Nowadays, most of the important information resources that the people require are available throu... more Nowadays, most of the important information resources that the people require are available through the Internet. The use of several sources in the Internet requires merging the information into a knowledge base in a reasonable way. We will use an ontology, an information technology that manages this knowledge in computers. Merging is an important task and many languages and tools have been developed to describe and process Internet content but the current languages (DAML+OIL, RDF, OWL, etc.) lack a complete expressiveness. For this reason, we present two important improvements to facilitate knowledge interchange: 1) The OM (ontology merging) notation that provides substantial improvements to these languages and 2) The OM algorithm, this is totally automatic in comparison with others (Prompt, Chimaera, OntoMerge, FCA-Merge, IF-Map and ISI) where the user manually solves the most important problems found in the merging
An exopolysaccharide (EPS) producing strain of Streptococcus thermophilus was evaluated for the p... more An exopolysaccharide (EPS) producing strain of Streptococcus thermophilus was evaluated for the production of Panela cheese using two total solids milk (TSM) concentrations (12.5 and 17.5 g/100 mL). This ropy strain increased cheese yield; nevertheless, with 12.5 TSM the increment was higher than with 17.5 TSM. Analysis of cheese composition showed that with 12.5 TSM, the ropy strain increased moisture, but did not change the fat or non fat solids on dry weight basis (dwb), suggesting that the increment of the yield is only due to water retention. In 17.5 TSM cheeses the ropy strain caused an increase in the moisture and fat (dwb), suggesting that besides water retention, fat also contributed to the yield. The difference in yield increment could be explained by cheese composition: higher fat content creates a more hydrophobic environment, which would expel more water than the cheese with lower fat content. Electron microscopy showed EPS attached to the protein matrix of the cheeses. In 17.5 TSM cheeses EPS was observed around the milk fat globules (MFG), confirming that higher TSM causes EPS to bind the MFG besides binding the protein matrix, retaining fat within the cheese. Sensory evaluation demonstrated that ropy cheeses were softer and creamier.
ABSTRACT Barley is the fourth cereal of greater importance at world-wide level, as well as at nat... more ABSTRACT Barley is the fourth cereal of greater importance at world-wide level, as well as at national level in México. Hidalgo and Tlaxcala are two of the states of greater production of barley. Between cereals, physical variations in their characteristics and properties exist, ...
Chemokines are members of the super family of cytokines necessary for leukocyte recruitment in ti... more Chemokines are members of the super family of cytokines necessary for leukocyte recruitment in tissues and lymphoid organs. The interferon-gamma inducible protein-10 (IP-10) chemo-attracts CXCR3-expressing cells, such as activated T lymphocytes and monocytes. We have genetically engineered a strain of Lactococcus lactis to secrete a biologically active murine IP-10 that interacts with human CXCR3, its homolog receptor, and chemo-attracts human CD3+ T lymphocytes.
It is clear how to compute the average of a set of numeric values; thus, handling inconsistent me... more It is clear how to compute the average of a set of numeric values; thus, handling inconsistent measurements is possible. Recently, using confusion, we showed a new way to compute the consensus (a kind of average) of a set of assertions about a non-numeric fact, such as the religion of John.This paper solves the same problem for a set of objects possessing several symbolic attributes. Suppose there is a murder, and we ask several observers about the height, sex, hair color and ethnicity of the killer. They report divergent observations. What is the most likely portrayal of the assassin? Given a bag of assertions about an object described by qualitative features, this paper tells how to assess the most plausible or “consensus” object description. It is the most likely description to be true, given the available information. It is the “centroid” of the bag. We also compute the inconsistency of the bag: how far apart the testimonies in the bag are. All observers are equally credible, so differences arise from perception errors, and from the limited accuracy of the individual findings.► We study assertions about objects containing qualitative values. ► These values can be represented by a hierarchy (a tree) containing them. ► The defined function conf (r,s) measures similarity of qualitative values r and s. ► Using conf, we find the centroid or consensus (an object) of a set of assertions. ► The “variance” or “disagreement” about this consensus object is also measured.
