Helping pregraduate students reach deep understanding of the second law of thermodynamics

Pregraduate students often have low success expectations toward their thermodynamics courses, which are often considered too abstract and remarkably difficult to understand. For this reason, they may not even try to reach any level of comprehension while settling for reproducing mathematical calculations and memorizing definitions to pass the exams. Traditional lectures on thermodynamics, focusing on mathematical deductions while neglecting the qualitative characterization of the concepts behind the equations, do not help in this respect. Aiming at a change in the teaching practice and focused on the second law of thermodynamics, the main goals of this work are to characterize the way of reasoning of the expert; to present a review on the most important learning difficulties encountered by students and categorize them into three groups: the disregard of qualitative understanding, the inherent conceptual difficulties, and those related to the students’ previous knowledge; and to propose some suitable teaching practices to assist instructors in this difficult but rewarding task

Stability of biocontrol products carrying Candida sake CPA-1 in starch derivatives as a function of water activity

[EN] The preservation and shelf-life of formulations of the biocontrol agent Candida sake CPA-1 and starch derivatives as a function of water activity (aW) were studied in terms of the physical stability of the products and cell viability. Formulations of biocontrol products (BCPs), based on combinations of potato starch and pregelatinised potato starch (F1 and F2) or maltodextrines (MD) (F3) containing cell protectants, were obtained by fluidised-bed drying. The carriers and the formulated products were stored at 20°C under different aW conditions. The water sorption and water plasticization behaviour of the different products were analysed through the water sorption isotherms and glass transition temperatures (Tg). Likewise, the viability of C. sake over time was determined as a function of the aW. The solubility of the products was also assessed. Although formulations stored at 20°C and low aW (≤ 0.33) exhibited a better shelf-life, a significant decrease in cell survival ratio after 180 storage days was observed. Cold storage (5°C) was required to better maintain the cell viability, thus prolonging the shelf-life of BCPs. Formulations containing MD were the most effective at preserving cell viability and also exhibited the highest water solubility. All the formulations were physically stable at ambient temperature; therefore, the cell stability is the critical point at which to establish both the aW levels and temperature during storage. Packaging the product using high water vapour barrier material and under cold storage would be necessary to ensure a high number of viable cells and an effective and competitive BCPThe authors are grateful to the Spanish Government for the financial support from the national project RTA2012-00067-C02 (Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, Spain and FEDER funds) and to the Conselleria d'Educacio of the Generalitat Valenciana, (Spain) for A. Marin's PhD grant.Marín-Gozalbo, A.; Atarés Huerta, LM.; Cháfer Nácher, MT.; Chiralt, A. (2017). Stability of biocontrol products carrying Candida sake CPA-1 in starch derivatives as a function of water activity. Biocontrol Science and Technology. 27(2):268-287. https://doi.org/10.1080/09583157.2017.1279587S26828727

Coating quality as affected by core particle segregation in fluidized bed processing

[EN] Fluidized bed coating is an important technique in the food powder industry, where often particles of a wide size distribution are dealt with. In this paper, glass beads of different particle size distribution were coated with sodium caseinate in a top-spray fluid bed unit. Positron Emission Particle Tracking (PEPT) was used to visualize and quantify the particle motion in the fluidized bed. Confocal Laser Scanning Microscopy combined with image analysis were used to investigate the effect of core particle size and its distribution on the thickness and quality of the coating. Particle size significantly affected the thickness and quality of the coating, due to differences in the corresponding fluidization patterns, as corroborated by PEPT observations. As the particle size distribution becomes narrower, segregation is less likely to occur. This results in a thicker coating which is, however, less uniform compared to when cores of a wider particle size distribution are spray coated. (C) 2012 Elsevier Ltd. All rights reserved.The authors wish to thank the financial support received from the Fund for Scientific Research-Flanders (Belgium) (F.W.O.-Vlaanderen), as well as from the Programa de Apoyo a la Investigacion y Desarrollo from the Universitat Politecnica de Valencia.Atarés Huerta, LM.; Depypere, F.; Pieters, J.; Dewettinck, K. (2012). Coating quality as affected by core particle segregation in fluidized bed processing. Journal of Food Engineering. 113(3):415-421. doi:10.1016/j.jfoodeng.2012.06.012S415421113

