Neuroendocrine effects of interferon alpha 2-a in healthy human subjects

The acute effects of interferon alpha-2a (3 x 10 IU im) on catecholamine and immunoreactive beta endorphin plasma levels, cortisol serum levels and lymphocyte beta 2-adrenoceptor density were evaluated in ten healthy volunteers. Interferon induced a significant increase in plasma norepinephrine; there was an increased norepinephrine standing response, too. On the contrary, epinephrine standing response was reduced by interferon. Lymphocyte beta 2-adrenoceptors decreased significantly after interferon administration; dissociation constant of binding was unchanged. Cortisol serum levels increased significantly with respect to control test, whereas immunoreactive beta endorphin did not change. These results support the hypothesis of functional relationships between neuroendocrine and immune systems; moreover they may be useful in clinical trials given the administration of interferon alpha in an increasing number of diseases.     

Neuroendocrine and behavioral effects of m-chlorophenylpiperazine administration in rhesus monkeys

The effects of m-chlorophenylpiperazine (mCPP), a serotonin receptor agonist, on the release of plasma prolactin (PRL), growth hormone (GH), and cortisol in the rhesus monkey were studied. mCPP was administered intravenously at doses of 0.5, 1.5, and 3.0 mg/kg. GH and cortisol were increased significantly at all doses whike PRL was significantly increased only following administration of 3.0 mg/kg mCPP. mCPP administration also produced behavioral alterations in each monkey, including sedation, penile erection, and defecation. PRL, GH and behavioral responses to mCPP were completely blocked by pretreatment with the serotonin anatgonist metergoline (MTG). However, pretreatment with MTG failed to entirely antagonize the cortisol response to mCPP. These data suggest that mCPP has prominent neuroendocrine and behavioral effects which are mediated, in part, by serotonergic mechanisms.     

Acute effects of blood flow restriction on exercise-induced free radical production in young and healthy subjects

The main purpose of this study was to investigate the acute local and systemic effects of low-load resistance exercise (30% 1RM) with partial vascular occlusion on exercise-induced free radical production and to compare these effects with other established training methods.

Fifteen young and healthy males (25?±?3 years) performed the following four sessions in a counterbalanced order on separate days: low-load resistance exercise (LI: 30% 1RM), low-load resistance exercise with blood flow restriction (LIBR: 30% 1RM), high-load resistance exercise (HI: 80% 1RM) and an additional session without exercise but blood flow restriction only (BR). Blood samples were obtained 15?min prior to and immediately after exercise sessions from the right index finger and first toe. To analyze concentrations of reactive oxygen species (ROS), electron paramagnetic resonance (EPR) spectroscopy was used. Additionally, mitochondrial ROS production was measured by adding inhibitors of electron transport chain complex III. There was an increased systemic ROS generation after the LIBR session from 0.837?±?0.093 to 0.911?±?0.099?µmol/l/min. However, no local or systemic time?×?condition interaction was detected for ROS production. Regarding mitochondrial ROS production, results were not different between the conditions. Although the low-load resistance exercise session with partial vascular occlusion elicited systemic increases of ROS production, no significant changes were seen on a local level. We assume that this ROS concentration might not be high enough to induce cellular damage but is rather involved in muscle remodulation. However, this needs to be confirmed by future research.     

Cardiovascular and parasympathetic effects of dexmedetomidine in healthy subjects

We evaluated the cardiovascular effects of intravenously (i.v.) and buccally administered dexmedetomidine, a selective alpha2-adrenoceptor agonist. Six healthy male subjects were studied unmedicated and after 2 micro g/kg i.v. or buccal doses of dexmedetomidine, using repeated recordings of ECG and blood pressure. Cardiac parasympathetic activity was estimated by measurements of high-frequency (HF) heart rate variability. Intravenous, but not buccal, dexmedetomidine raised systolic blood pressure by 11 +/- 5 mmHg (mean +/- SEM) and diastolic by 16 +/- 3 mmHg (maxima at 10 min). Later on, both i.v., and buccal dexmedetomidine produced a very similar hypotensive effect: on average, >or=10 mmHg reductions in systolic and diastolic pressure at 3 h. Intravenous dosing was followed by a decline in heart rate (-11 +/- 2 beats/min) accompanied by a trend toward enhanced HF variability (maximal effect at 10 min), which probably reflected baroreflex-mediated parasympathetic efferent neuronal activation. Buccal dexmedetomidine increased significantly the HF variability (maximum at 45 min) without influencing heart rate. We conclude that dexmedetomidine, when administered by a method that avoids concentration peaks, e.g., buccal dosing, can be used to produce a prolonged augmentation of cardiac parasympathetic efferent neuronal activity.     

