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PubMed2005

Multiple resistance of acetolactate synthase and protoporphyrinogen oxidase inhibitors in Euphorbia heterophylla biotypes.

Resistance to acetolactate synthase (ALS)-inhibiting herbicides in Brazil has been documented for six species. The probability to select biotypes of Euphorbia heterophylla (EPPHL) with multiple resistance increases in the same order of magnitude as the use of other herbicides belonging to only one mechanism of action. The objectives of this work were to evaluate the distribution of resistant populations (R) in the states of the Parana and Santa Catarina; to determine the existence of populations of EPHHL with multiple resistance to ALS and PROTOX inhibitors, and to confirm the occurrence of cross resistance to compounds of these mechanisms of action. Seeds of EPHHL of areas with suspected resistance had been sampled in 97 places during 2003. In the greenhouse experiment samples of each population were sprayed with imazethapyr or fomesafen, at only one rate. To identify the resistant ones they were sprayed with different levels of the herbicides imazethapyr and fomesafen. Later they were sprayed with diverse herbicides of the same mechanisms of action to confirm the multiple/cross resistance. There is widespread distribution in the region of populations with resistance to ALS inhibitors. Some biotypes demonstrated resistance to herbicides from the two mechanisms of action. The resistance factor (FR), or the relation of resistance between R and susceptible biotypes, confirms the existence of two biotypes of EPHHL with cross resistance to several herbicides inhibitors of ALS and PROTOX.

Acetolactate Synthase↗
PubMed2006

Regulation of hormone metabolism in Arabidopsis seeds: phytochrome regulation of abscisic acid metabolism and abscisic acid regulation of gibberellin metabolism.

In a wide range of plant species, seed germination is regulated antagonistically by two plant hormones, abscisic acid (ABA) and gibberellin (GA). In the present study, we have revealed that ABA metabolism (both biosynthesis and inactivation) was phytochrome-regulated in an opposite fashion to GA metabolism during photoreversible seed germination in Arabidopsis. Endogenous ABA levels were decreased by irradiation with a red (R) light pulse in dark-imbibed seeds pre-treated with a far-red (FR) light pulse, and the reduction in ABA levels in response to R light was inhibited in a phytochrome B (PHYB)-deficient mutant. Expression of an ABA biosynthesis gene, AtNCED6, and the inactivation gene, CYP707A2, was regulated in a photoreversible manner, suggesting a key role for the genes in PHYB-mediated regulation of ABA metabolism. Abscisic acid-deficient mutants such as nced6-1, aba2-2 and aao3-4 exhibited an enhanced ability to germinate relative to wild type when imbibed in the dark after irradiation with an FR light pulse. In addition, the ability to synthesize GA was improved in the aba2-2 mutant compared with wild type during dark-imbibition after an FR light pulse. Activation of GA biosynthesis in the aba2-2 mutant was also observed during seed development. These data indicate that ABA is involved in the suppression of GA biosynthesis in both imbibed and developing seeds. Spatial expression patterns of the AtABA2 and AAO3 genes, responsible for last two steps of ABA biosynthesis, were distinct from that of the GA biosynthesis gene, AtGA3ox2, in both imbibed and developing seeds, suggesting that biosynthesis of ABA and GA in seeds occurs in different cell types.

Abscisic Acid↗
PubMed1988

Experimental Studies on Lateral Root Formation in Radish Seedling Roots: II. Analysis of the Dose-Response to Exogenous Auxin.

Application of indoleacetic acid (IAA) and other auxins causes cultured radish (Raphanus sativus L. ;Scarlet Globe') seedling root segments to produce an increased frequency (FR, no. cm(-1)) of lateral roots (LR); in the absence of auxin, segments spontaneously form about 6 LR cm(-1). A dose-response study has revealed that the increase in FR follows a biphasic Michaelis-Menten relationship with the medium concentration of the undissociated form of IAA ([IAAH](m)). The fitted curve for phase I has a maximum response level (R(max)) of 5.2 LR per centimeter above the spontaneous FR; the [IAAH](m) giving half-maximal response (C(1/2)) is 21 nanomolar. For phase II, the values for R(max) and C(1/2) are 56 LR per centimeter and 11 micromolar, respectively. The response is variable in the transition concentration region between the two phases; in that region (but not, or much less commonly, at higher or lower [IAAH](m)), LR initiation may resume or continue after the first day. At and above 100 micromolar [IAAH](m), the roots are hyperstimulated and generally fail to respond. The developmental stage of LR formed in medium with very low [IAAH](m) (10 nanomolar) is enhanced compared to LR formed in medium lacking auxin; the stage is diminished at higher auxin levels, in inverse correlation with FR. Trends in the responses to NAA and IBA were similar, but NAA required only 0.03 times the dose of IAA, while IBA required 6 times the dose of IAA. These findings may be of use in a search for possible auxin receptors involved with LR initiation.

