The first collective protest of black African migrants in postcolonial France (1960–1975): a struggle for housing and rights

The study of the political activism of black African diasporas in France after the independence era remains a neglected area of research. This paper fills a gap in the literature by exploring the first notable postcolonial protests in the country by sub-Saharan migrants. The struggle of black African workers against their dire housing conditions opened up a ‘cycle of collective action’ that led to the better-known Sonacotra migrant hostels (foyers) rent strike of 1975–1980. Even before the Sonacotra strike, however, black African workers had been able to call on the authorities from both their origin and residence countries and to mobilize transnational networks in order to support their demands. This article provides the first comprehensive historical study of this decisive period. It highlights how ethnic ties are intertwined with political and social ones, focusing on the solidarities that these migrants developed in political networks and in their neighbourhoods.     

Radiation dose of digital radiography (DR) versus micro-dose x-ray (EOS) on patients with adolescent idiopathic scoliosis: 2016 SOSORT- IRSSD “John Sevastic Award” Winner in Imaging Research

Background

Patients with adolescent idiopathic scoliosis (AIS) frequently receive x-ray imaging at diagnosis and subsequent follow monitoring. The ionizing radiation exposure has accumulated through their development stage and the effect of radiation to this young vulnerable group of patients is uncertain. To achieve the ALARA (as low as reasonably achievable) concept of radiation dose in medical imaging, a slot-scanning x-ray technique by the EOS system has been adopted and the radiation dose using micro-dose protocol was compared with the standard digital radiography on patients with AIS.

Methods

Ninety-nine participants with AIS underwent micro-dose EOS and 33 underwent standard digital radiography (DR) for imaging of the whole spine. Entrance-skin dose was measured using thermoluminescent dosimeters (TLD) at three regions (i.e. dorsal sites at the level of sternal notch, nipple line, symphysis pubis). Effective dose and organ dose were calculated by simulation using PCXMC 2.0. Data from two x-ray systems were compared using independent-samples t-test and significance level at 0.05. All TLD measurements were conducted on PA projection only. Image quality was also assessed by two raters using Cobb angle measurement and a set of imaging parameters for optimization purposes.

Results

Entrance-skin dose from micro-dose EOS system was 5.9–27.0 times lower at various regions compared with standard DR. The calculated effective dose was 2.6?±?0.5 (μSv) and 67.5?±?23.3 (μSv) from micro-dose and standard DR, respectively. The reduction in the micro-dose was approximately 26 times. Organ doses at thyroid, lung and gonad regions were significantly lower in micro-dose (p?<?0.001). Data were further compared within the different gender groups. Females received significantly higher (p?<?0.001) organ dose at ovaries compared to the testes in males. Patients with AIS received approximately 16–34 times lesser organ dose from micro-dose x-ray as compared with the standard DR. There was no significant difference in overall rating of imaging quality between EOS and DR. Micro-dose protocol provided enough quality to perform consistent measurement on Cobb angle.

Conclusions

Entrance-skin dose, effective dose and organ dose were significantly reduced in micro-dose x-ray. The effective dose of a single micro-dose x-ray (2.6 μSv) was less than a day of background radiation. As AIS patients require periodic x-ray follow up for surveillance of curve progression, clinical use of micro-dose x-ray system is beneficial for these young patients to reduce the intake of ionizing radiation.

     

Effects of Bark Beetle Disturbance on Soil Nutrient Retention and Lake Chemistry in Glacial Catchment

Ecosystems - Forest ecosystems worldwide are subjected to human-induced stressors, including eutrophication and acidification, and to natural disturbances (for example, insect infestation,...     

Substrate-specific interactions with the heme-bound oxygen molecule of nitric-oxide synthase

We report the characterization by resonance Raman spectroscopy of the oxygenated complex (Fe(II)O(2)) of nitric-oxide synthases of Staphylococcus aureus (saNOS) and Bacillus subtilis (bsNOS) saturated with N(omega)-hydroxy-l-arginine. The frequencies of the nu(Fe-O) and nu(O-O) modes were 530 and 1135 cm(-), respectively, in both the presence and absence of tetrahydrobiopterin. On the basis of a comparison of these frequencies with those of saNOS and bsNOS saturated with l-arginine (nu(Fe-O) at 517 cm(-1) and nu(O-O) at 1123 cm(-1)) and those of substrate-free saNOS (nu(Fe-O) at 517 and nu(O-O) at 1135 cm(-1)) (Chartier, F. J. M., Blais, S. P., and Couture, M. (2006) J. Biol. Chem. 281, 9953-9962), we propose two models that account for the frequency shift of nu(Fe-O) (but not nu(O-O)) upon N(omega)-hydroxy-l-arginine binding as well as the frequency shift of nu(O-O) (but not nu(Fe-O)) upon l-arginine binding. The implications of these substrate-specific interactions with respect to catalysis by NOSs are discussed.     

