Barley Cultivar Sarab 1 Has a Characteristic Region on the Thylakoid Membrane That Protects Photosystem I under Iron-Deficient Conditions

The barley cultivar Sarab 1 (SRB1) can continue photosynthesis despite its low Fe acquisition potential via roots and dramatically reduced amounts of photosystem I (PSI) reaction-center proteins under Fe-deficient conditions. We compared the characteristics of photosynthetic electron transfer (ET), thylakoid ultrastructure, and Fe and protein distribution on thylakoid membranes among barley cultivars. The Fe-deficient SRB1 had a large proportion of functional PSI proteins by avoiding P700 over-reduction. An analysis of the thylakoid ultrastructure clarified that SRB1 had a larger proportion of non-appressed thylakoid membranes than those in another Fe-tolerant cultivar, Ehimehadaka-1 (EHM1). Separating thylakoids by differential centrifugation further revealed that the Fe-deficient SRB1 had increased amounts of low/light-density thylakoids with increased Fe and light-harvesting complex II (LHCII) than did EHM1. LHCII with uncommon localization probably prevents excessive ET from PSII leading to elevated NPQ and lower PSI photodamage in SRB1 than in EHM1, as supported by increased Y(NPQ) and Y(ND) in the Fe-deficient SRB1. Unlike this strategy, EHM1 may preferentially supply Fe cofactors to PSI, thereby exploiting more surplus reaction center proteins than SRB1 under Fe-deficient conditions. In summary, SRB1 and EHM1 support PSI through different mechanisms during Fe deficiency, suggesting that barley species have multiple strategies for acclimating photosynthetic apparatus to Fe deficiency.

Effects of Nodulation on Metabolite Concentrations in Xylem Sap and in the Organs of Soybean Plants Supplied with Different N Forms

The effects of nodulation on N metabolism in soybean plants supplied with various forms of N are not fully understood. Ureides are the principal forms of N transported from nodules, but nitrate and asparagine are the primary N compounds transported from roots supplied with NO3−. In this research, the effects of 1-day treatments of NO3−, NH4+, urea, or NO3− + NH4+ on N metabolite concentrations in xylem sap and each organ were compared between nodulated and non-nodulated soybeans. Capillary electrophoresis and colorimetry were used for the analysis. In the xylem sap of the nodulated plants with an N-free solution, ureides were the major N metabolites, followed by asparagine and glutamine. Ureides concentrations were much lower in the xylem sap of the non-nodulated soybeans. In the NO3− treatment, the concentrations of ureides in the xylem sap of the nodulated plants decreased compared to the control plants. In the NH4+, urea, and NO3− + NH4+ treatments, the concentrations of asparagine and glutamine increased significantly compared with the control and NO3− treatments. Similar changes with the N treatments were observed between the nodulated and non-nodulated soybeans, suggesting that nodulation does not have significant effects on the metabolism of absorbed N in roots.

"Live-Autoradiography" Technique Reveals Genetic Variation in the Rate of Fe Uptake by Barley Cultivars

Iron (Fe) is an essential trace element in plants; however, the available Fe in soil solution does not always satisfy the demand of plants. Genetic diversity in the rate of Fe uptake by plants has not been broadly surveyed among plant species or genotypes, although plants have developed various Fe acquisition mechanisms. The "live-autoradiography" technique with radioactive ⁵⁹Fe was adopted to directly evaluate the uptake rate of Fe by barley cultivars from a nutrient solution containing a very low concentration of Fe. The uptake rate of Fe measured by live autoradiography was consistent with the accumulation of Fe-containing proteins on the thylakoid membrane. The results revealed that the ability to acquire Fe from the low-Fe solution was not always the sole determinant of tolerance to Fe deficiency among barley genotypes. The live-autoradiography system visualizes the distribution of β-ray-emitting nuclides and has flexibility in the shape of the field of view. This technique will strongly support phenotyping with regard to the long-distance transport of nutrient elements in the plant body.

Suppressive effect of the deep placement of lime nitrogen on N2O emissions in a soybean field

Deep placement of slow-release nitrogen (N) fertilizers improves the growth and yield of soybean with a high N use efficiency. This study examined the effectiveness of deep placement of lime nitrogen (LN) in reducing N2O emissions in a soybean field and compared it with conventional fertilization. Before sowing soybeans, the starter N fertilizer (16 kg-N ha-1 ammonium sulfate) was mixed in the surface soil and the following four treatments were installed: the control with only the starter N (CT), conventional top-dressing of 60 kg-N ha-1 coated urea (CV), deep placement (20 cm depth) of 100 kg-N ha-1 urea (DU), and deep placement (20 cm depth) of 100 kg-N ha-1 LN (DL). The seasonal patterns of N2O emission rates measured using the closed chamber method differed among the treatments: in CT, N2O emissions were relatively low; in CV, N2O emissions derived from the top-dressed coated urea were observed from 91 days after sowing; in DU and DL, deeply-placed N was converted to N2O in the early growth stages. The cumulative N2O emissions in DL (1.8 kg-N ha-1) during the soybean cultivation period were significantly lower than those in DU (3.1 kg-N ha-1) and CV (2.8 kg-N ha-1), and slightly higher than CT (1.2 kg-N ha-1). The magnitude of N2O emissions was significantly lower in DL than DU, indicating that the choice of N fertilizer is important to reduce N2O emissions. Focusing on N2O emissions per unit coarse grain yield of soybeans, the value in DL was 0.45 g-N kg-1, which was significantly lower than 0.74 g-N kg-1 in CV. In conclusion, the deep placement of LN has the potential to be a sustainable farming method that can promote yields and reduce N2O emissions in soybean cultivation for high yield with N fertilization.

Application of Nitrate, Ammonium, or Urea Changes the Concentrations of Ureides, Urea, Amino Acids and Other Metabolites in Xylem Sap and in the Organs of Soybean Plants (Glycine max (L.) Merr.)