Physical and Antimicrobial Properties of Compression-Molded Cassava Starch-Chitosan Films for Meat Preservation

[EN] Cassava starch-chitosan films were obtained by melt bending and compression molding, using glycerol and polyethylene glycol as plasticizers. Both the starch/chitosan and the polymer/plasticizer ratios were varied in order to analyze their effect on the physical properties of the films. Additionally, the antimicrobial activity of 70:30 polymer:plasticizer films was tested in cold-stored pork meat slices as affected by chitosan content. All film components were thermally stable up to 200 A degrees C, which guaranteed their thermostability during film processing. Starch and chitosan had limited miscibility by melt blending, which resulted in heterogeneous film microstructure. Polyethylene glycol partially crystallized in the films, to a greater extent as the chitosan ratio increased, which limited its plasticizing effect. The films with the highest plasticizer ratio were more permeable to water vapor, less rigid, and less resistant to break. The variation in the chitosan content did not have a significant effect on water vapor permeability. As the chitosan proportion increased, the films became less stretchable, more rigid, and more resistant to break, with a more saturated yellowish color. The incorporation of the highest amount of chitosan in the films led to the reduction in coliforms and total aerobic counts of cold-stored pork meat slices, thus extending their shelf-life.The authors acknowledge the financial support provided by the Spanish Ministerio de Economia y Competividad (Projects AGL2013-42989-R and AGL2016-76699-R). Author Cristina Valencia-Sullca thanks the Peruvian Grant National Program (PRONABEC Grant).Valencia-Sullca, CE.; Atarés Huerta, LM.; Vargas, M.; Chiralt, A. (2018). Physical and Antimicrobial Properties of Compression-Molded Cassava Starch-Chitosan Films for Meat Preservation. Food and Bioprocess Technology. 11(7):1339-1349. https://doi.org/10.1007/s11947-018-2094-5S13391349117Alves, V. D., Mali, S., Beleia, A., & Grossmann, M. V. (2007). Effect of glycerol and amylose enrichment on cassava starch film properties. Journal of Food Engineering, 78(3), 941–946.ASTM (1995). Standard test methods for water vapour transmission of materials. In: Standards designations: E96-95. Annual book of ASTM standards (pp. 406-413). Philadelphia, PA: American Society for Testing and Materials.ASTM (1999). Standard test method for specular gloss. In: Designation (D523). Annual book of ASTM standards, Vol. 06.01. Philadelphia, PA: American Society for Testing and Materials.ASTM (2001). Standard test method for tensile properties of thin plastic sheeting. In: Standard D882 annual book of American standard testing methods. Philadelphia, PA: American Society for Testing and Materials.Atarés, L., Bonilla, J., & Chiralt, A. (2010). Characterization of sodium caseinate-based edible films incorporated with cinnamon or ginger essential oils. Journal of Food Engineering, 100(4), 678–687.Bonilla, J., Atarés, L., Vargas, M., & Chiralt, A. (2013). Properties of wheat starch film-forming dispersions and films as affected by chitosan addition. Journal of Food Engineering, 114(3), 303–312.Bonilla, J., Fortunati, E., Atarés, L., Chiralt, A., & Kenny, J. (2014). Physical, structural and antimicrobial properties of poly vinyl alcohol-chitosan biodegradable films. Food Hydrocolloids, 35, 463–470.Bourtoom, T., & Chinnan, M. S. (2008). Preparation and properties of rice starch–chitosan blend biodegradable film. LWT-Food Science and Technology, 41(9), 1633–1641.Cano, A., Jiménez, A., Cháfer, M., González-Martínez, C., & Chiralt, A. (2014). Effect of amylose: amylopectin ratio and rice bran addition on starch films properties. Carbohydrate Polymers, 111(0), 543–555.Carvalho, A. J. F. (2008). Starch: Major sources, properties and applications as thermoplastic materials. In M. N. Belgacem & A. Gandini (Eds.), Monomers, polymers and composites from renewable resources. Amsterdam: Elsevier.Chillo, S., Flores, S., Mastromatteo, M., Conte, A., Gerschenson, L., & Del Nobile, M. A. (2008). Influence of glycerol and chitosan on tapioca starch-based edible film properties. Journal of Food Engineering, 88(2), 159–168.Commission Regulation, 2005 (EC) No 2073/2005 of 15 November 2005 on microbiological criteria