Cyclical fate restriction: a new view of neural crest cell fate specification.

Neural crest cells are crucial in development, not least because of their remarkable multipotency. Early findings stimulated two hypotheses for how fate specification and commitment from fully multipotent neural crest cells might occur, progressive fate restriction (PFR) and direct fate restriction, differing in whether partially restricted intermediates were involved. Initially hotly debated, they remain unreconciled, although PFR has become favoured. However, testing of a PFR hypothesis of zebrafish pigment cell development refutes this view. We propose a novel 'cyclical fate restriction' hypothesis, based upon a more dynamic view of transcriptional states, reconciling the experimental evidence underpinning the traditional hypotheses.

Loss of phenotypic inheritance associated with ydcI mutation leads to increased frequency of small, slow persisters in Escherichia coli.

Whenever a genetically homogenous population of bacterial cells is exposed to antibiotics, a tiny fraction of cells survives the treatment, the phenomenon known as bacterial persistence [G.L. Hobby et al., Exp. Biol. Med. 50, 281-285 (1942); J. Bigger, The Lancet 244, 497-500 (1944)]. Despite its biomedical relevance, the origin of the phenomenon is still unknown, and as a rare, phenotypically resistant subpopulation, persisters are notoriously hard to study and define. Using computerized tracking we show that persisters are small at birth and slowly replicating. We also determine that the high-persister mutant strain of Escherichia coli, HipQ, is associated with the phenotype of reduced phenotypic inheritance (RPI). We identify the gene responsible for RPI, ydcI, which encodes a transcription factor, and propose a mechanism whereby loss of phenotypic inheritance causes increased frequency of persisters. These results provide insight into the generation and maintenance of phenotypic variation and provide potential targets for the development of therapeutic strategies that tackle persistence in bacterial infections.

Impact of Statins on Hematoma, Edema, Seizures, Vascular Events, and Functional Recovery After Intracerebral Hemorrhage.

BACKGROUND AND PURPOSE: The impact of statins on hematoma characteristics, perihemorrhagic edema (PHE), cardiovascular events, seizures, and functional recovery in patients with intracerebral hemorrhage (ICH) is insufficiently studied. METHODS: Patients with ICH of the prospective UKER-ICH (Universitätsklinikum Erlangen Cohort of Patients With Spontaneous Intracerebral Hemorrhage) study (URL: https://www.clinicaltrials.gov; Unique identifier: NCT03183167) were analyzed by multivariable regression modeling and propensity score matching, and PHE volumes were volumetrically assessed. Outcomes comprised hematoma characteristics, the impact of continuation, discontinuation, and initiation of statins on peak PHE extent, and the influence of statin treatment on the occurrence of seizures, cardiovascular adverse events, and functional recovery after ICH. RESULTS: A total of 1275 patients with ICH with information on statin treatment were analyzed. Statin treatment on hospital admission (21.7%) was associated with higher rates of lobar versus nonlobar ICH (odds ratio, 1.57 [1.03-2.40]; P=0.038). Initiation of statins after ICH was associated with increased peak PHE (ß=0.12, SE=0.06, P=0.008), whereas continuation versus discontinuation of prior statin treatment was not significantly associated with edema formation (P>0.10). There were no significant differences in the incidence of remote symptomatic seizures according to statin exposure during follow-up (statins: 11.5% versus no statins: 7.8%, subdistribution hazard ratio: 1.15 [0.80-1.66]; P=0.512). Patients on statins revealed less cardiovascular adverse events and more frequently functional recovery after 12 months (functional recovery: 57.7% versus 45.0%, odds ratio 1.67 [1.09-2.56]; P=0.019). CONCLUSIONS: Among statin users, lobar ICH occurs more frequently as compared with nonstatin users. While continuation of prior statin treatment appears to be safe regarding PHE formation, the initiation of statins during the first days after ICH may increase PHE extent. However, statins should be initiated thereafter (eg, at hospital discharge) to prevent cardiovascular events and potentially improve functional recovery.

High frequency of cerebrospinal fluid autoantibodies in COVID-19 patients with neurological symptoms.

