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Biomedical subjects

B Sharp

Publications and source records attributed to B Sharp.

At least 19 recordsLinked to original sources
PubMed1990

Beta-endorphin binding to naloxone-insensitive sites on a human mononuclear cell line (U937): effects of cations and guanosine triphosphate.

Some of the functional effects of beta-endorphin on immune cells are resistant to inhibition by naloxone. To further characterize the beta-[125I]endorphin-binding site mediating these effects and its response to cations and GTP, the human monocyte-like cell line U937 was used. Incubation of intact cells and beta-[125I]endorphin for 60 min at 4 C demonstrated a saturable, high affinity binding site [Kd = 1.2 +/- 0.5 X 10(-8) M (mean +/- SE; n = 4] competed by equimolar beta-endorphin and N-acetyl (Ac)-beta-endorphin but not by naloxone, morphine, or selective opiate receptor agonists. Competition studies showed that beta-endorphin-(6-31) and beta-endorphin-(28-31) were approximately 5- and 100-fold less potent, respectively, whereas beta-endorphin-(1-16) or -(1-27) was ineffective. Covalent cross-linking of beta-[125I]endorphin to intact cells and resolution by gel electrophoresis showed dominant bands at 59K and 44K and a minor band at 66K. The bands at 44K and 66K were completely displaced by increasing equivalent concentrations of beta-endorphin and N-Ac-beta-endorphin. Increasing concentrations of mono (Na+, K+)- and divalent (Ca2+, Mg2+, Mn2+) cations reduced the binding of beta-[125I]endorphin to U937 membrane; beta-[125I]endorphin binding to rat brain membrane showed similar cation sensitivity. GTP gamma-sulfate (GTP gamma S; 10(-4) M) alone reduced binding to U937 membrane by 25%. In the presence of Na+ (100 or 150 mM) or Mg2+ (10 mM), GTP gamma S reduced binding by an additional 50%. Moreover, GTP gamma S (10(-8)-10(-4) M) in the presence of Na+ (100 mM) reduced binding in a dose-dependent manner, whereas GMP was ineffective. In conclusion, beta-endorphin binds to sites on human U937 cells similar to those observed on normal murine splenocytes. Although naloxone insensitive, these sites exhibit properties, such as size, salt sensitivity, and coupling to a GTP-binding protein, that are similar to those observed for agonist binding to brain opiate receptors.

Animals↗
PubMed1989

Suppression of human peripheral blood mononuclear cell function by methadone and morphine.

Recent studies have shown that in vitro exposure of peripheral blood mononuclear cells (PBMC) to morphine results in suppressed respiratory-burst activity of monocytes and impaired interferon-gamma (IFN-gamma) production by lymphocytes. To investigate the potential in vivo effect of an opiate on these cell functions, PBMC were obtained from patients maintained on methadone. These freshly isolated mononuclear cells had a significantly impaired capacity to generate superoxide anion (O2-) in response to phorbol myristate acetate (PMA), while production of IFN-gamma by concanavalin A-stimulated cells was intact. After cell culture for 48 h, the defective O2- generating capacity was sustained. Also, culturing PBMC from healthy controls in the presence of methadone or morphine at concentrations as low as 10(-12) M caused significant suppression of PMA-stimulated O2- release. Because reactive oxygen intermediates produced by PBMC may participate in host defense against opportunistic pathogens in AIDS, these results underscore the need for investigations of the biological consequences of opiate-mediated immunosuppression.

Adult↗
PubMed1988

Corticotropin-releasing factor in cerebellar afferent systems: a combined immunohistochemistry and retrograde transport study.

