This review is focused on distribution and redistribution of trace elements in various tissues of different shrimp species, especially genus Penaeus. The possible roles of metallothionein in this regard are emphasized. Factors affecting heavy metals uptake and distribution have also been reviewed separately. Moreover, patterns of metals bioaccumulation and their order of occurrence have been evaluated. Another part of this paper deals with comparison of the related data from different aquatic environments as well as existing guidelines and limits for human consumption. Generally, the number of conducted studies in some related context, especially in the case of possible roles of metallothionein during storage of organisms is very limited.

Output from jet nebulisers is calibrated traditionally by weighing them before and after nebulisation, but the assumption that the weight difference is a close measure of aerosol generation could be invalidated by the concomitant process of evaporation. A method has been developed for measuring aerosol output directly by using a solute (fluoride) tracer and aerosol impaction, and this has been compared with the traditional weight loss method for two Wright, six Turbo, and four Micro-Cirrus jet nebulisers and two Microinhaler ultrasonic nebulisers. The weight loss method overestimated true aerosol output for all jet nebulisers. The mean aerosol content, expressed as a percentage of the total weight loss, varied from as little as 15% for the Wright jet nebulisers to 54% (range 45-61%) for the Turbo and Micro-Cirrus jet nebulisers under the operating conditions used. In contrast, there was no discrepancy between weight loss and aerosol output for the ultrasonic nebulisers. These findings, along with evidence of both concentrating and cooling effects from jet nebulisation, con Glass fibre filter onto which NaF laden aerosols impact jet nebuliser reservoir containing 1 % w/v NaF mm GF/A filters, through which air was drawn at 25 1/min. A higher flow rate and larger filter were used for the ultrasonic nebulisers because the filter could not be positioned as close to the source of nebulisation. After aerosol collection GF/A filters were removed and stored for later analysis. For flow rates of 15 1/min and above and for aerosols having a mass median diameter of 0 3 gm or more the collection efficiency of GF/A filters exceeds 99 9%.18 When a second filter was placed in series we detected no aerosol breakthrough.Analysis of aerosol output Total ionic strength adjustment buffer (TISAB; BDH Chemicals Ltd) was prepared as a 50% solution in distilled water, and 20 ml were added to each Whatman filter within 25 ml plastic Universal bottles. The bottles were then sealed and fluoride was allowed to desorb overnight. The recovery of fluoride from filters was complete (> 98%) and no fluoride was detected in unused filters. Fluoride analysis followed well established protocols.'9 Fluoride standards were prepared by microlitre injections of 5 0, 10-0, and 15-0 pl of 1 00% sodium fluoride into 20 ml aliquots of 50% TISAB buffer, resulting in 5-95E-5M, 1 19E'M, and 1 *78E'M fluoride solutions. Both standard and test solutions were equilibrated to 25°C in a water bath. Fluoride concentrations within the buffered solutions were then measured electrochemically with a fluoride specific ion electrode (Corning Ltd, Halstead) on a Corning 255 pH/ ion meter with a calomel reference electrode. This electrochemical system had a log-linear relation between concentration and activity (mV) from 10-'M to 10'M F. All solutions were continually agitated during analysis with an electromagnetic stirrer. An internal two point calibration was established with the 5 and 15 pl fluoride standards and its accuracy was checked with the 10 p1 standard....

Background The value of measuring airway responsiveness in asthma research is currently limited by the number of different methods used by different investigators, by the lack of a standardised method of expressing precision, and by an inability to equate the results of one method with those of another. Methods Two pairs of measurements of airway responsiveness to methacholine were performed in 20 asthmatic subjects, one pair using a dosimeter method (AR-D) and one pair using the conventional Wright nebuliser tidal breathing method (AR-W). The two methods normally use different techniques for quantifying changing levels in forced expiratory volume in one second (FEV,) after each dose of methacholine (the mean of the highest three of six measurements for AR-D, the lower of two measurements for AR-W), and different techniques for expressing measurements of airway responsiveness (the provoking dose (PD20) and the provoking concentration (PCQ0) respectively responsible for a 20% decrement in FEV,). Results The coefficient of repeatability (and hence precision) for the measurement of airway responsiveness was significantly better for AR-D (3.0) than for AR-W (10.9), but the technique for quantifying FEV, contributed more to this than the technique for delivering methacholine. A PCQ0 of 1 mg/ml with AR-W was equivalent to a PD,0 of 103 pg withConclusions It is practical as well as desirable to compare the precision of different techniques for the measurement of airway responsiveness and to derive conversion factors so that results may be equated. (Thorax 1993;48:239-243) Airway responsiveness provides a useful concept in understanding asthma and its measurement is valuable in asthma research. Of the various bronchoconstrictor stimuli used, nebulised methacholine is probably the most popular. At present several different methods of methacholine delivery are employed together with various different methods of expressing or measuring airway responsiveness. This limits the value of such measurements because the results from one laboratory cannot readily be compared with those from another. There is consequently a need to establish some means of defining precision in measurement-for example, coefficient of repeatability-and of equating results between methods.Of the two measurement methods which are currently most popular, that using the Wright nebuliser has become the conventional one throughout much of Canada, Australasia and Europe.' Aerosol is generated continuously over successive periods of two minutes from doubling concentrations of methacholine and is inhaled by the test subject during tidal breathing. The dose delivered consequently depends on tidal volume and ventilatory frequency as well as on aerosol output and so is not readily quantified, although it may be closely repeatable for the individual subject. As a result airway responsiveness is expressed by the provoking concentration of methacholine (rather than the delivered dose) which is estimated to provoke a 20% decrement in the forced expirator...

Concentrations of cadmium, lead, nickel and vanadium were determined in water, surficial sediments and the muscle of three demersal fish species (Epinephelus coioides, Psettodes erumei and Solea elongate) from 15 sampling sites in the northern part of Persian Gulf. Concentrations of the elements were determined using Inductively Coupled Plasma Mass Spectrometer. There were no significant differences among the sampling sites in Cd and Pb levels in the sediments. The highest concentrations of Ni and V in sediments were found near the southern coast of Qeshm Iland and Bandar Lengeh. Concentrations of Cd, Pb and Ni in the sediments were notably higher than global baseline values. Nearly in all cases the element concentrations in the sediments were considerably greater than RSA (ROPME Sea Area) and the ERL (Effects Range Low) guidelines. Significant differences among the sampling sites could be found for concentrations of all the four metals in water. The mean Ni, Pb and Cd levels in the water samples were relatively higher than those in some other regions of the Persian Gulf. Except few cases, the mean concentrations of the elements in muscle of the selected fish species were markedly below the international guidelines for human consumption.