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PubMed2004

Histologic analysis of pulpal revascularization of autotransplanted immature teeth after removal of the original pulp tissue.

The survival rate of replanted and autotransplanted teeth is mainly affected by the reaction of the pulp. Pulpal necrosis can cause periapical inflammation and inflammatory root resorption. The purpose of this study is to learn more about the pulpal changes in autotransplanted immature teeth whose pulp tissue was removed before transplantation. The experimental material consisted of 16 single-rooted teeth with open apices, from a beagle dog (3 months of age). At day 0, 4 teeth were extracted, the pulpal tissues were removed, and the teeth were then transplanted to their contralateral side. The same procedure was carried out on days 9, 16, and 23, each time for 4 single-rooted teeth. Longitudinal paraffin sections were made for histologic investigation. The results showed that, after 7 days, 2 of the 4 teeth had an ingrowth of new tissue over one fourth of their length. After 14 days, all 4 teeth had ingrowth (> or =one fourth of the pulp chamber). At the 21-day observation, more than half of the pulp chambers of all teeth were filled, and, after 30 days, there was total ingrowth in 3 of the 4 teeth. This new tissue consisted of well-organized and well-vascularized connective tissue.

Animals↗

PubMed2005

Element cycling in the dominant plant community in the Alpine tundra zone of Changbai Mountains, China.

Element cycling in the dominant plant communities including Rh. aureum, Rh. redowskianum and Vaccinium uliginosum in the Alpine tundra zone of Changbai Mountains in northeast China was studied. The results indicate that the amount of elements from litter decomposition was less than that of the plant uptake from soil, but that from plant uptake was higher than that in soil with mineralization process released. On the other hand, in the open system including precipitation input and soil leaching output, because of great number of elements from precipitation into the open system, the element cycling(except N, P) in the Alpine tundra ecosystem was in a dynamic balance. In this study, it was also found that different organ of plants had significant difference in accumulating elements. Ca, Mg, P and N were accumulated more obviously in leaves, while Fe was in roots. The degree of concentration of elements in different tissues of the same organ of the plants also was different, a higher concentration of Ca, Mg, P and N in mesophyll than in nerve but Fe was in a reversed order. The phenomenon indicates (1) a variety of biochemical functions of different elements, (2) the elements in mesophyll were with a shorter turnover period than those in nerve or fibre, but higher utilization rate for plant. Therefore, this study implies the significance of keeping element dynamic balance in the alpine tundra ecosystem of Changbai Mountains.

Biomass↗

PubMed1974

Morphogenesis in Selaginella: II. Auxin Transport in the Root (Rhizophore).

The rhizophore of Selaginella willdenovii Baker develops from the ventral angle meristem. The morphological nature of this organ has been in dispute. The purpose of this investigation was to obtain physiological evidence to support the contention that the rhizophore is a root and not a shoot. This was accomplished by studying the movement of (3)H-indoleacetic acid and (14)C-indoleacetic acid in Selaginella rhizophores. In 6-millimeter tissue segments, twice as much radioactivity accumulated in acropetal receivers as in basipetal. During 1 hour of transport in intact roots auxin traveled twice as far in the acropetal direction as basipetal. A significant amount of radioactivity transported in the tissue was found to co-chromatograph with cold indoleacetic acid. Decarboxylation accounted for 10% loss of activity from donors. The data provide sufficient physiological evidence that this organ is morphogenetically a root.

Journal Article↗

PubMed1999

A critical account on the inception of Striga seed germination.

The seeds of the parasitic weed Striga germinate in response to stimulants exuded by the roots of host plants and some nonhost plants. Literature data are summarized that support the view that strigolactones induce germination of parasitic weed seeds via a receptor-mediated mechanism. The suggestion by Lynn et al. that the strigol D-ring is solely responsible for germinating Striga seeds via a redox reaction was based on hypothesized structural similarities between the natural compound dihydrosorgoleone (SXSg) and the strigol D-ring. Experiments have shown that the mechanistic connection between SXSg and the strigol D-ring is not valid, and therefore the proposed redox mechanism for the induction of Striga seed germination by strigolactones does not hold.

Lactones↗

PubMed1996

Characterizing photosynthesis and transpiration of plant communities in controlled environments.

