Descent Of Testis Research Articles

Design, synthesis and pharmacological evaluation of cyclic mimetics of the insulin‐like peptide 3 (INSL3) B‐chain

Insulin-like peptide 3 (INSL3) is a peptide hormone belonging to the relaxin-insulin superfamily of peptides that plays important roles in testes descent, oocyte maturation and the control of male germ cell apoptosis. These actions are mediated via a specific G-protein coupled receptor, LGR8. Previous structure-activity studies have shown that the key binding site of INSL3 is situated within its B-chain. Recent studies in our laboratory have led to the identification of a cyclic peptide mimetic 2 of the INSL3 B-chain, which we have shown to compete with the binding of [33P]-relaxin to LGR8 expressed in HEK293T cells, and to inhibit cAMP-mediated signaling in these cells, i.e. it is an antagonist of INSL3. In order to further define the structure-activity relationships of cyclic analogues of the INSL3 B-chain, we used a structure-based approach to design a series of cyclic, disulfide-constrained INSL3 B-chain mimetics. To do this, we first created a model of the 3D structure of INSL3 using the crystal structure of human relaxin as a template. This model of INSL3 was then used as a template to design a series of disulfide-constrained mimetics of the INSL3 B-chain. The peptides were synthesized by solid-phase peptide synthesis using pseudoproline dipeptides to improve the synthesis outcome. Of the seven prepared INSL3 B-chain mimetics, three compounds were found to have partial displacement activity, while four were able to completely displace [33P]-relaxin from LGR8, including compounds that were markedly shorter than compound 2. The best of these, mimetic 6, showed significantly greater affinity for LGR8 than compound 2, but still displayed around 1000-fold less affinity for LGR8 than native INSL3. Analysis of selected mimetics for their alpha-helical content using circular dichroism (CD) spectroscopy revealed that, generally, the mimetics showed less than expected helicity. The inability of the compounds to display true native INSL3 structure is likely contributing to their reduced receptor binding affinity. We are currently examining alternative INSL3 B-chain mimetics that might better present key receptor binding residues in the native INSL3-like conformation.

Effects of separate and combined exposure to the pesticides methamidophos and chlorothalonil on the development of suckling rats

It has been suggested that, in some cases, exposure to environmental contaminants affects children more profoundly than adults. It is important to evaluate adverse health outcomes in children, a population susceptible to toxic chemicals and mixtures. We examined the effects that maternal exposure to two pesticides had on maturational aspects of offspring development during the nursing period. Nursing female rats were exposed to 1–4 mg/kg of intraperitoneal methamidophos, 200–800 mg/kg of chlorothalonil, or both. The higher doses of methamidophos affected pup viability by day 21 of life. Both pesticides, alone or together, affected body weight gain of dams and offspring. Developmental milestones evaluated in the pups were incisor eruption, ear unfolding, eye opening and testis descent. Although no clear dose–response relationship was established between these milestones and exposure to methamidophos or chlorothalonil, incisor eruption was accelerated in many groups, and the majority of rat offspring exposed to methamidophos presented later ear unfolding and eye opening than did the control group offspring. Sexual maturation (testis descent) was significantly delayed in some groups. For dams and pups alike, simultaneous exposure to both pesticides was not found to have a greater toxic effect than that resulting from exposure to only one of the two. Taken together, these results demonstrate exposure-related influences on several developmental measures. Detection of more subtle effects may be improved through the use of the developmental temporal response protocols utilized in this study.

