Phosphate Peak Research Articles

1H and 31P-magnetic resonance spectroscopy of cerebral infarction in rats

Magnetic resonance spectroscopy (MRS) allows the noninvasive study of metabolism in vivo. In order to further understand the time course of biochemical changes during cerebral infarction, we performed the MRS study with pathological analysis. The left middle cerebral artery (MCA) was occluded in spontaneously hypertensive male rats (SHR) by the method of Tamura et al. The spectra were obtained from the infarcted hemisphere by placing the surface coils over the left side of the calvarium. 31P and 1H-MRS were performed at 3 hours, 24 hours and 7 days after MCA occlusion. Ischemic lesions caused by the left MCA occlusion extended into the parietal lobe and caudate putamen. After 3 hours of ischemia, vacuolated neurophils and shrunken neurons were observed. At 24 hours, these changes were severe. After 7 days, infiltration of monocytes and capillary hyperplasia were seen, and neurons had disappeared. At the acute stage of ischemia the phosphocreatine/inorganic phosphate (PCr/Pi) peak ratio decreased. After 7 days of ischemia, these changes became obscure. The intracellular pH (pHi) decreased after 3 hours of ischemia and recovered almost to the control level at 24 hours post ischemia. Alkalosis was apparent 7 days after ischemia. This alkalosis might be due to increased permeability of the deteriorated blood brain barrier. Although the lactate level was high 24 hours post ischemia, the pHi was almost normal. The N-acetylaspartate/creatine ratio decreased significantly from the acute stage of stroke. This decrease correlated with pathological changes. The correlation of the magnetic resonance spectra with the histological results may opens aspects for monitoring stroke therapy and a new approach to tissue characterization.

Dynamic phosphorus-31 spectroscopy after fructose load in experimental biliary liver cirrhosis

The authors investigated the usefulness of dynamic phosphorus-31 magnetic resonance (MR) spectroscopy in the assessment of hepatic function by studying the effect of a fructose load on a rat model of liver cirrhosis. In vivo P-31 MR liver spectra of eight rats with bile duct ligature and 10 control rats were obtained every 4.6 minutes before and after intraperitoneal fructose load (10 mmol per kilogram of body weight). In the basal spectra of the experimental group, the phosphomonoester peak was higher than in the control group (P = .026). After the fructose load, the phosphomonoester peak increase and the inorganic phosphate peak decrease were significantly less marked in the experimental group (P = .003). There was a linear correlation between the serum level of bilirubin and the phosphomonoester increase (r = .61, P < .001). Dynamic P-31 MR spectroscopy may be useful in the assessment of hepatic function in chronic liver disease.

Infrared and Isotopic Evidence for Diagenesis of Bone Apatite at Dos Pilas, Guatemala: Palaeodietary Implications

The use of stable carbon isotopic analysis of bone apatite to reconstruct prehistoric diets is hindered by the possibility of diagenetic alteration of carbonate during burial. We examine apatite preservation in Classic Period Maya skeletal remains from Dos Pilas, Guatemala, using Fourier transform infrared spectroscopy (FTIR). We use weight % CO 2evolved from apatite, FTIR carbonate/phosphate absorbance ratios, phosphate peak splitting crystallinity indices, fluoride peaks, and stable oxygen isotopic ratios to identify diagenetic change in apatite chemistry. Isotopically light carbon taken up from burial soil is adequately removed from most Dos Pilas bone by treatment with dilute acetic acid, but more severe alteration cannot be reversed by standard preparation methods. Infrared criteria identify recrystallized apatite in a subset of Dos Pilas burials, that is accompanied by isotopic exchange, and that no longer preserves biogenic δ 13C. These results illustrate that comparatively recent bone may be diagenetically altered and demonstrate a need for systematic evaluation of mineral integrity in all archaeological bone prior to interpreting paleodiets with apatite δ 13C.