CO2 and water vapor fluxes of hydroponically grown wheat and soybean canopies were measured continuously in several environments with an open gas exchange system. Canopy CO2 fluxes reflect the photosynthetic efficiency of a plant community, and provide a record of plant growth and health. There were significant diurnal fluctuations in root and shoot CO2 fluxes, and in shoot water vapor fluxes. Canopy stomatal conductance (Gc) to water vapor was calculated from simultaneous measurements of canopy temperature (Tcan) and transpiration rates (Tr). Tr in the dark was substantial, and there were large diurnal fluctuations in both Gc and Tr. Canopy net Photosynthesis (Pnet), Tr, and Gc increased with increasing net radiation. Gc increased with Tr, suggesting that the stomata of plants in controlled environments (CEs) behave differently from field-grown plants. A transpiration model based on measurements of Gc was developed for CEs. The model accurately predicted Tr from a soybean canopy.

Carbon Dioxide↗

PubMed1996

Nucleolar organizer expression in Allium cepa L. chromosomes.

Roots from Allium cepa L. (cv. Francesa) bulbs in which a maximum of two nucleoli per nucleus developed were selected for this study. Five rDNA clusters were detected by fluorescent in situ hybridization on chromosomal squashes (2n = 16) with a rhodamine-labelled wheat rDNA repeat. The rDNA clusters were located on four chromosomes: the largest cluster occurred on the small arm of a single homologue of the smallest pair 8. Its homologue showed two different small rDNA clusters, one near each telomere. The two homologues of the satellited chromosomes 6 also showed different rDNA contents, which were intermediate to those found in pair 8. The same five well-differentiated hybridization signals were observed in interphase cells that were inactive in transcription because they were in dormant roots, or in proliferating ones in which the synthesis of the large rRNA precursor was prevented. After multipolarizing agent was applied in anaphase followed by inhibition of cytokinesis, multinucleate autotetraploid cells were formed, which often contained more than four nucleoli. Thus, at least two of the three nucleolar organizer regions that consistently failed to develop a nucleolus in normal mononucleate cells were capable of developing nucleoli when segregated into different nuclei in multinucleate cells.

Chromosome Mapping↗

PubMed2003

Root : shoot ratios, optimization and nitrogen productivity.

Plants respond to nitrogen availability by changing their root : shoot ratios. One hypothesis used to explain this allocation is that plants optimize their behaviour by maximizing their relative growth rate. The consequences of this hypothesis were investigated by formulating two models for root : shoot allocation, with and without explicit inclusion of maintenance respiration. The models also took into account that relative growth rate is a linear function of plant nitrogen concentration. The model without respiration gave qualitatively reasonable results when predictions were compared with observed results from growth experiments with birch and tomato. The explicit inclusion of maintenance respiration improved considerably the agreement between prediction and observation, and for birch was within the experimental accuracy. Further improvements will require additional details in the description of respiratory processes and the nitrogen uptake function. Plants growing under extreme nutrient stress may also optimize their behaviour with respect to other variables in addition to relative growth rate.

Betula↗

PubMed2005

210Po bioaccumulation in coastal sand dune wild legumes--Canavalia spp. of southwest coast of India.

In view of considerable natural background radioactivity reported from southwest coast of India, the current study documents bioaccumulation of 210Po in two dominant coastal sand dune perennial mat-forming wild legumes, Canavalia cathartica and C. maritima. Root, stem, leaf, mature beans, dry seeds and rhizosphere sand were analyzed for 210Po concentration. 210Po activity decreased in the order of leaves > roots > seeds > stems > beans. The highest 210Po activity was recorded in rhizosphere sand samples (5.78-5.88 Bq kg(-1)) followed by the leaf samples (3.27-3.07 Bq kg(-1)), while it was lowest in mature beans (0.13-0.20 Bq kg(-1)). 210Po activities or tissue moisture between plant species were not significantly different (p > 0.05; t-test). But 210Po activity vs. moisture differed significantly in all tissues (p = 0.0001), vegetative tissues (root, stem and leaf) (p = 0.0016), seeds (p = 0.0393) and proteins in seeds (p = 2.355 x 10(-6)) indicating the importance of moisture and protein in 210Po accumulation. Although 210Po has affinity for proteins, it did not concentrate too much in seed proteins of Canavalia. Concentration of 210Po in mature beans is at safe levels as fisher folk only consume tender pods occasionally. 210Po activity in Canavalia is compared with other plant materials. As the landraces of C. cathartica and C. maritima are distributed throughout pantropical coastal areas, the current study emphasizes on considering them as bioindicators to monitor 210Po in coastal sand dune biomes and in turn the health of coastal population.