BACKGROUND: COVID-19 intensive care patients can present with neurological syndromes, usually in the absence of SARS-CoV-2 in cerebrospinal fluid (CSF). The recent finding of some virus-neutralizing antibodies cross-reacting with brain tissue suggests the possible involvement of specific autoimmunity. DESIGN: Blood and CSF samples from eleven critically ill COVID-19 patients presenting with unexplained neurological symptoms including myoclonus, oculomotor disturbance, delirium, dystonia and epileptic seizures, were analyzed for anti-neuronal and anti-glial autoantibodies. RESULTS: Using cell-based assays and indirect immunofluorescence on unfixed murine brain sections, all patients showed anti-neuronal autoantibodies in serum or CSF. Antigens included intracellular and neuronal surface proteins, such as Yo or NMDA receptor, but also various specific undetermined epitopes, reminiscent of the brain tissue binding observed with certain human monoclonal SARS-CoV-2 antibodies. These included vessel endothelium, astrocytic proteins and neuropil of basal ganglia, hippocampus or olfactory bulb. CONCLUSION: The high frequency of autoantibodies targeting the brain in the absence of other explanations suggests a causal relationship to clinical symptoms, in particular to hyperexcitability (myoclonus, seizures). Several underlying autoantigens and their potential molecular mimicry with SARS-CoV-2 still await identification. However, autoantibodies may already now explain some aspects of multi-organ disease in COVID-19 and can guide immunotherapy in selected cases.

A systems biology approach uncovers the core gene regulatory network governing iridophore fate choice from the neural crest.

Multipotent neural crest (NC) progenitors generate an astonishing array of derivatives, including neuronal, skeletal components and pigment cells (chromatophores), but the molecular mechanisms allowing balanced selection of each fate remain unknown. In zebrafish, melanocytes, iridophores and xanthophores, the three chromatophore lineages, are thought to share progenitors and so lend themselves to investigating the complex gene regulatory networks (GRNs) underlying fate segregation of NC progenitors. Although the core GRN governing melanocyte specification has been previously established, those guiding iridophore and xanthophore development remain elusive. Here we focus on the iridophore GRN, where mutant phenotypes identify the transcription factors Sox10, Tfec and Mitfa and the receptor tyrosine kinase, Ltk, as key players. Here we present expression data, as well as loss and gain of function results, guiding the derivation of an initial iridophore specification GRN. Moreover, we use an iterative process of mathematical modelling, supplemented with a Monte Carlo screening algorithm suited to the qualitative nature of the experimental data, to allow for rigorous predictive exploration of the GRN dynamics. Predictions were experimentally evaluated and testable hypotheses were derived to construct an improved version of the GRN, which we showed produced outputs consistent with experimentally observed gene expression dynamics. Our study reveals multiple important regulatory features, notably a sox10-dependent positive feedback loop between tfec and ltk driving iridophore specification; the molecular basis of sox10 maintenance throughout iridophore development; and the cooperation between sox10 and tfec in driving expression of pnp4a, a key differentiation gene. We also assess a candidate repressor of mitfa, a melanocyte-specific target of sox10. Surprisingly, our data challenge the reported role of Foxd3, an established mitfa repressor, in iridophore regulation. Our study builds upon our previous systems biology approach, by incorporating physiologically-relevant parameter values and rigorous evaluation of parameter values within a qualitative data framework, to establish for the first time the core GRN guiding specification of the iridophore lineage.

Oral anticoagulation in patients with atrial fibrillation and acute ischaemic stroke: design and baseline data of the prospective multicentre Berlin Atrial Fibrillation Registry.