Mutation and Polymorphism Analyses of INSL3 and LGR8/GREAT in 62 Japanese Patients with Cryptorchidism

Background/Aims: Although insulin-like factor 3 (INSL3) and its receptor leucine-rich repeat-containing G protein-coupled receptor 8/G protein-coupled receptor affecting testis descent (LGR8/GREAT) are essential for the gubernacular development, mutations of INSL3 and LGR8/GREAT are infrequent in patients with cryptorchidism (CO), and there is no report documenting a positive association of CO with a polymorphism in INSL3 or LGR8/GREAT. Here, we further examined the relevance of INSL3 and LGR8/GREAT mutations and polymorphisms to the development of CO. Methods: Sixty-two Japanese CO patients and 60 fertile males were studied. INSL3 was analyzed by direct sequencing and restriction enzyme digestion, and LGR8/GREAT was examined by denaturing high-performance liquid chromatography followed by direct sequencing for exons with abnormal chromatogram patterns. Results: No definitive mutation was identified in both genes. Six polymorphisms were detected in INSL3 or LGR8/GREAT and Thr/Thr genotype of Ala60Thr polymorphism in INSL3 was strongly associated with CO (p = 0.0024, odds ratio = 5.3, 95% confidence interval = 1.7–17). Conclusion: The results, in conjunction with the previous data, suggest that mutations of INSL3 and LGR8/GREAT remain rare, and that the Thr/Thr genotype of Ala60Thr polymorphism in INSL3 may constitute a susceptibility factor for the development of CO.

Neurodevelopmental effects of perinatal fenarimol exposure on rats

Knowledge about the potential toxic effects of fenarimol, a widely used fungicide, is still limited. Fenarimol is an aromatase inhibitor and therefore can affect estrogen/androgen levels in vivo in rodents. In view of these facts, the aim of the present work was to study the effects of fenarimol maternal exposure during different critical phases in the development of central nervous system in rat pups, on early physical and neurobehavioral endpoints essential to their development. For that, the effects of the fungicide fenarimol (150 and 300 mg/kg) were examined at three different developmental stages in the rat: during the first 6 days of gestation, prenatal (15–21 days), or first 6 days of lactation. Three categories of the impact of fenarimol on neonatal growth and neurobehavioral development of offspring were assessed: (1) physical, (2) reflex and strength, and (3) motor coordination. Findings on the pups’ physical development did not indicate any significant alterations of the postnatal age at which specific developmental milestones were observed (pinna detachment, development of the fur, eruption of the incisor teeth, opening of the ears and eyes and testes descent). However, there was a reduced rate of weight gain in pups of mothers treated during lactation related to the earlier testing time periods (1–23 days of life). The study of the functional state of the rat pup nervous systems at different stages of postnatal development revealed some neurodevelopmental delays in righting reflex, climbing and grip response and locomotion (20–90 days of life) in the treated groups. Taken together, findings of this study emphasize that, as a result of fenarimol maternal exposure, some neuromuscular and behavioral deficits in nursing pups may occur principally during the last gestational period and lactation. These results could be the basis for further studies on molecular actions of fenarimol in order to predict better the biological consequences of this fungicide.

Solution Structure and Characterization of the LGR8 Receptor Binding Surface of Insulin-like Peptide 3

Insulin-like peptide 3 (INSL3), a member of the relaxin peptide family, is produced in testicular Leydig cells and ovarian thecal cells. Gene knock-out experiments have identified a key biological role in initiating testes descent during fetal development. Additionally, INSL3 has an important function in mediating male and female germ cell function. These actions are elicited via its recently identified receptor, LGR8, a member of the leucine-rich repeat-containing G-protein-coupled receptor family. To identify the structural features that are responsible for the interaction of INSL3 with its receptor, its solution structure was determined by NMR spectroscopy together with in vitro assays of a series of B-chain alanine-substituted analogs. Synthetic human INSL3 was found to adopt a characteristic relaxin/insulin-like fold in solution but is a highly dynamic molecule. The four termini of this two-chain peptide are disordered, and additional conformational exchange is evident in the molecular core. Alanine-substituted analogs were used to identify the key residues of INSL3 that are responsible for the interaction with the ectodomain of LGR8. These include Arg(B16) and Val(B19), with His(B12) and Arg(B20) playing a secondary role, as evident from the synergistic effect on the activity in double and triple mutants involving these residues. Together, these amino acids combine with the previously identified critical residue, Trp(B27), to form the receptor binding surface. The current results provide clear direction for the design of novel specific agonists and antagonists of this receptor.

