Arctic cyanobacterial mat community diversity decreases with latitude across the Canadian Arctic

Cyanobacterial mats are commonly reported as hotspots of microbial diversity across polar environments. These thick, multi-layered microbial communities provide a refuge from extreme environmental conditions, with many species able to grow and coexist despite the low allochthonous nutrient inputs. The visibly dominant phototrophic biomass is dependent on internal nutrient recycling by heterotrophic organisms within the mats, however the specific contribution of heterotrophic protists remains little explored. In this study, mat community diversity was examined along a latitudinal gradient (55-83°N), spanning subarctic taiga, tundra, polar desert, and the High Arctic ice shelves. The prokaryotic and eukaryotic communities were targeted respectively by V4 16S and V9 18S rRNA gene amplicon high-throughput sequencing. Prokaryotic and eukaryotic richness decreased, in tandem with decreasing temperatures and shorter seasons of light availability, from the subarctic to the High Arctic. Taxonomy-based annotation of the protist community revealed diverse phototrophic, mixotrophic and heterotrophic genera in all mat communities, with fewer parasitic taxa in High Arctic communities. Co-occurrence network analysis identified greater heterogeneity in eukaryotic than prokaryotic community structure among cyanobacterial mats across the Canadian Arctic. Our findings highlight the sensitivity of microbial eukaryotes to environmental gradients across northern high latitudes.

Society of pediatric liver transplantation: Current registry status 2011-2018

BACKGROUND

SPLIT was founded in 1995 in order to collect comprehensive prospective data on pediatric liver transplantation, including waiting list data, transplant, and early and late outcomes. Since 2011, data collection of the current registry has been refined to focus on prospective data and outcomes only after transplant to serve as a foundation for the future development of targeted clinical studies.

OBJECTIVE

To report the outcomes of the SPLIT registry from 2011 to 2018.

METHODS

This is a multicenter, cross-sectional analysis characterizing patients transplanted and enrolled in the SPLIT registry between 2011 and 2018. All patients, <18 years of age, received a first liver-only, a combined liver-kidney, or a combined liver-pancreas transplant during this study period.

RESULTS

A total of 1911 recipients from 39 participating centers in North America were registered. Indications included biliary atresia (38.5%), metabolic disease (19.1%), tumors (11.7%), and fulminant liver failure (11.5%). Greater than 50% of recipients were transplanted as either Status 1A/1B or with a MELD/PELD exception score. Incompatible transplants were performed in 4.1%. Kaplan-Meier estimates of 1-year patient and graft survival were 97.3% and 96.6%. First 30 days of surgical complications included reoperation (31.7%), hepatic artery thrombosis (6.3%), and portal vein thrombosis (3.2%). In the first 90 days, biliary tract complications were reported in 13.6%. Acute cellular rejection during first year was 34.7%. At 1 and 2 years of follow-up, 39.2% and 50.6% had normal liver tests on monotherapy (tacrolimus or sirolimus). Further surgical, survival, allograft function, and complications are detailed.

PRECEDENT: A randomized phase II trial comparing EC145 and pegylated liposomal doxorubicin (PLD) in combination, versus PLD alone, in subjects with platinum-resistant ovarian cancer

LBA5012b

Background: EC145, a conjugate of folic acid and desacetylvinblastine hydrazide binds with high affinity to the folate receptor (FR), found on > 90% of epithelial ovarian cancers. This abstract reports interim data on an international randomized, phase II study of EC145 + PLD compared with PLD alone, in women with platinum-resistant ovarian cancer. An independent Data Safety Monitoring Board (DSMB) has conducted a prespecified interim analysis on PFS and safety with results reported herein.

Methods: Women ≥ 18 with ECOG PS of 0-2 and ≤ 2 prior systemic cytotoxic regimens were randomized to receive EC145 (2.5 mg IV weeks 1 and 3) + PLD (50 mg/m2 IBW IV q 28 days) or PLD (50 mg/m2 IBW IV q 28 days) alone until progression or death.

Results: The interim analysis occurred after the 46th event out of a planned study total of 95 progressions or deaths. Demographic characteristics at screening such as age, cancer type, residual tumor after debulking, prior therapy, CA-125 and time from diagnosis were balanced between arms. RECIST mean sum tumor length was longer for the combination arm (122.7 mm vs. 81.3 mm). There was no statistical difference between study arms with regard to total adverse events, serious adverse events, or the number of subjects reporting at least one treatment-emergent drug-related serious adverse event resulting in discontinuation. The Table displays the results of the interim analysis of PFS. At the interim, there is also a trend toward benefit in overall survival for the combination arm with HR = 0.425 (p value of 0.064).

Conclusions: Results indicate a greater than doubling in median PFS for women with platinum-resistant ovarian cancer receiving EC145 and PLD over those receiving PLD alone. These interim data suggest that EC145 and PLD is the first combination to show a statistically significant delay in progression-free survival over standard therapy in women with platinum-resistant ovarian cancer.

