Myocardial Damage, Inflammation, Coagulation, and Platelet Activity During Catheter Ablation Using Radiofrequency and Pulsed-Field Energy.

BACKGROUND: Pulsed-field ablation (PFA) represents a new, nonthermal ablation energy for the ablation of atrial fibrillation (AF). Ablation energies producing thermal injury are associated with an inflammatory response, platelet activation, and coagulation activation. OBJECTIVES: This study aimed to compare the systemic response in patients undergoing pulmonary vein isolation (PVI) using pulsed-field and radiofrequency (RF) energy. METHODS: Patients with AF indicated for PVI were enrolled and randomly assigned to undergo PVI using RF (CARTO Smart Touch, Biosense Webster) or pulsed-field (Farapulse, Boston-Scientific) energy. Markers of myocardial damage (troponin I), inflammation (interleukin-6), coagulation (D-dimers, fibrin monomers, von Willebrand antigen and factor activity), and platelet activation (P-selectin, activated GpIIb/IIIa antigen) were measured before the procedure (T1), after trans-septal puncture (T2), after completing the ablation in the left atrium (T3), and 1 day after the procedure (T4). RESULTS: A total of 65 patients were enrolled in the pulsed-field ablation (n = 33) and RF ablation (n = 32) groups. Both groups were similar in baseline characteristics (age 60.5 ± 12.7 years vs 64.0 ± 10.7 years; paroxysmal AF: 60.6% vs 62.5% patients). Procedural and left atrial dwelling times were substantially shorter in the PFA group (55:09 ± 11:57 min vs 151:19 ± 41:25 min; P < 0.001; 36:00 ± 8:05 min vs 115:58 ± 36:49 min; P < 0.001). Peak troponin release was substantially higher in the PFA group (10,102 ng/L [IQR: 8,272-14,207 ng/L] vs 1,006 ng/L [IQR: 603-1,433ng/L]). Both procedures were associated with similar extents (>50%) of platelet and coagulation activation. The proinflammatory response 24 h after the procedure was slightly but nonsignificantly higher in the RF group. CONCLUSIONS: Despite 10 times more myocardial damage, pulsed-field ablation was associated with a similar degree of platelet/coagulation activation, and slightly lower inflammatory response. (The Effect of Pulsed-Field and Radiofrequency Ablation on Platelet, Coagulation and Inflammation; NCT05603637).

Analysis of Virus-Derived siRNAs in Strawberry Plants Co-Infected with Multiple Viruses and Their Genotypes.

Plants can be infected with multiple viruses. High-throughput sequencing tools have enabled numerous discoveries of multi-strain infections, when more than one viral strain or divergent genomic variant infects a single plant. Here, we investigated small interfering RNAs (siRNAs) in a single strawberry plant co-infected with several strains of strawberry mottle virus (SMoV), strawberry crinkle virus (SCV) and strawberry virus 1 (StrV-1). A range of plants infected with subsets of the initial viral species and strains that were obtained by aphid-mediated transmission were also evaluated. Using high-throughput sequencing, we characterized the small RNA fractions associated with different genotypes of these three viruses and determined small RNA hotspot regions in viral genomes. A comparison of virus-specific siRNA (vsiRNA) abundance with relative viral concentrations did not reveal any consistent agreement. Strawberry mottle virus strains exhibiting considerable variations in concentrations were found to be associated with comparable quantities of vsiRNAs. Additionally, by estimating the specificity of siRNAs to different viral strains, we observed that a substantial pool of vsiRNAs could target all SMoV strains, while strain-specific vsiRNAs predominantly targeted rhabdoviruses, SCV and StrV-1. This highlights the intricate nature and potential interference of the antiviral response within a single infected plant when multiple viruses are present.

Prediction of post-operative atrial fibrillation in patients after cardiac surgery using heart rate variability.

