Analysis of a Calcium Ion Binding System Composed of Two Different Sites

Using murexide (Mx), a metallochromic indicator, and a dual wavelength spectrophotometer with a high signal-to-noise ratio, the Ca(++) binding in a system containing two classes of binding sites was studied. Solutions with solute containing one or two classes of Ca(++) binding sites and without such solute were titrated with Ca(++) using Mx as an indicator of free Ca(++) concentration. Since curvilinear Scatchard plots are obtained from titration curves of solutes containing two classes of binding sites, a computer program was developed to resolve such plots into two linear partial plots, each corresponding to a single class of binding site. The validity of the procedure was examined with solutions of ethylene glycol bis(β-aminoethyl)-N-N′-tetraacetic acid, adenosine triphosphate (EGTA, ATP), or a mixture thereof. The method was also applied to biological material and it was found that a protein fraction isolated from rat skeletal muscle sarcotubular membranes, termed Fraction-2 (Fr-2), has two classes of binding sites for Ca(++); the association constants of the high affinity site and low affinity site are 4.3 × 10(5) M(-1) and 9 × 10(3) M(-1), respectively. The advantages and limitations of this methodology are discussed

A velhice, entre o normal e o patológico Old age, normality versus pathology

Com a ascensão do envelhecimento da população brasileira ao posto de 'problema social', assistimos a um crescimento cada vez maior do número de especialistas dedicados a este 'grupo etário': os geriatras e gerontólogos, que ocupam papel de destaque na formulação das novas formas de gestão da velhice. No entanto, a gerontologia parece ter problemas internos na sua formulação como campo de saber, que parecem comprometer sua consolidação como profissão e seu reconhecimento como disciplina científica. No presente artigo, procuramos chamar atenção para as dificuldades que a gerontologia encontra para delimitar seu campo e definir seu objeto. Sustentamos que tais dificuldades parecem derivar de uma questão central, que é a impossibilidade de serem delimitadas as fronteiras entre o normal e o patológico, na velhice. Por fim, analisamos a questão sob um ponto de vista histórico, à luz do processo de constituição do saber médico sobre o envelhecimento.<br>Since life expectancy of Brazilian population increased and aging was considered a "social problem", there has been a boom of specialists in old age. Gerontologists and geriatricians are now playing a relevant role in setting new trends to the management of issues related to old age. However, gerontology as a field of knowledge seems to have internal questions that apparently hinder its professional consolidation and its scientific recognition. In this article, the author focus the difficulties gerontology has in order to delimitate its field of action and to define the object of its studies. The author argues that such difficulties derive from a central point: the impossibility to delimitate the frontiers between what is normal and what is pathological in old age. He also analyzes the constitution of medical knowledge on aging in a historical perspective

Biological stress response terminology: Integrating the concepts of adaptive response and preconditioning stress within a hormetic dose-response framework.

Many biological subdisciplines that regularly assess dose-response relationships have identified an evolutionarily conserved process in which a low dose of a stressful stimulus activates an adaptive response that increases the resistance of the cell or organism to a moderate to severe level of stress. Due to a lack of frequent interaction among scientists in these many areas, there has emerged a broad range of terms that describe such dose-response relationships. This situation has become problematic because the different terms describe a family of similar biological responses (e.g., adaptive response, preconditioning, hormesis), adversely affecting interdisciplinary communication, and possibly even obscuring generalizable features and central biological concepts. With support from scientists in a broad range of disciplines, this article offers a set of recommendations we believe can achieve greater conceptual harmony in dose-response terminology, as well as better understanding and communication across the broad spectrum of biological disciplines

Biological stress response terminology: Integrating the concepts of adaptive response and preconditioning stress within a hormetic dose-response framework.

Many biological subdisciplines that regularly assess dose-response relationships have identified an evolutionarily conserved process in which a low dose of a stressful stimulus activates an adaptive response that increases the resistance of the cell or organism to a moderate to severe level of stress. Due to a lack of frequent interaction among scientists in these many areas, there has emerged a broad range of terms that describe such dose-response relationships. This situation has become problematic because the different terms describe a family of similar biological responses (e.g., adaptive response, preconditioning, hormesis), adversely affecting interdisciplinary communication, and possibly even obscuring generalizable features and central biological concepts. With support from scientists in a broad range of disciplines, this article offers a set of recommendations we believe can achieve greater conceptual harmony in dose-response terminology, as well as better understanding and communication across the broad spectrum of biological disciplines