Appleseed - restoration and resonance.

The successful restoration of the river that used to be the dirtiest in Europe shows that any water course can be brought back to life. Around the world, different approaches and different goals are being pursued in a multitude of river restoration projects, with barrier removals showing a growing trend.

Atrial fibrosis heterogeneity is a risk for atrial fibrillation in pigs with ischaemic heart failure.

BACKGROUND: Atrial fibrillation (AF) is the most common arrhythmia and is associated with considerable morbidity and mortality. Ischaemic heart failure (IHF) remains one of the most common causes of AF in clinical practice. However, ischaemia-mediated mechanisms leading to AF are still incompletely understood, and thus, current treatment approaches are limited. To improve our understanding of the pathophysiology, we studied a porcine IHF model. METHODS: In pigs, IHF was induced by balloon occlusion of the left anterior descending artery for 90 min. After 30 days of reperfusion, invasive haemodynamic measurements and electrophysiological studies were performed. Masson trichrome and immunofluorescence staining were conducted to assess interstitial fibrosis and myofibroblast activation in different heart regions. RESULTS: After 30 days of reperfusion, heart failure with significantly reduced ejection fraction (left anterior obique 30°, 34.78 ± 3.29% [IHF] vs. 62.03 ± 2.36% [control], p < .001; anterior-posterior 0°, 29.16 ± 3.61% vs. 59.54 ± 1.09%, p < .01) was observed. These pigs showed a significantly higher susceptibility to AF (33.90% [IHF] vs. 12.98% [control], p < .05). Histological assessment revealed aggravated fibrosis in atrial appendages but not in atrial free walls in IHF pigs (11.13 ± 1.44% vs. 5.99 ± .86%, p < .01 [LAA], 8.28 ± .56% vs. 6.01 ± .35%, p < .01 [RAA]), which was paralleled by enhanced myofibroblast activation (12.09 ± .65% vs. 9.00 ± .94%, p < .05 [LAA], 14.37 ± .60% vs. 10.30 ± 1.41%, p < .05 [RAA]). Correlation analysis indicated that not fibrosis per se but its cross-regional heterogeneous distribution across the left atrium was associated with AF susceptibility (r = .6344, p < .01). CONCLUSION: Our results suggest that left atrial cross-regional fibrosis difference rather than overall fibrosis level is associated with IHF-related AF susceptibility, presumably by establishing local conduction disturbances and heterogeneity.

The avisphere.

Florian Maderspacher introduces the 'birds' special issue.

Flightless birds.

"There is no greater anomaly in nature than a bird that cannot fly" - thus spoke Richard Owen, towering figure of Victorian biology, second only to Charles Darwin, who related this quote in his Origin of Species. Owen, who later became a strident critic of Darwin's theory, knew what he was talking about. In 1839, he received a bone fragment from New Zealand. Through his superior anatomy skills, Owen inferred that this was the femur of a bird, but a bird that must have been incredibly big and hence unable to fly. As more bones arrived, Owen concluded that they belonged to a group of bird that we now know as 'moa', some of which stood almost twice as tall as him and were among the largest birds that ever lived (Figure 1).

Evolution and development: From the pet shop to the pelagic zone.

Flying fish and some of their relatives have evolved the ability to elegantly escape predators by gliding through air. A new study - involving a pet shop zebrafish mutant - offers glimpses into how fins might have been modified to enable this stunt.

Six easy species - vignettes of biodiversity.

Florian Maderspacher introduces the special issue on biodiversity.

Paleontology: Snow falling on dinosaurs.

A treasure trove of dinosaur bones and teeth from Northern Alaska - many from juveniles and yearlings - reveals that dinosaurs lived year-round in the cold and dark environment of the high Arctic.

Cecidology: Anatomy of a biohack.

Galls are abnormal plant growths induced by animals, especially insects, to foster their own developing offspring. Which molecular malware gall-inducers use to hack into the plant's genetic programs is unclear. In an aphid, a gene affecting gall color has been discovered, part of a large family of putative effectors.

Sexual Selection: A Cross-Sword Puzzle.

Swordtail fish with their eponymous male ornament have long been a paradigm for how sexual selection works. Two studies now aim to dissect the genetic and developmental basis of the sword. They home in on similar regions of the swordtail genome but arrive at different candidate genes.

