Colourful coexistence of red and green picocyanobacteria in lakes and seas

Hutchinson's paradox of the plankton inspired many studies on the mechanisms of species coexistence. Recent laboratory experiments showed that partitioning of white light allows stable coexistence of red and green picocyanobacteria. Here, we investigate to what extent these laboratory findings can be extrapolated to natural waters. We predict from a parameterized competition model that the underwater light colour of lakes and seas provides ample opportunities for coexistence of red and green phytoplankton species. To test this prediction, we sampled picocyanobacteria of 70 aquatic ecosystems, ranging from clear blue oceans to turbid brown peat lakes. As predicted, red picocyanobacteria dominated in clear waters, whereas green picocyanobacteria dominated in turbid waters. We found widespread coexistence of red and green picocyanobacteria in waters of intermediate turbidity. These field data support the hypothesis that niche differentiation along the light spectrum promotes phytoplankton biodiversity, thus providing a colourful solution to the paradox of the plankton.     

ARP, a peptide derived from the stress-associated acetylcholinesterase variant, has hematopoietic growth promoting activities

BACKGROUND: Psychological stress induces rapid and long-lasting changes in blood cell composition, implying the existence of stress-induced factors that modulate hematopoiesis. Here we report the involvement of the stress-associated "readthrough" acetylcholinesterase (AChE-R) variant, and its 26 amino acid C-terminal domain (ARP) in hematopoietic stress responses. MATERIALS AND METHODS: We studied the effects of stress, cortisol, antisense oligonucleotides to AChE, and synthetic ARP on peripheral blood cell composition and clonogenic progenitor status in mice under normal and stress conditions, and on purified CD34 cells of human origin. We employed in situ hybridization and immunocytochemical staining to monitor gene expression, and 5-bromo-2-deoxyuridine (BrdU), primary liquid cultures, and clonogenic progenitor assays to correlate AChE-R and ARP with proliferation and differentiation of hematopoietic progenitors. RESULTS: We identified two putative glucocorticoid response elements in the human ACHE gene encoding AChE. In human CD34+ hematopoietic progenitor cells, cortisol elevated AChE-R mRNA levels and promoted hematopoietic expansion. In mice, a small peptide crossreacting with anti-ARP antiserum appeared in serum following forced swim stress. Ex vivo, ARP was more effective than cortisol and equally as effective as stem cell factor in promoting expansion and differentiation of early hematopoietic progenitor cells into myeloid and megakaryocyte lineages. CONCLUSIONS: Our findings attribute a role to AChE-R and ARP in hematopoietic homeostasis following stress, and suggest the use of ARP in clinical settings where ex vivo expansion of progenitor cells is required.     

Efficacy of N-Acetyl Cysteine in Traumatic Brain Injury

In this study, using two different injury models in two different species, we found that early post-injury treatment with N-Acetyl Cysteine (NAC) reversed the behavioral deficits associated with the TBI. These data suggest generalization of a protocol similar to our recent clinical trial with NAC in blast-induced mTBI in a battlefield setting [1], to mild concussion from blunt trauma. This study used both weight drop in mice and fluid percussion injury in rats. These were chosen to simulate either mild or moderate traumatic brain injury (TBI). For mice, we used novel object recognition and the Y maze. For rats, we used the Morris water maze. NAC was administered beginning 30–60 minutes after injury. Behavioral deficits due to injury in both species were significantly reversed by NAC treatment. We thus conclude NAC produces significant behavioral recovery after injury. Future preclinical studies are needed to define the mechanism of action, perhaps leading to more effective therapies in man.     

Zur Vitalfärbung an der Unterzungendrüse der Ratte

Ohne ZusammenfassungMeinem verehrten Lehrer, Herrn Prof.Tandler, danke ich für die geistige und materielle Unterstützung dieser Arbeit.     

Enhanced photosynthesis and redox energy production contribute to salinity tolerance in Dunaliella as revealed by homology-based proteomics

Salinity is a major limiting factor for the proliferation of plants and inhibits central metabolic activities such as photosynthesis. The halotolerant green alga Dunaliella can adapt to hypersaline environments and is considered a model photosynthetic organism for salinity tolerance. To clarify the molecular basis for salinity tolerance, a proteomic approach has been applied for identification of salt-induced proteins in Dunaliella. Seventy-six salt-induced proteins were selected from two-dimensional gel separations of different subcellular fractions and analyzed by mass spectrometry (MS). Application of nanoelectrospray mass spectrometry, combined with sequence-similarity database-searching algorithms, MS BLAST and MultiTag, enabled identification of 80% of the salt-induced proteins. Salinity stress up-regulated key enzymes in the Calvin cycle, starch mobilization, and redox energy production; regulatory factors in protein biosynthesis and degradation; and a homolog of a bacterial Na(+)-redox transporters. The results indicate that Dunaliella responds to high salinity by enhancement of photosynthetic CO(2) assimilation and by diversion of carbon and energy resources for synthesis of glycerol, the osmotic element in Dunaliella. The ability of Dunaliella to enhance photosynthetic activity at high salinity is remarkable because, in most plants and cyanobacteria, salt stress inhibits photosynthesis. The results demonstrated the power of MS BLAST searches for the identification of proteins in organisms whose genomes are not known and paved the way for dissecting molecular mechanisms of salinity tolerance in algae and higher plants.     

Distribution plasticity of the human estrogen receptor alpha in live cells: distinct imaging of consecutively expressed receptors

An amino-terminal fusion of the human estrogen receptor α (ER) with human O⁶-alkylguanine-DNA alkyltransferase (AGT) enabled the observation and distinction of consecutively expressed ER populations by sequential pulse labeling of the AGT tag with different fluorescent O⁶-alkylguanine derivatives in live cells. The application of agonists and antagonists led to the characteristic speckled redistribution of fluorescent receptors in the nucleus as visualized by confocal microscopy. To investigate where newly synthesized receptors were localized in individual cells with respect to their older relatives in response to extracellular chemical signals, receptor expression was continued for 4 h and newly synthesized receptors were labeled with a new fluorophore spectrally distinct from the first probe. This strategy enabled a time-resolved analysis of the formation of ER-enriched protein complexes in distinct nucleoplasmic compartments. Such complexes represent important but hitherto uncharacterized macromolecular structures involved in ER function. Different, long-lasting effects were observed depending on the type of ligand. For example, 4 h after pulsed application of the partial antagonist 4-hydroxytamoxifen, the second receptor population exhibited a speckled pattern in the cell nucleus that overlapped with the first receptor population pattern. This novel finding suggests that the intranuclear positioning of receptor aggregates is not random but influenced in a ligand-dependent manner. The antagonist ICI 182,780 (7-α-[9-(4.4,5,5,5-pentafluoropentylsulfinyl)nonyl]estra-1,3,5(10)-triene-3,17-β-diol), a potent drug used in cancer treatment, led to down-regulation of the first receptor population and newly expressed receptors accumulated in the cytoplasm. In contrast, the natural agonist 17β-estradiol resulted in significantly shorter effects. Four hours after ligand application, newly expressed receptors were homogeneously distributed in the nucleus as in untreated control cells. We present the pulse labeling of AGT-ER fusion proteins with different fluorophores as a novel tool for investigating the functional regulation of nuclear receptors in individual cells.     

A Long-Acting PYY3–36 Analog Mediates Robust Anorectic Efficacy with Minimal Emesis in Nonhuman Primates

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