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Biomedical subjects

H Akil

Publications and source records attributed to H Akil.

At least 217 records · Page 12Linked to original sources
PubMed1986

Further characterization of the extra-arcuate alpha-melanocyte stimulating hormone-like material in hypothalamus: biochemical and anatomical studies.

Previous studies had shown the existence of an extra-arcuate cell group in lateral hypothalamus which contains alpha-melanocyte stimulating hormone (a-MSH)-like immunoreactivity, but no other pro-opiomelanocortin (POMC) immunoreactivity. The question we have attempted to address in this series of studies is whether the material is indeed a-MSH or a cross-reacting material. Chromatographic studies failed to detect any material which is different from a-MSH or des-acetyl-a-MSH, suggesting that either the material is authentic a-MSH/des-acetyl-a-MSH, or that it is not detected by our RIAs. A series of manipulations including dissections of arcuate vs. extra-arcuate hypothalamic areas, treatment with colchicine, lesions with monosodium glutamate and knife cuts were aimed at isolating the extra-arcuate region and showing that it contains an excess of a-MSH over beta-endorphin (B-END), presumably deriving from the extra-arcuate group. However, all studies showed parallel changes in a-MSH and B-END, suggesting that we were not detecting a non-POMC derived a-MSH in these studies. This led to the tentative conclusion that the material was not a-MSH and was not being detected by our RIA's. This hypothesis was tested by further characterizing the material immunohistochemically. These studies led to the conclusion that the extra-arcuate material had a carboxy-terminal homology with a-MSH but differed from it in the midregion, since antisera directed at the 4-10 region of a-MSH failed to stain this non-POMC cell group. Finally, the anatomy of this extra-arcuate group is described, particularly the projections to the striatum, hippocampus, neocortex and olfactory bulb.

Animals↗
PubMed1986

Lateral hypothalamic innervation of the cerebral cortex: immunoreactive staining for a peptide resembling but immunochemically distinct from pituitary/arcuate alpha-melanocyte stimulating hormone.

The combination of retrograde transport of fluorescent dyes and indirect immunofluorescence has been used to study the putative neurotransmitter specificity of the tuberal lateral hypothalamic projection to the cerebral cortex. Injections of either fast blue or diamidino yellow dye into the cerebral cortex or hippocampus retrogradely labeled large, multipolar neurons scattered through the lateral hypothalamic area and zona incerta at the level of the ventromedial nucleus of the hypothalamus. Approximately 80% of these neurons stained immunohistochemically with an antiserum against alpha-melanocyte stimulating hormone (alpha-MSH). A second population of smaller, predominantly bipolar alpha-MSH-like immunoreactive neurons was seen in the arcuate nucleus and retrochiasmatic area, but none of these projected to the cerebral cortex. Immunohistochemical staining for ACTH (18-24), another proopiomelanocortin series peptide, or with an antiserum against alpha-MSH (4-10) demonstrated only the second of these cell groups. Our results indicate that the tuberal lateral hypothalamic projection to the cerebral cortex contains a substance similar but not identical to alpha-MSH, and that this material is probably not derived from the same proopiomelanocortin precursor as true alpha-MSH.

Adrenocorticotropic Hormone↗
PubMed1986

Detection of proopiomelanocortin mRNA by in situ hybridization with an oligonucleotide probe.

Synthetic oligonucleotide probes can be easily obtained and used, in contrast to cDNA cloning to develop probes, and thus the present study was carried out to determine whether such probes could also be useful for in situ hybridization. A 24-base synthetic oligonucleotide complementary to part of the alpha-melanocyte-stimulating hormone (alpha-MSH) coding region of proopiomelanocortin (POMC) mRNA was 5'-end-labeled by using [gamma-32P]ATP with T4 polynucleotide kinase or was 3' tailed by using [alpha-32P]dATP or [3H]dCTP with terminal deoxynucleotidyltransferase. Blot analysis of pituitary poly(A)+ RNA showed that the oligonucleotide hybridized to a single species with a molecular size of approximately 1200 nucleotides, consistent with that determined previously for POMC mRNA. The oligonucleotide, regardless of labeling method, hybridized to cells in the pituitary intermediate lobe, but not in the posterior lobe. Only the 3H-labeled probe gave resolution of individual pituitary anterior lobe cells. The specificity of the hybridization was determined by showing that the intermediate lobe signal was blocked by prehybridization of the tissue with unlabeled alpha-MSH oligonucleotide probe. Furthermore, the hybridized probe exhibited a sharp sigmoid curve when melted off. Finally, the oligonucleotide probe detected, in situ, the haloperidol-induced elevation of intermediate lobe POMC mRNA. Thus, the oligonucleotide probe exhibited hybridization in an anatomically and biochemically specific manner, and it detected a tissue-specific change in mRNA levels in situ.

