Hepatic and renal trace element concentrations in American alligators (Alligator mississippiensis) following chronic dietary exposure to coal fly ash contaminated prey.

Little is known about the propensity of crocodilians to bioaccumulate trace elements as a result of chronic dietary exposure. We exposed 36 juvenile alligators (Alligator mississippiensis) to one of four dietary treatments that varied in the relative frequency of meals containing prey from coal combustion waste (CCW)-contaminated habitats vs. prey from uncontaminated sites, and evaluated tissue residues and growth rates after 12 mo and 25 mo of exposure. Hepatic and renal concentrations of arsenic (As), cadmium (Cd) and selenium (Se) varied significantly among dietary treatment groups in a dose-dependent manner and were higher in kidneys than in livers. Exposure period did not affect Se or As levels but Cd levels were significantly higher after 25 mo than 12 mo of exposure. Kidney As and Se levels were negatively correlated with body size but neither growth rates nor body condition varied significantly among dietary treatment groups. Our study is among the first to experimentally examine bioaccumulation of trace element contaminants in crocodilians as a result of chronic dietary exposure. A combination of field surveys and laboratory experiments will be required to understand the effects of different exposure scenarios on tissue residues, and ultimately link these concentrations with effects on individual health.

The response of magnocellular neurons of the hypothalamo-neurohyphyseal system to hypophysectomy, nitric oxide synthase expression as well as survival and regeneration in developing vs. adult rats.

This study examined the age-related changes in nitric oxide synthase immunoreactivity (NOS-IR), survival and regeneration of magnocellular neurons in the hypothalamo-neurohypophyseal system (HNS) in rats following hypophysectomy. In adult animal, hypophysectomy induced a significant increase in NOS-IR in the supraoptic (SON), paraventricular nuclei (PVN) and median eminence (ME) by 3 days post-lesion. NOS sustained an increased level until 2 weeks after hypophysectomy and then returned to normal control level. In contrast, at postnatal day 7 (PN7), no obvious increase in NOS-IR was observed in the SON, PVN and ME following the injury compared with age-matched controls. At PN14, the same injury induced an increase in NOS-IR in SON, PVN and ME but the increase was more transient with peak NOS-IR at 3 days and returning to the corresponding control level at 1 week after hypophysectomy. In contrast to a striking age-dependent alteration in NOS-IR in the SON and PVN, hypophysectomy induced substantial degeneration of arginine vasopressin (AVP) and oxytocin (OT) neurons in the SON and PVN in both immature and adult rats and there was no obvious difference in neuronal survival after the same injury among these three groups of different ages by quantitative analysis. Following hypophysectomy, a large number of fibers were observed in the contact zone of the median eminence and the adjacent lumen of the third cerebral ventricle (V3) in adult rats, whereas few fibers could be found in the lumen of the V3 in the immature rats after the same injury. Relationships between NOS induction and magnocellular neuronal survival and regeneration were discussed.