Examining an Online Microbiology Game as an Effective Tool for Teaching the Scientific Process

This study investigates the effectiveness of the online Flash game Disease Defenders in producing knowledge gains for concepts related to the scientific process. Disease Defenders was specifically designed to model how the scientific process is central to a variety of disciplines and science careers. An additional question relates to the game's ability to shift attitudes toward science. Middle school classes from grades six to eight were assigned to the experimental group (n = 489) or control group (n = 367) and asked to participate in a three-session intervention. The sessions involved completing a pretest, a game play session, and taking a post-test. Students in the experimental group played Disease Defenders while students in the control group played an alternative science game. Results showed a significant increase in mean science knowledge scores for all grades in the experimental group, with sixth grade and seventh grade students gaining more knowledge than eighth grade students. Additionally, results showed a significant positive change in science attitudes only among sixth graders, who also rated their satisfaction with the game more favorably than students in higher grades. No differences in mean test scores were found between genders for science knowledge or science attitudes, suggesting that the game is equally effective for males and females

Epigenetic dominance of prion conformers

Although they share certain biological properties with nucleic acid based infectious agents, prions, the causative agents of invariably fatal, transmissible neurodegenerative disorders such as bovine spongiform encephalopathy, sheep scrapie, and human Creutzfeldt Jakob disease, propagate by conformational templating of host encoded proteins. Once thought to be unique to these diseases, this mechanism is now recognized as a ubiquitous means of information transfer in biological systems, including other protein misfolding disorders such as those causing Alzheimer's and Parkinson's diseases. To address the poorly understood mechanism by which host prion protein (PrP) primary structures interact with distinct prion conformations to influence pathogenesis, we produced transgenic (Tg) mice expressing different sheep scrapie susceptibility alleles, varying only at a single amino acid at PrP residue 136. Tg mice expressing ovine PrP with alanine (A) at (OvPrP-A136) infected with SSBP/1 scrapie prions propagated a relatively stable (S) prion conformation, which accumulated as punctate aggregates in the brain, and produced prolonged incubation times. In contrast, Tg mice expressing OvPrP with valine (V) at 136 (OvPrP-V136) infected with the same prions developed disease rapidly, and the converted prion was comprised of an unstable (U), diffusely distributed conformer. Infected Tg mice co-expressing both alleles manifested properties consistent with the U conformer, suggesting a dominant effect resulting from exclusive conversion of OvPrP-V136 but not OvPrP-A136. Surprisingly, however, studies with monoclonal antibody (mAb) PRC5, which discriminates OvPrP-A136 from OvPrP-V136, revealed substantial conversion of OvPrP-A136. Moreover, the resulting OvPrP-A136 prion acquired the characteristics of the U conformer. These results, substantiated by in vitro analyses, indicated that co-expression of OvPrP-V136 altered the conversion potential of OvPrP-A136 from the S to the otherwise unfavorable U conformer. This epigenetic mechanism thus expands the range of selectable conformations that can be adopted by PrP, and therefore the variety of options for strain propagation

Prion disease in transgenic mice expressing different ovine PrP scrapie susceptibility alleles.

1<p>The number of mice developing clinical signs of prion disease divided by the original number of inoculated mice is shown in parentheses.</p>2<p>Inoculations performed in Telling lab.</p>3<p>Inoculations performed in Hunter lab.</p

Representative OvPrP^Sc distribution in the CNS of diseased transgenic mice.

<p>OvPrP-V136 and OvPrP-A136 are indicated by blue and red text respectively. Times of onset of disease (d) for individual mice analyzed in histoblots are provided. Sections through the midbrain, pons and oblongata are shown for SSBP/1 infected Tg(OvPrP-A136)3533^+/− mice (<b>A</b> and <b>D</b>); Tg(OvPrP-V136)4166^+/− mice (<b>B</b> and <b>E</b>); and Tg(OvPrP-A/V) mice (<b>C</b> and <b>F</b>). In panels <b>G</b> and <b>H</b>, sections were not treated with PK and show distribution of total PrP. Histoblots in panels <b>A</b>–<b>G</b> were probed with mAb 6H4; histoblots in <b>D</b>–<b>H</b> were probed with mAb PRC5.</p

PMCA using defined seeds and substrates.

