Biomedical subjects

P van der Schoot

Publications and source records attributed to P van der Schoot.

At least 19 recordsLinked to original sources

PubMed2006

Isotropic-nematic interface and wetting in suspensions of colloidal platelets.

We study interfacial phenomena in a colloidal dispersion of sterically stabilized gibbsite platelets, exhibiting coexisting isotropic and nematic phases separated by a sharp horizontal interface. The nematic phase wets a vertical glass wall and polarized light micrographs reveal homeotropic surface anchoring both at the free isotropic-nematic interface and at the wall. On the basis of complete wetting of the wall by the nematic phase, as found in our density functional calculations and computer simulations, we analyze the balance between Frank elasticity and surface anchoring near the contact line. Because of weak surface anchoring, the director field in the capillary rise region is uniform. From the measured rise (6 microm) of the meniscus at the wall we determine the isotropic-nematic surface tension to be 3 nN/m, in quantitative agreement with our theoretical and simulation results.

Journal Article↗

PubMed2006

Influence of a random field on particle fractionation and solidification in liquid-crystal colloid mixtures.

The influence of a random-anisotropy (RA) type disorder on the phase separation of nematogen-colloid mixtures is studied theoretically by combining the phenomenological Landau-de Gennes, Carnahan-Starling, and hard-sphere crystal theories. We assume that the colloids enforce the RA disorder on the surrounding thermotropic liquid-crystal (LC) molecules. We adopt the Imry-Ma argument according to which the lower-temperature phase exhibits a domain-type pattern. The colloids impose a finite degree of orientational ordering even in the isotropic (paranematic) phase. In the ordered phase they give rise to a domain-type structure, resulting in the distorted nematic (speronematic) phase. The RA field opposes the phase separation tendency. With increasing disorder the difference between the paranematic and speronematic ordering decreases. Consequently there is a critical disorder, above which both phases become identical from the orientation point of view, but have different concentrations of colloids. We have also estimated another characteristic value of disorder above which the isotropic phase can exist only in a liquid state, the crystal phase being suppressed completely.

Anisotropy↗

PubMed2004

Continuous director-field transformation of nematic tactoids.

We theoretically investigate the director field inside spindle-shaped nematic droplets, known as tactoids. Tactoids typically form in dispersions of rod-like colloidal particles. By optimising the bulk elastic and surface energies, we find that the director field crosses over smoothly from a homogeneous to a bipolar configuration with increasing droplet size, in a process that we postulate to involve two virtual point defects that move in from infinity towards the poles on the surface of the droplet. Our calculations show that these hypothesised virtual defects become true surface point defects or boojums only in the limit of infinite droplet volume, and that the more elongated the droplets are, the larger their volume has to be before a uniform director field distorts so as to become discernibly bipolar. The theory agrees well with available experimental data on the size dependence of the aspect ratio of tactoids.

Biophysics↗

PubMed1999

Sex difference in target seeking behavior of developing cremaster muscles and the resulting first visible sign of somatic sexual differentiation in marsupial mammals.

