Social interaction, noise and antibiotic-mediated switches in the intestinal microbiota

The intestinal microbiota plays important roles in digestion and resistance against entero-pathogens. As with other ecosystems, its species composition is resilient against small disturbances but strong perturbations such as antibiotics can affect the consortium dramatically. Antibiotic cessation does not necessarily restore pre-treatment conditions and disturbed microbiota are often susceptible to pathogen invasion. Here we propose a mathematical model to explain how antibiotic-mediated switches in the microbiota composition can result from simple social interactions between antibiotic-tolerant and antibiotic-sensitive bacterial groups. We build a two-species (e.g. two functional-groups) model and identify regions of domination by antibiotic-sensitive or antibiotic-tolerant bacteria, as well as a region of multistability where domination by either group is possible. Using a new framework that we derived from statistical physics, we calculate the duration of each microbiota composition state. This is shown to depend on the balance between random fluctuations in the bacterial densities and the strength of microbial interactions. The singular value decomposition of recent metagenomic data confirms our assumption of grouping microbes as antibiotic-tolerant or antibiotic-sensitive in response to a single antibiotic. Our methodology can be extended to multiple bacterial groups and thus it provides an ecological formalism to help interpret the present surge in microbiome data.Comment: 20 pages, 5 figures accepted for publication in Plos Comp Bio. Supplementary video and information availabl

IFNAR1-Signalling Obstructs ICOS-mediated Humoral Immunity during Non-lethal Blood-Stage Plasmodium Infection

Funding: This work was funded by a Career Development Fellowship (1028634) and a project grant (GRNT1028641) awarded to AHa by the Australian National Health & Medical Research Council (NHMRC). IS was supported by The University of Queensland Centennial and IPRS Scholarships. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Regulation of MMP2 and MMP9 metalloproteinases by FSH and growth factors in bovine granulosa cells

Matrix metalloproteinases (MMP) are key enzymes involved in tissue remodeling. Within the ovary, they are believed to play a major role in ovulation, and have been linked to follicle atresia. To gain insight into the regulation of MMPs, we measured the effect of hormones and growth factors on MMP2 and MMP9 mRNA levels in non-luteinizing granulosa cells in serum-free culture. FSH and IGF1 both stimulated estradiol secretion and inhibited MMP2 and MMP9 mRNA abundance. In contrast, EGF and FGF2 both inhibited estradiol secretion but had no effect on MMP expression. At physiological doses, none of these hormones altered the proportion of dead cells. Although we cannot link MMP expression with apoptosis, the specific down regulation by the gonadotropic hormones FSH and IGF1 in vitro suggests that excess MMP2 and MMP9 expression is neither required nor desired for follicle development

Padeliporfin vascular-targeted photodynamic therapy versus active surveillance in men with low-risk prostate cancer (CLIN1001 PCM301): an open-label, phase 3, randomised controlled trial

