Mammalian reproductive function depends upon a neuroendocrine circuit that evokes the pulsatile release of gonadotropin hormones (luteinizing hormone and follicle-stimulating hormone) from the ...pituitary. This reproductive circuit is sensitive to metabolic perturbations. When challenged with starvation, insufficient energy reserves attenuate gonadotropin release, leading to infertility. The reproductive neuroendocrine circuit is well established, composed of two populations of kisspeptin-expressing neurons (located in the anteroventral periventricular hypothalamus, Kiss1AVPV, and arcuate hypothalamus, Kiss1ARH), which drive the pulsatile activity of gonadotropin-releasing hormone (GnRH) neurons. The reproductive axis is primarily regulated by gonadal steroid and circadian cues, but the starvation-sensitive input that inhibits this circuit during negative energy balance remains controversial. Agouti-related peptide (AgRP)-expressing neurons are activated during starvation and have been implicated in leptin-associated infertility. To test whether these neurons relay information to the reproductive circuit, we used AgRP-neuron ablation and optogenetics to explore connectivity in acute slice preparations. Stimulation of AgRP fibers revealed direct, inhibitory synaptic connections with Kiss1ARH and Kiss1AVPV neurons. In agreement with this finding, Kiss1ARH neurons received less presynaptic inhibition in the absence of AgRP neurons (neonatal toxin-induced ablation). To determine whether enhancing the activity of AgRP neurons is sufficient to attenuate fertility in vivo, we artificially activated them over a sustained period and monitored fertility. Chemogenetic activation with clozapine N-oxide resulted in delayed estrous cycles and decreased fertility. These findings are consistent with the idea that, during metabolic deficiency, AgRP signaling contributes to infertility by inhibiting Kiss1 neurons.
Multiple K(+) conductances are targets for many peripheral and central signals involved in the control of energy homeostasis. Potential K(+) channel targets are the KCNQ subunits that form the ...channels underlying the M-current, a subthreshold, non-inactivating K(+) current that is a common target for G-protein-coupled receptors. Whole-cell recordings were made from GFP (Renilla)-tagged neuropeptide Y (NPY) neurons from the arcuate nucleus of the hypothalamus using protocols to isolate and characterize the M-current in these orexigenic neurons. We recorded robust K(+) currents in the voltage range of the M-current, which were inhibited by the selective KCNQ channel blocker 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone dihydrochloride (XE991) (40 μm), in both intact males and ovariectomized, 17β-estradiol (E2)-treated females. Since NPY neurons are orexigenic and are active during fasting, the M-current was measured in fed and fasted male mice. Fasting attenuated the XE991-sensitive current by threefold, which correlated with decreased expression of the KCNQ2 and KCNQ3 subunits as measured with quantitative real-time PCR. Furthermore, E2 treatment augmented the XE991-sensitive M-current by threefold in ovariectomized (vs oil-treated) female mice. E2 treatment increased the expression of the KCNQ5 subunit in females but not KCNQ2 or KCNQ3 subunits. Fasting in females abrogated the effects of E2 on M-current activity, at least in part, by decreasing KCNQ2 and KCNQ3 expression. In summary, these data suggest that the M-current plays a pivotal role in the modulation of NPY neuronal excitability and may be an important cellular target for neurotransmitter and hormonal signals in the control of energy homeostasis in both males and females.
During the winter of 2004, 48 fecal samples were collected from live-trapped fox squirrels (Sciurus niger) from central Wyoming (Natrona County) and examined for species of Eimeria. Two species, ...Eimeria lancasterensis (prevalence, 65%) and Eimeria ontarioensis (prevalence, 27%), were identified. Genomic DNA sequences ITS1 and ITS2 were amplified, cloned, and sequenced. Additional sequences from E. lancasterensis isolated from a Delmarva fox squirrel (Sciurus niger cinereus) collected on Chincoteague Island, Virginia, were also identified. Comparison of pairwise distances suggests that E. lancasterensis from Wyoming and Virginia are conspecific. Maximum Parsimony tree construction identified 2 lineages, one E. ontarioensis and one E. lancasterensis; and both lineages had a strong bootstrap support (100%). The Maximum Parsimony analysis was unable to resolve the Wyoming and Virginia strains.
