Perceptual metrics for odorants: Learning from non-expert similarity feedback using machine learning

Defining perceptual similarity metrics for odorant comparisons is crucial to understanding the mechanism of olfactory perception. Current methods in olfaction rely on molecular physicochemical features or discrete verbal descriptors (floral, burnt, etc.) to approximate perceptual (dis)similarity between odorants. However, structural or verbal descriptors alone are limited in modeling complex nuances of odor perception. While structural features inadequately characterize odor perception, language-based discrete descriptors lack the granularity needed to model a continuous perception space. We introduce data-driven approaches to perceptual metrics learning (PMeL) based on two key insights: a) by combining physicochemical features with the user's perceptual feedback, we can leverage both structural and perceptual attributes of odors to define dissimilarity, and b) instead of discrete labels, user's perceptual feedback can be gathered as relative similarity comparisons, such as "Does molecule-A smell more like molecule-B, or molecule-C?" These triplet comparisons are easier even for non-experts users and offer a more effective representation of the continuous perception space. Experimental results on several defined tasks show the effectiveness of our approach in evaluating perceptual dissimilarity between odorants. Finally, we investigate how closely our model, trained on non-expert feedback, aligns with the expert's similarity judgments. Our effort aims to reduce reliance on expert annotations.

Comparing molecular representations, e-nose signals, and other featurization, for learning to smell aroma molecules

Recent research has attempted to predict our perception of odorants using Machine Learning models. The featurization of the olfactory stimuli usually represents the odorants using molecular structure parameters, molecular fingerprints, mass spectra, or e-nose signals. However, the impact of the choice of featurization on predictive performance remains poorly reported in direct comparative studies. This paper experiments with different sensory features for several olfactory perception tasks. We investigate the multilabel classification of aroma molecules in odor descriptors. We investigate single-label classification not only in fine-grained odor descriptors ('orange', 'waxy', etc.), but also in odor descriptor groups. We created a database of odor vectors for 114 aroma molecules to conduct our experiments using a QCM (Quartz Crystal Microbalance) type smell sensor module (Aroma Coder®V2 Set). We compare these smell features with different baseline features to evaluate the cluster composition, considering the frequencies of the top odor descriptors carried by the aroma molecules. Experimental results suggest a statistically significant better performance of the QCM type smell sensor module compared with other baseline features with F1 evaluation metric.

Improving artificial intelligence with games

Games continue to drive progress in the development of artifi cial intelligence.

Outsourcing Training without Uploading Data via Efficient Collaborative Open-Source Sampling

As deep learning blooms with growing demand for computation and data resources, outsourcing model training to a powerful cloud server becomes an attractive alternative to training at a low-power and cost-effective end device. Traditional outsourcing requires uploading device data to the cloud server, which can be infeasible in many real-world applications due to the often sensitive nature of the collected data and the limited communication bandwidth. To tackle these challenges, we propose to leverage widely available open-source data, which is a massive dataset collected from public and heterogeneous sources (e.g., Internet images). We develop a novel strategy called Efficient Collaborative Open-source Sampling (ECOS) to construct a proximal proxy dataset from open-source data for cloud training, in lieu of client data. ECOS probes open-source data on the cloud server to sense the distribution of client data via a communication- and computation-efficient sampling process, which only communicates a few compressed public features and client scalar responses. Extensive empirical studies show that the proposed ECOS improves the quality of automated client labeling, model compression, and label outsourcing when applied in various learning scenarios.

Outracing champion Gran Turismo drivers with deep reinforcement learning

Many potential applications of artificial intelligence involve making real-time decisions in physical systems while interacting with humans. Automobile racing represents an extreme example of these conditions; drivers must execute complex tactical manoeuvres to pass or block opponents while operating their vehicles at their traction limits¹. Racing simulations, such as the PlayStation game Gran Turismo, faithfully reproduce the non-linear control challenges of real race cars while also encapsulating the complex multi-agent interactions. Here we describe how we trained agents for Gran Turismo that can compete with the world's best e-sports drivers. We combine state-of-the-art, model-free, deep reinforcement learning algorithms with mixed-scenario training to learn an integrated control policy that combines exceptional speed with impressive tactics. In addition, we construct a reward function that enables the agent to be competitive while adhering to racing's important, but under-specified, sportsmanship rules. We demonstrate the capabilities of our agent, Gran Turismo Sophy, by winning a head-to-head competition against four of the world's best Gran Turismo drivers. By describing how we trained championship-level racers, we demonstrate the possibilities and challenges of using these techniques to control complex dynamical systems in domains where agents must respect imprecisely defined human norms.

FlavorGraph: a large-scale food-chemical graph for generating food representations and recommending food pairings

Food pairing has not yet been fully pioneered, despite our everyday experience with food and the large amount of food data available on the web. The complementary food pairings discovered thus far created by the intuition of talented chefs, not by scientific knowledge or statistical learning. We introduce FlavorGraph which is a large-scale food graph by relations extracted from million food recipes and information of 1,561 flavor molecules from food databases. We analyze the chemical and statistical relations of FlavorGraph and apply our graph embedding method to better represent foods in dense vectors. Our graph embedding method is a modification of metapath2vec with an additional chemical property learning layer and quantitatively outperforms other baseline methods in food clustering. Food pairing suggestions made based on the food representations of FlavorGraph help achieve better results than previous works, and the suggestions can also be used to predict relations between compounds and foods. Our research offers a new perspective on not only food pairing techniques but also food science in general.

