[Pyomyositis in children: Two cases of Staphylococcus aureus infection]. / Pyomyosite de l'enfant : deux cas d'infection à Staphylococcus aureus.

Pyomyositis is a term used to denote primary pyogenic infection of a skeletal muscle. It is a rare disease that was first described in immunodeficient patients living in tropical climates. Lately, however, cases involving healthy children have been described in temperate climates. The origin of primary pyomyositis remains unclear, although it is thought to be caused by seeding from transient bacteremia. Onset of disease is insidious, therefore necessitating rapid diagnosis to successfully select appropriate antibiotic therapy and avoid complications. The signs and symptoms of pyomyositis are nonspecific, which highlights the importance of maintaining a broad differential diagnosis including disease entities such as osteomyelitis and septic arthritis. Magnetic resonance imaging is considered the best imaging modality for distinguishing pyomyositis from other potential etiologies. Here, we present two cases of primary pyomyositis of the lower limb muscles in an 8-year-old boy and in an 11-year-old girl.

[Acute leukemia revealed by bone magnetic resonance imaging: Two pediatric case reports]. / Leucémie aiguë découverte par imagerie par résonance magnétique osseuse : deux observations pédiatriques.

Bone and joint pain are common causes of pediatric consultation for a variety of etiologies. The causes are mostly traumatic or infectious or have an inflammatory origin. Acute leukemia (AL) can sometimes begin with osteoarticular signs and radiological investigations such as magnetic resonance imaging (MRI) can help guide the diagnosis. We report on two cases of pediatric AL revealed by osteoarticular signs, with MRI helpful in the diagnostic procedure. In these children, the first signs were recurrent joint pain, with no blood count anomalies. There was a delay between the onset of arthralgia and diagnosis due to atypical presentation of the disease. MRI guided the investigations to the diagnosis of AL. The persistence of pain or inflammation must lead to considering a bone MRI and a complete blood count must be repeated in case of persistent inflammatory bone pain to avoid a missed diagnosis of blood disease.

[Staphylococcal tracheitis and toxic shock syndrome in a child]. / Laryngotrachéite à staphylocoque doré compliquée d'un syndrome de choc toxique.

Bacterial tracheitis should be raised as a possible cause in cases of severe febrile dyspnea. It can be life-threatening due to airway obstruction or, less frequently, due to toxic shock syndrome. We report the observation of toxic shock syndrome-complicated bacterial tracheitis in a 14-year-old boy. We describe the signs and symptoms of these conditions as well as the principles of treatment.

[Leukaemia cutis during acute aleukaemic myeloid leukaemia in a two-month-old infant]. / Leucémie cutanée révélatrice d'une leucémie aiguë myéloïde sans blastes circulants chez un nourrisson de deux mois.

BACKGROUND: Congenital cutaneous leukaemia is rare. PATIENTS AND METHODS: A two-month-old girl presented bluish cutaneous macules of the trunk, histological examination of which suggested acute myeloid leukaemia (LAM B 5). The blood picture was negative for circulating tumour cells and the outcome under chemotherapy was favourable at one year of follow-up. DISCUSSION: The prognosis of congenital leukaemia is serious. Aleukaemic congenital leukaemia is seen occasionally but is rare. The existence of multiple cutaneous tumours in newborn infants raises the possibility of TORCH infection and of other malignant tumours such as nephroblastoma or neuroblastoma.

[Small bowel volvulus due to midgut malrotation: value of Doppler sonography. A case report]. / Volvulus du grêle sur mésentère commun: intérêt de l'échographie Doppler. A propos d'un cas.

A case of small bowel volvulus due to midgut malrotation in a 4 years-old child complaining of vomiting and abdominal pain. Diagnosis was made by a Doppler ultrasound showing the volvulus and the intestinal malrotation. We are discussing the interest of this technique.

[Utilization of an equimolar mixture of oxygen-nitrous oxide in a general pediatric ward]. / Utilisation du mélange équimolaire oxygène-protoxyde d'azote dans un service de pédiatrie générale.

UNLABELLED: We report our experience of the utilization of the 50% oxygen-nitrous oxide mixture (nitrous oxide 50%) in our general pediatric ward after one year of use. PATIENTS AND METHODS: Between 1st April 1997 and 31st March 1998, children who had to undergo a painful procedure were proposed to inhale 50% nitrous oxide before the procedure. We evaluate pain, restlessness and adverse effects. RESULTS: The procedures (127 of them) were carried out in 90 children (61 boys). They were aged from 5 months to 15 years (mean: 5.7 years; median: 4.1 years). Indications were: lumbar puncture (n = 45), burning dressing (n = 29), venous cannulation (n = 12), minor surgery (n = 27), and miscellaneous (n = 14). Inhalation time was between 2 to 70 min (mean: 14.4 min; median: 11 min). Pain was absent or low in 106 cases (83.4%). Restlessness was absent or low in 100 cases (78.8%). Averse events were observed 12 times, but they were always minor and quickly reversible. CONCLUSION: Nitrous oxide (50%) can be used successfully in a general pediatric ward. Other studies are necessary to define the best conditions.

