Cerebral arterioles express the laminin subunits α4 and α5 in conjunction with α6ß4 integrin, but strongly downregulate laminin α4 during hypoxia-induced arteriogenic remodeling.

Previous studies have shown that expression of the endothelial laminin receptor α6ß4 integrin in the brain is uniquely restricted to arterioles. As exposure to chronic mild hypoxia (CMH, 8 % O2) stimulates robust angiogenic and arteriogenic remodeling responses in the brain, the goal of this study was to determine how CMH influences cerebrovascular expression of the ß4 integrin as well as its potential ligands, laminin 411 and 511, containing the α4 and α5 laminin subunits respectively, and then define how aging impacts this expression. We observed the following: (i) CMH launched a robust arteriogenic remodeling response both in the young (10 weeks) and aged (20 months) brain, correlating with an increased number of ß4 integrin+ vessels, (ii) while the laminin α4 subunit is expressed evenly across all cerebral blood vessels, laminin α5 was highly expressed preferentially on ß4 integrin+ arterioles, (iii) CMH-induced arteriolar remodeling was associated with strong downregulation of the laminin α4 subunit but no change in the laminin α5 subunit, (iv) in addition to its expression on arterioles, ß4 integrin was also expressed at lower levels on capillaries specifically in white matter (WM) tracts but not in the grey matter (GM), and (v), these observations were consistent in both the brain and spinal cord, and age had no obvious impact. Taken together, our findings suggest that laminin 511 may be a specific ligand for α6ß4 integrin and that dynamic switching of the laminin subunits α4 and α5 might play an instructive role in arteriogenic remodeling. Furthermore, ß4 integrin expression differentiates WM from GM capillaries, highlighting a novel and important difference.

Sarcomas in the groin and inguinal canal: A 16-year single-centre experience.

INTRODUCTION: Soft tissue sarcomas arising in the groin and inguinal canal can be difficult to diagnose and manage. This is in part explained by the complex anatomy of the region. Early referral to specialist centres has been advocated, as inadvertent excision of these tumours can jeopardise definitive treatment. We present our 16-year experience at a regional sarcoma service. MATERIALS AND METHODS: A retrospective review of patients treated for a sarcoma in the groin and inguinal canal within the North of England Bone and Soft Tissue Tumour Service was performed. Demographic information, along with therapeutic approach and outcomes, was recorded and analysed. RESULTS: A total of 67 patients were identified, out of which 18 presented with new lesions, 32 presented after having a previous inadvertent sarcoma excision, 10 had a planned resection and 7 presented with recurrent disease. Liposarcomas were the most common histological subtype (55%), and the spermatic cord the most common origin (45%). Fifty-seven patients had surgery for this condition, with seven incomplete excision. Regional flaps were used in 60% of the cases, to allow an adequate oncological resection and soft tissue cover. Patients who had undergone a previous inadvertent sarcoma excision did not have worse rates of local recurrence, metastases and disease-specific mortality. Kaplan-Meier disease-specific survival at 5 years was 82%. DISCUSSION: Inadvertent and inadequate groin sarcoma excision outside of specialist centres remains a problem despite clear guidance. Despite this, an aggressive oncological approach to inadequately managed tumours shows similar outcomes as tumour managed exclusively by our specialist centre.

Mild hypoxia triggers transient blood-brain barrier disruption: a fundamental protective role for microglia.

