Post-reproductive Period Research Articles

In vitro effects of both dopaminergic and enkephalinergic antagonists on the ovarian growth of Cherax quadricarinatus (Decapoda, Parastacidae), at different periods of the reproductive cycle

The in vitro effect of both spiperone (dopaminergic antagonist) and naloxone (enkephalinergic antagonist), was assayed on small pieces of ovary dissected from C. quadricarinatus females, with the eventual addition of some neuroendocrine organs, such as thoracic ganglion or eyestalk tissue. The incorporation of tritiated leucine by the ovary was measured in order to estimate the ovarian growth. During the post-reproductive period, both mentioned antagonists were able to significantly stimulate the ovary in the presence of thoracic ganglion, but did not produce any significant effect in the preparation containing ovary and eyestalk tissue, or only ovary. No significant effects of the assayed antagonists were noted during the pre-reproductive period. These results were in accordance with previous models describing the neuroendocrine control of crustacean reproduction, and represent new findings about the hormonal context in different periods of the reproductive cycle of crayfish. Besides, by means of the experimental combination of the tested antagonists with dopamine or met-enkephalin, a new model dealing with the interaction of these two neurotransmitters on the hormonal secretion of thoracic ganglion has been proposed.

Life history context of reproductive aging in a wild primate model.

The pace of reproductive aging has been of considerable interest, especially in regard to the long postreproductive period in modern women. Here we use data for both sexes from a 37-year longitudinal study of a wild baboon population to place reproductive aging within a life history context for this species, a primate relative of humans that evolved in the same savannah habitat as humans did. We examine the patterns and pace of reproductive aging, including birth rates and reproductive hormones for both sexes, and compare reproductive aging to age-related changes in several other traits. Reproductive senescence occurs later in baboon females than males. Delayed senescence in females relative to males is also found in several other traits, such as dominance status and body condition, but not in molar wear or glucocorticoid profiles. Survival, health, and well-being are the product of risk factors in morphological, physiological, and behavioral traits that differ in rate of senescence and in dependence on social or ecological conditions; some will be very sensitive to differences in circumstances and others less so.

Grandparental investment and the epiphenomenon of menopause in recent human history

AbstractThe effects of grandparental investment in relatives are apparent in human groups, suggesting that a postreproductive period in humans is selective. Although investment of relatives in kin produces obvious benefits for kin groups, selection for a postreproductive period in humans is not supported by evidence from chimpanzees. Instead, grandparental investment is likely a recent phenomenon of longevity, rather than an evolved feature.

Biological responses of the Sipha flava (Forbes, 1884) (Hemiptera: Aphididae) fed with different elephant grass genotypes

This work aimed to evaluate the effect of genotypes of elephant grass, Pennisetum purpureum Schum, on some biological aspects of Sipha flava (Forbes). Foliar disks of 15 elephant grass genotypes were used, on which individual nymphs up to 12 hours old were placed in dishes and kept at 25 oC, RH of 70 ± 10% and 12-hour photophase. We evaluated the number of instars, duration and survival of each instar and the entire nymphal period, duration of the pre-reproductive, reproductive and post-reproductive period, daily and total nymph production capacity and longevity of the adults and biological cycle (nymph-adult). The nymphs passed through four instars on all the elephant grass genotypes studied. There were no significant differences in the duration of the first and last nymph stages on the different genotypes, unlike observed for the intermediate instars and nymphal period . The biological parameters of the adult phase of the aphid, such as pre-reproductive, reproductive and post-reproductive period and longevity, were also affected by the genotype. Cameroon de Piracicaba and Guacu IZ2 were the most suitable genotypes for development of the aphids, providing higher values for overall production of nymphs/female, daily production of nymphs/female, reproductive period and adult longevity. On the other hand, the Sem Pelo genotype was the least suitable for the aphids’ development and reproduction according to the biological parameters studied.

