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Biomedical subjects

H Akil

Publications and source records attributed to H Akil.

At least 235 records · Page 13Linked to original sources
PubMed1985

Prodynorphin peptide immunocytochemistry in rhesus monkey brain.

The present study describes the immunocytochemical distribution of peptides derived from the prodynorphin precursor in the brain of the rhesus monkey (Macaca mulatta). Animals were treated with colchicine (intracerebroventricularly) prior to perfusion to enhance the observation of perikaryal immunoreactivity. Using antisera generated against dynorphin A(1-17), dynorphin B(1-13), and prodynorphin(186-208) (or bridge peptide), the anatomical distribution of dynorphin systems was mapped. The results indicate a widespread neuronal localization of immunoreactivity from the cerebral cortex to the caudal medulla. Anti-dynorphin B and anti-bridge peptide sera proved useful for the demonstration of neuronal perikarya, while the dynorphin A antiserum was best for localizing terminal projection fields. Immunoreactive perikarya are located in numerous brain loci, including the cingulate cortex, caudate nucleus, amygdala, hypothalamus (especially the magnocellular nuclei), thalamus, substantia grisea centralis, parabrachial nucleus, nucleus tractus solitarius, and other nuclei. In addition, fiber and terminal immunoreactivity are seen in varying densities in the striatum and pallidum, substantia innominata, hypothalamus, substantia nigra pars reticulata, parabrachial nucleus, spinal trigeminal nucleus, and other areas. The distribution of prodynorphin peptides in the brain of the monkey is similar to that described for the rat brain; however, significant differences also exist. Other interspecies differences in the anatomy of prodynorphin and proenkephalin neuronal systems in the monkey and human brain are further discussed.

Animals↗
PubMed1985

Corticotropin-releasing factor stimulation of adrenocorticotropin and beta-endorphin release: effects of acute and chronic stress.

The effects of acute and chronic stress on the release of ACTH and beta-endorphin in response to stimulation by ovine corticotropin-releasing factor (CRF) and arginine vasopressin were examined. Pituitaries were removed from rats who had received either acute stress, chronic stress daily for 14 days with the last stress occurring 24 h before decapitation, or chronic stress followed by an acute stress immediately before decapitation (chronic stress-acute stress). Pituitaries from naive unstressed animals were used as the control group. After processing into single cell suspensions, the pituitaries were incubated with various doses of CRF (10(-11) M to 10(-9) M) and AVP (10(-10) M to 10(-8) M). Release of ACTH and beta-endorphin into the medium was measured by RIA. A clear dose-dependent response to both releasers was seen in control pituitaries. In acute stress, a decreased responsiveness to arginine vasopressin and CRF was seen. This same blunted response was not seen in chronic stress even if the animals are stressed immediately before decapitation. At higher doses of CRF (10(-9) M) a substantially increased release of ACTH and beta-endorphin was seen in the chronically stressed rats. When the content of the anterior pituitary lobe was assayed in these animals, both chronic stress groups show increased content of ACTH and beta-endorphin, which may indicate an increase amount of ACTH and beta-endorphin in the releasable pools in chronic stress. In addition, the failure of further stress to alter the response to CRF in the chronic stress-acute stress group may indicate a down-regulation of the steroid feedback on the pituitary. However, it is clear that no down-regulation of the CRF receptor occurs in this chronic stress paradigm.

Adrenocorticotropic Hormone↗
PubMed1984

Localization of neurons containing pro-opiomelanocortin-related peptides in the hypothalamus and midbrain of the lizard, Anolis carolinensis: evidence for region-specific processing of beta-endorphin.

Immunohistochemical analyses of the lizard-brain, following colchicine pretreatment, revealed two populations of POMC-producing cell bodies located in medial-basal hypothalamus and the mesencephalic tegmentum. Analyses of extracts of lizard brain regions by radioimmunoassay and gel filtration chromatography indicate that beta-endorphin-sized and alpha-MSH-sized peptides are the major POMC-related end products. Evidence is presented for region-specific processing of beta-endorphin in the lizard brain.

Animals↗
PubMed1984

Beta-endorphin/ACTH immunocytochemistry in the CNS of the lizard Anolis carolinensis: evidence for a major mesencephalic cell group.

