[Results of experimental research on variations of serum cholinesterase in different estrual phases].
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Animals↗
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Results for “phase variation”
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[Variations in cardiac output in the early phase of liver declamping in a liver graft].
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Cardiac Output↗
[Variation in vascular permeability in the initial phase of experimental hypertension in the rat].
A transient increase of vascular permeability was observed during the initial phase of renovascular experimental hypertension. The intensity of the permeability-increase varied according to the vascular regions considered: the strongest increase was observed in the aorta-wall; next came the skin, and the smallest increase occurred in the brain. The highest permeability values were observed on the 4th day after induction of hypertension in the brain and in the skin, and on the 7th day only in the aorta. On the 14th day of hypertension, the permeability was back to normal in all the 3 vascular regions studied. Anthocyanoside treatment diminished the permeability increase induced by hypertension. The strongest protective action was observed in the brain, next in the aorta, and it was the weakest in the skin.
Animals↗
Diurnal variations in melatonin binding sites in the hamster brain: impact of melatonin.
The distribution of 125I-melatonin binding sites in the male Syrian hamster brain was recorded at 3 times over a 24 h period. The binding in the hypothalamus, hippocampus, medulla-pons and midbrain of the hamsters varied significantly over the 24 h period with different patterns and phases. No such variations were observed in the parietal cortex. Daily morning (10.00 h) or late afternoon (18.00 h) injections of melatonin for 28 days markedly increased the serum concentrations of melatonin at all times recorded. Serum concentrations of testosterone were significantly lower in animals injected with melatonin in the late afternoon than in the untreated controls; no such decrease was observed in animals injected in the morning despite the continuously elevated levels of circulating melatonin. The daily melatonin injections did not significantly affect 125I-melatonin binding in the hypothalamus, parietal cortex and medulla-pons. In the midbrain, 125I-melatonin binding decreased regardless of the time of injection. In the hippocampus, morning melatonin injections caused a marked decrease in 125I-melatonin binding at all times recorded whereas melatonin injected in the late afternoon led to a decrease in 125I-melatonin binding at 10.00 h only. These results indicate diurnal variations in 125I-melatonin binding sites in discrete brain areas of the golden hamster, persisting despite prolonged duration of elevated levels of circulating melatonin. The differential effects of timed melatonin injections on the hippocampal 125I-melatonin binding sites are positively correlated with the counter-antigonadal response produced by morning melatonin injections.
Animals↗
Experimental elevations of blood pressure induced as an internal stimulus during sleep in man: effects on cortical vigilance and response thresholds in different sleep stages.
The hypothesis that raising blood pressure (BP) during human sleep, by intravenous administration of angiotensin II, causes arousals was tested. BP was measured intraarterially during polygraphic sleep recordings. Twenty-seven intrasleep elevations of BP in two young adults over 2 nights were evaluated. The BP increases ranged from 16% to 74% of the preexperimental level for systolic BP and from 28% to 84% for diastolic BP. Eighty-one percent of all BP variations induced arousals, and the number of awakenings during elevated BP was 6.5 times higher than in control conditions. These results confirm the hypothesis that BP elevation is an internal stimulus inducing arousal reactions from sleep. The arousals were equally linked to the three phases of BP variation, i.e., rise, peak, and fall in BP, indicating that BP variation functions as a stimulus unit. Arousal thresholds varied with the different sleep stages. They were lowest in sleep stage 2, slightly higher in REM sleep, and highest in slow-wave sleep, in accordance with the thresholds for neutral external stimuli. The study demonstrates the relevance of BP when considering the physiological parameters of sleep-wake regulation.
Adult↗
Cell-cycle radiation response: role of intracellular factors.
We have been studying variations of radiosensitivity and endogenous cellular factors during the course of progression through the human and hamster cell cycle. After exposure to low-LET radiations, the most radiosensitive cell stages are mitosis and the G1/S interface. The increased activity of a specific antioxidant enzyme such as superoxide dismutase in G1-phase, and the variations of endogenous thiols during cell division are thought to be intracellular factors of importance to the radiation survival response. These factors may contribute to modifying the age-dependent yield of lesions or more likely, to the efficiency of the repair processes. These molecular factors have been implicated in our cellular measurements of the larger values for the radiobiological oxygen effect late in the cycle compared to earlier cell ages. Low-LET radiation also delays progression through S phase which may allow more time for repair and hence contribute to radioresistance in late-S-phase. The cytoplasmic and intranuclear milieu of the cell appears to have less significant effects on lesions produced by high-LET radiation compared to those made by low-LET radiation. High-LET radiation fails to slow progression through S phase, and there is much less repair of lesions evident at all cell ages; however, high-LET particles cause a more profound block in G2 phase than that observed after low-LET radiation. Hazards posed by the interaction of damage from sequential doses of radiations of different qualities have been evaluated and are shown to lead to a cell-cycle-dependent enhancement of radiobiological effects. A summary comparison of various cell-cycle-dependent endpoints measured with low- or high-LET radiations is given and includes a discussion of the possible additional effects introduced by microgravity.
