Die Rolle der mikrobiellen Biomasse und des mineralisch fixierten Ammoniums bei den Stickstoff-Transformationen in niedersächsischen Löß-Ackerböden unter Winter-Weizen. I. Poolgrößenveränderungen

Significance of microbial biomass and non-exchangeable ammonium with respect to the nitrogen transformations in loess soils of Niedersachsen during the growing season of winter wheat. I. Change of pool sizes Nitrogen transformations in loess soils have been examined by laboratory and field experiments. After straw application (· 8 t · ha^?1), N in microbial biomass (N_mic) increased by about 20 mg · kg^?1 soil (· 90 kg N · ha^?1 · 30 cm^?1) after 9 days of incubation (20 °C). Another laboratory experiment yielded an increase of about 400 mg of NH₄+-N · kg^?1 fixed by minerals within 1 h after addition of 1 M NH₄+-acetate. Defixation of the recently fixed NH₄+ after addition of 1 M KCl amounted to only 60 mg · kg^?1 within 50 days. In a field experiment with winter wheat 1991, an increase in N_mic of about 80 kg N · ha^?1 · 30 cm^?1 was observed from March to June. After July, growth of the microbes was limited by decreased soluble carbon concentrations in the rhizosphere. Different levels of mineral N-fertilizer (0, 177 and 213 kg N · ha^?1) did not affect significantly the microbial biomass. The same field experiment yielded a decrease of non-exchangeable ammonium on the “zero”-fertilized plot in spring by 200 kg N · ha^?1 · 30 cm^?1. The pool of fixed ammonium increased significantly after harvest. After conventional mineral N-fertilizer application (213 kg N · ha^?1). NH₄+-defixation was only about 120 kg N · ha^?1 · 30 cm^?1 until July.     

Untersuchungen über die mögliche Beeinflussung der Zwischenkalbezeit bei Rindern der Rasse "Deutsche Schwarzbunte"

Die Dauer der biologischen Rastzeit ist eine variable Grβe und wird von ver-schiedenen endogenen und exogenen Faktoren beeinfluβt. Eine Rastzeit unter 60 Ta-gen ist nur bei einem kleinen Prozentsatz der Tiere als biologisch anzusehen. Eine indi-viduelle durchschnittliche Zwischenkalbezeit von 341 bis 360 Tagen ist in der Landes-zucht trotz frühzeitiger Besamung post partum nur bei einem relativ kleinen Prozentsatz zu erreichen (16,5 %). Eine individuelle durchschnittliche Zwischenkalbezeit von 361 Bis 380 Tagen dürfte als Ausdruck guter Fruchtbarkeit bei den heutigen Fütte-rungs- und Haltungsbedingungen zu werten sein. Bei einer individuellen durchschnitt-lichen Zwischenkalbezeit von 381 bis 400 Tagen liegt der Verdacht vor, daβ Fütte-rungs- und Haltungsfehler sowie Geburts- und Puerperalstörungen die Ursache der ver-langerten Zwischenkalbezeit sind. Bei Kühen mit einer sehr hohen Milchleistung kann diese Zwischenkalbezeit noch als vertretbar angesehen werden. Tiere mit einer individuellen durchschnittlichen Zwischenkalbezeit von über 400 Tagen sind im allgemeinen ats Minusvarianten hinsichtlich Fruchtbarkeit einzustufen. Dies gilt allerdings nicht für Tiere mit einer weit über dem Herdendurchschnitt liegenden Milchleistung. Eine Ver-kurzung der individuellen durchschnittlichen Zwischenkalbezeit erscheint möglich durch: Verbesserung von Fütterung und Haltung; gutes Management; Fruchtbarkeits-uberwachung; Verbesserung der Geburtshygiene; tierärztliche Überwachung von Puer-perium und Gustreit; Prophylaxe und rechtzeitige Behandlung diagnostizierter Erkran-kungen .     

