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How Scratching Curbs the Itch?

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Itching brings with it that ever-increasing urge to scratch, which always works wonders, but not much is known about the physiological  mechanisms behind this phenomenon.

Now scientists have watched spinal nerves transmit that relief signal to the brain in monkeys, a possible step toward finding new treatments for persistent itching in people.
....click & see

Nerve cells play a key role in itching

More than 50 conditions can cause serious itching, including AIDS, Hodgkin’s disease and the side effects of chronic pain treatment, said Glenn Giesler, a neuroscientist at the University of Minnesota in Minneapolis. Some terminal cancer patients even cut back on pain medication just to reduce the itch, he said.

Scratching can lead to serious skin damage and infections in people with chronic itch, he said. So scientists want to find ways for such people to relieve their distress “without tearing up their skin,” he said.

While medications can relieve some kinds of itch, other cases resist current treatments.

Nobody knows just how scratching relieves itch. But the federally funded monkey study, reported Monday on the website of the journal Nature Neuroscience by Giesler and colleagues, takes a step in unraveling the mystery.

The scientists focused on a kind of spinal nerve that transmits the “itch” signal to the brain. The researchers sedated long-tailed macaques for the experiment and placed recording electrodes on their spinal nerves. They injected a chemical into a leg to produce itching. The nerves fired electrical signals in response. Then the researchers scratched the leg with a hand-held metal device that simulates three monkey fingers. The firing rate dropped — the apparent signature of the “relief” signal. In contrast, when researchers scratched the leg without causing an itch first, the firing rate jumped. So the nerves somehow “know” to react much differently if there’s an itch to be relieved than if there isn’t.

Sources: The Times Of India

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Spinal Shocks Can Control Parkinson’s

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By electrically stimulating the spinal cords of rodents, scientists have reversed some of the worst symptoms of Parkinson’s disease. As long as a  mild current flows up their spines and into their brains, the animals regain the ability to scamper around their cages, as if they were normal.
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The therapy, described in the journal Science, is a potential alternative to direct stimulation, which requires risky and invasive surgery to implant electrodes deep in the brain, researchers said. Only 30% of severely impaired Parkinson’s patients qualify for the operation.

Spinal cord stimulation would be less invasive and inherently safer, and it would reduce the amount of drugs needed to treat the disease, said the report’s lead author, Miguel Nicolelis, a neuroscientist at Duke. In the new treatment, animals whose brains were depleted of dopamine had tiny electrodes, the size of a fingernail, implanted on their spinal cords. Three seconds after a mild electrical stimulation began, they could move about normally.

The treatment was also effective when combined with L-dopa in further experiments; only two doses of L-dopa were needed to produce movement, compared with five doses when it was used by itself. Spinal cord stimulation represents a “big conceptual change” in how to treat Parkinson’s disease, Nicolelis said. Rather than looking at where things happen in the brain, the approach focuses on when things happen, as in the dynamic firing patterns of large circuits of neurons.

These circuits oscillate in harmony and underlie normal brain function. Parkinson’s patients have abnormal low-frequency oscillations in the brain regions controlling movement, Nicolelis said. Stimulation of the topmost layer of the spinal cord, which conveys touch sensations to the brain, may work by disrupting these abnormal oscillations, restoring normal firing patterns across multiple brain structures involved in the control of voluntary movements.

Sources: The Times Of India

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Hot Chillies Can Help Mitigate Pain

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Capsaicin, the active agent in spicy hot chili peppers, often acts as an irritant, but it may also be used to reduce pain.

………………...CLICK & SEE
Feng Qin, associate professor of physiology and biophysics at the University at Buffalo School of Medicine, and Jing Yao used capsaicin to unravel how pain-receptor systems can adapt to painful stimuli.

For example, adaptation happens when your eyes adjust from a dark movie theatre during a matinee to the bright sunlight outside. Whether pain receptors truly adapt or rescale their responses (versus simply desensitising) has been an open question.

Scientists had previously linked the analgesic or pain-relieving effects of capsaicin to a lipid called PIP2, found in cell membranes. When capsaicin is applied to the skin it induces a strong depletion of PIP2 in the cell membrane.

“The receptor acts like a gate to the neurons,” said Qin. “When stimulated it opens, letting outside calcium enter the cells until the receptor shuts down, a process called desensitisation.”

“The analgesic action of capsaicin is believed to involve this desensitization process. However, how the entry of calcium leads to the loss of sensitivity of the neurons was not clear,” he said, according to a Buffalo release.

Capsaicin creams are commonly sold over the counter as effective treatment for a variety of pain syndromes, from minor muscle or joint aches to those that are very difficult to treat, such as arthritis and neuropathic pain.

Sources:The Times Of India

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Diagnonistic Test

Fluorescein Angiography (Test for Diabetic Retinopathy)

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Alternative Names: Retinal photography; Eye angiography

Definition:
Fluorescein angiography is an eye test that uses an special dye and camera to look at blood flow in the retina and choroid……...CLICK & SEE

By looking into the back of your eye (the retina), eye doctors can see changes in the blood vessels there that show whether you are at risk for losing vision from diabetes or other causes. The earliest changes can be seen only with a special test called fluorescein angiography. For this test, a chemical that temporarily makes the blood vessels fluorescent and shows very tiny leaks in them is injected into one of your arm or hand veins while you are having your eyes examined.

This test is used to determine if there is proper circulation in the blood vessels of the retina. It can also be used to diagnose problems in the eye or to determine how well treatment is working.

Preparation  for the test:
You should arrange to have someone else drive you home from the eye doctor, because your eyes will be dilated; this can make your eyes sensitive to the sun and your vision blurry for a while.

You may be told to discontinue drugs that could affect the test. results. Tell your health care provide about any allergies, particularly reactions to iodine.

