Mechanism of Action of Cyclophilin A Explored by Metadynamics Simulations

Trans/cis prolyl isomerisation is involved in several biological processes, including the development of numerous diseases. In the HIV-1 capsid protein (CA), such a process takes place in the uncoating and recruitment of the virion and is catalyzed by cyclophilin A (CypA). Here, we use metadynamics simulations to investigate the isomerization of CA's model substrate HAGPIA in water and in its target protein CypA. Our results allow us to propose a novel mechanistic hypothesis, which is finally consistent with all of the available molecular biology data

Allosteric effects in cyclophilin mutants may be explained by changes in nano-microsecond time scale motions

The relationship between molecular motion and catalysis in enzymes is debated. Here, simulations of cyclophilin A and three catalytically-impaired mutants reveal a nanosecond-scale interconversion between active and inactive conformations, orders of magnitude faster than previously suggested

Using viral vectors as gene transfer tools (Cell Biology and Toxicology Special Issue: ETCS-UK 1 day meeting on genetic manipulation of cells)

In recent years, the development of powerful viral gene transfer techniques has greatly facilitated the study of gene function. This review summarises some of the viral delivery systems routinely used to mediate gene transfer into cell lines, primary cell cultures and in whole animal models. The systems described were originally discussed at a 1-day European Tissue Culture Society (ETCS-UK) workshop that was held at University College London on 1st April 2009. Recombinant-deficient viral vectors (viruses that are no longer able to replicate) are used to transduce dividing and post-mitotic cells, and they have been optimised to mediate regulatable, powerful, long-term and cell-specific expression. Hence, viral systems have become very widely used, especially in the field of neurobiology. This review introduces the main categories of viral vectors, focusing on their initial development and highlighting modifications and improvements made since their introduction. In particular, the use of specific promoters to restrict expression, translational enhancers and regulatory elements to boost expression from a single virion and the development of regulatable systems is described

Search for invisible modes of nucleon decay in water with the SNO+ detector

This paper reports results from a search for nucleon decay through invisible modes, where no visible energy is directly deposited during the decay itself, during the initial water phase of SNO+. However, such decays within the oxygen nucleus would produce an excited daughter that would subsequently deexcite, often emitting detectable gamma rays. A search for such gamma rays yields limits of 2.5×1029  y at 90% Bayesian credibility level (with a prior uniform in rate) for the partial lifetime of the neutron, and 3.6×1029  y for the partial lifetime of the proton, the latter a 70% improvement on the previous limit from SNO. We also present partial lifetime limits for invisible dinucleon modes of 1.3×1028  y for nn, 2.6×1028  y for pn and 4.7×1028  y for pp, an improvement over existing limits by close to 3 orders of magnitude for the latter two

Early life differences in behavioral predispositions in two Alligatoridae species

Behavioral predispositions are innate tendencies of animals to behave in a given way without the input of learning. They increase survival chances and, due to environmental and ecological challenges, may vary substantially even between closely related taxa. These diferences are likely to be especially pronounced in long-lived species like crocodilians. This order is particularly relevant for comparative cognition due to its phylogenetic proximity to birds. Here we compared early life behavioral predispositions in two Alligatoridae species. We exposed American alligator and spectacled caiman hatchlings to three different novel situations: a novel object, a novel environment that was open and a novel environment with a shelter. This was then repeated a week later. During exposure to the novel environments, alligators moved around more and explored a larger range of the arena than the caimans. When exposed to the novel object, the alligators reduced the mean distance to the novel object in the second phase, while the caimans further increased it, indicating diametrically opposite ontogenetic development in behavioral predispositions. Although all crocodilian hatchlings face comparable challenges, e.g., high predation pressure, the effectiveness of parental protection might explain the observed pattern. American alligators are apex predators capable of protecting their offspring against most dangers, whereas adult spectacled caimans are frequently predated themselves. Their distancing behavior might be related to increased predator avoidance and also explain the success of invasive spectacled caimans in the natural habitats of other crocodilians

Setorectomia posterior direita laparoscópica no tratamento dos tumores hepáticos Laparoscopic right posterior sectioniectomy for treating hepatic tumors

