Do warming-induced changes in quantity and stoichiometry of root exudation promote soil N transformations via stimulation of soil nitrifiers, denitrifiers and ammonifiers?

In a prior study, we demonstrated that pancreatic secretagogues increased both the uptake into and washout of 45Ca2+ from isolated mouse pancreatic acini. The net result of these processes was an initial fall in total acinar cell Ca2+ content. In the present study, we have employed subcellular fractionation of acini under conditions that minimized posthomogenization redistribution of Ca2+ in order to localize those organelles involved in intracellular Ca2+ fluxes. Homogenization and differential centrifugation of acini, preloaded with 45Ca2+ and subjected to a period of washout, showed that carbachol induced an increased loss of 45Ca2+ from all fractions isolated. The high-speed microsomal fraction lost 45Ca2+ to a greater extent than did whole acini; measurement of total Ca2+ by atomic absorption spectrometry showed a net loss of Ca2+ from this fraction. Purification of the lower-speed fractions indicated that carbachol increased 45Ca2+ exchange with both zymogen granules and mitochondria, but net Ca2+ levels in these organelles were unchanged. It was concluded that stimulation of pancreatic acini by carbachol results in the release of calcium from a microsomal compartment leading to a rise in cytoplasmic Ca2+, increased exchange with granule and mitochondrial Ca2+, and increased efflux of Ca2+ from the cell.

Download Full-text

Effects of nitrogen and phosphorus additions on nitrous oxide emission in a nitrogen-rich and two nitrogen-limited tropical forests

Biogeosciences ◽

10.5194/bg-13-3503-2016 ◽

2016 ◽

Vol 13 (11) ◽

pp. 3503-3517 ◽

Cited By ~ 8

Author(s):

Mianhai Zheng ◽

Tao Zhang ◽

Lei Liu ◽

Weixing Zhu ◽

Wei Zhang ◽

...

Keyword(s):

Nitrous Oxide ◽

Tropical Forests ◽

N2o Emission ◽

N Deposition ◽

Soil N ◽

N Addition ◽

Old Growth ◽

Old Growth Forest ◽

P Addition ◽

Stimulation Of

Abstract. Nitrogen (N) deposition is generally considered to increase soil nitrous oxide (N2O) emission in N-rich forests. In many tropical forests, however, elevated N deposition has caused soil N enrichment and further phosphorus (P) deficiency, and the interaction of N and P to control soil N2O emission remains poorly understood, particularly in forests with different soil N status. In this study, we examined the effects of N and P additions on soil N2O emission in an N-rich old-growth forest and two N-limited younger forests (a mixed and a pine forest) in southern China to test the following hypotheses: (1) soil N2O emission is the highest in old-growth forest due to the N-rich soil; (2) N addition increases N2O emission more in the old-growth forest than in the two younger forests; (3) P addition decreases N2O emission more in the old-growth forest than in the two younger forests; and (4) P addition alleviates the stimulation of N2O emission by N addition. The following four treatments were established in each forest: Control, N addition (150 kg N ha−1 yr−1), P addition (150 kg P ha−1 yr−1), and NP addition (150 kg N ha−1 yr−1 plus 150 kg P ha−1 yr−1). From February 2007 to October 2009, monthly quantification of soil N2O emission was performed using static chamber and gas chromatography techniques. Mean N2O emission was shown to be significantly higher in the old-growth forest (13.9 ± 0.7 µg N2O-N m−2 h−1) than in the mixed (9.9 ± 0.4 µg N2O-N m−2 h−1) or pine (10.8 ± 0.5 µg N2O-N m−2 h−1) forests, with no significant difference between the latter two. N addition significantly increased N2O emission in the old-growth forest but not in the two younger forests. However, both P and NP addition had no significant effect on N2O emission in all three forests, suggesting that P addition alleviated the stimulation of N2O emission by N addition in the old-growth forest. Although P fertilization may alleviate the stimulated effects of atmospheric N deposition on N2O emission in N-rich forests, this effect may only occur under high N deposition and/or long-term P addition, and we suggest future investigations to definitively assess this management strategy and the importance of P in regulating N cycles from regional to global scales.

Download Full-text

Photoperiodically Induced Changes in Glutamatergic Stimulation of LH Secretion in Male Syrian Hamsters: Role of Circulating Testosterone and Endogenous Opioids

General and Comparative Endocrinology ◽

10.1006/gcen.1994.1158 ◽

1994 ◽

Vol 96 (1) ◽

pp. 50-62 ◽

Cited By ~ 4

Author(s):

Francis J.P. Ebling ◽

Anju Mirakhur ◽

Elizabeth S. Maywood ◽

Michael H. Hastings

Keyword(s):

