Sur les réactions histochimiques des radicaux acides forts et notemment phosphate

Résumé L'auteur a étudié la spécificité des réactions considérées spécifiques des radicaux acides sur des modèles obtenus par sulfatation, phosphatation et carboxylation des diverses structures riches en groupes vic-glycols.L'auteur a ainsi démontré que toutes les réactions routinaires pour la visualisation des groupes sulfat sont aspécifiques, étant donné leur positivité aussi envers les radicaux phosphate.L'auteur démontre, au contraire, la spécificité de deux réactions, respectivement pour les radicaux sulfat et phosphate, déjà connues mais oubliées, et en propose des modifications.

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On the histochemical reactions of strong acid radicals with special reference to phosphate groups

Summary The specificity of the reactions which are presumed to be specific for acid radicals have been tested in model experiments by means of sulphatation, phosphorylation and carboxylation of structures being rich in vic-glycol groups. The non-specifity of all routine reactions for sulphate groups is proved because they are positive also for phosphate groups. Two other reactions were modified resulting in specifity for sulphate and phosphate groups, respectively.

     

Association of dystrobrevin and regulatory subunit of protein kinase A: a new role for dystrobrevin as a scaffold for signaling proteins

The dystrophin-related and -associated protein dystrobrevin is a component of the dystrophin-associated protein complex, which directly links the cytoskeleton to the extracellular matrix. It is now thought that this complex also serves as a dynamic scaffold for signaling proteins, and dystrobrevin may play a role in this context. Since dystrobrevin involvement in signaling pathways seems to be dependent on its interaction with other proteins, we sought new insights and performed a two-hybrid screen of a mouse brain cDNA library using beta-dystrobrevin, the isoform expressed in non-muscle tissues, as bait. Among the positive clones characterized after the screen, one encodes the regulatory subunit RIalpha of the cAMP-dependent protein kinase A (PKA). We confirmed the interaction by in vitro and in vivo association assays, and mapped the binding site of beta-dystrobrevin on RIalpha to the amino-terminal region encompassing the dimerization/docking domain of PKA regulatory subunit. We also found that the domain of interaction for RIalpha is contained in the amino-terminal region of beta-dystrobrevin. We obtained evidence that beta-dystrobrevin also interacts directly with RIIbeta, and that not only beta-dystrobrevin but also alpha-dystrobrevin interacts with PKA regulatory subunits. We show that both alpha and beta-dystrobrevin are specific phosphorylation substrates for PKA and that protein phosphatase 2A (PP2A) is associated with dystrobrevins. Our results suggest a new role for dystrobrevin as a scaffold protein that may play a role in different cellular processes involving PKA signaling.     

Methicillin-Sensitive and Methicillin-Resistant Staphylococcus aureus Nasal Carriage in a Random Sample of Non-Hospitalized Adult Population in Northern Germany

Objective

The findings from truly randomized community-based studies on Staphylococcus aureus nasal colonization are scarce. Therefore we have examined point prevalence and risk factors of S. aureus nasal carriage in a non-hospitalized population of Braunschweig, northern Germany.

Methods

A total of 2026 potential participants were randomly selected through the resident''s registration office and invited by mail. They were requested to collect a nasal swab at home and return it by mail. S. aureus was identified by culture and PCR. Logistic regression was used to determine risk factors of S. aureus carriage.

Results

Among the invitees, 405 individuals agreed to participate and 389 provided complete data which was included in the analysis. The median age of the participants was 49 years (IQR: 39–61) and 61% were females. S. aureus was isolated in 85 (21.9%; 95% CI: 18.0–26.2%) of the samples, five of which were MRSA (1.29%; 95% CI: 0.55–2.98%). In multiple logistic regression, male sex (OR = 3.50; 95% CI: 2.01–6.11) and presence of allergies (OR = 2.43; 95% CI: 1.39–4.24) were found to be associated with S. aureus nasal carriage. Fifty five different spa types were found, that clustered into nine distinct groups. MRSA belonged to the hospital-associated spa types t032 and t025 (corresponds to MLST CC 22), whereas MSSA spa types varied and mostly belonged to spa-CC 012 (corresponds to MLST CC 30), and spa-CC 084 (corresponds to MLST CC 15).

Conclusion

This first point prevalence study of S. aureus in a non-hospitalized population of Germany revealed prevalence, consistent with other European countries and supports previous findings on male sex and allergies as risk factors of S. aureus carriage. The detection of hospital-associated MRSA spa types in the community indicates possible spread of these strains from hospitals into the community.     

The oncolytic peptide LTX-315 triggers necrotic cell death

The oncolytic peptide LTX-315 has been designed for killing human cancer cells and turned out to stimulate anti-cancer immune responses when locally injected into tumors established in immunocompetent mice. Here, we investigated the question whether LTX-315 induces apoptosis or necrosis. Transmission electron microscopy or morphometric analysis of chromatin-stained tumor cells revealed that LTX-315 failed to induce apoptotic nuclear condensation and rather induced a necrotic phenotype. Accordingly, LTX-315 failed to stimulate the activation of caspase-3, and inhibition of caspases by means of Z-VAD-fmk was unable to reduce cell killing by LTX-315. In addition, 2 prominent inhibitors of regulated necrosis (necroptosis), namely, necrostatin-1 and cycosporin A, failed to reduce LTX-315-induced cell death. In conclusion, it appears that LTX-315 triggers unregulated necrosis, which may contribute to its pro-inflammatory and pro-immune effects.     

