Thermodynamic Description of Synergy in Solvent Extraction: I. Enthalpy of Mixing at the Origin of Synergistic Aggregation.

Revisiting aggregation of extractant molecules into water-poor mixed reverse micelles, we propose in this paper to identify the thermodynamic origins of synergy in solvent extraction. Considering that synergistic extraction properties of a mixture of extractants is related to synergistic aggregation of this mixture, we identify here the elements at the origin of synergy by independently investigating the effect of water, acid, and extracted cations. Thermodynamic equations are proposed to describe synergistic aggregation in the peculiar case of synergistic solvent extraction by evaluating critical aggregation concentration (CAC) as well as specific interactions between extractants due to the presence of water, acid and cations. Distribution of two extractant molecules in the free extractants and in reverse micelles was assessed, leading to an estimation of the in-plane interaction parameter between extractants in the aggregates as introduced by Bergström and Eriksson ( Bergström, M.; Eriksson, J. C. A Theoretical Analysis of Synergistic Effects in Mixed Surfactant Systems . Langmuir 2000 , 16 , 7173 - 7181 ). Based on this model, we study the N,N'-dimethyl-N,N'-dioctylhexylethoxymalonamide (DMDOHEMA) and di(2-ethylexyl) phosphoric acid (HDEHP) mixture and show that adding nitric acid enhances synergistic aggregation at the equimolar ratio of the two extractants and that this configuration can be related to a favored enthalpy of mixing.

An NSF function distinct from ATPase-dependent SNARE disassembly is essential for Golgi membrane fusion.

The precise biochemical role of N-ethylmaleimide-sensitive factor (NSF) in membrane fusion mediated by SNARE proteins is unclear. To provide further insight into the function of NSF, we have introduced a mutation into mammalian NSF that, in Drosophila dNSF-1, leads to temperature-sensitive neuroparalysis. This mutation is like the comatose mutation and renders the mammalian NSF temperature sensitive for fusion of postmitotic Golgi vesicles and tubules into intact cisternae. Unexpectedly, at the temperature that is permissive for membrane fusion, this mutant NSF binds to, but cannot disassemble, SNARE complexes and exhibits almost no ATPase activity. A well-charaterized NSF mutant containing an inactivating point mutation in the catalytic site of its ATPase domain is equally active in the Golgi-reassembly assay. These data indicate that the need for NSF during postmitotic Golgi membrane fusion may be distinct from its ATPase-dependent ability to break up SNARE pairs.

In vivo induction of interferon gamma expression in grey horses with metastatic melanoma resulting from direct injection of plasmid DNA coding for equine interleukin 12.

Whole blood pharmacokinetics of intratumourally injected naked plasmid DNA coding for equine Interleukin 12 (IL-12) was assessed as a means of in vivo gene transfer in the treatment of melanoma in grey horses. The expression of induced interferon gamma (IFN-g) was evaluated in order to determine the pharmacodynamic properties of in vivo gene transduction. Seven grey horses bearing melanoma were injected intratumourally with 250 µg naked plasmid DNA coding for IL-12. Peripheral blood and biopsies from the injection site were taken at 13 time points until day 14 post injection (p.i.). Samples were analysed using quantitative real-time PCR. Plasmid DNA was quantified in blood samples and mRNA expression for IFN-g in tissue samples. Plasmid DNA showed fast elimination kinetics with more than 99 % of the plasmid disappearing within 36 hours. IFN-g expression increased quickly after IL-12 plasmid injection, but varied between individual horses. Intratumoural injection of plasmid DNA is a feasible method for inducing transgene expression in vivo. Biological activity of the transgene IL-12 was confirmed by measuring expression of IFN-g.

Resection of ectopic mediastinal parathyroid glands with the da Vinci robotic system.

BACKGROUND: Mediastinal ectopic parathyroid adenoma is a frequent cause of persistent or recurrent hyperparathyroidism, traditionally treated by open surgery. Thoracoscopic access is associated with reduced morbidity in mediastinal surgery. The aim of this study was to evaluate the feasibility and effectiveness of robot-assisted dissection for mediastinal ectopic parathyroid glands. METHODS: Two patients with recurrent secondary hyperparathyroidism and three with complicated primary hyperparathyroidism were operated on between July 2004 and August 2008 for ectopic mediastinal parathyroid glands. Fusion of single-photon emission computed tomography and computed tomography led to an exact identification of the culprit glands. Surgery was performed thoracoscopically with the da Vinci robotic system using a three-trocar approach. RESULTS: All procedures were completed successfully with the robotic system. No perioperative morbidity or mortality was noted. Median operating time was 58 (range 42-125) min. Intraoperative parathyroid hormone reduction indicated complete resection. Median hospital stay was 3 (range 2-4) days. CONCLUSION: Robot-assisted dissection is a promising approach for resection of ectopic parathyroid glands in remote narrow anatomical locations such as the mediastinum.

