Utilization of mechanical power and associations with clinical outcomes in brain injured patients: a secondary analysis of the extubation strategies in neuro-intensive care unit patients and associations with outcome (ENIO) trial

Background: There is insufficient evidence to guide ventilatory targets in acute brain injury (ABI). Recent studies have shown associations between mechanical power (MP) and mortality in critical care populations. We aimed to describe MP in ventilated patients with ABI, and evaluate associations between MP and clinical outcomes. Methods: In this preplanned, secondary analysis of a prospective, multi-center, observational cohort study (ENIO, NCT03400904), we included adult patients with ABI (Glasgow Coma Scale ≤ 12 before intubation) who required mechanical ventilation (MV) ≥ 24 h. Using multivariable log binomial regressions, we separately assessed associations between MP on hospital day (HD)1, HD3, HD7 and clinical outcomes: hospital mortality, need for reintubation, tracheostomy placement, and development of acute respiratory distress syndrome (ARDS). Results: We included 1217 patients (mean age 51.2 years [SD 18.1], 66% male, mean body mass index [BMI] 26.3 [SD 5.18]) hospitalized at 62 intensive care units in 18 countries. Hospital mortality was 11% (n = 139), 44% (n = 536) were extubated by HD7 of which 20% (107/536) required reintubation, 28% (n = 340) underwent tracheostomy placement, and 9% (n = 114) developed ARDS. The median MP on HD1, HD3, and HD7 was 11.9 J/min [IQR 9.2-15.1], 13 J/min [IQR 10-17], and 14 J/min [IQR 11-20], respectively. MP was overall higher in patients with ARDS, especially those with higher ARDS severity. After controlling for same-day pressure of arterial oxygen/fraction of inspired oxygen (P/F ratio), BMI, and neurological severity, MP at HD1, HD3, and HD7 was independently associated with hospital mortality, reintubation and tracheostomy placement. The adjusted relative risk (aRR) was greater at higher MP, and strongest for: mortality on HD1 (compared to the HD1 median MP 11.9 J/min, aRR at 17 J/min was 1.22, 95% CI 1.14-1.30) and HD3 (1.38, 95% CI 1.23-1.53), reintubation on HD1 (1.64; 95% CI 1.57-1.72), and tracheostomy on HD7 (1.53; 95%CI 1.18-1.99). MP was associated with the development of moderate-severe ARDS on HD1 (2.07; 95% CI 1.56-2.78) and HD3 (1.76; 95% CI 1.41-2.22). Conclusions: Exposure to high MP during the first week of MV is associated with poor clinical outcomes in ABI, independent of P/F ratio and neurological severity. Potential benefits of optimizing ventilator settings to limit MP warrant further investigation

Modulation of prey size reveals adaptability and robustness in the cell cycle of an intracellular predator.

Despite a remarkable diversity of lifestyles, bacterial replication has only been investigated in a few model species. In bacteria that do not rely on canonical binary division for proliferation, the coordination of major cellular processes is still largely mysterious. Moreover, the dynamics of bacterial growth and division remain unexplored within spatially confined niches where nutrients are limited. This includes the life cycle of the model endobiotic predatory bacterium Bdellovibrio bacteriovorus, which grows by filamentation within its prey and produces a variable number of daughter cells. Here, we examined the impact of the micro-compartment in which predators replicate (i.e., the prey bacterium) on their cell-cycle progression at the single-cell level. Using Escherichia coli with genetically encoded size differences, we show that the duration of the predator cell cycle scales with prey size. Consequently, prey size determines predator offspring numbers. We found that individual predators elongate exponentially, with a growth rate determined by the nutritional quality of the prey, irrespective of prey size. However, the size of newborn predator cells is remarkably stable across prey nutritional content and size variations. Tuning the predatory cell cycle by modulating prey dimensions also allowed us to reveal invariable temporal connections between key cellular processes. Altogether, our data imply adaptability and robustness shaping the enclosed cell-cycle progression of B. bacteriovorus, which might contribute to optimal exploitation of the finite resources and space in their prey. This study extends the characterization of cell cycle control strategies and growth patterns beyond canonical models and lifestyles

An optimized workflow to measure bacterial predation in microplates.

The predatory bacterium invades and proliferates inside other bacteria by non-binary division. Here we describe a fluorescence-based technique for the immediate evaluation of predator density independently of plaque formation, an optimized setup to monitor predation in microplates, and the CuRveR package to quantify both prey killing and predator proliferation dynamics. This protocol allows to assess the impact of mutations or chemicals on predation. CuRveR also constitutes a user-friendly tool to analyze growth or decay data unrelated to predation. For complete details on the use and execution of this profile, please refer to Kaljević et al., 2021

Dual actions of lindane (γ-hexachlorocyclohexane) on calcium homeostasis and exocytosis in rat PC12 cells.