Endogenous Opioids ◽

Syrian Hamsters ◽

Induced Changes ◽

Lh Secretion ◽

Stimulation Of

Download Full-text

EFFECTS OF GROWING SEASON SOIL TEMPERATURE, MOISTURE, AND NH4-N ON SOIL NITROGEN

Canadian Journal of Soil Science ◽

10.4141/cjss74-054 ◽

1974 ◽

Vol 54 (4) ◽

pp. 403-412 ◽

Cited By ~ 20

Author(s):

C. A. CAMPBELL ◽

D. W. STEWART ◽

W. NICHOLAICHUK ◽

V. O. BIEDERBECK

Keyword(s):

Quantitative Relationship ◽

Growing Season ◽

Stepwise Multiple Regression ◽

Soil N ◽

N Transformations ◽

Temperature Changes ◽

Diurnal Patterns ◽

Multiple Regression Technique ◽

Time Required

Wood Mountain loam was wetted with water or (NH4)2SO4 solution to provide a factorial combination among three moisture and three NH4-N levels. Samples in polyethylene bags were incubated at 2.5-cm depths in fallow, and in an incubator that simulated the diurnal patterns of temperature fluctuation recorded in the field. During the growing season, treatments were sampled regularly for moisture, NO3− and exchangeable NH4-N. Similar determinations were made on in situ samples taken in fallow Wood Mountain loam. The incubator simulated the effects of growing season temperatures on soil N transformations satisfactorily. Pronounced increases or decreases in temperature led to flushes in N mineralization. However, in the 1972 growing season, temperature was suboptimal and temperature changes were generally small. Consequently, when a stepwise multiple regression technique was used to analyze the data, neither ammonification nor nitrification showed a quantitative relationship to temperature. Comparison of the nitrification occurring in laboratory-incubated soils with that occurring in situ led to the conclusion that 70 to 90% of the NO3-N produced in surface soil resulted from wetting and drying. Estimates of potentially ammonifiable soil N(No) and its rate of mineralization (k) were derived from cumulative ammonification by assuming that the laws of first-order kinetics were applicable. In the 10, 15, and 20% moisture treatments the average No was 27, 41, and 82 ppm, respectively. Under the conditions of this study, the time required to mineralize half of No was about 7 wk.

Download Full-text

Non-invasive stimulation of vagal afferents reduces gastric frequency

10.1101/773259 ◽

2019 ◽

Author(s):

Vanessa Teckentrup ◽

Sandra Neubert ◽

João C. P. Santiago ◽

Manfred Hallschmid ◽

Martin Walter ◽

...

Keyword(s):

Energy Expenditure ◽

Vagus Nerve ◽

Energy Homeostasis ◽

Resting Energy Expenditure ◽

Vagal Afferents ◽

Metabolic Effects ◽

Net Energy ◽

Non Invasive ◽

Induced Changes ◽

Stimulation Of

AbstractMetabolic feedback between the gut and the brain relayed via the vagus nerve contributes to energy homeostasis. We investigated in healthy adults whether non-invasive stimulation of vagal afferents impacts energy homeostasis via efferent effects on metabolism or digestion. In a randomized crossover design, we applied transcutaneous auricular vagus nerve stimulation (taVNS) while recording efferent metabolic effects using simultaneous electrogastrography (EGG) and indirect calorimetry. We found that taVNS reduced gastric myoelectric frequency (p =.008), but did not alter resting energy expenditure. We conclude that stimulating vagal afferents induces gastric slowing via vagal efferents without acutely affecting net energy expenditure at rest. Collectively, this highlights the potential of taVNS to modulate digestion by activating the dorsal vagal complex. Thus, taVNS-induced changes in gastric frequency are an important peripheral marker of brain stimulation effects.

Download Full-text

Localized myocardial responses to stimulation of small cardiac branches of the vagus

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1975.228.1.141 ◽

1975 ◽

Vol 228 (1) ◽

pp. 141-148 ◽

Cited By ~ 38

Author(s):

JA Armour ◽

WC Randall ◽

S Sinha

Keyword(s):

Cardiac Function ◽

Pulmonary Veins ◽

Contractile Force ◽

Laryngeal Nerve ◽

Electrical Excitation ◽

Superior Pulmonary Vein ◽

Discharge Rates ◽

Cervical Ganglion ◽

Induced Changes ◽

Stimulation Of

Direct electrical excitation of small cardiac branches from the thoracic vagus elicited highly localized and differential responses from individualized segments of the myocardium. For example, small nerves from the vagus at the level of the superior pulmonary veins frequently induced moderate inhibition in contractile force of the ipsilateral atrium with little or no influences elsewhere. Branches from more rostral levels of the thoracic vagus induced changes in atrial contractility, with or without changes in sinoauricular (SA) nodal discharge rates, and often with partial or complete artioventricular (AV) nodal blockade.Excitation of individual, small vagal branches sometimes initiated acceleration in artrial rate and augmentation in atrial contractile force concurrently with complete AV nodal blockade. The negative dromotropic response was eliminated by atropine, leaving only the positive chronotropic and inotropic changes, thus revealing the intermingling of both sympathetic and parasympathetic components even in these small branches. There are frequently in excess of 20 small branches from the vagal trunk between the level of the caudal cervical ganglion and the superior pulmonary vein on each side which will induce highly selective changes in cardiac function upon stimulation. Inhibitory branches are particularly concentrated in the region of the recurrent laryngeal nerve on either side.

