The science of sex and gender in human health: online courses to create a foundation for sex and gender accountability in biomedical research and treatment

Background

Sex and gender differences play a significant role in the course and outcome of conditions that affect specific organ systems in the human body. Research on differences in the effects of medical intervention has helped scientists develop a number of sex- and gender-specific guidelines on the treatment and management of these conditions. An online series of courses, “The Science of Sex and Gender in Human Health,” developed by the National Institutes of Health Office of Research on Women’s Health and the U.S. Food and Drug Administration Office of Women’s Health, examines sex and gender differences and their implications. Thus far, three online courses have been generated. The first course offers an overview of the scientific and biological basis for sex- and gender-related differences. The second course is focused on disease-specific sex and gender differences in health and behavior and their implications. Finally, the third course covers the influence of sex and gender on disease manifestation, treatment, and outcome.

Methods

Data were obtained using website analytics and post-course surveys.

Results

To date, over 1000 individuals have completed at least one course. Additionally, 600 users have received continuing education credit for completing a course in the series. Finally, the majority of respondents to the online course survey have indicated that the courses considerably enhanced their professional effectiveness.

Conclusions

“The Science of Sex and Gender in Human Health” online courses are freely available sources of information that provide healthcare providers and researchers with the resources to successfully account for sex and gender in their medical practice and research programs.

     

Effectiveness of chemical mutagenesis in multiple damage to one or both strands of plasmid DNA

Methods for site-directed multiple modification of DNA have been developed and used for modification of either one or two strands of plasmid DNA. Plasmid DNAs modified in the region of the tet gene were transformed into Escherichia coli cells and Tet colonies were screened. It was shown that multiple lesions in one DNA strand performed using either N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or sodium bisulfite were effectively repaired in the cell by error-free mechanism. In contrast, modification of two DNA strands led to induction of mutations. The efficiency of mutagenesis in the case of modification of a local region of one DNA strand with sodium bisulfite and modification of the other strand with MNNG was 1.1-7.9%. Mutations were analysed by restriction mapping and sequencing. All of them were G----A transitions.     

Genetic-gonadal-genitals sex (3G-sex) and the misconception of brain and gender,or, why 3G-males and 3G-females have intersex brain and intersex gender

The categorization of individuals as “male” or “female” is based on chromosome complement and gonadal and genital phenotype. This combined genetic-gonadal-genitals sex, here referred to as 3G-sex, is internally consistent in ~99% of humans (i.e., one has either the “female” form at all levels, or the “male” form at all levels). About 1% of the human population is identified as “intersex” because of either having an intermediate form at one or more levels, or having the “male” form at some levels and the “female” form at other levels. These two types of “intersex” reflect the facts, respectively, that the different levels of 3G-sex are not completely dimorphic nor perfectly consistent. Using 3G-sex as a model to understand sex differences in other domains (e.g., brain, behavior) leads to the erroneous assumption that sex differences in these other domains are also highly dimorphic and highly consistent. But parallel lines of research have led to the conclusion that sex differences in the brain and in behavior, cognition, personality, and other gender characteristics are for the most part not dimorphic and not internally consistent (i.e., having one brain/gender characteristic with the “male” form is not a reliable predictor for the form of other brain/gender characteristics). Therefore although only ~1% percent of humans are 3G-“intersex”, when it comes to brain and gender, we all have an intersex gender (i.e., an array of masculine and feminine traits) and an intersex brain (a mosaic of “male” and “female” brain characteristics).     

The impact of sex, gender and pregnancy on 2009 H1N1 disease

Children and young adults of reproductive age have emerged as groups that are highly vulnerable to the current 2009 H1N1 pandemic. The sex of an individual is a fundamental factor that can influence exposure, susceptibility and immune responses to influenza. Worldwide, the incidence, disease burden, morbidity and mortality rates following exposure to the 2009 H1N1 influenza virus differ between males and females and are often age-dependent. Pregnancy and differences in the presentation of various risk factors contribute to the worse outcome of infection in women. Vaccination and antiviral treatment efficacy also vary in a sex-dependent manner. Finally, sex-specific genetic and hormonal differences may contribute to the severity of influenza and the clearance of viral infection. The contribution of sex and gender to influenza can only be determined by a greater consideration of these factors in clinical and epidemiological studies and increased research into the biological basis underlying these differences.     

