Circadian analysis of mononuclear cells in the rat following pinealectomy and superior cervical ganglionectomy

Neuroimmune Interactions and Rhythmic Regulation of Innate Lymphoid Cells

The Earth’s rotation around its axis, is one of the parameters that never changed since life emerged. Therefore, most of the organisms from the cyanobacteria to humans have conserved natural oscillations to regulate their physiology. These daily oscillations define the circadian rhythms that set the biological clock for almost all physiological processes of an organism. They allow the organisms to anticipate and respond behaviorally and physiologically to changes imposed by the day/night cycle. As other physiological systems, the immune system is also regulated by circadian rhythms and while diurnal variation in host immune responses to lethal infection have been observed for many decades, the underlying mechanisms that affect immune function and health have only just started to emerge. These oscillations are generated by the central clock in our brain, but neuroendocrine signals allow the synchronization of the clocks in peripheral tissues. In this review, we discuss how the neuroimmune interactions create a rhythmic activity of the innate lymphoid cells. We highlight how the disruption of these rhythmic regulations of immune cells can disturb homeostasis and lead to the development of chronic inflammation in murine models.

Interpreting Stress Responses during Routine Toxicity Studies

Stress often occurs during toxicity studies. The perception of sensory stimuli as stressful primarily results in catecholamine release and activation of the hypothalamic–pituitary–adrenal (HPA) axis to increase serum glucocorticoid concentrations. Downstream effects of these neuroendocrine signals may include decreased total body weights or body weight gain; food consumption and activity; altered organ weights (e.g., thymus, spleen, adrenal); lymphocyte depletion in thymus and spleen; altered circulating leukocyte counts (e.g., increased neutrophils with decreased lymphocytes and eosinophils); and altered reproductive functions. Typically, only some of these findings occur in a given study. Stress responses should be interpreted as secondary (indirect) rather than primary (direct) test article–related findings. Determining whether effects are the result of stress requires a weight-of-evidence approach. The evaluation and interpretation of routinely collected data (standard in-life, clinical pathology, and anatomic pathology endpoints) are appropriate and generally sufficient to assess whether or not changes are secondary to stress. The impact of possible stress-induced effects on data interpretation can partially be mitigated by toxicity study designs that use appropriate control groups (e.g., cohorts treated with vehicle and subjected to the same procedures as those dosed with test article), housing that minimizes isolation and offers environmental enrichment, and experimental procedures that minimize stress and sampling and analytical bias.

This article is a comprehensive overview of the biological aspects of the stress response, beginning with a Summary (Section 1) and an Introduction (Section 2) that describes the historical and conventional methods used to characterize acute and chronic stress responses. These sections are followed by reviews of the primary systems and parameters that regulate and/or are influenced by stress, with an emphasis on parameters evaluated in toxicity studies: In-life Procedures (Section 3), Nervous System (Section 4), Endocrine System (Section 5), Reproductive System (Section 6), Clinical Pathology (Section 7), and Immune System (Section 8). The paper concludes (Section 9) with a brief discussion on Minimizing Stress-Related Effects (9.1.), and a final section explaining why Parameters routinely measured are appropriate for assessing the role of stress in toxicology studies (9.2.).

Inflammation in the avian spleen: timing is everything

Background

The synchrony of an organism with both its external and internal environment is critical to well-being and survival. As a result, organisms display daily cycles of physiology and behavior termed circadian rhythms. At the cellular level, circadian rhythms originate via interlocked autoregulatory feedback loops consisting of circadian clock genes and their proteins. These regulatory loops provide the molecular framework that enables the intracellular circadian timing system necessary to generate and maintain subsequent 24 hr rhythms. In the present study we examine the daily control of circadian clock genes and regulation of the inflammatory response by the circadian clock in the spleen.

Results

Our results reveal that circadian clock genes as well as proinflammatory cytokines, including Tnfά and IL-1β, display rhythmic oscillations of mRNA abundance over a 24 hr cycle. LPS-induced systemic inflammation applied at midday vs. midnight reveals a differential response of proinflammatory cytokine induction in the spleen, suggesting a daily rhythm of inflammation. Exogenous melatonin administration at midday prior to LPS stimulation conveys pleiotropic effects, enhancing and repressing inflammatory cytokines, indicating melatonin functions as both a pro- and anti-inflammatory molecule in the spleen.

