Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 266
Filtrar
2.
Nucleus ; 12(1): 21-41, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-33435791

RESUMO

Eukaryotic cells arose ~1.5 billion years ago, with the endomembrane system a central feature, facilitating evolution of intracellular compartments. Endomembranes include the nuclear envelope (NE) dividing the cytoplasm and nucleoplasm. The NE possesses universal features: a double lipid bilayer membrane, nuclear pore complexes (NPCs), and continuity with the endoplasmic reticulum, indicating common evolutionary origin. However, levels of specialization between lineages remains unclear, despite distinct mechanisms underpinning various nuclear activities. Several distinct modes of molecular evolution facilitate organellar diversification and  to understand which apply to the NE, we exploited proteomic datasets of purified nuclear envelopes from model systems for comparative analysis. We find enrichment of core nuclear functions amongst the widely conserved proteins to be less numerous than lineage-specific cohorts, but enriched in core nuclear functions. This, together with consideration of additional evidence, suggests that, despite a common origin, the NE has evolved as a highly diverse organelle with significant lineage-specific functionality.

4.
Trends Parasitol ; 2020 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-33309505

RESUMO

Differentiation is a central aspect of the parasite life cycle and encompasses adaptation to both host and environment. If we accept that evolution cannot anticipate an organism's needs as it enters a new environment, how do parasite differentiation pathways arise? The transition between vertebrate and insect stage African trypanosomes is probably one of the better studied and involves a cell-cycle arrested or 'stumpy' form that activates metabolic pathways advantageous to the parasite in the insect host. However, a range of stimuli and stress conditions can trigger similar changes, leading to formation of stumpy-like cellular states. We propose that the origin and optimisation of this differentiation program represents repurposing of a generic stress response to gain considerable gain-of-fitness associated with parasite transmission.

5.
J Card Surg ; 2020 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-33169445

RESUMO

OBJECTIVES: Management of infected prosthetic aortic grafts in the ascending and or root is complex and multifaceted. We report our diagnostic pathway, management and outcomes, identifying successful strategies. METHODS: This was a retrospective, single center, observational study. Consecutive patients who underwent management of infected aortic grafts in the ascending and/or root at our institution between October 1998 and December 2019 were included. The main outcome measures were: discharge from hospital alive with at least 1 year survival, operative mortality and success of primary treatment strategy. RESULTS: Twenty-six patients presented with infection of proximal aortic grafts and were managed through a number of strategies with an overall hospital-survival of 81% and 1 year survival of 69%. Twenty of them ultimately underwent redo surgery with 25% operative mortality (within 24 h of surgery). Five patients underwent washout and irrigation of which two were successfully treated and cured with adjunctive antibiotics and two went on to have staged explant and definitive surgery. Interval between surgery and infection was 42.5 ± 35.8 months. All patients had at least one major criterion and three minor criterions with no diagnostic uncertainty. The commonest primary strategy was 3a (definitive surgery), (13/26, 50%). CONCLUSIONS: Adopting a systematic and flexible patient specific approach to the diagnosis and management of patients with proximal aortic graft infections results in reasonable overall 1 year survival. In the majority of patients surgery is ultimately required in an attempt to achieve a curative treatment; however this comes with high operative mortality risk.

6.
PLoS Pathog ; 16(11): e1008932, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33141865

RESUMO

Livestock diseases caused by Trypanosoma congolense, T. vivax and T. brucei, collectively known as nagana, are responsible for billions of dollars in lost food production annually. There is an urgent need for novel therapeutics. Encouragingly, promising antitrypanosomal benzoxaboroles are under veterinary development. Here, we show that the most efficacious subclass of these compounds are prodrugs activated by trypanosome serine carboxypeptidases (CBPs). Drug-resistance to a development candidate, AN11736, emerged readily in T. brucei, due to partial deletion within the locus containing three tandem copies of the CBP genes. T. congolense parasites, which possess a larger array of related CBPs, also developed resistance to AN11736 through deletion within the locus. A genome-scale screen in T. brucei confirmed CBP loss-of-function as the primary mechanism of resistance and CRISPR-Cas9 editing proved that partial deletion within the locus was sufficient to confer resistance. CBP re-expression in either T. brucei or T. congolense AN11736-resistant lines restored drug-susceptibility. CBPs act by cleaving the benzoxaborole AN11736 to a carboxylic acid derivative, revealing a prodrug activation mechanism. Loss of CBP activity results in massive reduction in net uptake of AN11736, indicating that entry is facilitated by the concentration gradient created by prodrug metabolism.

