Increased acetylcholine and glutamate efflux in the prefrontal cortex following intranasal orexin‐A (hypocretin‐1)

Orexin/hypocretin neurons of the lateral hypothalamus and perifornical area are integrators of physiological function. Previous work from our laboratory and others has shown the importance of orexin transmission in cognition. Age‐related reductions in markers of orexin function further suggest that this neuropeptide may be a useful target for the treatment of age‐related cognitive dysfunction. Intranasal administration of orexin‐A (OxA) has shown promise as a therapeutic option for cognitive dysfunction. However, the neurochemical mechanisms of intranasal OxA administration are not fully understood. Here, we use immunohistochemistry and in vivo microdialysis to define the effects of acute intranasal OxA administration on: (i) activation of neuronal populations in the cortex, basal forebrain, and brainstem and (ii) acetylcholine (AC h) and glutamate efflux in the prefrontal cortex (PFC ) of Fischer 344/Brown Norway F1 rats. Acute intranasal administration of OxA significantly increased c‐Fos expression, a marker for neuronal activation, in the PFC and in subpopulations of basal forebrain cholinergic neurons. Subsequently, we investigated the effects of acute intranasal OxA on neurotransmitter efflux in the PFC and found that intranasal OxA significantly increased both AC h and glutamate efflux in this region. These findings were independent from any changes in c‐Fos expression in orexin neurons, suggesting that these effects are not resultant from direct activation of orexin neurons. In total, these data indicate that intranasal OxA may enhance cognition through activation of distinct neuronal populations in the cortex and basal forebrain and through increased neurotransmission of AC h and glutamate in the PFC .

     

DNA divergence in and around the alcohol dehydrogenase locus in five closely related species of Hawaiian Drosophila

The alcohol dehydrogenase (Adh) region from five planitibia subgroup species of Hawaiian picture-wing Drosophila has been cloned. A total of 15 kb of DNA in and around the Adh gene has been compared among the five species. Genetic distances were calculated to determine evolutionary relationships. These distances agree with previous distances determined by protein polymorphism and DNA hybridization techniques and can be interpreted in terms of specific island colonization and speciation (founder) events over the past 5 Myr. Examination of the restriction maps of the cloned Adh region from the five species shows many instances of small deletions, insertion of a transposable element in D. heteroneura, and the existence of a highly variable region on the 3' side of the Adh gene. Clustering relationships and rates of DNA change are calculated and compared with the relationship found for other species of Drosophila.      

Impact of Nutrition and Salinity Changes on Biological Performances of Green and White Sturgeon

Green and white sturgeon are species of high conservational and economic interest, particularly in the San Francisco Bay Delta (SFBD) for which significant climate change-derived alterations in salinity and nutritional patterns are forecasted. Although there is paucity of information, it is critical to test the network of biological responses underlying the capacity of animals to tolerate current environmental changes. Through nutrition and salinity challenges, climate change will likely have more physiological effect on young sturgeon stages, which in turn may affect growth performance. In this study, the two species were challenged in a multiple-factor experimental setting, first to levels of feeding rate, and then to salinity levels for different time periods. Data analysis included generalized additive models to select predictors of growth performance (measured by condition factor) among the environmental stressors considered and a suite of physiological variables. Using structural equation modeling, a path diagram is proposed to quantify the main linkages among nutrition status, salinity, osmoregulation variables, and growth performances. Three major trends were anticipated for the growth performance of green and white sturgeon in the juvenile stage in the SFBD: (i) a decrease in prey abundance will be highly detrimental for the growth of both species; (ii) an acute increase in salinity within the limits studied can be tolerated by both species but possibly the energy spent in osmoregulation may affect green sturgeon growth within the time window assessed; (iii) the mechanism of synergistic effects of nutrition and salinity changes will be more complex in green sturgeon, with condition factor responding nonlinearly to interactions of salinity and nutrition status or time of salinity exposure. Green sturgeon merits special scientific attention and conservation effort to offset the effects of feed restriction and salinity as key environmental stressors in the SFBD.     

Calcium Currents Are Enhanced by ��2��-1 Lacking Its Membrane Anchor

The accessory α₂δ subunits of voltage-gated calcium channels are membrane-anchored proteins, which are highly glycosylated, possess multiple disulfide bonds, and are post-translationally cleaved into α₂ and δ. All α₂δ subunits have a C-terminal hydrophobic, potentially trans-membrane domain and were described as type I transmembrane proteins, but we found evidence that they can be glycosylphosphatidylinositol-anchored. To probe further the function of membrane anchoring in α₂δ subunits, we have now examined the properties of α₂δ-1 constructs truncated at their putative glycosylphosphatidylinositol anchor site, located before the C-terminal hydrophobic domain (α₂δ-1ΔC-term). We find that the majority of α₂δ-1ΔC-term is soluble and secreted into the medium, but unexpectedly, some of the protein remains associated with detergent-resistant membranes, also termed lipid rafts, and is extrinsically bound to the plasma membrane. Furthermore, heterologous co-expression of α₂δ-1ΔC-term with Ca_V2.1/β1b results in a substantial enhancement of the calcium channel currents, albeit less than that produced by wild-type α₂δ-1. These results call into question the role of membrane anchoring of α₂δ subunits for calcium current enhancement.     