Conclusion

In summary, a daily oscillation of circadian clock genes and inflammatory cytokines as well as the ability of melatonin to function as a daily mediator of inflammation provides valuable information to aid in deciphering how the circadian timing system regulates immune function at the molecular level. However, further research is needed to clarify the precise mechanisms by which the circadian clock and melatonin have an impact upon daily immune functions in the periphery.

Are circadian rhythms the code of hypothalamic-immune communication? Insights from natural killer cells

Circadian rhythms in physiology and behavior are ultimately regulated at the hypothalamic level by the suprachiasmatic nuclei (SCN). This central oscillator transduces photic information to the cellular clocks in the periphery through the autonomic nervous system and the neuroendocrine system. The fact that these two systems have been shown to modulate leukocyte physiology supports the concept that the circadian component is an important aspect of hypothalamic-immune communication. Circadian disruption has been linked to immune dysregulation, and recent reports suggest that several circadian clock genes, in addition to their time-keeping role, are involved in the immune response. In this overview, we summarize the findings demonstrating that Natural Killer (NK) cell function is under circadian control.

Evidence supporting a circadian control of natural killer cell function

Natural killer (NK) cells participate in the immune response against infection and cancer. An emerging body of epidemiological data supports that circadian homeostasis may constitute a factor risk for cancer development. Physiological rhythms under circadian control persist in the absence of light entrainment and ultimately rely on a molecular clock. We have previously shown that NK cell cytolytic activity follows a daily rhythm and that NK cells enriched from light-entrained rats present 24-h oscillations of clock genes, cytolytic factors, and cytokines. To investigate whether these oscillations are under a genuine circadian control, we assessed the daily expression of clock genes (Per1, Per2, Clock, and Bmal1), a clock-controlled gene (Dbp), cytolytic factors (granzyme B and perforin), and cytokines (IFN-gamma and TNF-alpha) in NK cells enriched from rats maintained in constant darkness (DD). In addition, we investigated whether the disruption of the NK cell clock by RNA interference (RNAi) affects the expression of cytolytic factors and cytokines. Persistent 24-h oscillations were found in the expression levels of clock genes, cytolytic factors, and cytokines in NK cells enriched from DD rats. In addition, RNAi-mediated Per2 knockdown caused a significant decrease of granzyme B and perforin levels in the rat derived NK cell line RNK16. Taken together, these results provide evidence supporting that NK cell function is under circadian regulation.

Characterization of lymphocyte subsets over a 24-hour period in Pineal-Associated Lymphoid Tissue (PALT) in the chicken

BACKGROUND

Homeostatic trafficking of lymphocytes in the brain has important relevance to the understanding of CNS disease processes. The pineal gland of the chicken contains large accumulations of lymphocytes that suggest an important role related to homeostatic circadian neuro-immune interactions. The purpose of this initial study was to characterize the lymphocyte subsets in the pineal gland and quantitate the distribution and frequency of lymphocyte phenotypes at two time points over the 24-hour light:dark cycle.

RESULTS

PALT comprised approximately 10% of the total pineal area. Image analysis of immunocytochemically stained sections showed that the majority of lymphocytes were CD3+ (80%) with the remaining 20% comprising B-cells and monocytes (Bu-1+), which tended to distribute along the periphery of the PALT. T-cell subsets in PALT included CD4+ (75-80%), CD8+ (20-25%), TCRalphabeta/Vbeta1+ (60%), and TCRgammadelta+ (15%). All of the T-cell phenotypes were commonly found within the interfollicular septa and follicles of the pineal gland. However, the ratios of CD8+/CD4+ and TCRgammadelta+/TCRalphabeta/Vbeta1+ within the pineal tissue were each 1:1, in contrast to the PALT where the ratios of CD8+/CD4+ and TCRgammadelta+/TCRalphabeta/Vbeta1+ each approximated 1:4. Bu-1+ cells were only rarely seen in the pineal interstitial spaces, but ramified Bu-1+ microglia/macrophages were common in the pineal follicles. Effects of the 24-h light:dark cycle on these lymphocyte-pineal interactions were suggested by an increase in the area of PALT, a decline in the density of TCRalphabeta/Vbeta1+ cells, and a decline in the area density of Bu-1+ microglia at the light:dark interphase (1900 h) compared to the dark:light interphase (0700 h).

CONCLUSION

The degree of lymphocyte infiltration in the pineal suggests novel mechanisms of neuro-immune interactions in this part of the brain. Our results further suggest that these interactions have a temporal component related to the 24-hour light:dark cycle and that CD8+ and TCRgammadelta+ T-cells are preferentially recruited to the pineal follicles. Pineal microglia/macrophages were common and represent an important candidate for mediating these lymphocyte-pineal interactions via secretion of cytokines and chemokines.

