Epilepsy surgery improves regional glucose metabolism on PET scan. A case report.

A patient with medically intractable complex partial epilepsy was evaluated for epilepsy surgery by electro-encephalograph recording with depth electrodes and 18F-fluorodeoxyglucose positron emission tomography (PET). A small calcified arteriovenous malformation was excised from the left parietal lobe, and the patient became seizure free. Baseline and language stimulation PET scans were obtained preoperatively and 10 months postoperatively.

On the conductance heterogeneity in membrane channels formed by gramicidin A. A cooperative study.

The relative frequency of low-conductance variants of gramicidin A channels in lipid bilayers was determined in parallel experiments in two different laboratories. A common gramicidin stock solution was tested in both labs and, initially, gave rise to significantly different proportions (9% v. 23%) of "mini" channels in the two labs.

Investigation of the interaction between thallous ions and gramicidin A in dimyristoylphosphatidylcholine vesicles: a thallium-205 NMR equilibrium study.

This study reports the first direct observation of multiple occupancy of the gramicidin A channel by Tl+ ions. 205Tl NMR has been used to study the equilibrium binding of Tl+ by gramicidin A incorporated in sonicated dimyristoylphosphatidylcholine vesicles. It is shown that only multiple-channel occupancy can account for the 205Tl chemical shifts measured.

Equilibrium binding constants for the group I metal cations with gramicidin-A determined by competition studies and T1+-205 nuclear magnetic resonance spectroscopy.

The equilibrium binding constants of the Group I metal cations with gramicidin A in aqueous dispersions of lyso-PC have been determined using a combination of competitive binding with the T1+ ion and T1-205 NMR spectroscopy. The values of the binding constants at 34 degrees C are Li (32.2 M-1), Na (36.

Single-channel studies on linear gramicidins with altered amino acid side chains. Effects of altering the polarity of the side chain at position 1 in gramicidin A.

The modulation of gramicidin A single-channel characteristics by the amino acid side chains was investigated using gramicidin A analogues in which the NH2 terminal valine was chemically replaced by other amino acids. The replacements were chosen such that pairs of analogues would have essentially isosteric side chains of different polarities at position 1 (valine vs. trifluorovaline or hexafluorovaline; norvaline vs.

Equilibrium binding constants for Tl+ with gramicidins A, B and C in a lysophosphatidylcholine environment determined by 205Tl nuclear magnetic resonance spectroscopy.

Nuclear Magnetic Resonance (NMR) 205Tl spectroscopy has been used to monitor the binding of Tl+ to gramicidins A, B, and C packaged in aqueous dispersions of lysophosphatidylcholine. For 5 mM gramicidin dimer in the presence of 100 mM lysophosphatidylcholine, only approximately 50% or less of the gramicidin appears to be accessible to Tl+. Analysis of the 205Tl chemical shift as a function of Tl+ concentration over the 0.

Semisynthesis of linear gramicidins using diphenyl phosphorazidate (DPPA).

Sequential HPLC analysis has been used to optimize a synthetic scheme for the preparation of semisynthetic position 1 analogues of the channel-forming pentadecapeptide, gramicidin A. Diphenyl phosphorazidate (DPPA) was more efficient than dicyclohexylcarbodiimide (DCC) for the coupling of N-formyl amino acids to des(formyl-valyl) gramicidin A. The DPPA coupling proceeds rapidly, and with high yield, at 0 degree.

Gramicidin K, a new linear channel-forming gramicidin from Bacillus brevis.

A new gramicidin has been isolated from a commercial mixture of gramicidins A, B, and C. This new molecule, designated gramicidin K, contains formyl and ethanolamine blocking groups, has a molecular weight approximately 20% higher than gramicidin A, and is strongly retained on reversed-phase liquid chromatographic columns. Gramicidin K can be resolved into two components, one of which contains tyrosine.

Performance comparison of parameter estimation techniques for the quantitation of local cerebral blood flow by dynamic positron computed tomography.

