The Biology Lair

neurosciencestuff: Scientists identify molecular trigger for...

Tue, 21 May 2013 19:31:06 -0400

Scientists identify molecular trigger for Alzheimer’s disease

Researchers have pinpointed a catalytic trigger for the onset of Alzheimer’s disease – when the fundamental structure of a protein molecule changes to cause a chain reaction that leads to the death of neurons in the brain.

For the first time, scientists at Cambridge’s Department of Chemistry, led by Dr Tuomas Knowles, Professor Michele Vendruscolo and Professor Chris Dobson working with Professor Sara Linse and colleagues at Lund University in Sweden have been able to map in detail the pathway that generates “aberrant” forms of proteins which are at the root of neurodegenerative conditions such as Alzheimer’s.

They believe the breakthrough is a vital step closer to increased capabilities for earlier diagnosis of neurological disorders such as Alzheimer’s and Parkinson’s, and opens up possibilities for a new generation of targeted drugs, as scientists say they have uncovered the earliest stages of the development of Alzheimer’s that drugs could possibly target.

The study, published today in the Proceedings of the US National Academy of Sciences, is a milestone in the long-term research established in Cambridge by Professor Christopher Dobson and his colleagues, following the realisation by Dobson of the underlying nature of protein ‘misfolding’ and its connection with disease over 15 years ago.

The research is likely to have a central role to play in diagnostic and drug development for dementia-related diseases, which are increasingly prevalent and damaging as populations live longer.

In 2010, the Alzheimer’s Research UK showed that dementia costs the UK economy over £23 billion, more than cancer and heart disease combined. Just last week, PM David Cameron urged scientists and clinicians to work together to “improve treatments and find scientific breakthroughs” to address “one of the biggest social and healthcare challenges we face.”

The neurodegenerative process giving rise to diseases such as Alzheimer’s is triggered when the normal structures of protein molecules within cells become corrupted.

Protein molecules are made in cellular ‘assembly lines’ that join together chemical building blocks called amino acids in an order encoded in our DNA. New proteins emerge as long, thin chains that normally need to be folded into compact and intricate structures to carry out their biological function.

Under some conditions, however, proteins can ‘misfold’ and snag surrounding normal proteins, which then tangle and stick together in clumps which build to masses, frequently millions, of malfunctioning molecules that shape themselves into unwieldy protein tendrils.

The abnormal tendril structures, called ‘amyloid fibrils’, grow outwards around the location where the focal point, or ‘nucleation’ of these abnormal “species” occurs.

Amyloid fibrils can form the foundations of huge protein deposits – or plaques – long-seen in the brains of Alzheimer’s sufferers, and once believed to be the cause of the disease, before the discovery of ‘toxic oligomers’ by Dobson and others a decade or so ago.

A plaque’s size and density renders it insoluble, and consequently unable to move. Whereas the oligomers, which give rise to Alzheimer’s disease, are small enough to spread easily around the brain - killing neurons and interacting harmfully with other molecules - but how they were formed was until now a mystery.

The new work, in large part carried out by researcher Samuel Cohen, shows that once a small but critical level of malfunctioning protein ‘clumps’ have formed, a runaway chain reaction is triggered that multiplies exponentially the number of these protein composites, activating new focal points through ‘nucleation’.

It is this secondary nucleation process that forges juvenile tendrils, initially consisting of clusters that contain just a few protein molecules. Small and highly diffusible, these are the ‘toxic oligomers’ that careen dangerously around the brain cells, killing neurons and ultimately causing loss of memory and other symptoms of dementia.

“There are no disease modifying therapies for Alzheimer’s and dementia at the moment, only limited treatment for symptoms. We have to solve what happens at the molecular level before we can progress and have real impact,” said Dr Tuomas Knowles from Cambridge’s Department of Chemistry, lead author of the study and long-time collaborator of Professor Dobson and Professor Michele Vendruscolo.

“We’ve now established the pathway that shows how the toxic species that cause cell death, the oligomers, are formed. This is the key pathway to detect, target and intervene – the molecular catalyst that underlies the pathology.”

The researchers brought together kinetic experiments with a theoretical framework based on master equations, tools commonly used in other areas of chemistry and physics but had not been exploited to their full potential in the study of protein malfunction before.

The latest research follows hard on the heels of another ground breaking study, published in April of this year again in PNAS, in which the Cambridge group, in Collaboration with Colleagues in London and at MIT, worked out the first atomic structure of one of the damaging amyloid fibril protein tendrils. They say the years spent developing research techniques are really paying off now, and they are starting to solve “some of the key mysteries” of these neurodegenerative diseases.

“We are essentially using a physical and chemical methods to address a biomolecular problem, mapping out the networks of processes and dominant mechanisms to ‘recreate the crime scene’ at the molecular root of Alzheimer’s disease,” explained Knowles.

“Increasingly, using quantitative experimental tools and rigorous theoretical analysis to understand complex biological processes are leading to exciting and game-changing results. With a disease like Alzheimer’s, you have to intervene in a highly specific manner to prevent the formation of the toxic agents. Now we’ve found how the oligomers are created, we know what process we need to turn off.”

deconversionmovement: Hearing changes could be ancient in the...

