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31P nuclear magnetic resonance studies of Ehrlich ascites tumor cells.

High-resolution 31P nuclear magnetic resonance spectra at 145.7 MHz are reported for intact Ehrlich ascites tumor cells and their perchloric acid extracts. In the extracts it was possible to assign resonances to fructose 1,6-bisphosphates, dihydroxyacetone phosphate, ATP, ADP, AMP, Pi, NAD+, phosphorylcholine, glycero-3-phosphorylcholine, glycero-3-phosphorylethanolamine, and glyceraldehyde 3-phosphate from their chemical shifts, pH behavior, and spin couplings. All but glyceraldehyde 3-phosphate were observed and assigned in the intact cells. It was possible to show that the hydrolysis of fructose 1,6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde 3-phosphate is in equilibrium, that the dihydroxyacetone phosphate leads to glyceraldehyde 3-phosphate reaction is not, and that in the intact cell without added oxygen or glucose the reaction 2ADP in equilibrium ATP + AMP is in equilibrium. From the known pH dependence of the Pi resonance it was possible to show that during aerobic or anerobic glycolysis the difference between intracellular and extracellular pH values was less than 0.2 pH units. Upon oxygenation the ATP concentration increased while the ADP concentration fell. Introducing deoxyglucose depleted the ATP and resulted in an AMP signal and one from deoxyglucose 6-phosphate, which is transported and phosphorylated but not catabolized.

Adenine Nucleotides↗

31P nuclear magnetic resonance studies of bioenergetics and glycolysis in anaerobic Escherichia coli cells.

31P nuclear magnetic resonance spectra of glycolyzing, anaerobic Escherichia coli cells and their perchloric acid extracts were obtained at 145.7 MHz. Time-dependent intracellular concentrations of nucleoside di- and triphosphates, Pi, and sugar phosphates were measured during glycolysis with 2-min resolution, while intracellular and extra-cellular pH values were monitored simultaneously. Upon glucose addition, anaerobic E. coli cells rapidly produce acids and develop a transmembrane pH gradient (delta pH). Glycolysis rates were calculated from the changes in the external pH. It was found that glycolysis rates are strongly dependent on internal pH, sharply decreasing when the pH drops below approximately 7.2. The ATPase inhibitor, dicyclohexylcarbodiimide (DCCD), prevented NTP hydrolysis and inhibited delta pH formation. The uncoupler, carbonyl cyanide p-triflouromethoxyphenyl hydrazone (FCCP), drastically reduced both the delta pH and the NTP level. When the cells were previously treated with DCCD, FCCP collapsed the delta pH while the NTP levels remained high. It is concluded that ATP produced by glycolysis is hydrolyzed by the membrane ATPase to generate a delta pH and that FCCP stimulates ATP hydrolysis by ATPase and collapses the proton gradient.

Anaerobiosis↗

13C NMR study of transamination during acetate utilization by Saccharomyces cerevisiae.

13C NMR was used to follow the metabolism of [2- 13C]acetate and [1- 13C]acetate in aerobic suspensions of Saccharomyces cerevisiae. In the experiment with [2- 13C]acetate, the 13C label appeared first in glutamate C4 and subsequently in glutamate C2 and C3. After exhaustion of the acetate, the glutamate signals diminished and the aspartate C2 and C3 peaks increased. During a subsequent chase experiment with unlabeled acetate, the aspartate peaks decreased and the glutamate C2 and C3 peaks increased in intensity. These observations are interpreted in terms of an interplay between the glutamic-oxalacetic transaminase and Krebs cycle activity. This interpretation was confirmed by an experiment with the transaminase inhibitor 2-amino oxyacetate. During all of these experiments, we observed the formation of trehalose. The NMR gives a direct measurement of the label distribution and from that information it followed that the flows through the glyoxylate and the Krebs cycles are comparable. The intermediates citrate, succinate, fumarate, malate, phosphoenolpyruvate, 3-phosphoglycerate, and glucose 6-phosphate were identified in a 13C NMR spectrum of a perchloric acid extract taken during the metabolism of [2- 13C]acetate. Enrichment of the glutamate C5 position shows the existence of a futile cycle in which phosphoenolpyruvate, formed from oxaloacetate, returns to the Krebs cycle through pyruvate and acetyl CoA

Acetates↗

Immunological evidence for the in vivo occurrence of (2'-5')adenylyladenosine oligonucleotides in eukaryotes and prokaryotes.

