scholarly journals Iron release from recombinant N-lobe and single point Asp63 mutants of human transferrin by EDTA

1997 ◽  
Vol 328 (2) ◽  
pp. 439-445 ◽  
Author(s):  
Qing-Yu HE ◽  
B. Anne MASON ◽  
C. Robert WOODWORTH
Keyword(s):  
Single Point ◽  
Tight Binding ◽  
Structural Factors ◽  
Iron Release ◽  
Negative Effects ◽  
Major Pathway ◽  
Negative Effect ◽  
Decreasing Ph ◽  
Kinetic Mode

Transferrins bind ferric ion and deliver the iron to cells. The mechanism of the iron release has been studied kinetically, in vitro, with the aid of single point mutants in which the iron-binding ligand, Asp63 (aspartic acid-63, D63), has been changed to Ser, Asn, Glu and Ala. Iron release from the unmutated N-lobe of human serum transferrin (hTF/2N) by EDTA is influenced by a variety of factors. The rate-determining conformational-change mechanism may be a major pathway for iron release from hTF/2N's having a ‘closed’ conformation, which leads to a saturation kinetic mode with respect to ligand concentration. The effect of chloride depends on the protein conformation, showing a negative action in the case of tight binding and a positive action when the protein has an ‘open’ or ‘loose’ conformation. The negative effect of chloride could originate from the binding competition between chloride and the chelate to the active site for iron release, and the positive effect could derive from the synergistic participation of chloride in iron removal. The ‘open’ conformation may be induced by decreasing pH: the transitional point appears to be at about pH 6.3 for the wild-type hTF/2N; the ‘loose’ conformation may be facilitated by mutations at D63, which result in the loss of a key linking component in interdomain interactions of the protein. In the latter case, structural factors dominate over other potential negative effects because the weak interdomain contacts derived from the mutation of D63 cause the binding site to open easily, even at pH 7.4. Therefore chloride exhibits an accelerating action on iron release by EDTA from all the D63 mutants.

scholarly journals Dominant Negative Mutants Implicate STAT5 in Myeloid Cell Proliferation and Neutrophil Differentiation

Blood ◽  
1999 ◽  
Vol 93 (12) ◽  
pp. 4154-4166 ◽  
Author(s):  
Robert L. Ilaria ◽  
Robert G. Hawley ◽  
Richard A. Van Etten
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Cytokine Signaling ◽  
Transactivation Domain ◽  
Negative Effects ◽  
Murine Bone Marrow ◽  
Negative Effect

Abstract STAT5 is a member of the signal transducers and activation of transcription (STAT) family of latent transcription factors activated in a variety of cytokine signaling pathways. We introduced alanine substitution mutations in highly conserved regions of murine STAT5A and studied the mutants for dimerization, DNA binding, transactivation, and dominant negative effects on erythropoietin-induced STAT5-dependent transcriptional activation. The mutations included two near the amino-terminus (W255KR→AAA and R290QQ→AAA), two in the DNA-binding domain (E437E→AA and V466VV→AAA), and a carboxy-terminal truncation of STAT5A (STAT5A/▵53C) analogous to a naturally occurring isoform of rat STAT5B. All of the STAT mutant proteins were tyrosine phosphorylated by JAK2 and heterodimerized with STAT5B except for the WKR mutant, suggesting an important role for this region in STAT5 for stabilizing dimerization. The WKR, EE, and VVV mutants had no detectable DNA-binding activity, and the WKR and VVV mutants, but not EE, were defective in transcriptional induction. The VVV mutant had a moderate dominant negative effect on erythropoietin-induced STAT5 transcriptional activation, which was likely due to the formation of heterodimers that are defective in DNA binding. Interestingly, the WKR mutant had a potent dominant negative effect, comparable to the transactivation domain deletion mutant, ▵53C. Stable expression of either the WKR or ▵53C STAT5 mutants in the murine myeloid cytokine-dependent cell line 32D inhibited both interleukin-3–dependent proliferation and granulocyte colony-stimulating factor (G-CSF)–dependent differentiation, without induction of apoptosis. Expression of these mutants in primary murine bone marrow inhibited G-CSF–dependent granulocyte colony formation in vitro. These results demonstrate that mutations in distinct regions of STAT5 exert dominant negative effects on cytokine signaling, likely through different mechanisms, and suggest a role for STAT5 in proliferation and differentiation of myeloid cells.

scholarly journals Dominant Negative Mutants Implicate STAT5 in Myeloid Cell Proliferation and Neutrophil Differentiation

