SCIENCE sciencemag.org 16 AUGUST 2019 • VOL 365 ISSUE 6454 653PHOTO: NASA GODDARD
NEUROSCIENCE
Visualizing neuronal
activity in vivo
Imaging the changes in fluo-
rescence of voltage-sensitive
reagents would enable monitor-
ing of the activity of neurons in
vivo. Abdelfattah et al. created
such a voltage indicator by
designing a protein that com-
bines the voltage sensor domain
from microbial rhodopsin with
a domain that captures a dye
molecule with exceptional
brightness and photostability.
When the protein was expressed
in mice, flies, or zebrafish, they
could monitor single action
potentials in dozens of neurons
simultaneously for many min-
utes. —LBR
Science, this issue p. 699METABOLISM
Malleable muscle
metabolism
The effect of sex on physi-
ological processes such as
metabolism has not been suf-
ficiently studied, despite signs
that cellular-level processes can
be sexually dimorphic. During
fasting, skeletal muscles switch
from using carbohydrates to
fatty acids as a fuel source. Yang
et al. found that fasting induced
skeletal muscle in female mice
to produce brain-derived neuro-
trophic factor (BDNF), a protein
known for its role in synaptic
plasticity and neuronal survival.
Skeletal muscle deficiency of
BDNF in female mice, but not
in male mice, prevented this
metabolic switch and resulted in
myofiber necrosis and reduced
muscle strength. —WW
Sci. Signal. 12 , eaau1468 (2019).ENGINEERING
Decoding sweat to
monitor health
Our sweat carries biomol-
ecules, such as electrolytes,
metabolites, and hormones,
that can be used probe the
state of our bodies at a chemi-
cal level. Nyein et al. developed
a wearable microfluidic patchEdited by Caroline Ash
and Jesse Smith
IN OTHER JOURNALSNEUROSCIENCE
Social isolation biases
rodent data
Rodents are social animals,
and social isolation and barren
environments are stressful for
them. However, experimental
protocols sometimes insist on
single housing to obtain accuratemeasurements of biological
parameters or to avoid damage
to monitoring apparatus, such
as severing of EEG wires, or to
prevent aggressive behavior
from others. Manouze et al.
investigated the consequences
of animal housing conditions on
stress response and epilepsy
severity in rats and mice. Isolatedthat captures sweat, which they
used to predict whole-body
fluid and electrolyte loss during
exercise. Secretion rate and
sodium levels show a positive
correlation across regions of the
body and among study subjects.
Correlation between regional
fluid loss and whole-body water
loss could be used to track
hydration status. —JR
Sci. Adv. 10.1126/
sciadv.aaw9906 (2019).ROBOTICS
Lowering locomotion’s
metabolic cost
Walking and running require
different gaits, with each type of
motion putting a greater bias on
different muscles and joints. Kim
et al. developed a soft, fully por-
table, lightweight exosuit that is
able to reduce the metabolic rate
for both running and walking by
assisting each motion via the hip
extension (see the Perspective
by Pons). A waist belt holds
most of the mass, thus reducing
the cost of carrying the suit. By
tracking the motion of the user,
the suit is able to switch modes
between the two types of motion
automatically. —MSL
Science, this issue p. 668;
see also p. 636PLANT SCIENCE
Less space but greater
maize yield
To meet increasing demands for
food, modern agriculture works
with increasingly dense plantings.
Tian et al. identified a gene in teo-
sinte, the wild ancestor of maize,
and used it to alter maize such
that the plant has a narrower
architecture that nonetheless
allows leaves access to sunlight
(see the Perspective by Hake and
Richardson). The yield advantage
only becomes evident with the
high-density plantings charac-
teristic of modern agriculture,
perhaps explaining why this gene
was not brought into the fold
during the previous millennia of
maize domestication. —PJH
Science, this issue p. 658;
see also p. 640GALAXIESDust declines after a starburst
P
ost-starburst (PSB) galaxies recently experienced a
short episode of vigorous star formation, which has now
ceased. Li et al. have studied 58 PSB galaxies whose
starbursts ended 100 million to 800 million years
ago. By combining data from the ultraviolet to the far
infrared, they measure the mass of dust in PSB galaxies and
find that it declines approximately exponentially with time
since the starburst. The decline is too fast to be the result of
the residual star formation, so it may reflect dust destruction
by an active galactic nucleus. The dust and gas levels would
evolve to typical levels for early-type galaxies about a billion
years after the starburst. —KTS
Astrophys. J. 879 , 131 (2019).The mass of dust in galaxies decreases exponentially with time
since the end of their star formation phase.