AIMS: The Berlin Atrial Fibrillation Registry was designed to analyse oral anticoagulation (OAC) prescription in patients with atrial fibrillation (AF) and acute ischaemic stroke. METHODS AND RESULTS: This investigator-initiated prospective multicentre registry enrolled patients at all 16 stroke units located in Berlin, Germany. The ongoing telephone follow-up is conducted centrally and will cover 5 years per patient. Within 2014 and 2016, 1080 patients gave written informed consent and 1048 patients were available for analysis. Median age was 77 years [interquartile range (IQR) 72-83], 503 (48%) patients were female, and 254 (24%) had a transient ischaemic attack (TIA). Overall, 470 (62%) out of 757 patients with known AF and a (pre-stroke) CHA2DS2-VASc ≥ 1 were anticoagulated at the time of stroke. At hospital discharge, 847 (81.3%) of 1042 patients were anticoagulated. Thereof 710 (68.1%) received a non-vitamin K-dependent oral anticoagulant (NOAC) and 137 (13.1%) a vitamin K antagonist (VKA). Pre-stroke intake of a NOAC [odds ratio (OR) 15.6 (95% confidence interval, 95% CI 1.97-122)] or VKA [OR 0.04 (95% CI 0.02-0.09)], an index TIA [OR 0.56 (95% CI 0.34-0.94)] rather than stroke, heart failure [OR 0.49 (95% CI 0.26-0.93)], and endovascular thrombectomy at hospital admission [OR 12.9 (95% CI 1.59-104)] were associated with NOAC prescription at discharge. Patients' age or AF type had no impact on OAC or NOAC use, respectively. CONCLUSION: About 60% of all registry patients with known AF received OAC at the time of stroke or TIA. At hospital discharge, more than 80% of AF patients were anticoagulated and about 80% of those were prescribed a NOAC.

Prior antiplatelet therapy is not associated with larger hematoma volume or hematoma growth in intracerebral hemorrhage.

Hematoma volume (HV) and hematoma growth (HG) predict mortality and poor outcome in intracerebral hemorrhage (ICH). While the influence of oral anticoagulation on HV, HG and outcome is well established, the effect of prior antiplatelet therapy (APT) remains uncertain. We retrospectively examined data from all patients with acute, primary ICH, and baseline head CT admitted to our department between January 2005 and February 2014. HV were calculated by ABC/2 method. HG was defined as present if HV increased between baseline and follow-up CT ≥ 30% or ≥ 6 mL. We analyzed the influence of APT on HV, HG, and in-hospital mortality using univariate and multivariate analyses. In addition, we used propensity score matching to assess differences in in-hospital mortality rates. From 668 screened patients, 343 had primary ICH and fulfilled all inclusion criteria. APT was present in 99 patients (29%). Baseline median HV was 16 mL (IQR 6-46). HG occurred in 44 of 160 patients with follow-up CT (28%). In-hospital mortality was 10% (n = 36). APT was associated with older age, a mRS score before admission (pre-mRS) of > 2, and presence of cardiovascular comorbidities. We did not find an association between APT and larger baseline HV (p = 0.32), or HG (OR 0.8, 95% CI 0.4-1.9). After propensity score matching for age, pre-mRS, gender, and cardiovascular comorbidities, APT was not associated with higher in-hospital mortality (OR 1.90, 95% CI 0.85-4.24, p = 0.117). This study did not show a higher risk for larger HV, HG, or in-hospital mortality in primary ICH patients with APT.

Intracerebral Hemorrhage and Outcome After Thrombolysis in Stroke Patients Using Selective Serotonin-Reuptake Inhibitors.

