Use of a miniaturized test system for determining acute toxicity of toxicity identification evaluation fractions.

A miniaturized test system was developed and used to determine the acute toxicity of effluent fractions separated by HPLC to Daphnia magna and Pimephales promelas. The miniaturized test system consists of exposing test organisms in 1 ml of test solution using 48-well microtiter plates for the test vessels. Several factors were investigated to determine the acceptability of this test system. These factors included organism biomass to test solution ratio, toxicity of the microtiter plates to the organisms, dissolved oxygen in the test solution, partitioning of the test chemicals to the walls of the test vessels, and dilution of the test solution when the organisms are transferred. Toxicity of four reference chemicals to D. magna and P. promelas was also determined using the miniaturized test systems. It was concluded that the test system could be miniaturized and still provide results comparable to those obtained when standard U.S. EPA test procedures were used. The major benefit of using the miniaturized test system is that less solution is required for conducting a toxicity test. This becomes important when only a small amount of test solution is available, as might occur during a toxicity identification evaluation, after an effluent has been fractionated by HPLC. Other benefits include less space required to conduct a test, less time necessary to prepare test solutions, and a reduced volume of waste for disposal.

Identification of components in waste streams by electrospray and tandem mass spectrometry.

Highly polar, non-gas-chromatographable compounds have few unambiguous analysis protocols for environmental applications. A recent environmental investigation, concerning the identification of a non-gas-chromatographable yellow component in chemical waste water and in effluents from a biological wastewater treatment plant required the use of a number of analytical approaches. Electrospray mass spectrometry, tandem mass spectrometry, high-performance liquid chromatography, nuclear magnetic resonance, and molecular spectroscopy of commercial and synthesized chlorodinitrophenol isomers were required in order to identify the specific isomer causing the color. The present report summarizes the electrospray ionization and tandem mass spectrometric studies that were used. The mass spectrometric study shows that two different isomers of chlorodinitrophenol exhibit very different collision-induced dissociation (CID) spectra. Differences in the tandem mass spectra can be attributed to the different structures of the anions formed from these two different isomers. Instrumentation that uses electrospray ionization and produces CID mass spectra and optical absorption spectra in a single analysis may be required in order to produce highly specific information on non-gas-chromatographable compounds found in the environment.

Effects of nitrendipine on the course of experimental immunologic glomerulonephritis.

To test whether calcium entry blockers (CEB) affect the course of progressive renal disease, we examined a standardized model of antiglomerular basement membrane glomerulonephritis (GN) in rats with and without oral administration of the CEB, nitrendipine (Nit). Nit was given in chow pellets at a daily dose of approximately 20 mg. Nephritic control rats received standard chow (Co). A time-course study over 4 weeks revealed the following; mean systolic blood pressure in GN/Nit rats remained below 115 mm Hg throughout, while GN/Co rats developed mild hypertension with peak values of 135 +/- 8 at 4 weeks (p less than 0.05). Urinary albumin excretion before induction of GN was 1.2 +/- 0.4 mg/24 h; at weeks 1 and 4, GN/Co had 249 +/- 34 and 306 +/- 50 mg/24 h, respectively. GN/Nit had less albuminuria, with 107 +/- 25 and 172 +/- 21 mg/24 h, respectively (p less than 0.05). Clearance experiments in anesthetized rats at 4 weeks revealed significantly better preservation of renal function in GN/Nit vs. GN/Co rats: (renal vascular resistance: 90.2 +/- 24 vs. 402.2 +/- 160 mm Hg/ml/min; clearance of para-aminohippurate: 1.388 +/- 0.151 vs. 0.598 +/- 0.368 ml/min/100 g; clearance of inulin: 0.570 +/- 0.123 vs. 0.141 +/- 0.077 ml/min/100 g; urinary sodium excretion: 1.417 +/- 0.554 vs. 0.188 +/- 0.081 mumol/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Selective preconcentration of polynuclear aromatic hydrocarbons and polychlorinated biphenyls by in situ metal hydroxide precipitation.

An investigation of selective concentration of analytes from aqueous samples by in situ magnesium hydroxide precipitation, as described by Faltusz, has yielded the following results: the method is selective for polycyclic aromatic hydrocarbons and polychlorinated biphenyls of higher molecular weight: it discriminates strongly against acidic molecules, and other neutral and basic molecules are only partially recovered; a variety of metal hydroxides could evidently be used in this method, but magnesium appears to have practical advantages over some of the others; the reproducibility of analyses on pure water samples is acceptable (ca.20% relative standard deviation), but the results from natural samples show lower recovery and wider variability; a preliminary test, in which this method was used to discriminate against major amounts of interfering solutes, shows promise that this technique might have unique advantages in certain situations.

Effects of a calcium entry blocker on blood pressure and renal function during angiotensin-induced hypertension.

The effects of the calcium entry blocker nitrendipine on blood pressure (BP) and renal hemodynamics were studied in rats with angiotensin II (ANG II)-induced hypertension. The ANG II was infused subcutaneously by implanted osmotic minipumps for 14 to 16 days. There was a progressive rise in BP in ANG II-infused rats to levels 58 mm Hg above basal by Day 10, whereas control rats with sham pumps remained normotensive. Nitrendipine or vehicle was administered by gavage to groups of control and hypertensive rats for 5 days, and clearance experiments were performed with the rats under anesthesia on the last day. The prolonged infusion of ANG II increased the renal vascular resistance and reduced the glomerular filtration rate and renal Na+ excretion. At a dose of 3 mg/100 g body weight, nitrendipine had no consistent effects on BP or renal function of control rats. By contrast, in rats with ANG II-induced hypertension, nitrendipine normalized both the BP and the changes in renal vascular resistance and glomerular filtration rate. Despite the fall in BP, nitrendipine caused a marked diuresis and natriuresis. Moreover, nitrendipine increased Na+ excretion of conscious, ANG II-hypertensive rats but not of controls. Thus, nitrendipine appears to be highly effective in reversing ANG II-induced hypertension and Na+ retention. These findings also indicate that the hypertension, renal vasoconstriction, and Na+ retention accompanying prolonged ANG II infusions may be mediated by calcium-dependent mechanisms.

Nitrendipine reverses vasoconstriction and renal hemodynamic changes in experimental hypertension.

Nitrendipine, a calcium entry blocker, was administered by gavage (3 mg/100 g body weight/day) to rats with prolonged angiotensin-II-(AII) induced hypertension. AII was infused by osmotic minipump implanted subcutaneously. Persistent hypertension was established after 5 days. Normotensive control rats had empty sham pumps. Nitrendipine, administered from day 11 to 15 after pump implantation, normalized blood pressure consistently in AII rats, whereas it had no significant hypotensive effect in controls. Renal clearance experiments in anesthetized rats revealed that nitrendipine reversed all noted abnormalities of AII-infused rats, including hypertension and reductions in glomerular filtration rate, renal blood flow, and urinary sodium excretion. When receiving nitrendipine, sham controls did not show significant changes in blood pressure, renal function, or natriuresis. The results demonstrate that oral administration of nitrendipine is highly effective in normalizing blood pressure during prolonged AII-induced hypertension. The antihypertensive effect is achieved by this calcium entry blocker's vasodilatory action, supported by a marked natriuretic effect. By contrast, blood pressure and renal function of normotensive control rats were not appreciably affected by oral nitrendipine.