Search Results - (Author, Cooperation:D. A. Baker)

2014-02-28

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; DNA-Binding Proteins/deficiency/genetics/metabolism ; Female ; Gene Expression Regulation/*genetics ; Gene Silencing ; Genes, Protozoan/genetics ; Genome, Protozoan/genetics ; Germ Cells/cytology/*growth & development/metabolism ; Malaria/*parasitology ; Male ; Parasites/cytology/genetics/*physiology ; Plasmodium falciparum/cytology/*genetics/physiology ; Protozoan Proteins/genetics/metabolism ; Reproduction, Asexual ; Sex Differentiation/genetics ; Sexual Development/*genetics ; Transcription, Genetic/*genetics

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

Measurement of distribution of velocities of phases in pipe flow of a dense gas-solid suspension was facilitated by the use of an ion source in the form of a localized corona discharge and a downstream traversing electrostatic probe. The system utilizes the transient behavior of a corona discharge which provides a distinction of times of arrival of ions and solid particles of modified charges at a downstream probe. This probe system does not suffer the handicap of other available probe systems in a dense solid phase.

Electronic Resource

1471-0528

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Ovarian function was assessed by measuring plasma gonadotrophins, urinary oestrogen and urinary pregnanediol levels, every week for four weeks, in 34 women, aged 45 to 57 years, after withdrawal of oral contraceptive therapy. A rise in urinary pregnanediol excretion occurred in 14 patients suggesting that ovulation had occurred and that these patients were‘premenopausal'. Elevated serum gonadotrophin values and persistently low urinary oestrogen and pregnanediol excretion occurred in 13 patients suggesting ovarian failure or a‘postmenopausal’state. However, one apparently‘postmenopausal’patient later showed hormonal evidence of ovulation, indicating fluctuation in ovarian function. There were 7 patients with‘indeterminate’hormone profiles whose ovarian function was difficult to assess. All patients excreting more than 45 nmol of oestrogen a day had a spontaneous period within 45 days of stopping hormone therapy.

Electronic Resource

1089-7666

AIP Digital Archive

Physics

Steady-state current sustainment by oscillating field current drive (OFCD) utilizes a technique in which the toroidal and poloidal magnetic fields at the plasma surface are modulated at audio frequencies in quadrature. Experiments on the ZT-40M reversed field pinch [Fusion Technol. 8, 1571 (1985)] have examined OFCD over a range of modulation amplitude, frequency, and phase. For all cases examined, the magnitude of the plasma current is dependent on the phase of the modulations as predicted by theory. However, evidence of current drive has only been observed at relatively low levels of injected power. For larger modulation amplitudes, the data suggest that substantial current drive is offset by increased plasma resistance as a result of modulation enhanced plasma–wall interactions. The initial experimental results and supporting theoretical interpretations of OFCD are discussed.

Electronic Resource

1089-7666

AIP Digital Archive

Physics

Empirical modeling of the dependence of loop voltage on edge plasma conditions in the reversed field pinch is discussed. Specific concerns are raised regarding magnetohydrodynamic-based models that assume a large local dissipation of magnetic helicity at the plasma edge. A kinetic model is presented in which loop voltage can be affected by fast electrons carrying momentum directly to the walls or limiters, without a large edge helicity dissipation.

Electronic Resource

1399-3054

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] Coleus is particularly suitable for an investigation of this kind because the main vascular bundles are situated at the angles of the square stem. We used CaldwelFs split root technique on Coleus frederici. Cuttings were taken and a fortnight later the rooted stumps were carefully split from the ...

Electronic Resource

1399-3054

Blackwell Publishing Journal Backfiles 1879-2005

Biology

Moderate water stresses in the range 0 to −0.6 MPa applied with PEG 6000 to excised roots of Zea mays L. var. LG 11 induced increases of up to four-fold in the amount of abscisic acid (ABA) determined in the tissue after a 12 h period of xylem exudation. The ABA concentration of xylem exudate collected after a 2 h water stress also increased by up to four-fold. Salt stresses, induced with NaCl solutions, resulted in similar increases in the ABA concentrations. ABA concentrations in both root tissue and xylem exudate were highest 4 h after removal of the stress and then declined over a subsequent 8 h period. These results are interpreted in support of the concept that root-produced ABA may have a role in the fine control of the plant's water balance.

