Search PubMed⌕ Search

Biomedical subjects

E Michel

Publications and source records attributed to E Michel.

At least 55 records · Page 3Linked to original sources
PubMed1998

Integral and shell-MIP display algorithms in MR and CT three-dimensional models of the brain surface.

BACKGROUND AND PURPOSE: Our purpose was to demonstrate the use of integral and shell maximum intensity projection (shell-MIP) display algorithms in the 3-D CT and MR depiction of cerebral gyral and surface venous anatomy and disorders. These new algorithms are compared against MIP and shaded-surface-display (SSD) algorithms. METHODS: Integral and shell-MIP displays were generated from a specified number of proximal surface voxel layers in a 3-D model. Algorithmic models were compared on nine contrast-enhanced spoiled gradient-recalled acquisition in a steady state (SPGR) MR venograms for brain surface anatomic identification and detail. Seven CT venograms were compared for conspicuity of filling defects. Twelve contrast-enhanced preoperative planning 3-D MR models were rated for neurosurgical utility. RESULTS: A shell-MIP score of 7.00 and an integral score of 6.78 represented the highest mean subjective MR gyral quality (1-10 scale) followed by an SSD score of 3.89 and an MIP score of 1.06. Mean confidence scores for MR central sulcus identification (1-10 scale) were shell-MIP, 7.67; integral, 7.00; SSD, 3.22; and MIP, 1.00. Mean superficial venous quality MR ratings (1-10 scale) were shell-MIP, 8.22; MIP, 7.39; integral, 7.00; and SSD, 3.72. The mean number of cortical veins draining into each side of the superior sagittal sinus on MR was as follows: MIP, 6.19; integral, 6.06; shell-MIP, 5.94; and SSD, 3.81. Mean confidence scores for filling defect identification on CT venograms (1-5 scale) revealed a shell-MIP score of 4.36 and an integral score of 4.29 to be superior to a MIP score of 3.00. In selected cases, 3-D presurgical planning, prior to tumor resection, was clinically useful. CONCLUSION: Integral and shell-MIP are useful 3-D display algorithms for simultaneous display of superficial cerebral veins and gyri on MR images and of thrombosis on CT venograms.

Algorithms↗
PubMed1998

[Edeka does all--machine speech recognition in social medicine expert testimony].

UNLABELLED: Automatic speech recognition systems are already being used in spheres employing a restricted vocabulary. OBJECTIVE: Our aim was to investigate whether low-cost speech recognition software for PC is capable of being usefully employed in the sphere of sociomedicine. MATERIALS AND METHODS: To this end 34 representative pages of text (a total of 11,000 words) taken from expertises on cases of suspected medical malpractice (many different subspecialties) were dictated using IBM's "Voice Type Simply Speaking" software. Having completed a page, the resulting error rate was recorded, and the text was corrected before we proceeded with the dictation. Finally, 3 pages of text were re-dictated and the resulting error rate determined. RESULTS: The error rate in the previously unknown text ranged between 10 and 23 per cent (mean 15.9%) without any significant reduction during the training phase, while that in the re-dictated text was drastically reduced to less than 3 per cent. It became evident that once a word was corrected the system hardly ever repeated that particular mistake. CONCLUSION: The system's poor performance on unknown text and the missing reduction in the error rate during the training phase are obviously not due to any incompetence of the system but to the huge amount of technical jargon in the scope of medical writing. To attain an acceptable performance we suggest to either extend the training phase, or, preferably, to confine the application to a single medical subspecialty. Its overwhelming learning ability makes the system a serious candidate typist in the sphere of sociomedicine.

Expert Testimony↗
PubMed1997

Developmental control of heat shock and chaperone gene expression. Hsp 70 genes and heat shock factors during preimplantation phase of mouse development.

Heat shock genes are found in all organisms, and synthesis of heat shock proteins is induced by various stressors in nearly all the cells forming these organisms. However, a particular situation is noticed for hsp 70 genes in mouse embryos at the beginning of their development. First, spontaneous expression of hsp 70 is observed at the onset of zygotic genome activity. Second, inducible expression is delayed until morula or early blastocyst stages. A better understanding of both these points depends on a more careful analysis of hsp 70 expression in relation to their major regulators, the heat shock factors. In this review, we will see how the development of the preimplantation embryo highlights the complexity of heat shock gene regulation involving trans-cis interactions and the cellular and nuclear environment.

Animals↗
PubMed1997

Mutational analysis of the SOX9 gene in campomelic dysplasia and autosomal sex reversal: lack of genotype/phenotype correlations.

