An arrhythmogenic metabolite in atrial fibrillation

BACKGROUND

Long-chain acyl-carnitines (ACs) are potential arrhythmogenic metabolites. Their role in atrial fibrillation (AF) remains incompletely understood. Using a systems medicine approach, we assessed the contribution of C18:1AC to AF by analysing its in vitro effects on cardiac electrophysiology and metabolism, and translated our findings into the human setting.

METHODS AND RESULTS

Human iPSC-derived engineered heart tissue was exposed to C18:1AC. A biphasic effect on contractile force was observed: short exposure enhanced contractile force, but elicited spontaneous contractions and impaired Ca2+ handling. Continuous exposure provoked an impairment of contractile force. In human atrial mitochondria from AF individuals, C18:1AC inhibited respiration. In a population-based cohort as well as a cohort of patients, high C18:1AC serum concentrations were associated with the incidence and prevalence of AF.

CONCLUSION

Our data provide evidence for an arrhythmogenic potential of the metabolite C18:1AC. The metabolite interferes with mitochondrial metabolism, thereby contributing to contractile dysfunction and shows predictive potential as novel circulating biomarker for risk of AF.

The new myokine myonectin is significantly associated with type 2 diabetes in elderly patients

 

The novel myokine myonectin is predominantly expressed in skeletal muscle and is involved in the regulation of metabolic homeostasis. A putative association between myonectin and type 2 diabetes mellitus (T2DM) has been discussed controversially in current literature.

The purpose of this study was to investigate the association between myonectin and T2DM at different ages.

We measured myonectin in 410 vascular risk patients with a mean age of 66 years.

Myonectin did not correlate with age (r=−0.19; p=0.697). From our patients 219 (53%) were >65 years, with a mean age of 74 years and 191 ≤65 years, with a mean age of 57 years. The prevalence of T2DM was 40.6% vs. 42.4% in the older as compared to the younger age group. Myonectin concentrations were significantly decreased in elderly patients with T2DM compared to non-diabetic subjects (1.8 vs. 4.2 ng/ml; p=0.002), whereas no significant difference was observed in younger patients (2.6 vs. 2.3 ng/ml; p=0.183). Concordantly, regression analysis revealed an unadjusted odds ratio (OR) of 0.24 [0.07–0.81] (p=0.021) for the association between myonectin and T2DM in elderly patients but not in younger patients (OR=1.08 [0.80–1.45]; p=0.609). The association between myonectin and T2D; remained significant after adjusting for sex, body mass index, LDL cholesterol, HDL cholesterol, current smoking, as well as statin intake in elderly but remained non-significant in younger patients (OR=0.23 [0.07–0.81]; p=0.021 vs. OR=1.05 [0.76–1.46]; p=0.769).

We conclude that plasma myonectin levels are significantly associated with T2DM, particularly in elderly vascular risk patients.

Funding Acknowledgement

Type of funding sources: None.

Radioisotope albumin flux measurement of microvascular lung permeability: an independent parameter in acute respiratory failure?

Aim: To evaluate the extent to which single measurements of microvascular lung permeability may be relevant as an additional parameter in a heterogenous clinical patient collective with Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS). Methods: In 36 patients with pneumonia (13), non pneumogenic sepsis (9) or trauma (14) meeting the consensus conference criteria of ALI or ARDS double-isotope protein flux measurements (51Cr erythrocytes as intravascular tracer, Tc-99m human albumin as diffusible tracer) of microvascular lung permeability were performed using the Normalized Slope Index (NSI). The examination was to determine whether there is a relationship between the clinical diagnosis of ALI/ARDS, impaired permeability and clinical parameters, that is the underlying disease, oxygenation, duration of mechanical ventilation and mean pulmonary-artery pressure (PAP). Results: At the time of study, 25 patients presented with increased permeability (NSI > 1 × 10-3 min1) indicating an exudative stage of disease, and 11 patients with normal permeability. The permeability impairment correlated with the underlying disease (p >0.05). With respect to survival, there was a negative correlation to PAP (p <0.01). Apart from that no correlations between the individual parameters were found. Especially no correlation was found between permeability impairment and oxygenation, duration of disease or PAP. Conclusion: In ALI and ARDS, pulmonary capillary permeability is a diagnostic parameter which is independent from clinical variables. Permeability measurement makes a stage classification (exudative versus non exudative phase) of ALI/ARDS possible based on a measurable pathophysiological correlate.