Effect of Various Host-Plants on the Population Growth and Development of The Pea Aphid

The performance of the pea aphid, Acyrthosiphon pisum Harris (Homoptera: Aphididae) was studied on several Fabaceae species including: pea (Pisum sativum), broad bean (Vicia faba), alfalfa (Medicago sativa), bean (Phaseolus vulgaris) and red clover (Trifolium pratense). Alfalfa, bean and red clover were less accepted by the pea aphid than pea and broad bean. The pea aphid fed on the alfalfa, bean and red clover showed longer pre-reproductive, and shorter reproductive and post-reproductive periods. Alfalfa, bean and red clover also shortened and decreased fecundity of the pea aphid. Mean survival of the pea aphids fed on red clover and bean plants was reduced in comparison to pea aphid fed on pea and broad bean. The other studied population parameters: intrinsic rate of natural increase (rₘ), net reproduction (R₀) and mean generation time were also reduced in the case of the pea aphid on alfalfa, red clover and bean. The study of aphid development and reproduction demonstrated that pea and broad bean are suitable host plants for A. pisum while alfalfa, red clover and bean are not. It is likely that the rejection of alfalfa, red clover and bean by A. pisum was caused by chemical factors in these hosts.

The Impact of Temperature on Biological Aspects and Life Table ofRhopalosiphum padi(Hemiptera: Aphididae) Fed with Signal Grass

ABSTRACT The impact of temperature was evaluated on Rhopalosiphum padi (L.) (Hemiptera: Aphididae). Nymphs, 12-h-old, were placed individually in cylindrical plastic dishes (2.5 × 2.5 cm), with a layer of 1% agar in which leaf disks of signal grass had been placed. The nymphs were reared at 12, 16, 20, 24, 28, and 32°C ± 1°C, RH of 70 ± 10% and 12-h photophase. We evaluated number of instars, duration of each instar and the nymphal period, survival of instars, duration of the reproductive period, daily and total production of nymphs, and longevity of the nymphal and adult phases. To construct the life expectancy table and fecundity, daily observations were made of 70 nymphs at each temperature, from birth to death. Development of R. padi was faster with increased temperature, but they did not complete the last nymphal instar at 32°C. The same pattern occurred for the pre-reproductive, reproductive, and post-reproductive periods. The highest fecundity rates were between 16°C and 24°C. The highest fertility...

Effect of Host Plant on Biology and Life Table Parameters of Brevicoryne brassicae (Hemiptera: Aphididae)

Abstract The cabbage aphid, Brevicoryne brassicae L. (Hemiptera: Aphididae), is a key pest of oilseed rape, Brassica napus L., and produces economic damage. Commonly, life table parameters have been used to compare insect fitness on different varieties. Effects of four different varieties of oilseed rape (‘Zarfam’, ‘Licord’, ‘Hyola 401’, and ‘SLM046’) on biological aspects and fecundity life table parameters of B. brassicae were studied under laboratory conditions. There was no significant difference between the length of prereproductive, reproductive, postreproductive periods, and fecundity of aphid developing on different varieties. The maximum length of prereproductive, reproductive, and longevity periods of B. brassicae were observed in the Licord variety. The maximum fecundity of aphid was recorded on Hyola 401. The intrinsic rate of increase was estimated by using Euler-Lotka equation and was compared with those estimated using Wyatt and White's equation. Intrinsic rate of increase of B. brassicae (based on jackknife method) was 0.298, 0.294, 0.311, and 0.289 on Zarfam, Licord, Hyola 401, and SLM046, respectively. Feeding on SLM046 and Licord reduced the reproductive capacity of the cabbage aphid compared with the other varieties studied. However, statistical analysis of Wyatt and White output showed that calculated rm were higher than that Euler-Lotka equation and there was not significant difference between rm on different varieties. Aphid population growth 20 d after plant infestation showed no significant difference between numbers of produced aphids, but significant difference in the number of winged aphids.

