A heterogenous population of extracellular vesicles mobilize to the alveoli postinjury

BACKGROUND

Acute lung injury and subsequent resolution following severe injury are coordinated by a complex lung microenvironment that includes extracellular vesicles (EVs). We hypothesized that there is a heterogenous population of EVs recruited to the alveoli postinjury and that we could identify specific immune-relevant mediators expressed on bronchoalveolar lavage (BAL) EVs as candidate biomarkers of injury and injury resolution.

METHODS

Mice underwent 30% TBSA burn injury and BAL fluid was collected 4 hours postinjury and compared with sham. Extracellular vesicles were purified and single vesicle flow cytometry (vFC) was performed using fluorescent antibodies to quantify the expression of specific cell surface markers on individual EVs. Next, we evaluated human BAL specimens from injured patients to establish translational relevance of the mouse vFC analysis. Human BAL was collected from intubated patients following trauma or burn injury, EVs were purified, then subjected to vFC analysis.

RESULTS

A diverse population of EVs were mobilized to the alveoli after burn injury in mice. Quantitative BAL vFC identified significant increases in macrophage-derived CD44+ EVs (preinjury, 10.8% vs. postinjury, 13%; p < 0.05) and decreases in IL-6 receptor alpha (CD126) EVs (preinjury, 19.3% vs. postinjury, 9.3%, p < 0.05). Bronchoalveolar lavage from injured patients also contained a heterogeneous population of EVs derived from myeloid cells, endothelium, and epithelium sources, with CD44+ EVs being highly detected.

CONCLUSION

Injury causes mobilization of a heterogeneous population of EVs to the alveoli in both animal models and injured patients. Defining EV release after injury will be critical in identifying diagnostic and therapeutic targets to limit postinjury acute lung injury.

Funding the war in America: A look in the mirror

BACKGROUND

Health care political action committees (HPACs) historically contribute more to candidates opposing firearm restrictions (FRs), clashing with their affiliated medical societies. These societies have increasingly emphasized the prevention of firearm violence and it is not known if recent contributions by their HPACs have aligned with their stated goals. We hypothesized that such HPACs still contribute similar amounts toward legislators up for reelection opposing FR.

METHODS

We identified HPACs of medical societies endorsing one or both calls-to-action against firearm violence published in the Annals of Internal Medicine (2015, 2019). House of Representatives (HOR) votes on H.R.8, a background checks bill, were characterized from GovTrack. We compiled HPAC contributions between the H.R.8 vote and election to HOR members up for re-election from the National Institute on Money in Politics. Our primary outcome was total campaign contributions by H.R.8 stance. Secondary outcomes included percentage of politicians funded and total contributions.

RESULTS

Nineteen societies endorsed one or both call-to-action articles. Three hundred eighty-five of 430 HOR members ran for reelection in 2020. Those endorsing H.R.8 (n = 226, 59%) received $2.8 M for $4,750 (interquartile range [IQR], $1000-$15,500) per candidate. Those opposing (n = 159, 41%) received $1.5 M for $2,500 (IQR, $0-$11,000) per candidate ( p = 0.0057). Health care political action committees donated toward a median of 20% (IQR, 7-28) of candidates endorsing H.R.8 and 9% (IQR, 4-22) of candidates opposing H.R.8 ( p = 0.0014). Those endorsing H.R.8 received 1,585 total contributions for a median of 3 (IQR, 1-10) contributions per candidate, while those opposing received 834 total contributions for a median of 2 (IQR, 0-7) contributions per candidate ( p = 0.0029).

CONCLUSION

Politicians voting against background checks received substantial contributions toward reelection from the HPACs of societies advocating for firearm restrictions. However, this is the first study to suggest that HPAC's contributions have become more congruent with their respective societies. Further alignment of medical society goals and their HPAC political contributions could have a profound impact on firearm violence.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level III.

A majority of trauma-related deep venous thromboses resolve prior to discharge

Post-traumatic DVTs present unique challenges in patient populations with specific high-risk injury patterns. Duplex ultrasound (US) can be used to assess evolution of DVTs and may guide treatment for high-risk patients. We hypothesized that many DVTs resolve during the initial admission. Weekly duplex US are ordered on all trauma inpatients regardless of prior DVT at our facility. We reviewed US and outcomes data on all patients with lower extremity DVTs at our Level I trauma center from January 2012-December 2021. 392 patients were diagnosed with lower extremity DVT by US. 261 (67%) patients received follow-up US with a mean time to repeat US of 6 days. Of these, 91 (35%) patients experienced DVT resolution prior to the first follow-up US, and 141 (54%) patients experienced resolution prior to discharge. Mean time to resolution was 10 days. Over 50% of DVTs resolve before discharge and are detected by US. Further studies and post-discharge follow-up are needed to determine if patients with resolved DVTs can be managed without therapeutic anticoagulation.

Post-traumatic Liver Pseudoaneurysms: Rare but Serious Sequela

INTRODUCTION

The liver is the most commonly injured organ after blunt abdominal trauma. Nonoperative management is the standard of care in stable individuals. Liver injuries, particularly high-grade injuries, can develop pseudoaneurysms (PSAs), which can rupture and cause life-threatening bleeding, even after hospital discharge. There is no consensus on whether patients should receive predischarge contrast computed tomography (CT) screening, or at what time interval after injury, nor which patients are at the highest risk for PSA. The purpose of this study was to identify the rates of PSA in our population and potential risk factors for their formation.

METHODS

The trauma registry at our Level 1 urban trauma center was queried for patients admitted with liver injuries between 2015 and 2021. Demographic information was collected from the registry. Individual charts were then reviewed for timing of CT scans, CT findings, interventions, and complications. Liver injury grade was assessed using radiology reports or operative findings. The frequency of PSAs was then analyzed using descriptive statistics using Microsoft Excel and SPSS for odds ratio.

RESULTS

A total of 172 patients were admitted with liver injuries during the study period. 130 patients received a CT scan diagnosing liver injury, 42 were diagnosed with liver injury intraoperatively. Of the 130 patients (59.9%) which received follow-up CT scans, six (6.5%) developed PSA, four of which being from penetrating injuries (odds ratio, 6.95).

CONCLUSIONS

This study demonstrated a low incidence of PSA consistent with the known literature. We found the majority of the PSA developed following penetrating injury. This may represent a significant indication for follow-up imaging regardless of grade. A larger study will be necessary to identify those most at risk for PSA formation and determine the best PSA screening algorithm.

