Iodine-123 labelled nor-beta-CIT binds to the serotonin transporter in vivo as assessed by biodistribution studies in rats

Flavobacterium aurantiacum NRRL B-184 possesses the ability to degrade aflatoxin B1 in solution and in several food items. Aflatoxin B1 is a potent carcinogen that causes significant economic losses to the agricultural and food industry. The role of trace metal ions (Cu2+, Mn2+, Zn2+, and Co2+) were studied in an effort to understand the enzymatic system involved in aflatoxin B1 degradation by F aurantiacum. The effect of divalent chelators (EDTA and 1,10-phenanthroline [OPT]) in the presence of the trace metal ions was studied as well. Aflatoxin B1 (10 microg/ml) was added to 72-h cultures of F aurantiacum that had been washed and resuspended in phosphate buffer (pH 7.0). HPLC was used to determine aflatoxin B1 concentration in these cultures. Incubating cells at 30 degrees C with 1 and 10 mM Cu2+, Mn2+, and Zn2+ significantly decreased aflatoxin B degradation after 4 and 24 h (P < 0.05). Decreased degradation was also observed with 1 and 10 mM Cu2+ and Zn2+ after 48 h and with 0.1 mM Cu2+ after 24 and 48 h. Co2+ did not have a significant effect on aflatoxin B1 degradation. EDTA and OPT did not counter the inhibition in the presence of Cu2+. The addition of 1 mM EDTA countered the inhibition by 1 mM Mn2+ after 4 and 24 h, but 1 mM OPT did not counter the inhibition by 10 mM Mn2+ after 4 and 24 h. OPT countered the inhibition by 1 mM Zn2+ after 4 and 48 h. These trace elements inhibit aflatoxin B1 degradation by F aurantiacum. In addition, their presence necessitates higher concentrations (>1 mM) of EDTA and OPT for the removal of their inhibitory effect.     

ANALYSIS OF EXPERIMENTAL AND NUMERICAL RESULTS OF A TURBULENT SWIRLING FLOW IN A TUBE

In many applications swirling flow is used to enhance heat and mass transfer. One of the problems of modelling a turbulent swirling flow is the choice of the turbulent closure model which is acceptable for engineering purposes. To evaluate which model performs best, numerical results are compared with experimental data. Local velocity measurements are carried out on a swirling flow in a circular tube. The measurement method is hot-wire anemometry combined with visualization techniques. The numerical analysis is carried out using the k-ε model and the Algebraic Stress Model. In the experiment a symmetrical swirl was observed, Comparing the experimental data with the numerical results shows that the Algebraic Stress Model represents the experimental data quite well, whereas the k-ε model fails.     

Trp82 and Tyr332 are involved in two quaternary ammonium binding domains of human butyrylcholinesterase as revealed by photoaffinity labeling with [3H]DDF

Purified butyrylcholinesterase (BuChE) was photolabeled by [3H]-p-N, N-dimethylamino benzene diazonium ([3H]DDF) to identify the quaternary ammonium binding sites on this protein [Ehret-Sabatier, L. , Schalk, I., Goeldner, M., and Hirth, C. (1992) Eur. J. Biochem. 203, 475-481]. The covalent photoincorporation occurs with a stoichiometry of one mole of probe per mole of inactivated site and could be fully prevented by several cholinergic inhibitors such as tacrine or tetramethylammonium. After complete deglycosylation of the enzyme using N-glycosidase F, the alkylated protein was trypsinolyzed and the digests were analyzed by HPLC coupled to ES-MS. A direct comparison of tryptic fragments from labeled and unlabeled BuChE allowed us to identify the tryptic peptide Tyr61-Lys103 as carrying the probe. Purification of the labeled peptides by anion-exchange chromatography gave a major radioactive peak which was further fractionated by reversed-phase HPLC leading to three, well-resolved, radioactive peaks. Microsequencing revealed that two of these peaks contained an overlapping sequence starting at Tyr61, while the third peak contained a sequence extending from Thr315. Radioactive signals could be unambiguously attributed to positions corresponding to residues Trp82 and Tyr332. This labeling study establishes the existence of two different binding domains for quaternary ammonium in BuChE and exemplifies additional cation/pi interactions in cholinergic proteins. This work strongly supports the existence of a peripheral anionic site in BuChE, implying residue Tyr332 as a key element.     

Tailored versus realistic geometry in the inverse problem ofelectrocardiography

The stability and applicability of a previously developed inverse procedure for the noninvasive determination of the activation sequence of the human heart has been evaluated. In particular, the possibility of using a standard geometrical configuration representing the heart and the inhomogeneous volume conductor in this procedure has been tested. Results show that in order to obtain reliable inverse solutions, true "tailored" geometry should be used.     

Noise and dynamic range optimization of SAW transversal filters

A model for surface acoustic wave (SAW) transversal filters with special attention to the system and circuit designer's point of view is summarized. In the ideal situation the SAW transversal filter is driven with a voltage and the short-circuit current is sensed, which results in a minimization of the triple transit echo distortion. The aperture (width) of the SAW device is the only parameter that is not determined by the frequency dependence of the transfer and therefore it can be used to optimize the SAW device in relation to the electronic circuitry. Noise and dynamic range calculations on an amplifier-filter-amplifier configuration, are performed. It is shown that for a low noise floor at the input of the SAW device, the aperture of this device should be chosen large. However, the dynamic range of the amplifier-filter-amplifier configuration can be maximized by choosing a small aperture.     

Hygienic aspects of porcine gullets

In an attempt to elaborate good manufacturing practices, including the collection, processing and storage of porcine gullets, their bacterial condition immediately after collection (100 samples), as well as that of deep frozen gullets just before incorporation into meat products (40 samples), was assessed. Fresh gullets were found to be contaminated to a high degree: poured plate colony count at 30°C (PPCC) approximately 10(6) to 10(7) and Enterobacteriaceae approximately 10(3) to 10(4) cfu g(-1). Deep frozen gullets showed even higher counts: PPCC approximately 10(7) to 10(8) and Enterobacteriaceae approximately 10(4) to 10(5) cfu g(-1). Hygiene during collection was visually assessed in six abattoirs and found to be satisfactory in two, moderate in three and poor in one. The effects of processing, by cleaning or removal of the mucus membrane, on bacterial condition, pH, colour and odour were assessed before and during storage at 4°C and 20°C. Both cleaning and removal of the mucus membrane resulted in up to approximately a tenfold reduction of colony counts. After 7 days' storage at 4°C these were significantly lower than those of unprocessed gullets (P < 0·01). Processed gullets stored at 4°C were no longer fit for consumption after 4 days' storage. It being impossible to achieve a marked improvement in the bacteriological condition of gullets, the incorporation of these products into sausages should be discouraged and their use in petfoods only allowed under reasonable conditions of hygiene and chilling.