Translation ability of mitochondrial tRNAsSer with unusual secondary structures in an in vitro translation system of bovine mitochondria.

BACKGROUND: Metazoan mitochondrial (mt) tRNAs are structurally quite different from the canonical cloverleaf secondary structure. The mammalian mt tRNASerGCU for AGY codons (Y = C or U) lacks the entire D arm, whereas tRNASerUGA for UCN codons (N = A, G, C or U) has an extended anti-codon stem. It has been a long-standing problem to prove experimentally how these tRNAsSer work in the mt translation system. RESULTS: To solve the above-mentioned problem, we examined their translational abilities in an in vitro bovine mitochondrial translation system using transcripts of altered tRNASer analogues derived from bovine mitochondria. Both tRNASer analogues had almost the same ability to form ternary complexes with mt EF-Tu and GTP. The D-arm-lacking tRNASer GCU analogue had considerably lower translational activity than the tRNASerUGA analogue and produced mostly short oligopeptides, up to a tetramer. In addition, tRNASerGCU analogue was disfavoured by the ribosome when other tRNAs capable of decoding the cognate codon were available. CONCLUSION: Both mt tRNASerGCU and tRNASerUGA analogues with unusual secondary structure were found to be capable of translation on the ribosome. However, the tRNASerGCU analogue has some molecular disadvantage on the ribosome, which probably derives from the lack of a D arm.

Identification and characterization of mammalian mitochondrial tRNA nucleotidyltransferases.

The CCA-adding enzyme (ATP:tRNA adenylyltransferase or CTP:tRNA cytidylyltransferase (EC )) generates the conserved CCA sequence responsible for the attachment of amino acid at the 3' terminus of tRNA molecules. It was shown that enzymes from various organisms strictly recognize the elbow region of tRNA formed by the conserved D- and T-loops. However, most of the mammalian mitochondrial (mt) tRNAs lack consensus sequences in both D- and T-loops. To characterize the mammalian mt CCA-adding enzymes, we have partially purified the enzyme from bovine liver mitochondria and determined cDNA sequences from human and mouse dbESTs by mass spectrometric analysis. The identified sequences contained typical amino-terminal peptides for mitochondrial protein import and had characteristics of the class II nucleotidyltransferase superfamily that includes eukaryotic and eubacterial CCA-adding enzymes. The human recombinant enzyme was overexpressed in Escherichia coli, and its CCA-adding activity was characterized using several mt tRNAs as substrates. The results clearly show that the human mt CCA-adding enzyme can efficiently repair mt tRNAs that are poor substrates for the E. coli enzyme although both enzymes work equally well on cytoplasmic tRNAs. This suggests that the mammalian mt enzymes have evolved so as to recognize mt tRNAs with unusual structures.

Significance of ACE genotypes and medical treatments in childhood focal glomerulosclerosis.

BACKGROUND: There is little information on the significance of angiotensin-converting enzyme (ACE) genotypes and medical treatments in children with primary focal segmental glomerulosclerosis (FSGS). METHODS: A multicenter retrospective study was performed on the role of ACE genotypes and medical treatments in 43 Japanese children with FSGS (20 males and 23 females), including 17 children who progressed to end-stage renal failure during the mean observation period of 6.9 +/- (SD) 5.0 years. RESULTS: The incidence of the D allele of the ACE gene was higher in the whole group of 43 children with FSGS and in a subgroup of 28 steroid-resistant FSGS children (p < 0.05) than in the 130 children of the healthy control group (0.48, 0.48, and 0.33, respectively). ACE genotypes did not affect renal survival in the whole FSGS group nor in the steroid-resistant subgroup. Among the 28 steroid-resistant children, treatment with ciclosporin was effective in delaying the development of end-stage renal failure (p = 0.044), independently of other treatment regimens. CONCLUSION: The present study of Japanese children with FSGS showed that the D allele of the ACE gene is associated with the development of FSGS, but not associated with the progression of FSGS which was greatly ameliorated with ciclosporin, irrespective of ACE genotypes.

