Hate to burst your bubble
For years, the antibacterial soap industry as asserted their products kill bacteria and other pathogens more effectively than plain soap and water, that they’re much, much better at preventing illness and the spread of infections over the long haul.
Now the Food and Drug Administration is asking manufacturers to prove it.
This isn’t just another case of concerns about commercial hyperbole. An increasing number of scientists and public health groups fear the antibiotics used in these soaps are promoting resistance in the targeted microbes. Rising antibiotic resistance, however, is just part of the problem. A number of studies have shown that triclosan – a common antibacterial agent in these soaps – may interfere with human hormone activity.
The FDA action follows another bit of recent research news about personal hygiene: Washing your hands in hot water apparently offers no more hygienic benefit than using room temperature water.
A recent Vanderbilt University study found that hot water did not measurably improve the efficacy of the typical hand-washing experience.
“It is true that heat kills bacteria,” said study author Amanda Carrico. “However, the level of heat required to neutralize pathogens is beyond what is considered safe for prolonged human contact.”
The researchers noted too a downside to using all of that hot water to wash our collective hands to no great effect: It requires a lot of energy and significantly adds to greenhouse gas emissions worldwide.
They estimated that if Americans en mass used tepid water instead of warm or hot, the avoided energy use and prevented greenhouse gas emissions would be equivalent to the entire output of a nation the size of Barbados.
Polarized light micrograph of recrystallized saccharin, magnified 16 times. Image courtesy of Stefan Eberhard
Pretty sweet water
For backpackers and their ilk, one of the great thrills of outdoors life is finding a natural source of cool, crystalline water – a babbling brook, for example, or translucent stream rippling over a bed of clean river rock.
Between the stuff we dump into our waters intentionally and the stuff we don’t, North American waters are chockfull of more than just atoms of hydrogen and oxygen.
On the plus side (not really), the conglomeration is apparently sweet.
Canadian researchers, writing in PLOS ONE, report finding elevated concentrations of four artificial sweeteners: cyclamate (found in the Canadian version of Sweet ‘N Low, but not the U.S., where it’s banned), saccharin (American Sweet ‘N Low), sucralose (Splenda) and acesulfame (Sunett) in samples collected along the length of the Grand River in Ontario, Canada.
All four sweeteners are widely used, most commonly in diet drinks. They got into the Grand by way of 30 sewage treatment plants that apparently don’t remove artificial sweeteners before depositing treated water back in the river.
Unlike other chemicals detected in “natural” waters – antibiotics, perfumes, drugs – it’s not known whether long-term exposure to these sweeteners poses a health risk to humans or wildlife. Some contaminants have been linked to disrupting reproductive systems of fish and other aquatic organisms.
The researchers said the sweeteners do offer a bit of scientific utility. Sucralose and acesulfame are notably persistent in the environment. They do not break down quickly, which has allowed researchers to more effectively trace the travels of treated sewage, often for hundreds of miles.
Skeletal muscle attaches to joints and long bones and is under the control of the conscious brain. As you read this blog, occasionally typing on your keyboard, it’s skeletal muscle directing your fingers through their finely-tuned tap dance.
(FYI: Aside from skeletal, there are two other major muscle types in your body: smooth and cardiac. Smooth is involuntary and non-striated. Generally, it’s either fully contracted or fully relaxed. Your urinary bladder, lungs and the irises of your eyes are controlled by smooth muscle. Cardiac muscle is also involuntary – doing its job automatically – but striated, meaning parts of it are able to contract while other parts do not. Your heart is composed of cardiac muscle.)
In this confocal fluorescent light micrograph by Thomas Deerinck at the National Center for Microscopy and Imaging Research at UC San Diego, you’re looking at a cross-section of parallel skeletal muscle fibers (stained red due to the presence of the proteins actin and myosin) sheathed in a sugar-protein complex (green). Cell nuclei are stained blue.
There are roughly 700 muscles in the body, in all shapes and sizes. The biggest single muscle is the Gluteus maximus, one of three muscles that comprise each buttock. Our big butts help make it possible for us to stand, move upright and run. Indeed, a 2006 paper by Harvard and University of Utah researchers suggested giant glutes make humans the undisputed best long-distance runners in the history of life on Earth.
The widest skeletal muscle in the human body is the Lastissimus dorsi, which is Latin for “wide back.” It’s the muscle that begins at the spine, fans out and attaches at the other end to the upper arms.
The longest muscle is the Sartorius, which begins at the outside of the hip, runs down the upper leg and terminates inside the knee. The name Sartorius means “tailor,” so-called because this muscle allows one to cross one’s legs, purportedly a common position assumed by working tailors. The Sartorius also assists in flexing the knees and hips.
The Gluteus maximus often is dubbed the strongest muscle because it works to keep the entire body upright, but there are many ways to measure strength:
The muscles of the uterus, for example, must be strong enough to push a baby through the birth canal.
The heart beats continuously for as long as you live – more than 3 billion times in a person’s life, pumping approximately 2,500 gallons of blood every day.
