Characterization of d-Glucose Transport across Equine Jejunal Brush Border Membrane Using the Pig as an Efficient Model of Jejunal Glucose Uptake

To test the hypotheses that glucose transport capacity across the brush border membrane (BBM) of the large colon is lower than that of the small intestine in equids, and that small intestinal transport capacity in equids is lower than suids. d-glucose transport capacity (V_max) and affinity (K_M) across the BBM of the distal jejunum (DJ) and proximal large colon (PLC) of the pony and pig were measured. Mucosa was collected from the DJ and PLC of ponies (n = 4) and pigs (n = 3), flash-frozen in liquid nitrogen, and stored at −80°C. Jejunal and colonic BBM vesicles were manufactured, and d-glucose transport was determined. There was no detectable active uptake of glucose in the equine PLC. Compared with the pig DJ, d-glucose transport capacity was lower (2595 ± 331 vs. 655 ± 286 ρmol·mg protein⁻¹·s⁻¹, respectively, P < .01) and transport affinity tended to be lower (0.09 ± 0.07 vs. 0.27 ± 0.06 mM, respectively, P = .11) in the pony DJ. Compared with the pig DJ, d-glucose transport capacity (2,595 ± 331 vs. 571 ± 331 ρmol·mg protein⁻¹·s⁻¹, respectively, P < .001) and transport affinity (0.09 ± 0.07 vs. 0.54 ± 0.07 mM, respectively, P < .001) in the pig PLC were lower. Results show there is negligible d-glucose uptake across pony PLC, and capacity for d-glucose absorption across DJ BBM is fourfold lower in the pony compared with the pig. Results further exemplify, at a physiological level, the limited capacity of the equid small intestine to transport glucose relative to an omnivorous mammal, and the likely evolutionary adaptation of equids to low dietary levels of nonstructural carbohydrates.     

Assignment testing reveals multiple introduced source populations including potential ash hybrids (Fraxinus excelsior × F. angustifolia) in Ireland

Large-scale reforestation programmes are a major source of unwarranted gene flow and can have profound consequences on local genetic diversity. Recently, ash has been introduced to Ireland from continental Europe to stock plantations but has often exhibited poor stem form. It was not known whether these trees were Fraxinus excelsior, Fraxinus angustifolia or interspecific hybrids that are known to occur in continental Europe. F. excelsior is the only native ash in Ireland, so the introduced populations represent a potential threat for the genetic diversity of native populations. We characterized the introduced trees within two plantations (Clonee and Kildalkey) using morphological characters and six microsatellite markers. Samples from continental Europe were included for comparison. Plantations exhibited higher genetic diversity than control populations because our data suggest they contain a mixture of several provenances. There was a small but significant differentiation between plantations and control populations (Ф_CT = 0.0211). Bayesian analysis to infer population structure and to assign introduced individuals to reference populations clearly demonstrated the presence of hybrid individuals within the plantations. The percentage of trees detected with potential hybrid origin ranged from 28 to 58 % depending on the plantation and the threshold data analysis level chosen. Most hybrids could be considered cryptic because there was a lack of intermediate morphology for hybrid individuals that mainly clustered with F. excelsior. The results indicated that the source of material at the two plantation sites differed. Management options to minimize the impact of these introduced populations are discussed.     

Radial distribution of carbohydrate reserves in the trunk of declining European beech trees (Fagus sylvatica L.)

Context

European beech (Fagus sylvatica L.) is considered threatened by anticipated climate change, but the physiological causes of potential beech decline or mortality remains poorly understood.

Aims

The purpose of the present study was to fuel debate about the assumption that carbohydrate depletion is involved in the decline of mature European beech.

Methods

The health status of beech trees from a severely declining stand was visually assessed by examining their crown condition. Content and radial distribution of non-structural carbohydrates (starch and soluble carbohydrate) were analyzed in the trunks and compared to those reported earlier in trunks of healthy beech trees.

Results and discussion

The distribution of carbohydrate in the beech trunks recorded here seemed affected by decline. We found a stronger radial decrease of starch content than those reported earlier for healthy beech trees. Carbohydrate reserves appear partially maintained in the outermost rings while starch depletion occurred in older wood rings in declining trees that may be able to mobilize carbohydrate reserves from older wood rings in response to successive climatic constraints.     

One dominant gene conferring the resistance to the leafminer, Liriomyza trifolii(Burgess) Diptera: Agromyzidae in melon (Cucumis melo L.)

The line Nantais Oblong, a melon of Charentais type, was shown to be a source of resistance by antibiosis to the leafminer, Liriomyza trifolii (Burgess), Diptera, Agromyzidae. We studied the genetic control of this resistance in F2 and back-cross progenies from the cross between Nantais Oblong and Védrantais, a Charentais line susceptible to the leafminer. Tests were carried out on young plants in plastic cages with controlled infestation. Complete mortality of the L. trifolii larvae was used as indicator of plant resistance. Segregation ratios were consistent with monogenic dominant control of the resistance. The symbol Lt for Liriomyza trifolii resistance is proposed.     