An alcohol dehydrogenase gene, adh1, has been identified in the vascular wilt fungus Fusarium oxy... more An alcohol dehydrogenase gene, adh1, has been identified in the vascular wilt fungus Fusarium oxysporum f. sp. lycopersici. Reverse transcription polymerase chain reaction (RT-PCR) analysis revealed that adh1 is highly expressed in mycelia grown in potato dextrose liquid medium (PDB) under hypoxic conditions, as compared to mycelia grown under aerobic conditions. One spontaneous allyl alcohol-resistant (AllyR) mutant exhibited insertion of an incomplete F.oxysporum transposable element, while another mutant contained a short (13 nucleotide) deletion, in both cases interrupting the coding region of the adh1 gene. These mutations caused deficiency in Adh activity due to loss of the main constitutive isoform of Adh1, as well as alteration of different physiological parameters related to carbon and energy metabolism, including the ability to use ethanol as a carbon source under aerobic conditions; impaired growth under hypoxic conditions with glucose as the carbon source; and diminished production of ethanol in glucose-containing medium. Interestingly, the adh1 mutations resulted in a significant delay in fungal disease development in tomato plants. Complementation with the wild-type adh1 allele repaired all defects caused by mutation, indicating that the product of the adh1 gene has dual enzymatic functions (fermentative and oxidative), depending on culture conditions, and is also required for full fungal virulence.► An alcohol dehydrogenase gene, adh1, was identified in the fungus Fusarium oxysporum. ► adh1 is highly expressed in mycelia grown in PDB medium under hypoxic conditions. ► Allyl alcohol-resistant mutants showed alterations in adh1 leading to Adh1 deficiency. ► Adh1 has fermentative and oxidative functions, depending on culture conditions. ► Adh1 is required for the development of full fungal virulence.
Certain RNA molecules are known to be sequestered and stored as ribonucleoprotein particles (RNPs... more Certain RNA molecules are known to be sequestered and stored as ribonucleoprotein particles (RNPs) in many different tissues, particularly at some stages of metabolic quiescence. In this research RNPs from embryonic axes of mature maize seeds were isolated by sucrose and CsCl gradient centrifugation and characterized based on their RNA and protein contents. Two types of RNP particles of non-ribosomal nature were identified by northern blot analysis with specific probes: the 7S RNP and the signal recognition particle (SRP) particles which contain 5S rRNA and 7S RNA respectively. The proteins associated to these RNA molecules were the transcription factor TFIIIA-homologous protein associated to 7S RNP, and the p72, p68 and p54-GTPase proteins associated to SRP.
The greatest concentration of oak species in the world is believed to be found in Mexico. These s... more The greatest concentration of oak species in the world is believed to be found in Mexico. These species are potentially useful for reforestation because of their capacity to adapt to diverse environments. Knowledge of their geographic distribution and of species–environment relations is essential for decision-making in the management and conservation of natural resources. The objectives of this study were to develop a model of the distribution of Quercus emoryi Torr. in Mexico, using geographic information systems and data layers of climatic and other variables, and to determine the variables that significantly influence the distribution of the species. The study consisted of the following steps: (A) selection of the target species from a botanical scientific collection, (B) characterization of the collecting sites using images with values or categories of the variables, (C) model building with the overlay of images that meet the habitat conditions determined from the characterization of sites, (D) model validation with independent data in order to determine the precision of the model, (E) model calibration through adjustment of the intervals of some variables, and (F) sensitivity analysis using precision and concordance non-parametric statistics applied to pairs of images. Results show that the intervals of the variables that best describe the species’ habitat are the following: altitude from 1650 to 2750 amsl, slope from 0 to 66°; average minimum temperature of January from −12 to −3 °C; mean temperature of June from 11 to 25 °C; mean annual precipitation from 218 to 1225 mm; soil units: lithosol, eutric cambisol, haplic phaeozem, chromic luvisol, rendzina, luvic xerosol, mollic planosol, pellic vertisol, eutric regosol; type of vegetation: oak forest, oak–pine forest, pine forest, pine–oak forest, juniperus forest, low open forest, natural grassland and chaparral. The resulting model of the geographic distribution of Quercus emoryi in Mexico had the following values for non-parametric statistics of precision and agreement: Kappa index of 0.613 and 0.788, overall accuracy of 0.806 and 0.894, sensitivity of 0.650 and 0.825, specificity of 0.963, positive predictive value of 0.945 and 0.957 and negative predictive value of 0.733 and 0.846. Results indicate that the variable average minimum temperature of January, with a maximum value of −3 °C, is an important factor in limiting the species’ distribution.