In vitro generation of mature neutrophils from canine Lin- bone marrow cells

The major goal of this work was to describe the in vitro generation of mature functional neutrophils derived from a canine enriched haematopoietic progenitor cell population. We have utilised lineage depletion by immunomagnetic selection to isolate a canine haematopoietic progenitor cell population. The physical, immunological, metabolical and morphological methodologies employed in this study have permitted us to isolate and define a cell population enriched in Rh-123low and CD34+ cells. Irradiated pre-established long-term bone marrow cultures (LTBMC) were utilised to determine the self-renewal ability of lineage negative (Lin-) cells, as well as their capacity to differentiate into mature functional neutrophils. The authors demonstrate for the first time that canine neutrophils derived from Lin- cells are able to produce oxyradicals, express a specific neutrophil surface antigen, and contain gelatinase granules. These characteristics enable them to migrate through basement membranes to act as a first line defence mechanism. The fact that these cells are able to differentiate into functional mature cells, and give rise to long-term culture-initiating cells (LTC-IC) after 35 days of culture, allows the authors to assure that the isolated canine enriched haematopoietic cell population exhibit functional characteristics, associated with primitive haematopoietic cells.     

The host-parasite relationship in bovine neosporosis

Infection with the protozoan parasite Neospora caninum is thought to be a major cause of reproductive failure in cattle worldwide. Cattle infected with the parasite are three to seven times more likely to abort compared to uninfected cattle. The parasite may be transmitted to cattle through the ingestion of oocysts that are shed in the faeces of acutely infected dogs (definitive host of N. caninum) or by congenital infection from mother to foetus via the placenta. Interestingly, transplacental transmission can occur over consecutive pregnancies and congenitally infected heifers can transmit the parasite to their own offspring. This repeated vertical transmission observed in naturally infected cattle suggests that cattle do not easily develop effective immunity to the parasite, presenting a significant challenge to the development of a control strategy based on vaccination. Neosporosis is a disease of pregnancy and studying the bovine maternal and foetal immune responses during pregnancy will help us to understand the change in the balance between the parasite and the host that may result in disease of the foetus. Studies in non-pregnant cattle and in murine models of infection have shown the importance of T-helper 1-type immune responses involving pro-inflammatory cytokines, such as IFNgamma and IL-12, in limiting intracellular multiplication of the parasite. During pregnancy, changes occur in the immune system allowing the mother to accept the foetal allograft. Research in other species has stressed the crucial role of T-helper 2-type cytokines at the materno-foetal interface in maintaining the pregnancy and regulating the potentially damaging effect of Th-1 responses. Studies in cattle have shown that cell proliferation and IFNgamma responses may be significantly down-regulated around mid-gestation. This may mean that cattle are less able to cope with N. caninum infection at this time and are more likely to transmit the parasite to the foetus. Another important factor is the gestational age and hence immuno-competence of the foetus at the time of infection. Early in gestation, N. caninum infection of the placenta and subsequently the foetus usually proves fatal, whereas infection occurring in mid to late pregnancy may result in the birth of a congenitally infected but otherwise healthy calf. Studies of foetal immune responses have shown that at 14 weeks of gestation, lymphocytes only respond to mitogen, while by 24 weeks (mid-gestation), they respond to antigen by proliferating and releasing IFNgamma. Clearly, there are several factors influencing the outcome of N. caninum infection in pregnancy: the timing, quantity and duration of parasitaemia, the effectiveness of the maternal immune response and the ability of the foetus to mount an immune response against the parasite. The challenge is to design a vaccine that will prevent foetal infection by N. caninum. This is likely to involve a fine balancing act with the immune system that will allow intervention in a manner that will tip the host-parasite balance in favour of the host without compromising the pregnancy.     

Plasma endotoxin concentration in horses: a methods study

Background: Accurate determination of plasma endotoxin concentration is critical for ex vivo and in vitro cellular and molecular studies of endotoxemia in horses. However, reports are conflicting with respect to anticoagulant, handling, and sample preparation.

Objective:

Objective: The purpose of this study was to determine the effect of blood sample fraction and handling time on measurement of endotoxin concentration in horses.

Methods:

Methods: Whole blood, anticoagulated with 3.8% (0.12 M) sodium citrate (9:1), was collected from 5 healthy horses. Whole blood (WB), platelet-rich plasma (PRP), and platelet-poor plasma (PPP) were spiked with endotoxin (2 EU/mL). Endotoxin-spiked WB samples were centrifuged immediately to generate PRP for measurement. Endotoxin concentration was subsequently measured by Limulus amebocyte assay at 0, 15, 30, 45, and 60 minutes. Assays were performed in triplicate and results were analyzed using Student's t -test, with significance set at P < .05.

