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Biomedical subjects

T J O'Shea

Publications and source records attributed to T J O'Shea.

18 recordsLinked to original sources
PubMed2001

Cyclodiene insecticide, DDE, DDT, arsenic, and mercury contamination of big brown bats (Eptesicus fuscus) foraging at a Colorado Superfund site.

Rocky Mountain Arsenal (RMA) National Wildlife Area, near Denver, Colorado, is a Superfund site contaminated by past military and industrial uses, including pesticide manufacturing. From an ecosystem standpoint, the most critical contaminants at RMA are certain cyclodiene insecticides and metabolites, p,p'-DDE, p,p'-DDT, arsenic, and mercury. Bats are important ecosystem components that can be impacted by persistent contaminants because of their position in the food chain and their potential longevity and thus duration of exposure. Big brown bats (Eptesicus fuscus) were captured (n = 51) while foraging at RMA in the summers of 1997 and 1998 for determination of concentrations of contaminants of concern in carcasses, brains, and stomach contents. Adult females (n = 15) were also tracked by radiotelemetry to determine locations of nearest maternity roosts for sampling of guano for contaminant analysis and inspection for potential contaminant-induced mortality. Bats captured while foraging at RMA had measurable quantities of dieldrin and DDE in masticated insect samples from stomach contents and significantly higher concentrations of dieldrin, DDE, DDT, and mercury (juveniles) in carcasses than big brown bats (n = 26) sampled at a reference area 80 km to the north. Concentrations of dieldrin and DDE in brains of bats captured while foraging at RMA were also greater than in bats from the reference area, but not high enough to suggest mortality. Maximum concentrations of DDE, DDT, and cyclodienes in brains of big brown bats were found in adult males from RMA. Guano from the two closest known roosts had significantly higher concentrations of dieldrin, DDE, and mercury than guano from two roosts at the reference area. Dieldrin concentrations in carcasses of bats from RMA were highest in juveniles, followed by adult males and adult females. DDE concentrations in carcasses were lowest in adult females at both sites and highest in adult males at RMA. No contaminant-related mortality was obvious at the small maternity colonies near RMA. Big brown bats show higher contamination than most other mammals previously sampled at this site. Concentrations and proportions of samples with detectable residues of dieldrin in carcasses of big brown bats from RMA were similar to or exceeded reports for this species from elsewhere in the United States some 25 years ago, prior to or just following restrictions on use of this compound.

Animals↗
PubMed2000

Determination of free levels of phenytoin in human plasma by liquid chromatography/tandem mass spectrometry.

A liquid chromatography combined with tandem mass spectrometry assay for the determination of free levels of the highly protein bound drug phenytoin (5,5-diphenylhydantoin) in human plasma is described. The assay was demonstrated to be reliable, accurate and precise, and specific for phenytoin. The procedure involves isolation of the unbound drug from the drug/protein complex by ultrafiltration. Liquid-liquid extraction was employed to extract the resultant ultrafiltrate. PHT was separated on a 50 x 3 mm reversed-phase column using isocratic mobile phase conditions that yielded a run time of 1.5 min, enabling high throughput sample analysis. Linearity was obtained over the range 5.00 to 500 ng/ml. Both between-run and within-run coefficients of variation were less than 15% and accuracy's across the assay range were all within 100 +/- 10%. The assay was successfully implemented to support a clinical interaction study with phenytoin.

Anticonvulsants↗
PubMed1994

Organochlorine and metal contaminants in baleen whales: a review and evaluation of conservation implications.

The literature on organochlorine and metal contaminants in tissues of baleen whales includes data for approximately 1000 individuals in 10 species from various oceans of the world. Concentrations of these contaminants in tissues of baleen whales are low. Sources of variation in organochlorine concentrations in whales include age, sex, region of exposure, and feeding habits. Concentrations of sigma DDT and PCBs in baleen whales appear higher in the northern hemisphere than in the southern oceans, perhaps due to greater contamination of northern ecosystems and a higher incidence of fish in the diet. However, maximum concentrations are generally lower in tissues of baleen whales than in other marine mammal species, both on global and local scales. This is predictable based on the general distribution, habitats and trophic levels of baleen whales. We reviewed laboratory studies on the effects of selected organochlorine contaminants on direct mortality and impaired reproduction in other mammals, and critically examined observations attempting to link organochlorines to reproductive and population effects in marine mammals. There is no firm basis to conclude that the contaminants reviewed herein have affected baleen whale populations. Although more information on contaminants in baleen whales would be of value, as a matter of priority, research and management actions should focus on reducing human-caused mortality and increasing habitat carrying capacity for these species.

Animals↗
PubMed1994

Pharmaceutical and biomedical applications of capillary electrophoresis/electrochemistry.

