Microscopies,spectroscopies and spectrometries applied to marine corrosion of copper

Used in combination, surface analytical techniques can resolve spatial relationships between bacteria and localized corrosion, determine specific corrosion mechanisms and differentiate between abiotic and biotic processes. Confocal laser scanning microscopy and scanning vibrating electrode microscopy were used to demonstrate that marine bacteria and anodic sites are co‐located. Environmental scanning electron microscopy coupled with energy dispersive X‐ray spectros‐copy was used to demonstrate dealloying of nickel from copper: nickel alloys. X‐ray absorption spectroscopy, and transmission electron microscopy equipped with electron energy loss spectrometry were used to determine the speciation of copper associated with corrosion products.     

Inferring patterns of aggression from red howler monkey injuries

Venezuelan red howler monkeys in a semideciduous habitat typically survive injuries and disabilities. Intraspecific physical aggression was the most frequently observed and inferred cause of injury. Thirty-eight percent of 119 howlers of all ages examined during capture had scars or other evidence of “damage.” Overall, the sexes did not differ significantly in total number of injuries or number of individuals classified as “damaged.” The incidence of injury was not independent of age-sex class. The subadult male class had the highest percentage of “damaged” individuals. However, when total injuries per age class were examined for each sex separately, only females showed a pattern that was significantly different than expected based on age (i.e., exposure to injury factors). Subadult females experienced more injuries than expected, whereas adult females had fewer injuries. Troop status (resident troop, natal troop, or extratroop) was not significantly related to the number of injuries in adult and subadult males. Thin finding was not surprising, because adult and subadult males of all status classes are involved in aggression related to breeding competition. Extratroop females had more injuries than expected, and natal females had the fewest injuries. The higher incidence of injuries on subadult females and extratroop females is consistent with aggression-mediated emigration of some females and observed resistance to female immigration by resident females. Overall, 74% of injuries were located on anterior-ventral portions of the body, consistent with the face-to-face fighting observed in howlers. Sociobiological costs of aggression in red howlers are difficult to assess because many howlers, despite frequent and severe injury, subsequently survive and reproduce. We recommend caution in inferring mortality from injuries, especially when social mobility and emigration out of the study area are common.     

Iterative design of a simulation-based module for teaching evolution by natural selection

Background

This research builds on a previous study that looked at the effectiveness of a simulation-based module for teaching students about the process of evolution by natural selection. While the previous study showed that the module was successful in teaching how natural selection works, the research uncovered some weaknesses in the design. In this paper, we used design-based research to investigate how design changes to the module affected not only students' understanding of the concepts but also their usage of misconceptions in the assessments. We present results from two studies. In study 1, we looked at gains in understanding on a pre and post-assessment for students who used the revised version of the module. We also examined misconception uses in their answer selections. In study 2, we compared the performance on a summative assessment between students who used the revised version and students who used the original version of the module. We also looked at misconception uses in their answer selections.

Results

In study 1, we saw a significant improvement in the pre-post assessment for students who used the revised version. In study 2, we did not find a significant difference on the overall performance outcome between students who used the revised and those that used the original version of the module. In both studies, however, we saw a  lower use of misconceptions after students used the revised module. In particular, we saw less use of the adaptive mutation misconception, the belief that mutations are adaptive responses to the environment and are biased towards advantageous mutations. This is promising because in the previous study there was no evidence of decreased use of this misconception.

Conclusions

Students showed learning gains on all targeted key concepts, and reduced expression of all targeted misconceptions, which was not found previously for students using the older workbook version of the module. In particular, the revised version appears to help students overcome the adaptive mutation misconception. This article demonstrates how design-based research can contribute to the ongoing improvement of evidence-based instruction in undergraduate biology classrooms.

     

Characterization of and Functional Antigen Presentation by Central Nervous System Mononuclear Cells from Mice Infected with Theiler’s Murine Encephalomyelitis Virus

