Biogeography of microbial communities in high-latitude ecosystems: Contrasting drivers for methanogens, methanotrophs and global prokaryotes

Methane-cycling is becoming more important in high-latitude ecosystems as global warming makes permafrost organic carbon increasingly available. We explored 387 samples from three high-latitudes regions (Siberia, Alaska and Patagonia) focusing on mineral/organic soils (wetlands, peatlands, forest), lake/pond sediment and water. Physicochemical, climatic and geographic variables were integrated with 16S rDNA amplicon sequences to determine the structure of the overall microbial communities and of specific methanogenic and methanotrophic guilds. Physicochemistry (especially pH) explained the largest proportion of variation in guild composition, confirming species sorting (i.e., environmental filtering) as a key mechanism in microbial assembly. Geographic distance impacted more strongly beta diversity for (i) methanogens and methanotrophs than the overall prokaryotes and, (ii) the sediment habitat, suggesting that dispersal limitation contributed to shape the communities of methane-cycling microorganisms. Bioindicator taxa characterising different ecological niches (i.e., specific combinations of geographic, climatic and physicochemical variables) were identified, highlighting the importance of Methanoregula as generalist methanogens. Methylocystis and Methylocapsa were key methanotrophs in low pH niches while Methylobacter and Methylomonadaceae in neutral environments. This work gives insight into the present and projected distribution of methane-cycling microbes at high latitudes under climate change predictions, which is crucial for constraining their impact on greenhouse gas budgets.

Past climate-driven range shifts structuring intraspecific biodiversity levels of the giant kelp (Macrocystis pyrifera) at global scales

The paradigm of past climate-driven range shifts structuring the distribution of marine intraspecific biodiversity lacks replication in biological models exposed to comparable limiting conditions in independent regions. This may lead to confounding effects unlinked to climate drivers. We aim to fill in this gap by asking whether the global distribution of intraspecific biodiversity of giant kelp (Macrocystis pyrifera) is explained by past climate changes occurring across the two hemispheres. We compared the species' population genetic diversity and structure inferred with microsatellite markers, with range shifts and long-term refugial regions predicted with species distribution modelling (SDM) from the last glacial maximum (LGM) to the present. The broad antitropical distribution of Macrocystis pyrifera is composed by six significantly differentiated genetic groups, for which current genetic diversity levels match the expectations of past climate changes. Range shifts from the LGM to the present structured low latitude refugial regions where genetic relics with higher and unique diversity were found (particularly in the Channel Islands of California and in Peru), while post-glacial expansions following ~ 40% range contraction explained extensive regions with homogenous reduced diversity. The estimated effect of past climate-driven range shifts was comparable between hemispheres, largely demonstrating that the distribution of intraspecific marine biodiversity can be structured by comparable evolutionary forces across the global ocean. Additionally, the differentiation and endemicity of regional genetic groups, confers high conservation value to these localized intraspecific biodiversity hotspots of giant kelp forests.

Carrageenan from Gigartina skottsbergii: A Novel Molecular Probe to Detect SARS-CoV-2

The COVID-19 pandemic has caused an unprecedented health and economic crisis, highlighting the importance of developing new molecular tools to monitor and detect SARS-CoV-2. Hence, this study proposed to employ the carrageenan extracted from Gigartina skottsbergii algae as a probe for SARS-CoV-2 virus binding capacity and potential use in molecular methods. G. skottsbergii specimens were collected in the Chilean subantarctic ecoregion, and the carrageenan was extracted -using a modified version of Webber's method-, characterized, and quantified. After 24 h of incubation with an inactivated viral suspension, the carrageenan's capacity to bind SARS-CoV-2 was tested. The probe-bound viral RNA was quantified using the reverse transcription and reverse transcription loop-mediated isothermal amplification (RT-LAMP) methods. Our findings showed that carrageenan extraction from seaweed has a similar spectrum to commercial carrageenan, achieving an excellent proportion of binding to SARS-CoV-2, with a yield of 8.3%. Viral RNA was also detected in the RT-LAMP assay. This study shows, for the first time, the binding capacity of carrageenan extracted from G. skottsbergii, which proved to be a low-cost and highly efficient method of binding to SARS-CoV-2 viral particles.

Methane and carbon dioxide cycles in lakes of the King George Island, maritime Antarctica

Freshwater ecosystems are important contributors to the global greenhouse gas budget and a comprehensive assessment of their role in the context of global warming is essential. Despite many reports on freshwater ecosystems, relatively little attention has been given so far to those located in the southern hemisphere and our current knowledge is particularly poor regarding the methane cycle in non-perennially glaciated lakes of the maritime Antarctica. We conducted a high-resolution study of the methane and carbon dioxide cycle in a lake of the Fildes Peninsula, King George Island (Lat. 62°S), and a succinct characterization of 10 additional lakes and ponds of the region. The study, done during the ice-free and the ice-seasons, included methane and carbon dioxide exchanges with the atmosphere (both from water and surrounding soils) and the dissolved concentration of these two gases throughout the water column. This characterization was complemented with an ex-situ analysis of the microbial activities involved in the methane cycle, including methanotrophic and methanogenic activities as well as the methane-related marker gene abundance, in water, sediments and surrounding soils. The results showed that, over an annual cycle, the freshwater ecosystems of the region are dominantly autotrophic and that, despite low but omnipresent atmospheric methane emissions, they act as greenhouse gas sinks.

