Most students could explain that the light microscope was the tool first used to see cells and establish the cell theory.  However, as study turned toward the inner structures of the cell, electron microscopes and x-ray crystallography supplanted the light microscope as the favored research tool.  A microscope’s ability to magnify is limited by resolving power, the smallest separation the microscope can clearly view.  Because of interference between light waves, the resolving power of light microscopes sits close to 200 nm.  While many cellular organelles fall just within this range, studying anything finer than the larger organelles with traditional light microscopes is effectively impossible.

In 1931, a pair of German scientists realized they could achieve greater resolving power by shooting electrons at a sample instead of light waves.  The wavelength of an electron beam is much shorter than visible light, decreasing diffraction and enabling clear magnifications of up to 2 million times.  The improved resolution doesn’t come without a price, however.  Electron microscope samples must be prepared in a way that kills the specimen, meaning scientists can’t view living cells or watch cell functions as they occur.  Consequentially, much of cell research of that era centered on documenting the structure and minute details of subcellular components.

In a paradigm shift of cellular research, many scientists are now turning their focuses back to questions about how cell functions occur.  Researchers keen on studying cellular events as they happen have fueled a revolution of microscopy, bringing light microscopes, with their ability to study living samples, back into vogue.  Light microscopes have benefited from the improved design of the confocal microscope, the use of fluorescent molecules and the integration of computing power into the image formation process.  Collectively, these three improvements have restored the light microscope’s role as essential equipment.

Confocal microscopes represent a significantly different light microscope design than most people are familiar with.  This technique involves cutting thin pieces of a sample and viewing each individually, preventing interference from above and below the plane of view.  To further improve the image, confocal microscopes also focus narrow lasers on the sample, rather than blanketing the entire area with light waves.

Use of fluorophores, molecules able to emit light, has revolutionized light microscopy.  Organic molecules such as green fluorescent protein can be genetically engineered into organisms, enabling specific cell parts or cell types to glow on their own, aiding in locating and focusing.  Scientists such as Sunney Xie of Harvard have perfected the technique of adding fluorescent labels to a sample and using the emitted light to locate even individual molecules within a cell.

Improved computer technology has added the final piece to the light microscope puzzle, powering most modern techniques.  By filtering her microscope data through computer programs, Xiamowei Zhuang, another Harvard researcher, is able to focus in on individual fluorophores smaller than the microscope’s limit of resolution.  Using this initial data for calibration, Zhuang’s STORM technique is able to clear away the interference from the rest of the image.   

New technology and lab strategies have helped light microscopes reemerge as a powerful tool in examining the cell.  Despite the superior power of electron microscopes, they can’t help scientists watch neurons interact or genes activate, as light microscopes can.  While the scopes in the Zhuang lab bare no resemblance to the simple versions in classrooms across the country, they carry on the proud tradition of cellular research that reaches back to when Robert Hooke first placed a cork sample under his simple light microscope.

For more information:

Interactive confocal microscopy tutorials from Nikon :

http://www.microscopyu.com/tutorials/java/virtual/confocal/index.html

Fluorophore information from Olympus :

http://www.olympusfluoview.com/theory/fluorophoresintro.html

Dr. Steven Goldman and Jordan Lancaster applied several million heart cells, called cardiomyocytes, to an artificial patch and found that within 72 hours the cells began beating.  Surprising the scientists, the individual contractions of the cells spontaneously coordinated, causing the entire scaffolding to pulse in a remarkable parallel to in vivo heart tissue. 

Without input from the scientists, the rat heart cells settled into a rhythm of 70 beats per minute, slower than the 330-480 beats per minute typical of most rats.  The researchers found that the cells sped up their pace if subjected to electric shock, approaching up to 300 beats per minute if stimulated.  Most encouraging to the team was that as the cells increased their rate, they stayed in time with each other.

Heart cells beating outside the body isn’t an unusual concept.  Cardiomyocytes feature contractile proteins that help the cells pulse.  While it wasn’t unexpected that the cells would beat, it was assumed that they would pulse sporadically and independently of their neighbors.  Dr. Goldman was surprised with what happened.  “The fact that they beat synchronously and the whole thing contracts means that the cardiomyocytes are talking to each other.”

The patch they used as a framework is a biodegradable mesh formed from fibroblasts, a type of connective tissue involved in wound healing.  It was designed by Theregen, a regenerative medicine company, to help mend heart tissue.  The patch itself is currently in the clinical trial stage of the FDA approval process, but the application of living heart cells is a novel approach and will require significant testing before it would be available to patients.