We recently demonstrated that when mice are exposed to chronic mild hypoxia (CMH, 8% O2), blood vessels in the spinal cord show transient vascular leak that is associated with clustering and activation of microglia around disrupted vessels. Importantly, microglial depletion profoundly increased hypoxia-induced vascular leak, implying that microglia play a critical role maintaining vascular integrity in the hypoxic spinal cord. The goal of the current study was to examine if microglia play a similar vasculo-protective function in the brain. Employing extravascular fibrinogen leak as an index of blood-brain barrier (BBB) disruption, we found that CMH provoked transient vascular leak in cerebral blood vessels that was associated with activation and aggregation of Mac-1-positive microglia around leaky vessels. Interestingly, CMH-induced vascular leak showed regional selectivity, being much more prevalent in the brainstem and olfactory bulb than the cerebral cortex and cerebellum. Pharmacological depletion of microglia with the colony stimulating factor-1 receptor inhibitor PLX5622, had no effect under normoxic conditions, but markedly increased hypoxia-induced cerebrovascular leak in all regions examined. As in the spinal cord, this was associated with endothelial induction of MECA-32, a marker of leaky CNS endothelium, and greater loss of endothelial tight junction proteins. Brain regions displaying the highest levels of hypoxic-induced vascular leak also showed the greatest levels of angiogenic remodeling, suggesting that transient BBB disruption may be an unwanted side-effect of hypoxic-induced angiogenic remodeling. As hypoxia is common to a multitude of human diseases including obstructive sleep apnea, lung disease, and age-related pulmonary, cardiac and cerebrovascular dysfunction, our findings have important translational implications. First, they point to a potential pathogenic role of chronic hypoxia in triggering BBB disruption and subsequent neurological dysfunction, and second, they demonstrate an important protective role for microglia in maintaining vascular integrity in the hypoxic brain.

Overexpression of α5ß1 integrin and angiopoietin-1 co-operatively promote blood-brain barrier integrity and angiogenesis following ischemic stroke.

We previously demonstrated that cross-talk between α5ß1 integrin and the angiopoietin-1 (Ang1) / Tie2 receptor plays an important role in regulating brain endothelial angiogenic responses in the ischemic penumbra following cerebral ischemic stroke (CIS). However, a recent study suggested that stimulation of the α5ß1 integrin also has the potential of increasing blood-brain barrier (BBB) permeability after CIS, raising doubt about whether α5ß1 integrin stimulation by itself will protect against ischemic injury. In light of these conflicting roles, the goal of this study was to evaluate the impact of co-overexpression of α5 integrin and Ang1 on vascular remodeling and repair under cerebral ischemic conditions both in vivo following 90 min of ischemia by temporary occlusion of the middle cerebral artery, and in vitro. Our results demonstrate that as compared to mock-transfected controls, overexpression of α5 integrin alone didn't improve the outcomes in neurological score and size of infarct and caused worse BBB breakdown in the ischemic hemisphere, offsetting its beneficial angiogenic effects during the early stages of CIS. However, co-overexpression of α5 integrin with Ang1 led to smaller infarcts and improved neurological deficits, which at the molecular level was underpinned by reduced BBB breakdown and increased expression of endothelial tight junction proteins in the ischemic penumbra during the early stages of CIS. Furthermore, co-overexpression of α5 integrin and Ang1 synergistically promoted BEC proliferation during the early stage of CIS, resulting in increased blood vessel density at later stages. Positive effects of α5 integrin and Ang1 co-overexpression on endothelial proliferation and tight junction protein expression were also confirmed in vitro. Collectively, these data indicate that co-overexpression of Ang-1 and α5 integrin in combination confers synergistic vascular protection against cerebral ischemic injury without the negative side effects on BBB permeability, suggesting a novel combinatorial approach for the treatment of CIS.

Integrin α5ß1-Ang1/Tie2 receptor cross-talk regulates brain endothelial cell responses following cerebral ischemia.

