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PubMed1999

Protection against peroxynitrite.

Peroxynitrite formed in vivo from superoxide and nitric oxide can mediate oxidation, nitration, or nitrosation reactions, leading to impaired function, toxicity, and alterations in signaling pathways. Protection against peroxynitrite is important for defense of normal tissue, especially during inflammation. Biological protection against peroxynitrite is organized in three categories: prevention, interception, and repair. Prevention is the control of the formation of peroxynitrite precursors, nitric oxide and superoxide. Interception is by direct reaction with peroxynitrite, leading to non-toxic products. In this regard, organoselenium compounds, metalloporphyrin derivatives, and peroxidases (e.g. glutathione peroxidase and myeloperoxidase) exhibit high second-order rate constants with peroxynitrite. Ebselen, like glutathione peroxidase, protects in a catalytic fashion utilizing glutathione as reductant in the peroxynitrite reductase reaction. Protection by metalloporphyrins can be maintained through glutathione or ascorbate. Repair processes remove damaged products and restitute intact biomolecules.

Animals↗
PubMed1979

Inhibition of ovarian, placental, and adrenal steroidogenesis in the rhesus monkey by trilostane.

Trilostane inhibits adrenal, ovarian, and placental steroidogenesis when administered orally to rhesus monkeys. By inhibiting 3 beta-hydroxysteroid dehydrogenase activity, it causes an increase in circulating levels of pregnenolone. Trilostane reverses the stimulation of luteal progesterone production and the delay in onset on menstruation induced by human chorionic gonadotropin. In pregnant monkeys it reduces circulating progesterone levels and is an effective interceptive agent if given for 5 days beginning on day 16, 25, or 50 of gestation. Concurrent administration of progesterone prevents this interceptive effect. Trilostane reduces plasma cortisol levels at doses lower than those necessary to terminate pregnancy.

3-Hydroxysteroid Dehydrogenases↗
PubMed2000

Strategies used to stabilize the elbow joint challenged by inverted pendulum loading.

The stiffness of activated muscles may stabilize a loaded joint by preventing perturbations from causing large displacements and injuring the joint. Here the elbow muscle recruitment patterns were compared with the forearm loaded vertically (a potentially unstable inverted pendulum configuration) and with horizontal loading. Eighteen healthy subjects were studied with the forearm vertical and supinated and the elbow flexed approximately 90 degrees. In the first experiment EMG electrodes recorded activity of biceps, triceps, and brachioradialis muscles for joint torques produced (a) by voluntarily exerting a horizontal force isometrically (b) by voluntarily flexing and extending the elbow while the forearm was loaded vertically with 135N. The relationship between the EMG and the torque generated was quantified by the linear regression slope and zero-torque intercept. In a second experiment a vertical load increasing linearly with time up to 300N was applied. In experiment 1 the EMG-torque relationships for biceps and triceps had an intercept about 10% of maximum voluntary effort greater with the vertical compared to the horizontal force, the inverse was found for Brachioradialis, but the EMG-torque slopes for both agonist and antagonistic muscles were not different. In experiment 2 there were 29 trials with minimal elbow displacement and all the three muscles activated on the order of 11% of maximum activation to stabilize the elbow; 19 trials had small elbow extension and 14 trials small flexion requiring altered muscle forces for equilibrium; 7 trials ended in large unstable displacement or early termination of the test. An analysis indicate that the observed levels of muscle activation would only provide stability if the muscles' short-range stiffness was at the high end of the published range, hence the elbow was marginally stable. The stability analysis also indicated that the small elbow extension increased stability and flexion decreased stability.

Algorithms↗
PubMed1997

Fabric and elastic principal directions of cancellous bone are closely related.

