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At least 487 records · Page 27Linked to original sources
PubMed2006

The Arabidopsis heavy metal P-type ATPase HMA5 interacts with metallochaperones and functions in copper detoxification of roots.

Since copper (Cu) is essential in key physiological oxidation reactions, organisms have developed strategies for handling Cu while avoiding its potentially toxic effects. Among the tools that have evolved to cope with Cu is a network of Cu homeostasis factors such as Cu-transporting P-type ATPases that play a key role in transmembrane Cu transport. In this work we present the functional characterization of an Arabidopsis Cu-transporting P-type ATPase, denoted heavy metal ATPase 5 (HMA5), and its interaction with Arabidopsis metallochaperones. HMA5 is primarily expressed in roots, and is strongly and specifically induced by Cu in whole plants. We have identified and characterized plants carrying two independent T-DNA insertion alleles, hma5-1 and hma5-2. Both mutants are hypersensitive to Cu but not to other metals such as iron, zinc or cadmium. Interestingly, root tips from Cu-treated hma5 mutants exhibit a wave-like phenotype at early stages and later on main root growth completely arrests whereas lateral roots emerge near the crown. Accordingly, these lines accumulate Cu in roots to a greater extent than wild-type plants under Cu excess. Finally, yeast two-hybrid experiments demonstrate that the metal-binding domains of HMA5 interact with Arabidopsis ATX1-like Cu chaperones, and suggest a regulatory role for the plant-specific domain of the CCH Cu chaperone. Based on these findings, we propose a role for HMA5 in Cu compartmentalization and detoxification.

Adenosine Triphosphatases↗
PubMed2004

Zinopin--the rationale for its use as a food supplement in Traveller's thrombosis and motion sickness.

Venous thrombo-embolism (VTE) has been associated with periods of prolonged immobility during air, sea and road travel. Motion sickness (MS) has also been reported during both long and short journeys. Current prophylactic therapies for both these indications are generally associated with side effects. Physiological profiles of Pycnogenol and Standardized Ginger Root Extract (SGRE) representing active constituents of Zinopin have been described and reviewed in relation to their activities involved in the patho-physiology of VTE (Traveller's Sickness) and MS and their safe use as food supplement, in traveller's thrombosis and motion sickness. The pathophysiology of VTE and MS is discussed in light of epidemiological data and risk factors associated with these conditions. Rationale of development of Zinopin and its mechanism of action are discussed based on physiological synergy of Pycnogenol and SGRE. Conclusions are made in light of preliminary clinical findings obtained in an open controlled clinical trial. Further clinical study on Zinopin on these lines is suggested.

Dietary Supplements↗
PubMed1979

Urinary bladder and sphincter responses to stimulation of dorsal and ventral sacral roots.

The sacral spinal roots have a long intraspinal yet extradural pathway that makes them ideal for electrode implantation for the control of micturition. In the hope of identifying a specific motor pathway to the bladder within these roots, a study of 10 mongrel female dogs was undertaken: bladder and sphincter responses to stimulation of individual sacral roots, and to stimulation of the dorsal and ventral components of each root, were recorded urodynamically. The root producing greatest detrusor response was then divided into its motor and sensory components, and the central and peripheral ends of the latter were stimulated. We found that sphincter resistance to bladder emptying was diminished by removing the afferent dorsal roots from the stimulus field. The physiologic implications of this finding are discussed.

Afferent Pathways↗
PubMed1981

Physiological study of amino acid uptake and receptor desensitization: the GABA system in dorsal root ganglia.

GABA applied under microscopic vision (x320) to neurones of isolated DRG, triggers a depolarizing outflow of Cl-, as seen in intracellular recordings of large somata with myelinated fibres. Group C neurones have now also been examined with respect to diversity of GABA receptors. Cells of small diametre (less than 30 micrometers) responding to stimulation of slow conducting, (less than 2.5 m/sec) unmyelinated C fibres were studied for 2 reasons: 1) GABA probably depolarizes nerve endings and C fibres but conductance changes have not been determined, 2) the inference that, unlike group A, the group C neurones show an additional response to GABA by reducing the net influx of Ca++ during action potentials. As a first step in comparing group A with C neurones, it was found that all ganglion cells responded similarly to GABA with Cl--dependent depolarization and a rapid desensitization. This conclusion relies on combined physiological and pharmacological data and also on autoradiographs of glial GABA uptake. Results are considered to reflect direct actions of GABA on neuronal membranes and to be independent of secondary effects due to Na+-dependent transport of GABA into glia.

