Various incubation conditions of human hepatocytes were compared for their accuracy in predicting the in vivo hepatic clearance (CLH) of model compounds. The test compounds were the highly cleared, ...low protein bound naloxone (in vivo CLH = 25 ml min−1 kg−1; free fraction = 0.6), the medium clearance, highly protein bound midazolam (CLH = 12 ml min−1 kg−1; free fraction = 0.04) and the low clearance, highly protein bound bosentan (CLH = 3.9 ml min−1 kg−1; free fraction = 0.02). Each compound was tested in three 'hepatocyte systems', using resections from three donors, in the presence and absence of human serum. Those hepatocyte systems were: conventional primary cultures, freshly isolated suspensions and cryopreserved suspended hepatocytes. Except for a twofold overestimated CLH for bosentan from conventional primary cultures, and despite variable cryopreservation recoveries, similar predictions of CLH were recorded with all hepatocyte systems. Moreover, the CLH values obtained with cryopreserved suspended hepatocytes were similar to those obtained with freshly isolated suspensions. For midazolam and bosentan, the predicted in vivo CLH was markedly higher in the presence of serum, whereas serum had little influence on the scaled-up CLH of naloxone. In vivo, CLH was properly approached for naloxone and bosentan (particularly from experiments in the presence of serum), but it was strongly underestimated for midazolam (particularly in the absence of serum). Additional compounds need to be investigated to confirm the above findings as well as to assess why the clearances of some highly protein-bound compounds are still considerably underestimated.
Genetic predisposition to childhood cancer Abadie, C; Gauthier-Villars, M; Sirvent, N ...
Archives de pédiatrie : organe officiel de la Société française de pédiatrie
19, Številka:
8
Journal Article
Recenzirano
Tumor predisposition in children is rare, accounting for approximately 10% of all cancers in childhood. Tumor predisposition involves very rare tumors such as pleuropulmonary blastoma, adrenocortical ...carcinoma, hepatoblastoma, rhabdoid tumors, optic pathway glioma, as well as rare tumors such as retinoblastoma, medulloblastoma, nephroblastoma, or more frequent tumors such as sarcomas, neuroblastoma, and leukemias. The identification of these predispositions is important for improved management for both the child and relatives. Prenatal and preimplantation genetic diagnosis are options that could be considered for young parents in a perspective of future pregnancies. This manuscript describes the main tumor predispositions in childhood. From each histological subtype, the different diagnosis directions are discussed in view of these main tumor predispositions.
Isolated human hepatocytes have been shown to represent a valuable in vitro model to investigate the metabolism and cytotoxicity of xenobiotics. In addition, human hepatocyte transplantation and ...artificial liver support systems using isolated human hepatocytes are currently investigated as treatment for acute and chronic hepatic failure. In this regard, human hepatocyte banking by cryopreservation would be of great interest. In the present study, freshly isolated hepatocytes from resected liver biopsies of 28 separate donors (viability: 88±2%; plating efficiency: 79±5%) were cryopreserved using two different protocols, stepwise freezing (SF) or progressive freezing (PF), in combination (PF(+), SF(+)) or not (PF(−), SF(−)) with a 30
min preincubation in culture medium at 37
°C. Total recovery was higher after PF (38±3%) than after SF (12±2%). Preincubation prior to SF had no effect on plating efficiency of thawed hepatocytes (SF(−): 38±6% versus SF(+): 46±7%) while preincubation prior to PF increased plating efficiency of thawed hepatocytes (PF(−): 42±6% versus PF(+): 64±4%,
p<0.05). In attached cultured human cryopreserved/thawed hepatocytes (CH) from the PF(+) group, albumin production and glutathione content were not significantly different from those of the freshly isolated hepatocyte (FIH) cultures. Cells in CH monolayers appeared smaller than cells in FIH monolayers. In addition, the pattern of cytochrome P450- and UDP-glucuronosyl transferase-dependent isoenzyme activities and GST activity were different, suggesting a variability in the resistance to cryopreservation of the various liver hepatocyte populations. Taken all together, the results of the present study suggest that recovery of human hepatocytes after isolation prior to progressive freezing should allow human hepatocyte banking for use in pharmacotoxicology and cell therapy research purposes.
