15N Levels Research Articles

15N NMR study of azo-hydrazo tautomerism in some industrially produced azo dyes

15N NMR data (1J (15N, 1H) coupling constants and 15N chemical shifts) were used to characterize quantitatively azo-hydrazo tautomerism in some industrially produced azo dyes. Both 1J (15N, 1H) coupling constants and 15N chemical shifts were obtained at the natural abundance level of 15N using inverse detection of resonances. All three possible types of azo dye existence were found: (i) dyes existing completely in azo forms, (ii) dyes existing completely in hydrazo forms or (iii) dyes forming azo-hydrazo tautomeric equilibria.

Size-Reduced Basis Set Calculation of Accurate Isotropic Nuclear Magnetic Shieldings Using CTOCD-GRRO and GPRO Methods in Amino Acids and Oligopeptides

The origin-independent magnetically induced CTOCD-GRRO and -GPRO (after continuous transformation of the origin of the current density-gradient of ρ and gradient of a power of ρ) current densities are shown to vary linearly with respect to their own defining α and β parameters. The same is reflected in the connected magnetic properties, in particular the magnetic shielding. This is exploited to find values for α and β that, using small basis sets, provide isotropic nuclear magnetic shieldings matching an accurate prediction, chosen as the complete basis set limit. An application to the 20 naturally occurring amino acids shows that different nuclei require different values of the parameters, which have been determined at the BHandHLYP/6-31+G(d,p) level with or without consideration of diversified chemical environments. Using CTOCD-GRRO and -GPRO methods, equipped with the optimized parameters at this low-cost level of calculation, 1H, 13C, 15N, and 17O magnetic shielding constants in glutathione, ophthalmic acid, and thyrotropin-releasing hormone are predicted with nearly the same accuracy as that of much more expensive calculations.

15N NMR study of azo-hydrazo tautomerism: Past and present

15N NMR data (1J(15N, 1H) coupling constants and 15N chemical shifts) seem to be the most suitable ones to characterize azo-hydrazo tautomerism quantitatively. The reason is that nitrogen atoms of –NN−/−NH-N = fragments are directly involved in azo-hydrazo equilibrium.First data was measured and published in 1970 and 15N selectively enriched compounds had to be prepared since electro magnets were used in NMR spectrometers at that time providing very low resonance frequencies (from 60 to 100 MHz for protons) and have had, consequently, very low sensitivity. Moreover, a choice of 15N enriched 15N anilines was very limited and these compounds were relatively very expensive.At present, the situation is completely different. There has been a huge increase of NMR spectrometer frequencies used for measurement of NMR spectra and even routinely used NMR spectrometers having 400–600 MHz proton frequencies are sufficiently sensitive to provide 1J(15N, 1H) coupling constants and 15N chemical shifts at the natural abundance level of15N. Inverse detection of resonances is now routinely used. The lower magnetogyric ratio of appropriate nucleus the higher signal enhancement is achieved: this is the very case of the 15N isotope. Theoretical enhancement factor obtained for inverse detection of 15N compared with direct one is ca 300! Application of cryoprobes where electronics is chilled either by liquid nitrogen or even liquid helium reducing electric noise allows to reduce time of accumulation from 8 to 16 times!Some representative examples are presented both from past to present demonstrating the fact that thorough analyses of NMR spectra allow determining the proper constitutions of compounds studies and excluding the wrong ones.

Ratio of naturally retained 15N to 13C in rat brain regions as a marker of brain function and activity

Our aim in the present study was to clarify the activity-dependent and function-associated retention of stable isotopes (SIs) in rat brain regions. We measured regional distributions of the natural stable isotopes 15N and 13C in brain using a mass spectrometer with a dual inlet system and a double collector for ratiometry, and compared them with distributions obtained from internal organs and skeletal muscle. Although levels of 15N and 13C were very high in brain regions of prenatal rats, and robustly decreased after birth, developmental changes in brain regions became obvious when the ratio of 15N to 13C (abbreviated as 15N/13C) in each brain region was compared. A high correlation was observed between free motor activity and 15N/13C in the hippocampus, cerebrum, and striatum. A significantly higher 15N/13C was also observed in the hippocampus and striatum of rats with higher intelligence, which was evaluated by radial maze learning. Furthermore, 15N/13C in brain regions of trained rats were significantly higher than those of untrained age-matched rats. Our study suggests that the 15N/13C in a specific brain region may reflect the physiological feature of the region. This ratio may hence be applicable as a maker for pathological research on undiagnosed brain diseases.