Mon, 13 May 2013 20:27:38 -0400

deconversionmovement:

Hearing changes could be ancient in the human line

Comparison between hominins suggests modern middle-ear bones evolved early.

A study of two ancient hominins from South Africa suggests that changes in the shape and size of the middle ear occurred early in our evolution. Such alterations could have profoundly changed what our ancestors could hear — and perhaps how they could communicate.

Continue Reading

Age-defying: Master key of lifespan found in brain The brain’s...

Thu, 02 May 2013 19:31:59 -0400

Age-defying: Master key of lifespan found in brain

The brain’s mechanism for controlling ageing has been discovered – and manipulated to shorten and extend the lives of mice. Drugs to slow ageing could follow

Tick tock, tick tock… A mechanism that controls ageing, counting down to inevitable death, has been identified in the hypothalamus – a part of the brain that controls most of the basic functions of life.

By manipulating this mechanism, researchers have both shortened and lengthened the lifespan of mice. The discovery reveals several new drug targets that, if not quite an elixir of youth, may at least delay the onset of age-related disease.

The hypothalamus is an almond-sized puppetmaster in the brain. “It has a global effect,” says Dongsheng Cai at the Albert Einstein College of Medicine in New York. Sitting on top of the brain stem, it is the interface between the brain and the rest of the body, and is involved in, among other things, controlling our automatic response to the world around us, our hormone levels, sleep-wake cycles, immunity and reproduction.

While investigating ageing processes in the brain, Cai and his colleagues noticed that ageing mice produce increasing levels of nuclear factor kB (NF-kB)   – a protein complex that plays a major role in regulating immune responses. NF-kB is barely active in the hypothalamus of 3 to 4-month-old mice but becomes very active in old mice, aged 22 to 24 months.

To see whether it was possible to affect ageing by manipulating levels of this protein complex, Cai’s team tested three groups of middle-aged mice. One group was given gene therapy that inhibits NF-kB, the second had gene therapy to activate NF-kB, while the third was left to age naturally.

This last group lived, as expected, between 600 and 1000 days. Mice with activated NF-kB all died within 900 days, while the animals with NF-kB inhibition lived for up to 1100 days.

Crucially, the mice that lived the longest not only increased their lifespan but also remained mentally and physically fit for longer. Six months after receiving gene therapy, all the mice were given a series of tests involving cognitive and physical ability.

In all of the tests, the mice that subsequently lived the longest outperformed the controls, while the short-lived mice performed the worst.

Post-mortem examinations of muscle and bone in the longest-living rodents also showed that they had many chemical and physical qualities of younger mice.

Further investigation revealed that NF-kB reduces the level of a chemical produced by the hypothalamus called gonadotropin-releasing hormone (GnRH)  – better known for its involvement in the regulation of puberty and fertility, and the production of eggs and sperm.

To see if they could control lifespan using this hormone, the team gave another group of mice  – 20 to 24 months old  – daily subcutaneous injections of GnRH for five to eight weeks. These mice lived longer too, by a length of time similar to that of mice with inhibited NF-kB.

GnRH injections also resulted in new neurons in the brain. What’s more, when injected directly into the hypothalamus, GnRH influenced other brain regions, reversing widespread age-related decline and further supporting the idea that the hypothalamus could be a master controller for many ageing processes.

GnRH injections even delayed ageing in the mice that had been given gene therapy to activate NF-kB and would otherwise have aged more quickly than usual. None of the mice in the study showed serious side effects.

So could regular doses of GnRH keep death at bay? Cai hopes to find out how different doses affect lifespan, but says the hormone is unlikely to prolong life indefinitely since GnRH is only one of many factors at play. “Ageing is the most complicated biological process,” he says.

“There are dozens of pathways that people will look at thanks to this work,” says Richard Miller at the University of Michigan in Ann Arbor. Miller has previously demonstrated that an immunosuppressant drug called rapamycin can also extend life in mice (see “A guide to defying age”).

Since the hypothalamus  – and GnRH in particular  – regulate several major biological processes, it may be possible to influence ageing through related mechanisms, says Miller. He wants to look at possible dietary interventions, such as the indirect effect that spikes in glucose may have on the hypothalamus.

Stuart Maudsley at the National Institute on Aging in Baltimore, Maryland, agrees that the hypothalamus could be the route in for age-controlling drugs. “The body is all one big juicy system,” he says. The ideal drug would hit that system at its centre. “Activate that keystone and everything falls into place,” he says.

Though this is the first time that an explicit role has been found for GnRH in the ageing process, previous studies in humans have hinted at a link between longevity and fertility – in which the hormone is known to play a significant role.

As GnRH levels drop, so too does egg production and fertility. In a study presented this month at the annual meeting of the Population Association of America in New Orleans, Graziella Caselli at the University of Rome, Italy, and colleagues found that mothers in Sardinia who’d had their last child over the age of 45  – so were still fertile at a late age  – were significantly more likely to reach 100 than those who’d had their last child at a younger age. Since late fertility could be linked to higher levels of GnRH, Cai says those findings are a good match for his own. “There is likely to be some kind of biological correlation between ageing and reproduction,” he says.

“There are maybe 10 steps to controlling ageing,” says Miller. “We’ve taken the first two or three.” The first is simply accepting the idea that ageing can be slowed down, he says. “Many think it can’t. They are wrong.”

