Forms of goal-directed behavior as affected by induced changes in the level of endogenous beta-endorphin in rats

Marked alterations in feeding and defense behaviour and motor activity partly resembling the effects of exogenous beta-endorphin administration were demonstrated in the experiments on rats. These alterations were observed after immunization with beta-endorphin--bovine serum albumin conjugate (two subcutaneous injections at a 7-day interval at a dose of 75 micrograms, 1 mole BSA/6 moles beta-endorphin mixed with complete Freund's adjuvant). A decrease in beta-endorphin content in some brain structures was noted. Unlike control animals, the immunized rats revealed within 3-4 weeks an increase in food intake without any rise in body weight and practically no response to handling.     

Increase of beta-endorphin serum levels by human corticotropin-releasing factor does not affect beta-cell function in normal-weight men

Numerous studies have shown a rise of blood sugar concentrations and serum levels of pancreatic polypeptides after pharmacological doses of beta-endorphin. We tested the yet unknown influence of physiological fluctuations in beta-endorphin serum levels on glucose homeostasis by stimulating the pituitary secretion with CRF. 100 micrograms of human CRF or saline solution were intravenously injected in ten healthy male subjects at least one week apart. beta-endorphin serum levels rose significantly after the injection of CRF, but there was no change in blood sugar concentrations or serum levels of glucagon or insulin at all. We conclude that only a pharmacological dose of beta-endorphin influences glucose homeostasis.     

Effects of nomegestrol acetate administration on central and peripheral beta-endorphin and allopregnanolone in ovx rats

The aim of this study was to investigate the effects of nomegestrol acetate (NOMAc) on the central nervous system by analyzing the neurosteroid allopregnanolone and the opioid beta-endorphin (beta-endorphin). 104 Wistar female rats were used in this study; one group of fertile and one group of ovariectomized rats were used as control. The others were ovariectomized and they underwent a 2-week oral treatment of NOMAc (0.05, 0.1, 0.2, 0.5, 1mg/kg/day), alone or with 0.05 mg/kg/day of estradiol valerate (E2V). Allopregnanolone and beta-endorphin were assessed in different brain areas and in circulation. Ovariectomy decreased allopregnanolone anywhere except in the adrenal gland and E2V reversed the effects of ovariectomy. 0.5 and 1mg/kg/day of NOMAc increased allopregnanolone levels in hippocampus. Combined administration of 1mg/kg/day of NOMAc plus E2V induced a further increase of allopregnanolone levels in hippocampus, hypothalamus, and anterior pituitary. NOMAc (1mg/kg/day) decreased the adrenal content of allopregnanolone, both by itself and associated with E2V. NOMAc increased hippocampal and hypothalamic content of beta-endorphin at the highest doses, and it increased positively E2V action, at 1mg/kg/day, also in anterior pituitary and plasma. These findings reinforce the clinical data regarding the capability of NOMAc to modulate the pathways involved in mood and behaviour. In fact, due to the NOMAc action on hippocampus, hypothalamus, and anterior pituitary, our results highlight the selectivity of NOMAc on part of the limbic system and the anterior pituitary, regarding both allopregnanolone and beta-endorphin.     

Conformational studies of sequential polypeptides containing l-β-3,4-dihydroxyphenyl-α-alanine (DOPA) and l-glutamic acid

The conformations of random and sequential copolypeptides containing l-β-3,4-dihydroxyphenyl-α-alanine (DOPA) and l-glutamic acid (Glu) as well as their protected precursors have been investigated mainly by means of circular dichroism (c.d.) spectroscopy in chloroform or trimethylphosphate as solvent. Protected and deprotected DOPA-containing polypeptides showed a positive ellipticity hand at 285 nm due to the stacked side-chains. The c.d. behaviour depended on the amino acid sequence as well as the amino acid composition. In random copolypeptides, ellipticities versus DOPA content showed a smooth variation, without any sharp changes. This supported the conclusion that poly(DOPA) is a right-handed helix. Although the ellipticities were low compared with the values of a typical α-helix, deprotected DOPA-containing sequential polypeptides are helical from the results of the induced dichroic band at 285 nm and the infrared amide I and II absorption bands. The results obtained were compared with those of sequential polypeptides containing l-tyrosine and l-Glu.     