PURPOSE: Post-operative atrial fibrillation (PoAF) occurs in ~ 30% of patients after cardiac surgery. The etiology of PoAF is complex, but a disbalance in autonomic systems plays an important role. The goal of this study was to assess whether pre-operative heart rate variability analysis can predict the risk of PoAF. METHODS: Patients without a history of AF with an indication for cardiac surgery were included. Two-hour ECG recordings one day before surgery was used for the HRV analysis. Univariate and multivariate logistic regression, including all HRV parameters, their combination, and clinical variables, were calculated to find the best predictive model for post-operative AF. RESULTS: One hundred and thirty-seven patients (33 women) were enrolled in the study. PoAF occurred in 48 patients (35%, AF group); the remaining 89 patients were in the NoAF group. AF patients were significantly older (69.1 ± 8.6 vs. 63.4 ± 10.5 yrs., p = 0.002), and had higher CHA2DS2-VASc score (3 ± 1.4 vs. 2.5 ± 1.3, p = 0.01). In the multivariate regression model, parameters independently associated with higher risk of AF were pNN50, TINN, absolute power VLF, LF and HF, total power, SD2, and the Porta index. A combination of clinical variables with HRV parameters in the ROC analysis achieved an AUC of 0.86, a sensitivity of 0.95, and a specificity of 0.57 and was more effective in PoAF prediction than a combination of clinical variables alone. CONCLUSION: A combination of several HRV parameters is helpful in predicting the risk of PoAF. Attenuation of heart rate variability increases the risk for PoAF.

Left bundle branch area pacing results in more physiological ventricular activation than biventricular pacing in patients with left bundle branch block heart failure.

Biventricular pacing (Biv) and left bundle branch area pacing (LBBAP) are methods of cardiac resynchronization therapy (CRT). Currently, little is known about how they differ in terms of ventricular activation. This study compared ventricular activation patterns in left bundle branch block (LBBB) heart failure patients using an ultra-high-frequency electrocardiography (UHF-ECG). This was a retrospective analysis including 80 CRT patients from two centres. UHF-ECG data were obtained during LBBB, LBBAP, and Biv. Left bundle branch area pacing patients were divided into non-selective left bundle branch pacing (NSLBBP) or left ventricular septal pacing (LVSP) and into groups with V6 R-wave peak times (V6RWPT) < 90 ms and ≥ 90 ms. Calculated parameters were: e-DYS (time difference between the first and last activation in V1-V8 leads) and Vdmean (average of V1-V8 local depolarization durations). In LBBB patients (n = 80) indicated for CRT, spontaneous rhythms were compared with Biv (39) and LBBAP rhythms (64). Although both Biv and LBBAP significantly reduced QRS duration (QRSd) compared with LBBB (from 172 to 148 and 152 ms, respectively, both P < 0.001), the difference between them was not significant (P = 0.2). Left bundle branch area pacing led to shorter e-DYS (24 ms) than Biv (33 ms; P = 0.008) and shorter Vdmean (53 vs. 59 ms; P = 0.003). No differences in QRSd, e-DYS, or Vdmean were found between NSLBBP, LVSP, and LBBAP with paced V6RWPTs < 90 and ≥ 90 ms. Both Biv CRT and LBBAP significantly reduce ventricular dyssynchrony in CRT patients with LBBB. Left bundle branch area pacing is associated with more physiological ventricular activation.

A randomized comparison of HBP versus RVP: Effect on left ventricular function and biomarkers of collagen metabolism.

BACKGROUND: Right ventricular pacing (RVP) can result in pacing-induced cardiomyopathy (PICM). It is unknown whether specific biomarkers reflect differences between His bundle pacing (HBP) and RVP and predict a decrease in left ventricular function during RVP. AIMS: We aimed to compare the effect of HBP and RVP on the left ventricular ejection fraction (LVEF) and to study how they affect serum markers of collagen metabolism. METHODS: Ninety-two high-risk PICM patients were randomized to HBP or RVP groups. Their clinical characteristics, echocardiography, and serum levels of transforming growth factor ß1 (TGF-ß1), matrix metalloproteinase 9 (MMP-9), suppression of tumorigenicity 2 interleukin (ST2-IL), tissue inhibitor of metalloproteinase 1 (TIMP-1), and galectin 3 (Gal-3) were studied before pacemaker implantation and six months later. RESULTS: Fifty-three patients were randomized to the HBP group and 39 patients to the RVP group. HBP failed in 10 patients, who crossed over to the RVP group. Patients with RVP had significantly lower LVEF compared to HBP patients after six months of pacing (-5% and -4% in as-treated and intention-to-treat analysis, respectively). Levels of TGF-ß1 after 6 months were lower in HBP than RVP patients (mean difference -6 ng/ml; P = 0.009) and preimplant Gal-3 and ST2-IL levels were higher in RVP patients, with a decline in LVEF ≥5% compared to those with a decline of <5% (mean difference 3 ng/ml and 8 ng/ml; P = 0.02 for both groups). CONCLUSION: In high-risk PICM patients, HBP was superior to RVP in providing more physiological ventricular function, as reflected by higher LVEF and lower levels of TGF-ß1. In RVP patients, LVEF declined more in those with higher baseline Gal-3 and ST2-IL levels than in those with lower levels.