Maudsley reckons that we could see drugs that slow ageing in the next 20 years. Initially, though, research is likely to focus on delaying the onset of age-related diseases. “That could solve some real problems,” says Cai.

But since the hypothalamus has an effect on every cell in the body, Maudsley warns that interfering with it could lead to unwanted sequences of events. “You’re playing with fire,” he says.

Journal reference: Nature, 10.1038/nature12143

ucsdhealthsciences: Human lungs are composed of roughly 700...

Tue, 30 Apr 2013 18:22:46 -0400

ucsdhealthsciences:

Human lungs are composed of roughly 700 million of tiny, elastic air sacs called alveoli that pass oxygen into the body and remove carbon dioxide from it. Photo courtesy of David Gregory and Debbie Marshall, Wellcome Images

Bad fad

The “cinnamon challenge” doesn’t sound ominous: You’re supposed to attempt to swallow a tablespoon of ground cinnamon within 60 seconds without drinking any fluids. How bad can that be?

Bad enough.

In a recent paper in Pediatrics, researchers at the University of Miami describe what happens next: the ingested spice triggers a severe gag reflex, with immediate coughing, the sensation of burning in the mouth and likely vomiting.

All of which are apparently quite amusing to watch, judging from the popularity of Internet videos depicting kids (no surprise) attempting the challenge. In their paper, the University of Miami scientists reported at least 51,100 YouTube clips depicting people taking the challenge.

“One video was viewed more than 19 million times, predominantly by 13- to 24-year-olds, ages similar to people taking the Cinnamon Challenge and associated with the greatest need for conformity,” the researchers wrote.

If gagging and looking foolish were the sole results of swallowing a spoonful of cinnamon that would be one thing, but doctors say the health risks are much more serious: Inadvertently inhaling the ground cinnamon can result in choking, aspiration and pulmonary damage. Scores of challenge-takers have found themselves calling poison control centers, visiting emergency rooms - some have been hospitalized for collapsed lungs.

Cinnamon should be eaten, not inhaled. It’s a caustic power composed of cellulose fibers that do not dissolve or degrade in the lungs. The Miami scientists found no studies of cinnamon inhalation in humans, but did find one with rats. Inhaling the spice inflamed the rats’ lungs, predisposing delicate air sacs called alveoli and lung passages to lesions, thickening, loss of elasticity and scarring.

Scientists say that in people, the effects of inhaled cinnamon appear to be temporary and probably do not increase the risk of long-term damage, but in some they may trigger serious allergic reactions, including asthma, or worsen other existing lung conditions.

neurosciencestuff: Scientists reverse memory loss in animal...

Thu, 18 Apr 2013 19:31:04 -0400

neurosciencestuff:

Scientists reverse memory loss in animal brain cells

Neuroscientists at The University of Texas Health Science Center at Houston (UTHealth) have taken a major step in their efforts to help people with memory loss tied to brain disorders such as Alzheimer’s disease.

Using sea snail nerve cells, the scientists reversed memory loss by determining when the cells were primed for learning. The scientists were able to help the cells compensate for memory loss by retraining them through the use of optimized training schedules. Findings of this proof-of-principle study appear in the April 17 issue of The Journal of Neuroscience.

“Although much works remains to be done, we have demonstrated the feasibility of our new strategy to help overcome memory deficits,” said John “Jack” Byrne, Ph.D., the study’s senior author, as well as director of the W.M. Keck Center for the Neurobiology of Learning and Memory and chairman of the Department of Neurobiology and Anatomy at the UTHealth Medical School.

This latest study builds on Byrne’s 2012 investigation that pioneered this memory enhancement strategy. The 2012 study showed a significant increase in long-term memory in healthy sea snails called Aplysia californica, an animal that has a simple nervous system, but with cells having properties similar to other more advanced species including humans.

Yili Zhang, Ph.D., the study’s co-lead author and a research scientist at the UTHealth Medical School, has developed a sophisticated mathematical model that can predict when the biochemical processes in the snail’s brain are primed for learning.

Her model is based on five training sessions scheduled at different time intervals ranging from 5 to 50 minutes. It can generate 10,000 different schedules and identify the schedule most attuned to optimum learning.

“The logical follow-up question was whether you could use the same strategy to overcome a deficit in memory,” Byrne said. “Memory is due to a change in the strength of the connections among neurons. In many diseases associated with memory deficits, the change is blocked.”

To test whether their strategy would help with memory loss, Rong-Yu Liu, Ph.D., co-lead author and senior research scientist at the UTHealth Medical School, simulated a brain disorder in a cell culture by taking sensory cells from the sea snails and blocking the activity of a gene that produces a memory protein. This resulted in a significant impairment in the strength of the neurons’ connections, which is responsible for long-term memory.

To mimic training sessions, cells were administered a chemical at intervals prescribed by the mathematical model. After five training sessions, which like the earlier study were at irregular intervals, the strength of the connections returned to near normal in the impaired cells.

“This methodology may apply to humans if we can identify the same biochemical processes in humans. Our results suggest a new strategy for treatments of cognitive impairment. Mathematical models might help design therapies that optimize the combination of training protocols with traditional drug treatments,” Byrne said.

He added, “Combining these two could enhance the effectiveness of the latter while compensating at least in part for any limitations or undesirable side effects of drugs. These two approaches are likely to be more effective together than separately and may have broad generalities in treating individuals with learning and memory deficits.”

