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PubMed1982

Cell cycle-fluctuations in concentration of various elements in cytoplasm and in nucleus/chromatin of Physarum polycephalum.

The concentrations of Na, Mg, P, Cl, S, K, and Ca (m mol/kg dry wt) were measured during the cell cycle of P. polycephalum using electron-probe X-ray microanalysis. Significant cell cycle-associated fluctuations in the concentrations of all of these elements occurs in both the cytoplasm and the nucleus. In most cases the levels of each element were elevated during mitosis but greatly reduced during the S phase. Phosphorus and sulphur were concentrated in the nucleus/chromatin at metaphase. Ultrastructural analysis of these cells reveals a phase dependent variation in the density of the cytoplasmic ground substance which is most pronounced at mitosis. The changes seen in the cytoplasm occur not only in conjunction with the increased concentration of elements in the nucleus but also with the cessation of protoplasmic migration.

Cell Cycle↗
PubMed1980

The effect of prostaglandin F2 alpha and oxytocin on bovine myometrium in vitro.

Uterine strips were collected from cows during the follicular and the luteal phases as well as from cows with ovarian cysts. The strips were mounted in organ baths and the motility was recorded by a polygraph. After the spontaneous motility of the strips had reached a steady state the test substances PGF2 alpha and oxytocin were added to the bath at three different concentrations. Frequency, amplitude and duration of the spontaneous uterine concentrations were irregular in all strips recorded independent of reproductive stage. The spontaneous activity was most pronounced during the follicular phase. The variation between animals was greatest for cystic cows. PGF2 alpha always increased the activity of the uterus but the response was not dose related above a certain level (50 ng per ml bath fluid). Oxytocin on the other hand had a linear stimulatory effect for increasing doses (0.25, 2.5 and 25 mIU per ml bath fluid).

Animals↗
PubMed2000

Physiologic variations in dural venous sinus flow on phase-contrast MR imaging.

OBJECTIVE: Our study quantifies normal physiologic variations of dural sinus flow using phase-contrast MR imaging. SUBJECTS AND METHODS: Fifteen volunteers were imaged using nontriggered and triggered phase-contrast MR venography of the superior sagittal and transverse sinuses. Triggered scans were obtained during regular breathing; nontriggered scans were obtained during regular breathing, breath-holding, deep inspiratory breath-holding, and deep expiratory breath-holding. Analysis of variance, Bonferroni method, and Dunn post hoc analysis were used to determine any significant differences in the mean flow and velocity between the different breathing maneuvers. A paired t test was used to compare flow between sinuses during regular breathing. RESULTS: Deep inspiratory breath-holding and deep expiratory breath-holding resulted in a significant decrease in blood flow and velocity in all dural sinuses compared with regular breathing. During deep inspiratory breath-holding, blood flow decreased 30.8% in the superior sagittal sinus, 19.7% in the left transverse sinus, and 19.1% in the right transverse sinus. Similarly, during deep expiratory breath-holding, blood flow decreased 30.2% in the superior sagittal sinus, 20.8% in the left transverse sinus, and 20.3% in the right transverse sinus. The sum of the flow in the transverse sinuses was significantly greater than in the sagittal sinus. Normal pulsatility of dural sinus blood velocity was also characterized for all measured sinuses. CONCLUSION: Characterization of variations in dural sinus velocity and flow as a function of the cardiac cycle and breathing maneuvers, using phase-contrast MR imaging, may help separate physiologic from pathologic changes of flow resulting from conditions that influence the cerebrovascular circulation.

Adult↗
PubMedDate not supplied

Variations in blood flow waveforms in stenotic renal arteries by 2D phase-contrast cine MRI.

Waveform variations in blood flow measurements through stenotic renal arteries have been reported already with echo Doppler studies. We studied these variations with MRI in 14 patients (mean age, 60 years) with suspected renal arterial stenosis (24 patent arteries, four occluded). Flow measurements were successful in 15 arteries and unsuccessful in nine, due to practical limitations. Seven healthy younger volunteers (mean age, 28 years) and five healthy older volunteers (mean age, 58 years) were recruited for comparison purposes. In patients, the severity of stenoses was also assessed by digital subtraction angiography and intraarterially measured transstenotic pressure drops. We found flow patterns to be statistically significantly (P < 0.01) age-related. Younger healthy subjects showed shorter wave duration, higher diastolic flow, and total blood flow per minute. Also, with increasing stenosis severity, the systolic wave became more damped and the systolic wave duration became statistically significantly (P = .03) longer.

Adult↗
PubMed2003

Serum paraoxonase: effect of the apolipoprotein composition of HDL and the acute phase response.