Individual, temporal, and population-level variations in circulating 11-ketotestosterone and 17β-estradiol concentrations in the oyster toadfish Opsanus tau

Sex steroid hormones are important for reproduction in all vertebrates, but few studies examine inter-individual, temporal, and population-level variations, as well as environmental influences on circulating steroid levels within the same species. In this study we analyzed plasma 11-ketotoestosterone (11-KT) and 17β-estradiol (E 2) levels in the oyster toadfish to test for 1) individual and temporal variations by serially sampling the same individuals during the reproductive and post-reproductive period, 2) variations in steroid levels among toadfish obtained from different sources or maintained under different holding conditions, and 3) correlations with environmental parameters. Results from serial sampling showed marked inter-individual variations in male 11-KT levels in two separate groups of toadfish, but no temporal differences from June to September. Females also showed inter-individual variations in E 2 concentrations, but most had elevated levels late in the reproductive season coincident with oocyte growth prior to winter quiescence. E 2 concentration, but not 11-KT, was positively correlated with water temperature, and negatively correlated with daylength and lunar phase. Maricultured toadfish held under constant conditions had elevated levels of E 2 and 11-KT that should be considered when using these fish for experimentation. This study provides important comparative information on the relationship between individual variations in steroid levels, and how they relate to physiological and environmental correlates in a model marine teleost.

Effects of Fenvalerate and TBTC (EDCs) on life history characteristics of freshwater rotifer <i>Brachionus calyciflorus</i>

采用单克隆培养和群体培养的方法,研究了具有环境雌激素效应药物氰戊菊酯(Fenvalerate)和雌性雄性化激素效应药物三丁基氯化锡(TBTC)对萼花臂尾轮虫(Brachionus calyciflorus)生命周期中各发育阶段的历时以及种群增长的影响.结果表明,氰戊菊酯和TBTC对萼花臂尾轮虫的生长发育和种群增长有明显的效应.氰戊菊酯使生殖期延长(200和1000μg/L),生殖后期缩短,平均寿命也缩短(除1000μg/L),总产卵量和种群增长率升高;而经TBTC处理生殖前期延长(1和5μg/L),生殖期和生殖后期缩短,平均寿命也缩短,总产卵量和种群增长率较对照组也有下降.批次携卵量也受到两种药物的影响.且萼花臂尾轮虫的总产卵量随着氰戊菊酯和TBTC的浓度呈曲线相关,氰戊菊酯:Y=-0.6745X²+6.6884X+5.855(R²=0.7027);TBTC:Y=0.2054X²-2.3178X+16.666(R²=0.6535).研究表明环境雌激素氰戊菊酯和雌性雄性化激素TBTC对萼花臂尾轮虫生活史特征影响表现出一定差异.;Recent reports suggested that when certain contaminants may present in aquatic ecosystem at levels, it would disruptendocrine functions of a variety of aquatic invertebrates. For this hypothesis, we sought to determine whether the estrogeniccompound Fenvalerate and androgenic compound TBTC can individually inhibit the development and reproductive output of thefreshwater rotifer Brachionus calyciflorus. The present study focused on the life history characteristics of B. calyciflorus undereffects of different concentrations of Fenvalerate and TBTC. The result showed that Fenvalerate and TBTC had significant effectson the durations of different development stages of B. calyciflorus and the characterristics of its population growth. Treatmentwith Fenvalerate at the concentrations of 200 and 1000μg/L significantly lengthened the duration of reproductive period.However, the duration of pre-reproductive, post-reproductive periods and the lifespan were shortened. In treatment with 1 and5μg/L TBTC, the number of eggs and population growth rate were also increased compared to the control, however, thepre-productive period was significantly lengthened, and the reproductive, post-reproductive periods and the lifespan weresignificantly shortened compared to the control. The total number of eggs and population growth rate were both decreasedsignificantly when the rotifer was exposed to 0.001 and 1-5μg/L of the above contaminants, and the number of eggs wascurve-related with the concentrations of Fenvalerate and TBTC (Fenvalerate: Y=-0.6745X²+6.6884X+5.855(R²=0.7027); TBTC:Y=0.2054X²-2.3178X+16.666(R²=0.6535)). Consequently, Fenvalerate and TBTC showed differently effects on the durations ofdifferent development stages of B. calyciflorus and the characterristics of its population growth.

