The Role of Cytokinin in Organised Differentiation of Vascular Tissues

1993 ◽  
Vol 20 (5) ◽  
pp. 601 ◽  
Author(s):  
R Aloni
Keyword(s):  
Optimal Level ◽  
Ipt Gene ◽  
Vascular Differentiation ◽  
Vascular Tissues ◽  
Plant Body ◽  
Vessel Maturation ◽  
Sieve Tubes ◽  
Sieve Plates ◽  
Vessel Regeneration

The role of cytokinin as a limiting and controlling factor in the differentiation of vascular tissues in the plant body is discussed. Cytokinin controls the early stages of fibre differentiation in Helianthus stems and the regeneration of vessels and sieve tubes around a wound in Coleus internodes. The influence of cytokinin on cell differentiation in the vascular tissues varies according to its physiological levels and the levels of auxin. Cytokinin induces an acropetal polar pattern of vessel regeneration around a wound in internodes of Coleus. Similarly, adventitious roots induce acropetal polar patterns of vessel maturation in hypocotyls of Cucurbita. Cytokinin increases the sensitivity of the vascular cambium to the auxin stimulation, resulting in the highest ratio of phloem/xylem under the optimal level of cytokinin. High levels of cytokinin promote callose production on sieve plates. Studies of transgenic plants with altered levels of cytokinin (overexpressing the ipt gene) confirm the involvement of cytokinin in vascular differentiation.

Slime plugs do not inhibit surge flow in sieve tubes

1982 ◽  
Vol 60 (7) ◽  
pp. 1281-1284 ◽  
Author(s):  
Gregor F. Barclay
Keyword(s):  
P Protein ◽  
Heracleum Mantegazzianum ◽  
Sieve Tubes ◽  
Heracleum Sphondylium ◽  
Sieve Plates

Slime plugs, composed largely of P protein, on sieve plates in phloem of Heracleum mantegazzianum L. and Heracleum sphondylium Somm. and Lev. do not seem to be effective in preventing surge flow caused by loss of turgor, therefore calling into question the role of slime plugs in phloem.

The role of auxin in the removal of dormancy callose and resumption of phloem activity in Vitis vinifera

1991 ◽  
Vol 69 (8) ◽  
pp. 1825-1832 ◽  
Author(s):  
Roni Aloni ◽  
Ayala Raviv ◽  
Carol A. Peterson
Keyword(s):  
Vitis Vinifera ◽  
Key Words ◽  
Radial Direction ◽  
Fluorescent Dye ◽  
Vitis Vinifera L ◽  
Naphthaleneacetic Acid ◽  
Bud Break ◽  
Sieve Tubes ◽  
Sieve Plates

During winter the phloem of Vitis vinifera L. is dormant and is characterized by heavy deposits of callose on the sieve plates and lateral sieve areas of the sieve tubes. After bud break, the maturing leaves stimulate a nonpolar breakdown of this dormancy callose along the branch axis in the internodes located both above and below the leaves. However, the pattern of callose degradation in the radial direction is polar. It proceeds in a centrifugal direction so that the sieve tubes near the cambium become free of callose first and those adjacent to the periderm last. The effect of the leaves on the removal of dormancy callose can be replaced by auxin. Application of naphthaleneacetic acid to either the top or basal ends of excised dormant branches resulted in the removal of callose from sieve tubes, usually in less than a week. The fluorescent dye fluorescein was used to test phloem reactivation. Both acropetal and basipetal fluorescein movement occurred in sieve tubes in branches that were pretreated for 1 week with auxin, while much less movement of fluorescein occurred in the control branches, which remained dormant. Fluorescein translocation was observed in sieve tubes that had a reduced amount of callose and were wider than 20 μm, but was not detected in the narrow sieve tubes (diameters less than 15 μm) located next to the cambium. The possible roles of auxin, ethylene, and cytokinin in controlling callose levels in the sieve tubes are discussed. Key words: auxin, callose, fluorescein, Vitis vinifera, phloem, dormancy.

scholarly journals The role of selenium in the pathogenesis of thyroid disease

2019 ◽  
Vol 14 (4) ◽  
pp. 192-205 ◽  
Author(s):  
Ekaterina A. Troshina ◽  
Evgeniya S. Senyushkina ◽  
Maria A. Terekhova
Keyword(s):  
Immune Response ◽  
Thyroid Disease ◽  
Animal Experiments ◽  
Optimal Level ◽  
Thyroid Diseases ◽  
Autoimmune Thyroid Diseases ◽  
Autoimmune Thyroid ◽  
Increased Risk ◽  
Combined Deficiency

