First steps for integrating sex and gender considerations into basic experimental biomedical research

Sex reporting of cells used in cancer research: A systematic review

Sex and gender disparities in biomedical research have been emphasized to improve scientific knowledge applied for the health of both men and women. Despite sex differences in cancer incidence, prognosis, and responses to therapeutic agents, mechanistic explanations at molecular levels are far from enough. Recent studies suggested that cell sex is an important biological variable due to differences in sex chromosome gene expression and differences in events associated with developmental biology. The objective of this study was to analyze the reporting of sex of cells used in cancer research using articles published in Cancer Cell, Molecular Cancer, Journal of Hematology & Oncology, Journal for ImmunoTherapy of Cancer, and Cancer Research in 2020, and to examine whether there exists any sex bias. We found that the percentage of cells with sex notation in the article was 36.5%. Primary cells exhibited higher sex notation compared to cell lines. A higher percentage of female cells were used in cell cultures with sex notation. Also, sex-common cells omitted sex description more often compared to sex-specific cells. None of the cells isolated from embryo and esophagus reported the cell sex in the article. Our results indicate cell sex report in cancer research is limited to a small proportion of cells used in the study. These results call for acknowledging the sex of cells to increase the applicability of biomedical research discoveries.

Recommendations for a Better Understanding of Sex and Gender in the Neuroscience of Mental Health

There are prominent sex/gender differences in the prevalence, expression, and life span course of mental health and neurodiverse conditions. However, the underlying sex- and gender-related mechanisms and their interactions are still not fully understood. This lack of knowledge has harmful consequences for those with mental health problems. Therefore, we set up a cocreation session in a 1-week workshop with a multidisciplinary team of 25 researchers, clinicians, and policy makers to identify the main barriers in sex and gender research in the neuroscience of mental health. Based on this work, here we provide recommendations for methodologies, translational research, and stakeholder involvement. These include guidelines for recording, reporting, analysis beyond binary groups, and open science. Improved understanding of sex- and gender-related mechanisms in neuroscience may benefit public health because this is an important step toward precision medicine and may function as an archetype for studying diversity.

Sex as a biological variable for cardiovascular physiology

There have been ongoing efforts by federal agencies and scientific communities since the early 1990s to incorporate sex and/or gender in all aspects of cardiovascular research. Scientific journals provide a critical function as change agents to influence transformation by encouraging submissions for topic areas, and by setting standards and expectations for articles submitted to the journal. As part of ongoing efforts to advance sex and gender in cardiovascular physiology research, the American Journal of Physiology-Heart and Circulatory Physiology recently launched a call for papers on Considering Sex as a Biological Variable. This call was an overwhelming success, resulting in 78 articles published in this collection. This review summarizes the major themes of the collection, including Sex as a Biological Variable Within: Endothelial Cell and Vascular Physiology, Cardiovascular Immunity and Inflammation, Metabolism and Mitochondrial Energy, Extracellular Matrix Turnover and Fibrosis, Neurohormonal Signaling, and Cardiovascular Clinical and Epidemiology Assessments. Several articles also focused on establishing rigor and reproducibility of key physiological measurements involved in cardiovascular health and disease, as well as recommendations and considerations for study design. Combined, these articles summarize our current understanding of sex and gender influences on cardiovascular physiology and pathophysiology and provide insight into future directions needed to further expand our knowledge.

Practical solutions for including sex as a biological variable (SABV) in preclinical neuropsychopharmacological research

Recently, many funding agencies have released guidelines on the importance of considering sex as a biological variable (SABV) as an experimental factor, aiming to address sex differences and avoid possible sex biases to enhance the reproducibility and translational relevance of preclinical research. In neuroscience and pharmacology, the female sex is often omitted from experimental designs, with researchers generalizing male-driven outcomes to both sexes, risking a biased or limited understanding of disease mechanisms and thus potentially ineffective therapeutics. Herein, we describe key methodological aspects that should be considered when sex is factored into in vitro and in vivo experiments and provide practical knowledge for researchers to incorporate SABV into preclinical research. Both age and sex significantly influence biological and behavioral processes due to critical changes at different timepoints of development for males and females and due to hormonal fluctuations across the rodent lifespan. We show that including both sexes does not require larger sample sizes, and even if sex is included as an independent variable in the study design, a moderate increase in sample size is sufficient. Moreover, the importance of tracking hormone levels in both sexes and the differentiation between sex differences and sex-related strategy in behaviors are explained. Finally, the lack of robust data on how biological sex influences the pharmacokinetic (PK), pharmacodynamic (PD), or toxicological effects of various preclinically administered drugs to animals due to the exclusion of female animals is discussed, and methodological strategies to enhance the rigor and translational relevance of preclinical research are proposed.

Dissolving sodium hydrosulfide in drinking water is not a good source of hydrogen sulfide for animal studies

Hydrogen sulfide (H2S) has many physiological and pathological roles in the human body. Sodium hydrosulfide (NaHS) is widely used as a pharmacological tool for assessing H2S effects in biological experiments. Although H2S loss from NaHS solution is a matter of minutes, some animal studies use NaHS in solution as an H2S-donating compound in drinking water. This study addresses whether 30 μM NaHS in drinking water prepared in rat/mouse water bottles remains stable for at least 12-24 h, as presumed by some authors. NaHS solutions (30 μM) were prepared in drinking water and immediately transferred to rat/mice water bottles. Samples were obtained from the tip of water bottles and from inside of the bottles at 0, 1, 2, 3, 4, 5, 6, 12, and 24 h for sulfide measurement using the methylene blue method. Furthermore, NaHS (30 μM) was administered to male and female rats for two weeks, and serum sulfide concentrations were measured every other day in the first week and at the end of the second week. NaHS solution was unstable in the samples obtained from the tip of water bottles; it declined by 72% and 75% after 12 and 24 h, respectively. In the samples obtained from the inside of the water bottles, the decline in the NaHS was not significant until 2 h; however, it decreased by 47% and 72% after 12 and 24 h, respectively. NaHS administration did not affect serum sulfide levels in male and female rats. In conclusion, NaHS solution prepared in drinking water can not be used for H2S donation as the solution is unstable. This route of administration exposes animals to variable and lower-than-expected amounts of NaHS.

Considering hormones as sex- and gender-related factors in biomedical research: Challenging false dichotomies and embracing complexity

The inclusion of sex and gender considerations in biomedicine has been increasing in light of calls from research and funding agencies, governmental bodies, and advocacy groups to direct research attention to these issues. Although the inclusion of both female and male participants is often an important element, overreliance on a female-male binary tends to oversimplify the interactions between sex- and gender-related factors and health, and runs a risk of being influenced by cultural stereotypes about sex and gender. When biomedical researchers are examining how hormones associated with gender and sex may influence pathways of interest, it is of crucial importance to approach this work with a critical lens on the rhetoric used, and in ways that acknowledge the complexity of hormone physiology. Here, we document the ways in which discourses around sex, gender and hormones shape our scientific thinking and practice in biomedical research, and review how the existing scientific knowledge about hormones reflects a complex and dynamic reality that is often not reflected outside of specialist niches of hormone biology. Where biomedical scientists take up sex- and gender-associated hormones as a way of addressing sex and gender considerations, it is valuable for us to bring a critical lens to the rhetoric and discourses used, to employ a sex contextualist approach in designing experimentation, and be rigorous and reflexive about the approaches used in analysis and interpretation of data. These strategies will allow us to design experimentation that goes beyond binaries, and grapples more directly with the material intricacies of sex, gender, and hormones.