Biologia de aphis gossypii em plantas infectadas pelo vírus do mosaico das nervuras do algodoeiro

O objetivo deste trabalho foi avaliar a biologia do pulgão-do-algodoeiro, Aphis gossypii Glover (Hemiptera: Aphididae), em plantas de algodoeiro (Gossypium hirsutum L.) sadias e infectadas com o vírus causador do mosaico das nervuras. O experimento foi realizado em câmara climatizada mantida a 25±1 ºC, umidade relativa de 70±10% e fotofase de 12 horas. Os dois tratamentos corresponderam a pulgões que se alimentaram de plantas sadias e infectadas com o vírus. As unidades experimentais consistiram de placas de Petri contendo ágar-água a 1% solidificado e um disco foliar de plantas sadias ou infectadas, com 30 repetições cada uma. Os pulgões que se alimentaram de plantas infectadas tiveram menor duração da fase ninfal (4,5 dias) em relação àqueles que se alimentaram de plantas sadias (4,9 dias). Os períodos pré-reprodutivo, reprodutivo e pós-reprodutivo e a longevidade não foram influenciados pelo vírus. A maior mortalidade também foi observada em pulgões alimentados com plantas infectadas. O tempo decorrido entre gerações (T) e o tempo necessário para duplicar em número (TD) foram menores para pulgões que se alimentaram de plantas infectadas (9,74 e 1,66 dias respectivamente), as quais também acarretaram maior mortalidade ninfal. A taxa líquida de reprodução (Ro), a capacidade inata de aumentar em número (r m) e a razão finita de aumento (λ) foram favoráveis aos pulgões que se alimentaram de folhas de algodoeiro infectadas. Conclui-se que os pulgões mantidos em folhas de algodoeiro sadias atingiram melhores índices de desenvolvimento enquanto na reprodução os melhores índices são observados em pulgões mantidos em folhas infectadas.

The Akela-effect – Is there an evolutionary benefit from senators in mammals?

A characteristic feature of the life history of humans and some other species of social mammals is a long post-reproductive period. This condition is of a physiological nature in females (menopause), whereas in males it is largely of a behavioral nature. We discuss the hypothesis that old, post-reproductive individuals in these species may act as repositories of acquired knowledge, thereby providing an evolutionary benefit for their group. According to this view, the group's investment into the care for their older members is overcompensated by the benefits gained from the experience of these individuals (“senators”). This phenomenon is suggested to be largely independent from the degree of genetic relatedness within the group. We put forward a list of several necessary preconditions for the senator phenomenon to evolve. The presence or absence of these preconditions can be studied empirically.

Aleutian Disease Serology, Protein Electrophoresis, and Pathology of the European Mink (Mustela lutreola) from Navarra, Spain

The European mink, Mustela lutreola, has suffered a dramatic decline in Europe during the 20th century and is one of the most endangered carnivores in the world. The subpopulation of European mink from Navarra, Spain, estimated to number approximately 420, represents approximately two thirds of the total number of mink in Spain. Aleutian Disease Virus (ADV) is a parvovirus with a high degree of variability that can infect a broad range of mustelid hosts. The pathogenesis of this virus in small carnivores is variable and can be influenced by both host factors (e.g., species, American mink genotype, and immune status) and viral strain. A cross-sectional study was conducted during the pre-reproductive period of February-March 2004 and 2005 and the postreproductive period of September-December 2004. Mink were intensively trapped along seven rivers that were representative of the European mink habitat in Navarra. Antibody counter immunoelectrophoresis against ADV was performed on 84 European mink blood samples. All the samples were negative. Protein electrophoresis was performed on 93 plasma samples. Nine of those samples (9.6%) had gamma globulin levels exceeding 20% of the total plasma protein. Complete necropsies were performed on 23 cadavers of European mink collected in the area between 2000 and 2005. Seventeen of the mink (74%) had traumatic and hemorrhagic lesions compatible with vehicular impact injuries. Although there were no histopathologic lesions associated with ADV, this study documents the first description of a naturally occurring canine distemper virus infection in a European mink. In addition, pulmonary adiaspiromycosis in three European mink from Spain was reported.

