Mar 14, 2022 09:47 PM
(This post was last modified: Mar 14, 2022 09:54 PM by C C.)
High lead levels in mother's blood increases chance of bearing male offspring
http://www.tohoku.ac.jp/en/press/materna...pring.html
RELEASE: Higher lead levels in a mother's blood can increase the chance of her bearing male offspring, according to new research led by Japanese scientists at the Tohoku University Graduate School of Medicine.
The research, published on January 4 in the Science of the Total Environment, aimed to help explain an observed decline in the proportion of male to female births in Japan and elsewhere. "Generally, for every 100 females, 104 -107 males are born, says associate professor of medicine and lead study author Nozomi Tatsuta. "In recent years, the sex ratio has been declining worldwide, and the number of male births has been decreasing." Tatsuta cites data from a 2013 study of sex ratios at birth over six decades.
In demographic terms, the number of males per 100 females at birth is called the secondary sex ratio (SSR), which is known to be sensitive to certain environmental toxins. For example, "Previous studies have reported that the sex ratio is affected by exposure to chemical substances such as dioxins, as well as heavy metals such as methylmercury," says study author Kunihiko Nakai, professor of Development and Environmental Medicine. Noting that lead can reduce female fertility as well as male sperm quality, the researchers hypothesized that it could play a role in the SSR.
The study recruited pregnant female participants from the ongoing Japan Environment and Children's Study (JECS) sponsored by Japan's Ministry of Environment. The study covers a broad geographic swathe of Japan. The participants were classified into five groups according to their blood lead levels. The analysis was adjusted for family income and smoking status during pregnancy, which could also affect the secondary sex ratio (SSR). Blood samples were collected from 85,171 female participants during middle-late pregnancy and analyzed for lead concentrations.
Several analyses were used to examine the relationship between maternal lead levels and SSR -- a logistic regression, a sensitivity analysis, and a binomial distribution analysis -- and all three indicated an increase in the proportion of male births with higher maternal lead concentrations. The correlation between maternal lead exposure and sex ratio was consistent even after adjusting for other potential variables like father's age and exposure to lead on the job.
The findings may explain why the percentage of male births in Japan has been declining. The authors explain that, as restrictions in leaded gasoline and paint have been implemented, air lead levels have decreased, citing a 2021 study in Germany reporting a long-term trend of decreasing blood lead levels coincident with lower air lead levels. The similarly decreased air lead levels in Japan may explain the shift in sex ratio away from males.
This study has implications for public health. Guidelines for pregnant women are that blood lead levels should not exceed 50 nanograms per gram of blood. Yet, this study indicates that a maternal blood level of less than 1 nanogram per gram could affect the sex ratio of offspring.
The researchers call for further study of the correlation between lead and offspring sex ratio. "Since there are many factors other than lead exposure that are related to the sex ratio, it is still not fully understood to what extent maternal lead exposure affects the birth sex ratio," says study author Shoji F. Nakayama, lead exposure scientist for the JECS. Other factors they hope to examine in the future include the effect of paternal blood lead levels on sex ratio and the impacts of lead on frequency of miscarriages and stillbirths.
The authors caution that because lead can have toxic effects on a developing human brain, it should never be used as a means of trying to control the sex of offspring.
Endless forms most beautiful: Why evolution favors symmetry
https://www.uib.no/en/news/152523/why-ev...s-symmetry
RELEASE: From sunflowers to starfish, symmetry appears everywhere in biology. This isn't just true for body plans -- the molecular machines keeping our cells alive are also strikingly symmetric. But why? Does evolution have a built-in preference for symmetry?
An international team of researchers believe so, and have combined ideas from biology, computer science and mathematics to explain why. As they report in PNAS, symmetric and other simple structures emerge so commonly because evolution has an overwhelming preference for simple "algorithms" -- that is, simple instruction sets or recipes for producing a given structure.
"Imagine having to tell a friend how to tile a floor using as few words as possible," says Iain Johnston, a professor at the University of Bergen and author on the study. "You wouldn't say: put diamonds here, long rectangles here, wide rectangles here. You'd say something like: put square tiles everywhere. And that simple, easy recipe gives a highly symmetric outcome."
The team used computational modeling to explore how this preference comes about in biology. They showed that many more possible genomes describe simple algorithms than more complex ones. As evolution searches over possible genomes, simple algorithms are more likely to be discovered -- as are, in turn, the more symmetric structures that they produce. The scientists then connected this evolutionary picture to a deep result from the theoretical discipline of algorithmic information theory.
"These intuitions can be formalized in the field of algorithmic information theory, which provides quantitative predictions for the bias towards descriptive simplicity," says Ard Louis, professor at the University of Oxford and corresponding author on the study.
The study's key theoretical idea can be illustrated by a twist on a famous thought experiment in evolutionary biology, which pictures a room full of monkeys trying to write a book by typing randomly on a keyboard. Imagine the monkeys are instead trying to write a recipe. Each is far more likely to randomly hit the letters required to spell out a short, simple recipe than a long, complicated one. If we then follow any recipes the monkeys have produced -- our metaphor for producing biological structures from genetic information -- we will produce simple outcomes much more often than complicated ones.
