Technical advancements in molecular genetics have shown various mitochondrial DNA (mtDNA) abnormalities in patients with mitochondrial myopathies. Recently, it has been revealed that, in these patients, the nuclear DNA carries sequences similar to those of the mtDNA (nuclear pseudogene) and it has several point mutations previously reported to be pathogenic. We verified the existence of the T3250C and T3291C mutations, which we have found in patients with mitochondrial myopathy, in the authentic mitochondrial genome. A long polymerase chain reaction provides a powerful tool for avoiding nuclear pseudogene amplification and for ruling out ambiguity in the detection of the mutation for diagnosis.

We studied the proportion of deleted mitochondrial DNA in blood cells from patients with Pearson syndrome. Patient 1 is a 17-year-old female with Kearns-Sayre syndrome who survived Pearson syndrome. Patient 2 is a 5-year-old boy with Pearson syndrome who recovered from refractory anaemia but continues to have thrombocytopenia and neutropenia. Patient 3 is a female neonate who died with severe acidosis and pancytopenia at 14 days of age. Southern blot analysis was performed with total DNA from three patients' blood cells and two samples of bone marrow cells from one patient. In peripheral blood, patients with a higher proportion of deleted mitochondrial DNA had lower blood cell counts. In patient 2, the percentage of mutant mitochondrial DNA in bone marrow cells decreased as anaemia improved. This indicates that the proportion of deleted mitochondrial DNA in peripheral blood and in bone marrow has a tendency to correlate to the severity of haematological manifestation.

We report on a seven-year-old Japanese boy with Pearson syndrome, which is characterized by refractory sideroblastic anemia with vacuolization of marrow precursors and dysfunction of the exocrine pancreas, and caused by mitochondrial (mt) DNA deletions and duplications. Although analysis with Southern hybridization on his bone marrow cells at age one year or on the muscle at age five years did not detect any duplications of mtDNA, an analysis after death at age seven years detected them in the kidney, heart, and even in the bone marrow. Using long PCR to specifically amplify duplicated mtDNA, we found duplications in all biopsy and postmortem samples, indicating that duplications had been present in the patient since his early life, and that the number of duplications increased with age. The results indicate some dynamism in the mtDNA duplication and that the dynamism may imply clinical importance.

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The effects of weaning (abrupt dietary changes from breast milk to solid food) and corticosterone injection on antral gastrin-like immunoreactivity (G-LI) concentrations and antral G-LI biosynthesis were studied in rats. A single dose of corticosterone acetate was injected in one group of 7 day old rats, and a single dose of physiological saline was injected in another. Each group of rats was divided into two subgroups, one fed only rat breast milk until 25 days old and the other weaned at day 21. Inn on-cor t i cost erone treated unweaned rats, antral G-LI did not increase. In non-corticosterone treated weaned rats, antral G-LI was constant before weaning, then increased 4-fold to the adult level. In corticosterone treated unweaned rats, the antral G-LI on day 11 was twice than on day 7, and thereafter remained constant.In corticosterone treated weaned rats, antral G-LI increased after corticosterone treatment and increased again after weaning to reach the adult level at day 25. Gel filtration of pulse-chase incubated antral samples with l-[methyl-3H]methionine from unweaned rats without corticosterone administration showed Vo, fraction 19 (Fr. 19) and gastrin-34 (G34) peaks, but no gastrin-17 (G17) peak after 60 min of chase incubation, but at 120 min of chase incubation a G17 peak was present; corticosterone-treated and/or weaned (solid food alone) rat samples showed Vo, Fr. 19, G34 and G17 peaks at 30 min of pulse incubation.Gastrin has been isolated in two chemically de¬ fined main forms: big gastrin (gastrin-34, G34) and little gastrin (gastrin-17, G17); G17 is thought to be derived from G34 (Walsh 1977; Dockray et al. 1978). However, the physiological mechanisms responsible for initiating gastrin biosynthesis are not well understood. Recent studies have shown that the antral gastrin concentration increases greatly when weaning is started (Lichtenberger & Johnson 1974; Takeuchi et al. 1981). Peitsch et al. (1981) demonstrated that in unweaned young rats corticosterone injection caused an increase in antral gastrin concentration. The present study was undertaken to evaluate the effect of weaning and corticosterone administration on antral gastrin-like immunoreactivity concentration and bio¬ synthesis in young rats. Material and MethodsThe effect ofdietary changes and corticosterone adminis¬ tration on antral gastrin-like immunoreactivity (G-LI) concentration (Study I) Animak. Male Wistar rats were reared in individual cages in a temparature-and light-controlled room ( 12 h dark and 12 h light). Rats aged 7 to 25 days and adult rats (350 g, 15 weeks old) were divided into six groups.Group 1 rats were injected with a single dose of isotonic saline (0.1 ml) sc on day 7 and were placed in a cage with a mother. They were allowed to suckle ad libitum, but were given no access to solid food until 21 days old, when weaning (dietary changes from breast milk to solid food) was started. The lactating mothers were changed every 12 h. Group 2 rats were treated with isotonic saline, as in group I, and received breast m...