Cell Cycle↗
[Ultraviolet cytophotometry of a single live neuron in the crayfish mechanoreceptor].
Measurements of ultra-violet absorption by a live neuron, with 5-minutes' intervals, have shown variations in RNP content amounting almost 20% with a period of 30 min. The fact that these variations and their phase were independent from changes in the volume of RNP zone allows to relate them to the rhythm of macromolecule synthesis. When ultra-violet radiation was delivered in large doses, mean RNP content decreased with a latency 20 to 40 min, and 30- minutes' variations of RNP content were suppressed.
Animals↗
Central regulation of motor cortex neuronal responses to forelimb nerve inputs during precision walking in the cat.
1. The responses of neurones in forelimb motor cortex to impulse volleys evoked by single pulse electrical stimulation (at 1.5 or 2 times the threshold for most excitable nerve fibres) of the superficial radial (SR) and ulnar (UL) nerves of the contralateral forelimb were studied in awake cats both resting quietly and walking on a horizontal ladder. Nerve volley amplitude was monitored by recording the compound action potential elicited by the stimulus. 2. In the resting animal 34/82 (41%) cells yielded statistically significant responses to SR stimulation, and 20/72 (28%) responded to UL stimulation. Some responses were confined to or began with an increase in firing probability ('excitatory' responses) and others with a decrease in firing ('inhibitory' responses), typically including a brief interruption of the spike train (zero rate). Cells responding to both nerves usually yielded responses similar in type. Most (78%) response onset latencies were less than 30 ms. Responses involved the addition or subtraction of from 3.4 to 0.1 impulses stimulus-1 (most <1 impulse stimulus-1). The distribution of response sizes was continuous down to the smallest values, i.e. there was no 'gap' which would represent a clear separation into 'responsive' and 'unresponsive' categories. Responses were commonest in the lateral part of the pericruciate cortex, and commoner among pyramidal tract neurones (PTNs) than non-PTNs. 3. During ladder walking most cells generated a rhythmic step-related discharge; in assessing the size of responses to nerve stimulation (20 studied, from 13 cells) this activity was first subtracted. Response onset latencies (90% <30 ms) and durations showed little or no change. Although most cells were overall more active than during rest both 'excitatory' and 'inhibitory' responses in both PTNs and non-PTNs were often markedly reduced in large parts of the step cycle; over some (usually brief) parts responses approached or exceeded their size during rest, i.e. response size was step phase dependent. Such variations occurred without parallel change in the nerve compound action potential, nor were they correlated with the level of background firing at the time that the response was evoked. When responses to both nerves were studied in the same neurone they differed in their patterns of phase dependence. 4. The findings are interpreted as evidence for central mechanisms that, during 'skilled', cortically controlled walking, powerfully regulate the excitability of the somatic afferent paths from forelimb mechanoreceptors (including low threshold cutaneous receptors) to motor cortex. Retention (or enhancement) of responsiveness often occurred (especially for ulnar nerve) around footfall, perhaps reflecting a behavioural requirement for sensory input signalling the quality of the contact established with the restricted surface available for support.
Animals↗
Phase diagram of a binary symmetric hard-core Yukawa mixture.
We assess the accuracy of the self-consistent Ornstein-Zernike approximation for a binary symmetric hard-core Yukawa mixture by comparison with Monte Carlo simulations of the phase diagrams obtained for different choices of the ratio alpha of the unlike-to-like interactions. In particular, from the results obtained at alpha=0.75 we find evidence for a critical endpoint in contrast to recent studies based on integral equation and hierarchical reference theories. The variation of the phase diagrams with range of the Yukawa potential is investigated.
Journal Article↗
[Spectral analysis of blood pressure in patients with sleep related respiratory disorders].
Spectral analysis is a helpful tool to investigate the interaction of blood pressure, respiration and sleep (6). The analysis of systolic pressure is most suitable for the documentation of compressed spectral arrays, since there are less disturbances than from the heart rate. The method used in this study allows the discrimination and quantitative evaluation of periodic blood pressure oscillations associated with apneic and breathing phases. It could be shown that the amplitude of the pulsus paradoxus increases during episodes of obstructive snoring. Heavy snore showed rather stable respiratory frequencies during the whole night which was not found that distinctly in patients with obstructive sleep apnea. The parallel analysis of blood pressure variations and sleep phases revealed different mechanisms in the regulation of REM- and non-REM sleep which transfer sleep related breathing disorders from a periodic pattern in a nonperiodic one and hereby influence at least the regulation of heart rate and blood pressure.
