Amounts and degradability of dissolved organic carbon from foliar litter at different decomposition stages

Litter is one of the main sources of dissolved organic carbon (DOC) in forest soils and litter decomposition is an important control of carbon storage and DOC dynamics. The aim of our study was to evaluate (i) effects of tree species on DOC production and (ii) relationships between litter decomposition and the amount and quality of DOC. Five different types of leaves and needles were exposed in litterbags at two neighboring forest sites. Within 12 months we sampled the litterbags five times and leached aliquots of field moist litter in the laboratory. In the collected litter percolates we measured DOC concentrations and recorded UV and fluorescence spectra in order to estimate the aromaticity and complexity of the organic molecules. Furthermore, we investigated the biodegradability of DOC from fresh and decomposed litter during 6 weeks incubations. Fresh sycamore maple litter released the largest amounts of DOC reaching about 6.2% of litter C after applying precipitation of 94 mm. We leached 3.9, 1.6, 1.0 and 3.3% carbon from fresh mountain ash, beech, spruce and pine litter, respectively. In the initial phase of litter decomposition significantly decreasing DOC amounts were released with increasing litter mass loss. However, after mass loss exceeds 20% DOC production from needle litter tended to increase. UV and fluorescence spectra of percolates from pine and spruce litter indicated an increasing degree of aromaticity and complexity with increasing mass loss as often described for decomposing litter. However, for deciduous litter the relationship was less obvious. We assume that during litter decomposition the source of produced DOC in coniferous litter tended toward a larger contribution from lignin-derived compounds. Biodegradability of DOC from fresh litter was very high, ranging from 30 to 95% mineralized C. DOC from degraded litter was on average 34% less mineralizable than DOC from fresh litter. Taking into account the large DOC production from decomposed needles we can assume there is an important role for DOC in the accumulation of organic matter in soils during litter decomposition particularly in coniferous forests.     

Spatial changes of soil solution and mineral composition in the rhizosphere of Norway‐spruce seedlings colonized by Piloderma croceum

Ectomycorrhizae (ECM) or the root‐fungal association in forest ecosystems provide a unique soil microenvironment where soil properties and processes differ from the bulk soil. In this study, we would like to better understand the role of ECM systems in mineral weathering and its implications to soil formation and nutrient cycling in forest ecosystems. Specifically, we would like to document the spatial variations in the composition of soil solution and mineralogy of the rhizosphere as influenced by the ECM of Norway spruce + Piloderma croceum. Two‐month‐old seedlings of Norway spruce (control and colonized by P. croceum) were cultivated in special rhizotrons designed to allow spatial collection of soil solution. We used A and C horizons of a Dystric Cambisol collected from Höglwald forest near Munich. Micro suction cups (5 mm x 1mm) were installed in colonized and control rhizotrons, and soil solution was collected from September to November 2000. Our results show that the concentrations of NH , Ca²⁺, and Mg²⁺ in the soil solution were lower in <1.0 cm than in >3.0 cm distance from the roots of Norway spruce, due to the possible range of influence of Piloderma mycelium reaching about 2–3 cm from the surface of the mycorrhizal root. In the rhizotron with soil from the A horizon, a higher phosphorus content in Piloderma‐colonized seedlings was observed. X‐ray diffraction data indicate that chlorite and possibly mica are being transformed to 2:1‐expanding clay minerals (probably smectite) within <1.0 cm distance from roots. The spatial variations in soil solution composition and mineral transformation are likely to be due to Piloderma colonization and concentrated mycelial growth within <1.0 cm distance from the roots. This is also evident in more intricate growth of mycelia on surfaces of micaceous minerals as compared to quartz. We assume that Piloderma modifies soil solution and mineralogy through acquisition of essential elements for its own survival and/or for the uptake by plant roots. However, the presence of spontaneous infection with wildtype ECM in the control plots may have altered the influence of Piloderma and must be taken into consideration when interpreting our results.     

Synthesis and insect growth regulating activity of thiosemicarbazones of methyl 2-pyridyl ketones

Thirty-six thiosemicarbazones of methyl 2-pyridyl ketone and of some other methyl ketones were tested on Dysdercus cingulatus, Drosophila melanogaster, Locusta migratoria, Aedes aegypti, Tenebrio molitor and Musca domestica. Several derivatives were toxic, delaying or preventing ecdysis. The structure-activity relationship is discussed. The mode of action of these compounds appears to be different from that of juvenile hormones, anti-juvenile hormones, or chitin biosynthesis inhibitors.     

