Antipredatory behavior as an index of heavy-metal pollution? A test using snails and caddisflies.

The loss of behaviors that organisms use to avoid predation may serve as a sensitive indicator of pollution. We tested the hypothesis that a correlation exists in the field between heavy metal levels and antipredator behaviors. We examined the antipredator behavior of aquatic caddisfly larvae and snails at sites in the Coeur d'Alene basin of Northern Idaho which varied in their levels of heavy metals. We tested the antipredator response of Physella columbiana snails at 10 polluted lakes downstream from the Bunker Hill Environmental Protection Agency (EPA) Superfund cleanup site. We then compared their behavior to snails at 14 reference lakes. We placed the snails in a plastic testing apparatus, exposed them to an extract of crushed snail, and then monitored their movements to a normally preferred shaded area. We also tested the behavior of caddisfly larvae from 36 sites from a total of 6 streams/rivers adjacent to the Superfund site. Sites were located upstream and downstream of abandoned mines. We located active larvae of four genera, simulated predation by grasping the animals between thumb and forefinger (the larvae respond to being grasped by withdrawing into their case), lifted them from the water for 3 s, and then placed them in an adjacent, slower section of the stream. We then recorded how long it took each larvae to partially emerge from its case and attempt to move away. Unlike reference site snails, snails from heavy metal-polluted environments failed to exhibit antipredator behaviors in response to crushed conspecifics. These results are consistent with previous laboratory studies. We found no effect of heavy metals on the antipredatory behavior of caddisfly larvae.

Enhanced thermolability in anephric rabbits.

Uremic patients tend to have a lower than normal deep-body temperature. In addition, there is a clinical impression that uremic patients are also more thermolabile than healthy people; that is, in a warm environment, body temperature tends to be higher, and in a cold environment, body temperature tends to be lower than in healthy subjects. To test the hypothesis that uremia results in enhanced thermolability, nonoperated control (NO), nephrectomized (NX), and sham-nephrectomized (SHAM) rabbits were subjected to mild cold (5 degrees C) and heat (30 degrees C) stresses. At 48 hours postsurgery, the core temperature of NX rabbits was significantly lower than that of the NO or SHAM rabbits (P less than .01). Exposure to 5 degrees C resulted in a significant fall in body temperature of the NX (from 39.1 degrees C to 38.3 degrees C; P less than .05) rabbits compared to the NO rabbits. There was a tendency for body temperature of the SHAM rabbits to fall, and as a result, there was no significant difference in the change in body temperature between the SHAM and NX rabbits. Exposure to 30 degrees C resulted in virtually no change in the core temperature of the NO or SHAM rabbits, but did result in a significant rise in core temperature of the NX rabbits (P less than .02 and P less than .01 for respective comparisons), as well as a significant increase in mortality rate (P less than .02). Based on these data, we conclude that anephric animals are more thermolabile, and are less able to tolerate exposure to a warm environment, than are normal animals.

Polymyxin B use does not ensure endotoxin-free solution.

Polymyxin B is often added to in vitro samples to 'ensure' that endotoxin activity is removed. We present data, from the standard rabbit pyrogen test and the Limulus amebocyte lysate assay, that polymyxin B bound to a gel support will bind some, but not all, endotoxin. These data, in conjunction with previously published data by Morrison and Curry (1979), indicate that those studies that have relied on polymyxin B to inactivate endotoxin must be re-evaluated.

Cyanate and temperature regulation in anephric rabbits.

Knochel and Seldin proposed that the lowered body temperature observed during uremia was caused by an elevation in the circulating levels of cyanate. To test this hypothesis, normal rabbits were infused with varying concentrations of sodium cyanate. Infusion of pharmacological doses of cyanate (plasma concentration rose to 1,080 +/- 70 microM, n = 5) resulted in reductions in body temperature similar to that found during uremia; however, when normal rabbits were nephrectomized the plasma cyanate concentration only rose from 3.7 +/- 1.6 to 18 +/- 1.8 microM (n = 8) by 1-day postnephrectomy (body temperature fell 0.33 +/- 0.1 degrees C, n = 6). Plasma cyanate concentration did not rise further on days 2 and 3 postnephrectomy, despite a continued fall in body temperature. Infusion of cyanate in control rabbits to plasma concentrations attained 1-3 days postnephrectomy did not result in a fall in body temperature. Based on the failure of pathophysiological concentrations of cyanate to cause a reduction in the body temperature of normal rabbits, we conclude that cyanate is not responsible for the lowered body temperature associated with the acute response to uremia.

Hypoxic tolerance enhanced by beta-hydroxybutyrate-glucagon in the mouse.

A coorelation has been observed between increased blood ketones and the tolerance of mice to hypoxia (4-5% oxygen). In previous studies fasted mice, alloxan diabetic mice and mice given 1,3-butanediol were found to be ketotic and to have increased tolerance to hypoxia. We attempted to induce a similar increased hypoxic tolerance by direct elevation of blood ketones with IV and IP beta-hydroxybutyrate (BHB). No increase in hypoxic tolerance was observed with BHB alone. Inasmuch as fasting and alloxan diabetes are both associated with elevated blood glucagon (G), hypoxic tolerance tests were made 30 min after G alone or a combination of G plus BHB. The mice given G alone or BHB alone had hypoxic survival times not different from saline controls. The mice given G plus BHB had increased survival times that could not be explained on the basis of a G mediated alteration in blood BHB.