Puberty stage and spontaneous descent of acquired undescended testis: implications for therapy?

We assessed spontaneous descent of acquired undescended testis (UDT) at puberty. 299 Boys (aged 1.2-16.5 years, mean 9.4) with 350 acquired-UDT were examined annually during a 12.6-year period (mean 3.1). An acquired-UDT was defined as a previously intrascrotal testis which can no longer be manipulated into a stable scrotal position. Each year, position of the testis and pubertal development according to Tanner's stages were assessed. Early puberty was defined as puberty stage G2 (testicular volume 4-9 mL), mid-puberty as puberty stages G3 (testicular volume 10 mL) and G4 (testicular volume 11-15 mL), and late puberty as puberty stage G5 (testicular volume >15 mL). Follow-up was completed if spontaneous descent had occurred, if mid-pubertal orchidopexy (ORP) had to be performed, if the boy was lost for follow-up, or if pre-pubertal ORP was performed in another hospital. In 139 boys with 164 acquired-UDT follow-up was meanwhile completed. Twelve boys with 14 UDT were lost for follow-up. In an additional 16 boys with 21 UDT, ORP was performed in another hospital. In 98 of the remaining 129 (76.0%) acquired-UDT spontaneous descent at puberty occurred. Mean follow-up was 2.5 years (range 0.2-8.5). In 70 of 98 testes (71.4%) descent occurred in early puberty, in 26 of 98 testes (26.5%) in mid-puberty, and in two testes in late puberty. In 31 of 129 testes (24.0%) ORP had to be performed at mid (30 cases) or late (one case) puberty. In this series, 98 of 129 acquired-UDT (76.0%) descended spontaneously at puberty, whereas in 31 of 129 (24.0%) pubertal ORP was performed. If ORP is postponed until puberty stage G3 (testicular volume of 10 mL) three of four acquired-UDT will descend spontaneously.

Analogs of Insulin-like Peptide 3 (INSL3) B-chain Are LGR8 Antagonists in Vitro and in Vivo

Insulin-like peptide 3 (INSL3) is a member of the insulin superfamily that plays an important role in mediating testes descent during fetal development. More recently, it has also been demonstrated to initiate oocyte maturation and suppress male germ cell apoptosis. These actions are mediated via a specific G-protein-coupled receptor, LGR8. Little is known regarding the structure and function relationship of INSL3, although it is believed that the principal receptor binding site resides within its B-chain. We subsequently observed that the linear B-chain alone (INSL3B-(1-31)) bound to LGR8 and was able to antagonise INSL3 stimulated cAMP accumulation in HEK-293T cells expressing LGR8. Sequentially N- and C-terminally shortened linear analogs were prepared by solid phase synthesis and subsequent assay showed that the minimum length required for binding was residues 11-27. It was also observed that increased binding affinity correlated with a corresponding increase in alpha-helical content as measured by circular dichroism spectroscopy. Molecular modeling studies suggested that judicious placement of a conformational constraint within this peptide would increase its alpha-helix content and result in increased structural similarity to the B-chain within native INSL3. Consequently, intramolecularly disulfide-linked analogs of the B-chain showed a potentiation of INSL3 antagonistic activity, as well as exhibiting increased proteolytic stability, as assessed in rat serum in vitro. Administration of one of these peptides into the testes of rats resulted in a substantial decrease in testis weight probably due to the inhibition of germ cell survival, suggesting that INSL3 antagonists may have potential as novel contraceptive agents.