Deconstructing sex: Strategies for undoing binary thinking in neuroendocrinology and behavior

The scientific community widely recognizes that "sex" is a complex category composed of multiple physiologies. Yet in practice, basic scientific research often treats "sex" as a single, internally consistent, and often binary variable. This practice occludes important physiological factors and processes, and thus limits the scientific value of our findings. In human-oriented biomedical research, the use of simplistic (and often binary) models of sex ignores the existence of intersex, trans, non-binary, and gender non-conforming people and contributes to a medical paradigm that neglects their needs and interests. More broadly, our collective reliance on these models legitimizes a false paradigm of human biology that undergirds harmful medical practices and anti-trans political movements. Herein, we continue the conversations begun at the SBN 2022 Symposium on Hormones and Trans Health, providing guiding questions to help scientists deconstruct and rethink the use of "sex" across the stages of the scientific method. We offer these as a step toward a scientific paradigm that more accurately recognizes and represents sexed physiologies as multiple, interacting, variable, and unbounded by gendered preconceptions. We hope this paper will serve as a useful resource for scientists who seek a new paradigm for researching and understanding sexed physiologies that improves our science, widens the applicability of our findings, and deters the misuse of our research against marginalized groups.

Association of patent ductus arteriosus with fetal factors and endotypes of prematurity

During fetal life, the ductus arteriosus (DA) acquires the mechanisms for its postnatal closure following a thorough developmental program. This program can be interrupted by preterm birth and is also susceptible to alteration during fetal life by numerous physiological and pathological stimuli. In this review, we aim to summarize the evidence on how physiological and pathological factors affect DA development, eventually leading to patent DA (PDA). Specifically, we reviewed the associations of sex, race, and pathophysiological pathways leading to very preterm birth (endotypes) with PDA incidence and pharmacological closure. Summary of evidence suggests that there are no male-female differences in the incidence of PDA among very preterm infants. In contrast, risk of developing PDA appears to be higher in infants exposed to chorioamnionitis or who are small for gestational age. Finally, hypertensive disorders of pregnancy may be associated with a better response to pharmacological treatment of PDA. All of this evidence comes from observational studies and therefore associations do not imply causation. The current trend for many neonatologists is to wait for the natural evolution of preterm PDA. Continued research is needed to identify which fetal and perinatal factors modulate the eventual late closure of PDA in very and extremely preterm infants.

Bias Amplification in Gender, Gender Identity, and Geographical Affiliation

In the quest for greater equity in science, individual attitudes and institutional policies should also embrace greater diversity and inclusion of minority groups. This viewpoint calls for a broader definition of gender bias in STEM to include gender identity and for increased attention to the issue of bias amplification due to geographic affiliation in the field of computational chemistry and chemoinformatics. It briefly discusses some active interventions to tackle bias on gender, gender identity, and geographic affiliation in STEM.

Design a protocol to investigate the effects of climate change in vivo

Climate change has a variety of effects on communities and the environment, most of which have been directly addressed, such as floods, droughts, and fires. To date, the impacts of climate change on health in in vivo conditions have not been assessed, and no protocol has been developed in this regard. Therefore, the purpose of the current study is to develop a protocol as well as design and build a pilot to deal with climate change in vivo to show the direct effects of climate change on health. For this purpose, twenty specialists, comprising ten experts active in field climate and 10 experts in field medicine and anatomy, have been consulted to design the proposed exposure protocol using the Delphi method. According to the prepared protocol, an exposure pilot was then designed and built, which provides the climatic conditions for animal exposure with a fully automatic HMI-PLC system. The results showed the average 12:12-h day/night temperature, humidity, and circadian cycle for three consecutive ten-year periods selected for exposure of 1-month-old male rats. The duration of the exposure period is four months, which is equivalent to a ten-year climatic period. This study is a framework and a starting point for examining the effects of climate change on in vivo conditions that have not yet been considered.

Gender dimension in cardio-pulmonary continuum

Cardio-pulmonary diseases, which were once regarded as a man's illness, have been one of the leading causes of morbidity and mortality for both men and women in many countries in recent years. Both gender and sex influence the functional and structural changes in the human body and therefore play an important role in disease clinical manifestation, treatment choice, and/or response to treatment and prognosis of health outcomes. The gender dimension integrates sex and gender analysis in health sciences and medical research, however, it is still relatively overlooked suggesting the need for empowerment in the medical research community. Latest advances in the field of cardiovascular research have provided supportive evidence that the application of biological variables of sex has led to the understanding that heart disease in females may have different pathophysiology compared to males, particularly in younger adults. It has also resulted in new diagnostic techniques and a better understanding of symptomatology, while gender analysis has informed more appropriate risk stratification and prevention strategies. The existing knowledge in the pulmonary field shows the higher prevalence of pulmonary disorders among females, however, the role of gender as a socio-cultural construct has yet to be explored for the implementation of targeted interventions. The purpose of this review is to introduce the concept of gender dimension and its importance for the cardiopulmonary continuum with a focus on shared pathophysiology and disease presentation in addition to interrelation with chronic kidney disease. The review presents basic knowledge of what gender dimension means, and the application of sex and gender aspects in cardiovascular medicine with a specific focus on early pulmonary development, pulmonary hypertension, and chronic obstructive pulmonary disease (COPD). Early vascular aging and inflammation have been presented as a potential pathophysiological link, with further interactions between the cardiopulmonary continuum and chronic kidney disease. Finally, implications for potential future research have been provided to increase the impact of gender dimension on research excellence that would add value to everybody, foster toward precision medicine and ultimately improve human health.

Sex Differences in Patent Ductus Arteriosus Incidence and Response to Pharmacological Treatment in Preterm Infants: A Systematic Review, Meta-Analysis and Meta-Regression

A widely accepted concept in perinatal medicine is that boys are more susceptible than girls to complications of prematurity. However, whether this ‘male disadvantage of prematurity’ also involves persistent patent ductus arteriosus (PDA) has been scarcely investigated. Our aim was to conduct a systematic review and meta-analysis on studies addressing sex differences in the risk of developing PDA among preterm infants. We also investigated whether the response to pharmacological treatment of PDA differs between boys and girls. PubMed/Medline and Embase databases were searched. The random-effects male/female risk ratio (RR) and 95% confidence interval (CI) were calculated. We included 146 studies (357,781 infants). Meta-analysis could not demonstrate sex differences in risk of developing any PDA (37 studies, RR 1.03, 95% CI 0.97 to 1.08), hemodynamically significant PDA (81 studies, RR 1.00, 95% CI 0.97 to 1.02), or in the rate of response to pharmacological treatment (45 studies, RR 1.01, 95% CI 0.98 to 1.04). Subgroup analysis and meta-regression showed that the absence of sex differences was maintained over the years and in different geographic settings. In conclusion, both the incidence of PDA in preterm infants and the response rate to pharmacological treatment of PDA are not different between preterm boys and girls.

