A Breakthrough in Nerve Cell Regeneration

When you conjure up an image of cells, what do you see? What do you think? You may see a snapshot of an animal tissue, perhaps with actively dividing cells. That’s understandable because, as animals ourselves, we’re aware that cells come from other cells, thus the need to undergo mitosis, or cell division, frequently.

But one kind of mammalian animal cell does not fit that image—nerve cells. They do not arrange themselves as cells in a typical tissue do. Nerve cells are singular, with a long, sometimes very long, threadlike extension called an axon. And they don’t undergo mitosis frequently, except in embryos. This apparent aberration in the world of cells has puzzled scientists and medical researchers. If one could get nerve cells to behave more like other cells in terms of regeneration, a host of nerve-related diseases and damage could be reversed.

ScienceDaily published a story on January 26, 2009, reporting on exactly that kind of breakthrough, New Hope For Restoring Injured Nerves. A group of researchers at the University of Utah uncovered a pathway (a chain of molecular events) involving a gene that, when forced to be overactive, leads to repair of severed nerve cells in nematode worms. The gene is also found in mammalian genomes; thus, the researchers predict they will be able to replicate the study in mammals.

Finding a gene that produces a protein that aids in nerve cell repair in worms is not surprising. Gene theory predicts just that in organisms known to regenerate portions of their anatomy. It also is not necessarily surprising to find the same gene in mammalian systems, since evolutionary theory reveals our common ancestry. What did surprise researchers was that the pathway that results in nerve cell regeneration is not found in developing embryos.

Scientists have puzzled over the fact that nerve cells are regenerated in mammalian embryos and very young, rapidly developing mammals, but not in adults. The question was, what did mammals lose along the way to maturity? The pathway discovered in the new study “is unique in that it is not used by the nervous system during normal embryo development, yet it is absolutely required for regeneration,” one of the researchers said.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

Middle school curriculum usually includes some study of cells, genetics, and body systems. This story provides background for some authentic discussions allowing students to apply and extend their knowledge in these three areas. At the same time, it provides opportunity to reinforce concepts in methods of science.

Ask students what happens to a worm that gets cut in half by a gardener’s shovel? To a starfish whose leg is bitten off by a predator? What is regeneration? Have they ever wondered why humans cannot do the same? Do they know that mammalian embryos and very young mammals do have the ability to regenerate? How might regeneration be related to the science of genes? What does the idea of regeneration have to do with curing paralysis in humans?

Remind students of cell theory and show them some visuals of cells, and cells in tissues, organs, and systems. Show them some nerve cells. If they’ve studied the nervous system, they already have some notions regarding nerve cell structure and function. Explain that in paralysis, the nerve is severed and, in adults, not easily repaired.

Point out that scientists have uncovered the worms’ pathway that enables their nerve cells to regenerate. Ask how such a discovery could possibly be useful in mammalian systems? Remind students that all living things share some common characteristics, like cellular structure, DNA, and the ability to respond to stimuli. Is it possible that mammalian genomes could contain the same or similar genes that enable regeneration in worms? As predicted by evolutionary theory, the answer is yes!

So why can’t we regenerate nerve cells? Remind students, or explain, that genes have to be turned on in order to produce the necessary proteins that participate in a pathway culminating in regeneration. In this study, scientists methodically “knocked out” genes, one by one, in worms until they found the one primarily responsible for nerve cell regeneration. (There actually are four genes working together.) When the scientists created conditions that enabled the gene to increase its activity, producing ample protein associated with regeneration, nerve cell regeneration was rapid in adult worms. This confirmed their hypothesis regarding the activity of a particular gene on regeneration. It also enabled them to uncover the steps in the pathway from gene to cell regeneration. Knowing the steps allows scientists to hypothesize possible ways to enhance the pathway in order to induce regeneration in mammals.

Using this story allows you to facilitate student synthesis of knowledge from perhaps three different units in their curriculum around three fundamental theories: cell theory, gene theory and evolutionary theory. It also reinforces concepts associated with the Life Science content standard of the National Science Education Standards, as well as the History and Nature of Science content standard.

Here are additional resources from the National Science Digital Library Middle School Portal 2 (MSP2): Visit Cell City; Middle School Meets Evolution; Cell Differentiation; andCell Biology Animation.

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We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org.

This post was originally written by Mary LeFever and published January 27, 2009 in the Connecting News to the National Science Education Standards blog. The post was updated 3/22/12 by Jessica Fries-Gaither.

How Many Bacteria Species Can Coexist on a Single Hand? (And do girls really have cooties?)

Sounds like a riddle, but it’s not trivial. We’ll get back to that in a minute. First consider the scenario: The class arrives from physical education. Today’s activity was mat ball, a variation of dodge ball involving lots of kids and lots of contact with balls and mats. They’re pumped, a little sweaty and out of breath, and one or two are a few seconds late—probably not because they were washing their hands! Would you have students wash their hands in this scenario? Not likely. It’s just not part of the lesson plan.

