PubMed Health⌕ Search

Biomedical subjects

F Nicolas

Publications and source records attributed to F Nicolas.

At least 37 records · Page 2Linked to original sources
PubMed1995

In vitro evaluation of donor liver preservation fluids on human hepatocyte function.

Successful liver transplantation depends on adequate preservation of cellular function. We therefore tested the effects of two currently used liver preservation fluids, Euro-Collins (EC) solution and University of Wisconsin (UW) solution, on the viability and some functional activities of hepatocytes isolated from human livers. Cells in primary culture were maintained under hypoxic (95% N2/5% CO2) and hypothermic (4 degrees C) conditions for 24 h, either in EC or UW solution. This treatment did not result in significant hepatocyte damage, as judged by phase contrast microscopy, intracellular LDH release, and the MTT mitochondrial test. However, neutral red uptake indicated that lysosomal functions were slightly affected (35% decrease) when compared to control conditions. At the end of the hypoxia/hypothermia period, hepatocyte monolayers were incubated at 37 degrees C under normoxic conditions for 24 h, in order to simulate the reperfusion of a transplanted liver. Three drugs--midazolam, diazepam, zidovudine--were used as diagnostic substrates to check the metabolic abilities of human hepatocytes replaced in normal conditions. Both phase I (hydroxylation, demethylation) and phase II (glucuronidation) metabolic reactions were affected by the hypoxia/hypothermia shock. Indeed, a 30%-50% decrease in these activities was observed as compared to values obtained in control hepatocytes. No difference could, however, be found at the cellular level regarding the solution used for cold storage. These results suggest that the superiority of UW over EC solution, already reported in clinical practice after transplantation of preserved human livers, was not due to a better preservation of the hepatocytes.

Antimetabolites↗
PubMed1995

Analysis of glutamate receptors in primary cultured neurons from fetal rat forebrain.

In order to further analyze the development of glutamatergic pathways in neuronal cells, the expression of excitatory amino acid receptors was studied in a model of neurons in primary culture by measuring the specific binding of L-[3H]glutamate under various incubation conditions in 8-day-old intact living neurons isolated from the embryonic rat forebrain, as well as in membrane preparations from these cultures and from newborn rat forebrain. In addition, the receptor responsiveness to glutamate was assessed by studying the uptake of tetraphenylphosphonium (TPP+) which reflects membrane polarization. In the presence of a potent inhibitor of glutamate uptake, the radioligand bound to a total number of sites of 36.7 pmol/mg protein in intact cells incubated in a Tris buffer containing Na+, Ca2+, and Cl-, with a Kd around 2 microM. In the absence of the above ions, [3H]glutamate specific binding diminished to 14.2 pmol/mg protein with a Kd-value of 550 nM. Under both of the above conditions, similar Kd were obtained in membranes isolated from cultures and from the newborn brain. However, Bmax-values were significantly lower in culture membranes than in intact cells or newborn membranes. Displacement studies showed that NMDA was the most potent compound to inhibit [3H]glutamate binding in membranes obtained from cultured neurons as well as from the newborn brain, whereas quisqualate, AMPA, kainate and trans-ACPD were equally effective.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Increased plasma levels of human interleukin for DA1.a cells/leukemia inhibitory factor in sepsis correlate with shock and poor prognosis.

Animal study results have suggested a role in sepsis for human interleukin for DA1.a cells/leukemia inhibitory factor (HILDA/LIF). HILDA/LIF and interleukin-6 (IL-6) levels were prospectively studied by serial ELISAs in 34 septic patients. HILDA/LIF was detected in 11 of 34 patients at plasma levels of 100-37,000 pg/mL. Peak HILDA/LIF levels correlated with increased temperature and creatinine and IL-6 and with decreased arterial CO2 (P < .05). Multivariate analysis showed that shock and decreased arterial CO2 accounted for 75% of peak HILDA/LIF plasma variations (R2 = .753). Fatal outcome was most often associated with detectable HILDA/LIF (> 56 pg/mL) and peak IL-6 plasma levels > 850 pg/mL (sensitivity, 83%; specificity, 87%), but both (at respective levels of > 480 and > 850 pg/mL) were associated with fatal outcome. HILDA/LIF was detected in septic patients exhibiting shock, and its levels correlated with higher mortality and shorter survival.

