Article Triatominae Biochemistry goes to School: Evaluation of a Novel Tool for Teaching Basic Biochemical Concepts of Chagas Disease Vectors
Leonardo Rodrigues Cunha†,‡ Cecılia de Oliveira Cudischevitch†,‡ Alan Brito Carneiro†,‡ Gustavo Bartholomeu Macedo†,‡ Denise Lannes†,‡ rio Alberto Ma Cardoso da Silva Neto†,‡*
rio de Sinalizac¸a~o Celular (LabSiCel), Instituto de From the †Laborato dica Leopoldo de Meis, Universidade Federal do Rio de Bioquımica Me dio do Centro de Janeiro, Rio de Janeiro, Brasil, CEP 21941-902, ‡Pre ^ ncias da Sau de, Bloco D, Subsolo, Sala 05, Cidade Universitaria, Cie Ilha do Funda~o, Rio de Janeiro, Rio de Janeiro, Brasil, CEP 21941-902
Abstract We evaluate a new approach to teaching the basic biochemistry mechanisms that regulate the biology of Triatominae, major vectors of Trypanosoma cruzi, the causative agent of Chagas disease. We have designed and used a comic book, “Carlos Chagas: 100 years after a hero’s discovery” containing scientific information obtained by seven distinguished contemporary Brazilian researchers working with Triatominaes. Students (22) in the seventh grade of a public elementary school received the comic book. The study was then followed up by the use of Concept Maps elaborated by the students. Six Concept Maps elaborated by the students before the introduction of the comic book
Keywords: Chagas Concept Maps
disease;
education;
insect
biochemistry;
Introduction There are over 14,000 species of arthropods that feed on blood, spread over 400 genera and at least eight families, which are grouped into four different orders of insects [1]. From the standpoint of parasitology, hematophagy provides a scenario for the transmission of diseases to vertebrates. In order to complete their life cycle several pathogenic
*Address for correspondence to: Mario Alberto Cardoso da Silva Neto, Universidade Federal do Rio de Janeiro, Instituto de Bioquimica Medica, Av. Carlos Chagas Filho 373, Rio de Janeiro, Rio de Janeiro, Brazil 21941-902. E-mail: [email protected]. Received 3 October 2013; Accepted 5 March 2014 DOI 10.1002/bmb.20795 Published online 31 March 2014 in Wiley Online Library (wileyonlinelibrary.com)
Biochemistry and Molecular Biology Education
received an average score of 7. Scores rose to an average of 45 after the introduction of the comic book. This result suggests that a more attractive content can greatly improve the knowledge and conceptual understanding among students not previously exposed to insect biochemistry. In conclusion, this study illustrates an alternative to current strategies of teaching about the transmission of neglected diseases. It also promotes the diffusion of the scientific knowledge produced by Brazilian researchers that may stimulate students to choose a scientific career.CopyC 2014 by The International Union of Biochemistry right V and Molecular Biology, 42(4):323–330, 2014.
microorganisms, must move from one host to another, usually through vector saliva or by the excretion of contaminated feces close to the lesions produced in human skin by the vectors mouth parts [2]. Hematophagy arose several times between 65 and 145 million years ago and bloodsucking arthropods have evolved several different biochemical mechanisms that allow them to feed on blood. These include the host-seeking behavior, which is guided by a complex set of neuroendocrine circuits. Olfactory sensors indicate the presence of the host and its exact localization in the environment. Localization is usually achieved by the sensing of specific metabolic products released on host skin and in some cases processed by skin microbiota [3]. Blood ingestion is achieved by specialized mouth parts as well as by a wide array of anti-hemostatic molecules that counteract platelet aggregation, vasoconstriction, and blood clotting [4]. Blood digestion is the result of proteolytic attack of specific components of the blood, especially hemoglobin,
323
Biochemistry and Molecular Biology Education whose degradation will release the powerful pro-oxidant molecule heme [5]. Therefore, hematophagy relies on several antioxidant defenses in both insect gut and hemolymph that may include specific heme-binding molecules as well as specific pathways for its detoxification. Nutrients released by blood digestion will find their way through the insect gut and fat body, an organ that unites the biological functions of the mammalian liver and adipose tissue. The fat body is the site of vitellogenin (Vg) synthesis, the major component of insect eggs [6]. Together with a series of both essential and accessory molecules, Vg is required for egg development and will be packed usually through receptor-mediated endocytosis into growing oocytes inside the maternal body. Finally, once the egg is deposited in the environment, embryo development will take place and give rise to another blood feeder. The majority of endemic diseases belong to a group called neglected diseases, which usually affect the poorest populations in the tropics. Among them are parasitic diseases such as malaria, leishmaniasis and Chagas disease [7]. Chagas disease, or American trypanosomiasis, is caused by Trypanosoma cruzi; a protozoan parasite originally described in 1909 by Carlos Chagas, an investigator at Oswaldo Cruz Institute (Fiocruz) in Brazil. It is estimated that this endemic disease affects over 15 to 17 million people in Latin America, where 75 to 90 million people are currently at risk of infection [8]. An adequate policy for health education would provide disease prevention and treatment and should address all citizens. Therefore, the Ministry of Health, in conjunction with other areas of government such as Education and Social Welfare, should act together in order to achieve the widest dissemination of knowledge among people [9]. Rhodnius prolixus belongs to the order Hemiptera, suborder Heteroptera, family Reduviidae, subfamily Triatominae contains five to six tribes, with 17 genera, counting more than 130 species. The genera Rhodnius, Panstrongylus, and Triatoma are the most important as Chagas disease vectors, with R. prolixus as the primary representative (present in Brazil, Colombia, Venezuela, Guyana, Central America and southern Mexico). They are parametabolous insects having five nymphal instars and the adult stage. These insects are highly efficient blood feeders with the blood meal being crucial to molting, progression through the life cycle and reproduction. The fact that their life cycle and basic biology is so tightly regulated by a blood meal led the renowned insect physiologist Sir V.B. Wigglesworth to use Rhodnius as an experimental model. His work yielded many key discoveries about how insect physiology, molting, growth and reproduction are regulated [10]. Overall, studies of the biology of blood feeders have revealed several unique biochemical aspects based on recent experiments with R. prolixus. This species deploys very curious and sometimes exclusive biochemical and metabolic tricks to achieve its reproductive goals. The composition of its saliva and especially its action on human
324
skin are associated with unique anti-hemostatic components that include a family of proteins known as nitrophorins [4]. These proteins are themselves a cocktail of antihemostatic activities. They deliver nitric oxide to promote host vasodilation, inhibition of platelet aggregation, and the blocking of clotting, and they also possess anti-histaminic properties. In fact, these molecules are markers of coevolution between the human host and triatominae [11]. Bug saliva also contains immunosupressors such as lysophospholipids, derived from membrane components such as phosphatidylcholine. In the presence on T. cruzi, these bioactive lipids enhance parasite transmission in isolated host cells as well as systemically [12, 13]. Another major finding is the complex array of heme detoxification mechanisms in Rhodnius which include the polymerization of this molecule into hemozoin but also display specific pathways for the production of antioxidant molecules such as urate in response to heme ingestion [5]. Chagas disease is currently under control in most regions of the Americas and especially in Brazil. However, we must keep in mind (as well as in the government agenda) that multiple genus of Triatominae present in nature. Serve as a source of new species of triatomines that can easily occupy the niche of eliminated species. Moreover, the complete elimination of Triatoma infestans, a major vector of Chagas disease, still requires measures to identify and destroy residual foci. These concepts are applicable to any other disease caused by blood-sucking arthropods especially after the apparent control of the transmission. Given the importance of education as a tool to combat different diseases it is important that professionals in this area should not limit their actions to exclusively technical and mechanical processes of transferring knowledge. Instead, they need to explore new contents and learning activities involving their students daily lives. Science popularization is meant to familiarize the public with the nature of the work on science and the scientist’s life. This is how the great discoveries of science reach the population and fulfill the promise of an adequate education to combat various diseases, through the knowledge of mechanisms of contamination. The study focused on evaluating the effectiveness of using a comic book as a novel instructional strategy for introducing 7th grade students to the basic biochemical concepts of Chagas disease vectors conducted by Brazilian scientists in the last century after Carlos Chagas description of the disease. The evaluation is carried out by analyzing the change in students concepts of Chagas disease and its vector.
