Biomedical subjects

Lawrence J Rizzolo

Publications and source records attributed to Lawrence J Rizzolo.

9 recordsLinked to original sources

PubMed2006

Expression of JAM-A, AF-6, PAR-3 and PAR-6 during the assembly and remodeling of RPE tight junctions.

The tight junctions of the endothelial and epithelial regions of the blood-brain barrier are regulated by interactions with the neighboring tissue. We examined how the neural retina regulates the assembly of tight junctions in the retinal pigment epithelium (RPE). The proteins JAM-A, AF-6, PAR-3 and PAR-6 have been implicated in the assembly of other epithelial tight junctions. Using chick embryos and primary cell culture, we examined gene expression of these proteins during embryonic development, and whether retinal secretions regulate their expression. Three highly conserved RNA splice sites of AF-6 were identified in chick ocular tissues, but only two were expressed in RPE. JAM-A and AF-6 were expressed at relatively high levels early in development when adherens junctions form, but before tight junctions form. Expression of JAM-A and the AF-6 isoforms actually decreased when tight junctions were forming and expanding. The expression of PAR-3 and PAR-6 was constant. Despite the expression of these proteins in vitro (along with claudins, occludin, ZO-1 and ZO-2), the tight junctional networks that form were discontinuous (Rahner, C., Fukuhara, M., Peng, S., Kojima, S., Rizzolo, L.J., 2004. The apical and basal environments of the retinal pigment epithelium regulate the maturation of tight junctions during development. J. Cell Sci. 117, 3307-3318). The expression of these assembly proteins was unaffected by a retinal conditioned medium that induced the completion of tight junction formation. These data indicate that the early expression of the assembly proteins corresponds to the initial establishment of the adherens and tight junctions, but secretory products of the neural retina must induce the expression of additional proteins to complete the maturation process.

Age Factors↗

PubMed2006

Should we continue teaching anatomy by dissection when ...?

The central role that human dissection has long held in clinical education is being reevaluated in many institutions. Despite the impression that many institutions are abandoning dissection, very few have and most of those have reinstated dissection within a few years. What are the inherent qualities that lead institutions back to dissection? In our efforts to redesign a shortened dissection course, our consultations with a broad range of clinicians lead us to understand how the rhythms of clinical practice are modeled and developed in the small-group setting of the dissection laboratory. Following further consultation with colleagues who have experimented with different models of anatomy instruction, we discuss three themes in support of dissection. First, problem-solving in the dissection laboratory develops the habits-of-mind of clinical practice. Second, relating dissection to imaging modalities develops the spatial reasoning skills needed to understand computer simulations, interpret imaging data, and interact with surgeons, radiologists, and patients. Third, the human face of dissection fosters self-reflection and integration of the cognitive and affective skills required for medical practice. Through group process, the collaborative effort of dissection teams develops essential of attributes of clinical professionalism.

Anatomy↗

PubMed2006

Anatomical instruction and training for professionalism from the 19th to the 21st centuries.

For most of the 19th century, anatomists in the United States saw the affective, emotional aspects of human dissection as salient ingredients in professional formation. Professionalism (or "character") signified medical integrity and guaranteed correct professional conduct. As gross anatomy came under siege in the late-19th and early-20th centuries, crowded out of medical curricula by the new experimental sciences, medical educators rethought what it was that dissecting a human body stood to give medical students. As they embraced a new understanding of professionalism premised on an allegiance to science, anatomists celebrated the habits of mind and sensibility to scientific investigation that could be acquired at the dissecting table. One consequence was a deliberate distancing of gross anatomy from the "art of medicine," and with it a de facto suppression of attention to the affective components of human dissection. During this period in the opening decades of the 20th century, the norm of silence about the emotional dimensions of dissection was set in place. The confluence of various movements by the 1960s and 1970s both revived attention to the emotional experience of dissection and sparked a renewed discussion about the relationship between the affective components of learning anatomy and the professional formation of future healers. There is a need to balance the tension between the "affective" and "scientific" aspects of anatomy, and by extension the tension between the "art" and "science" of medical practice. One method is to use small-group "learning societies" as a means to cultivate and meld both dimensions of the professional ethic.

