Jens Dørup

Going Virtual with QuickTime VR: New Methods and Standardized Tools for Interactive Dynamic Visualization of Anatomical Structures

Continuing evolution of computer‐based multimedia technologies has produced QuickTime®, a multiplatform digital media standard that is supported by stand‐alone commercial programs and World Wide Web browsers. While its core functions might be most commonly employed for production and delivery of conventional video programs (e.g., lecture videos), additional QuickTime VR “virtual reality” features can be used to produce photorealistic, interactive “non‐linear movies” of anatomical structures ranging in size from microscopic through gross anatomic. But what is really included in QuickTime VR and how can it be easily used to produce novel and innovative visualizations for education and research? This tutorial introduces the QuickTime multimedia environment, its QuickTime VR extensions, basic linear and non‐linear digital video technologies, image acquisition, and other specialized QuickTime VR production methods. Four separate practical applications are presented for light and electron microscopy, dissectable preserved specimens, and explorable functional anatomy in magnetic resonance cinegrams. Anat Rec (New Anat) 261:64–77, 2000.

Ultrastructure of distal nephron cells in rat renal cortex

Distal nephron segments in the rat renal cortex contain distal convoluted tubule cells (DCT cells), connecting tubule cells (CNT cells), intercalated cells (I cells), and principal cells (P cells). The present study was carried out to expand present knowledge on the ultrastructure of these cells. The cells were sampled from superficial cortex and analyzed by electron microscopy. Several morphometric parameters were determined and statistical comparison between cell types was performed. Significant structural differences between the cell types were demonstrated. DCT cells showed the highest volume density of mitochondria whereas the amplification of basolateral membranes was higher in CNT cells than in I and P cells. The surface density of the membrane that bounds intermediate vesicles in the apical cytoplasm was twofold higher in I cells than in the other cell types. The morphological differentiation found in the present study adds to available evidence indicating a functional differentiation between the cell types and provides a reference for structure-function correlations in these cells.

Structural adaptation of intercalated cells in rat renal cortex to acute metabolic acidosis and alkalosis

The structural responses of cells in the distal convoluted, connecting, and collecting tubule to acute acid/base changes were investigated by electron microscopy. Acute metabolic acidosis was induced by administration of ammonium chloride, and acute metabolic alkalosis by potassium or sodium bicarbonate. Morphometric analyses were performed on micrographs of randomly selected distal nephron cells. No structural responses were found in distal convoluted tubule cells, connecting tubule cells, or principal cells but prominent changes were observed in intercalated cells (I cells). Thus, the surface density of the luminal membrane in I cells was significantly higher in acidotic animals and lower in KHCO3 alkalotic animals than in controls. On the contrary, the surface density of the membrane that bounds apical vesicles was higher in KHCO3 alkalotic and lower in acidotic animals than in controls. These results suggest that the luminal membrane is internalized during alkalosis and that the membrane that bounds apical vesicles is transferred to the luminal membrane during acidosis. Since a proton translocating ATPase may be present in the luminal membrane the observations are consistent with the possibility that cortical I cells participate in the maintenance of acid/base homeostasis.

The ultrastructural development of distal nephron segments in the human fetal kidney

SummaryThe ultrastructural development of the human distal nephron was studied in fetuses 14–18 weeks of gestational age. The three-dimensional course of the nephrons was traced in serial semi-thin sections. Single semi-thin sections containing defined distal nephron segments were then reembedded, thin-sectioned and analyzed by electron microscopy. In stage I (renal vesicle) and stage II (S-shaped body) epithelial cells were essentially similar in ultrastructure. In stage III there were only minor variations in cell ultrastructure between distal nephron segments, but distinct differences were observed between proximal and distal tubule cells, the former being the most differentiated. The segments which are present in nephrons of adult kidneys could be identified in stage IV and some ultrastructural differences recognized between the cells. However, the amplification of the baso-lateral membrane, which is prominent in iontransporting mature distal segments, was almost absent and the baso-lateral membrane area per unit tubule length was similar in all distal segments. Intercalated cells were present towards the end of the distal convoluted and in the connecting tubule in stage IV but the ampulla of the collecting tubule was composed of cells with a uniform ultrastructure. Cell ultrastructure varied again to some extent in the collecting tubule.The present observations demonstrate that distal nephron segments in the human kidney are structurally undifferentiated in the early fetal development and suggest that they only to a limited extent are capable of modifying the composition of the tubular fluid.

