Detection lactate

On the other hand, organic acids are more difficult to measure in the labs. Usually, these are measured by GC or HPLC. However, CE offers speed, precision, and specificity over other methods. Organic acids are important in inborn errors of metabolism, in infection, and different metabolic disorders. Many of these compounds have been measured by CE directly, or by indirect UV absorbency after addition of a UV absorbing compound such as benzoate, naphthalene sulfonate, imidazole, or benzylamine. For example, oxalate and citrate, which are important in stone formation, have been measured after urine dilution by both direct and indirect detections. Lactate, pyruvate, ascorbate, and oxalate were measured by CE in the CSF of patients in 10 min. Methylmalonic acid, which is a sensitive measure of vitamin Bi2 deficiency preceding any clinical symptoms or changes in the serum, has been determined in m-ine by CE after sample extraction and concentration. 

Simple FIA for lactate sensing are based on incorporation of LOD- or LDH-modified electrodes into flow injection systems. FIA based on enzyme reactors that contain LOD or LDH have also been developed for electrochemical or optical lactate sensing. Other enzyme electrodes or reactors can also be incorporated into lactate FIA systems, leading to the development of FIA systems that simultaneously detect lactate and other target molecules (Renneberg et ah, 1991). In addition, miniaturized flow cell that can be incorporated into FIA system (Nakamura et ah, 2001) and enzyme thermistor-based FIA has been developed (Chen et ah, 2011). 

Enzyme thermistors can be used to detect enzyme substrates by measuring the heat produced from exothermic enzymatic reactions. Chen et al. (2011) incorporated an enzyme thermistor into a flow system for lactate sensing. In their system, the enzyme thermistor comprised an enzyme column containing LOD and catalase, and a reference column was incorporated into the flow system to correct for nonspecific signals. This FIA was used to detect lactate in milk samples without sample pretreatment, with a linear range of 25nM-5.0mM. 

Thus, FIA systems for lactate sensing have predominantly been developed using electrochemical and optical detectors. Incorporation of other enzyme electrodes and reactors has led to the development of multisensing FIA systems. Finally, FIA systems based on enzyme thermistors have been developed for lactate sensing using LOD. Together, these FIA systems have been used to detect lactate in food samples and human blood samples. 

A major advantage of FIA systems is the ease of combination with other flow systems. In particular, FIA systems comprising sample dilution flow systems and lactate-sensing flow systems have been developed. Moreover, miniaturized flow cells such as uTAS have been developed for lactate sensing. Future incorporation of suitable flow systems into FIA will enable the development of miniaturized FIA systems that can automatically detect lactate in multiple samples without pretreatment. 

In addition to the previously described dehydrogenase-based CNT electrodes, electrochemical biosensors that employ other types of enzyme-modified CNTs have also been reported. Kowalewska and Kulesza applied CNTs with adsorbed redox mediator tetrathiafulvalene (TTF) for electrochemical detection of glucose." TTF-modified CNTs were found to facilitate electron transfer between GOx and the electrode surface for glucose detection. Jia et al. reported a similar strategy for the detection of lactate using MWCNTs modified with TTF and lactate oxidase. Since TTF does not cause skin irritation and the CNT/TTF platform also enables low-potential sensing of lactate, CNT/ TTF/lactate oxidase-based electrochemical biosensors conld be used to detect lactate in perspiration directly on human skin. This was accomplished by preparing temporary tattoos from CNT/ TTF/lactate oxidase-conductive carbon ink that was transferred onto a human subject s skin. ... 

Milk consists of 85—89% water and 11—15% total soflds (Table 1) the latter comprises soflds-not-fat (SNF) and fat. Milk having a higher fat content also has higher SNF, with an increase of 0.4% SNF for each 1% fat increase. The principal components of SNF are protein, lactose, and minerals (ash). The fat content and other constituents of the milk vary with the animal species, and the composition of milk varies with feed, stage of lactation, health of the animal, location of withdrawal from the udder, and seasonal and environmental conditions. The nonfat soflds, fat soflds, and moisture relationships are well estabhshed and can be used as a basis for detecting adulteration with water (qv). Physical properties of milk are given in Table 2. 

Multienzyme electrodes can increase sensitivity from micromolar to nanomolar detection levels (53,57). In this case the substrate is converted to a detectable product by one enzyme, then that product is recycled into the initial substrate by another enzyme resulting in an amplification of the response signal. For example, using lactate oxidase and lactate dehydrogenase immobilized in poly(vinyl chloride), an amplification of 250 was obtained for the detection oflactate (61). 

The results of metabolism studies with laboratory animals and livestock indicate that endosulfan does not bioconcentrate in fatty tissues and milk. Lactating sheep administered radiolabeled endosulfan produced milk containing less than 2% of the label. Endosulfan sulfate was the major metabolite in milk (Gorbach et al. 1968). A half-life of about 4 days was reported for endosulfan metabolites in milk from survivors of a dairy herd accidentally exposed to acutely toxic concentrations of endosulfan endosulfan sulfate accounted for the bulk of the residues detected in the milk (Braun and Lobb 1976). No endosulfan residues were detected in the fatty tissue of beef cattle grazed on endosulfan-treated pastures for 31-36 days (detection limits of 10 ppm for endosulfan, 40 ppm for endosulfan diol) the animals began grazing 7 days after treatment of the pastures. Some residues were detected in the fatty tissue of one animal administered 1.1 mg/kg/day of endosulfan in the diet for 60 days. No endosulfan residues were... 