Development and validation of an alternative disturbed skin model by mechanical abrasion to study drug penetration

Pharmaceuticals and cosmetics for dermal application are usually tested on healthy skin, although the primary permeation barrier, the stratum corneum, is often impaired by skin diseases or small skin lesions, especially on the hands. These skin conditions can considerably influence the permeation of chemicals and drugs. Furthermore, risk assessment for example of nanoparticles should be performed under various skin conditions to reflect the true circumstances. Therefore, an alternative and reproducible method for a high throughput of skin samples with impaired skin barrier was developed and verified by skin permeation studies (25 h) of caffeine, sorbic acid and testosterone compared to healthy (untreated) and tape-stripped skin. Skin barrier disruption was controlled by TEWL measurement.

Skin permeation of the three substances was increased in tape-stripped and abraded skin compared to untreated skin due to the reduced barrier integrity. Enhancement of drug uptake was highest for the most hydrophilic substance, caffeine, followed by sorbic acid and lipophilic testosterone. No significant difference in drug uptake studies was observed between the new abrasion method with an aluminum-coated sponge and the tape-stripping method. The obtained results demonstrate that this abrasion method is an alternative way to achieve a disturbed skin barrier for drug and chemical uptake studies.

Prognostic Value of Conventional Magnetic Resonance Imaging for Adult Patients with Brain Tumors

PURPOSE

Magnetic resonance imaging (MRI) is the pivotal diagnostic step in patients with brain tumors, and is performed before histological diagnosis is available. We hypothesized that conventional MRI is as accurate as tumor histology in differentiating malignant from benign clinical course.

METHODS

Two neuroradiologists blinded to any clinical information evaluated the first diagnostic MRI of 244 brain tumor patients before any treatment, using a self-developed standardized list of image criteria and prospectively determined world health organization (WHO) tumor grade and tumor entity. All patients were examined with at least T1- and T2-weighted spin echo sequences before and after contrast injection on 1 and 1.5-T MRI scanners. Following the patients prospectively for 8-13 years after diagnosis, we were able to use nonsurvival at 5 years as a criterion for malignity and reference for the prognostic accuracy of both MRI and tumor tissue histology.

RESULTS

The accuracy for predicting nonsurvival at 5 years was 91% (95% confidence interval (CI): 87-94%) for MRI and 92% (95% CI: 88-95%) for histology. The Kaplan-Meier survival curves of patients with benign and malignant brain tumors as diagnosed by MRI or histology differed significantly (p < 0.001). Histology confirmed benignity or malignity in 201 patients (82%, 95% CI: 77-87%). Sources of misdiagnosis were metastases diagnosed as astrocytoma WHO IV, atypical meningiomas, and low-grade astrocytoma with malignant transformation.

CONCLUSION

MRI appears as accurate as histology in predicting survival at 5 years after diagnosis. Histological diagnosis may be more specific, however, and is needed to assess the tumor's specific biology.

The prognostic value of IDH mutations and MGMT promoter status in secondary high-grade gliomas

Reports about the prognostic value of IDH mutations and the promoter region of the O6-Methyl-guanyl-methyl-transferase gene in secondary high-grade gliomas (sHGG) are few in number. We investigated the prognostic value of IDH mutations and methylation of the promoter region of the MGMT gene in 99 patients with sHGG and analyzed the clinical course of those tumors. Patients with sHGG were screened for IDH mutations by direct sequencing, and, for promoter status of MGMT gene, by the methylation-specific polymerase chain reaction. A total of 48 of 99 patients (48.5 %) had secondary anaplastic gliomas (Group 1), while 51 patients had secondary glioblastomas (Group 2). The median survival time after malignant progression of all patients with sHGG and with an IDH mutation was 4 years, which is significantly longer than in patients with wild-type IDH (1.2 years, p = 0.009). Patients' survival was not significantly influenced by the tumors' MGMT promoter status, both in Group 1- 9.7 years vs. 6.1 years, methylated vs. unmethylated promoter (p = 0.330)-as well as in Group 2-1.5 years vs. 1.6 years, methylated versus unmethylated promoter (p = 0.829). In our population, the IDH mutation status was not associated with increased PFS or median survival time in sGBM patients. However, patients with secondary anaplastic glioma and IDH mutation had a significantly improved outcome. In addition, IDH mutations are a more powerful prognostic marker concerning both PFS and MS than the MGMT promoter status in those patients.