Phytochemical Compounds from the Crop Byproducts of Tunisian Globe Artichoke Cultivars

The phytochemical composition in two Tunisian globe artichoke cultivars (bracts, leaves, and floral stems) was evaluated in the plant byproducts. The results indicated that the bracts contain the highest levels of total phenols, o‐diphenols, and flavonoids, whereas tannins seem to be more abundant in the leaves. Bracts from the ‘Violet d'Hyères’ cultivar possessed more total phenols (160.8 mg/g DW), flavonoids (64.9 mg/g DW), and anthocyanins (15.3 μg/g DW) than the ‘Blanc d'Oran’ bracts (134.5 mg/g DW, 51.2 mg/g DW, and 8.3 μg/g DW, resp.). Sixty‐four volatile compounds were identified in the headspace of globe artichoke material, particularly in the bracts. The volatile profile showed that sesquiterpene hydrocarbons and non‐terpene derivatives were the main volatiles emitted by the bracts in both cultivars. These results suggest that globe artichoke byproducts might represent a potential source of natural compounds, which could be used as nutraceuticals or as ingredients in the design of functional foods.     

Primula spectabilis Tratt. aerial parts: morphology, volatile compounds and flavonoids

The vacuolar and epicuticular flavonoids and the volatiles of the leaves and parts of flower of P. spectabilis Tratt., an endemic species in the Italian Oriental Alps, were investigated. From a MeOH extract of the leaves two flavone glycosides, 8-C-β-glucopyranosylluteolin 7-O-α-arabinofuranoside (1) and 6-C-α-arabinofuranosylapigenin (2) were isolated, in addition to a flavone and three flavonols already known from species of Primula. From an EtOH extract of leaf exudates, 7,3',4'-tri-O-methylquercetin was obtained. The structures were elucidated on the basis of their 1D 1H- and 13C NMR data and 2D NMR techniques, as well as of HPLC-MS. The volatiles emitted by the leaves were mainly constituted by non-terpene derivatives, followed by comparable proportions of hemiterpens, oxygenated monoterpenes and sesquiterpene hydrocarbons. In flowers, monoterpene hydrocarbons were the most represented chemical class followed by non-terpene derivatives. Different proportions of compounds were found when individual parts of flowers were examined separately; calyx produced a greater proportion (approx. 49.5%) of non-terpenes as its volatile metabolites. P. spectabilis has glandular trichomes in the hyaline margins of the epidermal depressions, distributed on the adaxial leaf blade. Glandular hairs were also present on the corolla. Correlations of phytochemical data with the morphological features of leaf, flower and glandular hair are discussed, and a hypothesis is proposed on the ecological roles of the flavonoids and volatile compounds on the general fitness of the species and cross-pollination strategies.     

Evidence for coupled biogenesis of yeast Gap1 permease and sphingolipids: essential role in transport activity and normal control by ubiquitination

Current models for plasma membrane organization integrate the emerging concepts that membrane proteins tightly associate with surrounding lipids and that biogenesis of surface proteins and lipids may be coupled. We show here that the yeast general amino acid permease Gap1 synthesized in the absence of sphingolipid (SL) biosynthesis is delivered to the cell surface but undergoes rapid and unregulated down-regulation. Furthermore, the permease produced under these conditions but blocked at the cell surface is inactive, soluble in detergent, and more sensitive to proteases. We also show that SL biogenesis is crucial during Gap1 production and secretion but that it is dispensable once Gap1 has reached the plasma membrane. Moreover, the defects displayed by cell surface Gap1 neosynthesized in the absence of SL biosynthesis are not compensated by subsequent restoration of SL production. Finally, we show that down-regulation of Gap1 caused by lack of SL biogenesis involves the ubiquitination of the protein on lysines normally not accessible to ubiquitination and close to the membrane. We propose that coupled biogenesis of Gap1 and SLs would create an SL microenvironment essential to the normal conformation, function, and control of ubiquitination of the permease.     

C-terminal fluorescent labeling impairs functionality of DNA mismatch repair proteins

The human DNA mismatch repair (MMR) process is crucial to maintain the integrity of the genome and requires many different proteins which interact perfectly and coordinated. Germline mutations in MMR genes are responsible for the development of the hereditary form of colorectal cancer called Lynch syndrome. Various mutations mainly in two MMR proteins, MLH1 and MSH2, have been identified so far, whereas 55% are detected within MLH1, the essential component of the heterodimer MutLα (MLH1 and PMS2). Most of those MLH1 variants are pathogenic but the relevance of missense mutations often remains unclear. Many different recombinant systems are applied to filter out disease-associated proteins whereby fluorescent tagged proteins are frequently used. However, dye labeling might have deleterious effects on MutLα's functionality. Therefore, we analyzed the consequences of N- and C-terminal fluorescent labeling on expression level, cellular localization and MMR activity of MutLα. Besides significant influence of GFP- or Red-fusion on protein expression we detected incorrect shuttling of single expressed C-terminal GFP-tagged PMS2 into the nucleus and found that C-terminal dye labeling impaired MMR function of MutLα. In contrast, N-terminal tagged MutLαs retained correct functionality and can be recommended both for the analysis of cellular localization and MMR efficiency.