Soybean (Glycine max (L.) Merr.) plants form root nodules and fix atmospheric dinitrogen, while also utilizing the combined nitrogen absorbed from roots. In this study, nodulated soybean plants were supplied with 5 mM N nitrate, ammonium, or urea for 3 days, and the changes in metabolite concentrations in the xylem sap and each organ were analyzed. The ureide concentration in the xylem sap was the highest in the control plants that were supplied with an N-free nutrient solution, but nitrate and asparagine were the principal compounds in the xylem sap with nitrate treatment. The metabolite concentrations in both the xylem sap and each organ were similar between the ammonium and urea treatments. Considerable amounts of urea were present in the xylem sap and all the organs among all the treatments. Positive correlations were observed between the ureides and urea concentrations in the xylem sap as well as in the roots and leaves, although no correlations were observed between the urea and arginine concentrations, suggesting that urea may have originated from ureide degradation in soybean plants, possibly in the roots. This is the first finding of the possibility of ureide degradation to urea in the underground organs of soybean plants.

Enhancement of Photosynthetic Iron-Use Efficiency Is an Important Trait of Hordeum vulgare for Adaptation of Photosystems to Iron Deficiency

Leaf iron (Fe) contents in Fe-deficiency-tolerant plants are not necessarily higher than that in Fe-deficiency-susceptible ones, suggesting an unknown mechanism involved in saving and allowing the efficient use of minimal Fe. To quantitatively evaluate the difference in Fe economy for photosynthesis, we compared the ratio of CO₂ assimilation rate to Fe content in newly developed leaves as a novel index of photosynthetic iron-use efficiency (PIUE) among 23 different barley (Hordeum vulgare L.) varieties. Notably, varieties originating from areas with alkaline soil increased PIUE in response to Fe-deficiency, suggesting that PIUE enhancement is a crucial and genetically inherent trait for acclimation to Fe-deficient environments. Multivariate analyses revealed that the ability to increase PIUE was correlated with photochemical quenching (qP), which is a coefficient of light energy used in photosynthesis. Nevertheless, the maximal quantum yield of photosystem II (PSII) photochemistry, non-photochemical quenching, and quantum yield of carbon assimilation showed a relatively low correlation with PIUE. This result suggests that the ability of Fe-deficiency-tolerant varieties of barley to increase PIUE is related to optimizing the electron flow downstream of PSII, including cytochrome b₆f and photosystem I.

Recent Advances in Carbon and Nitrogen Metabolism in C3 Plants

C and N are the most important essential elements constituting organic compounds in plants. The shoots and roots depend on each other by exchanging C and N through the xylem and phloem transport systems. Complex mechanisms regulate C and N metabolism to optimize plant growth, agricultural crop production, and maintenance of the agroecosystem. In this paper, we cover the recent advances in understanding C and N metabolism, regulation, and transport in plants, as well as their underlying molecular mechanisms. Special emphasis is given to the mechanisms of starch metabolism in plastids and the changes in responses to environmental stress that were previously overlooked, since these changes provide an essential store of C that fuels plant metabolism and growth. We present general insights into the system biology approaches that have expanded our understanding of core biological questions related to C and N metabolism. Finally, this review synthesizes recent advances in our understanding of the trade-off concept that links C and N status to the plant's response to microorganisms.

Characterization of Rhizobia for the Improvement of Soybean Cultivation at Cold Conditions in Central Europe

In central Europe, soybean cultivation is gaining increasing importance to reduce protein imports from overseas and make cropping systems more sustainable. In the field, despite the inoculation of soybean with commercial rhizobia, its nodulation is low. In many parts of Europe, limited information is currently available on the genetic diversity of rhizobia and, thus, biological resources for selecting high nitrogen-fixing rhizobia are inadequate. These resources are urgently needed to improve soybean production in central Europe. The objective of the present study was to identify strains that have the potential to increase nitrogen fixation by and the yield of soybean in German soils. We isolated and characterized 77 soybean rhizobia from 18 different sampling sites. Based on a multilocus sequence analysis (MLSA), 71% of isolates were identified as Bradyrhizobium and 29% as Rhizobium. A comparative analysis of the nodD and nifH genes showed no significant differences, which indicated that the soybean rhizobia symbiotic genes in the present study belong to only one type. One isolate, GMF14 which was tolerant of a low temperature (4°C), exhibited higher nitrogen fixation in root nodules and a greater plant biomass than USDA 110 under cold conditions. These results strongly suggest that some indigenous rhizobia enhance biological nitrogen fixation and soybean yield due to their adaption to local conditions.

Effects of Different Chemical Forms of Nitrogen on the Quick and Reversible Inhibition of Soybean Nodule Growth and Nitrogen Fixation Activity

