Search

OBJECTIVE: The objective of this study was to compare condyle shape between lateral temporomandibular joint (TMJ) images from axially corrected tomography and 3 panoramic radiography units with TMJ-specific programs. STUDY DESIGN: The TMJ from a single dry human skull was imaged with multidirectional tomography and the following 3 panoramic radiography units: Instrumentarium OP 100, Planmeca PM 2002 CC Proline, and Soredex Orthophos DS. A curve-fitting procedure (spline curves) was used to mathematically describe condyle outlines. One sample t tests were used to compare panoramic images against the tomograms (gold standard). RESULTS: A significant difference (P < .05) in condyle shape was found between TMJ tomography images and each of the 3 panoramic images. Images from the PM 2002 CC Proline demonstrated the smallest shape difference (13.4%), followed by the OP 100 (17.5%) and the Orthophos DS (24.8%). CONCLUSION: If panoramic radiography is to be used for the initial radiographic examination of the TMJ, practitioners should be aware of the potential for shape distortion of the condyle. [ABSTRACT FROM AUTHOR]

The effects of elevated concentrations of atmospheric carbon dioxide and ozone on diurnal patterns of photosynthesis have been investigated in field-grown spring wheat (Triticum aestivum). Plants cultivated under realistic agronomic conditions, in open-top chambers, were exposed from emergence to harvest to reciprocal combinations of two carbon dioxide and two ozone treatments: [CO2] at ambient (380 μmol mol-1, seasonal mean) or elevated (692 μmol mol-1) levels, [O3] at ambient (27 nmol mol-1 7 hr seasonal mean) or elevated (61 nmol mol-1) levels. After anthesis, diurnal measurements were made of flag-leaf gas-exchange and in Vitro Rubisco activity and content. Elevated [CO2] resulted in an increase in photoassimilation rate and a loss of excess Rubisco activity. Elevated (O3] caused a loss of Rubisco and a decline in photoassimilation rate late in flag-leaf development. Elevated [CO2] ameliorated O3 damage. The mechanisms of amelioration included a protective stomatal restriction of O3 flux to the mesophyll, and a compensatory effect of increased substrate on photoassimilation and photosynthetic control. However, the degree of protection and compensation appeared to he affected by the natural seasonal and diurnal variations in light, temperature and water status. [ABSTRACT FROM AUTHOR]

Two strains of Bacteroides intermedius BH20/30 and BH18/23, have been grown in anaerobic continuous culture under various conditions for periods up to 54 days. Strain BH20/30 grew over a relatively wide pH range from 5-8 with a maximum at pH 7.0 at a dilution rate (D) of 0.1 h-1 with a glucose limitation, while strain BH18/23 had an optimum between 5.8 and 7.3 and would not grow above and below this range. The maximum growth rate (μmax) for the latter strain was shown to be 0.23 h-1, or a doubling time of 3.0 at the upper limit of pH 7.3. The yield values (Yglucose) for strain BH18/23 reached 187-177 g cells (dry weight) per mole of glucose in the optimum pH range (6.0-7.0) and amino acid analysis of the spent medium indicated that these high values were the result of the combined use of glucose and amino acids; the cultures also exhibited proteolytic activity. The major acid end-products in the same pH range were formate and succinate with lesser concentrations of acetate, isovalerate and fumarate; small amounts of lactate appeared as the cells were stressed at pH values above 7.5 when the culture was 'washing out' of the chemostat. Glucose metabolism appeared to function through the glycolytic pathway in B. intermedius BH18/23 since the glycolytic inhibitors, sodium fluoride and sodium iodoacetate, completely inhibited glucose utilization as did the proton ionophore, gramicidin, and the ATPase inhibitor, N,N 1-dicyclohexylcarbodiimide (DCCD) inhibition by these latter compounds indicated that the saccharolytic Bacteroides utilize proton gradients generated by proton-extruding ATPase (H+/ATPase) to conserve energy. B. Intermedius BH18/23 was shown to possess in membrane preparations for enzyme II (glucose) of the P-enoplpyruvate phosphotransferase system (PTS) indicating that sugar transport by the organism occurs, at least in part, by this group translocation process. [ABSTRACT FROM AUTHOR]

