Bibliothek

Notizen: Abstract: We have found that the early response of axotomized rat retinal ganglion cells is characterized by the differential regulation of a number of fast axonally transported proteins. The abundance of 23 radiolabeled fast transported proteins was analyzed at 2 and 5 days after axotomy using two-dimensional gel electrophoresis. Corresponding changes in retinal GAP-43 mRNA were measured using northern analysis. Within 2 days of injury, 〉40% of the transported proteins analyzed, including GAP-43, showed increased labeling above control levels. Approximately 13% of transported proteins decreased below control levels, whereas the remainder did not change. Five days after axotomy, only GAP-43 and another fast transported protein, C3, continued to sustain measurable increased labeling above control levels; all previously elevated proteins appeared to have been down-regulated by this time, which corresponds to the onset of cell death. These differential changes were accompanied by parallel increases in GAP-43 mRNA. These results suggest that the molecular changes within rat retinal ganglion cells are differentially regulated within two stages subsequent to damage, initial regenerative growth followed by cell death.

Notizen: Abstract— Protein synthesis and axonal transport have been studied in regenerating peripheral nerves. Sciatic nerves of bullfrogs were unilaterally crushed or cut. The animals were killed 1, 2, or 4 weeks later, and 8th and 9th dorsal root ganglia removed together with sciatic nerves and dorsal roots. The ganglia were selectively labeled in vitro with [35S]-methionine. Labeled proteins, in dorsal root ganglia and rapidly transported to ligatures placed on the sciatic nerves and dorsal roots, were analyzed by two-dimensional polyacryl-amide gel electrophoresis. Qualitative analysis of protein patterns revealed no totally new proteins synthesized or rapidly transported in regenerating nerves. However, quantitative comparison of regenerating and contralateral control nerves revealed significant differences in abundance for some of the proteins synthesized in dorsal root ganglia, and for a few of the rapidly transported proteins. Quantitative analysis of rapidly transported proteins in both the peripheral processes (spinal nerves) and central processes (dorsal roots) revealed similar changes despite the fact that the roots were undamaged. The overall lack of drastic changes seen in protein synthesis and transport suggests that the neuron in its program of normal maintenance synthesizes and supplies most of the materials required for axon regrowth.

Notizen: 4-Hydroxynonenal (HNE), an aldehydic product of lipid peroxidation, up-regulates expression of the β-site APP cleaving enzyme (BACE-1), an aspartyl protease responsible for the β-secretase cleavage of amyloid precursor protein (AβPP), and results in increased levels of amyloid β (Aβ) peptide. The mechanisms underlying this remain unclear but are of fundamental importance because prevention of BACE-1 up-regulation is viewed as an important therapeutic strategy. In this study, we exposed NT2 neurons to a range of HNE concentrations (0.5–5 µm) that elicited an up-regulation of BACE-1 expression, a significant increase in intracellular and secreted levels of Aβ peptides as well as apoptosis involving poly-ADP ribose polymerase cleavage and activation of caspase 3. To delineate the molecular events involved in HNE-mediated BACE-1 activation, we investigated the involvement of stress-activated protein kinases (SAPK), signal transducers and activators of transcription (STAT) and serine–threonine kinase B/phosphatidylinositol phosphate 3 kinase (Akt/PtdIns3K). Using specific pharmacological inhibitors, our results show that activation of c-Jun N-terminal kinases and p38MAPK., but not STAT or Akt/PtdIns3K, pathways mediate the HNE-dependent up-regulation of BACE-1 expression. Therefore, HNE, an oxidative stress mediator detected in vivo in the brains of Alzheimer's disease patients, may play a pathogenetic role in Alzheimer's disease by selectively activating SAPK pathways and BACE-1 that regulate the proteolytic processing of AβPP.

