In vitro mitogenesis of peripheral blood lymphocytes from rainbow trout (Salmo gairdneri).

1. In vitro mitogenesis of rainbow trout peripheral blood lymphocytes (RBT PBL) was investigated to assess the applicability of this procedure in assessment of fish health. The assay variables of media, mitogen type and concentration, serum supplementation, lymphocyte isolation procedure, and duration of incubation were assessed. 2. Concanavalin A (Con A) stimulated greater proliferation of RBT PBL than did lipopolysaccharide (LPS), phytohemagglutinin (PHA), or pokeweed mitogen (PWM). 3. RBT PBL, cultured with 10 micrograms Con A/ml and incubated for four or five days, exhibited greater proliferation than with other treatment combinations. 4. The degree of Con A-induced PBL proliferation varied significantly (P less than 0.05) among fish. The mean was positively correlated with the relative standard deviation and thus exhibited significant heteroscedasticity. 5. Human serum, as an alternative to FBS supplementation of the culture medium, did not enhance RBT PBL proliferation or reduce variation in mean proliferation. 6. Power analysis with variance estimates from this study reveal that sample size requirements of further studies under the given conditions could severely limit the applicability of this procedure for RBT health assessment. Further work in this area should center around standardization of culture conditions pertaining to the source of protein supplementation.

Oxygen diffusion in the trout retina.

Oxygen tensions were measured in vivo within the different layers of the rainbow trout retina. Oxygen microelectrodes were advanced in 10 micron increments through the retinas and the PO2 measured at each location. Mean retinal PO2 ranged from 124 mmHg at the retinal-vitreal interface to 381 mmHg at the choriocapillaris. These data reaffirm that the cellular layers of the normal trout retina are continually exposed to supra-arterial oxygen tensions that are known to cause toxicity in other species. The intraretinal PO2 gradient was mathematically characterized and results indicate that the in vivo oxygen profile can be described by a two-component exponential function. In order to gain a better understanding of oxygen delivery to the retina, the data were also subjected to an analysis based upon the classical equation for planar diffusion. The trout retina is an excellent model for studying oxygen diffusion in vivo since this tissue is supplied with oxygen from a single source, thereby simplifying the mathematical analysis. Calculations yielded values of 1.86 X 10(-5) and 0.58 X 10(-5) ml O2 min-1 cm-1 atm-1 (at 9 degrees C) for the Krogh permeation coefficient (DS) for the photoreceptor region and the remaining neural retina, respectively.

Action of organophosphates on the electroretinogram of rainbow trout.

Electroretinograms (ERGs) were recorded in vitro from eyes of rainbow trout that had received intraperitoneal injections of either TOCP (triorthocresyl phosphate) or DEF (S, S, S-tributyl phosphorotrithioate). Data obtained after 24 h indicated that these organophosphates caused alterations in four of five ERG parameters in the case of TOCP and all five parameters in the DEF treated specimens. These data were compared with data obtained from experiments with eserine and carbachol and led to the conclusion that the effects of the organophosphates on the retina were independent of any cholinesterase inhibitor activity of the compounds. These organophosphates affect (a) the non-cholinergic photoreceptor layer of the retina which produces the a-wave ERG component, and (b) the other neural layers of the retina known to be responsible for generation of the b-wave component. Based on data obtained 15 days after exposure there was no evidence that TOCP or DEF has any delayed neurotoxic effect on the retina of rainbow trout.

Factors affecting 3H2O transfer capacity of isolated perfused trout gills.

Tritiated water (3H2O) transfer capacity (PdA) and vascular impedance (Zg) of isolated trout (Salmo gairdneri) gills perfused with or without epinephrine were studied under conditions of altered osmotic gradients, fluid stirring, perfusion rate (Qa), and efferent pressure (Pe). Transfer capacity was unaffected by osmotic gradients, indicating that 3H2O moves across gills by diffusion and that PdA is independent of hydraulic water movement. Fluid stirring increased PdA asymptotically, suggesting that boundary layers significantly affect diffusion across isolated gills. Transfer capacity was directly related to Qa; Zg was inversely related to Qa. The PdA results can be explained in terms of lamellar recruitment and the distribution of flow between secondary lamellae. Increased Qa reduced Zg due to recruitment and distension of gill vessels. Elevated Pe decreased Zg and PdA. The effects of Pe on Zg resulted from distension of the gill vasculature and increased venous drainage, whereas the effects of Pe on PdA can be explained by changes in the distribution of perfusion between secondary lamellae.

Short circuiting the ocular oxygen concentrating mechanism in the teleost Salmo gairdneri using carbonic anhydrase inhibitors.

Ocular oxygen concentration by the process of counter current multiplication in rainbow trout (Salmo gairdneri) was rapidly suppressed after intraperitoneal injections of the carbonic anhydrase inhibitor CL-11,366. The rapidity with which this drug acted suggested a short circuiting of the choroidal rete mirabile. A comparison was made between the time after injection of inhibitor at which oxygen concentrating ability was lost to the time after injection of inhibitor at which its presence in red blood cells, choroidal rete, pseudobranch, and retinal tissue was first noted. A scheme for the possible role of carbonic anhydrase from each of these tissues in the process of ocular oxygen concentration is given.