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Biomedical subjects

F Lenfant

Publications and source records attributed to F Lenfant.

At least 37 records · Page 2Linked to original sources
PubMed2000

Could heart rate variability analysis become an early predictor of imminent brain death? A pilot study.

UNLABELLED: Physiology of brain death is characterized by major disturbances of autonomic nervous system (ANS) activity which can lead to graft dysfunction. These findings exhibit the importance of early diagnosis of brain death to improve transplantation outcome. The aim of this prospective study was to assess whether heart rate variability (HRV) analysis, a noninvasive method to investigate ANS activity in comatose patients, could achieve this goal. A total of 14 brain-injured patients were included in the study as soon as they exhibited the clinical signs of imminent brain death. The electrocardiogram was then recorded from two leads with a Holter digital monitor. The clinical diagnosis of brain death was considered after an autonomic storm had occurred. HRV was assessed from 6 h before to 6 h after brain death in both time domain and spectral analysis, estimating either global ANS activity (index of variability, total power), parasympathetic activity (percentage of delta of R-R interval >50 ms, root mean square for successive interval differences, LnHF) or sympathetic activity (LnLF). Hourly averages of these variables were compared by using one-way analysis of variance. To assess whether HRV could per se diagnose brain death, receiver operating characteristic curves were generated for total power, root mean square for successive interval differences, and LnHF. We observed, for 6 h before brain death, a progressive extinction of the influence of the ANS on cardiovascular regulation. There was no activity in the two components of the ANS as soon as brain death occurred. HRV analysis appeared to be a very sensitive but a less specific method of diagnosing brain death. IMPLICATIONS: A total of 14 brain-injured patients with the clinical criteria of imminent brain death were enrolled for electrocardiogram recording and heart rate variability analysis (a noninvasive method to investigate autonomic nervous system activity). For 6 h before brain death, we observed a progressive extinction of autonomic nervous system activity which was not present as soon as brain death was clinically evoked.

Adult↗
PubMed1999

Primary cultured human thymic epithelial cells express both membrane-bound and soluble HLA-G translated products.

This report demonstrates that both membrane-bound and soluble HLA-G isoforms are present in primary cultured human thymic epithelial cells (TEC). HLA-G transcriptional isoforms have been detected by RT-PCR, using different sets of HLA-G specific primers. A flow cytometry analysis, using two anti-HLA-G mAbs, namely 87G and BFL.1, revealed the presence of HLA-G translated products at the cell surface of a subpopulation of TEC. Finally, it was shown that HLA-G soluble forms were secreted in TEC culture supernatant, using a sandwich ELISA with BFL.1 and W6/32 mAbs. These results confirm and extent those previously described showing that HLA-G expressing cells were detectable by immunohistochemistry in thymic medullary epithelial cells.

Cell Membrane↗
PubMed1999

[Use of the Fibroxy mask for bronchial fibroscopy and resuscitation].

Bronchial fibrescopy in intensive therapy patients raises the problem of oxygenation during the procedure. The Fibroxy mask allows fibrescopy with simultaneous O2 administration and manual or mechanical ventilation. This study, which included ten patients, assessed the benefits of this device. During fibrescopy, the heart rate, the mean arterial blood pressure, and the arterial oxygen saturation (SpO2) remained unchanged and only one short episode of desaturation occurred. The satisfaction index was high. However, this mask did not fit closely to the patient's face, and an additional assistant was required for efficient ventilation. Moreover, end-tidal CO2 could not be monitored satisfactorily. After some improvements, this device seems to be of value for bronchial fibrescopy in intensive therapy unit.

Bronchoscopes↗
PubMed1999

Effects of bupivacaine on human erythrocytes submitted to stress and evidence for an interaction between bupivacaine and flumazenil.

AIMS: To examine the effects of bupivacaine on erythrocytes submitted to an oxidative stress (AAPH) and to provide evidence for an in vitro interaction between bupivacaine and flumazenil. METHODS: Human erythrocytes were studied with or without AAPH in the presence of different concentrations of bupivacaine (0.15, 0.3, 0.9 and 1.8 mmol l-1 ), or flumazenil (0.16 mmol l-1 ) and with the association of flumazenil and two doses of bupivacaine (0.15 and 0.3 mmol l-1 ). Potassium efflux was measured by flame photometry at T0, and every 30 min for 2 h. RESULTS: In the absence of AAPH, extracellular potassium remained unchanged. Oxidative stress induced a significant increase in extracellular potassium, which was not modified by incubation with flumazenil. Bupivacaine significantly lowered the increase in extracellular potassium in a dose-related fashion. The association with flumazenil blunted the effects of bupivacaine. Discussion In this model, bupivacaine proved effective in protecting erythrocytes against oxidative stress. Flumazenil interacted with bupivacaine and blunted its protective effects.