Transmission of Diverse Variants of Strawberry Viruses Is Governed by a Vector Species.

Advances in high-throughput sequencing methods have boosted the discovery of multistrain viral infections in diverse plant systems. This phenomenon appears to be pervasive for certain viral species. However, our knowledge of the transmission aspects leading to the establishment of such mixed infections is limited. Recently, we reported a mixed infection of a single strawberry plant with strawberry mottle virus (SMoV), strawberry crinkle virus (SCV) and strawberry virus 1 (StrV-1). While SCV and StrV-1 are represented by two and three molecular variants, respectively, SmoV has three different RNA1 and RNA2 segments. In this study, we focus on virus acquisition by individual adult aphids of the Aphis gossypii, Aphis forbesi and Chaetosiphon fragaefolii species. Single-aphid transmission trials are performed under experimental conditions. Both different viruses and individual virus strains show varying performances in single aphid acquisition. The obtained data suggests that numerous individual transmission events lead to the establishment of multistrain infections. These data will be important for the development of epidemiological models in plant virology.

Beyond Self-Resistance: ABCF ATPase LmrC Is a Signal-Transducing Component of an Antibiotic-Driven Signaling Cascade Accelerating the Onset of Lincomycin Biosynthesis.

In natural environments, antibiotics are important means of interspecies competition. At subinhibitory concentrations, they act as cues or signals inducing antibiotic production; however, our knowledge of well-documented antibiotic-based sensing systems is limited. Here, for the soil actinobacterium Streptomyces lincolnensis, we describe a fundamentally new ribosome-mediated signaling cascade that accelerates the onset of lincomycin production in response to an external ribosome-targeting antibiotic to synchronize antibiotic production within the population. The entire cascade is encoded in the lincomycin biosynthetic gene cluster (BGC) and consists of three lincomycin resistance proteins in addition to the transcriptional regulator LmbU: a lincomycin transporter (LmrA), a 23S rRNA methyltransferase (LmrB), both of which confer high resistance, and an ATP-binding cassette family F (ABCF) ATPase, LmrC, which confers only moderate resistance but is essential for antibiotic-induced signal transduction. Specifically, antibiotic sensing occurs via ribosome-mediated attenuation, which activates LmrC production in response to lincosamide, streptogramin A, or pleuromutilin antibiotics. Then, ATPase activity of the ribosome-associated LmrC triggers the transcription of lmbU and consequently the expression of lincomycin BGC. Finally, the production of LmrC is downregulated by LmrA and LmrB, which reduces the amount of ribosome-bound antibiotic and thus fine-tunes the cascade. We propose that analogous ABCF-mediated signaling systems are relatively common because many ribosome-targeting antibiotic BGCs encode an ABCF protein accompanied by additional resistance protein(s) and transcriptional regulators. Moreover, we revealed that three of the eight coproduced ABCF proteins of S. lincolnensis are clindamycin responsive, suggesting that the ABCF-mediated antibiotic signaling may be a widely utilized tool for chemical communication. IMPORTANCE Resistance proteins are perceived as mechanisms protecting bacteria from the inhibitory effect of their produced antibiotics or antibiotics from competitors. Here, we report that antibiotic resistance proteins regulate lincomycin biosynthesis in response to subinhibitory concentrations of antibiotics. In particular, we show the dual character of the ABCF ATPase LmrC, which confers antibiotic resistance and simultaneously transduces a signal from ribosome-bound antibiotics to gene expression, where the 5' untranslated sequence upstream of its encoding gene functions as a primary antibiotic sensor. ABCF-mediated antibiotic signaling can in principle function not only in the induction of antibiotic biosynthesis but also in selective gene expression in response to any small molecules targeting the 50S ribosomal subunit, including clinically important antibiotics, to mediate intercellular antibiotic signaling and stress response induction. Moreover, the resistance-regulatory function of LmrC presented here for the first time unifies functionally inconsistent ABCF family members involving antibiotic resistance proteins and translational regulators.