for foodstuffs. In Official Journal of the European Union pp 338/1–338/26.Da Róz, A., Carvalho, A., Gandini, A., & Curvelo, A. (2006). The effect of plasticizers on thermoplastic starch compositions obtained by melt processing. Carbohydrate Polymers, 63(3), 417–424.Dang, K., & Yoksan, R. (2015). Development of thermoplastic starch blown film by incorporating plasticized chitosan. Carbohydrate Polymers, 115, 575–581.Dou, B., Dupont, V., Williams, P. T., Chen, H., & Ding, Y. (2009). Thermogravimetric kinetics of crude glycerol. Bioresource Technology, 100(9), 2613–2620.Fang, J., Fawler, P., Eserig, C., González, R., Costa, J., & Chamudis, L. (2005). Development of biodegradable laminate films derived from naturally occurring carbohydrate polymers. Carbohydrate Polymers, 60(1), 39–42.Hutchings, J. B. (1999). Food color and appearance (2nd ed.). Gaithersburg, Maryland, USA: Aspen Publishers, Inc..Jiménez, A., Fabra, M. J., Talens, P., & Chiralt, A. (2012a). Edible and biodegradable starch films: A review. Food Bioprocessing Technology, 5(6), 2058–2076.Jiménez, A., Fabra, M. J., Talens, P., & Chiralt, A. (2012b). Effect of re-crystallization on tensile, optical and water vapour barrier properties of corn starch films containing fatty acids. Food Hydrocolloids, 26(1), 302–310.López, O., Garcia, A., Villar, M., Gentili, A., Rodriguez, M., & Albertengo, L. (2014). Thermo-compression of biodegradable thermoplastic corn starch films containing chitin and chitosan. LWT-Food Science and Technology, 57(106), 106–1515.Mali, S., Grossmann, M. V. E., García, M. A., Martino, M. N., & Zaritsky, N. E. (2006). Effects of controlled storage on thermal, mechanical and barrier properties of plasticized films from different starch sources. Journal of Food Engineering, 75(4), 453–460.Mendes, J. F., Paschoalin, R. T., Carmona, V. B., Sena Neto, A. R. A., Marques, C. P., Marconcini, J. M., Mattoso, L. H. C., Medeiros, E. S., & Oliveira, J. E. (2016). Biodegradable polymer blends based on corn starch and thermoplastic chitosan processed by extrusion. Carbohydrate Polymers, 137, 452–458.Ortega-Toro, R., Jiménez, A., Talens, P., & Chiralt, A. (2014). Properties of starch–hydroxypropyl methylcellulose based films obtained by compression molding. Carbohydrate Polymers, 109, 155–165.Ortega-Toro, R., Morey, I., Talens, P., & Chiralt, A. (2015). Active bilayer films of thermoplastic starch and polycaprolactone obtained by compression molding. Carbohydrate Polymers, 127, 282–290.Pelissari, F., Grossmann, M., Yamashita, F., & Pineda, E. (2009). Antimicrobial, mechanical and barrier properties of cassava starch-chitosan films incorporated with oregano essential oil. Journal of Agricultural and Food Chemistry, 57(16), 7499–7504.Pelissari, F. M., Yamashita, F., García, M. A., Martino, M. N., Zaritzky, N. E., & Grossmann, M. V. E. (2012). Constrained mixture design applied to the development of cassava starch-chitosan blown films. Journal of Food Engineering, 108(2), 262–267.Song, R., Xue, R., He, L. H., Liu, Y., & Xiao, Q. L. (2008). The structure and properties of chitosan/polyethylene glycol/silica ternary hybrid organic-inorganic films. Chinese Journal of Polymer Science, 26(05), 621–630.v.Su, J. F., Huang, Z., Yuan, X. Y., Wang, X. Y., & Lim, M. (2010). Structure and properties of carboxymethyl cellulose/soy protein isolate blend edible films crosslinked by Maillard reactions. Carbohydrate Polymers, 79(1), 145–153.Thunwall, M., Boldizar, A., & Rigdahl, M. (2006). Compression molding and tensile properties of thermoplastic potato starch materials. Biomacromolecules, 7(3), 981–986.Tomé, L., Fernandes, S., Sadocco, P., Causio, J., Silvertre, A., Neto, P., & Freire, C. (2012). Antibacterial thermoplastic starch- chitosan based materials prepared by melt-mixing. BioResources, 7(3), 3398–3409.Villalobos, R., Chanona, J., Hernández, P., Gutiérrez, G., & Chiralt, A. (2005). Gloss and transparency of hydroxypropyl methylcellulose films containing surfactants as affected by their microstructure. Food Hydrocolloids, 19(1), 53–61.Xu, Y. X., Kim, K. M., Hanna, M. A., & Nag, D. (2005). Chitosan–starch composite film: Preparation and characterization. Industrial Crops and Products, 21(2), 185–192.Yang, L., & Paulson, A. T. (2000). Mechanical and water vapour barrier properties of edible gellan. Food Research International, 33(7), 563–570

