Biomedical subjects

J E McLean

Publications and source records attributed to J E McLean.

At least 19 recordsLinked to original sources

PubMed2006

Iron and arsenic release from aquifer solids in response to biostimulation.

Biostimulation has been used at various contaminated sites to promote the reductive dechlorination of trichloroethylene (TCE), but the addition of carbon and energy donor also stimulates bacteria that use Fe(III) as the terminal electron acceptor (TEA) in potential competition with dechlorination processes. Microcosm studies were conducted to determine the influence of various carbon donors on the extent of reductive dissolution of aquifer solids containing Fe(III) and arsenic. Glucose, a fermentable and respirable carbon donor, led to the production of 1500 mg Fe(II) kg(-1), or 24% of the total Fe in the aquifer sediment being reduced to Fe(II), whereas the same concentration of carbon as acetate resulted in only 300 mg Fe(II) kg(-1) being produced. The biogenic Fe(II) produced with acetate was exclusively associated with the solid phase whereas with fermentable carbon donors as whey and glucose, 22 and 54% of the Fe(II) was in solution. With fermentation, some of the metabolites appear to be electron shuttling chemicals and chelating agents that facilitate the reductive dissolution of even crystalline Fe(III) oxides. Without the presence of electron shuttling chemicals, only surficial Fe in direct contact with the bacteria was bioavailable, as illustrated when acetate was used. Regardless of carbon donor type and concentration, As concentrations in the water exceeded drinking water standards. The As dissolution appears to have been the result of the direct use of As as an electron acceptor by dissimilatory arsenic reducing bacteria. Our findings indicate that selection of the carbon and energy donor for biostimulation for remediation of chlorinated solvent impacted aquifers may greatly influence the extent of the reductive dissolution of iron minerals in direct competition with dechlorination processes. Biostimulation may also result in a significant release of As to the solution phase, contributing to further contamination of the aquifer.

Acetates↗

PubMed2006

Evaluation of the immunochromatographic CORIS Giardia-Strip test for rapid diagnosis of Giardia lamblia.

The aim of this study was to evaluate the performance of the CORIS Giardia-Strip test (CORIS Bioconcept, Gembloux, Belgium) as a rapid initial method for the routine diagnosis of giardiasis. Compared to a commercial ELISA-coproantigen test (ProSpect Giardia-ELISA-microplate assay; Remel, Lenexa, KS, USA), the commercial strip test had a sensitivity of 58%, a specificity of 99%, a positive predictive value of 93% and a negative predictive value of 93% (n=158). These results are comparable to those obtained using microscopy of direct wet-mounted stool. Since the CORIS Giardia-Strip test is simpler to perform, it can replace direct wet-mounted stool microscopy for the rapid diagnosis of giardiasis; however, its sensitivity is inferior to that of other immunochromatographic antigen detection tests and fresh stool samples are required for its use. Nevertheless, the results suggest that a positive CORIS Giardia-Strip test outcome does not need confirmation, while samples with negative results should be re-examined using another, more sensitive, test.

Animals↗

PubMed2005

Humic acid toxicity in biologically treated soil contaminated with polycyclic aromatic hydrocarbons and pentachlorophenol.

Contaminated soil from a land treatment unit at the Libby Groundwater Superfund Site in Libby, MT, was amended with 14C pyrene and incubated for 396 days to promote biodegradation and the formation of soil-associated bound residues. Humic and fulvic acids were extracted from the treated soil microcosms and analyzed for the presence of pyrene residues. Biologic activity promoted 14C association with the fulvic acid fraction, but humic acid-associated 14C did not increase with biologic activity. The Aboatox flash toxicity assay was used to assess the toxicity of humic and fulvic acid fractions. The fulvic acid gave no toxic response, but the humic acid showed significant toxicity. The observed toxicity was likely associated with pentachlorophenol, a known contaminant of the soil that was removed by solvent extraction of the humic acid and that correlated well with toxicity reduction.

Aliivibrio fischeri↗

PubMed2005

Comparison of different PCR protocols for the detection and diagnosis of Plasmodium falciparum.