Influence of pre-operative fluid infusion on volume status during oesophageal resection--a prospective trial.

BACKGROUND: Perioperative fluid therapy is controversially debated in surgery. In malnourished and hypovolaemic patients, a restrictive fluid regimen may lead to hypoperfusion and increased incidence of complications. The present prospective cohort study was performed to assess whether pre-operative i.v. fluid administration improves intraoperative cardiac preload in patients undergoing oesophageal resection. METHODS: Intraoperatively, the intrathoracic blood volume index (ITBVI) was monitored in 44 consecutive patients undergoing elective oesophagectomies with the transthoracic thermodilution technique. Twenty-two of these patients received a pre-operative i.v. fluid loading with a balanced crystalloid solution (1 ml/kg/h over 48 h). RESULTS: After induction of anaesthesia ITBVI was low but not different between the groups [767 (512-1314) vs. 775 (531-1200) ml/m(2), P=0.81]. In the intervention group, the extravascular lung water increased above normal levels during the operation. The groups did not differ in cardiac output, blood pressure, heart rate and central venous pressure. Post-operative morbidity was not different between the cohorts. CONCLUSION: Pre-operative i.v. fluid loading with crystalloid solutions could not be shown to improve the intraoperative volume status and cardiac function in this study. Randomised trials with other volume replacement techniques are recommended.

["Fast-track" rehabilitation in thoracic surgery. First experiences with a multimodal, interdisciplinary, and proven perioperative treatment course]. / "Fast-track-Rehabilitation" in der Thoraxchirurgie. Erste Erfahrungen mit einem interdisziplinären, multimodalen, beweisbegründeten und perioperativen Behandlungspfad.

OBJECTIVES: "Fast-track" rehabilitation is a multimodal perioperative treatment concept for accelerating postoperative recovery which has been already used successfully in visceral surgery. Of its use in thoracic surgery however, almost no data exist and the relevance of this concept for pulmonary operations is unknown. PATIENTS AND METHODS: In this prospective study we examined a new perioperative fast-track treatment concept for thoracic surgery and evaluated the results. This program employs detailed information of patients, intensive perioperative respiratory therapy, thoracic peridural analgesia, forced mobilization, and an early start of postoperative normal food intake. RESULTS: Fifty consecutive patients with benign or malignant diseases of the lung aged an average of 64 years (range 22-78) were operated on thoracoscopically (n=15) or with thoracotomy (n=35) and treated perioperatively using the fast-track program. All patients were mobilized beginning 4 h postoperatively and had normal food. The incidence of general postoperative complications was 0% in this study. Postoperative stay lasted 4.5 days (range 1.5-28.5). There was no increase in surgical complications, and 6% of the patients were readmitted. The patients' acceptance of this concept was high. CONCLUSION: Fast-track rehabilitation resulted in a decreased rate of general complications and accelerated rehabilitation in thoracic surgery.

[Minimally invasive thymus surgery]. / Minimal-invasive Chirurgie des Thymus.

There are absolute and relative indications for complete removal of the thymus gland. In the complex therapy of autoimmune-related myasthenia gravis, thymectomy plays a central role and is performed with relative indication. In case of thymoma with or without myasthenia, thymectomy is absolutely indicated. Thymus resection is further necessary for cases of hyperparathyroidism with ectopic intrathymic parathyroids or with certain forms of multiple endocrine neoplasia. The transcervical operation technique traditionally reflected the well-founded desire for minimal invasiveness for thymectomy. Due to the requirement of radicality however, most of these operations were performed using sternotomy. With the evolution of therapeutic thoracoscopy in thoracic surgery, several pure or extended minimally invasive operation techniques for thymectomy have been developed. At present uni- or bilateral, subxiphoid, and modified transcervical single or combination thoracoscopic techniques are in use. Recently a very precise new level of thoracoscopic operation technique was developed using robotic-assisted surgery. There are special advantages of this technique for thymectomy. An overview of the development and experiences with minimally invasive thymectomy is presented, including data from the largest series published so far.