Molecular characterization and exclusion of porcine GUSBas a candidate gene for congenital hernia inguinalis/scrotalis

BackgroundInguinal hernias are usually caused by a congenital defect, which occurs as a weakness of the inguinal canal. Porcine β-glucuronidase gene (GUSB) was chosen as functional candidate gene because of its involvement in degradation of hyaluronan within gubernacular tissue during descent of testes. Since a genome-wide linkage analysis approach has shown evidence that two regions on porcine chromosome 3 (SSC 3) are involved in the inheritance of hernia inguinalis/scrotalis in German pig breeds, GUSB also attained status as a positional candidate gene by its localization within a hernia-associated chromosomal region.ResultsA contig spanning 17,157 bp, which contains the entire GUSB, was assembled. Comparative sequence analyses were conducted for the GUSB gene locus. Single nucleotide polymorphisms (SNPs) located within the coding region of GUSB were genotyped in 512 animals. Results of transmission disequilibrium test (TDT) for two out of a total of five detected SNPs gave no significant association with the outcome of hernia in pigs.ConclusionOn the basis of our studies we are able to exclude the two analyzed SNPs within the porcine GUSB gene as causative for the transmission of inguinal hernia.

Testis and Antler Dysgenesis in Sitka Black-Tailed Deer on Kodiak Island, Alaska: Sequela of Environmental Endocrine Disruption?

It had been observed that many male Sitka black-tailed deer (Odocoileus hemionus sitkensis) on Kodiak Island, Alaska, had abnormal antlers, were cryptorchid, and presented no evidence of hypospadias. We sought to better understand the problem and investigated 171 male deer for phenotypic aberrations and 12 for detailed testicular histopathology. For the low-lying Aliulik Peninsula (AP), 61 of 94 deer were bilateral cryptorchids (BCOs); 70% of these had abnormal antlers. Elsewhere on the Kodiak Archipelago, only 5 of 65 deer were BCOs. All 11 abdominal testes examined had no spermatogenesis but contained abnormalities including carcinoma in situ–like cells, possible precursors of seminoma; Sertoli cell, Leydig cell, and stromal cell tumors; carcinoma and adenoma of rete testis; and microlithiasis or calcifications. Cysts also were evident within the excurrent ducts. Two of 10 scrotal testes contained similar abnormalities, although spermatogenesis was ongoing. We cannot rule out that these abnormalities are linked sequelae of a mutation(s) in a founder animal, followed by transmission over many years and causing high prevalence only on the AP. However, based on lesions observed, we hypothesize that it is more likely that this testis–antler dysgenesis resulted from continuing exposure of pregnant females to an estrogenic environmental agent(s), thereby transforming testicular cells, affecting development of primordial antler pedicles, and blocking transabdominal descent of fetal testes. A browse (e.g., kelp) favored by deer in this locale might carry the putative estrogenic agent(s).

Mouse Mutants of Relaxin, Insulin-Like 3 Peptide and their Receptors

Recently, mouse mutants of closely related relaxin (Rln1), insulin-like3 (Insl3), and GPCR receptors ( Lgr7 and Lgr8/Great) have been produced using gene targeting approach in ES cells and transgenesis. Analysis of their phenotype allowed an identification of the cognate ligand/receptors interactions, specific target organs, and physiological and developmental processes regulated by Rln and Insl3 signaling. Females deficient for Rln1 or Lgr7 exhibit undeveloped mammary gland nipples and increased parturition time during pregnancy. The Rln1 deficiency results in a buildup of fibrosis in different organs and an accumulation of collagen, concurrent with the known effects of Rln1 on extracellular matrix metabolism. Rln1-/- mice have an age-related progression of lung fibrosis with increasing collagen content and concentration, alveolar congestion, and bronchiole epithelium thickening. Male-specific abnormalities were detected in renal and cardiac function of the older Rln1-deficient animals; additionally, poor development of mutant male reproductive organs has been reported. The Insl3-/- or Lgr8-/- male mice exhibit high intraabdominal cryptorchidism. It is caused by the failure of gubernacular ligament differentiation, a structure mediating transabdominal testis descent during male embryogenesis. Transgenic mice with an overexpression of both hormones have been produced; they were instrumental in defining the specificity of Rln1 and Inls3 signaling. Mutant mice provide the experimental models to study the diverse actions of both hormones in vivo. Keywords: relaxin, insulin-like, lgr, gene targeting, mouse mutations

