Association of perioperative plasma concentration of neurofilament light with delirium after cardiac surgery: a nested observational study

BACKGROUND

Neurofilament light is a blood-based biomarker of neuroaxonal injury that can provide insight into perioperative brain vulnerability and injury. Prior studies have suggested that increased baseline and postoperative concentrations of neurofilament light are associated with delirium after noncardiac surgery, but results are inconsistent. Results have not been reported in cardiac surgery patients, who are among those at highest risk for delirium. We hypothesised that perioperative blood concentrations of neurofilament light (both baseline and change from baseline to postoperative day 1) are associated with delirium after cardiac surgery.

METHODS

This study was nested in a trial of arterial blood pressure targeting during cardiopulmonary bypass using cerebral autoregulation metrics. Blood concentrations of neurofilament light were measured at baseline and on postoperative day 1. The primary outcome was postoperative delirium. Regression models were used to examine the associations between neurofilament light concentration and delirium and delirium severity, adjusting for age, sex, race, logistic European System for Cardiac Operative Risk Evaluation, bypass duration, and cognition.

RESULTS

Delirium occurred in 44.6% of 175 patients. Baseline neurofilament light concentration was higher in delirious than in non-delirious patients (median 20.7 pg ml-1 [IQR 16.1-33.2] vs median 15.5 pg ml-1 [IQR 12.1-24.2], P<0.001). In adjusted models, greater baseline neurofilament light concentration was associated with delirium (odds ratio, 1.027; 95% confidence interval, 1.003-1.053; P=0.029) and delirium severity. From baseline to postoperative day 1, neurofilament light concentration increased by 42%, but there was no association with delirium.

CONCLUSIONS

Baseline neurofilament light concentration, but not change from baseline to postoperative day 1, was associated with delirium after cardiac surgery.

Tissue factor targeting peptide enhances nanoparticle binding and delivery of a synthetic specialized pro-resolving lipid mediator to injured arteries

Background

Specialized pro-resolving lipid mediators (SPM) such as resolvin D1 (RvD1) attenuate inflammation and exhibit vasculo-protective properties.

Methods

We investigated poly-lactic-co-glycolic acid (PLGA)-based nanoparticles (NP), containing a peptide targeted to tissue factor (TF) for delivery of 17R-RvD1 and a synthetic analog 17-R/S-benzo-RvD1 (benzo-RvD1) using in vitro and in vivo models of acute vascular injury. NPs were characterized in vitro by size, drug loading, drug release, TF binding, and vascular smooth muscle cell migration assays. NPs were also characterized in a rat model of carotid angioplasty.

Results

PLGA NPs based on a 75/25 lactic to glycolic acid ratio demonstrated optimal loading (507.3 pg 17R-RvD1/mg NP; P = ns) and release of RvD1 (153.1 pg 17R-RvD1/mg NP; P < .05). NPs incorporating the targeting peptide adhered to immobilized TF with greater avidity than NPs with scrambled peptide (50 nM: 41.6 ± 0.52 vs 32.66 ± 0.34; 100 nM: 35.67 ± 0.95 vs 23.5 ± 0.39; P < .05). NPs loaded with 17R-RvD1 resulted in a trend toward blunted vascular smooth muscle cell migration in a scratch assay. In a rat model of carotid angioplasty, 16-fold more NPs were present after treatment with TF-targeted NPs compared with scrambled NPs (P < .01), with a corresponding trend toward higher tissue levels of 17R-RvD1 (P = .06). Benzo-RvD1 was also detectable in arteries treated with targeted NP delivery and accumulated at 10 times higher levels than NP loaded with 17R-RvD1. There was a trend toward decreased CD45 immunostaining in vessels treated with NP containing benzo-RvD1 (0.76 ± 0.38 cells/mm2 vs 122.1 ± 22.26 cells/mm2; P = .06). There were no significant differences in early arterial inflammatory and cytokine gene expression by reverse transcription-polymerase chain reaction.

Conclusions

TF-targeting peptides enhanced NP-mediated delivery of SPM to injured artery. TF-targeted delivery of SPMs may be a promising therapeutic approach to attenuate the vascular injury response.

Highly Atherogenic Lipid Particles are Associated with Preeclampsia After Successful Fertility Treatment for Obese Women who have Unexplained Infertility

Atherogenic dyslipidemia-before or during pregnancy-may contribute to preeclampsia and subsequent cardiovascular disease risk. We performed a nested case-control study to further understand dyslipidemia associated with preeclampsia. The cohort consisted of participants in the randomized clinical trial "Improving Reproductive Fitness Through Pretreatment with Lifestyle Modification in Obese Women with Unexplained Infertility" (FIT-PLESE). FIT-PLESE was designed to study the effect of a pre-fertility treatment 16-week randomized lifestyle intervention program (Nutrisystem diet + exercise + orlistat vs. training alone) on improvement in live birth rate among obese women with unexplained infertility. Of the 279 patients in FIT-PLESE, 80 delivered a viable infant. Maternal serum was analyzed across five visits: before and after lifestyle interventions and also at three pregnancy visits (16, 24, and 32 weeks gestation). Apolipoprotein lipids were measured in a blinded fashion using ion mobility. Cases were those who developed preeclampsia. Controls also had a live birth but did not develop preeclampsia. Generalized linear and mixed models with repeated measures were used to compare the mean lipoprotein lipid levels of the two groups across all visits. Complete data were available for 75 pregnancies, and preeclampsia developed in 14.5% of the pregnancies. Cholesterol/high-density lipoprotein (HDL) ratios (p < 0.003), triglycerides (p = 0.012), and triglyceride/HDL ratios, all adjusted for BMI, were worse in patients with preeclampsia (p < 0.001). Subclasses a, b, and c of highly atherogenic, very small, low-density lipoprotein (LDL) particles were higher during pregnancy for the preeclamptic women (p < 0.05). Very small LDL particle subclass d levels were significantly greater only at 24 weeks (p = 0.012). The role of highly atherogenic, very small LDL particle excess in the pathophysiology of preeclampsia awaits further investigation.

First record of Trichophyton benhamiae isolated from domestic cats in Russia

We report a first case of Trichophyton benhamiae isolation from domestic cats in Russia. Genetically affiliated to European strains T. benhamiae were deposited in NCBI. T. benhamiae strains formed zonal cream-colored colonies, with reversum pigmentation ranging from intensive yellow to orange-brown in one and orange-brown to chocolate in the second strain. Mycelium is colorless, hyphae are septated, rapidly aging with the formation of arthrospores and microconidia. The formation of macroconidia was recorded after 48 hours. A favorable outcome of treatment was recorded after two weeks.

Third year medical student knowledge gaps after a virtual surgical rotation

INTRODUCTION

This study describes perceived knowledge gaps of third-year medical students after participating in a virtual surgical didactic rotation (EMLR) and shortened in-person surgery rotation during the COVID-19 Pandemic.