Interleukin 1 potentiates agonist-induced secretion of beta-endorphin in anterior pituitary cells

Interleukin 1 (IL-1) has been shown to potentiate the release of beta-endorphin induced by secretagogues, including corticotropin releasing factor (CRF) and phorbol ester (TPA), in the mouse AtT-20 pituitary tumor cell line (Fagarasan et al., PNAS, 1989, 86, 2070-2073). In cultured rat anterior pituitary cells, pretreatment with IL-1 caused only a small increase in beta-endorphin release but significantly potentiated CRF-and vasopressin-stimulated beta-endorphin secretion. Vasopressin stimulates the secretion of beta-endorphin in normal pituitary cells but not in AtT-20 cells. However, treatment of AtT-20 cells with IL-1 induced the expression of vasopressin-mediated beta-endorphin release; this effect of IL-1 was reduced after depletion of protein kinase C by prolonged treatment with TPA. The enhancement of CRF-stimulated beta-endorphin release by IL-1 was also reduced in AtT-20 cells after depletion of protein kinase C, and after treatment with staurosporine. These findings indicate that treatment with IL-1 amplifies receptor-mediated responses to the major physiological secretagogues in normal corticotrophs, and initiates a secretory response to vasopressin in AtT-20 cells.     

Discordances in the temporal pattern of the ACTH/beta-endorphin releasing effects of synthetic CRFs and partially purified bovine CRF in a superfusion system

Temporal characteristics of ACTH and beta-endorphin secretion induced by bovine hypothalamic CRF-A (void volume) and CRF-B (Kav = 0.583) separated by Sephadex G-100 were compared to those of synthetic ovine or rat CRF, sauvagine and vasopressin. Dispersed cells or minced fragments of rat adenohypophyses perifused in a column were exposed to various secretagogues, and ACTH and/or beta-endorphin concentrations of the effluent were measured by radioimmunoassays. CRF-A or CRF-B induced an immediate brisk rise of ACTH and beta-endorphin within 1 min after initiation of CRF perifusion. The maximum rate of ACTH or beta-endorphin secretion was reached 1-2 min later. Hormone secretion persisted throughout a 10-min exposure to these secretagogues. More than 80% of the total ACTH or beta-endorphin secretion induced by 10-min perifusion with bovine CRF occurred during exposure to CRF. With 10-min perifusion with 300 ng/ml ovine or rat CRF, the onset of the major CRF-stimulated ACTH or beta-endorphin secretion was markedly delayed compared to that following bovine CRF. During perifusion with ovine or rat CRF, a modest slow increase in ACTH or beta-endorphin secretion was observed. More than 60-70% of the total ACTH or beta-endorphin secretion induced by 10-min perifusion with rat or ovine CRF occurred after CRF withdrawal. The ACTH secretory patterns for sauvagine were very similar to those for synthetic rat or ovine CRF. These results suggest some qualitative differences between partially purified bovine CRF and synthetic ovine or rat CRF.     

Analysis of the nuclear envelope polypeptides by isoelectric focusing and electrophoresis

The more insoluble polypeptides of the avian erythrocyte nuclear envelope have been characterized by a two-dimensional electrophoretic procedure. Most of the polypeptides occur in two classes with isoelectric points of approximately 6.4 and 5.7 respectively. The more acidic class contains two polypeptides, P71 and one which contributes to an electrophoretic band previously identified as P55. The more basic class includes P75, P68, P61 and two or more polypeptides from the P55 band. There are four to six isoelectric point variants of each polypeptide in the more basic class, and the relative stain intensities for the variants are similar for the different polypeptides. These similarities in ionic properties suggest a chemical relationship between the polypeptides. These results are discussed in relation to the in vitro conversion of P75 to polypeptides of the same molecular weight as P68, P61 and P55.     