Journal Article↗
PubMed1978

Ultraviolet-B Radiation-induced Inhibition of Leaf Expansion and Promotion of Anthocyanin Production: Lack of Involvement of the Low Irradiance Phytochrome System.

Leaf discs from expanding leaves of Rumex patientia L. were exposed to 7 hours of visible plus different levels of ultraviolet radiation in the 290 to 315 nm waveband (UV-B) and then placed in darkness. Leaf disc expansion was reduced and anthocyanin production was increased in discs exposed to moderate or high levels of UV-B radiation when compared to control discs. The possibility that the inhibition of leaf expansion by UV-B radiation might be at least partially phytochrome-mediated was examined by giving discs brief red or far red irradiation following exposure to UV-B radiation. Brief red radiation (R) following treatment with moderate or high UV-B radiation did not alter the pattern of growth or anthocyanin production compared to discs placed in darkness following UV-B treatment. However, a posttreatment with far red radiation (FR) reduced the growth of discs subjected previously to either moderate UV-B or no UV-B irradiation to the level of growth of discs given high UV-B. FR posttreatment also decreased anthocyanin production in discs in moderate and high UV-B treatments. Effects of FR and UV-B radiation apparently do not involve the same mechanism. This was demonstrated by experiments in which FR following the UV-B treatments was in turn followed by R, which reversed the effects of the FR but did not alter the growth inhibition or increased anthocyanin production induced by moderate or high levels of UV-B radiation.

Journal Article↗
PubMed2003

Are NADP-dependent isocitrate dehydrogenases and ferredoxin-dependent glutamate synthase co-regulated by the same photoreceptors?

Activities of NADP-dependent isocitrate dehydrogenases (cytosolic and plastidic isoforms, ICDH1 and ICDH2; EC 1.1.1.42) and ferredoxin-dependent glutamate synthase (Fd-GOGAT; EC 1.4.7.1) in turions of Spirodela polyrhiza were all stimulated by light. Single or repeated red light (R) pulses induced the activity of the enzymes and this effect was reverted by subsequent far-red light (FR) pulses. The enzymes are, therefore, co-regulated by the low-fluence response of phytochrome. For ICDH, this is reported here for the first time. Neither an effect of the very low-fluence response nor of the FR-mediated high-irradiance response was detectable. Irradiance with continuous R resulted in enhanced enzyme activities and protein levels (Western analysis using polyclonal antibodies against ICDH1 and Fd-GOGAT). These additional effects of continuous R (called a "non-induction effect") could be inhibited for ICDH1 and ICDH2 by the inhibitor of photosynthetic electron transport, 3-(3',4'-dichlorophenyl)-1,1-dimethylurea, and are therefore related to the effect of photosynthesis. In contrast, the non-induction effect of Fd-GOGAT was resistant against this inhibitor. Moreover, hourly R pulses did not replace the effect of continuous R. The non-induction effect of light on the activity and protein level of Fd-GOGAT was therefore tentatively classified as an R-mediated high-irradiance response. The activity of Fd-GOGAT but not that of ICDHs was additionally regulated by a specific blue-light receptor. It can be concluded that the levels of ICDHs and Fd-GOGAT were coordinated by light but were not co-regulated by the same photoreceptors. Nitrate is necessary for the light regulation of both enzymes, contributing to the coordinated expression of the relevant genes.

Amino Acid Oxidoreductases↗
PubMed2001

Intracellular localization of phytochrome in Robinia pseudoacacia pulvini.

