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At least 883 records · Page 49Linked to original sources
PubMed1997

A scanning electron microscopy study of disturbances in the developing rat molar induced by cyclophosphamide.

Scanning electron microscopy was used to study the effect of cyclophosphamide (Cy) on molar development in 18 Sprague-Dawley rats from 15 to 48 days of age after birth. Doses of 30 mg/kg body weight of Cy dissolved in 1 ml 0.9% NaCl were given to the rats at 10 and 13 days of age. Eighteen control rats had injections of 1 ml 0.9% NaCl at the same ages. The most obvious changes in the experimental teeth were found in the developing roots of the first and second molars and in both the crown and roots of the third molar. The roots of the first and second molars were short and showed apical closure in the experimental rats. In addition to the disturbances in crown and root formation, the third molars were also significantly reduced in total size as compared with the third molars in the control rats.

Alopecia↗
PubMed1992

Evolutionary biology and pathology of vitamin D.

There is mounting evidence that essentially all fungi, plants and animals living on earth produce provitamin D. It is likely that once exposed to sunlight, these provitamins are converted to previtamin D. It is unclear why fungi, phytoplankton, zooplankton and plants have the capacity to produce such large quantities of provitamin D. It is likely, however, that provitamin D and possibly vitamin D play an important biologic role in these organisms. Buchala and Schmid found, for example, that vitamin D3 promoted adventitious root development. It may be that provitamin D has a more fundamental function in lower life forms. Provitamin D and its photoproducts have UV absorption spectra that overlap with the ultraviolet absorption spectra from ultraviolet radiation-sensitive macromolecules including DNA, RNA and proteins. Thus, provitamin D and photoisomers could serve as a photon sink, and therefore, act as a natural sunscreen to protect lower life forms from the damaging effects of the high energy ultraviolet radiation that they are exposed to. It is more clear, however, that amphibians, reptiles, birds, mammals and humans all require vitamin D and that the vitamin D must be metabolized to 1,25(OH)2D3 before it can carry-out its physiologic functions on calcium and bone metabolism. The intense research activities during the past decade on the antiproliferative and differentiation activities of 1,25(OH)2D3 has opened a new chapter for this vitamin/hormone. 1,25(OH)2D3 and its analogs are being developed for the treatment of psoriasis, breast cancer, and leukemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Genetic engineering of drought resistant potato plants by introduction of the trehalose-6-phosphate synthase (TPS1) gene from Saccharomyces cerevisiae.

In yeast, trehalose-6-phosphate synthase is a key enzyme for trehalose biosynthesis, encoded by the structural gene TPS1. Trehalose affects sugar metabolism as well as osmoprotection against several environmental stresses, such as heat and desiccation. The TPS1 gene of Saccharomyces cerevisiae was engineered under the control of the CaMV 35S promoter for constitutive expression in transgenic potato plants by Ti-plasmid of Agrobacterium-mediated transformation. The resulting TPS1 transgenic potato plants exhibited various morphological phenotypes in culture tubes, ranging from normal to severely retarded growth, including dwarfish growth, yellowish lancet-shaped leaves, and aberrant root development. However, the plants recovered from these negative growth effects when grown in a soil mixture. The TPS1 transgenic potato plants showed significantly increased drought resistance. These results suggest that the production of trehalose not only affects plant development but also improves drought tolerance.

Agrobacterium tumefaciens↗
PubMed2003

Implementation of the two-stage operation technique for the autotransplantation of teeth with closed apexes--a preliminary report.

Transplantation of teeth with incompletely formed apexes demonstrates a statistically better retention than the transplantation of fully-formed teeth because of the possibilities for reinnervation and revascularisation. However, with regard to the autotransplantation of teeth with completely developed roots, routine endodontic treatment is proposed, as the possibility to retain the vitality of dental pulp is doubtful. In this work the author wishes to present the implementation of the two-stage technique for the transplantation of fully-formed teeth. Observations confirm the possibility for reinnervation and revascularisation occurring after autotransplantation of teeth with closed apexes, which should encourage a cautious approach to the question of routine endodontic treatment following autotransplantation.

Adolescent↗
PubMed2003

In vitro control of fasciation in proliferating nucellar embryos of Mangifera indica L. var totapari red small for cloning.

