Collective chemotaxis and segregation of active bacterial colonies.

Still recently, bacterial fluid suspensions have motivated a lot of works, both experimental and theoretical, with the objective to understand their collective dynamics from universal and simple rules. Since some species are active, most of these works concern the strong interactions that these bacteria exert on a forced flow leading to instabilities, chaos and turbulence. Here, we investigate the self-organization of expanding bacterial colonies under chemotaxis, proliferation and eventually active-reaction. We propose a simple model to understand and quantify the physical properties of these living organisms which either give cohesion or on the contrary dispersion to the colony. Taking into account the diffusion and capture of morphogens complicates the model since it induces a bacterial density gradient coupled to bacterial density fluctuations and dynamics. Nevertheless under some specific conditions, it is possible to investigate the pattern formation as a usual viscous fingering instability. This explains the similarity and differences of patterns according to the physical bacterial suspension properties and explain the factors which favor compactness or branching.

[Role of laparoscopy in the diagnosis of peritoneal tuberculosis in endemic areas]. / Intérêt de la laparoscopie dans le diagnostic de la tuberculose péritonéale en zones endémiques.

The aim of our study is to demonstrate the difficulties of diagnosis of peritoneal tuberculosis in endemic areas and the value of laparoscopy for diagnostic confirmation. We report a retrospective study of 60 cases of peritoneal tuberculosis, collected from January 2004 to December 2009. The patients' median age was 41 years, and the sex ratio 0.4. The dominant reasons for consultation were pain and abdominal distension. Abdominal ultrasound found ascites in all patients. Computed tomography (CT) was performed in 30 patients and confirmed the ultrasound data. Paracentesis of the ascites took place in all patients, collecting exudative fluid in all cases; lymphocytes predominance in 83%. Screening for Mycobacterium tuberculosis in the ascites on direct examination and after culture was performed in 43 cases and negative in all of them. Surgical biopsy was performed laparoscopically in 29 patients and by laparotomy in 31 patients. Histological examination of the peritoneal biopsies confirmed the diagnosis of peritoneal tuberculosis in all cases.

Ileal pouch-anal anastomosis: Points of controversy.

Restorative proctocolectomy with ileal pouch-anal anastomosis has become the most commonly used procedure for elective treatment of patients with ulcerative colitis and familial adenomatous polyposis. Since its original description, the procedure has been modified in order to obtain optimal functional results with low morbidity and mortality, and yet provide a cure for the disease. In this review of the literature of restorative proctocolectomy with ileal pouch-anal anastomosis, we discuss these technical modifications, limiting our discussion to the current points of controversy. The current "hot topics" for debate are: indications for ileal pouch-anal or ileo-rectal anastomosis, indications for pouch surgery in the elderly, indeterminate colitis and Crohn's disease, the place of the laparoscopic approach, transanal mucosectomy with hand-sewn anastomosis vs. the double-stapled technique, the use of diverting ileostomy and the issue of the best route for delivery of pregnant women. Longer follow-up of patients and increased knowledge and experience with pouch surgery, coupled with ongoing prospective evaluation of the procedure are required to settle these issues.

[Small cell carcinoma of the ovary]. / Carcinome à petites cellules de l'ovaire.

Small cell carcinoma of the ovary of the hypercalcemic type is a rare tumor. We report a case in a 34-year-old patient, revealed by a pelvic pain. The imaging found a large mass of the right ovary. The patient had right oophorectomy and total hysterectomy, a left oophorectomy, pelvic and a para-aortic lymphadenectomy. She subsequently received 6 cycles of adjuvant chemotherapy followed by pelvic radiation therapy. The hypercalcemic small cell carcinoma of the ovary is a rare disease of poor prognosis. Treatment approaches include surgery, chemotherapy with the addition of radiotherapy.

Re-epithelialization: advancing epithelium frontier during wound healing.

