The disease mechanism of Rett syndrome (RTT) is not well understood. Studies in RTT mouse models have suggested a non-cell-autonomous role for astrocytes in RTT pathogenesis. However, it is not clear whether this is also true for human RTT astrocytes. To establish an in vitro human RTT model, we previously generated isogenic induced pluripotent stem cell (iPSC) lines from several RTT patients carrying different disease-causing mutations. Here, we show that these RTT iPSC lines can be efficiently differentiated into astroglial progenitors and glial fibrillary acidic protein-expressing (GFAP(+)) astrocytes that maintain isogenic status, that mutant RTT astrocytes carrying three different RTT mutations and their conditioned media have adverse effects on the morphology and function of wild-type neurons and that the glial effect on neuronal morphology is independent of the intrinsic neuronal deficit in mutant neurons. Moreover, we show that both insulin-like growth factor 1 (IGF-1) and GPE (a peptide containing the first 3 amino acids of IGF-1) are able to partially rescue the neuronal deficits caused by mutant RTT astrocytes. Our findings confirm the critical glial contribution to RTT pathology, reveal potential cellular targets of IGF-1 therapy and further validate patient-specific iPSCs and their derivatives as valuable tools to study RTT disease mechanism.

Extracellular accumulation of ␤-amyloid peptide (A␤) has been linked to the development of Alzheimer disease. The importance of intraneuronal A␤ has been recognized more recently. Although considerable evidence indicates that extracellular A␤ contributes to the intracellular pool of A␤, the mechanisms involved in A␤ uptake by neurons are poorly understood. We examined the molecular mechanisms involved in A␤-(1-42) internalization by primary neurons in the absence of apolipoprotein E. We demonstrated that A␤-(1-42) is more efficiently internalized by axons than by cell bodies of sympathetic neurons, suggesting that A␤-(1-42) uptake might be mediated by proteins enriched in the axons. Although the acetylcholine receptor ␣7nAChR, previously suggested to be involved in A␤ internalization, is enriched in axons, our results indicate that it does not mediate A␤-(1-42) internalization. Moreover, receptors of the low density lipoprotein receptor family are not essential for A␤-(1-42) uptake in the absence of apolipoprotein E because receptor-associated protein had no effect on A␤ uptake. By expressing the inactive dynamin mutant dynK44A and the clathrin hub we found that A␤-(1-42) internalization is independent of clathrin but dependent on dynamin, which suggests an endocytic pathway involving caveolae/lipid rafts. Confocal microscopy studies showing that A␤ did not colocalize with the early endosome marker EEA1 further support a clathrin-independent mechanism. The lack of co-localization of A␤ with caveolin in intracellular vesicles and the normal uptake of A␤ by neurons that do not express caveolin indicate that A␤ does not require caveolin either. Instead partial co-localization of A␤-(1-42) with cholera toxin subunit B and sensitivity to reduction of cellular cholesterol and sphingolipid levels suggest a caveolae-independent, raft-mediated mechanism. Understanding the molecular events involved in neuronal A␤ internalization might identify potential therapeutic targets for Alzheimer disease.In brains of individuals with Alzheimer disease (AD), 2 ␤-amyloid peptide (A␤) aggregates and accumulates as toxic fibrils in neuritic plaques and toxic soluble oligomers (1). A␤ is a 39 -43-amino acid peptide derived from the proteolytic cleavage of the amyloid precursor protein (APP) (2). The amyloid cascade hypothesis predicts that a gradual increase of A␤-(1-42) levels in brain interstitial fluid (3, 4) may lead to A␤ oligomerization and eventually to A␤ fibrillization (5). Current evidence indicates that intraneuronal accumulation of A␤ is an early pathological biomarker for the onset of AD and may contribute to the cascade of neurodegenerative events (6). The observation that cortical neurons that accumulate A␤-(1-42) in brains of Down syndrome patients are apoptotic (7, 8) provided additional indications of the importance of intracellular A␤ (7,8). Furthermore, microinjection of A␤-(1-42) or cDNA encoding A␤-(1-42) in cultured human neurons resulted in neurotoxicity (9). Besides, in the triple transgenic mouse model for AD t...

SummaryHow the direction of axon guidance is determined is not understood. In Caenorhabditis elegans the UNC-40 (DCC) receptor mediates a response to the UNC-6 (netrin) guidance cue that directs HSN axon development. UNC-40 becomes asymmetrically localized within the HSN neuron to the site of axon outgrowth. Here we provide experimental evidence that the direction of guidance can be explained by the stochastic fluctuations of UNC-40 asymmetric outgrowth activity. We find that the UNC-5 (UNC5) receptor and the cytoskeletal binding protein UNC-53 (NAV2) regulate the induction of UNC-40 localization by UNC-6. If UNC-40 localization is induced without UNC-6 by using an unc-53 mutation, the direction of UNC-40 localization undergoes random fluctuations. Random walk models describe the path made by a succession of randomly directed movement. This model was experimentally tested using mutations that affect Wnt/PCP signaling. These mutations inhibit UNC-40 localization in the anterior and posterior directions. As the axon forms in Wnt/PCP mutants, the direction of UNC-40 localization randomly fluctuates; it can localize in either the anterior, posterior, or ventral direction. Consistent with a biased random walk, over time the axon will develop ventrally in response to UNC-6, even though at a discrete time UNC-40 localization and outgrowth can be observed anterior or posterior. Also, axon formation is slower in the mutants than in wild-type animals. This is also consistent with a random walk since this model predicts that the mean square displacement (msd) will increase only linearly with time, whereas the msd increases quadratically with time for straight-line motion.

