Spatial subsetting enables integrative modeling of oral squamous cell carcinoma multiplex imaging data.

Oral squamous cell carcinoma (OSCC), a prevalent and aggressive neoplasm, poses a significant challenge due to poor prognosis and limited prognostic biomarkers. Leveraging highly multiplexed imaging mass cytometry, we investigated the tumor immune microenvironment (TIME) in OSCC biopsies, characterizing immune cell distribution and signaling activity at the tumor-invasive front. Our spatial subsetting approach standardized cellular populations by tissue zone, improving feature reproducibility and revealing TIME patterns accompanying loss-of-differentiation. Employing a machine-learning pipeline combining reliable feature selection with multivariable modeling, we achieved accurate histological grade classification (AUC = 0.88). Three model features correlated with clinical outcomes in an independent cohort: granulocyte MAPKAPK2 signaling at the tumor front, stromal CD4+ memory T cell size, and the distance of fibroblasts from the tumor border. This study establishes a robust modeling framework for distilling complex imaging data, uncovering sentinel characteristics of the OSCC TIME to facilitate prognostic biomarkers discovery for recurrence risk stratification and immunomodulatory therapy development.

Objective Activity Parameters Track Patient-specific Physical Recovery Trajectories After Surgery and Link With Individual Preoperative Immune States.

OBJECTIVE: The longitudinal assessment of physical function with high temporal resolution at a scalable and objective level in patients recovering from surgery is highly desirable to understand the biological and clinical factors that drive the clinical outcome. However, physical recovery from surgery itself remains poorly defined and the utility of wearable technologies to study recovery after surgery has not been established. BACKGROUND: Prolonged postoperative recovery is often associated with long-lasting impairment of physical, mental, and social functions. Although phenotypical and clinical patient characteristics account for some variation of individual recovery trajectories, biological differences likely play a major role. Specifically, patient-specific immune states have been linked to prolonged physical impairment after surgery. However, current methods of quantifying physical recovery lack patient specificity and objectivity. METHODS: Here, a combined high-fidelity accelerometry and state-of-the-art deep immune profiling approach was studied in patients undergoing major joint replacement surgery. The aim was to determine whether objective physical parameters derived from accelerometry data can accurately track patient-specific physical recovery profiles (suggestive of a 'clock of postoperative recovery'), compare the performance of derived parameters with benchmark metrics including step count, and link individual recovery profiles with patients' preoperative immune state. RESULTS: The results of our models indicate that patient-specific temporal patterns of physical function can be derived with a precision superior to benchmark metrics. Notably, 6 distinct domains of physical function and sleep are identified to represent the objective temporal patterns: ''activity capacity'' and ''moderate and overall activity (declined immediately after surgery); ''sleep disruption and sedentary activity (increased after surgery); ''overall sleep'', ''sleep onset'', and ''light activity'' (no clear changes were observed after surgery). These patterns can be linked to individual patients preopera-tive immune state using cross-validated canonical-correlation analysis. Importantly, the pSTAT3 signal activity in monocytic myeloid-derived suppressor cells predicted a slower recovery. CONCLUSIONS: Accelerometry-based recovery trajectories are scalable and objective outcomes to study patient-specific factors that drive physical recovery.

Risk factors for prolonged time to hospital discharge after ambulatory cholecystectomy under general anaesthesia. A retrospective cohort study.