Adult↗
Polarization phase in aberration compensation.
A phase/amplitude mask on the aperture of an imaging system results in a pupil function that is multiplicative with the lens function, resulting in a morphological transformation of the imaging wavefront. It was shown that such amplitude and phase functions can be implemented using polarization masks, with the advantage that the phase and amplitude can be controlled in real time and in some cases, independently of each other. The phase and amplitude variation over the mask can be controlled either by changing the polarization of the mask or by changing the input beam parameters. Wavefront tailoring using polarization-masked apertures is therefore feasible and may be utilized for focal shift and partial aberration compensation. For complete compensation of aberration, the phase distribution over the mask should be conjugate to that of the phase error of the aberrant wavefront, which necessitates the use of a continuously variable polarization mask. Since such a mask is difficult to implement, we have considered polarizing masks consisting of discrete polarized zones on the lens aperture, leading to polarization phase steps on the exit pupil of the imaging system. The simulation results presented in this paper show that effects of focal shift, partial compensation of primary spherical aberration and astigmatism can indeed be achieved by the proper use of polarization masked apertures.
Journal Article↗
Solvatochromic solvent polarity measurements and selectivity in reversed-phase liquid chromatography.
The ET(30) polarity values of binary acetonitrile-water and methanol-water mobile phases, used in reversed-phase liquid chromatography, were measured and compared with methylene selectivity (alpha CH2) for both traditional siliceous bonded phases and for a polystyrene-divinylbenzene resin reversed-phase material. The variation in methylene selectivity for both was found to correlate best with percent organic solvent in methanol-water mixtures, while the ET(30) polarity provided the best correlation in acetonitrile-water mixtures. The polymeric resin column was found to provide higher methylene selectivity than the siliceous bonded phase at all concentrations of organic solvent.
Acetonitriles↗
Acidogenic fermentation of source separated mixtures of vegetables and fruits wasted from supermarkets.
A pilot scale mesophilic anaerobic acidogenic fermenter was fed with mixtures of vegetables and fruits shredded by a hammer mill and mixed in a stock tank, in order to produce a liquid phase suitable as RBCOD source in denitrification and EBPR processes. Different operative conditions were studied working with a HRT in the range 1-12 days. The effluent coming from the fermenter was screw pressed, and the solid phase was recycled adopting different ratios to the fermenter, in order to define its effect on the final liquid phase composition. The variations of the VFA, lactate, methyl and ethyl alcohol concentrations, TCOD, SCOD and pH during more than one year were analysed and discussed both with reference to the fresh feed, and to the content of the fermenter. It was found that almost all the organic matter in the liquid phase inside the fermenter was represented by VFA (mainly acetate), lactate (in particular) and methyl and ethyl alcohols when HRT was longer than 6 days.
Acids↗
Application of linear optimization techniques to MRI phase contrast blood flow measurements.
The goal of this study was to use linear optimization techniques as a systematic method of cine phase contrast pulse sequence design and to apply this technique to the measurement of blood flow in vivo. The optimized waveforms were validated in a constant flow phantom with average velocities ranging from 5 to 50 cm/s. The same optimized sequence was also run in a segmented k-space variation with five phase encoding lines per segment. The magnetic resonance (MR) derived velocity measurements were accurate over the entire range of velocities tested (p < .05) in both cases. The same optimized pulse sequence was applied to the measurement of flow in main pulmonary artery of five normal volunteers and compared with stroke volumes and cardiac outputs calculated from right ventricular volume measurements. These measurements showed a mean difference between the MR phase contrast calculated stroke volume and the volumetric stroke volume measurement of 9.8 +/- 11.6%. The mean difference between the calculated phase contrast cardiac output and the volumetric cardiac output was 4.4 +/- 10%. These results imply that optimization techniques are an efficient method for designing cine phase contrast pulse sequences.
Adult↗
Polarization-transfer methods in solid-state magic-angle-spinning NMR: adiabatic CN pulse sequences.
An adiabatic double-quantum polarization-transfer experiment is described. It can be characterized as an adiabatic variant of the POST-C7 experiment. A continuous variation of the phase increment between pulses leads to the introduction of a fictitious Zeeman field that allows for an adiabatic passage through the recoupling condition. This results in a chemical-shift-offset-compensated adiabatic experiment, which leads to an efficient and broadbanded polarization transfer or to a double-quantum excitation. Similar variations of other C- or R-type experiments can be envisioned.
