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At least 451 records · Page 25Linked to original sources
PubMed2003

A novel high efficiency, low maintenance, hydroponic system for synchronous growth and flowering of Arabidopsis thaliana.

BACKGROUND: Arabidopsis thaliana is now the model organism for genetic and molecular plant studies, but growing conditions may still impair the significance and reproducibility of the experimental strategies developed. Besides the use of phytotronic cabinets, controlling plant nutrition may be critical and could be achieved in hydroponics. The availability of such a system would also greatly facilitate studies dealing with root development. However, because of its small size and rosette growth habit, Arabidopsis is hardly grown in standard hydroponic devices and the systems described in the last years are still difficult to transpose at a large scale. Our aim was to design and optimize an up-scalable device that would be adaptable to any experimental conditions. RESULTS: An hydroponic system was designed for Arabidopsis, which is based on two units: a seed-holder and a 1-L tank with its cover. The original agar-containing seed-holder allows the plants to grow from sowing to seed set, without transplanting step and with minimal waste. The optimum nitrate supply was determined for vegetative growth, and the flowering response to photoperiod and vernalization was characterized to show the feasibility and reproducibility of experiments extending over the whole life cycle. How this equipment allowed to overcome experimental problems is illustrated by the analysis of developmental effects of nitrate reductase deficiency in nia1nia2 mutants. CONCLUSION: The hydroponic device described in this paper allows to drive small and large scale cultures of homogeneously growing Arabidopsis plants. Its major advantages are its flexibility, easy handling, fast maintenance and low cost. It should be suitable for many experimental purposes.

Arabidopsis↗
PubMed2001

Different pathways are involved in phosphate and iron stress-induced alterations of root epidermal cell development.

Low bioavailability of phosphorus (P) and iron (Fe) induces morphogenetic changes in roots that lead to a higher surface-to-volume ratio. In Arabidopsis, an enlargement in the absorptive surface area is achieved by an increase in the length and frequency of hairs in roots of Fe- and P-deficient plants. The extra root hairs are often located in positions that are occupied with non-hair cells under normal conditions, i.e. over a tangential wall of underlying cortical cells. An involvement of auxin and ethylene in root epidermis cell development of Fe- and P-deficient plants was inferred from phenotypical analysis of hormone-related Arabidopsis mutants and from the application of substances that interfere with either synthesis, transport, or perception of the hormones. Application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid or the auxin analog 2,4-D caused a marked increase in root hair density in plants of all growth types and confers a phenotype characteristic of ethylene-overproducing mutants. Hormone insensitivity and application of hormone antagonists inhibited the initiation of extranumerary root hairs induced by Fe deficiency, but did not counteract the formation of extra hairs in response to P deprivation. A model is presented summarizing putative pathways for alterations in root epidermal cell patterning induced by environmental stress.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2000

An ancestral MADS-box gene duplication occurred before the divergence of plants and animals.

Changes in genes encoding transcriptional regulators can alter development and are important components of the molecular mechanisms of morphological evolution. MADS-box genes encode transcriptional regulators of diverse and important biological functions. In plants, MADS-box genes regulate flower, fruit, leaf, and root development. Recent sequencing efforts in Arabidopsis have allowed a nearly complete sampling of the MADS-box gene family from a single plant, something that was lacking in previous phylogenetic studies. To test the long-suspected parallel between the evolution of the MADS-box gene family and the evolution of plant form, a polarized gene phylogeny is necessary. Here we suggest that a gene duplication ancestral to the divergence of plants and animals gave rise to two main lineages of MADS-box genes: TypeI and TypeII. We locate the root of the eukaryotic MADS-box gene family between these two lineages. A novel monophyletic group of plant MADS domains (AGL34 like) seems to be more closely related to previously identified animal SRF-like MADS domains to form TypeI lineage. Most other plant sequences form a clear monophyletic group with animal MEF2-like domains to form TypeII lineage. Only plant TypeII members have a K domain that is downstream of the MADS domain in most plant members previously identified. This suggests that the K domain evolved after the duplication that gave rise to the two lineages. Finally, a group of intermediate plant sequences could be the result of recombination events. These analyses may guide the search for MADS-box sequences in basal eukaryotes and the phylogenetic placement of new genes from other plant species.

