Biology subjects

Kouba, C.

Publications and source records attributed to Kouba, C..

2 recordsLinked to original sources

bioRxiv2024

Tracking gonadotropin-releasing hormone-mediated movement in-vivo using quantum dot nanoparticles: insights into pathways leading to sperm release

As the number of conservation breeding programs for at-risk amphibians increase, application of assisted reproductive technologies (ARTs) has likewise grown, with hormone therapy being the most widely utilized technique. Significant interest has been raised for viable alternatives to traditional intracelomic injection for hormone treatment that may be simpler, require less hormone, induce a faster response and be more suitable for animals of different sizes or for minimal contact. We utilized quantum dot (QD) nanoparticles conjugated to GnRHa (GnRHa-QDs) as a means of monitoring exogenous GnRHa dispersal through living Fowlers toads to investigate how delivery route may affect hormone pathway and efficacy after intracelomic, nasal, and oral administration. Real-time GnRHa-QD movement was tracked using in vivo imaging while hormone binding and QD aggregation were validated using fluorescence microscopy and measurements of spermiation responses following the administration of unconjugated GnRHa, unconjugated QDs, and GnRHa-QDs GnRHa alone was found to induce spermiation in 58.3%, 76.9% and 92.3% of males when administered by intracelomic, oral and nasal routes, respectively. When given through intracelomic injection GnRHa-QD caused spermiation and dispersed throughout the abdominal cavity to then aggregate within the brain, heart, liver, gastrointestinal (GI) tract, kidneys, and testes while unconjugated QDs did not. By contrast, GnRHa-QDs administered by oral or nasal routes were observed moving to the tympanic membrane and down the throat to the GI tract of the toads, but only nasal-administered GnRHa-QDs showed organ aggregation and were only found in the kidneys. Unconjugated QDs exhibited similar in vivo signal dispersal as their conjugated counterparts initially but did not aggregate in any organs over time nor induce spermiation. Through the use of novel QD hormone conjugates, in vivo imaging, and histology we were able to gain insight into how hormone pathways and efficacy might be impacted by delivery route which result in variations in physiological response to hormone treatment.

physiology↗

bioRxiv2023

Oral administration of GnRH via a cricket vehicle stimulates spermiation in tiger salamanders (Ambystoma tigrinum)

More than 50% of caudates are threatened with extinction and are in need of ex-situ breeding programs to support conservation efforts and species recovery. Unfortunately, many salamander populations under human care can experience reproductive failure, primarily due to missing environmental cues necessary for breeding. Assisted reproductive technologies (ARTs) are a useful suite of techniques for overcoming or bypassing these missing environmental cues to promote breeding. Exogenous hormones are used to stimulate natural breeding behaviors or gamete expression for in-vitro fertilization or biobanking and are typically administered intramuscularly in caudates. While effective, intramuscular injection is risky to perform in smaller-bodied animals, resulting in health and welfare risks. This research investigated the spermiation response to hormone administration through a non-invasive oral route using the tiger salamander (Ambystoma tigrinum) as a model species. Male salamanders were randomly rotated six weeks apart through four treatments (n = 11 males/treatment) in which animals received a resolving dose of gonadotropin-releasing hormone (GnRH) as follows: (1) Prime-Only (0.0 {micro}g/g); (2) Low (0.25 {micro}g/g); (3) Medium (1.0 {micro}g/g); and (4) High (2.0 {micro}g/g). All males were given a GnRH priming dose (0.25 {micro}g/g) 24 hours prior to the resolving dose. Exogenous hormone was delivered inside of a cricket (Gryllodes sigillatus) that was presented as a food item by tweezers. Sperm samples were collected at 1, 3, 6, 9, 12, and 24 hours after the resolving dose and analyzed for quantity and quality. For all treatments, sperm concentration was produced in an episodic pattern over time. The Prime-Only treatment had a lower (p < 0.05) percent of sperm exhibiting normal morphology compared to treatments utilizing a resolving dose of GnRH. Overall, oral administration of GnRH is a feasible route of inducing spermiation in salamanders, yielding sperm of sufficient quantity and quality for in-vitro fertilization and biobanking efforts.

zoology↗