Electronic Resource

1572-9591

Springer Online Journal Archives 1860-2000

Energy, Environment Protection, Nuclear Power Engineering

Abstract This paper reports a collaborative effort of a team which formed at Los Alamos to investigate the announcement that “cold fusion” may be occurring in electrochemical cells using palladium cathodes and platinum anodes in a LiOD electrolyte. Four electrochemical cells were construced and operated for 3–5 weeks under various geometrical and electrical conditions. Nuclear diagnostic measurements included high and low resolution gamma-ray spectroscopy, integral neutron counting with well detectors and banks of3He tubes, and neutron spectroscopy withNE-213 scintillators. For one of the cells, the deuterium loading of the cathode was determined from resistance measurements to beD/Pd⩽ 0.8. No conclusive evidence was found for the production of neutrons or 2.223-MeV gammas above levels consistent with background. The results of the measurements of tritium levels in the cell electrolytes are also reported. Experiments to reproduce the observation of neutrons from high pressureTi-D 2 gas experiments were also performed with negative results.

Electronic Resource

1432-0428

Keywords Implantable glucose sensors

Springer Online Journal Archives 1860-2000

Medicine

Summary The evolution of glucose assay methods has been central to the development of present therapies for diabetes mellitus. However, new blood glucose assay capabilities, such as convenient and truly continuous monitoring, are now needed to foster a new era of close blood glucose control. The principles and present status of glucose sensors being developed that may fill these requirements are reviewed here. [Diabetologia (1997) 40: S 102–S 107]

Electronic Resource

1432-2048

Springer Online Journal Archives 1860-2000

Biology

Summary The flux of water, $$f_{{\text{H}}_{\text{2}} {\text{O}}}$$ , to the xylem of exuding root systems of Ricinus communis was controlled using a range of mannitol concentrations permitting the influence of this water flux on the potassium flux, f K, to be studied. The relationship between $$f_{{\text{H}}_{\text{2}} {\text{O}}}$$ and f K thus obtained was investigated, for a number of external concentrations of potassium, Cm, supplied as potassium nitrate. An analysis of these data indicated the presence of a water dependent and a water independent f K both of which varied with Cm. The water dependent f K shows a parabolic relationship with Cm for Cm values 〈1 mM followed by a sharp inflection and decline at higher Cm values whereas the water independent f K shows an hyperbolic relationship over the same range of Cm values. Uptake of potassium by exuding root systems was measured and shown to be dependent on the solute potential of the medium. The uptake was also shown to exhibit a dual absorption isotherm the kinetics of which indicate a low Km system (system 1) and a high Km system (system 2). The Km value obtained for system 1 is very similar to that obtained for the water independent f K. It is postulated that the water independent f K is contributed by that portion of f K arriving in the stele via the cortical symplast and is directly dependent on Cm. The water dependent f K is contributed by those ions moved across the root in response to centripetal water movement through the cortical cell walls.

Electronic Resource

1432-2048

Springer Online Journal Archives 1860-2000

Biology

Summary The water-extractable and ion-exchangeable fractions of the free space of maize roots for sodium ions has been determined. The free space of whole roots, excised roots and isolated stelar and cortical tissues, has been compared and the results examined for any evidence of a barrier between the cortex and the stele. Similarly the free space of whole roots and excised roots, from which the epidermal and outer cortical cells have been removed by shaving, has been compared and the results examined for any evidence of an epidermal barrier. Whole roots gave a free space value some 20% lower than excised roots. It was calculated that this difference could be accounted for if the cortical tissues only were considered in estimating the whole root value, that is if the stele was considered as participating in the excised root but not in the whole root. Samples in which isolated cortical and stelar material were measured together, or separately and the value calculated, gave similar values to those obtained for excised roots. These results are interpreted as evidence that a barrier to free diffusion exists between the cortical and the stelar tissues at or near the endodermis. Shaving both whole and excised roots increased the free space by about 35%. However, as this value was similar for both, it was concluded that the increase was due to the contribution of damaged cortical cells and does not indicate that the epidermis is an effective barrier to the diffusive entry of sodium ions into the root.