Geese mediate vegetation state changes with parallel effects on N cycling that leave nutritional legacies for offspring

AbstractAlong the coastal fringe of the Yukon–Kuskokwim River Delta in southwestern Alaska, geese maintain grazing lawns dominated by a rhizomatous sedge that, when ungrazed, transitions to a taller, less palatable growth form that is taxonomically described as a different species. Nutrients recycled in goose feces, in conjunction with grazing, are critical to the rapid, nutritious growth of grazing lawns, and selective foraging on lawns has positive life‐history consequences for goslings. To examine whether bidirectional vegetation shifts were accompanied by parallel changes in N cycling, we studied how 15N‐urea and 13C15N‐glycine were processed through soils and plants of native and recently reverted vegetation states. Biomass and plant 15N uptake from plots reverted to the tall growth form using exclosures and from those shifted to grazing lawns by experimental clipping and then goose grazing were identical to their native counterparts. Total recovery of 15N within the tall vegetation types was significantly greater than within grazing lawns, although when expressed on a per‐gram biomass basis, percentage of 15N recovery was significantly higher in grazing lawns compared with the tall vegetation state. Patterns of 13C enrichment in CO2 soil efflux showed rapid use of 13C‐glycine as a respiratory substrate within the first hour following injection, with both the timing and magnitude of efflux occurring at similar time points for all four vegetation types. However, higher soil respiration rates and a shorter half‐life for 13C‐glycine in soils from tall meadows resulted in a greater proportional loss of 13CO2 compared with grazing lawns. Despite daily‐to‐weekly tidal inundation, all of 15N from labeled substrates could be accounted for within 1 m of the injection grid from soils of both states after 30 d, with significant levels of 15N in soils and vegetation after one year. Geese have remarkably high fidelity to brood‐rearing areas, returning as adults to the same grazing lawns where they were raised as goslings. Our data suggest that the role fecal‐derived nutrients play in the positive feedback loop between geese and their food resources can provide a long‐term legacy that spans generations.

Disentangling nutritional pathways linking leafcutter ants and their co-evolved fungal symbionts using stable isotopes.

Leafcutter ants are the ultimate insect superorganisms, with up to millions of physiologically specialized workers cooperating to cut and transport vegetation and then convert it into compost used to cultivate co‐evolved fungi, domesticated over millions of years. We tested hypotheses about the nutrient‐processing dynamics governing this functional integration, tracing 15N‐ and 13C‐enriched substrates through colonies of the leafcutter ant Atta colombica. Our results highlight striking performance efficiencies, including rapid conversion (within 2 d) of harvested nutrients into edible fungal tissue (swollen hyphal tips called gongylidia) in the center of fungus gardens, while also highlighting that much of each colony's foraging effort resulted in substrate placed directly in the trash. We also find nutrient‐specific processing dynamics both within and across layers of the fungus garden, and in ant consumers. Larvae exhibited higher overall levels of 15N and 13C enrichment than adult workers, supporting that the majority of fungal productivity is allocated to colony growth. Foragers assimilated 13C‐labeled glucose during its ingestion, but required several days to metabolically process ingested 15N‐labeled ammonium nitrate. This processing timeline helps resolve a 40‐yr old hypothesis, that foragers (but apparently not gardeners or larvae) bypass their fungal crops to directly assimilate some of the nutrients they ingest outside the nest. Tracing these nutritional pathways with stable isotopes helps visualize how physiological integration within symbiotic networks gives rise to the ecologically dominant herbivory of leafcutter ants in habitats ranging from Argentina to the southern United States.

