PubMed Health⌕ Search

Biomedical subjects

M Koenig

Publications and source records attributed to M Koenig.

At least 19 recordsLinked to original sources
PubMed2006

Fast-electron transport and heating of solid targets in high-intensity laser interactions measured by K alpha fluorescence.

We present experimental results on fast-electron energy deposition into solid targets in ultrahigh intensity laser-matter interaction. X-ray K alpha emission spectroscopy with absolute photon counting served to diagnose fast-electron propagation in multilayered targets. Target heating was measured from ionization-shifted K alpha emission. Data show a 200 microm fast-electron range in solid Al. The relative intensities of spectrally shifted Al K alpha lines imply a mean temperature of a few tens of eV up to a 100 microm depth. Experimental results suggest refluxing of the electron beam at target rear side. They were compared with the predictions of both a collisional Monte Carlo and a collisional-electromagnetic, particle-fluid transport code. The validity of the code modeling of heating in such highly transient conditions is discussed.

Journal Article↗
PubMed2006

Treatment of isolated severe immune hemolytic anaemia associated with systemic lupus erythematosus: 26 cases.

The aim of this study was to evaluate the response to treatment and the long-term outcome in a cohort of patients in whom severe autoimmune hemolytic anaemia (AHA) was the leading manifestation of systemic lupus erythematosus (SLE). Twenty-six women with severe isolated AHA were included. Corticosteroids were used as the initial treatment for all patients in our study. An initial response was obtained in all but one patient (96%). The overall recurrence rate was three per 100 person-years, with an expected recurrence-free proportion of 73% with a 180 months median follow-up. Seven patients (27%) experienced a relapse of AHA. We found a higher proportion of pleuritis in relapsing patients. Only three patients experienced multiple relapses despite splenectomy and several immunosuppressants. Steroid-sparing effect of hydroxychloroquine and azathioprine could not be assessed because most of the patients received these treatments for other reasons than AHA. Intravenous immunoglobulins induced transient response in three cases. Splenectomy was efficient to definitively control AHA in one patient but two patients quickly experienced relapses while one patient did not benefit. Five patients received immunosuppressants that induced only transient responses. Rituximab was long-term efficient in one case. In conclusion, severe AHA is a serious complication of SLE that warrants appropriate management. On the basis of our experience, the ideal treatment of isolated AHA should be oral corticosteroids in first-line treatment. Our study does not support an important role for splenectomy. Patients refractory to conventional therapy should be treated either with few toxic immunosuppressive drugs, danazol or rituximab.

Adolescent↗
PubMed2005

[Pentoxifylline: a cheap substitute for anti-TNFalpha agents?].

PURPOSE: Pentoxifylline (PTX) is a phosphodiesterase inhibitor drug used to improve peripheral vascular disease. In vitro studies demonstrated that PTX has anti-TNFalpha properties. We did a selective review of clinical trials which used PTX in patients with inflammatory rheumatic and non-rheumatic diseases. CURRENT KNOWLEDGE AND KEY POINTS: Most of the identified clinical trials were uncontrolled and involved a low number of patients. Use of PTX in systemic lupus erythematous, Behçet's disease and sarcoidosis yielded significant preliminary results. Moreover, PTX markedly reduced proteinuria in several glomerulonephritis (lupus nephritis, membranous nephropathy, diabetic nephropathy). FUTURE PROSPECTS AND PROJECTS: Further randomized and controlled clinical trials are required to examine whether PTX can improve outcome in patients with inflammatory diseases. Meanwhile, PTX should not be used for the treatment of these diseases.

Clinical Trials as Topic↗
PubMed2005

Ultraintense laser-produced fast-electron propagation in gas jets.

We study the propagation of fast electrons in a gas at different densities. A large relativistic electron current is produced by focusing a short-pulse ultrahigh-intensity laser on a metallic target. It then propagates in a gas jet placed behind the foil. Shadowgraphy in the gas shows an electron cloud moving at sub-relativistic average velocities. The experiment shows (i) the essential role of the density of background material for allowing propagation of fast electrons, (ii) the importance of the ionization phase which produces free electrons available for the return current, and (iii) the effect of electrostatic fields on fast-electron propagation.