The stimulatory effect of beta-endorphin on the plasma prolactin levels was diminished in the rats treated with 6-hydroxydopamine

Intraventicular injection of beta-endorphin (beta LPH_61^?91) in urethane anesthetized male rats led to a dose dependent increase of plasma prolactin levels. Intravenous injection of apomorphine completely abolished the stimulatory effect of beta-endorphin. Animals treated with 6-hydroxydopamine (6-OHDA) and 6-OHDA plus desmethylimipramine showed inhibition of beta-endorphin induced prolactin release. These results suggest that beta-endorphin presynaptically inhibits the activity of dopaminergic neurones, leading to the stimulation of plasma prolactin levels.     

Secreted heat shock proteins in sunflower suspension cell cultures

Sunflower suspension cell cultures were subjected to different heat treatments and the electrophoretic patterns of heat-induced endocellular and secreted proteins were analyzed. In response to heat shock (3 h at 40°C), sunflower cells synthesized new polypeptides and secreted them into the medium, while the synthesis of other polypeptides was suppressed. Two major polypeptides of about 50 and 32 kDa were strongly induced. The two-dimensional electrophoretic analysis showed that the 32-kDa band is composed of at least four different polypeptides. Western blotting hybridizations of secreted proteins with various lectins were performed. The 32-kDa band gave a positive signal with concanavalin A. Received: 8 March 1996 / Revision received: 30 September 1996 / Accepted: 15 October 1996     

Restriction of placental growth in sheep enhances placental metabolism of fetal beta-endorphin-like immunoreactivity

The opioid polypeptide beta-endorphin is present in fetal blood but it is not clear whether its source is the fetus or the placenta. We therefore measured beta-endorphin in extracts of fetal femoral arterial and umbilical venous blood plasma in sheep by radioimmunoassay to determine whether the fetus or the placenta is the major source of beta-endorphin in the fetal circulation. Chromatographic analysis of extracts of fetal arterial plasma showed that beta-lipotropin and other precursors of beta-endorphin made only a minor contribution to the immunoreactivity detected. Concentrations of immunoreactive beta-endorphin were higher in the femoral artery than in the umbilical vein in fetal sheep between 113 and 128 days of pregnancy. Therefore the placenta removes beta-endorphin or a closely related polypeptide of fetal origin from the umbilical circulation in sheep at this stage of gestation. Acute hypoxaemia and hypoglycaemia increase the concentrations of immunoassayable beta-endorphin in blood plasma of adult and fetal sheep, but little is known about the effects of chronic hypoxaemia or hypoglycaemia on the circulating levels of beta-endorphin and related polypeptides in the fetus. Therefore we also measured immunoreactive beta-endorphin in blood plasma from fetal sheep in which growth retardation in association with restricted placental growth was produced by removal of endometrial caruncles before mating. Intra-uterine growth retardation was accompanied by chronic hypoglycaemia and chronic hypoxaemia in the fetuses. This was not associated with higher concentrations of beta-endorphin-like immunoreactivity in fetal arterial or umbilical venous plasma, but was accompanied by significantly increased placental extraction of fetal immunoreactive beta-endorphin from the umbilical circulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regulation of cellular alpha-MSH and beta-endorphin during stimulated secretion from intermediate pituitary cells: involvement of aspartyl and cysteine proteases in the control of cellular levels of alpha-MSH and beta-endorphin