The isotopic composition and diagenesis of human bone from Teotihuacan and Oaxaca, Mexico

We analyzed archaeological human bone from Teotihuacan and Oaxaca, dating from about 300 BC to 750 AD to distinguish ethnic groups within Teotihuacan using oxygen isotopes. Sixty-eight analyses of bone phosphate 6180 were made of 64 individuals. In addition to oxygen isotopic analysis, the bones were examined using FTIR spectra, with some additional DNAA and ICP-MS analyses. Little change occurs in the bone apatite until the amount of collagen (as combustible organics) has been reduced considerably, when the bone becomes softer and FTIR crystallinity increases. The 6180 of the phosphate (~p) appears to be unaltered even after extensive diagenesis and, probably, solution. On FTIR plots the relative area of the carbonate peak to the main phosphate peak decreases with diagenetic level. The bones absorb some metals rapidly after burial, for example uranium, which then leach out as diagenesis of the bone apatite progresses. Other metallic elements increase irregularly in concentration as alteration proceeds.

The lytic activity of the bee venom peptide melittin is strongly reduced by the presence of negatively charged phospholipids or chloroplast galactolipids in the membranes of phosphatidylcholine large unilamellar vesicles

We have investigated the dependence of the lytic activity of the bee venom peptide melittin on the lipid composition of its target membrane. The lysis of large unilamellar liposomes, measured as loss of the fluorescent dye carboxyfluorescein, in the presence of melittin was strongly reduced when the negatively charged lipids phosphatidylglycerol (PG) or phosphatidylserine (PS), or the plant chloroplast lipids monogalactosyldiacylglycerol (MGDG) or digalactosyldiacylglycerol (DGDG) were incorporated into egg phosphatidylcholine (EPC) membranes. This reduction was evident at concentrations below 10 wt% of the additional lipids. It was not due to reduced binding of melittin to the vesicles. It was also not related to a reduced insertion depth of the peptide into the bilayer, as shown by quenching of the intrinsic tryptophan fluorescence of the peptide by the aqueous quencher sodium nitrate. Fourier transform infrared spectroscopy (FTIR) revealed specific interactions of the peptide with the headgroups of the inhibitory lipids. The phosphate peak in PG was shifted by two wavenumbers after the addition of melittin. There was no shift in EPC or PS. Instead, in PS the COO − peak was strongly distorted in the presence of melittin. These data indicate ionic interactions between the basic peptide and the negative charges on the membrane surface. The galactolipids are uncharged. Here the evidence points to hydrogen bonding between melittin and OH-groups of the sugar headgroups. Liposomes containing DGDG were the only case where we found evidence for changes in fatty acyl chain motion due to the presence of melittin, from the CH 2-scissoring peaks.

Effects of active and passive recoveries on splitting of the inorganic phosphate peak determined by 31P-nuclear magnetic resonance spectroscopy.

Six male long-distance runners performed knee flexion exercises in a 2.1 T superconducting magnet. 31P MRS was used to investigate the splitting pattern of the inorganic phosphate (Pi) peak during active and passive recovery. During exercise splitting of the Pi peak into two was observed (high and low pH) and after exercise the manner in which the Pi peak disappeared was different in passive and active recoveries. During passive recovery, in which exercise was not performed at all, the high-pH Pi peak disappeared more rapidly than the low-pH Pi peak. The low-pH Pi peak remained at a similar acidified chemical shift as during exercise, and then gradually disappeared during passive recovery. Conversely, during active recovery in which unloaded exercise was followed, the high-pH Pi peak was reduced, but remained, whereas the low-pH Pi peak returned very quickly to the pre-exercise level and then disappeared. Teh recovery rate of the low pH during active recovery (0.095 +/- 0.019 pH units/min) was significantly faster than that during passive recovery (0.014 +/- 0.019 pH units/min) (p < 0.01). The slow disappearance of the low pH Pi peak during passive recovery can be explained by the halting of glycogenolysis and an insufficient oxygen supply to resting glycolytic fibers, whereas the quick disappearance observed with active recovery would have been due to elevated sufficient oxygen supply and efficient removal of lactate as a result of the maintained blood flow. Oxy-myoglobin and hemoglobin was also measured with near infrared spectroscopy.

