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Biomedical subjects

J Lehmann

Publications and source records attributed to J Lehmann.

At least 271 records · Page 15Linked to original sources
PubMed1983

Culture conditions for selective and enhanced release of various murine lymphokines (CSF, IL-2, MCF, MIF and TRF).

The production of the lymphokines colony stimulating factor (CSF), interleukin-2 (IL-2), macrophage cytotoxicity factor (MCF), macrophage migration inhibitory factor (MIF) and T cell replacing factor (TRF) was optimized from mouse spleen cell cultures stimulated with concanavalin A (Con A). The cultivation was performed in bioreactors which allow regulation of dissolved oxygen concentration. The oxygen supply influenced the yields of individual lymphokines in different ways. High oxygen concentration was beneficial for high release of IL-2 and MCF, whereas MIF and TRF were better produced at low oxygen concentrations. CSF release did not depend on oxygen supply. Upon stimulation with Con A, lymphokine activities in the culture supernatant reached an optimum or plateau after 24 h Lymphocytes continued with lymphokine release, when they were restimulated for further 24 h. in fresh medium and mitogen. CSF could be induced for at least 4 times. MCF was released during the first 3 inductions, whereas IL-2 and TRF were only produced during the first and second induction. These findings led to specific culture conditions for selective and enhanced production of individual lymphokines.

Animals↗
PubMed1983

Liquid-chromatographic determination of alpha- and gamma-tocopherols in erythrocytes, with fluorescence detection.

We have adapted to erythrocytes a method for the determination of alpha- and gamma-tocopherols in plasma and platelets. Erythrocytes (50 microL) were extracted with methanol containing tocol (internal standard) and pyrogallol. Tocopherols were partitioned into chloroform, washed, and injected in methanol onto a reversed-phase (C18) "high-performance" liquid-chromatographic column. The mobile phase was methanol/water (99/1 by vol) at a flow rate of 2 mL/min and detection was with a "high-performance" spectrophotofluorometer. The limit of detection for either tocopherol is 0.10 microgram/mL of packed cells. Analytical recoveries ranged from 93 to 104%. Some values for tocopherols in human erythrocytes are presented.

Blood Platelets↗
PubMed1983

Fibrous long-spacing collagen in the perineurium of human sural nerve.

Banded structures are reported to occur in the thickened perineurium of four normal human sural nerves (material from autopsy cases: one female and three males between 64 and 90 years old; three died of secondary complications of atherosclerosis, one died from cerebral contusion after an accident). The structures were found adjacent to typical perineurial cells as well as to fibroblast-like cells, and in association with an increased amount of basement membrane material. The pathologic significance of these structures is briefly discussed.

Aged↗
PubMed1983

[Loss of neurons in the granular layer of the cerebellum in epilepsy].

Morphometric examination of the neurons in the cerebellar granular layer in epilepsy showed a significant mean decrease in their number. There is no correlation between this reduction and the duration of epilepsy or frequency of seizures, respectively. The pattern of lesions reach from slight patchy cell loss to severe diffuse reduction of neurons. The diameters of the granular neuronal nuclei showed a great variability. There is no correlation between age and the distribution of these diameters.

Adolescent↗
PubMed1982

Factors determining steric course of enzymic glycosylation reactions: glycosyl transfer products formed from 2,6-anhydro-1-deoxy-D-gluco-hept-1-enitol by alpha-glucosidases and an inverting exo-alpha-glucanase.

Glycosyl transfer products were formed from 2,6-anhydro-1-deoxy-D-gluco-hept-1-enitol (heptenitol) by purified alpha-glucosidases from Candida tropicalis and rice and by an inverting exo-alpha-glucanase (glucodextranase) from Arthrobacter globiformis. The products were structurally defined through 1H and 13C NMR (nuclear magnetic resonance) spectra of their crystalline per-O-acetates in comparison with those of authentic methyl 1-deoxy-alpha- and methyl 1-deoxy-beta-D-gluco-heptuloside. 1-Deoxy-alpha-D-gluco-heptulosyl-(2 leads to 7)-heptenitol and 1-deoxy-alpha-D-gluco-heptulosyl-(2 leads to 7)-D-gluco-heptulose were produced by both the Candida alpha-glucosidase and the glucodextranase; 1-deoxy-alpha-D-gluco-heptulosyl-(2 leads to 5)- and 1-deoxy-alpha-D-gluco-heptulosyl-(2 leads to 7)-D-gluco-heptuloses by the rice alpha-glucosidase. These results, together with our earlier findings of sterospecific hydration of heptenitol catalyzed by the same enzymes [Hehre, E. J., Brewer, C. F., Uchiyama, T., Schlesselmann, P., & Lehmann, J. (1980) Biochemistry 19, 3557-3564], show the inadequacy of the long-accepted notion that carbohydrase-catalyzed reactions always lead to retention (or always lead to inversion) of substrate configuration. In particular, the finding that glucodextranase forms transfer products of alpha configuration and a hydration product of beta configuration from the same substrate provides a clear example of the functioning of acceptors rather than donor substrates in selecting the steric course of reactions catalyzed by a glycosylase. The circumstances under which acceptor cosubstrates might be expected to show this significant effect are discussed. The opportunity presumably would exist whenever carbonium ion mediated reactions are catalyzed by glycosylases that provide oppositely oriented approaches of different acceptors to the catalytic center.

Arthrobacter↗
PubMed1982

Characterization of the excitatory amino acid receptor-mediated release of [3H]acetylcholine from rat striatal slices.