BACKGROUND: Although predictive models have already integrated demographic factors and comorbidities as risk factors for a prolonged hospital stay, factors related to anaesthesia management in ambulatory surgery have not been yet characterized. This study aims to identify anaesthetic factors associated with a prolonged discharge time in ambulatory surgery. METHODS: All clinical records of patients who underwent ambulatory cholecystectomy in a French University Hospital (Hôpital Saint Antoine, Paris) between January 1st, 2012 and December 31st, 2018 were retrospectively reviewed. The primary endpoint was the discharge time, defined as the time between the end of surgery and discharge. A multivariable Cox proportional-hazards model was fitted to investigate the factors associated with a prolonged discharge time. RESULTS: Five hundred and thirty-five (535) patients were included. The median time for discharge was 150 min (interquartile range - IQR [129-192]). A bivariable analysis highlighted a positive correlation between discharge timeline and the doses-weight of ketamine and sufentanil. In the multivariable Cox proportional hazards model analysis, the anaesthesia-related factors independently associated with prolonged discharge time were the dose-weight of ketamine in interaction with the dose weight of sufentanil (HR 0.10 per increment of 0.1 mg/kg of ketamine or 0.2 µg/kg of sufentanil, CI 95% [0.01-0.61], p = 0.013) and the non-use of a non-steroidal anti-inflammatory drug (NSAID) (HR 0.81 [0.67-0.98], p = 0.034). Twenty patients (4%) had unscheduled hospitalization following surgery. CONCLUSION: Anaesthesia management, namely the use of ketamine and the non-use of NSAID, affects time to hospital discharge.

Integrated Single-cell and Plasma Proteomic Modeling to Predict Surgical Site Complications: A Prospective Cohort Study.

OBJECTIVE: The aim of this study was to determine whether single-cell and plasma proteomic elements of the host's immune response to surgery accurately identify patients who develop a surgical site complication (SSC) after major abdominal surgery. SUMMARY BACKGROUND DATA: SSCs may occur in up to 25% of patients undergoing bowel resection, resulting in significant morbidity and economic burden. However, the accurate prediction of SSCs remains clinically challenging. Leveraging high-content proteomic technologies to comprehensively profile patients' immune response to surgery is a promising approach to identify predictive biological factors of SSCs. METHODS: Forty-one patients undergoing non-cancer bowel resection were prospectively enrolled. Blood samples collected before surgery and on postoperative day one (POD1) were analyzed using a combination of single-cell mass cytometry and plasma proteomics. The primary outcome was the occurrence of an SSC, including surgical site infection, anastomotic leak, or wound dehiscence within 30 days of surgery. RESULTS: A multiomic model integrating the single-cell and plasma proteomic data collected on POD1 accurately differentiated patients with (n = 11) and without (n = 30) an SSC [area under the curve (AUC) = 0.86]. Model features included coregulated proinflammatory (eg, IL-6- and MyD88- signaling responses in myeloid cells) and immunosuppressive (eg, JAK/STAT signaling responses in M-MDSCs and Tregs) events preceding an SSC. Importantly, analysis of the immunological data obtained before surgery also yielded a model accurately predicting SSCs (AUC = 0.82). CONCLUSIONS: The multiomic analysis of patients' immune response after surgery and immune state before surgery revealed systemic immune signatures preceding the development of SSCs. Our results suggest that integrating immunological data in perioperative risk assessment paradigms is a plausible strategy to guide individualized clinical care.

Measuring the human immune response to surgery: multiomics for the prediction of postoperative outcomes.

PURPOSE OF REVIEW: Postoperative complications including infections, cognitive impairment, and protracted recovery occur in one-third of the 300 million surgeries performed annually worldwide. Complications cause personal suffering along with a significant economic burden on our healthcare system. However, the accurate prediction of postoperative complications and patient-targeted interventions for their prevention remain as major clinical challenges. RECENT FINDINGS: Although multifactorial in origin, the dysregulation of immunological mechanisms that occur in response to surgical trauma is a key determinant of postoperative complications. Prior research, primarily focusing on inflammatory plasma markers, has provided important clues regarding their pathogenesis. However, the recent advent of high-content, single-cell transcriptomic, and proteomic technologies has considerably improved our ability to characterize the immune response to surgery, thereby providing new means to understand the immunological basis of postoperative complications and to identify prognostic biological signatures. SUMMARY: The comprehensive and single-cell characterization of the human immune response to surgery has significantly advanced our ability to predict the risk of postoperative complications. Multiomic modeling of patients' immune states holds promise for the discovery of preoperative predictive biomarkers, ultimately providing patients and surgeons with actionable information to improve surgical outcomes. Although recent studies have generated a wealth of knowledge, laying the foundation for a single-cell atlas of the human immune response to surgery, larger-scale multiomic studies are required to derive robust, scalable, and sufficiently powerful models to accurately predict the risk of postoperative complications in individual patients.