Carbon Isotopes↗
Tumor and normal tissue motion in the thorax during respiration: Analysis of volumetric and positional variations using 4D CT.
PURPOSE: To investigate temporospatial variations of tumor and normal tissue during respiration in lung cancer patients. METHODS AND MATERIALS: In 14 patients, gross tumor volume (GTV) and normal tissue structures were manually contoured on four-dimensional computed tomography (4D-CT) scans. Structures were evaluated for volume changes, centroid (center of mass) motion, and phase dependence of variations relative to inspiration. Only volumetrically complete structures were used for analysis (lung in 2, heart in 8, all other structures in >10 patients). RESULTS: During respiration, the magnitude of contoured volumes varied up to 62.5% for GTVs, 25.5% for lungs, and 12.6% for hearts. The range of maximum three-dimensional centroid movement for individual patients was 1.3-24.0 mm for GTV, 2.4-7.9 mm for heart, 5.2-12.0 mm for lungs, 0.3-5.5 mm for skin markers, 2.9-10.0 mm for trachea, and 6.6-21.7 mm for diaphragm. During respiration, the centroid positions of normal structures varied relative to the centroid position of the respective GTV by 1.5-8.1 mm for heart, 2.9-9.3 mm for lungs, 1.2-9.2 mm for skin markers, 0.9-7.1 mm for trachea, and 2.7-16.4 mm for diaphragm. CONCLUSION: Using 4D-CT, volumetric changes, positional alterations as well as changes in the position of contoured structures relative to the GTV were observed with large variations between individual patients. Although the interpretation of 4D-CT data has considerable uncertainty because of 4D-CT artifacts, observer variations, and the limited acquisition time, the findings might have a significant impact on treatment planning.
Diaphragm↗
Adsorption of proteins from plasma to a series of hydrophilic-hydrophobic copolymers. II. Compositional analysis with the prelabeled protein technique.
Plasma protein adsorption is an important initial event in the response of tissue to foreign materials. Little is known about the way in which the chemical properties of materials influence the nature of the adsorbed layer and thus the later cellular responses. In this study, the amounts of fibrinogen, immunoglobulin G, albumin, and hemoglobin adsorbed from plasma to a series of HEMA-EMA random copolymers varying in hydrophilicity was measured. The adsorption of each protein varied in a characteristic way with copolymer composition probably reflecting a different affinity of the proteins for the various copolymers. A complex variation in the composition of the adsorbed protein layer on polymers varying in hydrophilicity was thus evident. Surface enrichment of the proteins, calculated as the ratio of the surface and bulk fraction of each protein, also varied with copolymer composition, and indicated substantial differences in the composition of the surface and bulk phases. Surface area variations among the copolymers, preferential adsorption of 125I proteins, and the possibility of structural degradation of 1,25I proteins in plasma were investigated but did not appear to influence the adsorption results. The ability of polymers to fractionate plasma proteins and concentrate them at their surface is concluded to be a key factor in the complex processes which determine the compatibility of polymers in vivo.
Adsorption↗
Shear waves in the diamond-anvil cell reveal pressure-induced instability in (Mg,Fe)O.
The emerging picture of Earth's deep interior from seismic tomography indicates more complexity than previously thought. The presence of lateral anisotropy and heterogeneity in Earth's mantle highlights the need for fully anisotropic elasticity data from mineral physics. A breakthrough in high-frequency (gigahertz) ultrasound has resulted in transmission of pure-mode elastic shear waves into a high-pressure diamond-anvil cell using a P-to-S elastic-wave conversion. The full elastic tensor (c(ij)) of high-pressure minerals or metals can be measured at extreme conditions without optical constraints. Here we report the effects of pressure and composition on shear-wave velocities in the major lower-mantle oxide, magnesiowüstite-(Mg,Fe)O. Magnesiowüstite containing more than approximately 50% iron exhibits pressure-induced c(44) shear-mode softening, indicating an instability in the rocksalt structure. The oxide closer to expected lower-mantle compositions ( approximately 20% iron) shows increasing shear velocities more similar to MgO, indicating that it also should have a wide pressure-stability field. A complete sign reversal in the c(44) pressure derivative points to a change in the topology of the (Mg,Fe)O phase diagram at approximately 50-60% iron. The relative stability of Mg-rich (Mg,Fe)O and the strong compositional dependence of shear-wave velocities (and partial differential c(44)/ partial differential P) in (Mg,Fe)O implies that seismic heterogeneity in Earth's lower mantle may result from compositional variations rather than phase changes in (Mg,Fe)O.
Journal Article↗