While migration of individuals has been shown to increase the persistence of small isolated populations through a process known as the "rescue effect," the demographic effects that pollen-mediated gene flow may have in plant populations are not known empirically. This study investigates the role that inbreeding depression plays in newly colonized populations of a common, dioecious, weedy species, Silene alba. Experimental greenhouse studies presented here show that S. alba displays high levels of inbreeding depression (expressed as lowered germination success) in progeny produced with inbreeding coefficients of 0.125 (half-sib mated), 0.250 (full-sib mated), and 0.375 (second-generation sib mated). In addition, it is shown that the degree of inbreeding depression in 12 natural colonies varies with the degree of isolation from other established populations. Significantly, data from experimental populations showed that gene flow into patches comprised of full sibs was higher than those observed into patches comprised of unrelated individuals and may serve to mitigate the effects of inbreeding depression. It is suggested that population connectivity through pollen-mediated gene flow may have substantial effects on the persistence of isolated colonies and on the spatial structure of a metapopulation in general.

A model of species interactions based on their use of shared resources was proposed in 1972 by Robert MacArthur and later expanded in an article (1980) and a book (1982) by David Tilman. This "resource-ratio theory" has been used to make a number of testable predictions about competition and community patterns. We reviewed 1,333 papers that cite Tilman's two publications to determine whether predictions of the resource-ratio theory have been adequately tested and to summarize their general conclusions. Most of the citations do not directly test the theory: only 26 studies provide well-designed tests of one or more predictions, resulting in 42 individual tests of predictions. Most of these tests were conducted in the laboratory or experimental microcosms and used primary producers in freshwater systems. Overall, the predictions of the resource-ratio theory were supported 75% of the time. One of the primary predictions of the model, that species dominance varies with the ratio of resource availabilities, was supported by 13 of 16 tests, but most other predictions have been insufficiently tested. We suggest that more experimental work in a variety of natural systems is seriously needed, especially studies designed to test predictions related to resource supply and consumption rates.

Summary. We have examined the toxicity and overall outcome of the Medical Research Council UKALL R1 protocol for 256 patients with relapsed childhood acute lymphoblastic leukaemia (ALL). Second remission was achieved in over 95% of patients. Two patients died during induction and seven patients died of resistant disease. The overall actuarial event-free survival (EFS) at 5 years for all patients experiencing a ®rst relapse was 46% (95% CI 40± 52). Duration of ®rst remission, site of relapse, age at diagnosis and sex emerged as factors of prognostic signi®cance. Fiveyear EFS was only 7% for children relapsing in the bone marrow within 2 years of diagnosis, but was 77% for those relapsing without bone marrow involvement > 2´5 years from diagnosis. All analyses in this report are by treatment received. For those receiving chemotherapy alone, the 5-year EFS was 48%; for autologous bone marrow transplantation (BMT), the 5-year EFS was 47%; for unrelated donor BMT, it was 52%; and for related donor BMT, the 5-year EFS was 45%. The groups, however, were not comparable with respect to risk factor pro®le, and therefore direct comparison of EFS is misleading. Adjustment for time to transplant and prognostic factors was used to reduce the effects of biases between treatment groups, but did not suggest bene®t for any particular treatment. There was failure of our planned randomization scheme in this trial with only 9% of those eligible being randomized, which highlights the dif®culties in running randomized trials especially in patients who have relapsed from a previous trial. The optimal treatment for relapsed ALL therefore remains uncertain. Alternative approaches are clearly needed for those with early bone marrow relapse if outcome is to improve.

Background: Surgical mortality data are collected routinely in high-income countries, yet virtually no low-or middle-income countries have outcome surveillance in place. The aim was prospectively to collect worldwide mortality data following emergency abdominal surgery, comparing findings across countries with a low, middle or high Human Development Index (HDI).Methods: This was a prospective, multicentre, cohort study. Self-selected hospitals performing emergency surgery submitted prespecified data for consecutive patients from at least one 2-week interval during July to December 2014. Postoperative mortality was analysed by hierarchical multivariable logistic regression.

