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At least 433 records · Page 24Linked to original sources
PubMed1989

The prevalence of taurodontism in Down's syndrome.

Taurodontism, a condition in which the pulp chambers of teeth are elongated, was observed in extracted lower molars of 12 out of 33 (36.4%) individuals with Down's syndrome (DS). It is suggested that this high prevalence is associated with a delayed ingrowth and fusion of the epithelial flaps of the developing root sheath and that taurodontism represents one of several characteristic morphological dental features in DS that result from decreased mitotic activity of cells in developing tooth germs.

Adolescent↗
PubMed2025

Integrative spatial transcriptomic analysis pinpoints the role of the ferroxidase, TaMCO3, in wheat root tip iron mobilization.

Roots play a critical role in the sensing and absorption of essential minerals from the rhizosphere. Iron (Fe) deficiency, for example, triggers a well-known series of physiological and molecular responses within roots that facilitate uptake, which differs between monocots and dicots. In monocots, little is known about the molecular responses that occur within specific root development zones in response to iron deprivation, and how these differences result in overall nutrient uptake. Here, we conducted a transcriptome analysis of wheat root tips under Fe deficiency (-Fe) and performed a comparative transcriptome analysis with the previous datasets generated from the whole root. Gene ontology analysis of differentially expressed genes highlighted the significance of oxidoreductase activity and metal/ion transport in the root tip, which are critical for Fe mobilization. Interestingly, wheat, an allohexaploid species consisting of three different genomes (A, B, and D) displayed varying gene expression levels arising from the three genomes that contributed to similar molecular functions. Detailed analysis of oxidoreductase function at the root tip revealed multiple multicopper oxidase (MCO) proteins, such as Fe-responsive TaMCO3, that likely contribute to the overall ferroxidase activity. Further characterization of TaMCO3 shows that it complements the yeast FET3 mutant and rescues the -Fe sensitivity phenotype of Arabidopsis atmco3 mutants by enhancing vascular Fe loading. Transgenic wheat lines overexpressing TaMCO3 exhibited increased root Fe accumulation and improved tolerance to -Fe by augmenting the expression of Fe-mobilizing genes. Our findings highlight the role of spatially resolved gene expression in -Fe responses, suggesting strategies to reprogram cells for improved nutrient stress tolerance.

Triticum↗
PubMed1990

Dentofacial development in long-term survivors of acute lymphoblastic leukemia. A comparison of three treatment modalities.

Ninety-seven children who were diagnosed with acute lymphoblastic leukemia before 10 years of age and treated with chemotherapy alone, chemotherapy plus 1800-cGy cranial irradiation (RT), or chemotherapy plus 2400-cGy RT were evaluated for effects of therapy on dentofacial development. All patients were seen at least 5 years postdiagnosis. Dental abnormalities were determined from panoramic radiographs, and craniofacial evaluations were made from lateral cephalometric radiographs. Ninety-one (94%) of all patients and 41 (100%) of patients younger than 5 years of age at diagnosis had abnormal dental development. The severity of these abnormalities was greater in children who received treatment before 5 years of age and in those who received RT. Observed dental abnormalities included tooth agenesis, arrested root development, microdontia, and enamel dysplasias. Craniofacial abnormalities occurred in 18 of 20 (90%) of those patients who received chemotherapy plus 2400-cGy RT before 5 years of age. Mean cephalometric values of this group showed significant deficient mandibular development. The results of this study suggest that the severity of dentofacial-developmental abnormalities secondary to antileukemia therapy are related to the age of the patient at the initiation of treatment and the use of cranial RT.

Adolescent↗
PubMed1996

Spontaneous rhythmic bursts induced by pharmacological block of inhibition in lumbar motoneurons of the neonatal rat spinal cord.

