The use of commercial immunoenzyme kits for the diagnosis of toxoplasmosis

The results of comparative study of sera obtained from donors and from several groups of patients with suspected toxoplasmosis are presented. The study has been carried out with the use of commercial enzyme immunoassay (EIA) kits: Toxoplasma gondii IgG EIA and Toxoplasma gondii IgM EIA manufactured by Labsystems (Finland), Sevatest ELISA IgG Toxo Micro I manufactured by Sevac (Czechoslovakia). Statistical processing of the results has confirmed the identity of these kits. The necessity of using evaluation criteria (the separation point, the scale for the interpretation of results) when working with the Sevac kits is emphasized. Comparative evaluation of antibody profiles in the sera under test suggests that the titer less than 1:1600 should be regarded as the separation point for these kits. IgM antibodies to T. gondii have been found only in 22% of patients with high titers of IgG antibodies.     

Analytical limits of four beta-glucuronidase and beta-galactosidase-based commercial culture methods used to detect Escherichia coli and total coliforms

Colilert (Colilert), Readycult Coliforms 100 (Readycult), Chromocult Coliform agar ES (Chromocult), and MI agar (MI) are beta-galactosidase and beta-glucuronidase-based commercial culture methods used to assess water quality. Their analytical performance, in terms of their respective ability to detect different strains of Escherichia coli and total coliforms, had never been systematically compared with pure cultures. Here, their ability to detect beta-glucuronidase production from E. coli isolates was evaluated by using 74 E. coli strains of different geographic origins and serotypes encountered in fecal and environmental settings. Their ability to detect beta-galactosidase production was studied by testing the 74 E. coli strains as well as 33 reference and environmental non-E. coli total coliform strains. Chromocult, MI, Readycult, and Colilert detected beta-glucuronidase production from respectively 79.9, 79.9, 81.1, and 51.4% of the 74 E. coli strains tested. These 4 methods detected beta-galactosidase production from respectively 85.1, 73.8, 84.1, and 84.1% of the total coliform strains tested. The results of the present study suggest that Colilert is the weakest method tested to detect beta-glucuronidase production and MI the weakest to detect beta-galactosidase production. Furthermore, the high level of false-negative results for E. coli recognition obtained by all four methods suggests that they may not be appropriate for identification of presumptive E. coli strains.     

Evaluation of three field test kits to detect microcystins from a public health perspective

Cyanobacteria blooms may present a public health concern in sources of drinking water and recreational water due to the production of toxins by some species, microcystins being the most commonly found. It is possible to detect microcystins using instrumental analyses and field test kits. While instrumental analysis methods are accurate, they are also costly, and in regions with a high incidence of blooms the time to report is lengthy (days). On the other hand, the use of commercially available test kits may provide quicker results at a lower cost. The purpose of this work was to evaluate three commercially available kits: the Immunochromatographic Strip Test for the Detection of Microcystins and Nodularins in Source Drinking Water at 1 μg/L (Abraxis strip test), the Abraxis Microcystin Tube Kit and the Envirologix QualiTube Kit. The evaluation of each kit focussed on the interpretation of the results by the end-user and the validity of a test kit was based on four indices: sensitivity, specificity, positive predictive rate (PPR) and negative predictive rate (NPR) (false positive/negative) based on the manufacturer's specifications. The results indicate that there are challenges in the visual interpretation of the results at levels close to the threshold value for each kit. The scope of each kit must be understood: free vs. total, qualitative vs. semiquantitative. For instance, the Envirologix Qualitube Kit does not provide a lysing agent, therefore it will underestimate the levels of total microcystin if a lysing step is not included. In the case of the Abraxis strip test, the kit provides information on the absence/presence of microcystin at a threshold value of 1 μg/L, but false positives were encountered.     

The use of 1,6-diphenylhexatriene to detect lipids on thin-layer chromatograms

1,6-diphenylhexatriene (DPH) fluoresces violet under long-wave uv light in the presence of lipid on silica gel thin-layer chromatograms. The DPH, sprayed as a solution in a volatile nonpolar solvent, detects submicrogram quantities of all lipid classes. It is a nondestructive marker and can be removed subsequently by elution with a petroleum ether (40–60°C).     

