(Mrs B. L.) Laura Sage Jones to Mr. Meredith (6 October 1962)

https://egrove.olemiss.edu/mercorr_pro/2010/thumbnail.jp

Phosphorylation does not prompt, nor prevent, the formation of alpha-synuclein toxic species in a rat model of Parkinson's disease

Phosphorylation is involved in numerous neurodegenerative diseases. In particular, alpha-synuclein is extensively phosphorylated in aggregates in patients suffering from synucleinopathies. However, the share of this modification in the events that lead to the conversion of alpha-synuclein to aggregated toxic species needed to be clarified. The rat model that we developed through rAAV2/6-mediated expression of alpha-synuclein demonstrates a correlation between neurodegeneration and formation of small filamentous alpha-synuclein aggregates. A mutation preventing phosphorylation (S129A) significantly increases alpha-synuclein toxicity and leads to enhanced formation of beta-sheet-rich, proteinase K-resistant aggregates, increased affinity for intracellular membranes, a disarrayed network of neurofilaments and enhanced alpha-synuclein nuclear localization. The expression of a mutation mimicking phosphorylation (S129D) does not lead to dopaminergic cell loss. Nevertheless, fewer but larger aggregates are formed, and signals of apoptosis are also activated in rats expressing the phosphorylation-mimicking form of alpha-synuclein. These observations strongly suggest that phosphorylation does not play an active role in the accumulation of cytotoxic pre-inclusion aggregates. Unexpectedly, the study also demonstrates that constitutive expression of phosphorylation-mimicking forms of alpha-synuclein does not protect from neurodegeneration. The role of phosphorylation at Serine 129 in the early phase of Parkinson's disease is examined, which brings new perspective to therapeutic approaches focusing on the modulation of kinases/phosphatases activity to control alpha-synuclein toxicity

Simulated beetle defoliation on willow genotypes in mixture and monotype plantations

The effect of simulated beetle damage (0%, 25%, 50% and 75% mechanical defoliation) on 12 willow genotypes, grown in short-rotation coppice, was studied in a modified criss-cross experimental design. The design enabled the above-ground effects Of monoculture and mixed planting to be assessed. Repeated measurements were modelled to produce derived variables in terms of time or, more appropriately, in terms of accumulated day length (i.e. 'developmental time') units. These derived variables were then analysed using the residual Maximum Likelihood (REML) method implemented in GenStat (TM) (2001). No significant. competition effect between the genotypes due to planting regime was detected. Genotypes Salix viminalis x Salix schwerinii 'Beagle' and S. viminalis x S. schwerinii 'Torhild' were found to have the greatest rate of increase in leaves regardless of defoliation and also the greatest height prior to defoliation. Genotype Salix dasyclados 'Loden' showed the highest rate of growth under the stress of defoliation. When assessing height at the end of the growing season, S. viminalis x S. schwerinii 'Olof' was the highest genotype for 25% and 75% levels of defoliation, but genotypes Salix aurita x Salix cinerea 'Delamere', Loden and S. viminalis x Salix burjatica 'Ashton Parfitt' appeared to be most tolerant by having consecutively lower base day lengths (i.e. increasing the accumulation of developmental units and the length of the growing season) for increasing defoliation. Shorter genotypes tended to be more tolerant, but of the higher genotypes reaching a control height of greater than 3 in by the end of the growing season, S. viminalis x S. schwerinii 'Tora' and Beagle performed best to 50% defoliation