Electronic Resource

1432-2048

Springer Online Journal Archives 1860-2000

Biology

Summary The chemical composition of exudate obtained from incisions made in the bark of the stem of actively growing Ricinus plants has been determined. The exudate had a high dry matter content (100–125 mg/ml), a high sugar content (80–106 mg/ml) which was solely sucrose, reducing sugars being absent. The amino acid composition was mainly glutamic and aspartic acids and threonine with a total amino acid concentration of 35.2 mM. The exudate had a pH of 8.0–8.2. Potassium was the major cation (60–112 mM) with sodium present at a lower concentration (2–12 mM). Of the divalent cations, calcium was at a low concentration (0.5–2.3 mM) and magnesium relatively higher (4.5–5.4 mM). Chloride was the major inorganic anion (10–19 mM). Phosphate concentration was relatively high (3.7–5.7 mM) and low concentrations of sulphate (0.3–0.5 mM) and bicarbonate (1.7 mM) were also present. Nitrate was absent. The ionic balance was maintained by the presence of relatively large quantities (30–47 meq/l) of organic anions, mainly malate. Bioassays revealed auxin, gibberellin and cytokinin activities in chromatographed exudate. Adenosine triphosphate was found in the exudate (0.40–0.60 mM). The analysis is dicussed with respect to the composition of phloem sap reported for other plant species.

Electronic Resource

1432-2048

Auxin ; Mass fragmentography ; Ricinus ; Xylem sap

Springer Online Journal Archives 1860-2000

Biology

Abstract Mass fragmentography employing a deuterated internal standard was used to make quantitative analyses of indole-3-acetic acid in xylem sap collected from Ricinus communis L. When contamination of the sap by microorganisms was reduced by frequent collection, levels of IAA were found to be less than 0.5 ng ml-1. It is therefore proposed that the transpiration stream does not play a significant role in the transport of IAA within the plant.

Electronic Resource

1432-2048

IAA ; Phloem sap ; Ricinus ; Tryptophan ; Xylem sap

Springer Online Journal Archives 1860-2000

Biology

Abstract Levels of free tryptophan in the leaves, phloem and xylem saps of Ricinus communis L. were determined by colorimetric assay. Values of 0.38 μg ml-1 in root pressure sap and 96.0 μg ml-1 in phloem sap were recorded. Tryptophan levels were highest in mature and senescing leaves. Levels of indoleacetic acid (IAA) in the phloem sap and leaves were determined by gas chromatography—mass spectrometry using a deuterated internal standard. A mean value of 13.0 ng ml-1 was recorded in phloem sap. The distribution in the leaves showed an inverse relationship to that of tryptophan, being highest in young leaves.

Electronic Resource

1432-2048

Phloem-loading ; Proton co-transport ; Ricinus ; Sugar transport

Springer Online Journal Archives 1860-2000

Biology

Abstract Loading of 14C-labelled sugars from the hollow petiole of Ricinus communis L. was stimulated by potassium and by low pH in that both the 14C-activity and the sugar concentration of phloem sap collected from a nearby incision increased. A pH drop was observed in the solution perfusing a hollow petiole. This pH drop was greater in the presence of potassium and less in the presence of sugars, while the uncoupler CCCP induced a pH rise in the perfusing solution. Sugars were detected in the perfusing solution when it was buffered at pH〉9. A model is proposed for a proton co-transport of sugars from the free space driven by a linked proton efflux/potassium influx pump.