1. The effects of blocking gamma-aminobutyric acid- and glycine-mediated synaptic transmission by bicuculline and strychnine on the neonatal rat isolated spinal cord were investigated by intracellular recording from motoneurons with the use of current-clamp and voltage-clamp techniques and by extracellular recording from homologous ventral roots of the L5 segment. 2. Bicuculline per se evoked irregular bursts of motoneuron membrane potential, often comprising individual events fused together. Strychnine alone did not elicit spontaneous bursting in the large majority of preparations. Simultaneous application of bicuculline and strychnine consistently induced regular rhythmic bursts (frequency approximately 2 per min, duration approximately 7 s), comprising a rapid depolarization followed by large-amplitude oscillations. 3. Burst frequency, duration, and intraburst oscillation time course were independent of motoneuron membrane potential. Burst and oscillation amplitude decreased with membrane depolarization and, under voltage-clamp conditions, inverted polarity near 0 mV. 4. The regular bursts produced by bicuculline and strychnine were blocked by 6-cyano-7-nitroquinoxaline-2,3-dione, tetrodotoxin, or Cd2+. 5. N-methyl-D-aspartate antagonists [R-5-aminophosphonovalerate or 3-((RS)-2-carboxypiperazine-4-yl)-propyl-1-phosphonate (CPP)] reversibly blocked or slowed down bursting induced by bicuculline and strychnine. Addition of cyclothiazide to the bicuculline and strychnine solution increased bursting frequency while preserving the regular burst structure; under these conditions bursts became insensitive to CPP. 6. In the presence of bicuculline and strychnine, 5-hydroxytryptamine (5-HT) increased burst frequency and decreased burst duration in a dose-dependent fashion. 7. In the presence of bicuculline and strychnine, L5 ventral roots developed synchronous rhythmic activity with a time course similar to that recorded from individual motoneurons. The rhythmic activity was accelerated by 5-HT on both roots, in accordance with observations on single motoneurons. 8. Rhythmic bursts thus appear to result from large, synchronous synaptic events generated by a network modulated by 5-HT and highly sensitive to variations in efficacy of glutamatergic synaptic transmission. These results show that in the rat spinal cord highly patterned motor output can occur despite block of inhibition.

Animals↗
PubMed1994

Blue light sensory systems in plants.

Plant development is influenced by many environmental stimuli, including light, temperature and gravity. Of these stimuli, light is of particular importance because plants depend on it for energy and, thus, for survival. Moreover, virtually all stages of plant development are regulated in part by light through the action of various photosensory systems. Examples of light-regulated processes include germination, stem growth, leaf and root development, tropic responses and flower induction. This review provides an analysis of recent investigations of blue light sensory systems in plants. Current results suggest that plants respond to blue light through a complex photosensory network that incorporates the action of multiple blue light perception systems.

Light↗
PubMed2001

Cellular compartmentation of ammonium assimilation in rice and barley.

This review describes immunolocalization studies of the tissue and cellular location of glutamine synthetase (GS; EC 6.3.1.2) and glutamate synthase (Fd GOGAT; EC 1.4.7.1 and NADH-GOGAT; EC 1.4.1.14) proteins in roots and leaves of rice (Oryza sativa L.) and barley (Hordeum vulgare L.). In rice, cytosolic GS (GS1) protein was distributed homogeneously through all cells of the root. NADH GOGAT protein was strongly induced and its cellular location altered by ammonium treatment, becoming concentrated within the epidermal and exodermal cells. Fd GOGAT protein location changed with root development, from a widespread distribution in young cells to becoming concentrated within the central cylinder as cells matured. Plastid GS protein was barely detectable in rice roots, but was the major isoform in leaves, being present in the mesophyll and parenchyma sheath cells. GS1 was specific to the vascular bundle, as was NADH GOGAT, whereas Fd GOGAT was primarily found in mesophyll cells. In barley roots, GS1 protein was found in the cortical and vascular parenchyma and its concentration was highest in N-deficient seedlings. Plastid GS protein was detected in both cortical and vascular cells, where different plastid forms, containing different concentrations of GS protein, were identified. In barley leaves, GS2 protein was detected in the mesophyll chloroplasts and GS1 was found in the mesophyll and vascular cells. N nutrition strongly influenced this distribution, with a marked increase in GS1 concentration in the vascular cells in response to nitrate and ammonium, and an increase in mesophyll GS2 concentration in nitrate-grown seedlings. Fd GOGAT protein was found in both the mesophyll and vascular plastids. These localization studies show that the GS/GOGAT cycle is highly compartmentalized at both the subcellular and cellular levels. Reasons for this compartmentation, and the roles of each isoform, are discussed.

Cell Compartmentation↗
PubMed1990

Experimental study of pulpotomy with calcium hydroxide-iodoform paste in dogs' immature permanent teeth.

