Category: Cells

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What Students Want to Know About Cells

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Cell Day 2014

During a live online chat dubbed “Cell Day,” scientists at NIGMS recently fielded questions about the cell and careers in research from middle and high school students across the country. Here’s a sampling of the questions and answers, some of which have been edited for clarity or length.

What color are cells?
While cells with lots of iron, like red blood cells, may be red, usually cells are colorless.

How many different types of cells can be found inside the human body?
There are about 200 cell types and a few trillion total cells in the human body. That does not include bacteria, fungi and mites that live on the body.

Is it possible to have too many or not enough cells?
The answer depends on cell type. For example, within the immune system, there are many examples of diseases that are caused by too many or not enough cells. When too many immune cells accumulate, patients get very large spleens and lymph nodes. When too few immune cells develop, patients have difficulty fighting infections.

How fast does it take for a cell to produce two daughter cells?
Some cells, for example bacterial ones, can produce daughter cells very fast when nutrients are available. The doubling time for E. coli bacteria is 20 minutes. Other cells in the human body take hours or days or even years to divide.

Do skin cells stretch or multiply when you gain weight?
The size of cells is tightly regulated and maintained so they do not stretch much. As the surface area of the body increases with weight gain, the number of skin cells increases.

Why do cells self-destruct?
The term for cellular self-destruction is “apoptosis” or “programmed cell death.” Apoptosis is very important for normal development of humans and other animals as it ensures that we do not have too many cells and that “unhealthy” cells can be eliminated without causing harm to the surrounding cells. For instance, did you know that human embryos have webbing between their fingers and toes (just like ducks!)? Apoptosis eliminates the cells that form the web so that you are born with toes and fingers.

In what field is there a need for new scientists?
I would say that there is a need for scientists who can work at the interface between the biological and biomedical sciences and the data sciences. Knowing sophisticated mathematics and having computer skills to address questions like ‘what does this biomedical data tell us about particular diseases’ is still a challenge.

What is a scientist’s daily work day like? Is all of your time spent in a lab testing or like in an office throwing ideas around?
There are lots of different kinds of jobs a scientist can have. Many work in labs where they get to do experiments AND throw ideas around. Working in a lab is a lot of fun—you learn things about the world that no one has known before (how cool is that?). Other important jobs that scientists can do include writing about science as a journalist, helping other scientists patent new technologies they invent as a patent agent or lawyer, or working on important scientific policy issues for the government or other organizations.

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Cool Image: Lighting up Brain Cells

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Neurons activated with red or blue light.

Neurons activated with red or blue light using algae-derived opsins. Credit: Yasunobu Murata/McGovern Institute for Brain Research at MIT.

The nerve cells, or neurons, lit up in blue and red in this image of mouse brain tissue are expressing algae-derived, light-sensitive proteins called opsins. To control neurons with light, scientists engineer the cells to produce particular opsins, most of which respond to light in the blue-green range. Then they shine light on the cell to activate it. Now, a team of researchers led by Ed Boyden of the Massachusetts Institute of Technology and Gane Ka-Shu Wong of the University of Alberta has discovered an opsin that responds to red light preferentially, enabling them to manipulate two groups of neurons simultaneously with different colors of light and get a more comprehensive look at how those two sets of brain cells interact. Other opsins have shown potential for vision restoration in animal studies, and, because red light causes less damage to tissue than blue-green light, this new opsin might eventually be used for such treatments in humans.

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Capitalizing on Cellular Conversations

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Fat cells
Fat cells such as these listen for incoming signals like FGF21, which tells them to burn more fat. Credit: David Gregory and Debbie Marshall. All rights reserved by Wellcome Images.

Living things are chatty creatures. Even when they’re not making actual sounds, organisms constantly communicate using chemical signals that course through their systems. In multicellular organisms like people, brain cells might call, “I’m in trouble!” signaling others to help mount a protective response. Single-celled organisms like bacteria may broadcast, “We have to stick together to survive!” so they can coordinate certain activities that they can’t carry out solo. In addition to sending out signals, cells have to receive information. To help them do this, they use molecular “ears” called receptors on their surfaces. When a chemical messenger attaches to a receptor, it tells the cell what’s going on and causes a response.

