Ecological succession of the microbial communities of an air-conditioning cooling coil in the tropics

Air-conditioning systems harbor microorganisms, potentially spreading them to indoor environments. While air and surfaces in air-conditioning systems are periodically sampled as potential sources of indoor microbes, little is known about the dynamics of cooling coil-associated communities and their effect on the downstream airflow. Here, we conducted a 4-week time series sampling to characterize the succession of an air-conditioning duct and cooling coil after cleaning. Using an universal primer pair targeting hypervariable regions of the 16S/18S ribosomal RNA, we observed a community succession for the condensed water, with the most abundant airborne taxon Agaricomycetes fungi dominating the initial phase and Sphingomonas bacteria becoming the most prevalent taxa toward the end of the experiment. Duplicate air samples collected upstream and downstream of the coil suggest that the system does not act as ecological filter or source/sink for specific microbial taxa during the duration of the experiment.

Polar freshwater cyanophage S-EIV1 represents a new widespread evolutionary lineage of phages

Cyanobacteria are often the dominant phototrophs in polar freshwater communities; yet, the phages that infect them remain unknown. Here, we present a genomic and morphological characterization of cyanophage S-EIV1 that was isolated from freshwaters on Ellesmere Island (Nunavut, High Arctic Canada), and which infects the polar Synechococcus sp., strain PCCC-A2c. S-EIV1 represents a newly discovered evolutionary lineage of bacteriophages whose representatives are widespread in aquatic systems. Among the 130 predicted open reading frames (ORFs) there is no recognizable similarity to genes that encode structural proteins other than the large terminase subunit and a distant viral morphogenesis protein, indicating that the genes encoding the structural proteins of S-EIV1 are distinct from other viruses. As well, only 19 predicted coding sequences on the 79 178 bp circularly permuted genome have homology with genes encoding proteins of known function. Although S-EIV1 is divergent from other sequenced phage isolates, it shares synteny with phage genes captured on a fosmid from the deep-chlorophyll maximum in the Mediterranean Sea, as well as with an incision element in the genome of Anabaena variabilis (ATCC 29413). Sequence recruitment of metagenomic data indicates that S-EIV1-like viruses are cosmopolitan and abundant in a wide range of aquatic systems, suggesting they have an important ecological role.

Total fibrin and fibrinogen degradation products in urine: a possible probe to detect illicit users of the physical-performance enhancer erythropoietin?

Erythropoietin (Epo) represents for some athletes the ultimate tool to gain an edge over their peer competitors. Underground information indicates that its usage is spreading at an epidemic pace since no analytical technique is yet available to detect its utilization. We hereby report observations obtained from analysis of urine specimens collected from top-level athletes after international-calibre competitions. Possible Epo misuse was evaluated by the measurement of urine total degradation products (TDPs), excretory fragments attributed by Sakakibara et al. to the fibrinolytic action of Epo. Markedly elevated urine TDP levels were measured in more than 13% of the 76 top-level athletes evaluated in this study. Analyses of urine specimens from a control hockey player group and from out-of-competition resting subjects indicate that the urine TDP content is not significantly influenced by exercise per se. Solid confirmation of TDP measurement as a sound probe to detect illicit Epo users should come from controlled studies with concomitant administration of Epo.

Dopamine inhibits prolactin secretion stimulated by the calcium channel agonist Bay-K-8644 through a pertussis toxin-sensitive G protein in anterior pituitary cells

In primary culture of anterior pituitary cells, BAY-K-8644, a calcium channel agonist, stimulated PRL secretion by 83% with EC50 of 18 nM. This effect was blocked by nifedipine, a calcium channel antagonist. The stimulations of PRL secretion induced by potassium (50 mM) and BAY-K-8644 were additive. Dopamine inhibited basal as well as BAY-K-8644-stimulated PRL secretion by 64% and 75%, respectively, and with respective EC50 values of 4.5 and 0.6 nM. In the presence of 50 mM K+, dopamine only partially blocks the dose-dependent stimulation of PRL secretion induced by the calcium channel agonist. The inhibitory dopamine effect was blocked by (+)butaclamol, a specific dopamine receptor antagonist. The dopamine response was also blocked by 1-sulpiride, a specific dopamine D2 receptor antagonist, and mimicked by RU 24926, a specific dopamine D2 receptor agonist, suggesting that the dopamine effect on BAY-K-8644-stimulated PRL secretion was mediated through a D2 dopamine receptor. Although unknown, the mechanism by which dopamine inhibited the BAY-K-8644-stimulated PRL secretion involves a GTP binding protein sensitive to Bordetella pertussis toxin. In fact, the dopamine inhibition of PRL secretion induced by the calcium channel agonist was blocked by the pretreatment of cells with the toxin. These results suggest that dopamine D2 receptors in lactotroph cells modulate calcium influx through a GTP binding protein.

Thyroid hormones modulate ornithine decarboxylase in the immature rat cerebellum

In this study, we measured ornithine decarboxylase (ODC) activity as a potential parameter to evaluate the response of the developing rat brain to thyroid hormones. In cerebellum, neonatal hyperthyroidism (40 micrograms thyroxine/100 g body weight daily from birth) increased ODC activity at 2 and 5 days of age and then accelerated its developmental decline. Conversely, ODC activity was decreased in 2- and 5-day-old hypothyroid rats (propylthiouracil to the mother), but it was not significantly different from normal thereafter. No significant differences were observed in the forebrain following either treatment. In hypothyroid rat cerebellum, a single injection of triiodothyronine (T3, 100 micrograms/100 g 18 h before sacrifice) increased significantly ODC activity at all ages. A dose-response study showed that 0.5 micrograms T3/100 g is sufficient to obtain maximal stimulation. Finally, administration of antiserum against rat growth hormone had no significant effect on ODC response to T3. These results show that ODC is a useful marker of thyroid state and tissue response in the neonatal rat cerebellum.