Search Results - (Author, Cooperation:L. Fitzgerald)

2015-09-17

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

1399-3054

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Ribonucleases (RNases) degrade RNA and exert a major influence on gene expression during development and in response to biotic and abiotic stresses. RNase activity typically increases in response to pathogen attack, wounding and phosphate (Pi) deficiency. Activity also increases during senescence and other programmed cell death processes. The air pollutant ozone (O3) often induces injury and accelerated senescence in many plants, but the biochemical mechanisms involved in these responses remain unclear. The objective of this study was to determine whether RNase activity and isozyme expression was stimulated in wheat (Triticum aestivum L.) flag leaves following treatment with O3. Plants were treated in open-top chambers with charcoal-filtered air (27 nmol O3 mol−1) (control) or non-filtered air plus O3 (90 nmol O3 mol−1) (O3) from seedling to reproductive stage. After exposure for 56 days, RNase activity was 2.1 times higher in flag leaf tissues from an O3-sensitive cultivar in the O3 treatment compared with the control, which generally coincided with foliar injury and lower soluble protein concentration, but not soluble leaf [Pi]. Soluble [Pi] in leaf tissue extracts from the O3 and control treatments was not significantly different. RNase activity gels indicated the presence of three major RNases and two nucleases, and their expression was enhanced by the O3 treatment. Isozymes stimulated in the O3 treatment were also stimulated in naturally senescent flag leaf tissues from plants in the control. However, soluble [Pi] in extracts from naturally senescent flag leaves was 50% lower than that found in green flag leaves in the control treatment. Thus, senescence-like pathological responses induced by O3 were accompanied by increased RNase and nuclease activities that also were observed in naturally senescent leaves. However, [Pi] in the leaf tissue samples suggested that O3-induced injury and accelerated senescence was atypical of normal senescence processes in that Pi export was not observed in O3-treated plants.

Electronic Resource

1365-3040

Blackwell Publishing Journal Backfiles 1879-2005

Biology

The inhibitory effects of tropospheric O3 on crop photosynthesis, growth, and yield have been documented in numerous studies over the past 35 years. In large part, the results of this research supported governmental regulations designed to limit tropospheric O3 levels to concentrations that affected crop production at economically acceptable levels. Recent studies have brought into question the efficacy of these concentration-based O3 standards compared with flux-based approaches that incorporate O3 uptake along with environmental and biotic factors that influence plant responses. In addition, recent studies provide insight into the biochemical mechanisms of O3 injury to plants. Current interpretations suggest that upon entry into the leaf intercellular space O3 rapidly reacts with components of the leaf apoplast to initiate a complex set of responses involving the formation of toxic metabolites and generation of plant defence responses that constitute variably effective countermeasures. Plant species and cultivars exhibit a range of sensitivity to O3, evident as heritable characteristics, that must reflect identifiable biochemical and molecular processes that affect sensitivity to O3 injury, although their exact makeup remains unclear. Ozone clearly impairs photosynthetic processes, which might include the effects on electron transport and guard cell homeostasis as well as the better-documented effects on carbon fixation via decreased Rubisco activity. Translocation of photosynthate could be inhibited by O3 exposure as well. Further, the influence of tropospheric O3 needs to be considered when assessing potential effects of rising concentrations of atmospheric CO2 on crop production. Advances in O3 flux modelling and improved understanding of biochemical and molecular effects of O3 on photosynthetic gas exchange and plant defence processes are leading to more complete, integrated assessments of O3 impacts on crop physiology that continue to support the rationale for maintaining or improving current O3 air quality standards as well as providing a basis for development of more O3-tolerant crop lines.

