Platelet-Induced Clumping of Plasmodium falciparum–Infected Erythrocytes from Malawian Patients with Cerebral Malaria—Possible Modulation In Vivo by Thrombocytopenia

Platelets may play a role in the pathogenesis of human cerebral malaria (CM), and they have been shown to induce clumping of Plasmodium falciparum–parasitized red blood cells (PRBCs) in vitro. Both thrombocytopenia and platelet-inducedPRBCclumping are associated with severe malaria and, especially, withCM.In the present study, we investigated the occurrence of the clumping phenomenon in patients with CM by isolating and coincubating their plasma and PRBCs ex vivo. Malawian children with CM all had low platelet counts, with the degree of thrombocytopenia directly proportional to the density of parasitemia. Plasma samples obtained from these patients subsequently induced weak PRBC clumping. When the assays were repeated, with the plasma platelet concentrations adjusted to within the physiological range considered to be normal, massive clumping occurred. The results of this study suggest that thrombocytopenia may, through reduction of platelet-mediated clumping of PRBCs, provide a protective mechanism for the host during CM

Genome-wide assessment of antimicrobial tolerance in Yersinia pseudotuberculosis under ciprofloxacin stress.

Yersinia pseudotuberculosis is a Gram-negative bacterium capable of causing gastrointestinal infection and is closely related to the highly virulent plague bacillus Yersinia pestis. Infections by both species are currently treatable with antibiotics such as ciprofloxacin, a quinolone-class drug of major clinical importance in the treatment of many other infections. Our current understanding of the mechanism of action of ciprofloxacin is that it inhibits DNA replication by targeting DNA gyrase, and that resistance is primarily due to mutation of this target site, along with generic efflux and detoxification strategies. We utilized transposon-directed insertion site sequencing (TraDIS or TnSeq) to identify the non-essential chromosomal genes in Y. pseudotuberculosis that are required to tolerate sub-lethal concentrations of ciprofloxacin in vitro. As well as highlighting recognized antibiotic resistance genes, we provide evidence that multiple genes involved in regulating DNA replication and repair are central in enabling Y. pseudotuberculosis to tolerate the antibiotic, including DksA (yptb0734), a regulator of RNA polymerase, and Hda (yptb2792), an inhibitor of DNA replication initiation. We furthermore demonstrate that even at sub-lethal concentrations, ciprofloxacin causes severe cell-wall stress, requiring lipopolysaccharide lipid A, O-antigen and core biosynthesis genes to resist the sub-lethal effects of the antibiotic. It is evident that coping with the consequence(s) of antibiotic-induced stress requires the contribution of scores of genes that are not exclusively engaged in drug resistance

A novel malaria vaccine candidate antigen expressed in Tetrahymena thermophila

Development of effective malaria vaccines is hampered by the problem of producing correctly folded Plasmodium proteins for use as vaccine components. We have investigated the use of a novel ciliate expression system, Tetrahymena thermophila, as a P. falciparum vaccine antigen platform. A synthetic vaccine antigen composed of N-terminal and C-terminal regions of merozoite surface protein-1 (MSP-1) was expressed in Tetrahymena thermophila. The recombinant antigen was secreted into the culture medium and purified by monoclonal antibody (mAb) affinity chromatography. The vaccine was immunogenic in MF1 mice, eliciting high antibody titers against both N- and C-terminal components. Sera from immunized animals reacted strongly with P. falciparum parasites from three antigenically different strains by immunofluorescence assays, confirming that the antibodies produced are able to recognize parasite antigens in their native form. Epitope mapping of serum reactivity with a peptide library derived from all three MSP-1 Block 2 serotypes confirmed that the MSP-1 Block 2 hybrid component of the vaccine had effectively targeted all three serotypes of this polymorphic region of MSP-1. This study has successfully demonstrated the use of Tetrahymena thermophila as a recombinant protein expression platform for the production of malaria vaccine antigens

Polyphenols act synergistically with doxorubicin and etoposide in leukaemia cell lines

The study aimed to assess the effects of polyphenols when used in combination with doxorubicin and etoposide, and to determine whether polyphenols sensitised leukaemia cells, causing inhibition of cell proliferation, cell cycle arrest and induction of apoptosis. This study is based on findings in solid cancer tumours, which have shown that polyphenols can sensitize cells to chemotherapy, and induce apoptosis and/or cell-cycle arrest. This could enable a reduction of chemotherapy dose and off-target effects, whilst maintaining treatment efficacy. Quercetin, apigenin, emodin, rhein and cis-stilbene were investigated alone and in combination with etoposide and doxorubicin in two lymphoid and two myeloid leukaemia cells lines. Measurements were made of ATP levels (using CellTiter-Glo assay) as an indication of total cell number, cell cycle progression (using propidium iodide staining and flow cytometry) and apoptosis (NucView caspase 3 assay and Hoechst 33342/propidium iodide staining). Effects of combination treatments on caspases 3, 8 and 9 activity were determined using Glo luminescent assays, glutathione levels were measured using the GSH-Glo Glutathione Assay and DNA damage determined by anti-γH2AX staining. Doxorubicin and etoposide in combination with polyphenols synergistically reduced ATP levels, induced apoptosis and increased S and/or G2/M phase cell cycle arrest in lymphoid leukaemia cell lines. However, in the myeloid cell lines the effects of the combination treatments varied; doxorubicin had a synergistic or additive effect when combined with quercetin, apigenin, emodin, and cis-stilbene, but had an antagonistic effect when combined with rhein. Combination treatment caused a synergistic downregulation of glutathione levels and increased DNA damage, driving apoptosis via caspase 8 and 9 activation. However, in myeloid cells where antagonistic effects were observed, this was associated with increased glutathione levels and a reduction in DNA damage and apoptosis. This study has demonstrated that doxorubicin and etoposide activity were enhanced by polyphenols in lymphoid leukaemia cells, however, differential responses were seen in myeloid cells with antagonistic responses seen in some combination therapies