Law, policy, biology, and sex: Critical issues for researchers

Researchers should be aware of how sex-difference science is (mis)applied in legal and policy contexts.

Human studies of mitochondrial biology demonstrate an overall lack of binary sex differences: A multivariate meta-analysis

Mitochondria are maternally inherited organelles that play critical tissue-specific roles, including hormone synthesis and energy production, that influence human development, health, and aging. However, whether mitochondria from women and men exhibit consistent biological differences remains unclear, representing a major gap in knowledge. This meta-analysis systematically examined four domains and six subdomains of mitochondrial biology (total 39 measures), including mitochondrial content, respiratory capacity, reactive oxygen species (ROS) production, morphometry, and mitochondrial DNA copy number. Standardized effect sizes (Hedge's g) of sex differences were computed for each measure using data in 2258 participants (51.5% women) from 50 studies. Only two measures demonstrated aggregate binary sex differences: higher mitochondrial content in women's WAT and isolated leukocyte subpopulations (g = 0.20, χ² p = .01), and higher ROS production in men's skeletal muscle (g = 0.49, χ² p < .0001). Sex differences showed weak to no correlation with age or BMI. Studies with small sample sizes tended to overestimate effect sizes (r = -.17, p < .001), and sex differences varied by tissue examined. Our findings point to a wide variability of findings in the literature concerning possible binary sex differences in mitochondrial biology. Studies specifically designed to capture sex- and gender-related differences in mitochondrial biology are needed, including detailed considerations of physical activity and sex hormones.

Sex and gender considerations in reporting guidelines for health research: a systematic review

Background

Despite growing recognition of the importance of sex and gender considerations in health research, they are rarely integrated into research design and reporting. We sought to assess the integration of sex, as a biological attribute, and gender, as a socially constructed identity, in published reporting guidelines.

Methods

We conducted a systematic review of published reporting guidelines listed on the EQUATOR website (www.equator-nework.org) from inception until December 2018. We selected all reporting guidelines (original and extensions) listed in the EQUATOR library. We used EndNote Citation Software to build a database of the statements of each guideline identified as a "full bibliographic reference" and retrieved the full texts. Reviewers independently extracted the data on use of sex and gender terms from the checklist/abstract/main text of guidelines. Data were analyzed using descriptive statistics and narrative synthesis.

Results

A total of 407 reporting guidelines were included; they were published between 1995 and 2018. Of the 407 guidelines, 235 (57.7%) mentioned at least one of the sex- and gender-related words. In the checklist of the reporting guidelines (n = 363), “sex” and “gender” were mentioned in 50 (13.8%) and 40 (11%), respectively. Only one reporting guideline met our criteria (nonbinary, appropriate categorization, and non-interchangeability) for correct use of sex and gender concepts. Trends in the use of "sex" and "gender" in the checklists showed that the use of “sex” only started in 2003, while “gender” has been in use since 1996.

Conclusions

We assessed the integration of sex and gender in reporting guidelines based on the use of sex- and gender-related words. Our findings showed a low use and integration of sex and gender concepts and their incorrect use. Authors of reporting guidelines should reduce this gap for a better use of research knowledge.

Trial registration PROSPERO no. CRD42019136491.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13293-021-00404-0.

Omission of sex and gender considerations is a recurring deficiency in research design and reporting

Integration of sex and gender considerations in health research reporting guidelines is very low

Three criteria were used to assess correct use of sex and gender concepts

Only one reporting guideline met the three criteria

A call to action is made to address these deficiencies

Lost in translation? Beyond sex as a biological variable in animal research

In this article, I develop a feminist posthumanist account of biomedical policymaking as a material-discursive intervention that shapes the emergence of phenomena in the scientific laboratory. The setting is United States (U.S.) biomedicine, where a recent policy of the National Institutes of Health has mandated the consideration of sex in basic and preclinical research. Called Sex as a Biological Variable (SABV), the mandate configures cell lines and animal models as the next frontier in the project of advancing gender equity in biomedical research. Given sex and gender are increasingly recognised as having complex, entangled, and dynamic effects on human health and illness, how do laboratory animals respond to their attempted enrolment in this regulatory intervention? Through a qualitative analysis of this policy domain, I show how laboratory animals reveal the context-specific character of sex, its multiplicity and elusiveness as a so-called biological variable, and the considerable work needed to shore up human ideologies of sex as a pervasive cross-species form of binary difference. I suggest that while regulatory interventions constrain patterns of mattering, they also serve as agential openings in which laboratory animals can 'kick back' and reconfigure the pursuit of knowledge, particularly as it relates to difference and health.

Mitochondrial phenotypes in purified human immune cell subtypes and cell mixtures

Using a high-throughput mitochondrial phenotyping platform to quantify multiple mitochondrial features among molecularly defined immune cell subtypes, we quantify the natural variation in mitochondrial DNA copy number (mtDNAcn), citrate synthase, and respiratory chain enzymatic activities in human neutrophils, monocytes, B cells, and naïve and memory T lymphocyte subtypes. In mixed peripheral blood mononuclear cells (PBMCs) from the same individuals, we show to what extent mitochondrial measures are confounded by both cell type distributions and contaminating platelets. Cell subtype-specific measures among women and men spanning four decades of life indicate potential age- and sex-related differences, including an age-related elevation in mtDNAcn, which are masked or blunted in mixed PBMCs. Finally, a proof-of-concept, repeated-measures study in a single individual validates cell type differences and also reveals week-to-week changes in mitochondrial activities. Larger studies are required to validate and mechanistically extend these findings. These mitochondrial phenotyping data build upon established immunometabolic differences among leukocyte subpopulations, and provide foundational quantitative knowledge to develop interpretable blood-based assays of mitochondrial health.

Gender Perspective in Research on Interventions in Children with Experiences of Parental Gender-Based Violence: Application of GPIHR Criteria

The aim of this study was to analyse the inclusion of a gender perspective (GP) in scientific production on interventions for a reduction in psychological distress in children who have experienced parental gender-based violence (CEXPGBV). To achieve this, a review of publications was carried out in the Web of Science, EBSCOhost, ProQuest and Cochrane Library databases. A total of 3418 records were found, and 44 items of research selected. For GP analysis, the questionnaire "Gender perspective in health research" (GPIHR) was applied and relationships with the terminology of violence were analysed, as well as the definition of term used, references to violence by men or received by women and the instruments used to assess these. Generally, the assessed studies do not contain a GP, since 70% of the GPIHR items were answered negatively. Likewise, 89% of research used general terms to refer to violence without referring to gender. These results show the importance of considering instruments such as GPIHR in both the planning and development of future research in order to avoid possible gender bias.

