Abstract  All presently used batteries contain reactive, corrosive or toxic components and require strong cases, usually made of steel. As a battery is miniaturized, the required case dominates its size. Hence, the smallest manufactured batteries are about 50 mm3 in size, much larger then the integrated circuits or sensors of functional analytical packages, as exemplified by implantable glucose sensors for diabetes management. The status of the miniaturization of the power sources of such implantable packages is reviewed. Three microcells, consisting only of potentially harmless subcutaneously implantable anodes and cathodes, are considered. Because their electrolyte would be the subcutaneous interstitial fluid, the cells do not have a case. One potentially implantable cell has a miniature Nafion-coated Zn anode and a biocompatible hydrogel-shielded Ag/AgCl cathode. The core innovation on which the cell is based is the growth of a hopeite-phase Zn2+ conducting solid electrolyte film on the discharging anode. The film blocks the transport of O2 to the Zn, preventing its corrosion, while allowing the necessary transport of Zn2+. The second cell, with the same anode, would have a bioinert hydrogel-shielded wired bilirubin oxidase-coated carbon cathode, on which O2 dissolved in the subcutaneous fluid would be electroreduced to water. In the third cell, the glucose of the subcutaneous interstitial would be electrooxidized to gluconolactone at an implanted wired glucose anode, similar to that tested now for continuous glucose monitoring in diabetic people, and O2 in the subcutaneous fluid would be electroreduced to water on its wired bilirubin oxidase cathode.

Abstract  Human Zn-alpha 2-glycoprotein (ZAG) in plasma samples from twelve populations was tested by immunoblotting after polyacrylamide gel isoelectric focusing. Eleven ZAG phenotypes produced by one common and nine rare alleles, including five new ones (ZAG*6-ZAG*10), were detected. Additionally, an application of separator IEF with N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) was found to be useful for discriminating the rare ZAG 7 band.

Abstract  High-speed chronoamperometry with Nafion-coated monoamine-sensitive electrodes was used to evaluate changes in the extracellular dopamine (DA) concentrations in the nucleus accumbens following each of a series of daily cocaine injections (15 mg/kg, i.p.; 5 days and challenge 3-4 days later) in freely moving rats. The first drug injection caused triphasic changes in the DA-dependent electrochemical signal. An initial transitory decrease in signal (equivalent of -45 nM DA) was followed by a slow increase (from 16 to 100 min; +155 nM) than a subsequent long-term and profound decrease (2-4 h; -100 to 200 nM). Subsequent daily injections did not cause an initial decrease; immediately after cocaine injection the signal increased rapidly to reach a peak of approximately 150-200 nM. The initial component of this signal increase (2-6 min) was more powerful with repeated daily injections, while the amplitude and duration of the signal increase were similar. Similar changes in locomotion were seen following repeated cocaine injections: movement activation occurred with shorter latency and reached a peak earlier, but total amount of counts was relatively stable. The gradual enhancement of the initial components of the electrochemical signal increase following repeated drug injections suggests that the mechanisms of conditioning contribute to the changes of mesolimbic DA accompanying development of cocaine sensitization.

Abstract  In the present study, we compared the changes in dopamine (DA) release and clearance in the striatum after unilateral 6-hydroxydopamine (6- OHDA) lesioning of the nigrostriatal DA pathway in urethane-anesthetized rats. High-speed in vivo chronoamperometric recording techniques using Nafion-coated carbon fiber electrodes were used to evaluate extracellular DA concentration. We found that DA release, induced by local KCl application in the striatum, was maximally suppressed 21 days after lesioning. DA clearance was also affected; however, the maximal effect occurred much earlier than changes in DA release. We found that 3-7 days after lesioning, extracellular DA concentration was significantly higher in the lesioned striatum after locally applying DA. Local application of nomifensine, which blocks high affinity DA uptake, did not further potentiate the amplitude and duration of DA overflow in these animals, suggesting that the high affinity uptake of DA was abolished 3-7 days after 6-OHDA lesioning. In conclusion, our data suggest that the time courses of changes in clearance and the release of DA are differentially affected by this selective neurotoxin.

Abstract  Evidence suggests that magnesium (Mg) deficiency may play a key role in cardiovascular disease. In particular, Mg deficiency may lead to a potentiation of platelet aggregation. However, the factor(s) regulating intracellular-free Mg concentration ([Mg2+]i) in platelets is not known. We studied the effects of insulin on the changes of [Mg2+]i in human platelets. Preincubation of hirudinized platelet-rich plasma with insulin had a dose- and time-dependent effect on the increase of [Mg2+]i measured in Mag-fura-2-loaded cells with a fluorescence spectrophotometer. The maximal effect was achieved by incubation with 200 microU/mL insulin for 30 min. [Mg2+]i increased from the basal value of 266 +/- 23 mumol to 355 +/- 46 (SD, P < 0.001). In the presence of an antiinsulin receptor monoclonal antibody the effect of insulin was abolished suggesting that the Mg transport mechanism was an insulin-receptor mediated process. Furthermore, the insulin-stimulated Mg transport was inhibited by the addition of chelating agent ethylenediaminete-traacetate while the receptor binding was not altered. These findings suggest that insulin can translocate Mg from the extracellular space. Insulin alone had no effect on the changes of intracellular calcium (Ca) concentration using Ca-Fura-2 as a probe. In addition, glucose (5 mg/mL) was not effective in altering either the Mg or Ca concentration. Insulin (100 microU/mL) decreased thrombin-induced platelet aggregation (washed platelets resuspended in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-Tyrode buffer). Similarly, the production of the proaggregatory eicosanoids thromboxane B2 was inhibited by insulin from 16 +/- 1 ng/10(8) platelets to 13 +/- 2 (P < 0.05). The results suggest that insulin, through the interactions with its receptors may be a key factor regulating, Mg transport in human platelets.

Abstract  Direct methanol fuel cell (DMFC) is promising as an energy conversion device for the replacement of conventional chemical cell in future, owing to its convenient fuel storage, high energy density and low working temperature. The development of DMFC technology is currently limited by catalyst poison and methanol crossover. To alleviate the methanol crossover, a novel fuel supply system based on ultrasonic atomization is proposed. Experimental investigations on this fuel supply system to evaluate methanol permeation rates, open circuit voltages (OCVs) and polarization curves under a series of conditions have been carried out and reported in this paper. In comparison with the traditional liquid feed DMFC system, it can be found that the methanol crossover under the ultrasonic atomization feed system was significantly reduced because the DMFC reaches a large stable OCV value. Moreover, the polarization performance does not vary significantly with the liquid feed style. Therefore, the cell fed by ultrasonic atomization can be operated with a high concentration methanol to improve the energy density of DMFC. Under the supply condition of relatively high concentration methanol such as 4M and 8M, the maximum power density fed by ultrasonic atomization is higher than liquid by 6.05% and 12.94% respectively.