Serial cerebrospinal fluid tryptophan and 5-hydroxy indoleacetic acid concentrations in healthy human subjects

The role of the serotonergic system in the pathogenesis of behavioral disorders such as depression, alcoholism, obsessive-compulsive disorder, and violence is not completely understood. Measurement of the concentration of neurotransmitters and their metabolites in cerebrospinal fluid (CSF) is considered among the most valid, albeit indirect, methods of assessing central nervous system function in man. However, most studies in humans have measured lumbar CSF concentrations only at single time points, thus not taking into account rhythmic or episodic variations in levels of neurotransmitters, precursors, or metabolites. We have continuously sampled lumbar CSF via subarachnoid catheter in 12 healthy volunteers, aged 20-65 years. One ml (every 10 min) CSF samples were collected at a rate of 0.1ml/min for 24-hour (h), and the levels of tryptophan (TRP) and 5-hydroxy indoleacetic acid (5-HIAA) were measured. Variability across all 12 subjects was significantly greater (P < 0.0001) than the variability seen in repeated analysis of a reference CSF sample for both 5-HIAA (32.0% vs 7.9%) and TRP (25.4% vs 7.0%), confirming the presence of significant biological variability during the 24-hr period examined. This variability could not be explained solely by meal related effects. Cosinor analysis of the 24-hr TRP concentrations from all subjects revealed a significant diurnal pattern in CSF TRP levels, whereas the 5-HIAA data were less consistent. These studies indicate that long-term serial CSF sampling reveals diurnal and biological variability not evident in studies based on single CSF samples.     

Biochemical responses of healthy subjects during dietary supplementation with L-arginine

Dietary supplements of L-arginine, a substrate for nitric oxide synthases, may promote formation of nitric oxide and thus may be of clinical benefit. However, the optimal level of L-arginine supplementation is unclear. The objective of this study was to evaluate the response of healthy individuals to increasing doses of L-arginine (as free acid). Twelve healthy subjects were recruited and instructed to take L-arginine for 1-week periods at daily doses of 3, 9, 21, and 30 g. At baseline and at the end of each week, 24-hour urine and fasting blood samples were collected, and weight, diastolic blood pressure, and systolic blood pressure were recorded. Samples were analyzed for L-arginine, L-citrulline, glycine, L-lysine, L-ornithine, asymmetric dimethy L-arginine, symmetric dimethy L-arginine, glucose, insulin (serum), creatinine, cGMP (urine), and total nitrates (serum and urine). Ten subjects reported adverse side effects at initial L-arginine doses of 21 g/day (five subjects) or 30 g/day (five subjects), respectively. Blood pressure and weight did not change during the supplementation period. Of the individual biochemical measures, only L-arginine, glycine, and L-ornithine concentrations changed significantly. The mean concentration of L-arginine reached a peak during supplementation at 9 g/d; however, individuals differed markedly in their response. Availability of L-arginine, relative to that of asymmetric dimethy L-arginine, increased significantly at both 9 g/day and 21 g/day. Mean values indicate that supplementation with 9 g/day of L-arginine, a dose associated with minimal adverse side effects, is sufficient to increase circulating L-arginine concentrations. However, subjects varied widely in their responses, indicating that L-arginine supplementation needs to be tailored to individuals.     

The effects of dietary restriction on oxidative stress in rodents

Oxidative stress is observed during aging and in numerous age-related diseases. Dietary restriction (DR) is a regimen that protects against disease and extends life span in multiple species. However, it is unknown how DR mediates its protective effects. One prominent and consistent effect of DR in a number of systems is the ability to reduce oxidative stress and damage. The purpose of this review is to comprehensively examine the hypothesis that dietary restriction reduces oxidative stress in rodents by decreasing reactive oxygen species (ROS) production and increasing antioxidant enzyme activity, leading to an overall reduction of oxidative damage to macromolecules. The literature reveals that the effects of DR on oxidative stress are complex and likely influenced by a variety of factors, including sex, species, tissue examined, types of ROS and antioxidant enzymes examined, and duration of DR. Here we present a comprehensive review of the existing literature on the effect of DR on mitochondrial ROS generation, antioxidant enzymes, and oxidative damage. In a majority of studies, dietary restriction had little effect on mitochondrial ROS production or antioxidant activity. On the other hand, DR decreased oxidative damage in the majority of cases. Although the effects of DR on endogenous antioxidants are mixed, we find that glutathione levels are the most likely antioxidant to be increased by dietary restriction, which supports the emerging redox-stress hypothesis of aging.     