Cancellous bone architecture and mechanics are intimately related. The trabecular architecture of cancellous bone is considered determined by its mechanical environment (Wolff's law), and the mechanical properties of cancellous bone are inversely determined by the trabecular architecture and material properties. Much effort has been spent in expressing these relations, but the techniques and variables necessary for this have not been fully identified. It is obvious, however, that some measure of architectural anisotropy (fabric) is needed. Within the last few years, volume-based measures of fabric have been introduced as alternatives to the mean intercept length method, which has some theoretical problems. This paper seeks to answer which of four different fabric measures best predicts finite element calculated mechanical anisotropy directions. Twenty-nine cancellous bone specimens were three-dimensionally reconstructed using the automated serial sectioning technique. A series of large-scale finite-element analyses were performed on each of the three-dimensional reconstructions to calculate the compliance matrix for each specimen, from which the mechanical principal directions were derived. The architectural anisotropy was determined in three-dimensional space for each specimen using mean intercept length (MIL), volume orientation (VO), star volume distribution (SVD) and star length distribution (SLD). Each of the architectural anisotropy results were expressed by a fabric tensor. Architectural main directions were determined from the fabric tensors and compared with the FE-calculated mechanical anisotropy directions. All architectural measures predicted the mechanical main directions rather well, which supports the assumption that mechanical anisotropy directions are aligned with fabric directions. MIL showed a significant, though very small (1.4 degrees), deviation from the primary mechanical direction. VO had difficulty in determining secondary and tertiary mechanical directions; its mean deviation was 8.9 degrees. SVD and SLD provided marginally better predictors of mechanical anisotropy directions than MIL and VO.

Animals↗
PubMed2002

Retention characteristics of an immobilized artificial membrane column in reversed-phase liquid chromatography.

Retention for a varied group of compounds on an immobilized artificial membrane column (IAM PC DD2) with a methanol-water mobile phase is shown to fit a second-order model for the retention factor (log k) as a function of the volume fraction of organic solvent. The numerical value of the intercept obtained by linear extrapolation to zero organic solvent (log k(w)) is shown to depend on the range of mobile phase composition used for the extrapolation. Each series of intercepts so obtained represents a different hypothetical distribution system as identified by the system constants of the solvation parameter model. Although a linear model is a poor fit for isocratic retention data, the linear solvent strength gradient model provides a reasonable estimate of isocratic retention factor values that are (slightly) larger than experimental values, but provide the same chemical information for the system. These preliminary results suggest that gradient elution may prove to be a rapid and useful method for creating system maps for column characterization and method development. In this work a system map is provided for methanol-water compositions from 0 to 60% (v/v) methanol and additional system constants for acetonitrile-water compositions containing 20 and 30% (v/v) acetonitrile. It is shown that the main factors contributing to retention on the IAM PC DD2 column are favorable cavity formation and dispersion interactions, electron lone pair interactions and the hydrogen-bond basicity of the sorbent. The latter feature more than any other distinguishes the IAM column from conventional chemically bonded phases. Interactions of a dipole-type (weakly) and inability to compete with the mobile phase as a hydrogen-bond acid reduce retention. A comparison of system constant ratios is used to demonstrate that the retention properties of the IAM column are not easily duplicated by conventional chemically bonded phases. The retention characteristics of the IAM column, however, are strongly correlated with the retention properties of pseudostationary phases used for micellar electrokinetic chromatography, which provide a suitable alternative to IAM columns for physical property estimations. By the same comparative method it is shown that retention on the IAM column possesses some similarity to biomembrane absorption processes, allowing suitable correlation models to be developed for the estimation of certain biopartitioning properties.

Chromatography, Liquid↗
PubMed1995

QTc behavior during treadmill exercise as a function of the underlying QT-heart rate relationship.

