Corey Hansen
NIR Phototherapy as Treatment for Chicken Brain Assymetries caused by 2,3,7,8-Tetrachlorio Dibenzo-P-Dioxin
BSES Senior Research 2005

In ovo exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been shown to induce gross asymmetries in developing chicken brains. This asymmetry has been observed and documented in several species including great blue herons, bald eagles, and cormorants [1-5]. Recent studies by Dr.Eells of UW-Milwaukee has shown that treatment with light emitting diodes (LEDs) of NIR (Near Infrared) light with peak wavelength of 670 nm (640-690 range) can increase wound healing and mitochondrial activity [6].

In this study we have examined the affects of NIR light treatment on chicken embryos exposed to varying doses of TCDD. Domestic chickens (Gallus gallus) were dosed, in ovo, with: No Inject Control (NIC), Vehicle Control (VC), 2, 20, and 200 parts per trillion TCDD, using a 10-µL Hamilton syringe. Sunflower oil was used as the vehicle. The TCDD was injected into the air sac of the egg through a small hole in the shell, which was immediately covered with paraffin wax. The dose groups were then split into groups that would either be treated with the NIR light or remain untreated. The NIR exposed eggs were "lighted" every 24 hours for 80 seconds, while a paired non-NIR treated egg was taken out of the incubator to minimize confounds. The embryos were allowed to come to hatch (21 days) and were then sacrificed approximately 24 hours post hatch. The birds were evaluated for brain asymmetries, oxidative stress enzymes, body and vital organ weight, yolk weight, length, mortality, for those that did not hatch, and time till hatch.

Brain measurements were done using an engineering ruler with 0.5 mm markings. Thirteen measurements were done on each side of the brain, and then repeated for two trials. Differences were indicated by absolute values then averaged for the two trials. Results show a decreased asymmetry for all groups exposed to TCDD. There was statistical significance shown in Figure 2, between dose groups within treatments and NIC and VC respectively. However, at the dose of maximum effect, 20 ppt, we see significance within light treatment. This shows that the NIR reduced the asymmetry of the brains in this dose group significantly, also shown in Figure 2. Other results from the study showed increased body and liver weight, and increased crown rump length (distance from top of head to tip of rump). The NIR treated birds also hatched earlier and had less residual yolk which allows us to assume they had higher yolk utilization during their development.

These results are exciting, and could point towards the use of NIR phototherapy in the health sciences. Some possible applications could include treatment of burn and crash victims, bone fractures, muscle/bone atrophy, skin grafts, and tissue damage.