Blood ◽  
1999 ◽  
Vol 93 (12) ◽  
pp. 4154-4166 ◽  
Author(s):  
Robert L. Ilaria ◽  
Robert G. Hawley ◽  
Richard A. Van Etten
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Cytokine Signaling ◽  
Transactivation Domain ◽  
Negative Effects ◽  
Murine Bone Marrow ◽  
Negative Effect

STAT5 is a member of the signal transducers and activation of transcription (STAT) family of latent transcription factors activated in a variety of cytokine signaling pathways. We introduced alanine substitution mutations in highly conserved regions of murine STAT5A and studied the mutants for dimerization, DNA binding, transactivation, and dominant negative effects on erythropoietin-induced STAT5-dependent transcriptional activation. The mutations included two near the amino-terminus (W255KR→AAA and R290QQ→AAA), two in the DNA-binding domain (E437E→AA and V466VV→AAA), and a carboxy-terminal truncation of STAT5A (STAT5A/▵53C) analogous to a naturally occurring isoform of rat STAT5B. All of the STAT mutant proteins were tyrosine phosphorylated by JAK2 and heterodimerized with STAT5B except for the WKR mutant, suggesting an important role for this region in STAT5 for stabilizing dimerization. The WKR, EE, and VVV mutants had no detectable DNA-binding activity, and the WKR and VVV mutants, but not EE, were defective in transcriptional induction. The VVV mutant had a moderate dominant negative effect on erythropoietin-induced STAT5 transcriptional activation, which was likely due to the formation of heterodimers that are defective in DNA binding. Interestingly, the WKR mutant had a potent dominant negative effect, comparable to the transactivation domain deletion mutant, ▵53C. Stable expression of either the WKR or ▵53C STAT5 mutants in the murine myeloid cytokine-dependent cell line 32D inhibited both interleukin-3–dependent proliferation and granulocyte colony-stimulating factor (G-CSF)–dependent differentiation, without induction of apoptosis. Expression of these mutants in primary murine bone marrow inhibited G-CSF–dependent granulocyte colony formation in vitro. These results demonstrate that mutations in distinct regions of STAT5 exert dominant negative effects on cytokine signaling, likely through different mechanisms, and suggest a role for STAT5 in proliferation and differentiation of myeloid cells.

scholarly journals The Halo Effect: Perceptions of Diffuse Threat and SVP Vote Share

2018 ◽  
Vol 14 (1) ◽  
pp. 27-54 ◽  
Author(s):  
Noemi Martig ◽  
Julian Bernauer
Keyword(s):  
Relative Proportion ◽  
Local Population ◽  
Halo Effect ◽  
Structural Factors ◽  
Right Wing ◽  
Multilevel Regression ◽  
Negative Effects ◽  
Electoral Success ◽  
People's Party ◽  
Negative Effect

Abstract The voter strength of right-wing populist parties is regularly attributed either to a feeling of threat from a high proportion of local foreigners or to the lack of opportunities for contact between the majority and the minority. This contribution is theoretically based on a synthesis of these perspectives, known as the Halo effect. Accordingly, it is not so much the local size of the local population, which is perceived as foreign, but rather its relative proportion in the surrounding countryside, which leads to a diffuse feeling of threat. The electoral success of the Swiss People’s Party (SVP) at the level of the Swiss municipalities serves as a basis for the empirical investigation, which is conducted alternatively with the proportions of the foreign and Muslim population. For both groups, spatial multilevel regression models provide indications of a coexistence of direct negative effects of minority populations on the share of the SVP (in the sense of the contact hypothesis) and of Halo effects, with the direct effects appearing to be somewhat more pronounced. Socio-structural factors can reduce these correlations (high unemployment neutralises the negative effect of the proportion of foreigners) or intensify these correlations (a higher income level accentuates the Halo effect for Muslims).

scholarly journals Advanced Glycation End Products Impair Cardiac Atrial Appendage Stem Cells Properties

2021 ◽  
Vol 10 (13) ◽  
pp. 2964
Author(s):  
Lize Evens ◽  
Ellen Heeren ◽  
Jean-Luc Rummens ◽  
Annelies Bronckaers ◽  
Marc Hendrikx ◽  
...  
Keyword(s):  
Stem Cells ◽  
Advanced Glycation End Products ◽  
Atrial Appendage ◽  
Advanced Glycation ◽  
Negative Effects ◽  
Glycation End Products ◽  
End Products ◽  
Negative Effect ◽  
Migration Capacity

