Biomedical subjects

G B Stefano

Publications and source records attributed to G B Stefano.

At least 127 records · Page 7Linked to original sources

PubMed1996

Evidence for morphine downregulating immunocytes during cardiopulmonary bypass in a porcine model.

Cardiopulmonary bypass is associated with both cellular immunosuppression and an inflammatory response. Previous studies have demonstrated that morphine, a naturally occurring substance, can downregulate granulocyte, monocyte and endothelial activity. It can even prevent the activation caused by exposing these cells to plasma obtained from patients undergoing cardiopulmonary bypass. The present study demonstrates that preadministering a high dose of morphine (3.3 mg/kg) to pigs prior to cardiopulmonary bypass also diminishes the activation levels of these cells. In animals not given morphine, monocyte activation levels were 45% compared to 14% exposed to the opiate. Granulocytes also exhibited the same statistically significant (P < 0.05) drop in cellular activation. Activation is determined by computer-assisted microscopic image analysis whereby cellular shape is indicative of the cells activity. Additionally, in animals pretreated with morphine, a twofold increase in the number of cells was obtained, indicating that the endothelium also was downregulated.

Animals↗

PubMed1996

The presence and effects of mammalian signal molecules in immunocytes of the insect Leucophaea maderae.

Opioid peptides activate immunocytes and opiate alkaloids inhibit this activation in the mussel, Mytilus edulis. Here we present evidence that cells of another invertebrate, Leucophaea maderae, can be influenced in a similar way by the Met-enkephalin analogue D-Ala2-Met5-enkephalin (DAMA) and morphine. Effects of different signal molecules on Leucophaea hemocytes were evaluated by computer-assisted image analysis of their conformational state. A small percentage of the untreated cells were found to display spontaneous conformational changes after 25 min of incubation without pharmacological agents which was noted as a decrease in both circularity factor and shape factor values. Activation caused the cells to become elliptical, a feature that appears to be characteristic of Leucophaea immunocytes. Administration of DAMA induced a similar activation of most of the cells. After 30 min these DAMA-activated cells started to display distinct locomotory activity not seen in the controls. alpha-Melanocyte-stimulating hormone (MSH, 10(-7)) added to the incubation medium after DAMA-activation caused the cells to return to their original "rounded" conformation. In addition, the presence of immunoreactive interleukin (IL-1), adrenocorticotropin (ACTH) and tumor necrosis factor (TNF) in the hemolymph was demonstrated. These data suggest an interaction between both vertebrate-type immunological signal molecules and neuropeptides in the regulation of immunological cells in Leucophaea.

Adrenocorticotropic Hormone↗

PubMed1996

The presence of the mu3 opiate receptor in invertebrate neural tissues.

A previous report demonstrated the presence of the newly discovered opiate alkaloid selective and opioid peptide insensitive mu3 receptor in ganglia of several invertebrate- and one vertebrate species as well as in microglial cells that had egressed from these ganglia after their maintenance in culture medium for several days. In the present study carried out in two representatives of invertebrates, the binding densities of this receptor determined in intact ganglia were compared with those in ganglia depleted of microglial cells. The aim was to ascertain whether the differences in binding capacity recorded in those two groups of ganglia might give an indication of the possible presence of this opiate receptor in nonmicroglial components of the nervous tissue, i.e., neurons. Within a period of 72 h of incubation, the gradual reduction in binding density had reached a plateau, in accordance with the termination of the egress of microglia. The fact that at least two thirds of the binding capacity of mu3 receptors were retained by the ganglia strongly suggests that part of this capacity may be attributed to neurons. This view is supported by additional data, in particular the demonstration of endogenous morphine in nervous tissue and its localization within distinct neurons.

Animals↗

PubMed1996

Neuroimmunologic implications in coronary artery disease.