A mathematic description of the behavior of the Bazett-corrected QTc interval during exercise was developed from the underlying relationship between the unadjusted QT interval and heart rate in 94 normal men. Measurements were made from digitized precordial lead V5 complexes that were averaged by computer over 20-second periods at upright control (mean rate, 78 beats/min), during moderate exercise (mean rate, 125 beats/min), and at peak effort (mean rate, 162 beats/min), using a gently graded treadmill protocol that produces small heart rate increments between 2-minute stages. Although the group mean QTc interval increased during early exercise and decreased during higher exercise workloads, the mean unadjusted QT interval decreased throughout exercise in a strongly linear relationship with increasing heart rate: QT[ms] = 481 - 1.32HR, R2 = .99, where HR stands for heart rate. As a consequence of this linearity, the behavior of the QTc interval over a range of heart rates generally found during exercise could be modeled as a function of the slope (m) and intercept (b) of the observed relationship, since the Bazett relationship QTc = QT[ms]/R-R0.5 can, in this context, be rewritten simply as QTc = (481 - 1.32HR)/(60/HR)0.5, which reproduces the observed biphasic QTc interval behavior. Plots of the generalized equation QTc = (b - mHR)/(60/HR)0.5 allow theoretical exploration of QTc interval behavior that might result from varied disorders with different slopes (m) and intercepts (b), and these regression-based descriptors of the QT-heart rate relationship may provide useful, additional definitions of normal and abnormal QT interval behavior during exercise.

Electrocardiography↗
PubMed1985

Comparisons of the potential utility of LHRH agonists and antagonists for fertility control.

Prospects for the use of LHRH analogs for human fertility control have been reviewed with particular reference to two highly potent representatives. Nafarelin acetate, the LHRH agonist, has a potency about 200 X that of LHRH and is consistently effective in suppressing gonadal function in females through a desensitization of LHRH receptors in the pituitary. Such agents show promise as ovulation inhibitors for women although concern has been expressed over the dangers of unopposed estrogen or alternatively hypoestrogenemia. Although early studies indicated luteolysis in women and interceptive action in baboons it is now clear that the LHRH agonists will not be useful clinically to terminate pregnancy. Wide species differences in the male response to LHRH agonists exist. Unfortunately azoospermia has not been achieved in men. The LHRH antagonists, typified by [N-Ac-D-Nal(2)1, D-pCl-Phe2, D-Trp3, D-hArg(Et2)6, D-Ala10]LHRH, require high doses to competitively inhibit responses to endogenous LHRH. Their advantages include a rapid induction of the hypogonadal state with apparently little species or sexual variation in response. Based on animal studies, preferable utility of the antagonists would lie in male contraception and pregnancy interception.

Abortion, Induced↗
PubMed1991

Venous waterfalls in coronary circulation.

Several studies of flow through collapsible tubing deformed by external pressures have led to a concept known as the "vascular waterfall". One hallmark of this state is a positive zero-flow pressure intercept (Pe) in flow-pressure curves. This intercept is commonly observed in the coronary circulation, but in blood-perfused beating hearts a vascular waterfall is not the only putative cause. To restrict the possibilities, we have measured flow-pressure curves in excised non-beating rabbit hearts in which the coronary arteries were perfused in a non-pulsatile way with a newtonian fluid (Ringers solution) containing potent vasodilator drugs. Under these circumstances, vascular waterfalls are believed to be the only tenable explanation for Pe. In physical terms the waterfall is a region where the vessel is in a state of partial collapse with a stabilized intraluminal fluid pressure (Pw). It is argued that the most probable site of this collapse was the intramural veins just before they reached the epicardial surface. In accord with the waterfall hypothesis, Pe increased as the heart became more edematous, but flow-pressure curves also became flatter, implying multiple waterfalls with differing Pws, leading to complete collapse of some of the venous channels. The principal compressive force is believed to have been the interstitial fluid pressure as registered through a needle (Pn) implanted in the left ventricular wall, but a small additional force (Ps) was probably due to swelling of interstitial gels. A method is presented for estimating Ps and Pw. Unlike rubber tubing, blood vessels are both collapsible and porous. Apparently because of increased capillary filtration, Pn was found to increase linearly with the perfusion pressure. Thus, Pw was not the same at all points on the flow-pressure curve. This finding has interesting implications with respect to the concept of coronary resistance.

Animals↗
PubMed1999

How efficient are central mechanisms for the learning and retention of coincident timing actions?

