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Biomedical subjects

C H Li

Publications and source records attributed to C H Li.

At least 235 records · Page 13Linked to original sources
PubMed1982

beta-Endorphin: synthesis and properties of human beta-endorphin-(1--28) and its analogs.

Three analogs of human beta-endorphin (beta h-EP) were synthesized by the solid-phage method: beta h-EP-(1--28) (I). [Gln8]-beta h-EP-(1--28) (II), and [D-Ala2, Gln8]-beta h-EP-(1--28) (III). Radioreceptor binding assay with use of tritiated beta h-EP as primary ligand gave relative potencies as follows: beta h-EP, 100; I, 85; II, 380; III, 146. Relative potencies in an analgesic assay were: beta h-EP; 100; I, 18; II, 36; III, 13.

Amino Acid Sequence↗
PubMed1982

Synthesis of human beta-endorphinyl-thiolglycine and its use for the preparation of affinity columns of beta-endorphin.

The peptide human beta-endorphinyl-thiolglycine (I) has been synthesized by the solid-phase method. The citraconyl derivative of peptide I was coupled to aminohexyl-Sepharose by reaction with silver nitrate/N-hydroxysuccinimide in water. The citraconyl groups were removed in aqueous acetic acid and the resulting resin was used in affinity chromatography for the purification of antisera to beta-lipotropin and beta-endorphin.

Amino Acids↗
PubMed1982

Beta-Endorphin. Opiate receptor-binding activity of synthetic analogs modified in the enkephalin segment in rat brain membrane and neuroblastoma x glioma hybrid cell.

The potency of a series of synthetic analogs of beta-endorphin in inhibiting binding of [3H2-Tyr27]-beta h-endorphin to either rat brain membranes or neuroblastoma x glioma hybrid cells (NG108-15) has been determined and compared with the previously determined analgesic potency. There is a very good correlation between inhibitory potency in membranes and cells, but the correlation between analgesic potency and inhibitory potency in either membranes or cells is not as good.

Animals↗
PubMed1982

Beta-Endorphin. Interaction of synthetic analogs having different chain lengths with morphine and enkephalin receptors in rat brain membranes.

Human beta-endorphin analogs with various chain lengths have been investigated for their potency in displacing tritiated dihydromorphine and Leu-enkephalin binding in rat brain membrane preparations. It was found that the reduction of chain length from residues 1-31 to 1-5 led to a gradual loss of preference for the morphined receptor. In addition, the extension of the chain length of the Met-ekephalin segment to the COOH-terminal glutamic acid modified the binding of the NH2-terminal sequence to the enkephalin receptor. The fact that camel beta-endorphin is more potent in displacing the two tritiated primary ligands than the human hormone is also reported herein.

Amino Acid Sequence↗
PubMed1982

Beta-Endorphin. Synthesis and properties of double-headed and related analogs.

A double-headed analog of human beta-endorphin (betah-EP), N,N'-bis (beta-endorphinyl)-cystine (II), has been synthesized by the solid-phase method, along with betah-EP-Cys(CH2CONH2)-OH (I) and [Tyr31]-betah-EP (III). Their relative potencies in a radioreceptor-binding assay were: betah-EP, 100; II, 235; I, 170; and III, 204. In the tail-flick test for analgesic activity their relative potencies were: betah-EP, 100; II, 86; I, 93; and III, 116.

Amino Acid Sequence↗
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

Growth hormone stimulates drug-induced porphyrin formation in liver cells maintained in a serum-free medium.

Human growth hormone and a few other related polypeptide hormones enhanced porphyrin formation induced by 2-allyl-2-isopropylacetamide in chick embryo liver cells maintained in a serum-free medium. The stimulatory effect of human growth hormone on drug-induced porphyrin formation was significant at 10 ng/ml and increased in a dose-dependent manner. Human growth hormone did not stimulate porphyrin formation in otherwise untreated cultures. These findings thus demonstrate a potentiating effect of growth hormones on hepatic porphyrin formation.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1981

Opiate receptor-binding activity of [D-Thr2,Thz5]-and [D-Met2,Thz5]-enkephalinamides.

The binding characteristics of two highly potent analgesic enkephalin analogs, [D-Thr2, Thz5]-and [D-Met2, Thz5]-enkephalinamide, to the rat brain membrane preparation have been investigated using tritiated Leu-enkephalin, human beta-endorphin or dihydromorphine as the primary ligand. Concentrations for 50% inhibiting activity of the enkephalin analogs are much lower in displacing tritiated dihydromorphine in comparison with that for the other two tritiated ligands. In addition, a correlation between analgesic potency and capacity to displace tritiated dihydromorphine is observed. These data may explain the high antinociceptive activity of the enkephalin analogs and support the hypothesis that the mu-receptor is involved with analgesia.

Animals↗
PubMed1981

Stimulation of aldosterone production by beta-melanotropin.

Experimental and clinical evidence suggests that a non-ACTH pituitary factor(s) is important in the regulation of aldosterone secretion in certain conditions. Earlier studies have suggested that beta-melanotrophin (beta-MSH) has only weak steroidogenic potency on the adrenal gland in the rat, but recently Challis et al.5 and Rudman et al.6 have reported that alpha- and beta-MSH have a trophic action on fetal adrenal gland. However, little is known about the effect of beta-MSH on aldosterone production. We recently reported that beta-lipotropin (beta-LPH) stimulates aldosterone production in rat capsular cells. As the amino acid sequence of beta-MSH is contained within the beta-LPH structure, we have now investigated the aldosterone-stimulating activity of synthetic beta-MSH. Our results indicate that beta-MSH causes a dose-dependent increase in aldosterone production in rat capsular cells which is blocked by a synthetic beta-MSH analogue. The synthetic hormone does not increase corticosterone production in decapsular cells.

Aldosterone↗