Marc Lemaître

A Novel Strategy for Human Papillomavirus Detection and Genotyping with SybrGreen and Molecular Beacon Polymerase Chain Reaction

Human papillomaviruses (HPVs) play an important role in the pathogenesis of cervical cancer. For identification of the large number of different HPV types found in (pre)malignant lesions, a robust methodology is needed that combines general HPV detection with HPV genotyping. We have developed for formaldehyde-fixed samples a strategy that, in a homogeneous, real-time fluorescence polymerase chain reaction (PCR)-based assay, accomplishes general HPV detection by SybrGreen reporting of HPV-DNA amplicons, and genotyping of seven prevalent HPV types (HPV-6, -11, -16, -18, -31, -33, -45) by real-time molecular beacon PCR. The false-positive rate of the HPV SybrGreen-PCR was 4%, making it well suited as a prescreening, general HPV detection technology. The type specificity of the seven selected HPV molecular beacons was 100% and double infections were readily identified. The multiplexing capacity of the HPV molecular beacon PCR was analyzed and up to three differently labeled molecular beacons could be used in one PCR reaction without observing cross talk. The inherent quantitation capacities of real-time fluorescence PCR allowed the determination of average HPV copy number per cell. We conclude that the HPV SybrGreen-PCR in combination with the HPV molecular beacon PCR provides a robust, sensitive, and quantitative general HPV detection and genotyping methodology.

Duality of Glutamatergic and Gabaergic Control of Pulsatile GnRH Secretion by Rat Hypothalamic Explants: I. Effects of Antisense Oligodeoxynucleotides using Explants Including or Excluding the Preoptic Area

Using antisense oligodeoxynucleotides we aimed to study the role of N‐methyl‐D‐aspartate (NMDA) and γ‐aminobutyric acid (GABA) receptors in the mechanism of Gonadotrophin‐releasing hormone (GnRH) secretion in vitro. Since GnRH cell bodies are located in the rat preoptic hypothalamus while most GnRH terminals are in the retrochiasmatic hypothalamus, we compared the effects of oligodeoxynucleotides on explants of the whole (preoptic area included) or retrochiasmatic hypothalamus. When GnRH secretion is evoked by muscimol and NMDA, a time‐related reduction of GnRH secretion is caused by antisense oligodeoxynucleotides for the β subunit of the GABAA receptor and the NR2A subunit of the NMDA receptor, respectively. After 6–7 h, binding studies of tritiated ligands show a decrease in GABA‐ and NMDA‐receptor expression. While these antisense effects are observed using whole explants, no such effects are seen using retrochiasmatic explants, indicating that the facilitatory GABAA and NMDA receptors are encoded in the preoptic area. Using several missense oligodeoxynucleotides or antisense for the NR2B and NR2C subunits of the NMDA receptor, the muscimol‐ and NMDA‐evoked release of GnRH is not affected. When spontaneous pulsatile GnRH secretion is studied, the NR2A antisense oligodeoxynucleotides cause an increase of the interpulse interval. This increase is seen using whole but not retrochiasmatic explants. In contrast, the GABAA and NR2C antisense oligodeoxynucleotides result in a reduction of GnRH interpulse interval. Such a reduction is seen using whole as well as retrochiasmatic explants, indicating that the GABAA and NMDA receptors which mediate inhibition of GnRH pulsatility are encoded in the retrochiasmatic hypothalamus. We conclude that NMDA receptors (NR2A subunit) encoded in the preoptic hypothalamus mediate a facilitatory effect on GnRH pulsatility while GABAA and NMDA (NR2C subunit) receptors encoded in the retrochiasmatic hypothalamus mediate an inhibition of GnRH pulsatility. Pulsatile GnRH secretion is affected differently than the agonist‐evoked release of GnRH suggesting that the GnRH secretory neurons and the GnRH pulse generator consist of different cellular entities.

Early prepubertal ontogeny of pulsatile gonadotropin-releasing hormone (GnRH) secretion: I. Inhibitory autofeedback control through prolyl endopeptidase degradation of GnRH.

GnRH[1–5], a subproduct resulting from degradation of GnRH by prolyl endopeptidase (PEP) and endopeptidase 24.15 (EP24.15) was known to account for an inhibitory autofeedback of GnRH secretion through an effect at the N-methyl-d-aspartate (NMDA) receptors. This study aimed at determining the possible role of such a mechanism in the early developmental changes in frequency of pulsatile GnRH secretion. Using retrochiasmatic explants from fetal male rats (day 20–21 of gestation), no GnRH pulses could be observed in vitro, whereas pulses occurred at a mean interval of 86 min from the day of birth onwards. This interval decreased steadily until day 25 (39 min), during the period preceding the onset of puberty. Based on GnRH[1–10] or GnRH[1–9] degradation and GnRH[1–5] generation after incubation with hypothalamic extracts, EP24.15 activity did not change with age, whereas PEP activity was maximal at days 5–10 and decreased subsequently until day 50. These changes were consistent with the ontogenetic variations...

Duality of Glutamatergic and Gabaergic Control of PulsatileGnRH Secretion by Rat Hypothalamic Explants: II. ReducedNR2C‐ and GABAA‐Receptor‐Mediated Inhibition atInitiation of Sexual Maturation

N‐methyl‐D‐aspartate (NMDA) receptors and γ‐aminobutyric acid (GABA) receptors are involved in the mechanism of pulsatile gonadotrophin‐releasing hormone (GnRH) secretion. The aim of this study was to elucidate the role of those receptors in the acceleration of pulsatile GnRH secretion seen at onset of puberty. Using hypothalamic explants from prepubertal (15 days), early pubertal (25 days) and adult (50 days) male rats, we studied the effects of pharmacological antagonists and antisense oligodeoxynucleotides on GnRH release evoked by NMDA and GABA receptor agonists as well as the interval between spontaneous GnRH secretory pulses. At the three studied ages, the muscimol‐evoked release of GnRH is similarly inhibited by the GABAA receptor antagonist bicuculline. In contrast, the frequency of pulsatility is stimulated by bicuculline as indicated by a reduction of the mean GnRH interpulse interval from 60 to 40 min and such an effect is seen at 15 days only. The GnRH interpulse interval is also reduced by GABAA receptor antisense oligodeoxynucleotides at 15 days while no effects are seen at 25 days. At the three studied ages, the NMDA‐evoked release of GnRH and the GnRH interpulse interval are similarly inhibited by 100 or 500 μM of the NMDA receptor antagonist 7‐chlorokynurenic acid (7CK). These effects are consistent with the increase of GnRH interpulse interval caused by NR2A antisense oligodeoxynucleotides at 15 days (86 vs 64 min in controls) as well as 25 days (44 vs 36 min). A low (5 μM) concentration of 7CK does not result in any effect except a reduction of GnRH interpulse interval which is seen at 15 days only. A similar reduction of GnRH interpulse interval is obtained using NR2C antisense oligodeoxynucleotides at 15 days (50 vs 64 min in controls) while no effects are seen at 25 days (35 vs 36 min). At 25 days, muscimol can prevent the developmental increase in frequency of pulsatile GnRH secretion. In summary, pulsatile GnRH secretion by the prepubertal hypothalamus characteristically involves an inhibition mediated through GABAA receptors and the NR2C subunit of NMDA receptors. Based on these data, we propose a model for the mechanism of the onset of puberty which involves the disappearance or inactivation of GABAergic neurons located in the retrochiasmatic hypothalamus and expressing the NR2C subtype of NMDA receptors.