In the brain, the amyloid β peptide (Aβ) exists extracellularly and inside neurons. The intracellular accumulation of Aβ in Alzheimer's disease brain has been questioned for a long time. However, there is now sufficient strong evidence indicating that accumulation of Aβ inside neurons plays an important role in the pathogenesis of Alzheimer's disease. Intraneuronal Aβ originates from intracellular cleavage of APP and from Aβ internalization from the extracellular milieu. We discuss here the different molecular mechanisms that are responsible for Aβ internalization in neurons and the links between Aβ internalization and neuronal dysfunction and death. A brief description of Aβ uptake by glia is also presented.

Introduction: Haemodialysis patients are at an increased risk of sarcopenia. Physical inactivity is now recognised as a major cause of muscle wasting in haemodialysis patients. It is unclear as to what and how much exercise is required to show benefit. We therefore performed a pilot study of cycling during haemodialysis. Methods: Patients underwent a progressive submaximal individualised cycling exercise, 3× a week during haemodialysis for 4 months using bed-cycle ergometers. Body composition was measured by multifrequency segmental bioimpedance and muscle function by 6-min walking test, and hand grip strength and pinch strength. Results: In total, 56% of patients in a dialysis centre fulfilled exercise study inclusion criteria and 13 (72.2%) of 18 patients completed the exercise programme, with the mean age of 64.0 ± 16.6 years and 76.9% being male. The 6-min walking test increased following exercise from 349 ± 105 to 398 ± 94.2 m, p < 0.05, as did both hand grip strength and pinch strength, with 20.4 ± 9.1 versus 23.4 ± 9.9 kg, p < 0.01, and 4.3 ± 1.8 versus 5.9 ± 2.4 kg, p < 0.05, respectively. There were no changes in appendicular muscle mass or other body composition detected with bioimpedance in either the exercise group, or 21 control patients, propensity matched for body composition, comorbidity and frailty. Muscle strength did not change in the control group. Haemodialysis sessional Kt/Vurea was greater at the end of the exercise programme compared to controls (1.63 ± 0.63 vs 1.21 ± 0.12, p < 0.01). Conclusion: The majority of dialysis centre patients met our exercise study entry criteria and could potentially benefit from cycling during haemodialysis. We found that muscle function and strength improved after a 4-month, thrice weekly cycling exercise programme.

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To understand how our brains function, it is necessary to know how neurons position themselves and target their axons and dendrites to their correct locations. Several evolutionarily conserved axon guidance molecules have been shown to help navigate axons to their correct target site. The Caenorhabditis elegans Eph receptor tyrosine kinase (RTK), VAB-1, has roles in early neuroblast and epidermal cell movements, but its roles in axon guidance are not well understood. Here, we report that mutations that disrupt the VAB-1 Eph receptor tyrosine kinase cause incompletely penetrant defects in axonal targeting and neuronal cell body positioning. The predominant axonal defect in vab-1 mutant animals was an overextension axon phenotype. Interestingly, constitutively active VAB-1 tyrosine kinase signaling caused a lack of axon outgrowth or an early termination phenotype, opposite to the loss-of-function phenotype. The combination of loss-of-function and gain-of-function analyses suggests that the VAB-1 Eph RTK is required for targeting or limiting axons and neuronal cells to specific regions, perhaps by transducing a repellent or stop cue.

Microbial contamination affects beverages’ lifetime, quality, and safety. Cucumber crops are seasonally spoiled because of the overproduction. The current study aimed to maximize the importance of natural preservatives and reduce the usage of artificial ones to prolong the cucumber juice’s storage life, enhance flavor, and control the microorganisms after protein isolate and organic acids supplementation. The additions included control (no addition), citric, benzoic acid, sodium salts, kidney bean pepsin hydrolysate (KPH), chicken egg protein isolate (CEPI), duck egg protein isolate (DEPI), and quail egg protein isolate (QEPI) as J-Control, J-Citric, J-Benzoic, J-sod. Citrate, J-sod. Benzoate, J-KPH, J-CEPI, J-DEPI, and J-QEPI, respectively. The antioxidant activity of these additives and juices was evaluated by DPPH radical scavenging activity. The antimicrobial activity, including antibacterial and antifungal activities, was evaluated by using disc assay and the radial growth of fungal mycelium, respectively. The phenolic compounds and flavonoids were estimated by a spectrophotometer as Gallic acid equivalent (GAE) and quercetin equivalent (QE), respectively. Moreover, chemical parameters such as pH, total soluble solids (TSS), Titratable acidity (TTA), and Vitamin C were evaluated by AOAC. Finally, the color properties were estimated by a spectrophotometer, using the Hunter method. KPH had higher significant (p ≤ 0.05) antioxidant activity (88%), along with antimicrobial activity. It significantly (p ≤ 0.05) reduced the growth of G+ and G− bacteria by 71–97% and 58–66% respectively. Furthermore, it significantly (p ≤ 0.05) inhibited the tested fungi growth by 70–88% and the other additives less than that. During the storage of cucumber juice for an interval of zero, two, four, and six months, the phenolic compounds and flavonoids were significantly (p ≤ 0.05) decreased. Consequently, the potential activity of the juice was reduced; in addition, pH and vitamin C were significantly (p ≤ 0.05) decreased during the storage period. Meanwhile, the TSS and Titratable acidity were significantly raised. As for color and sensory properties, J-sod. Benzoate, J-KPH, J-CEPI, and J-DEPI had significantly (p ≤ 0.05) high scores in color, taste, and flavor against the control. Generally, the usage of natural additives extends the cucumber juice’s lifetime and increased the manufacture of high-quality and valuable juice.