Long-Term Effect of Forskolin on the Activation of Adenylyl Cyclase in Astrocytes

Abstract: Long-term (48-h) forskolin treatment of rat astroglial cells led to a slight decrease (30–40%) in the response to isoproterenol, vasoactive-intestinal peptide, guanyl 5'-(βγ-imido)diphosphate, guanosine 5'- O -(3-thiotriphosphate) [GTP(S)], and AIF₄⁻ in crude membrane fractions. In contrast, the acute stimulatory effect of forskolin was increased by 1.25–1.5-fold. These two opposite effects of forskolin were mediated by a cyclic AMP-dependent mechanism. No changes in G_sα, G_iα, or Gβ protein levels could be determined by immunoblotting using specific antisera. No significant differences were observed in the ability of G proteins extracted from control and forskolin-treated cells to reconstitute a full adenylyl cyclase activity in membranes from S49 cyc⁻ cells, lacking G_sα protein. G_sα proteins were detected in two pools of membranes, one in the heavy sucrose fractions and the other in light sucrose fractions. Forskolin treatment of the cells shifted G_sα protein toward the light-density membranes. We did not find any significant change in the distribution of adenylyl cyclase. In contrast to the decreased stimulation of adenylyl cyclase activity by agonists acting via G_sα, observed in the crude membrane fraction, the responses of adenylyl cyclase to forskolin as well as to GTP(S) were increased in the purified plasma membrane fractions. These results may indicate that sensitization of the catalyst appears to be the dominant component in the astroglial cell response to long-term treatment by forskolin.     

Interplay Between Side Chain Pattern,Polymer Aggregation,and Charge Carrier Dynamics in PBDTTPD:PCBM Bulk‐Heterojunction Solar Cells

Poly(benzo[1,2‐b:4,5‐b′]dithiophene–alt–thieno[3,4‐c]pyrrole‐4,6‐dione) (PBDTTPD) polymer donors with linear side‐chains yield bulk‐heterojunction (BHJ) solar cell power conversion efficiencies (PCEs) of about 4% with phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) as the acceptor, while a PBDTTPD polymer with a combination of branched and linear substituents yields a doubling of the PCE to 8%. Using transient optical spectroscopy it is shown that while the exciton dissociation and ultrafast charge generation steps are not strongly affected by the side chain modifications, the polymer with branched side chains exhibits a decreased rate of nongeminate recombination and a lower fraction of sub‐nanosecond geminate recombination. In turn the yield of long‐lived charge carriers increases, resulting in a 33% increase in short circuit current (J _sc). In parallel, the two polymers show distinct grazing incidence X‐ray scattering spectra indicative of the presence of stacks with different orientation patterns in optimized thin‐film BHJ devices. Independent of the packing pattern the spectroscopic data also reveals the existence of polymer aggregates in the pristine polymer films as well as in both blends which trap excitons and hinder their dissociation.     

Corrugation Enabled Asymmetrically Ultrastretchable (95%) Monocrystalline Silicon Solar Cells with High Efficiency (19%)

Stretchable solar cells are of growing interest due their key role in realizing many applications such as wearables and biomedical devices. Ultrastretchability, high energy‐efficiency, biocompatibility, and mechanical resilience are essential characteristics of such energy harvesting devices. Here, the development of wafer‐scale monocrystalline silicon solar cells with world‐record ultrastretchability (95%) and efficiency (19%) is demonstrated using a laser‐patterning based corrugation technique. The demonstrated approach transforms interdigitated back contacts (IBC) based rigid solar cells into mechanically reliable but ultrastretchable cells with negligible degradation in the electric performance in terms of current density, open‐circuit voltage, and fill factor. The corrugation method is based on the creation of alternating grooves resulting in silicon islands with different shapes. The stretchability is achieved by orthogonally aligning the active silicon islands to the applied tensile stress and using a biocompatible elastomer (Ecoflex) as a stretchable substrate. The resulting mechanics ensure that the brittle silicon areas do not experience significant mechanical stresses upon asymmetrical stretching. Different patterns are studied including linear, diamond, and triangular patterns, each of which results in a different stretchability and loss of active silicon area. Finally, finite element method based simulation is conducted to study the generated deformation in the different patterned solar cells.     

