Lactate dehydrogenase was isolated in pure form from crude extract of the cestode Hymenoleois diminuta by heat treatment and column chromatography. The purified enzyme has a specific activity of 106 units per mg protein. The molecular weight of the purified protein was 75,000 as determined by Sephadex gel filtration and analytical ultracentrifugation. An equilibrium ultracentrifugation study suggests a subunit molecular weight of 39,000. From these data, a dimer form of the native enzyme is proposed.

The primary objectives of this research were to characterize the involvement of lactate dehydrogenase (LDH) in color stability of physiologically different bovine muscles, and to investigate the influence of lactate enhancement on the myoglobin redox state of bovine muscles. In experiment 1, three different bovine muscles; Longissimus lumborum (LD), Semimembranosus (SM), Psoas major (PM) were (n=7 respectively) cut into steaks, and displayed for 7 days. Instrumental color, LDH-B, LDH isozyme expression, and NADH were measured. In experiment 2, strip steaks (n=8) were cut into half, and one side was injected with oxamate (LDH inhibitor), and the other was injected with water. Surface color, LDH, and NADH were measured after 10 days. In experiment 3, the three bovine muscles (n=10) were enhanced with solutions containing lactate and/or phosphate. Steaks were stored and displayed for 14 days. Instrumental color, LDH-B, total reducing activity (TRA), and NADH were measured. In experiment 4, fifteen beef strip loins were divided individually into four equal sections, and one of six treatments containing phosphate and/or calcium lactate with or without irradiation (2.4 kGy) randomly assigned to each loin section (n=10). Steaks were packaged in highoxygen modified atmosphere package, irradiated, stored in the dark at 1°C for 14 days. Instrumental color, TRA, lipid oxidation, and NADH were measured. LD remained the most red, whereas PM was most discolored. LD had a significantly higher level of LDH-1 responsible for LDH-B activity as compared to SM and PM. Consequently, LD had a higher LDH-B, and more NADH (p < 0.05). Inclusion of oxamate inhibited LDH-B, decreased NADH, and consequently discolored more. Potassium lactate enhancement led to more NADH through elevated LDH flux and subsequently increased (p < 0.05) color stability of LD and PM throughout display. Loins with calcium lactate/phosphate maintained the most stable red color during display. Calcium lactate/phosphate in loins increased NADH concentration, TRA, and were the least oxidized over display. These results confirm the involvement of LDH in meat color stability through replenishment of NADH. Lactate enhancement promotes meat color stability by providing superior antioxidant capacity and increased reducing activity of myoglobin by elevating NADH concentration.

The objective of this study was to evaluate the effects of non-meat ingredients, blade tenderization and vacuum-tumbling on the textural, visual and sensory characteristics of steaks from Biceps femoris, Supraspinatus, Triceps brachii long head, and Longissimus dorsi muscles packaged in high oxygen, modified atomosphere (MAP) system. United Department of Agriculture (USDA) Select muscles (n=72) from each cut were obtained from a commercial processor over three processing days. Muscles were aged for five days at 4ºC. Denuded muscles within a processing day were randomly assigned to one of 24 treatments. This study was a 2 x 4 x 3 factorial arrangement where treatments were control, injection (injected or non-injected), blade tenderization (0, 1, or 2 passes) and vacuum-tumbling (0, 5, 10 or 20 minutes). Injected muscles contained up to 10% of a brine containing 1.55% potassium lactate, 0.1% sodium diacetate, 0.3% sodium tripolyphosphate blend and 0.4% salt in the final product. Muscles were vacuumtumbled and blade tenderized sequentially after injection. Steaks from the muscles were stored in a high oxygen (80% O2, 20% CO2) MAP system for 0, 3, 7, 10 and 14 days at 2ºC. Steaks were evaluated for package purge (%), Warner-Bratzler shear force (kg), cook loss (%), cook time (min), pH, CIE L* a* b* color space values and trained color panel scores on each storage day. A trained descriptive attribute sensory panel evaluated steaks on day 1 only. Warner-Bratzler shear force (P<0.01) and trained sensory panel results (P<0.05) showed that the addition of non-meat ingredients improved tenderness in all four muscles. Sensory detectable connective tissue was lower (P<0.01) in injected steaks for all muscles except in Biceps femoris steaks. Injected steaks had higher pH (P<0.01) measurements than non-injected treatments in all muscles except the Triceps brachii long head. Neither blade tenderization nor vacuum-tumbling had consistent effects in all four muscles. Vacuum-tumbled Biceps femoris steaks had lower bitter flavor aromatics (P<0.05). In conclusion, enhancing beef with non-meat ingredients had the greatest impact on the quality attributes of high connective tissue cuts and Longissimus dorsi steaks.

Konstanz, Universität, Thesis (doctoral), 2001.

