Nitrification, a key process in the global nitrogen cycle that generates nitrate through microbial activity, may enhance losses of fertilizer nitrogen by leaching and denitrification. Certain plants ...can suppress soil-nitrification by releasing inhibitors from roots, a phenomenon termed biological nitrification inhibition (BNI). Here, we report the discovery of an effective nitrification inhibitor in the root-exudates of the tropical forage grass Brachiaria humidicola (Rendle) Schweick. Named "brachialactone," this inhibitor is a recently discovered cyclic diterpene with a unique 5-8-5-membered ring system and a γ-lactone ring. It contributed 60-90% of the inhibitory activity released from the roots of this tropical grass. Unlike nitrapyrin (a synthetic nitrification inhibitor), which affects only the ammonia monooxygenase (AMO) pathway, brachialactone appears to block both AMO and hydroxylamine oxidoreductase enzymatic pathways in NITROSOMONAS: Release of this inhibitor is a regulated plant function, triggered and sustained by the availability of ammonium (NHFormula: see text) in the root environment. Brachialactone release is restricted to those roots that are directly exposed to NHFormula: see text. Within 3 years of establishment, Brachiaria pastures have suppressed soil nitrifier populations (determined as amoA genes; ammonia-oxidizing bacteria and ammonia-oxidizing archaea), along with nitrification and nitrous oxide emissions. These findings provide direct evidence for the existence and active regulation of a nitrification inhibitor (or inhibitors) release from tropical pasture root systems. Exploiting the BNI function could become a powerful strategy toward the development of low-nitrifying agronomic systems, benefiting both agriculture and the environment.
A comparison of the effects on rumen fermentation of three saponin rich tropical fruits supplemented to forage-based diets was completed using a rumen simulation technique (Rusitec). The diets ...contained either no tropical fruit or 100
mg/g of
Sapindus saponaria (crude saponins, 120
mg/g), 200
mg/g of
Enterolobium cyclocarpum (crude saponins, 19
mg/g) or 200
mg/g of
Pithecellobium saman (crude saponins, 17
mg/g). The four diets were evaluated with faunated and defaunated rumen fluid obtained from a single donor cow. Compared to the control diet,
P. saman decreased (
P<0.05) ammonia concentration of rumen fluid, and
E. cyclocarpum and
P. saman increased (
P<0.05)
n-butyrate proportion of total volatile fatty acids. Defaunation enhanced (
P<0.05) propionate proportion with corresponding reductions of acetate and
n-butyrate. Organic matter degradation of the
S. saponaria diet did not differ from that of the control diet but was higher (
P<0.05) with
P. saman and
E. cyclocarpum. Only one of the saponin rich fruits evaluated,
S. saponaria, decreased (
P<0.05) protozoal count (by 54%) and daily methane release (by 20%) relative to control, but without affecting the methanogen count. Defaunation suppressed methanogenesis by 43% over all diets (
P<0.05), and the effect of
S. saponaria on methane was more pronounced in defaunated (29%) versus faunated rumen fluid (14%). When related to organic matter apparently fermented, differences relative to the control diet persisted (
P<0.05), but methane release per unit of fibre degraded did not differ between the
S. saponaria diet and the control diet. This study demonstrated that supplementation with
S. saponaria is effective against ruminal methanogenesis, but that this was not exclusively an effect of the associated depression in protozoal count.
