Effects of root temperature on uptake of nitrate and ammonium ions by barley grown in flowing-solution culture

Summary Barley plants (Hordeum vulgare L.) grown from seed for 28 days in flowing solution culture were subjected to different root temperatures (3, 5, 7, 9, 11, 13, 17, 25°C) for 14 days with a common air temperature of 25/15°C (day/night). Uptake of NH₄ and NO₃ ions was monitored separately and continuously from solutions maintained at 10 M NH₄NO₃ and pH 6.0. Effects of root temperature on unit absorption rate , flux and inflow were compared. After 5 days , and increased with temperature over the range 3–11°C for NH₄ ions and over the range 3–13°C for NO₃ ions, with little change for either ion above these temperatures. Q₁₀ temperature coefficients for NH₄ ions (3–13°C) were 1.9, 1.7 and 1.6 for , and respectively, the corresponding values for NO₃ ions being 5.0, 4.5 and 4.6. For both ions, , and changed with time as did their temperature dependence over the range 3–25°C, suggesting that rates of ontogenetic development and the extent of adaptation to temperature may have varied among treatments.     

Water uptake by barley roots as affected by the osmotic and matric potential in the rhizosphere

Summary The water uptake rates of roots in saline soils are depressed by the simultaneously decreasing matric and osmotic water potentials in the soil surrounding the roots (rhizospheric soil). Unfortunately there are no reliable tools available for direct measurements of the effect of decreasing water potentials in the rhizospheric soil on the uptake rate of soil water by roots. This paper presents some results of a vegetation technique for studying the effect of different combinations of osmotic and matric water potentials in the rhizospheric soil on the water uptake rates of barley roots. Water uptake rates were reduced to a greater extent by decreasing soil matric water potentials than by decreasing soil osmotic water potentials. According to the results of this experiment, there was no relationship between the total soil water potential of a sandy soil and the water uptake rates when the roots were exposed to different combinations of and .     

The effect of fertilization on litter decomposition in clearfelled spruce stands

Summary The influence of NPK-fertilizer on decomposition of litter layers and deposited logging residues (brash) on a clearfelled Sitka spruce stand was followed during two years by zero-tension lysimetry and litterbags. Root development of second rotation planted trees on this peaty gley soil are restricted to the litter layers (LFH) and without fertilizer are dependent on its decomposition for release of nutrients. A comparison of fertilized and control plots showed few site differences and similar hydrological properties. Fertilizer addition (urea-N, rock-P and KCl) immediately raised leachate concentrations of NH₄−N, K and PO₄−P, the last remaining high over the period. NO₃−N increased dramatically in the second year leachates from the fertilized area. Within two years 45, 60 and 75% of added NPK respectively were recovered in leachates. Two-year-old litter in litterbags lost weight significantly more slowly after fertilization. The calculated values were 0.28 (control plot) and 0.15 (fertilized plot). Mean values were derived from individual regressions and allowed microsite variation to be assessed. The difference in is attributed to available C limitation although N concentration of needles increased on both plots, P concentration increased slowly on the control plot while K and Mg decreased on both. Ca concentrations doubled with fertilization and remained constant over two years. The rapid loss of fertilizer and slight response from planted trees indicate delayed application of fertilizers may be desirable.     

Are male rhesus monkeys more aggressive than females?

The justification for the “generalization that primate males are more aggressive than females” (Fedigan & Baxter, 1984) was tested in a troop of 24 captive rhesus monkeys. Males (N=9) were more dominant than females (N=15), i.e., they had more subordinate partners ( _m=17.0 vs. _f=6.6;p<0.01); hence, their aggression rate was higher ( _m=77.6 vs. _m=38.1;p<0.05). However, adjusting the rate of aggression according to the number of subordinate targets revealed no gender difference and males directed numbers of aggressive acts against individual subordinate partners that were not higher than those of females ( _m=4.4 vs. _f=5.4;p>0.1). It was concluded that aggressiveness is an individual attribute that is (1) independent of dominance status, and (2) independent of sex.     

