The thyroid: recent advances in normal and abnormal physiology.
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Age Factors↗
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Results for “Root physiology”
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Experimental studies on surgical treatment of avulsed spinal nerve roots in brachial plexus injury.
This review summarises studies aiming at a surgical treatment of spinal nerve root avulsions from the spinal cord in brachial plexus lesions. After dorsal root injury, regrowth of nerve fibres into the spinal cord occurs only in the immature animal. After ventral root avulsion and subsequent implantation into the spinal cord, neuroanatomical and neurophysiological data show that motoneurons are capable of producing new axons which enter the implanted root. Intra-neuronal physiological experiments demonstrate that new axons can conduct action potentials and elicit muscle responses. The neurons are reconnected in segmental spinal cord activity and respond to impulses in sensory nerve fibres. In primate experiments, implantation of avulsed ventral roots in the brachial plexus resulted in functional restitution. These studies indicate the possibility of surgical treatment of ventral root avulsion injuries in brachial plexus lesions in humans.
Action Potentials↗
Physiological and genetic analyses of aluminium tolerance in rice, focusing on root growth during germination.
Aluminium (Al) ion limits root growth of plants in acidic soils, and rice exhibits the highest level of Al-tolerance among graminous crops. To elucidate Al-tolerance mechanisms in rice, response to Al was compared between rice (Oryza sativa L., cv. Nipponbare) and wheat (Triticum aestivum L., cv. ET8), focusing on seminal root growth at seedling stage and germination stage. At seedling stage, rice and wheat were similarly sensitive to Al in both dose- and time-dependent manner during a 24-h Al exposure. On the contrary, at germination stage, rice was more tolerant to Al than wheat, and wheat roots displayed the loss of plasma membrane integrity more extensively than rice. A rice mutant exhibiting Al hypersensitivity at germination stage was obtained by screening 42,840 R2 progeny derived from the regenerated R0 plants of Nipponbare and thereafter confirmation of the mutant phenotype in R3 progeny. At germination stage, root growth of the mutant was strongly inhibited in the presence of Al but not in the absence of Al. However, at seedling stage, root growth of the mutant and wild type was similarly tolerant to Al. Taken together, we conclude that rice possesses Al-tolerant function that is under genetic control and specifically operates for root growth at germination stage, making rice more tolerant to Al than wheat.
Adaptation, Physiological↗
Reflex responses to stimulation of mechanoreceptors in the left ventricle and coronary arteries in anaesthetized dogs.
1. Previous work has shown that physiological increases in mean aortic root pressure, which change the pressure in both the coronary circulation and the left ventricle, result in reflex vasodilatation. This study was undertaken to attempt to localize the reflexogenic area mainly responsible for the reflex. 2. In anaesthetized, artificially ventilated dogs, cannulae connected to perfusion systems were inserted in the ascending aorta, left ventricular apex and left atrium. This allowed us to change the pressures in: (a) the aortic root including both the coronary arteries and the left ventricle; (b) aortic root and coronary arteries, at constant ventricular pressure; and (c) in the ventricle, with mean (although not pulse) aortic pressure constant. Aortic and carotid baroreceptors were perfused at constant pressure and reflex responses were determined from changes in perfusion pressures (flows constant) to a vascularly isolated hindlimb and to the remainder of the systemic circulation. 3. Combined changes in mean aortic root (coronary arterial) and ventricular systolic pressures consistently resulted in decreases in perfusion pressures. A change in only mean aortic root (coronary arterial) pressure, with ventricular pressure constant, also resulted in decreases in perfusion pressures and these were only a little smaller than those to the combined stimulus. Changes in ventricular systolic pressure resulted in responses averaging only about 30% of those to the combined stimulus. 4. Setting mean aortic root or ventricular systolic pressures at different levels did not affect the responses to changes in pressures in the other region. 5. These results show that physiological increases in pressure in the aortic root and coronary arteries, in the absence of changes in pressure in the left ventricle, cause reflex vasodilatation. The relatively small response occurring when ventricular pressure was changed could be due either to a contribution from ventricular receptors or to a change in the stimulus to coronary receptors resulting from changes in the ventricular or aortic pulse. 6. We conclude that the reflex effects of increases in mean aortic root pressure are due mainly to stimulation of coronary arterial baroreceptors.
Anesthesia↗
Analytical electron microscopical investigations on the apoplastic pathways of lanthanum transport in barley roots.
In transmission electron microscopy studies, lanthanum ions have been used as electron-opaque tracers to delineate the apoplastic pathways for ion transport in barley (Hordeum vulgare L.) roots. To localize La3+ on the subcellular level, e.g. in cell walls and on the surface of membranes, electron-energy-loss spectroscopy and electron-spectroscopic imaging were used. Seminal and nodal roots were exposed for 30 min to 1 mM LaCl3 and 10 mM LaCl3, respectively. In seminal roots, possessing no exodermis, La3+ diffusion through the apoplast was stopped by the Casparian bands of the endodermis. In nodal roots with an exodermis, however, La3+ diffusion through the cortical apoplast had already stopped at the tight junctions of the exodermal cell walls resembling the Casparian bands of the endodermis. Therefore, we conclude that in some specialized roots such as the nodal roots of barley, the physiological role of the endodermis is largely performed by the exodermis.
Hordeum↗
[Chemical behavior and ecological effects of pollutants acting on root-soil interface].
Root-soil interface is the main entrance of pollutants intruding into plant tissues and the special micro-ecosphere that can result in a series of ecological safety problems. In this review, the concept of root-soil interface is presented and it is suggested that root-soil interface behavior and effects of chemical pollutants should be grouped into two aspects as rhizosphere chemical behavior and ecological effects and root chemical behavior and ecological effects. These two aspects are theoretically discussed according to the latest research advances. Rhizosphere chemical behavior and ecological effects included rhizosphere pH environment and adsorptive behavior, rhizosphere oxidation-reduction behavior, rhizosphere chemical toxicology effects, rhizosphere microbiological effects, and rhizosphere bioenzymatic reaction etc., and root chemical behavior and ecological effects included root exudation, influence of enzymatic systems in roots, disturbance of normal physiological processes, change of cellular structure and function, and interference of structure and function of biological macromolecules. Particular attention should be paid to the significance as well as some problems of research on chemical behavior and ecological effects of pollutants acting root-soil interface in pollution ecology.
Adsorption↗
Physiological roles of calcium in light-induced gravitropism in Zea primary roots.
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Calcium↗
Phytophthora pseudosyringae sp. nov., a new species causing root and collar rot of deciduous tree species in Europe.
In several studies of oak decline in Europe, a semi-papillate homothallic Phytophthora taxon was consistently isolated, together with other Phytophthora species, from rhizosphere soil samples. It was also found associated with necrotic fine roots and stem necroses of Fagus sylvatica and Alnus glutinosa. Due to morphological and physiological similarities, the semi-papillate isolates were previously identified as P. syringae by various authors. The morphology, physiology and pathogenicity against fine roots of Quercus robur, Q. petraea and F. sylvatica, bark of A. glutinosa, leaves of Ilex aquifolium and apple fruits of this Phytophthora species are described and compared with those of related and similar Phytophthora species, namely P. ilicis, P. psychrophila, P. quercina, P. citricola and P. syringae. The phylogenetic placement on the basis of ITS and mtDNA sequence data was also examined. Isolates of this taxon produce colonies with stellate to rosaceous growth patterns and limited aerial mycelium on various agar media. Antheridia are predominantly paragynous. In water culture catenulate hyphal swellings and semi-papillate caducous sporangia, that are usually limoniform, ellipsoid or ovoid, are formed abundandly, mostly in lax or dense sympodia. This taxon is a moderately slow growing, low temperature species with optimum and maximum temperatures around 20 and 25 degrees C, respectively. Tested isolates are moderately aggressive to fine roots of oaks and beech, highly aggressive to holly leaves and apple fruits, and slightly pathogenic to alder bark. Thirteen tested isolates had an identical and distinct ITS sequence which was more similar to that of P. ilicis and P. psychrophila than any other known taxa. On the basis of their unique combination of morphological characters, colony growth patterns, cardinal temperatures for growth, growth rates, pathogenicity to oaks, beech, alder, apple and holly, their host range, and ITS and mtDNA sequences the semi-papillate caducous Phytophthora isolates from oaks, beech and alder are clearly separated from related and similar Phytophthora spp., and described as a new species, P. pseudosyringae sp. nov.
Alnus↗
[Allelopathy of decomposing pepper stalk on pepper growth].
With decomposing pepper stalk as test material, this paper studied its allelopathy on the growth of pepper plants. The results showed that after 60 days of decomposition, the decomposed pepper stalk could decrease the plant height, stem diameter, dry weights of above-and underground biomass, leaf area, and chlorophyll content of pepper plants by 0.0374 - 0.0646, 0.0020 - 0.0097, 0.0050 - 0.0355 and 0.0916 - 0.3584, 0.0016 - 0.0251, and 0.0043 - 0.0242 respectively. These inhibitory effects were enhanced after 120 days of decomposition, but the difference with CK was not significant. The root vigor and its SOD, POD and CAT activities of pepper plants were decreased, while the MDA content and relative conductivity were increased with the increasing concentration of decomposed pepper stalk and with the prolong of treating time. The allelopathic effects of decomposed pepper stalk on the physiological indices of pepper root activity ranged from 0.0163 to 0.6507, which was significantly higher than that of plant growth index.
Biomass↗
Membrane potential differences in bean roots.
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Fabaceae↗
Biomechanical studies on newly tailored artificial dental root.
Artificial roots must carry multiple forces during mastication. Stress distribution around a root depends upon the shape, material, and function of the root. Therefore, for biomechanical studies on artificial roots, triad research on the material, shape, and functional effect upon surrounding tissue is essential. For dental implants, there are two different functional systems against the masticatory force, i.e., gomphosis and ankylosis on osseointegration. Stress analyses of functioning new type (gomphosis) artificial roots were carried out in mandibular and maxilla models to study the triad effect using finite element analysis. The authors have already reported histological and biomechanical studies on the shape and functional effect. To observe the material effect biomechanically, artificial roots made of sintered hydroxyapatite and zirconium oxide were analyzed in the models. Thereafter, animal experiments using dogs were carried out to observe bone formation around artificial roots made of hydroxyapatite and zirconium oxide in the mandible and maxilla. The following results were obtained: The patterns of stress distribution around artificial roots of two different materials were not too different, and were exclusively dependent upon the root shape and structure of the jawbone. Around the artificial roots, bone formation coincided with a moderate stress distributing zone and principal stress trajectories. Through these experiments, the following conclusions were obtained: (a) Osteogenesis around artificial roots coincides with the stress distribution patterns. (b) Stress distribution patterns are dependent very little upon material properties but upon both the artificial root shape and the structure of the jawbone. (c) Optimization of the artificial root shape can be obtained by FEA in the models.
Animals↗
Actin-dependent fluid-phase endocytosis in inner cortex cells of maize root apices.
The fluorescent dye Lucifer Yellow (LY) is a well-known and widely-used marker for fluid-phase endocytosis. In this paper, both light and electron microscopy revealed that LY was internalized into transition zone cells of the inner cortex of intact maize root apices. The internalized LY was localized within tubulo-vesicular compartments invaginating from the plasma membrane at actomyosin-enriched pit-fields and individual plasmodesmata, as well as within adjacent small peripheral vacuoles. The internalization of LY was blocked by pretreating the roots with the F-actin depolymerizing drug latrunculin B, but not with the F-actin stabilizer jasplakinolide. F-actin enriched plasmodesmata and pit-fields of the inner cortex also contain abundant plant-specific unconventional class VIII myosin(s). In addition, 2,3 butanedione monoxime, a general inhibitor of myosin ATPases, partially inhibited the uptake of LY into cells of the inner cortex. Conversely, loss of microtubules did not inhibit fluid-phase endocytosis of LY into these cells. In conclusion, specialized actin- and myosin VIII-enriched membrane domains perform a tissue-specific form of fluid-phase endocytosis in maize root apices. The possible physiological relevance of this process is discussed.
Actins↗
Through form to function: root hair development and nutrient uptake.
Root hairs project from the surface of the root to aid nutrient and water uptake and to anchor the plant in the soil. Their formation involves the precise control of cell fate and localized cell growth. We are now beginning to unravel the complexities of the molecular interactions that underlie this developmental regulation. In addition, after years of speculation, nutrient transport by root hairs has been demonstrated clearly at the physiological and molecular level, with evidence for root hairs being intense sites of H(+)-ATPase activity and involved in the uptake of Ca(2+), K(+), NH(4)(+), NO(3)(-), Mn(2+), Zn(2+), Cl(-) and H(2)PO(4)(-).
Nitrogen↗
Genetic analysis of two tomato mutants affected in the regulation of iron metabolism.
Iron is one of the most important micronutrients for plants. Like other organisms, plants have developed active mechanisms for the acquisition of sufficient iron from the soil. Nevertheless, very little is known about the genetic mechanisms that control the active uptake. In tomato, two spontaneously derived mutants are available, which are defective in key steps that control this process. The recessive mutation chloronerva (chln) affects a gene which controls the synthesis of the non-protein amino acid nicotianamine (NA), a key component in the iron physiology of plants. The root system of the recessive mutant fer is unable to induce any of the characteristic responses to iron deficiency and iron uptake is thus completely blocked. We present a characterization of the double mutant, showing that the fer gene is epistatic over the chln gene and thus very likely to be one of the major genetic elements controlling iron physiology in tomato. In order to gain access to these two genes at the molecular level, both mutants were precisely mapped onto the high density RFLP map of tomato. The chln gene is located on chromosome 1 and the fer gene is on chromosome 6 of tomato. Using this high-resolution map, a chromosome walk has been started to isolate the fer gene by map-based cloning. The isolation of the fer gene will provide new insights into the molecular mechanisms of iron uptake control in plants.
Algal Proteins↗
Lateral root initiation in Marsilea quadrifolia. I. Origin and histogensis of lateral roots.
In Marsilea quadrifolia, lateral roots arise from modified single cells of the endodermis located opposite the protoxylem poles within the meristematic region of the parent root. The initial cell divides in four specific planes to establish a five-celled lateral root primordium, with a tetrahedral apical cell in the centre and the oldest merophytes and the root cap along the sides. The cells of the merophyte divide in a precise pattern to give rise to the cells of the cortex, endodermis, pericycle, and vascular tissues of the emerging lateral root. Although the construction of the parent root is more complicated than that of lateral roots, patterns of cell division and tissue formation are similar in both types of roots, with the various tissues being arranged in similar positions in relation to the central axis. Vascular connection between the lateral root primordium and the parent root is derived from the pericycle cells lying between the former and the protoxylem members of the latter. It is proposed that the central axis of the root is not only a geometric centre, but also a physiological centre which determines the fate of the different cell types.
Cell Differentiation↗
Functional change in the rat spinal cord by chronic spinal transection and possible roles of monoamine neurons.
Two types of spinal reflex responses, extensor reflex and ventral root potential, were compared physiologically and pharmacologically in acute and chronic spinal cord transected rats. The recovery curve of the extensor reflex, recorded as evoked electromyogram, in chronic spinal rats was strikingly different from that in acute spinal rats. Namely, shortening of the reflex amplitude suppression period (stimulus interval: 20 msec) and appearance of the supernormal period (30-60 msec) were observed in chronic spinal rats. The recovery curves of ventral root potential (monosynaptic reflex) and M wave were almost the same in both preparations. In the frequency depression curve, the amplitude of the extensor reflex in chronic spinal rats was higher at high frequency stimulation than that in acute spinal rats. 5-Hydroxytryptophan, 5-methoxy-N,N-dimethyltryptamine and quipazine enhanced the extensor reflex in chronic spinal rats with a potency of 200-400, 8 and 4 times stronger than that in acute spinal rats, respectively. These drugs did not show consistent effects on the monosynaptic reflex of ventral root potential in chronic spinal rats. These results strongly suggest that the spinal interneurons where descending serotonergic fibers terminate become supersensitive and functionally modified in chronic spinal rats. It is speculated that the supersensitivity of these interneurons may play an important role in spasticity.
5-Hydroxytryptophan↗
The effects of a high-carbohydrate diet on the stress-strain behavior of the periodontal ligament of the distal root of the mandibular first molar in hamsters.
We analyzed stress-strain curves in transverse sections at three different root levels of the cervical, middle, and apical regions of the distal root of the mandibular first molar in hamsters fed a high-carbohydrate (experimental group) or standard (control group) diet for 8 weeks. Each section was loaded in vitro at a rate of 5 mm/min in an extrusive direction. The rupture sites and the structures of birefringent collagen fibers in the periodontal ligament were also analyzed. The maximum shear stress, tangent modulus, and failure strain energy density of the periodontal ligament were significantly greater in the cervical region than in the middle and apical regions in both the control and experimental groups. The maximum shear stress, tangent modulus, and failure strain energy density of the periodontal ligament in the experimental group were significantly lower than those in the control group at the cervical and middle regions. The maximum shear strain was significantly greater in the experimental group than in the control group at the middle and apical regions. Histological sections showed that the periodontal ligament ruptured irregularly in both groups. The collagenous fibers of the ligament in the experimental group appeared to be thinner and less birefringent at the cervical and middle regions of the root. These results suggest that a high-carbohydrate diet differentially affects the collagen fibers in the periodontal ligament as a function of the root level, and that these effects are evident in changes in the mechanical properties of the ligament.
Analysis of Variance↗
Apexification & apexogenesis.
When there is pulpal involvement of permanent teeth with incompletely formed roots, techniques for the induction of apical closure should be completed before endodontic therapy is begun. Apexification is a method of inducing a calcified barrier at the apex of a nonvital tooth with incomplete root formation. Apexogenesis refers to a vital pulp therapy procedure performed to encourage physiological development and formation of the root end.
Adolescent↗