Canavalia↗

PubMed2000

Plant cells on earth and in space.

Two quite different types of plant cells are analysed with regard to transduction of the gravity stimulus: (i) Unicellular rhizoids and protonemata of characean green algae; these are tube-like, tip-growing cells which respond to the direction of gravity. (ii) Columella cells located in the center of the root cap of higher plants; these cells (statocytes) perceive gravity. The two cell types contain heavy particles or organelles (statoliths) which sediment in the field of gravity, thereby inducing the graviresponse. Both cell types were studied under microgravity conditions (10(-4) g) in sounding rockets or spacelabs. From video microscopy of living Chara cells and different experiments with both cell types it was concluded that the position of statoliths depends on the balance of two forces, i.e. the gravitational force and the counteracting force mediated by actin microfilaments. The actomyosin system may be the missing link between the gravity-dependent movement of statoliths and the gravity receptor(s); it may also function as an amplifier.

Actins↗

PubMed1989

Chiropractic distractive decompression in treating pelvic pain and multiple system pelvic organic dysfunction.

No data are available on the incidence of pelvic pain and organic dysfunction (PPOD) in patients suffering from low back pain. PPOD is not an uncommon finding in the low back pain patient. Women appear to be more frequently involved than men. The results of recent electrophysiologic investigations indicate that many patients with urological, bowel or anorectal dysfunction demonstrate evidence of denervation neuropathy in muscles innervated by the branches of the pudendal nerve. Six patients with low back pain meeting predetermined criteria, indicating the presence of PPOD as a result of suspected lower sacral nerve root compression (LSNRC) secondary to a mechanical disorder of the low back were treated with chiropractic distractive decompressive manipulation of the lumbar spine. Symptoms of PPOD, and indicators of LSNRC were assessed prior to the onset, and following the termination of treatment. It appears that selected indicators of LSNRC represent the most sensitive clinical signs of identifying the presence of PPOD which may respond to manipulative treatment, and may also provide the most sensitive measure of overall PPOD response. These findings, although preliminary suggest a possible etiology of PPOD in the low back pain patient with evidence of LSNRC. Further work in this area is encouraged.

Adult↗

PubMed2006

A mathematical model of plants as ecosystem engineers.

Understanding the structure and dynamics of plant communities in water-limited systems often calls for the identification of ecosystem engineers--key species that modify the landscape, redistribute resources and facilitate the growth of other species. Shrubs are excellent examples; they self-organize to form patterns of mesic patches which provide habitats for herbaceous species. In this paper we present a mathematical model for studying ecosystem engineering by woody plant species in drylands. The model captures various feedbacks between biomass and water including water uptake by plants' roots and increased water infiltration at vegetation patches. Both the uptake and the infiltration feedbacks act as mechanisms for vegetation pattern formation, but have opposite effects on the water resource; the former depletes the soil-water content under a vegetation patch, whereas the latter acts to increase it. Varying the relative strength of the two feedbacks we find a trade-off between the engineering capacity of a plant species and its resilience to disturbances. We further identify two basic soil-water distributions associated with engineering at the single patch level, hump-shaped and ring-shaped, and discuss the niches they form for herbaceous species. Finally, we study how pattern transitions at the landscape level feedback to the single patch level by affecting engineering strength.

Biomass↗

PubMed1968

Control of cell progression through the mitotic cycle by carbohydrate provision. I. Regulation of cell division in excised plant tissue.

A stationary phase in the root meristem of excised pea roots was established by prolonged carbohydrate deprivation in sterile culture medium. When the stationary phase had been established, cells that had collected in the G1 period of the mitotic cycle were induced to enter the S stage by subjection to relatively short intervals of carbohydrate provision (sucrose spurts). Progression and cycle location of the G1 cells induced to enter S were measured with tritiated thymidine and radioautography. The results indicated that the number of G1 cells induced to enter S increased directly with the spurt duration and that cells could be positioned and retained in the S and/or G2 periods by varying the duration of the spurt. The data support the hypothesis that S and maybe M stages have a relatively larger dependence on carbohydrate availability, and presumably a greater energy requirement, than G1 and G2.