Genetic variations of paraoxonase (PON) correlate with HDL cholesterol and apolipoprotein A-I (apoA-I), suggesting antiatherogenic properties. Atherosclerosis occurs naturally in humans and rabbits but not in mice. We compared variations of PON arylesterase activity (PON AEase, phenylacetate substrate) in humans, rabbits, and mice. In humans and rabbits, >95% of PON AEase is HDL associated. In mice, about 30% of PON AEase is lipid poor. In the absence of apoA-I in mice, total PON AEase is reduced and >60% is lipid poor. PON AEase level and distribution is restored in apoA-I-/- mice injected with adenoviruses encoding human apoA-I and in transgenic mice expressing human apoA-I at a steady-state level. Thus, while apoA-I is not required for the HDL association of PON AEase, induced variations in apoA-I correlate with changes in HDL-associated, but not lipid-poor, PON AEase. PON AEase associates only with apoA-I- or apoE-containing HDL but not VLDL. In the absence of both apoA-I and apoE, PON AEase is all-lipid-poor. PON AEase is displaced from HDL by ultracentrifugation and following incubation with serum amyloid A. Variations in the PON distribution between HDL and lipid-poor fractions may have important consequences in its antioxidant activity and in atherogenesis.

Acute-Phase Reaction↗
PubMed2005

Variation of the carrier-envelope phase of few-cycle laser pulses owing to the Gouy phase: a solid-state-based measurement.

The carrier-envelope phase of a laser pulse has recently become an important quantity in extreme nonlinear optics. Because of the topological Gouy phase, it changes while the pulse propagates through the focus of a lens. This variation is measured by a simple solid-state-based approach. The experimental results are analyzed by comparison with simple analytical model calculations.

Journal Article↗
PubMed2004

Frame-by-frame PRESS 1H-MRS of the brain at 3 T: the effects of physiological motion.

1H-MRS at high field has been increasingly utilized to study brain metabolism in healthy and pathological states. The aim of this work was to determine the effects of physiological motion on the results of this exam in the presence of the increased susceptibility differences at high field. Single voxel spectra of various regions in the human brain were acquired using frame-by-frame PRESS 1H-MRS at a 0.5 Hz sampling rate. The frame-by-frame variations of the FID phase and the frequency and fractional amplitude variations of the residual water-signal were analyzed. In the human brain the standard deviations of these variations were 3.9 +/- 0.5 degrees, 0.83 +/- 0.32 Hz, and 0.028 +/- 0.013 of the mean amplitude (n=15). In a motionless phantom, smaller phase and frequency variations were detected in water-suppressed acquisitions. However, the end effects of physiological motion on PRESS 1H-MRS of the brain at 3 T were negligible.

Algorithms↗
PubMed1981

Studies on ovarian and adrenal steroids at different phases of the menstrual cycle: II. A comparative assessment of the circadian variation in steroid and lutropin levels during the follicular, periovulatory and luteal phases.

In six normally menstruating women, ovarian and adrenal steroids and biologically active lutropin (LH) were measured in peripheral plasma samples collected every 3 h. during a period of 39 h. in the early follicular phase, periovulatory period or luteal phase of three consecutive cycles. The purpose of the study was to assess the influence of the phases of the cycle on the diurnal variation in the levels of different steroids and lutropin following the elimination of the between subject variation. Cortisol, 17-hydroxypregnenolone, dehydroepiandrosterone and androstenedione showed a marked circadian rhythm in all three phases of the cycle. No changes in the levels of cortisol, 17-hydroxypregnenolone and dehydroepiandrosterone with the phase of the cycle were observed when the "morning" samples were considered; however, when the "evening" samples were analyzed, the levels of these steroids were higher in the luteal phase than in the follicular phase. As a result of this increase, the amplitude of the circadian rhythm of these steroids considerably decreased in the luteal phase. The "morning" as well as the "evening" increase observed in the levels of androstenedione during the periovulatory period was not able to mask the circadian rhythm. A circadian rhythm in pregnenolone, 17-hydroxyprogesterone, testosterone, and dihydrotestosterone levels was detected only in certain phases of the cycle. All these steroids showed a circadian rhythm in the early follicular phase. The rhythm of pregnenolone and 17-hydroxyprogesterone was still present in the periovulatory period but was no longer detectable in the luteal phase, meanwhile that of testosterone and dihydrotestosterone was not demonstrable neither in the periovulatory period nor in the luteal phase. Compared to the levels of the follicular phase, an increase in pregnenolone and 17-hydroxyprogesterone levels was observed in the periovulatory period which was followed by a further rise in the luteal phase. This increase completely masked the circadian rhythm in the luteal phase. An inverse circadian rhythm in lutropin levels was detected during the luteal phase. The "morning" values were lower than those found during the "evening" period. No such changes were observed in the other phases of the cycle. In none of the phases studied did the levels of progesterone or estradiol show any circadian variation. The data indicate that a circadian rhythm in the peripheral levels of a given steroid mainly depends on the relative contributions of the ovaries and adrenals and that these contributions exhibit major differences at the various phases of the cycles. It is concluded that - in contradistinction to the situation in the human male - in normally menstruating women, the peripheral levels of steroids of predominantly gonadal origin do not exhibit a circadian rhythmicity.

