Mitochondrial creatine kinase activity in patients with disturbed energy generation in muscle mitochondria.

Eleven patients with an established disturbance in muscle mitochondrial energy generation, in whom no defect in the pyruvate dehydrogenase complex or in the complexes of the respiratory chain could be detected, were investigated for a possible deficiency of mitochondrial creatine kinase (Mi-CK) (EC 2.7.3.2). Four patients with a defect in one of the complexes of the respiratory chain were also investigated for Mi-CK activity. In none of the investigated patients was Mi-CK deficiency found. Surprisingly, two of the four patients with a defect in one of the respiratory chain complexes showed enhanced activity of Mi-CK. It is concluded that Mi-CK deficiency is not frequently found as a primary defect in patients with disturbance in mitochondrial energy generation, but more patients should be examined to allow a definite conclusion.

Evaluation of a daily dose of 25 micrograms vitamin K1 to prevent vitamin K deficiency in breast-fed infants.

Vitamin K prophylaxis is recommended to prevent the hazard of hemorrhage caused by vitamin K deficiency in young infants. A single administration after birth seems inadequate to completely prevent late haemorrhagic disease in breast-fed infants. The preventive effect of a daily oral dose of 25 micrograms vitamin K1, which is comparable to about half the dose ingested by formula-fed infants, was evaluated in 58 breast-fed infants. No clinical or biochemical signs of vitamin K deficiency occurred; PIVKA-II was not detectable, and vitamin K1 concentrations were moderately elevated. Vitamin K1 levels were negatively correlated with the number of hours elapsed since the most recent gift. Twenty to 28 h after the administration, median (P10-P90) levels were 1,262 (267-4,328), 1,072 (293-3,427), and 882 (329-2,070) pg/ml at 4, 8, and 12 weeks of age, respectively. Vitamin K1 levels in formula-fed infants (n = 10) were around 7,000 pg/ml. In conclusion, daily supplementation of 25 micrograms vitamin K1 can be recommended for breast-fed infants to prevent vitamin K deficiency beyond the neonatal period.

Maturation of mitochondrial and other isoenzymes of creatine kinase in skeletal muscle of preterm born infants.

We studied pre- and postnatal changes in total creatine kinase (CK) activity, mitochondrial creatine kinase (Mi-CK) activity and immunochemical reactivity with anti-Mi-CK antibodies in skeletal muscle specimens from 12 infants, 10 of them preterm born, after a pregnancy varying between 28 and 40 weeks. Our results demonstrate that Mi-CK is present in fetal human quadriceps muscle and that the specific activity of Mi-CK increases during prenatal development from week 28 to 40 by a factor about two. Generally, adult levels have not been reached at birth, indicating a further postnatal increase of the activity of the enzyme. The Mi-CK protein content also increases during prenatal development. These results suggest that in human skeletal muscle the expression and accumulation of Mi-CK starts at mid-gestation, later than is known to occur for cytosolic CK.

A method for quantitative measurement of mitochondrial creatine kinase in human skeletal muscle.

Defects in the mitochondrial energy generating system in patients with a mitochondrial myopathy are known to be localized in various enzyme complexes involved in energy production. Such a defect may exist at the level of mitochondrial creatine kinase (Mi-CK). On that account we have developed a method for measurement of the enzyme activity in human skeletal muscle biopsy material (greater than 10 mg). Interfering creatine kinase isoenzymes are removed by anion exchange and affinity chromatography. The activity of Mi-CK in reference skeletal muscle homogenates amounts to 240 +/- 88 mU/mg protein (30 +/- 8.0 mU/mg wet weight).

Postnatal development of pyruvate oxidation in quadriceps muscle of the rat.

In order to evaluate the age dependency of enzymes involved in the energy-generating system, skeletal muscle specimens from rats of different ages were investigated for several mitochondrial enzymes. [1-14C]pyruvate (+/- ADP) oxidation rates and pyruvate dehydrogenase complex (PDHC) activity increased significantly from low early values during the neonatal period to nearly adult values at the end of the suckling period. Other enzymes of the pyruvate oxidation route such as citrate synthase and cytochrome c oxidase showed similar patterns of development. Immunoblot studies of PDHC detected a clear increase in the intensity of the bands of the alpha subunits of E1 (pyruvate dehydrogenase) and E2 (dihydrolipoyl transacetylase) within the first 3 weeks of life. The ratio between the individual PDHC proteins indicated that E1 alpha, the regulatory subunit of the multienzyme complex, is the most rapidly increasing protein with age.

Familial selective IgA deficiency with circulating anti-IgA antibodies: a distinct group of patients?

Two families were investigated in which the mothers had selective IgA deficiency and circulating class-specific anti-IgA antibodies. Both gave birth to two children who were found to be IgA deficient. Three of these children developed anti-IgA antibodies before puberty. In vitro immunoglobulin production studies performed in the children of both families revealed an IgA B cell defect combined with IgA-specific excessive T suppressor function in all four. The mechanisms by which transplacental passage of maternal anti-IgA antibodies could have interfered with the developing IgA system in the offspring are discussed.

Four methods compared for measuring des-carboxy-prothrombin (PIVKA-II).

PIVKA-II (Protein Induced by Vitamin K Absence) is abnormal des-carboxylated prothrombin, which is present in vitamin K deficiency or in patients using warfarin. With a sensitive method for PIVKA-II, biochemical vitamin K deficiency can be established before clinical symptoms occur. We give an overview of methods used to detect PIVKA-II, and four selected methods are inter-compared: (a) measuring total factor II including PIVKA-II by using Echis carinatus snake venom as an activator of prothrombin; (b) measuring PIVKA-II by using snake venom as an activator of factor II after adsorption of functional factor II onto barium sulfate; (c) electrophoresis-immunofixation method; and (d) enzyme immunoassay. We found d to be the most sensitive and reliable method for PIVKA-II.