Effect of chitosan essential oil films on the storage-keeping quality of pork meat products

Edible films based on chitosan were prepared, with and without basil or thyme essential oils, with the aim of assessing their protective ability against lipid oxidation and their antimicrobial activity. Chitosan films had good oxygenbarrier properties, which were worsened by essential oil addition, especially when the film equilibrium moisture content increased. Due to the oxygen-barrier effect, all the films effectively protected pork fat from oxidation, in comparison to unprotected samples. In spite of the worsening of the oxygen-barrier properties, the films with essential oils were more effective than those of pure chitosan, which points to the chemical action of specific antioxidant compounds of the oils. Films were effective to control microbial growth in minced pork meat, although the incorporation of essential oils did not improve their antimicrobial activity. Throughout the storage, the films led to colour changes in minced pork meat associated with the conversion of myoglobin into metmyoglobin due to the reduction of the oxygen availability.The authors acknowledge the financial support provided by the Universitat Politecnica de Valencia (PAID-06-09-2834), Generalitat Valenciana (GV/2010/082) and Ministerio de Educacion y Ciencia (AGL2010-20694). Author J. Bonilla is deeply grateful to Generalitat Valenciana for a Santiago Grisolia Grant.Bonilla Lagos, MJ.; Vargas, M.; Atarés Huerta, LM.; Chiralt Boix, MA. (2014). Effect of chitosan essential oil films on the storage-keeping quality of pork meat products. Food and Bioprocess Technology. 7(8):2443-2450. https://doi.org/10.1007/s11947-014-1329-3S2443245078ASTM D3985. (1995). Standard test method for oxygen gas transmission rate through plastic films and sheeting using a coulometric sensor. West Conshohocken: American Society for Testing and Materials.Atarés, L., Pérez-Masiá, R., & Chiralt, A. (2011). The role of some antioxidants in the HPMC film properties and lipid protection in coated toasted almonds. Journal of Food Engineering, 104, 649–656.Aureli, P., Costantini, A., & Zolea, S. (1992). Antimicrobial activity of some plant essential oils against Listeria monocytogenes. Journal of Food Protection, 55, 344–348.Baranauskiene, R., Venskutoni, S. P. R., Viskelis, P., & Dambrauskiene, E. (2003). Influence of nitrogen fertilizers on the yield and composition of thyme (Thymus vulgaris). Journal of Agricultural and Food Chemistry, 51, 7751–7758.Bonilla, J., Atarés, L., Vargas, M., & Chiralt, A. (2012a). Edible films and coatings to prevent the detrimental effect of oxygen on food quality: possibilities and limitations. Journal of Food Engineering, 110, 208–213.Bonilla, J., Atarés, L., Vargas, M., & Chiralt, A. (2012b). Effect of essential oils and homogenization conditions on properties of chitosan-based films. Food Hydrocolloids, 26, 9–16.Burt, S. (2004). Essential oils: their antibacterial properties and potential applications in foods—a review. International Journal of Food Microbiology, 94, 223–253.Burt, S. A., & Reinders, R. D. (2003). Antibacterial activity of selected plant essential oils against Escherichia coli O157:H7. Letters in Applied Microbiology, 36, 162–167.Caner, C., Vergano, P. J., & Wiles, J. L. (1998). Chitosan film mechanical and permeation properties as affected by acid, plasticizer and storage. Journal of Food Science, 63, 1049–1053.Casariego, A., Souza, B. W. S., Cerqueira, M. A., Teixeira, J. A., Cruz, L., Díaz, R., et al. (2009). Chitosan/clay ‘films properties as affected by biopolymer and clay micro/nanoparticles’ concentrations. Food Hydrocolloids, 23, 1895–1902.Devlieghere, F., Vermeiren, L., & Debevere, J. (2004). New preservation technologies: possibilities and limitations. International Dairy Journal, 14, 273–285.Di Pasqua, R., Hoskins, N., Betts, G., & Mauriello, G. (2006). Changes in membrane fatty acids composition of microbial cells induced by addiction of thymol, carvacrol, limonene, cinnamaldehyde and eugenol in the growing media. Journal