Amino Acid Sequence↗
PubMed1984

Autotransplantation and replantation of tooth germs in monkeys. Effect of damage to the dental follicle and position of transplant in the alveolus.

The effect of damage to the follicle and of superficial positioning of tooth germs after replantation or autotransplantation was studied in green Vervet monkeys. Radiographs were taken immediately after surgery and 3, 6 and 9 months postoperatively, whereafter the animals were sacrificed. The tissue blocks were sectioned in step serial sections along a frontal plane and histologic and radiographic evaluation was made. Tooth germs whose follicle was either damaged or removed showed no sign of eruption, while tooth germs which were replanted with an intact follicle were fully erupted within 3 months. Non-operated control teeth were fully erupted within 6 months. Histologic examination revealed that roots of replanted teeth were only slightly shorter than the non-operated control teeth. Transplantation of tooth germs in different positions in relation to the alveolar crest showed that teeth placed in their original position attained an average tooth length of 12.5 mm, whereas teeth placed in a semi-erupted position achieved an average length of only 9.7 mm. A control group of non-operated incisors demonstrated an average tooth length of 13.7 mm. This study indicates that damage to the follicle at the time of replantation of tooth germs is of major importance for tooth eruption and that placing tooth germs in a semi-erupted position adversely influences later root development.

Alveolar Process↗
PubMed1994

Repression of the L-asparaginase gene during nodule development in Lupinus angustifolius.

Upon the establishment of an effective nitrogen-fixing symbiosis in amide-transporting plants the enzymatic activity and transcript levels of L-asparaginase are dramatically decreased. This decrease in L-asparaginase activity is essential for the correct functioning of the Rhizobium-legume symbiosis in lupin in which asparagine, synthesized from recently fixed nitrogen, is exported to aerial parts of the plant for use in growth and development. Concomitant with this decrease in L-asparaginase transcript a DNA-binding protein was detected in the nodules. This binding protein was not detectable in ineffective nodules, in nodules treated with nitrate, or in root tips, mature roots, developing flowers or developing seeds. The DNA-binding activity was shown to interact with a 59 bp sequence proximal to the transcription start site. Within this sequence a CTAAAAT direct repeat and a ACTGT/TGTCA incomplete inverted repeat were implicated in the binding of protein to the DNA by DNase I protection experiments. Competitive binding studies with synthesized binding sites were consistent with the CTAAAAT/TGTCA sequence pair proximal to the transcription start site having the highest affinity for the DNA-binding protein. We postulate that this DNA-binding protein is associated with repression of L-asparaginase gene expression in mature lupin root nodules.

Asparaginase↗
PubMed2001

Orthodontic treatment in long-term survivors after pediatric bone marrow transplantation.

Children treated for childhood cancers with both radiation and chemotherapy often exhibit disturbances in dental development. A retrospective analysis of treatment outcome in 10 orthodontically treated children was performed. A questionnaire was sent to each child's orthodontist, and 5 orthodontists reported that the patient's medical condition influenced their choice of treatment plan. Three orthodontists, all treating patients with severely disturbed root development, reported using lighter forces than they used with the average patient. With regard to complications related to orthodontic treatment, 1 of the 10 patients showed evidence of root resorption. In 4 of the 10 patients, the treatment result was judged to be unsatisfactory. This study showed that, although ideal treatment results were not always achieved, orthodontic treatment did not produce any harmful side effects in children who are long-term survivors of childhood cancer.

Adolescent↗
PubMed1994

Relations among motor unit types, generated forces and muscle length in single motor units of anaesthetized cat peroneus longus muscle.