The use of capillary electrophoresis/electrochemistry (CEEC) for the analysis of microdialysis samples obtained for pharmacokinetic and neurochemical studies is described, as well as the development of new types of electrodes and waveforms which increase the selectivity of this technique for specific classes of analytes. CEEC with a carbon fiber electrode was employed for the analysis of microdialysis samples. Microdialysis is an in vivo sampling technique that yields very small samples for analysis (less than 1 microL). Therefore, capillary electrophoresis, with its small volume requirements, is an excellent choice for the analytical method. CEEC was used to study the pharmacokinetics of L-dopa and the release of aspartate and glutamate following a high K+ infusion in the brain. Several modified electrodes which increase the applicability of CEEC in pharmaceutical and biomedical analysis are described. One of these is a gold/mercury electrode which is highly selective for thiols and was used for the determination of glutathione in a rat brain. An alternative method for the detection of thiols employed a chemically modified electrode containing cobalt phthalocyanine. In this case, an electrocatalyst reduces the overpotential of thiols at the carbon electrode and makes it possible to detect them at a much lower and more selective oxidation potential. This electrode was used for the detection of cysteine in urine. The development of pulsed amperometric detection for capillary electrophoresis is also described and is demonstrated by the detection of glucose in blood. Lastly, a method for the detection of peptides based on the formation of a copper complex and detection at a carbon fiber electrode is discussed.

Animals↗
PubMed1994

Separation and quantitation of the amino acid neurotransmitters in rat brain by capillary electrophoresis.

Capillary electrophoresis (CE) has been used to separate the CBI derivatives of the neurotransmitters gamma-aminobutyric acid, glycine, glutamate, aspartate, norepinephrine and dopamine from 18 other amino acids present in the rat brain. The procedure, which requires an injection volume of < 10 nl, gave detection limits of 24-40 fmol using UV detection at 420 nm. Efficiencies for the derivatized amino acids varied from 344,000 to 444,000 theoretical plates. The method was applied successfully to the quantitation of the amino acid neurotransmitters and several other amino acids in a rat brain homogenate.

Animals↗
PubMed1994

Manatees.

Explore the source record for details and available documents.

Animals↗
PubMed1993

Determination of peptides by capillary electrophoresis-electrochemical detection using on-column Cu(II) complexation.

A Cu(II)-coated capillary has been developed for the determination of peptides by capillary electrophoresis with electrochemical detection. Capillaries were prepared by forcing a solution 48 microM in CuSO4, 120 microM in tartaric acid, 2.4 mM in NaOH and 120 microM in KI through them for 25 min; the resulting capillaries are stable for at least 12 h. Under alkaline conditions, peptides complex with Cu(II) present on the walls of the capillary to form Cu(II)-peptide complexes which can be detected oxidatively at a carbon fiber electrode. Di-, tri-, tetra- and pentaglycine were determined with a detection limit of 7 x 10(-7) M for triglycine. N-Terminal-blocked peptides can also be determined via this method. This system is more sensitive than direct detection of peptides by UV at 210 nm and exhibits higher selectivity than commonly employed derivatization procedures based on reactions with a primary amine functionality.

Amino Acid Sequence↗
PubMed1992

Monitoring excitatory amino acid release in vivo by microdialysis with capillary electrophoresis-electrochemistry.

Capillary electrophoresis (CE) with electrochemical detection (ED) was used to determine extracellular levels of aspartate, glutamate and alanine in samples from the frontoparietal cortex of the rat which were obtained by microdialysis. The method was used to monitor the effect on the overflow of the excitatory amino acids aspartate and glutamate of an influx of high concentrations of potassium ion. Samples were derivatized with naphthalenedialdehyde-cyanide prior to analysis. Detection limits for aspartate and glutamate were 80 and 100 nM, respectively. CE-ED is extremely useful for the analysis of microdialysis samples because of the very small sample volumes required by this analytical technique. The use of ED provides the requisite sensitivity and allows verification of peak purity by voltammetry.

Amino Acids↗
PubMed1991

Nasitrema sp.-associated encephalitis in a striped dolphin (Stenella coeruleoalba) stranded in the Gulf of Mexico.

An immature female striped dolphin (Stenella coeruleoalba) found dead on a northwestern Florida beach in 1988 exhibited severe inflammation bilaterally in the dorsal and mid-thalamus in association with adult trematodes (Nasitrema sp.) and trematode eggs. Numerous specimens of Nasitrema sp. also were present in the pterygoid sinuses. Pneumonia in association with a heavy growth of Vibrio damsela was observed also. This report confirms the occurrence of Nasitrema sp.-associated encephalitis in striped dolphins and in small cetaceans from the Gulf of Mexico.