BACKGROUND AND PURPOSE: Selective serotonin-reuptake inhibitors (SSRIs) impair platelet function and have been linked to a higher risk of spontaneous intracerebral hemorrhage-an association that may be augmented by oral anticoagulants (OAC). We aimed to assess whether preadmission treatment with SSRIs in patients with acute ischemic stroke is associated with post-thrombolysis symptomatic intracerebral hemorrhage (sICH) and functional outcome. METHODS: A multicenter retrospective analysis was conducted in prospective registries of patients treated by thrombolysis within 4.5 hours of stroke onset. The association between preadmission treatment with SSRIs and sICH (ECASS II definition [European Cooperative Acute Stroke Study]) or unfavorable 3-month outcome (modified Rankin Scale >2) was assessed by logistic regression, taking into account potential interaction with concomitant use of antithrombotics. RESULTS: Six thousand two hundred forty-two patients were included (mean age, 70.1±14.0 years; median National Institutes of Health Stroke Scale, 9 [5-16]). Preadmission treatment with SSRIs was present in 4.3% (n=266) of patients. Overall, SICH rate was 3.9% (95% confidence interval [CI], 3.5%-4.4%; n=244), and SSRI use was not significantly associated with sICH in unadjusted (odds ratio [OR], 1.28; 95% CI, 0.72-2.27) or adjusted (OR, 1.30; 95% CI, 0.71-2.40) analysis. However, there was a significant interaction of concomitant use of OACs (international normalized ratio <1.7) and SSRI for occurrence of sICH (P=0.01). SICH was significantly more frequent in patients taking both OAC and SSRI (23.1%; 95% CI, 8.2%-50.3%) than in patients taking OAC but not SSRI (adjusted OR, 9.04; 95% CI, 1.95-41.89). Preadmission use of SSRI was associated with unfavorable 3-month outcome (unadjusted OR, 1.90; 95% CI, 1.48-2.46; adjusted OR, 1.59; 95% CI, 1.15-2.19). CONCLUSIONS: Preadmission treatment with SSRIs was not significantly associated with an increased risk of post-thrombolysis sICH in this cohort study. However, subgroup analysis suggested an increased risk of sICH in patients taking both SSRI and OAC. Preadmission treatment with SSRIs was associated with unfavorable outcome, which may reflect the prognostic significance of prestroke depression.

Spot Sign in Acute Intracerebral Hemorrhage in Dynamic T1-Weighted Magnetic Resonance Imaging.

BACKGROUND AND PURPOSE: In computed tomographic imaging of acute intracerebral hemorrhage spot sign on computed tomographic angiography has been established as a marker for hematoma expansion and poor clinical outcome. Although, magnetic resonance imaging (MRI) can accurately visualize acute intracerebral hemorrhage, a corresponding MRI marker is lacking to date. METHODS: We prospectively examined 50 consecutive patients with acute intracerebral hemorrhage within 24 hours of symptom onset. The MRI protocol consisted of a standard stroke protocol and dynamic contrast-enhanced T1-weighted imaging with a time resolution of 7.07 s/batch. Stroke scores were assessed at admission and at time of discharge. Volume measurements of hematoma size and spot sign were performed with MRIcron. RESULTS: Contrast extravasation within sites of the hemorrhage (MRI spot sign) was seen in 46% of the patients. Patients with an MRI spot sign had a significantly shorter time to imaging than those without (P<0.001). The clinical outcome measured by the modified Rankin Scale was significantly worse in patients with spot sign compared with those without (P≤0.001). Hematoma expansion was observed in the spot sign group compared with the nonspot sign group, although the differences were not significant. CONCLUSIONS: Spot sign can be detected using MRI on postcontrast T1-weighted and dynamic T1-weighted images. It is associated with worse clinical outcome. The time course of contrast extravasation in dynamic T1 images indicates that these spots represent ongoing bleeding.

Subtracted Dynamic MR Perfusion Source Images (sMRP-SI) provide Collateral Blood Flow Assessment in MCA Occlusions and Predict Tissue Fate.

OBJECTIVES: Collateral blood flow is accepted as a predictive factor of tissue fate in ischemic stroke. Thus, we aimed to evaluate a new method derived from MR perfusion source images to assess collateral flow in patients with ICA/MCA occlusions. METHODS: A total of 132 patients of the prospective 1000+ study were examined. MR perfusion source images were assessed according to Δimg_n = img_n + 1 - img_n - 1 using the five-grade Higashida collateral flow rating system. Higashida scores were correlated to mismatch (MM) volume, mismatch ratio, day 6 FLAIR lesion volumes and day 90 mRS. RESULTS: Patients with Higashida scores 3 and 4 had significantly lower admission NIHSS, smaller FLAIR day 6 lesion volumes (p < 0.001) and higher rates of better long-term outcome (mRS 0-2, p = 0.002). There was a linear trend for the association of Higashida grade 1 (p = 0.002) and 2 (p = 0.001) with unfavourable outcome (day 90 mRS 3-6), but no significant association was found for MM volume, MM ratio and day 90 mRS. Inter-rater agreement was 0.58 (95% CI 0.43-0.73) on day 1, 0.70 (95% CI 0.58-0.81) on day 2. CONCLUSION: sMRP-SI Higashida score offers a non-invasive collateral vessel and tissue perfusion assessment of ischemic tissue. The predictive value of Higashida rating proved superior to MM with regard to day 90 mRS. KEY POINTS: • Assessment of collateral flow using subtracted dynamic MR perfusion source imaging (sMRP-SI). • sMRP-SI offers additional information about morphological characteristics of ischemic brain tissue. • sMRP-SI collateral flow assessment proves superior to mismatch volume. • Better collateral flow was significantly associated with better outcome (day 90 mRS).

