Martín Martínez-Torres

Luteal development and progesterone levels during pregnancy of the viviparous temperate lizard Barisia imbricata imbricata (Reptilia: Anguidae).

The relationship between plasma progesterone (P(4)) levels and the formation and degeneration of the corpus luteum (CL) was assessed monthly during gestation of the viviparous lizard Barisia imbricata imbricata. Histochemical activity of the delta(5-4) isomerase 3 beta-hydroxysteroide dehydrogenase (delta(5-4)3beta-HSD) in the luteal tissue and embryonic development were also observed. Females were gravid throughout winter and great part of spring (late November or early December until late May or early June). Corpus luteum development occurred in the first third of gestation (December and January) when the embryo reached developmental stage 27. Four sequential stages were identified during development and three stages during regression of the CL. The follicular and thecal tissue participated in the formation of the luteal cell mass. According to Xaviers classification, the CL of B. i. imbricata is a subtype from Type III. The activity of delta(5-4)3beta-HSD was observed mainly in the luteal cell mass. The first degenerative changes in the CL were observed in the early second third of the gestation and continued gradually until parturition. Progesterone levels increased in early pregnancy and reached its highest level during January (3.07+/-1.04 ng/ml) when mature corpora lutea were present. Gradual diminution in progesterone concentrations occurred in the second and last third of pregnancy and coincided with advanced degenerative changes and diminution in histochemical activity of delta(5-4)3beta-HSD in the luteal tissue. These observations suggest that the CL is the major source of progesterone during pregnancy of B. i. imbricata.

FOLLICULAR DEVELOPMENT AND OVULATION DETERMINED BY ULTRASOUND IMAGING IN THE VIVIPAROUS LIZARD BARISIA IMBRICATA (REPTILIA: ANGUIDAE)

Abstract Ovarian follicular development and ovulation were studied by ultrasound scanning in the Mexican viviparous lizard Barisia imbricata. A linear ultrasound unit with variable capacity from 5 to 10 MHz was used. Vitellogenic follicle diameters ranged from 3.3 to 9.8 mm and were present in the lizards between September and December. Also, corpora lutea and uterine eggs were identified. The ultrasound is an excellent non-invasive technique to determine seasonal reproductive changes and can be combined with other techniques to monitor the reproductive process.

Paternal behavior in the Mongolian gerbil (Meriones unguiculatus): Estrogenic and androgenic regulation.

Here, we analyzed the effects of testosterone (T) and its metabolites, estradiol (E2) and dihydrotestosterone (DHT), on the onset of paternal behavior in virgin male Mongolian gerbils (Meriones unguiculatus). We hypothesized that T and E2, but not DHT, would facilitate the onset of paternal behavior. Seventy males displaying aggression toward pups were selected through a paternal behavior screening test. Forty males were bilaterally castrated. Of them, 10 were implanted with T, 10 with E2, and 10 with DHT, and 10 received no treatment. Another 30 males underwent a sham procedure. In these gerbils, T, E2 and DHT were measured to obtain the basal levels of these hormones. After treatment, the paternal behavior test was conducted again. Blood samples were obtained immediately after the administration of the test for the quantification of T, E2 and DHT by radioimmunoassay. Surprisingly, 100% of the males that received T, E2 and DHT implants stopped being aggressive and became paternal. Castrated and sham-operated males displayed no changes in their aggressive behaviors. This is the first report that T and its metabolites are involved in neuroendocrine mechanisms that inhibit aggression toward pups and facilitate paternal behavior in virgin male Mongolian gerbils. In addition, this is the first report of regulation of paternal behavior in a rodent by estrogenic and androgenic pathways.

