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Biomedical subjects

M A Bowers

Publications and source records attributed to M A Bowers.

6 recordsLinked to original sources
PubMed1997

Suspiciousness, mental simulation, and norm theory.

Seven studies were conducted to replicate the work of Miller, Turnbull, and McFarland (1989), who tested predictions from norm theory (Kahneman & Miller, 1986). The first three studies with stimulus materials identical to those used by Miller et al. failed to confirm that the ease with which the event might be mentally simulated affected the degree of suspiciousness. In Studies 4, 5, and 6, the improbable events were made objectively more probable, but this did not produce significant results. In the 7th study, the objective probability and attitude toward the target were varied. Although there was a main effect for ease of mental simulation, this effect was produced by only 1 of the 3 vignettes.

Adult↗
PubMed1992

Investigation of factors influencing urinary porphyrin excretion in rats: strain, gender, and age.

Urinary porphyrin excretion rates were evaluated in male rats of the Sprague-Dawley, Fischer 344, and Osborne-Mendel strains, and in female Fischer 344 rats, in order to identify an appropriate rat model for long-term studies of chemical-induced porphyria. Sprague-Dawley rats displayed a wide interanimal range in total 24-hr porphyrin excretion rates, from 0.9 to 59.6 nmol/24 hr (64-fold). Additionally, individual Sprague-Dawley rats varied by up to 5-fold in total porphyrins excreted from week to week over a 4-week period. Osborne-Mendel rats displayed a 12-fold interanimal difference in 24-hr total porphyrin excretion rates (ranging from 6.2 to 71.1 nmol/24 hr) and up to 4-fold individual variation from 1 week to another. In contrast, rats of the Fischer 344 strain displayed no significant differences in porphyrin excretion rates either among different animals or for individuals from week to week. Determination of individual porphyrin concentrations in the urine demonstrated that inconsistencies in total porphyrin concentration were attributable principally to differences in coproporphyrin concentrations. Frequency analysis of 24-hr coproporphyrin excretion levels among Sprague-Dawley rats demonstrated a widespread range encompassing low levels comparable to those of Fischer rats, high levels similar to those of most Osborne-Mendel rats, as well as intermediate levels. The mean total porphyrin excretion rate among female Fischer 344 rats was 1.2 +/- 0.51 nmol/24 hr, compared to 2.1 +/- 0.50 nmol/24 hr among male Fischer rats. Maturation and aging were found to have little influence on porphyrin excretion rates in male Fischer 344 rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1992

Gag proteins of the highly replicative MN strain of human immunodeficiency virus type 1: posttranslational modifications, proteolytic processings, and complete amino acid sequences.

The MN strain of human immunodeficiency virus type 1 was grown in H9 cells, concentrated by centrifugation, and disrupted, and proteins were purified by reversed-phase high-pressure liquid chromatography. Complete amino acid sequences were determined for the mature Gag proteins, showing natural proteolytic cleavage sites and the order of proteins (p17-p24-p2-p7-p1-p6) in the Gag precursors. At least two sequence variants of p24 and eight sequence variants of p17 were detected. The two most abundant variants of p24 and p17 represented at least 50% +/- 5% and 20% +/- 5% of their totals, respectively. These data suggest heterogeneity in the virus population, with 50% of the total virus containing the most abundant forms of p17 and p24 and 20% of the virus containing the second most abundant forms. The Gag precursors of these suggested viruses differ from each other by only 3 amino acid residues but differ from the precursors predicted by the published MN proviral DNA sequence by 10 residues. Electrospray ionization mass spectrometry analysis of the purified p24 forms showed that the measured molecular weight of the protein was 200 +/- 50 atomic mass units greater than the calculated molecular weight. The source of additional mass for the p24 forms was not determined, but the observation is consistent with previous suggestions that the protein is phosphorylated. Greater than 98% of the total recovered p17 was myristylated at the N-terminal glycine residue, and the measured molecular weights (as determined by electrospray ionization mass spectrometry) of the most abundant forms were within 3 atomic mass units of the calculated molecular weights (15,266).

Amino Acid Sequence↗
PubMed1992

Quantitative determination of porphyrins in rat and human urine and evaluation of urinary porphyrin profiles during mercury and lead exposures.

Measurement of urinary porphyrin excretion patterns (porphyrin profiles) is useful in the diagnosis and evaluation of diseases and disorders of porphyrin metabolism. However, experimental investigation of such disorders with rodent models has been hampered by the lack of an efficient procedure for the isolation and quantitative evaluation of porphyrins in rodent urine. This article describes an analytic procedure that overcomes the principal difficulties encountered with determination of porphyrins in rodent urine, including the loss of porphyrins during their isolation and interference of porphyrin fluorescence by contaminating materials. The procedure entails application of an acidified urine sample to a preconditioned C-18 preparatory column, preferential separation of essentially all potentially interfering contaminants by sequential phosphate-methanol elution, and selective isolation of porphyrins, which are then separated and quantitated by high-performance liquid chromatography and spectrofluorometric techniques. This method has been used to characterize urinary porphyrin excretion patterns in male rats and to define the distinctive changes in porphyrin profiles associated with prolonged exposure to porphyrinogenic metals. The porphyrin excretion patterns of male and female human subjects are also described. This method is applicable to the investigation of urinary porphyrin profile changes associated with exposure to a wide range of porphyrinogenic chemicals in both animals and human subjects.

Animals↗
PubMed1991

Urinary porphyrin profiles as biomarkers of trace metal exposure and toxicity: studies on urinary porphyrin excretion patterns in rats during prolonged exposure to methyl mercury.

Studies were conducted to define the specific changes in the urinary porphyrin excretion pattern (porphyrin profile) and the time course of those changes in rats exposed to mercury as methyl mercury hydroxide (MMH) at 5 or 10 ppm in the drinking water for up to 30 weeks. The urinary porphyrin profile elicited by MMH is uniquely characterized by highly elevated levels of 4- and 5-carboxyl porphyrins, and of a third atypical porphyrin with as yet undetermined chemical characteristics. Changes in the porphyrin profile were observed as early as 1 or 2 weeks following initiation of exposure to MMH at 10 or 5 ppm, respectively, and were sustained as long as 40 weeks following cessation of MMH treatment. The magnitude of the urinary porphyrin profile at either MMH dose level increased progressively during the course of mercury treatment and was highly correlated with the renal mercury concentration. A subsequent decline in the magnitude of the urinary porphyrin profile in animals exposed to 10 ppm MMH for more than 10 weeks was associated with the accumulation of high levels of Hg2+ in kidney cells and loss of renal functional status. These findings demonstrate that mercury elicits a unique change in the urinary porphyrin excretion pattern which is related to the dose and duration of mercury treatment. The association of urinary porphyrin excretion rates with renal mercury content and functional status suggests that urinary porphyrin profiles may serve as a useful biomarker of mercury accumulation and nephrotoxicity during prolonged mercury exposure.

Animals↗