Anatomy↗

PubMed2006

Design principles for developing an efficient clinical anatomy course.

The exponential growth of medical knowledge presents a challenge for the medical school curriculum. Because anatomy is traditionally a long course, it is an attractive target to reduce course hours, yet designing courses that produce students with less understanding of human anatomy is not a viable option. Faced with the challenge of teaching more anatomy with less time, we set out to understand how students employ instructional media to learn anatomy inside and outside of the classroom. We developed a series of pilot programs to explore how students learn anatomy and, in particular, how they combine instructional technology with more traditional classroom and laboratory-based learning. We then integrated what we learned with principles of effective instruction to design a course that makes the most efficient use of students' in-class and out-of-class learning. Overall, we concluded that our new anatomy course needed to focus on transforming how medical students think, reason, and learn. We are currently testing the hypothesis that this novel approach will enhance the ability of students to recall and expand their base of anatomical knowledge throughout their medical school training and beyond.

Anatomy↗

PubMed2006

Effects of culture conditions on heterogeneity and the apical junctional complex of the ARPE-19 cell line.

PURPOSE: ARPE-19 is a spontaneously transformed cell line of human RPE that is widely studied. This report examines its suitability for studying the tight junctions of the RPE. METHODS: ARPE-19 was maintained in standard medium or one of three reduced-serum medium formulations. The expression and distribution of cytoskeletal and junctional proteins were examined by immunocytochemistry, immunoblot analysis, and the reverse transcription-polymerase chain reaction. Barrier function was measured as the transepithelial electrical resistance (TER) and the transmonolayer diffusion of horseradish peroxidase (HRP). RESULTS: Unlike the original reports using passage-15 to -20 cells, commonly available strains of ARPE-19 exhibited a heterogeneous mixture of elongate and polygonal cells. Actin was distributed in stress fibers rather than circumferential bands. The TER was low, and the permeability of HRP was high. The expression of claudins and cytokeratins was heterogeneous. Partial differentiation could be induced in subsets of cells by manipulating the growth medium. A common effect was an increase in the expression of JAM-A, AF-6, and PAR-3 that correlated with a redistribution of actin filaments. This effect was accompanied by a 10x decrease in the permeability of HRP, but a minimal effect on TER. CONCLUSIONS: The properties of ARPE-19 appear to be changing in ways that may depend on how the cells are maintained and passaged. Caution should be exercised in comparing data between laboratories and in interpreting studies in which only a subset of cells may respond to experimental stimuli. Specialized media promoted the maturation of the adherens junction, but only a partial maturation of the tight junctions.

Cell Culture Techniques↗

PubMed2004

The apical and basal environments of the retinal pigment epithelium regulate the maturation of tight junctions during development.

A culture model has been established to study the gradual development of tight junctions during the embryogenesis of the chick retinal pigment epithelium. This study asks how closely the culture model reflects normal development and how the composition, structure and function of embryonic tight junctions are affected by the apical and basal environments. The study focused on the expression of claudins, the fine-structure of tight junctional strands and the transepithelial electrical resistance. Between embryonic days 7 and 14, patches of junctional strands gradually expanded and coalesced to form a continuous junction, in vivo. Although there was a corresponding increase in claudin expression, different claudins appeared at different times. In culture, the apical and basal environments acted synergistically to promote a continuous network of tight junctions with higher electrical resistance. Independently, pituitary extract or the secretory products of either embryonic fibroblasts or the retina promoted the formation of tight junctions. In combination, three effects were identified. With basally placed fibroblast conditioned medium, apical retinal medium increased transepithelial electrical resistance by affecting structure alone. With basally placed pituitary extract, apical retinal conditioned medium increased transepithelial electrical resistance by affecting structure and by modulating claudin expression in a manner that was consistent with development in vivo. Although embryonic day 7 and 14 cultures in retinal medium exhibited similar structure, the transepithelial electrical resistance of the embryonic day 14 cultures was higher. This higher transepithelial electrical resistance correlated with differences in claudin expression and localization. Therefore, this experimental model can isolate the effects of retinal secretions on structure and claudin expression, and can help us to determine how claudins affect function when structure is held constant.