A combined microbial and biogeochemical dataset from high-latitude ecosystems with respect to methane cycle

High latitudes are experiencing intense ecosystem changes with climate warming. The underlying methane (CH₄) cycling dynamics remain unresolved, despite its crucial climatic feedback. Atmospheric CH₄ emissions are heterogeneous, resulting from local geochemical drivers, global climatic factors, and microbial production/consumption balance. Holistic studies are mandatory to capture CH₄ cycling complexity. Here, we report a large set of integrated microbial and biogeochemical data from 387 samples, using a concerted sampling strategy and experimental protocols. The study followed international standards to ensure inter-comparisons of data amongst three high-latitude regions: Alaska, Siberia, and Patagonia. The dataset encompasses different representative environmental features (e.g. lake, wetland, tundra, forest soil) of these high-latitude sites and their respective heterogeneity (e.g. characteristic microtopographic patterns). The data included physicochemical parameters, greenhouse gas concentrations and emissions, organic matter characterization, trace elements and nutrients, isotopes, microbial quantification and composition. This dataset addresses the need for a robust physicochemical framework to conduct and contextualize future research on the interactions between climate change, biogeochemical cycles and microbial communities at high-latitudes.

Measurement(s)	microbial diversity • microbial abundances • cations and anions • trace elements
Technology Type(s)	MiSeq sequencing 16S rRNA gene • Real Time PCR • HPLC • ICP-MS
Sample Characteristic - Organism	bacteria • archaea
Sample Characteristic - Environment	lake water • lake sediment • wetland • peatland • soil • pond
Sample Characteristic - Location	Western Siberia • Alaska • Patagonia • Cape Horn province • Magellanic subantarctic ecoregion

Type specimen sequencing, multilocus analyses, and species delimitation methods recognize the cosmopolitan Corallina berteroi and establish the northern Japanese C. yendoi sp. nov. (Corallinaceae, Rhodophyta)

A partial rbcL sequence of the lectotype specimen of Corallina berteroi shows that it is the earliest available name for C. ferreyrae. Multilocus species delimitation analyses (ABGD, SPN, GMYC, bPTP, and BPP) using independent or concatenated COI, psbA, and rbcL sequences recognized one, two, or three species in this complex, but only with weak support for each species hypothesis. Conservatively, we recognize a single worldwide species in this complex of what appears to be multiple, evolving populations. Included in this species, besides C. ferreyrae, are C. caespitosa, the morphologically distinct C. melobesioides, and, based on a partial rbcL sequence of the holotype specimen, C. pinnatifolia. Corallina berteroi, not C. officinalis, is the cosmopolitan temperate species found thus far in the NE Atlantic, Mediterranean Sea, warm temperate NW Atlantic and NE Pacific, cold temperate SW Atlantic (Falkland Islands), cold and warm temperate SE Pacific, NW Pacific and southern Australia. Also proposed is C. yendoi sp. nov. from Hokkaido, Japan, which was recognized as distinct by 10 of the 13 species discrimination analyses, including the multilocus BPP.

Temperature differently affected methanogenic pathways and microbial communities in sub-Antarctic freshwater ecosystems

Freshwater ecosystems are responsible for an important part of the methane (CH₄) emissions which are likely to change with global warming. This study aims to evaluate temperature-induced (from 5 to 20 °C) changes on microbial community structure and methanogenic pathways in five sub-Antarctic lake sediments from Magallanes strait to Cape Horn, Chile. We combined in situ CH₄ flux measurements, CH₄ production rates (MPRs), gene abundance quantification and microbial community structure analysis (metabarcoding of the 16S rRNA gene). Under unamended conditions, a temperature increase of 5 °C doubled MPR while microbial community structure was not affected. Stimulation of methanogenesis by methanogenic precursors as acetate and H₂/CO₂, resulted in an increase of MPRs up to 127-fold and 19-fold, respectively, as well as an enrichment of mcrA-carriers strikingly stronger under acetate amendment. At low temperatures, H₂/CO₂-derived MPRs were considerably lower (down to 160-fold lower) than the acetate-derived MPRs, but the contribution of hydrogenotrophic methanogenesis increased with temperature. Temperature dependence of MPRs was significantly higher in incubations spiked with H₂/CO₂ (c. 1.9 eV) compared to incubations spiked with acetate or unamended (c. 0.8 eV). Temperature was not found to shape the total microbial community structure, that rather exhibited a site-specific variability among the studied lakes. However, the methanogenic archaeal community structure was driven by amended methanogenic precursors with a dominance of Methanobacterium in H₂/CO₂-based incubations and Methanosarcina in acetate-based incubations. We also suggested the importance of acetogenic H₂-production outcompeting hydrogenotrohic methanogenesis especially at low temperatures, further supported by homoacetogen proportion in the microcosm communities. The combination of in situ-, and laboratory-based measurements and molecular approaches indicates that the hydrogenotrophic pathway may become more important with increasing temperatures than the acetoclastic pathway. In a continuously warming environment driven by climate change, such issues are crucial and may receive more attention.