BACKGROUND: Vascular-targeted photodynamic therapy, a novel tissue-preserving treatment for low-risk prostate cancer, has shown favourable safety and efficacy results in single-arm phase 1 and 2 studies. We compared this treatment with the standard of care, active surveillance, in men with low-risk prostate cancer in a phase 3 trial. METHODS: This randomised controlled trial was done in 47 European university centres and community hospitals. Men with low-risk, localised prostate cancer (Gleason pattern 3) who had received no previous treatment were randomly assigned (1:1) to vascular-targeted photodynamic therapy (4 mg/kg padeliporfin intravenously over 10 min and optical fibres inserted into the prostate to cover the desired treatment zone and subsequent activation by laser light 753 nm with a fixed power of 150 mW/cm for 22 min 15 s) or active surveillance. Randomisation was done by a web-based allocation system stratified by centre with balanced blocks of two or four patients. Best practice for active surveillance at the time of study design was followed (ie, biopsy at 12-month intervals and prostate-specific antigen measurement and digital rectal examination at 3-month intervals). The co-primary endpoints were treatment failure (histological progression of cancer from low to moderate or high risk or death during 24 months' follow-up) and absence of definite cancer (absence of any histology result definitely positive for cancer at month 24). Analysis was by intention to treat. Treatment was open-label, but investigators assessing primary efficacy outcomes were masked to treatment allocation. This trial is registered with ClinicalTrials.gov, number NCT01310894. FINDINGS: Between March 8, 2011, and April 30, 2013, we randomly assigned 206 patients to vascular-targeted photodynamic therapy and 207 patients to active surveillance. Median follow-up was 24 months (IQR 24-25). The proportion of participants who had disease progression at month 24 was 58 (28%) of 206 in the vascular-targeted photodynamic therapy group compared with 120 (58%) of 207 in the active surveillance group (adjusted hazard ratio 0·34, 95% CI 0·24-0·46; p<0·0001). 101 (49%) men in the vascular-targeted photodynamic therapy group had a negative prostate biopsy result at 24 months post treatment compared with 28 (14%) men in the active surveillance group (adjusted risk ratio 3·67, 95% CI 2·53-5·33; p<0·0001). Vascular-targeted photodynamic therapy was well tolerated. The most common grade 3-4 adverse events were prostatitis (three [2%] in the vascular-targeted photodynamic therapy group vs one [<1%] in the active surveillance group), acute urinary retention (three [2%] vs one [<1%]) and erectile dysfunction (two [1%] vs three [1%]). The most common serious adverse event in the vascular-targeted photodynamic therapy group was retention of urine (15 patients; severe in three); this event resolved within 2 months in all patients. The most common serious adverse event in the active surveillance group was myocardial infarction (three patients). INTERPRETATION: Padeliporfin vascular-targeted photodynamic therapy is a safe, effective treatment for low-risk, localised prostate cancer. This treatment might allow more men to consider a tissue-preserving approach and defer or avoid radical therapy. FUNDING: Steba Biotech

Avaliação de programa de prevenção de obesidade em adolescentes de escolas públicas

OBJETIVO: Avaliar os efeitos de um programa de prevenção de obesidade sobre práticas alimentares de adolescentes de escolas públicas. MÉTODOS: Intervenção com 331 estudantes de 11 a 17 anos de 5º e 6º anos de duas escolas públicas estaduais de Niterói, RJ, em 2005. As escolas foram classificadas em escola de intervenção (EI) e escola de controle (EC) para comparação. Práticas alimentares foram abordadas em questionários auto-respondidos antes e após o período de intervenção: consumo de fast food, consumo de refrigerantes, substituição de refeições por lanches, consumo de frutas, verduras e legumes e tipo de alimentação consumida nos intervalos das aulas. Testes qui-quadrado e McNemar foram aplicados para comparar proporções, considerando valor de p < 0,05. RESULTADOS: Na linha de base participaram 185 estudantes da EI (82,2% dos elegíveis) e 146 estudantes da EC (70,5% dos elegíveis). Na fase pós-intervenção houve perda de 10,3% dos adolescentes da EI e 27,4% da EC. Não se observaram mudanças significativas nas práticas alimentares na EC. Na EI aumentou a proporção de estudantes que relataram não consumir lanches vendidos por ambulantes (de 36,7% para 50,6%; p = 0,02) e dos jovens que relataram não substituir almoço (de 44,5% para 65,2%; p < 0,01) e jantar (de 38,4% para 54,3%; p < 0,01) por lanches. A principal mudança favorável foi a redução na freqüência de consumo de lanches fast food na EI comparada à EC (72,7% vs 54,4%; p = 0,001). CONCLUSÕES: Mudanças favoráveis nas práticas alimentares dos adolescentes foram encontradas e estimulam a implantação de programas dessa natureza; contudo, intervenções de maior duração precisam ser implementadas e avaliadas quanto a sua efetividade