(Image courtesy: UC Berkeley)

cytofocus: Image from McGraw/Hill Publishing’s JUNQUERIA’S...

Wed, 17 Apr 2013 19:31:01 -0400

cytofocus:

Image from McGraw/Hill Publishing’s JUNQUERIA’S Basic Histology Text & Atlas 12 ed.

These are photographs of the columnar epithelium (magnified 300x their original size) of the lining villus of the human small intestine. The two photos are of the same tissue, side-by-side, depicting two different dying methods. I am sharing this specific photo with you because as these photos grow popular on the internet, very little is explained about the methods of microscopy.

TISSUE PREPARATIONS: Neither of these cells are their natural color. They are dyed by two different methods, explained later. The left is dyed using hematoxylin and eosin (H&E), and the right is dyed using the periodic acid-Schiff (PAS) stain. Before being fixed (preserved so the cell’s enzymes won’t destroy the tissue), dehydrated (water is extracted from the sample), cleared (dipped into a solvent that makes the tissue sample transparent) and embedded(mounted onto a slide, usually by plastic, to prevent shrinking or damage), these tissues are too thick to allow light to pass through them for any of these clear structures to be seen. What we want to see when we look through the microscope are the individual structures that compose the the tissues or cells we’re observing.

USES OF THESE IMAGES: Biological scientists, medical professionals and students learn about these dyes and how staining can affect the look of a tissue through a microscopic lens. Images such as these are typically used to study and identify the structures of a cell in two-dimensions. Everything shown is simply a cross-section of a three-dimensional image.

IMAGE DESCRIPTION: Typically, these micrographs only show a tiny section of a tissue and do not represent the entire component of a structure. The photo above only shows a small section of the villi of the small intestine. The digestive system’s tissues fold into themselves to increase the surface area, allowing your intestines to maximize the amount of nutrients they absorb. As a medical professional, it would be important to understand the mechanics of the cell to appreciate the physiology.

Both of these samples are seen through a bright-field microscope. This is typically the type of microscope you see in classrooms and the main tool used for studying slides in histology.

Image from University of Tasmania, Australia

Here you will see “epithelium” labeled, second highest word, or second from the left. That’s what we’re looking at here.

H&E STAINING: This is the most common form of laboratory staining. Dyes stick to acidic structures, like DNA, staining them blue. Everything else will typically stain pink. This is why the nuclei in this photo are visible, while many other components are hard to see.

PERIODIC ACID AND SCHIFF REAGENT: This staining is more complex and detailed in this photo because the structures are cotain polysaccarides (complex sugars), although this is not the case in other tissues. You can clearly see the goblet cells, cells which secret mucous, the cytoplasm between each columnar cell, and the cilia (small harlike structures shown as a deep purple lining).

From these two examples above, it is clear that the photo of the villi in the photo retrieved from the University of Tasmania were prepared with H&E staining. Can you see why this is true?

OTHER LINKS:
Basics of digestive system (video) — This video is pretty good because it explains the basics of the biochemistry, physiology and histology of digesting from the mouth to the colon.

H&E Staining (video) — This video shows how someone will stain a tissue using the H&E method. Even shows fixation, dehydration and clearing and mounting methods.

PAS staining of the cerebrum (video) — I chose this video because I wanted to show that PAS is not typically the best stain for every tissue sample. Different tissues have different cellular components, thus different chemical components. Here, the PAS staining does not give high-visibility to the cerebrum’s components but it does shine light on other structures, as the narrator explains.

REFERENCE(S): I wrote this using the 12th edition of JUNQUEIRA’S Basic Histology Text & Atlas by Anthony L. Mescher. Image was pulled from the supplemental CD ROM that comes with the book.

Written by Rinny. The new mod here!

natureofnature: Confocal micrograph showing the expression of...

Thu, 11 Apr 2013 19:30:51 -0400

natureofnature:

Confocal micrograph showing the expression of different fluorescent proteins in the stem of a thale cress seedling (Arabidopsis thaliana).

scinerds: The Truth About Why Microbes Make You Sick Between...

Wed, 10 Apr 2013 21:24:48 -0400

scinerds:

The Truth About Why Microbes Make You Sick

Between fevers, congestion and diarrhea, there are numerous ways that microbes can make us feel sick. But just how do microorganisms cause these symptoms?

At any given time, the microbes inside of our bodies outnumber our own cells by at least 10 to 1. In general, these tiny organisms are harmless — and often beneficial — to us, but some bacteria, viruses, fungi and protozoan parasites cause nasty diseases. For example, Escherichia coli can cause diarrhea, rhinovirus is behind the common cold and the fungus Cryptococcus neoformans can bring about a severe form of meningitis.

As you’ve probably guessed, there is no singular way that microbes make us sick — different biological mechanisms underlie different disease symptoms. So let’s go over some of the ways that microbes cause different symptoms. (Note: This is a general guide and is in no way meant to be a comprehensive description of every symptom you could possibly get.)

Immune Response

Many disease symptoms that befall us are actually caused by the immune system’s response to invading pathogenic microbes, rather than something the microbes are doing, specifically. Take, for instance, the common cold.

