Acceleration Of Sexual Maturation Research Articles

Long‐term changes in BMI and adiposity rebound among girls from Kraków (Poland) over the last 30 years (from 1983 to 2010)

Early adiposity rebound (AR, below 5 years) is an important predictor of adult obesity. The main purpose of this study was to explore changes in body weight and height, BMI, body fat, and AR timing in girls from Krakow within the last 3 decades. 1,970 girls were measured in 2010. Using the results of body height, weight and skin folds measurements, the BMI and %BF was calculated. The LMS method was used to constructed BMI and %BF centiles. Three fractions were distinguished in individual age groups of the subjects-below the 15th percentile (underweight girls), 50th percentile and above 85th percentile (overweight girls). These data were compared with the results from previous survey series (1983 and 2000). The mean age of the menarche onset were calculated by means of the probit method. The girls from last series are taller and heavier than girls measured in 1983. Before the time of AR, girls from last series have lowest BMI and %BF than girls from the first series. In spite of this, all girls measured in 2010 have the time of AR earlier than girls measured in 1983. The girls from the last series of measurements showed also acceleration of sexual maturation and the average menarche age was the earliest in them and equalled 12.68 years. AR cannot be explained only by changes in body adiposity. Early AR could be a marker of acceleration of development already in an early postnatal ontogenesis.

Methoprene treatment reduces the pre‐copulatory period in Anastrepha fraterculus (Diptera: Tephritidae) sterile males

AbstractAnastrepha fraterculus is a major fruit pest in South America. Ongoing studies support the implementation of the sterile insect technique (SIT) against this pest. Sexual readiness of sterile males is a key point for SIT application. The pre‐copulatory period of A. fraterculus males has not been reported before, but it is expected to last several days. An acceleration of sexual maturation was achieved in other Anastrepha species after topical applications of juvenile hormone analogues, like methoprene. Here, we studied the effect of methoprene on male sexual maturation, mating duration and sperm transfer in A. fraterculus as well as the impact of acetone (methoprene solvent) on survival. We also explored a method to deliver methoprene massively. Pheromone‐calling and mating ability were evaluated daily from adult emergence, and used as indicators of sexual maturity. Anastrepha fraterculus males showed a long pre‐copulatory period (7 days approximately), as other Anastrepha species. This process was accelerated after methoprene treatment (2.5 μg/μl), both in non‐irradiated and irradiated males which matured 2–3 days earlier. Mating duration for methoprene‐treated males was longer than for mature untreated males, however, no differences in sperm transfer were detected. Survival was not affected by acetone. Dipping pupae in methoprene allowed emerging males to mature as fast as those receiving topical application as adults. Dipping of pupae is a promising method to deliver massively methoprene and should be further investigated.

Prevention of Lesioning-Induced Precocious Puberty in Female Rats by Neonatal Implantation of Fetal Preoptic Tissue

Damage to the medial preoptic area (MPOA) was produced in one-day-old female rats by bilateral electrolytic lesions or by aspiration of preoptic tissue. Both procedures resulted in similar advancement of vaginal opening and the first ovulation. A further group of rats was lesioned or aspirated in the MPOA and immediately bilaterally implanted with medial preoptic tissue collected by the puncture method from 17-19-day-old female rat fetuses. After autopsy, tissue destruction and implants located in the MPOA could be identified in 5 females that showed significantly later onset of puberty than both the lesioned or aspirated and the untreated controls. The findings suggest that the elimination of neurones and not a stimulatory effect of electrolytic lesions on GnRH secretion is responsible for the acceleration of sexual maturation recorded after lesioning of the MPOA. Possible reasons for the failure to identify the grafts in most of the implanted females are discussed.

Neoteny and progenesis as two heterochronic processes involved in paedomorphosis in Triturus alpestris (Amphibia: Caudata).

Current theories on the evolution of paedomorphosis suppose that several ontogenetic pathways have appeared according to different selective pressures. The aim of this study was to find out whether two distinct processes can lead to paedomorphosis in the Alpine newt, Triturus alpestris. In this respect, we compared age structures of paedomorphic and metamorphic individuals in two newt populations where the two forms lived syntopically. Whereas paedomorphosis resulted in a slower rate of somatic development in one population, it resulted in an acceleration of sexual maturation in the other population. These processes correspond to neoteny and progenesis, respectively. These results suggest that phenotypic plasticity can result from contrasted ontogenetic pathways between two populations of the same species. They give support to models that consider gonadic development as the target of selection under different environmental pressures.

Role of the serotoninergic system in the acceleration of sexual maturation in wild Norway rats selected for reduced aggressiveness toward humans

The role of the serotoninergic system in acceleration of the sexual development of domesticated rats ( Rattus norvegicus) was assessed. The onset of age-related changes in hypothalamic serotonin during prepubertal period occurred earlier in domesticated than in aggressive male rats. Blockade of the serotoninergic system after p-chlorophenylalanine (PCPA) administration on days 40 and 44 delayed the development of the reproductive system in both aggressive and domesticated males. In 60-day-old rats treated with PCPA, levels of testosterone in plasma and the number of mature spermatozoa in epididymis were decreased compared to controls. At the same time, the administration of PCPA on days 30 and 34 did not modify basal testosterone secretion and other parameters in 60-day-old aggressive rats and produced a decrease similar to PCPA injections on days 40 and 44, although less pronounced, in the weights of testes in domesticated animals. Administration of 5-hydroxytryptophan (5-HTP), a precursor of serotonin synthesis, on days 30, 32, 34, 36 and 38 increased plasma testosterone levels and weights of the sex organs in 60-day-old domesticated males, but did not significantly affect the development of reproductive system in aggressive animals. These data indicate that serotonin stimulates sexual development of males during prepubertal period and this activating effect of serotonin occurs earlier in domesticated than in aggressive males. They also suggest that the acceleration in sexual maturation of domesticated rats could result from changes in the ontogenetic dynamic of hypothalamic serotonin induced by a selection for low aggressiveness towards man.

Ontogenetic model of ageing and disease formation and mechanisms of natural selection

It is known that increased mortality due to environmental hazards results, in the course of natural selection, in the shortening of maximum life span and acceleration of sexual maturation in a population subjected to an intensified pressure from external environment. As a consequence, the prereproductive period/maximum life span ratio appears to be approximately the same in each species. Mechanisms responsible for this are not clear yet. Since maximum life span is limited by both ageing and formation of certain diseases (in humans, the so-called main noninfectious diseases), the paper discusses four possible models of development of ageing and age-linked disease--ecological, genetic, degenerative (metabolic) and ontogenetic. It was found that it is the ontogenetic model only that can adequately account for the development of moderate shifts in the duration of both sexual maturation and maximum life span. It also provides the rationale for the pleotropic activity of genes during the development of the organism, its ageing and formation of age-connected diseases.

Acceleration of sexual maturation in female rats by male stimulation.

In comparison to controls reared in isolation, female rats reared in the presence of an adult male from weaning attained puberty 5 days earlier when living in groups or almost 9 days earlier when living singly with a male. Accelerated sexual development occurred in the absence of accelerated physical growth.