Striatal dopamine transporter binding in neuroleptic-naive patients with schizophrenia studied with positron emission tomography

OBJECTIVE: Recent in vivo imaging studies indicate a dysregulated presynaptic function of the striatal dopaminergic system in patients with schizophrenia. To further explore the basis of this phenomenon, the authors studied brain dopamine transporter binding in vivo in patients with first-episode, never-medicated schizophrenia. METHOD: Nine patients with schizophrenia and nine healthy matched comparison subjects were recruited. Striatal dopamine transporter binding was measured with positron emission tomography and a specific dopamine transporter ligand, [(18)F]CFT, a radiolabeled form of 2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane. RESULTS: Average caudate and putamen dopamine transporter binding potentials were almost identical in the patients and comparison subjects, but the patients lacked the right-left asymmetry of the caudate dopamine transporter binding seen in the comparison group. CONCLUSIONS: Average striatal dopamine transporter density is unaltered in neuroleptic-naive patients with schizophrenia. However, patients lack asymmetry in caudate dopamine transporter binding, which conforms with disrupted brain lateralization in this disorder.     

6-fluoroDOPA metabolism in rat striatum: time course of extracellular metabolites

6-[18F]Fluoro-L-DOPA (FDOPA) is an imaging agent used in the study of dopamine terminals in the living brain using positron emission tomography (PET). To better understand the role of tracer metabolism in dynamic FDOPA PET studies, the pharmacokinetics of individual FDOPA metabolites in extracellular space in the striata of anesthetized rats was investigated using in vivo microdialysis. Brain tissues were also analysed to obtain FDOPA metabolite distribution in the combined intracellular and extracellular spaces. Total extracellular [18F] radioactivity in rat striata was observed to rise and peak at 30 min post-injection (p.i.) and declined with clearance half-life of 2 h. In the extracellular space, the dominant FDOPA metabolite at early times was FDOPAC, followed by FHVA at 50 min, then F-sulfoconjugates at 70 min and finally 3-O-methyl-6-Fluoro-L-DOPA (3OMFD) at later times. These results are consistent with the sequential metabolism and brain clearance of L-DOPA and its metabolites. Analysis of whole striatal tissue confirmed the intraneuronal localization of fluorodopamine most likely stored in vesicles. A new but not unexpected finding was the enrichment of 3OMFD in intraneuronal striatal space which is perhaps a factor in its slow cerebral clearance. Since FDOPA PET data reflects the overall pharmacokinetics of several [18F]-metabolites, the observed different rates of formation and clearance and also different neuronal localization of each metabolite contribute to the measures obtained in dynamic FDOPA PET studies. These metabolic steps and their role in tracer kinetics are, thus, important factors to consider in ascribing physiologic significance to PET-derived measures.     

ROTEM monitoring of activated and non-activated prothrombin complex concentrate correction of dilutional coagulopathy

Objectives Prothrombin complex concentrates have been used to correct dilutional coagulopathy, but many preparations contain anticoagulants, such as heparin, to counteract their prothrombotic effects. These anticoagulants can interfere with haemostatic assays. The aim of this study was to monitor two different prothrombin complex concentrates for the treatment of albumin dilution in vitro, using rotational thromboelastometry with or without the heparin-antagonising agent protamine. Methods Citrated blood from 10 healthy volunteers was, in vitro, diluted 1:1 with 5% albumin and then corrected with a four-factor prothrombin complex concentrate with heparin anticoagulant (Confidex®) corresponding to a clinical dose of 43?IU/kg. Blood samples were tested with or without protamine. An activated prothrombin complex concentrate (APCC) (FEIBA®) without heparin in doses of 50?IU/kg and 100?IU/kg was also tested. Thromboelastometry was performed after recalcification. Results Albumin dilution significantly affected all thromboelastometry parameters. The four-factor PCC had an additional anticoagulant effect when added to the albumin-diluted blood; it was partially corrected by protamine for all parameters except maximum clot firmness. The APCC significantly improved all parameters, with over-correction of clotting time but only partial correction of maximum clot firmness. Conclusions The anticoagulant content of many prothrombin complex concentrates needs to be considered when performing in vitro testing. A heparin-free APCC better corrected an in vitro albumin-induced dilutional coagulopathy than a four-factor PCC, despite of blocking heparin with protamine.     