Anti-inflammatory and opioid-mediated effects of melatonin on experimental peritonitis in chickens

The immunomodulatory properties of melatonin (Mel) are generally recognized but the mechanisms of its action are not fully understood. In mammals, some of the immunomodulatory effects of Mel are mediated by opioids synthesized by immune cells under its influence. The present study was performed to examine whether Mel-induced opioids are involved in the immunomodulatory activity of Mel in chickens. Experimental peritonitis was evoked by a single ip injection of thioglycollate (TG), and half of the birds were pre-treated with Mel. Some of the Mel-treated birds were additionally pre-treated with naltrexone, an antagonist of opioid receptors. Control birds received an injection of saline, Mel or were untreated. At specific post-injection intervals chickens were sacrificed, the peritoneal cavity was flushed out and peritoneal leukocytes (PTLs) were counted. The activity of PTLs was measured in vitro by the level of reactive oxygen species (ROS). Splenocytes were isolated aseptically and mitogen-stimulated in vitro proliferation was assessed. In PTLs and splenocytes the expression of opioid (proopiomelanocortin and proenkephalin) genes was also examined. Mel exerted a bi-phasic effect on TG-induced peritonitis in chickens: initially it blocked the development of peritonitis, decreasing the number of PTLs and intracellular ROS level (anti-inflammatory action), and thereafter an increase in both PTL number and ROS level was observed (pro-inflammatory action). The pro-inflammatory effect occurred a few hours after the induction of expression of the proenkephalin gene in PTLs and both the proenkephalin and proopiomelanocortin genes in splenocytes. These effects were prevented by naltrexone, suggesting involvement of the opiatergic mechanism.

Comparative study of the heterophil phagocytic function in young and old ring doves (Streptopelia risoria) and its relationship with melatonin levels

A functional connection between the pineal gland (via the hormone melatonin) and the immune system has been suggested. In our previous results in the ring dove, we observed diurnal oscillations in the levels of this neurohormone in young animals and a decline in its plasma levels with advancing age (which is accompanied by the absence of diurnal rhythm). We also noted enhanced phagocytic activity of heterophils from old animals after in vitro incubation with both physiological and pharmacological doses of melatonin. Here, we evaluate the functional capacity of ring dove (Streptopelia risoria) heterophils in young (2 years of age) and old (8 years and more) animals at different times of day (0:00, 10:00 and 16:00, the times when the maximum, minimum, and mean values, respectively, of melatonin levels are observed in young animals). The phagocytic capacities for the ingestion of latex beads and Candida albicans were evaluated, as well as the oxidative metabolism which accompanies phagocytosis. At all three times of day studied, the heterophil phagocytic function with both latex and C. albicans was significantly greater in the young than in the old animals, and in the young animal cells it was significantly higher at 0:00. In addition, in the presence of latex beads, there was a significant decline at 10:00 and 0:00 of superoxide anion levels in the young animals relative to the old. In the young animals, there was a decline at 0:00 in comparison with both 10:00 and 16:00, and in the old animals there was a decline at both 0:00 and 16:00 compared with 10:00. These results could be due, at least in part, to the absence of a diurnal rhythm of melatonin in old animals, and to an enhancing effect of that hormone on young animals' heterophil phagocytic function, which would also neutralize the oxidative stress deriving from this immune function.

Circadian Rhythms of Granzyme B, Perforin, IFN-γ, and NK Cell Cytolytic Activity in the Spleen: Effects of Chronic Ethanol

Recent studies show that alterations in the body's biological rhythms can lead to serious pathologies, including cancer. Acute and chronic ethanol consumption impairs the immune system by causing specific defects in the cellular components of the innate immune response and by creating increased risk and susceptibility to infections and cancer. NK cells are critical for immune surveillance against infected and malignant cells. To assess whether NK cell function follows a circadian trend and to determine ethanol effects on this rhythm, we measured, over a 24-h period, mRNA and protein levels of granzyme B, perforin, and the cytokine IFN-gamma, as well as NK cell activity, in the splenocytes of ad libitum-fed, pair-fed, and ethanol-fed Sprague Dawley male rats. Circadian rhythms were found in mRNA and protein levels of granzyme B, perforin, and IFN-gamma. A circadian pattern was also detected in NK cell cytolytic activity. Our data further demonstrated how chronic ethanol suppressed NK cell activity by directly disrupting the circadian rhythms of granzyme B, perforin, and IFN-gamma. These findings identify the circadian functions of splenic NK cells and show the vulnerability of these rhythms to chronic ethanol.