It has previously been shown that, in the heterozygous state, mutations in the SOX9 gene cause campomelic dysplasia (CD) and the often associated autosomal XY sex reversal. In 12 CD patients, 10 novel mutations and one recurrent mutation were characterized in one SOX9 allele each, and in one case, no mutation was found. Four missense mutations are all located within the high mobility group (HMG) domain. They either reduce or abolish the DNA-binding ability of the mutant SOX9 proteins. Among the five nonsense and three frameshift mutations identified, two leave the C-terminal transactivation (TA) domain encompassing residues 402-509 of SOX9 partly or almost completely intact. When tested in cell transfection experiments, the recurrent nonsense mutation Y440X, found in two patients who survived for four and more than 9 years, respectively, exhibits some residual transactivation ability. In contrast, a frameshift mutation extending the protein by 70 residues at codon 507, found in a patient who died shortly after birth, showed no transactivation. This is apparently due to instability of the mutant SOX9 protein as demonstrated by Western blotting. Amino acid substitutions and nonsense mutations are found in patients with and without XY sex reversal, indicating that sex reversal in CD is subject to variable penetrance. Finally, none of 18 female patients with XY gonadal dysgenesis (Swyer syndrome) showed an altered SOX9 banding pattern in SSCP assays, providing evidence that SOX9 mutations do not usually result in XY sex reversal without skeletal malformations.

Child↗
PubMed1997

Frequency dependence of cerebrovascular impedance in preterm neonates: a different view on critical closing pressure.

The nonproportional relationship between instantaneous arterial blood pressure (BP) and cerebral blood flow velocity (CBFv) is well explained by the concept of critical closing pressure (CCP). We aimed to determine the frequency response of the neonatal cerebrovascular system, and to establish the exact mathematical relationship between cerebrovascular impedance and CCP under physiologic conditions. In 10 preterm neonates (gestational age, 25-32 weeks; birth weight, 685-1,730 g; age 1-7 days) we Doppler-traced CBFv of the internal carotid artery. Blood pressure was traced simultaneously. Critical closing pressure was graphically determined. Cerebrovascular impedance was calculated as the square root of the ratio of the corresponding peaks in the power spectra of BP and CBFv at zero frequency, and at heart rate (H) and harmonics (xH). Uniformly, the impedance between H and 3H (2 to 6 Hz) was reduced about fivefold, compared with the impedance at zero frequency. The cerebrovascular system behaves like a high-pass filter, leading to a reduction of the DC (direct current) component of CBFv (analogous to current) relative to that of the driving force BP (analogous to voltage). The frequency response of cerebrovascular impedance reflects the ratio of CCP and DC BP. A mathematical derivation of this relationship is given matching the observed results. Thus, both the CCP and the impedance approach are valid.

Birth Weight↗
PubMed1997

Evidence for the involvement of mouse heat shock factor 1 in the atypical expression of the HSP70.1 heat shock gene during mouse zygotic genome activation.

The mouse HSP70.1 gene, which codes for a heat shock protein (hsp70), is highly transcribed at the onset of zygotic genome activation (ZGA). This expression, which occurs in the absence of stress, is then repressed. It has been claimed that this gene does not exhibit a stress response until the blastocyst stage. The promoter of HSP70.1 contains four heat shock element (HSE) boxes which are the binding sites of heat shock transcription factors (HSF). We have been studying the presence and localization of the mouse HSFs, mHSF1 and mHSF2, at different stages of embryo development. We show that mHSF1 is already present at the one-cell stage and concentrated in the nucleus. Moreover, by mutagenizing HSE sequences and performing competition experiments (in transgenic embryos with the HSP70.1 promoter inserted before a reporter gene), we show that, in contrast with previous findings, HSE boxes are involved in this spontaneous activation. Therefore, we suggest that HSF1 and HSE are important in this transient expression at the two-cell stage and that the absence of typical inducibility at this early stage of development results mainly from the high level of spontaneous transcription of this gene during the ZGA.

Animals↗
PubMed1997

Cross-spectral analysis of cerebral autoregulation dynamics in high risk preterm infants during the perinatal period.