of Agricultural and Food Chemistry, 54, 2745–2749.Di Pierro, P., Sorrentino, A., Mariniello, L., Giosafatto, C. V. L., & Porta, R. (2011). Chitosan/whey protein film as active coating to extend Ricotta cheese shelf-life. LWT--Food Science and Technology, 44, 2324–2327.Fabra, M. J., Talens, P., Gavara, R., & Chiralt, A. (2012). Barrier properties of sodium caseinate films as affected by lipid composition and moisture content. Journal of Food Engineering, 109(3), 372–379.Gaysinsky, S., Davidson, P. M., Bruce, B. D., & Weiss, J. (2005). Growth inhibition of E. Coli O157:H7 and Listeria monocytogenes by carvacrol and eugenol encapsulated in surfactant micelles. Journal of Food Protection, 68, 2559–2566.Govaris, A., Botsoglou, E., Sergelidis, D., & Chatzopoulou, P. D. (2011). Antibacterial activity of oregano and thyme essential oils against Listeria monocytogenes and Escherichia coli O157:H7 in feta cheese packaged under modified atmosphere. LWT - Food Science and Technology, 44, 1240–1244.Han, J. H., & Gennadios, A. (2005). Edible films and coatings: a review. In J. H. Han (Ed.), Innovations in Food Packaging (pp. 39–262). Oxford: Elsevier Academic.Kim, J., Marshall, M. R., & Wei, C. I. (1995). Antibacterial activity of some essential oil components against five foodborne pathogens. Journal of Agricultural and Food Chemistry, 43, 2839–2845.Labuza, T. P. (1980). The effect of water activity on reaction kinetics of food deterioration. Food Technology, 34, 36–41.Mancini, R. A., & Hunt, M. C. (2005). Current research in meat color. Meat Science, 71, 100–121.Moure, A., Cruz, J. M., Franco, D., Dominguez, J. M., Sineiro, J., Dominguez, H., et al. (2001). Natural antioxidants from residual sources. Food Chemistry, 72, 145–171.Rao, M. S., Chander, R., & Sharma, A. (2005). Development of shelf-stable intermediate moisture meat products using active edible chitosan coating and irradiation. Journal of Food Science, 70, 325–331.Salame, M. (1986). Barrier polymers. In M. Bakker (Ed.), The Wiley encyclopedia of packaging technology (pp. 48–54). New York: Wiley.Sánchez-González, L., González-Martínez, C., Chiralt, A., & Cháfer, M. (2010). Physical and antimicrobial properties of chitosan–tea tree essential oil composite films. Journal of Food Engineering, 98, 443–452.Sánchez-González, L., Vargas, M., González-Martínez, C., Chiralt, A., & Cháfer, M. (2011a). Use of essential oils in bioactive edible coatings. Food Engineering Reviews, 3, 1–16.Sánchez-González, L., Cháfer, M., Hernández, M., Chiralt, A., & González-Martínez, C. (2011b). Antimicrobial activity of polysaccharide films containing essential oils. Food Control, 22, 1302–1310.Seydim, A. C., & Sarikus, G. (2006). Antimicrobial activity of whey protein based edible films incorporated with oregano, rosemary and garlic essential oils. Food Research International, 39, 639–644.Shan, B., Cai, Y. Z., Sun, M., & Corke, H. (2005). Antioxidant capacity of 26 spice extracts and characterization of their phenolic constituents. Journal of Agricultural and Food Chemistry, 53, 7749–7759.Singh, B., Falahee, M. B., & Adams, M. R. (2001). Synergistic inhibition of Listeria monocytogenes by nisin and garlic extract. Food Microbioliology, 18, 133–139.Vargas, M., Albors, A., Chiralt, A., & González-Martínez, C. (2006). Quality of cold-stored strawberries as affected by chitosan–oleic acid edible coatings. Postharvest Biology and Technology, 41, 164–171.Vargas, M., Albors, A., Chiralt, A., & González-Martínez, C. (2009). Characterization of chitosan–oleic acid composite films. Food Hydrocolloids, 23, 536–547.Vargas, M., Albors, A., & Chiralt, A. (2011). Application of chitosan-sunflower oil edible films to pork meat hamburgers. Procedia Food Science, 1, 39–43.Wan, J., Wilcock, A., & Coventry, M. J. (1998). The effect of essential oils of basil on the growth of Aeromonas hydrophila and Pseudomonas fluorescens. Journal of Applied Microbiology, 84, 152–158.Zivanovic, S., Chi, S., & Draughon, F. (2005). Antimicrobial activity of chitosan films enriched with essential oils. Journal of Food Science, 70, 45–51