Consider the microbe.

Florian Maderspacher introduces the microbiology special issue and asks how the study of microbes has shaped our understanding of evolution.

The long dark teatime of the cell.

Florian Maderspacher introduces the special issue 'the cell in evolution'.

Characterization of a porcine model of atrial arrhythmogenicity in the context of ischaemic heart failure.

Atrial fibrillation (AF) is a major healthcare challenge contributing to high morbidity and mortality. Treatment options are still limited, mainly due to insufficient understanding of the underlying pathophysiology. Further research and the development of reliable animal models resembling the human disease phenotype is therefore necessary to develop novel, innovative and ideally causal therapies. Since ischaemic heart failure (IHF) is a major cause for AF in patients we investigated AF in the context of IHF in a close-to-human porcine ischaemia-reperfusion model. Myocardial infarction (AMI) was induced in propofol/fentanyl/midazolam-anaesthetized pigs by occluding the left anterior descending artery for 90 minutes to model ischaemia with reperfusion. After 30 days ejection fraction (EF) was significantly reduced and haemodynamic parameters (pulmonary capillary wedge pressure (PCWP), right atrial pressure (RAP), left ventricular enddiastolic pressure (LVEDP)) were significantly elevated compared to age/weight matched control pigs without AMI, demonstrating an IHF phenotype. Electrophysiological properties (sinus node recovery time (SNRT), atrial/AV nodal refractory periods (AERP, AVERP)) did not differ between groups. Atrial burst pacing at 1200 bpm, however, revealed a significantly higher inducibility of atrial arrhythmia episodes including AF in IHF pigs (3/15 vs. 10/16, p = 0.029). Histological analysis showed pronounced left atrial and left ventricular fibrosis demonstrating a structural substrate underlying the increased arrhythmogenicity. Consequently, selective ventricular infarction via LAD occlusion causes haemodynamic alterations inducing structural atrial remodeling which results in increased atrial fibrosis as the arrhythmogenic atrial substrate in pigs with IHF.

Spectres of the Anthropocene.

Florian Maderspacher introduces the Anthropocene special issue.

Insect Olfaction: Once Swatted, Twice Shy.

While some mosquitoes are known to have an innate penchant for human hosts, new research details that they can learn, what they can learn and how they can learn.

Sensory Evolution: Trouble in the Cherry Orchard.

Understanding how and why some species become pests, while their relatives remain harmless, might help us control them. A new study looks at how sensory mechanisms evolved in an emerging pest fly species.

Evolution: Flight of the Ratites.

The flightless ratite birds are scattered all across the Southern hemisphere, on landmasses that have long been separated from each other. But how did they get there? They flew in from the North.

Spermidine, but not spermine, is essential for pigment pattern formation in zebrafish.

Polyamines are small poly-cations essential for all cellular life. The main polyamines present in metazoans are putrescine, spermidine and spermine. Their exact functions are still largely unclear; however, they are involved in a wide variety of processes affecting cell growth, proliferation, apoptosis and aging. Here we identify idefix, a mutation in the zebrafish gene encoding the enzyme spermidine synthase, leading to a severe reduction in spermidine levels as shown by capillary electrophoresis-mass spectrometry. We show that spermidine, but not spermine, is essential for early development, organogenesis and colour pattern formation. Whereas in other vertebrates spermidine deficiency leads to very early embryonic lethality, maternally provided spermidine synthase in zebrafish is sufficient to rescue the early developmental defects. This allows us to uncouple them from events occurring later during colour patterning. Factors involved in the cellular interactions essential for colour patterning, likely targets for spermidine, are the gap junction components Cx41.8, Cx39.4, and Kir7.1, an inwardly rectifying potassium channel, all known to be regulated by polyamines. Thus, zebrafish provide a vertebrate model to study the in vivo effects of polyamines.

Zoology: The Walking Heads.

An analysis of Hox genes reveals that the body of the adorably weird tardigrades is essentially a truncated front end. This illustrates that loss and simplification are a hallmark of the evolution of animal body plans.

Snail Chirality: The Unwinding.

Most snails are coiled clockwise, but in some species rare genetic variants with reverse coiling occur. Now, a molecular determinant of coiling direction has been identified, the cytoskeletal regulator formin.