Local CBF (LCBF) can be quantitated from positron computed tomographic (PCT) data and physiologically based mathematical models by several general methods. Those using a dynamic sequence of PCT scans allow the simultaneous estimation of both LCBF and p, the indicator's tissue-blood partition coefficient. This article presents a comparison of three rapid estimation techniques for use with inert diffusible radioindicators and serial PCT, each of which is based on the original Kety model.

Quantitation of local cerebral blood flow and partition coefficient without arterial sampling: theory and validation.

A new technique that requires neither arterial blood sampling nor prior knowledge of the indicator's tissue-blood partition coefficient has been developed for quantitation of local CBF. This technique arises from an existing method that uses the inert, freely diffusible gaseous tracer [18F]methyl fluoride (CH3(18)F) and positron computed tomography. The shape of the arterial blood curve is derived from continuous sampling of expired air.

On the recovery of Cys-containing peptides during peptide mapping by HPLC. Tryptic peptides of Trp-tRNA synthetase of E.coli.

Conditions are presented for separating the major tryptic peptides of E.coli tryptophanyl-transfer RNA synthetase by reversed-phase liquid chromatography using a water-methanol gradient in the presence of 0.1% trifluoroacetic acid.

Determination of regional cerebral blood flow in patients with cerebral infarction. Use of fluoromethane labeled with fluorine 18 and positron emission tomography.

Regional cerebral blood flow (rCBF) was determined using the tissue kinetic of fluoromethane labeled with fluorine 18 and positron emission tomography (PET) in 13 normal subjects and 21 patients with cerebrovascular diseases. The mean brain rCBF was 42.9 +/- 4.

Alternative approach to single-scan estimation of cerebral glucose metabolic rate using glucose analogs, with particular application to ischemia.

In the glucose analog method for determining local glucose utilization rates, time courses of tissue and plasma radioactivity are measured and then analyzed in terms of first-order exchange of label between tissue compartments. The rate of glucose utilization is assumed to have a fixed, linear relationship to the analog phosphorylation rate calculated from the fitted rate constants. Accurate estimation of the rate constants requires many hours of dynamic data acquisition.

5-A Fourier map of gramicidin A phased by deuterium-hydrogen solvent difference neutron diffraction.

Crystals of ion-free gramicidin A (P212121: a = 24.61, b = 32.28, c = 32.

Single-channel studies on linear gramicidins with altered amino acid sequences. A comparison of phenylalanine, tryptophane, and tyrosine substitutions at positions 1 and 11.

The relation between chemical structure and permeability characteristics of transmembrane channels has been investigated with the linear gramicidins (A, B, and C), where the amino acid at position 1 was chemically replaced by phenylalanine, tryptophane or tyrosine. The purity of most of the compounds was estimated to be greater than 99.99%.

Visual evoked potentials and positron emission tomographic mapping of regional cerebral blood flow and cerebral metabolism: can the neuronal potential generators be visualized?

Visual evoked potentials (VEPs) and visual evoked spectrum array (VESA) to flashes and pattern-reversal were correlated with regional cerebral blood flow (rCBF) or local cerebral glucose metabolism in 4 hemianopsic patients and one subject with cortical blindness. Normal VEPs, topographical distribution and occipital rCBF were noted in hemianopsic patients with macular sparing. A dissociation of topographical distribution of VEPs to flashes and pattern-reversal was demonstrated in one patient with hemianopsia and macular splitting.

Neutron computed tomography.

A neutron-transmission computed tomography scanning system has been built for scanning biological materials. An oxygen filtered beam of 2.35 MeV neutrons was used for the measurements.

The effect of pre-incubation on trypsin kinetics at low pH.

A possible source of discrepancy between kinetic and spectroscopic studies of the active site ionizations in the enzyme trypsin (EC 3.4.21.

Effect of thiamine deficiency, pyrithiamine and oxythiamine on pyruvate metabolism in rat liver and brain in vivo.

Rats were fed either a thiamine-deficient diet of diets containing pyrithiamine or oxythiamine. When symptoms of thiamine deficiency appeared, the animals were injected intraperitoneally with [2-14C] pyruvate six to twelve minutes prior to sacrifice. Free glutamic and aspartic acids were isolated from liver and brain and degraded.