Material and Methods Students We applied our methodology to 22 students (ages between 12 and 14 years old) in the seventh grade of the public elementary school Anısio Teixeira (EMAT) located in Serenata,
Basic Biochemical Concepts of Chagas Disease Vectors
40, Jardim Guanabara, Rio de Janeiro, Brazil. This school was chosen because it has a full class schedule and is located close to UFRJ. The school serves students from deprived areas in the surrounding neighborhood. In the morning, students have regular classes and in the afternoon several activities after school such as workshops and sports, according to the interest of each one. The students enrolled in the present study were those enrolled in the elective science laboratory offered by the school in the afternoon.
Topic Selection for the Scientific Content of the Comic Book We have analyzed the major contributions of contemporary Brazilian researchers working on the biology and biochemistry of Triatominae both in Brazil (Hatisaburo Masuda, UFRJ; Pedro Oliveira, UFRJ; Eloi Garcia, Fiocruz; Patricia Azambuja, Fiocruz; Antonio Teixeira, UnB, Jose Jurberg, Marcos Ribeiro, NIH, Bethesda, Fiocruz) and overseas (Jose MD). The researchers authorized the use of their images and information in writing. Their academic careers and major scientific contributions were summarized at the end of the comic book.
Production of the Comic Book The Laboratory of Cellular Signaling (LabSiCel) promoted the production of a comic book with the idea of allowing the introduction of complex scientific topics in the classroom. These concepts would be introduced in a natural, attractive and effective way allowing the students to understand the basic biochemistry behind the whole feeding process of the insect that transmits Chagas disease. The material also aims to shed light on the scientific careers of Brazilian scientists with important contributions to the knowledge of this theme. Therefore, we included a brief biography of each researcher. In the end, all the contents covered in the material are presented formally in a brief explanatory text.
Concept Maps A Concept Map is a schematic structure that represents a set of concepts embedded in a network of propositions. The Concept Map relies heavily on the meaningful learning theory of David Ausubel, who mentions that humans organize their knowledge through a hierarchy of concepts [14]. The construction of concept maps in the manner proposed by Novak and Gowin [15] considers a hierarchical structure of concepts that are presented through both a progressive differentiation and integrative reconciliation of one central concept [14]. It is a demonstration that a person can establish a clear connection to the existing information and also it is able to establish a clear interaction between the new and the previous existing knowledge. Prior knowledge serves as the basis for assigning meanings to new information, and this is presented in constant change as new information is acquired all time. The concept map is a way of
Cunha et al.
representing this process. Being analyzed at different times, is able to demonstrate the process of assigning new meanings to the initial concept evaluating the learner according to the conceptual constructs that he can create, that is, how it structures, hierarchizes, sets, associated, discrimination and integrates concepts. In the present work, this was the measurement tool of choice, since the purpose was to identify how elementary school students structure the new information presented by comic book. The material presented to the student information about the vector of Chagas disease without relating it directly to the disease. The production of a concept map starts with a key concept. Based on this concept the person adds another concept that relates to the initial one. Both concepts are organized as a flowchart (see as follows). The indispensable presence of a word or phrase linking the two causing two concepts forms a clear reasoning. Thus the relation of CONCEPT—CONNECTING WORDS—CONCEPT forms a proposition. The propositions generated from the key concept form a hierarchical structure. In this study a score is assigned to the propositions and hierarchies formed from the key concept, taking into account the cross-links. To analyze the efficiency of the approach to the biochemical issues related to the vector of Chagas disease in the comic book, the concept map assessment tool was chosen, taking into account the score table as descried Nowak and Gowin [16]. We compared three Concept Maps, produced at different times in order to analyze the performance of students before introducing our material, under the immediate effect of material and sometime after the intervention with the educational material through the scoring criteria suggested by Novak and Gowin. The Concept Map was given the keyword "Chagas Disease." At first the students were divided into six groups of three to four each. Their assembly concept maps began with the presentation of the methodology by one of us to the students. The process of map assembly was first explained using the keyword SCHOOL as an example. The production of the Concept Map was worked out by each group; then they were asked to produce a new Concept Map, but now with the keyword CHAGAS DISEASE. The idea of this concept map was to examine how much information the students brought to the classroom about the vector of Chagas disease. In the next visit to the school, students in the same groups formed the first time were presented with the comic book. After 2 hours exploring the new material students were asked for a second Concept Map on the same keyword. The analysis of this second map was designed to evaluate the immediate effect of the comic book tool. About 60 days later, we visited the school again and asked for a third Concept Map by the same group of students. This third round was designed to identify whether the students were still able to use the concepts contained in
325
Biochemistry and Molecular Biology Education
TABLE 1
Scoring criteria for Concept Maps
Classification criteria
Score
Propositions
1
Hierarchy
5
Transversal Links
10 FIG 1
Examples
1
the comic book and make meaningful connections between them. Four main criteria are used to analyze and classify a concept map: propositions, hierarchy, cross links and examples. The analysis of propositions is intended to verify keywords that connect two concepts, indicating their relationship and whether this is correct. As a second criterion applied to the Concept Maps, we analyzed hierarchy, where it checks the validity of the concepts more inclusive or broader themes that should be positioned hierarchically above the more specific concepts or subordinates. The cross-links are reviewed by joining two different horizontal themes to the same concept. If a student uses a link that is creative, it must also be taken into account and scored ensuring quality in the learning of the proposed subject [16]. Please check Table 1 for scores.
Statistical Analysis The results are presented as the means and standard errors of the mean. Normalized data were analyzed by One-way ANOVA using GraphPad Prism software. To compare the results we used the parametric and unpaired t test.
Olfactory receptors on the bugs heads localize the human host through the detection of major products of cell metabolism such as carbon dioxide. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
question should be used by teachers as an opportunity to discuss the morphology of the insect by analysis of what is or is not correct in what was shown in the illustration. The axis of the story goes from the first events of host perception by the blood feeder through its managing of ingested blood and ends in insect reproduction and oogenesis. Figure 1 shows that the bug mainly notices the presence of the host due to the release of carbon dioxide [17]. After landing on host skin the bug starts digging a hole with the aid of its mouthparts which are depicted here as a straw. Figure 2 shows the structure of bug mouthparts and how they allow both the pumping of insect saliva and the simultaneous withdrawal of blood. Blood-sucking arthropod saliva is a cocktail of several different molecules that counterct host hemostasis mechanisms (Fig. 3). In the case of R. prolixus a wide array of different molecules are described: the gas nitric oxide, proteins such as apyrase and nitricoxide carrying molecules (nitrophorins) and lysophosphatidylcholine [4–18]. Figure 4 shows that these “salivary agents” block the activation of host innate immunity and
Results Bug Biochemistry at a Glance The present study was designed to introduce basic biochemistry concepts about blood-sucking arthropods among high school students. The chosen insect is a major vector of Chagas disease in South America, R. prolixus. A strong emphasis was given towards the introduction of major findings on the biochemistry of this insect and especially those described by Brazilian researchers in the area. Therefore it provides the diffusion and an increased awareness of science in Brazil. The story’s central character, Don Barberinni, was inspired by the triatomine vector of Chagas disease itself. The character has an appealing novelty, as he does not follow the standards of a real insect. Instead he wears clothes, has teeth, has only two pairs of legs, walks on its two legs, talks, and uses a straw as mouth parts. These interventions contribute to the playful aspect of an attractive didactical material. The character is humanized to bring the subject as close as possible to the readers. This
326
FIG 2
In the comic book The proboscis is depicted as a straw through which the blood is sucked by the bug while saliva is pumped. Blood feeding relies on the generation of a blood pool under the skin. Jaws are designed from different proboscises breaking small blood vessels. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Basic Biochemical Concepts of Chagas Disease Vectors
FIG 3
Host hemostasis is counteracted by a cocktail of bioactive compounds present in vector saliva that is pumped into the skin. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
inhibit vasoconstriction. Figure 5 explains how a cibarial pump in the bug’s head can be so efficient at withdrawing blood in such a short time [19]. Blood digestion releases the powerful pro-oxidant molecule heme; in the comic book we have shown an industry where the process of blood digestion releases heme and heme toxicity is counteracted by its polymerization into hemozoin [20]. Following blood digestion, the released nutrients are used by the insect’s fat body to synthesize a set of proteins that will drive egg development. VVitellin, the major yolk protein, which will be degraded by maternal proteases soon after egg fertilization [6]. Lipophorin is a major source of phospholipids that will be incorporated into fast diving embryonic cells [6]. Rhodnius heme-binding protein (RHBP) is a source of heme for the embryo and Rhodnius calcium binding protein is a source of calcium [21]. These proteins are depicted as villains in the comic (data not shown).
