Introduction to electron microscopy university educational programme for secondary schools.

Transcription

1 Introduction to electron microscopy university educational programme for secondary schools. Eliza Rybska *1, Jerzy Błoszyk 2, 3 and Zbigniew Adamski 4, 5 1 The Faculty Laboratory for Teaching Biology and Natural Science. Faculty of Biology, Adam Mickiewicz University, Poznan, Poland, 2 Department of General Zoology/ 3 Natural History Collection, Faculty of Biology, Adam Mickiewicz University, Poznan, Poland, 4 Electron and Confocal Microscope Laboratory/ 5 Department of Animal Physiology and Developmental Biology, Faculty of Biology, Adam Mickiewicz University, Poznan, Poland Teaching programme of the secondary schools in Poland includes both theoretical and practical lessons concerning light microscopy. Also International Baccalaureate Programme (IB) demands diverse usage of light microscopes. At the same time basic rules of electron microscopy are learned. However, these types of microscopes are described only theoretically. Therefore, they seem to be little bit abstract for secondary school students. Hence, Faculty of Biology of Adam Mickiewicz University eagerly meets secondary schools half way and offers practical lessons for pupils who want to see and use electron microscopes. Of course, such lessons are limited in time and number, partially due to elaborated, time consuming and skill-demanding protocols, in part due to research and teaching activity of the university. However, we elaborated short teaching programme, which may be useful during secondary school teaching. It consists of introductory lecture, that describes basics of electron microscopy. Next, we present its application, practical usage and show importance of that devices in life sciences, medicine and industry. Then, we present transmission electron microscope (TEM) and supplementary equipment. Students acquire knowledge about preparation of samples (fixation, sectioning etc.) and observe samples (plant and animal cells, various tissues) under TEM. Fourth step is a kind of a brainstorming students plan, what they want to see under scanning electron microscope (SEM) and how it can be observed. They give a research question and state some hypotheses. They evaluate, whether they can use SEM for their research. Next, they prepare samples and observe them under SEM, with measurement and statistical analysis, if possible. The final step is presentation of data, organized as scientific mini-session, with posters and oral presentations given to the audience. In this chapter we show brief examples of protocols and ideas for scenarios of lessons organized for groups of secondary school students. With some limitations, whole programme or it s elements can also be applied for mid-school classes. Keywords electron microscopy practical; secondary school. Introduction Microscopy is one of the crucial techniques used in biology. Numerous types of microscopes are extensively used by science and bring many important scientific data (Curry, 2003, Adamski et al., this volume). Therefore, basics of microscopy are taught at various levels of teaching. In Poland, some elementary information about microscopy are given already in primary schools (Core Curriculum, Dz. U. z 2009, Nr 4, poz. 17). Next steps of teaching involve not only theoretical knowledge of basics of microscopy or simple presentation of their work, but also some experiments and observations. However, due to obvious limitations, these practical lessons are limited to simple light microscopy. The other, more sophisticated devices and methods are only briefly described. This refers to electron microscopy, too. Nevertheless, electronograms are presented when ultrastructure is taught, during cytology, botany, zoology, and physiology lessons. Obviously, practical knowledge or extended presentations can give them better understanding of the sophisticated methods of microscopy. Because of the abovementioned reasons, we decided to develop a course, at the Faculty of Biology of Adam Mickiewicz University, which shows, describes and brings electron microscopy closer to pupils. This programme consists of five parts, which are also steps to the next one: 1) introductory lecture, 2) TEM presentation, 3) planning SEM, 4) SEM practicals, and finally, 5) presentation of obtained data. The course we propose is in tune with both Polish and EU general university teaching system (Tab. I III). It is noteworthy to add, that the course demands teamwork, what promotes social skills among pupils. Due to school programme and limited time, we focus on basic forms TEM and SEM methods FORMATEX 977

