Interplay between plasma hormone profiles, sex and body condition in immature hawksbill turtles (Eretmochelys imbricata) subjected to a capture stress protocol

We investigated plasma hormone profiles of corticosterone and testosterone in immature hawksbill turtles (Eretmochelys imbricata) in response to a capture stress protocol. Further, we examined whether sex and body condition were covariates associated with variation in the adrenocortical response of immature turtles. Hawksbill turtles responded to the capture stress protocol by significantly increasing plasma levels of corticosterone over a 5 h period. There was no significant sex difference in the corticosterone stress response of immature turtles. Plasma testosterone profiles, while significantly different between the sexes, did not exhibit a significant change during the 5 h capture stress protocol. An index of body condition was not significantly associated with a turtle's capacity to produce plasma corticosterone both prior to and during exposure to the capture stress protocol. In summary, while immature hawksbill turtles exhibited an adrenocortical response to a capture stress protocol, neither their sex nor body condition was responsible for variation in endocrine responses. This lack of interaction between the adrenocortical response and these internal factors suggests that the inactive reproductive- and the current energetic- status of these immature turtles are important factors, that could influence plasma hormone profiles during stress. (C) 2003 Elsevier Inc. All rights reserved.

Three separable domains regulate GTP-dependent association of H-ras with the plasma membrane

The microlocalization of Ras proteins to different microdomains of the plasma membrane is critical for signaling specificity. Here we examine the complex membrane interactions of H-ras with a combination of FRAP on live cells to measure membrane affinity and electron microscopy of intact plasma membrane sheets to spatially map microdomains. We show that three separable forces operate on H-ras at the plasma membrane. The lipid anchor, comprising a processed CAAX motif and two palmitic acid residues, generates one attractive force that provides a high-affinity interaction with lipid rafts. The adjacent hypervariable linker domain provides a second attractive force but for nonraft plasma membrane microdomains. Operating against the attractive interaction of the lipid anchor for lipid rafts is a repulsive force generated by the N-terminal catalytic domain that increases when H-ras is GTP loaded. These observations lead directly to a novel mechanism that explains how H-ras lateral segregation is regulated by activation state: GTP loading decreases H-ras affinity for lipid rafts and allows the hypervariable linker domain to target to nonraft microdomains, the primary site of H-ras signaling.

Synthesis and characterization of nano-hetero-structured dy doped CeO2 solid electrolytes using a combination of spark plasma sintering and conventional sintering

Doped ceria (CeO2) compounds are fluorite-type oxides that show oxide ionic conductivity higher than yttria-stabilized zirconia in oxidizing atmosphere. As a consequence of this, considerable interest has been shown in application of these materials for low (500 degrees-650 degrees C) temperature operation of solid oxide fuel cells (SOFCs). To improve the conductivity in dysprosium (Dy) doped CeO2, nano-size round shape particles were prepared using a coprecipitation method. The dense sintered bodies with small grain sizes (< 300 nm) were fabricated using a combined process of spark plasma sintering (SPS) and conventional sintering (CS). Dy-doped CeO2 sintered body with large grains (1.1 mu m) had large micro-domains. The conductivity in the sintered body was low (-3.2 S/cm at 500 degrees C). On the other hand, the conductivity in the specimens obtained by the combined process was considerably improved. The micro-domain size in the grain was minimized using the present process. It is concluded that the enhancement of conductivity in dense specimens produced by the combined process (SPS+CS) is attributable to the microstructural changes within the grains.

