[Use of murine models for the study of obstructive sleep apnea syndrome in Down syndrome]

Down syndrome (DS), or trisomy 21, is a genetic disorder caused by the presence of an extra copy of chromosome 21, leading to various characteristic physical features as well as developmental and cognitive delays. Obstructive sleep apnea syndrome (OSAS) is a common disorder in both adult and pediatric patients with DS. Several characteristics of DS may contribute to the development or worsening of OSAS. Numerous murine models of DS exist. A number of studies have explored apneas and the risk of upper airway obstruction in these models, but up until now, only in adulthood.

Surgical management of vocal cord nodules in children: Trends and outcomes

OBJECTIVES

Vocal cord nodules (VCNs) are the most common cause of dysphonia in school-aged children, with potential negative impacts on quality of life including diminished self-esteem and academic performance. The standard of care for VCNs is conservative management which ranges from voice hygiene to speech therapy with a focus on voice otherwise known as voice therapy, with surgical excision reserved for refractory cases. Thus, few studies have analyzed outcomes of surgical management of VCNs. The purpose of this study is to assess the prevalence and efficacy of surgical excision of VCNs when compared to speech therapy.

METHODS

Children with VCNs seen at a single tertiary care institution between 2015 and 2020 were identified by ICD-9 code 478.5 and ICD-10 code J38.2. Demographics, objective voice assessment, intervention, and follow-up assessment data were reviewed. Frequencies, medians, and interquartile ranges were calculated. Time to resolution and improvement were assessed by Cox proportional hazards model. Univariate logistic regression was performed. A P value of <0.05 was considered statistically significant.

RESULTS

Three hundred sixty-eight patients diagnosed with VCNs were identified. 169 patients received intervention for VCNs, with 159 (43.2 %) receiving speech therapy alone and 5 (1.4 %) receiving surgery alone. On bivariate analysis, there was no significant difference in demographic features between treatment groups, however speech therapy patients did have a longer follow-up time. 154 patients underwent objective voice assessment at the time of VCN diagnosis. Among these patients, 95 (61.7 %) received speech therapy and 59 (40.3 %) received no intervention. Speech therapy patients had significantly higher pVHI scores, however there was no significant difference in CAPE-V Overall Severity scores or computerized voice assessment analysis. On Cox proportional hazards analysis, surgical intervention was associated with faster resolution and faster improvement of dysphonic symptoms. On binary logistic regression, surgery was associated with a significantly greater proportion of patients reporting resolution of dysphonic symptoms, however there was no significant difference in proportion of patients reporting improvement of dysphonia.

CONCLUSION

For most patients with VCNs, conservative measures such as voice hygiene and speech therapy remain first line, however certain patients may benefit from the rapid improvement and resolution of symptoms that surgical intervention may provide.

Characterizing Delirium and Associated Risk Factors Using the Cornell Assessment of Pediatric Delirium Score in Pediatric Burn Patients

Delirium is a syndrome of acute brain dysfunction with disturbance in consciousness and cognition that is increasingly recognized in critically ill pediatric patients. The Cornell Assessment of Pediatric Delirium (CAPD) tool is used to detect delirium in children of all ages and developmental stages in various hospital settings. To date, the incidence of delirium in the pediatric burn population has been poorly defined. In order to describe the incidence as well as risk factors for delirium in this patient population, we retrospectively reviewed patients <18 years of age admitted to our American Burn Association-verified pediatric burn center from March 2018 to May 2021 who underwent delirium screening using the CAPD tool. Patient demographics, burn characteristics, hospitalization details, and date of first positive delirium screening were collected, and χ2, Fisher's exact test, univariate, and multivariate analyses were performed. Delirium was identified in 42 (10.8%) of 389 patients meeting inclusion criteria. Patients screening positive for delirium were older (4 years [IQR: 2, 11] vs 2 years [IQR: 1, 6], P < .0005) and had larger TBSA burns (21.63% [IQR: 9, 42] vs 3.5% [IQR: 1.75, 6], P < .0001) than delirium-negative patients. Delirium-positive patients required a longer duration of mechanical ventilation (OR 4.23; 95% CI [1.16-15.39], P = .0289) and had higher TBSA burns (OR 1.12; 95% CI [1.06-1.17], P < .0001). Delirium-positive patients had 1.6 day longer length-of-stay adjusted for TBSA burned (95% CI [0.81-2.41], P < .0001). Compared to delirium-negative patients, delirium-positive patients had a 5.4-day longer PICU admission (95% CI [2.93-10.3]; P < .0001). Screening pediatric burn patients with risk factors known to be associated with delirium by using the CAPD score could improve delirium prevention and allow for early intervention.

