Biology subjects

Baehre, H.

Publications and source records attributed to Baehre, H..

4 recordsLinked to original sources

bioRxiv2023

Subcutaneous and orally self-administered high-dose carprofen in male and female mice: pharmacokinetics, tolerability and impact on cage-side pain indicators

Surgical interventions in mice are prerequisite in various research fields and require appropriate pain relief, not only to ensure animal welfare but also to avoid influence of pain on research findings. Carprofen is a non-steroidal anti-inflammatory drug that is commonly used as an analgesic for interventions inducing mild to moderate pain in animals. Despite its frequent use also in laboratory rodents, data on pharmacokinetics and side effects, and on its potential impact on behavioral pain indicators are rare. This study aimed to determine pharmacokinetic and tolerability profiles of high dose carprofen in male and female C57Bl/6J mice, administered via single subcutaneous injection (s.c.) and oral self-administration per drinking water (d.w.). Plasma concentrations of carprofen were measured at various time points, and side effects were evaluated using a modified Irwin test protocol, hematology and histopathology. Additionally, potential effects on behavioral pain indicators commonly used to assess post-surgical pain, such as the mouse grimace scale, wheel running activity, burrowing, nesting and grooming behavior were investigated. Quantification of carprofen in plasma revealed maximum plasma concentrations of 133.4 {+/-} 11.3 {micro}g/ml after 1 hour and an elimination half-life of 8.52 hour after single s.c. injection of 20 mg/kg carprofen. Oral self-administration of carprofen (25 mg/kg/24 h) resulted in a steady-state < 24 hours over 5 days after treatment start with plasma levels of around 60 {micro}g/ml. The carprofen-medicated water was highly accepted, and increased d.w. intake was observed in the first 24 hours after exposure for both sexes (p < 0.0001). Irwin test detected only minor side effects, and hematology and histopathology where without pathological findings that could be attributed to carprofen treatment. Except for a decrease of 49-70 % in wheel running activity in male mice, behavioral pain indicators were only very mildly affected. This study determined carprofen plasma levels in mice lying well above an estimated therapeutic concentration for both routes of administration. Carprofen was well tolerated at recommended high doses and may provide sufficient analgesia for minor interventions as well as be applied as a tolerable component in multimodal analgesic regimens.

pharmacology and toxicology↗

bioRxiv2022

Predicting butyrate- and propionate-forming bacteria of gut microbiota from sequencing data

BackgroundThe bacteria-derived short chain fatty acids (SCFAs) butyrate and propionate play important (distinct) roles in health and disease and understanding the ecology of respective bacteria on a community-wide level is a top priority in microbiome research. The aim of this study was to reveal members harboring main pathways for the production of those metabolites and assess the applicability of sequence data (metagenomics and 16S rRNA gene) to predict SCFAs production in vitro and in vivo. ResultsA clear split between butyrate- and propionate-forming bacteria was detected with only very few taxa exhibiting pathways for the production of both SCFAs. After in vitro growth of fecal communities from distinct donors (n=8) on different substrates (n=7) abundances of bacteria exhibiting pathways correlated with respective SCFA concentrations, in particular in the case of butyrate. While final growth differed markedly between cultures, communities showed high functional redundancies with comparable yields, i.e., concentration of metabolite per grown bacterium exhibiting pathway(s), irrespective of the donor and substrate used. For propionate, correlations were weaker indicating that its production is less imprinted into the core metabolism compared with butyrate-forming bacteria. Longitudinal measurements in vivo (five samples derived from 20 subjects) also revealed a correlation between abundances of pathway-carrying bacteria and concentrations of the two SCFAs. Additionally, lower bacterial cell concentrations, together with higher stool moisture, promoted overall bacterial activity (measured by flow cytometry and coverage patterns of metagenome-assembled genomes) that led to elevated SCFAs concentrations with over-proportional levels of butyrate. Butyrate concentrations displayed lower temporal stability than propionate, however, abundances of bacteria exhibiting the butyrate-forming pathway were more stable than those carrying pathways for propionate production. Predictions on pathway abundances based on 16S rRNA gene data using our in-house database worked well yielding similar results as metagenomic-based analyses. ConclusionsWe demonstrated that pathway abundances enable predictions on concentrations of SCFAs indicating that stimulating bacterial growth directly leads to more production of those compounds. The strong separation of gut microbiota into two functional communities facilitates the development of precision intervention strategies targeting either metabolite.

microbiology↗

bioRxiv2020

Minor pilin genes are involved in motility and natural competence in Synechocystis sp. PCC 6803

Cyanobacteria synthesize type IV pili, which are known to be essential for motility, adhesion and natural competence. They consist of long flexible fibres that are primarily composed of the major pilin PilA1 in Synechocystis sp. PCC 6803. In addition, Synechocystis encodes less abundant pilin-like proteins, which are known as minor pilins. The transcription of the minor pilin genes pilA5, pilA6 and pilA9-pilA11 is inversely regulated in response to different conditions. In this study, we show that the minor pilin PilA5 is essential for natural transformation but is dispensable for motility and flocculation. In contrast, a set of minor pilins encoded by the pilA9-slr2019 transcriptional unit are necessary for motility but are dispensable for natural transformation. Neither pilA5-pilA6 nor pilA9-slr2019 are essential for pilus assembly as mutant strains showed type IV pili on the cell surface. Microarray analysis demonstrated that the transcription levels of known and newly predicted minor pilin genes change in response to surface contact. A total of 120 genes were determined to have altered transcription between planktonic and surface growth. Among these genes, 13 are located on the pSYSM plasmid. The results of our study indicate that different minor pilins facilitate distinct pilus functions.

microbiology↗

bioRxiv2020

A rendezvous of two second messengers: The c-di-AMP receptor protein DarB controls (p)ppGpp synthesis in Bacillus subtilis

Many bacteria use cyclic di-AMP as a second messenger to control potassium and osmotic homeostasis. In Bacillus subtilis, several c-di-AMP binding proteins and RNA molecules have been identified. Most of these targets play a role in controlling potassium uptake and export. In addition, c-di-AMP binds to two conserved target proteins of unknown function, DarA and DarB, that exclusively consist of the c-di-AMP binding domain. Most likely these proteins transduce their signal by regulatory interactions with other proteins. Here, we have investigated the function of the c-di-AMP-binding protein DarB in B. subtilis, a protein consisting of two CBS (cystathionine-beta synthase) domains. We have used an unbiased search for DarB interaction partners and identified the (p)ppGpp synthetase/hydrolase Rel as a major interaction partner of DarB. (p)ppGpp is another second messenger that is formed upon amino acid starvation and under other stress conditions to stop translation and active metabolism. The interaction between DarB and Rel only takes place if the bacteria grow at very low potassium concentrations and intracellular levels of c-di-AMP are low. Indeed, c-di-AMP inhibits the binding of DarB to Rel. The interaction results in the Rel-dependent accumulation of pppGpp. Our results link potassium and c-di-AMP signaling to the stringent response and thus to the global control of cellular physiology.

microbiology↗