Structural basis for target site selection in RNA-guided DNA transposition systems.

CRISPR-associated transposition systems allow guide RNA-directed integration of a single DNA cargo in one orientation at a fixed distance from a programmable target sequence. We used cryo-electron microscopy (cryo-EM) to define the mechanism that underlies this process by characterizing the transposition regulator, TnsC, from a type V-K CRISPR-transposase system. In this scenario, polymerization of adenosine triphosphate-bound TnsC helical filaments could explain how polarity information is passed to the transposase. TniQ caps the TnsC filament, representing a universal mechanism for target information transfer in Tn7/Tn7-like elements. Transposase-driven disassembly establishes delivery of the element only to unused protospacers. Finally, TnsC transitions to define the fixed point of insertion, as revealed by structures with the transition state mimic ADP•AlF3 These mechanistic findings provide the underpinnings for engineering CRISPR-associated transposition systems for research and therapeutic applications.

Preferential inhibition of adaptive immune system dynamics by glucocorticoids in patients after acute surgical trauma.

Glucocorticoids (GC) are a controversial yet commonly used intervention in the clinical management of acute inflammatory conditions, including sepsis or traumatic injury. In the context of major trauma such as surgery, concerns have been raised regarding adverse effects from GC, thereby necessitating a better understanding of how GCs modulate the immune response. Here we report the results of a randomized controlled trial (NCT02542592) in which we employ a high-dimensional mass cytometry approach to characterize innate and adaptive cell signaling dynamics after a major surgery (primary outcome) in patients treated with placebo or methylprednisolone (MP). A robust, unsupervised bootstrap clustering of immune cell subsets coupled with random forest analysis shows profound (AUC = 0.92, p-value = 3.16E-8) MP-induced alterations of immune cell signaling trajectories, particularly in the adaptive compartments. By contrast, key innate signaling responses previously associated with pain and functional recovery after surgery, including STAT3 and CREB phosphorylation, are not affected by MP. These results imply cell-specific and pathway-specific effects of GCs, and also prompt future studies to examine GCs' effects on clinical outcomes likely dependent on functional adaptive immune responses.

Hemoglobin ß93 Cysteine Is Not Required for Export of Nitric Oxide Bioactivity From the Red Blood Cell.

BACKGROUND: Nitrosation of a conserved cysteine residue at position 93 in the hemoglobin ß chain (ß93C) to form S-nitroso (SNO) hemoglobin (Hb) is claimed to be essential for export of nitric oxide (NO) bioactivity by the red blood cell (RBC) to mediate hypoxic vasodilation and cardioprotection. METHODS: To test this hypothesis, we used RBCs from mice in which the ß93 cysteine had been replaced with alanine (ß93A) in a number of ex vivo and in vivo models suitable for studying export of NO bioactivity. RESULTS: In an ex vivo model of cardiac ischemia/reperfusion injury, perfusion of a mouse heart with control RBCs (ß93C) pretreated with an arginase inhibitor to facilitate export of RBC NO bioactivity improved cardiac recovery after ischemia/reperfusion injury, and the response was similar with ß93A RBCs. Next, when human platelets were coincubated with RBCs and then deoxygenated in the presence of nitrite, export of NO bioactivity was detected as inhibition of ADP-induced platelet activation. This effect was the same in ß93C and ß93A RBCs. Moreover, vascular reactivity was tested in rodent aortas in the presence of RBCs pretreated with S-nitrosocysteine or with hemolysates or purified Hb treated with authentic NO to form nitrosyl(FeII)-Hb, the proposed precursor of SNO-Hb. SNO-RBCs or NO-treated Hb induced vasorelaxation, with no differences between ß93C and ß93A RBCs. Finally, hypoxic microvascular vasodilation was studied in vivo with a murine dorsal skin-fold window model. Exposure to acute systemic hypoxia caused vasodilatation, and the response was similar in ß93C and ß93A mice. CONCLUSIONS: RBCs clearly have the fascinating ability to export NO bioactivity, but this occurs independently of SNO formation at the ß93 cysteine of Hb.

