David O. DeFouw

A survey of student perceptions of team-based learning in anatomy curriculum: favorable views unrelated to grades.

Team‐based learning (TBL) combines independent out of class preparation with in class small group discussion. We adopted TBL in teaching first year medical gross anatomy. In this study, we evaluated student perceptions of TBL by using a survey that elicited perceptions of both pedagogy and mode of learning. Anatomy lectures were replaced with required preclass readings, self‐assessment quizzes, small group discussions of assignments, and groups retaking the same quizzes for deeper learning. At the course conclusion, students were surveyed to assess their preference for TBL, their perceptions of TBL effectiveness, and their perceptions of successful interpersonal relationships within groups. Respondents (n = 317; 89% response) were asked to rate the extent that they agreed (−2 = strongly disagree; −1 = disagree; 0 = neutral; 1 = agree; and 2 = strongly agree). A principal components factor analysis with varimax rotation identified two 8‐item factors: “perceptions of TBL” and “perceptions of teamwork.” Internal consistency for each was high [Cronbachs alpha = 0.908 (preference for TBL); 0.884 (preference of teamwork)]. Results of one‐way analysis of variance between Honors/High Pass/Pass/Fail students indicated that Honors (n = 73) tended to rate perceptions of TBL higher than Pass (n = 54) [mean difference = 2.92; 95% CI (0.05, 5.79)], and also higher than Fail (n = 11) [mean difference = 6.30; 95% CI (1.13, 11.47)]. However, each had overallpositive ratings. No difference was noted between mean ratings of teamwork, which were also, overall, positive. We conclude that medical students view TBL favorably irrespective of their grades. Anat Sci Educ 2:150–155, 2009.

Mapping of the microcirculation in the chick chorioallantoic membrane during normal angiogenesis.

The microcirculation within the chorioallantoic membrane (CAM) of the chick is particularly well suited for in vivo observation and has been used extensively as an assay to detect angiogenic activity. Although progressive chronological expansion of the CAM capillary network occurs normally during embryogenesis, descriptions of the branching patterns of CAM pre- and postcapillary microvessels during embryonic development have not been recorded. In the present study chick embryos were incubated, using an established shell-less culture technique, and observed in vivo at Days 6, 10, and 14 of embryonic development. Morphometric analyses of photomicrographs of CAM microvessels were based upon the centripetal ordering method of microvascular mapping of the first three orders of pre- and postcapillary microvessels with the capillaries serving as the initial point of reference. For both pre- and postcapillary vessels, the number of first-order vessels exceeded the number of second-order vessels which, in turn, outnumbered third-order vessels during each observation period. First- and second-order vessels progressively increased in number from Day 6 to Day 14; however, the number of third-order vessels remained essentially constant during this period. Further, the number of precapillary vessels was greater than postcapillary vessels in their respective orders at Days 6 and 10; however, by Day 14 the numbers were comparable. Average diameters and lengths of the third-order vessels were greater than the second-order vessels which, in turn, were greater than the first-order vessels in both the pre- and postcapillary compartments. Further, mean lengths of each of the three vessel orders in both compartments decreased progressively and by Day 14 were significantly less than at Day 6. Average diameters of each vessel order, on the other hand, remained unchanged from Day 6 to Day 14. Finally, intercapillary distances, based on measurements from fluorescent micrographs obtained after microinjections of fluorescein isothiocyanate (FITC)-dextran, were substantially less at Day 10 and 14 than at Day 6. Based on these morphometric data, the endothelial precursor responsible for continuous neoformation of first- and second-order microvessels during embryogenesis remains uncertain. Whether existing first-, second-, or third-order vessel endothelia serve as this precursor or histodifferentiation of existing capillaries enables continuous expansion of the first- and second-order microvessels remains to be tested.