Animals↗
PubMed1986

Pro-dynorphin is endogenous to the anterior pituitary and is co-localized with LH and FSH in the gonadotrophs.

Pro-dynorphin peptides have been shown to exist in the anterior lobe of the pituitary gland. The dynorphin in the anterior lobe is distinct from that which is co-localized with vasopressin in the magnocellular system in both post-translational processing and regulation of release. Here, we report on the existence of pro-dynorphin mRNA, approximately 2400 nucleotides in length, in the anterior lobe. Furthermore, we present immunocytochemical evidence for the co-existence of dynorphin, LH and FSH in a subset of gonadotrophs. These findings suggest a possible role of pro-dynorphin products in the regulation of the hypothalamic-pituitary-gonadal axis.

Animals↗
PubMed1986

Pretranslational and posttranslational mechanisms for regulating beta-endorphin-adrenocorticotropin of the anterior pituitary lobe.

Stress-induced activation of secretion of ACTH and beta-endorphin (beta-END) from anterior lobe corticotrophs leads to both short term and longer term perturbation of the system. Immediately following an acute stress session, the rate of translation of the ACTH/beta-END precursor proopiomelanocortin appears accelerated by 50% and the rate of conversion of the precursor into products is doubled. These changes appear to take place at the translational and posttranslational level and reflect a better use of the preformed messenger RNA which compensates for the stress-induced peptide depletion. When the animal is subjected daily to the stress session, longer term mechanisms appear to emerge. The ACTH/beta-END stores in the gland are increased, apparently owing to an increase in transcription, as reflected by a small but significant increase in proopiomelanocortin messenger RNA. The posttranslational processing is no longer accelerated after further stress. This longer term mechanism appears to be pretranslational and to supplant the posttranslational mechanisms observed after acute stress. These two levels of control may represent different points in the regulation of this critical peptide system.

Adrenocorticotropic Hormone↗
PubMed1986

Cushing's syndrome secondary to ectopic corticotropin-releasing hormone-adrenocorticotropin secretion.

A 47-yr-old woman with severe Cushing's syndrome had a bronchial carcinoid secreting ACTH and corticotropin-releasing hormone (CRH) and associated pituitary corticotroph hyperplasia. While the clinical picture was consistent with the ectopic ACTH syndrome, the biochemical pattern was that of pituitary ACTH-dependent hypercortisolism. Both plasma ACTH and CRH levels were high. However, while plasma ACTH increased during metyrapone administration and decreased during administration of high dose of dexamethasone, plasma CRH levels did not change, suggesting a direct pituitary response to these testing maneuvers. Immunoperoxidase staining of the tumor tissue confirmed the presence of ACTH and CRH, and the finding of an ACTH and a CRH concentration gradient across the tumor bed indicated that the tumor was actively secreting these two hormones. Cytochemical heterogeneity was seen in the tumor, in which two distinct populations of cells, one secreting ACTH and beta-endorphin and the other secreting CRH, were identified. This patient, thus, had an unusual syndrome of ectopic ACTH and ectopic CRH secretion.

ACTH Syndrome, Ectopic↗
PubMed1986

Anomalous binding of DPDPE as a result of batch variability.

The binding of the delta selective agonist [3H]DPDPE to diencephalic rat brain tissue was examined. Although most material examined gave rise to a single receptor model, one commercial preparation (Amersham, batch 8) suggested a two receptor model. Purification by HPLC removed a minor component and restored a single receptor model to the major component.

Animals↗
PubMed1986

Multiple opioid receptor subtypes in the pituitary-adrenal axis: a cross-species study.

This study examines the multiple opioid receptor subtypes present in the pituitary-adrenal axis of several species using in vitro autoradiography. The monkey neural lobe was found to contain all three subtypes with a preponderance of kappa sites, while the rat and bovine neurohypophyses contained only kappa sites. In the adrenal, opioid receptor sites were found exclusively in the medulla and varied with species. Monkey adrenal contained predominantly delta sites with a relatively small number of kappa sites present, while bovine adrenal medulla had predominantly kappa sites and only a relatively small proportion of delta receptor sites. No specific opioid receptor binding could be detected in the rat adrenal. These results emphasize the importance of species-differences in understanding the role of opioids in neuroendocrine regulation.

Adrenal Glands↗
PubMed1986

Gamma-3-MSH and beta-endorphin in monkey pituitary.

The content and extent of processing of gamma-3-MSH and beta-endorphin were determined in the anterior (AL) and intermediate (IL) lobes of three monkey pituitaries. The peptides existed in equimolar amounts in each lobe. The processing of gamma-3-MSH paralleled that of beta-endorphin in each lobe; the primary products in AL were beta-lipotropin and a 9K form of gamma MSH, whereas in IL the predominant products were N-acetyl-beta-endorphin and gamma-3-MSH.

Animals↗
PubMed1986

Characterization of proopiomelanocortin mRNA detected by in situ hybridization.