Longevity of Beta Cells and Protein Complexes Revealed by Isotope Imaging

We discovered recently that long-lived cells (LLCs), such as neurons, contain long-lived proteins (LLPs) in the nucleus that can last a lifetime, and their decline during aging impairs nuclear function. Beta cells are LLCs with a slow cell replication process, yet it is unknown whether individual beta cells have different lifespans. We tested this hypothesis by using a hybrid microscopy and mapping platform (MIMS-EM) to identify beta cells and quantify cell and protein turnover in the islets of Langerhans. This is achieved by pulse-labelling mice with an 15N-rich diet followed by a chase period with a control 14N-rich diet for up to 2 years. Here, old cells and protein structures retain 15N while those that turnover incorporate 14N. The levels of 15N and 14N were measured with multi-isotope mass spectroscopy (MIMS) and the 15N-to-14N ratio reports on cell and protein turnover. Importantly, the MIMS data is correlated with scanning electron microscopy (EM) to create high-resolution maps of cells and intra-cellular structures overlaid with age information. Here we report the use of MIMS-EM on mouse islets to discover that beta cells have vastly different ages. In fact, while approximately 75% of beta cells replicate between 2-4 times, almost 25% of all beta cells does not replicate at all after weaning and remain quiescent for an entire lifetime, and therefore, are as old as cortical neurons. Such longevity was also found in other islet cell-types and at the protein super-complex level, where 15N accumulation on the primary cilium of beta cells strongly indicates that this important signaling structure is exceptionally long-lived. Strikingly, and similar to what is found in old rat neurons, beta cells from humans aged >60-years-old lose specific nuclear LLPs and show signs of impaired nuclear function. Together, our data shows that beta cell longevity is heterogeneous and identifies the loss of nuclear LLPs in human beta cells as a potential contributing factor to age-dependent loss of beta cell function. Disclosure R. Arrojo e Drigo: Stock/Shareholder; Self; VTV Therapeutics, Novo Nordisk A/S. B.H. Toyama: None. S. Tyagi: None. V. Lev-Ram: None. T.J.J. Deerinck: None. E.A. Bushong: None. R. Ramachandra: None. C. Lechene: None. M.H. Ellisman: None. M. Hetzer: None.

15N NMR study of (E)- and (Z)-2-(2-(2-hydroxy-4-nitrophenyl)hydrazono)-1-phenylbutane-1,3-diones. A suitable method for analysis of hydrazone isomers

The one- and two-dimensional 15N NMR spectra of (E)- and (Z)-2-(2-(2-hydroxy-4-nitrophenyl)hydrazono)-1-phenylbutane-1,3-diones (1) were measured and analysed and 15N chemical shifts and 1J (15N, 1H) coupling constants were used for characterization of these two compounds from the viewpoint of azo-hydrazo tautomerism. Both compounds exist completely in appropriate hydrazo forms in dimethyl sulfoxide.Advantages of 15N NMR spectroscopy application in determination of acidic proton positions and azo-hydrazo content determination are discussed. We would like to propose the application of 15N NMR data measured at the natural abundance level of 15N as the “first glance” and strongest evidence method for the existence of hydrazo form in azo dyes and for differentiation of E- and Z-isomers around C=Nβ double bond.

Foliar uptake of nitrogen from ant faecal droplets: An overlooked service to ant‐plants

Abstract Nutrient supplies to plants from ants are well known from specialised myrmecophytic symbioses and from plants growing in soil close to ant nests. However, above‐ground nutrient pathways may play a largely unrecognised role also in less specialised ant–plant interactions—the numerous facultative relationships, where ants forage on plants. In a laboratory experiment, weaver ants (Oecophylla smaragdina) were confined to the canopies of coffee (Coffea arabica) seedlings, excluding any ant‐to‐plant transfer of nutrients via the soil strata. When ants were fed 15N‐labelled glycine and subsequently deposited faecal droplets on the seedlings, coffee leaves showed increased levels of 15N and total nitrogen compared to control plants without ants. This was evident for both exposed leaves and leaves covered in plastic bags (i.e. not directly exposed to ants). Thus, nitrogen from ant excretions was absorbed through the coffee leaves, and subsequently, translocated within the plants and possibly leading to the observed higher shoot/root (wet weight) ratios observed on ant‐plants compared to controls. Synthesis. These results reveal an undescribed foliar uptake of ant‐provided nutrients. If this is a general mechanism, a vast amount of ant–plant interactions involves fertilisation. Foliar fertilisation by ants may be an important steady benefit to plants, which has driven the evolution of ant–plant mutualisms in parallel with the well‐recognised but probably more fluctuating benefit from herbivore protection. Given the world‐wide abundance of plant canopies foraged by ants, this nutrient pathway may be of high ecological significance.

