Prolonged hypokalemia causes vasopressin-resistant polyuria. We have recently shown that another cause of severe polyuria, chronic lithium therapy, is associated with decreased aquaporin-2 (AQP2) water channel expression (Marples, D., S. Christensen, E.I. Christensen, P.D. Ottosen, and S. Nielsen, 1995. J. Clin. Invest. , 95: 1838-1845). Consequently, we studied the effect in rats of 11 days' potassium deprivation on urine production and AQP2 expression and distribution. Membrane fractions were prepared from one kidney, while the contralateral kidney was perfusion-fixed for immunocytochemistry. Immunoblotting and densitometry revealed a decrease in AQP2 levels to 27 Ϯ 3.4% of control levels ( n ϭ 11, P Ͻ 0.001) in inner medulla, and 34 Ϯ 15% of controls ( n ϭ 5, P Ͻ 0.05) in cortex. Urine production increased in parallel, from 11 Ϯ 1.4 to 30 Ϯ 4.4 ml/day ( n ϭ 11, P Ͻ 0.01). After return to a potassium-containing diet both urine output and AQP2 levels normalized within 7 d. Immunocytochemistry confirmed decreased AQP2 labeling in principal cells of both inner medullary and cortical collecting ducts. AQP2 labeling was predominantly associated with the apical plasma membrane and intracellular vesicles. Lithium treatment for 24 d caused a more extensive reduction of AQP2 levels, to 4 Ϯ 1% of control levels in the inner medulla and 4 Ϯ 2% in cortex, in association with severe polyuria. The similar degree of downregulation in medulla and cortex suggests that interstitial tonicity is not the major factor in the regulation of AQP2 expression. Consistent with this furosemide treatment did not alter AQP2 levels. In summary, hypokalemia, like lithium treatment, results in a decrease in AQP2 expression in rat collecting ducts, in parallel with the development of polyuria, and the degree of downregulation is consistent with the level of polyuria induced, supporting the view that there is a causative link. ( J. Clin. Invest.

BackgroundAs more and more information technology (IT) resources become available both for support of campus- based medical education and for Web-based learning, it becomes increasingly interesting to map the information technology resources available to medical students and the attitudes students have towards their use.ObjectiveTo determine how extensively and effectively information handling skills are being taught in the medical curriculum, the study investigated Internet and computer availability and usage, and attitudes towards information technology among first-year medical students in Aarhus, Denmark, during a five-year period.MethodsIn the period from 1998 to 2002, students beginning the first semester of medical school were given courses on effective use of IT in their studies. As a part of the tutorials, the students were asked to complete a web-based questionnaire which included questions related to IT readiness and attitudes towards using IT in studies.ResultsA total of 1159 students (78%) responded. Overall, 71.7% of the respondents indicating they had access to a computer at home, a number that did not change significantly during the study period. Over time, the power of students' computers and the use of e-mail and Internet did increase significantly. By fall 2002, approximately 90% of students used e-mail regularly, 80% used the Internet regularly, and 60% had access to the Internet from home. Significantly more males than females had access to a computer at home, and males had a more positive attitude towards the use of computers in their medical studies. A fairly constant number of students (3-7%) stated that they would prefer not to have to use computers in their studies.ConclusionsTaken together with our experience from classroom teaching, these results indicate optional teaching of basic information technology still needs to be integrated into medical studies, and that this need does not seem likely to disappear in the near future.

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.

Kidney enlargement in streptozotocin (STZ) diabetic rats is well documented [1][2][3][4]. This growth is mainly due to hyperplasia and to a lesser extent to cellular hypertrophy [2,5]. After insulin treatment and normalization of blood glucose concentration (BGS), kidney weight and glomerular volume decrease [6]. However, little is known about how fast the morphology changes following normalization of BG by insulin treatment and about the morphology of the diabetic kidney after insulin treatment or fasting.In the present study, quantitative estimation of each tissue component was performed during experimental diabetes and during insulin treatment. The results were compared with the kidney weight response and morphology in fasted diabetic animals and with the kidney weight and morphology in normal animals with hyperglycaemia induced by i. v. glucose injection.Information on kidney morphology in hyperglycaemia and normoglycaemia is a prerequisite to understanding better the physiological abnormalities found in diabetic patients. Diabetologia (1997) 40: 802-809 Quantitative morphology of the rat kidney during diabetes mellitus and insulin treatment Summary A morphometric study was performed on moderately hyperglycaemic streptozotocin diabetic rats after 10 and 50 days of diabetes, and on groups of rats that, after initial hyperglycaemia for 50 days, were insulin treated for 2 h or for 5, 15 or 38 days. A group of hyperglycaemic diabetic animals were fasted for 18 h. Another group of rats had acute hyperglycaemia induced by intravenous glucose injection. After 10 and 50 days of diabetes, kidney weight was increased by 55 and 93 %. Glomerular volume, tubule length, and tubular and interstitial volume increased in diabetic animals compared with controls. After 4 h insulin treatment, the kidney weight was 20 % decreased; after 5 days it was 31 % decreased. After 38 days the kidney weight was still 26 % greater than in controls. In diabetic animals, 18 h fasting induced a 30 % decrease in kidney weight. In normal animals, acute hyperglycaemia induced a 22 % increase in kidney weight. Volume fractions of most kidney structures remained similar in all groups. However, the glomerular volume fraction was smaller during kidney enlargement, and the tubular volume fraction was larger after induced hyperglycaemia compared with controls. In conclusion, high blood glucose levels in diabetic and normal animals are associated with increased kidney weight. In hyperglycaemic diabetic animals, normalization of blood glucose after insulin treatment or fasting was followed by a decrease in kidney weight. [Diabetologia (1997) 40: 802-809] Keywords Diabetes mellitus, experimental, kidney, diabetic nephropathy, morphometry.Received: 14 October 1996 and in revised form: 4 April 1997Corresponding author: Dr. R. Rasch, Department of Cell Biology, Institute of Anatomy, University of Aarhus, Building 234, DK-8000 Aarhus C, Denmark Abbreviations: CN, Controls; DH10, diabetic, hyperglycaemic for 10 days; DH50, diabetic, hyperglycaemic for 5...

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