Cremaster muscles are present in both male and female developing and adult marsupial mammals. They are complex structures and composed of several distinct bundles of striated muscle fibers provided with: (1) a distinct and extensive innervation; (2) a distinct blood vascular supply; (3) a distinct tendineous origin on the anterosuperior iliac spine; and (4) distinct target structures. The muscles thus seem to be separate anatomical entities and not a part of one or more of the layers of the ventral abdominal wall musculature. Cremaster muscles in males are elongated, are larger than in females, and for the most part are a component of the funiculus spermaticus. They insert on the distal part of the tunica vaginalis. The distal parts of the muscles in females are flattened ("fan shaped") and insert over a broad area on the dorsal borders of the mammary glands. Muscles in males have no relation whatsoever to the male mammary glandular rudiments. Muscles in females are attached at the base of the uterine round ligament. The remarkable sex difference in target structures of marsupial cremaster muscles becomes noticeable during perinatal life when outgrowing muscles take a different path in males and females. The initial appearance of this sexually dimorphic trait precedes the sexual differentiation of the genital ducts and external genitalia. In fetal males, the cremaster muscles grow in the direction of the site where scrotal bulges initially appear in the subcutaneous layers and later on the inguinal skin surface. They also take the gubernacular core of the ventral abdominal wall and the attached peritoneal epithelium with them during this outgrowth process. Consequently, this results in the development of a slitlike evagination of the abdominal lumen as the primary step to development of the processus vaginalis, while the testis and adjacent mesonephros and its duct are still attached to the posterior abdominal wall. In fetal females, the outgrowing cremaster muscles pass along the gubernacular core and, subsequently, this structure develops further as the tip (attached to the tubo-uterine junction) of the intra-abdominally protruding and further developing uterine round ligament. The female cremaster muscles grow further into caudal direction to shape a dorsal border of the developing mammary glands. The early onset of this sexually dimorphic outgrowth of cremaster muscles indicates that the "classical hormones" of sexual differentiation (anti-Müllerian hormone [AMH] and steroidal androgens) are not involved in this process. It could thus depend on primary genetic control with male development associated with the male-limited activity of genes on the Y-chromosomes and female development as the default process. Alternatively, the process in males could be under the control of an as yet unidentified third fetal testicular hormone involved in sexual differentiation processes which must then show an unexpectely early (i.e., perinatal) onset of its secretion.

Animals↗

PubMed1996

Foetal genital development in Hyrax capensis, a species with primary testicondia: proposal for the evolution of Hunter's gubernaculum.

BACKGROUND: Control of testicular descent is poorly understood. There are a number of mammalian species in which testis descent does not occur, and the phenomenon is called testicondia. Analysis of foetal development of such species could contribute to a better understanding of the key events in anatomical development underlying testis descent. Specific attention is to be given to the development of the so-called gubernaculum of Hunter: a structure of complex architecture and composition, which extends from the caudal pole of the mesonephric remnants into the inguinal abdominal wall and which is present in most mammals but not in submammalian vertebrates. METHODS: Serially sectioned male and female foetuses of Hyrax capensis, a species in which testes remain close to the caudal pole of the kidneys throughout life, were analysed for architecture of the developing genital apparatus and the immediately surrounding structures. The results of this analysis were compared with those from a similar analysis of reptiles, of monotremata without testis descent, and of mammals with testis descent. RESULTS: Reptiles and Monotremata showed no gubernacular structures. Mammals with testis descent showed gubernacular growth and differentiation which varied between the sexes and with the stage of foetal development. Hyrax capensis foetuses showed the development of only one component of the gubernaculum: the gubernacular cord as a part of the mesonephric mesentery and extending between the caudal pole of the mesonephros (or mesonephric remnants in older foetuses) and the lateral bladder ligament. No part developed in the inguinal abdominal wall components, which are the primordia of the cremaster sacs in species with testis descent. CONCLUSION: Hyrax capensis shows only partial development of the gubernacular structures, and, specifically, the primordia of the cremaster sacs remain absent. Thus, this species lacks a key anatomical condition for testis descent. Gubernacular architecture in Hyrax capensis seems of a degree intermediate between egg laying monotremata mammals and mammals with testis descent. A model is proposed within which to understand the development of the gubernacular components within the mammalian class.

Animals↗

PubMed1996

Human (and some other primates') uterine teres ligament represents a mammalian developmental novelty.

BACKGROUND: The primordia of the structures developing into the mammalian male cremaster sacs emerge as well in females fetuses. In most species the structures developing from these primordia in females remain inconspicuous: the so-called uterine teres ligament consisting of a slender part across the uterine broad ligament and a more or less developed bulbous structure at the site where this ligament inserts into the inguinal abdominal bottom. Not many data are available concerning the growth, development, or function of the uterine teres ligament. In humans--and also in other "higher" female primates--the uterine teres ligament is a major structure consisting mainly of smooth musculature. It is attached to the ventral aspect of the tubo-uterine junction. From there it courses across the uterine broad ligament and extends, retroperitoneally, to the inguinal region where it pierces through the inguinal canal to end in the tissues ventral of the pubic bones. OBSERVATIONS: Analysis of the fetal development of the human uterine teres ligament, as compared with that of various other non-primate mammals, offers an explanation for its unusual anatomical condition. Evidence is conferred that, in human fetuses, there is no counterpart for the slender ligament across the broad ligament in other mammals. Instead, the homologue of the rudimentary bulbous structure in the abdominal bottom of non-primate females develops into a strong muscular structure which is directly connected to the (para-)menonephric duct wall. CONCLUSION: It is concluded that the human uterine teres ligament is to be judged a structure different from that of other, non-primate, mammals. It is speculated that the unusual structure of the human teres ligament is related to one or more of the many unusual features of human uterine development: as a single organ (uterus simplex), with a position deep in the abdominal cavity below the pelvic brim, and far away from the posterior abdominal wall. The unusual anatomical position may require an unusual construction of the uterine suspensory apparatus of which the teres ligament is one component.