<p>PMCA was performed for various times indicated. At each time point samples were either amplified by sonication (A), or matching control samples (C) received no sonication, and were therefore not amplified. Brain homogenates from healthy Tg(OvPrP-A136)3533^+/− and Tg(OvPrP-V136)4166^+/− mice served as sources of OvPrP-A136, OvPrP-V136 or mixtures of the two. In <b>A</b>, samples were seeded with sheep SSBP/1; in <b>B</b>, samples were seeded with brain extracts from diseased Tg(OvPrP-V136)4166^+/− mice [SSBP/1-V136(U) prions]; in <b>C</b>, samples were seeded with brain extracts from diseased Tg(OvPrP-A136)3533^+/− mice [SSBP/1-A136(S); in <b>D</b>, samples were seeded with extracts from diseased Tg(OvPrP-A/V) mice. Samples labeled 12* received no seed. The first three lanes of each immunoblot were loaded with the substrate(s) for each PMCA reaction, not treated with PK; the corresponding seed, not treated with PK; and, the same seed treated with PK. All other samples were digested with PK. Western blots were probed with mAbs 6H4 and PRC5 as indicated.</p

Characterization of transgenic mice expressing OvPrP-A136 and OvPrP-V136. A.

<p>Levels of transgene-expressed OvPrP in the CNS were estimated by semi-quantitative western blotting using mAb 6H4. Amounts of total protein loaded (µg) in each sample are shown. <i>Prnp^0/0</i>, mice in which the PrP gene is disrupted; FVB, wild type mice. Estimates of expression levels, shown as a percentage (%) of that in FVB mice, are based on densitometric analysis of signals from diluted samples. <b>B.</b> Survival curves of mice following inoculation with sheep SSBP/1 scrapie prions. Percent (%) affected mice refers to numbers of mice within an inoculated cohort manifesting progressive clinical signs associated with prion disease. <b>C.</b> Western blot analysis of PK-treated brain extracts of diseased Tg(OvPrP-A136)3533^+/− mice. SSBP/1 and CH1641 refer to mice inoculated with the respective prions. I and R refer to sheep SSBP/1 or CH1641 inocula, and brain extracts from recipient mice respectively.</p

Analyses of PrP^Sc in the brains of SSBP/1 infected mice.

<p>In <b>A</b> and <b>C</b>, densitometric analysis of immunoblots was used to measure the amounts of protease-resistant OvPrP^Sc as a function of GdnHCl concentration. The dose-response curve was plotted using a Gaussian non-linear least-square fit. Each point is the mean value derived from densitometric quantification of PK-resistant PrP in three diseased mouse brains. Error bars correspond to standard errors of the mean. <b>A.</b> Conformational stability analysis using mAb 6H4 of OvPrP^Sc-A136(S) in Tg(OvPrP-A136)3533^+/− mice (red line), OvPrP^Sc-V136(U) in Tg(OvPrP-V136)4166^+/− mice (blue line), and total OvPrP^Sc in Tg(OvPrP-A/V136) mice (black line). Black asterisks compare differences between OvPrP^Sc-A136(S) and total PrP^Sc in Tg(OvPrP-A136)3533^+/− and Tg(OvPrP-A/V) mice; blue asterisks compare differences between OvPrP^Sc-A136(S) in Tg(OvPrP-A136)3533^+/− mice and OvPrP^Sc-V136(U) in Tg(OvPrP-V136)4166^+/− mice. <b>C.</b> Conformational stability analysis using mAb PRC5 of OvPrP^Sc-A136(S) in Tg(OvPrP-A136)3533^+/− mice (solid line) and OvPrP^Sc-A136(U) in Tg(OvPrP-A/V136) mice (dashed line). *P<0.05, **P<0.005, ***P<0.001. In <b>B</b> and <b>D</b>, representative immunoblots of PK-resistant PrP in the brains of three mice from each infected cohort of Tg(OvPrP-A136)3533^+/−, Tg(OvPrP-V136)4166^+/−, and Tg(OvPrP-A/V136) mice using mAb 6H4 (<b>B</b>) and mAb PRC5 (<b>C</b>). Times of onset of disease for analyzed mice are also provided. OvPrP-V136 is indicated by blue symbols and text; OvPrP-A136 is indicated by red symbols and text.</p