A boy named Sue

One major lesson learned in the cognitive sciences is that even basic human cognitive capacities are extraordinarily complicated and elusive to mechanistic explanations. This is definitely the case for naming and identity. Nothing seems simpler than using a proper name to refer to a unique individual object in the world. But psychological research has shown that the criteria and mechanisms by which humans establish and use names are unclear and seemingly contradictory. Children only develop the necessary knowledge and skills after years of development and naming degenerates in unusual selective ways with strokes, schizophrenia, or Alzheimer disease. Here we present an operational model of social interaction patterns and cognitive functions to explain how naming can be achieved and acquired. We study the Grounded Naming Game as a particular example of a symbolic interaction that requires naming and present mechanisms that build up and use the semiotic networks necessary for performance in the game. We demonstrate in experiments with autonomous physical robots that the proposed dynamical systems indeed lead to the formation of an effective naming system and that the model hence explains how naming and identity can get socially constructed and shared by a population of embodied agents.

[The MEmbeR Multicenter Study on medical-occupational rehabilitation]

INTRODUCTION

MEmbeR is a prospective multi-center study on medical-occupational rehabilitation in Germany.

METHODS

196 neurological, psychiatric, orthopaedic, and internal medicine patients from 21 rehabilitation centres all across Germany have been enrolled and followed-up for 2 years after discharge. Primary outcome parameter was defined as return to work. Further, the SF-12 and a Mini-ICF-Rating have been used.

RESULTS

Mean age was 34.1 (9.9) years, length of stay 150.0 (223.5) days. Prior to occupational rehabilitation, 69.9% were unable to work, 2 years after discharge only 5.6%. Rate of participants seeking a job was reduced from 19.7% to 3.1%. In summary, 78.1% returned to work. Employed participants were younger (32.8 [9.7] vs. 38.5 [9.4] years, p=0.001) and less disabled (Degree of Disablement [GdB]: 20.0 [31.2] vs. 36.1 [33.7], p<0.05).

CONCLUSION

The multicenter cohort study MEmbeR provides further knowledge about the outcome of medical-occupational rehabilitation in Germany.

microRNAs and the regulation of glucose and lipid metabolism

Over recent years, metabolic disorders such as type 2 diabetes have finally become recognized as a major challenge to global health. The attention of scientists therefore has to focus on improving our understanding of the molecular mechanisms behind these diseases and towards the design of new drug therapy strategies. The pathophysiology of diabetes is undoubtedly complex, oftentimes characterized by varying states of insulin resistance and impaired beta-cell function; however, the identification of new pathways is constantly improving our understanding of the disease. We and others have recently shown that microRNAs (miRNAs) can play a role in insulin secretion and glucose homostasis. Thus, in this review, we will discuss the potential role of miRNAs in type 2 diabetes and related metabolic diseases.

SCA17 caused by homozygous repeat expansion in TBP due to partial isodisomy 6

An expanded polyglutamine domain in the TATA-binding protein (TBP) has been described in patients with spinocerebellar ataxia type 17 (SCA17) characterized by cerebellar ataxia associated with dementia. TBP is a general transcription initiation factor that regulates the expression of most eukaryotic genes transcribed by RNA polymerase II. SCA17, as an autosomal dominantly inherited progressive neurodegenerative disorder, is caused by heterozygous expansion of a CAG repeat coding for glutamine. Alleles with 27 to a maximum of 44 glutamine residues were found as the normal range, whereas expansions above 45 repeat units were considered pathological. Here, we present a patient with a very severe phenotype with a late onset but rapidly progressing ataxia associated with dementia and homozygous 47 glutamine residues caused by an apparent partial isodisomy 6. This extraordinary case has important implications for the insights of TBP and SCA17. The expanded polyglutamine domain in both TBP copies is not correlated with embryonic death indicating that the normal function of the protein is not disrupted by this kind of mutation but may account for the dementia seen in this patient.

Familial hemiplegic migraine with cerebellar ataxia and paroxysmal psychosis

Familial hemiplegic migraine is a rare autosomal dominant disorder associated with stereotypic neurologic aura phenomena including hemiparesis. So far two chromosomal loci have been identified. Families linked to the chromosome 19 locus display missense mutations within the CACNL1A4 gene. Here we report on a family with familial hemiplegic migraine and cerebellar ataxia with recurrent episodes of acute paranoid psychosis with anxiety and visual hallucinations associated with migraine attacks. Based on the clinical and haplotype evidence indicating linkage to chromosome 19 in this family, we hypothesize that a dysfunction of the mutated calcium channel may be involved not only in the development of hemiplegic migraine but also in the acute psychotic episodes observed in these patients.

