Field nodules of Alnus incana ssp. rugosa and Myrica gale exhibit pronounced acetylene-induced declines in nitrogenase activity

1997 ◽  
Vol 75 (9) ◽  
pp. 1415-1423 ◽  
Author(s):  
Christa R. Schwintzer ◽  
John D. Tjepkema
Keyword(s):  
Time Course ◽  
Nitrogenase Activity ◽  
Alnus Incana ◽  
Partial Recovery ◽  
Myrica Gale ◽  
Open Flow ◽  
Peak Rate ◽  
Flow Through ◽  
Speckled Alder ◽  
Initial Peak

The time course of acetylene reduction was examined in field nodules of speckled alder (Alnus incana ssp. rugosa (Du Roi) Claus.) and sweet gale (Myrica gale L.) with an open flow-through system. When detached speckled alder nodules were measured in the laboratory, there was an initial peak rate of nitrogenase activity between 2 and 3 min followed by pronounced declines to 50% of the peak rate (early summer) and 66% (late summer) at 9 min, after which there was little further change. Speckled alder nodules measured in the field while still attached to the plant also had a peak rate between 2 and 3 min. Most sweet gale nodules had a peak rate at 2–3 min and a sharp decline to 27% at 21 min followed by a partial recovery to 49% at 60 min. The time courses of field nodules of speckled alder and sweet gale were comparable with those of intact, growth chamber grown seedlings. The initial peak rate is the most accurate measure of nitrogenase activity and the only reliable way to measure this is with an open, flow-through system. We describe a simple, inexpensive, flow-through system for use in the field. Key words: acetylene-induced decline, Alnus incana ssp. rugosa, actinorhizal plants, Myrica gale, nitrogen fixation, nitrogenase activity.

Effect of elevated carbon dioxide in the root atmosphere on nitrogenase activity in three actinorhizal plant species

2001 ◽  
Vol 79 (9) ◽  
pp. 1010-1018 ◽  
Author(s):  
Christa R Schwintzer ◽  
John D Tjepkema
Keyword(s):  
Carbon Dioxide ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Alnus Glutinosa ◽  
Repeated Measurements ◽  
Myrica Gale ◽  
Black Alder ◽  
Low Concentrations ◽  
Speckled Alder

In wet soils, nitrogen-fixing root nodules are subjected to elevated CO2. Only a few studies have examined the effect of elevated CO2 on nitrogenase activity, and the results have been mixed. We examined intact black alder (Alnus glutinosa (L.) Gaertn.) and sweet gale (Myrica gale L.) seedlings and field-collected speckled alder (Alnus incana ssp. rugosa (Du Roi) Claus.) nodules to clarify the effects of elevated CO2. Nitrogenase activity was measured via acetylene reduction in an open, flow-through system. We found that repeated measurements of the peak rate of nitrogenase activity, the only reliable measure of nitrogenase activity, could be made on the same plant via 150-s exposures to acetylene separated by 20 min without acetylene. Our results for elevated CO2 consistently showed that it had little effect on nitrogenase activity at low concentrations and increasingly inhibited nitrogenase activity as the CO2 concentration increased. In black alder, 0.5 kPa CO2 had little effect, whereas 3.0 kPa CO2 reduced nitrogenase activity 31–35%. Sweet gale, was less sensitive to elevated CO2 and was unaffected by 1.5 kPa CO2. Black alder grown with the roots, but not the shoots, in 1.3 kPa CO2 showed only minimal acclimation to elevated CO2.Key words: acetylene reduction technique, actinorhizal plants, Alnus, carbon dioxide, Myrica gale, nitrogen fixation.

Seasonal pattern of energy use, respiration, and nitrogenase activity in root nodules of Myrica gale

1983 ◽  
Vol 61 (11) ◽  
pp. 2937-2942 ◽  
Author(s):  
Christa R. Schwintzer ◽  
John D. Tjepkema
Keyword(s):  
Energy Cost ◽  
Energy Use ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Seasonal Pattern ◽  
Uptake Ratio ◽  
Experimental Conditions ◽  
Myrica Gale ◽  
Net Production ◽  
N Requirement