Feminism, gender medicine and beyond: a feminist analysis of "gender medicine"

The feminist women's health movement empowered women's knowledge regarding their health and battled against paternalistic and oppressive practices within healthcare systems. Gender Medicine (GM) is a new discipline that studies the effect of sex/gender on general health. The international society for gender medicine (IGM) was embraced by the FDA and granted funds by the European Union to formulate policies for medical practice and research.We conducted a review of IGM publications and policy statements in scientific journals and popular media. We found that while biological differences between men and women are emphasized, the impact of society on women is under- represented. The effect of gender-related violence, race, ethnic conflicts, poverty, immigration and discrimination on women's health is seldom recognized. Contrary to feminist practice, GM is practiced by physicians and scientists, neglecting voices of other disciplines and of women themselves.In this article we show that while GM may promote some aspects of women's health, at the same time it reaffirms conservative positions on sex and gender that can serve to justify discrimination and disregard the impact of society on women's lives and health. An alternative approach, that integrates feminist thinking and practices into medical science, practice and policies is likely to result in a deep and beneficiary change in women's health worldwide.

Let's talk about sex: Differences in drug therapy in males and females

Professor Henry Higgins in My Fair Lady said, 'Why can't a woman be more like a man?' Perhaps unintended, such narration extends to the reality of current drug development. A clear sex-gap exists in pharmaceutical research spanning from preclinical studies, clinical trials to post-marketing surveillance with a bias towards males. Consequently, women experience adverse drug reactions from approved drug products more often than men. Distinct differences in pharmaceutical response across drug classes and the lack of understanding of disease pathophysiology also exists between the sexes, often leading to suboptimal drug therapy in women. This review explores the influence of sex as a biological variable in drug delivery, pharmacokinetic response and overall efficacy in the context of pharmaceutical research and practice in the clinic. Prospective recommendations are provided to guide researchers towards the consideration of sex differences in methodologies and analyses. The promotion of disaggregating data according to sex to strengthen scientific rigour, encouraging innovation through the personalisation of medicines and adopting machine learning algorithms is vital for optimised drug development in the sexes and population health equity.

Co-production, multiplied: Enactments of sex as a biological variable in US biomedicine

In 2016 the US National Institutes of Health introduced a policy mandating consideration of Sex as a Biological Variable (SABV) in preclinical research. In this article, I ask what, precisely, is meant by the designation of sex as a 'biological variable', and how has its inclusion come to take the form of a policy mandate? Given the well documented complexity of 'sex' and the degree to which it is politically and scientifically contested, its enactment via policy as a biological variable is not a given. I explore how sex is multiply enacted in efforts to legitimate and realize the SABV policy and consider how the analytical lens of co-production sheds light on how and why this occurs. I show that the policy works to reassert scientific and political order by addressing two institutional concerns: the so-called reproducibility crisis in preclinical research, and pervasive gender inequality across the institution of biomedicine. From here, the entity that underpins this effort - sex as a biological variable - becomes more than one thing, with enactments ranging from an assigned category, to an outcome, to a causal biological force in its own right. Sex emerges as simultaneously entangled with yet distinct from gender, and binary (female/male) yet complex in its variation. I suggest that it is in the very attempt to delineate natural from social order, and in the process create the conditions to privilege a particular kind of science and account of embodied difference, that ontological multiplicity becomes readily visible. That this multiplicity goes unrecognized points to the unifying role of an overarching ideological commitment to sex as a presumed binary and biological scientific object, the institutional dominance of which is never guaranteed.

Biological sex, not reproductive cycle, influences peripheral blood immune cell prevalence in mice

KEY POINTS

Traditionally the female sex, compared with the male sex, has been perceived as having greater variability in many physiological traits, including within the immune system. We investigated effects of biological sex and the female reproductive cycle on numbers of circulating leukocytes in C57BL/6J mice. We show that biological sex, but not female reproductive cyclicity, has a significant effect on peripheral blood immune cell prevalence and variability, and that sex differences were not consistent amongst common inbred laboratory mouse strains. We found that male C57BL/6J mice, compared with female mice, have greater variability in peripheral blood immunophenotype, and that this was influenced by body weight. We created summary tables for researchers to facilitate experiment planning and sample size calculations for peripheral immune cells that consider the effects of biological sex.

ABSTRACT

Immunophenotyping (i.e. quantifying the number and types of circulating leukocytes) is used to characterize immune changes during health and disease, and in response to pharmacological and other interventions. Despite the importance of biological sex in immune function, there is considerable uncertainty amongst researchers as to the extent to which biological sex or the female reproductive cycle influence blood immunophenotype. We quantified circulating leukocytes by multicolour flow cytometry in young C57BL/6J mice and assessed the effects of the reproductive cycle, biological sex, and other experimental and biological factors on data variability. We found that there are no significant effects of the female reproductive cycle on the prevalence of peripheral blood B cells, NK cells, CD4⁺ T cells, CD8⁺ T cells, monocytes, or neutrophils. Immunophenotype composition and variability do not significantly change between stages of the female reproductive cycle. There are, however, sex-specific differences in immune cell prevalence, with fewer monocytes, neutrophils, and NK cells in female mice. Surprisingly, immunophenotype is more variable in male mice, and weight is a significant contributing factor. We provide tools for researchers to perform a priori sample size calculations for two-group and factorial analyses. We show that immunophenotype varies between inbred mouse strains, and that using equal sample sizes of male and female mice is not always appropriate for within-sex evaluations of immune cell populations in peripheral blood.

Beyond the binary: Rethinking sex and the brain

The paper reviews the relations between sex and brain in light of the binary conceptualization of these relations and the challenges posed to it by the 'mosaic' hypothesis. Recent formulations of the binary framework range from arguing that the typical male brain is different from the typical female brain to claiming that brains are typically male or female because brain structure can be used to predict the sex category (female/male) of the brain's owner. These formulations are challenged by evidence that sex effects on the brain may be opposite under different conditions, that human brains are comprised of mosaics of female-typical and male-typical features, and that sex category explains only a small part of the variability in human brain structure. These findings led to a new, non-binary, framework, according to which mosaic brains reside in a multi-dimensional space that cannot meaningfully be reduced to a male-female continuum or to a binary variable. This framework may also apply to sex-related variables and has implications for research.

