Hydraulic properties of sphagnum peat moss and tuff (scoria) and their potential effects on water availability

The importance of macrostructure to root growth of ryegrass (L. perenne) seedlings sown on the soil surface was studied in two soils in which the macrostructure had resulted mainly from root growth and macro-faunal activity. Sets of paired soil cores were used, one of each pair undisturbed and the other ground and repacked to the field bulk density. Undisturbed and repacked soils were first compared at equal water potentials in the range −1.9 to −300 kPa. At equal water potential, the undisturbed soil always had the greater strength (penetration resistance), and root growth was always greater in the repacked soil with no macrostructure than it was in the soil with macrostructure intact. At equal high strength (low water potentials) it appeared that root growth was better when soils were structured. When strength was low (high water potentials), root growth was better in the unstructured soil. Soils were then compared during drying cycles over 21 days. The average rate at which roots grew to a depth of 60 mm, and also the final percentage of plants with a root reaching 60 mm depth, was greatest in repacked soils without macrostructure. The species of vegetation growing in the soil before the experiment affected root growth in undisturbed soil; growth was slower where annual grasses and white clover had grown compared with soil which had supported a perennial grass. It appears that relatively few roots locate and grow in the macrostructure. Other roots grow in the matrix, if it is soft enough to be deformed by roots. Roots in the matrix of a structured soil grow more slowly than roots in structureless soil of equal bulk density and water potential. The development of macrostructure in an otherwise structureless soil, of the type studied, is of no advantage to most roots. However, once a macrostructure has developed, the few roots locating suitable macropores are able to grow at low water potential when soil strength is high. The importance of macrostructure to establishing seedlings in the field lies in rapid penetration of at least a few roots to a depth that escapes surface drying during seasonal drought. ei]{gnB E}{fnClothier}     

Insulin-like growth factor I enhances the formation of type I collagen in hydrocortisone-treated human osteoblasts

We have studied the effect of insulin-like growth factor I (IGF-I) on the formation of osteocalcin and type I collagen in isolated human osteoblasts. IGF-I at and above 0.1 nM stimulated the formation of type I collagen as measured by the type I procollagen carboxyterminal peptide (PICP), in human osteoblasts, incubated for 72 hrs in serumfree conditions. The secretion of osteocalcin was not affected by IGF-I while 1,25(OH)₂ vitamin D₃ significantly enhanced the formation of osteocalcin. When human osteoblast-like cells were incubated with hydrocortisone (1 M), a significant decrease in the release of both PICP and osteocalcin was seen. Addition of IGF-I to human osteoblasts also treated with hydrocortisone normalized the PICP-formation but did not affect the suppressed osteocalcin-formation. These data indicate that IGF-I reverses selective effects of hydrocortisone on bone.     

Neuronotypic Differentiation Results in Reduced Levels and Altered Distribution of Synaptophysin in PC 12 Cells

Abstract: Several synaptic vesicle proteins including synap-tophysin and p65/synaptotagmin are expressed by the pheochromocytoma cell line PC12. Stimulation of these cells with nerve growth factor for 7 days induces morphologic neuronotypic differentiation, but the levels of synaptophysin are markedly reduced. Stimulation with cyclic AMP analogs also produces neuronotypic differentiation of PC12 cells, and the degree of morphologic differentiation induced by these agents parallels their ability to effect reduction in synaptophysin levels. By contrast, levels of p65/synaptotagmin are increased following neuronotypic differentiation. The contrasting effects of neuronotypic differentiation on levels of synaptophysin and p65/synaptotagmin indicate potential differences in the regulation of these proteins in PC12 cells. Immunocytochemical labeling of undifferentiated PC12 cells reveals concentrations of synaptophysin in the perinuclear region. After neuronotypic differentiation, there is reduction in perinuclear labeling and concentration of label in swellings along PC12 cell processes. At the ultra-structural level, synaptophysin labeling is found on similar organelles in both undifferentiated and nerve growth factor-stimulated PC12 cells. Although the highest labeling densities were seen on small clear vesicles, specific labeling was also seen on dense core vesicles. The presence of synaptophysin on both small clear vesicles and dense core vesicles indicates potential functional similarities in these vesicle types. The changes in the levels and immunocytochemical distribution of synaptophysin after neuronotypic differentiation suggest possible functional heterogeneity among morphologically similar populations of small clear vesicles.     

