Kevin Cliver Abnormal Bone composition in Female Juvenile American Alligators From a Pesticide-Polluted Lake (Lake Apopk

1. Kevin CliverAbnormal Bone composition in Female Juvenile American Alligators From a Pesticide-Polluted Lake (Lake Apopka, Florida) Lind, P. Monica; Milnes, Matthew R.; Lundberg, Rebecca; Bermudez, Dieldrich; Orberg, Jan; Guillette Jr., Louis J. Environmental Health Perspectives. Vol. 112 (3). March 2004. 359-362

2. Background • Test subject is the American alligator • Test sights are at the pesticide polluted Lake Apopka and Lake Woodruff located in Florida. • 1980 – Industrial pesticide spill in Lake Apopka contaminating it with endocrine active pesticides (DDT) and dicofol know as endocrine disrupting chemicals (EDC’s). • Estrogens exhibit dramatic influences on bones and are essential for bone homeostasis. • An increase in estrogenic levels increase the amount of bone tissue, and visa versa.

3. Hypothesis and aims of the study • Their hypothesis was that the contaminants present in the lake inhibit the natural and continuous resorption of bone tissue by the anti-androgenic and estrogenic actions of the pesticides, resulting in and increased bone mass when compared to alligators from unpolluted lakes. • Because 17ß-estroanol and testosterone play an important role in bone tissue homeostasis, the aim of the study was to examine possible effects on the skeleton of female juvenile alligators from a polluted lake with EDC’s.

4. Materials and Methods • 16 juvenile female alligators of equal age and size were collected by hand from the two lakes; contaminated Lake Apopka, and a reference lake Woodruff. • A lethal dose of sodium pentobarbital was given to the alligators. • The total length of the tibia (distance from the upper edge of the knee joint to the distal end of the bone) and the femur (distance from the upper edge of the hip joint to the distal end of the bone) were measured using an electronic caliper to the nearest .1mm

5. The coefficient of variance (CV) (mean +/- standard deviation) was calculated from 10 repeated measurements. • The tibia and femural diaphyses were scanned at the midpoint because this area is almost exclusively cortical bone. • The metaphyses of the tibia and femur were scanned at a point located 11.5 and 16%, respectivley, of total bone length from the proximal tip because of the high content of trabecular bone.

7. Analysis • They used the total cross-sectional area (including marrow cavity and cortical bone, in mm2), cortical area (mm2), cortical thickness (mm), cortical bone mineral content (mg/mm), cortical bone mineral density (BMD= mg/cm3), total BMD, and periosteal circumference (mm). • This was also done for trabercular bone in both the femur and the tibia.

8. Statistical Analysis The results obtained were evaluated by a one-way analysis of variance followed by a post hoc Fisher’s protected least difference test. Differences were considered significant at p < .05. If values are below .05 then a difference between groups is real and not due to chance. In this case, smaller p-values are better than larger ones.

9. Results • The tibial diaphyseal total BMD in females from Lake Apopka was significantly greater than that of females from Lake Woodruff (table 1). • Tibial trabecular BMD was 34% greater in Lake Apopka (table 2). • In addition, trabecular bone mineral content was 75% greater in Lake Apopka (table 2) and can be seen in figure 2. • Femural metaphyseal total BMD was 12% greater in Lake Apopka • Femural trabecular BMD was 30% greater in females from Lake Apopka (table 4).

13. Discussion • Five variables associated with bone structure differed significantly between the two groups of alligators. • 4 of the 5 were metaphyseal variables. • The metaphysis seems to be more sensitive to alteration compared to the diaphysis relative to the exposure to compounds present in Lake Apopka. • Unknown phenomenon has several hypotheses.

14. Hypotheses for abnormal growth in metaphysis • 1. Metaphyseal reagion might have a higher metabolic rate the the diaphyseal region because of the higher content of trabecular bone. • 2. Hormones influence skeletal morphology and physiology, but not all parts of the bone show similar responses. • 3. Contaminants can alter hormonal homeostasis would influence the morphology and function of systems dependent on those horomones.EDC’s can affect different hormonal systems such as: • Thyroid hormones critical for growth, differentiation, and metabolic regulation • Sex steroids which regulate the reproductive functions but have effects throughout the body.

15. Discussion Cont. • Results show that alligators from Lake Apopka are exposed to estrogenic compounds, because they observed an increase in both total and trabecular BMD, a characteristic of estrogen exposure in vertebrates. • Most likely these findings are due to either increased plasma levels of 17ß-estranol or direct effect of contaminates on processes controlling bone homeostasis. • Another possibility is an effect on both osteoblasts and osteoclasts resulting in the production and release of growth factor ß which may mediate actions of estrogen in bone.

16. My discussion • This article is important because it demonstrates that the alterations in morphology and physiology induced in free-ranging individuals by environments contaminated with endocrine-active compounds are not limited to just a few systems, such as the repoductive or immune system. • I would have included males into the study and also see if these differences persist into adulthood.