Lennart Nelson

Alterations in mitochondrial aconitase activity and respiration, and in concentration of citrate in some organs of mice with experimental or genetic diabetes

Aconitase Alloxan Citrate Diabetes Mitochondria Respiration

Changes in the content of ATP and GTP during the development of Xenopus laevis

Abstract The changes in average GTP and ATP content of developing Xenopus laevis embryos have been studied. Both nucleotides increase during the first cleavage stages and decrease thereafter. GTP shows a second maximum during gastrulation. The significance of these changes in relation to cellular processes like DNA-synthesis, formation of microtubules and micro-filaments, etc., is discussed.

Changes in Activity of Mitochondrial Enzymes during the Development of Xenopus laevis

Changes in activity of mitochondrial enzymes were studied during the embryonic development of Xenopus laevis.

Morphological differentiation of mitochondria in the early amphibian embryo

Abstract Three different cell types (epidermal cells, fibroblast-like Ruffini cells and undifferentiated cells) may be observed in cultures of cells isolated from the blastula of Ambystoma mexicanum . Electron micrographs show that the mitochondria in the two kinds of differentiated cells have the orthodox conformation; those in the undifferentiated cells the condensed conformation. Measurements of the area and the form factor demonstrate that the mitochondria in the differentiated cells are considerably larger than those in the undifferentiated cells, and that the three populations of mitochondria differ significantly from each other.

Effect of alloxan on the transport of dicarboxylate, tricarboxylate, pyruvate and glutamate in isolated mouse liver mitochondria

SummaryThe effect of alloxan on anion transport in isolated mouse liver mitochondria was studied with the swelling technique. Mitochondria pre-incubated with alloxan exhibited partial inhibition of the transport of malate, citrate, pyruvate and glutamate. 2n-butylmalonate caused complete inhibition of malate transport, and the translocation of citrate was completely blocked by 1,2,3-benzenetricarboxylate, while N-ethylmaleimide inhibited glutamate transport partially. The observation that alloxan inhibits different mitochondrial anion transport mechanisms emphasizes that the drug profoundly affects mitochondrial function.

Changes in the activities of mitochondrial carriers during the development of Xenopus laevis

Abstract The transport of the substrates phosphate, pyruvate, malate, fumarate, α-ketoglutarate, citrate, isocitrate and glutamate has been determined in mitochondria isolated from various developmental stages of Xenopus laevis . The carriers may be sub-divided into three groups with respect to the pattern of changes in activity: 1. 1. Pyruvate, tricarboxylate and glutamate/OH carriers, distinguished by low activities during the pregastrula stages and a subsequent increase in activity. 2. 2. Phosphate and α-ketoglutarate carriers, with a constant activity throughout development. 3. 3. Malate and fumarate carriers, highly active initially, but decreasing already after gastrulation. The results are discussed in relation to mitochondrial differentiation and the change from embryonic to adult metabolism.

Factors affecting the inhibition by alloxan, and effect of streptozotocin on phosphate transport in isolated mouse mitochondria

SummaryThe swelling technique evidenced inhibition of Pi transport in isolated mouse liver mitochondria by 1 mM or higher concentration of alloxan, while no effect was found with streptozotocin. Complete or partial protection against alloxan inhibition was found under the following conditions: preincubation at 4 °C, or pretreatment with Pi, glucagon, succinate, malate or pyruvate. Complete protection was observed in isolated mitochondria from mice injected with glucagon. No protection was seen under the following conditions: preincubation at 37 °C, addition of microsomes, or pretreatment with insulin or glucagon in the presence of glucagon antibodies. So-called light and heavy mitochondria were as sensitive to alloxan as those obtained with the routine technique. Alloxanic acid had no effect, and addition of cysteine or glutathione abolished the inhibition by alloxan. Alloxan inhibited Pi transport also in isolated lung mitochondria. The findings suggest a direct action of alloxan on mitochondrial Pi transport which is affected by the energetic state. A relationship seems to exist between protection against alloxan toxicityin vivo and protection under the present experimental conditions.