The intracellular localization of phytochrome in the pulvini of Robinia pseudoacacia L. was analyzed by immunogold electron microscopy after red (R; 15 min) and far-red (FR; 5 min) irradiation 2 h after the beginning of the photoperiod. Screening of the available antibodies by immunoblotting demonstrated that none of the oat (Avena sativa L.) anti-phytochrome A (phy A) monoclonal antibodies) (MAbs) detected Robinia phytochrome. A putative Robinia phy A was detected by immunoblotting using a MAb to mustard (Sinapis alba L.) phy A (CP 2/9). No cross-reactivity was observed in blots probed with a MAb against Cucumis sativus L. phy B (mAT1). Ultrathin sections of LR White resin-embedded pulvini were immunolabelled with CP 2/9 MAb. The labelling was restricted to cortical cells and there was no evidence of labelling either in the vascular system or in the epidermis. The pattern of labelling was the same in both extensor and flexor cells irrespective of whether phytochrome was in the far-red-absorbing (Pfr) state or had reverted to the red-absorbing (Pr) form. Isolated labels and clusters of labels were randomly distributed throughout the cytoplasm. Gold particles were also found in the interior of nuclei, chloroplasts and mitochondria.

Biological Transport↗
PubMed2006

Phytochrome structure and signaling mechanisms.

Phytochromes are a widespread family of red/far-red responsive photoreceptors first discovered in plants, where they constitute one of the three main classes of photomorphogenesis regulators. All phytochromes utilize covalently attached bilin chromophores that enable photoconversion between red-absorbing (P(r)) and far-red-absorbing (P(fr)) forms. Phytochromes are thus photoswitchable photosensors; canonical phytochromes have a conserved N-terminal photosensory core and a C-terminal regulatory region, which typically includes a histidine-kinase-related domain. The discovery of new bacterial and cyanobacterial members of the phytochrome family within the last decade has greatly aided biochemical and structural characterization of this family, with the first crystal structure of a bacteriophytochrome photosensory core appearing in 2005. This structure and other recent biochemical studies have provided exciting new insights into the structure of phytochrome, the photoconversion process that is central to light sensing, and the mechanism of signal transfer by this important family of photoreceptors.

Models, Molecular↗
PubMedDate not supplied

Phytochrome-mediated inhibition of coleoptile growth in rice: age-dependency and action spectra.

Phytochrome has been shown to be the major photoreceptor involved in the photo-inhibition of coleoptile growth in Japonica-type rice (Oryza sativa L.). We have characterized this typical photomorphogenetic response of rice using mutants deficient in phytochrome A (phyA) and phytochrome B (phyB) and with respect to age-dependency and action spectra. Seedlings were irradiated with a pulse of light 40 h or 80 h after germination (i.e. at an early or late developmental stage) and the final coleoptile length of these seedlings was determined. A saturating pulse of red light (R) had a stronger effect when it was given in the late stage than in the early stage. It was found that the photoinhibition is mediated by both the phyA and the phyB in the late stage but predominantly by phyB in the early stage. Consistent with many other reported responses, the photo-inhibition in the phyA mutant, which was observed in the early and late developmental stages and is thought to be mediated mainly by phyB, occurred in the low-fluence range (10(1)-10(3) micromol m(-2)) of R and was far-red-light (FR)-reversible; the photo-inhibition in the phyB mutant, which was observed in the late developmental stage and is thought to be mediated mainly by phyA, occurred in the very-low-fluence range (10(-2)-10(0) micromol m(-2)) and was FR-irreversible. The action spectra (350-800 nm at 50 nm intervals) obtained at the two developmental stages using phyA and phyB mutants indicated that both the phyB-mediated low-fluence response and the phyA-mediated very-low-fluence response have a major peak at 650 nm and a minor peak at 400 nm.

Cotyledon↗
PubMedDate not supplied

Changes in serum IgG oligosaccharide chains with prostate cancer progression.