Characterization of postdive recovery using sound recordings and its relationship to dive duration,exertion, and foraging effort of southern elephant seals (Mirounga leonina)

It is notoriously difficult to measure physiological parameters in cryptic free‐ranging marine mammals. However, it is critical to understand how marine mammals manage their energy expenditure and their diving behavior in environments where the predation risks are low and where survival is mainly linked to capacities to maintain physiological homeostasis and energy budget balance. Elephant seals are top marine predators that dive deeply and continuously when at sea. Using acoustic recorders deployed on two postbreeding southern elephant seals (SES) females, we developed methods to automatically estimate breathing frequency at the surface. Using this method, we found that seals took successive identical breaths at high frequency (0.29 Hz) when recovering at the surface and that breath count was strongly related to postdive surfacing time. In addition, dive depth was the main factor explaining surfacing time through the effects of dive duration and total underwater swimming effort exerted. Finally, we found that recovery does not only occur over one dive timescale, but over a multidive time scale for one individual. The way these predators manage their recovery will determine how they respond to the change in oceanic water column structure in the future.     

Vitamin D receptor gene variability as a factor influencing bone mineral density in pediatric patients

To determine the relationship between the polymorphism of vitamin D receptor gene and the bone mineral density in children. The study group consisted of 395 children aged 6–18 years. All patients underwent genotyping using the PCR-RFLP method within polymorphic loci BsmI (rs1544410), FokI (rs2228570), ApaI (rs7975232) and Taq I (rs731236) of the VDR gene. The BMD (g/cm², Z score) and BMC (g, Z score) by DXA method, as well as Z scores of the BUA, SOS and Stiffness ultrasound parameters were evaluated. Based on densitometry results, children were divided into 3 groups: I—Z score ± 1.0; II—Z score from −1.1 to −2.0; and III—Z score ≤ −2.1. A control group numbering 294 children was used for the purpose of allele frequency comparisons. The occurrence of studied polymorphism alleles in the control group did not significantly differ from the values expected according to the Hardy–Weinberg equilibrium (p values: 0.1224 for BsmI; 0.5958 for TaqI; 0.0817 for ApaI; and 0.8901 for FokI). Allele a ApaI carrier status in group III children was associated with an increased BMD (x = 0.8 vs 0.69, p = 0.0296) and BMC value (x = 28.76 vs 22.14, p = 0.0565) in spine projection results, Stiffness (x = −1.12 vs −1.91, p = 0.0347) and SOS (x = −1.43 vs −2.27, p = 0.0319) ultrasound parameters. In group II, significantly increased SOS values (−1.13 vs −1.73, p = 0.0378) were noted in f (FokI) carriers. The presence of aa ApaI and ff FokI polymorphisms favours a higher bone mass and better bone structure (decreased bone mass loss) in the analysed group.     

Fine structure of muscles in the tickHyalomma (Hyalomma) dromedarii (Ixodoidea: Ixodidae)

Skeletal and visceral muscles are distinguished in the unfed nymphHyalomma (Hyalomma) dromedarii according to position, structure and function. The skeletal muscles include the capitulum, dorsoventral and leg oblique muscles. Their muscle fibres have the striated pattern of successive sarcomeres whose thick myosin filaments are surrounded by orbitals of up to 12 thin actin filaments. The cell membrane invaginates into tubular system (T) extending deeply into the sarcoplasm and closely associated to cisternae of sarcoplasmic reticulum (SR). The T and SR forming two-membered dyads are considered to be the main route of calcium ions whose movements are synchronized with the motor impulse to control contraction and relaxation in most muscles. Two types of skeletal muscle fibres are recognized, and are suggested as representing different physiological phases.In the visceral-muscle fibres investing tick internal organs, the actin and myosin filaments are slightly interrupted, and the T and SR are well demonstrated. Both skeletal and visceral muscles are invaginated by tracheoles and innervated by nerve-axons containing synaptic vesicles.     