FIG 4
Cunha et al.
Vector saliva contains a wide array of antihemostatic molecules that block platelet aggregation, clotting and vasoconstriction. The left panel shows white blood cells paralyzed by the action of saliva containing the bioactive lipid lysophosphatidylcholine which thus prevents the immune response. The right panel shows the “agents of saliva” or nitrophorins heme-proteins that act against several aspects of host hemostasis. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
FIG 5
Cibarial pump. Layout features cibarial pump and its importance in accelerating the insect’s feeding. Once hemostasis is counteracted the effectiveness of blood feeding relies on this very potent mechanism to remove host blood in a short period of time. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Evaluation of the Material Among Elementary School Students Students were introduced to the comic book during the year 2009, the centennial anniversary of the description of Chagas disease. To evaluate the effectiveness of the comic book as teaching material, we analyzed the concept maps produced by the children at three different times. They initially produced a Concept Map taking into consideration the concepts they had learned in the classroom with their regular science teacher. At this point the comic book material was not presented nor mentioned. In general, these first maps had some invalid propositions and few concepts related to the key concept, and sometimes, no levels of hierarchy. A few days after the construction of the first Concept Map a second map was produced. These maps showed superior performance compared to the first ones (Fig. 6). Students were able to make valid and meaningful propositions in greater numbers than before and they included concepts that were not part of their daily lives in these propositions. Also the number of hierarchies increased in the second map and some cross-links appeared. However, some groups could not organize the concepts in hierarchical form, making only local connections between the concepts included in the map, or even linking concepts with appropriate propositions, without showing realistic
327
Biochemistry and Molecular Biology Education
FIG 6
Concepts used by students in different Concept Maps produced at different times. a, Map 1 shows the concepts that students had about Chagas’ disease before having access to the comic book “aCarlos Chagas—100 years after a hero’s discovery.” b, Map 2 refers to the time immediately after students have access to the material. Many scientific concepts are incoporated by students in this second round. c, Map 3 shows that the third round, two months after delivery of the comic book. Many concepts included in the second round are maintained.
connections between them. The final concept map was elicited within 60 days of the first contact with the material, but without consulting it. Many concepts that first appeared in the second Concept Map, were retained in the third map, where the formation of hierarchies in the organization of concepts appeared in most cases. The scores attained in the initial concept maps compared with the scores of concept maps in the second round show a dramatic increase in performance (Fig. 6). The third round was not worthy in that most groups performance was even higher, especially when it comes to the production of the Concept Map, forming hierarchical levels in greater numbers (Table 2). However, the number of concepts included in the third round was lower compared to maps produced in the second round. Table 2 shows the significant change that occurred in a comparison of the three rounds. A comparison of all map scores obtained in this study is shown in Fig. 7, which demonstrates that a large final increase in both the hierarchy and total number of concepts was observed for all groups exposed to this Methodology.
Discussion In this study we propose a new approach for teaching basic concepts regarding the biology and biochemistry of human disease vectors. We have chosen the vector of Chagas disease in the Americas for two main reasons: these insects bring
328
together a lot of unique biochemical mechanisms; and the study of Chagas disease is associated with the development of modern scientific research in Brazil, where Chagas disease is ^a and one of the major endemic diseases. According to Gouve Martins [22] children consider that characters in pictures, drawings and comics provide information that does not exactly match reality. This gives the teacher the possibility of promoting a student’s analysis of the content offered to him or her. A Concept Map is a visual representation of a small portion of the cognitive structure. It is an excellent tool to understand how students understand scientific theories. Errors and conceptual problems generally appear on maps as hierarchical map [23]. The assessment of Concept Maps is an important process for teachers and students to allow them to monitor the learning process. Thus we created the scoring criteria for maps taking into consideration the cognitive theory of Ausubel et al [24]. ^ neo [25], student learning is stimuAccording to Liba lated by their interests and needs. The material produced lead exactly to the interest of the learner in the facts mentioned in the comics. The results suggest that the students became more concerned with the concepts presented as long as they are in the reality. The tool chosen as a means of evaluating the students was the Concept Map, applied in three different moments: before introducing with the comic book, to take into consideration the knowledge that the student brought and his experiences in the classroom; after received the comic book; and after some weeks had passed,
Basic Biochemical Concepts of Chagas Disease Vectors
to examine whether the concepts appearing soon after exposure to the material were retained. The initial Concept Maps showed that they had no detailed knowledge about the subject, not demonstrating great variety among concepts related to the keyword. The first maps also lacked appropriate links between these concepts, showing little familiarity with the theme and trying to play on their maps with concepts obtained from regular textbooks. The concept map of round one revealed limitations between the group members with regard to the development of the subject. This was inferred from the presence of very few hierarchical levels, or even their complete absence.
TABLE 2
Concepts mentioned at each phase of map construction
Concepts
Map 1
FIG 7
Map 2
Map 3
X
X
Blood
X
X
Carbon Dioxide
X
X
Ac¸ai
X
Bug
X
Carlos Chagas
X
Chagoma
X
X
Erythrocyte
X
X
Feaces
X
X
Heme
X
X
Hemoglobin
X
X
Iron
X
X
Flagela
Oswaldo Cruz
X
X
Proboscis
X X
X
Cibarial pump
X
X
Receptors
X
X
Saliva
X
X
Scientist
X
Protozoan
Bite
X
X
Triatoma insfestans Trypanosoma cruzi
X X
X
Vector
X
White blood cells
X
Cunha et al.
X
Graph comparing the development of the Concept Maps of the six groups (G1–G6) in each of the three rounds of concept maps. A significant change can be seen in the structural development of the concepts in the second round compared to the first one. The third round of map construction shows that this structure was maintained or increased compared to the two previous occasions.
