Immobilization of biocatalysts in thermogels using the resonance nozzle for rapid drop formation and an organic solvent for gelling

Summary The resonance nozzle immobilization technique was tested with thermo-hardening hydrogels (agar, gellan and -carrageenan) and compared with the conventional needle technique. After nozzling the warm gel solution, the formed droplets were caught in an ice-cold two-phase system consisting of an organic solvent (n-butylacetate, hexane or nonane) as top phase, in which gelling occurred, and aqueous medium as bottom phase. The cells used were yeast cells (Saccharomyces cerevisiae), bacterial cells (Mycobacterium aurum L1), plant cells (Tagetes minuta) and insect cells (Spodoptera frugiperda). The retention of the respiration activity was used as a criterion for the suitability of the conditions applied. The relatively polar solvent n-butylacetate with the low log P value gave the poorest activity retention, which is in agreement with experimentally validated theory. For all gels, the resonance nozzle technique proved to give satisfactory results, although the retention of respiration activity was generally lower than obtained with the needle technique.     

Characterization of a new Bacillus stearothermophilus isolate: a highly thermostable α-amylase-producing strain

A novel strain of Bacillus stearothermophilus was isolated from samples of a potato-processing industry. Compared to known -amylases from other B. stearothermophilus strains, the isolate was found to produce a highly thermostable -amylase. The half-time of inactivation of this -amylase was 5.1 h at 80°C and 2.4 h at 90°C. The temperature optimum for activity of the -amylase was 70°C; the pH optimum for activity was relatively low, in the range 5.5–6.0. -Amylase synthesis was regulated by induction and repression mechanisms. An inverse relationship was found between growth rate and -amylase production. Low starch concentrations and low growth temperatures were favourable for enzyme production by the organism. At the optimal temperature for growth, 65°C, the -amylase was a growth-associated enzyme. The optimal temperature for -amylase production, however, was 40°C, with -amylase increasing from 3.9 units (U)/ml to 143 U/ml when lowering the growth temperature from 65°C to 40°C. Maximal -amylase production in a batch fermentor run at 65°C was 102 U/ml, which was 26-fold higher than in erlenmeyer flasks at 65°C. The dissolved O₂ concentration was found to be a critical factor in production of the -amylase.     

Differentiating Psychopathy from General Antisociality Using the P3 as a Psychophysiological Correlate of Attentional Allocation

Recent studies have shown that while psychopathy and non-psychopathic antisociality overlap, they differ in the extent to which cognitive impairments are present. Specifically, psychopathy has been related to abnormal allocation of attention, a function that is traditionally believed to be indexed by event-related potentials (ERPs) of the P3-family. Previous research examining psychophysiological correlates of attention in psychopathic individuals has mainly focused on the parietally distributed P3b component to rare targets. In contrast, very little is known about the frontocentral P3a to infrequent novel events in psychopathy. Thus, findings on the P3 components in psychopathy are inconclusive, while results in non-psychopathic antisocial populations are clearer and point toward an inverse relationship between antisociality and P3 amplitudes. The present study adds to extant literature on the P3a and P3b in psychopathy by investigating component amplitudes in psychopathic offenders (N = 20), matched non-psychopathic offenders (N = 23) and healthy controls (N = 16). Also, it was assessed how well each offender group was able to differentially process rare novel and target events. The offender groups showed general amplitude reductions compared to healthy controls, but did not differ mutually on overall P3a/P3b amplitudes. However, the psychopathic group still exhibited normal neurophysiological differentiation when allocating attention to rare novel and target events, unlike the non-psychopathic sample. The results highlight differences between psychopathic and non-psychopathic offenders regarding the integrity of the neurocognitive processes driving attentional allocation, as well as the usefulness of alternative psychophysiological measures in differentiating psychopathy from general antisociality.     