The pharmacological nature of the interaction of excitatory amino acids with striatal cholinergic neurons was investigated in vitro. Agonists of excitatory amino acid receptors evoked the release of [3H]acetylcholine from slices of rat striatum, in the presence of magnesium (1.2 mM). Removal of magnesium from the medium markedly increased the release of [3H]acetylcholine evoked by all excitatory amino acid receptor agonists tested, with the exception of kainate. In the absence but not the presence of magnesium, a clear rank order of potency was found: N-methyl-DL-aspartate = ibotenate greater than L-glutamate greater than L-aspartate greater than or equal to cysteate greater than kainate = quisqualate. The excitatory amino acid receptor mediating [3H]acetylcholine release resembles the N-methyl-D-aspartate preferring (N-type) receptor, as previously characterized electrophysiologically, according to 3 criteria: (1) rank order of potency of agonists; (2) magnesium-sensitivity; and (3) antagonism by 2-amino-5-phosphonovalerate. The release of [3H]acetylcholine evoked by N-methyl-DL-aspartate was blocked by tetrodotoxin (0.5 microM). Moreover, N-methyl-DL-aspartate failed to evoke [3H]acetylcholine release from slices of hippocampus, where cholinergic afferents, rather than interneurons, are found. These results suggest that excitatory amino acids act at receptors on the dendrites of striatal cholinergic interneurons, giving rise to action potentials and release of acetylcholine from cholinergic nerve terminals.

2-Amino-5-phosphonovalerate↗
PubMed1982

Muscarinic receptors on dopamine terminals in the cat caudate nucleus: neuromodulation of [3H]dopamine release in vitro by endogenous acetylcholine.

The directly acting muscarinic receptor agonist oxotremorine (1.8-10 microM) produced an increase in electrically evoked [3H] dopamine release from slices of the cat caudate. The maximal increase caused by oxotremorine was 40%, and was antagonized by the muscarinic receptor blocking agent atropine (0.1 microM). Exposure to the acetylcholinesterase (AChe) inhibitor physostigmine (1 microM) resulted in a 50% increase in electrically evoked [3H]dopamine release. The increase caused by physostigmine was also antagonized by atropine (0.1 microM). Atropine did not, however, alter the modulations in [3H]dopamine release mediated by the dopamine autoreceptor: the increase in electrically evoked [3H]dopamine release caused by the dopamine receptor antagonist S-sulpiride (0.1 microM) and the decrease caused by the dopamine receptor agonist pergolide (30 nM) were unaffected by atropine (0.1 microM). These results indicate that the muscarinic receptor-mediated and dopamine autoreceptor-mediated presynaptic effects on [3H]dopamine release are independent. The present results suggest that in the electrically depolarized caudate slice in vitro, released endogenous acetylcholine may interact with muscarinic receptors facilitating depolarization-evoked [3H]dopamine release, if AChE is inhibited. These muscarinic receptors may be located on dopamine nerve terminals. In the context of present neuroanatomical knowledge, the action of released endogenous acetylcholine on dopamine terminals may be a non-synaptic neuromodulation.

Acetylcholine↗
PubMed1982

Attempted affinity-labelling of beta-D-galactosidase from Escherichia coli with 2,6:3,4-dianhydro-1-deoxy-D-talo-hept-1-enitol.

The epoxides methyl 2,3-anhydro-beta-D-talopyranoside (1) and 2,6:3,4-dianhydro-1-deoxy-D-talo-hept-1-enitol (2), both prepared by improved methods, and 2,6:3,4-dianhydro-1-deoxy-D-gulo-hept-1-enitol (3) were applied as potential reagents for the affinity labelling of E. coli beta-D-galactosidase. Compounds 1 and 3 are ineffective as labelling reagents, whereas compound 2 irreversibly inhibits the enzyme activity. Deactivation is complete only when high concentrations (0.5M) of the inhibitor are applied over a relatively long period of time (24 h). Saturation kinetics cannot be observed. Nevertheless, the competitive inhibitor isopropyl 1-thio-beta-D-galactopyranoside protects the enzyme from irreversible deactivation by 2, indicating that the latter also reacts with the active site. Treatment of beta-D-galactosidase with 2,6:3,4-dianhydro-1-deoxy-D-talo-[4-3H]hept-1-enitol under conditions that effect deactivation of the enzyme to only a minor extent causes labelling of the protein at the molar ratio of 48:1. Specific, radioaffinity labelling of the active site of the enzyme cannot be thus achieved.

Affinity Labels↗
PubMed1982

Establishment and characterization of ferret cells in culture.

Cells derived from the brain of a 6 wk-old ferret have been subcultured over 100 times and have undergone over 400 population doublings in vitro. These cells, referred to as Mpf cells, have an absolute efficiency of colony formation in excess of 45%, exhibit a mean population doubling time of 12.5 h, possess ferret-specific antigens, and have isozymes with electrophoretic properties that are the same as those of isozymes found in ferret liver. The cells exhibit a cytopathic effect and support the synthesis of progeny virus when they are infected with the viruses of lymphocytic choriomeningitis, Newcastle disease, pseudorabies, Sindbis, vaccinia, and vesicular stomatitis. The passage level of the Mpf cells, their elapsed number of population doublings, their possession of ferret-specific antigens, and the comigration of four isozymes obtained from these cells and ferret liver define the cells as an established line of ferret cells.

Animals↗