When the rhinovirus gets into your upper respiratory tract and invades epithelial cells (those that line the cavities in the body), it triggers inflammatory and immune responses. Certain cells release histamines, which dilate your blood vessels and increase their permeability, allowing white blood cells and some proteins to get to the infected tissues.

You often experience nasal congestion because your inflamed blood vessels are now so large that they stuff you up. But histamines also affect the amount of mucus your body produces, as well as its viscosity — this altered mucus production, along with the increased fluid leakage from now-permeable capillaries, can cause a runny nose.

Similar immune system reactions take place when you develop pneumonia, which is most often caused by bacteria and viruses (especially the bacterium Streptococcus pneumonia). Your body has pretty decent defenses to keep microbes out of the lungs, including nose hairs that filter air and certain reflexes (coughing and sneezing) that shoot microorganisms that enter your body back out. But sometimes that’s just not enough.

If bacteria get inside the alveoli (tiny air sacs in the lungs), they can invade the spaces between cells and even travel to adjacent alveoli. Your immune system responds by once again inflaming your blood vessels and making them permeable, allowing white blood cells and proteins to come to the rescue. But this permeability allows fluids to seep into the alveoli, taking up space that’s needed for the oxygen-carbon dioxide exchange. You become somewhat oxygen deprived and exhibit the shortness of breath that’s a common symptom of pneumonia. Moreover, your respirations increase as you try to bring more oxygen in and blow more carbon dioxide out.

Pneumonia and the common cold are also marked by fever, something that also arises because of our immune system. When white blood cells called macrophages encounter bacteria or viruses in your system, they produce cell-signaling proteins called interleukin-1 (IL-1). These proteins do two things: They call in helper T-cells and they bind to certain hypothalamus receptors in your brain, causing a rise in your body temperature, which is thought to help kill some pathogenic microbes. Substances that induce fevers, such as IL-1, are called pyrogens; some bacteria can induce fevers with pyrogens, too.

Endotoxins

Bacteria are divided into two major groups based on the structure of their cell wall: Gram-negative and Gram-positive bacteria. The outer membrane of Gram-negative bacteria, such as E. coli and Salmonella, contains large molecules called lipopolysaccharides, which are made up of lipids and polysaccharide (sugar) chains.

These molecules are also called endotoxins (pdf), and they can act as pyrogens. When certain cells called phagocytes engulf the bacteria, lipopolysaccharides get released, which in turn causes macrophages to release IL-1. These proteins, as you know, cause fever.

But endotoxins can do a lot more than cause fever. For instance, if the bacteria Neisseria meningitides reaches the brain from the bloodstream, it can cause bacterial meningitis (Meningococcal meningitis). Endotoxins stimulate the synthesis of pro-inflammatory molecules called cytokines. So when the bacteria reaches the blood-brain barrier, a sharp inflammatory response ensues, causing cerebral blood vessels to leak protein and fluid, and swelling to develop in the membrane between the brain and skull.

These changes lead to an increase in intracranial pressure, resulting in the common meningitis symptoms of headache, stiff neck and sensitivity to bright lights. The pressure on nerves and decreased blood flow starves the brain of oxygen, leading to permanent brain damage and sometimes death.

The bacteria are more deadly if they stick to the bloodstream, where they can cause a blood infection called sepsis. This ability is partly due to the fact that N. meningitides’s endotoxin concentration is up to a 1,000 times greater than that other Gram-negative bacteria. The toxins target the heart and reduce its ability to pump blood, while also causing blood vessels throughout the body to rupture (more specifically, white blood vessels cause the breaks with the chemicals they release in response to the endotoxin).

As the vessels throughout the body leak, blood pressure drops and blood flow slows, leading to the failure of some major body organs and systems, including the kidneys, liver and central nervous system. The disease can manifest a number of conspicuous symptoms, such as fever, light-headedness, rapid heartbeat and skin rash (from the blood leaking under the skin).

Exotoxins

While only Gram-negative bacteria use endotoxins, both Gram-negative and Gram-positive bacteria can cause disease symptoms using exotoxins, a type of protein toxin. Exotoxins are grouped into categories based on their biologic effect on cells: Cytotoxins kill or damage cells, neurotoxins interfere with nerve impulses and enterotoxins affect the intestines.

Many well-known disease symptoms are traced back to exotoxins secreted by various bacteria. For example, the Gram-positive bacterium Streptococcus pyogenes releases three cytotoxins — one of its toxins damages blood capillaries, causing the infamous red rash of scarlet fever. Clostridium perfringens releases a toxin that disrupts normal cellular function and leads to the mass tissue necrosis commonly known as gangrene.

And when Corynebacterium diphtheriae is infected by a certain bacteriophage (bacteria-infecting virus), it can release the diphtheria toxin, which inhibits protein synthesis in cells and eventually causes their death. The cytotoxin can affect a wide range of tissues, and at high concentrations will produce diphtheria’s characteristic swollen neck, often called “bull neck.”

Bacterial neurotoxins are equally well known and scary. The uncontrollable spasms and convulsions of tetanus are all thanks to Clostridium tetani’s neurotoxin, which blocks the relaxation of skeletal muscles. Clostridium tetani’s relative, Clostridium botulinum, excretes a very potent neurotoxin that inhibits the release of the neurotransmitter acetylcholine — this inhibition prevents the transmission of nerve impulses to muscles, resulting in paralysis.

