Puberty acceleration in female mice induced with a partially purified male urine extract: effects on catecholamine release from the olfactory bulbs and hypothalamus

Effects of the COVID-19 pandemic on the incidence of central precocious puberty; a narrative review

Central precocious puberty (CPP) is the premature activation of the hypothalamus-pituitary-gonadal axis, resulting in the early development of secondary sexual characteristics. CPP classically occurs before the age of 8 years in girls and 9 years in boys. The aetiology of this precocious onset of puberty is governed by complex mechanistic interactions between genetic and environmental factors. The rates of CPP have been documented to have been rising before the COVID-19 pandemic; despite this, the incidence of CPP has increased exponentially since the start of the pandemic. There are multiple theories potentially explaining this change in incidence of CPP over COVID-19. These include the direct effect of SARS-coV-2 infection, increasing body mass index of adolescents over sequential lockdowns, changes in sleep patterns, increased use of electronic devices and levels of stress, and additionally potential earlier detection of signs of CPP by parents and carers. Whilst there is evidence from observational cohorts, case studies and animal models for each of these factors, it is difficult to definitively prove which has had the greatest impact due to the mainly retrospective nature of the human research that has been conducted. Moreover, studies set in diverse settings with varying population make comparison complex. Additionally, each country responded differently to the COVID-19 pandemic and the lockdowns varied between locations, hence the effect of lockdown was not equal or universal. Despite this, similar trends have been identified, with various lifestyle changes that occurred over the pandemic being potentially influential factors on the development of CPP.

The effects of the covid-19 pandemic on puberty: a cross-sectional, multicenter study from Turkey

BACKGROUNDS

During the Coronavirus-19 disease (Covid-19) pandemic it was observed that the number of girls presenting with early puberty had increased. The aim of this study was to carry out a retrospective evaluation of the characteristics of girls who had been referred for evaluation of precocious puberty in five different pediatric endocrinology units, before and during the pandemic.

METHODS

The study participants comprised 359 girls who were assigned into 2 groups a pre-pandemic group (n:214) and a pandemic group (n:145). Those participants (n:99) who had medical records in the follow-up period were classified into 3 subgroups according to the time of presentation and follow-up visits (group-1: first admission and follow-up visit before the pandemic, group-2: first admission before the pandemic, the follow-up visit during the pandemic, group-3: first admission and follow-up visit during the pandemic).

RESULTS

The age at presentation and age at pubertal onset were both significantly lower in the pandemic group than those in the pre-pandemic group(8.1 vs 8.6, p: < 0.001,7.7 vs 7.9,p:0.013, respectively). There was no significant difference between the body mass index standard deviation scores (BMI-SDS) values of the groups (0.57 vs 0.51, p:0.430). The initiation rate of pubertal suppression therapy at the time of presentation was significantly higher in the pandemic group compared to that of the pre-pandemic group (7.7%vs 27.5%), and in groups-2 & 3 compared to group-1, during follow-up (20%&44%vs 8%).

CONCLUSION

Our research showed that the onset of puberty occurred earlier in the pandemic period compared to the previous year, and the need for pubertal suppression therapy increased during the pandemic.

Precocious Puberty and Covid-19 Into Perspective: Potential Increased Frequency, Possible Causes, and a Potential Emergency to Be Addressed

A significant increase in precocious puberty, rapidly progressive puberty and precocious menarche has been reported in Italy since the initial lockdown because of the pandemic, and this could represent a new emergency to be addressed during this pandemic. There is a need, therefore, for further understanding and research. Many causes could account for this. Initially, it was thought that the changes in life-style, in screen time, and sleeping habits could be the cause but if considered individually these are insufficient to explain this phenomenon. Likely, changes in central nervous mediators, and an increase in catecholamines could contribute as a trigger, however, these aspects are poorly studied and understood as well as the real perceptions of these children. Finally, staying more indoors has certainly exposed these children to specific contaminants working as endocrine disruptors which could also have had an effect. It would be of utmost importance to compare this phenomenon worldwide with appropriate studies in order to verify what is happening, and gain a new insight into the consequences of the covid-19 pandemic and into precocious puberty and for future prevention.