Annual CO2 evolution, H2 evolution, and C2H2 reduction were measured in root nodules from a vigorous Myrica gale stand in a Massachusetts peatland at 3-week intervals in 1980. Nodule activity was approximately the same under the experimental conditions (excised nodules reducing C2H2) as in nature (attached nodules reducing N2) and the CO2 evolution to O2 uptake ratio averaged 1.07. Nitrogenase activity was first detectable in late May, reached its maximum [Formula: see text] in mid-July, and disappeared in late October. The seasonal pattern of CO2 evolution was similar except that it continued at low rates when nitrogenase activity was absent. Hydrogen evolution was barely detectable. The energy cost of nitrogen fixation, expressed as the molar CO2:C2H4 ratio, was relatively low [Formula: see text] throughout the period of substantial nitrogenase activity and had a mean annual value of 4.9. Annual N2 fixation was estimated to be 2.8 g N m−2year−1, contributing about 33% of the annual N requirement measured in 1979. Annual C use by nodules was about 21.0 g C m−2 year−1. If this C were available for additional net production, it would increase it by about 5.5%.

Dinitrogen fixation and nodulation by Frankia in Alnus incana as affected by inorganic nitrogen in pot experiments with peat

1983 ◽  
Vol 61 (11) ◽  
pp. 2956-2963 ◽  
Author(s):  
U. Granhall ◽  
T. Ericsson ◽  
M. Clarholm
Keyword(s):  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Inorganic Nitrogen ◽  
Experimental Period ◽  
Alnus Incana ◽  
Nitrogen Application ◽  
Noticeable Effect ◽  
Essential Nutrients ◽  
Pot Experiments ◽  
Ph Level

The effects of single large or repeated, exponentially increasing applications of nutrients, with or without inorganic nitrogen and at two pH levels, on the growth, nodulation, acetylene reduction, and nutrient uptake in Alnus incana (L.) Moench were investigated in pot experiments with peat under controlled laboratory conditions. The repeated application of inorganic nitrogen did not suppress nitrogenase activity until the last 2 weeks, whereas an initial, large, nitrogen application effectively inhibited nodulation and activity throughout the 40-day experimental period. The mode of nitrogen application was thus found to be more important than the total amounts applied. Shoot length, leaf area, shoot–root relations, dry-matter production, and nitrogen contents of plants were determined at the end of the experiment, as well as the effect of Frankia inoculations. Nitrogenase activity was determined three times, at 0, 3, and 5 weeks. N2 fixation (balance/acetylene reduction) was found to be maximal, 55% of total nitrogen uptake, in minus-N pots with single applications of essential nutrients. The fastest growth was, however, noted in pots with single applications of all nutrients, including N. Among the latter, pots inoculated with Frankia showed the best growth, in spite of low nitrogenase activity. The only noticeable effect of a raised pH level was a reduced endophyte activity in minus-N pots with single applications of essential nutrients, due to increased N mineralization in the peat.

Short-term emersion affects cardiac function and regional haemolymph distribution in the crab Cancer magister

1996 ◽  
Vol 199 (3) ◽  
pp. 569-578
Author(s):  
C Airriess ◽  
B Mcmahon
Keyword(s):  
Stroke Volume ◽  
Cardiac Function ◽  
Large Scale ◽  
Time Course ◽  
Beat Frequency ◽  
Heart Beat ◽  
Experimental Chamber ◽  
Cancer Magister ◽  
Flow Through ◽  
Cardiac Stroke Volume

Changes in cardiac function and arterial haemolymph flow associated with 6 h of emersion were investigated in the crab Cancer magister using an ultrasonic flowmeter. This species is usually found sublittorally but, owing to the large-scale horizontal water movements associated with extreme tides, C. magister may occasionally become stranded on the beach. Laboratory experiments were designed such that the emersion period was typical of those that might be experienced by this crab in its natural environment. The frequency of the heart beat began to decline sharply almost immediately after the start of the experimental emersion period. Cardiac stroke volume fell more gradually. The combined reduction in these two variables led to a maximum decrease in cardiac output of more than 70 % from the control rate. Haemolymph flow through all the arteries originating at the heart, with the exception of the anterior aorta, also declined markedly during emersion. As the water level in the experimental chamber fell below the inhalant branchial openings, a stereotypical, dramatic increase in haemolymph flow through the anterior aorta began and this continued for the duration of the emersion period. The rapid time course of the decline in heart-beat frequency and the increase in haemolymph flow through the anterior aorta suggest a neural mechanism responding to the absence of ventilatory water in the branchial chambers. These responses may be adaptations, respectively, to conserve energy by reducing the minute volume of haemolymph pumped by the heart and to protect the supply of haemolymph to cephalic elements of the central nervous system. The decline in cardiac stroke volume, which occurs more slowly over the emersion period, may be a passive result of the failure to supply sufficient O2 to meet the aerobic demands of the cardiac ganglion.