A novel biodegradable film based on κ-carrageenan activated with olive leaves extract

This research focused on the development of carrageenan based biodegradable films incorporated with olive leaves extract (OLE). OLE microbial inhibition and its total phenolics (TP) were evaluated. Carrageenan films were produced by casting technique and were characterized by thickness, water vapor permeability (WVP), color, mechanical properties, and infrared spectroscopy. In order to apply as lamb meat packaging, the antimicrobial effect of the films was investigated. Results showed that OLE inhibited E. coli growth and presented excellent TP (41.40 mgGAE/g). Thicknesses of the film with OLE (CAR-OLE) were approximately 28% higher than film without OLE. Addition of OLE reduced the WVP by approximately 54%. CAR-OLE was less resistant to breakage and more flexible showing darker color. FTIR showed interaction of carrageenan with OLE. Results revealed that CAR-OLE promoted 167-fold reduction in initial count of aerobic mesophiles indicating shelf-life extension of lamb meat and promising use as antimicrobial food packaging.

A new record of kelp Lessonia spicata (Suhr) Santelices in the Sub-Antarctic Channels: implications for the conservation of the "huiro negro" in the Chilean coast

The Katalalixar National Reserve (KNR) lies in an isolated marine protected area of Magellan Sub-Antarctic channels, which represent an important area for marine biodiversity and macroalgal conservation. The present study is the first report of the species Lessonia spicata, “huiro negro”, in the Magellan Sub-Antarctic channels. This finding has implications for macroalgal biogeography and conservation concerns in the Chilean coast. In the ecological assessments of the KNR in 2018 we found populations of L. spicata, specifically on rocky shores of Torpedo Island and Castillo Channel. The morphological identification and molecular phylogeny based on nuclear (ITS1) sequences revealed that these populations of Lessonia are within the lineage of L. spicata of central Chile. This report increases the species richness of kelps for the Magellan Sub-Antarctic Channels from two to three confirmed species (L. flavicans, L. searlesiana and L. spicata), and it also extends the southern distribution range of L. spicata. This species has high harvest demand and is moving towards southern Chile; thus, these populations should be considered as essential for macroalgal conservation in high latitudes of South America.

Long-term persistence of the floating bull kelp Durvillaea antarctica from the South-East Pacific: Potential contribution to local and transoceanic connectivity

Current knowledge about the performance of floating seaweeds as dispersal vectors comes mostly from mid latitudes (30°-40°), but phylogeographic studies suggest that long-distance dispersal (LDD) is more common at high latitudes (50°-60°). To test this hypothesis, long-term field experiments with floating southern bull kelp Durvillaea antarctica were conducted along a latitudinal gradient (30°S, 37°S and 54°S) in austral winter and summer. Floating time exceeded 200d in winter at the high latitudes but in summer it dropped to 90d, being still higher than at low latitudes (<45d). Biomass variations were due to loss of buoyant fronds. Reproductive activity diminished during long floating times. Physiological changes included mainly a reduction in photosynthetic (Fv/Fm and pigments) rather than in defence variables (phlorotannins and antioxidant activity). The observed long floating persistence and long-term acclimation responses at 54°S support the hypothesis of LDD by kelp rafts at high latitudes.

Chemical structure and biological properties of sulfated fucan from the sequential extraction of subAntarctic Lessonia sp (Phaeophyceae)

This work is related to the structural characterization of the sulfated polysaccharide from Lessonia sp and the study of its antioxidant and antiparasitic properties. Sequential extraction afforded D-mannitol as the only low MW sugar alcohol. Extraction with 2% CaCl2 afforded in 3.0% yield, a sulfated fucan (SF). Its major fraction (48.5% yield), isolated by ion-exchange chromatography corresponds to a linear polymer of α-l-fucopyranosil residues linked 1→3, sulfated at the O-4 and partially at O-2 positions. By alkaline extraction, sodium alginate (10.3% yield) was obtained. The antioxidant capacity of SF by ESR showed high elimination index (IC50, mg/mL) of hydroxyl (0.27), alkoxy (10.05), and peroxyl (82.88) radicals in relation to commercial mannitol. SF showed activity against the epimastigote form of Trypanosoma cruzi parasite (250 μg/mL) and low cytotoxicity in murine cells (367 μg/mL). The elimination capacity of radicals in aqueous medium of SF would allow its potential biomedical application.

