Doxycycline

How does the presence of Doxycycline in embryonic chicken eggs effect the development of the embryo?

We hypothesize that injecting 78 µg/100mL and 156 µg/100mL will have a dose dependent effect, slowing the development of chicken embryos the more doxycycline injected. 

Doxycycline is a common antibiotic used for a variety of bacterial infections and although it is generally discouraged for use during pregnancy, little research has been conducted on the effects of this antibiotic on embryonic chicken development. Doxycycline is a type of tetracycline antiobiotic, which targets the 30S subunit of ribosomes. This ultimately impairs the ability of tRNA from binding to the ribosome and translating genetic material into essential proteins. There is no clear comparable dosage of doxycycline to treat chicken embryos to that of  humans, so we will be exploring will dosaging. 

On day 1, we will inject either 78 µg/100mL or 156 µg/100mL of doxycycline in PBS as our low and high dose respectfully. Along with a control group injected with just PBS.  We will use an egg puncturing device to make a tiny hole in the egg. Then we will insert 0.1mL of the respective solution directly into the yolk of the egg. The tiny hole will be covered back up with tape. The eggs will be returned to the incubator for one week. On day 8, we will extract the embryo outside of the egg. To do this we will carefully cut a hole in the egg about the size of a quarter. Using a plastic spoon, we will assist the transfer of the embryo to a Bioptechs EDU Series Culture Dish Control System (Butler, PA) set at 41 degrees Celsius to keep the embryo warm. We will aslo be using desk lamps to maintain heat in this environment. We will measure heartrate with the heart still in the embryo. After collecting the heart rate, we will transfer the embryo to a pan and position an iPhone camera at a fixed position above the embryo to take photos of it. Using ImageJ, we will measure trunk size, head size, length of embryo and any other abnormalities.  

For our eggs injected with just PBS, they had a higher rate of underdevelopment than those injected with the low and high dose. Across the board, there was no significant difference between the heart rate of any of the tested groups. Similarly, all the injected groups showed no significant difference in eye diameter, however, the negative control proved to have bigger, more developed eyes. The results for the eye diameter proved to be similar and representative of the other measurements taken: trunk size, brain width, and brain height. 

On day 8 of development, eggs were identified as developed, unfertilized, or underdeveloped (slight vasculature). Measurements such as heart rate, trunk length, eye diameter, and brain size were analyzed from the developed embryos. It was noted that neither the low dose nor the high dose had statistically significant differences when compared to the positive control, however, for all analysis other than heart rate, each injected egg group proved to be less developed than the negative control (uninjected group). Previous research have eluded to doxycycline causing an ipairment in embryonic morphological development when administered doxycycline. With lack of sufficient data, it is difficult to draw any conclusions with a proper level of confidence. Further research involving more than one administration of doxycycline or administration at different points of development could enhance this area of study.