose-response functions of each age group were found to incorporate the weight factor previously computed for adult males, i.e., W0.81. Discrete, parallel regressions represented each life stage and sex. When compared on a weight factor basis, guppies became progressively more susceptible to dieldrin with each successive age class. Comparing adults only, males were more resistant than females. Evidence was gathered from the literature to show that the above equation applies furthermore to dose-response studies in which animals of varying size are given known amounts of toxicant, toxin, or drug. Consequently, the above equation may be generally employed to empirically establish the character of the relationship between dose and response when the size of the animals differ. Relative measures of toxic potency, e.g., LD50 and LC50, representing different sizes of an animal may be derived from the above equation and expressed in the useful form, LD50 = XWh, where X is the antilog of the abscissal value of log ( M W h ) corresponding to the 50% response level. This latter equation may also be derived from the commonly used function log LD50 = log a + b log W.

Evaluation of human health hazards on use of dichlorvos (DDVP), especially in resin strips

Public concern over the possible health hazards resulting from the widespread use and misuse of dichlorvos (O,O-dimethyl 2,2-dichlorovinyl phosphate; DDVP) resin strips has increased substantially in recent months eight years after the introduction of this unique formulation and three-to-five years after they became common in household use. In part, this concern stems from legitimate questions that have remained unanswered; on the other hand, anxieties regarding problems such as the persistent pesticides and the disposal of out-dated nerve gas munitions, constantly presented in the mass media, can be transferred to the dichlorvos strips. Attacks on the strips (Linford 1970, Sherrill 1970, Anonymous 1970 a) and reassurances from one of the manufacturers (Slomka 1970) and others (Cavagna and Vigliani 1970) have thus far not resolved all of the questions of public health significance. Further, observation of the use of these strips in situations contrary to label specifications raises additional questions.

Carbon tetrachloride-induced retention of sulfobromophthalein in the plasma of rainbow trout.

Carbon Tetrachloride-Induced Retention of Sulfobromophthalein in the Plasma of Rainbow Trout. Gingerich, W. H., Weber, L. J., and Larson, R. E. (1978). Toxicol. Appl. Pharmacol. 43 , 147–158. Carbon tetrachloride was evaluated as a potential hepatotoxic agent in rainbow trout. Plasma half-lives of sulfobromophthalein (BSP) increased in proportion to the dose of CCl 4 administered, and histological examination of liver sections indicated that morphological damage, including necrosis of hepatocytes surrounding central veins, also had occurred. High plasma hemoglobin concentrations, hemoglobinuria, and a significant increase in relative body weight were observed in trout following intoxication. To exclude the possibility that plasma BSP clearance in treated fish had been impaired by high plasma hemoglobin concentrations, plasma BSP disappearance studies were conducted in two groups of fish following prolonged infusion of either bilirubin 40 μg/kg/min) or hemoglobin (250 μg/kg/min). In these studies, plasma BSP disappearance was not affected by high plasma concentrations of either compound, and it was either bilirubin (40 μg/kg/min) or hemoglobin (250 μg/kg/min). In these studies, plasma BSP disappearance was not affected by high plasma concentrations of either compound, and it was therefore concluded that the retention of BSP in plasma of fish treated with CCl 4 could not be explained by attendant intravascular hemolysis. Carbon tetrachloride appears to serve as a useful model hepatotoxic agent in rainbow trout and further, retention of BSP in the plasma may be a useful index by which to evaluate liver dysfunction in this fish.

Predator-Prey Interactions of Fishes Under the Influence of Ammonia'

Abstract Food consumption and growth rates of a predator, the largemouth bass (Micropterus salmoides), and the behavior of both the predator and its prey, the mosquitofish (Gambusia affinis), were sensitive indices of sublethal effects of ammonia on predator-prey interactions. Prey consumption and growth rates of bass in control tests increased with increasing prey densities. Ammonia concentrations of 0.63 and 0.86 mg/liter NH3 substantially decreased prey consumption and growth of bass in test tanks stocked with densities of 30, 60, and 120 mosquitofish. At a given ammonia concentration, there were greater decreases in prey consumption and growth of bass at higher prey densities. This can be attributed in part to the bass being more sensitive than mosquitofish to ammonia and to the harassment of the predator by the prey which occurred at high ammonia concentrations and high prey densities.