Adult↗

PubMed1996

Autonomous testicular hormonal control of fetal gubernaculum development in rabbits: a re-examination of histological slides in the legacy of the late Professor Alfred Jost.

The present study investigated whether the male differentiation of the gubernacular primordia depends on fetal pituitary control. Therefore, gubernaculum development was analysed in the same histological preparations that the late Professor Alfred Jost had used to examine the effects of fetal decapitation on the other parts of the developing genitalia. Decapitation had taken place at the onset of sexual differentiation (day 19 after conception) and the results examined just before the expected birth (day 28 after conception). Fetal decapitation had no noticeable effect on the development of these large and complex male-specific structures. It was concluded (1) that fetal control of male gubernaculum development operates through a mechanism different from that involved in male differentiation of the other component parts of the genitalia and (2) that this mechanism is not under fetal pituitary control. The results thus provide further support for the existence of a separate fetal hormone to bring about male differentiation of the gubernacular primordia.

Androgens↗

PubMed1996

Anti-müllerian hormone in relation to the growth and differentiation of the gubernacular primordia in mice.

The present study analysed gubernaculum development in mice that had been induced, through transgenesis, to express human anti-Müllerian hormone (h-AMH) throughout prenatal life. Growth and differentiation of the gubernacular primordia were assessed through the analysis of serial, transverse or sagittal, histological sections of the lower abdomen. Transgenic males and females expressed biologically active amounts of h-AMH as measured by sensitive and specific ELISA and evidenced through the regression, in females, of Müllerian ducts after day 13 of prenatal life. Gubernacular primordia became distinguishable at the same age in control and transgenic male and female fetuses on day 12 after coitus. In both groups gubernacular cords (inguinal folds of the genital mesenteries) increased in length more in females than in males while gubernacular cones showed larger growth in males. h-AMH thus appeared not to affect the sexually dimorphic pattern of growth and development of these structures. Growth and differentiation of the gubernacular primordia was further examined in 18-day-old control and h-AMH transgenic fetuses that had been exposed to testosterone propionate injected into their mothers on days 12 and 14 of pregnancy. Testosterone treatment affected, to a minor extent, the growth of the female gubernacular cords: these were reduced in length (but had a larger surface area) compared with controls. The gubernacular cones were slightly increased in length but male-like differentiation of the tissues of the cones into a muscular and mesenchymal component was not noticed to any extent. The observations thus add experimental support to the contention that AMH, even in combination with testosterone, is not effective in establishing the male pattern of gubernacular primordia development.

Animals↗

PubMed1996

Studies on the role of TRH and corticosterone in the regulation of prolactin and thyrotrophin secretion during lactation.