Nucellar tissue contained in ovular halves of young fruits of Mangifera indica L. totapari red small, a dwarfing rootstock, differentiated fasciated embryonal structures in presence of 6-benzylaminopurine [BAP(0.15 mg l(-1))], 6-(gamma-gamma-dimethylallylamino) purine [2iP(0.15 mg l(-1))] and indole-3-acetic acid [(IAA(0.5 mg l(-1))] incorporated in the semisolid medium during 50-60 days. Due to embryonal fasciation, hardly 2-3 well-formed embryos could be obtained per culture of proliferating embryos. Of the 3 ethylene inhibitors [L-alpha-(2-aminoethoxyvinyl)-glycine-HCl (AVG), AgNO3 and salicylic acid (SA)] used, embryonal fasciation and necrosis of intervening tissue was completely controlled by 3-4 subcultures of fasciated mass of embryos under the influence of AVG (0.05 mg l(-1)) in presence of adenine sulphate [AdS (50 mg l(-1))] incorporated in the same medium. Almost synchronized development of isolated embryos, measuring ca 2 cm in length, was observed in a different medium used in liquid stationary state and supplemented, particularly with stress-producing substances [abscisic acid (ABA, 0.01 mg l(-1)); and polyethylene glycol (PEG, 100 mg l(-1))] besides certain other modifications. About 34% convertibility of processed embryos was obtained during a period of 90 days. The plantlets had well-developed roots along with laterals which were longer than leafy shoots. In vitro raised plants survived ex vitro for about 2 months.

Abscisic Acid↗
PubMed2004

[Effect of straw return to field and fertilization in autumn on dryland corn growth and on water and fertilizer efficiency].

A ten years location experiment of various kinds straw return to field and deep fertilization in autumn was conducted in Shouyang dryland experimental area of Shanxi Province to study their effect on the growth and yield of dryland corn, the use efficency of soil water and fertilizer, and the changes of soil fertility. The results showed that this kind of experimental method could better solve the contradiction of deep fertilization with maintaining soil moisture and keeping a full stand of seedlings in spring, and the competition of water and fertilizer between the degradation of crop remains and the seedlings. What is more, the abundant resources of crop remains were used more sufficiently, the activity of soil microorganisms was more active, and soil fertility was obviously improved, which was proved by the complete and strong seedlings and developed roots, the photosynthesis and transpiration rates were enhanced, the water use efficiency (WUE) was increased by 3.26 - 3.51 kg x hm(-2) x mm(-1), and the accumulated water consumption was decreased by 8.1 - 264.5 mm. During plant growth period, the utilization rate of fertilizer N and P could increase 3.9% - 13.9% and 3.0% - 9.1%, respectively, and the use efficiency of water and fertilizer was higher. The ten years accumulated yield increased 12.10 - 17.27 t x hm(-2), a rise of 25.6% - 36.5%, and in the meantime, higher soil fertility and productivity were maintained.

China↗
PubMedDate not supplied

[Signal role of nitric oxide in plants].

Discovery of nitric oxide (NO*) as a key endogenous molecule, which regulates metabolism among very distantly related organisms, stimulated intensive research related to its multiple functions in plants. NO* exerts its cellular effects as toxic agent, metabolism regulator, second messenger during elicitation of different defense responses. It can induce various processes in plants, including programmed cell death, stomatal closure, seed germination and root development. Currently, elucidation of NO* signaling role in regulation of cellular responses is a "hot spot" of modern cell biology.

Nitric Oxide↗
PubMedDate not supplied

[Measuring the distance of the wisdom teeth from the occlusal plane as forensic-odontological method for chronological age determination].

As part of an epidemiological study on tooth eruption it was attempted to define easily accessible criteria for age estimation in living human beings based on the distance of the wisdom teeth from the occlusal plane. 253 cast models of 149 female and 104 male patients were used for evaluation. Due to the great variability observed in the eruption of the wisdom teeth, only a small fraction of the total number of 10,924 cast models was suitable for investigation. Only teeth with the axis being perpendicular to the plane of occlusion during eruption according to radiological and clinical findings were included. After defining these inclusion criteria, the distance of the wisdom teeth from the plane of occlusion was determined and correlated to the age of the subjects. The results confirmed the known large variability concerning wisdom tooth eruption and did not show any reliable relation between age and distance values. Nevertheless, a remarkable finding that may be relevant for forensic odontostomatology was seen in one case where the lower wisdom teeth were taller than the occlusal plane, although the female patient was younger than 14 years. The upper molars were retained and root development was incomplete.

Adolescent↗
PubMed2005

In vitro response of encapsulated somatic embryos of Lagerstroemia indica L.

A method to produce encapsulatable units for synthetic seeds was developed in L. indica. Somatic embryos were harvested from leaf derived embryogenic callus on Murashige and Skoog's basal medium supplemented with 2, 4-dichlorophenoxy acetic acid (2, 4-D, 0.5 mg/l), 6-benzyl amino purine (BAP, 1 mg/l) and ascorbic acid (AA, 50 mg/l). The embryos were encapsulated in alginate beads and dehydrated. Germination ability of the artificial seeds were investigated. The frequency of regeneration from the encapsulated embryos was significantly affected by (i) the concentration of alginate (ii) the duration of storage, and (iii) the effect of different types of media. A 2% sodium alginate concentration on MS salts resulted in significantly higher germination frequencies than at other concentrations. L. indica showed maximum germination on MS medium (93.84%) after 6 weeks of culture. The germinated synthetic seeds with well developed roots and shoots were transferred successfully to green house. This is the first report on artificial seeds in Lagerstroemnia indica.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2005

[Establishment and optimization of in vitro regeneration system for Plantago major L].

