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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01 Jan 1999
TL;DR: Analysis of the results of field and laboratory studies in A. niloticus allowed an understanding of the mechanisms involved in regulation of the reproductive cycle and development of models of the reproduction-dependent outbreak of A.niloticus in 1987 in Burkina Faso.
Abstract: A better understanding of rodent population dynamics and strategies for surviving in various habitats can be gained from combined studies of genetics, ecology, ecophysiology and chronobiology. Each of these disciplines can contribute complementary information to improve rodent pest management (RPM). Field studies of the ecophysiology of several species ( Arvicanthis niloticus and Mastomys huberti living in wet habitats; Arvicanthis niloticus in easily flooded habitats; Mastomys erythroleucus and Taterillus gracilis in semi-arid habitats; Taterillus petteri in arid habitats) reveal a set of phase-relationships between the annual cycles of reproduction, mobility and metabolism, and the annual cycle of climate and trophic conditions in rodent habitats, defined here as the ‘vital-cycle’. Improvement of RPM spatial and temporal strategies directed to control mortality, mobility and reproduction should thus be adapted to the vital-cycle according to species and habitat. Analysis of the results of field and laboratory studies in A. niloticus living in easily flooded habitats, allowed an understanding of the mechanisms involved in regulation of the reproductive cycle and development of models of the reproduction-dependent outbreak of A. niloticus in 1987 in Burkina Faso. We also describe data related to other species and discuss the advantages of integrating a chronobiological approach to the study of population mobility and mobility-dependent outbreaks.
8 citations
Cites background from "Pineal Gland and Humidity Effects o..."
...1991), relative humidity (Haldar and Saxena 1988), food and water (Bronson 1989), chemical signals like 6methoxy-2-benzoxazolinone secreted by plants during germination (Neal and Alibhai 1991), social factors like pheromones or rodent density, elements of the landscape structure (Delattre et al....
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...Examples include temperature (Vivien-Roels and Pévet 1983; Ouarour et al. 1991), relative humidity (Haldar and Saxena 1988), food and water (Bronson 1989), chemical signals like 6- methoxy-2-benzoxazolinone secreted by plants during germination (Neal and Alibhai 1991), social factors like…...
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...They include daylength (Happold 1983; Khammar and Brudieux 1986, 1987), air humidity (Müller 1977; Haldar and Saxena 1988), temperature (Vivien-Roels and Pévet 1983), length of the dry season (Packer 1983), rainfall via increased water intake (Yahr and Kessler 1975; Beatley 1976; Christian 1979), rainfall via variation in the quality and the quantity of foods (Delany and Happold 1979), rainfall via a triggering effect of substances found in germinating plants (Negus and Berger 1977; Sanders et al....
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...They include daylength (Happold 1983; Khammar and Brudieux 1986, 1987), air humidity (Müller 1977; Haldar and Saxena 1988), temperature (Vivien-Roels and Pévet 1983), length of the dry season (Packer 1983), rainfall via increased water intake (Yahr and Kessler 1975; Beatley 1976; Christian 1979),…...
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TL;DR: It can be suggested that thymus derived melatonin protects thymic T-cells from testosterone induced seasonal oxidative stress, apoptosis and also acts as a potent paracrine factor for maintenance of redox status to ensure thymocyte survival.
6 citations
05 Nov 2014-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: Investigation of daily/nycthemeral variation in expression of melatonin receptor subtypes MT1/MT2 in the lymphoid organs of a tropical squirrel suggests that there exists a temporal window of sensitivity in the target organs to the melatonin signal that is regulated by modulation ofMelatonin receptor expression which might be involved in mediating the photoperiodic effects ofmelatonin in the control of seasonal immune physiology.
Abstract: Seasonal variations in immune functions point toward the involvement of melatonin in its regulation. These chronobiotic effects are exerted by receptors present on the immunocompetent cells. The present study investigated daily/nycthemeral variation in expression of melatonin receptor subtypes MT1/MT2 in the lymphoid organs (spleen/thymus) of a tropical squirrel, Funambulus pennanti. The receptor expression was noted every 4 h interval over 24 h under natural light-dark cycle, during two seasons and was correlated with peripheral level of melatonin. The MT1/MT2 receptor expression displayed higher levels at the time of dusk (light-dark transition; 1800 hours), while plasma melatonin was still low compared to the preceding time point. The receptors were downregulated during the nighttime with a minimum expression at 0200 hours. Thymus, during the long day length, showed a tissue-specific pattern of receptor expression with a minimum expression at 0600 hours. Results suggest that photoperiod by modulation of melatonin level inversely regulates the receptor expression. The observations imply that there exists a temporal window of sensitivity in the target organs to the melatonin signal that is regulated by modulation of melatonin receptor expression which might be involved in mediating the photoperiodic effects of melatonin in the control of seasonal immune physiology.
5 citations
Cites background or methods from "Pineal Gland and Humidity Effects o..."
...Adult male squirrels, F. pennanti, belonging to the family Sciuridae, were collected from the vicinity of Varanasi (latitude 25°18′N, longitude 83°01′E) during the summer (May–June) and winter months (Dec–Jan)....
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...To access our hypothesis, we selected two extreme weather conditions, summer and winter of the Indian tropics, which also marks the onset and cessation of the reproductive activity in this seasonally breeding squirrel (Haldar and Saxena 1988)....
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...The peak activity is found from the middle of March to May (Haldar and Saxena 1988)....
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...The squirrels collected during summer (May–June: temp max 46 °C and min 30 °C, humidity 67.23 % and day length 13.42 hours) and winter (Dec–Jan: temp max 13.0 °C and min 2.0 °C, humidity 82.14 % and day length 10.35 hours) were killed at 4 h interval over 24 h to note the effect of natural seasonal day length on melatonin receptor MT1 and MT2 expression in lymphoid organs (spleen and thymus) of F. pennanti....
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TL;DR: It is demonstrated that the precise timing and appropriate dose of melatonin administration is essential to maximize the amelioration of circadian rhythm–related disorders in a diurnal model.
Abstract: Melatonin, an essential pineal hormone, acts as a marker of the circadian clock that regulates biological rhythms in animals. The effects of exogenous melatonin on the circadian system of nocturnal...
4 citations
TL;DR: It is suggested that depending upon the reproductive status, short and long photo-period affected differently the gonadal and pineal gland activity of this bat.
Abstract: Photoperiodic sensitivity of gonad in relation to pineal gland activity was noted during two important reproductive phases i.e. reproductively active (February- March) and inactive (July- August) phases of nocturnal flying mammal, Cynopterus sphinx of Indian tropical origin. They were exposed to experimental long (Light: Dark in hours; 16L: 8D) and short (8L: 16D) photoperiods for 30 days during both the reproductive phases. Exposure to the long photoperiod (LP) during reproductively active phase had no significant effect on pineal gland, gonad and its hormonal concentration. However, exposure to short photoperiod (SP) induced a decrease in gonadal activity and increase in pineal activity (as judged by the gland weight, histology, low level of estradiol / testosterone and high level of melatonin in plasma). Increased melatonin and decreased estrogen levels following the short photoperiod exposure caused abortion in females, which were undergoing delayed embryonic development during reproductive i...
3 citations
Cites background from "Pineal Gland and Humidity Effects o..."
...…seasonal chronology of the events of the reproductive cycle of the tropical rodents reveals that the ecofactors (temperature, rainfall and humidity) other than lights are equally important (Haldar and Saxena 1988 ; Haldar and Srivastava 1992) in influencing both pineal and gonadal function....
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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