The goal is to develop a living band-aid created from the mesh and heart cells, which could be attached directly to damaged cardiac tissue.  As demonstrated by this study, it seems likely that the newly applied cells could communicate with the existing heart tissue and match the pulse rate of the patient’s heart.  The researchers are hopeful that as the patch disintegrates, the healthy cells will remain and help replace the damaged cells.  If successful, this work could forge powerful new techniques in medicine’s fight against heart disease.

For more information:

Video of the beating heart cells with excellent explanation of the research : http://www.sciencefriday.com/videos/watch/10230

Explanation of Heart Attacks from the National Institutes of Health : http://www.nhlbi.nih.gov/health/dci/Diseases/HeartAttack/HeartAttack_WhatIs.html

For more information:

Information about BAT from Colorado State University :

            http://www.vivo.colostate.edu/hbooks/pathphys/misc_topics/brownfat.html

For more about this research :

            http://www.eurekalert.org/pub_releases/2009-07/dci-sce072709.php

Scientists from the University of Utah have developed a new method of applying microelectrodes to a person’s brain.  The innovation provides a new tool for prosthesis control and epilepsy treatment.  Previously, the two options for reading neurological signals were a cap, featuring limited capabilities, and microelectrodes threaded directly into the brain.  The new technique blankets the brain with a series of electrodes, giving better neural resolution than the cap but being less invasive than the implanted probes.  The new technique still requires extensive surgery, meaning candidates for the procedure would represent those in extreme need.

Under the microscope, the Golgi appears as a stack of flattened membranes.  These membranes, called cisternae, pass molecules from one level to the next, chemically modifying them along the way.  The cisternae, which typically number in the single digits, make up the four functional regions of the Golgi : cis-Golgi network (closest to the center of the cell), cis-Golgi, medial-Golgi and trans-Golgi (closest to the outer membrane of the cell).  Each functional region has a different set of enzymes with varying roles in modifying organic compounds such as proteins and lipids.

A typical trip through the Golgi for a protein starts in the endoplasmic reticulum, where the protein is built by ribosomes and folded as it moves along.  The protein is secreted from the ER via vesicles, which proceed to and merge into the cis-Golgi network.  After this point, the protein moves outward, through the cis-Golgi and medial-Golgi, being modified and altered in each cisternae.  By the time it is packaged and released from the trans-Golgi, the protein has been transformed from a winding strand of amino acids into a functional protein.  Some of the changes the Golgi might make to a protein would include glycosylation, addition of sugar groups, and phosphorylation, addition of phosphate groups.  The Golgi may also add a signal sequence to help guide the protein to its eventual location. 

As if the Golgi’s role isn’t wide-reaching enough, it has further impact on cell structure.  Lysosomes, digestive structures found in some cells, are formed with help from the Golgi.  It is also known that they have a currently undetermined role in apoptosis, the programmed death of the cell. 

These unknowns join with question marks at various stages of the protein modification process to make the Golgi an organelle shrouded in mystery.  Recent research gives reason to believe that increased understanding is on the way.  In an experiment advanced by an undergraduate student at Rensselaer Polytechnic Institute, researchers have developed an artificial Golgi Apparatus capable of modifying heparan sulfate, a complex sugar related to the important medicine heparin. 

Built on a chip, the synthetic Golgi is comprised of a maize-like structure, with different molecules and enzymes in each compartment.  Magnets move the molecules along through the structure.  While the design can only simulate one function of a true Golgi, it does allow experimentation on the organelle’s possible mechanisms that wouldn’t have been possible before.  Specifically, the researchers are trying to find a more effective way to acquire heparin, an anticoagulant used to prevent blood clotting.  Currently heparin is harvested from slaughtered animals, introducing high risk of contamination.

Whether it is modifying lipids, glycoslyating an enzyme or playing a role in cell death, the Golgi has undeniable importance to the cell.  Fortunately new research has brought a spotlight to this essential cell part.  Just as innumerable proteins owe their functionality to its contributions, the Golgi is owed more detailed treatment than the “packaging and shipping” label that is so often the beginning and end of its mention in discussions of the cell.