To investigate the healing process and continuous root development following pulpotomy with improved calcium hydroxide-iodoform paste, the authors performed an experimental study of pulpotomy in immature permanent teeth. Thirty five incompletely formed root canals in dogs were used, and radiographical and histopathological observations were made. The results lead to the conclusion that pulpotomy with improved calcium hydroxide-iodoform paste is a very effective treatment for immature permanent teeth.

Animals↗
PubMed1999

A plant regulator controlling development of symbiotic root nodules.

Symbiotic nitrogen-fixing root nodules on legumes are founded by root cortical cells that de-differentiate and restart cell division to establish nodule primordia. Bacterial microsymbionts invade these primordia through infection threads laid down by the plant and, after endocytosis, membrane-enclosed bacteroids occupy cells in the nitrogen-fixing tissue of functional nodules. The bacteria excrete lipochitin oligosaccharides, triggering a developmental process that is controlled by the plant and can be suppressed. Nodule inception initially relies on cell competence in a narrow infection zone located just behind the growing root tip. Older nodules then regulate the number of nodules on a root system by suppressing the development of nodule primordia. To identify the regulatory components that act early in nodule induction, we characterized a transposon-tagged Lotus japonicus mutant, nin (for nodule inception), arrested at the stage of bacterial recognition. We show that nin is required for the formation of infection threads and the initiation of primordia. NIN protein has regional similarity to transcription factors, and the predicted DNA-binding/dimerization domain identifies and typifies a consensus motif conserved in plant proteins with a function in nitrogen-controlled development.

Amino Acid Sequence↗
PubMed1999

Treatment of lower second premolar agenesis by autotransplantation: four-year evaluation of eighty patients.

The frequency of agenesis of the second lower premolar is 2.5-4%. In growing patients, early extraction of the deciduous molar and subsequent closure of the space is a common therapy, but in some cases space closure is deemed unlikely and autotransplantation is an alternative. The aim of the study was to analyze the outcome of autotransplantation in replacing missing lower second premolars and to evaluate the associated presurgical orthodontic treatment. The material consisted of records of all patients with teeth transplanted to the lower second premolar region during the period 1988-89 at the Department of Oral Surgery, Eastman Institute, Stockholm. The following variables were registered: sex, age, number of transplanted teeth, donor tooth, root development, recipient site, orthodontic treatment, persisting temporary molar, total number of congenitally missing teeth, the surgeon responsible, and clinical and radiological follow-up variables. Of 110 transplanted teeth, 99 had not completed root formation, and in 11 teeth the root formation was completed. The success rates after 4 years were 92% and 82%, respectively. Both premolars and molars served as donor teeth, but the main donor tooth was the upper second premolar. Fourteen percent had been orthodontically treated only because of the transplantation, i.e. to open the space for the donor tooth. Treatment of agenesis of the second lower premolar by autotransplantation has a good prognosis. In growing individuals the transplant not only maintains growth and development of the alveolar ridge but also provides a permanent solution to the agenesis.

Adolescent↗
PubMed1995

[Outcome of wisdom tooth germ transplantation].

In 68 patients, 79 tooth germs of the third molar were transplanted. Out of this group, 43 patients with 50 transplantations under-went a follow-up examination. All surgery was performed by one surgeon. Retrospectively, we tried to establish whether the success of postoperative healing depends on the donor and receiver regions. Crossing the jaw border clearly worsens the prognosis for transplantation. Altogether 9 transplantations turned out to be failures, 7 of which had been transplanted from the upper to the lower jaw. The results of this investigation showed incomplete root development in 34%, the necessity of endodontic treatment in 6% and enlarged periodontal pockets in 8%. Ankylosed teeth were found in 10%; we did not see any root resorptions.

Adolescent↗
PubMed1997

Replantation of an inverted lower second premolar germ.

During the initial X-ray control of a 10-year-old female orthodontic patient, a late development and an inverted position of the lower left second premolar was seen. 4.3 years later the tooth with its follicle was replanted in the upright position, preserving the second deciduous molar; at that time the root development was at an early stage. At a follow-up control 4 years after the surgical procedure the replanted tooth had erupted and the sensibility response was normal. Its root, however, although completed, could not reach the length and especially the width (in the apical half) of the contralateral premolar. This relative reduction in width seems to follow a temporary thickening of that part of the root formed during the first period after replantation. The anamnestic data suggest that physiologic exfoliation of the deciduous molar took place.

