Verticillium dahliae Vta3 promotes ELV1 virulence factor gene expression in xylem sap, but tames Mtf1-mediated late stages of fungus-plant interactions and microsclerotia formation.

Verticillium transcription activator of adhesion 3 (Vta3) is required for plant root colonization and pathogenicity of the soil-borne vascular fungus Verticillium dahliae. RNA sequencing identified Vta3-dependent genetic networks required for growth in tomato xylem sap. Vta3 affects the expression of more than 1,000 transcripts, including candidates with predicted functions in virulence and morphogenesis such as Egh16-like virulence factor 1 (Elv1) and Master transcription factor 1 (Mtf1). The genes encoding Elv1 and Mtf1 were deleted and their functions in V. dahliae growth and virulence on tomato (Solanum lycopersicum) plants were investigated using genetics, plant infection experiments, gene expression studies and phytohormone analyses. Vta3 contributes to virulence by promoting ELV1 expression, which is dispensable for vegetative growth and conidiation. Vta3 decreases disease symptoms mediated by Mtf1 in advanced stages of tomato plant colonization, while Mtf1 induces the expression of fungal effector genes and tomato pathogenesis-related protein genes. The levels of pipecolic and salicylic acids functioning in tomato defense signaling against (hemi-) biotrophic pathogens depend on the presence of MTF1, which promotes the formation of resting structures at the end of the infection cycle. In summary, the presence of VTA3 alters gene expression of virulence factors and tames the Mtf1 genetic subnetwork for late stages of plant disease progression and subsequent survival of the fungus in the soil.

Bipolar radio-frequency-induced thermofusion of intestinal tissue - In vivo evaluation of a new fusion technique in an experimental study.

PURPOSE: Bipolar radio-frequency-induced thermofusion (BiRTh) of intestinal tissue might replace conventional stapling devices which are associated with technical and functional complications. Previous results of our study group confirmed the feasibility to fuse intestinal tissue using BiRTh-induced thermofusion ex vivo. The aim of this study was now to evaluate the efficacy of fusing intestinal tissue in vivo by BiRTh-induced thermofusion. MATERIALS AND METHODS: In male Wistar rats a blind bowel originating from the caecum was closed either by BiRTh (n = 24) or conventional suture (n = 16). At 6 h, 48 h, 4 days, and 2 weeks after the procedure caecum bursting pressure was measured to compare both groups. RESULTS: In total 18 of 21 (85.7%) thermofused and 15 of 16 (93.7%) sutured cecal stumps were primarily tight and leakage-proof (p > 0.05). The operative time was comparable in both groups without significant differences. Both groups showed increases in bursting pressure over the post-operative period. The mean bursting pressure for thermofusion was 47.8, 48.3, 55.2, and 68.0 mmHg, compared to 69.8, 51.5, 70.0 and 71.0 mmHg in the hand-sutured group (p > 0.05) after 6 h, 48 h, 4 days, and 2 weeks, respectively. CONCLUSION: These results suggest that BiRTh-induced thermofusion is a safe and feasible method for fusing intestinal tissue in this experimental in vivo model and could be an innovative approach for achieving gastrointestinal anastomoses.

Clusters of spreading depolarizations are associated with disturbed cerebral metabolism in patients with aneurysmal subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: We studied the dynamics of extracellular brain tissue concentrations of glucose, lactate, pyruvate, and glutamate during the occurrence of spreading depolarizations (SDs) in patients with aneurysmal subarachnoid hemorrhage. METHODS: In this prospective observational study, patients with aneurysmal subarachnoid hemorrhage received multimodal cerebral monitoring, including intracranial pressure, cerebral microdialysis, and subdural electrocorticography. RESULTS: Seven of the 17 recruited patients had intracerebral hemorrhage, acute ischemia and severe brain oedema leading to acute ischemic neurological deficits associated with early disturbance of metabolism at the recording site. They displayed a total of 130 SDs. The remaining 10 patients without acute ischemic neurological deficits exhibited 138 single SDs and 68 SDs in clusters. In patients without acute ischemic neurological deficits, clustered SDs were associated with a significant transient decrease in glucose and increase in lactate compared with baseline during the first 140 minutes after SDs. Moreover, the number of clustered SDs correlated with the outcome (R=-0.659; P<0.01). CONCLUSIONS: SDs can propagate in nonischemic human brain tissue. Clusters of SDs are related to metabolic changes suggestive of ongoing secondary damage in primarily nonischemic brain tissue.

