The effect of iron chelate fertilization of poplar upon CO2-uptake,leaf size,and content of leaf pigments and iron

Summary Potted poplars (strainsmarilandica, serotina andFlachslanden ofPopulus euramericana) which developed iron-deficiency symptoms (chlorosis of upper leaves, winter die-back of leader, flushing of lateral buds) were treated with a soil application of iron chelate to study the effect of iron nutrition upon CO₂-uptake, iron and pigment content of leaves, and leaf size of a tree species. Foliar content of each iron, chlorophyll, -carotene, lutein, and violaxanthin was significantly increased by the treatment. Chlorophyll b proved to be particularly sensitive to iron supply and the Q^a/b was also significantly altered.CO₂-uptake increased in fertilized and non-fertilized leaves with increasing light up to 40,000 Lux, but fertilized leaves assimilated more CO₂ than non-fertilized leaves, especially at light intensities from 5,000 Lux upwards. The assimilatory number was decreased by the iron application since larger amounts of chlorophyll were present in fertilized leaves. If CO₂-uptake was based upon an area unit basis the fertilizer effect became distinct even at 500 Lux. Thus CO₂-uptake is a quick, valuable measure of fertilizer responses.In severe cases, iron deficiency also affects leaf size and thus indirectly reduces photosynthetic activity. A chelate application during the growing season will not affect the size of leaves already formed but may considerably increase the size of leaves formed subsequent to the treatment.     

Induction of microspore embryogenesis inBrassica napus L. by gamma irradiation and ethanol stress

Summary Gamma irradiation and ethanol stress treatments redirected pollen development to an embryo formation pathway inBrassica napus. Less than 0.01% of microspores developed into embryos at 25°C compared to approximately 2% at 32°C. However, subsequent to gamma irradiation and ethanol treatments up to 1% and 0.7% of microspores formed embryos at 25°C, respectively. Gamma irradiation also enhanced embryogenesis at 32°C. The possible importance of these findings is discussed in relation to microspore embryogenesis.     

Respiratory sinus arrhythmia in the denervated human heart

We performed this study to test whether the denervated human heart has the ability to manifest respiratory sinus arrhythmia (RSA). With the use of a highly sensitive spectral analysis technique (cross correlation) to define beat-to-beat coupling between respiratory frequency and heart rate period (R-R) and hence RSA, we compared the effects of patterned breathing at defined respiratory frequency and tidal volumes (VT), Valsalva and Mueller maneuvers, single deep breaths, and unpatterned spontaneous breathing on RSA in 12 normal volunteers and 8 cardiac allograft transplant recipients. In normal subjects R-R changes closely followed changes in respiratory frequency (P less than 0.001) but were little affected by changes in VT. On the R-R spectrum, an oscillation peak synchronous with respiration was found in heart transplant patients. However, the average magnitude of the respiration-related oscillations was 1.7-7.9% that seen in normal subjects and was proportionally more influenced by changes in VT. Changes in R-R induced by Valsalva and Mueller maneuvers were 3.8 and 4.9% of those seen in normal subjects, respectively, whereas changes in R-R induced by single deep breaths were 14.3% of those seen in normal subjects. The magnitude of RSA was not related to time since the heart transplantation, neither was it related to patient age or sex. Thus the heart has the intrinsic ability to vary heart rate in synchrony with ventilation, consistent with the hypothesis that changes, or rate of changes, in myocardial wall stretch might alter intrinsic heart rate independent of autonomic tone.     

Transforming growth factor-beta 1 enhances the suppression of human hematopoiesis by tumor necrosis factor-alpha or recombinant interferon-alpha

The effects of transforming growth factor-beta 1 (TGF-beta 1) on human hematopoiesis were evaluated in combination with two other regulatory cytokines, namely, recombinant human tumor necrosis factor-alpha (TNF-alpha) and recombinant human interferon-alpha (rIFN-alpha). Combinations of TNF-alpha and TGF-beta 1 resulted in a synergistic suppression of colony formation by erythroid progenitor cells (BFU-E) and an additive suppression of granulocyte-macrophage (CFU-GM) and multipotential (CFU-GEMM) progenitor cells. In addition, TGF-beta 1 synergized with rIFN-alpha to suppress CFU-GM formation, while the combined suppressive effects of both cytokines on CFU-GEMM and BFU-E were additive. When TGF-beta 1 was tested with TNF-alpha or IFN-alpha on granulocyte/macrophage colony-stimulating factor (GM-CSF)-stimulated bone marrow cells in a 5-day proliferation assay, the antiproliferative effects of TGF-beta 1 and TNF-alpha were additive, while those with TGF-beta 1 and rIFN-alpha were synergistic. A similar pattern was seen in the suppression of the myeloblastic cell line KG-1 where TGF-beta 1 in combination with TNF-alpha resulted in an additive suppression while inhibition by TGF-beta 1 and IFN-alpha was synergistic. These results demonstrate for the first time the cooperative effects between TGF-beta and TNF-alpha and IFN-alpha in the suppression of hematopoietic cell growth, raising the possibility that TGF-beta might be used in concert with TNF-alpha or IFN-alpha in the treatment of various myeloproliferative disorders.     

