Corticogenesis and folding process of the neopallium in the South American plains vizcacha, Lagostomus maximus.

The plains vizcacha, Lagostomus maximus, is a precocial hystricomorph rodent with a gyrencephalic brain. This work aimed to perform a time-lapse analysis of the embryonic brain cortical development in the plains vizcacha to establish a species-specific temporal window for corticogenesis and the gyrencephaly onset. Additionally, a comparative examination with evolutionarily related rodents was conducted. Embryos from 40 embryonic days (ED) until the end of pregnancy ( ∼ $\sim $ 154 ED) were evaluated. The neuroanatomical examination determined transverse sulci at 80 ED and rostral lateral and caudal intraparietal sulci around 95 ED. Histological examination of corticogenesis showed emergence of the subplate at 43 ED and expansion of the subventricular zone (SVZ) and its division into inner and outer SVZs around 54 ED. The neocortical layers formation followed an inside-to-outside spatiotemporal gradient beginning with the emergence of layers VI and V at 68 ED and establishing the final six neocortical layers around 100 ED. A progressive increment of gyrencephalization index (GI) from 1.005 ± 0.003 around 70 ED, which reflects a smooth cortex, up to 1.07 ± 0.009 at the end of gestation, reflecting a gyrencephalic neuroanatomy, was determined. Contrarily, the minimum cortical thickness (MCT) progressively decreased from 61 ED up to the end of gestation. These results show that the decrease in the cortical thickness, which enables the onset of neocortical invaginations, occurs together with the expansion and subdivision of the SVZ. The temporal comparison of corticogenesis in plains vizcacha with that in relative species reflects a prenatal long process compared with other rodents that may give an evolutionary advantage to L. maximus as a precocial species.

Neurovascular description in the South American plains vizcacha, Lagostomus maximus (Chinchilloidea, Caviomorpha). A study involving evolutionarily related species of Caviomorpha and Muroidea.

Oxygenated blood is required for the adequate metabolic activity of the brain. This is supplied by the circle of Willis (CoW) and the vertebrobasilar and carotid systems. The CoW ensures blood flow in case of arterial stenosis or occlusion. Different animal models have been explored for the CoW morphological and functional study. This work aims to characterize the vascular architecture of the CoW of the plains vizcacha, Lagostomus maximus (Suborder: Hystricomorpha), and to compare it with evolutionarily related species of Caviomorpha and Muroidea. The blood supply in adult plains vizcachas was studied using latex cerebrovascular casts and angiography. A caudo-rostral flow direction was determined, beginning in the spinal and vertebral arteries and converging in the basilar artery which bifurcates in the carotid-basilar communication in the caudal communicating arteries. In the first third of its course, the caudal cerebral arteries project laterally, and the middle and rostral cerebral arteries bifurcate from their rostral terminal segment, supplying the temporo-parietal and frontal cortex. The CoW architecture is mainly conserved between rodent species. Likewise, the small neurovascular variations observed could be considered phylogenetic morphological variations more than evolutionary adaptations. The absence of the rostral communicating artery that generates the rostral open architecture of the CoW in the vizcacha as in the other analyzed species, supports the need for a revision of the CoW classical function as a security system. Finally, this work supports the importance of expanding our understanding of brain anatomy among species, which may contribute to a better understanding of functional neuroanatomy.

Hypothalamic GnRH expression and pulsatility depends on a balance of prolactin receptors in the plains vizcacha, Lagostomus maximus.