Adenosine-induced expression of interleukin-6 in astrocytes through protein kinase A and NF-IL-6

In various neurologic diseases, astrocytes express interleukin-6 (IL-6), which is an endogenous pyrogen, a neuroprotective factor, and a regulator of the blood-brain barrier. The expression of IL-6 in astrocytes is stimulated by extracellular adenosine through A(2B) receptors. To investigate the signaling cascade that induces IL-6 gene transcription further, we transfected primary mouse astrocytes with a reporter gene construct, in which luciferase expression is directed by the human IL-6 promoter. Expression of PKI, an inhibitor of protein kinase A (PKA), interfered with IL-6 transcription indicating that PKA mediates the effect of adenosine. The CAAT box of the IL-6 promoter is necessary for the stimulation by adenosine as a mutation in this element reduced the stimulation by adenosine. Indeed, the cAMP agonist forskolin increased the binding of the transcription factors NF-IL-6 and C/EBPdelta to the CAAT box of the IL-6 promoter in nuclear extracts of astrocytes. Inhibition of the de novo synthesis of NF-IL-6 by cycloheximide or an antisense oligonucleotide reduced the enhancement of NF-IL-6 binding to the CAAT box and inhibited stimulation of IL-6 transcription by forskolin. In addition, overexpression of NF-IL-6 induced IL-6 transcription. This suggests that adenosine induces the de novo synthesis of NF-IL-6 through activation of PKA and thereby stimulates transcription of IL-6 in astrocytes.

Expression of cell death-associated phospho-c-Jun and p53-activated gene 608 in hippocampal CA1 neurons following global ischemia

Persistent activation of c-Jun N-terminal kinases (JNKs) and phosphorylation of c-Jun has been shown in various cell death paradigms. Inhibition of the JNK signal transduction pathway prevented neuronal cell death both in vitro and in vivo. In the present study, nuclear phospho-c-Jun immunoreactivity became apparent selectively in vulnerable hippocampal CA1 neurons at 24 h after transient global cerebral ischemia. A high constitutive expression of phospho-JNK1 was detected by immunoblot analysis of hippocampal extracts. Expression of JNK interacting protein-1 (JIP-1), which facilitates JNK signaling, remained unchanged in post-ischemic hippocampal neurons. By contrast, p53-activated gene 608 (PAG608), which promotes cell death in vitro, was strongly induced in post-ischemic CA1 neurons. Our data suggest that transcription factors p53 and phospho-c-Jun may contribute to programmed CA1 cell death following ischemia.

Thrombolysis in acute ischemic stroke: controlled trials and clinical experience

Thrombolytic therapy with recombinant tissue plasminogen activator (rtPA) is approved in the United States for treatment of acute ischemic stroke. Approval was granted after a large, randomized, placebo-controlled study by the National Institute of Neurological Disorders and Stroke (NINDS) showed a significant improvement in 3-month outcomes with rtPA despite a significant risk for symptomatic hemorrhage. Two other trials, the first and second European Cooperative Acute Stroke Study (ECASS I and II), have shown comparable results, but neither was statistically positive for the predefined primary end point. An analysis of the risk/benefit profile of rtPA therapy based on the results of these three trials indicates that the treatment is effective and, when administered within 3 hours of symptom onset at a dose of 0.9 mg/kg, the benefits by far outweigh the risks for eligible patients. Even with the 6-hour time window of the two ECASS trials, a combined analysis of the three studies shows the number of disabled or dead patients to be significantly reduced. Preliminary data collected on the use of rtPA outside of clinical trials in the United States and Europe suggest that, when rtPA is used according to the trial protocol, the risks and benefits are similar to those observed in clinical trials. However, even within the United States, rtPA is underutilized. The most substantial treatment barrier is the narrow time window, which may be expanded if long-term experience shows that this is possible. Most stroke patients arrive at the hospital too late to be eligible for screening and treatment. Education of the public and physicians may help to overcome this difficulty.

Brain-derived neurotrophic factor improves long-term potentiation and cognitive functions after transient forebrain ischemia in the rat

We investigated the effect of brain-derived neurotrophic factor (BDNF) on hippocampal long-term potentiation (LTP) and cognitive functions after global cerebral ischemia in the rat. After four-vessel occlusion, BDNF was administered via an osmotic minipump continuously over 14 days intracerebroventricularly. Electrophysiological experiments were performed 14 days after cerebral ischemia. Test stimuli and tetanization were delivered to the Schaffer collaterals of the hippocampus and field excitatory postsynaptic potentials (fEPSP) were recorded in the CA1 region. Cognitive impairment was analyzed repeatedly with a passive avoidance test, a hole-board test, and with an activity center on the same animal. In sham-operated animals, LTP was consistantly induced after delivering a tetanus (increase of initial slope of fEPSP to 173 +/- 12% of baseline; n = 6). After transient forebrain ischemia LTP could not be induced (117 +/- 4% of baseline; n = 7). In ischemic animals treated with BDNF, LTP could be induced (168 +/- 28% of baseline; n = 8). Transient forebrain ischemia resulted in a significant decrease in spatial discrimination performance but not of associative memory. The ratios for working memory (WM) and reference memory (RM) 15 days after ischemia were lower in the ischemic rats (n = 10) than in the sham-operated control animals (n = 10; WM: 22 +/- 6 vs 72 +/- 7; RM: 30 +/- 7 vs 72 +/- 5). Postischemic intracerebroventricular BDNF infusion increased both WM (63 +/- 4; n = 10) and RM (58 +/- 5; n = 10). The spontaneous locomotor activity did not differ significantly in the three groups. These data indicate a protective effect of BDNF for synaptic transmission and cognitive functions after transient forebrain ischemia.