BACKGROUND: Changes of serum IgG oligosaccharide chain structure have been found in B cell lineage tumors and autoimmune diseases. Currently, the cancer-associated carbohydrate epitopes CA72-4 and CA15-3 are used as serum tumor markers. In the present study, we analyzed the structure of serum IgG oligosaccharide chains in prostate cancer (PCa) patients using the simple new method of fluorophore-associated carbohydrate electrophoresis (FACE). We also evaluated the relationship between changes of serum IgG oligosaccharide chain structure and serum concentration of prostate-specific antigen (PSA). MATERIALS AND METHODS: The structure of serum IgG oligosaccharide chains from 12 PCa patients (6 localized cancer, 6 metastatic cancer) and 10 healthy controls was evaluated by FACE. PSA levels in serum were determined by enzyme immunoassay. RESULTS: Fr 1 (monogalactosyl oligosaccharide) and Fr 2 (digalactosyl oligosaccharide) decreased significantly (p<0.05), while Fr 4 (agalactosyl IgG oligosaccharide) increased with PCa tumorprogression. The Fr 4/Fr 1+2 ratio in metastatic PCa patients was significantly higher than in healthy controls (p<0.05), and there was a significant correlation (r=0.84, p<0.05) between serum PSA levels and the Fr 4/Fr 1+2 ratio in all patients with PCa. CONCLUSION: The changes of serum IgG oligosaccharide chain structure with PCa progression are based on the abnormality of glycosylation in PCa metastasis. Therefore, the analysis of serum IgG oligosaccharide chain structure by FACE may be an auxiliary indicator of PSA for monitoring PCa progression.

Aged↗
PubMed1969

Phytochrome in cultured wild carrot tissue. I. Synthesis.

Stable levels of P(FR) occur in light-grown suspension cultures of wild carrot. Upon darkening such tissue, P(R) accumulates until the high P(R) level characteristics of dark-grown tissue is reached. Data are compatible with the idea of an equilibrium between processes of synthesis and destruction in tissue grown in the light. Reappearance of phytochrome also follows light-induced pigment destruction in dark-grown tissue. The rate of P(R) appearance is similar in both cases. The rate of disappearance of P(FR), however, is slower in light-grown tissue than in dark-grown tissue.

Journal Article↗
PubMedDate not supplied

Prediction of chemical carcinogenicity from molecular structure.

Carcinogens represent a serious threat to human health. In vivo determination of carcinogenicity is time-consuming and expensive, thus in silico models to predict chemical carcinogenicity are highly desirable for virtual screening of compound libraries of both pharmaceutically and other commercially interesting molecules. In the present study, a PLS-DA (partial least squares discriminant analysis) model was developed to predict carcinogenicities in each of four rodent models: male mouse (MM), female mouse (FM), male rat (MR), and female rat (FR). The data set that was used contained over 520 compounds from both the NTP and the FDA databases. All the models were built from the same molecular descriptor system, which is based on atom typing [Sun, H. J. Chem. Inf. Comput. Sci. 2004, 44, 748-757], enabling the comparison of atomic contributions to carcinogenicity with respect to species and gender. Using four components, the models were able to achieve excellent fitting and prediction, with r(2) = 0.987 and q(2) = 0.944 for MM, r(2) = 0.985 and q(2) = 0.950 for FM, r(2) = 0.989 and q(2) = 0.962 for MR, and r(2) = 0.990 and q(2) = 0.965 for FR. The models were further validated by response permutation testing and external validation, and the results indicated that the models were both statistically significant and predictive. Variable influence on projection (VIP) analysis identified the key atom types and fragments that contributed to carcinogenicities and response differences across species and gender.

Animals↗
PubMed2005

Circumnutation of rice coleoptiles: its occurrence, regulation by phytochrome, and relationship with gravitropism.

It has been found that coleoptiles of dark-grown rice (Oryza sativa L.) seedlings undergo regular circumnutation in circular orbits with periods of about 180 min. Both clockwise and counter-clockwise movements were observed, but individual coleoptiles continued to rotate only in one direction. Light-grown seedlings did not show circumnutation. In fact, dark-grown seedlings were found to cease circumnutating in response to a pulse of red light (R). This light-induced inhibition of circumnutation was demonstrated to involve both a FR-inducible very-low-fluence response, solely mediated by phytochrome A, and a FR-reversible low-fluence response, mediated by phytochrome B and/or C. The R-induced inhibition of circumnutation showed temporal agreement with the R-induced inhibition of coleoptile growth, suggesting that the former results from the latter. However, about 25% of growth activity remained after R treatment, indicating that circumnutation is more specifically regulated by phytochrome. The R-treated coleoptile showed gravitropism. Investigation of the growth differential for gravitropic curvature revealed that gravitropic responsiveness was rather enhanced by R. The results suggested that gravitropism is not a cause of circumnutation. It remained probable, however, that gravity perception is a part of the mechanism of circumnutation. It is speculated that the circumnutation investigated aids the seedling shoot in growing through the soil.

