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PubMed1988

1987 Kreshover lecture. Gene regulation in the development of oral tissues.

The regulatory processes associated with tooth formation are being investigated by the identification of when, where, and how cell adhesion molecules (CAMs), substrate adhesion molecules (SAMs), dentin phosphoprotein, enamel gene products, and intermediate cementum products are expressed during sequential developmental stages of morphogenesis, cytodifferentiation, dentin, enamel and cementum extracellular matrix (ECM) formation, and biomineralization. Instructive and permissive signaling is required for both morphogenesis and cytodifferentiation based upon in vitro organotypic culture studies in serumless, chemically-defined medium. Intrinsic developmental instructions, independent of exogenous growth factors, mediate tooth morphogenesis from the initiation of the dental lamina through crown and initial root development. Recent progress using recombinant DNA methods has advanced descriptions of several dental structural genes. The complete nucleic acid sequence for mouse amelogenin has been defined. This sequence is located on the mouse X chromosome and on the human X and Y chromosomes. This discussion summarizes recent results using experimental embryology, recombinant DNA technology, and immunocytology in the context of instructive epithelial-mesenchymal interactions associated with epithelial differentiation into ameloblasts, ectomesenchyme differentiation into odontoblasts, and dentin and enamel ECM biomineralization. The tooth organ provides opportunities at several levels of biological organization to investigate cellular, molecular, and developmental processes.

Animals↗
PubMed2003

Ectopic expression of atRSZ33 reveals its function in splicing and causes pleiotropic changes in development.

Splicing provides an additional level in the regulation of gene expression and contributes to proteome diversity. Herein, we report the functional characterization of a recently described plant-specific protein, atRSZ33, which has characteristic features of a serine/arginine-rich protein and the ability to interact with other splicing factors, implying that this protein might be involved in constitutive and/or alternative splicing. Overexpression of atRSZ33 leads to alteration of splicing patterns of atSRp30 and atSRp34/SR1, indicating that atRSZ33 is indeed a splicing factor. Moreover, atRSZ33 is a regulator of its own expression, as splicing of its pre-mRNA is changed in transgenic plants. Investigations by promoter-beta-glucuronidase (GUS) fusion and in situ hybridization revealed that atRSZ33 is expressed during embryogenesis and early stages of seedling formation, as well as in flower and root development. Ectopic expression of atRSZ33 caused pleiotropic changes in plant development resulting in increased cell expansion and changed polarization of cell elongation and division. In addition, changes in activity of an auxin-responsive promoter suggest that auxin signaling is disturbed in these transgenic plants.

Agrobacterium tumefaciens↗
PubMed1969

Temperature Regulation of Endogenous Gibberellin Activity and Development of Tulipa gesneriana L.

The changes in the contents of free and bound gibberellin-like activity (GA) of Tulipa gesneriana L. cv. Ralph during development under 2 temperature conditions were studied. The results show that the content of free GA of bulbs grown at 18 degrees increased by 67% over the initial level during development. The bound GA showed a slight initial increase and was followed by a rapid decrease. In contrast, bulbs treated at 13 degrees showed a marked decline in free GA and a 2-fold increase in the content of bound GA. However, after the transfer of these bulbs from 13 degrees to 18 degrees the free GA increased to the initial level while the bound GA decreased to a low level.The rate of floral shoot and root development and time of flowering were accelerated at 18 degrees as compared to 13 degrees .From the data obtained, it was suggested that a temperature-sensitive interconversion mechanism between free and bound GA exists in tulip bulbs and that there is apparent synthesis or transformation of these phytohormones during development of the bulbs.

Journal Article↗
PubMed2006

Preserving pulpal health of a geminated maxillary lateral incisor through multidisciplinary care.