Germination of Opuntia tomentosa seeds collected during 1998 was evaluated using treatments of sc... more Germination of Opuntia tomentosa seeds collected during 1998 was evaluated using treatments of scarification (H2SO4), gibberellic acid (GA3), dry heat, soaking, light, after-ripening and stratification at constant and alternating temperatures. Seeds were positive photoblastic, germinated best at constant temperatures, and showed a combined dormancy (physiological and physical). Acid scarification, GA3, and heating induced germination, soaking and stratification did not. After 15 and 18 months, GA3 inhibited germination. Dormancy of seeds collected during 2000 was overcome with a short scarification. Differences between baths could be due to 1998 was very dry due to “El Niño”. It is important to identify maternal effects.
The effects of heat treatments of milk and whey prior to lactose hydrolysis with Kluyveromyces la... more The effects of heat treatments of milk and whey prior to lactose hydrolysis with Kluyveromyces lactis β-galactosidase were studied. It was observed that heat treatment of milk significantly increases lactase activity, with a maximum activity increase found when milk was heated at 55°C. In whey from 55 up to 75°C, β-galactosidase activity decreased slightly. Nevertheless, heating whey at 85°C for 30 min raised the rate of hydrolysis significantly. Electrophoretic patterns and UV spectra proved that the activity change correlated with milk protein denaturation, particularly that of β-lactoglobulin. Heating whey permeate did not increase the enzyme activity as heating whole whey; but heating whey prior to ultrafiltration also resulted in enzyme activation. Measurement of free sulfhydryl (SH) groups in both whey and heated whey permeate showed that the liberation of free SH is highly correlated to the change of the activity. Furthermore, this activation can be reversed by oxidizing the reactive sulfhydryl groups, proving that the observed effect may be related to the release of free SH to the medium, rather than to the denaturation of a thermolabile protein inhibitor.
Opuntia tomentosa seeds have physiological dormancy and a permeable but hard funicular envelope t... more Opuntia tomentosa seeds have physiological dormancy and a permeable but hard funicular envelope that restricts water uptake and embryo growth. Dormancy break, germination, and changes in the funiculus were compared in laboratory-stored seeds and in those buried for 7 months at different microsites and later exhumed and stored in the laboratory. The funicular envelopes of both lots were examined with a scanning electron microscope (SEM). Seeds in both lots were: scarified with H2SO4 (0, 45, 60 and 90 min), treated with gibberellins (0, 1000 and 2000 ppm) and germinated at the same ages (0, 2, 4, 7, and 10 months after exhumation) at 24 °C. Light effect was determined at 24 °C and 20–35 °C. In laboratory-stored seeds germination was low. Exhumed seeds germinated in ∼50%, the remaining ones required scarification and gibberellins, but lost dormancy two months later. Gibberellins reduced germination heterogeneity, and scarification reduced germination; the adverse effect of scarification was offset by gibberellins. Exhumed seeds germinated mainly in darkness at 20–35 °C and partially in far red light at both temperatures. SEM showed that fungi eroded the funiculus reducing its resistance. O. tomentosa could form a seed bank, ensuring its survival under heterogeneous environments.