This study describes the effects of litter size and acute suckling on the synthesis and release of hypothalamic TRH, as indirectly estimated by determination of hypothalamic prothyrotrophin-releasing hormone (proTRH) mRNA and median eminence TRH content. The effects of litter size (five or ten pups) were studied throughout lactation, while suckling-induced acute changes were analyzed on day 13 of lactation in dams with ten pups. In view of the enhanced adrenal activity during lactation and recent evidence that corticosteroids have negative effects on hypothalamic TRH, we also studied adrenalectomized (ADX) dams treated with corticosterone to maintain basal plasma corticosterone levels. In addition to an increased plasma level of prolactin (PRL), adrenal weight and plasma corticosterone increased, while plasma TSH, tri-iodothyronine (T3), thyroxine (T4) and free T4 (FT4) levels decreased during lactation. Litter size correlated positively with plasma PRL, adrenal weight and plasma corticosterone. No effect of litter size was observed on plasma T3, but rats with ten pups had lower plasma TSH, T4 and FT4 than rats with a five-pup litter. Compared with dioestrous rats, lactating rats showed an increased hypothalamic proTRH mRNA content on day 2, but not on days 8 and 15 of lactation. Median eminence TRH in lactating rats gradually increased until day 15 and decreased thereafter. Acute suckling, after a 6-h separation of mother and pups, rapidly increased plasma PRL and corticosterone in the mothers, but had no effects on plasma TSH and thyroid hormone levels. Hypothalamic proTRH mRNA increased twofold after 0.5 h of suckling, and then gradually returned to presuckling values after 6 h. Compared with sham-operated rats, corticosterone-substituted ADX rats with ten pups had increased plasma PRL and TSH, hypothalamic proTRH mRNA and pituitary TSH beta mRNA on day 15 of lactation. Moreover, while acute suckling did not enhance TSH release in sham-operated rats, it provoked not only PRL but also TSH release in corticosterone-substituted ADX dams. It is concluded that suckling exerts a rapid, positive effect on hypothalamic proTRH mRNA content. However, the concurrent enhanced adrenal activity has negative effects on hypothalamic proTRH gene expression resulting in a suppressed hypophysial-thyroid axis during lactation. While TRH appears to play a role in PRL release during the first days of lactation and during acute suckling, TRH seems not important in maintaining PRL secretion during continued suckling.

Adrenalectomy↗

PubMed1996

Towards a rational terminology in the study of the gubernaculum testis: arguments in support of the notion that the cremasteric sac should be considered the gubernaculum in postnatal rats and other mammals.

There is need for a consistent definition of structures caudal to the testis that variously are termed 'gubernaculum testis' as a basis for understanding the emergence and sexually dimorphic further growth and differentiation of this specifically mammalian structure. Rodent fetuses undergo a stage of development during which there is almost complete unanimity as to the definition of the 'gubernaculum' as a papilla-like structure (often called conus inguinalis) protruding from the area of the internal inguinal ring. This structure shows at least 3 readily distinguishable components before birth. Postnatally, the papilla-like gubernaculum starts to undergo inversion to become the tunica of the sac-like processus vaginalis. The 3 components of the fetal gubernaculum develop further uninterruptedly, but with a different spatial arrangement, as parts of the wall of a sac rather than as parts of a papilla-like structure. Comparison of this process in rodents with that in other mammals (pig, horse, man) revealed an essentially identical emergence of a papilla-shaped gubernaculum with similar constituents. Initial development of the processus vaginalis also began with the inversion of the gubernacular papilla. Cattle fetuses appeared exceptional as outgrowth of the processus vaginalis occurred without a preceding papilla-shaped gubernaculum in the area of the inner inguinal ring. The findings lead to the following conclusions. (1) In rodents, the whole of the postnatally developing processus vaginalis, including therefore its cremasteric muscles but without the attached genital mesentery, is to be viewed as the male postnatal gubernaculum. Sexual differentiation of the gubernacular primordia includes a sex-specific effect on the morphogenesis of all constituents of the processus vaginalis sac including cremasteric muscle cells. (2) Gubernacular growth and differentiation appear essentially a uniform process throughout the placentalia mammalian class; only quantitative differences occur in the extent of initial development of an intra-abdominal conus inguinalis and later cremaster muscles.

Animals↗

PubMed1996

Bilateral cryptorchidism in a dog with persistent cranial testis suspensory ligaments and inverted gubernacula: report of a case with implications for understanding normal and aberrant testis descent.