AIM: To report the multidisciplinary care of an unaesthetic geminated maxillary lateral incisor tooth, which allowed its preservation in the mouth. SUMMARY: Preoperative examination of an unsightly geminated maxillary lateral incisor (tooth 22) demonstrated two pulp chambers and open apices, with normal pulp sensitivity responses. At surgery, a periodontal mucoperiosteal flap was reflected and the distal part of the geminated tooth was removed. The exposed root canal of the preserved tooth was sealed with mineral trioxide aggregate (MTA). The extraction socket and osseous defect was grafted with decalcified freeze-dried bone allograft (DFDBA) before flap closure. During follow-up, distal caries in tooth 22 and a diastema between tooth 22 and 23 were managed with composite resin restorations. Forty-two months postoperatively, normal thermal and electrical pulp sensitivity tests confirmed pulp health. Convincing apexogenesis and dentinogenesis of the developing root was confirmed by radiographic examination. Acceptable periodontal health including 3-4 mm clinical probing depths was achieved. Optimizing aesthetics and occlusion was accomplished without orthodontic treatment.

Aluminum Compounds↗
PubMed2006

Carbohydrate-binding module of a rice endo-beta-1,4-glycanase, OsCel9A, expressed in auxin-induced lateral root primordia, is post-translationally truncated.

We report the cloning of a glycoside hydrolase family (GHF) 9 gene of rice (Oryza sativa L. cv. Sasanishiki), OsCel9A, corresponding to the auxin-induced 51 kDa endo-1,4-beta-glucanase (EGase). This enzyme reveals a broad substrate specificity with respect to sugar backbones (glucose and xylose) in beta-1,4-glycans of type II cell wall. OsCel9A encodes a 640 amino acid polypeptide and is an ortholog of TomCel8, a tomato EGase containing a carbohydrate-binding module (CBM) 2 sequence at its C-terminus. The expression of four rice EGase genes including OsCel9A showed different patterns of organ specificity and responses to auxin. OsCel9A was preferentially expressed during the initiation of lateral roots or subcultured root calli, but was hardly expressed during auxin-induced coleoptile elongation or in seed calli, in contrast to OsCel9D, a KORRIGAN (KOR) homolog. In situ localization of OsCel9A transcripts demonstrated that its expression was specifically up-regulated in lateral root primordia (LRP). Northern blotting analysis showed the presence of a single product of OsCel9A. In contrast, both mass spectrometric analyses of peptide fragments from purified 51 kDa EGase proteins and immunogel blot analysis of EGase proteins in root extracts using two antibodies against internal peptide sequences of OsCel9A revealed that the entire CBM2 region was post-translationally truncated from the 67 kDa nascent protein to generate 51 kDa EGase isoforms. Analyses of auxin concentration and time course dependence of accumulation of two EGase isoforms suggested that the translation and post-translational CBM2 truncation of the OsCel9A gene may participate in lateral root development.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2002

Functional significance of the alternative transcript processing of the Arabidopsis floral promoter FCA.

The Arabidopsis gene FCA encodes an RNA binding protein that functions to promote the floral transition. The FCA transcript is alternatively processed to yield four transcripts, the most abundant of which is polyadenylated within intron 3. We have analyzed the role of the alternative processing on the floral transition. The introduction of FCA intronless transgenes resulted in increased FCA protein levels and accelerated flowering, but no role in flowering was found for products of the shorter transcripts. The consequences of the alternative processing on the FCA expression pattern were determined using a series of translational FCA-beta-glucuronidase fusions. The inclusion of FCA genomic sequence containing the alternatively processed intron 3 restricted the expression of the transgene predominantly to shoot and root apices and young flower buds. Expression of this fusion also was delayed developmentally. Therefore, the alternative processing of the FCA transcript limits, both spatially and temporally, the amount of functional FCA protein. Expression in roots prompted an analysis of root development, which indicated that FCA functions more generally than in the control of the floral transition.

Alternative Splicing↗
PubMedDate not supplied

Disturbances in the oral cavity in pediatric long-term survivors after different forms of antineoplastic therapy.