Effects of luteectomy in early pregnancy on the maintenance of gestation and plasma progesterone concentrations in the viviparous temperate lizard Barisia imbricata imbricata

BackgroundSeveral studies have shown that the corpus luteum is the principal source of progesterone during the gravidity period in reptiles; however, its participation in the maintenance of gestation in the viviparous squamata is in dispute. The effects of ovariectomy or luteectomy vary according to the species and the time at which the procedure is performed. In this paper, we describe the effects of luteectomy during early pregnancy on the maintenance of gestation and progesterone concentrations in the temperate Mexican viviparous lizard Barisia imbricata imbricata.MethodsTwenty-four lizards were subjected to three different treatments: luteectomy, sham luteectomy or non-surgical treatment, and blood samples were obtained before and after surgical treatment at different stages of gestation to determine the effects of luteectomy on the maintenance of gestation and progesterone concentrations.ResultsSpontaneous abortion was not observed in any of the females. However, luteectomy provoked abnormal parturition and a significant reduction in the number of young born alive. Parturition was normal in untreated females as well as those submitted to sham luteectomy. The surgical treatment also caused a significant reduction in progesterone concentrations in luteectomised females during early and middle gestation. However, no significant differences in hormone concentrations were observed among the three groups during late gestation or immediately post-parturition.ConclusionsOur observations indicate that the presence of the corpus luteum is not necesary for the maintenance of gestation, but that it does participate in parturition control. Moreover, the corpus luteum of the viviparous lizard B. i. imbricata produces progesterone, at least during the first half of pregnancy, and that an extra-ovarian source of progesterone must maintain gestation in the absence of luteal tissue.

Hemipenes in females of the mexican viviparous lizard Barisia imbricata (Squamata: Anguidae): an example of heterochrony in sexual development

The sexual development of saurians follows a similar pattern to that described for other amniotes. Changes in the timing or sequence of development events are known as heterochrony. We describe the pattern of sexual development in the viviparous Mexican lizard Barisia imbricata and report heterochrony in the regression of hemipenes in this lizard. We collected gestating females; some lizards were subjected to partial hysterectomy and the embryos were processed using routine histological technique to assess gonadal development; the remaining embryos were used to assess the development of hemipenes. Other pregnant females were kept in captivity in individual terraria until the time of delivery. All neonates were sexed by eversion of hemipenes and some of their body characteristics were recorded. Several neonates were sacrificed and processed to establish gonadal histology and the young of the remaining litters were maintained in captivity to observe the fate of the hemipenes in both sexes. Gonadal development began at embryonic stage 33 and the hemipenes were visible at the same stage. In the neonates, the ovary contained oogonias and ovarian follicles, whereas the testicles showed testicular cords. All neonates had hemipenes and sex could only be established through direct observation of the reproductive ducts and gonadal histology. The hemipenes regression in the females begins after approximately 7 months of postnatal development and concludes at about 15 months of age. We think that the delayed regression of the hemipenes reflects evolutionary differences among reptiles and may be an indication of a stage in the evolutionary process of this species.

Histochemical activity of 5-4-isomerase-3-B hydroxy steroid dehydrogenase in the ovary of the viviparous mexican lizard Sceloporus mucronatus (Reptilia: Prhynosomatidae) and interelationship with progesterone levels during pregnancy

Objective To relate the histological characteristics and histochemical Δ5−4-isomerase-3 beta hydroxy steroid dehydrogenase (Δ5−43β-HSD) activity of the corpora lutea (CL) and the atresic vitellogenic follicles (AVF) with progesterone (P4) plasma concentrations in three different times of gestation (early, medium and late) in the viviparous lizard Sceloporus mucronatus (S. mucronatus).

An increase in estradiol facilitates the onset of paternal behavior in the dwarf hamster (Phodopus campbelli)

ABSTRACT In the dwarf hamster (Phodopus campbelli), activational effects of testosterone (T) and estradiol (E2) in the regulation of paternal behavior have been repeatedly rejected because peripheral concentrations of E2 do not change across the reproductive cycle of males. Further, castration no affected paternal behavior despite that both T and E2 concentrations decreased significantly. However, the role of these hormones has not been evaluated in models of castration and hormonal replacement in virgin males. Here, we analysed the effects of E2 and T in paternal behavior in virgin male dwarf hamster (Phodopus campbelli). Thirty paternal (PAT) males were bilaterally castrated; of them, 10 were implanted with T, 10 with E2 and 10 males received no treatment. Other 10 PAT males underwent sham‐castration. Seventeen aggressive (AGG) males were also bilaterally castrated; of these, 10 AGG received E2 replacement, 7 were not treated. Other 7 AGG males were submitted to sham‐castration. Following treatments, paternal behavior tests were conducted again. T and E2 levels in plasma were quantified by radioimmunoassay (RIA). The results showed that the treatments did not affect the paternal behavior of males that were initially paternal. Neither castration nor sham‐castration surgery affected the behavior of AGG males. However, when these males were treated with E2 and the concentrations of this hormone increase significantly they became paternal. Our data suggest that an increase in E2 levels shifted infanticidal behavior to paternal behavior in dwarf hamster. HighlightsAn increase in E2 facilitates transitions from aggressive males to paternal.Changes in T and E2 had no effect in paternal activities in paternal males from the beginning.Low concentrations of E2 may be the cause of infanticidal behavior.

