More Retrieval Attempts are Associated with Poorer Functional Outcome After Unsuccessful Thrombectomy.

PURPOSE: In mechanical thrombectomy, it has been hypothesized that multiple retrieval attempts might the improve reperfusion rate but not the clinical outcome. In order to assess a potential harmful effect of a mechanical thrombectomy on patient outcome, the number of retrieval attempts was analyzed. Only patients with a thrombolysis in cerebral infarction (TICI) score of 0 were reviewed to exclude the impact of eventual successful reperfusion on the mechanical hazardousness of repeated retrievals. METHODS: In this study 6635 patients who underwent endovascular thrombectomy (EVT) for acute large vessel occlusion (LVO) from the prospectively administered multicenter German Stroke Registry were screened. Insufficient reperfusion was defined as no reperfusion (TICI score of 0), whereas a primary outcome was defined as functional independence (modified Rankin scale [mRS] 0-2 at day 90). Propensity score matching and multivariable logistic regressions were then performed to adjust for confounders. RESULTS: A total of 377 patients (7.8%) had a final TICI score of 0 and were included in the study. After propensity score matching functional independence was found to be significantly more frequent in patients who underwent ≤ 2 retrieval attempts (14%), compared to patients with > 2 retrieval attempts (3.9%, OR 0.29, 95% CI 0.07-0.73, p = 0.009). After adjusting for age, sex, admission NIHSS score, and location of occlusion, more than two retrieval attempts remained significantly associated with lower odds of functional independence at 90 days (OR 0.2, 95% CI 0.07-0.52, p = 0.002). CONCLUSION: In patients with failure of reperfusion, more than two retrieval attempts were associated with a worse clinical outcome, therefore indicating a possible harmful effect of multiple retrieval attempts.

Early TICI 2b or Late TICI 3-Is Perfect the Enemy of Good?

BACKGROUND AND PURPOSE: A Thrombolysis in Cerebral Infarction (TICI) score of 3 has been established as therapeutic goal in endovascular therapy (EVT) for acute ischemic stroke; however, in the case of early TICI2b reperfusion, the question remains whether to stop the procedure or to continue in the pursuit of perfection (i.e., TICI 2c/3). METHODS: A total of 6635 patients were screened from the German Stroke Registry. Patients who underwent EVT for occlusion of the middle cerebral artery (M1 segment), with final TICI score of 2b/3 were included. Multivariable logistic regression was performed with functional independence (modified Rankin Scale, mRS at day 90 of 0-2) as the dependent variable. RESULTS: Of 1497 patients, 586 (39.1%) met inclusion criteria with a final TICI score of 2b and 911 (60.9%) with a TICI score of 3. Patients who achieved first-pass TICI3 showed highest odds of functional independence (Odds ratio [OR] 1.71, 95% confidence interval [95% CI] 1.18-2.47). Patients who achieved TICI2b with the second pass (OR 0.53, 95% CI 0.31-0.89) or with three or more passes (OR 0.44, 95% CI 0.27-0.70) had significantly worse clinical outcomes compared to first-pass TICI2b. TICI3 at the second pass was by trend better than first-pass TICI2b (OR 1.55, 95% CI 0.98-2.45), but TICI3 after 3 or more passes (OR 0.93, 95% CI 0.57-1.50) was not significantly different from first-pass TICI2b. CONCLUSION: First-pass TICI2b was superior to TICI2b after ≥ 2 retrievals and comparable to TICI3 at ≥ 3 retrievals. The potential benefit in outcome after achieving TICI3 following further retrieval attempts after first-pass TICI2b need to be weighed against the risks.

Incomplete or failed thrombectomy in acute stroke patients with Alberta Stroke Program Early Computed Tomography Score 0-5 - how harmful is trying?

BACKGROUND AND PURPOSE: It is currently unknown whether mechanical thrombectomy (MT) for ischaemic stroke patients with low initial Alberta Stroke Program Early Computed Tomography Score (ASPECTS) is clinically beneficial or even harmful. The purpose of this study was to investigate whether failed or incomplete MT in acute large vessel occlusion stroke with an initial ASPECTS ≤ 5 is associated with worse clinical outcome compared to patients not undergoing MT. METHODS: This observational cohort study included a consecutive sample of patients with anterior circulation stroke and initial ASPECTS ≤ 5 admitted between March 2015 and August 2019. Failed recanalization was defined as Thrombolysis in Cerebral Infarction (TICI) score 0-2a, and incomplete recanalization as TICI 2b. Clinical outcome was assessed using the modified Rankin Scale (mRS) at 90 days defining very poor clinical outcome as mRS > 4. RESULTS: One hundred and seventy patients were included. Ninety-nine patients underwent MT and 71 patients received best medical treatment only. Clinical outcome after failed or incomplete MT (TICI 0-2b) was significantly better compared to patients with medical treatment only (median mRS 5, interquartile range 4-6 vs 5-6, P = 0.03). In multivariable logistic regression analysis, failed or incomplete MT (TICI 0-2b) showed a significantly reduced likelihood for very poor outcome (odds ratio 0.39, 95% confidence interval 0.19-0.83, P = 0.01). Failed MT (TICI 0-2a) was not associated with a worse outcome compared to best medical treatment. CONCLUSIONS: Patients with failed or incomplete recanalization results (TICI 0-2b) showed a reduced likelihood for very poor outcome compared with those who did not receive MT. Evidence from randomized trials is needed to confirm that even failed or incomplete MT is not harmful in these patients.