Antibodies directed against the peroxisomal targeting signal of firefly luciferase recognize multiple mammalian peroxisomal proteins

We have previously shown that the peroxisomal targeting signal in firefly luciferase consists of the COOH-terminal three amino acids of the protein, serine-lysine-leucine (Gould, S.J., G.A. Keller, N. Hosken, J. Wilkinson, and S. Subramani, 1989. J. Cell Biol. 108:1657-1664). Antibodies were raised against a synthetic peptide that contained this tripeptide at its COOH terminus. Immunofluorescence and immunocryoelectron microscopy revealed that the anti-peptide antibodies specifically detected peroxisomes in mammalian cells. Further characterization revealed that the antibodies were primarily directed against the COOH-terminal three amino acids of the peptide. In Western blot experiments, the antibodies recognized 15-20 rat liver peroxisomal proteins, but reacted with only a few proteins from other subcellular compartments. These results provide independent immunological evidence that the peroxisomal targeting signal identified in firefly luciferase is present in many peroxisomal proteins.     

Direct evidence for an intracellular role for IFN-gamma. Microinjection of human IFN-gamma induces Ia expression on murine macrophages

An intracellular action for IFN-gamma was detected by using microinjection technology. Human IFN-gamma (huIFN-gamma) does not ordinarily act on murine cells because it fails to bind to murine cell surface receptors. However, when huIFN-gamma was microinjected into murine macrophages, a time and dose-dependent induction of Ia was detected by autoradiography on the surface of injected and neighboring cells. These results imply a direct role for internalized IFN-gamma and show that huIFN-gamma, although it fails to be recognized by murine cell surface receptors, can act internally on murine cells. The effect on Ia gene expression induced by microinjected huIFN-gamma was in part indirect: granulocyte/macrophage-CSF (GM-CSF) was released by IFN-gamma-injected macrophages, and this secondary mediator appeared to induce Ia on neighboring cells, inasmuch as anti-GM-CSF blocked Ia induction. Anti-GM-CSF also partially blocked Ia induction by extracellular murine IFN-gamma on murine macrophages. Thus, at least some of the Ia induction attributed to IFN-gamma was mediated by GM-CSF.     

Analysis of Chlamydomonas reinhardtii histones and chromatin

Chromatin spreads made from isolated nuclei of the unicellular green alga Chlamydomonas reinhardtii show the beaded fibers typical of eukaryotic polynucleosomes. Micrococcal nuclease digestions confirmed the presence of nucleosomes with a repeat length of 189 base pairs, essentially the same as typical mammalian cells. Basic nuclear proteins extracted from isolated nuclei or chromatin with 1 M calcium chloride and 0.3 M hydrochloric acid are resolved into seven major components by electrophoresis in the presence of sodium dodecyl sulfate (SDS). These seven components were subjected to qualitative peptide mapping with V8 protease on SDS gels for comparison with the major histone components of calf thymus. Finally, the C. reinhardtii basic nuclear proteins were fractionated by reversed phase high performance liquid chromatography and their amino acid composition determined. From these studies, we conclude that C. reinhardtii has a full complement of the five histones with properties very similar to those of both higher animals and higher plants.     

Net increase of pluripotential hematopoietic precursors in suspension culture in response to IL-1 and IL-3

A new short-term suspension culture system is described in which pluripotential hematopoietic precursors from mouse bone marrow increase 8 to 12 times in number over a 4-day period. The increase is shown to derive from myeloid precursors undergoing repeated cell divisions prior to definitive lineage restriction. The response, which occurs in the absence of any pre-formed feeder layer, depends on dual stimulation by both IL-1 and IL-3, and the maximum effect depends on the presence of both factors together from the initiation of the cultures. The observations extend the known range of targets of IL-1 and IL-3 to include primitive pluripotential precursors capable of some degree of self-renewal, and provide a specific and relatively simple assay both for the precursors and the soluble factors which regulate them.     

Amplification of small signals by voltage-gated sodium channels in drone photoreceptors

Summary Photoreceptor cells of the drone,Apismellifera , have a voltage-gated Na⁺ membrane conductance that can be blocked by tetrodotoxin (TTX) and generates an action potential on abrupt depolarization: an action potential is triggered by the rising phase of a receptor potential evoked by an intense light flash (Autrum and von Zwehl 1964; Baumann 1968). We measured the intracellular voltage response to a small (9%), brief (30 ms) decrease in light intensity from a background, and found that its amplitude was decreased by 1M TTX. The response amplitude was maximal when the background intensity depolarized the cell to –38 mV. With intensities depolarizing the cell membrane to –45 to –33 mV the average response amplitude was decreased by TTX from 1.2mV to 0.5mV. TTX is also known to decrease the voltage noise during steady illumination (Ferraro et al. 1983) but, despite this, the ratio of peak-to-peak signal to noise was, on average, decreased by TTX. The results suggest that drone photoreceptors use voltage-gated Na⁺ channels for graded amplification of responses to small, rapid changes in light intensity.Abbreviations TTX tetrodotoxin - V _i intracellular potential with respect to the bath - V _o extracellular potential - V _m,V _i-V _o approximate transmembrane potential - S amplitude of the voltage response to an 8.9% decrease in light intensity - N voltage noise, usually measured as root mean square voltage deviation as described in Methods