The role of seladin-1/DHCR24 in cholesterol biosynthesis, APP processing and Abeta generation in vivo

The cholesterol-synthesizing enzyme seladin-1, encoded by the Dhcr24 gene, is a flavin adenine dinucleotide-dependent oxidoreductase and regulates responses to oncogenic and oxidative stimuli. It has a role in neuroprotection and is downregulated in affected neurons in Alzheimer's disease (AD). Here we show that seladin-1-deficient mouse brains had reduced levels of cholesterol and disorganized cholesterol-rich detergent-resistant membrane domains (DRMs). This was associated with inefficient plasminogen binding and plasmin activation, the displacement of beta-secretase (BACE) from DRMs to APP-containing membrane fractions, increased beta-cleavage of APP and high levels of Abeta peptides. In contrast, overexpression of seladin-1 increased both cholesterol and the recruitment of DRM components into DRM fractions, induced plasmin activation and reduced both BACE processing of APP and Abeta formation. These results establish a role of seladin-1 in the formation of DRMs and suggest that seladin-1-dependent cholesterol synthesis is involved in lowering Abeta levels. Pharmacological enhancement of seladin-1 activity may be a novel Abeta-lowering approach for the treatment of AD.     

The effect of estrogen on muscle damage biomarkers following prolonged aerobic exercise in eumenorrheic women

This study assessed the influence of estrogen (E₂) on muscle damage biomarkers [skeletal muscle - creatine kinase (CK); cardiac muscle - CK-MB] responses to prolonged aerobic exercise. Eumenorrheic women (n=10) who were physically active completed two 60-minute treadmill running sessions at ∼60-65% maximal intensity during low E₂ (midfollicular menstrual phase) and high E₂ (midluteal menstrual phase) hormonal conditions. Blood samples were collected prior to exercise (following supine rest), immediately post-, 30 min post-, and 24 hours post-exercise to determine changes in muscle biomarkers. Resting blood samples confirmed appropriate E₂ hormonal levels Total CK concentrations increased following exercise and at 24 hours post-exercise were higher in the midfollicular low E₂ phase (p<0.001). However, CK-MB concentrations were unaffected by E₂ level or exercise (p=0.442) resulting in the ratio of CK-MB to total CK being consistently low in subject responses (i.e., indicative of skeletal muscle damage). Elevated E₂ levels reduce the CK responses of skeletal muscle, but had no effect on CK-MB responses following prolonged aerobic exercise. These findings support earlier work showing elevated E₂ is protective of skeletal muscle from exercise-induced damage associated with prolonged aerobic exercise.     

Improvements for Observing Anthurium (Araceae) Floral Structures by Light Microscopy

Three major obstacles must be overcome In the anatomical study of Anthurium floral structure and embryo development including presence of mucilage, hardened carpel walls, and hardened seed coat in the developing fruit and seed. Fixation in 6% glutaraldehyde and 1% cetylpyridinium chloride in 0.05 M sodium cacodylate, pH 6.8, effectively fixed or removed mucilage from the locules of Anthurium andraeanum Hort. in spadices. This treatment enhanced infiltration of the embedding medium through the hardened carpel wall into the locule space and decreased the quantity and size of holes in the embedding block during sectioning. Specimens 16 weeks after pollination could be fixed, infiltrated, and observed without physical removal of the seed coat. Embryos may be excised from the seed at later stages without compromising embryo structure.     

Thymol and Carvacrol Prevent Cisplatin‐Induced Nephrotoxicity by Abrogation of Oxidative Stress,Inflammation, and Apoptosis in Rats

The aim of the present study is to assess the possible protective effects of thymol and carvacrol against cisplatin (CP)‐induced nephrotoxicity. A single dose of CP {6 mg/kg, intraperitoneally (i.p.)} injected to male rats revealed significant increases in serum urea, creatinine, and tumor necrosis factor alpha levels. It also increased kidney contents of malondialdehyde and caspase‐3 activity with significant reduction in serum albumin, kidney content of reduced glutathione as well as catalase, and superoxide dismutase activity as compared to that of the control group. In contrast, administration of thymol {20 mg/kg, orally (p.o.)} and/or carvacrol (15 mg/kg, p.o.) for 14 days before CP injection and for 7 days after CP administration restored the kidney function and examined oxidative stress parameters. In conclusion, thymol was more effective nephroprotective than carvacrol. Moreover, a combination of thymol and carvacrol had a synergistic nephroprotective effect that might be attributed to antioxidant, anti‐inflammatory, and antiapoptotic activities.     

Quantifying conformational changes in GPCRs: glimpse of a common functional mechanism

Background

G-protein-coupled receptors (GPCRs) are important drug targets and a better understanding of their molecular mechanisms would be desirable. The crystallization rate of GPCRs has accelerated in recent years as techniques have become more sophisticated, particularly with respect to Class A GPCRs interacting with G-proteins. These developments have made it possible for a quantitative analysis of GPCR geometrical features and binding-site conformations, including a statistical comparison between Class A GPCRs in active (agonist-bound) and inactive (antagonist-bound) states.