A few weeks after the first production of a concept map, students were given the comic book “Carlos Chagas: 100 years after a hero’s discovery.” Shortly after their reading of the comic book a new Concept Map was elicited with no material serving as support for consultation. The concept maps produced after contact with the comic showed a performance far superior than those of round one. Students had increased the number of concepts related to the keyword, and on introducing then into their maps they were able to include a greater degree of complexity by making appropriate links between them. There was also a significant increase in levels of hierarchy among the concept of the second round. We infer that the students, at least initially, accepted and became interested in the material, and therefore showed greater resourcefulness in dealing with the concepts. In the third round, sixty days after the presentation of the material, the Concept Maps generated showed that a certain affinity with the previous content was in charge of the comics. Although insertion of complex concepts was less frequent than is the second concept map, hierarchical levels and the propositions of the third map were more significant. In some groups, the performance in test scores increased compared to previous maps. Scores on concept maps show the actual improvement in performance regarding the development of the addressed content. The students showed greater self confidence and property of the mechanisms of olfaction and feeding of the vector of Chagas disease. A very significant and positive change regarding complex scientific information is to keep it in a language that can be understood by the ordinary citizen. When students learn a specific subject using Concept Maps, they develop their own understanding through the internalization of
329
Biochemistry and Molecular Biology Education information. To construct the concept maps students need to develop an initial understanding of the concepts they are studying before being able to represent their knowledge through the map [26]. Thus their regular teacher should be able to participate in the activity, guiding their observations and their development within a constructivist framework that supports the new stance of the teacher as a mentor or facilitator of knowledge [25]. The present material provides a type of content suitable for meaningful discussions in the classroom. Teachers have access to a more attractive material and present contents very limited in textbooks, which usually arouse little interest among students. The comic emerges as a tool for challenging the learner and may, depending on in accordance the teachers approach, encourage the student to further inquiry on the subjects covered, there by expanding the topic being discussed. The results presented in this report do not guarantee that the students have acquired the knowledge, but they do show a significant change with regard to ownership and development of content. It is also possible to identify a different attitude of students toward the concepts they have worked out. The work gives the students greater “ownership” which is in accordance with the assumptions of the Law of Directives and Basis of Brazilian Education where the school must develop the students ability to learn in order to acquire the knowledge and skills, as well as knowledge of the natural environment for the formation of attitudes and values [27]. In conclusion, it is important to note that only individuals who are adequately prepared are not at the mercy of vectorborne diseases. Therefore, it is important that the ordinary citizen, a candidate for contamination through the vectors of major diseases, is well informed about the discoveries of modern science, not only with regard to the disease itself but also the mechanism of and its transmission.
Acknowledgments The authors thank the directors of Escola Municipal Anısio ~ o de Amparo a Pesquisa Carlos ChaTeixeira and Fundac¸a gas Filho do Estado do Rio de Janeiro, Brazil, FAPERJ. This study was possible due to the grants by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) through Instituto Nacional de Ciencia e Tecnologia em Entomologia Molecular (INCT-EM). This study is dedicated to the memory of Dr. Alexandre A. Peixoto.
[5] Grac¸a-Souza, A. V., Maya-Monteiro, C., Paiva-Silva, G. O., Braz, G. R., Paes, M. C., Sorgine, M. H., Oliveira, M. F., and Oliveira, P. L. (2006) Adaptations against heme toxicity in blood-feeding arthropods. Insect Biochem. Mol. Biol. 36, 322-335. [6] Atella, G. C., Gondim, K. C., Machado, E. A., Medeiros, M. N., Silva-Neto, M. A., and Masuda, H. (2005) Oogenesis and egg development in triatomines: a biochemical approach. Ann. Acad. Bras. Cienc. 77, 405-430. dica da [7] Krettli, A. U. (2008). Grandes Endemias no Brasil. Gazeta Me Bahia 78, 74-78. [8] Coura, J. R. and Borges-Pereira, J. (2010) Chagas disease: 100 years after its discovery. A systemic review. Acta Trop. 115, 5-13. ~o, D. (2000) Refundac¸a ~o do Sistema Nacional de Sau rum de. In Fo [9] Serra de Economia da Sa ude. Porto 89-102. [10] Edwards, J. S. (1998). Sir Vincent Wigglesworth and the coming of age of insect development. Int. J. Dev. Biol. 42, 471-473. [11] Ribeiro, A. L., Nunes, M. P., Teixeira, M. M., and Rocha, M. O. (2012) Diagnosis and management of Chagas disease and cardiomyopathy. Nat. Rev. Cardiol. 9, 576-589. [12] Mesquita, R. D., Carneiro, A. B., Bafica, A., Gazos-Lopes, F., Takiya, C. M., Souto-Padron, T., Vieira, D. P., Ferreira-Pereira, A., Almeida, I. C., Figueiredo, R. T., Porto, B. N., Bozza, M. T., Grac¸a-Souza, A. V., Lopes, A. H., Atella, G. C., and Silva-Neto, M. A. (2008) Trypanosoma cruzi infection is enhanced by vector saliva through immunosuppressant mechanisms mediated by lysophosphatidylcholine. Infect. Immun. 76, 5543-5552. [13] Silva-Neto, M. A., Fampa, P., Caiaffa, C. D., Carneiro, A. B., and Atella, G. C. (2010) Cell signaling during Trypanosoma cruzi development in triatominae. Open Parasitol. J. 1, 188-194. ^ncias Cognic¸a ~o. [14] Tavares, R. (2007) Construindo mapas conceituais. Cie 12, 72-785. ~o, Cornell University Press, [15] Nowak, J. D. (1977) A teoria da educac¸a Ithaca, New York. tamo, [16] Nowak, J. D. and Gowin, D. B. (1996) Aprender a aprender, Pla ~ es te cnicas, Lisboa. Edic¸o lora-Luna, F., Perret, J. L., and Guerin, P. M. (2004) Appetence behav[17] Ota iours of the triatomine bug Rhodnius prolixus on a servosphere in response to the host metabolites carbon dioxide and ammonia. J. Comp. Physiol. A Neuroethol. Sens. Neural Behav. Physiol. 190, 847-854. [18] Silva-Neto, M. A., Carneiro, A. B., Silva-Cardoso, L., and Atella, G. C. (2012) Lysophosphatidylcholine: A novel modulator of Trypanosoma cruzi transmission. J. Parasitol. Res. 2012, 1-8. [19] Soares, A. C., Carvalho-Tavares, J., Gontijo, N. F., dos Santos, V. C., Teixeira, M. M., and Pereira, M. H. (2006) Salivation pattern of Rhodnius prolixus (Reduviidae; Triatominae) in mouse skin. J. Insect Physiol. 52, 468-472. [20] Oliveira, M. F., Silva, J. R., Dansa-Petretski, M., de Souza, W., Lins, U., Braga, C. M., Masuda, H., and Oliveira P. L. (1999) Haem detoxification by an insect. Nature 400, 517-518 [21] Silva-Neto, M. A., Atella, G. C., Fialho, E., Paes, M. C., Zingali, R. B., Petretski, J. H., Alves, E. W., and Masuda, H. (1996) Isolation of a calciumbinding phosphoprotein from the oocytes and hemolymph of the bloodsucking insect Rhodnius prolixus. J. Biol. Chem. 271, 30227-30232. ^a, G. and Martins, I, in Espac¸os e Imagens na Escola, R. Ross, [22] Gouve Ed., (2001) Nilda Alves e Paulo Sgarbi, Rio de Janeiro. pp. 41-58. [23] Dorough, D. K. and Rye, J. A. (2007) Mapping for understanding. Sci. Teach. 64, 37-41.
References [1] Richards, O. W. and Davies, R. G. (1984) Tratado de Entomologia IMMS. Classificacao y Biologia, Vol. II, Barcelona. [2] Neves, D. P., Melo, A. L., Linardi, P. M., and Vitor, R. W. A. (2005) Para~o Paulo. sitologia Humana, Atheneu, Sa [3] Zwiebel, L. J. and Takken, W. (2004) Olfactory regulation of mosquitohost interactions. Insect Biochem. Mol. Biol. 34, 645-652. [4] Champagne, D. E. (2005) Antihemostatic molecules from saliva of blood-feeding arthropods. Pathophysiol. Haemost. Thromb. 34, 221-227.
330
[24] Ausubel, D. P., Novak, J. D. and Hanesian, H. (1980) Psicologia Educacional, 2nd ed., Interamericana, Rio de Janeiro. ^neo, J. L. (1994) Dida tica. Colec¸a ~o Magiste rio 2 grau, 23rd ed., [25] Liba ~ Serie Formador, Sao Paulo. [26] Vekiri, I. (2002) What is the value of graphical displays in learning? Ed. Psychol. Rev 14, 261. ^ncia da Repu blica do Brasil: Lei de Diretrizes e Bases, 9, 394– [27] Preside ~o III. Avaliable from: http://www.planalto.gov.br/ccivil_ 1996, Cap II, Sec¸a 03/leis/l9394.htm. Accessed on october 5, 2011.
