Effects of cyclopiazonic acid and dexamethasone on serotonin-induced calcium responses in vascular smooth muscle cells

We previously observed that sarcoendoplasmic reticulum Ca(2+) ATPase (SERCA) blockade by cyclopiazonic acid (CPA) significantly potentiates serotonin (5-hydroxytryptamine (5-HT))-induced vascular contractions. Furthermore, 5-HT receptor antagonist methysergide partially inhibited CPA-potentiated 5-HT contractions. In the present study, we further investigated whether SERCA inhibition potentiates 5-HT-induced Ca(2+) responses along with attenuating the receptor antagonism by store-operated Ca(2+) (SOC) entry and protein kinase C (PKC)-mediated mechanisms. The effects of dexamethasone that was previously shown to induce SOC entry and enhance 5-HT responses were also tested. For this purpose, intracellular Ca(2+) levels were monitored in A7r5 embryonic rat vascular smooth muscle cells by spectrofluorometry using the fluorescent indicator fura-2. The results showed that CPA, although not dexamethasone, significantly potentiated 5-HT-induced Ca(2+) elevations. Ketanserin partially decreased 5-HT-induced and CPA-potentiated Ca(2+) elevations whereas both PKC inhibitor D-sphingosine and SOC entry blocker 2-aminoethoxydiphenyl borate (2-APB) abolished the remaining responses. The data suggests that diminished antagonistic effect on 5-HT-induced Ca(2+) elevations in the presence of SERCA inhibition is induced by SOC entry and PKC activation

Complexation between hydrophobically modified polymers and amylose. Gelation and competition by surfactants.

Aqueous mixtures of hydrophobically modified polymers (HMP) with amylose have been investigated by rheology and 1H NMR. Amylose can cross-link HMP chains by forming single-helical inclusion complexes with the hydrophobic side chains of the HMP, leading to thermoreversible, elastic, and thixotropic gels at ambient temperatures. The complexation ability, the strength of the association, and the viscoelastic behaviour of the gels vary with the concentrations of amylose and HMP. The rheology of the gels can be further controlled by the length of the alkyl chains of the HMP and by the addition of short hydrophilic ”spacers” between the alkyl chains and the HMP backbone. An increase in the alkyl chain length gives larger increase in the gel strength than a similar increase in spacer length. Linear surfactants also form inclusion complexes with amylose. Two types of structures, loose fibrous networks and unilamellar vesicles, were observed by cryogenic transmission electron microscopy of dilute aqueous mixtures of amylose and sodium dodecyl sulfate. Both types of structures are believed to consist of inclusion complexes where SDS-molecules are enclosed in amylose helices. Surfactants can compete with the amylose-HMP complexation. The strength of the competition varies with the length and bulkiness of the hydrophobic ”tail” of the surfactant. In mixtures of surfactant, amylose, and HMP, the HMP hydrophobes are engaged in two types of complexes, i.e., mixed micelles with added surfactant and inclusion complexes with amylose, over a large concentration range of the added surfactant. A range of different surfactants, when added to amylose-free HMP solutions, were found to give rise to the well-established viscosity maximum with increasing surfactant concentration, due to a mixed micellization between surfactant molecules and the hydrophobic side chains of the HMP. The surfactants affect both the lifetime and the structure of the HMP – surfactant network. The viscosity maximum is the result of two opposing effects of increasing surfactant concentration: an increase in the lifetime of mixed micellar cross-links and a decrease in the number of cross-links. The difference in viscosifying ability between different surfactant is due to differences in the lifetimes of the mixed micellar cross-links

Dialogstudie under en kemilaboration

Syftet med denna studie är att undersöka hur vuxna elever med olika studiegång kommunicerar med varandra för att uppnå begreppsförståelse. Undersökningen tar också upp om sättet för kommunikation skiljer sig åt mellan elevgrupper. Tre grupper av komvuxelever spelades in på band under en kemilaboration. Dialogen analyserades sedan. Undersökningen tyder på att reguljära elever har ett tydligare kommunikationsmönster än distanselever. Reguljära elever pratar mer på jämlik nivå och har livligare diskussioner jämfört med distanseleverna. Elever som har svenska som första språk kommunicerar annorlunda med varandra än elever som har svenska som andra språk. Även samarbetet under laborationen skiljer sig åt mellan reguljära elever och distanselever, där reguljära elever samarbetar mer

Gels of hydrophobically modified ethyl (hydroxyethyl) cellulose cross-linked by amylose: Effects of hydrophobe architecture

Previous work has shown that amylose (AM) can cross-link hydrophobically modified polymers by inclusion complexation, whereby thermoreversible cold-setting gels are formed. Here we investigate the complexation of AM with different samples of hydrophobically modified ethyl(hydroxyethyl) cellulose (HMEHEC), distinguished by differences in the architecture of the hydrophobes (the hydrophobic side chains). All hydrophobes, except one, were based on linear alkyl chains, but with varying chain lengths (C-12-C-14). In addition, some samples contained short hydrophilic "spacers", consisting of 2-5 ethylene oxide units, between the alkyl chains and the EHEC backbone. Gels of varying strength were obtained for the different AM/HMEHEC samples. The alkyl chain length seemed to be the major factor affecting the gel strength, with longer alkyl chains giving stronger gels. For similar alkyl chain lengths, stronger gels were obtained when a spacer was present. Addition of AM caused a small increase of the cloud points of HMEHECs with C-14 hydrophobes in water. Time-dependent effects and effects of the sample preparation procedure were also investigated. The reversibility of the gelation with respect to shear was confirmed. A gel destroyed by added surfactant was shown to reform on removal of the surfactant by dialysis