Quick ion chromatographic determination of sulfate alone in soil extracts and natural waters

Abstract In a typical ion chromatographic (IC) method for seven common anions, the sulfate (SO4 2‐) ion elutes last with a total run time of 8–10 minutes. Although the IC method is accurate and precise, it is deemed slow when samples are to be analyzed for SO4 2‐ alone. We have developed a quick IC method for the determination of SO4 2‐ alone with a run time of 3 min (20 samples/hour). The experiments were performed on Lachat's chemically‐suppressed IC. An anion exchange column (4.6 mm ID x 50 mm long) was specifically designed that can resolve the SO4 2‐ peak from chloride (C1‐), nitrate (NO3 ‐). and phosphate (HPO4 2‐) peaks. The eluent used was 7.0 mM NaHCO3 + 0.5 mM Na2CO3 at the rate of 1.8 mL/min. Using a 100 μL sample loop, the method has a dynamic range of 0.1 to 10 mg SO4 2‐/L with a detection limit of 29.5 μg SO4 2‐/L. The IC method was applied to the determination of SO4 2‐ in drinking water and soil extracts. Sulfate was extracted from soil by equilibrating a 4‐g soil sample for 30 min with 20...

Effects of Active and Passive Recoveries on Splitting of the Inorganic Phosphate Peak Determined by 31P-Nuclear Magnetic Resonance Spectroscopy

Effects of Active and Passive Recoveries on Splitting of the Inorganic Phosphate Peak Determined by 31P-Nuclear Magnetic Resonance Spectroscopy

Optimization of the response of phosphate separated by capillary zone electrophoresis

The response of phosphate, which is highly variable in capillary zone electrophoresis (CZE) using silica capillaries, was optimized by monitoring the absorption of phosphate onto the capillary surface. A capillary conditioning regime is described which facilitates maximum response for phosphate without significantly extending the total analysis time. The described regime also allowed excellent precision (⩽0.36%sr, n= 10) to be achieved with regard to absolute migration time for phosphate as well as chloride, bromide, sulfate and hydrogencarbonate. Using this regime, the precisions for the phosphate peak area and height were 9 and 5.5%sr, respectively (n= 10).

Metabolism of 3‐ and 4‐phosphorylated phosphatidylinositols in stomatal guard cells of Commelina communis L.