The Efficacy and Safety of Hybrid Ablations for Atrial Fibrillation.

OBJECTIVES: This study sought to comprehensively determine the procedural safety and midterm efficacy of hybrid ablations. BACKGROUND: Hybrid ablation of atrial fibrillation (AF) (thoracoscopic ablation followed by catheter ablation) has been used for patients with nonparoxysmal AF; however, accurate data regarding efficacy and safety are still limited. METHODS: Patients with nonparoxysmal AF underwent thoracoscopic, off-pump ablation using the COBRA Fusion radiofrequency system (Estech) followed by a catheter ablation 3 months afterward. The safety of the procedure was assessed using sequential brain magnetic resonance and neuropsychological examinations at baseline (1 day before), postoperatively (2-4 days for brain magnetic resonance imaging or 1 month for neuropsychological examination), and at 9 months after the surgical procedure. Implantable loop recorders were used to detect arrhythmia recurrence. Arrhythmia-free survival (the primary efficacy endpoint) was defined as no episodes of AF or atrial tachycardia while off antiarrhythmic drugs, redo ablations or cardioversions. RESULTS: Fifty-nine patients (age: 62.5 ± 10.5 years) were enrolled, 37 (62.7%) were men, and the mean follow-up was 30.3 ± 10.8 months. Thoracoscopic ablation was successfully performed in 55 (93.2%) patients. On baseline magnetic resonance imaging, chronic ischemic brain lesions were present in 60.0% of patients. New ischemic lesions on postoperative magnetic resonance imaging were present in 44.4%. Major postoperative cognitive dysfunction was present in 27.0% and 17.6% at 1 and 9 months postoperatively, respectively. The probability of arrhythmia-free survival was 54.0% (95% CI: 41.3-66.8) at 1 year and 43.8% (95% CI: 30.7-57.0) at 2 years. CONCLUSIONS: The thoracoscopic ablation is associated with a high risk of silent cerebral ischemia. The midterm efficacy of hybrid ablations is moderate.

Nonselective versus selective His bundle pacing: An acute intrapatient speckle-tracking strain echocardiographic study.

INTRODUCTION: We aimed to compare the acute differences in left ventricular (LV) function and mechanical synchrony during nonselective His bundle pacing (ns-HBP) versus selective His bundle pacing (s-HBP) using strain echocardiography. METHODS AND RESULTS: Consecutive patients with permanent His bundle pacing, in whom it was possible to obtain both s-HBP and ns-HBP, were studied in two centers. In each patient, echocardiography was performed sequentially during s-HBP and ns-HBP. Speckle-tracking echocardiography parameters were analyzed: Global longitudinal strain (GLS), the time delay between peak systolic strain in the basal septal and basal lateral segments (BS-BL delay), peak strain dispersion (PSD) and strain delay index. Right ventricle function was assessed using tricuspid annular plane systolic excursion (TAPSE) and tissue Doppler velocity of the lateral tricuspid annulus (S'). A total of 69 patients (age: 75.6 ± 10.5 years; males: 75%) were enrolled. There were no differences in LV ejection fraction and GLS between s-HBP and ns-HBP modes: 59% versus 60%, and -15.6% versus -15.7%, respectively; as well as no difference in BS-BL delay and strain delay index. The PSD value was higher in the ns-HBP group than in the s-HBP group with the most pronounced difference in the basal LV segments. No differences in right ventricular function parameters (TAPSE and S') were found. CONCLUSION: The ns-HBP and s-HBP modes seem comparable regarding ventricular function. The dyssynchrony parameters were significantly higher during ns-HBP, however, the difference seems modest and clarification of its impact on LV function requires a larger long-term study.