Oral health and disturbances in dental development were studied in long-term survivors after antineoplastic therapy. Fifty-seven children treated with combination chemotherapy and 19 children treated with total body irradiation (TBI) prior to bone marrow transplantation (BMT) were examined. The variables studied were dental caries, salivary flow, salivary microbial counts, enamel disturbances, and disturbances in dental development. The results showed no increased caries experience in children treated with BMT or chemotherapy compared with controls. Children treated with BMT had a significantly lower salivary secretion rate of 0.7 +/- 0.4 ml/min, compared with 1.1 +/- 0.5 in the chemotherapy group, and 1.3 +/- 0.6 in the control group (P < 0.05). The clinical examination showed equal numbers of teeth affected by disturbances in enamel mineralization in the BMT and chemotherapy groups. A mean 15.9 +/- 8.2 teeth were affected by disturbances in root development in the BMT group compared with 1.2 +/- 1.6 in the chemotherapy group (P < 0.001). The results show that children who are long-term survivors of pediatric malignant diseases exhibit a wide range of disturbances in the oral cavity. In this study the most severe disturbances are found in children treated with total body irradiation prior to BMT.

Antineoplastic Agents↗
PubMed2004

Nitric oxide and nitric oxide synthase activity in plants.

Research on NO in plants has gained considerable attention in recent years mainly due to its function in plant growth and development and as a key signalling molecule in different intracellular processes in plants. The NO emission from plants is known since the 1970s, and now there is abundant information on the multiple effects of exogenously applied NO on different physiological and biochemical processes of plants. The physiological function of NO in plants mainly involves the induction of different processes, including the expression of defence-related genes against pathogens and apoptosis/programmed cell death (PCD), maturation and senescence, stomatal closure, seed germination, root development and the induction of ethylene emission. NO can be produced in plants by non-enzymatic and enzymatic systems. The NO-producing enzymes identified in plants are nitrate reductase, and several nitric oxide synthase-like activities, including one localized in peroxisomes which has been biochemically characterized. Recently, two genes of plant proteins with NOS activity have been isolated and characterized for the first time, and both proteins do not have sequence similarities to any mammalian NOS isoform. However, different evidence available indicate that there are other potential enzymatic sources of NO in plants, including xanthine oxidoreductase, peroxidase, cytochrome P450, and some hemeproteins. In plants, the enzymatic production of the signal molecule NO, either constitutive or induced by different biotic/abiotic stresses, may be a much more common event than was initially thought.

Nitric Oxide↗
PubMed1987

Redistribution of Schwann cells in developing feline L7 ventral spinal roots.

The length and distribution of Schwann cells along fibres in the ventral root L7 of the developing cat have been studied electron microscopically in serial sections. The average Schwann cell length at the beginning of myelin formation - the 'initial internodal length' - was 118 micron (110 micron in alpha-axons and 124 micron in gamma-axons). The number of Schwann cells found in a fully developed root segment was already present at the beginning of the myelination. It showed no systematic age-dependent variation from the beginning of myelination to adulthood. The Schwann cells associated with alpha-axons increased their length 12.6 times during this period, while the root elongated 5.6 times. About 50% of the Schwann cells had to be eliminated in order to make the elongation of the remaining Schwann cells possible. Corresponding calculations from the mean length of Schwann cells associated with gamma-axons, showed that about 50% too few Schwann cells were associated with the gamma-axons during the period of initial myelination of the alpha-axons. At birth, when the myelination of gamma-axons had just begun, both the large surplus along alpha-axons and the deficit along gamma-axons had disappeared. We suggest that Schwann cells are eliminated from the alpha-axons and re-utilized along the gamma-axons. During this process of cellular redistribution, affected cells constitute so-called aberrant Schwann cells.

Age Factors↗
PubMed1990

A radiographic four-year follow-up study of asymptomatic mandibular third molars in young adults.

