Continuous monitoring of extracellular lactate concentration by microdialysis lactography for the study of rat muscle metabolism in vivo

A method is described for the measurement and on-line monitoring of muscular extracellular lactate concentration in both anaesthetized and freely moving rats. This method is based on microdialysis sampling and lactic dehydrogenase-catalysed nicotinamide adenine dinucleotide, reduced (NADH)-fluorescence detection techniques. In vivo calibration revealed a resting extracellular lactate concentration of 1.92 +/- 0.13 mmol/l (+/- SEM) in the gastrocnemius muscle of adult male Wistar rats (n = 6), while the average whole-blood lactate level was 0.76 +/- 0.12 mmol/l (+/- SEM). This measured extracellular lactate concentration was 1.73-times higher than that deduced from the arterial lactate concentration. Blocking glycolysis with iodoacetate reduced the extracellular lactate concentration to 52 + 6% (+/- SEM, n = 4) of the resting level. The extracellular lactate concentration in rat gastrocnemius muscle had increased to significantly (P less-than-or-equal-to 0.05) different levels, 2.4 +/- 0.03 (+/- SEM) or 4.0 +/- 0.55 (+/- SEM) times the control value, 1 h after aortic clamping (n = 3) or cardiac arrest (n = 3), respectively. Stimulation of the sciatic nerve induced elevations of the extracellular lactate concentration in the tibialis anterior muscle which were linearly related to the recorded isometric force-time integral. We also monitored on-line the changes in extracellular lactate concentration in the tibialis anterior muscle of a swimming rat. Our results indicate that microdialysis lactate reflects also intracellular metabolism. Lactography may be a useful alternative to biopsies and nuclear magnetic resonance spectroscopy in clinical medicine and physiology for the monitoring of metabolism in vivo

Optical Dynamics of the Reaction Center of Photosystem II. A Hole-Burning and Photon-Echo Study

Photon-echo and transient hole-burning experiments on the P-band of the reaction center of photosystem II are reported which show that the P-band exhibits a large homogeneous width. A photon-echo signal with a decay time of 500 ps is also observed in the same spectral region and assigned to extraneous chlorophyll. These observations are discussed with reference to the bacterial reaction center and photosystem I.

Bioplastics

In a first aspect, the invention thus pertains to thermoplastic processable compositions (base compositions) comprising one or more flours, one or more polymers, optionally plasticizers, optionally fillers and optionally additives, characterized in that at least one of the polymers is present in the form of its water-redispersible polymer powder or as aqueous polymer dispersion, whereby the compositions contain less than 12% by weight of polyvinyl alcohol, based on the total amount of polymeric components of the composition

Bioplastics

In a first aspect, the invention thus pertains to thermoplastic processable compositions (base compositions) comprising one or more flours, one or more polymers, optionally plasticizers, optionally fillers and optionally additives, characterized in that at least one of the polymers is present in the form of its water-redispersible polymer powder or as aqueous polymer dispersion, whereby the compositions contain less than 12% by weight of polyvinyl alcohol, based on the total amount of polymeric components of the composition