The Frq-Frh Complex Light-Dependently Delays Sfl1-Induced Microsclerotia Formation in Verticillium dahliae.

The vascular plant pathogenic fungus Verticillium dahliae has to adapt to environmental changes outside and inside its host. V. dahliae harbors homologs of Neurospora crassa clock genes. The molecular functions and interactions of Frequency (Frq) and Frq-interacting RNA helicase (Frh) in controlling conidia or microsclerotia development were investigated in V. dahliae JR2. Fungal mutant strains carrying clock gene deletions, an FRH point mutation, or GFP gene fusions were analyzed on transcript, protein, and phenotypic levels as well as in pathogenicity assays on tomato plants. Our results support that the Frq-Frh complex is formed and that it promotes conidiation, but also that it suppresses and therefore delays V. dahliae microsclerotia formation in response to light. We investigated a possible link between the negative element Frq and positive regulator Suppressor of flocculation 1 (Sfl1) in microsclerotia formation to elucidate the regulatory molecular mechanism. Both Frq and Sfl1 are mainly present during the onset of microsclerotia formation with decreasing protein levels during further development. Induction of microsclerotia formation requires Sfl1 and can be delayed at early time points in the light through the Frq-Frh complex. Gaining further molecular knowledge on V. dahliae development will improve control of fungal growth and Verticillium wilt disease.

Tomato Xylem Sap Hydrophobins Vdh4 and Vdh5 Are Important for Late Stages of Verticillium dahliae Plant Infection.

Verticillium dahliae causes economic losses to a wide range of crops as a vascular fungal pathogen. This filamentous ascomycete spends long periods of its life cycle in the plant xylem, a unique environment that requires adaptive processes. Specifically, fungal proteins produced in the xylem sap of the plant host may play important roles in colonizing the plant vasculature and in inducing disease symptoms. RNA sequencing revealed over 1500 fungal transcripts that are significantly more abundant in cells grown in tomato xylem sap compared with pectin-rich medium. Of the 85 genes that are strongly induced in the xylem sap, four genes encode the hydrophobins Vdh1, Vdh2, Vdh4 and Vdh5. Vdh4 and Vhd5 are structurally distinct from each other and from the three other hydrophobins (Vdh1-3) annotated in V. dahliae JR2. Their functions in the life cycle and virulence of V. dahliae were explored using genetics, cell biology and plant infection experiments. Our data revealed that Vdh4 and Vdh5 are dispensable for V. dahliae development and stress response, while both contribute to full disease development in tomato plants by acting at later colonization stages. We conclude that Vdh4 and Vdh5 are functionally specialized fungal hydrophobins that support pathogenicity against plants.

Bipolar radiofrequency-induced thermofusion of intestinal anastomoses--feasibility of a new anastomosis technique in porcine and rat colon.

PURPOSE: In recent years, vessel sealing has become a well-established method in surgical practice for sealing and transecting vessels. Since this technology depends on the fusion of collagen fibers abundantly present in the intestinal wall, it should also be possible to create intestinal anastomoses by thermofusion. Bipolar radiofrequency-induced thermofusion of intestinal tissue may replace traditionally used staples or sutures in the future. The aim of this study was to evaluate the feasibility of fusing intestinal tissue ex vivo by bipolar radiofrequency-induced thermofusion. MATERIALS AND METHODS: An experimental setup for temperature-controlled bipolar radiofrequency-induced thermofusion of porcine (n = 30) and rat (n = 18) intestinal tissue was developed. Colon samples were harvested and then anastomosed, altering compressive pressure to examine its influence on anastomotic bursting pressure during radiofrequency-induced anastomotic fusion. For comparison, mechanical stapler anastomoses of porcine colonic samples and conventional suturing of rat colonic samples identical to those used for fusion experiments were prepared, and burst pressure was measured. RESULTS: All thermofused colonic anastomoses were primarily tight and leakage proof. For porcine colonic samples, an optimal interval of compressive pressure (1,125 mN/mm(2)) with respect to a high amount of burst pressure (41 mmHg) was detected. The mean bursting pressure for mechanical stapler anastomosis was 60.7 mmHg and did not differ from the thermofusion (p = 0.15). Furthermore, the mean bursting pressure for thermofusion of rat colonic samples was up to 69.5 mmHg for a compressive pressure of 140 mN/mm(2). CONCLUSION: These results confirm the feasibility to create experimental intestinal anastomoses using bipolar radiofrequency-induced thermofusion. The stability of the induced thermofusion showed no differences when compared to that of conventional anastomoses. Bipolar radiofrequency-induced thermofusion of intestinal tissue represents an innovative approach for achieving gastrointestinal anastomoses.