Proteomic analysis of the mammalian mitochondrial ribosome. Identification of protein components in the 28 S small subunit.

The mammalian mitochondrial ribosome (mitoribosome) has a highly protein-rich composition with a small sedimentation coefficient of 55 S, consisting of 39 S large and 28 S small subunits. In the previous study, we analyzed 39 S large subunit proteins from bovine mitoribosome (Suzuki, T., Terasaki, M., Takemoto-Hori, C., Hanada, T., Ueda, T., Wada, A., and Watanabe, K. (2001) J. Biol. Chem. 276, 21724-21736). The results suggested structural compensation for the rRNA deficit through proteins of increased molecular mass in the mitoribosome. We report here the identification of 28 S small subunit proteins. Each protein was separated by radical-free high-reducing two-dimensional polyacrylamide gel electrophoresis and analyzed by liquid chromatography/mass spectrometry/mass spectrometry using electrospray ionization/ion trap mass spectrometer to identify cDNA sequence by expressed sequence tag data base searches in silico. Twenty one proteins from the small subunit were identified, including 11 new proteins along with their complete cDNA sequences from human and mouse. In addition to these proteins, three new proteins were also identified in the 55 S mitoribosome. We have clearly identified a mitochondrial homologue of S12, which is a key regulatory protein of translation fidelity and a candidate for the autosomal dominant deafness gene, DFNA4. The apoptosis-related protein DAP3 was found to be a component of the small subunit, indicating a new function for the mitoribosome in programmed cell death. In summary, we have mapped a total of 55 proteins from the 55 S mitoribosome on the two-dimensional polyacrylamide gels.

Structural compensation for the deficit of rRNA with proteins in the mammalian mitochondrial ribosome. Systematic analysis of protein components of the large ribosomal subunit from mammalian mitochondria.

The mammalian mitochondrial ribosome (mitoribosome) is a highly protein-rich particle in which almost half of the rRNA contained in the bacterial ribosome is replaced with proteins. It is known that mitochondrial translation factors can function on both mitochondrial and Escherichia coli ribosomes, indicating that protein components in the mitoribosome compensate the reduced rRNA chain to make a bacteria-type ribosome. To elucidate the molecular basis of this compensation, we analyzed bovine mitoribosomal large subunit proteins; 31 proteins were identified including 15 newly identified proteins with their cDNA sequences from human and mouse. The results showed that the proteins with binding sites on rRNA shortened or lost in the mitoribosome were enlarged when compared with the E. coli counterparts; this suggests the structural compensation of the rRNA deficit by the enlarged proteins in the mitoribosome.

Efficacy of long-term azathioprine for relapsing nephrotic syndrome.

Seven patients who had an initial attack of nephrotic syndrome in childhood and had frequent relapses even after cyclophosphamide therapy were given a 2-year course of azathioprine. The mean annual relapse rates decreased from 2.4+/-0.5 in the year preceding azathioprine to 0.4+/-0.8 in the 1st and 2nd years after its initiation. All six patients who were observed for more than 6 months after discontinuation of the therapy were relapse free for this period. Average doses of prednisolone could also be decreased in the 2nd and subsequent years after the therapy. There were no significant toxic effects. Long-term azathioprine therapy may be well tolerated and effective for nephrotic patients with frequent relapses.

Prominent medial hypertrophy of renal arterioles in an infant with hyporeninemic hypoaldosteronism.

We describe an 11-month-old boy who presented clinically with hyperkalemic renal tubular acidosis due to hyporeninemic hypoaldosteronism. Persistent hyperchloremic acidosis and mild azotemia were present. All abnormal laboratory values were corrected by the administration of fludrocortisone. Renal biopsy showed prominent medial hypertrophy of renal arterioles and interstitial fibrosis, which closely resemble those of the gene-targeted mice with disruption of the renin angiotensin system. This is the first case report raising the possibility that a defective renin angiotensin system in infancy may lead to tubulointerstitial damage with medial hypertrophy of intrarenal arterioles.

Voiding function study with ultrasound in male and female neonates.