The secondary structure of Kluyveromyces lactis beta-galactosidase was determined by circular dic... more The secondary structure of Kluyveromyces lactis beta-galactosidase was determined by circular dichroism. It is mainly a beta-type protein, having 22% beta-turns, 14% parallel beta-sheet, 25% antiparallel beta-sheet, 34% unordered structure, and only 5% alpha-helix. The structure-activity relationship as a function of the pH was also studied. The pH conditions leading to the highest secondary structure content (100% ellipticity) of the enzyme was found at pH 7.0; at pH 6.5-7.0, the percent ellipticity decreased slightly, suggesting little structural change, but the activity decreased significantly, probably because of variations in critical residues. On the other hand, at pH's above 7.0, a more noticeable change in ellipticity was observed due to structural changes; the CD analysis showed a small increase in the helical content toward higher pH, whereas the maximum activity was found at pH 7.5, meaning that the changes produced in the secondary structure at this pH favored the interaction between the enzyme and the substrate.
Prion diseases or transmissible spongiform encephalopathies are a group of fatal neurodegenerativ... more Prion diseases or transmissible spongiform encephalopathies are a group of fatal neurodegenerative diseases caused by an abnormal form of prion protein (PrPsc). In this study, we developed a sensitive histochemical detection of PrPsc deposits in a Gertsmann-Sträussler-Scheinker disease (GSS) patient using toluidine blue-O staining, a specific reagent to stain mucins and mucopolysaccharides. Detection of prion deposits correlated with immunohistochemistry using anti-prion antibodies. Control assays were performed using amyloid-β (Aβ) plaques from Alzheimer's disease (AD) brains. Our results demonstrated that toluidine blue-O staining allowed to recognize 69.1±2.6% of the total plaques recognized by the anti-prion antibody. Furthermore, in the 15 studied brain regions from the GSS patient, toluidine blue-O revealed the same recognition pattern as anti-prion labeling. Toluidine blue-O stained specifically the prion deposits but not the Aβ plaques in AD brains. The specificity of the technique was confirmed in a Creutzfeldt-Jakob disease brain. This method opens several possibilities for postmortem diagnoses. Our results also suggest the relevance of specific post-translational modifications of PrPsc, identified by toluidine blue-O, that might participate in the transformation of PrPc to PrPsc.
Nowadays, most of the important information resources that the people require are available throu... more Nowadays, most of the important information resources that the people require are available through the Internet. The use of several sources in the Internet requires merging the information into a knowledge base in a reasonable way. We will use an ontology, an information technology that manages this knowledge in computers. Merging is an important task and many languages and tools have been developed to describe and process Internet content but the current languages (DAML+OIL, RDF, OWL, etc.) lack a complete expressiveness. For this reason, we present two important improvements to facilitate knowledge interchange: 1) The OM (ontology merging) notation that provides substantial improvements to these languages and 2) The OM algorithm, this is totally automatic in comparison with others (Prompt, Chimaera, OntoMerge, FCA-Merge, IF-Map and ISI) where the user manually solves the most important problems found in the merging
An exopolysaccharide (EPS) producing strain of Streptococcus thermophilus was evaluated for the p... more An exopolysaccharide (EPS) producing strain of Streptococcus thermophilus was evaluated for the production of Panela cheese using two total solids milk (TSM) concentrations (12.5 and 17.5 g/100 mL). This ropy strain increased cheese yield; nevertheless, with 12.5 TSM the increment was higher than with 17.5 TSM. Analysis of cheese composition showed that with 12.5 TSM, the ropy strain increased moisture, but did not change the fat or non fat solids on dry weight basis (dwb), suggesting that the increment of the yield is only due to water retention. In 17.5 TSM cheeses the ropy strain caused an increase in the moisture and fat (dwb), suggesting that besides water retention, fat also contributed to the yield. The difference in yield increment could be explained by cheese composition: higher fat content creates a more hydrophobic environment, which would expel more water than the cheese with lower fat content. Electron microscopy showed EPS attached to the protein matrix of the cheeses. In 17.5 TSM cheeses EPS was observed around the milk fat globules (MFG), confirming that higher TSM causes EPS to bind the MFG besides binding the protein matrix, retaining fat within the cheese. Sensory evaluation demonstrated that ropy cheeses were softer and creamier.
