Does intranasal dexmedetomidine provide adequate plasma concentrations for sedation in children: a pharmacokinetic study.

BACKGROUND: Atomised intranasal dexmedetomidine administration is an attractive option when sedation is required for paediatric diagnostic procedures, as vascular access is not required. The risk of haemodynamic instability caused by dexmedetomidine necessitates better understanding of its pharmacokinetics in young children. To date, intranasal dexmedetomidine pharmacokinetics has only been studied in adults. METHODS: Eighteen paediatric patients received dexmedetomidine 1 or 2 µg kg-1 intranasally or 1 µg kg-1 i.v. Plasma concentrations were determined by liquid chromatography/mass spectrometry. Non-compartmental analysis provided estimates of Cmax and Tmax. Volume of distribution, clearance, and bioavailability were estimated by simultaneous population PK analysis of data after intranasal and i.v. administration. Dexmedetomidine plasma concentration-time profiles were evaluated by simulation for intranasal and i.v. administration. RESULTS: An average peak plasma concentration of 199 pg ml-1 was achieved 46 min after 1 µg kg-1 dosing and 355 pg ml-1 was achieved 47 min after 2 µg kg-1 dosing. A two-compartment pharmacokinetic model, with allometrically scaled parameters, adequately described the data. Typical bioavailability was 83.8% (95% confidence interval 69.5-98.1%). CONCLUSION: Mean arterial plasma concentrations of dexmedetomidine in infants and toddlers approached 100 pg ml-1, the low end reported for sedative efficacy, within 20 min of an atomised intranasal administration of 1 µg kg-1. Doubling the dose to 2 µg kg-1 reached this plasma concentration within 10 min and achieved almost twice the peak concentration. Peak plasma concentrations with both doses were reached within 47 min of intranasal administration, with an overall bioavailability of 84%.

Exercises for mechanical neck disorders: A Cochrane review update.

BACKGROUND: Neck pain (NP) is disabling and costly. OBJECTIVES: To assess the effectiveness of exercise on pain, disability, function, patient satisfaction, quality of life (QoL) and global perceived effect (GPE) in adults with NP. METHODS: We searched computerised databases up to May 2014 for randomized controlled trials (RCTs) comparing exercise to a control in adults with NP with/without cervicogenic headache (CGH) or radiculopathy. Two reviewers independently conducted selection, data abstraction and assessed risk of bias. Meta-analyses were performed to establish pooled standardised mean differences (SMDp). The Grade of Recommendation, Assessment, Development and Evaluation (GRADE) was used to summarise the body of evidence. MAIN RESULTS: The following exercises (27 trials) were supported by 'Moderate GRADE' evidence: For chronic NP, 1) cervico-scapulothoracic and upper extremity (UE) strengthening for moderate to large pain reduction immediately post treatment (IP) and at short-term (ST) follow-up; 2) scapulothoracic and UE endurance training for a small pain reduction (IP/ST); 3) cervical, shoulder and scapulothoracic strengthening and stretching exercise for a small to large pain reduction in the long-term (LT) (SMDp -0.45 [95%CI: -0.72 to -0.18]) and function improvement; 4) cervico-scapulothoracic strengthening/stabilisation exercises for pain and function at intermediate-term (IT) (SMDp -14.90 [95%CI: -22.40 to -7.39]). 5) mindfulness exercises (Qigong) for minor improved function but not GPE (ST). For chronic CGH, cervico-scapulothoracic strengthening and endurance exercises including pressure biofeedback for small/moderate improvement of pain, function and GPE (IP/LT). AUTHORS' CONCLUSIONS: Specific strengthening exercises of the neck, scapulothoracic and shoulder for chronic NP and chronic CGH are beneficial. Future research should explore optimal dosage.

[Is scanning electron microscopy a pertinent tool for the analysis of periprostethic breast capsules?]. / Le microscope électronique à balayage environnemental est-il un outil pertinent pour l'analyse des capsules périprothétiques mammaires ?