[Demands of private gastroenterologists for collaborative treatment concepts with clinics. Results of a Germany-wide survey]. / Welche Anforderungen stellen niedergelassene Gastroenterologen an integrierte Versorgungskonzepte mit Kliniken? Ergebnisse einer deutschlandweiten Umfrage.

BACKGROUND: New demands and possibilities of collaboration between hospitals and private practices in Germany have appeared, now that the way has been opened legally. A poll was conducted to analyse the current status of collaboration between outpatient gastroenterologists and hospital surgical departments and to identify possible future collaborations. MATERIALS AND METHODS: One thousand twenty-six private practices specialising in endoscopy were found by contacting the Association of Statutory Health Insurance Physicians and additional internet research. Of these, 50% were randomly selected (513 private practices) and contacted by mail with anonymous questionnaires about cooperation with their clinical partners. Two hundred three (39.6%) practices responded, of which 200 could be analysed. RESULTS: Of all practices reached, 75% considered the cooperation with clinics very valuable or even exceptional. Still, almost half (46%) suggested necessary improvements in these collaborations. Around a third of all contacted colleagues were already involved in projects following integrated care models. In about 80% of all participants, the main interest in integrated models was specified to be common therapy planning. CONCLUSION: The data analysis of this study shows a substantial interest of private-practice gastroenterologists in close collaboration with hospitals. It is now up to the hospitals to open contracts with their medical outpatient partners.

[First clinical experience with a video presentation informing patients before surgery for inguinal hernia]. / Videoinformationsfilm vor Leistenhernienoperationen. Erste klinische Erfahrungen.

BACKGROUND: Although it is a significant part of surgical treatment, informing patients beforehand seems to be more and more neglected, mainly due to the enormous amount of work and time pressure on surgical personnel. MATERIAL AND METHODS: A video clip explaining groin hernia surgical repair was produced as additional information for patients. In it, visual material from actual practice describes the disease, the operation itself, all the perioperative aspects, and patients' own experiences. In a prospective comparison study, the length of patient education, its quality, patient satisfaction, and the duration of hospitalization and time off work were compared between patients who saw the video clip (n=50) and those who did not (n=50). RESULTS AND CONCLUSION: In summary, the time spent informing the video group was shorter (P<0.05) and their total satisfaction and evaluation of the information material were both higher (P>0.05) for comparable duration of treatment and time off work. This informative video was adopted without problems in our daily clinical life and, besides reducing the time needed to inform patients, it has significantly improved patient understanding of the operative procedure and their satisfaction with treatment.

[Management of post-traumatic isolated adrenal haematoma]. / Prise en charge des hématomes post-traumatiques isolés de la surrénale.

We report three cases of isolated adrenal haematoma diagnosed at admission to the Emergency Department. Post-traumatic adrenal haematoma have been observed in 2% of patients with abdominal injury and can be life threatening in cases of bilateral haemorrhage with risk of acute adrenocortical insufficiency. Diagnosis remains difficult due to absence of clinical and biological specific parameters. Therefore, abdominal CT examination should be the gold standard in management of abdominal trauma patients.

Substantially reduced risk of cancer of the aerodigestive tract in subjects with variant--463A of the myeloperoxidase gene.

Myeloperoxidase (MPO), an enzyme that is highly expressed in neutrophil leukocytes, transforms precarcinogens such as benzo(a)pyrene and aromatic amines to highly reactive intermediates. A G/A polymorphism located 463 bp upstream of exon 1 in the promoter region strongly reduces MPO mRNA expression. In a matched case-control study, 196 lung cancer, 245 laryngeal cancer, and 255 pharyngeal cancer patients from the Berlin area were investigated for frequency of the G-463A polymorphism by PCR/RFLP, using AciI. They were matched by age and gender to hospital patients without known malignancies. Moreover, 270 healthy volunteers were genotyped, obtaining 61.1% of individuals with MPO genotype -463G/G, 34.8% of individuals with genotype G/A, and 4.1% of individuals with genotype A/A. In lung and laryngeal cancer patients, but not in pharyngeal cancer patients, mutant genotypes were significantly less frequent. Crude odds ratios for carriers of one or two A alleles, compared to wild-type G/G, were 0.58 [95% confidence interval (CI), 0.38-0.88; P = 0.011] for lung cancer patients, 0.63 (95% CI, 0.43-0.92; P = 0.017) for laryngeal cancer patients, and 0.82 (95% CI, 0.57-1.17; P = 0.27) for pharyngeal cancer patients. The relative risks, adjusted for age, gender, and extent of cigarette smoking were 0.47 (95% CI, 0.28-0.79; P = 0.004), 0.66 (95% CI, 0.44-1.01; P = 0.054), and 0.75 (95% CI, 0.51-1.12; P = 0.16) for lung, larynx, and pharyngeal cancer, respectively. Strikingly, relative risk for carriers of -463A among adenocarcinoma of the lung was 0.24 (95% CI, 0.10-0.58; P = 0.002). Two cases with larynx cancer, one case with lung cancer, and one reference subject displayed novel G/A mutations at -297 nucleotide and -296 nucleotide, destroying a constitutive AciI cleavage site. Our data finally suggest that the MPO -463A variant is a protective factor in the etiology of lung and larynx cancer, but possibly not of pharyngeal cancer.

