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Biomedical subjects

N Ling

Publications and source records attributed to N Ling.

At least 379 records · Page 21Linked to original sources
PubMed1980

Primary structure of ovine hypothalamic somatostatin-28 and somatostatin-25.

The primary structure of the NH2-terminally extended somatostatins isolated from ovine hypothalamic extracts, one containing 28 residues and the other 25, has been determined. The structure of somatostatin-28 is Ser-Ala-Asn-Ser-Asn-Pro-Ala-Met-Ala-Pro-Arg-Glu-Arg-Lys-Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys-OH; the shorter one, somatostatin-25, has the same sequence as somatostatin-28 except that the first three NH2-terminal residues are deleted. The two peptides as isolated were found to be oxidized at the methionine residue to the methionine sulfoxide. Their structures were established by subjecting the native peptides to direct sequence analysis in a Beckman 890C sequencer and identifying the released phenylthiohydantoin derivatives by high-performance liquid chromatography. Their structures were confirmed by trypsin digestion and isolation of all the tryptic peptides, followed by amino acid analysis of the tryptic fragments. Moreover, some of the tryptic peptides were matched with their respective synthetic replicates on high-performance liquid chromatography.

Amino Acid Sequence↗
PubMed1980

Locomotor activation induced by infusion of endorphins into the ventral tegmental area: evidence for opiate-dopamine interactions.

beta-Endorphin in nanomole quantities produced a stimulation of locomotor activity when infused into the region of the dopamine cell bodies of the ventral tegmental area (VTA) in rats. alpha-, gamma-, and des-Tyr-gamma-endorphin produced similar effects, but the D-alanine analogues of alpha and gamma-endorphin produced a larger and longer-lasting activation, presumably reflecting their resistance to degradation. This locomotor activation was reversible by pretreatment with naloxone and by destruction of the terminal projections of the mesocorticolimbic dopamine system originating in the VTA. These results demonstrate that locally infused endorphin can interact with the opioid receptors in the VTA, and they suggest a means by which endorphins activate limbic excitability.

Animals↗
PubMed1980

Purification of peptides: an efficient procedure for the separation of peptides from amino acids and salt.

A novel method for the separation of peptides from amino acids and salts has been developed. Separation is achieved by passage of the sample through a column of octadecasilyl-silica (ODS). Peptides, but not amino acids and salts, are strongly retained by ODS in an aqueous mobile phase and can be recovered by elution with an aqueous-alcoholic mobile phase. The method is applicable to most peptides and is fast and simple. Moreover, it is characterized by good recovery yields and high sample capacity.

Amino Acids↗
PubMed1980

Isolation and characterization of rat pancreatic somatostatin.

A peptide representing the major form of somatostatin-like immunoreactivity was isolated from 600 rat pancreata by using anti-somatostatin affinity chromatography, gel permeation chromatography and reverse-phase high-performance liquid chromatography (HPLC). The isolated peptide elutes with the same retention time as synthetic somatostatin-14 in isocratic HPLC and its amino acid composition is in agreement with that of the tetradecapeptide. We propose that the structure of the major rat pancreatic somatostatin is identical to that of somatostatin-14 characterized in other species.

Amino Acids↗
PubMed1979

Opioid peptides excite pyramidal neurons and evoke epileptiform activity in hippocampal transplants in oculo.

The effect of opiate peptide administration on the electrical activity of intraocular hippocampal transplants was studied. Similar to observations in situ, the administration of beta-endorphin or methionine enkephalin produces a concentration-dependent increase in the firing rate of identified pyramidal neurons within hippocampal formation transplants. In addition, these peptides elicit a profound increase in 'EEG' amplitude, which ultimately develops into epileptiform activity. The ability of naloxone to either reverse or prevent the peptide-induced changes in both single unit and EEG activity supports the hypothesis that the excitatory response of the hippocampus to opioid peptides is mediated via an opiate receptor. The results of this study also suggest that the excitatory response to the opiate peptides in hippocampus is the result of alterations in intrinsic neuronal circuitry and is not dependent upon extra-hippocampal afferents.

Animals↗
PubMed1979

Opioid activities of fragments of beta-endorphin and of its leucine65-analogue. Comparison of the binding properties of methionine- and leucine-enkephalin.

For characterisation in vitro, four parallel assays were used: the guinea-pig ileum and mouse vas deferens as pharmacological models at 36 degrees C and the inhibition of binding of [3H]-naltrexone, [3H]-leucine-enkephalin and [3H]-methione-enkephalin at 0 degrees C. The Leu65-analogue of beta-andorphin and its fragments (61-65, 61-76 and 61-77) have a lower affinity to the [3H]-naltrexone binding site of mu-receptors than the corresponding Met65-peptides wereheas no such difference was found for the [3H]leucine-enkephalin binding sites or delta-receptors. When the binding of [3H]-methionine-enkephalin or [3H]-leucine-enkephalin was inhibited by cold ligands interacting with delta-, mu-, or kappa-receptors, no evidence was obtained for more than one type of delta-binding site.