BACKGROUND: The neonatal period has been characterized as a time when males have a much higher incidence of urinary infection and severe ureteral reflux than females. However, little information about the voiding function in the neonatal period is available. METHODS: The bladder urine volumes, before and after voiding, and urinary flow rates were determined with the use of noninvasive voiding-provocation maneuvers and ultrasound in the apparently normal neonates. RESULTS: There was no significant difference in the prevoid bladder urine volume between the two sexes. After they were stimulated to enhance the tension of their abdominal wall musculature, 65 of 118 females (55.1%) and 64 of 115 males (55.7%) voided. The voiding was observed in 94 (81.0%) of the 116 neonates who had had a prevoid volume above 12 ml. The residual urine expressed as a percentage of the prevoid volume was significantly higher in the males (median, 12.0% in males vs. 3.0% in females, P < 0.01), with the values being above 20% in 26 (41%) of the 64 males compared with 10 (15%) of the 65 females (P < 0.01). Urinary flow rates, determined in 52 neonates, were significantly smaller in males than in females (mean +/- SD, 2.6 +/- 0.9 g/second vs. 3.8 +/- 1.3 g/second, respectively, P < 0.001). CONCLUSION: This voiding function study with ultrasound using noninvasive voiding-provocation maneuvers successfully revealed that male neonates have a larger residual urine volume and smaller urinary flow rates than female neonates. This study should be useful for the diagnosis of voiding dysfunction in children with abnormal urinary symptoms.

Vesicoureteral reflux in male and female neonates as detected by voiding ultrasonography.

BACKGROUND: Vesicoureteral reflux (VUR) is assumed to be congenital, and its early diagnosis is desired in order to prevent acquired renal damage. However, the incidence of VUR in neonates remains to be revealed. METHODS: Two thousand newborn babies (1048 boys and 952 girls) underwent voiding ultrasonography (an ultrasound examination of urinary tract during provoked voiding). Those who showed transient renal pelvic dilation during voiding, who had small kidneys, or who subsequently developed urinary infection underwent voiding cystourethrography. RESULTS: Transient renal pelvic dilation was observed in 16 babies (0.8%), including one boy with small kidneys. Among the rest of the babies, one boy had a small kidney, and nine babies subsequently developed urinary infection. Voiding cystourethrography revealed VUR in 24 ureters of 16 children (11 boys and 5 girls). Dimercaptosuccinate renoscintigraphy confirmed small kidneys, with generally reduced tracer uptake in a total of three boys, all having VUR. Voiding ultrasonography detected transient renal pelvic dilation in 17 (71%) of the 24 kidneys with VUR and, strikingly, 16 of the 17 (94%) kidneys with high-grade VUR (grade III or more). CONCLUSION: This study effectively detected VUR in 0.8% of the neonates (mostly of high grades and predominantly in males) and voiding ultrasonography showed a decided usefulness for the detection of VUR. The male preponderance of VUR in neonates was considered to be due to the occurrence of congenitally small kidneys, with reflux found exclusively in males and easier ultrasound detection of VUR in male neonates because the majority of diagnoses are reported to be high grades of VUR.

Endothelin subtype A receptor antagonist induces osteopenia in growing rats.

Previous studies suggested that endothelin (ET) peptides are involved in bone metabolism. We examined the effects of long-term blockade of the ET(A) receptor, a receptor subtype primarily involved in the anabolic actions of ET, on bone mineral status in growing rats. Eight-week-old rats injected intraperitoneally with FR139317 50 mg/kg body weight, a specific ET(A) receptor antagonist, for 2 or 4 weeks were compared with control rats injected with vehicle only. Treatment with FR139317 caused a significant decrease in bone mass in the lumbar spine as determined by dual-energy x-ray absorptiometry (DXA). FR139317-induced osteopenia was associated with a significant decrease in the serum osteocalcin concentration but no change in the urinary excretion of pyridinium cross-links of collagen. Our findings indicate that long-term blockade of the ET(A) receptor reduces bone formation and induces osteopenia in growing rats. Our results suggest that ET produced by vascular endothelial cells plays an important role in bone growth and metabolism in vivo.

