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Biomedical subjects

C H Li

Publications and source records attributed to C H Li.

At least 361 records · Page 20Linked to original sources
PubMed1978

beta-endorphin: synthesis and biological activity of shortened peptide chains.

Three analogs of beta-endorphin have been synthesized by the solid-phase method: betac-endorphin-(1--5)-(28--31), betac-endorphin-(6--31) and betah-endorphin-(1--5)-(16--31). The analgesic activities of these synthetic peptides relative to that of the parent molecule are reported. All three peptides at high doses exhibit either no or much weaker analgesic activity than beta-endorphin. These data suggest that the entire beta-endorphin molecule is necessary for full in vivo analgesic activity.

Amino Acid Sequence↗
PubMed1978

Synthesis and biological activity of ovine beta-lipotropin-(41--91)-henkaipentekontapeptide.

The 51-residue peptide ovine beta-lipotropin-(41--91) has been synthesized by the solid-phase method in about 5% overall yield. The synthetic product was characterized by partition chromatography on agarose gel, thin-layer chromatography in two solvent systems, paper electrophoresis at two pH values, polyacrylamide gel electrophoresis, amino acid analyses of acid and enzymic hydrolysates, and bioassay for lipolytic and melanotropic activities. The synthetic peptide is about 5.4 times as active on a weight basis as ovine beta-lipotropin in the lipolytic assay. In the melanotropic assay, it was about 2.4 times more active than the beta-lipotropin but only 5% as active as bovine beta-melanotropin. It had negligible opiate activity in the guinea pig ileum assay.

Amino Acid Sequence↗
PubMed1978

beta-Endorphin: synthesis and analgesic activity of several analogs modified in positions 2 and 5.

The solid-phase syntheses of [Sar2]-, [Ala2]-, [D-Leu2]-, [D-Lys2]-beta-endorphins and [Pro5]-, [Leu5]-, [D-Leu5]-, [D-Ala2, D-Leu5]-beta-endorphins are described. The synthetic peptides were purified by chromatography on carboxymethylcellulose and partition chromatography on Sephadex G-50. They were characterized by partition chromatography on agarose, thin-layer chromatography, paper electrophoresis, and amino acid analyses of acid and enzymic hydrolysates. Bioassay of the synthetic analogs for analgesic activity by the tail-flick method showed the D-Leu2 analog to be 48% as potent as betah-endorphin while the Ala2, D-Lys2, Leu5, and [D-Ala2, D-Leu5] analogs were 8 to 17% as active. The Sar2, D-Leu5, and Pro5 analogs were less than 1% as potent.

Amino Acid Sequence↗
PubMed1978

Synthesis and opiate activity of human beta-endorphin analogs with various chain lengths.

The synthesis of beta h-endorphin -(1--15), -(1--21), -(1--26), -(1--28) and -(1--29) have been accomplished by the solid-phase method. The opiate activities of the peptides were measured in the guinea pig ileum assay. Their relative potencies were beta h-endorphin (beta h-EP), 1.00; Met-enkephalin, 0.25: beta h-EP-(1--15), 0.17; beta H-EP-(1--21), 0.46; beta H-EP-(1-26), 0.48; beta h-EP-(1--28), 0.89; beta h-EP-(1--29), 1.04.

Amino Acid Sequence↗
PubMed1978

Isolation and properties of two fragments from plasmin digests of human choriomammotropin.

Two fragments have been isolated and characterized from plasmin digests of human choriomammotropin. It was shown that these two fragments were derived from the cleavage of the Arg-Arg (positions 133-134) and the Lys-Gln (positions 140--141) bonds of the hormone: one has 133 amino acids and the other 51 amino acids. Both fragments were biologically and immunologically inactive.

Amino Acid Sequence↗
PubMed1978

betah-endorphin: antidiuretic effects in rats.

Human beta-endorphin (betah-EP) inhibits urine flow in rats. This antidiuretic effect of the peptide occurs after intravenous and intraventricular injections. Intravenously, betah-EP is 24 times more potent than morphine. Intraventricularly, betah-EP is 24 times more potent than morphine. Intraventricularly, betah-EP is effective at doses (0.45 microgram) which have no antidiuretic activity when injected intravenously. This fact suggests that one site of the antidiuretic action of betah-endorphin may be in the central nervous system. Animals tolerant to morphine are also tolerant to the antidiuretic effects of betah-endorphin.

Animals↗
PubMed1978

On the isolation of human pituitary hormones.

Six human pituitary hormones can be obtained from a single batch of human pituitary glands by the procedure described. Starting from an acetone powder of the glands, the hormones are segregated into three fractions; one containing GH and PRL, a second containing the glycoprotein hormones, and the third fraction containing smaller peptides including ACTH and MSH. Clinical grade GH is extracted from the residue at alkaline pH, followed by a series of ammonium sulfate and pH fractionations. Further chromatography on G-100 yields a highly purified GH preparation. FSH is purified by chromatography on carboxymethyl cellulose at pH 5.4 followed by gel filtration on G-100 and fractionation on sulfopropyl Sephadex C-50 at pH 5.4. LH and TSH are separated by DEAE-cellulose chromatography at pH 9.5. The GH and glycoprotein hormones are recovered in a highly purified form and good yields. The GH is obtained in an active form which is easily soluble and well suited for clinical use. A large part of the PRL is also saved during the extraction procedure.

Adrenocorticotropic Hormone↗
PubMed1978

Human somatotropin. 55. Synthesis and growth-promoting activity of peptide analogs of the carboxyl terminal plasmin fragment.

Three analogs of the carboxyl terminal plasmin fragment of human somatotropin, [Nle 170, Ala165, 182, 189]-human somatotropin-(145-191), [Nle170, Ala165, 182, 189]-human somatotropin-(140-191), and [Lys135,136, 138, Glu137, 139, Nle170, Ala165, 182, 189]-human somatotropin-(135-191) have been synthesized by the solid-phase method. The synthetic peptides were assayed for growth-promoting activity and their potency was found to be comparable to that of [S-carbamideomethylcysteine165,182, 189]-human somatotropin-(141-191) which was derived from the native hormone.

Amino Acid Sequence↗
PubMed1978

Reaction of ovine prolactin with 2-(2-nitrophenylsulfenyl)-3-methyl-3'-bromoindolemine.

The two tryptophan bonds at positions 91 and 150 in ovine prolactin have been cleaved by the use of 2-(2-nitrophenylsulfenyl)-3-methyl-3'-bromoindolemine. The reaction yielded three products: a small fragment containing residues 92-150, a large fragment consisting of residues 1-91 and 151-199 joined by a disulfide bond, and a derivative containing uncleaved but oxidized prolactin. The yield of the two fragments was 38% and 26%, respectively, indicating a cleavage of approximately 55% for each tryptophan residue. The products were characterized by exclusion chromotography, amino acid analysis, isoelectric focusing on polyacrylamide, circular dichroism spectra, two-dimensional chromatography/electrophoresis on tryptic digests, and ultraviolet absorption spectra. The oxidized but uncleaved product had immunological activity, whereas the two fragments had none. None of these derivatives was active as assayed by the pigeon crop-sac test.

Animals↗