Similarly, the muscles of the eyes are constantly repositioning them. In an hour of reading, the external muscles of the eyes will make nearly 10,000 coordinated movements.
And let’s say something for the tongue, which is a bundle of tireless muscles. While eating, it moves around mixing food to aid digestion. It binds and contorts to make speech. Even when you’re asleep, it’s constantly pushing saliva down the throat.
But arguably the strongest muscle, at least based upon its weight, is the masseter or primary jaw muscle. When all of the muscles of the jaw are working together, humans can apply a bite force up to 55 pounds on the incisors and more than 200 pounds on the molars.
That’s nothing compared to the maximum chomping power of Tyrannosaurus rex (12,800 pounds), of course, but it still would hurt.
Digitally enhanced image of human heart. Wellcome Images.
Caf-fiends in a can
If your heart beats faster at the thought of quaffing a cold can of energy drink (think Red Bull, Monster, Rockstar and their ilk), there may be something wrong with you more worrisome than your sense of taste.
Almost nobody drinks these hugely popular concoctions for their sublime flavor. They are consumed almost entirely for the much touted neurological jolt derived from an overabundance of stimulating caffeine (as much as three times more than in a comparable serving of coffee or soda) and ingredients like B vitamins, the amino acid taurine, guarana, a South American plant with a higher caffeine concentration than coffee, ginseng and ginkgo biloba.
Judging from sales - $12.5 billion in 2012 in the U.S. alone – these commercial energy drinks deliver their promised punch – and worse.
A report presented this week at the Radiological Society of North America found that energy drinks appear to adversely alter heart function. Specifically, they can cause rapid heart rate, palpitations, a blood pressure spike and, possibly, seizures or death.
If that’s not enough of an eye-opener, consider this statistic from the Substance Abuse and Mental Health Services Administration: Each year almost 21,000 energy drink consumers find themselves in hospital emergency rooms being treated for unwanted side effects of the beverages.
So next time you need something to snap you awake, try water – eight icy cold ounces dashed to the face generally does the trick.
Human goblet cell. Image courtesy of the University of Edinburgh, Wellcome Images
Raise a glass to the goblet cell
In a paper published last week in Virology Journal, Pascal Gagneux and colleagues at UC San Diego School of Medicine describe how influenza A viruses snip through the protective mucus net to both infect respiratory cells – and then later cut their way out infect other cells.
Mucus is usually deemed a disgusting annoyance, but really it’s not. (Sorry, couldn’t resist.) It is oil in the human engine, lubricating the passages of the mouth, nose, sinuses, throat, lungs and gastrointestinal tract, preventing underlying epithelial tissues from drying out. It’s also a sort of sticky flypaper, trapping unwanted substances like bacteria and dust before they can too deeply penetrate the fairly pristine and sterile inner body.
Each day, a healthy person churns out about 4 to 6 cups of mucus. Most of it trickles down your throat unnoticed. The little factories that make mucus are called goblet cells. It’s an apt moniker because goblet cells are little more than vessels filled to the brim with globules of mucin. That’s a globule cell in the image above; the mucin globules colored blue.
Mucins are glycosylated proteins, but you can think of them more simply as dehydrated bits of mucus packed inside a globule cell. Once released into the water-rich environment of your airways, however, they expand rapidly, absorbing water to reach full, gooey size within 20 milliseconds. That’s one-thousandth of a second. That’s fast. A single flap of a hummingbird’s wing takes 5 to 80 milliseconds.
The rapid release allows goblet cells to respond almost instantly to many different stimuli, from inhaled microbes to a mouthful of eye-watering wasabi.
Tongue bacteria. Image courtesy of Steve Gschmeissner
That’s a mouthful
This week, Rob Stein at NPR concluded his series on the human microbiome with a look at research investigating how our multitudinous intestinal bacteria may influence brain development and function. Turns out that old notion about “gut feelings” might have a biological basis.
These days, microbiome research is on everybody’s tongue, and thus the inspiration for today’s image: a colorized scanning electron micrograph of bacteria residing on a human tongue.
It should be no surprise that the human mouth is home to hundreds of microbial species. After all, it’s warm, moist and frequently open for business. It doesn’t start that way. A newborn has no bacteria in its oral cavity, but that soon changes – and changes even more as the mouth develops. Gums, cheeks and emerging teeth all provide distinct environmental niches for different bacterial species.
Some of these species are beneficial, aiding in digestion, for example. Many others are offer no direct benefit, but are helpful in occupying space that might otherwise be taken up by nastier bugs, such as those that cause tooth decay, periodontal diseases and worse. Poor oral hygiene has been linked to poor health elsewhere, including a higher risk of heart attack and cardiovascular disease.
Like fingerprints, everyone’s tongue is different. It’s the same with the assemblages of bacteria that call our mouths home. A recent microbial survey identified almost 400 different species in the mouths of 100 participants representing four different ethnic affiliations. Only 2 percent of the bacterial species were present in all of the individuals, albeit in different concentrations according to ethnicity. Eight percent were detected in 90 percent of the group. But most interestingly, said the researchers, each ethnic group – non-Hispanic blacks, whites, Chinese and Latinos – was identifiable by its own “signature” of shared microbes.