7.
Trends Parasitol ; 2020 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-33127331

RESUMO

The unicellular trypanosomatids belong to the phylum Euglenozoa and all known species are obligate parasites. Distinct lineages infect plants, invertebrates, and vertebrates, including humans. Genome data for marine diplonemids, together with freshwater euglenids and free-living kinetoplastids, the closest known nonparasitic relatives to trypanosomatids, recently became available. Robust phylogenetic reconstructions across Euglenozoa are now possible and place the results of parasite-focused studies into an evolutionary context. Here we discuss recent advances in identifying the factors shaping the evolution of Euglenozoa, focusing on ancestral features generally considered parasite-specific. Remarkably, most of these predate the transition(s) to parasitism, suggesting that the presence of certain preconditions makes a significant lifestyle change more likely.

8.
Braz J Cardiovasc Surg ; 35(5): 607-613, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-33118723

RESUMO

OBJECTIVE: To describe our experience of nine patients with extra-anatomical bypass for clinically ischemic distal limb during repair of acute Type A aortic dissection (ATAAD). METHODS: We retrospectively examined a series of nine patients who underwent surgery for ATAAD. We identified a subset of the patients who presented with concomitant radiographic and clinical signs of lower limb ischemia. All but one patient (axillobifemoral bypass) underwent femorofemoral crossover grafting by the cardiac surgeon during cooling. RESULTS: One hundred eighty-one cases of ATAAD underwent surgery during the study period with a mortality of 19.3%. Nine patients had persistent clinical evidence of lower limb ischemia (4.9%) and underwent extra-anatomical bypass during cooling. Two patients underwent additional fasciotomies. Mean delay from symptoms to surgery in these nine patients was 9.5 hours. Two patients had bilateral amputations despite revascularisation and, of note, had long delays in presentation for surgery (> 12 hours). There were no mortalities during these inpatient episodes. Outpatient radiographic follow-up at the first opportunity demonstrated 100% patency. CONCLUSION: Our experience suggests that, during complicated aortic dissection, limb ischemia may have a devastating outcome including amputation when diagnosis and referral are delayed. Early diagnosis and surgery are crucial in preventing this potentially devastating complication.

9.
J Vasc Surg ; 2020 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-33068762

RESUMO

OBJECTIVE: To report outcome and identify predictors of mortality after open descending thoracic aneurysm (DTA) and thoracoabdominal aortic aneurysm (TAAA) repair in a specialist aortic centre. METHODS: This was a retrospective observational cohort study. Consecutive patients who underwent surgery at our institution between October 1998 and December 2019 were included. The main outcome measures were mortality and major morbidity. Multivariate analysis was used to identify predictors of mortality. RESULTS: 430 patients underwent DTA (n=157) and TAA (n=273) repair; 151 underwent surgery non-electively. Forty-eight (11.6%) died within 30 days of surgery. Thirty-day mortality was lower after elective surgery (3.1% after DTA repair and 9.9% after TAAA repair), whereas non-elective surgery carried a 30-day mortality of 17.9%. Fourteen additional patients died in hospital after 30 days, one after non-elective DTA repair and 13 after TAAA repair (10 elective), all but one extent II. In-hospital mortality for the whole cohort improved over time, as the activity volume increased, except for patients undergoing extent II TAAA repair. Predictors of in-hospital mortality were: age ≥70 (OR 3.36; 95%CI=1.79-6.32, P<0.001); extent II repair (OR 4.39; 95%CI=2.34-8.21), P<0.001); non-elective surgery (OR 2.72; 95%CI=1.44, 5.12), P=0.002); out-of-hours surgery (OR 8.17; 95%CI=2.16-30.95), P=0.002), left ventricular ejection fraction <30% (OR 9.86; 95%CI=1.91-50.86, P<0.006) and surgery for degenerative aneurysm (OR=2.20; 95%CI=1.12-4.31, P=0.02).The incidence of stroke and paraplegia was 7.1% and zero after DTA repair; 9.9% and 3.3% after TAAA repair. Haemodialysis was necessary in 5.1% of cases after DTA repair and 22.7% after TAAA repair. CONCLUSION: Open thoracoabdominal aortic surgery carries significant risk to life, which is related to age, extent of aortic replacement, timing of surgery and left ventricular function. Morbidity is considerable. Understanding these risks is fundamental for patient selection and the consent process of potential candidates for surgery particularly in the elderly.