Background: During myocardial infarction (MI), billions of cardiomyocytes are lost. The optimal therapy should effectively replace damaged cardiomyocytes, possibly with stem cells able to engraft and differentiate into adult functional cardiomyocytes. As such, cardiac atrial appendage stem cells (CASCs) are suitable candidates. However, the presence of elevated levels of advanced glycation end products (AGEs) in cardiac regions where CASCs are transplanted may affect their regenerative potential. In this study, we examine whether and how AGEs alter CASCs properties in vitro. Methods and Results: CASCs in culture were exposed to ranging AGEs concentrations (50 µg/mL to 400 µg/mL). CASCs survival, proliferation, and migration capacity were significantly decreased after 72 h of AGEs exposure. Apoptosis significantly increased with rising AGEs concentration. The harmful effects of these AGEs were partially blunted by pre-incubation with a receptor for AGEs (RAGE) inhibitor (25 µM FPS-ZM1), indicating the involvement of RAGE in the observed negative effects. Conclusion: AGEs have a time- and concentration-dependent negative effect on CASCs survival, proliferation, migration, and apoptosis in vitro, partially mediated through RAGE activation. Whether anti-AGEs therapies are an effective treatment in the setting of stem cell therapy after MI warrants further examination.

scholarly journals Evaluation of the In Vitro Fungicidal Activity of Summer Savory and Lavender Essential Oils Against Fusarium solani

2021 ◽  
Vol 5 (4) ◽  
pp. 795-805
Author(s):  
Gözdenur ÇAKAR ◽  
Işıl SARAÇ SİVRİKAYA ◽  
Ersin KARAKAYA ◽  
Abdullah GÜLLER
Keyword(s):  
Essential Oils ◽  
Fusarium Solani ◽  
Vascular Wilt ◽  
Negative Effects ◽  
Fusarium Spp ◽  
Antifungal Effect ◽  
Vascular Origin ◽  
Negative Effect ◽  
Lavandula Officinalis

Fusarium spp is one of the major phytopathogenic microfungus strains causing severe losses in many economically cultivated crops. The soil-borne pathogen Fusarium solani has historically been considered a serious agent across the globe, causing vascular wilt and root rot in agroeconomic crops and eventually leading to plant death. Three different concentrations (1 µl, 2 µl, and 4 µl) of essential oils (EO) extracted from lavender (Lavandula officinalis L.) and summer savory (Satureja hortensis L.) plants were mixed separately with PDA medium, and their antifungal effect against F. solani was investigated in vitro. When the results of the experiment were evaluated statistically, it was determined that the increasing concentrations of summer savory essential oil repressed the mycelial growth of the fungus, while lavender oil did not have any positive or negative effects. The inhibition activity of summer savory EO on F. solani was calculated as 43, 53, and 90% at the concentrations of 1, 2, and 4 µl, respectively. In this study, it was found that summer savory EO, even at a minimum dose, had a negative effect on agriculturally important wilt agent. In this context, it can be asserted that summer savory EO is a promising natural substance for the development of various fungicide solutions to prevent fungal diseases caused by vascular origin.

Synergistic promoting influence of citric acid, spinach and garlic on the bioavailability of iron and zinc from legumes

2016 ◽  
Author(s):  
Yu-Wei Luo ◽  
Jing Li
Keyword(s):  
Citric Acid ◽  
Phytic Acid ◽  
Tannic Acid ◽  
Positive Influence ◽  
Negative Effects ◽  
Plant Foods ◽  
Zinc Bioavailability ◽  
Iron And Zinc ◽  
Negative Effect

Inherent phytic acid and tannins interfere with bioavailability of iron and zinc from plant-based foods. Food acidulants, b-carotene-rich vegetables and Allium spices are understood to promote mineral in vitro bioavailability from legumes. In this study, it has been verified whether these promoters would counter negative effects of phytate and tannin on bioavailability of iron and zinc from legumes. Combinations of promoters – citric acid, spinach and garlic with phytic acid and tannin exogenously added individually were examined for their influence on iron and zinc bioavailability from the legumes. Effect of these promoters was generally dominant in the presence of phytic acid or tannic acid. The negative effect of the inhibitor was not only annulled, but also the positive influence of the promoter was fully retained. This information helps to evolve diet-based strategy to maximize mineral bioavailability and prevent deficiency situations prevalent in population dependent on plant foods.