The objective of this study was to test whether the use of tannin-rich shrub legume forage is advantageous for methane mitigation and metabolic protein supply at unchanged energy supply when ...supplemented in combination with tannin-free legumes to sheep. In a 6 x 6 Latin-square design, foliage of two tannin-rich shrub legume species (Calliandra calothyrsus and Flemingia macrophylla) were used to replace either 1/3 or 2/3, respectively, of a herbaceous high-quality legume (Vigna unguiculata) in a diet composed of the tropical grass Brachiaria brizantha and Vigna in a ratio of 0.55 : 0.45. A Brachiaria-only diet served as the negative control. Each experimental period lasted for 28 days, with week 3 serving for balance measurement and data collection inclusive of a 2-day stay of the sheep in open-circuit respiration chambers for measurement of gaseous exchange. While Vigna supplementation improved protein and energy utilisation, the response to the partial replacement with tannin-rich legumes was less clear. The apparent total tract digestibilities of organic matter, NDF and ADF were reduced when the tannin-rich plants partially replaced Vigna, and the dose-response relationships were mainly linear. The tannin-rich plants caused the expected redistribution of more faecal N in relation to urinary N. While Flemingia addition still led to a net body N retention, even when fed at the higher proportion, adding higher amounts of Calliandra resulted in body protein mobilisation in the growing lambs. With respect to energy, supplementation of Vigna alone improved utilisation, while this effect was absent when a tannin-rich plant was added. The inclusion of the tannin-rich plants reduced methane emission per day and per unit of feed and energy intake by up to 24% relative to the Vigna-only-supplemented diet, but this seems to have been mostly the result of a reduced organic matter and fibre digestion. In conclusion, Calliandra seems less apt as protein supplement for ruminants while Flemingia could partially replace a high-quality legume in tropical livestock systems. However, methane mitigation would be small due to associated reductions in N and energy retention.
Two experiments with the gas pressure transducer technique were conducted to investigate the effects of different types and levels of tannins. Forage samples were incubated in batch cultures together ...with rumen fluid and digestion medium in order to model rumen fermentation dynamics
in vitro. In Experiment 1, graded levels (0, 25, 50, 75 and 100
mg/g of forage dry matter (DM)) of purified condensed tannins (CT) obtained from four tanniniferous tropical shrub legumes,
Flemingia macrophylla,
Leucaena leucocephala and two provenances of
Calliandra calothyrsus (San Ramón and Patulul), were added to a CT-free mixture of the grass
Brachiaria humidicola and the herbaceous legume
Vigna unguiculata. The statistical models used for data evaluation included the two main effects (origin and level of CT) and their interaction. Apart from dose-dependent effects (P<0.001) there were clear plant-specific effects (mostly P<0.001) in fermentation dynamics,
in vitro DM degradation and apparent degradation of N-containing compounds. Tannins from
C. calothyrsus had the most pronounced effects on fermentation dynamics and nutrient degradation, followed by
F. macrophylla and
L. leucocephala. Within
C. calothyrsus, CT from the provenance San Ramón suppressed asymptotic gas production and DM degradation to a larger extent (P<0.05) than CT from the provenance Patulul. Low addition (25
mg/g
DM) of CT from
C. calothyrsus was only slightly detrimental while high CT levels (75 and 100
mg/g
DM) had clearly negative effects on asymptotic gas production and DM degradation. In a first incubation in Experiment 2, the grass in mixtures with foliage of the different tanniniferous shrub legumes was incubated with graded levels of polyethylene glycol (PEG) corresponding to 0/3, 1/3, 2/3 and 3/3 of the contents of CT in these mixtures. In a second incubation, all mixtures based on tanniniferous shrub legumes and mixtures containing non-tanniniferous shrub legumes (
Cratylia argentea,
Desmodium velutinum) or a herbaceous legume (
V. unguiculata) were tested without PEG and with 80
g/kg supplementary PEG. In general, addition of PEG had no effect (P>0.05) on fermentation parameters in non-tanniniferous legumes. With tanniniferous species, response curves in fermentation parameters were mostly non-linear reaching a plateau at a PEG:CT-ratio between 1:3 and 2:3. One exception was that undegraded dietary N decreased (P<0.05) with increasing PEG addition until the highest level. In conclusion, the study demonstrated that to a large extent the effects of CT-rich plants on
in vitro ruminal fermentation can be explained by the specific CT properties. Furthermore, apart from binding CT, PEG seems to have no major side-effects on ruminal fermentation, and for most fermentation variables and species, PEG supplementation equivalent to the CT content in the forage mixtures seems sufficient to prevent negative effects of CT on fermentation parameters.