Amino Acids↗
PubMed1999

Three years of clinical evaluation of endodontically treated teeth by 15 F CO2 laser microprobe: in vivo study.

OBJECTIVE: Evaluation of the efficiency of 15 F CO2 laser microprobe, in cases of periapical lesions. The elimination of the pathological reaction caused by certain species of bacteria by reduction of reinfection and stimulation of osteogenesis. SUMMARY BACKGROUND DATA: Until now, no suitable delivery fiber existed for CO2 laser endodontic radiation in the apical region where it is most difficult to eliminate the pulp tissue using conventional methods. To overcome this problem, Sharplan Lasers designed a microprobe that reaches closer to the apex, distributing the energy density to a smaller area of the root canal, thus favorably increasing the thermal effects. METHODS: The study was conducted on 900 teeth, corresponding to 1512 root canals, divided in two groups. Four hundred sixty-eight were new cases, carefully selected according to strict parameters such as wide periapical translucency over 1 mm, supported by digital x-ray, with a lesion of 3 mm and more. All root canals were mechanically prepared in the conventional method up to size 35, Physiological saline solution served as rinsing solution and the root canals were treated by 15 F CO2 laser microprobe for 60 pulses repeatedly. The temperature at the surrounding tissue of the root did not exceed 38 degrees C. RESULTS: Filling of the canal was possible at the same appointment, without antibiotic treatment. Four hundred thirty-two of the cases, which were referred to us by other dentists after an unsuccessful treatment according to the classic therapy, were treated by the same laser therapy. Follow-up was performed by clinical examination, and a digital x-ray was taken, during and after treatment as well as after 3, 6, 9, and 12 months. CONCLUSIONS: There is a 98% success rate in both study groups, according to objective criteria for successful treatment including reduction of apical translucency after 2-6 months, freedom from clinical complaints, and no need for periapical surgery.

Humans↗
PubMed2000

Short root mutant of Lotus japonicus with a dramatically altered symbiotic phenotype.

Legume plants carefully control the extent of nodulation in response to rhizobial infection. To examine the mechanism underlying this process we conducted a detailed analysis of the Lotus japonicus hypernodulating mutants, har1-1, 2 and 3 that define a new locus, HYPERNODULATION ABERRANT ROOT FORMATION (Har1), involved in root and symbiotic development. Mutations in the Har1 locus alter root architecture by inhibiting root elongation, diminishing root diameter and stimulating lateral root initiation. At the cellular level these developmental alterations are associated with changes in the position and duration of root cell growth and result in a premature differentiation of har1-1 mutant root. No significant differences between har1-1 mutant and wild-type plants were detected with respect to root growth responses to 1-aminocyclopropane1-carboxylic acid, the immediate precursor of ethylene, and auxin; however, cytokinin in the presence of AVG (aminoetoxyvinylglycine) was found to stimulate root elongation of the har1-1 mutant but not the wild-type. After inoculation with Mesorhizobium loti, the har1 mutant lines display an unusual hypernodulation (HNR) response, characterized by unrestricted nodulation (hypernodulation), and a concomitant drastic inhibition of root and shoot growth. These observations implicate a role for the Har1 locus in both symbiotic and non-symbiotic development of L. japonicus, and suggest that regulatory processes controlling nodule organogenesis and nodule number are integrated in an overall mechanism governing root growth and development.

Mutation↗
PubMed1999

Statoliths motions in gravity-perceiving plant cells: does actomyosin counteract gravity?