Bradykinin induces interleukin-6 expression in astrocytes through activation of nuclear factor-kappaB

Bradykinin, a mediator of inflammation, is produced in the brain during trauma and stroke. It is thought to open the blood-brain barrier, although the mechanism is unclear. We have investigated, therefore, the effect of bradykinin on the expression of interleukin-6 (IL-6), a putative modulator of the blood-brain barrier, in astrocytes. IL-6 gene transcription was evaluated by transient transfection of the human IL-6 promoter linked to the luciferase gene. In murine astrocytes, bradykinin stimulated IL-6 secretion and gene transcription. The effect of bradykinin was blocked by KN-93, an inhibitor of Ca2+/calmodulin-dependent protein kinases, and by bisindolylmaleimide I, an inhibitor of protein kinase C, suggesting the involvement of these protein kinases. Mutations in the multiple response element and the binding site for nuclear factor-kappaB (NF-kappaB), but not in other known elements of the IL-6 promoter, interfered with induction of IL-6 transcription. The involvement of NF-kappaB was supported further by the finding that overexpression of nmIkappaB alpha, a stable inhibitor of NF-kappaB, inhibited the induction of IL-6 by bradykinin. Bradykinin activated NF-kappaB in primary astrocytes as shown by increased DNA binding of NF-kappaB. These data demonstrate that bradykinin stimulates IL-6 expression through activation of NF-kappaB, which may explain several inflammatory effects of bradykinin.

Inhibition of caspases prevents cell death of hippocampal CA1 neurons, but not impairment of hippocampal long-term potentiation following global ischemia

An essential role for caspases in programmed neuronal cell death has been demonstrated in various in vitro studies, and synthetic caspase inhibitors have recently been shown to prevent neuronal cell loss in animal models of focal cerebral ischemia and traumatic brain injury, respectively. The therapeutic utility of caspase inhibitors, however, will depend on preservation of both structural and functional integrity of neurons under stressful conditions. The present study demonstrates that expression and proteolytic activity of caspase-3 is up-regulated in the rat hippocampus after transient forebrain ischemia. Continuous i.c.v. infusion of the caspase inhibitor N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethyl ketone significantly attenuated caspase-3-like enzymatic activity, and blocked delayed cell loss of hippocampal CA1 neurons after ischemia. Administration of N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethyl ketone, however, did not prevent impairment of induction of long-term potentiation in post-ischemic CA1 cells, suggesting that caspase inhibition alone does not preserve neuronal functional plasticity.

[Moderate hypothermia for the treatment of malignant middle cerebral artery infarct]

Moderate hypothermia was induced in 30 patients with malignant middle cerebral artery (MCA) territory infarction. Patients were kept at 33 degrees C body-core temperature for 48 to 72 h, and ICP, CPP, and brain temperature were monitored. Outcome at 4 weeks and at 3 months after the stroke as well as side effects of moderate hypothermia were analysed. Mortality of malignant MCA infarction could be reduced from 80% in historical controls, to 43% (13/30) under hypothermia. During hypothermia elevated ICP values could be significantly reduced. Herniation due to a secondary rise of ICP after rewarming was the cause of death in all 13 patients. The most frequent complication of moderate hypothermia was pneumonia in 12 of the 30 patients (40%). Other severe side effects of hypothermia could not be detected. Moderate hypothermia may improve clinical outcome in patients with malignant MCA infarction.

Brain-derived neurotrophic factor prevents neuronal death and glial activation after global ischemia in the rat

The expression of brain-derived neurotrophic factor (BDNF) and its receptor tyrosine kinase B are both increased after global ischemia. Therefore, a protective action of BDNF against the delayed degeneration of vulnerable neurons has been suggested. We have investigated the neuroprotective action of BDNF in global ischemia induced by a four-vessel occlusion in the rat. Following reperfusion, 0.06 microg/hr BDNF was continuously administered intracerebroventricularly with an osmotic minipump. Rats were sacrificed up to 7 days after ischemia and neuronal degeneration was identified by terminal transferase and biotin-dUTP nick end labeling (TUNEL) staining. Additionally, the glial reaction was investigated immunohistochemically and by measuring the activation of immunological nitric oxide synthase protein expression. Postischemic intracerebroventricular infusion of BDNF prevented neuronal death in the vulnerable CA1 region of the hippocampus. Additionally, astroglial activation and macrophage infiltration, which were observed in association with neuronal death, were inhibited by BDNF. This was paralleled by an inhibition of inducible nitric oxide synthase (iNOS) expression in the hippocampus. Thus, the observed neuroprotective effects of continuous BDNF administration after reperfusion suggest a therapeutic potential for BDNF in cerebral ischemia.

