afracturedreality:

Numerous HIV-1 particles (pink) leave a cultured HeLa cell (brown). These viruses lack their vpu gene and thus cannot detach from the cell’s tethering factor, BST2. Each viron particle is ~120 nm in diameter. The image was captured with a Zeiss Merlin ultra hi-res scanning electron microscope.

Since 1987, the FDA has approved more than 30 antiviral drugs, including 12 HIV protease inhibitors and one integrase inhibitor. These drugs stop ~99% of viral replication, essentially transforming HIV infection from a deadly disease to a chronic one.

By Thomas Deerinck, NCMIR, USCD

(via molecularlifesciences)

ANN:

Manga artist Hirohiko Araki has drawn the cover of volume 130’s issue 5 of the American biological journal Cell, at the request of two Japanese authors published in this issue. Dr. Mitsutoshi Setou and Dr. Hiroshi Ageta are part of a team that identified a protein named SCRAPPER that helps regulate synaptic activity in the nervous system. Among other potential benefits, the findings reported in the “Ubiquitin Ligase for Synaptic Tuning” article will aid research on Alzheimer’s disease and strokes.

According to the issue, Araki’s art depicts SCRAPPER as a purple humanoid “putting blue heart-shaped ubiquitins on the red RIM creatures.” Araki drew the illustration with the scientific direction of Drs. Setou and Ageta.

(via bekindplzrewind)

Peroxisomes are ubiquitous organelles found in most known eukaryotic cells. They perform both vital catabolic and anabolic functions within cells to ensure the host’s health and survival are promoted.

Peroxisomes are a membrane-bound organelle with an electron-dense matrix, lacking an obvious internal structure. They have several functions:

• Oxidation and detoxification: Peroxisomes have the odd quality of both generating and degrading hydrogen peroxide (H²O²) in exactly the same compartment. The organelle contains many oxidative enzymes which use oxygen to remove hydrogen ions from organic substrates.

R + O² > R’ + H²O²

H²0² is removed by peroxidase, by peroxidation:

2H²O² > 2H²O + O²

 Enzymes which detoxify are also present. They work in the same manner: oxidising toxic substances (such as formaldehyde, or alcohol) by peroxidation reaction:

H²O² + R’ H² > R’ + 2H²O

This detoxification is particularly prevalent in kidney cells. Accumulation of hydrogen peroxide is incredibly dangerous and can cause massive amounts of cell damage. As you get older and your peroxisomes and mitochondria become less effective, one of the damaging substances which accumulates is H²O² and is one of the main factors of aging.

• Fatty acid breakdown: Also known as beta-oxidation. Although the mitochondria is more famously associated with this particular task, the peroxisome is capable of quickly breaking down fatty acids of more than 12 carbons long: something the mitochondria has issues with. The long chains are oxidised, two carbons at a time, until they become small enough for the mitochondria to handle.
• Biosynthesis of plasmalogens: Plasmalogens are a very important class of lipid which constitutes ~80-90% of myelin (a material which wraps around the axons of neurons to increase conduction of electrical signalling). Unsurprisingly, people with peroxisome disorders tend to have defects within their nervous system.

There are many other, more minor, functions of the peroxisome, and if you are interested I do suggest reading up on them.

Unlike mitochondria, peroxisomes do not have their own genome. Therefore, all proteins are shuttled into the peroxisome after being coded for by the cell nucleus and translated and modified by the ER/Golgi. Most proteins destined for the peroxisome have a three amino acid signal sequence at their C-terminal end, recognised by soluble peroxisome receptors called PEX. PEX receptors bind the proteins in the cytosol and embed themselves in the membrane of the peroxisome, releasing the cargo inside, before returning to the cytosol. It is this mechanism of transportation which, when faulty, forms the basis of peroxisomal disorders.

Zellweger Syndrome

The PEX3 receptor is responsible for the docking of proteins destined for the membrane, intended to become receptors themselves. In Zellweger syndrome, this PEX3 is faulty. This means other receptors can not dock within the membrane, and if there are no receptors, no cargo can be delivered. This creates ‘ghost peroxisomes’ - essentially membrane-bound bags of absolutely nothing. It is an autosomal recessive disorder characterised by leukodystrophy. Myelin is severely impaired, white matter in the brain is heavily underdeveloped, and long-chain fatty acids float freely in the blood. The condition is lethal, and patients do not usually survive past one year of age. There are no treatments available.

Photo: Peroxisomes individually fluorescently tagged in green, showing how ubiquitous they are within your cells. Other structures present: nucleus (blue), mitochondria (red).

neurosciencestuff:

New form of cell division found

Researchers at the University of Wisconsin Carbone Cancer Center have discovered a new form of cell division in human cells.