We have previously demonstrated that in response to cerebral ischemia (CI), the growth factor angiopoietin-1 (Ang1) and α5ß1 integrin are both induced in cerebral vessels, which likely provide positive signals driving the endogenous angiogenic response and vascular protection after CI. However, the precise relationship between endothelial Ang1 and α5ß1 integrin after CI remains poorly understood. Here, we investigated the effects of the interaction between the Ang1/Tie2 system and α5ß1 integrin on brain endothelial cells (BECs) under cerebral ischemic conditions in vivo and in vitro. Immunofluorescence analysis demonstrated that integrin α5ß1 co-localized with Tie2/phosphorylated Tie2 on cerebral vessels in the penumbra. The in vitro study showed that oxygen-glucose deprivation/restoration (OGD/R) induced the expression of the Ang1 receptor Tie2 on BECs in a manner similar to that for integrin α5 and Ang1 in response to OGD/R, accompanied by increased activation of Tie2 and its downstream effectors focal adhesion kinase (FAK) and Akt. Knockdown of α5 integrin markedly suppressed OGD/R-induced Tie2 receptor activation in BECs, while in contrast, priming BECs with Ang1 promoted the expression of α5 integrin as well as the Tie2 downstream transcription factor Ets-1 in OGD-treated BECs. In line with this, Ets-1 knockdown significantly attenuated Ang1-mediated upregulation of α5 integrin. Functionally, Ang1 induced cell migration and tube formation of BECs after OGD, but this effect was inhibited by diminishment of the levels of α5 integrin in BECs. Taken together, our data indicate that the Ang1/Tie2 system cross-talks with integrin α5ß1 in BECs after CI, which may contribute to the endogenous angiogenic vascular protective response following CI.

Optimizing performance through stress training - An educational strategy for surgical residents.

BACKGROUND: Stress management programs improve efficacy in aviation, military, and professional sports; however, similar educational strategies have not been adopted in surgical training. We have evaluated the effectiveness of a stress management program for surgical residents. METHODS: From 2011 to 2016, 137 surgical residents participated in a prospective, blinded study. The intervention group (n = 65) underwent training in self-awareness, focus, relaxation, positive self-talk, visualization, and team building. All participants subsequently completed a high-stress trauma simulation, requiring diagnosis and management of a life-threatening problem. Study endpoints included measures of procedural efficiency, and physiologic and subjective measurements of anxiety. RESULTS: Residents with stress training came to an accurate diagnosis 21% faster than controls (mean diagnosis time: 2.2 vs. 2.8 min; p = 0.04), and performed with greater technical accuracy (mean OSAT scores: 9.4 vs. 8.9; p = 0.03). Both cohorts exhibited similar physiologic and subjective anxiety metrics after simulation. CONCLUSIONS: Stress management education may enhance technical performance in surgical trainees during simulation. This underscores the need for early, comprehensive stress training in surgical residency.

Endothelial α6ß4 integrin protects during experimental autoimmune encephalomyelitis-induced neuroinflammation by maintaining vascular integrity and tight junction protein expression.

BACKGROUND: Extracellular matrix (ECM) proteins play critical functions regulating vascular formation and function. Laminin is a major component of the vascular basal lamina, and transgenic mice deficient in astrocyte or pericyte laminin show defective blood-brain barrier (BBB) integrity, indicating an important instructive role for laminin in cerebral blood vessels. As previous work shows that in the normal brain, vascular expression of the laminin receptor α6ß4 integrin is predominantly restricted to arterioles, but induced on all vessels during neuroinflammation, it is important to define the role of this integrin in the maintenance of BBB integrity. METHODS: α6ß4 integrin expression was analyzed using dual immunofluorescence (dual-IF) of brain sections taken from the mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). To investigate the role of endothelial α6ß4 integrin, transgenic mice lacking ß4 integrin in endothelial cells (ß4-EC-KO) and wild-type (WT) littermates were subject to EAE, and clinical score and various neuropathological parameters were examined by immunofluorescence. In addition, ß4 integrin null brain endothelial cells (BECs) were examined in culture for expression of tight junction proteins using immunocytochemistry and flow cytometry. RESULTS: Cerebrovascular expression of ß4 integrin was markedly upregulated during EAE progression, such that by the acute stage of EAE (day 21), the vast majority of blood vessels expressed ß4 integrin. In the EAE model, while the ß4-EC-KO mice showed the same time of disease onset as the WT littermates, they developed significantly worse clinical disease over time, resulting in increased clinical score at the peak of disease and maintained elevated thereafter. Consistent with this, the ß4-EC-KO mice showed enhanced levels of leukocyte infiltration and BBB breakdown and also displayed increased loss of the endothelial tight junction proteins claudin-5 and ZO-1. Under pro-inflammatory conditions, primary cultures of ß4KO BECs also showed increased loss of claudin-5 and ZO-1 expression. CONCLUSIONS: Taken together, our data suggest that α6ß4 integrin upregulation is an inducible protective mechanism that stabilizes the BBB during neuroinflammatory conditions.