An assessment of differing PCR protocols for the diagnosis of Plasmodium falciparum infection was performed on samples from an area of holoendemic malaria transmission in western Burkina Faso. The PCR protocols had generally high sensitivities (>92%) and specificities (>69%), but the negative predictive values (NPV) were moderate and differed widely among the PCR protocols tested. These PCR protocols that amplified either the P. falciparum pfcrt gene or the small subunit ribosomal DNA were the most reliable diagnostic tools. However, the moderate NPV imply that more than one PCR protocol should be used for diagnosis in holoendemic areas.

Adolescent↗

PubMed2001

Multiple inhibitor analysis of the brequinar and leflunomide binding sites on human dihydroorotate dehydrogenase.

Brequinar and the active metabolite of leflunomide, A77 1726, have been clearly shown to inhibit human dihydroorotate dehydrogenase (DHODH), but conflicting mechanisms for their inhibition have been reported. DHODH catalyses the conversion of dihydroorotate (DHO) to orotate concurrent with the reduction of ubiquinone. This study presents data that indicates brequinar is a competitive inhibitor versus ubiquinone; A77 1726 is noncompetitive versus ubiquinone and both are uncompetitive versus DHO. 2-Phenyl 5-quinolinecarboxylic acid (PQC), the core moiety of brequinar also shows competitive inhibition versus ubiquinone. Multiple inhibition experiments indicate that PQC (and thus brequinar) and A77 1726 have overlapping binding sites. Both PQC and A77 1726 are also mutually exclusive with barbituric acid (a competitive inhibitor versus DHO). In addition, we failed to observe brequinar binding to E.orotate by isothermal titration calorimetry (ITC). These results indicate that the E.DHO.inhibitor and E.orotate.inhibitor ternary complexes do not form. The absence of these complexes is consistent with the two-site ping-pong mechanism reported for DHODH. This kinetic data suggests that recent crystal structures of human DHODH complexed with orotate and A77 1726 or brequinar may not represent the relevant physiological binding sites for these inhibitors [Liu, S., Neidhardt, E. A., Grossman, T. H., Ocain, T., and Clardy J. (2000) Structure 8, 25-33].

Aniline Compounds↗

PubMed2001

Fate of pyrene in contaminated soil amended with alternate electron acceptors.

Creosote-contaminated soil samples from the Libby Ground Water Contamination Superfund Site in Libby, MT, were amended with the potential alternate electron acceptors (AEA) nitrate (KNO3), manganese oxide (MnO2), and amorphous iron oxyhydroxide (FeOOH) and incubated at low oxygen tensions (0-6% O2). The fate of 14C-pyrene was evaluated with respect to the different soil amendments. The fate of 14C from the radiolabeled pyrene with regard to mineralization and bound residue formation within soil humic fractions was not significantly different from controls for the iron and manganese amended soils. Nitrate amendments appeared to stimulate 14C-pyrene mineralization at a level of 170 mg NO3-N kg(-1), and inhibit mineralization at 340 mg NO3-N kg(-1). The stimulatory effect did not appear to be the result of nitrate serving as an electron acceptor. Although AEA amendments did not significantly affect the rate or extent of 14C-pyrene mineralization, results of oxygen-deprived incubations (purged with N2) indicate that AEA may be utilized by the microbial community in the unsaturated contaminated soil system.

Biodegradation, Environmental↗

PubMed2001

Two- and three-factor solutions of the WAIS-III.