GCMC-surface area of carbonaceous materials with N-2 and Ar adsorption as an alternative to the classical BET method

In this paper we apply a new method for the determination of surface area of carbonaceous materials, using the local surface excess isotherms obtained from the Grand Canonical Monte Carlo simulation and a concept of area distribution in terms of energy well-depth of solid–fluid interaction. The range of this well-depth considered in our GCMC simulation is from 10 to 100 K, which is wide enough to cover all carbon surfaces that we dealt with (for comparison, the well-depth for perfect graphite surface is about 58 K). Having the set of local surface excess isotherms and the differential area distribution, the overall adsorption isotherm can be obtained in an integral form. Thus, given the experimental data of nitrogen or argon adsorption on a carbon material, the differential area distribution can be obtained from the inversion process, using the regularization method. The total surface area is then obtained as the area of this distribution. We test this approach with a number of data in the literature, and compare our GCMC-surface area with that obtained from the classical BET method. In general, we find that the difference between these two surface areas is about 10%, indicating the need to reliably determine the surface area with a very consistent method. We, therefore, suggest the approach of this paper as an alternative to the BET method because of the long-recognized unrealistic assumptions used in the BET theory. Beside the surface area obtained by this method, it also provides information about the differential area distribution versus the well-depth. This information could be used as a microscopic finger-print of the carbon surface. It is expected that samples prepared from different precursors and different activation conditions will have distinct finger-prints. We illustrate this with Cabot BP120, 280 and 460 samples, and the differential area distributions obtained from the adsorption of argon at 77 K and nitrogen also at 77 K have exactly the same patterns, suggesting the characteristics of this carbon.

Plasma delipidation process induces rapid regression of atherosclerosis and mobilisation of adipose tissue

Cholesterol is a major component of atherosclerotic plaques. Cholesterol accumulation within the arterial intima and atherosclerotic plaques is determined by the difference of cellular cholesterol synthesis and/or influx from apo B-containing lipoproteins and cholesterol efflux. In humans, apo A-I Milano infusion has led to rapid regression of atherosclerosis in coronary arteries. We hypothesised that a multifunctional plasma delipidation process (PDP) would lead to rapid regression of experimental atherosclerosis and probably impact on adipose tissue lipids. In hyperlipidemic animals, the plasma concentrations of cholesterol, triglyceride and phospholipid were, respectively, 6-, 157-, and 18-fold higher than control animals, which consequently resulted in atherosclerosis. PDP consisted of delipidation of plasma with a mixture of butanol-diisopropyl ether (DIPE). PDP removed considerably more lipid from the hyperlipidemic animals than in normolipidemic animals. PDP treatment of hyperlipidemic animals markedly reduced intensity of lipid staining materials in the arterial wall and led to dramatic reduction of lipid in the adipose tissue. Five PDP treatments increased apolipoprotein A1 concentrations in all animals. Biochemical and hematological parameters were unaffected during PDP treatment. These results show that five PDP treatments led to marked reduction in avian atherosclerosis and removal of lipid from adipose tissue. PDP is a highly effective method for rapid regression of atherosclerosis.

Regulation of albumin endocytosis by PSD95/Dlg/ZO-1 (PDZ) scaffolds - Interaction of Na+-H+ exchange regulatory factor-2 with ClC-5

The constitutive reuptake of albumin from the glomerular filtrate by receptor-mediated endocytosis is a key function of the renal proximal tubules. Both the Cl- channel ClC-5 and the Na+-H+ exchanger isoform 3 are critical components of the macromolecular endocytic complex that is required for albumin uptake, and therefore the cell-surface levels of these proteins may limit albumin endocytosis. This study was undertaken to investigate the potential roles of the epithelial PDZ scaffolds, Na+-H+ exchange regulatory factors, NHERF1 and NHERF2, in albumin uptake by opossum kidney ( OK) cells. We found that ClC-5 co-immunoprecipitates with NHERF2 but not NHERF1 from OK cell lysate. Experiments using fusion proteins demonstrated that this was a direct interaction between an internal binding site in the C terminus of ClC-5 and the PDZ2 module of NHERF2. In OK cells, NHERF2 is restricted to the intravillar region while NHERF1 is located in the microvilli. Silencing NHERF2 reduced both cell-surface levels of ClC-5 and albumin uptake. Conversely, silencing NHERF1 increased cell-surface levels of ClC-5 and albumin uptake, presumably by increasing the mobility of NHE3 in the membrane and its availability to the albumin uptake complex. Surface biotinylation experiments revealed that both NHERF1 and NHERF2 were associated with the plasma membrane and that NHERF2 was recruited to the membrane in the presence of albumin. The importance of the interaction between NHERF2 and the cytoskeleton was demonstrated by a significant reduction in albumin uptake in cells overexpressing an ezrin binding-deficient mutant of NHERF2. Thus NHERF1 and NHERF2 differentially regulate albumin uptake by mechanisms that ultimately alter the cell-surface levels of ClC-5.