The regulation of cellular levels of alpha-melanocyte stimulating factor (alpha-MSH) and beta-endorphin in response to stimulated secretion from intermediate pituitary cells in primary culture was investigated in this study. Regulation of the cell content of alpha-MSH and beta-endorphin occurred in two phases consisting of (a) initial depletion of cellular levels of these peptide hormones during short-term secretion (3 h) induced by isoproterenol, forskolin, or phorbol myristate acetate (PMA) which was followed by (b) long-term (24 h) increases in cellular levels of alpha-MSH and beta-endorphin in response to stimulated secretion induced by isoproterenol and PMA. In short-term experiments (3 h), cellular levels of alpha-MSH and beta-endorphin were reduced by 30-50% during stimulated secretion of these peptide hormones by isoproterenol (agonist for the beta-adrenergic receptor), forskolin that activates protein kinase A (PKA), and PMA that activates protein kinase C (PKC). Moreover, dopamine inhibited isoproterenol-induced depletion of cellular alpha-MSH and beta-endorphin. During long-term incubation of cells (24 h) with isoproterenol, cellular alpha-MSH and beta-endorphin were increased to twice that of controls (unstimulated cells). Treatment with PMA for 24 h also increased cellular levels of alpha-MSH and beta-endorphin. Moreover, cellular levels of alpha-MSH and beta-endorphin were decreased during long-term treatment of cells with an aspartyl protease inhibitor, pepstatin A, and with the cysteine protease inhibitor E64c. These results implicate aspartyl and cysteine proteases in the cellular production of alpha-MSH and beta-endorphin that requires proteolytic processing of their common precursor proopiomelanocortin (POMC). These findings demonstrate the parallel regulation of cellular levels of alpha-MSH and beta-endorphin during their cosecretion, which may involve aspartyl and cysteine proteases in the metabolism of these peptide hormones.     

Effects of dynorphin A(1-13) and of fragments of beta-endorphin on blood pressure and heart rate of anesthetized rats.

The effect on blood pressure and heart rate of central administration of dynorphin A(1-13) and of beta-, gamma-, and alpha-endorphin related peptides was studied in urethane-anesthetized rats. Intracerebroventricular (i.c.v., 0.1-10 micrograms) administration of beta-endorphin resulted in a dose-dependent, naltrexone-reversible hypotension and bradycardia. N-terminally modified fragments of beta-endorphin did not reduce blood pressure and heart rate. On the other hand, a dose of 10 micrograms of beta-endorphin(1-27), which lacks the four C-terminal amino acid residues of beta-endorphin, induced a fall in blood pressure and had a biphasic effect on heart rate. These responses, however, were resistant to pretreatment with naltrexone. None of the fragments of beta-endorphin smaller than beta-endorphin(1-27) affected blood pressure when administered i.c.v. in a dose of 10 micrograms. A small transient bradycardia was observed after i.c.v. administration of 10 micrograms of beta-endorphin(1-26), alpha, and gamma-endorphin. The naltrexone-reversible bradycardic response of alpha- and gamma-endorphin was not present in des-tyrosine- and des-enkephalin-alpha- and gamma-endorphin and also not in alpha-endorphin(10-16) and gamma-endorphin(10-17). Upon i.c.v. administration (0.1-50 micrograms) a dose-dependent, naltrexone-reversible decrease in blood pressure and heart rate was induced by dynorphin A(1-13). The present data indicate a hypotensive influence of beta-endorphin, beta-endorphin(1-27), and dynorphin A(1-13), whereas other fragments of beta-endorphin had little or no effect on the cardiovascular parameters investigated.     

Hypothalamo-pituitary portal blood concentrations of beta-endorphin during suckling in the ewe

Matched hypothalamo-pituitary portal and jugular blood samples were collected over about 6 h from 7 lactating Corriedale ewes penned with their lambs, and a careful record was kept of ewe/lamb behaviour. Hypothalamo-pituitary portal blood concentrations of beta-endorphin were measured by radioimmunoassay and the secretion rates were calculated; these were related to peripheral plasma prolactin and LH concentrations, and the sucking bouts of the lambs. Basal LH concentrations remained less than 1 ng/ml with 0-2 pulses of 1.5-3.5 ng/ml amplitude per 6-h collection period. Prolactin secretion was episodic with individual baselines varying from 24 to 286 ng/ml, and peak concentrations of 50-631 ng/ml. Portal beta-endorphin was secreted in an episodic pattern with individual baseline secretion rates varying from 0.125 to 0.495 ng/min, and peak secretion rates of 0.768 to 3.216 ng/min. A close correlation was seen between sucking bouts and the secretion of portal beta-endorphin and peripheral prolactin; 86% of sucking bouts resulted in a significant release of beta-endorphin, and 46% of sucking bouts resulted in a significant release of prolactin. These results show that hypothalamic beta-endorphin is released in response to the sucking stimulus. This provides support for the hypothesis that, during lactation, beta-endorphin acts within the hypothalamus to reduce GnRH release and hence depress pituitary gonadotrophin secretion.     

