Category: Cells

Science Snippet: The Marvels of Membranes

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Like skin that covers and protects our bodies, membranes surround and protect cells and organelles. Membranes are semi-fluid barriers composed mainly of lipids and proteins. They provide structure; control the import and export of molecules such as ions, nutrients, and toxins; and support cellular communication.

An illustration of a cell cut in half with gray lines indicating its borders and borders of adjacent cells. The cell contains a variety of round and oblong structures in several colors.
A cross section of a cell with its membrane and adjacent cell membranes outlined in gray. The colorful structures are organelles with membranes. Credit: Judith Stoffer.

The lipids that compose membranes are primarily phospholipids. (Cholesterol is another lipid often present in membranes that helps regulate their stiffness.) Phospholipids have hydrophilic (water-loving) “heads” and hydrophobic (water-fearing) “tails.” Within the human body, a water-loving environment, they line up so that their tails face one another and their heads point outward. In membranes, this alignment makes a bilayer barrier that is two lipid molecules deep.

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In Other Words: The Pathways Inside Our Bodies

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For many people, the word pathway may bring to mind stepping stones in a garden or a trail through a forest. But when biologists talk about a pathway, they’re referring to a series of actions among molecules in a cell that leads to a certain product or change within that cell. Pathways maintain balance during walking, control how the eyes’ pupils respond to light, and affect skin’s reaction to changing temperature. They control our bodies’ responses to the world, and errors in them can lead to disease.

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Career Conversations: Q&A with Biologist Akhila Rajan

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A headshot of Dr. Akhila Rajan. Dr. Akhila Rajan. Credit: Fred Hutchinson Cancer Research Center.

“What makes being a scientist exciting is that I don’t know what I’m going to find tomorrow,” says Akhila Rajan, Ph.D., an assistant professor in the basic sciences division at Fred Hutchinson Cancer Research Center in Seattle, Washington. Dr. Rajan is supported by an NIGMS early stage investigator Maximizing Investigators’ Research Award. These awards provide stable and flexible funding for a program of research that falls within NIGMS’ mission. Check out the highlights of our interview with Dr. Rajan to learn about her research and journey as a scientist.

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Cool Images: Spooky and Spectacular

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It’s the spookiest time of the year! To celebrate Halloween, we’re showcasing scientific images that capture the spirit of the holiday, from a brain shaped like a bat to protein “cobwebs” in a quail embryo. Check out our image and video gallery for even more scientific photos, illustrations, and videos.

Cool Images
A tadpole-shaped creature outlined in blue, with branching green structures throughout its body.
The eerie green “skeleton” in this photo is really the vasculature (blood vessels) of a zebrafish embryo. The blue areas are cell bodies. Zebrafish are useful research organisms for studying development because their eggs and embryos are see-through, making it easy for scientists to watch changes take place.
Credit: Andreas Velten, Eliceiri Lab, University of Wisconsin-Madison.
Fourteen mosquito larvae resembling orange worms grouped together.
Researchers edited the genes of these creepy-crawly mosquito larvae using a technique called CRISPR (clustered regularly interspaced short palindromic repeats). This species of mosquito, Culex quinquefasciatus, can transmit diseases including West Nile virus, Japanese encephalitis virus, and avian malaria. The gene-editing toolkit used on these larvae could ultimately help stop Culex quinquefasciatus from spreading pathogens.
Credit: Gantz Lab, University of California, San Diego.
Weblike structures over a group of green spots.
The “cobwebs” in this image are actually a protein called vimentin in a quail embryo. The green spots are cell nuclei. Vimentin is part of the cytoskeleton and helps cells maintain their structure and resist mechanical stress. The protein is found in many animals and in humans.
Credit: Evan Zamir, Georgia Tech.