ABSTRACT Barley is the fourth cereal of greater importance at world-wide level, as well as at nat... more ABSTRACT Barley is the fourth cereal of greater importance at world-wide level, as well as at national level in México. Hidalgo and Tlaxcala are two of the states of greater production of barley. Between cereals, physical variations in their characteristics and properties exist, ...
Chemokines are members of the super family of cytokines necessary for leukocyte recruitment in ti... more Chemokines are members of the super family of cytokines necessary for leukocyte recruitment in tissues and lymphoid organs. The interferon-gamma inducible protein-10 (IP-10) chemo-attracts CXCR3-expressing cells, such as activated T lymphocytes and monocytes. We have genetically engineered a strain of Lactococcus lactis to secrete a biologically active murine IP-10 that interacts with human CXCR3, its homolog receptor, and chemo-attracts human CD3+ T lymphocytes.
It is clear how to compute the average of a set of numeric values; thus, handling inconsistent me... more It is clear how to compute the average of a set of numeric values; thus, handling inconsistent measurements is possible. Recently, using confusion, we showed a new way to compute the consensus (a kind of average) of a set of assertions about a non-numeric fact, such as the religion of John.This paper solves the same problem for a set of objects possessing several symbolic attributes. Suppose there is a murder, and we ask several observers about the height, sex, hair color and ethnicity of the killer. They report divergent observations. What is the most likely portrayal of the assassin? Given a bag of assertions about an object described by qualitative features, this paper tells how to assess the most plausible or “consensus” object description. It is the most likely description to be true, given the available information. It is the “centroid” of the bag. We also compute the inconsistency of the bag: how far apart the testimonies in the bag are. All observers are equally credible, so differences arise from perception errors, and from the limited accuracy of the individual findings.► We study assertions about objects containing qualitative values. ► These values can be represented by a hierarchy (a tree) containing them. ► The defined function conf (r,s) measures similarity of qualitative values r and s. ► Using conf, we find the centroid or consensus (an object) of a set of assertions. ► The “variance” or “disagreement” about this consensus object is also measured.
An alcohol dehydrogenase gene, adh1, has been identified in the vascular wilt fungus Fusarium oxy... more An alcohol dehydrogenase gene, adh1, has been identified in the vascular wilt fungus Fusarium oxysporum f. sp. lycopersici. Reverse transcription polymerase chain reaction (RT-PCR) analysis revealed that adh1 is highly expressed in mycelia grown in potato dextrose liquid medium (PDB) under hypoxic conditions, as compared to mycelia grown under aerobic conditions. One spontaneous allyl alcohol-resistant (AllyR) mutant exhibited insertion of an incomplete F.oxysporum transposable element, while another mutant contained a short (13 nucleotide) deletion, in both cases interrupting the coding region of the adh1 gene. These mutations caused deficiency in Adh activity due to loss of the main constitutive isoform of Adh1, as well as alteration of different physiological parameters related to carbon and energy metabolism, including the ability to use ethanol as a carbon source under aerobic conditions; impaired growth under hypoxic conditions with glucose as the carbon source; and diminished production of ethanol in glucose-containing medium. Interestingly, the adh1 mutations resulted in a significant delay in fungal disease development in tomato plants. Complementation with the wild-type adh1 allele repaired all defects caused by mutation, indicating that the product of the adh1 gene has dual enzymatic functions (fermentative and oxidative), depending on culture conditions, and is also required for full fungal virulence.► An alcohol dehydrogenase gene, adh1, was identified in the fungus Fusarium oxysporum. ► adh1 is highly expressed in mycelia grown in PDB medium under hypoxic conditions. ► Allyl alcohol-resistant mutants showed alterations in adh1 leading to Adh1 deficiency. ► Adh1 has fermentative and oxidative functions, depending on culture conditions. ► Adh1 is required for the development of full fungal virulence.
