Showing papers by "Chandana Haldar published in 2006"

Melatonin prevents X-ray irradiation induced oxidative damagein peripheral blood and spleen of the seasonally breeding rodent, Funambulus pennanti during reproductively active phase

Abstract: Purpose: Biological effects of X-ray irradiation and protection by melatonin on the immune status of a tropical rodent, Funambulus pennanti, was examined by estimating oxidative damage of peripheral blood and spleen and protection by melatonin treatment.Material and methods: Seventy squirrels were divided into 4 sets of 25, 25, 10 and 10 having subdivisions into a total of eight groups. Squirrels of set 1 (groups A and B) received only normal saline, set 2 (groups C and D) received 25 μg/100 g body weight (bwt) melatonin and set 3 (groups E and F) received 25 μg/100 g bwt vitamin E for four weeks. Groups G and H of set 4 received high doses of melatonin (0.5 mg/100 g bwt) 30 min prior to and 30 min after X-ray irradiation, respectively, and were sacrificed 1 h after irradiation. Groups B and D were sacrificed after 4 h, 24 h, 48 h and 72 h of irradiation for total leukocyte count (TLC) in peripheral blood, percent apoptotic cells and lipid peroxidation (LPO) in spleen while group F was sacrificed after 4 ...

Annual reproductive synchronization in ovary and pineal gland function of female short-nosed fruit bat, Cynopterus sphinx.

Abstract: We studied the annual correlation of ovarian activity and pineal gland in relation with seasonal variation and gestation of a tropical zone short-nosed fruit bat Cynopterus sphinx. Female bats showed bimodal polyestry (February/March and September/October) in their reproductive cycle. Plasma estradiol concentration ran parallel with ovarian activity and had an inverse relation with pineal mass and peripheral melatonin concentration. Due to the delayed embryonic development in the uterus (October-March) of female bats, interestingly, the uterine activity did not show a parallel relation with ovarian activity and estradiol level. Further, compared with normal non-pregnant females, melatonin level was high during gestation and delayed embryonic development phase. This suggests that the reproductive synchrony and annual variation in ovarian activity of this nocturnal flying mammal differ from other common tropical mammals. The delayed embryonic development in bats might be an adaptive strategy for the unfavorable conditions of the seasons and might be regulated by high peripheral estradiol and melatonin concentration.

Reproductive phase dependent circadian variations of plasma melatonin, testosterone, thyroxine and corticosterone in Indian palm squirrel, Funambulus pennanti

Abstract: To explain the complex mechanism of environmental influence along with internal hormonal (factors) milieu on daily variations in the circulating levels of melatonin, testosterone, thyroxine and corticosterone were analyzed with the help of inferential statistics (Cosinor rhythmometry) in a seasonally breeding tropical rodent, F. pennanti during the reproductively active (RAP) and inactive phases (RIP). Plasma melatonin, thyroxine and corticosterone levels exhibited a significant circadian oscillation during both the active and inactive phases of the annual reproductive cycle. Melatonin showed higher amplitude during RIP in the circulating plasma. Testosterone presented a peak level during evening hours (16:00 – 18:00 h) during RAP only. The phase of thyroxine was noted ∼09:76 h and ∼10.35 h during active and inactive phases, respectively. Corticosterone showed a peak level at ∼12.00 h during both phases of the reproductive cycle. Further, in this tropical rodent, the minimum difference in photope...

Adaptive Significance of Annual Variation in Immune Parameters and Endogenous Hormones (Melatonin and Thyroxine) of a Tropical Rodent Funambulus pennanti

Abstract: The significance of annual variation in metabolic (thyroxine) and chronobiotic (melatonin) hormones in relation to immune adaptation of the Indian palm squirrel was investigated. The squirrel is summer breeder and, hence, remains healthy during reproductively active phase (Feb - Aug) when melatonin level is low and thyroxine level is high. Our data show that the circulating levels of melatonin (MEL) and thyroxine (T 4 ) have their respective annual rhythms, which are inversely related. Thyroxine level is low during the winter months (Sep-Jan) when metabolic activity of this rodent is also low. During this period melatonin level is high because of the short photoperiod and the squirrels indicate poor reproductive activity, with low gonadal steroids, which could be due to high circulating melatonin. The immune parameters also present an annual rhythmicity, which is parallel with circulating melatonin level, but inversely related to thyroxine level. This suggests that the metabolic hormone, thyroxine, and the chronobiotic hormone, melatonin, might be responsible for maintenance of the immune system to adapt the rodent for the rigors of the seasonal environmental changes.