HIV-1 Vpr-mediated G2 arrest involves the DDB1-CUL4AVPRBP E3 ubiquitin ligase

Human immunodeficiency virus type 1 (HIV-1) viral protein R (Vpr) has been shown to cause G2 cell cycle arrest in human cells by inducing ATR-mediated inactivation of p34cdc2, but factors directly engaged in this process remain unknown. We used tandem affinity purification to isolate native Vpr complexes. We found that damaged DNA binding protein 1 (DDB1), viral protein R binding protein (VPRBP), and cullin 4A (CUL4A)--components of a CUL4A E3 ubiquitin ligase complex, DDB1-CUL4A(VPRBP)--were able to associate with Vpr. Depletion of VPRBP by small interfering RNA impaired Vpr-mediated induction of G2 arrest. Importantly, VPRBP knockdown alone did not affect normal cell cycle progression or activation of ATR checkpoints, suggesting that the involvement of VPRBP in G2 arrest was specific to Vpr. Moreover, leucine/isoleucine-rich domain Vpr mutants impaired in their ability to interact with VPRBP and DDB1 also produced strongly attenuated G2 arrest. In contrast, G2 arrest-defective C-terminal Vpr mutants were found to maintain their ability to associate with these proteins, suggesting that the interaction of Vpr with the DDB1-VPRBP complex is necessary but not sufficient to block cell cycle progression. Overall, these results point toward a model in which Vpr could act as a connector between the DDB1-CUL4A(VPRBP) E3 ubiquitin ligase complex and an unknown cellular factor whose proteolysis or modulation of activity through ubiquitination would activate ATR-mediated checkpoint signaling and induce G2 arrest.     

Specificity and mechanism of JMJD2A, a trimethyllysine-specific histone demethylase

JMJD2A is a JmjC histone demethylase (HDM) that catalyzes the demethylation of di- and trimethylated Lys9 and Lys36 in histone H3 (H3K9me2/3 and H3K36me2/3). Here we present the crystal structures of the JMJD2A catalytic domain in complex with H3K9me3, H3K36me2 and H3K36me3 peptides. The structures reveal that histone substrates are recognized through a network of backbone hydrogen bonds and hydrophobic interactions that deposit the trimethyllysine into the active site. The trimethylated epsilon-ammonium cation is coordinated within a methylammonium-binding pocket through carbon-oxygen (CH...O) hydrogen bonds that position one of the zeta-methyl groups adjacent to the Fe(II) center for hydroxylation and demethylation. Mutations of the residues comprising this pocket abrogate demethylation by JMJD2A, with the exception of an S288A substitution, which augments activity, particularly toward H3K9me2. We propose that this residue modulates the methylation-state specificities of JMJD2 enzymes and other trimethyllysine-specific JmjC HDMs.     

The heme environment of mouse neuroglobin. Evidence for the presence of two conformations of the heme pocket

Neuroglobin (Ngb) is a newly discovered oxygen-binding heme protein that is primarily expressed in the brain of humans and other vertebrates. To characterize the structure/function relationships of this new heme protein, we have used resonance Raman spectroscopy to determine the structure of the heme environment in Ngb from mice. In the Fe(2+)CO complex, two conformations of the Fe-CO unit are present, one of which arises from an open conformation of the heme pocket in which the CO is not interacting with any nearby residue, and the other arises from a closed conformation where a positively charged residue near the CO group stabilizes the complex. For the Fe(2+)O(2) complex, we detect a single nu(Fe-OO) stretching mode at a frequency similar to that of oxymyoglobins and oxyhemoglobins of vertebrates (571 cm(-1)). Based on the Fe-C-O frequencies of the closed conformation of Ngb, a highly polar distal environment is indicated from which the O(2) off-rate is predicted to be lower than that of Mb. In the absence of exogenous ligands, a heme pocket residue coordinates to the heme iron, forming a six-coordinate complex, thereby predicting a low on-rate for exogenous ligands. These structural properties of the heme pocket of Ngb are discussed with respect to its proposed in vivo oxygen delivery function.     