Plantago major is not only used as medicinal herb but also an important model plant of ecology. Little work has been reported on the tissue culture of P. major. A reproducible system for direct shoot morphogenesis and callus induction of Plantago major L. 'Giant Turkish' was described. Using seed as explants, the adventitious buds were obtained 4 to 5 weeks following incubation on MS medium supplemented with 0.2 mg/L IAA and 1.0 mg/L TDZ. The frequency of adventitious buds was as high as 100%. The average number of buds per explant was 14.6. Random amplified polymorphic DNA analysis on 9 regenerants indicated that somaclonal variation occurred at DNA level. Using leaves as explants, calli were easily induced on MS medium supplemented with 1.0 mg/L NAA 3 weeks following inoculation. The frequency of callus induction can be as high as 98%. On MS medium containing 4.0 mg/L 6-BA, 25% of calli differentiated and the mean number of buds per piece of callus was 2.8. The buds developed roots on 11/2 MS medium and formed plantlets, 90% of which survived when transplanted to greenhouse.

Plantago↗
PubMed1991

A study of natal teeth in Hong Kong Chinese.

The purpose of this study was to review cases of natal teeth in babies born between January 1984 and December 1988 at the Queen Elizabeth Hospital Hong Kong. There were 53678 births at the hospital during this period and 48 babies had natal teeth, a prevalence of 1:1118. The 48 babies had 72 natal teeth, all mandibular central incisors. The natal teeth in two babies were supernumerary teeth of a predeciduous dentition. Twenty nine natal teeth were extracted because they were hypermobile, three were extracted because they traumatized the ventral surface of the babies's tongue, and 16 were not extracted. The subjects were reviewed one day after the initial examination, and then after 1 week, 1 month and at 6-month intervals. No appreciable space loss occurred following the extractions. Root development occurred in teeth that were not extracted, but the crowns were hypoplastic in three cases.

Female↗
PubMed1990

Management of teeth with open apexes and necrotic pulps: representative cases.

This paper briefly reviews the pros and cons of five methods used to treat a tooth with a necrotic pulp and an open apex (incompletely developed root), and presents representative treatments of open apex cases. These treatments include customized cone, short-fill, periapical surgery, apexification, and one-visit apexification.

Adult↗
PubMed1988

[Morphological characteristics of inter-radicular space of the first and second lower permanent molars].

In this study, 537 extracted molars (261 first and 276 second molars) with well developed roots were examined to assess the width of the interradicular space and the shape of the furcation vault. The roots were set widely apart in 91.6% of the first and 64.8% of the second permanent molars, while the roots set closely together were observed in 8.4% and 27.9% of the first and second molars, respectively. Fuseg roots were found in second molars only, in 7.2% of cases. A flat furcation fornix was detected in 18.3% of the first and 14.0% of the second molars, whereas a convex shape was observed in 20.7% of the first and 10.5% of the second molars, respectively (P less than 0.001). A convex shape of furcation was found in 8.0% of the first and 27.3% of the second molars, respectively (P less than 0.001). Interradicular ridge was present in a very high percentage (52.9% of the first and 48.0% of the second molars). A concave shape of furcation fornix was statistically more frequent in molars with closely set roots for the first and second permanent molars (P less than 0.001). It seemed that the width of the interradicular space had no influence on the prevalence of interradicular bridges, regardless of type of molars involved.

Humans↗
PubMed1987

Staged salvage reconstruction of grade-IV and V spondylolisthesis.

Sixteen patients who had Grade-IV or V spondylolisthesis underwent a staged reconstruction for the salvage of a failed result of previous procedures. The indications for operation were incapacitating pain, radicular pain, pseudoclaudication, or the inability to stand upright. All patients had shown progression of the deformity after the previous surgery. At an average length of follow-up of fifty-two months, all patients had resumed normal activities and were free of the pain and symptoms of spinal stenosis. The complications included delayed union in six patients and a traumatic pseudarthrosis in one patient. In all of these patients a solid fusion was obtained after additional surgery. In five patients, neuropathy of the fifth lumbar-nerve root developed after surgery; it resolved in three patients. From this work, it is concluded that staged reconstructive surgery is feasible in patients who have Grade-IV or V spondylolisthesis with incapacitating pain and deformity that interfere with normal function. The benefits outweighed the risks in this very select group of patients.