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Diversity and distribution of marine microbial eukaryotes in the Arctic Ocean and adjacent seas

We analyzed microbial eukaryote diversity in perennially cold arctic marine waters by using 18S rRNA gene clone libraries. Samples were collected during concurrent oceanographic missions to opposite sides of the Arctic Ocean Basin and encompassed five distinct water masses. Two deep water Arctic Ocean sites and the convergence of the Greenland, Norwegian, and Barents Seas were sampled from 28 August to 2 September 2002. An additional sample was obtained from the Beaufort Sea (Canada) in early October 2002. The ribotypes were diverse, with different communities among sites and between the upper mixed layer and just below the halocline. Eukaryotes from the remote Canada Basin contained new phylotypes belonging to the radiolarian orders Acantharea, Polycystinea, and Taxopodida. A novel group within the photosynthetic stramenopiles was also identified. One sample closest to the interior of the Canada Basin yielded only four major taxa, and all but two of the sequences recovered belonged to the polar diatom Fragilariopsis and a radiolarian. Overall, 42% of the sequences were <98% similar to any sequences in GenBank. Moreover, 15% of these were <95% similar to previously recovered sequences, which is indicative of endemic or undersampled taxa in the North Polar environment. The cold, stable Arctic Ocean is a threatened environment, and climate change could result in significant loss of global microbial biodiversity.

Algicidal effects of a novel marine pseudoalteromonas isolate (class Proteobacteria, gamma subdivision) on harmful algal bloom species of the genera Chattonella, Gymnodinium, and Heterosigma

During a bacterial survey of the Huon Estuary in southern Tasmania, Australia, we isolated a yellow-pigmented Pseudoalteromonas strain (class Proteobacteria, gamma subdivision), designated strain Y, that had potent algicidal effects on harmful algal bloom species. This organism was identified by 16S rRNA sequencing as a strain with close affinities to Pseudoalteromonas peptidysin. This bacterium caused rapid cell lysis and death (within 3 h) of gymnodinoids (including Gymnodinium catenatum) and raphidophytes (Chattonella marina and Heterosigma akashiwo). It caused ecdysis of armored dinoflagellates (e.g., Alexandrium catenella, Alexandrium minutum, and Prorocentrum mexicanum), but the algal cultures then recovered over the subsequent 24 h. Strain Y had no effect on a cryptomonad (Chroomonas sp.), a diatom (Skeletonema sp.), a cyanobacterium (Oscillatoria sp.), and two aplastidic protozoans. The algicidal principle of strain Y was excreted into the seawater medium and lost its efficacy after heating. Another common bacterial species, Pseudoalteromonas carrageenovora, was isolated at the same time and did not have these algicidal effects. The minimum concentrations of strain Y required to kill G. catenatum were higher than the mean concentrations found in nature under nonbloom conditions. However, the new bacterium showed a chemotactic, swarming behavior that resulted in localized high concentrations around target organisms. These observations imply that certain bacteria could play an important role in regulating the onset and development of harmful algal blooms.

Vertical Flux of Biogenic Carbon in the Ocean: Is There Food Web Control?

Models of biogenic carbon (BC) flux assume that short herbivorous food chains lead to high export, whereas complex microbial or omnivorous food webs lead to recycling and low export, and that export of BC from the euphotic zone equals new production (NP). In the Gulf of St. Lawrence, particulate organic carbon fluxes were similar during the spring phytoplankton bloom, when herbivory dominated, and during nonbloom conditions, when microbial and omnivorous food webs dominated. In contrast, NP was 1.2 to 161 times greater during the bloom than after it. Thus, neither food web structure nor NP can predict the magnitude or patterns of BC export, particularly on time scales over which the ocean is in nonequilibrium conditions.

Canal master instrumentation: an in vitro study of separation frequency

Ninety resin blocks were instrumented by three different operators using the Canal Master Instrumentation system. The frequency of file separation among three operators of varying endodontic experience (novice dental student to endodontist) was compared. Twenty-one of 87 (24%) of the instruments were separated. The #50 Canal Master file failed most frequently (5 of 21). Three ledges (3 of 90 samples) were created by the novice operator with the Canal Master rotary instruments which could not be bypassed. Separation rates among the operators ranged from 12 of 27 (novice) to 4 of 30 (endodontist). The results suggest that the Canal Master file may be prone to fracture in vitro and that there may be a "learning curve" to proficient Canal Master use.

Nanosecond fluorescence spectroscopy of pyrenebutyrate anti-pyrene antibody complexes

The utility of the long-lived fluorophore, pyrene, as a probe in nanosecond fluorescence depolarization measurements was investigated using pyrenebutyrate bound in the combining sites of rabbit antipyrenebutyrate immunoglobulin G. The time dependent anisotropy decay data points showed very little scatter in the time interval 0-350 ns, which is more than three times the comparable time interval observed with epsilon-1-dimethylamino-5-naphthalenesulfonyllysine (DNS-lysine) bound in the combining sites of anti-DNS antibodies [Holowka, D.A., and Cathou, R.E. (1976), Biochemistry 15, 3379]. Thus, the use of pyrene can significantly extend the range of macromolecular rotational correlation times that can be measured by the single photon technique. In the present investigation, we confirmed the presence of Fab segmental fexibility in immunoglobulin G molecules specific for a hapten different from DNS-lysine. We obtained a value of about 135 ns for the longer rotational correlation time which probably represents global rotation of the entire molecule. In the course of these experiments, we have also found that the combining sites of antipyrenebutyrate antibodies are, as expected, relatively nonpolar.