Discriminating between energetic content and dietary composition as an explanation for dietary restriction effects

A reduction in dietary calories has been shown to prolong life span in a wide variety of taxa, but there has been much debate about confounding factors such as nutritional composition of the diet, or reallocation of nutrients from reduced reproduction. To disentangle the contribution of these different mechanisms to extension of life span, we study the effect of caloric restriction on longevity and fecundity in two species of sugar-feeding parasitoid wasps. They have a simple diet that consists of carbohydrates only, and they do not resorb eggs, which rules out the proposed alternative explanations for beneficial effects of caloric restriction. Two caloric restriction treatments were applied: first, dietary dilution to investigate the effect of carbohydrate concentration in the diet; and second, intermittent feeding to examine the effect of feeding frequency on longevity and fecundity. Only the dietary dilution treatment showed an effect of caloric restriction with the highest longevity recorded at 80% sucrose (w/v). No effect of dietary regime was found on fecundity. We also measured the weight increase of the parasitoids after feeding to obtain an estimate of consumption. A constant quantity of the sugar solution was consumed in all dietary dilution treatments, hence caloric intake was proportional to sucrose concentrations. Although the present study does not disqualify the relevance of nutrient composition in other species, our data unequivocally demonstrate that caloric restriction alone is sufficient to extend life span and invalidate alternative explanations.     

Effect of citrulline on muscle functions during moderate dietary restriction in healthy adult rats

Low calorie diets are designed to reduce body weight and fat mass, but they also lead to a detrimental loss of lean body mass, which is an important problem for overweight people trying to lose weight. In this context, a specific dietary intervention that preserves muscle mass in people following a slimming regime would be of great benefit. Leucine (LEU) and Citrulline (CIT) are known to stimulate muscle protein synthesis (MPS) in post-prandial and post-absorptive state, respectively. This makes them interesting bioactive components to test in the context of dietary restriction. We tested the concept of combining LEU and CIT in adult female rats. We postulated that the sequential administration of LEU (mixed in chow) and CIT (given in drinking water before a rest period) could be beneficial for preservation of muscle function during food restriction. Sixty female rats (22 weeks old) were randomized into six groups: one group fed ad libitum with a standard diet (C) and five food-restricted groups (60 % of spontaneous intake for 2 weeks) receiving a standard diet (R group), a CIT-supplemented diet (0.2 or 1 g/kg/day, CIT0.2 group and CIT1 group, respectively), a LEU-supplemented diet (1.0 g/kg/day) or a CIT + LEU-supplemented diet (CIT + LEU 1.0 g/kg/day each). At the end of the experiment, body composition, muscle contractile properties and muscle protein synthesis (MPS) rate were studied in the tibialis anterior muscle. Dietary restriction tended to decrease MPS (R: 2.5 ± 0.2 vs. C: 3.4 ± 0.4 %/day, p = 0.06) and decrease muscle strength (R: 3,045 ± 663 vs. C: 5,650 ± 661 A.U., p = 0.03). Only CIT administration (1 g/kg) was able to restore MPS (CIT1: 3.4 ± 0.3 vs. R: 2.5 ± 0.2 %/day, p = 0.05) and increase muscle maximum tetanic force (CIT1: 441 ± 15 vs. R: 392 ± 22 g, p = 0.05) and muscle strength (CIT1: 4,259 ± 478 vs. R: 3,045 ± 663 A.U., p = 0.05). LEU had no effect and CIT + LEU supplementation had few effects, limited to adipose mass and fatigue force. The results of this study highlight the ability of CIT alone to preserve muscle function during dietary restriction. Surprisingly, LEU antagonized some effects of CIT. The mechanisms involved in this antagonistic effect warrant further study.     