Basic Biochemical Concepts of Chagas Disease Vectors
Leonardo Rodrigues Cunha†,‡ Cecılia de Oliveira Cudischevitch†,‡ Alan Brito Carneiro†,‡ Gustavo Bartholomeu Macedo†,‡ Denise Lannes†,‡ rio Alberto Ma Cardoso da Silva Neto†,‡*
rio de Sinalizac¸a~o Celular (LabSiCel), Instituto de From the †Laborato dica Leopoldo de Meis, Universidade Federal do Rio de Bioquımica Me dio do Centro de Janeiro, Rio de Janeiro, Brasil, CEP 21941-902, ‡Pre ^ ncias da Sau de, Bloco D, Subsolo, Sala 05, Cidade Universitaria, Cie Ilha do Funda~o, Rio de Janeiro, Rio de Janeiro, Brasil, CEP 21941-902
Abstract We evaluate a new approach to teaching the basic biochemistry mechanisms that regulate the biology of Triatominae, major vectors of Trypanosoma cruzi, the causative agent of Chagas disease. We have designed and used a comic book, “Carlos Chagas: 100 years after a hero’s discovery” containing scientific information obtained by seven distinguished contemporary Brazilian researchers working with Triatominaes. Students (22) in the seventh grade of a public elementary school received the comic book. The study was then followed up by the use of Concept Maps elaborated by the students. Six Concept Maps elaborated by the students before the introduction of the comic book
Keywords: Chagas Concept Maps
disease;
education;
insect
biochemistry;
Introduction There are over 14,000 species of arthropods that feed on blood, spread over 400 genera and at least eight families, which are grouped into four different orders of insects [1]. From the standpoint of parasitology, hematophagy provides a scenario for the transmission of diseases to vertebrates. In order to complete their life cycle several pathogenic
*Address for correspondence to: Mario Alberto Cardoso da Silva Neto, Universidade Federal do Rio de Janeiro, Instituto de Bioquimica Medica, Av. Carlos Chagas Filho 373, Rio de Janeiro, Rio de Janeiro, Brazil 21941-902. E-mail: [email protected]. Received 3 October 2013; Accepted 5 March 2014 DOI 10.1002/bmb.20795 Published online 31 March 2014 in Wiley Online Library (wileyonlinelibrary.com)
Biochemistry and Molecular Biology Education
received an average score of 7. Scores rose to an average of 45 after the introduction of the comic book. This result suggests that a more attractive content can greatly improve the knowledge and conceptual understanding among students not previously exposed to insect biochemistry. In conclusion, this study illustrates an alternative to current strategies of teaching about the transmission of neglected diseases. It also promotes the diffusion of the scientific knowledge produced by Brazilian researchers that may stimulate students to choose a scientific career.CopyC 2014 by The International Union of Biochemistry right V and Molecular Biology, 42(4):323–330, 2014.
microorganisms, must move from one host to another, usually through vector saliva or by the excretion of contaminated feces close to the lesions produced in human skin by the vectors mouth parts [2]. Hematophagy arose several times between 65 and 145 million years ago and bloodsucking arthropods have evolved several different biochemical mechanisms that allow them to feed on blood. These include the host-seeking behavior, which is guided by a complex set of neuroendocrine circuits. Olfactory sensors indicate the presence of the host and its exact localization in the environment. Localization is usually achieved by the sensing of specific metabolic products released on host skin and in some cases processed by skin microbiota [3]. Blood ingestion is achieved by specialized mouth parts as well as by a wide array of anti-hemostatic molecules that counteract platelet aggregation, vasoconstriction, and blood clotting [4]. Blood digestion is the result of proteolytic attack of specific components of the blood, especially hemoglobin,
323
Biochemistry and Molecular Biology Education whose degradation will release the powerful pro-oxidant molecule heme [5]. Therefore, hematophagy relies on several antioxidant defenses in both insect gut and hemolymph that may include specific heme-binding molecules as well as specific pathways for its detoxification. Nutrients released by blood digestion will find their way through the insect gut and fat body, an organ that unites the biological functions of the mammalian liver and adipose tissue. The fat body is the site of vitellogenin (Vg) synthesis, the major component of insect eggs [6]. Together with a series of both essential and accessory molecules, Vg is required for egg development and will be packed usually through receptor-mediated endocytosis into growing oocytes inside the maternal body. Finally, once the egg is deposited in the environment, embryo development will take place and give rise to another blood feeder. The majority of endemic diseases belong to a group called neglected diseases, which usually affect the poorest populations in the tropics. Among them are parasitic diseases such as malaria, leishmaniasis and Chagas disease [7]. Chagas disease, or American trypanosomiasis, is caused by Trypanosoma cruzi; a protozoan parasite originally described in 1909 by Carlos Chagas, an investigator at Oswaldo Cruz Institute (Fiocruz) in Brazil. It is estimated that this endemic disease affects over 15 to 17 million people in Latin America, where 75 to 90 million people are currently at risk of infection [8]. An adequate policy for health education would provide disease prevention and treatment and should address all citizens. Therefore, the Ministry of Health, in conjunction with other areas of government such as Education and Social Welfare, should act together in order to achieve the widest dissemination of knowledge among people [9]. Rhodnius prolixus belongs to the order Hemiptera, suborder Heteroptera, family Reduviidae, subfamily Triatominae contains five to six tribes, with 17 genera, counting more than 130 species. The genera Rhodnius, Panstrongylus, and Triatoma are the most important as Chagas disease vectors, with R. prolixus as the primary representative (present in Brazil, Colombia, Venezuela, Guyana, Central America and southern Mexico). They are parametabolous insects having five nymphal instars and the adult stage. These insects are highly efficient blood feeders with the blood meal being crucial to molting, progression through the life cycle and reproduction. The fact that their life cycle and basic biology is so tightly regulated by a blood meal led the renowned insect physiologist Sir V.B. Wigglesworth to use Rhodnius as an experimental model. His work yielded many key discoveries about how insect physiology, molting, growth and reproduction are regulated [10]. Overall, studies of the biology of blood feeders have revealed several unique biochemical aspects based on recent experiments with R. prolixus. This species deploys very curious and sometimes exclusive biochemical and metabolic tricks to achieve its reproductive goals. The composition of its saliva and especially its action on human
324
skin are associated with unique anti-hemostatic components that include a family of proteins known as nitrophorins [4]. These proteins are themselves a cocktail of antihemostatic activities. They deliver nitric oxide to promote host vasodilation, inhibition of platelet aggregation, and the blocking of clotting, and they also possess anti-histaminic properties. In fact, these molecules are markers of coevolution between the human host and triatominae [11]. Bug saliva also contains immunosupressors such as lysophospholipids, derived from membrane components such as phosphatidylcholine. In the presence on T. cruzi, these bioactive lipids enhance parasite transmission in isolated host cells as well as systemically [12, 13]. Another major finding is the complex array of heme detoxification mechanisms in Rhodnius which include the polymerization of this molecule into hemozoin but also display specific pathways for the production of antioxidant molecules such as urate in response to heme ingestion [5]. Chagas disease is currently under control in most regions of the Americas and especially in Brazil. However, we must keep in mind (as well as in the government agenda) that multiple genus of Triatominae present in nature. Serve as a source of new species of triatomines that can easily occupy the niche of eliminated species. Moreover, the complete elimination of Triatoma infestans, a major vector of Chagas disease, still requires measures to identify and destroy residual foci. These concepts are applicable to any other disease caused by blood-sucking arthropods especially after the apparent control of the transmission. Given the importance of education as a tool to combat different diseases it is important that professionals in this area should not limit their actions to exclusively technical and mechanical processes of transferring knowledge. Instead, they need to explore new contents and learning activities involving their students daily lives. Science popularization is meant to familiarize the public with the nature of the work on science and the scientist’s life. This is how the great discoveries of science reach the population and fulfill the promise of an adequate education to combat various diseases, through the knowledge of mechanisms of contamination. The study focused on evaluating the effectiveness of using a comic book as a novel instructional strategy for introducing 7th grade students to the basic biochemical concepts of Chagas disease vectors conducted by Brazilian scientists in the last century after Carlos Chagas description of the disease. The evaluation is carried out by analyzing the change in students concepts of Chagas disease and its vector.