In mammals, gestation is considered a physiological hyperprolactinemia status. Prolactin (PRL) is one of the modulators of gonadotropin-releasing hormone (GnRH) neurons function. The South American plains vizcacha (Lagostomus maximus) is a unique model to study the regulation of hypothalamic GnRH neurons by direct and indirect steroid-dependent pathways. The aim was to characterize the hypothalamic expression of endocrine markers in vizcacha during gestation as well as their response to experimental induced hyperprolactinemia. The possible involvement of PRL regulatory pathways on GnRH in the context of hypothalamic and pituitary reactivation in mid-gestating vizcachas was discussed. Using two in vivo approaches, we determined changes in the hypothalamic expression and distribution of prolactin receptor (PRLR), tyrosine hydroxylase (TH), and dopamine type 2 receptor. A significant increment in the number of tuberoinfundibular dopaminergic (TIDA) neurons was determined in the arcuate nucleus from early to term pregnancy. On the other hand, at preoptic area, the number of both TH+PRLR+ and GnRH+PRLR+ double-labeled neurons significantly decreased at mid-pregnancy probably allowing the recovery of GnRH expression indicating that both types of neurons may represent the key points of PRL indirect and direct pathways modulating GnRH. Moreover, in a model of induced hyperprolactinemic vizcachas, the inhibitory effect of PRL on GnRH at both expression and delivery levels were confirmed. These results suggest the concomitant participation of both PRL regulatory pathways on GnRH modulation and pinpoint the key role of PRL on GnRH expression enabling the recovery of the hypothalamic activity during the gestation in this species.

Achieving full-term pregnancy in the vizcacha relies on a reboot of luteal steroidogenesis in mid-gestation (Lagostomus maximus, Rodentia).

Reactivation of the hypothalamic-pituitary-ovarian (HPO) axis triggered by the decline in serum progesterone in mid-gestation is an uncommon trait that distinguishes the vizcacha from most mammals. Accessory corpora lutea (aCL) developed upon this event have been proposed as guarantors of the restoration of the progesterone levels necessary to mantain gestation. Therefore, the steroidogenic input of primary CL (pCL) vs aCL was evaluated before and after HPO axis-reactivation (BP and AP respectively) and in term pregnancy (TP). Nonpregnant-ovulated females (NP) were considered as the pCL-starting point group. In BP, the ovaries mainly showed pCL, whose LH receptor (LHR), StAR, 3ß-HSD, 20α-HSD, and VEGF immunoexpressions were similar or lower than those of NP. In AP, luteal reactivity increased significantly compared to the previous stages, and the pool of aCL developed in this stage represented 20% of the ovarian structures, equaling the percentage of pCL. Both pCL and aCL luteal cells shared similar histological features consistent with secretory activity. Although pCL and aCL showed equivalent labeling intensity for the luteotropic markers, pCL were significantly larger than aCL. Towards TP, both showed structural disorganization and loss of secretory characteristics. No significant DNA fragmentation was detected in luteal cells throughout gestation. Our findings indicate that the LH surge derived from HPO axis-reactivation targets the pCL and boost luteal steroidogenesis and thus progesterone production. Because there are many LHR-expressing antral follicles in BP, they also respond to the LH stimuli and luteinize without extruding the oocyte. These aCL certainly contribute but it is the steroidogenic restart of the pCL that is the main force that restores progesterone levels, ensuring that gestation is carried to term. Most importantly, the results of this work propose luteal steroidogenesis reboot as a key event in the modulation of vizcacha pregnancy and depict yet another distinctive aspect of its reproductive endocrinology.

Melatonin is involved in the modulation of the hypothalamic and pituitary activity in the South American plains vizcacha, Lagostomus maximus.

Melatonin, the key messenger of photoperiodic information, is synthesized in the pineal gland by arylalkylamine N-acetyltransferase enzyme (AANAT). It binds to specific receptors MT1 and MT2 located in the hypothalamus and pituitary gland. Melatonin can modulate the reproductive axis affecting the secretion of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH). The South American plains vizcacha, Lagostomus maximus, shows natural poliovulation of up to 800 oocytes per estrous cycle, a 154-day long pregnancy, and reactivation of the reproductive axis at mid-gestation with pre-ovulatory follicular recruitment, presence of active corpora lutea, and variations of the endocrine status. Here we analyzed the involvement of melatonin in the modulation of the hypothalamic and pituitary gland physiology of vizcacha thorough several approaches, including histological localization of melatoninergic system components, assessment of melatoninergic components expression throughout the reproductive cycle, and evaluation of the effect of melatonin on hypothalamic and pituitary activities during the follicular and luteal phases of the estrous cycle. AANAT and melatonin receptors were localized in the pineal gland and preoptic area of the hypothalamus. Increase in pineal AANAT and serum melatonin expression was observed as pregnancy progressed, with the lowest hypothalamic MT1 and MT2 levels at mid-pregnancy. Pulsatility assays demonstrated that melatonin induces GnRH and LH secretion at luteal phase. The melatoninergic system effects on hypothalamic and pituitary gland hormones secretion during pregnancy pinpoint to melatonin as a potential key factor underlying the reactivation of the reproductive axis activity at mid-gestation.