Gliosarcoma: Neuroimaging and Immunohistochemical Findings.

BACKGROUND AND PURPOSE: Gliosarcoma (GSC) is an intra-axial lesion which often abuts a dural margin and is composed of glial and mesenchymal elements. This lesion is considered a variant of isocitrate dehydrogenase (IDH)-wild type glioblastoma (GBM). The purpose of this study is to evaluate the imaging and molecular features of GSC in a large patient cohort. METHODS: Pathology-proved GSC cases were collected from our quaternary care center spanning the last 16 years and IDH status was documented. Older GSC cases without prior immunohistochemical testing underwent tissue block staining to obtain IDH status. When available, p53, phosphate and tensin (PTEN), MIB-1, EGFR amplification, and MGMT methylation were recorded and imaging findings tabulated. Logistic regression analyses were performed to determine correlation of molecular markers and imaging characteristics. RESULTS: A total of 25 cases were identified (21 de novo, 4 post-treatment). All lesions contacted a dural, pial, or ependymal surface and were negative for an IDH R132H mutation, including postradiation GSC. In total, 16 of 16 cases showed nonamplification of EGFR/CEP7, 2 of 16 demonstrated MGMT methylation, and multiple lesions demonstrated p53 and PTEN mutations. Imaging features included areas of nodular thickening in necrotic lesions which appeared to abut the site of dural contact. There was no significant correlation of molecular markers with imaging characteristics. CONCLUSION: GSC was IDH(-) in all cases, supporting the current understanding of this lesion being a wild-type GBM variant. Additional molecular markers demonstrated no significant correlation with imaging findings in this cohort.

Using CT texture analysis to differentiate between nasopharyngeal carcinoma and age-matched adenoid controls.

OBJECTIVES: To investigate the use of texture analysis to quantitatively distinguish nasopharyngeal carcinoma (NPC) from normal adenoid on CT. METHODS: In this IRB-approved, retrospective study, nasopharyngeal tissues in 13 patients with NPC and 13 control patients were manually contoured, segmented, and imported to an in-house developed texture analysis program, which extracted 41 texture features. Basic descriptive statistics were performed to evaluate for differences in texture parameters between NPC and controls. RESULTS: Statistically significant differences between NPC and controls were seen in 32 of 41 texture features. These significant differences were present in 11 of 12 histogram features, 4 of 5 gray-level co-occurrence matrix features, 7 of 11 gray-level run length features, 4 of 4 gray-level gradient matrix features, and 6 of 9 Laws features. CONCLUSION: Significant differences in many texture features were seen between NPC and normal adenoids. CT texture analysis may aid in differentiating NPC from normal adenoid tissue.

Decreased microbiome diversity in the HIV small airway epithelium.

BACKGROUND: Persons living with human immunodeficiency virus (PLWH) face an increased burden of chronic obstructive pulmonary disease (COPD). Repeated pulmonary infections, antibiotic exposures, and immunosuppression may contribute to an altered small airway epithelium (SAE) microbiome. METHODS: SAE cells were collected from 28 PLWH and 48 HIV- controls through bronchoscopic cytologic brushings. DNA extracted from SAE cells was subjected to 16S rRNA amplification and sequencing. Comparisons of alpha and beta diversity between HIV+ and HIV- groups were performed and key operational taxonomic units (OTUs) distinguishing the two groups were identified using the Boruta feature selection after Random Forest Analysis. RESULTS: PLWH demonstrated significantly reduced Shannon diversity compared with HIV- volunteers (1.82 ± 0.10 vs. 2.20 ± 0.073, p = 0.0024). This was primarily driven by a reduction in bacterial richness (23.29 ± 2.75 for PLWH and 46.04 ± 3.716 for HIV-, p < 0.0001). Phyla distribution was significantly altered among PLWH, with an increase in relative abundance of Proteobacteria (p = 0.0003) and a decrease in Bacteroidetes (p = 0.0068) and Firmicutes (p = 0.0002). Six discriminative OTUs were found to distinguish PLWH from HIV- volunteers, aligning to Veillonellaceae, Fusobacterium, Verrucomicrobiaceae, Prevotella, Veillonella, and Campylobacter. CONCLUSIONS: Compared to HIV- controls, PLWH's SAE microbiome is marked by reduced bacterial diversity and richness with significant differences in community composition.