Adrenal Glands↗
PubMed2001

Thermo-Raman studies on NaH(2)PO(4)-H(2)O for dehydration, condensation, and phase transformation.

Thermo-Raman spectroscopy was applied to study the thermal properties of NaH(2)PO(4)-2H(2)O from room temperature up to 600 degrees C. Raman spectra recorded at every degree of the temperature interval by monitoring the internal modes gave the microscopic picture of dehydration of NaH(2)PO(4)-2H(2)O, the condensation of NaH(2)PO(4), and the phase transformation of NaPO(3). The spectral variation observed could distinguish two steps of dehydration, resulting in the formation of NaH(2)PO(4)-H(2)O and NaH(2)PO(4) as compositional species from NaH(2)PO(4)-2H(2)O. The thermo-Raman intensity (TRI) and differential thermo-Raman intensity (DTRI) thermograms also showed two steps of dehydration in the temperature range from 42 to 52 degrees C and from 60 to 72 degrees C with a maximum rate at 48 and 68 degrees C, respectively. Furthermore, condensation resulted in sodium dihydrogen diphosphate (Na(2)H(2)P(2)O(7)) and sodium metaphosphate (NaPO(3)) in two steps at 212-224 and 260-360 degrees C, respectively. Clear evidence in the spectral variation representing two phase transformations of NaPO(3) at the temperature of 345 and 515 degrees C with three different polymorphs (phase III, phase II, and phase I of NaPO(3) in increasing order of temperature) was also observed. The thermal methods thermogravimetry, differential thermogravimetry, differential thermal analysis, and differential scanning calorimetry also supported the results but could not give a clear idea due to the lack of direct structural information.

Journal Article↗
PubMed1977

Dynamics of upper urinary tract. III. The activity of renal pelvis during pressure variations.

In one phase of an analysis of renal pelvis activity in pigs "in vivo," controlled pressure changes were induced in the pelvis and electromyogram registrations were taken from both pelvis and ureter. Animals were anesthetized and the changes in intrapelvic pressure were effected by drainage or infusion via a catheter introduced into the pelvis through the parenchyma of the kidney. Frequency of pelvic activity increased temporarily under pressure increase and reduced temporarily under pressure fall. These phenomena were more emphatic when rapid pelvic pressure rise was induced by infusion. The observations lend weight to previous observations of changing pelvic activity during pressure and diuresis change, and also support the hypothesis that pelvic function is a stretch response, i.e., that the smooth muscle of the pelvis reacts just as does other smooth muscle. Observation of cessation in ureter activity during drainage while pelvic activity continues suggests that, under normal conditions, ureteric activity depends not on conduction of a pelvic impulse alone, but on a combination of such an impulse with a urine bolus.

Action Potentials↗
PubMed1982

Thyrotropin-like immunoreactivity in the pituitary and three brain regions of the female rat: diurnal variations and the effect of thyroidectomy.

A method for extracting and assaying TSH-like immunoreactivity (TSH-LI) in regions of the central nervous systems (CNS) of individual rats was developed and validated. Serial dilutions of tissue extracts paralleled dilutions of purified rat TSH standard in the RIA, and tissue TSH-LI comigrated electrophoretically with TSH standard. TSH-LI was measured in the pituitary (PIT), the medial basal hypothalamus (MBH), the remainder of the hypothalamus (HYPO), and the cerebral cortex (CC). Female rats were maintained on a normal 12-h light, 12-h dark cycle (LD; onset of light, 0730 h) or an inverted 12-h light, 12-h dark cycle (DL; onset of light, 1930 h) for 3 weeks and then killed at 4-h intervals throughout the day. Another group of rats on the LD photoperiod were either thyroidectomized or sham thyroidectomized and killed 3 weeks later at 1000 h. Diurnal variations of TSH-LI were present in the PIT, MBH, HYPO, and CC on the LD photoperiod (P less than 0.05). The acrophases of MBH, HYPO, and CC TSH-LI diurnal variations occurred soon after the onset of darkness, whereas the PIT TSH-LI variation peaked soon after the onset of light. Inverting the photoperiod inverted the PIT TSH-LI diurnal variation, but central nervous system TSH-LI variations were not phase shifted after 3 weeks on the inverted photoperiod. Thyroidectomy elevated plasma and MBH TSH-LI levels (P less than 0.05), but PIT, HYPO, and CC TSH-LI levels were not significantly different from those in sham-operated controls. These results indicated that brain TSH concentrations could change under different physiological states independently of changes in PIT or plasma TSH. Although brain TSH exhibited diurnal variations, the data suggested that the phase of these variations was not set by the light-dark cycle.

