How to Make a Beetle Out of Wood: Multi-Elemental Stoichiometry of Wood Decay,Xylophagy and Fungivory

The majority of terrestrial biomass is wood, but the elemental composition of its potential consumers, xylophages, differs hugely from that of wood. This causes a severe nutritional imbalance. We studied the stoichiometric relationships of 11 elements (C, N, P, K, Ca, Mg, Fe, Zn, Mn, Cu, Na) in three species of pine-xylem-feeding insects, Stictoleptura rubra, Arhopalus rusticus (Coleoptera, Cerambycidae) and Chalcophora mariana (Coleoptera, Buprestidae), to elucidate their mechanisms of tissue growth and to match their life histories to their dietary constraints. These beetles do not differ from other Coleoptera in their absolute elemental compositions, which are approximately 1000 (N), 100 (P, Cu) and 50 (K, Na) times higher than in dead but undecayed pine wood. This discrepancy diminishes along the wood decay gradient, but the elemental concentrations remain higher by an order of magnitude in beetles than in highly decayed wood. Numerical simulation of the life history of S. rubra shows that feeding on nutrient-poor undecayed wood would extend its development time to implausible values, whereas feeding on highly decomposed wood (heavily infected with fungi) would barely balance its nutritional budget during the long development period of this species. The changes in stoichiometry indicate that the relative change in the nutrient levels in decaying wood cannot be attributed solely to carbon loss resulting from decomposer respiration: the action of fungi substantially enriches the decaying wood with nutritional elements imported from the outside of the system, making it a suitable food for wood-eating invertebrates.     

Use of Wishart Prior and Simple Extensions for Sparse Precision Matrix Estimation

A conjugate Wishart prior is used to present a simple and rapid procedure for computing the analytic posterior (mode and uncertainty) of the precision matrix elements of a Gaussian distribution. An interpretation of covariance estimates in terms of eigenvalues is presented, along with a simple decision-rule step to improve the performance of the estimation of sparse precision matrices and associated graphs. In this, elements of the estimated precision matrix that are zero or near zero can be detected and shrunk to zero. Simulated data sets are used to compare posterior estimation with decision-rule with two other Wishart-based approaches and with graphical lasso. Furthermore, an empirical Bayes procedure is used to select prior hyperparameters in high dimensional cases with extension to sparsity.     

Distribution of sulphate and iduronic acid residues in heparin and heparan sulphate

1. A method was developed for determination of the uronic acid composition of heparin-like glycosaminoglycans. Polymers or oligosaccharides are degraded to monosaccharides by a combination of acid hydrolysis and deamination with HNO₂. The resulting uronic acid monosaccharides (accounting for about 70% of the uronic acid contents of the starting materials) are isolated and converted into the corresponding aldono-1,4-lactones, which are separated by g.l.c. The calculated ratios of glucuronic acid/iduronic acid are reproducible within 5%. 2. Samples of heparin from pig intestinal mucosa (molar ratio of sulphate/disaccharide unit, 2.40) and heparan sulphate from human aorta (sulphate/disaccharide ratio, 0.46) were subjected to uronic acid analysis. l-Iduronic acid constituted 77% and 19% respectively of the total uronic acid contents. 3. The correlation between the contents of sulphate and iduronic acid indicated by this finding also applied to the fractionated deamination products of the two polymers. The sulphated fragments varied in size from disaccharide to octasaccharide (or larger) and showed sulphate/disaccharide molar ratios in the range of 0.05–2.0. The proportion of iduronic acid increased with increasing ester sulphate contents of the oligosaccharides. 4. Previous studies on the biosynthesis of heparin in a cell-free system have shown that l-iduronic acid residues are formed by C-5 epimerization of d-glucuronic acid units at the polymer level; the process requires concomitant sulphation of the polymer. The results obtained in the present structural study conform to these findings, and suggest further that similar mechanisms may operate in the biosynthesis of heparan sulphate. The epimerization reaction appears to be linked to the sulphation of hydroxyl groups but does not seem to require sulphation of the target uronic acid residues. The significance of sulphamino groups in relation to the formation of iduronic acid is unknown.     

Incidence of peptic ulcer disease in Gothenburg, 1985.

OBJECTIVE--To determine the incidence and age distribution of peptic ulcer disease in adults in Gothenburg. DESIGN--Retrospective study of patients with symptoms over one year. SETTING--All gastroenterology and x ray departments. PATIENTS--Any patient found to have an active ulcer crater during 1985. MAIN OUTCOME MEASURES--Sex, age, past history of gastrointestinal ulcers, and smoking habit. RESULTS--In 1985, 1402 peptic ulcers were diagnosed in 1137 adults. Over half (403; 54%) of the ulcers in men and 393 (60%) ulcers in women were in patients aged over 60. All types of ulcer showed increasing incidence with age. The sex ratio of patients aged 40-50 with peptic ulcers was 1:1. Nearly half (109; 48%) of ulcers diagnosed for the first time in men and 129 (57%) of such ulcers in women were in patients aged over 60. Elderly men and women were also more likely to develop haemorrhage. CONCLUSIONS--In Gothenburg there is a surprisingly high incidence of peptic ulcer disease, which increases considerably with age, possibly explained by the availability of modern diagnostic techniques as 1121 (80%) ulcers had been diagnosed by gastroscopy. Compared with earlier studies there was no difference in the incidence between men and women aged 40-50.     