Darkening of Plant Tissues during in vitro Cultivation and Methods for its Prevention

2020 ◽  
Vol 36 (2) ◽  
pp. 26-42
Author(s):  
B.R. Kuluev
Keyword(s):  
Phenolic Compounds ◽  
Callus Formation ◽  
Plant Biotechnology ◽  
In Vitro Cultivation ◽  
Negative Effects ◽  
Wide Range ◽  
Negative Effect ◽  
Oxidative Transformations ◽  
Tissue Browning

One of the most common problems in the plant in vitro propagation is the tissue browning and subsequent necrosis, resulting from the oxidation of phenolic compounds, secondary metabolites produced in response to injury and released into the nutrient medium. This process is one of the main reasons for the decrease in the efficiency of callus formation, somatic embryogenesis, regeneration and genetic transformation of plants in vitro. Moreover, oxidative browning often leads to culture death. Therefore, the current problems in genetic and cellular engineering of a wide range of plant species can be solved only by preventing or reducing the negative effects of browning of in vitro cultures caused by the oxidative transformations of phenolic compounds into quinones toxic to cells. This review is devoted to the description of the main existing methods to prevent these adverse transformations. Various chemicals with antioxidant and adsorbing properties are used in plant biotechnology for this purpose, but there are no general approaches to solve the problem. Although the choice of the method to minimize the negative effect of phenolic compound oxidation depends, firs of all, on the species and variety of the plant, some agents, such as ascorbic acid, activated carbon, silver nitrate, can be considered as universal and quite effective in preventing oxidative darkening of explants in vitro. phenolic compounds, oxidative browning, polyphenol oxidase, tissue browning, in vitro, microclonal plant propagation The work was funded on the theme АААА-А17-117102740098-8.

scholarly journals EFFECTS OF SUCROSE ON METABOLIZE POOL SIZES AND RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE/OXYGENASE ACTIVITY IN STRAWBERRY PLANTLETS CULTIVATED IN VITRO

HortScience ◽  
1994 ◽  
Vol 29 (4) ◽  
pp. 250b-250
Author(s):  
Chafik Hdider ◽  
Yves Desjardins
Keyword(s):  
Time Course ◽  
Photosynthetic Capacity ◽  
Tight Binding ◽  
Net Photosynthesis ◽  
Negative Effects ◽  
Slow Increase ◽  
Bisphosphate Carboxylase ◽  
Phosphorylated Compounds ◽  
Pool Sizes

To identify the physiological and biochemical events leading to the negative effects of sucrose in culture medium on the photosynthetic capacity of plantlets cultivated in vitro, time-course changes in photosynthesis, metabolize pool sizes, and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity were investigated in strawberry (Fragaria × ananassa Duch. cv. Kent) plantlets following their transfer to medium with or without sucrose. When the plantlets grown in medium without sucrose were transferred to a similar medium with 30 g sucrose/liter, their net photosynthesis decreased and their level of phosphorylated compounds increased with time. In addition, initial Kcat, total Kcat, and the activation state of Rubisco decreased in these plantlets. Conversely, when the plantlets grown in medium with 30 g sucrose/liter were transferred to a similar medium without sucrose, their net photosynthesis slowly increased with time and their level of phosphorylated compounds slowly decreased. A slow increase with time of initial Kcat, total Kcat, and the activation state of Rubisco was also observed in these plantlets. The results of the present research suggest that the reduced photosynthetic capacity of strawberry plantlets cultivated in vitro in the presence of sucrose was the consequence of reduced Rubisco efficiency due to its deactivation and the possible presence of a putative tight binding inhibitor.

scholarly journals Uridine Prevents Negative Effects of OXPHOS Xenobiotics on Dopaminergic Neuronal Differentiation

Cells ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1407
Author(s):  
Eldris Iglesias ◽  
M. Pilar Bayona-Bafaluy ◽  
Alba Pesini ◽  
Nuria Garrido-Pérez ◽  
Patricia Meade ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Oxidative Phosphorylation ◽  
Neuronal Differentiation ◽  
Fetal Brain ◽  
Global Dna Methylation ◽  
Protective Agent ◽  
Negative Consequences ◽  
Negative Effects ◽  
Negative Effect

Neuronal differentiation appears to be dependent on oxidative phosphorylation capacity. Several drugs inhibit oxidative phosphorylation and might be detrimental for neuronal differentiation. Some pregnant women take these medications during their first weeks of gestation when fetal nervous system is being developed. These treatments might have later negative consequences on the offspring’s health. To analyze a potential negative effect of three widely used medications, we studied in vitro dopaminergic neuronal differentiation of cells exposed to pharmacologic concentrations of azidothymidine for acquired immune deficiency syndrome; linezolid for multidrug-resistant tuberculosis; and atovaquone for malaria. We also analyzed the dopaminergic neuronal differentiation in brains of fetuses from pregnant mice exposed to linezolid. The drugs reduced the in vitro oxidative phosphorylation capacity and dopaminergic neuronal differentiation. This differentiation process does not appear to be affected in the prenatally exposed fetus brain. Nevertheless, the global DNA methylation in fetal brain was significantly altered, perhaps linking an early exposure to a negative effect in older life. Uridine was able to prevent the negative effects on in vitro dopaminergic neuronal differentiation and on in vivo global DNA methylation. Uridine could be used as a protective agent against oxidative phosphorylation-inhibiting pharmaceuticals provided during pregnancy when dopaminergic neuronal differentiation is taking place.