Abstract The serotonin system responds to the ovarian steroids, estradiol (E) and progesterone (P), in women and female animal models. In macaques, ovarian steroid administration to ovariectomized ...(Ovx) individuals improves serotonin neural function through actions on pivotal serotonin-related genes and proteins, such as TPH2 (tryptophan hydroxylase 2), SERT (serotonin reuptake transporter), and the 5HT1A autoreceptor. In addition, ovarian steroid administration reduces gene and protein expression in the caspase-independent pathway and reduces DNA fragmentation in serotonin neurons. This study examines the hypothesis that long-term ovariectomy will lead to a loss of serotonin neurons and compromised gene expression in serotonin neurons. Female Japanese macaques were ovariectomized or tubal ligated ( n =5/group) at 3 years of age and returned to their natal troop. After 3 years, the animals were collected, administered a fenfluramine challenge to determine global serotonin availability, and then euthanized. Fev, TPH2, SERT, and 5HT1A expression were examined with digoxigenin in situ hybridization (ISH) and quantitative image analysis. Cell number, positive pixel area, and average pixel density were determined. In the Ovx group, Fev, TPH2, SERT, and 5HT1A showed a significant decease in average and total cell number and positive pixel area. The reduction in Fev-positive neurons suggests that there were fewer serotonin neurons in Ovx animals compared to ovary-intact animals. The decrease in TPH2 in the Ovx animals was consistent with earlier results in 5-month Ovx animals, but it may be due to the decrease in cell number rather than a decrease in expression on an individual cell basis. The decrease in SERT and 5HT1A in long-term Ovx differed from previous studies in short-term Ovx. In summary, long-term ovarian steroid loss resulted in fewer serotonin neurons and overall lower Fev, TPH2, SERT, and 5HT1A gene expression. This may be due to serotonin cell death or to a negative impact on a long-term developmental process in young female macaques.
GnRH agonists are used to treat gonadal steroid-dependent disorders in humans and contracept animals. These agonists are thought to work by desensitizing gonadotropes to GnRH, thereby suppressing FSH ...and LH secretion. It is not known whether changes occur in the cellular composition of the pituitary gland following chronic GnRH agonist exposure.
Adult male Sprague-Dawley rats were treated with a sham, deslorelin, or deslorelin plus testosterone implant for 41.0±0.6 days. In a second experiment, rats were castrated and treated with deslorelin and/or testosterone. Pituitary sections were labeled immunocytochemically for FSHβ and LHβ, or αGSU.
Deslorelin suppressed testis weight by two thirds and reduced plasma FSH and LH in intact rats. Deslorelin decreased the percentage of gonadotropes but the effect was specific to the FSHβ-ir cells. Testosterone did not reverse the deslorelin-induced reduction in the overall gonadotrope population. However, in the presence of testosterone, the proportion of gonadotropes that was FSHβ-ir increased in the remaining gonadotropes. There was no effect of treatment on the total LHβ-ir cell population although the loss of FSHβ in bi-hormonal cells increased the proportion of mono-hormonal LHβ-ir gonadotropes. The castration-induced plasma LH and FSH increases were suppressed by deslorelin, testosterone or both. Castration increased both LH-ir and FSH-ir without increasing the overall gonadotrope population; thus increasing the proportion of bi-hormonal cells. Deslorelin suppressed these increases. Testosterone increased FSH-ir in deslorelin-treated castrate rats. Deslorelin did not affect αGSU immunoreactivity, suggesting that the gonadotrope population
per se
is not eliminated by deslorelin but the ability of gonadotropes to synthesize FSHβ is compromised.
We hypothesize that the FSH dominant suppression may be central to the long-term contraceptive efficacy of deslorelin in the male.