PURPOSE: Scanning electron microscopy (SEM) is a powerful analytical tool that allows the study of interactions between commonly used biomaterials and the human body. In conventional SEM (HiVac), hydrated biological samples cannot be analyzed in their natural state and must be dried and metallized. The primary goal of this study is to present recent developments in SEM, notably Environmental SEM (ESEM). The secondary objective is to define the potential utility of these new technologies in the study of periprosthetic breast capsules. MATERIALS AND METHODS: Our pilot study group prospectively included 10 patients with breast cancer undergoing 2-stage expander to implant reconstruction. Periprosthetic breast capsule specimens were sampled during expander removal. Each sample was analyzed using both HiVac and ESEM modalities. Energy dispersive X-ray (EDX) studies were also conducted in order to assess the chemical composition of the capsular tissue samples. Under each observation mode, comparisons of samples' three-dimensional surface relief, cellular composition and biofilm presence were made. For each image, a score from 1-3 on a Likert scale was attributed by three independent experts in electron microscopy. RESULTS: HiVac mode was found to be superior to ESEM for the assessment of the three main study parameters (surface relief, cellularity, biofilm). The quality of the EDX analysis was equivalent under both SEM modalities. CONCLUSION: HiVac mode was shown to be more appropriate than ESEM for the global analysis of periprosthetic breast capsules. EDX analysis permits the identification of atypical chemical elements in tissue samples.

Ceruloplasmin-induced aggregation of P19 neurons involves a serine protease activity and is accompanied by reelin cleavage.

The cytoarchitectural organization of the nervous system depends partly on extracellular serine proteases, including reelin. This 400K protein, which also exists as the N-terminally-derived 300K and 180K fragments, acts through binding to the lipoprotein receptors apolipoprotein E receptor 2 (ApoER2) and very low-density lipoprotein receptor (VLDLR). Ceruloplasmin (CP), a multifunctional protein found in the circulation and also expressed on glial cells, was shown to bind to, and induce aggregation of neurons newly differentiated from P19 embryonic stem cells. This indicated a potential developmental role of CP in neuronal organization, possibly in relation with reelin and other extracellular serine proteases. Therefore, we analysed the effect of cell-impermeant, large spectrum, serine protease inhibitors on CP-induced neuroaggregation and studied reelin expression. Soybean trypsin inhibitor and aprotinin (SBTI+Apro) inhibited CP neuroaggregative action. Undifferentiated and neurally-differentiating cultures secreted the 400K reelin. The 180K fragment was present during and after differentiation whereas the 300K species was barely detectable. However, CP stimulated generation of the 300K in the differentiated neuronal cultures, and SBTI+Apro abolished this CP effect. Time course profiles and function-blocking antibody indicated that neuroaggregation does not depend on the generation of the 300K fragment or on reelin action. CP neuroaggregative action thus involves a pericellular serine protease, different from reelin. On the other hand, the CP stimulation of reelin cleavage is in line with a possible role of CP in nervous system development. Since P19 cells express ApoER2 and VLDLR, they can help understanding relationships existing between CP, reelin and intervening protease(s).

Association of FMR1 repeat size with ovarian dysfunction.

BACKGROUND: Women who carry the FMR1 premutation allele have a significantly increased risk for ovarian dysfunction. We hypothesize that molecular characteristics of the FMR1 gene may explain this increased risk. METHODS: Thus, we examined the effect of FMR1 CGG repeat size and related factors on measures of ovarian dysfunction using data from 507 women with a wide range of repeat sizes. RESULTS AND CONCLUSIONS: We found a significant positive association of repeat size with ovarian dysfunction, but have preliminary evidence that this relationship is non-linear. We suggest that FMR1 repeat size in the lower range (<80 repeats) contributes to the variation in age at menopause; thus, FMR1 could be considered a quantitative trait locus. More importantly, when repeat size exceeds this threshold, the increase in risk for ovarian dysfunction is clinically significant. Intriguingly, this risk appears to plateau, or perhaps decrease, among women with very high repeats (> or =100 repeats).

The blue copper ceruloplasmin induces aggregation of newly differentiated neurons: a potential modulator of nervous system organization.

Ceruloplasmin (CP) is a copper-dependent ferroxidase. It regulates iron metabolism and is involved in inflammation, angiogenesis, and protection against oxidative stress. CP also modulates K(+) channel activity in neuroblastoma cells and affects cardiodynamics of isolated hearts. Considering the presence of CP in the nervous system and the importance of iron ions and K(+) channels in neuronal activity, we postulated a role of CP in neuronal development. This hypothesis was tested using the P19 mouse embryonal carcinoma cell line, a model of neuronal differentiation. Addition of CP to the culture medium of newly differentiated P19 neurons induced cell aggregation within 24 h. This effect was concentration-dependent half-maximal at 50 nM, and not associated with necrosis, apoptosis or changes in secretory function. Deglycosylated CP was aggregative but not denatured CP, copper salts, His(2)Cu complex, or other copper enzymes or serum proteins. CP-induced aggregation was less pronounced with aging neurons and seemed not to involve K(+) channels. Immunocytofluorescence analysis demonstrated that digoxigenin-labeled CP bound to P19 neurons and the proportion of responding neurons decreased with aging. The interaction of digoxigenin-labeled CP with neurons was half-maximal at 120 nM by enzyme-linked immunosorbent assay and displaced by unlabeled CP. Our data indicate a specific aggregative action of CP on young neurons in vitro, possibly involving CP receptors. A potential developmental role of CP in nervous system organization is thus demonstrated.

