RESUMEN

We investigated the influence of acclimation on results of in situ bioassays with cutthroat trout in metal-contaminated streams. Cutthroat trout (Oncorhynchus clarki) were held for 21 days (1) in live containers at a reference or "clean" site having dissolved metals near detection limits (0.01 microg/L cadmium [Cd] and 2.8 microg/L zinc [Zn]; hardness 32 mg/L as CaCO(3)) and (2) at a site in a mining-impacted watershed having moderately increased metals (0.07 microg/L Cd and 38 to 40 microg/L Zn; hardness 50 mg/L as CaCO(3)). The 96-hour survival of each treatment group was then tested in situ at five sites from September 5 to 9, 2002, and each group exhibited a range of metal concentrations (0.44 to 39 microg/L arsenic [As], 0.01 to 2.2 microg/L Cd, and 0.49 to 856 microg/L Zn). Survival was 100% at three sites for both treatments. However, a higher percentage of metal-acclimated fish survived at the site with the second highest concentrations of Cd and Zn (0.90 and 238 microg/L, respectively) compared with fish acclimated at the reference site (100% vs. 55%, respectively). Survival was 65% for acclimated fish and 0% for metal-naïve fish at the site with the largest metal concentrations (2.2 microg/L Cd and 856 microg/L Zn). Water collected from the site with the largest concentrations of dissolved metals (on October 30, 2002) was used in a laboratory serial dilution to determine 96-hour LC(50) values. The 96-hour LC(50) estimates of naïve fish during the in situ and laboratory experiments were similar (0.60 mug Cd/L and 226 microg Zn/L for in situ and 0.64 microg Cd/L and 201 microg Zn/L for laboratory serial dilutions). However, mortality of naïve cutthroat trout tested under laboratory conditions was more rapid in dilutions of 100%, 75%, and 38% site water than in situ experiments.

Asunto(s)

RESUMEN

The Hanford Nuclear Reservation in south central Washington was claimed by the federal government as a site for the production of plutonium. During the course of production and operation of the facilities at Hanford, radionuclides and chromium were discharged directly into the river and also contaminated the groundwater. This study was designed to assess the effects of chromium (Cr) on Chinook salmon (Oncorhynchus tshawytscha) fertilization under exposure conditions similar to those of the Hanford Reach of the Columbia River. Chinook salmon gametes were exposed to aqueous Cr concentrations ranging from 0 to 266 microg Cr l(-1). The current ambient water-quality criteria (AWQC) established for the protection of aquatic life (United States Environmental Protection Agency [USEPA] 1986) is 11 microg Cr l(-1). Cr has been measured in pore water from bottom sediments of the Columbia River at concentrations >600 microg Cr l(-1). Under exposure conditions designed to closely mimic events that occur in the river, the fertilization of Chinook salmon eggs was not affected by concentrations of Cr ranging from 11 to 266 microg Cr l(-1). Data suggest that the instantaneous nature of fertilization likely limits the potential effects of Cr on fertilization success. As a result, the current AWQC of 11 mug Cr l(-1) is most likely protective of Chinook salmon fertilization.

Asunto(s)

RESUMEN

Our group is developing an artificial lung as a bridge to transplant. We evaluated the sheep pulmonary artery (PA) for the presence or absence of a septum, which may increase PA resistance and affect artificial lung flow. We also measured the PA size to determine whether it is a suitable conduit for artificial lung implantation using a PA-PA shunt. Adult Suffolk ewes in two groups were studied. Group 1 consisted of animals (n = 12, 30-43 kg) prepared for thoracotomy. Group 2 (n = 21, 30-43 kg) consisted of postmortem dissections. In both groups, the length and girth of the PA was measured. The heart and lungs were removed on all postmortem animals (group 2), the ductus arteriosum was crosscut, and the common PA was incised. The average length of the PA in live animals was 5.5 cm and the average diameter was 2.2 cm. The average length of the PA in postmortem animals was 4.8 cm and the average diameter was 2.0 cm. All pulmonary arteries were aseptate, and the ligamentum arteriosum in each PA was not patent. We conclude that the PA is not a source of increased resistance and is a suitable conduit for artificial lung implantation in the PA-PA configuration.

Asunto(s)

RESUMEN

We investigated changes in cardiac output and organ blood flow induced by medetomidine in sheep and determined changes in cardiac output and organ blood flow after reversal of medetomidine-induced sedation by atipamezole. Eight sheep were chronically instrumented. Medetomidine was infused IV to target plasma levels of 0, 0.8, 1.6, 3.2, 6.4, and 12.8 ng/mL for 25 min each, followed by a 5-min infusion of atipamezole. Hemodynamic values and organ blood flow (using colored microspheres) were measured just before medetomidine infusion (baseline), at the end of each medetomidine infusion step, and 30 min after the administration of atipamezole. Medetomidine (12. 8 ng/mL) decreased cardiac output from 6.3 +/- 1.0 to 3.2 +/- 0.7 L/min (P < 0.0001) and increased systemic vascular resistance from 1310 +/- 207 to 3467 +/- 1299 dynes. s(-1). cm(-5) (P < 0.0001). Blood flow decreased in the cerebral cortex from 1.29 +/- 0.40 to 0. 66 +/- 0.12 mL. g(-1). min(-1) (P < 0.0001), left ventricle from 2. 11 +/- 0.61 to 1.40 +/- 0.40 mL. g(-1). min(-1) (P < 0.0001), kidney from 8.28 +/- 3.17 to 6.07 +/- 2.65 mL. g(-1). min(-1) (P < 0.0001), skin from 0.09 +/- 0.04 to 0.05 +/- 0.02 mL. g(-1). min(-1) (P < 0. 0001), intestine from 0.56 +/- 0.13 to 0.27 +/- 0.07 mL. g(-1). min(-1) (P < 0.0001), and skeletal muscle from 0.28 +/- 0.15 to 0.04 +/- 0.01 mL. g(-1). min(-1) (P < 0.0001). Blood flow in the liver (hepatic artery) increased from 0.05 +/- 0.03 to 0.24 +/- 0.16 mL. g(-1). min(-1) (P < 0.0001). After atipamezole infusion, cardiac output and systemic vascular resistance returned to baseline, but the cerebral cortex, left ventricle, and renal blood flows remained below baseline at 0.89 +/- 0.22, 1.37 +/- 0.50, and 6.25 +/- 2.76 mL. g(-1). min(-1), respectively; skeletal muscle blood flow increased above baseline to 0.44 +/- 0.27 mL. g(-1). min(-1), spleen blood flow decreased below baseline to 1.65 +/- 0.61 mL. g(-1). min(-1) (P < 0.0001), and liver, intestine, and lung blood flows returned to baseline values. In conclusion, medetomidine decreased and redistributed organ blood flow in sheep. Atipamezole reversed the medetomidine-induced hemodynamic changes, but redistributed blood flow from the brain, heart, and kidney to the skeletal muscle.

Asunto(s)

Asunto(s)