Power spectrum analysis of EEG in a translational nonhuman primate model after chronic exposure to low levels of the common marine neurotoxin, domoic acid.

Domoic acid (DA), the focus of this research, is a marine algal neurotoxin and epileptogen produced by species in the genus Pseudo-nitzschia. DA is found in finfish and shellfish across the globe. The current regulatory limit for DA consumption (20 ppm in shellfish) was set to protect humans from acute toxic effects, but there is a growing body of evidence suggesting that regular consumption of DA contaminated seafood at or below the regulatory limit may lead to subtle neurological effects in adults. The present research uses a translational nonhuman primate model to assess neurophysiological changes after chronic exposure to DA near the regulatory limit. Sedated electroencephalography (EEG) was used in 20 healthy adult female Macaca fascicularis, orally administered 0.075 and 0.15 mg DA/kg/day for at least 10 months. Paired video and EEG recordings were cleaned and a Fast Fourier Transformation was applied to EEG recordings to assess power differences in frequency bands from 1-20 Hz. When DA exposed animals were compared to controls, power was significantly decreased in the delta band (1-4 Hz, p < 0.005) and significantly increased in the alpha band (5-8 Hz, p < 0.005), theta band (9-12 Hz, p < 0.01), and beta band (13-20 Hz, p < 0.05). The power differences were not dose dependent or related to the duration of DA exposure, or subtle clinical symptoms of DA exposure (intentional tremors). Alterations of power in these bands have been associated with a host of clinical symptoms, such as deficits in memory and neurodegenerative diseases, and ultimately provide new insight into the subclinical toxicity of chronic, low-dose DA exposure on the adult primate brain.

Alterations in biochemical functions during hyperthermic isolation-perfusion of the human liver.

Hyperthermia (42-42.5 degrees) was applied to the liver of eight patients with cancer in the liver by a technique of isolation-perfusion. Hepatic functional integrity was assessed during perfusion through measurement of multiple perfusate constituents. Data from seven perfusions were available for analysis. During perfusion there was an increase in perfusate lactate, pyruvate, glucose, urea, potassium, alkaline phosphatase, SGOT, and LDH. All increases in these constituents were significant (P less than 0.05) except for potassium. Lactate accumulated throughout the perfusion from an initial level of 3.8 +/- 1.0 mM to 7.6 +/- 3.5 mM at 4 hr. Pyruvate increased over the first 3 hr of perfusion from 0.14 +/- 0.06 mM to 0.80 +/- 0.37 mM before declining to 0.54 +/- 0.24 mM at 4 hr. The L/P (lactate/pyruvate) ratio decreased during perfusion to less than 10 in the first 2 hr, but rose to within normal limits by the end of perfusion. The decreases in L/P ratios were significant (P less than 0.05). Initially there was a rapid rise in perfusate glucose concentrations from 4.5 +/- 0.8 mM to 20.7 +/- 5.4 mM at 2 hr with nonsignificant changes thereafter. Urea levels increased from 0.64 +/- 0.22 mM to 1.92 +/- 0.76 mM. Perfusate potassium increased from the initial level of 7.0 +/- 1.0 mM during perfusion to 8.3 +/- 1.7 mM at 2 hr before declining. SGOT, LDH, and alkaline phosphatase increased during perfusion from 21 +/- 15, 142 +/- 48, and 16 +/- 6 to 176 +/- 22, 472 +/- 53 and 52 +/- 42, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Canine liver isolation-perfusion at normo- and hyperthermic temperatures with perfluorochemical emulsion (Fluosol-43).

A perfluorocarbon emulsion, Fluosol-43, was used as a blood substitute for oxygen transport during isolation-perfusion of the dog liver at 37 and 43 degrees C. Preservation of hepatic functional integrity was assessed through analysis of perfusate constituents and animal survival after perfusion. Flow to the liver during perfusion was greater than 1 ml/min/g with one-third of total flow provided through the hepatic artery and two-thirds through the protal vein. Perfusion duration was 3 h. The pO2 gradient across th liver indicated that oxygen was consumed during perfusion at both temperatures. The expected rise in pCO2 and decrease in pH of the outflow perfusate is consistent with active aerobic metabolism. Perfusate chemistries lactate, pyruvate, glucose, urea, total alpha-amino acids, ketone bodies and SGPT demonstrated that hepatic functional integrity was maintained during perfusion. Significant differences (p less than 0.05) between temperatures occurred in the perfusate levels of lactate, pyruvate, L/P ratios, glucose and total alpha-amino acids. Animal survival after a 3-hour perfusion was 3/4 at 37 degrees C, and 2/5 at 43 degrees C. After perfusion, SGPT levels were significantly higher in dogs subjected to perfusion at 43 degrees C. The success of these experiments demonstrates that perfusion of the liver with Fluosol-43 was not in itself hepatotoxic, and that Fluosol-43 may allow perfusion of the liver at 43 degrees C with only wild toxicity.

A technique for isolated hyperthermic liver perfusion.

Hyperthermia, either alone or combined with chemotherapy, has been shown to be effective in treating cancer. Because some investigators believe that regional hyperthermia may be more effective than whole body hyperthermia, we developed a technique to heat only the liver to 42-43 degrees for 4 hr. The procedure was adapted from a previously described animal model and was performed in four humans. Vascular isolation of the liver was accomplished by cannulating the hepatic artery, the portal vein, and the inferior vena cava followed by occluding the suprahepatic vena cava and the liver was then perfused with blood and nutrients from an oxygenated reservoir. Preliminary results show radiologic and histologic evidence of tumor necrosis or cessation of tumor growth in three of the patients. We believe this technique is safe enough for clinical experimental use and deserves further investigation.

A technique for isolation perfusion of the canine liver with survival.

A technique of isolation perfusion of the canine liver was developed as a model for treating cancer limited to the liver. Preservation of hepatic functional integrity was dependent on maintenance of near physiologic conditions for the perfusion. Flow to the liver, 1 ml/min/g, was provided by gravity to the portal vein at two thirds total flow, and by pump to the hepatic artery at one third total flow. Utilizing the technique described, six dogs died 4-12 hr after a 1-hr perfusion. The dogs received Ringer's lactate solution IV and had a rising blood lactate to greater than 9 mM and a rising lactate/pyruvate ratio. After changing IV fluids to nonlactate containing solutions, 4/6 dogs survived a 1-hr perfusion at 37 degrees. Blood lactate concentrations remained below 6 mM (alpha less than 0.05) during perfusion, and the lactate/pyruvate ratios remained in a physiologic range on comparison to the nonsurvivors (alpha less than 0.05). Mild elevations occurred in the SGOT and SGPT with the peak on the first postoperative day of 93 +/- 54 and 79 +/- 56, respectively, but returned to normal within 4-7 days. Perfusate chemistries lactate, pyruvate, glucose, total alpha-amino acids, ketone bodies, SGOT, and SGPT demonstrated that hepatic functional integrity was maintained during the 1-hr perfusion. Hepatic function as assessed was no different between survivors and nonsurvivors. Hypoglycemia (glucose less than 2 mM) contributed to the two deaths. Tolerance of the dog to the temporary anhepatic state may be the limiting factor to prolonged perfusions.