scholarly journals Hormesis in Plants: The Role of Oxidative Stress, Auxins and Photosynthesis in Corn Treated with Cd or Pb

2020 ◽  
Vol 21 (6) ◽  
pp. 2099 ◽  
Author(s):  
Eugeniusz Małkowski ◽  
Krzysztof Sitko ◽  
Michał Szopiński ◽  
Żaneta Gieroń ◽  
Marta Pogrzeba ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Shoot Growth ◽  
Photosynthetic Apparatus ◽  
Growth Stimulation ◽  
Photosynthetic Parameters ◽  
Toxic Substances ◽  
Wide Range ◽  
The Common ◽  
Stimulation Of

Hormesis, which describes the stimulatory effect of low doses of toxic substances on growth, is a well-known phenomenon in the plant and animal kingdoms. However, the mechanisms that are involved in this phenomenon are still poorly understood. We performed preliminary studies on corn coleoptile sections, which showed a positive correlation between the stimulation of growth by Cd or Pb and an increase in the auxin and H2O2 content in the coleoptile sections. Subsequently, we grew corn seedlings in hydroponic culture and tested a wide range of Cd or Pb concentrations in order to determine hormetic growth stimulation. In these seedlings the gas exchange and the chlorophyll a fluorescence, as well as the content of chlorophyll, flavonol, auxin and hydrogen peroxide, were measured. We found that during the hormetic stimulation of growth, the response of the photosynthetic apparatus to Cd and Pb differed significantly. While the application of Cd mostly caused a decrease in various photosynthetic parameters, the application of Pb stimulated some of them. Nevertheless, we discovered that the common features of the hormetic stimulation of shoot growth by heavy metals are an increase in the auxin and flavonol content and the maintenance of hydrogen peroxide at the same level as the control plants.

The role of root‐associated microbes in growth stimulation of plants under saline conditions

2021 ◽  
Author(s):  
Han‐Qing Liu ◽  
Xiang‐Bin Lu ◽  
Zi‐Han Li ◽  
Chang‐Yan Tian ◽  
Jie Song
Keyword(s):  
Growth Stimulation ◽  
Stimulation Of

scholarly journals The Role of the Fibronectin IGD Motif in Stimulating Fibroblast Migration

2007 ◽  
Vol 282 (49) ◽  
pp. 35530-35535 ◽  
Author(s):  
Christopher J. Millard ◽  
Ian R. Ellis ◽  
Andrew R. Pickford ◽  
Ana M. Schor ◽  
Seth L. Schor ◽  
...  
Keyword(s):  
Fibroblast Migration ◽  
Wide Range ◽  
Migration Stimulating Factor ◽  
Function Relationship ◽  
Relationship Of ◽  
Stimulating Factor ◽  
Insight Into ◽  
Stimulation Of

The motogenic activity of migration-stimulating factor, a truncated isoform of fibronectin (FN), has been attributed to the IGD motifs present in its FN type 1 modules. The structure-function relationship of various recombinant IGD-containing FN fragments is now investigated. Their structure is assessed by solution state NMR and their motogenic ability tested on fibroblasts. Even conservative mutations in the IGD motif are inactive or have severely reduced potency, while the structure remains essentially the same. A fragment with two IGD motifs is 100 times more active than a fragment with one and up to 106 times more than synthetic tetrapeptides. The wide range of potency in different contexts is discussed in terms of cryptic FN sites and cooperativity. These results give new insight into the stimulation of fibroblast migration by IGD motifs in FN.

Mechanism of Action and In Vivo Role of Platelet-Derived Growth Factor

1999 ◽  
Vol 79 (4) ◽  
pp. 1283-1316 ◽  
Author(s):  
Carl-Henrik Heldin ◽  
Bengt Westermark
Keyword(s):  
Growth Factor ◽  
Protein Tyrosine Kinase ◽  
Growth Stimulation ◽  
Receptor Activation ◽  
Platelet Derived Growth Factor ◽  
Cellular Effects ◽  
Structural And Functional Properties ◽  
Stimulation Of

Platelet-derived growth factor (PDGF) is a major mitogen for connective tissue cells and certain other cell types. It is a dimeric molecule consisting of disulfide-bonded, structurally similar A- and B-polypeptide chains, which combine to homo- and heterodimers. The PDGF isoforms exert their cellular effects by binding to and activating two structurally related protein tyrosine kinase receptors, denoted the α-receptor and the β-receptor. Activation of PDGF receptors leads to stimulation of cell growth, but also to changes in cell shape and motility; PDGF induces reorganization of the actin filament system and stimulates chemotaxis, i.e., a directed cell movement toward a gradient of PDGF. In vivo, PDGF has important roles during the embryonic development as well as during wound healing. Moreover, overactivity of PDGF has been implicated in several pathological conditions. The sis oncogene of simian sarcoma virus (SSV) is related to the B-chain of PDGF, and SSV transformation involves autocrine stimulation by a PDGF-like molecule. Similarly, overproduction of PDGF may be involved in autocrine and paracrine growth stimulation of human tumors. Overactivity of PDGF has, in addition, been implicated in nonmalignant conditions characterized by an increased cell proliferation, such as atherosclerosis and fibrotic conditions. This review discusses structural and functional properties of PDGF and PDGF receptors, the mechanism whereby PDGF exerts its cellular effects, and the role of PDGF in normal and diseased tissues.

