Comparison of two lignin-degrading fungi:Phlebia radiata andPhanerochaete chrysosporium

Summary The ligninolytic enzymes ofPhlebia radiata were produced in static conditions earlier developed forPhanerochaete chrysosporium. The production pattern of lignin peroxidases resembled that ofP. chrysosporium. The extracellular proteins ofPhlebia radiata were separated by isoelectric focusing. Four proteins with acidic isoelectric points (4.15) were detected by peroxidase staining. The peroxidases ofP. radiata reacted with antibodies produced against a peroxidase ofPhanerochaete chrysosporium and vice versa. Thus the lignin peroxidases of the two fungi have major similarities despite slight differences in their isoelectric points and molecular weights. Veratryl alcohol was produced by both fungi and degraded to veratraldehyde, two lactones and a quinone by the ligninolytic cultures.     

Purification and properties of an aryl-alcohol dehydrogenase from the white-rot fungus Phanerochaete chrysosporium

An intracellular aryl-alcohol dehydrogenase (previously referred to as aryl-aldehyde reductase) was purified from the white-rot fungus Phanerochaete chrysosporium. The enzyme reduced veratraldehyde to veratryl alcohol using NADPH as a cofactor. Other aromatic benzaldehydes were also reduced, but not aromatic ketones. Methoxy-substituted rings were better substrates than hydroxylated ones. The enzyme was also able to reduce a dimeric aldehyde (4-benzyloxy-3-methoxybenzaldehyde). The highest reduction rate was measured when 3,5-dimethoxybenzaldehyde was used as a substrate. On SDS/PAGE the purified enzyme showed one major band with a molecular mass of 47 kDa, whereas gel filtration suggested a molecular mass of 280 kDa. Polyclonal antibodies raised against the gel purified 47-kDa protein were able to immunoprecipitate the aryl-alcohol dehydrogenase indicating that its activity possibly resides entirely in this protein fragment. The pI of the enzyme was 5.2 and it was most active at pH 6.1. The aryl-alcohol dehydrogenase was partially inhibited by typical oxidoreductase inhibitors.     

Potassium permeability of fetal rat pancreatic islets: abnormal sensitivity to glucose.

Potassium channels of fetal rat islets have been recently reported to be inadequately regulated by stimulation with glucose when compared to islets of adult rats. Though in patch clamp experiments the properties of their KATP-channels were shown to be comparable to those from adult rats, until now no closure could be demonstrated with the technique measuring the 86Rb+ efflux. Using this technique, in the presence of a basal (3 mM) glucose concentration the 86Rb+ efflux was completely insensitive to a stimulation with glucose (5.6 mM) or tolbutamide. In contrast, in islets perifused in the absence of glucose the introduction of a low glucose concentration (3 mM) or stimulation with tolbutamide alone inhibited the 86Rb+ efflux, confirming the presence of functioning KATP-channels. The absolute value of the 86Rb+ efflux rate in the absence of glucose was, however, much lower in fetal rat islets as normally observed in adult rat islets. Apart from this, the ATP content of fetal rat islets remained unchanged at either glucose concentration tested. It is suggested that in islets of fetal rats a K+ permeability is present and can be inhibited by glucose and tolbutamide but in contrast to islets of adult rats the K+ efflux is already maximally inhibited in the presence of 3 mM glucose. This may be one reason why pancreatic islets of fetal rats do not respond to glucose-stimulation with an adequate calcium uptake and insulin release.     

Can tree-ring δ<Superscript>15</Superscript>N be used as a proxy for foliar δ<Superscript>15</Superscript>N in European beech and Norway spruce?

Key message

For long-term environmental investigations, tree-ring δ ¹⁵ N values are inappropriate proxies for foliar δ ¹⁵ N for both Fagus sylvatica and Picea abies under moderate N loads.

Abstract

Currently it is unclear whether stable nitrogen isotope signals of tree-rings are related to those in foliage, and whether they can be used to infer tree responses to environmental changes. We studied foliar and tree-ring nitrogen (δ¹⁵N) and carbon (δ¹³C) isotope ratios in European beech (Fagus sylvatica L.) and Norway spruce (Picea abies L.) from six long-term forest monitoring sites in Switzerland together with data on N deposition and soil N availability, as well as a drought response index over the last two decades. For both species, tree-ring δ¹⁵N and δ¹³C values were less negative compared to foliar δ¹⁵N and δ¹³C values, most likely due to recycling and reallocation of N within the tree and fractionation processes associated with the transport of sucrose and the formation of tree-rings, respectively. Temporal trends recorded in foliar δ¹⁵N were not reflected in tree-ring δ¹⁵N, with much higher variations in tree-rings compared to foliage. Soil N availability and N deposition were partially able to explain changes in foliar δ¹³C, while there were no significant correlations between environmental variables and either tree-ring or foliar δ¹⁵N. Our results suggest an uncoupling between the N isotopic composition of tree-rings and foliage. Consequently, tree-ring δ¹⁵N values are inappropriate proxies of foliar δ¹⁵N values under low-to-moderate N deposition loads. Furthermore, at such low levels of deposition, tree-ring δ¹⁵N values are not recommended as archives of tree responses to soil C/N or bulk N deposition.