The first function of the skin is to serve as a protective barrier against the environment. Its loss of integrity as a result of injury or illness may lead to a major disability and the first goal of healing is wound closure involving many biological processes for repair and tissue regeneration. In vivo wound healing has four phases, one of them being the migration of the healthy epithelium surrounding the wound in the direction of the injury in order to cover it. Here, we present a theoretical model of the re-epithelialization phase driven by chemotaxis for a circular wound. This model takes into account the diffusion of chemoattractants both in the wound and the neighbouring tissue, the uptake of these molecules by the surface receptors of epithelial cells, the migration of the neighbour epithelium, the tension and proliferation at the wound border. Using a simple Darcy's law for cell migration transforms our biological model into a free-boundary problem, which is analysed in the simplified circular geometry leading to explicit solutions for the closure and making stability analysis possible. It turns out that for realistic wound sizes of the order of centimetres and from experimental data, the re-epithelialization is always an unstable process and the perfect circle cannot be observed, a result confirmed by fully nonlinear simulations and in agreement with experimental observations.

[Acute occlusion with fever in a Tunisian woman]. / Syndrome occlusif fébrite aigu chez une tunisienne.

The purpose of this report is to describe a case of idiopathic segmental infarction of the great omentum, in a Tunisian woman, who presented with acute right hypchondrial pain simulating cholecystitis. Abdominal CT scan is the modality of choice. If symptoms resist medical treatment or complications occur, laparoscopic excision is the best therapeutic technique.

Contour instabilities in early tumor growth models.

Recent tumor growth models are often based on the multiphase mixture framework. Using bifurcation theory techniques, we show that such models can give contour instabilities. Restricting to a simplified but realistic version of such models, with an elastic cell-to-cell interaction and a growth rate dependent on diffusing nutrients, we prove that the tumor cell concentration at the border acts as a control parameter inducing a bifurcation with loss of the circular symmetry. We show that the finite wavelength at threshold has the size of the proliferating peritumoral zone. We apply our predictions to melanoma growth since contour instabilities are crucial for early diagnosis. Given the generality of the equations, other relevant applications can be envisaged for solving problems of tissue growth and remodeling.

Mutual adaptation of a Faraday instability pattern with its flexible boundaries in floating fluid drops.

Hydrodynamic instabilities are usually investigated in confined geometries where the resulting spatiotemporal pattern is constrained by the boundary conditions. Here we study the Faraday instability in domains with flexible boundaries. This is implemented by triggering this instability in floating fluid drops. An interaction of Faraday waves with the shape of the drop is observed, the radiation pressure of the waves exerting a force on the surface tension held boundaries. Two regimes are observed. In the first one there is a coadaptation of the wave pattern with the shape of the domain so that a steady configuration is reached. In the second one the radiation pressure dominates and no steady regime is reached. The drop stretches and ultimately breaks into smaller domains that have a complex dynamics including spontaneous propagation.

Effective line tension and contact angles between membrane domains in biphasic vesicles.

Inhomogeneities in membranes give rise to localized interactions at the interface between domains in two-component vesicles. The corresponding energy is expressed as a line tension between the two phases. In this paper we study the implications of the thickness mismatch between domains which has been experimentally reported to be of order 20-30% and the conditions under which the induced line tension can destabilize the domains in inhomogeneous vesicles. For asymmetric lipidic membranes we prove an increase of the line tension and the existence of a contact angle. Adsorption of impurities is also examined, our scope being the extension of the Canham-Helfrich model to describe elastic deformations and chemical interactions arising at microscopic scales. This mismatch effect may have important consequences for the stability of very small domains.

Peritoneal tuberculosis.

The peritoneum is one of the locations outside the most common pulmonary tuberculosis. Peritoneal tuberculosis poses a public health problem in endemic regions of the world. The phenomenon of migration, the increased use of immunosuppressive therapy and the epidemic of AIDS have contributed to a resurgence of this disease in regions where it was previously controlled. The aim of this review is to expose the clinical, biologic end radiologic futures of the peritoneal tuberculosis and to present the methods of diagnosis and treatment. The diagnosis of this disease is difficult and still remains a challenge because of its insidious nature, the variability of presentation and limitations of available diagnostic tests. The disease usually presents a picture of lymphocytic exudative ascites. There are many complementary tests with variable sensitivities and specificities to confirm the diagnosis of peritoneal tuberculosis. Isolation of mycobacteria by culture of ascitic fluid or histological examination of peritoneal biopsy ideally performed by laparoscopy remains the investigation of choice. The role of PCR, ascitic adenosine deaminase, interferon gamma and the radiometric BACTEC system can improve the diagnostic yield. An antituberculous treatment with group 1 of the WHO for 6 months is sufficient in most cases.