Hypoxia induces apelin expression in human adipocytes

Adipokines play a central role in the development of diseases associated with insulin resistance and obesity. Hypoxia in adipose tissue leads to a dysregulation of the expression of adipokines. The effect of hypoxia on the more recently identified adipokine apelin in human adipocytes is unclear. Therefore, we aimed at investigating the role of hypoxia on the expression of the adipokine apelin. Differentiated human Simpson-Golabi-Behmel syndrome (SGBS) adipocytes were cultured under hypoxic conditions for varying time periods. A modular incubator chamber was used to create a hypoxic tissue culture environment (defined as 1% O(2), 94% N, and 5% CO(2)). In addition, hypoxic conditions were mimicked by using CoCl(2). The effect of hypoxia on the expression of the investigated adipokines was measured by real-time PCR and the secretion of apelin was quantified by ELISA. Induction of hypoxia significantly induced mRNA expression of leptin and apelin in differentiated SGBS adipocytes compared with the normoxic control condition. Expression of adiponectin was significantly decreased by hypoxia. In addition, the amount of secreted apelin protein in response to hypoxia was elevated compared to untreated cells. Furthermore, we could demonstrate that the observed hypoxia-induced induction of apelin mRNA expression is in the first phase dependent on HIF-1α. In our study, we could demonstrate for the first time that apelin expression and secretion by human adipocytes are strongly induced under hypoxic conditions and that the early response on hypoxia with apelin induction is dependent on HIF-1α.

BM cells giving rise to MSC in culture have a heterogeneous CD34 and CD45 phenotype

BACKGROUND

Mesenchymal stromal cells (MSC) isolated from adult human BM are characterized by their fibroblast-like morphology, adherent growth and capacity to differentiate into adipocytes, osteocytes, chondrocytes, cardiomyocytes and neuroprogenitors. After culturing these cells in vitro, they express the cell-surface molecules CD44, CD90, SH2 and SH3, and are negative for CD34 and the hematopoietic marker CD45. The aim of this study was to characterize the in vivo phenotype of MSC relative to the expression of CD34 and CD45.

METHODS

BM mononuclear cells were stained with Ab against both molecules and separated into the CD34(+), CD34(-), CD45(+) CD34(+), CD45(high+) CD34(-), CD45(med,low+) CD34(-) and CD45(-) CD34(-) subpopulations, which were then cultured under the same conditions and analyzed for growth of MSC.

RESULTS

A small population of MSC arose from the CD45(+) CD34(+) fraction, although the majority was obtained from the CD45(-) CD34(-) subpopulation. MSC from all fractions could be differentiated into adipocytes and osteocytes. In addition, MSC from the CD34(+) and CD34(-) fractions were shown to differentiate into chondrocytes. After in vitro culture, MSC from both fractions possessed the same phenotype, which was negative for CD34 and CD45.

DISCUSSION

MSC from the CD45(+) CD34(+) fraction change their phenotype under in vitro conditions.

Infant carrying: The role of increased locomotory costs in early tool development

Among the costs of reproduction, carrying one's infant incurs one of the greatest drains on maternal energy, simply because of the added mass alone. Because of the dearth of archaeological evidence, however, how early bipeds dealt with the additional cost of having to carry infants who were less able to support their body weight against gravity is not particularly well understood. This article presents evidence on the caloric drain of carrying an infant in one's arms versus having a tool with which to sling the infant and carry her passively. The burden of carrying an infant in one's arms is on average 16% greater than having a tool to support the baby's mass and seems to have the potential to be a greater energetic burden even than lactation. In addition, carrying a baby in one's arms shortens and quickens the stride. An anthropometric trait that seems to offset some of the increased cost of carrying a baby in the arms is a wider bi-trochanteric width.