For more information:

Background on Camillo Golgi from the Nobel Prize :

http://nobelprize.org/nobel_prizes/medicine/articles/golgi/index.html

Golgi information from Cytochemistry.net :

http://www.cytochemistry.net/Cell-biology/golgi.htm

Stem cells, cells not differentiated into a particular role, represent a potentially powerful medical tool.  They are defined by the unique abilities to differentiate into multiple cell types and continually divide.  Somatic stem cells (also called adult stem cells) are found within most of an organism’s tissues throughout its life; however these cells are multipotent, only capable of forming a specific set of cell types.  Embryonic stem cells present a much more attractive option from a medical prospective because they are pluripotent, having the ability to become a wide range of cell types.

Problems arise from the fact that pluripotent stem cells are exclusively found in embryos.  Obtaining embryonic stem cells (ESC) requires the destruction of unused embryos from in vitro fertilization techniques (the idea that stem cell research depends on abortion is mistaken).  For some, the source of the cells represents a moral bridge that cannot be crossed, while others argue that science should do whatever it can to save lives.  Despite the benefit embryonic stem cells could offer medically, the moral controversy slowed and, eventually, stopped implementation of the technology.  The social and political climate compelled scientists to seek alternative sources of pluripotent cells.

Such a potential solution was developed in 2006 by a group of Japanese researchers who managed to coax mouse skin cells into becoming pluripotent stem cells.  The technique involved using a genetically reprogrammed retrovirus to force the skin cells to create several proteins that are characteristic of embryonic stem cells.  The inserted genes encoded transcription factors, such as Oct 3/4 and Sox family genes, which control what other genes are turned on or off.  The resulting cells, dubbed induced pluripotent stem cells (iPS), mirrored the morphology, growth rate and other general characteristics of embryonic stem cells.  The same strategy created human iPS in 2007, giving stem cell research a second chance.

However, not all researchers were convinced that iPS cells are truly pluripotent.  Embryonic stem cells are clearly capable of developing into all cell types, as evidenced by normal embryo development.  iPS cells may look and act like embryonic stem cells, but until it could be shown that an entire organism can develop from one, their pluripotency was debatable.  July 2009 started poorly for iPS proponents, with published research showing that there are slight differences in the genes expressed in induced pluripotent stem cells and embryonic stem cells.  However, later in the month, two teams of Chinese scientists established the pluripotency of iPS cells by using them to grow entire mice.

Both labs verified the cells could differentiate into any tissue or cell type by tricking them molecularly into growing as an embryo would.  The techniques involved were difficult and inefficient, requiring numerous tries before success was achieved.  This experimentation was done solely as a proof of the iPS potency, with all researchers involved voicing the immorality of using iPS cells for human reproduction. 

With the versatility of iPS cells confirmed and social controversy avoided, research using them should surge forward.  While there are no magic bullets in medicine, the applications of stem cells are close to limitless.  From mediating heart repair to helping scientists better understand cancer, stem cells have the power to become an essential tool in modern medicine.  While somatic stem cells provide numerous opportunities, access to pluripotent cells that don’t invite moral conflict will open the door to accessing the depth of that potential.

For more information:

Stem cell basics from NIH :

http://stemcells.nih.gov/info/basics/

Interactive tutorials from the University of Utah :

http://learn.genetics.utah.edu/content/tech/stemcells/

Müller, destined to become one of 19^th century Germany’s most respected scientists, came from humble beginnings as the son of a shoe-maker.  He might have followed in his father’s footsteps if not for Johannes Schulze, a noted educator, who recognized his powerful potential and convinced young Müller’s father to send him to school.  Johannes excelled and began studying medicine and, due to a serendipitous decision by his university, studied under a professor who urged him toward microscopy.

Due to a rather diverse set of research experiences during his formative years, Müller developed a philosophy of scientific research unique at the time.  He rejected the idea of relying solely on either research data or theorizing, instead proposing to carefully observe natural phenomena and attempt to find the underlying patterns.  His uncanny ability to distill the meaning behind his work, not simply observe it, was the core of his life-long success.  His approach also exercised firm influence on the research practices of his students.

Müller made dramatic contributions to the fields of anatomy and physiology, studying everything from the nervous system to molecules in the blood.  A signature characteristic of his research was a tendency to study the same processes in different organisms, rather that only one, hoping to gain a glimpse of how several organisms solve the same problems. 

