Cerebral Collateral Circulation in Carotid Artery Disease

Carotid artery disease is common and increases the risk of stroke. However, there is wide variability on the severity of clinical manifestations of carotid disease, ranging from asymptomatic to fatal stroke. The collateral circulation has been recognized as an important aspect of cerebral circulation affecting the risk of stroke as well as other features of stroke presentation, such as stroke patterns in patients with carotid artery disease. The cerebral circulation attempts to maintain constant cerebral perfusion despite changes in systemic conditions, due to its ability to autoregulate blood flow. In case that one of the major cerebral arteries is compromised by occlusive disease, the cerebral collateral circulation plays an important role in preserving cerebral perfusion through enhanced recruitment of blood flow. With the advent of techniques that allow rapid evaluation of cerebral perfusion, the collateral circulation of the brain and its effectiveness may also be evaluated, allowing for prompt assessment of patients with acute stroke due to involvement of the carotid artery, and risk stratification of patients with carotid stenosis in chronic stages. Understanding the cerebral collateral circulation provides a basis for the future development of new diagnostic tools, risk stratification, predictive models and new therapeutic modalities. In the present review we discuss basic aspects of the cerebral collateral circulation, diagnostic methods to assess collateral circulation, and implications in occlusive carotid artery disease

Extracorporeal membrane oxygenation for neonatal congenital diaphragmatic hernia: The initial single-center experience in Taiwan

Background/Purpose Extracorporeal membrane oxygenation (ECMO) is a treatment option for stabilizing neonates with congenital diaphragmatic hernia (CDH) in a critical condition when standard therapy fails. However, the use of this approach in Taiwan has not been previously reported. Methods The charts of all neonates with CDH treated in our institute during the period 2007–2014 were reviewed. After 2010, patients who could not be stabilized with conventional treatment were candidates for ECMO. We compared the demographic data of patients with and without ECMO support. The clinical course and complications of ECMO were also reviewed. Results We identified 39 neonates with CDH with a median birth weight of 2696 g (range, 1526–3280 g). Seven (18%) of these patients required ECMO support. The APGAR score at 5 minutes differed significantly between the ECMO and non-ECMO groups. The survival rate was 84.6% (33/39) for all CDH patients and 57.1% (4/7) for the ECMO group. The total ECMO bypass times in the survivors was in the range of 5–36 days, whereas all nonsurvivors received ECMO for at least 36 days (mean duration, 68 days). Surgical bleeding occurred in four of seven patients in the ECMO group. Conclusion The introduction of ECMO rescued some CDH patients who could not have survived by conventional management. Prolonged (i.e., > 36 days) ECMO support had no benefit for survival

Intravascular tissue reactions induced by various types of bioabsorbable polymeric materials: correlation between the degradation profiles and corresponding tissue reactions

Several different bioabsorbable polymeric coil materials are currently used with the goal of improving treatment outcomes of endovascular embolization of intracranial aneurysms. However, little is known about the correlation between polymer degradation profiles and concomitant tissue responses in a blood vessel. The authors describe in vitro degradation characteristics of nine different polymeric materials and their corresponding tissue responses induced in rabbit carotid arteries. Mass loss and molecular weight loss of nine commercially available bioabsorbable sutures were evaluated in vitro up to16 weeks. The same nine materials, as well as platinum coils, were implanted into blind-end carotid arteries (n = 44) in rabbits, and their tissue reactions were evaluated histologically 14 days after the implantation. Five of the nine polymers elicited moderate to strong tissue reactions relative to the remaining materials. While polymer mass loss did not correlate with their histologic findings, polymers that showed a faster rate of molecular weight loss had a tendency to present more active tissue reactions such as strong fibrocellular response around the implanted material with a moderate inflammatory cell infiltration. Maxon exhibited the fastest rate of molecular weight loss and poly-l-lactic acid the slowest. The rate of molecular weight loss may be an important factor that is associated with the degree of bioactivity when bioabsorbable polymers are implanted into blood vessels. For further quantitative analysis, additional experiments utilizing established aneurysm models need to be conducted

Function-Related Positioning of the Type II Secretion ATPase of <em>Xanthomonas campestris</em> pv. campestris

<div><p>Gram-negative bacteria use the type II secretion (T2S) system to secrete exoproteins for attacking animal or plant cells or to obtain nutrients from the environment. The system is unique in helping folded proteins traverse the outer membrane. The secretion machine comprises multiple proteins spanning the cell envelope and a cytoplasmic ATPase. Activity of the ATPase, when copurified with the cytoplasmic domain of an interactive ATPase partner, is stimulated by an acidic phospholipid, suggesting the membrane-associated ATPase is actively engaged in secretion. How the stimulated ATPase activity is terminated when secretion is complete is unclear. We fused the T2S ATPase of <i>Xanthomonas campestris</i> pv. campestris, the causal agent of black rot in the crucifers, with fluorescent protein and found that the ATPase in secretion-proficient cells was mainly diffused in cytoplasm. Focal spots at the cell periphery were detectable only in a few cells. The discrete foci were augmented in abundance and intensity when the secretion channel was depleted and the exoprotein overproduced. The foci abundance was inversely related to secretion efficiency of the secretion channel. Restored function of the secretion channel paralleled reduced ATPase foci abundance. The ATPase foci colocalized with the secretion channel. The ATPase may be transiently associated with the T2S machine by alternating between a cytoplasmic and a machine-associated state in a secretion-dependent manner. This provides a logical means for terminating the ATPase activity when secretion is completed. Function-related dynamic assembly may be the essence of the T2S machine.</p> </div

Augmentation of XpsE-ECFP foci abundance and intensity by depleting the <i>xpsD</i> gene and overexpressing α-amylase.

