Biomedical subjects
Publications and source records attributed to G Malpuech.
With the use of the generalized Gross-Pitaevskii equation it is shown that exciton polaritons in semiconductor microcavities form a linearly polarized condensate having two branches of the excitation spectrum. The splitting between these branches is strongly anisotropic. This anisotropy noticeably affects the real-space dynamics of polariton condensates.
Adrenal hypoplasia congenita (AHC) is an extremely uncommon disease of early onset. This condition can be lethal in the absence of adapted treatment. Some of these diseases are related to changes in the gene DAX1 that encodes a member of the superfamily of hormone nuclear receptors. It is a transcriptional repressor that is central in the morphogenesis of the adrenals and the gonadic differentiation. Here we report on four cases of X- linked AHC. In the first two familial cases, mutations were identified and mothers were heterozygotes. Abnormally low levels of estriol were evidenced during the pregnancy leading to an early diagnosis and adapted care of the affected male neonates. These children are doing well with a 21-and 20 months follow-up with hormone replacement at the present time. The two last cases corresponded to a contiguous gene syndrome associating AHC to glycerol-kinase deficiency that was revealed respectively at six days and seven years of age by acute adrenal insufficiency.
We report the first observation of oscillations of the electromagnetic field in an optical superlattice based on porous silicon. These oscillations are an optical equivalent of well-known electronic Bloch oscillations in crystals. Elementary cells of our structure are composed by microcavities whose coupling gives rise to the extended collective modes forming optical minigaps and minibands. By varying thicknesses of the cavities along the structure axis, we have created an effective electric field for photons. A very high quality factor of the confined optical state of the Wannier-Stark ladder may allow lasing in porous silicon-based superlattices.
We present the quantum theory of momentum and spin relaxation of exciton-polaritons in microcavities. We show that giant longitudinal-transverse splitting of the polaritons mixes their spin states, which results in beats between right- and left-circularly polarized photoluminescence of microcavities, as was recently experimentally observed [Phys. Rev. Lett. 89, 077402 (2002)]]. This effect is strongly sensitive to the bosonic stimulation of polariton scattering.
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We present the theory of the dynamics of the polariton amplifier in the region of small polariton densities. We give an analytical solution for the polariton condensate density matrix and show that the formation of a coherent quantum state is possible. Once the condensate is formed, the coherence becomes macroscopically long living. Polariton amplifier represents, therefore, an optical memory element, where the input weak coherent signal can be amplified and kept.
BRCA1 and BRCA2 breast cancer susceptibility genes encode proteins, the normal cellular functions of which are complex and multiple, and germ-line mutations in individuals predispose both to breast and to ovarian cancer. There is nevertheless substantial evidence linking BRCA1 and BRCA2 to homologous recombination and DNA repair, to transcriptional control and to tissue proliferation. There is controversy regarding the localization of BRCA1 and BRCA2 proteins to either nucleus or cytoplasm and whether the expression is present in premeiotic germ cells or can still be expressed in mitotic spermatogonia. We report herein an immunohistochemical study of BRCA1 and BRCA2 distribution in a rather unusual tissue (an ovotestis), which addresses this issue.
A theoretical concept of resonant Rayleigh scattering (RRS) of exciton-polaritons in multiple quantum wells (QWs) is presented. The optical coupling between excitons in different QWs can strongly affect the RRS dynamics, giving rise to characteristic temporal oscillations on a picosecond scale. Bragg and anti-Bragg arranged QW structures with the same excitonic parameters are predicted to have drastically different RRS spectra. Experimental data on the RRS from multiple QWs show the predicted strong temporal oscillations at small scattering angles, which are well explained by the presented theory.
Life-threatening haemolysis in children with autoimmune haemolytic anaemia (AIHA) occurs rarely. Many cases of severe autoimmune disease are currently treated with immunosuppressive high-dose chemotherapy and autograft. We report here a case of a child with severe AIHA who did not respond to conventional treatments, but was cured with an autologous peripheral blood CD34(+) cell transplantation. After d 16 post autograft, no further red cell transfusions were required. At 20 months post autograft, haematological complete remission persists.
