Poissons, grenouilles, femmes et hommes: the appropriation and retention of archetypal systems for reproduction

In contradistinction to other biological systems, the reproductive mechanisms in sexually reproducing species are unique in that their success relies upon a synchronous interaction between two separate individuals. Reproduction has become increasingly more efficient as higher forms have developed internal fertilization and gestation. Although our anthropomorphic perspective has dominated the understanding of reproductive processes, 'recent discoveries' make it clear that this reproductive efficiency has been gained by retention of previously present biological mechanisms whose origins are in the vestigial excretory tracts and ducts which are the precursors of the reproductive tract. We refer to these as 'archetypal systems'. They include the interaction between sex steroid sensitive tissues and sex steroids, the renin-angiotensin system and the macrophage/monokine response to infection. Through these mechanisms the reproductive tracts have maintained control over the microenvironment in which the reproductive processes occur. Thus, gamete development in male and female, and fertilization and early embryonic existence in the female tract prior to implantation still occur in compartments which are extracorporeal, i.e., separated from blood or subendothelial spaces, and are controlled by cellular mechanisms found in ancient excretory tracts. Since the majority of the changes between lower forms and contemporary mammals are anatomical modifications which have favoured the success of these extracorporeal events within the developing, generally land-based mammals, we should take special note of lower animals, understanding the evolutionary appropriation of mechanisms designed to furnish the suitable microenvironment from the surrounding tissues.(ABSTRACT TRUNCATED AT 250 WORDS)     

精子获能与激素调节作用

精子获能的发现和体外获能的成功是体外受精的基础。有关精子体内和体外获能的实质及获能机制 ,以及存在于雌性生殖道或精浆中的激素包括雌激素、孕酮、催乳素和前列腺素及肽类生长因子如表皮生长因子 ( EGF)、受精促进肽 ( FPP)、白细胞介素 ( IL)等对精子获能的作用已有较多的研究报道 ,这些研究将进一步推动体外受精在人类辅助生殖和动物繁殖中的应用     

On sexual behavior and sex-role reversal

Sex is not about reproduction; sex is about (re-)combination of DNA. Sex, not reproduction, always involves physical contact between two individuals; to achieve this, strategies of sexual behavior evolved. Sexual behavior, therefore, did not evolve as part of a reproductive strategy, but evolved to enable exchange of genetic material. In multicellular organisms the situation is more complicated than in unicellular organisms, as it is impossible for each cell within a multicellular body to have sex with another cell. Hence, evolution selected a system in which the possibility to have sex was limited to only one cell-line: the germ cells. As a result, sex adopted the character of fertilization, and sex and reproduction became inseparably linked. Still, in some species, including humans, sexual behavior still exhibits features of its evolutionary past: in humans (like in bonobo's) most sexual activity and many sexual behavioral patterns have nothing to do with reproduction (masturbation, homosexual behavior, for example); in humans, sexual behavior also became associated with other strategic objectives, such as intensifying the pair bond, expression of love or power. Different genders – male and female – evolved, and each gender evolved typical gender-related sexual and reproductive strategies as well. In most multicellular species, these strategies became inextricably mixed, and sexual behavior increasingly more – and in most species even exclusively – ‘served’ the interests of reproduction: sexual behavior became more or less synonymous with reproductive behavior. In most species, the ‘mix’ of sexual and reproductive strategies evolved into typical gender-related patterns of behavior, that is, in typical ‘sex-roles’. Often, males are bigger and more ‘beautiful’ (?= more intensely ornamented) than females; males compete with each other for access to females; males court females, while females choose males (‘female choice’). However, ecological circumstances may cause a reversal of sex-roles, resulting in a situation in which females are bigger and more intensely ornamented than males, females compete for access to males, females court males and only males invest in care for the young, provided they are relatively certain of their paternity. Also, as in the case of the spotted hyena, females may be highly virilized and be socially dominant. This ‘sex-role reversal’ is seen, e.g., when males are relatively rare due to high predation pressure, or when the process of reproduction is very risky for the same reason: then it is ‘better’ that males, with their plenty of sperm, are wasted, than females with their few, precious eggs. It can be argued, with women being the fair sex, exhibiting competitive behavior and with an actively displaying courtship, and with men investing heavily in their offspring, meanwhile taking all (cultural) kinds of measures to guarantee their paternity, that humans, too, exhibit some degree of sex-role reversal.     