They believe it serves as a natural back-up mechanism during faulty cell division, preventing some cells from going down a path that can lead to cancer.

“If we could promote this new form of cell division, which we call klerokinesis, we may be able to prevent some cancers from developing,” says lead researcher Dr. Mark Burkard, an assistant professor of hematology-oncology in the department of medicine at the UW School of Medicine and Public Health.

Burkard presented the finding on Monday, Dec. 17 at the annual meeting of the American Society for Cell Biology in San Francisco.

(View a short video of the process here)

There’s also a YouTube video for the same video here

(via infectiousdiseases)

twarda:

Apoptosis. Exuse me my engrish.

It can be seen here: http://twarda8.deviantart.com/gallery/?catpath=/&offset=180#/d3i1kvc

Cute

Cell fractionation is the process of separating organelles and biomolecules from cells. There are three primary ways of doing this:

• Differential centrifugation
• Velocity sedimentation
• Equilibrium sedimentation

Before any one of these three processes can be performed, homogenisation of the sample to be tested must first occur. The sample is added to an isotonic buffer solution and broken down using one of four common methods: detergent application to lyse the membranes, shear force to literally tear the cells apart, forcing the cells through a tiny space by high pressure, or high frequency sound. The result is a soup containing all the cellular organelles, called homogenate.

In differential centrifugation, the homogenate is first added to a centrifuge and spun around at various speeds and times to create the following samples:

• Homogenate spun at 600g for 3 minutes produces a pellet of the largest organelles (nuclei, cytoskeleton) and a semi-viscous liquid called supernatant 1 containing the rest of the organelles. The pellet is removed.
• Supernatant 1 is then spun at 6000g for 8 minutes to create a pellet containing mitochondria, lysosomes, and peroxisomes. Supernatant 2 is also produced. Pellet is removed.
• Supernanant 2 spun at 40,000g for 30 minutes to produce a pellet containing microsomes - functional fragments of the ER and Golgi apparatus. Supernatant 3 produced, pellet removed.
• Supernatant 3 spun at 100,000g for 90 minutes to create a pellet containing ribosomes, large biomolecules and viruses. The supernatant created here is just cytosolic fluid.

Velocity and equilibrium sedimentation work in a similar manner. They are both variants of a gradient based centrifugation system.

In velocity sedimentation, a shallow gradient containing 5-20% sucrose is added to a centrifuge tube. The sample is then laid on top neatly and the tube undergoes centrifugation. Organelles are separated by size. Two bands are created within the tube: slow-sedimentary band near the top and a fast-sedimentary band near the bottom. The base of the tube is pierced and the fractions collected. Takes between 3-4 hours to complete.

In equilibrium sedimentation, a steep gradient of 20-75% sucrose is added to a tube and the sample is dispersed throughout it before centrifugation. Creates two bands: one low-buoyant density sample near the top and one high-buoyancy density sample near the bottom. This process takes days to complete and velocity sedimentation is prefered in lab settings.

bpod-mrc:

Prison Cells

These cells are trapped – stuck inside tiny square ‘rooms’ each 100,000 times smaller than a prison cell. In order to escape, they’re going to need some help from the outside. Each cell (with its membrane highlighted in green and nucleus in turquoise) has been injected with different amounts of magnetic nanoparticles: tiny pieces of metal highlighted in blue. At the flick of a switch, the particles tug the imprisoned cells towards magnets on the outside. The cell in the top right, which received the strongest magnetic shove, has developed filopodia – spiky ‘legs’ which show the cell is about to slither for freedom. Tiny man-made tools may soon be used to guide the movement of cells in our bodies, too. A helpful nudge in the right direction might one day lead stem cells into place in a damaged organ or put the brakes on cancer cells, all by remote control.

Written by John Ankers

—

• Dino Di Carlo
• University of California, Los Angeles, USA
• Reprinted by permission from Macmillan Publishers Ltd: Nature Methods Copyright 2012
• Published in Nature Methods 9: 1113-1119

sciencephotolibrary:

Cell infected with HIV. Coloured scanning electron micrograph (SEM) of HIV particles (red) budding from the membrane of a host cell. HIV (human immunodeficiency virus) attacks CD4+ T-lymphocytes (specialised white blood cells), which are crucial in the body’s immune system. It enters the cell and makes many copies of itself, which then destroy the cell as they emerge through its membrane. This severely weakens the immune system, causing AIDS (acquired immunodeficiency syndrome).

Credit: THOMAS DEERINCK, NCMIR/SCIENCE PHOTO LIBRARY

(via infectiousdiseases)

universe-of-waves:

meiosis in sperm cells

(via olduvaigorge)