Comparing recurrence between cautery techniques in pediatric epistaxis

OBJECTIVE

To compare the risk of recurrent epistaxis between children treated with silver nitrate (SN) in the office or electrocautery (EC) in the operating room (OR).

METHODS

Patients aged 2-18 diagnosed with epistaxis (ICD R04.0) in 2018 and treated with SN or EC were retrospectively reviewed. Epistaxis laterality, history of nasal trauma, and personal or family history of a bleeding disorder were recorded. Patients with prior cautery or epistaxis secondary to a procedure were excluded. Recurrence was defined as initial encounter after cautery with documented epistaxis. Patients were followed up into 2022 to track onset of recurrence. Time to recurrence between SN and EC was compared with hazard curves with predictors for recurrence analyzed via Cox's proportional hazard regression.

RESULTS

Among 291 patients cauterized for epistaxis, 62 % (n = 181) received SN compared to 38 % (n = 110) who underwent EC. There was significantly higher risk of recurrence when treated with SN compared to EC (Hazard ratio 2.45, 95 % CI: 1.57-3.82, P < 0.0001). Median time to recurrence was not statistically different between techniques (6.39 months (SN) (IQR: 2.33, 14.82) vs. 4.11 months (EC) (IQR: 1.18, 20.86), P = 0.4154). Complication rates were low for both groups (1.16 % (SN) vs. 0 % (EC), P > 0.05).

CONCLUSION

Among patients with epistaxis, risk of recurrence is significantly higher in those cauterized with SN compared to EC. Time to recurrence is not significantly different between cautery techniques.

Assessing the Relationship Between Infection Frequency and Risk of Post-Tonsillectomy Hemorrhage

OBJECTIVE

To determine the relationship between frequency of tonsillitis and the risk of post-tonsillectomy hemorrhage (PTH) in pediatric patients undergoing tonsillectomy for recurrent tonsillitis.

METHODS

After obtaining IRB approval from Nationwide Children's Hospital, charts for all patients who underwent a total tonsillectomy in 2017 for recurrent or chronic tonsillitis were retrospectively reviewed (n = 424). Patients were divided into 2 cohorts based on the frequency of tonsillitis prior to surgery: those meeting the 1-year criteria with 7 or more infections in the past year (n = 100), and those who did not meet criteria defined as those with fewer than 7 infections in the past year (n = 324). The primary outcome of interest was PTH. Comparison of cohorts and frequency of PTH were assessed using bivariate analyses. Kaplan-Meier curves were used to compare time to onset of hemorrhage between primary vs. secondary PTH. Generalized mixed and logistic regression models were used to evaluate risk of hemorrhage following tonsillectomy.