Within the plant kingdom the stomatal guard cell is presented as a model system of inositol 1,4,5‐trisphosphate [Ins(1,4,5)P3]‐mediated signal transduction. Despite this it is only recently that the phosphoinositide components of animal signal transduction pathways have been identified in stomatal guard cells. Interestingly, stomatal guard cells contain both 3‐ and 4‐phosphorylated phosphatidylinositols though their relative contributions to signalling remain undefined. An appraisal of the routes of synthesis and rates of turnover of these phosphatidylinositols would appear timely as the in vivo biosynthesis of these components is a much neglected facet of the phosphoinositide‐mediated signalling paradigm as purported to apply to plants.A non‐equilibrium [32P]Pi labelling strategy and enzymic and chemical dissection of labelled phosphatidylinositols have been used to address not only the route of synthesis but also the rates of turnover of phosphatidylinositols in stomatal guard cells of Commelina communis L.The specific activity of the ATP pool of isolated guard cells was found to increase over a 4 h period when labelled from [32P]Pi. In separate experiments, isolated guard cells were labelled over a 40–240 min period, their lipids extracted, deacylated and resolved by HPLC. Glycerophosphoinositol phosphate (GroPInsP) and glycerophosphoinositol bisphosphate (GroPInsP2) peaks were desalted and enzymically cleaved with alkaline phosphatase and human erythrocyte ghosts, respectively. The monoester phosphate in phosphatidylinositol 4‐monophosphate (PtdIns4P) accounted for 90–97% of the [32P]Pi label while the 4‐ and 5‐monoester phosphates of phosphatidylinositol 4,5‐bisphosphate [PtdIns(4,5)P2] accounted for typically 39% and 61% respectively. Therefore, the evidence is consistent with synthesis of PtdIns(4,5)P2 by successive 4‐ and 5‐phosphorylation of phosphatidylinositol (PtdIns). This study therefore represents the first report of the pathway of the synthesis of 4‐ and 5‐phosphorylated phosphatidylinositols in a single defined hormone‐responsive plant cell type.The monoester phosphate in phosphatidylinositol 3‐monophosphate (PtdIns3P) accounted for 83–95% of the 32P label. It was not possible, however, to determine the route of synthesis of phosphatidylinositol 3,4‐bisphosphate [PtdIns(3,4)P2] owing to the rapid attainment of equilibrium between the 3‐ and 4‐monoester phosphates of PtdIns(3,4)P2, each containing approximately 50% of the label at just 40 min of labelling. Turnover of PtdIns3P was quicker than that of PtdIns4P. Similarly, turnover of PtdIns(3,4)P2 was quicker than that of PtdIns(4,5)P2, and in mass terms PtdIns(3,4)P2 appeared to predominate over PtdIns(4,5)P2. By analogy with animal systems, in which signalling molecules such as PtdIns(4,5)P2 show considerable basal turnover, the evidence presented is consistent with signalling roles for PtdIns3P and PtdIns(3,4)P2 in addition to those previously indicated for PtdIns(4,5)P2 in stomatal guard cells.

31P NMR study of acute toxic effects of cadmium chloride on rat liver.

In this study, acute effects of cadmium ions (Cd2+) on energy metabolism in rat livers were analyzed in vivo after intravenous administration using 31P NMR. Both inorganic phosphate (Pi) and nucleotide triphosphate (NTP) peaks of in vivo Cd-treated livers gradually decreased over a 6-h period. In the extract, NTP peaks in Cd-treated livers were lower, as in the in vivo experiments, but the Pi peak was significantly higher than the control. The apparent decrease in Pi in in vivo liver treated with Cd could be caused by the reduced visibility of Pi because of its uptake into mitochondria from cytoplasm, accompanied by the uncoupling of oxidative phosphorylation by Cd2+. These results indicated that total Pi in the hepatocytes increases after Cd administration. However, only 10% of Pi was visible in Cd-treated livers in vivo, whereas 34% of Pi was visible in controls. Significant increases in phosphocholine and glycerophosphocholine were also observed in extracts of Cd-treated livers.

Formation and characterization of anodic titanium oxide films containing Ca and P.

Commercially pure titanium was anodized in an electrolytic solution that was dissolved calcium and phosphorus compounds in water, and an AOFCP (anodic titanium oxide film containing Ca and P) was formed. It was found that sodium beta-glycerophosphate (beta-GP) and calcium acetate (CA) were suitable for the electrolytes to form the AOFCP having an equivalent Ca/P ratio to hydroxyapatite (HA). The AOFCP was characterized by scanning electron microscopy (SEM), an energy-dispersive X-ray microanalysis (EDX), and X-ray diffraction (XRD). Numerous micropores and microprojections were observed on the AOFCP by SEM. The composition of the AOFCP, which was measured by EDX, changed according to beta-GP and CA concentration, and the electrolytic voltage. Ca and P in the AOFCP seem to be incorporated into the TiO2 matrix from CA and beta-GP in the electrolyte during the anodic oxidation. Despite the existence of Ca and P in the AOFCP, no calcium phosphate peak was detected by XRD, and the AOFCP consisted of anatase and only a little rutile. The AOFCP, whose contents of Ca and P were low, had a high adhesive strength after soaking in a simulated body fluid for 300 days. When the AOFCP having an equivalent Ca/P ratio to HA was hydrothermally heated at 300 degrees C, HA crystals were precipitated on the AOFCP and completely covered the surface.