Animals↗
PubMed1992

Phase-separation inhibitors and prevention of selenite cataract.

The variation of the phase-separation temperature (Tc) was studied in lenses during formation of cataracts induced by a subcutaneous injection of sodium selenite. In normal control animals, the Tc decreased monotonically with increasing age. Approximately 2 days after administration of the selenite the Tc decreased sharply to a minimum, and then at day 4 the Tc increased dramatically toward body temperature. Mature irreversible cataracts formed approximately 6 days after injection of the selenite. Intraperitoneal administration of WR-77913, a phase-separation inhibitor, prevented the abnormal variation of Tc in vivo. When injected into control animals without selenite, WR-77913 produced no abnormal variation in Tc. The results confirm that Tc is a sensitive measure of early changes in the lens and that opacification associated with abnormal variation in Tc can be prevented in vivo by using a phase-separation inhibitor.

Amifostine↗
PubMed2004

Variation of the microbial activity during the acclimation phase of a SBR system degrading 4-chlorophenol.

The variation of microbial activity during acclimation to 4-chlorophenol (4CP) in an aerobic automated sequencing batch reactor was studied. The results show a reduction in degradation time as the acclimation process occurred. During acclimation for an initial concentration of 50 mg 4CP/L, degradation time was reduced from 40 h to 50 min after 10 cycles. In the case of an initial concentration of 100 mg/L, degradation time was reduced from 52 h to 1.16 h, also after 10 cycles. Doubling the initial concentration of a previously acclimated sludge produces only a slight increase in degradation time. It was found that as acclimation took place, the affinity of the consortia to biodegrade the toxic increased, whereas the ability to biodegrade acetate decreased. The evolution of the substrate uptake rate over time during the acclimation period was highly correlated with an exponential relationship. It was also observed that acclimation decreased both the production of a toxic metabolite and the sludge volumetric index.

Acclimatization↗
PubMed1993

Frequency statistical method for evaluating cosine invariants of three-phase relationships.

A new variation on the established procedure to evaluate three-phase structure invariants through quadrupole relationships is described. This method differs from earlier algebraic formulations in that the cosine-invariant estimates are based on a conditional observed frequency distribution of magnitude of E magnitudes for the quadrupole, rather than on the values of the magnitudes themselves. Successful applications of this method to a number of structures that ranged in size from 84 to 317 independent non-hydrogen light atoms are given.

Crystallography↗
PubMed1993

DNA synthesis and ploidy in non-Hodgkin's lymphomas demonstrate intrapatient variation depending on circadian stage of cell sampling.

Significant circadian cell cycle variations with a maximal number of cells in S-phase during the night have been found in a series of 24 patients (18 men and 6 women) with histologically established non-Hodgkin's lymphomas. Pathological lymph nodes of a total of 26 patients were punctured and aspirated by fine needle technique every 4 h during a single 24-h time span. Twenty-four patients (92.3%) had Stage III or IV disease. Twelve patients (46.1%) had low grade, 10 patients (38.5%) had intermediate grade, and 4 patients (15.4%) had high grade lymphomas according to the Working Formulation. The samples were analyzed by flow cytometry, and DNA synthesis (S-phase) and ploidy were determined according to circadian stage. The individual mean 24-h S-phase varied from 2.2 +/- 1.2% (mean +/- SD) to 24.0 +/- 3.3%. Within the group of patients with low grade lymphomas, a wide range in mean S-phase from 2.4 +/- 1.2% to 9.2 +/- 2.8% was observed. The percentage variation within each patient between the lowest and highest S-phase as compared to the lowest value (range of change) during the 24-h time span varied from 21 to 353%, with a mean range of change of 128 +/- 19%. When each individual S-phase series was converted to percent of mean and combined for analysis by one-way analysis of variance to test for time-effect across 2 12-h time spans (8 p.m.-8 a.m. versus 8 a.m.-8 p.m.), S-phase variation according to circadian stage was found to be statistically significant (P < 0.004), with higher values found in the 8 p.m.-8 a.m. time span. By single cosinor analysis, S-phase yielded a near significant P value of 0.069 for the least-squares fit of a 24-h cosine to all data as percent of mean, with the acrophase found to be near midnight (0.05 h). For those patients with low and intermediate grade lymphomas and with mean S-phase values < 10.0%, we found that mean S-phase was higher during winter (5.8 +/- 0.4%) than during spring (3.8 +/- 0.3%) or during fall (3.6 +/- 0.3%) (P < 0.001, analysis of variance). Twenty-one of the 26 patients (80.8%) had an aneuploid, hypodiploid, or near diploid population in one or several of the repeated samples. For the whole series, the DNA indices for the aneuploid populations varied from 1.09 to 1.96, the median DNA index being 1.20.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Intensity artifacts in MRI caused by gradient switching in an animal-size NMR magnet.