Scientists are following the dialogue, learning how cell signals affect health and disease. They’re also starting to take part in the cellular conversations, inserting their own comments with the goal of developing therapies that set a diseased system right.

Continue reading this new Inside Life Science article

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Learning More About Our Partners in Digestion

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Bacteroides ovatus
Bacteroides ovatus. Credit: Eric Martens, University of Michigan Medical School.

After eating, we don’t do all the work of digestion on our own. Trillions of gut bacteria help us break food down into the simple building blocks our cells need to function. New research from an international team co-led by Eric Martens of the University of Michigan Medical School has uncovered how a strain of beneficial gut bacteria, Bacteroides ovatus, digests complex carbohydrates called xyloglucans that are found in fruits and vegetables. The researchers traced the microorganism’s digestive ability to a single piece of the genome. They also examined a publicly available set of genomic data, which included information from both humans and their resident bacteria, and found that more than 90 percent of 250 adults harbored at least one Bacteroides strain with xyloglucan-digesting capabilities. These results underscore the importance of the bacteria to human health and nutrition.

This work also was funded by the National Institute of Diabetes and Digestive and Kidney Diseases.

Learn more:
University of Michigan News Release
University of Michigan Host Microbiome Initiative
Gut Reactions and Other Findings About Our Resident Microbes from Inside Life Science
Body Bacteria from Findings Magazine

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Cool Image: Denying Microbial Moochers

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V. cholerae and V. cholerae

 

Productive V. cholerae (yellow) and exploitive V. cholerae (red). Credit: Carey Nadell, Princeton University.

What looks like an abstract oil painting is actually an image of several cholera-causing V. cholerae bacterial communities. These communities, called biofilms, include productive and exploitive microbial members. The industrious bacteria (yellow) tend to thrive in denser biofilms (top) while moochers (red) thrive in weaker biofilms (bottom). In an effort to understand this phenomenon, Princeton University researchers led by Bonnie Bassler discovered two ways the freeloaders are denied food. They found that some V. cholerae cover themselves with a thick coating to prevent nutritious carbon- and nitrogen-containing molecules from drifting over to the scroungers. In addition, the natural flow of fluids over biofilms can wash away any leftovers. Encouraging such bacterial fairness could boost the efficient breakdown of organic materials into useful products, such as biofuels. On the other hand, counteracting it could lead to better treatment of illnesses, like cholera, by starving the most productive bacteria and thereby weakening the infection.

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Visualizing Vessels

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Blood vessels in a mouse retina
Blood vessels in a mouse retina visualized using cutting-edge imaging technology. Credit: Tom Deerinck and Mark Ellisman, NCMIR.

For poets and lovers, the eyes are the windows of the soul. For scientists and doctors, blood vessels at the back of the eye are windows into many diseases.

Blood vessel abnormalities can indicate a variety of serious conditions such as atherosclerosis (hardening of the arteries), heart attacks and strokes. But most vessels are buried beneath skin and other tissues, making them difficult to examine without surgery.

There’s one exception—in the eye. Unlike anywhere else in the body, larger vessels on the retina at the back of the eye are directly visible through the pupil, requiring essentially only light and magnifying lenses to view.

These vessels are used to diagnose glaucoma and diabetic eye disease. Because they display characteristic changes in people with high blood pressure, some researchers hope retinal vessels might one day help predict an impending stroke, congestive heart failure or other diseases stemming from dangerously high blood pressure.

The medical importance of retinal vessels piqued the interest of scientists funded by the National Institutes of Health at the National Center for Microscopy and Imaging Research (NCMIR) at the University of California, San Diego, who captured this micrograph image of mouse retinal vessels.

Continue reading this new Inside Life Science article

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Dendrites Show Ability to Regenerate After Injury

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Dendrites
Cutting off the dendrites from nerve cells in fruit flies revealed that they can regenerate. Credit: Melissa Rolls, Penn State University.