An Informed Consent Program Enhances Surgery Resident Education.

OBJECTIVE: First-year residents often obtain informed consent from patients. However, they typically receive no formal training in this area before residency. We wished to determine whether an educational program would improve residents' comfort with this process. DESIGN: Our institution created an informed consent educational program, which included a didactic component, a role-play about informed consent, and a simulation exercise using standardized patients. Residents completed surveys before and after the intervention, and responses to survey questions were compared using the signed-rank test. SETTING: This study took place at Temple University Hospital, a tertiary care institution in Philadelphia, PA. PARTICIPANTS: First-year surgery and emergency medicine residents at Temple University Hospital in 2014 participated in this study. Thirty-two residents completed the preintervention survey and 27 residents completed the educational program and postintervention survey. RESULTS: Only 37.5% had ever received formal training in informed consent before residency. After participating in the educational program, residents were significantly more confident that they could correctly describe the process of informed consent, properly fill out a procedure consent form, and properly obtain informed consent from a patient. Their comfort level in obtaining informed consent significantly increased. They found the educational program to be very effective in improving their knowledge and comfort level in obtaining informed consent. In all, 100% (N = 27) of residents said they would recommend the use of the program with other first-year residents. CONCLUSIONS: Residents became more confident in their ability to obtain informed consent after participating in an educational program that included didactic, role-play, and patient simulation elements.

Cerebral ischemia-induced angiogenesis is dependent on tumor necrosis factor receptor 1-mediated upregulation of α5ß1 and αVß3 integrins.

BACKGROUND: The pro-inflammatory cytokine, tumor necrosis factor-α (TNF-α), is expressed in ischemic tissue and is known to modulate angiogenesis; however, the role of the two distinct TNF-α receptors, TNFR1 and TNFR2, in mediating angiogenic signaling after cerebral ischemic stroke is relatively unknown. METHODS: C57BL6 mice were subject to 90 min of ischemia by temporary occlusion of the middle cerebral artery (MCAO) and given daily intra-cerebroventricular injections of antibodies against TNFR1, TNFR2 or control IgG (doses of 10, 50, and 100 ng/day) for 4 days following 90 min MCAO. Vascular remodeling and α5ß1 and αVß3 integrin expression were then examined in the brains of these mice after 4, 7, and 14 days post-ischemia. In parallel in vitro studies, flow cytometry was used to determine the influence of TNF-α on proliferation and integrin expression of human brain microvascular endothelial cells (HBMECs). RESULTS: The post-ischemic cerebral angiogenic response was inhibited by antibodies against TNFR1 but not TNFR2, and this correlated with reduced endothelial proliferation and decreased α5ß1 and αVß3 integrin expression after 4 and 7 days post-ischemia. Consistent with these findings, in vitro studies showed that TNF-α induced endothelial proliferation and upregulation of α5ß1 and αVß3 integrins was abrogated by anti-TNFR1 but not anti-TNFR2 antibodies in cultured HBMECs. In addition, blocking antibodies to α5ß1 and αVß3 integrins significantly inhibited TNF-α-induced HBMEC proliferation. CONCLUSIONS: Our results suggest that TNFR1-mediated signaling plays a critical role in triggering angiogenic integrins and subsequent angiogenic responses following cerebral ischemia. These novel findings could form a platform for future therapeutic strategies aimed at stimulating angiogenesis following cerebral ischemia.

Extracellular matrix composition determines astrocyte responses to mechanical and inflammatory stimuli.

