Mitochondrial DNA (mtDNA) content is thought to remain stable over the preimplantation period of human embryogenesis that is, therefore, suggested to be entirely dependent on ooplasm mtDNA capital. We have explored the impact of two disease-causing mutations [m.3243A>G myopathy, encephalopathy, lactic acidosis and stroke-like syndrome (MELAS) and m.8344A>G myoclonic epilepsy associated with ragged-red fibers (MERRF)] on mtDNA amounts in human oocytes and day 4-5 preimplantation embryos. The mtDNA amount was stable in MERRF and control materials, whereas gradually increasing from the germinal vesicle of oogenesis to the blastocyst stage of embryogenesis in MELAS cells, MELAS embryos carrying ∼3-fold higher mtDNA amount than control embryos (P = 0.0003). A correlation between mtDNA copy numbers and mutant loads was observed in MELAS embryos (R(2) = 0.42, P < 0.0013), suggestive of a compensation for the respiratory chain defect resulting from high mutation levels. These results suggest that mtDNA can replicate in early embryos and emphasize the need for sufficient amount of wild-type mtDNA to sustain embryonic development in humans.
Net fluxes of sodium and potassium ions were determined in sodium-loaded, potassium-depleted erythrocytes from 370 white subjects, 194 of whom had essential hypertension or had been born to parents with essential hypertension. Findings were compared with those in 86 controls who were normotensive and did not have a family history of hypertension.Compared with controls all patients with essential hypertension had a low sodium to potassium ratio secondary to a deficit in the sodium-potassium cotransport system. A similar abnormality was found in subjects born to parents with essential hypertension, the prevalences of a deficient cotransport system in such subjects being 53 6% (52 out
A genetic analysis of 96 pedigrees has confirmed our previously published report and demonstrated an autosomal recessive mode of inheritance for idiopathic haemochromatosis.
Three generations have been analyzed in each family: the sibship of the patient; the parents of the patient; the offspring of the patient. All the data are consistent with a recessive autosomal transmission: (1) An increased rate of consanguineous matings was found among the parents of the patients. (2) Not a single patient having the disease (latent or manifat) was found among either the parents or the children of the probands. (3) Three distinct levels of iron stores ‐ normal, slightly increased and heavily overloaded ‐ have been statistically separated in the haemochroma‐totic families. (4) The result of a segregation analysis has shown a percentage of parsom with heavy iron overloads per sibship corresponding to that expected for a recessive autosomal transmission, taking into account a penetrance of 0.20 in the female (the estimate used in this study).
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