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Biomedical subjects

L Gráf

Publications and source records attributed to L Gráf.

At least 55 records · Page 3Linked to original sources
PubMed1983

Met-enkephalin binding to opiate receptors is not functionally coupled to biodegradation.

Using synaptosomal rat brain membranes, the degradation of Met-enkephalin in both free and receptor-bound form was measured, together with the dissociation of Met-enkephalin from the receptors. The results show that the degradation rate of initially receptor-bound Met-enkephalin is significantly smaller than either the rate of dissociation from the receptors or that of the degradation of free Met-enkephalin. These data suggest that intact Met-enkephalin dissociates from the receptors and then it becomes a target for the same membrane-associated peptidases that split free Met-enkephalin. This view is supported by the good fitness of the measured degradation of initially receptor-bound Met-enkephalin to the predicted degradation curve calculated from the dissociation rate of receptor-bound Met-enkephalin and the degradation rate of free Met-enkephalin.

Animals↗
PubMed1982

Human somatotropin. Selective removal with trypsin of residues 135-145 from the hormone molecule with no loss of biological activities.

A 11-residue segment, sequence positions 135-145, has been cleaved selectively from the human somatotropin molecule by limited digestion of the hormone with trypsin at pH 6.0 in 90% (v/v) glycerol. Differences between the tertiary structures of the native and trypsin-modified hormones have been demonstrated by circular dichroism spectroscopy. Despite these conformational differences, the biological properties of intact hormone and its modified form appeared to be very similar, as tested by two receptor-binding assays, radioimmunoassay, and the rat tibia test.

Amino Acid Sequence↗
PubMed1982

A serine-proteinase inhibitor (Boc-D-Phe-Pro-Arg-H) inhibits the secretion of adrenocorticotropin- and beta-endorphin-immunoreactive peptides in vitro.

The effects of a potent serine protease inhibitor, Boc-D-Phe-Pro-Arg-H, on the secretion and content of ACTH and beta-endorphin-like immunoreactivities of cultured rat anterior pituitary cells were studied. Basal release of the hormones was not affected by the drug but secretion in response to stalk-median eminence extracts was inhibited. The inhibitor did not effect the amount of ACTH or beta-endorphin in the medium plus the cells, nor did it change the ratio of the lipotropin and beta-endorphin-like immunoreactivities. Thus the compound seems to affect the release of ACTH and beta-endorphin, but not the processing of lipotropin to beta-endorphin.

Adrenocorticotropic Hormone↗
PubMed1981

Two contiguous thrombin fragments of human somatotropin form a functionally active recombinant, but the two homologous fragments from sheep hormone do not.

Two thrombin fragments of reduced-carbamidomethylated human somatotropin representing the full primary structure of the native hormone (residues 1-134 and 135-191) have been found to form a recombinant molecule with properties similar to those of reduced-carbamidomethylated human somatotropin as shown by circular dichroism spectroscopy, two receptor-binding assays, and radioimmunoassay. In contrast, the homologous thrombin fragments of reduced-carbamidomethylated sheep hormone (residues 1-133 and 134-191) do not undergo recombination. Furthermore, neither the reduced-alkylated nor the reduced and nonalkylated C-terminal thrombin fragment of sheep hormone is able to interact with the reduced-carbamidomethylated N-terminal thrombin fragment of human hormone, under conditions which favor the recombination of the two human somatotropin fragments.

Amino Acid Sequence↗
PubMed1981

Further evidence for the neuroleptic-like activity of gamma-endorphin.

gamma-Endorphin inhibits the amphetamine-induced stereotypy in rats with an approximate ED50 of 0.3 mg/kg. SC. The anti-amphetamine effect of gamma-endorphin can be antagonized to a certain extent by both the dopamine receptor stimulant 2-bromo-ergocryptine and the opiate receptor antagonist naloxone.

Animals↗
PubMed1981

Human somatotropin: covalent reconstitution of two polypeptide contiguous fragments with thrombin.

Thrombin has been shown to resynthesize the Arg134-Thr135 peptide bond between the 134- and 57-residue thrombin fragments of reduced and carbamidomethylated human somatotropin at pH 6.0 in 90% (vol/vol) glycerol. The maximal amount of synthesis was about 20% as estimated by sodium dodecyl sulfate gel electrophoresis and radioreceptor assay. The resynthesized polypeptide was isolated and shown to be indistinguishable from the reduced and carbamidomethylated hormone when tested by two receptor-binding assays, radioimmunoassay, and rat tibia test.

Amino Acid Sequence↗
PubMed1981

beta-Endorphin: demonstration of a tertiary structure in aqueous solution.

Difference spectra generated during thermolysin digestion of camel beta-endorphin at pH 8.2 or at pH 6.5 indicate rapid blue shifting of the near-UV absorption bands of the NH2-terminal tyrosine. A similar spectral change is not observed for the NH2-terminal tyrosine in [Met]enkephalin when it is digested under similar conditions. These results suggest that enzymatic digestion destroys or alters some structural interaction between the NH2-terminal tyrosyl residue of the endorphin and a residue(s) within the COOH-terminal segment of the molecule. Peptide mapping of the digest as a function of time suggests that cleavage of the bond linking the alanine-21 and isoleucine-22 residues produces most of the observed effect. These data provide evidence for the existence of a tertiary structure for beta-endorphin in aqueous solutions.

Endorphins↗