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.

[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.

[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.

[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.

[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.

[Laparoscopic treatment of perforated duodenal ulcer: 84 cases in Tunisia]. / Traitement laparoscopique des ulcères duodénaux perforés: 84 cas en Tunisie.

INTRODUCTION: The purpose of this study was to evaluate the feasibility, efficacy and safety of the laporascopic treatment of perforated duodenal ulcer. METHODS: This retrospective study included patients who underwent laparoscopic treatment of perforated duodenal ulcer during the seven-year period from 2001 to 2007. The procedure included direct suture of the perforated ulcer followed by peritoneal lavage. All patients received medical treatment including Helicobacter pylori eradication and proton pump inhibitor therapy. RESULTS: A total of 84 patients underwent laparoscopic surgery for perforated duodenal ulcer during the study period. There were 81 men and 3 women with a mean age of 28 years. Laparoscopic examination confirmed diagnosis of perforated duodenal ulcer in all cases. Direct suture of the ulcer was successful in 72 cases. In the remaining 12 cases conversion to open surgery was necessary due to difficulty in achieving peritoneal lavage in 6 cases, ulcer size and edge friability in 5, and septic shock in one. The mean duration of the procedure was 95 minutes (range, 60 to 180 minutes). The mean postoperative complication rate was 15.4%. Complications included peritonintis in one case and digestive fistula in one. There were no postoperative deaths. All patients were re-examined after 25 months. Two patients presented recurrences after the laparoscopic treatment and required tri-therapy. CONCLUSION: Laparoscopic suture of perforated duodenal ulcer is safe and effective. It avoids the need for laparotomy that is associated with a risk for septic and parietal complications. Since medical treatment is effective for ulcerous disease, there are currently no indications for radical treatment.

[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.

[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.

Structure and transcription of the actin gene of Trypanosoma brucei.

In Trypanosoma brucei, the actin gene is present in a cluster of two, three, or four tandemly linked copies, depending on the strain. Each cluster seems to exist in two allelic versions, as suggested by the polymorphism of both gene number and restriction fragment length in the DNA from cloned trypanosomes. The amplification of the gene copy number probably occurs through unequal sister chromatid exchange. The chromosomes harboring the actin genes belong to the large size class. The coding sequence was 1,128 nucleotides long and showed 60 to 70% homology to other eucaryotic actin genes. Surprisingly, this homology seemed weaker with Trypanosoma congolense, Trypanosoma cruzi, Trypanosoma vivax, Trypanosoma mega, or Leishmania actin-specific sequences. The mRNA was around 1.6 kilobases long and was synthesized at the same level in bloodstream and procyclic forms of the parasite. Large RNA precursors, up to 7.7 kilobases, were found in a pattern identical in strains containing either two or three gene copies. Probing of the flanking regions of the gene with either steady-state or in vitro transcripts, as well as S1 nuclease protection and primer extension experiments, allowed mapping of the 3' splice site of the actin mRNA, 38 nucleotides upstream from the translation initiation codon. A variably sized poly(dT) tract was found about 30 base pairs ahead of the splice site. The largest detected actin mRNA precursor seemed to give rise to at least two additional stable mRNAs. The RNA polymerase transcribing the actin gene exhibited the same sensitivity to inhibition by alpha-amanitin as that transcribing both the spliced leader and the bulk of polyadenylated mRNAs.

Roughness of moving elastic lines: crack and wetting fronts.

We investigate propagating fronts in disordered media that belong to the universality class of wetting contact lines and planar tensile crack fronts. We derive from first principles their nonlinear equations of motion, using the generalized Griffith criterion for crack fronts and three standard mobility laws for contact lines. Then we study their roughness using the self-consistent expansion. When neglecting the irreversibility of fracture and wetting processes, we find a possible dynamic rough phase with a roughness exponent of zeta=1/2 and a dynamic exponent of z=2. When including the irreversibility, we conclude that the front propagation can become history dependent, and thus we consider the value zeta=1/2 as a lower bound for the roughness exponent. Interestingly, for propagating contact line in wetting, where irreversibility is weaker than in fracture, the experimental results are close to 0.5, while for fracture the reported values of 0.55-0.65 are higher.

[Pyogenic abscess of the breast: clinical and therapeutic aspects]. / Abcès du sein à pyogènes: aspects cliniques et thérapeutiques.