Mammary gland-specific regulation of GNRH and GNRH-receptor gene expression is likely part of a local autoregulatory system in female vizcachas (Rodentia: Chinchillidae).

In addition to key mammotrophic hormones such as the pituitary prolactin (PRL) and the ovarian steroids progesterone and estradiol, there are local factors that modulate the tissue dynamics of the mammary glands during pregnancy and lactation. By immunohistochemistry and RT-PCR, we found local transcription and translation of gonadotropin-releasing hormone (GNRH), GNRH receptor (GNRHR), PRL and PRL receptor (PRLR) in mammary glands of adult vizcachas during pregnancy and lactation. Both GNRH and GNRHR showed a lag between protein expression and gene transcription throughout the gestational period: while the highest transcription levels of these genes were recorded at early-pregnancy, the epithelial immunoexpressions of both showed their maximum during lactation. RIA results corroborated the presence of GNRH in mammary glands at all the analyzed stages and confirmed the maximum amount of this peptide in the lactating group. Significant amounts of GNRH were detected in milk samples as well. Conversely, PRL and PRLR shared similar protein and gene expression profiles, all exhibiting maximum values during lactation. GNRH peptide content in mammary glands of females with sulpiride-induced hyperprolactinemia (HP) was significantly lower than that of control females (CT). Although PRL mRNA levels remained unchanged, there was a marked increase in theα-lactalbumin (LALBA) transcription in mammary glands of HP- vs CT-females. These results suggest that after targeting mammary glands, PRL stimulates the expression of milk protein genes, but also, tempers the local expression of GNRH. Mammary gland-explantssupplemented with a GNRH analogue (GN-explants) had no differences in terms of PRLR orLALBA transcription levels compared to CT-explants, so the mammary PRLR signaling would not appear to be modulated by GNRH. Yet, mRNA expression levels of both GNRH and the GNRHR-downstream factor, EGR1, were significantly higher in GN-explants compared to that of CT which would point to a GNRH-positive feedback mechanism. In summary, the local coupled expression of GNRH, GNRHR and EGR1 in the mammary gland throughout pregnancy of vizcachas, the PRL-dependent mammary GNRH secretion as well as the GNRH positive feedback on its own transcription suggest an autocrine-paracrine regulatory mechanism and propose an active role for GNRH in mammary gland tissue remodeling.

PTEN and FOXO3 expression in the prenatal and postnatal human ovary.

PURPOSE: The objective of this study was to analyse the expression and cellular localization of FOXO3, pFOXO3 and PTEN throughout human ovary development both before and after birth. METHODS: Foetal, pubertal and adult paraffin-embedded ovarian samples were analysed by immunohistochemistry for cellular localization of FOXO3, pFOXO3 and PTEN proteins. Protein and mRNA expression were analysed by western blot and real time PCR, respectively, from fresh biopsies. RESULTS: PTEN was not detected by immunohistochemistry in germ cells and follicles of foetal, pubertal and adult ovaries. Occasional PTEN immunoreactive granulosa cells were found in atretic antral follicles in the adult ovary. Western blot analysis showed low levels of PTEN protein. Nuclear FOXO3-expressing primordial follicles represented a variable proportion of the ovarian reserve. The presence of FOXO3-expressing primordial follicles was very low in foetal ovary; although always represented in a low proportion, prevalence increased during pubertal and adult life. CONCLUSION: Our results seem to indicate that two subpopulations of primordial follicles, i.e. nuclear FOXO3-expressing and no FOXO3-expressing primordial follicles are found in the postnatal human ovary. This scenario suggests that FOXO3 could be acting as in the mouse model, preventing primordial follicle activation. However, the strategy would not be an "all or nothing" system as in mouse ovary but rather a selected subpopulation of primordial follicles preserved to ensure long-term fertility.