METHODS

Open-ended and Likert questions were administered at the end of the virtual rotation and inperson-surgical rotation to medical students. Three blinded coders identified themes by semantic analysis.

RESULTS

82 students (51% of all MS3s) participated in the EMLR. Semantic analysis revealed gaps in perioperative management (Post-EMLR:18.4%, Post-Inpatient:26.5%), anatomy (Post-EMLR:8.2%, PostInpatient:26.5%). and surgical skills (Post-EMLR: 43.0%, Post-Inpatient: 44.1%). Students also described gaps related to OR etiquette (Post-EMLR: 12.2%, Post-Inpatient: 8.8%) and team dynamics/the hidden curriculum (Post- Inpatient:26.6%). There was a significant improvement in perceived confidence to perform inpatient tasks after completing the inpatient clinical experience (p ≤ 0.01).

CONCLUSION

Virtual interactive didactics for cognitive skills development cannot replace a full clinical surgical experience for third-year medical students. Future curricula should address perceived gaps.

17R/S-Benzo-RvD1, a synthetic resolvin D1 analogue, attenuates neointimal hyperplasia in a rat model of acute vascular injury

BACKGROUND

Persistent inflammation following vascular injury drives neointimal hyperplasia (NIH). Specialized lipid mediators (SPM) mediate resolution which attenuates inflammation and downstream NIH. We investigated the effects of a synthetic analogue of resolvin D1 (RvD1) on vascular cells and in a model of rat carotid angioplasty.

METHODS

Human venous VSMC and endothelial cells (EC) were employed in migration, cell shape, toxicity, proliferation and p65 nuclear translocation assays. Murine RAW 264.7 cells were utilized to test the effect of pro-resolving compounds on phagocytic activity. A model of rat carotid angioplasty was used to evaluate the effects of 17R/S-benzo-RvD1 (benzo-RvD1) and 17R-RvD1 applied to the adventitia via 25% Pluronic gel. Immunostaining was utilized to examine Ki67 expression and leukocyte recruitment. Morphometric analysis was performed on arteries harvested 14 days after injury.

RESULTS

Exposure to benzo-RvD1 attenuated PDGF- stimulated VSMC migration across a range of concentrations (0.1-100 nM), similar to that observed with 17R-RvD1. Pre-treatment with either Benzo-RvD1 or 17R-RvD1 (10, 100nM) attenuated PDGF-BB-induced VSMC cytoskeletal changes to nearly baseline dimensions. Benzo-RvD1 demonstrated modest anti-proliferative activity on VSMC and EC at various concentrations, without significant cytotoxicity. Benzo-RvD1 (10nM) inhibited p65 nuclear translocation in cytokine-stimulated EC by 21% (p<0.05), similar to 17R-RvD1. Consistent with pro-resolving activities of other SPM, both 17R-RvD1 and benzo-RvD1 increased the phagocytic activity of RAW 264.7 cells against S. Aureus and Zymosan particles. There were no significant differences in Ki-67 or CD45 staining observed on day 3 after angioplasty. Periadventitial treatment with benzo-RvD1 reduced carotid neointimal area at 14 days compared to control (0.08 mm2 v. 0.18 mm2; p<0.05), with similar efficacy to 17R-RvD1.

CONCLUSIONS

17R/S-benzo-RvD1 and 17R-RvD1 exhibit similar pro-resolving and anti-migratory activity in cell-based assays, and both compounds attenuated NIH following acute arterial injury in rats. Further studies of the mechanisms of resolution following vascular injury, and the translational potential of SPM analogues, are indicated.

Accuracy of self- and proxy-rated hearing among older adults with and without cognitive impairment

BACKGROUND

Hearing loss is highly prevalent among older adults with cognitive impairment and may exacerbate neuropsychiatric symptoms and affect interactions with others. Although audiometry is the gold standard for measuring hearing, it is not always used in research or clinical settings focused on the care of individuals with cognitive impairment. Subjective assessments of hearing, both self- and proxy-rated, are widespread but may not adequately capture the presence of hearing loss as compared to audiometry. This study investigates the concordance between subjective and objective hearing assessments among older adults with and without cognitive impairment and evaluates factors associated with concordance.

METHODS

Participants were a subset of the Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS), a prospective cohort study representing four US communities with adjudicated cognitive diagnoses and audiometric data, totaling 3326 self-rated and 520 proxy-rated hearing assessments. Sensitivity and specificity were calculated, and multivariable logistic regression estimated the magnitude of the association between the concordance of hearing assessments and variables of interest.

RESULTS

Sensitivity and specificity for self-rated hearing status were 71.2% and 85.9% among cognitively normal older adults, 61.1% and 84.9% among persons with MCI, and 52.6% and 81.2% among persons with dementia, respectively. For proxy-rated hearing, sensitivity and specificity were 65.7% and 83.3% for persons with MCI and 73.3% and 60.3% for persons with dementia, respectively. Female sex was positively associated with concordance for self-rated hearing assessments.

CONCLUSIONS

The low sensitivity of self- and proxy-rated hearing assessments compared to audiometry suggests that hearing loss among older adults with cognitive impairment may go underreported and unaddressed in subjective assessments. Clinicians and researchers should recognize the limitations of using self- and proxy-rated hearing assessments as measures of hearing status and incorporate objective audiometric evaluation whenever possible.

Prevalence of Tympanic Membrane Perforations Among Adolescents, Adults, and Older Adults in the United States

Tympanic membrane (TM) perforations can occur at any age, but limited population-level data are available. Using data from the National Health and Nutrition Examination Survey, we performed a cross-sectional analysis of the prevalence and population estimates for TM perforations among individuals ≥12 years old in the United States. Overall, TM perforations have a prevalence of 2.1% (95% CI, 1.7%-2.6%), corresponding to 5.8 million Americans. Across the life course, older adults have the highest prevalence of TM perforations at 6.1% (95% CI, 4.7%-7.6%), corresponding to nearly 3 million Americans, as opposed to a prevalence of 0.6% (95% CI, 0.3%-0.9%) in adolescents, which equates to 0.2 million Americans. Males and females have a similar prevalence at 2.3% (95% CI, 1.6%-3.0%) among males and 2.0% (95% CI, 1.4%-2.6%) among females. These prevalence and population estimates provide the first US-based population estimates of the burden of TM perforations over the life course.

The GSDMB rs7216389 SNP is associated with chronic rhinosinusitis in a multi-institutional cohort

BACKGROUND

Chronic rhinosinusitis (CRS) is a multifactorial disease with a high co-occurrence with asthma. In this multicohort study, we tested whether single nucleotide polymorphisms (SNPs) associated with childhood asthma and rhinovirus (RV)-associated disease are related to an increased susceptibility to adult CRS in a multicohort retrospective case-control study.

