Ecologic stability of the dysaerobic biofacies during the Late Paleozoic

Late Paleozoic faunas found in sediments of dysaerobic origin represent a unique community type that remained essentially unchanged from the Middle Devonian to the Early Permian. This dysaerobic community had the following unique characteristics: (1) dominance by vagile molluscs, with suspension-feeding brachiopods, bryozoans, corals and echinoderms usually subordinate; (2) a trophic structure dominated by deposit feeders and carnivorous or scavenging cephalopods; (3) small body size as the result of high juvenile mortality and possibly stunting; and (4) preservation of most individuals as pyritic stein-kerns. All these characteristics are directly linked to the low oxygen levels of the dysaerobic environment. The relative stability of the deeper water, dysaerobic environment is consistent with Sanders' Stability-Time Hypothesis. The dysaerobic environment apparently offered a refuge for more archaic biotas that evolved in nearshore environments of the early Paleozoic.     

Interlaboratory variability of disc diffusion and agar dilution susceptibility tests with cefamandole and cephalothin

Reproducibility of antimicrobic susceptibility tests was estimated by examining control data accumulated during a multicenter study for evaluating cefamandole and cephalothin. The precision of agar dilution minimal inhibitory concentrations was compared with the standardized Bauer-Kirby disc method. Regression lines were established for each antimicrobic and were used to calculate the range of minimal inhibitory concentration values that corresponded to the observed ranges in zone sizes, thus permitting a comparison of the two types of procedures. The precision of the disc method was equal to or greater than that of the agar dilution method.     

Rapid and simple assay for feruloyl and p-coumaroyl esterases

A rapid, simple and sensitive method for detection of ferulic and p-coumaric acids using HPLC has been developed which can be used to determine the respective phenolic acid esterase activities of microorganisms. Prior concentration, purification or derivatization of the samples are not required. As little as 0.5 mg ferulic or p-coumaric acid/I could be detected and estimated in < 1 h. The method is specific for the two phenolic acids sice no interference by other components was observed.The authors are with the Department of Microbiology and Biochemistry, University of the Orange Free State (UOFS), PO Box 339, Bloemfontein 93000, South Africa     

The Quantum Yield of Photoinactivation of Photosystem II in Pea Leaves is Greater at Low Than High Photon Exposure

The quantum yield of PSII photoinactivation in pea leaves atlow photon exposure was 3 x 10^-7 mol PSII per mol photons absorbedby PSII and 2.5 x 10^-8 at high photon exposures (mol photonsm^-2), regardless of photomodulation of chloroplasts. We postulatethat the doseresponse behaviour of PSII photoinactivation, whichdepends on the number of photons absorbed, results from thebalance of light consumption with supply. (Received July 18, 1995; Accepted August 8, 1995)     

An automated climbing apparatus to measure chemotherapy-induced neurotoxicity in Drosophila melanogaster

We have developed a novel model system in Drosophila melanogaster to study chemotherapy-induced neurotoxicity in adult flies. Neurological deficits were measured using a manual geotactic climbing assay. The manual assay is commonly used; however, it is laborious, time-consuming, subject to human error and limited to observing one sample at a time. We have designed and built a new automated fly-counting apparatus that uses a “video capture-particle counting technology” to automatically measure 10 samples at a time, with 20 flies per sample. Climbing behavior was assessed manually, as in our previous studies, and with the automated apparatus within the same experiment yielding statistically similar results. Both climbing endpoints as well as the climbing rate can be measured in the apparatus, giving the assay more versatility than the manual assay. Automation of our climbing assay reduces variability, increases productivity and enables high throughput drug screens for neurotoxicity.