Arctic zooplankton develop large energy reserves, as an adaptation to strong seasonality, making them valuable prey items. We quantified the energy content (kJ g
−1
dry weight) of abundant krill ...(arcto-boreal
, Thysanoessa inermis
and boreal,
Meganyctiphanes norvegica
) and amphipods (Arctic,
Themisto libellula
and sub-Arctic-boreal,
Themisto abyssorum
) in the Barents Sea in late summer (August) and early winter (December). Variation in energy content was attributed to species-specific traits and body size categories, the latter in part as a proxy for ontogeny.
T. inermis
had the highest energy content, (Aug: 26.8 ± 1.5 (SD) kJ g
−1
) and remained similar from summer to winter. Energy content increased in
M. norvegica
and decreased in both amphipod species, with the lowest energy content being in
T. abyssorum
(Dec: 17.8 ± 0.8 kJ g
−1
). The effect of body size varied between species, with energy content increasing with size in
T. inermis
and
T. libellula
, and no change with size in
M. norvegica
and
T. abyssorum
. The reproductive stages of
T. libellula
differed in energy content, being highest in gravid females. Energy content varied with species’ dependence on energy storage. Our findings highlight how phylogenetically and morphologically similar prey items cannot necessarily be considered equal from a predator´s perspective. Energetically, the northern
T. inermis
was higher quality compared to the more southern
M. norvegica
, and mostly so during summer. Ecological models and management strategies should consider such variation in prey quality, especially as Arctic borealization is expected to change species composition and the energetic landscape for predators.
The effects of climate change are leading to pronounced physical and ecological changes in the Arctic Marginal Ice Zone (MIZ). These are not only of concern for the research community but also for ...the tourism industry dependent on this unique marine ecosystem. Tourists increasingly become aware that the Arctic as we know it may disappear due to several environmental threats, and want to visit the region before it becomes irrevocably changed. However, 'last-chance tourism' in this region faces several challenges. The lack of infrastructure and appropriate search and rescue policies are examples of existing issues in such a remote location. Additionally, tourism itself may further amplify the physical and ecological changes in the Arctic region. In this article, we provide an interdisciplinary analysis of the links between the MIZ, climate change and the tourism industry. We also identify existing regulations and the need for new ones concerning operations in the MIZ and in the Arctic Ocean.
Trypanosoma brucei procyclic forms possess three different malate dehydrogenase isozymes that could be separated by hydrophobic interaction chromatography and were recognized as the mitochondrial, ...glycosomal and cytosolic malate dehydrogenase isozymes. The latter is the only malate dehydrogenase expressed in the bloodstream forms, thus confirming that the expression of malate dehydrogenase isozymes is regulated during the
T. brucei life cycle. To achieve further biochemical characterization, the genes encoding mitochondrial and glycosomal malate dehydrogenase were cloned on the basis of previously reported nucleotide sequences and the recombinant enzymes were functionally expressed in
Escherichia coli cultures. Mitochondrial malate dehydrogenase showed to be more active than glycosomal malate dehydrogenase in the reduction of oxaloacetate; nearly 80% of the total activity in procyclic crude extracts corresponds to the former isozyme which also catalyzes, although less efficiently, the reduction of
p-hydroxyphenyl-pyruvate. The rabbit antisera raised against each of the recombinant isozymes showed that the three malate dehydrogenases do not cross-react immunologically. Immunofluorescence experiments using these antisera confirmed the glycosomal and mitochondrial localization of glycosomal and mitochondrial malate dehydrogenase, as well as a cytosolic localization for the third malate dehydrogenase isozyme. These results clearly distinguish
Trypanosoma brucei from
Trypanosoma cruzi, since in the latter parasite a cytosolic malate dehydrogenase is not present and mitochondrial malate dehydrogenase specifically reduces oxaloacetate.
The crystal structure of tyrosine aminotransferase
(TAT) from the parasitic protozoan Trypanosoma cruzi,
which belongs to the aminotransferase subfamily Iγ,
has been determined at 2.5 Å resolution ...with the
R-value R = 15.1%. T. cruzi
TAT shares less than 15% sequence identity with aminotransferases
of subfamily Iα but shows only two larger topological
differences to the aspartate aminotransferases (AspATs).
First, TAT contains a loop protruding from the enzyme surface
in the larger cofactor-binding domain, where the AspATs
have a kinked α-helix. Second, in the smaller substrate-binding
domain, TAT has a four-stranded antiparallel β-sheet
instead of the two-stranded β-sheet in the AspATs.
The position of the aromatic ring of the pyridoxal-5′-phosphate
cofactor is very similar to the AspATs but the phosphate
group, in contrast, is closer to the substrate-binding
site with one of its oxygen atoms pointing toward the substrate.