The third edition of the Wechsler Adult Intelligence Scale manual reports four-factor solutions for the WAIS-III, and subsequent research has validated four-factor solutions for a variety of samples. These four factors consistently correspond to the four Factor Indexes that are yielded by the WAIS-III. However, the WAIS-III still provides Verbal and Performance IQs, in addition to the Indexes, making it desirable to examine two-factor solutions as well. In addition, because the Wechsler literature includes much interpretation of three-factor solutions, these solutions were likewise examined. Principal factor analysis followed by Varimax and Oblimin rotations of two and three factors were performed on data for the total WAIS-III sample ages 16 to 89 years (N=2,450). The two-factor solutions were viewed as a construct validation of Wechsler's two separate IQs, although the Working Memory subtests tended to load higher on the Performance scale than on their intended scale (Verbal); three-factor solutions were interpreted within the context of Horn's expanded fluid-crystallized theory and research on working memory. Both the two- and three-factor Varimax-rotated solutions were related to similar factor analyses conducted previously for the Wechsler Adult Intelligence Scale-Revised and the Wechsler Intelligence Scale for Children-III. Coefficients of congruence between like-named factors consistently exceeded .90, and usually .98, across different Wechsler batteries.

Adolescent↗

PubMed2000

Effect of weight reduction, obesity predisposition, and aerobic fitness on skeletal muscle mitochondrial function.

We used (31)P magnetic resonance spectroscopy to measure maximal mitochondrial function in 12 obesity-prone women before and after diet-induced weight reduction and in 12 matched, never-obese, and 7 endurance-trained controls. Mitochondrial function was modeled after maximum-effort plantar flexion from the phosphocreatine recovery time constant (TC(PCr)), the ADP recovery time constant (TC(ADP)), and the rate of change in PCr during the first 14 s of recovery (OxPhos). Weight reduction was not associated with a significant change in mitochondrial function by TC(PCr), TC(ADP), or OxPhos. Mitochondrial function was not different between postobese and never-obese controls by TC(PCr) [35.1 +/- 2.5 (SE) vs. 34.6 +/- 2.5 s], TC(ADP) (22.9 +/- 1.8 vs. 21.2 +/- 1.8 s), or OxPhos (0.26 +/- 0. 03 vs. 0.25 +/- 0.03 mM ATP/s), postobese vs. never-obese, respectively. However, TC(ADP) was significantly faster (14.5 +/- 2. 3 s), and OxPhos was significantly higher (0.38 +/- 0.04 mM ATP/s) in the endurance-trained group. These results suggest that maximal mitochondrial function is not impaired in normal-weight obesity-prone women relative to their never-obese counterparts but is increased in endurance-trained women.

Adult↗

PubMed1999

Communication forms and functions of children and adults with severe mental retardation in community and institutional settings.

The forms and functions of expressive communication produced by 84 individuals with severe mental retardation were assessed, using a structured communication sampling procedure. Symbolic communication acts were produced by 39 participants, and 27 of these symbolic communicators produced one or more multiword/multisymbol utterances. Of the remaining participants, 38 produced intentional but nonsymbolic communication acts; 7 were not observed to produce any intentional communication. For all participants who produced intentional communication, there were significantly more imperative than declarative communication acts. Significant differences in the frequencies and functions of communication acts produced by these participants were associated with differences in their communication levels (contact gesture, distal gesture, or symbolic), age (child vs. adult), and residential status (community home vs. large facility).

Adult↗

PubMed1999

Marine population structure in an anadromous fish: life-history influences patterns of mitochondrial DNA variation in the eulachon, Thaleichthys pacificus.

Due to the apparent decline in size of a number of populations, eulachon, Thaleichthys pacificus, have recently become the focus of a conservation movement in the northeast Pacific. Little is known of the marine life-history phase of this anadromous fish, and although it has been suggested that eulachon spawning in different rivers may form distinct populations, nothing is known of their population structure. Molecular genetic data were used to investigate population structure and possible management schemes. Mitochondrial DNA genotypes, determined through restriction fragment length polymorphisms (RFLP) analysis, were resolved in fish from several rivers throughout the geographical range of eulachon. Our data support the idea that extant eulachon populations result from postglacial dispersal from a single Wisconsinan glacial refuge. Further, while three of the 37 haplotypes recovered account for approximately 79% of the samples, many private haplotypes were observed, suggesting possible regional population structure. While a great deal of genetic variation was observed (37 haplotypes in 315 samples), an AMOVA showed that > 97% of the total variation was detected within populations. As yet, it is unclear whether genetically distinct populations of eulachon exist, or if these fish may be treated as one or a few large populations. Results were tested against predictions made from hypotheses concerning the origin and persistence of subdivided populations in marine species, and seem to be more consistent with the Member-Vagrant hypothesis than isolation by distance. Eulachon present an interesting situation that illustrates the difficulties involved in defining management units in organisms with high levels of gene flow.