And Miles to Go Before We Sleep: EAST Diversity and Inclusivity Progress and Remaining Challenges

OBJECTIVE

The aim of this study was to examine the diversity, equity, and inclusion landscape in academic trauma surgery and the EAST organization.

SUMMARY BACKGROUND DATA

In 2019, the Eastern Association for the Surgery of Trauma (EAST) surveyed its members on equity and inclusion in the #EAST4ALL survey and assessed leadership representation. We hypothesized that women and surgeons of color (SOC) are underrepresented as EAST members and leaders.

METHODS

Survey responses were analyzed post-hoc for representation of females and SOC in academic appointments and leadership, EAST committees, and the EAST board, and compared to the overall respondent cohort. EAST membership and board demographics were compared to demographic data from the Association of American Medical Colleges.

RESULTS

Of 306 respondents, 37.4% identified as female and 23.5% as SOC. There were no significant differences in female and SOC representation in academic appointments and EAST committees compared to their male and white counterparts. In academic leadership, females were underrepresented ( P < 0.0001), whereas SOC were not ( P = 0.08). Both females and SOC were underrepresented in EAST board membership ( P = 0.002 and P = 0.043, respectively). Of EAST's 33 presidents, 3 have been white women (9%), 2 have been Black, non-African American men (6%), and 28 (85%) have been white men. When compared to 2017 AAMC data, women are well-represented in EAST's 2020 membership ( P < 0.0001) and proportionally represented on EAST's 2019-2020 board ( P > 0.05).

CONCLUSIONS

The #EAST4ALL survey suggests that women and SOC may be underrepresented as leaders in academic trauma surgery. However, lack of high-quality demographic data makes evaluating representation of structurally marginalized groups challenging. National trauma organizations should elicit data from their members to re-assess and promote the diversity landscape in trauma surgery.

Decreasing use of pancreatic necrosectomy and NSQIP predictors of complications and mortality

BACKGROUND

Surgical pancreatic necrosectomy (SPN) is an option for the management of infected pancreatic necrosis. The literature indicates that an escalating, combined endoscopic, interventional radiology and minimally invasive surgery "step-up" approach, such as video-assisted retroperitoneal debridement, may reduce the number of required SPNs and ICU complications, such as multiple organ failure. We hypothesized that complications for surgically treated severe necrotizing pancreatitis patients decreased during the period of adoption of the "step-up" approach.

METHODS

The American college of surgeons national surgery quality improvement program database (ACS-NSQIP) was used to find SPN cases from 2007 to 2019 in ACS-NSQIP submitting hospitals. Mortality and Clavien-Dindo class 4 (CD4) ICU complications were collected. Predictors of outcomes were identified by univariate and multivariate analyses.

RESULTS

There were 2457 SPN cases. SPN cases decreased from 0.09% in 2007 to 0.01% in 2019 of NSQIP operative cases (p < 0.001). Overall mortality was 8.5% and did not decrease with time. CD4 complications decreased from 40 to 27% (p < 0.001). There was a 65% reduction in SPN cases requiring a return to the operating room. Multivariate predictors of complications were emergency general surgery (EGS, p < 0.001), serum albumin (p < 0.0001) and modified frailty index (mFI) (p < 0.0001). Multivariate predictors of mortality were EGS (p < 0.0001), serum albumin (p < 0.0001), and mFI (p < 0.04). The mFI decreased after 2010 (p < 0.001).

CONCLUSION

SPNs decreased after 2010, with decreasing CD4 complications, decreasing reoperation rates and stable mortality rates, likely indicating broad adoption of a "step-up" approach. Larger, prospective studies to compare indications and outcomes for "step up" versus open SPN are warranted.

Precision targeting of the vagal anti-inflammatory pathway attenuates the systemic inflammatory response to burn injury

BACKGROUND

The systemic inflammatory response (SIRS) drives late morbidity and mortality after injury. The α7 nicotinic acetylcholine receptor (α7nAchR) expressed on immune cells regulates the vagal anti-inflammatory pathway that prevents an overwhelming SIRS response to injury. Nonspecific pharmacologic stimulation of the vagus nerve has been evaluated as a potential therapeutic to limit SIRS. Unfortunately, the results of clinical trials have been underwhelming. We hypothesized that directly targeting the α7nAchR would more precisely stimulate the vagal anti-inflammatory pathway on immune cells and decrease gut and lung injury after severe burn.

METHODS

C57BL/6 mice underwent 30% total body surface area steam burn. Mice were treated with an intraperitoneal injection of a selective agonist of the α7nAchR (AR-R17779) at 30 minutes postburn. Intestinal permeability to 4 kDa FITC-dextran was measured at multiple time points postinjury. Lung vascular permeability was measured 6 hours after burn injury. Serial behavioral assessments were performed to quantify activity levels.

RESULTS

Intestinal permeability peaked at 6 hours postburn. AR-R17779 decreased burn-induced intestinal permeability in a dose-dependent fashion (p < 0.001). There was no difference in gut permeability to 4 kDa FITC-dextran between sham and burn-injured animals treated with 5 mg/kg of AR-R17779. While burn injury increased lung permeability 10-fold, AR-R17779 prevented burn-induced lung permeability with no difference compared with sham (p < 0.01). Postinjury activity levels were significantly improved in burned animals treated with AR-R17779.

CONCLUSION

Directly stimulating the α7nAchR prevents burn-induced gut and lung injury. Directly targeting the α7nAChR that mediates the cholinergic anti-inflammatory response may be an improved strategy compared with nonspecific vagal agonists.

CHRFAM7A expression in mice increases resiliency after injury

INTRODUCTION

The CHRNA7 gene encodes the α-7 nicotinic acetylcholine receptor (α7nAchR) that regulates anti-inflammatory responses to injury; however, only humans express a variant gene called CHRFAM7A that alters the function of α7nAChR; CHRFAM7A expression predominates in bone marrow and monocytes/macrophages where the CHRFAM7A/CHRNA7 ratio is highly variable between individuals. We have previously shown in transgenic mice that CHRFAM7A increased emergency myelopoiesis from the bone marrow and monocyte/macrophage expression in lungs.

MATERIALS AND METHODS

CHRFAM7A transgenic mice are compared to age- and gender-matched wild-type (WT) siblings. We utilized a model of sepsis using LPS injection to measure survival. Lung vascular permeability was measured after severe burn injury in WT vs. CHRFAM7A transgenic mice. Bone marrow CHRFAM7A expression was evaluated using adoptive transfer of CHRFAM7A transgenic bone marrow into WT mice.