Carbohydrate Metabolism↗

PubMed2006

Identification of a Sed5-like SNARE gene LjSYP32-1 that contributes to nodule tissue formation of Lotus japonicus.

We identified a Sed5-like clone LjSYP32-1 which contributes to nodule tissue formation and plant growth in Lotus japonicus. In the L. japonicus expressed sequence tag (EST) clone databases of Kazusa DNA Research Institute, another syntaxin-related clone (LjSYP32-2) was also detected, and the nucleotide and amino acid sequences of these two clone are very similar to each other. Real-time PCR and promoter analysis indicated that expression of LjSYP32-1 was dominant compared with LjSYP32-2 in the various plant organs. Promoter analysis and in situ hybridization revealed that LjSYP32-1 was expressed significantly in the inner cortex cell layer surrounding the infected zone of young nodules and in the meristem area of developing lateral root. To explore the function and physiological role of LjSYP32-1 in nodules and other plant organs, stable transformation lines of L. japonicus expressing either sense or antisense LjSYP32-1 were prepared. The antisense plants showed a significantly retarded plant growth phenotype, suggesting a role for LjSYP32-1 in supporting plant growth. In the same transgenic lines, the plants were capable of forming nodules, but the acetylene reduction activity was reduced by around 50% per plant. The nodules were much smaller and some nodules were fused to each other by sharing the inner cortex. The rate of occurrence of such irregular nodules was twice that observed in wild-type plants. The data suggest that LjSYP32-1 contributes to the support of plant growth and normal nodule tissue differentiation.

Amino Acid Sequence↗

PubMed1999

Cytokine secretion of periodontal ligament fibroblasts derived from human deciduous teeth: effect of mechanical stress on the secretion of transforming growth factor-beta 1 and macrophage colony stimulating factor.

The periodontal ligament may play an important role in tooth eruption, root development and resorption. The tissue physiologically receives mechanical force during mastication. We focused on the effects of intermittent mechanical strain on the cytokine synthesis of periodontal ligament (PDL) fibroblasts in vitro. The cells were derived from human periodontal ligament of deciduous teeth (HPLF-Y) and permanent teeth (HPLF). The two kinds of PDL cells and human gingival fibroblasts (HGF) were cultured in flexible bottomed culture plates. The cells were mechanically stretched at 5% elongation, 3-cycles/min for 24 h on d 7 in culture using a Flexercell strain unit. After the stretching, we measured DNA content and alkaline phosphatase activity in the cell layer, transforming growth factor beta 1 (TGF-beta 1) and macrophage colony stimulating factor (M-CSF) contents in the conditioned medium. The TGF-beta 1 level in the conditioned medium of HPLF was significantly higher than that of HPLF-Y and HGF. It was stimulated by mechanical stretching only on HPLF, whereas no significant effect was observed on HPLF-Y and HGF. M-CSF secretion was inhibited by the stretching on all of HPLF, HPLF-Y and HGF. 1 alpha, 25 dihydroxy vitamin D3 (D3) stimulated M-CSF secretion into the culture medium of both HPLF and HPLF-Y, but the stretching inhibited M-CSF secretion and completely blocked the enhancement by D3. These data suggest that periodontal ligament cells synthesize and secrete the molecules as autocrine or paracrine factors that affect bone remodelling and root resorption and the level of those factors change in response to mechanical stress.

Alkaline Phosphatase↗

PubMedDate not supplied

Food and nutrient intakes by pregnant Nigerian adolescents during the third trimester.

We assessed the food and nutrient intakes of pregnant adolescent Nigerians during the third trimester of pregnancy. The study was hospital based and the subjects consisted of 101 adolescents (47 urban and 54 rural) and 20 controls (primigravidae, 20 to 25 y old) who attended antenatal clinics. The 3-d weighed-intake technique was used to obtain information on food intake. For all cohorts, the results showed that the bulk of the foods derived from three main food groups, namely roots or tubers, cereals, and legumes. Older adolescents (17.5 to 19 y) in urban areas had the highest energy intake (5.9 MJ/d), and the younger urban adolescents (15 to 17 y) had the lowest (5.2 MJ/d) energy intake. Mean protein intake levels for urban adolescents (37.7 g/d) did not differ significantly (P > 0.05) from mean intake levels (35.3 g/d) for rural subjects. Dietary iron intake was similar in all cohorts including controls, and only 32.3% to 39.3% of the recommended daily allowance for iron was met by the subjects. Approximately 30% of subjects individually achieved 100% of the recommended levels of zinc. Mean intakes as percentages of the recommended daily allowance by adolescent subjects were 50.7% for calcium, 29.2% for copper, and 28.5% for folate. There is urgent need to monitor the nutrition status of pregnant women in the area.

