Lack of effect of alpha- and beta-adrenergic inhibition on forearm glucose uptake despite differences in forearm blood flow in healthy humans

Insulin has both sympathoexcitatory and vasodilatory actions. It is unclear how these interact to affect muscular glucose uptake. The current study was designed to determine the systemic and local contributions of alpha- and beta-adrenergic activity to muscle glucose uptake. Forearm blood flow (FBF, plethysmography), arterial-venous glucose difference (AV-diff), and forearm glucose uptake (FGU) were measured during a 40-mU/m(2)/min insulin infusion with 120 minutes of euglycemia in 6 normal subjects (age, 28.8 +/- 4.9 years, mean +/- SD). Each subject was studied 5 times, once each with intravenous propranolol (IV PROP, 80 microg/min), intravenous phentolamine (IV PHEN, 500 microg/min), intra-arterial propranolol (IA PROP, 25 microg/min), intra-arterial phentolamine (IA PHEN, 12 microg/min/100 mL forearm tissue), and saline (SAL). FBF did not change during insulin with SAL, IA PROP, or IV PROP, but increased during insulin with IA PHEN and IV PHEN (P <.05). Despite the increased glucose delivery during insulin plus IA PHEN and IV PHEN, FGU did not differ between study sessions at any time during the insulin infusion. This was due to the lower AV-diff during insulin with IA PHEN and IV PHEN compared to the other studies (P <.05). AV-diff negatively correlated with FBF at the end of the insulin infusion (P <.001) for all studies. In normal humans, inhibition of basal sympathetic activity does not alter muscular glucose uptake. The increased insulin-induced vasodilation during alpha-adrenergic inhibition suggests that insulin-induced sympathetic activation prevents excess vasodilation. This inhibition does not alter glucose uptake because changes in flow are counterbalanced by changes in glucose extraction.

Increased natural killer-cell mobilization and cytotoxicity during marital conflict

Natural killer (NK) cells are reproducibly mobilized into the circulation in response to intense physical exercise or acute psychological stress, and altered expression of adhesion molecules potentially contributes to NK-cell mobilization. Studies of leukocyte mobilization during acute stress have used psychological stressors which facilitate tight experimental control but have limited applicability to everyday life. We therefore used a laboratory model of marital conflict as an experientially meaningful acute stressor to elucidate relationships among conflict, cardiovascular reactivity, and altered leukocyte phenotype and function. Forty-one ethnically diverse, nondistressed, healthy married couples were asked to discuss a specific problem in their marriage for 15 min. Blood pressure and heart rate were measured before, during, and after the discussion, and blood was remotely drawn at the same time points to quantify numbers of specific leukocyte subsets, NK-cell adhesion molecule expression, and NK cytotoxicity. Couples responded to the conflict task with cardiovascular reactivity; increases in the percentages of circulating NK cells and CD8(+) T cells and decreases in the percentage of circulating CD4(+) T cells; decreases in the percentage of NK cells that express L-selectin; and increases in NK-cell cytotoxicity without a commensurate increase in per-cell cytotoxicity. Rapid downregulation or shedding of L-selectin (CD62L) from NK cells did not contribute to their mobilization during conflict. Instead, CD62L(-) NK cells were mobilized while CD62L(+) NK cells were selectively retained in the vascular marginating pool and/or in extravascular tissue. From a broader perspective, the data support the hypothesis that altered trafficking of specific leukocyte subsets is an integral component of the fight-or-flight response to an acute stressor.

Psychosocial predictors of natural killer cell mobilization during marital conflict

This study examined how specific emotions relate to autonomic nervous and immune system parameters and whether cynical hostility moderates this relationship. Forty-one married couples participated in a 15-min discussion about a marital problem. Observers recorded spouses' emotional expressions during the discussion, and cardiovascular, neuroendocrine, and immunologic parameters were assessed throughout the laboratory session. Among men high in cynical hostility, anger displayed during the conflict was associated with greater elevations in systolic and diastolic blood pressure, cortisol, and increases in natural killer cell numbers and cytotoxicity. Among men low in cynical hostility, anger was associated with smaller increases in heart rate and natural killer cell cytotoxicity. These findings suggest that models describing the impact of stress on physiology should be refined to reflect the joint contribution of situational and dispositional variables.