Cotyledon↗
PubMed2004

The role of alpha-folate receptor-mediated transport in the antitumor activity of antifolate drugs.

PURPOSE: Raltitrexed, pemetrexed, lometrexol, and ZD9331 are antifolate drugs transported into cells via the ubiquitously expressed reduced-folate carrier. They display also high affinity for the alpha-folate receptor (alpha-FR), a low capacity folate transporter that is highly overexpressed in some epithelial tumors. The role of alpha-FR in the activity of the antifolates has been evaluated in two alpha-FR-overexpressing cell lines grown in a physiological concentration of folate (20 nM R,S-Leucovorin). EXPERIMENTAL DESIGN AND RESULTS: A431-FBP cells (transfected with the alpha-FR) were 3-5-fold more sensitive to the antifolates than A431 cells. KB cells (constitutive alpha-FR overexpression) were less sensitive to the drugs when coexposed to 1 microM folic acid to competitively inhibit binding to the alpha-FR. Raltitrexed, pemetrexed, and lometrexol are polyglutamated in cells leading to drug retention, e.g., the raltitrexed 4- and 24-h IC(50)s in A431 cells were approximately 0.6 and 0.008 microM, respectively, compared with 0.003 microM for 72-h continuous exposure. A431-FBP cells were approximately 3-fold more sensitive to raltitrexed and pemetrexed at all exposure times. ZD9331 is not polyglutamated, and the 4- and 24-h IC(50)s in A431 cells were >100 and approximately 100 microM, respectively, reducing to 2 and 0.1 microM, respectively, in A431-FBP cells. The ZD9331 4- and 24-h IC(50)s in KB cells were 20 and 1 microM, respectively, and reversible by coaddition of 1 microM folic acid. An in situ thymidylate synthase assay demonstrated continued thymidylate synthase inhibition after ZD9331-treated A431-FBP and KB, but not A431, cells were placed in drug-free medium for 16 h. A model is proposed in which the antifolates accumulate in the alpha-FR/endosomal apparatus, leading to slow release into the cytoplasm. In particular, this leads to cellular retention of the nonpolyglutamatable ZD9331. CONCLUSIONS: Antifolate drugs, particularly ZD9331, have the potential for increased efficacy in tumors that highly overexpress the alpha-FR.

Antimetabolites, Antineoplastic↗
PubMed1981

Prolonged microwave irradiation of rats: effects on concurrent operant behavior.

Two measures of performance were used to study the effects of pulse-modulated microwave radiation (PM MWR) on schedule-controlled operant behavior of rats: 1) cued (SD), fixed-ratio (FR) bar pressing for food reinforcement; and 2) noncued (Sd) bar pressing in the absence of food reinforcement. The animals were irradiated and the behavioral data were obtained concurrently, during daily three-hour sessions, five days per week for six to nine weeks. Each experiment began with a two to three-week baseline interval of sham irradiation; a two to three-week interval of sham irradiation followed the irradiation phase. The irradiated animals were exposed to 1.3-Ghz PM MWR (pulse width of 1 microsecond at 600 pulses per second) at whole-body, average specific absorbed-dose rates of from 1.5-6.7 m W/g. Control and irradiated animals were tested in identical, cylindrical waveguide exposure/behavioral assemblies; different groups of irradiated and sham-irradiated animals were used for each dose rate. At 1.5 mW/g, the levels of SD operant responding by control and irradiated animals were comparable, and showed similar progressive diminutions over the course of each daily session. Sd operant responding was more variable, but again comparable, with both groups showing similar, progressive declines in rate of responding during each session. At 3.6 mW/g, no specific effects on SD operant response rates were observed. However, there was an initial and transient increase in the rate of extinction of Sd responding. At 6.7 mW/g, SD response rates were slightly reduced, whereas there was a major reduction in noncued (Sd) operant responding followed by a sharp rebound during the first post-MWR week. This marked reduction in Sd operant responding at MWR onset was in contrast to the relative stability and persistence of FR responding for food reinforcement.