APACHE↗
PubMed1995

Comparative metabolism of 3'-azido-3'-deoxythymidine in cultured hepatocytes from rats, dogs, monkeys, and humans.

3'-Azido-3'-deoxythymidine (AZT), the main antiretroviral drug used against Human Immunodeficiency Virus, was approved by the Food and Drug Administration in 1987 with only little knowledge concerning its metabolism. The aim of our study was to evaluate the interspecies variability of AZT metabolism in primary cultures of hepatocytes, freshly isolated from rats, dogs, monkeys, and humans. Cultures were exposed to 10 or 100 microM [3H]AZT. Extracellular and intracellular compartments were analyzed using a HPLC method. Intracellular and extracellular metabolic patterns were qualitatively similar, but very low amounts of AZT and metabolites were detected within hepatocytes. In all species, the 3'-azido-3'-deoxy-5'-O-beta-D-glucopyranuronosylthymidine (GAZT) was identified as the major metabolite of AZT. In addition to this glucuronide, two minor peaks were detected: one coeluting with 3'-amino-3'-deoxythymidine(AMT); and the other with a retention time corresponding, on the basis of the publications in this field, to 3'-amino-3'-deoxythymidine glucuronide. However, further investigation allowed this compound to be characterized as tritiated water, possibly representing a catabolic endproduct of AZT. Although glucuronidation was the main metabolic pathway in the four species studied, AZT biotransformation rate was much lower in rat and dog hepatocytes than in monkey and human ones. Finally, an excellent correlation was obtained between in vivo and in vitro metabolic data.

Animals↗
PubMed1994

Opposite effects of cyclohexyladenosine and theophylline on hypoxic damage in cultured neurons.

To study the central effects of adenosine on hypoxia, the influence of treatment by the A1 receptor agonist cyclohexyladenosine (1 microM) or by the antagonist theophylline (10 microM) was tested on cell damage in a model of neuronal culture. Whereas theophylline enhanced cell injury induced by 8 h hypoxia, cyclohexyladenosine decreased lactate dehydrogenase leakage, abolished the transient increase in 2-D-deoxyglucose transport and improved cell morphology. Such actions might involve regulation of excitatory amino acid release and maintenance of calcium homeostasis.

Adenosine↗
PubMed1994

Characterization of adenosine receptors in a model of cultured neurons from rat forebrain.

The neuromodulator adenosine is acting through specific receptors coupled to adenylate cyclase via G-proteins. The expression of both adenosine receptors A1 and A2 as well as forskolin binding sites was investigated by radioligand binding techniques in 8-day-old neurons isolated from fetal rat forebrain and cultured in chemically-defined medium. Adenosine A1 receptors were specifically labeled with [3H]chloro-N6-cyclopentyladenosine (CCPA), whereas [3H]CGS 21680 was used for the analysis of A2 receptors. Cultured neurons exhibited high affinity binding sites for CCPA (Bmax = 160 fmol/mg protein; Kd = 2.9 nM), and for CGS 21680 (Bmax = 14 fmol/mg protein; Kd = 1.7 nM). These data correlate well with those obtained in crude membranes isolated from the newborn rat forebrain. The incubation of culture membranes in the additional presence of guanylyl-5'-imidodiphosphate (Gpp(NH)p, a GTP analogue) led to significantly increased Kd-values, suggesting the association of adenosine receptors with G-proteins. Finally, cultured neurons also bound specifically [3H]forskolin with characteristics close to those found in the newborn brain, indicating that cultured neurons appear as an appropriate model for studying the neuromodulatory properties of adenosine.

Adenosine↗
PubMed1994

Pulmonary circulation evaluation before cavopulmonary connections: the cavopulmonary bypass.