FKHRL1-mediated expression of Noxa and Bim induces apoptosis via the mitochondria in neuroblastoma cells

Protein kinase-B (PKB) and its target, the forkhead transcription factor like 1 (FKHRL1)/FoxO3a, have been suggested as regulators of neurotrophin-mediated cell survival in neuronal cells. We analyzed human neuroblastoma cells and found that FKHRL1 was phosphorylated, suggesting its inactivation. To study FKHRL1 function, we infected SH-EP and NB15 cells with a 4OH-tamoxifen-regulated FKHRL1(A3)ER(tm) transgene. Activation of FKHRL1 promoted cytochrome-c release and caspase-dependent apoptosis. FKHRL1 induced TRAIL and the BH3-only proteins Noxa and Bim, implicating both extrinsic and intrinsic death pathways. However, expression of dnFADD did not inhibit FKHRL1-induced cell death, whereas Bcl2 protected against apoptosis. This excluded the death-receptor pathway and suggested that cell death decision is regulated by Bcl2-rheostat. Importantly, RNAi knockdown of Noxa or Bim decreased apoptosis, indicating that Noxa and Bim cooperate to mediate FKHRL1-induced cell death. We conclude that Noxa and Bim establish a connection between FKHRL1 and mitochondria, and that both BH3-only proteins are critically involved in FKHRL1-induced apoptosis in neuroblastoma.

Impact of inspired substance concentrations on the results of breath analysis in mechanically ventilated patients

A well-defined relationship has to exist between substance concentrations in blood and in breath if blood-borne volatile organic compounds (VOCs) are to be used as breath markers of disease or health. In this study, the impact of inspired substances on this relationship was investigated systematically. VOCs were determined in inspired and expired air and in arterial and mixed venous blood of 46 mechanically ventilated patients by means of SPME, GC/MS. Mean inspired concentrations were 25% of expired concentrations for pentane, 7.5% for acetone, 0.7% for isoprene and 0.4% for isoflurane. Only if inspired concentrations were <5% did substance disappearance rates from blood and exhalation rates correlate well. Exhaled substance concentrations depended on venous and inspired concentrations. Patients with sepsis had higher n-pentane and lower acetone concentrations in mixed venous blood than patients without sepsis (2.27 (0.37-8.70) versus 0.65 (0.33-1.48) nmol L-1 and 69 (22-99) versus 18 (6.7-56) micromol L-1). n-Pentane and acetone concentrations in breath showed no differences between the patient groups, regardless whether or not expired concentrations were corrected for inspired concentrations. In mechanically ventilated patients, concentration profiles of volatile substances in breath may considerably deviate from profiles in blood depending on the relative amount of inspired concentrations. A simple correction for inspired substance concentrations was not possible. Hence, substances having inspired concentrations>5% of expired concentrations should not be used as breath markers in these patients without knowledge of concentrations in blood and breath.

Fibrous Cap Thickness and Smooth Muscle Cell Apoptosis in High-grade Carotid Artery Stenosis

OBJECTIVE

There is growing evidence that, in high-grade internal carotid artery (ICA) stenosis, continuous fibrous cap thinning is not mandatory for plaque rupture and symptom development. The possibility that smooth muscle cell (SMC) apoptosis is involved in loss of fibrous cap volume has only been examined in a limited number of patients with high grade carotid artery stenosis.

METHODS

Endarterectomy specimens from n = 38 consecutive patients undergoing surgery for high-grade ICA stenosis (> or = 70%) were transversely sectioned at 2 mm intervals. Plaque instability was defined clinically, by a history of recent ischemic symptoms (< 60 days before surgery; n = 19) attributable to the stenosis, or histopathologically by the presence of plaque rupture (n = 14). Detailed morphometric analyses of the fibrous cap was based on routine stains; for DNA in situ end labeling the TUNEL technique was used. SMCs were identified by immunostaining for SMC actin.

RESULTS

We found no significant difference between symptomatic/asymptomatic or ruptured/unruptured plaque with respect to various morphometric measures of the fibrous cap (i.e. mean area, number of plaque sections with fibrous cap, necrotic core-to-lumen distance at its thinnest or thickest part). The mean (+/- SD) apoptotic SMCs per thousand within the fibrous cap was significantly higher in symptomatic vs. asymptomatic (64.53 +/- 77.3 vs. 6.71 +/- 11.9; P<0.001) but not in ruptured plaques (43.3 +/- 64.4 vs. 30.1 +/- 60.9; P=0.117).

CONCLUSIONS

These data suggest that continuous thinning of the fibrous cap is not an essential prerequisite for plaque rupture in ICA stenosis. Symptomatic, but not ruptured plaque, were associated with the highest number of apoptotic SMC. Thus, it seems unlikely that SMC apoptosis promotes plaque rupture by fibrous cap thinning.