[Disease picture of myotonic muscular dystrophy in patients with large CTG triplet expansion]

Myotonic dystrophy is an autosomal dominant multisystem disorder involving muscle, brain, heart, eyes, and endocrine organs. The underlying mutation is an expanding trinucleotide CTG repeat in the 3'prime untranslated region of a serine-threonine kinase gene on chromosome 19q. A statistical correlation exists between the CTG copy number and the severity of the disease. Infants with severe congenital myotonic dystrophy have been shown to have on average a greater amplification of the CTG repeat than is seen in the non-congenital myotonic dystrophy population. However, not all patients with many CTG copies develop congenital myotonic dystrophy. We present 13 patients with more than 1500 CTG trinucleotide repeats and show their variable clinical course.

Neurochemical monitoring of fatal middle cerebral artery infarction

BACKGROUND

Microdialysis is a method for neurochemical monitoring that has been applied more frequently over the past few years in patients suffering from subarachnoid hemorrhage, acute brain injury, and stroke. It is used to study the course of extracellular molecules of low molecular weight, such as excitatory amino acids or metabolic end products.

CASE DESCRIPTION

We report the case of a 43-year-old patient suffering from left hemispheric stroke with a space-occupying postischemic edema leading to a considerable mass effect on the contralateral side. For treatment of severe edema, hypothermia was initiated. The microdialysis and intracranial pressure probe were placed into the noninfarcted hemisphere. A massive increase in levels of glutamate, glycerine, and the lactate-pyruvate ratio was measured 24 hours before intracranial pressure elevation was observed and brain death occurred.

CONCLUSIONS

Monitoring excitatory amino acids, glycerine as a membrane component, and lactate-pyruvate ratio as an energy marker by microdialysis is a useful tool to increase our understanding of biochemical events in secondary brain damage. For future prevention of secondary ischemia in patients with massive stroke, close neurochemical monitoring might be valuable to improve therapy, particularly in the critically ill.

Moderate hypothermia in the treatment of patients with severe middle cerebral artery infarction

BACKGROUND AND PURPOSE

Animal research and clinical studies in head trauma patients suggest that moderate hypothermia may improve outcome by attenuating the deleterious metabolic processes in neuronal injury. Clinical studies on moderate hypothermia in the treatment of acute ischemic stroke patients are still lacking.

METHODS

Moderate hypothermia was induced in 25 patients with severe ischemic stroke in the middle cerebral artery (MCA) territory for therapy of postischemic brain edema. Hypothermia was induced within 14+/-7 hours after stroke onset and achieved by external cooling with cooling blankets, cold infusions, and cold washing. Patients were kept at 33 degreesC body-core temperature for 48 to 72 hours, and intracranial pressure (ICP), cerebral perfusion pressure, and brain temperature were monitored continuously. Outcome at 4 weeks and 3 months after the stroke was analyzed with the Scandinavian Stroke Scale (SSS) and Barthel index. The side effects of induced moderate hypothermia were analyzed.

RESULTS

Fourteen patients survived the hemispheric stroke (56%). Neurological outcome according to the SSS score was 29 (range, 25 to 37) 4 weeks after stroke and 38 (range 28 to 48) 3 months after stroke. During hypothermia, elevated ICP values could be significantly reduced. Herniation caused by a secondary rise in ICP after rewarming was the cause of death in all remaining patients. The most frequent complication of moderate hypothermia was pneumonia in 10 of the 25 patients (40%). Other severe side effects of hypothermia could not be detected.

CONCLUSIONS

Moderate hypothermia in the treatment of severe cerebral ischemia is not associated with severe side effects. Moderate hypothermia can help to control critically elevated ICP values in severe space-occupying edema after MCA stroke and may improve clinical outcome in these patients.

["Paradoxical" herniation after decompressive trephining]

The intracranial space is divided into two large compartments by the tentorium. The hydrostatic pressure of spinal fluid is responsible for buoyancy of the brain within these compartments. In patients with craniectomy this equilibrium is exposed to atmospheric pressure. We report on four cases of reversible herniation after either bilateral or unilateral decompressive craniectomy performed for increased intracranial pressure (ICP) and failure of conservative ICP treatment. All four patients had survived a severe neurological disease (encephalitis, subdural haematoma, stroke) which required craniectomy to control raised ICP. All were successfully weaned from the ventilator and awake and CT scans showed no space-occupying lesion anymore. The patients showed a typical "sunken pattern" at the trepanation site. All patients developed clinical signs of transtentorial herniation (i.e. unilateral dilated pupils, deteriorated alertness, and extensor posturing) shortly after either diagnostic or presumed therapeutic lumbar puncture. One patient developed herniation a second time while in the typical 30 degrees upright position. After craniectomy, transtentorial herniation is possible even in the absence of increased ICP. It is related to a negative gradient between atmospheric and intracranial pressure, which is enhanced by changes in the CSF compartment following lumbar puncture. Lumbar puncture should be avoided if possible and, when necessary, only be performed in the head-down position. Acute therapy in these cases is quite simple; it requires flat or even head-down positioning and early cranioplasty.