Photochemistry of dyes and fluorochromes used in biology and medicine: some physicochemical background and current applications

An overview of the basic principles of photochemistry is presented to facilitate discussion of fluorescence, quenching and quantum yields. These topics in turn provide the foundation for an account of fluorescence spectroscopy and its application to microscopy. A brief overview of light microscopy and the application of fluorescence microscopy is given. The influences of molecular features, such as aromatic character and substitution patterns, on color and fluorescence are described. The concept of color fading is considered with particular reference to its effect on microscopic preparations. A survey of representative fluorescent probes is provided, and their sensitivity, application, and limitations are described. The phototoxicity of fluorescent molecules is discussed using biomembranes and DNA as examples of targets of toxicity. Photodynamic therapy, a relatively new clinical application of phototoxicity, is described. Both anticancer and antimicrobial applications are noted, and an assessment is given of the current ideas on the ideal physicochemical properties of the sensitizing agents for such applications.     

Is EEG-biofeedback an Effective Treatment in Autism Spectrum Disorders? A Randomized Controlled Trial

EEG-biofeedback has been reported to reduce symptoms of autism spectrum disorders (ASD) in several studies. However, these studies did not control for nonspecific effects of EEG-biofeedback and did not distinguish between participants who succeeded in influencing their own EEG activity and participants who did not. To overcome these methodological shortcomings, this study evaluated the effects of EEG-biofeedback in ASD in a randomized pretest–posttest control group design with blinded active comparator and six months follow-up. Thirty-eight participants were randomly allocated to the EEG-biofeedback, skin conductance (SC)-biofeedback or waiting list group. EEG- and SC-biofeedback sessions were similar and participants were blinded to the type of feedback they received. Assessments pre-treatment, post-treatment, and after 6 months included parent ratings of symptoms of ASD, executive function tasks, and 19-channel EEG recordings. Fifty-four percent of the participants significantly reduced delta and/or theta power during EEG-biofeedback sessions and were identified as EEG-regulators. In these EEG-regulators, no statistically significant reductions of symptoms of ASD were observed, but they showed significant improvement in cognitive flexibility as compared to participants who managed to regulate SC. EEG-biofeedback seems to be an applicable tool to regulate EEG activity and has specific effects on cognitive flexibility, but it did not result in significant reductions in symptoms of ASD. An important finding was that no nonspecific effects of EEG-biofeedback were demonstrated.     

Medium optimization for spore production of Coniothyrium minitans using statistically‐based experimental designs

Statistically‐based experimental designs were used to optimize a chemically defined solid medium for the spore production of Coniothyrium minitans. In the first optimization step the influence of starch, urea, phosphate, magnesium, calcium, thiamin and trace elements on spore production was evaluated using a fractional factorial design. Starch and trace elements influenced spore production positively while urea affected spore production negatively. The other components had no significant influence on spore production. In the second and third steps the concentrations of starch, urea and trace elements were further optimized using central composite designs and response surface analysis. This optimization strategy allowed the spore production to be increased by a factor 7 from 4 × 10⁹ to almost 3 × 10¹⁰ spores per Petri dish of 9 cm diameter. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 92–100, 1999.     

Cortisol stress response and histopathological alteration index in Clarias gariepinus exposed to sublethal concentrations of Qua Iboe crude oil and rig wash

The histological effect on and stress response of post juvenile Clarias gariepinus exposed to Qua Iboe crude oil and rig wash were investigated. Fish weighing 60–90 g and measuring 16–18 cm were exposed for 7–28 days to 8.00 ml^?1 Qua Iboe crude oil and 0.0018 ml^–1 rig wash, both being 0.1 of the 96 hr LC₅₀. Blood samples of C. gariepinus were collected every seven days and evaluated for stress by measuring cortisol concentration. The gills and liver were studied and scored for Gill Alteration Index (GAI) and Hepatic Alteration Index (HAI), respectively. There was an increase in cortisol level up to the 7th and 14th day among the group exposed to Qua Iboe crude oil, with a decrease on the 21st and 28th day. The rig wash group increased in cortisol level up to the 7th day and decreased slightly on the 14th day, after which the trend became irregular. The toxic effects of the Qua Iboe crude oil and rig wash were time dependent, as shown by the histopathological alteration index (HAI) of gill and liver. After 28 days of exposure, the gills had irreparable damage due to high frequency of cellular necrosis and degeneration, whereas the liver had from moderate to severe damage due to the high frequency of cellular degeneration and inflammation. Qua Iboe crude oil and rig wash are both toxic to C. gariepinus, therefore their indiscriminate discharge to the environment must be discouraged.