In preterm infants intraventricular hemorrhage occurs predominantly within the perinatal period, which may be due to a "lost autoregulation" of cerebral blood flow (CBF). In this study, perinatal autoregulation dynamics were investigated in high risk preterm infants by cross-spectral analysis (CSA), which is a statistical tool in the analysis of time series. In 15 ventilated preterm infants of 25-32 gestational weeks, a total number of 30 records were made between 24 and 96 h of life. Doppler-derived CBF velocity (CBFv), used as a quantitative measure for CBF, and direct mean arterial blood pressure (MABP) were measured continuously for 10 min. The spectral power of low frequency (LF, 0.02-0.2 Hz) oscillations in CBFv and MABP was quantified by spectral analysis. From the results of CSA, a LF phase-shift between the CBFv and MABP LF oscillations was calculated in each record. Within the study group, the LF spectral power of CBFv and MABP was initially low and increased significantly until 96 h of life. The LF phase-shift was about 0 degrees at 24 h and increased significantly to 55 degrees at 96 h of life. The initially low LF spectral power of CBFv and MABP may indicate a perinatal depression of autonomic nervous centers, which are thought to control LF oscillations of vital parameters. In the light of a high pass filter model for autoregulation, the initially low LF phase-shift may indicate an initially impaired autoregulation, which supports the "lost autoregulation" hypothesis.

Cerebrovascular Circulation↗
PubMed1996

Are adult transcranial Doppler systems suitable for application in neonates?

UNLABELLED: Transcranial Doppler systems have not been available for monitoring of cerebral blood flow velocities in neonates because of potential hazardous effects of energy output from standard instruments developed for adult application. Aim of the study was to test commercially available transcranial Doppler instruments for their applicability in neonates and to develop guidelines for adaptation for safe neonatal use. Energy output of five commercially available transcranial Doppler instruments was measured with a hydrophone system and a radiation force balance. At the highest setting and at the nominal 10% attenuation level, five out of five and two out of five instruments, respectively, had an energy output above the recommended limits. Power reduction was not linear in one instrument. Evaluation of safety devices (alarm, freeze mode, energy reduction facilities, display of energy values) showed that none of the tested instruments had an optimal setting for safe neonatal application. CONCLUSION: Commercially available transcranial Doppler instruments should be evaluated critically for their energy output prior to their application in neonates. Special software for neonatal application of transcranial Doppler systems should be developed in order to provide extremely low energy output levels and devices for indication of duration of Doppler insonation and energy output.

Humans↗
PubMed1996

Ventilator-associated sinus arrhythmia in a preterm neonate--an indicator for a mature autonomic nervous system?

According to control theory, the interactions between respiration and heart rate (i.e. respiratory sinus arrhythmia, RSA, and breath amplitude sinus arrhythmia, BASA) reflect the inner workings of the physiological control systems of respiration and circulation. This paper reports on a preterm neonate (28.5 weeks old, 940 g) who showed the presence of ventilation-associated sinus arrhythmia (VASA) under moderate artificial ventilation. His heart rate variability was entrained to the ventilatory stimulus. VASA and entrainment suggest that the parasympathetic part of the autonomic nervous system might be more mature than expected in some preterm neonates.

Arrhythmia, Sinus↗
PubMed1995

Critical closing pressure in preterm neonates: towards a comprehensive model of cerebral autoregulation.

In preterm neonates, intraventricular haemorrhage is linked to the dysfunction of cerebral autoregulation (AR). We aimed at tracing the critical closing pressure (CCP) in order to quantify AR and to reveal its inner workings. In an observational study, 10 preterm neonates (median, range: ga 28 weeks, 25 to 32 weeks; bw 1070, 685 to 1730 g; age 2d, 1 to 7 d) were continuously Doppler traced (a. carotis interna) for > 10 min. Systemic blood pressure (BP, a. umbilicalis, a. radialis, a. temporalis) was recorded simultaneously (> 1200 cardiac cycles each). Systolic BP was on average 11 mmHg above CCP. There was a striking parallel between both variables, even in cases of sudden spontaneous BP fluctuations > 30% (r = 0.72, 0.41 to 0.99), while systolic cerebral blood flow velocity remained largely unaffected (r = -0.15, -0.75 to 0.53), indicating a properly functioning AR. CCP was 28 mmHg, 14 to 38 mmHg. Based on our data, a physiological model of AR is developed, integrating anatomy, metabolic and neuronal pathways with former physiologic findings--including low frequency cycling of cerebral blood flow velocity. Tracing of CCP is thought to have the potential to identify infants with impaired AR. Since this method is noninvasive and independent of angle of insonation (thus rendering it uncritical in probe fixation), it is a promising tool for sustained monitoring of cerebral haemadynamics in the clinical setting.

Blood Flow Velocity↗
PubMed1995

Decreased cervicovaginal production of both IgA1 and IgA2 subclasses in women with AIDS.