[Neuropathological findings after cardiac surgery-retrospective study over 6 years]

Neuropathologische Untersuchungen sollen dazu beitragen, die Ursachen der zentralnervösen Komplikationen nach Herzoperationen aufzudecken und die Rate der postoperativen neurologisch-kognitiven Störungen zu reduzieren. Unter diesem Aspekt haben wir die Gehirne von 262 nach herzchirurgischen Operationen (Bypass-, Klappenoperationen und Herztransplantationen) Verstorbenen untersucht. Es finden sich Zirkulationsstörungen (Makro- und Mikroblutungen, Infarkte, Subarachnoidalblutungen, hypoxämische Hirnschäden) in 128 Fällen (49%), davon kommen 33 Fälle als Todesursache in Betracht (12,6%). Als Ursachen der Infarkte sind neben einer stenosierenden Arteriosklerose von Hirnarterien und Thromboembolien (Operationsgebiet, Myokardinfarkte) in seltenen Fällen Fettembolien (2), Fremdkörperembolien (1) und Mikroembolien durch Megakaryozyten zu nennen. Weiterhin bestehen entzündliche Veränderungen in 17 Fällen, davon meist Septikopyämien (12 Fälle) durch Pilze oder Bakterien, und in 5 Fällen ließen sich Gliaknötchen als mögliches Substrat einer viralen oder Autoimmunencephalitis (Bickerstaff) nachweisen. Als Nebenbefund fand sich noch ein Morbus Alzheimer (37 Fälle, 14% des Materials) bei älteren Patienten, zum Teil mit einer Amyloidangiopatie, jedoch nicht als Todesursache und nicht als Ursache größerer Hirnblutungen. Da die Arbeit eine Autopsiestudie darstellt, ist eine Übertragung der gefundenen Veränderungen auf die Gesamtgruppe der operierten Herzpatienten mit neurologisch-kognitiven Störungen nur bedingt möglich ist. Auf jeden Fall spielen im eigenen Material umfangreiche mikroembolische Ereignisse (Fettembolie, Fremdkörperembolie), wie sie oft in der Literatur angegeben werden, keine entscheidende Rolle. Es finden sich aber, in unterschiedlicher Häufigkeit in den einzelnen untersuchten Operationsgruppen, besonders nach Klappenoperationen, Mikroblutungen der weißen Substanz, die nicht zum Tode führen. Sie könnten, ebenso wie die gelegentlich auftretenden Gliaknötchen, nach Resorption und Vernarbung postoperativ bei den Patienten neurologisch- kognitive Störungen verursachen.

Komplexe regionale Schmerzsyndrome CRPS I und II

INTRODUCTION

The results of clinical studies have raised doubts on the effectiveness of regional sympathetic blocks with guanethidine (IVRSB) in patients suffering from complex regional pain syndrome (CRPS). We conducted a retrospective analysis of long-term results in our patients and searched for possible factors predicting long-term outcome after IVRSB:

METHODS

After approval by our ethics commission and written informed consent, 42/44 patients were included. We documented diagnosis, history, therapy and long-term result from charts. Long-term results were also obtained from a questionnaire administered to the patients. These were defined as very good (reduction of pain > or =75%), good (pain reduction <75% and > or =50%), moderate (pain reduction <50% and > or =25%) or poor (pain reduction <25%). The association of a moderate or poor outcome with the factors age, gender, duration of time until therapy, pain intensity before therapy, dose of applied guanethidine and duration of therapy was calculated by odds ratio. Confidence intervals for the odds ratios were determined by Woolfs approximation.

RESULTS

After a mean duration of 18 months, the outcome was classified as very good in 14, good in 13, moderate in 5 and poor in 10 patients. An increased rate of moderate or poor outcome was associated with age<60 years (OR=4.00, CI 1.04-15.26), male gender (OR=2.93, CI 0.71-12.11) and duration of therapy>2 weeks (OR=3.27, CI 0.86-12.36). The factors duration of time until therapy, initial pain intensity and total dose of guanethidine were not associated with increased rates of moderate or poor outcome.

CONCLUSION

We only seldom observed a complete functional restoration after CRPS. Male patients <60 years showed an increased risk of developing chronic pain. It remains unclear whether the risk of chronic pain reflects different responses to therapy or differences in the natural course of the disease in our patients. A meta-analysis of randomised trials of IVRSB in CRPS failed to prove the effectiveness of this intervention. If other investigations confirm our impression, future studies of CRPS-treatments should be planned and analysed with regard to the possible influence of the natural course and different risks of chronic pain among patients with CRPS.