The genital system of a dog with bilateral intra-abdominal testes is described. External virilisation was normal except for an empty scrotum. Internally there was a prostate of normal macroscopic and histological appearances and, bilaterally, a fully developed male genital tract. Testicular vasculature was normal. Cranial to each testis, there was a strong ligament lying at the free edge of the gonadal/genital mesentery and running between the cranial tip of the testis/epididymis and the area craniolateral of the ipsilateral kidney. It was impossible to push the testes into the inguinal canal because of this strong ligament. Caudal to each testis, there was an elongated whitish structure between the caudal pole of the epididymis and the area of the internal inguinal ring. On closer inspection this structure appeared to be the inverted and elongated processus vaginalis sac. There was a minor ligament at the free border of the inguinal fold of the genital mesentery between the tip of this inverted processus vaginalis and the adjacent junction of the cauda epididymidis and vas deferens. The findings suggest that persistence of the fetal cranial gonadal suspensory ligaments could have been the major aetiological factor in this case of cryptorchidism. Their persistence could have prevented caudal outgrowth of the processus vaginalis with its consequent development into an intra-abdominal papilla-like structure. Inappropriate persistence of the cranial suspensory ligaments in male rodents, pig, and cattle has been associated with insufficient exposure of their primordia to androgen during fetal life. It is uncertain whether a similar deficiency could underlie persistence of these structures in the present specimen. The findings add further weight to the hypothesis that regression of the cranial gonadal suspensory ligament in males is a key event in the process of testis descent. The human homologue of this ligament deserves more attention in the analysis and treatment of human cryptorchidism.

Animals↗

PubMed1995

Developmental pattern and regulation by androgens of androgen receptor expression in the urogenital tract of the rat.

Distribution and regulation of androgen receptor expression during fetal and neonatal virilization of the rat fetus was assessed by immunohistochemistry. In mesonephric duct derivatives the androgen receptor expression became evident first in the efferent ductules and epididymis (on fetal day 14), subsequently in the vas deferens and finally in the seminal vesicle. Mesenchymal cells of the urogenital tubercle were positive for androgen receptors from fetal day 14 onwards. In the mesenchymal cells of the prostate anlagen, androgen receptor positive cells were found first on fetal day 16. Administration of 5alpha-dihydrotestosterone to pregnant rats from day 11 to day 20 of gestation caused a stabilization of the wolffian duct in female fetuses. The androgen receptor expression pattern became similar as found in mail fetuses, and showed an increase in density and in frequency of androgen receptor positive cells. Administration of the androgen antagonist flutamide during the same interval caused a reduction in density and frequency of androgen receptor positive cells in male fetuses. These findings indicate that androgens enhance the expression of androgen receptors in the developing rat genital tract by induction of androgen receptor positive cells, and by increasing the frequency. The developmental pattern of androgen receptor expression in the rat mesonephric duct system reflects the androgen-responsiveness of the ducts, and is consistent with induction of the androgen receptor along the ducts by testosterone reaching these structures in an exocrine fashion.

Androgen Antagonists↗

PubMed1995

Development of the gubernaculum and processus vaginalis in freemartinism: further evidence in support of a specific fetal testis hormone governing male-specific gubernacular development.

BACKGROUND: Freemartinism occurs in some species of ruminants and affects most female bovine fetuses in heterosexual, multiple pregnancies owing to fusion of the chorionic blood circulations soon after implantation. Maldevelopment of the ovaries and Müllerian ducts have been described and recognized as resulting from exposure of their respective primordia to an excess of anti-Müllerian hormone. The present study aimed to analyse the prenatal growth and development of the gubernaculum in freemartins to find out its possible affliction through foetal testis hormones derived from their male co-twin. METHODS: Histological sections of young and drawings and photographs of further developed freemartins and control male and female bovine foetuses were analysed. The specimens had been collected earlier for analysis of the time course of male and female gonadal and genital development and its impairment associated with freemartinism. RESULTS: The gubernaculum of 35-40-day-old male and female fetuses was in the initial stage of development and of similar appearance in all specimens. Gubernacula of 60-70-day-old male fetuses differed from those of females of similar age in various respects: the male gubernaculum size was larger and extension of the processus vaginalis was deeper. Freemartins showed an intermediate development with some individuals resembling male and others resembling female agemates. During further development, gubernacula in males developed into muscular cremaster sacs, whereas those in females generally did not develop beyond the size and structural complexity of 70-day-old foetuses. Beyond day 70 of fetal life, gubernaculum development in freemartins definitely showed male characteristics with respect to size and growth of a processus vaginalis with a cremaster muscular wall. The male-like pattern of the outgrowth of the processus vaginalis changed during the second half of prenatal life. Rather than its further deepening as in males, this structure became inverted to become emerging as a papilla-like structure from the inguinal abdomen bottom. An explanation is proposed for this unprecedented inversion, taking into account: (1) the faster and higher reaching rightsided ascent of the kidneys and gonads, (2) the femalelike outgrowth of the cranial gonadal suspensory ligaments, and (3) the absence of scrotum development. The ovaries and mesonephric remnants in developing freemartins, during their ascent together with the kidneys while remaining attached to the bottom of the developing processus vaginalis sacs via the gubernaculum ligament, are proposed to act together to pull up the bottom of the processus vaginalis sacs. From this action, "inverted hernia sacs" result as the irreversible consequence. CONCLUSION: The data support the concept that foetal testes act, via as an yet unidentified third hormone, to establish malelike development of gubernacula into muscular cremaster sacs. Further work is required to reveal the identity of this hormone. Furthermore, the apparent similarity of the freemartins' inverted processus vaginalis sacs and the fetal rodents' gubernacular cones suggests that the ruminants' and rodents' processus vaginalis are essentially similar structures. Thus there is no longer an urgent need to distinguish between two different types of gubernaculum development and testis descent in rodents and ruminants, respectively, and involving or not fetal gubernacular cones. The present observations may thus contribute to the development of a unified hypothesis for sexually dimorphic development of the gubernaculum throughout the mammalian class.