Exercise-induced splitting of the inorganic phosphate peak: investigation by time-resolved 31P-nuclear magnetic resonance spectroscopy.

To investigate the splitting of the inorganic phosphate (Pi) peak during exercise and recovery, a time-resolved 31phosphorus nuclear magnetic resonance spectroscopy (31P-MRS) technique was used. Seven healthy young sedentary male subjects performed knee flexion exercise in the prone position inside a 2.1-T magnet, with the surface coil for 31P-MRS being placed on the biceps femoris muscle. After a 1-min warm-up without loading, the exercise intensity was increased by 0.41 W at 15-s intervals until exhaustion, followed by a 5-min recovery period. The 31P-MRS were recorded every 5 s during the rest-exercise-recovery sequence. Computer-aided contour analysis and pixel imaging of the Pi and phosphocreatine peaks were performed. Five of the seven subjects showed two distinct Pi peaks during exercise, suggesting two different pH distributions in exercising muscle (high pH and low pH region). In these five subjects, the high-pH increased rapidly just after the onset of exercise, while the low-pH peak increased gradually approximately 60 s after the onset of exercise. During recovery, the disappearance of the high-pH peak was more rapid than that of the low-pH peak. These findings suggest that our method 31P-MRS provides a simple approach for studying the kinetics of the Pi peak and intramuscular pH during exercise and recovery.

NMR studies of 1H resonances in the 10-18-ppm range for aspartate aminotransferase from Escherichia coli.

We have recorded 500-MHz 1H NMR spectra in the 10-18-ppm range for aspartate aminotransferase from Escherichia coli and for three specific mutant forms. Histidine 143 has been replaced by either alanine or asparagine. In the third mutant, tryptophan 140 has been replaced by phenylalanine. The NMR spectrum of the native enzyme is very similar to that of porcine cytosolic aspartate aminotransferase in the most downfield region. However, the resonances of the proton on the ring nitrogen of the pyridoxal 5'-phosphate (peak A) and on the His-143 imidazole ring (peak B) of the E. coli enzyme are broader and more readily lost at low pH or higher temperatures than those of the porcine enzyme. The possible role of tautomerism in promoting such broadening is discussed. In the histidine mutant proteins, peak A of the pyridoxal 5'-phosphate form is too broad to see under most conditions but is clearly present in the pyridoxamine phosphate form. Peak B is missing in the 2 histidine mutants. Observation of nuclear Overhauser effects further confirms the identity of B as the resonance of HN epsilon 2 of His-143 and that of peak D at approximately 11.8 ppm as HN epsilon 2 of His-189. The mutant spectra also provide insight into electronic interactions between groups in and near the active site which confirm and supplement conclusions drawn from spectra of porcine cAspAT. While no clear loss of a peak was observed for the Trp-140 mutant in its free form, the spectrum of the succinate complex lacked a strong band at 11.26 ppm. This may represent the Trp-140 indole NH proton which has been shifted downfield by binding to a succinate carboxylate group. While our results confirm the basic similarity of cytosolic aspartate aminotransferase and E. coli aspartate aminotransferase 1H NMR spectra, they also point out differences that may be useful in identifying resonances. A large number of mutant proteins have been prepared for the E. coli enzyme. The present results provide essential information for future study of these mutants and for study of NMR spectra of isotopically labeled enzyme.