Animals↗

PubMed2003

Apical and basal regulation of the permeability of the retinal pigment epithelium.

PURPOSE: The functional characteristics of tight junctions in the outer blood-retinal barrier change during embryonic development and in the presence of disease. A culture model of developing retinal pigment epithelium (RPE) was used to examine the regulation of the tight junctions. METHODS: RPE from chick embryos was cultured on filters that separated the apical and basal medium compartments. Cultures were maintained in various combinations of serum-free medium, serum-free medium that was conditioned by neural retinas, or serum-free medium that was supplemented with bovine pituitary extract, serum, or various hormones. Function was monitored by the transepithelial electrical resistance (TER) or the permeation of small organic tracers. Structure was monitored by immunofluorescence and freeze-fracture electron microscopy. RESULTS: Functional analysis indicated differences in permeability among RPE of different embryonic age and culture conditions. In serum-free medium, the tight junctions were leaky or failed to form. Barrier properties increased if pituitary extract was added to the basal medium chamber or retina-conditioned medium was added to the apical chamber. Retina-conditioned medium was more effective at organizing tight junctional strands into a continuous network, but bovine pituitary extract appeared to modulate the permeability of that network. In combination, they synergistically elevated the TER to physiological levels. Although the thyroid hormone T3 had no effect, serum in the apical medium chamber inhibited the ability of RPE cells to respond to retina-conditioned medium. CONCLUSIONS: Diffusible factors secreted by the neural retina acted synergistically with basolateral stimulation to regulate the structure and function of RPE tight junctions. Serum on the apical side of the RPE monolayer inhibited the ability of retinal factors to upregulate the tight junction barrier.

Animals↗

PubMed2002

Human dissection: an approach to interweaving the traditional and humanistic goals of medical education.

Anatomy remains one of the core courses of medical school, but the time devoted to it is decreasing. To accommodate the explosion of medical knowledge, educators search to streamline the curriculum. Because it is time-consuming, dissection comes under increased scrutiny. Even in the face of these pressures to reduce course hours, I would like to propose broadening, not reducing, the responsibilities of the anatomy instructor. Anatomy instructors can play a crucial role in helping medical schools meet the critical need to cultivate humanistic values, especially in the arena of end-of-life care. Anatomy can--and should--play an important role in a curriculum-wide effort to address this issue. Just as dissection remains an essential technique to teach three-dimensional concepts, the cadaver dissection lab is an ideal place to introduce concepts of humanistic care. The lab evokes the students' memories, speculations, and fears about serious illness in themselves, their families, and loved ones. Some programs address these reactions with supplemental activities, such as journaling, essay writing, and small group discussion. Valuable as these activities may be, anatomy instructors can achieve more by recognizing their role as a mentor, who can integrate humanistic values into traditional course objectives in a way that adds little time to the curriculum. The attitude of the instructor in ministering to the students' needs as they undertake the emotionally charged task of dissection can provide a model for how the students will respond, in turn, to the hopes and fears of their patients-and to their own reactions to dying. This approach will allow students to implement and practice humanistic values immediately, laying a foundation for their clinical training.

Anatomy↗

PubMed2002

Correlation of Web usage and exam performance in a human anatomy and development course.

Course materials for a Human Anatomy and Development Course were placed on the World Wide Web (WWW). The materials included a lab manual, lecture notes and slides, faculty-generated atlases, Web links, and examinations. The lab manual, lecture notes, and atlases were also provided as black-and-white hardcopy. The Office of Education assigned students a code name that allowed them to use the Web site and take exams anonymously. Student Web use was tracked and correlated with their performance on the final examination. Overall use patterns revealed that most students used the Web site to prepare for examinations, but not for daily studying. Old examinations were the most accessed documents; lecture notes were the least accessed. The access patterns of the students with top 20, middle 20 (closest to the mean), and bottom 20 scores on the final examination were compared. In general, there was little difference between the middle and top groups. Students in the bottom group used computer resources significantly less than the other groups. In a second analysis, the 10 students who used the Web site most frequently scored below the mean. The study suggests that interactive exercises will be heavily used, but that the preparation of all course materials for the WWW may not be an efficient use of institutional resources.

Achievement↗