Now, let’s not forget about the wonderful enterotoxins that screw up our intestines. Vibrio cholerae’s cholera toxin (pdf) affects the ion transport and water balance in the intestines, causing epithelial cells to discharge large amounts of fluids and electrolytes. Some toxins produced by E. coli work in a similar way to the cholera toxin, while others are known to affect the intestinal blood vessels, causing bloody diarrhea.

And more!

Though we’ve covered quite a bit already, we’ve really only brushed the surface of how microbes bring about disease symptoms. Diarrhea, for example, can also come about when the single-celled parasite Giardia lamblia coats the intestines and prevents nutrient absorption. And the pain and frequent urination associated with urinary tract infections result from inflammation (pain from inflammation occurs only when the appropriate sensory nerve endings are in the inflamed area).

In addition, boils and other abscesses (such as those from a staph infection) can develop after bacteria populate a cut or break in the skin. Neutrophils, which are a type of white blood cells, rush to the infection, leading to inflammation. Eventually, pus forms from the mixture of old white blood cells, dead skin cells and bacteria.

And let’s not even get into viruses, which produce symptoms by triggering immune responses (like the rhinovirus), interfering with cells’ normal processes or destroying cells by exploding out of them.

The ways in which microbes produce disease symptoms are about as varied as the microbes themselves. Some microorganisms mess with our bodily functions, while others are satisfied with just destroying our cells. And, of course, there are all of those pathogens that turn our own immune system against us. Evil buggers.

atomstargazer: This is What Human Cells Look Like in...

Wed, 03 Apr 2013 19:30:42 -0400

atomstargazer:

This is What Human Cells Look Like in Space

Astronaut photos of Earth from space are undeniably amazing, but snapshots of inner space — particularly human cells — can be spectacular, too.

A new photo of human cells in space taken on the International Space Station looks more like art than science. The image, titled “Goldfinger” by scientists, reveals a monocyte immune cell as a hauntingly translucent, reddish-orange object tipped with green accents.

The human cell photo in space was taken on the station under “simulated gravity” conditions using the European Space Agency’s Kubik incubator, which includes a centrifuge to mimic gravity in the weightlessness of space, ESA officials said in an image description.

sarah-oconnell: Rendering of a European Hare Skull (Lepus...

Sat, 30 Mar 2013 19:30:42 -0400

sarah-oconnell:

Rendering of a European Hare Skull (Lepus timidus) in perspective for my Independent Study. Carbon dust on vellum.

ohyeahdevelopmentalbiology: fuckyeahneuroscience: Video: First...

Sun, 24 Mar 2013 19:30:54 -0400

ohyeahdevelopmentalbiology:

fuckyeahneuroscience:

Video: First MRI movies capture fetal brain wiring up

The first images have been captured of the fetal brain at different stages of its development. The work gives a glimpse of how the brain’s neural connections form in the womb, and could one day lead to prenatal diagnosis and treatment of conditions such as autism and schizophrenia.

We know little about how the fetal brain grows and functions – not only because it is so small, says Moriah Thomason of Wayne State University in Detroit, but also because “a fetus is doing backflips as we scan it”, making it tricky to get a usable result.

Undeterred, Thomason’s team made a series of functional magnetic resonance imaging (fMRI) scans of the brains of 25 fetuses between 24 and 38 weeks old. Each scan lasted just over 10 minutes, and the team kept only the images taken when the fetus was relatively still.

The researchers used the scans to look at two well-understood features of the developing brain: the spacing of neural connections and the time at which they developed. As expected, the two halves of the fetal brain formed denser and more numerous connections between themselves from one week to the next. The connections tended to begin in the middle of the brain and spread outward as the brain continued to develop.

Thomason says that the team is now scanning up to 100 fetuses at different stages of development. These scans might allow them to start to see variation between individuals. They are also applying algorithms to the scanning program that will help correct for the fetus’s movements, so fewer scans will be needed in future.

Once they understand what a normal fetal brain looks like, the researchers hope to study brains that are forming abnormal connections. Disorders such as schizophrenia or autism, for instance, are believed to start during development and might be due to faulty brain connections. Understanding the patterns that characterise these diseases might one day allow physicians to spot early warning signs and intervene sooner. Just as importantly, such images might improve our understanding of how these conditions develop in the first place, Thomason says.

Emi Takahashi of Boston Children’s Hospital says that one way to do this would be to follow a large group of children after they are born, and look back at the prenatal scans of those who later develop a brain disorder. Although she says the study is a very good first step, understanding the miswiring of the brain is so difficult that it may be some time before the results of such work become useful in clinical settings.

neuromorphogenesis: Video game ‘exercise’ for an hour a day may...

Wed, 20 Mar 2013 22:51:44 -0400

neuromorphogenesis:

Video game ‘exercise’ for an hour a day may enhance certain cognitive skills

Regular game play improves performance on tasks that use similar mental processes as video game

Playing video games for an hour each day can improve subsequent performance on cognitive tasks that use similar mental processes to those involved in the game, according to research published March 13 in the open access journal PLOS ONE by Adam Chie-Ming Oei and Michael Donald Patterson of Nanyang Technological University, Singapore.