Trophic ecology of two co-existing Sub-Antarctic limpets of the genus Nacella: spatio-temporal variation in food availability and diet composition of Nacella magellanica and N. deaurata

Interactions between algae and herbivores can be affected by various factors, such as seasonality and habitat structure. Among herbivores inhabiting marine systems, species of the order Patellogastropoda are considered key organisms in many rocky coasts of the world. Nacella species are one of the most dominant macro-herbivores on the rocky shores of the sub-Antarctic ecoregion of Magellan. However, the importance of its key role must be associated with its trophic ecology. The objective of this work was to evaluate spatial and temporal variabilities in the dietary composition of two intertidal Nacella species, considering grazing on macro- (macroalgae) and microscopic (periphyton) food. The composition of periphyton and the availability of macroalgae in the winter and summer seasons were examined at two localities of the Magellanic province, alongside the gut contents of N.magellanica and N.deaurata. The dietary composition differed between the two Nacella species, as well as between seasons and locations. The differences observed in the diet of the two species of Nacella may be mainly due to their respective distributions in the intertidal zone. Both species presented a generalist strategy of grazing, which is relationed to the seasonality of micro- and macroalgae availability and to the variability of the assemblages between the localities. This research was the first to perform a detailed study of the diet of intertidal Nacella species.

Initial report on methane and carbon dioxide emission dynamics from sub-Antarctic freshwater ecosystems: A seasonal study of a lake and a reservoir

The sub-Antarctic Magellanic ecoregion is a part of the world where ecosystems have been understudied and where the CH₄ cycling and emissions in lakes has not ever been reported. To fill that knowledge gap, a lake and a reservoir located at 53°S were selected and studied during three campaigns equally distributed over one year. Among the parameters measured were CH₄ and CO₂ emissions, as well their dissolved concentrations in the water column, which were determined with high spatial resolution. No ebullition was observed and the CH₄ flux ranged from 0.0094 to 4.47mmolm^-2d^-1 while the CO₂ flux ranged from -22.95 to 35.68mmolm^-2d^-1. Dissolved CH₄ concentrations varied over more than four orders of magnitude (0.025-128.75μmolL^-1), and the dissolved carbon dioxide ranged from below the detection limit of our method (i.e., 0.15μmolL^-1) to 379.09μmolL^-1. The high spatial resolution of the methods used enabled the construction of bathymetric maps, surface contour maps of CH₄ and CO₂ fluxes, and transect contour maps of dissolved oxygen, temperature, and dissolved greenhouse gases. Overall, both lakes were net greenhouse gas producers and were not significantly different from temperate lakes located at a similar northern latitudes (53°N), except that ebullition was never observed in the studied sub-Antarctic lakes.

Genetics, Gene Flow, and Glaciation: The Case of the South American Limpet Nacella mytilina

Glacial episodes of the Quaternary, and particularly the Last Glacial Maximum (LGM) drastically altered the distribution of the Southern-Hemisphere biota, principally at higher latitudes. The irregular coastline of Patagonia expanding for more than 84.000 km constitutes a remarkable area to evaluate the effect of Quaternary landscape and seascape shifts over the demography of near-shore marine benthic organisms. Few studies describing the biogeographic responses of marine species to the LGM have been conducted in Patagonia, but existing data from coastal marine species have demonstrated marked genetic signatures of post-LGM recolonization and expansion. The kelp-dweller limpet Nacella mytilina is broadly distributed along the southern tip of South America and at the Falkland/Malvinas Islands. Considering its distribution, abundance, and narrow bathymetry, N. mytilina represents an appropriate model to infer how historical and contemporary processes affected the distribution of intraspecific genetic diversity and structure along the southern tip of South America. At the same time, it will be possible to determine how life history traits and the ecology of the species are responsible for the current pattern of gene flow and connectivity across the study area. We conducted phylogeographic and demographic inference analyses in N. mytilina from 12 localities along Pacific Patagonia (PP) and one population from the Falkland/Malvinas Islands (FI). Analyses of the mitochondrial gene COI in 300 individuals of N. mytilina revealed low levels of genetic polymorphism and the absence of genetic differentiation along PP. In contrast, FI showed a strong and significant differentiation from Pacific Patagonian populations. Higher levels of genetic diversity were also recorded in the FI population, together with a more expanded genealogy supporting the hypothesis of glacial persistence of the species in these islands. Haplotype genealogy, and mismatch analyses in the FI population recognized an older and more complex demographic history than in PP. Demographic reconstructions along PP suggest a post-LGM expansion process (7.5 ka), also supported by neutrality tests, mismatch distribution and maximum parsimony haplotype genealogies. Migration rate estimations showed evidence of asymmetrical gene flow from PP to FI. The absence of genetic differentiation, the presence of a single dominant haplotype, high estimated migration rates, and marked signal of recent demographic growth, support the hypothesis of rapid post-glacial expansion in N. mytilina along PP. This expansion could have been sustained by larval and rafting-mediated dispersal of adults from northernmost populations following the Cape Horn Current System. Marked genetic differentiation between PP and FI could be explained through differences in their respective glacial histories. During the LGM, Pacific Patagonia (PP) was almost fully covered by the Patagonian Ice Sheet, while sheet coverage in the FI ice was restricted to small cirques and valleys. As previously recorded in the sister-species N. magellanica, the FI rather than represent a classical glacial refugium for N. mytilina, seems to represent a sink area and/or a secondary contact zone. Accordingly, historical and contemporary processes, contrasting glacial histories between the analyzed sectors, as well as life history traits constitute the main factors explaining the current biogeographical patterns of most shallow Patagonian marine benthic organisms.