Neuroendocrine correlates of behavioral polymorphism in white-throated sparrows

Interspecific differences in the neuropeptide systems of the lateral septum (LS) often parallel differences in social behavior. In rodents, some closely related species that differ in aggressive behavior also differ according to the level of vasopressin (VP) innervation of the LS. In songbirds, the neuropeptides vasotocin (VT) and vasoactive intestinal peptide (VIP) affect aggression when administered directly to the LS. Here, we tested whether the density of VT or VIP innervation of the LS reflects patterns of intraspecific behavioral polymorphism in male and female white-throated sparrows (Zonotrichia albicollis), in which the "white-stripe" (WS) morph behaves more aggressively than the "tan-stripe" (TS) morph. We found that the WS birds had more VT-immunoreactivity (IR) than the TS birds in the ventrolateral subdivision of the caudal LS (LSc.vl) and in the medial portion of the bed nucleus of the stria terminalis (BSTm). In addition, the TS birds had more densely stained VIP-IR in the LSc.vl than the WS birds. Males had more VT-IR than females in the LSc.vl and BSTm, and more VIP-IR in the LSc.vl. We also report sex and morph differences in VIP-IR in the basal hypothalamus, where VIP is synthesized and released into the portal vasculature. Males had nearly twice as many VIP-immunoreactive (ir) neurons in the infundibular nucleus than did females, and birds of the WS morph had more densely stained VIP-IR in the median eminence than TS birds. Our results support the hypothesis that differences in these neuropeptide systems underlie inter- and intraspecific differences in social behavior across vertebrates.     

Supraorbital transcutaneous neurostimulation has sedative effects in healthy subjects

Background

Transcutaneous neurostimulation (TNS) at extracephalic sites is a well known treatment of pain. Thanks to recent technical progress, the Cefaly^® device now also allows supraorbital TNS. During observational clinical studies, several patients reported decreased vigilance or even sleepiness during a session of supraorbital TNS. We decided therefore to explore in more detail the potential sedative effect of supraorbital TNS, using standardized psychophysical tests in healthy volunteers.

Methods

We performed a double-blind cross-over sham-controlled study on 30 healthy subjects. They underwent a series of 4 vigilance tests (Psychomotor Vigilance Task, Critical Flicker Fusion Frequency, Fatigue Visual Numeric Scale, d2 test). Each subject was tested under 4 different experimental conditions: without the neurostimulation device, with sham supraorbital TNS, with low frequency supraorbital TNS and with high frequency supraorbital TNS.

Results

As judged by the results of three tests (Psychomotor Vigilance Task, Critical Flicker Fusion Frequency, Fatigue Visual Numeric Scale) there was a statistically significant (p < 0.001) decrease in vigilance and attention during high frequency TNS, while there were no changes during the other experimental conditions. Similarly, performance on the d2 test was impaired during high frequency TNS, but this change was not statistically significant.

Conclusion

Supraorbital high frequency TNS applied with the Cefaly^® device decreases vigilance in healthy volunteers. Additional studies are needed to determine the duration of this effect, the underlying mechanisms and the possible relation with the stimulation parameters. Meanwhile, this effect opens interesting perspectives for the treatment of hyperarousal states and, possibly, insomnia.

     

Neuroendocrine and behavioral implications of endocrine disrupting chemicals in quail

