The regulation of respiration and growth of potato tuber callus by endogenous ethylene. Suppression of ethylene action by 2,5-norbornadiene

The growth (fresh and dry weight increase) of potato tuber ( Solanum tuberosum L. cv. Bintje) callus discs was stimulated by incubation in air with 500 ppm 2,5-norbornadiene (NBD, a competitive inhibitor of ethylene action) and inhibited by incubation in air with 4 000 ppm NBD. Ethylene formation by the callus was stimulated by NBD. The development of the alternative pathway, measured in isolated mitochondria was inhibited by NBD in a concentration-dependent way. The alternative pathway capacity, measured in vivo, was inhibited by 4 000 ppm NBD, but not by 500 ppm. Uninhibited in vivo respiration, which consists of cytochrome path activity and alternative path activity, was stimulated by the treatment with 500 ppm NBD. The main contribution to this stimulation was made by the cytochrome pathway. In 4 000 ppm NBD-treated callus, uninhibited respiration seemed to be unaffected as a consequence of an inhibited cytochrome path activity, which was compensated by a stimulated alternative path activity. Both in 500 and 4 OIK) ppm NBD-treated callus the alternative path activity in vivo was stimulated.
The regulatory role for endogenous ethylene in potato tuber callus is discussed in relation to: 1) The induction of respiratory pathways, 2) the supply of reduction equivalents in vivo and 3) growth.     

The effects of abscisic acid on growth and respiratory characteristics of potato tuber tissue discs

Incubation of potato tuber tissue discs on B5 medium supplemented with 1-naphtyl-acetic acid (NAA) led to callus formation, irrespective of the presence of kinetin; without NAA no callus formation occurred. Incubation in the presence of abscisic acid (ABA) reduced the increases in fresh weight and dry weight both in callus-forming and in non-callus-forming tissue. Mitochondrial respiration was lowered by ABA as well. The induction of the alternative, CN-resistant pathway was inhibited by the presence of ABA, especially in mitochondria from non-callus-forming tissue.The in vivo respiration of the callus-forming tissue was higher than that of the non-callus-forming tissue. Total respiration, cytochrome pathway activity and the capacity of the alternative pathway were all lowered in callus-forming tissue by treatment with ABA. The in vivo activity of the alternative pathway was low in all tissue types, especially after ABA-treatment. The slight stimulation by hydroxamates of the oxygen uptake of callus-forming tissue incubated on medium with NAA and ABA indicates the involvement of a hydroxamate-activated peroxidase in the oxygen uptake of this tissue; this peroxidase seemed not to participate in the oxygen uptake of the other tissues types.In non-callus-forming tissue the oxygen uptake of ABA-treated tissue was very low and almost completely resistant to the combined addition of inhibitors of both the cytochrome and the alternative pathway, indicating that the in vivo activity of the mitochondria in the oxygen uptake of the tissue was very low. The possible causes for this ABA-effect are discussed. In non-callus-forming tissue the treatment with ABA creates a situation which is comparable with that observed in intact potato tubers. This situation is characterized by a tissue respiration lower than that of the isolated mitochondria and an alternative pathway capacity that is low or absent.     

Estimates of hierarchical variation in flower morphology in natural populations ofScleranthus annuus (Caryophyllaceae), an inbreeding annual

The variation in two sets of morphological characters of the flowers of the highly inbreedingScleranthus annuus (Caryophyllaceae) was assessed using 15–20 plants from each of 20 natural populations from the southernmost region of Sweden. The stamen fertility data set consisted of 10 characters describing the degree of fertility of the ten stamens/staminoids, while the sepal/gynoecium data set comprised 10 sepal characters, together with style and stigma length. Substantial variation was found in both the degree of development and the fertility of the stamens, the degree of variability in stamen fertility being related to stamen position within the flower. Considerable variation was found in the characters of the sepal and the gynoecium. Hierarchical analyses of variance indicated that 29% of the variation in total male reproductive effort was distributed among populations, 28% among plants within populations and 43% represented within-plant variation. The corresponding averages for the characters from the sepal/gynoecium data set are 26, 38, and 35%: a greater proportion of the total variance in female reproductive characters is accounted for by among individual variation than is the case with the male reproductive characters. Significance tests of Mahalanobis distances derived by canonical variate analyses indicated that all populations were significantly separated using the sepal/gynoecium data set, while only 50% of the pairwise comparisons on the basis of the stamen fertility data set were significant. Cluster analysis did not reveal any aggregation of the populations. The incongruence of the two data sets and their ability to discriminate between the populations is discussed.     