Sexual Arousal by Higher‐ and Lower‐Ranking Partner: Manifestation of a Mating Strategy?

BackgroundHigh hierarchical status is associated with increased reproduction success in mammals. However the subordinate males are not totally eliminated from reproduction due to mate choice and alternative male strategies. Thus; the sexual arousal by higher‐ranking or lower‐ranking partner in humans may represent a proximate mechanism for realizing a reproductive strategy.AimTo evaluate possible connection between mating strategy and sexual arousal by lower‐ranking and higher‐ranking partner.Materials and MethodsMarkers of possible reproductive success (the number and gender of relatives and self‐reported attractiveness) were evaluated by questionnaire‐based study on students (110 men and 195 women, aged 19 to 29, mean age 22.5 ± 2.10SD).Main Outcome MeasureThe correlation between markers of reproductive success and the sexual arousal by lower‐ and higher‐ranking partner.ResultsArousal by lower‐ranking partner correlated positively with proportion of males in relatives (Spearman's r, males: 0.219*; females: 0.161*) and with self‐reported attractiveness (males: r = 0.223*); arousal by higher‐ranking partner correlated positively with self‐attractiveness (females: r = 0.191*).DiscussionWe found markers of reproductive success despite of reduced number of offspring in nowadays population.ConclusionThe sexual arousal by lower‐ and/or higher‐ranking partner appears to be a manifestation of a successful reproductive strategy, e.g. behavior connected to natural human behavior. Moreover, the sexual arousal by overemphasized hierarchy (e.g. dominant‐slave play) considered to be a part of sadomasochistic sex (or so called BDSM) may represent an overemphasised manifestation of this reproductive strategy. *P < 0.05. Jozifkova E, and Konvicka M. Sexual arousal by higher‐ and lower‐ranking partner: Manifestation of a mating strategy?     

Increased prevalence of sexually transmitted viral infections in women: the role of female sex hormones in regulating susceptibility and immune responses

Sexually transmitted infections (STIs) caused by viruses, including HSV-2, HIV-1, HPV, are among the most prevalent infectious diseases worldwide and a major cause of morbidity and mortality. Despite decades of effort, the attempts to develop efficacious vaccines against viral STIs have failed repeatedly, with the exception of the recent HPV vaccine. Given the higher prevalence rates of STIs in women, it is becoming clear that a better understanding of gender-specific differences in STIs may be critical for the development of preventative strategies for these diseases. In order to gain this insight, it is important to examine the distinct microenvironment of the female reproductive tract, the site of primary infection, since it can significantly influence the outcome of infection. An important biological factor in the female reproductive tract is the presence of female sex hormones, estrogen and progesterone, which are produced endogenously primarily by the ovaries and commonly provided exogenously via the use of hormonal contraceptives. Here we review our current knowledge of the role played by the female sex hormones in regulating susceptibility and immune responses to viral sexually transmitted infections and whether this could contribute to higher prevalence of STIs in women. Manipulating the microenvironment of the female genital tract with sex hormones may contribute to the development of improved immunization strategies against sexually transmitted infections.     

MUC1/episialin: a critical barrier in the female reproductive tract

The female reproductive tract must resist microbial infections as well as support embryonic development, implantation and placentation. Reproductive tract mucins, in general, and Muc1/episialin, in particular, play key roles in implantation related events and in protection from microbial infection. High levels of mucin expression in the lower reproductive tract presumably affords protection against infection while down-regulation of uterine mucins has been suggested to provide access to the uterine surface. The present studies demonstrate that mucins, particularly Muc1, are effective barriers to embryo attachment. Furthermore, a strain of female Muc1 null mice in normal housing displays chronic infection and inflammation of the lower reproductive tract and markedly reduced fertility rates. This phenotype is not observed when Muc1 nulls are housed in a pathogen-free environment indicating that this phenotype results from chronic microbial exposure. Only normal endogenous flora were isolated from the reproductive tracts of affected Muc1 null mice, suggesting that these bacterial species become opportunistic with loss of the mucin barrier. Staphylococcal adherence to lower reproductive tract epithelia was found to be mediated by cell surface mucin carbohydrates. Collectively, these studies demonstrate a critical barrier role for Muc1 in various aspects of female reproductive tract physiology.     