Journal Article↗
PubMed2005

[Primary and atypical facial pain: diagnosis and treatment].

PURPOSE: Facial pain is a frequently encountered symptom in general medical practice and encompass a wide group of facial problems. As correct diagnosis can usually be reached by history and physical examination for well defined typical clinical entities (trigeminal neuralgia, cluster headache) atypical facial pain may have many other potential causes (sinuses infection, temporomandibular joint syndrome, dental disorders...) so that diagnosis not appear an easy task. CURRENT KNOWLEDGE AND KEYPOINTS: Anatomical and physiological organization of facial nociceptive system, particularly trigeminal system, may explain the variability of facial pain. Although symptoms have been clearly identified mechanism of pain production remains controversial. Several factors (psychological, neurological, endocrine...) and mechanisms (neuropathic, vascular, myoarticular) may coexist and explain trouble in diagnosing and treating facial pain. FUTURE PROSPECTS AND PROJECTS: Better knowledge in identifying the cause of facial pain may lead to improve patient care and avoid patient frustration, medical nomadism, repetitive dental and otolaryngologic procedures, and finally non-compliance with treatment.

Facial Nerve Diseases↗
PubMed2005

[Extrapontine myelinolysis of favorable outcome in a patient with autoimmune polyglandular syndrome].

INTRODUCTION: Extrapontine myelinolysis is a well-known complication of hyponatremia and its treatment. It rarely occurs without central pontine myelinolysis, usually after overly rapid correction of hyponatremia. Its prognosis is considered poor. EXEGESIS: We report the case of a patient with autoimmune polyglandular syndrome with subacute adrenal failure responsible of severe hyponatremia. Despite a well-conducted treatment, the patient developed acute anxiety, catatonia, dysphagia and parkinsonism revealing extrapontine myelinolysis demonstrated on MRI. Outcome was favorable. CONCLUSION: Extrapontine myelinolysis may occur in the absence of central pontine myelinolysis despite a treatment of hyponatremia conducted according to published guidelines. Treatment should be extremely cautious when hyponatremia has been lasting for more than 48 hours.

Adrenal Gland Diseases↗
PubMed2005

[Spontaneous hypothermia: a series of ten cases, place of Shapiro's syndrome].

SUBJECT: Hypothermia (defined as a core temperature lower than 35 degrees C) may result from accidental causes (exposure to cold, drug intoxications), from endocrine disorders (hypothyroidism), or from central or peripheral neurological disease. Among the causes of spontaneous hypothermia, the place of spontaneous periodic hypothermia or Shapiro's syndrome, of which less than 50 cases in children or adults have been reported, remains unclear. METHODS: Case series of spontaneous hypothermia in adults, from a register of the French Society of Internal Medicine (SNFMI). RESULTS: The ten collected cases of spontaneous hypothermia are heterogeneous. In half of the cases, an often ill-labeled psychiatric illness and/or epilepsy and/or anti-psychotic medication were found contributive. Only 5 cases at best seem to conform to the pattern of spontaneous periodic hypothermia or Shapiro's syndrome (in which agenesis of corpus callosum is typically found). In such cases, the episodes of hypothermia start with profuse hyperhidrosis suggesting a paroxystic reset of the hypothalamic thermostat with a lower temperature set point. In none of the cases was found a significant encephalic lesion. None of the treatment trials with anti-epileptics or cyproheptadine were found useful. Spontaneous hypothermia, whether periodic or not, seems to have an unpredictable course, with long periods of remission, and a benign long-term outcome. CONCLUSIONS: Spontaneous hypothermia is a symptom of likely multifactorial etiology. Even in cases conforming to the definition of Shapiro's syndrome, central nervous system anomalies are not unequivocal. No specific treatment for spontaneous hypothermia, whether periodic or not, can be recommended in the current state of knowledge.