Bicuspid↗
PubMed1980

Effects of radiation on the developing dentition and supporting bone.

Underdevelopment of teeth after exposure to radiation has been observed since the early experiments with X rays. Two patients had been irradiated at young ages for embryonal rhabdomyosarcomas. For the patient treated with radiation at age 4 for a lesion in the submandibular area, root development of the mandibular teeth stopped, but the teeth nevertheless erupted. In the patient treated with radiation at age 9 for a tumor in the left cheek, bone apposition in the left side of the mandible failed to continue at the same rate as on the right side. Although new megavoltage radiation machines have reduced the chances of bone complications in adults, developing bone and structures are still significantly affected by radiation.

Adolescent↗
PubMedDate not supplied

Dental development and molar root length in children with cleidocranial dysplasia.

Cleidocranial dysplasia (CD) is an autosomal dominant skeletal disorder with characteristic dental findings of numerous supernumerary teeth and noneruption of permanent teeth. This investigation compared the dental development and root lengths of the mandibular first permanent molar in 11 CD patients with those of 22 healthy, normal children matched for race, age and sex. The results showed that children with CD experienced a delay in dental development of approximately 3 years compared with normal children (P < 0.05). In addition, the root lengths of the mandibular first permanent molar were significantly longer than those of the comparison children (17.8 +/- 1.6 mm vs 13.6 +/- 1.2 mm (P < 0.001). This study thus revealed two significant clinical features of CD: 1) severe delay in dental development, and 2) excessive root lengths of mandibular permanent first molars. These features may be important in the pathogenesis of delayed dental eruption observed in this disorder.

Adolescent↗
PubMed1981

Sexual dimorphism in the development, emergence, and agenesis of the mandibular third molar.

Bilateral agenesis was encountered in about 9% of the cases, with no significant sexual difference. The right and left mandibular third molars had the same pattern of development and emergence. The slight advance of girls over boys at the crown-completion stage was similar to previous observations on other mandibular teeth, particularly the second molar. The root development course of the third molar was faster in males than in females; this sexual dimorphism was much greater for retarded cases than for advanced cases. At the apex closure, the difference between median ages of males and females was 1.5 yr. Alveolar emergence tended to occur at a lower developmental stage in advanced cases compared with retarded cases.

Adolescent↗
PubMed2003

Root surface areas in long-term survivors of childhood cancer.

Treatment regimes for childhood cancer are known to affect the root development in the long-term survivors (LTS) but the available the data is subjective in nature with very few quantitative data in the literature. This study aimed to quantify the root surface area (RSA) of mandibular teeth in LTS compared with controls and relate this to the treatment regime and also to the age at which the cancer was diagnosed. Panoramic radiographs were obtained from 69 LTS and an equal number of appropriately matched healthy controls. RSA were calculated using Computer Linked Image Analysis. RSA in the LTS were found to be significantly smaller as compared with controls. Also, RSA were the least in those LTS who had Total Body Irradiation followed by Bone Marrow Transplantation (TBI/BMT) compared with other treatment regimes, the difference being statistically significant for all teeth studied. There was no relationship between the RSA and the age at which the cancer was diagnosed. Smaller root areas have implications for the oral health of LTS, as bone loss around such teeth will compromise further their periodontal support thus jeopardising the long-term survival of the tooth.

Adolescent↗
PubMed2001

Cell-specific patterns of Cbfa1 mRNA and protein expression in postnatal murine dental tissues.

Cbfa1 (core binding factor alpha 1) is a transcription factor that is a key determinant of the osteoblastic lineage. Recent data showed that Cbfa1 is also highly expressed in early stages of tooth development and is involved in crown morphogenesis and cytodifferentiation of odontoblasts. Here we report the mRNA expression and protein localization of Cbfa1 in the mouse dentition in (later) stages of crown and root development. In addition to osteoblasts, osteocytes, chondrocytes, odontoblasts, dental follicle cells, cementoblasts and periodontal ligament cells, we report also Cbfa1 expression in dental epithelial cells (secretory and maturation ameloblasts) and several non-mineralizing cell types (hair follicles, ducts of salivary glands, and junctional epithelium of the gingiva).

Age Factors↗
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↗