Hans von Gersdorff was one of Germany’s most noted surgeons during the late 15th and early 16th centuries, though little is known about the personal life or background of the man. He is best remembered for his illustrated Feldbuch der Wundartzney or Fieldbook of Surgery.
Based largely upon the writings of famed medieval surgeon Guy de Chauliac, Gersdorff’s tome was widely used as a basic surgical text for many years, most notably for its advice on limb amputation, which Gersdorff was reputed to be much experienced, with at least 200 procedures.
Feldbuch contained numerous woodcut images of surgical procedures, such as trephining and bone setting, anatomical schematics and diseases or medical conditions, such as leprosy. The woodcuts were done by Johann Ulrich Wechtlin.
Many of the images created by Gersdorff and Wechtlin were quite technical, if not always complete or precisely accurate. The image above, known as “Wound Man,” is likely intended to be more evocative in nature – a quick guide to injuries that military surgeons might see on a battlefield.
Gersdorff died in 1529 at the age of 74, presumably the consequence of old age and not from one of the mortal afflictions above.
Yesterday’s announcement of a $100 million gift from businessman and philanthropist T. Denny Sanford to create the Sanford Stem Cell Clinical Center at UC San Diego marks a major step in the journey to deliver the therapeutic potential of stem cells to actual patients-in-need.
It’s a long road, of course, with plenty of hills and valleys ahead, but as the process goes forward, a look back at some of the UC San Diego stem cell research fueling that effort.
- Scanning electron micrograph (false color) of a human induced pluripotent stem cell-derived neuron. Thomas Deerinck/UC San Diego
- A human neuron derived from stem cells in the brain of a mouse. Alysson Muotri/UC San Diego
- Stem cell-derived human neurons (red and green) in the spinal cord of a rat. Martin Marsala/UC San Diego
- Two neurospheres (clusters of brain cells) derived from human induced pluripotent stem cells send neuronal processes (green) to connect to each other. The red indicate the nuclei of cells. Alysson Muotri/UCSD
- Neurons derived from induced pluripotent stem cells of patients with Alzheimer’s disease. Larry Goldstein/UC San Diego
Speaking of rats (OK, we weren’t but now that the subject’s been mentioned), we present the above laser scanning confocal micrograph of an en face section of epithelium of a rat’s tongue, produced by Tom Deerinck at the National Center for Microscopy and Imaging Research at UC San Diego.
The image slightly penetrates the superficial epithelium of the tongue and uses a variety of stains to highlight distinct structures. Most notable is the cross-hatched mesh of striated muscle fibers, whose actin (a contractile protein) glows fluorescently red. Cell DNA is stained blue. Cell membranes are highlighted in green.
Rats, of course, have long had a voice in medical research. They are among science’s most cherished model organisms, employed by researchers everywhere to study everything from autism to spinal cord injuries to the warming effects of eating durian while taking the painkiller paracetamol, otherwise known as acetaminophen, the active ingredient in Tylenol.
Some rat models are the product of targeted genetic engineering, but mostly they are useful for just being appallingly similar to human beings, biologically speaking. Or as in the case of the naked mole rat, utterly unlike us. The naked mole rat is a favorite in cancer research because, oddly enough, it is cancer-resistant. In decades of study, not a single incident of cancer has been detected in a naked mole rat, which makes it a fitting model for finding new ways to fight the disease.
Don’t yawn. Gotcha!
All vertebrates yawn spontaneously.
It’s not clear why, exactly, we all yawn. The scientific-sounding explanation that yawning allows us to suck in extra, rejuvenating amounts of oxygen is a myth. There’s no evidence that yawning affects levels of oxygen in the bloodstream, blood pressure or heart rate.
Contagious yawning is something else altogether, but equally mysterious. It happens when you see someone else yawning. It can happen if you just imagine someone else yawning.
Contagious yawning is believed to be an ancient act of social bonding employed by myriad species to signal their open-mouthed, involuntary empathy with others. Persons with autism, for example, are less likely to catch a yawn than others, though it’s not clear whether it’s a lack of empathy or merely inattention to facial cues.
Contagious yawning isn’t restricted to the same species. While it’s tough to induce a fish to yawn (apparently some do), it’s possible to make a dog yawn – or a chimpanzee.
A new study reports that chimps yawn after watching humans yawn, but it’s selective. Elainie Madsen, an evolutionary psychologist at Lund University in Sweden, explains in this video that young chimpanzees unfamiliar with a yawning human don’t necessarily gape in response, but older chimps that have spent time with the yawner are quite likely to yawn in harmony.
Contagious yawning comes naturally, but not immediately. It’s a learned behavior for both chimps and humans, not really catching on until the yawnee is three or four years old.
(Question: How many times did you yawn reading this story? On average, a normal, healthy adult yawns seven to nine times each day; each yawn lasting about six seconds.)