The flocculus and paraflocculus of cat and sheep cerebellum were studied with immunohistochemical methods, using antisera to corticotropin-releasing factor (CRF). CRF immunoreactivity was present within 3 populations of varicose nerve fibers. One population of CRF-immunoreactive (CRF-IR) fibers appeared to appose Purkinje cell somata and to follow their dendrites into the molecular layer. This arrangement suggested they were climbing fibers. A second group of CRF-IR profiles reminiscent of mossy fibers was widely distributed throughout the granule cell layer. A third population of CRF-IR fibers was present as a beaded plexus lying parallel to the pial surface, above and subadjacent to the Purkinje cell layer. The fibers of this plexus extended into the Purkinje cell layer and surrounded these somata. The source of some of the CRF-IR fibers within the flocculus and paraflocculus was determined by a retrograde axonal transport study utilizing the fluorescent tracer Fast blue (FB) in combination with the immunohistochemical localization of CRF. It was determined that CRF-IR perikarya within the inferior olivary nucleus gave rise to a population of climbing fibers within those lobules. Furthermore, all divisions of the inferior olive were found to contain CRF-IR somata. This latter finding suggests the potential for CRF-IR climbing fiber projections from the inferior olive to other regions of the cerebellar cortex. The existence of CRF-IR mossy fibers and fibers within the ganglionic plexus suggests the possibility of CRF-IR afferent projections from other regions of the brain stem to the flocculus and paraflocculus.

Afferent Pathways↗
PubMed1987

Opioid-mediated suppression of cultured peripheral blood mononuclear cell respiratory burst activity.

Opiate addiction and stress have been associated with altered immune responses. In this study, we evaluated the influence of morphine and the stress responsive opioid peptide beta-endorphin (beta-END) on O-2 and H2O2 production by cultured human peripheral blood mononuclear cells. Exposure of these cells during 48 hr of culture to morphine and beta-END at pharmacologically (10(-8) M) and physiologically (10(-12) M) relevant concentrations, respectively, markedly suppressed peripheral blood mononuclear cell O-2 and H2O2 release in response to the respiratory burst stimuli opsonized zymosan and phorbol myristate acetate. Both opioids also induced a minimal, but statistically significant, increase in resting O-2 and H2O2 generation. The modulatory effects of morphine and beta-END on peripheral blood mononuclear cell oxygen metabolism appeared to involve a classical opioid receptor, because opioid activity was blocked by naloxone and was not observed with N-acetylated-beta-END. Using purified lymphocyte and monocyte preparations, we determined that although opioids directly increase monocyte-resting oxygen metabolism, lymphocytes are the primary target cell in opioid-mediated suppression of monocyte respiratory burst activity. The release of a suppressive product from opioid-triggered lymphocytes was inhibited by cyclosporine. Based on the results of this study, we propose that opioid-mediated suppression of mononuclear phagocyte respiratory burst activity is another factor to be considered in the immunodeficiency of opiate addiction and stress.

Adult↗
PubMed1987

Opioid-mediated suppression of interferon-gamma production by cultured peripheral blood mononuclear cells.

Mounting evidence suggests that opiate addiction and stress are associated with impaired cell-mediated immunity. We tested the hypothesis that morphine and the endogenous opioid beta-endorphin (beta-END), a pituitary peptide released in increased concentrations during stress, can suppress the production of the key macrophage-activating lymphokine interferon-gamma (IFN-gamma) by cultured human peripheral blood mononuclear cells (PBMNC). Using a radioimmunoassay to measure IFN-gamma, we found that exposure of PBMNC to biologically relevant concentrations of both opioids significantly inhibited IFN-gamma generation by cells stimulated with concanavalin A and varicella zoster virus. Studies of the mechanism of suppression revealed (a) a classical opioid receptor is involved (suppression was antagonized by naloxone and was specific for the NH2 terminus of beta-END), (b) monocytes are the primary target cell for opioids (monocyte-depleted lymphocyte preparations showed little suppression), and (c) reactive oxygen intermediates (ROI) and prostaglandin E2 are important mediators (scavengers of ROI and indomethacin eliminated the suppression). Based on these findings we suggest that opioid-triggered release of inhibitory monocyte metabolites may play a role in the immunodeficiency associated with narcotic addiction and stress.

Blood Cells↗
PubMed1986

Endogenous opioid peptides: do they mediate the acute antihypertensive action of clonidine in humans?

The involvement of endogenous opioid peptides in the antihypertensive action of acutely administered clonidine, a centrally acting adrenergic agonist, was studied in humans. Eight hypertensive subjects received clonidine 0.2 mg orally, naloxone 8 mg i.v. followed by a 0.13 mg/min infusion, and both drugs together on separate days. Clonidine resulted in a significant decrease in mean blood pressure, which was not affected by concomitant treatment with naloxone. Naloxone alone or with clonidine caused significant elevations in plasma aldosterone, not mediated by increased plasma renin activity. Plasma beta-endorphin was not increased after clonidine administration. In humans, the antihypertensive effects of acute clonidine administration do not appear to be mediated by the release or action of endogenous opioids.

