Mycobacterium marinum Causes a Latent Infection that Can Be Reactivated by Gamma Irradiation in Adult Zebrafish

The mechanisms leading to latency and reactivation of human tuberculosis are still unclear, mainly due to the lack of standardized animal models for latent mycobacterial infection. In this longitudinal study of the progression of a mycobacterial disease in adult zebrafish, we show that an experimental intraperitoneal infection with a low dose (∼35 bacteria) of Mycobacterium marinum, results in the development of a latent disease in most individuals. The infection is characterized by limited mortality (25%), stable bacterial loads 4 weeks following infection and constant numbers of highly organized granulomas in few target organs. The majority of bacteria are dormant during a latent mycobacterial infection in zebrafish, and can be activated by resuscitation promoting factor ex vivo. In 5–10% of tuberculosis cases in humans, the disease is reactivated usually as a consequence of immune suppression. In our model, we are able to show that reactivation can be efficiently induced in infected zebrafish by γ-irradiation that transiently depletes granulo/monocyte and lymphocyte pools, as determined by flow cytometry. This immunosuppression causes reactivation of the dormant mycobacterial population and a rapid outgrowth of bacteria, leading to 88% mortality in four weeks. In this study, the adult zebrafish presents itself as a unique non-mammalian vertebrate model for studying the development of latency, regulation of mycobacterial dormancy, as well as reactivation of latent or subclinical tuberculosis. The possibilities for screening for host and pathogen factors affecting the disease progression, and identifying novel therapeutic agents and vaccine targets make this established model especially attractive.     

Gestational and Early Infancy Exposure to Margarine Fortified with Vitamin D through a National Danish Programme and the Risk of Type 1 Diabetes: The D-Tect Study

The objective of the study was to assess whether gestational and early infancy exposure to low dose vitamin D from a mandatory margarine fortification programme in Denmark influenced the risk of developing type 1 diabetes (T1D) before age of 15 years. The study population included all individuals born in Denmark from 1983 to 1988 and consisted of 331,623 individuals. The 1^st of June 1985, which was the date of issue of the new ministerial order cancelling mandatory fortification of margarine with vitamin D in Denmark, served as a reference point separating the studied population into various exposure groups. We further modelled birth cohort effects in children developing T1D as a linear spline, and compared the slopes between the birth cohorts with various prenatal and infancy exposures to vitamin D fortification. In total, 886 (0.26%) individuals developed T1D before the age of 15 years. The beta coefficients (95% CI), or slopes, for linear birth cohort effect in log Hazard Ratio (HR) per one month of birth in individuals born during the periods of gestational exposure, wash-out, and non-exposure were: 0.010 (-0.002/0.021), -0.010 (-0.035/0.018), and 0.008 (- 0.017/0.032), respectively. The beta coefficients (95% CI) for individuals born during the periods of first postnatal year exposure, wash-out, and non-exposure were: 0.007 (-0.016/0.030), 0.006 (-0.004/0.016), and 0.007 (-0.002/0.016), respectively. In conclusion, we found no evidence to support that exposure to low dose vitamin D from the Danish mandatory margarine fortification regimen during gestational and first postnatal year of life changed the risk of developing T1D before the age of 15 years.     

Real‐time monitoring of herbivore induced volatile emissions in the field

When plants are damaged by herbivorous insects they emit a blend of volatile organic compounds (VOCs) which include a range or terpenoids and green leaf volatiles (GLVs) formed via different metabolic pathways. The precise timing of these emissions upon the onset of herbivore feeding has not been fully elucidated, and the information that is available has been mainly obtained through laboratory based studies. We investigated emissions of VOCs from Populus tremula L. ×P. tremuloides Michx. during the first 20 h of feeding by Epirrita autumnata (autumnal moth) larvae in a field site. The study was conducted using Proton Transfer Reaction‐Mass Spectrometry (PTR‐MS) to measure emissions online, with samples collected for subsequent analysis by complementary gas chromatography‐mass spectrometry for purposes of compound identification. GLV emission peaks occurred sporadically from the outset, indicating herbivore activity, while terpene emissions were induced within 16 h. We present data detailing the patterns of monoterpene (MT), GLV and sesquiterpene (SQT) emissions during the early stages of herbivore feeding showing diurnal MT and SQT emission that is correlated more with temperature than light. Peculiarities in the timing of SQT emissions prompted us to conduct a thorough characterization of the equipment used to collect VOCs and thus corroborate the accuracy of results. A laboratory based analysis of the throughput of known GLV, MT and SQT standards at different temperatures was made with PTR‐MS. Enclosure temperatures of 12, 20 and 25°C had little influence on the response time for dynamic measurements of a GLV or MT. However, there was a clear effect on SQT measurements. Elucidation of emission patterns in real‐time is dependent upon the dynamics of cuvettes at different temperatures.     