RESULTS

Among a total cohort of 424 patients undergoing tonsillectomy, 23.58% (n = 100) met criteria while 76.42% (n = 324) did not. A total of 8.73% (n = 37) patients experienced PTH. Compared to those who did not meet criteria, those who met criteria had a higher odds of developing PTH; however, this was not significant (OR: 1.42 [95% CI: 0.67, 2.98], P = .3582). Estimated probability of developing PTH for those who met criteria was 11% [95% CI: 6.19, 18.81] compared to 8.03% [95% CI: 5.52, 11.54] for those who did not meet criteria. Among all PTH cases, 5.41% (n = 2) were primary hemorrhage while 94.59% (n = 35) were secondary hemorrhage with 50% of those with secondary PTH having experienced hemorrhage within 6 days [95% CI: 5, 7] of tonsillectomy. Patients with neuromuscular conditions had significantly higher odds of PTH (OR: 4.75 [95% CI: 1.19, 18.97], P = .0276).

CONCLUSION

Patients who met the 1-year criteria for tonsillectomy did not have a significantly higher odds of PTH. Further research is needed to better evaluate the relationship between infection frequency and risk of PTH.

Legal epidemiology of paediatric dog bite injuries

BACKGROUND

Dog bite injuries cause over 100 000 paediatric emergency department visits annually. Our objective was to analyse associations between regional dog ownership laws and incidence of paediatric dog bites.

METHODS

This observational study used an online search to locate local dog-related policies within Ohio cities. Data collected by Ohio Partners For Kids from 2011 through 2020 regarding claims for paediatric dog bite injuries were used to compare areas with and without located policies and the incidence of injury.

RESULTS

Our cohort consisted of 6175 paediatric patients with dog bite injury encounters. A majority were white (79.1%), male (55.0%), 0-5 years old (39.2%) and did not require hospital admission (98.1%). Seventy-nine of 303 cities (26.1%) had city-specific policies related to dogs. Overall, the presence of dog-related policies was associated with lower incidence of dog bite injury claims (p=0.01). Specifically, metropolitan areas and the Central Ohio region had a significantly lower incidence when dog-related policies were present (324.85 per 100 000 children per year when present vs 398.56 when absent; p<0.05; 304.87 per 100 000 children per year when present vs 411.43 when absent; p<0.05).

CONCLUSIONS

The presence of city-specific dog-related policies is associated with lower incidence of paediatric dog bite injury claims, suggesting that local policy impacts this important public health issue. There are limited dog-related policies addressing dog bite prevention, with inconsistencies in breadth and depth. Creating consistent, practical requirements among policies with vigorous enforcement could ameliorate public health concerns from paediatric dog bite injuries.

Perceptions of telemedicine at a pediatric otolaryngology-head and neck surgery program

Objective

With few studies investigating the effectiveness of telemedicine (TM) in pediatric otolaryngology (ear, nose, and throat; ENT), its role in clinical practice is unclear. The objective of this study was to investigate provider perspectives regarding utility of TM in pediatric ENT practice.

Methods

A survey gauging the relative merits of TM visits for common pediatric ENT chief complaints and postoperative visits was distributed to all pediatric ENT providers at a tertiary care, free-standing children’s hospital. Respondents were asked to assess the effectiveness of TM visits compared with in-person visits for completing the following tasks: history collection, physical examination, medical decision-making, and patient counseling.

Results

Providers rated TM visits as less useful than in-person visits for completing the most predefined tasks but did identify advantages in history taking via TM for the majority of complaints. Compared with providers with ≥10 years of experience, those with <10 years of experience found TM to be more effective than the in-person appointment for making clinical decisions for patients presenting with recurrent/chronic pharyngitis, neck masses, and stridor/noisy breathing. Opinions regarding the utility of TM for postoperative visits were mixed, with adenoidectomy, tonsillectomy and superficial procedures being most frequently deemed appropriate for TM.

Conclusions

The introduction of TM to pediatric ENT faces limitations in detailed examination of areas not accessible without specialized instrumentation. Due to its strength in history taking, results suggest an asynchronous, ‘store and forward’ encounter followed by an in-person physical examination to confirm the diagnosis and treatment plan could be beneficial.