Occipital intraosseous dermoid cyst with restricted diffusion on magnetic resonance imaging in a child.

A 4-year-old girl presented repeatedly with a complicated occipital mass, which was erroneously treated as a pyogenic granuloma. Imaging performed before a planned surgical resection detected an underlying intraoccipital dermoid with a sinus tract to the skin surface and extension into the posterior fossa. This case highlights the value of high-resolution computed tomography imaging for depiction of anatomic details and the value of magnetic resonance imaging for differential diagnosis and surgical management. A comprehensive literature review of intraosseous dermoid cyst and detailed discussion of the differential diagnoses are provided.

Randomized controlled trial of emergency department initiated smoking cessation counselling and referral to a community counselling service.

OBJECTIVE: Worldwide, tobacco smoke is still the leading cause of preventable morbidity and mortality. Many smokers develop chronic smoking-related conditions that require emergency department (ED) visits. However, best practices for ED smoking cessation counselling are still unclear. METHODS: A randomized controlled trial was conducted to determine whether an "ask, advise, and refer" approach increases 12-month, 30-day quit rates in the stable adult ED smoking population compared to usual care. Patients in the intervention group were referred to a community counselling service that offers a quitline, a text-based program, and a Web-based program. Longitudinal intention-to-treat analyses were performed. RESULTS: From November 2011 to March 2013, 1,295 patients were enrolled from one academic tertiary care ED. Six hundred thirty-five were allocated to usual care, and 660 were allocated to intervention. Follow-up data were available for 70% of all patients at 12 months. There was no statistically significant difference in 12-month, 30-day quit rates between the two groups. However, there was a trend towards higher 7-day quit attempts, 7-day quit rates, and 30-day quit rates at 3, 6, and 12 months in the intervention group. CONCLUSION: In this study, there was a trend towards increased smoking cessation following referral to a community counselling service. There was no statistically significant difference. However, if ED smoking cessation efforts were to provide even a small positive effect, such an intervention may have a significant public health impact given the extensive reach of emergency physicians.

Deep Immune Profiling of an Arginine-Enriched Nutritional Intervention in Patients Undergoing Surgery.

Application of high-content immune profiling technologies has enormous potential to advance medicine. Whether these technologies reveal pertinent biology when implemented in interventional clinical trials is an important question. The beneficial effects of preoperative arginine-enriched dietary supplements (AES) are highly context specific, as they reduce infection rates in elective surgery, but possibly increase morbidity in critically ill patients. This study combined single-cell mass cytometry with the multiplex analysis of relevant plasma cytokines to comprehensively profile the immune-modifying effects of this much-debated intervention in patients undergoing surgery. An elastic net algorithm applied to the high-dimensional mass cytometry dataset identified a cross-validated model consisting of 20 interrelated immune features that separated patients assigned to AES from controls. The model revealed wide-ranging effects of AES on innate and adaptive immune compartments. Notably, AES increased STAT1 and STAT3 signaling responses in lymphoid cell subsets after surgery, consistent with enhanced adaptive mechanisms that may protect against postsurgical infection. Unexpectedly, AES also increased ERK and P38 MAPK signaling responses in monocytic myeloid-derived suppressor cells, which was paired with their pronounced expansion. These results provide novel mechanistic arguments as to why AES may exert context-specific beneficial or adverse effects in patients with critical illness. This study lays out an analytical framework to distill high-dimensional datasets gathered in an interventional clinical trial into a fairly simple model that converges with known biology and provides insight into novel and clinically relevant cellular mechanisms.