INTRODUÇÃO: A ressecção de neoplasias no setor posterior direito costuma ser um desafio técnico pela dificuldade de sua abordagem. Adicionalmente, as hepatectomias laparoscópicas tem se tornado alternativa interessante em virtude de muitas vantagens (baixa morbidade, curto tempo de internação, retorno precoce as atividades laborais e bons resultados cosméticos). OBJETIVO: Relatar experiência em doentes submetidos à setorectomia posterior direita laparoscópica por uma única equipe. MÉTODOS: Cinco doentes foram operados entre novembro de 2008 a agosto de 2010. A idade variou de 21 a 63 anos com mediana de 43 anos. Foram quatro mulheres e um homem. A causa das neoplasias foi: adenoma (n=2), hepatocarcinoma (n=1) e metástases (n=2). A lesão foi solitária em três casos (60 %). A média do tamanho das lesões foi 3,3 cm (1,8-5). Foram analisados: tempo cirúrgico, sangramento operatório, morbimortalidade, tempo de internação e tempo de retorno à atividade habitual. RESULTADOS: A média de tempo cirúrgico foi de 160 minutos (90-260). A de sangramento intra-operatório foi de 200 ml (0-500). Nenhum doente foi transfundido. Não houve mortalidade e a morbidade foi nula. A mediana de internação foi de três dias (2-5). A mediana de retorno às atividades cotidianas foi de 12 dias (7-20). A mediana de seguimento foi de 13 meses (1-20). Não houve recidiva de lesão. CONCLUSÃO: A setorectomia posterior direita laparoscópica representa boa opção tática para o tratamento dos tumores hepáticos situados no setor posterior do lobo direito. É opção segura que evita grandes incisões com morbimortalidade. Também apresenta bom resultado cosmético e retorno precoce ao trabalho.<br>BACKGROUND: Resection of neoplasms arising in the posterior right sector is usually a technical challenge due to approach difficulties. Additionally, laparoscopic hepatectomy has become an interesting alternative with several advantages (low morbidity, short hospital stay, early return work activities and good cosmetic results). AIM: To report a series of patients who underwent laparoscopic right posterior sectioniectomy performed by a single surgical team. METHODS: Five patients were operated. Their ages ranged from 21 to 63 years (median 43 years). There were four women and one man. Etiology of the neoplasm was: adenoma (n=2), hepatocellular carcinoma (n=1) and metastasis (n=2). There was a single lesion in three cases (60 %). The mean lesion diameter was 3,3 cm (1,8-5). It was analyzed: operative time, intraoperative bleeding, morbidity, length of stay and time of return to usual activity. RESULTS: The mean surgical time was 160 minutes (90-260). The mean intraoperative blood loss was 200 ml (0-500). None of the patients received transfusions. There was no mortality and no morbidity. The median hospital stay was three days (2-5). The median length of time taken to return to day-to-day activities was 12 days (7-20). The median follow-up period was 13 months (1-20). There was no tumor recurrence. CONCLUSION: Laparoscopic right posterior sectioniectomy (bi-segmentectomy VI + VII) is a good option to treat hepatic tumors located in the posterior sector of the right lobe. It is a safe procedure that avoids large incisions with no mortality or morbidity is this series. This approach also bring good cosmetic result and early return to work

Monitoring neuron and astrocyte interactions with a 3D cell culture system

Methods are described for the generation and analysis of 3D co-culture models in which astrocyte and neuronal behavior can be studied. Cells may be obtained from a variety of sources, then cultured within collagen hydrogels to explore cellular responses and interactions in response to substances under test or under conditions that mimic physiological or pathological environments. Cell populations are labelled then either mixed within gels or arranged as separate adjacent populations, with further options including directing the self-alignment of cells to form anisotropic 3D cultures. Immunofluorescence staining and confocal microscopy can be used to capture image data from 3D structures and detailed protocols are provided for obtaining reliable results. Finally, 3D image analysis of confocal microscopy data is discussed, providing guidance on how astrocyte and neuronal features can be quantified