Neocortical Anatomy in the South American Plains Vizcacha, Lagostomus maximus, Reveals Different Strategies in Encephalic Development among Hystricomorpha and Myomorpha Rodents.

Depending on the presence or absence of sulci and convolutions, the brains of mammals are classified as gyrencephalic or lissencephalic. We analyzed the encephalic anatomy of the hystricomorph rodent Lagostomus maximus in comparison with other evolutionarily related species. The encephalization quotient (EQ), gyrencephaly index (GI), and minimum cortical thickness (MCT) were calculated for the plains vizcacha as well as for other myomorph and hystricomorph rodents. The vizcacha showed a gyrencephalic brain with a sagittal longitudinal fissure that divides both hemispheres, and 3 pairs of sulci with bilateral symmetry; that is, lateral-rostral, intraparietal, and transverse sulci. The EQ had one of the lowest values among Hystricomorpha, while GI was one of the highest. Besides, the MCT was close to the mean value for the suborder. The comparison of EQ, GI, and MCT values between hystricomorph and myomorph species allowed the detection of significant variations. Both EQ and GI showed a significant increase in Hystricomorpha compared to Myomorpha, whereas a Pearson's analysis between EQ and GI depicted an inverse correlation pattern for Hystricomorpha. Furthermore, the ratio between MCT and GI also showed a negative correlation for Hystricomorpha and Myomorpha. Our phylogenetic analyses showed that Hystricomorpha and Myomorpha do not differ in their allometric patterning between the brain and body mass, GI and brain mass, and MCT and GI. In conclusion, gyrencephalic neuroanatomy in the vizcacha could have developed from the balance between the brain size, the presence of invaginations, and the cortical thickness, which resulted in a mixed encephalization strategy for the species. Gyrencephaly in the vizcacha, as well as in other Hystricomorpha, advocates in favor of the proposal that in the more recently evolved Myomorpha lissencephaly would have arisen from a phenotype reversal process.

Unexpected low genetic variation in the South American hystricognath rodent Lagostomus maximus (Rodentia: Chinchillidae).

The South American plains vizcacha, Lagostomus maximus inhabits primarily the Pampean and adjoining Espinal, Monte and Chaquenean regions of Argentina. In order to study the population genetic structure of L. maximus, a fragment of 560 bp of the mitochondrial DNA hypervariable region 1from 90 individuals collected from the 3 subspecies and 8 groups along Argentina was amplified and analyzed. We found 9 haplotypes. The haplotype network did not show an apparent phylogeographical signal. Although low levels of genetic variation were found in all the subspecies and groups analyzed, a radiation of L. maximus would have occurred from the North and Center of the Pampean region toward the rest of its geographic range in Argentina. Low levels of genetic diversity, the existence of a single genetically distinct population in Argentina and changes of its effective size indicate that metapopulation processes and changes in human population dynamics during the late-Holocene were important factors shaping the population genetic structure of L. maximus in Argentina.

Structural organization, GABAergic and tyrosine hydroxylase expression in the striatum and globus pallidus of the South American plains vizcacha, Lagostomus maximus (Rodentia, Caviomorpha).

