Hasil untuk "Reproduction"

A. Agarwal, Gurpriya Virk, C. Ong et al.

Infertility affects approximately 15% of couples trying to conceive, and a male factor contributes to roughly half of these cases. Oxidative stress (OS) has been identified as one of the many mediators of male infertility by causing sperm dysfunction. OS is a state related to increased cellular damage triggered by oxygen and oxygen-derived free radicals known as reactive oxygen species (ROS). During this process, augmented production of ROS overwhelms the body's antioxidant defenses. While small amounts of ROS are required for normal sperm functioning, disproportionate levels can negatively impact the quality of spermatozoa and impair their overall fertilizing capacity. OS has been identified as an area of great attention because ROS and their metabolites can attack DNA, lipids, and proteins; alter enzymatic systems; produce irreparable alterations; cause cell death; and ultimately, lead to a decline in the semen parameters associated with male infertility. This review highlights the mechanisms of ROS production, the physiological and pathophysiological roles of ROS in relation to the male reproductive system, and recent advances in diagnostic methods; it also explores the benefits of using antioxidants in a clinical setting.

A. Agarwal, Anamar Aponte-Mellado, B. Premkumar et al.

Oxidative stress (OS), a state characterized by an imbalance between pro-oxidant molecules including reactive oxygen and nitrogen species, and antioxidant defenses, has been identified to play a key role in the pathogenesis of subfertility in both males and females. The adverse effects of OS on sperm quality and functions have been well documented. In females, on the other hand, the impact of OS on oocytes and reproductive functions remains unclear. This imbalance between pro-oxidants and antioxidants can lead to a number of reproductive diseases such as endometriosis, polycystic ovary syndrome (PCOS), and unexplained infertility. Pregnancy complications such as spontaneous abortion, recurrent pregnancy loss, and preeclampsia, can also develop in response to OS. Studies have shown that extremes of body weight and lifestyle factors such as cigarette smoking, alcohol use, and recreational drug use can promote excess free radical production, which could affect fertility. Exposures to environmental pollutants are of increasing concern, as they too have been found to trigger oxidative states, possibly contributing to female infertility. This article will review the currently available literature on the roles of reactive species and OS in both normal and abnormal reproductive physiological processes. Antioxidant supplementation may be effective in controlling the production of ROS and continues to be explored as a potential strategy to overcome reproductive disorders associated with infertility. However, investigations conducted to date have been through animal or in vitro studies, which have produced largely conflicting results. The impact of OS on assisted reproductive techniques (ART) will be addressed, in addition to the possible benefits of antioxidant supplementation of ART culture media to increase the likelihood for ART success. Future randomized controlled clinical trials on humans are necessary to elucidate the precise mechanisms through which OS affects female reproductive abilities, and will facilitate further explorations of the possible benefits of antioxidants to treat infertility.

A. Agarwal, R. Saleh, M. Bedaiwy

Sourav Roy, Tusar Saha, Z. Zou et al.

Anthony F. C. Wallace

Despite its relative brevity, Walter Benjamin’s essay “The Work of Art in the Age of Mechanical Reproduction,” continues to inspire significant scholarly attention as a major work in the history of modern aesthetic and political criticism. The essay is credited with developing an insightful interpretation of the role technological reproduction plays in shaping aesthetic experience; more specifically, Benjamin catalogues the significant effects of film and photography on the decline of autonomous aesthetic experience. After fleeing the Nazi government in 1933, Benjamin moved to Paris, from where he published the first edition of “Work of Art” in 1936 (Brodersen XV). This publication appeared in French translation under the direction of Raymond Aron in volume 5, no. 1 of the Zeitschrift für Sozialforschung. Benjamin subsequently rewrote the essay and after editorial work by Theodore and Margarethe Adorno it was posthumously published in its commonly recognized form in his Schriften of 1955 (Wolin 183-4).

Robin A. Schwenke, B. Lazzaro, M. Wolfner

Sunil Kumar, Anupama Sharma

Abstract Background Cadmium (Cd) is a non-essential toxic heavy metal, an environmental toxicant, and toxic at a low concentration, and it has no known beneficial role in the human body. Its exposure induces various health impairments including hostile reproductive health. Objective The present review discusses the information on exposure to Cd and human reproductive health impairments including pregnancy or its outcome with respect to environmental and occupational exposure. Methods The present review provides current information on the reproductive toxic potential of Cd in humans. The data were collected using various websites and consulting books, reports, etc. We have included recent data which were published from 2000 onward in this review. Results Cd exposure affects human male reproductive organs/system and deteriorates spermatogenesis, semen quality especially sperm motility and hormonal synthesis/release. Based on experimental and human studies, it also impairs female reproduction and reproductive hormonal balance and affects menstrual cycles. Based on the literature, it might be concluded that exposure to Cd at low doses has adverse effects on both human male and female reproduction and affects pregnancy or its outcome. Further, maternal prenatal Cd exposure might have a differential effect on male and female offspring especially affecting more female offspring. Hence, efforts must be made to prevent exposure to Cd. Conclusion Cd affects both male and female reproduction, impairs hormone synthesis/regulation and deteriorates pregnancy rate or its outcome even at lower doses.