Electronic Resource

1365-2486

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Energy, Environment Protection, Nuclear Power Engineering

Geography

A critical global climate change issue is how increasing concentrations of atmospheric CO2 and ground-level O3 will affect agricultural productivity. This includes effects on decomposition of residues left in the field and availability of mineral nutrients to subsequent crops. To address questions about decomposition processes, a 2-year experiment was conducted to determine the chemistry and decomposition rate of aboveground residues of soybean (Glycine max (L.) Merr.) grown under reciprocal combinations of low and high concentrations of CO2 and O3 in open-top field chambers. The CO2 treatments were ambient (370 μmol mol−1) and elevated (714 μmol mol−1) levels (daytime 12 h averages). Ozone treatments were charcoal-filtered air (21 nmol mol−1) and nonfiltered air plus 1.5 times ambient O3 (74 nmol mol−1) 12 h day−1. Elevated CO2 increased aboveground postharvest residue production by 28–56% while elevated O3 suppressed it by 15–46%. In combination, inhibitory effects of added O3 on biomass production were largely negated by elevated CO2. Plant residue chemistry was generally unaffected by elevated CO2, except for an increase in leaf residue lignin concentration. Leaf residues from the elevated O3 treatments had lower concentrations of nonstructural carbohydrates, but higher N, fiber, and lignin levels. Chemical composition of petiole, stem, and pod husk residues was only marginally affected by the elevated gas treatments. Treatment effects on plant biomass production, however, influenced the content of chemical constituents on an areal basis. Elevated CO2 increased the mass per square meter of nonstructural carbohydrates, phenolics, N, cellulose, and lignin by 24–46%. Elevated O3 decreased the mass per square meter of these constituents by 30–48%, while elevated CO2 largely ameliorated the added O3 effect. Carbon mineralization rates of component residues from the elevated gas treatments were not significantly different from the control. However, N immobilization increased in soils containing petiole and stem residues from the elevated CO2, O3, and combined gas treatments. Mass loss of decomposing leaf residue from the added O3 and combined gas treatments was 48% less than the control treatment after 20 weeks, while differences in decomposition of petiole, stem, and husk residues among treatments were minor. Decreased decomposition of leaf residues was correlated with lower starch and higher lignin levels. However, leaf residues only comprised about 20% of the total residue biomass assayed so treatment effects on mass loss of total aboveground residues were relatively small. The primary influence of elevated atmospheric CO2 and O3 concentrations on decomposition processes is apt to arise from effects on residue mass input, which is increased by elevated CO2 and suppressed by O3.

Electronic Resource

1365-2036

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Aim : To conduct a placebo-controlled functional brain imaging study to assess the effect of the 5-hydroxytryptamine-3 receptor antagonist, alosetron, on irritable bowel syndrome symptoms, regional brain activation by rectosigmoid distension and associated perceptual and emotional responses.Methods : Fifty-two non-constipated irritable bowel syndrome patients (28 female) were enrolled in a randomized, placebo-controlled trial with alosetron (1–4 mg b.d.). Thirty-seven patients completed both brain scans following randomization. Rectosigmoid stimulation was performed with a computer-controlled barostat. Changes in regional cerebral blood flow were assessed using H215O positron emission tomography. Stimulus ratings and changes in gastrointestinal symptoms were assessed using verbal descriptor scales.Results : Alosetron, but not placebo, treatment was associated with a decrease in symptom ratings, and reductions in emotional stimulus ratings. Compared to baseline, alosetron treatment was associated with reduced regional cerebral blood flow in bilateral frontotemporal and various limbic structures, including the amygdala. Compared to placebo, decreases in activity of the amygdala, ventral striatum, hypothalamus and infragenual cingulate gyrus were significantly greater after alosetron.Conclusions : In non-constipated irritable bowel syndrome patients, 3 weeks of treatment with a 5-hydroxytryptamine-3 receptor antagonist decreases brain activity in response to unanticipated, anticipated and delivered aversive rectal stimuli in structures of the emotional motor system, and this is associated with a decrease in gastrointestinal symptoms.