The striatum is an essential component of the basal ganglia that regulatessensory processing, motor, cognition, and behavior. Depending on the species, the striatum shows a unique structure called caudate-putamen as in mice, or its separation into two regions called caudate and lenticular nuclei, the latter formed by putamen and globus pallidus areas, as in primates. These structures have two compartments, striosome and matrix. We investigated the structural organization, GABAergic and tyrosine hydroxylase (TH) expression in the striatum and globus pallidus of the South American plains vizcacha, Lagostomus maximus. Its striatum showed regionalization arising from the presence of an internal capsule, and a similar organization to a striosome-matrix compartmentalization. GABAergic neurons in the matrix of caudate exhibited parvalbumin, calretinin, calbindin, GAD65, and NADPH-d-immunoreactivity. These were also expressed in cells of the putamen with the exception of calretinin showing neurofibers localization. Globus pallidus showed parvalbumin- and GAD65-immunoreactive cells, and calretinin- and calbindin-immunoreactive neuropil, plus GABA-A-immunoreactive neurofibers. NADPH-d-, GAD65- and GABA-A-immunoreactive neurons were larger than parvalbumin-, calretinin-, and calbindin-immunoreactive cells, whereas calbindin-immunoreactive cells were the most abundant. In addition, TH-immunoreactive neuropil was observed in the matrix of the striatum. A significant larger TH-immunoreactive area and neuron number was found in females compared to males. The presence of an internal capsule suggests an adaptive advantage concerning motor and cognitive abilities favoring reaction time in response to predators. In an anatomy-evolutive perspective, the striatum of vizcacha seems to be closer to that of humans than to that of laboratory traditional models such as mouse.

The ovarian germinal reserve and apoptosis-related proteins in the infant and adolescent human ovary.

BACKGROUND: Normal pubertal ovary displays all stages of follicular development and a biased BAX/BCL2 protein ratio in favor of pro-apoptotic BAX protein comparable to the adult ovary. However, adolescents suffering malignant extra-gonadal disease show a limited follicle development after cytotoxic drug treatment and a reduced capacity of in vitro follicle growth. We evaluated the expression of pro- and anti-apoptotic members of the BCL2 gene family, the FAS/FAS-L proteins from the extrinsic apoptosis pathway, the germ-cell-specific marker VASA, the pluripotency marker OCT3/4, and markers of early and late apoptosis in the ovary of pubertal patients with malignant extra-gonadal disease, which received or not pre-surgery chemotherapy, entering a cryopreservation program. RESULTS: Ovarian biopsies from 12 adolescent girls were screened for follicle count and expression of VASA, OCT3/4, BAX, BCL2, MCL1L and S, cleaved-BID, FAS/FAS-L and CASPASE 3 through immunohistochemistry, western blot and RT-PCR. All stages of folliculogenesis, from primordial to antral follicle, were present in all 12 patients analyzed. VASA and most of the screened apoptosis-related genes showed a pattern of immune-expression comparable to that previously reported. OCT3/4 showed a cytoplasmic localization in the great majority of the primordial follicles; however, in some cases the localization was nuclear. In addition, OCT3/4B showed a significant reduction compared to OCT3/4A. Unexpectedly, BCL2 was detected at all stages of folliculogenesis, associated to the Balbiani's body in the primordial follicles, regardless of whether patients had or had not received chemotherapy, ruling out the possibility that its expression is a protective response to chemotherapy. CONCLUSIONS: These findings reveal new information on the morphological status of the follicular reserve and the expression of apoptosis-related genes in histologically normal adolescent ovary from patients undergoing extragonadal cancer. The unexpected expression of apoptosis-inhibiting BCL2 protein, both in patients that had or had not received chemotherapy, opens a new avenue for thorough investigations. Moreover, the nuclear localization of OCT3/4 protein in primordial follicle-enclosed oocytes suggests a possible increased activity of ovarian stem cells in response to chemotherapy and/or extragonadal cancer. This new information can be essential for a better managing of in vitro culture of follicles that can be removed by filtration from preserved ovarian tissue, especially in girls that entered a cryopreservation program.

Pituitary estrogen receptor alpha is involved in luteinizing hormone pulsatility at mid-gestation in the South American plains vizcacha, Lagostomus maximus (Rodentia, Caviomorpha).