Adult↗
PubMed1985

Severe hypertension induced by naloxone.

To evaluate the role of endogenous opioid peptides in regulating the blood pressure of hypertensive individuals, we administered the opiate antagonist, naloxone. One individual developed a severe hypertensive response, mean arterial pressure rising from a baseline of 107 mmHg to 147 mmHg 145 min after naloxone injection and infusion. After stopping naloxone, his blood pressure rapidly returned to baseline. Re-challenge with naloxone and clonidine resulted in a modest reduction of blood pressure in contrast to the profound hypotension induced by clonidine alone during a third session. Thus, endogenous opioids appear to regulate blood pressure in some hypertensive patients and opiate antagonists must be administered with caution to these individuals.

Blood Pressure↗
PubMed1984

Studies of naloxone-induced secretion of beta-endorphin immunoreactivity in dogs.

The stimulating effect of naloxone on plasma beta-endorphin immunoreactivity (beta EI) was examined in dogs. Intravenous naloxone at 5, 1, or 0.1 mg/kg caused a significant increase in beta EI while doses of 0.01 or 0.001 mg/kg had no effect. The peak plasma beta EI levels occurred at 25 mins after naloxone. The neurotransmitter and antagonists metergoline, atropine, diphenhydramine and phentolamine all failed to significantly alter basal beta EI secretion; further, they all failed to prevent the increase in beta EI resulting from naloxone administration. Dexamethasone prevented the naloxone-induced rise in beta EI. Our results suggest naloxone's effect on beta EI is not mediated through several neurotransmitter systems known to affect ACTH secretion. Additionally, beta EI secreted in response to naloxone appears to originate mainly from the anterior lobe of the pituitary.

Animals↗
PubMed1984

Somatostatin-14 and -28 in the male rat reproductive system.

Somatostatin-14 (SRIF-14) has been shown to occur throughout the male rat reproductive system by SRIF radioimmunoassay, Sephadex G-50 exclusion chromatography, and parallel line analysis. SRIF-28 was found only in the epididymis. The highest concentrations of total SRIF-like immunoreactivity (SLI), representing the combined concentrations of SRIF-14 and SRIF-28, were measured in the prostates of 1 1/2- and 3-month-old Sprague-Dawley rats. The levels of SLI in prostates from 9-month-old males were about 10% that of the younger animals. Dilution curves for extracts of all reproductive tissues were parallel with synthetic SRIF-14.

Animals↗
PubMed1984

Thyrotropin-releasing hormone levels decrease in hypothalamus of aging rats.

Because hypothalamic and extrahypothalamic levels of thyrotropin-releasing hormone immunoreactivity (TRH-IR) undergo profound changes during the prenatal and early postnatal period in rats, similar effects with advanced aging were anticipated. For this reason we measured hypothalamic and reproductive tissue levels of TRH-IR, hypothalamic levels of somatostatin (SRIF), and beta-endorphin (EP), serum levels of prolactin (Prl), growth hormone (GH), thyrotropin (TSH), and thyroxine (T4) in young, sexually mature and 24-28 month-old male Long-Evans and Sprague-Dawley rats. Hypothalamic and prostatic levels of TRH-IR were consistently reduced as were the levels of T4 in old rats compared to young controls. Aging did not change the ratio of TRH to the major TRH-like peptide in prostates, as determined by high pressure liquid chromatography (HPLC) or the levels of hypothalamic SRIF and EP. All of the hypothalamic TRH-IR in both old and young male rats consisted of TRH by HPLC. Falling hypothalamic TRH levels and TRH secretory capacity may play a role in the blunted TSH response to cold stress in old rats.

Aging↗
PubMed1984

Failure to confirm consistent stimulation of growth hormone by diazepam.

Diazepam has been reported to influence pituitary hormone secretion, with several studies claiming that diazepam provokes growth hormone release. Normal volunteers were therefore examined for anterior pituitary responsiveness to 10 mg diazepam i.v. and p.o. The drug had no significant effect on the secretion of prolactin or thyrotropin when compared to control saline injections in all subjects. Growth hormone response was variable; serum growth hormone increased significantly in only 4 of 10 patients after i.v. diazepam and in only 1 of 7 subjects tested with oral diazepam. Serum cortisol rose in only 1 subject, precluding a stress-related explanation for the increase in growth hormone. We conclude that diazepam inconsistently stimulates growth hormone secretion and should not be relied upon as a test of growth hormone reserve.