Circadian rhythms in surface molecules of rat blood lymphocytes

The present article examines whether the expression of certain surface molecules that trigger immune responses shows a circadian rhythm. We also analyzed the rhythms in the number and percentage of lymphocyte subpopulations, in the leukocyte differential counts, and in the total red and white blood cell counts. Blood samples obtained from rats at 2-h intervals for 24 h were stained with several mouse monoclonal antibodies directed against lymphocyte surface molecules and processed by flow cytometry. The number of B, total T, Tgammadelta, Th, and Ts/c cells followed a 24-h rhythm with a peak in the first half of the resting period. The expression of CD45, CD5, CD3, and CD4 followed a circadian rhythm. Their acrophases suggested temporal association between CD45 and CD5 at the end of the active phase and between CD4 and CD3 at the beginning of this phase. This temporal organization could have an important role for immune cell function.

The effect of melatonin on peripheral blood cells during total body irradiation in rats

Melatonin, has been reported to participate in the regulation of a number of important physiological and pathological process. It has also the ability to protect the genetic material of hematopoietic cells of mice from damaging effects of acute total body irradiation. The objective of this study was to the potential radioprotective effects of pharmacological doses of melatonin in total body irradiated rat's peripheral blood cells. Forty adult rats were divided into 4 equal groups. Group 1 received no melatonin or irradiation (control group), while group 2 received only melatonin (5 mg/kg, i.p.). Group 3 received only total body irradiation (RT) by 5 Gy of gamma irradiation only and group 4 received RT plus melatonin (5 mg/kg, i.p., 30 min before RT). An hour and a half following RT, blood samples were taken. Leukocytes and thrombocytes number and hemoglobin levels were measured in all groups. Five mg/kg dose of melatonin significantly protected leukocytes and as well as thrombocytes number against y irradiation. There were no significant differences between Hb levels. Our results suggest that melatonin administration prior to irradiation prevented radiation damage on peripheral blood cells. Melatonin radioprotection is achieved by its ability as a scavenger for free radicals generated by ionizing radiation and acts probably as a growth factor, especially for granulocytes in bone marrow.

Diurnal changes in lung tumor clearance and their relation to NK cell cytotoxicity in the blood and spleen

Natural killer cell cytotoxicity (NKCC) was reported to manifest a circadian rhythm, peaking during wakefulness in both human blood and rat spleen. Using F344 rats, we investigated whether such fluctuations (i) reflect changes in NK cell numbers or in cytotoxicity per cell; (ii) coincide in the blood and spleen; (iii) correspond with clearance of NK-sensitive tumor cells from the lungs and (iv) influence formation of lung metastases. Two rat groups were housed in opposite 12:12 hr lighting regimens. Two hours after the onset of light or dark, both groups were either sacrificed or intravenously inoculated with tumor cells to study the following indices: NKCC and NK cell numbers in the spleen (n = 29) and blood (n = 79), lung clearance of tumor cells (n = 142) and lung metastasis (n = 69). The tumor employed, MADB106, is an NK-sensitive mammary adenocarcinoma that metastasizes only to the lungs. The results indicated that, during the dark phase, splenic NKCC increased (37% higher lytic unit [LU](50)) mostly due to a 28.9% higher percentage of NK cells in the spleen. In contrast, blood NKCC decreased by 42.5% (LU(20)) and this decline was independent of circulating NK cell numbers, which remained constant. Lung tumor clearance increased in the dark (up to 42% lower retention 9 hr after inoculation), but no corresponding changes in the number of metastases were observed 3 weeks later. We conclude that diurnal changes in rats' NKCC are organ-specific, involve changes in both cell distribution and activity and may affect short-term in vivo indices of NK tumoricidal activity.

Relationship between the annual rhythms in melatonin and immune system status in the tropical palm squirrel, Funambulus pennanti

Melatonin (MEL) regulation of seasonal variation in immunity has been studied extensively in temperate mammals. This report is the first on a tropical mammal, the Indian palm squirrel, F. pennanti. In response to the annual environmental cycle, we studied the rhythms of plasma MEL and the immune parameters of total blood leucocytes, absolute blood lymphocytes and blastogenic responses of blood, thymus and spleen lymphocytes. We found that in parallel with MEL all the immune parameters increased during the month of April onward, when natural day length, temperature, humidity and rainfall were increasing. Maximum values occurred during November (reproductively inactive phase) when the values of all the physical factors were comparatively low. Lowest values occurred during January-March (reproductively active phase) when the values of the physical factors were lowest. In order to establish a clear interrelationship between the pineal MEL and the immune system function, we manipulated these squirrels with exogenous MEL (25mg/100 g B wt/day) at 1730 h during their pineal inactive phase (March) while another group was pinealectomized (Px) during November when their pineal was active. The MEL injection significantly increased all the immune parameters, while Px decreased them significantly. Hence, we suggest that MEL is immuno-enhancing for this tropical squirrel, and plays an important role in the maintenance of its immunity in accordance with the seasonal changes in environmental factors and gonadal status.