Signal transduction pathways induced by GM-CSF in microglia: significance in the control of proliferation

Communication between cells of the central nervous system (CNS) and of the immune system is accomplished by a network of cytokines and growth factors. Certain cytokines and growth factors cause activation of microglia, contributing to inflammatory states in the CNS. Granulocyte-macrophage colony-stimulating factor (GM-CSF) has numerous effects on microglia, ranging from induction of proliferation to changes in morphology. GM-CSF is also a growth factor for cells of the myeloid lineage, and the signal tranduction induced by GM-CSF in these cells has been extensively studied. Most notably, the importance of the Jak/STAT and MAP kinase pathways in mitogenesis has been shown in many different systems. We show here that primary microglia and a microglia cell line, BV-2, have a Jak/STAT expression pattern and GM-CSF inducibility similar to that of monocytes and macrophages. Primary microglia and BV-2 cells expressed identical Jak/STATs: Jakl, Jak2, Jak3, Tyk2, STAT1alpha/beta, STAT3, STAT5A, STAT5B, and STAT6. In addition, GM-CSF induced Jak2, STAT5A, and STAT5B in BV-2 cells, as it does in monocytes and macrophages. Immunocytochemical analysis showed that STAT5 translocates to the nucleus following GM-CSF stimulation of microglia. We also found the MAP kinases, ERK1 and ERK2, to be phosphorylated in microglia and BV-2 cells following induction by GM-CSF. Jak2, STAT5A, STAT5B, and ERKs are known to be important in controlling cellular proliferation. Drugs that block these pathways may become tools to control inflammation in the CNS by limiting microglial proliferation.

Psychosocial predictors of natural killer cell mobilization during marital conflict

This study examined how specific emotions relate to autonomic nervous and immune system parameters and whether cynical hostility moderates this relationship. Forty-one married couples participated in a 15-min discussion about a marital problem. Observers recorded spouses' emotional expressions during the discussion, and cardiovascular, neuroendocrine, and immunologic parameters were assessed throughout the laboratory session. Among men high in cynical hostility, anger displayed during the conflict was associated with greater elevations in systolic and diastolic blood pressure, cortisol, and increases in natural killer cell numbers and cytotoxicity. Among men low in cynical hostility, anger was associated with smaller increases in heart rate and natural killer cell cytotoxicity. These findings suggest that models describing the impact of stress on physiology should be refined to reflect the joint contribution of situational and dispositional variables.

Temporal kinetics and cellular phenotype of TNF p55/p75 receptors in experimental allergic encephalomyelitis

TNF-alpha and LT-alpha are thought to be involved in the immunopathology of CNS demyelinating diseases. Both cytokines induce cellular effects through 55-kDa type-1 receptors (R1) and 75-kDa type-2 receptors (R2). To date, no study has specifically identified the various cell populations that express TNF receptors (TNFR) in the inflammatory and demyelinating mouse model, EAE. Phenotyping the TNFR positive cells is important in determining when and where the ligands may be acting and playing a role in disease pathology. We observed an upregulation of TNF R1 and R2 mRNA in high endothelial venules (HEVs) in the lymph node and CNS before the onset of EAE (preclinical phase). This upregulation of TNFR expression in HEVs was followed by a rapid increase in leukocytes within the CNS after the onset of clinical disease. The temporal kinetics of these data suggest that HEVs become activated early, probably through the release of pro-inflammatory cytokines originating from circulating leukocytes. An increase in TNFR on HEVs would make these cells more susceptible to TNF-induced changes, such as increasing cellular adhesion molecules, thereby further facilitating the trafficking of leukocytes into the CNS parenchyma.

Expression of green fluorescent protein in oligodendrocytes in a time- and level-controllable fashion with a tetracycline-regulated system

Developments in transgenic technology have greatly enhanced our ability to understand the functions of various genes in animal models and relevant human diseases. The tetracycline (tet)-regulated transactivation system for inducing gene expression allowed us to control the expression of exogenous genes in a temporal and quantitative way. The ability to manipulate a cell-specific promoter enabled us to express one particular protein in a single type of cell. The combination of a tetracycline system and a tissue-specific promoter has led us to the development of an innovative gene expression system, which is able to express genes in a cell type-specific and time- and level-controllable fashion. An oligodendrocyte-specific myelin basic protein (MBP) gene promoter controls the reversed tet-inducible transactivator. The green fluorescent protein (GFP) gene was placed under the control of the human cytomegalovirus (CMV) basic promoter in tandem with seven tet-responsive elements (TRE), binding sites for the activated transactivator. Upon the addition of doxycycline (DOX, a tetracycline derivative), tet transactivators became activated and bound to one or more TRE, leading to the activation of the CMV promoter and the expression of GFP in oligodendrocytes. We have successfully expressed GFP and luciferase at high levels in oligodendrocytes in a time- and dose-dependent fashion. In the absence of DOX, there was almost no GFP expression in oligodendroglial cultures. Graded levels of GFP expression were observed after induction with DOX (0.5 to 12.5 microg/ml). Our data indicate that this inducible gene expression system is useful for the study of gene function in vivo and for the development of transgenic animal models relevant to human diseases such as multiple sclerosis.