Ribosome-Mediated Attenuation of vga(A) Expression Is Shaped by the Antibiotic Resistance Specificity of Vga(A) Protein Variants.

Vga(A) protein variants confer different levels of resistance to lincosamides, streptogramin A, and pleuromutilins (LSAP) by displacing antibiotics from the ribosome. Here, we show that expression of vga(A) variants from Staphylococcus haemolyticus is regulated by cis-regulatory RNA in response to the LSAP antibiotics by the mechanism of ribosome-mediated attenuation. The specificity of induction depends on Vga(A)-mediated resistance rather than on the sequence of the riboregulator. Fine tuning between Vga(A) activity and its expression in response to the antibiotics may contribute to the selection of more potent Vga(A) variants because newly acquired mutation can be immediately phenotypically manifested.

Can QRS morphology be used to differentiate between true septal vs. apparently septal lead placement? An analysis of ECG of real mid-septal, apparent mid-septal, and apical pacing.

The location of the pacemaker lead is based on the shape of the lead on fluoroscopy only, typically in the left and right anterior oblique positions. However, these fluoroscopy criteria are insufficient and many leads apparently considered to be in septum are in fact anchored in anterior wall. Periprocedural ECG could determine the correct lead location. The aim of the current analysis is to characterize ECG criteria associated with a correct position of the right ventricular (RV) lead in the mid-septum. Patients with indications for a pacemaker had the RV lead implanted in the apex (Group A) or mid-septum using the standard fluoroscopic criteria. The exact position of the RV lead was verified using computed tomography. Based on the findings, the mid-septal group was divided into two subgroups: (i) true septum, i.e. lead was found in the mid-septum, and (ii) false septum, i.e. lead was in the adjacent areas (anterior wall, anteroseptal groove). Paced ECGs were acquired from all patients and multiple criteria were analysed. Paced ECGs from 106 patients were analysed (27 in A, 36 in true septum, and 43 in false septum group). Group A had a significantly wider QRS, more left-deviated axis and later transition zone compared with the true septum and false septum groups. There were no differences in presence of q in lead I, or notching in inferior or lateral leads between the three groups. QRS patterns of true septum and false septum groups were similar with only one exception of the transition zone. In the multivariate model, the only ECG parameters associated with correct lead placement in the septum was an earlier transition zone (odds ratio (OR) 2.53, P = 0.001). ECGs can be easily used to differentiate apical pacing from septal or septum-close pacing. The only ECG characteristic that could help to identify true septum lead position was the transition zone in the precordial leads. ClinicalTrials.gov identifier: NCT02412176.

Improvement in the quality of life of patients with persistent or long-standing persistent atrial fibrillation after hybrid ablation.

BACKGROUND: Hybrid ablation (i.e., a combination of a thoracoscopic surgical ablation followed by a catheter ablation) is a treatment option for patients with non-paroxysmal atrial fibrillation (AF). Despite its promising efficacy, it is a surgical procedure with a relatively high risk of complications that could affect the quality of life (QoL) of patients, even when sinus rhythm is restored. OBJECTIVE: To describe changes in the QoL of patients with non-paroxysmal AF before and after a hybrid ablation. METHODS: Patients after hybrid ablation for persistent or long-standing persistent AF were prospectively studied. Follow-up visits were scheduled at 1, 3, 6, 9, and 12 months. The maintenance of SR was assessed using 1-week Holter recordings at 6 and 12 months and 24-h Holter recordings at 3 and 9 months, or via an implantable loop recorder. QoL was assessed using the Atrial Fibrillation Effect on Quality-of-life (AFEQT) and the EuroQoL-5Dimensions (EQ-5D) questionnaires before and 12 months after ablation. RESULTS: Seventy-five patients (49 men, age 62.9 ± 8.45 years, 48 (64%) with long-standing persistent AF) were enrolled. Fifty-two (69.3%, SR group) were AF-free during the 12-month follow-up, 16 (21.3%, PAROX group) had only paroxysms of AF after ablation, and 7 (9.3%, PERM group) were on rate control due to permanent AF reoccurrence. The AFEQT score increased significantly in the SR group from 59.9 ± 19.4 to 91.4 ± 10.8 (p < 0.001), and in the PAROX group from 58.8 ± 19.0 to 81.5 ± 14.1 (p = 0.002) but remained unchanged in the PERM group (44.6 ± 7.5 vs. 47.4 ± 5.5, p = 0.24). The EQ-5D score significantly decreased in the descriptive part (from 7.90 ± 2.61 to 6.64 ± 1.90, p = 0.0001) and increased on the visual analog scale (from 63.56 ± 19.11 to 79.30 ± 16.9, p < 0.0001) in the SR group. In the PAROX group, no significant change was present on either the descriptive part (p = 0.3) or in the visual analog scale (p = 0.48). Similarly, no significant changes were present on either the descriptive part (p = 0.93) or the visual analog scale (p = 0.4) in the PERM group. CONCLUSION: The QoL of patients with non-paroxysmal AF and patients with AF paroxysms, after successful hybrid ablation, improved significantly in patients with SR. No significant improvement was present in patients on rate control after an unsuccessful ablation.