OBJECTIVE: The goal of this retrospective work was to study the clinical aspects and the principles of management of the abscess of the breast in order to determine a convenient and recent therapeutic attitude. PATIENTS AND METHODS: Our retrospective survey concerns 114 cases of breast abscess collected in a surgery department over a period of 14 years, from 1990 to 2003. All patients have been operated and the diagnosis confirmed through the operation. The puerperal abscesses have been noted in 31 cases. RESULTS: One hundred and four women and ten men were concerned, with a sex-ratio of 0.1. The medium age was 33 years old for the women and 42 years for the men. The diagnosis was based on the clinical criteria, confirmed by the ultrasonography in 11 cases out of 16 and by the mammary puncture in 15 cases out of 22. Two non-puerperal abscesses have revealed an infiltrating canal carcinoma. The Staphylococcus aureus was the germ the most frequently met, concerning 8 cases out of 16. The surgical biopsies carried out in 52 cases revealed a fibrocystic mastopathy in six cases, a canalar ectasia in two cases and an infiltrating canalar carcinoma in two cases. The surgical treatment, performed in any case, was associated to an anti-staphylococcus antibiotherapy. The recurrence of the abscess has been observed in four cases. DISCUSSION AND CONCLUSION: The frequency of pyogenic abscess of the breast, particularly the puerperal abscesses, has considerably decreased. The non-puerperal abscesses often pose a differential diagnosis problem with the very aggressive inflammatory cancers. The percutaneous ultrasonography guided drainage must be proposed in first intention to treat the abscesses of the breast. However, surgical treatment is still valid with an abscess either relapsing or chronic, or else the failure of the non-operative processes.

[Arterial injury as a complication of lumbar disc surgery]. / Le cas clinique du mois. Plaie artérielle compliquant une chirurgie discale lombaire.

Vascular complications are unusual after lumbar disc surgery. Iliac artery injury is the most common. The vascular injury may cause severe bleeding and hypotension. If the injury is missed, an arteriovenous fistula may develop. This complication is fortunately the most common. We describe the case of a 41 year-old man who was operated on for lumbar disc herniation. A few hours after surgery, he had developed prolonged hypotension leading to the diagnosis of iatrogenic vascular injury. The CT scan confirmed the diagnosis of right common iliac tear with voluminous retroperitoneal haematoma. Emergent surgery was carried on with success.

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.

[Sarcomas of the small intestine]. / Sarcomes du grêle.

Sarcomas of the small intestine are rare, clearly differentiated, malignant, mesenchymatous tumours that can be of smooth muscle, Schwann cell or fibroblastic origin. From a clinical point of view, the pain and abdominal mass are the 2 types of symptoms that frequently reveal the disease. In rare cases, sarcomas of the small intestine are manifested by an acute complication. No imaging method can clearly confirm the diagnosis. Before immunohistochemistry, differential diagnosis was made on undifferentiated mesenchymatous "stromal" tumours, which are also rare. Exeresis must be complete and without perforation of the tumour because of the risk of locoregional relapse. The benefits provided by chemotherapy and radiotherapy are limited because of the low mitotic activity of the tumour cells and its weak vascularisation. Long-term survival is limited by poor prognosis criteria: high grade malignancy, size greater than 5 cm, tumour extension, perforation of the tumour, quality of surgical resection and histological type.

[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.

Compound effects of bisulphite ion on frog skeletal muscle.

To characterize the structures of the nicotinic cholinoceptors in the frog rectus abdominis muscle, group-selective reagents have been used. Possible modifications of the excitation-contraction coupling have also been studied. The effect of the bisulphite ion on skeletal muscle has been demonstrated earlier at presynaptic and postsynaptic levels. Another report questioned whether these effects were significant to the contractile process in general. The present study shows that bisulphite induced qualitative and quantitative changes in the muscular response to acetylcholine and electrical stimulation. The intervention is likely at the level of excitation-contraction coupling as well as at the previously proposed sites.

S.E.M. study of urease-induced crystalluria in the presence of hydroxamic derivatives.

The effect of 3 hydroxamic acid derivatives on urease-induced crystalluria was studied in vitro. Acetohydroxamic acid is more effective than salicylhydroxamic and gentisohydroxamic acids in inhibiting the kinetic of urease enzymatic reaction and in retarding the formation of struvite and apatite. Crystal deposits studied by scanning electron microscope (S.E.M.) and X-ray microanalysis indicated that acetohydroxamic acid favours the formation of large crystals of struvite, and less aggregation is observed. Salicyl and gentiso derivatives favour the formation of brushite together with struvite and apatite.