METHODS

Participants at two tertiary academic rhinology centers, University of Arizona (UofA) and University of Pennsylvania (UPenn) were recruited. Cases were defined as those with physician diagnosed CRS (UofA, n = 149; UPenn, n = 250), and healthy controls were those without CRS (UofA, n = 66; UPenn, n = 275). Genomic DNA was screened for the GSDMB rs7216389 SNP and CDHR3 rs6967330 SNP. Gene dosage, or the number of combined risk alleles in a single subject was calculated. Meta-analysis of the association between GSDMB or CDHR3 genotypes and CRS was performed and additive gene dosage effect for each population calculated using p for trend.

RESULTS

A meta-analysis revealed a combined increased risk for CRS in subjects with the GSDMB rs7216389 SNP (odds ratio [OR] 1.40; 95% confidence interval [CI], 1.16-1.76; p = 0.004). Both the UofA (OR 1.73; 95% CI, 1.23-2.43; p = 0.002) and UPenn (OR 1.27; 95% CI, 1.02-1.58; p = 0.035) populations showed a significant positive association between the number of combined risk alleles of GSDMB rs7216389 SNP and CDHR3 rs6967330 SNP and risk for CRS.

CONCLUSION

Carriers of the GSDMB rs7216389 SNP and CDHR3 rs6967330 SNP are at increased susceptibility for CRS. These data suggest that therapeutic approaches to target aberrant responses to RV infection may play a role in the treatment of unified airway disease.

Where Do We Go From Here? Assessing Medical Students' Surgery Clerkship Preparedness During COVID-19

INTRODUCTION

The impact of COVID-19 on surgical education has been profound, and clinical learning experiences transitioned to virtual formats. This study investigated the impact of virtual experiences created to facilitate learning during the pandemic for medical students.

METHODS

We performed a cohort study to determine the perceived clinical preparedness for medical students enrolled in the preclinical surgery pilot course, surgical Extended Mastery Learning Rotation (EMLR), and longitudinal surgical clerkship (LC). The preclinical surgery pilot course took place before COVID-19 disruptions, and the EMLR and LC experiences took place virtually. Specialty choice was examined in the EMLR and LC cohorts. Performance on the NBME surgical assessments was analyzed among students enrolled in the traditional clerkship and pandemic-disrupted courses and compared to national data using a two-sample t-test.

RESULTS

Compared to preclinical students, EMLR and LC students demonstrated improvements in their perceived surgical clerkship readiness. After the 3-week EMLR course, in the setting of completing only one-third of the clerkship year, students had an average NBME Surgical Self-Assessment Exam score of 72 (SD 12), comparable to the national average of 71 (SD 9) p = 0.33. The average shelf exam score for students (N = 24) enrolled in the traditional clerkship (block 1), prior to COVID-19, disruptions was 66 (SD 9) compared to an average score of 69 (SD 9) for the longitudinal clerkship students (N = 20) that took the shelf exam later in the year (p = 0.36). COVID-19 disruptions did not affect specialty choice. All LC students have decided on a specialty; 50% nonsurgical and 50% surgical. From the EMLR cohort, 36% and 38% plan to pursue surgical and nonsurgical specialties, respectively, with 26% still undecided.

CONCLUSIONS

Courses were well-liked and will be implemented in future clerkships. Surgical educators demonstrated flexibility and creativity in the development of the EMLR. Despite COVID-19 disruptions, medical students made progress in their clinical skills and foundational science knowledge. COVID-19 disruptions did not appear to impact specialty choice.

The variable direct cost and cost drivers of transoral endoscopic thyroidectomy vestibular approach

Background

As transoral endoscopic thyroidectomy vestibular approach grows in popularity, there is a need for data on cost in order to better characterize its value to patients. To this end, we compared the variable direct cost of transoral endoscopic thyroidectomy vestibular approach and transcervical approach thyroidectomy and determined which factors drive the increased cost for the transoral approach.

Methods

Patients undergoing thyroid lobectomy and total thyroidectomy that met inclusion criteria for transoral endoscopic thyroidectomy vestibular approach, including those patients that opted for management via the transcervical approach, between 8/2016 and 4/2019 were reviewed. The variable direct cost for the surgical encounter was collected and means were compared between the transoral and transcervical cohorts for lobectomy and total thyroidectomy respectively. The operative time independent variable direct cost was similarly compared between cohorts.

Results

Out of 238 patients, 118 (50%) were managed via transoral endoscopic thyroidectomy vestibular approach and 120 (50%) were managed via transcervical approach thyroidectomy. Mean variable direct cost, our primary outcome, was $4,455 (SD 1,129, 95% CI: 4,204-4,706) for transoral lobectomy and $3,179 (SD 687, 95% CI: 2,990-3,369) for transcervical lobectomy [t(132.05)=8.09, P<0.001] representing a difference in cost of $1,276 (SD 158, 95% CI: 964-1,587). Mean variable direct cost was $4,681 (SD 829, 95% CI: 4,405-4,957) for transoral total thyroidectomy and $3,645 (SD 876, 95% CI: 3,431-3,858) for transcervical total thyroidectomy [t(79.92)=5.98, P<0.001], representing a difference in cost of $1,036 (SD 173, 95% CI: 691-1,381). Differences in energy devices alone account for $487.53 and $447.96 of the cost differences, respectively.

Conclusions

The differences in mean variable direct cost between transoral endoscopic vestibular approach and transcervical approach for lobectomy and total thyroidectomy were $1276 and $1036 respectively, amounts far less than some believe them to be. This data will be invaluable as we ultimately aim to define the value of transoral endoscopic thyroidectomy vestibular approach.

[Small salivary glands in the paratonsillar space in children]

Was to study the changes in the small salivary glands in chronic tonsillitis and paratonsillar abscess in children. A histological examination of the palatine tonsils of 22 children aged 5 to 14 years old who had a paratonsillar abscess and 18 children suffering from chronic tonsillitis was carried out. Fragments of small salivary glands, located both superficially, in the mucous membrane between the stratified squamous non-keratinizing epithelium and the lymphoid tissue of the palatine tonsils, and between the muscles of the amygdala were found in 42 of the 80 (52.5%) tonsils studied. Along with the unchanged glandular structure, 26 (61.9%) samples revealed areas of destruction foci in small salivary glands with signs of inflammatory and compensatory regenerative activity. The presence of separate interlobular ducts of the salivary glands with pronounced periductal lymph - macrophage infiltration was noted. The subepithelial lymph-macrophage infiltrates found in the lamina propria are associated with the exit of the excretory ducts of the salivary glands to the surface of the mucous membrane. Many thin-walled veins are surrounded by perivascular lymphocellular infiltrates. The inflammatory and post-inflammatory changes in the small salivary glands revealed by us in children with chronic tonsillitis do not exclude their participation in the pathogenesis of paratonsillitis. At the same time, inflammation in the salivary gland can be both primary, as a result of its infection with live microorganisms from the tissues of the tonsil, and secondary, due to the compression of the excretory ducts by the edematous tissue of the tonsil in acute tonsillitis.