Certain RNA molecules are known to be sequestered and stored as ribonucleoprotein particles (RNPs... more Certain RNA molecules are known to be sequestered and stored as ribonucleoprotein particles (RNPs) in many different tissues, particularly at some stages of metabolic quiescence. In this research RNPs from embryonic axes of mature maize seeds were isolated by sucrose and CsCl gradient centrifugation and characterized based on their RNA and protein contents. Two types of RNP particles of non-ribosomal nature were identified by northern blot analysis with specific probes: the 7S RNP and the signal recognition particle (SRP) particles which contain 5S rRNA and 7S RNA respectively. The proteins associated to these RNA molecules were the transcription factor TFIIIA-homologous protein associated to 7S RNP, and the p72, p68 and p54-GTPase proteins associated to SRP.
The greatest concentration of oak species in the world is believed to be found in Mexico. These s... more The greatest concentration of oak species in the world is believed to be found in Mexico. These species are potentially useful for reforestation because of their capacity to adapt to diverse environments. Knowledge of their geographic distribution and of species–environment relations is essential for decision-making in the management and conservation of natural resources. The objectives of this study were to develop a model of the distribution of Quercus emoryi Torr. in Mexico, using geographic information systems and data layers of climatic and other variables, and to determine the variables that significantly influence the distribution of the species. The study consisted of the following steps: (A) selection of the target species from a botanical scientific collection, (B) characterization of the collecting sites using images with values or categories of the variables, (C) model building with the overlay of images that meet the habitat conditions determined from the characterization of sites, (D) model validation with independent data in order to determine the precision of the model, (E) model calibration through adjustment of the intervals of some variables, and (F) sensitivity analysis using precision and concordance non-parametric statistics applied to pairs of images. Results show that the intervals of the variables that best describe the species’ habitat are the following: altitude from 1650 to 2750 amsl, slope from 0 to 66°; average minimum temperature of January from −12 to −3 °C; mean temperature of June from 11 to 25 °C; mean annual precipitation from 218 to 1225 mm; soil units: lithosol, eutric cambisol, haplic phaeozem, chromic luvisol, rendzina, luvic xerosol, mollic planosol, pellic vertisol, eutric regosol; type of vegetation: oak forest, oak–pine forest, pine forest, pine–oak forest, juniperus forest, low open forest, natural grassland and chaparral. The resulting model of the geographic distribution of Quercus emoryi in Mexico had the following values for non-parametric statistics of precision and agreement: Kappa index of 0.613 and 0.788, overall accuracy of 0.806 and 0.894, sensitivity of 0.650 and 0.825, specificity of 0.963, positive predictive value of 0.945 and 0.957 and negative predictive value of 0.733 and 0.846. Results indicate that the variable average minimum temperature of January, with a maximum value of −3 °C, is an important factor in limiting the species’ distribution.
Germination of Opuntia tomentosa seeds collected during 1998 was evaluated using treatments of sc... more Germination of Opuntia tomentosa seeds collected during 1998 was evaluated using treatments of scarification (H2SO4), gibberellic acid (GA3), dry heat, soaking, light, after-ripening and stratification at constant and alternating temperatures. Seeds were positive photoblastic, germinated best at constant temperatures, and showed a combined dormancy (physiological and physical). Acid scarification, GA3, and heating induced germination, soaking and stratification did not. After 15 and 18 months, GA3 inhibited germination. Dormancy of seeds collected during 2000 was overcome with a short scarification. Differences between baths could be due to 1998 was very dry due to “El Niño”. It is important to identify maternal effects.
The effects of heat treatments of milk and whey prior to lactose hydrolysis with Kluyveromyces la... more The effects of heat treatments of milk and whey prior to lactose hydrolysis with Kluyveromyces lactis β-galactosidase were studied. It was observed that heat treatment of milk significantly increases lactase activity, with a maximum activity increase found when milk was heated at 55°C. In whey from 55 up to 75°C, β-galactosidase activity decreased slightly. Nevertheless, heating whey at 85°C for 30 min raised the rate of hydrolysis significantly. Electrophoretic patterns and UV spectra proved that the activity change correlated with milk protein denaturation, particularly that of β-lactoglobulin. Heating whey permeate did not increase the enzyme activity as heating whole whey; but heating whey prior to ultrafiltration also resulted in enzyme activation. Measurement of free sulfhydryl (SH) groups in both whey and heated whey permeate showed that the liberation of free SH is highly correlated to the change of the activity. Furthermore, this activation can be reversed by oxidizing the reactive sulfhydryl groups, proving that the observed effect may be related to the release of free SH to the medium, rather than to the denaturation of a thermolabile protein inhibitor.