The outcome of Fontan-type procedures is dependent on several risk factors, among which pulmonary vascular resistances (PVRs) are an important component. Preoperative calculation of PVR entails several potential sources of error, particularly in patients with pulmonary atresia or multiple sources of pulmonary blood flow. In an attempt to develop a reliable test that accurately assesses the hemodynamic patterns of the pulmonary vascular bed before a Fontan procedure, a simulation of Fontan-type circulation was achieved in 13 patients by a partial cardiopulmonary bypass between the main pulmonary artery and both venae cavae (cavopulmonary bypass). During cavopulmonary bypass, pressures and resistances were recorded. Immediately after cavopulmonary bypass, the circulation was converted to standard cardiopulmonary bypass and the cavopulmonary connection was carried out. Preoperative pulmonary vascular resistance indexes were assessed roughly by the arteriovenous oxygen difference in systemic and pulmonary beds. There was no correlation between preoperative and perioperative calculations of pulmonary vascular resistance indexes (r = 0.24; p = not significant). Hemodynamic data available for all patients then were correlated to the early postoperative outcome assessed by a subjective four-point scale. A positive, significant correlation was found with intraoperative PVR (r = 0.90; p < 0.001), indexed PVR (r = 0.90; p < 0.001), and the pulmonary to systemic vascular resistance ratio (r = 0.98; p < 0.0001). Two of 13 patients had a 4-mm fenestration in the atrial baffle. No mortality or morbidity was related to the procedure. The absolute values of PVR and pulmonary vascular resistance indexes were strikingly higher than generally admitted for this type of procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Conventional cardiopulmonary bypass in neonates. A physiological approach--10 years of experience at Marie-Lannelongue Hospital.

There is still controversy about the optimal method of venoarterial cardiopulmonary bypass (CPB) for correction of congenital heart disease in neonates and young infants. High rates of CPB-related morbidity and mortality are still reported. Since 1980, conventional CPB with double caval cannulation with right-angled cannulae has been used in the high majority of neonates at Marie-Lannelongue Hospital. The extracorporeal circuit was miniaturized to be primed with a volume as small as possible. Priming (500 ml) was done with packed red cells and fresh frozen plasma. CPB was conducted at 30% haematocrit and normal ranges of flow rate, arterial pressure, systemic vascular resistances and oxygen delivery. These normal physiological parameters were also maintained during hypothermia. During the last two years, 151 neonates below 15 days old who underwent open-heart surgery were reviewed. The overall hospital mortality was 7.24%. None of the survivors had postoperative complications related to CPB. All physiological and biological values remained within normal ranges during the postoperative course.

Cardiopulmonary Bypass↗
PubMed1994

GPI membrane anchor is determinant in intracellular accumulation of apical plasma membrane proteins in the non-polarized human colon cancer cell line HT-29 18.

We have compared the intracellular localization of plasma membrane proteins anchored either with a transmembrane segment or with a glycosylphosphatidylinositol moiety to estimate the effects of membrane anchor on protein segregation in the non-polarized form of the human colon cancer cell line HT-29 18. We have monitored two endogenous proteins: the carcinoembryonic antigen, a glycosylphosphatidylinositol protein and the transmembrane protein dipeptidyl peptidase IV, and two transfected proteins: the glycosylphosphatidylinositol protein Thy-1 and an engineered transmembrane form of Thy-1. Using immunocytochemistry on ultra-thin cryosections and confocal microscopy, we detected a carcinoembryonic antigen-rich vesicular compartment, excluding classical pre-lysosomal and lysosomal markers such as mannose 6-phosphate receptor, lamp-1 and cathepsin D. This compartment, where carcinoembryonic antigen accumulated, excluded the transmembrane protein dipeptidyl peptidase IV and was reduced during the polarization of the cells. Moreover, the glycosylphosphatidylinositol form of Thy-1 also accumulated in the carcinoembryonic antigen-rich compartment whereas the transmembrane form of Thy-1 was excluded. We proposed that, in the non-polarized HT-29 18 cells, accumulation of glycosylphosphatidylinositol proteins independently of transmembrane proteins reveals different intracellular fates for proteins according to their anchor in the plasma membrane.

Carcinoembryonic Antigen↗
PubMed1993

Expression of adenosine A1 receptors in cultured neurons from fetal rat brain.