Anesthetics, Local↗
PubMed1999

Soluble HLA-G: purification from eukaryotic transfected cells and detection by a specific ELISA.

PROBLEM: The detection of soluble forms of human leukocyte antigen-G molecule (sHLA-G) at the maternal-fetal interface suggest that sHLA-G may play a role during pregnancy. To study the potential functions of sHLA-G, we developed a procedure to detect and produce such HLA-G isoforms. METHOD OF STUDY: Transfected cell lines expressing either sHLA-G1s cDNA (JAR-G1s) or an sHLA-G monochain DNA (Fox-G-mono) containing extracellular domains of HLA-G linked to the human beta 2-microglobulin were used. Specific sHLA-G enzyme-linked immunosorbent assay (ELISA), using anti-HLA-G monoclonal antibodies (mAbs) (87G and BFL.1) as coating antibodies and the biotinylated HLA class I mAb, W6/32, to reveal the bound molecules, was then developed. RESULTS: To assess the specificity of the ELISA, we tested cell culture supernatants from the trophoblast-derived JEG-3 cell line and the HLA-G1s-transfected JAR cells, and we detected sHLA-G in both supernatants. sHLA-G monochain was also detected by ELISA in transfected cell supernatants using the conformational mAb, W6/32, showing that the conformation of sHLA-G monochain was proper. Using the same ELISA, sHLA-G was detected in various samples of amniotic fluid. To test the potential role of sHLA-G, sHLA-G has been purified by immunoaffinity columns, using W6/32 mAb, from culture supernatants of HLA-G1s or sHLA-G monochain-transfected cells. CONCLUSION: These important tools will be useful both for the detection of sHLA-G in various biological fluids and in functional tests.

Amniotic Fluid↗
PubMed1998

Absence of imprinting of HLA class Ia genes leads to co-expression of biparental alleles on term human trophoblast cells upon IFN-gamma induction.

Human trophoblast cells have developed various efficient regulatory mechanisms to prevent cell surface expression of the classical HLA-A, -B, and (but not always) -C class I molecules. This allows them to escape maternal alloimmune attack during pregnancy. However, recent results have demonstrated that such a lack of expression could be reversed in villous cytotrophoblast cells purified from term placenta by in vitro IFN-gamma treatment. In this context, we investigated whether both maternal and paternal HLA class Ia antigens were co-dominantly expressed in such trophoblast cells. Using polymerase chain reaction sequence-specific primers for HLA-A and HLA-C alleles, we detected transcripts of both paternal and maternal origins, showing that these genes were not affected by genomic imprinting, at least in term placenta. After in vitro IFN-gamma treatment, the polymorphic HLA-A and HLA-B antigens of both parental origins become detectable at the cell surface, as assessed by flow cytometry and/or complement-dependent microtoxicity test. Appearance of paternal antigens on trophoblast cells upon IFN-gamma induction raises the question of the in vivo biological consequences of this phenomena, in term of materno-fetal tolerance and in particular of a potential allogeneic cytotoxic immune response.

Alleles↗
PubMed1997

[Predictive factors of short-term mortality in patients with severe head injury].

OBJECTIVES: To define hazard factors of early mortality in severe brain injured patients. PATIENTS AND METHODS: An open prospective study was conducted in 125 brain injured patients with initial Glasgow coma score below 8. Different vital parameters were recorded daily during the first 10 days of resuscitation. Computed tomography (CT) scan classification of the Traumatic Coma Data Bank, the Glasgow coma score, the SAPS score and the influence of neurosurgery were assessed. RESULTS: In exclusive parameters analysis, a Glasgow coma score below 6, the presence of a midline shift of more than 5 mm on the initial brain CT scan, high or mixed density lesion of more than 25 cc, as well as mean blood pressure below 90 mm Hg were respectively correlated with early death. Low mean blood pressure led to low brain perfusion pressure in patients with intracranial hypertension. CONCLUSION: We defined 3 independent predictive factors of early mortality: the Glasgow coma scale, CT scan classification and mean blood pressure below 90 mm Hg. The main goal of the resuscitation in severe brain insult patients must be to obtain a sufficient brain perfusion pressure. This often requires the use of vasoactive drugs.

Adult↗
PubMed1997

Interferon-gamma rescues HLA class Ia cell surface expression in term villous trophoblast cells by inducing synthesis of TAP proteins.

