Calanus finmarchicus seasonal cycle and diapause in relation to gene expression, physiology, and endogenous clocks: Calanus finmarchicus seasonal rhythmicity

The copepod Calanus finmarchicus plays a crucial role in the north Atlantic food web. Its seasonal life cycle involves reproduction and development in surface waters before overwintering in diapause at depth. Although diapause has been studied for more than a century, the factors responsible for the initiation and termination of it are still unclear. Endogenous clocks have been identified as potent tools for photoperiod measurement and seasonal rhythmicity in many terrestrial species, but knowledge of these remains scarce in the marine realm. Focusing on the dominant CV copepodid stage, we sampled a population of C. finmarchicus from a Scottish sea loch to characterize population dynamics, several physiological parameters, and diel and seasonal expression rhythms of 35 genes representing different metabolic pathways, including the circadian clock machinery. This generated a detailed overview of the seasonal cycle of C. finmarchicus including the most extensive field dataset on circadian clock gene expression in a marine species to date. Gene expression patterns revealed distinct gene clusters upregulated at different phases of the copepod's seasonal cycle. While diel clock cycling was restricted to the active spring/summer phase, many clock genes exhibited the highest expression during diapause. Our results provide new insights into diapause on physiological and genetic levels. We suggest that photoperiod, in interaction with internal and external factors (lipid content, temperature, food availability) and the endogenous clock mechanism, plays an important role in the timing of diapause in C. finmarchicus

Circadian Clock Involvement in Zooplankton Diel Vertical Migration

Biological clocks are a ubiquitous ancient and adaptive mechanism enabling organisms to anticipate environmental cycles and to regulate behavioral and physiological processes accordingly [1]. Although terrestrial circadian clocks are well understood, knowledge of clocks in marine organisms is still very limited [2, 3, 4, 5]. This is particularly true for abundant species displaying large-scale rhythms like diel vertical migration (DVM) that contribute significantly to shaping their respective ecosystems [6]. Here we describe exogenous cycles and endogenous rhythms associated with DVM of the ecologically important and highly abundant planktic copepod Calanus finmarchicus. In the laboratory, C. finmarchicus shows circadian rhythms of DVM, metabolism, and most core circadian clock genes (clock, period1, period2, timeless, cryptochrome2, and clockwork orange). Most of these genes also cycle in animals assessed in the wild, though expression is less rhythmic at depth (50–140 m) relative to shallow-caught animals (0–50 m). Further, peak expressions of clock genes generally occurred at either sunset or sunrise, coinciding with peak migration times. Including one of the first field investigations of clock genes in a marine species [5, 7], this study couples clock gene measurements with laboratory and field data on DVM. While the mechanistic connection remains elusive, our results imply a high degree of causality between clock gene expression and one of the planet’s largest daily migrations of biomass. We thus suggest that circadian clocks increase zooplankton fitness by optimizing the temporal trade-off between feeding and predator avoidance, especially when environmental drivers are weak or absent [8]

Calanus finmarchicus diel and seasonal rhythmicity in relation to endogenous timing under extreme polar photoperiods

Changing environmental conditions cause poleward distribution shifts in many marine organisms including the northern Atlantic key zooplankton species Calanus finmarchicus. The copepod has diel cycles of vertical migration and feeding, a seasonal life cycle with diapause in winter and a functioning circadian clock. Endogenous clock mechanisms control various aspects of rhythmic life and are heavily influenced by environmental light conditions. Here we explore how the extreme seasonal change in photoperiod (day length) in a high Arctic fjord affects circadian clock functioning as well as diel and seasonal cycles in C. finmarchicus. Expression of clock genes was measured in the active life phase at the end of midnight sun, in early diapause when photoperiod was ~12 h, and in late diapause during the polar night. While the clock maintained diel rhythmicity under extremely long photoperiods, it became arrhythmic during diapause. This was probably not due to a lack of light but was related to the physiological state of diapause. Seasonal expression analyses of 35 genes show distinct patterns for each investigated life phase. C. finmarchicus is able to maintain diel clock rhythmicity at photoperiods close to 24 h, and it is discussed how this may be related to the nature of the marine environment. The work also evaluates the potential negative consequences of rigid clock-based seasonal timing in a polar environment exposed to climate change and with high interannual variability

Retrospective audit of antibiotic use in a university general pediatrics department using hospital pharmacy dispensing data

Antibiotics are among the most frequently prescribed drugs in children’s hospitals, which is why regular monitoring of antibiotic use in hospitals is of great importance. This retrospective audit (60 months, January 2014 – December 2018) analyzes the antibiotic consumption at a university inpatient department of general pediatrics including neonatal and pediatric intensive care based on pharmacy dispensing data in units of grams per 100 patient days and in Defined Daily Doses per 100 patient days. The results provide potential targets for Antibiotic Stewardship interventions. Conversely, this audit elicits methodological limitations of the method of antibiotic surveillance in pediatrics recommended by the Robert Koch Institute, Berlin

Pott's puffy tumor: a need for interdisciplinary diagnosis and treatment

Pott’s puffy tumor (PPT) is an infection of the frontal sinus with subperiosteal and intracranial abscess formation and one of the rare entities in pediatrics. We present a series of four cases of PPT that occurred in two children (6 and 9 years) and in two young adults (17 and 19 years). All patients were treated by an interdisciplinary team of pediatric, neurosurgical, ENT, radiological, and neuroradiological specialists. Antibiotic treatment was combined with single endoscopic surgery in one case and combined endoscopic sinus surgery with an open transcranial approach to drain intracranial abscess formation in three cases. It is important to be aware that PPT occurs in children with the finding of intracranial abscess formation. Therefore, a close interdisciplinary cooperation for successful treatment is needed in this rare disease

Transdiagnostic inflexible learning dynamics explain deficits in depression and schizophrenia

Deficits in reward learning are core symptoms across many mental disorders. Recent work suggests that such learning impairments arise by a diminished ability to use reward history to guide behaviour, but the neuro-computational mechanisms through which these impairments emerge remain unclear. Moreover, limited work has taken a transdiagnostic approach to investigate whether the psychological and neural mechanisms that give rise to learning deficits are shared across forms of psychopathology. To provide insight into this issue, we explored probabilistic reward learning in patients diagnosed with major depressive disorder (n = 33) or schizophrenia (n = 24) and 33 matched healthy controls by combining computational modelling and single-trial EEG regression. In our task, participants had to integrate the reward history of a stimulus to decide whether it is worthwhile to gamble on it. Adaptive learning in this task is achieved through dynamic learning rates that are maximal on the first encounters with a given stimulus and decay with increasing stimulus repetitions. Hence, over the course of learning, choice preferences would ideally stabilize and be less susceptible to misleading information. We show evidence of reduced learning dynamics, whereby both patient groups demonstrated hypersensitive learning (i.e. less decaying learning rates), rendering their choices more susceptible to misleading feedback. Moreover, there was a schizophrenia-specific approach bias and a depression-specific heightened sensitivity to disconfirmational feedback (factual losses and counterfactual wins). The inflexible learning in both patient groups was accompanied by altered neural processing, including no tracking of expected values in either patient group. Taken together, our results thus provide evidence that reduced trial-by-trial learning dynamics reflect a convergent deficit across depression and schizophrenia. Moreover, we identified disorder distinct learning deficits

Toxicity of three types of arsenolipids : species-specific effects in Caenorhabditis elegans

This work was supported by the German Research Foundation (DFG), grant number SCHW 903/10-1 and the Austrian Science Fund (FWF), project number I2412-B21. MA was supported in part by grants from the NIEHS, R01ES10563 and R0107331.Peer reviewedPostprin