Morphological effects of ceramide on DMPC/DHPC bicelles

Freeze fracture electron microscopy and dynamic light scattering were applied to characterize the morphological changes of DMPC/DHPC bicellar systems induced by the addition of ceramides. The results demonstrate a tendency of the DMPC/DHPC aggregates to evolve forming elongated or tubular structures with the increase of the temperature. At 20°C, low concentrations of ceramide promote the appearance of elongated structures with twisted zones. Higher concentrations of this lipid lead to the formation of liposomes along the elongated structures. The increase of the temperature to 40°C induces the growth of the structures containing low concentrations of ceramide forming branched aggregates. In samples with high amounts of ceramide, the increase of temperature causes phase separation and the formation of a mixed system composed by liposomes and multilamellar tubules. The morphological effects induced by ceramides in this new membrane model give new insights for the role played by this lipid in biological membranes.     

Tomography of insulating biological and geological materials using focused ion beam (FIB) sectioning and low-kV BSE imaging

Tomography in a focused ion beam (FIB) scanning electron microscope (SEM) is a powerful method for the characterization of three-dimensional micro- and nanostructures. Although this technique can be routinely applied to conducting materials, FIB–SEM tomography of many insulators, including biological, geological and ceramic samples, is often more difficult because of charging effects that disturb the serial sectioning using the ion beam or the imaging using the electron beam. Here, we show that automatic tomography of biological and geological samples can be achieved by serial sectioning with a focused ion beam and block-face imaging using low-kV backscattered electrons. In addition, a new ion milling geometry is used that reduces the effects of intensity gradients that are inherent in conventional geometry used for FIB–SEM tomography.     

Cryogenic EBSD on ice: preserving a stable surface in a low pressure SEM

Naturally deformed ice contains subgrains with characteristic geometries that have recently been identified in etched surfaces using high-resolution light microscopy (LM). The probable slip systems responsible for these subgrain boundary types can be determined using electron backscattered diffraction (EBSD), providing the etch features imaged with reflected LM can be retained during EBSD data acquisition in a scanning electron microscope (SEM). Retention of the etch features requires that the ice surface is stable. Depending on the pressure and temperature, sublimation of ice can occur. The equilibrium temperature for a low pressure SEM operating at 1 × 10(-6) hPa is about -112°C and operating at higher temperatures causes sublimation. Although charging of uncoated ice samples is reduced by sublimation, important information contained in the etch features are removed as the surface sublimes. We developed a method for collecting EBSD data on stable ice surfaces in a low pressure SEM. We found that operating at temperatures of <-112°C reduced sublimation so that the original etch surface features were retained. Charging, which occurred at low pressures (<1.5 × 10(-6) to 2.8 × 10(-5) hPa) was reduced by defocusing the beam. At very low pressures (<1.5 × 10(-6) hPa) the spatial resolution with a defocused beam at 10 kV was about 3 μm in the x-direction at -150°C and 0.5 μm at -120°C, because at higher temperature charging was less and only a small defocus was needed to compensate it. Angular resolution was better than 0.7° after orientation averaging. Excellent agreement was obtained between LM etch features and EBSD mapped microstructures. First results are shown, which indicate subgrain boundary types comprised of basal (tilt and twist) and nonbasal dislocations (tilt boundaries).     

Thymic stromal lymphopoietin: a cytokine that promotes the development of IgM+ B cells in vitro and signals via a novel mechanism

A novel cytokine from a thymic stromal cell line (thymic stromal lymphopoietin (TSLP)) promotes the development of B220+/IgM+ immature B cells when added to fetal liver cultures, long term bone marrow cultures, or bone marrow cells plated in semisolid medium. Because the activities of TSLP overlap with those of IL-7 in some in vitro assays, we compared the signaling mechanisms employed by TSLP and IL-7. Proliferation of a factor-dependent pre-B cell line (NAG8/7) in response to either TSLP or IL-7 was inhibited by anti-IL-7R alpha mAbs, suggesting that the functional TSLP receptor complex uses IL-7R alpha. In contrast, three different Abs to the common cytokine receptor gamma-chain had no effect on the response of these cells to TSLP, indicating that the functional TSLP receptor complex does not use the common cytokine receptor gamma-chain. Both cytokines induced activation of Stat5, but only IL-7 induced activation of the Janus family kinases Jak1 and Jak3. In fact, TSLP failed to activate any of the four known Janus family kinases, suggesting that Stat5 phosphorylation is mediated by a novel mechanism. Taken together, these data support the idea that TSLP can make unique contributions to B lymphopoiesis and indicate that it does so by mechanisms distinct from IL-7.     

