The immunogold labeling for glutamate and glutamine was studied at the electron microscopic level in hippocampal slice cultures following inhibition of L-glutamine synthetase [L-glutamate :ammonia ligase (ADP-forming) ; EC 6 .3 .1 .2] . In control cultures, glutamate-like immunoreactivity was highest in terminals, intermediate in pyramidal cell bodies, and low in glial cells . Glutamine-like immunoreactivity was high in glial cells, intermediate in pyramidal cell bodies, and low in terminals . After inhibition of glutamine synthetase with L-methionine sulfoximine, glutamate-like immunoreactivity was reduced by 52% in terminals and increased nearly fourfold in glia . Glutamine-like immunoreactivity was reduced by 66% in glia following L-methionine sulfoximine, but changed little in other compartments . In cultures that were treated with both L-methionine sulfoximine and glutamine (1 .0 mM), glutamate-like immunoreactivity was maintained at control levels in terminals, whereas in glia glutamate-like immunoreactivity was increased and glutamine-like immunoreactivity was decreased to a similar extent as in cultures treated with L-methionine sulfoximine alone . We conclude that (a) glutamate accumulates in glia when the flux through glutamine synthetase is blocked, emphasizing the importance of this pathway for the handling of glutamate ; and (b) glutamine is necessary for the maintenance of a normal level of glutamate in terminals, and neither reuptake nor de novo synthesis through pathways other than the glutaminase reaction is sufficient . Abbreviations used : GLN-LT, glutamine-like immunoreactivity ;Glu-LI, glutamate-like immunoreactivity; MSO, i .-methionine sulfoximine.

Background Little information is available about the geo-economic variations in demographics, management, and outcomes of patients with acute respiratory distress syndrome (ARDS). We aimed to characterise the effect of these geo-economic variations in patients enrolled in the Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG SAFE). Methods LUNG SAFE was done during 4 consecutive weeks in winter, 2014, in a convenience sample of 459 intensivecare units in 50 countries across six continents. Inclusion criteria were admission to a participating intensive-care unit (including transfers) within the enrolment window and receipt of invasive or non-invasive ventilation. One of the trial's secondary aims was to characterise variations in the demographics, management, and outcome of patients with ARDS. We used the 2016 World Bank countries classification to define three major geo-economic groupings, namely European high-income countries (Europe-High), high-income countries in the rest of the world (rWORLD-High), and middle-income countries (Middle). We compared patient outcomes across these three groupings. LUNG SAFE is registered with ClinicalTrials.gov, number NCT02010073. Findings Of the 2813 patients enrolled in LUNG SAFE who fulfilled ARDS criteria on day 1 or 2, 1521 (54%) were recruited from Europe-High, 746 (27%) from rWORLD-High, and 546 (19%) from Middle countries. We noted significant geographical variations in demographics, risk factors for ARDS, and comorbid diseases. The proportion of patients with severe ARDS or with ratios of the partial pressure of arterial oxygen (PaO 2) to the fractional concentration of oxygen in inspired air (F I O 2) less than 150 was significantly lower in rWORLD-High countries than in the two other regions. Use of prone positioning and neuromuscular blockade was significantly more common in Europe-High countries than in the other two regions. Adjusted duration of invasive mechanical ventilation and length of stay in the intensive-care unit were significantly shorter in patients in rWORLD-High countries than in Europe-High or Middle countries. High gross national income per person was associated with increased survival in ARDS; hospital survival was significantly lower in Middle countries than in Europe-High or rWORLD-High countries. Interpretation Important geo-economic differences exist in the severity, clinician recognition, and management of ARDS, and in patients' outcomes. Income per person and outcomes in ARDS are independently associated.

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Background Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. MethodsIn this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middleincome countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality. Findings Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42•4% vs 44•2%; absolute difference -1•69 [-9•58 to 6•11] p=0•67; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5-8] vs 6 [5-8] cm H 2 O; p=0•0011). ICU mortality was higher in MICs than in HICs (30•5% vs 19•9%; p=0•0004; adjusted effect 16•41% [95% CI 9•52-23•52]; p<0•0001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0•80 [95% CI 0•75-0•86]; p<0•0001).Interpretation Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status.

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