Using 3D animations to teach intracellular signal transduction mechanisms: taking the arrows out of cells

Traditional methods of teaching intracellular biological processes and pathways use figures or flowcharts with the names of molecules linked with arrows. Many veterinary students, presented with such material, simply memorize the names or chemical structures of the molecules and are then likely to forget the material once the examination is completed. To address this problem, the authors designed, created, and field-tested new teaching media that incorporate realistic three-dimensional (3D) animations depicting the dynamic changes that occur in intracellular molecules during cellular activation. Testing found that veterinary students taught using traditional teaching media (e.g., lectures, handouts, textbooks) are proficient in memorizing the names and order of intracellular molecules but unable to appreciate the interactions between these elements or their spatial relationships within cells. In contrast, more than 90% of veterinary students taught using 3D animations not only recall the facts about the intracellular elements but also develop accurate mental images of the interactions among these molecules and their spatial relationships. These findings strongly suggest that the comprehension of complex biological processes by veterinary students can be enhanced by the use of dynamic 3D depictions of these processes in the classroom.     

La chromatographie sur couche mince: Principes et possibilités

Résumé Après un bref rappel des avantages de la chromatographie de surface sur la chromatographie sur colonne, on compare les avantages et les inconvénients respectifs de la chromatographie sur couche mince et de la chromatographie sur papier. Les méthodes générales de la chromatographie sur couche mince (CCM) sont présentées (préparation des couches, types de couches, dépot des échantillons à analyser, CCM analytique, CCM préparative, moyens de développement des chromatogrammes). Les principes généraux des divers types de chromatographie (adsorption, partage direct, partage inversé, relargage, exclusion-diffusion, échange d'ions, spécifique) qui peuvent être mis en oeuvre sont rappelés et des exemples concrets sont donnés dans chaque cas. Les problèmes de l'électrophorése et de la chromato-electrophorése sur couche mince sont également évoqués. Bien que cette méthode analytique soit le plus simple et le puissant moyen de séparation des corps en mélange, il est nécessaire de rappeler que bien des erreurs de conception sont à la base de son manque de développement dans certains domaines (chromatographie des substances hydrosolubles par exemple). A titre d'exemple on rappelle que la première chromatographie de relargage et la première chromato-electrophorése basse tension n'ont été réalisées que tout récemment.

---

Summary After a brief summary of the advantages of surface chromatography compared to column chromatography, the respective advantages and inconveniences of thin-layer and paper chromatography are compared. The general methods of thin-layer chromatography are presented (preparation of the layers, types of layers, deposition of the samples to be analyzed, analytical TLC, preparative TLC, methods for developing the chromatograms). The general principles of the various types of chromatography (adsorption, direct partition, reverse partition, salting out, exclusion-diffusion, ion-exchange, specific chromatography) that may be used are reminded of, and concrete examples given in each case. The problems of electrophoresis and thin layer chromato-electrophoresis are also treated. Though this analytical method be the simplest and most powerful means for the isolation of components in mixtures, it is necessary to remind that quite a number of errors in the conception are responsible for its lack of development in certain fields (water soluble substances chromatography, for instance). As an example one might remember that the first salting-out chromatography, and the first low-tension chromatoelectrophoresis have been developed only very recently.

---

Zusammenfassung Die Vorzüge der Oberflächen-Chromatographie gegenüber der Säulen-Chromatographie wurden kurz aufgezählt und die Besonderheiten der Dünnschicht- und der Papier-Chromatographie verglichen. Die Grundlagen der DC werden erklärt (Vorbereitung der Schicht, Arten der Schicht, Auftragen der Proben, analytische DC, vorbereitende DC, Entwicklungsverfahren der Chromatogramme). Anschließend werden die grundsätzlichen Verfahren der verschiedenen Typen von Chromatographie erörtert (Adsorption, direkte Trennung, inversierte Trennung, Aussalzen, Diffusion, Ionenaustausch, spezifische Verfahren), die praktisch infrage kommen. Für jeden Typ werden Beispiele gegeben. Die Probleme der Elektrophorese und der Elektrophorese-DC werden ebenfalls behandelt. Obwohl diese Analysenmethode das einfachste und stärkste Trennverfahren für Stoffgemische ist, so muß daran erinnert werden, daß ihre Entwicklung in gewissen Gebieten durch Fehler in der Auffassung gehemmt worden ist, zum Beispiel ihre Anwendung für wasserlösliche Stoffe. Verfasser weist darauf hin, daß die erste Aussalz-DC und die erste Niederspannungs-Chromato-Elektrophorese erst ganz kürzlich realisiert wurden.

---

---

Avec la collaboration technique de MademoiselleCh. Thommegay et de MademoiselleA.-M. Drapier.     

Ballistic 2-d imaging through scattering walls using an ultrafast optical kerr gate

An ultrafast optical shutter was used to image ultrasmall objects hidden behind scattering walls by a procedure that selects in time the ballistic component and rejects the scattered diffusive light. Scattering walls used in this experiment included human breast tissue, chicken breast tissue, and a water suspension of polystyrene particles with scattering coefficients up to 21.7. Submillimeter resolution was achieved for two-dimensional ballistic images of a single point, a double-point fluorescence source, and a bar test chart in or behind these different turbid media.     

Comparative study of Kenaf varieties and growing conditions and their effect on kraft pulp quality

Kenaf (Hibiscus cannabinus L.) is an annual plant which produces a very high fiber yield per hectare and has demonstrated to be a suitable material for pulping. The crop conditions influence fiber production, but there is no information about their effect on pulp quality. The aim of this work was to study the effect of kenaf varieties and crop conditions (watering dose and harvesting time) on sulfate pulp quality. The study has been made on bast fiber sulfate pulps due to their high added value. The quality criteria were fiber dimensions, chemical composition and pulp quality. Kenaf variety or crop conditions have significant effect on fiber dimensions, holocellulose content, kappa number and breaking strength. To obtain high fiber yield and good delignified pulps it is recommended to grow the Salvador variety and to employ advance harvesting. Received: 20 January 1999