Between February and August 1997, 53 patients with enterovirus meningitis were hospitalized in Clermont-Ferrand, France. All but one were children. Echovirus type 30 was involved in 70% of cases with identified serotype. The outbreak ceased on August 8. Two months later, a neonate was admitted to the neonatal unit with an echovirus type 30 meningitis thought to be acquired at delivery. Twenty days later a nosocomial outbreak of echovirus type 30 involving five neonates occurred. Two of them presented with meningitis and two with febrile seizure; One was asymptomatic. The retrospective examination of the maternal sera in a neutralization test, using the index case strain as a source of antigen, showed that none of the neonates was passively immunized before hospitalization. The use of genome detection in cerebrospinal fluid allowed rapid diagnosis and infection was contained by re-inforcing hygiene measures. Prospective examination of stools in the neonatal and paediatric units showed no further occurrences of the disease. No sporadic case was observed in the general population. Hence, nosocomial infections can occur a long time after an outbreak in the general population; rapid diagnosis with molecular tools is useful both for a definite diagnosis in patients already hospitalized, and to act as a rapid alert, even in intervals between seasonal outbreaks.
X-linked mental retardation (XLMR) includes distinct entities in which mental deficiency is either associated with specific abnormalities (syndromal) or not (nonsyndromal). We report on the clinical, neuropsychological, and laboratory findings and linkage analysis in one family with XLMR and isolated growth hormone deficiency (IGHD). Mental retardation was associated in 3 males and 5 females with short stature, microcephaly, and particular facial traits, i.e., high curved forehead, midface hypoplasia, and concave nasal bridge with nasal end of normal size and broad traits. Significant lod scores (Zmax >2) at a recombination fraction of theta = 0 were detected for 6 marker loci between DXS178 (Xq22.1) and DXS292 (Xq27.2). This mapping region overlaps that of XLMR with IGHD, recently reported by Hamel et al. [1996: Am J Med Genet 64:35-41] (Xq24-q27.3), and that of agammaglobulinemia with IGHD (Xq21.33-q22.2). This observation may confirm the suspicion of a gene involved in growth hormone regulation being localized in Xq.
The kinetics of peripheral blood progenitor cell (PBPC) release induced by G-CSF-alone at 10 microg/kg/day were monitored daily in 42 children with solid tumors and leukemias. Median 16- and 27-fold enrichment of circulating CD34+ cells and granulocyte-macrophage colony-forming units (CFU-GM) was noted with peak values occurring after the 4th or the 5th G-CSF dose. Individual values of PBCD34+ cell levels in patients with solid tumors were not significantly different after the 4th and after the 5th dose. The day-of-collection PBCD34+ cell concentration was related to the harvested CD34+ cell (P = 0.0001) and CFU-GM numbers (P = 0.0001). No correlations were found between PBPC enrichment and either patient age, body weight, diagnosis or pre-mobilization treatment duration. The median numbers of 1.1 x 10(6) CD34+ cells/kg and 28.1 x 10(4) CFU-GM/kg were derived from one patient's blood volume processed. Nineteen patients received G-CSF-alone primed grafts and had successful engraftment. Our data indicate that in 88% of children a single standard leukapheresis is sufficient to obtain a minimum graft (2 x 10(6) CD34+ cell and/or 10 x 10(4) CGU-GM per kg) whether undertaken after the 4th dose of G-CSF or the 5th.
To clarify the factors that may affect the peripheral blood stem cell (PBSC) collection in children weighing < or = 15 kg, a consecutive registry of 109 leukapheresis procedures was analyzed. Collections were performed on a COBE Spectra separator. In 65.1% of the procedures, the peripheral vein, together with a central catheter inserted routinely at diagnosis, or 2 peripheral veins were used to access/return. For 84.4% of the procedures, the extracorporeal line was primed with red blood cells. The median granulocyte-macrophage colony forming unit (CFU-GM) number derived from 1 patient's blood volume processed was 13.8 x 10(4)/kg. Six times, a collection series failed, always in children treated for > or = 26 weeks and 4 of those times in children weighing < or = 11 kg. The patient's age, diagnosis, duration of preleukapheresis treatment, and mobilization regimens did not significantly affect the collection yield. Twenty-four transplantations were performed. The median times to neutrophils >0.5 x 10(9)/L and platelets >20 x 10(9)/L were 13 and 20 days, respectively. We conclude that even in very small children, leukapheresis can be performed safely, allowing adequate PBSC collection for transplantation and/or in vitro manipulations.