Use of the force-velocity test to determine the optimal braking force for a sprint exercise on a friction-loaded cycle ergometer

A group of 15 untrained male subjects pedalled on a friction-loaded cycle ergometer as fast as possible for 5–7 s to reach the maximal velocity (V{immax}) against different braking forces (F _B). Power was averaged during a complete crank rotation by adding the power dissipated againstF _B to the power necessary to accelerate the flywheel. For each sprint, determinations were made of peak power output ( ) power output attained atV _max ( ) calculated as the product ofV _max andF _B and the work performed to reachV _max expressed in mean power output ( ). The relationships between these parameters andF _B were examined. A biopsy taken from the vastus lateralis muscle and tomodensitometric radiographs of both thighs were taken at rest to identify muscle metabolic and morphometric properties. The value was similar for allF _B. Therefore, the average of values was defined as corrected maximal power ( ). This value was 11 higher than the maximal power output uncorrected for the acceleration. Whereas the determination did not require high loads, the highest value ( ) was produced when loading was heavy, as evidenced by the -F _B parabolic relationship. For each subject, the braking force ( ) giving was defined as optimal. The , equal to 0.844 (SD 0.108) N · kg⁻¹ bodymass, was related to thigh muscle area (r = 0.78,P < 0.05). The maximal velocity ( ) reached against this force seemed to be related more to intrinsic fibre properties (% fast twitch b fibre area and adenylate kinase activity). Thus, from the determination, it is suggested that it should be possible to predict the conditions for optimal exercise on a cycle ergometer.     

The dissociation and separation of bovine adenohypophysial cells

Bovine adenohypophysial tissue was dissociated by sequential enzymatic incubation in a continuous flow system. Dispersed cells separated into discrete fractions after centrifugation in isopycnic bovine serum albumin gradients. The dispersed and separated cells were prepared for microscopic identification and differential counts by centrifugal cytology. Radioimmunoassays for LH, FSH, TSH, and Prl were used to corroborate the differential counts and determine the homogeneity of the fractions. The thyrotrophs banded at an average density ( ) of 1.0417, the FSH-secretory cells at , the LH-secretory cells at , and the Prl-secretory cells at . A 7–16 fold enrichment of different cell populations was possible. In bovine hypophyses each hormone appears to be formed by specific cells: the average TSH concentrations of the thyrotrophs were 5.1 pg/cell and the average LH and FSH concentrations were 4.7 and 4.9 pg/cell for LH-and FSH-secreting cells, respectively. The average Prl concentration was 4.9 pg/cell for Prl-secreting cells.     

Dynamics of cardiorespiratory function in Standardbred horses during different intensities of constant-load exercise

Summary Six Standardbred horses were used to evaluate the time course of pulmonary gas exchange, ventilation, heart rate (HR) and acid base balance during different intensities of constant-load treadmill exercise. Horses were exercised at approximately 50%, 75% and 100% maximum oxygen uptake ( max) for 5 min and measurements taken every 30 s throughout exercise. At all work rates, the minute ventilation, respiratory frequency and tidal volume reached steady state values by 60 s of exercise. At 100% max, the oxygen consumption ( ) increased to mean values of approximately 130 ml/kg·min, which represents a 40-fold increase above resting . At the low and moderate work rates, showed no significant change from 30 s to 300 s of exercise. At the high work rate, the mean at 30 s was 80% of the value at 300 s. The HR showed no significant change over time at the moderate work rate but differing responses at the low and high work rates. At the low work rate, the mean HR decreased from 188 beats/min at 30 s to 172 beats/min at 300 s exercise, whereas at the high work rate the mean HR increased from 204 beats/min at 30 s to 221 beats/min at 300 s exercise. No changes in acid base status occurred during exercise at the low work rate. At the moderate work rate, a mild metabolic acidosis occurred which was nonprogressive with time, whereas the high work rate resulted in a progressive metabolic acidosis with a base deficit of 16 mmol/l by 300 s exercise. It is concluded that the kinetics of gas exchange during exercise are more rapid in the horse than in man, despite the relatively greater change in in the horse when going from rest to high intensity exercise.Symbols and abbreviations E minute ventilation - V _T tidal volume - oxygen uptake - carbon dioxide output - oxygen pulse - ventilatory equivalent for oxygen - ventilatory equivalent for carbon dioxide - R respiratory exchange ratio - HR heart rate - SBC standard bicarbonate - STPD standard temperature and pressure dry - BTPS body temperature and pressure saturated - arterial oxygen content - arteriovenous oxygen content difference - Rf respiratory frequency     

