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Shaking Death

In the 1950s and 60s, a fatal epidemic called kuru swept through the South Fore tribe of Papua New Guinea, killing over 1,000 people. Kuru means “shaking death” which is consistent to the first symptoms of the victims: tremors, headaches and loss of motor skills, since the disease affected the cerebellum, which is responsible for co-ordinarting movement. Soon the victims weren’t able to stand or eat, they sometimes lost speech and developed open sores, and then finally died six to twelve months later. It was discovered that the epidemic was linked to the tribe’s ritual of mortuary cannibalism—consuming the brains of the recently deceased. Kuru began to disappear when cannibalism was outlawed, and yet a few cases still occurred up into the 2000s, suggesting that the disease has an incubation period of up to 50 years. Kuru belongs to a class of neurodegenerative diseases that also includes what is commonly known as “Mad Cow Disease,” and is caused by abnormally folded proteins called prions. These proteins are present in all cells in their normal form, but the abnormal ones are infectious agents, able to ‘flip’ other proteins into the abnormal prion shape that then flip others, and on and on like dominoes. They gradually cause nerve cells to degenerate and die—and since nerve cells cannot be replaced, the brain tissue takes on a sponge-like appearance as it slowly dies. So, Kuru was originally caused by the victims consuming infected brain material, which then infected their own brain tissue and turned it to spongy mush.

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Scientists have successfully removed the extra copy of chromosome 21 in cell cultures derived from a person with Down syndrome.

The cells of people with the condition contain three copies of chromosome 21 rather than the usual pair.

A triplicate of any chromosome is a serious genetic abnormality called a trisomy. Trisomies account for almost one-quarter of pregnancy loss from spontaneous miscarriages, according to the research team.


The mature retina contains five classes of neurons: photoreceptors (purple), horizontal cells (yellow), bipolar neurons (green), amacrine cells (pink and blue), and ganglion cells (pink and blue). In this cross section of an adult mouse retina, only a subset of bipolar cells, “the ON bipolar cells” are visible by their expression of GFP (green). The pink and blue speckled striations at the bottom of the image mark the fiber layer, which contains the ganglion cell axons that will form the optic nerve.

By Rachel Wong, University of Washington



Nerve cells and glial cells, coloured scanning electron micrograph (SEM). The nerve cells have small cell bodies (blue/pink) and fine extensions called axons and dendrites (blue). The glial cells (red) have large cell bodies with thicker extensions. Neurons are responsible for passing information around the central nervous system (CNS) and from the CNS to the rest of the body. Glial cells are nervous system cells that provide the neurons with structural support and protection.



The 6 phases of the cell cycle (from top left) are shown for 2 cells in the embryo of the marine worm Cerebratulus marginatus. Each image is a projection of a 40-80 0.3-μm confocal section: interphase, microtubules are long and diffuse; prophase, chromosomes condense and small asters appear; prometaphase, the nuclear envelope breaks down but the spindle is not yet built; metaphase, chromosomes aligned at the spindle equator; anaphase, sister chromatids separate along the spindle as astral microtubules grow; telophase, cleavage furrow constricts around astral microtubules and the central spindle as 2 nuclei reassemble.

By George von Dassow, University of Oregon



Human chromosomes, coloured scanning election micrograph (SEM). Chromosomes are a packaged form of the genetic material DNA (deoxyribonucleic acid). The DNA condenses into chromosomes during cell replication for ease of division and transport into the new cell. Each chromosome consists of two identical strands (chromatids), aligned parallel to each other and joined at an area called the centromere. Magnification: x11,800 when printed at 10 centimetres wide.


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