The human basal forebrain integrates the old and the new

Acquisition of new learning is challenged by the phenomenon of proactive interference (PI), which occurs when previous learning disrupts later learning. Whereas human neuroimaging studies have focused on the cortical contributions to interference resolution, animal studies demonstrate that efficient resolution of PI depends on cholinergic modulation from basal forebrain (BF). Whether the BF promotes PI resolution in humans is unknown. Here, we adapted a PI paradigm from animal studies for use in a functional MRI experiment. During PI resolution, neurologically intact subjects recruited a BF network that included afferent anterior and posterior cortical sites associated with efficient memory acquisition and perceptual processing. Despite normal performance, nonamnesic patients with alcoholism, which is known to disrupt BF function, did not activate a BF network but instead invoked anterior cortical sites traditionally associated with executive function. These results provide evidence for parallel neural systems, each with the potential to resolve interference in the face of competing information.     

Varietal differences of quinoa’s tolerance to saline conditions

Aims

This study aimed to assess varietal differences of quinoa’s tolerance to salinity and to investigate physiological mechanisms conferring these differences.

Methods

Production of biomass in fourteen varieties grown under saline conditions was analysed in a pot experiment. For two contrasting varieties, the Danish variety Titicaca and the Bolivian variety Utusaya gas exchange, chlorophyll content index (CCI), fluorescence and ion relations were studied.

Results

Responses to salinity differed greatly among the varieties; least affected were two varieties from the Bolivian altiplano and a variety from Peru. Titicaca and Utusaya both had substantially increased K+ concentrations in the leaf sap. But, Utusaya was much more efficient in restricting xylem Na+ loading. Xylem Na+ and K+ loading were found to be uncoupled. Utusaya maintained a relatively high stomatal conductance resulting in an only 25% NaCl-induced reduction in net CO₂ assimilation compared to a 67% reduction in salt treated Titicaca plants. Maximum photochemical efficiency of PSII was not affected by salinity.

Conclusion

In addition to maintaining high gas exchange, tolerant varieties better control xylem Na+ loading. To what extent this control is related to radial root Na+ uptake or to the activity of Na+/H+-exchangers at the xylem parenchyma boundary remains to be studied.     

In vitro biosynthesis of the cyanogenic glucoside taxiphyllin in Triglochin maritima

When l-tyrosine and NADPH were incubated with a microsomal fraction from Triglochin maritima seedlings, 4-hydroxymandelonitrile (measured as 4-hydroxybenzaldehyde and HCN) and 4-hydroxyphenylacetonitrile were synthesized. Taxiphyllin, a cyanogenic glucoside occurring in this plant, was formed when UDPglucose and a soluble protein fraction from T. maritima, were also included in the assay. The above glucosyl transferase activity also produced taxiphyllin when incubated with R,S-4-hydroxymandelonitrile and UDPglucose. No trace of dhurrin, the enantiomer of taxiphyllin, was detected. The highest microsomal activity was found in 5- to 6-day-old etiolated seedlings. It was absolutely necessary to remove all seed coats from the seedlings in order to obtain an active microsomal fraction.     

Einfluss von 2,3,5-Trijodbenzoesäure auf die Blütenbildung und die vegetative Gestaltung von Kalanchoë Blossfeldiana

Zusammenfassung In die Blätter vonKalanchoë Bloßfeldiana wurde bei variierter photoperiodischer Behandlung 2,3,5-Trijodbenzoesäure in verschiedenen Verdünnungen (15000–11 000 000) eingespritzt.Weder im Langtag noch im Kurztag konnte dadurch eine Förderung des Blühens erreicht werden, sondern in allen Fällen trat Blühhemmung ein. Die Hemmung war um so stärker, je höher die TJBS-Konzentration war.Auch das vegetative Wachstum wurde mit zunehmender TJBS-Konzentration gehemmt.Außerdem bewirkte die TJBS Verwachsungen zwischen Haupt- und Nebenstengeln, sowie sonderbare Mißbildungen an den sich neu bildenden Blättern: becher- bis tütenförmige Verwachsungen und fast oder völlig geschlossene kropfartig-keulenförmige Hohlgebilde am Sproßende. Sie gingen entweder in dieser Form schließlich zugrunde, oder wurden—was häufiger eintrat—von einem neuen Sproß durchwachsen. Dieser Sproß konnte wieder ebenso starke Mißbildungen haben, oder er trug —meistens—weniger extreme Abnormitäten. Oft hatte er auch normale Blätter, die aber nicht paarweise gegenständig, sondern wechselständig oder zu dreien quirlständig waren.Die Mißbildungen waren um so stärker, je höher die Konzentration der injizierten TJBS-Lösung war; mit zunehmender Entfernung von der Injektionsstelle und mit zunehmender Zeit seit der Einspritzung nahmen sie ab.Aus den Beobachtungen beim Blühen wird Stellung zur Blühhemmtheorie genommen.Mit 10 Textabbildungen.Hans Fitting zum 75. Geburtstag gewidmet.     

Cytotaxonomische Beiträge zur Flora der Ostalpenländer,II

Ohne Zusammenfassung     

C6-aldehyde formation from linolenic acid in fruit cells cultured in vitro

Heterotrophic plant cells of three apple cultivars, two pear cultivars, strawberry, and tomato were cultured in vitro. Cell homogenates in the presence of linolenic acid formed n-hexanal, (Z)-3-hexenal, (E)-2-hexenal, and, in one apple cultivar, (Z)-3-hexenol and its acetate. Homogenates of photomixotropic apple cv. Goldparmäne cells contained eight times more (E)-2-hexenal than homogenates of non-green cells.     