scholarly journals Photosynthetic characteristics of the freshwater red alga Batrachospermum delicatulum (Skuja) Necchi & Entwisle

2005 ◽  
Vol 19 (1) ◽  
pp. 125-137 ◽  
Author(s):  
Orlando Necchi Júnior ◽  
Abner H.S. Alves
Keyword(s):  
Inorganic Carbon ◽  
Photosynthetic Apparatus ◽  
High Capacity ◽  
Temporal Distribution ◽  
Red Alga ◽  
Photosynthetic Characteristics ◽  
Photosynthetic Parameters ◽  
Wide Range ◽  
Freshwater Red Algae ◽  
Two Peaks

Six populations of the freshwater red alga Batrachospermum delicatulum (Skuja) Necchi & Entwisle, including gametophyte and 'Chantransia' stage, were analysed in culture and natural conditions applying chlorophyll fluorescence and oxygen evolution. Parameters derived from the photosynthesis-irradiance curves indicated adaptation to low irradiance for all populations, which was characterized by photoinhibition, low values of Ik and Ic and high values of a. Data from both techniques revealed significant differences among populations and phases for most photosynthetic parameters. Similarly, photosynthesis responded differently to variations in temperature in each population with similar rates under a wide range of temperature. No consistent pattern was found when the same population or phase was tested, suggesting high capacity to adjust the photosynthetic apparatus to distinct conditions of irradiance and temperature. pH experiments showed a decreasing trend towards higher pH or higher rates at pH 6.5, suggesting, respectively, higher affinity to inorganic carbon as CO2 or indistinct use of bicarbonate and CO2. The diurnal pattern of photosynthesis essentially agree with that for seaweeds and freshwater red algae, consisting of two peaks: a first (generally higher) during the morning and a second (typically lower) in the afternoon. Photosynthetic characteristics of B. delicatulum (Skuja) Necchi & Entwisleexhibited a wide range of responses to irradiance, temperature and pH/inorganic carbon, reflecting its wide tolerance to these variables, which probably contributes to its wide spatial and temporal distribution.

Central nystagmus. III. Functional correlations of mesodiencephalic nystagmogenic center

1959 ◽  
Vol 197 (2) ◽  
pp. 454-460 ◽  
Author(s):  
F. Bergmann ◽  
J. Lachmann ◽  
M. Monnier ◽  
P. Krupp
Keyword(s):  
Electrical Stimulation ◽  
Eye Movements ◽  
Vestibular Nuclei ◽  
Rabbit Brain ◽  
Vestibular Nystagmus ◽  
Posterior Commissure ◽  
Common Substrate ◽  
The Common ◽  
Stimulation Of

Transverse cuts at various levels of the rabbit brain stem have different effects on vestibular nystagmus and on central nystagmus elicited by electrical stimulation of the mesodiencephalic nystagmogenic area. While transections rostral to the sensitive region enhance both, probably by elimination of inhibitory influences from cortex or retina, transections caudal to this region, but rostral to the colliculi, abolish central nystagmus only. Transections at the level of the inferior colliculus abolish vestibular nystagmus only, while intermediate cuts may eliminate either response. When central nystagmus alone survives, its character is changed in a specific way indicating the important role of the vestibular nuclei in normal central nystagmus. These observations lead to an approximate localization of the common substrate for conjugate eye movements involved both in central and vestibular nystagmus. Longitudinal cuts through the posterior commissure provoke a temporary disconjugated nystagmus not described hitherto.

scholarly journals Exploring the Role of Phenylalanine Residues in Modulating the Flexibility and Topography of the Active Site in the Peroxygenase Variant PaDa-I

2020 ◽  
Vol 21 (16) ◽  
pp. 5734
Author(s):  
Joaquin Ramirez-Ramirez ◽  
Javier Martin-Diaz ◽  
Nina Pastor ◽  
Miguel Alcalde ◽  
Marcela Ayala
Keyword(s):  
Hydrogen Peroxide ◽  
Cytochrome P450 ◽  
Active Site ◽  
Bulk Solution ◽  
Computational Studies ◽  
Organic Substrates ◽  
Oxidation Reactions ◽  
Heme Group ◽  
Wide Range