The effects of differing recovery patterns following intermittent exercise on blood lactate and subsequent performance were examined. Fourteen male subjects completed three randomly assigned experimental protocols. Each protocol consisted of eight 45s-bouts of cycling on a Monark cycle ergometer at 120% of VO$ sb2$ max interposed with five minute recovery periods. Each protocol ended with a maximal performance task consisting of a 45s all-out cycling test. Recovery patterns included passive, cycling (45% of VO$ sb2$ max), and arm cranking (45% of VO$ sb2$ max). Results revealed similar blood lactate concentrations in the passive and arm cranking conditions but significantly lower (p $<$.05) levels in the cycling condition. Mean power outputs measured from the performance task were significantly higher (p $<$.05) in the cycling and arm cranking recovery conditions. The correlation between blood lactate levels and mean power output was low (r = $-$0.28), suggesting that other factors were influencing subsequent performance.

Thesis--Veterinaer- og Lanbohøjskole, Copenhagen. / Summary in Danish. Bibliography: p. 199-[221].

The role of L-Lactate has expanded from an energy metabolite to a signaling molecule in neurons. Studies have shown that L-Lactate plays a role in neuroprotection and in NMDAR-dependent long-term memory formation. The aim of this dissertation is to characterize the role of L-Lactate as a signaling molecule and understand the molecular mechanism through which L-Lactate potentiates NMDAR signal. Using mass spectrometry, I monitored the time-dependent changes in the phosphoproteome of cortical neuronal cultures in response to Lactate. The phosphoproteomic analysis highlighted a number of cytoskeletal proteins involved in synapse remodeling as well as axon guidance that were regulated by L-Lactate. In addition, I found that L-Lactate induced phosphorylation of proteins involved in the MAPK pathway, as reported in an earlier study. I hypothesize the involvement of CaMKII in this mechanism. CaMKII is one of the most abundant kinases in the brain and plays a role in learning and memory via interaction with NMDAR. Using CaMKII inhibitors and mutants of the NMDAR subunit GluN2B, the findings in this dissertation provide evidence for the involvement of CaMKII, specifically, the interaction between CaMKIIa and GluN2B, as a requirement for the L-Lactate mediated potentiation of NMDAR signal. In addition, to gain insight into the evolution of lactate from a metabolite to a signaling molecule, this study explores the evolution of glutamate as a signaling molecule in multicellular organisms so it may serve as a model for evolution of metabolites like lactate into signaling molecules. For this purpose, the model organism Hydra was used, since it belongs to phylum Cnidaria, evolutionarily one of the first phyla to have a nervous system. In order to explore whether glutamate receptors, particularly, NMDAR are functionally expressed in Hydra and are localized in neurons, a line of transgenic Hydra expressing a calcium indicator (GCaMP6s) in neurons was generated. With the transgenic Hydra line, I attempted to measure the in vivo response of neurons in Hydra to glutamate. This study highlights several ground work experiments with an extensive discussion of implications and challenges and an outlook for future investigations.

No description available.

No description available.

Les objectifs de ce travail expérimental étaient : 1. Évaluer la place de la lactatémie capillaire comme dispositif de monitorage de l’ischémie et de la reperfusion tissulaire. 2. Comparer le suivi local du taux de lactate, au niveau du compartiment ischémié, par rapport au taux systémique du lactate lors des l’ischémie de membre, l’ischémie intestinale ainsi que durant le choc hémorragique. La mesure capillaire du taux de lactate pourrait permettre: 1. d’affirmer l’existence d’une ischémie tissulaire régionale. Le taux systémique du lactate ne permet ce diagnostic, 2. de confirmer l’efficacité d’une reperfusion au niveau d’un membre préalablement ischémique tandis que la mesure systémique des lactates ne le permet pas. L’affirmation de l’efficacité de la reperfusion et de sa constance, par une mesure aussi simple que la lactatémie capillaire compartimentale représente une avancée majeure en comparaison avec les autres méthodes existantes. La mesure capillaire du taux de lactate systémique dans une situation d’hypoperfusion par choc hémorragique n’est pas associée à augmentation du taux de lactate intra-musculaire. / Our objectives for this experimental work were: 1. Assessment of capillary lactate for tissue ischemia and reperfusion monitoring. 2. Compare the local and systemic capillary lactate time course during compartmental ischemia insults like limb ischemia, intestinal ischemia or during hemorrhagic shock. The capillary measurement of the lactate in IR could be interesting for: 1. Assessing a limb or intestinal tissue ischemia. On the opposite, the systemic measurement could not assess this diagnosis. 2. Assessing the efficiency of a limb reperfusion. On the opposite, the systemic measurement could not assess this diagnosis. The systemic capillary lactate measurement during haemorrhagic shock related hypo perfusion could not be associated with an increase in intra muscular lactate.