Opuntia tomentosa seeds have physiological dormancy and a permeable but hard funicular envelope t... more Opuntia tomentosa seeds have physiological dormancy and a permeable but hard funicular envelope that restricts water uptake and embryo growth. Dormancy break, germination, and changes in the funiculus were compared in laboratory-stored seeds and in those buried for 7 months at different microsites and later exhumed and stored in the laboratory. The funicular envelopes of both lots were examined with a scanning electron microscope (SEM). Seeds in both lots were: scarified with H2SO4 (0, 45, 60 and 90 min), treated with gibberellins (0, 1000 and 2000 ppm) and germinated at the same ages (0, 2, 4, 7, and 10 months after exhumation) at 24 °C. Light effect was determined at 24 °C and 20–35 °C. In laboratory-stored seeds germination was low. Exhumed seeds germinated in ∼50%, the remaining ones required scarification and gibberellins, but lost dormancy two months later. Gibberellins reduced germination heterogeneity, and scarification reduced germination; the adverse effect of scarification was offset by gibberellins. Exhumed seeds germinated mainly in darkness at 20–35 °C and partially in far red light at both temperatures. SEM showed that fungi eroded the funiculus reducing its resistance. O. tomentosa could form a seed bank, ensuring its survival under heterogeneous environments.
The secondary structure of Kluyveromyces lactis beta-galactosidase was determined by circular dic... more The secondary structure of Kluyveromyces lactis beta-galactosidase was determined by circular dichroism. It is mainly a beta-type protein, having 22% beta-turns, 14% parallel beta-sheet, 25% antiparallel beta-sheet, 34% unordered structure, and only 5% alpha-helix. The structure-activity relationship as a function of the pH was also studied. The pH conditions leading to the highest secondary structure content (100% ellipticity) of the enzyme was found at pH 7.0; at pH 6.5-7.0, the percent ellipticity decreased slightly, suggesting little structural change, but the activity decreased significantly, probably because of variations in critical residues. On the other hand, at pH's above 7.0, a more noticeable change in ellipticity was observed due to structural changes; the CD analysis showed a small increase in the helical content toward higher pH, whereas the maximum activity was found at pH 7.5, meaning that the changes produced in the secondary structure at this pH favored the interaction between the enzyme and the substrate.
Prion diseases or transmissible spongiform encephalopathies are a group of fatal neurodegenerativ... more Prion diseases or transmissible spongiform encephalopathies are a group of fatal neurodegenerative diseases caused by an abnormal form of prion protein (PrPsc). In this study, we developed a sensitive histochemical detection of PrPsc deposits in a Gertsmann-Sträussler-Scheinker disease (GSS) patient using toluidine blue-O staining, a specific reagent to stain mucins and mucopolysaccharides. Detection of prion deposits correlated with immunohistochemistry using anti-prion antibodies. Control assays were performed using amyloid-β (Aβ) plaques from Alzheimer's disease (AD) brains. Our results demonstrated that toluidine blue-O staining allowed to recognize 69.1±2.6% of the total plaques recognized by the anti-prion antibody. Furthermore, in the 15 studied brain regions from the GSS patient, toluidine blue-O revealed the same recognition pattern as anti-prion labeling. Toluidine blue-O stained specifically the prion deposits but not the Aβ plaques in AD brains. The specificity of the technique was confirmed in a Creutzfeldt-Jakob disease brain. This method opens several possibilities for postmortem diagnoses. Our results also suggest the relevance of specific post-translational modifications of PrPsc, identified by toluidine blue-O, that might participate in the transformation of PrPc to PrPsc.
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