Statocytes from plant root caps are characterized by a polar arrangement of cell organelles and sedimented statoliths. Cortical microtubules and actin microfilaments contribute to development and maintenance of this polarity, whereas the lack of endoplasmic microtubules and prominent bundles of actin microfilaments probably facilitates sedimentation of statoliths. High-resolution video microscopy shows permanent motion of statoliths even when sedimented. After immunofluorescence microscopy using antibodies against actin and myosin II the most prominent labeling was observed at and around sedimented statoliths. Experiments under microgravity have demonstrated that the positioning of statoliths depends on the external gravitational force and on internal forces, probably exerted by the actomyosin complex, and that transformation of the gravistimulus evidently occurs in close vicinity to the statoliths. These results suggest that graviperception occurs dynamically within the cytoplasm via small-distance sedimentation rather than statically at the lowermost site of sedimentation. It is hypothesized that root cap cells are comparing randomized motions with oriented motions of statoliths and thereby perceiving gravity.

Actomyosin↗
PubMed1986

How roots perceive and respond to gravity.

Graviperception by plant roots is believed to occur via the sedimentation of amyloplasts in columella cells of the root cap. This physical stimulus results in an accumulation of calcium on the lower side of the cap, which in turn induces gravicurvature. In this paper we present a model for root gravitropism integrating gravity-induced changes in electrical potential, cytochemical localization of calcium in cells of gravistimulated roots, and the interdependence of calcium and auxin movement. Key features of the model are that 1) gravity-induced redistribution of calcium is an early event in the transduction mechanism, and 2) apoplastic movement of calcium through the root-cap mucilage may be an important component of the pathway for calcium movement.

Abscisic Acid↗
PubMed1989

Site of graviperception in roots: a re-examination.

Two lines of evidence have been cited to support the assertion that the root cap is the sole site of graviperception in the root. The first evidence is based on surgical removal of the cap, which abolishes the response to gravity. This is sufficient to conclude that the cap is involved in gravitropism, but not to conclude that the cap is the site of graviperception. The second is based on the results of centrifugation experiments, in which different parts of the plant are subjected to different centrifugal forces. The data from such experiments have been cited to support the conclusion that the perception of gravity is limited to the rootcap. However, these data actually support the conclusion that gravity is perceived throughout the root tip, and not only in the root cap. We believe that the data support the conclusion that the root cap is involved in root gravitropism, but that there is inadequate evidence to conclude that the cap is the sole site of graviperception.

Centrifugation↗
PubMed2006

A novel role for abscisic acid emerges from underground.

The continuous formation of lateral roots is a vital part of establishing a root system and enables plants to react with developmental plasticity to changing soil conditions. Evidence is accumulating that abscisic acid (ABA), which is known to be involved in stress responses, has an important role in lateral root formation. An ABA receptor mutant, fca-1, shows an altered response to ABA during lateral root formation. Interestingly, ABA seems to have distinct roles at different stages in lateral root development. The emerging role of ABA in lateral root development fits well with its general functional properties as a stress hormone, including its role in dormancy.

Abscisic Acid↗
PubMed1997

Citric acid demineralization of cementum and dentin: the effect of the storage medium.

The purpose of this study was to see if the root surface topography of teeth, stored in saline and subsequently treated with citric acid, differred from the root surface topography of teeth that were treated immediately upon extraction, 12 freshly extracted adult human permanent teeth, with proximal surfaces free of caries and periodontal disease, were treated in succession. The crowns were removed at the level of periodontal attachment, the teeth sectioned buccal-lingually and a treatment area deligniated on each proximal section. The treatment area of 6 teeth was root planed to expose dentin (D) and scaled to remove adherent tissue and leave a cementum surfaces (C) on the other 6 teeth. A coronal-apical groove down the middle of the treatment area divided it into approximately equal parts or experimental regions. One proximal section of each tooth was placed in physiologic saline (S) and treated after 6 weeks of storage while the other proximal section was freshly treated (F). Treatment consisted of applying a 30% citric acid (CA) solution (pH = 1.60) for 5 min. Cotton pellets soaked in the citric acid solution were placed (P) on one half of the experimental area and heavily burnished (B) on the other half. Treatment areas were subsequently prepared for scanning electron microscopy analysis. Assessment was made of (i) the % of surface area tufted, (ii) fibril tufting depth (0.3) and (iii) fibril tufting density (1.3). Similarities were found in the data for both storage methods (F and S) across each application technique (P or B) and each tooth surface (D or C) with respect to the (i) % area tufted and (ii) frequency distribution of tufting depth scores. As for the application techniques, the data for burnishing was greater than placed across each storage method (F or S) and each tooth surface (D or C) for the same two parameters. The results of the study indicated that 6-week physiologic saline storage does not affect root surface demineralization by citric acid, as assessed by SEM.