RESULTS

Here, we demonstrate that CHRFAM7A expression results in an anti-inflammatory phenotype with an improved survival to LPS and decreased acute lung injury in a severe cutaneous burn model compared to WT.

CONCLUSIONS

These data suggest that the relative expression of CHRFAM7A may alter resiliency to injury and contribute to individual variability in the human systemic inflammatory response (SIRS) to injury.

Don't mess with the pancreas! A multicenter analysis of the management of low-grade pancreatic injuries

INTRODUCTION

Current guidelines recommend nonoperative management (NOM) of low-grade (American Association for the Surgery of Trauma-Organ Injury Scale Grade I-II) pancreatic injuries (LGPIs), and drainage rather than resection for those undergoing operative management, but they are based on low-quality evidence. The purpose of this study was to review the contemporary management and outcomes of LGPIs and identify risk factors for morbidity.

METHODS

Multicenter retrospective review of diagnosis, management, and outcomes of adult pancreatic injuries from 2010 to 2018. The primary outcome was pancreas-related complications (PRCs). Predictors of PRCs were analyzed using multivariate logistic regression.

RESULTS

Twenty-nine centers submitted data on 728 patients with LGPI (76% men; mean age, 38 years; 37% penetrating; 51% Grade I; median Injury Severity Score, 24). Among 24-hour survivors, definitive management was NOM in 31%, surgical drainage alone in 54%, resection in 10%, and pancreatic debridement or suturing in 5%. The incidence of PRCs was 21% overall and was 42% after resection, 26% after drainage, and 4% after NOM. On multivariate analysis, independent risk factors for PRC were other intra-abdominal injury (odds ratio [OR], 2.30; 95% confidence interval [95% CI], 1.16-15.28), low volume (OR, 2.88; 1.65, 5.06), and penetrating injury (OR, 3.42; 95% CI, 1.80-6.58). Resection was very close to significance (OR, 2.06; 95% CI, 0.97-4.34) (p = 0.0584).

CONCLUSION

The incidence of PRCs is significant after LGPIs. Patients who undergo pancreatic resection have PRC rates equivalent to patients resected for high-grade pancreatic injuries. Those who underwent surgical drainage had slightly lower PRC rate, but only 4% of those who underwent NOM had PRCs. In patients with LGPIs, resection should be avoided. The NOM strategy should be used whenever possible and studied prospectively, particularly in penetrating trauma.

LEVEL OF EVIDENCE

Therapeutic Study, level IV.

Methamphetamine Use is Associated with Increased Surgical Site Infections after Trauma Laparotomy

BACKGROUND

Methamphetamine (METH) use causes significant vasoconstriction, which can be severe enough to cause bowel ischemia. Methamphetamines have also been shown to alter the immune response. These effects could predispose METH users to poor wound healing, increased infections, and other post-operative complications. We hypothesized that METH users would have longer length of stay and higher rates of complications compared to non-METH users.

METHODS

The trauma registry for our urban Level 1 trauma center was searched for patients that received an exploratory laparotomy from 2016 to 2019. A total 204 patients met criteria and 52 (25.5%) were METH positive. Length of stay (LOS), ventilator days, abbreviated injury scale (AIS), and wound class were compared using nonparametric statistics. Age and injury severity score (ISS) were compared using a Student's t-test. A Chi Square or Fisher's Exact test was used to compare sex, mechanism of injury, and rates of infectious complications.

RESULTS

Methamphetamine-positive patients had a significantly higher rate of surgical site infections (7.4% versus 0%, P = 0.001). Patients that developed surgical site infection had equivalent rates of smoking and diabetes, as well as equivalent abdominal AIS and wound class compared to those who did not develop surgical site infection. Hospital and ICU LOS, ventilator days, ISS, and mortality were equivalent between METH positive and negative patients. Rates of other infectious complications were the same between groups.

CONCLUSIONS

Methamphetamine use is associated with an increased rate of surgical site infection after trauma laparotomy. Other serious complications and mortality were not affected by METH use.

The brain-gut axis: A prime therapeutic target in traumatic brain injury

Traumatic brain injury (TBI) is a significant cause of morbidity and mortality in trauma patients. The primary focus of treating TBI is to prevent additional injury to the damaged brain tissue, known as secondary brain injury. This treatment can include treating the body's inflammatory response. Despite promise in animal models, anti-inflammatory therapy has failed to improve outcomes in human patients, suggesting a more targeted and precise approach may be needed. There is a bidirectional axis between the intestine and the brain that contributes to this inflammation in acute and chronic injury. The mechanisms for this interaction are not completely understood, but there is evidence that neural, inflammatory, endocrine, and microbiome signals all participate in this process. Therapies that target the intestine as a source of inflammation have potential to lessen secondary brain injury and improve outcomes in TBI patients, but to develop these treatments we need to better understand the mechanisms behind this intestinal inflammatory response.

Outcomes in Delayed Drainage of Hemothorax

BACKGROUND

Prompt drainage of traumatic hemothorax is recommended to prevent empyema and trapped lung. Some patients do not present the day of their trauma, leading to their delayed treatment. Delayed drainage could be challenging as clotted blood may not evacuate through a standard chest tube. We hypothesized that such delays would increase the need for surgery or secondary interventions.

METHODS

Our trauma registry was reviewed for patients with a hemothorax admitted to our level 1 trauma center from 1/1/00 to 4/30/19. Patients were included in the delayed group if they received a drainage procedure >24 hours after injury. These patients were matched 1:1 by chest abbreviated injury score to patients who received drainage <24 hours from injury.

RESULTS

A total of 19 patients with 22 hemothoraces received delayed drainage. All but 3 patients had a chest tube placed as initial treatment. Four patients received surgery, including 3 who initially had chest tubes placed. Longer time to drainage increased the odds of requiring intrathoracic thrombolytics or surgery. In comparison, 2 patients who received prompt drainage received thrombolytics (P = .11) and none required surgery (P = .02). Patients needed surgery when initial drainage was on or after post-injury day 5, but pigtail catheter drainage was effective 26 days after injury.

DISCUSSION

Longer times from injury to intervention are associated with increased likelihood of needing surgery for hemothorax evacuation, but outcomes were not uniform. A larger, multicenter study will be necessary to provide better characterization of treatment outcomes for these patients.