Unspecific peroxygenases (UPOs) are fungal heme-thiolate enzymes able to catalyze a wide range of oxidation reactions, such as peroxidase-like, catalase-like, haloperoxidase-like, and, most interestingly, cytochrome P450-like. One of the most outstanding properties of these enzymes is the ability to catalyze the oxidation a wide range of organic substrates (both aromatic and aliphatic) through cytochrome P450-like reactions (the so-called peroxygenase activity), which involves the insertion of an oxygen atom from hydrogen peroxide. To catalyze this reaction, the substrate must access a channel connecting the bulk solution to the heme group. The composition, shape, and flexibility of this channel surely modulate the catalytic ability of the enzymes in this family. In order to gain an understanding of the role of the residues comprising the channel, mutants derived from PaDa-I, a laboratory-evolved UPO variant from Agrocybe aegerita, were obtained. The two phenylalanine residues at the surface of the channel, which regulate the traffic towards the heme active site, were mutated by less bulky residues (alanine and leucine). The mutants were experimentally characterized, and computational studies (i.e., molecular dynamics (MD)) were performed. The results suggest that these residues are necessary to reduce the flexibility of the region and maintain the topography of the channel.

Observing and Influencing Alertness in Individuals With Profound Intellectual and Multiple Disabilities in Multisensory Environments

2012 ◽  
Vol 11 (1) ◽  
pp. 5-19 ◽  
Author(s):  
Vera Munde ◽  
C. Vlaskamp ◽  
W. J. Post ◽  
A. J. J. M. Ruijssenaars ◽  
B. Maes ◽  
...  
Keyword(s):  
Multiple Disabilities ◽  
Target Population ◽  
Auditory Stimuli ◽  
Learning And Development ◽  
Video Recordings ◽  
Multilevel Logistic Regression Analysis ◽  
Wide Range ◽  
Direct Support ◽  
Stimulation Of

While alertness is widely acknowledged as one of the most important preconditions for learning and development, individuals with profound intellectual and multiple disabilities (PIMD) experience a wide range of difficulties in the contact with their environment. The aim of the present study was to identify aspects of stimulation situations that influence the alertness levels of individuals in the target population.Based on video recordings of 24 participants, alertness levels and environmental conditions were scored. Descriptive analyses and multilevel logistic regression analysis were used to identify the aspects of the stimulation situation that were related to occurrence of alertness.The results show that visual stimuli (optimally in combination with auditory stimuli) produced the highest alertness levels. Furthermore, the effects of stimuli outweighed the effect of time. The role of direct support persons is thus especially important in alertness stimulation of individuals with PIMD.

Theta rhythm, attention and transcranial stimulation method

2021 ◽  
Author(s):  
N.A. Karatygin ◽  
I.I. Korobeinikova
Keyword(s):  
Theta Rhythm ◽  
Brain Plasticity ◽  
Oscillatory Activity ◽  
Transcranial Stimulation ◽  
Memory And Attention ◽  
Gamma Rhythm ◽  
Wide Range ◽  
Stimulation Method ◽  
Stimulation Of

Noninvasive methods of transcranial stimulation in clinical and research activity have become widely applied for the last few years. Due to the high spatial and temporal resolution, these methods allow to explore oscillatory processes that underlie important cognitive functions on a new level. In particular, researchers got an opportunity to influence rhythmic processes, which provide function of attention by these methods. By the way, stimulation of different brain zones with theta-rhythm frequency appears to be interesting, as far as oscillations of attention on this frequency reveal itself both in external activity of subject and in oscillatory activity of neurons and neural ensembles. Aim – analysis and summarize of domestic and foreign researches with usage of transcranial stimulation method to identify role of theta-rhythm in attention processes. Analysis of modern data concerning significance of theta-rhythm in organization of attention processes was performed analyzed. Different modes of transcranial stimulation methods, that allow to discover fundamental role of theta-rhythm in oscillatory activity of neural assembles, which are the base for attention mechanisms were considered. The review noted that the method of transcranial magnetic stimulation (TMS), which is based on the principle of electromagnetic induction with potential excellent temporal and sufficiently decent spatial resolution, is extensively widely used. Usually, TMS is performed with usage single-pulse, paired-pulse, or repetitive rhythmic stimulation. In current review special attention is salaried to the theta burst stimulation protocol. It was suggested that current protocol hypothesizes to influence brain plasticity and simulates the effect of theta-gamma coupling, which is to change the amplitude of the potentials at the frequency of the gamma rhythm depending on the theta wave phase. During the applying of the TMS different variants, several research methodological approaches were applied. Thus, usage of TMS may disrupt functioning in certain cortex areas , also it is possible to increase the oscillatory activity of a particular region at a particular frequency and to enhance or decrease the synchronization of remote cortical areas in a certain frequency range. These approaches may be used directly during the execution of the test task by the subjects or in the period prior the test performing. Many researches show that transcranial stimulation of some zones of cortex contributes to the achievement of better results of examinee in tests on memory and attention. This effect is most often observed while usage of stimulation with theta-rhythm frequency. Improvement of memory and attention functions has high practical meaning for wide range of activity. Understanding of regularities and mechanisms of stimulation with theta-rhythm frequency would allow to create systems and protocols of stimulation, which would effectively improve these functions for the long period.

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