The South American plains vizcacha, Lagostomus maximus, is a caviomorph rodent native from Argentina, Bolivia and Paraguay. It shows peculiar reproductive features like pre-ovulatory follicle recruitment during pregnancy with an ovulatory process at around mid-gestation. We have described the activation of the hypothalamic - pituitary - ovarian (HPO) axis during pregnancy. A progressive decrease of progesterone (P4) at mid-pregnancy elicits the delivery of gonadotropin-releasing hormone (GnRH) with the consequent secretion of follicle stimulating hormone (FSH) and estradiol (E2) followed by luteinizing hormone (LH) release resulting in follicular luteinization and the P4 concentration recover. Pituitary gland is the central regulator of the HPO axis being E2 a key hormone involved in the regulation of its activity. In this work we analyzed the action of E2 on the pituitary response to the GnRH wave as well as its involvement on LH secretion at mid-gestation in L. maximus. The expression of GnRHR at the pituitary pars distalis showed a significant decrease at mid-pregnancy compared to early- and term-gestating females. ERα showed a significant increment from mid-gestation whereas ERß did not show variations throughout pregnancy; whereas the LH expression in the pituitary pars distalis showed a significant increase at mid-gestation, concordantly with serum LH, which was followed by a decrease at term-gestation with similar values than at early-pregnancy. The number of cells with co-localization of ERα and GnRHR showed a decline at mid-pregnancy related to early- and term-gestation, whereas the cells with co-localization of ERα and LH increased at mid- and term-pregnancy. On the other hand, ex vivo measuring of LH pulsatility showed a significant increment in the total mass of LH delivered at mid-pregnancy followed by a decrease at term-gestation. The stimulation of ERα with the PPT specific agonist induced a significant increment in the total mass of LH released, whereas no changes were determined when ERß was stimulated with its specific agonist MPP. These results suggest that LH pulsatility rise at mid-pregnancy would be enabled by the increase of E2 acting through ERα.

Age-related and photoperiodic variation of the DAZ gene family in the testis of the Syrian hamster (Mesocricetus auratus).

SummaryThe Deleted in AZoospermia (DAZ) gene family regulates the development, maturation and maintenance of germ cells and spermatogenesis in mammals. The DAZ family consists of two autosomal genes, Boule and Dazl (Daz-like), and the Daz gene on chromosome Y. The aim of this study was to analyze the localization of DAZL and BOULE during testicular ontogeny of the seasonal-breeding Syrian hamster, Mesocricetus auratus. We also evaluated the testicular expression of DAZ family genes under short- or long-photoperiod conditions. In the pre-pubertal and adult testis, DAZL protein was found mainly in spermatogonia. BOULE was found in the spermatogonia from 20 days of age and during the pre-pubertal and adult period it was also detected in spermatocytes and round spermatids. DAZL and BOULE expression in spermatogonia was strictly nuclear only in 20-day-old hamsters. We also detected the novel mRNA and protein expression of BOULE in Leydig cells. In adult hamsters, Dazl expression was increased in regressed testis compared with non-regressed testis and DAZL protein expression was restricted to primary spermatocytes in regressed testis. These results show that DAZL and BOULE are expressed in spermatogonia at early stages in the Syrian hamster, then both proteins translocate to the cytoplasm when meiosis starts. In the adult regressed testis, the absence of DAZL in spermatogonia might be related to the decrease in germ cell number, suggesting that DAZ gene family expression is involved in changes in seminiferous epithelium during photoregression.

Local production of neurostradiol affects gonadotropin-releasing hormone (GnRH) secretion at mid-gestation in Lagostomus maximus (Rodentia, Caviomorpha).

Females of the South American plains vizcacha, Lagostomus maximus, show peculiar reproductive features such as massive polyovulation up to 800 oocytes per estrous cycle and an ovulatory process around mid-gestation arising from the reactivation of the hypothalamic-hypophyseal-ovary (H.H.O.) axis. Estradiol (E2) regulates gonadotropin-releasing hormone (GnRH) expression. Biosynthesis of estrogens results from the aromatization of androgens by aromatase, which mainly occurs in the gonads, but has also been described in the hypothalamus. The recently described correlation between GnRH and ERα expression patterns in the hypothalamus of the vizcacha during pregnancy, with coexpression in the same neurons of the medial preoptic area, suggests that hypothalamic synthesis of E2 may affect GnRH neurons and contribute with systemic E2 to modulate GnRH delivery during the gestation. To elucidate this hypothesis, hypothalamic expression and the action of aromatase on GnRH release were evaluated in female vizcachas throughout pregnancy. Aromatase and GnRH expression was increased significantly in mid-pregnant and term-pregnant vizcachas compared to early-pregnant and nonpregnant females. In addition, aromatase and GnRH were colocalized in neurons of the medial preoptic area of the hypothalamus throughout gestation. The blockage of the negative feedback of E2 induced by the inhibition of aromatase resulted in a significant increment of GnRH-secreted mass by hypothalamic explants. E2 produced in the same neurons as GnRH may drive intracellular E2 to higher levels than those obtained from systemic circulation alone. This may trigger for a prompt GnRH availability enabling H.H.O. activity at mid-gestation with ovulation and formation of accessory corpora lutea with steroidogenic activity that produce the necessary progesterone to maintain gestation to term and guarantee the reproductive success.