Palladium-catalyzed sequential alkylation-alkenylation reactions and their application to the synthesis of fused aromatic rings.

The synthesis of fused aromatic carbocycles from aryl iodides and difunctional acceptors is outlined. This methodology is based on a palladium-catalyzed aromatic substitution followed by an intramolecular Heck sequence. Under the optimized conditions (Pd(OAc)(2) (10 mol %), tri-2-furylphosphine (20-30 mol %), norbornene (2 equiv), Cs(2)CO(3) (2 equiv), CH(3)CN, reflux), bromoenoates react with aryl iodides bearing numerous substituents (F, Cl, CF(3), Me, etc.). The expanded description of our initial work as well as the use of polysubstituted aryl iodides is described.

Deglycosylated ceruloplasmin maintains its enzymatic, antioxidant, cardioprotective, and neuronoprotective properties.

Ceruloplasmin (CP), an important serum antioxidant, is a blue copper glycoprotein with ferroxidase and oxidase activities. Among other physiological actions, plasma CP was shown to protect isolated rat hearts and cultured P19 neurons exposed to oxidative stress conditions, raising the possibility of using this protein in the treatment of cardiac and neuronal diseases related to oxidative damage. However, since therapeutic applications of CP must be compatible with restrictions in the administration of blood derivatives to humans, there is a need to produce the protein by genetic engineering. To help in the choice of adequate expression systems, we undertook this study to determine if the carbohydrate moiety on the protein is essential for its functions. CP was completely deglycosylated using N-glycosidase F under nondenaturing conditions. Deglycosylated CP was found to retain most of the conformational, antioxidant, and enzymatic properties of the native protein in vitro. Moreover, both forms of the protein had similar cardioprotective and neuronoprotective effects against oxidative stress as evaluated with isolated rat hearts undergoing ischemia-reperfusion and with cultured P19 neurons exposed to xanthine-xanthine oxidase. The data thus indicate that the carbohydrate moiety of CP is not essential for its enzymatic and protective actions. Accordingly, even the use of expression systems that do not glycosylate mammalian proteins could provide a recombinant CP that retains its therapeutic potential.

RhoB expression is induced after the transient upregulation of RhoA and Cdc42 during neuronal differentiation and influenced by culture substratum and microtubule integrity.

RhoGTPases are important intracellular signalling switches in the regulation of cytoskeleton organization. They likely have an important role in ontogenesis because cytoskeletal rearrangements accompany cell differentiation and specialization. Western blotting showed that protein expression of RhoA, RhoB and Cdc42 RhoGTPases dramatically increased, in a programmed manner, during neuronal differentiation of P19 mouse embryonal carcinoma cells with retinoic acid. RhoA and Cdc42 expression were sequentially upregulated and peaked during the commitment period while that of RhoB was induced in post-mitotic neurons. Although RhoB had a higher expression on matrices allowing cell spreading and neurite elongation, it was distributed throughout cell volume by immunocytofluorescence and associated with various cell compartments by centrifugal subfractionation, suggesting a role not restricted at neurites at this stage of differentiation. RhoA and Cdc42 were mainly cytosolic and RhoB particulate in the P19 cell model. Treatment of cells with cytoskeleton disruptors showed that poisons of microtubules but not of actin filaments or neurofilaments increased the cytosolic level of RhoB. The results indicate that RhoA, Cdc42 and RhoB must intervene at specific stages of neuronal development and there exists a relationship between RhoB expression/distribution, the microtubule network and the extracellular matrix during this process.

Long term follow-up of intravesical Bacillus Calmette-Guerin for the treatment of bladder transitional cell carcinoma.