Adult↗
PubMed1992

Effects of catechol compound administration on nerve growth factor synthesis in the peripheral nervous system.

The effects of the intraperitoneal administration of catechol compounds on nerve growth factor (NGF) synthesis in the peripheral nervous system were examined in Wistar male rats. Five injections of 4-methylcatechol (4-MC) during a three-day period caused a threefold to fourfold increase in the NGF content of organs with sympathetic innervation (heart, submandibular gland) and the sciatic nerve. Next, we investigated time-dependent changes in the NGF content after a single injection of 2 micrograms of 4-MC. A transient increase in the NGF content was detected in the heart and submandibular gland at 16 hours after administration. In the sciatic nerve, a transient increase in the NGF content was noted at 20 hours in the nerve segments on the distal side, and at 24 hours in the segments on the proximal side. In the superior cervical ganglion and dorsal root ganglion, i.e., the locations of the sympathetic and sensory nerve cell bodies, an increase in the NGF content was detected between 32 and 40 hours. Therefore, catechol compounds stimulate NGF synthesis in the peripheral nervous system, and NGF induced by 4-MC is transported retrogradely in the axon to the soma in a physiological manner. Furthermore, in the dorsal root ganglion and superior cervical ganglion, the use of substance P and tyrosine hydroxylase activity as biochemical markers of sensory and sympathetic neurons has demonstrated the biological activity of newly-synthesized NGF induced by catechol compounds.

Animals↗
PubMed2004

Nutrient uptake as a contributing explanation for deep rooting in arid and semi-arid ecosystems.

Explanations for the occurrence of deep-rooted plants in arid and semi-arid ecosystems have traditionally emphasized the uptake of relatively deep soil water. However, recent hydrologic data from arid systems show that soil water potentials at depth fluctuate little over long time periods, suggesting this water may be rarely utilized or replenished. In this study, we examine the distributions of root biomass, soil moisture and nutrient contents to 10-m depths at five semi-arid and arid sites across southwestern USA. We couple these depth distributions with strontium (Sr) isotope data that show deep (>1 m) nutrient uptake is prevalent at four of the five sites. At all of the sites, the highest abundance of one or more of the measured nutrients occurred deep within the soil profile, particularly for P, Ca2+ and Mg2+. Phosphate contents were greater at depth than in the top meter of soil at three of five sites. At Jornada, for example, the 2-3 m depth increment had twice the extractable P as the top meter of soil, despite the highest concentrations of P occurring at the surface. The prevalence of such deep resource pools, and our evidence for cation uptake from them, suggest nutrient uptake as a complementary explanation for the occurrence of deep-rooted plants in arid and semi-arid systems. We propose that hydraulic redistribution of shallow surface water to deep soil layers by roots may be the mechanism through which deep soil nutrients are mobilized and taken up by plants.

Biomass↗
PubMed2004

Determination of cell fate in apical meristems.

Although roots and shoots exhibit profound differences in their pattern of organogenesis, both apices share the capacity for indeterminate growth. Ongoing molecular and genetic analyses have revealed relatively little overlap between the genes that regulate organogenesis in the root and shoot apices. In the shoot, an ensemble of transcription factors lays the foundations for the leaf, in which indeterminacy is exchanged for more limited and polarized growth. Class-I KNOX genes are downregulated in the anlagen of the leaf early in its establishment, but are maintained in other regions of the shoot apex. This persistent expression of KNOX genes may serve to prevent the precocious determination of apical initial derivatives, and thus may allow the production of a large number of pluripotent cells from a relatively small number of stem cells. Greater commonality between roots and shoots is seen in mechanisms that underlie histogenesis and radial-patterning processes. Recent work suggests that undetermined stem cells in both the root and the shoot may be maintained by related mechanisms, which feature regulation of WUSCHEL-like organizer activities by feedback mechanisms that involve receptor-like kinases.

Gene Expression Regulation, Plant↗