Apoptosis is the process by which cells in the body die in a controlled and predictable way because they have DNA damage or are no longer needed. The term comes from a Greek word meaning “falling off,” as in leaves falling from a tree.
When a cell undergoes apoptosis, it shrinks and pulls away from its neighbors. As the cytoskeleton that gives it shape and structure collapses, the envelope around the cell’s nucleus breaks down, and its DNA breaks into pieces. Its surface changes, signaling its death to other cells and leading a healthy cell to engulf the dying one and recycle its components.
What looks like a bubbling lava lamp is actually part of an egg cell’s maturation process. In many animals, the egg cell develops alongside sister cells. These sister cells are called nurse cells in the fruit fly (Drosophila melanogaster), and their job is to “nurse” an immature egg cell, or oocyte. Toward the end of oocyte development, the nurse cells transfer all their contents into the oocyte in a process called nurse cell dumping. This video captures this transfer, showing significant shape changes on the part of the nurse cells (blue), which are powered by wavelike activity of the protein myosin (red).
“A scientific career is really worth it,” says Hong Liu, Ph.D., an assistant professor of biochemistry and molecular biology at Tulane University School of Medicine in New Orleans, Louisiana. Check out the highlights of our interview with Dr. Liu below to learn about his journey as a scientist and his advice for students.
Q: What makes a career in science exciting?
A: I think there are at least two things that make a science career very exciting. The first is that doing science means you have freedom to explore a lot of new ideas. The second thing is it’s rewarding. The “rewarding” I’m talking about here is not like how much money you can make. It’s rewarding in the answers you find and the new knowledge you reveal.
Did you know that the lack of a single enzyme is responsible for lactose intolerance, a common condition that causes people to have trouble digesting milk? Fortunately, the enzyme is available in an over-the-counter pill for lactose-intolerant people who want to enjoy dairy products. Enzymes are molecules—almost always proteins—that speed up chemical reactions by reducing the amount of energy needed for the reactions to proceed. Without them, many processes in our bodies would essentially grind to a halt.
Our blood appears red for the same reason the planet Mars does: iron. The element may bring to mind cast-iron pans, wrought-iron fences, or ancient iron tools, but it’s also essential to life on Earth. All living organisms, from humans to bacteria, need iron. It’s crucial for many processes in the human body, including oxygen transport, muscle function, proper growth, cell health, and the production of several hormones.
Iron is the reason both our blood and the planet Mars appear red. The element also makes up the majority of Earth’s core and generates the planet’s magnetic field. Credit: Compound Interest. CC BY-NC-ND 4.0. Click to enlarge
A cross-section of a cell showing organelles. Credit: Judith Stoffer.
Welcome to our tour of the cell! Imagine you’ve shrunk down to about 3 millionths of your normal size. You are now about 0.5 micrometers tall (a micrometer is 1/1,000th of a millimeter). At this scale, a medium-sized human cell looks as long, high, and wide as a football field. But you can’t see nearly that far. Clogging your view is a rich stew of molecules, fibers, and various cell structures called organelles. Like the internal organs in your body, organelles in the cell each have a unique biological role to play.
The Nucleus and Its Closest Neighbor
Our first stop is the somewhat spherical structure about 50 feet in diameter. It’s the nucleus—basically the cell’s brain. The nucleus is the most prominent organelle and can occupy up to 10 percent of the space inside a cell. It contains the equivalent of the cell’s genetic material, or DNA.
Proteins play a role in virtually every activity in the body. They make up hair and nails, help muscles move, protect against infection, and more. Many NIGMS-funded researchers study the rich variety of proteins in humans and other organisms to shed light on their roles in health and disease.
Although zinc may appear last on nutrition labels, it’s the second-most abundant trace element in our bodies, behind only iron. (Trace elements are molecules our bodies need in small amounts to stay healthy). Zinc is crucial for a well-functioning immune system, wound healing, physical growth, the senses of taste and smell, and the construction of proteins and DNA. It can also partner with oxygen to form zinc oxide, a compound that scatters ultraviolet light and can act as a protective barrier over inflamed skin. Many sunscreens, burn ointments, diaper creams, and other skin treatments contain zinc oxide.
Zinc may help shorten colds, and it’s part of a compound that can protect skin from ultraviolet light. The element is also used to coat other metals and prevent rusting. Credit: Compound Interest. CC BY-NC-ND 4.0. Click to enlarge
When someone mentions aging, you may think of visible changes, like graying hair. Scientists can see signs of aging in cells, too. Understanding how basic cell processes are involved in aging is a first step to help people lead longer, healthier lives. NIGMS-funded researchers are discovering how aging cells change and applying this knowledge to health care.
Discovering the Wisdom of Worms
C. elegans with a ribosomal protein glowing red and muscle fibers glowing green. Credit: Hannah Somers, Mount Desert Island Biological Laboratory.
Aric Rogers, Ph.D., and Jarod Rollins, Ph.D., assistant professors of regenerative biology and medicine at Mount Desert Island (MDI) Biological Laboratory in Bar Harbor, Maine, are investigating aging by studying a tiny roundworm, Caenorhabditis elegans. Researchers often study C. elegans because, though it may seem drastically different from humans, it shares many genes and molecular pathways with us. Plus, its 2- to 3-week lifespan enables researchers to quickly see the effects of genetic or environmental factors on aging.
Drs. Rogers and Rollins investigate how C. elegans expresses genes differently under dietary restriction, enabling it to live longer. Understanding how genes are expressed when organisms live an extended life sheds light on the genetics underlying aging. This information could help researchers develop drugs or behavior modification programs that prolong life and delay the onset of age-related diseases such as heart disease, diabetes, cancer, and dementia.
Most of the mouthwatering dishes in a Thanksgiving feast share a vital ingredient: salt! Though the words “salt” and “sodium” are often used interchangeably, table salt is actually a compound combining the elements sodium and chloride. Table salt is the most common form that sodium takes on Earth. Many other sodium compounds are also useful to us. For instance, you might use baking soda, also known as sodium bicarbonate, in preparing Thanksgiving treats. Sodium compounds are also used in soaps and cosmetics and in producing paper, glass, metals, medicines, and more.
The best-known sodium compound is table salt (sodium chloride). Sodium also gives traditional streetlights their yellow glow and is essential for muscle and nerve function. Credit: Compound Interest. CC BY-NC-ND 4.0. Click to enlarge