OBJECTIVE: To review the long-term follow-up, in terms of recurrence and progression, of transitional cell carcinoma of the bladder treated with intravesical BCG with the following indications: CIS, Ta and T1. MATERIALS AND METHODS: Ninety-two patients who had received complete course of BCG between 1987 and 1993 were included in the study and followed for an average of 59 months (range 12 to 102). RESULTS: The recurrence and progression were looked at. Patients treated with BCG for Carcinoma in situ, 11 of 19 (53%) remained tumor-free after 1 or 2 courses of BCG for the duration of the follow-up (mean 4.9 years, range 1.5 to 8.5 years). For patients treated for recurring tumors, 17 of 50 (34%) had no recurrences after 1 or 2 courses of BCG with the same follow-up. When facing multiple tumors, 10 of 23 (43%) patients did not experience recurrences. Therefore, in the 92 patients treated, 38 presented no recurrences after 1 or 2 courses of BCG, for a success rate of 41%. In terms of progression, of the 19 patients treated with BCG for CIS, 4 (21%) went on to develop muscle invasive disease. Of the 50 patients treated for recurrent tumors, 2 (4%) eventually developed lamina propria invasion (initial lesion was a Ta tumor), 4 (8%) carcinoma in situ and 7 (14%) muscle invasive disease, for an overall progression rate of 26% in this group. Of the 25 patients treated for multiple tumors, 1 (4%) developed CIS and 3 (12%) presented with muscle invasive disease, for an overall progression rate of 16% for the duration of the follow-up. Therefore, 21 of 92 (23%) patients had progression of their disease following BCG therapy. No prognostic factors for recurrence or progression could be identified in these tumors. CONCLUSION: When indications warrant its use, BCG is effective in reducing recurrences and limiting progression in TCC of the bladder. Recurrence within 2 years of treatment is, however, a sign of poor prognosis and other therapeutic options should be sought.

Coordinate regulation of neuroendocrine convertase PC2 and peptide 7B2 in P19 neurons.

Convertases are proteases responsible for the bioactivation of many proteins and peptides having a potential role in ontogenesis. As a model to study regulation of convertases in embryo, we use the P19 embryonal carcinoma cell line, which can differentiate into various cell types. The expression of convertase PC2 and its specific binding peptide 7B2 are co-induced during neuronal differentiation of P19 cells. We investigated the possibility that expression of both proteins may be coregulated by T3 and dexamethasone, activators of nuclear receptors, isobutylmethylxanthine, and dibutyryl cAMP, activators of protein kinase A, and phorbol 12-myristate 13-acetate, an activator of protein kinase C. Western blotting results show that expression of PC2 and 7B2 can be upregulated by modulators of the protein kinases, and upregulation needs not be strictly stoichiometric.

Conversion and storage of somatostatin are established before response to secretagogue stimuli in P19 neurons.

In mature neurons, neuropeptides are synthesized via limited proteolysis of propolypeptides by convertases. The bioactive peptides are then stored in secretory granules until they are released extracellularly upon the induction of a fusion between granules and the plasma membrane, in response to secretagogues. We used the mouse P19 embryonic carcinoma cells as a model to determine if the capacities to convert and store neuropeptides and to secrete them in a regulated fashion are established coordinately during neuronal differentiation. We have previously shown that both undifferentiated P19 cells and their neuronal derivatives express the largely distributed furin, PACE4 and PC5 convertases, whereas only neuronal derivatives express the neuroendocrine convertase PC2. In addition, undifferentiated cells displayed furin- rather than PC2-like converting capacities. The present work demonstrates that day 8 P19 neurons mainly convert prosomatostatin (proSS) to somatostatin-14 (SS-14) using HPLC and radioimmunoassay (RIA) analyses, indicating that P19 cells acquire PC2-like converting capacities as a consequence of neuronal differentiation. SS-14 was predominantly intracellular in neuronal cells which were shown to express several granins, markers of granules, by Western blotting. However, cell membrane depolarization with 50 mM K+, a general secretagogue stimulus, evoked the release of SS-14 by day 12, but not by day 8, P19 neurons. The results thus demonstrate that capacities to convert and store neuropeptides can be established before coupling of stimulus-secretion during neuronal differentiation.

Long-term followup of initial Ta grade 1 transitional cell carcinoma of the bladder.

