Vacuolar ion channels: Roles in plant nutrition and signalling

Vacuoles play various roles in many physiologically relevant processes in plants. Some of the more prominent are turgor provision, the storage of minerals and nutrients, and cellular signalling. To fulfil these functions a complement of membrane transporters is present at the tonoplast. Prolific patch clamp studies have shown that amongst these, both selective and non-selective ion channels participate in turgor regulation, nutrient storage and signalling. This article reviews the physiological roles, expression patterns and structure function properties of plant vacuolar anion and cation channels that are gated by voltage and ligands.     

Ricca’s factors as mobile proteinaceous effectors of electrical signaling

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Heterogeneity of network and coding states in mouse CA1 place cells

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Landscape geometry and travelling waves in the larch budmoth

Travelling waves in cyclic populations refer to temporal shifts in peak densities moving across space in a wave‐like fashion. The epicentre hypothesis states that peak densities begin in specific geographic foci and then spread into adjoining areas. Travelling waves have been confirmed in a number of population systems, begging questions about their causes. Herein we apply a newly developed statistical technique, wavelet phase analysis, to historical data to document that the travelling waves in larch budmoth (LBM) outbreaks arise from two epicentres, both located in areas with high concentrations of favourable habitat. We propose that the spatial arrangement of the landscape mosaic is responsible for initiating the travelling waves. We use a tri‐trophic model of LBM dynamics to demonstrate that landscape heterogeneity (specifically gradients in density of favourable habitat) alone, is capable of inducing waves from epicentres. Our study provides unique evidence of how landscape features can mould travelling waves.     

The hypercycle,traveling waves,and Wright's equation

A formal relation between the hypercycle equation and the delay differential equation of E. M. Wright is exhibited using a traveling waves approach. Several unsolved questions in either problem can be related and interpreted, in particular new motivation for the study of Wright's equation is obtained.     

Predominance of poorly reopening single Na+ channels and lack of slow Na+ inactivation in neonatal cardiocytes

Summary Elementary Na⁺ currents through single cardiac Na⁺ channels were recorded at –50 mV in cell-attached patches from neonatal rat cardiocytes kept at holding potentials between –100 and –120 mV.Na⁺ channel activity may occur as burst-like, closely-timed repetitive openings with shut times close to 0.5–0.6 msec, indicating that an individual Na⁺ channel may reopen several times during step depolarization. A systematic quantiative analysis in 19 cell-attached patches showed that reopening may be quite differently pronounced. The majority, namely 16 patches, contained Na⁺ channels with a low tendency to reopen. This was evidenced from the average value for the mean number of openings per sequence, 2.5. Strikingly different results were obtained in a second group of three patches. Here, a mean number of openings per sequence of 3.42, 3.72, and 5.68 was found. Ensemble averages from the latter group of patches revealed macroscopic Na⁺ currents with a biexponential decay phase. Reconstructed Na⁺ currents from patches with poorly reopening Na⁺ channels were devoid of a slow decay component. This strongly suggests that reopening may be causally related to slow Na⁺ inactivation. Poorly pronounced reopening and, consequently, the lack of slow Na⁺ inactivation could be characteristic features of neonatal cardiac Na⁺ channels.     

AH jump duration is associated with elimination of slow pathway during ablation of atrioventricular nodal reentrant tachycardia

IntroductionAblating the slow pathway (SP) is the superior treatment for atrioventricular nodal reentrant tachycardia (AVNRT) with a low complication rate. However, the ablation of the SP could result in either complete elimination or modification of the SP. We aimed to investigate whether the duration of AH jump pre-ablation associated with the outcome of elimination of SP.MethodsWe included 56 patients with typical AVNRT (slow-fast), 20 males and 36 females, aged 44.2 ± 15.1 years. Slow pathway ablation was performed using classical approach. Univariate and multivariate analysis was performed for potential predictors of SP elimination.ResultsTypical AVNRT was inducible in all patients. Post-ablation, non-inducibility of AVNRT was obtained in all 56 (100%) patients, with SP elimination in 33 (61%) patients and SP modification in 23 (39%) patients. Patients with SP elimination had significantly longer AH jump than patients with SP modification. Cox regression analysis showed that AH jump duration was the independent predictor of SP elimination, in which every 20 ms increase in AH jump duration was associated with 1.30 higher rate of SP elimination. Furthermore, ROC curve analysis indicated that the AH jump duration of ≥100 ms had 6.14 times higher probability for complete elimination of the SP with a sensitivity of 79%, specificity of 70%, PPV of 79% and NPV of 70%.ConclusionsAH jump duration pre-ablation is associated with complete elimination of slow pathway during AVNRT ablation.     

