The apical complex of Toxoplasma gondii is widely believed to serve essential functions in both invasion of its host cells (including human cells), and in replication of the parasite. The understanding of apical complex function, the basis for its novel structure, and the mechanism for its motility are greatly impeded by lack of knowledge of its molecular composition. We have partially purified the conoid/apical complex, identified ~200 proteins that represent 70% of its cytoskeletal protein components, characterized seven novel proteins, and determined the sequence of recruitment of five of these proteins into the cytoskeleton during cell division. Our results provide new markers for the different subcompartments within the apical complex, and revealed previously unknown cellular compartments, which facilitate our understanding of how the invasion machinery is built. Surprisingly, the extreme apical and extreme basal structures of this highly polarized cell originate in the same location and at the same time very early during parasite replication.

The characteristic profile of Millennial Generation students, driving many educational reforms, can be challenged by research in a number of fields including cognition, learning style, neurology, and psychology. This evidence suggests that the current aggregate view of the Millennial student may be less than accurate. Statistics show that Millennial students are considerably diverse in backgrounds, personalities, and learning styles. Data are presented regarding technological predilection, multitasking, reading, critical thinking, professional behaviors, and learning styles, which indicate that students in the Millennial Generation may not be as homogenous in fundamental learning strategies and attitudes as is regularly proposed. Although their common character traits have implications for instruction, no available evidence demonstrates that these traits impact their fundamental process of learning. Many curricular strategies have been implemented to address alleged changes in the manner by which Millennial students learn. None has clearly shown superior outcomes in academic accomplishments or developing expertise for graduating students and concerns persist related to the successful engagement of Millennial students in the process of learning. Four factors for consideration in general curricular design are proposed to address student engagement and optimal knowledge acquisition for 21st century learners.

Abstract. Experiments are described supporting the proposition that the assembly of stress fibers in nonmuscle cells and the assembly of myofibrils in cardiac cells share conserved mechanisms. Double staining with a battery of labeled antibodies against membraneassociated proteins, myofibrillar proteins, and stress fiber proteins reveals the following: (a) dissociated, cultured cardiac myocytes reconstitute intercalated discs consisting of adherens junctions (AJs) and desmosomes at sites of cell-cell contact and sub-sarcolemmal adhesion plaques (SAPs) at sites of cellsubstrate contact; (b) each AJ or SAP associates proximally with a striated myofibril, and conversely every striated myofibril is capped at either end by an AJ or a SAP; (C) the invariant association between a given myofibril and its SAP is especially prominent at the earliest stages of myofibrillogenesis; nascent myofibrils are capped by oppositely oriented SAPs; (d) the insertion of nascent myofibrils into AJs or into SAPs invariably involves vinculin, a-actin, and sarcomeric ot-actinin (s-ot-actinin); (e) AJs are positive for A-CAM but negative for talin and integrin; SAPs lack A-CAM but are positive for talin and integrin; (f) in cardiac cells all ot-actinin-containing structures invariably are positive for the sarcomeric isoform, o~-actin and related sarcomeric proteins; they lack non-sot-actinin, -y-actin, and caldesmon; (g) in fibroblasts all ot-actinin-containing structures are positive for the non-sarcomeric isoform, -y-actin, and related nonsarcomeric proteins, including caldesmon; and (h) myocytes differ from all other types of adherent cultured cells in that they do not assemble authentic stress fibers; instead they assemble stress fiber-like structures of linearly aligned I-Z-I-like complexes consisting exclusively of sarcomeric proteins. CONSIDERABLE information has accumulated regarding the molecular composition and possible functions of the submembranous complexes into which stress fibers insert (4,5,11,26,34,46). In cell-cell junctions of the adherens type the distal tips of the microfilament bundles insert into submembranous F-actin/o~-actinin/vinculin complexes that often involve additional membrane-associated molecules such as A-CAM (31, 60), radixin (58) etc. A somewhat different class of submembranous complexes characterizes the termini of stress fibers where they insert into the cell-substrate junctions of spread, nontranslocating cultured ceils. These F-actin/ot-actinin/vinculin complexes, known as adhesion plaques (APs),t are also positive for talin (11), paxillin (59), integrin (17), and other proteins. APs are also sites for a Ca2 § protease (5) and a1. Abbreviations used in this paper: AJ, adherens junction; AP, adhesion plaque; MHC, myosin heavy chain; s, sarcomeric; SAP, subsarcolemmal adhesion plaque.protein kinase C (35) suggesting they may be involved in transmembrane signaling. In both the adherens junction (AJs) and the APs, ct-actinin appears to play a bifunctional role. Distally, facing the inner surface of the c...

Based on the assumption that a conserved differentiation program governs the assembly of sarcomeres in skeletal muscle in a manner analogous to programs for viral capsid assembly, we have defined the temporal and spatial distribution of 10 muscle-specific proteins in mononucleated myoblasts as a function of the time after terminal cell division. Single cells in mitosis were identified in monolayer cultures of embryonic chicken pectoralis, followed for selected time points (0-24 h postmitosis) by video time-lapse microscopy, and then fixed for immunofluorescence staining. For convenience, the myoblasts were termed x-h-old to define their age relative to their mitotic "birthdate." All 6 h myoblasts that emerged in a mitogen-rich medium were desmin+ but only 50% were positive for a alpha-actin, troponin-I, alpha-actinin, MyHC, zeugmatin, titin, or nebulin. By 15 h postmitosis, approximately 80% were positive for all of the above proteins. The up-regulation of these 7 myofibrillar proteins appears to be stochastic, in that many myoblasts were alpha-actinin+ or zeugmatin+ but MyHC- or titin- whereas others were troponin-I+ or MyHC+ but alpha-actinin- or alpha-actin-. In 15-h-old myoblasts, these contractile proteins were organized into nonstriated myofibrils (NSMFs). In contrast to striated myofibrils (SMFs), the NSMFs exhibited variable stoichiometries of the sarcomeric proteins and these were not organized into any consistent pattern. In this phase of maturation, two other changes occurred: (1) the microtubule network was reorganized into parallel bundles, driving the myoblasts into polarized, needle-shaped cells; and (2) the sarcolemma became fusion-competent. A transition from NSMFs to SMFs took place between 15 and 24 h (or later) postmitosis and was correlated with the late appearance of myomesin, and particularly, MyBP-C (C protein). The emergence of one, or a string of approximately 2 mu long sarcomeres, was invariably characterized by the localization of myomesin and MyBP-C to their mature positions in the developing A-bands. The latter group of A-band proteins may be rate-limiting in the assembly program. The great majority of myoblasts stained positively for desmin and myofibrillar proteins prior to, rather than after, fusing to form myotubes. This sequential appearance of muscle-specific proteins in vitro fully recapitulates myofibrillar assembly steps in myoblasts of the myotome and limb bud in vivo, as well as in nonmuscle cells converted to myoblasts by MyoD. We suggest that this cell-autonomous myoblast differentiation program may be blocked at different control points in immortalized myogenic cell lines.

As anatomy course hours have decreased, it has become increasingly important to provide tools that facilitate laboratory task efficiency. Digital video clips were created to present dissection guidance to medical students. The video clips communicate challenging aspects of the dissection process with succinct visual demonstrations easily accessed via an online course site. Students were asked to complete a survey designed to assess the quality and utility of the videos. Survey respondents indicated that the videos enhanced the quality of the anatomy course as well as their individual performances. This teaching tool enhances student competencies in human gross anatomy.