Does melatonin modulate beta-endorphin, corticosterone, and pain threshold?

Converging lines of evidence suggest that the pineal hormone, melatonin, may regulate changes in pain threshold by modulating fluctuations in opioid receptor expression and levels of beta-endorphin (beta-END). This study investigated whether the circadian oscillation in plasma melatonin is involved in the modulation of plasma beta-END immunoreactivity (beta-END-ir), and whether fluctuations in pain threshold measured using the hotplate test are contingent upon the fluctuation of these two hormones in Rattus Norvegicus. The role of melatonin was explored using light-induced functional pinealectomy (LFPX) to suppress nocturnal melatonin release. Pinealectomized rats were found to have significantly elevated levels of beta-END-ir compared to control animals at both photophase (398 +/- 89 pg/ml versus 180 +/- 23 pg/ml) and scotophase (373 +/- 45 pg/ml versus 203 +/- 20 pg/ml) test-periods, thus supporting the putative melatonin-opioid axis. Similarly, latency to pain threshold of LFPX rats was significantly longer when compared to control animals at photophase (7.3 +/- 1.4 sec versus 4.8 +/- 0.7 sec) and scotophase (6.3 +/- 0.7 sec versus 5.1 +/- 0.7 sec). Previous studies have produced conflicting data regarding the role of the pineal system in modulating levels of corticosterone (CORT). We observed a moderate, but non-significant, increase in the CORT concentration of LFPX rats during the photophase test period.

The role of granulocyte-macrophage-colony stimulating factor, cortisol, and melatonin in the regulation of the circadian rhythms of peripheral blood cells in healthy volunteers and patients with breast cancer

The circulating blood cells show highly reproducible circadian rhythms. However, the factors that regulate these rhythms are not well understood. In the current study, we examined the diurnal variations of peripheral blood cells (white blood cells, neutrophils, lymphocytes), granulocyte-macrophage-colony stimulating factor (GM-CSF), and melatonin levels, and considered the role of melatonin on these rhythms in healthy volunteers and in patients with early breast cancer. Fourteen premenopausal patients with early stage breast cancer (T2, N1 tumors) and 10 premenopausal healthy volunteers were included in the study. Blood samples were taken every 4 hr for a period of 24 hr. Peripheral blood cells were counted by automated analyser and also from peripheral blood films. GM-CSF levels were measured by ELISA and melatonin levels by radioimmunoassay (RIA). Serum melatonin, cortisol, and GM-CSF levels, and peripheral blood cell counts showed significant circadian rhythms in healthy volunteers. Except for GM-CSF, these circadian rhythms were found not to be suppressed in early breast cancer patients. While there were significant correlations of serum GM-CSF and cortisol levels with peripheral blood cell counts in healthy volunteers, only lymphocyte counts were found to be significantly correlated with serum GM-CSF and cortisol levels in patients with breast cancer. Serum melatonin levels were found to be significantly correlated with lymphocyte counts in both groups. Our results suggest that peripheral blood cells show significant circadian rhythms in both healthy volunteers and in patients with stage II (T2, N1) breast cancer, and GM-CSF, cortisol, and melatonin may have a role in the regulation of peripheral blood cell counts.

Correlation between the circadian rhythm of melatonin, phagocytosis, and superoxide anion levels in ring dove heterophils

