Shade affects responses to drought and flooding - acclimation to multiple stresses in bittersweet (Solanum dulcamara L.).

Plants exposed to environmental stress often respond by a change in their phenotypic traits. These changes in trait expression may alleviate the negative effect of such stress factors. However, if multiple stresses are present, responses are likely to be less predictable and hence do not necessarily correlate to plant performance. This study tested if this expectation was true, by subjecting Solanum dulcamara plants to various simultaneous stress factors. Plants were grown in well-watered conditions, drought or flooding, and exposed to either full light or shade for 4 weeks. Shoot and root biomass, stem morphological parameters, such as height, number of nodes and length of stem internodes, and leaf traits like length, specific leaf area, chlorophyll content and stomatal conductance were determined. Both variation in light and in water availability typically caused slower growth, and resulted in distinct phenotypic changes in stem, leaf and root traits. However, effects of stresses on the expression of traits were not always additive. Instead, some combined stress responses (e.g. leaf size) appeared to be limited by physical or physiological constraints, whereas other responses were opposite to each other (e.g. root:shoot ratio), resulting in an intermediate phenotype in the combined stress treatment. These data suggest that in natural conditions, where combined stress factors are likely to be present, the optimal phenotype may not necessarily be expressed. Responses of plants to multiple stress factors may therefore not be associated with immediate advantages in terms of increased performance.

Differential responses of two wetland graminoids to high ammonium at different pH values.

Enhanced soil ammonium (NH4+) concentrations in wetlands often lead to graminoid dominance, but species composition is highly variable. Although NH4+ is readily taken up as a nutrient, several wetland species are known to be sensitive to high NH4+ concentrations or even suffer toxicity, particularly at low soil pH. More knowledge about differential graminoid responses to high NH4+ availability in relation to soil pH can help to better understand vegetation changes. The responses of two wetland graminoids, Juncus acutiflorus and Carex disticha, to high (2 mmol·l(-1) ) versus control (20 µmol·l(-1) ) NH4+ concentrations were tested in a controlled hydroponic set up, at two pH values (4 and 6). A high NH4+ concentration did not change total biomass for these species at either pH, but increased C allocation to shoots and increased P uptake, leading to K and Ca limitation, depending on pH treatment. More than 50% of N taken up by C. disticha was invested in N-rich amino acids with decreasing C:N ratio, but only 10% for J. acutiflorus. Although both species appeared to be well adapted to high NH4+ loadings in the short term, C. disticha showed higher classic detoxifying responses that are early warning indicators for decreased tolerance in the long term. In general, the efficient aboveground biomass allocation, P uptake and N detoxification explain the competitive strength of wetland graminoids at the expense of overall biodiversity at high NH4+ loading. In addition, differential responses to enhanced NH4+ affect interspecific competition among graminoids and lead to a shift in vegetation composition.

Natural variation of submergence tolerance among Arabidopsis thaliana accessions.

• The exploitation of natural variation in Arabidopsis thaliana (Arabidopsis) provides a huge potential for the identification of the molecular mechanisms underlying this variation as a result of the availability of a vast array of genetic and genomic resources for this species. Eighty-six Arabidopsis accessions were screened for natural variation in flooding tolerance. This forms the first step towards the identification and characterization of the role of candidate genes contributing to flooding tolerance. • Arabidopsis accessions at the 10-leaf stage were subjected to complete submergence in the dark. Survival curves were plotted to estimate median lethal times as a measure of tolerance. Flooding-associated survival parameters, such as root and shoot oxygen content, initial carbohydrate content and petiole elongation under water, were also measured. • There was a significant variation in submergence tolerance among Arabidopsis accessions. However, the order of tolerance did not correlate with root and shoot oxygen content or initial amounts of shoot starch and total soluble sugars. A negative correlation was observed between submergence tolerance and underwater petiole elongation. • Arabidopsis accessions show considerable variation in the ability to tolerate complete submergence, making it a good species in which to identify and characterize genes and to study mechanisms that contribute to survival under water.

Salmon calcitonin in the treatment of post herpetic neuralgia.