Effect of gender differences and voluntary exercise on antioxidant capacity in rats

The effects of gender difference and voluntary exercise on antioxidant capacity in rats were evaluated. The subjects were divided into two groups, physically active and sedentary. In the sedentary group, the level of hydroxyl radical in the liver was higher (P<0.001) in male rats than in female rats, however, in the physically active group, the level in male rats was lower (P<0.05) than in female rats. The levels of reduced glutathione (GSH) in physically active males and females were higher compared to those in the sedentary group. The physically active group also showed an increase in antioxidant enzymes, such as glutathione peroxidase (GPx), glutathione reductase (GR) and superoxide dismutase activities. The level of liver GSH was higher in physically active females than in physically active males. For both groups, GPx and GR activities in females were significantly higher than in males. These results indicate that female rats have an intrinsically higher antioxidant capacity, which resulted in increased levels of GSH via the glutathione redox cycle and gamma-glutamyl cycle enzymes. The adaptation to altered antioxidant capacity, induced by physical activity, appeared to be affected by gender differences.     

Effects of negative air ions,noise, sex and age on maze learning in rats

An equal number of male and female rats of the King-Holtzman hybrid breed, divided into two age groups (group A₁ : 21–30 days old and group A₂ : 90–100 days old), were exposed to two levels of noise: N₀ = 30 db and N₁ = 90 db, (Ref. 0.0002μ bar), and three levels of negative air ions: I_O = no measurable ion concentration, I₁ = 7 × 10⁶ ions/cm³ and I₂ = 7 × 10⁷ ions/cm³. Time and error scores of 240 rats running a modified Lashley left-right maze with an escape-from-water motive served as criteria. A randomized complete blocks design with replications (2×3×2×2×10) was selected for treatment by analysis of variance. The results indicate that (a) the males show significantly lower error score in negatively ionized air; and (b) the females swim significantly faster than males under all investigated conditions with no apparent effect of noise or ions on their performance.

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Zusammenfassung Eine gleiche Anzahl m?nnlicher und weiblicher Ratten (n = 120) des King-Holtzman Stammes, unterteilt in 2 Altersgruppen (21–30 und 90–100 Tage) wurden zwei Ger?uschintensit?ten (30 db und 90 db) und 3 Konzentrationen negativer Luftionen I₀: nicht messbar niedrig, I₁:7×10⁶, I₂:7×10⁷ Ionen/cm³ ausgesetzt. Die Wirkung wurde geprüft an der Schwimmzeit und der Anzahl Fehler der Tiere im Lasley-Links-Rechts-Labyrinth. Das Motiv zum Schwimmen war, aus dem Wasser zu entkommen. Die Auswertung durch Varianzanalyse erfolgte unter Nachbildung randomisierter kompletter Blockentwürfe. Die Ergebnisse zeigen, dass (a) die M?nnchen bei negativ ionisierter Luft signifikant weniger Fehler machten und (b) die Weibchen unter allen Bedingungen schneller schwammen als die M?nnchen, ohne dass das L?rmniveau oder die Luftionisation darauf einen Einfluss hatten.

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Resume Un nombre égal de rats males et femelles (120 de chaque) de la race King-Holtzman futdivisé en deux groupes d'age (21 à 30 jours et 90 à 100 jours). Ils furent exposés à 2 intensités auditives (30 et 90 db) et à 3 concentrations d'ions négatifs: I₀ non mesurables (faible), I₁ : 7 × 10⁶ et I₂: 7 × 10⁷ ions/cm³. Les effets d'un tel traitement furent examinés au moyen de deux critères: le temps pris pour sortir de l'eau et le nombre de fautes commises dans un labyrinthe droitegauche de Laslay. Pour l'analyse des variances, on a adopté une répartition due au hasard avec répétitions (2×3×2×2×10). On peut en conclure que: (a) les males font moins d'erreurs dans l'air ionisé négativement et cela de fa?on significative et (b) les femelles ont nagé plus vite que les males dans toutes les conditions de l'essai. Ni le bruit ni le degré d'ionisation ne semblent avoir d'influence sur leur comportement.

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This study was supported in part by a grant from the Faculty Research Fund of the University of Oklahoma.     