Characterization and quantification of karlotoxins by liquid chromatography–mass spectrometry

Karlodinium veneficum is a cosmopolitan dinoflagellate with a worldwide distribution in mesohaline temperate waters. The toxins from K. veneficum, or karlotoxins (KmTxs), which have been implicated in fish kill events, have been purified from monoalgal cultures, and shown to possess hemolytic, cytotoxic and ichthyotoxic activities. Three karlotoxins (KmTx 1–1, KmTx 1–3 and KmTx 2) have been isolated from two different North American strains of K. veneficum and characterized using liquid chromatography–mass spectrometry (LC–MS). KmTx 1 karlotoxins have a UV absorption maximum (λ_max 225 nm) at lower wavelengths than KmTx 2 karlotoxins (λ_max 235 nm). The exact masses and predicted empirical formulae for the karlotoxins (KmTx 1–1, 1308.8210, C₆₇H₁₂₀O₂₄; KmTx 1–3, 1322.8637, and C₆₉H₁₂₆O₂₃; KmTx 2, 1344.7938, C₆₇H₁₂₁ClO₂₄) were determined using high resolution mass spectrometry. Although the individual toxins produce a single peak in reverse phase high performance liquid chromatography (HPLC), MS revealed congeners co-eluting within each peak. These congeners could be separated under normal phase chromatography and revealed a single hydroxylation being responsible for the mass differences. Multistage MS (MSⁿ) showed that the three KmTxs and their congeners share a large portion of their structures including an identical 907 amu core fragment.

These data were used to develop a quantitative LC–MS assay for karlotoxins from cultures and environmental samples. The sensitivity afforded by MS detection compared to UV absorbance allowed toxin quantification at 0.2 ng when injected on column. Aqueous solutions of karlotoxins were found to quantitatively adsorb to PTFE and nylon membrane filters. Aliquots from whole cultures or environmental samples could be concentrated and desalted by adsorption to PTFE syringe filters and karlotoxins eluted with methanol for analysis by LC–MS. This simplified solid phase cleanup afforded new data indicating that each karlotoxin may also exist as sulfated derivatives and also provided a rapid detection method for karlotoxin from environmental samples and whole cultures.     

A new cyanogenic glycoside from Hordeum vulgare

From leaf extracts of 10-day-old seedlings of barley, a new cyanogenic glycoside has been isolated. This compound is 2-β-d-glucopyranosyl-oxy-3-methyl-(2R )-butyronitrile, the epimer of heterodendrin.     

N-Acetyl Aspartic Acid (NAA) and N-Acetyl Aspartylglutamic Acid (NAAG) in Human Ventricular,Subarachnoid, and Lumbar Cerebrospinal Fluid

N-Acetylaspartic and N-acetylaspartylglutamic acid concentrations in human ventricular, subarachnoid and lumbar cerebrospinal fluid were measured by combined gas chromatography-mass spectrometry using selected ion monitoring with deuterated internal standards. N-Acetylaspartate concentrations were in the range 55, 9, and 1 M, respectively; N-acetylaspartylglutamate concentrations in the same fluids were in the range 8, 3 and 4 M, respectively. There did not appear to be any difference in lumbar fluid concentrations of either compound between control subjects, schizophrenic patients, Alzheimer's disease patients and a pooled group of patients with neurological degeneration. Ventricular concentrations of both compounds were greatly increased in deceased patients suggesting that maintenance of their intracellular concentrations is probably energy dependent. The concentrations of these compounds in lumbar cerebrospinal fluid from living, and ventricular cerebrospinal fluid from deceased subjects were weakly correlated with one another. In lumbar fluid neither compound appeared to be correlated with age. Analysis of serially collected lumbar samples from two subjects showed a weak concentration gradient for both compounds. Neither antipsychotic medication nor the acid transport inhibitor probenecid had any effect on lumbar concentrations of either compound. Attempts to use anion exchange high pressure liquid chromatography with UV detection for measurement of the low concentrations of N-acetylaspartate found in cerebrospinal fluid from living subjects were unsuccessful.     

Inhibition of nuclear import mediated by the Rev-arginine rich motif by RNA molecules

The HIV-1 Rev protein plays a pivotal role in viral replication, and therefore, inhibition of its function should block the progression of the virus-induced immune deficiency syndrome (AIDS). Here, RNA molecules have been shown to inhibit import of the HIV-1 Rev protein into nuclei of permeabilized cells. Nuclear uptake of biotinylated recombinant His-tagged Rev-GFP was assessed in nuclear extracts from digitonin-permeabilized cells by binding to either importin beta-receptors or nickel molecules immobilized on a microtiter plate. Using this method together with fluorescence microscopy, we determined that nuclear import of Rev is inhibited by the addition of a reticulocyte lysate which routinely is used as a source of nuclear import receptors. This inhibition was released by treatment with the RNase enzyme. Also t-RNA molecules and the oligoribonucleotide RRE IIB, namely, the second stem structure of the Rev responsive element (RRE) of the viral RNA, inhibit Rev nuclear import. Similar results were obtained when BSA molecules with covalently attached Rev-arginine rich motif (ARM) peptides were used as a nuclear transport substrate, indicating that the nuclear import inhibition of the Rev protein is due to the presence of the ARM domain. Binding experiments revealed that the RNA molecules inhibit the interaction between the ARM region and importin beta, implying that the RNA prevents the formation of the import complex. The implication of our results for the regulation of the nuclear import of Rev as well as for the use of RNA molecules as antiviral drugs is discussed.