Dynamic downregulation of Nogo receptor expression in the rat forebrain by amphetamine

Nogo receptors (NgRs) are a family of cell surface receptors that are broadly expressed in the mammalian brain. These receptors could serve as an inhibitory element in the regulation of activity-dependent axonal growth and spine and synaptic formation in the adult animal brain. Thus, through balancing the structural response to changing cellular and synaptic inputs, NgRs participate in constructing activity-dependent morphological plasticity. Psychostimulants have been well documented to induce morphological plasticity critical for addictive properties of stimulants, although underlying molecular mechanisms are poorly understood. In this study, we initiated a study to investigate the response of NgRs to a stimulant. We tested the effect of acute administration of amphetamine on protein expression of two principal NgR subtypes (NgR1 and NgR2) in the rat striatum, medial prefrontal cortex (mPFC) and hippocampus. We found that a single injection of amphetamine induced a rapid and time-dependent decrease in NgR1 and NgR2 expression in the striatum and mPFC. A relatively delayed and time-dependent decrease in expression of the two receptors was seen in the hippocampus. The drug-induced decrease in NgR1 and NgR2 expression in the three forebrain regions was dose-dependent. A behaviorally active dose of the drug was required to trigger a significant reduction in NgR1 and NgR2 expression. These data indicate that NgRs are subject to the regulation by the stimulant. Amphetamine exposure exerts the inhibitory modulation of basal NgR1 and NgR2 expression in the key structures of reward circuits in vivo.     

Phylogenetic clustering of wingbeat frequency and flight‐associated morphometrics across insect orders

Wingbeat frequency in insects is an important variable in aerodynamic and energetic analyses of insect flight and often is studied on a family‐ or species‐level basis. Meta‐analyses of these studies report order‐level patterns suggesting that flight strategy is moderately well conserved phylogenetically. Studies incorporated into these meta‐analyses, however, use variable methodologies across different temperatures, which may confound results and phylogenetic patterns. In the present study, a high‐speed camera is used to measure wingbeat frequency in a wide variety of species (n = 102) under controlled conditions aiming (i) to determine the validity of previous meta‐analyses showing phylogenetic clustering of flight strategy and (ii) to identify new evolutionary patterns between wingbeat frequency, body mass, wing area, wing length and wing loading at the order level. All flight‐associated morphometrics significantly affect wingbeat frequency. Linear models show that wing area explains the most amount of variation in wingbeat frequency (r² = 0.59, P ≤ 0.001), whereas body mass explains the least (r² = 0.09, P ≤ 0.01). A multiple regression model incorporating both body mass and wing area is the best overall predictor of wingbeat frequency (r² = 0.84, P ≤ 0.001). Order‐level phylogenetic patterns across relationships are consistent with previous studies. Thus, the present study provides experimental validation of previous meta‐analyses and provides new insights into phylogenetically conserved flight strategies across insect orders.     

Are recruitment patterns of the trunk musculature compatible with a synergy based on the maximization of endurance?

To verify that maximization of endurance is important among the functional criteria determining trunk muscle activation patterns, symmetric and asymmetric exertions were simulated using a detailed model consisting of 114 muscle slips crossing the lumbosacral junction and employing a cost function which maximizes endurance. First, the question whether meaningful comparisons can be made between activity predictions for individual muscle slips and surface EMG data recorded from larger anatomical entities was addressed. This was answered affirmatively, since activation patterns predicted by a coarse and a middle version of the model, in which activation was constrained to be equal within 14 or 32 groups of muscle slips, were similar to those predicted with each muscle slip controlled independently. Median correlation coefficients between activity vectors predicted by the simplified models and the detailed model were 0.88 and 0.97, respectively. The coarse model underestimated the endurance capacity by a median of 21%, the middle model by only 0.7%. Second, predicted activities within anatomical entities defined at this level of detail were compared to reference data derived from the literature (Lavender et al. 1992, Human Factors 34, 239–247; 1992, Journal of Orthopaedic Research 10, 691–700; Vink et al., 1988, Electromyography and Clinical Neurophysiology 28, 517–525). The predicted activity patterns of the crector spinae, external oblique and rectus abdominis muscles closely resembled the EMG patterns (r² = 0.48–0.99). Furthermore, the observed distribution of activity between parts of the crector spinae muscle was adequately predicted.     