Differences in substrate specificities of T. cruzi
TAT and subfamily Iα aminotransferases can be attributed
by modeling of substrate complexes mainly to this different
position of the cofactor-phosphate group. Absence of the
arginine, which in the AspATs fixes the substrate side-chain
carboxylate group by a salt bridge, contributes to the
inability of T. cruzi TAT to transaminate acidic
amino acids. The preference of TAT for tyrosine is probably
related to the ability of Asn17 in TAT to form a hydrogen
bond to the tyrosine side-chain hydroxyl group.
No one knows for sure how the future will look. However, there is no better time than today to begin envisioning and creating our preferred future. This article discusses several factors that will ...impact the future of nursing staff development. Twenty-one predictions are offered that include: change, restructuring, teamwork, leadership development, paradigms, support networks, staff development roles, learning, value of life experiences, patient education, cultural diversity, and technology. Strategies for educators to position themselves for the future are suggested. The future is ours to create. The intent of this manuscript is to challenge staff development educators to create visions and develop strategies to construct the preferred future of their roles and the nursing staff development function.
Abstract only
Dysfunctional Notch and Wnt signaling contributes to poor muscle regeneration and increased fibrosis in aged skeletal muscle. 20‐ hydroxyecdysone (20E), a phytoecdysteroid produced by ...the plant Ajuga turkestanica, increases muscle strength in young rats. The objective of this study was to determine if an extract from A. turkestanica (ATE), enriched in phytoecdysteroids, affects Notch and Wnt signaling in skeletal muscle of aged mice. Aged male C57BL/6 mice (20 mo) received ATE, 20E, or vehicle (CT) for 28 days. Immunohistochemistry on tricep brachii was performed using antibodies directed to Notch and Wnt signaling markers. Delta ligand expression in the triceps of ATE‐treated mice decreased relative to CT (p = 0.024) and 20E‐treated mice (p = 0.039). There was a non significant decrease of active beta‐catenin expression (33%) in triceps of 20E‐treated mice, compared to ATE or CT. H&E staining revealed fewer centrally‐located nuclei with 20E treatment compared to CT or ATE, suggesting fewer cycles of muscle regeneration with 20E. In conclusion, phytoecdysteroids, individually or in an enriched extract, did not rejuvenate Notch signaling or influence Wnt signaling in aged sedentary mouse skeletal muscle. However, 20E appears to attenuate the age‐related muscle regeneration process as evidenced by fewer centrallyn‐ucleated fibers. Supported in part by a USDA Kannapolis Scholars Fellowship.
It is well documented that the activity of Na+,K+-ATPase can be inhibited by the arachidonic acid metabolite, 20-hydroxyeicosa-tetraenoic acid (20 HETE). Evidence is presented here that this effect ...is mediated by protein kinase C (PKC). PKC inhibitors abolished 20 HETE inhibition of rat Na+,K+-ATPase in renal tubular cells. 20 HETE caused translocation of PKC alpha from cytoplasm to membrane in COS cells. It also inhibited Na+,K+-ATPase activity in COS cells transfected with rat wild-type renal Na+,K+-ATPase alpha1 subunit, but not in cells transfected with Na+,K+-ATPase alpha1, where the PKC phosphorylation site, serine 23, had been mutated to alanine. PKC-induced phosphorylation of rat renal Na+,K+-ATPase, as well as of histone was strongly enhanced by 20 HETE at the physiologic calcium concentration of 1.3 microM, but not at the calcium concentration of 200 microM. The results indicate that phospholipase A2-arachidonic acid-20 HETE pathway can exert important biological effects via activation of PKC and that this effect may occur in the absence of a rise in intracellular calcium.
Tyrosine aminotransferase was purified to homogeneity from epimastigotes of Trypanosoma cruzi by a method involving chromatography on DEAE-cellulose, gel filtration on Sephacryl S-200 and ...chromatography on Mono Q in an f.p.l.c. system. The purified enzyme showed a single band in SDS/PAGE, with an apparent molecular mass of 45 kDa. Since the apparent molecular mass of the native enzyme, determined by gel filtration, is 91 kDa, the native enzyme is a dimer of similar subunits. The amino-acid composition was determined, as well as the sequences of three internal peptides obtained by CNBr cleavage at Met residues. Both criteria suggest considerable similarity with the tyrosine aminotransferases from rat and from human liver. The enzyme contains nine 1/2 Cys residues, three free and the others forming three disulphide bridges. The enzyme is not N-glycosylated. The isoelectric point is 4.6-4.8. The optimal pH for the reaction of the enzyme with tyrosine as a substrate is 7.0. The apparent Km values for tyrosine, phenylalanine and tryptophan, with pyruvate as a co-substrate, were 6.8, 17.9 and 21.4 mM, respectively, whereas those for pyruvate, alpha-oxoglutarate and oxaloacetate, with tyrosine as a substrate, were 0.5, 38 and 16 mM respectively. The purified tyrosine aminotransferase acts as an alanine aminotransferase as well and the activity seems to reside in the same enzyme molecule. The results suggest that the enzyme is a general aromatic-amino-acid transaminase, with high sequence similarity to tyrosine aminotransferases from rat and human liver.
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