Prevalence of potential smoking-related conditions among tobacco users in the emergency department and their perception that their visit may be smoking-related.

OBJECTIVES: Patients who are tobacco users present to the emergency department (ED) with many medical conditions that are causally or potentially causally related to smoking. Previous studies have shown increased cessation rates for patients who accurately perceive that their ED visit is smoking-related. Our study goals were 1) to determine the prevalence of potential smoking-related conditions among tobacco users at a tertiary care academic ED, and 2) to determine which medical conditions are more or less likely to be perceived by patients as smoking-related. METHODS: We included adults≥19 years of age who reported smoking within 30 days of their ED visit, and were enrolled in a randomized controlled trial (ClinicalTrials.gov, NCT01454375) from December 1, 2011 to August 31, 2012. Patients were asked whether they perceived their ED visit to be related to smoking. ED discharge diagnoses were coded as smoking-related or not smoking-related based on the 2004 U.S. Surgeon General's Report. RESULTS: We included 893 patients (62% male; mean age=40±15), of which 120 (13%) had a visit for a potential smoking-related condition: 6 (5%) of neoplasm, 18 (15%) of cardiovascular disease, 67 (56%) of respiratory disease, 3 (3%) of reproductive complication, 7 (6%) of postoperative complication, 9 (8%) of dental disease, 9 (8%) of peptic ulcer disease, 0 (0%) of eye condition, and 1 (1%) of bony condition. Of the potential smoking-related conditions, 46 (38%) were perceived by patients to be possibly smoking-related: 61% of cardiovascular disease, 33% of neoplasm, 43% of respiratory disease, 22% of dental disease, 14% of postoperative complication, 11% of peptic ulcer disease, and 0% of the remaining conditions. CONCLUSION: In this study, 13% of all ED visits among smokers were for a potential smoking-related condition, of which 38% were perceived by patients to be smoking-related. Education to increase awareness of smoking-related conditions may increase cessation rates.

Drosophila adducin regulates Dlg phosphorylation and targeting of Dlg to the synapse and epithelial membrane.

Adducin is a cytoskeletal protein having regulatory roles that involve actin filaments, functions that are inhibited by phosphorylation of adducin by protein kinase C. Adducin is hyperphosphorylated in nervous system tissue in patients with the neurodegenerative disease amyotrophic lateral sclerosis, and mice lacking ß-adducin have impaired synaptic plasticity and learning. We have found that Drosophila adducin, encoded by hu-li tai shao (hts), is localized to the post-synaptic larval neuromuscular junction (NMJ) in a complex with the scaffolding protein Discs large (Dlg), a regulator of synaptic plasticity during growth of the NMJ. hts mutant NMJs are underdeveloped, whereas over-expression of Hts promotes Dlg phosphorylation, delocalizes Dlg away from the NMJ, and causes NMJ overgrowth. Dlg is a component of septate junctions at the lateral membrane of epithelial cells, and we show that Hts regulates Dlg localization in the amnioserosa, an embryonic epithelium, and that embryos doubly mutant for hts and dlg exhibit defects in epithelial morphogenesis. The phosphorylation of Dlg by the kinases PAR-1 and CaMKII has been shown to disrupt Dlg targeting to the NMJ and we present evidence that Hts regulates Dlg targeting to the NMJ in muscle and the lateral membrane of epithelial cells by controlling the protein levels of PAR-1 and CaMKII, and consequently the extent of Dlg phosphorylation.

Semi-quantitative expression of tissue inhibitor of matrix metalloproteinase-2 in cancer of uterine cervix.