Electronic Resource

1432-2072

Key words Locomotion ; Headbobbing ; Yawning ; Stereotypy ; Place conditioning ; Sensitization ; Repeated administration ; Dopamine receptor ; Dopamine D3 receptor ; Dopamine D2-like receptor ; Autoreceptor

Springer Online Journal Archives 1860-2000

Medicine

Abstract  Low doses of the dopamine D3-preferring agonist 7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT) produce a behavioral profile that is opposite to that produced by the psychomotor stimulants cocaine and amphetamine. For example, low doses of 7-OH-DPAT produce conditioned place aversion and hypolocomotion, whereas psychomotor stimulants produce conditioned place preference (CPP) and hyperlocomotion. In experiment 1, the effects of low doses of 7-OH-DPAT (0.01–0.1 mg/kg) on d-amphetamine-induced (1 mg/kg) motor behaviors and CPP were assessed. In experiment 2, the effects of 0.1 mg/kg 7-OH-DPAT on d-amphetamine (0–10 mg/kg) dose-response curves for the same behaviors were examined. During conditioning, drug injections were paired with a distinct compartment, whereas saline injections were paired with another compartment. Locomotion and headbobbing were measured following acute and repeated drug administration during conditioning and place conditioning was assessed 24 h following the last conditioning day. In experiment 1, d-amphetamine-induced locomotion was dose-dependently decreased by 7-OH-DPAT following repeated administration, which was probably due to the emergence of headbobbing, a behavior not observed with d-amphetamine alone. d-Amphetamine-CPP was not altered by co-administration of 0–0.03 mg/kg 7-OH-DPAT, but was attenuated by co-administration of 0.1 mg/kg 7-OH-DPAT. In experiment 2, 7-OH-DPAT co-administered with low doses of d-amphetamine (0–0.5 mg/kg) produced a decrease in locomotion following acute administration. However, 7-OH-DPAT produced sensitization of locomotion at the 0.5 mg/kg dose of d-amphetamine and an increase in headbobbing at the 0.5–10 mg/kg doses of d-amphetamine following repeated administration. In contrast, d-amphetamine-CPP was attenuated by co-administration of 7-OH-DPAT. These findings suggest that 0.1 mg/kg 7-OH-DPAT attenuates the reinforcing effects of d-amphetamine despite enhancing stereotypic behaviors.

Electronic Resource

1432-2048

Springer Online Journal Archives 1860-2000

Biology

Summary Steles isolated from maize roots grown under non-sterile conditions showed an increase in ion absorption capacity and in the rate of oxygen uptake when washed for 24 h, although the levels of protein and of several hydrolytic and respiratory tnzymes fell over the same period. Fresh isolated cortex showed higher activity than fresh steles in relation to both ion absorption and respiration. The large increase with washing in the ion absorption capacity of the steles was not observed when the tissue was isolated from roots grown under sterile conditions. These results are discussed in relation to proposed mechanisms for the radial transport of ions across the root and to the effect of micro-organisms on ion absorption studies in higher plant cells.

Electronic Resource

1432-2048

Springer Online Journal Archives 1860-2000

Biology

Summary Exudate can be obtained from incisions made in the bark of the stem of actively growing Ricinus plants. 14C-labelled assimilates from a fed leaf are rapidly detected in the exudate. This movement was both acropetal and basipetal from the fed leaf, at rates of over 100 cm h-1. Estimated rates within intact plants were 80–84 cm h-1. In contrast with xylem sap obtained from the same plant, the exudate obtained had an alkaline pH (8.2), a high dry matter content (10–12.5%), high sugar content (8–10%) which was predominantly sucrose; high potassium content (60–80 mM) and low calcium content (0.5–1.0 mM). It is concluded, on the basis of the present evidence, that the exudate is a true sample of the sieve tube sap undergoing translocation.

Electronic Resource

1432-2048

Springer Online Journal Archives 1860-2000

Biology

Electronic Resource