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Biomedical subjects

J Lehmann

Publications and source records attributed to J Lehmann.

At least 325 records · Page 18Linked to original sources
PubMed1977

1,5-anhydro-2-deoxy-3-O-(2-deoxy-beta-D-arabino-hexopyranosyl)-D-arabino-hex-1-enitol, the by-product in the enzymic hydration of D-glucal by beta-D-glucosidase from emulsin.

The by-product (3) in the hydration of D-glucal (1) catalyzed by emulsin beta-D-glucosidase has been identified as 1,5-anhydro-2-deoxy-3-O-(2-deoxy-beta-D-arabino-hexopyranosyl)-D-arabino-hex-1-enitol. Two models for the formation of 3 are discussed, involving transfer of a 2-deoxy-D-arabino-hexopyranosyl cation to HO-3 of D-glucal (glycon transfer) and transfer of an allylic D-pseudoglucal cation to HO-1 of 2-deoxy-D-arabino-hexopyranose (aglycan transfer). The enzymic production of 3 is highly regiospecific, which lends support to the second model and implies the presence of a specific binding-site for the aglycon moiety.

Binding Sites↗
PubMed1977

The stereochemistry of the addition of glycerol to D-galactal, catalyzed by beta-D-galactosidase.

On incubation with beta-D-galactosidase, D-galactal-2-d (1) plus glycerol yielded 1-deoxyglycerol-1-yl 2-deoxy-beta-D-lyxo-hexopyranoside-2(S)-d. By 1H-n.m.r. analysis, it was shown that the hydrogen atom introduced on C-2 is trans-related to the aglycon moiety. In contrast to this stereospecific, enzyme-catalyzed addition, the reaction of phenol with peracetylated 1, catalyzed by p-toluenesulfonic acid, which yields phenyl 3,4,6-tri-O-acetyl-2-deoxy-alpha-D-lyxo-hexopyranoside-2-d, was shown to entail both a trans and a cis addition.

Catalysis↗
PubMed1977

Evaluation of the combination of tryptophan and ECT in the treatment of depression. I. Clinical analysis.

A double-blind evaluation of the antidepressant efficacy of treatment with a combination of orally administered L-tryptophan (L-TP) and electroconvulsive therapy (ECT) was made in patients suffering from endogenous depression. The patients were randomly assigned to two groups, one treated with L-TP (6 g daily) and unilateral ECT, the other with placebo and unilateral ECT. L-TP treatment was initiated at least 1 day before the first ECT and terminated 4 days after the last ECT. There was a good agreement between the two groups in several measures of antidepressant efficacy: doctors' and patients' ratings of depressive symptoms, and doctors' global rating of therapeutic effect 4 days and 1 month after the last ECT. In the L-TP group, however, there was a significantly better effect on retardation symptoms in the nurses' rating scale. This difference, which is not consistent with other measures of amelioration, contributes, at most, to a marginal therapeutic addition to the antidepressant effect of ECT. It is concluded that oral administration of L-TP, in the dose of 6 g daily, is not of practical value for potentiating the antidepressant efficacy of ECT.

5-Hydroxytryptophan↗
PubMed1976

Relative autoxidative and photolytic stabilities of tocols and tocotrienols.

The relative stabilities of selected individual tocols and tocotrienols and of equimolar mixtures of either alpha- plus gamma- or alpha- plus delta- tocopherols were determined in methyl myristate and methyl linoleate during autoxidation and photolysis. Solutions containing 0.05% of the appropriate tocopherol(s) or tocotrienols were subjected to UV light (254 nm) or to a flow of 4.3 ml/min of oxygen, both at 70 C. Tocopherols (T) and tocotrienols (T-3) were determined by gas chromatography without preliminary separation or purification. Under photolytic conditions, stabilities in increasing order in methyl myristate were gamma-T-3 less than alpha-T-3 less than delta-T less than alpha-T less than gamma-T less than 5,7-T less than beta-T and in methyl linoleate were alpha-T less than alpha-T-3 less than or equal to gamma-T-3 less than or equal to beta-T less than or equal to 5,7-T less than gamma-T less than delta-T. A solvent effect on the initial rate of photolysis was observed for 5-methyl substituted tocols but not for the tocols with an unsubstituted 5-position or for the tocotrienols. Under autoxidative conditions, stabilities in increasing order in methyl myristate were alpha-T = alpha-T-3 less than beta-T-3 less than gamma-T-3 less than delta-T-3 less than gamma-T less than delta-T = beta-T and in methyl linoleate were alpha-T less than alpha-T-3 less than gamma-T-3 less than beta-T less than gamma-T less than delta-T. Tocopherols were much more stable during autoxidation in methyl myristate than they were in methyl linoleate. In mixtures, there was no significant protection of alpha-tocopherol by either gamma- or delta-tocopherol under any of the conditions used. However, alpha-tocopherol was highly effective in protecting gamma- and delta-tocopherols in methyl myristate during both photolysis and autoxidation and in methyl linoleate during photolysis. During autoxidation in methyl linoleate, alpha-tocopherol protection of gamma- and delta-tocopherols after 24 hr was slight tough measurable.

Chromatography, Gas↗
PubMed1976

[Behavior of leucine aminopeptidase from bovine eye lens in guanidine hydrochloride. Dissociation and reassociation].

The dissociation and reassociation behavior of the hexameric leucine aminopeptidase (LAP) in solutions of 0.5 to 6 M guanidine-HC1 (Gu-HC1) was investigated by means of thin layer chromatography on Sephadex G-200 superfine. Up to 0.5 M Gu - hc1 the hexameric LAP-structure remains intact. In 0.75 to 2 M Gu - HC1 the enzyme dissociates nearly completely into its half-molecules (LAP-trimers, MW 160000 +/- 10,000). In 2.5 and 2.75 M Gu - HC1 a mixture of LAP-monomers (subunits) (MW 60000 +/- 5000) and trimers was to be found. Treatment with beta-mercapto ethanol increases the portion of monomers. Only monomers occurred in 3 to 6 M Gu - HC1. Parallel to the dissociation, a loss of the essential zinc (half life: 10.5 and 3.5 hours in 1 M and 4 M Gu - HC1 resp.) and a decrease of the enzymatic activity (30 min after treatment with 1 M and 4 M Gu - HC1 50% and 1% resp. residual activity) of the observed. On the other hand, the enzyme was activated by dilute solutions of Gu - HC1 (0.1 to 0.3 M: max. increase 50%). Removal of the denaturant causes reassociation of all types of fragments to hexameric LAP which was indistinguishable from the native LAP in Ouchterlony immune diffusion test. The reassociation was accompanied by a small increase in activity only.

Animals↗