Effects of epidural anaesthesia on intestinal oxygenation in pigs

BACKGROUND

Perioperative intestinal hypoperfusion is a major contributing factor leading to organ dysfunction. It can be caused by stress as a result of surgical manipulation or hypoxia. Additionally, anaesthesia can affect intestinal oxygenation. This animal study was designed to assess the effects of reduced regional sympathetic nervous activity induced by thoracic epidural anaesthesia on intestinal oxygenation.

METHODS

After ethical approval, 16 anaesthetized and acutely instrumented pigs were randomly assigned to two groups (epidural anaesthesia alone vs epidural anaesthesia plus volume loading). The epidural anaesthesia aimed for a T5-T12 block. Measurements were at baseline and after 1 and 2 h.

RESULTS

Epidural anaesthesia was associated with a decrease in mean arterial blood pressure and pronounced mesenteric vasodilatation. Mesenteric blood flow did not change. Intestinal oxygen uptake, mucosal tissue oxygen partial pressure and tissue carbon dioxide partial pressure remained unchanged.

CONCLUSIONS

Despite marked systemic hypotension, epidural anaesthesia did not affect intestinal oxygenation. There was no benefit obtained from volume loading.

Analysis of volatile disease markers in blood

BACKGROUND

The diagnostic potential of breath analysis has been limited by a lack of knowledge on origin, distribution, and metabolism of the exhaled substances. To overcome this problem, we developed a method to assess trace amounts of hydrocarbons (pentane and isoprene), ketones (acetone), halogenated compounds (isoflurane), and thioethers (dimethyl sulfide) in the blood of humans and animals.

METHODS

Arterial and venous blood samples were taken from mechanically ventilated patients. Additional blood samples were taken from selected vascular compartments of 19 mechanically ventilated pigs. Volatile substances were concentrated by means of solid-phase microextraction (SPME), separated by gas chromatography, and identified by mass spectrometry.

RESULTS

Detection limits were 0.02-0.10 nmol/L. Venous concentrations in pigs were 0.2-1.3 nmol/L for isoprene, 0-0.3 nmol/L for pentane, and 1.2-15.1 nmol/L for dimethyl sulfide. In pigs, substances were not equally distributed among vascular compartments. In humans, median arteriovenous concentration differences were 3.58 nmol/L for isoprene and 1.56 nmol/L for pentane. These values were comparable to pulmonary excretion rates reported in the literature. Acute respiratory distress syndrome (ARDS) patients had lower isoprene concentration differences than patients without ARDS.

CONCLUSIONS

The SPME method can detect volatile substances in very low concentrations in the blood of humans and animals. Analysis of volatile substances in vascular compartments will enlarge the diagnostic potential of breath analysis.

Breathing pattern and perception at different levels of volume assist and pressure support in volunteers

OBJECTIVE

Volume assist (VA) amplifies the breathing effort whereas pressure support ventilation (PSV) provides a fixed, effort-independent ventilatory support. According to the concept of VA, its level should compensate for the pathologically increased (additional) elastance (Eadd). However, it is unclear whether breathing subjects prefer an exact compensation of Eadd and whether they are able to adjust the support level by themselves.

DESIGN

Prospective, interventional study.

SETTING

Laboratory.

SUBJECTS

Twelve healthy volunteers, nine females, three males, aged 21-33 yrs.

INTERVENTIONS

Increased Eadd was generated by banding of the thorax and abdomen. Volunteers breathed via a mouthpiece with VA or PSV using a positive end-expiratory pressure of 5 cm H2O (0.5 kPa). The study was subdivided into two parts. In part I, volunteers were instructed to adjust the level of VA and PSV themselves starting from three different, randomly applied levels in each mode (2, 8, 14 cm H2O or cm H2O/L; 0.2, 0.8, 1.4 kPa[/L]). In part II, 20 levels of VA and PSV (1-20 cm H2O or cm H2O/L, 0.1-2 kPa[/L]) were randomly selected by an investigator and estimated by the volunteers using a visual analog scale. Additionally, the breathing pattern was characterized.