Differential expression and function of PACAP and VIP receptors in four human colonic adenocarcinoma cell lines.

Human colonic adenocarcinoma cell lines have conserved several features of the native tissue. Among these is the expression of cell surface receptors for hormones and neurotransmitters that may be involved in the regulation of proliferation and differentiation processes in these cancer cells. Here, we confirm that high-affinity binding sites for the Vasoactive Intestinal Polypeptide (VIP) and for the VIP analogue Pituitary Adenylate-Cyclase Activating Polypeptide (PACAP), were expressed in 4 human colonic adenocarcinoma cell lines, HT29, SW403, DLD-1 and Caco-2, that spontaneously displayed variable phenotypic properties in culture. We demonstrated that after long-term treatments, VIP and PACAP significantly reduced cell proliferation in the 4 cell lines and modulated intracellular cAMP and cGMP levels. Furthermore, conspicuous differences were observed from one cell type to another concerning expression of the receptor subsets or the effects of the neuropeptides on cell growth and on cyclic nucleotides production.

Glucocorticoid receptor binding site in the mouse alpha-amylase 2 gene mediates response to the hormone.

Amylase gene expression has been shown to be positively regulated by glucocorticoids. Previous reports have suggested that this effect is indirect. We have addressed this question in a mouse exocrine pancreas cell line, 266-6, in which basal level of expression of amylase mRNA is low but inducible by glucocorticoids. In these cells the effect of glucocorticoids is not inhibited by cycloheximide at early time points. Reporter plasmids containing 224 base pairs of mouse amylase 5'-flanking DNA are positively regulated by glucocorticoids in gene transfer experiments. Glucocorticoid receptor purified from rat liver binds to the amylase promoter from position -56 to -33 and at the start of transcription. Site-directed mutation at the upstream position (-47 to -42) eliminates response to glucocorticoids in transient gene transfer experiments. Thus, glucocorticoid regulation of the mouse amylase gene is a direct effect and is mediated via a receptor binding site in the promoter region of the gene. Inhibition of the hormone response by cycloheximide at later time points after induction suggests the additional requirement for a short-lived factor. The DNA binding domain of the glucocorticoid receptor binds to a single site in the amylase promoter as a monomer, suggesting that both receptor binding sites as well as an additional short-lived factor are required to obtain induction.

Short term benefits for laparoscopic colorectal resection.