Propagation and Seedling Cultivation of the Endemic Species Nothofagus alessandrii Espinosa in Central Chile

Nothofagus alessandrii is an endemic and endangered species from the Maule Region of Central Chile. The forests it once dominated have been severely degraded and fragmented by human activities, and it is estimated that only 350 ha remain. Yet, available information for propagation and nursery plant cultivation of this species is conspicuously lacking. Future efforts to restore this ecosystem type will rely, in large part, on advancing the capacity to propagate and cultivate this highly threatened species. To this end, we studied the response (germination process and nursery growth) of viable seeds of N. alessandrii to different pre‐germination treatments, sowing times, and slow‐release fertilizer. The highest germination percentages were obtained with cold stratification for periods of 30 and 45 days (84.9 and 82.6%, respectively). Sowing time was also relevant, with seeds obtaining highest germination rates (53%) when sowing during spring season (September) as well as the best growth rates. Both cold stratification and GA₃ treatments can provide adequate germination percentage and similar seedling quality. After one nursery season, no clear effect of slow‐release fertilizer on plant growth was observed. The results of this study provide important baseline information for propagation and nursery techniques for restoration programs of N. alessandrii.     

The observation of quasi-molecular ions from a protein neurotoxin (MW 7821) using 127I-plasma desorption mass spectroscopy

Fast heavy ions, i.e. 90 MeV ¹²⁷I from the Uppsala tandem accelerator have been used to desorb and ionize molecules from a cobra venom neurotoxin. The protein is built up by 71 amino acid residues in a single polypeptide chain, tightly cross-linked by 5 disulfide bridges. The molecular weight as confirmed by protein sequence analysis is 7821. The ions were mass analyzed by the time-of-flight technique. This is to our knowledge the largest protein for which it has been possible to detect quasimolecular ions by a mass spectrometric technique.     

The mollusc fauna along a depth transect in the Faroe Shetland Channel: Is there a relationship with internal waves?

From boxcore and dredge samples taken along a depth transect across the Faroe Shetland Channel (FSC) in 1997 and 1999, molluscs were sorted and identified. On the basis of their numerical abundance, the stations could be clustered into three groups, reflecting the depth extension of the main water masses in the FSC. Between 400 and 500 m depth, both the number of taxa per sample and the number of specimens, were highest. Bivalves were mainly caught by the boxcorer and the dredge was best suited to collect the epifaunal gastropods. According to the literature, at mid-slope depths, resuspension is increased by the action of internal waves, which leads to the development of intermediate nepheloid layers. This increased concentration of suspended matter may serve as a food source of low quality. Likewise the low amounts of suspended matter with a relatively high quality of particulate organic matter, such as from ∼400 and ∼700 m may act similarly and explain the relative high abundance of filter feeders at these depths. However, in the various multivariate analyses we could not distinguish the fauna from these depths from that collected from other sites. We observed, however, a pattern in the depth distribution of feeding guilds across the slope of the FSC. Deposit feeders demonstrated a trend of decreasing numbers with depth. Filter-feeding taxa were found to have peaks at depths of approximately 350 m, between 500 and 600 m and between 700 and 800 m. This observation supports the idea that the fauna at the deep sites reflects the locally high cross-slope currents and the subsequent increased amounts or availability of food with a better quality, which seems to be related to resuspension events.