Preliminary investigations of the physiological adjustments associated with compensatory growth in juvenile brook charr (Salvelinus fontinalis)

Various physiological factors suspected to govern or be influenced by growth or feed intake of brook charr (80–120 g) were examined under long and short fasting periods during the year. A control (fed to satiation) was included. During winter, fasting (14 and 28 days) followed by refeeding led to a complete compensation. In summer, longer fasting (39 and 61 days) was applied to exacerbate the physiological response. Compensatory growth was observed in the restricted groups, and overall, adjustments/variations in growth and physiological indicators (feed conversion ratio, organosomatic index, enzymatic activities [CS, TRY, CHY]) were more pronounced. Degree of compensation reached was positively related to the deprivation duration. The summer experiment clearly suggests that compensatory growth takes place in two stages after a long starvation period (61 days): (1) restoration of the digestive system (PSI) followed by enzyme activities (trypsin and chymotrypsin) and (2) rebuilding of somatic tissues.     

Studies on the diagnosis of hop stunt viroid in fruit trees: Identification of new hosts and application of a nucleic acid extraction procedure based on non-organic solvents

A non-radioactive digoxigenin-labelled RNA probe specific for hop stunt viroid (HSVd) diagnosis has been developed. The high sensitivity and specificity of this RNA probe in dot blot hybridizations to nucleic acids from field samples, allowed the confirmation of the presence of HSVd in apricot (Prunus armeniaca L.) and its detection in two fruit tree species not previously described as hosts of this pathogen, almond (Prunus dulcis Miller) and pomegranate (Punica granatum L.). This result supports and extends the notion of the world wide distribution of HSVd, infecting cultivated fruit trees. HSVd was also found to accumulate to much higher levels in mature apricot fruits than in leaves. Additionally, a sample processing procedure which does not involve the use of organic solvents was demonstrated to render faithful results when used for viroid detection. The combined reliability and facility of use of both this extraction procedure and the non-radioactive probe will benefit agronomic investigations addressing the detection and eradication of HSVd. Other applications of the work described here, as the study of possible causal relations between specific disorders and HSVd infection, are also discussed.     

Evolutionary discrimination of mammalian conserved non-genic sequences (CNGs)

Analysis of the human and mouse genomes identified an abundance of conserved non-genic sequences (CNGs). The significance and evolutionary depth of their conservation remain unanswered. We have quantified levels and patterns of conservation of 191 CNGs of human chromosome 21 in 14 mammalian species. We found that CNGs are significantly more conserved than protein-coding genes and noncoding RNAS (ncRNAs) within the mammalian class from primates to monotremes to marsupials. The pattern of substitutions in CNGs differed from that seen in protein-coding and ncRNA genes and resembled that of protein-binding regions. About 0.3% to 1% of the human genome corresponds to a previously unknown class of extremely constrained CNGs shared among mammals.     

Modeling carbon stock dynamics under fallow and cocoa agroforest systems in the shifting agricultural landscape of Central Cameroon

With increasing concerns raised by climate change, understanding biological processes within cocoa (Theobroma cacao L.) agroforest (CAF) and fallow systems is a prerequisite for developing actions related to emission reduction in the shifting agricultural landscape of Cameroon. Carbon (C) stocks and accretion were assessed and modeled in various C components (large trees, small trees, dead wood, litter, roots, soil, and total C) of fallow and CAF systems along a 50-year chronosequence. Several functions were empirically fitted to a time series of C stocks. Large tree, soil, and total C stocks were best described by a logistic growth function while that for small trees by a rational quadratic function. The best-fitted functions explained 72–96 % of C stock accumulation over time. Two metrics describing C stock accretion were derived from these functions: the point of maximum C growth and the C growth coefficient (GC). The rate of maximum growth of total C stock was reached after 12–13 years in both fallow and CAF, with maximum GCs of 6.9 and 6.3 Mg C ha^?1 year^?1, respectively. Over the 50-year period, the GCs of total C stocks varied between 0.2 and 6.9 Mg C ha^?1 year^?1, with quick accumulation within the first decade that then slowed until it levelled off after 45 years. Over a period of about 30 years, both systems sequestered a total of ~200 Mg C ha^?1. This indicates that cocoa agroforests, a main source of income for local populations, can also provide significant climate change mitigation services.     

Discrepancies between the isolation of Salmonella from mesenteric lymph nodes and the results of serological screening in slaughter pigs

Most Salmonella control programmes are based on serological testing in the slaughterhouse. However, from a point of view of carcass contamination, it is rather the presence of Salmonella spp. in the animal at the time of slaughter that is important. The aim of this cross-sectional study was to investigate the possible discrepancies between the isolation of Salmonella spp. in the mesenteric lymph nodes and the results of serological screening. In total, 1821 fattening pigs originating from 60 Belgian farrow-to-finish herds were sampled in the slaughterhouse. The serum samples were analysed using an indirect mix-ELISA for the presence of Salmonella antibodies and evaluated at 3 cut-off values namely 10, 20, and 40% Optical Density (OD). All mesenteric lymph node samples were submitted to qualitative Salmonella isolation and a representative number of isolates was serotyped. From each herd, 30 animals were screened both serologically and bacteriologically and the herd was considered as positive when at least one sample was positive. At the herd level, 83.6% (cut-off OD 40%) to 100.0% (cut-off OD 10%) of the herds from which Salmonella had been isolated were evaluated as seropositive. At the individual level, only 34.5% (cut-off OD 40%) to 82.8% (cut-off OD 10%) of the animals from which Salmonella had been isolated were seropositive. Overall, a weak agreement was found between bacteriology and serology for Salmonella diagnosis. If pig herds are categorised using serological tests in the slaughterhouse, one should be aware of the fact that slaughter pigs can still harbour Salmonella spp. in the mesenteric lymph nodes, without being detected in serological tests. The cut-off value used to evaluate a sample as serologically positive and the number of samples per herd are of major importance to classify herds correctly in order to protect human health.