Pediatric dog bite injuries in the USA: a systematic review

Introduction

Dog bites are one of the leading causes of non-fatal emergency room visits in children. These injuries not only cause physical harm but can lead to long-term psychological stress. This study evaluated the current literature related to pediatric dog bite injuries to identify research gaps which should be prioritized to improve a major public health concern.

Methods

We performed a keyword search of PubMed, Scopus, and OVID Medline databases (January 1980– March 2020) for all published studies focused on dog bite injuries in the pediatric population (≤18 years of age) using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

Results

Out of 1859 abstracts screened, 43 studies involving 86 880 patients were included. Twenty-nine studies were retrospective chart reviews characterizing the epidemiology of dog bites and their associated treatment outcomes; six were prospective cohort studies; two were cross-sectional studies; and six were experimental studies. Synthesized results demonstrate that children <9 years of age suffer the greatest burden of injuries, with children <6 years of age at higher risk of more severe injuries involving the head, neck, and face.

Conclusion

Studies analyzing the prevention or psychosocial consequences of dog bites injuries are needed.

Assessing the use of telehealth for the surgical management of recurrent otitis media

OBJECTIVE

To compare the incidence of middle ear effusion (MEE) at the time of bilateral tympanostomy tube insertion (BTI) for recurrent acute otitis media (rAOM) patients initially seen in-office or via telehealth.

METHODS

After obtaining IRB approval from Nationwide Children's Hospital, a total of 524 patients evaluated for rAOM were retrospectively reviewed after being divided into two cohorts: those seen via a telehealth visit from April to June of 2020 (n = 140), and those seen via an in-person visit from April to June of 2019 (n = 384). Recommendation for BTI was captured for each patient following their visit. Clinical characteristics documented at the time of the visit, such as history of intramuscular (IM) antibiotic use and hearing or speech concerns were also captured to determine whether both telehealth and in-person cohorts were similar in clinical presentation. For BTI patients, the presence or absence of MEE in either ear at the time of BTI was recorded. Patients with cleft palate or prior BTI were excluded.

RESULTS

51.43% (72/140) of patients in the telehealth cohort were recommended for BTI. Of those recommended, 87.50% (63/72) underwent BTI. Of these, 31.75% (20/63) had a MEE at the time of BTI. In the in-office cohort, 69.01% (265/384) of patients were recommended for BTI. Of those recommended, 92.83% (246/265) underwent BTI. Of these, 69.92% (172/246) had a MEE at the time of BTI.

CONCLUSION

There were significantly less middle ear effusions in the telehealth cohort compared to the in-office cohort (p < 0.0001). It is well understood that telehealth is limited in its physical exam capabilities. It is possible that the use of telehealth for the surgical management of rAOM may lead to more procedures on patients without MEE.

Correlation of anorectal malformation complexity and associated urologic abnormalities

BACKGROUND

Patients with anorectal malformations (ARM) commonly have associated urologic anomalies. Few large studies exist to accurately characterize the incidence or associations between severity of malformation and urologic diagnosis. The purpose of our study was to determine the incidence of urologic diagnoses in a large cohort of children with ARM and evaluate for any correlation between severity of ARM and the incidence and number of associated urologic diagnoses.

METHODS

A retrospective review was performed of patients with ARM treated at our pediatric colorectal center. All patients underwent protocolized urologic screening. ARM subtypes were ordered with increasing severity as follows in males: perineal, bulbar, prostatic and bladder neck fistulae. Females were similarly categorized as perineal, vestibular and vaginal fistulae followed by cloaca with <3 cm common channel and cloaca with >3 cm common channel. The following urologic diagnoses were assessed to determine whether a correlation existed with the severity of the ARM subtype: hydronephrosis, vesicoureteral reflux (VUR), solitary kidney, renal ascent anomalies (ectopic or pelvic), renal fusion anomalies (horseshoe or cross fused kidney), duplex kidney, hypospadias and undescended testicle. ARM subtypes were defined by distal rectal anatomy.

