Biliopancreatic diversion with duodenal switch

In 1990 Scopinaro's technique of biliopancreatic diversion with distal gastrectomy (DG) and gastroileostomy was modified. A sleeve gastrectomy with duodenal switch (DS) was used instead of the distal gastrectomy; and the length of the common channel was made 100 cm instead of 50 cm. A questionnaire and a prescription for blood work were sent to 252 patients who underwent DG a mean 8.3 years ago (range 6-13 years) and 465 patients who underwent DS 4.1 years ago (range 1.7-6.0 years). The questionnaire response rate was 93%, and laboratory work was completed for 65% of both groups. The mean weight loss after DG was 37 +/- 21 kg and after DS 46 +/- 20 kg. There were fewer side effects after DS: The number of daily stools was lower (p < 0.0002), as was the prevalence of diarrhea (p < 0.01), vomiting (p < 0.001), and bone pain (p < 0.001). Greater benefits related to several aspects of life were reported after DS than DG (p < 0.0001). The mean serum levels of ferritin, calcium, and vitamin A were higher (p < 0.001), and parathyroid hormone was lower. The yearly revision rate for excessive malabsorption was 1.7% per year after DG and 0.1% per year after DS. The two procedures were equally efficient for treating co-morbid conditions such as diabetes, hypertension, and hypercholesterolemia. Biliopancreatic diversion with sleeve gastrectomy/duodenal switch and a 100-cm common limb was shown to produce greater weight loss with fewer side effects.

Liver pathology and the metabolic syndrome X in severe obesity

The metabolic syndrome X, characterized by insulin resistance, dyslipidemia, hypertension, and a male, visceral distribution of adipose tissue, is associated with increased morbidity and mortality from several prevalent diseases, such as diabetes, cancers, myocardial infarction, and stroke. Because the liver has a central role in carbohydrate, lipid, and steroid metabolism, we investigated the relationships between liver pathology and the metabolic syndrome. Blood chemistry, anthropometry (waist/hip circumference ratio), and intraoperative routine knife biopsies of the liver were obtained in 551 (112 men) severely obese patients (body mass index, 47 +/- 9; mean +/- SD) undergoing antiobesity surgery. Steatosis was found in 86%, fibrosis in 74%, mild inflammation or steatohepatitis in 24%, and unexpected cirrhosis in 2% (n = 11) of the patients. The risk of steatosis was 2.6 times greater in men than in women (P < 0.0001). With each addition of 1 of the 4 components of the metabolic syndrome, elevated waist/hip ratio, impaired glucose tolerance, hypertension, and dyslipidemia, the risk of steatosis increased exponentially from 1- to 99-fold (P < 0.001). Fibrosis correlated with steatosis (r = 0.56; P < 0.0001), whereas patients with diabetes or impaired glucose tolerance had a 7-fold increased risk of fibrosis (P < 0.0001). Diabetes, steatosis, and age were all significant indicators of cirrhosis, whereas inflammation was only associated with age. We conclude that the metabolic syndrome via impaired glucose tolerance is strongly correlated with steatosis, fibrosis, and cirrhosis of the liver.

Prevalence, clinical characteristics, and risk factors for insomnia in the context of breast cancer

STUDY OBJECTIVES

To estimate the prevalence of insomnia, describe clinical characteristics of sleep difficulties, assess the influence of cancer on the insomnia course, and identify potential risk factors involved in the development of insomnia among women who had received radiotherapy for non metastatic breast cancer.

DESIGN

A sample of 300 consecutive women who had been treated with radiotherapy for non metastatic breast cancer first completed an insomnia screening questionnaire. Participants who reported sleep difficulties were subsequently interviewed over the phone to evaluate further the nature, severity, duration, and course of their insomnia.

SETTING

N/A.

