Jonker Lab

The fetus typically grows and matures in a low-lipid intrauterine environment. However, circulating fetal lipid levels may rise with maternal dyslipidemia or infection, and are always higher after birth no… read more

When the placenta doesn’t work properly to transfer nutrients and oxygen from the mother to the fetus, it causes the fetus to grow slowly and changes development of the fetal… read more

Fetal lipid levels are normally low but can rise with maternal dyslipidemia, infection, or after birth. How immature organs respond to early lipid exposure isn’t well understood. In this study,… read more

In many sheep research groups, maternal analgesia is delayed until after fetal surgery due to concerns about maternal or fetal side effects. Research scholar Sarah Alaniz led this study to… read more

We just published a correction to our study on the physiology of late-gestation fetuses exposed to high lipid levels. After the original publication, we realized the Oil Red O staining… read more

Circulating lipid levels are typically low during fetal development but rise sharply at birth. Premature infants are exposed to these elevated lipid levels earlier than expected, but how does the… read more

The KNDy neurons, located in the hypothalamic arcuate nucleus, play a crucial role in regulating the pathways responsible for masculinizing the male brain. In this study, we explored how these… read more

Hypoplastic left heart syndrome (HLHS) is a congenital anomaly that poses a serious threat to life immediately after birth. Without prompt intervention through a series of life-saving surgeries, infants with… read more

Finding genes that maintain a stable expression level across large developmental windows is a real challenge. In our research, we’ve developed a novel method to normalize gene expression in the… read more

Most cardiomyocytes, the muscle cells that pump blood, are formed during fetal development and typically last a lifetime. Surprisingly, many of these cells undergo programmed cell death around the time… read more

Cardiac troponins are molecules essential for heart muscle contraction and are commonly used as biomarkers to detect heart damage when they appear in the bloodstream. It’s well known that levels… read more

While critical for brain development, circulating lipids in the fetus are low. After birth, however, breastmilk and other forms of neonatal nutrition are rich in lipids, leading to a sharp… read more

During fetal development, the heart primarily relies on carbohydrates for energy, as fatty acids are in limited supply. But after birth, the availability of circulating fatty acids increases dramatically, prompting… read more

Hypoplastic Left Heart Syndrome (HLHS) is a rare but devastating congenital heart defect. In babies born with this condition, the left side of the heart—particularly the left ventricle—fails to develop… read more

How does a fetus become masculinized? It turns out, it’s not just about testosterone—it’s about a complex back-and-forth between the developing brain and the gonads. We’ve known for a while… read more

Contraction in the muscle cells of the mature heart begins at specialized areas where signals on the cell surface are passed inside. These areas are called “dyads” because there are… read more

The workload of the heart and skeletal muscles change significantly at the time of birth. However, it is not well understood how blood supply changes to these muscles in this… read more

The workload of the heart and skeletal muscles change significantly at the time of birth. However, it is not well understood how blood supply changes to these muscles in this… read more

Despite birth being a universal experience that profoundly changes cardiovascular physiological, little is known about how the coronaries change at this pivotal moment. We studied how blood flow to the… read more

Masculinization of the fetal brain depends on testosterone produced by the fetal testis. In turn, production of testosterone by the fetal testis is under the control of other hormones. GnRH… read more

Skeletal muscle growth in the fetus requires oxygen. Chronic anemia changes the oxygen environment of the fetus, and can reduce oxygen availability in some fetal organs and tissues. This study… read more

Despite efforts by the NIH and others over the past decades some groups of people, including those that are Black, Hispanic/Latino, and indigenous Americans, are deeply under-represented in the biomedical… read more

The hormones “insulin-like growth factor 1” (IGF-1) and insulin are both critical for normal fetal growth. Experimentally increased IGF-1 increases fetal size, but decreases fetal insulin levels. In this study… read more

The hormone “insulin-like growth factor 1” (IGF-1) stimulates increased growth in some fetal organs. But growth requires more than activation of pro-growth signaling pathways, it also requires a supply of… read more

The coronary arteries are what supplies oxygen to the working muscle of the heart. We can increase the amount of heart muscle in the fetal sheep by giving it IGF-1.… read more

Steps of sexual differentiation occurs in specific phases during fetal development. Early in development it is not clear if certain brain pathways that regulate release of sex steroids are intact… read more

When blood flow into a heart chamber is increased, it causes the chamber to fill more. That distention makes the chamber adapt over time. This paper is about what happens… read more