Animals↗
PubMed1990

Regional brain morphometry and lissencephaly in the Sirenia.

Neuroanatomical structure was examined in the brains of West Indian manatees (Trichechus manatus) using computer-based morphometric methods. Although manatees have a small relative brain size, volume estimates of the major brain regions indicate that the telencephalon comprises 71% of total brain volume and is 90% cerebral cortex. These values are comparable to those seen among a diversity of taxa having large relative brain size, including many primates. Manatee brains also exhibit well-defined cortical lamination. The measured gyration index (an index of cortical folding) was 1.06, representing a highly lissencephalic condition. These findings demonstrate that small relative brain size and lissencephaly do not constrain the elaboration of internal brain structures. The marked lissencephalic condition is unusual for brains of this absolute size range, and may be related to the thickness of the cortical gray matter and underlying white matter.

Animals↗
PubMed1984

Pathologic findings in manatees in Florida.

Necropsy and microscopic examinations of 16 West Indian manatees (Trichechus manatus) revealed that the mortality of many of the animals was associated with environmental factors such as human-inflicted trauma and cold winters. Natural disease processes accounted for the death of only 1 manatee. In 3 manatees, the cause of death could not be determined.

Animals↗
PubMed1981

Effects of dietary nickel on mallards.

Thirty breeding pairs of mallards (Anas platyrhynchos) were randomly assigned to one of five treatment groups and were fed breeder mash containing 0, 12.5, 50.0, 200.0, or 800.0 ppm Ni (as the sulfate) for 90 d. Ni ingestion had no effect on egg production, hatchability, or survival of ducklings. After 90 d birds were bled, sacrificed, and necropsied. There were no significant differences in hematocrit; concentrations of hemoglobin, plasma triglyceride, and cholesterol; of plasma activities of ornithine carbamoyltransferase and alanine aminotransferase. A black tarry feces was noted in the high Ni dose group at necropsy, but no gross or histopathologic lesions were observed. Although absolute concentrations of Ni in tissues were low, there were significant accumulations in kidneys of birds fed Ni at all dietary levels and in feathers, blood, and livers of birds fed high doses of Ni compared with controls.

Animals↗
PubMed1980

DDT contamination at Wheeler National Wildlife Refuge.

Disposal of industrial waste resulted in massive DDT contamination at Wheeler National Wildlife Refuge, Alabama. Nearly a decade after the cessation of DDT manufacturing at the facility responsible, concentrations of DDT residues in the local fauna are still high enough to suggest avian reproductive impairment and mortality. Populations of fish-eating birds are low, endangered species are being exposed, and muscle lipids of game birds contain up to 6900 parts of DDT (isomers and metabolites) per million.

Animals↗
PubMed1980

Organochlorine pollutants in small cetaceans from the Pacific and south Atlantic Oceans, November 1968-June 1976.

Organochlorine residues were analyzed in blubber, brain, or muscle tissues of 69 individuals representing 10 species of small cetaceans. Collections were made from November 1968 through June 1976 at localities in the Eastern Tropical Pacific and along the coasts of California, Hawaii, Japan, and Uruguay, Relations of residue concentrations between tissues are described for DDE and PCBs in two dolphin species. sigma DDT and PCB residues in blubber of most of the 19 individuals of the five southern California species sampled exceed concentrations that are associated with reproductive impairment in pinnipeds, although the nature of such associations is not well defined. The sigma DDT residue of 2,695 ppm in blubber of one California coastal Tursiops truncatus is one of the highest concentrations reported in tissues of members of any population of wild mammals. Except for one rough-toothed dolphin (Steno bredanensis) from Maui, Hawaii, all individuals from all localities surveyed were contaminated with organochlorine compounds. Seventeen different organochlorines were detected; greatest diversity occurred near Japan and California. This is the first report of several of these compounds in tissues of any species of marine mammals. The o,p'-isomers and metabolites of DDT were detected unusually frequently. Ratios of p,p'-DDT to p,p'-DDE in blubber of cetaceans from waters off countries where use of this pesticide has been relatively recent and ongoing were at least an order of magnitude higher than in cetaceans from United States waters.

Analysis of Variance↗
PubMed1980

Influence of a local source of DDT pollution on statewide DDT residues in waterfowl wings, northern Alabama, 1978-79.

Heavy DDT contamination resulting from a former DDT manufacturing plant in northern Alabama has influenced statewide averages of DDT, DDE, and TDE residues in duck wings tested in the National Pesticide Monitoring Program. In states where contaminant levels in duck wings are high, residue analyses of wings categorized by finer geographic subdivision may be useful in defining the areas of heaviest contamination.

Alabama↗