A monoclonal antibody highly specific for (2'-5')adenylyladenosine oligonucleotides was used together with a 125I-labeled analog of this compound to detect and quantify phosphorylated and nonphosphorylated (2'-5')adenylyladenosine oligonucleotides in a variety of tissues and cells. These oligonucleotides were first assayed as a whole in perchloric acid extracts and then further individually characterized by HPLC analysis. Their sensitivity to alkaline phosphatase, snake venom phosphodiesterase, and T2 RNase was systematically checked. Nonphosphorylated (2'-5')adenylyladenosine oligonucleotides were found in mammalian tissues as well as in yeast and bacteria. In normal mouse brain, lung, heart, pancreas, spleen, kidney, and liver their concentrations ranged from 10 to 200 pmol/g wet weight, depending on tissue and strain. The oligonucleotides were mainly dimers, trimers, tetramers, and pentamers. In addition, phosphorylated (2'-5')adenylyladenosine oligonucleotides were shown in liver and kidney extracts.

Adenine Nucleotides↗

Combining solid-state and solution-state 31P NMR to study in vivo phosphorus metabolism.

Otherwise unavailable information concerning the distribution of phosphorylated compounds in biological systems is obtained by a combined solid-state/solution-state NMR approach, illustrated here for oocytes from Rana pipiens. General methodology is developed, and further extensions are proposed. The following conclusions pertain to the specific system under examination. (i) Nucleoside phosphates can be observed by magic-angle sample spinning of the lyophilized material. (ii) The solid-state NMR technique of dipolar decoupling provides no additional resolution of the phospholipid and phosphoprotein components of the yolk. However, cellular death produces sufficient pH changes to cause the phospholipid and protein phosphate peaks to become resolvable. The concentration of nucleoside phosphates also decreases. (iii) The phospholipid and phosphoprotein components are shown by computer simulation to be present in a ratio of 40:60, respectively. (iv) The amounts of inorganic phosphate, nucleoside phosphates, and sugar phosphates are determined by solution-state NMR observation of the perchloric acid extract of the oocytes.

Animals↗

Chemical and functional correlates of postischemic renal ATP levels.

Renal energy metabolism was investigated before, during, and after ischemic insults of varying durations with in vivo 31P NMR spectroscopy. The postischemic recovery of renal ATP was found to be a biphasic process regardless of the length of the ischemia. This two-stage recovery consisted of a quick initial component immediately upon reflow followed by a slower, more gradual return toward preischemic levels. To characterize the source of each phase of the recovery, kidneys were extracted with perchloric acid at the end of the different periods of ischemia (before reflow). Concentrations of adenine nucleotides and breakdown products adenosine, inosine, and hypoxanthine were determined by 1H NMR spectroscopy. Excellent correlation was found between the residual nucleotide pool and the magnitude of the initial phase of ATP recovery. Additionally, the renal ATP content after 120 min of reflow was shown to have a strong correlation with subsequent functional recovery. These experiments show that in vivo 31P NMR can provide new and dynamic information concerning the biochemical recovery from ischemia. Furthermore, this data has the potential to predict the eventual functional recovery of the organ.

Adenosine Diphosphate↗

Trypanosoma cruzi contains major pyrophosphate stores, and its growth in vitro and in vivo is blocked by pyrophosphate analogs.

High field (31)P nuclear magnetic resonance spectroscopy showed that inorganic pyrophosphate (P(2)O(7)(4-)) is more abundant than ATP in Trypanosoma cruzi, the causative agents of Chagas' disease. These results were confirmed by specific analytical assays, which showed that in epimastigotes, the concentrations of inorganic pyrophosphate and ATP were 194.7 +/- 25.9 and 37.6 +/- 5.5 nmol/mg of protein, respectively, and for the amastigote form, the corresponding concentrations were 358.0 +/- 17.0 and 36.0 +/- 1.9 nmol/mg of protein. High performance liquid chromatographic analysis of perchloric acid extracts of epimastigotes labeled for 3 h with (32)P-orthophosphate showed a significant incorporation of the precursor into inorganic pyrophosphate. Inorganic pyrophosphate was not uniformly distributed in T. cruzi but was shown by (31)P-NMR and chemical analysis to be particularly associated with acidocalcisomes, organelles shown previously to contain large amounts of phosphorus and various elements. Electron microscopy analysis of pyrophosphatase-treated permeabilized epimastigotes showed disappearance of the electron density of the acidocalcisomes. Nonmetabolizable analogs of pyrophosphate, currently used for the treatment of bone resorption disorders, selectively inhibited the proliferation of intracellular T. cruzi amastigotes and produced a profound suppression in the number of circulating trypomastigotes in mice with an acute infection of T. cruzi, offering a potentially new route to chemotherapy.