The Acrolepiopsis assectella silk cocoon: kairomonal function and chemical characterisation

Two soluble sericin-like polypeptides, B1 and B2, from leek moth (Acrolepiopsis assectella) cocoons trigger host-acceptance behaviour in the parasitoid, Diadromus pulchellus (Proc. Roy. Soc. London B 269 (2002) 1879). We found that these polypeptides were particularly cysteine-rich and lost their ability to trigger host-acceptance behaviour after being denatured and purified. This suggests that inter-disulphide bonds and the secondary structure of B1 and B2 are important for their biological activity. We also isolated six insoluble polypeptides (or polypeptides of low solubility) from A. assectella cocoons. At least four of these polypeptides triggered host-acceptance behaviour. The strongest responses were observed with P22, a light-chain fibroin or a seroin-peptide, and P100, a sericin-like polypeptide that is probably more strongly associated with the silk core than are B1 and B2. In conclusion, several polypeptides from different parts of the A. assectella silk-cocoon (the insoluble core and coating of the silk thread) are able to elicit host-acceptance behaviour in D. pulchellus females. These polypeptides belong to different silk protein families and are used as kairomones by this specialist parasitoid.     

beta-Endorphin-(1-27) inhibits the spinal beta-endorphin-induced release of Met-enkephalin

The effect of intraventricular beta-endorphin-(1-27) on the spinal release of Met-enkephalin induced by intraventricular beta-endorphin was studied using the intrathecal superfusion technique in urethane anesthetized rats. Intraventricular injection of beta-endorphin at a dose of 15 micrograms released Met-enkephalin from the spinal cord. This release of Met-enkephalin induced by beta-endorphin was significantly reduced by beta-endorphin-(1-27), 60 micrograms, injected intraventricularly. Injection of beta-endorphin (1-27) itself did not cause any release of Met-enkephalin. The finding is in line with the previous report that beta-endorphin (1-27) inhibited the analgesia induced by beta-endorphin.     

Early changes in morphology and polypeptide pattern of plastids from watermelon cotyledons induced by benzyladenine or light are very similar

Watermelon ( Citrullus vulgaris Schrad. cv. Fairfax) cotyledons were excised from the embryo and grown in the dark for 4 days. They were then transferred to 10 μm benzyladenine (BA) solution or illuminated with white light. We have compared changes in ultrastructure of the plastids and of their polypeptide pattern induced by the two treatments.
At the end of the 4-day-period in the dark the plastids differentiated to amyloplasts and had few polypeptides: only the two subunits of ribulose bisphosphate carboxylase (RuBP) were clearly observed. Both light and BA induced starch depletion and gratia formation after 12–24 h. BA was less efficient than light in inducing thylakoid formation and more efficient in inducing starch depletion. After 6 h both factors induced the appearance of the same new polypeptides in the 28–53 kDa range. Most prominent among them is a 32 kDa band. Light is much more effective in inducing the formation of a 29 kDa band than is BA. In mature chloroplasts this band stains very strongly, while the 32 kDa band disappears. We suggest that the 29 kDa polypeptide is the light harvesting complex (LHC), since a purified LHC preparation from cotyledons grown either on water in light or on BA in the dark migrates on the polyacrylamide gel as a single 29 kDa band.     

