Biomedical subjects
B M Cox
Publications and source records attributed to B M Cox.
Reduction of opioid binding in neuroblastoma x glioma cells grown in medium containing unsaturated fatty acids.
Neuroblastoma x glioma cells NG108-15 were cultured in lipid-free medium supplemented with fatty acids of various chain length and unsaturation. Binding of 3H-labelled [DAla2]-[DLeu5]-enkephalin by membranes of cells grown in saturation fatty acids of different chain length was not significantly different from that of the control On the other hand, a proportional decrease of binding capacity with no change in residual receptor affinity was noticed when cells were cultured in medium containing fatty acids of increasing unsaturation. This decrease was time dependent and reached a maximum at about 48 h. Binding of [3H]dihydromorphine and [3H]naloxone was similarly affected. In contrast, when membranes of cells grown in normal medium were preincubated up to 3 h with unsaturated fatty acid and tested for opioid binding, no significant reduction was observed. Examination of the fatty acid composition of phospholipid from cells grown in linolenate indicated that a significant alteration of the acyl composition has occurred. To evaluate the underlying cause of this type of inhibition, the effect of linolenic acid on cell growth and protein synthesis was examined. When cells were cultured in 100 microM of this fatty acid, both growth and protein synthesis were retarded by 28% and 19%, respectively. Since opiate receptors are proteineous in nature, a reduction of protein synthesis may partially account for the loss of opioid binding activity. On the other hand, an increase of membrane fluidity is known to affect a number of cellular functions, including ligand-receptor recognition. Whether this can offer a satisfactory explanation for our observations remains to be established.
Dynorphin immunoreactivity in pituitary.
Tissue ir-dynorphin has been shown to be associated with three components separable by gel filtration. Similar components were found in both pituitary and brain, although there are differences in the relative amounts of each component in each tissue. Anterior lobe of rat pituitary contains predominantly the component with highest apparent molecular weight, while the component with smallest apparent molecular weight, which is the major form in neurointermediate lobe, was absent. Exposure of rats to NaCl resulted in a parallel depletion of ir-dynorphin and ir-[Arg]-vasopressin neurointermediate lobe stores. Thus a role for dynorphin, acting in concert with vasopressin, or in the regulation of vasopressin release, appears possible.
Synthesis and anticholinergic properties of the enantiomers of 4-(isopropylamino)-2-(2-pyridyl)-2-phenylbutyramide, the mono-N-dealkylated metabolite of disopyramide.
The 2R and 2S enantiomers of 4-isopropyl-2-(2-pyridyl)-2-phenylbutyramide [(2R)-2 and (2S)-2] were prepared from the respective 2R and 2S enantiomers of disopyramide [(2R)-1 and (2S)-1] by oxidation with peracid, Cope elimination, and subsequent zinc/HCl reduction of the resulting hydroxylamines (2R)-3 and (2S)-3. The enantiomers were tested as antagonists to the contraction of guinea pig ileum longitudinal muscle produced in response to electrically stimulated release of acetylcholine. The enantiomers showed IC50 values of 5.0 X 10(-6) and 14 X 10(-6) M for (2S)-2 and (2R)-2 respectively, about a 3-fold difference between enantiomers. Data are presented showing direct antagonism of acetylcholine in the guinea pig ileum assay. In a comparison of the anticholinergic effects of 2 and 1, the metabolite (2) was slightly less potent than disopyramide (1).
Immunoreactive dynorphin in mammalian spinal cord and dorsal root ganglia.
The distribution of immunoreactive dynorphin (ir-dynorphin) has been determined in dorsal and ventral aspects of spinal cord and in dorsal root ganglia of rabbit and rat. Concentrations are highest in dorsal root, with intermediate levels in ventral cord and low levels in dorsal root ganglia of both species. Levels of ir-dynorphin are relatively uniform over examined segments (vertebrae C2-S3) of rabbit spinal cord and dorsal root ganglia. Gel permeation chromatography of extracts from rabbit dorsal and ventral spinal cord and dorsal root ganglia revealed at least three immunoreactive components of differing molecular size in all three structures. Multiple unilateral or bilateral dorsal rhizotomy (vertebrae C5-T1) in rat did not affect levels of ir-dynorphin in spinal cord. As reported [Goldstein, A. & Ghazarossian, V. E. (1980) Proc. Natl. Acad. Sci. USA 77, 6207-6210], midthoracic spinal transection was without effect. Within the spinal cord, the neuropeptide appears, most probably, to be contained in short-axoned neurons. We surmise that this potent opioid peptide may participate in the processing of sensory information in spinal cord.