The past few years have been actively discussing the role of individual macro- and micronutrients as factors regulating the functional activity of organs and systems and reducing the risk of developing a number of diseases, including thyroid diseases. Selenium is one of the most important and intensively studied at present microelements. According to several studies, its low plasma level is associated with an increased risk of developing autoimmune thyroid diseases. In animal experiments, it was shown that a combined deficiency of selenium and iodine leads to more pronounced hypothyroidism than iodine deficiency alone. Some authors believe that cretinism in the newborn is a consequence of the combined deficiency of these two elements in the mother. It is also important that the optimal level of selenium is necessary both to initiate an immune response and to regulate an excessive immune response, as well as chronic inflammation. The review article discusses the relationship between selenium and thyroid pathology, discusses the role of selenium in the physiology of the thyroid gland and in the development of autoimmune diseases. The biochemical aspects of the pathogenesis of thyroid disease are presented.

Role of Cytokinin in Vessel Regeneration in Wounded Coleus Internodes

1991 ◽  
Vol 67 (6) ◽  
pp. 543-548 ◽  
Author(s):  
F. STUART BAUM ◽  
RONI ALONI ◽  
CAROL A. PETERSON
Keyword(s):  
Vessel Regeneration

4. What is the optimal level of enforcement?

2021 ◽  
pp. 38-47
Author(s):  
Ariel Ezrachi
Keyword(s):  
Law Enforcement ◽  
Economic Analysis ◽  
Crucial Role ◽  
Competition Law ◽  
Optimal Level ◽  
Competition Law Enforcement ◽  
Laissez Faire ◽  
Economic Understanding ◽  
Competitive Activities

‘What is the optimal level of enforcement?’ focuses on competition law enforcement. All competition jurisdictions acknowledge the central and crucial role of economic analysis in shaping competition prosecution. Greater economic understanding has improved the structure of competition law through legal presumptions and thresholds, enforcement guidelines, and a greater understanding of the gravity and consequences of anti-competitive activities. Indeed, there has been an ever-increasing ‘economization’ of antitrust, as more jurisdictions rely on economic analysis to determine whether intervention is needed. When markets work well, competition enforcers are better off adopting a ‘laissez-faire’ approach (leaving the market to take its own course). Distinguishing pro-competitive activities from anti-competitive activities poses a challenge.

scholarly journals Growth Effect of Public Debt: The Role of Government Effectiveness and Trade Balance

Economies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 62 ◽  
Author(s):  
Mindaugas Butkus ◽  
Janina Seputiene
Keyword(s):  
Trade Balance ◽  
Turning Point ◽  
Institutional Quality ◽  
Trade Deficit ◽  
Threshold Level ◽  
Optimal Level ◽  
Growth Effect ◽  
Role Of Government ◽  
Government Effectiveness

A growing number of recent works support the idea of debt threshold level (turning point), above which debt starts reducing economic growth. However, estimated threshold varies sharply across studies and gives a little insight into what the optimal level of debt is. The point is that there is no single turning point that could be applied to all countries and a proper investigation is needed on factors, which shape the debt impact on growth. This study aims to investigate whether debt threshold level depends on government effectiveness (one of the aspects of countries’ institutional quality) and trade balance. Our SYS-GMM estimates (and alternatively OLS and LSDV for robustness check) are based on the unbalanced panel of 152 countries over the period of 1996–2016 and on two strategies: (i) splitting of sample into subsamples according to trade balance and government effectiveness and (ii) including debt and government effectiveness, debt and trade deficit interactions. The obtained results are in line with those which confirm inverted U-shaped debt-growth relationship with clear debt turning point dependence on government effectiveness. However, effective governance is not enough to avoid the negative debt effect. Trade balance seems to be more crucial factor than institutional quality, on which threshold level depends.

scholarly journals The Role of Physiological Vitamin C Concentrations on Key Functions of Neutrophils Isolated from Healthy Individuals

Nutrients ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1363 ◽  
Author(s):  
Stephanie M. Bozonet ◽  
Anitra C. Carr
Keyword(s):  
Vitamin C ◽  
Immune Cell ◽  
Dehydroascorbic Acid ◽  
Optimal Level ◽  
Neutrophil Function ◽  
Neutrophil Extracellular Trap ◽  
Healthy Individuals ◽  
Healthy Humans ◽  
Ascorbate Uptake