The immunocytochemical distribution of beta-endorphin and other proopiomelanocortin (POMC) peptides in the central nervous system of the lizard Anolis carolinensis was determined. Colchicine pretreatment was used to enhance perikaryal immunoreactivity. A major finding of this study is the localization of a previously undetected mesencephalic cell group which exhibits immunoreactivity to beta-endorphin, ACTH, and alpha-MSH. The perikarya of these neurons are large, bipolar, and situated in the mesencephalic tegmental area. They appear to project to the mesencephalic central gray and other brainstem structures. In contrast, the immunoreactive parvicellular perikarya of the medial-basal hypothalamus, corresponding to the POMC perikarya of the rodent arcuate nucleus, exhibit major rostral projections to various telencephalic and diencephalic structures. The exact extent of fiber projections and innervation patterns arising from either of these two groups is not clear at this time and will require further analyses. Scattered fiber immunoreactivity was also seen in the medial cerebral cortex and the striatal complex, regions which apparently are not innervated by beta-endorphin fibers in the rodent brain. Also, no immunoreactivity was seen to an antiserum to the 16K peptide of POMC. Other similarities and differences in the brain distribution of POMC in reptiles and mammals are discussed.

Adrenocorticotropic Hormone↗
PubMed1984

Strategies for studying opioid peptide regulation at the gene, message and protein levels.

Three opioid peptide precursors have been isolated and characterized in endocrine and nervous tissue: pro-opiomelanocortin, pro-enkephalin, and pro-dynorphin. Since each of those opioid peptide systems have been extensively characterized both biochemically and anatomically, this review will focus on strategies for studying the regulation of these systems at the levels of gene transcription, message translation, post-translational processing, secretion, and target cell receptor interaction.

Animals↗
PubMed1984

Proopiomelanocortin peptide immunocytochemistry in rhesus monkey brain.

The immunocytochemical distribution of proopiomelanocortin (POMC) peptides (beta-endorphin, ACTH, alpha-MSH, 16K fragment) was studied in the brain of the rhesus monkey (Macaca mulatta). Some animals were administered colchicine intracerebroventricularly prior to sacrifice to enhance the visualization of perikaryal immunoreactivity. Immunoreactive perikarya are localized to hypothalamic infundibular nucleus, giving rise to several distinct projections. Rostral projections extend through midline diencephalic and preoptic areas, and enter the telencephalon. Along this course, immunoreactive fibers are seen in midline hypothalamic and preoptic nuclei, nucleus of the diagonal band, olfactory tubercle, nucleus accumbens, bed nucleus of stria terminalis, septum, and other limbic structures in telencephalon. Caudal to the anterior commissure, some fibers ascend dorsally to enter the midline thalamus, which they innervate. Lateral projections of the infundibular perikarya course through the medial-basal hypothalamus, dorsal to the optic tracts, and enter the amygdala region where they innervate more medially situated amygdaloid nuclei. Caudal projections of the POMC neurons also extend through midline diencephalon, some coursing along a periventricular path to innervate midline hypothalamic and thalamic nuclei. This projection extends into the mesencephalic substantia grisea centralis and may also contribute to the innervation of more dorsally situated nuclei in the pons and medulla, such as the parabrachial nuclei and nucleus tractus solitarius. Other caudal projections originating in the hypothalamus course through the ventral tegmentum of mesencephalon and pons and may contribute to the innervation of midline raphe and other ventrally situated nuclei in the pons and medulla. The distribution of immunoreactive perikarya and fibers in the brain of rhesus monkey is strikingly similar to that found in the rat brain. However, subtle differences appear to exist in the innervation patterns of particular brain regions.

Adrenocorticotropic Hormone↗
PubMed1984

Anatomical relationship between opioid peptides and receptors in rhesus monkey brain.

