Micropropagation of Rollinia mucosa (JACQ.) baill

Summary A protocol for in vitro propagation of Rollinia mucosa, an important medicinal plant, was developed. The presence of 500 mg l⁻¹ polyvinylpyrrolidone (PVP) during explant excision was important to avoid browning. Axillary buds, adventitious buds, and shoot cluster proliferation were achieved from epicotyl and hypocotyl explants from nursery-grown seedlings. The highest direct organogenesis percentage from hypocotyl explants was obtained upon culture of explants on Murashige and Skoog medium supplemented with 2.2 μM benzyladenine (BA) plus 2.32 μM kinetin. Epicotyl explants display highest regeneration frequency on a medium containing 8.8 μM BA and 0.54 μM naphthaleneacetic acid. Gibberellic acid was necessary for shoot elongation. Root induction was observed when shoots were pretreated with activated charcoal for 7 d in the dark before culture on Woody Plant Medium supplemented with 49.21 μM indolebutyric acid for 10 d. Root development was observed when 20 g l⁻¹ sucrose was used. Rooted plantlets were acclimatized and grown in the greenhouse.     

Depletion of taurine in the adult rat retina

Taurine is the major free amino acid of the vertebrate retina. Treatment of rats with guanidinoethyl sulfonate (GES), a taurine analogue which competes with taurine for transport sites, leads to depletion of 60% of retinal taurine with little effect on other free amino acids. Supplementation of the diet with 0.3% taurine gives partial protection against depletion, confirming that taurine-GES competition underlies part of the effects. The magnitude of the depletion suggests the importance of taurine transport across the blood-retinal barrier for the maintenance of retinal taurine levels.     

Medicinal plants of the Argentine Yungas plants of the Las Yungas biosphere reserve, Northwest of Argentina, used in health care

We have compared the species richness of medicinal plants and the differential patterns of use amongst settlements in the Andean communities of Northwest Argentina which have differing levels of isolation. About 259 ethnoespecies, belonging to 74 plant families, were included, representing between 70 and 80% of the total estimate. The results indicate that Coronopus didymus is the most relevant and important species. The method of use of medicinal plants and the ailments treated by rural doctors compared to those of the layperson is different. Native and exotic plants are used differently according to the body system treated. There are some relationships between internal and external use and body systems and recipes. The greater medicinal species richness found in the less isolated locations is due to external enriching cultural influences.     

Continuous-flow NMR culture system for mammalian cells

A continuous-flow NMR culture system for mammalian cells has been developed on which ³¹P-NMR experiments under complete and strictly physiologic conditions have been performed. Observations on the response of the cellular metabolism to stresses such as starvation, low temperature and changes in environmental pH monitored by ³¹P-NMR are reported. The response of the intracellular pH relative to the external pH of the growth medium is studied. We find that under the experimental conditions used there exists a ΔpH varying between less than 0.2 and more than 0.6 pH units. These results are compatible with those obtained using other techniques.     

Trypsin and α-amylase inhibitors are differentially induced in leaves of amaranth (Amaranthus hypochondriacus) in response to biotic and abiotic stress

Seeds of Amaranthus hypochondriacus L. are known to accumulate a trypsin-inhibitor (ATI) member of the potato-I inhibitor family and an α -amylase inhibitor (AAI), possessing a knottin-like fold. They are believed to have a defensive role due to their inhibition of trypsin-like enzymes and α -amylases of insect pests. In this work, both inhibitory activities were found in leaves of young A. hypochondriacus plants. High constitutive levels of foliar inhibitory activity against bovine trypsin and insect α -amylases were detected in in vitro assays. Trypsin inhibitory activity was further increased by exposure to diverse treatments, particularly water stress. Salt stress, insect herbivory and treatment with exogenous methyl jasmonate (MeJA) or abscisic acid (ABA) also induced trypsin inhibitor activity accumulation, although to a lesser degree. In gel and immunoblot analyses showed that foliar trypsin inhibitor activity was constituted by at least three different inhibitors of approximately 29, 8 (including ATI) and 3 kDa, respectively. These inhibitors showed differing patterns of accumulation in response to diverse treatments. On the other hand, significant increases in α -amylase inhibitor activity and AAI levels were detected in leaves of insect-damaged, MeJA- and ABA-treated A. hypochodriacus plantlets, but not in those subjected to water- or salt-stress. A differential induction of trypsin inhibitor activity and α -amylase inhibitor accumulation in response to insect herbivory by two related species of lepidopterous larvae was observed, whereas mechanical wounding failed to induce either inhibitor. The overall results suggest that trypsin and α -amylase inhibitors could protect A. hypochondriacus against multiple types of stress.     

Effects of growth state and amines on cytoplasmic and vocuolar pH, phosphate and polyphosphate levels in Saccharomyces cerevisiae: a P-nuclear magnetic resonance study

The vacuoles of logarithmic and stationary stage cells were compared by ³¹P-NMR with regard to pH, orthophosphate (P_i) content and average size of polyphosphate. The vacuoles of stationary cells had lower pH higher P_i content, and polyphosphates of longer average chain lenght, although total polyphosphate content was about the same as in logarithmic cells. The lower vacuolar pH in stationary cells was the major cause of a larger cytoplasmic-vacuolar pH gradient. Addition of NH₄Cl, (NH₄)₂SO₄, methylamine or amantadine at pH 8 to cells in either stage caused an icnrease in both cytoplasmic and vacuolar pH, with little or no change in the cytoplasmic-vacuolar pH gradient. However, the administration of ammonium salts to the cells at pH 8.0 resulted in rapid hydrolysis of the intravacuolar polyphosphate to tripolyphosphate and P_i, with attendant redistribution of P_i between the vacuolar and cytoplasmic compartments.     

The singularly perturbed Hodgkin-Huxley equations as a tool for the analysis of repetitive nerve activity

A qualitative analysis of the Hodgkin-Huxley model (Hodgkin and Huxley 1952), which closely mimics the ionic processes at a real nerve membrane, is performed by means of a singular perturbation theory. This was achieved by introducing a perturbation parameter that, if decreased, speeds up the fast variables of the Hodgkin-Huxley equations (membrane potential and sodium activation), whereas it does not affect the slow variables (sodium inactivation and potassium activation). In the most extreme case, if the perturbation parameter is set to zero, the original four-dimensional system degenerates to a system with only two differential equations. This degenerate system is easier to analyze and much more intuitive than the original Hodgkin-Huxley equations. It shows, like the original model, an infinite train of action potentials if stimulated by an input current in a suitable range. Additionally, explanations for the increased sensitivity to depolarizing current steps that precedes an action potential can be found by analysis of the degenerate system. Using the theory of Mishchenko and Rozov (1980) it is shown that the degenerate system does not only represent a simplification of the original Hodgkin-Huxley equations but also gives a valid approximation of the original model at least for stimulating currents that are constant within a suitable range.