Chiroptical characterization of homopolymeric block fractions in alginates

Homopolymannuronic and homopolyguluronic fractions were obtained by partial hydrolysis of the alkaline extracts from the brown seaweeds Ascoseira mirabilis, Desmarestia menziessi, Desmarestia ligulata and Durvillaea sp. collected in southern Chile. Full characterization of the fractions was achieved by FT-IR and NMR spectroscopy. Total hydrolysis with 90% formic acid of the homopolymeric fractions allowed the preparation of mannuronic and guluronic acids. Both monomers and homopolymeric fractions as neutral salts were studied by CD and ORD. Chiroptical spectra were similar in shape and sign to those previously published in the literature, and permitted to assign D configuration to mannuronic acid and L configuration to guluronic acid in alginic acids. Specific optical rotation values at the sodium D light for the homopolymannuronic (∼-100°) and homopolyguluronic (∼-110°) acid fractions were obtained. These high negative values are proposed for the assignment of the absolute configuration of monomers in homopolymeric fractions.

Differential responses of tetrasporophytes and gametophytes of Mazzaella laminarioides (Gigartinales, Rhodophyta) under solar UV radiation

The effects of solar UV radiation on mycosporine-like amino acids (MAAs), growth, photosynthetic pigments (Chl a, phycobiliproteins), soluble proteins (SP), and C and N content of Mazzaella laminarioides tetrasporophytes and gametophytes were investigated. Apical segments of tetrasporophytes and gametophytes were exposed to solar radiation under three treatments (PAR [P], PAR+UVA [PA], and PAR+UVA+UVB [PAB]) during 18 d in spring 2009, Punta Arenas, Chile. Samples were taken after 2, 6, 12, and 18 d of solar radiation exposure. Most of the parameters assessed on M. laminarioides were significantly influenced by the radiation treatment, and both gametophytes and tetrasporophytes seemed to respond differently when exposed to high UV radiation. The two main effects promoted by UV radiation were: (i) higher synthesis of MAAs in gametophytes than tetrasporophytes at 2 d, and (ii) a decrease in phycoerythrin, phycocyanin, and SPs, but an increase in MAA content in tetrasporophytes at 6 and 12 d of culture. Despite some changes that were observed in biochemical parameters in both tetrasporophytes and gametophytes of M. laminarioides when exposed to UVB radiation, these changes did not promote deleterious effects that might interfere with the growth in the long term (18 d). The tolerance and resistance of M. laminarioides to higher UV irradiance were expected, as this intertidal species is exposed to variation in solar radiation, especially during low tide.

Richness, systematics, and distribution of molluscs associated with the macroalga Gigartina skottsbergii in the Strait of Magellan, Chile: A biogeographic affinity study

Knowledge about the marine malacofauna in the Magellan Region has been gained from many scientific expeditions that were carried out during the 19th century. However, despite the information that exists about molluscs in the Magellan Region, there is a lack of studies about assemblages of molluscs co-occurring with macroalgae, especially commercially exploitable algae such as Gigartina skottsbergii, a species that currently represents the largest portion of carrageenans within the Chilean industry. The objective of this study is to inform about the richness, systematics, and distribution of the species of molluscs associated with natural beds in the Strait of Magellan. A total of 120 samples from quadrates of 0.25 m(2) were obtained by SCUBA diving at two sites within the Strait of Magellan. Sampling occurred seasonally between autumn 2010 and summer 2011: 15 quadrates were collected at each site and season. A total of 852 individuals, corresponding to 42 species of molluscs belonging to Polyplacophora (9 species), Gastropoda (24), and Bivalvia (9), were identified. The species richness recorded represents a value above the average richness of those reported in studies carried out in the last 40 years in sublittoral bottoms of the Strait of Magellan. The biogeographic affinity indicates that the majority of those species (38%) present an endemic Magellanic distribution, while the rest have a wide distribution in the Magellanic-Pacific, Magellanic-Atlantic, and Magellanic-Southern Ocean. The molluscs from the Magellan Region serve as study models for biogeographic relationships that can explain long-reaching patterns and are meaningful in evaluating possible ecosystemic changes generated by natural causes or related to human activities.

Global environmental changes: setting priorities for Latin American coastal habitats

As the effects of the Global Climate Changes on the costal regions of Central and South Americas advance, there is proportionally little research being made to understand such impacts. This commentary puts forward a series of propositions of strategies to improve performance of Central and South American science and policy making in order to cope with the future impacts of the Global Climate Changes in their coastal habitats.

Towards a model of postglacial biogeography in shallow marine species along the Patagonian Province: lessons from the limpet Nacella magellanica (Gmelin, 1791)

BACKGROUND

Patagonia extends for more than 84,000 km of irregular coasts is an area especially apt to evaluate how historic and contemporary processes influence the distribution and connectivity of shallow marine benthic organisms. The true limpet Nacella magellanica has a wide distribution in this province and represents a suitable model to infer the Quaternary glacial legacy on marine benthic organisms. This species inhabits ice-free rocky ecosystems, has a narrow bathymetric range and consequently should have been severely affected by recurrent glacial cycles during the Quaternary. We performed phylogeographic and demographic analyses of N. magellanica from 14 localities along its distribution in Pacific Patagonia, Atlantic Patagonia, and the Falkland/Malvinas Islands.

