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J Peeling

Publications and source records attributed to J Peeling.

65 records · Page 4Linked to original sources
PubMed1989

Forebrain ischemia studied using magnetic resonance imaging and spectroscopy.

A combination of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) has been used to follow the time course of changes resulting from forebrain ischemia in the rat. The 31P MRS demonstrates that the level of high energy metabolites decreases significantly during the 10 min ischemic period but returns to normal after 1 h of reperfusion. MRI shows no change after 1 h of reperfusion but significant changes in the striatum after 24 h and in the hippocampus after 48 h. These changes correlate well with histopathology. Diabetic rats have shown the effect of hyperglycemia in accentuation of ischemic and post ischemic pH changes. Conversely, diabetic rats maintained severely hypoglycemic with insulin showed little variation in pH during or following the ischemic insult. The results emphasize the importance of both MRS and MRI in following the temporal profile and distribution of ischemic neuronal injury.

Animals↗
PubMed1989

High-resolution 31P nuclear magnetic resonance study of Chlamydia trachomatis: induction of ATPase activity in elementary bodies.

ATPase activity of elementary bodies (EBs) of Chlamydia trachomatis was investigated by using high-resolution 31P nuclear magnetic resonance spectroscopy. ATPase activity was detected in EBs of C. trachomatis serovars A, B, and L2 after treatment with the reducing agents 2-mercaptoethanol and glutathione. ATPase activity was oligomycin sensitive and magnesium ion dependent. EBs heated at 60 degrees C for 10 min or pretreated with Triton X-100 before exposure to 2-mercaptoethanol did not exhibit ATPase activity. Monoclonal antibody to the major outer membrane protein abrogated ATPase activity of EBs, whereas monoclonal antibody to chlamydial lipopolysaccharide only marginally reduced the level of ATPase activity. These findings suggest that EBs possess intrinsic ATPase activity and that cysteine-rich outer membrane proteins of EBs are important in the regulation of ATPase activity. The major outer membrane protein may be the major route through which ATP accesses ATPase.

Adenosine Triphosphatases↗
PubMed1989

Nuclear magnetic resonance study of regional metabolism after forebrain ischemia in rats.

Proton nuclear magnetic resonance (NMR) spectroscopy of perchloric acid tissue extracts has been used to follow serial postischemic changes in the levels of metabolites in the hippocampus, cerebellum, frontal lobes, and parietal/occipital lobes in a rat model of short-duration (10 minutes) forebrain ischemia. Shortly (10 minutes, 1 hour) after the ischemic insult, the levels of the amino acids alanine and gamma-aminobutyric acid are elevated and that of glutamate is depressed in all regions except the cerebellum. The levels of these species return to control values by 24 hours postischemia. No changes are observed in the levels of aspartate or N-acetylaspartate. Greatly elevated levels of acetate 10 minutes postischemia, particularly in the hippocampus, may be due in part to metabolic degradation of fatty acids released due to membrane breakdown. Elevated levels of lactate persist for up to 7 days postischemia, suggesting that normal mitochondrial functioning is not fully restored following the ischemic insult.

Acetates↗
PubMed1988

1H and 13C nuclear magnetic resonance studies of plasma from patients with primary intracranial neoplasms.

Plasma from patients with malignant and benign primary intracranial neoplasms and from healthy control subjects has been examined using proton (1H) and carbon-13 nuclear magnetic resonance (NMR) spectroscopy. Some features in the spectra of plasma from patients with malignant tumors differ significantly (p less than 0.01) from the corresponding features in the spectra of plasma from control subjects and from patients with benign tumors. The NMR spectral parameters vary consistently with the Kernohan grade of astrocytoma, which may suggest that they give a measure of tumor growth kinetics. The observed spectral differences are shown to be due to elevated levels of monounsaturated and polyunsaturated fatty acid residues in the plasma of cancer patients. It is proposed that these lipid residues arise from cell membranes shed from cells in growing tumors. The ability to follow tumor growth kinetics directly may be of considerable importance in elucidating the effects of primary intracranial neoplasm therapy.

Adult↗
PubMed1976

An experimental and theoretical investigation of the core level spectra of a series of amino acids, dipeptides and polypeptides.

A series of simple amino acids, dipeptides and polypeptides have been studied experimentally by electron spectroscopy for chemical analysis and the results theoretically quantified using the charge potential model and semi-empirically computed charge distributions, and non-empirical calculations of absolute and relative binding energies for model systems. Core binding energies are shown to be characteristic of given structural features and the experimental data taken in conjunction with the model theoretical calculations indicate a zwitterionic structure with extensive intermolecular hydrogen bonding for simple amino acids in the solid state.

Amino Acids↗
PubMedDate not supplied

1H NMR properties of N-acetylaspartylglutamate in extracts of nervous tissue of the rat.