Influence of hormonal contraceptives on peripheral vascular function and structure in premenopausal females: a review

Hormonal contraceptives are one of the most widely used prescriptions for premenopausal women worldwide. Although the risk of venous and arterial cardiovascular events (e.g., deep vein thrombosis, arterial clotting) with hormonal contraceptives, specifically oral contraceptive pills, has been established, the literature on early risk indicators, such as peripheral vascular structure and function has yet to be consolidated. The purpose of this review is to summarize literature examining the impact of different hormonal contraceptives on vascular function and structure, including consideration of phasic differences within a contraceptive cycle, and to propose future directions for research. It is evident that hormonal contraceptive use appears to impact both macrovascular and microvascular endothelial function, with phasic differences in some contraceptive types dependent on progestin type, the ratio of ethinyl estradiol-to-progestin, and route of administration. However, hormonal contraceptives do not appear to impact smooth muscle function in the macrovasculature or microvasculature, arterial stiffness, or vascular structure. Underlying mechanisms for observed impacts and areas of future research are discussed. This review provides timely consolidation of research examining hormonal contraceptives and peripheral vascular function and structure and provides guidance on considerations for hormonal contraceptive use in study design.

Sex and gender considerations in implementation interventions to promote shared decision making: A secondary analysis of a Cochrane systematic review

Background

Shared decision making (SDM) in healthcare is an approach in which health professionals support patients in making decisions based on best evidence and their values and preferences. Considering sex and gender in SDM research is necessary to produce precisely-targeted interventions, improve evidence quality and redress health inequities. A first step is correct use of terms. We therefore assessed sex and gender terminology in SDM intervention studies.

Materials and methods

We performed a secondary analysis of a Cochrane review of SDM interventions. We extracted study characteristics and their use of sex, gender or related terms (mention; number of categories). We assessed correct use of sex and gender terms using three criteria: “non-binary use”, “use of appropriate categories” and “non-interchangeable use of sex and gender”. We computed the proportion of studies that met all, any or no criteria, and explored associations between criteria met and study characteristics.

Results

Of 87 included studies, 58 (66.7%) mentioned sex and/or gender. The most mentioned related terms were “female” (60.9%) and “male” (59.8%). Of the 58 studies, authors used sex and gender as binary variables respectively in 36 (62%) and in 34 (58.6%) studies. No study met the criterion “non-binary use”. Authors used appropriate categories to describe sex and gender respectively in 28 (48.3%) and in 8 (13.8%) studies. Of the 83 (95.4%) studies in which sex and/or gender, and/or related terms were mentioned, authors used sex and gender non-interchangeably in 16 (19.3%). No study met all three criteria. Criteria met did not vary according to study characteristics (p>.05).

Conclusions

In SDM implementation studies, sex and gender terms and concepts are in a state of confusion. Our results suggest the urgency of adopting a standardized use of sex and gender terms and concepts before these considerations can be properly integrated into implementation research.

Sexes on the brain: Sex as multiple biological variables in the neuronal control of feeding

Neuronal interactions at the level of vagal, homeostatic, and hedonic circuitry work to regulate the neuronal control of feeding. This integrative system appears to vary across sex and gender in the animal and human worlds. Most feeding research investigating these variations across sex and gender focus on how the organizational and activational mechanisms of hormones contribute to these differences. However, in limited studies spanning both the central and peripheral nervous systems, sex differences in feeding have been shown to manifest not just at the level of the hormonal, but also at the chromosomal, epigenetic, cellular, and even circuitry levels to alter food intake. In this review, we provide a brief orientation to the current understanding of how these neuronal systems interact before dissecting selected studies from the recent literature to exemplify how feeding physiology at all levels can be affected by the various components of sex.

Thymus Regeneration and Future Challenges

Thymus regenerative therapy implementation is severely obstructed by the limited number and expansion capacity in vitro of tissue-specific thymic epithelial stem cells (TESC). Current solutions are mostly based on growth factors that can drive differentiation of pluripotent stem cells toward tissue-specific TESC. Target-specific small chemical compounds represent an alternative solution that could induce and support the clonal expansion of TESC and reversibly block their differentiation into mature cells. These compounds could be used both in the composition of culture media designed for TESC expansion in vitro, and in drugs development for thymic regeneration in vivo. It should allow reaching the ultimate objective - autologous thymic tissue regeneration in paediatric patients who had their thymus removed in the course of cardiac surgery.

Does diversity go beyond sex and gender? Gender as social category of diversity training in health profession education - a scoping review

Background: Sex and gender are social categories of diversity. Diversity can be perceived with an intersectional framework as it demonstrates the intersecting categories that might contribute to oppression, inequality, power and privilege. This article focused on what aspects were considered in diversity training programmes for health professions and the role of sex/gender in this context. Method: This scoping review focuses on the social categories mentioned in diversity education of health professionals. Articles on diversity training for health professionals were searched for in the Web of Science database using the keywords gender, diversity, training, education and health professions. Twelve articles were finally included in this review. Thematic analysis was employed to summarise information deduced from articles. Findings: Gaps in the aspects included in diversity training were identified. Findings show that culture was mostly discussed, whereas sex/gender and lesbian, gay, bisexual, transgender, queer and intersex (LGBTQI) were focused on only to a minor extent. Cultural diversity training includes self-reflection on one's own culture, whereas a comparable tool for sex/gender and LGBTQI is missing. Additionally, other social categories of diversity, such as disability or age, are largely absent. Conclusion: Diversity should be incorporated in its full breadth in health profession education and not fragmented. Additionally, other social categories such as gender might benefit from including self-reflection on these categories in addition to reflecting on the role of power and privilege in order to increase self-awareness for diversity. In this way, othering of the population might be prevented and healthcare can be improved for all.

Sex-specific metabolic and functional differences in human umbilical vein endothelial cells from twin pairs

BACKGROUND AND AIMS

Gonadal hormones are mainly thought to account for sex and gender differences in the incidence, clinical manifestation and therapy of many cardiovascular diseases. However, intrinsic sex differences at the cellular level are mostly overlooked. Here, we assessed sex-specific metabolic and functional differences between male and female human umbilical vein endothelial cells (HUVECs).

METHODS

Cellular metabolism was investigated by bioenergetic studies (Seahorse Analyser) and a metabolomic approach. Protein levels were determined by Western blots and proteome analysis. Vascular endothelial growth factor (VEGF)-stimulated cellular migration was assessed by gap closure. HUVECs from dizygotic twin pairs were used for most experiments.

RESULTS

No sex differences were observed in untreated cells. However, sexual dimorphisms appeared after stressing the cells by serum starvation and treatment with VEGF. Under both conditions, female cells had higher intracellular ATP and metabolite levels. A significant decline in ATP levels was observed in male cells after serum starvation. After VEGF, the ratio of glycolysis/mitochondrial respiration was higher in female cells and migration was more pronounced.

CONCLUSIONS

These results point to an increased stress tolerance of female cells. We therefore propose that female cells have an energetic advantage over male cells under conditions of diminished nutrient supply. A more favourable energy balance of female HUVECs after serum starvation and VEGF could potentially explain their stronger migratory capacity.

