The porin and the permeating antibiotic: A selective diffusion barrier in gram-negative bacteria

Gram-negative bacteria are responsible for a large proportion of antibiotic resistant bacterial diseases. These bacteria have a complex cell envelope that comprises an outer membrane and an inner membrane that delimit the periplasm. The outer membrane contains various protein channels, called porins, which are involved in the influx of various compounds, including several classes of antibiotics. Bacterial adaptation to reduce influx through porins is an increasing problem worldwide that contributes, together with efflux systems, to the emergence and dissemination of antibiotic resistance. An exciting challenge is to decipher the genetic and molecular basis of membrane impermeability as a bacterial resistance mechanism. This Review outlines the bacterial response towards antibiotic stress on altered membrane permeability and discusses recent advances in molecular approaches that are improving our knowledge of the physico-chemical parameters that govern the translocation of antibiotics through porin channel

A four-helix bundle stores copper for methane oxidation

Methane-oxidising bacteria (methanotrophs) require large quantities of copper for the membrane-bound (particulate) methane monooxygenase (pMMO). Certain methanotrophs are also able to switch to using the iron-containing soluble MMO (sMMO) to catalyse methane oxidation, with this switchover regulated by copper. MMOs are Nature’s primary biological mechanism for suppressing atmospheric levels of methane, a potent greenhouse gas. Furthermore, methanotrophs and MMOs have enormous potential in bioremediation and for biotransformations producing bulk and fine chemicals, and in bioenergy, particularly considering increased methane availability from renewable sources and hydraulic fracturing of shale rock. We have discovered and characterised a novel copper storage protein (Csp1) from the methanotroph Methylosinus trichosporium OB3b that is exported from the cytosol, and stores copper for pMMO. Csp1 is a tetramer of 4-helix bundles with each monomer binding up to 13 Cu(I) ions in a previously unseen manner via mainly Cys residues that point into the core of the bundle. Csp1 is the first example of a protein that stores a metal within an established protein-folding motif. This work provides a detailed insight into how methanotrophs accumulate copper for the oxidation of methane. Understanding this process is essential if the wide-ranging biotechnological applications of methanotrophs are to be realised. Cytosolic homologues of Csp1 are present in diverse bacteria thus challenging the dogma that such organisms do not use copper in this location

Three-Dimensional Characterization of the Vascular Bed in Bone Metastasis of the Rat by Microcomputed Tomography (MicroCT)

BackgroundAngiogenesis contributes to proliferation and metastatic dissemination of cancer cells. Anatomy of blood vessels in tumors has been characterized with 2D techniques (histology or angiography). They are not fully representative of the trajectories of vessels throughout the tissues and are not adapted to analyze changes occurring inside the bone marrow cavities. Methodology/Principal Findings We have characterized the vasculature of bone metastases in 3D at different times of evolution of the disease. Metastases were induced in the femur of Wistar rats by a local injection of Walker 256/B cells. Microfil®, (a silicone-based polymer) was injected at euthanasia in the aorta 12, 19 and 26 days after injection of tumor cells. Undecalcified bones (containing the radio opaque vascular casts) were analyzed by microCT, and a first 3D model was reconstructed. Bones were then decalcified and reanalyzed by microCT; a second model (comprising only the vessels) was obtained and overimposed on the former, thus providing a clear visualization of vessel trajectories in the invaded metaphysic allowing quantitative evaluation of the vascular volume and vessel diameter. Histological analysis of the marrow was possible on the decalcified specimens. Walker 256/B cells induced a marked osteolysis with cortical perforations. The metaphysis of invaded bones became progressively hypervascular. New vessels replaced the major central medullar artery coming from the diaphyseal shaft. They sprouted from the periosteum and extended into the metastatic area. The newly formed vessels were irregular in diameter, tortuous with a disorganized architecture. A quantitative analysis of vascular volume indicated that neoangiogenesis increased with the development of the tumor with the appearance of vessels with a larger diameter. Conclusion This new method evidenced the tumor angiogenesis in 3D at different development times of the metastasis growth. Bone and the vascular bed can be identified by a double reconstruction and allowed a quantitative evaluation of angiogenesis upon time

The discourse about infraction act embodied embodied in the Statute of the Child and Adolescent