We accept a certain lack of sanitation mostly because it’s not feasible to allow 26-30 kids to wash their hands several times a day. We try to take solace in the hand sanitizers, though rumor has it there’s no substitute for warm water, soap and a minute of scrubbing.

Low-temperature electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times. Each individual bacterium is oblong shaped. Photo by Eric Erbe, digital colorization by Christopher Pooley, both of USDA, ARS, EMU. Wikimedia Commons.

So what’s the big deal? Most bacteria on our skin are harmless or beneficial, right? How many could there be anyway? Well, CBCnews.ca recently published a story, Women lead men in bacteria types, hands down  that might surprise you. Researchers were surprised to find the incredible number of different bacteria species found among 51 college students’ hands and the very low number of species shared by all students. Further, there was a difference between left and right hands. And finally, there was a significant difference between men and women.

According to the news article,

They [researchers] identified 4,742 species of bacteria overall, only five of which were on every hand . . . The average hand harboured 150 species of bacteria. Not only did individuals have few types of bacteria in common, the left and right hands of the same individual shared only about 17 per cent of the same bacteria types . . .

Researchers suspect differences between left-and right-hand bacteria diversity have to do with each hand’s interactions with environment that can alter the hand’s conditions in terms of oil or salinity, for example. Differences between men and women might have to do with hormone production or slight variations in pH. Researchers commented that, for the subjects involved in this study, hand washing did not appear to remove the bacteria. It is important to note the study did not measure mass of bacteria present or population sizes for each species, only the diversity of species present.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

The National Science Education Standards Content Standard F states:

As a result of activities in grades 5-8, all students should develop understanding of

  • Personal health
  • Populations, resources, and environments
  • Natural hazards
  • Risks and benefits
  • Science and technology in society

The ideas in this news article connect to the bullets above. The following discussion highlights the ideas in the list.

Ask students if they’ve ever had a bacterial infection. What caused it? What are bacteria? Many will state they are harmful, disease causing germs. How common do they believe bacteria are? Are they in contact with any right now? How do they protect themselves against bacterial disease? Lead students to understand that many kinds of bacteria are harmless and, in fact, beneficial. Our digestion is aided by bacteria, for example. Bacteria are used in the production of yogurt and cottage cheese, among other foods. You can show them photomicrographs indicating bacteria are distinct cells, but quite small. Bacteria impact our personal health in both positive and negative ways.

How are bacteria connected to populations, resources and environments? Remind students that a group of the same kind of bacteria living in the same area is a population. Can a human hand be an adequate environment with resources to support a bacteria population? How many kinds of bacteria do you think might be able to coexist on a single human hand? Entertain all students’ guesses. Share only the numbers from the story with them. How do their guesses compare with the numbers reported?

Try some true or false questions:

1. There is no difference in the kinds of bacteria found on the same person’s right and left hand.

2. Men and women have the same kinds of bacteria on their hands.

3. Among a group of people, there is a high number of different kinds of bacteria that all people share.

Share the rest of the findings reported in the article. Ask students to generate inferences to account for the variation reported. What questions can they generate related to the findings? What kind of tests do they think would be good to conduct next and why?

You can connect the idea of natural hazards to changes in bacteria populations if you care to. After a flood for example, the biggest threat is disease due to polluted water, from overflow of sewage mixing with drinking-water supplies. At times like these, the bacteria populations found on flood-ravaged persons’ hands can be expected to differ from those found under normal conditions.

What are the risks and benefits involved in controlling bacteria through various methods: sanitation, sterilization, irradiation, and antibiotics, for example? What are the risks and benefits of using helpful bacteria to control or minimize the occurrence of harmful bacteria in food?

What role does technology play in public health policies regarding available vaccinations, medicines, and public education campaigns? See the Centers for Disease Control webpage for additional ideas and information at http://www.cdc.gov/ncidod/guidelines/guidelines_topic_bacterial.htm

To find lessons and activities that would support this topic of study, please search the MSP2 Educational Digital Library – http://www.msteacher2.org/page/search-the-msp2-collection-of?q=bacteria&action=Search. Terms such as germs or bacteria will get you started.

We Want Your Feedback

We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org.

This post was originally written by Mary LeFever and published November 10, 2008 in the Connecting News to the National Science Education Standards blog. The post was updated 2/29/12 by Jessica Fries-Gaither.

Celebrate Women’s History Month with STEM Stories

The STEM Stories website features a growing collection of digital resources that highlight the lives and work of individuals involved in STEM fields (mainly women). It combines compelling personal stories and multimedia to interest intermediate and middle school students in STEM subjects and careers.