Surgery Clerkship Curriculum Changes at an Academic Institution during the COVID-19 Pandemic

PROBLEM

The COVID-19 pandemic has suspended the surgery clinical clerkship for third-year medical students at numerous institutions across the world. As a result, educators and students have adapted rapidly. There is a paucity of precedents regarding urgent and brusque formal curricular changes for medical students enrolled in surgical clinical rotations.

APPROACH

The University of California, San Francisco Department of Surgery created a surgically focused extended mastery learning rotation (EMLR). The surgery clerkship leadership designed a curriculum consisting of multiple learning strategies compatible with virtual learning environments. The primary aims of the newly developed EMLR were to help students consolidate their foundational science knowledge before their return to clinical medicine in an altered learning environment. The EMLR is currently underway, and further studies are necessary to evaluate its effectiveness.

Long-term Impact of Hearing Aid Provision or Cochlear Implantation on Hearing Handicap

OBJECTIVES/HYPOTHESIS

Previous research has shown hearing handicap to be reduced following hearing aid use or cochlear implantation in short-to-medium follow-up periods, yet the impact of interventions for hearing loss on hearing handicap in the long term remains understudied. This article reports hearing handicap at 6 months, 12 months, and 5 years after either hearing aid provision or cochlear implantation.

STUDY DESIGN

Observational study.

METHODS

A study of 115 participants from the Studying Multiple Outcomes after Aural Rehabilitative Treatment (SMART) study cohort assessed self-reported hearing handicap using the Hearing Handicap Inventory for the Elderly Screening version (HHIE-S) at baseline, 6 months, 12 months, and 5 years. Generalized estimating equations (GEE) were used to estimate the population mean HHIE-S score over time, accounting for the correlated nature of repeated measures data, and multiple imputation with chained equations was performed to impute missing data.

RESULTS

Compared to baseline, mean HHIE-S scores after hearing aid provision were significantly reduced at 6 months (mean = -7.96, 95% confidence interval [CI]: -10.40, -5.53), 12 months (mean = -6.58, 95% CI: -9.26, -3.90), and 5 years (mean = -4.58, 95% CI: -7.87, -1.30). After cochlear implantation, mean hearing handicap scores were also significantly lower compared to baseline at 6 months (mean = -8.18, 95% CI: -11.07, -5.30), 12 months (mean = -10.04, 95% CI: -12.92, -7.16), and 5 years (mean = -8.97, 95% CI: -12.92, -7.16).

CONCLUSIONS

This study found short-term benefits from hearing aids and cochlear implantation on hearing handicap were maintained over 5 years. Laryngoscope, 131:1122-1126, 2021.

Association of Hearing Loss With Neuropsychiatric Symptoms in Older Adults With Cognitive Impairment

Neuropsychiatric symptoms (NPS) in persons with dementia (PWD) are common and can lead to poor outcomes, such as institutionalization and mortality, and may be exacerbated by sensory loss. Hearing loss is also highly prevalent among older adults, including PWD.

OBJECTIVE

This study investigated the association between hearing loss and NPS among community- dwelling patients from a tertiary memory care center.

DESIGN, SETTING, AND PARTICIPANTS

Participants of this cross-sectional study were patients followed at the Johns Hopkins Memory and Alzheimer's Treatment Center who underwent audiometric testing during routine clinical practice between October 2014 and January 2017.

OUTCOME MEASUREMENTS

Included measures were scores on the Neuropsychiatric Inventory-Questionnaire and the Cornell Scale for Depression in Dementia.

RESULTS

Participants (n = 101) were on average 76 years old, mostly female and white, and had a mean Mini-Mental State Examination score of 23. We observed a positive association between audiometric hearing loss and the number of NPS (b = 0.7 per 10 dB; 95% confidence interval [CI]: 0.2, 1.1; t = 2.86; p = 0.01; df = 85), NPS severity (b = 1.3 per 10 dB; 95% CI: 0.4, 2.5; t = 2.13; p = 0.04; df = 80), and depressive symptom severity (b = 1.5 per 10 dB; 95% CI: 0.4, 2.5; t = 2.83; p = 0.01; df = 89) after adjustment for demographic and clinical characteristics. Additionally, the use of hearing aids was inversely associated with the number of NPS (b = -2.09; 95% CI -3.44, -0.75; t = -3.10; p = 0.003; df = 85), NPS severity (b = -3.82; 95% CI -7.19, -0.45; t = -2.26; p = 0.03; df = 80), and depressive symptom severity (b = -2.94; 95% CI: -5.93, 0.06; t = 1.70; p = 0.05; df = 89).

CONCLUSION

Among patients at a memory clinic, increasing severity of hearing loss was associated with a greater number of NPS, more severe NPS, and more severe depressive symptoms, while hearing aid use was associated with fewer NPS, lower severity, and less severe depressive symptoms. Identifying and addressing hearing loss may be a promising, low-risk, non-pharmacological intervention in preventing and treating NPS.

Long-Term Outcomes from an Intraoperative Bleb Needling Procedure Augmented with Continuous Infusion

PURPOSE

To investigate long-term outcomes of a modified bleb needling technique performed in the operating room in controlling intraocular pressure (IOP) and to report risk factors for procedure failure.

DESIGN

Retrospective, observational cohort study.

PARTICIPANTS

One hundred six eyes of 98 consecutive patients undergoing intraoperative bleb needling with a continuous infusion of balanced salt solution at the Wilmer Eye Institute, Johns Hopkins Hospital, in the setting of a failed trabeculectomy or express shunt, between May 2011 and December 2015.

METHODS

Postoperative data were collected between May 2011 and August 2019. Success was defined as achieving a previously determined target IOP regardless of (qualified success) or without (complete success) glaucoma medications. Patients who underwent additional glaucoma surgery were censored in the survival analysis.

MAIN OUTCOME MEASURES

Primary outcome measures included IOP, attainment of target IOP, and number of glaucoma medications used at different time points pre- and post-operatively.

RESULTS

Needling was performed in 106 eyes at an average of 4.3 years from the time of trabeculectomy (standard deviation [SD], 6.5 years) and an average baseline IOP of 20.7 mmHg (SD, 7.2 mmHg). Further glaucoma surgery was required for 33 eyes. We observed a 70% qualified success rate with a mean IOP lowering of 25% (95% confidence interval [CI], 13.8%-36.4%) at 1 year after surgery and a 52% qualified success rate and 44.3% reduction in IOP (95% CI, 34.9%-53.6%) at 5 years after surgery. Nearly half and a third of the eyes did not require medications after 1 and 5 years, respectively. The average medication reduction was 0.8 at year 1 (95% CI, 0.5-1.1) and 0.4 at year 5 (95% CI, -0.2 to 1.0). Postoperative complications were uncommon. Poorer outcomes were not associated with the age of the bleb but were more likely in Black patients.

