Nitrogen transfer in litter mixture enhances decomposition rate,temperature sensitivity,and C quality changes

Background and aims

Litter decomposition is a critical process in terrestrial ecosystems and, since in natural conditions plant litter occurs in mixtures, understanding the interactive effects of mixed litter is of great ecological relevance. In this context, we test the hypothesis that N transfer between high quality litter to N-poor substrates are at the base of synergistic interactions, positively affecting litter decay rate, temperature sensitivity, and changes of organic C quality.

Methods

We carried out a manipulative experiment using four organic substrates, encompassing a wide range of biochemical quality (Hedera helix and Quercus ilex leaf litter, cellulose strips and woody sticks), each decomposing either separately or in matched pair mixtures for 360 days. Organic substrates were characterized for mass loss, C and N content and by ¹³C CPMAS NMR to assess biochemical quality changes.

Results

Litter response to mixing was related to the biochemical quality of the components in the mixture: additive when substrates with similarly high (H. helix and Q. ilex) or low (cellulose and wood) N content were paired, but synergistic when substrates with contrasting N content were associated (either of the two leaf litters with either cellulose or wood). Overall, no antagonist effects were observed in this experiment. Interestingly, decomposition of cellulose and wood showed an higher temperature sensitivity, compared to monospecific substrates, when paired with N rich materials. Significant N transfer was found from N rich litter to N poor substrates and ¹³C CPMAS NMR showed rapid changes of C quality of cellulose and wood sticks only when paired with N rich litter.

Conclusions

Our findings support the hypothesis that mixing litters of different quality, with quality expressed in terms of C/N ratio and N content, increases decomposition rate and temperature sensitivity of the lower quality substrates.     

Improved Flutter Ablation Outcomes Using a 10mm-tip Ablation Catheter

Introduction

Radiofrequency(RF) ablation has become the first line of therapy for atrial flutter(AFL). Advances in catheter and mapping technologies have led to better understanding and different approaches for treating this arrhythmia. We describe the results of different approaches to ablate this arrhythmia.

Materials and Methods

A cohort of 198 patients with isthmus dependent AFL. The techniques used were: 10mm-tip catheter with power set to 100w, 8mm-tip catheter with power set to 60W and irrigated tip catheter.

Results

212 procedures, including redos were done in 198 consecutive patients. We used irrigated tip catheters in 14 procedures, 8mm-tip in 55 procedures, and 10mm-tip in 143 procedures. Bidirectional block was achieved in 97.6% of cases with all techniques, with no difference among them. Procedure time was shorter in the 10mm-tip versus 8mm-tip(69.6±30.6min vs.105±43min) or irrigated tip(180±90min) (P<0.05). Fluoroscopy time was also shorter in the 10mm-tip versus 8mm-tip (24±18min vs. 37±23min) or irrigated tip (110±25min)(P<0.05). The cumulative incidence of failure during follow-up was 1.2%/year in the 10mm, 10.1%year in the 8mm and 6.9%year in the irrigated tip. The survival free of a new procedure was significantly higher among 10mm patients.

Conclusions

In our series we found a high rate of acute success with the use of different techniques for AFL ablation. Procedure and fluoroscopic times were shorter with the use of 10mm-tip as compared with the others techniques. The long-term risk of recurrence was lower when we used the 10mm-tip catheter and the survival free of a second procedure was higher among patients treated with this catheter.     

Two-dimensional mass spectrometric mapping

The identification and relative quantification of proteins in closely related biological samples is the backbone for many investigations in systems biology and for the discovery of biomarkers. While two-dimensional gel-based methodologies are still widely used for comparative proteomic studies, the recent advent of gel-free methodologies may allow the analysis of a larger number of samples in an automated fashion. Most of the technologies presented in this review require a chemical modification of proteins before analysis, and rely on the relative intensities of mass spectrometry signals for protein quantification. In particular, two-dimensional mass spectrometric mapping methodologies provide a visual representation of mass spectrometric data, thus facilitating the identification of differences in relative protein abundance.     

Thyroid and hypoxic stress in the newt Triturus carnifex

When specimens of the newt Triturus carnifex, under anaesthesia by submersion in a 0.2% chlorbutol solution for 25 min, are isolated in a respiratory chamber at 18 degrees C containing water with only 1.3 ppm of oxygen, they consume the oxygen completely in about 3 hr, but they can stay alive for many more hours and wake up with no apparent exterior consequences. Hypoxia induces rapid onset of hepatic steatosis and melanosis, as well as a controlled haemolytic process involving a pool of red blood cells of the same order of size as that held as a reserve in the spleen by animals in an aerial habitat. At the origin of the phenomena is an intense response by the hypophysis, histologically detectable 1 hr from the onset of treatment and confirmed 2 hr later by a highly significant increase in the plasma thyroidstimulating hormone (TSH) concentration compared with the controls (41.5 +/- 13.7 microU/L vs. 15.5 +/- 6.2; P < 0.005). The thyroid follicles react by reabsorbing their colloid, but instead of an increase in the plasma free T3 and T4 concentrations, fT3 falls significantly (1.5 +/- 0.3 pg/mL vs., the 2.4 +/- 0.7; P < 0.05), whereas fT4 remains stationary (4.0 +/- 0.5 pg/mL vs. 4.6 +/- 0.8; N.S.). After 6 hr, the plasmatic TSH concentration is still higher than in the controls (27.0 +/- 3.0 microU/L vs. 15.5 +/- 6.2; P < 0.05), whereas fT3 and fT4 remain stable (1.5 +/- 0.3 and 4.4 +/- 0.5 pg/mL, respectively). If T3 or T4 labelled with 125I is administered prior to hypoxia, after 6 hr of treatment the radioactivity is found to be limited exclusively to the liver and kidney; the thyroid, gall bladder and gut result negative, and this does not agree with hypotheses of hormone inactivation by deiodination, sulphation or glucuronidation. This apparently peculiar endocrine path has not been observed in previous studies on hypoxia in vertebrates, because the experiments were always designed to analyse plasma hormone levels after at least 24 hr of hypoxia or during chronic treatments, losing the most interesting phases of the endocrine response. The possibility that the hypoxic newt possesses alternative or complementary metabolic pathways to anaerobic glycolysis to sustain steatogenesis and melanogenesis and maintain the same cardiac activity as the controls is briefly discussed.     