Fifty-five asymptomatic mandibular third molars (M3) in 34 dental students (mean age 20.6 years at the start of the study) were followed radiographically for 4 years. Based on clinical evaluation the 55 teeth included 20 almost erupted, 13 partly erupted and 22 non-erupted M3. The following were assessed on the radiographs: root development, level of eruption, sagittal angulation, resorption, pericoronitis/bony pockets/paradental cysts and widening of the periodontal space/dentigerous cysts. The state of 21 teeth (38 per cent) was radiographically changed at the end of the observation period. The most remarkable finding was that 15 teeth changed their sagittal angulation, all in a distal direction; five mesioangular to vertical, five vertical to distoangular, five mesioangular to distoangular. Radiographically, 13 M3 moved to a more advanced level of eruption. No real pathological osseous lesions and no root resorption were observed at initial or follow-up examinations. It is concluded that there are frequent essentially unpredictable changes in the position of M3 after the age of 19 years which may influence decisions on their removal or preservation.

Adult↗
PubMed2006

Potential use of the plant antioxidant network for environmental exposure assessment of heavy metals in soils.

In recent years, awareness has risen that the total soil content of pollutants by itself does not suffice to fully assess the potential ecotoxicological risks involved. Chemical analysis will require to be complemented with biological assays in a multidisciplinary approach towards site specific ecological risk assessment (SS-ERA). This paper evaluates the potential use of the plants' antioxidant response to metal-induced oxidative stress to provide a sensitive biological assay in SS-ERA. To this end, plants of Phaseolus vulgaris were grown for two weeks on 15 soils varying in contamination level. Morphological parameters and enzymatic plant responses were measured upon harvest. Foliar concentrations of the (heavy) metals Al, Cu, Cd, Cr, Fe, Mn, Ni, Pb, Zn were also determined. Metal mobility in the soil was further assessed by determining soil solution and NH4OAc extractable levels. In general more significant correlations were observed between plant responses and foliar metal concentrations or exchangeable/soluble levels than between plant responses and the total soil content. The study demonstrates the potential use of the plants' antioxidant defence mechanisms to assess substrate phytotoxicity for application in SS-ERA protocols. However, the system, based on calculation of a soil Phytotoxicity Index (PI), will require adaptation and fine-tuning to meet the specific needs for this type of environmental monitoring. Large variation was observed in phytotoxicity classification based on the various test parameters. The thresholds for classification of the various morphological and enzymatic response parameters may require adaptation according to parameter stress sensitivity in order to decrease the observed variation. The use of partial PI's (leaves and roots separately) may in addition increase the sensitivity of the system since some metals show specific effects in one of both organs only. Loss of biological functionality of enzymes, as was observed for ICDH in one of the more strongly contaminated soils, may also be recognized as an additional stress symptom when assigning phytotoxicity classification, whereas the current system only considers increasing enzymatic capacities. Other easily distinguishable parameters, which could be added to the current indexation are: failure to germinate and the incapacity to develop roots in the toxic substrate. Additional research will be required to determine the possible application range of soil properties for this biological assay and to further improve its performance in SS-ERA.

Antioxidants↗
PubMed1982

Canine eruption into grafted bone in maxillary alveolar cleft defects.

Forty-six patients with clefts of the alveolus who had received alveolar bone grafts (secondary osteoplasties) at ages 7-14 years, were studied. A total of 64 affected canines from 18 bilateral and 28 unilateral alveolar cleft patients was available. Follow up orthopantomographs were examined to determine the state of root development and spontaneous canine movement through the grafted site. The postoperative observation period ranged from 2-8 years (mean 4.3 +/- 1.5). All test canines erupted through the graft. Spontaneous eruption occurred for 27% of test canines, 17% required surgical uncovering (either bony or soft tissue), and 56% required surgical uncovering and orthodontic assistance to accomplish eruption. All patients required orthodontic treatment to accomplish arch alignment. The prognosis for canine eruption through a graft site is most favorable if the graft is performed at 1/4-1/2 canine root formation and when the patient is aged 9-12 years. The post graft observation period is very important and requires complete cooperation between the orthodontist and the surgeon.