Material and Methods Students We applied our methodology to 22 students (ages between 12 and 14 years old) in the seventh grade of the public elementary school Anısio Teixeira (EMAT) located in Serenata,
Basic Biochemical Concepts of Chagas Disease Vectors
40, Jardim Guanabara, Rio de Janeiro, Brazil. This school was chosen because it has a full class schedule and is located close to UFRJ. The school serves students from deprived areas in the surrounding neighborhood. In the morning, students have regular classes and in the afternoon several activities after school such as workshops and sports, according to the interest of each one. The students enrolled in the present study were those enrolled in the elective science laboratory offered by the school in the afternoon.
Topic Selection for the Scientific Content of the Comic Book We have analyzed the major contributions of contemporary Brazilian researchers working on the biology and biochemistry of Triatominae both in Brazil (Hatisaburo Masuda, UFRJ; Pedro Oliveira, UFRJ; Eloi Garcia, Fiocruz; Patricia Azambuja, Fiocruz; Antonio Teixeira, UnB, Jose Jurberg, Marcos Ribeiro, NIH, Bethesda, Fiocruz) and overseas (Jose MD). The researchers authorized the use of their images and information in writing. Their academic careers and major scientific contributions were summarized at the end of the comic book.
Production of the Comic Book The Laboratory of Cellular Signaling (LabSiCel) promoted the production of a comic book with the idea of allowing the introduction of complex scientific topics in the classroom. These concepts would be introduced in a natural, attractive and effective way allowing the students to understand the basic biochemistry behind the whole feeding process of the insect that transmits Chagas disease. The material also aims to shed light on the scientific careers of Brazilian scientists with important contributions to the knowledge of this theme. Therefore, we included a brief biography of each researcher. In the end, all the contents covered in the material are presented formally in a brief explanatory text.
Concept Maps A Concept Map is a schematic structure that represents a set of concepts embedded in a network of propositions. The Concept Map relies heavily on the meaningful learning theory of David Ausubel, who mentions that humans organize their knowledge through a hierarchy of concepts [14]. The construction of concept maps in the manner proposed by Novak and Gowin [15] considers a hierarchical structure of concepts that are presented through both a progressive differentiation and integrative reconciliation of one central concept [14]. It is a demonstration that a person can establish a clear connection to the existing information and also it is able to establish a clear interaction between the new and the previous existing knowledge. Prior knowledge serves as the basis for assigning meanings to new information, and this is presented in constant change as new information is acquired all time. The concept map is a way of
Cunha et al.
representing this process. Being analyzed at different times, is able to demonstrate the process of assigning new meanings to the initial concept evaluating the learner according to the conceptual constructs that he can create, that is, how it structures, hierarchizes, sets, associated, discrimination and integrates concepts. In the present work, this was the measurement tool of choice, since the purpose was to identify how elementary school students structure the new information presented by comic book. The material presented to the student information about the vector of Chagas disease without relating it directly to the disease. The production of a concept map starts with a key concept. Based on this concept the person adds another concept that relates to the initial one. Both concepts are organized as a flowchart (see as follows). The indispensable presence of a word or phrase linking the two causing two concepts forms a clear reasoning. Thus the relation of CONCEPT—CONNECTING WORDS—CONCEPT forms a proposition. The propositions generated from the key concept form a hierarchical structure. In this study a score is assigned to the propositions and hierarchies formed from the key concept, taking into account the cross-links. To analyze the efficiency of the approach to the biochemical issues related to the vector of Chagas disease in the comic book, the concept map assessment tool was chosen, taking into account the score table as descried Nowak and Gowin [16]. We compared three Concept Maps, produced at different times in order to analyze the performance of students before introducing our material, under the immediate effect of material and sometime after the intervention with the educational material through the scoring criteria suggested by Novak and Gowin. The Concept Map was given the keyword "Chagas Disease." At first the students were divided into six groups of three to four each. Their assembly concept maps began with the presentation of the methodology by one of us to the students. The process of map assembly was first explained using the keyword SCHOOL as an example. The production of the Concept Map was worked out by each group; then they were asked to produce a new Concept Map, but now with the keyword CHAGAS DISEASE. The idea of this concept map was to examine how much information the students brought to the classroom about the vector of Chagas disease. In the next visit to the school, students in the same groups formed the first time were presented with the comic book. After 2 hours exploring the new material students were asked for a second Concept Map on the same keyword. The analysis of this second map was designed to evaluate the immediate effect of the comic book tool. About 60 days later, we visited the school again and asked for a third Concept Map by the same group of students. This third round was designed to identify whether the students were still able to use the concepts contained in
325
Biochemistry and Molecular Biology Education
TABLE 1
Scoring criteria for Concept Maps
Classification criteria
Score
Propositions
1
Hierarchy
5
Transversal Links
10 FIG 1
Examples
1
the comic book and make meaningful connections between them. Four main criteria are used to analyze and classify a concept map: propositions, hierarchy, cross links and examples. The analysis of propositions is intended to verify keywords that connect two concepts, indicating their relationship and whether this is correct. As a second criterion applied to the Concept Maps, we analyzed hierarchy, where it checks the validity of the concepts more inclusive or broader themes that should be positioned hierarchically above the more specific concepts or subordinates. The cross-links are reviewed by joining two different horizontal themes to the same concept. If a student uses a link that is creative, it must also be taken into account and scored ensuring quality in the learning of the proposed subject [16]. Please check Table 1 for scores.
Statistical Analysis The results are presented as the means and standard errors of the mean. Normalized data were analyzed by One-way ANOVA using GraphPad Prism software. To compare the results we used the parametric and unpaired t test.
Olfactory receptors on the bugs heads localize the human host through the detection of major products of cell metabolism such as carbon dioxide. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
question should be used by teachers as an opportunity to discuss the morphology of the insect by analysis of what is or is not correct in what was shown in the illustration. The axis of the story goes from the first events of host perception by the blood feeder through its managing of ingested blood and ends in insect reproduction and oogenesis. Figure 1 shows that the bug mainly notices the presence of the host due to the release of carbon dioxide [17]. After landing on host skin the bug starts digging a hole with the aid of its mouthparts which are depicted here as a straw. Figure 2 shows the structure of bug mouthparts and how they allow both the pumping of insect saliva and the simultaneous withdrawal of blood. Blood-sucking arthropod saliva is a cocktail of several different molecules that counterct host hemostasis mechanisms (Fig. 3). In the case of R. prolixus a wide array of different molecules are described: the gas nitric oxide, proteins such as apyrase and nitricoxide carrying molecules (nitrophorins) and lysophosphatidylcholine [4–18]. Figure 4 shows that these “salivary agents” block the activation of host innate immunity and
Results Bug Biochemistry at a Glance The present study was designed to introduce basic biochemistry concepts about blood-sucking arthropods among high school students. The chosen insect is a major vector of Chagas disease in South America, R. prolixus. A strong emphasis was given towards the introduction of major findings on the biochemistry of this insect and especially those described by Brazilian researchers in the area. Therefore it provides the diffusion and an increased awareness of science in Brazil. The story’s central character, Don Barberinni, was inspired by the triatomine vector of Chagas disease itself. The character has an appealing novelty, as he does not follow the standards of a real insect. Instead he wears clothes, has teeth, has only two pairs of legs, walks on its two legs, talks, and uses a straw as mouth parts. These interventions contribute to the playful aspect of an attractive didactical material. The character is humanized to bring the subject as close as possible to the readers. This
326
FIG 2
In the comic book The proboscis is depicted as a straw through which the blood is sucked by the bug while saliva is pumped. Blood feeding relies on the generation of a blood pool under the skin. Jaws are designed from different proboscises breaking small blood vessels. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Basic Biochemical Concepts of Chagas Disease Vectors
FIG 3
Host hemostasis is counteracted by a cocktail of bioactive compounds present in vector saliva that is pumped into the skin. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
inhibit vasoconstriction. Figure 5 explains how a cibarial pump in the bug’s head can be so efficient at withdrawing blood in such a short time [19]. Blood digestion releases the powerful pro-oxidant molecule heme; in the comic book we have shown an industry where the process of blood digestion releases heme and heme toxicity is counteracted by its polymerization into hemozoin [20]. Following blood digestion, the released nutrients are used by the insect’s fat body to synthesize a set of proteins that will drive egg development. VVitellin, the major yolk protein, which will be degraded by maternal proteases soon after egg fertilization [6]. Lipophorin is a major source of phospholipids that will be incorporated into fast diving embryonic cells [6]. Rhodnius heme-binding protein (RHBP) is a source of heme for the embryo and Rhodnius calcium binding protein is a source of calcium [21]. These proteins are depicted as villains in the comic (data not shown).