Diurnal rhythm of plasma immunoreactive beta-endorphin and its relationship to sleep stages and plasma rhythms of cortisol and prolactin.
To determine the diurnal rhythm of plasma beta-endorphin (beta-End), 10 healthy male volunteers between the ages of 20 and 32 yr were studied in a sleep laboratory setting for a 24-h period. Blood samples were taken through an indwelling catheter at 0800, 1000, 1400, 1800, 2200, 2300, and 2400 h and then half-hourly until 0730 h, and they were then assayed for total beta-End-like immunoreactivity (ir beta-End), PRL, and cortisol. Subjects were habituated by spending the night before the study in the sleep laboratory with an indwelling catheter and electrodes for sleep recording in place. There was a clear diurnal variation of ir beta-End, with lowest levels between 2200 and 0330 h and highest levels between 0400 and 1000 h. There was no evidence for direct entrainment with sleep stage. There was a close correlation with cortisol levels, suggesting a similar secretory pattern for beta-End and PRL in only 5 of the subjects. Because the beta-End antiserum used has a cross-reactivity of 30% with beta-lipotropin gel permeation chromatography was done on extracts of plasma taken at 1400, 2400, 0400, and 0730 h for each subject. The peak in the beta-End elution position showed a clear diurnal variation similar to that of ir beta-End.
Levels of immunoreactive dynorphin in brain and pituitary of Brattleboro rats.
The very potent opioid peptide, dynorphin, has recently been shown by radioimmunoassay and immunocytochemical techniques to be selectively concentrated in the pars nervosa of pituitary, suggesting a possible association of dynorphin with the neurohypophyseal hormones, vasopressin and oxytocin. In this study, we report that pituitary and brain contents of immunoreactive dynorphin in homozygote Brattleboro rats (unable to synthesize vasopressin) are similar to those in heterozygote animals and in normal Long-Evans rats. Thus, the syntheses of immunoreactive dynorphin and vasopressin in the hypothalamo-hypophyseal tract appear to be independently regulated.
Comparative anticholinergic potencies of R- and S- disopyramide in longitudinal muscle strips from guinea pig ileum.
Explore the source record for details and available documents.
Ascorbate decreases ligand binding to neurotransmitter receptors.
Explore the source record for details and available documents.
The use of ascorbate as a probe of opioid receptor structure: evidence for two independent mechanisms of receptor destruction by ascorbate.
Ascorbate (20mM) pretreatment of brain membrane suspensions at 37 degrees produced a rapid irreversible loss of specific opioid binding. There was no reduction in specific 3H-halo-peridol binding. Ascorbate induced loss of opioid binding under these experimental conditions was not blocked by low concentrations of EDTA or MN++. In contrast, the slowly developing loss of opioid binding during exposure to 1 mM ascorbate at 23 degrees was completely inhibited by 10(-5)M EDTA or Mn++. At 37 degrees, D-isoascorbate, and several other reducing agents (glutathione, dithiothreitol, cysteine) produced a loss of opioid binding similar to that seen with ascorbate. It is concluded that 1 mM ascorbate at 23 degrees, and 20 mM ascorbate at 37 degrees, destroy opioid binding sites by two independent mechanisms. Lipid peroxidation is implicated at low ascorbate concentrations; a reductive process appears to be responsible for the ascorbate induced loss of binding at higher concentrations.
Opioid binding properties of brain and peripheral tissues: evidence for heterogeneity in opioid ligand binding sites.
Explore the source record for details and available documents.
Characteristics of peptide and alkaloid opiate binding sites in brain and peripheral tissues.
Explore the source record for details and available documents.
Characteristics of the increased response to electrical stimulation of ileum preparations from morphine pretreated guinea pigs.
Explore the source record for details and available documents.
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.
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.
Stereospecific opiate binding in bovine adrenal medulla.
Explore the source record for details and available documents.
Ascorbate destruction of opiate stereospecific binding in guinea pig brain homogenate.
Explore the source record for details and available documents.
Rapid purification of beta-endorphin by high-performance liquid chromatography.
Explore the source record for details and available documents.