Science Snippet: Brush Up on Biofilms

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A biofilm is a highly organized community of microorganisms that develops naturally on certain surfaces. Typically, biofilms are made up of microbes and an extracellular matrix that they produce. This matrix can include polysaccharides (chains of sugars), proteins, lipids, DNA, and other molecules. The matrix gives the biofilm structure and helps it stick to a surface.

Formation of a biofilm often involves a process called quorum sensing. In this process, microbes detect when they reach a certain population density and change their behavior in ways that help them function as a community.

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Make Like a Cell and Split: Comparing Mitosis and Meiosis

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Your body is made up of trillions of cells that all originate from just one—a fertilized egg. The massive multiplication of cells after conception is possible thanks to cell division, which occurs when one cell splits into two. Cell division not only enables growth but also replaces damaged or dead cells and makes reproduction possible. There are two kinds of cell division: mitosis and meiosis.

On the left, a cell goes through the stages of mitosis to split into two cells that each have two sets of chromosomes. On the right, a cell goes through the phases of meiosis to divide into four cells that each have a single set of chromosomes. Mitosis is shown on the left, and meiosis is shown on the right. Credit: Judith Stoffer. Click to enlarge
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Cool Images: Beautiful Bits of Blue

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Most cells are naturally colorless, which is why scientists often use fluorescent tags and other tools to color cell structures and make them easier to study. (Check out the Pathways imaging issue for more on scientific imaging techniques). Here, we’re showcasing cell images that feature shades of blue. Visit our Image and Video Gallery for additional images of cells in all the colors of the rainbow, as well as other scientific photos, illustrations, and videos.

Cool Images
Many blue circles, each surrounded by yellow dots. All the structures are encased in gray webs.
Mitochondria appear in yellow and cell nuclei in blue in this photo of cow cells. The gray webs are the cells’ cytoskeletons. Mitochondria generate energy, nuclei store DNA, and the cytoskeleton gives cells shape and support.
Credit: Torsten Wittmann, University of California, San Francisco.
A large circle made up of light blue dots, with darker blue spots underneath and outside of it.
Here, stem cells (light blue) are growing on fibroblasts (dark blue). Stem cells are of great interest to researchers because they can develop into many different cell types. Fibroblasts are the most common cell type in connective tissue. They secrete collagen proteins that help build structural frameworks, and they play an important role in wound healing.
Credit: California Institute for Regenerative Medicine.
Two blue circles encapsulated in red threads and surrounded by other scattered blue circles.
These smooth muscle cells were grown from stem cells. Smooth muscle cells are found in the walls of certain organs, such as the stomach, and can’t be controlled voluntarily. Red indicates smooth muscle proteins, and blue indicates nuclei.
Credit: Deepak Srivastava, Gladstone Institutes, via CIRM.

Science Snippet: Apoptosis Explained

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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.

On the left, two large cells with clear, smooth edges. On the right, two smaller cells with ragged edges.
Two cells in a healthy state (left) and entering apoptosis (right). Credit: Hogan Tang of the Denise Montell Lab, Johns Hopkins School of Medicine.
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Cool Video: A Biological Lava Lamp

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Several spheres contorting and lighting up inside a cone-shaped structure.
Credit: Jasmin Imran Alsous and Jonathan Jackson, Martin Lab, Massachusetts Institute of Technology.

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).

Researchers created the video using a confocal laser scanning microscope. Learn about this type of microscope and other scientific imaging tools by stepping into our virtual imaging lab, and check out more basic science videos and photos in the NIGMS Image and Video Gallery.

This post is a great supplement to Pathways: The Imaging Issue.

The video was taken using a confocal laser scanning microscopy (sometimes shortened to just “confocal microscopy”), one of the techniques mentioned in the Pathways timeline (1970s).

Learn more in our Educator’s Corner.

Career Conversations: Q&A with Molecular Biologist Hong Liu

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A scientist wearing a lab coat and holding a pipette in front of a workbench with scientific instruments.
Dr. Hong Liu in the lab.
Credit: Courtesy of Dr. Hong Liu.

“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.

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