Regulation of the properties of the heme-NO complexes in nitric-oxide synthase by hydrogen bonding to the proximal cysteine

Nitric-oxide synthase (NOS) catalyzes the formation of NO and citrulline from l-arginine and oxygen. However, the NO so formed has been found to auto-inhibit the enzymatic activity significantly. We hypothesized that the NO reactivity is in part controlled by hydrogen bonding between the conserved tryptophan residue (position 409 in the neuronal isoform of NOS (nNOS)) and the cysteine residue that forms the proximal bond to the heme. By using resonance Raman spectroscopy and NO as a probe of the heme environment, we show that in the W409F and W409Y mutants of the oxygenase domain of the neuronal enzyme (nNOSox), the Fe-NO bond in the Fe3+NO complex is weaker than in the wild type enzyme, consistent with the loss of a hydrogen bond on the sulfur atom of the proximal cysteine residue. The weaker Fe-NO bond in the W409F and W409Y mutants might result in a faster rate of NO dissociation from the ferric heme in the Trp-409 mutants as compared with the wild type enzyme, which could contribute to the lower accumulation of the inhibitory NO-bound complexes observed during catalysis with the Trp-409 mutants (Adak, S., Crooks, C., Wang, Q., Crane, B. R., Tainer, J. A., Getzoff, E. D., and Stuehr, D. J. (1999) J. Biol. Chem. 274, 26907-26911). The optical and resonance Raman spectra of the Fe2+NO complexes of the Trp-409 mutants differ from those of the wild type enzyme and indicate that a significant population of a five-coordinate Fe2+NO complex is present. These data show that the hydrogen bond provided by the Trp-409 residue is necessary to maintain the thiolate coordination when NO binds to the ferrous heme. Taken together our results indicate that the heme environment on the proximal side of nNOS is critical for the formation of a stable iron-cysteine bond and for the control of the electronic properties of heme-NO complexes.     

Identification of the ligands to the ferric heme of Chlamydomonas chloroplast hemoglobin: evidence for ligation of tyrosine-63 (B10) to the heme

We have studied the unusual heme ligand structure of the ferric forms of a recombinant Chlamydomonas chloroplast hemoglobin and its several single-amino acid mutants by EPR, optical absorbance, and resonance Raman spectroscopy. The helical positions of glutamine-84, tyrosine-63, and lysine-87 are suggested to correspond to E7, B10, and E10, respectively, in the distal heme pocket on the basis of amino acid sequence comparison of mammalian globins. The protein undergoes a transition with a pK of 6.3 from a six-coordinate high-spin aquomet form at acidic pH to a six-coordinate low-spin form. The EPR signal of the low-spin form for the wild-type protein is absent for the Tyr63Leu mutant, suggesting that the B10 tyrosine in the wild-type protein ligates to the heme as tyrosinate. For the Tyr63Leu mutant, a new low-spin signal resembling that of alkaline cytochrome c (a His-heme-Lys species) is resolved, suggesting that the E10 lysine now coordinates to the heme. In the wild-type protein, the oxygen of the tyrosine-63 side chain is likely to share a proton with the side chain of lysine-87, suggested by the observation of a H/D sensitive resonance Raman line at 502 cm(-)(1) that is tentatively assigned as a vibrational mode of the Fe-O bond between the iron and the tyrosinate. We propose that the transition from the high-spin to the low-spin form of the protein occurs by deprotonation and ligation to the heme of the B10 tyrosine oxygen, facilitated by strong interaction with the E10 lysine side chain.     

The basolateral sorting signals of the thyrotropin and luteinizing hormone receptors: an unusual family of signals sharing an unusual distal intracellular localization, but unrelated in their structures

The mechanisms of the basolateral targeting of G protein-coupled receptors remain largely unknown. Mutagenesis experiments have allowed us to identify the basolateral sorting signals of the TSH and LH receptors expressed in Madin-Darby canine kidney cells and thyroid follicular FRT cells. Unexpectedly these signals (amino acids 731-746 and 672-689, respectively) share an unusual localization in the distal part of the intracellular domain of the receptors at a marked distance from the membrane. When grafted onto the p75-neurotropin receptor, these signals redirect this normally apically expressed protein to the basolateral cell surface. They are independent of the endocytosis signal. The basolateral sorting signals of TSH, LH, and FSH receptors do not exhibit primary sequence homology with each other or with any other known signal. Furthermore, circular dichroism studies show that the three signals exhibit distinct secondary structures. The TSH receptor has a stable helical structure, the LH receptor has both helix and beta-sheet structures, and the FSH receptor sorting signal has a main random coil structure. This means that even in closely-related receptors different secondary structures can be found for basolateral signals unrelated to internalization signals. This observation contrasts with what is known about basolateral signals related to internalization signals for which a common beta-turn structure has been described. Deletion of the basolateral sorting signals results in apical targeting of the receptors, suggesting the existence of apical sorting information. However, a soluble form of the TSH receptor, which harbors all N- and putative O-linked oligosaccharides, is secreted in a nonpolarized fashion. This implies that apical sorting information must be located elsewhere, either in the transmembrane or in the intracellular domains of the receptor.