Paired sera and cervicovaginal secretions from 35 HIV-1-infected women representing different CDC stages of HIV infection were evaluated for total IgA, IgA1 and IgA2, for IgA, IgA1 and IgA2 to gp160, and for albumin. Age-matched healthy women (n = 45) served as controls. The secretion rates of total IgA, IgA1 and IgA2 were evaluated by calculating their relative coefficients of excretion by reference to albumin. In HIV-infected women, total IgA1 and IgA2 in sera and in cervicovaginal secretions increased proportionately as early as stages II + III and more markedly at stage IV. By contrast, the secretion rates of total IgA IgA1 and IgA2 were markedly reduced in AIDS women, the IgA2 secretion rate decreasing significantly as early as stages II + III. This apparent discrepancy was probably the result of increased transudation of serum-borne immunoglobulins into the vaginal cavity, since albumin levels in cervicovaginal secretions increased significantly according to the stages of disease. HIV-reactive IgA antibodies in serum, as in cervicovaginal secretions, were principally found within the IgA1 subclass. In women at stage IV, a high local production of IgA1 to gp160 occurred in spite of the impairment of cervicovaginal IgA synthesis, probably because of marked genital HIV replication at advanced stages.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Modulation of DNA topology by flaR, a new gene from Listeria monocytogenes.

We report the identification of a previously unknown Listeria monocytogenes gene, flaR, which modulates DNA topology. Through the analysis of a Tn917 non-motile mutant, LOSC1, in which production of flagellin was abolished, we have identified a bacterial component involved in gene regulation. The transposon had inserted in flaR, an open reading frame of 531 bp, followed by a second open reading frame of 1252 bp in reverse orientation. On the L. monocytogenes physical map, flaR was located in a different region from that of the flaA gene encoding flagellin. Transcriptional analysis showed that the flaR gene product affects the flaA expression and negatively regulates its own expression. When expressed in Escherichia coli, flaR encodes a protein of 18 kDa (FlaR) whose transcription is osmoregulated. In addition, FlaR also influences the expression of reporter genes containing supercoiling-sensitive promoters such as proU or ompC. The data presented here suggest that FlaR is a histone-like bacterial protein which acts at specific sites to influence DNA topology and, therefore, transcription. flaR is the first gene of this class to be described in Gram-positive pathogenic bacteria.

Amino Acid Sequence↗
PubMed1995

[Death due to drug addiction in Ile-de-France].

The aim of a cooperative study, carried out by the Paris Forensic Medicine Institute and the French National Institute of Health and Medical Research (INSERM SC8) was to assess the number of drug addiction-related deaths occurring in the Paris region in 1990. There were 253 deaths including 92 in Paris and 161 in Paris suburbs. A large percentage of these deaths were not recorded in the National death statistics registry (only 36% of all the deaths and only 24% of the Paris deaths had been registered). The overall drug addiction mortality in the Paris region is 29.4 per million inhabitants and is highest among the 25-29 year age group. Rates decrease rapidly after 30 years of age and are extremely low after 40. Mortality is highest in unmarried men and in the inactive population with a wide variability according to site of residence. Rates are much higher in Paris than in the suburbs. For the 20-29 year population in Paris, drug addiction has an important impact on the mortality figures for the general population, causing 12% of all deaths. It is the third cause of death after AIDS and suicide.

Adolescent↗
PubMed1994

Cyclic variation pattern of cerebral blood flow velocity and postconceptional age.

In preterm neonates, the risk for intracerebral haemorrhage is linked to immaturity of cerebral autoregulation. The preterm's 2-5/min cyclic variation pattern of cerebral blood flow velocity is thought to reflect the degree of immaturity of autoregulation--a speculation to be tested. In a cross-sectional study 15 infants (gestational age 26-40 weeks, postconceptional age (PCA) 26-42 weeks, age 1-99 days were investigated. We performed a 10 min pulsed Doppler tracing on an internal carotid artery by means of a computer controlled 5 MHz Duplex device. Systolic velocity (Vs) was recorded pulse by pulse. After appropriate data transformation, in all infants the Fast Fourier Transform of the time course of Vs revealed the presence of a 2-5/min cyclic variation pattern (one sample z-test, P < 0.0001). There was no significant correlation between proportionate spectral power of the 2-5/min frequency band and either PCA (r = 0.23, P = 0.42) or age (r = 0.41, P = 0.13). Between 26 and 42 weeks PCA, the cycling phenomenon is constant thus not reflecting cerebral maturation, and its presence does not mean immaturity of cerebral autoregulation.

Age Factors↗