Activity of neurons in the preoptic area and their participation in reproductive senescence: preliminary findings

Alterations in the hypothalamic-pituitary-gonadal axis in females determine the transition from regular to irregular reproductive cycles, with loss of fertility. Stimulation of noradrenergic neurons of the anteroventral periventricular neurons (AVPV) is essential for regular reproductive cycles. Therefore, we examined the activity of neurons of the AVPV and measure the noradrenaline (NE) of acyclic rats, in constant estrus, and compared it with that of cyclic rats in estrus. Female cyclic (4-5months) and acyclic (17-18months) rats were euthanized at 10, 14, and 18h in estrus. Brains were processed for immunoreactivity to antigens related to Fos (FRA) in AVPV, and the NE was determined by HPLC-ED. Plasma concentrations of LH, FSH, E2 and P4 were determined. In the acyclic animals, plasma LH was higher but the FSH was lower. There was decreasing P4 at different times, while the E2 was constant and lower in acyclic rats. FRA-ir expression in AVPV neurons of acyclic rats as well as turnover of NE was higher when compared with cyclic group. The preliminary findings showed increased activity in AVPV neurons in aging contribute to changes in the temporal pattern of neuroendocrine signaling, compromising the accuracy of inhibitory and stimulatory effects, causing irregularity in the estrous cycle and determining reproductive senescence.

Age-specific reproductive investment in female burying beetles: independent effects of state and risk of death

1.How much should an individual invest in reproduction as it grows older? Answering this question involves determining whether individuals measure their age as the time left for future reproduction or as the rate of deterioration in their state. Theory suggests that in the former case individuals should increase their allocation of resources to reproduction as opportunities for future breeding dwindle, and terminally invest when they breed for the last time. In the latter case they should reduce their investment in reproduction with age, either through adaptive reproductive restraint or as a passive by-product of senescence.
2.Here we present the results of experiments on female burying beetles, Nicrophorus vespilloides, in which we independently manipulated the perceived risk of death (by activating the immune system) and the extent of deterioration in state (by changing age of first reproduction and/or prior investment in reproduction).
3.We found that the risk of death and state each independently influenced the extent of reproductive investment. Specifically, we found a state-dependent decline in reproductive investment as females grew older that could be attributed to both adaptive reproductive restraint and senescence. A perceived increase in the risk of death, induced by activation of the immune system, caused females to switch from a strategy of reproductive restraint to terminal investment. Nevertheless, absolute reproductive investment was lower in older females, indicating constraints of senescence.
4.Our results show that a decline in reproductive investment with age does not necessarily constitute evidence of reproductive senescence but can also result from adaptive reproductive restraint.
5.Our results further suggest that the extent of reproductive investment is dependent on several different intrinsic cues and that the particular blend of cues available at any given age can yield very different patterns of investment. Perhaps this explains why age-related reproductive investment patterns seen in nature are so diverse.

Atividade dos neurônios do núcleo anterovental periventricular e sua participação no envelhecimento reprodutivo de ratas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Reproductive biology of female Rikuzen sole (Dexistes rikuzenius)*

The annual ovarian cycle, mode of maturation, age at maturity, and potential fecundity of female Rikuzen sole (Dexistes rikuzenius) from the North Pacific Ocean off the coast of Japan were studied by 1) histological examination of the gonads, 2) measurement and observation of the oocytes, and 3) by otolith aging. The results indicated that ovulation occurs from September to December and peaks between September and October. Vitellogenesis began again soon after the end of the current season. Maturity was divided into eight phases on the basis of oocyte developmental stages. Mature ovaries contained developing oocytes and postovulatory follicles but no recruiting oocytes, indicating that this species has group-synchronous ovaries and is a multiple spawner. Almost all females matured first at an age of 1+ year and spawned every year until at least age 8+ years. Potential fecundity increased exponentially with body length and the most fecund fish had 15 times as many oocytes as the least fecund fish. Potential fecundity and relative fecundity were both positively correlated with age from 1 to 6+ years, but were negatively correlated, probably because of senescence, in fish over 7 years. These results emphasize that the total productivity of a D. rikuzenius population depends not only on the biomass of females older than 1+ but also on the age structure of the population.

Ethylene and senescence processes

Senescence is a vitally important sequence of events in the latter phase of the life cycle of a plant that determines yield and reproductive success. In many species, and in different plant organs, ethylene is a key regulator of senescence and an increased understanding of the way the hormone functions will enable the timing and location of senescence to be manipulated in order to improve yield, quality and longevity. This chapter examines the physiological and molecular regulation of senescence in different plant organs and introduces the concept of the ‘senescence window’ in which plant organs are receptive to ethylene-mediated senescence cues. Several studies have attempted to elucidate global patterns of the regulation of senescence, which have enabled the function of ethylene to be placed in the context of the involvement of other, often antagonistic, hormones in the execution of senescence and downstream processes. Finally, we examine the consequences of senescence for post-harvest biology, an area where the control of ethylene action has been actively sought in order to control precisely the timing of senescence and ripening processes so that crop quality can be enhanced and maintained.