Adolescent↗
PubMed1996

A mutation in protein phosphatase 2A regulatory subunit A affects auxin transport in Arabidopsis.

The phytohormone auxin controls processes such as cell elongation, root hair development and root branching. Tropisms, growth curvatures triggered by gravity, light and touch, are also auxin-mediated responses. Auxin is synthesized in the shoot apex and transported through the stem, but the molecular mechanism of auxin transport is not well understood. Naphthylphthalamic acid (NPA) and other inhibitors of auxin transport block tropic curvature responses and inhibit root and shoot elongation. We have isolated a novel Arabidopsis thaliana mutant designated roots curl in NPA (rcn1). Mutant seedlings exhibit altered responses to NPA in root curling and hypocotyl elongation. Auxin efflux in mutant seedlings displays increased sensitivity to NPA. The rcn1 mutation was transferred-DNA (T-DNA) tagged and sequences flanking the T-DNA insert were cloned. Analysis of the RCN1 cDNA reveals that the T-DNA insertion disrupts a gene for the regulatory A subunit of protein phosphatase 2A (PP2A-A). The RCN1 gene rescues the rcn1 mutant phenotype and also complements the temperature-sensitive phenotype of the Saccharomyces cerevisiae PP2A-A mutation, tpd3-1. These data implicate protein phosphatase 2A in the regulation of auxin transport in Arabidopsis.

Amino Acid Sequence↗
PubMedDate not supplied

[Auto-transplantation of tooth germs. Discussion and presentation of 3 treated cases].

The authors examine the theoretical possibilities of human dental transplants: autologous, homologous and heterologous. They, then discuss-with reference to autologous transplants-an autotransplant as an alternative to prosthodontic treatment. This would apply both to traditional prosthodontic treatment and on implants or orthodontic treatment aiming at filling dental gaps. They show both general and local counterindications against this operational method the knowledge of which is necessary for an adequate selection of patients. They stress the determining factors for a successful autotransplant: 1) particular care with the choice of the germ to be transplanted taking into account its morphology and the stage of root development; 2) adequate surgical preparation of the receiving site in relation to the size of the germ to be transplanted; 3) suitable surgical technique entailing a particular care in the manipulation of soft and hard tissues and of the germ and appropriate conditions of sterilization; 4) use of appropriate retention means to ensure stability of the transplanted germ so as to favour cellular proliferation and reduce osteoclastic activity; 5) reduction of occlusal pressure on the transplanted germ. The authors describe for example's sake 3 out of 32 cases treated with the documentation of the achieved long-term success. They also analyse the possible causes of failure of such operational method (careless manipulation of the germ, incorrect surgical technique, removal of the germ in a too early stage of its development, too long exposure of the germ outside the oral cavity, poor oral hygiene, caries, periodontal disease, occlusal trauma.

Adolescent↗
PubMed2006

Specialized 'dauciform' roots of Cyperaceae are structurally distinct, but functionally analogous with 'cluster' roots.

When grown in nutrient solutions of extremely low [P] (<or=1.0 microm), the sedge Schoenus unispiculatus Benth. (Cyperaceae) develops dauciform roots, which are short and carrot shaped, and produce dense numbers of long root hairs. It has been suggested that dauciform roots of monocotyledonous sedges function to acquire P from nutrient-poor, P-fixing soils in a manner similar to that of cluster (proteoid) roots developed by some dicotyledonous species, but without evidence to substantiate this claim. To elucidate the ecophysiological role of dauciform roots, we assessed carboxylate exudation, internal carboxylate and P concentrations and O(2) uptake rates during dauciform root development. We showed that O(2) consumption was fastest [9 nmol O(2) g(-1) fresh mass (FM) s(-1)] and root [P] greatest (0.4 mg P g(-1) FM) when dauciform roots were young and rapidly developing. Citrate was the most abundant carboxylate in root tissues at all developmental stages, and was most concentrated (22.2 micromol citrate g(-1) FM) in young dauciform roots, decreasing by more than half in mature dauciform roots. Peak citrate-exudation rates (1.7 nmol citrate g(-1) FM s(-1)) occurred from mature dauciform roots, and were approximately an order of magnitude faster than those from roots of species without root clusters, and similar to those of mature proteoid (cluster) roots of Proteaceae. Both developing and mature dauciform roots had the capacity to acidify (but not alkalinize) the rhizosphere. Anatomical studies showed that epidermal cells in dauciform roots were greatly elongated in the transverse plane; epidermal cells of parent roots were unmodified. Although structurally distinct, the physiology of dauciform roots in sedges appears to be analogous to that of proteoid roots of Proteaceae and Fabaceae, and hence, dauciform roots would facilitate access to sorbed P and micronutrients from soils of low fertility.

Carboxylic Acids↗