We compared the adaptive strategy and retention capacity of a deafferented subject and control subjects when intercepting, with a sliding-throw, an apparent movement coming at various speeds. Subjects were submitted to five practice sessions (30 trials per session) and to a retention test. The throwing kinematics was analysed, and spatial and temporal performance errors were measured. With practice, the deafferented subject showed modifications in movement initiation strategies and throwing patterns. With a slow apparent movement, the deafferented subject's initial behavior was characterized by short movement initiation and movement times. With practice, she showed an important increase in movement time in session 5, allowing longer visual control and leading to better temporal and spatial accuracy than that shown in session 1. In the retention session, the deafferented patient showed a late movement initiation strategy, similar to that of the control subjects. This increased movement initiation time was accompanied by an improved temporal accuracy compared to the deafferented subject's early results. However, spatial accuracy improvement was labile and could not be maintained over the retention interval. At the fast speed, all temporal components of the response, namely, movement initiation time (MIT), movement time (MT), and disk travel time (DTT), were similar for the deafferented and control subjects. Overall, the deafferented subject reduced her temporal error through practice, though without attaining the control subjects' accuracy. However, with a fast-moving stimulus, she showed a deteriorated spatial accuracy, even doubling her spatial errors at retention. In brief, the deafferented subject achieved proper temporal (perceptivo-cognitive) lasting control of her interceptive action, whereas spatial (sensorimotor) regulation raised mnemonic problems.

Afferent Pathways↗
PubMed1998

Diurnally changing effects of locomotor activity on body temperature in laboratory mice.

In mice circadian body temperature curves are masked due to the effect of motor activity. However, body temperature will not immediately reflect activity, but rather the integrated activity over IT minutes (integration time) and after a certain delay (lag), and the sensitivity to such masking may change throughout the circadian cycle. The aims of the present investigation were to estimate IT and lag, to quantify the effect of motor activity on body temperature at different times of the day, and, using these results, to draw temperature curves that are closer to the endogenous one. Activity and body temperature of adult male laboratory mice were recorded telemetrically at 10-min intervals. Animals were housed in air-conditioned rooms (T = 22+/-2 degrees C; relative humidity: 55-65%) with a light-dark cycle of 12 h:12 h (light from 0700 to 1900 hours) and food and water available ad lib. The diurnal activity and body temperature rhythms were similar with a main maximum during the dark time and a secondary maximum immediately following lights-on. Nearly all changes of activity were reflected in body temperature. IT and lag were established on the basis of the best correlation between body temperature and activity (overlapping 4-h sections of 12 days) for all combinations of IT from 10 to 90 min and lag from 0 to 50 min (10-min steps each). The overall means of IT and lag were 40 and 0 min, respectively. During the dark time the values were somewhat larger, but not significantly so. The correlation between activity and body temperature was significantly better in the light time compared to the dark time. The sensitivity of the body temperature to changes in activity was investigated by linear regression analysis for every hour over 12 days (IT = 40 min, lag = 0 min). The gradients assessed by regression analysis showed a diurnal pattern with maximal values during the light time (p < 0.01). Thus, body temperature was raised by activity more during the light time (minimum of body temperature and activity) than during the dark time. The intercepts showed a nearly sinusoidal diurnal pattern with maximal values in the middle of the dark time. Accepting that the intercepts correspond to zero activity at a certain time of day, one might use them to get a curve that is closer to the endogenous body temperature rhythm. Mechanisms (circadian and thermoregulatory) that might cause the diurnally changing sensitivity of body temperature to activity are discussed.

Animals↗
PubMed1997

Morphological determinants of peripheral lung mechanical changes induced by capsaicin.

We studied the morphological elements associated with airway and pulmonary tissue responses to capsaicin in mechanically ventilated guinea pigs. Lungs were excised and frozen in liquid nitrogen 3 and 20 min after capsaicin infusion (1 or 100 micrograms/kg i.v.). Using image analysis, we obtained contraction index (CI) and peribronchial edema area (CUFF) for both central (C) and peripheral airways (P). We also assessed alveolar size (mean linear intercepts, Lm) and tissue distortion (standard deviation of the number of intercepts, SDI). Multiple regression analysis showed significant associations between pulmonary tissue resistance (Rti) and CUFFP (p < 0.001); pulmonary dynamic elastance and SDI (p = 0.002); and airway resistance and CUFFC (p < 0.0001). Our results suggest that increases in Rti observed in guinea pigs after capsaicin infusion are primarily dependent on changes in the small airways, mainly peribronchiolar edema; the increase in lung elastance is related to distortion of parenchymal tissues; and large airway edema contributes significantly to airway resistance.