An estimate of pollen carryover by ants in a natural population of Scleranthus perennis L. (Caryophyllaceae)

Summary Pollen carryover by ants was estimated in a natural population of Scleranthus perennis L. (Caryophyllaceae) using fluorescent dye as a pollen analogue.A highly significant exponential decrease in deposition of dye grains in a sequence of flowers visited by the main flowr visitor, Formica (S.) rufibarbis F., was observed with most grains being deposited in the first few flowers visited. At most 12 flowers were visited in a sequence.The mean between-flower transfer distance was estimated to be 6.2 cm, within-plant pollen transfers being recorded as zero. When all within-plant movements were excluded the mean was 22.5 cm. The distribution of transport distances differed from what I observed for honey-bees which occasionally foraged on dense stands of S. perennis. Calculations made on the deposition of dye grains transferred by ants showed that 7% of the dye grains deposited in the first flower visited after the dye source may reach a flower situated c. 30 cm from the dye source.     

Influence of osmotic stress on the respiration of potato tuber callus

Potato tuber ( Solanum tuberosum L. cv. Bintje) callus shows a decrease in fresh weight and an increase in dry weight upon transfer to nutrient medium supplemented with 0.3 or 0.5 M mannitol. The osmolarity of the intracellular fluid increases simultaneously. Probably mannitol is taken up from the medium till the osmolarity of the tissue is in equilibrium with that of the medium. After osmotic adaptation, on a medium with 0.5 M mannitol, growth is negligible, although the tissue retains its viability.
Respiration increases upon transfer to medium with extra mannitol, especially when expressed on a fresh weight basis. On this basis cytochrome and alternative pathway capacities do not change appreciably. The respiratory increase is exclusively caused by an increased engagement of the alternative pathway. The participation of this pathway in uninhibited respiration increases from about 10 to 90% upon transfer to medium with extra mannitol. The increase in respiration is partly correlated with the decrease in fresh weight upon transfer. Per disc, the capacities of the cytochrome and alternative pathway decline. Yet, total respiration per disc significantly increases due to the increased participation of the alternative pathway. This results in an almost equal ATP-production per disc before and after transfer. We suggest, that the alternative pathway functions as a reserve capacity in potato callus, which is switched on when ATP-production coupled to the cytochrome pathway is impaired.     

Importance of dormancy and sink strength in sprouting of onions (Allium cepa) during storage

In onion ( Allium cepa L.) postponement of sprouting is necessary to achieve long term storage. We studied the factors determining sprouting during dry storage at 16°C. The period to visible sprouting depends on the length of the dormancy period, if present, and on the growth rate of the sprout. In the three cultivars tested, sprouts were initiated within 2 weeks after harvest indicating the absence of a real dormancy period. Sprout length increased linearly during storage. The mitotic activity of the apex decreased before harvest, was low at the transition from scale to leaf formation, and increased again when the sprout was initiated. From a few weeks before harvest, the initially high fructan content of the scales decreased, leading to a large increase in fructose. The sprout always contained enough carbohydrates for growth (between 50 and 60 mg g⁻¹ dry weight, of which 30% was fructan). The activity of sucrose synthase (EC 2.4.1.13) increased as the sprout grew, indicating an increase in sink strength. Invertase (EC 3.2.1.26) was absent in all bulb organs, during the various developmental stages. Although carbohydrates and enzymes were available for fast sprouting, sprout growth was still linear instead of exponential during dry storage at temperatures favorable for growth (16°C). The relative importance of factors determining sprouting are discussed.     

Plasmidome-Analysis of ESBL-Producing Escherichia coli Using Conventional Typing and High-Throughput Sequencing

Infections caused by Extended spectrum β-lactamase (ESBL)-producing E. coli are an emerging global problem, threatening the effectiveness of the extensively used β-lactam antibiotics. ESBL dissemination is facilitated by plasmids, transposons, and other mobile elements. We have characterized the plasmid content of ESBL-producing E. coli from human urinary tract infections. Ten diverse isolates were selected; they had unrelated pulsed-field gel electrophoresis (PFGE) types (<90% similarity), were from geographically dispersed locations and had diverging antibiotic resistance profiles. Three isolates belonged to the globally disseminated sequence type ST131. ESBL-genes of the CTX-M-1 and CTX-M-9 phylogroups were identified in all ten isolates. The plasmid content (plasmidome) of each strain was analyzed using a combination of molecular methods and high-throughput sequencing. Hidden Markov Model-based analysis of unassembled sequencing reads was used to analyze the genetic diversity of the plasmid samples and to detect resistance genes. Each isolate contained between two and eight distinct plasmids, and at least 22 large plasmids were identified overall. The plasmids were variants of pUTI89, pKF3-70, pEK499, pKF3-140, pKF3-70, p1ESCUM, pEK204, pHK17a, p083CORR, R64, pLF82, pSFO157, and R721. In addition, small cryptic high copy-number plasmids were frequent, containing one to seven open reading frames per plasmid. Three clustered groups of such small cryptic plasmids could be distinguished based on sequence similarity. Extrachromosomal prophages were found in three isolates. Two of them resembled the E. coli P1 phage and one was previously unknown. The present study confirms plasmid multiplicity in multi-resistant E. coli. We conclude that high-throughput sequencing successfully provides information on the extrachromosomal gene content and can be used to generate a genetic fingerprint of possible use in epidemiology. This could be a valuable tool for tracing plasmids in outbreaks.     