The change of acute phase protein haptoglobin in cattle during spontaneous labor and Caesarean section with or without torsio uteri intrapartum

The change of haptoglobin concentration in cattle with dystocia after torsio uteri which lead to Caesarean section is regarded in contrast to haptoglobin concentrations in cattle at parturitions with undisturbed puerperium and Caesarean section without torsio uteri intra partum. Animals with natural parturition had low haptoglobin concentrations with slight changes, for a slightly increased haptoglobin concentration was seen as physiologic. Also surgical treatment such as Caesarean section did not result in changes of haptoglobin concentration. Thus, the curve of animal patients with anomalies concerning position or with a too large fetus (relatively or absolutly) was nearly identical to the curve of animals with regular parturitions over the first four days after surgery. Not before the fifth day after surgery, a moderate increase of haptoglobin could be observed. Animals with dystocia after torsio uteri intra partum showed significantly higher haptoglobin concentrations in contrast to controls over the time of investigation. The correlation of haptoglobin concentrations in animal patients with torsio uteri bin concentration shortly after surgery an additionally significant increase of haptoglobin concentration could be observed in later fertile cattles but not in later infertile cattle with torsio uteri. In two cows with torsio uteri and ovariohysterectomy haptoglobin concentrations decreased rapidly. Haptoglobin concentration may serve as an indicator for the degree of impairment of the uterus during a parturition as well as a predictor for regenerative potential.     

Emergence of Salmonella epidemics: the problems related to Salmonella enterica serotype Enteritidis and multiple antibiotic resistance in other major serotypes

Two major changes in the epidemiology of salmonellosis occurred in the second half of the 20th century: the emergence of food-borne human infections caused by S. Enteritidis and by multiple-antibiotic resistant strains of Salmonella. This review updates information on the S. Enteritidis pandemic and focuses on the emergence of Salmonella, carrying the SGI1 antibiotic resistance gene cluster, resistant to extended-spectrum cephalosporins, or resistant to fluoroquinolones. The factors responsible for the emergence of these Salmonella strains could be either of human origin or related to bacterial genome evolution. However, our increasing understanding of the molecular fluidity of the genome shows that any attempt to counteract bacteria results in further bacterial evolution or adaptation of other bacteria to take place in the new free ecological niche. In these conditions, we can ask who is faster: humans who want to eliminate bacterial pathogens or bacteria that continuously evolve to gain new niches.     

The in vitro developmental competence of oocytes from juvenile calves is related to follicular diameter

This study investigated the relationship between follicle size (FS) and developmental competence of calf oocytes. Cumulus-oocyte-complexes (COCs) from follicles>8 (L-COCs; n=19), 4-8 (M-COCs; n=54), and 2-3 mm (S-COCs; n=155) were recovered from non-stimulated 1-4 months old dairy calves post mortem and ex vivo (laparoscopy), and in parallel from slaughtered adult cows from follicles of identical size categories [>8 (n=91); 4-8 (n=138); 2-3 mm (n=193)]. Morphologically intact COCs were subjected to in vitro maturation, fertilization, and embryo culture. Cleavage rate (CR; 46 h post-insemination=p.i.), rate of morulae/blastocysts (M/Bl; day 7 p.i.), and blastocysts (Bl; day 9 p.i.) were recorded. FS had no effect on the CR in calves. However, calf L-COCs yielded the highest rates of M/Bl and Bl compared with the two other size categories (P<0.05). In contrast, calf S- and M-COCs gave similar rates of M/Bl, whereas the proportion of Bl was lowest for S-COCs (P<0.05). This was almost identical to findings in cows, except that the CR was highest for L-COCs and M/Bl yields were lowest for S-COCs (P<0.05). There were no differences between calf and cows with regard to CR for the respective FS categories. L-COCs from calves and cows yielded similar rates of M/Bl and Bl, whereas calf S- and M-COCs yielded lower rates of Bl than S- and M-COCs from cows and a lower rate of M/Bl when S-and M-COCs were analyzed as one group (P<0.05). Whereas the CR was similar in calves and cows, calf COCs yielded lower rates of M/Bl and Bl (P<0.05). In conclusion, the results show that the developmental competence of calf oocytes is higher in those derived from follicles larger than 8 mm, and thus are almost equally as competent as cow oocytes derived from follicles of identical size. This suggests that calf oocytes acquire developmental competence within the large follicle, potentially due to a process similar to prematuration of the oocyte in the adult cow. It is proposed that procedures that facilitate prematuration, such as "coasting" following a preceding superstimulation, might increase the developmental competence of calf oocytes.     