Studies in our laboratory have focused on endocrine, neuroendocrine, and behavioral components of reproduction in the Japanese quail. These studies considered various stages in the life cycle, including embryonic development, sexual maturation, adult reproductive function, and aging. A major focus of our research has been the role of neuroendocrine systems that appear to synchronize both endocrine and behavioral responses. These studies provide the basis for our more recent research on the impact of endocrine disrupting chemicals (EDCs) on reproductive function in the Japanese quail. These endocrine active chemicals include pesticides, herbicides, industrial products, and plant phytoestrogens. Many of these chemicals appear to mimic vertebrate steroids, often by interacting with steroid receptors. However, most EDCs have relatively weak biological activity compared to native steroid hormones. Therefore, it becomes important to understand the mode and mechanism of action of classes of these chemicals and sensitive stages in the life history of various species. Precocial birds, such as the Japanese quail, are likely to be sensitive to EDC effects during embryonic development, because sexual differentiation occurs during this period. Accordingly, adult quail may be less impacted by EDC exposure. Because there are a great many data available on normal development and reproductive function in this species, the Japanese quail provides an excellent model for examining the effects of EDCs. Thus, we have begun studies using a Japanese quail model system to study the effects of EDCs on reproductive endocrine and behavioral responses. In this review, we have two goals: first, to provide a summary of reproductive development and sexual differentiation in intact Japanese quail embryos, including ontogenetic patterns in steroid hormones in the embryonic and maturing quail. Second, we discuss some recent data from experiments in our laboratory in which EDCs have been tested in Japanese quail. The Japanese quail provides an excellent avian model for testing EDCs because this species has well-characterized reproductive endocrine and behavioral responses. Considerable research has been conducted in quail in which the effects of embryonic steroid exposure have been studied relative to reproductive behavior. Moreover, developmental processes have been studied extensively and include investigations of the reproductive axis, thyroid system, and stress and immune responses. We have conducted a number of studies, which have considered long-term neuroendocrine consequences as well as behavioral responses to steroids. Some of these studies have specifically tested the effects of embryonic steroid exposure on later reproductive function in a multigenerational context. A multigenerational exposure provides a basis for understanding potential exposure scenarios in the field. In addition, potential routes of exposure to EDCs for avian species are being considered, as well as differential effects due to stage of the life cycle at exposure to an EDC. The studies in our laboratory have used both diet and egg injection as modes of exposure for Japanese quail. In this way, birds were exposed to a specific dose of an EDC at a selected stage in development by injection. Alternatively, dietary exposure appears to be a primary route of exposure; therefore experimental exposure through the diet mimics potential field situations. Thus, experiments should consider a number of aspects of exposure when attempting to replicate field exposures to EDCs.     

Combined effects of vibration and noise on palmar sweating in healthy subjects

The combined effects of vibration and noise on palmar sweating were studied experimentally in healthy subjects. Ten subjects were exposed to vibration at an acceleration of 100 m.sec-2 root mean square at a frequency of 125 Hz, a noise level of 105 dB(A) at a frequency of 1000 Hz and both stimuli together. Vibration was applied to the right hand and noise to both ears from headphones. Palmar sweating was measured by the ventilated capsule method. Vibration caused a marked increase in palmar sweating of the right hand directly exposed to vibration and also of the left hand not exposed to vibration. Simultaneous vibration and noise caused a greater increase in palmar sweating than by each of the factors separately. The combined effects tended to be greater in subjects who were more susceptible to vibration or noise.     

Feedback effects of circulating norepinephrine on sympathetic outflow in healthy subjects

The amplitude of low-frequency (LF) oscillations of heart rate (HR) usually reflects the magnitude of sympathetic activity, but during some conditions, e.g., physical exercise, high sympathetic activity results in a paradoxical decrease of LF oscillations of HR. We tested the hypothesis that this phenomenon may result from a feedback inhibition of sympathetic outflow caused by circulating norepinephrine (NE). A physiological dose of NE (100 ng.kg(-1).min(-1)) was infused into eight healthy subjects, and infusion was continued after alpha-adrenergic blockade [with phentolamine (Phe)]. Muscle sympathetic nervous activity (MSNA) from the peroneal nerve, LF (0.04-0.15 Hz) and high frequency (HF; 0.15-0.40 Hz) spectral components of HR variability, and systolic blood pressure variability were analyzed at baseline, during NE infusion, and during NE infusion after Phe administration. The NE infusion increased the mean blood pressure and decreased the average HR (P < 0.01 for both). MSNA (10 +/- 2 vs. 2 +/- 1 bursts/min, P < 0.01), LF oscillations of HR (43 +/- 13 vs. 35 +/- 13 normalized units, P < 0.05), and systolic blood pressure (3.1 +/- 2.3 vs. 2.0 +/- 1.1 mmHg2, P < 0.05) decreased significantly during the NE infusion. During the NE infusion after PHE, average HR and mean blood pressure returned to baseline levels. However, MSNA (4 +/- 2 bursts/min), LF power of HR (33 +/- 9 normalized units), and systolic blood pressure variability (1.7 +/- 1.1 mmHg2) remained significantly (P < 0.05 for all) below baseline values. Baroreflex gain did not change significantly during the interventions. Elevated levels of circulating NE cause a feedback inhibition on sympathetic outflow in healthy subjects. These inhibitory effects do not seem to be mediated by pressor effects on the baroreflex loop but perhaps by a presynaptic autoregulatory feedback mechanism or some other mechanism that is not prevented by a nonselective alpha-adrenergic blockade.