PURPOSE: We evaluate the long-term outcome of initial Ta grade 1 transitional cell carcinoma. MATERIALS AND METHODS: A total of 152 patients with initial Ta grade 1 bladder tumor were followed for a mean of 76 months (range 6 to 241). Recurrence was defined as positive findings on cystoscopy or biopsy. Progression was defined as an increase in tumor grade or stage. RESULTS: Tumor recurrence in 83 of 152 patients (55%) was noted within 12 months of followup in 38 patients (46%), between 12 and 24 in 11 (13%), and between 24 and 60 in 22 (27%). A significant number of recurrences (12, 14%) were diagnosed more than 60 months after the first tumor. Of 83 patients with recurrence 31 (37%) had progression, including 21 to grade 2 and 2 to grade 3 disease. Carcinoma in situ was diagnosed in 3 patients and 5 had muscle invasive disease. Progression occurred more than 24 months after initial diagnosis in 20 patients and more than 60 months after first tumor event (2 had carcinoma in situ and 2 had muscle invasive disease) in 12. CONCLUSIONS: Ta grade 1 bladder transitional cell carcinomas have a high recurrence rate and progression is not uncommon. These findings warrant close long-term followup, even when in some settings the trend is to discontinue followup after 5 years without any abnormal findings.

Membrane topography of the renal phosphate carrier NaPi-2: limited proteolysis studies.

The rat sodium/phosphate cotransporter NaPi-2 is a 70 kDa polypeptide (p70) for which eight transmembrane segments have been predicted. We have shown that p70 exists predominantly as p45 and p40 fragments which are linked by disulfide bonds. In this work, the p40 fragment, corresponding to the C-terminus of NaPi-2, was purified from renal brush-border membranes using non-reducing and then reducing column electrophoresis followed by enzymatic deglycosylation and SDS-PAGE. The N-terminal sequence obtained for this fragment, VEAIG, indicates that the formation of p45 and p40 arises from the cleavage of p70 between arginine-319 and valine-320. In order to determine the membrane topography of NaPi-2, brush-border membrane vesicles were digested with various proteases and the transporter-derived proteolytic peptides were subsequently identified by Western blotting using N- and C-terminal-directed antibodies. Our results lead us to propose an alternative topographical model in which p45 and p40 possess three transmembrane domains each and indicate that the processing site of p70 for the generation of p45 and p40 is localized in a large protein core facing the extracellular milieu. This localization of the cleavage site indicated that NaPi-2 could either be processed intracellularly by vesicular proteases or extracellularly by secretory proteases or by brush-border membrane ectoenzymes.

Convertase PC2 and the neuroendocrine polypeptide 7B2 are co-induced and processed during neuronal differentiation of P19 embryonal carcinoma cells.

Convertases of the subtilisin/kexin family are responsible for the biological activation of a variety of pro-proteins, pro-hormones, and pro-trophic factors, and thus can modulate various aspects of embryonic development. We investigated the expression of each convertase by Northern hybridization during cell differentiation in vitro, using the mouse embryonal carcinoma cell line P19 as a model. The neuroendocrine convertase PC2 and 7B2, its specific binding protein, are co-induced during neuronal differentiation of P19 cells with retinoic acid, whereas the other convertases are not or follow different patterns of temporal expression. The mature forms of PC2 and 7B2 proteins are detected together by immunoblotting following induction of mRNA expression, indicating that these proteins are processed early during brain development. These results demonstrate that PC2 and 7B2 gene expression and protein processing are in a close temporal association during neuronal differentiation and point to the value of the P19 cell model to study the significance and the regulation of this relationship in mammalian brain development.

Predictors of achieving stable housing in a mentally ill homeless population.

Relationships among demographic characteristics, diagnostic groups, presenting problems, and service use were examined in two groups of mentally ill persons: a group of 60 formerly homeless persons who had been housed for at least 24 months and a group of 60 persons who remained homeless. Use of eight types of services over a 26-month period was examined. Women were significantly more likely to be housed than men. Individuals whose primary presenting problem was subsistence needs were more likely to be housed than those whose primary problem was mental, illness or substance abuse. Those with a diagnosis of personality disorder used fewer services. Housed individuals were more likely to use services than those who were homeless.

The Juvenile Arthritis Quality of Life Questionnaire--development of a new responsive index for juvenile rheumatoid arthritis and juvenile spondyloarthritides.