In-hospital stroke recurrence and stroke after transient ischemic attack: frequency and risk factors.

BACKGROUND AND PURPOSE: We aimed to assess the risk of recurrent ischemic events during hospitalization for stroke or transient ischemic attack (TIA) with optimal current management and to identify associated risk factors. METHODS: We performed a retrospective analysis of all patients treated for acute ischemic stroke or TIA in 3 stroke units between 2010 and 2013. Recurrent stroke was defined as new persisting (≥24 hours) neurological deficit occurring >24 hours after the index event and not attributable to other causes of neurological deterioration. Cox proportional hazard regression identified risk factors associated with recurrent stroke. RESULTS: The study included 5106 patients. During a median length of stay of 5 days (interquartile range, 4-8), stroke recurrence (or stroke after TIA) occurred in 40 patients (0.8%) and was independently associated with history of TIA, symptomatic carotid stenosis (≥70%), or other determined etiology. Patients with recurrent stroke and other determined etiology had cervical arterial dissection (n=2), primary angiitis of the central nervous system (n=1), giant cell arteritis (n=1), and lung cancer with nonbacterial thrombotic endocarditis (n=1). In patients with initial TIA or minor stroke (National Institutes of Health Stroke Scale ≤5) recurrence was associated additionally with pneumonia after the inciting ischemic event but before stroke recurrence. Patients with initial stroke and aphasia had a lower stroke recurrence rate and there were no recurrences in patients with lacunar stroke. Recurrence was associated with significantly higher in-hospital mortality (17.5% versus 3.1%; P<0.001). CONCLUSIONS: In-hospital stroke recurrence was low with optimal current management. Patients with a history of TIA, severe symptomatic carotid stenosis, or uncommon causes of stroke were at higher risk. Pneumonia was associated with a higher risk of stroke recurrence in patients with initial TIA or minor stroke but not in the overall population studied. Aphasia may bias the detection rate by concealing new neurological symptoms.

Follow-up C-reactive protein level is more strongly associated with outcome in stroke patients than admission levels.

The value of C-reactive protein (CRP) as a prognostic tool in stroke patients is unclear. The aim of this study is to explore the prognostic impact of CRP levels assessed at different time points on functional outcome in a large cohort of thrombolysed acute stroke patients. All thrombolysed stroke patients admitted to our department were entered in an open, prospective database. Clinical and demographic data were recorded. CRP was measured upon admission, within 24 h, and in the following days. Functional outcome was assessed using the modified Rankin Scale (mRS) at 3 months. Among 1242 thrombolysed patients, we found a statistically significant difference in median CRP values upon admission, within 24 h, and follow-up with respect to outcome parameters (p < 0.001) including symptomatic intracerebral hemorrhage (sICH; p < 0.001). In regression models, follow-up CRP showed better predictive properties for outcome parameters compared to CRP assessed upon admission or within 24 h. The ROC analysis showed a good predictive value of follow-up CRP concerning dependent outcome [c-statistic 0.71 (95 % CI 0.67-0.75) p < 0.001] and mortality [c-statistic 0.70 (95 % CI 0.66-0.75) p < 0.001]. After adjustment for risk factors, follow-up CRP, but not admission CRP, was independently associated with dependent outcome (OR 2.67, 95 % CI 1.76-4.06; p < 0.001), mortality (OR 2.53, 95 % CI 1.50-4.25; p < 0.001), and sICH (OR 3.03, 95 % CI 1.51-6.06; p = 0.002). Follow-up CRP is strongly associated with functional outcome, sICH, and mortality after 90 days in thrombolysed stroke patients.