A functional role for melatonin is its relationship to circadian timing mechanisms. In addition, there has recently been assumed to be a functional connection between the pineal gland and the immune system in mammals and birds, with some findings showing melatonin to be a free radical scavenger and general antioxidant. The present study investigates the possible relationship between the circadian rhythm of melatonin and the ingestion capacity as well as superoxide anion levels of ring dove (Streptopelia risoria) heterophils. In birds, heterophils, with their ability to ingest and kill different antigens, play a central role in the host defence mechanism. All determinations were made during 24 hr periods at 2 hr intervals. Radioimmunoassay showed an increase of melatonin serum levels during the dark period (from 20:00 to 07:00 hr) with a maximum at 04:00 hr, and a significant decline during the hours of light with a minimum at 16:00 hr. Similarly, the phagocytic index was enhanced during the night, with the maximum at approximately 04:00 hr and the minimum at approximately 18:00 hr. The same was the case in relation to phagocytic percentage. However, the superoxide anion levels were lower during darkness (minimum at 04:00 hr) and higher during the light period (maximum at 14:00 hr). In conclusion, our findings show that one pineal-mediated effect on the immune system may be a direct action of melatonin on phagocytosis and the phagocytic biochemical process, and that this neurohormone might act as an antioxidant.

Diurnal rhythm in ornithine decarboxylase activity and noradrenergic and cholinergic markers in rat submaxillary lymph nodes

Diurnal variations in lymph node ornithine decarboxylase activity were examined in submaxillary lymph nodes of rats injected with Freund's complete adjuvant or its vehicle. After immunization, lymph node ornithine decarboxylase activity increased by about 10-fold. Both in immunized and non-immunized rats, a significant diurnal variation in ornithine decarboxylase activity was found, with a maximal activity at early (i.e. 13.00 h, vehicle) or late afternoon (i.e. 17.00 h, Freund's adjuvant). Injection of Freund's adjuvant during daylight or at night resulted in similar day-night differences in submaxillary lymph node ornithine decarboxylase activity. In rats subjected to the sympathetic postganglionic denervation (by ipsilateral superior cervical ganglionectomy) or the preganglionic parasympathetic decentralization (by chorda tympani section) of submaxillary lymph nodes, nyctohemeral variations in ornithine decarboxylase were still present, showing a maximum at 17.00 h. Superior cervical ganglionectomy augmented lymph node ornithine decarboxylase while chorda tympani section decreased it. When a unilateral superior cervical ganglionectomy plus chorda tympani section was performed, the diurnal changes in ornithine decarboxylase were abolished. [3H]Norepinephrine uptake and tyrosine hydroxylase activity attained their maxima in submaxillary lymph nodes at early night. After immunization, these two presynaptic indicators of sympathetic activity in submaxillary lymph nodes augmented significantly. Neuronal [3H]choline uptake and [3H]choline conversion into acetylcholine (two indicators of cholinergic activity) also augmented in lymph nodes of rats injected with Freund's adjuvant. In immunized rats, maxima in [3H]choline uptake and [3H]acetylcholine synthesis were found at 13.00-17.00 h while in non-immunized rats, a maximum in acetylcholine synthesis was found at 17.00 h. The results are compatible with the view that the autonomic nervous system plays a role in circadian changes of immune responsiveness in lymphoid tissue and that a significant augmentation of presynaptic autonomic activity takes place during immunization in lymphoid tissue.

Environmental lighting alters the infection process in an animal model of AIDS

In this study, we examined the effects of altered environmental lighting on the infection process of a murine leukemia virus, E-55(+), which induces a thymic lymphoma/leukemia in 100% of BALB.K mice inoculated as adults. One to two weeks after inoculation, high levels of proviral DNA are usually found. This is followed by an asymptomatic period of many weeks during which proviral DNA becomes essentially undetectable. Leukemia develops approximately 28 weeks postinoculation. In this experiment, one group of mice was exposed a consistent 10L: 14D cycle while a second was maintained in constant light (LL). A third group was exposed to a rotating cycle characterized by phase shifting a 10L: 14D cycle every three 24-h days (rLD). All cycles began 2 weeks prior to inoculation and were maintained thereafter. Animals were sacrificed at 1, 5, 10, and 15 weeks, and hematopoietic tissue was examined for proviral DNA content. At 1 week, LL- and rLD-exposed animals showed considerably less proviral DNA in bone marrow and spleen compared with controls. At 15 weeks, thymuses from controls were showing signs of infection whereas tissue from LL and rLD mice remained at background levels. We conclude that environmental lighting does alter the infective pattern displayed by this retrovirus, although whether this effect is mediated by changes in the target stem cells or through immunoenhancement has not yet been determined.