A 2-year-old baby with Downs syndrome, cryptorchidism and testicular tumour

Seminomas are rare germ cell tumours. It occurs usually in men aged over 50 years. Seminomas differ genetically and clinically from germ cell tumours. They have a late age of onset and rarely metastasise. The incidence of testicular carcinoma (seminoma) in patients of Down syndrome has recently been emphasised. One of the predisposing factors for seminoma is undescended testis which not only results in spermatogenic arrest but also in carcinoma in situ. This triad of abnormalities that is cryptorchidism, oligozoospermia and testicular cancer is known as testicular dysgenesis syndrome (TDS). Since there is an increased incidence of tumourogenesis in Down syndrome cases the cryptorchid condition may result in an increased risk for testicular carcinogenesis and its early onset and poor prognosis. Therefore all Down syndrome cases with cryptorchidism should be counselled to go in for surgical descent of testis at the earliest age and also to come for regular follow up for early detection for any foci of malignancy. This is the youngest testicular seminoma ever reported in human. This tumour occurred in a 2-year-old child and it is possible that Trisomy 21 may predispose to early onset of seminoma and such cases should be under regular follow up. Thus improved understanding and identification of various urogenital anomalies associated with Down syndrome will aid in better management of these cases. This case report and review of literature all suggest that Down syndrome is associated with an increased risk of development of seminoma and that too at an early age. This advocates a need for thorough gonadal examination in all cases of Down syndrome.

Postnatal development of rat pups is altered by prenatal methamphetamine exposure

There are studies showing that drug abuse during pregnancy may have impairing effect on progeny of drug-abusing mothers. Methamphetamine (MA) is one of the most common illicit drugs throughout the world. The purpose of the present study was to assess the effect of prenatal MA exposure on postnatal development of rat pups before the time of separation from their mothers. Female rats were injected with MA (5 mg/kg daily) for the duration of their pregnancy. Pups were then tested throughout the lactation period. They were weighed daily and the ano-genital distance was measured on postnatal day (PD) 1. Development of postural motor reaction was tested by righting reflex on surface between PD 1 and 12, and righting reflex in mid-air after PD 12 until successfully accomplished. On PD 15 homing test was examined as a test of pup acute learning. On PD 23 sensory-motor coordination was examined using the rotarod and bar-holding tests. Additionally, the markers of physical maturation, such as eye opening, testes descent in males and vaginal opening in females were also recorded. The birth weight in prenatally MA-exposed pups was lower than in controls or saline-exposed pups regardless of sex. There were no changes induced by prenatal MA exposure in weight gain or in sexual maturation. In righting reflexes, we demonstrated that pups exposed prenatally to MA were slower in righting reflex on surface and that they accomplished the test of righting reflex in mid-air later than controls or saline-exposed pups. The performance of homing test was not affected by prenatal drug exposure. The sensory-motor coordination was impaired in prenatally MA-exposed pups when testing in the rotarod test. Also, the number of falls in the bar-holding test was higher in MA-exposed pups than in controls. There were no sex differences in any measures. Thus, the present study demonstrated that prenatal MA exposure impairs development of postural motor movements of rat pups during the first 3 weeks after birth, while not affecting physical or sexual maturation.

Cryptorchidism: an indicator of testicular dysgenesis?