Peritoneal fluid environment and infertility

The PF environment is one that hosts the processes of ovulation, gamete transportation, fertilization, and early embryonic development. The cellular and acellular constituents of this dynamic fluid are in a constant interactive state, being influenced by the physiologic events of the menstrual cycle and pelvic disease processes; these constituents probably influence disease manifestation and reproduction. The importance of understanding this zone of early reproductive life has been now recognized. We hope that future investigations will define the exact role(s) of known components and some yet-to-be defined substances of PF in disease processes that affect reproductive function. With better understanding of normal and abnormal events in this pelvic microenvironment, we can develop rationales for novel treatment modalities.     

The oviductal cilia and Kartagener's syndrome

Women who have Kartagener's syndrome (primary ciliary dyskinesia) may or may not be fertile. The bronchial mucociliary clearance is reduced markedly in most of these women; this has led investigators to the conclusion that the cilia in the respiratory tract are immotile, and that "beating cilia may have no indispensable role in the female reproductive tract." Yet motile cilia are considered by many workers to be essential for normal ovum transport. More recently, bizarre ciliary motion has been described in the respiratory cilia of Kartagener's women. Our hypothesis was that the dyskinetic ciliary activity (or immotility) would be the same in both the respiratory and reproductive tracts and thus explain the fertility (or lack of it) in Kartagener's women. This report shows an identical ultrastructure and absolute immotility of cilia in both the respiratory tract and reproductive tract of a woman with Kartagener's syndrome who has never conceived. From this concordance, we suggest that the fertility of Kartagener's women is explained by the dyskinetic motion of oviductal cilia, and that the ciliated endosalpinx is essential for human reproduction.     

Polyspermy prevention: facts and artifacts?

The purpose of this review is to open a debate as to whether or not oocytes actively repel supernumerary sperm or in nature final sperm : oocyte ratios are so low that polyspermy preventing mechanisms are not necessary. Before encountering the oocyte, spermatozoa need to be primed, either by environmental factors as in animals exhibiting external fertilization, or by factors from the female reproductive tract, as in mammals. The spermatozoon must then recognize and interact with the outer layers of the oocyte and progression of the fertilizing spermatozoon through these layers is further controlled and modulated by a precise sequence of signals in situ. Removal of these outer coats may not inhibit fertilization, however does interfere with the dynamics of sperm-oocyte interaction. We propose that monospermy in mammals and sea urchins, under natural conditions, is ensured by the controlled and gradual encounter of a minimum number of spermatozoa with the oocyte and that fine tuning is ensured by the structural and molecular organization of the oocyte and its surrounding coats. We suggest that laboratory experiments using oocytes deprived of their investments and exposed to unnaturally high concentrations of spermatozoa are artifactual and argue that the conclusions leading to the hypothesis of a fast electrical block to polyspermy are unfounded. Under laboratory conditions the majority of spermatozoa, although motile and capable of attaching to the oocyte surface, are either physiologically incompetent or attach to areas of the oocyte surface that do not support entry.     

Medical, legal and ethical aspects of fertility preservation in cancer survivor

In recent years the number of the young women in fertile age which are oncologically treated is increasing. For these women chemotherapy and radiotherapy introduces potential risk of reproductive dysfunctions. Present techniques of assisted reproduction are offering possibilities to save reproductive functions even after the oncological treatment. As a perspective outlook seems to be frozen premature oocytes with IVM and fertilisation. With these fertility savings methods are naturally coming up some of the ethical and legal issues.     

Male reproductive proteins and reproductive outcomes

Male reproductive proteins (MRPs), associated with sperm and semen, are the moieties responsible for carrying male genes into the next generation. Evolutionary biologists have focused on their capacity to control conception. Immunologists have shown that MRPs cause female genital tract inflammation as preparatory for embryo implantation and placentation. These observations argue that MRPs are critically important to reproductive success. Yet the impact of male reproductive proteins on obstetrical outcomes in women is largely unstudied. Epidemiologic and clinical observations suggest that shorter-duration exposure to MRPs prior to conception may elevate the risk for preeclampsia. A limited literature has also linked sexual behavior to bacterial vaginosis and preterm birth. We offer a clinical opinion that MRPs may have broad implications for successful reproduction, potentially involved in the composition of vaginal microflora, risks of preterm birth and preeclampsia, and success of assisted reproduction.     