Adolescent↗
PubMed2002

Molecular cloning and cytochemical analysis of exopolygalacturonase from carrot.

Exopolygalacturonase (exo-PGase, EC 3.2.1.67) attacks the non-reducing terminus of the polygalacturonic acid in pectic molecules, releasing galacturonic acid. We cloned the cDNA of exo-PGase purified from cell homogenates of suspension-cultured carrot ( Daucus carota L. cv. Kintoki) cells. The nucleotide sequence of the cDNA (1.4 kb) contains an open reading frame that encodes a 391-amino-acid polypeptide. Sequence homology research showed 97.9% identity to the glycoprotein EP4 obtained from cultured carrot cells and 49.3% identity to the ENOD8 gene product of alfalfa ( Medicago sativa). However, no significant similarity was found to known PGases. The Southern hybridization pattern indicated that this exo-PGase protein is a member of a small-sized gene family. Predominant expression of the exo-PGase gene was detected by in situ hybridization and immunohistochemistry in the root apical meristem and in the elongation region, but not in the root cap. A cross-immunoresponse with anti-exo-PGase also occurred in the root nodule meristem of alfalfa. These results suggest that this exo-PGase plays a role in the degradation of pectic molecules during root development.

Amino Acid Sequence↗
PubMed2006

Whole-genome analysis of the SHORT-ROOT developmental pathway in Arabidopsis.

Stem cell function during organogenesis is a key issue in developmental biology. The transcription factor SHORT-ROOT (SHR) is a critical component in a developmental pathway regulating both the specification of the root stem cell niche and the differentiation potential of a subset of stem cells in the Arabidopsis root. To obtain a comprehensive view of the SHR pathway, we used a statistical method called meta-analysis to combine the results of several microarray experiments measuring the changes in global expression profiles after modulating SHR activity. Meta-analysis was first used to identify the direct targets of SHR by combining results from an inducible form of SHR driven by its endogenous promoter, ectopic expression, followed by cell sorting and comparisons of mutant to wild-type roots. Eight putative direct targets of SHR were identified, all with expression patterns encompassing subsets of the native SHR expression domain. Further evidence for direct regulation by SHR came from binding of SHR in vivo to the promoter regions of four of the eight putative targets. A new role for SHR in the vascular cylinder was predicted from the expression pattern of several direct targets and confirmed with independent markers. The meta-analysis approach was then used to perform a global survey of the SHR indirect targets. Our analysis suggests that the SHR pathway regulates root development not only through a large transcription regulatory network but also through hormonal pathways and signaling pathways using receptor-like kinases. Taken together, our results not only identify the first nodes in the SHR pathway and a new function for SHR in the development of the vascular tissue but also reveal the global architecture of this developmental pathway.

Arabidopsis↗
PubMed2006

Competition for pulsed resources: an experimental study of establishment and coexistence for an arid-land grass.

In arid environments, episodically-pulsed resources are important components of annual water and nutrient supply for plants. This study set out to test whether seedlings have an increased capacity for using pulsed resources, which might then improve establishment when in competition with older individuals. A second aim was to determine whether there is a trade-off in competitive strategies when resources are supplied continuously at low concentrations, or as pulses with pronounced inter-pulse periods. A glasshouse experiment used a target-neighbour design of size-asymmetric competition, with juveniles of Panicum antidotale (blue panicgrass) introduced into contrasting densities of adult plants. Stable isotopes of nitrogen were used for measuring plant resource uptake from pulses, and tolerance to inter-pulse conditions was assessed as the mean residence time (MRT) of nitrogen. A higher root/shoot ratio and finer root system enhanced the capacity of juveniles to use resources when pulsed, rather than when continuously supplied. Higher resource uptake during pulses improved the establishment of juvenile Panicum in mixed cultures with older individuals. However, a trade-off was observed in plant strategies, with juveniles showing a lower MRT for nitrogen, which suggested reduced tolerance to resource deficit during inter-pulse periods. Under field conditions, higher utilization of pulsed resources would lead to the improved seedling establishment of Panicum adjacent to "nurse" plants, whereas mature plants with well-developed roots, exploiting a greater soil volume, maintain more constant resource uptake and retention during inter-pulse periods.