Hormonal behavior correlates with follicular recruitment at mid-gestation in the South American plains vizcacha, Lagostomus maximus (Rodentia, Caviomorpha).

In mammals, hormonal regulation during gestation is crucial for embryo implantation and pregnancy success. This regulation is controlled through the level of progesterone (P4) that blocks the activity of the hypothalamic-hypophyseal-gonadal (HHG) axis. Previous studies in the pregnant South American plains vizcacha, Lagostomus maximus, have shown that the HHG axis activates around mid-gestation, promoting pre-ovulatory follicle formation. However, the characterization of the hormonal dynamics throughout gestation and its ovarian correlation has not been studied in depth. We studied the ovarian dynamics of L. maximus and its correlation with the hormonal profile during gestation, analyzing serum levels of P4, 17ß-estradiol (E2), 4Δ-androstenedione (A4), luteinizing hormone (LH) and follicle stimulating hormone (FSH) as well as the ovarian distribution and expression of their receptors. Additionally, we have analyzed the folliculogenesis and accessory corpora lutea (ACL) formation. P4 showed two concentration peaks reaching its highest level at mid-gestation decreasing at 91-100days post-coitum. P4 decrease is followed by an increase of circulating levels of A4, E2, FSH and LH and with an elevated number of antral/pre-ovulatory follicles which express PGR, ESR1, ESR2, AR, LHR and FSHR. In addition, ACL with oocyte retention and cytoplasmic lipid droplets in luteal cells were detected at this time point. These results show that in L. maximus the decrease of P4 level from mid-gestation enables follicular recruitment until pre-ovulatory stage and the development of functional ACL.

ERα and GnRH co-localize in the hypothalamic neurons of the South American plains vizcacha, Lagostomus maximus (Rodentia, Caviomorpha).

Gonadotropin-releasing hormone (GnRH) is the key regulator of the hypothalamic-pituitary-gonadal axis. Estradiol (E2) affects GnRH synthesis and delivery. Hypothalamic estrogen receptors (ER) modulate GnRH expression acting as transcription factors. The South American plains vizcacha, Lagostomus maximus, is able to ovulate up to 800 oocytes per reproductive cycle, and shows continuous folliculogenesis with pre-ovulatory follicle formation and an ovulatory event at mid-gestation. The aim of this work was to analyze the hypothalamic expression of ER in the vizcacha at different gestational time-points, and its relationship with GnRH expression, serum luteinizing hormone (LH) and E2. The hormonal pattern of mid-gestating vizcachas was comparable to ovulating-females with significant increases in GnRH, LH and E2. Hypothalamic protein and mRNA expression of ERα varied during pregnancy with a significant increase at mid-gestation whereas ERß mRNA expression did not show significant variations. Hypothalamic immunolocalization of ERα was observed in neurons of the diagonal band of Brocca, medial preoptic area (mPOA), periventricular, suprachiasmatic, supraoptic (SON), ventromedial, and arcuate nuclei, and medial eminence, with a similar distribution throughout gestation. In addition, all GnRH neurons of the mPOA and SON showed ERα expression with no differences across the reproductive status. The correlation between GnRH and ERα at mid-gestation, and their co-localization in the hypothalamic neurons of the vizcacha, provides novel information compared with other mammals suggesting a direct action of estrogen as part of a differential reproductive strategy to assure GnRH synthesis during pregnancy.