A 78-year-old man with severe chronic obstructive pulmonary disease presented to our pain medicine clinic for treatment of post herpetic neuralgia. Pharmacotherapy with tricyclic antidepressants, anticonvulsants, tramadol and traditional analgesics had failed, primarily due to adverse drug effects, particularly sedation, dizziness and nausea. Consequently, intravenous salmon calcitonin was administered, based on evidence of efficacy in the treatment of other neuropathic pain syndromes and its relatively benign side-effects profile. The patient reported immediate and sustained improvement in his post herpetic neuralgia for over two months, without adverse effects from the calcitonin therapy.

Density-induced plant size reduction and size inequalities in ethylene-sensing and ethylene-insensitive tobacco.

Plant competition for light is a commonly occurring phenomenon in natural and agricultural vegetations. It is typically size-asymmetric, meaning that slightly larger individuals receive a disproportionate share of the light, leaving a limited amount of light for the initially smaller individuals. As a result, size inequalities of such stands increase with competition intensity. A plant's ability to respond morphologically to the presence of neighbour plants with enhanced shoot elongation, the so-called shade avoidance response, acts against the development of size inequalities. This has been shown experimentally with transgenic plants that cannot sense neighbours and, therefore, show no shade avoidance responses. Stands of such transgenic plants showed a much stronger development of size inequalities at high plant densities than did wild type (WT) stands. However, the transgenic plants used in these experiments displayed severely hampered growth rates and virtually no response to neighbours. In order to more precisely study the impact of this phenotypic plasticity on size inequality development, experiments required plants that have normal growth rates and reduced, but not absent, shade avoidance responses. We made use of an ethylene-insensitive, transgenic tobacco genotype (Tetr) that has wild type growth rates and moderately reduced shade avoidance responses to neighbours. Here, we show that the development of size inequalities in monocultures of these plants is not affected unambiguously different from wild type monocultures. Plots of Tetr plants developed higher inequalities for stem length than did WT, but monocultures of the two genotypes had identical CV (Coefficient of Variance) values for shoot biomass that increased with plant density. Therefore, even though reduced shade avoidance capacities led to the expected higher size inequalities for stem length, this does not necessarily lead to increased size inequalities for shoot biomass.

Flooding tolerance of Carex species in relation to field distribution and aerenchyma formation.

The flooding tolerance of Carex species was studied in relation to their field distribution and their capacity to form root aerenchyma under controlled conditions. In an alpine meadow, six Carex species were selected which were distributed in a clear zonation correlating with water content of the soil. Carex sempervirens and C. ferruginea were only found on nonflooded soil, the latter species preferring moister conditions. Carex davalliana and C. nigra were both associated with water-saturated soil, whereas C. limosa and C. rostrata preferred partially submerged conditions. Carex davalliana and C. limosa were bound to flooded soils with a relatively high redox potential and horizontally flowing groundwater. Carex rostrata and C. nigra grew in stagnant soil-flooded conditions with low soil redox potentials. The amount of aerenchyma in the roots of all species increased when grown in oxygen-deficient stagnant agar. This increase in root porosity, combined with increased root diameter, presumably improved internal aeration of the roots. Although all species survived experimental soil flooding, partial submergence was lethal to C. sempervirens and, surprisingly, also to the wetland species C. davalliana. Carex ferruginea showed a reduced growth rate during partial submergence. The three other species, all wetland plants, reached highest biomass production under soil-flooded and partially submerged conditions, with slower growth on free-draining soil. It is concluded that aerenchyma is not constitutive in the Carex species under study, and is best developed in Carex species from wetlands. Species with less aerenchyma perform poorly when soil-flooded, but conditions of partial submergence could even affect species with a considerable amount of root aerenchyma.

Effects of the developmental state of the tissue on the competence for flower bud regeneration in pedicel explants of tobacco.