Superior cervical ganglionectomy suppresses circadian corticotropic rhythms in male rats in the short term (5 days) and long term (10 days)

Superior cervical ganglionectomy (SCGx) has drastic effects on numerous hormonal circadian rhythms and particularly on pineal melatonin secretion. We investigated the hormonal consequences of ablation of the superior cervical ganglion on the corticotropic circadian rhythms in the male rat. Plasma were obtained by sampling blood every 4 h, using a chronic carotid cannula. Adreno-corticotropin hormone (ACTH) was assayed by radioimmunoassay (RIA) and corticosterone (B) by radiocompetition. Urinary 6-sulphatoxymelatonin (aMT6s), considered as an index of the pineal gland activity, was assayed by specific RIA: a decrease in the aMT6s concentration after ganglionectomy was taken as proof of adequate surgical operation. Control animals showed classical circadian rhythms for ACTH and B with basal values during the light phase and circadian peaks around the light/dark interface. Five and ten days after ganglionectomy, the circadian rhythms of ACTH and B were suppressed. In addition, the mean ACTH concentrations increased significantly 10 days after ganglionectomy compared to those in sham-operated rats and 5 days post-operation group. The mean plasma corticosterone levels were similar in those three groups of animals. This is the first study demonstrating the suppressive effect of superior cervical ganglionectomy on the circadian corticotropic hormonal cycle.

Brain-applied magnetic fields and immune response: role of the pineal gland

In an attempt to clarify the mechanisms underlying immunopotentiation induced by prolonged exposure of the rat brain to static magnetic fields, and to evaluate the role of the pineal gland in that phenomenon, experiments were carried out on the following groups of adult rats (maintained under a 12 hr light/12 hr dark photoperiod): pinealectomized rats (Px); rats with micromagnets implanted to the occipito-parietal region of the skull (M); rats pinealectomized and implanted with micromagnets to the skull (PxM); sham-pinealectomized rats with non-magnetic beads implanted to the occipito-parietal area of the skull (ShPxMx); and intact controls (IC). Twenty-one days after surgery, animals of all groups were immunized with sheep red blood cells and tested for plaque forming cell (PFC) response and serum hemagglutinin level. Humoral immune reactions decreased significantly in Px rats, while increased markedly in M rats in comparison to the ShPxMx and IC controls. Compromised immune function induced by pinealectomy was restored by prolonged exposure of the brain to magnetic fields (PxM rats). Thus reconstituted immune responsiveness in PxM rats reached the level observed in controls, but was lower than that in M rats. The results imply that magnetic fields applied to the rat brain may exert their immunoenhancing activity in the absence of the pineal gland. However, this activity of magnetic fields is more pronounced in the presence of the pineal organ. The latter finding suggests the involvement of the pineal in the immunopotentiation induced by magnetic fields, but does not imply that magnetic fields operate solely via the pineal gland.(ABSTRACT TRUNCATED AT 250 WORDS)

T-lymphocyte subsets in otherwise healthy patients with herpes zoster and relationships to the duration of acute herpetic pain

T-lymphocyte subsets (CD3, CD4, and CD8 lymphocytes) in peripheral blood, parameters of cell-mediated immunity, were serially measured in 62 otherwise healthy Japanese patients with herpes zoster (HZ), and the findings were compared with those of 20 age-matched healthy controls who had had varicella but not HZ. Our objective was to elucidate whether there were changes in cell-mediated immunity, even in immunocompetent patients with HZ, and to investigate relationships between these variables and the duration of acute herpetic pain (AHP). All the patients underwent repeated sympathetic nerve blocks until pain was relieved. As compared with controls, there were slight increases in the percentages of CD4 lymphocytes (helper/inducer) and highly significant increases in the percentages of CD8 lymphocytes (suppressor/cytotoxic), resulting in marked decreases in CD4/CD8 ratios in the acute phase of HZ. The percentages of CD3 lymphocytes (pan-T lymphocytes) did not differ significantly. The duration of AHP was analyzed in 49 patients in whom T-lymphocyte subsets were measured more than twice. There was a weak but statistically significant positive linear correlation between age and the duration of AHP (r = 0.43, P < 0.01). There were statistically highly significant positive linear correlations between the number of days on which percentages of CD3 (r = 0.72, P < 10(-8)) and CD4 lymphocytes (r = 0.60, P < 10(-5)), and CD4/CD8 ratios (r = 0.62, P < 10(-5)) reached the maximum values after the onset of HZ and the duration of AHP. These correlation coefficients were higher than that between age and the duration of AHP.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunocytochemical and circadian biochemical analysis of neuroactive amino acids in the pineal gland of the rat: effect of superior cervical ganglionectomy