In this review, the role of the macrophage in the pathophysiology of coronary artery disease (CAD) is examined. The central interaction of macrophage, endothelial cell and smooth muscle cell in the context of hyperlipidemia is considered. The macrophage appears to be at the beginning of a chain of events that starts with elevated low density lipoprotein (LDL). Stress, particularly in those with a core hostility, may be associated not only with higher catecholamine levels but also with higher serum lipid levels. These lipids will in turn be processed to oxidized LDL by macrophage and endothelial cells. Oxidized LDL molecules will contribute to atherosclerotic plaquing. A side effect of such plaque formation may be a diminished vasodilatory response to the nitric oxide (NO) produced by macrophages and endothelium. Indeed, paradoxical vasoconstriction occurs in atherosclerosis in response to neurotransmitters such as serotonin and acetylcholine, which under normal circumstances cause vasodilation. There also is evidence that both macrophages and endothelial cells can regulate NO production through a specific mu 3 morphine receptor, an effect that can be blocked by naloxone. The clinical effectiveness of morphine and nitroglycerin in CAD patients may relate to these mechanisms. More research will be needed to elucidate the neuroimmunologic basis for atherosclerosis with prospects for better treatment and management in future.

Animals↗

PubMed1996

Met-enkephalin and morphiceptin modulate a GABA-induced inward current in the CNS of Lymnaea stagnalis L.

1. The interaction between GABA and opioid peptides (met-enkephalin and morphiceptin) was studied on the identified, isolated and internally perfused neurons of Lymnaea stagnalis L. (Gastropoda, Basommatophora). 2. GABA (10(-7)-10(-5)M) activated a Cl-dependent inward current with about -20 mV equilibrium potential. Slow and fast GABA-induced inward currents were recorded with different kinetic parameters in distinct identified neurons. 3. Both types of GABA-induced inward currents were reduced or blocked by met-enkephalin (10(-7)-10(-5)M) and morphiceptin (10(-7)-10(-5)M) in a dose-dependent manner. GABA-activated fast inward current was modulated in a biphasic way in some neurons. Opioid reduction of the GABA-activated slow inward current was reversible, whereas the fast current was not. 4. The reversible inhibition of the GABA-induced slow inward current produced by met-enkephalin or morphiceptin was naloxone (10(-5)-10(-4)M)-sensitive, whereas the irreversible block of the fast GABA response was not antagonised by naloxone. Some additive effects between GABA and the peptides were also noted. 5. The modulatory effect of the opioid peptides on the GABA response altered the peak current, the time-to-peak and inactivation time-course of the GABA-induced current. 6. Thus, the identified, isolated and internally perfused neurons of Lymnaea stagnalis L. provide a useful model for studying postsynaptic mechanisms of interaction between GABA and opioid peptides. This interaction is a phenomenon of evolutionary significance because of it is also found in mammals.

Animals↗

PubMed1996

Adrenocorticotropin--a central trigger in immune responsiveness: tonal inhibition of immune activation.

Adrenocorticotropin is known for its key role in mediating neuroendocrine responses, especially in response to stress. Recently, it has been recognized to have direct immunomodulatory actions, most of which are suppressive. This is a widely conserved action which occurs in invertebrates and vertebrates. This conservation illustrates the fundamental nature of adrenocorticotropin's immunomodulatory action. Such a mechanism of action helps explain why the immunocytes themselves can serve as a source of adrenocorticotropin. Regulation of adrenocorticotropin production and action is complex and the result is an integration of multiple mechanisms. Serum adrenocorticotropin levels fluctuate in response to stimulatory and inhibitory factors. Further, peptidases can specifically process adrenocorticotropin into smaller active fragments, inactive peptides or into peptides with different activities. These proteolytic enzymes have a differential tissue and cellular distribution. Immune stimulating factors such as interleukin-1 can overcome adrenocorticotropin inhibition and secondarily, block adrenocorticotropin production through the release of corticosteroids. With an endogenous presence and complex regulation it has been difficult to characterize adrenocorticotropin's role in the immune system. Here, we propose that adrenocorticotropin is a tonis regulator of immune response, i.e. it tonally inhibits immunocytes which undergo disinhibition as the result of exposure to stimulatory signals, e.g. cytokines, neuropeptides, etc. Thus, adrenocorticotropin appears to set the threshold for immunoactivation by controlling the degree of immunoexcitability.

Adjuvants, Immunologic↗

PubMed1996

A novel view of opiate tolerance.

