Membrane conductance patterns during fertilization are sperm dependent in two sea urchin species

The influence of the egg and sperm on the conductance changes at fertilization in the sea urchin were investigated through cross-fertilization of two Hawaiian species, Tripneustes gratilla and Pseudoboletia indiana. The current-voltage (I-V) relation, measured in voltage-clamped eggs at intervals over the period 2-16 min following the rise to a positive membrane potential that signals sperm attachment, differs significantly in the two species. The magnitude of the conductance change depends on the species of the fertilizing sperm in both homologous and heterologous crosses. This supports the hypothesis that currents during this period arise from sperm membrane channels incorporated into the egg at sperm-egg fusion. Measurements of conductance during the first 90 sec, which includes the period of the major inward current correlated with cortical granule breakdown and elevation of the fertilization envelope, showed that the magnitude and timing of the maximum current also differed in the two species. This conductance change presumably involves an activation of egg membrane channels initiated by the sperm and would be expected to be characteristic of the egg species. However, in cross-fertilized eggs the magnitude and timing of the conductance change over this period also depends on the species of the sperm with little identifiable egg contribution, indicating that the fertilizing sperm can modulate the egg response to influence these events.     

Sh3pxd2b mice are a model for craniofacial dysmorphology and otitis media

Craniofacial defects that occur through gene mutation during development increase vulnerability to eustachian tube dysfunction. These defects can lead to an increased incidence of otitis media. We examined the effects of a mutation in the Sh3pxd2b gene (Sh3pxd2b(nee)) on the progression of otitis media and hearing impairment at various developmental stages. We found that all mice that had the Sh3pxd2b(nee) mutation went on to develop craniofacial dysmorphologies and subsequently otitis media, by as early as 11 days of age. We found noteworthy changes in cilia and goblet cells of the middle ear mucosa in Sh3pxd2b(nee) mutant mice using scanning electronic microscopy. By measuring craniofacial dimensions, we determined for the first time in an animal model that this mouse has altered eustachian tube morphology consistent with a more horizontal position of the eustachian tube. All mutants were found to have hearing impairment. Expression of TNF-α and TLR2, which correlates with inflammation in otitis media, was up-regulated in the ears of mutant mice when examined by immunohistochemistry and semi-quantitative RT-PCR. The mouse model with a mutation in the Sh3pxd2b gene (Sh3pxd2b(nee)) mirrors craniofacial dysmorphology and otitis media in humans.     

Ethanol-induced hypothermia and ethanol consumption in the rat are affected by low-level microwave irradiation

Microwave irradiation of rats by circularly polarized, 2,450-MHz, pulsed waves (2-μs pulses; 500 pps) was performed in waveguides to determine effects on ethanol-induced hypothermia and on ethanol consumption. Rats injected intraperitoneally with ethanol (3 g/kg in a 25% v/v water solution) immediately after 45 min of microwave irradiation exhibited attenuation of the initial rate of fall in body temperature, which was elicited by the ethanol, but exhibited no significant difference in maximal hypothermia as compared with that of sham-irradiated rats. Microwave irradiation did not affect the consumption of a 10% sucrose (w/v) solution by water-deprived rats. However, it enhanced the consumption of a solution of 10% sucrose (w/v) + 15% ethanol (v/v) by water-deprived animals. These results were obtained at a specific absorption rate (SAR) of 0.6 W/kg, which rate of energy dosing would require a power density of 3–6 mW/cm² if exposure of the animals had occurred to a 12-cm plane wave.     

Taste-smell interactions are tastant and odorant dependent

Four experiments were conducted to assess the nature of taste–smellinteractions. In the first experiment, the ability of strawberryodor to modify the sweetness of sucrose was investigated. Thiswas accomplished by having subjects rate the sweetness of whipped-creamstimuli with and without strawberry odor over time. The stimuliwere swallowed to augment retronasal stimulation of the olfactorysystem. It was found that strawberry odor tended to enhancethe maximal sweetness and total rating time of the stimuli.In the second experiment, it was found that peanut butter odordid not enhance sweetness, thus demonstrating that an odor'sability to enhance sweetness is odor-dependent, In the thirdexperiment, it was demonstrated that strawberry odor did notenhance the saltiness of sodium chloride indicating that anodor's ability to enhance taste is tastant-dependent. In thefourth experiment, it was shown that 85% of the strawberry odorant'sability to enhance sweetness was eliminated by pinching thenostrils. This suggests that the influence of the strawberryodorant on sweetness was olfactory rather than gustatory. Itwas concluded that an odor's influence on taste is both odorantand tastant dependent.     