Animals↗

PubMed1999

A front end to a theory of picture recognition.

We describe the results of four picture-recognition memory experiments in which we systematically manipulated four variables: stimulus duration, stimulus contrast, the duration of a blank gap between successive presentations of the same stimulus, and the presence or absence of a noise mask that immediately followed stimulus offset. The patterns of obtained data confirmed a simple extension of a theory previously used to account for digit recall data. This theory consists of a low-pass linear-filter front end that generates a sensory response from the physical stimulus, followed by an information-sampling process whose instantaneous sampling rate is based in part on the sensory response magnitude. The data confirm both qualitative and quantitative theoretical predictions, some of which were previously untestable in digit recall tasks because of ceiling effects that were not present in our picture-recognition tasks. We describe the role of our theory within the broader family of picture-memory theories, and we briefly discuss our theory's unification of two salient facets of visual behavior: information acquisition on the one hand, and phenomenological appearance on the other hand.

Contrast Sensitivity↗

PubMed1999

Expression and characterization of E. coli-produced soluble, functional human dihydroorotate dehydrogenase: a potential target for immunosuppression.

Human dihydroorotate dehydrogenase (huDHODH) is essential for de novo biosynthesis of pyrimidines and the target of two immunosuppressive drugs, brequinar and the leflunomide metabolite A77-1726 (Chen et al., 1992; Davis et al., 1996). Using a T7 RNA polymerase expression system, we produced huDHODH as a fusion protein containing an amino-terminal decahistidine tag. Escherichia coli growth and expression conditions were optimized to enhance huDHODH solubility and to permit purification of the enzyme in the absence of detergent. Soluble huDHODH, purified by a simple two-step procedure, was catalytically active, monomeric, and contained a flavin mononucleotide (FMN) cofactor in a 1:1 FMN/protein molar ratio. Kinetic analysis showed that huDHODH uses a two site ping-pong mechanism, where DHO is oxidized at one site and the second substrate, ubiquinone, is reduced at the other. This result is consistent with the mechanism proposed for bovine liver DHODH (Hines and Johnston, 1989).

Animals↗

PubMed1998

Black-white differences on the Strong Interest Inventory General Occupational Themes and Basic Interest Scales at ages 16 to 65.

Black-white differences on the Strong Interest Inventory were examined for a heterogeneous sample of 756 Whites and 85 Blacks aged 16 to 65 years. Multivariate and univariate analyses of variance and covariance were conducted. Race, gender, and IQ were independent variables; the six Holland General Occupational Themes and the 23 Basic Interest Scales were dependent variables; and educational attainment was the covariate. All interactions were nonsignificant, but race was consistently a significant main effect. In general, Whites scored higher than Blacks on Realistic and Investigative themes and scales, and Blacks scored higher in the Social, Enterprising, and Conventional areas. These findings were viewed in the context of counselors' and psychologists' roles in interpreting interest pattern of Black individuals.

Adolescent↗

PubMed1998

An investigation into the relationship between interests and intelligence.

This article relates the six General Occupational Themes (GOTs) and the 23 Basic Interest Scales (BISs) yielded by the Strong Interest Inventory (SII) to age, gender, and performance on the KAIT. The sample included 936 males and females aged 16 to 65 years. MANOVAs and MANCOVAs (covarying education) were conducted, followed by univariate ANOVAs and ANCOVAs. IQ level on KAIT was significantly related to the Investigative and Realistic themes and to numerous interest scales, most notably Writing, Nature, Teaching, Mathematics, and Art. The discrepancy between fluid and crystallized intelligence on the KAIT related significantly to a few variables, but relationships were generally small in magnitude. Significant relationships with age were few; gender related significantly to most variables, consistent with previous research. These findings were interpreted in the context of previous research on the Strong, and on the integration of interests and intellect.

