Another factor perhaps affecting the differences in absolute protein levels between cerebral vessels and cremaster arterioles relates to differences in adventitial structure that we have previously demonstrated. It could be argued that these differences impact the access of the biotinylation reagents. We believe this to be unlikely, however, as the biotinylation reagents are small in regard to molecular weight and it was previously shown that the molecules easily penetrate the vascular wall. Further, while this could theoretically effect the magnitude of the protein expression levels it would not impact the a to b subunit ratios nor the distribution between the plasma membrane and cytosol. As both the cell surface biotinylation approach and measurements performed in crude membrane fractions showed qualitatively similar same results, the conclusion that protein expression levels are greater in cerebral vessels appears robust. In summary, significant differences exist with respect to the BKCa splice variants expressed in cremaster muscle arterioles compared with small arteries from the cerebral vasculature. Specifically, a higher expression level of the STREX variant of the a-subunit was observed in arterioles from cremaster muscle. While functional significance of this finding is yet to be fully demonstrated, it appears that it does not affect the plasma membrane location of the channels as.95% of a-subunit was found to be at the cell surface in both vessel preparations. In contrast, a marked difference in the detectable expression level was observed, with cerebral arteries expressing a-subunit protein at a level 20 times greater than that of cremaster arterioles. Trehalose alpha-Dglucopyranoside) is widely present in many organisms including yeasts, fungi, bacteria, plants and insects, but not in mammals. The synthesis of intracellular trehalose plays important functions in yeasts. It constitutes an endogenous storage of carbon and energy, it acts as stabilizer of cellular membranes and proteins and also functions as stress protector in yeast and fungi. Trehalose synthesis takes place in a sequential two-step reaction: trehalose 6-phosphate is synthesized from UDP-glucose and glucose 6-phosphate in a reaction catalyzed by a Mg-dependent trehalose 6-phosphate synthase. Then, a trehalose phosphatase, coded by the gene TPS2, dephosphorylates trehalose-6-phosphate to release free trehalose. Trehalose hydrolysis is essentially confined to a specific class of a-glucosidases that cleaves off the disaccharide, rendering two molecules of glucose, the enzyme trehalase . Most fungi possess two specialized and apparently unrelated trehalases, which differ in location, catalytic properties and regulation. Apoptosis is a naturally occurring event in placental cells. It plays an important role in placenta growth, turnover, senescence and parturition.