FIG 4
Cunha et al.
Vector saliva contains a wide array of antihemostatic molecules that block platelet aggregation, clotting and vasoconstriction. The left panel shows white blood cells paralyzed by the action of saliva containing the bioactive lipid lysophosphatidylcholine which thus prevents the immune response. The right panel shows the “agents of saliva” or nitrophorins heme-proteins that act against several aspects of host hemostasis. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
FIG 5
Cibarial pump. Layout features cibarial pump and its importance in accelerating the insect’s feeding. Once hemostasis is counteracted the effectiveness of blood feeding relies on this very potent mechanism to remove host blood in a short period of time. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Evaluation of the Material Among Elementary School Students Students were introduced to the comic book during the year 2009, the centennial anniversary of the description of Chagas disease. To evaluate the effectiveness of the comic book as teaching material, we analyzed the concept maps produced by the children at three different times. They initially produced a Concept Map taking into consideration the concepts they had learned in the classroom with their regular science teacher. At this point the comic book material was not presented nor mentioned. In general, these first maps had some invalid propositions and few concepts related to the key concept, and sometimes, no levels of hierarchy. A few days after the construction of the first Concept Map a second map was produced. These maps showed superior performance compared to the first ones (Fig. 6). Students were able to make valid and meaningful propositions in greater numbers than before and they included concepts that were not part of their daily lives in these propositions. Also the number of hierarchies increased in the second map and some cross-links appeared. However, some groups could not organize the concepts in hierarchical form, making only local connections between the concepts included in the map, or even linking concepts with appropriate propositions, without showing realistic
327
Biochemistry and Molecular Biology Education
FIG 6
Concepts used by students in different Concept Maps produced at different times. a, Map 1 shows the concepts that students had about Chagas’ disease before having access to the comic book “aCarlos Chagas—100 years after a hero’s discovery.” b, Map 2 refers to the time immediately after students have access to the material. Many scientific concepts are incoporated by students in this second round. c, Map 3 shows that the third round, two months after delivery of the comic book. Many concepts included in the second round are maintained.
connections between them. The final concept map was elicited within 60 days of the first contact with the material, but without consulting it. Many concepts that first appeared in the second Concept Map, were retained in the third map, where the formation of hierarchies in the organization of concepts appeared in most cases. The scores attained in the initial concept maps compared with the scores of concept maps in the second round show a dramatic increase in performance (Fig. 6). The third round was not worthy in that most groups performance was even higher, especially when it comes to the production of the Concept Map, forming hierarchical levels in greater numbers (Table 2). However, the number of concepts included in the third round was lower compared to maps produced in the second round. Table 2 shows the significant change that occurred in a comparison of the three rounds. A comparison of all map scores obtained in this study is shown in Fig. 7, which demonstrates that a large final increase in both the hierarchy and total number of concepts was observed for all groups exposed to this Methodology.
Discussion In this study we propose a new approach for teaching basic concepts regarding the biology and biochemistry of human disease vectors. We have chosen the vector of Chagas disease in the Americas for two main reasons: these insects bring
328
together a lot of unique biochemical mechanisms; and the study of Chagas disease is associated with the development of modern scientific research in Brazil, where Chagas disease is ^a and one of the major endemic diseases. According to Gouve Martins [22] children consider that characters in pictures, drawings and comics provide information that does not exactly match reality. This gives the teacher the possibility of promoting a student’s analysis of the content offered to him or her. A Concept Map is a visual representation of a small portion of the cognitive structure. It is an excellent tool to understand how students understand scientific theories. Errors and conceptual problems generally appear on maps as hierarchical map [23]. The assessment of Concept Maps is an important process for teachers and students to allow them to monitor the learning process. Thus we created the scoring criteria for maps taking into consideration the cognitive theory of Ausubel et al [24]. ^ neo [25], student learning is stimuAccording to Liba lated by their interests and needs. The material produced lead exactly to the interest of the learner in the facts mentioned in the comics. The results suggest that the students became more concerned with the concepts presented as long as they are in the reality. The tool chosen as a means of evaluating the students was the Concept Map, applied in three different moments: before introducing with the comic book, to take into consideration the knowledge that the student brought and his experiences in the classroom; after received the comic book; and after some weeks had passed,
Basic Biochemical Concepts of Chagas Disease Vectors
to examine whether the concepts appearing soon after exposure to the material were retained. The initial Concept Maps showed that they had no detailed knowledge about the subject, not demonstrating great variety among concepts related to the keyword. The first maps also lacked appropriate links between these concepts, showing little familiarity with the theme and trying to play on their maps with concepts obtained from regular textbooks. The concept map of round one revealed limitations between the group members with regard to the development of the subject. This was inferred from the presence of very few hierarchical levels, or even their complete absence.
TABLE 2
Concepts mentioned at each phase of map construction
Concepts
Map 1
FIG 7
Map 2
Map 3
X
X
Blood
X
X
Carbon Dioxide
X
X
Ac¸ai
X
Bug
X
Carlos Chagas
X
Chagoma
X
X
Erythrocyte
X
X
Feaces
X
X
Heme
X
X
Hemoglobin
X
X
Iron
X
X
Flagela
Oswaldo Cruz
X
X
Proboscis
X X
X
Cibarial pump
X
X
Receptors
X
X
Saliva
X
X
Scientist
X
Protozoan
Bite
X
X
Triatoma insfestans Trypanosoma cruzi
X X
X
Vector
X
White blood cells
X
Cunha et al.
X
Graph comparing the development of the Concept Maps of the six groups (G1–G6) in each of the three rounds of concept maps. A significant change can be seen in the structural development of the concepts in the second round compared to the first one. The third round of map construction shows that this structure was maintained or increased compared to the two previous occasions.