Six adult African-type hair sheep (BW = 40.3 +/- 6.3 kg) fitted with ruminal and duodenal cannulas were subjected to four treatments. Sheep were offered basal diets at a rate of 80 g of DM/kg of ...metabolic BW (equivalent to ad libitum access) consisting either of a low-quality grass hay (Brachiaria dictyoneura, 3.7% CP, DM basis) alone or in combination with a forage legume (Cratylia argentea, 18.6% CP, DM basis) in a 3:1 ratio (DM basis). In addition, 0 or 8 g of DM of Sapindus saponaria fruits (12.0% crude saponins, DM basis) per kilogram of metabolic BW was administered intraruminally. Supplementation of C. argentea increased intakes of OM (+21%; P < 0.01) and CP (+130%; P < 0.001), as well as ruminal fluid ammonia N concentrations (from 2.40 to 8.43 mg/dL; P < 0.001). Apparent OM and N digestibilities were not affected by legume addition, but ADF digestibility decreased by 10% (P < 0.01). Total ruminal VFA concentration was unchanged, but acetate:propionate was lower (P < 0.01) and isobutyrate proportion was greater (P < 0.001) with the legume addition. Legume supplementation increased duodenal flows of total N (+56%; P < 0.001), nonammonia N (+52%; P < 0.001), ruminal escape N (+80%; P < 0.001), and microbial N (+28%; P < 0.05). Microbial efficiency was not affected by legume addition. Supplementation of S. saponaria increased (P < 0.05) dietary OM intake by 14%, but had no effect on CP intake and ruminal fluid ammonia concentration or on OM and N digestion. Digestibility of ADF was decreased (P < 0.01) by 10% with S. saponaria as was acetate:propionate (P < 0.001) and the isobutyrate proportion (P < 0.001). Ruminal protozoa counts increased (P < 0.01) by 67% with S. saponaria. Duodenal N flows were not significantly affected by S. saponaria supplementation, except for microbial N flow (+34%; P < 0.01). Microbial efficiency was greater (P < 0.05) by 63% with the addition of S. saponaria. Few interactions between legume and S. saponaria supplementation were observed. The NDF digestibility was decreased with S. saponaria in the grass-alone diet, but not in the legume-supplemented diet (interaction; P < 0.05). Interactions were absent in ruminal fermentation measures and duodenal N flow, indicating that effects were additive. Results suggest that, even when not decreasing ruminal protozoa count, supplementation of S. saponaria fruits is a beneficial way to improve ruminal VFA profile, microbial efficiency, and duodenal flow of microbial protein in sheep fed tropical grass-alone or grass-legume diets.
Key points
Mice with Ca2+–calmodulin‐dependent protein kinase (CaMKII) constitutive pseudo‐phosphorylation of the ryanodine receptor RyR2 at Ser2814 (S2814D+/+ mice) exhibit a higher open probability ...of RyR2, higher sarcoplasmic reticulum (SR) Ca2+ leak in diastole and increased propensity to arrhythmias under stress conditions.
We generated phospholamban (PLN)‐deficient S2814D+/+ knock‐in mice by crossing two colonies, S2814D+/+ and PLNKO mice, to test the hypothesis that PLN ablation can prevent the propensity to arrhythmias of S2814D+/+ mice.
PLN ablation partially rescues the altered intracellular Ca2+ dynamics of S2814D+/+ hearts and myocytes, but enhances SR Ca2+ sparks and leak on confocal microscopy.
PLN ablation diminishes ventricular arrhythmias promoted by CaMKII phosphorylation of S2814 on RyR2.
PLN ablation aborts the arrhythmogenic SR Ca2+ waves of S2814D+/+ and transforms them into non‐propagating events.
A mathematical human myocyte model replicates these results and predicts the increase in SR Ca2+ uptake required to prevent the arrhythmias induced by a CaMKII‐dependent leaky RyR2.