Properties of biopolymer dispersions and films used as carriers of the biocontrol agent Candida sake CPA-1

[EN] The use of biocontrol agents (BCA) for controlling plant diseases is an alternative to reduce the use of pesticides. Their performance can be improved when applied in combination with coatings. Films and coatings formulated from different biopolymers were characterized as to their barrier and optical properties to analyse their impact on fruit when applied as carriers of the BCA Candida sake CPA-1. The properties of the film-forming dispersions were more affected by the type of polymer than by the incorporation of surfactants. Sodium caseinate formed the thickest coatings, but these were very thin in every case, which led to there being no predicted relevant effect on the gas exchanges of the fruit. The cell viability in the films was good during film drying, especially in the case of protein films; however, it decreased after storage.The authors are grateful to the Spanish Government for the financial support through project RTA2012-00067-0O2 and to the Conselleria d'Educacio of the Generalitat Valenciana, (Spain) for A. Marin's PhD grant (VALi+d 2013). The authors are also thankful to IRTA group, headed by Dra. Neus Teixido, for their assistance in the microbiological study.Marín-Gozalbo, A.; Atarés Huerta, LM.; Cháfer Nácher, MT.; Chiralt, A. (2017). Properties of biopolymer dispersions and films used as carriers of the biocontrol agent Candida sake CPA-1. LWT - Food Science and Technology. 79:60-69. https://doi.org/10.1016/j.lwt.2017.01.024S60697

A novel form of human disease with a protease-sensitive prion protein and heterozygosity methionine/valine at codon 129: Case report

