Study of thunderstorm activity in Volyn Region and in Ukraine using the data of Blitzortung online resource

The article contains the results of statistical and graphical analysis of thunderstorm activity in Ukraine and within Volyn Region, in particular, following the study of the dynamic maps archive available at the online resource Blitzortung.org (lightnings and thunderstorms in real time). It describes the principles and results of activities of Blitzortung.org, a community of lightning direction sensors owners and users, and presents the developed algorithm of the methodology of reading dynamic maps available at this resource. Regional analysis of the archival maps on the website Blitzortung.org for 2008-2019 for the territory of Volyn Region made it possible to establish the following changes of the thunderstorm activity dynamics: the total number of thunderstorm days more than doubled (from 30 to 68.3 days on average); the number of thunderstorms increased in April (it was a rare phenomenon earlier); the number of thunderstorms increased significantly in May, for some years the number of thunderstorm days in May reached certain summer months (June and July); most thunderstorms are of frontal origin, storm fronts come from the west, north and southwest. The number of frontal thunderstorms tends to increase, therefore indicating increased atmospheric instability and the number of natural meteorological phenomena associated with such instability; the average monthly number of thunderstorm days in Volyn Region also increased for all months of the year with no exception. The analysis of storm activity within the whole territory of Ukraine during the period of 2018-2019 indicated the presence of clear regional features and differences. The increase in thunderstorm activity is observed in the western (50-100%) and southern (15-50%) regions of the country, and partly in the north. The number of thunderstorm days in the eastern part of Ukraine is close to the climatic normal. At the same time, the analysis needs to be clarified and detailed throughout the whole network of meteorological stations of Ukraine whose data can be compared with the results of the study of archival maps available at Blitzortung.org.

Bidirectional flow of action potentials in axons drives activity dynamics in neuronal cultures

Objective: Recent technological advances are revealing the complex physiology of the axon and challenging long-standing assumptions. Namely, while most action potential (AP) initiation occurs at the axon initial segment in central nervous system neurons, initiation in distal parts of the axon has been reported to occur in both physiological and pathological conditions. The functional role of these ectopic APs, if exists, is still not clear, nor its impact on network activity dynamics. Approach: Using an electrophysiology platform specifically designed for assessing axonal conduction we show here for the first time regular and effective bidirectional axonal conduction in hippocampal and dorsal root ganglia cultures. We investigate and characterize this bidirectional propagation both in physiological conditions and after distal axotomy. Main results: A significant fraction of APs are not coming from the canonical synapse-dendrite-soma signal flow, but instead from signals originating at the distal axon. Importantly, antidromic APs may carry information and can have a functional impact on the neuron, as they consistently depolarize the soma. Thus, plasticity or gene transduction mechanisms triggered by soma depolarization can also be affected by these antidromic APs. Conduction velocity is asymmetrical, with antidromic conduction being slower than orthodromic. Significance: Altogether these findings have important implications for the study of neuronal function in vitro, reshaping our understanding on how information flows in neuronal cultures.

Neuronal population activity dynamics reveal a low-dimensional signature of operant learning

Learning engages a high-dimensional neuronal population space spanning multiple brain regions. We identified a low-dimensional signature associated with operant conditioning, a ubiquitous form of learning in which animals learn from the consequences of behavior. Using single-neuron resolution voltage imaging, we identified two low-dimensional motor modules in the neuronal population underlying Aplysia feeding. Our findings point to a temporal shift in module recruitment as the primary signature of operant learning.

Effects of anthropic activity dynamics on mangrove ecosystems’ degradation in Caracol County – Haiti

Anthropization process and climatic changes, mainly deforestation and sea level rise, are factors significantly contributing to the most evident loss of mangrove ecosystems. The aim of our study is to analyze variables related to the effects of the dynamics of human activities closely associated with these ecosystems’ degradation. The Geographic Information System tool allowed identifying and comparing soil use and occupation variations based on information provided by 140 randomly chosen participants in Caracol County - Haiti. Interviews were carried out in loco between March and November 2020. Based on results statistically analyzed through multivariate regression tests, the most significant exploratory variable for the mangroves’ degradation process (p<0.05) was “mangrove occupation”, regardless of age, sex, schooling, time in the same residence, profession, home distance from the mangrove, landslide events, and risk of floods. We have concluded that distance from home, ecological function, intervention in biodiversity conservation, as well as water-climatic and geo-physical threats are factors closely correlated to mangroves’ environmental conservation and management (p<0.05).

Dynamic dichotomy of accumbal population activity underlies cocaine sensitization

Locomotor sensitization (LS) is an early behavioral adaptation to addictive drugs, driven by the increase of dopamine in the Nucleus Accumbens (NAc). However, the effect on accumbal population activity remains elusive. Here we used single cell calcium imaging in mice to record the activity of dopamine-1-receptor (D1R) and dopamine-2-receptor (D2R) expressing spiny projection neurons (SPNs) during cocaine LS. Acute exposure to cocaine elevated D1R SPN activity and reduced D2R SPN activity, albeit with high variability between neurons. During LS, the number of D1R and D2R neurons responding in opposite directions increased. Moreover, preventing LS by inhibition of the ERK signaling pathway decreased the number of cocaine responsive D1R SPNs, but had little effect on D2R SPNs. These results indicate that accumbal population dichotomy is dynamic and contains a subgroup of D1R SPNs that eventually drives LS. Insights into the drug-related activity dynamics provides a foundation for understanding the circuit-level addiction pathogenesis.

Predicting Individual Cell Division Events from Single-Cell ERK and Akt Dynamics

Predictive determinants of stochastic single-cell fates have been elusive, even for the well-studied mammalian cell cycle. What drives proliferation decisions of single cells at any given time? We monitored single-cell dynamics of the ERK and Akt pathways, critical cell cycle progression hubs and anti-cancer drug targets, and paired them to division events in the same single cells using the non-transformed MCF10A epithelial line. Following growth factor treatment, in cells that divide both ERK and Akt activities are significantly higher within the S-G2 time window (~8.5-40 hours). Such differences were much smaller in the pre-S-phase, restriction point window which is traditionally associated with ERK and Akt activity dependence, suggesting unappreciated roles for ERK and Akt in S through G2. Machine learning algorithms show that simple metrics of central tendency in this time window are most predictive for subsequent cell division; median ERK and Akt activities classify individual division events with an AUC=0.76. Surprisingly, ERK dynamics alone predict division in individual cells with an AUC=0.74, suggesting Akt activity dynamics contribute little to the decision driving cell division in this context. We also find that ERK and Akt activities are less correlated with each other in cells that divide. Network reconstruction experiments demonstrated that this correlation behavior was likely not due to crosstalk, as ERK and Akt do not interact in this context, in contrast to other transformed cell types. Overall, our findings support roles for ERK and Akt activity throughout the cell cycle as opposed to just before the restriction point, and suggest ERK activity dynamics are substantially more important than Akt activity dynamics for driving cell division in this non-transformed context. Single cell imaging along with machine learning algorithms provide a better basis to understand cell cycle progression on the single cell level.