BACKGROUND: Colorectal resections are common surgical procedures all over the world. Laparoscopic colorectal surgery is technically feasible in a considerable amount of patients under elective conditions. Several short-term benefits of the laparoscopic approach to colorectal resection (less pain, less morbidity, improved reconvalescence and better quality of life) have been proposed. OBJECTIVES: This review compares laparoscopic and conventional colorectal resection with regards to possible benefits of the laparoscopic method in the short-term postoperative period (up to 3 months post surgery). SEARCH STRATEGY: We searched MEDLINE, EMBASE, CancerLit, and the Cochrane Central Register of Controlled Trials for the years 1991 to 2004. We also handsearched the following journals from 1991 to 2004: British Journal of Surgery, Archives of Surgery, Annals of Surgery, Surgery, World Journal of Surgery, Disease of Colon and Rectum, Surgical Endoscopy, International Journal of Colorectal Disease, Langenbeck's Archives of Surgery, Der Chirurg, Zentralblatt für Chirurgie, Aktuelle Chirurgie/Viszeralchirurgie. Handsearch of abstracts from the following society meetings from 1991 to 2004: American College of Surgeons, American Society of Colorectal Surgeons, Royal Society of Surgeons, British Assocation of Coloproctology, Surgical Association of Endoscopic Surgeons, European Association of Endoscopic Surgeons, Asian Society of Endoscopic Surgeons. SELECTION CRITERIA: All randomised-controlled trial were included regardless of the language of publication. No- or pseudorandomised trials as well as studies that followed patient's preferences towards one of the two interventions were excluded, but listed separately. RCT presented as only an abstract were excluded. DATA COLLECTION AND ANALYSIS: Results were extracted from papers by three observers independently on a predefined data sheet. Disagreements were solved by discussion. 'REVMAN 4.2' was used for statistical analysis. Mean differences (95% confidence intervals) were used for analysing continuous variables. If studies reported medians and ranges instead of means and standard deviations, we assumed the difference of medians to be equal to the difference of means. If no measure of dispersion was given, we tried to obtain these data from the authors or estimated SD as the mean or median. Data were pooled and rate differences as well as weighted mean differences with their 95% confidence intervals were calculated using random effects models. MAIN RESULTS: 25 RCT were included and analysed. Methodological quality of most of these trials was only moderate and perioperative treatment was very traditional in most studies. Operative time was longer in laparoscopic surgery, but intraoperative blood was less than in conventional surgery. Intensity of postoperative pain and duration of postoperative ileus was shorter after laparoscopic colorectal resection and pulmonary function was improved after a laparoscopic approach. Total morbidity and local (surgical) morbidity was decreased in the laparoscopic groups. General morbidity and mortality was not different between both groups. Until the 30th postoperative day, quality of life was better in laparoscopic patients. Postoperative hospital stay was less in laparoscopic patients. AUTHORS' CONCLUSIONS: Under traditional perioperative treatment, laparoscopic colonic resections show clinically relevant advantages in selected patients. If the long-term oncological results of laparoscopic and conventional resection of colonic carcinoma show equivalent results, the laparoscopic approach should be preferred in patients suitable for this approach to colectomy.

"Fast-track"-rehabilitation in surgery, a multimodal concept.

The rates of postoperative local surgical complications (e.g. wound-infection, abscess, anastomotic leakage) and the postoperative mortality have markedly decreased over the past decades. However the occurrence of general medical complications (e.g. cardio-pulmonary or renal dysfunction, nosocomial infections, thromboembolism) after abdominal surgery is still frequent with an incidence of 20-60% (1-6). "Fast-track"-surgery, also called "Fast-track"-rehabilitation or "ERAS" (enhanced recovery after surgery) programme, is a combination of different pre- and intraoperative measures, which have been mainly validated in elective colonic surgery, but they can be principally employed in all surgical settings. With this approach it is possible to accelerate the postoperative convalescence and reduce the rate of general complications markedly (4, 7-10).

[Fast track rehabilitation in colonic surgery: results of a prospective trial]. / Réhabilitation rapide en chirurgie colique: résultats d'une étude prospective.

OBJECTIVE: In elective large bowel surgery the incidence of general complications with standard perioperative care is up to 27%. Hospital discharge occurs 10 to 15 days after a conventional or laparoscopic colonic resection. The aim of a fast track management is to reduce the number of general complications and the length of hospital stay. MATERIAL AND METHODS: We prospectively evaluated a multimodal protocol in our service utilizing a combined thoracic epidural analgesia, an early mobilization and oral nutrition to accelerate postoperative recovery after elective colonic surgery. RESULTS: One hundred thirty-two consecutive patients aged an average of 66 years (range 22-88) were operated by laparotomy (n =71) or laparoscopy (n =61) and treated with the fast track rehabilitation protocol. Surgical complications occurred in 15 patients (11 %), four of these had an anastomotique leakage (3%). General complications occurred in 11 patients (8 %), the mortality was 1 %. The median length of hospital stay was four days (range 3-77) and 14 patients (11%) had to be readmitted. CONCLUSION: Application of a fast track rehabilitation protocol lowered the number of general complications and reduced the duration of hospital stay in our study.

Integrated regulation of pressure and flow in the coronary microcirculation.