Electron microscope analysis of tissue components identified and located by computer-assisted 3-D reconstructions: ultrastructural segmentation of the developing human proximal tubule

A method is described for ultrastructural analysis of renal tubules after precise identification of tubule segments by computerized 3-D reconstruction at the light microscope level. Semithin serial sections were cut of entire nephrons and 3-D coordinate information was obtained by digitization of tubule cross sections in the semithin sections. With the aid of the computer the tubule axis was traced from one section to the other. Precise lengths and positions of the tubules in three dimensions were calculated and stereoscopic images generated. The method was used to analyze the 3-D structure of developing human nephrons, and the ultrastructural development of the proximal tubule. Ultrastructural segmentation of the proximal tubule was demonstrated in the human fetal nephron in developmental stage IV.

Ultrastructure of three-dimensionally localized distal nephron segments in superficial cortex of the rat kidney.

The ultrastructure of superficial distal nephron segments was analyzed after precise localization of tubule cross sections using computer-assisted three-dimensional reconstructions. Five systems of tubules, each with three interconnected distal tubules, were reconstructed and the lengths of the post macula densa segment of the distal straight tubule (DST), the distal convoluted tubule (DCT), the connecting tubule (CNT), and the initial collecting tubule (ICT) were determined. Each cortical collecting duct (CCD) was in continuity with only one tubule in contact with the renal capsule. In three of the five reconstructions, the two nonsubcapsular tubules fused and had a common connection to the subcapsular tubule. The length, between the macula densa (MD) and the confluence, of subcapsular tubules (2.68 +/- 0.15 mm) significantly exceeded the length of tubules not in contact with the renal capsule (2.05 +/- 0.10 mm). This difference was mainly due to a longer ICT in subcapsular tubules. Subcapsular tubules always contacted the renal capsule in the early DCT and often again in the ICT. Cells in the early DCT showed more microvilli on the luminal surface and more infoldings of basolateral membranes than cells in the late DCT. The ultrastructure of intercalated cells (I cells) varied within a range of different manifestations and the ultrastructural variation of I cells was similar in all the analyzed tubule segments. Connecting tubule cells and principal cells were similar in ultrastructure in all tubule segments and cortical levels analyzed.

Survey of attitudes towards curriculum reforms among medical teachers in different socio-economic and cultural environments

Background: Curriculum reforms in medical schools require cultural and conceptual changes from the faculty. Aims and Methods: We assessed attitudes towards curriculum reforms in different academic, economic, and social environments among 776 teachers from 2 Western European medical schools (Belgium and Denmark) and 7 medical schools in 3 countries in post-communist transition (Croatia, Slovenia, Bosnia and Herzegovina). The survey included a 5-point Likert-type scale on attitudes towards reforms in general and towards reforms of medical curriculum (10 items each). Results: Teaching staff from medical schools in Bosnia and Herzegovina had a more positive attitude towards reforms of medical curriculum (mean score 36.8 out of maximum 50 [95% CI 36.1 to 37.3]) than those from medical schools in Croatia or Slovenia (30.7 [29.8 to 31.6]) or Western Europe (27.7 [27.1 to 28.3]) (P < 0.001, ANOVA). Significant predictors of positive attitudes towards medical curriculum reform in post-communist transition countries, but not in Western European schools, was younger age, as well as female gender in Bosnia and Herzegovina. Conclusions: Factors influencing faculty attitudes may not be easy to identify and may be specific for different settings. Their identification and management is necessary for producing sustainable curriculum reform.

A comprehensive assessment of medical schools in Bosnia and Herzegovina

Objectives  To perform internal and external evaluations of all 5 medical schools in Bosnia and Herzegovina against international standards.

A Comparison of technologies for database-driven websites for medical education

Static web pages may be easy to setup using text processors or user-friendly web editing software. However, some basic knowledge of the implementation (HTML) is usually needed for final editing and maintenance. As a result many static web pages are left without appropriate updating. With a database driven, dynamic approach web contents may change through user interaction, the pages are usually easier to maintain, and design elements are separated from contents. Database driven solutions (or content management systems) for larger organizations may be purchased at many different levels of complexity. For smaller systems, such as separate courses or projects, they may, however, be developed locally. The present study compares four alternative technologies for database driven web pages. Each technology offers advantages and disadvantages and many issues need to be considered when selecting platform. The present study demonstrates that database driven web pages may be effectively deployed using free Open Source software. Details may be found at www.intermed.dk/datadriven.