The role of intra-abdominal pressure in spinal unloading

Previous studies on how an increase in intra-abdominal pressure (IAP) effects the loading of the lumbar spine during back extension show diverging results. From a critical review of the literature we deduce a simplified, but consistent, model of the mechanisms involved in IAP-induced unloading of the lumbar spine. The model is then expanded by explicitly incorporating equilibrium equations for the pressurised abdomen and the abdominal wall. It is shown that the unloading effect of IAP can be viewed as that of a pressurised column of fixed cross-sectional area, between the rib cage and pelvis. Different abdominal forms are examined and a form with zero longitudinal curvature is found to have some important mechanical benefits for the generation of IAP-induced alleviation of compressive loading of the lumbar spine.     

Differential control during maximal concentric and eccentric loading revealed by characteristics of the electromyogram

Maximal eccentric loading has been associated with higher levels of spindle afferent activity but lower levels of integrated EMG as compared to maximal concentric loading. Elbow flexor EMG was recorded from 17 subjects during concentric (CONC) and eccentric (ECC) elbow flexion at 70° s⁻¹ using a Kin-Com dynamometer. We hypothesized that peak EMG amplitude would be more sensitive to fluctuations in facilitation by the spindle primary afferents via the segmental stretch reflex pathway, and that the mean EMG would be more reflective of the ongoing level of muscle activation. A ratio of peak to mean EMG (P/M EMG ratio) was predicted to be larger during maximal eccentric loading than maximal concentric loading. The peak EMG (P<0.013) and the P/M EMG ratio (P<0.001) were significantly greater during the ECC condition than the CONC condition. In a subgroup of three subjects who underwent 3 weeks of eccentrically biased weight training, EMG, peak torque and torque variability were assessed before and after training. P/M EMG ratio decreased, while peak torque and torque variability increased following the training. Differences in the P/M EMG ratio appear to reflect differences in the way eccentric and concentric muscle actions are controlled and do not simply represent less control during the eccentric task.     

Passive heat loading links lipolysis and regulation of fibroblast growth factor-21 in humans

There is relativley little information on the serum biomarkers of heat stress. Therefore, the goal of this study was to verify the effect of passive heat loading (PHL) on the expression of fibroblast growth factor-21 (FGF21) and free fatty acids (FFAs). Four PHL protocols based on intensity (39 °C vs. 43 °C, leg immersion, 30 min) and type (leg vs. half immersion, 42 °C, 30 min) were used. Each protocol was applied on a 2 day cycle to 12 healthy adult males (age, 22.4±2.9 years; height, 174.1±4.6 cm; weight, 71.3±5.6 kg; body mass index, 23.1±3.0). The subjects were categorized into two groups according to the study design (randomized, with a parallel trial). Body temperature, FGF21 and FFAs were determined prior to PHL, immediately and 60 min after PHL. Body temperature was significant higher (43 °C) than the 39 °C measured under identical PHL type (leg immersion). PHL was effective for the expression of FGF21 and for lipolysis. The quantitative levels of FGF21 and FFA increased with increasing temperature (39 °C<42 °C<43 °C). A significant difference in the quantitative levels of FGF21 and FFAs was also evident based on the type of PHL (leg<half immersion) even when PHL was applied at the same temperature (42 °C). In conclusion, PHL was effective for expressing FGF21 and for lipolysis. Therefore, PHL may be expected to help in the reduction of body fat. Additionally, when the identical type (leg immersion) of PHL is applied, a loading temperature of 43 °C is more effective for expressing FGF21 and for lipolysis than temperatures of 39 °C and 42 °C, and half immersion is more effective than leg immersion at 42 °C.     

Nitrogen loading into an urban estuary: Lake Pontchartrain (Louisiana,U.S.A.)

We constructed a nitrogen loading budget for the Lake Pontchartrain watershed located north of New Orleans, Louisiana (U.S.A.). Water quality measurements, discharge estimates, and literature values were used to establish the annual and seasonal variations in loading rates for total nitrogen and nitrate. The relatively stable annual loadings (million kg N) are about 10× that of the pre-settlement nitrogen loading, and come from atmosphere (1.3), the watershed (7.8), pumped urban runoff from New Orleans (1.0), and leakage through the Bonnet Carré flood control structure (0.5–0.9). Relatively minor additional amounts come from nitrogen fixation in the Lake. Occasional openings of the Bonnet Carré Spillway (for flood protection) could triple the annual average loading within 1–2 months. Proposed smaller diversions (for wetland restoration) could raise present N loadings by 50%. The results of water quality management, flood protection and wetland restoration may thus have conflicting effects on the Lake's phytoplankton community, which is primarily nitrogen limited. Lowering the total nitrogen loading, however, seems quite possible, especially given that the present loadings are almost all reducible through existing technology, especially sewerage treatment. The analysis demonstrates that the consequences of ecosystem restoration efforts, continued population growth and flood protection to estuarine nitrogen budgets are intertwined with each other, have a seasonal component, and are changing as policies evolve.     