EARLY RESPONSIVE TO DEHYDRATION 15, a negative regulator of abscisic acid responses in Arabidopsis

EARLY RESPONSIVE TO DEHYDRATION 15 (ERD15) is rapidly induced in response to various abiotic and biotic stress stimuli in Arabidopsis (Arabidopsis thaliana). Modulation of ERD15 levels by overexpression or RNAi silencing altered the responsiveness of the transgenic plants to the phytohormone abscisic acid (ABA). Overexpression of ERD15 reduced the ABA sensitivity of Arabidopsis manifested in decreased drought tolerance and in impaired ability of the plants to increase their freezing tolerance in response to this hormone. In contrast, RNAi silencing of ERD15 resulted in plants that were hypersensitive to ABA and showed improved tolerance to both drought and freezing, as well as impaired seed germination in the presence of ABA. The modulation of ERD15 levels not only affected abiotic stress tolerance but also disease resistance: ERD15 overexpression plants showed improved resistance to the bacterial necrotroph Erwinia carotovora subsp. carotovora accompanied with enhanced induction of marker genes for systemic acquired resistance. We propose that ERD15 is a novel mediator of stress-related ABA signaling in Arabidopsis.     

Flow cytometric analysis of glyoxalase-1 expression in human leukocytes

Altered glyoxalase‐1 (GLO‐1) activity and expression is associated with the development of late diabetic complications, malignancy and oxidative stress‐ and aging‐related diseases. In the present study, we developed a flow cytometry method for GLO‐1 detection in human leukocytes isolated from peripheral blood samples to investigate GLO‐1 expression in leukocyte subsets from type 1 and 2 diabetes mellitus patients (n = 11) and healthy subjects (n = 8). The flow cytometry analysis of GLO‐1 in leukocytes showed that expression index of GLO‐1‐positive cells was slightly increased in mononuclear leukocytes from diabetic patients. This result correlated with the increase in GLO‐1 activity in the whole blood samples of type 2 diabetes patients. In conclusion, the present study demonstrates that flow cytometry is suitable for the detection of the GLO‐1 enzyme in human leukocytes and that this method could be used to investigate the fast adaptation of the glyoxalase system related to the pathogenesis of late complications of diabetes mellitus and other glycation stress‐related disorders. Copyright © 2011 John Wiley & Sons, Ltd.     

Comparative analysis of phycoerythrin production in cryptophytes

Journal of Applied Phycology - Phycobiliproteins are pigments with uses in pharmacology, cosmetics, foods, and as fluorescent probes in biochemistry. Cryptophyte microalgae are one possible source...     

Dynamic association of human insulin receptor with lipid rafts in cells lacking caveolae

Cholesterol-sphingolipid rich plasma membrane domains, known as rafts, have emerged as important regulators of signal transduction. The adipocyte insulin receptor (IR) is localized to and signals via caveolae that are formed by polymerization of caveolins. Caveolin binds to IR and stimulates signalling. We report that, in liver-derived cells lacking caveolae, autophosphorylation of the endogenous IR is dependent on raft lipids, being compromised by acute cyclodextrin-mediated cholesterol depletion or by antibody clustering of glycosphingolipids. Moreover, we provide evidence that IR becomes recruited to detergent-resistant domains upon ligand binding and that clustering of GM2 ganglioside inhibits IR signalling apparently by excluding the ligand-bound IR from these domains. Our results indicate that, in cells derived from liver, an important insulin target tissue, caveolae are not required for insulin signalling. Rather, the dynamic recruitment of the ligand-bound IR into rafts may serve to regulate interactions in the initiation of the IR signalling cascade.