From the In the Spotlight menu, you’ll meet 10 present-day women who are featured in depth, with interviews, photo albums and more.  They include dolphin communication researcher Diana Reiss, atmospheric chemist Susan Solomon, biologist and astronaut Millie Hughes-Fulford, and robotics engineer Heather Knight. (Heather helped work on the Rube Goldberg machine sequence for the OK-Go music video This Too Shall Pass).  On the Clips tab, the database includes short videos that introduce individuals working in varied STEM careers.  The Profiles tab lets you search biographies about women working in STEM fields throughout history.  Some include photo albums, such as Mary Pennington, Rachel Carson, and Virginia Apgar. (Tip:  double-click on images to see a larger view).

The project team, headed by Lois McLean and Rick Tessman (McLean Media) created STEM Stories with girls in mind, drawing on design ideas from an after-school club for at-risk middle and high school girls. In a 2010 pilot, more than 200 students (Grades 4–7) in Nevada County, California, used the site in classroom activities. In one school, fourth- and seventh-grade students worked in pairs to create pop-up books based on featured individuals. Survey results found no major differences between the responses of boys and girls. In fact, teachers reported that students did not even comment on or question the site’s emphasis on women. And, although the website focuses on personal stories, most students also reported learning something new about science and engineering.

STEM Stories was funded through a grant from the NSF’s Research on Gender in Science in Engineering Program (#HRD-0734004). New content is being added every month, including more current and historical photos, profiles, videos, and interactives.

To introduce your students to the STEM Stories site, try these activities:

STEM Stories Treasure Hunt

STEM Stories Crossword Puzzle

STEM Stories Lesson Ideas


We Want Your Feedback
We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org. Post updated 4/19/2012.

Cells Without A Microscope

No access to a microscope? Check out the Exploratorium’s Microscope Imaging Station — you can see videos of sea urchin cells dividing, stem cells, a zebrafish heart cell beating, and more. Any of the images here can be used in educational settings.

You can also build a cell model, and “scale up” cell and organelle dimensions to human scale. If a cell was the size of my head, how big would a mitochrondria be? Or, build a 3D diaorama inside a shoebox. One teacher uses the analogy of a school — the nucleus is the principal’s office, the DNA is the school files, the teachers are the ribosomes, the students would be proteins, and the school bus is a vesicle. Or, list a set of different analogies (the cell is like “The Simpsons”, the cell is like “a city”) and let students choose, and make their set of analogical functions.

You can also model a cell membrane using soap film. You can stick a wet finger through a bubble film, just like plasma membranes are selectively permeable. See this activity here.

This Traits of Life website at the Exploratorium has a set of online interactives and downloadable posters and articles.

You can do a play or drama about the cell — here’s an example about the Immune System from a teaching tips podcast.

Original posting on the sciencegeekgirl blog

Investigating Cell Size

How big are cells? Ask most middle school students that question, and they’ll tell you that cells are very small – even microscopic! But what if you asked them to compare the size of cells in a whale and a shrew?

That’s the engaging scenario laid out in “Whale and Shrew,” a formative assessment probe from Uncovering Student Ideas in Science, Volume 2: 25 More Formative Assessment Probes (NSTA Press, 2007). The probe unearths a subtle, yet fundamental concept of cell theory – that there are natural constraints that necessarily limit cell size. How can you help your students reach this conclusion?

An inquiry-based activity provides an opportunity for students to answer the question, “How does the size of a cell affect its ability to exchange materials with its environment?” Or, more simply stated, “Why are cells small?”

These two activities could be used as is, or they could be adapted for a guided inquiry experience. Both involve analyzing how the surface area to volume ratio affects the rate of diffusion in cubes of various sizes. Each uses different materials and a slightly different procedure.

Cell Size and Division
Students test”cells” made of agar and phenolphtalein with sodium hydroxide. They observe the rate of diffusion (evident by color change) in 1x1x1, 2x2x2, and 3x3x3 cubes.

Experiment on Cell Surface Area and Volume
In this lesson, students test “cells” made of potatoes with Lugol’s solution. They observe the rate of diffusion (evidenced by color change) in cubes with a length of 0.5 cm, 1 cm, 1.5 cm, 2 cm, 2.5 cm, and 3 cm. They also calculate the surface area, volume, and ratio of surface area to volume of all cubes.

How can you turn these activities into an inquiry-based lesson? We recommend starting with the probe to assess student thinking and spark interest. Next, you may ask students to generate a testable question based on the probe, or you may choose to provide the question for them. Students can then plan and conduct an investigation using the materials specified in either one of the lessons. Prompt students to generate claims and draw conclusions based on evidence from the investigation.

Teachers of younger students (grades 5 and 6) may wish to use the potatoes and Lugol’s solution, while an 8th grade teacher may have access to agar, phenolpthalein, and sodium hydroxide. Teachers may also modify this activity by removing the surface area and volume calcuations and instead relying on the qualitative observations made during the activity. Either way, students will gain new insight into why cells in any organism are small.

We Want Your Feedback
We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org. Post updated 4/11/2012.