2 Course content 1. Introductory lecture The lecture focuses on basics of electron microscopy. We explain that electrons can be treated both as subatomic particles and as waves. Next, structure of microscopes is shown and briefly described. As the third thing, we discriminate between transmission and scanning microscope, describe techniques used to prepare samples. As a last point application of both types of microscopes in various branches of science is shown. We expect, that after this lecture pupils will describe electron microscopes, characterize their structure and mechanism of obtaining images. They will also be able to give numerous examples of electron microscopy usage in various branches of science, not only in biology, but also in medical or technical sciences. The whole lecture takes about 2 hours. It is illustrated with electronograms and finally evolves into discussion about possible usage of the electron microscopes nowadays and in a future. 2. Transmission electron microscopy - presentation Next, pupils are invited to TEM facility. They are acquainted with this type of microscope in practice. The structure of TEM is shown, as well as ultramicrotomes, grids, fixatives etc. They can observe some of the steps of sample preparation, e.g. fixation, dehydration, embedding, sectioning. The final step of this part is observation of various biological samples under TEM. We emphasize high resolution and magnification power as two very important virtues of TEM. Pupils are taught how to distinguish between plant and animal cell, how to recognize various organelles on the basis of the number of biological membranes and other characteristic features. They try to find connection between number and location of specific organelles and their role. We show for example gut columnar cells and pupils try to find connection between: a) presence of microvilli in midgut cells and their role in these cells, b) high number and location of mitochondria and transport across membrane or presence of cilia, c) presence of rough endoplasmic reticulum and activity of gut cells. Due to complicated and time-consuming method of sample preparation, we do not organize practical course concerning TEM. 3. Scanning electron microscope - presentation After finishing TEM activities, pupils move to scanning electron microscope. As in case of TEM, they are familiarized with the microscope, additional equipment (sputter coater, critical point dryer) and methods of sample preparation. They observe the simple method of preparation of dry and hard samples like hair, seeds, arthropods, coins etc. After that, they can observe these samples under SEM. By showing pictures of the same objects taken under light microscopes, we put special attention to the resolution as advantage of SEM. Participants of the course are also acquainted with software which enables measurement of various structures. For example, the participants give samples of their hair. Then they can compare their condition and refer it to cosmetics they use (or they do not use), measure the thickness of hair. Here, we put special attention to circumstances, which are necessary for properly carried out experiments (control, measurement at the same height of the hair, repetition). After that, we smoothly move to the next point participants plan to organize their own research using scanning microscope. 4. Plan of the experiments on SEM Now, pupils are asked to form a research question and to state the hypothesis, which can be proved or rejected after simple research with usage of SEM. The participants work in small groups (3-4 people). First, they make a kind of brainstorming within their groups. Then, they share their ideas (they state a research question, a hypothesis, show the plan of their experiments) with other groups. After constructive discussion, they can modify/perform their experiment or if they are unlucky, form reorganize their research plan. Under supervision of university teaching staff they plan the schedule of the experiment. After some hours, in the next day, they bring their samples and prepare specimens for SEM. 5. Scanning electron microscopy - practicals After planning, pupils carry out their experiments. Here are some examples of research questions: a) What material is the best for bike saddle production? b) Do different types of chocolate differ in structure? c) Effect of eyelash cosmetics on their thickness. d) What is the size of pollen grains of various species? e) Structure of eggshell of various species FORMATEX 978

3 Current Microscopy Contributions to Advances in Science and Technology (A. Méndez-Vilas, Ed.) With the help of the personnel of the EM laboratory, they are preparing the samples and observe them under SEM (Fig. 1). If measurement is necessary, they carry it out. After that, they collect their row data and electronograms. Fig. 1. Student prepare bird s eggshell for SEM activity. 6. Presentation of data The next step, presentation of data can be carried out at schools or at the university. We want to pay special attention to the effective cooperation within groups. Pupils prepare oral presentations or posters and present them to the audience: scientists, teachers and colleagues. This step demands a plenty of their own work, like for example choosing proper type of presentation of results, data analysis using statistical methods, showing image magnification, choosing properties of printing etc. This demands effective teamwork, responsibility and role shearing. Usually, this is their first team research and first public presentation. To some extent and with obvious limitations, some elements of this layout can be adapted to lower schools. Short presentation of SEM is interesting even for kindergartens (Fig. 2). Fig. 2. Kindergarteners observe objects visible under SEM. To sum up, the course gives a plenty of useful knowledge to the pupils, either of the field of cellular biology and histology or microscopy itself. It brings to the schools the methods, which are usually just theoretically described. We think that this type of course develops creativity, diligence and effective teamwork. Several forms of transfer of knowledge are used: lecture, presentation, discussion, experimental work. For many pupils it is the first or even the only time when they can take part in scientific work. Therefore, this kind of course is highly advisable to schools FORMATEX 979

4 Table I. Aims of the course. A1 A2 A3 A4 A5 A6 A7 A8 Physical basics of electron microscopy, with reference to light microscopy Structure of electron microscopes, with reference to light microscopy Types of electron microscopes Preparation of samples Electron microscopy imaging Ultrastructure of various types of cells structure and function of specific organelles Electron microscopy in science Scientific research planning, experimentation, data analysis, data presentation Table II. Expected effects of teaching Effects of teaching After completing the course, the participant should be able to: Ref. to the aim (A) E1 explain the basics of light and electron microscopy A1, A2, A3 E2 characterize similarities and differences between scanning and transmission electron microscopes A2, A3, A5 E3 describe the basic methods of sample preparation A3, A4 E4 recognize various types of cells, various organelles and find connection between cell structure and function A5, A6 E5 describe usage of electron microscopy in various branches of science A3, A4, A5, A6, A7 E6 plan scientific research and how to carry it out A3, A4, A5, A7, A8 E7 analyze scientific data and how to present it A5, A8 Table. III. Programme content Content Description of the programme content Ref. to effects of teaching (E) C1 Microscopes history and state-of the art E1 C2 The need of electron microscopes in science E1 C3 Basics of electron microscopy E1, E2 C4 Sample preparation E2, E3 C5 Safety precautions during work E2, E3, E4 C6 Observation of various structures under electron microscopes E4 C7 Electron microscopy in science nowadays usage and possible usage in a future E5 C8 Scientific research using scanning electron microscope E2, E3, E5, E6 C9 Data analysis, data presentation. E5, E FORMATEX 980

5 [1] Core Curriculum, in Polish - Podstawa programowa, Rozporządzenie Ministra Edukacji Narodowej z 23 grudnia 2008 roku w sprawie podstawy programowej Dz. U. z 2009, Nr 4, poz. 17 [2] Adamski Z., Rybska E., Błoszyk J. Pros and cons of scanning electron microscopy as a research method in acarology. This volume. [3] Curry A., Electron microscopy and the investigation of new infectious diseases. International Journal of Infectious Diseases I Vol. 7, Number 4, pp FORMATEX 981