Animals↗
PubMed1998

Modified sperm stress test: a simple assay that predicts sperm-related abnormal in-vitro fertilization.

Loss of sperm motility is associated with the process of sperm senescence and occurs at different rates within a given normal or abnormal sperm population. Reactive oxygen species attack cell membrane phospholipids, generating fatty acid peroxides and other degradation products, that also have deleterious effects on sperm motility and fertilizing ability. The objective of this investigation was to study a modification of the original sperm stress test (MOST), changing the culture medium to one offering transitional metals and shortening the total test time, to ascertain whether it can predict fertilization under these laboratory conditions. A total of 41 semen samples was obtained from patients undergoing in-vitro fertilization (IVF) at our institution. Semen samples were grouped into those producing total fertilization rates (FR) within normal limits (>50%) and those showing low total FR (<50%). The normal FR group had a significantly greater MOST mean value than the low FR group (0.71 versus 0.44). Furthermore, there was a statistically significant correlation between the MOST score and ungrouped fertilization rates (r = 0.53, P = 0.0004). Diagnostic statistics for MOST ratio values predicting <50% FR showed an optimal threshold of 0.39. Collectively, sensitivity, specificity, positive predictive value and negative predictive value have their largest values at this threshold. Taking into account the above mentioned threshold figures, there is a significant association between MOST and FR categories (P = 0.0009). In conclusion, MOST is a simple assay that has significant predictive value for sperm related IVF abnormalities.

Adult↗
PubMed1964

REINFORCEMENT OF DRINKING BY RUNNING: EFFECT OF FIXED RATIO AND REINFORCEMENT TIME.

Rats were required to complete varying numbers of licks (FR), ranging from 10 to 300, in order to free an activity wheel for predetermined times (CT) ranging from 2 to 20 sec. The reinforcement of drinking by running was shown both by an increased frequency of licking, and by changes in length of the burst of licking relative to operant-level burst length. In log-log coordinates, instrumental licking tended to be a linear increasing function of FR for the range tested, a linear decreasing function of CT for the range tested. Pause time was implicated in both of the above relations, being a generally increasing function of both FR and CT.

Alcohol Drinking↗
PubMed2004

Single-step, self-etch adhesives behave as permeable membranes after polymerization. Part III. Evidence from fluid conductance and artificial caries inhibition.

PURPOSE: To test the hypothesis that formation of inhibition zones by bonded restorations in artificially-induced carious dentin lesions is related to the permeability of the self-etch adhesives. METHODS: Fluid conductance of four single-step self-etch adhesives (Prompt L-Pop, Etch&Prime 3.0, One-Up Bond F and Reactmer Bond), and a control two-step self-etch adhesive (UniFil Bond) were measured after sound dentin surfaces were:(1) acid-etched; (2) polished to produce smear layers; (3) bonded with the adhesive; each at 20 cm hydrostatic pressure (hp). Osmotic fluid conductance was also determined for the bonded dentin after immersion in 4.8 M CaCl2 at 0 cm hp. For artificial caries inhibition, a non-fluoride releasing (NFR) two-step self-etch adhesive (UniFil Bond) and a fluoride-releasing (FR) single-step adhesive (Reactmer Bond) were used in combination with a NFR composite (Metafil CX) or a FR restorative material (Reactmer Paste). Artificial caries were induced in these restorations, from which 120 +/- 10 microm thick sections and the effect of caries inhibition were quantitatively assessed with polarizing light microscopy and image analysis. RESULTS: Fluid conductance after bonding with the single-step adhesives Prompt L-Pop and Etch&Prime 3.0 were not significantly different from those recorded from smear layer-covered dentin. Although better seals were achieved with One-Up Bond F and Reactmer Bond, fluid conductance at 20 cm hp was significantly higher than the two-step self-etch adhesive UniFil Bond. Osmotic conductance at 0 cm hp were not significantly different from normal fluid conductance at 20 cm hp. The sizes of artificial carious lesions in UniFil Bond were significantly higher irrespective of whether a FR or NFR composite was used. Significant reduction in lesion size occurred in Reactmer Bond with the use of a NFR composite, and even more so with the use of a FR composite.

Acid Etching, Dental↗