CONCLUSIONS

Reductions in IOP were maintained in most patients over the long term using a modified bleb needling technique, despite an average time from trabeculectomy of over 4 years. No significant adverse events were observed. Bleb needling may defer or avoid more invasive procedures such as tube-shunts or repeat trabeculectomy.

Specialized pro-resolving lipid mediators in cardiovascular disease, diagnosis, and therapy

Persistent inflammation is the key aggravator in many cardiovascular diseases, including atherosclerosis, aneurysm, injury/reperfusion, thrombosis, and neointimal hyperplasia following surgical or percutaneous interventions. Resolution is an active process orchestrated by specialized pro-resolving lipid mediators (SPMs) which tamp down acute inflammatory signals, promote healing and facilitate a return to homeostasis. SPMs are endogenously derived from poly-unsaturated fatty acids, and their biologic activity is mediated via specific G-protein coupled receptor binding. The potency of SPM in regulating the inflammatory response has encouraged investigation into their therapeutic and diagnostic use in cardiovascular pathologies. Herein we describe the translational groundwork which has established the synthesis and interactions of SPM in cardiovascular and hematologic cells, the therapeutic effects of SPM in animal models of cardiovascular disease, and some early technologies that harness and attempt to optimize SPM delivery and "resolution pharmacology". Further studies are required to precisely determine the mechanisms of resolution in the cardiovascular system and to determine the clinical settings in which SPM can be utilized to optimize patient outcomes.

A Systematic Review of Exposure to Bisphenol A from Dental Treatment

INTRODUCTION

Dental composite restorations and dental sealants containing bisphenol A glycidyl methacrylate (BisGMA) are commonly used materials in dentistry. Bisphenol A (BPA) is used to manufacture BisGMA and can be a by-product in BisGMA-based dental materials. BPA is an endocrine-disrupting chemical that may affect reproductive, psychological, cognitive, and endocrine-related health. We conducted a systematic review of clinical studies that measured urinary BPA (uBPA) concentrations before and after dental treatment to evaluate the extent to which individuals are exposed to BPA from dental treatment.

METHODS

Eligibility included studies that measured uBPA concentrations before and after dental treatment with any type of resin-based dental material. We searched PubMed, Cochrane, Web of Science, Virtual Health Library, Science Direct, ProQuest, and Clinical Trials with no date or language restrictions to identify published studies. We summarized eligible studies across participant characteristics, amount of treatment, and time of follow-up measures. Because methods of measuring uBPA varied, our primary outcome was the direction and percentage change between baseline and 24 h posttreatment and at later time points as available.

RESULTS

We identified 1,190 abstracts and 7 eligible studies: 4 in children and 3 in adults. In all studies, BPA concentrations increased 24 h after treatment. The 2 studies with the largest sample sizes found statistically significant increases >40% in uBPA concentrations at 24 h posttreatment (both P values <0.01). The 1 study to examine uBPA concentrations beyond 1 mo posttreatment found that concentrations returned to baseline by 14 d after treatment and remained at baseline 6 mo after treatment.

CONCLUSIONS

Our findings suggest that uBPA concentrations increase 24 h after dental treatment. One study showed that uBPA concentrations return to baseline by 14 d. Additional research is needed to determine the magnitude of change from pre- to post-dental treatment and the trajectory of uBPA concentrations posttreatment.

KNOWLEDGE TRANSFER STATEMENT

BPA is an endocrine-disrupting chemical that may have negative human health effects. Our findings suggest that urinary BPA concentrations increase in the short term after dental treatment. The extent to which such an increase may affect the health of patients remains an open question, particularly since there are no established thresholds for safety or harm related to BPA exposure.

[The significance of antistreptolysin O characteristics for the determination of indications for tonsillectomy in the children]

The objective of the present work was to evaluate the diagnostic significance of the measurement of the antistreptolysin O (ASLO) titers in the children presenting with chronic tonsillitis for determining the indications for tonsillectomy. The study included 54 patients at the age varying from 4 to 17 years who had undergone bilateral tonsillectomy for the treatment of chronic tonsillitis. The diagnosis was confirmed by the results of the histological study of the removed amygdalae. Prior to surgery, all the patients had been subjected to the bacteriological investigation of the smears taken from the surface of the palatal tonsils. The titers of antistreptolysin O in the serum were determined with the use of the kinetic nephelometric technique before, 6 and 12 months after the surgical intervention. The results of the measurements were treated using the Statzilla software package (version 3.2, R Foundation for Statistical Computing, Vienna, Austria). Streptococcus pyogenes (group A) was identified only in 7 (13%) patients. The initially enhanced content of ASLO ranging from 273 to 1880 IU/ml was documented in 42 (77.7%) of the 54 patients. Twelve patients had the ASLO titers within the normal limits (from 13 to 124 IU/ml). The removal of palatal tonsils resulted in a significant decrease of the ASLO titers in the patients who had presented with the initially enhanced content of antistreptolysin O (p < 0.05); nevertheless, their ASLO titers remained higher than the normal values in 69% and 82% of the patients examined within 6 and 12 months after the surgical intervention, respectively. The patients who had exhibited the high levels of antistreptolysin O during the preoperative period did not experience normalization of this parameter after surgery. It is concluded, taking into account the absence of correlation between the enhancement of serum antistreptolysin O titers and the presence of group A beta-chemolytic Streptococci (BCSA), that the result of the measurement of ASLO titers can not be considered as a valid indication for tonsillectomy in the children.

[Proinflammatory cytokine content in the saliva of children suffering from chronic tonsillitis]

INTRODUCTION

We have examined 92 children aged between 6 and 15, suffering from chronic tonsillitis (CT). Tumor necrosis factor (TNF-α) and interleukin 1β and 6 (IL-1β and IL-6) contents have been defined in saliva. The control set comprised 17 healthy children. Cytokine content was defined with the enzyme multiplied immunoassay sets (Vektor Best Ltd., Russia) by enzyme-linked immunosorbent assay. The statistic analysis and data processing were carried out with statistic analysis programs (version 3.2, R Foundation for Statistical Computing, Vienna, Austria).

RESULTS

The content of cytokines TNF-α, IL-1, IL-6 in CT children's saliva was high against the healthy children, yet the statistically significant differences were only noted for IL-6. In the CT group the median value of this factor (12.5) was significantly higher than in the control set (6.72) (p=0.01 in Mann-Whitney assessment). IL-6 was chosen as the basic factor for the mathematic model; its combinations in the form of a multi-factor logistic regression were given consideration. From out of the three possible models there was just one that had all the coefficients statistically significantly different from zero (TNF-α - IL-6). It was chosen as the basic diagnostic model for chronic tonsillitis. The created model's sensitivity is 80.4%, while its specificity is 82.4%.

