The assembly of lipid-linked oligosaccharides in plant and animal membranes.

Membrane preparations from growing regions of pea stems and actively-dividing mouse L-cells form lipid-linked saccharides from GDP-mannose and UDP-N-acetylglucosamine. These lipids have properties which are consistent with those of mono- and di-phosphoryl polyisoprenyl derivatives. In experiments using plant membranes, the monophosphoryl derivative labeled with GDP-(14C) mannose contains mannose only, while the diphosphoryl derivative labeled with the same nucleotide sugar is heterogeneous, containing oligosaccharides corresponding to mannosaccharides of 5, 7, and 9--12 residues. Only the diphosphoryl polyisoprenyl derivatives are labeled with UDP-(14C)glucosamine and these contain predominantly chitobiose and N-acetylglucosamine itself. Unlabeled GDP-mannose added after UDP-N-acetyl-(14C)glucosamine results in the formation of higher lipid-linked oligosaccharides which are apparently the same as those which are labeled with GDP-(14C)mannose alone. Incubation of the membranes with GDP-(14C)mannose in the presence of Mn2+, unlabeled UDP-glucose or unlabeled UDP-N-acetylglucosamine results in marked changes in the accumulation of both the polyisoprenyl monophosphoryl mannose and polyisoprenyl diphosphoryl oligosaccharides. Animal cell membranes synthesise lipid-linked oligosaccharides when incubated with UDP-N-acetylglucosamine and GDP-mannose. These oligosaccharides are similar in size to those synthesised by the plant membranes but their formation is more efficient. The potential roles of these compounds in glycoprotein biosynthesis in both plant and animal tissues is discussed.     

The mass spectra of dimethoxyamphetam1ne Hydrochlorides

The six dimethoxyamphetamine hydrochlorides give weak but distinguishable mass spectra useful for analytical purposes. The principal fragmentation pathways are discussed in terms of the changing aromatic substitution pattern.     

An EPR study of a triplet state center in (NH4)2SO4

Heating ammonium sulphate to near its dissociation temperature and then quenching to room temperature produces a stable triplet state center that is identified as NH₂⁺. The symmetry of the EPR spectra indicates that the center is located in two non equivalent sites with each of these sites having slightly different EPR parameters and two measurably differents orientations. Thus the center is apparently occupying the positions of the NH₄⁺ groups in the perfect lattice. A study is made of this center both at room temperature and also well below the ferroelectric phase transition of (NH₄)₂SO₄. It is found that above and below the transition temperature (?50°C) there is very little temperature dependence of the EPR spectra but at the phase transition there is an abrupt change in the spectra. The number of detectable centers doubles below the phase transition indicating that the inversion symmetry of the NH₂⁺ sites is eliminated at the transition temperature.     

Comparison of tumor histology to dynamic contrast enhanced magnetic resonance imaging-based physiological estimates

Purpose

The purpose of this study was to compare histologically determined cellularity and extracellular space to dynamic contrast-enhanced magnetic resonance imaging (DCE MRI)-based maps of a two-compartment model's parameters describing tumor contrast agent extravasation, specifically tumor extravascular extracellular space (EES) volume fraction (v_e), tumor plasma volume fraction (v_p) and volume-normalized contrast agent transfer rate between tumor plasma and interstitium (K_TRANS/V_T).

Materials and Methods

Obtained v_e, v_p and K_TRANS/V_T maps were estimated from gadolinium diethylenetriamine penta-acetic acid DCE T₁-weighted gradient-echo images at resolutions of 469, 938 and 2500 μm. These parameter maps were compared at each resolution to histologically determined tumor type, and the high-resolution 469-μm maps were compared with automated cell counting using Otsu's method and a color-thresholding method for estimated intracellular (V_{intracellular}) and extracellular (V_{extracellular}) space fractions.

