The clinical activities regarding sleep disordered breathing (SDB) have been sharply interrupted during the initial phase of the COVID-19 epidemic throughout Europe. In the last months, activities have gradually restarted, according to epidemiological phase of COVID-19 and National recommendations. The recent increase in cases throughout Europe obliges to reconsider management strategies of SDB accordingly. Diagnosis of SDB and initiation of treatment pose some specific problems to be addressed to preserve safety of the patients and health personnel. This perspective document by a group of European sleep experts aims at summarising some different approaches followed in Europe and United States, which reflect National recommendations according to the epidemiological phase of the COVID-19 infection. Respiratory sleep medicine will likely change in the near future, and use of telemedicine will grow to avoid unnecessary risks and continue to provide optimal care to the patients. The document also covers pediatric sleep studies and indications for titration of noninvasive ventilation, as well as precautions to be followed by patients who are already on positive airway pressure treatment. A single consensus document developed by the European Respiratory Society and National Societies would be desirable to harmonise SDB management throughout Europe.
Mitochondrial malate dehydrogenase shows a complex regulation pattern in the presence of citrate. Previously published results indicate that this enzyme is activated by citrate in the NAD(+)----NADH direction and inhibited in the opposite direction. Moreover, high concentrations of L-malate or oxaloacetate produce deviations from the Michaelis-Menten behaviour. Results reported in this paper clearly show that citrate both activates and inhibits mitochondrial malate dehydrogenase in the same direction (NAD(+)----NADH), and in the same reaction medium, depending on substrate concentration. This surprising effect has made it necessary to propose a new kinetic mechanism that extends those previously suggested and allows us to explain both the citrate effect (activating or inhibitory) and the effect of high concentrations of L-malate and oxaloacetate.
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