10.
Rev. bras. cir. cardiovasc ; 35(5): 607-613, Sept.-Oct. 2020. tab
Artigo em Inglês | LILACS-Express | LILACS, Sec. Est. Saúde SP | ID: biblio-1137336

RESUMO

Abstract Objective: To describe our experience of nine patients with extra-anatomical bypass for clinically ischemic distal limb during repair of acute Type A aortic dissection (ATAAD). Methods: We retrospectively examined a series of nine patients who underwent surgery for ATAAD. We identified a subset of the patients who presented with concomitant radiographic and clinical signs of lower limb ischemia. All but one patient (axillobifemoral bypass) underwent femorofemoral crossover grafting by the cardiac surgeon during cooling. Results: One hundred eighty-one cases of ATAAD underwent surgery during the study period with a mortality of 19.3%. Nine patients had persistent clinical evidence of lower limb ischemia (4.9%) and underwent extra-anatomical bypass during cooling. Two patients underwent additional fasciotomies. Mean delay from symptoms to surgery in these nine patients was 9.5 hours. Two patients had bilateral amputations despite revascularisation and, of note, had long delays in presentation for surgery (> 12 hours). There were no mortalities during these inpatient episodes. Outpatient radiographic follow-up at the first opportunity demonstrated 100% patency. Conclusion: Our experience suggests that, during complicated aortic dissection, limb ischemia may have a devastating outcome including amputation when diagnosis and referral are delayed. Early diagnosis and surgery are crucial in preventing this potentially devastating complication.

11.
J Card Surg ; 2020 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-32981073

RESUMO

The emergence of severe acute respiratory syndrome coronavirus 2 in December 2019, presumed from the city of Wuhan, Hubei province in China, and the subsequent declaration of the disease as a pandemic by the World Health Organization as coronavirus disease 2019 (COVID-19) in March 2020, had a significant impact on health care systems globally. Each country responded to this disease in different ways, however this was done broadly by fortifying and prioritizing health care provision as well as introducing social lockdown aiming to contain the infection and minimizing the risk of transmission. In the United Kingdom, a lockdown was introduced by the government on March 23, 2020 and all health care services were focussed to challenge the impact of COVID-19. To do so, the United Kingdom National Health Service had to undergo widespread service reconfigurations and the so-called "Nightingale Hospitals" were created de novo to bolster bed provision, and industries were asked to direct efforts to the production of ventilators. A government-led public health campaign was publicized under the slogan of: "Stay home, Protect the NHS (National Health Service), Save lives." The approach had a significant impact on the delivery of all surgical services but particularly cardiac surgery with its inherent critical care bed capacity. This paper describes the impact on provision for elective and emergency cardiac surgery in the United Kingdom, with a focus on aortovascular disease. We describe our aortovascular activity and outcomes during the period of UK lockdown and present a patient survey of attitudes to aortic surgery during COVID-19 pandemic.

12.
Elife ; 92020 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-32762841

RESUMO

Mutations in the Trypanosoma brucei aquaporin AQP2 are associated with resistance to pentamidine and melarsoprol. We show that TbAQP2 but not TbAQP3 was positively selected for increased pore size from a common ancestor aquaporin. We demonstrate that TbAQP2's unique architecture permits pentamidine permeation through its central pore and show how specific mutations in highly conserved motifs affect drug permeation. Introduction of key TbAQP2 amino acids into TbAQP3 renders the latter permeable to pentamidine. Molecular dynamics demonstrates that permeation by dicationic pentamidine is energetically favourable in TbAQP2, driven by the membrane potential, although aquaporins are normally strictly impermeable for ionic species. We also identify the structural determinants that make pentamidine a permeant although most other diamidine drugs are excluded. Our results have wide-ranging implications for optimising antitrypanosomal drugs and averting cross-resistance. Moreover, these new insights in aquaporin permeation may allow the pharmacological exploitation of other members of this ubiquitous gene family.