Ecto-Protein Kinase and Surface Protein Phosphorylation in PC12 Cells: Interactions with Nerve Growth Factor

Abstract: The phosphorylation of surface proteins by ectoprotein kinase has been proposed to play a role in mechanisms underlying neuronal differentiation and their responsiveness to nerve growth factor (NGF). PC 12 clones represent an optimal model for investigating the mode of action of NGF in a homogeneous cell population. In the present study we obtained evidence that PC12 cells possess ectoprotein kinase and characterized the endogenous phosphorylation of its surface protein substrates. PC12 cells maintained in a chemically defined medium exhibited phosphorylation of proteins by [γ-³²P]ATP added to the medium at time points preceding the intracellular phosphorylation of proteins in cells labeled with ³²P_i. This activity was abolished by adding apyrase or trypsin to the medium but was not sensitive to addition of an excess of unlabeled P_i. As also expected from ecto-protein kinase activity, PC12 cells catalyzed the phosphorylation of an exogenous protein substrate added to the medium, dephospho-α-casein, and this activity competed with the endogenous phosphorylation for extracellular ATP. Based on these criteria, three protein components migrating in sodium dodecyl sulfate gels with apparent molecular weights of 105K, 39K, and 20K were identified as exclusive substrates of ecto-protein kinase in PC12 cells. Of the phosphate incorporated into these proteins from extracellular ATP, 75–87% was found in phosphothreonine. The phosphorylation of the 39K protein by ecto-protein kinase did not require Mg²⁺, implicating this activity in the previously demonstrated regulation of Ca²⁺-dependent, high-affinity norepinephrine uptake in PC12 cells by extracellular ATP. The protein kinase inhibitor K-252a inhibited both intra- and extracellular protein phosphorylation in intact PC12 cells. Its hydrophilic analogue K-252b, had only minimal effects on intracellular protein phosphorylation but readily inhibited the phosphorylation of specific substrates of ecto-protein kinase in PC12 cells incubated with extracellular ATP, suggesting the involvement of ecto-protein kinase in the reported inhibition of NGF-induced neurite extension by K-252b. Preincubation of PC12 cells with 50 ng/ml of NGF for 5 min stimulated the activity of ecto-protein kinase toward all its endogenous substrates. Exposure of PC12 cells to the same NGF concentration for 3 days revealed another substrate of ecto-protein kinase, a 53K protein, whose surface phosphorylation is expressed only after NGF-induced neuronal differentiation. In the concentration range (10–100 μM) at which 6-thioguanine blocked NGF-promoted neurite outgrowth in PC12 cells, 6-thioguanine effectively inhibited the phosphorylation of specific proteins by ecto-protein kinase. This study provides the basis for continued investigation of the involvement of ecto-protein kinase and its surface protein substrates in neuronal differentiation, neuritogenesis, and synaptogenesis.     

RELATIONSHIP BETWEEN NUCLEOSIDE DIPHOSPHATE KINASE ACTIVITY AND LIGHT-LIMITED GROWTH RATE IN THE MARINE DIATOM THALASSIOSIRA PSEUDONANA (BACILLARIOPHYCEAE)1

Light-limited cultures of the marine diatom Thalassiosira pseudonana (Hustedt) Hasle and Heimdal (3H clone) were grown over a range of growth rates between 0.06 and 1.64 d^?1. Variations in cell volume, cell quotas of carbon, nitrogen, and protein, and maximal activity of the enzyme nucleoside diphosphate kinase (NDPK) were measured and examined as a function of growth rate. NDPK from T. pseudonana showed K_m values of 0.24 and 0.68 mM for thymidine 5′-diphosphate and adenosine 5′-triphosphate (ATP), respectively, which are similar to those found for NDPK from a variety of organisms, from bacteria to mammals. An apparent activation enthalpy of 3.52 kCal·mol^?1 was determined from Arrhenius plots. No thermodynamic transition points were noted over a temperature range from 10° to 25°C. NDPK activity was significantly correlated with growth rate but not with cell volume, carbon, nitrogen, or protein; for interspecific comparisons, normalization of enzyme activity to cell number may be most meaningful. NDPK activity per cell versus growth rate followed a U-shaped relationship, being relatively constant between 0.5 and 1.0 d^?1 and rising at higher and lower growth rates. Over this range, enzyme activity may be regulated by substrate concentration (ATP or other nucleoside triphosphates) or by adenylate energy charge. At higher growth rates where energy charge and substrate concentrations are probably high, changes in enzyme concentration appear to be required. The reasons for a rise in enzyme activity at low growth rate is unclear. Simultaneous measurement of nucleoside di- and triphosphate levels alongside NDPK measurements may help clarify the relationship, but these preliminary experiments indicate that NDPK is of limited usefulness as an index of in situ growth rate.     