EFFECT OF TRANSCUTANEOUS NERVE STIMULATION ON MICROCIRCULATION IN INTACT SKIN AND BLISTER WOUNDS IN HEALTHY VOLUNTEERS

Healthy non-smoking volunteers participated in two experimental studies in which the circulatory changes induced by transcutaneous nerve stimulation (TENS) were quantified by two different methods. In experimental series 1 (intact skin), nine volunteers were given TENS on the left lower leg for 60 minutes on three occasions at different frequencies each time (2 Hz, 100 Hz, and sham). Changes in blood flow were assessed by laser Doppler imaging technique every five minutes. The mean blood flow increased by 40% during low frequency TENS and by 12% during high frequency TENS. There was no change in mean blood flow during sham stimulation. In experimental series 2 (blister wound), the circulatory changes induced by TENS were studied by intravital video microscopy and computerised image analysis in standard blister wounds on the lower leg. The microcirculatory blood flow, measured as red blood cell velocity (RBC-V) in 5-14 individual capillaries in each wound, was assessed before and during 45 minutes of TENS (2 Hz and 100 Hz). Mean RBC-V increased by 23% during low frequency TENS (n = 6) and by 17% during high frequency TENS (n = 8). The results show that: laser Doppler imaging and intravital video microscopy techniques can be used to study events at the microcirculatory level; the blister wound is an interesting new standard wound for use in clinical studies; and TENS stimulates the peripheral cirulation.     

Adverse events related to the new psychoactive substance 3-fluorophenmetrazine – results from the Swedish STRIDA project

Background: New psychoactive substances (NPS) are often poorly pharmacologically documented and the production is unregulated, implying high risks for toxic side effects. This report from the STRIDA project describes analytically confirmed non-fatal intoxications involving the phenmetrazine analogue 3-fluorophenmetrazine (3-FPM).

Study design and methods: Observational case series of patients with suspected acute NPS exposure requiring hospital care. Blood and urine samples were collected from patients presenting in emergency departments (ED) or intensive care units (ICU), after consultation with the Swedish Poisons Information Centre (PIC). Laboratory analysis was performed by multi-component liquid chromatography–mass spectrometry. Clinical data were collected during PIC consultations and retrieved from medical records.

Results: From November 2014 to October 2015, eight cases were registered as 3-FPM or “phenmetrazine” intoxications at the PIC after consultation. During the same period, analysis of STRIDA project samples confirmed 3-FPM use in a total of 19 patients (84% men) aged 22–54 (median 30) years. 3-FPM was detected in 15 out of 19 serum (2.7–1416?ng/mL) and in 14 out of 14 urine (1.0–6857?μg/mmol creatinine) samples. All patients were also tested positive for other psychoactive substances, with benzodiazepines being most common (57% of the cases). Ten patients were monitored in the ED for <4?h, while six needed ICU monitoring of which five were graded as severe intoxications (Poisoning Severity Score 3). Prominent clinical signs were tachycardia (47%), depressed consciousness (42%), agitation/anxiety (37%), delirium (37%), dilated pupils (26%), and seizures (16%). All patients survived.

Conclusion: In 19 patients testing positive for 3-FPM, a high incidence of severe clinical features was demonstrated. However, as all patients had also used other psychoactive substances, it was difficult to identify a unique toxidrome for 3-FPM. The results further showed that many 3-FPM intoxications would have been missed, if relying solely on information from PIC consultations. These results emphasize the importance of performing bioanalytical investigation in cases of suspected NPS intoxication.     

Caspase-mediated degradation of human 5-lipoxygenase in B lymphocytic cells

5-Lipoxygenase (5-LO) is a tightly regulated enzyme in the synthesis of bioactive lipids from arachidonic acid. Here, we demonstrate that 5-LO is regulated by caspases, which are signaling molecules that control critical biological processes by means of specific limited proteolysis. Cell splitting of the Epstein-Barr virus-transformed B lymphocytic cell line BL41-E95-A caused a pronounced, but transient, reduction of functional 5-LO protein, accompanied by the appearance of a 62-kDa 5-LO cleavage product. In parallel, splitting of BL41-E95-A cells induced activation of caspase-6 (casp-6) and casp-8. Caspase activation and 5-LO degradation were blocked by the protein-synthesis inhibitor cycloheximide, and cell-permeable peptide inhibitors of casp-6 and casp-8 prevented 5-LO cleavage. Activation of casp-6 and casp-8 was connected to subsequent enhancement of cell proliferation, whereas selective caspase inhibition blocked cell growth. Last, isolated human 5-LO was cleaved by recombinant casp-6 in vitro to a 58-kDa fragment. Based on site-directed mutagenesis studies, 5-LO is cleaved by casp-6 after Asp-170, which in a homology-based 3D model of 5-LO is located on the enzyme periphery. We suggest that splitting of BL41-E95-A cells induces de novo synthesis of a protein involved in the activation of casp-6, which cleaves 5-LO.