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Journal ArticleDOI

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

01 Sep 1988-Journal of Pineal Research (Blackwell Publishing Ltd)-Vol. 5, Iss: 5, pp 411-418
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.
Citations
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Book ChapterDOI
01 Jan 2002
TL;DR: On pense, en effet, que le stress engendré par les fortes densités déclenche une augmentation de l'agressivité, un effondrement reproductif and des perturbations comportementales qui amplifient l'impact des prédateurs.
Abstract: Nombre d'espèces de rongeurs ravagent les cultures et/ou sont des vecteurs de maladies. Ces nuisances sont dramatiques les années où certaines de ces populations pullulent. Les services de protection des végétaux des pays sahéliens, ne disposant pas d'un système d'alerte précoce, engagent une lutte curative basée sur des épandages massifs de rodenticides (Feilder, 1988 a ; Sicard, 1995 a). Cette réaction agressive pour l'environnement est peu utile car les pullulations déclenchent de puissants mécanismes de normalisation démographique (Conway, 1981 ; Poulet, 1982). On pense, en effet, que le stress engendré par les fortes densités déclenche une augmentation de l'agressivité, un effondrement reproductif et des perturbations comportementales qui amplifient l'impact des prédateurs. C'est pourquoi nombre d'expertises insistent sur la nécessité de prévoir les pullulations pour intervenir en amont (Singleton et al., 1999). L'IRD, en partenariat avec la recherche au Sud et au Nord, étudie donc les mécanismes des pullulations pour caractériser les situations à risque. La valorisation des résultats nécessitant l'élaboration d'un réseau d'alerte sahélien, une collaboration est nécessaire avec l'unité de coordination technique régionale de protection des végétaux (UCTR/PV) de l'Institut du Sahel rattaché au Comité inter-Etat de lutte contre la sécheresse au Sahel (Cilss) (Sicard et ai, 1995).

2 citations

Journal ArticleDOI
TL;DR: Melatonin may have facilitated the energy “trade‐off” between reproductive and immune mechanisms, thereby providing an advantage to the seasonal breeders for their survival during stressful environmental conditions.

2 citations


Cites background from "Pineal Gland and Humidity Effects o..."

  • ...These squirrels are seasonal (LD) breeders, and details of their breeding pattern, habit, and habitat have been published before (Haldar and Saxena, 1988)....

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Journal ArticleDOI
TL;DR: Thiouracil and metyrapone administered during the progression phase of the annual reproductive cycle inhibited gonadal development in the Indian palm squirrel and led to normal gonadal regression during the late breeding phase.
Abstract: Thiouracil and metyrapone administered during the progression phase of the annual reproductive cycle inhibited gonadal development in the Indian palm squirrel, Funambulus pennanti. In a further experiment, these drugs led to normal gonadal regression during the late breeding phase. Thyroxine and corticosterone treatment, on the other hand, maintained the gonads continuously in breeding condition, unlike those of controls, which exhibited characteristic post-reproductive regression. Since hypofunction of the thyroid and adrenal glands had inhibitory effects on the initiation of seasonal gonadal growth, and hyperactivity affects post-reproductive regression, it is suggested that an optimal level of hormones is required for the normal breeding cycle in this subtropical mammal. The results are discussed in terms of an interrelationship between the seasonal thyroid, adrenal, and gonad cycles under natural conditions.

1 citations

Journal ArticleDOI
TL;DR: In this article, the effects of morning and evening injections of pineal 5-methoxyindoles (MI), melatonin (aMT) and 5methoxytryptamine (MT) for 60 continuous days, were observed on the testes of sham-operated (SO) and pinealectomized (Px) Indian palm squirrel, Funambulus pennanti maintained under different photoperiods during the gonad active phase.
Abstract: Effects of morning and evening injections of pineal 5-methoxyindoles (MI), melatonin (aMT) and 5-methoxytryptamine (MT), for 60 continuous days, were observed on the testes of sham-operated (SO) and pinealectomized (Px) Indian palm squirrel, Funambulus pennanti maintained under different photoperiods during the gonad active phase. Long photoperiod (LP) of 14L:10D appeared stimulatory to the testes and caused a significant increase in the weight and seminiferous tubule diameter of both SO and Px animals, as compared to the animals under natural day-length (NDL). Short photoperiod (SP) of 10L:14D had an inhibitory influence and reduced the testes weight and its tubule diameter. aMT and MT injections during evening hours significantly reduced testes weight and tubule diameter of SO and Px animals under NDL, LP and SP. However morning injections, under all conditions, were without any significant effect. The results suggest an inhibitory effect of aMT and MT, under above photoperiodic conditions, on the testes of this tropical mammal. The time of administration of the MI is important in the expression of the effect.

1 citations

References
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Book
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

Journal ArticleDOI
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

Journal ArticleDOI
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

Book ChapterDOI
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

Journal ArticleDOI
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