The 1H NMR spectrum of the putative neurotransmitter dipeptide N-acetylaspartylglutamate (NAAG) is described, along with its identification in acid extracts of tissues of the central and peripheral nervous systems of the rat. The N-acetyl methyl resonance of NAAG (2.058 ppm) is close to that of N-acetylaspartate (NAA, 2.022 ppm), a prominent signal in 1H NMR spectra of the brain. The tissue concentration of NAAG is such that resonances of NAAG do not contribute greatly to 1H NMR spectra of the brain, except in studies of the brain stem or thalamus. In the spinal cord and peripheral nerves the level of NAAG is similar to that of NAA, and NAAG is a major metabolite contributing to the 1H NMR spectrum. The implications of these observations for 1H NMR spectra in vivo are discussed.

Animals↗
PubMedDate not supplied

Biological effects of magnetic fields: chronic exposure of the nematode Panagrellus redivivus.

The Panagrellus redivivus bioassay, an established monitor of adverse toxic effects of different environments, has been used to study the biological effects of exposure to static and time-varying uniform and gradient magnetic fields, and to time-varying magnetic field gradients superimposed on a static uniform magnetic field of 2.35 Tesla. Temporally stationary magnetic fields have no effect on the fitness of the test animals. Time-varying magnetic fields cause some inhibition of growth and maturation in the test populations. The combination of pulsed magnetic field gradients in a static uniform magnetic field also has a small detrimental effect on the fitness of the test animals.

Animals↗
PubMedDate not supplied

Phosphate energy metabolism during domoic acid-induced seizures.

The effect of domoic acid-induced seizure activity on energy metabolism and on brain pH in mice was studied by continuous EEG recording and in vivo 31P nuclear magnetic resonance (NMR) spectroscopy. Mice were divided into ventilated (n = 6) and nonventilated (n = 7) groups. Baseline EEG was 0.1-mV amplitude with frequence of > 30-Hz and of 4-5 Hz. After intraperitoneal (i.p.) administration of domoic acid (6 mg/kg), electrographic spikes appeared at increasing frequency, progressing to high-amplitude (0.1-0.8 mV) continuous seizure activity (status epilepticus). In ventilated mice, the [31P]NMR spectra showed that high-energy phosphate levels and tissue pH did not change after domoic acid administration or during the intervals of spiking or status epilepticus. Nonventilated mice showed periods of EEG suppression accompanied by decreases in the levels of high-energy phosphate metabolites and in pH, corresponding to episodic respiratory suppression during the spiking interval. In all animals, status epilepticus was followed by a marked decrease in EEG amplitude that progressed rapidly to isoelectric silence. [31P]NMR spectra obtained after this were indicative of total energy failure and tissue acidosis. In a separate group of ventilated mice (n = 4), domoic acid-induced status epilepticus was accompanied initially by an increase in mean arterial blood pressure (MAP) that slowly returned to baseline level. Isoelectric silence was accompanied by a decrease in MAP to 75 +/- 8 mm Hg. These experiments suggest that domoic acid-induced seizures are not accompanied by an increase in substrate demand that exceeds supply.

Adenosine Triphosphate↗
PubMedDate not supplied

Effect of sustained pyridoxine treatment on seizure susceptibility and regional brain amino acid levels in genetically epilepsy-prone BALB/c mice.

Epilepsy-prone and epilepsy-resistant substrains were selectively bred from a strain of BALB/c mice; audiogenic-sensitive epilepsy-prone animals showed enhanced sensitivity to chemical convulsants. Treatment with pyridoxine (100 mg/L in drinking water) initiated at mating and continued throughout pregnancy and the life of the offspring abolished the enhanced sensitivity to chemical convulsants and reduced the severity of audiogenic seizures. Withdrawal of pyridoxine restored the enhanced seizure sensitivity. [1H] Nuclear magnetic resonance (NMR) spectroscopy of perchloric acid extracts of tissue was used to determine the concentrations of several compounds [N-acetylaspartate (NAA), GABA, glutamate, aspartate, alanine, taurine, creatine, cholines, inositol] in the hippocampus, neocortex, brainstem, and cerebellum of untreated and pyridoxine-treated 6-week-old female animals. The ratios of the concentrations of excitatory to inhibitory putative neurotransmitter amino acids tended to be higher in epilepsy-prone animals, with the most pronounced difference being a significantly elevated glutamate/GABA ratio in every brain region examined. Pyridoxine treatment abolished this imbalance in the hippocampus, brainstem, and cerebellum, but not in the neocortex. Treatment of epilepsy-resistant animals with pyridoxine using the same protocol decreased the glutamate/GABA concentration ratio in the hippocampus, brainstem, and neocortex and resulted in impaired development of the animals. The amino acid imbalance and the accompanying seizure susceptibility in these genetically epilepsy prone mice may originate from an inborn error in pyridoxine metabolism or in a pyridoxine-dependent enzyme system.

Acoustic Stimulation↗