Mineralisation of crop residues on the soil surface or incorporated in the soil under controlled conditions

In the present work, we compare the effect of mature crop residues mixed into a ferralitic soil or placed as a single layer on soil surface on the mineralisation of C and N over 55 days. As residues, we used dry stems of rice, soybean, sorghum, brachiaria and wheat. There were no significant effects of residue placement on C mineralisation kinetics. Decomposition of the residues on the soil surface slightly increased net N mineralisation for residues having the smallest C/N ratio

Therapeutic Benefit of Radial Optic Neurotomy in a Rat Model of Glaucoma

Radial optic neurotomy (RON) has been proposed as a surgical treatment to alleviate the neurovascular compression and to improve the venous outflow in patients with central retinal vein occlusion. Glaucoma is characterized by specific visual field defects due to the loss of retinal ganglion cells and damage to the optic nerve head (ONH). One of the clinical hallmarks of glaucomatous neuropathy is the excavation of the ONH. The aim of this work was to analyze the effect of RON in an experimental model of glaucoma in rats induced by intracameral injections of chondroitin sulfate (CS). For this purpose, Wistar rats were bilaterally injected with vehicle or CS in the eye anterior chamber, once a week, for 10 weeks. At 3 or 6 weeks of a treatment with vehicle or CS, RON was performed by a single incision in the edge of the neuro-retinal ring at the nasal hemisphere of the optic disk in one eye, while the contralateral eye was submitted to a sham procedure. Electroretinograms (ERGs) were registered under scotopic conditions and visual evoked potentials (VEPs) were registered with skull-implanted electrodes. Retinal and optic nerve morphology was examined by optical microscopy. RON did not affect the ocular hypertension induced by CS. In eyes injected with CS, a significant decrease of retinal (ERG a- and b-wave amplitude) and visual pathway (VEP N2-P2 component amplitude) function was observed, whereas RON reduced these functional alterations in hypertensive eyes. Moreover, a significant loss of cells in the ganglion cell layer, and Thy-1-, NeuN- and Brn3a- positive cells was observed in eyes injected with CS, whereas RON significantly preserved these parameters. In addition, RON preserved the optic nerve structure in eyes with chronic ocular hypertension. These results indicate that RON reduces functional and histological alterations induced by experimental chronic ocular hypertension

The epidemiology and natural history of depressive disorders in Hong Kong's primary care

Background: Depressive disorders are commonly managed in primary care and family physicians are ideally placed to serve as central providers to these patients. Around the world, the prevalence of depressive disorders in patients presenting to primary care is between 10-20%, of which around 50% remain undiagnosed. In Hong Kong, many barriers exist preventing the optimal treatment and management of patients with depressive disorders. The pathways of care, the long term outcomes and the factors affecting prognosis of these patients requires closer examination. Methods/Design. The aim of this study is to examine the prevalence, incidence and natural history of depressive disorders in primary care and the factors influencing diagnosis, management and outcomes using a cross-sectional study followed by a longitudinal cohort study. Doctors working in primary care settings across Hong Kong have been invited to participate in this study. On one day each month over twelve months, patients in the doctor's waiting room are invited to complete a questionnaire containing items on socio-demography, co-morbidity, family history, previous doctor-diagnosed mental illness, recent mental and other health care utilization, symptoms of depression and health-related quality of life. Following the consultation, the doctors provide information regarding presenting problem, whether they think the patient has depression, and if so, whether the diagnosis is new or old, and the duration of the depressive illness if not a new diagnosis. If the doctor detects a depressive disorder, they are asked to provide information regarding patient management. Patients who consent are followed up by telephone at 2, 12, 26 and 52 weeks. Discussion. The study will provide information regarding cross-sectional prevalence, 12 month incidence, remission rate, outcomes and factors affecting outcomes of patients with depressive disorders in primary care. The epidemiology, outcomes, pathways of care, predictors for prognosis and service needs for primary care patients with depressive disorders will be described and recommendations made for policy and service planning. © 2011 Chin et al; licensee BioMed Central Ltd.published_or_final_versio

A Fat Higgs with a Magnetic Personality

We introduce a novel composite Higgs theory based on confining supersymmetric QCD. Supersymmetric duality plays a key role in this construction, with a "fat" Higgs boson emerging as a dual magnetic degree of freedom charged under the dual magnetic gauge group. Due to spontaneous color-flavor locking in the infrared, the electroweak gauge symmetry is aligned with the dual magnetic gauge group, allowing large Yukawa couplings between elementary matter fields and the composite Higgs. At the same time, this theory exhibits metastable supersymmetry breaking, leading to low-scale gauge mediation via composite messengers. The Higgs boson is heavier than in minimal supersymmetric theories, due to non-decoupling D-terms and a large F-term quartic coupling. This theory predicts quasi-stable TeV-scale pseudo-modulini, some of which are charged under standard model color, possibly giving rise to long-lived R-hadrons at the LHC.Comment: 33 pages, 6 figures, 6 table