The Kinetics of Intestinal Permeability in a Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality among trauma patients. Increased intestinal permeability plays an important role in the inflammatory process that accompanies TBI, and therapies that prevent this permeability change may improve outcomes in TBI patients. Different animal models have been developed to test permeability changes, but there has been no agreement on when permeability should be tested after TBI. Here, we describe a method for creating the TBI mouse model and for measuring intestinal permeability. We also detail our permeability measurements at different time points after TBI to help guide future experimental design. The TBI is made using a controlled cortical impact model with the cortical impactor set to speed 6 m/s, depth 3 mm, dwell time 0.2 s, and tip size 3 mm to produce a severe TBI. Permeability is measured at 2, 4, 6, and 24 hr after TBI by removing a piece of terminal ileum, tying the ends, filling the lumen with FITC-labeled dextran, and then measuring how much of the dextran moves into the surrounding solution bath over time using a fluorescent plate reader. Our results show that peak permeability occurs between 4 and 6 hr after TBI. We recommend that future experiments incorporate permeability measurements 4 to 6 hr after TBI in order to take advantage of this peak permeability. © 2020 Wiley Periodicals LLC. Basic Protocol: Mouse CCI traumatic brain injury model and intestinal permeability measurement.

Using Machine Learning to Make Predictions in Patients Who Fall

BACKGROUND

As the population ages, the incidence of traumatic falls has been increasing. We hypothesize that a machine learning algorithm can more accurately predict mortality after a fall compared with a standard logistic regression (LR) model based on immediately available admission data. Secondary objectives were to predict who would be discharged home and determine which variables had the largest effect on prediction.

METHODS

All patients who were admitted for fall between 2012 and 2017 at our level 1 trauma center were reviewed. Fourteen variables describing patient demographics, injury characteristics, and physiology were collected at the time of admission and were used for prediction modeling. Algorithms assessed included LR, decision tree classifier (DTC), and random forest classifier (RFC). Area under the receiver operating characteristic curve (AUC) values were calculated for each algorithm for mortality and discharge to home.

RESULTS

About 4725 patients met inclusion criteria. The mean age was 61 ± 20.5 y, Injury Severity Score 8 ± 7, length of stay 5.8 ± 7.6 d, intensive care unit length of stay 1.8± 5.2 d, and ventilator days 0.7 ± 4.2 d. The mortality rate was 3% and three times greater for elderly (aged 65 y and older) patients (5.0% versus 1.6%, P < 0.001). The AUC for predicting mortality for LR, DTC, and RFC was 0.78, 0.64, and 0.86, respectively. The AUC for predicting discharge to home for LR, DTC, and RFC was 0.72, 0.61, and 0.74, respectively. The top five variables that contribute to the prediction of mortality in descending order of importance are the Glasgow Coma Score (GCS) motor, GCS verbal, respiratory rate, GCS eye, and temperature.

CONCLUSIONS

RFC can accurately predict mortality and discharge home after a fall. This predictive model can be implemented at the time of patient arrival and may help identify candidates for targeted intervention as well as improve prognostication and resource utilization.

Sexual Harassment during Residency Training: A Cross-Sectional Analysis

The reality of sexual harassment is unmasking in many fields, and medical trainees constitute a vulnerable and at-risk group. We report the prevalence of sexual harassment among GI, internal medicine, and pediatric residents, with a focus on identifying underlying reasons for lack of victim reporting. A modified previously validated Department of Defense survey on sexual harassment was e-mailed to 261 GI, 132 pediatric, and 271 internal medicine program directors. Three hundred eighty-one residents responded to the survey. Female trainees were more likely to be subject to sexual harassment (83% vs 44%, P <0 .0001). Offensive and/or suggestive jokes and comments were the most common type of harassment experienced. Most residents were unlikely to report the offender (87% females, 93% males). Although 77 per cent of residents believed they would be supported by their program if they reported a sexual harassment event, only 43 per cent were aware of institutional support in place for victims at their program. Although there is a persistently high incidence of harassment in training, the avenues in which to report it are largely unknown and underused. Further research should focus on evidence-based interventions to encourage reporting and to design institutional programs for victims of sexual harassment.

Sexual Harassment during Residency Training: A Cross-Sectional Analysis

The reality of sexual harassment is unmasking in many fields, and medical trainees constitute a vulnerable and at-risk group. We report the prevalence of sexual harassment among GI, internal medicine, and pediatric residents, with a focus on identifying underlying reasons for lack of victim reporting. A modified previously validated Department of Defense survey on sexual harassment was e-mailed to 261 GI, 132 pediatric, and 271 internal medicine program directors. Three hundred eighty-one residents responded to the survey. Female trainees were more likely to be subject to sexual harassment (83% vs 44%, P <0 .0001). Offensive and/or suggestive jokes and comments were the most common type of harassment experienced. Most residents were unlikely to report the offender (87% females, 93% males). Although 77 per cent of residents believed they would be supported by their program if they reported a sexual harassment event, only 43 per cent were aware of institutional support in place for victims at their program. Although there is a persistently high incidence of harassment in training, the avenues in which to report it are largely unknown and underused. Further research should focus on evidence-based interventions to encourage reporting and to design institutional programs for victims of sexual harassment.

Direct Peritoneal Resuscitation Reduces Lung Injury and Caspase 8 Activity in Brain Death

Background: Acute brain death (ABD) is associated with inflammation and lung injury. Direct peritoneal resuscitation (DPR) improves blood flow to the vital organs after ABD. DPR reduces lung injury, but the mechanism for this is unknown. Methods: Male Sprague-Dawley rats were randomized to five groups (n = 8/group): (1) Sham (no ABD); (2) Targeted intravenous fluid (TIVF) (ABD plus enough IVF to maintain a MAP of 80 mmHg) at 2 hours post-resuscitation (RES); (3) ABD + TIVF + DPR (TIVF and 30 cc intraperitoneal 2.5% Delflex) at 2 hours post-RES; (4) ABD + TIVF at 4 hours post-RES; and (5) ABD + TIVF + DPR at 4 hours post-RES. Messenger RNA (mRNA) levels were measured using Qiagen qRT PCR. Protein levels were assessed using quantitative ELISAs and the Luminex MagPix system. Results: Use of DPR caused 5.8-fold downregulation of mRNA expression for TNF-α and 2.7-fold decrease for the TNF receptor compared to TIVF alone. Caspase 8 mRNA was also downregulated. Protein levels for TNF-α, TNF receptor, caspase 8, NFκB, and NFκB inhibitor kinase, which promotes dissociation of NFκB inhibitor, were reduced by DPR. Cell death markers M30 and M65 were also decreased with DPR. Conclusions: Use of DPR caused changes in the expression of multiple mRNAs and proteins in the caspase 8 apoptotic pathway. These data represent a mechanism through which DPR exerts its beneficial effects within the lung tissue.