Arterial blood gases in conscious rats exposed to hypoxia, hypercapnia, or both.

Adult male rats were anesthetized and catheters were implanted in the caudal artery. Soon after recovery from short-lasting anesthesia, a total of 20 groups of six each were individually exposed to five different oxygen levels varying from 21.0 to 9.0% combined with four CO2 levels ranging from 0 to 12.9% at a mean barometric pressure of 744 Torr. Arterial blood samples were collected and analyzed for pH, Po2, and Pco2 before and near the end of 20-min exposures. During an air-breathing control period, pH averaged 7.466 plus or minus 0.020 SD, Paco2 41.2 plus or minus 1.9 Torr and Pao2 91.8 plus or minus 3.5 Torr. During hypoxia, Pao2 levels were similar to that of acutely hypoxic humans. Rats apparently differ from man in that blood buffering is greater, resulting in a higher pH during air breathing and a smaller [H-+] increase with increasing Paco2. Differences between arterial and inspired CO2 were about 10 Torr at 60 and 90 Torr Plco2 and were not influenced by Plo2.     

Fatty acids in liver microsomal lipids of rats exposed to hypoxia, tetrachloromethane, or both

Arachidonic and docosahexaenoic acid in hepatic microsomal lipids from male Sprague-Dawley rats are greatly lowered when the animals have been exposed to tetrachloromethane; at the same time, palmitic, oleic and linoleic acid are significantly increased. Hypoxia alone causes similar derangements, but to a lesser extent. These are largely corrected 18 h after exposure; the effects induced by tetrachloromethane are persistent. The increases in 16:0, 18:1 and 18:2 suggest that in both cases microsomal enzymes involved in fatty acid metabolism are inhibited, either reversibly or irreversibly. Reduction of oxygen partial pressure during tetrachloromethane exposure has little effect upon hepatotoxicity as judged by hepatic enzymes in serum; only the onset of their release into the bloodstream is earlier.     

Virtual navigation in humans: the impact of age, sex, and hormones on place learning

Certain cognitive processes, including spatial ability, decline with normal aging. Spatial ability is also a cognitive domain with robust sex differences typically favoring males. However, tests of spatial ability do not seem to measure a homogeneous class of processes. For many, mentally matching rotated three-dimensional images is the gold standard for measuring spatial cognition in humans, while the Morris water task (MWT) is a preferred method in the domain of nonhuman animal research. The MWT is sensitive to hippocampal damage, a structure critical for normal learning and memory and often implicated in age-related cognitive decline. A computerized (virtual) version of the MWT (VMWT) appears to require and engage human hippocampal circuitry, and has proven useful in studying sex differences and testing spatial learning theories. In Experiment 1, we tested participants (20-90 years of age) in the VMWT and compared their performance to that on the Vandenberg Mental Rotation Test. We report an age-related deficit in performance on both tasks. In Experiment 2, we tested young (age 20-39) and elderly (age >60) participants in the VMWT and correlated their performance to the circulating levels of testosterone and cortisol. Our findings indicate that the persistence of male spatial advantage may be related to circulating testosterone, but not cortisol levels, and independent of generalized age-related cognitive decline.     

The impact of culture on sex assignment and gender development in intersex patients.

The appearance of the external genitalia is the major determinant of the social sex, which is announced at or shortly after birth. In the absence of normal development of the external genitalia, definitive gender assignment and its announcement have to be postponed. While over the past 20 years the pathogenesis of most disorders causing abnormal development of the genitalia have been elucidated, our knowledge regarding the impact of these defects upon the psychosexual development is rather rudimentary. This information, however, is needed not only to establish criteria for correct sex assignment but also to design relevant outcome studies. Culture is an important part of the context in which decisions are made on sex assignment of patients with abnormalities of the external genitalia. Cultural differences in dealing with intersexuality and intersex individuals not only influences the patient's own psychosexual development but also medical decisions regarding sex assignment and consecutive management. There is evidence that attitudes concerning gender and sexuality, including the acceptance of intersexuality, differ significantly between various cultures. Thus cross-cultural studies might allow a new approach in dealing with intersexed persons, their families, and their social background, a most important aspect considering the recent discussions and criticisms of patients and individuals affected with intersex disorders.     