Aging↗
PubMed1988

Re- and allotransplantation of teeth--an experimental study in monkeys.

In each of six monkeys one of the permanent lateral incisors with uncompleted root development was replanted. At the same time the contralateral incisors in four of the monkeys were allotransplanted by pairs. The remaining two contralateral incisors served as controls. After 4 weeks and 4 months, respectively, three monkeys were decapitated and the upper lateral incisors with adjacent periodontal tissue were examined histologically. The replanted teeth in five cases had a vital pulp. In the sixth case, however, the replanted incisor exhibited pulpitis and partial necrosis of the pulp. The periodontal membrane had a normal histologic appearance. In two cases a small area of arrested root resorption was observed. With the allotransplanted teeth the histologic appearance was altered. After 4 weeks a pronounced inflammatory reaction was observed in both the pulpal tissue and the periodontal membrane. The pulp was in most cases necrotic, and marked root resorption was observed. Most of the allotransplanted teeth were resorbed and replaced by an irregular hard tissue that resembled osteoid, which in many cases was connected with the tooth remnants by ankylosis. These results indicate that allotransplanted teeth, in contrast to replanted teeth, exhibit the characteristic features of an allograft rejection, including an inflammatory reaction and resorption.

Animals↗
PubMed1990

[Study of dental maturity in children aged 3-16 years in Chengdu].

Dental maturity was studied in a group of 903 healthy children (boys: 465, girls: 438) born in Chengudu from 1972 through 1988. Dental maturity was estimated by the method of Demirjian and Goldstein, which is based on the development of seven left mandibular permanent teeth; teeth formation was studied. The standard and curves of dental maturity for Chengdu children (boys and girls) were constructed. At 3-5 years old, boys had their dental maturity slightly earlier than girls; there was no significant difference between boys and girls (P greater than 0.05). At the age of 7-14, girls were more advanced than boys (P less than 0.05). Developmental curves of seven left mandibular permanent teeth were plotted. The sexual difference was smaller at the crown developmental stage, and it increased during the root development. In all, girls were more advanced by 0.45 year than boys. The maximum average difference was 0.85 year for the canine. The time that each developmental stage has taken was shorter in 50% of girls as compared with that in boys, and it was longer in 28% of girls. There was no difference between boys and girls in the remaining 22% of cases.

Adolescent↗
PubMed2006

Interactions between the arbuscular mycorrhizal (AM) fungus Glomus intraradices and nontransformed tomato roots of either wild-type or AM-defective phenotypes in monoxenic cultures.

Monoxenic symbioses between the arbuscular mycorrhizal (AM) fungus Glomus intraradices and two nontransformed tomato root organ cultures (ROCs) were established. Wild-type tomato ROC from cultivar "RioGrande 76R" was employed as a control for mycorrhizal colonization and compared with its mutant line (rmc), which exhibits a highly reduced mycorrhizal colonization (rmc) phenotype. Structural features of the two root lines were similar when grown either in soil or under in vitro conditions, indicating that neither monoxenic culturing nor the rmc mutation affected root development or behavior. Colonization by G. intraradices in monoxenic culture of the wild-type line was low (<10%) but supported extensive development of extraradical mycelium, branched absorbing structures, and spores. The reduced colonization of rmc under monoxenic conditions (0.6%) was similar to that observed previously in soil. Extraradical development of runner hyphae was low and proportional to internal colonization. Few spores were produced. These results might suggest that carbon transfer may be modified in the rmc mutant. Our results support the usefulness of monoxenically obtained mycorrhizas for investigation of AM colonization and intraradical symbiotic functioning.

Fungi↗