13.
Vasc Endovascular Surg ; 54(8): 756-759, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32787696

RESUMO

PURPOSE: To report a case who required a thoracic endovascular stenting (TEVAR) following the deployment of frozen elephant trunk due to false lumen expansion. CASE REPORT: A 47 years old male patient undergone emergency repair of acute type A aortic dissection in 2011 with bioprosthetic aortic root conduit. Seven years later he presented with moderate aortic valve disease and expanding chronic dissection of the aortic arch, therefore a redo operation with replacement of the prosthetic aortic valve, ascending aorta, total arch and deployment of frozen elephant trunk and he was discharged in good health. Several days post discharge he presented with new onset of chest pain and a new dissection involved the thoracoabdominal aorta was noted pressing on the true lumen and the frozen elephant trunk. Following a multi-disciplinary team meeting, TEVAR was deemed as a most appropriate approach and this was achieved successfully, and patient was discharged. At 1 year of follow up, he remains well and asymptomatic. CONCLUSION: Close imaging follow-up following deployment of a FET is mandatory. A new acute Type B aortic dissection distal to the FET, that causes false lumen propagation parallel to the stented portion, is a surgical emergency and further intervention mandated.


Assuntos
Aneurisma Dissecante/cirurgia , Aneurisma da Aorta Torácica/cirurgia , Implante de Prótese Vascular/instrumentação , Prótese Vascular , Procedimentos Endovasculares/instrumentação , Falha de Prótese , Stents , Aneurisma Dissecante/diagnóstico por imagem , Aneurisma da Aorta Torácica/diagnóstico por imagem , Implante de Prótese Vascular/efeitos adversos , Procedimentos Endovasculares/efeitos adversos , Humanos , Masculino , Pessoa de Meia-Idade , Resultado do Tratamento
15.
PLoS Negl Trop Dis ; 14(7): e0008458, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32644992

RESUMO

Defining mode of action is vital for both developing new drugs and predicting potential resistance mechanisms. Sensitivity of African trypanosomes to pentamidine and melarsoprol is predominantly mediated by aquaglyceroporin 2 (TbAQP2), a channel associated with water/glycerol transport. TbAQP2 is expressed at the flagellar pocket membrane and chimerisation with TbAQP3 renders parasites resistant to both drugs. Two models for how TbAQP2 mediates pentamidine sensitivity have emerged; that TbAQP2 mediates pentamidine translocation across the plasma membrane or via binding to TbAQP2, with subsequent endocytosis and presumably transport across the endosomal/lysosomal membrane, but as trafficking and regulation of TbAQPs is uncharacterised this remains unresolved. We demonstrate that TbAQP2 is organised as a high order complex, is ubiquitylated and is transported to the lysosome. Unexpectedly, mutation of potential ubiquitin conjugation sites, i.e. cytoplasmic-oriented lysine residues, reduced folding and tetramerization efficiency and triggered ER retention. Moreover, TbAQP2/TbAQP3 chimerisation, as observed in pentamidine-resistant parasites, also leads to impaired oligomerisation, mislocalisation and increased turnover. These data suggest that TbAQP2 stability is highly sensitive to mutation and that instability contributes towards the emergence of drug resistance.


Assuntos
Aquagliceroporinas/metabolismo , Resistência a Medicamentos , Tripanossomicidas/farmacologia , Trypanosoma brucei brucei , Tripanossomíase Africana/parasitologia , Sequência de Aminoácidos , Animais , Aquagliceroporinas/química , Estabilidade Proteica
16.
Ann Cardiothorac Surg ; 9(3): 228-229, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32551257
17.
Cell Microbiol ; 22(11): e13243, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32597009

RESUMO

Trypanosomatids regulate gene expression mainly at the post-transcriptional level through processing, exporting and stabilising mRNA and control of translation. In most eukaryotes, protein synthesis is regulated by phosphorylation of eukaryotic initiation factor 2 (eIF2) at serine 51. Phosphorylation halts overall translation by decreasing availability of initiator tRNAmet to form translating ribosomes. In trypanosomatids, the N-terminus of eIF2α is extended with threonine 169 the homologous phosphorylated residue. Here, we evaluated whether eIF2α phosphorylation varies during the Trypanosoma cruzi life cycle, the etiological agent of Chagas' disease. Total levels of eIF2α are diminished in infective and non-replicative trypomastigotes compared with proliferative forms from the intestine of the insect vector or amastigotes from mammalian cells, consistent with decreased protein synthesis reported in infective forms. eIF2α phosphorylation increases in proliferative intracellular forms prior to differentiation into trypomastigotes. Parasites overexpressing eIF2αT169A or with an endogenous CRISPR/Cas9-generated eIF2αT169A mutation were created and analysis revealed alterations to the proteome, largely unrelated to the presence of µORF in epimastigotes. eIF2αT169A mutant parasites produced fewer trypomastigotes with lower infectivity than wild type, with increased levels of sialylated mucins and oligomannose glycoproteins, and decreased galactofuranose epitopes and the surface protease GP63 on the cell surface. We conclude that eIF2α expression and phosphorylation levels affect proteins relevant for intracellular progression of T. cruzi.