Ecoimmunology: is there any room for the neuroendocrine system?

Ecological Immunology assumes that immunological defenses must be minimized in terms of cost (energy expenditure). To reach this goal, a complex and still largely unexplored strategy has evolved to assure survival. From invertebrates to vertebrates, an integrated immune-neuroendocrine response appears to be crucial for the hierarchical redistribution of resources within the body according to the specific ecological demands. Thus, on the basis of experimental data on the intimate relationship between stress and immune responses that has been maintained during evolution, we argue that a broader perspective based on the integration of immune and neuroendocrine responses should be adopted to describe the comprehensive strategy that the body utilizes to adapt to dynamic environmental conditions. We discuss the hypothesis that a bow-tie architecture might be suitable to describe the variety of immune-neuroendocrine inputs that continuously target cells and organs while, at the same time, fulfilling the basic requirement of minimizing the cost of immune-neuroendocrine responses. Bow-tie architectures are able to convert a variety of stimuli (fan in) into a wide range of fine-tuned responses (fan out) by passing through the integrating activity of a core (knot) constituted by a limited number of elements. Finally, we argue that the ecologically negotiated immune-neuroendocrine strategies may have deleterious effects in the post-reproductive period of life when, at least in humans, chronic, low-grade, systemic inflammation develops, in accordance with the antagonistic pleiotropy theory of aging.

Intersexual variation in the seasonal behaviour and depth distribution of a freshwater temperate fish, the largemouth bass

Because fish are poikilothermic, water temperature is regarded as a primary factor influencing their activity and behaviour. Rarely have field studies been conducted with the spatiotemporal resolution to enable rigorous quantitative assessments of that relationship. Furthermore, there have been few studies that have considered the influence of sex on the seasonal behaviour of fish. Twenty largemouth bass ( Micropterus salmoides (Lacepède, 1802)) were implanted with coded acoustic telemetry transmitters and remotely tracked in near real time in a small lake in Ontario, Canada, via a whole-lake hydrophone array between 1 November 2004 and 30 September 2005. Fish inhabited the deepest waters and were least active during the winter months under ice. During the warmest months, fish were most active and inhabited the littoral zone. Sex-specific differences were noted year-round. Reproductive males were less active and inhabited shallower depths during the spawning and post-reproductive periods. Reproductive males inhabited the deepest depths during winter and fall, with nonreproductive males at the shallowest depths. Throughout the year, the behaviour of nonreproductive males and females was similar. While differences in behaviour of bass are primarily driven by water temperature, sex and reproductive status play important roles year-round, especially during and after the reproductive period.

Effects of Salinity on Survival, Growth, Reproductive and Life Span Characteristics of Artemia Populations from Urmia Lake and Neighboring Lagoons

This study deals with effects of different salinities on the survival, growth, reproductive and lifespan characteristics of three Artemia populations from Urmia Lake and small lagoons at the vicinity of the lake under laboratory conditions. Experimental salinities ranged from 75 to 175 g L(-1). Salinity was proved to have significant impact on the majority of the characters studied in this survey. Growth and survival in bisexual A. urmiana and parthenogenetic Artemia from Lake Urmia were significantly higher with respect to the parthenogenetic Artemia from lagoons at most of the salinities tested. Reproductive characteristics such as total number of broods, total offspring number of offspring in each brood and number of offspring at each day of reproductive period reduced with increasing salinity. Moreover higher salinity prolonged the prereproductive period but shortened the total reproductive period. Higher salinities also affected the percentage of encystment and post-reproductive period, showing significantly higher values in parthenogenetic populations in comparison to bisexual A. urmiana.