Cryptorchidism is a common ailment of new-born boys, affecting 1-9% of full term boys at birth. Cryptorchidism has been associated with an increased risk of testicular cancer and reduced fertility. Aetiology of cryptorchidism remains obscure in most cases. Familial occurrence suggests a heritable susceptibility to cryptorchidism; however, seasonal variation in the incidence of cryptorchidism suggests that environmental factors also contribute. Testicular descent is characterised by androgen-dependent regression of cranial suspensory ligament and androgen + insulin-like hormone 3 (Ins l3)-dependent gubernacular outgrowth. Even though hormonal defects are rarely detected in patients, both hypo-and hypergonadotropic hormonal patterns have been associated with cryptorchidism. Moreover, cryptorchid boys have significantly reduced serum androgen bioactivity at 3 months of age when normal boys have a strong surge of reproductive hormones. Defects in Ins l3 action cause cryptorchidism in male mice, and over-expression in female mice causes ovarian descent. Defects in leucine-rich repeat-containing G-protein-coupled receptor 8/G-protein-coupled receptor affecting testis descent (LGR8/GREAT), the receptor for Ins l3, manifest the same phenotype as Ins l3 knockout mutants. Even though mutations found in Ins l3 and LGR8/GREAT genes are not a common cause of cryptorchidism in patients, it remains to be resolved whether low Ins l3 levels during development are associated with cryptorchidism. Cryptorchidism may reflect foetal testicular dysgenesis that may later manifest as subfertility or testicular cancer.

Broad thumb-hallux (Rubinstein-Taybi) syndrome 1957-1988

This presentation records the early history of the description of the broad thumb-hallux syndrome and attempts to update the current state of knowledge about this syndrome. Information was collected and reviewed on 571 individuals from the world literature, from communications with colleagues and families of affected individuals, and from personal observation. The diagnosis was established in most cases by confirming the concurrence of the constellation of major diagnostic criteria, including broad short terminal phalanges of the thumbs and halluces, with or without angulation deformity; characteristic facial appearance with beaked or straight nose, antimongoloid slant of palpebral fissures, apparent or clinical hypertelorism and grimacing smile; stature and head circumference (OFC) below 50th centile; mental, motor, social, and language retardation; stiff awkward gait; and incomplete or delayed descent of testes in males. Information on associated clinical factors, familial occurrence, and cytogenetic findings is presented.

Restricted Expression of LGR8 in Intralaminar Thalamic Nuclei of Rat Brain Suggests a Role in Sensorimotor Systems

LGR8 was recently identified as a cognate receptor for insulin-like peptide-3 (INSL3), and INSL3-LGR8 signaling is best known for its role in testis descent during development. LGR8 mRNA has been detected in various human tissues including brain, but the regional and cellular distribution of LGR8 expression in the mammalian central nervous system is unknown. Therefore, in this study we investigated the presence and localization of LGR8 mRNA in rat brain using reverse transcription-polymerase chain reaction and in situ hybridization histochemistry. Results revealed a distinct distribution of LGR8 in forebrain, with transcripts principally restricted to the posterior thalamus and highest densities detected in the parafascicular nucleus of both adult and developing rats. Unexpectedly, INSL3 mRNA was not detected in brain by similar methods, but preliminary electrophysiologic studies of parafascicular neurons revealed that INSL3 altered their activity. These findings suggest that LGR8 signaling may be involved in sensorimotor control in the rat and perhaps other species, particularly via actions on parafascicular neurons that project to basal ganglia and are depleted in Parkinson's disease.

Characterization of the Rat INSL3 Receptor

Human LGR8, initially discovered as a low-affinity relaxin receptor, has now been characterized as the INSL3 receptor. To investigate LGR8 function in the rat, an LGR8 ortholog was identified in the rat genome, and the full-length sequence was cloned and expressed. Rat LGR8 bound INSL3 with high affinity, clearly demonstrating that it is the rat INSL3 receptor. Interestingly, native rat relaxin did not activate rat LGR8, indicating that relaxin is not an endogenous ligand for rat LGR8. LGR8 mRNA expression was demonstrated in the gubernaculum at the time of testis descent and in the testis associated with germ cells.

LGR8 Signal Activation by the Relaxin-like Factor

The relaxin-like factor (RLF) is thought to be responsible for the intra-abdominal migration of the testis during mammalian development. Our latest studies of RLF and LGR8 have revealed that the N-terminal region of the A chain is not required for receptor binding but is indispensable for cyclic AMP generation. RLF derivatives with six residues deleted from the N terminus of the A chain are active, whereas further truncation, up to the first A chain cysteine (A-10), yields tightly binding ligands devoid of signaling activity. These derivatives are specific competitive inhibitors (RLFi) of RLF. Although receptor binding is dependent upon B chain residues, the N-terminal region of the A chain is a generic trigger of the trans-membrane signaling activity.

