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Biomedical subjects

M Tarkpea

Publications and source records attributed to M Tarkpea.

5 recordsLinked to original sources
PubMed1989

Comparison between two Microtox test procedures.

A comparison between the two Microtox test procedures, the standard test and the 100% test, has been made. In the standard Microtox bioassay, effluents can be tested up to a concentration of 45%. The 100% test method, however, has been developed for screening effluents with an EC50 value greater than 45%. The relationship between 5-min EC50 values according to the two methods has been studied with a two-way ANOVA analysis for 14 effluents or process waters and one unpurified municipal wastewater sample. All samples were tested twice with a 3-month interval. An F ratio of 15.46 (n = 56) showed that the test methods differed significantly at the 0.1% level. Nevertheless none of the samples had a drastically different EC50 value when tested by the two methods. Both the treatment of the bacteria and the calculation of the EC50 values, which also affect the width of the 95% fiducial limits, differ in the two procedures. The confidence intervals were found to be 10.4 times broader in the 100% tests than in the corresponding standard test. Although the methods differ from each other both in performance and in statistical comparison of the results, both of them could be useful as prescreening methods for determining toxicity to aquatic organisms.

Bacteria↗
PubMed1986

Comparison of the Microtox test with the 96-hr LC50 test for the harpacticoid Nitocra spinipes.

A comparison between the static 96-hr LC50 test with the brackish water harpacticoid Nitocra spinipes and the Microtox (Beckman Instruments, Inc.) screening method has been done. The relationship between the two bioassays were evaluated for 16 pure and technical chemicals and 11 complex effluents from different types of industries. The correlation between the 96-hr LC50 values for Nitocra and the 5-, 15-, and 30-min effective concentration (EC50) for pure and technical chemicals had R2 values ranging between 0.751 and 0.796. A somewhat better correlation was shown between the two test methods for the complex effluents with R2 values ranging from 0.903 to 0.927. The sensitivity of the two tests for the actual types of samples were found to be in the same order of magnitude. Investigations concerning pretreatments of three chemicals (dibutyl phthalate, 1-octanol, and pentachlorophenol) fairly insoluble in water (less than 1000 mg/liter) have been done. Three solvents, acetone, dimethyl sulfoxide (DMSO), and propylene glycol, were studied with the Microtox system in a low concentration (500 mg/liter). Acetone exerted a slightly stimulatory effect and propylene glycol a slight reduction effect on bacterial luminescence.

Acetone↗
PubMed1986

The use of the bivalve Mytilus edulis as a test organism for bioconcentration studies. II. The bioconcentration of two 14C-labeled chlorinated paraffins.

The bioconcentration of two 14C-labeled chlorinated paraffins (CP) has been studied in a flow-through test system using the common mussel Mytilus edulis. Both CPs showed a rapid uptake rate and the CP with C16 carbon chain and 34% chlorination had a bioconcentration factor (BCF) of about 7000 (fresh weight). The CP with a C12 carbon chain and 69% chlorination had a very high BCF of almost 140,000 which on a lipid weight basis corresponds to a BCF of around 8,000,000. The C12-CP showed a slow depuration rate in analogy with what has been observed earlier in fish. Radioactivity was recovered from both the fat and protein fractions after exposure to the C12-CP with a level in the protein of about two orders of magnitude lower than in the fat. It is concluded that studies with CPs so far reported indicate that short carbon chain/high chlorinated chlorinated paraffins are strongly bioaccumulating and persistent chemicals.

Animals↗
PubMed1985

The use of the bivalve Mytilus edulis as a test organism for bioconcentration studies. I. Designing a continuous-flow system and its application to some organochlorine compounds.

Most bioconcentration studies have previously been carried out using fish as a test organism. Equally important is the use of bivalves for this purpose, from both an ecological and an economic point of view. A continuous-flow system has thus been designed for use also with extremely hydrophobic substances and evaluated using 2,4',5-trichlorobiphenyl, methoxychlor, pentachlorobenzene, and lindane. The variation of the uptake in the individuals after 3 weeks' exposure was quite small (relative standard errors varied from 10.1 to 15.3% depending on the test substance), indicating a high degree of reproducibility. The bivalves, however, are known to close their valves under unfavorable conditions, which occasionally may bias the results. To overcome this disadvantage, it is suggested that an internal standard--i.e., a chemically defined compound--be added to the water simultaneously with the test substances. Although there is a principal risk for interactive effects, unexpected variations in the uptake can thus be compensated for by relating the concentration of the test substance to the concentration of the internal standard in the organisms. Comparisons between continuous-flow systems and static systems have also been made. It is concluded that continuous-flow systems are more suitable for studying hydrophobic compounds than static systems.

Animals↗