Pineal Gland and Humidity Effects on Testicular Function of the Indian Palm Squirrel, Funambulus pennanti

Photoimmunomodulation and melatonin

Abstract: The seasons, and daily physical rhythms can have a profound effect on the physiology of the living organism, which includes immune status. The immune system can be influenced by a variety of signals and one of them is photic stimulus. Light may regulate the immunity through the neuroendocrine system leading to the most recent branch of research the “Photoimmunomodulation”. Mammals perceive visible light (400–700 nm) through some specialized photoreceptors located in retina like retinal ganglion cells (RGC). This photic signal is then delivered to the visual cortex from there to the suprachiasmatic nucleus (SCN) of the hypothalamic region. Melatonin – one of the universally accepted chronobiotic molecule secreted by the pineal gland is now emerging as one of the most effective immunostimulatory compound in rodents and as oncostatic molecule at least in human. Its synthesis decreases with light activation along with norepinephrine and acetylcholine. The changes in level of melatonin may lead to alterations (stimulatory/inhibitory) in immune system. The evidences for the presence of melatonin receptor subtypes on lymphoid tissues heralded the research area about mechanism of action for melatonin. Further, melatonin receptor subtypes-MT1 and MT2 was noted on pars tuberalis, SCN and on lymphatic tissues suggesting a direct action of melatonin in modulation of immunity by photoperiod as well. The nuclear receptors (ROR, RZR etc.) of melatonin are known for its free radical scavenging actions and might be indirectly controlling the immune function.

Photoperiodic regulation of MT1 and MT2 melatonin receptor expression in spleen and thymus of a tropical rodent Funambulus pennanti during reproductively active and inactive phases.

Abstract: Photoperiodic regulation of melatonin receptor types on target tissues, such as lymphatic organs, has never been explored for any seasonal breeder. In the present study, we accessed the high affinity membrane melatonin receptors MT1 and MT2 expression dynamics in lymphoid organs (i.e., spleen and thymus) of a seasonally breeding rodent Funambulus pennanti during two major reproductive phases (i.e., active and inactive), when the internal hormonal (melatonin and gonadal steroid) as well as the ecological conditions were entirely different. Photoperiod regulates circulatory melatonin level; hence, we noted the effect of different photoperiodic regimes (long; 16L:8D and short; 10L:14D photoperiod) equivalent to summer and winter daylength on membrane melatonin receptor MT1 and MT2 expression in spleen and thymus. We have correlated the melatonin receptor expression with two major hormones varying seasonally (i.e., melatonin and testosterone) also being responsible for modulation of immunity of a seasonal breeder. Differential immunoreactivity of MT1 and MT2 receptor in spleen and thymus of F. pennanti suggests an involvement of both the receptor types in signal transduction of photoperiod for seasonal immunomodulation, because in the tropical zone, a slight difference (1:45–2 h) in daylength may change reproductive physiology and immunity of animals for adaptation. Our above suggestion receives strong support from the experiment of photoperiodic exposure on MT1 and MT2 expression at the translational level, where long daylength decreased the circulatory melatonin level and melatonin receptor expression in both lymphatic tissues. On the other hand, under short daylength, expression of MT1 and MT2 receptor increased in both spleen and thymus along with concomitant increase in circulatory melatonin level. Differential hormonal level of melatonin and gonadal hormones during reproductively active and inactive phase and its direct relation with melatonin receptor expression dynamics in lymphoid organs could be

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

Abstract: 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.

Seasonal changes in adrenal and gonadal activity in the quail, Perdicula asiatica: involvement of the pineal gland

Abstract: The present study assessed annual adrenal gland activity in the Indian tropical Jungle bush quail, Perdicula asiatica. We also elucidated the role of the annual variations in gonadal steroids and melatonin in the regulation of its activity. Increasing day length (photoperiod), ambient temperature and rainfall are positively correlated with adrenal and gonadal functions, and inversely related to pineal gland activity. Pineal, adrenal and gonadal weights showed cyclical patterns relative to environmental factors, which were also correlated with plasma melatonin, corticosterone and gonadal steroids, respectively. In both sexes of P. asiatica, pineal gland weight and/or plasma melatonin levels were inversely related to adrenal lipids, (e.g. phospholipids, free and esterified cholesterol) and plasma corticosterone levels. Melatonin levels also showed an inverse relationship with plasma testosterone and estradiol levels. These studies indicate that changes in environmental factors promote annual variations in adrenal and gonadal activity probably by modulating the pineal gland. Melatonin receptors have been localized in the pars tuberalis, adrenal gland and gonads of birds, the pineal gland may, therefore, mediate environmental stimuli indirectly and directly to down regulate adrenal and gonadal activity, which run in parallel in this species.

Photoperiod–Testicular–Immune Interaction in a Seasonal Breeder Indian Palm Squirrel Funambulus pennanti During the Reproductively Inactive and Active Phases

Abstract: The differential effect of long (LD; 16 : 8 h light/dark), short (SD; 10 : 14 h light/dark) and natural day length (NDL; 12 : 12 h light/dark) during the reproductively inactive (RIP) and active (RAP) phases was assessed in relation to immunity and reproductive function of a tropical rodent Funambulus pennanti. They presented high immunity and low testicular activity during RIP and an opposite during RAP. SD increased spleen and thymus weight, leukocyte and lymphocyte counts, cell mediated immunity [i.e. blastogenic response in terms of percentage stimulation ratio of splenocytes and thymocytes (when challenged with concanavalin A)] and delayed type hypersensitivity to oxazolone. SD during RIP increased the above mentioned parameters and reduced testes weight compared to NDL groups. During RAP, LD reduced all the immunological parameters when compared with NDL and SD experiencing groups of RIP and RAP phases. The LD group reduced the immunological parameters compared to RAP, suggesting that LD had always an inhibitory effect on immune status being independent of reproductive phases. The intensity of the stimulatory effects of SD and inhibitory effects of LD during both reproductive phases was significantly different. We exposed another set of squirrels to the above photoperiodic schedule for prolonged period (30 weeks) during RAP. A clear testicular refractoriness followed by immunorefractoriness was observed in the group experiencing SD and LD for 30 weeks. The photorefractoriness presented by the testes was inversely related to the immunorefractoriness. The peripheral melatonin level of those squirrels reflected the photoperiodic signal perceived by squirrels for immunomodulation and gonadal function, suggesting that immune system and gonadal function might have coevolved.