Direct peritoneal resuscitation reduces inflammation in the kidney after acute brain death

Brain death is associated with significant inflammation within the kidneys, which may contribute to reduced graft survival. Direct peritoneal resuscitation (DPR) has been shown to reduce systemic inflammation after brain death. To determine its effects, brain dead rats were resuscitated with normal saline (targeted intravenous fluid) to maintain a mean arterial pressure of 80 mmHg; DPR animals also received 30 cc of intraperitoneal peritoneal dialysis solution. Rats were euthanized at 0, 2, 4, and 6 h after brain death. Pro-inflammatory cytokines were measured using ELISA. Levels of IL-1β, TNF-α, and IL-6 in the kidney were significantly increased as early as 2 h after brain death and significantly decreased with DPR. Levels of leukocyte adhesion molecules ICAM and VCAM increased after brain death and were decreased with DPR (ICAM 2.33 ± 0.14 vs. 0.42 ± 0.04, P = 0.002; VCAM 82.6 ± 5.8 vs. 37.3 ± 1.9, P = 0.002 at 4 h) as were E-selectin and P-selectin (E-selectin 25,605 vs. 16,144, P = 0.005; P-selectin 82.5 ± 3.3 vs. 71.0 ± 2.3, P = 0.009 at 4 h). Use of DPR reduces inflammation and adhesion molecule expression in the kidneys, and is associated with reduced macrophages and neutrophils on immunohistochemistry. Using DPR in brain dead donors has the potential to reduce the immunologic activity of transplanted kidneys and could improve graft survival.

Mitigation of cross-beam energy transfer in inertial-confinement-fusion plasmas with enhanced laser bandwidth

Cross-beam energy transfer (CBET) is a significant energy-loss mechanism in directly driven inertial-confinement-fusion (ICF) targets. One strategy for mitigating CBET is to increase the bandwidth of the laser light, thereby disrupting the resonant three-wave interactions that underlie this nonlinear scattering process. Here, we report on numerical simulations performed with the wave-based code lpse that show a significant reduction in CBET for bandwidths of 2-5 THz (corresponding to a normalized bandwidth of 0.2%-0.6% at a laser wavelength of 351nm) under realistic plasma conditions. Such bandwidths are beyond those available with current high-energy lasers used for ICF, but could be achieved using stimulated rotation Raman scattering in diatomic gases like nitrogen.

Moped Crashes are Just as Dangerous as Motorcycle Crashes

Mopeds’ (MP) limited speed gives the impression that they are safer than motorcycles (MCs), but factors other than speed may contribute to crash outcome. Records of patients involved in MC or MP crashes evaluated at the University of Louisville Hospital emergency department between 2010 and 2014 were reviewed. Among patients who required hospital admission, the frequency of rib fractures, hemo- or pneumothorax, abdominal injury, extremity injury, and vertebral body fractures were greater in the MC group, whereas head and facial injuries were more common in the MP group. Positive toxicology screens were equivalent (MC 51.8% vs MP 56.8%, P = 0.25), and fewer MP riders wore helmets (33.8% vs 9.2%, P < 0.01). The injury severity score for MC was higher (15.2 vs 13.9, P = 0.039), but mortality was equivalent between groups (7.5 vs 7.6%, P = 0.98). Among patients discharged from the emergency department with minor injuries, frequency of all injury types were equivalent. Although MC patients had a statistically higher injury severity score, differences were clinically similar with equal mortality rate. Moped riders are just as likely to suffer death or serious injury after a crash compared with MC riders, and injury prevention efforts should be aimed at both groups.

Moped Crashes Are Just as Dangerous as Motorcycle Crashes

Mopeds' (MP) limited speed gives the impression that they are safer than motorcycles (MCs), but factors other than speed may contribute to crash outcome. Records of patients involved in MC or MP crashes evaluated at the University of Louisville Hospital emergency department between 2010 and 2014 were reviewed. Among patients who required hospital admission, the frequency of rib fractures, hemo- or pneumothorax, abdominal injury, extremity injury, and vertebral body fractures were greater in the MC group, whereas head and facial injuries were more common in the MP group. Positive toxicology screens were equivalent (MC 51.8% vs MP 56.8%, P = 0.25), and fewer MP riders wore helmets (33.8% vs 9.2%, P < 0.01). The injury severity score for MC was higher (15.2 vs 13.9, P = 0.039), but mortality was equivalent between groups (7.5 vs 7.6%, P = 0.98). Among patients discharged from the emergency department with minor injuries, frequency of all injury types were equivalent. Although MC patients had a statistically higher injury severity score, differences were clinically similar with equal mortality rate. Moped riders are just as likely to suffer death or serious injury after a crash compared with MC riders, and injury prevention efforts should be aimed at both groups.

Damage-associated molecular patterns in resuscitated hemorrhagic shock are mitigated by peritoneal fluid administration

Conventional resuscitation (CR) of hemorrhagic shock (HS), a significant cause of trauma mortality, is intravenous blood and fluids. CR restores central hemodynamics, but vital organ flow can drop, causing hypoperfusion, hypoxia, damage-associated molecular patterns (DAMPs), and remote organ dysfunction (i.e., lung). CR plus direct peritoneal resuscitation (DPR) prevents intestinal and hepatic hypoperfusion. We hypothesized that DPR prevents lung injury in HS/CR by altering DAMPs. Anesthetized male Sprague-Dawley rats were randomized to groups ( n = 8/group) in one of two sets: 1) sham (no HS, CR, or DPR), 2) HS/CR (HS = 40% mean arterial pressure (MAP) for 60 min, CR = shed blood + 2 volumes normal saline), or 3) HS/CR + DPR. The first set underwent whole lung blood flow by colorimetric microspheres. The second set underwent tissue collection for Luminex, ELISAs, and histopathology. Lipopolysaccharide (LPS) and DAMPs were measured in serum and/or lung, including cytokines, hyaluronic acid (HA), high-mobility group box 1 (HMGB1), Toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 protein (MYD88), and TIR-domain-containing adapter-inducing interferon-β (TRIF). Statistics were by ANOVA and Tukey-Kramer test with a priori P < 0.05. HS/CR increased serum LPS, HA, HMGB1, and some cytokines [interleukin (IL)-1α, IL-1β, IL-6, and interferon-γ]. Lung TLR4 and MYD88 were increased but not TRIF compared with Shams. HS/CR + DPR decreased LPS, HA, cytokines, HMGB1, TLR4, and MYD88 levels but did not alter TRIF compared with HS/CR. The data suggest that gut-derived DAMPs can be modulated by adjunctive DPR to prevent activation of lung TLR-4-mediated processes. Also, DPR improved lung blood flow and reduced lung tissue injury. Adjunctive DPR in HS/CR potentially improves morbidity and mortality by downregulating the systemic DAMP response.