The depressing (negative) effect of oestradiol benzoate on the in vitro secretion of LH and FSH by the pituitary gland of the LRH-pretreated long-term ovariectomized rat changes into the augmentative (positive) effect after discontinuation of the LRH-pretreatment

1985 ◽  
Vol 110 (3) ◽  
pp. 329-337 ◽  
Author(s):  
G. A. Schuiling ◽  
H. Moes ◽  
T. R. Koiter
Keyword(s):  
Depressing Effect ◽  
Ovx Rats ◽  
Gonadotrophin Secretion ◽  
Oestradiol Benzoate ◽  
Negative Effect ◽  
Positive Effect ◽  
Perifusion System

Abstract. The effect of pretreatment in vivo with oestradiol benzoate on in vitro secretion of LH and FSH was studied in long-term ovariectomized (OVX) rats both at the end of a 5-day continuous in vivo pretreatment with LRH and 4-days after cessation of such LRH pretreatment. Rats were on day 0 sc implanted with osmotic minipumps which released LRH at the rate of 250 ng/h. Control rats were implanted with a piece of silicone elastomer with the dimensions of a minipump. On days 2 and 4 the rats were injected with either 3 μg EB or with oil. On day 5 part of the rats were decapitated and the in vitro autonomous (i.e. non-LRH-stimulated) and 'supra-maximally' LRHstimulated release of LH and FSH was studied using a perifusion system. From other rats the minipumps were removed on day 5 and perifusion was performed on day 9. On the 5th day of the in vivo LRH pretreatment the pituitary LH/FSH stores were partially depleted; the pituitaries of the EB-treated rats more so than those of the oil-injected rats. EB alone had no significant effect on the content of the pituitary LH- and FSH stores. On day 9, i.e. 4 days after removal of the minipumps, the pituitary LH and FSH contents had increased in both the oil- and the EB injected rats, but had not yet recovered to control values. In rats not subjected to the 5-days pretreatment with LRH EB had a positive effect on the supra-maximally LRH-stimulated secretion of LH and FSH as well as on the non-stimulated secretion of LH. EB had no effect on the non-stimulated secretion of FSH. After 5 days of in vivo pretreatment with LRH only, the in vitro non-stimulated and supra-maximally LRH-stimulated secretion of both LH and FSH were strongly impaired, the effect correlating well with the LRH-induced depletion of the pituitary LH/FSH stores. In such LRH-pretreated rats EB had on day 5 a negative effect on the (already depressed) LRH-stimulated secretion of LH (not on that of FSH). EB had no effect on the non-stimulated LH/FSH secretion. It could be demonstrated that the negative effect of the combined LRH/EB pretreatment was mainly due to the depressing effect of this treatment on the pituitary LH and FSH stores: the effect of oestradiol on the pituitary LRH-responsiveness (release as related to pituitary gonadotrophin content) remained positive. In LRH-pretreated rats, however, this positive effect of EB was smaller than in rats not pretreated with LRH. Four days after removal of the minipumps there was again a positive effect of EB on the LRH-stimulated secretion of LH and FSH as well as on the non-stimulated secretion of LH. The positive effect of EB on the pituitary LRH-responsiveness was as strong as in rats which had not been exposed to exogenous LRH. The non-stimulated secretion of FSH was again not affected by EB. The results demonstrate that the effect of EB on the oestrogen-sensitive components of gonadotrophin secretion consists of two components: an effect on the pituitary LRH-responsiveness proper, and an effect on the pituitary LH/FSH stores. The magnitude of the effect of EB on the LRH-responsiveness is LRH dependent: it is very weak (almost zero) in LRH-pretreated rats, but strong in rats not exposed to LRH as well as in rats of which the LRH-pretreatment was stopped 4 days previously. Similarly, the effect of EB on the pituitary LH and FSH stores is LRH-dependent: in the absence of LRH, EB has no influence on the contents of these stores, but EB can potentiate the depleting effect of LRH on the LH/FSH-stores. Also this effect disappear after cessation of the LRH-pretreatment.

Sign in / Sign up

Export Citation Format

Share Document