BACKGROUND: The fragile X mental retardation syndrome is the most common cause of inherited mental retardation. Identification of the unstable mutation responsible for the disease has allowed the design of a fully reliable molecular test for the diagnosis of the disease and for genetic counselling (identification of clinically normal carriers and prenatal diagnosis). We started in July 1991 to search for the mutation in mentally retarded probands, with no known cause for their phenotype. We present the results of a 42-month experience. POPULATION AND METHODS: One thousand and one hundred fourty-nine probands were analysed. In case of a positive diagnosis, an extension of the molecular study to relatives was proposed. DNA samples were studied by Southern blot following EcoRI or EcoRI + EagI digestion. Clinical data were collected from referring clinicians. RESULTS: Seventy-three carriers of a full mutation were identified, belonging to 52 families. The mean age of the fragile X probands was 16 +/- 14 years, which is very surprising for a disease that causes significant manifestations by the age of 2 to 3 years. This indicates an insufficient knowledge about this disease in France. Most of the demands for the test were from clinical geneticists. This diagnosis is of major importance for genetic counselling, as illustrated by the following study of 108 women at risk in these families. CONCLUSIONS: The importance of an early diagnosis followed by an extended family study, for carrier screening and prevention of this severe disease, justifies molecular testing on any child with mental retardation or significant language delay of unknown cause, in the absence of clinical signs formally excluding a fragile X diagnosis.
The authors observed a 4-year-old girl who has Rasmussen's encephalitis. She started with frequent localized and generalized seizures. Standard antiepileptic treatment was almost ineffective. The frequency of the generalized seizures decreased, but the myoclonic jerks of the left part of the body persisted. An EEG showed partial status epilepticus. The results of the CT scan were normal. Antibodies to viruses were absent from the blood and cerebrospinal fluid. An MR scan showed a T2-weighted hypersignal zone in the right frontal region. Intravenous bolus injections of corticosteroids and drips of immunoglobulins were inefficient, and we started plasma exchanges which have continued for 9 months. The clinical state stabilized, and the images on the MR scan improved, but the results of the EEG did not improve. The authors discuss the effect of the plasma exchange, the use of which is questionable in this disease.
The relative contribution of diarrheagenic Escherichia coli was examined during a 1-year prospective study of hospitalized children in Clermont-Ferrand, France, including 220 case patients (with diarrhea) and 211 matched controls. Fecal isolates were characterized by means of their pattern of adherence to HEp-2 cells and by colony hybridization with DNA probes specific for the six categories of diarrheagenic E. coli. No enteroinvasive or enterotoxigenic E. coli isolates were isolated. Twenty-eight (6.5%) eae-positive isolates and 39 (9%) enteroaggregative E. coli isolates characterized with the aggregative adherence probe and/or by their adherence pattern were detected; they were equally distributed among the patients and the controls. Diffusely adhering E. coli was the predominant pathotype: 30.7% were detected by their adherence pattern and 13.7% were detected with the daaC probe. They were isolated with similar frequencies from the patients and the controls, thereby showing no association with diarrhea. However, daaC-positive strains were significantly associated with a past record of urinary tract infections. These results suggest that the diffusely adhering E. coli organisms isolated in the present study are not true intestinal pathogens but may be regarded as resident colonic strains.
We studied the androgen receptor gene in a large kindred with complete androgen insensitivity syndrome and negative receptor-binding activity, single-strand conformation polymorphism (SSCP) analysis and sequencing identified a 13 base pair deletion within exon 4. This was responsible for a predictive frameshift in the open reading frame and introduction of a premature stop codon at position 783 instead of 919. The deletion was reproduced in androgen receptor wildtype cDNA and transfected into mammalian cells. Western blot showed a smaller androgen receptor of 94 kDa for the transfected mutated cDNA instead of 110 kDa. Androgen-binding assay of the mutated transfected cells assessed the lack of androgen-binding. Gel retardation assay demonstrated the ability of the mutant to bind target DNA; however, the mutant was unable to transactivate a reporter gene. Although the role of the partial deletion in the lack of androgen action was expected, in vitro analyses highlight the role of the abnormal C-terminal portion in the inhibition of the receptor transregulatory activity of the protein causing androgen resistance in this family.
BACKGROUND: Systemic Malassezia furfur (Mf) infections are only seen in neonates and immunocompromised patients. CASE REPORT: A 2-year-8-month-old boy was given chemotherapy for mediastinal T cell lymphoma. Meningeal relapse supervened 10 months later, requiring polychemotherapy plus CNS irradiation followed by bone marrow transplantation. Three days after transplantation, fever associated with neutropenia required administration of ceftazidime, amikacin, vancomycin plus acyclovir followed by amphotericin B, cefotaxime plus erythromycin. Blood cultures were negative, but blood swears showed yeasts into polynuclear cells after cytocentrifugation; these yeasts were also present in the central catheter removed after a few days course of amphotericin B, flucytosine plus fluconazole. The patient was then given GM-CSF subcutaneously (5 micrograms/kg/day), followed by progressive correction of aplasia and cure of the Mf infection. CONCLUSION: This is a new case of systemic Mf infection seen in an immunocompromised child receiving parenteral nutrition with lipids.