Gender Differences in Throwing Revisited: Sensorimotor Coordination in a Virtual Ball Aiming Task

Numerous studies have demonstrated that boys throw balls faster, farther and more accurately than girls. This may be largely due to well-known anatomical and muscle-physiological differences that play a central role in overarm throwing. With the objective to understand the potential contribution of the equally essential coordinative aspects in throwing for this gender difference, this large cross-sectional study examined a simplified forearm throw that eliminated the requirements that give males an advantage.While the overall performance error indeed became similar in the age groups younger than 20 years and older than 50 years, it was attenuated for middle-aged individuals. The gender differences remained in individuals who reported no throwing experience, but females with throwing experience reached similar performance as males. Two fine-grained spatiotemporal metrics displayed similar age-dependent gender disparities: while overall, males showed better spatiotemporal coordination of the ball release, age group comparisons specified that it was particularly middle-aged females that made more timing errors and did not develop a noise-tolerant strategy as males did. As throwing experience did not explain this age-dependency, the results are discussed in the context of spatial abilities and video game experience, both more pronounced in males. In contrast, a measure of rhythmicity developed over successive throws only revealed weak gender differences, speaking to the fundamental tendency in humans to fall into rhythmic patterns. Only the youngest individuals between 5 and 9 years of age showed significantly less rhythmicity in their performance. This computational study was performed in a large cohort in the context of an outreach activity, demonstrating that robust quantitative measures can also be obtained in less controlled environments. The findings also alert that motor neuroscience may need to pay more attention to gender differences.

Sex × Gender and Sexual Orientation in Relation to Stress Hormones and Allostatic Load

In this selective review, emerging literature linking biological sex, sociocultural gender, and sexual orientation to stress hormone functioning and multisystemic physiological dysregulations are summarized. Beyond sex as a binary biological variable, continuums of sex hormones, gender roles, gender identity, and sexual orientation each uniquely help delineate pathways and mechanisms linked to stress-related disease trajectories. This implicates glucocorticoid functioning and allostatic load, the “wear and tear” of chronic stress in synergy with unhealthy behaviors. Clinical considerations are also discussed for the field of gender medicine.

Health disparities between binary and non binary trans people: A community-driven survey

Background: Genderqueer and nonbinary () people have remained largely invisible in health research. Previous research shows worse outcomes on health indicators for trans people when compared with cisgender controls, but the differences between binary trans and GQNB individuals are inconclusive. Aims: To compare overall health and well-being of GQNB people with controls of trans men and trans women, taking into account the impact of the additive effect of their socio-economic position, as well as their current need for gender affirming medical interventions. Methods: A community-driven survey was conducted in 2016 in five countries (Georgia, Poland, Serbia, Spain, and Sweden). Self-reported health and general well-being were analysed for differences between binary trans and GQNB respondents. The effects of multiple control variables (age, economic situation, educational level, belonging to an ethnic, religious, sexual or ability minority group, sex assigned at birth) as well as the current need for gender affirming medical interventions were controlled for. Results: The sample consisted of 853 respondents aged 16 and older, with 254 trans women (29.8%), 369 trans men (43.2%), and 230 GQNB people (26%). GQNB respondents showed significantly worse self-reported health and worse general well-being in comparison to binary trans respondents. Additional negative impacts of having a lower educational level, having more economic stress, and belonging to a disability minority group were found. Being in need of gender affirming medical interventions contributed significantly to worse self-reported health, whereas being younger contributed to worse general well-being. Discussion: In understanding health disparities between binary trans and GQNB people, it is necessary to take into account the additive effect of multiple socio-economic positions, and the current need for gender affirming medical interventions. The high proportion of GQNB respondents who report worse health outcomes highlights the need for policy makers and health-care providers in creating nonbinary-inclusive environments.

Factors affecting sex-related reporting in medical research: a cross-disciplinary bibliometric analysis

BACKGROUND

Clinical and preclinical studies have shown that there are sex-based differences at the genetic, cellular, biochemical, and physiological levels. Despite this, numerous studies have shown poor levels of inclusion of female populations into medical research. These disparities in sex inclusion in research are further complicated by the absence of sufficient reporting and analysis by sex of study populations. Disparities in the inclusion of the sexes in medical research substantially reduce the utility of the results of such research for the entire population. The absence of sex-related reporting are problematical for the translation of research from the preclinical to clinical and applied health settings. Large-scale studies are needed to identify the extent of sex-related reporting and where disparities are more prevalent. In addition, while several studies have shown the dearth of female researchers in science, few have evaluated whether a scarcity of women in science might be related to disparities in sex inclusion and reporting. We aimed to do a cross-disciplinary analysis of the degree of sex-related reporting across the health sciences-from biomedical, to clinical, and public health research-and the role of author gender in sex-related reporting.

METHODS

This bibliometric analysis analysed sex-related reporting in medical research examining more than 11·5 million papers indexed in Web of Science and PubMed between 1980 and 2016 and using sex-related Medical Subject Headings as a proxy for sex reporting. For papers that were published between 2008 and 2016 and could be matched with PubMed, we assigned a gender to first and last authors on the basis of their names, according to our gender assignment algorithm. We removed papers for which we could not determine the gender of either the first or last author. We grouped papers into three disciplinary categories (biomedical research, clinical medicine, and public health). We used descriptive statistics and regression analyses (controlling for the number of authors and representation of women in specific diseases, countries, continents, year, and specialty areas) to study associations between the gender of the authors and sex-related reporting.

FINDINGS

Between Jan 1, 1980, and Dec 31, 2016, sex-related reporting increased from 59% to 67% in clinical medicine and from 36% to 69% in public health research. But for biomedical research, sex remains largely under-reported (31% in 2016). Papers with female first and last authors had an increased probability of reporting sex, with an odds ratio of 1·26 (95% CI 1·24 to 1·27), and sex-related reporting was associated with publications in journals with low journal impact factors. For publications in 2016, sex-related reporting of both male and female is associated with a reduction of -0·51 (95% CI -0·54 to -0·47) in journal impact factors.

INTERPRETATION

Gender disparities in the scientific workforce and scarcity of policies on sex-related reporting at the journal and institutional level could inhibit effective research translation from bench to clinical studies. Diversification in the scientific workforce and in the research populations-from cell lines, to rodents, to humans-is essential to produce the most rigorous and effective medical research.

FUNDING

Canada Research Chairs.