Astrocytes perform critical homeostatic physiological functions in the central nervous system (CNS) and are robustly responsive to injury, inflammation, or infection. We hypothesized that the components of the extracellular matrix (ECM), which are known to vary during development and in response to disease, determine astrocytic responses to injury and inflammation. We examined the response of primary astrocyte cultures grown on different ECM proteins to a mechanical wound (i.e., scratch). ECM substrates selected were laminin (Ln), vitronectin (Vn), fibronectin (Fn) or Tenascin C (TnC). We found that regrowth of the scratch wound was ECM dependent: recovery was arrested on fibronectin (Fn), almost complete on either Vn, Ln, or TnC. To determine whether ECM responses were also influenced by inflammation, we treated ECM plated cultures with interleukin-1ß (IL-1ß). We found that IL-1ß arrested astrocyte growth on Ln, accelerated astrocyte growth on Fn and had no significant effect on astrocyte growth on TnC or Vn. We also determined that blocking ß1integrins, the major class of receptors for all ECM proteins tested, prevented the robust response of astrocytes exposed to TnC, Ln and Vn, and also inhibited the robust effect of IL-1ß to stimulate astrocyte growth on Fn. In addition, we evaluated downstream targets of integrin signaling, specifically the mammalian target of rapamycin (mTOR), and determined that activation of this pathway contributed to the response of astrocytes grown on TnC, but not on Ln, Vn or Fn. These findings provide new insights into the role of ECM as a source of heterogeneity of glial responses that may have important implications for neuropathological sequelae.

"Permissive hypoventilation" in a swine model of hemorrhagic shock.

BACKGROUND: Many penetrating trauma patients in severe hemorrhagic shock receive positive pressure ventilation (PPV) upon transport to definitive care, either by intubation (INT) or bag-valve mask (BVM). Using a swine hemorrhagic shock model that simulates penetrating trauma, we proposed that severely injured patients may have better outcomes with "permissive hypoventilation," where manual breaths are not given and oxygen is administrated passively via face mask (FM). We hypothesized that PPV has harmful physiologic effects in severe low-flow states and that permissive hypoventilation would result in better outcomes. METHODS: The carotid arteries of Yorkshire pigs were cannulated with a 14-gauge catheter. One group of animals (n = 6) was intubated and manually ventilated, a second received PPV via BVM (n = 7), and a third group received 100% oxygen via FM (n = 6). After placement of a Swan-Ganz catheter, the carotid catheters were opened, and the animals were exsanguinated. The primary end point was time until death. Secondary end points included central venous pressure, cardiac output, lactate levels, serum creatinine, CO2 levels, and pH measured in 10-minute intervals. RESULTS: Average survival time in the FM group (50.0 minutes) was not different from the INT (51.1 minutes) and BVM groups (48.5 minutes) (p = 0.84). Central venous pressure was higher in the FM group as compared with the INT 10 minutes into the shock phase (8.3 mm Hg vs. 5.2 mm Hg, p = 0.04). Drop in cardiac output (p < 0.001) and increase in lactate (p < 0.05) was worse in both PPV groups throughout the shock phase. Creatinine levels were higher in both PPV groups (p = 0.04). The FM group was more hypercarbic and acidotic than the two PPV groups during the shock phase (p < 0.001). CONCLUSION: Although permissive hypoventilation leads to respiratory acidosis, it results in less hemodynamic suppression and better perfusion of vital organs. In severely injured penetrating trauma patients, consideration should be given to immediate transportation without PPV.

Analysis of TNF-alpha-mediated cerebral pericyte remodeling.

As well as being a central regulator of inflammatory and immune-mediated events, TNF-α also influences vascular remodeling, resulting in alterations in the structure and function of blood vessels. In addition to endothelial cells, pericytes are another type of vascular cell that significantly contribute to the development, maturation, stabilization, and remodeling of blood vessels. To investigate the regulatory influence of different factors on pericyte behavior, we recently described a novel yet simple approach of isolating and culturing highly pure, high density cultures of mouse brain pericytes. In this chapter, we briefly describe this culture system, as well as methods for examining different aspects of pericyte behavior, including cell adhesion, cell migration, and cell proliferation. These assays can be used to examine the influence of TNF-α or any other factor on pericyte behavior.

Examining vascular remodeling in the hypoxic central nervous system.

