Inclusion of Females Does Not Increase Variability in Rodent Research Studies

The underrepresentation of female subjects in animal research has gained attention in recent years, and new NIH guidelines aim to address this problem early, at the grant proposal stage. Many researchers believe that use of females will hamper research because of the need for increased sample sizes, and increased costs. Here I review empirical research across multiple rodent species and traits that demonstrates that females are not more variable than males, and that for most traits, female estrous cyclicity need not be considered. I present statistical simulations illustrating how factorial designs can reduce the need for additional research subjects, and discuss cultural issues around the inclusion of male and female subjects in research

Exploring the Effects of Hypoxia on Sulfate Reducing Anaerobes

Exploring the Effects of Hypoxia on Sulfate Reducing Anaerobes Annaliese K. Jones Sponsor: Bethany Jenkins, Cell and Molecular Biology As a student about to graduate with a degree in Biological Sciences, I find myself faced with the need to find my own independent research interests and scientific voice. As a result of my interests in the fields of both microbiology and ecology, I am drawn to questions surrounding the role and behavior of microorganisms in the environment. With climate change being an issue capturing the attention of a large portion of the scientific community, I have chosen to focus my attention on environmentally active microbes that reside in estuarine sediments, specifically Narragansett Bay, RI. These microbes may be affected by periods of marine hypoxia (defined by the Environmental Protection Agency as oxygen concentrations lower than 2 mg of O2/L of H2O). Hypoxia results from a combination of factors including nutrient loading, and stratification of the surface water from freshwater riverine inputs and warm surface water temperatures. These conditions promote phytoplankton blooms and subsequent oxygen depletion when dead phytoplankton biomass falls to sediments and is consumed by microorganisms that respire O2 as part of their metabolism. Climate change has been shown to exacerbate the problem of hypoxic ocean waters by increasing stratification and warming as well as by causing large changes in rainfall patterns, enhancing runoff of freshwater and nutrients to coastal ecosystems. Microbes residing in marine sediments impacted by hypoxia are responsible for a significant portion of the global cycling of nutrients, processes critical for life on land as well as in the ocean. Given these facts, I am particularly interested in how hypoxia impacts microbes that are involved in the cycling of sulfur (S) and in the cycling of nitrogen (N) in sediments from Narragansett Bay that experience seasonal hypoxia. Previous research conducted in Dr. Jenkins’ lab has revealed that a gene involved in N fixation, nifH, is highly expressed only during periods of hypoxia. When this gene was sequenced it was discovered that the environmental samples from Narragansett Bay were most closely related to those from groups of sulfate reducing bacteria. This led me to question the effects of hypoxia on sulfate reducing bacteria, if the processes of nitrogen fixation and sulfate reduction would display a link, and to determine the phylogenetic relationship of active S reducers to active N fixers. With this previous research serving as a point of comparison, I have chosen to examine the presence and expression of dsrB, a gene involved in the sulfate reduction pathway, during periods of seasonal hypoxia in Narragansett Bay, RI. I have done this by using molecular techniques (examining both the presence (DNA) and expression (RNA) of dsrB) to account for change bacterial sulfate reduction during periods when nitrogen fixers are expressing their genes. Sequence data from this gene (dsrB) was also used to identify the organisms responsible for sulfate reduction in Greenwich Bay. Results show a relationship between communities responsible for both processes based on gene expression and comparative community composition. Keywords: environmental microbiology, nutrient cycling bacteria, gene expression, hypoxia, climate chang

Frank Beach award winner: Neuroendocrinology of Group Living

Why do members of some species live in groups while others are solitary? Group living (sociality) has often been studied from an evolutionary perspective, but less is known about the neurobiology of affiliation outside the realms of mating and parenting. Colonial species offer a valuable opportunity to study nonsexual affiliative behavior between adult peers. Meadow voles (Microtus pennsylvanicus) display environmentally induced variation in social behavior, maintaining exclusive territories in summer months, but living in social groups in winter. Research on peer relationships in female meadow voles demonstrates that these selective preferences are mediated differently than mate relationships in socially monogamous prairie voles, but are also impacted by oxytocin and HPA axis signaling. This review addresses day-length dependent variation in physiology and behavior, and presents the current understanding of the mechanisms supporting selective social relationships in meadow voles, with connections to lessons from other species

Familiarity and Mate Preference Assessment with the Partner Preference Test

In contrast to traditional laboratory animals, prairie voles form socially monogamous partnerships in the wild and exhibit lasting social preferences for familiar individuals-both mates and same-sex peers-in the laboratory. Decades of research into the mechanisms supporting pair bonding behavior have made prairie voles an important model organism for the study of social relationships. The partner preference test is a laboratory test of familiarity preference that takes place over an extended interval (typically 3 hr), during which test subjects can directly interact with conspecifics and often engage in resting side-by-side contact (i.e., huddling). The use of this test has enabled study of the neural pathways and mechanisms involved in promoting or impairing relationship formation. The tendency to form partner preferences is also used as a behavioral indicator of the effects of early life experiences and environmental exposures. While this test was developed to assess the extent of social preference for mates in prairie voles, it has been adapted for use in other social contexts and in multiple other species. This article provides instructions for conducting the classic partner preference test, as well as variations including same-sex peer partner preference tests. The effects of several protocol variations are examined, including duration of cohousing, separation interval, use of tethers versus barriers, linear versus branched apparatus configuration, and duration of the test. The roles of social variables including sex of the focal individual, sex of conspecifics, reproductive state, and use of the test in other species are then considered. Finally, sample data are provided along with discussion of scoring and statistical analysis of partner preference tests