Biological Nitrogen Fixation by Legumes and N Uptake by Coffee Plants

Green manures are an alternative for substituting or supplementing mineral nitrogen fertilizers. The aim of this study was to quantify biological N fixation (BNF) and the N contribution derived from BNF (N-BNF) to N levels in leaves of coffee intercropped with legumes grown on four family farms located in the mountainous region of the Atlantic Forest Biome in the state of Minas Gerais, Brazil. The following green manures were evaluated: pinto peanuts (Arachis pintoi), calopo (Calopogonium mucunoides), crotalaria (Crotalaria spectabilis), Brazilian stylo (Stylosanthes guianensis), pigeon pea (Cajanus cajan), lablab beans (Dolichos lablab), and velvet beans (Stizolobium deeringianum), and spontaneous plants. The experimental design was randomized blocks with a 4 × 8 factorial arrangement (four agricultural properties and eight green manures), and four replications. One hundred grams of fresh matter of each green manure plant were dried in an oven to obtain the dry matter. We then performed chemical and biochemical characterizations and determined the levels of 15N and 14N, which were used to quantify BNF through the 15N (δ15N) natural abundance technique. The legumes C. mucunoides, S. guianensis, C. cajan, and D. lablab had the highest rates of BNF, at 46.1, 45.9, 44.4, and 42.9 %, respectively. C. cajan was the legume that contributed the largest amount of N (44.42 kg ha-1) via BNF.C. cajan, C. spectabilis, and C. mucunoides transferred 55.8, 48.8, and 48.1 %, respectively, of the N from biological fixation to the coffee plants. The use of legumes intercropped with coffee plants is important in supplying N, as well as in transferring N derived from BNF to nutrition of the coffee plants.

Phase Shift Analysis of P 14C Scattering at the Energy of the 2 S 1/2 Resonance

The phase shift analysis for determination of the 2S1/2 resonance at 1.5 MeV was carried out on the basis of the known experimental measurements of the excitation functions of the p14C elastic scattering at four angles from 90 to 165 grad. and more than 100 energy values in the range from 600-800 to 2200-2400 keV. The obtained shape of the resonance 2S1/2 phase shift coincides with the characteristics of the corresponding level of 15N in whole, and the suggested potential acceptably describe this scattering phase shift.

Ectomycorrhizal Communities on the Roots of Two Beech (Fagus sylvatica) Populations from Contrasting Climates Differ in Nitrogen Acquisition in a Common Environment.

Beech (Fagus sylvatica), a dominant forest species in Central Europe, competes for nitrogen with soil microbes and suffers from N limitation under dry conditions. We hypothesized that ectomycorrhizal communities and the free-living rhizosphere microbes from beech trees from sites with two contrasting climatic conditions exhibit differences in N acquisition that contribute to differences in host N uptake and are related to differences in host belowground carbon allocation. To test these hypotheses, young trees from the natural regeneration of two genetically similar populations, one from dryer conditions (located in an area with a southwest exposure [SW trees]) and the other from a cooler, moist climate (located in an area with a northeast exposure [NE trees]), were transplanted into a homogeneous substrate in the same environment and labeled with (13)CO2 and (15)NH4 (+). Free-living rhizosphere microbes were characterized by marker genes for the N cycle, but no differences between the rhizospheres of SW or NE trees were found. Lower (15)N enrichment was found in the ectomycorrhizal communities of the NE tree communities than the SW tree communities, whereas no significant differences in (15)N enrichment were observed for nonmycorrhizal root tips of SW and NE trees. Neither the ectomycorrhizal communities nor the nonmycorrhizal root tips originating from NE and SW trees showed differences in (13)C signatures. Because the level of (15)N accumulation in fine roots and the amount transferred to leaves were lower in NE trees than SW trees, our data support the suggestion that the ectomycorrhizal community influences N transfer to its host and demonstrate that the fungal community from the dry condition was more efficient in N acquisition when environmental constraints were relieved. These findings highlight the importance of adapted ectomycorrhizal communities for forest nutrition in a changing climate.

Hyperpolarization of "Neat" Liquids by NMR Signal Amplification by Reversible Exchange.