Results

The top five K_TRANS/V_T values obtained from each tumor at 469 and 938 μm resolutions are significantly different from those obtained at 2500 μm (P<.0001) and from one another (P=.0014). Using these top five K_TRANS/V_T values and the corresponding tumor EES volume fractions v_e, we can statistically differentiate invasive ductal carcinomas from noninvasive papillary carcinomas for the 469- and 938-μm resolutions (P=.0017 and P=.0047, respectively), but not for the 2500-μm resolution (P=.9008). The color-thresholding method demonstrated that v_e measured by DCE MRI is statistically similar to histologically determined EES. The V_{extracellular} obtained from the color-thresholding method was statistically similar to the v_e measured with DCE MRI for the top 10 K_TRANS/V_T values (P>.05). DCE MRI-based K_TRANS/V_T estimates are not statistically correlated with histologically determined cellularity.

Conclusion

DCE MRI estimates of tumor physiology are a limited representation of tumor histological features. Extracellular spaces measured by both DCE MRI and microscopic analysis are statistically similar. Tumor typing by DCE MRI is spatial resolution dependent, as lower resolutions average out contributions to voxel-based estimates of K_TRANS/V_T. Thus, an appropriate resolution window is essential for DCE MRI tumor diagnosis. Within this resolution window, the top K_TRANS/V_T values with corresponding v_e are diagnostic for the tumor types analyzed in this study.     

X-rays from antiprotonic helium in helium gas

X-ray transitions to the 4F, 3D, and 2P atomic levels of p?He have been observed with antiprotons stopped in He gas at 4 and 1.1 atm NT. The population by radiative transitions of the 3D level in gas Y_M(4atm) = (28±14)% and Y_M(1.1 atm) = (43±22)% exceeds by more than one order of magnitude that measured in liquid He. The annihilation width of the 3D level Γ^a_3D = 2.8±1.0 × 10^?3eV is determined from the ratio between the numbers of X-rays feeding and depopulating the 3D level. The strong-interaction shift of the 2P level ε(2P) = ?14±6 eV is obtained by inputting the $\text{p}\text{He}$ experimental X-ray yields into a cascade calculation, the results of which are in good agreement with well-established data from muonic, pionic, and kaonic helium.     

Comparison between two sufficient conditions for improvement of an optimal steady-state process by periodic operation

Two sufficient conditions for improvement of performance by cycling beyond that obtained at the best steady state are compared. It is shown that Condition I, which is derived from relaxed steady-state analysis, is always stronger than Condition II, which results from the maximum principle. That is, in every case in which Condition II guarantees improvement, Condition I does also. However, there are examples where Condition I assures improvement, while Condition II fails to indicate the possibility of greater performance by cyclic operation.     

α-Substituted diisopropylbenzene hydroperoxides for low-temperature SBR polymerization

Four pure hydroperoxides were evaluated as initiators for the polymerization of styrene–butadiene rubber (SBR) at 5°C. These materials were the meta and para isomers of mono- and dihydroperoxy-diisopropylbenzene. Results showed that the monohydroperoxides produced somewhat faster reactions than a control hydroperoxide, p-menthane hydroperoxide. Response to mercaptan level adjustments was good, providing polymer with a Mooney viscosity in the 50 to 60 range. The reaction rate with the dihydroperoxides was slower, but again provided polymer with a satisfactory viscosity. Basic physical property measurements on polymers prepared with the pure hydroperoxides or control hydroperoxides showed only minor differences. It is anticipated that these differences can be eliminated by small adjustments in the compound recipe.     

Radiating shock measurements in the Z-pinch dynamic hohlraum

The Z-pinch dynamic hohlraum is an x-ray source for high energy-density physics studies that is heated by a radiating shock to radiation temperatures >200 eV. The time-dependent 300-400 eV electron temperature and 15-35 mg/cc density of this shock have been measured for the first time using space-resolved Si tracer spectroscopy. The shock x-ray emission is inferred from these measurements to exceed 50 TW, delivering >180 kJ to the hohlraum.