It has been reported that supply of nitrate to culture solution rapidly and reversibly inhibits nodule growth and nitrogen fixation activity of soybean. In this study, the effects of ammonium, urea, or glutamine on nodule growth and nitrogen fixation activity are compared with that for nitrate. Soybean plants were cultivated with a nitrogen-free nutrient solution, then 1 mM-N of nitrate, ammonium, glutamine, or urea were supplied from 12 DAP until 17 DAP. Repression of nodule growth and nitrogen fixation activity at 17 DAP were observed by ammonium, urea, and glutamine like nitrate, although the inhibitory effects were milder than nitrate. The removal of nitrogen from the culture solutions after nitrogen treatments resulted in a recovery of the nodule growth. It was found that the glutamine treatment followed by N-free cultivation gave highest nitrogen fixation activity about two times of the control. Tracer experiments with ¹⁵N and ¹³C were performed to evaluate the translocation of N and C to the different tissues. Culture solutions containing a ¹⁵N-labeled nitrogen source were supplied from 21 DAP, and the whole shoots were exposed to ¹³CO₂ for 60 min on 23 DAP, and plants were harvested on 24 DAP. The percentage distribution of ¹⁵N in nodules was highest for ammonium (1.4%) followed by glutamine (0.78%), urea (0.32%) and nitrate (0.25%). The percentage distribution of ¹³C in the nodules was highest for the control (11.5%) followed by urea (5.8%), glutamine (2.6%), ammonium (2.3%), and nitrate (2.3%). The inhibitory effects of nitrogen compounds appeared to be related to a decrease in photoassimilate partitioning in the nodules, rather than ¹⁵N transport into the nodules. The free amino acid concentrations after nitrogen treatments were increased in the nodules and leaves by nitrate, in the roots by ammonium, in the stems by urea, and the roots, stems, and leaves by glutamine treatment. The concentrations of asparagine, aspartate, and glutamine were increased after nitrogen treatments. By the long-term supply of nitrogen for 2-weeks, nitrate significantly increased the lateral roots and leaf growth. The long-term supply of urea and glutamine also promoted the lateral roots and leaf growth, but ammonium suppressed them.

Transcriptome and Metabolome Analyses Reveal That Nitrate Strongly Promotes Nitrogen and Carbon Metabolism in Soybean Roots, but Tends to Repress It in Nodules

Leguminous plants form root nodules with rhizobia that fix atmospheric dinitrogen (N₂) for the nitrogen (N) nutrient. Combined nitrogen sources, particular nitrate, severely repress nodule growth and nitrogen fixation activity in soybeans (Glycine max [L.] Merr.). A microarray-based transcriptome analysis and the metabolome analysis were carried out for the roots and nodules of hydroponically grown soybean plants treated with 5 mM of nitrate for 24 h and compared with control without nitrate. Gene expression ratios of nitrate vs. the control were highly enhanced for those probesets related to nitrate transport and assimilation and carbon metabolism in the roots, but much less so in the nodules, except for the nitrate transport and asparagine synthetase. From the metabolome analysis, the concentration ratios of metabolites for the nitrate treatment vs. the control indicated that most of the amino acids, phosphorous-compounds and organic acids in roots were increased about twofold in the roots, whereas in the nodules most of the concentrations of the amino acids, P-compounds and organic acids were decreased while asparagine increased exceptionally. These results may support the hypothesis that nitrate primarily promotes nitrogen and carbon metabolism in the roots, but mainly represses this metabolism in the nodules.

The Pharmacokinetic Exposure to Fexofenadine is Volume-Dependently Reduced in Healthy Subjects Following Oral Administration With Apple Juice

Pharmacokinetic exposures to fexofenadine (FEX) are reduced by apple juice (AJ); however, the relationship between the AJ volume and the degree of AJ‐FEX interaction has not been understood. In this crossover study, 10 healthy subjects received single doses of FEX 60 mg with different volumes (150, 300, and 600 mL) of AJ or water (control). To identify an AJ volume lacking clinically meaningful interaction, we tested a hypothesis that the 90% confidence interval (CI) for geometric mean ratio (GMR) of FEX AUC_AJ/AUC_water is contained within a biocomparability bound of 0.5–2.0, with at least one tested volume of AJ. GMR (90% CI) of AUC_{AJ 150mL}/AUC_water, AUC_{AJ 300mL}/AUC_water, and AUC_{AJ 600mL}/AUC_water were 0.903 (0.752–1.085), 0.593 (0.494–0.712), and 0.385 (0.321–0.462), respectively. While a moderate to large AJ‐FEX interaction is caused by a larger volumes of AJ (e.g., 300 to 600 mL), the effect of a small volume (e.g., 150 mL) appears to be not meaningful.

3-T MRI safety assessments of magnetic dental attachments and castable magnetic alloys

OBJECTIVES

To assess the safety of different magnetic dental attachments during 3-T MRI according to the American Society for Testing and Materials F2182-09 and F2052-06e1 standard testing methods and to develop a method to determine MRI compatibility by measuring magnetically induced torque.

METHODS

The temperature elevations, magnetically induced forces and torques of a ferromagnetic stainless steel keeper, a coping comprising a keeper and a cast magnetic alloy coping were measured on MRI systems.

RESULTS

The coping comprising a keeper demonstrated the maximum temperature increase (1.42 °C) for the whole-body-averaged specific absorption rate and was calculated as 2.1 W kg⁻¹ with the saline phantom. All deflection angles exceeded 45°. The cast magnetic alloy coping had the greatest deflection force (0.33 N) during 3-T MRI and torque (1.015 mN m) during 0.3-T MRI.

CONCLUSIONS

The tested devices showed minimal radiofrequency (RF)-induced heating in a 3-T MR environment, but the cast magnetic alloy coping showed a magnetically induced deflection force and torque approximately eight times that of the keepers. For safety, magnetic dental attachments should be inspected before and after MRI and large prostheses containing cast magnetic alloy should be removed. Although magnetic dental attachments may pose no great risk of RF-induced heating or magnetically induced torque during 3-T MRI, their magnetically induced deflection forces tended to exceed acceptable limits. Therefore, the inspection of such devices before and after MRI is important for patient safety.