Both selective and nonselective His bundle, but not myocardial, pacing preserve ventricular electrical synchrony assessed by ultra-high-frequency ECG.

BACKGROUND: Right ventricular myocardial pacing leads to nonphysiological activation of heart ventricles. Contrary to this, His bundle pacing preserves their fast activation. Ultra-high-frequency electrocardiography (UHF-ECG) is a novel tool for ventricular depolarization assessment. OBJECTIVE: The purpose of this study was to describe UHF-ECG depolarization patterns during myocardial and His bundle pacing. METHODS: Forty-six patients undergoing His bundle pacing to treat bradycardia and spontaneous QRS complexes without bundle branch block were included. UHF-ECG recordings were performed during spontaneous rhythm, pure myocardial para-Hisian capture, and His bundle capture. QRS duration, QRS area, depolarization time in specific leads, and the UHF-ECG-derived ventricular dyssynchrony index were calculated. RESULTS: One hundred thirty-three UHF-ECG recordings were performed in 46 patients (44 spontaneous rhythm, 28 selective His bundle, 43 nonselective His bundle, and 18 myocardial capture). The mean QRS duration was 117 ms for spontaneous rhythm, 118 ms for selective, 135 ms for nonselective, and 166 ms for myocardial capture (P < .001 for nonselective and myocardial capture compared to each of the other types of ventricular activation). The calculated dyssynchrony index was shortest during spontaneous rhythm (12 ms; P = .02 compared to selective and P = .09 compared to nonselective), and it did not differ between selective and nonselective His bundle capture (16 vs 15 ms; P > .99) and was longest during myocardial capture of the para-Hisian area (37 ms; P < .001 compared to each of the other types of ventricular activation). CONCLUSION: In patients without bundle branch block, both types of His bundle, but not myocardial, capture preserve ventricular electrical synchrony as measured using UHF-ECG.

Novel ultra-high-frequency electrocardiogram tool for the description of the ventricular depolarization pattern before and during cardiac resynchronization.

INTRODUCTION: The present study introduces a new ultra-high-frequency 14-lead electrocardiogram technique (UHF-ECG) for mapping ventricular depolarization patterns and calculation of novel dyssynchrony parameters that may improve the selection of patients and application of cardiac resynchronization therapy (CRT). METHODS: Components of the ECG in sixteen frequency bands within the 150 to 1000 Hz range were used to create ventricular depolarization maps. The maximum time difference between the UHF QRS complex centers of mass of leads V1 to V8 was defined as ventricular electrical dyssynchrony (e-DYS), and the duration at 50% of peak voltage amplitude in each lead was defined as the duration of local depolarization (Vd). Proof of principle measurements was performed in seven patients with left (left bundle branch block) and four patients with right bundle branch block (right bundle branch block) before and during CRT using biventricular and His-bundle pacing. RESULTS: The acquired activation maps reflect the activation sequence under the tested conditions. e-DYS decreased considerably more than QRS duration, during both biventricular pacing (-50% vs -8%) and His-bundle pacing (-77% vs -13%). While biventricular pacing slightly increased Vd, His-bundle pacing reduced Vd significantly (+11% vs -36%), indicating the contribution of the fast conduction system. Optimization of biventricular pacing by adjusting VV-interval showed a decrease of e-DYS from 102 to 36 ms with only a small Vd increase and QRS duration decrease. CONCLUSIONS: The UHF-ECG technique provides novel information about electrical activation of the ventricles from a standard ECG electrode setup, potentially improving the selection of patients for CRT and application of CRT.

