This article shows the ultrastructural architecture of larval zebrafish (Danio rerio) neuromuscular junctions in three dimensions. We compare classical electron microscopy fixation techniques with high-pressure freezing followed by freeze substitution (HPF/FS) in combination with electron tomography. Furthermore, we compare the structure of neuromuscular junctions in 4- and 8-dpf zebrafish larvae with HPF/FS because this allows for close-to-native ultrastructural preservation. We discovered that synaptic vesicles of 4-dpf zebrafish larvae are larger than those of 8-dpf larvae. Furthermore, we describe two types of dense-core vesicles and quantify a filamentous network of small filaments interconnecting synaptic vesicles as well as tethers connecting synaptic vesicles to the presynaptic cell membrane. In the center of active zones, we found elaborate electron-dense projections physically connecting vesicles of the synaptic vesicle pool to the presynaptic membrane. Overall this study establishes the basis for systematic comparisons of synaptic architecture at high resolution in three dimensions of an intact vertebrate in a close-to-native state. Furthermore, we provide quantitative information that builds the basis for diverse systems biology approaches in neuroscience, from comparative anatomy to cellular simulations.

Repeated bolus doses of thiopentone or Althesin were administered to 10 patients every 240 s while cerebral electrical activity was recorded with the Cerebral Function Monitor (CFM). Peripheral venous blood samples were collected at 60 and 225 s after each bolus dose for the measurement of plasma concentrations of the drugs. Significant correlations in the range r = 0.56-0.96 (P = 0.02-0.00001) between plasma thiopentone or alphaxalone concentrations and the upper and lower edges of the CFM trace were found. For the patients with relatively poor correlations, better correlations were obtained when 60- and 225-s sample were analysed separately.

A description is given of a new microprocessor-based device for EEG analysis. The Cerebral Function Analysing Monitor (CFAM) analyses the EEG amplitude and frequency distribution. It produces a detailed plot of amplitude trends and separate traces of the percentage activity in each of the classical EEG frequency bands. Its clinical application was studied in five patients anaesthetized with thiopentone, and nitrous oxide and halothane in oxygen. During maintenance of anaesthesia, there was a gradual decrease in EEG amplitude and shift towards lower frequency EEG activity. Discontinuation of nitrous oxide resulted in a marked increase in EEG amplitude and an increase in alpha and beta band activity. Discontinuation of halothane resulted in smaller alterations in the CFAM trace. This device provides easily interpreted processed EEG data and merits further investigation.

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