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Biomedical subjects

A Gorchein

Publications and source records attributed to A Gorchein.

At least 19 recordsLinked to original sources
PubMed1992

Sustained high plasma 5-aminolaevulinic acid concentration in a volunteer: no porphyric symptoms.

The pathogenesis of the acute porphyric attack is not known. One hypothesis is that porphyrin precursors, especially 5-aminolaevulinic acid (ALA), are toxic for neuronal tissue. This was tested by infusing ALA in a male volunteer after a loading dose at a rate of 50-80 mg h-1 for 92.5 h. During the experiment plasma ALA concentration was 9-11 mumol 1-l and porphobilinogen concentration 3-6 mumol 1-l which are the levels seen during acute attacks. Urinary excretion of these porphyrin precursors was also markedly increased. ALA infusion caused no subjective symptoms and no change in pulse rate, blood pressure, or autonomic nerve function or conduction velocity of peripheral nerves. Photosensitivity was not demonstrable. It is concluded that sustained high plasma ALA concentration does not cause porphyria-like symptoms.

Aminolevulinic Acid↗
PubMed1990

Measurement of 5-aminolaevulinate synthase activity by gas-liquid chromatography with electron-capture detection.

A specific assay for 5-aminolaevulinate synthase activity is described, with a sensitivity comparable with that of radiochemical assays. It is based on measurement by g.l.c. with electron-capture detection of the pentafluorobenzyl ester of the ethyl acetoacetate pyrrole derivative of 5-aminolaevulinic acid, and of the corresponding compound from 6-amino-5-oxohexanoic acid used as internal standard. Enzyme activity has been measured in homogenates of rat liver, spleen, kidney and brain, and in human lymphocytes.

5-Aminolevulinate Synthetase↗
PubMed1987

delta-Aminolaevulinic acid in plasma, cerebrospinal fluid, saliva and erythrocytes: studies in normal, uraemic and porphyric subjects.

delta-Aminolaevulinic acid (ALA) was determined by g.l.c. with electron-capture detection. Normal plasma level was 92 nmol/l (SD = 39, n = 89, range 24-270 nmol/l). ALA was undetectable in 35 of 53 samples of normal cerebrospinal fluid (limit of assay 2 nmol/l). The mean of the other 18 samples was 19 nmol/l (SD = 10, range 6-36 nmol/l). Salivary ALA was generally only 10-30% of the plasma level in normal and porphyric subjects. Erythrocytes of normal and porphyric subjects contained no detectable ALA and were impermeable to its entry. ALA clearance correlated closely with that of creatinine, consistent with it being excreted by glomerular filtration with limited tubular reabsorption. In chronic renal failure, serum ALA was elevated to a maximum of three to four times the normal, but its urinary excretion was reduced, in keeping with lessened production. In two cases of acute intermittent porphyria with overwhelming neuropathy the maximum plasma levels of ALA were 9 and 12 mumol/l. Haematin infusion decreased the ALA levels but without obvious clinical benefit. Limited neurological recovery occurred without major reduction in plasma levels of ALA. One subject's attack was precipitated by pregnancy. The neonate was apparently normal, despite high levels of ALA in maternal plasma throughout gestation and a high level of ALA in the cord blood. The observations described here do not support the view that ALA may be directly neurotoxic.

Adult↗
PubMed1979

Pharmacological properties of kryptopyrrole and its oxidation products on isolated sciatic nerve of rat and on guinea-pig ileum.

1 Kryptopyrrole (2, 4-dimethyl, 3-ethylpyrrole) inhibited conduction in rat sciatic nerve by a local anaesthetic action. 2 Tone and both spontaneous and electrically-induced contractions of guinea-pig ileum were also inhibited by kryptopyrrole. The concentration of kryptopyrrole required for 50% inhibition of a maximum twitch tension (ID50) was 0.085 mM. 3 Oxidation products of kryptopyrrole with chromatographic properties similar to those of urinary constituents reported in schizophrenia and hepatic porphyrias had little or no effect at similar concentrations. 4 Dose-response curves to exogenous acetylcholine in guinea-pig ileum were shifted to the right by kryptopyrrole, with loss of parallelism and reduction in the maximum contraction. 5 Acetylcholine overflow from ileal segments at rest and during electrical stimulation was reduced by kryptopyrrole. 6 These results on ileal segments are consistent with kryptopyrrole having both a post-junctional site of action, presumably directly on the muscle, and a pre-junctional site reducing the output of acetylcholine from the myenteric plexus. 7 The significance of these findings is discussed in relation to a possible clinical pathological role for these compounds.

Acetylcholine↗
PubMed1973

Control of magnesium-protoporphyrin chelatase activity in Rhodopseudomonas spheroides. Role of light, oxygen, and electron and energy transfer.

1. Magnesium-protoporphyrin chelatase activity, previously shown in whole cells of Rhodopseudomonas spheroides, could not be demonstrated in cell-free extracts prepared in different ways, although spheroplasts retained moderate activity. Slight activity was detected also in whole cells of Rhodospirillum rubrum. 2. The effects on the activity of the enzyme of inhibitors of electron and energy transfer were studied in whole cells of Rps. spheroides. Amytal, rotenone, azide and cyanide inhibited at low pO(2) in the dark but not under anaerobic conditions in the light. Antimycin A and 2-heptyl-4-hydroxyquinoline N-oxide, as well as uncouplers and oligomycin, inhibited under all environmental conditions. 3. The effects on magnesium chelatase activity of intermediates of the tricarboxylic acid cycle, of thenoyltrifluoroacetone, of a number of artificial electron donors or acceptors, of various quinones and of the oxidation-reduction indicator dyes Benzyl Viologen and Methyl Viologen are described. 4. It was concluded that electron transport between a b-type and a c-type cytochrome as well as associated energy conservation and transformation reactions were essential for activity. There was also a specific requirement for ATP. 5. Exogenous protoporphyrin and magnesium protoporphyrin monomethyl ester were incorporated into bacteriochlorophyll or late precursors by whole cells. 6. Evidence is presented that the insertion of magnesium was the only step inhibited by oxygen in the biosynthetic pathway between protoporphyrin and bacteriochlorophyll.

Amobarbital↗