A few weeks after the first production of a concept map, students were given the comic book “Carlos Chagas: 100 years after a hero’s discovery.” Shortly after their reading of the comic book a new Concept Map was elicited with no material serving as support for consultation. The concept maps produced after contact with the comic showed a performance far superior than those of round one. Students had increased the number of concepts related to the keyword, and on introducing then into their maps they were able to include a greater degree of complexity by making appropriate links between them. There was also a significant increase in levels of hierarchy among the concept of the second round. We infer that the students, at least initially, accepted and became interested in the material, and therefore showed greater resourcefulness in dealing with the concepts. In the third round, sixty days after the presentation of the material, the Concept Maps generated showed that a certain affinity with the previous content was in charge of the comics. Although insertion of complex concepts was less frequent than is the second concept map, hierarchical levels and the propositions of the third map were more significant. In some groups, the performance in test scores increased compared to previous maps. Scores on concept maps show the actual improvement in performance regarding the development of the addressed content. The students showed greater self confidence and property of the mechanisms of olfaction and feeding of the vector of Chagas disease. A very significant and positive change regarding complex scientific information is to keep it in a language that can be understood by the ordinary citizen. When students learn a specific subject using Concept Maps, they develop their own understanding through the internalization of
329
Biochemistry and Molecular Biology Education information. To construct the concept maps students need to develop an initial understanding of the concepts they are studying before being able to represent their knowledge through the map [26]. Thus their regular teacher should be able to participate in the activity, guiding their observations and their development within a constructivist framework that supports the new stance of the teacher as a mentor or facilitator of knowledge [25]. The present material provides a type of content suitable for meaningful discussions in the classroom. Teachers have access to a more attractive material and present contents very limited in textbooks, which usually arouse little interest among students. The comic emerges as a tool for challenging the learner and may, depending on in accordance the teachers approach, encourage the student to further inquiry on the subjects covered, there by expanding the topic being discussed. The results presented in this report do not guarantee that the students have acquired the knowledge, but they do show a significant change with regard to ownership and development of content. It is also possible to identify a different attitude of students toward the concepts they have worked out. The work gives the students greater “ownership” which is in accordance with the assumptions of the Law of Directives and Basis of Brazilian Education where the school must develop the students ability to learn in order to acquire the knowledge and skills, as well as knowledge of the natural environment for the formation of attitudes and values [27]. In conclusion, it is important to note that only individuals who are adequately prepared are not at the mercy of vectorborne diseases. Therefore, it is important that the ordinary citizen, a candidate for contamination through the vectors of major diseases, is well informed about the discoveries of modern science, not only with regard to the disease itself but also the mechanism of and its transmission.
Acknowledgments The authors thank the directors of Escola Municipal Anısio ~ o de Amparo a Pesquisa Carlos ChaTeixeira and Fundac¸a gas Filho do Estado do Rio de Janeiro, Brazil, FAPERJ. This study was possible due to the grants by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) through Instituto Nacional de Ciencia e Tecnologia em Entomologia Molecular (INCT-EM). This study is dedicated to the memory of Dr. Alexandre A. Peixoto.
[5] Grac¸a-Souza, A. V., Maya-Monteiro, C., Paiva-Silva, G. O., Braz, G. R., Paes, M. C., Sorgine, M. H., Oliveira, M. F., and Oliveira, P. L. (2006) Adaptations against heme toxicity in blood-feeding arthropods. Insect Biochem. Mol. Biol. 36, 322-335. [6] Atella, G. C., Gondim, K. C., Machado, E. A., Medeiros, M. N., Silva-Neto, M. A., and Masuda, H. (2005) Oogenesis and egg development in triatomines: a biochemical approach. Ann. Acad. Bras. Cienc. 77, 405-430. dica da [7] Krettli, A. U. (2008). Grandes Endemias no Brasil. Gazeta Me Bahia 78, 74-78. [8] Coura, J. R. and Borges-Pereira, J. (2010) Chagas disease: 100 years after its discovery. A systemic review. Acta Trop. 115, 5-13. ~o, D. (2000) Refundac¸a ~o do Sistema Nacional de Sau rum de. In Fo [9] Serra de Economia da Sa ude. Porto 89-102. [10] Edwards, J. S. (1998). Sir Vincent Wigglesworth and the coming of age of insect development. Int. J. Dev. Biol. 42, 471-473. [11] Ribeiro, A. L., Nunes, M. P., Teixeira, M. M., and Rocha, M. O. (2012) Diagnosis and management of Chagas disease and cardiomyopathy. Nat. Rev. Cardiol. 9, 576-589. [12] Mesquita, R. D., Carneiro, A. B., Bafica, A., Gazos-Lopes, F., Takiya, C. M., Souto-Padron, T., Vieira, D. P., Ferreira-Pereira, A., Almeida, I. C., Figueiredo, R. T., Porto, B. N., Bozza, M. T., Grac¸a-Souza, A. V., Lopes, A. H., Atella, G. C., and Silva-Neto, M. A. (2008) Trypanosoma cruzi infection is enhanced by vector saliva through immunosuppressant mechanisms mediated by lysophosphatidylcholine. Infect. Immun. 76, 5543-5552. [13] Silva-Neto, M. A., Fampa, P., Caiaffa, C. D., Carneiro, A. B., and Atella, G. C. (2010) Cell signaling during Trypanosoma cruzi development in triatominae. Open Parasitol. J. 1, 188-194. ^ncias Cognic¸a ~o. [14] Tavares, R. (2007) Construindo mapas conceituais. Cie 12, 72-785. ~o, Cornell University Press, [15] Nowak, J. D. (1977) A teoria da educac¸a Ithaca, New York. tamo, [16] Nowak, J. D. and Gowin, D. B. (1996) Aprender a aprender, Pla ~ es te cnicas, Lisboa. Edic¸o lora-Luna, F., Perret, J. L., and Guerin, P. M. (2004) Appetence behav[17] Ota iours of the triatomine bug Rhodnius prolixus on a servosphere in response to the host metabolites carbon dioxide and ammonia. J. Comp. Physiol. A Neuroethol. Sens. Neural Behav. Physiol. 190, 847-854. [18] Silva-Neto, M. A., Carneiro, A. B., Silva-Cardoso, L., and Atella, G. C. (2012) Lysophosphatidylcholine: A novel modulator of Trypanosoma cruzi transmission. J. Parasitol. Res. 2012, 1-8. [19] Soares, A. C., Carvalho-Tavares, J., Gontijo, N. F., dos Santos, V. C., Teixeira, M. M., and Pereira, M. H. (2006) Salivation pattern of Rhodnius prolixus (Reduviidae; Triatominae) in mouse skin. J. Insect Physiol. 52, 468-472. [20] Oliveira, M. F., Silva, J. R., Dansa-Petretski, M., de Souza, W., Lins, U., Braga, C. M., Masuda, H., and Oliveira P. L. (1999) Haem detoxification by an insect. Nature 400, 517-518 [21] Silva-Neto, M. A., Atella, G. C., Fialho, E., Paes, M. C., Zingali, R. B., Petretski, J. H., Alves, E. W., and Masuda, H. (1996) Isolation of a calciumbinding phosphoprotein from the oocytes and hemolymph of the bloodsucking insect Rhodnius prolixus. J. Biol. Chem. 271, 30227-30232. ^a, G. and Martins, I, in Espac¸os e Imagens na Escola, R. Ross, [22] Gouve Ed., (2001) Nilda Alves e Paulo Sgarbi, Rio de Janeiro. pp. 41-58. [23] Dorough, D. K. and Rye, J. A. (2007) Mapping for understanding. Sci. Teach. 64, 37-41.
References [1] Richards, O. W. and Davies, R. G. (1984) Tratado de Entomologia IMMS. Classificacao y Biologia, Vol. II, Barcelona. [2] Neves, D. P., Melo, A. L., Linardi, P. M., and Vitor, R. W. A. (2005) Para~o Paulo. sitologia Humana, Atheneu, Sa [3] Zwiebel, L. J. and Takken, W. (2004) Olfactory regulation of mosquitohost interactions. Insect Biochem. Mol. Biol. 34, 645-652. [4] Champagne, D. E. (2005) Antihemostatic molecules from saliva of blood-feeding arthropods. Pathophysiol. Haemost. Thromb. 34, 221-227.
330
[24] Ausubel, D. P., Novak, J. D. and Hanesian, H. (1980) Psicologia Educacional, 2nd ed., Interamericana, Rio de Janeiro. ^neo, J. L. (1994) Dida tica. Colec¸a ~o Magiste rio 2 grau, 23rd ed., [25] Liba ~ Serie Formador, Sao Paulo. [26] Vekiri, I. (2002) What is the value of graphical displays in learning? Ed. Psychol. Rev 14, 261. ^ncia da Repu blica do Brasil: Lei de Diretrizes e Bases, 9, 394– [27] Preside ~o III. Avaliable from: http://www.planalto.gov.br/ccivil_ 1996, Cap II, Sec¸a 03/leis/l9394.htm. Accessed on october 5, 2011.
Basic Biochemical Concepts of Chagas Disease Vectors