Download Full-text

Modulation of gut mucosal biofilms

British Journal Of Nutrition ◽

10.1079/bjn20041346 ◽

2005 ◽

Vol 93 (S1) ◽

pp. S35-S40 ◽

Cited By ~ 72

Author(s):

Brigitta Kleessen ◽

Michael Blaut

Keyword(s):

Colonic Mucosa ◽

Mucosal Barrier ◽

Mucus Layer ◽

Faecal Flora ◽

New Approach ◽

Serovar Typhimurium ◽

Health Promoting ◽

Gut Mucosal Barrier ◽

Induced Changes ◽

Stimulation Of

Non-digestible inulin-type fructans, such as oligofructose and high-molecular-weight inulin, have been shown to have the ability to alter the intestinal microbiota composition in such a way that members of the microbial community, generally considered as health-promoting, are stimulated. Bifidobacteria and lactobacilli are the most frequently targeted organisms. Less information exists on effects of inulin-type fructans on the composition, metabolism and healthrelated significance of bacteria at or near the mucosa surface or in the mucus layer forming mucosa-associated biofilms. Using rats inoculated with a human faecal flora as an experimental model we have found that inulin-type fructans in the diet modulated the gut microbiota by stimulation of mucosa-associated bifidobacteria as well as by partial reduction of pathogenicSalmonella enterica subsp. entericaserovar Typhimurium and thereby benefit health. In addition to changes in mucosal biofilms, inulin-type fructans also induced changes in the colonic mucosa stimulating proliferation in the crypts, increasing the release of mucins, and altering the profile of mucin components in the goblet cells and epithelial mucus layer. These results indicate that inulin-type fructans may stabilise the gut mucosal barrier. Dietary supplementation with these prebiotics could offer a new approach to supporting the barrier function of the mucosa.

Download Full-text

The simulated N deposition accelerates net N mineralization and nitrification in a tropical forest soil

Biogeosciences ◽

10.5194/bg-16-4277-2019 ◽

2019 ◽

Vol 16 (21) ◽

pp. 4277-4291

Author(s):

Yanxia Nie ◽

Xiaoge Han ◽

Jie Chen ◽

Mengcen Wang ◽

Weijun Shen

Keyword(s):

N Deposition ◽

Functional Genes ◽

Net N Mineralization ◽

Soil N ◽

Wet Season ◽

Inorganic N ◽

N Transformations ◽

N Transformation ◽

Soil N Transformation ◽

N Additions

Abstract. Elevated nitrogen (N) deposition affects soil N transformations in the N-rich soil of tropical forests. However, the change in soil functional microorganisms responsible for soil N cycling remains largely unknown. Here, we investigated the variation in soil inorganic N content, net N mineralization (Rm), net nitrification (Rn), inorganic N leaching (Rl), N2O efflux and N-related functional gene abundance in a tropical forest soil over a 2-year period with four levels of N addition. The responses of soil net N transformations (in situ Rm and Rn) and Rl to N additions were negligible during the first year of N inputs. The Rm, Rn, and Rl increased with the medium nitrogen (MN) and high nitrogen (HN) treatments relative to the control treatments in the second year of N additions. Furthermore, the Rm, Rn, and Rl were higher in the wet season than in the dry season. The Rm and Rn were mainly associated with the N addition-induced lower C:N ratio in the dry season but with higher microbial biomass in the wet season. Throughout the study period, high N additions increased the annual N2O emissions by 78 %. Overall, N additions significantly facilitated Rm, Rn, Rl and N2O emission. In addition, the MN and HN treatments increased the ammonia-oxidizing archaea (AOA) abundance by 17.3 % and 7.5 %, respectively. Meanwhile, the HN addition significantly increased the abundance of nirK denitrifiers but significantly decreased the abundance of ammonia-oxidizing bacteria (AOB) and nosZ-containing N2O reducers. To some extent, the variation in functional gene abundance was related to the corresponding N-transformation processes. Partial least squares path modelling (PLS-PM) indicated that inorganic N contents had significantly negative direct effects on the abundances of N-related functional genes in the wet season, implying that chronic N deposition would have a negative effect on the N-cycling-related microbes and the function of N transformation. Our results provide evidence that elevated N deposition may impose consistent stimulatory effects on soil N-transformation rates but differentiated impacts on related microbial functional genes. Long-term experimentation or observations are needed to decipher the interrelations between the rate of soil N-transformation processes and the abundance or expression of related functional genes.

Download Full-text