Shrinking factors of hyperbranched polysaccharide from fungus

The branched structure properties of hyperbranched polysaccharides (TM3a and TM3b), extracted from sclerotia of Pleurotus tuber-regium, were studied by using laser light scattering and viscometry. The configurational shrinking factor (g) and viscometric shrinking factor (g′) of TM3a and TM3b were discussed, where curdlan and pullulan were taken as the linear references for derivation of g and g′. The dependences of g factor, g′ factor, and Flory factor (Φ_branched) on weight average molecular weight (M_w) were established to be g = 1.07 × 10²$M_{\text{w}}^{-0.48\pm 0.09}$, g′ = 3.63 × 10¹$M_{\text{w}}^{-0.43\pm 0.01}$, and Φ_branched = 7.08 × 10²⁰$M_{\text{w}}^{0.39\pm 0.1}$ for TM3a in 0.25 M LiCl/DMSO at 25 °C, when curdlan acted as the linear reference. A power law relationship g′ = 2.71 × 10^?1g^?0.61±0.1 for TM3a was found, and the exponent was approximately same to 0.60 established by Kurata et al. for polystyrene star molecules. The dependence of g factor on M_w for TM3b was found to be g = 1.99 × 10²$M_{\text{w}}^{-0.53\pm 0.02}$, when pullulan was used as the linear reference. On the basis of Zimm–Stockmayer equation for tetrafunctional units, molecular weight of branching unit (M₀) deduced from nonlinear curve fitting of g versus M_w was 8739 ± 564 g/mol and 3961 ± 1245 g/mol for TM3a and TM3b, respectively. The effect of different linear reference curves and polydispersity was discussed. This work gave valuable information on branched structure characterization and insights into the biosynthetic pathways of the hyperbranched polysaccharide from fungus.     

Reverse Na+/Ca2+-exchange mediated Ca2+-entry and noradrenaline release in Na+-loaded peripheral sympathetic nerves

[³H]noradrenaline ([³H]NA) released from sympathetic nerves in the isolated main pulmonary artery of the rabbit was measured in response to field stimulation (2 Hz, 1 ms, 60 V for 3 min) in the presence of uptake blockers (cocaine, 3 × 10⁻⁵ M and corticosterone, 5 × 10⁻⁵ M). The [³H]NA-release was fully blocked by the combined application of the selective and irreversible ‘N-type’ voltage-sensitive Ca²⁺-channel (VSCC)-blocker ω-conotoxin (ω-CgTx) GVIA (10⁻⁸ M) and the ‘non-selective’ VSCC-blocker aminoglycoside antibiotic neomycin (3 × 10⁻³ M). Na⁺-loading (Na⁺-pump inhibition by K⁺-free perfusion) was required to elicit further NA-release after blockade of VSCCs (ω-CgTx GVIA + neomycin). In K⁺-free solution, in the absence of functioning VSCCs (ω-CgTx GVIA + neomycin), the fast Na⁺-channel activator veratridine (10⁻⁵ M) further potentiated the nerve-evoked release of [³H]NA. This NA-release was significantly inhibited by KB-R7943, and fully blocked by $\text{C}{\text{a}}_{\text{o}}^{2+}-\text{removal}$. However, Li⁺-substitution was surprisingly ineffective. The non-selective K⁺-channel blocker 4-aminopyridine (4-AP, 10⁻⁴ M) also further potentiated the nerve-evoked release of NA in K⁺-free solution. This potentiated release was concentration-dependently inhibited by KB-R7943, significantly inhibited by Li⁺-substitution and abolished by $\text{C}{\text{a}}_{\text{o}}^{2+}-\text{removal}$.It is concluded that in Na⁺-loaded sympathetic nerves, in which the VSCCs are blocked, the reverse Na⁺/Ca²⁺-exchange-mediated Ca²⁺-entry is responsible for transmitter release on nerve-stimulation. Theoretically we suppose that the fast Na⁺-channel and the exchanger proteins are close to the vesicle docking sites.     