Trophic state and water turn-over time in six choked coastal lagoons in Brazil

Comparison of total phosphorus and chlorophyll-a concentration, nutrient loading, and water turn-over time in six shallow choked lagoons along the coast of the state of Rio de Janeiro, Brazil, established that water turn-over time is related to the trophic state of the lagoons with additional anthropogenic nutrient loading affecting this relationship. Turnover time was calculated as a flushing half-life from rainfall, evaporation, runoff, and tidal exchange data, and trophic state was calculated from the quantity and quality of dissolved inorganic nutrients, total phosphorus, and chlorophyll-a standing stock. Flushing half-life of the lagoons ranged between 1 and 27 days, annual phosphorus areal loading from 3 to 18 mg m^–2d^–1, and chlorophyll-a standing stock from 6 to 160 mg M^–2     

Kinesio taping influences the mechanical behaviour of the skin of the low back: A possible pathway for functionally relevant effects

Despite claims of functional benefits of kinesio tape application, little mechanistic evidence exists to support physiological pathways to achieve these benefits. As kinesio tape is adhered directly to the skin, it can be supposed that any pathway needs to first achieve effects at this level. To address this, two layers of the skin, the combined epidermis and dermis, as well as the hypodermis were studied. Specifically, -kinematic measures of skin surface stretch and retraction, as well as ultrasound measures of skin thickness, were made along all edges of kinesio tape applied over the low back. Results demonstrated that the more superficial skin layer (combined epidermis and dermis), but not the deeper hypodermis, was significantly stretched (p = .0001) and thinner (p = .0016) at either end of the tape, and significantly retracted (p < .0001) and thicker (p = .0001) along the lateral edges of the tape. These results were partly dependent upon spine posture; skin retraction along the tape edges was only apparent in neutral and flexed (but not extended) spine postures, while skin thinning at the tape ends was only apparent in neutral and extended (but not flexed) spine postures. Hypodermal thickness was not affected by kinesio tape application at any location or in any posture. In summary, measured deformations at the skin surface and within the epidermal and dermal regions provide plausible pathways through which kinesio tape could achieve its claimed benefits.     

The relationship between lumbopelvic flexibility and sitting posture in adult women

Clinical observations have suggested that limited hamstring flexibility may be associated with sagittal spinal curvatures in spine flexed postures. Thus, limited hamstring flexibility may be related to large amounts of spine flexion in “slumped” sitting postures which could contribute to low back pain and injury. The aim of this study was to determine if hamstring and pelvic flexibility are associated with flexed sitting postures using a backless office chair. Forty-one healthy female adults aged 18–69 years were recruited. Subjects performed the Sit-and-Reach test to determine maximum flexibility values and lumbar and pelvic angles were measured with accelerometers. Participants then completed a standardized typing task for a 10-minute sitting trial at an ergonomically adjusted workstation. The results showed no association between hamstring flexibility and seated lumbar spine and pelvic angles (p = 0.999, η² = 0.000; p = 0.901, η² = 0.006). Greater pelvic flexibility was associated with a more upright lumbar sitting posture (p = 0.023; η² = 0.132) but with no specific pelvic sitting posture (p = 0.660; η² = 0.005). Different movement strategies during the Sit-and-Reach test were detected: all participants moved through their lumbar spine; but only those with ‘excellent’ flexibility also used their pelvis. Individuals in the ‘excellent’ flexibility group were significantly shorter than those with ‘poor’ and ‘good’ flexibility (p = 0.020; η² = 0.190). In conclusion, hamstring flexibility does not influence sitting posture but pelvic flexibility does. Other factors such as acetabulofemoral joint limitations, consciousness of posture, or the seat itself may also influence sitting posture. Different movement strategies as well as height appear to contribute to the Sit-and-Reach test which should be researched further.