scholarly journals Recovery of central and peripheral neuromuscular fatigue after exercise

2017 ◽  
Vol 122 (5) ◽  
pp. 1068-1076 ◽  
Author(s):  
T. J. Carroll ◽  
J. L. Taylor ◽  
S. C. Gandevia
Keyword(s):  
Muscle Function ◽  
Time Course ◽  
Central Fatigue ◽  
Exercise Bout ◽  
Complete Recovery ◽  
Peripheral Fatigue ◽  
Partial Recovery ◽  
Long Duration ◽  
Intracellular Ca ◽  
Generating Capacity

Sustained physical exercise leads to a reduced capacity to produce voluntary force that typically outlasts the exercise bout. This “fatigue” can be due both to impaired muscle function, termed “peripheral fatigue,” and a reduction in the capacity of the central nervous system to activate muscles, termed “central fatigue.” In this review we consider the factors that determine the recovery of voluntary force generating capacity after various types of exercise. After brief, high-intensity exercise there is typically a rapid restitution of force that is due to recovery of central fatigue (typically within 2 min) and aspects of peripheral fatigue associated with excitation-contraction coupling and reperfusion of muscles (typically within 3–5 min). Complete recovery of muscle function may be incomplete for some hours, however, due to prolonged impairment in intracellular Ca2+ release or sensitivity. After low-intensity exercise of long duration, voluntary force typically shows rapid, partial, recovery within the first few minutes, due largely to recovery of the central, neural component. However, the ability to voluntarily activate muscles may not recover completely within 30 min after exercise. Recovery of peripheral fatigue contributes comparatively little to the fast initial force restitution and is typically incomplete for at least 20–30 min. Work remains to identify what factors underlie the prolonged central fatigue that usually accompanies long-duration single joint and locomotor exercise and to document how the time course of neuromuscular recovery is affected by exercise intensity and duration in locomotor exercise. Such information could be useful to enhance rehabilitation and sports performance.

Effect of Coadministered Water on theIn VivoPerformance of Oral Formulations Containing N-Acetylcysteine: AnIn VitroApproach Using the Dynamic Open Flow-Through Test Apparatus

2017 ◽  
Vol 14 (12) ◽  
pp. 4272-4280 ◽  
Author(s):  
Maximilian Sager ◽  
Felix Schneider ◽  
Philipp Jedamzik ◽  
Markus Wiedmann ◽  
Ellen Schremmer ◽  
...  
Keyword(s):  
Test Apparatus ◽  
Open Flow ◽  
Oral Formulations ◽  
Flow Through

scholarly journals PKCε Phosphorylates and Mediates the Cell Membrane Localization of RhoA

ISRN Oncology ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-9
Author(s):  
Tizhi Su ◽  
Samuel Straight ◽  
Liwei Bao ◽  
Xiujie Xie ◽  
Caryn L. Lehner ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Cell Membrane ◽  
Cell Invasion ◽  
Time Course ◽  
Time Lapse ◽  
Kinase C ◽  
Phosphorylation Event ◽  
Phosphopeptide Mapping ◽  
First Time ◽  
Initial Peak

Protein kinase Cε (PKCε) signals through RhoA to modulate cell invasion and motility. In this study, the multifaceted interaction between PKCε and RhoA was defined. Phosphopeptide mapping revealed that PKCε phosphorylates RhoA at T127 and S188. Recombinant PKCε bound to recombinant RhoA in the absence of ATP indicating that the association between PKCε and RhoA does not require an active ATP-docked PKCε conformation. Activation of PKCε resulted in a dramatic coordinated translocation of PKCε and RhoA from the cytoplasm to the cell membrane using time-lapse fluorescence microscopy. Stoichiometric FRET analysis revealed that the molecular interaction between PKCε and RhoA is a biphasic event, an initial peak at the cytoplasm and a gradual prolonged increase at the cell membrane for the entire time-course (12.5 minutes). These results suggest that the PKCε-RhoA complex is assembled in the cytoplasm and subsequently recruited to the cell membrane. Kinase inactive (K437R) PKCε is able to recruit RhoA to the cell membrane indicating that the association between PKCε and RhoA is proximal to the active catalytic site and perhaps independent of a PKCε-RhoA phosphorylation event. This work demonstrates, for the first time, that PKCε phosphorylates and modulates the cell membrane translocation of RhoA.

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