The active length-tension curves of identified single motor units (MUs) belonging to peroneus longus muscle (PL) of anaesthetized adult cats were obtained by eliciting isometric single twitches and tetani. The recorded responses were evaluated by measuring the peak tension amplitude and the tension-time area at muscle lengths extending throughout the physiological length range of the muscle (mean 5.5 mm, standard deviation +/- 0.8). The muscle lengths at which each tested MU developed its maximal twitch (Ltw) and tetanic (Lte) tensions were determined and compared with the muscle length (Lo) at which the stimulation of all the alpha-axons, innervating PL and contained in L7 ventral root, developed their maximal twitch tension. The mean of single MU Ltw values was at Lo +1.08 +/- 1.1 mm. Slow MUs showed the longest values of Ltw (Lo +1.6 +/- 1.0 mm). Single MUs stimulated at tetanic frequencies presented their Lte at values shorter than Lo (Lo - 2.8 +/- 1.7 mm). Slow MUs had the shortest Lte (Lo - 3.4 +/- 1.5 mm). For all the units Lte was shorter than Ltw. Ltw and Lte were, respectively, negatively and positively correlated with the developed tension. Optimal length values also appeared to be related to the MU types. The possibility is discussed that the muscle and tendon compliances and the high non-linearities to the applied forces are the main factors which can determine the differences among Lo, Ltw and Lte values. The relationships between MU type and optimal length values are suggested to be, at least partly, an epiphenomenon due to the different contraction strengths of the various MU types.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗
PubMed1997

Multiple isoforms of neuregulin are expressed in developing rat dorsal root ganglia.

Accumulating evidence suggests that neuregulin (NRG) plays special roles in the development of the mammalian nervous system. We have already identified NRG as a survival factor for Schwann cells during development. In this report, we have studied all possible NRG isoforms and expression of NRG in the developing rat dorsal root ganglia (DRG) and compared them with those of brain and spinal cord. Neural NRG isoforms comprise common immunoglobulin and epidermal growth factor domains. Various different transcripts were characterized, which arose by alternative splicing in several regions: N-terminal (exon 1 or 2), spacer (exon 5), juxtamembrane (exon 9 or 10), and cytoplasmic (exon 12, 13, or 14) domains. At least 13 novel isoforms among 16 splice variants were identified. The transmembrane isoforms of NRG are dominant forms in developing rat DRG. The mRNA expression of NRG isoforms in DRG is similar to that in spinal cord, while in brain the expression is much less. The mRNA in DRG was found at similar levels from birth to postnatal day 7 of the premyelinating stage, and it decreased afterward. Our results suggest that several NRGs, including isoforms not reported before, play a role as survival factors for Schwann cells in the premyelinating stage.

Aging↗
PubMed1997

Effects of dental trauma on the pulp.

Infection of the root canal system following dental trauma induces pulp and periapical disease and prevents healing of previously healthy pulp. A clinical goal in treating trauma is the maintenance of pulp vitality, and clinicians should be aware of factors that influence pulp healing. The learning objective of this article is to review the factors and techniques that influence pulp vitality and examine the influence pulp has on the healing of adjacent tissues. The potential routes for bacterial infection of the root canal system are discussed, with the clinical crown as the primary portal of entry. Uncomplicated and complicated crown fractures, as well as the crown-root and root fractures, are reviewed. Complications in pulp healing include canal obliteration, disturbed root development, apexogenesis, apexification, and the various forms of resorption.

Alveolar Process↗
PubMed1995

Root formation.

This paper provides an overview of recent studies that have enhanced our understanding of the biological mechanisms that operate during root development. For the most part, these studies have been performed on rodents. As significant species differences have been shown to exist, this data cannot necessarily be extrapolated to the human model. The events associated with root odontoblast differentiation are reviewed in comparison to similar events in coronal odontoblast differentiation. Morphological as well as phenotypic differences are outlined and the inductive role of the epithelial root sheath is discussed. Both acellular and cellular cementum formation are reviewed highlighting morphological and phenotypic differences. The potential influence of the epithelial root sheath in the formation of both tissues is compared and contrasted. Finally, a discussion of the fate of the epithelial root sheath is presented with emphasis placed upon the possible roles of apoptosis and epithelium-mesenchymal transition.

