Effect of ownership structure on stock market liquidity : evidence from Tunisia

Cette thèse analyse le lien entre la gouvernance d'entreprise et la liquidité par une validation empirique sur un échantillon d'entreprises cotées sur le marché boursier tunisien. Ce choix est motivé par le fait que les différences dans les systèmes de gouvernance entre les pays dans plusieurs aspects (concentration de la propriété, identité des actionnaires…) pourraient avoir des effets différents sur la liquidité des titres. Plus spécifiquement, nous nous proposons d'étudier, l'effet d'un mécanisme de gouvernance interne sur le coût de liquidité pour en déduire l'impact sur le coût du capital et par la suite la performance espérée des firmes. Dans un premier temps, nous appréhendons le concept de liquidité et mesurons son degré. Dans un deuxième temps, nous étudions la relation entre la liquidité et la performance des entreprises. La contribution du coût du service d'immédiateté se traduit par un escompte additionnel sur le coût du capital et la valeur des sociétés. Les résultats trouvés montrent que les fourchettes de prix sont reliées positivement à la rentabilité des fonds propres en valeur de marché. Ces résultats confirment que les entreprises les moins liquides doivent suggérer une rentabilité supérieure aux investisseurs (une prime d'illiquidité) afin de compenser la ponction des coûts de transactions sur la rentabilité de leurs portefeuilles. Enfin, nous constatons que la liquidité est un facteur non négligeable dans le domaine de la gouvernance d'entreprise dans la mesure où les grands actionnaires affectent négativement la liquidité des titres de l'entreprise. Nos résultats concluent à des implications différentes quant à l'identité des actionnaires. Les insiders augmentent les coûts de liquidité en raison de leur accès à l'information privée et pertinente. De même, une participation institutionnelle dans l'entreprise réduit la liquidité de ses titres mesurée par l'impact sur les prix.This thesis analyzes the link between corporate governance and liquidity by an empirical validation on a sample of companies listed on the Tunisian stock market. We propose in the first chapter an overview of theoretical models and empirical concept of liquidity. In the second chapter, we are a part, an empirical study on stock liquidity in our sample, performing a descriptive analysis of the microstructure of the Tunisian financial market to highlight the degree of liquidity. In a second step, we study the relationship between liquidity and firm performance. We propose in the third chapter a presentation of models operating the link between liquidity and value firm through the ownership structure. We are also interested in this chapter to the impact of liquidity cost on the performance and value of companies. The contribution of the service cost of immediacy translates into an additional discount on the cost of capital and the value of companies. In the fourth chapter, we conduct a comprehensive study of the influence of the liquidity of Tunisian companies on their performance. In a third step, we study the impact of ownership structure on liquidity. This part includes two chapters. The fifth chapter is devoted to the development of assumptions made in explaining the link between ownership concentration and liquidity. In the sixth chapter, we test our research hypotheses on the influence of the characteristics of the structure of corporate ownership on the stock liquidity

A primary hepatic lymphoma in a patient with Crohn's disease receiving thiopurine and anti-TNF therapy: a case report

Primary hepatic lymphoma is a rare variant of non-Hodgkin's lymphoma with an incidence of 0.016% of all non-Hodgkin lymphomas. The most common histologic subtype is large diffuse B-cell lymphoma. Pathogenesis is not clearly established and undergoing immunosuppressive therapy has been proposed as a risk factor for primary hepatic lymphoma. We report an intriguing case study, featuring a 23-year-old male patient with Crohn's Disease who had been receiving a combination therapy of thiopurine and anti-TNF for 6 years and was diagnosed with primary hepatic diffuse large B-cell lymphoma