Airway Resistance↗
PubMed2002

Measurement of steroid sex hormones in serum: a comparison of radioimmunoassay and mass spectrometry.

Concern has been raised about the adequacy of radioimmunoassays to measure steroid sex hormones in population studies. We compared steroid sex hormone measurements in serum by radioimmunoassay with mass spectrometry. Four male and four female serum pools with known relative concentrations of steroid sex hormones were measured multiple times by both methods. Because measurements are expected to increase linearly with concentration for each sex, we examined whether the linear regressions of hormone measurements on concentration were the same for radioimmunoassay and mass spectrometry. Estradiol, estrone, androstenedione, testosterone, and dehydroepiandrosterone sulfate were measured in female pools; testosterone, dihydrotestosterone, androstenedione, and dehydroepiandrosterone sulfate were measured in male pools. Regression slopes for radioimmunoassay and mass spectrometry measurements were comparable for all hormones except androstenedione, which had a steeper slope when measured by mass spectrometry (P < or = 0.02). Intercepts for radioimmunoassay and mass spectrometry were similar and close to zero for estradiol, androstenedione, dehydroepiandrosterone sulfate, and in male samples, testosterone. For testosterone in female samples, estrone, and dihydrotestosterone, radioimmunoassay and mass spectrometry intercepts differed significantly. Standard deviations of individual measurements by radioimmunoassay and mass spectrometry differed by hormone and serum concentration; neither method consistently measured hormone concentrations with less variability. Our findings suggest that although absolute concentrations may differ for some hormones, radioimmunoassay and mass spectrometry can yield similar estimates of between subject differences in serum concentrations of most steroid sex hormones commonly measured in population studies. Relative power of studies using radioimmunoassay and mass spectrometry will depend on the hormones measured and their serum concentrations.

Adolescent↗
PubMed2001

Influences of visual pitch and visual yaw on visually perceived eye level (VPEL) and straight ahead (VPSA) for erect and rolled-to-horizontal observers.

Localization within the space in front of an observer can be specified along two orthogonal physical dimensions: elevation ('up', 'down') and horizontal ('left','right'). For the erect observer, these correspond to egocentric dimensions along the long and short axes of the body, respectively. However, when subjects are rolled-to-horizontal (lying on their sides), the correspondence between the physical and egocentric dimensions is reversed. Employing egocentric coordinates, localization can be referred to a central perceptual point-visually perceived eye level (VPEL) along the long axis of the body, and visually perceived straight ahead (VPSA) along the short axis of the body. In the present experiment, measurements of VPEL and of VPSA were made on each of eight subjects who were either erect or rolled-to-horizontal while monocularly viewing a long 2-line stimulus (two parallel, 64 degrees -long lines separated by 50 degrees ) in otherwise complete darkness that was centered on the eye of the observer and was tilted out of the frontoparallel plane by a variable amount and direction (from -30 degrees to +30 degrees in 10 degrees steps). The stimulus tilt was either around an axis through the center of the two eyes (pitch; VPEL was measured) or around the long axis of the body that passed through the center of the viewing eye (yaw; VPSA was measured). Large variations in the localization settings were measured that were systematic with stimulus tilt. The slopes of the functions plouing the deviations from veridicality against the orientation of the 2-line stimulus ('induction functions') were larger for the rolled-to-horizontal observer than for the erect observer for both VPEL and VPSA, and for a given body orientation were larger for the VPEL discrimination than for the VPSA discrimination; the influences of body orientation in physical space and the direction of the discrimination relative to the body were lineraly additive. Both the y-intercepts of the induction functions and the central perceptual point measured in complete darkness were lower when the norm setting by the subject was along the vertical than when it was along the horizontal; this held for both the VPEL and VPSA discriminations. The systematic effects of body orientation on the slopes and of line orientation on the y-intercepts and dark values result from an effect of gravity on the settings and fit well to a general principle: any departure from erect posture increases the induction effects of the visual stimulus. The effect of gravity is consistent with the effect of gravity in previous work in high-g environments with the VPEL discrimination.