Opiate substances occur as natural compounds in various invertebrate and vertebrate neural tissues. Recently we have discovered a novel opiate alkaloid-selective and opioid peptide-insensitive receptor, designated mu 3, that provides further evidence of the existence of separate morphine processes. Interestingly morphine biosynthesis appears to be linked to the dopamine pathway. Based on studies documenting the presence of morphine after stress, e.g., trauma, it is noted that this signal substance emerges after a timely delay. From this we speculate that this molecule can serve a specific effect to downregulate physiological processes after stress. We conclude that tolerance represents a natural process that terminates its action. In this regard a morphine hypothesis may be essential to a complete picture of motive circuitry. A speculative view of the psychiatric implications in schizophrenia, depression, and autism are presented with this in mind.

Alkaloids↗

PubMed1996

Opioid and opiate immunoregulatory processes.

The discovery of the ability of the nervous system to communicate through "public" circuits with other systems of the body is attributed to Ernst and Berta Scharrer, who described the neurosecretory process in 1928. Indeed, the immune system has been identified as another important neuroendocrine target tissue. Opioid peptides are involved in this communication (i.e., neuroimmune) and with that of autoimmunoregulation (communication between immunocytes). The significance of opioid neuropeptide involvement with the immune system is ascertained from the presence of novel delta, mu, and kappa receptors on inflammatory cells that result in modulation of cellular activity after activation, as well as the presence of specific enzymatic degradation and regulation processes. In contrast to the relatively uniform antinociceptive action of opiate and opioid signal molecules in neural tissues, the presence of naturally occurring morphine in plasma and a novel mu3, opiate-specific receptor on inflammatory cells adds to the growing knowledge that opioid and opiate signal molecules may have antagonistic actions in select tissues. In examining various disorders (e.g., human immunodeficiency virus, substance abuse, parasitism, and the diffuse inflammatory response associated with surgery) evidence has also been found for the involvement of opiate/opioid signaling in prominent mechanisms. In addition, the presence of similar mechanisms in man and organisms 500 million years divergent in evolution bespeaks the importance of this family of signal molecules. The present review provides an overview of recent advances in the field of opiate and opioid immunoregulatory processes and speculates as to their significance in diverse biological systems.

Animals↗

PubMed1995

Effect of prolonged exposure to morphine on responsiveness of human and invertebrate immunocytes to stimulatory molecules.

This study deals with a novel role of morphine in the modulation of cellular responsiveness to immunostimulatory substances that, at first glance, appears to be in contrast to the well documented immunoinhibitory short-term effects of opiate alkaloids on cells simultaneously exposed to stimulatory molecules. Vertebrate and invertebrate immunocytes pre-exposed to morphine (10(-6) M) in vitro for at least 24 h prior to the administration of lipopolysaccharide (LPS; 1.0 micrograms/ml) or other immunoactivating substances have revealed a distinct enhancement of their responsiveness to these signals, e.g. monocytes exposed to LPS alone resulted in 21% activation, whereas the morphine pretreated level was at 40% (P < 0.01). Prolonged pretreatment with morphine of naive human monocytes had the same effect on their sensitivity to plasma from patients having undergone cardiopulmonary bypass (CPB) operations followed by a diffuse inflammatory response. These results suggest that endogenous opiates may participate, in more than one way, in re-establishing an organism's readiness to meet a new demand on its immune system. Additional support for the concept of a role of endogenous opiates in immunomodulation was obtained by the results of in vivo tests with experimentally induced stress in Mytilus. Following their stress-induced stimulation, these animals' immunocytes could be shown to become exposed for some time to a measurable rise in endogenous morphine-like material (9 pmol/ml increasing to 59). These immunocytes, like those preincubated with exogenous morphine, displayed a heightened sensitivity to stimulation by LPS (control 21.3 +/- 3.1% activation compared to 47.2 +/- 5.1) when the morphine levels dropped. The mechanism of this enhancement of responsiveness to immunostimulation following the prolonged exposure of immunocytes to morphine, and its relationship with the known short-term immunoinhibitory opiate effects on the immune system, remains to be ascertained.

Animals↗

PubMed1995

Presence of the mu3 opiate receptor in endothelial cells. Coupling to nitric oxide production and vasodilation.