PATIENTS OR PARTICIPANTS

N/A.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Nineteen percent (n=56) of the participants met diagnostic criteria for an insomnia syndrome. In most cases (95%), insomnia was chronic. The onset of insomnia followed the breast cancer diagnosis in 33% of the patients and 58% of the patients reported that cancer either caused or aggravated their sleep difficulties. Factors associated with an increased risk for insomnia were sick leave, unemployment, widowhood, lumpectomy, chemotherapy, and a less severe cancer stage at diagnosis. Among women with insomnia symptoms, the risk to meet diagnostic criteria for an insomnia syndrome was higher in those who were separated and had a university degree.

CONCLUSIONS

Insomnia is a prevalent and often chronic problem in breast cancer patients. Although it is not always a direct consequence of cancer, pre-existing sleep difficulties are often aggravated by cancer. It is therefore important to better screen breast cancer patients with insomnia and offer them an appropriate treatment.

Mycorrhizal networks: a review of their extent, function, and importance

It is well known from laboratory studies that a single mycorrhizal fungal isolate can colonize different plant species, form interplant linkages, and provide a conduit for interplant transfer of isotopic carbon, nitrogen, phosphorus, or water. There is increasing laboratory and field evidence that the magnitude and direction of transfer is influenced by physiological source–sink gradients between plants. There is also evidence that mycorrhizal fungi play a role in regulating transfer through their own source–sink patterns, frequency of links, and mycorrhizal dependency. Although it is plausible that connections are extensive in nature, field studies have been hampered by our inability to observe them in situ and by belowground complexity. In future, isotopic tracers, morphological observations, microsatellite techniques, and fluorescent dyes will be useful in the study of networks in nature. Mycorrhizal networks have the potential to influence patterns of seedling establishment, interplant competition, plant diversity, and plant community dynamics, but studies in this area are just beginning. Future plant community studies would benefit from concurrent experimental use of fungal network controls, isotopic labeling, direct observation of interplant linkages, and long-term observation in the field. In this paper, we review recent literature on mycorrhizal networks and interplant carbon transfer, suggest future research directions, and highlight promising scientific approaches.Key words: common mycorrhizal network, carbon transfer, source–sink, establishment, competition, diversity.

Effects of maternal surgical weight loss in mothers on intergenerational transmission of obesity

BACKGROUND AND OBJECTIVES

By studying cardiometabolic risk factors in children born after maternal biliopancreatic diversion bariatric surgery (AMS) compared with those in children born before maternal surgery (BMS), we tested the hypothesis that significant maternal weight loss may modify obesity-related factors transmitted via the intrauterine environment.

DESIGN

Anthropometry and fasting blood levels were studied in 49 mothers who had lost 36 +/- 1.8% body weight sustained for 12 +/- 0.8 yr and their 111 children (54 BMS and 57 AMS) aged 2.5-26 yr.

RESULTS

AMS children had lower birth weight (2.9 +/- 0.1 AMS vs. 3.3 +/- 0.1 kg BMS, P = 0.003) associated with a reduced prevalence of macrosomia (1.8 AMS vs. 14.8% BMS, P = 0.03) with no difference in underweight. At the time of follow-up, AMS children exhibited 3-fold lower prevalence of severe obesity (11 vs. 35%, P = 0.004), greater insulin sensitivity (homeostasis model assessment of insulin resistance index 3.4 +/- 0.3 vs. 4.8 +/- 0.5, P = 0.02), improved lipid profile (cholesterol/high-density lipoprotein cholesterol 2.96 +/- 0.11 vs 3.40 +/- 0.18, P = 0.03; high-density lipoprotein cholesterol 1.50 +/- 0.05 vs. 1.35 +/- 0.05 mmol/liter, P = 0.04), lower C-reactive protein (0.88 +/- 0.17 vs. 2.00 +/- 0.34 microg/ml, P = 0.004), and leptin (11.5 +/- 1.5 vs.19.7 +/- 2.5 ng/ml, P = 0.005) and increased ghrelin (1.28 +/- 0.06 vs.1.03 +/- 0.06 ng/ml, P = 0.005) than BMS offspring (AMS vs. BMS, respectively, for all).