RESULTS

A total of 712 patients were included in our study with a mean age of 4 years and of whom 45% were male. The overall rate of urologic anomalies was greater in males than females (65% vs 56% p < 0.026). In both sexes, the rate of urologic anomalies increased with increasing severity of ARM subtype (p<0.00010) finding that males with bladder neck fistula and females with cloacal malformations, particularly with long common channels, being the highest incidence. In males and females, the rate of hydronephrosis increased as the complexity of ARM increased and this correlated significantly (p < 0.0001 vs p < 0.0003 respectively). Similarly, the incidence of VUR also increased as complexity of ARM increased in both males and females (p = 0.01 and p<0.0001 respectively). The remaining urologic diagnoses were not significantly correlated with severity of ARM.

CONCLUSIONS

Urologic anomalies occur at a high rate in children with ARM and appear to increase in frequency with increasing complexity of ARM subtype. These findings stress the importance of proper ARM screening and proactive collaboration with a clinician with expertise in pediatric urology early in the management of such children to improve early recognition of urologic diagnoses.

LEVEL OF EVIDENCE

Level III.

Maternal dietary omega-3 deficiency worsens the deleterious effects of prenatal inflammation on the gut-brain axis in the offspring across lifetime

Maternal immune activation (MIA) and poor maternal nutritional habits are risk factors for the occurrence of neurodevelopmental disorders (NDD). Human studies show the deleterious impact of prenatal inflammation and low n-3 polyunsaturated fatty acid (PUFA) intake on neurodevelopment with long-lasting consequences on behavior. However, the mechanisms linking maternal nutritional status to MIA are still unclear, despite their relevance to the etiology of NDD. We demonstrate here that low maternal n-3 PUFA intake worsens MIA-induced early gut dysfunction, including modification of gut microbiota composition and higher local inflammatory reactivity. These deficits correlate with alterations of microglia-neuron crosstalk pathways and have long-lasting effects, both at transcriptional and behavioral levels. This work highlights the perinatal period as a critical time window, especially regarding the role of the gut-brain axis in neurodevelopment, elucidating the link between MIA, poor nutritional habits, and NDD.

Baseline Renal Volumes in Children Born With Cloacal Anomalies

OBJECTIVE

To better understand why children born with cloacal anomalies are at a high risk of renal insufficiency, this study aims to determine baseline renal volume in children with cloacal anomalies compared to controls. We hypothesized children with cloacal anomalies would be born with less renal volume.

METHODS

An IRB approved database of children with cloacal anomalies was reviewed. Controls were female patients with 2-vessel umbilical cord or preauricular tags who underwent screening renal ultrasound. Children were included if they had a renal ultrasound in the first 3 months of life. Cloacal exstrophy, horseshoe and cross-fused ectopic kidneys were excluded. Total and individual kidney volumes were compared between the 2 groups.

RESULTS

The study cohort consisted of 109 patients, 46 (42.2%) cloaca patients and 63 (57.8%) controls. In unadjusted analyses, average total renal volume for cloaca and control patients was 22.4 cm³ vs 25.5 cm³ respectively (P = .1006), and there was no significant difference when adjusting for age (P = .3915). The estimated difference in renal unit volume between cloaca patients without solitary kidneys and controls was -1.6 cm³ (95%C.I.: -3.6, 0.4; P = .1201), and there was no significant difference when adjusting for age (P = .4725). The age-adjusted difference in renal unit volume between cloaca patients with solitary kidney and controls was 1.8 cm³ (95%CI: -1.1, 4.8; P = .2148).

CONCLUSIONS

Children with cloacal anomalies have similar baseline renal volumes as children without cloacal anomalies. Therefore, the increased risk of renal insufficiency in this patient population appears to be due to renal injury postnatally.