We report NMR Signal Amplification by Reversible Exchange (SABRE) hyperpolarization of the rare isotopes in “neat” liquids, each composed only of an otherwise pure target compound with isotopic natural abundance (n.a.) and millimolar concentrations of dissolved catalyst. Pyridine (Py) or Py derivatives are studied at 0.4% isotopic natural abundance 15N, deuterated, 15N enriched, and in various combinations using the SABRE-SHEATH variant (microTesla magnetic fields to permit direct 15N polarization from parahydrogen via reversible binding and exchange with an Ir catalyst). We find that the dilute n.a. 15N spin bath in Py still channels spin order from parahydrogen to dilute 15N spins, without polarization losses due to the presence of 14N or 2H. We demonstrate P15N ≈ 1% (a gain of 2900 fold relative to thermal polarization at 9.4 T) at high substrate concentrations. This fundamental finding has a significant practical benefit for screening potentially hyperpolarizable contrast agents without labeling. The capability of screening at n.a. level of 15N is demonstrated on examples of mono- and dimethyl-substituted Py (picolines and lutidines previously identified as promising pH sensors), showing that the presence of a methyl group in the ortho position significantly decreases SABRE hyperpolarization.

Soil Plus Foliar Nitrogen Application increases Cotton Growth and Salinity Tolerance

Soil or foliar application of nitrogen (N) can increase plant growth and salinity tolerance in cotton, but a combination of both methods is seldom studied under salinity stress. A pot experiment was conducted to study the effects of soil application (S), foliar application (F), and a combination of both (S+F) with labeled nitrogen (15N) on cotton growth, N uptake and translocation under salinity stress (ECe = 12.5 dS m−1). Plant biomass, leaf area, leaf chlorophyll (Chl) content, leaf net photosynthetic (Pn) rate, levels of 15N and [Na+] and K+/ Na+ ratio in plant tissues were determined at 3, 7, 14 and 28 days after N application (DAN). Results showed that soil or foliar nitrogen fertilization improved plant biomass, leaf area per plant and leaf photosynthesis, and a combination of soil- plus foliar-applied N was superior to either S or F alone under salinity stress. Although foliar application favored a rapid accumulation of leaf N and soil application a rapid accumulation of root N, S+F enhanced N accumulation in both leaf and root under salinity stress. The combined N application also maintained significantly greater [K+] and K+/Na+ than either soil or foliar application alone. Therefore, the improved plant growth and salinity tolerance under S+F relative to soil or foliar N application alone was attributed to the increased total uptake of N, balanced N concentrations in different tissues through enhanced uptake and accumulation in both leaves and roots, and higher ratio of K+/Na+.

Carbon quality affects the nitrogen partitioning between plants and soil microorganisms

We investigated how the carbon quality of soil amendments based upon their carbon (C)-to-nitrogen (N) -ratio and their degree of aromaticity influence soil N transformations and affect N partitioning between soils, plants and microorganisms. A better understanding of these interactions might offer the possibility to optimize N use efficiency in agriculture. We performed a randomized pot experiment with winter wheat and compared the influence of naturally 13C labelled soil additives in three increasing condensation degrees, i.e. corn silage, hydrochar and pyrochar, in combination with three levels of 15N labelled NO3− on plant growth and N allocation. Corn silage, a lignocellulose material with a wide C-to-N-ratio and low condensation degree, which was also used as starting material for the two other amendments, favoured microbial growth and activity while simultaneously leading to N deficiency in wheat plants. In contrast, hydrochar and pyrochar positively influenced plant growth independent of their C-to-N-ratio and their degree of aromaticity. After adding hydrochar, plants did not take up the added fertilizer N but obviously used NH4+ from mineralized hydrochar to meet their N demands. After adding pyrochar, fertilizer NO3− was used effectively by plants and fertilizer levels were still visible in the soil, while microbial activity was low. Our results clearly demonstrate that C quality strongly affects the N partitioning in the plant–soil–microorganism system. Hydrochars with a low degree of condensation that are slowly degraded by soil microorganisms might substitute N fertilizers whereas highly condensed pyrochars decreasing the soil microbial activity might enhance the N use efficiency of plants.