Discovery of XEN445: A potent and selective endothelial lipase inhibitor raises plasma HDL-cholesterol concentration in mice

Endothelial lipase (EL) activity has been implicated in HDL metabolism and in atherosclerotic plaque development; inhibitors are proposed to be efficacious in the treatment of dyslipidemia related cardiovascular disease. We describe here the discovery of a novel class of anthranilic acids EL inhibitors. XEN445 (compound 13) was identified as a potent and selective EL inhibitor, that showed good ADME and PK properties, and demonstrated in vivo efficacy in raising plasma HDLc concentrations in mice.     

User and Provider Acceptability of Intermittent Screening and Treatment and Intermittent Preventive Treatment with Dihydroartemisinin-Piperaquine to Prevent Malaria in Pregnancy in Western Kenya

Background

The World Health Organization recommends intermittent preventive treatment in pregnancy (IPTp) with sulphadoxine-pyrimethamine (SP) alongside long-lasting insecticide-treated nets (LLIN) and case management for reducing the risks associated with malaria in pregnancy in areas of moderate-to-high transmission in sub-Saharan Africa. Due to increasing Plasmodium falciparum resistance to SP, the search for alternative drugs or strategies to control malaria in pregnancy is a priority. We assessed the acceptability among pregnant women and health providers of intermittent screening and treatment (ISTp) and IPTp with dihydroartemisinin-piperaquine (DP) as alternative strategies in the context of an un-blinded clinical trial.

Methods

Qualitative data were collected through ten focus group discussions with women participating in a randomized controlled trial to evaluate ISTp or IPTp with DP (multi-day regimen) versus IPTp with SP (single dose) in western Kenya. Individual in-depth interviews were conducted with 26 health providers working in the trial facilities and trial staff.

Results

Women appreciated the advantages of being tested with a rapid diagnostic test (RDT) at every ANC visit (although a few women disliked finger pricks) and accepted that they would not receive any antimalarial when tested RDT-negative. There were differences in women’s experiences of the efficacy of antimalarials between the trial arms, with more women in the IPTp-SP arm reporting they had experienced malaria episodes. Side effects were experienced among women taking DP and SP. Although women and trial staff reported adherence to the full DP regimen within the trial, health providers were not confident that women would adhere to multi-day regimens in non-trial settings. Health providers recognized the advantages of ISTp in reducing unnecessary exposure to drugs, but lacked confidence in the reliability of RDTs compared to microscopy.

Conclusions

Our findings indicate that, within a trial context, ISTp-DP and IPTp-DP were generally acceptable among both users and providers and were regarded as potentially valuable alternatives to IPTp-SP. Several challenges were identified the most important of which was concerns with achieving adherence to DP in non-trial settings, requiring operational feasibility studies in routine health systems. Policy adoption of ISTp with RDTs would require a major shift in thinking among health providers due to lack of confidence in RDTs.     

Trends in forest condition,threats and conservation action as derived from participatory monitoring in coastal Kenya

The coastal forests of Kenya are conservation priorities hosting high levels of biodiversity. Monitoring of biodiversity in these forests is therefore necessary to understand and reverse negative trends in good time. Using the Important Bird Area (IBA) monitoring framework, a participatory approach, state (habitat condition), pressure (threats) and response (conservation action) indicators of twelve coastal Kenya forest IBAs were assessed from 2004 to 2011. Trends for these indicators were assessed at six sites for which sufficient data existed: Arabuko‐Sokoke, Dakatcha Woodlands, Gede Ruins, Lower Tana River, Shimba Hills and Taita Hills, and baselines were described for remaining six. Changes were always small, but state deteriorated in Gede, Lower Tana and Shimba Hills, remained the same (unfavourable) in Arabuko‐Sokoke and Dakatcha, and improved in Taita Hills. Pressure reduced in Arabuko‐Sokoke, Dakatcha and Taita Hills, deteriorated in Lower Tana and Shimba Hills and remained the same (medium) in Gede. Response improved in Dakatcha, remained the same (medium) in Shimba Hills, and deteriorated in the rest. As there was an apparent overall deterioration in the forests assessed, improved management of the protected sites and increased conservation action through community engagement around protected areas and within the nonprotected IBAs are recommended.