Quan-Hui Liu, M. Ajelli, A. Aleta et al.

Significance The analysis of real epidemiological data has raised issues of the adequacy of the classic homogeneous modeling framework and quantities, such as the basic reproduction number in real-world situations. Based on high-quality sociodemographic data, here we generate a multiplex network describing the contact pattern of the Italian and Dutch populations. By using a microsimulation approach, we show that, for epidemics spreading on realistic contact networks, it is not possible to define a steady exponential growth phase and a basic reproduction number. We show the operational use of the instantaneous reproduction rate as a good descriptor of the transmission dynamics. The basic reproduction number is one of the conceptual cornerstones of mathematical epidemiology. Its classical definition as the number of secondary cases generated by a typical infected individual in a fully susceptible population finds a clear analytical expression in homogeneous and stratified mixing models. Along with the generation time (the interval between primary and secondary cases), the reproduction number allows for the characterization of the dynamics of an epidemic. A clear-cut theoretical picture, however, is hardly found in real data. Here, we infer from highly detailed sociodemographic data two multiplex contact networks representative of a subset of the Italian and Dutch populations. We then simulate an infection transmission process on these networks accounting for the natural history of influenza and calibrated on empirical epidemiological data. We explicitly measure the reproduction number and generation time, recording all individual-level transmission events. We find that the classical concept of the basic reproduction number is untenable in realistic populations, and it does not provide any conceptual understanding of the epidemic evolution. This departure from the classical theoretical picture is not due to behavioral changes and other exogenous epidemiological determinants. Rather, it can be simply explained by the (clustered) contact structure of the population. Finally, we provide evidence that methodologies aimed at estimating the instantaneous reproduction number can operationally be used to characterize the correct epidemic dynamics from incidence data.

G. Childs, Angela K Odle, M. MacNicol et al.

A healthy nutritional state is required for all aspects of reproduction and signaled by the adipokine leptin. Leptin acts in a relatively narrow concentration range; too much or too little will compromise fertility. The leptin signal timing is important to prepubertal development in both sexes. In the brain, leptin acts on ventral premammillary (PMV) neurons which signal kisspeptin (Kiss1) neurons to stimulate gonadotropin releasing hormone neurons (GnRH). Suppression of Kiss1 neurons occurs when AgRP neurons are activated by reduced leptin, because leptin normally suppresses these orexigenic neurons. In the pituitary, leptin stimulates production of GnRH receptors (GnRHR) and follicle-stimulating hormone (FSH) at midcycle, by activating pathways that de-repress actions of the mRNA translational regulatory protein Musashi. In females, rising estrogen stimulate a rise in serum leptin, which peaks at midcycle, synchronizing with nocturnal Luteinizing hormone (LH) pulses. The normal range of serum leptin levels (10-20 ng/ml) along with gonadotropins and growth factors, promote ovarian granulosa and theca cell functions and oocyte maturation. In males, the prepubertal rise in leptin promotes testicular development. However, a decline in leptin levels in prepubertal boys reflects inhibition of leptin secretion by rising androgens. In adult males, leptin levels are 10-50% of those in females, and high leptin inhibits testicular function. The obesity epidemic has elucidated leptin resistance pathways with too much leptin in either sex leading to infertility. Under conditions of balanced nutrition however, the secretion of leptin is timed and regulated within a narrow level range that optimizes its trophic effects.

Elizabeth A. Levin, T. Bridges

Stefania Barca

Zhidong Cao, Qingpeng Zhang, Xin Lu et al.

We estimate the effective reproduction number for 2019-nCoV based on the daily reported cases from China CDC. The results indicate that 2019-nCoV has a higher effective reproduction number than SARS with a comparable fatality rate.

Jing Xu, M. P. Bernuci, M. Lawson et al.