Lead as an inductor of some morphological and functional changes in synaptosomes from rat brain

Summary 1. The effect of lead (in vivo) on the uptake of GABA, dopamine, and histidine as a precursor of histamine in synaptosomes obtained from chronically lead-treated rats was studied.2. Lead decreased the uptake of GABA, increased the uptake of dopamine, and did not change the uptake of histidine. These effects were independent of calcium concentration.3. Lead administration to the rat changed the morphology of the synaptosomes, as manifested in the decreased number of synaptic vesicles and disturbed mitochondrial structure.4. The results suggest the existence of several mechanisms of lead toxicity on uptake, related to individual neurotransmitters, which are not necessarily connected with a Pb²⁺/Ca²⁺ interaction.     

On the inducibility of nitrate transport by tobacco cells

The question as to whether the nitrate transport system is induced by nitrate was addressed using a cell suspension of the XD line of Nicotiana tabacum L. cv. Xanthi as an experimental system. The cells were grown on area as the sole nitrogen source, and tungstate was used to render nitrate reductase non-functional. To avoid shock due to vacuum filtration, the cells, were harvested by gravity filtration. Nitrate uptake by cells, which were harvested, transferred to fresh medium, and immediately exposed to nitrate (freshly harvested cells), displayed a lag period of about 3 h.
In cells which were given incubation periods in fresh medium before exposure to nitrate (preincubated cells), the lag period was considerably shortened. After 3 h of preincubation in the absence of nitrate (recovered cells), the lag period was almost completely eliminated. Cycloheximide inhibited nitrate uptake by recovered cells within minutes, and prevented the development of nitrate uptake in freshly harvested cells. Cycloheximide did not affect uptake of α-aminoisobutyric acid (AIB) within the first 2 h after its addition. Recovery of the membrane potential from a low value just after the harvest of the cells to a maximal value 3 h later, was observed using the lipophilic cation methyltriphenylphosphonium (MTPP⁺), supplied at low concentrations, as a probe. Depolarization of the membrane potential by MTPP⁺, at the millimolar range, caused a rapid inhibition of nitrate uptake by recovered cells. The results indicate that nitrate transport by the XD cells depends on the membrane potential and on protein components with short half life. In addition, it requires a continuous protein synthesis. The effects of physical manipulation on nitrate uptake are discussed.     

Reproductive collapse in European beech results from declining pollination efficiency in large trees

Climate warming increases tree mortality which will require sufficient reproduction to ensure population viability. However, the response of tree reproduction to climate change remains poorly understood. Warming can reduce synchrony and interannual variability of seed production (“masting breakdown”) which can increase seed predation and decrease pollination efficiency in trees. Here, using 40 years of observations of individual seed production in European beech (Fagus sylvatica), we showed that masting breakdown results in declining viable seed production over time, in contrast to the positive trend apparent in raw seed count data. Furthermore, tree size modulates the consequences of masting breakdown on viable seed production. While seed predation increased over time mainly in small trees, pollination efficiency disproportionately decreased in larger individuals. Consequently, fecundity declined over time across all size classes, but the overall effect was greatest in large trees. Our study showed that a fundamental biological relationship—correlation between tree size and viable seed production—has been reversed as the climate has warmed. That reversal has diverse consequences for forest dynamics; including for stand- and biogeographical-level dynamics of forest regeneration. The tree size effects suggest management options to increase forest resilience under changing climates.     

Correction or transfer of immunodeficiency due to TNF-LT alpha deletion by bone marrow transplantation.

BACKGROUND: Mice with inactivated tumor necrosis factor (TNF) and lymphotoxin alpha (LT alpha) genes have profound abnormalities of the immune system including lymphocytosis, lack of lymph nodes, undifferentiated spleen, hypoimmunoglobulinaemia, and defective Ig class switch. Here, we asked whether this phenotype is due to incompetent lymphohemopoietic progenitors or to a defective environment. MATERIALS AND METHODS: Lethally irradiated TNF-LT alpha-deficient and wild-type mice received bone marrow cells from either TNF-LT alpha-deficient or wild-type mice. The reconstitution and transfer of the phenotype was followed by morphological and functional analyses. RESULTS: Bone marrow cells from wild-type mice restored the synthesis of TNF and LT alpha, corrected the splenic microarchitecture, normalized the lymphocyte counts in the circulation, and repopulated the lamina propria with IgA-producing plasma cells of TNF-LT alpha-deficient mice. Furthermore, the formation of germinal centers in the spleen and the defective Ig class switch in response to a T-cell dependent antigen was corrected, while no lymph nodes were formed. Conversely, the TNF-LT alpha phenotype could be transferred to wild-type mice by bone marrow transplantation after lethal irradiation. CONCLUSIONS: These data demonstrate that most TNF- and LT alpha-producing cells are bone marrow derived and radiosensitive, and that the immunodeficiency due to TNF-LT alpha deletion can be corrected to a large extent by normal bone marrow cell transplantation. The genotype of the donor bone marrow cells determines the functional and structural phenotype of the TNF-LT alpha-deficient adult murine host, with the exception of lymph node formation. These findings may have therapeutic implications for the restoration of genetically defined immunodeficiencies in humans.