Semiquantitative immunocytochemistry by immuno-gold techniques revealed differences in the spatial distribution of glutamate, glutamine, and taurine within the pineal gland, with greatest labeling over pinealocytes, glia, and endothelia, respectively. At the subcellular level, glutamate labeling tended to be highest over pinealocyte synaptic ribbons and mitochondria, and lowest over lipid inclusions. Pineal levels of glutamate, glutamine and taurine, as measured by high performance liquid chromatography, did not vary over a light: dark cycle. Superior cervical sympathetic denervation, which abolishes pineal melatonin synthesis, resulted in a nearly 50% reduction in pineal glutamate levels, but had no effect on levels of glutamine and taurine. Other amino acids (alanine, arginine, aspartate, serine) were reduced by 23%-33% following sympathectomy. These data suggest an important role for glutamate in pinealocyte function(s) possibly related to the noradrenergic innervation of the gland.

Sympathetic denervation and chronic serotonin uptake blockade by fluoxetine do not affect pineal gland 5-hydroxyindole acetic acid: evidence that oxidative deamination of pineal serotonin is a property of the pinealocyte

This investigation tested the hypothesis that oxidative deamination of 5HT in the pineal gland occurs primarily in cellular compartments other than the pinealocyte (i.e., noradrenergic nerve terminals and glia). Following sympathetic denervation of the pineal gland by bilateral superior cervical sympathectomy, pineal levels of 5HT and its oxidative metabolite, 5HIAA, were measured by HPLC from samples collected at six time points over the 24 h photoperiod. The role of glia in 5HT deamination was further examined by chronic treatment with the 5HT uptake blocker, fluoxetine (10 mg/kg). Sympathectomy abolished the circadian rhythms of both 5HT and 5HIAA, but had no statistically significant effect on the ratio of 5HIAA/5HT compared to sham-operated and intact controls over the 24 h period. Pineal daytime levels of both 5HT and 5HIAA were unaffected by fluoxetine treatment. These findings indicate that the pinealocyte is an important cellular compartment for 5HT oxidative metabolism.

Exogenous melatonin modifies the circadian rhythm but does not increase the level of some immune parameters in the chicken

The effect of daily injection of the pineal hormone melatonin and naltrexone, an opioid antagonist, on the circadian rhythm and the level of immune parameters (plaque forming cell [PFC] number, serum agglutinin titer, lymphoid gland weight, total white blood cells (WBC) and their fraction number, and serum lysozyme [LZ] content) was examined in White Leghorn cockerels and female BALB/c mice kept in LD 12:12. Animals were immunized ip with sheep red blood cells (SRBC) to stimulate their immune system. Subcutaneous injections of melatonin, naltrexone, or both drugs together were made 2 hr before the end of light, for 4 or 5 days, beginning on the day of immunization. The day following the fifth injection, chickens were sacrificed over a 24 hr period every 4 hr (experiment I) or twice daily, i.e., at the beginning of light and dark phases (experiment II). Mice were killed on the day following the fourth injection at the beginning of light, and splenic PFC number was determined (experiment III). In experiment I, the existence of the diurnal rhythm was evaluated by cosinor analysis. Melatonin injections entrained the circadian rhythm in anti-SRBC serum agglutinins, but it did not influence circadian rhythmicity in other parameters examined. The circadian rhythm in total WBC number and their fractions was entrained by naltrexone treatment. Melatonin injections did not affect either the diurnal mean of parameters examined or the weight of lymphoid organs. Splenic PFC number in chickens was diminished by both melatonin and naltrexone injections, whereas in mice it was increased by melatonin, and naltrexone antagonized that effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Sex and strain differences in the circadian rhythm fluctuation of endocrine and immune function in the rat: implications for rodent models of autoimmune disease

This study compares 24-h basal patterns of corticosterone and immunoreactivity for Lewis and Fischer (F344) strain rats. Significant differences in the circadian rhythm of plasma corticosterone were found across sex and strain. Male Lewis rats exhibited significantly lower 24-h corticosterone levels relative to female Lewis and male F344 rats. In addition, male Lewis rats were found to have higher mononuclear cell counts than female Lewis or male F344 rats, particularly in the peripheral blood and spleen compartments. Levels of CD4-bearing lymphocytes in blood, lymph node, and spleen were found to be higher in Lewis rats compared to the F344 strain over a 24-h period. In general, percentages of CD8- and major histocompatibility complex (MHC) class II-bearing lymphocytes were shown to vary over 24 h in all compartments across strains. Given that the Lewis rat has low basal levels of circulating corticosterone, and comparatively higher numbers of CD4-bearing lymphocytes, these factors may play a causative role in the known susceptibility of this strain to many experimental models of autoimmune disease.