Serotonergic correlation with anger and aggressive behavior in acute stroke patients: an intensity dependence of auditory evoked potentials (IDAP) study.

Anger and aggressive behavior (AB) are two of the main post-stroke behavioral manifestations, which could imply both an anger trait (TA) or a state condition of anger (SA). Serotonergic system is thought to play an inhibitory control on aggressive impulse. Nevertheless, whether 5HT has the same role in TA and in SA, is still debated. Intensity dependence of auditory evoked potentials (IDAP) is thought to be inversely related to the central 5HT tone. The aim of this study was to evaluate, in acute stroke patients, the 5HT system involvement in AB by IDAP. Consecutive stroke patients were evaluated and compared with healthy controls. The Spielberger Trait Anger Scale (STAS) was used to assess AB, SA and TA. Patients with AB and TA showed a significantly increased IDAP value, whereas patients with SA had a significantly lower IDAP; this indicates an increased 5HT tone. In acute stroke patients with AB, there is a decreased central 5HT tone. Surprisingly, we found an opposite 5HT feature between patients with TA and those showing SA, suggesting that the hypothesis of aggression based on 5HT deficiency requires further investigations. This might open new strategies in the treatment of post-stroke AB.

An iterative genetic and dynamical modelling approach identifies novel features of the gene regulatory network underlying melanocyte development.

The mechanisms generating stably differentiated cell-types from multipotent precursors are key to understanding normal development and have implications for treatment of cancer and the therapeutic use of stem cells. Pigment cells are a major derivative of neural crest stem cells and a key model cell-type for our understanding of the genetics of cell differentiation. Several factors driving melanocyte fate specification have been identified, including the transcription factor and master regulator of melanocyte development, Mitf, and Wnt signalling and the multipotency and fate specification factor, Sox10, which drive mitf expression. While these factors together drive multipotent neural crest cells to become specified melanoblasts, the mechanisms stabilising melanocyte differentiation remain unclear. Furthermore, there is controversy over whether Sox10 has an ongoing role in melanocyte differentiation. Here we use zebrafish to explore in vivo the gene regulatory network (GRN) underlying melanocyte specification and differentiation. We use an iterative process of mathematical modelling and experimental observation to explore methodically the core melanocyte GRN we have defined. We show that Sox10 is not required for ongoing differentiation and expression is downregulated in differentiating cells, in response to Mitfa and Hdac1. Unexpectedly, we find that Sox10 represses Mitf-dependent expression of melanocyte differentiation genes. Our systems biology approach allowed us to predict two novel features of the melanocyte GRN, which we then validate experimentally. Specifically, we show that maintenance of mitfa expression is Mitfa-dependent, and identify Sox9b as providing an Mitfa-independent input to melanocyte differentiation. Our data supports our previous suggestion that Sox10 only functions transiently in regulation of mitfa and cannot be responsible for long-term maintenance of mitfa expression; indeed, Sox10 is likely to slow melanocyte differentiation in the zebrafish embryo. More generally, this novel approach to understanding melanocyte differentiation provides a basis for systematic modelling of differentiation in this and other cell-types.

Brain death determination in patients with veno-arterial extracorporeal membrane oxygenation: A systematic study to address the Harlequin syndrome.

