Biology subjects

Mueller, S. J.

Publications and source records attributed to Mueller, S. J..

3 recordsLinked to original sources

bioRxiv2023

A temperature-controlled, circular maintenance system for studying growth and development of pelagic tunicates (Salps)

Salps are pelagic tunicates that are able to form large blooms under favorable conditions by alternating between sexual and asexual reproduction. While their role in the regional carbon cycle is receiving attention, our knowledge of their physiology is still limited. This knowledge gap is mainly due to their fragile gelatinous nature, which makes it difficult to capture intact specimens and maintain them in the laboratory. We present here a modified kreisel tank system, that was tested onboard using the Southern Ocean salp Salpa thompsoni and station-based using the Mediterranean species Salpa fusiformis. Successful maintenance over days to weeks allowed us to obtain comparable relative growth and developmental rates as in situ, and provided insight into their potential life cycle strategies. By providing a starting point for successful maintenance, we hope to stimulate future experimental research on this understudied taxonomic group.

physiology↗

bioRxiv2022

Predicting cell stress and strain during extrusion bioprinting

Bioprinting of living cells can cause major shape deformations, which may severely affect cell survival and functionality. While the shear stresses occurring during cell flow through the printer nozzle have been quantified to some extent, the extensional stresses occurring as cells leave the nozzle into the free printing strand have been mostly ignored. Here we use Lattice-Boltzmann simulations together with a finite-element based cell model to study cell deformation at the nozzle exit. Our simulation results are in good qualitative agreement with experimental microscopy images. We show that for cells flowing in the center of the nozzle extensional stresses can be significant, while for cells flowing off-center their deformation is dominated by the shear flow inside the nozzle. From the results of these simulations, we develop two simple methods that only require the printing parameters (nozzle diameter, flow rate, bioink rheology) to (i) accurately predict the maximum cell stress occurring during the 3D bioprinting process and (ii) approximately predict the cell strains caused by the elongational flow at the nozzle exit.

biophysics↗

bioRxiv2021

Vagus nerve stimulation increases stomach-brain coupling via a vagal afferent pathway

Maintaining energy homeostasis is vital and supported by vagal signaling between digestive organs and the brain. Previous research has established a gastric network in the brain that is phase synchronized with the rhythm of the stomach, but tools to perturb its function were lacking. Here, we investigated the effect of acute right-sided transcutaneous auricular vagus nerve stimulation (taVNS) versus sham stimulation (randomized crossover-design) on stomach-brain coupling. In line with preclinical research, taVNS increased stomach-brain coupling in the nucleus of the solitary tract (NTS) and the midbrain while boosting coupling across the brain. Crucially, in the cortex, taVNS-induced changes in coupling occurred primarily in transmodal regions and were associated with changes in hunger ratings as indicators of the subjective metabolic state. Hence, taVNS alters stomach-brain coupling via an NTS-midbrain pathway that signals gut-induced reward, potentially paving the way for novel treatments in disorders such as Parkinsons disease or depression. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=160 SRC="FIGDIR/small/463517v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@39c673org.highwire.dtl.DTLVardef@113b785org.highwire.dtl.DTLVardef@175af94org.highwire.dtl.DTLVardef@15a2fbc_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LITranscutaneous vagus nerve stimulation (taVNS) can emulate interoceptive signals C_LIO_LItaVNS boosts stomach-brain coupling in the brainstem, midbrain, and transmodal cortex C_LIO_LItaVNS-induced changes in stomach-brain coupling mirror subjective hunger ratings C_LI

neuroscience↗