MEASUREMENTS AND MAIN RESULTS

Eadd (7.1 +/- 1.5 cm H2O/L [0.7 +/- 0.2 kPa/L], mean +/- sd) corresponded almost exactly to the "self-adjusted" VA level of part I (7.0 +/- 3.3 cm H2O/L [0.7 +/- 0.3 kPa/L]) and to the adequate level of part II (8-9 cm H2O/L [0.8-0.9 kPa/L]). The accordant PSV levels were 5.7 +/- 2.6 cm H2O (0.6 +/- 0.3 kPa) and 6-7 cm H2O (0.6-0.7 kPa). The breathing pattern was less influenced by changes of the support level with VA compared with PSV, which may explain in part the greater comfort of VA.

CONCLUSIONS

We confirmed the theoretical assumption that VA should be adapted to Eadd. Furthermore, we demonstrated that conscious subjects are able to adjust the level of VA and PSV themselves.

Radioisotope albumin flux measurement of microvascular lung permeability: an independent parameter in acute respiratory failure?

AIM

To evaluate the extent to which single measurements of microvascular lung permeability may be relevant as an additional parameter in a heterogenous clinical patient collective with Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS).

METHODS

In 36 patients with pneumonia (13), non pneumogenic sepsis (9) or trauma (14) meeting the consensus conference criteria of ALI or ARDS double-isotope protein flux measurements (51Cr erythrocytes as intravascular tracer, Tc-99m human albumin as diffusible tracer) of microvascular lung permeability were performed using the Normalized Slope Index (NSI). The examination was to determine whether there is a relationship between the clinical diagnosis of ALI/ARDS, impaired permeability and clinical parameters, that is the underlying disease, oxygenation, duration of mechanical ventilation and mean pulmonary-artery pressure (PAP).

RESULTS

At the time of study, 25 patients presented with increased permeability (NSI > 1 x 10(-3) min-1) indicating on exudative stage of disease, and 11 patients with normal permeability. The permeability impairment correlated with the underlying disease (p > 0.05). With respect to survival, there was a negative correlation to PAP (p < 0.01). Apart from that no correlations between the individual parameters were found. Especially no correlation was found between permeability impairment and oxygenation, duration of disease or PAP.

CONCLUSION

In ALI and ARDS, pulmonary capillary permeability is a diagnostic parameter which is independent from clinical variables. Permeability measurement makes a stage classification (exudative versus non exudative phase) of ALI/ARDS possible based on a measurable pathophysiological correlate.

Transthyretin and transferrin in hemangioblastoma stromal cells

Hemangioblastoma, a rare benign tumor of the CNS, consists of two main components: capillaries and stromal cells. Despite many efforts, the histogenesis of stromal cells is still unknown. We took a new approach to clarify the origin of stromal cells using immunohistochemical methods. Paraffin-embedded tissue of 24 surgically removed hemangioblastomas of the CNS was examined with antibodies against transthyretin, transferrin, vimentin, NSE, protein S-100, CK 8, KL-1, EMA, CD34, factor VIII rAg, and collagen IV. Stromal cells showed a positive reaction with anti-transthyretin in 12 of 24 hemangioblastomas, a positive reaction with anti-transferrrin, to a different extent, in 13 of 24 cases, and many stromal cells expressed basal membrane collagen IV on the cell surface in 19 of 24 cases. The expression of transthyretin and transferrin in stromal cells of hemangioblastomas is reported for the first time, thus providing an antigenic profile of hemangioblastoma stromal cells that is very similar to that of immature choroid plexus epithelium. These findings support the notion that hemangioblastoma stromal cells may originate from the embryonal plexus epithelium. We discuss our results with special regard to stromal cell histogenesis, including a review of the literature.

CO(2)-controlled sampling of alveolar gas in mechanically ventilated patients

A newly designed gas-sampling device using end-tidal CO(2) to separate dead space gas from alveolar gas was evaluated in 12 mechanically ventilated patients. For that purpose, CO(2)-controlled sampling was compared with mixed expiratory sampling. Alveolar sampling valves were easily controlled via CO(2) concentration. Concentrations of four volatile substances were determined in the expired and inspired gas. Isoflurane and isoprene, which did not occur in the inspired air, had ratios of end-tidal to mixed expired concentrations of 1.75 and 1.81, respectively. Acetone and pentane, found in both the inspired and expired air, showed ratios of 0.96 and 1.0, respectively. Precision of concentration measurements was between 2.4% (isoprene) and 11.2% (isoflurane); reproducibility (as coefficient of variation) was 5%. Because the only possible source of isoflurane and isoprene in this setting was patients' blood, selective enrichment of alveolar gas was demonstrated. By using the new sampling technique, sensitivity of breath analysis was nearly doubled.