Electronic Resource

0303-7207

Myometrium ; Parturition ; Uterus

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Medicine

Electronic Resource

0303-7207

(Rat) ; 5-HT"2 receptor ; Collagenase induction ; Myometrium ; Parturition ; Uterus

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Medicine

Electronic Resource

0303-7207

Myometrium ; Smooth muscle ; Uterus ; mRNA

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Medicine

Electronic Resource

1432-1793

Springer Online Journal Archives 1860-2000

Biology

Abstract Rates of ammonia excretion, and respiration to excretion (atomic O:N) ratios were measured for three species of scleractinian coral from the Bahamas, during August 1986 and March 1987, to test the hypothesis that zooxanthellate reef species have lower rates of amino acid catabolism and higher dependence on lipid and carbohydrate catabolism than nonzooxanthellate species. Freshly collected individuals of two reef species,Montastrea annularis andAcropora cervicornis, have significantly lower mean ammonia excretion rates [51 ± 66 nmol (mg-at N)−1 h−1 and 192 ± 172 nmol (mg-at N)−1 h−1, respectively] than those of the tropical nonzooxanthellate speciesTubastrea coccinea [257 ± 68 nmol (mg-at N)−1 h−1]. The temperate nonzooxanthellate coralAstrangia poculata has mean excretion rates [632 ± 242 nmol (mg-at N)−1 h−1] which are much higher than those of all three tropical species. O:N ratios for the two reef species were generally greater than 300, while those of the nonzooxanthellate species ranged from 17 to 39 forT. coccinea and from 8 to 12 forA. poculata. The two reef species conserve nitrogen by having relatively low rates of amino acid catabolism, and support most of their metabolic needs by catabolizing the lipids and carbohydrates they receive from their zooxanthellae. The tropical nonzooxanthellate species has lower rates of ammonia excretion and respiration, and higher O:N ratios than the temperate nonzooxanthellate coral, which may be an indication that the former has less food available to it. The ammonia production rates of the reef species would support doubling times (growth rates) of the zooxanthellae of 13 to 22 d. These growth rates agree with observed rates obtained by mitotic index methods, and with suggestions that growth of zooxanthellae within many corals may be nitrogen-limited.

Electronic Resource

1573-5079

dosimetry ; photoreactivation ; photoprotection ; stratospheric ozone ; PS II, UV-B protocols

Springer Online Journal Archives 1860-2000

Biology

Abstract It has been suggested that increases in ground-level UV-B, as a result of stratospheric ozone depletion, may have major deleterious effects on crop photosynthesis and productivity. The direct consequences of such effects have been projected by some as a world-wide decrease in crop yields of 20–25%. Further losses, or unrealized gains, have also been suggested as a result of increased UV-B counteracting the beneficial effects of elevated atmospheric CO2. Deleterious UV-B effects may be largely partitioned between damage to the plant genome and damage to the photosynthetic machinery. Direct damage to DNA is a common result of absorption of high energy UV-B photons. However, most plants possess repair mechanisms adequate to deal with the levels of damage expected from projected increases in ground-level UV-B. In addition, most plants have the ability to increase production of UV-absorbing compounds in their leaves as a result of exposure to UV-B, UV-A and visible radiation. These compounds contribute substantially to reducing UV-B damage in situ. It has also been shown that in some plants, under the proper conditions, almost every facet of the photosynthetic machinery can be damaged directly by very high UV-B exposures. However, electron transport, mediated by Photosystem II (PS II) appears to be the most sensitive part of the system. Various laboratories have reported damage to virtually all parts of the PS II complex from the Mn binding site to the plastoquinone acceptor sites on the opposite surface of the thylakoid membrane. However, a critical review of the literature with emphasis on exposure protocols and characterization of the radiation environment, revealed that most growth chamber and greenhouse experiments and very many field experiments have been conducted at unrealistic or indeterminate UV-B exposure levels, especially with regard to the spectral balance of their normal radiation environment. Thus, these experiments have led directly to large overestimates of the potential for damage to crop photosynthesis and yield within the context of 100 year projections for stratospheric ozone depletion. Indeed, given the massive UV-B exposures necessary to produce many of these effects, we suggest it is unlikely that they would occur in a natural setting and urge reconsideration of the purported impacts of projected increases of UV-B on crop productivity.

