Renal function and fluoride formation and excretion during enflurane anaesthesia

Central circulation, renal function, and fluoride formation and excretion were studied in nine patients during enflurane anaesthesia and surgery. Cardiac output and mean systemic arterial pressure remained unchanged compared with preoperative control values. During anaesthesia and surgery, urine flow rate, inulin clearance, PAH clearance and fractional sodium excretion were 60, 65, 55, and 45% of control values, respectively. Mean peak plasma level of fluoride was 20.0 microM. It was reached 4 hours after termination of anaesthesia. Fluoride clearance (CF) decreased from 23.9 ml . min-1 to 2.7 ml . min-1 during anaesthesia. Postoperative, CF increased to 41.6 and 76.0 ml . min-1, respectively, during two consecutive measurement periods. There was no correlation between plasma fluoride levels and depression of any renal function variable.

[Natural fluorides. The distinction between technically produced and naturally occurring fluorides in caries prophylaxis]

In the controversial discussion of the bio-availability of fluoride in caries prophylaxis by fluoridation, fluorides coming from the geochemical circulation to the biochemical circulation are sometimes differentiated from synthetic fluorides introduced into fluoride medication. The question as to whether such a differentiation is essential can be answered from the physical-chemical point of view. This requires a wide field of scientific research starting with geochemistry and the knowledge of fluoride deposits, sedimentology, hydrology, technology of inorganic and organic fluorine compounds, thermodynamics of dissolved fluorides, up to biocrystallography and biochemistry of fluorine.

Kinetics of methoxyflurane biotransformation with reference to substrate inhibition

The kinetics of biotransformation of methoxyflurane by rat hepatic microsomes in vitro was studied. The rate of biotransformation as measured by analysis of metabolites continued to increase even at near-saturation concentrations of the anesthetic. Methoxyflurane biotransformation followed either an unbounded curve with empirical formula y = a ln(bx + 1) or an asymptotic curve with formula (see article) No substrate inhibition was observed. Total fluoride Vmax of 135.1 mmumol F-/mg protein/30' was increased to 931.9 by phenobarbital induction; free fluoride Vmax from 39.2 to 403.2. Thus, enzyme induction shifted biotransformation to the production of greater amounts of inorganic free fluoride metabolites than organic fluoride-containing metabolites. Phenobarbital induction caused qualitative as well as quantitative alteration in the biotransformation of methoxyflurane.

The metabolism of p-fluorobenzoic acid by a Pseudomonas sp

A species of Pseudomonas previously used to study the degradation of p-fluorophenylacetic acid was used to investigate the degradation of p-fluorobenzoic acid. During growth on the latter substrate all organic fluorine was released into the culture medium as fluoride. Several metabolic intermediates were isolated from the culture medium of resting cells. The major compounds have been identified as 4-fluorocatechol, β-acetylacrylic acid, (+)-4-carboxymethyl-4-fiuorobut-2-enolide, (−)-4-carboxymethyl-but-2-enolide, and β-ketoadipic acid. A small quantity of a compound tentatively identified as β-fiuoroacrylic acid was also isolated. On the basis of these findings, together with respiratory studies on p-fluorobenzoic acid grown cells with various substrates, two metabolic pathways are proposed which involve elimination of fluorine at either of two alternative stages in the breakdown of p-fluorobenzoic acid.

The metabolism of p-fluorophenylacetic acid by a Pseudomonas sp. I. Isolation and identification of intermediates in degradation

A Pseudomonas sp. capable of growing on p-fluorophenylacetic acid as sole carbon source has been isolated using the enrichment culture technique. All the organic fluorine is released into the culture medium as fluoride ion during growth. A number of fluorinated intermediates have been isolated from the culture medium when resting cells were incubated with the substrate. Using infrared, nuclear magnetic resonance, and mass spectroscopic techniques together with chemical degradative procedures, these have been identified as D(+)-monofluorosuccinic acid, trans-3-fluoro-3-hexenedioic acid, (−)-4-carboxymethyl-4-fluorobutanolide, 4-fluoro-2-hydroxyphenylacetic acid, and 4-fluoro-3-hydroxyphenylacetic acid.

The metabolism of p-fluorophenylacetic acid by a Pseudomonas sp. II. The degradative pathway

A Pseudomonas sp. grown on p-fluorophenylacetic acid is adapted to the metabolism of phenylacetic acid, 3-fluoro-3-hexenedioic acid, monofluorosuccinic acid, monofluorofumaric acid, β-ketoadipic acid, and β-hydroxyadipic acid. Cell suspensions catalyze the lactonization of 3-fluoro-3-hexenedioic acid to give 4-carboxymethyl-4-fluorobutanolide. The results suggest that 3-fluoro-3-hexenedioic acid is an intermediate in the degradation of p-fluorophenylacetic acid, and may be metabolized by two alternate pathways, depending on the lactone formed. 4-Carboxymethyl-4-fluorobutanolide may be hydrolyzed to give 3-hydroxy-3-fluoroadipic acid, which spontaneously eliminates hydrogen fluoride to give β-ketoadipic acid. Alternatively, 3-fluoro-3-hexenedioic acid may lactonize to form 4-carboxymethyl-3-fluorobutanolide, which is then hydrolyzed to 3-keto-4-fluoroadipic and cleaved to form acetate and monofluorosuccinic acid. The latter is converted to fluorofumaric acid by fumarase to give 2-fluoromalic acid. This unstable compound decomposes to oxaloacetate and hydrogen fluoride. The mechanism of ring cleavage and the mode of formation of 3-fluoro-3-hexenedioic acid are uncertain but may involve partial reduction of the aromatic ring before oxidative cleavage.