The competence of pedicel explants of tobacco (Nicotiana tabacum L. cv Samsun) to regenerate flower buds in response to auxin was manipulated by preincubating excised tissues in the absence of auxin. When exposed to 1 micromolar 1-naphthaleneacetic acid, these tissues formed fewer buds than controls that were not preincubated. The number of buds eventually formed correlated with the 1-naphthaleneacetic acid concentration in the tissue 6 hours after the start of hormone application. The internal concentrations in pretreated explants were lower than in tissues that were not pretreated due to diminished uptake per milligram fresh weight and increased hormone conjugation. The change in the developmental state induced by auxin deprivation had a dual effect on bud regeneration: (a) the pretreatment caused fewer buds to be formed at any 1-naphthaleneacetic acid concentration tested, and (b) a higher auxin concentration in the medium was required to get a maximum bud number on precultured explants. An increase of the 1-naphthaleneacetic acid concentration in the medium led to an elevated hormone level in freshly cut as well as in preincubated tissues. It was concluded that the developmental state of the tissue directly affects the maximum number of buds that can be regenerated. Apart from that there is an indirect effect exerted via modulation of the ratio between external and internal auxin concentration. The change in this ratio can be compensated for by an adjustment of the auxin concentration in the medium.

The dose of 1-naphthaleneacetic acid determines flower-bud regeneration in tobacco expiants at a large range of concentrations.

Short-term applications of very high concentrations of 1-naphthaleneacetic acid (NAA) to expiants from flower stalks of tobacco (Nicotiana tabacum L. cv. Samsun) induced flower-bud regeneration to the same extent as longer or continuous incubation on lower concentrations. The maximum number of flower buds per explant after 15 d of culture was obtained not only by continuous culturing at 1 µmol·l(-1) NAA but also by 12 h of culturing at 22 µmol·l(-1) or 0.5 h at 220 µmol· l(-1), followed by incubation on medium without auxin for the remaining period. Continuous application of such high concentrations resulted in callus formation or caused the death of the explanted tissue. In all experiments in which auxin concentration and time of application were independently varied, the product of concentration and time determined the number of buds formed. Most, but not all, of the NAA taken up by the tissues was converted into conjugates. In expiants which had received a dose which was optimal for regeneration, the internal concentration of free NAA remaining beyond the pulse period was between 1.7 and 6.2 µmol·l(-1). Suboptimal applications led to lower values, supraoptimal treatments to much higher internal concentrations. The physiological effect, which depends on the internal hormone concentration, thus manifested itself as dose-dependent with regard to applied hormone.

The dose of 1-naphthaleneacetic acid determines flower-bud regeneration in tobacco explants at a large range of concentrations.

Short-term applications of very high concentrations of 1-naphthaleneacetic acid (NAA) to expiants from flower stalks of tobacco (Nicotiana tabacum L. cv. Samsun) induced flower-bud regeneration to the same extent as longer or continuous incubation on lower concentrations. The maximum number of flower buds per explant after 15 d of culture was obtained not only by continuous culturing at 1 µmol·l(-1) NAA but also by 12 h of culturing at 22 µmol·l(-1) or 0.5 h at 220 µmol· l(-1), followed by incubation on medium without auxin for the remaining period. Continuous application of such high concentrations resulted in callus formation or caused the death of the explanted tissue. In all experiments in which auxin concentration and time of application were independently varied, the product of concentration and time determined the number of buds formed. Most, but not all, of the NAA taken up by the tissues was converted into conjugates. In expiants which had received a dose which was optimal for regeneration, the internal concentration of free NAA remaining beyond the pulse period was between 1.7 and 6.2 µmol·l(-1). Suboptimal applications led to lower values, supraoptimal treatments to much higher internal concentrations. The physiological effect, which depends on the internal hormone concentration, thus manifested itself as dose-dependent with regard to applied hormone.

Bleeding symptoms in carriers of hemophilia A and B.

In order to investigate the bleeding tendency in clinically identified carriers of hemophilia, a self-administered questionnaire was held among 135 carriers of hemophilia A and B, 25 females with relatives with hemophilia and a matched group consisting of 60 females without relatives with hemophilia. Carriers of hemophilia appeared to suffer more often from bleeding than their relatives or the matched unrelated control group. A relation was seen between factor VIII:C or IX:C activity and the tendency to bleed. Obligatory carriers with normal factor VIII:C levels showed no bleeding tendency and were in this respect similar to a group of 25 females with relatives with hemophilia. This study shows that it is important to assay factor VIII:C or IX:C also in those women in whom the carrier status has already been established otherwise.

