Portable negative pressure environment to protect staff during aerosol-generating procedures in patients with COVID-19.

Patients with COVID-19 often need therapeutic interventions that are considered high aerosol-generating procedures. These are either being performed by healthcare providers with potentially inadequate personal protective equipment or the procedures are being delayed until patients clear their viral load. Both scenarios are suboptimal. We present a simple, cost-effective method of creating a portable negative pressure environment using equipment that is found in most hospitals to better protect healthcare providers and to facilitate more timely care for patients with COVID-19.

Continuous Negative Pressure Operative Field Barrier for Combined Open Tracheostomy and Percutaneous Endoscopic Gastrostomy Tube Placement During Coronavirus Disease 2019.

Respiratory failure in coronavirus disease 2019 (COVID-19) patients with prolonged endotracheal intubation may require a tracheostomy and percutaneous endoscopic gastrostomy (PEG) tube placement to facilitate recovery. Both techniques are considered high-risk aerosol-generating procedures and present a heightened risk of exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) for operating room personnel. We designed, simulated, and implemented a portable, continuous negative pressure, operative field barrier system using standard equipment available in hospitals to enhance health care provider safety during high-risk aerosol-generating procedures.

Reducing transmission of COVID-19 using a continuous negative pressure operative field barrier during oral maxillofacial surgery.

Oral and maxillofacial surgery in patients with suspected or confirmed COVID-19, presents a high risk of exposure and cross contamination to the operative room personnel. We designed, simulated and implemented a continue negative pressure operative field barrier to provide an additional layer of protection, using standard equipment readily available in most operative rooms during oral and maxillofacial procedures.

Compartmental localization of gamma-aminobutyric acid type B receptors in the cholinergic circuitry of the rabbit retina.

Although many effects of gamma-aminobutyric acid (GABA) on retinal function have been attributed to GABA(A) and GABA(C) receptors, specific retinal functions have also been shown to be mediated by GABA(B) receptors, including facilitation of light-evoked acetylcholine release from the rabbit retina (Neal and Cunningham [1995] J. Physiol. 482:363-372). To explain the results of a rich set of experiments, Neal and Cunningham proposed a model for this facilitation. In this model, GABA(B) receptor-mediated inhibition of glycinergic cells would reduce their own inhibition of cholinergic cells. In turn, muscarinic input from the latter to the glycinergic cells would complete a negative-feedback circuitry. In this study, we have used immunohistochemical techniques to test elements of this model. We report that glycinergic amacrine cells are GABA(B) receptor negative. In contrast, our data reveal the localization of GABA(B) receptors on cholinergic/GABAergic starburst amacrine cells. High-resolution localization of GABA(B) receptors on starburst amacrine cells shows that they are discretely localized to a limited population of its varicosities, the majority of likely synaptic-release sites being devoid of detectable levels of GABA(B) receptors. Finally, we identify a glycinergic cell that is a potential muscarinic receptor-bearing target of GABA(B)-modulated acetylcholine release. This target is the DAPI-3 cell. We propose, based on these data, a modification of the Neal and Cunningham model in which GABA(B) receptors are on starburst, not glycinergic amacrine cells.

Hemodynamic effects of left atrial or left ventricular cannulation for acute circulatory support in a bovine model of left heart injury.

Our objective was to examine the hemodynamic effects of a trans-aortic axial flow catheter (Impella CP) in the left ventricle (LV) versus left atrial (LA) to femoral artery bypass using a centrifugal pump (TandemHeart: TH) in a bovine model of acute LV injury. In three male calves, we performed sequential activation of a CP then TH device in each animal. After 60 minutes of left anterior descending artery ligation, a CP was activated at maximal power. The CP was then removed and the TH activated at 5,500 then a maximum of 7,500 rotations per minute (RPM). The CP generated a maximum 3.1 ± 0.2 L/minute (LPM) of flow, whereas the TH at 5,500 and 7,500 RPM generated 3.1 ± 0.4 and 4.4 ± 0.3 LPM. At 3.1 LPM, the CP and TH reduced LV stroke work (LVSW) similarly. The TH reduced stroke volume, whereas the CP did not. The CP reduced end-systolic pressure, whereas the TH did not. At a maximum flow of 4.4 LPM, the TH provided a greater reduction in LVSW than maximal CP activation. This is the first report to compare the hemodynamic effects of trans-aortic LV unloading versus LA-to-femoral artery (FA) bypass.

Quantitative assessment of DNA fragmentation and beta-amyloid deposition in insular cortex and midfrontal gyrus from patients with Alzheimer's disease.

It has been suggested that the neurodegeneration that occurs with Alzheimer's disease (AD) may result from apoptosis, a process of programmed cell death. Neuronal injury, induced by abnormal aggregates of beta-amyloid peptide, has been identified as an apoptotic trigger. In the present study, brain tissue samples were obtained from the insular cortex (INS) and midfrontal gyrus (MFG) of Alzheimer subjects and age-matched, nondemented controls. Tissue sections from all samples were alternately stained by an in situ TUNEL assay to identify 3' termini DNA strand breaks characteristic of apoptosis or immunohistochemically for beta-amyloid deposition in senile plaques. The incidence of DNA fragmentation detected in pyramidal neurons was relatively infrequent overall, but was significantly higher in AD compared to controls. AD subjects consistently exhibited a dense accumulation of plaques, with a twofold greater concentration in MFG as INS. There was no significant difference in pyramidal cell number regardless of subject or brain region. Taken together, our results indicate that the TUNEL assay may be revealing cell damage rather than cell loss. Our finding of a moderate correlation between the incidence of TUNEL-positive cells and plaque density implicates beta-amyloid as one of multiple factors provoking cell injury in AD. A notable contribution of this study is the identification of distinctive neuropathologies co-occurring in two brain regions interconnected with each other and with limbic and cortical areas typically damaged during AD.

Dendritic compartmentalization of chloride cotransporters underlies directional responses of starburst amacrine cells in retina.

The mechanisms in the retina that generate light responses selective for the direction of image motion remain unresolved. Recent evidence indicates that directionally selective light responses occur first in the retina in the dendrites of an interneuron, i.e., the starburst amacrine cell, and that these responses are highly sensitive to the activity of Na-K-2Cl (NKCC) and K-Cl (KCC), two types of chloride cotransporter that determine whether the neurotransmitter GABA depolarizes or hyperpolarizes neurons, respectively. We show here that selective blockade of the NKCC2 and KCC2 cotransporters located on starburst dendrites consistently hyperpolarized and depolarized the starburst cells, respectively, and greatly reduced or eliminated their directionally selective light responses. By mapping NKCC2 and KCC2 antibody staining on these dendrites, we further show that NKCC2 and KCC2 are preferentially located in the proximal and distal dendritic compartments, respectively. Finally, measurements of the GABA reversal potential in different starburst dendritic compartments indicate that the GABA reversal potential at the distal dendrite is more hyperpolarized than at the proximal dendrite due to KCC2 activity. These results thus demonstrate that the differential distribution of NKCC2 on the proximal dendrites and KCC2 on the distal dendrites of starburst cells results in a GABA-evoked depolarization and hyperpolarization at the NKCC2 and KCC2 compartments, respectively, and underlies the directionally selective light responses of the dendrites. The functional compartmentalization of interneuron dendrites may be an important means by which the nervous system encodes complex information at the subcellular level.