Evidence for the generation of hydroxyl radical during arachidonic acid metabolism by human platelets

Reactive oxygen species, probably hydroxyl radicals (OH.), have been suggested to be generated during arachidonic acid (AA) metabolism and, once released, these species can modify the rate and extent of various reactions involved in AA metabolism. We have studied this phenomenon in washed human platelets. OH. generation was quantitated using 14C-benzoic acid as a specific trap in a continuous ionization chamber system. Resting platelets did not produce any detectable signal, whereas addition of AA resulted in gradual OH. production with peak values detected at approximately 20 min. Similar studies conducted under nitrogen or after boiling the platelets almost abolished OH. generation. Aspirin had no significant effect, whereas 5,8,11,14-eicosatetraynoic acid decreased the signal by greater than 90%, thus suggesting that OH. is produced primarily through the lipoxygenase pathway. Superoxide dismutase (SOD) and catalase had no effect and, as expected, phenol and mannitol decreased OH. production considerably, by greater than 50% and 90%, respectively. Azide and cyanide also reduced the OH. generation by about two thirds. We conclude that OH. is generated during AA metabolism by human platelets. It is primarily produced via the lipoxygenase pathway and may require a heme-dependent peroxidase. This highly reactive oxidant may play an important role in normal and abnormal hemostasis.     

Behavioral and Subjective Effects of Ethanol: Relationship to Cerebral Metabolism Using PET

This study examined the effects of ethanol on regional cerebral metabolic rate using positron emission tomography (PET). The study explored the relationship between the mood-altering effects of ethanol and its effects on regional cerebral glucose utilization (CMRglu) in eight healthy male volunteers. In the first phase of the study, the subjects participated in a behavioral preference procedure conducted in a recreational environment to determine their responses to ethanol (0.5 g/kg) in a naturalistic setting. They then participated in three PET sessions, receiving at three to seven day intervals, in counterbalanced order, placebo, 0.5 g/kg or 0.8 g/kg ethanol. PET scans were conducted using a PETT-VI scanner with F-18-2-fluoro-2-deoxyglucose (FDG) as the tracer. The mood-altering effects of ethanol were measured in both the naturalistic and the PET phases of the study. Ethanol produced comparable effects on mood in the naturalistic and the PET settings (i.e., increases in positive mood). The lower dose of ethanol produced variable effects on whole brain and regional CMRglu across subjects. There was some suggestion that certain regional metabolic changes after ethanol were correlated with subjective responses to the drug. The higher dose of ethanol decreased whole brain CMRglu in most subjects. All regions were affected about equally. It was concluded that the mood-altering effects of ethanol are not related in a simple manner to regional changes in CMRglu.     

Atypical chronic lymphocytic inflammation with pontocerebellar perivascular enhancement responsive to steroids (CLIPPERS), primary angiitis of the CNS mimicking CLIPPERS or overlap syndrome? A case report

A novel type of encephalomyelitis was first described as chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) in 2010 and few additional patients were reported since then. Partially due to its unknown aetiology and a lack of pathognomonic features some have suggested that CLIPPERS may not represent a distinct disease, but rather a syndrome with different underlying aetiologies. Here we report a 49-year-old German female who presented with a number of clinical and paraclinical features described as typical for CLIPPERS, while additionally showing symptoms and findings compatible with primary angiitis of the CNS (PACNS). This case may establish a previously unnoted link between two poorly understood autoimmune conditions of the CNS.     

Dynamic changes of cerebral oxygenation measured by brain tissue oxygen pressure and near infrared spectroscopy

Abstract

The aim of this study was to find out whether a correlation exists between changes in brain tissue oxygen pressure (ti-p0₂) and hemoglobin oxygenation (Hb02) measured by near-infrared spectroscopy. We studied 10 patients with severe head injury. A ti-p0₂ monitoring device was introduced in the frontal white matter as soon as possible after administration. Additionally a NIRS sensor Was placed at the forehead. All data were recorded simultaneously. 'Changes of the ti-p0₂ curve were defined as events with the following criteria: > 10% change from the baseline value, > 3 min duration, clearly not an artifact. 137 events were found with a mean change of ti-p0₂ of 8.3 ± 10.2 mmHg. In 77.4% we observed a corresponding change of the Hb02. In 7 patients we found a good correlation (r> 0.7) between change ti-p0₂ and change Hb0₂. In 3 patients the correlation was poor. The reason for poor correlation might be poor signal quality of the NIRS sensor or inhomogenous distribution of ischemic areas in the whole brain. We conclude that under the condition of a stable NIRS signal and a diffuse brain lesion, changes of ti-p0₂ are well reflected by NIRS. [Neural Res 1997; 19: 246-248]