Pseudomonas Strains Induce Transcriptional and Morphological Changes and Reduce Root Colonization of Verticillium spp.

Phytopathogenic Verticillia cause Verticillium wilt on numerous economically important crops. Plant infection begins at the roots, where the fungus is confronted with rhizosphere inhabiting bacteria. The effects of different fluorescent pseudomonads, including some known biocontrol agents of other plant pathogens, on fungal growth of the haploid Verticillium dahliae and/or the amphidiploid Verticillium longisporum were compared on pectin-rich medium, in microfluidic interaction channels, allowing visualization of single hyphae, or on Arabidopsis thaliana roots. We found that the potential for formation of bacterial lipopeptide syringomycin resulted in stronger growth reduction effects on saprophytic Aspergillus nidulans compared to Verticillium spp. A more detailed analyses on bacterial-fungal co-cultivation in narrow interaction channels of microfluidic devices revealed that the strongest inhibitory potential was found for Pseudomonas protegens CHA0, with its inhibitory potential depending on the presence of the GacS/GacA system controlling several bacterial metabolites. Hyphal tip polarity was altered when V. longisporum was confronted with pseudomonads in narrow interaction channels, resulting in a curly morphology instead of straight hyphal tip growth. These results support the hypothesis that the fungus attempts to evade the bacterial confrontation. Alterations due to co-cultivation with bacteria could not only be observed in fungal morphology but also in fungal transcriptome. P. protegens CHA0 alters transcriptional profiles of V. longisporum during 2 h liquid media co-cultivation in pectin-rich medium. Genes required for degradation of and growth on the carbon source pectin were down-regulated, whereas transcripts involved in redox processes were up-regulated. Thus, the secondary metabolite mediated effect of Pseudomonas isolates on Verticillium species results in a complex transcriptional response, leading to decreased growth with precautions for self-protection combined with the initiation of a change in fungal growth direction. This interplay of bacterial effects on the pathogen can be beneficial to protect plants from infection, as shown with A. thaliana root experiments. Treatment of the roots with bacteria prior to infection with V. dahliae resulted in a significant reduction of fungal root colonization. Taken together we demonstrate how pseudomonads interfere with the growth of Verticillium spp. and show that these bacteria could serve in plant protection.

Verticillium longisporum Elicits Media-Dependent Secretome Responses With Capacity to Distinguish Between Plant-Related Environments.

Verticillia cause a vascular wilt disease affecting a broad range of economically valuable crops. The fungus enters its host plants through the roots and colonizes the vascular system. It requires extracellular proteins for a successful plant colonization. The exoproteomes of the allodiploid Verticillium longisporum upon cultivation in different media or xylem sap extracted from its host plant Brassica napus were compared. Secreted fungal proteins were identified by label free liquid chromatography-tandem mass spectrometry screening. V. longisporum induced two main secretion patterns. One response pattern was elicited in various non-plant related environments. The second pattern includes the exoprotein responses to the plant-related media, pectin-rich simulated xylem medium and pure xylem sap, which exhibited similar but additional distinct features. These exoproteomes include a shared core set of 221 secreted and similarly enriched fungal proteins. The pectin-rich medium significantly induced the secretion of 143 proteins including a number of pectin degrading enzymes, whereas xylem sap triggered a smaller but unique fungal exoproteome pattern with 32 enriched proteins. The latter pattern included proteins with domains of known pathogenicity factors, metallopeptidases and carbohydrate-active enzymes. The most abundant proteins of these different groups are the necrosis and ethylene inducing-like proteins Nlp2 and Nlp3, the cerato-platanin proteins Cp1 and Cp2, the metallopeptidases Mep1 and Mep2 and the carbohydrate-active enzymes Gla1, Amy1 and Cbd1. Their pathogenicity contribution was analyzed in the haploid parental strain V. dahliae. Deletion of the majority of the corresponding genes caused no phenotypic changes during ex planta growth or invasion and colonization of tomato plants. However, we discovered that the MEP1, NLP2, and NLP3 deletion strains were compromised in plant infections. Overall, our exoproteome approach revealed that the fungus induces specific secretion responses in different environments. The fungus has a general response to non-plant related media whereas it is able to fine-tune its exoproteome in the presence of plant material. Importantly, the xylem sap-specific exoproteome pinpointed Nlp2 and Nlp3 as single effectors required for successful V. dahliae colonization.

