Outcomes of bell-bottom technique compared to standard endovascular aneurysm repair.

OBJECTIVE: The bell-bottom technique is a widely used technique to treat aortoiliac aneurysms with preservation of the hypogastric arteries. The published data are scarce with conflicting results regarding the evolution. The aim of this study was to compare the outcomes of patients submitted to endovascular abdominal aortic aneurysm repair with standard technique (S-EVAR) versus bell-bottom technique. METHODS: This retrospective cohort study compared the outcomes of standard endovascular aneurysm repair (<16 mm iliac limbs) and bell-bottom technique (≥16 mm iliac limbs) in a tertiary vascular center between 2010 and 2015. The end points of this study were type IB endoleak, reintervention and 30-day mortality. The follow-up protocol included CT scans within 30 days of implantation and 12 months. Duplex ultrasound was performed yearly thereafter. RESULTS: Two hundred and three patients were treated with bell-bottom technique (n = 84, mean age 72.2 ± 8.9) and S-EVAR (n = 119, mean age 72.7 ± 8.4). The overall 30-day mortality was 1.9%, with no significant difference between groups. There was higher prevalence of coronary heart disease in the bell-bottom technique group compared to the S-EVAR group (41.6% vs. 18.4%, p < 0.01). One patient in the S-EVAR group (0.85%) and four patients in the bell-bottom technique (4.6%) developed type IB endoleak. The mean follow-up period was 35.2 ± 30.4 months. By Kaplan-Meier analysis, freedom from type IB endoleak in 80 months was 85.2% in the bell-bottom technique group and 98.7% in the S-EVAR group (p = 0.05). The freedom from reintervention in 80 months was 74.0% in the bell-bottom technique group and 94.1% in the S-EVAR group (p = 0.6). CONCLUSIONS: This study shows lower freedom from type IB endoleak in the bell-bottom group compared to the standard repair group. There is no significant difference in reoperation rate and 30-day mortality.

O impacto da tecnologia no tratamento do trauma vascular iatrogênico cervicotorácico: estudo de dois casos com intervalo de três décadas e revisão da literatura / he impact of technology on treatment of iatrogenic cervicothoracic vascular traumas: a study of two cases three decades apart and a review of the literature

Complicações relacionadas ao acesso venoso cervicotorácico, como os pseudoaneurismas (PAs), podem ser devastadoras. Neste artigo, apresentamos dois casos semelhantes em que o avanço tecnológico impactou no diagnóstico, tratamento e resultados. Ambos pacientes apresentaram volumoso PA após a tentativa de punção venosa profunda. O primeiro caso, em 1993, diagnosticado por duplex scan , revelou grande PA oriundo da artéria subclávia direita. A artéria foi abordada por esternotomia mediana com extensão supraclavicular. O PA originava-se do tronco tireocervical, tratado com simples ligadura. No segundo caso, em 2017, angiotomografia revelou um PA originário da artéria vertebral, que foi tratado com técnica endovascular, mantendo a perviedade do vaso. Ambos evoluíram satisfatoriamente, apesar de abordagens bastante diferentes. A lesão vascular cervicotorácica representa um desafio propedêutico e terapêutico, com alto risco de ruptura. Os avanços tecnológicos diminuem os riscos de lesões vasculares com acesso cirúrgico difícil e devem estar entre as opções do cirurgião vascular

Complications such as pseudoaneurysms (PA) related to cervicothoracic venous access can be devastating. In this article, we present two similar cases in which technological advances impacted diagnosis, treatment, and results. Both patients developed massive PA after deep venous puncture attempts. The first case occurred in 1993 and was diagnosed by a duplex scan that revealed a large PA originating from the right subclavian artery. The artery was approached by median sternotomy with supraclavicular extension. The PA originated from the thyrocervical trunk and was treated with simple ligation. The second case was in 2017. Angiotomography revealed a PA originating in the vertebral artery, which was treated with endovascular techniques, maintaining vessel patency. Both patients progressed satisfactorily, despite quite different approaches. Cervicothoracic vascular lesions represent a diagnostic and therapeutic challenge, where the risk of rupture is high. Technological advances have reduced the risks involved in management of vascular injuries with difficult surgical access

Two-step interrogation then recognition of DNA binding site by Integration Host Factor: an architectural DNA-bending protein.

The dynamics and mechanism of how site-specific DNA-bending proteins initially interrogate potential binding sites prior to recognition have remained elusive for most systems. Here we present these dynamics for Integration Host factor (IHF), a nucleoid-associated architectural protein, using a µs-resolved T-jump approach. Our studies show two distinct DNA-bending steps during site recognition by IHF. While the faster (∼100 µs) step is unaffected by changes in DNA or protein sequence that alter affinity by >100-fold, the slower (1-10 ms) step is accelerated ∼5-fold when mismatches are introduced at DNA sites that are sharply kinked in the specific complex. The amplitudes of the fast phase increase when the specific complex is destabilized and decrease with increasing [salt], which increases specificity. Taken together, these results indicate that the fast phase is non-specific DNA bending while the slow phase, which responds only to changes in DNA flexibility at the kink sites, is specific DNA kinking during site recognition. Notably, the timescales for the fast phase overlap with one-dimensional diffusion times measured for several proteins on DNA, suggesting that these dynamics reflect partial DNA bending during interrogation of potential binding sites by IHF as it scans DNA.