Animals↗
PubMed1979

The influence of electro-acupuncture on naloxone-induced morphine withdrawal. II. Elevation of immunoassayable beta-endorphin activity in the brain but not the blood.

The effect of electro-acupuncture in the treatment of naloxone precipitated morphine withdrawal in mice was studied. Thirty minutes of acupuncture was enough to suppress withdrawal behaviors by more than 60%. Concomitant to the decrease of withdrawal behavior, there was a significant increase of brain beta-endorphin level in the acupunctured animals. Plasma beta-endorphin level of the treated and untreated group was not significantly different.

Acupuncture Therapy↗
PubMed1978

beta-Endorphin induces nonconvulsive limbic seizures.

The endogenous opioid peptide, beta-endorphin, induces nonconvulsive limbic epileptiform activity when administered intraventricularly to rats. Epileptiform activity is elicited by beta-endorphin in doses that are devoid of analgesic or behavioral signs. Equimolar intraventricular doses of morphine or of the enkephalin analog [DAIa2,Met5]enkephalin-NH2 fail to elicit this limbic epileptiform activity. These observations, together with the recent immunohistochemical localization of beta-endorphin to midline limbic structures, suggest that beta-endorphin may have an important role in the regulation of limbic excitability.

Animals↗
PubMed1978

Neurons containing beta-endorphin in rat brain exist separately from those containing enkephalin: immunocytochemical studies.

Well-characterized antisera to porcine beta-endorphin were used to localize immunoreactive sites in cryostat sections of formaldehyde-fixed rat brain by indirect immunohistochemistry. Specificity was established by absorption of immune sera with synthetic peptide fragments. Specific immunoreactivity was localized to neuronal perikarya in the basal tuberal hypothalamus, and to varicose nerve fibers which were distributed to midline nuclear areas throughout the diencephalon and anterior pons. These patterns of reactivity were unaffected by preabsorption of the immune sera with millimolar concentrations of Met5- or Leu5-enkephalin or alpha-endorphin. The beta-endorphin immunoreactive structures were morphologically separate from those cells and fibers reported to react with antisera to the enkephalins. One anti-beta-endorphin serum gave additional immunoreactivity with myelinated axons in limbic cortical zones; when absorbed with purified rat myelin basic protein, only the specific patterns of immunoreactivity remained. Thus, discrete beta-endorphin-containing neuronal circuits exist in rat brain and are anatomically distinguishable from enkephalin-containing nerve cell and fiber pathways.

Animals↗
PubMed1978

In vitro release of [5-methionine]enkephalin and [5-leucine]-enkephalin from the rat globus pallidus.

Endogenous [5-methionine]enkephalin (Metenkephalin) and [5-leucine]enkephalin (Leu-enkephalin) are released from perfused slices of rat globus pallidus by increased K(+) in a Ca(2+)-dependent manner. Tissue perfused for 40 min contained only 26% of the Met-enkephalin and 44% of the Leu-enkephalin found in the freshly dissected tissue. After perfusion, the mean (+/-SEM) ratio (wt/wt) of Met-enkephalin to Leu-enkephalin was 3.4 +/- 0.2 compared with 5.8 +/- 0.2 in the fresh tissue. The degradation of trace amounts of synthetic [(3)H]enkephalins in the perfusing medium during stimulated release seems to reflect the accelerated degradation of enkephalin released from the tissue: 63% of the Met-enkephalin and 23% of the Leu-enkephalin were degraded in a medium containing bacitracin (30 mug/ml). The mean ratio (wt/wt) of the Met-enkephalin to the Leu-enkephalin recovered after release by exposure of slices to 50 mM K(+) was 2.7 +/- 0.3. When perfusates were corrected for degradation, this ratio increased to about 5.5 which is higher than that found in the perfused tissue. The differences in release, tissue loss, and catabolism of the two enkephalins may be reflecting differences in the metabolic systems operating on the pentapeptides, but this interpretation will have to be validated by in vivo release experiments. In any event these observations strongly suggest that both enkephalins can be considered candidate neurotransmitters in the rat globus pallidus.

Animals↗
PubMed1978

Immunoreactive endorphins, lipotropins and corticotropins in a human nonpituitary tumor: evidence for a common precursor.

The immunoreactive (RIA), ACTH, LPH, alpha endorphin (alpha End) and beta End in an extract of a human pancreatic islet cell carcinoma causing the ectopic ACTH syndrome were assayed after gel exclusion chromatography. In addition to "big", "intermediate" and "little" ACTHs, beta lipotropin (beta LPH) and gamma LPH, the eluate fractions contained RIA-alpha End and -beta End. The major RIA-beta End component appeared to be h beta LPH, which has beta End as its carboxy-terminus, but significant concentrations of a component that coeluted with synthetic p beta End were also found. Small amounts of RIA-alpha End were found in two peaks, one that may have represented 1-76 h beta LPH, with alpha End as its carboxy-terminus, and one probably representing alpha End itself. RIA-ACTH, -LPH and -beta End were found in the void volume fractions. Thus, a human nonpituitary tumor that produced ACTH and LPHs also produced endorphins, all perhaps deriving from a common precursor.

Adenoma, Islet Cell↗