PURPOSE: The Harlequin syndrome may occur in patients treated with venoarterial extracorporal membrane oxygenation (VA-ECMO), in whom blood from the left ventricle and the ECMO system supply different parts of the body with different paCO2-levels. The purpose of this study was to compare two variants of paCO2-analysis to account for the Harlequin syndrome during apnea testing (AT) in brain death (BD) determination. MATERIALS AND METHODS: Twenty-seven patients (median age 48 years, 26-76 years; male n = 19) with VA-ECMO treatment were included who underwent BD determination. In variant 1, simultaneous arterial blood gas (ABG) samples were drawn from the right and the left radial artery. In variant 2, simultaneous ABG samples were drawn from the right radial artery and the postoxygenator ECMO circuit. Differences in paCO2-levels were analysed for both variants. RESULTS: At the start of AT, median paCO2-difference between right and left radial artery (variant 1) was 0.90 mmHg (95%-confidence intervall [CI]: 0.7-1.3 mmHg). Median paCO2-difference between right radial artery and postoxygenator ECMO circuit (variant 2) was 3.3 mmHg (95%-CI: 1.5-6.0 mmHg) and thereby significantly higher compared to variant 1 (p = 0.001). At the end of AT, paCO2-difference according to variant 1 remained unchanged with 1.1 mmHg (95%-CI: 0.9-1.8 mmHg). In contrast, paCO2-difference according to variant 2 increased to 9.9 mmHg (95%-CI: 3.5-19.2 mmHg; p = 0.002). CONCLUSIONS: Simultaneous paCO2-analysis from right and left distal arterial lines is the method of choice to reduce the risk of adverse effects (e.g. severe respiratory acidosis) while performing AT in VA-ECMO patients during BD determination.

Severe renal impairment is associated with symptomatic intracerebral hemorrhage after thrombolysis for ischemic stroke.

BACKGROUND AND PURPOSE: Patients with renal impairment (RI) have an increased risk of both thrombotic and hemorrhagic events. We aimed to clarify whether RI increases the risk of intracerebral hemorrhage (ICH) after intravenous thrombolysis with recombinant tissue plasminogen activator. METHODS: Patients who received intravenous thrombolysis with recombinant tissue plasminogen activator within 4.5 hours of symptom onset were retrospectively analyzed. Creatinine levels on admission served to calculate glomerular filtration rate (GFR) to estimate RI according to International Classification of Diseases criteria. Effect of RI on symptomatic ICH (sICH) was assessed using dichotomized (GFR <90 and <30 mL/min) and continuous GFR (centered data to test for linear and centered and squared data to test for curvilinear association). RESULTS: Of the 740 patients included, 83% had any RI (GFR <90 mL/min) and 5% had severe RI (GFR <30 mL/mL); 4.6% experienced sICH. Univariate comparisons revealed higher prevalence of sICH in patients with severe RI (P<0.01) but not with any RI. GFR as a continuous variable (centered and squared) was also associated with sICH (P=0.02), but GFR on its own was not. Severe RI and GFR (centered and squared) remained independently associated with sICH in multiple regression analyses. CONCLUSIONS: Severe RI (GFR <30 mL/min) is associated with sICH after intravenous thrombolysis with recombinant tissue plasminogen activator. The association is curvilinear. Severe RI must be taken into account when balancing the risk-benefit ratio of intravenous thrombolysis with recombinant tissue plasminogen activator.

Glycosylated hemoglobin A1 predicts risk for symptomatic hemorrhage after thrombolysis for acute stroke.

BACKGROUND AND PURPOSE: Symptomatic intracerebral hemorrhage (sICH) is the most feared acute complication after intravenous thrombolysis. The aim of this study was to determine the predictive value of parameters of glycosylated hemoglobin A1 (HbA1c) on sICH. METHODS: In a retrospective single center series, 1112 consecutive patients treated with thrombolysis were studied. Baseline blood glucose was obtained at admission. HbA1c was determined within hospital stay. A second head computed tomography was obtained after 24 hours or when neurological worsening occurred. Modified Rankin Scale was used to assess outcome at 90 days. RESULTS: A total of 222 patients (19.9%) had any hemorrhage; 43 of those had sICH (3.9%) per Safe Implementation of Treatments in Stroke definition and 95 (8.5%) per National Institute of Neurological Disorders and Stroke definition; 33.2% of patients had a dependent outcome (modified Rankin Scale score 3-5). In univariate analysis history of diabetes mellitus, HbA1c, blood glucose, and National Institute of Health Stroke Scale score on admission were associated with any hemorrhage and sICH. In multivariate analysis National Institute of Health Stroke Scale score, a history of diabetes mellitus, and HbA1c were predictors of sICH per National Institute of Neurological Disorders and Stroke, and only HbA1c when Safe Implementation of Treatments in Stroke criteria were used. CONCLUSIONS: In our study, HbA1c turns out to be an important predictor of sICH after thrombolysis for acute stroke. These results suggest that hemorrhage after thrombolysis may be a consequence of long-term vascular injury rather than of acute hyperglycemia, and that HbA1c may be a better predictor than acute blood glucose or a history of diabetes mellitus.