Chemotherapy and radiation therapy often result in reduced fertility. Patients receiving gonadotoxic treatment should be informed of options for fertility preservation and future reproduction prior to such treatment. Reproduction in the context of cancer also raises a number of ethical issues related to the welfare of both patients and offspring. This document replaces the document titled, "Fertility preservation and reproduction in patients facing goandotoxic therapies," last published in 2013.

Jamie M Studer, Wesley P. Schweer, N. Gabler et al.

Manganese (Mn) is the twelfth most abundant element in the earth's crust and is widely distributed throughout the surface of the planet, naturally occurring in rocks, soil, water, and food. As an essential trace mineral in diets, Mn is required for a variety of metabolic functions including skeletal system development, energy metabolism, enzyme activation, nervous system function, immune system function, and reproductive hormone function. Manganese has effects on reproductive hormone function as a cofactor for enzymes necessary for cholesterol synthesis. Production of steroid hormones necessary for reproduction is dependent on the availability of cholesterol as a precursor. There is also evidence that Mn has effects on reproduction due to actions at the hypothalamus. Because Mn is used for manufacturing of steel, recent research has focused on the effects of Mn toxicity as a result of occupational endeavors rather than evaluating the optimal Mn inclusion rate for mammalian growth and development, reproductive function, immune function, etc. The objective of this review is to address the functions of Mn in reproduction of animals but there is also a focus on other areas of mammalian biology affected by Mn functions, with an emphasis on domestic swine (Sus scrofa).

Dwi Puspa Sukma Viranda, Rochmah Kurnijasanti, Kadek Rachmawati et al.

This study aims to determine the effect of porang (Amorphophallus oncophyllus) tuber extract on the histopathological features of the testicle of alloxan induced rats (Rattus norvegicus). Thirty male rats were randomly divided into six groups. Rats in group C- were injected with distilled water, while rats in groups C+, T0, T1, T2, and T3 were injected with 120 mg/kg bw alloxan. Blood glucose was measured three days after alloxan injection. Rats in groups C- and C+ were then administered with 1% Na-CMC, whereas rats in groups T0, T1, T2, and T3 were then administered with 45mg/kg bw metformin, and 100, 200, and 400 mg/kg bw of porang tuber extract, respectively. All solution were given orally once every day for 14 days. Spermatogenic activity was assessed using the Johnsen scoring system and analyzed by Kruskal-Wallis, followed by the Mann-Whitney test. The diameter and epithelial thickness of the seminiferous tubule were measured using image raster software and analyzed using Anova followed by Duncan's test. The results showed that spermatogenesis score, diameter, and epithelial thickness of seminiferous tubule of group C+ were smaller (p <0.05) than group C-. Spermatogenesis scores of groups T0, T1, T2, and T3 were higher (p <0.05) than group C+. Seminiferous tubule diameter and epithelial thickness in groups T0, T1, and T2 were greater (p <0.05) than group C+. It could be concluded that porang tuber extract at a dose of 200 mg/kg bw improved the spermatogenesis score, diameter seminiferous tubule, and thickness of the epithelium of diabetic rats.

Hadas Weiss

Social reproduction is a lens through which to analyse the persistence of society over time, even as its human and material components keep changing. Its main value is in identifying and explaining tensions that emerge between the logic that reproduces society, and the continued survival (biological reproduction) and wellbeing of the population. Its origins are in Karl Marx’s critique of capitalist society, as governed by a drive towards accumulation. Initially, anthropologists have sought inspiration from Marx in examining the reproduction of non-capitalist societies, but they have since largely joined adjacent disciplines in focusing on capitalism. Modern social reproduction theory has proceeded from blind spots in Marx’s analysis, primarily regarding the role of women and domestic work in maintaining current workers and non-workers. From there, it has expanded to examine other fault lines in the reproduction of capitalist society. Contemporary strands of social reproduction theory attend to crises that emerge with respect to care work and livelihoods as finance becomes the main motor of accumulation. They also underline ways in which the reproduction of society reproduces inequalities within it. For ethnographers, attention to social reproduction illuminates the entanglements of any chosen fieldsite and plights therein with broader dynamics of accumulation.