Sperm competition in mammals

Although Darwin identified the evolutionary significance of competition between males in the context of reproduction, it is only in the past few decades that we have begun to appreciate the importance of competition at the gametic level. Sperm competition, defined as competition between the sperm of two or more males for fertilization of the same set of ova, is now recognised as a key selective force shaping male reproductive anatomy, physiology and behaviour across diverse animal groups, including mammals. The aim of this article is to provide a brief review of the selective consequences of sperm competition in mammals, with emphasis on recent theoretical advances and empirical controversies. Evidence of female influences on sperm competition outcomes in mammals is also discussed, and it is concluded that understanding the selective pressures driving coevolution between male and female reproductive traits remains a major challenge for researchers in this field.     

Sperm competition in mammals

Although Darwin identified the evolutionary significance of competition between males in the context of reproduction, it is only in the past few decades that we have begun to appreciate the importance of competition at the gametic level. Sperm competition, defined as competition between the sperm of two or more males for fertilization of the same set of ova, is now recognised as a key selective force shaping male reproductive anatomy, physiology and behaviour across diverse animal groups, including mammals. The aim of this article is to provide a brief review of the selective consequences of sperm competition in mammals, with emphasis on recent theoretical advances and empirical controversies. Evidence of female influences on sperm competition outcomes in mammals is also discussed, and it is concluded that understanding the selective pressures driving coevolution between male and female reproductive traits remains a major challenge for researchers in this field.     

On sexual behavior and sex-role reversal

Sex is not about reproduction; sex is about (re-)combination of DNA. Sex, not reproduction, always involves physical contact between two individuals; to achieve this, strategies of sexual behavior evolved. Sexual behavior, therefore, did not evolve as part of a reproductive strategy, but evolved to enable exchange of genetic material. In multicellular organisms the situation is more complicated than in unicellular organisms, as it is impossible for each cell within a multicellular body to have sex with another cell. Hence, evolution selected a system in which the possibility to have sex was limited to only one cell-line: the germ cells. As a result, sex adopted the character of fertilization, and sex and reproduction became inseparably linked. Still, in some species, including humans, sexual behavior still exhibits features of its evolutionary past: in humans (like in bonobo's) most sexual activity and many sexual behavioral patterns have nothing to do with reproduction (masturbation, homosexual behavior, for example); in humans, sexual behavior also became associated with other strategic objectives, such as intensifying the pair bond, expression of love or power. Different genders - male and female - evolved, and each gender evolved typical gender-related sexual and reproductive strategies as well. In most multicellular species, these strategies became inextricably mixed, and sexual behavior increasingly more - and in most species even exclusively - 'served' the interests of reproduction: sexual behavior became more or less synonymous with reproductive behavior. In most species, the 'mix' of sexual and reproductive strategies evolved into typical gender-related patterns of behavior, that is, in typical 'sex-roles'. Often, males are bigger and more 'beautiful' (= more intensely ornamented) than females; males compete with each other for access to females; males court females, while females choose males ('female choice'). However, ecological circumstances may cause a reversal of sex-roles, resulting in a situation in which females are bigger and more intensely ornamented than males, females compete for access to males, females court males and only males invest in care for the young, provided they are relatively certain of their paternity. Also, as in the case of the spotted hyena, females may be highly virilized and be socially dominant. This 'sex-role reversal' is seen, e.g., when males are relatively rare due to high predation pressure, or when the process of reproduction is very risky for the same reason: then it is 'better' that males, with their plenty of sperm, are wasted, than females with their few, precious eggs. It can be argued, with women being the fair sex, exhibiting competitive behavior and with an actively displaying courtship, and with men investing heavily in their offspring, meanwhile taking all (cultural) kinds of measures to guarantee their paternity, that humans, too, exhibit some degree of sex-role reversal.     

Oxidative stress and redox regulation of gametogenesis,fertilization, and embryonic development

Oxidative stress caused by elevated reactive oxygen species (ROS) is one of the predominant causes of both male and female infertility. Oxidative stress conditions cause either cell death or senescence by oxidation of cellular molecules including nucleic acid, proteins, and lipids. It is particularly important to minimize oxidative stress when in vitro fertilization is performed for the purpose of assisted reproduction. The problems associated with assisted reproductive technology are becoming evident, and it is now the time to clarify its mechanisms and cope with them. On the other hand, the beneficial roles of ROS, such as intracellular signaling, have become evident. The antithetical functions of ROS make it more difficult to overcome the problems caused by oxidative stress. Despite the difficulty in understanding mammalian reproduction, the mechanisms and problems can be gradually unveiled by advanced technology such as genetic modification of animals.     

The origins of human sexuality: procreation or recreation?