Seasonal changes in the activation of crossbridge motions of isolated thick filament from Limulus striated muscle

Summary In dynamic light scattering, measurements of the intensity-intensity time correlation function from a suspension of rod-like particles of length L could reveal dynamical information related to translational and internal motions of those particles. For a suspension of thick filaments isolated from the myosin-regulated, striated muscles of Limulus at KL>1 (where K is the scattering vector), the average characteristic linewidth ( ) increased with the addition of Ca²⁺ or with the depletion of ATP. The increase in the with the addition of Ca²⁺ could be due to the presence of energy-requiring, high-frequency motions of the crossbridges activated by Ca²⁺. The increase in which occurred with the depletion of ATP was assumed to be mainly due to the thermal motions of the crossbridges after they had moved radially away from the filament backbone. The percentage increase in following the addition of Ca²⁺ was found to be seasonal, i.e., values of obtained from thick filaments isolated between the middle of June and the middle of September were smaller than those obtained during the rest of the year. The effect of temperature on the percentage increase in was also different. The increase showed a maximum at about 35°C during the summer and at about 25°C at other times. However, the percentage increase in developed under ATP-depleted conditions showed no temperature-related maximum. The number of bound Ca²⁺ per myosin molecule was 1 during the summer and 2 at other times.Abbreviations DLS dynamic light scattering - L length - K scattering vector - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - average characteristic line width Deceased     

Correlation between cell density,membrane fluidity,and the availability of transferrin receptors in friend erythroleukemic cells

Undifferentiated Friend erythroleukemic cells (FL cells) acquire membrane microviscosity ( ), in accord with the culture cell density. At low cell density poise, whereas at confluency it increases to poise. Concomitantly, the total number of available transferrin receptors per cell decreases by about 80% upon increase in cell density. Modulation of membrane microviscosity, by artificial alteration of the membrane cholesterol level, mediates similar modulations of the availability of the transferrin receptors. The correlation between the availability of the transferrin receptors and the membrane lipid fluidity may take part in the overt decrease in iron uptake by erythroid cells along the erythropoiesis pathway.     

Linkage analysis using multiple DNA polymorphic markers in normal families and in families with fragile X syndrome

Summary Linkage data, using the polymorphic markers 52A (DXS51), F9, 4D-8(DXS98), and St14(DXS52), are presented from 14 fragile X pedigrees and from 7 normal pedigrees derived from the collection of the Centre d'Étude du Polymorphisme Humaine. A multipoint linkage analysis indicates that the most probable order of these four loci in normal families is DXS51-F9-DXS98-DXS52. Recombination frequencies ( ) corresponding to maximum LOD scores ( ) were obtained by two-point linkage analysis for a nuber of linkage groups, including: DXS51-F9 ( =5.94, =0.03), F9-DXS98 ( =0.51, =0.26), F9-DXS52 ( =0.84, =0.27), and DXS98-DXS52 ( =0.32, =0.20). A multipoint linkage analysis of these loci, including the fragile X locus, was also performed for the fragile X population and the data support the relative order (DSX51, F9, DXS98)-FRAXA-DXS52. Recombination frequencies and maximum LOD scores, which again were derived from two-point linkage analyses, were obtained for the linkage groups DXS51-F9 ( =9.96, =0) and F9-DXS52 ( =0.07, =0.45), as well as for the groups DXS51-FRAXA ( =2.42, =0.15), F9-FRAXA ( =1.30, =0.18), DXS98-FRAXA ( =0.05 =0.36), and DXS52-FRAXA ( =2.42 =0.15). The linkage data was further tested for the presence of genetic heterogeneity both within and between the fragile X and normal families for the intervals DXS51-F9, F9-DXS52, F9-FRAXA, and DXS52-FRAXA using a modification of the A test. Except for the interval F9-FRAXA (P<0.10) there was no evidence of genetic heterogeneity for each of the various linkage groups examined. The heterogeneity detected for the interval F9-FRAXA, however, was most likely due to one family (Fx-28) that displayed very tight linkage between these two loci.     