Isozymes of Lactate Dehydrogenase Are Used to Detect Myocardial Infarctions... 

Studies of release of noradrenaline from sympathetic neurons provided the first convincing evidence that impulse (Ca +)-dependent release of any transmitter depended on vesicular exocytosis. Landmark studies carried out in the 1960s, using the perfused cat spleen preparation, showed that stimulation of the splenic nerve not only led to the detection of noradrenaline in the effluent perfusate but the vesicular enzyme, DpH, was also present. As mentioned above, this enzyme is found only within the noradrenaline storage vesicles and so its appearance along with noradrenaline indicated that both these factors were released from the vesicles. By contrast, there was no sign in the perfusate of any lactate dehydrogenase, an enzyme that is found only in the cell cytosol. The processes by which neuronal excitation increases transmitter release were described in Chapter 4. 

In addition to enzyme activity, the concentration of an nonelectroactive substrate can be determined electrochemically by this technique. By keeping the substrate (analyte) the limiting reagent, the amount of product produced is directly related to the initial concentration of substrate. Either kinetic or equilibrium measurements can be used. Typically an enzyme which produces NADH is used because NADH is readily detected electrochemically. Lactate has been detected using lactate dehydrogenase, and ethanol and methanol detected using alcohol dehydrogenase... 

Grootveld et al. (1994) employed this technique to investigate radiolytic, damage to biomolecules present in human body fluids. 7-Radiolysis of healthy or rheumatoid human serum (5.00 kGy) in the presence of atmospheric O2 gave rise to reproducible elevations in the concentration of NMR-detectable acetate, which are predominantly ascribable to the prior oxidation of lactate to pyruvate by OH radical followed by oxidative decarboxylation of pyruvate by radiolytically generated H2O2 and/or further OH radicals (Equations 1.7 and 1.8). 

Figure 9 A synthetic mixture of water-soluble carboxylic acids separated by anion-exchange chromatography. Column 0.3 cm x 300 cm Diaoion CA 08, 16-20 p (Mitsubishi Kasei Kogyo). Eluant 200 mM HC1. Detection reaction with Fe3-benzohy-droxamic acid-dicyclohexy carbodiimide-hydroxylamine perchlorate-triethyl amine with absorbance at 536 nm. Analytes (1) aspartate, (2) gluconate, (3) glucuronate, (4) pyroglutamate, (5) lactate, (6) acetate, (7) tartrate, (8) malate, (9) citrate, (10) succinate, (11) isocitrate, (12) w-butyrate, (13) a-ketoglutarate. (Reprinted with permission from Kasai, Y., Tanimura, T., and Tamura, Z., Anal. Chem., 49, 655, 1977. 1977 Analytical Chemistry).

Plasma levels of diisopropyl methylphosphonate were measured in a single lactating Jersey cow after the sixth day of diisopropyl methylphosphonate oral administration (10 mg/kg/day) by gelatin capsule (Ivie 1980). For the first 5 days the cow was given unlabeled compound and fed hay ad libitum. The diisopropyl methylphosphonate administered on the 6th day was labeled with carbon 14. Based on measurements of label in the plasma, absorption in the cow paralleled that in rats and dogs, with the highest concentration detected in the plasma at 2 hours after administration. 

The study of diisopropyl methylphosphonate distribution in a lactating Jersey cow was the only study that used multiple doses of diisopropyl methylphosphonate (Ivie 1980). In this single cow, radioactivity was detected in the blood 2 hours after dosing with [14C]-radiolabeled compound but not in the tissues. The animal had received diisopropyl methylphosphonate in one gelatin capsule for 5 days before the radiolabeled dose was administered. If tissue uptake in the cow was similar to that in dogs, measurements made 2 hours after dosing may not have provided an opportunity to measure tissue uptake of label. After 24 hours, 0.1% of the administered label was found in the cow s milk (Ivie 1980). 

M6. Maekawa, M., Sudo, K., Kitajima, M., Matsuura, Y Li, S. S.-L., and Kanno, T., Detection and characterization of new genetic mutations in individuals heterozygous for lactate dehydroge-nase-B (H) deficiency using DNA conformation polymorphism analysis and silver staining. Hum. Genet. 91, 163-168 (1993). 

Ichihara, H., Fukushima, T., Imai, K. (1999).. Enantiomeric determination of d- and L-lactate in rat serum using high-performance liquid chromatography with a cellulose-type chiral stationary phase and fluorescence detection. Anal. Biochem. 269, 379-385. 

They observed abrupt changes in the slope of Arrhenius plots for reactions catalyzed by NADH oxidase and p-lactate oxidase that correlate well with phase transitions detected by the ESR spectra of the nitroxide spin labels bound covalently to the enzymes (Table 5.4). 

With the specific suitable oxidases, lactate, choline and glucose could be assayed. Concentration measurements of these metabolites could be performed over at least two decades wit a detection limit of 10 pM for lactate and choline and 20 pM for glucose. 

Marquette C.A., Degiuli A., Blum L.J., Electrochemiluminescent biosensors array for the concomitant detection of choline, glucose, glutamate, lactate, lysine and urate, Biosens. Bioelectron. 2003 19 433-439. 

Hikima S., Kakizaki T., Hasebel K., Enzyme sensor for L-lactate using differential pulse amperometric detection, Fresen. J. Anal. Chem. 1995 351(2-3) 237-240. 

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