Dermal tissue fibrosis in patients with chronic venous insufficiency is associated with increased transforming growth factor-β1 gene expression and protein production

PURPOSE Pathologic dermal degeneration in patients with chronic venous insufficiency (CVI) is characterized by aberrant tissue remodeling that results in stasis dermatitis, tissue fibrosis, and ulcer formation. The cytochemical processes that regulate these events are unclear. Because transforming growth factor-beta(1) (TGF-beta(1)) is a known fibrogenic cytokine, we hypothesized that the increased production of TGF-beta(1) would be associated with CVI disease progression. METHODS Seventy-eight punch biopsy specimens of the lower calf (LC) and the lower thigh (LT) of 52 patients were snap frozen in liquid nitrogen and stratified into four groups according to the Society for Vascular Surgery/International Society for Cardiovascular Surgery CEAP classification (C, clinical; E, etiologic; A, anatomic distribution; and P, pathophysiology). One set of LC biopsy specimens were analyzed for TGF-beta(1) gene expression with quantitative reverse transcriptase-polymerase chain reaction: healthy skin, n = 6; class 4, n = 6; class 5, n = 5; and class 6, n = 7. A second set of biopsy specimens from the LC and LT were analyzed for the amount of bioactive TGF-beta(1) with a certified cell line 64 mink lung epithelial bioassay: healthy skin, n = 8; class 4, n = 23; class 5, n = 13; and class 6, n = 10. The location of TGF-beta(1) was determined at the light and electron microscopy level with immunocytochemistry and immunogold (IMG) labeling. Multiple comparisons were analyzed with a one-way analysis of variance and the Student-Newman-Keuls post hoc tests. The LC and LT comparisons were analyzed with a two-tailed unpaired t test. RESULTS The TGF-beta(1) gene transcripts for control subjects and patients in classes 4, 5, and 6 were 7.02 +/- 7.33, 43.33 +/- 9.0, 16.13 +/- 7.67, and 7.22 +/- 0.56 x 10(-14) mol/microg total RNA, respectively. The transcripts were significantly elevated in class 4 patients only (P </=.05). The amount of active TGF-beta(1) in picograms/gram of tissue from LC and LT biopsy specimens as compared with healthy skin biopsy specimens were as follows: healthy skin, <1. 0 pc/g; class 4: LC, 5061 +/- 1827 pc/g; LT, 317.3 +/- 277 pc/g; class 5: LC, 8327 +/- 3690 pc/g; LT, 193 +/- 164 pc/g; and class 6: LC, 5392 +/- 1800 pc/g; LT, 117 +/- 61 pc/g. Differences between healthy skin and the skin of the patients in classes 4 and 6 were significant (P </=.05 and P </=.01, respectively). Differences between the LC and LT biopsy specimens within each CVI group were also significant: class 4, P </=.003; class 5, P </=.008; and class 6, P </=.02. Immunocytochemistry results of healthy skin showed TGF-beta(1) staining of epidermal basal cells only. CVI dermal biopsy results demonstrated positive staining in epidermal basal cells, fibroblasts, and leukocytes. Many leukocytes had positive staining of intracellular granules, which appeared morphologically similar to mast cells. IMG labeling results demonstrated gold particles in the leukocytes and collagen fibrils of the extracellular matrix. CONCLUSION Our study indicated that activated leukocytes traverse perivascular cuffs and release active TGF-beta(1). Positive TGF-beta(1) staining results of dermal fibroblasts were observed and suggest that fibroblasts are the targets of activated interstitial leukocytes. Increased protein production, despite normal levels of gene transcripts in patients in classes 5 and 6, suggests that alternate mechanisms other than gene transcription regulate protein production. A potential mechanism for quick access and release is storage of TGF-beta(1) in the extracellular matrix. IMG labeling to collagen fibrils support this possibility. Furthermore, TGF-beta(1) was exclusively elevated in areas of clinically active disease, indicating a regionalized response to injury. These data suggest that alterations in tissue remodeling occur in patients with CVI and that dermal tissue fibrosis in CVI is regulated by TGF-beta(1).