Adolescent↗

PubMed1997

De novo heme proteins from designed combinatorial libraries.

We previously reported the design of a library of de novo amino acid sequences targeted to fold into four-helix bundles. The design of these sequences was based on a "binary code" strategy, in which the patterning of polar and nonpolar amino acids is specified explicitly, but the exact identities of the side chains is varied extensively (Kamtekar S, Schiffer JM, Xiong H, Babik JM, Hecht MH, 1993, Science 262:1680-1685). Because of this variability, the resulting collection of amino acid sequences may include de novo proteins capable of binding biologically important cofactors. To probe for such binding, the de novo sequences were screened for their ability to bind the heme cofactor. Among an initial collection of 30 binary code sequences, 15 are shown to bind heme and form bright red complexes. Characterization of several of these de novo heme proteins demonstrated that their absorption spectra and resonance Raman spectra resemble those of natural cytochromes. Because the design of these sequences is based on global features of polar/ nonpolar patterning, the finding that half of them bind heme highlights the power of the binary code strategy, and demonstrates that isolating de novo heme proteins does not require explicit design of the cofactor binding site. Because bound heme plays a key role in the functions of many natural proteins, these results suggest that binary code sequences may serve as initial prototypes for the development of large collections of functionally active de novo proteins.

Amino Acid Sequence↗

PubMed1996

Profiles of Hispanic adolescents and adults on the Holland Themes and Basic Interest Scales of the Strong Interest Inventory.

The Strong Interest Inventory and its predecessors have been the subject of decades of research. Many studies have used Holland's Six General Occupational Themes, and some have explored the 23 Basic Interest Scales. The literature addresses IQ in vocational counseling and includes studies relating Holland's themes and the 23 interest scales. The subjects included a nationwide sample of 894 13- to 65-yr.-olds tested during the standardization of the Kaufman Adolescent and Adult Intelligence Test. Multivariate analyses of variance were conducted with age, gender, and IQ on the intelligence test as independent variables, and the six Holland themes and 23 interest scales as dependent variables. IQ was related to Investigative and Artistic themes. Individuals with high IQs scored nearly one standard deviation higher than individuals with low IQs on each of these scales. A number of Basic Interest Scales correlated significantly with IQs, most of which were associated with either the Investigative or Artistic themes. Correlations of IQ with Holland Themes and scores on Basic Interest Scales were observed for both genders. The information gained from an individually administered intelligence test can enhance interpretation of the Holland themes and interest scales for vocational counseling.

Adolescent↗

PubMed1996

Reported communication abilities of individuals with severe mental retardation.

Little is known about the distribution of communication skills among individuals with severe mental retardation. The present study was designed to obtain basic descriptive information about the reported expressive communication status and other associated sensory and behavioral characteristics of four representative samples of this overall population. These samples include both children and adults and individuals living in large residential facilities as well as those living at home or in smaller, more natural community environments. Results of this study, based on completed questionnaires for 211 subjects, revealed a wide range of communication abilities in this population, with a significantly larger percentage of adults than children communicating at symbolic levels.

Adult↗

PubMed1995

The fluid and crystallized abilities of white, black, and Hispanic adolescents and adults, both with and without an education covariate.

Data from the standardization sample of the Kaufman Adolescent and Adult Intelligence Test (KAIT) were used to examine race/ethnic differences on the Horn-Cattell fluid and crystallized constructs. Samples included 768 individuals aged 11 to 24 years (575 White, 117 Black, 76 Hispanic) and 1,160 individuals aged 25 to 94 years (972 White, 124 Black, 64 Hispanic). Multivariate and univariate analyses were conducted, with and without an educational attainment covariate. Race/ethnic group was related significantly to performance on fluid and crystallized variables. Whites generally outscored Blacks and Hispanic on the diverse measures, namely, on tasks dependent on school learning (crystallized), and on those that reflect novel problem solving (fluid). These results maintained even with educational attainment covaried. Hispanics tended to perform better on fluid than on crystallized tests.

Adolescent↗