Positions of pluripotency genes and hepatocyte-specific genes in the nucleus before and after mouse ES cell differentiation

Spatial positioning of genes in the cell nucleus plays an important role in the regulation of genomic functions. Evidence for changes in gene positioning associated with transcriptional activity has been reported. However, our understanding of this phenomenon is still quite limited. We examined how pluripotency genes and hepatocyte-specific genes behave during the differentiation of mouse embryonic stem (ES) cells into hepatocytes, by targeting the loci of the Klf4, Nanog, Oct4, Sox2, Cyp7α1, Pck1, Tat, and Tdo2 genes, and using three-dimensional fluorescence in situ hybridization analyses. We found that each gene has a distinctly inherent localization profile in the ES cell nucleus. During differentiation, the Klf4, Nanog, Oct4, Cyp7α1, Pck1, and Tat loci shifted toward the nuclear center, while the Sox2 and Tdo2 loci shifted toward the periphery. The Klf4, Nanog, Oct4, and Tdo2 seem to prefer the outer regions, rather than the inner regions, when they are active. We also found that the radial positioning of the focused genes in the hepatocyte cell nucleus was highly correlated with the local GC content and the gene density of the surrounding region, but not with gene activity.

Effect of nitrate on nodule and root growth of soybean (Glycine max (L.) Merr.)

The application of combined nitrogen, especially nitrate, to soybean plants is known to strongly inhibit nodule formation, growth and nitrogen fixation. In the present study, we measured the effects of supplying 5 mM nitrate on the growth of nodules, primary root, and lateral roots under light at 28 °C or dark at 18 °C conditions. Photographs of the nodulated roots were periodically taken by a digital camera at 1-h intervals, and the size of the nodules was measured with newly developed computer software. Nodule growth was depressed approximately 7 h after the addition of nitrate under light conditions. The nodule growth rate under dark conditions was almost half that under light conditions, and nodule growth was further suppressed by the addition of 5 mM nitrate. Similar results were observed for the extending growth rate of the primary root as those for nodule growth supplied with 5 mM nitrate under light/dark conditions. In contrast, the growth of lateral roots was promoted by the addition of 5 mM nitrate. The 2D-PAGE profiles of nodule protein showed similar patterns between the 0 and 5 mM nitrate treatments, which suggested that metabolic integrity may be maintained with the 5 mM nitrate treatment. Further studies are required to confirm whether light or temperature condition may give the primary effect on the growth of nodules and roots.

Nitrogen Fixation and Translocation in Young Sugarcane (Saccharum officinarum L.) Plants Associated with Endophytic Nitrogen-Fixing Bacteria

The tracer (15)N(2) was used to investigate sites of N(2) fixation and the possible translocation of the fixed N. Young sugarcane plants (Saccharum officinarum L.) from a stem cutting were exposed to (15)N(2)-labeled air in a 500 mL plastic cylinder. Plants fed (15)N(2) for 7 days were grown in normal air for a further chase period. After 21 days, about half of the N originating in the stem cutting had been transported to the shoot and roots, suggesting that the cutting played a role in supplying N for growth. After 3 days of feeding, the percentage of N derived from (15)N(2) was higher in the roots (2.22%) and stem cutting (0.271%) than the shoot (0.027%). Most of the fixed N was distributed in the 80% ethanol-insoluble fractions in each plant part, and the (15)N fixed either in the roots or in the stem cutting remained there and was not appreciably transported to the shoot. The results were quite different from the fate of fixed N in soybean nodules, which is rapidly transported from nodules to roots and shoots.

Azelnidipine is a calcium blocker that attenuates liver fibrosis and may increase antioxidant defence

BACKGROUND AND PURPOSE

Oxidative stress plays a critical role in liver fibrogenesis. Reactive oxygen species (ROS) stimulate hepatic stellate cells (HSCs), and ROS-mediated increases in calcium influx further increase ROS production. Azelnidipine is a calcium blocker that has been shown to have antioxidant effects in endothelial cells and cardiomyocytes. Therefore, we evaluated the anti-fibrotic and antioxidative effects of azelnidipine on liver fibrosis.

EXPERIMENTAL APPROACH

We used TGF-β1-activated LX-2 cells (a human HSC line) and mouse models of fibrosis induced by treatment with either carbon tetrachloride (CCl(4) ) or thioacetamide (TAA).

KEY RESULTS

Azelnidipine inhibited TGF-β1 and angiotensin II (Ang II)-activated α1(I) collagen mRNA expression in HSCs. Furthermore, TGF-β1- and Ang II-induced oxidative stress and TGF-β1-induced p38 and JNK phosphorylation were reduced in HSCs treated with azelnidipine. Azelnidipine significantly decreased inflammatory cell infiltration, pro-fibrotic gene expressions, HSC activation, lipid peroxidation, oxidative DNA damage and fibrosis in the livers of CCl(4) - or TAA-treated mice. Finally, azelnidipine prevented a decrease in the expression of some antioxidant enzymes and accelerated regression of liver fibrosis in CCl(4) -treated mice.

CONCLUSIONS AND IMPLICATIONS

Azelnidipine inhibited TGF-β1- and Ang II-induced HSC activation in vitro and attenuated CCl(4) - and TAA-induced liver fibrosis, and it accelerated regression of CCl(4) -induced liver fibrosis in mice. The anti-fibrotic mechanism of azelnidipine against CCl(4) -induced liver fibrosis in mice may have been due an increased level of antioxidant defence. As azelnidipine is widely used in clinical practice without serious adverse effects, it may provide an effective new strategy for anti-fibrotic therapy.

Enhancement of the nitrogen fixation efficiency of genetically-engineered Rhizobium with high catalase activity

The vktA catalase gene, which had been cloned from Vibrio rumoiensis S-1T having extraordinarily high catalase activity, was introduced into the root nodule bacterium, Rhizobium leguminosarum bv. phaseoli USDA 2676. The catalase activity of the vktA-transformed R. leguminosarum cells (free-living) was three orders in magnitude higher than that of the parent cells and this transformant could grow in a higher concentration of exogenous hydrogen peroxide (H2O2). The vktA-transformant was inoculated to the host plant (Phaseolus vulgaris L.) and the nodulation efficiency was evaluated. The results showed that the nitrogen-fixing activity of nodules was increased 1.7 to 2.3 times as compared to the parent. The levels of H2O2 in nodules formed by the vktA-transformant were decreased by around 73%, while those of leghemoglobins (Lba and Lbb) were increased by 1.2 (Lba) and 2.1 (Lbb) times compared with the parent. These results indicated that the increase of catalase activity in rhizobia could be useful to improve the nitrogen-fixing efficiency of nodules by the reduction of H2O2 content concomitantly with the enhancement of leghemoglobins contents.