Initial confinement of opiate receptors to the nervous system has recently been broadened to several other cell types. Based on the well established hypotensive effect of morphine, we hypothesized that endothelial cells may represent a target for this opiate substance. Endothelial cells (human arterial and rat microvascular) contain a high affinity, saturable opiate binding site presumed to mediate the morphine effects that is stereoselectively and characteristically antagonized by naloxone. This opiate alkaloid-specific binding site is insensitive to opioid peptides. It is, therefore, considered to be the same subtype of opiate receptor (designated mu3) used in the mediation of morphine in other cell types exhibiting the same binding profile. Experiments with endothelial cultures and the aortic ring of rats cultured in vitro demonstrate that morphine exerts direct modulatory control over the activities of endothelial cells, which leads to vasodilation. It induces the production of nitric oxide, a process that is sensitive to naloxone antagonism and nitric oxide synthase inhibition. In contrast with that of opiates, the administration of opioid peptides does not induce nitric oxide production by endothelial cells. In conclusion, the data presented above reveal a novel site of morphine action, endothelial cells, where a mu3 receptor is coupled to nitric oxide release and vasodilation.

Animals↗

PubMed1995

Occurrence of the opiate alkaloid-selective mu3 receptor in mammalian microglia, astrocytes and Kupffer cells.

Evidence is presented for occurrence of opiate alkaloid-selective, opioid-peptide-insensitive receptor binding sites, labeled with [3H]morphine, in primary cultures of cat microglia and cat astrocytes, as well as on highly purified preparations of rat Kupffer cells. These receptors have been designated mu3 on the basis of their close similarity to receptors first found to be present on human peripheral blood monocytes. Exposure of the microglia to morphine and etorphine caused marked quantifiable changes in cellular morphology, including assumption of a more rounded shape and retraction of cytoplasmic processes; in contrast, several opioid peptides were without effect on morphology. The effects of morphine on microglial morphology were blocked by the opiate antagonist naloxone. These effects of drugs on morphology were as predicted for action via the mu3 receptor. Opiate alkaloid binding sites previously detected on the rat C6 glioma cell line were also characterized here as of the mu3 receptor subtype. It is proposed that mu3 receptors have broad distribution in different macrophage cell types of bone marrow lineage, including microglia and Kupffer cells. Furthermore, these receptors are not restricted to cells of bone marrow lineage, since they are also present on astrocytes.

Alkaloids↗

PubMed1995

Antagonizing effect of morphine on the mobility and phagocytic activity of invertebrate immunocytes.

In the present study we have demonstrated that lipopolysaccharide (LPS) acts as an activator in the immunocytes of molluscs Planorbarius corneus, Mytilus edulis, and the insect Leucophaea maderae. This stimulatory effect, demonstrated by cellular conformational changes, is concentration- and time-dependent, and is antagonized by morphine. The inhibitory effect of morphine can be counteracted by naloxone. Morphine inhibitory action on immunocyte activity is also demonstrated by a decrease in the phagocytic activity. These data suggest that the downregulation of morphine is not limited to vertebrates but is also present in invertebrates.

Animals↗

PubMed1995

Murine macrophage cell lines contain mu 3-opiate receptors.

Opiate alkaloid-selective, opioid peptide-insensitive mu 3 receptors are present in three murine macrophage cell lines (J774.2; RAW 264.7; BAC1.2F5). The receptor binds morphine, its active metabolite morphine 6-glucuronide and certain other alkaloids, but not morphine 3-glucuronide or any of the opioid peptides tested. The cell lines thus provide valuable model systems for investigation of mu 3-opiate receptors, previously demonstrated to mediate inhibitory effects of morphine on activation of human peripheral blood macrophages (monocytes).

Animals↗

PubMed1995

Human granulocytes contain an opiate alkaloid-selective receptor mediating inhibition of cytokine-induced activation and chemotaxis.

Human peripheral blood granulocytes previously were found to contain opioid delta 2-receptors mediating stimulation by opioid peptides of chemotaxis. Studies presented in this work indicate that granulocytes also contain opiate alkaloid-selective, opioid peptide-insensitive receptors mediating inhibition by morphine and other opiates of cytokine-induced activation and chemotaxis. Binding studies with [3H]morphine and [3H]diprenorphine ([3H]DPN) indicated the presence of receptor sites, at considerable density with affinities and selectivity for opiates comparable with those of the mu 3-receptor of human peripheral blood monocytes (macrophages). The influence of the guanosine 5'-triphosphate (GTP) analogue GppNHp on binding indicated that the granulocyte receptor was linked to a G protein. Morphine but not opioid peptides interfered with activation and/or chemotaxis of the granulocytes induced by TNF-alpha, IL-1 alpha, IL-8, and FMLP (chemotactic peptide). These effects of morphine were blocked by the antagonist naloxone. Levorphanol inhibited TNF-alpha-induced activation, and also potentiated the inhibition by morphine. Furthermore, in binding assays, levorphanol enhanced the affinity of the receptor for morphine. Dextrorphan had no effect on activation or chemotaxis, and it also had no effect on binding, indicative of stereoselectivity for the effect of levorphanol. It is concluded that human granulocytes contain opiate alkaloid-selective mu 3-receptors that mediate inhibitory effects of morphine on cellular activation by cytokines.