There are many mechanisms that contribute to the regulation of coronary blood flow including vasodilatory metabolites, myogenic regulation, flow- or shear stress-mediated vasodilation, and neurohumoral influences. It is interesting to note that coronary arterioles of varying sizes appear to possess different sensitivities to these regulatory factors, but each appears to dominate the control of a particular segment of the microvasculature. For example, during metabolic hyperemia the smallest arterioles seem to be most sensitive to the effects of metabolites, but metabolic and myogenic mechanisms that dictate the tone of upstream microvessels likely act in concert to facilitate the overall adjustments in coronary vasomotor tone. Neurohumoral mechanisms, seem to modulate the robustness of these intrinisic adjustments, perhaps by restraining the extent of vasodilation. The purpose of this review is to discuss these many regulatory mechanisms and also present a framework by which the vasoactive reactions elicited by these different mechanisms are integrated into coordinated responses of the entire coronary vascular network.

Effects of oxygen tension on endothelium dependent responses in canine coronary microvessels.

STUDY OBJECTIVE: The aim was to determine the direct effects of oxygen tension on endothelium dependent vasodilator responses in canine coronary microvessels. DESIGN: Coronary microvessels were isolated and studied in vitro in a no flow constant pressure state using a video dimension analysing system. Microvessels were exposed to different partial pressures of oxygen. Endothelium dependent responses to acetylcholine and A23187 calcium ionophore were obtained with and without indomethacin during hyperoxia and normoxia, and compared to responses during hypoxia. Dose-response curves were also obtained to the direct smooth muscle dilator nitroprusside during normoxia and hypoxia. The reversibility of the effects of hypoxia on the acetylcholine response was studied after return to hyperoxic conditions following hypoxia. EXPERIMENTAL MATERIAL: Coronary microvessels (58-150 micron diameter) were obtained from adult mongrel dogs of either sex. MEASUREMENTS AND MAIN RESULTS: Exposure of preconstricted microvessels to hypoxia alone [PO2 5.8(0.4)kPa] resulted in a 25.9(SEM 6.8)% relaxation that was abolished by indomethacin [0.35(2.9)% relaxation]. Acetylcholine elicited dose dependent vasodilatation, with no significant differences in sensitivity between normoxia [PO2 14.6(0.04) kPa] and hypoxia: EC50 = 0.023 v 0.027 mumol.litre-1, respectively. During hyperoxia [PO2 80.2(6.0) kPa] there was a significant increase in the EC50 value to 0.09 mumol.litre-1 (hypoxia and normoxia v hyperoxia). After inhibition of prostaglandin synthesis with indomethacin, the sensitivity to acetylcholine was significantly decreased during hypoxia (EC50 = 0.16 mumol.litre-1) when compared to normoxia and hyperoxia. Indomethacin alone did not alter the acetylcholine response during normoxia and hyperoxia. As with acetylcholine, the sensitivity of indomethacin treated microvessels to A23187 was also decreased during hypoxia when compared to hyperoxia. There was no difference in the nitroprusside response during hypoxia and hyperoxia. The decreased vasodilator response to acetylcholine after hypoxia was persistent up to 2 h after return to hyperoxic conditions. CONCLUSIONS: Hypoxia decreases vasodilatation due to endothelium dependent relaxing factor, and oxygen tension has an important influence on both receptor dependent and receptor independent endothelium dependent vasodilator responses in coronary microvessels. Hypoxia also induces a prostaglandin mediated dilatation of preconstricted coronary microvessels. The effects of hypoxia on endothelium dependent responses are persistent up to 2 h.

Evidence for an ectophosvitin kinase activity that phosphorylates a 123 kDa endogenous substrate on a human colonic adenocarcinoma cell (HT 29).

When HT 29 cells grown as a monolayer were incubated in a synthetic medium in presence of 0.1 microM [gamma 32P]-ATP, the radioactivity was incorporated predominantly into three major endogenous polypeptides of 123 kDa, 50 kDa and 46 kDa. The radioactive proteins could be detected as soon as 30 s after the addition of the labelled ATP. When exogenous substrates such as casein or phosvitin were added in the synthetic medium, these proteins became phosphorylated. The phosvitin-kinase activity was released in the culture medium following an incubation of the cells with phosvitin. Depletion of the enzymatic activity from the cell surface as well as competition between phosvitin and endogenous substrates led specifically to the inhibition of the 123 kDa polypeptide phosphorylation. At low density, endogenous phosphorylation increased with the cell number, whereas on the contrary it decreased at high cell density. We concluded that the surface of HT 29 cells expressed several protein kinase activities. We have characterized one of them as an ectophosvitin kinase which phosphorylated specifically a 123 kDa polypeptide and whose expression or accessibility varied according to cell density.