Venous velocity of the right femoral vein decreases in the right lateral decubitus position compared to the supine position: a cause of postoperative pulmonary embolism?

The right lateral decubitus position is a risk factor for postoperative pulmonary embolism. We examined postural changes of femoral vein velocity in order to elucidate the mechanism. Thirty patients scheduled for general thoracic surgery were enrolled in this study. The common femoral veins on both sides were examined by color-duplex ultrasound for venous caliber and velocity when the patients were in the right lateral, left lateral, and supine positions. The maximum diameters of the right femoral vein in the right lateral decubitus position and the left femoral vein in the left decubitus position were significantly larger than those in the other positions. The venous velocity of the right femoral vein in the right lateral decubitus position was significantly smaller than that in the supine position, while the velocity of the left femoral vein in the left lateral decubitus position was not significantly decreased. We speculate that the decreased venous velocity of the right femoral vein in the right lateral decubitus position could result in a deep venous thromboembolism in the right leg, making this position a possible risk factor for postoperative pulmonary embolism.</p

MyD88 Is Required for Protection from Lethal Infection with a Mouse-Adapted SARS-CoV

A novel human coronavirus, SARS-CoV, emerged suddenly in 2003, causing approximately 8000 human cases and more than 700 deaths worldwide. Since most animal models fail to faithfully recapitulate the clinical course of SARS-CoV in humans, the virus and host factors that mediate disease pathogenesis remain unclear. Recently, our laboratory and others developed a recombinant mouse-adapted SARS-CoV (rMA15) that was lethal in BALB/c mice. In contrast, intranasal infection of young 10-week-old C57BL/6 mice with rMA15 results in a nonlethal infection characterized by high titer replication within the lungs, lung inflammation, destruction of lung tissue, and loss of body weight, thus providing a useful model to identify host mediators of protection. Here, we report that mice deficient in MyD88 (MyD88−/−), an adapter protein that mediates Toll-like receptor (TLR), IL-1R, and IL-18R signaling, are far more susceptible to rMA15 infection. The genetic absence of MyD88 resulted in enhanced pulmonary pathology and greater than 90% mortality by day 6 post-infection. MyD88−/− mice had significantly higher viral loads in lung tissue throughout the course of infection. Despite increased viral loads, the expression of multiple proinflammatory cytokines and chemokines within lung tissue and recruitment of inflammatory monocytes/macrophages to the lung was severely impaired in MyD88−/− mice compared to wild-type mice. Furthermore, mice deficient in chemokine receptors that contribute to monocyte recruitment to the lung were more susceptible to rMA15-induced disease and exhibited severe lung pathology similar to that seen in MyD88−/−mice. These data suggest that MyD88-mediated innate immune signaling and inflammatory cell recruitment to the lung are required for protection from lethal rMA15 infection

Lung pathology in rMA15 infected WT and MyD88^−/− mice.

<p>To assess lung damage and pulmonary inflammation throughout the course of virus infection, we evaluated hematoxylin and eosin stained lung tissue sections from 2, 4 and 6 dpi. WT mice at 2 dpi exhibited pronounced lung inflammation characterized by perivascular cuffing (filled arrowhead), endothelial and epithelial atypia (vacuolization and disruption of normal epithelium and endothelium), with minor denuding bronchiolitis (empty arrowhead) as seen in MyD88^−/− mice. Similar to what was seen at early times post infection, WT mice on 4 dpi show an exacerbation of the inflammatory infiltrate (filled arrowhead) seen on 2 dpi, PBV edema was not observed. By 6 dpi, normal bronchiolar epithelial architecture is restored but inflammatory infiltrates are still present. At 2 dpi, MyD88-/- mice exhibited a denuding bronchiolitis characterized by an extrusion of airway epithelial cells into the lumen of the airway (empty arrowhead) and epithelial/endothelial atypia, but did not exhibit any obvious signs of inflammation like peribronchivascular (PBV) or peri-venular immune cell infiltration. On 4 dpi, MyD88^−/− mice continue to exhibit a denuding bronchiolitis (empty arrowhead), epithelial/endothelial atypia, and now show PBV edema without a pronounced immune cell infiltration around the airway though perivascular cuffing was observed (filled arrowhead). Interestingly, by 6 dpi, the severity of PBV edema and denuding bronchiolitis in MyD88^−/− mice had waned, and signs of immune cell infiltration were evident, with marked PBV infiltrates and perivascular cuffing (filled arrowhead) even more severe than that seen in WT mice at similar times post infection. Overall, the host immune response to the virus was similar in quality and quantity, but delayed in onset by 5–6 days in the MyD88^−/− mice. Vascular and bronchiolar lumen are labeled as VL and BL, respectively.</p

rMA15 induction of proinflammatory genes is reduced in MyD88^−/− mice.