Aging and Fertility Patterns in Wild Chimpanzees Provide Insights into the Evolution of Menopause

Human menopause is remarkable in that reproductive senescence is markedly accelerated relative to somatic aging, leaving an extended postreproductive period for a large proportion of women. Functional explanations for this are debated, in part because comparative data from closely related species are inadequate. Existing studies of chimpanzees are based on very small samples and have not provided clear conclusions about the reproductive function of aging females. These studies have not examined whether reproductive senescence in chimpanzees exceeds the pace of general aging, as in humans, or occurs in parallel with declines in overall health, as in many other animals. In order to remedy these problems, we examined fertility and mortality patterns in six free-living chimpanzee populations. Chimpanzee and human birth rates show similar patterns of decline beginning in the fourth decade, suggesting that the physiology of reproductive senescence was relatively conserved in human evolution. However, in contrast to humans, chimpanzee fertility declines are consistent with declines in survivorship, and healthy females maintain high birth rates late into life. Thus, in contrast to recent claims, we find no evidence that menopause is a typical characteristic of chimpanzee life histories.

Sequence analysis of retinoic acid receptor α, β and γ isoforms in the lizard, Podarcis sicula

Vitamin A and its principal biologically active derivative, retinoic acid (RA), play a fundamental role in diverse processes, such as proliferation, differentiation, morphogenesis, metabolism and apoptosis of many types of cells. In addition, RA has been shown to be involved in the regulation of testicular function. These effects are mediated by interaction with two families of nuclear receptors, retinoic acid receptor (RAR) and retinoid X receptor (RXR), each with three subtypes α, β and γ. The physiological involvement of retinoids in testicular function has been conducted mainly in mammals. Recently, we found that exogenous all- trans-retinoic acid impairs spermatogenesis and enhance testicular germ cell apoptosis in the lizard, Podarcis sicula, a seasonal breeder. To further investigate the role of retinoic acid in lizard, we focus this work principally on the characterization of lizard retinoic acid receptors (α, β and γ isoforms). RARα is 2720 bp long with a putative ORF between 699 and 2133. A Kozac sequence is present at 696 and a putative poly-adenilation site is present in position 2612. The RARα sequence shares 87% homology with mouse RARα mRNA while it has 76 and 80% homology with lizard RARβ and γ mRNAs. RARβ is 2478 bp long showing a putative ORF between 196 and 1543. A canonical Kozac sequence is present at 193 and a putative poly-adenilation site is present at 2294. RARβ shares 91% homology with mouse RARβ mRNA and has 76% homology with both RARα and γ. RARγ is 2416 bp long. With a putative ORF between 444 and 1818. A Kozac sequence is present at 441 and a putative poly-adenilation site is present at 2288. RARγ shares 86% homology with mouse RARβ mRNA and has 80 and 76% homology with both RARα and β respectively. It is worth to note that, as in mouse, the 5′UTR of all isoforms is TATA and CAAT less. Both Northern blot and PCR analyses indicate that lizard testis expresses only RARα and RARβ mRNAs, while RARγ mRNA transcript was not found. In the period analysed, RARβ was expressed during the gonadal full activity (May) and RARα was present in the post-reproductive period (August). During the autumnal recrudescence (October) RARα and RARβ are co-expressed and, as indicated by quantitative PCR analysis, RARβ mRNA levels are lower than RARα ones. Thus, the appearance and abundance of each receptor correspond to a specific phase of lizard reproductive cycle, allow us to hypothesize that each RAR subtype could play a specific role in the regulation of spermatogenetic activity. The results of the present study show, for the first time, the characterization of RAR mRNAs in the testis of lizard P. sicula, whose expression is related to the different phase of reproductive cycle. Moreover, the γ form, is principally expressed in the skin during the March–July period, having probably a role in regulating skin homeostasis and colour livery, which are important factor in mating during the reproductive cycle.