RESULTS

Mitochondrial (COI) DNA analyses of 357 individuals of N. magellanica revealed an absence of genetic differentiation in the species with a single genetic unit along Pacific Patagonia. However, we detected significant genetic differences among three main groups named Pacific Patagonia, Atlantic Patagonia and Falkland/Malvinas Islands. Migration rate estimations indicated asymmetrical gene flow, primarily from Pacific Patagonia to Atlantic Patagonia (Nem=2.21) and the Falkland/Malvinas Islands (Nem=16.6). Demographic reconstruction in Pacific Patagonia suggests a recent recolonization process (< 10 ka) supported by neutrality tests, mismatch distribution and the median-joining haplotype genealogy.

CONCLUSIONS

Absence of genetic structure, a single dominant haplotype, lack of correlation between geographic and genetic distance, high estimated migration rates and the signal of recent demographic growth represent a large body of evidence supporting the hypothesis of rapid postglacial expansion in this species in Pacific Patagonia. This expansion could have been sustained by larval dispersal following the main current system in this area. Lower levels of genetic diversity in inland sea areas suggest that fjords and channels represent the areas most recently colonized by the species. Hence recolonization seems to follow a west to east direction to areas that were progressively deglaciated. Significant genetic differences among Pacific, Atlantic and Falkland/Malvinas Islands populations may be also explained through disparities in their respective glaciological and geological histories. The Falkland/Malvinas Islands, more than representing a glacial refugium for the species, seems to constitute a sink area considering the strong asymmetric gene flow detected from Pacific to Atlantic sectors. These results suggest that historical and contemporary processes represent the main factors shaping the modern biogeography of most shallow marine benthic invertebrates inhabiting the Patagonian Province.

The Parkinson's disease protein LRRK2 impairs proteasome substrate clearance without affecting proteasome catalytic activity

Leucine-rich repeat kinase 2 (LRRK2) mutations are the most common known cause of Parkinson's disease (PD). The clinical features of LRRK2 PD are indistinguishable from idiopathic PD, with accumulation of α-synuclein and/or tau and/or ubiquitin in intraneuronal aggregates. This suggests that LRRK2 is a key to understanding the aetiology of the disorder. Although loss-of-function does not appear to be the mechanism causing PD in LRRK2 patients, it is not clear how this protein mediates toxicity. In this study, we report that LRRK2 overexpression in cells and in vivo impairs the activity of the ubiquitin-proteasome pathway, and that this accounts for the accumulation of diverse substrates with LRRK2 overexpression. We show that this is not mediated by large LRRK2 aggregates or sequestration of ubiquitin to the aggregates. Importantly, such abnormalities are not seen with overexpression of the related protein LRRK1. Our data suggest that LRRK2 inhibits the clearance of proteasome substrates upstream of proteasome catalytic activity, favouring the accumulation of proteins and aggregate formation. Thus, we provide a molecular link between LRRK2, the most common known cause of PD, and its previously described phenotype of protein accumulation.

UVB radiation induces changes in the ultra-structure of Iridaea cordata

Iridaea cordata cultivated in the presence of UVB radiation (UVBR) was studied using transmission electron microscopy. Apical segments were cultivated in 0.97Wm(-2) of UVBR for 40 days, 3h a day, and compared to a negative control (UVBR absent). UVBR caused modifications, mainly in the cortical cells, including an increased number of cell wall-producing vesicles, in addition to thicker and denser cellular walls, compared to the control. Additionally, cells were observed with an irregular contour and without defined organelles. The increase of cell-wall thickness could be interpreted as an acclimation to UVBR, which could lead to protection from this radiation.

Effect of N-acetylcysteine administration on intraoperative plasma levels of interleukin-4 and interleukin-10 in liver transplant recipients

We investigated whether intraoperative administration of N-acetylcysteine (NAC) in liver transplant recipients ameliorated their inflammatory responses by increasing intraoperative plasma levels of interleukin (IL)-4 and IL-10. This prospective, randomized, double-blind clinical trial included liver transplant recipients randomly assigned to the NAC-treated (n = 25) or the placebo (n = 25) group. The NAC-treated group received 100 mg/kg dissolved in 5% dextrose over 15 minutes during the anhepatic phase, followed by a continuous infusion of 50 mg/kg in 5% dextrose over the next 24 hours, whereas the placebo group received equal amounts of 5% dextrose solution during the same time. Peripheral blood samples were drawn in EDTA-containing tubes after induction of anesthesia (I-1); at 15 minutes into the anhepatic phase (I-2) prior to the administration of NAC or placebo; at 5 minutes before reperfusion (I-3); at 10 minutes after reperfusion (I-4); at 20 minutes after reperfusion (I-5); at 60 minutes after reperfusion (I-6); and at 1 hour after completion of the liver transplantation (I-7). Cytokine levels were determined using a technique which combined enzyme-linked immunosorbent assay (ELISA) and flow cytometry. Plasma IL-4 levels were significantly higher among the NAC-treated group than the placebo group at I-3 (P = .046) and I-4 (P = .041). Plasma IL-10 levels showed significant enhancement in the NAC-treated group at 5 minutes before reperfusion (I-3; P = .007). We concluded that intraoperative NAC administration during the anhepatic phase of liver transplantation significantly increased recipient IL-4 plasma levels before and after reperfusion, and IL-10 plasma values before reperfusion (I-3). These enhancements seemed to be associated with a protective effect against reperfusion injury.