Human placental trophoblast cells that constitute the materno-fetal interface during pregnancy escape maternal alloimmune attack. The different trophoblast cell subpopulations have developed efficient regulatory mechanisms to prevent expression of beta2-microglobulin-associated HLA class Ia molecules at their cell surface. We previously reported the presence of HLA class Ia messages in villous cytotrophoblast cells and in the syncytiotrophoblast differentiated in vitro purified from term placenta. In this study, we found that these transcripts are translated in heavy chain proteins that are endoglycosidase H sensitive and thus retained in the endoplasmic reticulum or cis-Golgi. Moreover, these class Ia heavy chains can be co-immunoprecipitated with the chaperone protein calnexin resident in the endoplasmic reticulum. When these trophoblast cells are treated with interferon (IFN)-gamma, part of the class Ia heavy chains become endoglycosidase H resistant, demonstrating that they have left the endoplasmic reticulum. Furthermore, after such a treatment, these heavy chains are detectable at the cell surface of these trophoblast cells, as assessed by two-color flow cytometry analysis and immunoprecipitation of cell surface biotinylated proteins using the W6/32 anti-HLA class I monoclonal antibody (mAb). IFN-gamma treatment induces a significant enhancement of the transcription of transporters associated with antigen processing (TAP1 and TAP2) rather than an increase of HLA class I or beta2-microglobulin messages. Finally, we demonstrate that an anti-TAP1 mAb co-immunoprecipitates TAP1 proteins and HLA class Ia heavy chains in these IFN-gamma-treated trophoblast cells. Thus, the constitutive absence of HLA class Ia cell surface expression in term villous cytotrophoblast and syncytiotrophoblast is likely to be due to a lack of transporter proteins that participate in the proper assembly of these molecules in the endoplasmic reticulum. Such a defect can be modified upon IFN-gamma treatment.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Endothelial cells in chorionic fetal vessels of first trimester placenta express HLA-G.

Using four different HLA-G-recognizing monoclonal antibodies (mAb), we investigated whether this nonclassical HLA class I molecule could be expressed in placental cell types other than extravillous cytotrophoblasts (evct) in which HLA-G has already been detected. Immunohistochemical analysis was performed on serial cryosections of first trimester placenta as well as on maternal decidual tissue. In addition to some proliferative evct, the recently described BFL.1 mAb also slightly stained some villous cytotrophoblast (vct) stem cells located near cell columns and cell islands, which until now have been considered as HLA-G negative. The same staining pattern was obtained with the 16G1 mAb raised against the soluble HLA-G isoform, whereas neither 87G nor HCA2 reacted with vct but did strongly label the invasive populations of evct, including interstitial and endovascular trophoblasts. Surprisingly, BFL.1 strongly and reproducibly stained endothelial cells in the fetal capillaries present in the mesenchymal core of the chorionic villi, whereas none of the other surrounding cellular components were stained. The same specific labeling was obtained, although with less intensity, with the three other HLA-G-recognizing mAb. In contrast, maternal endothelial cells present in spiral arteries of the decidua parietalis remained unstained. This unexpected cellular localization suggests that HLA-G may be present as a soluble form during the whole period of fetal vascularization and/or exert a nonimmunological function related to the endothelial cell type, in particular in the angiogenesis process which is highly active, until term, in chorionic villi.

Blood Vessels↗
PubMed1997

[Assessment of a new light guide (Trachlight) for tracheal intubation].

OBJECTIVE: To assess the learning curve of a new lighwand device, Trachlight (Laerdal), for blind orotracheal intubation in patients without foreseen difficulty in airway management. STUDY DESIGN: Open, prospective, clinical study. USERS: Twelve persons practicing anaesthesia (specialists, trainees, nurses) underwent videotape learning and manikin training with ten successful intubation manoeuvres required with the device. METHODS: Each person had to carry out a tracheal intubation in ten consecutive patients undergoing scheduled surgery and without history or clinical sign of difficults airway management. RESULTS: One hundred and twenty patients were included. The overall success rate with the Trachlight was 87%. An easy learning curve was obtained as demonstrated by the low failure rate in the first three patients, and by the success rate on the first or second attempt in the last four patients. There was no significant difference in failure rate with or without muscle relaxation (10 vs 20%, NS). Finally, all failures with the Trachlight were followed by successful intubation using direct laryngoscopy, and no traumatic complications were recorded with the device. CONCLUSION: Trachlight is a new lightwand device enabling blind tracheal intubation with a easy learning curve in patients without difficulty in airway management, even for non-selected operators.

Adult↗
PubMed1997

[Use of Glasgow coma scale by anesthesia and intensive care internists in brain injured patients].