Capsule implosions for continuum x-ray backlighting of opacity samples at the National Ignition Facility

Direct drive implosions of plastic capsules have been performed at the National Ignition Facility to provide a broad-spectrum (500-2000 eV) X-ray continuum source for X-ray transmission spectroscopy. The source was developed for the high-temperature plasma opacity experimental platform. Initial experiments using 2.0 mm diameter polyalpha-methyl styrene capsules with ∼20 μm thickness have been performed. X-ray yields of up to ∼1 kJ/sr have been measured using the Dante multichannel diode array. The backlighter source size was measured to be ∼100 μm FWHM, with ∼350 ps pulse duration during the peak emission stage. Results are used to simulate transmission spectra for a hypothetical iron opacity sample at 150 eV, enabling the derivation of photometrics requirements for future opacity experiments.

Danger on the Farm: A Comparison of Agricultural and Animal-Related Injuries

Animal-related injuries are common in rural areas. Agricultural workers can suffer severe injuries involving farm machinery or falls. The spectrum of injuries related to rural activities is poorly defined and characterizing these injuries will improve injury prevention efforts. Records for injured patients admitted between 2010 and 2013 were retrospectively reviewed. Patients with a mechanism of injury involving a large animal or with the injury site listed as “farm” were included. Patients with agricultural injuries (n = 85) were older with more multisystem injuries than patients injured by animals (n = 132) but the Injury Severity Score was equivalent. There was no difference in intensive care unit length of stay, ventilator days, or mortality. There was no difference in frequency of solid organ injury, pelvic fractures, rib fractures, or hemo- or pneumothorax between groups. Animal injuries had more frequent traumatic brain injuries (22.4% vs 10.5%, P = 0.03), whereas agricultural injuries had more vertebral fractures (20.5% vs 9.2%). Of toxicology screens performed, 25 per cent (22/88) were positive. No significant differences were found between occupational versus recreational animal injuries. Agricultural and animal-related injuries have different characteristics but Injury Severity Score and mortality were similar. Severe injuries from both mechanisms are common in rural communities and injury prevention activities are needed in both settings.

Danger on the Farm: A Comparison of Agricultural and Animal-Related Injuries

Animal-related injuries are common in rural areas. Agricultural workers can suffer severe injuries involving farm machinery or falls. The spectrum of injuries related to rural activities is poorly defined and characterizing these injuries will improve injury prevention efforts. Records for injured patients admitted between 2010 and 2013 were retrospectively reviewed. Patients with a mechanism of injury involving a large animal or with the injury site listed as "farm" were included. Patients with agricultural injuries (n = 85) were older with more multisystem injuries than patients injured by animals (n = 132) but the Injury Severity Score was equivalent. There was no difference in intensive care unit length of stay, ventilator days, or mortality. There was no difference in frequency of solid organ injury, pelvic fractures, rib fractures, or hemo- or pneumothorax between groups. Animal injuries had more frequent traumatic brain injuries (22.4% vs 10.5%, P = 0.03), whereas agricultural injuries had more vertebral fractures (20.5% vs 9.2%). Of toxicology screens performed, 25 per cent (22/88) were positive. No significant differences were found between occupational versus recreational animal injuries. Agricultural and animal-related injuries have different characteristics but Injury Severity Score and mortality were similar. Severe injuries from both mechanisms are common in rural communities and injury prevention activities are needed in both settings.

Direct Peritoneal Resuscitation Alters Hepatic miRNA Expression after Hemorrhagic Shock

BACKGROUND

MicroRNAs (miRNAs) are small segments of noncoding RNA that regulate gene expression and protein function, and therefore are key regulators of cellular processes including those of the inflammatory cascade after hemorrhagic shock (HS). We have previously shown that direct peritoneal resuscitation (DPR), as an adjunct to traditional IV fluid resuscitation, improves visceral blood flow and reduces pro-inflammatory cytokines released during HS. The effects of DPR on hepatic miRNA (miR) expression patterns after resuscitated HS are not known.

STUDY DESIGN

Male Sprague-Dawley rats were divided into 3 groups: sham (no HS); conventional resuscitation (CR; HS, then resuscitated with shed blood and 2 volumes of saline); and DPR (CR plus 30 mL peritoneal dialysis solution). Animals were sacrificed at 4 hours, and miRNAs were measured using reverse transcription polymerase chain reaction.

RESULTS

Use of DPR downregulated 68 of 92 hepatic miRNAs compared with only 2 of 92 upregulated when compared with CR alone, p < 0.01). Specifically, miR-9-5p, miR-122-5p, and miR-146, which regulate NFκB, were downregulated 4.1-, 3.4-, and 0.86-fold, respectively; miR-29a and miR-126 were upregulated 0.88- and 3.7-fold when DPR was compared with CR.

CONCLUSIONS

Adding DPR downregulated most hepatic miRNAs compared with CR alone. Some miRNAs were affected more significantly, suggesting that although this clinical intervention causes a near-global downregulation of hepatic miRNA, it still targets specific inflammatory pathways. Use of DPR for resuscitation of patients in HS may reduce hepatic inflammation to improve patient outcomes after hemorrhage.

Measurements of electron density and temperature profiles in plasma produced by Nike KrF laser for laser plasma instability research

A grid image refractometer (GIR) has been implemented at the Nike krypton fluoride laser facility of the Naval Research Laboratory. This instrument simultaneously measures propagation angles and transmissions of UV probe rays (λ = 263 nm, Δt = 10 ps) refracted through plasma. We report results of the first Nike-GIR measurement on a CH plasma produced by the Nike laser pulse (∼1 ns FWHM) with the intensity of 1.1 × 10(15) W/cm(2). The measured angles and transmissions were processed to construct spatial profiles of electron density (ne) and temperature (Te) in the underdense coronal region of the plasma. Using an inversion algorithm developed for the strongly refracted rays, the deployed GIR system probed electron densities up to 4 × 10(21) cm(-3) with the density scale length of 120 μm along the plasma symmetry axis. The resulting n(e) and T(e) profiles are verified to be self-consistent with the measured quantities of the refracted probe light.