To determine whether opioid peptide-receptor pharmacological association found in vitro (e.g., enkephalin-delta, dynorphin-kappa) predict anatomical relationships in situ, immunocytochemical and receptor autoradiographic studies were carried out on adjacent sections from the same brains of formaldehyde-perfused rhesus monkeys. Apparent mu and kappa opioid receptors (labeled, respectively, by [3H] naloxone and [3H]bremazocine under different incubation conditions), but not delta opioid receptors (labeled by [3H]D-Ala2, D-Leu5-enkephalin), survived the fixation procedure, and were found to be colocalized throughout the brain. We have observed complex associations between these binding sites and one, two, or all three opioid peptide systems (i.e., proopiomelanocortin, proenkephalin, and prodynorphin) in different brain regions. These multiple opioid peptide-receptor subtype associations are apparent, for example, in neural systems involved in the processing of pain stimuli, and may be important for mediating different types of analgesia. Since differential processing of proenkephalin and prodynorphin can give rise to opioids of varying receptor selectivities, the colocalization of opioid receptor subtypes may signify that such processing is a key regulatory event in determining which receptor subtype is activated and, thus, the physiological consequences of opioid neurotransmission.

Animals↗
PubMed1983

Some of the alpha-NH2-acetylated beta-endorphin-like material in rat and monkey pituitary and brain is acetylated alpha- and beta-endorphin.

There are several studies demonstrating the existence of alpha-NH2-acetylated (N-Ac) forms of beta-endorphin in the intermediate lobe of several species (1,4,6). These include N-Ac-beta-endorphin (1-31), N-Ac-beta-endorphin (1-27) and N-Ac-beta-endorphin (1-26). The existence of N-acetylation of brain beta-endorphin is more controversial (5,6). Using molecular sieving, HPLC, and several radioimmunoassays, either directed at the midportion of beta-endorphin or at only N-acetylated opioids, we have studied brain multiple forms (cf. Akil, 1982). We have noted that little or no acetylation of beta-endorphin-sized material occurs in hypothalamus, and a small amount of N-acetylation appears to take place in the midbrain and the medulla. These results will be described in detail elsewhere (Akil et al., in preparation), but point the fact that processing of beta-endorphin (1-31) in brain is different than either lobe, with the production of beta-endorphin (1-27) and beta-endorphin (1-26) being more predominant in brain terminal areas than in the neuro-intermediate lobe. In the course of these experiments we noted the existence of a smaller-sized material which reacted with our N-acetyl-beta-endorphin antibody. The following study describes the partial characterization of this material as N-Ac-alpha- and N-Ac-beta-endorphin (i.e., the N-acetylated forms of beta-endorphin (1-17) and beta-endorphin (1-16).

Animals↗
PubMed1983

POMC in rhesus anterior pituitary and plasma: evidence of N-acetylated beta-endorphin and alpha-MSH.

Pro-opiomelanocortin (POMC) related peptides have been studied in rat tissue and plasma, but they have not been well characterized in the rhesus monkey. Since monkey pituitary may be more similar to the human pituitary than the rat, we have characterized POMC related peptides by immunocytochemical, multiple radioimmunoassays (RIA's) and molecular sieving chromatography. Immunocytochemical staining demonstrated N-acetylated- beta-endorphin (N-Ac- beta-End) and alpha-MSH in a few corticotrophs. RIA's of crude anterior pituitary extract and molecular sieving chromatography demonstrates that the major portion is beta-End sized with a significant proportion being N-acetylated and an alpha-MSH peak. Molecular sieving chromatography of extracted plasma demonstrated a similar pattern to that seen in the anterior pituitary. These data suggest that rhesus monkey processes POMC differently than rat or man.

Animals↗
PubMed1983

Postnatal ontogeny of acetylated and non-acetylated B-endorphin in rat pituitary.

Extracts of the anterior lobe and intermediate lobe of postnatal (P) (Day P1, P7, P14, P21, P28, P35, P42) and adult male Sprague-Dawley rats were analyzed by both a Beta-endorphin (B-END) radioimmunoassay and a radioimmunoassay for N-acetyl-B-END. In the anterior lobe, on P1, less than 2% of the adult level of B-END was present. By P42 this level had increased to 21% of adult levels. In the intermediate lobe, on P1, the B-END levels were less than 0.1% of the adult level, and by P42 this level approached approximately 45% of the adult levels. N-acetylated B-END was identified in both anterior lobe and intermediate lobe from P1 through adulthood. In the anterior lobe at P1, N-acetyl-B-END immunoreactivity contributes approximately 25% of the total B-END immunoreactivity. This level drops to less than 10% by P21, and to adult-like levels by P42 (less than 5%). On the other hand, in the intermediate lobe, the N-acetyl-B-END levels start at 70% of the total B-END immunoreactivity at P1 and by P14 reaches adult-like proportions of 90% or more of the total B-END immunoreactive material.