MAP 4: occurrence in mouse tissues

A polyclonal antiserum to a microtubule-associated protein (MAP) from mouse neuroblastoma cells (MAP 4) was used to examine the distribution of this protein in mouse tissues. Immunoblots of neuroblastoma cell microtubule protein preparations demonstrated that the antiserum reacted with a triplet of proteins at 215,000-240,000 mol wt. Antibodies affinity purified from any of the bands showed cross- reaction with the other bands, indicating these polypeptides were all immunologically related. Antibodies specific to MAP 4 decorated microtubules in cultured murine cells fixed with glutaraldehyde, and diffuse staining was seen following treatment of cells with nocodazole. The antiserum reacted with MAP 4 in extracts of brain, heart, liver, and lung from adult mouse; the triplet in brain was more closely spaced than in the other tissues or neuroblastoma cells. In kidney, spleen, and stomach, only a single band (band 4) was labeled; this band was immunologically related to the triplet and was also present in all tissues positive for the triplet. Skeletal muscle, sperm, and peripheral blood contained no reactive polypeptides. After taxol- induced polymerization, the MAP 4 triplet was preferentially associated with the microtubule pellet whereas band 4 remained in the supernatant. These data indicate that there is tissue specificity in the distribution of MAP 4, and that some tissues contain a polypeptide related to MAP 4 (band 4) that does not bind to microtubules in vitro.     

Plasma levels of beta-endorphin, prolactin and gonadotropins in male athletes after an international nordic ski race

Plasma beta-endorphin, prolactin (PRL), FSH and LH were measured in 17 volunteer male subjects at rest and under the stress caused by a long-distance nordic ski race. The race induced increased levels of beta-endorphin and PRL in all skiers. The changes in PRL with exercise were significantly related to the changes in beta-endorphin (r = 0.69, p less than 0.001). Furthermore, the highly trained skiers training over 150 km.week-1 of nordic ski showed consistently higher post-exercise beta-endorphin and PRL levels than the moderately trained skiers who trained for 20 km.week-1. In addition the race induced slight falls in FSH and LH; however plasma gonadotropin levels did not show any correlation with plasma beta-endorphin concentrations and did not differ between the two groups of skiers. These results suggest that endogenous opioid peptides may modulate PRL secretion in heavy exercise, since they are of minor importance in the release of FSH and LH in such a situation. The observations also suggest that the degree of previous training and the exercise intensity do seem to be responsible for the hormonal changes.     

Bile protein secretion in the rat stimulated by taurocholate: effect of chloroquine

The biliary protein excretion during sodium taurocholate induced choleresis was studied in normal rats and in rats treated with the lysosomotropic agent, chloroquine. The analysis of the protein component in bile was made on SDS-polyacrilamide gel, and the individual polypeptides were quantitated by densitometry. The excretion of bile polypeptides was compared with that of lysosomal acid phosphatase. The biliary excretion of polypeptides of molecular mass lower than and equal to 54 kDa was markedly stimulated by taurocholate-induced choleresis. Chloroquine treatment of rats diminished the biliary excretion of such polypeptides and also inhibited their excretion induced by taurocholate. The behaviour of these polypeptides was well correlated to that of the lysosomal marker. The biliary excretion of polypeptide bands of a higher molecular mass (up to 140 kDa) did not show major changes during taurocholate-induced choleresis in any of the groups. The results indicate that biliary excretion of proteins in the rat may be either stimulated by taurocholate or may be independent of the bile salt. The former requires the functional integrity of chloroquine-sensitive hepatocyte compartments, which may involve the lysosomes.     

Polypeptides of Acrolepiopsis assectella cocoon (Lepidoptera: Yponomeutoidea): an external host-acceptance kairomone for the parasitoid Diadromus pulchellus (Hymenoptera: Ichneumonidae)

Contact kairomones are essential for host-acceptance behaviour by female parasitoids. In the solitary endoparasitoid wasp, Diadromus pulchellus, this behaviour depends mainly on compound(s) in the cocoon of their host, Acrolepiopsis assectella pupae. Extracts of empty cocoons and polypeptides extracted from cocoons were tested in acceptance behaviour assays using cotton fibre lures bearing extracts. Extractions with solvents of increasing polarity indicated that the active compounds were polar, while SDS-PAGE showed that four glycopolypeptides contained enough information to trigger host-acceptance behaviour in female wasps. This kairomonal activity was found to be due to the protein moieties, and was independent of any glycosylation. These four glycopolypeptides might be two variants of two soluble sericin-like polypeptides differing in their degree of glycosylation.