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.     

A genetic method to resolve gender complements investigations on sex ratios in Rumex acetosa

The perennial dioecious weed, Rumex acetosa, possesses sex chromosomes (XX in females, XY1Y2 in males). Yet, the operational sex ratios are female-biased. Until now, sex ratio studies in R. acetosa, as in most plants, have relied on data obtained at sexual maturity. To resolve gender among the seeds and nonflowering plants of R. acetosa, a genetic method involving a DNA marker located on both Y chromosomes has now been developed and applied. The results suggest that the sex ratios are about 1 : 1 in the whole seed pool, but that a significant female bias develops by the time of flowering. Since the age of sexually mature plants is two years or more, the time frame during which the female bias present at sexual maturity develops can be several years. It appears that male seeds germinate at a lower rate and males suffer from a greater mortality during the years-long lifespan of R. acetosa. However, there are no considerable sex-related differences in vegetative vigour.     

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).     

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.     

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.     

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.     

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.     

Effects of direct electric fields,noise, sex and age on maze learning in rats

Equal numbers 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. 0.002µbar), and three levels of direct electric field intensities: E₀ = electric field strength of zero; E₁ = 1,600 v/m; and E₂ = 16,000 v/m. 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) adult rats pre-exposed to electric fields showed significantly lower error scores than young rats, regardless of sex or the noise condition; (b) after exposure to electric fields all rats swam faster than their controls; (c) after exposure to noise females showed significantly higher time scores than males under the same conditions, regardless of age; and (d) when subjected to the combined effect of electric fields and noise males showed significantly lower time scores than females under the same conditions, regardless of age.

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Zusammenfassung Zwei Altersgruppen (21–30 und 90–100 Tage) männlicher and weiblicher Ratten des King-Holtzman-Stammes wurden 2 Lärmintensitäten (30 db und 90 db) und 3 elektrischen Feldstärken (0, 1.600 v/m und 16.000 v/m) ausgesetzt und die Lernfähigkeit beim Schwimmen im modifizierten Lashley linksrechts Maze geprüft. Das Kriterium waren die Zeit und die Anzahl Fehler bei dem Versuch aus dem Wasser zu entkommen. Auswertung der Messungen durch Varianzanalyse unt er Nachbildung kompletter Blockentwürfe. Die Ergebnisse zeigen: (a) Erwachsene Ratten, die vorher elektrischen feldern ausgesetzt wurden, wiesen signifikant weniger fehler auf als junge Ratten, unabhängig vom Geschlecht und Lärmbedingungen; (b) nach der Exponierung in elektrischen Feldern schwammen alle Ratten schneller als die unbehandelten Kontrollen; (c) nach Lärmeexponierung zeigten weibliche Ratten signifikant höhere Trefferzeiten als Männchen unter den gleichen Bedingungen ohne Beziehung zum Alter und (d) bei gleichzeitiger Anwendung von elektrischen Feldern und Lärm wiesen die Männchen niedrigere Trefferzeiten auf als die Weibchen. Alter spielte dabei keine Rolle.

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Resume Des rats de la race King-Holzman, mâles et femelles, de deux groupes d'âge (21 à 30 et 90 à 100 jours) ont été exposes à deux intensités accoustiques (30 et 90 db) et à 3 champs électriques (0, 1.600 et 16. 000 v/m). On a alors examiné leur capacité d'apprendre à nager dans un labyrinthe droite-gauche de Lashley modifié. Les critères d'examen furent le temps et le nombre de fautes commises pour sortir de l'eau. Les observations furent ensuite traitées par l'analyse de variances en tenant compte de répétitions (2 × 3 × 2 × 2 × 10). Les résultats montrent: (a) Les rats adultes préalablement exposés à des champs électriques on fait moins fautes que de jeunes individus et cela de façon significative quels que soient le sexe ou les conditions de bruit; (b) après avoir été exposés à des champs électriques, tous les rats ont nagé plus vite que les bêtes de contrôle; (c) après exposition au bruit, les femelles ont présenté des temps de sortie significativement plus élevés que les mâles pris dans des conditions identiques et cela quel qu'en soit l'âge et (d) après exposition simultanée au bruit et aux champs électriques, les mâles se sont trouvés moins habiles que les femelles, sans incidence de l'âge.

     

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.     

Influences of gender and sex hormones on hypoxic ventilatory response in cats.

Hypoxic ventilatory response (HVR) is known to be increased by female as well as male sex hormones, but whether there are differences in HVR between men and women remains unclear. To determine whether gender differences exist in HVR, we undertook systematic comparisons of resting ventilation and HVR in awake male and female cats. Furthermore to explore the potential contribution of sex hormones to gender differences observed, we compared neutered and intact cats of both sexes. Resting ventilation differed among the four groups, but differences disappeared with correction for body weight. Intact females had a lower end-tidal PCO2 than intact male cats (females: 31.6 +/- 0.4 Torr vs. males: 33.6 +/- 0.4 Torr, P less than 0.05), indicating an increased alveolar ventilation per unit CO2 production. HVR expressed as the shape parameter A was similar among the four groups of animals. However, baseline (hyperoxic; end-tidal PO2 greater than 200 Torr) minute ventilation [VI(PO2 greater than 200)] differed among the groups. Therefore we normalized HVR by dividing the shape parameter A by VI(PO2 greater than 200) to compare the relative hypoxic chemosensitivity among the various groups of animals. In addition, we further normalized HVR for body weight, because body size influences ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nonshivering thermogenesis capacity associated to mitochondrial DNA haplotypes and gender in the greater white-toothed shrew, Crocidura russula

A selection gradient was recently suggested as one possible cause for a clinal distribution of mitochondrial DNA (mtDNA) haplotypes along an altitudinal transect in the greater white-toothed shrew, Crocidura russula (Ehinger et al. 2002). One mtDNA haplotype (H1) rare in lowland, became widespread when approaching the altitudinal margin of the distribution. As H1 differs from the main lowland haplotype by several nonsynonymous mutations (including on ATP6), and as mitochondria play a crucial role in metabolism and thermogenesis, distribution patterns might stem from differences in the thermogenic capacity of different mtDNA haplotypes. In order to test this hypothesis, we measured the nonshivering thermogenesis (NST) associated with different mtDNA haplotypes. Sixty-two shrews, half of which had the H1 haplotype, were acclimated in November at semioutdoor conditions and measured for NST throughout winter. Our results showed the crucial role of NST for winter survival in C. russula. The individuals that survived winter displayed a higher significant increase in NST during acclimation, associated with a significant gain in body mass, presumably from brown fat accumulation. The NST capacity (ratio of NST to basal metabolic rate) was exceptionally high for such a small species. NST was significantly affected by a gender x haplotype interaction after winter-acclimation: females bearing the H1 haplotype displayed a better thermogenesis at the onset of the breeding season, while the reverse was true for males. Altogether, our results suggest a sexually antagonistic cyto-nuclear selection on thermogenesis.     

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.     

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.