DISCUSSION

The revealed IL-6 dominance in saliva at CT can be is attributable to permanent antigenic challenge characteristic of the toxic allergic CT since, as previously shown, there are living proliferating microorganisms in the palatal tonsil tissues and their blood- and lymph vessels at CT.

CONCLUSION

The conducted ROC-analysis has demonstrated high sensitivity and specificity of the mathematical model, which enabled us to recommend determination of IL-6 in the saliva of the children suffering from CT as an additional diagnostic criterion.

The effect of maxillary sinus antrostomy size on the sinus microbiome

BACKGROUND

The optimal maxillary antrostomy size to surgically treat sinusitis is not well known. In this study, we examined clinical metrics of disease severity and symptom scores, measured secreted inflammatory markers, and characterized the sinus microbiome to determine if there were significant differences in outcome between different maxillary ostial sizes.

METHODS

Prospective randomized, single-blinded clinical trial enrolling 12 individuals diagnosed with recurrent acute or chronic rhinosinusitis. Each patient was blinded and randomized to receive minimal maxillary ostial dilation via balloon sinuplasty on 1 side vs a mega-antrostomy on the contralateral side. Data collected included symptom scores (20-item Sino-Nasal Outcome Test [SNOT-20]), endoscopy, and radiologic Lund-Mackay scores. During surgery and at their postoperative visit swabs were obtained from each maxillary sinus, and 16S DNA and inflammatory cytokine levels analyzed. The use of each patient as their own control allowed us to minimize confounding variables.

RESULTS

There was statistically significant improvement in SNOT-20 symptom scores postoperatively in all patients. There were no significant differences between maxillary ostial size in postoperative endoscopy scores, cytokine profile, or bacterial burden. There were statistically significant differences in relative postoperative abundance of Staphylococcus, Lactococcus, and Cyanobacteria between the mega-antrostomy and mini-antrostomy.

CONCLUSIONS

The method used in surgical maxillary antrostomies had no effect on endoscopy scores or cytokine profiles. Microbiome analysis determined significant differences between the different antrostomy sizes in postoperative Staphylococcus, Lactococcus, and Cyanobacteria abundance. The clinical significance of these changes in the sinus microbiome are not known but may be a result of increased access to postoperative sinonasal irrigations.

Dental Pathology of the California Bobcat (Lynx rufus californicus)

Skulls from 277 California bobcats (Lynx rufus californicus) were examined macroscopically and by radiography. The majority of the skulls were from adult animals (79.8%). The skulls were from 128 male (46.2%) and 114 female (41.2%) animals and gender was unknown for the remainder. The majority (95.6%) of teeth were present for examination. Only 16 teeth were identified as absent congenitally and 15 of these were incisor teeth. Teeth with abnormal morphology were rare (0.5%). The two most common abnormalities were unusually large crowns of the maxillary first molar teeth and bigemination of the mandibular incisor teeth. Teeth with an abnormal number of roots were uncommon (n = 68). Sixty-three teeth had abnormal roots, mostly the presence of two roots instead of one for the maxillary first molar tooth. The most prevalent dental lesions found in the California bobcat were attrition/abrasion (85.2%), periodontitis (56.0%) and tooth fractures (50.9%). Less common dental lesions were endodontal disease (n = 114 teeth) and tooth resorption (n = 73 teeth).

Early stroke risk and ABCD2 score performance in tissue- vs time-defined TIA: a multicenter study

OBJECTIVES

Stroke risk immediately after TIA defined by time-based criteria is high, and prognostic scores (ABCD2 and ABCD3-I) have been developed to assist management. The American Stroke Association has proposed changing the criteria for the distinction between TIA and stroke from time-based to tissue-based. Research using these definitions is lacking. In a multicenter observational cohort study, we have investigated prognosis and performance of the ABCD2 score in TIA, subcategorized as tissue-positive or tissue-negative on diffusion-weighted imaging (DWI) or CT imaging according to the newly proposed criteria.

METHODS

Twelve centers provided data on ABCD2 scores, DWI or CT brain imaging, and follow-up in cohorts of patients with TIA diagnosed by time-based criteria. Stroke rates at 7 and 90 days were studied in relation to tissue-positive or tissue-negative subcategorization, according to the presence or absence of brain infarction. The predictive power of the ABCD2 score was determined using area under receiver operator characteristic curve (AUC) analyses.

RESULTS

A total of 4,574 patients were included. Among DWI patients (n = 3,206), recurrent stroke rates at 7 days were 7.1%(95% confidence interval 5.5-9.1) after tissue-positive and 0.4% (0.2-0.7) after tissue-negative events (p diff < 0.0001). Corresponding rates in CT-imaged patients were 12.8% (9.3-17.4) and 3.0% (2.0-4.2), respectively (p diff < 0.0001). The ABCD2 score had predictive value in tissue-positive and tissue-negative events (AUC = 0.68 [95% confidence interval 0.63-0.73] and 0.73 [0.67-0.80], respectively; p sig < 0.0001 for both results, p diff = 0.17). Tissue-positive events with low ABCD2 scores and tissue-negative events with high ABCD2 scores had similar stroke risks, especially after a 90-day follow-up.

CONCLUSIONS

Our findings support the concept of a tissue-based definition of TIA and stroke, at least on prognostic grounds.

Prospective follow-up oral food challenge in food protein-induced enterocolitis syndrome

OBJECTIVES

To determine tolerance rates to cow's milk and soy and to suggest guidelines for follow-up oral food challenges (FU-OFCs) in infantile food protein-induced enterocolitis syndrome (FPIES).

METHODS

The authors analysed the data of 23 patients with infantile FPIES who underwent two or more FU-OFCs and were followed up until over 2 years of age. The first FU-OFCs were performed at 6 months of age, and patients were randomly allocated to cow's milk (n = 11) or soy (n = 12) challenge starting groups. Second and third FU-OFCs were performed at 2-month intervals in a crossed and switched-over manner.

RESULTS

Tolerance rates to cow's milk and soy were 27.3% and 75.0% at 6 months of age, 41.7% and 90.9% at 8 months and 63.6% and 91.7% at 10 months, respectively. Patients outgrew cow's milk and soy intolerance at age 20 and 14 months.

CONCLUSIONS

In infantile FPIES, the first FU-OFC should be performed with soy at 6-8 months of age and cow's milk FU-OFC should be conducted at over 12 months of age. Infants with FPIES were observed to outgrow food sensitivities during the first 2 years of life.