Emergency Conversion to General Anesthesia Is a Tolerable Risk in Patients Undergoing Mechanical Thrombectomy.

BACKGROUND AND PURPOSE: Mechanical thrombectomy for acute ischemic stroke is performed with the patient under local anesthesia, conscious sedation, or general anesthesia. According to recent trials, up to 16% of patients require emergency conversion to general anesthesia during mechanical thrombectomy. This study investigated the procedural and clinical outcomes after emergency conversion in comparison with local anesthesia, conscious sedation, and general anesthesia. MATERIALS AND METHODS: This retrospective study included 254 patients undergoing mechanical thrombectomy for acute large-vessel occlusion. The procedure was started with the patient either under local anesthesia, conscious sedation, or general anesthesia. Emergency conversion was defined as induction of general anesthesia during mechanical thrombectomy. The primary outcomes were successful reperfusion (TICI 2b/3) and functional independence (mRS at 90 days, ≤2). RESULTS: Twenty-five patients (9.8%) required emergency conversion to general anesthesia. The time from admission to flow restoration was increased under general anesthesia (median, 137 minutes) and emergency conversion (median, 138 minutes) compared with local anesthesia (median 110 minutes). After adjustment for confounders, emergency conversion to general anesthesia and primary general anesthesia had comparable chances of successful reperfusion (OR = 1.28; 95% CI, 0.31-5.25). Patients with emergency conversion had a tendency toward higher chances of functional independence (OR = 4.48; 95% CI, 0.49-40.86) compared with primary general anesthesia, but not compared with local anesthesia (OR = 0.86; 95% CI, 0.14-5.11) and conscious sedation (OR = 1.07; 95% CI, 0.17-6.53). CONCLUSIONS: Patients with emergency conversion did not have lower chances of successful reperfusion or functional independence compared those with primary general anesthesia, and time to flow restoration was also similar. We found no evidence supporting the primary induction of general anesthesia in patients at risk for emergency conversion.

Expansion of activated human naïve T-cells precedes effector function.

Naïve T-cells divide and mature, both functionally and phenotypically, upon stimulation through the T-cell receptor. Although much is known about the overall changes that occur in naïve cells upon TCR stimulation, and the different memory/effector populations that arise following stimulation, the relationship between cell division and functional and phenotypical changes that occur after activation is poorly understood. Here, we examine the early stages of human naïve and antigen-experienced T-cell activation, and the relationship between cell division and acquisition of effector function during the transition from resting antigen-experienced or naïve T-cells into effector cells. Stimulated naïve T-cells proliferate prior to acquisition of effector function, as measured by cytokine production and expression of effector-associated cell surface molecules. Additionally, we show that interlukin-7 (IL-7) can drive proliferation of naïve T-cells without TCR:MHC peptide interactions. IL-7 alone does not, however, drive the proliferation of antigen-experienced T-cells. Memory T-cells will divide in response to exogenous IL-7 but only in the presence of naïve T-cells and IL-2. This study contributes to the current understanding of the mechanistic differences between naïve and memory T-cell responses by defining the functional and phenotypic changes that occur to T-cells after stimulation.

Functional characterisation of mycobacterial DNA gyrase: an efficient decatenase.

A rapid single step immunoaffinity purification procedure is described for Mycobacterium smegmatis DNA gyrase. The mycobacterial enzyme is a 340 kDa heterotetrameric protein comprising two subunits each of GyrA and GyrB, exhibiting subtle differences and similarities to the well-characterised Escherichia coli gyrase. In contrast to E.coli gyrase, the M.smegmatis enzyme exhibits strong decatenase activity at physiological Mg2+ concentrations. Further, the enzymes exhibited marked differences in ATPase activity, DNA binding characteristics and susceptibility to fluoroquinolones. The holoenzyme showed very low intrinsic ATPase activity and was stimulated 20-fold in the presence of DNA. The DNA-stimulated ATPase kinetics revealed apparent K0.5 and kcat of 0.68 mM and 0.39 s(-1), respectively. The dissociation constant for DNA was found to be 9.2 nM, which is 20 times weaker than that of E.coli DNA gyrase. The differences between the enzymes were further substantiated as they exhibited varied sensitivity to moxifloxacin and ciprofloxacin. In spite of these differences, mycobacterial DNA gyrase is a functionally and mechanistically conserved enzyme and the variations in activity seem to reflect functional optimisation for its physiological role during mycobacterial genome replication.