The radial growth phase of malignant melanoma: multi-phase modelling, numerical simulations and linear stability analysis.

Cutaneous melanoma is disproportionately lethal despite its relatively low incidence and its potential for cure in the early stages. The aim of this study is to foster understanding of the role of microstructure on the occurrence of morphological changes in diseased skin during melanoma evolution. The authors propose a biomechanical analysis of its radial growth phase, investigating the role of intercellular/stromal connections on the initial stages of epidermis invasion. The radial growth phase of a primary melanoma is modelled within the multi-phase theory of mixtures, reproducing the mechanical behaviour of the skin layers and of the epidermal-dermal junction. The theoretical analysis takes into account those cellular processes that have been experimentally observed to disrupt homeostasis in normal epidermis. Numerical simulations demonstrate that the loss of adhesiveness of the melanoma cells both to the basal laminae, caused by deregulation mechanisms of adherent junctions, and to adjacent keratynocytes, consequent to a downregulation of E-cadherin, are the fundamental biomechanical features for promoting tumour initiation. Finally, the authors provide the mathematical proof of a long wavelength instability of the tumour front during the early stages of melanoma invasion. These results open the perspective to correlate the early morphology of a growing melanoma with the biomechanical characteristics of its micro-environment.

[Intrauterine device and pelvic tumor: two case reports of pelvic actinomycosis with pseudotumor from tropical zones]. / Dispositif intra-utérin et tumeur pelvienne: 2 observations sous les tropiques d'actinomycose pelvienne pseudotumorale.

Pelvic actinomycosis is a rare chronic disease caused by actinomycete species. The pseudotumorous form is the most common and often leads to misdiagnosis. The purpose of this report is to describe two cases of pelvic actinomycosis involving women with a history of intrauterine contraceptive device (IUD) use. Diagnosis was based on pelvic mass and the findings of surgery undertaken for suspicion of an advanced ovarian tumor with hepatic metastasis in one case and for a tumor of the right ovary in the other case. Diagnosis was confirmed by histological examination of a biopsy specimen in the first case and of the surgical specimen (right ovariectomy) in the second case. Long-term antibiotic therapy was effective in both patients. Based on these two cases and review of the literature, discussion focuses on diagnostic pitfalls, natural course, and therapeutic options for this particular infection.

[Gallbladder diaphragm: an unusual cause of acute alithiasic cholecystitis complicated of biliary peritonitis]. / Diaphragme vésiculaire : une cause inhabituelle de cholécystite aiguë alithiasique compliquée de péritonite biliaire.

The gallbladder diaphragm is a very rare abnormality of the embryogenesis. It is an exceptional cause of biliary peritonitis. We report a 54-year-old man who presented with hepatic colic for the past 2 years. Imaging disclosed evidence of alithiasic cholecystitis on gallbladder diaphragm. The coelioscopic exploration confirmed the diagnosis and an associated presence of a biliary peritonitis. A cholecystectomy and a peritoneal washing were performed. The histological examination ruled in the diagnosis of cholecystitis on gallbladder diaphragm. The embryogenesis, the histological and morphological features as well as the treatment are discussed.

[Intestinal perforation in a Tunisian woman: peritonitis due to a fishbone]. / Un coup de poignard abdominal chez un tunisien: péritonite par arête de poisson.

Diagnosis of foreign body perforation of the gastrointestinal tract can be difficult. The purpose of this report is to describe a case of acute peritonitis after perforation of the ileum by a fish bone that was detected by computed tomography.

[Isolated abscess of the thoracic and abdominal wall: an exceptional form of tuberculosis]. / Abcès de la paroi thoracique et abdominale isolé : une forme exceptionnelle de tuberculose.

