Glucocorticoid-regulated localization of cell surface glycoproteins in rat hepatoma cells is mediated within the Golgi complex.

Glucocorticoid hormones regulate the post-translational maturation and sorting of cell surface and extracellular mouse mammary tumor virus (MMTV) glycoproteins in M1.54 cells, a stably infected rat hepatoma cell line. Exposure to monensin significantly reduced the proteolytic maturation and externalization of viral glycoproteins resulting in a stable cellular accumulation of a single 70,000-Mr glycosylated polyprotein (designated gp70). Cell surface- and intracellular-specific immunoprecipitations of monensin-treated cells revealed that gp70 can be localized to the cell surface only in the presence of 1 microM dexamethasone, while in uninduced cells gp70 is irreversibly sequestered in an intracellular compartment. Analysis of oligosaccharide processing kinetics demonstrated that gp70 acquired resistance to endoglycosidase H with a half-time of 65 min in the presence or absence of hormone. In contrast, gp70 was inefficiently galactosylated after a 60-min lag in uninduced cells while rapidly acquiring this carbohydrate modification in the presence of dexamethasone. Furthermore, in the absence or presence of monensin, MMTV glycoproteins failed to be galactosylated in hormone-induced CR4 cells, a complement-selected sorting variant defective in the glucocorticoid-regulated compartmentalization of viral glycoproteins to the cell surface. Since dexamethasone had no apparent global effects on organelle morphology or production of total cell surface-galactosylated species, we conclude that glucocorticoids induce the localization of cell surface MMTV glycoproteins by regulating a highly selective step within the Golgi apparatus after the acquisition of endoglycosidase H-resistant oligosaccharide side chains but before or at the site of galactose attachment

Ray-tracing in pseudo-complex General Relativity

Motivated by possible observations of the black hole candidate in the center of our galaxy and the galaxy M87, ray-tracing methods are applied to both standard General Relativity (GR) and a recently proposed extension, the pseudo-complex General Relativity (pc-GR). The correction terms due to the investigated pc-GR model lead to slower orbital motions close to massive objects. Also the concept of an innermost stable circular orbit (ISCO) is modified for the pc-GR model, allowing particles to get closer to the central object for most values of the spin parameter $a$ than in GR. Thus, the accretion disk, surrounding a massive object, is brighter in pc-GR than in GR. Iron K$\alpha$ emission line profiles are also calculated as those are good observables for regions of strong gravity. Differences between the two theories are pointed out.Comment: revised versio

Collective Modes of Tri-Nuclear Molecules

A geometrical model for tri-nuclear molecules is presented. An analytical solution is obtained provided the nuclei, which are taken to be prolately deformed, are connected in line to each other. Furthermore, the tri-nuclear molecule is composed of two heavy and one light cluster, the later sandwiched between the two heavy clusters. A basis is constructed in which Hamiltonians of more general configurations can be diagonalized. In the calculation of the interaction between the clusters higher multipole deformations are taken into account, including the hexadecupole one. A repulsive nuclear core is introduced in the potential in order to insure a quasi-stable configuration of the system. The model is applied to three nuclear molecules, namely $^{96}$Sr + $^{10}$Be + $^{146}$Ba, $^{108}$Mo + $^{10}$Be + $^{134}$Te and $^{112}$Ru + $^{10}$Be + $^{130}$Sn.Comment: 24 pages, 9 figure

A Solvable Model for Many Quark Systems in QCD Hamiltonians

Motivated by a canonical, QCD Hamiltonian we propose an effective Hamiltonian to represent an arbitrary number of quarks in hadronic bags. The structure of the effective Hamiltonian is discussed and the BCS-type solutions that may represent constituent quarks are presented. The single particle orbitals are chosen as 3-dimensional harmonic oscillators and we discuss a class of exact solutions that can be obtained when a subset of single-particle basis states is restricted to include a certain number of orbital excitations. The general problem, which includes all possible orbital states, can also be solved by combining analytical and numerical methods.Comment: 24 pages, 2 figures, research articl

Self diffusion in a system of interacting Langevin particles

The behavior of the self diffusion constant of Langevin particles interacting via a pairwise interaction is considered. The diffusion constant is calculated approximately within a perturbation theory in the potential strength about the bare diffusion constant. It is shown how this expansion leads to a systematic double expansion in the inverse temperature $\beta$ and the particle density $\rho$. The one-loop diagrams in this expansion can be summed exactly and we show that this result is exact in the limit of small $\beta$ and $\rho\beta$ constant. The one-loop result can also be re-summed using a semi-phenomenological renormalization group method which has proved useful in the study of diffusion in random media. In certain cases the renormalization group calculation predicts the existence of a diverging relaxation time signalled by the vanishing of the diffusion constant -- possible forms of divergence coming from this approximation are discussed. Finally, at a more quantitative level, the results are compared with numerical simulations, in two-dimensions, of particles interacting via a soft potential recently used to model the interaction between coiled polymers.Comment: 12 pages, 8 figures .ep

Left ventricular relaxation at rest and during handgrip in aortic valve disease before and after valve replacement

In 14 patients (pts) with aortic valve disease (A VD) left ventricular (LV) relaxation was assessed by the time constant (T) of LV pressure (tipmanometer) fall before and 19 months after successful aortic valve replacement (A VR). 12 control pts (CO) were studied by the same technique. Preoperative LV ejection fraction in AVD (64%) and in CO (69%) did not differ. In AVD T was increased (60 ms) as compared to the CO (38 ms, P< 0.05). During handgrip (HG) there was a similar increase of LV peak systolic pressure (LVSP), heart rate and peak measured contractile element velocity of shortening in A VD and in the CO. L V end-diastolic pressure varied minimally in both groups. T decreased during handgrip in CO (38 to 33 ms, P<0.01) and remained unchanged in A VD. Following AVR T at rest decreased insignificantly to 52 ms, but remained increased (P<0.025) as compared with CO. During postoperative HG however, a decrease to 47ms (P<0.05) was noted. Postoperative angiographic LV muscle mass (105 g/m2) and LVSP at rest (137 mmHg) remained elevated (P<0.02) as compared to CO (72 g/m2; 119 mmHg). It is concluded that (1) in A VD with normal ejection performance L V relaxation at rest is prolonged and the reaction of relaxation to HG is abnormal despite preserved contractile response, (2) following A VR the response of LV relaxation to HG becomes normal and (3) elevated postoperative T at rest appears to be related to residual hypertrophy and probably also to the still increased LVSP rather than to intrinsic disturbances of myocardial relaxatio

Quasiparticle Band Structure and Density Functional Theory: Single-Particle Excitations and Band Gaps in Lattice Models

We compare the quasiparticle band structure for a model insulator obtained from the fluctuation exchange approximation (FEA) with the eigenvalues of the corresponding density functional theory (DFT) and local density approximation (LDA). The discontinuity in the exchange-correlation potential for this model is small and the FEA and DFT band structures are in good agreement. In contrast to conventional wisdom, the LDA for this model overestimates the size of the band gap. We argue that this is a consequence of an FEA self-energy that is strongly frequency dependent, but essentially local.Comment: 8 pages, and 5 figure