When a bone breaks, it might slice axons—the part of nerve cells that sends information to other cells—and potentially cause loss of mobility or feeling. Prior research had shown that a damaged nerve cell could repair such an injury through the regrowth of axons. Scientists at Penn State University wondered if dendrites—the part of nerve cells that receive information from other nerve cells—could also regenerate. To find out, Melissa Rolls and her team cut off the dendrites from nerve cells in fruit flies. Instead of dying, as was expected, the cells regrew dendrites. The research also revealed that dendrite regeneration happens independently of axon regeneration, leading investigators to believe there are two separate regeneration pathways: one for axons and one for dendrites. Learning more about this new dendrite regrowth pathway might one day lead to new approaches for healing injured nerve cells, including those damaged after a stroke.

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Rolls Lab

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Animal Cells ‘Reach Out and Touch’ to Communicate

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Cytonemes in the fruit fly tracheal system.
Threadlike cytonemes (at right) convey signals between cells in the developing fruit fly tracheal system. Credit: Sougata Roy, University of California, San Francisco. View larger image

Scientists have long known that multicellular organisms use biological molecules produced by one cell and sensed by another to transmit messages that, for instance, guide proper development of organs and tissues. But it’s been a puzzle as to how molecules dumped out into the fluid-filled spaces between cells can precisely home in on their targets.

Using living tissue from fruit flies, a team led by Thomas Kornberg of the University of California, San Francisco, has shown that typical cells in animals can talk to each other via long, thin cell extensions called cytonemes (Latin for “cell threads”) that may span the length of 50 or 100 cells. The point of contact between a cytoneme and its target cell acts as a communications bridge between the two cells.

Until now, only nerve cells (neurons) were known to communicate this way. “This is an exciting finding,” says NIGMS’ Tanya Hoodbhoy. “Neurons are not the only ‘reach out and touch someone’ cells.”

This work also was funded by NIH’s National Heart, Lung, and Blood Institute.

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Cool Image: Visualizing Viral Activity

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Viral RNA (red) in an RSV-infected cell. Credit: Eric Alonas and Philip Santangelo, Georgia Institute of Technology and Emory University. 

Viral RNA (red) in an RSV-infected cell. Credit: Eric Alonas and Philip Santangelo, Georgia Institute of Technology and Emory University.

What looks like a colorful pattern produced as light enters a kaleidoscope is an image of a cell infected with respiratory syncytial virus (RSV) illuminated by a new imaging technology. Although relatively harmless in most children, RSV can lead to bronchitis and pneumonia in others. Philip Santangelo of the Georgia Institute of Technology and Emory University, along with colleagues nationwide, used multiply-labeled tetravalent RNA imaging probes (MTRIPS) to observe the entry, assembly and replication of RSV inside a living cell. Once introduced into RSV-plagued cells, the MTRIPS latched onto the viral RNA (in the image, red) without altering the level of infectivity. This led to fluorescent RSV viral particles that let the researchers track the viral RNA in host cells and better understand what the virus was doing. The knowledge gained from this new technique might aid in the development of RSV antiviral drugs and possibly a vaccine. Scientists could also one day use the imaging approach to study other RNA viruses, such as the flu and Ebola.

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Cool Images: Holiday Season Cells

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Yeast cells deficient in zinc and the Tsa1 protein have protein tangles. Credit: Colin MacDiarmid and David Eide, University of Wisconsin-Madison.

Yeast cells deficient in zinc and the Tsa1 protein have protein tangles. Credit: Colin MacDiarmid and David Eide, University of Wisconsin-Madison.

Just in time for the holidays, we’ve wrapped up a few red and green cellular images from basic research studies. In this snapshot, we see a group of yeast cells that are deficient in zinc, a metal that plays a key role in creating and maintaining protein shape. The cells also lack a protein called Tsa1, which normally keeps proteins from sticking together. Green areas highlight protein tangles caused by the double deficiency. Red outlines the cells. Protein clumping plays a role in many human diseases, including Parkinson’s and Alzheimer’s, so knowledge of why it happens—and what prevents it in healthy cells—could aid the development of treatments.

See more festive images!