The scientists show that a wide range of biological structures and systems, from proteins to RNA and signaling networks, adopt algorithmically simple structures with probabilities as predicted by this theory. Going forward, they plan to investigate the predictions that their theory makes for biases in larger-scale developmental processes.
http://www.tohoku.ac.jp/en/press/materna...pring.html
RELEASE: Higher lead levels in a mother's blood can increase the chance of her bearing male offspring, according to new research led by Japanese scientists at the Tohoku University Graduate School of Medicine.
The research, published on January 4 in the Science of the Total Environment, aimed to help explain an observed decline in the proportion of male to female births in Japan and elsewhere. "Generally, for every 100 females, 104 -107 males are born, says associate professor of medicine and lead study author Nozomi Tatsuta. "In recent years, the sex ratio has been declining worldwide, and the number of male births has been decreasing." Tatsuta cites data from a 2013 study of sex ratios at birth over six decades.
In demographic terms, the number of males per 100 females at birth is called the secondary sex ratio (SSR), which is known to be sensitive to certain environmental toxins. For example, "Previous studies have reported that the sex ratio is affected by exposure to chemical substances such as dioxins, as well as heavy metals such as methylmercury," says study author Kunihiko Nakai, professor of Development and Environmental Medicine. Noting that lead can reduce female fertility as well as male sperm quality, the researchers hypothesized that it could play a role in the SSR.
The study recruited pregnant female participants from the ongoing Japan Environment and Children's Study (JECS) sponsored by Japan's Ministry of Environment. The study covers a broad geographic swathe of Japan. The participants were classified into five groups according to their blood lead levels. The analysis was adjusted for family income and smoking status during pregnancy, which could also affect the secondary sex ratio (SSR). Blood samples were collected from 85,171 female participants during middle-late pregnancy and analyzed for lead concentrations.
Several analyses were used to examine the relationship between maternal lead levels and SSR -- a logistic regression, a sensitivity analysis, and a binomial distribution analysis -- and all three indicated an increase in the proportion of male births with higher maternal lead concentrations. The correlation between maternal lead exposure and sex ratio was consistent even after adjusting for other potential variables like father's age and exposure to lead on the job.
The findings may explain why the percentage of male births in Japan has been declining. The authors explain that, as restrictions in leaded gasoline and paint have been implemented, air lead levels have decreased, citing a 2021 study in Germany reporting a long-term trend of decreasing blood lead levels coincident with lower air lead levels. The similarly decreased air lead levels in Japan may explain the shift in sex ratio away from males.
This study has implications for public health. Guidelines for pregnant women are that blood lead levels should not exceed 50 nanograms per gram of blood. Yet, this study indicates that a maternal blood level of less than 1 nanogram per gram could affect the sex ratio of offspring.
The researchers call for further study of the correlation between lead and offspring sex ratio. "Since there are many factors other than lead exposure that are related to the sex ratio, it is still not fully understood to what extent maternal lead exposure affects the birth sex ratio," says study author Shoji F. Nakayama, lead exposure scientist for the JECS. Other factors they hope to examine in the future include the effect of paternal blood lead levels on sex ratio and the impacts of lead on frequency of miscarriages and stillbirths.
The authors caution that because lead can have toxic effects on a developing human brain, it should never be used as a means of trying to control the sex of offspring.
Endless forms most beautiful: Why evolution favors symmetry
https://www.uib.no/en/news/152523/why-ev...s-symmetry
RELEASE: From sunflowers to starfish, symmetry appears everywhere in biology. This isn't just true for body plans -- the molecular machines keeping our cells alive are also strikingly symmetric. But why? Does evolution have a built-in preference for symmetry?
An international team of researchers believe so, and have combined ideas from biology, computer science and mathematics to explain why. As they report in PNAS, symmetric and other simple structures emerge so commonly because evolution has an overwhelming preference for simple "algorithms" -- that is, simple instruction sets or recipes for producing a given structure.
"Imagine having to tell a friend how to tile a floor using as few words as possible," says Iain Johnston, a professor at the University of Bergen and author on the study. "You wouldn't say: put diamonds here, long rectangles here, wide rectangles here. You'd say something like: put square tiles everywhere. And that simple, easy recipe gives a highly symmetric outcome."
The team used computational modeling to explore how this preference comes about in biology. They showed that many more possible genomes describe simple algorithms than more complex ones. As evolution searches over possible genomes, simple algorithms are more likely to be discovered -- as are, in turn, the more symmetric structures that they produce. The scientists then connected this evolutionary picture to a deep result from the theoretical discipline of algorithmic information theory.
"These intuitions can be formalized in the field of algorithmic information theory, which provides quantitative predictions for the bias towards descriptive simplicity," says Ard Louis, professor at the University of Oxford and corresponding author on the study.
The study's key theoretical idea can be illustrated by a twist on a famous thought experiment in evolutionary biology, which pictures a room full of monkeys trying to write a book by typing randomly on a keyboard. Imagine the monkeys are instead trying to write a recipe. Each is far more likely to randomly hit the letters required to spell out a short, simple recipe than a long, complicated one. If we then follow any recipes the monkeys have produced -- our metaphor for producing biological structures from genetic information -- we will produce simple outcomes much more often than complicated ones.
The scientists show that a wide range of biological structures and systems, from proteins to RNA and signaling networks, adopt algorithmically simple structures with probabilities as predicted by this theory. Going forward, they plan to investigate the predictions that their theory makes for biases in larger-scale developmental processes.