Chemical characterization of urinary volatile compounds ofPeromyscus californicus, a monogamous biparental rodent

The urinary profiles of adult female and male California mice were examined to determine the volatile compounds that may affect reproduction. The urinary volatiles identified by gas chromatography-mass spectrometry (GC-MS) include ketones, pyrazines, alkanes, nitrile, and aldehyde. None of volatile compounds was specific to males or females. The concentration of urinary volatiles in pregnant and lactating females was significantly higher than in virgin females. Male urinary volatile concentrations were similar to those of pregnant and lactating females. The GC profiles of both sexes were distinguished by a high percentage (36%) of pyrazine derivatives that were also in unusually high concentrations. These compounds may play a wide-ranging role in the control of reproduction in the California mouse.

Communication by olfactory signals in rabbits: its role in reproduction

Rabbits use a variety of olfactory signals to transmit information related with reproduction. Such cues are produced in skin glands (submandibular, anal, Harder's, lachrymal, preputial) and the mammary gland-nipple complex. Some signals are transmitted by active behaviors, for example, chin-marking, urination, and defecation, while others are transmitted passively (e.g., mammary pheromone (MP) and inguinal gland secretions). We show that sex steroids regulate: chinning frequency and the chin gland's size, weight and secretory activity in bucks and does by acting on specific brain regions or on the chin gland, respectively. The "mammary pheromone," identified in milk as 2-methyl-but-2-enal, is essential for guiding the pups to the nipples, but its origin (mammary gland, ventral skin, nipple) remains to be determined. Estradiol, progesterone, and prolactin regulate the emission of an olfactory cue that also triggers nipple-search behavior in the pups, but its chemical identity and relation with the MP are unclear.

Somatosensory stimuli evoke norepinephrine release in the anterior ventromedial hypothalamus of sexually receptive female rats

We used in vivo brain microdialysis to determine the role of specific copulatory stimuli in mating-induced release of norepinephrine in the lateral ventromedial hypothalamus (VMH) of hormone-treated, sexually receptive female rats. Ovariectomized rats implanted with a unilateral guide cannula aimed at the ventrolateral VMH received systemic injections of estradiol benzoate daily for 2 days before and progesterone 4 h before the initiation of a 1-h behavioural test. Dialysis probes were lowered immediately after progesterone administration, and 20-min dialysis samples were collected until 1 h after the termination of behavioural testing. Norepinephrine content of dialysates was quantified by high performance liquid chromatography with electrochemical detection. During mating tests with male rats, dialysate levels of norepinephrine increased significantly over baseline in sexually receptive females with probe placements in the anterior but not posterior VMH. Norepinephrine levels were unchanged if rats were nonreceptive, even if males mounted vigorously and probes were located in the anterior VMH. Hormone-treated females that were placed on male-soiled bedding for 1 h showed no changes in dialysate levels of norepinephrine. Similarly, females in which vaginocervical stimulation was prevented by a vaginal mask failed to show increased levels of norepinephrine in dialysates collected from the anterior VMH, even if they displayed high levels of lordosis behaviour. Thus, the release of norepinephrine is not a result of executing the lordosis posture. The findings suggest that mating-induced increases in norepinephrine release in hormone-treated, sexually receptive rats are confined to the anterior VMH and that somatosensory rather than chemosensory stimuli evoke norepinephrine release. Moreover, experiments with vaginal masks indicate that vaginocervical stimulation is necessary for mating-evoked norepinephrine release in the anterior VMH.

Hormonal integration of neurochemical and sensory signals governing female reproductive behavior

This review focuses on findings from our laboratory regarding mechanisms by which the ovarian steroid hormones, estradiol (E2) and progesterone (P), act in the hypothalamus (HYP) to regulate the expression of lordosis, an important component of female reproductive behavior in rats and many other species. The first section summarizes recent work suggesting that cGMP, perhaps via P-receptor activation, may be an intracellular mediator of the facilitatory actions of a variety of hormones and neurotransmitters on lordosis behavior in E2-primed rats. In the second section, we focus on E2 and P regulation of norepinephrine (NE) neurotransmission in the HYP. We review evidence that ovarian hormones act both peripherally and centrally to determine whether NE is released in the HYP in response to copulatory stimuli. We also suggest that the steroid milieu determines the cellular responses of hypothalamic neurons to released NE, favoring the activation of pathways implicated in the facilitation of both lordosis behavior and the preovulatory gonadotropin surge. It is likely that E2 and P have similar actions on other neurotransmitter and neuromodulator systems, thereby maximizing the probability that females are sexually receptive during the periovulatory period.