Relevance of intracranial hypertension for cerebral metabolism in aneurysmal subarachnoid hemorrhage. Clinical article.

OBJECT: Intracranial hypertension, defined as intracranial pressure (ICP) >/= 20 mm Hg, is a complication typically associated with head injury. Its impact on cerebral metabolism, ICP therapy, and outcome has rarely been studied in patients with aneurysmal subarachnoid hemorrhage (aSAH); such an assessment is the authors' goal in the present study. METHODS: Cerebral metabolism was prospectively studied in 182 patients with aSAH. The database was retrospectively analyzed with respect to ICP. Patients were classified into 2 groups based on ICP. There were 164 with low ICP (<20 mm Hg) and 18 with high ICP (>or=20 mm Hg, measured>6 hours/day). Cerebral microdialysis parameters of energy metabolism, glycerol, and glutamate levels were analyzed hourly from the brain parenchyma of interest for 7 days. The 12-month outcome in these patients was evaluated. RESULTS: In the high ICP group, extended ICP therapy including decompressive craniectomy was necessary in 7 patients (39%). Cerebral glycerol levels and the lactate/pyruvate ratio were pathologically increased on Days 1-7 after aSAH (p<0.001). The excitotoxic neurotransmitter glutamate and glycerol, a marker of membrane degradation, further increased on Days 5-7, probably reflecting the development of secondary brain damage. An ICP>or=20 mm Hg was shown to have a significant influence on the 12-month Glasgow Outcome Scale (GOS) score (p=0.001) and was a strong predictor of mortality (OR=24.6; p<0.001). Glutamate (p=0.012), the lactate/pyruvate ratio as a marker of anaerobic metabolism (p=0.028), age (p<0.001), and Fisher grade (p=0.001) also influenced the GOS score at 12 months. CONCLUSIONS: The authors confirmed the relevance of intracranial hypertension as a severe complication in patients with aSAH. Because high ICP is associated with a severely deranged cerebral metabolism and poor outcome, future studies focusing on metabolism-guided, optimized ICP therapy could help minimize secondary brain damage and improve prognosis in patients with aSAH.

Cerebral microdialysis for detection of bacterial meningitis in aneurysmal subarachnoid hemorrhage patients: a cohort study.

INTRODUCTION: Bacterial meningitis (BM) is a severe complication in patients with aneurysmal subarachnoid haemorrhage (SAH). Clinical signs of meningitis are often masked by SAH-related symptoms, and routine cerebrospinal fluid (CSF) analysis fails to indicate BM. Microdialysis (MD) is a technique for monitoring cerebral metabolism in patients with SAH. A cohort study was performed to investigate the value of MD for the diagnosis of BM. METHODS: Retrospectively, 167 patients with SAH in an ongoing investigation on cerebral metabolism monitored by MD were analysed for the presence of BM and related MD changes. Diagnosis of BM was based on microbiological CSF culture or clinical symptoms responding to antibiotic treatment, combined with an increased CSF cell count and/or fever. Levels of MD parameters before and after diagnosis of BM were analysed and compared with the spontaneous course in controls. RESULTS: BM developed in 20 patients, of which 12 underwent MD monitoring at the time of diagnosis. A control group was formed using 147 patients with SAH not developing meningitis. On the day BM was diagnosed, cerebral glucose was lower compared with the value three days before (p = 0.012), and the extent of decrease was significantly higher than in controls (p = 0.044). A decrease in cerebral glucose by 1 mmol/L combined with the presence of fever >or= 38 degrees C indicated BM with a sensitivity of 69% and a specificity of 80%. CSF chemistry failed to indicate BM, but the cell count increased during the days before diagnosis (p < 0.05). CONCLUSIONS: A decrease in MD glucose combined with the presence of fever detected BM with acceptable sensitivity and specificity, while CSF chemistry failed to indicate BM. In patients with SAH where CSF cell count is not available or helpful, MD might serve as an adjunct criterion for early diagnosis of BM.

Decompressive craniectomy in aneurysmal subarachnoid hemorrhage: relation to cerebral perfusion pressure and metabolism.