The impact of technology on treatment of iatrogenic cervicothoracic vascular traumas: a study of two cases three decades apart and a review of the literature.

Complications such as pseudoaneurysms (PA) related to cervicothoracic venous access can be devastating. In this article, we present two similar cases in which technological advances impacted diagnosis, treatment, and results. Both patients developed massive PA after deep venous puncture attempts. The first case occurred in 1993 and was diagnosed by a duplex scan that revealed a large PA originating from the right subclavian artery. The artery was approached by median sternotomy with supraclavicular extension. The PA originated from the thyrocervical trunk and was treated with simple ligation. The second case was in 2017. Angiotomography revealed a PA originating in the vertebral artery, which was treated with endovascular techniques, maintaining vessel patency. Both patients progressed satisfactorily, despite quite different approaches. Cervicothoracic vascular lesions represent a diagnostic and therapeutic challenge, where the risk of rupture is high. Technological advances have reduced the risks involved in management of vascular injuries with difficult surgical access.

Global analysis of ion dependence unveils hidden steps in DNA binding and bending by integration host factor.

Proteins that recognize and bind to specific sites on DNA often distort the DNA at these sites. The rates at which these DNA distortions occur are considered to be important in the ability of these proteins to discriminate between specific and nonspecific sites. These rates have proven difficult to measure for most protein-DNA complexes in part because of the difficulty in separating the kinetics of unimolecular conformational rearrangements (DNA bending and kinking) from the kinetics of bimolecular complex association and dissociation. A notable exception is the Integration Host Factor (IHF), a eubacterial architectural protein involved in chromosomal compaction and DNA recombination, which binds with subnanomolar affinity to specific DNA sites and bends them into sharp U-turns. The unimolecular DNA bending kinetics has been resolved using both stopped-flow and laser temperature-jump perturbation. Here we expand our investigation by presenting a global analysis of the ionic strength dependence of specific binding affinity and relaxation kinetics of an IHF-DNA complex. This analysis enables us to obtain each of the underlying elementary rates (DNA bending/unbending and protein-DNA association/dissociation), and their ionic strength dependence, even under conditions where the two processes are coupled. Our analysis indicates interesting differences in the ionic strength dependence of the bi- versus unimolecular steps. At moderate [KCl] (100-500 mM), nearly all the ionic strength dependence to the overall equilibrium binding affinity appears in the bimolecular association/dissociation of an initial, presumably weakly bent, encounter complex, with a slope SK(bi) ≈ 8 describing the loglog-dependence of the equilibrium constant to form this complex on [KCl]. In contrast, the unimolecular equilibrium constant to form the fully wrapped specific complex from the initial complex is nearly independent of [KCl], with SK(uni) < 0.5. This result is counterintuitive because there are at least twice as many ionic protein-DNA contacts in the fully wrapped complex than in the weakly bent intermediate. The following picture emerges from this analysis: in the bimolecular step, the observed [KCl]-dependence is consistent with the number of DNA counterions expected to be released when IHF binds nonspecifically to DNA whereas in the unimolecular reorganization step, the weak [KCl]-dependence suggests that two effects cancel one another. On one hand, formation of additional protein-DNA contacts in the fully wrapped complex releases bound counterions into bulk solution, which is entropically favored by decreasing [salt]. On the other hand, formation of the fully wrapped complex also releases tightly bound water molecules, which is osmotically favored by increasing [salt]. More generally, our global analysis strategy is applicable to other protein-DNA complexes, and opens up the possibility of measuring DNA bending rates in complexes where the unimolecular and bimolecular steps are not easily separable.

The SnAC domain of SWI/SNF is a histone anchor required for remodeling.

The SWI/SNF chromatin remodeling complex changes the positions where nucleosomes are bound to DNA, exchanges out histone dimers, and disassembles nucleosomes. All of these activities depend on ATP hydrolysis by the catalytic subunit Snf2, containing a DNA-dependent ATPase domain. Here we examine the role of another domain in Snf2 called SnAC (Snf2 ATP coupling) that was shown previously to regulate the ATPase activity of SWI/SNF. We have found that SnAC has another function besides regulation of ATPase activity that is even more critical for nucleosome remodeling by SWI/SNF. We have found that deletion of the SnAC domain strongly uncouples ATP hydrolysis from nucleosome movement. Deletion of SnAC does not adversely affect the rate, processivity, or pulling force of SWI/SNF to translocate along free DNA in an ATP-dependent manner. The uncoupling of ATP hydrolysis from nucleosome movement is shown to be due to loss of SnAC binding to the histone surface of nucleosomes. While the SnAC domain targets both the ATPase domain and histones, the SnAC domain as a histone anchor plays a more critical role in remodeling because it is required to convert DNA translocation into nucleosome movement.