The Association Between App-Administered Depression Assessments and Suicidal Ideation in User Comments: Retrospective Observational Study

Background

Many people use apps to help understand and manage their depression symptoms. App-administered questionnaires for the symptoms of depression, such as the Patient Health Questionnaire-9, are easy to score and implement in an app, but may not be accompanied by essential resources and access needed to provide proper support and avoid potential harm.

Objective

Our primary goal was to evaluate the differences in risks and helpfulness associated with using an app to self-diagnose depression, comparing assessment-only apps with multifeatured apps. We also investigated whether, what, and how additional app features may mitigate potential risks.

Methods

In this retrospective observational study, we identified apps in the Google Play store that provided a depression assessment as a feature and had at least five user comments. We separated apps into two categories based on those having only a depression assessment versus those that offered additional supportive features. We conducted theoretical thematic analyses over the user reviews, with thematic coding indicating the helpfulness of the app, the presence of suicidal ideation, and how and why the apps were used. We compared the results across the two categories of apps and analyzed the differences using chi-square statistical tests.

Results

We evaluated 6 apps; 3 provided only a depression assessment (assessment only), and 3 provided features in addition to self-assessment (multifeatured). User comments for assessment-only apps indicated significantly more suicidal ideation or self-harm (n=31, 9.4%) compared to comments for multifeatured apps (n=48, 2.3%; X²₁=43.88, P<.001). Users of multifeatured apps were over three times more likely than assessment-only app users to comment in favor of the app’s helpfulness, likely due to features like mood tracking, journaling, and informational resources (n=56, 17% vs n=1223, 59% respectively; X²₁=200.36, P<.001). The number of users under the age of 18 years was significantly higher among assessment-only app users (n=40, 12%) than multifeatured app users (n=9, 0.04%; X²₁=189.09, P<.001).

Conclusions

Apps that diagnose depression by self-assessment without context or other supportive features are more likely to be used by those under 18 years of age and more likely to be associated with increased user distress and potential harm. Depression self-assessments in apps should be implemented with caution and accompanied by evidence-based capabilities that establish proper context, increase self-empowerment, and encourage users to seek clinical diagnostics and outside help.

Respiratory viral panels and pediatric airway evaluation: The role of testing for upper respiratory infections to stratify perioperative risk

OBJECTIVES

Children admitted with stridor and respiratory distress comprise a complex patient group that requires the otolaryngologist to decide when to assess and intervene with direct laryngoscopy and bronchoscopy (DLB). Historically, the diagnosis of viral upper respiratory tract infection (URTI) can lead to postponement of surgery due to concerns of perioperative complications related to acute illness. Respiratory viral panels (RVP) are often used to confirm the presence of recent or active viral infection and can affect the differential diagnosis of upper airway obstruction. This study examined whether positive RVP testing is associated with perioperative complications and operative findings in pediatric patients undergoing inpatient DLB.

METHODS

A retrospective chart review of 132 pediatric patient encounters was performed. Viral testing results, DLB indication, DLB findings, and perioperative complications were compared.

RESULTS

Sixty encounters (45.5%) involved a positive RVP, and 72 (54.5%) involved a negative RVP. Those with positive RVP were less likely to have a preoperative structural airway diagnosis (P =.0250) and more likely to have a history of recurrent upper respiratory infections (P =.0464). The most common reason for DLB was the need to assess the airway due to concern for structural pathology. Anatomic abnormalities were seen in a majority of encounters (77.3%) Laryngospasm occurred in 1 (1.7%) RVP positive and 1 (1.4%) RVP negative encounter, and 2 (2.8%) RVP negative encounters required reintubation. No other major complications were observed. No association was noted between RVP results and incidence of major or minor complication.

CONCLUSIONS

Major perioperative complications after surgical intervention with DLB for the management of complex, inpatient children with stridor and respiratory distress are rare. RVP positivity, specific pathogens identified on RVP, and presence of URI symptoms were not associated with perioperative complications.

