Altered cardiovascular reactivity and osmoregulation during hyperosmotic stress in adult rats developmentally exposed to polybrominated diphenyl ethers (PBDEs).

Polybrominated diphenyl ethers (PBDEs) and the structurally similar chemicals polychlorinated biphenyls (PCBs) disrupt the function of multiple endocrine systems. PCBs and PBDEs disrupt the secretion of vasopressin (VP) from the hypothalamus during osmotic activation. Since the peripheral and central vasopressinergic axes are critical for osmotic and cardiovascular regulation, we examined whether perinatal PBDE exposure could impact these functions during physiological activation. Rats were perinatally dosed with a commercial PBDE mixture, DE-71. Dams were given 0 (corn oil control), 1.7 (low dose) or 30.6 mg/kg/day (high dose) in corn oil from gestational day (GD) 6 through postnatal day (PND) 21 by oral gavage. In the male offspring exposed to high dose PBDE plasma thyroxine and triiodothyronine levels were reduced at PND 21 and recovered to control levels by PND 60 when thyroid stimulating hormone levels were elevated. At 14-18 months of age, cardiovascular responses were measured in four groups of rats: Normal (Oil, normosmotic condition), Hyper (Oil, hyperosmotic stress), Hyper PBDE low (1.7 mg/kg/day DE-71 perinatally, hyperosmotic stress), and Hyper PBDE high (30.6 mg/kg/day DE-71 perinatally, hyperosmotic stress). Systolic blood pressure (BP), diastolic BP, and heart rate (HR) were determined using tail cuff sphygmomanometry and normalized to pretreatment values (baseline) measured under basal conditions. Hyperosmotic treatment yielded significant changes in systolic BP in PBDE exposed rats only. Hyper PBDE low and high dose rats showed 36.1 and 64.7% greater systolic BP responses at 3h post hyperosmotic injection relative to pretreatment baseline, respectively. No treatment effects were measured for diastolic BP and HR. Hyper and Hyper PBDE rats showed increased mean plasma osmolality values by 45 min after injection relative to normosmotic controls. In contrast to Hyper rats, Hyper PBDE (high) rats showed a further increase in mean plasma osmolality at 3h (358.3±12.4mOsm/L) relative to 45 min post hyperosmotic injection (325.1±11.4mOsm/L). Impaired osmoregulation in PBDE-treated animals could not be attributed to decreased levels of plasma vasopressin. Our findings suggest that developmental exposure to PBDEs may disrupt cardiovascular reactivity and osmoregulatory responses to physiological activation in late adulthood.

Multiphoton imaging of actin filament formation and mitochondrial energetics of human ACBT gliomas.

We studied the three-dimensional (3D) distribution of actin filaments and mitochondria in relation to ACBT glioblastoma cells migration. We embedded the cells in the spheroid form within collagen hydrogels and imaged them by in situ multiphoton microscopy (MPM). The static 3D overlay of the distribution of actin filaments and mitochondria provided a greater understanding of cell-to-cell and cell-to-substrate interactions and morphology. While imaging mitochondria to obtain ratiometric redox index based on cellular fluorescence from reduced nicotinamide adenine dinucleotide and oxidized flavin adenine dinucleotide we observed differential sensitivity of the migrating ACBT glioblastoma cells to femtosecond laser irradiation employed in MPM. We imaged actin-green fluorescent protein fluorescence in live ACBT glioma cells and for the first time observed dynamic modulation of the pools of actin during migration in 3D. The MPM imaging, which probes cells directly within the 3D cancer models, could potentially aid in working out a link between the functional performance of mitochondria, actin distribution and cancer invasiveness.

Dietary exposure to aroclor 1254 alters central and peripheral vasopressin release in response to dehydration in the rat.

Central vasopressin (VP) release from magnocellular neuroendocrine cells (MNCs) in the supraoptic nucleus (SON) occurs from their somata and dendrites within the SON several hours after acute dehydration, and is an important autoregulatory mechanism influencing the systemic release of VP from MNC terminals in the posterior pituitary. To begin to explore the impact of polychlorinated biphenyls (PCBs) on brain mechanisms of body fluid regulation, both central and systemic VP release in response to acute dehydration were assessed in adult male rats fed the commercial PCB mixture Aroclor 1254 (30 mg/kg/day) for 15 days. Water intake and body weight were recorded daily, and on day 15 rats were dehydrated by intraperitoneal injection of 3.5 M saline (controls received physiological saline) and sacrificed 4-6 h later. Intranuclear VP release was measured in SON tissue punches in vitro, and systemic VP release was measured in the same rats. SON prepared from dehydrated PCB-naive rats released significantly more VP than did SON from control rats (4.9 +/- 0.8 vs. 2.7 +/- 0.4 pg/ml/microg). In contrast, while Aroclor 1254 exposure had no effect on baseline water intake, weight gain, or plasma osmolality responses to dehydration in PCB-fed rats, the SON failed to respond with increased VP release during dehydration. Consistent with previous studies showing an inhibitory effect of central VP on plasma VP output, dehydrated PCB-fed rats had an exaggerated 863% increase in plasma VP over basal levels, compared to a 241% increase in PCB-naive rats, suggesting that the MNC system is subtly disrupted.

Lateral hypothalamic signaling mechanisms underlying feeding stimulation: differential contributions of Src family tyrosine kinases to feeding triggered either by NMDA injection or by food deprivation.

In rats, feeding can be triggered experimentally using many approaches. Included among these are (1) food deprivation and (2) acute microinjection of the neurotransmitter l-glutamate (Glu) or its receptor agonist NMDA into the lateral hypothalamic area (LHA). Under both paradigms, the NMDA receptor (NMDA-R) within the LHA appears critically involved in transferring signals encoded by Glu to stimulate feeding. However, the intracellular mechanisms underlying this signal transfer are unknown. Because protein-tyrosine kinases (PTKs) participate in NMDA-R signaling mechanisms, we determined PTK involvement in LHA mechanisms underlying both types of feeding stimulation through food intake and biochemical measurements. LHA injections of PTK inhibitors significantly suppressed feeding elicited by LHA NMDA injection (up to 69%) but only mildly suppressed deprivation feeding (24%), suggesting that PTKs may be less critical for signals underlying this feeding behavior. Conversely, food deprivation but not NMDA injection produced marked increases in apparent activity for Src PTKs and in the expression of Pyk2, an Src-activating PTK. When considered together, the behavioral and biochemical results demonstrate that, although it is easier to suppress NMDA-elicited feeding by PTK inhibitors, food deprivation readily drives PTK activity in vivo. The latter result may reflect greater PTK recruitment by neurotransmitter receptors, distinct from the NMDA-R, that are activated during deprivation-elicited but not NMDA-elicited feeding. These results also demonstrate how the use of only one feeding stimulation paradigm may fail to reveal the true contributions of signaling molecules to pathways underlying feeding behavior in vivo.