Isolated thoracic parietal involvement is a very rare form of tuberculosis and multifocal localization is exceptional. It often poses a diagnostic problem with parietal tumours requiring recourse to surgical biopsy. We report a case of tuberculous abscess localized to the anterior and superior part of the chest wall with a second abdominal localization but without any pulmonary involvement. The patient was a woman of 56 years presenting with a one-year history of a swelling to the right of the sternum accompanied after several months by a second swelling to the right side of the abdomen. The radiological and biological investigations revealed a parietal tumour in two separate areas. The diagnosis was confirmed by histological examination of a surgical biopsy and bacteriological examination of a percutaneous aspirate of the collection. Standard anti-tuberculosis treatment was given for nine months with good clinical and radiological resolution. In this case report, we study the anatomical and clinical features of this condition and discuss the diagnostic difficulties.

[Two pelvic tumors which should not be operated, lymphoma of Burkitt and actinomycosis]. / Le lymphome de Burkitt et l'actinomycose, deux tumeurs pelviennes qu'il ne faut pas opérer.

The treatment of the pelvic tumors depends of their histological nature. Some of them require only one medical treatment without recourse to surgery. We report two rare cases of pelvic tumors occurring in young adults. For the first case, actinomycosic nature was related to the histological study of the surgical biopsies. Concerning the second case, the lymphatic nature of a tumor of the low rectum was retained on the immunohistochimic study of the endoscopic biopsies. The evolution was uneventful in the two cases after a medical treatment containing penicillin G or a chemotherapy. We discuss at the time of these two observations the diagnostic difficulties and the therapeutic methods of these rare affections.

Continuum model of epithelial morphogenesis during Caenorhabditis elegans embryonic elongation.

The purpose of this work is to provide a biomechanical model to investigate the interplay between cellular structures and the mechanical force distribution during the elongation process of Caenorhabditis elegans embryos. Epithelial morphogenesis drives the elongation process of an ovoid embryo to become a worm-shaped embryo about four times longer and three times thinner. The overall anatomy of the embryo is modelled in the continuum mechanics framework from the structural organization of the subcellular filaments within epithelial cells. The constitutive relationships consider embryonic cells as homogeneous materials with an active behaviour, determined by the non-muscle myosin II molecular motor, and a passive viscoelastic response, related to the directional properties of the filament network inside cells. The axisymmetric elastic solution at equilibrium is derived by means of the incompressibility conditions, the continuity conditions for the overall embryo deformation and the balance principles for the embryonic cells. A particular analytical solution is proposed from a simplified geometry, demonstrating the mechanical role of the microtubule network within epithelial cells in redistributing the stress from a differential contraction of circumferentially oriented actin filaments. The theoretical predictions of the biomechanical model are discussed within the biological scenario proposed through genetic analysis and pharmacological experiments.

[Severe rectal bleeding in an Tunisian woman: colonic tuberculosis mimicking a tumor]. / Une rectorragie sévère sous les tropiques.

Since colonic tuberculosis is uncommon and its bifocal pseudo-tumor form is exceptional, differential diagnosis with the colonic cancer is exceedingly difficult. The purpose of this report is to describe a case of primary colonic tuberculosis in two separate locations discovered in a patient presenting with persistent massive hematochezia. A 69-year-old woman was examined for hematochezia, abdominal pain and recent weight loss. Colonoscopy revealed the presence of two ulcerated tumor-like lesions in right colon. One of these lesions caused significant stenosis. Histological examination of biopsy specimens was inconclusive. Colonic tumor with bleeding was considered as the most likely diagnosis. Surgical exploration demonstrated one tumor in the cecum and another in the ascending colon. Right hemicolectomy was performed. Histological examination of the surgical specimen demonstrated a granulomatous reaction pattern with caseous necrosis. Conventional antituberculosis treatment led to clinical improvement.

[The solid pseudopapillary tumor of pancreas: two cases and literature review]. / Tumeurs pseudopapillaires et solides du pancréas: deux observations et revue de la littérature.

Solid pseudopapillary tumor (SPT) of the pancreas is a rare exocrine pancreatic tumor behaving in a low-grade fashion, with limited local invasion risk and a rare metastatic evolution. We report SPT in two young females, revealed by abdominal pain and an epigastric mass. The diagnosis of a cystic tumor was based on abdominal ultrasound and CT data in the first case and on MRI in the second. A distal pancreatectomy and splenectomy were successfully performed in the first case and a central pancreatectomy in the second. Histological study confirmed the diagnosis of SPT of the pancreas.