Purification and characterization of myonase from X-chromosome linked muscular dystrophic mouse skeletal muscle.

A chymotrypsin-like proteinase, designated myonase, was successfully purified to homogeneity from X-chromosome linked muscular dystrophic mouse skeletal muscle by affinity chromatography on agarose conjugated with lima bean trypsin inhibitor as ligand. The molecular mass of the purified myonase was determined to be 26 kDa by SDS-PAGE and to be 25,187 Da by mass spectrometry. The native enzyme is a single chain molecule and a monomeric protein without sugar side-chains. The nucleotide sequence of myonase mRNA is similar to mouse mast cell proteinase 4 (MMCP-4) cDNA. This is the first report of a native enzyme whose amino acid sequence closely corresponds to MMCP-4 cDNA. Myonase has chymotrypsin-like activities and hydrolyzes the amide bonds of synthetic substrates having Tyr and Phe residues at the P1 position. Myonase is most active at pH 9 and at high concentration of salts. Myonase preferentially hydrolyzes the Tyr4-Ile5 bond of angiotensin I and the Phe20-Ala21 bond of amyloid beta-protein, and it is less active towards the Phe8-His9 bond of angiotensin I and the Phe4-Ala5 and Tyr10-Glu11 bonds of amyloid beta-protein. Myonase is completely inhibited by such serine proteinase inhibitors as chymostatin, diisopropylfluorophosphate and phenylmethylsulfonyl fluoride, but not by p-tosyl-L-phenylalanine chloromethyl ketone, p-tosyl-L-lysine chloromethyl ketone, pepstatin, E-64, EDTA, and o-phenanthroline. It is also inhibited by lima bean trypsin inhibitor, soy bean trypsin inhibitor, and human plasma alpha1-antichymotrysin. These properties match those of chymase, but unlike chymase, myonase does not interact with heparin in the regulation of its activity. Myonase was immunohistochemically localized in myocytes, but not in mast cells.

Chronic erythropoietin treatment enhances endogenous nitric oxide production in rats.

To examine the effect of chronic administration of recombinant human erythropoietin (rHuEPO) on endogenous nitric oxide (NO) activity, we treated Sprague-Dawley rats with rHuEPO (100 IU kg-1 or 300 IU kg-1) or a corresponding vehicle for 2 weeks, administered subcutaneously on alternate days. Treatment elicited increases in haematocrit and systolic blood pressure in a dose-dependent fashion. Simultaneous administration of NG-nitro-L-arginine methyl ester (L-NAME, 20 mg dl-1 of drinking water), but not aminoguanidine (400 mg dl-1), induced a further significant rise in blood pressure. The effect of L-NAME was inhibited by a large dose of L-arginine (2.0 g dl-1). Polycythaemia and hypertension induced by chronic rHuEPO therapy were associated with increased urinary NO2- and NO3- (NOx-) excretion, while co-administration of L-NAME, but not aminoguanidine, reduced NOx- excretion. Our results indicate that chronic rHuEPO treatment has a significant pressor effect, but induces a compensatory increase in the steady-state release of NO by constitutive NO synthase in normal rats. Such enhanced NO synthesis may act as a protective mechanism against the hypertensive effect of rHuEPO.

Congenitally small kidneys with reflux as a common cause of nephropathy in boys.

Congenital maldevelopment is sometimes found in small kidneys with ureteral reflux. However, the incidence of congenitally small kidneys and the frequency of its association with ureteral reflux remains unknown. Ultrasound scanning, performed in 4,000 apparently healthy neonates or young infants (males 2,129, females 1,871), detected 51 children suspected of having small kidneys. A careful ultrasound re-examination performed one month later in 45 of the 51 children confirmed small kidneys in eight children, one bilateral and seven unilateral. Dimercaptosuccinate (DMSA) renoscintigraphy revealed small kidneys with generally diminished uptake in six infants and no uptake unilaterally in the other two infants. One of the 12 children, who had normal findings on the initial scanning and subsequently developed urinary infection, was later diagnosed having unilateral small kidney with generally reduced DMSA uptake. All seven infants having small kidneys with reduced tracer uptake were male (incidence, 1:300 boys). All eight small kidneys in the seven boys and four of the six contralateral non-small kidneys were associated with ureteral reflux, while neither of the two infants with a non-functioning kidney had ureteral reflux. Serial ultrasounds documented the poor growth of all small kidneys. Thus, congenitally small kidneys with generally diminished DMSA uptake were highly associated with ureteral reflux and especially observed in boys.