AMP-activated protein kinase: a core signalling pathway in the heart

Over the past decade, AMP-activated protein kinase (AMPK) has emerged as an important intracellular signalling pathway in the heart. Activated AMPK stimulates the production of ATP by regulating key steps in both glucose and fatty acid metabolism. It has an inhibitory effect on cardiac protein synthesis. AMPK also interacts with additional intracellular signalling pathways in a coordinated network that modulates essential cellular processes in the heart. Evidence is accumulating that AMPK may protect the heart from ischaemic injury and limit the development of cardiac myocyte hypertrophy to various stimuli. Heart AMPK is activated by hormones, cytokines and oral hypoglycaemic drugs that are used in the treatment of type 2 diabetes. The tumour suppressor LKB1 is the major regulator of AMPK activity, but additional upstream kinases and protein phosphatases also contribute. Mutations in the regulatory gamma2 subunit of AMPK lead to an inherited syndrome of hypertrophic cardiomyopathy and ventricular pre-excitation, which appears to be due to intracellular glycogen accumulation. Future research promises to elucidate the molecular mechanisms responsible for AMPK activation, novel downstream AMPK targets, and the therapeutic potential of targeting AMPK for the prevention and treatment of myocardial ischaemia or cardiac hypertrophy.

Permeate flux inflection due to concentration polarization in crossflow membrane filtration: A novel analytic approach

A convection-diffusion equation for membrane filtration is analytically solved assuming fast crossflow velocity of a simple shear flow tangential to the membrane surface. In the direction normal to the membrane surface, solute concentration varies in a partially exponential and partially power-wise manner. The permeate flux in an asymptotic limit is proportional to the inverse square root of the distance from the inlet of the membrane channel. Osmotic pressure due to retained solutes on the membrane surface controls the profile of the permeate flux, which undergoes an inflection along the tangential direction if applied pressure is more than four times the feed osmotic pressure.

Liver and circulating NK1.1(+)CD3(-) cells are increased in infection with attenuated Salmonella typhimurium and are associated with reduced tumor in murine liver cancer

An attenuated (DeltacyA, Deltacrp) strain of Salmonella typhimurium (chi4550) containing a gene for human IL-2 (chi4550pIL2) reduces hepatic tumor burden when orally inoculated into mice with liver cancer; however, wild-type S. typhimurium is also associated with cancer regression. Therefore, experiments were designed to clarify the invasiveness and the anti-tumor properties of three strains of S. typhimurium. S. typhimurium chi4550pIL2, chi4550, or wild type (WT) was incubated with mature Caco-2 and HT-29 enterocytes, and S. typhimurium internalization was assessed. For infectivity experiments, mice were orally inoculated with saline or 10(9)S. typhimurium chi4550pIL2, chi4550, or WT; 48 h later mice were sacrificed for analysis of cecal bacteria and S. typhimurium translocation to mesenteric lymph nodes. For experiments involving tumor implantation, four groups were studied: saline control, tumor alone, chi4550pIL2+tumor, and chi4550+tumor. Mice were orally inoculated with saline or S. typhimurium and underwent laparotomy 24 h later with 5 x 10(4) MCA38 murine adenocarcinoma cells injected into the spleen. On day 14, liver tumors were counted and peripheral blood and hepatic lymphocyte populations were analyzed by FACScan. Attenuated S. typhimurium exhibited decreased internalization by cultured enterocytes and decreased infectivity after oral inoculation. Mice treated with chi4550pIL2 or chi4550 had fewer liver tumors and increased populations of hepatic and circulating NK1.1(+)CD3(-) lymphocytes compared to mice treated with saline (P < 0.01). These data suggest that attenuated S. typhimurium may have an application as an anti-tumor agent.

A slow wave investigation of working memory biases in mood disorders

Mood-congruent working memory biases were examined in a delayed matching to sample paradigm using the slow wave (SW) event-related brain potential (ERP) component. Mood-congruent working memory biases, indexed by SW amplitudes, were demonstrated among individuals experiencing a major depressive episode (MDE) and nondepressed controls but not individuals with dysthymia. However, analyses of symptom severity demonstrated that those with dysthymia exhibited significantly less negative SW amplitudes with increasing depressive mood severity, whereas individuals with major depression demonstrated more negative SW amplitudes with increasing depressive mood severity. These results are discussed in the context of diagnostic specificity for cognitive biases associated with working memory of mood-disordered individuals.

Wnt receptors and Wnt inhibitors are expressed in gradients in the developing telencephalon

The caudomedial margin of the medial pallium, known as the cortical hem, expresses several Wnt genes that have been shown to be crucial for cortical development. We examined the expression of members of the Frizzled (mFz) family of Wnt receptors and the Secreted Frizzled Related Protein (SFRP) family of Wnt inhibitors during telencephalic development. We found that mFz-5 and mFz-8 are specifically expressed in the neocortical neuroepithelium and excluded from the hippocampal neuroepithelium in early telencephalic development, whereas mFz-9 and mFz-10 have expression domains confined to the medial pallium. In addition, SFRP-1 and SFRP-3 are expressed in opposing anterolateral to caudomedial gradients within the telencephalic ventricular zone throughout corticogenesis.

Pax-6 regulates expression of SFRP-2 and Wnt-7b in the developing CNS

Wnt signaling regulates a wide range of developmental processes such as proliferation, cell migration, axon guidance, and cell fate determination. In this report, we studied the expression of secreted frizzled related protein-2 (SFRP-2), which codes for a putative Wnt inhibitor, in the developing nervous system. SFRP-2 is expressed in several discrete neuroepithelial domains, including the diencephalon, the insertion of the eminentia thalami into the caudal telencephalon, and the pallial-subpallial boundary (PSB). We also noted that Wnt-7b expression was similar to SFRP-2 expression. Because many of these structures are disrupted in Pax-6 mutant mice, we examined SFRP-2 and Wnt-7b expression in the forebrains of Pax-6 Sey/Sey mice. We found that Pax-6 mutants lack SFRP-2 expression in the PSB and diencephalon. Interestingly, Pax-6 mutants also lack Wnt-7b expression in the PSB, but Wnt-7b expression in the diencephalon is preserved. Furthermore, in the spinal cord of Pax-6 mutants, SFRP-2 and Wnt-7b expression was greatly reduced. Our results suggest that by virtue of its apposition to Wnt-7b expression, SFRP-2 may modulate its function, particularly at boundaries such as the PSB, and that changes in Wnt signaling contribute to the phenotype of Pax-6 mutants.