Adolescent↗

PubMed2004

Assessing the phylogeny of Frankia-actinorhizal plant nitrogen-fixing root nodule symbioses with Frankia 16S rRNA and glutamine synthetase gene sequences.

Actinomycetes from the genus Frankia induce nitrogen-fixing root nodules on actinorhizal plants in the "core rosid" clade of eudicots. Reported here are nine partial Frankia 16S rRNA gene sequences including the first from host plants of the rosaceous genera Cercocarpus and Chamaebatia, 24 partial glutamine synthetase (GSI; glnA) sequences from Frankia in nodules of 17 of the 23 actinorhizal genera, and the partial glnA sequence of Acidothermus cellulolyticus. Phylogenetic analyses of combined Frankia 16S rDNA and glnA sequences indicate that infective strains belong to three major clades (I-III) and that Clade I strains consisting of unisolated symbionts from the Coriariaceae, Datiscaceae, Rosaceae, and Ceanothus of the Rhamnaceae are basal to the other clades. Clock-like mutation rates in glnA sequence alignments indicate that all three major Frankia clades diverged early during the emergence of eudicots in the Cretaceous period, and suggest that present-day symbioses are the result of an ancestral symbiosis that emerged before the divergence of extant actinorhizal plants.

DNA, Bacterial↗

PubMed1998

Design and performance of the Phyto-Nutri-Tron: a system for controlling the root and shoot environment for whole-plant ecophysiological studies.

A controlled environment system, termed the Phyto-Nutri-Tron (PNT), has been established to study whole plant ecophysiological responses to multiple environmental factors. The PNT is a computer-controlled highly flexible growth facility with independent control of the shoot and the root environment. The facility consists of two growth cabinets each containing four separate hydroponic growth systems. The growth cabinets can be used as assimilation chambers with individual control of temperature, humidity, light, CO2 and monitoring of O2. The hydroponic growth systems are connected to nutrient supply units with disinfection systems and individual control of temperature, pH and oxygen. The ionic composition of the solutions has automated feedback control through a PO4 autoanalyzer and a flow injection analyzer which also analyzes NH4+, NO2- and NO3-. Other ions are automatically monitored by ICP-AES. The system has automated calibration procedures of the analytical equipment and prolonged studies of plant growth can be performed under constant environmental conditions. This paper describes the design and construction of the PNT, the results of a number of tests showing the degree of control of environmental factors and the results of a comparative study on NH4+ and NO3- uptake kinetics by Juncus effusus conducted in the PNT demonstrate the use of the PNT in ecophysiological studies.

Computer Systems↗

PubMed2006

Ant-gardens of tropical Asian rainforests.

Ant-garden (AG) associations are systems of epiphytic plants and arboricolous (i.e., tree-living) ants, in which the ants build fragile carton nests containing organic material. They collect and incorporate seeds or fruits of epiphytes that then germinate and grow on the nest [sensu Corbara et al. (1999) 38:73-89]. The plant roots stabilize the nest carton. AGs have been well-known in the neotropics for more than 100 years. In contrast, reports on similar associations in the paleotropics are scarce so far. After discovering a first common AG system on giant bamboo [Kaufmann et al. (2001) 48:125-133], we started a large-scale survey for AGs in Peninsular Malaysia, Borneo, Java, and southern Thailand. A great variety of AG systems (altogether including 18 ant species and 51 plant species) was discovered and is described in the present paper. The high number of species participating in AG associations was reflected by a great variability in the specific appearances of the nest gardens. Frequently, further groups of organisms (e.g., hemipteran trophobionts, fungi) were also involved. Preference patterns of particular ant and epiphyte species for each other and for particular phorophytes (carrier trees) were detected. We integrate domatia-producing, so-called ant-house epiphytes in our study and compare their phases of establishment, as well as other characteristics, to "classical" AGs, coming to the conclusion that they should be regarded only as a special type of AG epiphyte and not as a separate ecological category.

Animals↗