Cardiovascular and immune responses to acute psychological stress in young and old women: a meta-analysis

OBJECTIVE

To describe the relationships between cardiovascular and natural killer (NK) cell number changes on acute psychological stress in women.

METHOD

Data from eight different studies were analyzed. A total of 128 healthy female subjects, 85 younger (18-45 years) and 43 older (49-87 years), had been subjected to a speech stressor (N = 80) or a mental effort stressor (N = 48), mental arithmetic, or the Stroop test. Correlations between changes in NK cell numbers, systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) were computed. Meta-analysis programs were used to study correlations across studies and to examine whether correlations differed with stressors or age.

RESULTS

In all studies, significant increases over baseline were observed for each variable. Across studies, the mean weighted r between changes in HR, DBP, and SBP was medium (rw = .25) to large (rw = .64). A medium to large average correlation between HR and NK changes (rw = .37) was observed, whereas average correlations of changes in NK cell numbers with blood pressure changes were small to medium (rw < or = .23). Correlations between changes in NK cell numbers and cardiovascular variables were homogeneous across studies, whereas mutual correlations between cardiovascular variables were heterogeneous. One moderator variable showed itself: correlations between HR and DBP reactions were larger in studies with older than younger subjects.

CONCLUSION

NK cell changes and HR responses induced by acute stress in women are regulated, to some extent, by the same mechanisms. Neither the type of stressor nor age seem to be very important when considering correlations between NK cell and cardiovascular changes. This study integrates information about NK cell and cardiovascular responses in women that can be used as reference material in future studies.

Differential expression, cytokine modulation, and specific functions of type-1 and type-2 tumor necrosis factor receptors in rat glia

Tumor necrosis factor alpha (TNF alpha) and lymphotoxin alpha (LT alpha) induce pleiotropic cellular effects through low-affinity 55 kDa type-1 receptors (TNFR1, CD120a) and high-affinity 75 kDa type-2 receptors (TNFR2, CD120b). Both cytokines have potent biological effects on glial cells and are strongly implicated in the pathology of central nervous system (CNS) demyelinating diseases. However, to date, neither constitutive nor cytokine-induced TNFR expression by glial cells have been definitively characterized. We therefore characterized TNF receptors at the molecular, protein, and functional levels in rat astrocytes, microglia, and oligodendrocytes. Northern blotting demonstrated that all three types of glia constitutively transcribed a single TNFR1 mRNA. IFN gamma increased transcript levels in all three types of glia, but TNF alpha increased levels only in oligodendrocytes Microglia constitutively transcribed three distinct TNFR2 mRNAs, levels of which were increased by either IFN gamma or TNF alpha. In contrast, astrocytes and oligodendrocytes constitutively transcribed nearly undetectable levels of TNFR2 mRNAs, and levels were not affected by IFN gamma, TNF alpha, or oligodendrocyte maturation. Immunocytochemical staining of glial cells corroborated Northern data by demonstrating that glia express a parallel pattern of TNFR proteins on their cell surfaces. In co-cultures of microglia plated atop irradiated astrocytes, human TNF alpha (which, on mouse cells, binds TNFR1 exclusively) induced microglial cell proliferation, whereas murine TNF alpha (which binds both TNFRs) did not. Collectively, the data show that microglia, a primary source of TNF alpha at CNS inflammatory sites, express both TNFR1 and TNFR2, whereas astrocytes and oligodendrocytes, whose embryological origin differs from that of microglia, predominantly express TNFR1. TNF alpha increases expression of TNFR1 by oligodendrocytes whereas it increases expression of TNFR2 by microglia. Microglia proliferation data suggest that signals transduced through TNFR2 directly or indirectly inhibit signals transduced through TNFR1. Different patterns of TNFR expression by glia at sites of CNS inflammation may be critical in determining whether TNF has activational, proliferative, or cytotoxic effects on these cells.