We examined the phenotype and function of cells infiltrating the central nervous system (CNS) of mice persistently infected with Theiler’s murine encephalomyelitis virus (TMEV) for evidence that viral antigens are presented to T cells within the CNS. Expression of major histocompatibility complex (MHC) class II in the spinal cords of mice infected with TMEV was found predominantly on macrophages in demyelinating lesions. The distribution of I-A^s staining overlapped that of the macrophage marker sialoadhesin in frozen sections and coincided with that of another macrophage/microglial cell marker, F4/80, by flow cytometry. In contrast, astrocytes, identified by staining with glial fibrillary acidic protein, rarely expressed detectable MHC class II, although fibrillary gliosis associated with the CNS damage was clearly seen. The costimulatory molecules B7-1 and B7-2 were expressed on the surface of most MHC class II-positive cells in the CNS, at levels exceeding those found in the spleens of the infected mice. Immunohistochemistry revealed that B7-1 and B7-2 colocalized on large F4/80⁺ macrophages/microglia in the spinal cord lesions. In contrast, CD4⁺ T cells in the lesions expressed mainly B7-2, which was found primarily on blastoid CD4⁺ T cells located toward the periphery of the lesions. Most interestingly, plastic-adherent cells freshly isolated from the spinal cords of TMEV-infected mice were able to process and present TMEV and horse myoglobin to antigen-specific T-cell lines. Furthermore, these cells were able to activate a TMEV epitope-specific T-cell line in the absence of added antigen, providing conclusive evidence for the endogenous processing and presentation of virus epitopes within the CNS of persistently infected SJL/J mice.Theiler’s murine encephalomyelitis virus (TMEV) is a picornavirus that induces a lifelong persistent central nervous system (CNS) infection leading to a chronic CNS demyelinating disease when inoculated intracerebrally into susceptible strains of mice. Infected mice develop progressive symptoms of gait disturbance, spastic hind limb paralysis, and urinary incontinence (39), histologically related to perivascular and parenchymal mononuclear cell infiltration and demyelination of white matter tracts within the spinal cord (8, 9, 38). Several lines of evidence have demonstrated that demyelination is immunologically mediated. These include the ability of nonspecific immunosuppression with cyclophosphamide (37), antithymocyte serum (36), and anti-CD4 or anti-major histocompatibility complex (MHC) class II monoclonal antibodies (MAbs) (14, 16, 63) to inhibit or prevent disease and the ability of TMEV-specific tolerance to prevent induction of disease (28). In the highly susceptible SJL/J mouse strain, current evidence indicates that the myelin damage is initiated by TMEV-specific CD4⁺ T cells targeting virus antigen (16, 28, 45, 46, 54), while the chronic stage of the disease also involves CD4⁺ myelin epitope-specific T cells primed via epitope spreading (48). Thus, the immune response itself may be deleterious to CNS function, as exemplified in humans by multiple sclerosis (MS), for which TMEV infection serves as a model.The identity of the cells responsible for initiating and sustaining immune responses in the CNS remains controversial. The CNS lacks normal lymphatic circulation and tissue and is shielded from the systemic circulation by a specialized continuous vascular endothelium (6). There are specialized cells within the CNS with the potential to present antigens to T cells. In vitro, astrocytes (11, 59) and microglia (3, 13), particularly when treated with gamma interferon (IFN-γ), are capable of expressing MHC class II and presenting antigens to T cells. However, studies such as these have relied on the ability to isolate and continuously culture cells from neonatal or embryonic brain and have assumed that such cells are representative of the adult populations in vivo. Antigen presentation by neonatal cells in long-term culture may not faithfully reproduce the in vivo state in adult animals, as the ability of microglia directly isolated from adult rats to present myelin basic protein (MBP) to T-cell lines in vitro was found to differ from that of neonatally derived microglia (12). In addition, studies using allogeneic bone marrow chimeras between strains of mice or rats have generally supported the idea that cells of hematopoietic origin, i.e., microglia and macrophages, are the principal antigen-presenting cells (APCs) in the CNS active during the initiation of experimental autoimmune encephalomyelitis (EAE) (20, 22, 50). Although they are much more abundant than microglia, astrocytes are less potent when inducing EAE in chimeras (50).The role of antigen presentation in the CNS during TMEV-induced demyelination has not been addressed directly. We previously showed that a relatively large fraction of the CD4⁺, but not CD8⁺, T cells isolated from the spinal cords of TMEV-infected mice expressed high-affinity interleukin-2 (IL-2) receptor (IL-2R), a marker of recent T-cell activation. In addition, TMEV-specific CD4⁺ T cells could be demonstrated in the spinal cord infiltrates of TMEV-infected mice (54). This finding raises the possibility that T cells are locally activated within the target tissue and participate directly in the pathogenesis of disease. Macrophages (5, 41, 56), astrocytes (7, 56), and oligodendroglia (55, 56) in TMEV-infected mice contain virus and conceivably could present viral antigens to pathogenic CD4⁺ T cells within the CNS. Isolated microglia (34) and astrocytes (17) have been shown to support persistent viral infection in vitro, and astrocytes derived from neonatal mice have been shown to present TMEV to T cells in vitro (2). To examine whether CNS cells present viral antigens and participate in the pathogenesis of TMEV-induced demyelination, the expression of MHC class II and B7 costimulatory molecules was examined in detail. Based on our previous results showing that a large proportion of CD4⁺ T cells isolated from the CNS of TMEV-infected mice bear markers of recent activation, we also asked if mononuclear cells isolated from the CNS of TMEV-infected mice were capable of presenting viral antigens leading to the functional activation of Th1 lines in vitro.