CONCLUSIONS

This unique study of children aged 2.5-26 yr born before and after maternal antiobesity surgery demonstrated improvements in cardiometabolic markers sustained into adolescence, attributable to an improved intrauterine environment.

Biliopancreatic Diversion with a New Type of Gastrectomy

In an attempt to improve the results of biliopancreatic diversion in the treatment of morbid obesity, two aspects of the procedure performed at Laval Hospital were modified to reduce adverse physiological consequences. The distal gastrectomy was replaced by a parietal gastrectomy which preserves vagal continuity along with the lesser curvature, and leaves intact the antro-pyloroduodenal pump. The duodenum was stapled shut and nutrients were diverted through a duodeno-ileal anastomosis. The biliopancreatic diverting intestinal limb was anastomosed to the nutrient ileal limb 100 cm proximal to the ileocaecal valve instead of 50 cm proximal to it, thus doubling the length of the common ileal absorptive segment. Weight loss after either operation was greater than 70% of initial excess weight. Following the new operation, there was a lesser prevalence of side-effects, especially loose stools and malodorous gas, a lesser degree of hypocalcemia and no hypoalbuminemia. The duodenum recanalized at the staple line in 20% of the patients who had the new operation. When data from these patients were excluded, weight loss following the new operation was greater than that seen after the old one. The prevalence of side-effects and the degree of calcium and protein malabsorption remained significantly lower. Weight loss remained satisfactory with a common limb measuring 100 cm. The parietal gastrectomy was not restrictive as shown by the failure to lose further weight when the duodenal stapled diversion failed. Weight loss was thus mainly a function of biliopancreatic diversion, but increased weight loss in the new procedure despite a doubling of the common ileal limb suggests that parietal gastrectomy contributed to weight loss. Because duodenal recanalization can be corrected surgically and now prevented, the modified biliopancreatic bypass is preferred.

Mycorrhizal networks: des liaisons dangereuses?

Mycorrhizal associations, by which most land plants receive mineral nutrition, are diffuse and often non-specific. A common mycorrhizal network is formed when fungal mycelia colonize and link together the roots of two or more plants, sometimes of different species. Here, we discuss recent work showing how, under realistic ecological conditions, such networks can affect the physiology and ecology of plants by facilitating interplant nutrient exchange, acting as inoculum reservoirs for seedlings and altering plant competitive abilities. Although mechanisms for their evolutionary emergence remain unclear, investigating mycorrhizal networks profoundly modifies our understanding of plant communities.

Ectomycorrhizal fungal succession in mixed temperate forests

Ectomycorrhizal (ECM) fungal communities of Douglas-fir (Pseudotsuga menziesii) and paper birch (Betula papyrifera) were studied along a chronosequence of forest development after stand-replacing disturbance. Previous studies of ECM succession did not use molecular techniques for fungal identification or lacked replication, and none examined different host species. Four age classes of mixed forests were sampled: 5-, 26-, 65-, and 100-yr-old, including wildfire-origin stands from all four classes and stands of clearcut origin from the youngest two classes. Morphotyping and DNA sequences were used to identify fungi on ECM root tips. ECM fungal diversities were lower in 5-yr-old than in older stands on Douglas-fir, but were similar among age classes on paper birch. Host-specific fungi dominated in 5-yr-old stands, but host generalists were dominant in the oldest two age classes. ECM fungal community compositions were similar in 65- and 100-yr-old stands but differed among all other pairs of age classes. Within the age range studied, site-level ECM fungal diversity reached a plateau by the 26-yr-old age class, while community composition stabilized by the 65-yr-old class. Simple categories such as 'early stage', 'multi stage', and 'late stage' were insufficient to describe fungal species' successional patterns. Rather, ECM fungal succession may be best described in the context of stand development.

