Characterization of a PRL protein tyrosine phosphatase from Plasmodium falciparum

Isoprenylated proteins have important functions in cell growth and differentiation of eukaryotic cells. Inhibitors of protein prenylation in malaria have recently shown strong promise as effective antimalarials. In studying protein prenylation in the malaria protozoan parasite Plasmodium falciparum, we have shown earlier that the incubation of P. falciparum cells with (3)H-prenol precursors resulted in various size classes of labeled proteins. To understand the physiological function of prenylated proteins of malaria parasites, that are targets of prenyltransferase inhibitors, we searched the PlasmoDB database for proteins containing the C-terminus prenylation motif. We have identified, among other potentially prenylated proteins, an orthologue of a PRL (protein of regenerating liver) subgroup protein tyrosine phosphatases, termed PfPRL. Here, we show that PfPRL is expressed in the parasite's intraerythrocytic stages, where it partially associates with endoplasmic reticulum and within a subcompartment of the food vacuole. Additionally, PfPRL targeting parallels that of apical membrane antigen-1 in developing merozoites. Recombinant PfPRL shows phosphatase activity that is preferentially inhibited by a tyrosine phosphatase inhibitor suggesting that PfPRL functions as a tyrosine phosphatase. Recombinant PfPRL can also be farnesylated in vitro. Inhibition of malarial farnesyltransferase activity can be achieved with the heptapetide RKCHFM, which corresponds to the C-terminus of PfPRL. This study provides the first evidence for expression of enzymatically active PRL-related protein tyrosine phosphatases in malarial parasites, and demonstrates the potential of peptides derived from Plasmodium prenylated proteins as malarial farnesyltransferase inhibitors.     

Sustained expression of microRNA-155 in hematopoietic stem cells causes a myeloproliferative disorder

Mammalian microRNAs are emerging as key regulators of the development and function of the immune system. Here, we report a strong but transient induction of miR-155 in mouse bone marrow after injection of bacterial lipopolysaccharide (LPS) correlated with granulocyte/monocyte (GM) expansion. Demonstrating the sufficiency of miR-155 to drive GM expansion, enforced expression in mouse bone marrow cells caused GM proliferation in a manner reminiscent of LPS treatment. However, the miR-155-induced GM populations displayed pathological features characteristic of myeloid neoplasia. Of possible relevance to human disease, miR-155 was found to be overexpressed in the bone marrow of patients with certain subtypes of acute myeloid leukemia (AML). Furthermore, miR-155 repressed a subset of genes implicated in hematopoietic development and disease. These data implicate miR-155 as a contributor to physiological GM expansion during inflammation and to certain pathological features associated with AML, emphasizing the importance of proper miR-155 regulation in developing myeloid cells during times of inflammatory stress.     

Decline of serum HBV DNA and no change apportioned by the same hepatic parenchyma cell volume from hepatic fibrosis stage 1 to stage 4 during the natural history of chronic hepatitis B

During the initial phase of chronic hepatitis B virus (HBV) infection, serum HBV DNA levels are high. Contrarily, fibrosis, cirrhosis and hepatocellular carcinoma have been found in patients with lower serum HBV DNA levels. The aim of this study is to clarify HBV DNA level dynamics of serum apportioned by the same hepatic parenchyma cell volume (HPCV) in hepatic fibrosis stages 1-4 during the natural history of chronic hepatitis B. Serum HBV DNA levels were evaluated by real-time polymerase chain reaction. Further, serum HBV DNA levels were apportioned by and compared with the same HPCV in hepatic fibrosis stages 1-4, respectively. Serum HBV DNA levels were 8.91 x 10(6) +/- 4.37 x 10(1), 8.13 x 10(6) +/- 7.41 x 10(1), 9.55 x 10(5) +/- 1.02 x 10(2), and 4.07 x 10(5) +/- 7.24 x 10(1) copies/ml, respectively; there were differences among hepatic fibrosis stages 1-4 (p < 0.021-0.000). However, serum HBV DNA levels apportioned by the same volume of hepatic parenchyma cells in hepatic fibrosis stages 1-4 were 3.47 x 10(10) +/- 8.71 x 10(2), 1.02 x 10(11) +/- 9.55 x 10(2), 1.41 x 10(10) +/- 2.57 x 10(3), and 3.72 x 10(10) +/- 3.02 x 10(3) with HPCV proportions 65.9, 62.7, 58.9, and 53.3%, respectively; there were no differences among hepatic fibrosis stages 1-4 (p > 0.203-0.967).Following the progression of hepatic fibrosis from stage 1 to 4, ongoing decline of HPCV is responsible for a declining trend of serum HBV DNA levels.     