Analysis of Variance↗
PubMed2003

Comparisons of coarse and fine versions of two carbons for reducing the bioavailabilities of sediment-bound hydrophobic organic contaminants.

Coarse (whole) and finely ground Ambersorb 1500 and coarse and fine coconut charcoal were compared as to their efficiencies in scavenging organic contaminants desorbed from sediment. Aqueous slurries of a test sediment spiked (1 ppm) with p,p(')-DDE (DDE), 2,2('),5,5(')-tetrachlorobiphenyl (TCB), naphthalene (NAP), or phenanthrene (PHEN), and containing 1% levels of the test carbons were treated by shaking at 35 degrees C while exposed to clusters of low-density polyethylene membrane (detox spiders). Controls consisted of spiked sediments and detox spiders but no added carbon of any kind and thus represented unimpeded bioavailabilities (to the spiders). After the treatments--agitation periods from 2.5 to 60 h, depending on contaminant hydrophobicity--the exposed detox spiders were analyzed. The fine carbon of either type was more effective than its coarser variant in obstructing contaminant bioavailabilities. The finer variants of both carbons obstructed the bioavailabilities of NAP and PHEN equally well as did the coarser variants of both. Whole Ambersorb 1500 and coarse coconut charcoal were similarly ineffective in intercepting TCB and DDE. Ground Ambersorb 1500 obstructed virtually all bioavailability of all four contaminants and was far more effective than fine coconut charcoal in intercepting DDE and TCB. An additional experiment compared the effectiveness of ground Ambersorb 1500 and fine coconut charcoal in obstructing the bioavailabilities from sediment of a broad array of spiked organochlorine pesticides. The performance of ground Ambersorb 1500 was again found to be superior; the bioavailable levels of each of the 27 pesticides were markedly lower in the presence of ground Ambersorb 1500 than in the presence of fine coconut charcoal.

Biological Availability↗
PubMed2001

Effects of bulk precipitation pH and growth period on cation enrichment in precipitation beneath the canopy of a beech (Fagus moesiaca) forest stand.

The effects of bulk precipitation pH and growth period (growing and dormant) on cation enrichment beneath foliage were examined in a beech (Fagus moesiaca) forest stand during a 48-month period. The bulk precipitation pH values ranged from 4.2 to 7.2. The lowest values were observed in winter due to fossil fuel combustion in a nearby big city. The ratio of monthly ion fluxes of throughfall plus stemflow over monthly ion fluxes of bulk precipitation was chosen as an index of cation enrichment and, therefore, as the dependent variable. Bulk precipitation pH and growth period were chosen as independent factors. Precipitation interception (%) by tree canopies was also taken into account. It was found that the pH factor was significant only for H+ ion enrichment suggesting neutralization of H+ ions in the beech canopy, whereas Mg2+ and K+ enrichment were greater in the growing period, probably as a result of leaching. Crown interception was negatively significant for NH4+-N enrichment.

Acid Rain↗
PubMed2003

Quantifying the effects of forestry practices on the recovery of upland streams and lochs from acidification.

