Contributions toward understanding the biodiversity of Passiflora in North America: Updates and a new combination from the Baja California Peninsula,Mexico and vicinity

The Baja California Peninsula and surrounding landmasses harbor an abundant flora in an otherwise harsh and arid environment. Of the many plant groups native to this peninsular and insular region, passionflowers (Passiflora, Passifloraceae) are represented by several conspicuous taxa that all belong to a single lineage, section Dysosmia. Basic questions remain regarding this group, particularly the taxonomic status among the Passiflora arida complex. Therefore, we investigated the claims of endemism, habitat characteristics, and taxon boundaries with in section Dysosmia in the Baja California region using extensive sampling of herbarium specimens and iNaturalist observations. We confirmed that only one of the native Passiflora taxa (P. fruticosa) was endemic to the Baja California Peninsula, with an additional taxon (P. palmeri) considered near‐endemic. Environmental data revealed significant distinctions between the habitats of many of the native taxa as well as within the P. arida complex, especially with respect to precipitation and temperature tolerances. Geometric morphometric analyses of leaf shape were largely not successful at separating taxa, indicating leaf shape may not be a good indicator of taxon identity in this particular group. Based on ecological differences and discrete macro‐ and micromorphological features, a varietal name is here synonymized and a new combination is proposed: Passiflora pentaschista.     

p21(Cip1) and p27(Kip1) regulate cell cycle reentry after hypoxic stress but are not necessary for hypoxia-induced arrest

We investigated the role of the cyclin-dependent kinase inhibitors p21(Cip1) and p27(Kip1) in cell cycle regulation during hypoxia and reoxygenation. While moderate hypoxia (1 or 0.1% oxygen) does not significantly impair bromodeoxyuridine incorporation, at very low oxygen tensions (0.01% oxygen) DNA replication is rapidly shut down in immortalized mouse embryo fibroblasts. This S-phase arrest is intact in fibroblasts lacking the cyclin kinase inhibitors p21(Cip1) and p27(Kip1), indicating that these molecules are not essential elements of the arrest pathway. Hypoxia-induced arrest is accompanied by dephosphorylation of pRb and inhibition of cyclin-dependent kinase 2, which results in part from inhibitory phosphorylation. Interestingly, cells lacking the retinoblastoma tumor suppressor protein also display arrest under hypoxia, suggesting that pRb is not an essential mediator of this response. Upon reoxygenation, DNA synthesis resumes by 3.5 h and reaches aerobic levels by 6 h. Cells lacking p21, however, resume DNA synthesis more rapidly upon reoxygenation than wild-type cells, suggesting that this inhibitor may play a role in preventing premature reentry into the cell cycle upon cessation of the hypoxic stress. While p27 null cells did not exhibit rapid reentry into the cell cycle, cells lacking both p21 and p27 entered S phase even more aggressively than those lacking p21 alone, revealing a possible secondary role for p27 in this response. Cdk2 activity is also restored more rapidly in the double-knockout cells when returned to normoxia. These studies reveal that restoration of DNA synthesis after hypoxic stress, but not the S phase arrest itself, is regulated by p21 and p27.     

Caveolin 1-mediated regulation of receptor tyrosine kinase-associated phosphatidylinositol 3-kinase activity by ceramide

Previous studies have indicated that proapoptotic stresses downregulate the phosphatidylinositol 3-kinase [PI(3)K]/Akt survival pathway via the activation of acid-sphingomyelinase (A-SMase) and ceramide production. Ceramide induces apoptosis and inhibits PI(3)K activity without altering expression, association, or phosphorylation of receptors, adapter proteins, or PI(3)K subunits. PI(3)K inhibition by ceramide is associated with recruitment of caveolin 1 to PI(3)K-associated receptor complexes within lipid raft microdomains. Overexpression of caveolin 1 alone is sufficient to alter PI(3)K activity and sensitizes fibroblasts to ceramide-induced cell death. Most importantly, antisense expression of caveolin 1 dramatically reduces ceramide-induced PI(3)K deregulation and results in a loss-of-function stress response similar to that in A-SMase-deficient cells. Stress-induced recruitment of caveolin 1 to receptor complexes was found to be dependent on A-SMase since cell lines deficient in A-SMase did not exhibit caveolin 1 association with PI(3)K receptor complexes. Thus, a genetic link between A-SMase activation and caveolin 1-induced inhibition of PI(3)K activity exists. These results led us to propose that stress-induced changes in raft microdomains lead to altered receptor tyrosine kinase signal transduction through the modulation of caveolin 1 by ceramide.     

Comparison of hypoxia-induced replication arrest with hydroxyurea and aphidicolin-induced arrest

Severe levels of hypoxia (oxygen concentrations of less that 0.02%) have been shown to induce a rapid S-phase arrest. The mechanism behind hypoxia-induced S-phase arrest is unclear, we show here that it was not mediated by a shortage of nucleosides and was not dependent on p53, p21 or Hif 1alpha status. The drugs aphidicolin and hydroxyurea both induce rapid replication arrest and have been used throughout the literature to study the ATR-mediated response to stalled replication. We have shown previously that hypoxia induces ATR-dependent phosphorylation of p53, Chk1 and histone H2AX. Using comet-assays to detect DNA-damage we found that both aphidicolin and hydroxyurea induced significant levels of DNA-damage while hypoxia did not. Here we show that like aphidicolin and hydroxyurea, hypoxia induces phosphorylation of Nbs1 at serine 343 and Rad17 serine 645. Hypoxia-dependent phosphorylation of Nbs1 and Rad17 was ATM-independent and therefore likely to be a result of the ATR kinase activity. In contrast, p53 was phosphorylated differentially in response to the three treatments considered here. p53 was phosphorylated at serine 15 in response to all three treatments but was only phosphorylated at serine 20 in response to the drug treatments. We propose that treatment with either aphidicolin or hydroxyurea leads to not only replication arrest but also DNA-damage and therefore both ATM and ATR-mediated signaling. In contrast replication arrest induced by severe hypoxia is sensed exclusively through ATR, with ATM only having a role to play after re-oxygenation.     