Adult↗
PubMed2005

[Mutation of the aprataxin gene presenting with Charcot-Marie-Tooth-like neuropathy and cerebellar ataxia].

BACKGROUND: Phenotype-genotype correlations, generally based on predominant associated signs, are being increasingly used to distinguish different types of autosomal recessive cerebellar ataxias (ARCA). CASE REPORTS: Two brothers developed signs of cerebellar ataxia with peripheral axonal motor and sensory neuropathy, distal muscular atrophy, pes cavus and steppage gait as seen in Charcot-Marie-Tooth neuropathy. The examination also showed oculomotor apraxia. Sural nerve biopsy revealed conspicuous reduction in the density of myelinated fibres but preservation of unmyelinated nerve fibres. Blood tests revealed low serum albumin and elevated cholesterol. A homozygous W279X truncating mutation was identified in exon 6 of the APTX gene, confirming the diagnosis of cerebellar ataxia with oculomotor apraxia type 1 (AOA1). CONCLUSIONS: These cases illustrate the presentation of AOA1 type of ARCA and discuss the role of peripheral neuropathy in the differential diagnostic of the ARCAs variants.

Brain↗
PubMed2005

[Contrast media kinetic in multi-slice helical CT cannot detect rectal cancer recurrence with certainty].

PURPOSE: Evaluation of different parameters of contrast media enhancement for the differentiation between scar tissue and local recurrence of rectal cancer. MATERIALS AND METHODS: We included 83 patients after operation and radiotherapy of rectal cancer. In total, 20 local recurrences were diagnosed. After administration of 75 ml Iopromide (370 mg/ml) and a delay of 65 s, the whole abdomen and pelvis were scanned in a collimation of 4 x 2.5 mm and 12.5 mm table feed per rotation. The suspected tissue was marked by the freehand ROI option in every slice and the minimum, average and maximum densities were calculated. A local recurrence was suspected if maximum density was higher than 90 HU after admission of contrast media. In addition we calculated the maximum difference of density as the difference between maximum and minimum density. RESULTS: The minimum and average densities showed no reliable differences for patients with or without local recurrence (minimum density 4 HU ( +/- 12 HU) vs. 13 HU ( +/- 21 HU), P = 0.23, average density 48 HU ( +/- 10 HU), vs. 48 HU ( +/- 17 HU)), P = 0.52. The patients suffering from local recurrence showed higher maximum densities and a higher maximum difference than the patients without recurrence (maximum density 111 HU ( +/- 13 HU) vs. 81 HU ( +/- 24 HU), P = 0.02, maximum difference 103 HU ( +/- 20 HU) vs. 76 HU ( +/- 31 HU), P = 0.06. These differences were not significant. We calculated a sensitivity of 0.6, a specificity of 0.83, a positive predictive value of 0.52 and an accuracy of 0.77. CONCLUSION: It is not possible to diagnose a recurrent rectal cancer by density values alone.

Aged↗
PubMed2005

Giant axonal neuropathy: clinical and genetic study in six cases.

BACKGROUND: Giant axonal neuropathy (GAN) is a severe recessive disorder characterised by variable combination of progressive sensory motor neuropathy, central nervous system (CNS) involvement, and "frizzly" hair. The disease is caused by GAN gene mutations on chromosome 16q24.1. AIMS: To search for GAN gene mutations in Turkish patients with GAN and characterise the phenotype associated with them. METHODS: Linkage and mutation analyses were performed in six affected patients from three consanguineous families. These patients were also investigated by cranial magnetic resonance imaging (MRI) and electroencephalography (EEG). Electromyography (EMG) was performed in heterozygous carriers from family 1 and family 3. RESULTS: Linkage to 16q24.1 was confirmed by haplotype analysis. GAN mutations were identified in all families. Family 1 had the R293X mutation, previously reported in another Turkish family. Families 2 and 3, originating from close geographical areas, shared a novel mutation, 1502+1G>T, at the donor splice site of exon 9. All patients displayed a common phenotype, including peripheral neuropathy, cerebellar ataxia, and frizzly hair. Cranial MRI showed diffuse white matter abnormalities in two patients from family 1 and the patient from family 3, and minimal white matter involvement in the patient from family 2. EMG of a heterozygous R293X mutation carrier showed signs of mild axonal neuropathy, whereas a 1502+1G>T mutation carrier had normal EMG. EEG abnormalities were found in three patients. CONCLUSION: These findings highlight the association of CNS involvement, in particular white matter abnormalities, with peripheral neuropathy in GAN. The phenotypical consequences of both mutations (when homozygous) were similar.