Animals↗
PubMedDate not supplied

Dens evaginatus: a review.

A review of the developmental dental anomaly, dans evaginatus, and a discussion of its clinical management is presented. Fracture or wear of the tubercle of dens evaginatus frequently results in pulp necrosis and early periapical infection, often prior to completion of root formation. Early recognition of this anomaly, followed by timely treatment can prevent the loss of pulp vitality in these teeth. Patients presenting with nonvital teeth and incomplete root development have been successfully treated by apexification followed by conventional endodontic therapy.

Bicuspid↗
PubMed1996

Treatment of crown fractures with pulp exposure.

Thirty permanent incisors with vital pulps and complicated crown fractures were treated by a partial pulpotomy (Cvek technique). This consisted of amputation of 1 to 2 mm of the exposed pulp, placement of calcium hydroxide powder, and a temporary restoration. Clinical and radiographic assessment of the hard tissue barrier was done after 3 months and again after 1 to 8 years. The treatment was successful in all incisors. No differences were found in stage of root development, size of exposure, and length of time exposed. In conclusion, the partial pulpotomy technique is a successful and permanent treatment for crown fractures with pulp exposure regardless of the size of exposure, the maturity of the root, or the interval between accident and dental treatment.

Adolescent↗
PubMed2001

Isolation of the first putative peroxidase cDNA from a conifer and the local and systemic accumulation of related proteins upon pathogen infection.

Peroxidases are associated with the active defence reactions in higher plants in response to foreign organisms. They are involved in the oxidation of phenolic compounds in cell walls, polymerization of lignin and suberin, and in several other oxidation processes but the exact function of individual peroxidases is not known. We have isolated a cDNA encoding the putative defence-related and basic plant peroxidase SPI2 (spruce pathogen-induced 2), with an estimated molecular mass of 34 kDa, from roots of Norway spruce (Picea abies) seedlings. This is the first description of the isolation of a complete cDNA encoding a putative peroxidase from a gymnosperm. The transcript was present in the roots of healthy seedlings, and during infection with the pathogen Pythium dimorphum there was a rapid initial increase followed by a dramatic reduction of the transcript. The 34 kDa mature SPI2 protein was detected in both the developing root and shoot of healthy seedlings and increased amounts of SPI2 and increased accumulation of highly basic peroxidase isoforms was observed in roots after infection. In addition, two SPI2-related proteins with apparent molecular masses of 38 and 39 kDa, were also detected. Both these proteins accumulated in roots only after infection, and the 39 kDa protein was in addition detected in shoots of root-infected seedlings. Thus, both SPI2 and the SPI2-related proteins accumulate as a local response, in roots, and as a systemic response to infection the 39 kDa protein accumulates in the shoot.

Amino Acid Sequence↗
PubMed2001

The exodermis: a variable apoplastic barrier.

The exodermis (hypodermis with Casparian bands) of plant roots represents a barrier of variable resistance to the radial flow of both water and solutes and may contribute substantially to the overall resistance. The variability is a result largely of changes in structure and anatomy of developing roots. The extent and rate at which apoplastic exodermal barriers (Casparian bands and suberin lamellae) are laid down in radial transverse and tangential walls depends on the response to conditions in a given habitat such as drought, anoxia, salinity, heavy metal or nutrient stresses. As Casparian bands and suberin lamellae form in the exodermis, the permeability to water and solutes is differentially reduced. Apoplastic barriers do not function in an all-or-none fashion. Rather, they exhibit a selectivity pattern which is useful for the plant and provides an adaptive mechanism under given circumstances. This is demonstrated for the apoplastic passage of water which appears to have an unusually high mobility, ions, the apoplastic tracer PTS, and the stress hormone ABA. Results of permeation properties of apoplastic barriers are related to their chemical composition. Depending on the growth regime (e.g. stresses applied) barriers contain aliphatic and aromatic suberin and lignin in different amounts and proportion. It is concluded that, by regulating the extent of apoplastic barriers and their chemical composition, plants can effectively regulate the uptake or loss of water and solutes. Compared with the uptake by root membranes (symplastic and transcellular pathways), which is under metabolic control, this appears to be an additional or compensatory strategy of plants to acquire water and solutes.