[The infant with leukemia]. / De zuigeling met leukemie.

Infant leukemia is rare and especially in newborn leukemoid reactions should be excluded by careful cytogenetic analysis before starting cytotoxic therapy. Infants have either acute lymphoblastic leukemia, monoblastic leukemia or acute undifferentiated leukemia. At present they have a bad outlook due to many coinciding unfavorable initial disease characteristics: high leukocyte count, liver and spleen enlargement, meningeal involvement, no expression of common ALL antigen, and a high frequency of pseudodiploid cells, that is with a translocation 4;II. The immaturity of organs and systems makes it difficult to treat these infants, and requires optimal supportive care. Therapeutic protocols for prospective clinical trials for leukemia in this age group are urgently needed.

Defect in B cell function in HTLV III/LAV positive hemophilia patients.

The capacity of the peripheral blood lymphocytes (PBL) to generate an antibody response in vitro T cell-dependent antigen ovalbumin was studied in 12 severe hemophilia patients who were otherwise in good health. PBL from four of 12 patients were not capable of generating such a response after stimulation in vitro, whereas all controls were normal. This negative plaque-forming cell (PFC) response coincided with the presence of antibodies directed toward human T-lymphotropic virus III/lymphadenopathy-associated virus (HTLV-III/LAV). Only one patient with antibodies against HTLV-III/LAV had a normal PFC response. The negative PFC response was not due to a deficient T helper cell activity, nor to an excessive T suppressor cell function. However, in the peripheral blood of these four patients, the presence of activated B cells that are refractory to antigen-specific T helper cell signals and secrete specific antibodies spontaneously could be demonstrated. Most of the patients showed a hyperimmunoglobulinemia. No correlation between the T4/T8 ratio and the level of the PFC response was demonstrable. From the data obtained in these investigations we raise the hypothesis that infection with HTLV-III/LAV in hemophilia patients will lead to in vivo (pre)activation of B cells that results in unresponsiveness or decreased response to antigen-specific signals.

Disappearance of factor VIII:C antibodies in patients with haemophilia A upon frequent administration of factor VIII in intermediate or low dose.

In 18 haemophilia A patients with antibodies against factor VIII:C (F VIII:c) the effect of regular treatment with factor VIII (F VIII) in intermediate or low dose was studied. All patients with previous maximal F VIII:c antibody levels between 5 and 60 Bethesda Units per millilitre (BU/ml) showed a decrease of antibody level and normal F VIII recovery within 1-2 months. From nine patients with previous maximal antibody levels above 60 BU/ml four showed a decrease of antibody level within 2-26 months. In four young patients F VIII prophylactic therapy was started or continued as soon as there was evidence of F VIII:c antibody activity. In three of these patients F VIII recovery normalized within a few months.

[The influence of endogenous insulin and glucagon on the free fatty acids in the circulating blood plasma]. / Die invloed van endogene insulien en glukagon op die vry vetsure in die sirkulerende bloedplasma.

The effect of increased endogenous plasma insulin and glucagon concentrations on the free fatty acid (FFA) levels in the circulating blood was investigated in sheep, 2 baboons and 1 vervet monkey. Elevation of the plasma insulin level was obtained by vagal stimulation or intravenous glucose administration and vagal stimulation, whereas increased glucagon levels were induced by sympathetic stimulation, increased plasma insulin levels, with simultaneous increased plasma glucose concentrations (in our experiments with sheep), produced a pronounced lowering of the FFA levels. From this observation a lipogenetic function could be ascribed to insulin. However, in the primate experiments, increased plasma insulin without concomitant glucose administration caused an elevation of FFA levels, and would indicate a lipolytic rather than a lipogenetic action of insulin. Increased glucagon levels, as produced by sympathetic stimulation, did not alter the FFA concentrations significantly. It thus appears that glucagon has no lipolytic effect, as claimed by previous investigators. In our experiment on the vervet monkey, sympathetic stimulation, with increased plasma glucagon, even caused a decrease in FFA levels.