Adolescent↗
PubMed2004

Fast electron heating of a solid target in ultrahigh-intensity laser pulse interaction.

We report one of the first measurements of induced heating due to the transport of a fast electron beam generated by an ultrashort pulse laser interaction with solid targets. Rear-side optical reflectivity and emissivity have been used as diagnostics for the size and temperature of the heated zone. A narrow spot has been observed of the order of the laser focus size. Values up to approximately 10 eV at the target back surface were inferred from the experimental data and compared with the predictions of a hybrid collisional-electromagnetic transport simulation.

Journal Article↗
PubMed2004

Generation of a double shock driven by laser.

The feasibility and reliability of a multiple laser shock generation to study the equation of state surface off the principal Hugoniot curve and to approach an isentropic compression has been demonstrated. The technique is based on the use of a double laser pulse. A strong shock was generated in iron targets precompressed by a first weak shock. The effect of precompression was studied. The experiment was performed at the Laboratoire pour l'Utilisation des Lasers Intenses laboratory.

Journal Article↗
PubMed2004

Aprataxin gene mutations in Tunisian families.

The authors report clinical and genetic study of 13 patients from three unrelated Tunisian families with an early onset cerebellar ataxia associated with oculomotor apraxia. Cerebellar ataxia with oculomotor apraxia 1 (AOA1) represents a clinically heterogeneous disease caused by mutations in the aprataxin gene. Two novel mutations were identified, the complete deletion of the gene, which seems to not correlate with an increased severity of the disease, and a splice mutation on the acceptor splice site of exon 7.

Adolescent↗
PubMed2004

K(alpha) fluorescence measurement of relativistic electron transport in the context of fast ignition.

Electron transport within solid targets, irradiated by a high-intensity short-pulse laser, has been measured by imaging K(alpha) radiation from high- Z layers (Cu, Ti) buried in low- Z (CH, Al) foils. Although the laser spot is approximately 10 microm [full width at half maximum (FWHM)], the electron beam spreads to > or =70 microm FWHM within <20 microm of penetration into an Al target then, at depths >100 microm, diverges with a 40 degree spreading angle. Monte Carlo and analytic models are compared to our data. We find that a Monte Carlo model with a heuristic model for the electron injection gives a reasonable fit with our data.

Journal Article↗
PubMed2004

Observation of laser driven supercritical radiative shock precursors.

We present a supercritical radiative shock experiment performed with the LULI nanosecond laser facility. Using targets filled with xenon gas at low pressure, the propagation of a strong shock with a radiative precursor is evidenced. The main measured shock quantities (electronic density and propagation velocity) are shown to be in good agreement with theory and numerical simulations.

Journal Article↗
PubMed2004

Hugoniot data for carbon at megabar pressures.

We present an experimental point for the carbon equation of state (EOS) at megabar pressures, obtained by laser-driven shock waves. The rear side emissivity of "two-materials two-steps" targets (Al-C) was recorded with space and time resolution and, by applying the impedance mismatch method, allowed a direct determination of relative EOS points. Experiments were performed at the PALS and LULI laboratories using carbon samples with two different values of initial density, in order to explore a wider region of the phase diagram. Previously unreached pressures were obtained. The results are compared with previous experiments and with available theoretical models and seem to show a high compressibility of carbon at megabar pressures.

Journal Article↗