Evidence for a role of oestrogen receptor-related receptor in the regulation of male sexual behaviour in the moth Agrotis ipsilon

The oestrogen receptor-related receptors (ERRs) are orphan nuclear receptors that were originally identified on the basis of their close homology to the oestrogen receptors. The three mammalian ERR genes participate in the regulation of vital physiological processes including reproduction, development and metabolic homeostasis. Although unique ERRs have been found in insects, data on the function and regulation of these receptors remain sparse. In the present study, a 2095-bp full-length cDNA encoding an ERR, termed AiERR, was isolated from males of the moth Agrotis ipsilon and deposited in the GenBank database under the accession number KT944662. The predicted AiERR protein shared an overall identity of 47-82% with other known insect and mammalian ERR homologues. AiERR exhibited a broad tissue expression pattern with the detection of one transcript of approximately 2 kb in the primary olfactory centres, the antennal lobes (AL). In adult males, the amount of AiERR mRNA in the AL increased concomitantly with age and responses to the female-emitted sex pheromone. Moreover, AiERR knockdown induced an inhibition in the sex pheromone-orientated flight of male. Using A. ipsilon as a model, our study demonstrates that the insect ERR is critical for the performance of male sexual behaviour, probably by acting on central pheromone processing.

Two-dimensional gel proteome reference map of blood monocytes

Background:

Blood monocytes play a central role in regulating host inflammatory processes through chemotaxis, phagocytosis, and cytokine production. However, the molecular details underlying these diverse functions are not completely understood. Understanding the proteomes of blood monocytes will provide new insights into their biological role in health and diseases.

Results:

In this study, monocytes were isolated from five healthy donors. Whole monocyte lysates from each donor were then analyzed by 2D gel electrophoresis, and proteins were detected using Sypro Ruby fluorescence and then examined for phosphoproteomes using ProQ phospho-protein fluorescence dye. Between 1525 and 1769 protein spots on each 2D gel were matched, analyzed, and quantified. Abundant protein spots were then subjected to analysis by mass spectrometry. This report describes the protein identities of 231 monocyte protein spots, which represent 164 distinct proteins and their respective isoforms or subunits. Some of these proteins had not been previously characterized at the protein level in monocytes. Among the 231 protein spots, 19 proteins revealed distinct modification by protein phosphorylation.

Conclusion:

The results of this study offer the most detailed monocyte proteomic database to date and provide new perspectives into the study of monocyte biology.

Distinct proteome features of plasma microparticles

Plasma microparticles (MPs) are spherical cell membrane fragments derived from either apoptotic or activated cells. Characterized by a rich phospholipid moiety and many protein constituents, MPs normally circulate in the blood and contribute to numerous physiological processes. In disease states, MPs derived from the injured organ likely contain valuable markers for determining the site, type, and extent of disease pathology. However, the basic protein characteristics of plasma MPs have yet to be described. In this study, MPs from a pooled plasma sample derived from 16 healthy donors, all of group A blood type, were prepared by ultracentrifugation. Flow cytometry confirmed that a majority of these MPs are smaller than 1 microm. Factor Xa generation assay revealed the presence of tissue factor activity in these MPs, confirming MPs' role in initiating blood coagulation. The MP proteome was analyzed by two-dimensional (2-D) gel electrophoresis performed in triplicate, and compared with a 2-D gel of pooled whole plasma and blood platelets. Overall, plasma MPs displayed distinct protein features and a greater number of protein spots (1021-1055) than that detected in whole plasma (331-370). Protein spots expressed in high abundance in the MP proteome were then excised and submitted for protein identity determination. This process provided protein identification for 169 protein spots and reported their relative protein quantities within the MP proteome. These 169 protein spots represented 83 different proteins and their respective isoforms. Thirty of these proteins have never before been reported in previous proteome analyses of human plasma. These results provide unprecedented information on the MP proteome and create a basis for future studies to understand MP biology and pathophysiology.