A pesquisa tem como objetivo analisar o discurso sobre o ato infracional materializado no Estatuto da Criança e do Adolescente (ECA, 1990) e nos outros artigos jurídicos que se relacionam ao tema, sob a perspectiva teórica e metodológica da Análise do Discurso Pêcheutiana e da Psicanálise lacaniana. Para essas duas áreas do saber, a linguagem é estruturada por um furo, apresentando como composição lógica a equivocidade e a ambiguidade. Seguindo essa concepção, primeiramente, analisamos o funcionamento do discurso do Direito, especificamente no que se refere ao conceito de lei, de infração e de sanção; na sequência, apresentamos o processo sócio-histórico sobre a transgressão na adolescência, conforme as legislações, ao mesmo tempo em que delimitamos o corpus da pesquisa (recorte dos artigos jurídicos). Consideramos que esta lei opera como um dispositivo de controle da prática de ato infracional e que o funcionamento do discurso do Direito mascara a estrutura faltante da Lei e da linguagem. Essas observações nos levaram a traçar o fio discursivo dos outros capítulos - o sujeito do direito, o sujeito do desejo e a forma-sujeito-, já que todo discurso não é sem sujeito. Analisamos as posições ocupadas pelo adolescente que comete o ato infracional na visão dos regulamentos jurídicos, que têm como finalidade estabilizar o funcionamento social. Na continuação, articulamos o sujeito do direito, o ato infracional e as medidas socieducativas como manifestações do discurso capitalista, onde a norma jurídica ganha um estatuto de fetiche, assim como as mercadorias. Ao supormos a existência do sujeito do desejo, não tomamos o ato infracional somente como produto e condição do contexto social e econômico, pois há a singularidade do autor do ato. Concluímos que as legislações não produzem um lugar Simbólico para o sujeito, apenas um lugar Imaginário, como conferem o Estado e o ECA ao ofertar a ideologia de um sujeito de direito e a forma-sujeito de pessoa em desenvolvimento. Desse modo, a criação dos termos ato infracional e medida socioeducativa são interpretadas como efeitos de sentido do eu idealizado proposto pela ideologia capitalista e pela concepção psicológica de desenvolvimento. Nas condições de produção do ECA o adolescente é concebido como alguém passível de ser educado e cujo lugar de sujeito do desejo é ignorado. Portanto, o ato infracional configura-se como um sintoma social e um mal-estar na sociedade pós-moderna e a medida socioeducativa apresenta-se como um fracasso no que diz respeito a uma normalização do sujeito.This research aims to analyze the discourse on infraction act embodied in the Statute of the Child and Adolescent (ECA, 1990) and other legal articles that relate to the theme, from the theoretical and methodological perspective of Pêcheutiana Discourse Analysis and Lacanian Psychoanalysis. For these two areas of knowledge, language is structured by a hole, presenting as logic composition the equivocality and ambiguity. First, we analyze the functioning of the discourse of law, specifically with regard to the concept of law, the offense and sanction; following, we present the socio-historical process of transgression in adolescence, according to the legislation, while we delimit the research corpus (clipping of legal articles). We believe that this law operates as a control device of the practice of an offense and that the operation of the discourse of law masks the missing structure of law and language. These observations led us to trace the discursive thread of the other chapters - the subject of the right, the subject of desire and form-subject - since all speech is not without a subject. We analyzed the positions occupied by the adolescent who commits the offense in view of the legal regulations, which are intended to stabilize the social functioning. In continuation, we articulated the subject of law, infraction and educational measures as manifestations of capital.ist discourse, where the legal norm gains a fetish status, as well as goods. By assuming the existence of the subject of desire, we do not take offense only as the product and condition of the social and economic context, because there is uniqueness of the author of the act. We conclude that the laws do not produce a symbolic place for the subject, just an imaginary place, as conferring the State and the ECA to offer the ideology of a \"subject of law\" and the form-subject \"developing person\". Thus, the creation of the terms offense and socio-educational measures is idealized sense of the idealized \"I\" suggested by capitalist ideology and concept of development. Inside conditions of production of the ECA, adolescent is conceived as someone capable of being educated and whose place of subject of desire is ignored. Therefore, the infraction act configures itself as a social symptom and malaise in postmodern society and the socio-educational measures constitute a failure when it comes to a normalization of the subject

Cobalt, chromium and nickel affect hydroxyapatite crystal growth in vitro

Metals are widely used in orthopaedics and recent studies have reported that patients with metal implants have a significant increase of metal levels in serum and synovial fluid. Femoral neck fracture occurred in some patients with metal-on-metal implants for unknown reasons. Recently, bone quality has emerged as an important factor of bone strength and few studies have investigated the effects of metal ions on hydroxyapatite properties. In the present study, we investigated the effects of Co²⁺, Cr³⁺ and Ni²⁺ on hydroxyapatite (HA) growth in vitro, using carboxymethylated poly(2-hydroxyethyl methacrylate) (pHEMA) as a biomaterial for calcification. We have demonstrated that metal ions reduced the quantity of mineral formed at the surface of the polymer and decreased the ratio Ca/P by 1.12-, 1.05- and 1.08-fold for Cr²⁺, Cr³⁺ and Ni²⁺ respectively. Furthermore, the size of calcospherites was significantly increased in the metal-doped HA compared to the controls, indicating a possible effect of metal ions on the crystal lattice. Indeed, the presence of metal ions increased the crystal size as well as the crystallinity of HA and reduce the lattice parameter c of the HA framework. The information obtained from this work suggests that the quality of the mineral around metallic implants could be altered. However, further investigation should be conducted to further elucidate the effects of metal incorporation on bone mineral and the functional consequences

Paget's disease of the mandible

Paget's disease (PD) is a chronic progressive disease of the bone characterized by abnormal bone resorption and deposition affecting either single bone (monostotic) or many bones (polyostotic) with uncertain etiology. We report a case of isolated mandibular involvement in a 65-year-old female patient, clinically asymptomatic with abnormally increased alkaline phosphatase level (1 368.1 U/l). Although prevalence of PD is common in western countries, but rare in Asian chapter, that too isolated mandibular involvement, considering this fact, we report this case of PD for documentation