The persistent organochlorine pesticide lindane is still abundantly found in the environment and in human and animal tissue samples. Lindane induces a wide range of adverse health effects, which are at least partially mediated via the known inhibition of GABA(A) and glycine receptors. Additionally, lindane has been reported to increase the basal intracellular Ca(2+) concentration ([Ca(2+)](i)). As Ca(2+) triggers many cellular processes, including cell death and vesicular neurotransmitter release (exocytosis), we investigated whether lindane affects exocytosis, Ca(2+) homeostasis, production of reactive oxygen species (ROS) and cytotoxicity in neuroendocrine PC12 cells. Amperometric recordings and [Ca(2+)](i) imaging experiments with fura-2 demonstrated that lindane (≥ 10 μM) rapidly increases basal exocytosis and basal [Ca(2+)](i). Additional imaging and electrophysiological recordings revealed that this increase was largely due to a lindane-induced membrane depolarization and subsequent opening of N- and P/Q-type voltage-gated Ca(2+) channels (VGCC). On the other hand, lindane (≥ 3 μM) induced a concentration-dependent but non-specific inhibition of VGCCs, thereby limiting the lindane-induced increase in basal [Ca(2+)](i) and exocytosis. Importantly, the non-specific inhibition of VGCCs also reduced stimulation-evoked exocytosis and Ca(2+) influx. Though lindane exposure concentration-dependently increased ROS production, cell viability was not affected indicating that the used concentrations were not acute cytotoxic. These combined findings indicate that lindane has two, partly counteracting effects. Lindane causes membrane depolarization, thereby increasing basal [Ca(2+)](i) and exocytosis. In parallel, lindane inhibits VGCCs, thereby limiting the basal effects and reducing stimulation-evoked [Ca(2+)](i) and exocytosis. This study further underlines the need to consider presynaptic, non-receptor-mediated effects in human risk assessment

Uncovering the choreography of the chromosome during the non-binary cell cycle of the predatory bacterium Bdellovibrio bacteriovorus

In bacteria, the dynamics of chromosome replication and segregation are tightly coordinated with cell cycle progression, and largely rely on specific spatiotemporal arrangement of the chromosome. Whereas these key processes are mostly investigated in species that divide by binary fission, they remain mysterious in bacteria producing larger number of descendants. Here, we establish the predatory bacterium Bdellovibrio bacteriovorus as a model to investigate the non-binary processing of a circular chromosome. We found that its single chromosome is extremely compacted in a polarized nucleoid that excludes freely-diffusing proteins during the non-proliferative stage of the cell cycle. A binary-like cycle of DNA replication and asymmetric segregation is followed by multiple asynchronous rounds of replication and progressive ParABS­-dependent partitioning, uncoupled from cell division. Finally, we provide the first evidence for an on-off behavior of the ­ParB protein, which localizes at the centromere in a cell cycle-regulated manner. Altogether, our findings support a model of complex chromosome choreography leading to the generation of variable, odd or even numbers of offspring, and highlight the adaptation of conserved mechanisms to achieve non-binary reproduction in bacteria

Chromosome choreography during the non-binary cell cycle of a predatory bacterium

In bacteria, the dynamics of chromosome replication and segregation are tightly coordinated with cell-cycle progression and largely rely on specific spatiotemporal arrangement of the chromosome. Whereas these key processes are mostly investigated in species that divide by binary fission, they remain mysterious in bacteria producing larger number of descendants. Here, we establish the predatory bacterium Bdellovibrio bacteriovorus as a model to investigate the non-binary processing of a circular chromosome. We found that its single chromosome is highly compacted in a polarized nucleoid that excludes freely diffusing proteins during the non-proliferative stage of the cell cycle. A binary-like cycle of DNA replication and asymmetric segregation is followed by multiple asynchronous rounds of replication and progressive ParABS-dependent partitioning, uncoupled from cell division. Finally, we provide the first evidence for an on-off behavior of the ParB protein, which localizes at the centromere in a cell-cycle-regulated manner. Altogether, our findings support a model of complex chromosome choreography leading to the generation of variable, odd, or even numbers of offspring and highlight the adaptation of conserved mechanisms to achieve non-binary reproduction

CONVOLUTION APPROACH TO THE πNN SYSTEM

The unitary NN−πNN model contains a serious theoretical flaw: unitarity is obtained at the price of having to use an effective πNN coupling constant that is smaller than the experimental one. This is but one aspect of a more general renormalization problem whose origin lies in the truncation of Hilbert space used to derive the equations. Here we present a new theoretical approach to the πNN problem where unitary equations are obtained without having to truncate Hilbert space. Indeed, the only approximation made is the neglect of connected three-body forces. As all possible dressings of one-particle propagators and vertices are retained in our model, we overcome the renormalization problems inherent in previous πNN theories. The key element of our derivation is the use of convolution integrals that have enabled us to sum all the possible disconnected time-ordered graphs. We also discuss how the convolution method can be extended to sum all the time orderings of a connected graph. This has enabled us to calculate the fully dressed NN one pion exchange potential. We show how such a calculation can be used to estimate the size of the connected three-body forces neglected in the new πNN equations. Early indications are that such forces may be negligible