13 February 2019

Salt in Mind

Welcome back. Some time ago, Vicki and I visited an art museum and dined in its very nice café. Our selected dishes were preceded by pieces of special bread, which Vicki enjoyed but I found too salty.  

Salt (sodium chloride)
on a saucer.
My distaste for salt is probably due to my mother’s judicious use of the mineral. An exceptional cook, she leaned toward undersalting having once oversalted the entrée she prepared when hosting a guest of my father.

Or maybe my dislike arose grabbing a bite to eat with friends during high school or when we were all back in town. My salt taste buds joined the witness protection program watching the guys reach for the salt shaker before tasting the already salty pizza, hamburger, hotdog or other fine-dining fare.

Of course, nowadays, with the concern about salt and high blood pressure, I’m grateful that I was never big on salt. And woe is us, there’s always research with a new concern about salt. Before I discuss one such study, I’d better review the latest guidelines to be sure we’re dining at the same table.

Healthy Level of Sodium
The Dietary Guidelines for Americans 2015-2020 recommends that adults and children ages 14 years and older limit sodium, which is primarily consumed as salt (sodium chloride), to less than 2300 milligrams (mg) per day. That’s about 1000 mg/day less than our current average consumption, yet it’s the highest level likely to pose no health risk to almost everyone.

The recommendation is based on evidence of a relationship between increased sodium intake and increased blood pressure. While there’s also evidence of an association between sodium intake and cardiovascular disease, that evidence is not as consistent as the evidence on blood pressure, a surrogate indicator of cardiovascular disease.

Salt and Dementia
OK, the new concern about salt? Weill Cornell Medicine researchers linked a diet rich in salt to an increased risk of dementia and cerebrovascular (brain and its blood vessels) diseases.

If it makes you feel any better, the work reported thus far was limited to mice. Mice were fed food with 4% and 8% salt, the latter being comparable to the high end of human consumption. After eight weeks, magnetic resonance imaging of the mice showed significantly lower resting cerebral blood flow in the cortex and hippocampus, areas of the brain involved in learning and memory.

The researchers also found the excess salt suppressed functioning of cells lining blood vessels to the brain (endothelial cells). This caused a reduction of nitric oxide, a gas the cells produce to relax the blood vessels and increase blood flow.

After some mice were put back on their regular diet for four weeks, their cerebral blood flow and blood vessel cell function returned to normal. But mice that continued on the high salt diet developed dementia as measured by different criteria (object recognition test, maze test and nest building).

The researchers performed additional experiments toward understanding the biological mechanisms linking high salt intake with dementia and preventing the suppression of nitric oxide, and work continues.

Wrap Up
I could relax if reducing sodium was as simple as not reaching for the salt shaker. Unfortunately, most of the sodium we eat comes from packaged, processed, store-bought and restaurant foods. A study of 450 adults from three U.S. metropolitan areas, for example, found sodium in processed and restaurant foods accounted for 71% of the participants’ sodium intake! Only 11% was added at home, either in cooking or at the table.

If you compare nutrition labels, such as the two cold cereals shown here, be sure to take the serving size (at top) into account.
There’s some evidence that potassium intake can help balance the effects of sodium; however, overall diet, lifestyle and exercise are likely to be more important. One appendix in the Dietary Guidelines report is devoted to physical activity recommendations.

So, join me in reading the labels. As we cut back on sugar, let’s try to do the same with sodium. And thanks for stopping by.

Example articles on health risks related to salt and sodium: www.hsph.harvard.edu/nutritionsource/salt-and-sodium/sodium-health-risks-and-disease/
Sodium recommendations in Dietary Guidelines for Americans 2015-2020 8th Edition: health.gov/dietaryguidelines/2015/guidelines/chapter-1/a-closer-look-inside-healthy-eating-patterns/#other-components
Study linking salt to dementia in Nature Neuroscience journal: www.nature.com/articles/s41593-017-0059-z
Article on study on ScienceDaily website: www.sciencedaily.com/releases/2018/01/180116131306.htm
Study on sources of sodium in U.S. diet in Circulation journal: circ.ahajournals.org/content/135/19/1775
Example article on potassium and health (also see first article cited above): www.heart.org/HEARTORG/Conditions/HighBloodPressure/MakeChangesThatMatter/How-Potassium-Can-Help-Control-High-Blood-Pressure_UCM_303243_Article.jsp#.WmyesjdryUk

A version of this blog post appeared earlier on www.warrensnotice.com.

