Entrainment of vastus medialis complex activity differs between genders

Introduction: That the vastus medialis oblique (VMO) is a functional unit of the vastus medialis (VM) is disputed. Delayed VMO activation predicts patellofemoral pain, which has higher rates in women. Methods: Single MUs and surface electromyogram (EMG) were collected from the VMO and VM of 9 men and 9 women. Men were tested once; women were tested during 5 menstrual phases. Coherence was assessed for motor unit (MU) firings within and between the VM and VMO using multilevel logistic models to determine statistical significance. Results: Compared with women, men have 741% (MU pairs) and 256% (MU‐EMG pairs) greater odds of common drive (0–5 Hz ) coherent oscillations. MU pairs from the VMO and the dual VM/VMO complex have 228% and 212% greater odds of coherent oscillations in the beta band (15–35 Hz ) compared with VM pairs. Conclusions: The VM and VMO are neurologically different muscles; control of the VM complex is sexually dimorphic. Muscle Nerve 53 : 633–640, 2016     

Baclofen prevents the elevated plus maze behavior and BDNF expression during naloxone precipitated morphine withdrawal in male and female mice

In previous studies we have shown that baclofen, a selective GABA_B receptor agonist, prevents the somatic expression and reestablishes the dopamine and μ‐opioid receptors levels, modified during naloxone‐precipitated morphine withdrawal syndrome in male and female mice. There are no previous reports regarding sex differences in the elevated plus maze (EPM) and the expression of BDNF in morphine‐withdrawn mice. The present study analyses the behavioral and biochemical variations during morphine withdrawal in mice of both sexes, and whether these variations are prevented with baclofen. Swiss‐Webster albino prepubertal mice received morphine (2 mg/kg, i.p.) twice daily, for 9 consecutive days. On the 10th day, one group of morphine‐treated mice received naloxone (opioid receptor antagonist; 6 mg/kg, i.p.) 1 h after the last dose of morphine to precipitate withdrawal. A second group received baclofen (2 mg/kg, i.p.) before naloxone administration. The EPM behavior was measured during 15 min after naloxone injection. The expression of BDNF‐positive cells was determined by immunohistochemistry. Withdrawn male mice showed a higher percentage of time spent and number of entries to the open arms compared to withdrawn female mice. Baclofen prevented this behavior in both sexes. BDNF expression decreased in the AcbC, BNST, CeC, and CA3 of the hippocampus while increased in the BLA of morphine withdrawn male. Baclofen pretreatment prevented the BDNF expression observed in morphine withdrawn male mice in all the brain areas studied except in the CeC. Baclofen prevention of the EPM behavior associated to morphine withdrawal could be partially related to changes in BDNF expression. Synapse, 2016 . © 2016 Wiley Periodicals, Inc. Synapse 70:187–197, 2016. © 2016 Wiley Periodicals, Inc.     

Differential effects of stress on microglial cell activation in male and female medial prefrontal cortex

Susceptibility to stress-linked psychological disorders, including post-traumatic stress disorder and depression, differs between men and women. Dysfunction of medial prefrontal cortex (mPFC) has been implicated in many of these disorders. Chronic stress affects mPFC in a sex-dependent manner, differentially remodeling dendritic morphology and disrupting prefrontally mediated behaviors in males and females. Chronic restraint stress induces microglial activation, reflected in altered microglial morphology and immune factor expression, in mPFC in male rats. Unstressed females exhibit increased microglial ramification in several brain regions compared to males, suggesting both heightened basal activation and a potential for sex-dependent effects of stress on microglial activation. Therefore, we assessed microglial density and ramification in the prelimbic region of mPFC, and immune-associated genes in dorsal mPFC in male and female rats following acute or chronic restraint stress. Control rats were left unstressed. On the final day of restraint, brains were collected for either qPCR or visualization of microglia using Iba-1 immunohistochemistry. Microglia in mPFC were classified as ramified, primed, reactive, or amoeboid, and counted stereologically. Expression of microglia-associated genes (MHCII, CD40, IL6, CX3CL1, and CX3CR1) was also assessed using qPCR. Unstressed females showed a greater proportion of primed to ramified microglia relative to males, alongside heightened CX3CL1–CX3CR1 expression. Acute and chronic restraint stress reduced the proportion of primed to ramified microglia and microglial CD40 expression in females, but did not significantly alter microglial activation in males. This sex difference in microglial activation could contribute to the differential effects of stress on mPFC structure and function in males versus females.     