Vitamin C (ascorbate) is important for neutrophil function and immune health. Studies showing improved immune function have primarily used cells from scorbutic animals or from individuals with infectious conditions or immune cell disorders. Few studies have focused on the requirements of neutrophils from healthy adults. Therefore, we have investigated the role of vitamin C, at concentrations equivalent to those obtained in plasma from oral intakes (i.e., 50–200 µmol/L), on key functions of neutrophils isolated from healthy individuals. Cells were either pre-loaded with dehydroascorbic acid, which is rapidly reduced intracellularly to ascorbate, or the cells were activated in the presence of extracellular ascorbate. We measured the effects of enhanced ascorbate uptake on the essential functions of chemotaxis, oxidant production, programmed cell death and neutrophil extracellular trap (NET) formation. We found that neutrophils isolated from healthy individuals already had replete ascorbate status (0.35 nmol/106 cells), therefore they did not uptake additional ascorbate. However, they readily took up dehydroascorbic acid, thus significantly increasing their intracellular ascorbate concentrations, although this was found to have no additional effect on superoxide production or chemotaxis. Interestingly, extracellular ascorbate appeared to enhance directional mobilityin the presence of the chemoattractant formyl-methionyl-leucyl-phenylalanine (fMLP). Stimulation of the cells in the presence of ascorbate significantly increased intracellular ascorbate concentrations and, although this exhibited a non-significant increase in phosphatidylserine exposure, NET formation was significantly attenuated. Our findings demonstrate the ability of neutrophils to regulate their uptake of ascorbate from the plasma of healthy humans to maintain an optimal level within the cell for proper functioning. Higher oral intakes, however, may help reduce tissue damage and inflammatory pathologies associated with NET formation.

The clinical utility of neuron-specific enolase serum levels as a biomarker for Merkel cell carcinoma.

2019 ◽  
Vol 37 (15_suppl) ◽  
pp. 9570-9570 ◽  
Author(s):  
Linde M. van Veenendaal ◽  
Eduardo Bertolli ◽  
Catharina M. Korse ◽  
W. Martin. C. Klop ◽  
Margot Et Tesselaar ◽  
...  
Keyword(s):  
Cell Carcinoma ◽  
Merkel Cell Carcinoma ◽  
Cox Regression ◽  
Neuron Specific Enolase ◽  
Distant Metastases ◽  
Serum Levels ◽  
Optimal Level ◽  
Rank Test ◽  
Merkel Cell

9570 Background: To date no adequate biomarker for Merkel Cell carcinoma (MCC) has been identified. The introduction of immunotherapy (IT) for metastatic MCC increases the need for a biomarker. Serum Neuron-specific enolase (NSE) has already been tested and is commonly used as a biomarker for several small cell malignancies. However, the role of NSE in MCC is still unclear. Aim: To investigate the role of NSE as a biomarker in MCC. Methods: A prospective cohort of MCC patients treated from 2016 to July 2018 was analyzed. Kaplan Meier curves with log rank test, Cox regression and mixed models were used to analyze NSE. A separate evaluation was performed for patients treated with IT. Results: A total of 78 patients (42 males, median age 71 years, stage I&II, III and IV MCC in 37(47%), 39(50%) and 2(3%) patients at time of diagnosis with 474 NSE levels (median 15 ; IQR 12,6-22 ng/ml were included. Baseline NSE (n=36) had no influence on survival or progression. During follow-up (FU) NSE levels correlated with tumorload (p=0,01) with increase of 15 ng/ml per class (no tumorload, localized MCC, nodal and distant metastases, respectively). NSE level during FU was able to detect progression (AUC 0,89). Several cut off values were evaluated. A NSE of 18,2 ng/ml was considered the most optimal level for clinical use (sensitivity 91%, specificity 78%, PPV 48%, NPV 98% to detect progression). During IT (n=16; 195 NSE values) all complete responders (n=7) had a normalized NSE (<18,2 ng/ml), all partial responders (n=3) had a decreasing NSE. In non-responders (n=6) all NSE levels remained elevated, one patient responded after switching to different IT with normalizing NSE values. Conclusions: NSE seems to be a valuable biomarker in MCC. NSE correlates with tumorload; is able to rule out progression and distinguishes responders from non-responders during IT.

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