Geometry optimization of organometallic compounds using a modified extended-Hückel formalism

The modified extended-Huckel method suggested recently by Calzaferri and co-workers has been parametrized for organometallic compounds in order to have at hand a semiempirical tool allowing for rapid optimization of their geometries. The model is based on (i) the introduction of an approximate two-body repulsiveelectrostatic energy term and (ii) the use of a distance-dependent Wolfsberg-Helmholz formula, K = 1 + Ked(RAH-do)f, or 1-2 and 1-3 interactions. The optimum values for the K, 6 parameters determined for given classes of metalligand interactions have been found to be transposable to systems exhibiting several types of ligands such as aromatic rings, carbonyls, phosphines, etc. The overall performance of the model is satisfactory, as it leads for a series of more than 30 organometallic compounds to average error bars of 0.058 and 0.039 A on metal-ring and metal-carbonyl bond distances, respectively, and of 2.6' on bond angles

Application of a modified EHMO-ASED formalism to the determination of the structural parameters of organometallics

The parametrization of the EHMO-ASED method we have recently suggested for organometallics is shown to be also applicable, in principle without any modification, to derive the major structural parameters of second-row transition metal systems such as carbonyls or metallocenes. Furthermore, this model leads to satisfactory results when used to calculate the structure of compounds as large as (N-methylindole)tricarbonylchromium(0) or (phenylo.xazoline) tricarbonylchromlum(0) with full geometry optimization of the ligands

Quantum chemical investigation of the structure and reactivity of indole derivatives of tricarbonylchromium(0)

In a theoretical investigation of the structure and reactivity of indole derivatives of tricarbonylchromium(0), we have used two different semi-empirical quantum chemical models derived from the extended Hückel molecular-orbital (EHMO) formalism. The first one, based on the atom-superposition and electron-delocalization (ASED) method, is used to optimize the geometry of the systems; it is shown to lead to results in satisfactory agreement with experiment in the case of the complex for which X-ray structural data are available, the average errors being 0.03-0.05 Å for bond distances and 5° for bond angles. The second one consists of a local reactivity index, made of the intermolecular interaction energy between the organometallic substrate and a model reactant. It is seen that this procedure is able to reproduce the experimental trends as to the most reactive regions of the systems investigated towards nucleophilic and electrophilic addition reactions

Isolation and Characterization of a Primary Proximal Tubular Epithelial Cell Model from Human Kidney by CD10/CD13 Double Labeling

<div><p>Renal proximal tubular epithelial cells play a central role in renal physiology and are among the cell types most sensitive to ischemia and xenobiotic nephrotoxicity. In order to investigate the molecular and cellular mechanisms underlying the pathophysiology of kidney injuries, a stable and well-characterized primary culture model of proximal tubular cells is required. An existing model of proximal tubular cells is hampered by the cellular heterogeneity of kidney; a method based on cell sorting for specific markers must therefore be developed. In this study, we present a primary culture model based on the mechanical and enzymatic dissociation of healthy tissue obtained from nephrectomy specimens. Renal epithelial cells were sorted using co-labeling for CD10 and CD13, two renal proximal tubular epithelial markers, by flow cytometry. Their purity, phenotypic stability and functional properties were evaluated over several passages. Our results demonstrate that CD10/CD13 double-positive cells constitute a pure, functional and stable proximal tubular epithelial cell population that displays proximal tubule markers and epithelial characteristics over the long term, whereas cells positive for either CD10 or CD13 alone appear to be heterogeneous. In conclusion, this study describes a method for establishing a robust renal proximal tubular epithelial cell model suitable for further experimentation.</p></div

Sorting proximal tubular cells using specific antibodies.

<p>(A) Fluorescence plot showing cells labeled with antibodies against CD10 (APC: allophycocyanin) and CD13 (PE: phycoerythrin). FACS analysis revealed about 4% double-positive cells. (B) Fluorescence plot showing cells treated with isotypes to both antibodies to determine the upper threshold for non-specific fluorescence.</p

Evaluation of PT cells and CD10/CD13 double-negative cells phenotypic stability.

