Biomedical subjects

Michael D Mitchell

Publications and source records attributed to Michael D Mitchell.

5 recordsLinked to original sources

PubMed2006

Identification of novel peptide safety markers for exocrine pancreatic toxicity induced by cyanohydroxybutene.

Historically, serum amylase and lipase levels have been used to indicate pancreas injury; however, these enzyme levels are often not predictive of pathology. In an effort to discover novel biomarkers of pancreatic acinar cell injury, we analyzed serum and pancreas tissue from cyanohydroxybutene (CHB)-treated male IGS rats using proteomics methods. CHB produces an "edematous pancreatitis," characterized by depletion of zymogen granules, acinar cell apoptosis, and mild to moderate inflammation. Secondary necrosis occurs at higher doses. Rats were treated with 150 mg/kg of CHB and samples were collected at 4, 8, and 24 h. Analyses of serum tryptic digests by surface-enhanced laser desorption-ionization mass spectrometry revealed two novel peptide biomarkers (RA1609 and RT2864) that were predictive of pancreatic damage. Levels of RA1609 decreased, while levels of RT2864 increased by 8 h following CHB treatment. The changes in RA1609 and RT2864 were detected in media from CHB-treated primary rat acini, demonstrating that these peptides are either of pancreatic cell origin or are produced by proteases released from acinar cells. Sequencing revealed that RA1609 is a fragment of rat albumin (accession number P02770, residues 348-360) and RT2864 is a portion of either rat trypsin III (accession number P08426, residues 39-65) or bovine trypsin (accession number P00760, residues 35-61). These two peptides, and possibly other fragments of serum proteins that are digested by pancreatic proteases, may be useful as safety markers for exocrine pancreatic toxicity during drug development or as biomarkers for the diagnosis and/or grading of severity of pancreatic disease.

Acute Disease↗

PubMed2006

Evaluation of two novel peptide safety markers for exocrine pancreatic toxicity.

Current markers of exocrine pancreatic toxicity have historically been poor indicators for both early diagnosis of disease and prediction of disease severity. Recently we identified two peptide markers (RA1609 and RT2864) of pancreatic toxicity that are target organ specific. In order to evaluate sensitivity of these markers versus current standard tests for pancreatic damage (i.e., lipase), we measured amylase and lipase, as well as RA1609 and RT2864 marker levels, in serum from rats treated with four doses (50-200 mg/kg) of the model pancreatic toxicant cyanohydroxybutene (CHB). In addition, to determine whether these peptide markers could detect pancreatic injury induced by different toxicants and in different species, we measured RA1609 and RT2864 marker levels in rats treated with the pancreatic toxicant caerulein, and in mice treated with CHB. RA1609 and RT2864 peptide markers proved to be more sensitive than amylase or lipase in detecting pancreatic damage, especially at an early time point (8 h) following CHB administration. The peptide markers also accurately predicted pancreatic injury induced by caerulein in rats. These markers were sensitive in detecting very mild pancreatic damage following CHB administration in mice, which are less susceptible to CHB-induced pancreatic toxicity. In addition, a species comparison of the RA1609 albumin fragment sequence indicated that cleavage of albumin from pancreatic proteases produces a similar fragment marker in several species, including humans. To determine whether the comparable human albumin fragment could be detected in sera from pancreatitis patients, we analyzed sera from normal individuals and from patients with diabetes, vasculitis, pancreatic cancer, and pancreatitis. It was found that markers corresponding to the fragments found in rat serum (RA1609 and RT2864) were present in human serum, and changes in these were indicative of and specific to pancreatitis. In conclusion, the RA1609 and RT2864 peptides are sensitive indicators of exocrine pancreatic damage that may be useful as safety markers for general pancreatic toxicity in multiple species.

Acute Disease↗

PubMed2006

Removal of two waterborne pathogenic bacterial strains by activated carbon particles prior to and after charge modification.

Waterborne diseases constitute a threat to public health despite costly treatment measures aimed at removing pathogenic microorganisms from potable water supplies. This paper compared the removal of Raoultella terrigena ATCC 33257 and Escherichia coli ATCC 25922 by negatively and positively charged types of activated carbon particles. Both strains display bimodal negative zeta-potential distributions in stabilized water. Carbon particles were suspended to an equivalent external geometric surface area of 700 cm2 in 250 mL of a bacterial suspension, with shaking. Samples were taken after different durations for plate counting. Initial removal rates were less elevated for the positively charged carbon particle than expected, yielding the conclusion that bacterial adhesion under shaking is mass-transport limited. After 360 min, however, the log-reduction of the more negatively charged R. terrigena in suspension was largest for the positively charged carbon particles as compared with the negatively charged ones, although conditioning in ultrapure or tap water of positively charged carbon particles for 21 days eliminated the favorable effect of the positive charge due to counterion adsorption from the water. Removal of the less negatively charged E. coli was less affected by aging of the (positively charged) carbon particles, confirming the role of electrostatic interactions in bacterial removal by activated carbon particles. The microporous, negatively charged coconut carbon performed less than the mesoporous, positively charged carbon particle prior to conditioning but did not suffer from loss of effect after conditioning in ultrapure or tap water.

Bacteria↗

PubMed2006

Proteomics: recent applications and new technologies.

Interest in proteomics as a tool for drug development and a myriad of other applications continues to expand at a rapid rate. Proteomic analyses have recently been conducted on tissues, biofluids, subcellular components and enzymatic pathways as well as various disease and toxicological states, in both animal models and man. In addition, several recent studies have attempted to integrate proteomics data with genomics and/or metabonomics data in a systems biology approach. The translation of proteomic technology and bioinformatics tools to clinical samples, such as in the areas of disease and toxicity biomarkers, represents one of the major opportunities and challenges facing this field. An ongoing challenge in proteomics continues to be the analysis of the serum proteome due to the vast number and complexity of proteins estimated to be present in this biofluid. Aside from the removal of the most abundant proteins, a number of interesting approaches have recently been suggested that may help reduce the overall complexity of serum analysis. In keeping with the increasing interest in applications of proteomics, the tools available for proteomic analyses continue to improve and expand. For example, enhanced tools (such as software and labeling procedures) continue to be developed for the analysis of 2D gels and protein quantification. In addition, activity-based probes are now being used to tag, enrich and isolate distinct sets of proteins based on enzymatic activity. One of the most active areas of development involves microarrays. Antibody-based microarrays have recently been released as commercial products while numerous additional capture agents (e.g. aptamers) and many additional types of microarrays are being explored.

Animals↗

PubMedDate not supplied

Role of metabolism in drug-induced idiosyncratic hepatotoxicity.

Rare adverse reactions to drugs that are of unknown etiology, or idiosyncratic reactions, can produce severe medical complications or even death in patients. Current hypotheses suggest that metabolic activation of a drug to a reactive intermediate is a necessary, yet insufficient, step in the generation of an idiosyncratic reaction. We review evidence for this hypothesis with drugs that are associated with hepatotoxicity, one of the most common types of idiosyncratic reactions in humans. We identified 21 drugs that have either been withdrawn from the U.S. market due to hepatotoxicity or have a black box warning for hepatotoxicity. Evidence for the formation of reactive metabolites was found for 5 out of 6 drugs that were withdrawn, and 8 out of 15 drugs that have black box warnings. For the other drugs, either evidence was not available or suitable studies have not been carried out. We also review evidence for reactive intermediate formation from a number of additional drugs that have been associated with idiosyncratic hepatotoxicity but do not have black box warnings. Finally, we consider the potential role that high dosages may play in these adverse reactions.

Animals↗