Protein toxicity to aphids: Anin vitro test onAcyrthosiphon pisum

Recent progress in plant transformation for insect resistance has increased the interest in the potential toxicity of proteins towards insect pests. While studies have been targeted to a large array of insect species, phloem-feeding Homoptera have not been investigated yet. The paper describes a routine test for screening toxicity and growth inhibition of purified proteins in artificial diets onAcyrthosiphon pisum (Harris). Twenty-five commercially available proteins of different classes were tested and compared to some non-protein chemicals (an insecticide, an antibiotic …).A. pisum proved to be very sensitive to all proteases tested and to some venoms with general cytolytic properties. A plant lectin, concanavalin A, displayed significant toxicity and growth inhibition, while various proteins such as a soybean proteinase inhibitor, a chitinase, and bovine serum albumin showed measurable impairments of growth only at higher dose (≥250 μg.ml⁻¹). Some proteins were without short-term effect onA. pisum physiology. The influence of these results on aphid-plant interactions are discussed.

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Résumé L'effet de protéines alimentaires sur les insectes phloémophages, dont les pucerons, n'a jamais été étudié. Nous proposons ici un test biologique standardisé sur milieu artificiel permettant d'analyser les effets de différentes classes de protéines sur la physiologie d'A. pisum. La validité de ce test est éprouvée (protocole, reproductibilité) et les différentes données récoltées (mortalité et inhibition de croissance) permettent de définir des paramètres toxicologiques tels que concentration létale 50 ou concentration inhibitrice 50. Cette caractérisation toxicologique a été réalisée sur 25 protéines appartenant à des classes différentes, ainsi que plusieurs substances non protéiques utilisées comme témoin de toxicité (insecticide, antibiotique, inhibiteur de synthèse protéique et glucoside phénolique). Les regroupements de protéines par proximités de profils toxicologiques ont été corrélés aux activités biochimiques des différentes protéines. Les implications de ces résultats sur les interactions plante-puceron sont discutées, ainsi que le potentiel d'une stratégie de création de variétés transgéniques résistantes aux pucerons.

     

Vegetative growth and productivity ofEichhornia azurea with special emphasis on leaf dynamics

The lifeform and the biological production of pure stands ofEichhornia azurea Kunth in three lakes in tropical Brazil were studied. The lifeform ofE. azurea is termed ‘semi-emergent’, because the plant has well developed trailing stems just under the water, and the aerial lamina emerges with the thick petiole. The density of shoot apices was 9.9, 17.2 and 17.1 m⁻² in Lake Dom Helvecio, Lake Jacaré and Lake Carioca, respectively. The mean daily increment of the apical shoot biomass was between 1.8 and 4.8 g m⁻² day⁻¹. The mean leaf life-span in Lake Dom Helvecio, Lake Jacaré and Lake Carioca was estimated to be 78, 49 and 64 days in the wet season and 73, 70 and 73 days in the dry season, respectively. The stem life-span was estimated to be about 28 months. Starch content in the current years' stem ranged from 24 to 118 mg g⁻¹ dry matter with fluctuations, the amplitude of which decreased with age. The differences for most of the growth parameters, such as density of shoot apices, daily increment of biomass and leaf life-span, between dry and wet season are smaller than those among the three lakes. Both the decrease in daily dry matter production and the increase in leaf life-span occurred in order from Lake Dom Helvecio to Lake Jacaré and Lake Carioca. The low productivity ofE. azurea is considered to be related to a low leaf area index, a long time interval for the emergence of new leaves, long leaf life-span and a low capacity for branching.     

Research Progress on Anti-Inflammatory Mechanisms of Black Ginseng

In recent years, black ginseng, a new type of processed ginseng product, has attracted the attention of scholars globally. Ginsenoside and ginseng polysaccharide, the main active substances of black ginseng, have been shown to carry curative effects for many diseases. This article focuses on the mechanism of their action in anti-inflammatory response, which is mainly divided into three aspects: activation of immune cells to exert immune regulatory response; participation in inflammatory response-related pathways and regulation of the expression level of inflammatory factors; effect on the metabolic activity of intestinal flora. This study identifies active anti-inflammatory components and an action mechanism of black ginseng showing multi-component, multi-target, and multi-channel characteristics, providing ideas and a basis for a follow-up in-depth study of its specific mechanism.