Assimilation and translocation of nitrogen and carbon in Curcuma alismatifolia Gagnep

Curcuma or Siam tulip (Curcuma alismatifolia Gagnep.) is an ornamental flowering plant with two underground storage organs, rhizomes and storage roots. Characteristics of N and C assimilation and transport in curcuma were investigated. The plants were treated with (15)NH(4) (+) + (15)NO(3) (-) and (13)CO(2) at 10, 13 or 21 weeks after planting. Plants were sampled at several stages up to 32 weeks. The C stored in old storage roots was used rapidly during the first 10 weeks; after which N stored in old rhizomes and old storage roots were used. The daily gain in C depending on photosynthesis was remarkably high between 10 and 21 weeks. However, the daily gain in N was relatively constant throughout the growth period. The (15)N absorbed at 10 weeks was initially accumulated in leaves and roots, but some was transported to flowering organs at 13 weeks. At harvest, 41% of (15)N was recovered in new rhizomes and 17% in new storage roots. After (13)CO(2) exposure at 10 and 13 weeks, the distribution of (13)C among organs was relatively constant in subsequent stages. When given (13)CO(2) at 21 weeks, a large amount of labelled C was recovered in new storage roots and new rhizomes at harvest. Both new rhizomes and new storage roots stored N and C, however, rhizomes played a more important role in supplying N, while storage roots provided C.

Rapid quantification of cyanamide by ultra-high-pressure liquid chromatography in fertilizer, soil or plant samples

A rapid and simple method for determination of cyanamide in fertilizer, soil and plants has been developed. In this method, cyanamide is extracted with 2% acetic acid and the extract separated by centrifugation. It is then purified by passing through a membrane filter. The extract was derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl-carbamate and the derivatized compound separated by ultra-high-pressure liquid chromatography. It is then detected with a UV detector at 260 nm by the same method as is used for amino acid analysis. The proposed method is fast, simple and cheap and also has good selectivity and sensitivity for the determination of cyanamide in a wide range of biotic and abiotic materials.

The autoregulation of nodulation mechanism is related to leaf development

To understand the autoregulation of nodulation (AON) system, in which leguminous plants control the nodule number, we examined the details of the characteristics of hypernodulation soybean mutants NOD1-3 and NOD3-7. A microscopic study showed that NOD1-3 and NOD3-7 produced small-size leaves due to the smaller number of leaf cells, compared with the Williams parent. These phenotypes were not affected by inoculation with bradyrhizobia or nitrate supply. The AON signaling might be related to the control system of leaf cell proliferation. This hypothesis was strongly supported by the finding that activation of AON in wild types by inoculation leads to an increase in the cell number of leaves.

An outbreak of psittacosis in a bird park in Japan

An outbreak of psittacosis related to a bird park occurred in Matsue City, Shimane Prefecture, Japan, during winter 2001. Seventeen cases of psittacosis (12 visitors, three staff, and two student interns) were confirmed. A cohort study was conducted among the park staff and students to determine the risk factors for the development of acute serologically confirmed psittacosis (SCP) infection. Being 'bird staff' had an increased risk of SCP infection (RR 3.96, 95% CI 1.48-10.58). Entering the staff building, where ill birds were maintained without proper isolation, was also associated with an increased risk of SCP infection (RR 3.61, 95% CI 1.03-12.6). Isolation of ill birds and quarantine measures were found to be insufficient. Dehumidifiers and a high-pressure water spray under a closed ventilation environment may have raised the concentration of Chlamydophila psittaci in the hothouses. Bird park staff and visitors should be educated about psittacosis.

Objective and subjective hardness of a test item used for evaluating food mixing ability

The aim of this study was to compare objective and subjective hardness of selected common foods with a wax cube used as a test item in a mixing ability test. Objective hardness was determined for 11 foods (cream cheese, boiled fish paste, boiled beef, apple, raw carrot, peanut, soft/hard rice cracker, jelly, plain chocolate and chewing gum) and the wax cube. Peak force (N) to compress each item was obtained from force-time curves generated with the Tensipresser. Perceived hardness ratings of each item were made by 30 dentate subjects (mean age 26.9 years) using a visual analogue scale (100 mm). These subjective assessments were given twice with a 1 week interval. High intraclass correlation coefficients (ICCs) for test-retest reliability were seen for all foods (ICC > 0.68; P < 0.001). One-way anova found a significant effect of food type on both the objective hardness score and the subjective hardness rating (P < 0.001). The wax cube showed significant lower objective hardness score (32.6 N) and subjective hardness rating (47.7) than peanut (45.3 N, 63.5) and raw carrot (82.5 N, 78.4) [P < 0.05; Ryan-Einot-Gabriel-Welsch (REGW)-F]. A significant semilogarithmic relationship was found between the logarithm of objective hardness scores and subjective hardness ratings across twelve test items (r = 0.90; P < 0.001). These results suggest the wax cube has a softer texture compared with test foods traditionally used for masticatory performance test, such as peanut and raw carrot. The hardness of the wax cube could be modified to simulate a range of test foods by changing mixture ratio of soft and hard paraffin wax.