Suppression of laser nonuniformity imprinting using a thin high-z coating

Imprinting of laser nonuniformity is a limiting factor in direct-drive inertial confinement fusion experiments, particularly when available laser smoothing is limited. A thin (∼400  Å) high-Z metal coating is found to substantially suppress laser imprint for planar targets driven by pulse shapes and intensities relevant to implosions on the National Ignition Facility while retaining low adiabat target acceleration. A hybrid of indirect and direct drive, this configuration results in initial ablation by x rays from the heated high-Z layer, creating a large standoff for perturbation smoothing.

Implementation of focal zooming on the Nike KrF laser

In direct drive inertial confinement laser fusion, a pellet containing D-T fuel is imploded by ablation arising from absorption of laser energy at its outer surface. For optimal coupling, the focal spot of the laser would continuously decrease to match the reduction in the pellet's diameter, thereby minimizing wasted energy. A krypton-fluoride laser (λ = 248 nm) that incorporates beam smoothing by induced spatial incoherence has the ability to produce a high quality focal profile whose diameter varies with time, a property known as focal zooming. A two-stage focal zoom has been demonstrated on the Nike laser at the Naval Research Laboratory. In the experiment, a 4.4 ns laser pulse was created in which the on-target focal spot diameter was 1.3 mm (full width at half maximum) for the first 2.4 ns and 0.28 mm for the final 2 ns. These two diameters appear in time-integrated focal plane equivalent images taken at several locations in the amplification chain. Eight of the zoomed output beams were overlapped on a 60 μm thick planar polystyrene target. Time resolved images of self-emission from the rear of the target show the separate shocks launched by the two corresponding laser focal diameters.

Family engagement regarding the critically ill patient

The Institute of Medicine strongly recommends a health care system that supports family members. Nowhere is the need for family-centered care greater than with critically ill patients. Simplistically, family-centered care is primarily about communication. Unfortunately, family perception of communication in the intensive care unit (ICU) is quite poor. This article reviews some strategies to improve communication, including family meetings and family presence at resuscitation. It also highlights some of the areas within the realm of ICU care in which family engagement is particularly important, including advance directives, end-of-life care, brain death, and organ donation.

Tissue distribution and histopathological effects of titanium dioxide nanoparticles after intravenous or subcutaneous injection in mice

Nanoparticles can be formed following degradation of medical devices such as orthopedic implants. To evaluate the safety of titanium alloy orthopedic materials, data are needed on the long-term distribution and tissue effects of injected titanium nanoparticles in experimental animals. In this study, we evaluated the tissue distribution and histopathological effects of titanium dioxide (TiO(2)) nanoparticles (approximately 120 nm diameter) in mice after intravenous (i.v.; 56 or 560 mg kg(-1) per mouse) or subcutaneous (s.c.; 560 or 5600 mg kg(-1) per mouse) injection on two consecutive days. Animals were examined 1 and 3 days, and 2, 4, 12 and 26 weeks after the final injection. When examined by light microscopy, particle agglomerates identified as TiO(2) were observed mainly in the major filtration organs - liver, lung and spleen - following i.v. injection. Particles were still observed 26 weeks after injection, indicating that tissue clearance is limited. In addition, redistribution within the histological micro-compartments of organs, especially in the spleen, was noted. Following s.c. injection, the largest particle agglomerates were found mainly in the draining inguinal lymph node, and to a lesser extent, the liver, spleen and lung. With the exception of a foreign body response at the site of s.c. injection and the appearance of an increased number of macrophages in the lung and liver, there was no histopathological evidence of tissue damage observed in any tissue at any time point.

Basic hydrodynamics of Richtmyer-Meshkov-type growth and oscillations in the inertial confinement fusion-relevant conditions

In inertial confinement fusion (ICF), the possibility of ignition or high energy gain is largely determined by our ability to control the Rayleigh-Taylor (RT) instability growth in the target. The exponentially amplified RT perturbation eigenmodes are formed from all sources of the target and radiation non-uniformity in a process called seeding. This process involves a variety of physical mechanisms that are somewhat similar to the classical Richtmyer-Meshkov (RM) instability (in particular, most of them are active in the absence of acceleration), but differ from it in many ways. In the last decade, radiographic diagnostic techniques have been developed that made direct observations of the RM-type effects in the ICF-relevant conditions possible. New experiments stimulated the advancement of the theory of the RM-type processes. The progress in the experimental and theoretical studies of such phenomena as ablative RM instability, re-shock of the RM-unstable interface, feedout and perturbation development associated with impulsive loading is reviewed.

Stability of a shock-decelerated ablation front

Experimental study of a shock-decelerated ablation front is reported. A planar solid plastic target is accelerated by a laser across a vacuum gap and collides with a lower-density plastic foam layer. While the target is accelerated, a fast Rayleigh-Taylor (RT) growth of the seeded single-mode perturbation at the ablation front is observed. After the collision, the velocity of the ablation front is seen to remain constant. The reshock quenches the RT growth but does not trigger any Richtmyer-Meshkov growth at the ablation front, which is shown to be consistent with both theory and simulations.

Sex chromosome complement affects social interactions in mice

Sex differences in behavior can be attributed to differences in steroid hormones. Sex chromosome complement can also influence behavior, independent of gonadal differentiation. The mice used for this work combined a spontaneous mutation of the Sry gene with a transgene for Sry that is incorporated into an autosome thus disassociating gonad differentiation from sex chromosome complement. The resulting genotypes are XX and XY(-) females (ovary-bearing) along with XXSry and XY(-)Sry males (testes-bearing). Here we report results of basic behavioral phenotyping conducted with these mice. Motor coordination, use of olfactory cues to find a food item, general activity, foot shock threshold, and behavior in an elevated plus maze were not affected by gonadal sex or sex chromosome complement. In a one-way active avoidance learning task females were faster to escape an electric shock than males. In addition, sex chromosome complement differences were noted during social interactions with submissive intruders. Female XY(-) mice were faster to follow an intruder than XX female mice. All XY(-) mice spent more time sniffing and grooming the intruder than the XX mice, with XY(-) females spending the most amount of time in this activity. Finally, XX females were faster to display an asocial behavior, digging, and engaged in more digging than XXSry male mice. All of these behaviors were tested in gonadectomized adults, thus, differences in circulating levels of gonadal steroids cannot account for these effects. Taken together, these data show that sex chromosome complement affects social interaction style in mice.