Heparin inhibits induction of nitric oxide synthase by cytokines in rat brain microvascular endothelial cells

The inflammatory reaction following ischemic brain injury involves bioactive mediators released mainly from leukocytes. The aim of this in vitro-study was to evaluate possible modulatory actions of heparin on nitric oxide synthesis induced by proinflammatory cytokines. Rat microvascular brain endothelial cells were isolated from adult rat brains and treated with interferon-gamma (IFN-gamma) and interleukin-1beta (IL-1beta) with or without heparin. The expression of inducible nitric oxide synthase (iNOS) mRNA and the iNOS protein activity was analyzed by reverse transcription polymerase chain reaction (RT-PCR) and Griess reagent, respectively. Heparin in a dose-dependent manner attenuated the increase in iNOS expression and NO release after cytokine activation. Thus, in addition to its anticoagulatory effect, heparin may also be effective in the prevention of inflammatory reaction after cerebral ischemia.

Acute ischaemic stroke: revascularizing therapy. Stroke Council of the American Heart Association

The principal goals of thrombolytic therapy for stroke are early restitution of cerebral blood flow, reduction of ischaemia, and attenuation of neurological disability through lysis of an occluding thrombus and consequent rapid restoration of circulation in the affected territory. Therapy should be initiated as soon as possible, at least within 4-6 h of stroke onset, to prevent major infarction and to salvage the hypoperfused but potentially viable zone adjacent to the central ischaemic area known as the ischaemic penumbra. This survey focuses on the safety and efficacy of thrombolytic therapy in acute ischaemic stroke in clinical trials. The results of two successful major randomized studies using tissue plasminogen activator (t-PA) were recently published. Intravenous thrombolysis seemed to be effective in improving functional and neurological outcome in a clearly defined subgroup of patients meeting the inclusion criteria of the studies. However, the identification of those patients proved to be difficult and depended on expertise in recognizing the early infarction signs on initial computed tomography. Since treating ineligible patients is associated with an unacceptable risk of intracranial bleeding complications and death, intravenous thrombolysis should only be performed at selected centres in selected patients.

Reoxygenation increases the release of reactive oxygen intermediates in murine microglia

Respiratory burst activity of murine microglial cells was investigated in vitro under normoxic and hypoxic conditions with a chemoluminometric assay. Hypoxia for 24 hours reduced the release of extracellular reactive oxygen intermediates (ROIs), whereas reoxygenation increased the chemoluminescence more than sevenfold. Blockade of potassium channels inhibited the increase of oxidative burst after reoxygenation, indicating that potassium ions, which were increased in the supernatant of hypoxic microglial cells, were involved in this activation process. Also, blockade of voltage-gated calcium channels with nifedipine attenuated the increased release of ROIs. With fura-2 analysis, it was shown that the activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase by potassium ions was mediated by calcium influx via voltage-gated calcium channels. Thus, influx of calcium ions through voltage-gated channels activates the NADPH oxidase in microglial cells during reoxygenation. By the increased production of ROIs, microglial cells may add to the reperfusion injury after ischemia in vivo.

Manganese augments nitric oxide synthesis in murine astrocytes: a new pathogenetic mechanism in manganism?

Since manganese (Mn2+) is known to be sequestered in glial cells, we investigated possible neurotoxic mechanisms involving astrocytes in vitro. Low concentrations of Mn2+ were toxic only in astrocyte-neuronal cocultures but not in pure astrocyte or neuronal cultures. As a possible mediator of manganese-derived neurotoxicity, we measured the production of nitric oxide in astrocytes. Manganese, but not other transition metals, dose dependently increased iNOS mRNA and protein levels and the release of nitric oxide in activated astrocytes. This effect was specific for astrocytes, since we observed no stimulation in microglial cells. The observations suggest that besides the known inhibition of mitochondrial function the neurotoxic effect of manganese in low concentrations might be mediated by the increased production of nitric oxide in astrocytes.

Muscular involvement in the Holt-Oram syndrome

Holt-Oram syndrome is an autosomal dominant disorder characterised by radial ray and congenital heart defects. Recently, a gene for this disorder has been identified on chromosome 12q24.1, encoding a T box transcription factor. However, the functional role of the gene product is not completely understood. We present results of neurological, radiological, and muscle magnetic resonance imaging (MRI) investigations in 13 patients from eight unrelated families. Besides heart defects, clinical signs ranged from thenar abnormalities to bilateral phocomelia. The former were present in all patients. MRI showed hypoplasia of discrete muscles which clinically showed as non-progressive weakness. The structural pattern of residual muscles was normal on MRI, which together with normal muscular power, electromyography, and muscle enzyme investigations excluded a progressive neuromuscular disorder. The number and location of hypoplastic muscles correlated with the severity of skeletal involvement. Thus, patients with hypoplasia of large and proximal muscles had phocomelia, and those with mere intrinsic hand muscle hypoplasia had only a triphalangeal thumb or no skeletal malformation. On the basis of these observations, we conclude that disturbed fetal limb muscle development is involved in the bony malformations of the upper limbs.

Superoxide dismutase activity in serum of patients with acute cerebral ischemic injury. Correlation with clinical course and infarct size

BACKGROUND AND PURPOSE

Superoxide dismutase (SOD) is one of the major free radical scavenging systems that might play a role in both degenerative and acute diseases of the central nervous system.