Abscisic Acid↗
PubMed2002

Dental development after successful treatment of infantile osteopetrosis with bone marrow transplantation.

A 3-week-old boy was diagnosed with congenital osteopetrosis. He underwent a bone marrow transplant at 6 weeks of age. At 3 years of age the primary teeth had all erupted, but the canines and the first molars totally lacked root development. The teeth were smaller in size and had evidence of both enamel hypomineralization and hypoplasia. In the permanent dentition, multiple missing teeth were found. The incisors were conical and the mandibular laterals were extremely small. All permanent teeth had normal eruption. This case shows that dental development and eruption of teeth can be reconstituted in a child with congenital osteopetrosis. Bone marrow transplantation induces normalization of osteoclast function, which is a prerequisite for normal dental development and eruption of teeth.

Amelogenesis Imperfecta↗
PubMed1989

Accessory root formation on a lower medial incisor.

Accessory root formation on a lower medial incisor dating from the eighth century was observed. The accessory root consisted structurally of dentin (corresponding to the root of the tooth) covered with cement but had no radicular canal. It is therefore not a real supernumerary root. Postmortem deformation was excluded by examination of the alveolar bone. It must have been formed at the time of root development, through a lesion of Hertwig's sheath, as a result of a trauma.

Dentin↗
PubMed1997

Use of calcium hydroxide for apical barrier formation and healing in non-vital immature permanent teeth: a review.

OBJECTIVE: To review the use of calcium hydroxide for induction of apical barrier formation and healing in immature permanent teeth. INTRODUCTION: Pulp necrosis is a frequent complication of dental trauma in immature permanent teeth. Endodontic treatment of these teeth is often complicated. The walls of the root canals are frequently divergent and the apices immature, making debridement and obturation difficult. The aim of treatment is induction of apical healing which may be defined as apical closure through formation of mineralised tissue and repair of the periapical tissues. Calcium hydroxide is the material of choice for apical barrier formation and healing. RESULTS: The use of calcium hydroxide for apical barrier formation is successful in 74-100% of cases irrespective of the proprietary brand used. The average length of time for apical barrier formation is approximately 5 to 20 months. Control of infection and adequate cleaning of the root canal are very important for apical healing. CONCLUSIONS: While the success rate of apical barrier formation using calcium hydroxide is high, long-term follow-up of these teeth is necessary. Problems such as failure to control infection, recurrence of infection and cervical root fracture may occur. The latter is more frequent in immature luxated teeth with the least root development.

Bacterial Infections↗
PubMed1984

CNS effects of mechanically produced spina bifida.

Neural-tube defects were produced by one of two mechanical perturbations in an amphibian model system: newly-formed neural tubes were slit dorsally, or an intrinsic mass (an eye primordium transplanted to the neural plate) was introduced to prevent dorsal closure. Electron microscopic analyses showed that the resulting CNS distortions invariably included paired spinal-cord tubes that developed ciliated central canals surrounded by cellular layers and rimmed laterally by axon-filled marginal zones. Specific axon tracts grew in appropriate locations through the regions of simple diastematomyelia. Even in the most histologically distorted regions, ventral roots developed, axons were myelinated, and neuromuscular synapses formed in adjacent muscles. On the other hand, an excess of cells populated the defects and in histologically distorted regions the axon tracts were clearly less well organized than in normal animals. Neural-crest cells and the notochord did not appear to be affected. In addition, distant neurons and axon tracts appeared normal. These mechanical lesions could produce spina bifida without hydrocephalus. It is concluded that mechanical lesions to the forming neural tube will produce mainly local effects with a strong tendency toward diastematomyelia.

Animals↗