Human serum metabolic profiles are age dependent

Understanding the complexity of aging is of utmost importance. This can now be addressed by the novel and powerful approach of metabolomics. However, to date, only a few metabolic studies based on large samples are available. Here, we provide novel and specific information on age‐related metabolite concentration changes in human homeostasis. We report results from two population‐based studies: the KORA F4 study from Germany as a discovery cohort, with 1038 female and 1124 male participants (32–81 years), and the TwinsUK study as replication, with 724 female participants. Targeted metabolomics of fasting serum samples quantified 131 metabolites by FIA‐MS/MS. Among these, 71/34 metabolites were significantly associated with age in women/men (BMI adjusted). We further identified a set of 13 independent metabolites in women (with P values ranging from 4.6 × 10^?04 to 7.8 × 10^?42, α_corr = 0.004). Eleven of these 13 metabolites were replicated in the TwinsUK study, including seven metabolite concentrations that increased with age (C0, C10:1, C12:1, C18:1, SM C16:1, SM C18:1, and PC aa C28:1), while histidine decreased. These results indicate that metabolic profiles are age dependent and might reflect different aging processes, such as incomplete mitochondrial fatty acid oxidation. The use of metabolomics will increase our understanding of aging networks and may lead to discoveries that help enhance healthy aging.     

Endothelial nanoparticle binding kinetics are matrix and size dependent

Nanoparticles are increasingly important in medical research for application to areas such as drug delivery and imaging. Understanding the interactions of nanoparticles with cells in physiologically relevant environments is vital for their acceptance, and cell–particle interactions likely vary based on the design of the particle including its size, shape, and surface chemistry. For this reason, the kinetic interactions of fluorescent nanoparticles of sizes 20, 100, 200, and 500 nm with human umbilical vein endothelial cells (HUVEC) were determined by (1) measuring nanoparticles per cell at 37 and 4°C (to inhibit endocytosis) and (2) modeling experimental particle uptake data with equations describing particle attachment, detachment, and internalization. Additionally, the influence of cell substrate compliance on nanoparticle attachment and uptake was investigated. Results show that the number of binding sites per cell decreased with increasing nanoparticle size, while the attachment coefficient increased. By comparing HUVEC grown on either a thin coating of collagen or on top of three‐dimensional collagen hydrogel, nanoparticle attachment and internalization were shown to be influenced significantly by the substrate on which the cells are cultured. This study concludes that both particle size and cell culture substrate compliance appreciably influence the binding of nanoparticles; important factors in translating in vitro studies of nanoparticle interactions to in vivo studies focused on therapeutic or diagnostic applications. Biotechnol. Bioeng. 2011;108: 2988–2998. © 2011 Wiley Periodicals, Inc.     

DAP-kinase-mediated morphological changes are localization dependent and involve myosin-II phosphorylation

DAP-kinase (DAPk) is a Ser/Thr kinase that regulates cytoplasmic changes associated with programmed cell death. It is shown here that a GFP-DAPk fusion, which partially localized to actin stress fibers, induced extensive membrane protrusions. This phenotype correlated with changes in myosin-II distribution and with increased phosphorylation of the myosin-II regulatory light chain (RLC). A mutant lacking the cytoskeletal-interacting region (GFP-DAPkDeltaCyto) displayed diffuse cytoplasmic localization, and induced peripheral membrane blebbing, instead of the extensive protrusions. In contrast, deletion of the ankyrin repeats led to mislocalization of the kinase to focal contacts, where it failed to elicit any changes in cell morphology. While both wild-type DAPk and DAPkDeltaCyto induced RLC phosphorylation independently of the Rho-activated kinase ROCK, only the wild type led to increases in stress-fiber associated phospho-RLC. Thus, the precise intracellular localization of DAPk is critical for exposure to its substrates, including the RLC, which mediate varying morphologic changes.     