MK-801 and male odours induce c-fos expression in the AOB of juvenile female mice

The odours of adult males, which accelerate the timing of puberty of female mice, activate c-fos in the accessory olfactory bulb (AOB). To test the hypothesis that NMDA receptors are involved in the male odour-induced increase in c-fos expression, we studied the effects of the non-competitive NMDA receptor agonist MK-801 on male odour-induced c-fos expression in the AOB of juvenile female mice. Surprisingly, MK-801 increased FOS-like immunoreactivity (FLI) within the AOB in the absence of male odour and had no effect on male odour-induced c-fos expression. We suggest that MK-801 increases AOB mitral cell activity by disinhibiting GABAergic granule cells, resulting in increased c-fos expression throughout the AOB.

Acceleration of puberty onset in female mice by male urinary proteins

1. Puberty onset in female mice is accelerated by exposure to conspecific adult male urine, which acts through the vomeronasal organ and the accessory olfactory system. A distinctive component of adult male mouse urine is the major urinary protein complex (MUP), which is a lipocalin; it has a hydrophobic pocket that binds small endogenous volatile molecules. The MUP gene family also codes for a hexapeptide, which has four residues in common with the N-terminal region of MUP. 2. MUP, the volatiles bound to MUP and the MUP-related hexapeptide have been tested for the induction of puberty acceleration by measuring the increase in uterus weight related to the first pro-oestrus phase. MUP, together with its bound volatiles, induces puberty acceleration. Its activity is retained even when the volatiles have been removed either by organic extraction or competition displacement with a high-affinity ligand. 3. MUP-related hexapeptide also induces puberty acceleration in female mice. In contrast, the odorants bound to MUP do not exert this effect. 4. It is proposed that the vomeronasal organ contains receptors that recognize the short N-terminal consensus sequence, N-Glu-Glu-Ala-X-Ser (where X is a polar residue), common to both MUP and the hexapeptide.

The effect of estrogen administration in vivo upon catecholamine release in vitro from superfused hypothalamic tissue of ovariectomized pre-pubertal and adult mice

In the present report we examined the effects of estrogen upon catecholamine release from superfused medial basal hypothalamic tissue fragments of pre-pubertal ovariectomized CD-1 mice. Prepubertal mice treated with estradiol benzoate (EB--5 micrograms x 2 days, sc), showed significantly reduced amounts of dopamine but no changes in norepinephrine release in response to a depolarizing concentration of potassium (30 mmol/L) compared with their respective groups receiving the oil vehicle. Since EB treatment reduced potassium stimulated dopamine release in these pre-pubertal mice, in a second experiment we compared the effects of EB versus oil vehicle treatment upon potassium stimulated dopamine release from the hypothalamus of the ovariectomized adult female mouse. Similar to that observed in the pre-pubertal mouse, EB treatment significantly reduced the amount of potassium stimulated dopamine release. Interestingly, the absolute amounts of potassium stimulated dopamine release was substantially greater in adult compared with pre-pubertal mice. These results demonstrate that the hypothalamic dopaminergic system of both pre-pubertal and adult mice show relatively similar responses to estrogen treatment but differ in absolute amounts of dopamine released.

Effective induction of pregnancy block by electrical stimulation of the mouse accessory olfactory bulb coincident with prolactin surges

Electrical stimulation (0.33 Hz, 0.2 mA) applied bilaterally to the accessory olfactory bulb (AOB) of newly mated female mice revealed that stimulation for 4 h was sufficient to produce pregnancy block providing stimulation is given for two separate 2-h periods coincident with prolactin surges. Stimulation for two 1-h periods coincident with prolactin surges or two 2-h periods between prolactin surges was without effect. These results indicate that electrical stimulation of the AOB can faithfully reproduce pheromone-induced pregnancy block and support the view that prolactin is the hormone mainly responsible for the olfactory block to pregnancy.

Cocaine attenuates puberty acceleration in female house mice

The onset of puberty in female house mice is advanced by exposure to a male urinary pheromone. This study tested whether cocaine could modify the juvenile female mouse's response to this pheromone. Puberty acceleration, as measured by uterine weight change, is inhibited by daily SC administration of 30 or 40 mg/kg body weight cocaine HCl between 20 and 26 days of age. Two daily injections of 20 mg/kg cocaine reduced both uterine development and body weight gain. Thus, cocaine may reduce an animals' reproductive fitness by isolating it from its social environment. At higher doses, cocaine can delay body growth, as well as the onset of puberty.