Trade-Off Relationship between Melatonin and Gonadal Steroid on Melatonin Receptor (MEL 1A R) Expression in Lymphoid Tissue

Abstract: Endogenous melatonin is involved in regulation of reproductive function of the photoperiodic species. A circannual rhythmicity of the pineal gland in relation to reproduction has been observed in a tropical seasonally breeding mammal, Funambulus pennanti. A trade-off relation is known to exist between melatonin and the gonadal steroids. In vitro suppression of splenocyte proliferation by testosterone and the reversal of this effect by melatonin supplementation have already been reported. Melatonin receptors have been detected in the lymphoid tissues by binding of 2-[ 125 I] iodomelatonin to splenocytes and thymocytes. We analyzed the presence of melatonin receptor adopting Western blot technique. We found that MTl receptor protein, one of the variants of melatonin receptor, is expressed in both the thymus and spleen tissue and the expression is suppressed by testosterone treatment. This substantiates the direct immunomodulatory role of melatonin. To find the significance of steroid toxicity at molecular level, particularly testosterone, it is important to study its effect on the expression pattern of these receptors.

Melatonin, Gestation and Fetal Development

Abstract: The pineal gland, the transducer of several environmental cues through its hormone, melatonin, is known to play a critical role in the reproduction of several seasonally breeding mammals. The role of pineal gland in the control of male reproduction is already established beyond doubt. The logical hypothesis that the pineal gland would be involved in the aspects of female reproduction, particularly gestation, embryonic development and fetal growth, has been tested in a few seasonally breeding mammals and this paper reviews the outcome as of now. Evidence for establishment of an inverse relationship before pregnancy followed by moderately high activity with a positive correlation during pregnancy and a sudden increase in pineal activity during parturition has been produced, which suggests that high melatonin level has something to do with parturition or early abortion. The pineal gland perhaps maintains the normal physiology during gestation and post-parturition periods. This is further reflected in the prolactin levels of fetal sheep which is modulated by the photoperiod experienced by the mother during gestation. Maternal photoperiodic exposures during gestation and lactation periods alter the neonatal growth and sexual maturation of the Indian palm squirrel via the maternal transfer of photoperiodic information through the pineal gland, as aspect known as "pineal programming". The primary source of melatonin for the fetus is the maternal pineal gland, which is transferred across the placenta during conception and, later after parturition, through the milk, which suggests that a maternally generated melatonin rhythm would be expressed in fetal cerebrospinal fluid as well as in the circulation. Further, maternal melatonin is necessary for normal somatic growth and postnatal development of reproductive organs of the offspring. Melatonin ultimately affects reproductive activity by modulating hypothalamic neuroendocrine circuits whose activity is necessary for gonadal function. The influence of melatonin on reproductive development begins during the prenatal period and extends into the postnatal life. Photoperiodic information, mediated via the pineal gland may be important for maintaining gestational physiology as well as postpartum recovery in female rodents. Further, melatonin has been shown to play adaptive role in the maintenance of delayed embryonic development in bats. Correlation between a developmental decline in melatonin levels and the timing of puberty in humans led to the speculation that melatonin regulates the timing of puberty in the human. These studies on the influence of melatonin on gestation indicate two major inferences viz., melatonin could be one of the major hormones establishing homeostasis during gestation since any disturbance in the level of melatonin causes abortion, and melatonin is one of the hormones of great adaptive significance for embryonic diapause.