Modification of metabolism of transplantable and spontaneous murine tumors by the nitric oxide synthase inhibitor, nitro-L-arginine

Purpose : To determine the effects of the nitric oxide synthase inhibitor, nitro-L-arginine on energy metabolism in transplantable and spontaneous murine tumors. Methods and Materials : The responses of the transplantable murine tumor SCCVII/Ha and a range of spontaneously arising murine mammary adenocarcinomas to 10 mg/kg IV nitro-L-arginine were examined using in vivo 31P magnetic resonance spectroscopy (MRS). The influence of Hypnorm/Hypnovel anesthesia on the response to nitro-L-arginine was also determined in the SCCVII/Ha tumors. Data were expressed as changes in the inorganic phosphate peak area relative to the sum of all peak areas from the 31P MR spectrum, or Pi/total. Results : Nitro-L-arginine at 10 mg/kg IV increased Pi/total 2–3-fold in the SCCVII/Ha tumors for at least 2 h after administration, in both anesthetized and nonanesthetized mice, consistent with increased tumor hypoxia. Similar increases in Pi/total were observed after 10 mg/kg IV nitro-L-arginine in 13 spontaneous murine tumors from three different mouse strains, where anesthetic was used. Conclusion : The results indicate that tumor metabolism may be modified by an inhibitor of nitric oxide synthesis, that this modification occurs in both transplantable and spontaneous murine tumors and is not affected by anesthetic.

High performance ion chromatography measurement of sulfate in 20 mM phosphate extracts of soil

Abstract High Performance Ion Chromatography (HPIC) methods for measuring sulfate in 20 mM phosphate extracts of soil need to cope with low sulfate (down to 0.1 ppm S) in up to 5000 times the molar concentration of phosphate and potassium or calcium, a diversity of solutes including organic compounds, and colloidal particles. Anions were detected by electrical conductivity rather than indirect photometry, because interference from the high phosphate concentration on sulfate measurements was much less, particularly under acid conditions. Orthophosphate has a much lower limiting equivalent conductivity than sulfate, and H2PO4 ‐ has only half the conductivity of HPO4 2‐. Also, H2PO4 ‐ is retained less, and in acid gives a wide peak separation from sulfate. Under the acid conditions proposed the phosphate peak is negative, and elutes just after the solvent front, thus eliminating interference on sulfate. By making the acid pH of the eluent that of the extractant, pH 4, baseline changes were also minimized. El...

Phosphorous and Proton Spectroscopy in Relation to near Incarceration and Incarceration of the Human Brain

We report 3 cases of 31P and 1H MR spectroscopy (MRS) performed at different stages on patients with clinical signs of near or fulminant incarceration of the brain. The measurements were made on a whole body, 1.5 T scanner. 1H-MRS was obtained with the STEAM sequence and 31P-spectra were obtained using the chemical shift imaging technique. Medical treatment including controlled ventilation and sedation of the patients was carried out during the examination. The first patient was evaluated on days 6 and 10 after evacuation of an acute subdural haematoma. An intracranial pressure of 35 mm Hg was registered during the first examination. The 2nd patient had suffered a spontaneous intracerebral haemorrhage and showed clinical signs of imminent incarceration during the examination. The 3rd patient showed clinical signs of incarceration just prior to the examination. In the 1st patient 1H-MRS showed a 3-fold increase in the concentration of choline-containing compounds and a small decrease in N-acetyl aspartate from the 1st to the 2nd examination, which we interpret as a loss of neurones. In case 2 only small changes in metabolism could be detected, indicating that, despite signs of imminent clinical incarceration, the energy supply to the brain was substantial. 1H-MRS of the 3rd patient showed massive lactate concentration, and 31P-MRS revealed the total absence of high-energy phosphorous compounds leaving only one single peak of inorganic phosphate, indicating irreversible brain death.

Regulation of intracellular pH in guinea pig cerebral cortex ex vivo studied by 31P and 1H nuclear magnetic resonance spectroscopy: role of extracellular bicarbonate and chloride.