Liver pathology and the metabolic syndrome X in severe obesity

The metabolic syndrome X, characterized by insulin resistance, dyslipidemia, hypertension, and a male, visceral distribution of adipose tissue, is associated with increased morbidity and mortality from several prevalent diseases, such as diabetes, cancers, myocardial infarction, and stroke. Because the liver has a central role in carbohydrate, lipid, and steroid metabolism, we investigated the relationships between liver pathology and the metabolic syndrome. Blood chemistry, anthropometry (waist/hip circumference ratio), and intraoperative routine knife biopsies of the liver were obtained in 551 (112 men) severely obese patients (body mass index, 47 +/- 9; mean +/- SD) undergoing antiobesity surgery. Steatosis was found in 86%, fibrosis in 74%, mild inflammation or steatohepatitis in 24%, and unexpected cirrhosis in 2% (n = 11) of the patients. The risk of steatosis was 2.6 times greater in men than in women (P < 0.0001). With each addition of 1 of the 4 components of the metabolic syndrome, elevated waist/hip ratio, impaired glucose tolerance, hypertension, and dyslipidemia, the risk of steatosis increased exponentially from 1- to 99-fold (P < 0.001). Fibrosis correlated with steatosis (r = 0.56; P < 0.0001), whereas patients with diabetes or impaired glucose tolerance had a 7-fold increased risk of fibrosis (P < 0.0001). Diabetes, steatosis, and age were all significant indicators of cirrhosis, whereas inflammation was only associated with age. We conclude that the metabolic syndrome via impaired glucose tolerance is strongly correlated with steatosis, fibrosis, and cirrhosis of the liver.

Architecture of the wood-wide web: Rhizopogon spp. genets link multiple Douglas-fir cohorts

*The role of mycorrhizal networks in forest dynamics is poorly understood because of the elusiveness of their spatial structure. We mapped the belowground distribution of the fungi Rhizopogon vesiculosus and Rhizopogon vinicolor and interior Douglas-fir trees (Pseudotsuga menziesii var. glauca) to determine the architecture of a mycorrhizal network in a multi-aged old-growth forest. *Rhizopogon spp. mycorrhizas were collected within a 30 x 30 m plot. Trees and fungal genets were identified using multi-locus microsatellite DNA analysis. Tree genotypes from mycorrhizas were matched to reference trees aboveground. Two trees were considered linked if they shared the same fungal genet(s). *The two Rhizopogon species each formed 13-14 genets, each colonizing up to 19 trees in the plot. Rhizopogon vesiculosus genets were larger, occurred at greater depths, and linked more trees than genets of R. vinicolor. Multiple tree cohorts were linked, with young saplings established within the mycorrhizal network of Douglas-fir veterans. A strong positive relationship was found between tree size and connectivity, resulting in a scale-free network architecture with small-world properties. *This mycorrhizal network architecture suggests an efficient and robust network, where large trees play a foundational role in facilitating conspecific regeneration and stabilizing the ecosystem.

Inter-plant communication through mycorrhizal networks mediates complex adaptive behaviour in plant communities

Adaptive behaviour of plants, including rapid changes in physiology, gene regulation and defence response, can be altered when linked to neighbouring plants by a mycorrhizal network (MN). Mechanisms underlying the behavioural changes include mycorrhizal fungal colonization by the MN or interplant communication via transfer of nutrients, defence signals or allelochemicals. We focus this review on our new findings in ectomycorrhizal ecosystems, and also review recent advances in arbuscular mycorrhizal systems. We have found that the behavioural changes in ectomycorrhizal plants depend on environmental cues, the identity of the plant neighbour and the characteristics of the MN. The hierarchical integration of this phenomenon with other biological networks at broader scales in forest ecosystems, and the consequences we have observed when it is interrupted, indicate that underground 'tree talk' is a foundational process in the complex adaptive nature of forest ecosystems.