Plasma haptoglobin concentration in cattle with surgically corrected torsio uteri intrapartum

In 26 cows with surgically corrected torsio uteri intra partum, severity of disease, wound healing and secondary diseases were correlated with plasma haptoglobin concentration. The objective of the investigation was to determine, if an increased plasma haptoglobin concentration indicates the severity of disease respectively expected wound healing disorders or secondary diseases. The degree of severity of disease was determined by rectally diagnosed elasticity of the uterus before the surgery. In the present investigation, the severity of a uterine torsion intra partum could not be evaluated by determining the plasma haptoglobin concentration. In 9 of 11 days of investigation there was no significant difference in the plasma haptoglobin concentration of animals with an elastic uterus (animals with good prognosis) in contrast to cows with tight uterus (patients with poor prognosis) found. The significant differences on the 6th and 7th day post surgery are related to secondary diseases in patients with poor prognosis, which develop evidently earlier and form stronger. The correlation of all cows with--to those without secondary illnesses shows, that 10 days post surgery patients with secondary diseases have a significant higher plasma haptoglobin concentration (p < 0.05) compared to animals without secondary illnesses. No correlations existed between plasma haptoglobin concentration and wound healing in the examined cattle. A postoperatively increase of haptoglobin indicates a higher risk of secondary illnesses and complications.     

Immune response to Rhodococcus equi ATCC 33701-secreted proteins in mice and identification of immunogenic recombinant proteins by dot-blotting

Rhodococcus equi remains a significant pathogen, causing severe pneumonia in foals. The development of vaccines and serologic diagnosis could be greatly facilitated by studying the humoral immune response to this equine pathogen. In this study, a crude extract of R. equi ATCC 33701-secreted proteins combined with the Montanide® ISA70 adjuvant was found to be highly immunogenic in mice with the highest titer of 99,000 on day 42 after the first subcutaneous immunization. This immune response was dependent on the quantity of proteins injected and the presence of adjuvant. By dot-blotting, eight recombinant secreted proteins were identified to react strongly with sera from immunized mice. Of these eight proteins, four were detected as immunogenic only when administered in conjunction with adjuvant. This screening strategy led to the identification of promising new candidates for vaccine development.     

Citric acid extraction—An underestimated method in forest nutrition?

Since recent studies reveal citric acid to be favorable for estimating plant‐available P in soils, we investigated if it can also be used for assessing other nutrients. According to our results, it provides stronger correlations with the tree nutrition for Mg (beech, spruce), Ca+K (beech) and Fe (spruce) than the standard methods for determining exchangeable cations. Thus, when estimating plant‐available P by citric acid‐extraction, these cations should be additionally measured in ICP analysis.     

Improved RP‐HPLC and anion‐exchange chromatography methods for the determination of amino acids and carbohydrates in soil solutions

In spite of their low concentrations in soil solutions, low–molecular weight organic substances (LMWOS) such as amino acids, sugars, and uronic acids play a major role in the cycles of C and N in soil. With respect to their low concentrations and to possible matrix interferences, their analysis in soil leachates is a challenging task. We established two HPLC (high‐performance liquid chromatography) methods for the parallel determination of amino acids and carbohydrates in soil leachates. The pre‐column derivatization of amino acids with an o‐phthaldialdehyde (OPA) mercaptoethanol solution yields quantitation limits between 0.03 and 0.44 µmol L^–1 and S_D values of <8.3% (n = 9). High‐performance anion‐exchange chromatography (HPAEC) on a Dionex CarboPac PA 20 column with a NaOH acetate gradient combined with pulsed amperometric detection (PAD) was used for the determination of carbohydrates. The calibration curves obtained for 11 carbohydrates showed excellent linearity over the concentration range from 0.02 to 50.0 mg L^–1. Recovery studies revealed good results for all analytes (89%–108%). Interferences from Hg(II) salts and chloroform used for stabilization of the leachates did not occur with both chromatographic methods. The optimized method was successfully used for quantitative determinations of amino acids and carbohydrates in soil leachates.