06 February 2019

A Light on Bats

Welcome back. Several years ago, I blogged about a species of bat whose tongue is longer than its body (The Ecuadorian Bat).

I began that post by describing how I’d once swung a broom, baseball-bat style, to annihilate a bat flying frantically in our living room. I also confessed to later feeling remorse, explaining, Who knew of the ecological and economic importance of bats? In those years, Batman dressed the part, yet Dracula was their only spokesperson.

Importance of Bats
Yes, like other mammals, bats can carry rabies and other diseases, bugs and ticks, and yes, under the right conditions, their feces (guano) can transmit disease. But many of the more than 1200 bat species consume vast quantities of insects (including mosquitoes!), annually saving agriculture billions of dollars in pest control. Other bats pollinate plants; fruit-eating bats disperse seeds.

And guano? It’s a valuable resource that’s been used as a fertilizer for centuries. You’ll find it online and in your local retail stores.

Little brown bat with symptoms of white-nose syndrome in N.C.
(photo by Gabrielle Graeter, N.C. Wildlife Resources Commission from commons.wikimedia.org/wiki/File:Little_brown_bat_from_Avery_County_with_fungus_on_nose_(5429328341).jpg)

White-Nose Syndrome
I wrapped up that 2012 blog post noting bats are in trouble, and it’s gotten worse. White-nose syndrome, caused by the fungal pathogen Pseudogymnoascus destructans (P. destructans), has killed millions of bats in North America since it was first documented in New York State in 2006. One of the most severe wildlife diseases ever recorded, it has now spread to 33 states and 7 of Canada’s 10 provinces. The long-term effects will not be known for decades.

The P. destructans fungus infects skin of the bat muzzle, ears and wings. Bats are infected during winter hibernation when their body temperature lowers to the temperature growth range of the cold-loving fungus, about 39-68°F (4–20°C).

Once infected, irritation from the fungus causes frequent awakening from hibernation, increasing the amount of energy the bats would otherwise use. Infected bats experience depleted fat reserves, weight loss, dehydration, electrolyte imbalances and death.

Cluster of little brown bats with symptoms of white-nose syndrome in N.Y.
(photo by Alan Hicks, N.Y.S. Dept. of Environmental Conservation from www.fws.gov/midwest/endangered/mammals/inba/WNSphotos.html)
Signs of the disease include visible white fungal growth, excessive or unexplained deaths at the hibernation site, abnormal hibernation activity and wing damage. Notably, these clinical signs likely reflect more advanced disease stages.

Breakthrough Research
In a study published about a year ago, collaborating scientists from the U.S. Forest Service, U.S. Department of Agriculture and the University of New Hampshire sought to gain insight into the origins and adaptations of P. destructans through genome annotation--identifying the locations of genes and all of the coding regions in a genome, and determining what the genes do.

The researchers generated annotated genomes for P. destructans and six non-pathogenic species of the same genus. Through comparative genomics, they discovered that P. destructans lacked a key DNA-repair enzyme. To test this potential vulnerability, they exposed the seven Pseudogymnoascus species to four DNA-damaging agents: ultraviolet (UV) light and three chemical agents (methyl methanesulfonate, 4-nitroquinoline and camptothecin).

P. destructans exhibited extreme sensitivity to UV light. This led to further testing with different wavelengths and intensities of UV light. They found the fungus was especially sensitive to the UV light wavelength of 254 nanometers. A moderate dose exposure, which could be achieved in only a few seconds, killed over 99%.
Percent survival of colony forming units of Pseudogymnoascus destructans (bottom, orange graph) and six non-pathogenic Pseudogymnoascus species (other graphs) exposed to three intensities of UV light of 254 nm.
(from www.nature.com/articles/s41467-017-02441-z)
Wrap Up
Methods to treat white nose syndrome with UV light are being actively pursued; however, the challenge of saving or protecting populations of bats in their natural environment is immense.

Along with pointing to the fungus’s vulnerability to UV light, the study produced one other finding of interest. The genomics analyses suggest that P. destructans evolved alongside Eurasian bat species for millions of years. Unlike in North America, its presence in Europe and Asia does not cause significant mortality.

