Effect of nitrogen fertilization and irrigation on soil microbial activities and population dynamics — a field study

In a field experiment, net nitrogen (N) mineralization and immobilization were studied in relation to: 1) population dynamics and activities of N-metabolizing soil microbial communities, 2) changes in substrate-induced respiration (SIR) and 3) potential urease acitvity. Nitrogen fertilization (80 kg NO₃-N ha^-1) without irrigation induced additional N mineralization up to 280 kg N ha^-1. Net N-mineralization was weakly correlated to cell numbers of ammonifying and NH₄⁺-oxidizing microorganisms. Potential urease activity, respiration activity, and substrate-induced respiration activity were not correlated with the amount of mineralized nitrogen. Irrigation significantly increased potential urease activity of the soil microflora. Substrate induced respiration activity and basal respiration activity of the soil microflora were highest in the unfertilized and non irrigated treatment. But greatest differences were detected between the two sampling dates. NO₂^--oxidizing and ammonifying microbial populations increased, while populations of NH₄⁺-oxidizing and denitrifying microorganisms decreased with time. The results of this study demonstrate the interaction of nitrogen fertilizer application and irrigation on population dynamics of N-transforming soil microorganisms and microbial activities under field conditions. Detailed microbiological investigations of this type improve our understanding of nitrogen transformations in soil and suggest possible reasons of nitrogen losses, so that N fertilizer can be used more effectively and N losses be reduced.     

IMAGING DIAGNOSIS–SCLEROSING ENCAPSULATING PERITONITIS IN A DOG

An approximately 5‐month‐old American Staffordshire terrier was presented with a history of recurrent peritoneal effusion. Abdominal radiographs and ultrasound showed a loculated effusion in the ventral abdomen with dorsal displacement of abdominal organs, hepatomegaly and rounding of liver and splenic margins. Computed tomography demonstrated centrally located gastrointestinal segments surrounded by a thin soft tissue band and a thickened peritoneal lining. At necropsy a fibrous membrane continuous with liver and splenic capsules encapsulated all abdominal organs. Microscopically the abdominal wall and fibrous capsule consisted of an irregular thick layer of hypocellular connective tissue. The final diagnosis was sclerosing encapsulating peritonitis.     

Site-specific formation of Maillard, oxidation, and condensation products from whey proteins during reaction with lactose

Heat treatment of dairy products leads to structural changes of proteins, which can severely decrease the nutritional value [Mauron, J. J. Nutr. Sci. Vitaminol. (Tokyo) 1990, 36 (Suppl. 1), S57-69]. In this study, model solutions of the two main whey proteins, alpha-lactalbumin and beta-lactoglobulin, respectively, were incubated with lactose, and modifications were monitored by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Lactulosyl residues were the most abundant modifications of alpha-lactalbumin and beta-lactoglobulin. Up to four of these adducts were identified on the proteins. Enzymatical digest with endoproteinase AspN prior to mass spectrometric analysis allowed the detection of further modifications and their localization in the amino acid sequence. Most prominent modifications were lactulosyllysine, Nepsilon-carboxymethyllysine, oxidation of lysine to aminoadipic semialdehyde, oxidation of methionine to methionine sulfoxide, cyclization of N-terminal glutamic acid to a pyrrolidone, and oxidation of cysteine or tryptophan. The presence of methionine oxidation was deduced from a control protein that had been oxidized by hydrogen peroxide. These studies establish MALDI-TOF-MS as a reliable tool to monitor chemical modifications of nutritional proteins during food processing.     

Wood characteristics of Podocarpus oleifolius var. macrostachyus (Parl.) Buchholz and Gray native to Costa Rica: their significance for wood utilization

Due to over-exploitation in the past, native conifer species in many tropical countries are hardly available anymore for wood utilization. In the last decades Costa Rica has undertaken considerable efforts to study the silvicultural characteristics of the native species of the family Podocarpaceae, in particular Podocarpus oleifolius var. macrostachyus (Parl.) Buchholz and Gray, in order to evaluate its suitability for cultivation in mixed plantations with preference for native species. However, sufficient information on the structural, chemical and physical characteristics of the wood of this species are not available. This investigation reports on selected wood characteristics of old-growth trees from the Cordillera de Talamanca (approximately 2,700 m a.s.l.), Costa Rica. Tracheids occupy 93% of total volume; average tracheid length is 4 mm, wall thickness ranges 2.5–4.5 (–6.5) μm throughout the annual increment. Lignin content is between 33.6 and 34.7% excluding any lignin-like compounds. Cellular UV microspectrophotometry reveals that the compound middle lamella (CML) and S2 layer are characterized by a higher absorbance than is commonly observed in e.g. Pinaceae, and with a distinct gradient from S1 to S3. The carbohydrate (cellulose and hemicelluloses) composition reflects the typical proportions as found in other conifers. A low content of organic extractives explains the only moderate (white rot) to low (brown rot) natural durability of the heartwood against wood destroying fungi. The wood density (12% mc) ranges 0.5–0.68 g cm^-3; compression strength (44±2.38 MPa) and corresponding modulus of elasticity (8,600±1,720 MPa) indicate good elastomechanical properties. Accordingly, the wood is recommended for multiple indoor enduses. For exterior applications, effective protective measures and/or preservative treatment are required. Dedicated to Prof. Dr. Dr. h.c. mult. Walter Liese on the occasion of his 80th birthday     

GnRH‐agonist deslorelin implant alters the progesterone release pattern during early pregnancy in gilts

The aim of this study was to investigate the relationship of progesterone (P) and luteinizing hormone (LH) during recognition and establishment of pregnancy in the gilt. Therefore, the effects of eliminating episodic LH pulses on P patterns were determined during early pregnancy. To this end, a slow‐release GnRH implant deslorelin was used for GnRH down‐regulation. A group of gilts (GnRHa, n = 8) was implanted with the GnRH‐agonist on Day 11 of pregnancy, while a control group (C, n = 5) was treated with a non‐impregnated placebo implant. Blood was collected via a vena cava caudalis catheter at 10‐min intervals for 8 hr on Day 16 and 21 of pregnancy. As expected, the GnRH implant reduced LH secretion (p < 0.01) and abolished LH pulses completely at Day 16 and Day 21 of pregnancy. On Day 16, there was no difference in P levels between the treatments. However, on Day 21, the GnRH‐agonist treatment led to significantly increased P concentrations (p < 0.01) compared with the control gilts. Progesterone was secreted in a pulsatile manner in both treatment groups and no relationship between LH pulsatility and P pulsatility was observed. In conclusion, abolishment of LH pulsatility did not affect the pulsatile pattern of P secretion but led to an unexpected overall increase in P on Day 21 of pregnancy; this effect was delayed and occurred 10 days after commencing treatment with the GnRH depot agonist. The elevation of P on Day 21 of pregnancy in the GnRHa group suggests either a reduced negative feedback effect or an increased autocrine response by the corpora lutea.