The switching of magnetic field gradients in MRI gives rise to eddy currents in the structural components of superconducting magnet systems. The associated magnetic fields cause intensity artifacts which are particularly severe in some animal-size systems. We treat theoretically three mechanisms which cause intensity artifacts in one-dimensional projection images obtained by a spin-echo technique. The first is an off-resonance effect, caused by applying the refocusing pulse before the read compensation gradient pulse has decayed sufficiently. The other two mechanisms are caused by a spatial dependence of the phase accumulated by the spins at the time of formation of the echo, as a result of the eddy current fields. First, interference causes a loss of transverse magnetization because of a variation in the phase of spins which lie on the same isochromat during the read gradient pulse. Second, a variation of the phase of the spins in a direction orthogonal to the isochromats causes spins throughout the sample to refocus at different times. These two mechanisms are fundamentally different, since interference can occur even if the main magnetic field is homogeneous, whereas improper refocusing does not. It is shown that there is no loss of intensity by the interference mechanism if phase encoding is used to form two-dimensional images. This may well be a major reason why images obtained by 2DFT have been found to be generally superior to those obtained by projection reconstruction. Experimentally, the distribution of intensity in one-dimensional projection images of a square slice phantom is compared with theoretical intensities, estimated using eddy current field reported in the preceding paper.

Artifacts↗
PubMed1997

Wall shear rate distribution in an abdominal aortic bifurcation model: effects of vessel compliance and phase angle between pressure and flow waveforms.

The goal of this study was to determine how vessel compliance (wall motion) and the phase angle between pressure and flow waves (impedance phase angle) affect the wall shear rate distribution in an atherogenic bifurcation geometry under sinusoidal flow conditions. Both rigid and elastic models replicating the human abdominal aortic bifurcation were fabricated and the wall shear rate distribution in the median plane of the bifurcation was determined using the photochronic flow visualization method. In the elastic model, three phase angle conditions were simulated (+12, -17, -61 deg), and the results compared with those obtained in a similar rigid model. The study indicates a very low (magnitude close to zero) and oscillatory wall shear rate zone within 1.5 cm distal to the curvature site on the outer (lateral) wall. In this low shear rate zone, unsteadiness (pulsatility) of the flow greatly reduces the mean (time-averaged) wall shear rate level. Vessel wall motion reduces the wall shear rate amplitude (time-varying component) up to 46 percent depending on the location and phase angle in the model. The mean wall shear rate is less influenced by the wall motion, but is reduced significantly in the low shear region (within 1.5 cm distal to the curvature site on the outer wall), thus rendering the wall shear rate waveform more oscillatory and making the site appear more atherogenic. The effect of the phase angle is most noteworthy on the inner wall close to the flow divider tip where the mean and amplitude of wall shear rate are 31 and 23 percent lower, respectively, at the phase angle of -17 deg than at -61 deg. However, the characteristics of the wall shear rate distribution in the low shear rate zone on the outer wall that are believed to influence localization of atherosclerotic disease, such as the mean wall shear rate level, oscillation in the wall shear rate waveform, and the length of the low and oscillatory wall shear rate zone, are similar for the three phase angles considered. The study also showed a large spatial variation of the phase angle between the wall shear stress waveform and the circumferential stress waveform (hoop stress due to radial artery expansion in response to pressure variations) near the bifurcation (up to 70 deg). The two stresses became more out of phase in the low mean shear rate zone on the outer wall (wall shear stress wave leading hoop stress wave as much as 125 deg at the pressure-flow phase angle of -61 deg) and were significantly influenced by the impedance phase angle.

Aorta, Abdominal↗