Neuronal activation associated with paternal and aversive interactions toward pups in the Mongolian gerbils ( Meriones unguiculatus )

ABSTRACT Approach/avoid model is used to analyze the neural regulation of maternal behavior in the laboratory rat. This model proposes that the medial preoptic area (mPOA) and bed nucleus of stria terminalis (BNST) are brain regions involved in facilitating mechanisms. By contrast, anterior hypothalamic nucleus (AHN), ventromedial hypothalamic nucleus (VMH), and periaqueductal gray participate in the inhibiting mechanisms of neural regulation of maternal behavior. We hypothesized that there are also facilitating and inhibiting mechanisms in the neural regulation of paternal behavior. Here, we determined which neural areas are activated during paternal and aversive interactions with pups in the Mongolian gerbils (Meriones unguiculatus). By testing paternal behavior, we selected 40 males aggressive toward pups and 20 paternal males. These males were organized into six groups of 10 animals in each group: aggressive males that interacted with pups (AGG‐pups) or candy (AGG‐candy), paternal males that interacted with pups (PAT‐pups) or candy (PAT‐candy), and males with testosterone (T)‐induced paternal behavior that interacted with pups (IPAT‐pups) or candy (IPAT‐candy). After interacting with pups or candy, the brains were extracted and analyzed for immunoreactivity (ir) with c‐fos. Males that interacted with pups had significantly higher c‐fos‐ir in the mPOA/BNST than males that interacted with candy. Males that displayed aggression had significantly higher c‐fos‐ir in the AHN, VMH, and periaqueductal gray than aggressive males that interacted with candy. These results suggest that in the neural regulation of paternal behavior in the Mongolian gerbil underlie positive and negative mechanisms as occurs in maternal behavior. HIGHLIGHTSAnalyzing the neural regulation of paternal behavior with the approach/avoid model is novel.mPOA/BNST are part of the positive mechanism of neural regulation of paternal behavior.AHN/VMH are part of the negative mechanism of neural regulation of paternal behavior.A decrease in the testosterone level was observed in aggressive males that interacted with the pups.Neural regulation of paternal behavior is according to the approach/avoid model.

Does the conceptus of the viviparous lizard Barisia imbricata imbricata participates in the regulation of progesterone production and the control of luteolysis

It is generally accepted that progesterone is necessary to maintain gestation; however, the mechanisms that control the production of this steroid remain unknown. The corpus luteum has been assigned a central role in the maintenance of gestation based on its capacity to produce progesterone. A pseudopregnancy model was performed in a viviparous lizard, Barisia imbricata imbricata, to determine whether the absence of embryos would affect the pattern of progesterone production or the corpus luteum histology. Blood samples were obtained prior to ovulation and at 8, 16, and 24 weeks after ovulation (pseudopregnant and pregnant lizards), as well as one day after parturition (pregnant lizards) or 32 weeks after ovulation (pseudopregnant lizards). The corpus luteum was surgically removed one day after blood samples were obtained. Blood aliquots from nongravid females were obtained at similar timepoints. We found a significant reduction in plasma progesterone concentrations at 24 and 32 weeks post-ovulation in pseudopregnant lizards compared with those observed at similar times in intact pregnant lizards, whereas the progesterone levels in non-gestant lizards remained significantly lower than in either pseudopregnant or pregnant lizards. Moreover, we observed that the histological appearance of the corpus luteum from pseudogestational females (obtained 24 and 32 weeks post-ovulation) differed from the corpora lutea from lizards in late gestation and intact parturient lizards. These observations suggest that the conceptus participates in the regulation of progesterone production in late gestation and also in luteolysis control.