Animals↗

31P NMR spectroscopy of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania major. Evidence for high levels of condensed inorganic phosphates.

High resolution (31)P nuclear magnetic resonance spectra at 303.6 MHz (corresponding to a (1)H resonance frequency of 750 MHz) have been obtained of perchloric acid extracts of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania major, the causative agents of African sleeping sickness, Chagas' disease, and leishmaniasis. Essentially complete assignments have been made based on chemical shifts and by direct addition of authentic reference compounds. The results indicate the presence of high levels of short chain condensed polyphosphates: di-, tri-, tetra-, and pentapolyphosphate. (31)P NMR spectra of purified T. brucei, T. cruzi, and L. major acidocalcisomes, calcium and phosphorus storage organelles, indicate that polyphosphates are abundant in these organelles and have an average chain length of 3.11-3.39 phosphates. In the context of the recent discovery of several pyrophosphate-utilizing enzymes in trypanosomatids, the presence of these inorganic polyphosphates implies a critical role for these molecules in these parasites and a potential new route to chemotherapy.

Animals↗

Ex vivo analysis of lactate and glucose metabolism in the rat brain under different states of depressed activity.

Brain metabolism of glucose and lactate was analyzed by ex vivo NMR spectroscopy in rats presenting different cerebral activities induced after the administration of pentobarbital, alpha-chloralose, or morphine. The animals were infused with a solution of either [1-(13)C]glucose plus lactate or glucose plus [3-(13)C]lactate for 20 min. Brain metabolite contents and enrichments were determined from analyses of brain tissue perchloric acid extracts according to their post-mortem evolution kinetics. When amino acid enrichments were compared, both the brain metabolic activity and the contribution of blood glucose relative to that of blood lactate to brain metabolism were linked with cerebral activity. The data also indicated the production in the brain of lactate from glycolysis in a compartment other than the neurons, presumably the astrocytes, and its subsequent oxidative metabolism in neurons. Therefore, a brain electrical activity-dependent increase in the relative contribution of blood glucose to brain metabolism occurred via the increase in the metabolism of lactate generated from brain glycolysis at the expense of that of blood lactate. This result strengthens the hypothesis that brain lactate is involved in the coupling between neuronal activation and metabolism.

Alanine↗

The effect of wild blueberry (Vaccinium angustifolium) consumption on postprandial serum antioxidant status in human subjects.

The aim of the present study was to determine whether the consumption of wild blueberries (Vaccinium angustifolium), a concentrated source of non-nutritive antioxidant phytochemicals, would enhance postprandial serum antioxidant status in healthy human subjects. A single-blinded crossover study was performed in a group of eight middle-aged male subjects (38-54 years). Subjects consumed a high-fat meal and a control supplement followed 1 week later by the same high-fat meal supplemented with 100.0 g freeze-dried wild blueberry powder. Upon brachial vein catheterization, fasting and postprandial serum samples were taken sequentially and analysed for lipids and glucose and for serum antioxidant status. Serum antioxidant status was determined using the oxygen radical absorbance capacity (ORAC) assay and the total antioxidant status (TAS) assay. The wild-blueberry treatment was associated with a significant treatment effect as determined by the ORAC assay (water-soluble fraction ORAC(perchloric acid (PCA)), P=0.04). Significant increases in serum antioxidant status above the controls were observed at 1 h (ORAC(PCA) (8.5 % greater), P=0.02; TAS (4.5 % greater), P=0.05), and 4 h (ORAC(total) (15.0 % greater), P=0.009; ORAC(acetone) (16.0 % greater), P=0.007) post-consumption of the high-fat meal. In conclusion, the consumption of wild blueberries, a food source with high in vitro antioxidant properties, is associated with a diet-induced increase in ex vivo serum antioxidant status. It has been suggested that increasing the antioxidant status of serum may result in the reduced risk of many chronic degenerative diseases.

Analysis of Variance↗

Reverse-phase ion-pairing high-performance liquid chromatography of phosphocreatine, creatine and creatinine in equine muscle.

A simple, robust and reproducible analytical method for the determination of phosphocreatine (PCr), creatine (Cr) and creatinine (Cn) in equine skeletal muscle is presented. The technique used isocratic reverse-phase ion-pairing high-performance liquid chromatography. Neutralized perchloric acid extracts of equine muscle biopsies were analysed and the values obtained were compared with determinations from an established enzymic procedure. Good resolution of all three metabolites was achieved within a retention time of less than 11 min. Linearity for each metabolite within the concentration range in the samples was demonstrated. Peak purity was specifically addressed. The abolition of each creatine in a pooled extract by enzymic incubation showed no underlying peaks. It was concluded that peaks were free of co-eluents which would otherwise lead to an overestimation of PCr, Cr and Cn concentrations.

