Study of the mechanisms involved in the bradykinin-induced contraction of the pig iris sphincter muscle in vitro

This study was designed to investigate the mechanisms by which bradykinin induces contraction of the pig iris sphincter muscle in vitro. Addition of bradykinin, Lys-bradykinin and Met-Lys-bradykinin to the pig iris sphincter resulted in a graded contraction with a mean EC(50s) of 21, 11 and 5 nM, respectively. The bradykinin B(1) receptor agonist des-Arg(9)-bradykinin only caused a slight contraction, measured 6 h after the tissue was set up. The B(2) receptor antagonists FR 173657 ((E)-3-(6-acetamido-3-pyridyl)-N [N-2-4-dichloro-3-[(2-methyl-8-quinolinyl) oxymethyl] phenyl]-N-methylamino-carbonyl-ethyl] acrylamide) and Hoe 140 (D-Arg(0)-[Hyp(3), Thi(5), D-Tic(7), Oic(8)]-bradykinin produced a graded shift to the right associated with marked inhibition of the bradykinin-induced contraction. Atropine, guanethidine or tetrodotoxin significantly reduced the bradykinin-induced contraction. Dazoxiben, an inhibitor of thromboxane A(2), and MK-571 (3-(3-(2-(7-chloro-2-quinolinyl) ethenyl) phenyl ((3-dimethyl amino-3oxo-propyl) thio) methyl) propanoic acid, a leukotriene D(4) receptor-selective antagonist, also caused inhibition of the bradykinin-mediated contraction. Cyclooxygenase-1 and -2 inhibitors, indomethacin, ibuprofen, valeryl salicylate and NS 398 (N-[2-(cyclohexyloxy)-4-nitrophenyl]methanosulfonamide) all significantly inhibited the bradykinin-mediated contraction without affecting the carbachol-induced contraction of the pig iris sphincter. Taken together, these results indicate that the bradykinin-mediated contraction of the pig iris sphincter muscle seems to be mediated primarily by the activation of the B(2) receptor release of acetylcholine, noradrenaline and both cyclooxygenase-1 and -2 metabolites besides the release of leukotriene D(4) and tromboxane A(2) from the arachidonic acid pathway.     

Genetic homogeneity of mutational spectrum of group‐A xeroderma pigmentosum in Tunisian patients

Background Xeroderma Pigmentosum (XP) is a rare autosomal recessive disorder characterized by cutaneous and ocular alterations. Eight genes, Xeroderma Pigmentosum group A (XPA) to Xeroderma Pigmentosum group G (XPG) and Xeroderma Pigmentosum group V (XPV), are known to be responsible for the disease and products of these genes are involved in the repair of deoxyribonucleic acid (DNA) lesions generated by UV radiation. Several XP patients suffer from neurological defects, found in the XPA (the most common form), D and G groups. The aim of this study was to investigate the mutational spectrum of XPA in Tunisia, in order to propose a simple tool for molecular diagnosis. Methods This study was carried out on six unrelated families with nine Tunisian XPA patients. Clinical features were recorded. As a previous study showed the presence of the R228X mutation in Tunisia, patients were first screened for this mutation by polymerase chain reaction‐restriction fragment length polymorphism and then confirmed by direct sequencing. Results The results showed that all patients carried the XPA R228X mutation. This mutation corresponds to a C to T transition, which creates a premature stop codon at position 228, thus causing a DNA repair defect. Conclusions The XPA R228X mutation is common in Tunisian population. This mutation is associated with a relatively moderate phenotype of the XPA. As all explored patients presented the recurrent mutation XPA R228X, a potential founder effect was searched and confirmed by haplotype analysis. Taking into account similar genetic background, investigation of this mutation should allow a cost effective and rapid diagnosis of XPA in north‐African populations.     