Thanks for stopping by.

Background on bats:
White-nose syndrome:
Study of white-nose syndrome’s sensitivity to UV light in Nature Communications journal: www.nature.com/articles/s41467-017-02441-z
Forest Service public release and example articles on UV light sensitivity study:
National Fish and Wildlife Foundation's Bats for the Future Fund: www.nfwf.org/bats/Pages/home.aspx

A version of this blog post appeared earlier on www.warrensnotice.com.

31 January 2019

Circadian Wound Healing

Welcome back. I’ve got a fascinating topic, but before I begin, you’ll have to promise not to try to verify the findings of the research study I’ll be reviewing--you know, don’t try this at home, kids. Agreed? OK.

The study found that daytime wounds heal faster than nighttime wounds. It’s all very logical when you realize that wound healing falls under the spell of circadian rhythms. Here’s the story.

Circadian Rhythms
I wrote briefly about circadian rhythms in a blog post on the cause of Roosters’ Crowing. Circadian rhythms are physical, mental and behavioral changes that follow the 24-hour diurnal cycle and are found in most living things--microbes, animals and plants.

Our bodies’ biological clocks.
(Graphic by Katherine Streeter
for National Public Radio, 2015)
Circadian rhythms are produced and their timing regulated by each organism’s biological clocks. Note that “clocks” is plural. The biological clocks are composed of specific protein molecules that interact in cells in nearly every tissue and organ in the body. The brain synchronizes all those the clocks.

(By the way, the 2017 Nobel Prize in Physiology or Medicine was given for discoveries of molecular mechanisms controlling circadian rhythm.)

Although natural factors within the body produce circadian rhythms, they’re also affected by external factors, especially daylight. Jet lag is one example of how altering the cycle can speed, slow or reset the body’s clocks as well as circadian rhythms.

What Happens with a Wound?

My scraped
knee (selfie).
Ouch! You cut your finger (or scrape your knee). Fibroblast cells, which are responsible for making an extracellular matrix and collagen to help skin cells with the repair, waste no time in getting to the wound.

Movement of the fibroblast cells relies on actin, a protein that, in addition to being involved in cell migration, shares the responsibility for forming the contractile filaments of muscle cells.

Circadian Rhythm Healing

To investigate the circadian influence on healing, researchers from the UK’s Medical Research Council’s Laboratory of Molecular Biology in Cambridge first led experiments with cells in lab petri dishes. They found fibroblasts filled scratches faster during the day than at night apparently because genes that control actin are more active during the day.

They then found similar results in experiments with mice. Fibroblasts took twice as long to reach a new wound site if the wound occurred during the mice’s normal rest period of their 24-hour cycle than during the mice’s active waking period.

Pursuing these findings further with humans, the researchers analyzed cases from the International Burn Injury Database. They observed that the time of burn injury significantly affected the rate of healing. Daytime wounds healed about 60% faster than comparable nighttime wounds.

Wrap Up
While the study extends our understanding of circadian rhythms and cell-based biological clocks, the authors emphasize the need for additional research.

If the results are confirmed, how could that affect medical decisions? Should a patient’s circadian rhythm be considered when scheduling surgery? Can drugs be formulated to put a site of injury into daytime status?

Interesting, no? Thanks for stopping by.

Example articles on circadian rhythms:
Background on fibroblasts:
Study on circadian influence on fibroblasts in Science Translational Medicine journal: stm.sciencemag.org/content/9/415/eaal2774
Article on study on New Scientist website: www.newscientist.com/article/2152754-daytime-injuries-heal-twice-as-fast-as-wounds-sustained-at-night/
International Burn Injury Database: www.ibidb.org/

A version of this blog post appeared earlier on www.warrensnotice.com.

29 January 2019

Who Needs Livestock?

Welcome back. Did you hear? The U.S. Department of Agriculture estimated the average American would consume a record high of 222.2 pounds of red meat and poultry in 2018.

Here’s the question: Can we cut back on livestock in agriculture? Do we really need all those farm animals? Livestock production is bad for the environment. Eating 222.2 pounds of meat is bad for our health. Should I go on? Maybe not, but I will or there’d be no blog post.