Body temperatures during rest and exercise in residents and sojourners in hot climate

Rectal (T_re), mean skin temperature ( _sk) and sweating rate ( ) were measured in 4 residents of temperate climate under acute moderate heat exposure (designated EE in such an experimental situation), after 3 weeks in India (designated as EI) and in 8 Indian residents (designated as II) both at rest and during submaximal exercises at 2 different intensities. At rest, T_re is higher in EI (37.6°C) than in EE (36.8°C, P<0.01) and reaches 37.8°C in II. At the end of exercise, the increment in T_re seems to depend on work load only and to be independent of thermal environment; S follows a similar pattern in the 3 groups of subjects: _sk is altered neither by exercise nor acclimatization. Under chronic heat exposure compared to acute conditions: (1) identical is achieved with higher T_re and similar _sk so that the linear relationships vs T_re is shifted to the right. (2) the T_re — _sk difference is greater at rest and during exercise: hence, skin blood flow, calculated from heat balance equation diminishes. In hot climate, a rise in T_re seems to be an adaptive response which allows the body to reduce skin blood flow.     

The\dot V_A /\dot Q resolution of inert gas dataresolution of inert gas data

The non-uniqueness of distributions satisfying inert gas retention data without error is studied. The ability of such data to resolve blood flows at particular values is discussed through the application of linear programming and Backus-Gilbert theory. It is shown that the resolution deteriorates away from the extremes of low and high .     

Selenium deficiency in yugoslavia

Data on selenium (Se) deficiency in Yugoslavia are presented. The results include Se content of soil, cereal crops, and garlic grown in these soils, and human serum and scalp hair from several towns and regions. All data indicate a serious Se deficiency: soil (n=140), the mean value of 200±69.6 μg/kg Se; wheat, (58) = 20.5 ± 12.4 μg/kg; corn, (79) = 13.7 ± 13.6 μg/kg; and garlic, (66) = 13.7 ± 17.1 μg/kg Se. Analyses of human tissue show a very low Se status of the Yugoslav population: serum, (n=875) = 50.0 ± 18.0 μg/L and scalp hair, (388) = 94 ± 16 μg/kg Se. In some regions, Se contents of grain, garlic, and human serum and hair are approaching those in the low-Se belt in China. It is assumed that very low Se status of a human population could be a risk factor in the development of Balkan Endemic Nephropathy (BEN) and in a high incidence of urinary tract tumors (UTT) in endemic areas. A portion of these results were presented at the International Symposium on Selenium, Belgrade, May 12–15, 1991, Abstracts p.1, Serbian Academy of Sciences and Arts.     

Skeletal muscle [(V)\dot]O2 \dot V_{O_2 } in rat and lemming: Effect of blood flow rate

Summary The rate of oxygen consumption ( ) by skeletal muscle was investigated in isolated perfused hindlimbs of laboratory rats and lemmings (Lemmus). In both species, increased in proportion to blood flow rate, even at flow rates 4–5 times above resting level. The slope of the line relating to skeletal muscle blood flow was significantly greater in the lemming than in the rat. This may be related to the inverse relationship between body weight and metabolic rate. These data support the hypothesis that in small animals a dependent relationship exists between blood flow and skeletal muscle .     

The height and weight of Kuwaiti pre-school children

This paper consider the effect of age-grouping on the distribution of two variables, namely, height and weight of pre-school children subject to growth. Assuming straight line regression models for the dependence of expected values as well as variances and covariance of height and weight was investigated by Ehrenberg's law-like model. Ehrenberg's law-like relationship between height and weight, Log , was applied to Kuwaiti children under 7 years of age. It was found that the relationship log was a good fit for Kuwaiti boys and girls except for children under 1 year where the results were significantly different from the expected value     

Comment on biomass diversity in ecology

It is observed that a dynamical continuity equation for biomass distribution yields the asymptotic steady-state exponential dependencen=A exp( ) exhibited by certain fishery data, wherem is the biomass of an individual,n is the number of individuals per unit biomass interval, andA, are positive constants. This dynamical approach to biomass distribution is an alternative to the global maximization principle proposed recently by Lurié and Wagensberg.     