Elucidation of the beta-carotene hydroxylation pathway in Arabidopsis thaliana

The first dedicated step in plant xanthophyll biosynthesis is carotenoid hydroxylation. In Arabidopsis thaliana, this reaction is performed by both heme (LUT1 and LUT5) and non-heme (CHY1 and CHY2) hydroxylases. No mutant completely abolishing alpha- or beta-carotene hydroxylation has been described to date. We constructed double and triple mutant combinations in CHY1, CHY2, LUT1, LUT5 and LUT2 (lycopene epsilon-cyclase). In chy1chy2lut2, 80% of leaf carotenoids is represented by beta-carotene. In chy1chy2lut5, beta-carotene hydroxylation is completely abolished, while hydroxylation of the beta-ring of alpha-carotene is still observed. The data are consistent with a role of LUT5 in beta-ring hydroxylation, and with the existence of an additional hydroxylase, acting on the beta-ring of alpha-, but not beta-carotene.     

Is polyandry a common event among wild populations of the pest Ceratitis capitata?

In many insect species, females can mate more than once and store sperm from more than one male. An assessment and understanding of polyandry in the field can be important for pest species with a high colonization potential, such as the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), which is also highly polyphagous and among the most destructive agricultural insects. The use of polymorphic microsatellite markers, combined with different statistical approaches, provides evidence that polyandry occurs in two C. capitata natural populations, one population from the Greek island of Chios and one population from Rehovot, in Israel. The observed different level of polyandry is discussed in relation to the genetic diversity, seasonality, and demography of the two populations. When polyandry is present, paternity analysis also indicates that one male, presumably the last, tends to sire most of the progeny. Polyandry and paternity skew may have important implications for the evolution of the species, in terms of maintenance of the genetic variability. Moreover, these aspects of the mating behavior, i.e., remating frequency and paternity skew, may locally affect the sterile insect technique, the most commonly applied control strategy against C. capitata.     

Reconstruction of Late Pleistocene-Holocene palaeobathymetries from Ostracoda on the Tyrrhenian continental shelf

Quantitative analyses of ostracod assemblages from three cores recovered on the Tyrrhenian shelf (Gaeta and Salerno Gulfs) have been applied to construct palaeobathymetric curves. Palaeoclimatic curves obtained from planktonic foraminifera, calcareous nanoplankton, pteropods and pollen are available for the same cores, in addition to sedimentological, mineralogical, geochemical (δ¹⁸O, ¹⁴C, C/N, CaCO₃) and volcanological data with regard to the two cores from the Salerno Gulf. The palaeobathymetric curves reflect the climatic events through the Late Pleistocene-Holocene interval. The climatic events of the Last Glacial (and within it, the Last Glacial Maximum), the Late Glacial (with Oldest Dryas, Bølling-Allerød, Younger Dryas events) and Postglacial have been recognised. The palaeobathymetric curves are also in agreement with palaeoclimatic curves of planktonic assemblages and pollen.     

The new enneanuclear nickel carbonyl anion [Ni9(CO)16] and its relationships with the [Ni12(CO)21] and [Ni6Rh3(CO)17] clusters

The reaction of [N(PPh₃)₂]₂[Ni₆(CO)₁₂] with Cu(PPh₃)_xCl (x=1, 2), as well as the degradation of [N(PPh₃)₂]₂[H₂Ni₁₂(CO)₂₁] with PPh₃, affords the new and unstable dark orange–brown [N(PPh₃)₂]₂[Ni₉(CO)₁₆].THF salt in low yields. This salt has been characterized by a CCD X-ray diffraction determination, along with IR spectroscopy and elemental analysis. The close-packed two-layer metal core geometry of the [Ni₉(CO)₁₆]²⁻ dianion is directly related to that of the bimetallic [Ni₆Rh₃(CO)₁₇]³⁻ trianion and may be envisioned to be formally derived from the hcp three-layer geometry of [Ni₁₂(CO)₂₁]⁴⁻ by the substitution of one of the two outer [Ni₃(CO)₃(μ−CO)₃]²⁻ layers with a face-bridging carbonyl group.     

Affinity-capture reagents for protein arrays

The simultaneous identification and quantitative measurement of the production levels of thousands of different proteins in a biological specimen remains an unachieved goal of modern proteomic research. Advances in the development of microarray-based platforms for highly parallel detection of proteins have therefore received a considerable impulse during the last few years. Here, we review the existing reagents for affinity capture of protein targets, as well as the techniques used for their immobilization on solid supports and methods for the detection of binding events, underlining the problems and the opportunities in this continuously evolving research field.