In situ hybridization is a method for detecting specific nucleotide sequences by using a labeled complementary nucleic acid probe. We have characterized in situ hybridization in rat pituitary using a cDNA probe directed against a portion of proopiomelanocortin (POMC) mRNA to show its specificity in tissue sections. This characterization includes the size of the target mRNA from tissue processed for in situ hybridization, the dissociation pattern of the cDNA:mRNA hybrid, and quantitation of changes in POMC mRNA levels in the rat pituitary intermediate lobe detected both by in situ hybridization and "dot blot" techniques.

Animals↗
PubMed1985

Induction of the intermediate pituitary by stress: synthesis and release of a nonopioid form of beta-endorphin.

beta-Endorphin in the intermediate lobe of the pituitary gland is posttranslationally modified to produce opioid inactive peptides. Whether these are metabolites or biologically relevant products has not been known. It was found that repeated stress induces increased biosynthesis and release of beta-endorphin-like substances from the intermediate lobe of rats and that opioid-inactive N-acetylated beta-endorphin-(1-31) is selectively made and liberated. The possible role of this nonopioid product and the selective release of peptide forms are discussed.

Animals↗
PubMed1985

Analysis of opioid and non-opioid end products of pro-dynorphin in the substantia nigra of the rat.

The substantia nigra is among the richest pro-dynorphin terminal field regions in the rat brain. We therefore contrasted processing in this area to the known processing in the posterior pituitary. Fractionation of acid extracts of the posterior pituitary by gel filtration followed by analysis by radioimmunoassay indicated that the molar ratio of dynorphin A(1-17) to dynorphin A(1-8) averaged 1:2. The levels of dynorphin A-related end products to alpha-neo-endorphin and bridge peptide (a 2K nonopioid end product of pro-dynorphin) were approximately equimolar; however, the levels of dynorphin B-sized material were 50% lower than dynorphin A levels. Similar analyses of acid extracts of the substantia nigra also indicated that the levels of dynorphin A, alpha-neo-endorphin, and bridge peptide were approximately equimolar. In this terminal field the levels of dynorphin B-sized material were approximately 60% lower than dynorphin A. A striking feature of the nigral system was that the molar ratio of dynorphin A(1-17) to dynorphin A(1-8) averaged 1:16. Thus, in the nigra, dynorphin A(1-17) is primarily a biosynthetic intermediate rather than as an end product.

Animals↗
PubMed1985

Changes in releasability of ACTH and beta-endorphin with chronic stress.

The activation of the hypothalamic pituitary adrenal axis by stress is well-known. Using inescapable intermittent footshock as a stressor in rats, we have previously demonstrated a rise in circulating plasma Beta-endorphin/Beta-LPH which parallels the rise in plasma ACTH, the primary POMC derived peptides released by anterior lobe. In addition, the rise in ACTH is accompanied by approximately a tenfold rise in plasma corticosteroids. Short term anterior lobe pituitary cultures from rats who have received inescapable intermittent footshock for 30 minutes show a blunted dose response curves to the ACTH releasing secretagogues arginine vasopressin (AVP) and ovine corticotropin releasing factor (oCRF). Similarly a blunted dose response curves to secretagogues can be seen by either the addition of dexamethasone (0.5 nM) to the culture medium or pretreatment of the rats with 1 mg dexamethasone intraperitoneally 90 minutes prior to decapitation. Thus, glucocorticoids may play a role in the blunted response to secretagogues seen in anterior lobe cultures from acutely stressed rats. We now report that chronically stressed rats exhibit increased releasability of ACTH and Beta-endorphin/Beta-LPH products by oCRF, suggesting an increase of the peptides in the releasable pool.

Adrenocorticotropic Hormone↗
PubMed1985

Steady state levels of pro-dynorphin-related end products in the striatum and substantia nigra of the adult rhesus monkey.

Analysis of an acid extract of the striatum of the rhesus monkey revealed that the molar ratio of dynorphin A(1-8)-sized material and dynorphin (A(1-17)-sized material is approximately 1:1. In addition, the molar ratios of the dynorphin A-related end products to both dynorphin B(1-13)-sized material and alpha-neo-endorphin-sized material were approximately 1:1. Fractionation of an acid extract of the substantia nigra by gel filtration and reverse phase HPLC revealed the following molar ratios for pro-dynorphin-related end products. The molar ratio of dynorphin A(1-8) to dynorphin A(1-17) is approximately 6:1. The molar ratios of dynorphin A-related end products to dynorphin B(1-13) and alpha-neo-endorphin were approximately 0.5 and 0.8, respectively. Comparisons between proteolytic processing patterns of pro-dynorphin in the striatum and the substantia nigra of the rhesus monkey are considered. In addition, comparisons between pro-dynorphin processing in the substantia nigra of the rhesus monkey and the substantia nigra of the rat are discussed.

Animals↗