Patterns of population structure at microsatellite and mitochondrial DNA markers in the franciscana dolphin (Pontoporia blainvillei).

The franciscana dolphin, Pontorporia blainvillei, is an endemic cetacean of the Atlantic coast of South America. Its coastal distribution and restricted movement patterns make this species vulnerable to anthropogenic factors, particularly to incidental bycatch. We used mitochondrial DNA control region sequences, 10 microsatellites, and sex data to investigate the population structure of the franciscana dolphin from a previously established management area, which includes the southern edge of its geographic range. F-statistics and Bayesian cluster analyses revealed the existence of three genetically distinct populations. Based on the microsatellite loci, similar levels of genetic variability were found in the area; 13 private alleles were found in Monte Hermoso, but none in Claromecó. When considering the mitochondrial DNA control region sequences, lower levels of genetic diversity were found in Monte Hermoso, when compared to the other localities. Low levels of gene flow were found between most localities. Additionally, no evidence of isolation by distance nor sex-biased dispersal was detected in the study area. In view of these results showing that populations from Necochea/Claromecó, Monte Hermoso, and Río Negro were found to be genetically distinct and the available genetic information for the species previously published, Argentina would comprise five distinct populations: Samborombón West/Samborombón South, Cabo San Antonio/Buenos Aires East, Necochea/Claromecó/Buenos Aires Southwest, Monte Hermoso, and Río Negro. In order to ensure the long-term survival of the franciscana dolphin, management and conservation strategies should be developed considering each of these populations as different management units.

Aptamers: current challenges and future prospects.

INTRODUCTION: Aptamers are oligonucleotide molecules raised in vitro from large combinatorial libraries of nucleic acids and developed to bind to targets with high affinity and specificity. Whereas novel target molecules are proposed for therapeutic intervention and diagnostic, aptamer technology has a great potential to become a source of lead compounds. AREAS COVERED: In this review, the authors address the current status of the technology and highlight the recent progress in aptamer-based technologies. They also discuss the current major technical limitations of aptamer technology and propose original solutions based on existing technologies that could result in a solid aptamer-discovery platform. EXPERT OPINION: Whereas aptamers have shown to bind to targets with similar affinities and specificities to those of antibodies, aptamers have several advantages that could outweigh antibody technology and open new opportunities for better medical and diagnostic solutions. However, the current status of the aptamer technology suffers from several technical limitations that slowdown the progression of novel aptamers into the clinic and makes the business around aptamers challenging.

Sequence analysis, tissue distribution and molecular physiology of the GnRH preprogonadotrophin in the South American plains vizcacha (Lagostomus maximus).

Gonadotropin-releasing hormone (GnRH) is the regulator of the hypothalamic-hypophyseal-gonadal (HHG) axis. GnRH and GAP (GnRH-associated protein) are both encoded by a single preprohormone. Different variants of GnRH have been described. In most mammals, GnRH is secreted in a pulsatile manner that stimulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The South-American plains vizcacha, Lagostomus maximus, is a rodent with peculiar reproductive features including natural poly-ovulation up to 800 oocytes per estrous cycle, pre-ovulatory follicle formation throughout pregnancy and an ovulatory process which takes place at mid-gestation and adds a considerable number of secondary corpora lutea. Such features should occur under a special modulation of the HHG axis, guided by GnRH. The aim of this study was to sequence hypothalamic GnRH preprogonadotrophin mRNA in the vizcacha, to compare it with evolutionarily related species and to identify its expression, distribution and pulsatile pattern of secretion. The GnRH1variant was detected and showed the highest homology with that of chinchilla, its closest evolutionarily related species. Two isoforms of transcripts were identified, carrying the same coding sequence, but different 5' untranslated regions. This suggests a sensitive equilibrium between RNA stability and translational efficiency. A predominant hypothalamic localization and a pulsatile secretion pattern of one pulse of GnRH every hour were found. The lower homology found for GAP, also among evolutionarily related species, depicts a potentially different bioactivity.