Mice with constitutive pseudo‐phosphorylation at Ser2814‐RyR2 (S2814D+/+) have increased propensity to arrhythmias under β‐adrenergic stress conditions. Although abnormal Ca2+ release from the sarcoplasmic reticulum (SR) has been linked to arrhythmogenesis, the role played by SR Ca2+ uptake remains controversial. We tested the hypothesis that an increase in SR Ca2+ uptake is able to rescue the increased arrhythmia propensity of S2814D+/+ mice. We generated phospholamban (PLN)‐deficient/S2814D+/+ knock‐in mice by crossing two colonies, S2814D+/+ and PLNKO mice (SD+/+/KO). SD+/+/KO myocytes exhibited both increased SR Ca2+ uptake seen in PLN knock‐out (PLNKO) myocytes and diminished SR Ca2+ load (relative to PLNKO), a characteristic of S2814D+/+ myocytes. Ventricular arrhythmias evoked by catecholaminergic challenge (caffeine/adrenaline) in S2814D+/+ mice in vivo or programmed electric stimulation and high extracellular Ca2+ in S2814D+/− hearts ex vivo were significantly diminished by PLN ablation. At the myocyte level, PLN ablation converted the arrhythmogenic Ca2+ waves evoked by high extracellular Ca2+ provocation in S2814D+/+ mice into non‐propagated Ca2+ mini‐waves on confocal microscopy. Myocyte Ca2+ waves, typical of S2814D+/+ mice, could be evoked in SD+/+/KO cells by partially inhibiting SERCA2a. A mathematical human myocyte model replicated these results and allowed for predicting the increase in SR Ca2+ uptake required to prevent the arrhythmias induced by a Ca2+–calmodulin‐dependent protein kinase (CaMKII)‐dependent leaky RyR2. Our results demonstrate that increasing SR Ca2+ uptake by PLN ablation can prevent the arrhythmic events triggered by SR Ca2+ leak due to CaMKII‐dependent phosphorylation of the RyR2‐S2814 site and underscore the benefits of increasing SERCA2a activity on SR Ca2+‐triggered arrhythmias.
Key points
Mice with Ca2+–calmodulin‐dependent protein kinase (CaMKII) constitutive pseudo‐phosphorylation of the ryanodine receptor RyR2 at Ser2814 (S2814D+/+ mice) exhibit a higher open probability of RyR2, higher sarcoplasmic reticulum (SR) Ca2+ leak in diastole and increased propensity to arrhythmias under stress conditions.
We generated phospholamban (PLN)‐deficient S2814D+/+ knock‐in mice by crossing two colonies, S2814D+/+ and PLNKO mice, to test the hypothesis that PLN ablation can prevent the propensity to arrhythmias of S2814D+/+ mice.
PLN ablation partially rescues the altered intracellular Ca2+ dynamics of S2814D+/+ hearts and myocytes, but enhances SR Ca2+ sparks and leak on confocal microscopy.
PLN ablation diminishes ventricular arrhythmias promoted by CaMKII phosphorylation of S2814 on RyR2.
PLN ablation aborts the arrhythmogenic SR Ca2+ waves of S2814D+/+ and transforms them into non‐propagating events.
A mathematical human myocyte model replicates these results and predicts the increase in SR Ca2+ uptake required to prevent the arrhythmias induced by a CaMKII‐dependent leaky RyR2.
The tumor necrosis factor (TNF) family member APRIL (A proliferation inducing ligand) is a disease promoter in B-cell malignancies. APRIL has also been associated with a wide range of solid ...malignancies, including colorectal cancer (CRC). As evidence for a supportive role of APRIL in solid tumor formation was still lacking, we studied the involvement of APRIL in CRC. We observed that ectopic APRIL expression exacerbates the number and size of adenomas in Apc(Min) mice and in a mouse model for colitis-associated colon carcinogenesis. Furthermore, knockdown of APRIL in primary spheroid cultures of colon cancer cells and both mouse and human CRC cell lines reduced tumor clonogenicity and in vivo outgrowth. Taken together, our data therefore indicate that both tumor-derived APRIL and APRIL produced by non-tumor cells is supportive in colorectal tumorigenesis.