<p>Abstract</p> <p>Background</p> <p>Sporadic Creutzfeldt-Jakob disease (sCJD) is a rare neurodegenerative disorder in humans included in the group of Transmissible Spongiform Encephalopathies or prion diseases. The vast majority of sCJD cases are molecularly classified according to the abnormal prion protein (PrP^Sc) conformations along with polymorphism of codon 129 of the PRNP gene. Recently, a novel human disease, termed "protease-sensitive prionopathy", has been described. This disease shows a distinct clinical and neuropathological phenotype and it is associated to an abnormal prion protein more sensitive to protease digestion.</p> <p>Case presentation</p> <p>We report the case of a 75-year-old-man who developed a clinical course and presented pathologic lesions compatible with sporadic Creutzfeldt-Jakob disease, and biochemical findings reminiscent of "protease-sensitive prionopathy". Neuropathological examinations revealed spongiform change mainly affecting the cerebral cortex, putamen/globus pallidus and thalamus, accompanied by mild astrocytosis and microgliosis, with slight involvement of the cerebellum. Confluent vacuoles were absent. Diffuse synaptic PrP deposits in these regions were largely removed following proteinase treatment. PrP deposition, as revealed with 3F4 and 1E4 antibodies, was markedly sensitive to pre-treatment with proteinase K. Molecular analysis of PrP^Scshowed an abnormal prion protein more sensitive to proteinase K digestion, with a five-band pattern of 28, 24, 21, 19, and 16 kDa, and three aglycosylated isoforms of 19, 16 and 6 kDa. This PrP^Scwas estimated to be 80% susceptible to digestion while the pathogenic prion protein associated with classical forms of sporadic Creutzfeldt-Jakob disease were only 2% (type VV2) and 23% (type MM1) susceptible. No mutations in the PRNP gene were found and genotype for codon 129 was heterozygous methionine/valine.</p> <p>Conclusions</p> <p>A novel form of human disease with abnormal prion protein sensitive to protease and MV at codon 129 was described. Although clinical signs were compatible with sporadic Creutzfeldt-Jakob disease, the molecular subtype with the abnormal prion protein isoforms showing enhanced protease sensitivity was reminiscent of the "protease-sensitive prionopathy". It remains to be established whether the differences found between the latter and this case are due to the polymorphism at codon 129. Different degrees of proteinase K susceptibility were easily determined with the chemical polymer detection system which could help to detect proteinase-susceptible pathologic prion protein in diseases other than the classical ones.</p

Functional Analysis of the Arlequin Mutant Corroborates the Essential Role of the ARLEQUIN/TAGL1 Gene during Reproductive Development of Tomato

Reproductive development of higher plants comprises successive events of organ differentiation and growth which finally lead to the formation of a mature fruit. However, most of the genetic and molecular mechanisms which coordinate such developmental events are yet to be identified and characterized. Arlequin (Alq), a semi-dominant T-DNA tomato mutant showed developmental changes affecting flower and fruit ripening. Sepals were converted into fleshy organs which ripened as normal fruit organs and fruits displayed altered ripening features. Molecular characterization of the tagged gene demonstrated that it corresponded to the previously reported TOMATO AGAMOUS-LIKE 1 (TAGL1) gene, the tomato ortholog of SHATTERPROOF MADS-box genes of Arabidopsis thaliana, and that the Alq mutation promoted a gain-of-function phenotype caused by the ectopic expression of TAGL1. Ectopic overexpression of TAGL1 resulted in homeotic alterations affecting floral organ identity that were similar to but stronger than those observed in Alq mutant plants. Interestingly, TAGL1 RNAi plants yielded tomato fruits which were unable to ripen. They displayed a yellow-orange color and stiffness appearance which are in accordance with reduced lycopene and ethylene levels, respectively. Moreover, pericarp cells of TAGL1 RNAi fruits showed altered cellular and structural properties which correlated to both decreased expression of genes regulating cell division and lignin biosynthesis. Over-expression of TAGL1 is able to rescue the non-ripening phenotype of rin and nor mutants, which is mediated by the transcriptional activation of several ripening genes. Our results demonstrated that TAGL1 participates in the genetic control of flower and fruit development of tomato plants. Furthermore, gene silencing and over-expression experiments demonstrated that the fruit ripening process requires the regulatory activity of TAGL1. Therefore, TAGL1 could act as a linking factor connecting successive stages of reproductive development, from flower development to fruit maturation, allowing this complex process to be carried out successfully