Trends in long-term chemistry data are presented for 37 acidified upland streams and lochs, located in four areas (A, B, C and D) across Scotland, to provide a comparison between recovery rates of moorland catchments and forest catchments at different stages of the management cycle. For all sites, non-marine sulfate (nm-SO(4)) showed a significant decline in annual median concentrations, the greatest decline being in streams draining felled catchments, which showed a 50% greater decline than catchments with moorland or young, aggrading forests. A similar pattern was found for chloride (Cl) concentrations in Area C, which reflected the reduced interception of sea-salt aerosols following clearfelling. However, high elevation moorland sites in Area D also revealed significant declines in Cl while trends in aggrading forest sites in this area were insignificant. Alkalinity (ALK) and pH increased more at sites where felling had taken place than at moorland or young forest sites while aggrading forest catchments appeared to be most resistant to changes in pH and ALK. Associated with these acid-base changes was a corresponding decline in labile aluminium (Al-L) concentrations. The pattern of nitrate (NO(3)) change was especially affected by the timing of felling in forested catchments. Large negative trends in NO(3) at stream sites were associated with felling during the early part of the study period. This downward trend was further enhanced as NO(3) concentrations fell below pre-felling levels as the second rotation crop became established. Few forest sites showed significant increases in NO(3) due to felling in the latter part of the study period. Most moorland loch sites showed a small but significant increase in NO(3,) probably in response to similar increases in N deposition and/or climatic impacts. Dissolved organic carbon (DOC) increased significantly at both forest and moorland sites, however, the extent of these increasing trends appeared to be positively correlated with absolute DOC concentrations. Despite the complex response of streams and lochs during the various stages of the forest cycle, especially for NO(3), both forest and moorland catchments showed generally similar and rapid responses to reductions in S deposition. Nevertheless, forested sites are still more acid and have higher concentrations of toxic forms of Al than moorland sites. Although the proposed emission reductions in Europe are likely to result in a continuing decline in S and N loadings to catchments, the continuing policy of planting second rotation forests in these acidified catchments may, in the long-term, delay or halt chemical and biological recovery. However, in the short-term, any increase in the uptake of N deposition by aggrading forests should help to counteract the acidifying effects of a small increase in the interception of S and N compounds.

Acid Rain↗
PubMed1983

Biological assay for zinc availability in wheat germ.

Our objective was to develop a method to determine the bioavailability of zinc in wheat germ. Weanling rats were fed for 10 days a Zn-free diet supplemented with different levels of Zn, with or without 2% wheat germ. Zinc concentrations of either tibia or femurs were plotted directly against Zn added to the diet, giving two lines that were essentially parallel. A multiple regression model was used to obtain a common slope but different intercepts for the lines. The amount of available Zn was calculated by taking the ratio of the difference in intercepts to the common slope. The result showed that wheat germ contained 163.7 micrograms Zn/g, of which 86.7% was bioavailable to the rat.

Animal Feed↗
PubMed1997

Foliar and soil uptake of 134Cs and 85Sr by grape vines.

The foliar and soil uptake of 134Cs and 85Sr by grape vines and their subsequent translocation to fruits and to the other plant compartments is described. Grape vine plants growing in pots and kept in an open field were contaminated with 134Cs and 85Sr in ionic form by sprinkling on the aerial part, or by addition to the soil. Sprinkling was effected at the stage of ripening of the grapes. Interception, determined by analysing all the leaves picked from three plants after the sprinkling, was approx. 50% of the sprayed activity. Soil contamination was effected after the fruit setting, 1 month earlier than sprinkling. At ripening, the whole plant was picked. Berries, leaves, shoots, stems, roots and soil were analysed by gamma spectrometry. Activities of the different parts of the plant were expressed as: (a) translocation factors of intercepted activity for foliar treatment; (b) transfer factors of activity applied to the soil for soil treatment. Both factors were calculated per unit of fresh weight, or referred to the total biomass of the plant compartment. Leaf-to-fruit translocation factors per unit of weight are of the order of magnitude of 10(-1) for 134Cs and of 10(-2) for 85Sr. One/two order of magnitude lower are soil-to-fruit transfer factors: 10(-3) both for 134Cs and for 85Sr. Radiocesium behaves quite differently from radiostrontium, but the behaviour of both radionuclides within the grape vine is independent of the path of absorption, by leaves or by roots. 134Cs is absorbed more easily than 85Sr by plant foliage, but is absorbed with more difficulty than 85Sr by roots. After absorption by either route, radiocesium concentrates mainly in the fruit compartment of the plant, whereas radiostrontium concentrates in the foliar compartment. Loss from the aerial part of the plant is higher for 85Sr than for 134Cs. 85Sr remains more available in soil than 134Cs, is more absorbed by roots and is more leached downward. After foliar contamination, the dominant pathway of radionuclides to reach the soil is by dislodging of non-absorbed radionuclides or senescent cells from the aerial part of the plant by action of wind and rain.

Biological Transport↗