Time course of intraoperative cytokine levels in liver transplant recipients

We evaluated the levels of several cytokines (interleukin [IL]-2, IL-4, IL-6, IL-10, tumor necrosis factor [TNF]-alpha, and interferon [IFN]-gamma) in plasma samples obtained before surgical intervention (T0) and during intraoperative liver transplantation: after induction of anesthesia (I-1), 15 minutes of anhepatic phase (I-2), 5 minutes before reperfusion (I-3), 10 minutes after reperfusion (I-4), 20 minutes after reperfusion (I-5), 60 minutes after reperfusion (I-6), and 1 hour after liver transplantation (I-7). Cytokine levels were determined using a technique which combines ELISA technique and flow cytometry. The study was approved by the local clinical research (ethics) committee. Written informed consent was obtained from patients' relatives. Twenty patients (14 men, 6 women) aged 23 to 61 years, recipients of a liver transplantation were studied. The cytokine IL-2 plasma values were maintained during the whole study period, with a slight increase at 15 minutes of anhepatic phase (I-2). IL-4 showed a peak value 20 minutes after reperfusion (I-5). IL-6 increased its plasma value starting at 15 minutes of anhepatic phase (I-2), maintaining high concentrations during the whole intraoperative period. IL-10 increased progressively, reaching a maximum 1 hour after transplantation (I-7). TNF-alpha reached maximum plasma levels 20 minutes after reperfusion (I-5), whereas IFN-gamma showed a peak at 15 minutes of anhepatic phase (I-2). Our results indicate that the anhepatic phase (I-2) is the earliest phase during which proinflammatory and anti-inflammatory cytokines, such as IL-6 and IL-10, respectively, are involved during liver transplantation. We conclude that IL-6 is the first cytokine involved in the inflammatory response during liver transplantation.

Early postoperative response of cytokines in liver transplant recipients

We evaluated the early postoperative response of several cytokines (IL-2, IL-4, IL-6, IL-10, TNF-alpha, IFN-gamma) prior to liver transplantation (T(0)) as well as 1, 6, and 12 hours and 1, 2, 3, 5, and 7 days afterward. Cytokine concentrations were correlated with serum levels of bilirubin as a predictor of postoperative complications. Cytokine levels were determined in plasma samples from 16 liver transplant recipients (13 men, 3 women) aged 43 to 61 years. IL-6 and IL-10 reached their maximum concentrations 1 hour after transplantation. Each increase in IL-6 correlated to a rise in IL-10. IL-2, IL-4, TNF-alpha, and IFN-gamma had a particular time-course for each patient studied. Bilirubin fell to almost normal values but not in cases of postoperative complications, where IL-6 showed values four times higher compared to those of liver transplant recipients who did not show postoperative complications. IL-6 and IL-10 plasma concentrations and serum bilirubin level might be useful as a predictive factor of postoperative complications in liver transplant recipients.

Proinsulin in development: New roles for an ancient prohormone

In postnatal organisms, insulin is well known as an essential anabolic hormone responsible for maintaining glucose homeostasis. Its biosynthesis by the pancreatic beta cell has been considered a model of tissue-specific gene expression. However, proinsulin mRNA and protein have been found in embryonic stages before the formation of the pancreatic primordium, and later, in extrapancreatic tissues including the nervous system. Phylogenetic studies have also confirmed that production of insulin-like peptides antecedes the morphogenesis of a pancreas, and that these peptides contribute to normal development. In recent years, other roles for insulin distinct from its metabolic function have emerged also in vertebrates. During embryonic development, insulin acts as a survival factor and is involved in early morphogenesis. These findings are consistent with the observation that, at these stages, the proinsulin gene product remains as the precursor form, proinsulin. Independent of its low metabolic activity, proinsulin stimulates proliferation in developing neuroretina, as well as cell survival and cardiogenesis in early embryos. Insulin/proinsulin levels are finely regulated during development, since an excess of the protein interferes with correct morphogenesis and is deleterious for the embryo. This fine-tuned regulation is achieved by the expression of alternative embryonic proinsulin transcripts that have diminished translational activity.

Time course of antioxidant enzyme activities in liver transplant recipients

Reactive oxygen species (ROS) play a central role in ischemia-reperfusion injury after organ transplantation. They are degraded by endogenous radical scavengers such as antioxidant enzymes. The purpose of this study was to evaluate the temporal variations of antioxidant enzyme activities in liver transplant recipients. The study was performed in 13 liver transplant patients (11 men and 2 women). Blood samples were obtained pre- and postsurgical intervention: before transplant (T(0)), and 1, 6, 12, 24, 48, and 72 hours, as well as 5 and 7 days thereafter. We determined total and specific superoxide dismutase (SOD) activity, catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GR) activities as well as malondialdehyde (MDA) and low-density lipoproteins (LDL). The results showed increased SOD and mainly GPX activities after liver transplantation, which correlated with MDA levels. Total SOD activity was mainly represented by Mn-SOD (75%) and Cu,Zn-SOD (25%), whereas Fe-SOD was not detected. In conclusion, the enhanced antioxidant enzyme activities reported in this study indicated a control of oxidative stress generated in liver transplantation. In this sense, although MDA levels showed an enormeous increase at 1 hour after transplantation, the lipid peroxidation was compensated for by GPX activity.