Müller’s students, which included Virchow and Schwann, noted his discussion of microscopy in his medical lectures, something that surely impacted the work of both these noted scientists.  He was one of the first medical researchers to advocate extensive use of microscopes.  Indeed, he might have made the discoveries that led to the cell theory himself if it weren’t for his wide range of research interests.  Schwann was one of Müller’s favorite students and they worked closely together, with Müller eventually applying Schwann’s discovery that cells are the basic unit of life to research on tumors and other medical issues. 

It is doubtless that Müller’s views on living things, research practices and intellectual support were essential in the paths that Schwann and Virchow both took in their contributions to science.  Even though Schleiden wasn’t one of Müller’s students, Johannes published one of Schleiden’s early papers about the cell.  His impact on the development of the cell theory isn’t often commented on, but Johannes Peter Müller had a hand in the education and career development of the three men most directly credited with the theory.  His support and more subtle influence had made it all possible.

For more information:

A biography of Müller

http://vlp.mpiwg-berlin.mpg.de/essays/data/enc22?p=1

National Human Genome Research Institute (NHGRI) researchers have recently discovered a common origin for the disproportionately short and curved legs present in several dog breeds.  The charm of dachshunds and basset hounds largely lies in those short legs, which is a standard characteristic for almost 20 breeds.  The genetic condition, chondrodysplasia, is similar to the disproportionately short limbs found in the type of human dwarfism called hypochondroplasia.

Genetic analysis, published in Science, reveals that each of these dog breeds owe their iconic body style to a single evolutionary event, rather than developing the same appearance separately.  What really surprised the researchers was that the mutation was due to a retrogene being introduced to the dog genome.

Retrogenes are formed when the typical flow of information, DNA to mRNA to protein, is interrupted.  A retrogene is formed if mRNA information is ‘reverse transcribed’ back into DNA, typically by a retrovirus enzyme, and re-implanted into the genome.  This can cause problems with gene expression, either imcreasing protein production or producing the protein at the wrong time.  It is the later of the two that presents the mutation in the case of short legged dogs.

The retrogene in question is a duplicate copy of growth regulator FDF4.  The misplaced copy of FDF4 is thought to turn on certain growth receptors at the wrong time during fetal development.

This research has obvious significance to the veterinarian and dog breeder communities, but the impact of these findings will reach far beyond that narrow scope.  It was previously hypothesized that retrogenes could play a role in evolution, but this is the first documented case of a retrogene making such an important impact on development of a species.  It is doubtless that this discovery will jump-start a search for other examples of retrogene-mediated evolutionary change.

Additionally, this research may give new clues to scientists studying human dwarfism.  Two thirds of human hypochondroplasia cases are already shown to result from a mutation in FGFR3, but thus far there is no gene connected with the remaining cases.  FDF4 will certainly be researched as a possible culprit.

 According to the Central Dogma of Biology, DNA is the primary genetic material and is copied into RNA code, which in turn serves as the instructions for building proteins.  In retroviruses, however, genetic information is stored as RNA.  After the RNA is injected into the host cell during an infection, the RNA copied into DNA in a process called reverse transcription.  The newly created viral DNA, called provirus, is then integrated into the host organism’s genome and passed along during subsequent cell divisions.  In the future, this provirus can ‘wake up’ and stage a major infection on the host.

Retroviruses are fairly simple particles, with few notable components.  The outside of the retrovirus is a membrane layer, unlike most viruses.  There are only a few proteins the virus needs to do its job.  GAG proteins help locate the cell type the virus seeks to attack.  Reverse transcriptase is the enzyme responsible for copying the virus’ RNA code into DNA.  Integrase inserts the viral DNA into the host’s chromosomes.  Because the retrovirus’ genes assemble its proteins linked together instead of individually, proteases are needed to help separate the proteins after they are made.

The unique ways that retroviruses attack their hosts complicate these infections in a few ways.  Because the retrovirus inserts the provirus DNA into the host’s DNA, it can interfere with the organism’s genes. If the provirus lands in the middle of functional piece of DNA it could prevent that gene from working correctly, possibly causing cell death or cancer.  In cases where the viral DNA inserts itself between genes, the provirus never leaves, becoming part of the host’s genome.  Remarkably, 5-8% of the human genome consists of the remains of viral genes in our evolutionary past.

Retroviruses also present problems to those who try to develop cures.  Most genes change over little from one generation to the next because DNA can be stably copied many times.  Reverse transcriptase, however, has a tendency to make mutation-causing mistakes.  As a result, retroviruses change rapidly over time, foiling many possible treatments and making vaccination very difficult.