Animals↗

On the accurate measurement of serotonin in whole blood.

Levels of serotonin (5-hydroxytryptamine; 5-HT) in whole blood reflect the levels in the platelets, but there are problems with instability of 5-HT in measurement of whole blood extracts. We therefore developed and validated an assay for whole blood 5-HT using HPLC with fluorometric detection. The procedure involved collecting blood in EDTA vacutainer tubes and aliquoting it with internal standard, alpha-methyl-5-HT, before freezing. The aliquots were thawed on ice and proteins precipitated with perchloric acid containing EDTA and ascorbic acid. The 5-HT was stable in fresh whole blood for 24 h after sampling when stored at room temperature, refrigerated, or ice-cooled. Measurements of the levels of 5-HT in blood collected in heparin, citrate or EDTA were similar, but in blood collected in ACD-buffer the levels were approximately 25% lower. Cell lysis by sonication decreased the 5-HT levels, but this was compensated for by the internal standard. Determinations of 5-HT by HPLC were in good agreement with those by gas chromatography - mass spectrometry. The intra-individual variability between days was 3.6% (n=6). However, single and repeated ingestion of bananas, which are rich in 5-HT, elevated 5-HT in whole blood, indicating dietary influences on platelet 5-HT.

Adult↗

Determination of histamine in fish using an enzymic method.

The present paper describes a quick and simple enzymic method for evaluating histamine content in fish. After preparing a perchloric acid extract, it was neutralized to pH 6.8 with KOH. The action of a diamine oxidase on the histamine caused the formation of hydrogen peroxide. The addition of a second enzyme, a peroxidase, in the presence of hydrogen peroxide and a chromogen (leuco crystal violet) in reduced form (colourless) facilitated its oxidation into crystal violet (coloured). Following a two-hour incubation period, absorbance was measured at 596 nm. The correlation between histamine level and absorbance was acceptable in the concentration range from 3 to 30 mg/kg of histamine (r = 0.9946; p < 0.001). The accuracy of the method, expressed by CV, varied between 2.6% and 4.9%, and the recovery between 95.7% and 100.1%, depending on the concentration of analyte in the sample. The diamine oxidase used was very selective in relation to the histamine. Only the presence of tyramine, when histamine concentration was low (< 10 mg/kg), tended to interfere to a slight degree in the technique. Using a regression analysis, no statistically significant differences were found between the results obtained from the analysis of 18 tuna fish samples by HPLC and the enzymic method (r = 0.9867; p < 0.001).

Animals↗

Influence of heavy metals upon the retention and mobilization of polonium-210 in rats.

PURPOSE: To provide information about the tissue retention and mobilization of the alpha-emitting radionuclide, polonium-210 (210Po), in rats under combined exposure to heavy metal ions and the chelating agent, 2, 3-dimercaptopropane-1-sulfonate (DMPS). MATERIALS AND METHODS: Rats were pre-exposed intraperitoneally to either CdCl2 or Pb(CH3COO)2. 9 or 15 h later they received 210Po nitrate intravenously. The retention and excretion of 210Po via the urine and faeces of pre-exposed rats, as well as in pre-exposed rats treated with DMPS, were followed. The radioactivity due to 210Po in a broad spectrum of body tissues and excreta was measured by the liquid scintillation counting after sample digestion in a mixture of perchloric acid and hydrogen peroxide. The immunohistochemical localization of metallothioneins (MT) was studied using a mixture of murine monoclonal antibodies directed against MT I+II. RESULTS: The present study revealed different tissue distributions of polonium-210 in the rats pre-exposed to lead or cadmium ions when compared with that in 210Po only controls. Under combined exposure to Pb or Cd, the spontaneous excretion of 210Po was enhanced and could be further enhanced by treatment with DMPS. Treatment with this chelator was efficient even when its start was postponed until 24h after internal contamination of the body with 210Po. CONCLUSIONS: Polonium-210 is bound in vivo to binding sites on various biomolecules, among them erythrocytic enzymes and MT. This phenomenon explains the different affinity and overall distribution of 210Po in control body tissues. When the appropriate binding sites are occupied by lead or cadmium, enhanced natural excretion of polonium-210 occurs.

