Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Inquiry-Based Learning for Physics Courses within the Russian Schooling System

Introduction: this article discusses the didactic and methodological problems of implementing inquiry-based learning into Russian schools. It is especially relevant now as new educational standards were introduced. Literature review showed that while implementing inquiry-based learning schools in different countries face the same difficulties, some of which are related to teachers’ professional competence. The goal of the research is to develop a theoretical framework for inquiry-based learning which includes patterns, educational process design, as well as an algorithm for teachers’ work. Materials and Methods: the research analyzed normative documents for school education, research and methodological literature on research-based education. We also designed the process of research-based education for the school course of physics. Summative, research and formative teaching experiments were carried out, as well as questionnaire survey and interviews for physics teachers. We also tested the students of Nizhny Novgorod schools and first-year students of Lobachevsky State University of Nizhny Novgorod. Results: the result of the research is the didactic basis for the theory of modelling inquiry-based learning in physics. We stated the patterns of learning process, algorithm for teachers and a generic model of a research class. Pedagogical experiment (implementing this model) showed a statistically reliable increase in the required standard of students’ research skills. Discussion and Conclusions: the study proved the efficiency of the proposed models for inquiry-based learning. The practical value of the work is a developed algorithm of educational process that can be used to increase teachers’ competence in inquiry-based teaching based on the integration of school and college level education

Contribution of synchronized GABAergic neurons to dopaminergic neuron firing and bursting

Presented herein ventral tegmental area microcircuit model challenges the classical view that GABA neurons exclusively reduce dopamine neuron firing and bursting. Rather, high levels of synchrony amongst GABA neurons can produce increases in firing and bursting of the dopamine neuron. Dopamine bursting can be produced in the absence of bursty excitatory input, if the neuron receives transiently synchronized GABA input. We provide an explanation of the mechanisms whereby GABA neurons could contribute to dopamine neuron burst firing., In the ventral tegmental area (VTA), interactions between dopamine (DA) and γ-aminobutyric acid (GABA) neurons are critical for regulating DA neuron activity and thus DA efflux. To provide a mechanistic explanation of how GABA neurons influence DA neuron firing, we developed a circuit model of the VTA. The model is based on feed-forward inhibition and recreates canonical features of the VTA neurons. Simulations revealed that γ-aminobutyric acid (GABA) receptor (GABAR) stimulation can differentially influence the firing pattern of the DA neuron, depending on the level of synchronization among GABA neurons. Asynchronous activity of GABA neurons provides a constant level of inhibition to the DA neuron and, when removed, produces a classical disinhibition burst. In contrast, when GABA neurons are synchronized by common synaptic input, their influence evokes additional spikes in the DA neuron, resulting in increased measures of firing and bursting. Distinct from previous mechanisms, the increases were not based on lowered firing rate of the GABA neurons or weaker hyperpolarization by the GABAR synaptic current. This phenomenon was induced by GABA-mediated hyperpolarization of the DA neuron that leads to decreases in intracellular calcium (Ca2+) concentration, thus reducing the Ca2+-dependent potassium (K+) current. In this way, the GABA-mediated hyperpolarization replaces Ca2+-dependent K+ current; however, this inhibition is pulsatile, which allows the DA neuron to fire during the rhythmic pauses in inhibition. Our results emphasize the importance of inhibition in the VTA, which has been discussed in many studies, and suggest a novel mechanism whereby computations can occur locally

The rate and regularity of the DA neuron firing receiving asynchronous synaptic Glu and GABA inputs.

<p>(A1) The firing rate. Balanced activity of Glu and GABA populations results in low-frequency DA neuron firing (between black lines) (A2) Coefficient of variation (CV) of the ISI. For majority of <i>g</i>_<i>NMDA</i>, <i>g</i>_<i>GABA</i> values, CV<0.5, indicating low variability in DA neuron firing. (B 1–5) Balanced asynchronous GABA and Glu inputs provide constant noisy levels of inhibition and excitation respectively and result in DA firing rates similar to the background firing rates.</p

Balance of NMDA and GABA receptor activation and two ways of eliciting bursts or pauses of the DA neuron.

<p>(A) Tonic co-activation of NMDA and GABA receptors balances each other and supports low frequency firing in the DA neuron model. Transient deactivation of NMDAR produces a pause, whereas deactivation of GABAR results in a high-frequency burst. (B) Heat plot of the frequency distribution on the plane of NMDAR and GABAR conductances. The insert illustrates a smooth frequency decrease during application of GABAR conductance (<i>g</i>_<i>NMDA</i> = 0 mS/cm²). (C) As an alternative to the deactivation of NMDAR in (A), a pause may be produced by further activation of GABAR. (D) Strengthening NMDA excitation produces a burst, even if GABAR activation initially blocks firing. (E) Activation of GABAR can rescue DA neuron from depolarization block. To match the experimental conditions in Lobb at al. (2010) [<a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1005233#pcbi.1005233.ref050" target="_blank">50</a>], we set α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) current to 0.</p

The subthreshold sodium current changes the type of transition to hyperpolarized rest state induced by GABAR activation.

<p>In both cases the growing GABAR conductance leads to a downward shift of the voltage nullcline (solid folded curve). (A) In the pure Ca²⁺-K⁺ mechanism for voltage oscillations, inhibition leads to a transition to the rest state through an Andronov-Hopf bifurcation, which occurs with little change in the firing frequency. The Andronov-Hopf bifurcation is defined as the disappearance of a closed trajectory representing firing (limit cycle) by shrinking in amplitude and merging with an equilibrium state. (B) If the Ca²⁺-K⁺ mechanism is augmented by a subthreshold Na⁺ current, the transition occurs through a Saddle-Node on Invariant Circle bifurcation (SNIC), which corresponds to a gradual decrease in the frequency to zero. The SNIC bifurcation is defined as the emergence of new equilibrium states that interrupt the limit cycle.</p

Tonic activation of NMDAR may change the excitability type from the first to the second.

<p>(A) The boundary between type I and type II excitability in the DA neuron shifts down with respect to the reversal potential of an ohmic synaptic current as NMDAR conductance grows. (B1-2) Two voltage traces illustrating the excitability types. For any synaptic reversal potential <i>E</i>_<i>eff</i> and NMDAR conductance from the grey region of type I excitability on panel (A), ramping the ohmic synaptic conductance <i>g</i>_<i>eff</i> increases the interspike intervals and then blocks firing. For the parameters from type II region, ramping the ohmic synaptic conductance blocks firing without the decrease in the frequency.</p

Coding of the reward value by type I and type II DA neurons.

<p>(A) Raster of type I DA neuron in response to gradually increasing input strengths/ reward value. (B) Frequency responses of the type I DA neuron to different reward values. (C) Raster of the type II DA neuron in response to gradually increasing input strengths/ reward values. (D) Frequency responses of type II DA neuron to different reward values. (E) F-I curves of type I (blue) and type II (red) DA neurons. Due to a discontinuity in the F-I curve, type II DA neurons are unable to encode low reward values.</p

Model parameters.

<p>Model parameters.</p