Adult↗

PubMed1995

Schistosoma mansoni: the presence and potential use of opiate-like substances.

The present study demonstrates that morphine- and codeine-like molecules are present in Schistosoma mansoni following HPLC separation and identification with an appropriate commercially available antibody. Furthermore, the endogenous material, corresponding to morphine, mimics authentic morphine in its ability to induce immunocyte rounding and immobility, an action that is naloxone sensitive. The codeine-like material is not found at high concentrations compared to the morphine-like material, indicating, as in mammals and Mytilus edulis, the potential rapid conversion of codeine to morphine. Coincubation with human leukocytes increases the endogenous level of this material in adult worms, indicating the presence of a positive feedback loop. Last, EDTA, a chelator of divalent cations, has a strong stimulating effect in the synthesis of morphine-like material by the worm as noted by higher levels of this material in its presence. Taken together, the results suggest that this parasite may utilize this immune downregulating molecule in its effort to escape host immunosurveillance as well as in inhibiting an immune response directed against itself.

Analgesics, Opioid↗

PubMed1995

The biology of deception: the reluctance to accept the cognitive animal.

Cognitive ability did not appear de novo in man. Despite our ability to recognize limited cognitive behavioral characteristics in animals, there has been no outcry to proclaim this phenomenon. Man's image of himself solely possessing cognition has taken advantage of the illusory potential in intersubjectivity and placed him outside of reality. This deception, however, has positive survival value since it is man's self-proclaimed responsibility to excel beyond other simple animal species. However, at this point in evolution, we must allow our cognitive ability to reform itself and, in so doing, evolve with the benefit of the knowledge that this ability is itself creating. By recognizing that animals may have limited cognitive ability, we only enhance our self-esteem, not diminish it.

Animals↗

PubMed1995

The biology of deception: the evolution of cognitive coping as a denial-like process.

We speculate that the development of cognitive processes provided such endowed animals with an additional coping strategy in dealing with stress. This ability depends on a unifying consciousness appearing to control or regulate the many individual processes that potentially summate to make up the mind. Without this unifying component, the significance and uniqueness of this coping strategy would be lost. The cognitive mind would also have to develop, of course by chance, a strong bias to believe in a highly organized world, since this is what would have survival value within one lifetime. This sense of unity as a coping strategy is really a deception or illusion, in that it imposes perceived order. Thus, the biology of deception has been an important development leading to man as a cognitive creative being. Our premise here extends this notion and suggests that denial-like processes are at the core of the cognitive coping mechanisms we have evolved as humans.

Adaptation, Psychological↗

PubMed1995

The biology of deception: emotion and morphine.

The biology of deception suggests that denial-like processes are at the core of the cognitive coping. In this regard, with cognitive ability, one associates or assumes that this process occurs by way of a 'rational' mind. Such a detailed cognitive process as being rational would also lead, counter intuitively, to inactivity and or major delays in conclusion reaching. Thus, our perceived rationality may also be a deceptive behavioral response. Of equal noteworthyness, man is also 'emotional'. We surmise that emotion represents the pre-cognitive short-cut to overcome this potential for excessive rationality. In this light, we may explain certain psychiatric disorders such as obsessive-compulsive behavior as emotional extremes dealing with cognitive habits used to bind anxiety operating most probably at the pre-cognitive level. Given recent discoveries in neuroimmunology and an understanding of naturally occurring morphine as both an immune and neurological down-regulatory substance we hypothesize that abnormalities associated with emotional extremes may be due, in part, to morphinergic imbalances.

Adaptation, Psychological↗