Administration, Oral↗
PubMed1983

Adrenocortical response to corticotropin is inhibited by gamma 3-MSH antisera in normotensive and spontaneously hypertensive rats.

In order to further investigate the coordinate action of pro-corticotropin/endorphin-derived peptides on adrenal steroidogenesis, we have evaluated the effects of highly specific antisera to synthetic rat gamma 3-MSH (1-27) peptide (gamma 3-MSH Ab) on corticosterone, 18-hydroxycorticosterone and aldosterone responses to ACTH (1-24) in chronically cannulated spontaneously hypertensive rats (SHR) and their normotensive controls (WKY). Antisera eliminated the ACTH induced rise of all three corticosteroids. It had no effect on basal corticosteroid levels. Our results offer further evidence that the potentiating action of gamma 3-MSH may play an important role in modulating ACTH induced steroidogenesis.

18-Hydroxycorticosterone↗
PubMed1983

Endemic goiter in Vietnam.

Endemic goiter involves about 15% of the population of Vietnam. To define the role of various factors which contribute to endemic goiter in Vietnam, we surveyed 935 people in Vancon, a lowland commune with goiter appearing only in the past decade, and 619 people in Dich Giao, a highland commune with endemic goiter treated erratically with iodized salt. In Dich Giao, cassava, a goitrogenic food, constitutes half of the dietary caloric intake. The prevalence of goiter was 45% in Vancon and 28% in Dich Giao. Laboratory studies were carried out in a subgroup of 63 subjects in Vancon, 52 subjects in Dich Giao, and a control group of 46 women in Hanoi. The mean serum TSH levels were 1.4 +/- 0.1 (+/- SE) microU/ml in Hanoi, 3.6 +/- 0.5 microU/ml in Vancon (P less than 0.001), and 2.4 +/- 0.2 microU/ml in Dich Giao (P less than 0.05). The mean serum T4 concentrations were similar in the three groups, but the mean free T4 concentration was low in Vancon. Serum T3 levels and the T3 to T4 ratios were significantly elevated in the goitrous regions. The mean serum thyroglobulin (Tg) concentrations were 27 +/- 3 ng/ml in Hanoi, 101 +/- 20 ng/ml in Vancon (P less than 0.01), and 44 +/- 5 ng/ml in Dich Giao (P less than 0.01). The 4-h thyroid uptake was higher in Vancon than in Hanoi. The urinary iodine concentration was low in both goitrous regions, and urinary thiocyanate was increased in Dich Giao, reflecting the ingestion of cassava. For all regions combined, there was a direct correlation between serum TSH and T3 and between serum TSH and Tg. In Vancon, where iodine deficiency was more severe, there was an inverse correlation between thyroid uptake and the urinary iodine concentration; thyroid uptake correlated directly with serum T3, the T3 to T4 ratio, and serum Tg. In Dich Giao, there was no correlation between urinary thiocyanate and thyroid uptake or urinary iodine levels. The data show that low iodine intake is a major factor in the causation of goiter in Vancon, where iodine deficiency had not been suspected. The ingestion of cassava in Dich Giao did not cause a major change in thyroid hormone economy even though iodine intake was marginally low; the data suggest that the goitrogenic effect of cassava is easily overcome by supplementary iodine, even when it is ingested irregularly.

Adolescent↗
PubMed1982

Domperidone elevates rat plasma beta-endorphin-immunoreactivity when administered peripherally but not intracerebroventricularly.

Domperidone, a dopamine receptor antagonist which apparently does not penetrate the blood-brain barrier in rats was administered to adult males. Domperidone 500 micrograms and 100 micrograms, given through intracarotid cannula, significantly elevated plasma beta-endorphin-immunoreactivity (beta-EP-I) at +15 min. To show that only a peripheral site(s) of action is implicated, domperidone was given to rats by cannulae implanted into both lateral ventricles. Plasma beta-EP-I was unaffected by this route of administration. These results suggest that plasma beta-EP-I is tonically inhibited by dopamine acting at site(s) outside of the blood-brain barrier.

Animals↗