General foundation for the nonlinear ponderomotive four-force in laser-plasma interactions

The interaction of electromagnetic radiation with plasmas is studied in relativistic four-vector formalism. A gauge and Lorentz invariant ponderomotive four-force is derived from the time dependent nonlinear three-force of Hora (1985). This four-force, due to its Lorentz invariance, contains new magnetic field terms. A new gauge and Lorentz invariant model of the response of plasma to electromagnetic radiation is then devised. An expression for the dispersion relation is obtained from this model. It is then proved that the magnetic permeability of plasma is unity for a general reference frame. This is an important result since it has been previously assumed in many plasma models.

Fluorinated-plasma modification of polyetherimide films

Ultem 1000 polyetherimide films prepared by cast-evaporating technique were covered with a 1H,1H,2H-tridecafluoro-oct-1-ene (PFO) plasma-polymerized layer. The effects of the plasma exposure time on the surface composition were studied by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and surface energy analysis. The surface topography of the plasma layer was deduced from scanning electron microscopy. The F/C ratio for plasma-polymerized PFO under the input RF power of 50 W can be as high as 1.30 for 480 s and similar to 0.4-2 at % of oxygen was detected, resulting from the reaction of long-lived radicals in the plasma polymer with atmospheric oxygen. The plasma deposition of fluorocarbon coating from plasma PFO reduces the surface energy from 46 to 18.3 mJ m(-2). (c) 2006 Wiley Periodicals, Inc.

Molecular dissection of the Munc18c/syntaxin4 interaction: Implications for regulation of membrane trafficking

Sec1p/Munc18 (SM) proteins are believed to play an integral role in vesicle transport through their interaction with SNAREs. Different SM proteins have been shown to interact with SNAREs via different mechanisms, leading to the conclusion that their function has diverged. To further explore this notion, in this study, we have examined the molecular interactions between Munc18c and its cognate SNAREs as these molecules are ubiquitously expressed in mammals and likely regulate a universal plasma membrane trafficking step. Thus, Munc18c binds to monomeric syntaxin4 and the N-terminal 29 amino acids of syntaxin4 are necessary for this interaction. We identified key residues in Munc18c and syntaxin4 that determine the N-terminal interaction and that are consistent with the N-terminal binding mode of yeast proteins Sly1p and Sed5p. In addition, Munc18c binds to the syntaxin4/SNAP23/VAMP2 SNARE complex. Pre-assembly of the syntaxin4/Munc18c dimer accelerates the formation of SNARE complex compared to assembly with syntaxin4 alone. These data suggest that Munc18c interacts with its cognate SNAREs in a manner that resembles the yeast proteins Sly1p and Sed5p rather than the mammalian neuronal proteins Munc18a and syntaxin1a. The Munc18c-SNARE interactions described here imply that Munc18c could play a positive regulatory role in SNARE assembly.

New insights into the interaction of hydrogen atoms with boron-substituted carbon

Boron substitution in carbon materials has been comprehensively investigated using the density functional theory method. It was found that there is a correlation between the stability of the graphene sheet, the distribution of T electrons, the electrostatic potential, and the capability for hydrogen-atom adsorption. Boron substitution destabilizes the graphene structure, increases the density of the electron wave around the substitutional boron atoms, and lowers the electrostatic potential, thus improving the hydrogen adsorption energy on carbon. However, this improvement is only ca. 10-20% instead of a factor of 4 or 5. Our calculations also show that two substitutional boron atoms provide consistent and reliable results, but one substitutional boron results in contradictory conclusions. This is a warning to other computational chemists who work on boron substitution that the conclusion from one substitutional boron might not be reliable.