Quantitative and Qualitative Changes in Peroxidase of Cucurbita Pepo Cultivars Stressed with Heavy Metals

Seedlings of two cultivars of zucchini (Cucurbita pepo L.) Courgette d'Italie (CI) and Courgette d'Alger (CA) were pre-treated with various concentrations of cadmium, copper and zinc for 30 d. High accumulation of heavy metals especially in the roots was showed. Peroxidase activity was affected according to the type of metal added, concentration, and the plant cultivar used. In leaves and roots of the CI control plants peroxidase activities were 50 and 17 % higher than in the CA control plants. Treatment with Cd (5 μg g⁻¹), Cu (200 μg g⁻¹), and Zn (500 μg g⁻¹) increased peroxidase activities in CA but decreased it in CI both in leaves and roots. Heavy metals tested lead also to some qualitative changes characterized by appearance of new isoforms of peroxidase. The results show the possibility to use the activities of peroxidase as biomarkers for Cd, Cu and Zn stresses. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cell Wall-Bound Phenolic Acid and Lignin Contents in Date Palm as Related to its Resistance to Fusarium Oxysporum

The root cell walls of the resistant cultivars of the date palm were more resistant to the action of the cell wall-degrading enzymes (CWDE) of Fusarium oxysporum f. sp. albedinis than those of the susceptible cultivars. Date palm roots contain four cell wall-bound phenolics identified as p-hydroxybenzoic acid, p-coumaric acid, ferulic acid and sinapic acid. The contents of p-coumaric acid and ferulic acid in the resistant cultivars (IKL, SLY, BSTN) were about 2 times higher than those in the susceptible cultivars (BFG, JHL, BSK). The contents of p-hydroxybenzoic acid and sinapic acid in the resistant cultivars were 8.4 and 4.5 times, respectively, higher than those in the susceptible cultivars. The lignin contents in roots of the resistant cultivars were 1.8 times higher than those of the susceptible cultivars. The cell wall-bound phenols accumulated particularly in resistant cultivars reduced strongly the mycelial growth and the CWDE production in vitro.     

Uptake of ferrous iron histidinate, a promoter of lipid peroxidation, by Ehrlich ascites tumor cells

The kinetics of the uptake of Fe(II)-histidinate, a known promoter of lipid peroxidation, into Ehrlich ascites tumor (EAT) cells and the intracellular binding of iron were studied in vitro. EAT cells (27.10(6)/ml) were incubated in Hanks' balanced salts solution at 37 degrees C for various time intervals in the presence of FeSO4 (1 mM) and L-histidine (10 mM). Total iron was determined by the 1,10-phenanthroline/ascorbate method and ferric iron by reaction with 5-sulfosalicylic acid; the difference was ascribed to ferrous iron. Total iron decreased rapidly in the medium (242 nmol within the first 10 min), and a corresponding increase of total iron (saturation value 376 nmol after 60 min) was determined within the cells, after the cellular proteins had been solubilized with 6 M urea. In the absence of EAT cells, Fe(II)-histidinate was readily oxidized to Fe(III)-histidinate by oxygen, but this reaction was strongly retarded by the tumor cells. The uptake of iron histidinate occurred in the oxidized state, while an uptake of ferrous iron could not be proven unambiguously. When EAT cells were saturated with iron, it was found that 93% of intracellular iron was bound to water-insoluble proteins and 7% was associated with soluble proteins, while no unbound iron was detectable by the method used. It was concluded that, despite the high uptake of total iron, only a very small portion of the intracellular iron was available as a redox catalyst for lipid peroxidation.     

Lateralization defects and ciliary dyskinesia: lessons from algae

Flagella and cilia are two very similar organelles that "beat" to move cells and to propel fluid over tissues. They are highly conserved, being found in organisms ranging from prokaryotes to plant and animal eukaryotes. In humans, cilia are present in almost every organ, and several human conditions involve dysfunctional cilia; for example, lateralization defects, where the positions of organs are reversed, and primary ciliary dyskinesia, a rare condition where patients suffer from recurrent respiratory infections. In this article, we will discuss how information gained from studies on algae has aided research into these human diseases. These studies found a variety of functions that was previously unsuspected, renewing interest in cilia.