Land surface modellers need measurable proxies to
constrain the quantity of carbon dioxide (CO2) assimilated by
continental plants through photosynthesis, known as gross primary production
(GPP). ...Carbonyl sulfide (COS), which is taken up by leaves through their
stomates and then hydrolysed by photosynthetic enzymes, is a candidate GPP
proxy. A former study with the ORCHIDEE land surface model used a fixed
ratio of COS uptake to CO2 uptake normalised to respective ambient
concentrations for each vegetation type (leaf relative uptake, LRU) to
compute vegetation COS fluxes from GPP. The LRU approach is known to have
limited accuracy since the LRU ratio changes with variables such as
photosynthetically active radiation (PAR): while CO2 uptake slows under
low light, COS uptake is not light limited. However, the LRU approach has
been popular for COS–GPP proxy studies because of its ease of application
and apparent low contribution to uncertainty for regional-scale
applications. In this study we refined the COS–GPP relationship and
implemented in ORCHIDEE a mechanistic model that describes COS uptake by
continental vegetation. We compared the simulated COS fluxes against
measured hourly COS fluxes at two sites and studied the model behaviour and
links with environmental drivers. We performed simulations at a global scale,
and we estimated the global COS uptake by vegetation to be −756 Gg S yr−1,
in the middle range of former studies (−490 to −1335 Gg S yr−1). Based
on monthly mean fluxes simulated by the mechanistic approach in ORCHIDEE, we
derived new LRU values for the different vegetation types, ranging between
0.92 and 1.72, close to recently published averages for observed values of
1.21 for C4 and 1.68 for C3 plants. We transported the COS using the monthly
vegetation COS fluxes derived from both the mechanistic and the LRU
approaches, and we evaluated the simulated COS concentrations at NOAA sites.
Although the mechanistic approach was more appropriate when comparing to
high-temporal-resolution COS flux measurements, both approaches gave similar
results when transporting with monthly COS fluxes and evaluating COS
concentrations at stations. In our study, uncertainties between these two
approaches are of secondary importance compared to the uncertainties in the
COS global budget, which are currently a limiting factor to the potential of
COS concentrations to constrain GPP simulated by land surface models on the
global scale.
Le pleuropneumoblastome (PPB) est une tumeur rare de l’enfant. Le diagnostic différentiel entre sa forme kystique (type 1) et une malformation adénomatoide kystique (MAKP) de type 4 est difficile.
...Nous rapportons les cas de 2 nourrissons pris en charge pour MAKP avec imagerie atypique.
Cas 1 : Un nourrisson de 8mois a présenté plusieurs bronchiolites et une pneumopathie gauche. Une radio a montré des images kystiques pulmonaires et le scanner a mis en évidence une image kystique cloisonnée lobaire supérieure gauche avec des vaisseaux atypiques pariétaux de drainage. L’analyse de la pièce de lobectomie supérieure gauche a révélée un PPB type 1. Cas 2 : Un nouveau-né a présenté une détresse respiratoire. La radio montrait une image kystique pulmonaire gauche, le scanner montrait une lésion kystique mutlicloisonnée avec des vaisseaux atypiques dans les cloisons. L’analyse après tumorectomie à J2 a révélé un PPB type 1.
La découverte au sein d’une masse kystique pleuropulmonaire du nourrisson évocatrice de MAKP de cloisons vascularisées doit faire penser à un PPB de type 1 et doit faire anticiper la chirurgie pour limiter le risque oncologique. Une prise en charge oncologique et une recherche de mutation de DICER1 doivent être envisagées.
Abstract Beckwith–Wiedemann syndrome (BWS) is a rare overgrowth syndrome associated with an increased risk in childhood tumours. The phenotypic variability in BWS reflects its molecular ...heterogeneity. This syndrome is a multigenic disorder caused by dysregulation of imprinted growth regulatory genes in the 11p15.5 region. The most commonly reported tumours in this syndrome are tumours of embryologic origin such as Wilms tumours, hepatoblastomas, neuroblastomas, rhabdomyosarcomas and adrenocortical carcinomas. We report the case of a 10-year-old patient diagnosed with BWS, harbouring a CDKN1C ( p57KIP2 ) mutation, who developed a T-type acute lymphoblastic leukaemia. To our knowledge it is the first report of an acute lymphoblastic leukaemia of T-type in a child with BWS. We discuss the possibility of a link between BWS and leukaemia via one of the few known negative regulator of hematopoiesis, the transforming growth factor beta pathway, depending upon the up-regulation of CDKN1C.
The effects of fibrates on cytochrome P450 4A (CYP4A) expression have not been clearly evaluated in human hepatocytes, human being reported as a non-responsive species.
We have evaluated the effects ...of clofibrate, bezafibrate (BEZA), WY-14643, nafenopin and ciprofibrate at the concentration of 250
μM on CYP4A expression in primary cultures of rat and human hepatocytes.
BEZA greatly induced mRNA expression in both species. Eight out of 10 human cultures responded to BEZA 250
μM. CYP4A-dependent activity was increased in rat, but not in human hepatocytes. The antioxidant
N-acetylcysteine (Nac) enhanced the inducing effect of BEZA on mRNA expression, this potentialization being higher in human compared to rat hepatocytes. By contrast, Nac decreased the inducing effect of BEZA on CYP4A-dependent activity in rat and had either no effect or decreased the activity in BEZA-treated human hepatocytes.
In conclusion, the cellular environment appears as an important parameter to take into account when studying CYP4A induction and could partly explain interspecies differences in the complex regulation of CYP4A expression.
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