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Sustaining Lake Superior : an extraordinary lake in a changing world
A compelling exploration of Lake Superior's conservation recovery and what it can teach us in the face of climate change.
Book
Comparison of Echocardiographic Indices Used to Predict Fluid Responsiveness in Ventilated Patients
Abstract
Rationale
Assessment of fluid responsiveness relies on dynamic echocardiographic parameters that have not yet been compared in large cohorts.
Objectives
To determine the diagnostic accuracy of dynamic parameters used to predict fluid responsiveness in ventilated patients with a circulatory failure of any cause.
Methods
In this multicenter prospective study, respiratory variations of superior vena cava diameter (∆SVC) measured using transesophageal echocardiography, of inferior vena cava diameter (∆IVC) measured using transthoracic echocardiography, of the maximal Doppler velocity in left ventricular outflow tract (∆VmaxAo) measured using either approach, and pulse pressure variations (∆PP) were recorded with the patient in the semirecumbent position. In each patient, a passive leg raise was performed and an increase of aortic velocity time integral greater than or equal to 10% defined fluid responsiveness.
Measurements and Main Results
Among 540 patients (379 men; age, 65 ± 13 yr; Simplified Acute Physiological Score II, 59 ± 18; Sequential Organ Failure Assessment, 10 ± 3), 229 exhibited fluid responsiveness (42%). ∆PP, ∆VmaxAo, ∆SVC, and ∆IVC could be measured in 78.5%, 78.0%, 99.6%, and 78.1% of cases, respectively. ∆SVC greater than or equal to 21%, ∆VmaxAo greater than or equal to 10%, and ∆IVC greater than or equal to 8% had a sensitivity of 61% (95% confidence interval, 57–66%), 79% (75–83%), and 55% (50–59%), respectively, and a specificity of 84% (81–87%), 64% (59–69%), and 70% (66–75%), respectively. The area under the receiver operating characteristic curve of ∆SVC was significantly greater than that of ∆IVC (P = 0.02) and ∆PP (P = 0.01).
Conclusions
∆VmaxAo had the best sensitivity and ∆SVC the best specificity in predicting fluid responsiveness. ∆SVC had a greater diagnostic accuracy than ∆IVC and ∆PP, but its measurement requires transesophageal echocardiography.
Journal Article
Control of excitatory CNS synaptogenesis by astrocyte-secreted proteins Hevin and SPARC
Astrocytes regulate synaptic connectivity in the CNS through secreted signals. Here we identified two astrocyte-secreted proteins, hevin and SPARC, as regulators of excitatory synaptogenesis in vitro and in vivo. Hevin induces the formation of synapses between cultured rat retinal ganglion cells. SPARC is not synaptogenic, but specifically antagonizes synaptogenic function of hevin. Hevin and SPARC are expressed by astrocytes in the superior colliculus, the synaptic target of retinal ganglion cells, concurrent with the excitatory synaptogenesis. Hevin-null mice had fewer excitatory synapses; conversely, SPARC-null mice had increased synaptic connections in the superior colliculus. Furthermore, we found that hevin is required for the structural maturation of the retinocollicular synapses. These results identify hevin as a positive and SPARC as a negative regulator of synapse formation and signify that, through regulation of relative levels of hevin and SPARC, astrocytes might control the formation, maturation, and plasticity of synapses in vivo.
Journal Article
Dolls of doom : a tale of terror
Thirteen-year-old Jasmine Richards has always been afraid of dolls, so finding herself in a room full of decorative dolls in an extremely creepy hotel on the north shore of Lake Superior is a nightmare to begin with--but these dolls are at the heart of the deadly secret of the hotel, aptly named Devil's Mooring.
Book
Postpartum ischemic stroke due to persistent left superior vena cava to left atrium after DORV repair: a case report and literature review
Background
Persistent left superior vena cava (PLSVC) is the most common thoracic venous anomaly and is often associated with complex congenital heart disease (CHD). Venous drainage typically occurs into the right atrium via the coronary sinus (CS). However, in 10–20% of cases, it drains into the left atrium, producing a right-to-left shunt that may result in symptoms and cerebrovascular complications.