Intermittent trimethoprim-sulfamethoxazole in children with vesicoureteral reflux.

The effectiveness of intermittent low-dose trimethoprim-sulfamethoxazole (TMP-SMZ) for the prophylaxis of recurrent urinary infection is well established in adults. The present study assessed the effectiveness and safety of intermittent low-dose TMP-SMZ in 35 children (24 boys, 11 girls, aged 1 month to 9 years, median age 5 months) with vesicoureteral reflux; 18 children had bilateral reflux. A total of 53 refluxing ureters were graded as I in 2, II in 16, III in 19, IV in 14, and V in 2 cases. The children were given 1 mg/kg body weight of trimethoprim together with 5 mg/kg of sulfamethoxazole at bedtime every other day for 6-50 months (mean +/- SD, 22.9 +/- 11.7 months). None of the boys had a recurrence of urinary infection, while 2 of the 11 girls had a total of 7 recurrences during the prophylaxis period, with a recurrence rate of 0.027 per patient month in girls. Both girls were over 3 years and had a mildly unstable bladder. Transient neutropenia (< 1,000/microliter) developed in 2 infants during the prophylaxis period, but disappeared spontaneously. Intermittent low-dose TMP-SMZ seemed very effective for the prevention of recurrent urinary infection in children with ureteral reflux even of higher grades.

Persistent hypercholesterolaemia in frequently relapsing steroid-responsive nephrotic syndrome.

OBJECTIVE: To investigate long-term changes of serum cholesterol levels in children with frequently relapsing steroid-responsive nephrotic syndrome (NS). METHODOLOGY: Serum cholesterol values just before and during or immediately after 'relapse' were reviewed and the incidence of hypercholesterolaemia (> or = 200 mg/dL) was determined in eight patients (M:F, 6:2). RESULTS: The patients with frequently relapsing NS usually showed hypercholesterolaemia (mean incidence, 81%) just before 'relapse' during clinical remission, as well as in relapse (mean incidence, 96%). A high incidence of steroid therapy was also found in each case (mean, 89%) just before relapse. CONCLUSIONS: Our results demonstrate that children with frequently relapsing NS have prolonged periods of hypercholesterolaemia, even during clinical remission. It is suggested that serum lipid profiles be monitored carefully in such patients.

Use of ultrasonography in the detection of ureteric reflux in children suspected of having urinary infection.

The present study investigated whether ultrasonography was effective in detecting ureteric reflux in children suspected of having urinary infection. Seventeen children with febrile episodes and pyuria were enrolled. The ultrasound examination revealed ballooning of the renal pelvis during bladder contraction in 4 children, dilatation of the distal ureters in 6, and small kidney in 2. Cystography was performed on the 6 children with these ultrasound abnormalities and 1 child with two episodes of suspected urinary infection. Four children showed reflux. All of the 4 children had been found to have renal pelvic ballooning on ultrasound. None of the 10 children who did not undergo cystography had recurrence of urinary infection or significant bacteriuria during a median follow-up period of 12 months. Thus, scanning during bladder contraction was effective in detecting significant ureteric reflux.

Age-related changes of urinary nitrite/nitrate excretion in normal children.

We measured the urinary excretion of nitrite/nitrate, stable metabolites of nitric oxide, using the brucine method in 90 healthy normal children (47 boys and 43 girls), aged from 1.0 to 17.1 years, to establish the age-related normal range in children. The urinary nitrite/nitrate excretion was highest in the youngest children and decreased in an age-dependent manner to reach constant levels at about 12 years of age in both sexes. The data may be useful in identifying sick children with abnormal nitric oxide production.