METHODS

We measured SOD activity in the serum of 41 patients with acute ischemic stroke with a chemiluminometric assay based on the generation of oxygen free radicals by xanthine and xanthine oxidase.

RESULTS

SOD activity was significantly lower in patients with ischemic stroke than in age-matched control patients with nonvascular, neurological illnesses (n = 24; P < .034, Wilcoxon rank test). The activity was inversely correlated with the size of infarction on CT (P = .01, Spearman correlation) and the severity of neurological deficits (P < .001, Spearman correlation). The decreased SOD activity recovered within 5 days after stroke to values found in serum of control patients.

CONCLUSIONS

Our data suggest that the SOD activity in serum is reduced in stroke patients, and replacement of antioxidative activity could be beneficial in the acute treatment of cerebral ischemia.

Barraquer-Simons syndrome (with sensorineural deafness): a contribution to the differential diagnosis of lipodystrophy syndromes

Among the lipodystrophies, the Barraquer-Simons syndrome is a rare condition. We describe a 27-year-old woman with progressive loss of subcutaneous fat after 15 years first affecting the face and spreading to the upper part of the body. She also suffered from deafness and had marked changes in cranial MRI. We discuss possible differential diagnosis such as the Cockayne, SHORT and Berardinelli-Seip syndrome.

Stimulation of interleukin-6 secretion and gene transcription in primary astrocytes by adenosine

During cerebral ischemia, the expression of interleukin-6 (IL-6), which has neuroprotective properties, increases. To understand the underlying mechanism, the regulation of IL-6 expression by neurotransmitters that accumulate during cerebral ischemia was investigated. Adenosine stimulated IL-6 secretion in primary astrocytes four- to 10-fold. The effect was concentration dependent, the EC50 being approximately 8 microM. Although the nonselective analogue 2-chloroadenosine (2CA) increased IL-6 secretion to a similar extent, the A1-selective agonist N6-cyclopentyladenosine or the A2a agonist CGS-21680 had only a marginal effect on IL-6 secretion. IL-6 secretion stimulated by 2CA (10 microM) was inhibited by the nonselective adenosine antagonist 8-(p-sulfophenyl)theophylline, whereas the A1-selective antagonist 8-cyclopentyl-1,3-dipropylxanthine or the A2a-selective antagonist 8-(3-chlorostyryl)caffeine had no effect, to a concentration of 0.1 microM. Transcription of the IL-6 gene was investigated by transfecting primary astrocytes with a reporter fusion gene containing the human IL-6 promoter (-179/+12). 2CA stimulated IL-6 gene transcription 2.5-fold. Mutations of the binding site for NF-kappaB or NF-IL6 abrogated the response to 2CA. Thus, an increase of extracellular adenosine during focal cerebral ischemia may stimulate IL-6 expression via A2b receptors. The induction of IL-6 expression appears to involve a transcriptional effect that depends on NF-kappaB and NF-IL6.

Plasma insulin-like growth factor I and IGF binding protein 3 levels in patients with acute cerebral ischemic injury

BACKGROUND AND PURPOSE

The insulin-like growth factors (IGF) are synthesized in the brain and are involved in fetal brain development. An increased expression of IGF-I and IGF-II occurs in cerebral regions with neuronal damage after experimental hypoxic injury. Furthermore, the expression of mRNAs coding for IGF-I and the binding proteins IGFBP-2 and IGFBP-3 is augmented in response to unilateral ischemia in animal models. The secretory dynamics of IGF-I in human cerebral ischemia have not yet been investigated.

METHODS

Plasma IGF-I and IGFBP-3 were measured sequentially in 20 patients with acute ischemic stroke (within 24 hours and 3, 5, and 10 days thereafter). For analysis the patients were assigned to three groups according to the diameter of the infarct area as measured on CT scan: small (< 1.5 cm), moderate (> or = 1.5 cm and < or = 5 cm), and large (> 5 cm). Eight age-matched patients with nonvascular, neurological illnesses served as controls.

RESULTS

Plasma IGF-I and IGFBP-3 plasma concentrations after acute cerebral ischemia were strikingly lower than those in control subjects and healthy individuals reported in the literature. Plasma IGF-I levels in patients with large infarcts were significantly statistically lower than those in control subjects (P < .05), and plasma IGFBP-3 levels were significantly lower than those in control subjects on days 5 and 10.

CONCLUSIONS

IGF-I and IGFBP-3 plasma levels are decreased in patients after cerebral ischemia. After acute ischemic stroke, increased demand for growth factors, altered tissue distribution, and accelerated metabolic clearance rate or central inhibition of the somatotrophic axis may contribute to these low plasma concentrations. Growth factors such as IGF-I and IGFBP-3 may play an important role in the pathophysiology of acute cerebral ischemia, and growth factors may have a considerable effect on future therapeutic regimens.