Noise-induced transitions in gene circuits: A perturbative approach for slow noise.

We consider a generic class of gene circuits affected by nonlinear extrinsic noise. To address this nonlinearity we introduce a general perturbative methodology based on assuming timescale separation between noise and gene dynamics, with fluctuations exhibiting a large but finite correlation time. We apply this methodology to the case of the toggle switch, and by considering biologically relevant log-normal fluctuations, we find that the system exhibits noise-induced transitions. The system becomes bimodal in regions of the parameter space where it would be deterministically monostable. We show that by including higher order corrections our methodology allows one to obtain correct predictions for the occurrence of transitions even for not so large correlation time of the fluctuations, thereby overcoming limitations of previous theoretical approaches. Interestingly we find that at intermediate noise intensities the noise-induced transition in the toggle switch affects one of the genes involved, but not the other one.

Zebrafish pigment cells develop directly from persistent highly multipotent progenitors.

Neural crest cells are highly multipotent stem cells, but it remains unclear how their fate restriction to specific fates occurs. The direct fate restriction model hypothesises that migrating cells maintain full multipotency, whilst progressive fate restriction envisages fully multipotent cells transitioning to partially-restricted intermediates before committing to individual fates. Using zebrafish pigment cell development as a model, we show applying NanoString hybridization single cell transcriptional profiling and RNAscope in situ hybridization that neural crest cells retain broad multipotency throughout migration and even in post-migratory cells in vivo, with no evidence for partially-restricted intermediates. We find that leukocyte tyrosine kinase early expression marks a multipotent stage, with signalling driving iridophore differentiation through repression of fate-specific transcription factors for other fates. We reconcile the direct and progressive fate restriction models by proposing that pigment cell development occurs directly, but dynamically, from a highly multipotent state, consistent with our recently-proposed Cyclical Fate Restriction model.

Baroreflex sensitivity to predict malignant middle cerebral artery infarction.

BACKGROUND AND PURPOSE: Hemicraniectomy has been shown to be an effective treatment of life-threatening edema (LTE) in malignant middle cerebral artery infarction when performed early. Identifying patients who will develop LTE is therefore imperative. We hypothesize that autonomic shift toward sympathetic dominance may relate to LTE formation. We aimed to investigate the predictive potential of baroreflex sensitivity (BRS) as a marker of autonomic balance for calculating the course of large middle cerebral artery infarction. METHODS: Patients with middle cerebral artery infarction >2/3 of the territory and BRS measurement at admission were analyzed. BRS was estimated using the cross-correlational method. Demographic, clinical, and radiological data including stroke severity, infarct size, and basal ganglia involvement were recorded. Malignant course with LTE was defined as clinical deterioration and midline shift ≥5 mm in the first 48 hours. RESULTS: Eighteen (62.8%) patients developed LTE. Patients with LTE had lower BRS (2.3 versus 4.4 mm Hg/ms, P=0.007), larger infarcts (214 versus 144 mL, P=0.03), more frequent involvement of the basal ganglia (14 versus 4, P=0.03), and more often underwent thrombolysis combined with endovascular intervention (6 versus 0, P=0.04). In a multivariate model, BRS (OR, 0.36; CI, 0.14-0.93; P=0.03) and basal ganglia involvement (OR, 11.53; CI, 1.15-115.9; P=0.04) were independent predictors for LTE. This model correctly classified 86.2% of the malignant cases. CONCLUSIONS: Decreased BRS, mirroring sympathetic activation, and basal ganglia involvement were associated with development of malignant course with LTE in large middle cerebral artery infarction. The predictive relevance of our findings needs to be confirmed in further studies.