Simple models including energy and spike constraints reproduce complex activity patterns and metabolic disruptions

In this work, we introduce new phenomenological neuronal models (eLIF and mAdExp) that account for energy supply and demand in the cell as well as the inactivation of spike generation how these interact with subthreshold and spiking dynamics. Including these constraints, the new models reproduce a broad range of biologically-relevant behaviors that are identified to be crucial in many neurological disorders, but were not captured by commonly used phenomenological models. Because of their low dimensionality eLIF and mAdExp open the possibility of future large-scale simulations for more realistic studies of brain circuits involved in neuronal disorders. The new models enable both more accurate modeling and the possibility to study energy-associated disorders over the whole time-course of disease progression instead of only comparing the initially healthy status with the final diseased state. These models, therefore, provide new theoretical and computational methods to assess the opportunities of early diagnostics and the potential of energy-centered approaches to improve therapies.     

Anwendung der automatisierten Festphasenextraktion bei der Bestimmung von Ochratoxin A

For some foodstuffs, determination of the mycotoxin ochratoxin A (OTA) requires time consuming clean up by means of solid phase extraction (SPE). Therefore a system for automated SPE was tested for cleaning up roasted coffee as a possible way of shortening preparation time. Validation of the method in accordance to the so called “Concept '98” led to a LOD of 0.2 μg/kg and a recovery rate of 92%. By using the described procedure with samples of roasted coffee the OTA contents varied between the LOD and 3.4 μg/kg. This method was also used to determine ochratoxin A in liquorice roots, ginger and valerian.

Presented at the 26^th Mykotoxin Workshop in Herrsching, Germany, May 17–19, 2004     

Sex-hormone-binding globulin and albumin concentrations in human cerebrospinal fluid

Polyacrylamide gel electrophoresis of plasma and concentrated cerebrospinal fluid (CSF) preincubated with tritium labelled 5 alpha-dihydrotestosterone (DHT) showed identical migration of the radioactivity, indicating the presence of sex-hormone-binding globulin (SHBG) in human CSF. The concentrations of SHBG (measured as the binding capacity) and albumin were measured in concentrated CSF (12 women and 1 man) and samples of plasma of some patients (9 women). SHBG could not be detected in 6 of the CSF samples, and the mean value of the determinable samples was 42.3 +/- 13.4 pmol/l. The mean +/- SE of the SHBG concentration in plasma was 90.8 +/- 8.9 nmol/l and the mean albumin concentrations in CSF and plasma were 3.4 +/- 0.6 mumol/l and 670 +/- 107 mumol/l respectively. The distribution ratio for SHBG over the blood-CSF barrier was 10 times higher than for albumin. It was concluded that the SHBG-binding in the CSF is negligible but that the albumin-binding may contribute to the CSF concentrations of testosterone and estradiol, which are 10-25% above the plasma unbound concentrations.