Constitutively activating mutation in WASP causes X-linked severe congenital neutropenia

The Wiskott-Aldrich syndrome protein (WASP; encoded by the gene WAS) and its homologs are important regulators of the actin cytoskeleton, mediating communication between Rho-family GTPases and the actin nucleation/crosslinking factor, the Arp2/3 complex. Many WAS mutations impair cytoskeletal control in hematopoietic tissues, resulting in functional and developmental defects that define the X-linked Wiskott-Aldrich syndrome (WAS) and the related X-linked thrombocytopenia (XLT). These diseases seem to result from reduced WASP signaling, often through decreased transcription or translation of the gene. Here we describe a new disease, X-linked severe congenital neutropenia (XLN), caused by a novel L270P mutation in the region of WAS encoding the conserved GTPase binding domain (GBD). In vitro, the mutant protein is constitutively activated through disruption of an autoinhibitory domain in the wild-type protein, indicating that loss of WASP autoinhibition is a key event in XLN. Our findings highlight the importance of precise regulation of WASP in hematopoietic development and function, as impairment versus enhancement of its activity give rise to distinct spectra of cellular defects and clinical phenotypes.

A slow wave investigation of working memory biases in mood disorders

Mood-congruent working memory biases were examined in a delayed matching to sample paradigm using the slow wave (SW) event-related brain potential (ERP) component. Mood-congruent working memory biases, indexed by SW amplitudes, were demonstrated among individuals experiencing a major depressive episode (MDE) and nondepressed controls but not individuals with dysthymia. However, analyses of symptom severity demonstrated that those with dysthymia exhibited significantly less negative SW amplitudes with increasing depressive mood severity, whereas individuals with major depression demonstrated more negative SW amplitudes with increasing depressive mood severity. These results are discussed in the context of diagnostic specificity for cognitive biases associated with working memory of mood-disordered individuals.

Clostridium difficile toxins A and B can alter epithelial permeability and promote bacterial paracellular migration through HT-29 enterocytes

Clostridium difficile toxins A and B are the widely recognized etiologic agents of antibiotic-associated diseases ranging from diarrhea to pseudomembranous colitis. We hypothesized that C. difficile toxins may alter intestinal epithelial permeability and facilitate bacterial penetration of the intestinal epithelial barrier. Experiments were designed to clarify the effects of C. difficile toxins A and B on the flux of inert particles across HT-29 enterocyte monolayers, and to correlate these results with bacteria-enterocyte interactions. In all experiments, mature, confluent HT-29 cultures were preincubated 16 h with toxin A or B (1-100 ng/mL). To study alterations in epithelial permeability, toxin-treated enterocytes were incubated with 5 pM solutions of 10- and 40-kD inert dextran particles. Toxin A, but not toxin B, was associated with increased dextran flux through enterocyte monolayers. To study bacteria-enterocyte interactions, toxin-treated enterocytes were incubated with 10(8) Salmonella typhimurium, Proteus mirabilis, or Escherichia coli. Although numbers of internalized bacteria were generally unaffected, both toxins were associated with increased bacterial adherence, as well as increased bacterial transmigration through enterocyte monolayers. Bacterial transmigration was significantly greater using toxin A- compared to toxin B-treated enterocytes, consistent with the observation that dextran flux was significantly greater using toxin A- compared to toxin B-treated enterocytes. Thus intestinal colonization with toxigenic C. difficile may facilitate bacterial penetration of the intestinal epithelium by a mechanism involving increased permeability of the intestinal epithelial barrier.

Autoinhibition and activation mechanisms of the Wiskott-Aldrich syndrome protein

The Rho-family GTPase, Cdc42, can regulate the actin cytoskeleton through activation of Wiskott-Aldrich syndrome protein (WASP) family members. Activation relieves an autoinhibitory contact between the GTPase-binding domain and the carboxy-terminal region of WASP proteins. Here we report the autoinhibited structure of the GTPase-binding domain of WASP, which can be induced by the C-terminal region or by organic co-solvents. In the autoinhibited complex, intramolecular interactions with the GTPase-binding domain occlude residues of the C terminus that regulate the Arp2/3 actin-nucleating complex. Binding of Cdc42 to the GTPase-binding domain causes a dramatic conformational change, resulting in disruption of the hydrophobic core and release of the C terminus, enabling its interaction with the actin regulatory machinery. These data show that 'intrinsically unstructured' peptides such as the GTPase-binding domain of WASP can be induced into distinct structural and functional states depending on context.

Clostridium difficile toxins may augment bacterial penetration of intestinal epithelium

BACKGROUND

Clostridium difficile can be recovered from many high-risk hospitalized patients receiving broad-spectrum antibiotic therapy. Clostridium difficile toxins A and B have been associated with increased intestinal permeability in vitro and there is growing evidence that increased intestinal permeability may be a common mechanism whereby enteric bacteria penetrate the intestinal epithelium.

HYPOTHESIS

Clostridium difficile-induced alterations in the intestinal barrier facilitate microbial penetration of the intestinal epithelium, which in turn facilitates the translocation of intestinal bacteria.

DESIGN

Mature Caco-2 enterocytes were pretreated with varying concentrations of toxin A or toxin B followed by 1 hour of incubation with pure cultures of either Salmonella typhimurium, Escherichia coli, or Proteus mirabilis. The effects of toxins A and B on enterocyte viability, cytoskeletal actin, and ultrastructural topography were assessed using vital dyes, fluorescein-labeled phalloidin, and scanning electron microscopy, respectively. The toxins' effects on bacterial adherence and bacterial internalization by cultured enterocytes were assessed using enzyme-linked immunosorbent assay and quantitative culture, respectively. Epithelial permeability was assessed by changes in transepithelial electrical resistance and by quantifying paracellular bacterial movement through Caco-2 enterocytes cultivated on permeable supports.

RESULTS

Neither toxin A nor toxin B had a measurable effect on the numbers of enteric bacteria internalized by Caco-2 enterocytes; however, both toxins were associated with alterations in enterocyte actin, decreased transepithelial electrical resistance, and increased bacterial adherence and paracellular transmigration.

CONCLUSION

Clostridium difficile toxins A or B may facilitate bacterial adherence and penetration of the intestinal epithelial barrier.

Concentration Polarization of Interacting Solute Particles in Cross-Flow Membrane Filtration

A theoretical approach for predicting the influence of interparticle interactions on concentration polarization and the ensuing permeate flux decline during cross-flow membrane filtration of charged solute particles is presented. The Ornstein-Zernike integral equation is solved using appropriate closures corresponding to hard-spherical and long-range solute-solute interactions to predict the radial distribution function of the solute particles in a concentrated solution (dispersion). Two properties of the solution, namely the osmotic pressure and the diffusion coefficient, are determined on the basis of the radial distribution function at different solute concentrations. Incorporation of the concentration dependence of these two properties in the concentration polarization model comprising the convective-diffusion equation and the osmotic-pressure governed permeate flux equation leads to the coupled prediction of the solute concentration profile and the local permeate flux. The approach leads to a direct quantitative incorporation of solute-solute interactions in the framework of a standard theory of concentration polarization. The developed model is used to study the effects of ionic strength and electrostatic potential on the variations of solute diffusivity and osmotic pressure. Finally, the combined influence of these two properties on the permeate flux decline behavior during cross-flow membrane filtration of charged solute particles is predicted. Copyright 1999 Academic Press.