HISTORICAL ARCHIVE OF THE AEGEAN – ERGANI: DOCUMENTATION, MANAGEMENT AND PUBLICATION OF CULTURAL HERITAGE RESOURCES ON THE SEMANTIC WEB

This paper introduces the Historical Archive of the Aegean, its archival resources and the ways in which this material is treated using Semantic Web technologies and tools to the benefit of a wide community of users and researchers

Synaptic Defects in the Spinal and Neuromuscular Circuitry in a Mouse Model of Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a major genetic cause of death in childhood characterized by marked muscle weakness. To investigate mechanisms underlying motor impairment in SMA, we examined the spinal and neuromuscular circuitry governing hindlimb ambulatory behavior in SMA model mice (SMNΔ7). In the neuromuscular circuitry, we found that nearly all neuromuscular junctions (NMJs) in hindlimb muscles of SMNΔ7 mice remained fully innervated at the disease end stage and were capable of eliciting muscle contraction, despite a modest reduction in quantal content. In the spinal circuitry, we observed a ∼28% loss of synapses onto spinal motoneurons in the lateral column of lumbar segments 3–5, and a significant reduction in proprioceptive sensory neurons, which may contribute to the 50% reduction in vesicular glutamate transporter 1(VGLUT1)-positive synapses onto SMNΔ7 motoneurons. In addition, there was an increase in the association of activated microglia with SMNΔ7 motoneurons. Together, our results present a novel concept that synaptic defects occur at multiple levels of the spinal and neuromuscular circuitry in SMNΔ7 mice, and that proprioceptive spinal synapses could be a potential target for SMA therapy

Potentially toxic concentrations of triethyl lead in Black Forest rainwater samples

Recently, speculation has grown that the European forest damage may be caused by the continual exposure of trees to rainwater containing trialkyl lead salts1 (R3PbX; R = ethyl, methyl). These are degradation products of tetraalkyl lead (R4Pb) which are added to petroleum as anti-knock agents; they inhibit tubulin polymerization2,3 and are highly toxic to mammalian and plant cells4. Here we describe the analysis of rainwater samples collected at two sites in the Black Forest, FRG. Total lead content was measured by atomic absorption and found to be in the range previously determined for rural areas5. The portion of R3PbX was assayed by the inhibition of pork brain tubulin polymerization. R3PbX was present in one-third of all rainwater samples. The highest concentration was 0.3 µM, that is 103 times higher than previously reported5. For comparison, 1 µM R3PbX killed soybean cells or neuroblastoma cells in culture4

Thiol group reactivity and polymerization of actin in the presence of ATP analogs

We have investigated polymerization and the number of SH-groups of monomeric actin exposed in the presence of (β,γ)-substituted ATP-analogs. Actin, when depolymerized in a buffer containing 10 equiv. of APPCP exposes 4 thiol groups. The time course of the SH-titration is similar to that obtained when F-actin is depolymerized in a nucleotide free buffer. When actin is depolymerized in a buffer containing 10 equiv. of APPNP it also exposes 4 thiols. However, thiol-titration follows different kinetics. While one SH group reacts quickly the reaction of 3 others is retarded. We conclude that APPNP exhibits a shielding effect on part of the thiols for a period of time, while APPCP does not. In agreement with this, in the presence of APPNP yield of polymerization as well as stability against denaturation are distinctly higher than without added nucleotide or in the presence of APPCP. In line with this a hydrolysis product, most probably APPNH2, was associated with the filaments, as indicated by the replacement of tritiated ADP during polymerization, and from analysis of the attached nucleotide. Under the same conditions APPCP replaced tritiated ADP only to a small extent. The data indicate that APPNP interacts with monomeric actin much less than ATP and still less than ADP, but more so APPCP, APPNP is cleaved by actin ATPase and a hydrolysis product is incorporated into filaments

Changes in OD at 235 nm do not correspond to the polymerization step of actin

Discrepancies were observed when the polymerization of rabbit muscle actin was monitored by delta OD235 and viscometry (eta). For example, in the presence of (beta,gamma)-methyleno ATP, the delta OD signal was as large as with ATP although polymerization was very poor (eta 1.1, compared with eta = 1.7 in the presence of ATP). Furthermore, when monomeric actin, kept for 1 h in the presence of a stoichiometric equivalent of ADP, was exposed to conditions favoring polymerization (addition of MgCl2), a considerable delta OD235 signal appeared, although the actin had completely lost its polymerizability (eta = 1.0). We conclude that the observed changes in OD235 cannot reflect polymerization itself, but must be caused by another reaction preceding the assembly. Under normal conditions, this reaction is supposed to be the slowest step of filament formation and so to determine the velocity of the whole process. In conclusion, monitoring of actin polymerization by delta OD235 is a valid method only when polymerization has been assessed by another, independent method