The use of genetic probes to detect microorganisms in biomining operations

Summary Microorganisms are currently used for the recovery of copper from mining dumps of low-grade ore. One of the most important microorganisms involved in copper-solubilization isThiobacillus ferrooxidans, although many other microbial genera are also thought to be implicated. A mining dump poses some special problems for the industrial microbiologist because it represents a non-sterile and heterogeneous substrate. Consequently, to enhance our knowledge of the role of microorganisms in metal recovery we must identify the indigenous microorganisms and understand their respective contributions to the process. In addition, when a superior strain of microorganism is developed in the laboratory, by genetic engineering or by other means, we must have a method to evaluate the maintenance of such a strain in the mining dump. In this paper, we describe DNA homology studies, using dot blot and Southern blot analysis of hybridizations of both whole genomic DNA and cloned DNA sequences, to identify and enumerate several bioleaching microorganisms. We demonstrate that it is possible to identify different species of microorganisms and, in one case, to discriminate between different strains of a single species. It is also possible to identify and quantitate certain species in a mixed culture. DNA hybridization analysis has several advantages over the more conventional bacteriological methods of identification, especially in a complex bioleaching situation.     

Developmental shifts in computations used to detect environmental controllability

Accurate assessment of environmental controllability enables individuals to adaptively adjust their behavior—exploiting rewards when desirable outcomes are contingent upon their actions and minimizing costly deliberation when their actions are inconsequential. However, it remains unclear how estimation of environmental controllability changes from childhood to adulthood. Ninety participants (ages 8–25) completed a task that covertly alternated between controllable and uncontrollable conditions, requiring them to explore different actions to discover the current degree of environmental controllability. We found that while children were able to distinguish controllable and uncontrollable conditions, accuracy of controllability assessments improved with age. Computational modeling revealed that whereas younger participants’ controllability assessments relied on evidence gleaned through random exploration, older participants more effectively recruited their task structure knowledge to make highly informative interventions. Age-related improvements in working memory mediated this qualitative shift toward increased use of an inferential strategy. Collectively, these findings reveal an age-related shift in the cognitive processes engaged to assess environmental controllability. Improved detection of environmental controllability may foster increasingly adaptive behavior over development by revealing when actions can be leveraged for one’s benefit.     

Oligonucleotide hybridization used to detect short non-contiguous sequences.

We describe the use of an oligonucleotide construction as a hybridization probe to detect short noncontiguous regions of sequence identity. Oligonucleotides complementary to various portions of the conserved heptamer and nonamer sequences flanking immunoglobulin variable region genes at the 3' end were used in this model system. We show that short oligonucleotides alone (7 bp or 9 bp) cannot be used as hybridization probes, but a construction containing both conserved sequences linked by a bridge will hybridize. The bridge is formed by degenerate bases (any base potentially at each position) and serves to maintain the spacing originally present between heptamer and nonamer. We show that such a bridging oligonucleotide probe can be used for hybridization analysis both on Southern blots and in bacterial screening.     

A laboratory class experiment to detect and quantify lovastatin in commercial medicaments

This article describes a laboratory class experiment for an undergraduate Biochemistry course for Chemistry students. The experimental work involves the extraction of lovastatin from a medicament utilized in the treatment of hypercholesterolemic patients, and its determination by spectroscopy and by reversed-phase high-performance liquid chromatography. The entire experiment can be performed in one laboratory period, e.g. less than one day.     

The use and abuse of pollinators by fungi

Some fungi use flower-visiting insects to facilitate sexual reproduction or to disperse spores. These fungi have evolved elaborate techniques, such as floral mimicry and the invasion of extant flower parts, for attracting 'pollinators'. Recent research shows that fungal exploitation of pollinators has the potential to affect floral evolution, pollination ecology, plant life history traits, as well as disease-transmission dynamics and fungal evolution.     

The use and abuse of population viability analysis

A recent study by Brook et al. empirically tested the performance of population viability analysis (PVA) using data from 21 populations across a wide range of species. The study concluded that PVAs are good at predicting the future dynamics of populations. We suggest that this conclusion is a result of a bias in the studies that Brook et al. included in their analyses. We present arguments that PVAs can only be accurate at predicting extinction probabilities if data are extensive and reliable, and if the distribution of vital rates between individuals and years can be assumed stationary in the future, or if any changes can be accurately predicted. In particular, we note that although catastrophes are likely to have precipitated many extinctions, estimates of the probability of catastrophes are unreliable.