BACKGROUND AND OBJECTIVE: Because matrix metalloproteinase-2 (MMP-2) is associated with tumor progression and tissue inhibitor of MMP-2 (TIMP-2) selectively inhibits MMP-2, we investigate the implication of TIMP-2 in carcinogenesis of uterine cervix. METHODS: Twenty-six cervical cancer tissues and their normal counterparts were collected to evaluate semi-quantitative mRNA expression of TIMP-2. Eighty-two cervical cancer, 26 high-grade and 26 low-grade dysplasia, and 26 normal tissues were collected to construct tissue microarrays for immunohistochemical study. We evaluated TIMP-2 immunoreactivity using H scores in cervical carcinogenesis. Semi-quantitative expression of MMP-2 was also detected for comparison. RESULTS: Cervical cancer tissues exhibited statistically lower semi-quantitative TIMP-2 (P = 0.028) or higher MMP-2 (P = 0.036) mRNA expression than their normal counterparts. None of cervical cancer tissues exerted elevated TIMP-2 and reduced MMP-2 mRNA expression simultaneously. Cancer tissues have significantly lower TIMP-2 or higher MMP-2 H scores than high-grade and low-grade dysplasia or normal tissues of uterine cervix. CONCLUSIONS: Low expression of TIMP-2 or high expression of MMP-2 is semi-quantitatively demonstrated in cancer of uterine cervix. TIMP-2 is implicated in cervical carcinogenesis.

Ventricular catheter placement accuracy in non-stereotactic shunt surgery for hydrocephalus.

We aimed to compare the accuracy of different shunt catheter approaches to the lateral ventricle in adults with hydrocephalus. We conducted a retrospective review of 138 consecutive patients with hydrocephalus undergoing freehand initial shunt surgery. Of these, 79 had a post-operative brain scan and therefore the results were available for analysis. Scans were graded for successful catheter tip placement in the ventricular target zones: the frontal horn for frontal and occipital approaches, and the atrium for the parietal approach. Ventricular target zones were successfully catheterized in 85% of parietal and 64% of frontal shunts (this difference is not statistically significant). In contrast, only 42% of occipital shunts were correctly placed (p<0.01). Therefore, parietal and frontal catheters are more likely to be placed successfully in the target ventricle. This may be due to the smaller range of successful trajectories open to the occipital approach. Solutions to this problem may include using the theoretically favourable frontal approach for freehand surgery or using stereotactic guidance.

The Fas system confers protection against alveolar disruption in hyperoxia-exposed newborn mice.

The functional significance of the Fas/Fas-ligand (FasL) system in hyperoxia-induced lung injury and alveolar disruption in newborn lungs in vivo remains undetermined. To assess the role of the Fas/FasL system, we compared the effects of hyperoxia (95% O2 from birth to Postnatal Day [P]7) in Fas-deficient lpr mice and wild-type mice. Alveolar disruption was more severe in hyperoxic lpr mice than in wild-type mice. In addition, a transient alveolarization defect was noted in normoxic lpr mice. Hyperoxia induced marked up-regulation of pulmonary Fas expression in wild-type mice, as well as elevated mRNA levels of pro-apoptotic Bax, Bad, and Bak. Pulmonary apoptotic activity was similar in hyperoxic wild-type and lpr mice. In contrast, lung growth and proliferation, assessed by stereologic volumetry and Ki67 proliferation studies, were significantly higher in hyperoxic wild-type mice compared with lpr mice, suggesting the Fas/FasL system has a pro-proliferative role in hyperoxic conditions. Levels of the prosurvival MAPkinase, pERK1/2, were significantly higher in hyperoxic wild-type mice compared with lpr mice, while pAkt levels were similar. These data suggest that the primary role of the Fas/FasL system in hyperoxic newborn lungs is pro-proliferative, rather than pro-apoptotic, and likely mediated through a Fas-ERK1/2 pathway. Fas-induced proliferation and lung growth in hyperoxic newborn lungs may counteract, in part, the detrimental effects of apoptosis mediated by non-Fas pathways, such as pro-apoptotic Bax/Bcl-2 family members. The capacity of the Fas/FasL signaling pathway to mediate protective rather than destructive functions in hyperoxic newborn lungs highlights the versatility of this complex pathway.