Autotaxin interacts with lipoprotein(a) and oxidized phospholipids in predicting the risk of calcific aortic valve stenosis in patients with coronary artery disease

BACKGROUND

Studies have shown that lipoprotein(a) [Lp(a)], an important carrier of oxidized phospholipids, is causally related to calcific aortic valve stenosis (CAVS). Recently, we found that Lp(a) mediates the development of CAVS through autotaxin (ATX).

OBJECTIVE

To determine the predictive value of circulating ATX mass and activity for CAVS.

METHODS

We performed a case-control study in 300 patients with coronary artery disease (CAD). Patients with CAVS plus CAD (cases, n = 150) were age- and gender-matched (1 : 1) to patients with CAD without aortic valve disease (controls, n = 150). ATX mass and enzymatic activity and levels of Lp(a) and oxidized phospholipids on apolipoprotein B-100 (OxPL-apoB) were determined in fasting plasma samples.

RESULTS

Compared to patients with CAD alone, ATX mass (P < 0.0001), ATX activity (P = 0.05), Lp(a) (P = 0.003) and OxPL-apoB (P < 0.0001) levels were elevated in those with CAVS. After adjustment, we found that ATX mass (OR 1.06, 95% CI 1.03-1.10 per 10 ng mL^-1 , P = 0.001) and ATX activity (OR 1.57, 95% CI 1.14-2.17 per 10 RFU min^-1 , P = 0.005) were independently associated with CAVS. ATX activity interacted with Lp(a) (P = 0.004) and OxPL-apoB (P = 0.001) on CAVS risk. After adjustment, compared to patients with low ATX activity (dichotomized at the median value) and low Lp(a) (<50 mg dL^-1 ) or OxPL-apoB (<2.02 nmol L^-1 , median) levels (referent), patients with both higher ATX activity (≥84 RFU min^-1 ) and Lp(a) (≥50 mg dL^-1 ) (OR 3.46, 95% CI 1.40-8.58, P = 0.007) or OxPL-apoB (≥2.02 nmol L^-1 , median) (OR 5.48, 95% CI 2.45-12.27, P < 0.0001) had an elevated risk of CAVS.

CONCLUSION

Autotaxin is a novel and independent predictor of CAVS in patients with CAD.

Biological profiles in subjects with recurrent acute coronary events compared with subjects with long-standing stable angina

BACKGROUND

At one end of the clinical spectrum of coronary artery disease (CAD) are subjects who have had repeated acute ischemic events, and at the other end are those with long-standing angina who have never been unstable. This study tests the hypothesis that a specific biological profile can distinguish these 2 extreme groups and predict acute coronary events.

METHODS AND RESULTS

Blood levels of lipoprotein(a), homocysteine, tissue plasminogen activator, plasminogen activator inhibitor-1, C-reactive protein (CRP), fibrinogen, and von Willebrand factor were compared in 3 groups of 50 subjects each: (1) those with previous multiple acute coronary events, (2) age-matched subjects with >/=3 years of stable angina and no prior acute coronary events, and (3) matched controls without evidence of atherosclerotic disease and a normal coronary angiogram. All subjects were followed for 4.0 years. Lipoprotein(a), homocysteine, tissue plasminogen activator, and plasminogen activator inhibitor-1 were similar in both CAD groups and significantly higher than in the control group. However, compared with subjects with long-standing stable angina, those with previous multiple coronary events had higher values of CRP (5.7+/-5.4 versus 3.0+/-5.2 mg/L, P=0.012), fibrinogen (3.38+/-0.75 versus 2.92+/-0.64 g/L, P=0.001), and von Willebrand factor (1.60+/-0.55 versus 1.25+/-0.36 U/mL, P=0.0003). On follow-up, myocardial infarction and unstable angina occurred in 42% of the group with multiple events, 4% of the stable angina group (P<0.0001), and none of the control subjects. In the 100 patients with CAD, CRP was 4.9 mg/L in those with and 1.8 mg/L in those without new instability (P<0.0001). In a multivariate analysis, only CRP distinguished those with follow-up acute coronary events (adjusted odds ratio 5.9, 95% CI 2.0 to 17.9; P=0.002). A baseline CRP >3.5 mg/L had a relative risk of 7.6 (2.6 to 21.7, P=0.0002) for subsequent acute events.