Photo collage of US livestock.
(from www.ag.ndsu.edu/piercecountyextension/livestock)
The Case Against Livestock
In my post on the World Scientists’ Warning to Humanity (Wake Up, World!), one recommended step to sustainability was promoting dietary shifts toward mostly plant-based foods. To be clear, that was the scientists’ pitch for the environment, not human diet.

UN Food and Agricultural
Organization 2006 report
“Livestock’s Long Shadow–
environmental issues
and options.”

A prime example of the reason behind that recommendation was provided in a 2006 report by U.N. Food and Agriculture Organization (FAO). The livestock sector was ranked as one of the top two or three contributors to the most serious local to global environmental problems.

According to that FAO report, the livestock sector accounts for 70% of all agricultural land, is a key factor in deforestation and water use, plays possibly the lead role in reducing biodiversity and bears responsibility for 18% of greenhouse gas emissions (measured in CO2 equivalent), which was scaled down to 14.5% in a 2014 FAO report on livestock and climate.

Regarding human dietary health, I’ll just point to the Dietary Guidelines for Americans 2015-2020, which recommends lower intake of meats as well as of processed meats and processed poultry.

Most recent dietary guidelines for Americans.
(from health.gov/dietaryguidelines/2015/guidelines/)
Remove All Livestock?
Researchers from Virginia Tech and the USDA’s Dairy Forage Research Center asked how food supply adequacy and greenhouse gas emissions would be affected if all livestock were removed from U.S. agriculture.

To answer that question and, in essence, establish the boundary condition for further discussion and research, they drew upon the best available data to quantify and model U.S. agriculture.

Nutrient Requirements

Considering 39 nutrients (protein, carbohydrates, vitamins, minerals, amino acids, fatty acids), 36 of which are required to maintain life and health, the researchers determined that animal-derived foods currently provide energy (24% of total), protein (48%), essential fatty acids (23%–100%) and essential amino acids (34%–67%) available for human consumption in the U.S.

Their modeling showed plants-only agriculture produced 23% more food than agriculture with livestock; however, it met fewer requirements for essential nutrients. When nutritional adequacy was evaluated using least-cost diets, plants-only diets showed more nutrient deficiencies, a greater excess of energy and a need to consume a greater amount of food solids.

Greenhouse Gas Emissions
Using published life cycle assessments to calculate carbon emissions associated with food production, the researchers estimated agricultural greenhouse gas emissions decreased 28% without animals. But this reduction did not fully counterbalance the animal contribution (49% in their model), and it reduced total U.S. greenhouse gas emissions by only 2.6%.

U.S. agricultural greenhouse gas
emissions with and without animals.

(from www.pnas.org/content/114/48/E10301.full)
Other Factors
Going beyond food supply and greenhouse gas, the researchers noted that the U.S. livestock industry employs 1.6 million people and accounts for $31.8 billion in exports. Livestock recycles more than 47.6 million tons of human-inedible food and fiber processing byproducts, converting them into human-edible food, pet food, industrial products and 4.4 million tons of nitrogen fertilizer.

Wrap Up
The study suggests that eliminating livestock from U.S. agriculture would reduce greenhouse gas emissions, yet the resulting food supply would be incapable of meeting the population’s nutritional requirements. Although the requirements of individuals can be met with plant-based diets, achieving that for an entire population would be a challenge, especially as regards essential micronutrients.

80-cow rotary milking parlor on dairy farm with over 8000 cows.
(2009 photo by Kyle McDaniel from Wisconsin State Journal, 4 March 2010)
Increasing the efficiency of livestock production is one alternative goal, but I also wonder if we might shift a bit toward one animal--edible insects. (Don’t gag!) As I described in my blog post Entomophagy, their nutritional value can be comparable to or better than meat and fish, and they emit fewer greenhouse gasses than most livestock, require less land and are much more efficient at converting feed to protein than conventional livestock.

Think bugs, and thanks for stopping by.

2006 UN FAO report, Livestock’s Long Shadow: www.fao.org/docrep/010/a0701e/a0701e00.HTM
2014 UN FAO report, Tackling Climate Change Through Livestock: www.fao.org/3/a-i3437e.pdf
Advisory Report: 2015–2020 Dietary Guidelines for Americans: health.gov/dietaryguidelines/2015-scientific-report/
Study on removing animals from U.S. agriculture in Proc. of the National Academy of Sciences: www.pnas.org/content/114/48/E10301.full
2016 study of edible insects’ nutritional and sensory quality in NFS Journal:

A version of this blog post appeared earlier on www.warrensnotice.com.

