RESUMO
A mathematical model of the Münch pressure-flow hypothesis for long-distance transport of carbohydrates via sieve tubes is constructed using the Navier-Stokes equation for the motion of a viscous fluid and the van't Hoff equation for osmotic pressure. Assuming spatial dimensions that are appropriate for a sieve tube and ensuring suitable initial profiles of the solute concentration and solution velocity lets the model become mathematically tractable and concise. In the steady-state case, it is shown via an analytical expression that the solute flux is diffusion-like with the apparent diffusivity coefficient being proportional to the local solute concentration and around seven orders of magnitude greater than a diffusivity coefficient for sucrose in water. It is also shown that, in the steady-state case, the hydraulic conductivity over one metre can be calculated explicitly from the tube radius and physical constants and so can be compared with experimentally determined values. In the time-dependent case, it is shown via numerical simulations that the solute (or water) can simultaneously travel in opposite directions at different locations along the tube and, similarly, change direction of travel over time at a particular location along the tube.
Assuntos
Metabolismo dos Carboidratos , Pressão Osmótica , Estruturas Vegetais/fisiologia , Algoritmos , Transporte Biológico , Simulação por Computador , Difusão , Cultura em Câmaras de Difusão/instrumentação , Modelos Biológicos , Sacarose/metabolismo , Fatores de Tempo , Água/química , Água/metabolismoRESUMO
Manufacture of an Ayurvedic arsenic-containing compound is described, which is currently in use in India to control blood counts of patients with haematological malignancies. The efficacy and side effects of this compound are evaluated in the light of the fact that arsenic was recognised to be of use in the control of blood counts from patients with chronic myeloid leukaemia as long as 100 years ago, in the West.
Assuntos
Antineoplásicos/uso terapêutico , Arsenicais/uso terapêutico , Contagem de Células Sanguíneas/efeitos dos fármacos , Leucemia/tratamento farmacológico , Ayurveda , Metais/uso terapêutico , Enxofre/uso terapêutico , Antineoplásicos/efeitos adversos , Antineoplásicos/síntese química , Arsenicais/síntese química , Arsenicais/história , Criança , História do Século XIX , História do Século XX , História Antiga , Humanos , Índia , Ceratose/induzido quimicamente , Leucemia/sangue , Transtornos da Pigmentação/induzido quimicamente , Plantas Medicinais , Esplenomegalia/tratamento farmacológicoRESUMO
A brief review of the history of human leukemia, first identified as a new disease in 1845, is given as a personal perspective related to the re-examination of dogmas surrounding the disease. The paper addresses the question of what kind of disease leukemia is, and how far the adherence to dogma has shaped the firm belief that leukemia is a malignancy.
Assuntos
Leucemia/história , Leucemia/terapia , Adulto , Criança , Feminino , França , História do Século XVIII , História do Século XIX , História do Século XX , Humanos , Japão , Leucemia/mortalidade , Masculino , Pessoa de Meia-Idade , Reino UnidoRESUMO
Further biochemical investigations were performed in a case of glucose-6-phosphate dehydrogenase deficiency--called the "Vienna" deficiency variant on account of its biochemical characterization. It was found that the "Vienna" deficiency variant shows increased enzyme protein at a reduced specific activity. Gel filtration on Sephadex-G-200 produced a molecular weight identical with that of the normoenzyme; the different cochromatographic behaviour on hydroxylapatite appears attributable to a sequence modification of the amino acids.