The importance of selection and reporting of the sex of experimental animals

Biased use of males and females in animal studies or omitting specific details of the sex of animals used in publications limits reproducibility, hampers the pace and likelihood of new discoveries and invites adverse events in ensuing clinical research. Hence unbiased use of males and females in animal studies and specific reporting of animal details are increasingly required by funding bodies and scientific journals worldwide. An analysis to determine how males and females are used in animal studies involving the Commonwealth Scientific and Industrial Research Organisation (CSIRO) was undertaken as part of a process to review and further support best practice. In the study 178 publications that contain animal studies and include CSIRO researchers published between January 2014 and December 2016 were analysed for the sex of animals used. The overall sex distribution was males only 26.4% (47/178), females only 15.7% (28/178), males and females 18.0% (32/178) and sex of animals unspecified 39.9% (71/178). Reasons for this distribution include species biology, farming practices and commercial relevance. Although including sex as an experimental variable provides the most information, using both sexes in an animal study requires careful consideration and planning. Furthermore, there are valid biological and experimental reasons why sex distribution in a study may not be balanced. Biological reasons include cases where the severity of disease in a given model differs between males and females, superior husbandry or production traits in one sex and hermaphroditic species that change sex with age. Examples where experiments can only be undertaken in one sex of animal include animal models of female breast cancer, female reproductive traits, male fertility studies and post-castration welfare outcomes. Where there is no biological or experimental reason for using a single sex of animal, future studies should obtain an estimate of sex effect either from the literature or with a pilot study, and experiments should be planned and reported accordingly.

Sex bias in preclinical research and an exploration of how to change the status quo

There has been a revolution within clinical trials to include females in the research pipeline. However, there has been limited change in the preclinical arena; yet the research here lays the ground work for the subsequent clinical trials. Sex bias has been highlighted as one of the contributing factors to the poor translation and replicability issues undermining preclinical research. There have been multiple calls for action, and the funders of biomedical research are actively pushing the inclusion of sex as a biological variable. Here, we consider the current standard practice within the preclinical research setting, why there is a movement to include females and why the imbalance exists. We explore organizational change theory as a tool to shape strategies needed at an individual and institute level to change the status quo. The ultimate goal is to create a scientific environment in which our preclinical research automatically implements sex-sensitive approaches. LINKED ARTICLES: This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

The odd couple: using biomedical and intersectional approaches to address health inequities

Background: Better understanding and addressing health inequities is a growing global priority.

Objective: In this paper, we contribute to the literature examining complex relationships between biological and social dimensions in the field of health inequalities. Specifically, we explore the potential of intersectionality to advance current approaches to socio-biological entwinements.

Design: We provide a brief overview of current approaches to combining both biological and social factors in a single study, and then investigate the contributions of an intersectional framework to such work.

Results: We offer a number of concrete examples of how intersectionality has been used empirically to bring both biological and social factors together in the areas of HIV, post-traumatic stress disorder, female genital circumcision/mutilation/cutting, and cardiovascular disease.

Conclusion: We argue that an intersectional approach can further research that integrates biological and social aspects of human lives and human health and ultimately generate better and more precise evidence for effective policies and practices aimed at tackling health inequities.

Let's Talk About Sex: Integrating Sex as a Biological Variable Into Epilepsy Research

There is a long history of underrepresentation of women and female animals being studied in scientific research, which has resulted in gaps in knowledge and at times, inaccurate clinical recommendations. There is a gradual shift in the mindset of the scientific community on this issue, in part related to policy changes enacted by the National Institute of Health (NIH). Sex must now be accounted for as a biological variable in both basic and clinical research. This review discusses the history of evolving policies on inclusion of sex-informed data in scientific research, and the ways in which epilepsy researchers can approach future studies in a manner that takes sex as a biological variable into account.

Beyond sex and gender difference in funding and reporting of health research

BACKGROUND

Understanding sex and gender in health research can improve the quality of scholarship and enhance health outcomes. Funding agencies and academic journals are two key gatekeepers of knowledge production and dissemination, including whether and how sex/gender is incorporated into health research. Though attention has been paid to key issues and practices in accounting for sex/gender in health funding agencies and academic journals, to date, there has been no systematic analysis documenting whether and how agencies and journals require attention to sex/gender, what conceptual explanations and practical guidance are given for such inclusion, and whether existing practices reflect the reality that sex/gender cannot be separated from other axes of inequality.

METHODS

Our research systematically examines official statements about sex/gender inclusion from 45 national-level funding agencies that fund health research across 36 countries (covering the regions of the EU and associated countries, North America, and Australia) and from ten top-ranking general health (the top five in "science" and the top five in "social science") and ten sex- and/or gender-related health journals. We explore the extent to which agencies and journals require inclusion of sex/gender considerations and to what extent existing strategies reflect state of the art understandings of sex/gender, including intersectional perspectives.

RESULTS

The research highlights the following: (a) there is no consistency in whether sex/gender are mentioned in funding and publishing guidelines; (b) there is wide variation in how sex/gender are conceptualized and how researchers are asked to address the inclusion/exclusion of sex/gender in research; (c) funding agencies tend to prioritize male/female equality in research teams and funding outcomes over considerations of sex/gender in research content and knowledge production; and (d) with very few exceptions, agency and journal criteria fail to recognize the complexity of sex/gender, including the intersection of sex/gender with other key factors that shape health.

CONCLUSIONS

The conceptualization and integration of sex/gender needs to better capture the interacting and complex factors that shape health-an imperative that can be informed by an intersectional approach. This can strengthen current efforts to advance scientific excellence in the production and reporting of research. We provide recommendations and supporting questions to strengthen consideration of sex/gender in policies and practices of health journals and funding agencies.

Sex and Gender Differences Research Design for Basic, Clinical, and Population Studies: Essentials for Investigators

A sex- and gender-informed perspective increases rigor, promotes discovery, and expands the relevance of biomedical research. In the current era of accountability to present data for males and females, thoughtful and deliberate methodology can improve study design and inference in sex and gender differences research. We address issues of motivation, subject selection, sample size, data collection, analysis, and interpretation, considering implications for basic, clinical, and population research. In particular, we focus on methods to test sex/gender differences as effect modification or interaction, and discuss why some inferences from sex-stratified data should be viewed with caution. Without careful methodology, the pursuit of sex difference research, despite a mandate from funding agencies, will result in a literature of contradiction. However, given the historic lack of attention to sex differences, the absence of evidence for sex differences is not necessarily evidence of the absence of sex differences. Thoughtfully conceived and conducted sex and gender differences research is needed to drive scientific and therapeutic discovery for all sexes and genders.

[Integration of sex/gender into environmental health research. Results of the interdisciplinary research network Sex/Gender-Environment-Health (GeUmGe-NET)]

The comprehensive consideration of sex/gender in health research is essential to increase relevance and validity of research results. Contrary to other areas of health research, there is no systematic summary of the current state of research on the significance of sex/gender in environmental health. Within the interdisciplinary research network Sex/Gender-Environment-Health (GeUmGe-NET) the current state of integration of sex/gender aspects or, respectively, gender theoretical concepts into research was systematically assessed within selected topics of the research areas environmental toxicology, environmental medicine, environmental epidemiology and public health research on environment and health. Knowledge gaps and research needs were identified in all research areas. Furthermore, the potential for methodological advancements by using gender theoretical concepts was depicted. A dialogue between biomedical research, public health research, and gender studies was started with the research network GeUmGe-NET. This dialogue has to be continued particularly regarding a common testing of methodological innovations in data collection and data analysis. Insights of this interdisciplinary research are relevant for practice areas such as environmental health protection, health promotion, environmental justice, and environmental health monitoring.