The expression of adenosine A1 receptors was investigated using [3H]2-chloro-N6-cyclopentyladenosine (CCPA) in 8-day-old cultured neurons from fetal rat forebrain grown in serum-free medium. [3H]CCPA bound specifically and with high affinity (Kd = 2.9 nM) to a homogeneous population of sites. Displacement of CCPA binding by various adenosine derivatives indicated that A1 receptors were selectively labeled. The presence of Gpp(NH)p, a GTP analogue, reduced significantly the binding affinity (Kd = 12.2 nM), suggesting that A1 receptors detected in intact cultured cells are linked to associated G proteins.

Adenosine↗
PubMed1991

Physiological and pharmacological properties of adenosine: therapeutic implications.

Adenosine is a nucleoside which has been shown to participate in the regulation of physiological activity in a variety of mammalian tissues, and has been recognized as a homeostatic neuromodulator. It exerts its actions via membrane-bound receptors which have been characterized using biochemical, electrophysiological and radioligand binding techniques. Adenosine has been implicated in the pharmacological actions of several classes of drugs. A number of studies strongly suggest that the nucleoside may regulate cellular activity in many pathological disorders and, in that respect, adenosine derivatives appear as promising candidates for the development of new therapeutic compounds, such as anticonvulsant, anti-ischemic, analgesic and neuroprotective agents.

Adenosine↗
PubMed1991

[Anesthesia and intensive care for heart-lung transplantation].

Since Shumway carried out the first successful heart-lung transplant (HLT) in Stanford in 1981, HLT has become a new therapeutic means for patients with end-stage pulmonary disease or arterial hypertension. However, it is still rarely carried out because of a lack of donors and the complexity of the surgery and postoperative course. This review described the criteria for proper donor and recipient selection, as well as the anaesthetic and postoperative management of HLT patients at Marie Lannelongue Hospital. The lack of suitable organ grafts results, at least in part, from improper donor management. Pulmonary oedema by fluid overloading and excessive haemodilution should be carefully prevented. Low doses of catecholamines and vasopressin maintain circulatory stability and convenient organ function. The indications for HLT (primary pulmonary hypertension, Eisenmenger's complex, and end-stage bronchopulmonary disease) are all characterized by severe pulmonary hypertension, hypoxaemia and cardiac failure. Careful anaesthetic induction is required to avoid circulatory collapse. Cardiopulmonary bypass (CPB) should be started early, so that mediastinal dissection may be carried out in satisfactory haemodynamic conditions. After unclamping the aorta, circulatory support with fluid and catecholamine infusion is often required. High inspired oxygen fraction and end-expiratory positive pressure may be required because of reperfusion pulmonary oedema. Blood transfusion is often needed as there are major blood losses due to dissection of the posterior mediastinum during CPB. Postoperative catecholamine administration is prolonged over several days. Negative fluid balance is often necessary to reduce pulmonary oedema. Improvement in surgical technique, early extubation, and late prescription of steroids have reduced the incidence of tracheal complications. Acute renal failure often occurs as a result of prolonged CPB, hypovolaemia, drug nephrotoxicity and sepsis. Bacterial complications (pneumonia, mediastinitis) are the main causes of early death. After the 15th postoperative day, opportunistic infections and allograft rejection are the main complications. Since 1981, major advances in HLT recipient management resulted in improved survival rates (70-80% at 1 year, and 60-70% at 2 years for the best teams). Despite the complexity of management, and the longterm threat of obliterative bronchiolitis, HLT is, at present time, the only possibility for these young patients to recover a normal quality of life.

Anesthesia, General↗
PubMed1991

Functional changes in cultured neurons following transient asphyxia.

Functional responses of cultured neurons from rat cortex and hippocampus to transient hypoxia/asphyxia was studied by the measurement of [3H]2-deoxy-D-glucose (2DG) specific uptake. Hypoxic insult was induced by incubating the cells in 5% CO2/95% N2 or in 1 mM NaCN-containing culture medium for various periods of time. Cell morphology, lactate dehydrogenase efflux and protein levels were also examined. Twenty-four hours following hypoxia (6 to 8 h in an anaerobic atmosphere or 90 min in the presence of NaCN) 2DG specific transport was significantly enhanced, without morphological alteration. Cell injury was evident three days post-hypoxia, with a significantly reduced rate of cellular metabolism. The data suggest indirectly that postanoxic release of excitatory amino acids may be responsible for 'delayed neuronal death'.

Animals↗