INTRODUCTION: Outcome is poor in aneurysmal subarachnoid hemorrhage (SAH) patients with intracranial hypertension. As one treatment option for increased intracranial pressure (ICP), decompressive craniectomy (DC) is discussed. Its impact on cerebral metabolism and outcome in SAH patients is evaluated in this pilot study. METHODS: A prospectively collected database of cerebral metabolism in SAH patients was analyzed retrospectively for individuals developing high ICP (>20 mmHg > 6 h/day, n = 18). Patients with intracranial hypertension were classified into groups with (n = 7) and without DC (n = 11). An age-matched control group was established (n = 89). Cerebral perfusion pressure (CPP) and high ICP treatment were analyzed for 7 days after SAH (or 72 h after craniectomy, respectively). Cerebral microdialysates were analyzed hourly. Twelve-month outcome was evaluated. RESULTS: Groups were comparable for age, WFNS grade, and outcome. ICP was significantly reduced by DC (P < 0.01), however, in 43% of patients the effect was transient. An increase in the lactate/pyruvate ratio (P < 0.001) and glycerol levels (>200 muM) was observed before DC. In the DC group, glucose (P = 0.005) and pyruvate (P = 0.04) were higher, while glycerol levels were lower (P = 0.007) compared to the non-DC group, reflecting better aerobic glucose utilization and reduced cellular stress. CONCLUSION: Outcome was poor in all SAH patients with intracranial hypertension. Although glucose utilization was improved after DC, no improvement in outcome could be shown for this small patient population. Future studies will have to demonstrate whether markers of cerebral crisis may support the decision for DC in aneurysmal SAH patients.

Hyperglycemia and cerebral glucose in aneurysmal subarachnoid hemorrhage.

OBJECTIVE: To determine whether hyperglycemia exerts deleterious effects via cerebral energy metabolism and to illuminate the effects of cerebral high/low glucose in patients with aneurysmal subarachnoid hemorrhage. DESIGN AND SETTING: Prospective, nonrandomized single-center study over a 2-year period in an intensive care unit at a primary-level university hospital. PATIENTS: 28 subarachnoid hemorrhage patients (age 53 +/- 10 years, WFNS grade 2.8 +/- 1.5) classified as asymptomatic (n = 5) or symptomatic with acute focal or delayed ischemic neurological deficits (n = 23). MEASUREMENTS AND RESULTS: Hyperglycemia (> 7.8 mmol/l; >140 mg/dl) was more frequent in symptomatic patients and was reflected in higher glycerol concentrations than in asymptomatic patients. In all patients a microdialysis catheter was inserted into the tissue at risk; dialysates were collected hourly for 10 days. Cerebral low-glucose episodes (0.6 mmol/l) and high-glucose episodes (>2.6 mmol/l) occurred independently of blood glucose levels. During high-glucose episodes cerebral microdialysate levels were normal, while cerebral low glucose, occurring more frequently in symptomatic patients, was associated with severe cellular distress (increase in lactate/pyruvate ratio, glutamate, glycerol) and with unfavorable outcome if combined with hyperglycemia. CONCLUSIONS: Although hyperglycemia was more frequent in symptomatic patients and associated with high glycerol levels, hyperglycemia was not related to cerebral high glucose. It appears that the association of adverse outcome with acute-phase hyperglycemia is not mediated by cerebral glucose metabolism. Cerebral low glucose was associated with severe metabolic distress and may present a target for therapy to improve clinical outcome.

Insulin-related decrease in cerebral glucose despite normoglycemia in aneurysmal subarachnoid hemorrhage.

INTRODUCTION: Hyperglycaemia following aneurysmal subarachnoid hemorrhage (SAH) is associated with complications and impaired neurological recovery. The aim of this study was to determine the effect of insulin treatment for glucose control on cerebral metabolism in SAH patients. METHODS: This prospective, nonrandomized study was conducted in 31 SAH patients in an intensive care unit (age 52 +/- 10 years, World Federation of Neurological Surgeons grade 2.9 +/- 1.6). A microdialysis catheter was inserted into the vascular territory of the aneurysm after clipping. Blood glucose levels above 140 mg/dl were treated with intravenous insulin and the microdialysates were analyzed hourly for the first 12 hours of infusion. RESULTS: No hypoglycaemia occurred. Twenty-four patients were treated with insulin for glucose control. Higher age and World Federation of Neurological Surgeons score were risk factors for need for insulin treatment (P < 0.05). Although blood glucose remained stable after initiation of insulin infusion, insulin induced a significant decrease in cerebral glucose at 3 hours after onset of the infusion until the end of the observation period (P < 0.05), reflecting high glucose utilization. The lactate:pyruvate ratio and glutamate did not increase, excluding ischaemia as possible cause of the decrease in glucose. Glycerol tended toward higher values at the end of the observation period (9 to 12 hours), reflecting either tissue damage after SAH or the beginning of cellular distress after insulin infusion. CONCLUSION: Higher SAH grade was among the risk factors for need for insulin. Intensive glycaemic control using insulin induced a decrease of cerebral glucose and a slight increase in glycerol, though blood glucose remained normal. Future studies might detect relevant metabolic derangements when insulin treatment starts at low cerebral glucose levels, and may allow us to design a strategy for avoidance of insulin-induced metabolic crisis in SAH patients.