Experimental benchmark for an improved simulation of absolute soft-x-ray emission from polystyrene targets irradiated with the Nike laser

Absolutely calibrated, time-resolved spectral intensity measurements of soft-x-ray emission (hnu approximately 0.1-1.0 keV) from laser-irradiated polystyrene targets are compared to radiation-hydrodynamic simulations that include our new postprocessor, Virtual Spectro. This new capability allows a unified, detailed treatment of atomic physics and radiative transfer in nonlocal thermodynamic equilibrium conditions for simple spectra from low-Z materials as well as complex spectra from high-Z materials. The excellent agreement (within a factor of approximately 1.5) demonstrates the powerful predictive capability of the codes for the complex conditions in the ablating plasma. A comparison to data with high spectral resolution (E/deltaE approximately 1000) emphasizes the importance of including radiation coupling in the quantitative simulation of emission spectra.

Calibration of an extreme-ultraviolet transmission grating spectrometer with synchrotron radiation

The responsivity of an extreme-ultraviolet transmission grating spectrometer with silicon photodiode detectors was measured with synchrotron radiation. The spectrometer was designed to record the absolute radiation flux in a wavelength bandpass centered at 30 nm. The transmission grating had a period of 200 nm and relatively high efficiencies in the +1 and the -1 diffraction orders that were dispersed on either side of the zero-order beam. Three photodiodes were positioned to measure the signals in the zero order and in the +1 and -1 orders. The photodiodes had aluminum overcoatings that passed the desired wavelength bandpass centered at 30 nm and attenuated higher-order radiation and wavelengths longer than approximately 80 nm. The spectrometer's responsivity, the ratio of the photodiode current to the incident radiation power, was determined as a function of the incident wavelength and the angle of the spectrometer with respect to the incident radiation beam. The spectrometer's responsivity was consistent with the product of the photodiode responsivity and the grating efficiency, both of which were separately measured while removed from the spectrometer.

Flow cytometric enumeration of micronucleated reticulocytes: high transferability among 14 laboratories

This laboratory previously described a single-laser flow cytometric method, which effectively resolves micronucleated erythrocyte populations in rodent peripheral blood samples. Even so, the rarity and variable size of micronuclei make it difficult to configure instrument settings consistently and define analysis regions rationally to enumerate the cell populations of interest. Murine erythrocytes from animals infected with the malaria parasite Plasmodium berghei contain a high prevalence of erythrocytes with a uniform DNA content. This biological model for micronucleated erythrocytes offers a means by which the micronucleus analysis regions can be rationally defined, and a means for controlling interexperimental variation. The experiments described herein were performed to extend these studies by testing whether malaria-infected erythrocytes could also be used to enhance the transferability of the method, as well as control intra- and interlaboratory variation. For these studies, blood samples from mice infected with malaria, or treated with vehicle or the clastogen methyl methanesulfonate, were fixed and shipped to collaborating laboratories for analysis. After configuring instrumentation parameters and guiding the position of analysis regions with the malaria-infected blood samples, micronucleated reticulocyte frequencies were measured (20,000 reticulocytes per sample). To evaluate both intra- and interlaboratory variation, five replicates were analyzed per day, and these analyses were repeated on up to five separate days. The data of 14 laboratories presented herein indicate that transferability of this flow cytometric technique is high when instrumentation is guided by the biological standard Plasmodium berghei.

Vision readiness of the reserve forces of the U.S. Army

In 1996 and 1997, the Army conducted an exercise to assess the ability to rapidly mobilize the reserve forces. In accordance with Army requirements, each soldier was evaluated to determine if he or she met vision and optical readiness standards. Of the 1,947 individuals processed through the optometry section, 40% met vision requirements without correction and 32% met vision requirements with their current spectacles. The remaining 28% required examination. A major impediment to processing reserve units for deployment is the lack of vision and optical readiness. In the mobilization for the Persian Gulf War, significant delays were incurred because of the time required to perform eye examinations and fabricate eyewear. However, as a result of this exercise, current prescriptions will be available in the event of mobilization. To ensure readiness, all units should perform such exercises periodically.

Evaluation of the rodent micronucleus assay by a 28-day treatment protocol: Summary of the 13th Collaborative Study by the Collaborative Study Group for the Micronucleus Test (CSGMT)/Environmental Mutagen Society of Japan (JEMS)-Mammalian Mutagenicity Study Group (MMS)

To examine whether micronucleus tests can be incorporated into general toxicology assays, we performed micronucleus tests applying the treatment protocols typically used in such assays. In this 13th Collaborative Study of the CSGMT, both rats and mice were tested, although rats were used in the majority of the studies. Fifteen mutagens were tested in rats, mainly by oral (p.o.) administration. Micronucleus induction was evaluated 2, 3, and 4 days, and 1, 2, 3, and 28 days after the beginning of the treatment in the peripheral blood, and at 28 days in the bone marrow. Of the 15 chemicals that induced micronuclei in rats in short-term assays, two chemicals (1,2-dimethylhydrazine.2HCl and mitomycin C) were negative in all our experiments, possibly because of insufficient dose levels. The remaining 13 were positive within the estimated dose range of a general toxicology assay, suggesting the possibility of integrating the micronucleus assay into general toxicology assays. Three patterns were observed in micronucleus induction during the period of repeated treatment: (1) gradual increases in micronucleus frequency with sequential doses, (2) a peak at 3-5 days followed by gradual decreases in micronucleus frequency with sequential doses, and (3) a rapid increase in micronucleus frequency followed by a plateau. We evaluated factors that might have been involved in those patterns, such as the spleen function, target organ exposure, extramedullary hematopoiesis, hypothermia, and hypoxia. Another factor we considered was dosage. Because the dosages employed in a general toxicity assay are usually lower than those used in short-term micronucleus assays, this discrepancy was considered the greatest potential problem for integrating the micronucleus assay into general toxicology assays. Our results indicate that the integration of the micronucleus assay into a 28-day toxicological assay is feasible. To serve this purpose, blood samples collected 4 days after the beginning of treatment and blood and bone marrow samples collected at autopsy should be examined. Furthermore, although it is recognized that mice may be suitable for performing independent micronucleus assays, we propose that rats can provide biologically important and relevant information regarding potential chemical mutagens that can be evaluated under conditions used in the conduct of general toxicology studies.

Flow cytometry assay for counting micronucleated erythrocytes: development process

Development of any new assay proceeds in several phases. When an assay is intended for regular use to support regulatory decision-making, there are significant additional stages in the development process beyond the initial description of the method. In this paper we discuss some of the studies related to the development of a flow cytometric method for counting micronuclei in rodent erythrocytes. Studies related to fixation methods and conditions, standardization of DNA staining, and antibody staining are discussed. These studies, while not part of the formal description of the method, are needed as part of the preparation for the formal validation of the method. In addition, the lessons learned in transferring the method to other laboratories are briefly discussed in relation to defining the final protocol.