Split for two adults: what is the real feasibility?

INTRODUCTION

A split liver for two adults is a good theoretical option but the number of cases is low. We have tried to assess the feasibility of this technique.

MATERIALS AND METHODS

From April 2002 to April 2004, we evaluated 81 donors of which only 59 (72.8%) were used for transplantation of which 10 were grafted in other centers (pediatric or emergency code). Among the 49 donors the criteria for splitting were: ages >14 and <50 years, weight >70 and <100 kg, less than 3 days in the intensive care unit (ICU), hemodynamic stability, Na(+) < 160 mg/L, liver enzymes elevated no more than twofold, no macroscopic steatosis, and procurement in our hospital.

RESULTS

The mean donor age was 50.7 years (range: 16 to 77) of whom 25 were men (51%). The mean weight was 65.7 kg (range: 50 to 100) and days of ICU stay, 3 (range: 1 to 23). Six grafts (12%) were split. The reasons for not splitting were: age (n = 26 [53%]), weight (n = 17 [34.7%]), UCI >3 days (n = 9 [18.3%]), Na(+) > 160 (n = 1 [2%]), blood liver test elevated (n = 5 [10.2%]), steatosis (n = 6 [12.2%]), and procurement outside our center (n = 20 [40.8%]). The donors not suitable for splitting had: only one criteria (n = 12 [24.4%]; 2 (n = 23 [46.9%], 3 (n = 6 [12.2%]) or 4 (n = 2 [4.1%]). If we had had two suitable recipients, we could performed six more liver transplantations (12.2% increase).

CONCLUSIONS

The theoretical feasibility of a split liver for two adults is 12.2%, but the actual probability is lower because of lack of two adequate candidates.

Mycophenolate Mofetil–Induced Neutropenia in Liver Transplantation

BACKGROUND

Mycophenolate mofetil (MMF) is a potent, safe immunosuppressive agent for rescue therapy of acute and chronic rejection in orthotopic liver transplant recipients. It helps to reduce the serious toxic side effects of calcineurin inhibitors (CNIs). The side effects of MMF, such as bone marrow toxicity, have been reported. Herein we report four patients who underwent liver transplantation and developed neutropenia while receiving MMF.

METHODS

Between April 2002 and October 2003, we performed 24 liver transplants in 25 patients. Eighteen patients were given MMF for the following reasons: renal failure in nine (50%); treatment of acute rejection in three (16.6%); primary prophylaxis of rejection in five (27.7%); and CNI withdrawal in one (5.5%).

RESULTS

Of the 18 patients treated with MMF, there were 11 men (61.1%) and seven women (38.8%), with an overall mean age of 55.5 years. This therapy was ceased in four patients due to neutropenia (22%). Discontinuation of MMF was followed by a rapid and spontaneous rise in neutrophils in two patients. Granulocyte colony stimulating factor (GCSF) was administered to one patient and in another a bone marrow biopsy was performed due to persistent anemia, leukopenia, and thrombocytopenia. The mean time from starting MMF to the development of neutropenia was 4 months. Only the third patient showed elevated levels of MMF.

CONCLUSIONS

MMF is a potent immunosuppressive agent in liver transplantation. However, because serious hematologic toxicity has been reported, we recommend caution in administration and careful monitoring of blood levels.

Postlaparoscopic cholecystectomy bile leak secondary to an accessory duct of Luschka

Complications produced by the sectioning of a nonvisualized duct of Luschka are uncommon during laparoscopic cholecystectomy. From 1999 through 2003, we performed 1351 laparoscopic cholecystectomies in our department and observed 2 cases (0.15%) of bile leakage due to duct of Luschka injury. Injury during laparoscopic cholecystectomy is usually produced by an excessively deep plane of dissection and by the anatomical localization of this accessory duct. Clinical symptoms are scarce after duct of Luschka injury. Numerous diagnostic methods have been used to detect these injuries. Nevertheless, careful clinical examination is still of the utmost importance. Noninvasive treatments are usually effective. In patients who present with acute abdomen, as in our cases, or who are not cured by noninvasive treatments, exploratory laparotomy is the best approach. The surgical treatment consists of a lavage of the abdominal cavity, closure of the duct of Luschka, and intraoperative cholangiography to confirm that the biliary tree is intact.

Retroperitoneal actinomycosis due to dropped gallstones

Dropped bile and gallstones after accidental perforation of the biliary gallbladder is a frequent event during laparoscopic cholecystectomy and is generally of no clinical importance. However, calculi left in the abdominal cavity can produce a series of severe late complications. We present a patient with retroperitoneal actinomycosis produced by dropped gallstones after a laparoscopic cholecystectomy.