Functional Properties Of The Hemoglobin From The South American Snake Mastigodryas Bifossatus.

The hemolysate of Mastigodryas bifossatus shows two major hemoglobins with very close isoelectric points, and four different globin chains. The stripped hemolysate exhibits a low alkaline Bohr effect (delta log P50/delta pH = -0.30 between pH 7 and 8) and a decrease of the co-operativity from 2.3 to unity when the pH increases from 6.15 to 8.5. In the presence of ATP, large changes in the oxygen affinity and co-operativity are observed. The Bohr effect rises to -0.46 and the n50 values stay at around 3 in the pH range 6-9. An increase in temperature induces a large decrease in the oxygen affinity for the stripped hemolysate. In the pH range between 7.5 and 8.5, the values of delta H in kcal/M are around 10 fold larger for the stripped protein than for the protein in the presence of ATP. Measurements of rapid kinetics of oxygen dissociation and carbon monoxide binding reflect the ATP sensitivity observed in equilibrium experiments.1091085-9

Lack of conventional oxygen-linked proton and anion binding sites does not impair allosteric regulation of oxygen binding in dwarf caiman hemoglobin

In contrast to other vertebrate hemoglobins (Hbs) whose high intrinsic O2 affinities are reduced by red cell allosteric effectors (mainly protons, CO2, organic phosphates, and chloride ions), crocodilian Hbs exhibit low sensitivity to organic phosphates and high sensitivity to bicarbonate (HCO3—), which is believed to augment Hb-O2 unloading during diving and postprandial alkaline tides when blood HCO3— levels and metabolic rates increase. Examination of α- and β-globin amino acid sequences of dwarf caiman (Paleosuchus palpebrosus) revealed a unique combination of substitutions at key effector binding sites compared with other vertebrate and crocodilian Hbs: β82Lys→Gln, β143His→Val, and β146His→Tyr. These substitutions delete positive charges and, along with other distinctive changes in residue charge and polarity, may be expected to disrupt allosteric regulation of Hb-O2 affinity. Strikingly, however, P. palpebrosus Hb shows a strong Bohr effect, and marked deoxygenation-linked binding of organic phosphates (ATP and DPG) and CO2 as carbamate (contrasting with HCO3— binding in other crocodilians). Unlike other Hbs, it polymerizes to large complexes in the oxygenated state. The highly unusual properties of P. palpebrosus Hb align with a high content of His residues (potential sites for oxygenation-linked proton binding) and distinctive surface Cys residues that may form intermolecular disulfide bridges upon polymerization. On the basis of its singular properties, P. palpebrosus Hb provides a unique opportunity for studies on structure-function coupling and the evolution of compensatory mechanisms for maintaining tissue O2 delivery in Hbs that lack conventional effector-binding residues

Orientação sobre o uso de vitamina A na saúde escolar: comparação de técnicas pedagógicas Orientation on the use of vitamin A in school health: comparision of pedagogical techniques