Notizen: Abstract: Confusion appears to have arisen in the literature regarding the designation of α-and β-tubulin in polyacrylamide gels. The presence or absence of 8 M-urea in sodium dodecyl sulfate (SDS) polyacrylamide gels leads to different patterns for unalkylated tubulin subunits (and other proteins), making difficult the designation of the α and β subunits by original definition using electrophoretic mobility in the molecular weight dimension. The specific biochemical property of posttranslational tyrosylation of the α subunit has been used to identify further this subunit. Under all conditions tested, the β subunit has been found to be more acidic than the α subunit, with isoelectric point differences that agree with theoretical and published values. If the tubulin subunits are reduced and alkylated, the β subunit migrates more rapidly in SDS polyacrylamide gels, with or without urea present. However, unalkylated tubulin subunits can comigrate or even reverse their relative mobility if 8 M-urea-SDS polyacrylamide gels are used for subunit separation. The results also confirm the earlier reports that the post-translational tyrosylation of protein appears exclusively restricted to α-tubulin and can be demonstrated in an in vivo situation. In addition, the results suggest that only the α2 subunit of tubulin is tyrosylated.

Notizen: While endeavouring to formulate these remarks I have come to suspect that there may possibly lurk in the title of my paper a misleading implication. The word “contribution” would seem to connote on the part of the Protestant churches a deliberate and concerted effort toward the triumph of religious liberty. Those of us who today prize ecclesiastical freedom would like to feel that our colonial ancestors of their own free will and choice undertook the march to liberty. Liberal-minded historians in particular are prone to sing the praises of this individual or that church for furthering this advance; they are inclined to gloss over or to apologize for the men and the institutions that hindered it.

Notizen: The effects of extremes of post-mortem cooling on properties relevant to the inclusion of rabbit meat in products have been investigated. Covered and uncovered carcasses were cooled post-mortem by slow chilling (+ 12°C), rapid chilling (OOC) or rapid freezing (-30°C).There was little difference in effect on quality between slow chilling and rapid freezing. Rapid chilling produced the shortest sarcomere lengths in Musculus longissirnus dorsi, and this is attributed to indirectly induced shortening. Rapid chilling reduced significantly the water holding capacity, increased the resistance to compression and extrusion of the raw comminutes, and reduced the shear stress of the heated fine comminute. It is suggested that the decrease in WHC with rapid chilling results not from cold shortening but from the better integrity of the 2 line.

Notizen: Abstract: After the goldfish optic nerve was crushed, the total amount of protein in the nerve decreased by about 45% within 1 week as the axons degenerated, began to recover between 2 and 5 weeks as axonal regeneration occurred, and had returned to nearly normal by 12 weeks. Corresponding changes in the relative amounts of some individual proteins were investigated by separating the proteins by two-dimensional gel electrophoresis and performing a quantitative analysis of the Coomassie Brilliant Blue staining patterns of the gels. In addition, labelling patterns showing incorporation of [3H]proline into individual proteins were examined to differentiate between locally synthesized proteins (presumably produced mainly by the glial cells) and axonal proteins carried by fast or slow axonal transport. Some prominent nerve proteins, ON1 and ON2 (50–55 kD, pI ∼6), decreased to almost undetectable levels and then reappeared with a time course corresponding to the changes in total protein content of the nerve. Similar changes were seen in a protein we have designated NF (∼130 kD, pI ∼5.2). These three proteins, which were labelled in association with slow axonal transport, may be neurofilament constituents. Large decreases following optic nerve crush were also seen in the relative amounts of α- and β-tubulin, which suggests that they are localized mainly in the optic axons rather than the glial cells. Another group of proteins, W2, W3, and W4 (35–45 kD, pI 6.5–7.0), which showed a somewhat slower time course of disappearance and were intensely labelled in the local synthesis pattern, may be associated with myelin. A small number of proteins increased in relative amount following nerve crush. These included some, P1 and P2 (35–40 kD, pIs 6.1–6.2) and NT (∼50 kD, pI ∼5.5), that appeared to be synthesized by the glial cells. Increases were also seen in one axonal protein, B (∼45 kD, pI ∼4.5), that is carried by fast axonal transport, as well as in two axonal proteins, HA1 and HA2 (∼60 and 65 kD respectively, pIs 4.5–5.0), that are carried mainly by slow axonal transport. Other proteins, including actin, that showed no net changes in relative amount (but presumably changed in absolute amount in direct proportion to the changes in total protein content of the nerve), are apparently distributed in both the neuronal and nonneuronal compartments of the nerve.