Two distinct conformational states define the interaction of human RAD51‐ATP with single‐stranded DNA

An essential mechanism for repairing DNA double‐strand breaks is homologous recombination (HR). One of its core catalysts is human RAD51 (hRAD51), which assembles as a helical nucleoprotein filament on single‐stranded DNA, promoting DNA‐strand exchange. Here, we study the interaction of hRAD51 with single‐stranded DNA using a single‐molecule approach. We show that ATP‐bound hRAD51 filaments can exist in two different states with different contour lengths and with a free‐energy difference of ~4 k_BT per hRAD51 monomer. Upon ATP hydrolysis, the filaments convert into a disassembly‐competent ADP‐bound configuration. In agreement with the single‐molecule analysis, we demonstrate the presence of two distinct protomer interfaces in the crystal structure of a hRAD51‐ATP filament, providing a structural basis for the two conformational states of the filament. Together, our findings provide evidence that hRAD51‐ATP filaments can exist in two interconvertible conformational states, which might be functionally relevant for DNA homology recognition and strand exchange.     

Effects of load and tone on the mechanics of isolated human bronchial smooth muscle

Isotonic and isometric properties of nine human bronchial smoothmuscles were studied under various loading and tone conditions. Freshlydissected bronchial strips were electrically stimulated successively atbaseline, after precontraction with10⁷ M methacholine (MCh),and after relaxation with10⁵ M albuterol (Alb).Resting tension, i.e., preload determining optimal initial length(L_o) atbaseline, was held constant. Compared with baseline, MCh decreasedmuscle length to 93 ± 1%L_o(P < 0.001) before any electricalstimulation, whereas Alb increased it to 111 ± 3%L_o(P < 0.01). MCh significantlydecreased maximum unloaded shortening velocity (0.045 ± 0.007 vs.0.059 ± 0.007 L_o/s), maximalextent of muscle shortening (8.4 ± 1.2 vs. 13.9 ± 2.4%L_o), and peakisometric tension (6.1 ± 0.8 vs. 7.2 ± 1.0 mN/mm²). Alb restored all thesecontractile indexes to baseline values. These findings suggest that MChreversibly increased the number of active actomyosin cross bridgesunder resting conditions, limiting further muscle shortening and activetension development. After the electrically induced contraction,muscles showed a transient phase of decrease in tension below preload.This decrease in tension was unaffected by afterload levels but wassignificantly increased by MCh and reduced by Alb. These findingssuggest that the cross bridges activated before, but not during, theelectrically elicited contraction may modulate the phase of decrease intension below preload, reflecting the active part of resting tension.     

Regulation of middle cerebral artery blood velocity during recovery from dynamic exercise in humans.

We sought to examine the regulation of cerebral blood flow during 10 min of recovery from mild, moderate, and heavy cycling exercise by measuring middle cerebral artery blood velocity (MCA V). Transfer function analyses between changes in arterial blood pressure and MCA V were used to assess the frequency components of dynamic cerebral autoregulation (CA). After mild and moderate exercise, the decreases in mean arterial pressure (MAP) and mean MCA V (MCA Vm) were small. However, following heavy exercise, MAP was rapidly and markedly reduced, whereas MCA Vm decreased slowly (-23 +/- 4 mmHg and -4 +/- 1 cm/s after 1 min for MAP and MCA Vm, respectively; means +/- SE). Importantly, for each workload, the normalized low-frequency transfer function gain between MAP and MCA Vm remained unchanged from rest to exercise and during recovery, indicating a maintained dynamic CA. Similar results were found for the systolic blood pressure and systolic MCA V relationship. In contrast, the normalized low-frequency transfer function gain between diastolic blood pressure and diastolic MCA V (MCA Vd) increased from rest to exercise and remained elevated in the recovery period (P < 0.05). However, MCA Vd was quite stable on the cessation of exercise. These findings suggest that MCA V is well maintained following mild to heavy dynamic exercise. However, the increased transfer function gain between diastolic blood pressure and MCA Vd suggests that dynamic CA becomes less effective in response to rapid decreases in blood pressure during the initial 10 min of recovery from dynamic exercise.     

Growth assessment of children exposed to low frequency electromagnetic fields at the Abu Sultan area in Ismailia (Egypt)

A cross-sectional study was carried out to assess the growth of 780 children of both sexes, aged between 0-12 years, and living at two different areas in Ismailia, Egypt, with approximately similar socioeconomic standards. Based on a designed questionaire, the exposed group was formed of 390 children from the Abu Sultan area. They were chosen from families living within 50 meters nearby high voltage electric power lines. Another 390 children from the El-Sheikh Zayed area were chosen as the control group. Standard anthropometric measurements were carried out for each child. Plain X-ray was done on the hands of 200 randomly selected children from both groups (100 each) to assess their bone maturation. In the exposed group the weight was significantly decreased only at birth, while the circumferences of the head and chest as well as the height were significantly reduced at all studied ages. The radiological study revealed a significant delay in carpal bone ossification of the exposed children. In conclusion: Exposure to low frequency electromagnetic fields emerged from high voltage electric power lines increases the incidence of growth retardation of children. Isolating these power lines in a scientific way in order to shield both the magnetic and electric fields or removing them far away from the inhabitant areas is recommended.