Date of Award

7-2014

Degree Name

MS in Biological Sciences

Department

Biological Sciences

Advisor

Christine R Strand

Abstract

Reptiles exhibit neurogenesis throughout the brain during adulthood. However, very few studies have quantified telencephalon-wide neurogenesis in adulthood, and no studies have performed these investigations in snakes. Quantifying neurogenesis in the adult snake is essential to understanding class-wide adult neurogenesis and providing insight into the evolution of this trait. The thymidine analog 5-bromo-2’-deoxyuridine (BrdU) was used to quantify cell proliferation, migration, and survival in the ball python (Python regius). First, to determine the proper dose of BrdU for injection we subcutaneously injected 50mg/kg, 100mg/kg, and 250mg/kg into 15 adult male P. regius. We found the 250mg/kg dose marked significantly more cells than the 50mg/kg dose, but not the 100mg/kg dose. Then we subcutaneously injected 100mg/kg BrdU into 15 juvenile male P. regius at 3 different time points (2 days, 2 weeks, 2 months) prior to sacrifice to quantify proliferation, migration, and survival of cells in several telencephalic subregions. After sectioning and immunohistochemical staining, we found proliferation to be highest in the accessory olfactory bulb (AoB), retrobulbar regions (AD, AV), dorsal ventricular ridge (DVR), and dorsolateral amygdala/lateral amygdala (DLA/LA). Of the proliferating cells, the proportions of cells that migrated after 2 weeks were highest in the ventral lateral region (VL), anterior medial and lateral cortices (aMC, aLC), and anterior NS (aNS). After 2 months, the highest proportional survival was in the AoB, aLC, aMC, aNS, DVR, and ventral medial regions (VM). Regions involved in long-term functions like spatial memory may require less proliferation and longer survival, while regions involved in short-term functions undergo more proliferation with higher relative attrition.

Supplemental Movie 2.mov (610 kB)
A 3-dimensional model of supraventricular ependymal surface area used for counting cell density for 3 BrdU treatments.

Supplemental Movie 3.mov (816 kB)
P. regius brain reassembled as a 3D image in ImageJ using Java3D for experiment 2. Colors only denote different regions and no other factors.

3D Proliferation (Converted).mov (603 kB)
Heat map representing proliferation (2 days) in the telencephalon of P. regius. Hot colors (yellow, orange, red) represent areas of high proliferation, while cold colors (purple, blue, light blue) represent areas of low proliferation. The rostral end and caudal end are topmost and bottommost, respectively.

3D Migration (Converted).mov (475 kB)
Heat map representing migration (2 weeks) in the telencephalon of P. regius. Hot colors (yellow, orange, red) represent areas of high migration, while cold colors (purple, blue, light blue) represent areas of low migration. The rostral end and caudal end are topmost and bottommost, respectively.

3D Survival (Converted).mov (479 kB)
Heat map representing survival (2 months) in the telencephalon of P. regius. Hot colors (yellow, orange, red) represent areas of high proliferation, while cold colors (purple, blue, light blue) represent areas of low proliferation. The rostral end and caudal end are topmost and bottommost, respectively.

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