<p>Fluorescence microscopy of (A) plasmid-encoded XpsE-ECFP in <i>xpsD</i>⁻ (XC1708, top) or <i>xpsD</i>⁺ (XC1701, bottom), (B) chromosome-encoded XpsE-ECFP in <i>xpsD</i>⁻ (XC1753, top) or <i>xpsD</i>⁺ (XC1751, bottom) strain, and (C) chromosome-encoded XpsE-ECFP in <i>xpsD</i>⁻ (XC1753, top) or <i>xpsD</i>⁺ (XC1751, bottom) strain, each supplemented with the plasmid pAmy encoding the full-length α-amylase. Scale bar, 5 µm. (D) Quantitative analysis of foci abundance by plasmid-encoded XpsE-ECFP (p) or chromosome-encoded XpsE-ECFP (c) in the genetic background of <i>xpsD</i>⁺ or <i>xpsD</i>⁻, with or without overexpressed α-amylase (Amy). Data are mean foci counts per 60 cells from 3 independent fields. * P = 0.052; *** P<0.001.</p

A proposed model of the type II secretion system depicting secretion-coupled positioning of the ATPase.

<p>(A) Before the exoprotein (designated S) reaches the secretion channel containing secretin (designated D), the ATPase (designated E) is present in cytoplasm as an ATP-free monomer. (B) As the exoprotein stalls at the entrance of the secretion channel, the ATPase, as an ATP-bound hexamer, convenes to the membrane-bound machine by direct interaction with the bitopic cytoplasmic membrane protein L. (C) ATP hydrolysis by the ATPase presumably drives assembly of pseudopilus from pseudopilins (designated G, H, I, J, K), which are primarily localized in cytoplasmic membrane or in association with the presumed ‘platform’ of F protein, to push the exoprotein through the gated channel. (D) As the exoprotein successfully passes through the secretion channel, the ATPase disperses from a membrane-bound state to cytoplasm. The dynamic status of cytoplasmic membrane proteins (F, L, M, C) and pseudopilins is speculative. OM, CW and CM, outer membrane, cell wall and cytoplasmic membrane, respectively.</p

Fluorescence microscopy of the plasmid-encoded XpsE-ECFP complementing the <i>xpsE</i>-null strain.

<p>(A) Starch plate assay for α-amylase secretion. The parental strain (XC1701, designated as wt) and the <i>xpsE</i>-null strain (XC1723, designated as <i>xpsE</i>⁻) are positive and negative controls, respectively. XpsE-enhanced cyan fluorescent protein (ECFP) represents the presence of a plasmid carrying an <i>xpsE-ecfp</i> gene. (B) Immunoblot analysis of protein abundance of plasmid-encoded XpsE-ECFP in the parental (wt), the <i>xpsE</i>-null (<i>xpsE</i>⁻) strain or the strain lacking all <i>xps</i> genes (<i>xps</i>⁻) as detected by anti-XpsE antiserum (top panel), and its stability, as detected by anti-GFP antiserum (bottom panel). The numbers depict different transformants. The plasmid-encoded XpsE-ECFP is indicated by an arrow and the chromosomal XpsE by an arrowhead. * and **, cross-reactive band in the <i>X. campestris</i> pv. campestri cell lysate interacting with anti-XpsE and anti-GFP antisera, respectively. (C) Fluorescence microscopy images of the plasmid-encoded XpsE-ECFP in the <i>xpsE</i>-null (<i>xpsE</i>⁻) strain or the strain lacking all <i>xps</i> genes (<i>xps</i>⁻). In both cases, the transformant labeled #1 was examined. The parental strain (wt) expressing the XpsE devoid of ECFP is included as a negative control. Top: visualized for ECFP; middle: visualized for the fluorescent membrane dye FM4-64; bottom: merged fluorescent images of ECFP and FM4-64. XpsE-ECFP foci appearing at the cell periphery are indicated by an arrowhead. Scale bar, 5 µm.</p

Colocalization of chromosome-encoded XpsE-ECFP foci with those of secretin by confocal microscopy.

<p>The <i>xpsD</i>⁻ strain (XC1753) was supplemented with the partially functional XpsD(MH62) (the 1^st row) or secretion-proficient XpsD(MH64) (the 2^nd row) or the wild-type XpsD (the 3^rd row) or an empty vector (the 4^th row) and immunostained for XpsD::Myc with monoclonal antibody against Myc and fluorescence-labeled with Alexa Fluor 488. The XpsE-ECFP fluorescence is shown in green (left panels) and the immunostained XpsD::Myc in red (central panels). Shown in the last column are merged images (right panels). Scale bar, 2 µm.</p

Reduced XpsE-ECFP foci abundance parallelled by secretion recovery in the secretion channel.

<p>(A) Immunoblot analysis of protein level of XpsD in cellular fraction (labeled as C) and secreted α-amylase in supernatant (labeled as S). The <i>xpsD</i>⁻ mutant (XC1753) supplemented with the XpsD(MH62), wild-type XpsD (XpsD) or empty vector (vector) was grown in liquid media containing L-arabinose at increasing concentrations. Arrowhead indicates XpsD; *, cross-reactive band. (B) Quantitative analysis of XpsE-ECFP foci abundance in various strains grown in media with increasing concentrations of L-arabinose. Data are mean foci counts per 60 cells from 3 independent fields. *** P<0.001.</p