Computational Handbook of Statistics

Abstract: 1. Organizing Data and Some Simple Computations. 2. Confidence Intervals. 3. Correlation and Related Topics. 4. Analysis of Variance. 5. Supplemental Computations for Analysis of Variance. 6. Multivariate Analyses. 7. Nonparametric Tests, Miscellaneous Tests of Significance, and Indexes of Relationships. Appendices. Normal-Curve Areas. Critical Values of "Student's" t Statistic. Critical Values for Sandler's A Statistic. Values of the Chi-Square Statistic. Probabilities of the F Distribution. Fisher's z Transformation for Pearson's r Correlation Coefficient. Critical Values of Pearson's r Correlation Coefficient for Five Alpha Significance Levels. Critical Values of the U Statistic of the Mann-Whitney Test. Critical Values for Hartley's Maximum F Ratio Significance Test for Homogeneity of Variances. Significant Studentized Ranges for Duncan's New Multiple-Range Test. Significant Studentized Ranges for the Newman-Keuls' and Tukey Mulitple-Comparison Tests. Dunnett's Test: Comparison of Treatment Means with a Control. Critical Values of Wilcoxon's t Statistic for the Matched- Pairs, Signed-Ranks Test. Coefficients for Orthogonal Polynomials. Cumulative Probability Distribution for r', the Total Number of Runs Up or Down. Sample Size and Power.

The Pineal and Its Hormones in the Control of Reproduction in Mammals

Abstract: ONLY A LITTLE over a decade ago, any discussion of the function of the pineal gland included qualifying adjectives such as alleged, supposed, and putative. In the same vein, since it connoted a hormonal function, rather than referring to the pineal as a gland, the phrase pineal organ was usually employed to describe this portion of the epithalamus. However, this is no longer the case, at least in mammals. By the usual criteria in endocrinology, the pineal now fulfills all the qualifications of an organ of internal secretion. Several major discoveries revolutionized ideas concerning the function of the pineal gland. Certainly, as noted frequently in other reviews, the isolation and identification of N-acetyl-5-methoxytryptamine (melatonin), a pineal hormone, from bovine pineal tissue by Lerner et al. (1, 2) provided a strong impetus for subsequent investigations on this sometimes exasperating organ. At least as important as this discovery, however, were the observations that light and darkness govern both ...

Circadian and circannual fluctuations of pineal indoleamines (serotonin and melatonin) in Testudo hermanni Gmelin (Reptilia, Chelonia). I. Under natural conditions of photoperiod and temperature.

Abstract: Tortoise pineal serotonin and melatonin levels show marked circadian and circannual rhythms in a natural environment. These rhythms have been analyzed by applying a least square fitting procedure to determine the parameters entering sine or cyclic gaussian functions compared to the experimental values. In these reptiles, as in mammals and birds, serotonin is synthesized during the day, while melatonin is synthesized at night. Both the maximum concentration and the amplitude of circadian fluctuations are increased during the breeding season; circadian rhythms disappear completely during winter and hibernation. The physiological significance of these rhythms remains to be determined and needs further investigation.

Annual rhythms: Perspective

Abstract: The habitats of most organisms are subject to pronounced seasonal fluctuations. Literally all physical environmental factors important to an organism—like temperature, day length, and rainfall—vary with season to such an extent that most plants and animals could not escape the necessity of developing adaptational strategies to cope with them. The most obvious expression of this necessity is that many biological activities are concentrated or restricted to the times of the year when they are most likely to be successful. This is true, for instance, of reproduction, which is timed in such a way that the growth of the offspring occurs when environmental conditions are most favorable, that is, late spring and summer. Other seasonally restricted activities include behavioral, physiological, and morphological processes by which organisms overcome or avoid severe winter or extreme summer conditions, that is, dormancy, diapause, hibernation, and migration. Developmental processes like molt of skins, furs, and plumages are often inserted between reproduction and the processes occurring in winter. In addition, numerous physiological functions like basal metabolism or growth rate change continuously with the time of year as a direct or indirect consequence of environmental seasonal variations (for reviews, see, e.g., Immelmann, 1963b, 1967, 1971; Aschoff, 1955; Lack, 1950; Murton and Westwood, 1977; Farner and Follett, 1979).

The independency of an intact pineal gland of the inhibition by 5-methoxytryptamine of the reproductive organs in the male hamster.

Abstract: Subcutaneous injections fo 25 micrograms of 5-methoxytryptamine (5-MT) in oil into intact and pinealectomized male hamsters given between 4.30 p.m. and 5 p.m. (light on from 5 a.m. to 7 p.m.; 14 L/10 D) for 54 consecutive days caused involution of the testes. 5-MT, however, is more effective when the pineal is present. These results indicate that melatonin is not the only pineal factor inducing gonadal atrophy in the hamster. 5-MT seems even more effective than melatonin in so far as it is, contrary to melatonin under the same experimental conditions, also effective in the absence of the pineal. Like melatonin, 5-MT appears to be implicated in the control of the reproductive function.