<p>(A) Fluorescence plot showing PT cells labeled with antibodies against CD10 (APC: allophycocyanin) and CD13 (PE: phycoerythrin) after four passages. Flow cytometry revealed about 94% double-positive cells. (B) Relative percentage of CD10/CD13 double-positive cells at passages 2, 3, 4 and 5 in the PT cells populations (n = 4). NS: non-significant (p>0.05). (C) Representative western blots for PT cells over 5 passages. Blots were incubated with antibodies against aquaporin-1, N-cadherin, MUC1. The β-actin protein was used as an internal control (D) Fluorescence plot showing the CD10/CD13 double-negative cell population labeled with antibodies against CD10 and CD13 after two passages. Flow cytometry revealed about 15% double-negative cells.</p

Expression of differentiation markers in different cell populations.

<p>Representative western blots for (1) unsorted cells, (2) CD10/CD13 double-positive cells, (3) CD10⁺ cells, (4) CD13⁺ cells and (5) CD10/CD13 double-negative cells. Blots were incubated with antibodies against aquaporin-1, N-cadherin, MUC1. The β-actin protein was used as an internal control. Proteins were extracted from cells at passage 2.</p

Continuous positive airway pressure for respiratory support during COVID-19 pandemic: a frugal approach from bench to bedside

International audienceBackground We describe a frugal approach (focusing on needs, performance, and costs) to manage a massive influx of COVID-19 patients with acute hypoxemic respiratory failure (AHRF) using the Boussignac valve protected by a filter (&quot;Filter Frugal CPAP&quot;, FF-CPAP) in and out the ICU.Methods (1) A bench study measured the impact of two filters with different mechanical properties on CPAP performances, and pressures were also measured in patients. (2) Non-ICU healthcare staff working in COVID-19 intermediate care units were trained with a video tutorial posted on a massive open online course. (3) A clinical study assessed the feasibility and safety of using FF-CPAP to maintain oxygenation and manage patients out of the ICU during a massive outbreak.Results: Bench assessments showed that adding a filter did not affect the effective pressure delivered to the patient. The resistive load induced by the filter variably increased the simulated patient's work of breathing (6-34%) needed to sustain the tidal volume, depending on the filter's resistance, respiratory mechanics and basal inspiratory effort. In patients, FF-CPAP achieved pressures similar to those obtained on the bench. The massive training tool provided precious information on the use of Boussignac FF-CPAP on COVID-19 patients. Then 85 COVID-19 patients with ICU admission criteria over a 1-month period were studied upon FF-CPAP initiation for AHRF. FF-CPAP significantly decreased respiratory rate and increased SpO(2). Thirty-six (43%) patients presented with respiratory indications for intubation prior to FF-CPAP initiation, and 13 (36%) of them improved without intubation. Overall, 31 patients (36%) improved with FF-CPAP alone and 17 patients (20%) did not require ICU admission. Patients with a respiratory rate &gt; 32 breaths/min upon FF-CPAP initiation had a higher cumulative probability of intubation (p &lt; 0.001 by log-rank test).Conclusion: Adding a filter to the Boussignac valve does not affect the delivered pressure but may variably increase the resistive load depending on the filter used. Clinical assessment suggests that FF-CPAP is a frugal solution to provide a ventilatory support and improve oxygenation to numerous patients suffering from AHRF in the context of a massive outbreak

Ultrastructural morphology of cells.

<p>PT cells at passage 4 were seeded onto (A) uncoated transwell filters (×20 000), (B, C) collagen IV-coated filters (×20 000, ×140 000) and (D) Matrigel®-coated filters (×12 000). CD10/CD13 double-negative cells at passage 4 were seeded onto (E) uncoated transwell filters (×12 000) and (F) collagen IV-coated filters (×20 000). PT cells displayed a polarized morphology and exhibited tight junctions (TJ), long microvilli (M) and desmosomes (D). CD10/CD13 double-negative cells displayed a polarized morphology and exhibited tight junctions and short microvilli.</p

Representative morphology of primary CD10/CD13 double-negative cells, CD10/CD13 cells double-positive, CD13⁺ and CD10⁺cells.

<p>(A) Primary cultures at passage 2 in serum-free medium. (B) Primary cultures at passage 2 in medium with 10% FBS. Magnification: ×100.</p