Leaf growth responses to ABA are temperature dependent

The robustness of a leaf elongation bioassay was evaluated byconducting trials with detached shoots of wheat at several differenttemperatures. Leaf elongation rate (LER) was monitored for shootsfed either an artificial xylem solution or xylem solution plus10^–3mol m^–3 abscisic acid (ABA). Consistent resultswere obtained when periodic ruler measurements of many shootswere made and compared with simultaneous measurements on a singleshoot made with a linearly variable displacement transducer(LVDT). ABA treatment consistently inhibited leaf growth; however,the magnitude of the inhibition was dependent on the temperatureat which the assay was conducted. Interpretation of resultsfrom such bioas-says in terms of ABA concentration suppliedto the detached shoots is complicated by this observation sincethere is no unique relationship between leaf growth inhibitionand ABA concentration. The results are discussed in terms ofchemical signalling affecting the growth rate of plants in dryingsoil. Key words: ABA, leaf growth, temperature, leaf elongation bioassay     

Thermodynamics and dynamics of amyloid peptide oligomerization are sequence dependent

Aggregation of the full‐length amyloid‐β (Aβ) and β2‐microglobulin (β2m) proteins is associated with Alzheimer's disease and dialysis‐related amyloidosis, respectively. This assembly process is not restricted to full‐length proteins, however, many short peptides also assemble into amyloid fibrils in vitro. Remarkably, the kinetics of amyloid‐fibril formation of all these molecules is generally described by a nucleation‐polymerization process characterized by a lag phase associated with the formation of a nucleus, after which fibril elongation occurs rapidly. In this study, we report using long molecular dynamics simulations with the OPEP coarse‐grained force field, the thermodynamics and dynamics of the octamerization for two amyloid 7‐residue peptides: the β2m83‐89 NHVTLSQ and Aβ16‐22 KLVFFAE fragments. Based on multiple trajectories run at 310 K, totaling 2.2 μs (β2m83‐89) and 4.8 μs (Aβ16‐22) and starting from random configurations and orientations of the chains, we find that the two peptides not only share common but also very different aggregation properties. Notably, an increase in the hydrophobic character of the peptide, as observed in Aβ16‐22 with respect to β2m83‐89 impacts the thermodynamics by reducing the population of bilayer β‐sheet assemblies. Higher hydrophobicity is also found to slow down the dynamics of β‐sheet formation by enhancing the averaged lifetime of all configuration types (CT) and by reducing the complexity of the CT transition probability matrix. Proteins 2009. © 2008 Wiley‐Liss, Inc.     

Motility and flagellum synthesis in Halobacillus halophilus are chloride dependent

The motility of Halobacillus halophilus as observed on swarm agar plates was strictly dependent on the chloride concentration. Cl(-) was apparently not used as the coupling ion for flagellar rotation. Cells grown in the absence of chloride were devoid of flagella, but flagellation was restored upon the addition of chloride. These experiments indicate that chloride is involved in synthesis of flagella in H. halophilus.     