Sex in basic research: concepts in the cardiovascular field

Women and men, female and male animals and cells are biologically different, and acknowledgement of this fact is critical to advancing medicine. However, incorporating concepts of sex-specific analysis in basic research is largely neglected, introducing bias into translational findings, clinical concepts and drug development. Research funding agencies recently approached these issues but implementation of policy changes in the scientific community is still limited, probably due to deficits in concepts, knowledge and proper methodology. This expert review is based on the EUGenMed project (www.eugenmed.eu) developing a roadmap for implementing sex and gender in biomedical and health research. For sake of clarity and conciseness, examples are mainly taken from the cardiovascular field that may serve as a paradigm for others, since a significant amount of knowledge how sex and oestrogen determine the manifestation of many cardiovascular diseases (CVD) has been accumulated. As main concepts for implementation of sex in basic research, the study of primary cell and animals of both sexes, the study of the influence of genetic vs. hormonal factors and the analysis of sex chromosomes and sex specific statistics in genome wide association studies (GWAS) are discussed. The review also discusses methodological issues, and analyses strength, weaknesses, opportunities and threats in implementing sex-sensitive aspects into basic research.

Bias against research on gender bias

The bias against women in academia is a documented phenomenon that has had detrimental consequences, not only for women, but also for the quality of science. First, gender bias in academia affects female scientists, resulting in their underrepresentation in academic institutions, particularly in higher ranks. The second type of gender bias in science relates to some findings applying only to male participants, which produces biased knowledge. Here, we identify a third potentially powerful source of gender bias in academia: the bias against research on gender bias. In a bibliometric investigation covering a broad range of social sciences, we analyzed published articles on gender bias and race bias and established that articles on gender bias are funded less often and published in journals with a lower Impact Factor than articles on comparable instances of social discrimination. This result suggests the possibility of an underappreciation of the phenomenon of gender bias and related research within the academic community. Addressing this meta-bias is crucial for the further examination of gender inequality, which severely affects many women across the world.

A simple method to assess group difference in RT-qPCR reference gene selection using GeNorm: The case of the placental sex

Normalization with proper reference genes is a crucial step in obtaining accurate mRNA expression levels in RT-qPCR experiments. GeNorm and NormFinder are two commonly used software packages that help in selecting the best reference genes, based on their expression stability. However, GeNorm does not take into account a group variable, such as sample sex, in its calculation. We demonstrate a simple calculation step to assess the variability of such parameters by multiplying the GeNorm M value with the difference of Cq values between groups. To test this, we used 28 reference gene candidates, to analyze 20 placental samples (10 of each sex), and by using HPRT1 (lower Cq values in male placentas (P = 0.017)), as a target gene. Our calculation demonstrates that the RPL30 – GAPDH reference gene combination is the better option to assess small placental sex differences in mRNA level, versus the selection obtained from GeNorm or NormFinder. The HPRT1 normalized mRNA expression level is different between placental sexes, using RPL30 and GAPDH as reference genes (P = 0.01), but not when using genes suggested by GeNorm or NormFinder. These results indicate that the proposed calculation is appropriate to assess small variations in mRNA expression between 2 groups.

Integrating sex and gender into neurodegeneration research: A six-component strategy

Introduction

Despite important sex differences, there remains a paucity of studies examining sex and gender differences in neurodegeneration. The Canadian Consortium on Neurodegeneration in Aging (CCNA), a national network of researchers, provides an ideal platform to incorporate sex and gender.

Methods

CCNA's Women, Gender, Sex and Dementia program developed and implemented a six-component strategy involving executive oversight, training, research collaboration, progress report assessment, results dissemination, and ongoing manuscript review. The inclusion of sex and gender in current and planned CCNA projects was examined in two progress reporting periods in 2016.

Results

Sex and gender research productivity increased substantially for both preclinical (36%–45%) and human (56%–60%) cohorts. The main barrier was lack of funding.

Discussion

The Women, Gender, Sex and Dementia strategy resulted in a major increase of sex and gender into research on neurodegenerative disorders. This best practice model could be utilized by a wide variety of large multidisciplinary groups.

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There is a paucity of research on sex and gender in neurodegenerative disorders.

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A six-component strategy to integrate sex and gender into research was developed.

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Strategy implemented in national network of researchers studying neurodegeneration.

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Sex and gender research productivity increased for preclinical and human research.

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Strategy could be adapted and utilized across various multidisciplinary groups.

Event-Related Potentials as Biomarkers of Behavior Change Mechanisms in Substance Use Disorder Treatment

Substance use disorders (SUDs) are one of the most prevalent psychiatric conditions and represent a significant public health concern. Substantial research has identified key processes related to reinforcement and cognition for the development and maintenance of SUDs, and these processes represent viable treatment targets for psychosocial and pharmacological interventions. Research on SUD treatments has suggested that most approaches are comparable in effectiveness. As a result, recent work has focused on delineating the underlying mechanisms of behavior change that drive SUD treatment outcome. Given the rapid fluctuations associated with the key neurocognitive processes associated with SUDs, high-temporal-resolution measures of human brain processing, namely event-related potentials (ERPs), are uniquely suited to expand our understanding of the underlying neural mechanisms of change during and after SUD treatment. The value of ERPs in the context of SUD treatment are discussed along with work demonstrating the predictive validity of ERPs as biomarkers of SUD treatment response. Example associations between multiple ERP components and psychosocial and/or pharmacological treatment outcome include the P3a and P3b (in response to neutral and substance-related cues), the attention-related negativities (e.g., N170, N200), the late positive potential, and the error-related negativity. Also addressed are limitations of the biomarker approach to underscore the need for research programs evaluating mechanisms of change. Finally, we emphasize the advantages of ERPs as indices of behavior change in SUD treatment and outline issues relevant for future directions in this context.

A Guide for the Design of Pre-clinical Studies on Sex Differences in Metabolism

In animal models, the physiological systems involved in metabolic homeostasis exhibit a sex difference. Investigators often use male rodents because they show metabolic disease better than females. Thus, females are not used precisely because of an acknowledged sex difference that represents an opportunity to understand novel factors reducing metabolic disease more in one sex than the other. The National Institutes of Health (NIH) mandate to consider sex as a biological variable in preclinical research places new demands on investigators and peer reviewers who often lack expertise in model systems and experimental paradigms used in the study of sex differences. This Perspective discusses experimental design and interpretation in studies addressing the mechanisms of sex differences in metabolic homeostasis and disease, using animal models and cells. We also highlight current limitations in research tools and attitudes that threaten to delay progress in studies of sex differences in basic animal research.