Preventing phosphorylation of dystroglycan ameliorates the dystrophic phenotype in mdx mouse

Loss of dystrophin protein due to mutations in the DMD gene causes Duchenne muscular dystrophy. Dystrophin loss also leads to the loss of the dystrophin glycoprotein complex (DGC) from the sarcolemma which contributes to the dystrophic phenotype. Tyrosine phosphorylation of dystroglycan has been identified as a possible signal to promote the proteasomal degradation of the DGC. In order to test the role of tyrosine phosphorylation of dystroglycan in the aetiology of DMD, we generated a knock-in mouse with a phenylalanine substitution at a key tyrosine phosphorylation site in dystroglycan, Y890. Dystroglycan knock-in mice (Dag1Y890F/Y890F) had no overt phenotype. In order to examine the consequence of blocking dystroglycan phosphorylation on the aetiology of dystrophin-deficient muscular dystrophy, the Y890F mice were crossed with mdx mice an established model of muscular dystrophy. Dag1Y890F/Y890F/mdx mice showed a significant improvement in several parameters of muscle pathophysiology associated with muscular dystrophy, including a reduction in centrally nucleated fibres, less Evans blue dye infiltration and lower serum creatine kinase levels. With the exception of dystrophin, other DGC components were restored to the sarcolemma including α-sarcoglycan, α-/β-dystroglycan and sarcospan. Furthermore, Dag1Y890F/Y890F/mdx showed a significant resistance to muscle damage and force loss following repeated eccentric contractions when compared with mdx mice. While the Y890F substitution may prevent dystroglycan from proteasomal degradation, an increase in sarcolemmal plectin appeared to confer protection on Dag1Y890F/Y890F/mdx mouse muscle. This new model confirms dystroglycan phosphorylation as an important pathway in the aetiology of DMD and provides novel targets for therapeutic intervention

Targeted Delivery of Chemotherapy Agents Using a Liver Cancer-Specific Aptamer

Using antibody/aptamer-drug conjugates can be a promising method for decreasing toxicity, while increasing the efficiency of chemotherapy.In this study, the antitumor agent Doxorubicin (Dox) was incorporated into the modified DNA aptamer TLS11a-GC, which specifically targets LH86, a human hepatocellular carcinoma cell line. Cell viability tests demonstrated that the TLS11a-GC-Dox conjugates exhibited both potency and target specificity. Importantly, intercalating Dox into the modified aptamer inhibited nonspecific uptake of membrane-permeable Dox to the non-target cell line. Since the conjugates are selective for cells that express higher amounts of target proteins, both criteria noted above are met, making TLS11a-GC-Dox conjugates potential candidates for targeted delivery to liver cancer cells.Considering the large number of available aptamers that have specific targets for a wide variety of cancer cells, this novel aptamer-drug intercalation method will have promising implications for chemotherapeutics in general

Falls in young, middle-aged and older community dwelling adults: perceived cause, environmental factors and injury

BACKGROUND: Falls in older people have been characterized extensively in the literature, however little has been reported regarding falls in middle-aged and younger adults. The objective of this paper is to describe the perceived cause, environmental influences and resultant injuries of falls in 1497 young (20–45 years), middle-aged (46–65 years) and older (> 65 years) men and women from the Baltimore Longitudinal Study on Aging. METHODS: A descriptive study where participants completed a fall history questionnaire describing the circumstances surrounding falls in the previous two years. RESULTS: The reporting of falls increased with age from 18% in young, to 21% in middle-aged and 35% in older adults, with higher rates in women than men. Ambulation was cited as the cause of the fall most frequently in all gender and age groups. Our population reported a higher percentage of injuries (70.5%) than previous studies. The young group reported injuries most frequently to wrist/hand, knees and ankles; the middle-aged to their knees and the older group to their head and knees. Women reported a higher percentage of injuries in all age groups. CONCLUSION: This is the first study to compare falls in young, middle and older aged men and women. Significant differences were found between the three age groups with respect to number of falls, activities engaged in prior to falling, perceived causes of the fall and where they fell

Evidence for inhibition of cholinesterases in insect and mammalian nervous systems by the insect repellent deet

<p>Abstract</p> <p>Background</p> <p>N,N-Diethyl-3-methylbenzamide (deet) remains the gold standard for insect repellents. About 200 million people use it every year and over 8 billion doses have been applied over the past 50 years. Despite the widespread and increased interest in the use of deet in public health programmes, controversies remain concerning both the identification of its target sites at the olfactory system and its mechanism of toxicity in insects, mammals and humans. Here, we investigated the molecular target site for deet and the consequences of its interactions with carbamate insecticides on the cholinergic system.</p> <p>Results</p> <p>By using toxicological, biochemical and electrophysiological techniques, we show that deet is not simply a behaviour-modifying chemical but that it also inhibits cholinesterase activity, in both insect and mammalian neuronal preparations. Deet is commonly used in combination with insecticides and we show that deet has the capacity to strengthen the toxicity of carbamates, a class of insecticides known to block acetylcholinesterase.</p> <p>Conclusion</p> <p>These findings question the safety of deet, particularly in combination with other chemicals, and they highlight the importance of a multidisciplinary approach to the development of safer insect repellents for use in public health.</p

Interatomic potentials and solvation parameters from protein engineering data for buried residues

Van der Waals (vdW) interaction energies between different atom types, energies of hydrogen bonds (H‐bonds), and atomic solvation parameters (ASPs) have been derived from the published thermodynamic stabilities of 106 mutants with available crystal structures by use of an originally designed model for the calculation of free‐energy differences. The set of mutants included substitutions of uncharged, inflexible, water‐inaccessible residues in α‐helices and β‐sheets of T4, human, and hen lysozymes and HI ribonuclease. The determined energies of vdW interactions and H‐bonds were smaller than in molecular mechanics and followed the “like dissolves like” rule, as expected in condensed media but not in vacuum. The depths of modified Lennard‐Jones potentials were −0.34, −0.12, and −0.06 kcal/mole for similar atom types (polar–polar, aromatic–aromatic, and aliphatic–aliphatic interactions, respectively) and −0.10, −0.08, −0.06, −0.02, and nearly 0 kcal/mole for different types (sulfur–polar, sulfur–aromatic, sulfur–aliphatic, aliphatic–aromatic, and carbon–polar, respectively), whereas the depths of H‐bond potentials were −1.5 to −1.8 kcal/mole. The obtained solvation parameters, that is, transfer energies from water to the protein interior, were 19, 7, −1, −21, and −66 cal/moleÅ 2 for aliphatic carbon, aromatic carbon, sulfur, nitrogen, and oxygen, respectively, which is close to the cyclohexane scale for aliphatic and aromatic groups but intermediate between octanol and cyclohexane for others. An analysis of additional replacements at the water–protein interface indicates that vdW interactions between protein atoms are reduced when they occur across water.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106915/1/111984_ftp.pd

Neigbourhood ethnic composition and social participation of young people in England

We analyse how neighbourhood ethnic diversity and segregation affect adolescents' social participation in England. We distinguish between participation in `purposeful activities' - such as sports and volunteering - and hanging around with friends. We suggest a novel identification strategy to address the problem of endogeneity of ethnic diversity and segregation. We find that ethnic diversity decreases hanging around, while ethnic segregation increases it. No effects are found on participation in purposeful activities