     

B cell-deficient (mu MT) mice have alterations in the cytokine microenvironment of the gut-associated lymphoid tissue (GALT) and a defect in the low dose mechanism of oral tolerance

Peripheral immune tolerance following i.v. administration of Ag has been shown to occur in the absence of B cells. Because different mechanisms have been identified for i.v. vs low dose oral tolerance and B cells are a predominant component of the gut-associated lymphoid tissue (GALT) they may play a role in tolerance induction following oral Ag. To examine the role of B cells in oral tolerance we fed low doses of OVA or myelin oligodendrocyte glycoprotein to B cell-deficient ( microMT) and wild-type C57BL/6 mice. Results showed that the GALT of naive wild-type and microMT mice was characterized by major differences in the cytokine microenvironment. Feeding low doses of 0.5 mg OVA or 250 microg myelin oligodendrocyte glycoprotein resulted in up-regulation of IL-4, IL-10, and TGF-beta in the GALT of wild-type but not microMT mice. Upon stimulation of popliteal node cells, in vitro induction of regulatory cytokines TGF-beta and IL-10 was observed in wild-type but not microMT mice. Greater protection against experimental autoimmune encephalomyelitis was found in wild-type mice. Oral tolerance in microMT and wild-type mice was found to proceed by different mechanisms. Anergy was observed from 0.5 mg to 250 ng in microMT mice but not in wild-type mice. Increased Ag was detected in the lymph of microMT mice. No cytokine-mediated suppression was found following lower doses from 100 ng to 500 pg in either group. These results demonstrate the importance of the B cell for the induction of cytokine-mediated suppression associated with low doses of Ag.     

Use of oxytocin and cloprostenol to facilitate semen collection by electroejaculation or transrectal massage in bulls

Two experiments were conducted with 24 bulls in which semen collection was attempted by transrectal massage (RM) and electroejaculation (EE). In experiment 1, bulls received the following treatments on successive semen collection days: saline 10 min prior to electroejaculation (control); saline 10 min prior to 2 min of transrectal massage followed by electroejaculation; cloprostenol (CLO) 10 min prior to 2 min of transrectal massage followed by electroejaculation; oxytocin (OXY) 10 min prior to 2 min of transrectal massage followed by electroejaculation. Transrectal massage consisted of general, back and forth motion over the ampullae, prostate and urethra with a flattened hand.

In experiment 2, bulls received saline (control), oxytocin, or cloprostenol 10 min before attempting semen collection by transrectal massage. Massage was applied specifically to the ampullae for a maximum of 5 min or until a semen sample was obtained. Electroejaculation was attempted in all bulls following transrectal massage.

In experiment 1, semen was obtained in <1% of bulls by transrectal massage. However, by using an improved massage technique in experiment 2, semen was obtained in 97.2% of attempts. Semen was obtained in 96.9 and 98.9% of attempts by electroejaculation in experiments 1 and 2, respectively.

Oxytocin treatment increased the time to penile protrusion during electroejaculation in experiment 1 and during massage in experiment 2. In experiment 1, oxytocin decreased the time to semen emission and tended to decrease the number of electroejaculation stimuli to semen emission. Cloprostenol treatment, in experiment 1, resulted in an increased number of electroejaculation stimuli to penile protrusion, but did not affect the number of stimuli required for semen emission.

Massage of the ampullae prior to electroejaculation reduced both the time to semen emission and the number of electroejaculation stimuli required for semen emission. Transrectal massage of the ampullae was very effective in this experiment for producing semen emission, but quantity of semen samples was less than for electroejaculation. The usefulness of transrectal massage for semen collection in breeding soundness evaluations needs to be investigated further under field conditions.     

Tree mineral nutrition is deteriorating in Europe

The response of forest ecosystems to increased atmospheric CO₂ is constrained by nutrient availability. It is thus crucial to account for nutrient limitation when studying the forest response to climate change. The objectives of this study were to describe the nutritional status of the main European tree species, to identify growth‐limiting nutrients and to assess changes in tree nutrition during the past two decades. We analysed the foliar nutrition data collected during 1992–2009 on the intensive forest monitoring plots of the ICP Forests programme. Of the 22 significant temporal trends that were observed in foliar nutrient concentrations, 20 were decreasing and two were increasing. Some of these trends were alarming, among which the foliar P concentration in F. sylvatica, Q. Petraea and P. sylvestris that significantly deteriorated during 1992–2009. In Q. Petraea and P. sylvestris, the decrease in foliar P concentration was more pronounced on plots with low foliar P status, meaning that trees with latent P deficiency could become deficient in the near future. Increased tree productivity, possibly resulting from high N deposition and from the global increase in atmospheric CO₂, has led to higher nutrient demand by trees. As the soil nutrient supply was not always sufficient to meet the demands of faster growing trees, this could partly explain the deterioration of tree mineral nutrition. The results suggest that when evaluating forest carbon storage capacity and when planning to reduce CO₂ emissions by increasing use of wood biomass for bioenergy, it is crucial that nutrient limitations for forest growth are considered.