Human sexuality has multiple meanings, although reproduction is considered the focus of sexual activity. In spite of this, human sexuality began to lose its exclusive reproductive meaning very early in the evolution of the genus Homo and, with a concealed ovulation and a female accessible to the male during the entire menstrual cycle, the need became that of avoiding, rather than seeking conception during intercourse. The ‘contraceptive revolutions’ of the 20th century (sex without reproduction, reproduction without sex, reproduction in menopause and, one day, reproduction without gametes) are having a major impact on the lives of individual couples and women. At the same time, this tumultuous progress drew the attention of religious moralists, since ethics have always focused on sexuality and its moral regulation. Catholic ethicists have been at the forefront of the battle against ‘dehumanizing’ the reproductive process, whereas Judaism took a much more open position. Early Christian teaching on sexuality, focused on abstinence; this is because Christ himself defined celibacy as a better life choice for human beings. Drawing on this basis, early Church fathers developed the concept, upheld until the 20th century, that intercourse is totally justifiable only in order to procreate. Today, some cautious overtures are being made and the Church has recognized that sexuality can be expression of conjugal love independent from procreation.     

Innate and adaptive immunity at mucosal surfaces of the female reproductive tract: stratification and integration of immune protection against the transmission of sexually transmitted infections

This review examines the multiple levels of pre-existing immunity in the upper and lower female reproductive tract. In addition, we highlight the need for further research of innate and adaptive immune protection of mucosal surfaces in the female reproductive tract. Innate mechanisms include the mucus lining, a tight epithelial barrier and the secretion of antimicrobial peptides and cytokines by epithelial and innate immune cells. Stimulation of the innate immune system also serves to bridge the adaptive arm resulting in the generation of pathogen-specific humoral and cell-mediated immunity. Less understood are the multiple components that act in a coordinated way to provide a network of ongoing protection. Innate and adaptive immunity in the human female reproductive tract are influenced by the stage of menstrual cycle and are directly regulated by the sex steroid hormones, progesterone and estradiol. Furthermore, the effect of hormones on immunity is mediated both directly on immune and epithelial cells and indirectly by stimulating growth factor secretion from stromal cells. The goal of this review is to focus on the diverse aspects of the innate and adaptive immune systems that contribute to a unique network of protection throughout the female reproductive tract.     

Dysplasia of the lower genital tract in the female monkey, Macaca fascicularis, the crab-eating macaque from Southeast Asia

Seventy-eight female reproductive tracts from mature Macaca fascicularis caught in the wild were examined histologically for evidence of dysplasia in inmature (metaplastic) and native (mature) squamous epithelium of the cervix and vagina. This series contained equal numbers of experimental animals and control and/or breeding colony animals. Five of 39 experimental animals showed dysplasia, whereas six animals with definite and two with questionable dysplasia were found in 39 control and breeding colony animals. On the basis of the foregoing facts, it would appear that these dysplastic lesions were of spontaneous origin and of undetermined etiology. Therefore, those investigators who experiment upon the reproductive tract of this species of monkey should be wary of interpreting any given experiment as “causing” dysplasia. Monkeys of this same species, born and reared in our Primate Center, have been examined for comparable dysplastic lesions of the lower female genital tract. None was found thus far but the study is continuing.     

Role of activins in the male reproductive tract

The search for gonadal proteins that regulate pituitary FSH led to the isolation of inhibins and activins. As members of the transforming growth factor beta (TGFbeta) superfamily of growth and differentiation factors, these proteins have been shown subsequently to affect a range of tissues and systems beyond their role in reproduction. Studies on the expression and synthesis of activins in the male reproductive tract have localized these proteins in the testis, epididymis and prostate. In general, activins regulate cell proliferation and, consequently, the expression and localization of activin subunit mRNAs and proteins within these organs must be discrete. Activin ligand bioactivity is dependent on the presence of the appropriate receptors and signalling systems, but activin ligand formation or access to receptors is regulated by the formation of inhibins or by activin-binding proteins such as follistatin. This review examines the evidence that the capacity to synthesize activins and to regulate activin bioactivity resides in the cells of the male reproductive tract. It is concluded that activins exert their effects through local (autocrine or paracrine) mechanisms, rather than through endocrine systems. The interplay between the inhibins or follistatins provides a degree of regulation of activin bioactivity before ligand signalling events. The challenge for the future is to determine whether there is any difference between the action of individual activin ligands or whether these proteins are functionally redundant, indicating that compensatory mechanisms are essential for male reproductive tract function.