Alternative sources of pluripotent stem cells: scientific solutions to an ethical dilemma

Stem cell researchers in the United States have faced a quagmire of uncertainty due to multiple factors: the ethical divide over the use of embryos for research, the lack of clarity in federal guidelines governing this research, the restrictive patent situation surrounding the generation of new human embryonic stem (HES) cell lines; and the limits on types of research eligible for federal funding. In this commentary, we describe how recent advances in derivation of hES cell-like lines may allow at least some of these uncertainties to be resolved. More importantly, we suggest that the derivation of hES cell-like lines by morally acceptable methods would not only avoid the corrosive effects of a protracted ethical debate over stem cell research, but would also allow U.S. researchers to access federal funds and compete on a more level international playing field.     

Validation and quantification of an in vitro model of continuous infusion of submicron-sized particles

Wear particles produced from total joint replacements have been shown to stimulate a foreign body and chronic inflammatory reaction that results in periprosthetic osteolysis. Most animal models that simulate these events have used a single injection of particles, which is not representative of the clinical scenario, in which particles are continuously generated. The goal of this study was to evaluate the feasibility of an osmotic pump for the continuous delivery of clinically relevant submicron-sized particles over an extended period of time. Blue-dyed polystyrene particles and retrieved ultra-high molecular weight polyethylene (UHMWPE) particles, both suspended in mouse serum, were loaded into an Alzet mini-osmotic pump. Pumps were attached to vinyl tubing that ended with hollow titanium rods, simulating a metal implant, which was suspended in a collection vessel. The number of particles collected was evaluated over 2- and 4-week time periods. Delivery of both the polystyrene and UHMWPE particles was feasible over pump concentrations of 10(9) to 10(11) particles per pump. Furthermore, delivery efficiency of polystyrene particles decreased with increasing initial particle concentration, whereas delivery efficiency of UHMWPE particles increased slightly with increasing initial particle concentration. For UHMWPE, approximately one-third of the particles in the pump were collected at 4 weeks. This in vitro study has quantified the efficiency of a unique particle pumping system that may be used in future in vivo investigations to develop a murine model of continuous particle infusion.     

Eliminating toe-fixing pattern can improve standing and gait pattern of children with cerebral palsy in a qualitative way

Toe-fixing pattern has been observed to be a compensatory strategy for children with cerebral palsy (CP) to gain body stability. It has been shown that application of toe sponges could eliminate the toe fixing, and thus would force the children with CP to use the potential resources of their impaired postural system. The aim of this study was to investigate the immediate regression and treatment effects of toe-sponges application on standing and walking patterns in children with CP. A controlled experimental study was conducted, involving 24 school-aged children with CP who were ambulatory with or without walking aids. Twelve children in the experimental group wore toe sponges for 3 weeks whereas the other 12 children in the control group did not. The results did not show a significant difference indicating immediate regression after application of toe sponges in all children or a treatment effect in the experimental group after wearing the toe sponges for 3 weeks. Qualitative improvement of walking pattern in the experimental group was, however, observed. It was believed that the effect of toe-sponge application on improving the standing and walking patterns in children with CP was masked by the children shifting the compensation from toe flexion to the other body parts. Issues that need to be considered in the further studies were suggested.     

NOTES: human experience

Human natural orifice translumenal endoscopic surgery (NOTES) is already being reported from numerous centers, and the results seem promising. There are key issues to be addressed and benefits over traditional safe procedures need to be demonstrated. Interestingly, however, human NOTES seem to be progressing at a fast pace compared with the evolution of surgical procedures or techniques described previously. This article examines the current status of NOTES in humans, the challenges, and the implications on the future of minimal access surgery.