Non-gamer participants played five different games on their smartphones for an hour a day, five days of the week for one month. Each participant was assigned one game. Some played games like Bejeweled where participants matched three identical objects or an agent-based virtual life simulation like The Sims, while others played action games or had to find hidden objects, as in Hidden Expedition.

After this month of ‘training’, the researchers found that people who had played the action game had improved their capacity to track multiple objects in a short span of time, while hidden object, match three objects and spatial memory game players improved their performance on visual search tasks. Though previous studies have reported that action games can improve cognitive skills, the authors state that this is the first study that compared multiple video games in a single study and show that different skills can be improved by playing different games. They add that video games don’t appear to cause a general improvement in mental abilities. Rather like muscles that can be trained with repetitive actions, repeated use of certain cognitive processes in video games can improve performance on other tasks as well.

freshphotons: 5-day old zebrafish head (20X), Confocal Dr....

Sat, 16 Mar 2013 19:30:38 -0400

freshphotons:

5-day old zebrafish head (20X), Confocal Dr. Hideo Otsuna, University of Utah Medical Center, Department of Neurobiology and Anatomy Salt Lake City, Utah

medicalschool: World’s First Bionic Eye Receives FDA Approval...

Sun, 10 Mar 2013 20:30:34 -0400

medicalschool:

World’s First Bionic Eye Receives FDA Approval

http://goo.gl/SQ36e

The new retinal prosthesis, called Argus II, can restore partial sight to people blinded by a degenerative eye disease. The Argus II works by substituting a small array of electrodes for the light-sensing cells that normally react to light by sending an electric signal toward the back of the retina. Those signals are relayed to the optic nerve behind the eye, and travel back along the nerve to the brain. In people with the genetic disease Retinitis pigmentosa, which affects about 100,000 people in the U.S. today, those light-sensing cells gradually stop working, resulting in total blindness. In addition to the electrode array, which is implanted in the retina at the back of the eye, the Argus II system consists of a small video camera attached to a pair of eyeglasses and a visual processor the user carries around their waist. Data from the video camera is sent to the visual processor and then back to the glasses, where it is transmitted wirelessly to the embedded electrodes.

Do you know what the thymus does? The thymus is a primary...

Sat, 09 Mar 2013 14:01:00 -0500

Do you know what the thymus does?

The thymus is a primary lymphoid tissue; along with bone marrow, it is the site where T lymphocytes, components of adaptive immunity, develop. While T cells complete maturation in the thymus, B cells complete development in the bone marrow.

Secondary lymphoid tissues, on the other hand, are sites where fully developed B and T lymphocytes circulate awaiting activation by pathogens. These include the spleen, appendix, tonsil, adenoid, Peyer’s patch, etc.

Image from David B. Fankhauser, Ph.D, University of Cincinnati Clermont College

Fig Trees Kill Larval Insects? Plants and insects have...

Fri, 22 Feb 2013 19:30:57 -0500

Fig Trees Kill Larval Insects?

Plants and insects have co-evolved for millions and millions of years. We all know that bees, for example, help plants fertilize by transferring pollen from flower to flower, and in return, they get nectar from the plants.

According to an article online, when wasps lay their eggs inside figs but fail to pollinate the plant, the fig tree drops the larvally-inhabited fig to the ground, killing the larvae.

This may seem like an act of revenge on behalf of the fig tree, but is it really? The fig-wasp relationship initially evolved as a mutualistic one, providing services on both ends. The wasp obtains a suitable home for its larvae to grow and hatch from, and the fig tree gets pollinated.

If one end of the deal isn’t upheld, it is at a cost to the other party. The relationship reaches an imbalance as figs are energetically exploited as they house a parasite. To restore to imbalance and maintain the relationship, the figs simply dispose of a “selfish” wasp’s quite possibly “selfish” offspring.

You can read more here.

Article: “Study: Trees retaliate when fig wasps don’t service them,” Cornell Chronicle

Image Credit: Copyright Christian Ziegler, www.naturphoto.de

Behold: the Damselfly penis. Damselflies are interesting insects...

Thu, 21 Feb 2013 19:30:50 -0500

Behold: the Damselfly penis.

Damselflies are interesting insects as far as the evolution of sexual reproduction. Males will grip onto females for hours during copulation to “protect” the females from other males.

Perhaps more interestingly, the damselfly penis has a neat little morphological adaptation visible in the above scanning electron micrograph that allows the male to manually scoop out the sperm of previous males from the female reproductive tract. From an evolutionary perspective, such an adaptation ensures that the successful male’s genes only are passed onto the next generation, improving his reproductive fitness.

Image Credit: Science Photo Library

hello! I'm a high school student who is hoping to major in medicine/biology one day. I was just curious, is there any aspect of history of medical biology you are interested in? or any aspect of medical biology that intrigues you?

Wed, 20 Feb 2013 23:14:00 -0500

Hello there!

I definitely find the history of immunology exciting because scientists have only truly begun to explore the field within the last couple of decades. For example, it wasn’t until the late 1970’s, through Susumu Tonegawa’s ground-breaking experiments, that we were able to understand how antibodies are formed. (And antibodies are a BIG deal.) So in a sense, this chapter in the history of biomedicine is being written now, which is pretty exciting.

I’m actually a Biology & Psychology double major, so I’m also interested in clinical psychology and where it overlaps with biology.