The role of transmembrane processes that are dependent on external anions in the regulation of cerebral intracellular pH (pHi), high-energy metabolites, and lactate was investigated using 31P and 1H NMR spectroscopy in an ex vivo brain slice preparation. During oxygenated superfusion, removal of external HCO3-/CO2 in the presence of Na+ led to a sustained split of the inorganic phosphate (Pi) peak so that the pHi indicated by one part of the peak was 0.38 pH units more alkaline and by the other part 0.10 pH units more acidic at 5 min than in the presence of HCO3-. The pH in the compartment with a higher pHi value returned to 7.29 +/- 0.04 by 10.5 min of superfusion in a HCO3(-)-free medium, whereas the pHi in an acidic compartment was reduced to 7.02. In the presence of 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid or the absence of external Cl-, removal of HCO3- caused alkalinization without split of the Pi peak. Both treatments reduced the rate of pHi normalization following alkalinization. Simultaneous omission of external HCO3- and Na+ did not inhibit alkalinization of the pHi following CO2 exit. All these data show that the acid loading mechanism at neutral pHi is mediated by an Na(+)-independent anion transport. During severe hypoxia, pHi dropped from 7.29 +/- 0.05 to 6.13 +/- 0.16 and from 7.33 +/- 0.03 to 6.67 +/- 0.05 in the absence and presence of HCO3-, respectively, in Na(+)-containing medium. Lactate accumulated to 18.7 +/- 2.8 and 19.6 +/- 1.5 mmol/kg under the respective conditions. In the HCO3(-)-free medium supplemented with 1 mM amiloride, the pHi fell only to 6.94 +/- 0.08 despite the lactate concentration of 18.9 +/- 2.4 mmol/kg.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphorous and proton spectroscopy in relation to near incarceration and incarceration of the human brain

We report 3 cases of 31P and 1H MR spectroscopy (MRS) performed at different stages on patients with clinical signs of near or fulminant incarceration of the brain. The measurements were made on a whole body, 1.5 T scanner. 1H-MRS was obtained with the STEAM sequence and 31P-spectra were obtained using the chemical shift imaging technique. Medical treatment including controlled ventilation and sedation of the patients was carried out during the examination. The first patient was evaluated on days 6 and 10 after evacuation of an acute subdural haematoma. An intracranial pressure of 35 mm Hg was registered during the first examination. The 2nd patient had suffered a spontaneous intracerebral haemorrhage and showed clinical signs of imminent incarceration during the examination. The 3rd patient showed clinical signs of incarceration just prior to the examination. In the 1st patient 1H-MRS showed a 3-fold increase in the concentration of choline-containing compounds and a small decrease in N-acetyl aspartate from the 1st to the 2nd examination, which we interpret as a loss of neurones. In case 2 only small changes in metabolism could be detected, indicating that, despite signs of imminent clinical incarceration, the energy supply to the brain was substantial. 1H-MRS of the 3rd patient showed massive lactate concentration, and 31P-MRS revealed the total absence of high-energy phosphorous compounds leaving only one single peak of inorganic phosphate, indicating irreversible brain death.

Dynamic of α-1-Adrenoceptor Mediated Degradation of Membrane Phospholipids in Cultured Rat Cardiomyocytes

In many cell types, agonists can stimulate both phosphoinositide (PtdIns) and phosphatidylcholine (PC) hydrolysis by activating specific phospholipases. Using cultures of neonatal rat cardiomyocytes we have verified the existence of an α 1-adrenoceptor mediated hydrolysis of PtdIns and PC. PtdIns breakdown, evaluated as inositol phosphate production, occurred in the early phase of cell stimulation, while PC hydrolysis, evaluated as choline metabolite production, was evidenced at longer stimulation times. The appearance of a delayed peak of choline phosphate and the invariance of free choline in the intracellular water phase strongly suggest the involvement of a specific PC-phospholipase C, generating choline phosphate and diacylglycerol, the activator of protein kinase C. Since it is plausible that various metabolites of signal-induced degradation of membrane phospholipids may take part in long term physiological responses, PC breakdown could be involved in cellular mechanisms that require prolonged protein kinase C activation.