Abstract

Exposure to ionizing radiation may have deleterious effects on physical and mental health, with an increased risk of proton radiation for astronauts traveling outside Earth's atmosphere into lower earth orbit. In animal models, radiation has been shown to suppress neurogenesis in the subgranular zone of the hippocampus, a key area for learning and memory. Furthermore, some evidence suggests that compounds found in fruits and vegetables (e.g. polyphenols) may offer some protection against the cellular effects of radiation. Few studies have looked at the effects of proton radiation on the central nervous system, even though proton radiation is the most prevalent ionizing radiation in space. This study determined whether a polyphenol-rich diet could offer enough protection from the effects of radiation to maintain complex cognitive and fine motor skills such as those required by astronauts. Ninety-six C57BL/6 mice (48 receiving pomegranate juice and 48 receiving sugar water control in their drinking bottles) underwent a battery of behavioral tests to assess baseline cognitive and motor functions and were then either irradiated with proton radiation (2 Gy at 150 MeV/n at 1-2 Gy/min) or sham irradiated. 2 Gy is the approximate dose of radiation to which an astronaut on a long-term mission to Mars may be exposed. Post-radiation behaviors were assessed 1-2 days after irradiation and again two months later to determine radiation-related behavioral changes. Radiation affected depression- and avoidance behaviors. Pomegranate juice was found to be protective against radiation-induced depression, but had gender-specific affects for avoidance behavior. In addition, pomegranate juice seemed to have a greater effect on males than females, inducing behavior similar to that of females in tests of motor coordination and activity levels. Furthermore, the birth of new glial cells and neurons in the hippocampus was quantified using immunohistochemistry for BrdU+/DCX+ cells. Radiation suppressed cell proliferation (BrdU+) and neurogenesis in the dentate gyrus (BrdU+/DCX+) of the hippocampus. Pomegranate juice increased neurogenesis (DCX+) in the hippocampus of non-irradiated mice. These data highlight the importance of understanding the complex gender-specific interactions between diet, behavior, and neuropathology, and suggest that pomegranate juice may protect against some radiation-induced deficits.

LLU Discipline

Experimental Psychology

Department

Psychology

School

School of Behavioral Health

First Advisor

Hartman, Richard E.

Second Advisor

Haerich, Paul

Third Advisor

Pop, Viorela

Fourth Advisor

Vermeersch, David

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

January 2013

Date (Title Page)

6-1-2013

Language

English

Library of Congress/MESH Subject Headings

Ionizing radiation - toxicology; Radiation effects; Antioxidants;

Subject - Local

Proton radiation; Pomegranates; Hippocampus; Behavior; Ionizing radiation; Antioxidants; Neurogenesis; Central nervous system; Polyphenols; Radiation-induced depression

Type

Dissertation

Page Count

160 p.

Digital Format

Application/PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses & Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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