Detection system of Cryptosporidium parvum oocysts by brackish water benthic shellfish (Corbicula japonica) as a biological indicator in river water

The brackish water benthic shellfish, Corbicula japonica, was experimentally exposed to Cryptosporidium parvum oocysts at 1.51x10(4)oocysts/clam/day for 7 or 14 days. Oocysts were predominantly eliminated through the feces of Corbicula japonica in both cases by microscopic and PCR methods. The fecal excretion rates of oocysts within 4 days after the last exposure to Corbicula japonica were 87.6% for the 7-day exposure group and 86.0% for the 14-day exposure group. The tissue residue level of oocysts in the gastrointestinal tract 3 days after the last exposure was 2.7% of total exposed oocysts and that of 7 days was 1.1% for the 7-day exposure case and 1.6 and 0.5% for the 14-day exposure case, respectively, maintaining infectivity to cultured cells (HCT-8) in vitro. At the same time, field tests of Corbicula japonica for collecting oocysts showed that this clam could certainly collect Cryptosporidium parvum oocysts in the natural river and, furthermore, the gene type of C. parvum could be also identified proving its effectiveness as a biological indicator. The present study showed that the brackish water benthic shellfish Corbicula japonica may be capable of gathering and preserving Cryptosporidium parvum oocysts to a considerable extent under the natural ecological conditions, and further suggests the effectiveness of Corbicula japonica as a practical and general bioindicator for estimates of river water contamination by oocysts of Cryptosporidium parvum.

Influence of food platform width of mandibular removable partial denture on food mixing ability

The aim of this study was to clarify the influence of food platform width on food mixing ability in patients with mandibular removable partial dentures (RPDs). Twelve subjects (six males and six females, mean age 56.8 years) with intact dentition except for unilaterally missing mandibular first and second molars participated in the study. The food platforms of their RPDs were made of light polymerized composite and three platform conditions were evaluated. A food platform (Control condition) had 7 mm width with a central focus on the top of the residual ridge. Narrowed platforms (5 mm) were created by trimming a lingual portion (Buccally oriented occlusion, Buccal condition) or a buccal portion (Lingually oriented occlusion, Lingual condition) from the control. Subjects chewed a standardized wax cube which provided an estimate of food mixing ability [Mixing Ability Index (MAI)] for each of the three platforms. A significant effect (P < 0.001) on the MAI was found for food platform type (repeated measures one-way analysis of variance). Tukey multiple comparisons found significant differences of MAI between Control condition (1.05 +/- 0.26) and Buccal condition (0.86 +/- 0.23) (P = 0.032), and between Control and Lingual condition (0.54 +/- 0.37) (P < 0.001). Furthermore, MAI with Lingual condition was significantly smaller than that with Buccal condition (P < 0.001). These results suggest that reduction in the width of the food platform may impair masticatory function and the buccal portion of mandibular food platform of RPD is more critical for food mixing than the lingual portion of the platform.

The influence of altered occlusal guidance on condylar displacement during submaximal clenching

As cited in literatures, canine protected occlusion has a potential to reduce clenching induced temporomandibular joint loadings. However, these previous studies did not perform a control of the clenching level which differed with the depending occlusal conditions. This result may be due largely to an associated reduced jaw closing muscle activity. The present study has investigated clenching induced condylar displacements with controlled clenching level. Twenty healthy human subjects (15 males and five females with an average age of 26.5 years) volunteered to participate in this study. Metallic occlusal overlays were fabricated for the lower working side canine and overlaid to the second molar and the non-working side second molar in order to simulate a canine protected occlusion, group function occlusion and bilateral balanced occlusion. Electromyographic (EMG) activity from the bilateral masseter, anterior temporalis, and posterior temporalis was recorded. These signals were rectified, summarized, and presented to each subject using an oscilloscope screen. Using this visual feedback, subjects were asked to perform clenching tasks at a 50% level of maximal voluntary contraction exerted with simulated group function occlusion and three-dimensional condylar displacements were recorded. An experimental occlusal pattern that shows statistically significant affects on condylar displacements (anova: P<0.001) was found. When compared with the simulated canine protected occlusion, the simulated group function occlusion caused smaller working side condylar displacement and the simulated bilateral balanced occlusion caused significantly smaller non-working side and working side condylar displacements. These results suggest that the increased working side tooth contacts have a potential to reduce working side joint loadings, and a balancing side contact has a potential to reduce non-working side joint loadings, under the laboratory condition where the clenching level is controlled.

Detection of improvement in the masticatory function from old to new removable partial dentures using mixing ability test

The aim of this study was to determine the sensitivity of the Mixing Ability Test to detect improvement of masticatory function in subjects on transition from old to new removable partial dentures. Thirty-two subjects (seven males, 25 females, mean age 65.0 years) with distal extension partially edentulous area in mandible and/or maxilla participated in the study. The following reasons were presented for replacing the old removable partial dentures with new ones: fracture and/or poor fitness of retainers, extraction of abutment teeth, poor fitness of denture base, severe wear of artificial teeth and request for metal base dentures. Masticatory function with old and new removable partial dentures after an adaptation period (mean 27.4 weeks) was evaluated by the Mixing Ability Test. Subjects were asked to masticate five two-coloured wax cubes with each removable partial denture. Mixing Ability Index was obtained from the colour mixture and shape of the masticated cubes. Wilcoxon signed-rank test was used to test the difference of Mixing Ability Indexes between old and new removable partial dentures. The mixing ability indexes with new removable partial dentures (mean+/- s.d.: 0.70+/- 0.68) was significantly higher (P<0.001) than those with old removable partial dentures (-0.11+/-1.13). The results suggest that the Mixing Ability Test was capable of detecting improvement in masticatory function with new removable partial dentures.