[Self-induced cutaneous lesions in Prader-Willi syndrome]. / Lésions cutanées auto-induites au cours du syndrome de Prader-Willi.

INTRODUCTION: The Prader-Labhart-Willi syndrome was first described in 1956. Prader-Labhart-Willi syndrome is the most common genetic form of human obesity and the incidence of Prader-Labhart-Willi syndrome has been estimated to 1 in 10,000 or 25,000 live births. Skin-picking was frequently reported in Prader-Labhart-Willi syndrome and two patients who displayed repetitive skin picking are described. OBSERVATIONS: Two childrens (6 year-old girl and 7 year-old boy) were examined and noted superficial ulcers of their arms and legs. This cutaneous lesions were induced by children themselves. Skin-picking, in our cases, were associated with behavior problems (temper tantrums, violence). CONCLUSIONS: Skin-picking appears to occur in the great majority of patients with Prader-Labhart-Willi syndrome and constitutes a minor criteria of diagnosis. Hypopigmentation in Prader-Labhart-Willi syndrome appears to be as common as previously features. Significant differences in hair color, sun sensitivity and complexion were found between those patients with chromosome 15 deletion and those with normal chromosome. Association between obesity (onset before 6 years) and skin picking constitute a sign for diagnosis of Prader-Labhart-Willi syndrome.

Binding of cytosolic aconitase to the iron responsive element of porcine mitochondrial aconitase mRNA.

The 5' end of porcine mitochondrial aconitase mRNA contains an iron responsive element (IRE)-like secondary structure (T. Dandekar, R. Stripecke, N. K. Gray, B. Goosen, A. Constable, H. E. Johansson, and M. W. Hentze (1991) EMBO J. 10, 1903-1909). A protein from a liver extract binds to a mitochondrial aconitase RNA probe and supports the identification of this sequence as an IRE. Purified cytosolic aconitase but not the mitochondrial enzyme binds to this IRE as well as to a ferritin IRE. All forms of cytosolic aconitase, [4Fe-4S] enzyme, [3Fe-4S] enzyme and apoenzyme bind with similar affinity. A Kd of 0.25 nM was calculated for the apoaconitase-IRE interaction from Scatchard analysis. These results support the conclusion that cytosolic aconitase is an IRE-binding protein which may regulate translation of mitochondrial aconitase mRNA.

Cellular regulation of the iron-responsive element binding protein: disassembly of the cubane iron-sulfur cluster results in high-affinity RNA binding.

The translation of ferritin mRNA and degradation of transferrin receptor mRNA are regulated by the interaction of an RNA-binding protein, the iron-responsive element binding protein (IRE-BP), with RNA stem-loop structures known as iron-responsive elements (IREs) contained within these transcripts. IRE-BP produced in iron-replete cells has aconitase (EC 4.2.1.3) activity. The protein shows extensive sequence homology with mitochondrial aconitase, and sequences of peptides prepared from cytosolic aconitase are identical with peptides of IRE-BP. As an active aconitase, IRE-BP is expected to have an Fe-S cluster, in analogy to other aconitases. This Fe-S cluster has been implicated as the region of the protein that senses intracellular iron levels and accordingly modifies the ability of the IRE-BP to interact with IREs. Expression of the IRE-BP in cultured cells has revealed that the IRE-BP functions either as an active aconitase, when the cells are iron-replete, or as an active RNA-binding protein, when the cells are iron-depleted. We compare properties of purified authentic cytosolic aconitase from beef liver with those of IRE-BP from tissue culture cells and establish that characteristics of the physiologically relevant form of the protein from iron-depleted cells resemble those of cytosolic aconitase apoprotein. We demonstrate that loss of the labile fourth iron atom of the Fe-S cluster results in loss of aconitase activity, but that more extensive cluster alteration is required before the IRE-BP acquires the capacity to bind RNA with the affinity seen in vivo. These results are consistent with a model in which the cubane Fe-S cluster is disassembled when intracellular iron is depleted.

Purification and characterization of cytosolic aconitase from beef liver and its relationship to the iron-responsive element binding protein.

