Pineal Gland and Humidity Effects on Testicular Function of the Indian Palm Squirrel, Funambulus pennanti
TL;DR: Results indicate that the pineal gland may be implicated in mediating the humdity information to control the male gonadal function in the Indian palm squirrel, Funambulus pennanti.
Abstract: The effect of two different conditions of humidity (80 +/- 5% and 40 +/- 5%) under stimulatory photoperiod (14L/10D) and high temperature (38 +/- 2 degrees C) was studied on the testes and accessory sex organs of the Indian palm squirrel, Funambulus pennanti, during the sexually active phase. High humidity (80 +/- 5%) reduced significantly the testes weight of the sham-operated animals as compared to the controls under natural environmental conditions but had no effect on that of pinealectomized animals. Moderate humidity (40 +/- 5%) did not affect the testes of sham-operated as well as pinealectomized animals, as compared to the respective controls. The seminal and prostatic weights showed no significant difference in high or moderate humidity conditions. However, the epididymal weight of the animals exposed to high humidity was significantly reduced in sham-operated animals only. Thus, these results indicate that the pineal gland may be implicated in mediating the humidity information to control the male gonadal function in the Indian palm squirrel, Funambulus pennanti.
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TL;DR: The results indicated that the efficacy of melatonin to overcome oxidative stress was significantly better than quercetin, supporting the idea that melatonin is a better antioxidant and immunomodulator as compared to other alternatives and perhaps may be employed in the development of effective therapeutics against ROS dominated diseases.
19 citations
TL;DR: It is demonstrated that the palm squirrel circadian system is entrainable to melatonin at both times of day tested, ZTs 0 and 12, in contrast to previous melatonin entrainment studies in other species, where entrainments generally occured at only one phase.
Abstract: Exogenous melatonin induces phase shifts in circadian rhythms according to a phase response curve in nocturnal rodents, several nonmammalian diurnal species, and humans. Daily administration of melatonin entrains rhythms within a narrow circadian window of sensitivity in these species. Entrainment to exogenous melatonin has not previously been demonstrated in a (nonhuman) diurnal mammal. The authors examined the effects of daily melatonin administration (via food) in the diurnal Indian palm squirrel, Funambulus pennanti. The effects of melatonin or vehicle were examined at two times of day: zeitgeber time 0 (ZT 0: light onset time) and ZT 12 (dark onset time). In addition to melatonin- and vehicle-treated squirrels, there was a third group of squirrels that received no treatment. Squirrels were held initially under 12:12 light-dark (LD) cycles, and melatonin (1 mg/kg) or vehicle was administered in food (a raisin) at either ZT 0 or ZT 12 for a total of 17 days. On the third day of treatment, constant lighting (LL) was imposed. Treatment continued at the same ZTs for a further 14 days. The number of days before free-running commenced under constant conditions was assessed for squirrels in each treatment group. Results showed that regardless of the ZT of administration, the number of days before free-running commenced was significantly greater in melatonin-treated squirrels than in vehicle-treated and untreated squirrels, and there was no difference between vehicle-treated and untreated squirrels. Although there was not a significant difference in the number of days before free-running commenced between the two times of administration, the results showed a trend for greater sensitivity to melatonin at ZT 12. This study has therefore demonstrated that the palm squirrel circadian system is entrainable to melatonin at both times of day tested, ZTs 0 and 12. This finding is in contrast to previous melatonin entrainment studies in other species, where entrainment generally occurred at only one phase, around circadian times 10 to 12. Interspecies differences in response to melatonin were discussed.
17 citations
Additional excerpts
...(Haldar and Saxena, 1988) and females (Singh, 1993) of the species....
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TL;DR: It is concluded that specific phase relation (12-hr) between circadian serotonergic and dopaminergic oscillations may induce breeding condition in regressing gonad of Indian Palm Squirrel during post-reproductive phase of annual gonadal cycle.
Abstract: Specific temporal relationship (12-hr) of serotonin and dopamine activity was induced by precursor drugs (5-HTP and L-DOPA) in Indian Palm SquirrelFunambulus pennanti during testicular regression phase. This treatment established breeding condition unlike control, which experienced complete atrophy of testes and accessory sex organs.
14 citations
Cites background from "Pineal Gland and Humidity Effects o..."
...While photoperiod has full control on the breeding cycle of hamsters (Reiter, 1975) in Indian Palm Squirrel, other environmental factor (humidity) determines the termination of seasonal breeding (Haldar and Saxena, 1988)....
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...annual reproduction in Indian Palm Squirrel, Funambulus pennanti and increased humidity is reported to initiate annual testicular regression during August/September (Haldar and Saxena, 1988)....
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...The onset of gonadal recrudescence may possibly be the beginning of scotorefractory phase when the reproductive system no longer responds to the inhibitory effects of short days (Haldar and Saxena, 1988)....
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...Full reproductive condition is maintained till July/ August followed by a seasonal regressive phase (Haldar and Saxena, 1988)....
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TL;DR: Investigations with different doses of 5-HTP revealed that the phase resetting effect is dose-dependent, and the shape of the phase–response curve (PRC) has a strong similarity to PRCs obtained using some serotonergic agents.