Aside from that, I’m really big on functional morphology within evolutionary contexts. You’d be really surprised how much you have in common with a shark or a pigeon, and how much in medicine is explained by our evolutionary history!

Top: “Single optical section through the whole gut of a...

Wed, 20 Feb 2013 22:47:20 -0500

Top: “Single optical section through the whole gut of a Drosophila melanogaster larva expressing a reporter for Notch signaling pathway activity (green), and stained with cytoskeletal (red) and nuclear (blue) markers.”

Bottom: A mature male Drosophila Melanogaster fly. These organisms are common in biological research - you may know them just as the common “fruit fly.”

Image Credit:

Larval Gut - Jessica Von Stetina, via the Nikon Small World Competition

Mature Male Fly - André Karwath

sagansense: For the first time, scientists believe they have...

Tue, 05 Feb 2013 19:31:03 -0500

sagansense:

For the first time, scientists believe they have collected life-forms from deep under the Antarctic ice.

Last week, a team found and collected microbes in a lake hidden under more than a half-mile of ice. (Related: “Race Is On to Find Life Under Antarctic Ice.”)

Among other things, the discovery may shed light on what lies under the icy moons of Jupiter and Saturn.

The newfound life-forms have little connection to life on the earth’s surface and many apparently survive by “eating rocks,” team member Brent Christner said in an interview from the U.S. McMurdo Station, after spending several weeks working at a remote field site at Lake Whillans.

That may explain how life on other celestial objects—such as on the moons of Jupiter and Saturn—survive in the absence of available carbon.

“The conditions faced by organisms in Lake Whillans are quite parallel to what we think it would be like on those icy moons,” Christner said.

“What we found tells us a lot about extreme life on Earth,” and how similar life beyond Earth might survive.

Making a Living in Ice
A 50-member U.S. team broke through to the 20-square-mile (50-square-kilometer) subglacial lake on January 28, and had two days of 24-hour sunlight to bring up samples before the borehole began to close. A day of reaming the hole was followed by two more days of sample collection.

The scientists are now returning with a four-day haul of lake water, lake bottom sediments, and hundreds of dishes of living organisms that are being cultured for intensive study in the United States.

An early task will be to make sure the newfound microbes were not introduced while drilling through the ice into the lake, which involved a hot-water drilling technique designed to greatly reduce or eliminate any contamination that might come from other kerosene-based drilling technology, Christner said.

Christner said that a commonly used dye was added to the water to illuminate the DNA of the microscopic organisms, and a substantial green glow told scientists that microbes were indeed present. Many of the organisms are likely chemolithotrophs, which rely on inorganic compounds of iron, sulfur, and other elements for nourishment.

Montana State’s John Priscu, chief biologist of the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) program, said lab work at the drill site determined that microbial cells were present—and that they were alive.

“I believe it is safe to say that subglacial lake beneath the Whillans Ice Stream supports a microbial assemblage that is growing within this dark and cold habitat” of 31 degrees Fahrenheit (-0.5 Celsius), he wrote in an email.

DNA sequencing in the U.S. “will tell us who they are and, together with other experiments, tell us how they make a living.”

Hidden Lakes
The U.S. team is one of three digging into what is now known to be a vast system of lakes and streams deep below the surface of Antarctica. (See “Chain of Cascading Lakes Discovered Under Antarctica.”)

A British team attempting to drill into much deeper Lake Ellsworth had to return home in December because of equipment failure, but a Russian team is also at work now retrieving a core of water from Lake Vostok.

With much fanfare, the Lake Vostok core was pulled up last year from more than 2.5 miles (4 kilometers) below the frigid surface. Vostok is much deeper and larger than any other Antarctic lake, and both it and Ellsworth lie under much colder ice and are believed to have less deep subsurface water flowing in and out than does Whillans.

The existence of subglacial lakes and streams in Antarctica is a relatively new discovery, and the size of this wet world under the ice has only been grasped in recent years. (See Antarctic pictures by National Geographic readers.)

Helen Fricker, a glaciologist at the Scripps Institution of Oceanography and a principal investigator of the Whillans team, first described Lake Whillans in 2007.

Using satellite data, she and her colleagues discovered a periodic rising and falling of the ice surface above the Whillans Ice Stream between 2003 and 2006, and concluded that a lake was likely underneath.

The dynamics of Antarctic ice has taken on a much greater significance in the era of global warming, since some 90 percent of Earth’s fresh water sits on the continent.

Although the lakes themselves are not affected by warming, how they interact with the region’s ice is important to predicting the future behavior of the ice sheets.

For instance, understanding whether the ice is moving more quickly toward the surrounding ocean is a key goal of the WISSARD project, which is part of a larger U.S. National Science Foundation project to understand the ice movements, glaciers, and biology of the ice sheet of West Antarctica.

More Work to Be Done
For Christner, a specialist in Antarctic biology at Louisiana State University, the work has only just begun.

Two labs were brought to the Whillans site by a caravan of trucks from McMurdo: One to perform a quick analysis of the lake water, and the other to examine sediment.

Christner’s team is charged with culturing samples in dishes so they can be studied more extensively later. He said some of the microbe species, including bacteria and archaea, may be unique, but many may well be found elsewhere—at great ocean depths and deep underground.