The dominant role of exogenous or endogenous interleukin-1 beta on expression and activity of inducible nitric oxide synthase in rat microvascular brain endothelial cells

In the brain large amounts of nitric oxide are produced in response to various pathological stimuli such as infectious agents, ischemia and trauma. Although it is known that endothelial cells can express the inducible isoform of nitric oxide synthase (iNOS) upon activation, the impact of different cytokines on iNOS expression in rat microvascular endothelial cells remains unclear. We now investigated iNOS mRNA expression and enzyme activity in primary cell cultures of rat microvascular brain endothelial cells after treatment with the proinflammatory cytokines interleukin-1beta (IL-1beta), Tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) alone or in combination. Cells were characterized by immunocytochemistry staining for von-Willebrand-factor and the rat brain endothelial antigen recognized by monoclonal antibody Ox2. iNOS-enzyme activity was determined by measurement of nitrite in the supernatants of cell culture using the Griess-reaction. In addition mRNA expression was analysed by RT-PCR with iNOS and IL-1beta specific primers. All cells in the endothelial cell culture were found to express the antigenic phenotype vWF+/Ox2+/Ox43-, thus identifying the cells as rat brain endothelial cells of microvascular origin. IL-1beta was the only cytokine that as a single stimulus induced iNOS mRNA expression and iNOS-enzyme activity in these endothelial cells. All combinations of two cytokines, including that of TNF-alpha and IFN-gamma--or the triple combination led to expression of iNOS-mRNA and active protein. Cell activation by the combination of TNF-alpha + IFN-gamma led to an early expression of IL-1beta by the endothelial cells suggesting iNOS induction as a consequence of endogenous IL-1beta production under this challenge. The experiments prove that rat brain microvascular endothelial cells express iNOS and produce large amounts of NO under inflammatory conditions. Furthermore, our results indicate a decisive role of IL-1beta in iNOS expression and NO generation.

Barbiturate coma in severe hemispheric stroke: useful or obsolete?

Barbiturates are administered in a variety of clinical conditions to control elevated intracranial pressure (ICP). However, their routine use to treat elevated ICP has been questioned because it may cause severe side effects. We therefore investigated the effect of high-dose barbiturate therapy on ICP and outcome in patients with severe brain edema after severe middle cerebral artery (MCA) or hemispheric infarction. Barbiturate coma was induced with thiopental infusion in 60 patients with critically increased ICP due to large hemispheric or MCA territory infarction, defined by CT. ICP was monitored in all patients during barbiturate therapy. Barbiturate coma was induced after a standardized treatment protocol for increased ICP after failure of osmotherapy and mild hyperventilation. During barbiturate administration, cerebral perfusion pressure (CPP) and mean arterial pressure were recorded. Clinical outcome of these patients and the individual effect on ICP were analyzed. Only five of 60 patients who were treated with barbiturate coma survived (8%). All other patients died after transtentorial herniation with subsequent brain death. Barbiturate infusion was followed by a drop in ICP in 50 patients and showed no effect on ICP values in 10 patients. CPP decreased with a mean of 9 mm Hg (range, 5 to 20 mm Hg). Although barbiturates were initially effective, only in some patients was ICP control sustained. Severe side effects of barbiturate therapy, besides arterial hypotension, were seen in 15 patients (25%). Barbiturate coma in the therapy of increased ICP after severe ischemic hemispheric stroke can lower critically elevated ICP levels. However, it seems to have no positive effect on neurologic outcome.

Intraventricular brain-derived neurotrophic factor reduces infarct size after focal cerebral ischemia in rats

Brain-derived neurotrophic factor (BDNF), acting through the high-affinity receptor tyrosine kinase (TrkB), is widely distributed throughout the central nervous system and displays in vitro trophic effects on a wide range of neuronal cells, including hippocampal, cerebellar, and cortical neurons. In vivo, BDNF rescues motorneurons, hippocampal, and substantia nigral dopaminergic cells from traumatic and toxic brain injury. After transient middle cerebral artery occlusion (MCAO), upregulation of BDNF-mRNA in cortical neurons suggests that BDNF potentially plays a neuroprotective role in focal cerebral ischemia. In the current study, BDNF (2.1 micrograms/d) in vehicle or vehicle alone (controls) was delivered intraventricularly for 8 days, beginning 24 hours before permanent middle cerebral artery occlusion by intraluminal suture in Wistar rats (n = 13 per group). There were no differences in physiological variables recorded during surgery for the two groups. Neurological deficit (0 to 4 scale), which was assessed on a daily basis, improved in BDNF-treated animals compared with controls (P < 0.05; analysis of variance and Scheffe's test). There were no significant differences in weight in BDNF-treated animals and controls during the experiment. After elective killing on day 7 after MCAO, brains underwent 2,3,5-triphenyltetrazolium chloride staining for calculation of the infarct volume and for histology (hematoxylin and eosin and glial fibrillary acid protein). The mean total infarct volume was 83.1 +/- 27.1 mm3 in BDNF-treated animals and 139.2 +/- 56.4 mm3 in controls (mean +/- SD; P < 0.01, unpaired, two-tailed t-test). The cortical infarct volume was 10.8 +/- 7.1 mm3 in BDNF-treated animals and 37.9 +/- 19.8 mm3 in controls (mean +/- SD; P < 0.05; unpaired, two-tailed t-test), whereas ischemic lesion volume in caudoputaminal infarction was not significantly different. These results show that pretreatment with intraventricular BDNF reduces infarct size after focal cerebral ischemia in rats and support the hypothesis of a neuroprotective role for BDNF in stoke.