You must sign an informed consent form. You must remove contact lenses before the test.

Tell the health care provider if you may be pregnant.


How the Test Is Performed
Eye drops that make the pupil dilate will be given. You will be asked to place your chin on a chin rest, and your forehead against a support bar to keep your head still during the test.

Fluorescein angiography->…..CLICK & SEE

The health care provider will take pictures of the inside of your eye. After the first group of pictures are taken, a special dye called fluorescein is injected into your vein, usually at the bend of the elbow. A special camera takes pictures of the dye as it moves through the blood vessels in the back of the eye.

More photographs are taken up to 20 minutes after the injection.

What happens when the test is performed?
You have drops put into your eye to make the pupil dilate (open), and you have to wait for about half an hour while the drops take effect. Before giving you any other medicine, your doctor might first examine your eyes for signs of bleeding or debris outside of your retina arteries; these are signs of more advanced eye disease from diabetes. Then a nurse inserts a small needle into one of the veins in your arm or hand so that you can have a dose of medicine injected. Your doctor uses a special eye camera to take pictures of your retina. You look into one side of the camera while your doctor looks through the other side. The camera shines a dim blue light into your eye, which causes the dye flowing through the retina arteries to show up as fluorescent green. The doctor takes a collection of pictures of your eyes to review more closely later.

This color retinal photograph demonstrates nonproliferative diabetic retinopathy. The image is centered on the macula (the part of the retina responsible for central fine vision) with part of the optic nerve seen on the left of the photo (left eye). There are hemorrhages within the retinal tissue on the right side of the photograph.

How the Test Will Feel
When the needle is inserted , some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

When the dye is injected, you may have mild nausea and a warm sensation. These symptoms are usually very brief.

Normal Results:
A normal result means the vessels appear a normal size and there are no blockages or leakages.
Back to TopWhat Abnormal Results Mean
If blockage or leakage is present, the pictures will map the location for possible treatment.

An abnormal value on a fluorescein angiography may be due to:

*Blood flow (circulatory) problems
*Cancer
*Diabetic or other retinopathy
*Inflammation or edema
*Macular degeneration
*Microaneurysms — enlargement of capillaries in the retina
*Tumors
*Swelling of the optic disc

Additional conditions under which the test may be performed:

Retinal detachment
Retinal vessel occlusion
Retinitis pigmentosa

Risk Factors:
There are no special risks from this test, although your vision may be blurry for an hour or more after the test because your pupils are dilated. The dye fluorescein is excreted from your body in your urine, which might give your urine a bright or discolored appearance for a day.

There is a slight chance of infection any time the skin is broken. Rarely, a person is hypersensitive to the dye and may experience:

*Dizziness or faintness
*Dry mouth or increased salivation
*Hives
*Increased heart rate
*Metallic taste in mouth
*Nausea and vomiting
*Sneezing
*Serious allergic reactions are rare.

Your urine will be darker, and possibly orange in color, for a day or two after the test.

Must you do  after the test is over?
You will need to wear sunglasses for a few hours until your pupils are no longer dilated.

Considerations:
People with cataracts will have less accurate test results.

How long is it before the result of the test is known?
Your doctor can often discuss the results of the test with you at the end of your visit. He or she might recommend treatment (such as eye laser treatments) if your test reveals retina disease.

Click to see:->How does diabetes affect the retina?

Resources:
https://www.health.harvard.edu/diagnostic-tests/fluorescein-angiography.htm
http://health.nytimes.com/health/guides/test/fluorescein-angiography/overview.html

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Featured

How Light Sensors in Eye Work

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Neuro-scientists have unravelled how newly discovered light sensors in the eye detect light and communicate with the brain.
click & see

These light sensors are a small number of nerve cells in the retina that contain melanopsin molecules.

Unlike conventional light-sensing cells in the retina-rods and cones, melanopsin-containing cells are not used for seeing images.

Instead, they monitor light levels to adjust the body’s clock and control constriction of the pupils in the eye, among other functions.

“These melanopsin-containing cells are the only other known photoreceptor besides rods and cones in mammals, and the question is, how do they work,” said Michael Do, a postdoctoral fellow in neuro-science at Johns Hopkins.

“We want to understand some fundamental information, like their sensitivity to light and their communication to the brain,” he informed.

Using mice, the team first tested the light sensitivity of these cells by flashing light at the cells and recording the electrical current generated by one cell.

They found that these cells are very insensitive to light, in contrast to rods, which are very sensitive and therefore enable us to see in dim light at night, for example.

According to Do, the melanopsin-containing cells are less sensitive than cones, which are responsible for our vision in daylight.

“The next question was, what makes them so insensitive to light? Perhaps each photon they capture elicits a tiny electrical signal. Then there would have to be bright light-giving lots of captured photons for a signal large enough to influence the brain. Another possibility is that these cells capture photons poorly,” said Do.

To figure this out, the team flashed dim light at the cells. The light was so dim that, on average, only a single melanopsin molecule in each cell was activated by capturing a photon.

They found that each activated melanopsin molecule triggered a large electrical signal. Moreover, to their surprise, the cell transmits this single-photon signal all the way to the brain, said a Johns Hopkins release.

Yet the large signal generated by these cells seemed incongruous with their need for such bright light. “We thought maybe they need so much light because each cell might also contain very few melanopsin molecules, decreasing their ability to capture photons,” said King-Wai Yau, a professor of neuroscience at Hopkins.

When they did the calculations, the research team found that melanopsin molecules are 5,000 times sparser than other light-capturing molecules used for image-forming vision.

“It appears that these cells capture very little light. However, once captured, the light is very effective in producing a signal large enough to go straight to the brain,” said Yau.

Sources: The Telegraph (Kolkata, India)

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