Gubernacular fibroblasts express the androgen receptor during testis descent in cryptorchid rats treated with human chorionic gonadotrophin

Cryptorchidism was provoked in 3 day old rats treated with 17-beta-estradiol over 30 days to identify the cells that express the androgen receptor (AR) during experimental testis descent in the gubernaculum. In one group of animals, testis descent was induced with human chorionic gonadotrophin (hCG) applied daily for 5 or 10 days. A correlative study using a testosterone radioimmunoassay with electron microscopy and immunocytochemical detection of AR was performed in gubernacula of hCG treated and untreated control animals. The gubernaculum of rats undergoing testes descent showed a dramatic increase in the number of AR-positive cells. These were located in the connective tissue among smooth muscle cells in the gubernacular cord and between striated muscle fibers in the bulb. In both regions, the AR-positive cells were identified as fibroblasts. Several clusters of amorphous material appeared in the extracellular matrix of the connective tissue in hCG treated rats. Our results suggest that testosterone induces the expression of AR in gubernacular fibroblasts which seem to degrade the extracellular matrix during gubernacular involution.

Maternal exposure to diphenhydramine during the fetal period in rats: Effects on physical and neurobehavioral development and on neurochemical parameters

Previous research from our laboratory suggested that the administration of antihistaminics (H 1 receptor antagonists) to pregnant Wistar rats throughout pregnancy altered brain sexual differentiation and dopaminergic physiology of the offspring. In the present study, we assessed the effects of 20 mg/kg diphenhydramine (DPH) administration to pregnant rats during the fetal period of pregnancy [Gestation Days (GDs) 16–21], a critical period for brain sexual differentiation and central nervous system (CNS) maturation. Maternal body weight and water and food consumption were measured during pregnancy and offspring physical and behavioral development were evaluated during lactation. Offspring open-field behavior was assessed at 21 and 100 days of age. After the final open-field test, male and female sexual behavior, stereotypy following an apomorphine challenge, striatal content of dopamine (DA), the dopamine metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA), serotonin (5-HT) and the serotonin metabolite 5-hydroxyindolacetic acid (5-HIAA) were assessed. There were no significant treatment-related changes in maternal reproductive parameters, but DPH treatment decreased maternal body weight gain during the treatment period. Offspring physical parameters were not altered in the treated group, and no significant treatment-related changes were found in female open-field measures, sexual behavior or in striatal neurochemical measurements. However, delayed testis descent and altered patterns of sexual behavior occurred in male offspring accompanied by increased striatal DA, decreased striatal DOPAC as well as reduced DOPAC/DA, HVA/DA and 5-HIAA/5-HT ratios. Taken together, these data suggest that exposure to DPH during the fetal period of rat development altered postnatal CNS maturation and sexual development of male offspring via changes in striatal bioamine systems.

Molecular and genetic regulation of testis descent and external genitalia development

Testicular descent as a prerequisite for the production of mature spermatozoa and normal external genitalia morphogenesis, and therefore facilitating copulation and internal fertilization, are essential developmental steps in reproduction of vertebrate species. Cryptorchidism, the failure of testis descent, and feminization of external genitalia in the male, usually in the form of hypospadias, in which the opening of the urethra occurs along the ventral aspect of the penis, are the most frequent pediatric complications. Thus, elucidating the molecular mechanisms involved in the regulation of testis descent and the formation of external genitalia merits a special focus. Natural and transgenic rodent models have demonstrated both morphogenic processes to be under the control of a plethora of genetic factors with complex time-, space-, and dose-restricted expression pattern. The review elucidates the molecular mechanisms involved in the regulation of testis descent and the formation of external genitalia and, wherever possible, assesses the differences between these rodent animal models and other mammalian species, including human.