Living to die and dying to live: the survival strategy behind leaf senescence

Senescence represents the final developmental act of the leaf, during which the leaf cell is dismantled in a coordinated manner to remobilize nutrients and to secure reproductive success. The process of senescence provides the plant with phenotypic plasticity to help it adapt to adverse environmental conditions. Here, we provide a comprehensive overview of the factors and mechanisms that control the onset of senescence. We explain how the competence to senesce is established during leaf development, as depicted by the senescence window model. We also discuss the mechanisms by which phytohormones and environmental stresses control senescence, as well as the impact of source-sink relationships on plant yield and stress tolerance. In addition, we discuss the role of senescence as a strategy for stress adaptation and how crop production and food quality could benefit from engineering or breeding crops with altered onset of senescence.

Radiometrical, hormonal and biological correlates of skeletal growth in the female rat from birth to senescence

OBJECTIVE We investigated the skeletal growth profile of female rats from birth to senescence (100weeks) on the basis of sequential radiometrical, hormonal and biochemical parameters. DESIGN Weaning rats entered the study which was divided into two sections: a) sequential measurements of vertebral and tibial growths and bone mineral density (BMD), estimation of mineral content of the entire skeleton (BMC) and chemical analysis of vertebral Ca; and b) determination of basal and pulsatile growth hormone (rGH), insulin-like growth hormone (IGF-I), estradiol (E2), parathyroid hormone (PTH), osteocalcin (OC) and urinary d-pyridinoline (dp) throughout the experimental period. RESULTS Vertebral and tibial growths ceased at week 25 whereas BMD and BMC as well as total vertebral Ca exhibited a peak bone mass at week 40. rGH pulsatile profiles were significantly higher in younger animals coinciding with the period of active growth and IGF-I peaked at 7weeks, slowly declining thereafter and stabilizing after week 60. OC and dp closely paralleled IGF-I coinciding with the period of enhanced skeletal growth, remaining thereafter in the low range indicative of reduced bone turnover. E2 increased during reproductive life but the lower values subsequently recorded were still in the physiological range, strongly suggesting a protective role of this steroid on bone remodeling. PTH followed a similar profile to E2, but the significance of this after completion of growth remains unclear. CONCLUSIONS Mechanisms governing skeletal growth in the female rat appear similar to those in humans. Bone progression and attainment of peak bone mass are under simultaneous control of rGH, IGF-I and calciotropic hormones and are modulated by E2. This steroid seems to protect the skeleton from resorption before senescence whereas the role of PTH in this context remains uncertain.

The “Iranian ART Revolution”: infertility, assisted reproductive technology, and third-party donation in the Islamic Republic of Iran

Infertility is a social onus for women in Iran, who are expected to produce children early within marriage. With its estimated 1.5 million infertile couples, Iran is the only Muslim country in which assisted reproductive technologies (ARTs) using donor gametes and embryos have been legitimized by religious authorities and passed into law. Th is has placed Iran, a Shia-dominant country, in a unique position vis-à-vis the Sunni Islamic world, where all forms of gamete donation are strictly prohibited. In this article, we first examine the “Iranian ART revolution” that has allowed donor technologies to be admitted as a form of assisted reproduction. Then we examine the response of Iranian women to their infertility and the profound social pressures they face. We argue that the experience of infertility and its treatment are mediated by women’s socioeconomic position within Iranian society. Many women lack economic access to in vitro fertilization (IVF) technologies and fear the moral consequences of gamete donation. Thus, the benefits of the Iranian ART revolution are mixed: although many Iranian women have been able to overcome their infertility through ARTs, not all women’s lives are improved by these technologies.

Cellular senescence and longevity of osteophyte-derived mesenchymal stem cells compared to patient-matched bone marrow stromal cells

This study aimed to determine the cellular aging of osteophyte-derived mesenchymal cells (oMSCs) in comparison to patient-matched bone marrow stromal cells (bMSCs). Extensive expansion of the cell cultures was performed and early and late passage cells (passages 4 and 9, respectively) were used to study signs of cellular aging, telomere length, telomerase activity, and cell-cycle-related gene expression. Our results showed that cellular aging was more prominent in bMSCs than in oMSCs, and that oMSCs had longer telomere length in late passages compared with bMSCs, although there was no significant difference in telomere lengths in the early passages in either cell type. Telomerase activity was detectable only in early passage oMSCs and not in bMSCs. In osteophyte tissues telomerase-positive cells were found to be located perivascularly and were Stro-1 positive. Fifteen cell-cycle regulator genes were investigated and only three genes (APC, CCND2, and BMP2) were differentially expressed between bMSC and oMSC. Our results indicate that oMSCs retain a level of telomerase activity in vitro, which may account for the relatively greater longevity of these cells, compared with bMSCs, by preventing replicative senescence. J. Cell. Biochem. 108: 839-850, 2009. (c) 2009 Wiley-Liss, Inc.

Factors affecting reproductive performance of the prawn, Penaeus monodon

The growth of the Penaeus monodon prawn aquaculture industry in Australia is hampered by a reliance on wild-caught broodstock. This species has proven difficult to breed from if broodstock are reared in captivity. Studies were therefore carried out to investigate factors controlling reproduction and influencing egg quality. Results of the studies revealed that patterns of nutrient accumulation during early ovary development are altered by captive conditions, possibly contributing to reduce larval quality. The sinus gland hormones were shown, together with the environment, to regulate two stages of ovary development. In a separate study it was further revealed that the hormone methyl farnesoate (MF) could negatively regulate the final stages of ovary development. Lastly it was shown that broodstock reared in captivity are less likely to mate and that this is due to inherent problems in both the male and the female prawns.