Paroxysmal nocturnal haemoglobinuria (PNH) cells are deficient in glycosylphosphatidylinositol (GPI) linked antigens due to a somatic mutation of the PIG-A gene in a haemopoietic stem cell. It appears that a PNH clone reaches detectable proportions only when there is selection in its favour. GPI-deficient T lymphocytes have been identified in patients treated with CAMPATH-1H, a monoclonal antibody against the GPI-linked CD52 molecule. CAMPATH-1H selects for cells that are deficient in CD52 (such as PNH-like cells) promoting the development of a PNH-like clone (analogous to PNH). We report that 10/15 patients with chronic lymphocytic leukaemia developed PNH-like lymphocytes after therapy with CAMPATH-1H. The remaining five patients developed no PNH-like cells at any stage, including one patient who received 12 weeks of therapy. The inactivating PIG-A mutation has been identified in one patient. This mutation was detectable by an extremely sensitive mutation-specific PCR-based analysis in the patient's mononuclear cells prior to CAMPATH-1H therapy. The frequency and phenotype of GPI-deficient lymphocytes after CAMPATH-1H and the detection of a PIG-A mutation in the lymphocytes prior to CAMPATH-1H therapy indicated that such mutations were present in a very small proportion of cells prior to selection in their favour by CAMPATH-1H. This suggests that a large proportion of individuals have cells with PIG-A mutations that are not detectable by flow cytometry and thus may have the potential to develop PNH.

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Introduction: Helicobacter pylori screening and treatment has been proposed as a cost‐effective method of preventing gastric cancer. Aim: To assess, in a randomized controlled trial, the efficacy of therapy in eradicating H. pylori as part of a screening programme, and to report the adverse events associated with this strategy. Methods: Subjects between the ages of 40–49 years were randomly selected from the lists of 36 primary care centres. Participants attended their local practice and H. pylori status was determined by 13C‐urea breath test. Infected subjects were randomized to receive omeprazole 20 mg b.d., clarithromycin 250 mg b.d. and tinidazole 500 mg b.d. for 7 days (OCT) or identical placebos. Eradication was determined by a 13C‐urea breath test 6 months and 2 years after the first visit. Successful eradication was defined as two negative 13C‐urea breath tests or one negative and one missing test. Adverse events and compliance were assessed at the 6‐month visit. Results: A total of 32 929 subjects were invited to attend, 8407 were evaluable, and 2329 (28%) of these were H. pylori‐positive. A total of 1161 subjects were randomized to OCT and 1163 to placebo; over 80% returned for a repeat 13C‐urea breath test on at least one occasion. The eradication rates in those allocated to OCT were as follows: intention‐to‐treat, 710 out of 1161 (61%; 95% confidence interval: 58–64%); evaluable 710 out of 967 (73%; 95% CI: 71–76%); took all medication 645 out of 769 (84%; 95% CI: 81–87%). Adverse events occurred in 45% of the treatment group and in 18% of the placebo group (relative risk 2.5; 95% CI: 2.1–2.9). Compliance, male gender, no antibiotic prescription in the subsequent 2 years and experiencing a bitter taste with the medication were independently associated with treatment success. Conclusions: The OCT regimen has an eradication rate of 61% in intention‐to‐treat analysis and is therefore less successful in treating H. pylori as part of a screening programme compared with hospital studies in dyspeptic patients.

Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. abstract: Pollen dispersal by animals varies extensively because of differences in pollinator visitation rates among plants, dissimilar pollination by the various pollinators that visit individual plants, and stochastic variation in deposition as an individual pollinator disperses a plant's pollen to subsequently visited recipient flowers. Such variation reduces expected female and male success if seed production decelerates with increasing pollen receipt, because less than average receipt diminishes mean seed production more than copious pollination increases it (Jensen's inequality). We report empirical studies of the nature and magnitude of pollen dispersal variance, which provide the basis for a numerical model of the consequences of dispersal for expected seed production. Model fitting revealed that dispersal of Brassica napus pollen by bumblebees and especially butterflies exhibited much more variation than is expected of a binomial process and was best modeled as a beta-binomial process with a constant mean. Overdispersion arose primarily during pollen dispersal by individual insects, since differences between individuals of the same pollinator type were limited. Our model revealed variance limitation as a previously unrecognized, substantial, and ubiquitous component of pollen limitation of seed production. Variance limitation should select for floral traits that increase pollinator visitation, reduce dispersal variance, or reduce the postpollination nonlinearities that cause Jensen's inequality.