Animals↗

A 700 MHz 1H-NMR study reveals apoptosis-like behavior in human K562 erythroleukemic cells exposed to a 50 Hz sinusoidal magnetic field.

PURPOSE: To study cell damage and possible apoptosis in K562 human erythroleukemic cells exposed for 2 h to an extremely low frequency (ELF) 50 Hz sinusoidal magnetic field with a magnetic induction of either 1 or 5 mT using high resolution proton nuclear magnetic resonance (1H-NMR) spectroscopy. MATERIALS AND METHODS: One-dimensional 1H-NMR spectra were obtained on whole K562 cells and perchloric acid extracts of these cells. In addition, two-dimensional 1H-NMR spectra were also acquired. Cell damage was examined by lactate dehydrogenase release and changes in cell growth were monitored by growth curve analyses, bromodeoxyuridine incorporation and Ki67 antigen localization. Cell death (necrosis and apoptosis) were also studied by using the chromatin dye Hoechst 33258. RESULTS: The variations in numerous metabolites observed with 1H-NMR reveal apoptosis-like behavior in response of K562 cells to ELF fields. CONCLUSION: 1H-NMR can be extremely useful in studying the effects of ELF fields on cells. In particular, the variations in metabolites which suggest apoptosis-like behavior occur when the cells are not identifiable as apoptotic by more traditional techniques.

Apoptosis↗

Total selenium concentration in various waters of Turkey.

The total selenium levels of 335 water samples of Turkey were determined by a spectrofluorometric method. The samples were digested in nitric-perchloric acid mixture, potential interferences were masked with disodium EDTA-HONH2.HCl and selenium was complexed with freshly prepared 2,3-diaminonaphthalene solution and estimated spectrofluorometrically after extraction in cyclohexane. The selenium content of various waters (rain, tap, mineral, sea, lake, river, bottled drinking waters and collected drinking waters from 42 cities in Turkey) were determined. The selenium levels were compared with the literature data from different countries.

Fresh Water↗

Assessment of in vivo oxidative lipid metabolism following acute microcystin-LR-induced hepatotoxicity in rats.

Oxidative lipid metabolism as a result of acute cyanobacterial toxin-induced hepatotoxicity was monitored in male Sprague-Dawley rats using electron spin resonance (ESR) spectroscopy and image-guided proton nuclear magnetic resonance (1H-NMR) spectroscopy. ESR spectroscopy, coupled with spin trapping, was used to trap and detect lipid-derived radicals, formed in rat livers after acute in vivo exposure (LD50) to the cyanobacterial toxin, microcystin-LR (MCLR). A statistically significant increase in the levels (spectral peak integrals) of lipid radicals was detected in MCLR-treated livers (p < 0.05) (n = 8), in comparison to control livers (n = 6). In order to monitor lipid metabolism, before and for a period of 3 h, following toxin exposure, in vivo proton image-guided NMR spectroscopy was used. A statistically significant decrease in the levels of lipid methylene hydrogen resonances (spectral peak integrals) was observed from MCLR-treated livers (n = 6) 2 and 3 h post-exposure (p < 0.05), in comparison to controls (n = 6). Image-guided NMR spectroscopy was also used to detect significant decreasing levels of in vivo glutamine/glutamate, following exposure to MCLR. Biochemical assessment of perchloric extracts of liver glutamine and glutamate levels correlated with NMR spectroscopy results. Lactate levels measured as perchloric acid extracts, were also found to significantly decrease. In addition, assessment of serum enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were used to confirm hepatotoxicity (n = 20). This study strongly suggests that oxidative stress related processes are involved in in vivo microcystin-induced hepatotoxicity in mammals, and may play an integral role in MCLR-induced toxicity.

Alanine Transaminase↗

Effective purification of nonspecific cross-reacting antigens with phosphatidylinositol-specific phospholipase C.

Two molecular species of nonspecific cross-reacting antigens, NCA-90 and NCA-50 with mol. wts. of 90,000 and 50,000, respectively, were effectively extracted with phosphatidylinositol-specific phospholipase C (PI-PLC) from human lung tissues, followed by extraction with perchloric acid, immunoaffinity chromatography with anti-NCA adsorbent, and gel filtration on a TSK G3000SW column. The yields of NCA were about 2 times more than those obtained by the usual method without PI-PLC. Addition of 0.05 unit of PI-PLC to 1 g of lung tissue and incubation at 37 degrees C for 1 h with continuous shaking seem to be practically sufficient for NCA extraction. The immunochemical properties of the NCAs thus obtained were found to be identical to those of NCAs obtained by the ordinary method.

Antigens↗