Influence of body size and developmental stage of coho salmon (Oncorhynchus kisutch) on lethality of several toxicants

Acute 96 h bioassays were conducted on coho salmon (Oncorhynchus kisutch) to determine their sensitivity to each of four toxicants during development. Alevins, swim-up fry and juveniles (up to 175 days post-hatch) were exposed to lethal concentrations of copper, zinc, nickel, or pentachlorophenol each week to monitor changes in susceptibility as the fish grew. Fish exhibited a high degree of susceptibility to all of the toxicants during the alevin stage. Swim-up fry showed drastic changes in sensitivity followed by more sustained patterns of change in the subsequent juvenile stage. Lethality could be related to both concentration of toxicant (C) and some exponential function of body weight (W) by the use of the multiple regression equation, Y = a + b(lnC) + g(lnW) where Y is the percent mortality expressed in probits. Through the use of this weighted expression of toxicity it was observed that coho alevins were consistently more sensitive to the toxicants than the juveniles. An exponential relationship between toxicity and weight could be calculated as -g/b. This exponent was found to be specific for each toxicant tested and changed in magnitude as the fish progressed through the various stages of development. Results indicated that lethality (LC50s) varied from one stage of development to the next, but within any defined stage, the relationship between toxicity and body weight was relatively constant.

Hepatic accumulation, metabolism and biliary excretion of sulfobromophthalein by rainbow trout (Salmo gairdneri)

Abstract 1. 1. Hepatic accumulation, metabolism and biliary excretion of the organic anion sulfobromophthalein (BSP) were studied in the rainbow trout. 2. 2. Hepatic accumulation of this compound was relatively rapid; more than half of a single i.v. dose was found in the livers of trout after only 15 min. 3. 3. Biliary excretion appeared to be the rate-limiting step in the overall transfer of BSP from plasma to bile. 4. 4. As many as six separate fractions of BSP could be resolved by thin-layer chromatography; three of which reacted with ninhydrin and were probably associated with amino acids. 5. 5. Hepatic excretory processes for this compound in the trout are compared with those of other species.

The effect of carbon tetrachloride on the total plasma protein concentration of rainbow trout, Salmo gairdneri

Abstract 1. The effect of a single i.p. injection of CCl4 on total plasma protein and albumin concentrations was measured in the rainbow trout. 2. CCl4 treatment caused a significant reduction in total plasma protein concentration at 12, 24 and 36 hr post-treatment. 3. At 24 hr post-treatment plasma albumin concentration was significantly reduced only in fish given the highest dose of CCl4 (2.0 ml/kg). 4. Several factors, including intestinal inflammation and hemorrhages, could have contributed to the decreased plasma protein concentration in the trout.

Quantification of the joint effects of mixtures of hepatotoxic agents: Evaluation of a theoretical model in mice

Abstract An approach previously developed for studying the effects of toxic mixtures on whole organism performances (i.e., growth, mortality) was evaluated to determine its applicability and limitations at the organ system level. The approach was tested by quantifying the hepatotoxic effects of carbon tetrachloride (CCl 4 ), monochlorobenzene (MCB), acetaminophen (ACET), and selected mixtures of these compounds in male albino CF-1 mice. Based upon parallel dose-response curves, concentration addition was predicted for the mixtures of both CCl 4 + MCB and CCl 4 + ACET. The actual dose-response relationship for each mixture was empirically determined and compared to the predicted curves. In the case of the CCl 4 + MCB mixture, the observed dose-response curve did not deviate from that predicted on the basis of concentration addition. However, a similar comparison for the CCl 4 + ACET mixture revealed a statistical difference between the observed and predicted curves. The joint effects for the mixture of CCl 4 + MCB is thus classified as concentration additive. The model proves to be adequate in predicting, classifying, and describing the joint effects of these hepatotoxicants.

Alterations in diurnal pineal hydroxyindole-O-methyltransferase (HIOMT) activity in steelhead trout (Salmo gairdneri) associated with changes in environmental background color

Abstract 1. 1. The effects of dark versus light background on pineal hydroxyindole- O -methyltransferase (HIOMT) activity was studied in steelhead trout. 2. 2. In an 8l:16D photoregimen a diurnal HIOMT rhythm persisted under both background conditions. However, the relative enzymatic activities during the light and dark portions of the photoperiod were in opposition. 3. 3. It is suggested that the background color plays an important role in the manifestation of the pineal HIOMT response to photoperiod seen in this species.