Orbital Tumor Revealing a Systemic Sarcoidosis

Ocular involvement is seen in approximately 25% of patients with sarcoidosis. Uveitis is the most common ocular manifestation, but sarcoidosis may involve any part of the eye. Orbital manifestations of sarcoidosis are uncommon with few series in the literature. A 65-year-old woman presented with redness of the right eye and painless, unilateral eyelid swelling. Orbital scanning revealed mass infiltrating the soft tissue of the inferior right orbital quadrant. Biopsy results showed nodular, noncaseating granulomas consistent with sarcoidosis. The complete systemic workup revealed systemic manifestations of sarcoidosis at the time of examination with hilar and mediastinal lymphadenopathies noted on CT scan. The orbital surgical treatment was followed by systemic prednisone therapy with good response. Although rare, orbital sarcoidosis must be considered in the evaluation of orbital tumors in elderly patients. A search for systemic findings should be undertaken and appropriate therapy should be instituted

Intravenous leiomyomatosis of the uterus: still discovered on anatomopathological examination

Background: Leiomyomas beyond the uterus are defined by benign smooth muscle cell tumors outside of the uterus. Intravenous leiomyomatosis is a rare type of uterine leiomyoma and is characterized by the formation and growth of benign leiomyoma tissue within the vascular wall. Herein, we present a case of Intravenous leiomyomatosis successfully treated by surgical removal and a review of actual medical recommendations.Case presentation: A 49 - year-old woman, maghrébin, G3 P2, no family history of uterine myomas mentioned, having systemic arterial hypertension, presented to our department with hypogastric pain and abnormal uterine bleeding in the prior five months resulting in anemia which required iron supplementation. On physical examination the vital signs were normal. A palpable mass in the hypogastrium was noted. The rest of the exam was unremarkable. Pelvic ultrasound showed a huge uterus with multiple heterogeneous leiomyomas, including at least one intracavity. Computed tomography scans and magnetic resonance imaging were not done initially due to the unaffordability of the patient. The initial diagnosis was leiomyoma. The decision to perform a total abdominal hysterectomy and bilateral salpingo-oophorectomy was taken. The abdomen was opened by a midline vertical incision. During surgery, multiple subserosal, intramural and submucosal fibroids ranging from 2 cm × 3 cm to 10 cm × 10 cm were seen. On pathological examination, the uterus measured 19 cm in the largest diameter and weighed 1.3 kg. The cut section showed white nodular myometrial masses. Microscopically, intravascular growth of benign smooth muscle cells is found within venous channels lined by endothelium. The diagnosis of Intravenous leiomyomatosis of the uterus without malignant transformation was retained. The patient was monitored for 14 months and subsequent computed tomography did not reveal any evidence of tumor recurrence. The follow-up will be performed annually till the age of menopause.Conclusion: Intravenous leiomyomatosis is a benign, rare and potentially lethal pathology. It especially affects premenopausal women with a history of uterine myoma, whether operated on or not. They require close and prolonged follow-up because of the high risk of recurrence

Prognostic significance of high circulating sHLA‐G in ovarian carcinoma

HLA-G is a non-classical major histocompatibility complex class Ib molecule. Its expression has been described in various cancer types, including ovarian cancer. HLA-G molecule has been implicated in immune escape and in progression of ovarian tumor cells. Our goal was to assess if total soluble (s)HLA-G molecules or HLA-G5 and sHLA-G1 isoforms could be considered as circulating ovarian tumor biomarkers, we measured the concentration of these molecules in ovarian carcinoma patients stratified according with their clinicopathological parameters. sHLA-G, sHLA-G1 and HLA-G5 concentrations were dosed in plasma samples by sandwich-ELISA. The sHLA-G dimerization was analyzed after immunoprecipitation and SDS-PAGE migration. Total sHLA-G and sHLA-G1 levels were significantly represented in plasma of ovarian carcinoma patients compared to healthy controls. sHLA-G1 isoform concentration was highly represented in ovarian carcinoma compared to HLA-G5 isoforms. Additionally, high sHLA-G molecules have been found in aged patients, as well as in patients with advanced stages, and those with metastatic lymph nodes and those with distant metastasis. Elsewhere, sHLA-G monomers were highly represented in ovarian carcinoma patients compared to controls. sHLA-G plasmatic protein was highly represented in ovarian carcinoma. In effect, HLA-G might be considered as a new checkpoint molecule that could be used to assess progression and recurrence of the disease, thus placing it as a potential biomarker for advanced and complicated ovarian carcinoma