Tocopheramine succinate and tocopheryl succinate: Mechanism of mitochondrial inhibition and superoxide radical production

Tocopherols (TOH) are lipophilic antioxidants which require the phenolic OH group for their redox activity. In contrast, non-redox active esters of α-TOH with succinate (α-TOS) were shown to possess proapoptotic activity in cancer cells. It was suggested that this activity is mediated via mitochondrial inhibition with subsequent ${\text{O}}_2^{\text{<mglyph src="https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/16/entities/rad"></mglyph>}-}$ production triggering apoptosis and that the modification of the linker between the succinate and the lipophilic chroman may modulate this activity. However, the specific mechanism and the influence of the linker are not clear yet on the level of the mitochondrial respiratory chain. Therefore, this study systematically compared the effects of α-TOH acetate (α-TOA), α-TOS and α-tocopheramine succinate (α-TNS) in cells and submitochondrial particles (SMP). The results showed that not all cancer cell lines are highly sensitive to α-TOS and α-TNS. In HeLa cells α-TNS did more effectively reduce cell viability than α-TOS. The complex I activity of SMP was little affected by α-TNS and α-TOS while the complex II activity was much more inhibited (IC₅₀ = 42 ± 8 μM α-TOS, 106 ± 8 μM α-TNS, respectively) than by α-TOA (IC₅₀ >1000 μM). Also the complex III activity was inhibited by α-TNS (IC₅₀ = 137 ± 6 μM) and α-TOS (IC₅₀ = 315 ± 23 μM). Oxygen consumption of NADH- or succinate-respiring SMP, involving the whole electron transfer machinery, was dose-dependently decreased by α-TOS and α-TNS, but only marginal effects were observed in the presence of α-TOA. In contrast to the similar inhibition pattern of α-TOS and α-TNS, only α-TOS triggered ${\text{O}}_2^{\text{<mglyph src="https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/16/entities/rad"></mglyph>}-}$ formation in succinate- and NADH-respiring SMP. Inhibitor studies excluded complex I as ${\text{O}}_2^{\text{<mglyph src="https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/16/entities/rad"></mglyph>}-}$ source and suggested an involvement of complex III in ${\text{O}}_2^{\text{<mglyph src="https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/16/entities/rad"></mglyph>}-}$ production. In cancer cells only α-TOS was reproducibly able to increase ${\text{O}}_2^{\text{<mglyph src="https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/16/entities/rad"></mglyph>}-}$ levels above the background level but neither α-TNS nor α-TOA. Furthermore, the stability of α-TNS in liver homogenates was significantly lower than that of α-TOS. In conclusion, this suggests that α-TNS although it has a structure similar to α-TOS is not acting via the same mechanism and that for α-TOS not only complex II but also complex III interactions are involved.     

Flexible chain conformation of (1 → 3)-β-d-glucan from Poria cocos sclerotium in NaOH/urea aqueous solution

A water-insoluble polysaccharide (PCS3-II) extracted from sclerotium of Poria cocos was identified as a linear (1 → 3)-β-d-glucan by ¹³C NMR and gas chromatography. Aqueous 0.5 M NaOH/0.2 M urea was a good solvent for PCS3-II and the dependence of intrinsic viscosity ([η]) on weight-average molecular weight (M_w) was established in the M_w range from 7.68 × 10⁴ to 5.14 × 10⁵ to be [η] = 3.39 × 10^?2 $M_{\text{W}}^{0.62}{\text{cm}}^3{\text{g}}^{-1}$ at 25 °C by using laser light scattering and viscometry. The chain conformation parameters of PCS3-II in the 0.5 M NaOH/0.2 M urea solution was 2.3 (± 0.3) nm for persistence length (q), 580 g mol^?1 nm^?1 for molar mass per unit contour length (M_L), 0.8 (± 0.2) nm for the diameter of the chain (d) and 3.63 for limited characteristic ratio (C_∞). The results revealed, for the first time, that PCS3-II existed as a flexible chain in 0.5 M NaOH/0.2 M urea aqueous solution.     

Assessment of the Monitor Unit Objective tool for VMAT in the Eclipse treatment planning system

Aim

This work aims to achieve the highest possible monitor units (MU) reduction using the MU Objective tool included in the Eclipse treatment planning system, while preserving the plan quality.