Mapping the transition state for DNA bending by IHF.

How DNA-bending proteins recognize their specific sites on DNA remains elusive, particularly for proteins that use indirect readout, which relies on sequence-dependent variations in DNA flexibility/bendability. The question remains as to whether the protein bends the DNA (protein-induced bending) or, alternatively, "prebent" DNA conformations are thermally accessible, which the protein captures to form the specific complex (conformational capture). To distinguish between these mechanisms requires characterization of reaction intermediates and, in particular, snapshots of the transition state along the recognition pathway. We present such a snapshot, from measurements of DNA bending dynamics in complex with Escherichia coli integration host factor (IHF), an architectural protein that bends specific sites on λ-DNA in a U-turn by creating two sharp kinks in DNA. Fluorescence resonance energy transfer measurements in response to laser temperature-jump perturbation monitor DNA bending. We find that nicks or mismatches that enhance DNA flexibility at the site of the kinks show 3- to 4-fold increase in DNA bending rates that reflect a 4- to 11-fold increase in binding affinities, while sequence modifications away from the kink sites, as well as mutations in IHF designed to destabilize the complex, have negligible effect on DNA bending rates despite >250-fold decrease in binding affinities. These results support the scenario that the bottleneck in the recognition step for IHF is spontaneous kinking of cognate DNA to adopt a partially prebent conformation and point to conformational capture as the underlying mechanism of initial recognition, with additional protein-induced bending occurring after the transition state.

New insights into the transition pathway from nonspecific to specific complex of DNA with Escherichia coli integration host factor.

To elucidate the nature of the transition-state ensemble along the reaction pathway from a nonspecific protein-DNA complex to the specific complex, we have carried out measurements of DNA bending/unbending dynamics on a cognate DNA substrate in complex with integration host factor (IHF), an architectural protein from E. coli that bends its cognate site by approximately 180 degrees . We use a laser temperature jump to perturb the IHF-DNA complex and monitor the relaxation kinetics with time-resolved FRET measurements on DNA substrates end-labeled with a FRET pair. Previously, we showed that spontaneous bending/kinking of DNA, from thermal disruption of base-pairing/-stacking interactions, may be the rate-limiting step in the formation of the specific complex (Kuznetsov, S. V.; Sugimura, S.; Vivas, P.; Crothers, D. M.; Ansari, A. Proc. Natl. Acad. Sci. USA 2006, 103, 18515). Here, we probe the effect of varying [KCl], which affects the stability of the complex, on this rate-limiting step. We find that below approximately 250 mM KCl, the observed relaxation kinetics are from the unimolecular bending/unbending of DNA, and the relaxation rate kr is independent of [KCl]. Above approximately 300 mM KCl, dissociation of the IHF-DNA complex becomes significant, and the observed relaxation process includes contributions from the association/dissociation step, with kr decreasing with increasing [KCl]. The DNA bending step occurs with a positive activation enthalpy, despite the large negative enthalpy change reported for the specific IHF-DNA complex (Holbrook, J. A.; Tsodikov, O. V.; Saecker, R. M.; Record, M. T., Jr. J. Mol. Biol. 2001, 310, 379). Our conclusion from these studies is that in the uphill climb to the transition state, the DNA is kinked, but with no release of ions, as indicated by the salt-independent behavior of k(r) at low [KCl]. Any release of ions in the unimolecular process, together with conformational changes in the protein-DNA complex that facilitate favorable interactions and that contribute to the negative enthalpy change, must occur as the system leaves the transition state, downhill to the final complex.

Direct observation of DNA bending/unbending kinetics in complex with DNA-bending protein IHF.

Regulation of gene expression involves formation of specific protein-DNA complexes in which the DNA is often bent or sharply kinked. Kinetics measurements of DNA bending when in complex with the protein are essential for understanding the molecular mechanism that leads to precise recognition of specific DNA-binding sites. Previous kinetics measurements on several DNA-bending proteins used stopped-flow techniques that have limited time resolution of few milliseconds. Here we use a nanosecond laser temperature-jump apparatus to probe, with submillisecond time resolution, the kinetics of bending/unbending of a DNA substrate bound to integration host factor (IHF), an architectural protein from Escherichia coli. The kinetics are monitored with time-resolved FRET, with the DNA substrates end-labeled with a FRET pair. The temperature-jump measurements, in combination with stopped-flow measurements, demonstrate that the binding of IHF to its cognate DNA site involves an intermediate state with straight or, possibly, partially bent DNA. The DNA bending rates range from approximately 2 ms(-1) at approximately 37 degrees C to approximately 40 ms(-1) at approximately 10 degrees C and correspond to an activation energy of approximately 14 +/- 3 kcal/mol. These rates and activation energy are similar to those of a single A:T base pair opening inside duplex DNA. Thus, our results suggest that spontaneous thermal disruption in base-paring, nucleated at an A:T site, may be sufficient to overcome the free energy barrier needed to partially bend/kink DNA before forming a tight complex with IHF.