Hemispheric Asymmetry on the Electroencephalogram during General Anesthesia Responsive to Blood Pressure Manipulations.

The electroencephalogram (EEG) has been extensively used to detect ischemia and the need for shunting during carotid endarterectomy. Limited literature exists using EEG data to detect ischemia in other surgeries. This case report depicts a 65-year-old man, with extensive vascular history including complete left carotid occlusion and severe right carotid stenosis, who presented for left first rib resection and left subclavian vein balloon angioplasty. Following induction of general anesthesia, frontal EEG (SedLine; Masimo Corporation, Irvine, CA, USA) demonstrated hemispheric asymmetry, which nearly resolved with vasoactive support. At three distinct periods, discordance reoccurred necessitating a higher mean arterial pressure threshold. This case demonstrates EEG patterns concerning for focal spectrographic ischemia and highlights the potential use of EEG signals to capture hypoperfusion and direct vasoactive therapy.

Regulation of l- and d-Aspartate Transport and Metabolism in Acinetobacter baylyi ADP1.

The regulated uptake and consumption of d-amino acids by bacteria remain largely unexplored, despite the physiological importance of these compounds. Unlike other characterized bacteria, such as Escherichia coli, which utilizes only l-Asp, Acinetobacter baylyi ADP1 can consume both d-Asp and l-Asp as the sole carbon or nitrogen source. As described here, two LysR-type transcriptional regulators (LTTRs), DarR and AalR, control d- and l-Asp metabolism in strain ADP1. Heterologous expression of A. baylyi proteins enabled E. coli to use d-Asp as the carbon source when either of two transporters (AspT or AspY) and a racemase (RacD) were coexpressed. A third transporter, designated AspS, was also discovered to transport Asp in ADP1. DarR and/or AalR controlled the transcription of aspT, aspY, racD, and aspA (which encodes aspartate ammonia lyase). Conserved residues in the N-terminal DNA-binding domains of both regulators likely enable them to recognize the same DNA consensus sequence (ATGC-N7-GCAT) in several operator-promoter regions. In strains lacking AalR, suppressor mutations revealed a role for the ClpAP protease in Asp metabolism. In the absence of the ClpA component of this protease, DarR can compensate for the loss of AalR. ADP1 consumed l- and d-Asn and l-Glu, but not d-Glu, as the sole carbon or nitrogen source using interrelated pathways. IMPORTANCE A regulatory scheme was revealed in which AalR responds to l-Asp and DarR responds to d-Asp, a molecule with critical signaling functions in many organisms. The RacD-mediated interconversion of these isomers causes overlap in transcriptional control in A. baylyi. Our studies improve understanding of transport and regulation and lay the foundation for determining how regulators distinguish l- and d-enantiomers. These studies are relevant for biotechnology applications, and they highlight the importance of d-amino acids as natural bacterial growth substrates.