The c-kit receptor protein in the testis of green frog Rana esculenta: seasonal changes in relationship to testosterone titres and spermatogonial proliferation

The green frog Rana esculenta is a seasonal breeder. The cyclic changes between almost arrested and highly activated spermatogenesis offer an ideal model to study basic mechanisms of spermatogenesis. In this study, we demonstrated, to our knowledge for the first time, c-kit receptor positive cells in the testis of this amphibian. The presence of c-kit receptor protein was confirmed by western blotting (Wb) analyses carried out in the testis during all the three main phases of the sexual cycle. The antibody recognized a band of about 150 kDa that was correlated with the positive staining in the germinal epithelium. The immunolabelling for c-kit receptor, evaluated by immunohistochemistry (IHC), was localized in I and II spermatogonia (SPG), in I and II spermatocytes, in both elongating spermatids and spermatozoa and in the Leydig cells. Furthermore, c-kit expression showed a seasonal pattern connected with both testicular and plasma profiles of testosterone during the reproductive cycle. The highest expression of c-kit receptor occurred during the reproductive period, when the testis exhibited the maximum concentration of testosterone. In this period, the mitotic activity of germ cell, assessed by both Wb and IHC analyses for proliferating cell nuclear antigen (PCNA), was intensive. Indeed, during the post-reproductive period, testosterone titres were the lowest and the expression of both PCNA and c-kit receptor protein in the testis, although present, is minor when compared with the reproductive phase. This evidence suggests that cell division can continue sufficiently to accumulate SPG for the next spring, when new germinal cells undergo multiplication. Finally, during the pre-reproductive period, testosterone levels begin to increase and mitotic activity of germinal epithelium is comparably enhanced. These events seem to precede the period of maximum stimulated spermatogonial proliferation, i.e. the reproductive period. These results suggest that the c-kit receptor may play a role in germ cell proliferation and provide a basis for future detailed investigation of regulatory factors of the proliferation of SPG.

Synthetic seminal plasma peptide inhibits testosterone production in frog testis in vitro

The role of synthetic seminal plasma peptide, designed using biochemical and mass spectroscopy analyses of native peptides extracted from seminal plasma, was studied in amphibian (Rana esculenta) testicular steroidogenesis. Production of testosterone and prostaglandin F(2alpha) was determined by incubating frog testes with synthetic peptide in vitro. Analysis of the data showed a dose-dependent inhibition of testosterone production (43% at 10(-5) M concentration) without prostaglandin F(2alpha) synthesis being affected. Determination of the peptide activity during the annual R. esculenta reproductive cycle showed inhibition of testosterone production in post-reproductive and recovery periods, suggesting a possible involvement of peptide in gonad steroidogenesis.

Sex Differences in Body Fat Parameters from the Early Reproductive to the Postreproductive Period of Life: A Multivariate Analysis

Sex diversity has been observed for many body parameters, and special attention has been paid to changes during puberty and menopause. In the present study we performed a multivariate analysis on several body fat parameters to obtain a synthetic overview of sex differences from the early reproductive period to the postreproductive period. The sample study is composed of 373 healthy Italian adults (294 females and 79 males). We have examined the amount of fat (in kilograms, as measured by dual-energy x-ray absorptiometry) in the left arm, left leg, left trunk hemisphere, right arm, right leg, and right trunk hemisphere, waist to hip ratio, and BMI. The sex differentiation from the early reproductive to the postreproductive period of life has been based on differences between the position of male and female centroids on the discriminant functions obtained for various periods of life. The difference between males and females increases suddenly after 20 years, reaching a maximum at 30 years. In the period between 30 and 40 years the difference decreases quickly, and after 40 years the difference is relatively small and remains practically constant. The fact that maximum sex differentiation coincides with age of best reproductive efficiency points to a relationship between the body parameters investigated and hormone production related to human reproduction.