Dead cells don't form tumors: HIF-dependent cytotoxins

Elimination or reduction of tumor burden is the primary goal of cancer therapy. Strategies to achieve this goal with the fewest adverse effects to the patient are an area of intense investigation. Elevated protein levels of hypoxia-inducible factor (HIF) are commonly found in solid tumors, while rarely found in healthy tissue. Numerous studies have suggested that HIF activity is essential for the development of solid tumors. Thus, inhibition of HIF represents an attractive therapeutic target for eradicating tumors. The search for small molecules that target and inhibit HIF activity is currently underway. We propose an alternate approach: to directly target and kill HIF-activated tumor cells. This approach is advantageous in that cells with activated HIF will be eliminated directly. Specific elimination of HIF-activated cells represents a potential mechanism for inhibiting tumor growth, with the potential advantage of sparing the patient of the normal tissue toxicity associated with current treatment options.     

Home-based versus hospital-based cardiac rehabilitation after myocardial infarction or revascularisation: design and rationale of the Birmingham Rehabilitation Uptake Maximisation Study (BRUM): a randomised controlled trial [ISRCTN72884263]

Background

Cardiac rehabilitation following myocardial infarction reduces subsequent mortality, but uptake and adherence to rehabilitation programmes remains poor, particularly among women, the elderly and ethnic minority groups. Evidence of the effectiveness of home-based cardiac rehabilitation remains limited. This trial evaluates the effectiveness and cost-effectiveness of home-based compared to hospital-based cardiac rehabilitation.

Methods/design

A pragmatic randomised controlled trial of home-based compared with hospital-based cardiac rehabilitation in four hospitals serving a multi-ethnic inner city population in the United Kingdom was designed. The home programme is nurse-facilitated, manual-based using the Heart Manual. The hospital programmes offer comprehensive cardiac rehabilitation in an out-patient setting.

Patients

We will randomise 650 adult, English or Punjabi-speaking patients of low-medium risk following myocardial infarction, coronary angioplasty or coronary artery bypass graft who have been referred for cardiac rehabilitation.

Main outcome measures

Serum cholesterol, smoking cessation, blood pressure, Hospital Anxiety and Depression Score, distance walked on Shuttle walk-test measured at 6, 12 and 24 months. Adherence to the programmes will be estimated using patient self-reports of activity. In-depth interviews with non-attendees and non-adherers will ascertain patient views and the acceptability of the programmes and provide insights about non-attendance and aims to generate a theory of attendance at cardiac rehabilitation. The economic analysis will measure National Health Service costs using resource inputs. Patient costs will be established from the qualitative research, in particular how they affect adherence.

Discussion

More data are needed on the role of home-based versus hospital-based cardiac rehabilitation for patients following myocardial infarction and revascularisation, which would be provided by the Birmingham Rehabilitation Uptake Maximisation Study (BRUM) study and has implications for the clinical management of these patients. A novel feature of this study is the inclusion of non-English Punjabi speakers.     

NADPH-oxidase-driven oxygen radical production determines chondrocyte death and partly regulates metalloproteinase-mediated cartilage matrix degradation during interferon-γ-stimulated immune complex arthritis

In previous studies we have found that FcγRI determines chondrocyte death and matrix metalloproteinase (MMP)-mediated cartilage destruction during IFN-γ-regulated immune complex arthritis (ICA). Binding of immune complexes (ICs) to FcγRI leads to the prominent production of oxygen radicals. In the present study we investigated the contribution of NADPH-oxidase-driven oxygen radicals to cartilage destruction by using p47phox^-/- mice lacking a functional NADPH oxidase complex. Induction of a passive ICA in the knee joints of p47phox^-/- mice resulted in a significant elevation of joint inflammation at day 3 when compared with wild-type (WT) controls as studied by histology. However, when IFN-γ was overexpressed by injection of adenoviral IFN-γ in the knee joint before ICA induction, a similar influx of inflammatory cells was found at days 3 and 7, comprising mainly macrophages in both mouse strains. Proteoglycan depletion from the cartilage layers of the knee joints in both groups was similar at days 3 and 7. Aggrecan breakdown in cartilage caused by MMPs was further studied by immunolocalisation of MMP-mediated neoepitopes (VDIPEN). VDIPEN expression in the cartilage layers of arthritic knee joints was markedly lower (between 30 and 60%) in IFN-γ-stimulated arthritic p47phox^-/- mice at day 7 than in WT controls, despite significant upregulation of mRNA levels of various MMPs such as MMP-3, MMP-9, MMP-12 and MMP-13 in synovia and MMP-13 in cartilage layers as measured with quantitative RT-PCR. The latter observation suggests that oxygen radicals are involved in the activation of latent MMPs. Chondrocyte death, determined as the percentage of empty lacunae in articular cartilage, ranged between 20 and 60% at day 3 and between 30 and 80% at day 7 in WT mice, and was completely blocked in p47phox^-/- mice at both time points. FcγRI mRNA expression was significantly lower, and FcγRII and FcγRIII were higher, in p47phox^-/- mice than in controls. NADPH-oxidase-driven oxygen radical production determines chondrocyte death and aggravates MMP-mediated cartilage destruction during IFN-γ-stimulated IC-mediated arthritis. Upregulation of FcγRI by oxygen radicals may contribute to cartilage destruction.