T. Garner, James Hester, A. Carothers et al.

Abstract Zinc is a critical component in a number of conserved processes that regulate female germ cell growth, fertility, and pregnancy. During follicle development, a sufficient intracellular concentration of zinc in the oocyte maintains meiotic arrest at prophase I until the germ cell is ready to undergo maturation. An adequate supply of zinc is necessary for the oocyte to form a fertilization-competent egg as dietary zinc deficiency or chelation of zinc disrupts maturation and reduces the oocyte quality. Following sperm fusion to the egg to initiate the acrosomal reaction, a quick release of zinc, known as the zinc spark, induces egg activation in addition to facilitating zona pellucida hardening and reducing sperm motility to prevent polyspermy. Symmetric division, proliferation, and differentiation of the preimplantation embryo rely on zinc availability, both during the oocyte development and post-fertilization. Further, the fetal contribution to the placenta, fetal limb growth, and neural tube development are hindered in females challenged with zinc deficiency during pregnancy. In this review, we discuss the role of zinc in germ cell development, fertilization, and pregnancy with a focus on recent studies in mammalian females. We further detail the fundamental zinc-mediated reproductive processes that have only been explored in non-mammalian species and speculate on the role of zinc in similar mechanisms of female mammals. The evidence collected over the last decade highlights the necessity of zinc for normal fertility and healthy pregnancy outcomes, which suggests zinc supplementation should be considered for reproductive age women at risk of zinc deficiency. Summary sentence An overview of the recent discoveries on the role of zinc in the reproductive processes of mammalian females including oogenesis, folliculogenesis, ovulation, maturation, fertilization, and pre- and post-implantation development.

G. Valsamakis, G. Chrousos, G. Mastorakos

Stress is one of the commonest and underappreciated causes of reproductive frailty in women. The stress system leads to adaptive responses via mobilization of hormonal systems. Adaptability and resistance to stress are fundamental to life. The response to stressors depends on the type of stressor, the timing and duration of stress, the genetic predisposition, personality characteristics, and the way of coping with stress. The hypothalamic-pituitary-adrenal (HPA) axis has a direct inhibitory action on the hypothalamic-pituitary-ovarian (HPO) axis at multiple levels. Acute and chronic stress impairs reproduction, eventually acting on varying mechanisms. Undernutrition, over-training, and psychological stress contribute to hypothalamic amenorrhea via reduced HPO activity. In utero stress exposure is a significant predictor of subsequent adult telomere length. Some of the metabolic consequences of intrauterine growth restriction can be mitigated by ensuring early appropriate catch-up growth, while avoiding excessive weight gain if relative hypercortisolism is not installed. The effect of maternal stress on fetuses regarding fetal HPA axis responsiveness (increased or decreased) remains under investigation. Maternal stress and depression are associated with structural and functional changes of brain parts such as hippocampus. In utero stress modifies epigenetically components of the HPA axis which can be transmitted transgenerationally.

Francesca Mancuso, Iva Arato, Catia Bellucci et al.

IntroductionAmong substances released into the environment by anthropogenic activities, the heavy metal cadmium (Cd) is known to induce severe testicular injury causing male subfertility/infertility. Zinc (Zn) is another heavy metal that, unlike Cd, is physiologically present in the testis, being essential for spermatogenesis. We aimed to examine the possibility that 50 µM ZnCl2 could counteract the toxic effects induced by Cd in an in vitro model of porcine prepubertal Sertoli cells (SCs) exposed to both subtoxic (5 μM) and toxic (10 μM) concentrations of CdCl2 for 48 h.Materials and MethodsApoptosis, cell cycle, and cell functionality were assessed. The gene expression of Nrf2 and its downstream antioxidant enzymes, ERK1/2, and AKT kinase signaling pathways were evaluated.Materials and ResultsWe found that Zn, in co-treatment with subtoxic and toxic Cd concentration, increased the number of metabolically active SCs compared to Cd exposure alone but restored SC functionality only in co-treatment with subtoxic Cd concentration with respect to subtoxic Cd alone. Exposure of Cd disrupted cell cycle in SCs, and Zn co-treatment was not able to counteract this effect. Cd alone induced SC death through apoptosis and necrosis in a dose-dependent manner, and co-treatment with Zn increased the pro-apoptotic effect of Cd. Subtoxic and toxic Cd exposures activated the Nrf2 signaling pathway by increasing gene expression of Nrf2 and its downstream genes (SOD, HO-1, and GSHPx). Zn co-treatment with subtoxic Cd attenuated upregulation on the Nrf2 system, while with toxic Cd, the effect was more erratic. Studying ERK1/2 and AKT pathways as a target, we found that the phosphorylation ratio of p-ERK1/2 and p-AKT was upregulated by both subtoxic and toxic Cd exposure alone and in co-treatment with Zn.DiscussionOur results suggest that Zn could counteract Cd effects by increasing the number of metabolically active SCs, fully or partially restoring their functionality by modulating Nrf2, ERK1/2, and AKT pathways. Our SC model could be useful to study the effects of early Cd exposure on immature testis, evaluating the possible protective effects of Zn.