Somatic cell cloning: the ultimate form of nuclear reprogramming?

With the increasing difficulties associated with meeting the required needs for organs used in transplantation, alternative approaches need to be considered. These include the use of stem cells as potential sources of specialized cells, the ability to transdifferentiate cell types in culture, and the development of complete organs that can be used in humans. All of the above goals will require a complete understanding of the factors affecting cell differentiation and nuclear reprogramming. To make this a reality, however, techniques associated with cloning and genetic modifications in somatic cells need to be continued to be developed and optimized. This includes not only an enhancement of the rate of homologous recombination in somatic cells, but also a thorough understanding of the nuclear reprogramming process taking place during nuclear transfer. The understanding of this process is likely to have an effect beyond the area of nuclear transfer and assist with better methods for transdifferentiation of mammalian cells.     

Immunosuppression after kidney transplantation: current stragegies and drug interactions

The success of kidney transplantation has improved over the last decade largely due to new immunosuppressive agents that resulted in decrease in incidence and severity of acute cellular rejection. Minimizing the adverse effects of immunosuppressive agents is essential to improving long-term survival. This article reviews the current immunosuppressive agents available to the clinician, their side effects and interaction with other medications. Current immunosuppressive protocols are also discussed including newer steroid avoidance protocols and calcineurin avoidance protocol.     

Seminal clotting and fibrinolytic balance: a possible physiological role in the male reproductive system

Semen contains enzymes and inhibitors of the haemostatic system as well as the high molecular weight seminal vesicle (HMW-SV) proteins. The former may have roles in seminal clotting and in liquefaction through "fibrinolytic" activity, which may ultimately affect fertility. Although a limited number of studies have addressed the subject, the role of clotting and fibrinolytic factors in semen remains poorly understood. The liquefaction time and the distribution of components vary across split ejaculates. This may have an important bearing on the way clotting/fibrinolytic factors in semen are assessed. Semen contains tissue factor (TF, Thromboplastin, CD142), which originates from the prostate and is associated with prostasomes. The function of TF (and prostasomes) in semen is still a matter for speculation. Recently the presence of minute amounts of factor VII in semen has been demonstrated but its importance is uncertain. Semen also contains a thrombin-like enzyme, prothrombin fragments 1 and 2 (F1+2), D-dimer (DD) and thrombin-antithrombin (TAT) complexes. The presence of several fibrinolytic factors has been demonstrated in semen but few questions about their potential impact on semen quality have been raised. Factors found include tissue plasminogen activator (t-PA), urinary plasminogen activator (u-PA) and plasmin. There are also traces of fibrinogen, plasminogen, plasminogen activator inhibitor-1 (PAI-1), factor VIII coagulant activity (VIII:c) and fibrin monomers. The co-ordinate expression of both TF and PAI-1 by decidual cells of the endometrium is believed to be important in maintaining haemostasis during endovascular trophoblast invasion. Kallikrein-like serine protease inhibitors including prostate specific antigen (PSA) are known to be present in semen at high concentrations. In semen PSA is also found in a complex form with protein C inhibitor (PCI) with mutually inhibitory consequences. A better understanding of the spectrum of coagulating and liquefaction agents in semen to include classical haemostatic processes and the pathogenesis resulting from any imbalances between or within either system may provide the basis for the development of more selective and efficient agents affecting global fertility. Here we review aspects of male reproductive physiology in the light of recent findings concerning conventional clotting/fibrinolytic systems in human semen with a view to stimulating further research.     

Epsilon protein kinase C lengthens the quiescent period between spontaneous contractions in rat ventricular cardiac myocytes and trabecula

We have observed a lengthening of the duration between spontaneous cardiac contractions under conditions that preferentially activate the epsilon protein kinase C (PKC) isozyme. Therefore, we investigated whether this response could be selectively mediated by PKC in neonatal cardiac myocytes (NCMs) and adult rat ventricular trabeculae. Contraction of NCMs was monitored using light scattering techniques and trabecular force generation was monitored in tissue baths using a force transducer. The involvement of the PKC isozyme was confirmed using an PKC-selective translocation inhibitor and Western blot translocation assays. In NCMs 3 nM 4- phorbol 12-myristate-13-acetate (PMA) treatment preferentially activates (translocates) PKC. In this study 3 nM 4- PMA induced a 2-fold increase in contractile amplitude and a 14-fold increase in the quiescent period between contractions in NCMs. Extracellular adenosine 5-triphosphate (ATP) also enhanced contractile amplitude by 1.7-fold and the quiescent period duration by 8-fold. The enhancement of quiescent period duration was attenuated by an PKC-selective translocation inhibitor. To investigate these relationships in intact myocardium, we studied spontaneously beating adult rat ventricular trabecula. In these fibers contractile amplitude was only modestly enhanced; however, the quiescent period was lengthened by 4.5-fold following a 15-min exposure to 3 nM 4- PMA. 4- PMA treatment also promoted arrhythmogenesis and increased the association of PKC with the particulate fraction in these fibers. Our results suggest that PKC may influence a specific phase of ventricular myocyte spontaneous beating. A better understanding of PKC modulation of spontaneous cardiac contraction may improve our understanding of the molecular events contributing to ventricular automaticity.     

Diagnosis and treatment of bacterial meningitis

This review focuses on recent advances of topical interest regarding the diagnosis and treatment of common causes of bacterial meningitis occurring in children beyond the neonatal period. Tuberculous meningitis is beyond the scope of this review.