Various combinations of a low-tannin herbaceous legume (
Vigna unguiculata) and foliage of tanniniferous shrub legumes (
Calliandra calothyrsus,
Flemingia macrophylla and
Leucaena leucocephala) or a ...low-tannin shrub legume (
Cratylia argentea), all mixed together with a low-quality tropical grass (
Brachiaria humidicola), were tested
in vitro for differences in the effects on ruminal fermentation. Two experiments with the gas transducer technique were carried out, where each forage mixture was tested either with or without polyethylene glycol in order to be able to identify tannin-related effects (
n
=
3). In Experiment 1, a stepwise replacement of
V. unguiculata by
C. calothyrsus (5:0, 4:1, 3:2, 2:3, 1:4, 0:5) at a legume proportion of 1/3 or 2/3 in the mixture was evaluated. Together with two grass-alone and four pure legume treatments this added up to 30 treatments. In Experiment 2,
V. unguiculata was gradually replaced by each of the four shrub legumes (3:0, 2:1, 1:2, 0:3) in grass–legume ratios of 2:1, adding up, together with two grass-alone treatments, to 28 treatments. When added alone,
V. unguiculata resulted in high fermentative activity as measured by gas production and kinetics as well as low proportion of undegraded crude protein. When
V. unguiculata was replaced by the low-tannin
C. argentea in Experiment 2, there was no noticeable difference (P>0.05) in fermentative activity. In both experiments, the effect of the substitution of
V. unguiculata by tanniniferous shrub legumes resulted in a declining gas production and an increasing proportion of undegraded crude protein (P<0.001). However, the extent of these changes depended on the level of replacement and the shrub legume species (P<0.001). The results of Experiment 2 illustrate that this was the consequence not only of different tannin contents (less adverse effects with
L. leucocephala than with
C. calothyrsus) but also differences in the chemical properties of the tannins present in these shrub legume species (much less adverse effects with
L. leucocephala than with
F. macrophylla despite similar tannin contents). Furthermore these results indicate that, once the extent of the effects of a tanniniferous legume is known, one may calculate the maximal level of replacement of a low-tannin legume in a grass diet possible without negative effects on ruminal fermentation. This allows to improve dry season grass-based diets with as few as possible of the expensive and less well growing low-tannin legume.
We conducted an experiment to determine the effects of concentration and astringency of extractable and bound condensed tannins (CT) in tropical legumes on intake, digestibility, and nitrogen (N) ...utilization by sheep. The test legumes (Desmodium ovalifoium and Flemingia macrophylla) had similar concentrations of extractable CT (90 g/kg DM) but different concentrations of bound CT and astringency of tannins. Chopped, sun-dried forage of each legume was sprayed with either water (control) or polyethylene glycol (PEG, 35 g/kg of DM) to bind extractable CT and fed daily (26 g/kg BW) to eight sheep with ruminal and duodenal cannulas. The sheep also received starch-extracted cassava meal intraruminally (4 g/kg BW) as a constant source of readily fermentable carbohydrates. Intake of the two legumes was not different (P 0.05), but it increased an average of 10% (P .01) when extractable CT were reduced from 90 to 50 g/kg of DM with PEG. Ruminal and total tract digestibilities of OM, NDF, and ADF were greater (P .01) with D. ovalifolium than with F. macrophylla and increased for both legumes with the addition of PEG. Greater (P .01) N flow to the duodenum, N absorbed from the intestine, and fecal N were observed with F. macrophylla than with D. ovalifolium. Extraction of CT with PEG resulted in less (P .05) ruminal escape protein and less (P 0.01) fecal N with both legumes, but apparent postruminal N digestion was not affected. Changes in the concentration of extractable CT in tropical legumes can significantly affect forage intake, digestion, and N utilization by sheep
Congenital Pulmonary Airway Malformation (CPAM) has an estimated prevalence between 0.87 and 1.02/10,000 live births and little is know about their pathogenesis. To improve our knowledge on these ...rare malformations, we analyzed the cellular origin of the two most frequent CPAM, CPAM types 1 and 2, and compared these malformations with adjacent healthy lung and human fetal lungs.
We prospectively enrolled 21 infants undergoing surgical resection for CPAM. Human fetal lung samples were collected after termination of pregnancy. Immunohistochemistry and proteomic analysis were performed on laser microdissected samples.
CPAM 1 and 2 express mostly bronchial markers, such as cytokeratin 17 (Krt17) or α-smooth muscle actin (ACTA 2). CPAM 1 also expresses alveolar type II epithelial cell markers (SPC). Proteomic analysis on microlaser dissected epithelium confirmed these results and showed distinct protein profiles, CPAM 1 being more heterogeneous and displaying some similarities with fetal bronchi.
This study provides new insights in CPAM etiology, showing clear distinction between CPAM types 1 and 2, by immunohistochemistry and proteomics. This suggests that CPAM 1 and CPAM 2 might occur at different stages of lung branching. Finally, the comparison between fetal lung structures and CPAMs shows clearly different protein profiles, thereby arguing against a developmental arrest in a localized part of the lung.
PDF
