Plant cytokinin analogues with inhibitory activity on cyclin-dependent kinases exert their antiproliferative effect through induction of apoptosis initiated by the mitochondrial pathway: determination by a multiparametric flow cytometric analysis

OBJECTIVE: Regulation of the cell cycle by cyclin-dependent kinase (CDK) activity occurs at multiple levels and is often altered in human cancers. Therefore, CDK activity has been targeted for drug discovery, and a number of small molecules have now been identified as CDK inhibitors. Plant cytokinin analogues with CDK inhibitory activity and antiproliferative effects were studied to characterize the cellular basis of the cytotoxic effect. METHODS: The IC(50) value (concentration at which 50% of the cell proliferation is inhibited) and AC(50) value (concentration at which 50% of the cell population is apoptotic) were determined by flow cytometry and microscopy, respectively. A new multiparametric flow cytometric analysis was used to study the sequence of different apoptotic events. In this assay, analysis of phosphatidylserine exposure, mitochondrial membrane depolarization, activation of caspases and DNA condensation were combined. RESULTS: Treatment of Jurkat and KG1 cells with the CDK inhibitors results in a decrease of viable cells and a parallel increase in percentage of apoptotic cells. Apoptosis was accompanied by a rapid decrease of mitochondrial membrane potential, which precedes DNA condensation, exposure of phosphatidylserine and activation of caspases. CONCLUSIONS: The main cellular mechanism of the antiproliferative effect of plant cytokinin analogues with CDK inhibitory activity is the induction of apoptosis. The multiparametric flow cytometric technique allowed to follow the kinetics of various aspects of apoptotic cell changes and demonstrated that cytokinin analogue-induced apoptosis starts through the mitochondrial pathway. This technique could also become of value for the rapid screening of pro-apoptotic properties of chemotherapeutic compounds.     

The hormonal activity of the postmenopausal ovary.

The origin of plasma sex hormones in postmenopausal women was studied by determining plasma levels under basal conditions, after ACTH stimulation, and after dexamethasone suppression, as well as after hCG stimulation. Values obtained in postmenopausal women were compared with values observed during the follicular phase of the cycle in young women on the one hand, and with values in ovariectomized women of postmenopausal age on the other hand. All sex steroid levels studied with the exception of estrone, were significantly lower in postmenopausal women than in young women during the early follicular phase of the cycle. In ovariectomized women only androgen levels (testosterone, androstenedione, dihydrotestosterone, and to a lesser extent dehydroepiandrosterone,) were lower than in normal postmenopausal women, estrogen, 17 hydroxyprogesterone, and progesterone levels being similar. ACTH increased all plasma steroid levels except estradiol, whereas after dexamethasone, all sex hormone levels were significantly decreased. hCG stimulation finally caused an increase of borderline statistical significance in testosterone, dehydroepiandrosterone, and 17-hydroxyprogesterone levels. We have concluded from this study that the adrenal cortex is almost the exclusive source of plasma estradiol, estrone, progesterone, and 17OH progesterone and the most important source of plasma dehydroepiandrosterone; that the postmenopausal ovary appears to be responsible for about 50% of plasma testosterone and 30% of androstenedione levels; and that hCG stimulation with 5000 IU daily for 3 days, hardly influences steroid secretion by postmenopausal ovaries.     

Isolated rupture of the left atrial appendage after blunt chest trauma

Traumatic cardiac damage is caused by penetrating or blunt injury.The majority of disruptures in blunt trauma are the result of deceleration traumas.We present the case of an 8-year-old boy who fell off his horse. Afterwards the horse stepped on his chest. He was successfully treated for pericardial tamponade due to an isolated left appendage rupture. The lesion was probably caused by a sudden elevated intra-atrial blood pressure during chest compression.     

From classical sternotomy to truly endoscopic mitral valve surgery: a step by step procedure

Background: There is an increasing tendency towards minimally invasive valve surgery and various surgical techniques have been proposed to realise this goal. The aim of the present study was to describe our current surgical technique and clinical experience with respect to an endoscopic technique that allows the surgeon to perform an operation through a series of small intercostal ports.

Methods: After a learning experience with thoracoscopic left internal mammary to left anterior descending coronary artery bypass surgery, we adopted the endocardiopulmonary bypass technique to perform mitral valve surgery. The technique requires exclusive use of video-assisted surgery and control by transoesophageal echocardiography (TEE). Surgery requires long instruments and extra-corporeal knot tying. Between February 1997 and November 2001, 259 patients were operated on. Mitral valve repair was performed in 190 of them. One patient had a redo procedure using this approach to correct a paravalvular leak, but all other procedures were primary interventions.

Results: In all patients, surgery was performed using a 2 inch working port and two additional half-inch trocar-ports. Five patients required a conversion to median sternotomy: three because of inadequate size of the femoral vessels and two because of intraoperative aortic dissection. Hospital mortality included two patients, and seven patients required late reoperation (four of these were as a result of endocarditis).

Conclusions: Endoscopic mitral valve surgery is demanding, but feasible. Once the appropriate skills are acquired, both patient and surgeon can enjoy the benefits of this exciting new technique.