Community resources for clients with mobility problems

Clients are leaving the hospital "quicker and sicker," and they frequently have acute care needs that must be met by resources outside the hospital setting. Community resources are diverse, vary widely from place to place, and have no central administration. Thus, using them can be challenging for both the nurse, client, and family. Reimbursement mechanisms underlie a person's ability to use resources and receive health care. By presenting two actual case scenarios where clients have mobility problems commonly seen by orthopaedic nurses, the authors discuss the community resources available, avenues of access to them, and their reimbursement mechanisms.     

Aldosterone in obesity

Plasma aldosterone levels were measured in adults whose body mass index ranged from lean to obese. Blood was drawn while subjects rested supine for 30-90 minutes. Aldosterone was higher in obese subjects, but could not be explained by renin or K+. The best predictors of plasma aldosterone were abdominal obesity measured as waist/hip ratio or by CT scan, and insulin resistance measured by insulin or oral glucose tolerance tests, or euglycemic clamp. In one cohort, these correlations were limited to women; in the other, they were also found in men. In the women with a strong correlation between aldosterone and visceral fat, aldosterone also correlated with cortisol and DHEA-S. The data are consistent with an effect of visceral fat on adrenal steroidogenesis. Visceral adipocytes have a high rate of triglyceride turnover, and their circulation drains directly to the liver. In an experiment based on these characteristics, rat hepatocytes responded to fatty acids by releasing an unidentified secretagogue that stimulated aldosterone production by rat adrenal glomerulosa cells. The clinical data suggest that aldosterone participates in hypertension associated with the "Insulin Resistance Syndrome". The adrenal in viscerally obese subjects may be driven by a secretagogue released from the liver by fatty acids from abdominal adipocytes.     

Edematogenic and myotoxic activities of the duvernoy’s gland secretion of <i>Philodryas olfersii</i> from the north-east region of Argentina

Philodryas olfersii is found in South America, from Amazonas to Patagonia. It is important to characterize the venom of P. olfersii, who inhabits the North-East region of Argentina, since snake venoms are known to exhibit considerable variability in composition and biological activities. In this work, mice weighing 18-20 g (n = 4 for each experimental group) were used. For the edematogenic activity mice were injected s.c. in the right foot pad with 50 µl of solutions containing different amounts of venom, whereas the left foot pad was injected with 50 µl of PBS. Two hours after injection mice were killed by cervical dislocation and both feet were cut off and weighed individually. For the myotoxic activity mice were injected i.m. with 100 µl of solutions containing 40 µg of venom. Blood samples were extracted after 1, 3, 6, 8, 10, 12, 14, 16 and 24 h of venom injection to determinate serum CPK activity and mice were sacrificed at the same time intervals to obtain the inoculated gastrocnemius muscle. They were fixed with Bouin solution and stained with Hematoxylin-Eosin. Results showed that P. olfersii venom exhibits a high edematogenic activity (MED = 0.31 µg) and a moderate myotoxic activity. Myonecrosis reached its highest level after 12 h of venom injection as shown by plasmatic CPK levels (5,401 ± 330 IU/l) and microscopic assay. It demonstrates the potential toxicity of the venom of P. olfersii, who inhabits the North-East region of Argentina. It also reinforces the original warning concerning the potential danger of bites by colubrids.     

运用模糊聚类分析方法整编翰林桥站流量资料初探

主要对水文资料整编采用模糊聚类分析的方法进行尝试，利用计算机定线，使得水文资料整编全面计算机化作了初步的探索，取得一定的效果。