Morphometric assessment of the dermal microcirculation in patients with chronic venous insufficiency

PURPOSE Ultrastructural assessments of the dermal microcirculation in patients with chronic venous insufficiency have been limited to qualitative morphologic descriptions of venous ulcer edges or venous stasis dermatitis. The purpose of this investigation was to quantify differences in endothelial cell structure and local cell type with emphasis on leukocytes and their relationship to arterioles, capillaries, and postcapillary venules (PCVs). METHODS Two 4.0 mm punch biopsies were obtained from areas of dermal stasis skin changes in the gaiter region of the leg, as well as from noninvolved areas of skin in the ipsilateral thigh, from 35 patients: CEAP class 4 (11 patients), class 5 (9 patients), class 6 (10 patients), and five normal skin biopsies from patients without chronic venous insufficiency. Electron microscopy was performed on sections at 6700x and 23,800x magnification. At 6700x endothelial cell thickness was determined, and the number of fibroblasts, leukocytes, and mast cells were recorded relative to their proximity to arterioles, capillaries, and PCVs. Similarly, at 23,800x endothelial cell vesicle density, interendothelial junctional widths, and basal lamina thickness (cuff width) were measured. Preliminary evaluation for the presence of transforming growth factor-beta 1 (TGF-beta 1) was performed on three patients using reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS Quantitative measurements demonstrated increased mast cell content for class 4 and 5 patients around arterioles and PCVs and increased macrophage numbers for class 6 patients around PCVs (p < 0.05). Fibroblasts were the most common cells observed; however, no differences were demonstrated between groups. No differences were observed in interendothelial junctional widths or vesicle densities in arterioles, capillaries, or PCVs. Basal lamina thickness was increased only at the capillary level (p < 0.05). The results of RT-PCR for TGF-beta 1 messenger RNA were positive in the three patients studied. CONCLUSIONS Our data suggest that (1) mast cells play a role in the pathogenesis of chronic venous insufficiency; (2) the effects of mast cells, macrophages, or both may be mediated in part by TGF-beta 1; and (3) capillary cuff formation is not associated with widened interendothelial gap junctions, but may be a result of enhanced vesicular transport rate or conformational changes in the interendothelial glycocalyx.

Team-based learning in anatomy: an efficient, effective, and economical strategy.

Team‐based learning (TBL) strategy is being adopted in medical education to implement interactive small group learning. We have modified classical TBL to fit our curricular needs and approach. Anatomy lectures were replaced with TBL that required preparation of assigned content specific discussion topics (in the text referred as “discussion topics”), an individual self‐assessment quiz (IRAT), analysis of the discussion topics, and then the team retaking the same quiz (GRAT) for discussion and deeper learning. Embryology and clinical correlations were given as lectures. Unit examinations consisted of graded IRAT and GRAT. The National Board of Medical Examiners (NBME) Subject Examination was the comprehensive final examination. To evaluate the effect of TBL on student performance we compared the departmental and NBME subject examination scores between the traditional and TBL curricula. We collected five years of data on student performance in TBL‐based anatomy and lecture‐based preclinical courses. Our results show that departmental and NBME subject examination scores for TBL‐based anatomy were higher than those for lecture‐based anatomy. We subsequently compared average NBME scores for anatomy with those in other preclinical courses that were lecture‐based. Average NBME anatomy scores were significantly higher than those for all the lecture‐based preclinical courses. Since the introduction of TBL in anatomy, student performance has progressively improved in the NBME subject examination. Students perceived TBL as a motivator to be a responsible team member and to contribute to collective learning by the team. Further, it reinforced self‐directed learning and fostered an appreciation for peer respect. Interestingly, these perceptions were uniform irrespective of student course performance. Anat Sci Educ.