21 January 2019

Opossums, Continued

Welcome back. Continuing the blog post Learning About Opposums, I had just described looking out the window in the early afternoon to see an opossum followed by Vicki’s cat Mindy. I’ve no idea if Mindy spotted the opossum out foraging, or if Mindy happened upon the opossum’s transient home and chased the animal out into the open.

I first saw the two on the northwest side of our building. Switching windows, I watched the opossum walk steadily around to the south side, with Mindy about 10 to 20 feet behind, sort of stalking, sort of just acting curious. I finally lost sight of the opossum around a pile of branches. Presumably, Mindy got too close as I saw her running away.

Enough. I’d better get on with what else I learned about opossums. 

Opossum dining in a trash can.
(Multiple websites)
Opossums are opportunistic omnivores, eating whatever they find. Considered sanitation workers of the ecosystem, they dine on dead animals, plants and fruit; insects, earthworms, snails and grubs; and may hunt small rodents, birds and chicks, frogs and snakes. They apparently have partial or total immunity to venom from rattlesnakes, cottonmouths and other pit vipers.

Orphaned baby opossums in
dead mother’s pouch.

(Photo from
Breeding and Offspring
Opossum breeding season is generally between January and July, though it varies somewhat with geographic location. The gestation period is short, 12 to 13 days. Females (“jills” as opposed to “jacks”) may deliver 1 to 3 litters of 4 to over 20 “joeys,” 1 to 3 times a year; two litters of 4 to 9 is most common. Newborn joeys are about the size of honeybees.

Young opossums cling to
their mother after leaving
the pouch.
(Multiple websites)
No more than 13 joeys from the large litters survive because the mothers have only 13 nipples. Observations vary but the joeys are normally weaned by 60 to 90 days. On leaving the pouch, they stay with their mother, initially clinging to her, until they are on their own no later than 4 months from birth.

The young opossums are vulnerable to predators. Vicki’s cats, for example, would likely go after very young opossums should they wander or be pushed from the pouch.

Opossum threatening
with all 50 teeth.

(Multiple websites)
Despite having 50 teeth, the most of any mammal, opossums are shy and non-aggressive. When threatened, they may run, growl, hiss, screech, arch their back with fur erect, bare their teeth, drool, urinate and defecate.

They can bite, of course, but if all else fails, they normally faint and play possum, an involuntary response that gives the appearance and odor of a sick or dead animal. They roll onto their side, become stiff, close their eyes or stare, and bare their teeth, tongue hanging out, as saliva foams around the mouth and a foul-smelling fluid is secreted from anal glands. They may remain in this state for minutes to hours.

Opossum playing possum.
(Multiple websites)

Health Concerns
Opossums tend to be very clean, spending much of their time grooming like domestic cats. A 2014 research study that exposed several wild animals to Lyme-disease carrying ticks labeled opossums the winner at ridding the world of ticks. The opossums licked off and swallowed over 90% of the ticks.

Although there have been cases of opossums with rabies, it’s rare. Their resistance to rabies is thought to be related to the opossum's low body temperature (94-97°F) and strong immune system.

Opossums are known to carry a variety of bacterial and viral diseases, such as equine protozoal myeloencephalitis, which mostly affects horses when they ingest feed or water contaminated with opossum feces.

Wrap Up
Opossums should be left alone. They are not cut out to be pets.

If one remains in your area or keeps returning to it, try to eliminate the attraction, which can be challenging. Opossums scored better than cats, dogs, rats and rabbits on ability to remember. They tend to outcompete other creatures for food. Remove any food, keep doors and windows closed, and leave an outdoor light on. 

Logo of the Opossum Society
of the United States.
If help or information is needed, contact a wildlife rehabilitator or the Opossum Society of the United States (see P.S.), whose members are dedicated to opossum rehabilitation and education.

Thanks for stopping by.

Opossum vs possum: writingexplained.org/opossum-vs-possum-difference
Selected background references:
Study of opossums’ ability to kill ticks: www.caryinstitute.org/newsroom/opossums-killers-ticks
Opossum Society of the United States: opossumsocietyus.org/

A version of this blog post appeared earlier on www.warrensnotice.com.