Case presentation
A 23-year-old woman with a history of double-outlet right ventricle corrected at age 13 presented in the postpartum period with dysarthria, left central facial palsy and left hemiparesis. Brain MRI angiography revealed right middle cerebral artery (M2) occlusion, and she underwent thrombolysis and thrombectomy. Suspecting a cardioembolic event, transesophageal echocardiography with left-arm agitated saline injection revealed early left atrial opacification and delayed right-sided filling via a residual ventricular septal defect —suggesting a PLSVC draining into the left atrium. Cardiac CT confirmed CS agenesis and a PLSVC connected to the left atrial roof. She was discharged on enoxaparin.
Conclusions
PLSVC is a vascular anomaly with an estimated prevalence of 0.2-3% in the general population and 1-12% among CHD patients. A dilated CS on transthoracic echocardiography should prompt a bubble test; early opacification of the left chambers after left-arm saline injection suggests drainage to the left atrium. Cardiac CT, MRI or invasive angiography can clarify the anatomy.
PLSVC has clinical implications including technical considerations for percutaneous procedures and cardiac surgery, a predisposition for arrhythmias, and —when draining into the left atrium— an increased risk of cerebrovascular events. Closure of a PLSVC draining into the left atrium should be considered in symptomatic patients or those at high risk of paradoxical embolism, following anatomical assessment.
In pregnant women with CHD, cardiac risk assessment, multimodal imaging and multidisciplinary follow-up are crucial due to associated hemodynamic changes and hypercoagulable state.
Journal Article
Skating wild on an inland sea
\"Let's go! Experience the magic of skating on wild ice. Two children wake up to hear the lake singing, then the wind begins wailing ... or is it a wolf? They bundle up and venture out into the cold, carrying their skates. On the snow-covered shore, they spot tracks made by fox, deer, hare, mink, otter ... and the wolf! In the bay, the ice is thick and smooth. They lace up their skates, step onto the ice, stroking and gliding, and the great lake sings again. In her signature poetic style, Jean E. Pendziwol describes the exhilarating experience of skating on the wild ice of Lake Superior, including the haunting singing that occurs as the ice expands and contracts. Accompanied by Todd Stewart's breathtaking illustrations, this book will make us all long to skate wild!\"-- Provided by publisher.
Book
Transcriptomic neuron types vary topographically in function and morphology
Neuronal phenotypic traits such as morphology, connectivity and function are dictated, to a large extent, by a specific combination of differentially expressed genes. Clusters of neurons in transcriptomic space correspond to distinct cell types and in some cases—for example,
Caenorhabditis elegans
neurons
1
and retinal ganglion cells
2
,
3
–
4
—have been shown to share morphology and function. The zebrafish optic tectum is composed of a spatial array of neurons that transforms visual inputs into motor outputs. Although the visuotopic map is continuous, subregions of the tectum are functionally specialized
5
,
6
. Here, to uncover the cell-type architecture of the tectum, we transcriptionally profiled its neurons, revealing more than 60 cell types that are organized in distinct anatomical layers. We measured the visual responses of thousands of tectal neurons by two-photon calcium imaging and matched them with their transcriptional profiles. Furthermore, we characterized the morphologies of transcriptionally identified neurons using specific transgenic lines. Notably, we found that neurons that are transcriptionally similar can diverge in shape, connectivity and visual responses. Incorporating the spatial coordinates of neurons within the tectal volume revealed functionally and morphologically defined anatomical subclusters within individual transcriptomic clusters. Our findings demonstrate that extrinsic, position-dependent factors expand the phenotypic repertoire of genetically similar neurons.
Transcriptomic profiling of neurons from the zebrafish optic tectum identified more than 60 cell types; functional imaging revealed that response tuning, morphology and connectivity of specific cell types vary systematically with the neurons’ positions in the tissue.
Journal Article