Androgens↗

PubMed1995

Studies on the fetal development of the gubernaculum in cetacea.

BACKGROUND: Adult cetacean males, like non-mammalian vertebrates and other testicond mammals, have intra-abdominal testes. There is no evidence of a processus vaginalis in them. Testicondia in cetaceans is considered secondary as they are judged, evolutionarily, the descendants of terrestrial mammals (ungulates) with testis descent. A possible argument in support of the latter contention would be that cetacean fetuses develop gubernacula which are the primordia of the processus vaginalis and other structures associated with testis descent in other placental mammals. The present study intended to analyse cetacean fetuses in this respect. METHODS: Serial sections of 25 fetuses (total body length between 39.5 and 160 mm) of 4 cetacean species (Delphinus delphis, Phocoena phocoena, Eschrichtius robustus, Physeter catodon) were examined with special attention to the presence or absence of structures homologous to the gubernaculum of other placental mammals (rats and humans). RESULTS: Gubernacular primordia were observed in fetuses from about the time of onset of sexual differentiation. Their shape and anatomical relationship with the surrounding structures were similar as those in mammals with testis descent. The gubernaculum in males developed into a large mass of dense connective tissue in the ventral-caudal abdominal region at the site of the insertion of the mesonephric inguinal ligament and associated to the tip of the internal abdominal oblique muscle. No (or only very little) development of a processus vaginalis was noticed. CONCLUSIONS: The results demonstrate initial emergence of mammalian-like gubernacular primordia in cetacean fetuses without their further development to elaborate structures required for testis descent. The findings support the view that cetaceans are secondarily testicond. It is suggested that (1) absence of the pelvic girdle together with (2) the development of structures in and beyond the caudal abdominal region, particularly the caudal hypaxial musculature, precludes the outgrowth, into caudal direction, of hollow organs (such as the processus vaginalis) from the abdominal cavity.

Animals↗

PubMed1995

Effect of constant light on parturition and postpartum reproduction in the rat.

Light-dark (LD) cyclicity contributes to a number of reproductive events in the rat, including estrus cyclicity, and the timing of parturition and postpartum estrus. Constant light (LL) disrupts the female's cyclicity, and fertility is typically diminished. To ascertain whether constant light similarly diminishes the fertility of postpartum females, LL and LD animals were compared over three successive pregnancies on several reproductive measures including parturition, postpartum estrus and spontaneous ovulation, the timing of estrus relative to parturition, and the number, body weights, and viability of offspring. While the 24 h pattern of parturition differed for LL and LD groups, postpartum estrus and ovulation occurred reliably in both groups. The LD group showed greater variation in the birth-estrus interval, the result of a delayed estrus in those females giving birth late in the light phase. The likelihood of spontaneous ovulation and overall successful reproduction was high for both groups. Thus, unlike the cycling female, the fertility of the postpartum female is relatively unaffected by constant light. As such, these findings suggest that LD cyclicity is not critical for postpartum ovulation and estrus.

