The goal of my anthropology internship was threefold. One, I wanted to complete advanced hours in my anthropology Bachelor of Science degree, and second, I wanted to have practical experience that applied to both anthropology and laboratory science. Finally, I wanted to have an experience that would correlate to medical school and a medical career. I feel I have achieved all three during my internship at the Southwest Foundation for Biomedical Research (now renamed Texas Biomedical Research Institute), Department of Genetics in San Antonio.
I assisted with measuring fetal baboon growth plates, which were collected as part of a maternal nutrient restriction study. The hypothesis was that moderate global maternal nutrient restriction would in fact, alter the bone development of the fetus. After running numerous statistics, we found that it has. This has important implications for bone development and aging later in life. Through the internship, I was not only able to study bones but, I was also given the chance to study them at an early stage in their development as largely cartilaginous tissue. Exposure to this type of research will help me stand out among all the many other medical school applicants as well as when applying for residency later on.
There are many reasons for using baboons as a model for researching human disease and conditions. First, humans and baboons share extremely similar genetic sequencing. Additionally, the physiological similarities are vast and wide-ranging. These qualities make the baboon ideal for studying complex human diseases, such as diabetes and osteoporosis, which involve many different genes and environmental factors. Another important reason for using baboons in biomedical research is that in facilities such as the Southwest Foundation for Biomedical Research’s Primate Research Center, all of the environmental and dietary conditions can be controlled to ideal conditions, which is impossible to do with human subjects. Finally, the baboon genome is close to being fully mapped, giving us a unique and information-rich opportunity for more study.
My first few days involved reading extensively about bone histology. First, I learned about bone formation, particularly the long bone transforming from cartilage into calcified cortical bone tissue, a process known as endochondral ossification. When bones are first developing, they mostly consist of a cartilaginous matrix of hyaline cartilage. The epiphyses, or ends of the bones, are not fused and in some cases will not be completely fused far into adulthood. The epiphyses are loosely connected to the diaphysis, the shaft part of the bone, via the metaphysis, which contains the epiphyseal growth plate. Within the growth plate, there are zones of development. After the cells mature, they become chondrocytes and begin to organize themselves into columns as mitotic activity intensifies and extracellular material is formed; this is known as the proliferative zone. Next, the chondrocytes undergo enlargement and hypertrophy, and they experience cell death as they become completely calcified bone. This zone, the hypertrophic zone, is the last phase marking the boundary of the growth plate. In the study in which I participated, I measured length and area of these growth plate zones.
After in depth study of bone formation, I moved on to practical lab work. One project included the reorganization of numerous bone specimens’ storage in lab freezers. Our task involved the cataloguing and moving of bones into specific storage freezers by animal identification number and parts. For example, all of the long bones needed to be located in the freezers, found in an Excel spreadsheet, moved and stored in particular freezers, and then re-catalogued in the same spreadsheet. The purpose, of course, was to continue to keep track of all of the bone specimens collected and contained at the Foundation. We repeated the process with the thoracic/ rib and vertebrae sections, the skulls, and miscellaneous bones.
I spent the majority of my time at the lab measuring the dimensions of the growth plate zones, then calculating the dimensions as a percent of the entire bone length and cell density. Using the BIOQUANT OSTEO Image Analysis System for Bone Histomorphometry, which includes an extremely sensitive microscope and associated metric software, I was able to measure the areas on the slide specimens in real time with on-screen images.
After calculating percentages and running numerous statistics on SPSS, a common statistics software program, I found that there were significant differences between the control group’s fetal humeral growth plates and those from nutrient-restricted group. The most significant of all was the decrease in the size of the hypertrophic zone of the nutrient-restricted group. Because hypertrophy of the chondrocytes initially requires some intracellular glycogen storage, we have concluded that the nutrient-restricted animals either did not have enough glycogen to store or, were not able to store what they had. Although there is not much information available about why cells may not be able to store glycogen, I have not given up the search!
Altered endochondral ossification is important because it could affect the bone integrity later in life, meaning osteoporosis for some.