18.
J Biol Chem ; 295(24): 8331-8347, 2020 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-32354742

RESUMO

Introduced about a century ago, suramin remains a frontline drug for the management of early-stage East African trypanosomiasis (sleeping sickness). Cellular entry into the causative agent, the protozoan parasite Trypanosoma brucei, occurs through receptor-mediated endocytosis involving the parasite's invariant surface glycoprotein 75 (ISG75), followed by transport into the cytosol via a lysosomal transporter. The molecular basis of the trypanocidal activity of suramin remains unclear, but some evidence suggests broad, but specific, impacts on trypanosome metabolism (i.e. polypharmacology). Here we observed that suramin is rapidly accumulated in trypanosome cells proportionally to ISG75 abundance. Although we found little evidence that suramin disrupts glycolytic or glycosomal pathways, we noted increased mitochondrial ATP production, but a net decrease in cellular ATP levels. Metabolomics highlighted additional impacts on mitochondrial metabolism, including partial Krebs' cycle activation and significant accumulation of pyruvate, corroborated by increased expression of mitochondrial enzymes and transporters. Significantly, the vast majority of suramin-induced proteins were normally more abundant in the insect forms compared with the blood stage of the parasite, including several proteins associated with differentiation. We conclude that suramin has multiple and complex effects on trypanosomes, but unexpectedly partially activates mitochondrial ATP-generating activity. We propose that despite apparent compensatory mechanisms in drug-challenged cells, the suramin-induced collapse of cellular ATP ultimately leads to trypanosome cell death.

19.
SLAS Discov ; 25(9): 1064-1071, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32400260

RESUMO

Leucyl aminopeptidases (LAPs) are involved in multiple cellular functions, which, in the case of infectious diseases, includes participation in the pathogen-host cell interface and pathogenesis. Thus, LAPs are considered good candidate drug targets, and the major M17-LAP from Trypanosoma cruzi (LAPTc) in particular is a promising target for Chagas disease. To exploit LAPTc as a potential target, it is essential to develop potent and selective inhibitors. To achieve this, we report a high-throughput screening method for LAPTc. Two methods were developed and optimized: a Leu-7-amido-4-methylcoumarin-based fluorogenic assay and a RapidFire mass spectrometry (RapidFire MS)-based assay using the LSTVIVR peptide as substrate. Compared with a fluorescence assay, the major advantages of the RapidFire MS assay are a greater signal-to-noise ratio as well as decreased consumption of enzyme. RapidFire MS was validated with the broad-spectrum LAP inhibitors bestatin (IC50 = 0.35 µM) and arphamenine A (IC50 = 15.75 µM). We suggest that RapidFire MS is highly suitable for screening for specific LAPTc inhibitors.

20.
PLoS One ; 15(4): e0231697, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32298348

RESUMO

To determine the feasibility of complex home-based phenotyping, 1,876 research participants from the customer base of 23andMe completed an online version of a Pain Sensitivity Questionnaire (PSQ) as well as a cold pressor test (CPT) which is used in clinical assessments of pain. Overall our online version of the PSQ performed similarly to the original pen-and-paper version. Construct validity of the PSQ total was demonstrated by internal consistency and consistent discrimination between more and less painful items. Criterion validity was demonstrated by correlation with pain sensitivity as measured by the CPT. Within the same cohort we performed a cold pressor test using a layperson description and household equipment. Comparison with published reports from controlled studies revealed similar distributions of cold pain tolerance times (i.e., time elapsed before removing the hand from the water). Of those who elected to participate in the CPT, a large majority of participants did not report issues with the test procedure or noncompliance with the instructions (97%). We confirmed a large sex difference in CPT thresholds in line with published data, such that women removed their hands from the water at a median of 54.2 seconds, with men lasting for a median time of 82.7 seconds (Kruskal-Wallis statistic, p < 0.0001), but other factors like age or current pain treatment were at most weakly associated, and inconsistently between men and women. We introduce a new paradigm for performing pain testing, called testing@home, that, in the case of cold nociception, showed comparable results to studies conducted under controlled conditions and supervision of a health care professional.


Assuntos
Medição da Dor/métodos , Limiar da Dor , Adulto , Idoso , Temperatura Baixa/efeitos adversos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Dor/etiologia , Caracteres Sexuais , Fatores Sexuais , Inquéritos e Questionários , Adulto Jovem
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA