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PubMed2006

Electrical measurement of tree root absorbing surfaces by the earth impedance method: 2. Verification based on allometric relationships and root severing experiments.

We validated, by means of allometric relationships and root severing experiments, the modified earth impedance method developed for measuring absorbing root surfaces. For the allometric studies, a series of 350 small and large trees of six broadleaf and coniferous species in several experimental sites was examined. We found a good linear ln-ln fit between absorbing root surface area and basal area (or stem cross-sectional area at the root collar in seedlings) over a range of stem diameters from 0.5-55 cm. The absorbing root surface area also changed consistently with crown projected area and the root-accessed area (territory) of the tree. At the whole-tree level, absorbing root surface area reached about 70 times that of basal area and 40% of crown projected area, or roughly 1/3 of the root-accessed area in Norway spruce (in this species, the ratio was relatively larger in small trees and smaller in large trees). The absorbing root surfaces of mechanically severed parts of Norway spruce root systems changed in about the same proportions as the geometrically determined parts of the severed root systems. These results are promising and support field applications of the method in biological and ecological studies.

Absorption↗
PubMed1983

Aberrant peripheral nerves and microneuromas in otherwise normal medullas.

The occurrence of aberrant peripheral nerve (PN) fibers in otherwise normal medullas was studied in 1,016 consecutively autopsied patients. Fine, myelinated PN fibers occurred as small parallel bundles or microneuromas about arteries and arterioles exclusively in the dorsal half of the medulla. They were more common in male than female patients, but were not related to any specific systemic disease process. The PN lesions were not found in patients under 20 years of age, but were observed in 1.5, 9.6, and 16.4% of those patients 20-49, 50-69, and 70-89 years of age, respectively. We regard these lesions as aberrant nerve fibers regenerated from cranial nerve roots rather than normally developed vascular nerves. We postulate that cranial nerve roots are subject to shearing or compression by strenuous motion of the neck in the course of ordinary activities and that the nerve fibers thus severed regenerate and grow into the pia-arachnoid and perivascular spaces to form the PN lesions. These PN lesions may become exaggerated under various abnormal circumstances such as overt traumatic injury and long-standing diseases affecting the medulla or cranial nerve roots.

Adolescent↗
PubMed2004

Interaction between Vitis vinifera and grape phylloxera: changes in root tissue during nodosity formation.

BACKGROUND AND AIMS: The interaction between the gall-forming grapevine parasite, phylloxera, and the susceptible grapevine species Vitis vinifera was investigated. METHODS: Phylloxera and grapevines were cocultivated using both potted and micropropagated grapevines. Development of nodosities on primary roots was studied by microscopy and histochemistry, and nodosities were analysed for biochemical changes and changes in gene expression. KEY RESULTS: Within a nodosity, phylloxera fed at a site in the root cortex. Nodosity development was characterized by swelling of the root tissue distal to the feeding site, lack of development of a suberized endodermis, and starch and amino acid accumulation, and was eventually followed by root necrosis. No evidence of a defence response was observed in pre-necrotic nodosities, but defence-type responses were observed in tissue adjacent to necrotic regions. Changes in gene expression were not detected by northern hybridization using DNA probes encoding a range of V. vinifera transcripts. CONCLUSIONS: Nodosities on V. vinifera potentially function as nutrient reservoirs, and defence responses to phylloxera attack were not detected.

Animals↗
PubMed2006

In vitro anti-cariogenic activity of dichloromethane fraction from Rheum undulatum L. root.

This study aimed to evaluate in vitro effects of Rheum undulatum L. root on the development of dental caries, especially its effects on viability, dental plaque formation, and glycolytic acid production of Streptococcus mutans and Streptococcus sobrinus. Methanol extract of Rheum undulatum L. root and its fractions were prepared and tested. Among the test extract and fractions, dichloromethane fraction (DF) showed the most active antibacterial activity (inhibition zone: 13-17 mm) against S. mutans and S. sobrinus in a disc diffusion method. Minimal inhibitory concentrations (MICs) of DF against these bacteria ranged from 0.25 to 0.5 mg/mL. Furthermore, DF significantly inhibited the caries-inducing factors of these bacteria. At sub-MIC levels, DF inhibited in vitro dental plaque formation by S. mutans and S. sobrinus (IC50= 0.079 and 0.142 mg/mL, respectively), which was caused, in part, by the inhibitory effect on the activity of glucosyltransferases. A significant reduction of glycolytic acid production was found at the concentration as low as 0.032 mg/mL for S. mutans and 0.063 mg/mL for S. sobrinus. The possible bioactive compounds that are inducing in vitro anti-cariogenic activity of DF are unknown. Based on the preliminary phytochemical analysis, the activity of DF may be related to the presence of anthraquinones, cardiac glycosides, coumarines, sterols/terpenes, and phenolics. These results indicate that DF is probably useful for the control of dental plaque formation and subsequent dental caries development.

Anti-Bacterial Agents↗
PubMed1980

Cortical Air Spaces (Aerenchyma) in Roots of Corn Subjected to Oxygen Stress: STRUCTURE AND INFLUENCE ON UPTAKE AND TRANSLOCATION OF RUBIDIUM IONS.

When the seminal root system of 14-day-old corn (Zea mays cv. Dekalb 202) was subjected to O(2) stress, nodal roots with well developed cortical air spaces (aerenchyma) grew into the deoxygenated solution. Microscopic examination showed that there was extensive breakdown of cells in the midcortex of these roots, while the stele, endodermis, and inner layer of cortical cells remained complete, as did the outer layers of the cortex and the epidermis. Occasional files of intact cells, and the wall residues of collapsed cells, crossed the space between inner and outer cortex. Experiments with short, intact root segments with and without air spaces showed that in the presence of O(2) the ability to absorb and translocate (86)Rb(+), per unit volume or length of root, was little affected by cortical degeneration. The distribution across root sections of recently supplied strontium and rubidium, determined by electron microprobe analysis, indicated that in roots with air spaces the strands of wall residues bridging the cortex could be involved in maintaining the conduction of ions from the outer cortex up to the endodermis.

Journal Article↗
PubMed1995

Formation of lateral root meristems is a two-stage process.

In both radish and Arabidopsis, lateral root initiation involves a series of rapid divisions in pericycle cells located on the xylem radius of the root. In Arabidopsis, the number of pericycle cells that divide to form a primordium was estimated to be about 11. To determine the stage at which primordia are able to function as root meristems, primordia of different stages were excised and cultured without added hormones. Under these conditions, primordia that consist of 2 cell layers fail to develop while primordia that consist of at least 3-5 cell layers develop as lateral roots. We hypothesize that meristem formation is a two-step process involving an initial period during which a population of rapidly dividing, approximately isodiametric cells that constitutes the primordium is formed, and a subsequent stage during which meristem organization takes place within the primordium.

Arabidopsis↗
PubMedDate not supplied

Aberrant root formation: review of root genesis and three case reports.

The mechanism of root formation and tooth eruption is a complex process which is not fully understood. Prior to a tooth emerging into the oral cavity, root genesis is initiated by derivatives of the enamel organ. The dental follicle mediates an eruption pathway allowing for movement of the developing tooth in a coronal direction. As the tooth moves towards the oral cavity, root formation occurs passively in the resulting space. Failure of the enamel organ and dental follicle to properly coordinate may result in complications in the eruption process. This clinical report presents 3 cases of isolated, unerupted teeth with dysmorphology of the roots. The process of root development and tooth eruption is also briefly reviewed.

Adolescent↗
PubMed1995

Developmental regulation of ribosomal protein L16 genes in Arabidopsis thaliana.

Lateral roots can be synchronously induced in Arabidopsis by a brief auxin treatment. An early event in the development of a lateral root primordium is the accumulation of mRNAs encoding ribosomal proteins. In situ hybridizations show that mRNA encoding one ribosomal protein, L16, accumulates in all rapidly proliferating tissues including the shoot and root apical meristems and lateral root primordia. To understand further the mechanisms by which ribosomal proteins are coordinately synthesized, two genes encoding the ribosomal protein L16 were isolated from Arabidopsis thaliana. Promoter sequences from each RPL16A and RPL16B were fused to the beta-glucuronidase reporter gene GUS. The promoter of RPL16B(from -848 to -19) conferred X-Gluc staining in proliferating tissues including the shoot and root apical meristems. When GUS was expressed from the RPL16A promoter (from -875 to -22), X-Gluc staining was observed in cells in the root stele and in anthers. When seedlings transformed with either promoter construct were treated with auxin to induce lateral roots, X-Gluc staining accumulated in the lateral root primordia by 16 h after induction. Transcription of the RPL16B promoter appears to be correlated with cell division, while transcription of the RPL16A promoter is very cell specific. Expression of two genes encoding L16 during the early phase of lateral root initiation and in developing pollen may serve to increase levels of ribosomal proteins during the rapid growth of these tissues.

Amino Acid Sequence↗
PubMed1986

Effects of Tabtoxinine-beta-Lactam on Nitrogen Metabolism in Avena sativa L. Roots.

The effects of tabtoxinine-beta-lactam (T-beta-L) on nitrate uptake and glutamine synthetase (GS) and nitrate reductase (NR) activities in roots of Avena sativa seedlings were determined. Seven-day-old oat seedlings placed in a 10 mm KNO(3) and 0.5 mm T-beta-L solution for 24 hours took up T-beta-L and lost approximately 90% of their root GS activity. [(3)H]-T-beta-L taken up by roots of seven-day-old oat seedlings was associated with GS immunoprecipitated from the extract of these roots. Total nitrate uptake and in vivo NR activity were decreased approximately 50% in the T-beta-L treated roots. However, T-beta-L uptake did not affect the induction phases of nitrate uptake or reduction, nor did it inhibit in vitro NR activity. Thus, the decrease in nitrate uptake and reduction is a secondary effect of T-beta-L action. Roots of seven-day-old oat seedlings were inoculated with Pseudomonas syringae pv tabaci (Tox+) and the pathogen population in the rhizosphere was estimated by dilution plate count; 6 x 10(13) bacteria were recovered after 3 days, as compared to the original inoculation with 7 x 10(9) bacteria, indicating a significant growth of the pathogen in the rhizosphere. The bacteria recovered from the rhizosphere caused chlorosis in tobacco leaves and produced T-beta-L in culture; 1 x 10(14) bacteria were recovered from roots of seedlings inoculated with P. syringae pv tabaci (Tox-) using the same inoculation and assay procedure as for the pv tabaci (Tox+). Extracts of surface-sterilized roots previously inoculated with P. syringae pv tabaci (Tox+) did not produce viable bacterial cultures when plated out on a complete medium. Oat seedlings growing in sand culture and inoculated with P. syringae pv tabaci (Tox+) had developed chlorosis, and root GS activity had declined to less than 10% of controls after 3 days. Conversely, seedlings inoculated with P. syringae pv tabaci (Tox-) never developed chlorosis and maintained normal levels of GS activity. All oat plants inoculated with P. syringae pv tabaci (Tox+) died within 7 days after inoculation as compared to the plants inoculated with P. syringae pv tabaci (Tox-) which grew to maturity.

Journal Article↗
PubMed1993

Novel surgical strategies to correct neural deficits following experimental spinal nerve root lesions.

In attempts to correct neural deficits following avulsion trauma, novel experimental strategies were developed. In rats, spinal roots were replanted superficially in the dorsal horn following dorsal root avulsion and concomitant denervation by ganglionectomy. Outgrowth from cord neurons in the dorsal horn into the implanted dorsal root was demonstrated by means of retrograde HRP labeling. Double labeling experiments showed that some of these neurons had retained their central projections while extending new processes into the implanted root. After dorsal root avulsion, sensory pathways might be reconstructed by substituting the lost input from damaged primary sensory neurons with induced peripheral outgrowths from secondary neurons. In primates, intraspinal replantation of avulsed ventral nerve roots was investigated as a surgical treatment for motor deficits that develop after severe brachial plexus injury. Two to 3 months after surgery there were EMG signs of reinnervation in previously denervated muscles, which were shortly followed by evidence of clinical recovery. A gradual improvement in the function of the affected arm occurred and motor behavior became normalized, although the EMG activity in the reinnervated muscles at maximal contraction was still reduced. The outcome of these experimental studies indicates that reconstructive surgery applied to the brachial plexus might be of value to restore functional deficits induced by traumatic spinal nerve root avulsions also in man.

Animals↗
PubMed2005

Arabidopsis H+-PPase AVP1 regulates auxin-mediated organ development.

The transport of auxin controls developmental events in plants. Here, we report that in addition to maintaining vacuolar pH, the H+-pyrophosphatase, AVP1, controls auxin transport and consequently auxin-dependent development. AVP1 overexpression results in increased cell division at the onset of organ formation, hyperplasia, and increased auxin transport. In contrast, avp1-1 null mutants have severely disrupted root and shoot development and reduced auxin transport. Changes in the expression of AVP1 affect the distribution and abundance of the P-adenosine triphosphatase and Pinformed 1 auxin efflux facilitator, two proteins implicated in auxin distribution. Thus, AVP1 facilitates the auxin fluxes that regulate organogenesis.

Adenosine Triphosphatases↗
PubMed1994

Changing root system architecture through inhibition of putrescine and feruloyl putrescine accumulation.

Plant roots provide anchorage and absorb the water and minerals necessary for photosynthesis in the aerial parts of the plant. Since plants are sessile organisms, their root systems must forage for resources in heterogeneous soils through differential branching and elongation [(1988) Funct. Ecol. 2, 345-351; (1991) Plant Roots: The Hidden Half, pp. 3-25, Marcel Dekker, NY]. Adaptation to drought, for instance, can be facilitated by increased root growth and penetration. Root systems thus develop as a function of environmental variables and the needs of the plant [(1988) Funct. Ecol. 2, 345-351; (1986) Bot. Gaz. 147, 137-147; (1991) Plant Roots: The Hidden Half, pp. 309-330, Marcel Dekker, NY]. We show, in a model system consisting of excised tobacco roots, that both alpha-DL-difluoromethylornithine (an inhibitor of putrescine biosynthesis) and the rolA gene (from the root-inducing transferred DNA of Agrobacterium rhizogenes) stimulate overall root growth and cause a conversion in the pattern of root system formation, producing a dominant or 'tap' root. These morphological changes are correlated with a depression in the accumulation of polyamines and their conjugates.

Coumaric Acids↗
PubMed2001

Expression of Pcdh15 in the inner ear, nervous system and various epithelia of the developing embryo.

We previously determined that Protocadherin 15 (Pcdh15) is associated with the Ames waltzer mutation in the mouse. Here we describe where the Pcdh15 gene is expressed at specific times during mouse development using RNA in situ hybridization. The expression of Pcdh15 is found in the sensory epithelium in the developing inner ear, in Rathke's pouch, and broadly throughout the brain with the highest level of expression being detected at embryonic day 16 (E16). Pcdh15 transcripts are also found in the developing eye, dorsal root ganglion, and the dorsal aspect of the neural tube, floor plate and ependymal cells adjacent to the neural canal. Additionally, expression is also detected in the developing glomeruli of the kidney, surface of the tongue, vibrissae, bronchi of the lung, and in the epithelium of the olfactory apparatus, gut and lung.

Animals↗
PubMed1998

Amino acid carriers of Ricinus communis expressed during seedling development: molecular cloning and expression analysis of two putative amino acid transporters, RcAAP1 and RcAAP2.

This study reports on the isolation of two putative amino acid carrier cDNAs, RcAAP1 and RcAAP2, from Ricinus communis. Northern analysis shows that RcAAP1 and RcAAP2 are expressed abundantly in the cotyledon and root tissues of developing seedlings and at lower levels in the endosperm and hypocotyl. In the mature plant low expression was observed in the source and sink leaves. We have further characterized the expression of RcAAP1 in Ricinus roots by in situ hybridization. The transcripts are localized in many cell types of the root tip region, including the epidermal and cortical cells, but the highest expression was observed in the cells of the stele situated adjacent to the xylem poles. This is the first report describing the cellular expression of an amino acid transporter in roots, and the results are discussed in relation to the physiological role of this transporter.

Amino Acid Sequence↗
PubMed1975

Histological study on the postnatal development and sequence of eruption of the maxillary cheek-teeth of rabbits (Oryctolagus cuniculus).

The development and sequence of eruption of the maxillary cheek-teeth of rabbits were studied by histological methods. The presence of three deciduous molars which were replaced by correspondent premolars and of three permanent molars without predecessors was confirmed. The eruption of the maxillary deciduous molars was shown to begin at 4 days postnatally and that of the permanent molar at 9 days, while the eruption of the premolars occurs from 24 days on, replacing the deciduous molars which are exfoliated. The last tooth to erupt is the M3. At 32 days all the permanent cheek-teeth are erupted. The deciduous molars are completely developed at birth, root resorption starting at 4 days. On the first day the premolars are in the bell stage and in the M1 and M2 amelogenesis is taking place. After 27 days the development of the permanent maxillary cheek-teeth is completed. Dentinogenesis, amelogenesis and cementogenesis were observed in all of them.

Age Factors↗
PubMed2001

Aortic root replacement and coronary interposition using a cryopreserved allograft and its branch.

This communication describes a modified aortic root replacement technique using a cryopreserved allograft consisting of the aortic conduit and its branch. This method was applied in a patient suffering from infective pseudoaneurysm which had developed after aortic root replacement using an artificial graft with a mechanical aortic valve. A piece of the innominate artery obtained from the aortic allograft was used for interposition between the fragile left coronary artery root and the main conduit of the allograft.

Aneurysm, False↗
PubMed2005

The putative high-affinity nitrate transporter NRT2.1 represses lateral root initiation in response to nutritional cues.

Lateral root initiation is strongly repressed in Arabidopsis by the combination of high external sucrose and low external nitrate. A previously isolated mutant, lin1, can overcome this repression. Here, we show that lin1 carries a missense mutation in the NRT2.1 gene. Several allelic mutants, including one in which the NRT2.1 gene is completely deleted, show similar phenotypes to lin1 and fail to complement lin1. NRT2.1 encodes a putative high-affinity nitrate transporter that functions at low external nitrate concentrations. Direct measurement of nitrate uptake and nitrate content in the lin1 mutant seedlings established that both are indeed reduced. Because repression of lateral root initiation in WT plants can be relieved by increased concentrations of external nitrate, it is surprising to find that repression is also relieved by a defect in a component of the high-affinity nitrate uptake system. Furthermore, lateral root initiation is increased in lin1 relative to WT even when seedlings are grown on nitrate-free media, suggesting that the mutant phenotype is nitrate-independent. These results indicate that NRT2.1 is a repressor of lateral root initiation and that this role is independent of nitrate uptake. We propose that Arabidopsis NRT2.1 acts either as a nitrate sensor or signal transducer to coordinate the development of the root system with nutritional cues.

Alleles↗
PubMed2001

Evolution and genetics of root hair stripes in the root epidermis.

Root hair pattern develops in a number of different ways in angiosperm. Cells in the epidermis of some species undergo asymmetric cell divisions to form a smaller daughter cell from which a hair grows, and a larger cell that forms a non-hair epidermal cell. In other species any cell in the epidermis can form a root hair. Hair cells are arranged in files along the Arabidopsis root, located in the gaps between underlying cortical cell files. Epidermal cells overlying a single cortical cell file develop as non-hair epidermal cells. Genetic analysis has identified a transcription factor cascade required for the formation of this pattern. WEREWOLF (WER) and GLABRA2 (GL2) are required for the formation of non-hair epidermal cells while CAPRICE (CPC) is required for hair cell development. Recent analyses of the pattern of epidermal cells among the angiosperms indicate that this striped pattern of cell organization evolved from non-striped ancestors independently in a number of diverse evolutionary lineages. The genetic basis for the evolution of epidermal pattern in angiosperms may now be examined.

Biological Evolution↗