RESUMEN

U.S. regulatory agencies commonly require effluent toxicity testing with Ceriodaphnia dubia--a practice that has led to the criticism that this species and test protocol often does not reflect local taxa or site-specific conditions. Using an indigenous test species may produce a more realistic model of local effects and may minimize test endpoint variance due to regional differences in water quality. This study addressed the substitution of C. dubia with Daphnia ambigua for toxicity testing in the southeastern United States. This investigation determined that D. ambigua could be laboratory cultured with only minimal changes to established regulatory protocol and that the life-cycle characteristics of this species were conducive to traditional acute and chronic aquatic toxicity test methods used with other daphnids. Acute toxicity tests showed that D. ambigua was less sensitive to some toxicants (sodium chloride, copper sulfate, and sodium lauryl sulfate) but more sensitive to others (chlorpyrifos). Chronic tests with copper sulfate and sodium chloride resulted in lower EC50S for D. ambigua reproduction with both compounds. When exposed to low-alkalinity, low-pH stream waters typical of many southeastern United States watersheds, C. dubia demonstrated a significant reproductive depression in two of three streams tested, whereas D. ambigua experienced no chronic effect. These results suggest that D. ambigua may serve as a suitable surrogate for C. dubia as an toxicity indicator species in these types of receiving streams.

Asunto(s)

RESUMEN

Sprague-Dawley rats received deionized water (controls) during 28 days or drinking water with added D-proline, L-proline, D-aspartic acid or L-aspartic acid corresponding to a mean daily load of approximately 50 mg amino acid enantiomer kg-1 body weight. Parameters indicating the physiological status (food intake and body weight, glutamic-oxalic-transaminase, glutamic-pyruvic-transaminase, alkaline phosphatase, urea and creatinine in serum, and creatine and osmomolality of urine) were determined. After 28 days the weights of the supposed target organs of toxicity (kidney, liver, brain, thymus) were determined and organs were inspected for macroscopic and microscopic alterations. No pathological changes in the organs were observed and no signs of subacute toxicity (liver, kidney) were found. In serum, homogenates of liver, kidney and brain, and in part, in urine, the amounts of D-amino acids (D-AAs) were quantitatively determined using chiral phase capillary gas chromatography-selected ion monitoring mass spectrometry. Significant levels of certain D-AAs (Ala, Pro, Ser, Asx, Glx, Orn and Lys) were already detectable in kidney and liver homogenates and serum of controls. In brain homogenates the highest amounts among the D-AAs were found for D-Ser (up to 382 nmol g-1), moderate amounts for D-Ala, D-Asx and D-Glx, and, in a few cases, trace amounts for D-Orn and D-Lys (1-2 nmol g-1). D-Pro was not detected either in the brains of controls or in the brains of animals loaded with D-Pro. Feeding with D-Pro resulted in a 20-30 fold increased renal excretion of D-Pro at the end of the experiment. Continuous feeding with D-Asp did not increase renal excretion of this enantiomer, but in the serum, higher amounts (0.8-4.0 mumol-1) were determined in comparison to the control group (0.3-0.9 mumol-1). Feeding with D-Pro led to an increase of this enantiomer in serum (1.3-10.5 mumol-1). Feeding with D-Asp did not increase its amounts in brain homogenates (38 and 43 nmol g-1) in comparison to controls.

Asunto(s)

RESUMEN

A new extraction and partition step was introduced into the well established multi-residue method of Specht and Tillkes (DFG method S 19) replacing dichloromethane by ethyl acetate/cyclohexane (1+1). In addition, more simple working conditions were obtained. Results of fortification experiments with organochlorine, organophosphorus and organonitrogen pesticides showed good agreement with those obtained by the formerly published method.

RESUMEN

Blaine Creek is a fifth-order stream located in eastern Kentucky that has been subject to contamination by oil brines, surface mining, and a coal fly ash settling pond discharge. Toxicity tests, effluent and receiving water chemical monitoring, and Blaine Creek benthic sampling were used to evaluate the effect of the ash pond effluent on the creek. Reproductive impairment of Ceriodaphnia was demonstrated at effluent concentrations ranging from 30 to 100%, but no instream impact on benthic invertebrates could be found at effluent flows that provided up to 65% of the creek's discharge. Correlation and regression analysis of physicochemical versus benthic monitoring data indicated that upstream oil brine contamination and scouring of the creek's predominately shifting sand substrate during rainfall events were the primary factors affecting the benthic fauna, and appeared to override potential effects from other sources. These results demonstrated the value of integrated field/laboratory investigations for effluent impact assessments.

RESUMEN

A pressure-limited ventilator (Bourns BP-200, Anaheim, CA) and a simple, manually operated constant flow ventilator were studied using a commercially available infant lung simulator (Bourns LS-130, Anaheim, CA). The characteristics of inspiratory pressure-time relationships during ventilation with these ventilators were analyzed. The analytic properties of the inspiratory phase of the pressure-time curve were related to simulator resistance and compliance. A mathematical model was constructed relating the initial rapid rise of the pressure curve to simulator resistance and the subsequent slope of the curve to simulator compliance. Qualitatively similar tracings were obtained with the BP-200 during normal ventilation, with simulated airway obstruction and thoracic restriction. These findings suggest that monitoring pressure-time relationships may be useful in the qualitative assessment of resistance and compliance during pressure-limited ventilation of neonates.

Asunto(s)

RESUMEN

In parallel with the study on the correlation between increased mucosal permeability and the secretagogue effect of deoxycholate on the perfused rat colon, we examined the mucosal morphology by scanning and transmission electron microscopy. Dependent on concentration (2, 4, and 8 mmol/l), the treated mucosa showed structurally altered 'ballooned' absorptive cells, severely injured sloughing cells, and exfoliated cells lying on the surface. In spite of these changes, the continuity of the epithelial lining was maintained. Patchy defects exposing the lamina densa of the basement membrane could be observed only in specimens artificially altered by cell loss through vigorous rinsing. Clusters of extruded cells were still seen attached to the mucosal surface in the region between the openings of neighbouring crypts when net transfer of fluid and permeability after a period of recovery had returned to control levels. These findings support the hypothesis that fluid filtration during perfusion with deoxycholate occurs via a paracellular pathway through a leaky, damaged epithelium.

Asunto(s)

RESUMEN

1. The influence of oxyphenisatin (OP), a diphenolic laxative, and deoxycholate (DC) on the transfer of sodium and water in an everted sac preparation of stripped rat colon was investigated. 2. OP (10(-5) M, mucosal side) and DC (3 X 10(-4) M, mucosal side) completely blocked net water and sodium absorption. Net movements from the serosal to the mucosal side could not be induced by higher concentrations of the drugs. 3. Unidirectional sodium movements in both directions were increased by OP and DC. 4. The effect of DC on the sodium flux from the serosal to the mucosal side was reversible. 5. The potassium content of the mucosal epithelium was not changed by DC and OP. 6. The integrity of the epithelium, as judged by light microscopy, was not disturbed by either drug under the experimental conditions. 7. It is concluded that DC and OP do not interfere with active transport mechanisms but increase the permeability of the epithelium to sodium.

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)