Neurobiology of Stress

The neurobiology of stress and the neurobiology of social behavior are deeply intertwined. The social environment interacts with stress on almost every front: social interactions can be potent stressors; they can buffer the response to an external stressor; and social behavior often changes in response to stressful life experience. This review explores mechanistic and behavioral links between stress, anxiety, resilience, and social behavior in rodents, with particular attention to different social contexts. We consider variation between several different rodent species and make connections to research on humans and nonhuman primates

Sex Bias in Neuroscience and Biomedical Research

Female mammals have long been neglected in biomedical research. The NIH mandated enrollment of women in human clinical trials in 1993, but no similar initiatives exist to foster research on female animals. We reviewed sex bias in research on mammals in 10 biological fields for 2009 and their historical precedents. Male bias was evident in 8 disciplines and most prominent in neuroscience, with single-sex studies of male animals outnumbering those of females 5.5 to 1. In the past half-century, male bias in non-human studies has increased while declining in human studies. Studies of both sexes frequently fail to analyze results by sex. Underrepresentation of females in animal models of disease is also commonplace, and our understanding of female biology is compromised by these deficiencies. The majority of articles in several journals are conducted on rats and mice to the exclusion of other useful animal models. The belief that non-human female mammals are intrinsically more variable than males and too troublesome for routine inclusion in research protocols is without foundation. We recommend that when only one sex is studied, this should be indicated in article titles, and that funding agencies favor proposals that investigate both sexes and analyze data by sex

Selectivity and Sociality: Aggression and Affiliation Shape Vole Social Relationships

The formation of selective social relationships is not a requirement of group living; sociality can be supported by motivation for social interaction in the absence of preferences for specific individuals, and by tolerance in place of social motivation. For species that form selective social relationships, these can be maintained by preference for familiar partners, as well as by avoidance of or aggression toward individuals outside of the social bond. In this review, we explore the roles that aggression, motivation, and tolerance play in the maintenance of selective affiliation. We focus on prairie voles (Microtus ochrogaster) and meadow voles (Microtus pennsylvanicus) as rodent species that both exhibit the unusual tendency to form selective social relationships, but differ with regard to mating system. These species provide an opportunity to investigate the mechanisms that underlie social relationships, and to compare mechanisms supporting pair bonds with mates and same-sex peer relationships. We then relate this to the role of aggression in group composition in a comparative context

Life in Groups: The Roles of Oxytocin in Mammalian Sociality

In recent decades, scientific understanding of the many roles of oxytocin (OT) in social behavior has advanced tremendously. The focus of this research has been on maternal attachments and reproductive pair-bonds, and much less is known about the substrates of sociality outside of reproductive contexts. It is now apparent that OT influences many aspects of social behavior including recognition, trust, empathy, and other components of the behavioral repertoire of social species. This review provides a comparative perspective on the contributions of OT to life in mammalian social groups. We provide background on the functions of OT in maternal attachments and the early social environment, and give an overview of the role of OT circuitry in support of different mating systems. We then introduce peer relationships in group-living rodents as a means for studying the importance of OT in non-reproductive affiliative behaviors. We review species differences in oxytocin receptor (OTR) distributions in solitary and group-living species of South American tuco-tucos and in African mole-rats, as well as singing mice. We discuss variation in OTR levels with seasonal changes in social behavior in female meadow voles, and the effects of OT manipulations on peer huddling behavior. Finally, we discuss avenues of promise for future investigation, and relate current findings to research in humans and non-human primates. There is growing evidence that OT is involved in social selectivity, including increases in aggression toward social outgroups and decreased huddling with unfamiliar individuals, which may support existing social structures or relationships at the expense of others. OT’s effects reach beyond maternal attachment and pair bonds to play a role in affiliative behavior underlying “friendships”, organization of broad social structures, and maintenance of established social relationships with individuals or groups

Adaptive Significance of Natural Variations in Maternal Care in Rats: A Translational Perspective

A wealth of data from the last fifty years documents the potency of early life experiences including maternal care on developing offspring. A majority of this research has focused on the developing stress axis and stress-sensitive behaviors in hopes of identifying factors impacting resilience and risk-sensitivity. The power of early life experience to shape later development is profound and has the potential to increase fitness of individuals for their environments. Current findings in a rat maternal care paradigm highlight the complex and dynamic relation between early experiences and a variety of outcomes. In this review we propose adaptive hypotheses for alternate maternal strategies and resulting offspring phenotypes, and ways to distinguish between these hypotheses. We also provide evidence underscoring the critical role of context in interpreting the adaptive significance of early experiences. If our goal is to identify risk-factors relevant to humans, we must better explore the role of the social and physical environment in our basic animal models