Gonadotropin-releasing hormone (GnRH) agonists are used as an alternative to surgical castration for treatment of gonadal steroid-dependent disorders such as prostate cancer, endometriosis, uterine ...fibroids and central precocious puberty. The efficacy of these agonists is hypothesized to rely on their ability to internalize and downregulate the GnRH receptor, despite substantial evidence against such a mechanism; other means may be responsible, such as gonadotrope loss and/or depletion of gonadotropins—the hypothesis of this thesis. In adult male rats treated with the GnRH agonist deslorelin, gonadotropes synthesizing follicle-stimulating hormone (FSH) β were specifically and strongly suppressed in density through an androgen-independent mechanism; this effect outlasted the period of treatment. These are the first findings showing potentially long-lasting cytoarchitectural changes in the pituitary gland after treatment with a GnRH agonist.
Abstract
The stellar velocity ellipsoid of the solar neighbour (d < 200 pc) is re-examined using intermediate-old mono-abundance stellar groups with high-quality chemistry data together with ...parallaxes and proper motions from Gaia DR1. We find the average velocity dispersion values for the three space velocity components for the thin and thick discs of (σU, σV, σW)thin = (33 ± 4, 28 ± 2, 23 ± 2) and (σU, σV, σW)thick = (57 ± 6, 38 ± 5, 37 ± 4) km s−1, respectively. The mean values of the ratio between the semi-axes of the velocity ellipsoid for the thin disc are found to be σV/σU = 0.70 ± 0.13 and σW/σU is 0.64 ± 0.08, while for the thick disc σV/σU = 0.67 ± 0.11 and σW/σU is 0.66 ± 0.11. Inputting these dispersions into the linear Strömberg relation for the thin disc groups, we find the Sun's velocity with respect to the Local Standard of Rest in Galactic rotation to be V⊙ = 13.9 ± 3.4 km s−1. A relation is found between the vertex deviation and the chemical abundances for the thin disc, ranging from −5 to +40° as iron abundance increases. For the thick disc we find a vertex deviation of luv ∼− 15°. The tilt angle (luw) in the U–W plane for the thin disc groups ranges from −10 to +15°, but there is no evident relation between luw and the mean abundances. However, we find a weak relation for luw as a function of iron abundances and α-elements for most of the groups in the thick disc, where the tilt angle decreases from −5 to −20° when Fe/H decreases and α/Fe increases. The velocity anisotropy parameter is independent of the chemical group abundances and its value is nearly constant for both discs (β ∼ 0.5), suggesting that the combined disc is dynamically relaxed.
The stellar velocity ellipsoid of the solar neighbour is re-examined using intermediate-old mono-abundances stellar groups with high quality chemistry data together with parallaxes and proper motions ...from Gaia DR1. We find the average velocity dispersion values for the three space velocity components for the thin and thick disc of (\sigma_{U},\sigma_{V},\sigma_{W})_{thin} = (33 \pm 4, 28 \pm 2, 23 \pm 2) and (\sigma_{U},\sigma_{V},\sigma_{W})_{thick} = (57 \pm 6, 38 \pm 5, 37 \pm 4) km s^{-1}, respectively. The mean values of the ratio between the semi-axes of the velocity ellipsoid for the thin disc are found to be, \sigma_{V}/\sigma_{U} = 0.70 \pm 0.13 and \sigma_{W}/\sigma_{U} is 0.64 \pm 0.08, while for the thick disc \sigma_{V}/\sigma_{U} = 0.67 \pm 0.11 and \sigma_{W}/\sigma_{U} is 0.66 \pm 0.11. Inputting these dispersions into the linear Str\"omberg relation for the thin disc groups, we find the Sun's velocity with respect to the LSR in Galactic rotation to be V_{\sun} = 13.9 \pm 3.4 km s^{-1}. A relation is found between the vertex deviation and the chemical abundances for the thin disc, ranging from -5 to +40^{\circ} as iron-abundance increases. For the thick disc we find a vertex deviation of l_{uv} \sim -15^{\circ}. The tilt angle (l_{uw}) in the U-W plane for the thin disc groups ranges from -10 to +15^\circ, but there is no evident relation between l_{uw} and the mean abundances. However we find a weak relation for l_{uw} as a function of iron abundances and \alpha-elements for most of the groups in the thick disc, where the tilt angle decreases from -5 to -20^\circ when Fe/H decreases and \alpha/Fe increases. The velocity anisotropy parameter is independent of the chemical group abundances and its value is nearly constant for both discs (\beta \sim 0.5), suggesting that the combined disc is dynamically relaxed.
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