Results

Here we implement algorithms for the analysis of interhelical angles, distances, interactions and binding-site volumes in the transmembrane domains of 25 Class A GPCRs (7 active and 18 inactive). Two interhelical angles change in a statistically significant way between average inactive and active states: TM3-TM6 (by -9°) and TM6-TM7 (by +12°). A third interhelical angle: TM5-TM6 shows a trend, changing by -9°. In the transition from inactive to active states, average van der Waals interactions between TM3 and TM7 significantly increase as the average distance between them decreases by >2 Å. Average H-bonding between TM3 and TM6 decreases but is seemingly compensated by an increase in H-bonding between TM5 and TM6. In five Class A GPCRs, crystallized in both active and inactive states, increased H-bonding of agonists to TM6 and TM7, relative to antagonists, is observed. These protein-agonist interactions likely favour a change in the TM6-TM7 angle, which creates a narrowing in the binding pocket of activated receptors and an average ~200 ų reduction in volume.

Conclusions

In terms of similar conformational changes and agonist binding pattern, Class A GPCRs appear to share a common mechanism of activation, which can be exploited in future drug development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-015-0567-3) contains supplementary material, which is available to authorized users.     

Patterns of roost site selection and use by Southern Ground-Hornbills in north-eastern South Africa

Different habitats may be used for the needs of various aspects of an animal’s life. Southern Ground-Hornbill Bucorvus leadbeateri groups announce their presence within year-round territories by calling at dawn from their overnight roost sites. Knowledge on ground-hornbill roosting habits is limited. Groups roost in large trees, apparently close to where they end up after daily foraging. We investigated patterns of roost site selection and use for four Southern Ground-Hornbill groups in the Associated Private Nature Reserves, north-eastern South Africa, based on data from GPS-satellite transmitters. The number of roost sites used per month averaged 15.4 ± 4.7 across all groups, indicating little evidence of strong preferences for specific sites. This number was least when groups were breeding, decreasing throughout the early wet season (October–December) and was lowest during the late wet season (January–March) when actively breeding groups frequently roosted close to the nest (54–83% of roosts <1 000 m of the nest). As might be expected, the mean monthly number of nights per roost peaked during the breeding season (December–January). Riparian habitats were preferred for roosting during the breeding season, whereas disturbed areas, as well as Combretumand mopane-dominated habitats were preferred during the dry non-breeding season. Adequate large trees not only for nesting, but also for roosting, particularly in riparian habitats, may therefore be an important and potentially limiting factor for the successful reproduction of Southern Ground-Hornbills.     

Gastrointestinal and immunological responses of senior dogs to chicory and mannan-oligosaccharides

Thirty-four senior dogs (pointers 8 - 11 years, beagles 9 - 11 years) were used to evaluate the effects of oligosaccharides on nutritional and immunological characteristics. Dogs were randomly allotted to treatments [1% chicory (CH), 1% mannan-oligosaccharide (MOS), 1% chicory + 1% MOS (CM), or no supplementation (control, CON)] in a parallel design with a 4 week baseline period followed by a 4 week treatment period. Dietary supplementation with MOS or CM tended (P = 0.07) to increase food intake due, in part, to an increase in fermentable fibre and a decrease in energy content of the diet. Although wet faecal output increased (P < 0.05) for dogs supplemented with MOS or CM, when corrected for food intake, no differences were noted. The CM treatment increased (P < 0.05) faecal score (1 = hard and dry, 5 = watery liquid), although these scores remained in a desirable range (3 to 3.5). Chicory supplementation increased (P = 0.07) fat digestibility. Chicory or MOS increased (P  0.05) faecal bifidobacteria concentrations 0.4 and 0.5 log₁₀ cfu/g DM, respectively, compared to the CON, while MOS decreased (P < 0.05) faecal E. coli concentrations. Oligosaccharides did not affect white blood cell (WBC) concentrations, but CH and CM tended to increase (P = 0.10) neutrophil concentrations compared to control dogs. Peripheral lymphocyte concentrations were decreased in dogs supplemented with MOS (P = 0.06) and CM (P < 0.05). Chicory and MOS alter faecal microbial populations and certain indices of the immune system of senior dogs.     

A new technique for staining mast cells using ferroin

We describe here a new method for specific staining of mast cells using ferroin. Different hamster tissues were fixed in 4% formalin and processed for paraffin embedding. Sections were stained with hematoxylin followed by ferroin acidified with 2.5 N sulfuric acid to pH 4.0. Mast cells stained an intense orange color that contrasted markedly with bluish violet nuclei. High contrast was also observed when ferroin colored sections were counterstained with light green instead of hematoxylin. To evaluate the specificity of the stain, hamster cheek pouch sections were stained with toluidine blue, alcian blue-safranin O, and ferroin. Quantitative evaluation of mast cells stained with the three techniques showed no statistical difference. The simplicity and selectivity of this method is sufficient for image analysis of mast cells.