Results:

Results: Mean endotoxin concentrations in 2 EU/mL-spiked WB were significantly different from those in PPP at all time points tested. Recovery of endotoxin in PRP generated from WB was significantly diminished after just 15 minutes.

Conclusion:

Conclusion: PRP generated from WB is significantly more reliable than PPP in determining endotoxin concentration ex vivo. Measurement of endotoxin in PRP generated from WB was significantly diminished after 15 min, identifying a time frame within which to process blood samples for endotoxin analysis.     

Proteome analysis of the sarcoplasmic fraction of pig semimembranosus muscle: implications on meat color development

Two-dimensional electrophoresis was used to investigate sarcoplasmic protein expression in pig Semimembranosus muscles sampled 20 min after slaughter. Two groups (light and dark) of 12 animals were selected from 1000 pigs, based on meat L values measured 36 h postmortem. Twenty-two proteins or fragments (p < 0.05) were differentially expressed. Muscles leading to darker meat had a more oxidative metabolism, indicated by more abundant mitochondrial enzymes of the respiratory chain, hemoglobin, and chaperone or regulator proteins (HSP27, alphaB-crystallin, and glucose-regulated protein 58 kDa). Conversely, enzymes of glycolysis were overexpressed in the lighter group. Such samples were also characterized by higher levels of glutathione S-transferase omega, which can activate the RyR calcium channels, and higher levels of cyclophilin D. This protein pattern is likely to have severe implications on postmortem metabolism, namely, acceleration of ATP depletion and pH fall and subsequent enhanced protein denaturation, well-known to induce discoloration.     

A comparison of extradural and intravenous methadone on intraoperative isoflurane and postoperative analgesia requirements in dogs

Objective To compare the effects of intravenous (IV) and extradural (ED) methadone on end‐tidal isoflurane concentration (Fe ′ISO) and postoperative analgesic requirements in dogs undergoing femoro‐tibial joint surgery. Study Design Randomized, blinded, clinical study. Animals Twenty‐four healthy client‐owned dogs undergoing surgical repair of ruptured cruciate ligaments. Methods Dogs were randomly assigned to two groups of 12 animals and received either ED or IV methadone (0.3 mg kg^?1 diluted with saline to 0.2 mL kg^?1). Pre‐anaesthetic medication was IV acepromazine (0.05 mg kg^?1). Anaesthesia was induced with propofol and maintained initially with an Fe ′ISO of 1.0% delivered in oxygen. Methadone was injected with the dogs in sternal recumbency; the observer was unaware of the administration route. At 10 minutes (stimulation 1) and 20 minutes (stimulation 2) after methadone administration pelvic limb reflexes were tested by digit‐clamping. The time at skin incision (stimulation 3), joint‐capsule incision (stimulation 4), tibial tuberosity drilling (stimulation 5), fabellar suturing (stimulation 6) and extracapsular tightening (stimulation 7) were noted. Changes in heart rate (HR) and respiratory rate and arterial blood pressure associated with surgery were recorded along with the corresponding Fe ′ISO. After 20 minutes of anaesthesia, Fe ′ISO was decreased to the minimum required to maintain stable anaesthesia. Immediately after tracheal extubation, 1, 2, 3 and 6 hours postoperatively and on the morning after surgery, the degree of pain present was assessed using a numerical rating scale. The HR, respiratory rates and blood pressure were also recorded at these times. Serum cortisol and blood glucose concentrations were measured before pre‐anaesthetic medication and at each postoperative pain scoring interval except at 1 and 2 hours. Ketoprofen (2 mg kg^?1), carprofen (4 mg kg^?1) or meloxicam (0.2 mg kg^?1) were given by subcutaneous injection whenever pain scoring indicated moderate discomfort was present. Results Controlled ventilation was required in six dogs which stopped breathing after IV methadone. The median Fe ′ISO at stimulus 5 was 1.0% in the IV and 0.83% in the ED group. At stimulus 6, Fe ′ISO was 1.0% in the IV and 0.8% in the ED group; the difference was statistically significant (p ≤ 0.05). There was no significant difference in the duration of postoperative analgesia associated with administration route. Conclusions Extradural methadone significantly reduces the isoflurane requirement compared with IV methadone during femoro‐tibial joint surgery in dogs. Clinical relevance Extradural methadone provides safe and effective pain relief in dogs undergoing cruciate ligament repair.