OBJECTIVE: To develop a disease specific measure of quality of life for application in children with juvenile rheumatoid arthritis and juvenile spondyloarthritides-the Juvenile Arthritis Quality of Life Questionnaire (JAQQ). METHODS: Patients and their parents were interviewed by a trained interviewer using a questionnaire focusing on physical function, psychosocial function, and general symptoms to determine the most appropriate items to include in the JAQQ. Respondents volunteered items and scored them for frequency of occurrence and importance. Items so generated were scored by a panel of experts for potential responsiveness and categorized into dimensions. Item number was reduced using this scoring system. The product was then pretested to confirm its construct validity and responsiveness. Thereafter, it was distributed to clinical experts to establish face and content validity. RESULTS: 91 patients, mean age 10.35 years (range 1.25-18.0), mean disease duration 3.99 years, and their parents were included in the interview process. 220 items generated were ultimately reduced to 85. Pretesting this version of the instrument in a further 30 patients showed it to have construct validity and responsiveness and led to a further reduction in items to 74, distributed in 4 dimensions: gross motor function (17 items), fine motor function (16 items), psychosocial function (22 items), and general symptoms (19 items). Face and content validity were established in 20 clinicians. Scaling was by 7 point Likert scale to enhance responsiveness. English and French versions were developed. CONCLUSION: The JAQQ measures physical and psychosocial function and an array of general symptoms. Preliminary data suggest it is valid and responsive and thus might have potential in clinical trials.

Influence of water chlorination on the counting of bacteria with DAPI (4',6-diamidino-2-phenylindole).

Counting bacteria in drinking water samples by the epifluorescence technique after 4',6-diamidino-2-phenylindole (DAPI) staining is complicated by the fact that bacterial fluorescence varies with exposure of the cells to sodium hypochlorite. An Escherichia coli laboratory-grown suspension treated with sodium hypochlorite (5 to 15 mg of chlorine liter-1) for 90 min was highly fluorescent after DAPI staining probably due to cell membrane permeation and better and DAPI diffusion. At chlorine concentrations greater than 25 mg liter-1, DAPI-stained bacteria had only a low fluorescence. Stronger chlorine doses altered the DNA structure, preventing the DAPI from complexing with the DNA. When calf thymus DNA was exposed to sodium hypochlorite (from 15 to 50 mg of chlorine liter-1 for 90 min), the DNA lost the ability to complex with DAPI. Exposure to monochloramine did not have a similar effect. Treatment of drinking water with sodium hypochlorite (about 0.5 mg of chlorine liter-1) caused a significant increase in the percentage of poorly fluorescent bacteria, from 5% in unchlorinated waters (40 samples), to 35 to 39% in chlorinated waters (40 samples). The presence of the poorly fluorescent bacteria could explain the underestimation of the real number of bacteria after DAPI staining. Microscopic counting of both poorly and highly fluorescent bacteria is essential under these conditions to obtain the total number of bacteria. A similar effect of chlorination on acridine orange-stained bacteria was observed in treated drinking waters. The presence of the poorly fluorescent bacteria after DAPI staining could be interpreted as a sign of dead cells.

Catastrophic haemorrhage in a case of paediatric primary antiphospholipid syndrome and factor II deficiency.

The first case of primary antiphospholipid syndrome associated with recurrent life-threatening haemorrhages, due to the coexistence of acquired prothrombin deficiency, is described. Attention is drawn to the difficulty in diagnosing this situation, and therapeutic options are reviewed. Evidence is presented that implicates prothrombin as the protein cofactor for this lupus anticoagulant.

Proteolytic profile of recombinant pro-opiomelanocortin in embryonal carcinoma P19 cells: conversion to beta-lipotropin and secretion are inhibited following incubation with canavanine.

A variety of proteins and peptides are produced through limited proteolysis of precursors at paired basic residues. This proteolytic bioactivation is carried out by subtilisin-like proteases, called convertases. The mRNAs of several convertases are expressed during prenatal life as well as in P19 embryonal carcinoma cells, which are a model of the totipotent cells of the embryo before and at the time of implantation. To determine whether converting activities accompany convertase mRNA expression in the early embryo, we transferred the gene of pro-opiomelanocortin (POMC) into P19 cells, by lipofection, and searched for the presence of mature peptides by high-performance liquid chromatography and radioimmunoassay techniques. In P19 cells, POMC, a precursor of several endocrine peptides, is mainly processed to beta-lipotropin rather than to beta-endorphin, both peptides having been identified by their immunoreactivity, polarity, and molecular size. These results indicate that converting capacities appear early in the embryo and that they are more similar to the activity of furin and of convertase PC1 than that of convertase PC2 in their cleavage selectivity of POMC sites. Efficiency of POMC processing can reach 50%, suggesting that convertases, with other proteases, can have an important role in ontogenesis. As for other peptide precursors in endocrine cells, the conversion of POMC in P19 cells was inhibited by the biosynthetic replacement of its arginine residues by the analog canavanine. However, the incorporation of canavanine into P19 cells also inhibited peptide secretion, suggesting that inhibition of conversion in these cells as well as in endocrine cells could indirectly result from the impairment of intracellular traffic and not only from a direct inhibition of the converting activity.