In recent reports attention has been drawn to the extensive amino acid homology between pig heart, yeast, and Escherichia coli aconitases (EC 4.2.1.3) and the iron-responsive element binding protein (IRE-BP) of mammalian cells [Rouault, T. A., Stout, C. D., Kaptain, S., Harford, J. B. & Klausner, R. D. (1991) Cell 64, 881-883.; Hentze, M. W. & Argos, P. (1991) Nucleic Acids Res. 19, 1739-1740.; Prodromou, C., Artymiuk, P. J. & Guest, J. R. (1992) Eur. J. Biochem. 204, 599-609]. Iron-responsive elements (IREs) are stem-loop structures located in the untranslated regions of mRNAs. IRE-BP is required in the posttranscriptional regulation of ferritin mRNA translation and stabilization of transferrin receptor mRNA. In spite of substantial homology between the amino acid sequences of mammalian mitochondrial aconitase and IRE-BP, the mitochondrial protein does not bind IREs. However, there is a second aconitase, found only in the cytosol of mammalian tissues, that might serve as an IRE-BP. To test this possibility, we have prepared sufficient quantities of the heretofore poorly characterized beef liver cytosolic aconitase. This enzyme is isolated largely in its active [4Fe-4S] form and has a turnover number similar to that of mitochondrial aconitase. The EPR spectra of the two enzymes are markedly different. The amino acid composition, molecular weight, isoelectric point, and the sequences of six random peptides clearly show that these physicochemical and structural characteristics are identical to those of IRE-BP, and that c-aconitase is distinctly different from m-aconitase. In addition, both cytosolic aconitase and IRE-BP can have aconitase activity or function as IRE-BPs, as shown in the following paper and elsewhere [Zheng, L. Kennedy, M. C., Blondin, G. A., Beinert, H. & Zalkin, H. (1992) Arch. Biochem. Biophys., in press]. This leads us to the conclusion that cytosolic aconitase is IRE-BP.

Cytotoxic T lymphocyte responses in the peripheral blood of children born to human immunodeficiency virus-1-infected mothers.

Cytotoxic T lymphocytes (CTL) are present at high activities in adult patients infected with the human immunodeficiency virus (HIV). In this report, CTL effectors were identified in peripheral blood mononuclear cells (PBMC) of children born to HIV-1-infected mothers. These CTL killed HLA-matched HIV-1-infected H9 target cells or doubly transfected P815-A2-env, gag or nef mouse tumor cells, which expressed the viral antigens in association with HLA-A1/A3 or HLA-A2, respectively. HIV-1-specific CTL were detected early after birth (less than 2 months) and remained present during the asymptomatic phase of the infection. As in HIV-1-infected adults, HIV-specific CTL declined with disease progression. Surprisingly, HIV-1-specific CTL were detected in the PBMC of three children who subsequently became seronegative.

Theoretical study of the multiline EPR signal from the S(2) state of the oxygen evolving complex of photosystem II: Evidence for a magnetic tetramer.

The Oxygen evolving complex of plant photosystem II is made of a manganese cluster that gives rise to a low temperature EPR multiline signal in the S(2) oxidation state. The origin of this EPR signal has been addressed with respect to the question of the magnetic couplings between the electron and nuclear spins of the four possible Mn ions that make up this complex. Considering Mn(III) and Mn(IV) as the only possible oxidation states present in the S(2) state, and no large anisotropy of the magnetic tensors, the breadths of the EPR spectra calculated for dimers and trimers with S = (1/2) have been compared with that of the biological site. It is concluded that neither a dinuclear nor a trinuclear complex made of Mn(III) and Mn(IV) can be responsible for the multiline signal; but that, by contrast, a tetranuclear Mn complex can be the origin of this signal. The general shape of the experimental spectrum, its particular hyperfine pattern, the positions of most of the hyperfine lines and their relative intensities can be fit by a tetramer model described by the following six fitting parameters: g approximately 1.987, A(1) approximately 122.4 10(-4) cm(-1), A(2) approximately 87.2 10(-4) cm(-1), A(3) approximately 81.6 10(-4) cm(-1), A(4) approximately 19.1 10(-4) cm(-1) and deltaH = 24.5 G. A second model described by parameters very close to those given above except for A(4) approximately 77.5 10(-4) cm(-1) gives an equally good fit. However, no other set of parameters gives an EPR spectrum that reproduces the hyperfine pattern of the S(2) multiline signal. This demonstrates that in the S(2) state of the oxygen evolving complex, the four manganese ions are organized in a magnetic tetramer.

Assessment of chemical toxicity using mammalian mitochondrial electron transport particles.

New spectrophotometric bioassay procedures have been developed for evaluating chemical toxicity, using electron transport particles isolated from bovine heart mitochondria, based on the ability of many toxic chemicals to interfere with the integrated function of electron transport enzymes. The sensitivity of the mitochondrial assay is compared to published sensitivities of other in vivo and in vitro toxicity testing methods. Regression analysis of logarithmically transformed toxicity values for 42 chemicals, including 8 pesticides, 5 drugs, 6 metals, 8 alcohols, 5 respiratory inhibitors, 4 phenols, and 2 phthalates, indicates excellent correlation between the sensitivity of the new assays and the sensitivity of mammalian cytotoxicity studies (r2 = 0.86). Data from aquatic exposure toxicity tests conducted in fish are also highly correlated with the mitochondrial assay results (r2 = 0.79). However, correlation of data from these methods with median lethal dose studies conducted in rats is not as good because of the inability of in vitro and aquatic exposure analyses to account for the gastrointestinal absorption, hepatic metabolism, and excretion processes which modify toxic responses following oral administration.