Vein interposition cuffs decrease the intimal hyperplastic response of polytetrafluoroethylene bypass grafts

PURPOSE The modification of the distal anastomosis of polytetrafluoroethylene (PTFE) bypass grafts with vein interposition cuffs (VCs) has been reported to increase graft patency. However, the mechanisms that are responsible for this improved patency are unclear. Because intimal hyperplasia (IH) is a primary cause of prosthetic graft failure, we hypothesized that VCs affect the distal anastomosis by decreasing the IH response of the outflow artery. METHODS Twenty-three female domestic Yorkshire pigs (mean weight, 35 kg) underwent 42 femoral PTFE bypass grafting procedures. The PTFE bypass grafts were separated into the following three groups according to distal anastomotic configuration: end-to-side anastomoses (ES), VCs, and cuffs constructed with PTFE (PCs). Four femoral arteries from two pigs served as healthy controls. At sacrifice, the grafts were perfusion fixed, and the distal anastomoses harvested at 1 and 4 weeks. The specimens were hemisected and serially sectioned to identify the heel, toe, and mid-anastomotic regions. The sections were cut into 5-microm segments and analyzed for intima and media thickness and area, intima/media area ratio, and the distribution of IH in the vein cuff. The roles of transforming growth factor-beta1 and platelet-derived growth factor-BB in IH development were assessed with immunohistochemistry. RESULTS IH development was significantly lower at all areas of the anastomosis, with VCs compared with ES and PCs at 4 weeks (P </=.001). IH decreased in VCs from 1 to 4 weeks in all areas of the anastomosis (P </=.001). PCs showed pronounced IH at the mid-anastomosis as compared with VCs and ES (P </=.001). IH was most pronounced at the toe with ES and PCs (P </=.001). Qualitatively, VCs altered the site of IH development, sparing the recipient artery with preferential thickening of the vein cuff and formation of a pseudointima at the vein-PTFE interface. Immunohistochemistry results showed positive staining for transforming growth factor-beta1, platelet-derived growth factor-BB, and smooth muscle alpha-actin in the hyperplastic intima. CONCLUSION PTFE bypass grafts with VCs had less IH develop than did grafts with ES and PC anastomoses. IH regression in VCs at 4 weeks suggests compensatory vessel wall remodeling mediated by the presence of the VC. Furthermore, VCs caused a redistribution of hyperplasia to the vein-PTFE interface, delaying IH-induced outflow obstruction in the recipient artery. The marked increase in IH with PCs, despite a similar geometric configuration to VCs, suggests that the biologic properties of autogenous tissue dissipate IH development. Similarly, the flow patterns in PCs and VCs should be identical, which suggests a less important role of hemodynamic forces in VC-mediated protection.

A morphometric analysis of isolated perfused dog lungs after acute oncotic edema.

Abstract Established stereologic techniques were used to evaluate morphologic changes in isolated-perfused dog lungs after induction of severe, acute oncotic edema. Lung volumes that were occupied by the connective tissue spaces surrounding extraalveolar vessels and airways were increased. Likewise, thickness of the parenchymal interstitium (interstitial compartment of the air-blood barrier) was increased, which created an overall increase in mean thickness of the barrier. In the cellular compartment of the air-blood barrier, cytoplasmic volumes of the endothelial and type I epithelial cells occupied by pinocytotic vesicles were increased. In addition, the number of vesicles opening directly onto the luminal and abluminal cellular surfaces was increased. Thus, transendothelial and transepithelial vesicular transport may contribute to edema formation in isolated perfused dog lungs. The production of oncotic edema was also associated with an increase in alveolar surface density while the proportion of the alveolar septa occupied by capillary contents was decreased.