CONCLUSIONS

An inflammatory biological profile distinguished patients with previous multiple acute coronary events from those with long-standing stable angina and predicted acute coronary instability.

MycoDB, a global database of plant response to mycorrhizal fungi

Plants form belowground associations with mycorrhizal fungi in one of the most common symbioses on Earth. However, few large-scale generalizations exist for the structure and function of mycorrhizal symbioses, as the nature of this relationship varies from mutualistic to parasitic and is largely context-dependent. We announce the public release of MycoDB, a database of 4,010 studies (from 438 unique publications) to aid in multi-factor meta-analyses elucidating the ecological and evolutionary context in which mycorrhizal fungi alter plant productivity. Over 10 years with nearly 80 collaborators, we compiled data on the response of plant biomass to mycorrhizal fungal inoculation, including meta-analysis metrics and 24 additional explanatory variables that describe the biotic and abiotic context of each study. We also include phylogenetic trees for all plants and fungi in the database. To our knowledge, MycoDB is the largest ecological meta-analysis database. We aim to share these data to highlight significant gaps in mycorrhizal research and encourage synthesis to explore the ecological and evolutionary generalities that govern mycorrhizal functioning in ecosystems.

Access to mycorrhizal networks and roots of trees: importance for seedling survival and resource transfer

Mycorrhizal networks (MNs) are fungal hyphae that connect roots of at least two plants. It has been suggested that these networks are ecologically relevant because they may facilitate interplant resource transfer and improve regeneration dynamics. This study investigated the effects of MNs on seedling survival, growth and physiological responses, interplant resource (carbon and nitrogen) transfer, and ectomycorrhizal (EM) fungal colonization of seedlings by trees in dry interior Douglas-fir (Pseudotsuga menziesii var. glauca) forests. On a large, recently harvested site that retained some older trees, we established 160 isolated plots containing pairs of older Douglas-fir "donor" trees and either manually sown seed or planted Douglas-fir "receiver" seedlings. Seed- and greenhouse-grown seedlings were sown and planted into four mesh treatments that served to restrict MN access (i.e., planted into mesh bags with 0.5-, 35-, 250-microm pores, or without mesh). Older trees were pulse labeled with carbon (13CO2) and nitrogen (15NH4(15)NO3) to quantify resource transfer. After two years, seedlings grown from seed in the field had the greatest survival and received the greatest amounts of transferred carbon (0.0063% of donor photo-assimilates) and nitrogen (0.0018%) where they were grown without mesh; however, planted seedlings were not affected by access to tree roots and hyphae. Size of "donor" trees was inversely related to the amount of carbon transferred to seedlings. The potential for MNs to form was high (based on high similarity of EM communities between hosts), and MN-mediated colonization appeared only to be important for seedlings grown from seed in the field. These results demonstrate that MNs and mycorrhizal roots of trees may be ecologically important for natural regeneration in dry forests, but it is still uncertain whether resource transfer is an important mechanism underlying seedling establishment.

Effects of clearcut logging and tree species composition on the diversity and community composition of epigeous fruit bodies formed by ectomycorrhizal fungi

