PubMed · 8688639
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B G Clare. 1995. Agrocins.. https://doi.org/10.1016/b978-0-7506-9095-9.50032-0
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We show that the BMP ortholog Gbb can signal by a retrograde mechanism to regulate synapse growth of the Drosophila neuromuscular junction (NMJ). gbb mutants have a reduced NMJ synapse size, decreased neurotransmitter release, and aberrant presynaptic ultrastructure. These defects are similar to those we observe in mutants of BMP receptors and Smad transcription factors. However, whereas these BMP receptors and signaling components are required in the presynaptic motoneuron, Gbb expression is required in large part in postsynaptic muscles; gbb expression in muscle rescues key aspects of the gbb mutant phenotype. Consistent with this notion, we find that blocking retrograde axonal transport by overexpression of dominant-negative p150/Glued in neurons inhibits BMP signaling in motoneurons. These experiments reveal that a muscle-derived BMP retrograde signal participates in coordinating neuromuscular synapse development and growth.
BACKGROUND: This study improved small bowel preservation using University of Wisconsin (UW) solution in conjunction with hypothermic luminal perfusion. METHODS: Small bowels from Sprague-Dawley rats (n=4) were flushed vascularly with modified UW solution and flushed luminally: group 1, none (clinical control); group 2, UW solution; group 3, 1-hr oxygenated perfusion then static storage with UW; and group 4, 24-hr continuous oxygenated perfusion with UW. Energetics, lipid peroxidation, and histology were assessed during 24 hr at 4 degrees C. RESULTS: After 12 hr, adenosine triphosphate ranged from 0.5 to 0.8 micromol/g in groups 1 to 3 compared with 1.5 micromol/g in group 4. Even after 24 hr, levels in group 4 were more than twofold greater than levels in groups 1 to 3. Energy charge values ([adenosine triphosphate+adenosine diphosphate/2]/total adenylates) decreased from fresh tissue values of 0.69 in all groups except group 4 throughout 24-hr perfusion. Malondialdehyde (MDA; a product of lipid peroxidation) doubled within 4 hr in group 1 and remained high throughout storage. In groups 3 and 4, MDA levels increased as the time of perfusion increased; group 2 showed no elevated MDA levels at any time. After 12 hr, histologic integrity was superior in groups 3 and 4; however after 24 hr, the best Park's grade was observed in group 3 (median grade 4) compared with groups 1 (grade 7) and 4 (grade 6). CONCLUSIONS: Our data indicate that perfusion clearly improves tissue energetics; however, mucosal integrity is superior with only a brief 1-hr period of luminal perfusion, despite limited improvements in energetics.
The overexpression of p27, a cyclin-dependent kinase (CDK) inhibitor, has been shown to effectively inhibit cell growth at the G1-phase of different cell lines, potentiating a valid genetic strategy for cell proliferation control. In order to characterize the energy requirements after p27 overexpression in CHO cells expressing SEAP (secreted form of the human alkaline phosphatase enzyme), key metabolic parameters were evaluated. Cell growth inhibition led to a significant increase in cell size concomitant with a 2-fold increase in cell protein content. The simultaneous increase of the intracellular proteolytic activity with protein content suggests higher protein synthesis. A general 2-fold increase in oxygen, glutamine and glucose consumption rates, coupled with an increase in lactate and ammonia production was observed. p27 overexpression led to a significant increase in the intracellular pool of AMP (8.5-fold), ADP (6-fold) and, more uncommonly, ATP (4.5-fold). Nevertheless, cells were able to maintain the equilibrium among the three adenine nucleotides since both the ATP/ADP ratio and the energy charge values remained similar to those observed with non-growth inhibited cells. This work shows that the observed 4-fold increase in SEAP specific productivity after cell growth inhibition by p27, occurred concomitantly with a higher expenditure of cell energy. This characterization of cell metabolism becomes important in demonstrating the applicability of growth inhibition systems.