Developmental, Reproductive & Evolutionary Biology Program

On Earth, gravity is constant. In spaceflight, gravity becomes a variable environmental stimulus—from the greater g-loads at launch to the microgravity aboard the ISS. To better understand the developmental response of mammals to gravity, we created an experiment that used a 24-foot centrifuge to create conditions of hypergravity. Starting at 1 g, we applied chronic acceleration over time until we reached 2 g, and then we looked at the graded effects across systems. Specifically, we looked at the metabolic changes in mammary glands. Would animals lactate? Would hormones be disrupted? Our experiment enabled us to draw a direct line between mammary metabolic activity and g-load.

To understand how animals adjust to conditions of hypergravity, we conducted follow-up experiments to examine mating of males and females after they experienced conditions of hypergravity on the centrifuge. We followed the estrous cycles while they spun, then mated the males and females. We could see the stimulus of hypergravity influencing biological stems in a dramatic way. There was a delay in the time it took females to get pregnant, but they eventually became pregnant.

Mammalian birth requires a highly regulated synchrony of tissue to propel a fetus from the womb. Connexin-43 is a gap junction protein that synchronizes the actions of the uterine cells at time of birth. Our experiment revealed less protein, but due to the reduced effectiveness of the contractions, birth required twice as many contractions in flight compared to ground controls during the same time period.

Foundational changes in pregnancy can occur that are persistent over the lifetime of an individual. Recent advances in biomedicine have given us new awareness of fetal programming; that is, what happens during pregnancy makes a difference to offspring as they grow. Epidemiological studies based on data from the Dutch Famine of 1944-45, in which pregnant mothers only received half the calories they needed, revealed that the Dutch experienced much higher rates of chronic diseases such as diabetes, high blood pressure, and obesity than are typically seen in a wealthy population. We are conducting experiments to help us understand how rodent babies will respond to fetal stress. Researchers in our lab are examining cells, tissues, and entire organisms from our previous 2 g study to help us understand post-natal development and formation in a physiological system. Specifically, we are looking at an enzyme that is protective of the fetus when it is exposed to the stress hormone corticosteroid.

To learn more about current and upcoming research projects in the NASA Space Biology Program, search the Task Book: Biological and Physical Sciences Division and Human Research Program. Our online database of research projects includes project descriptions, annual research results, research impacts, and a listing of publications resulting from this NASA-funded research.

A searchable archive of NASA life sciences research is available at the Life Sciences Data Archive.

Experiments that explore the molecular response of terrestrial biology to spaceflight have generated vast amounts of genomics data that are now publicly available for download from GeneLab.

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