Reciprocal inhibition of human motoneurons with different firing frequencies

A study was made of the effect of reciprocal inhibition on individual firing motoneurons in the extensor carpi ulnaris and soleus muscle in human subjects. Peristimulus histograms (PSH) were plotted at different average frequency of motoneuron firing ( ) and the change in duration of interspike intervals (ISI) was analyzed. For reciprocal inhibition, as for other types of inhibition, is a factor in the effectiveness of motoneuron inhibition. The duration of inhibition apparent in the PSH, the sizes of zones of inhibition effectiveness in the ISIs and lengthening of the intervals are dependent on . For all motoneurons, the low range is most favorable for effective inhibition. The dependence of effectiveness of a volley on the time of its arrival within the ISI is also analyzed.Institute for Problems of Information Transmission, Russian Academy of Sciences, Moscow. Translated from Neirofiziologiya, Vol. 24, No. 6, pp. 643–653, November–December, 1992.     

Influence of lifting technique on perceptual and cardiovascular responses to submaximal repetitive lifting

Oxygen consumption ( O₂), heart rate, ventilation and central rating of perceived exertion (RPE) in repetitive lifting while executing squat and stoop techniques were investigated in ten male forestry workers. In all five mass/frequency combinations studied, O₂ was significantly higher for the squat than for the stoop technique. No differences were found in RPE between the techniques. The O₂ and RPE recordings were also related to those obtained during maximal repetitive lifting (same lifting technique) and maximal treadmill running. The O₂ expressed as a percentage of that obtained during maximal repetitive lifting with the same lifting technique was defined as relative aerobic intensity (% O_{2max, lifting}). The % O_{2max, lifting} was not significantly different between the techniques except for the lowest mass lifted (1 kg). This study therefore would support the hypothesis that RPE is more closely related to % O_{2max, lifting} than to absolute aerobic intensity. Related to maximal treadmill running, it was demonstrated for both lifting techniques that relative RPE (percentage of the RPE during maximal running) was more accurate than relative O₂ (percentage of maximal O₂ during maximal running) for determining the % O_{2max, lifting} in repetitive lifting. The study showed that the higher O₂ during squat. lifting compared to stoop lifting was caused by the O₂ expended in lifting and lowering the body rather than the O₂ expended lifting and lowering the external mass. It was concluded that the stoop technique was not superior to the squat technique in terms of central RPE. Based on % O_{2max, lifting}, there may be a rationale for choosing the stoop technique during repetitive lifting with light masses, but not with heavy masses.     

Polymorphisme électrophorétique des protéines et enzymes sériques et érythrocytaires chez le chimpanzé (Pan troglodytes)

Summary The electrophoretic mobilities of serum enzymes and other proteins were investigated at 35 loci in 25 unrelated individuals of the chimpanzee Pan troglodytes. In this population the mean average of individual polymorphism is =0181, and the average level of heterozygoty =0.022. The same pattern of individual variability is found in Pan troglodytes and Homo sapiens.     

Ammonium-limited growth and uptake by Oscillatoria agardhii in chemostat cultures

Growth of Oscillatoria agardhil was studied in ammonium-limited chemostat cultures, at various dilution rates (=growth rates, μ). The uptake kinetics for ammonium of nitrogen (ammonium or nitrate)-limited chemostat cultures also was investigated. The kinetics of ammonium-limited growth could be adequately described by both the Monod and Droop equations, and were closely similar to the nitrate-limited growth kinetics of this species. The uptake kinetics for ammonium showed similarities as well as differences with the uptake kinetics for nitrate. The similarities were apparent in the uptake capacity values for ammonium and nitrate , which were identical, high and independent of μ. The differences were to be found in the half-saturation constants for ammonium uptake and nitrate uptake , the former being hardly influenced by μ. A consitutive, high affinity, system is likely to operate in the uptake and assimilation of ammonium by nitrogen-limited O. agardhii. The use of ammonium uptake parameters in studies of growth-limiting factors in nature can provide information as to whether a nitrogen-limitation prevails in natural habitats of this species.