Scale‐dependent longitudinal patterns in mussel communities

1. Species richness and assemblage patterns of organisms are dictated by numerous factors, probably operating at multiple scales. Freshwater mussels (Unionidae) are an endangered, speciose faunal group, making them an interesting model system to study the influence of landscape features on organisms. In addition, landscape features that influence species distributions and the scale at which the factors have the greatest impact are important issues that need to be answered to conserve freshwater mussels. 2. In this study, we quantified freshwater mussel communities at 16 sites along three mid‐sized rivers in the south‐central United States. We addressed the following questions: (i) Are there predictable longitudinal changes in mussel community composition? (ii) What landscape variables best explain shifts in community composition? and (iii) At what scale do landscape variables best predict mussel community composition? 3. After controlling for the influence of longitudinal position along the stream, we compared mussel distributions to a suite of hypothesised explanatory landscape variables across multiple scales – catchment scale (entire drainage area), buffer scale (100‐m riparian buffer of the entire catchment) and reach scale (100‐m riparian buffer extending 1 km upstream from the sampling site). 4. We found a significant and consistent longitudinal shift in dominant mussel species across all three rivers, with community composition strongly related to distance from the headwaters, which is highly correlated with stream size. After accounting for stream size, variables at the buffer scale were the best predictors of mussel community composition. After accounting for catchment position, mean channel slope was the best explanatory variable of community composition and appeared in all top candidate models at the catchment and buffer scales. Coverage of wetland and urban area were also correlated with community composition at the catchment and buffer scales. 5. Our results suggest that landscape‐scale habitat factors influence mussel community composition. Landscape features at the buffer scale performed best at determining community composition after accounting for position in the catchment; thus, further protection of riparian buffers will help to conserve mussel communities.     

H-Ras signaling and K-Ras signaling are differentially dependent on endocytosis

Endocytosis is required for efficient mitogen-activated protein kinase (MAPK) activation by activated growth factor receptors. We examined if H-Ras and K-Ras proteins, which are distributed across different plasma membrane microdomains, have equal access to the endocytic compartment and whether this access is necessary for downstream signaling. Inhibition of endocytosis by dominant interfering dynamin-K44A blocked H-Ras but not K-Ras-mediated PC12 cell differentiation and selectively inhibited H-Ras- but not K-Ras-mediated Raf-1 activation in BHK cells. H-Ras- but not K-Ras-mediated Raf-1 activation was also selectively dependent on phosphoinositide 3-kinase activity. Stimulation of endocytosis and endocytic recycling by wild-type Rab5 potentiated H-Ras-mediated Raf-1 activation. In contrast, Rab5-Q79L, which stimulates endocytosis but not endocytic recycling, redistributed activated H-Ras from the plasma membrane into enlarged endosomes and inhibited H-Ras-mediated Raf-1 activation. Rab5-Q79L expression did not cause the accumulation of wild-type H-Ras in enlarged endosomes. Expression of wild-type Rab5 or Rab5-Q79L increased the specific activity of K-Ras-activated Raf-1 but did not result in any redistribution of K-Ras from the plasma membrane to endosomes. These results show that H-Ras but not K-Ras signaling though the Raf/MEK/MAPK cascade requires endocytosis and endocytic recycling. The data also suggest a mechanism for returning Raf-1 to the cytosol after plasma membrane recruitment.     

Rat islet isolation yield and function are donor strain dependent

Effective rat islet isolation is pertinent for successful islet transplantation and islet studies in vitro. To determine which rat strain yields the highest number of pure and functional islets, four commonly used rat strains were compared with regard to islet yield, islet purity and islet function. Secretory responses were assessed by stimulation with glucose, and by stimulation with glucose plus 3-isobutyl-1-methylxanthine (IBMX). We show that rat islet function and isolation yield are donor strain dependent. Albino Oxford (AO) rats donated twice as many islets than Wistar, Lewis and Sprague Dawley (SD) rats. Stimulation with glucose plus IBMX resulted in an average five-fold increase of the stimulation index of AO, Lewis, Wistar and SD rats compared to stimulation with glucose only. AO islets had improved secretory responses after a one-week culture period, but required the addition of IBMX to glucose to elicit a distinguished stimulated insulin secretion after 2 days of culture. Islets from SD rats showed inferior results with regard to purity immediately after isolation and with regard to function after short- and after long-time culture. Because Lewis islets possessed the highest secretory response to glucose (without IBMX) immediately after isolation, Lewis rats may be preferred as islet donors for immediate use. The addition of IBMX to glucose for in vitro functional testing is recommended because it elicits high insulin secretory responses of islets regardless of the rat strain. AO rats are preferred for culture experiments since the number of experimental animals is reduced two-fold compared to Lewis, Wistar and SD rats.