The week’s most astounding developments from the neobiological frontier.

October 26, 2023

Everything you always wanted to know about the immune system but were afraid to ask

A catalog of the immune system appears this week estimating the total mass, number, and distribution of immune cells throughout the human body, and it’s a stunner. Based on the historic medical definition of a 20–30-year-old healthy male of average height and weight (5’9” and 160 pounds), researchers at the Weizmann Institute of Science in Rehovot, Israel, estimated the number and weight of cells all over the body. They found that the average human has approximately 1.8 trillion immune cells in their blood, bones, skin, gut, and other tissues. Together, immune cells weigh more than two and a half pounds, and the new catalog provides “an integrative quantitative view of the immune system [that] facilitates the development of models,” the researchers write. PNAS

Estimates of immune cell populations by cell type and tissue, grouped by primary systems. Ron Sender (created with BioRender.com)

Should “We the people” include AIs?

Even though our modern legal system is a purely human invention that’s almost exclusively concerned with the rights and obligations of people, many non-living and living non-human things have come to enjoy legal “personhood” under the law—including animals, rivers, and corporations. But water flows downhill without intention. Animals do what’s in their nature. Corporations are legal and intellectual constructs incapable of thought or action that’s not directed by a human hand or mind. Now a provocative perspective from legal experts at Vanderbilt University and Stanford University suggests autonomous AIs could become the latest non-human entity to similarly enter the legal system as a legal subject—but with one major difference: instantiation. No river, animal, or corporation has ever itself appeared in court or defended its rights in any form without human representation. AIs may very well do just that in the future. “A legal singularity is afoot,” they write. So could you sue an AI? Consider instead that someday soon an AI might be able to sue you. Science

Rethinking menopause: Should we call it “oopause” instead?

Cats, dogs, and many other mammals don’t menstruate. Unlike women, who in their fertile years shed their uterine lining as part of a monthly cycle, those other mammals simply reabsorb the lining. Because they don’t menstruate, by definition, they do not experience a cessation of menstruation—or what we call menopause—at the age of 45–55 or its equivalent in cat or dog years. According to two researchers at the German Cancer Research Center in Heidelberg, that should be enough to redefine this biologically significant stage of life, which is finally starting to get the attention it deserves. “We call for the definition of the end of reproductive potential to be ‘‘oopause,’’ the permanent age-associated cessation of ovulation across all mammalian species” they write. Cell

Chimpanzees also go through menopause

As if by kismet, another paper this week shatters the long-held belief among biologists that menopause (or oopause) is exceedingly rare among mammals—that it only happens in humans and a few species of toothy whales. Most mammal moms, from meadow mice to manatees, never stop ovulating and are still fertile at the end of their lives. But now researchers at UCLA and the University of Arizona have found another group of mammals that is more human-like in this way. Following a 21-year study at Kibale National Park in Uganda of fertility and mortality rates among 185 wild chimpanzees, the closest living relative of humans, they show that female chimps experience menopause very similar to human women—with a flurry of hormonal changes around 50 years of age, an end of ovulation, and with many more years of life ahead of them. Science

Tai chi for Parkinson’s disease

Drug therapy for Parkinson’s is effective at improving its debilitating movement symptoms like resting tremor, stiffness, and bradykinesia (the slowness of movement). But Parkinson’s is a progressive disease marked by the loss of neurons in certain parts of the brain, and no drug on the market is “neuroprotective,” able to stymie the loss of brain cells or slow the disease’s progression. Could the solution be combining drug therapy with tai chi—the ancient Chinese martial art that’s often practiced in the West as a form of moving meditation? Testing this idea, researchers at Shanghai Jiao Tong University in China enrolled 330 people with Parkinson’s disease in a placebo-controlled clinical trial. All were given standard drug therapies, about half were given an hour of tai chi training twice a week, and they were all followed for an average of 4.3 years. Compared to the control group, the trainees showed delayed progression, continuous life quality improvement, fewer sleep and cognition problems, less drug dosage increases, and fewer falls. Journal of Neurology, Neurosurgery, and Psychiatry

Traditional Chinese medicine faces skepticism when the mechanism is unclear

What Tu Youyou did 50 years ago is legendary. From sweet wormwood, a traditional Chinese fever remedy she had read about in a 1,600-year-old book, she isolated artemisinin. That compound became a frontline drug for malaria, saving millions of lives, winning the Nobel Prize for Tu, and inspiring generations of drug designers to dream of discovering a hidden wormwood of their own. But isolating an active ingredient and making it into a drug is one thing. How comfortable is modern medicine with remedies that work even if we don’t have the foggiest clue how? That question was put to the test this week after a double-blind, randomized clinical trial of 3,777 adults in China who suffered a specific type of heart attack known as a STEMI were given a medicine called tongxinluo. It’s an oddball concoction of seven plants mixed with the crushed up carapaces and freeze-dried bodies of five creepy crawlers—cockroaches, centipedes, leeches, cicadas, and scorpions. The clinical trial showed it’s cardioprotective, according to doctors at the Chinese Academy of Medical Sciences and Peking Union Medical College who tested it. People who took tongxinluo had better outcomes and longer survival. Wait one sec, writes the executive editor of the journal where the study appears. Unless its specific active ingredient is isolated, “skepticism will remain,” he writes. JAMA

Individual differences in distractibility

What accounts for a person’s inherent distractibility? According to psychologists at the University of Michigan, it’s three things: bright shiny objects and other external stimuli, debilitating intrusive thoughts, and plain-old simple mind wandering. Even though these are distinct, the researchers write, they can be tied together in one single, hulking higher-order factor they call “general distractibility” or little d. In their study, they found little d to be associated with both ADHD in some people and intense hyperfocus in others. That means… Wait… what were we talking about again? PLOS One