The correlation of 3D DT-MRI fiber disruption with structural and mechanical degeneration in porcine myocardium.

Evaluation of structural parameters following a myocardial infarction (MI) is important to assess left ventricular function and remodeling. In this study, we assessed the capability of 3D diffusion tensor magnetic resonance imaging (DT-MRI) to assess tissue degeneration shortly after an MI using a porcine model of infarction. Two days after an induced infarction, hearts were explanted and immediately scanned by a 3T MRI scanner with a diffusion tensor imaging protocol. 3D fiber tracks and clustering models were generated from the diffusion-weighted imaging data. We found in a normal explanted heart that DT-MRI fibers showed a multilayered helical structure, with fiber architecture and fiber density reflecting the integrity of muscle fibers. For infarcted heart explants, we observed either a lack of fibers or disruption of fibers in the infarcted regions. Contours of the disrupted DT-MRI fibers were found to be consistent with the infarcted regions. Both histological and mechanical analysis of the infarcted hearts suggested DT-MRI fiber disruption correlated with altered microstructure and tissue mechanics. The ability of 3D DT-MRI to accurately distinguish viable myocardium from dead myocardium only 2 days post infarct without the use of radioisotopes or ionotropic agents makes it a promising approach to evaluate cardiac damage early post-MI.

A public health evaluation of recreational water impairment.

Water quality objectives for body contact recreation (REC-1) in Newport Bay, CA are not being attained. To evaluate the health implications of this non-attainment, a comprehensive health-based investigation was designed and implemented. Bacterial indicator data indicate that exceedances of the water quality objectives are temporally sporadic, geographically limited and most commonly occur during the time of the year and/or in areas of the bay where the REC-1 use is low or non-existent. A disease transmission model produced simulated risk estimates for recreation in the Bay that were below levels considered tolerable by the US EPA (median estimate 0.9 illnesses per 1,000 recreation events). Control measures to reduce pathogen loading to Newport Bay are predicted to reduce risk by an additional 16% to 50%. The results of this study indicate that interpreting the public health implications of fecal indicator data in recreational water may require a more rigorous approach than is currently used.

Effects of pico-tesla electromagnetic field treatment on wound healing in rats.

OBJECTIVE: To evaluate the effects of a pico-tesla electromagnetic field (PTEF) on healing of sutured and open skin wounds and clinicopathologic variables in rats. ANIMALS: 64 male Fischer-344 rats. PROCEDURE: An incision made in the dorsal aspect of the neck was sutured (n = 32) or left open to heal (32). In each group, 16 rats were not PTEF-treated (controls). Wound treatment consisted of exposure to a PTEF once daily. Rats in each group were euthanatized at days 2, 4, 7, and 14. Wounds were evaluated via tensiometry (sutured wounds), digital planimetry (open wounds), laser Doppler perfusion imaging, bacteriologic culture, and histologic examination. Blood samples were collected from all rats for analysis. RESULTS: At day 14, sutured wounds in PTEF-treated rats were stronger (ultimate stress) and tougher (strain energy) than were sutured wounds in control rats. Open wounds in PTEF-treated rats contracted more quickly at days 2 and 4 than did those in control rats. Compared with control wounds, histologic changes (indicative of improved healing) in sutured and open wounds in PTEF-treated rats were detected as early as day 4. Laser Doppler perfusion measurements, results of CBCs, serum biochemical analyses, and bacteriologic cultures were not different between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Exposure to the PTEF caused no adverse effects on clinicopathologic, histologic, or bacteriologic variables tested in this study. It appears that PTEF is a safe form of adjuvant treatment for wounds and improves strength of sutured wounds and speeds contraction of open wounds.

Risk-based approach to evaluate the public health benefit of additional wastewater treatment.

The City of Stockton, CA operates a wastewater treatment facility that discharges tertiary treated effluent during the summer and secondary treated effluent during the winter to the San Joaquin River. Investigations were carried out between 1996 and 2002 to provide insight regarding the potential public health benefit that may be provided by year-round tertiary treatment. A hydraulic model of the San Joaquin River and a dynamic disease transmission model integrated a wide array of disparate data to estimate the level of viral gastroenteritis in the population under the two treatment scenarios. The results of the investigation suggest that risk of viral gastroenteritis attributable to the treatment facility under the existing treatment scheme is several orders of magnitude below the 8-14 illnesses per 1000 recreation events considered tolerable by U.S. EPA, and winter tertiary treatment would further reduce the existing risk by approximately 15-50%. The methodologies employed herein are applicable to other watersheds where additional water treatment is being considered to address public health concerns from recreation in receiving waters.

Controlled release of oxytetracycline in sheep.

A novel biodegradable injectable formulation of oxytetracycline (OTC) was administered subcutaneously to sheep at a dose of 40 mg/kg. Blood samples were collected from the jugular vein at predetermined time intervals. The concentration of OTC in plasma was analyzed by an HPLC method. The concentrations of OTC in plasma were maintained at or above 0.5 microg/ml (minimum inhibitory concentration) for approximately 6 days. The pharmacokinetic parameters of OTC in sheep were also determined by monitoring the plasma concentration of OTC after a single intravenous injection of a commercially available OTC formulation at 10 mg/kg body weight. The in vivo release profiles of OTC from the biodegradable injectable formulations in sheep were determined from the plasma concentration time profiles by the deconvolution method using PCDCON software. The in vitro release of OTC from the biodegradable injectable formulation was tested in phosphate buffer (pH 7.4), containing 0.686% w/v of sodium sulfite as antioxidant. The correlation between the in vitro and in vivo release of OTC from the injectable formulation was also evaluated. The results of the in vivo evaluation of the formulation in sheep indicated that a controlled release biodegradable injectable dosage form of OTC for food animals is feasible.

A non-terminal surgical procedure for chronic collection of exocrine pancreatic secretions from unrestrained dogs (Canis familiaris).

The ability of dogs to adaptively modulate secretion by the exocrine pancreas to match changes in the amounts and sources of macronutrients is poorly understood. We evaluated the use of re-entrant pancreatic catheters as a non-terminal, temporary approach for the chronic collection of exocrine pancreatic secretion using unrestrained dogs fed diets differing in composition. Re-entrant catheters were surgically placed in the accessory pancreatic duct of two adult mongrel dogs. Secretions were collected for 40 days, during which the dogs were fed three diets with different amounts and sources of macronutrients. The volume of secretion was recorded, protein content was measured, and the activities of trypsin, chymotrypsin, amylase, and lipase were assayed. Inter-dog variation was detected for the volume of secretion (ml/h) but not for protein content (mg/ml) or activities (U/ml) of the enzymes. The volume and composition of the secretion differed among diets. The responses were delayed about 4 days, were transient, and did not coincide with the changes in diet composition. We found that the re-entrant catheters were suitable for studying the exocrine pancreatic secretion of dogs. Our findings were inconclusive about the influence of diet but suggested that adult dogs have a limited and nonspecific response of pancreatic secretion.