Abstract: We report that l-5-hydroxytryptophan (5-HTP), a serotonin precursor, resets the overt circadian rhythm in the Indian pygmy field mouse, Mus terricolor, in a phase- and dose-dependent manner. We used wheel running to assess phase shifts in the free-running locomotor activity rhythm. Following entrainment to a 12:12 h light–dark cycle, 5-HTP (100 mg/kg in saline) was intraperitoneally administered in complete darkness at circadian time (CT)s 0, 3, 6, 9, 12, 15, 18, and 21, and the ensuing phase shifts in the locomotor activity rhythm were calculated. The results show that 5-HTP differentially shifts the phase of the rhythm, causing phase advances from CT 0 to CT 12 and phase delays from CT 12 to CT 21. Maximum advance phase shift was at CT 6 (1.18 ± 0.37 h) and maximum delay was at CT 18 (−2.36 ± 0.56 h). No extended dead zone is apparent. Vehicle (saline) at any CT did not evoke a significant phase shift. Investigations with different doses (10, 50, 100, and 200 mg/kg) of 5-HTP revealed that the phase resetting effect is dose-dependent. The shape of the phase–response curve (PRC) has a strong similarity to PRCs obtained using some serotonergic agents. There was no significant increase in wheel-running activity after 5-HTP injection, ruling out behavioral arousal-dependent shifts. This suggests that this phase resetting does not completely depend on feedback of the overt rhythmic behavior on the circadian clock. A mechanistic explanation of these shifts is currently lacking.
14 citations
Cites methods from "Pineal Gland and Humidity Effects o..."
...The age of each wild-caught mouse was estimated to the nearest week using skull size and body weight as markers, after the manner described by Haldar and Saxena (1988) and modified here for our use....
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TL;DR: Not only the duration of natural sunlight but the intensity of sunlight expressed by solar insolation affects the circulatory level of melatonin and melatonin receptor expression in this wild tropical rodent, F. pennanti.
Abstract: We analyzed the effect of natural solar insolation and artificial photoperiodic conditions on melatonin MT1 receptor expression of a tropical rodent, Funambulus pennanti. Melatonin mediates reproductive and circadian responses and regulates the production of a large number of cytokines, including interleukin-2 (IL-2), via modulation of MT1 receptor expression. Maximum pineal activity, resulting in high melatonin level, low melatonin receptor expression, and increased splenic mass, was noted in the winter months, while an opposite effect was noted during the summer months. Further, constant light exposure mimicked an “enhanced summer”-like condition with significant hyposplenia, and an opposite effect was observed with constant dark exposure with significant splenomegaly in F. pennanti. In the annual study, a slight increase in melatonin level was noted during the monsoon period, when the duration of photoperiod was the same but the amount of solar insolation and direct radiation decreased. The present study found that not only the duration of natural sunlight (i.e., photoperiod) but the intensity of sunlight expressed by solar insolation affects the circulatory level of melatonin and melatonin receptor expression in this wild tropical rodent. An increase in the circulatory level of melatonin induced a decrease in its receptor subtype MT1 expression in splenic cells, both at the transcriptional and translational levels, thus reflecting autoregulatory down-regulation of melatonin receptors. Therefore, in our animal model, F. pennanti melatonin may be suggested as a molecular messenger of photoperiodic signals (duration and intensity) directly acting via MT1 receptor regulation to adapt the immune system of animals residing in the tropical zone. (Author correspondence: chaldar2001@yahoo.com)
14 citations
Cites background from "Pineal Gland and Humidity Effects o..."
...During this period, mostly dark clouds of cumulo-nimbus origin cover the sky (Gadgil, 2006; Haldar & Saxena, 1988a, 1988b)....
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...The relationship between annual rhythms in melatonin and immune system status in Funambulus pennanti has previously been established (Haldar & Saxena, 1988b; Haldar et al., 2001)....
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...The photoperiodic regulation of the melatonin rhythm makes the pattern of the hormone concentration an endocrine calendar for seasonally breeding animals (Haldar & Saxena, 1988a, 1988b; Pévet et al., 2002; Reiter, 1991, 1993)....
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References
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01 Jan 1968
TL;DR: In this paper, the authors present an analysis of correlation and correlation coefficients for the Mann-Whitney Test, the Newman-Keuls' and Tukey Mulitple-Comparison Tests, and the Signed-Pairs, Signed-Ranks Test.
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.
2,042 citations
TL;DR: By the usual criteria in endocrinology, the pineal now fulfills all the qualifications of an organ of internal secretion.
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 ...
1,229 citations
TL;DR: Tortoise pineal serotonin and melatonin levels show marked circadian and circannual rhythms in a natural environment and the physiological significance of these rhythms remains to be determined and needs further investigation.
73 citations
01 Jan 1981
TL;DR: The habitats of most organisms are subject to pronounced seasonal fluctuations, and 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.
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).
38 citations
TL;DR: Results indicate that melatonin is not the only pineal factor inducing gonadal atrophy in the hamster, and 5-MT seems even more effective than melatonin under the same experimental conditions, also effective in the absence of the pineal.
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.
28 citations