Effect of different classes of inhibitors on DNA gyrase from Mycobacterium smegmatis.

Quinolones, coumarins, cyclothialidines, CcdB and microcin B17 inhibit DNA gyrase. Information regarding these various inhibitors comes from studies performed with the enzyme from Escherichia coli, and subsequent analyses have also primarily been confined to this system. We have carried out a detailed analysis of the effect of various groups of inhibitors on Mycobacterium smegmatis gyrase and demonstrate differential susceptibility of the E. coli and M. smegmatis gyrases. Interestingly, M. smegmatis gyrase was refractory to the plasmid-borne proteinaceous inhibitors CcdB and microcin B17. Ciprofloxacin, a fluoroquinolone, showed a 10-fold reduction in efficacy against M. smegmatis compared with E. coli gyrase. We have also shown that etoposide, an antineoplastic drug, inhibits DNA gyrase activity by trapping the gyrase-DNA complex. DNA gyrases from both E. coli and M. smegmatis were susceptible to etoposide at comparable levels.

IFN-gamma-independent autocrine cytokine regulatory mechanism in reprogramming of macrophage responses to bacterial lipopolysaccharide.

Macrophages are now well recognized to have a critical role in both innate and acquired immunity. The sentinel macrophage function is highly regulated and serves to allow for intrinsic plasticity of the innate immune responses to potential environmental signals. However, the mechanisms underlying the dynamic properties of the cellular arm of innate immunity are poorly understood. Therefore, we have conducted a series of in vitro studies to evaluate the contribution of immunoregulatory cytokines, such as IFN-gamma, IL-10, and IL-12, in modulation of macrophage responses. We found that macrophages from IFN-gamma knockout (IFN-gamma(-/-)) mice exhibit only marginal LPS-induced TNF-alpha, IL-12, and NO responses, all of which can be fully restored in the presence of rIFN-gamma. Pretreatment with substimulatory LPS concentrations led to reprogramming of IFN-gamma(-/-) macrophage responses in a dose-dependent manner that manifested by an increased TNF-alpha and IL-12, but not NO, production upon the subsequent LPS challenge. These reprogramming effects were substantially attenuated and profoundly enhanced in macrophages from IL-12(-/-) and IL-10(-/-) mice, respectively, as compared with those modulated in macrophages from the congenic wild-type mice. LPS-dependent reprogramming was also fully reproduced in macrophages isolated from SCID mice after immunodepletion of NK cells. Our data strongly imply that cytokine (TNF-alpha and IL-12), but not NO, responses in macrophages may, at least in part, be governed by an autocrine IFN-gamma-independent regulatory mechanism reciprocally controlled by IL-10 and IL-12. This mechanism may serve as an alternative/coherent pathway to the canonical IFN-gamma-dependent induction of antimicrobial and tumoricidal activity in macrophages.

The additional 165 amino acids in the B protein of Escherichia coli DNA gyrase have an important role in DNA binding.

DNA gyrase is the only enzyme known to negatively supercoil DNA. The enzyme is a heterotetramer of A(2)B(2) subunit composition. Alignment of the primary sequence of gyrase B (GyrB) from various species shows that they can be grouped into two classes. The GyrB of Gram-negative eubacteria has a stretch of about 165 amino acids in the C-terminal half, which is lacking in other GyrB subunits and type II topoisomerases. In Escherichia coli, no function has so far been attributed to this stretch. In this study, we have tried to assess the function of this region both in vivo and in vitro. A deletant (GyrBDelta160) lacking this region is non-functional in vivo. The holoenzyme reconstituted from gyrase A (GyrA) and GyrBDelta160 shows reduced but detectable supercoiling and quinolone-induced cleavage activity in vitro. GyrBDelta160 retains its ability to bind to GyrA and novobiocin. However, when reconstituted with GyrA, the deletant shows greatly impaired DNA binding. The intrinsic ATPase activity of the GyrBDelta160 is comparable to that of wild type GyrB, but this activity is not stimulated by DNA. These studies indicate that the additional stretch present in GyrB is essential for the DNA binding ability of E. coli gyrase.