Electronic Resource

1573-5036

Carbohydrates ; CO2 ; lignin ; nitrogen ; proanthocyanidins ; soil respiration

Springer Online Journal Archives 1860-2000

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Abstract Increased atmospheric carbon dioxide (CO2) concentration will likely cause changes in plant productivity and composition that might affect soil decomposition processes. The objective of this study was to test to what extent elevated CO2 and N fertility-induced changes in residue quality controlled decomposition rates. Cotton (Gossypium hirsutum L.) was grown in 8-l pots and exposed to two concentrations of CO2 (390 or 722 μmol mol-1) and two levels of N fertilization (1.0 or 0.25 g l-1 soil) within greenhouse chambers for 8 wks. Plants were then chemically defoliated and air-dried. Leaf, stem and root residues were assayed for total non-structural carbohydrates (TNC), lignin (LTGA), proanthocyanidins (PA), C and N. Respiration rates of an unsterilized sandy soil (Lakeland Sand) mixed with residues from the various treatments were determined using a soda lime trap to measure CO2 release. At harvest, TNC and PA concentrations were 17 to 45% higher in residues previously treated with elevated CO2 compared with controls. Leaf and stem residue LTGA concentrations were not significantly affected by either the elevated CO2 or N fertilization treatments, although root residue LTGA concentration was 30% greater in plants treated with elevated CO2. The concentration of TNC in leaf residues from the low N fertilization treatment was 2.3 times greater than that in the high N fertilization treatment, although TNC concentration in root and stem residues was suppressed 13 to 23% by the low soil N treatment. PA and LTGA concentrations in leaf, root and stem residues were affected by less than 10% by the low N fertilization treatment. N concentration was 14 to 44% lower in residues obtained from the elevated CO2 and low N fertilization treatments. In the soil microbial respiration assay, cumulative CO2 release was 10 to 14% lower in soils amended with residues from the elevated CO2 and low N fertility treatments, although treatment differences diminished as the experiment progressed. Treatment effects on residue N concentration and C:N ratios appeared to be the most important factors affecting soil microbial respiration. The results of our study strongly suggest that, although elevated CO2 and N fertility may have significant impact on post-harvest plant residue quality of cotton, neither factor is likely to substantially affect decomposition. Thus, C cycling might not be affected in this way, but via simple increases in plant biomass production.

Electronic Resource

0148-7280

capacitation of sperm ; ultrastructure of sperm ; Life and Medical Sciences ; Cell & Developmental Biology

Wiley InterScience Backfile Collection 1832-2000

Biology

Human sperm with a high zona-free hamster egg-penetration ability were obtained by centrifuging freshly ejaculated sperm through a discontinuous two-step (47% and 90%) Percoll gradient at 600g at room temperature for 30 min. Highly motile sperm with good penetration ability were recovered in the pellet fraction (Per-sperm), whereas those with low penetration ability were in the gradient interface. The increased penetration ability of Per-sperm, as compared to sperm capacitated by other methods such as a single-tube swim-up or multiple-tube swim-up preparation, was not due to an increased proportion of acrosome reacted sperm. Rather, transmission electron microscopy indicated that Per-sperm were devoid of coating envelopes, which were present around both the head and tail regions of noncapacitated and single-tube swim-up sperm. Changes to the surface of Per-sperm were demonstrated by their decreased interaction with UEA I lectin, which binds specifically to fucose residues. Removal of the coating envelopes as well as other changes on the sperm surface may lead to an enhanced binding of Per-sperm to the oocyte. In addition, 99% of Per-sperm contained chromatin that was fully condensed. By contrast, about 15% of swim-up sperm still possessed incompletely condensed chromatin. With a higher penetration ability, “clean” appearance, and homogeneity of condensed chromatin, Per-sperm are recommended for insemination and studies of human sperm capacitation.

5 Ill.

Electronic Resource