Large-scale analysis of gene expression profiles during early stages of root nodule formation in a model legume, Lotus japonicus

Gene expression profiles during early stages of formation of symbiotic nitrogen-fixing nodules in a model legume Lotus japonicus were analyzed by means of a cDNA array of 18,144 non-redundant expressed sequence tags (ESTs) isolated from L. japonicus. Expression of a total of 1,076 genes was significantly accelerated during the successive stages that represent infection of Mesorhizobium loti, nodule primordium initiation, nodule organogenesis, and the onset of nitrogen fixation. These include 32 nodulin and nodulinhomolog genes as well as a number of genes involved in the catabolism of photosynthates and assimilation of fixed nitrogen that were previously known to be abundantly expressed in root nodules of many legumes. We also identified a large number of novel nodule-specific or enhanced genes, which include genes involved in many cellular processes such as membrane transport, defense responses, phytohormone synthesis and responses, signal transduction, cell wall synthesis, and transcriptional regulation. Notably, our data indicate that the gene expression profile in early steps of Rhizobium-legume interactions is considerably different from that in subsequent stages of nodule development. A number of genes involved in the defense responses to pathogens and other stresses were induced abundantly in the infection process, but their expression was suppressed during subsequent nodule formation. The results provide a comprehensive data source for investigation of molecular mechanisms underlying nodulation and symbiotic nitrogen fixation.

Finite element contact stress analysis of the RPD abutment tooth and periodontal ligament

OBJECTIVES

The purpose of this study was to determine the influence of the occlusal rest position in removable partial dentures on the displacement of the abutment tooth and the stress distribution in the periodontal ligament (PL).

METHODS

We constructed three-dimensional finite element models of the mandibular first and second premolars. A layer of the PL and a mesial or distal occlusal rest were produced on the second premolar as an abutment. A zero displacement was prescribed on the outer surface of the PL and the first premolar. In each simulation, the rest was moved 0.05 mm vertically to the apical direction, with or without restriction of horizontal movements. We simulated the contact phenomena on the abutment surfaces, and calculated the movements of the abutment and stress distributions in the PL.

RESULTS

We observed a maximum distal displacement of 42 microm at the buccal cusp of the abutment and a principal compressive stress of 0.35 MPa in the PL when the abutment was vertically loaded by a distal rest that was allowed to move horizontally. However, the displacements and stresses were relatively small, and were all within the physiological limitations of the tissues. The restriction of the horizontal movement of the rests was effective in reducing the horizontal displacements of the abutment, regardless of the rest position.

CONCLUSIONS

The single vertical load exerted from either the mesial or distal rest on the abutment was unlikely to cause any mechanical damage to its supporting tissues.

Salmonella Enteritidis outbreak associated with a school-lunch dessert: cross-contamination and a long incubation period, Japan, 2001

A Salmonella Enteritidis (SE) outbreak in Japan was investigated with an observational study, analytical epidemiology and bacteriological examination (including phage typing). The outbreak occurred among 96 schoolchildren, and was caused by SE phage type 1. The outbreak source was dessert buns served at a school lunch (RR 42.55, 95 % CI 5.93-305.11, P < 0.001). The buns were probably cross-contaminated from eggs from a factory with a history of SE-contaminated products. The incubation period was longer than usual (3-16 days, median 8 days). A low contaminating dose may account for the long incubation period and low attack rate. Outbreak detection was hampered by the absence of routine Salmonella surveillance in Japan. The investigation was complicated by concurrent illnesses from other SE phage types. It was successful, in part, because adequate food samples were available for microbiological testing.

Effect of metal strengthener length on stress distribution in acrylic denture bases: a finite element study

This study investigated the influence of metal strengthener length on stress created in acrylic denture bases in relation to location of the vertical support to the dentures. Finite element analysis was conducted to calculate stress generated in the straps of 2 mm-thickness and 18 mm-width that were reinforced with metal strengtheners of five different lengths. A vertical biting force of 60 N was directed on one end of each strap, while the other end was fixed. Vertical movements were restricted at one of the three support locations between the centre of the strap and the loading site. When the straps were vertically supported near the loading site, greater maximum tensile stresses were seen in the straps with relatively short strengtheners than those shown in the straps with longer strengtheners. The metal strengtheners with sufficient length may provide a preventive denture design against the acrylic fractures.

ProNectin F-grafted-ethylene vinyl alcohol copolymer (EVAL) as a liquid type material for treating cerebral aneurysm—An in vivo and in vitro study

The authors aimed to develop a liquid material for embolization of aneurysms. In vitro and in vivo performances of the new embolic material were examined by cell culture and using an aneurysm model made in common carotid arteries (CCAs) of adult rats. Engineered protein ProNectin F (PnF), which contains 13 sites of an arginine-glycine-aspartic acid (RGD), was grafted onto ethylene vinyl alcohol copolymer (EVAL-g-PnF). The liquid material, EVAL-g-PnF dissolved in DMSO, was infused into an aneurysm model. The blood segments were harvested 2, 5, and 14 days and examined histologically. A number of bovine coronary artery endothelial cells became able to attach to and form cobblestone-like islands on the EVAL by incorporating PnF. The aneurysm model infused with the EVAL-g-PnF solution revealed that the aneurysm lumen was filled with proliferated fibroblasts and macrophages. On the other hand, the aneurysm model treated with unmodified EVAL showed that the cavity was almost filled with EVAL mass and that fibroblasts and macrophages filled a narrow space between the EVAL mass and the cavity wall. The results indicate that EVAL-g-PnF could be more suitable for reorganizing the cavity of an aneurysm than native EVAL.

3-D Finite element analysis of all-ceramic posterior crowns

The purpose of this study was to evaluate the stress distribution under various loading conditions within posterior all-ceramic crowns. A three-dimensional finite element model representing a lower first molar was constructed. Variations of the model had two types of single layer all-ceramic crowns (Dicor and Empress) and two types of double layer all-ceramic crowns (In-Ceram and Empress2) cemented. A load of 600 N, simulating the maximum bite force, was applied vertically to the crowns. Loads of 225 N, simulating masticatory force, were applied from three directions (vertically, at a 45 degrees angle, and horizontally). In the test simulating maximum bite force, the maximum tensile stresses on all crowns (17.4-19.4 MPa) concentrated around the loading points. In the masticatory force simulation test, the specimens experienced maximum tensile stresses of 19.7-27.0 MPa under a horizontal load and 10.8-10.9 MPa under a vertical load. When the load was applied horizontally, the maximum tensile stress was observed around the loading points on the surface in the case of the single layer crowns, and of the cervical area of the inner core of the double layer crowns. Within the limitation of this study, it was found that the strength of occlusal contact points is important to the integrity of posterior all-ceramic crowns and that bite forces applied from the horizontal direction are a critical factor.