Biological significance of promoter hypermethylation of p14/ARF gene: Relationships to p53 mutational status in Tunisian population with colorectal carcinoma

One of the most important pathways which are frequently affected in colorectal cancer is p53/ (MDM2)/p14ARF pathway. We aim to determine the methylation pattern of p14/ARF in relation to mutation of p53. This correlation was studied to investigate whether their alterations could be considered as a predictor factor of prognosis in colorectal cancer and whether it can be useful in early-stage diagnosis. Statistical analyses show that p14/ARF hypermethylation was correlated with rectum location (p?=?0.004), primary TNM stage (p?=?0.016), and advanced Astler–Coller stage (p?=?0.024). The RT-PCR that revel 31 % of patients did not express p14/ARF mRNA or at very low level. A high concordance between CpG hypermethylation and the low levels (p?<?0.005) was shown. In addition, our analyses demonstrate that patients with mutation in the p53 gene have a lack of the protein expression (p?<?0.005). This category with negative expression of p53 had a shorter survival rate (p?<?0.005). On the one hand, MSP pattern of p14/ARF were correlated with a lack of p53 expression (p?=?0.007). We found that p53/p14ARF pathway was frequently deregulated among our patients. In our study, we demonstrate that hypermethylation of p14/ARF occurs early during CRC tumorogenesis. However, we did not find correlation between p14/ARF and survival. These results suggest that p14/ARF methylation pattern may constitute a predictor factor of CRC in early stage but it could not be considered as a prognostic factor. On the other hand and because of the reversibility of the methylation mechanism, it may be appropriate to target the demethylation of p14/ARF to develop new drogues for CRC.     

Changes in renal hemodynamics in streptozotocin-induced diabetic rats with L-ascorbic acid supplementation

The present study was designed to investigate whether L-ascorbic acid (AA) supplementation could prevent changes in renal hemodynamics in diabetic rats or not. The experiments were carried out in 48 male Sprague-Dawley rats. Diabetes mellitus was induced in rats by intravenous injection with streptozotocin (STZ) (55 mg/kg.bw), while the control rats were received citrate buffer alone. The renal hemodynamics was examined after the supplementation of AA (1 mg/l) for 8 and 16 weeks. The results demonstrated that AA could retard the increase (p<0.05) in renal vascular resistance (RVR) significantly compared with diabetic rats (STZ). Besides, at week 16, the effective renal plasma flow (ERPF) and the glomerular filtration rate (GFR) of STZ-AA were significantly higher than those of STZ (p<0.05). In conclusion, supplementation of AA was able to ameliorate the renal dysfunction in STZ-induced diabetic rats by decrease in RVR concomitant with an increase in both ERPF and GFR.     

Effect of purified Russell’s viper venom-factor X activator (RVV-X) on renal hemodynamics, renal functions, and coagulopathy in rats

Acute renal failure (ARF) is the most frequent and a serious complication in victims of Russell’s viper snakebites. Russell’s viper venom-factor X activator (RVV-X) has been identified as a main procoagulant enzyme involving coagulopathy, which might be responsible for changes in renal hemodynamics and renal functions. Here, we purified RVV-X from crude Russell’s viper venom to study renal hemodynamics, renal functions, intravascular clot, and histopathological changes in Sprague-Dawley rats. Changes in renal hemodynamics and renal functions were evaluated by measuring the mean arterial pressure, glomerular filtration rate (GFR), effective renal plasma flow (ERPF), effective renal blood flow (ERBF), renal vascular resistance (RVR), and fractional excretion of electrolytes. After 10 min, rats receiving both crude venom and purified RVV-X decreased GFR, ERPF, and ERBF and increased RVR. These changes correlated to renal lesions. Along with the determination of intravascular clot, rats injected with purified RVV-X increased the average D-dimer level and reached a peak at 10 min, declined temporarily, and then reached another peak at 30 min. The temporal association between clots and renal dysfunction was observed in rats within 10 min after the injection of purified RVV-X. These findings suggested RVV-X as a major cause of renal failure through intravascular clotting in the renal microcirculation.     

Unusual presentation of a sarcoid patient: multiple arterial and venous thrombosis with chest lymphadenopathy

We depict a case of a 32 year old Mediterranean man, presenting with pulmonary embolism, and diffuse arterial thrombosis of the lower extremities. CT angiography revealed bilateral pulmonary artery occlusions and a mediastinal lymphadenopathy. Duplex Ultrasound of the lower extremities showed no deep venous thrombosis, but occluded popliteal arteries bilaterally with extension to the right distal superficial femoral artery. Mediastinoscopy with hilar lymph node biopsy showed noncaseating granulomas consistent with sarcoidosis. Thrombophilia profile revealed factor II, MTHFR, and factor XIII gene mutations with markedly elevated homocysteine level of 139 μmol/l. This is an atypical rare case of sarcoidosis presenting with pulmonary embolism and multiple arterial thrombosis. T. J. Rebeiz and R. Mahfouz contributed equally to the work and should both be considered as first authors.