Differentiation of the microvascular endothelium during early angiogenesis and respiratory onset in the chick chorioallantoic membrane

The present study served to determine the extent of microvascular endothelial differentiation during early stages of morphogenesis (days 4.5-5.5 of the 21-day incubation) in the chick chorioallantoic membrane (CAM). CAMs, which serve as the embryonic lung, were prepared for intravital injections of a graded series of FITC-dextrans and subsequent ultrastructural morphometric analyses of the microvascular units. The precapillary, capillary, and postcapillary microvascular segments presented a continuous endothelium that was substantially thicker than that of adult lung endothelia (DeFouw, 1988). Further, plasmalemmal vesicles were uniformly sparse, while endothelial vacuoles, of variable diameters, were present continuously in the proliferating microvascular units. Average widths and depths of the interendothelial clefts were uniform and suggested complete structural differentiation from the onset of CAM morphogenesis. Based on our recent estimates of CAM microvascular permeability coefficients (Rizzo et al., 1995), the observed endothelial ultrastructure was associated with microvascular selectivity comparable to that of adult pulmonary microvessels (Lanken et al., 1985). Therefore, despite incomplete ultrastructural differentiation of the early CAM microvascular endothelium, these angiogenic microvessels presented adult-like barrier properties. Further they were less permeable than (Wu et al., 1993; Yuan et al., 1993) and ultrastructurally distinct from (Kohn et al., 1992) certain tumorigenic microvessels. Thus, angiogenesis is likely not a routinely homogeneous process, and CAM microvascular permeability characteristics may be teleologically significant.

The arterial wall response to intimal injury in an experimental model.

Repair of occult arterial injuries is advocated to prevent thrombosis, arteriovenous fistula, and pseudoaneurysm formation. However, recent clinical series describe the healing of arterial intimal injuries and recommend nonoperative therapy. To investigate the arterial wall response to intimal injury, we created intimal flaps in 46 canine femoral arteries. The intimal flaps were imaged by arteriography, angioscopy, and intravascular ultrasound acutely, and at one and three weeks and five months post-injury. Lumen area was measured using caliper techniques (arteriography) and computerized video planimetry (angioscopy, intravascular ultrasound). Intimal and medial thickness were measured by intravascular ultrasound prior to harvest for histologic evaluation by light microscopy. Analysis of 32 patent arteries was performed after exclusion of 14 thrombosed arteries. Residual lumen area (mm2) correlated closely among the imaging modalities at one week (8.7±1.1, 7.3±2.0, 6.9±1.8), three weeks (4.2±0.9, 2.9±1.0, 2.7±0.8), and five months (5.3±0.9, 5.0±0.5, 5.0±0.9). Maximal intimal and medial thickness occurred three weeks post-injury, coincident with the maximal reduction in lumen area. Although intimal injuries can cause acute and delayed arterial thromboses, observation may be appropriate in selected cases. The evaluation of those patients chosen for nonoperative therapy should extend beyond three weeks, as this is the time of maximal arterial wall response with a continued potential for adverse clinical events.

Variations in cellular attenuation and vesicle numerical densities in capillary endothelium and type I epithelium of isolated, perfused dog lungs after acute severe edema formation

Morphometric comparisons of nonedematous and edematous isolated, perfused dog lungs establish that there are significant differences between the degree of cellular attenuation and vesicle numerical densities in endothelial and type I epithelial cells of the alveolar septa after edema production. In nonedematous isolated lungs the extent of endothelial and epithelial attenuation was greater on the thin sides of the septa. In the edematous lungs, the differential of greater thin-side attenuation was maintained for the endothelium but not for the epithelium where the extent of attenuation in the septal thick segments was increased. Vesicle numerical densities were approximately doubled in the cells on both sides of the septa in the edematous lungs. The endothelial vesicle densities were greater in the septal thin segments than in the septal thick segments in both the nonedematous and the edematous isolated lungs. The epithelial vesicle densities, on the other hand, were similar on the thin and thick sides of the septa in the nonedematous and edematous lung preparations. Although the contribution of vesicles to cellular function in the alveolar septa remains uncertain, further evaluation of vesicular transport should include the possible variability of this function with the varying degrees of cellular attenuation on the two anatomically distinct sides of the septa.