Drosophila TNF Modulates Tissue Tension in the Embryo to Facilitate Macrophage Invasive Migration.

Migrating cells penetrate tissue barriers during development, inflammatory responses, and tumor metastasis. We study if migration in vivo in such three-dimensionally confined environments requires changes in the mechanical properties of the surrounding cells using embryonic Drosophila melanogaster hemocytes, also called macrophages, as a model. We find that macrophage invasion into the germband through transient separation of the apposing ectoderm and mesoderm requires cell deformations and reductions in apical tension in the ectoderm. Interestingly, the genetic pathway governing these mechanical shifts acts downstream of the only known tumor necrosis factor superfamily member in Drosophila, Eiger, and its receptor, Grindelwald. Eiger-Grindelwald signaling reduces levels of active Myosin in the germband ectodermal cortex through the localization of a Crumbs complex component, Patj (Pals-1-associated tight junction protein). We therefore elucidate a distinct molecular pathway that controls tissue tension and demonstrate the importance of such regulation for invasive migration in vivo.

Leptochlorella corticola gen. et sp. nov. and Kalinella apyrenoidosa sp. nov.: two novel Chlorella-like green microalgae (Trebouxiophyceae, Chlorophyta) from subaerial habitats.

The diversity of green microalgae in subaerial habitats remains largely unexplored and a number of new genus- and species-level lineages have been discovered recently. The traditional green algal genus, Chlorella, which accommodated coccoid unicellular green algal species with globular to oval cells, reproducing entirely by autospores, has been found to be polyphyletic. In this study, we provide a detailed characterization of two strains of microalgae isolated from tree bark in the Mediterranean. These algae share the general Chlorella-like morphology and their 18S rRNA and rbcL gene sequences place them in the Trebouxiophyceae. Strain CAUP H8401 forms an independent trebouxiophycean lineage, together with three previously published 18S rRNA gene environmental sequences of undescribed microalgae, which were retrieved from profoundly different habitats. In contrast, strain CAUP H7902 is related to Kalinella bambusicola in the Watanabea clade of the Trebouxiophyceae on the basis of its 18S rRNA gene sequence. This relationship is also supported by the rbcL gene sequence, acquired from the type strain of K. bambusicola. The investigated strains are described as representatives of a novel species in a new genus, Leptochlorella corticola gen. et sp. nov., and a novel species, Kalinella apyrenoidosa sp. nov., according to the International Code of Nomenclature for Algae, Fungi and Plants.

A multilocus phylogeny of the desmid genus Micrasterias (Streptophyta): evidence for the accelerated rate of morphological evolution in protists.

Micrasterias, the name of which is derived from the Greek for 'little star', comprises possibly the most spectacularly shaped desmids (Desmidiales, Streptophyta). Presently, the genus Micrasterias includes about 60 traditional species, the majority of which were described in the early 19th century. We used a comprehensive multigene dataset (including SSU rDNA, psaA, and coxIII loci) of 34 Micrasterias taxa to assess the relationships between individual morphological species. The resulting phylogeny was used to assess the patterns characterizing the morphological evolution of this genus. The phylogenetic analysis led to the recognition of eight well-resolved lineages that could be characterized by selected morphological features. Apart from the members of Micrasterias, three species belonged to different traditional desmid genera (Cosmarium, Staurodesmus, and Triploceras) and were inferred to be nested within the genus. Morphological comparisons of these species with their relatives revealed an accelerated rate of morphological evolution. Mapping morphological diversification of the genus on the phylogenetic tree revealed profound differences in the phylogenetic signal of selected phenotypic features. Whereas the branching pattern of the cells clearly correlated with the phylogeny, cell complexity possibly reflected rather their adaptive morphological responses to environmental conditions. Finally, ancestral reconstruction of distribution patterns indicated potential origin of the genus in North America, with additional speciation events occurring in the Indo-Malaysian region.