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Heracleum mantegazzianum growth phases and furocoumarin content.

The observation of photocontact dermatitis from Heracleum mantegazzianum Sommier et Levier in 2 gardeners at work prompted the analysis of furocoumarin content of stem, leaves and fruits of the plant during a period of 1 year. Their concentration was found to be maximal in fruit, intermediate in leaf, and minimal in stem. Psoralen was the most prevalent substance in the leaf and bergapten in the fruit. In the stem, in contrast, individual furocoumarins were found in lower but variable concentrations. 3 furocoumarin seasonal peaks were observed in the leaf: the maximal peak occurred in June, the intermediate in August, the minimal in November. This trend corresponds to 3 biological phases of the weed.

5-Methoxypsoralen↗

Conditions relevant to the occurrence of acid-fast bacilli in sphagnum vegetation.

Biotopes with intact sphagnum vegetation were studied in Naustdal, West Norway: the health district with the former highest leprosy incidence rates in Norway. Concentration of acid-fast bacilli and concentration of non-cultivable acid-fast bacilli found in the vegetation fluid were compared with a series of variables related to the local environment and to the samples of vegetation. In bivariate analyses high concentrations were found in biotopes with orientation toward South, with a high coverage of vascular plants and with presence of Ericaceae. High concentrations were also found where dry weight of a vegetation was high, where pH in the fluid was low and where dry weight of the fluid was high. In a multivariate analysis, log-linear model, based on concentration of acid-fast bacilli as the dependent variable and orientation, pH, dry weight of vegetation and dry weight of fluid as the independent variables, all two-factor effects including the dependent variable were retained in the model. Furthermore, orientation versus dry weight of vegetation and dry weight of fluid versus dry weight of vegetation were retained.

Bacillus↗

Phytostat for continuous culture and automatic sampling of plant-cell suspensions.

An apparatus for growing plant cells in suspension culture is described; it may be used for continuous or batch culture, and is equipped with a valve for automatic collection of samples. Aeration is by continuous bubbling of air into the culture through fritted glass. Normal culture-duplication times are from 30 to 35 hours.

Automation↗

Hernandulcin: an intensely sweet compound discovered by review of ancient literature.

Ancient Mexican botanical literature was systematically searched for new plant sources of intensely sweet substances. Lippia dulcis Trev., a sweet plant, emerged as a candidate for fractionation studies, and hernandulcin, a sesquiterpene, was isolated and judged by a human taste panel as more than 1000 times sweeter than sucrose. The structure of the sesquiterpene was determined spectroscopically and confirmed by chemical synthesis. Hernandulcin was nontoxic when administered orally to mice, and it did not induce bacterial mutation.

Animals↗

2005: signaling breakthroughs of the year.

2005 was particularly notable for the range and scope of exciting advances in cell signaling research. Nominations from leading scientists ranged from plant signaling, neurobiology, and immunology to systems biology and structural biology. In plant biology, a new piece added to a long-standing puzzle in auxin signaling was discovered. The exploitation and regulation of RNA in cell signaling was also in the limelight. Intriguing new twists were highlighted in relation to functional and dysfunctional signaling in the brain, calcium-mediated signals, and the innate immune response. Finally, mathematical and statistical analysis of biochemical networks provided new insights into the circuitry of cell signaling pathways.

Biology↗

Teaching resources. Model of the TIR1 pathway for auxin-mediated gene expression.

Auxin mediates numerous plant responses, some of which have been shown to require transcriptional regulation. One auxin response pathway, which depends on the relief of transcriptional repression, is mediated by TIR1 (transport inhibitor response protein 1). TIR1 is an auxin receptor and also a subunit of an SCF-type ubiquitin ligase. In the presence of a low concentration of auxin in the nucleus, members of the Aux/IAA family of transcriptional repressors bind to ARF proteins and inhibit the transcription of specific auxin response genes. Increased nuclear concentrations of auxin promote auxin binding to TIR1, causing the Aux/IAA proteins to associate with TIR1 and leading to their degradation by a proteasome-mediated pathway. This decreases the concentration of Aux/IAA proteins in the nucleus and thereby enables the expression of certain auxin response genes.

Arabidopsis Proteins↗

Teaching resources. Movement of macromolecules in plant cells through plasmodesmata.

Plasmodesmata are intercellular organelles in plants that allow the passage of molecules between plant cells. Movement through plasmodesmata may allow transcription factors expressed in one cell to move into adjacent cells, thereby regulating gene expression non-cell autonomously. The two animations illustrate (i) movement of a protein through an individual plasmodesma and (ii) an experiment to detect the movement of the transcription factor through plasmodesmata from the L1 layer of a plant meristem into the L2 and L3 layers. These two animations would be useful in teaching plant biology or plant development or a cell biology class discussing mechanisms of intercellular transport.

Biological Transport↗

Dr. Ward's Case.

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Animals↗