In vivo 13C-NMR studies on the metabolism of the lugworm Arenicola marina

Metabolic response in Arenicola marina to limiting oxygen as reflected in the 1H-NMR oxymyoglobin signal

Many intertidal animals can endure prolonged periods of environmental stress and have developed strategies to preserve a functioning energy state in the cell. Recent 1H/31P-NMR techniques have allowed investigators to monitor directly mammalian tissue metabolism in vivo. In particular, the signals of myoglobin (Mb) offer a unique opportunity to explore the intracellular oxygen-partial-pressure [p(O2)] interaction in Arenicola marina, a standard model to study hypoxia tolerance in invertebrates. The present study reveals that the 1H-NMR MbO2 signal at -2.9 ppm is detectable in tissue and reflects directly the oxygenated state. As the p(O2) declines, MbO2 saturation and oxygen consumption decrease. However, phosphotaurocyamine concentration remains unaltered until the MbO2 saturation falls below 33%. The extracellular to intracellular p(O2) gradient appears substantial. The study establishes the 1H-NMR technique as an approach to measure the intracellular p(O2) with an oxygenated state marker and presents the interrelationship between oxygen and the metabolic adaptation during hypoxic stress.

The Pasteur effect in facultative anaerobic metazoa

The existence and the regulatory mechanisms of the Pasteur effect in facultative anaerobic metazoa are discussed. There are three reasons for the controversy surrounding this phenomenon. 1) The different definitions of the Pasteur effect, 2) the antagonistic effect of metabolic depression and its species specific response to hypoxia, as well as 3) the laboratory-specific differences in the experimental procedures for analyzing the Pasteur effect and its regulation. This review aims to clarify the confusion about the existence of the Pasteur effect in facultative anaerobic metazoa and to offer possible molecular mechanisms.

H-NMR signal of Arenicola marina myoglobin in vivo as an index of tissue oxygenation

Key questions on how intertidal animals adapt to hypoxic stress center on the high energy phosphate response to decreasing oxygenation. With recent 1H/31P-NMR techniques to monitor mammalian tissue metabolism, a novel approach has emerged to observe potentially the intracellular oxygen interaction in invertebrates. The present study indicates that Arenicola marina, a standard model for intertidal animals, exhibits a distinct set of Mb 1H-NMR signals in vivo, corresponding to the two isolated Mb isoforms. Specifically both deoxy-Mb I and deoxy-Mb II exhibit paramagnetically shifted signals at 93.4 ppm and 92.5 ppm at 25 degrees C, respectively, which arise from the proximal histidyl NdeltaH. These signals reflect the cellular oxygenation state and indicate clearly that the phosphotaurocyamine level begins to drop at the onset of anoxia and declines gradually to 50% of control after 3.5 h. 1H Mb spectra indicate protein heterogeneity originating from heme as well as structural disorder.

Multinuclear magnetic resonance studies of boar seminal plasma

Multinuclear magnetic resonance studies were performed on aqueous solutions of lyophilisates of boar seminal plasma. 1H- and 13C-NMR spectral assignments were obtained by one- and two-dimensional experiments. Four prominent constituents were identified in the lyophilisate as well as in the original seminal plasma: inositol (95% myo-inositol, 5% scyllo-inositol), citrate, lactate and glycerophosphorylcholine (GPC). The concentrations of these compounds were evaluated from appropriate 1H- and 13C-NMR resonances using biochemically determined citrate as reference. 31P-NMR spectroscopy confirmed the presence of GPC and revealed phosphorylcholine, glycerophosphorylserine and glycerophosphorylethanolamine as further components.

Futile cycling of glycogen in Fibrobacter succinogenes as shown by in situ 1H-NMR and 13C-NMR investigation

Glycogen was synthesized during all the growth phases in the rumen anaerobic cellulolytic bacterium Fibrobacter succinogenes. Glycogen synthesis and degradation were monitored using in situ 13C and 1H-NMR spectroscopy in resting cells of F. succinogenes. The cells were incubated at 37 degrees C under anaerobic conditions with [1-13C]glucose and [2-13C]glucose. 1H-NMR spectra were used to quantify enrichment by 13C of metabolism products. Glucose was utilized for energy requirements of the bacterium, essentially via the Embden-Meyerhof pathway, leading to the synthesis of succinate and acetate, while glycogen was stored. From [1-13C]glucose, labeling occurred on C2 of succinate and acetate, and on both C1 and C6 of glycogen, the labeling on C1 being predominant. The C6-labeling of glycogen may be explained by scrambling and reversal of the glycolytic pathway at the triose-phosphate and fructose 1,6-bisphosphate level. When the bacteria were incubated first with [1-13C]glucose, then washed and incubated with [2-13C]glucose, the pattern of 13C labeling in the products of the metabolism, as shown by 13C and 1H-NMR spectra, indicated that glycogen was degraded at the same time as it was being stored, suggesting futile cycling of glycogen. The hydrolysis of previously stored glycogen can provide, in the presence of glucose, up to 30% of the carbon source for the bacteria.