Biology subjects

Busch, R.

Publications and source records attributed to Busch, R..

3 recordsLinked to original sources

bioRxiv2025

Zebrafish facility report on implementation of artificial plants as structural enrichment

There is a broad consensus that husbandry conditions of laboratory animals need constant improvement to guarantee optimal animal welfare and research data quality. Zebrafish (Danio rerio) as one of the main animal models in biomedicine and toxicology are currently kept in barren tanks in most experimental setups, as well as in animal husbandry. Structural enrichment with artificial plants is currently discussed as a potential refinement measure to provide a more diverse environment. It was shown, that this can reduce stress and improve cognitive abilities, survival rate and fertility in these animals. Still, concerns remain regarding its long-term benefits and drawbacks. Therefore, we introduced artificial plants in our husbandry tanks, and evaluated over a one-year period if in our specific system, the benefits would outweigh the risks. Comparing six different lines of zebrafish raised in enriched tanks or under our standard conditions, we saw no significant difference in terms of sex ratio, fertility or pathogen burden. Enrichment increased the survival rate of 4 % during upbringing, albeit not statistically significant due to high variation. When analyzing zebrafish behavior in their 8 L home-tanks, we found less zebrafish in areas close to the plants but rather a preference for the open water in the middle or opposite side of the tank. This effect was even more pronounced at lower holding densities of less than 4 fish per liter. In summary, we found that introducing structural enrichment to our zebrafish facility carried low cost and no detrimental effects for the animals but at the same time benefits were difficult to determine in our readouts as our survival rates already were very high without these measures. We like to encourage other animal facilities to evaluate enrichment measures to ensure a broader discussion on long-term benefits of structural enrichment in zebrafish husbandry systems.

animal behavior and cognition↗

bioRxiv2024

The Impact of Model Assumptions in Interpreting Cell Kinetic Studies

Author summaryStable isotope labelling is one of the best available methods for quantifying cell dynamics in vivo, particularly in humans where the absence of toxicity makes it preferable over other techniques such as CFSE or BrdU. Interpretation of stable isotope labelling data necessitates simplifying assumptions. Here we investigate the impact of three of the most commonly used simplifying assumptions (that the cell population of interest is closed, that the population of interest is kinetically homogeneous, and that the population is spatially homogeneous) and suggest pragmatic ways in which the resulting errors can be reduced.

immunology↗

bioRxiv2020

Quality control of HLA-DR molecules by the lysosomal aspartyl protease, cathepsin D

Major histocompatibility complex class II (MHCII) molecules display peptides on antigen-presenting cells (APCs) for inspection by CD4+ T cells. MHCII surface levels and life span are regulated post-translationally by peptide loading and ubiquitin-dependent lysosomal targeting, but proteases responsible for MHCII protein degradation remain unidentified. Here, we examined the role of aspartyl proteases in MHCII protein degradation and characterised the form of MHCII that is degraded. Exposure of immature monocyte-derived dendritic cells (MoDCs) and KG-1 acute myeloid leukaemia cells to the aspartyl protease inhibitor, pepstatin A (PepA), caused accumulation of human leukocyte antigen (HLA)-DR molecules in intracellular vesicles. Statistically significant PepA effects on MHCII protein expression were also observed in murine APCs. In KG-1 cells, cathepsin D (CatD) was the sole expressed aspartyl protease, and shRNA-mediated knockdown ablated the PepA effect, providing formal proof of CatD involvement. In vitro, CatD initiated specific cleavage of recombinant DR at F54, a site flanking the peptide-binding groove. Immunochemical characteristics of PepA-rescued DR molecules in KG-1 cells were consistent with selective CatD attack on HLA-DR molecules that lack association with the MHCII chaperone, invariant chain, or with stably bound peptide. We propose that CatD has a critical role in the selective lysosomal disposal of mature HLA-DR molecules that have lost, or never acquired, bound peptide, explaining how MHCII protein life span is coupled to peptide loading.

biochemistry↗