The objective of this study was to examine the effects of stand age and tree species composition on the abundance, diversity, and community composition of epigeous fruit bodies formed by ectomycorrhizal (ECM) fungi in the Interior Cedar Hemlock zone of British Columbia. Fruit bodies were collected and identified in May, June, August, September, and October of 1996, 1997, 1998, and 1999 from transects located in new (5 year old) plantations and mature (75–125 year old) wild forests composed of relatively pure Betula papyrifera Marsh. (paper birch), relatively pure Pseudotsuga menziesii var. glauca (Beissn.) Franco (interior Douglas-fir), and mixtures of the two tree species. A total of 187 fungal taxa were collected during the study, of which 185 occurred in mature forests and only 17 occurred in the plantations. Thirty-four taxa were unique to mature predominantly birch forests, 35 were unique to mature predominantly Douglas-fir forests, 17 were unique to mixed mature forests, and 68 taxa were found in all three mature forest types. The abundance of fruit bodies in mature forests varied widely among sampling years and generally increased with annual precipitation. ECM species richness differed between stand ages but not among forest compositions in both plantations and mature forests. Lactarius glyciosmus , Hygrophorus eburneus var. eburneus , and Cortinarius armillatus were more abundant in mature birch than mature Douglas-fir forests. Lactarius torminosus , Leccinum scabrum var. scabrum , and Rozites caperatus were also found predominantly in mature birch and mixed forests, whereas Gomphidius subroseus was more abundant in Douglas-fir forests than in birch and mixed mature forests. Russula brevipes was also found predominantly in mature Douglas-fir and mixed forests. Our results indicate that clearcutting has a profound effect on abundance and composition of ECM fruit bodies, and that changes in forest tree species composition may lead to shifts in ECM fungal community composition.

Decline of ectomycorrhizal fungi following a mountain pine beetle epidemic

Forest die-off caused by mountain pine beetle (MPB; Dendroctonus ponderosa) is rapidly transforming western North American landscapes. The rapid and widespread death of lodgepole pine (Pinus contorta) will likely have cascading effects on biodiversity. One group particularly prone to such declines associated with MPB are ectomycorrhizal fungi, symbiotic organisms that can depend on pine for their survival, and are critical for stand regeneration. We evaluated the indirect effects of MPB on above- (community composition of epigeous sporocarps) and belowground (hyphal abundance) occurrences of ectomycorrhizal fungi across 11 forest stands. Along a gradient of mortality (0-82% pine killed), macromycete community composition changed; this shift was driven by a decrease in the species richness of ectomycorrhizal fungi. Both the proportion of species that were ectomycorrhizal and hyphal length in the soil declined with increased MPB-caused pine mortality; < 10% of sporocarp species were ectomycorrhizal in stands with high pine mortality compared with > 70% in stands without MPB attacks. The rapid range expansion of a native insect results not only in the widespread mortality of an ecologically and economically important pine species, but the effect of MPB may also be exacerbated by the concomitant decline of fungi crucial for recovery of these forests.

Transfer of 13 C between paired Douglas-fir seedlings reveals plant kinship effects and uptake of exudates by ectomycorrhizas

Processes governing the fixation, partitioning, and mineralization of carbon in soils are under increasing scrutiny as we develop a more comprehensive understanding of global carbon cycling. Here we examined fixation by Douglas-fir seedlings and transfer to associated ectomycorrhizal fungi, soil microbes, and full-sibling or nonsibling neighbouring seedlings. Stable isotope probing with 99% ¹³ C-CO₂ was applied to trace ¹³ C-labelled photosynthate throughout plants, fungi, and soil microbes in an experiment designed to assess the effect of relatedness on ¹³ C transfer between plant pairs. The fixation and transfer of the ¹³ C label to plant, fungal, and soil microbial tissue was examined in biomass and phospholipid fatty acids. After a 6 d chase period, c. 26.8% of the ¹³ C remaining in the system was translocated below ground. Enrichment was proportionally greatest in ectomycorrhizal biomass. The presence of mesh barriers (0.5 or 35 μm) between seedlings did not restrict ¹³ C transfer. Fungi were the primary recipients of ¹³ C-labelled photosynthate throughout the system, representing 60-70% of total ¹³ C-enriched phospholipids. Full-sibling pairs exhibited significantly greater ¹³ C transfer to recipient roots in two of four Douglas-fir families, representing three- and fourfold increases (+ c. 4 μg excess ¹³ C) compared with nonsibling pairs. The existence of a root/mycorrhizal exudation-hyphal uptake pathway was supported.