Novel PVC-based membrane sensors selective for vanadyl ions.

Poly(vinyl chloride) based membranes of di-(2-ethylhexyl)phosphoric acid (DEHPA) and dibutyl(butyl)phosphonate (DBBP) have been prepared and investigated as VO(2+)-selective sensors. The membranes containing DEHPA/DBBP and sodium tetraphenylborate, an anion excluder, show near-Nernstian/Nernstian response in the concentration range approximately 10(-5)-10(-1) M. The sensors exhibit a fast response time and good selectivity for VO(2+) over a number of other cations. Quantitative determination of vanadium in waste V(2)O(5) catalyst has been achieved by these sensors and they have also been used as indicator electrodes for the determination of the end point in the potentiometric titration of VO(2+) against EDTA.

Calcium, calmodulin and protein kinase C dependence of platelet shape change.

Platelet shape change (PSC) represents the initial phase of platelet activation and is normally investigated in ethylene diamine tetraacetic acid (EDTA) containing platelet rich plasma (PRP); EDTA is a potent chelator of calcium and therefore reduces ionized calcium to negligible levels. It is therefore assumed that it is a process independent of calcium. To test the hypothesis that PSC may be dependent upon intracellular calcium, we examined the effect of 8-(N,N-Diethylamino) octyl 3,4,5-Trimethoxybenzoate hydrochloride (TMB-8), an inhibitor of intercellular calcium mobilization on PSC. It produced a dose dependent inhibition of PSC. We then examined whether PSC was dependent upon calmodulin and protein kinase C, a calcium dependent enzyme which is cardinal to platelet aggregation. Both calmidazolium, a specific inhibitor of calmodulin, and H-9, a specific inhibitor of protein kinase C, produced dose dependent inhibition of PSC. Finally, we investigated whether GP IIb/IIIa receptor which binds fibrinogen was involved in PSC; DMP 728 [(cyclic [D-2-amino-butyryl-N2-methyl-L-arginyl-glycyl-L-aspartyl-3- (a min o-methyl-benzoic acid], methanesulfonic acid salt] a potent GP IIb/IIIa receptor antagonist was without any effect on PSC. We conclude that PSC is a calcium, calmodulin and protein kinase C dependent process like platelet aggregation but that it does not require extracellular calcium or the participation of platelet GP IIb/IIIa complex.

Effects of source leukocyte collection on the immune system.

This study was initiated in order to assess any immunologic effects that source leukocyte concentrate collection might have on double-bag plasmapheresis donors. Previous studies have shown that surveillance parameters, such as T versus non-T lymphocyte subpopulations, showed no abnormal values in donors with as many as 500 visits over a 12-year period. The present study demonstrates that the frequency and the total number of leukocyte donations do not effect the lymphocyte subpopulations and functions observed. No significant changes were noted for specific and nonspecific stimulation, natural killer (NK) cell activity, lymphocyte surface markers and a variety of functional parameters. For example, the apheresis donors manifested no differences in NK cell activity, human leukocyte interferon production, IgG synthesis by B cells and percent suppression of both IgG synthesis and mixed lymphocyte cultures, when compared to non-apheresed donors.