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Biomedical subjects

B M Cox

Publications and source records attributed to B M Cox.

At least 19 recordsLinked to original sources
PubMed1979

Pharmacological and immunological characterization of the Leu5 analogue of human beta-endorphin.

The potencies of beta h-endorphin, Met (O)5-beta h-endorphin, and synthetic Leu5-beta h-endorphin have been compared in three bioassays of opioid activity, and in two radioimmunoassays. In all assays, a peptide isolated from hemodialysates from a psychotic patient behaved like Leu5-beta h-endorphin; it has been distinguished unambiguously from beta h-endorphin and Met(O)5-beta h-endorphin. Leu5-beta h-endorphin was one-fifth as potent as beta h-endorphin in guinea pig ileum myenteric plexus, but was only slightly less active in mouse vas deferens and in guinea pig brain opiate receptor binding assay. The low cross-reactivity of Leu5-beta h-endorphin relative to beta h-endorphin with an antiserum raised to beta-endorphin suggests that the preferred solution conformations of these peptides are different. In all bioassays beta h-endorphin was 2- to 3-fold less potent than beta c-endorphin.

Animals↗
PubMed1979

Experimental alterations of endorphin levels in rat pituitary.

Endorphin (END) levels in rat pituitary were assessed with the opiate receptor binding assay. Procedures reported to alter hormone secretion from END-rich intermediate or anterior lobes were examined for their effect on END content. Lesions of the paraventricular nucleus (PVN) had no significant effect on END content. Ingestion of 2% NaCl reduced END levels in a significant majority of the animals. Suckling, a natural physiological stimulus, significantly elevated neurointermediate lobe END. Footshock and immobilization each evoked 40--50% reductions in anterior lobe END content. Pituitary ENDs are thus affected by many of the same stimuli that also promote release of a number of peptide hormones derived from the same biosynthetic precursor. However, separate mechanisms likely exist for control of secretion of these peptides from anterior and neurointermediate lobe.

Animals↗
PubMed1977

Distribution of endorphins (peptides with morphine-like pharmacological activity) in pituitary.

Endorphin was found in the pituitary gland of rat, sheep, pig, cow and man. In bovine pituitary, highest concentrations have been found in that part of the posterior lobe containing the pars intermedia, although endorphin was also present in the pars distalis. Analysis by gel filtration and adsorption chromatography suggested that the major endorphins from rat, pig and cow pituitary were similar, with apparent molecular weights in the range 3000-3500 daltons.

Animals↗
PubMed1977

Opiate receptors.

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Affinity Labels↗
PubMed1977

Opiate binding and effect in ileum preparations from normal and morphine pretreated guinea-pigs.

1 Dose-response curves for normorphine in the absence and presence of naloxone have been obtained from myenteric plexus-longitudinal muscle strip preparations from normal and morphine pretreated guinea-pigs. In addition, the high affinity stereospecific binding of [3H]-etorphine has been measured in homogenates of the same tissue. 2 Higher concentrations of normorphine were required to produce 50% inhibition of the electrically stimulated contractions of strip preparations from morphine pretreated animals. There was also an increase in the slope of linearized dose-response curves in opiate-tolerant preparations. Maximum opiate effect was unchanged, and responses to exogenous acetylcholine were not affected by the pretreatment. 3 There was a slight increase in the apparent equilibrium constant for naloxone after morphine pretreatment. 4 Tolerance to opiate effect was not accompanied by a change in the affinity or number of stereospecific binding sites for [3H]-etorphine. Hill plots of [3H]-etorphine binding in both control and morphine pretreated preparations gave slopes close to unity. 5 Most of these results can be explained by the assumption that in tolerant preparations, a certain fractional opiate receptor occupation threshold must be exceeded before opiate effects become apparent. It is suggested that the tissue adapts toward a threshold equivalent to the mean receptor occupancy attained during the period of opiate drug pretreatment.

Acetylcholine↗
PubMed1976

Further characterization of morphine-like peptides (endorphins) from pituitary.

Pituitary peptides with opioid pharmacologic action (endorphins) can exist in several forms with different basicities and molecular weights from about 3000 to less than 1000 daltons. Partial purification yielded an endorphin at least 4 times more potent than normorphine and 16 times more potent than the endogenous brain pentapeptide methionine enkephalin. It is proposed that pituitary endorphin or a similar peptide in brain may be the precursor of brain enkephalin.

Adrenocorticotropic Hormone↗
PubMed1976

Opioid activity of a peptide, beta-lipotropin-(61-91), derived from beta-lipotropin.

The pituitary peptide beta-lipotropin displays essentially no opoid activity in a preparation of guinea pig ileum or in the opiate receptor binding assay. However, a fragment, beta-lipotropin-(61-91), with the enkephalin sequence (Tyr-Gly-Gly-Phe-Met) at its NH2-terminus, has typical opioid effects in these two assays.

Amino Acid Sequence↗