Animals↗

PubMed1995

Luteolytic and antiluteolytic effect of the antiprogestagen RU486 in pseudopregnant rats.

To study the effects of the antiprogestagen RU486 on luteal activity in pseudopregnant rats, adult female rats made pseudopregnant by sterile copulation were given daily injections with oil vehicle or with RU486 (2 mg/day) either during the entire period of pseudopregnancy (day 1 till day 14) or during the second half of pseudopregnancy (day 8 till day 14). Blood was taken every other day to measure serum concentrations of progesterone. At autopsy, on day 15, the weights of ovaries, isolated corpora lutea and pituitary glands were recorded. In a second study using the same experimental protocol, blood was taken via a jugular vein cannula on days 8, 9, 10 and 11 after induction of pseudopregnancy; on each of these days blood samples were taken at 0700, 0800 and 0900 h, and at 1700, 1800 and 1900 h to measure plasma concentrations of prolactin, LH and progesterone. Administration of RU486 from day 1 of pseudopregnancy onwards had no effect on the increasing concentrations of serum progesterone during the first half of pseudopregnancy. Thereafter progesterone concentrations of serum progesterone during the first half of pseudopregnancy. Thereafter progesterone concentrations increased further in RU486-treated rats whereas they decreased in oil-treated pseudopregnant rats. Administration of RU486 from day 8 of pseudopregnancy onwards resulted in a decline in progesterone concentrations in serum on day 10 followed by ovulation on day 11. Plasma LH concentrations in rats treated with RU486 from day 1 of pseudopregnancy were higher than those in oil-treated rats on days 8, 9, 10 and 11.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Perinatal development of gubernacular cones in rats and rabbits: effect of exposure to anti-androgens.

In male rats gubernacular cones develop during the latter half of prenatal life. Inversion of these papilla-like organs after birth is the first step to postnatal growth of the muscular cremaster sacs. The factors regulating prenatal growth and differentiation or postnatal inversion of these gubernacular cones are unknown. The lack of a detailed and unequivocal description of the normal gubernacular cone growth is judged at least partially responsible for this ignorance. The present study therefore describes the normal development of the gubernacular cones in male and female rats from day 14 of fetal life. Androgens are hypothesized to control male gubernacular cone development but recent evidence throws doubt upon this proposal. Therefore, the second part of this study describes perinatal development of gubernacular cones in male rat foetuses exposed to the anti-androgen flutamide from day 10 after conception. Quantitatively normal growth occurred prior to birth, indicating no role of androgen in this process. Excessive growth in length was noticed during the neonatal period together with delay of gubernacular cone inversion. These developmental alterations did not represent direct anti-androgen-induced modifications of gubernacular cones development as the alterations were not observed in flutamide-exposed neonatally castrated animals. Failure of androgens to affect directly perinatal gubernacular cone growth could represent a rat-specific feature. Fetal rabbits show the development of similar structures during the second half of fetal life.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

The name cranial ovarian suspensory ligaments in mammalian anatomy should be used only to indicate the structures derived from the foetal cranial mesonephric and gonadal ligaments.

The term ovarian suspensory ligament appears ambiguous when human adult anatomy textbooks are compared with human embryology or with general mammalian anatomy textbooks. The term ovarian suspensory ligament in laboratory rodents and domestic animals indicates homologous structures during foetal (the cranial mesonephric and gonadal ligaments) and later life (the cranial mesonephric ligament derivatives). In human foetal anatomy textbooks ovarian suspensory ligament is generally applied to this same ligament. However, in human adult anatomy textbooks ovarian suspensory ligament is widely applied to the part of the (uterine) broad ligament which contains the uterine and ovarian blood and lymphatic vessels and nerves. This inconsistency in human anatomy books raises confusion on the nature of the foetal and adult ovarian suspensory ligaments and inconsistencies in the description of the normal anatomical relationships of the ovaries between humans and other mammals. For the proper understanding of normal gonadal growth and development within the abdomen, it is important to maintain a consistent nomenclature of the cranial ovarian structures. The current practice in veterinary and other mammalian textbooks offers a solid point of departure.

Animals↗