The Influence of Altered Rainfall Regimes on Early Season N Partitioning Among Early Phenology Annual Plants, a Late Phenology Shrub, and Microbes in a Semi-arid Ecosystem

In Mediterranean-type ecosystems, nitrogen (N) accumulates in soil during dry summer months and rapidly becomes available during early season rain events. The availability of early season N could depend on the size of rainfall events, soil microbial activity, and phenology of the plant community. However, it is poorly understood how precipitation patterns affect the fate of early season N. Microbes and plants with early phenology may compete strongly for early season N but theory suggests that microbial N storage can meet plant N demands later in the season. Using a 15N tracer and rainfall manipulation we investigated the fate of early season N. N allocation patterns differed substantially between microbes, early and late phenology plants. As expected early phenology annuals and microbes took up 15N, within 1 day, whereas a late-phenology shrub allocated 15N to leaves later in the season. We saw no evidence for microbial storage of early season N; the peak of 15N in shrub leaves did not coincide with detectable levels of 15N in the microbial biomass or labile soil pool. This suggests that shrubs were able to access early season N, store and allocate it for growth later in the season. Although we saw no evidence of microbial N storage, N retention in soil organic matter (SOM) was high and microbes may play an important role in sequestering N to SOM. Plant N uptake did not respond significantly to 1 year of rainfall manipulation, but microbes were sensitive to dry conditions. 1 year after 15N addition shrubs had resorbed up to half of the N from leaves whereas N in annuals remained as dead leaf litter. Differences in end-of-season N partitioning between dead and living biomass in the two vegetation types suggest that plant species composition could affect N availability in the following growing season, but it may take several years of altered precipitation patterns to produce rainfall-dependent changes.

Factors affecting the molecular structure and mean residence time of occluded organics in a lithosequence of soils under ponderosa pine

Occluded, or intra-aggregate, soil organic matter (SOM) comprises a significant portion of the total C pool in forest soils and often has very long mean residence times (MRTs). However, occluded C characteristics vary widely among soils and the genesis and composition of the occluded organic matter pool are not well understood. This work sought to define the major controls on the composition and MRT of occluded SOM in western U.S. conifer forest soils with specific focus on the influence of soil mineral assemblage and aggregate stability. We sampled soils from a lithosequence of four parent materials (rhyolite, granite, basalt, and dolostone) under Pinus ponderosa. Three pedons were excavated to the depth of refusal at each site and sampled by genetic horizon. After density separation at 1.8 g cm−3 into free/light, occluded and mineral fractions, the chemical nature and mean residence time of organics in each fraction were compared. SOM chemistry was explored through the use of stable isotope analyses, 13C NMR, and pyrolysis GC/MS. Soil charcoal content estimates were based on 13C NMR analyses. Estimates of SOM MRT were based on steady-state modeling of SOM radiocarbon abundance measurements. Across all soils, the occluded fraction was 0.5–5 times enriched in charcoal in comparison to the bulk soil and had a substantially longer MRT than either the mineral fraction or the free/light fraction. These results suggest that charcoal from periodic burning is the primary source of occluded organics in these soils, and that the structural properties of charcoal promote its aggregation and long-term preservation. Surprisingly, aggregate stability, as measured through ultrasonic dispersion, was not correlated with occluded SOM abundance or MRT, perhaps raising questions of how well laboratory measurements of aggregate stability capture the dynamics of aggregate turnover under field conditions. Examination of the molecular characteristics of the occluded fraction was more conclusive. Occluded fraction composition did not change substantially with soil mineral assemblage, but was increasingly enriched in charcoal with depth relative to bulk SOM. Enrichment levels of 13C and 15N suggested a similar degree of microbial processing for the free/light and occluded fractions, and molecular structure of occluded and free/light fractions were also similar aside from charcoal enrichment in the occluded fraction. Results highlight the importance of both fire and aggregate formation to the long-term preservation of organics in western U.S. conifer forests which experience periodic burning, and suggest that the composition of occluded SOM in these soils is dependent on fire and the selective occlusion of charcoal.