Understanding the biology of sex and gender differences: using subgroup analysis and statistical design to detect sex differences in clinical trials

In May 2000, a General Accounting Office (GAO) report revealed that although women are now participating in clinical trials in numbers proportionate to their numbers in the general population, data collected in these trials are not routinely analyzed by sex.[1] Without such sex analysis, clinically relevant information about potentially lifesaving treatments could be lost. In July 2001, the Society for Women's Health Research convened a workshop to address strategies for conducting subgroup analyses to detect sex differences. Workshop participants concluded that understanding sex differences will enable medical researchers to design healthcare interventions for both men and women more effectively and that one can plan for and conduct sex analysis without compromising the quality of the study or making the study prohibitively expensive.     

Androgen threshold to activate copulation differs in male rats prenatally exposed to alcohol, stress, or both factors.

Few male rats prenatally exposed to a combination of alcohol and stress copulate spontaneously. This study determined adult sensitivity to testosterone (T) in males prenatally exposed to alcohol, to stress, or to both factors. Sexually naive males were tested with receptive females following castration and implantation of 20-, 30-, or 45-mm Silastic T-filled capsules. Serum T levels provided by these implants were measured. The behavior shown by males exposed only to prenatal alcohol did not differ from untreated control animals at any T dosage. Prenatal stress alone diminished the copulatory potential below control levels only when the intermediate T dosage was provided. Few males exposed to both alcohol and stress copulated under the lowest or the intermediate dose of adult T replacement, but most ejaculated normally when the largest capsule was implanted. The threshold to the sexual behavior-activating-properties of adult T exposure was moderately raised by prenatal stress but was severely affected when prenatal stress was combined with alcohol. We conclude that a diminished sensitivity to androgen in adulthood underlies some copulatory deficits resulting from treatments that alter fetal T levels. Such deficits may be concealed when behavior is evaluated in gonadally intact animals.     

Dystroglycan does not contribute significantly to kidney development or function, in health or after injury

Dystroglycan (DG or DAG1) is considered a critical link between the basement membrane and the cytoskeleton in multiple tissues. DG consists of two subunits, an extracellular α-subunit that binds laminin and other basement membrane components, and a transmembrane β-subunit. DG-null mouse embryos die during early embryogenesis because DG is required for Reichert's membrane formation. DG also forms an integral part of the dystrophin-glycoprotein complex in muscle. Although no human DG mutations have been reported, multiple forms of muscular dystrophy have been linked to DG glycosylation defects, and targeted deletion of muscle DG causes muscular dystrophy in mice. Moreover, DG is widely distributed in endothelial and epithelial cells, including those in the kidney. There has therefore been significant interest in DG's role in the kidney, especially in podocytes. Previous reports suggested that DG's disturbance in podocytes might cause glomerular filtration barrier abnormalities. To fully understand DG's contribution to nephrogenesis and kidney function, we used a conditional DG allele and a variety of Cre mice to systematically delete DG from podocytes, ureteric bud, metanephric mesenchyme, and then from the whole kidney. Surprisingly, none of these conditional deletions resulted in significant morphological or functional abnormalities in the kidney. Furthermore, DG-deficient podocytes did not show increased susceptibility to injury, and DG-deficient kidneys did not show delayed recovery. Integrins are therefore likely the primary extracellular matrix receptors in renal epithelia.     

How to study the impact of sex and gender in medical research: a review of resources

There is a growing appreciation by the biomedical community that studying the impact of sex and gender on health, aging, and disease will lead to improvements in human health. Sex- and gender-based comparisons can inform research on disease mechanisms and the development of new therapeutics as well as enhance scientific rigor and reproducibility. This review will assist basic researchers, clinical investigators, as well as epidemiologists, population, and social scientists by providing an annotated bibliography of currently available resource tools on how to consider sex and gender as independent variables in research design and methodology. These resources will assist investigators applying for funding from the National Institutes of Health since all grant applicants will be required (as of January 25, 2016) to address the role of sex as a biological variable in vertebrate animal and human studies.     