The goal of this chapter is to highlight techniques used to determine the role of molecular mechanisms involved in remodeling of cerebral blood vessels. Enhanced vascularization in the central nervous system (CNS) is seen in many diseases including stroke, cancer, and multiple sclerosis (MS). However, despite the prevalence of this phenomenon in these different pathological conditions, the exact nature of how it occurs still remains unclear. To better understand the process of cerebrovascular remodeling, we use the chronic hypoxia model, in which a vigorous and robust angiogenic remodeling response takes place. In this model, mice are placed in a hypoxic chamber (8 % O2 for up to 14 days), which results in strong vascular remodeling and increased vessel density within the CNS. Using an immunofluorescent (IF)-based approach, different aspects of this vascular remodeling response can be examined. By employing this method, we have shown that chronic mild hypoxia triggers both angiogenic (capillary sprouting) and arteriogenic (widening of arterial vessels) responses. Furthermore, we have used this system to define both the expression pattern and potential role of candidate adhesion molecules in this vascular remodeling process. Thus, the techniques described in this chapter can be used to define the importance of different molecular mechanisms in vascular remodeling in the CNS.

Early active mobilization following UCL repair With Mitek bone anchor.

Ulnar collateral ligament (UCL) injuries of the thumb are common. Surgical repair is accepted as the treatment of choice for complete rupture of the ligament. Biomechanical studies have suggested that Mitek bone anchor repairs are potentially safe and strong enough to allow early controlled active mobilization. To date, there have been no studies to compare early active mobilization following Mitek bone anchor repair to standard postoperative rehabilitation involving thumb spica immobilization for the first 4 to 6 weeks. We performed a small pilot randomized control trial to assess the outcome of this new rehabilitation technique to that of standard immobilization following UCL repair with Mitek bone anchor. Our results show that on average early active mobilization leads to an earlier return to full hand function (6 vs. 8 wk) and an earlier return to work (7 vs. 11 wk). There is no difference in the final range of motion achieved. We suggest that Mitek bone anchor repairs for UCL ruptures are robust enough to allow early active mobilization and that a larger trial is warranted to assess whether early active mobilization is superior to standard rehabilitation.

Microglia are the major source of TNF-α and TGF-ß1 in postnatal glial cultures; regulation by cytokines, lipopolysaccharide, and vitronectin.

Damage to the central nervous system (CNS) leads to increased production of TNF-α and TGF-ß1 cytokines that have pro- or anti-inflammatory actions, respectively. To define whether astrocytes or microglia express these cytokines, prior studies have used mixed glial cultures (MGC) to represent astrocytes, thought these results are inevitably complicated by the presence of contaminating microglia within MGC. To clarify the cellular source of these cytokines, here we employed a recently described method of preparing microglia-free astrocyte cultures, in which neural stem cells (NSC) are differentiated into astrocytes. Using ELISA to quantify cytokine production in three types of glial culture: MGC, pure microglia or pure astrocytes, this showed that microglia but not astrocytes, produce TNF-α, and that this expression is increased by LPS, IFN-γ, and to a lesser extent by vitronectin, but decreased by TGF-ß1. In contrast, TGF-ß1 was produced by microglia and astrocytes, though at 10-fold higher levels by microglia. TGF-ß1 expression in microglia was increased by vitronectin and to a lesser extent by TNF-α and LPS, but astrocyte TGF-ß1 expression was not regulated by any factor tested. In summary, our data reveal that microglia, not astrocytes are the major source of TNF-α and TGF-ß1 in postnatal glial cultures, and that microglial production of these antagonistic cytokines is tightly regulated by cytokines, LPS, and vitronectin.

Examining prehospital intubation for penetrating trauma in a swine hemorrhagic shock model.

