The Influence of water salinity on the free amino acid concentration in muscle and hepatopancreas of adult shrimps, Penaeus japonicus

Variations of the total free amino acid (FAA) pool and the content of specific amino acids have been measured in the muscle and hepatopancreas of adult shrimps, Penaeus japonicus, acclimatized at five water salinities: 38, 32, 26, 20 and 14%‰ The FAA content is always higher in muscle than in hepatopancreas at all tested salinites. On the other hand, the hepatopancreas exhibits the highest concentrations of essential amino acids. Two steps in the evolution of FAA content can be observed, the first one regarding decrease in salinity from 38 to 20%‰ and the second one, when salinity goes below 20%_°. The first step can be characterized by a 16% decrease of total FAA content in the muscle and a 36% increase in the hepatopancreas. In muscle, the variations are mainly due to changes in non-essential FAA content, whereas in the hepatopancreas, they are linked to variations in essential FAA content. The other step is characterized by a drastic increase in moisture and decrease in FAA content in both studied organs when water salinity is 14%‰ The total FAA content is about 40% lower in shrimps at 14%_° compared to 38%‰ seawater salinity. During adaptation, the FAA pool (mainly NEFAAs) of muscle seems to be directly related to osmoregulation, whereas in the hepatopancreas, its evolution seems to be linked with energy expenditure and protein synthesis. The results are evaluated in order to elucidate the role of FAA in intracellular osmoregulation and in relation to animal ecology.     

Primary astroglial cultures

Conclusion Primary cultures from neonatal rat brain consist mainly of astroglial cells, immunohistochemically identified by GFAp and S-100. As other cells than astrocytes may survice in the culture, specific markers for the expected cells were used. Cells with phagocytic properties, endothelial-like cells, oligoblasts, ependymal cells and mesenchymal cells were identified. No neurons have so far been detected.The astroglial cells have a high-affinity uptake for glutamate, aspartate GABA, taurine and hypotaurine, while there is probably a non-saturable uptake of norepinephrine, dopamine and 5-HT. The enzymes MAO, COMT, GABA-T and GS have been demonstrated. It thus seems that astrocytes take part in the inactivation of neurotransmitters, although amino acids and monoamines are taken up with different mechanisms.The presence of receptors for different neurotransmitters and neuromodulators has been demonstrated on astrocytes.Astroglial-enriched cultures from various brain regions have shown that the cells express specialized functional properties concerning neurotransmitter uptake, metabolizing enzymes and receptor density.Astroglial cell differentiation in culture is shortly reviewed and one possibility to affect this maturation by co-cultivation with neuronal containing cultures is point out.     

A common structural blueprint for plant UDP-sugar-producing pyrophosphorylases

Plant pyrophosphorylases that are capable of producing UDP-sugars, key precursors for glycosylation reactions, include UDP-glucose pyrophosphorylases (A- and B-type), UDP-sugar pyrophosphorylase and UDP-N-acetylglucosamine pyrophosphorylase. Although not sharing significant homology at the amino acid sequence level, the proteins share a common structural blueprint. Their structures are characterized by the presence of the Rossmann fold in the central (catalytic) domain linked to enzyme-specific N-terminal and C-terminal domains, which may play regulatory functions. Molecular mobility between these domains plays an important role in substrate binding and catalysis. Evolutionary relationships and the role of (de)oligomerization as a regulatory mechanism are discussed.     

Thioredoxin can influence gene expression by affecting gyrase activity

The expression of many genes of facultatively photosynthetic bacteria of the genus Rhodobacter is controlled by the oxygen tension. Among these are the genes of the puf and puc operons, which encode proteins of the photosynthetic apparatus. Previous results revealed that thioredoxins are involved in the regulated expression of these operons, but it remained unsolved as to the mechanisms by which thioredoxins affect puf and puc expression. Here we show that reduced TrxA of Rhodobacter capsulatus and Rhodobacter sphaeroides and oxidized TrxC of R.capsulatus interact with DNA gyrase and alter its DNA supercoiling activity. While TrxA enhances supercoiling, TrxC exerts a negative effect on this activity. Furthermore, inhibition of gyrase activity strongly reduces puf and puc expression. Our results reveal a new signaling pathway by which oxygen can affect the expression of bacterial genes.     

The Novel Membrane Protein TMEM59 Modulates Complex Glycosylation,Cell Surface Expression,and Secretion of the Amyloid Precursor Protein

Ectodomain shedding of the amyloid precursor protein (APP) by the two proteases α- and β-secretase is a key regulatory event in the generation of the Alzheimer disease amyloid β peptide (Aβ). At present, little is known about the cellular mechanisms that control APP shedding and Aβ generation. Here, we identified a novel protein, transmembrane protein 59 (TMEM59), as a new modulator of APP shedding. TMEM59 was found to be a ubiquitously expressed, Golgi-localized protein. TMEM59 transfection inhibited complex N- and O-glycosylation of APP in cultured cells. Additionally, TMEM59 induced APP retention in the Golgi and inhibited Aβ generation as well as APP cleavage by α- and β-secretase cleavage, which occur at the plasma membrane and in the endosomes, respectively. Moreover, TMEM59 inhibited the complex N-glycosylation of the prion protein, suggesting a more general modulation of Golgi glycosylation reactions. Importantly, TMEM59 did not affect the secretion of soluble proteins or the α-secretase like shedding of tumor necrosis factor α, demonstrating that TMEM59 did not disturb the general Golgi function. The phenotype of TMEM59 transfection on APP glycosylation and shedding was similar to the one observed in cells lacking conserved oligomeric Golgi (COG) proteins COG1 and COG2. Both proteins are required for normal localization and activity of Golgi glycosylation enzymes. In summary, this study shows that TMEM59 expression modulates complex N- and O-glycosylation and suggests that TMEM59 affects APP shedding by reducing access of APP to the cellular compartments, where it is normally cleaved by α- and β-secretase.     

A cyp19a1b‐gfp (aromatase B) transgenic zebrafish line that expresses GFP in radial glial cells

Aromatase is an enzyme that catalyzes the synthesis of estrogen in gonads and brain. Teleost fish express aromatase (AroB) strongly in the brain facilitating its detailed examination. To understand the function of AroB in the brain, we generated transgenic zebrafish that expresses green fluorescent protein (GFP) driven by the brain aromatase cyp19a1b promoter. GFP was found in the radial glial cells of transgenic larvae and adult fish that overlap with AroB immunoreactivity in the correct temporal and spatial pattern. GFP was also coexpressed with radial cell marker BLBP, but was not in neurons. In addition, GFP expression in the radial glial cells was stimulated by estrogen, same as endogenous AroB expression. Thus, this transgenic line faithfully mimics the regulation of AroB expression in radial glial cells. It provides a powerful tool to further characterize progenitor radial cells in adult and developing fish and to evaluate estrogenic activities of xenoestrogens and phytoestrogens. genesis 47:67–73, 2009. © 2008 Wiley‐Liss, Inc.     

Retino-fugal projections in congenitally monophthalmic fish and anurans

Summary Intra-ocular deposition of horseradish peroxidase was used to visualize optic tract projections in normal and congenitally monophthalmic catfish and Xenopus. In neither species was evidence for an increased ipsilateral visual component found in congenitally one-eyed specimens. This indicates that competition between axons from both eyes is not an important mechanism for fiber distribution in the chiasm during ontogeny. Furthermore, it suggests that enhanced ipsilateral components, previously noted in unilaterally enucleated fish and anurans, are caused by debris of degenerated axons.