<p>WT (black bars) and MyD88^−/− mice (white bars) were inoculated intranasally with PBS (grey bars) or 10⁵ pfu rMA15. At 2, 4, and 6 dpi, mice were euthanized and total lung RNA was analyzed for mRNA expression by qRT-PCR. Levels of gene transcription for Type I and Type III interferons (A), proinflammatory chemokines (B) and proinflammatory cytokines (C) were assessed. Data are normalized to 18S rRNA and are expressed as the relative fold increase over PBS inoculated mice. The data presented are the means from 3–4 mice per timepoint ± the standard error of the means. *, P<0.05.</p

Chemokine receptors contribute to protection from mouse-adapted SARS-CoV infection.

<p>To assess the importance of chemokine receptors in SARS-CoV pathogenesis we infected CCR1, CCR2, and CCR5 deficient mice with a recombinant mouse adapted SARS-CoV (rMA15). (A) Mice were monitored for changes in body weight at 24 h intervals. Each data point represents the mean ± the standard deviation. On days 3–14 dpi (*), the differences in the weights of CCR1 and CCR2 mice as compared to WT mice were statistically different by Mann-Whitney test with a P value cutoff of 0.05. On days 3–13 dpi (**), the differences in the weights of CCR5 deficient and WT mice were statistically different by Mann-Whitney test with a P value cutoff of 0.05 (B) Mice were monitored for mortality and the data is expressed as percent survival. (C) To assess the lung damage and degree of pulmonary inflammation in chemokine receptor deficient mice, we evaluated hematoxylin and eosin stained lung sections from 2 dpi. Signs of inflammation and virus induced lung pathology are evident in wild-type mice on 2 dpi with peribronchivascular cuffing (filled arrowhead) caused by infiltrating immune cells, apoptosis of the airway epithelium, and a mild denuding bronchiolitis (empty arrowhead). In contrast, mice deficient in either CCR1, CCR2, or CCR5 exhibited more prominent airway epithelial cell apoptosis, a severe denuding bronchiolitis with an accumulation of cohesive apoptotic debris within the airway (empty arrowhead) , and perivenular/periarterial cuffing (filled arrowhead) but there was a distinct lack of cuffing around the affected airways. Bronchiolar and vascular lumen is labeled as “BL” and “VL”, respectively.</p

Recruitment of inflammatory monocytes/macrophages to the SARS-CoV infected lung is delayed in MyD88^−/− mice as compared to WT mice.

<p>10 wk old B6 WT or MyD88^−/− mice were inoculated intranasally with PBS or 10⁵ pfu rMA15. (A) At 2 dpi, lung leukocytes were isolated as described in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1000240#s4" target="_blank">Materials and Methods</a> and analyzed by flow cytometry. Histograms are representative of three mice. Two independent experiments gave similar results. (B) Percent inflammatory monocytes/macrophages of total lung leukocytes isolated from mock (□), rMA15-infected WT (▪), or rMA15-infected MyD88^−/− (▪) mice at 2 dpi. (C) Total numbers of inflammatory monocytes/macrophages isolated from mock (□), rMA15-infected WT (▪), or rMA15-infected MyD88^−/− (▪) mice at 2 dpi. (D) Percent inflammatory monocytes/macrophages of total lung leukocytes (left panel) and total numbers of inflammatory monocytes/macrophages (right panel) isolated from mock (□), rMA15-infected WT (▪), or rMA15-infected MyD88-/-n (▪) mice at 4 dpi.</p

Virus replication is sustained and distribution is more widespread within the lungs of MyD88^−/− mice as compared to WT mice.

<p>5 µM paraffin-embedded sections derived from the lung tissue of WT and MyD88^−/− mice were hybridized with an ³⁵S-UTP-labeled riboprobe complementary to either the N gene of SARS-CoV (Urbani) or to the EBER2 gene from Epstein-Barr virus (data not shown). Images (magnification, 100×) are representative of at least three mice.</p