Expression of ICAM-1, VCAM-1, L-selectin, and leukosialin in the mouse central nervous system during the induction and remission stages of experimental allergic encephalomyelitis

Adhesion molecules facilitate infiltration of leukocytes into the central nervous system (CNS) of mice with experimental allergic encephalomyelitis (EAE). Expression of the adhesion molecules ICAM-1 (CD54), VCAM-1 (CD106), L-selectin (CD62L), and leukosialin (CD43) was analyzed via immunocytochemistry 4-28 days after the injection of encephalitogen into EAE-susceptible SWXJ mice. Constitutive ICAM-1 expression on large-diameter CNS vessels was upregulated on post-injection days 8, 11, 14 and 18 (concurrent with de novo expression on smaller capillaries and glial cells), partially downregulated by day 23, and back to control levels by day 28. Constitutive VCAM-1 expression was upregulated by day 14 and back to control levels by day 28. Upregulation of ICAM-1 temporally coincided with the immigration of CD4+ lymphocytes and L-selectin+ leukocytes into the CNS, while downregulation coincided with their emigration. The infiltration of CD43+ leukocytes also coincided with the upregulation of vascular adhesion molecules, but CD43+ cells remained in the CNS after ICAM-1 and VCAM-1 had returned to control levels. Cellular infiltration and adhesion-molecule expression preceded EAE clinical symptoms by a minimum of 3 days, suggesting a causal role of adhesion molecules in the initiation of CNS inflammation. However, prophylactic injections of monoclonal antibodies against either ICAM-1, L-selectin, or CD43, did not ameliorate the clinical severity of EAE in this model.

Similarity of taste reactivity responses to alcohol and sucrose mixtures in rats

The orofacial responses of rats following infusion of taste solutions were examined in two experiments. In the first experiment, naive rats were presented with a 6% alcohol solution and three sucrose mixtures (sucrose combined with quinine hydrochloride, hydrochloric acid, and sodium chloride, respectively) on separate trials and the resulting taste reactivity was examined. The only difference among the solutions was that alcohol elicited a significantly larger number of aversive responses (e.g., gapes, passive drips) than the sucrose mixtures. In the second experiment, naive rats were trained to avoid 6% alcohol using standard conditioned aversion procedures; rats were then tested for reactivity to the three sucrose mixtures and the alcohol solution. With the alcohol solution, trained rats displayed significantly fewer ingestive responses and significantly more aversive responses than control rats. The response of trained rats to the sucrose + quinine solution was similar to that of alcohol: fewer ingestive responses and more aversive responses than control rats. The number of aversive responses to the alcohol and the sucrose + quinine mixture by the trained rats did not differ significantly. Reactivity to the sucrose + hydrochloric acid and sucrose + sodium chloride solutions did not differ between trained rats and control rats. The results suggest that a sucrose + quinine solution has a perceived taste (as revealed by elicited orofacial reflexes) similar to alcohol and that the sucrose mixture is avoided by rats with alcohol aversions because it is unpalatable.

Taste reactivity to alcohol in rats

Rats were infused intraorally with 4 concentrations of ethanol (3%, 6%, 9%, and 12%), and their subsequent oral, facial, and bodily responses were videotaped and analyzed. Naive rats did not display significant changes in ingestive-type responding over the concentrations tested. A significant increase in aversive responses was noted, with the largest number of aversive responses found with the 12% solution. Initial reactivity failed to predict subsequent consumption when rats were given free access to the same alcohol concentrations during 2-bottle tests. Reactivity testing after the period of alcohol access indicated that only the aversive responding changed significantly from the initial reactivity, with rats showing fewer aversive responses. The results indicated how the taste of alcohol is perceived by naive rats and how this perception is changed after consummatory experience with alcohol.

Taste reactivity to alcohol in rats

Rats were infused intraorally with 4 concentrations of ethanol (3%, 6%, 9%, and 12%), and their subsequent oral, facial, and bodily responses were videotaped and analyzed. Naive rats did not display significant changes in ingestive-type responding over the concentrations tested. A significant increase in aversive responses was noted, with the largest number of aversive responses found with the 12% solution. Initial reactivity failed to predict subsequent consumption when rats were given free access to the same alcohol concentrations during 2-bottle tests. Reactivity testing after the period of alcohol access indicated that only the aversive responding changed significantly from the initial reactivity, with rats showing fewer aversive responses. The results indicated how the taste of alcohol is perceived by naive rats and how this perception is changed after consummatory experience with alcohol.