Food‐Restriction Lowers the Acoustic Startle Response in both Male and Female Rats,and, in Combination with Acute Ghrelin Injection,Abolishes the Expression of Fear‐Potentiated Startle in Male Rats

Food restriction has been reported to reduce anxiety‐like behaviour in male rats, whereas the effects of food restriction on anxiety in female rats are less clear. Ghrelin is a peptide hormone produced and secreted in the stomach that stimulates food intake and is considered to play a role in reward and emotional responses such as fear expression. Under food restriction, endogenous ghrelin levels increase. In the present study, we examined the effect of moderate food restriction (80% of ad libitum fed weight), with or without an acute application of a small dose of exogenous ghrelin intended to cause an immediate hunger response, on the expression of the acoustic startle reflex (ASR). This was carried out under basal conditions (baseline ASR to 90‐ and 95‐dB noise bursts), and in the presence of a light cue associated with a mild foot‐shock, as measured by fear‐potentiated startle, which compares the proportional change in ASR in the presence of the conditioned stimulus. The results obtained show that food‐restriction reduces basal ASR in both male and female rats, apart from any concomitant change in motor activity, suggesting that food‐restriction reduces anxiety levels in both sexes. In addition, the data show that food‐restriction reduces fear‐potentiated startle in male but not female rats. Acute ghrelin injection, prior to fear‐potentiated startle testing, eliminates the expression of fear‐potentiated startle in food‐restricted male rats alone, suggesting a role for ghrelin in the reduction of fear expression in food‐restricted male rats. These data imply that, although food‐restriction decreases anxiety in both sexes, learned fear responses remain intact after food‐restriction in female but not male rats.     

Gender Differences in Trajectories of Lower Extremity Function in Older Adults: Findings From the International Mobility in Aging Study

ObjectivesWe examined the lower extremity function trajectories of older men and women over 4 years and baseline predictors of these trajectories.DesignLongitudinal analysis of an international cohort study.Settings and participantsOlder adults from the International Mobility in Aging Study (IMIAS) aged between 65 and 74 years at baseline.MeasuresPhysical performance of the lower extremities was measured in 2012, with follow-ups in 2014 and in 2016, using the Short Physical Performance Battery (SPPB). Group-based trajectory analysis of physical performance by gender was performed. Multinomial logistic regression was used to derive relative risk ratios with 95% confidence intervals between the physical performance trajectories and the potential baseline predictors in men and women separately.ResultsThree physical performance trajectories were identified in men and women: high-stable (30.0% vs 35.5%), gradual functional decline (63.1% vs 54.3%), and rapid functional decline (6.9% vs 10.2%). Common baseline characteristics associated with memberships in the gradual functional decline and rapid functional decline trajectory groups in men and women were age, single marital status, and multiple chronic conditions (>3). Among men, depression was a strong predictor of the membership in the rapid functional decline trajectory group. Women in the rapid functional decline trajectory group were more likely to be obese, with feminine and undifferentiated gender roles, and have poor self-rated health at baseline.Conclusions/ImplicationsThere are gender differences in the physical performance trajectories and related factors among older adults. Programs aiming at preventing or slowing functional decline in old age should be sensitive to gender.     

Young adolescents' perceived activity space risk,peer networks,and substance use

Adolescent substance use is a developmentally contingent social practice that is constituted within the routine social-environment of adolescents' lives. Few studies have examined peer networks, perceived activity space risk (risk of substance use at routine locations), and substance use. We examined the moderating influence of peer network characteristics on the relationship between perceived activity space risk and substance use among a sample of 250 urban adolescents. Significant interactions were found between peer networks and perceived activity space risk on tobacco and marijuana use, such that protective peer networks reduced the effect of activity place risk on substance use. A significant 3-way interaction was found on marijuana use indicating that gender moderated peer network's effect on activity space risk. Conditional effect analysis found that boys' peer networks moderated the effect of perceived activity space risk on marijuana use, whereas for girls, the effect of perceived activity space risk on marijuana use was not moderated by their peer networks. These findings could advance theoretical models to inform social–environmental research among adolescents.     

Age as a moderator of the secular trend for grip strength in Canada and the United States

Purpose: To determine whether grip strength changed on average over recent decades at each of two age levels (children and adolescents versus adults) in Canada and the US.

Methods: For each sex, weighted least squares regression analyses were performed on mean grip strength values as reported in studies conducted from the 1960s onwards.

Results: Grip strength did not change significantly as a function of year tested in children and adolescents, whereas it declined as a negatively accelerated function of year tested in adults.

Conclusion: The results are contrary to what might be expected given that body weight has increased in both countries in recent decades and given that grip strength has been found to be positively correlated with body weight. It is suggested that there was a concurrent change in a factor that operated to counteract the effect of increased body weight on grip strength, a prime candidate being a decrease in levels of serum vitamin D. It is also suggested that the secular decline in adult grip strength can be explained by a factor that affects muscular function but which has a long latency period, a prime candidate here being obesity history.     

Although female patients with ankylosing spondylitis score worse on disease activity than male patients and improvement in disease activity is comparable,male patients show more radiographic progression during treatment with TNF-α inhibitors

Background

The clinical presentation of ankylosing spondylitis (AS) differs between genders. Our aim was to investigate differences in disease activity, disease outcome and treatment response between male and female AS patients before and after starting tumor necrosis factor (TNF)-α inhibitors in daily clinical practice.