Extreme gender flexibility: using a phylogenetic framework to infer the evolution of variation in sex allocation, phylogeography, and speciation in a genus of bidirectional sex changing fishes(Lythrypnus, Gobiidae)

The genus Lythrypnus is a group of marine gobies that exhibit extreme gender flexibility as bidirectional sex changers. The genus consists of 20 described species and several undescribed species that are distributed in the Americas. Five species have been characterized with respect to sex allocation and gonad morphology. The hormonal, morphological, and behavioral aspects of sex change have been studied extensively for one species, L. dalli. These data, however, have not been interpreted in an evolutionary context because a phylogenetic hypothesis has not previously been proposed for the genus Lythrypnus. We propose the first phylogenetic hypothesis for the genus based on molecular data from three mitochondrial genes (12s, ND2, and Cytb), one nuclear gene (Rag1) and one nuclear intron (S7). We also include three previously undescribed Lythrypnus species. Our results support the monophyly of the genus with L. heterochroma, an Atlantic species, as the basal taxon. After the divergence of L. heterochroma, there are two main clades, one comprised of species distributed in the Atlantic, the other comprised of species distributed in the Pacific. These data indicate an Atlantic origin for the genus, followed by divergence after the closure of the Isthmus of Panama. Our data also support the monophyly of three previously described species complexes, the L. rhizophora complex and L. dalli complex in the Pacific, and the L. mowbrayi complex in the Atlantic. We mapped patterns of sex allocation within this genus onto the fully resolved and supported topology, and found that sexual plasticity and gender flexibility is likely a synapomorphy for the genus. Overall our results create a well-supported framework to understand the phylogeography of the genus, and to interpret the evolution of sex allocation in Lythrypnus gobies.     

Little evidence that condition,stress indicators,sex ratio,or homozygosity are related to landscape or habitat attributes in declining woodland birds

Habitat loss, fragmentation and degradation are drivers of major declines in biodiversity and species extinctions. The actual causes of species population declines following habitat change are more difficult to discern and there is typically high covariation among the measures used to infer the causes of decline. The causes of decline may act directly on individual fitness and survival, or through disruption of population processes. We examined the relationships among configuration, extent and status of native vegetation and three commonly used indicators of individual body condition and chronic stress (haemoglobin level, haematocrit, residual body mass condition index) in 13 species of woodland‐dependent birds in south‐eastern Australia. We also examined two measures of changes to population processes (sex ratio and individual homozygosity) in ten species and alleic richness in five species. We found little support for relationships between site or landscape characteristics and individual or population response variables, notwithstanding that our simulations showed we had sufficient power to detect relatively small effects. We discuss possible causes of the absence of detectable habitat effects in this system and the implications for the usefulness of individual body condition and easily measured haematological indices as indicators of the response of avian populations to habitat change.     

The effects of sex ratio and density on the expression of gender in the polychaeteCapitella capitata

Summary Large natural populations of the marine polychaeteCapitella capitata (species type I) contain males, females, and occasionally, hermaphrodites. Environmental conditions control the occurrence of hermaphrodites. At low density or in groups with female-biased sex ratios, males develop into hermaphrodites, and hermaphrodites are common. Crosses suggest that females are heterogametic, and males and hermaphrodites are homogametic. Heterogametic females do not become hermaphrodites.This study shows that in homogametic individuals, environmental conditions determine not only the development of hermaphroditism but also the expression of initial gender. Homogametic individuals can express either male or female gender initially, and homogametic individuals of either gender can develop subsequently into simultaneous hermaphrodites. The choice of initial gender depends on isolation. Most homogametic juveniles become females if reared alone but males if reared with other conspecifics. Homogametic males readily develop into hermaphrodites if females are rare. In contrast, homogametic females rarely become hermaphrodites.     

Impact of sex hormones, insulin, growth factors and peptides on cartilage health and disease

Sex hormones contribute to the pathogenesis of osteoarthritis (OA) in both sexes. OA is normally not seen in pre-menopausal women, whereas men may develop the disease as early as the 30th year of life. OA also shows increased incidence in association with diseases such as diabetes mellitus. Recent years have seen characterization of essential components of a functional endocrinal network in the articular cartilage comprising not only sex hormones but apparently insulin, growth factors and various peptides as well. In this review, we summarize the latest information regarding the influence of sex hormones, insulin, growth factors and some peptides on healthy cartilage and their involvement in osteoarthritis. Both animal and human research data were considered. The results are presented in an information matrix that identifies what is known, with supporting references, and identifies areas for further investigation.