Quick and reversible inhibition of soybean root nodule growth by nitrate involves a decrease in sucrose supply to nodules

The upper part of a nodulated soybean root hydroponically cultured in a glass bottle was monitored using a computer microscope under controlled environmental conditions, and the diameter of individual nodules was measured from 10-24 d after planting. The diameter of a root nodule attached to the primary root increased from 1 mm to 6 mm for 2 weeks under nitrogen-free conditions. The increase in diameter of the nodules was almost completely stopped after 1 d of supplying 5 mM nitrate, and was due to the cessation of nodule cell expansion. However, nodule growth quickly returned to the normal growth rate following withdrawal of nitrate from the solution. The reversible depression of nodule growth by nitrate was similar to the restriction of photoassimilate supply by continuous dark treatment for 2 d followed by normal light/dark conditions. In addition, the inhibitory effect of nitrate was partially alleviated by the addition of 3% (w/v) sucrose to the medium. Plant leaves were exposed to (11)C or (14)C-labelled carbon dioxide to investigate the effects of 5 mM nitrate on the translocation and distribution of photosynthates to nodules and roots. Supplying 5 mM nitrate stimulated the translocation rate and the distribution of labelled C in nitrate-fed parts of the roots. However, the (14)C partitioning to nodules decreased from 9% to 4% of total (14)C under conditions of 5 mM nitrate supply. These results indicate that the decrease in photoassimilate supply to nodules may be involved in the quick and reversible nitrate inhibition of soybean nodule growth.

Influence of working side contacts on masticatory function for mandibular distal extension removable partial dentures

The aim of this study was to clarify the influence of working side contacts for masticatory function for a distal extension removable partial denture. Five subjects who had edentulous arches from second premolar to second molar opposing natural teeth participated. Working side contacts were altered by using three types of artificial teeth attached to the denture base. A-form teeth made contact with opposite teeth while acting as the working side in a lateral excursion. The cusp angles of B- and C-form teeth were decreased by 10 degrees and 20 degrees, respectively compared with A-form teeth. B-and C-form teeth discluded with opposite teeth on the working side. Subjects were asked to perform two kinds of masticatory performance test. Obtained data were evaluated by the repeated-measures anova and the Tukey test for multiple comparisons. Results revealed that there was a significant difference (P=0.001) in the three types of teeth in the mixing ability test and the value of A-form teeth was statistically less value than those of the other teeth. However, there was no significant difference in the comminuting ability test. These results suggested that working side contacts between artificial teeth and opposite natural teeth influenced mixing ability, but not comminuting ability.

Validity and reliability of a newly developed method for evaluating masticatory function using discriminant analysis

The objective of the study was to assess validity and reliability of a newly developed method for evaluating mixing ability of masticatory function. A two-coloured paraffin wax cube was used as a test food in the mixing ability test. Eleven full dentate and 33 denture wearers participated in the validity assessment. They were divided into three groups according to their dental state. Validity was assessed by the Spearman's coefficient of correlations between the mixing ability test and the sieving method used as a 'gold standard' test of the masticatory performance. The subjects were asked to masticate the test foods for 5, 7, 10, 15, 20 and 30 strokes in each test. Significant correlations (P < 0.001) were obtained in natural dentition group (r(s) = 0.66), in denture-natural dentition group (r(s) = 0.72) and in denture-denture group (r(s) = 0.56). In the reliability assessment, three full dentate subjects were asked to repeat the mixing ability test a number of times. The intraclass correlation coefficients were 0.94 in interexaminer consistency, 0.98 in intra-examiner consistency, 0.89 in test-retest consistency and 0.99 in measuring consistency. These results indicated that the mixing ability test had the validity and the reliability for evaluation of the masticatory performance.

Bone mineral density of the mandible in ovariectomized rats: analyses using dual energy X-ray absorptiometry and peripheral quantitative computed tomography

INTRODUCTION

Although previous studies have shown that maxillary molar extraction in ovariectomized (OVX) animals causes mandibular loss of bone, it is still questionable as to whether estrogen deficiency affects mandibles with functional occlusion.

MATERIALS AND METHODS

To answer this question, 13-week-old female Sprague-Dawley rats were bilaterally OVX or sham-operated. After 109 days, the bone mineral density (BMD) of the femurs and mandibles was measured using dual-energy X-ray absorptiometry (DEXA) and peripheral quantitative computed tomography (pQCT).

RESULTS

In DEXA analysis, although the BMD of the total mandible of the OVX rats was similar to that of the sham-operated rats, the BMD of the condylar region in the OVX rats had decreased by 12.5%. In pQCT analysis, decrease in trabecular BMD of the mandibular bone was detectable but low in the molar region (maximal 13%), whereas no difference was seen in cortical BMD. In the femurs, the trabecular bone prominently decreased in OVX rats (30% decrease in pQCT analysis) as previously reported.

CONCLUSION

This study revealed regional differences in the mandibular bone decrease in OVX rats. Although the mechanism of low susceptibility of the mandible to estrogen-deficient conditions remains unknown, it is likely that mechanical stress derived from functional occlusion is preventing bone loss in this pathological condition. Furthermore, this study demonstrated the advantage of pQCT in analyzing rat mandibular bone.