First Insight into the Genome Sequence of Clostridium thermobutyricum DSM 4928, a Butyrate-Producing Moderate Thermophile.

The moderately thermophilic and Gram-positive bacterium Clostridium thermobutyricum is strictly anaerobic and forms subterminally located endospores. It was isolated from horse manure compost. C. thermobutyricum produces butyrate as the main fermentation product. The draft genome consists of one circular chromosome (3.425 Mb) and contains 3,201 predicted protein-coding genes.

High ICP as trigger of proinflammatory IL-6 cytokine activation in aneurysmal subarachnoid hemorrhage.

OBJECTIVE: There is a rising debate about the role of inflammation in the pathogenesis of complications after aneurysmal subarachnoid hemorrhage (SAH) such as intracranial hypertension (intracranial pressure, ICP >20 mmHg). This study aimed to analyse the origin of interleukin-6 (IL-6) in respect to ICP and cerebral metabolism in SAH patients. METHODS: Prospectively, IL-6 was measured in three compartments, the extracellular fluid (ECF) monitored by cerebral microdialysis (MD), cerebrospinal fluid (CSF) and plasma for 10 days after SAH (days 0-4, three times daily; days 5-10, two times daily). Patients were classified having intracranial hypertension (n=7) or normal ICP (n=17) during 10 days after bleeding. Glasgow outcome scale (GOS) was assessed after 3 and 6 months. RESULTS: Patient groups were comparable for age, WFNS and Fisher grade. Intracranial hypertension was associated with an inflammatory response, indicating activation of the inflammatory cascade in the brain (ECF) and systemic circulation with high IL-6 and C-reactive protein (CRP) plasma levels after SAH, the latter associated with unfavourable outcome. The data suggest the ECF but not the CSF as main origin of IL-6 in the systemic circulation in the presence of intracranial hypertension in SAH. DISCUSSION: Intracranial hypertension is associated with a strong activation of the inflammatory cascade in the brain and systemic circulation, and might be underestimated as proinflammmatory trigger in the pathogenesis of complications after SAH. Future therapies targeting anti-inflammatory response in plasma may help to reduce the inflammatory cascade responsible for development of intracranial hypertension.

Imaging of hypoxic-ischemic penumbra with (18)F-fluoromisonidazole PET/CT and measurement of related cerebral metabolism in aneurysmal subarachnoid hemorrhage.

This study aimed to characterize hypoxic, but salvageable, tissue imaged by (18)F-fluoromisonidazole ((18)F-FMISO), combining with perfusion-computed tomography (PCT) for regional cerebral blood flow (rCBF) measurement and metabolism by microdialysis (MD) in aneurysmal subarachnoidal hemorrhage (SAH) patients. (18)F-FMISO positron-emission tomography (PET)/CT was performed within the period of possible vasospasm (day 6.8+/-3 after SAH) in seven SAH patients. In parallel, rCBF was determined within the MD region of interest (MD-ROI) (n=5). The MD catheter was inserted into the brain parenchyma with highest risk for ischemia; extracellular levels of glutamate and energy metabolites were registered at time of PET and hourly for 10 days. Twelve-month outcome was evaluated. In asymptomatic patients (n=3) no hypoxia was detected and glutamate levels were low (<10 mmol/L), whereas symptomatic patients had higher glutamate concentrations (P<0.001). Increased (18)F-FMISO uptake within the MD-ROI (n=3) was related to higher glutamate levels, while rCBF was above the ischemic range. Hypoxia (increased (18)F-FMISO uptake) was present in symptomatic patients and associated with relevant metabolic derangement of extracellular glutamate levels, whereas energy metabolism and rCBF were preserved. This technique has the potential to improve our understanding of the role of cellular hypoxia in aneurysmal SAH.