BACKGROUND: Prehospital intubation does not result in a survival advantage in patients experiencing penetrating trauma, yet resistance to immediate transportation to facilitate access to definitive care remains. An animal model was developed to determine whether intubation provides a survival advantage during severe hemorrhagic shock. We hypothesized that intubation would not provide a survival advantage in potentially lethal hemorrhage. METHODS: After starting a propofol drip, Yorkshire pigs were intubated (n = 6) or given bag-valve mask ventilation (n = 7) using 100% oxygen. The carotid artery was cannulated with a 14-gauge catheter, and a Swan-Ganz catheter was placed under fluoroscopy using a central venous introducer. After obtaining baseline hemodynamic and laboratory data, the animals were exsanguinated through the carotid line until death. The primary end point was time until death, while secondary end points included volume of blood shed, temperature, cardiac index, mean arterial pressure, lactic acid, base excess, and creatinine levels measured in 10-minute intervals. RESULTS: There was no difference in time until death between the two groups (51.1 [2.5] minutes vs. 48.5 [2.4] minutes, p = 0.52). Intubated animals had greater volume of blood shed at 30 minutes (33.6 [4.4] mL/kg vs. 28.5 [4.3] mL/kg, p = 0.03), 40 minutes (41.7 [4.7] mL/kg vs. 34.9 [3.8] mL/kg, p = 0.04), and 50 minutes (49.2 [8.6] mL/kg vs. 40.2 [1.0] mL/kg, p = 0.001). In addition, the intubated animals were more hypothermic at 40 minutes (35.5°C [0.4°C] vs. 36.7°C [0.2°C], p = 0.01) and had higher lactate levels (2.4 [0.1] mmol/L vs. 1.8 [0.4] mmol/L, p = 0.04) at 10 minutes. Cardiac index (p = 0.66), mean arterial pressure (p = 0.69), base excess (p = 0.14), and creatinine levels (p = 0.37) were not different throughout the shock phase. CONCLUSION: Intubation does not convey a survival advantage in this model of severe hemorrhagic shock. Furthermore, intubation in the setting of severe hemorrhagic shock may result in a more profuse hemorrhage, worse hypothermia, and higher lactate when compared with bag-valve mask ventilation.

TNF-α promotes cerebral pericyte remodeling in vitro, via a switch from α1 to α2 integrins.

BACKGROUND: There is increasing evidence to suggest that pericytes play a crucial role in regulating the remodeling state of blood vessels. As cerebral pericytes are embedded within the extracellular matrix (ECM) of the vascular basal lamina, it is important to understand how individual ECM components influence pericyte remodeling behavior, and how cytokines regulate these events. METHODS: The influence of different vascular ECM substrates on cerebral pericyte behavior was examined in assays of cell adhesion, migration, and proliferation. Pericyte expression of integrin receptors was examined by flow cytometry. The influence of cytokines on pericyte functions and integrin expression was also examined, and the role of specific integrins in mediating these effects was defined by function-blocking antibodies. Expression of pericyte integrins within remodeling cerebral blood vessels was analyzed using dual immunofluorescence (IF) of brain sections derived from the animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). RESULTS: Fibronectin and collagen I promoted pericyte proliferation and migration, but heparan sulfate proteoglycan (HSPG) had an inhibitory influence on pericyte behavior. Flow cytometry showed that cerebral pericytes express high levels of α5 integrin, and lower levels of α1, α2, and α6 integrins. The pro-inflammatory cytokine tumor necrosis factor (TNF)-α strongly promoted pericyte proliferation and migration, and concomitantly induced a switch in pericyte integrins, from α1 to α2 integrin, the opposite to the switch seen when pericytes differentiated. Inhibition studies showed that α2 integrin mediates pericyte adhesion to collagens, and significantly, function blockade of α2 integrin abrogated the pro-modeling influence of TNF-α. Dual-IF on brain tissue with the pericyte marker NG2 showed that while α1 integrin was expressed by pericytes in both stable and remodeling vessels, pericyte expression of α2 integrin was strongly induced in remodeling vessels in EAE brain. CONCLUSIONS: Our results suggest a model in which ECM constituents exert an important influence on pericyte remodeling status. In this model, HSPG restricts pericyte remodeling in stable vessels, but during inflammation, TNF-α triggers a switch in pericyte integrins from α1 to α2, thereby stimulating pericyte proliferation and migration on collagen. These results thus define a fundamental molecular mechanism in which TNF-α stimulates pericyte remodeling in an α2 integrin-dependent manner.