Aging↗
PubMed1983

[3H] dynorphin binding to guinea pig and rat brain.

[3H] Dynorphin can be shown to bind to the brains of both rat and guinea pigs with approximately 50% specific binding. Characterization of the binding in terms of multiple opiate receptor types supports the kappa selectivity of dynorphin in guinea pig. However, in rat brain, a substantial proportion of the [3H] dynorphin binding is displaced by morphine, suggesting a mu as well as kappa component. Consequently, in rat, dynorphin may show effects at both mu and kappa receptors in vivo.

Animals↗
PubMed1983

Pro-dynorphin peptides are found in the same neurons throughout rat brain: immunocytochemical study.

It is known that the opioid peptide dynorphin A has a broad distribution throughout the neuraxis. Recent biochemical studies have extended the sequence of dynorphin A by 15 amino acids to include another [Leu]enkephalin-containing peptide known as dynorphin B. These sequence data have been validated by the elucidation of the structure of the hypothalamic mRNA coding for alpha- and beta-neo-endorphin, dynorphin A, and dynorphin B. Using specific antisera directed against each of the three opioid peptides, we have studied their cellular distribution in rat brain. Their distribution patterns are extremely similar, if not identical. Furthermore, all three peptide immunoreactivities can be localized to the same cells in five nuclear groups throughout the brainstem--the supraoptic nucleus, the paraventricular nucleus, a group of cells in the lateral hypothalamic area, the nucleus parabrachialis, and the nucleus tractus solitarius. The sequence of a common precursor for dynorphin A, B, and alpha- and beta-neo-endorphin was deduced from hypothalamic mRNA. The ability to localize all three peptides together within cells in widely placed nuclei strongly supports the use of the same biosynthetic precursor for the neo-endorphin and dynorphin peptides in other parts of the central nervous system as well.

Animals↗
PubMed1983

Selective alterations of opiate receptor subtypes in monosodium glutamate-treated rats.

Neonatal treatment of rats with monosodium glutamate (MSG) has been demonstrated to destroy cell bodies of neurons in the arcuate nucleus including the brain beta-endorphin (B-END) system. The effects on opiate receptors of the loss of B-END is unknown. Neonatal rats were treated with MSG as previously described. After reaching maturity (7-9 months), MSG-treated rats and litter-matched untreated control rats were decapitated and brains dissected into brain regions. Opiate receptor assays were run with [3H]morphine (mu receptor ligand) and [3H]D-alanine2-D-leucine5 (DADL) enkephalin (delta receptor ligand) for each brain region for both MSG and control rats simultaneously. Scatchard plot analyses showed a selective increase in delta receptors in the thalamus only. No corresponding change in mu receptors in the thalamus was found. The cross-competition IC50 data supported this conclusion, showing a loss in the potency of morphine in displacing [3H]DADL enkephalin in the thalamus of MSG-treated rats. This shift in delta receptors produced an IC50 displacement pattern in thalamus, ordinarily a mu-rich area, similar to that of striatum or cortex, delta-rich areas, again indicating an increase in delta receptors. Similar changes in delta receptors in other brain regions were not found. These results represent one of the few examples of a selective and localized shift in delta with no change in mu sites. Furthermore, the delta increase may reflect an up-regulation of the receptors in thalamus after chronic loss of the endogenous opioid B-END.

Animals↗
PubMed1983

Human plasma beta-endorphin-like peptides: a rapid, high recovery extraction technique and validation of radioimmunoassay.

This is a report of the development, calibration, and validation of a series of techniques required to measure beta-endorphin (beta-END)-like immunoreactivity in human plasma, including sieve and affinity chromatography. The RIA, which uses the antibody Brenda, is very sensitive (IC50 = 5-15 fmol/tube at a final concentration of 1:40,000). The extraction process, which uses the Sep-Pak C18 cartridge (Waters Associates, Inc.), is simple and rapid and has a recovery rate of more than 90%. It extracts proopiomelanocortin, beta-lipotropin, and beta-END. Physiological validation was provided by the measurement of beta-END-like immunoreactivity in a pool of plasma of normal humans (2.25 fmol/ml plasma), two pregnant women at term (9.5 and 10.75 fmol/ml), and one patient with Nelson's disease (2 pmol/ml plasma).

Animals↗