Effect of applied force and blade speed on histopathology of bone during resection by sagittal saw

A sagittal saw is commonly used for resection of bone during joint replacement surgery. During sawing, heat is generated that can lead to an increase in temperature at the resected surface. The aim of this study was to determine the effect of applied thrust force and blade speed on generating heat. The effect of these factors and their interactions on cutting temperature and bone health were investigated with a full factorial Design of Experiments approach for two levels of thrust force, 15N and 30N, and for two levels of blade oscillation rate, 12,000 and 18,000 cycles per minute (cpm). In addition, a preliminary study was conducted to eliminate blade wear as a confounding factor. A custom sawing fixture was used to crosscut samples of fresh bovine cortical bone while temperature in the bone was measured by thermocouple (n=40), followed by measurements of the depth of thermal necrosis by histopathological analysis (n=200). An analysis of variance was used to determine the significance of the factor effects on necrotic depth as evidenced by empty lacunae. Both thrust force and blade speed demonstrated a statistically significant effect on the depth of osteonecrosis (p<0.05), while the interaction of thrust force with blade speed was not significant (p=0.22). The minimum necrotic depth observed was 0.50mm, corresponding to a higher level of force and blade speed (30N, 18,000cpm). Under these conditions, a maximum temperature of 93°C was measured at 0.3mm from the kerf. With a decrease in both thrust force and blade speed (15N, 12,000cpm), the temperature in the bone increased to 109°C, corresponding to a nearly 50% increase in depth of the necrotic zone to 0.74mm. A predictive equation for necrotic depth in terms of thrust force and blade speed was determined through regression analysis and validated by experiment. The histology results imply that an increase in applied thrust force is more effective in reducing the depth of thermal damage to surrounding bone than an increase in blade speed.

Breastfeeding and Weaning in Renaissance Italy: The Medici Children

Abstract Exploration of the Medici Chapels in the Basilica of San Lorenzo in Florence, Italy, revealed the burials of nine infantile members of the Medici family. Eight children were found in the intact tomb of the last Grand Duke GianGastone (1671-1737), and another child was exhumed from the Chapel of Grand Duke Ferdinando I (1549-1609). Skeletal ages ranged from newborn to 5 years, suggesting an identification with infantile members of the family. A paleonutritional study has been performed on the bone samples of all members of the Medici family exhumed so far. Carbon and nitrogen stable isotope analysis of bone collagen was used to detect the timing of the weaning process in this population. The (15)N values of the Medici children are significantly higher than those of adults, indicating that these infants were breastfed for a long time period. In particular, the levels of (15)N are high before the second year but decrease in older children, evidently after weaning, reaching the levels of adults. During the Renaissance, it was the common opinion that children should not be weaned before the second year of life. Archival documents suggest that the Medici children were never weaned before that age and, in most cases, even some months later. Combination of paleonutritional data and historical sources allowed reconstruction of the breastfeeding and weaning patterns of this aristocratic Renaissance class.

Tomato root transcriptome response to a nitrogen-enriched soil patch.

BackgroundNitrogen (N), the primary limiting factor for plant growth and yield in agriculture, has a patchy distribution in soils due to fertilizer application or decomposing organic matter. Studies in solution culture over-simplify the complex soil environment where microbial competition and spatial and temporal heterogeneity challenge roots' ability to acquire adequate amounts of nutrients required for plant growth. In this study, various ammonium treatments (as 15N) were applied to a discrete volume of soil containing tomato (Solanum lycopersicum) roots to simulate encounters with a localized enriched patch of soil. Transcriptome analysis was used to identify genes differentially expressed in roots 53 hrs after treatment.ResultsThe ammonium treatments resulted in significantly higher concentrations of both ammonium and nitrate in the patch soil. The plant roots and shoots exhibited increased levels of 15N over time, indicating a sustained response to the enriched environment. Root transcriptome analysis identified 585 genes differentially regulated 53 hrs after the treatments. Nitrogen metabolism and cell growth genes were induced by the high ammonium (65 μg NH4+-N g-1 soil), while stress response genes were repressed. The complex regulation of specific transporters following the ammonium pulse reflects a simultaneous and synergistic response to rapidly changing concentrations of both forms of inorganic N in the soil patch. Transcriptional analysis of the phosphate transporters demonstrates cross-talk between N and phosphate uptake pathways and suggests that roots increase phosphate uptake via the arbuscular mycorrhizal symbiosis in response to N.ConclusionThis work enhances our understanding of root function by providing a snapshot of the response of the tomato root transcriptome to a pulse of ammonium in a complex soil environment. This response includes an important role for the mycorrhizal symbiosis in the utilization of an N patch.