Stress training for the surgical resident.

BACKGROUND: Much effort in surgical education is placed on the development of clinical judgment and technical proficiency. However, little focus is placed on the management of stress associated with surgical performance. The inability to manage stress may lead to poor patient care, attrition from residency, and surgeon burnout. METHODS: A blinded, matched, comparison group study to evaluate the efficacy of an educational program designed to improve surgical resident performance during stressful scenarios was conducted. The experimental group (n = 11) participated in stress training sessions, whereas the control group (n = 15) did not. Both groups then completed a simulation during which stress was evaluated using objective and subjective measures, and resident performance was graded using a standardized checklist. RESULTS: Performance checklist scores were 5% higher in the experimental group than the control group (P = .54). No change existed in anxiety state according to the State Trait Anxiety Inventory (P = .34) or in heart rate under stress (P = .17) between groups. CONCLUSIONS: There was a trend toward improved performance scoring but no difference in anxiety levels after stress training. However, 91% of residents rated the stress training as valuable.

Still making the case against prehospital intubation: a rat hemorrhagic shock model.

BACKGROUND: Prehospital intubation does not appear to result in a survival advantage for patients experiencing penetrating trauma; yet, there is still resistance to the practice of "scoop and run" to speed access to advanced care. An animal model was used to determine whether intubation provides a survival advantage during potentially lethal hemorrhage. METHODS: The carotid arteries of Sprague-Dawley rats were cannulated, and mean arterial pressure (MAP) was measured. One group of animals (n = 10) was intubated and placed on a ventilator, whereas the other (n = 9) was administered with 100% oxygen via nose cone. Rats were exsanguinated to a MAP of 40 mm Hg and then bled periodically to maintain a MAP between 40 mm Hg and 45 mm Hg. The primary end-point was time until death. Secondary end-points included lactic acid and base excess levels measured in blood collected at 30-minute intervals after inducing shock. RESULTS: There was no significant difference in time until death between the intubated and nose cone groups (85.5 vs. 93.3 minutes, p = 0.60). Intubated animals had higher lactic acid levels at 90 minutes (6.1 vs. 3.5 mmol/L; p = 0.02) and 120 minutes (7.7 vs. 2.6 mmol/L, p = 0.03) after the initiation of shock. In addition, intubated animals had worse base excess at 90 minutes (-13.5 vs. -7.9 mmol/L, p = 0.04). CONCLUSION: Intubation does not result in a survival advantage in this rat model of hemorrhagic shock. Positive pressure ventilation may cause decreased venous return and accentuate end-organ hypoperfusion. Large animal studies are needed to further investigate these findings.

Chronic cerebral hypoxia promotes arteriogenic remodeling events that can be identified by reduced endoglin (CD105) expression and a switch in ß1 integrins.

Chronic cerebral hypoxia leads to a strong vascular remodeling response, though little is known about which part of the vascular tree is modified, or whether this response includes formation of new arterial vessels. In this study, we examined this process in detail, analyzing how hypoxia (8% O(2) for 14 days) alters the size distribution of vessels, number of arteries/arterioles, and expression pattern of endoglin (CD105), a marker of angiogenic endothelial cells in tumors. We found that cerebral hypoxia promoted the biggest increase in the number of medium to large size vessels, and this correlated with increased numbers of alpha smooth muscle actin (α-SMA)-positive arterial vessels. Surprisingly, hypoxia induced a marked reduction in CD105 expression on brain endothelial cells (BECs) within remodeling arterial vessels, and these BECs also displayed an angiogenic switch in ß1 integrins (from α6 to α5), previously described for developmental angiogenesis. In vitro, transforming growth factor (TGF)-ß1 also promoted this switch of BEC ß1 integrins. Together, these results show that cerebral hypoxia promotes arteriogenesis, and identify reduced CD105 expression as a novel marker of arteriogenesis. Furthermore, our data suggest a mechanistic model whereby BECs in remodeling arterial vessels downregulate CD105 expression, which alters TGF-ß1 signaling, to promote a switch in ß1 integrins and arteriogenic remodeling.