O trabalho tem por objetivo comparar a eficácia de técnicas de ensino em motivar a criança em assimilar a importância dos alimentos ricos em vitamina A, e as conseqüências da falta desses nutrientes para o organismo. Foi elaborado material didático com 2 técnicas pedagógicas: uma baseada em um texto de conotação literária e outra, em teatro de fantoches. O estudo foi desenvolvido com alunos da 3ª série do ciclo básico da Escola Municipal Orlando Paulino da Costa, na zona rural de Alfenas, através da aplicação de questionários. Os resultados demonstraram que as técnicas pedagógicas empregadas promoveram aprendizagem de conceitos em relação à vitamina A e incentivo para o consumo de alimentos ricos nesses nutrientes. Não se verificaram diferenças significativas entre as técnicas pedagógicas (Teste de Comparação das Proporções, com p<0,05), uma vez que ambas utilizam os mesmos princípios metodológicos. Concluímos que a aplicação de métodos lúdicos é um incentivador para a reeducação alimentar. Propõe-se, então, o uso desses recursos nas escolas para a aprendizagem de conteúdos de saúde e alimentação.<br>Compare the efficiency teaching techniques with respect to their ability to motivate children in the assimilation of the importance of foods rich in vitamin A and the consequences of the absence of these nutrients for the organism. A didactic material comprising two pedagogical techniques was drawn up: one was based on a text with literary connotation and the other with theater marionettes. The study was developed by third grade students in an elementary school - Escola Municipal Orlando Paulino da Costa (local governement school) - located in the rural area of Alfenas, Minas Gerais, by applying questionnaires. Results demonstrated that the pedagogical techniques used provided learning of concepts related to vitamin A and that they incentivated the consumption of food products containing this vitamin. No significant differences were detected between the pedagogical techniques (Proportion Comparison Test, with p< 0.05), since they both make the use of the same methodological principles. We conclude that the application of playing methods was a stimulus to nourishing education. Thus, we propose to use these resources in schools so that children can learn health and nourishment issues

Functional behavior of tortoise hemoglobin Geochelone denticulata Comportamento funcional da hemoglobina da tartaruga Geochelone denticulata

The hemolysate from Geochelone denticulata contains two main hemoglobin components, as shown by ion exchange chromatography and polyacrylamide gel electrophoresis (PAGE). Electrophoresis under dissociating conditions showed three types of globin chains. The apparent molecular mass, as determined by gel filtration on Sephadex G-200, was compatible with tetrameric Hb, which was unable to polymerize. The G. denticulata Hb has a P50 value of 9.56 mm Hg at pH 7.4. The Hb oxygenation appears to be under the control of organic phosphates and hydrogen ion since it is strongly affected by those species. In the presence ATP or IHP the P50 values increased to 29.51 mm Hg and 54.95 mm Hg, respectively, at pH 7.4. The n50 was generally lower than 1.5 in stripped Hb, suggesting a dissociation of tetramers. In the presence of organic phosphates n50 values increased to approximately 2.5. The Bohr effect was evident in oxygen equilibrium experiments. The hematocrit (32%) and Hb concentration (5.7 mM as heme) of G. denticulata blood were substantially larger than those of G. carbonaria, but the methemoglobin levels were similar in both species, approximately 1%. Thus, the oxygen capacity of blood appears to be higher in G. denticulata than in G. carbonaria, particularly considering the functional properties of their Hbs, which would guarantee the survival of animals.<br>O hemolisado de Geochelone denticulata contém dois componentes principais, de acordo com a cromatografia de troca iônica e PAGE. Eletroforese sob condições dissociantes mostrou 3 tipos de cadeias de globina. A massa molecular aparente, determinada pela filtração em gel sobre Sephadex G-200, foi compatível com Hb tetramérica que foi incapaz de polimerizar. A Hb de G. denticulata tem valor de P50 de 9,56 mm Hg em pH 7,4. A oxigenação da Hb parece estar sob controle de fosfatos orgânicos e íons hidrogênio, uma vez que ela é fortemente afetada por essas espécies. Na presença de ATP ou IHP, os valores de P50 aumentaram para 29,51 mm Hg e 54,95 mm Hg, respectivamente, a pH 7,4. O n50 foi geralmente menor que 1,5 na Hb stripped, sugerindo dissociação de tetrâmeros. Na presença de fosfatos orgânicos, os valores de n50 aumentaram para aproximadamente 2,5. O efeito Bohr foi evidente nos experimentos de equilíbrio com oxigênio. O hematócrito de 32% e a concentração de Hb de 5,7 mM em heme no sangue de G. denticulata foram substancialmente maiores do que da G. carbonaria, mas os níveis de metahemoglobina foram similares em ambas as espécies, aproximadamente 1%. Portanto, a capacidade de oxigenação do sangue parece ser maior na G. denticulata, particularmente considerando as propriedades funcionais da Hb, que garantiria a sobrevivência dos animais