Apex and Bristol cultivars of oilseed rape (Brassica napus) were irradiated with 0.63 W m-2 of UV-B over 5 d. Analyses of the response of net leaf carbon assimilation to intercellular CO2 concentration were used to examine the potential limitations imposed by stomata, carboxylation velocity and capacity for regeneration of ribulose 1,5-bisphosphate on leaf photosynthesis. Simultaneous measurements of chlorophyll fluorescence were used to estimate the maximum quantum efficiency of photosystem II (PSII) photochemistry, the quantum efficiency of linear electron transport at steady-state photosynthesis, and the light and CO2-saturated rate of linear electron transport. Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) content and activities were assayed in vitro. In both cultivars the UV-B treatment resulted in decreases in the light-saturated rate of CO2 assimilation, which were accompanied by decreases in carboxylation velocity and Rubisco content and activity. No majoreffects of UV-B were observed on end-product inhibition and stomatallimitation of photosynthesis or the rate of photorespiration relative to CO2 assimilation. In the Bristol cultivar, photoinhibition of PSII and loss of linear electron transport activity were observed when CO2 assimilation was severely inhibited. However, the Apex cultivar exhibited no major inhibition of PSII photochemistry or linear electron transport as the rate of CO2 assimilation decreased. It is concluded that loss of Rubisco is a primary factor in UV-B inhibition of CO2 assimilation. [ABSTRACT FROM AUTHOR]

This study investigated the interacting effects of carbon dioxide and ozone concentrations on the growth and yield of spring wheat (Triticum aestivum L. cv. Wembley). Plants were exposed from time of sowing to harvest to reciprocal combinations of two carbon dioxide and two ozone treatments: [CO2] at 350 or 700 μmol mol-1, and [O3] at < 5 or 60 μmol mol-1. Records of leaf emergence, leaf duration and tillering were taken throughout leaf development. At harvest, biomass, yield and partitioning were analysed. Our data showed that elevated [CO2] fully protected against the detrimental effect of elevated [O3] on biomass, but not yield. [ABSTRACT FROM AUTHOR]

Rising levels of atmospheric CO2 will have profound, direct effects on plant carbon metabolism. In this study we used gas exchange measurements, models describing the instantaneous response of leaf net CO2 assimilation rate (A) to intercellular CO2 partial pressure (Ci), in vitro enzyme activity assay, and carbohydrate assay in order to investigate the photosynthetic responses of wheat (Triticum aestivum L., cv. Wembley) to growth under elevated partial pressures of atmospheric CO2 (Ca). At flag leaf ligule emergence, the modelled, in vivo, maximum carboxylation velocity for RuBisCO was significantly lower in plants grown at elevated Ca than in plants grown at ambient Ca (70 Pa compared with 40 Pa). By 12 d after ligule emergence, no significant difference in this parameter was detectable. At ligule emergence, plants grown at elevated Ca exhibited reduced in vitro initial activities and activation states of RuBisCO. At their respective growth Ci values, the photosynthesis of 40-Pa-grown plants was sensitive to p(O2) and top(CO2), whereas that of 70-Pagrown plants was insensitive. Both sucrose and starch accumulated more rapidly in the leaves of plants grown at 70 Pa. At flag leaf ligule emergence, modelled non-photorespiratory respiration in the light (Rd) was significantly higher in 70-Pa-grown plants than in 40-Pa-grown plants. By 12 d after ligule emergence no significant differences in Rd were detectable. [ABSTRACT FROM AUTHOR]

Elevated [CO2] has been shown to protect photosynthesis and growth of wheat against moderately elevated [O3]. To investigate the role of ozone exclusion and detoxification in this protection, spring wheat (Triticum aestivum L. cv. Wembley) was grown from seed, in controlled-environment chambers, under reciprocal combinations of [CO2] at 350 or 700 μmol mol-1 and [O3] peaking at < 5 or 60 nmol mol-1, respectively. Cumulative ozone dose to the mesophyll and antioxidant status were determined throughout flag leaf development. Catalase activity correlated with rates of photorespiration and declined in response to elevated [CO2] and/or [O3]. Superoxide dismutase activity was not significantly affected by either condition. Neither ascorbate nor glutathione content was enhanced by elevated [CO2]. In wheat, at moderately elevated [O3], our results show that stomatal exclusion plays a major role in the protective effect of elevated [CO2] against O3 damage. [ABSTRACT FROM AUTHOR]