OBJECTIVE: To evaluate the quality and reliability of the Glasgow coma scale (GCS) score when determined, in head trauma patients, by trainees in anaesthesiology. STUDY DESIGN: Prospective survey. USERS: One hundred trainees in their first to fourth year of training in anaesthesiology. METHODOLOGY: A questionnaire completed by the trainees concerning: demographic data; place, time and qualification of the physician determining the first GCS score; time and qualification of the physician determining the subsequent GCS score; assessment of the GCS score in case of asymmetrical motor response, tracheal intubation, bilateral eyelid oedema, or circulatory or ventilatory failure. RESULTS: Sixty questionnaires were available for analysis. Lack of compliance with the rules for the GCS score evaluation resulted in many errors by most of the trainees. Only a few of them determined an accurate GCS score in cases of asymmetric motor response or impossibility to determine verbal or ocular response. Finally, GCS scores were determined later only very rarely. CONCLUSION: In order to provide optimal care and allow an accurate assessment of therapeutic efficiency, special attention should be given to the teaching of the GCS scoring method in head trauma patients.

Anesthesiology↗
PubMed1997

The interchain disulfide bond between TCR alpha beta heterodimers on human T cells is not required for TCR-CD3 membrane expression and signal transduction.

In the present paper, it was attempted to define the amino acids or regions on TCR beta molecules that determine the TCR alpha-TCR beta interaction. Sequence studies on HBP-ALL variant cells with an intrinsic deficiency in TCR alpha beta dimer formation elucidated a conserved amino acid motif in the TCR-C beta beta-strand E, = Y(C)(L)(S)SRLR(V)(S)(A); this motif seems to represent one interaction area for the TCR alpha-TCR beta interaction. In addition, amino acids in the connecting peptide may be shaped in a precise structure (by the interactions with CD3 molecules?) involved in TCR alpha-TCR beta dimerization. This result was supported by the finding that the interchain disulfide bond between TCR alpha and beta chains is not required for membrane expression or transmembrane signal transduction of TCR alpha beta-CD3 complexes. Finally, comparative results from two membrane TCR-CD3-negative Jurkat variants R4.9 and E6.E12 suggest that TCR-C beta exon 1- and 2-encoded amino acids are important for the TCR beta-CD3 gamma epsilon association.

Amino Acid Sequence↗
PubMed1996

All four core histone N-termini contain sequences required for the repression of basal transcription in yeast.

Nucleosomes prevent the recognition of TATA promoter elements by the basal transcriptional machinery in the absence of induction. However, while Saccharomyces cerevisiae histones H3 and H4 contain N-terminal regions involved in the activation and repression of GAL1 and in the expression of heterochromatin-like regions, the sequences involved in repressing basal transcription have not yet been identified. Here, we describe the mapping of new N-terminal domains, in all four core histones (H2A, H2B, H3 and H4), required for the repression of basal, uninduced transcription. Basal transcription was monitored by the use of a GAL1 promoter-URA3 reporter construct whose uninduced activity can be detected through cellular sensitivity to the drug, 5-fluoroorotic acid. We have found for each histone that the N-terminal sequences repressing basal activity are in a short region adjacent to the structured alpha-helical core. Analysis of minichromosome DNA topology demonstrates that the basal domains are required for the proper folding of DNA around the chromosomal particle. Deletion of the basal domain at each histone significantly decreases plasmid superhelical density, which probably reflects a release of DNA from the constraints of the nucleosome into the linker region. This provides a means by which basal factors may recognize otherwise repressed regulatory elements.

Acetylation↗
PubMed1996

[Hemodynamic changes induced by apnea test in patients with brain death].

OBJECTIVE: In France, an apnoea test is compulsory to confirm brain death. This test results in a major hypercarbia and respiratory acidosis. This study aimed to assess haemodynamic changes elicited by the apnoea test. STUDY DESIGN: Prospective clinical study. PATIENTS: Fifteen patients with brain death METHODS: Before the apnoea test, the lungs were ventilated with pure oxygen for 20 minutes. Thereafter, the test was conducted with continuous oxygen flow through the endotracheal tube, and SpO2 monitoring. Blood gases and haemodynamic parameters, including systemic arterial pressure, pulmonary artery pressure, pulmonary artery occlusion pressure, cardiac index and right ventricular function parameters were assessed before, during and 20 minutes after the apnoea test. Mean values at the various times were compared. RESULTS: Hypercarbia and acidosis induced a major pulmonary hypertension and an increase in cardiac output, associated with a decrease in systemic vascular resistances. Despite pulmonary hypertension and acidosis, right ventricular function was maintained. All haemodynamic modifications were reversed by reventilation. CONCLUSION: Apnoea test induces a reversible pulmonary hypertension that is seemingly not deleterious for right ventricular function. Apnoea test probably does not alter viability of the donor's organs.

Acidosis, Respiratory↗