An analog of myristic acid with selective toxicity for African trypanosomes.

Trypanosoma brucei, the protozoan parasite responsible for African sleeping sickness, evades the host immune response through the process of antigenic variation. The variant antigen, known as the variant surface glycoprotein (VSG), is anchored to the cell surface by a glycosyl phosphatidylinositol (GPI) structure that contains myristate (n-tetradecanoate) as its only fatty acid component. The utilization of heteroatom-containing analogs of myristate was studied both in a cell-free system and in vivo. Results indicated that the specificity of fatty acid incorporation depends on chain length rather than on hydrophobicity. One analog, 10-(propoxy)decanoic acid, was highly toxic to trypanosomes in culture although it is nontoxic to mammalian cells.     

Influence of extreme K:Na ratios and high substrate salinity on plant metabolism of crops differing in salt tolerance

K⁺/Na⁺ and Cl^‐ effects on activity of amylases as well as on their isoenzyme pattern in leaves of bushbeans and sugarbeets at the beginning of salinity stress were investigated, in plants grown in water culture under controlled environmental conditions. Alpha‐ and beta‐amylase activity in beans increased, particularly due to K⁺ and Cl^‐ supplied. In sugarbeets amylase activity remained unchanged as a result of K/Na treatment in combination with Cl and decreased using SO₄ ^2‐ as counterion. A direct correlation of amylase activity to the starch content of both species was not detctable. Particularly α‐but also ß‐amylase was most strongly inhibited by KCl “in vitro”. Independent on their origin, amylases from bushbeans and sugarbeets did not show any differences in ionic inhibition “in vitro”. The isoenzyme pattern of the species was different, but no clear ionic effect was detectable. Amylolytic activity is evidently not a causative factor for restricted starch mobilization in leaves under an early salinity stress. It is suggested that amylases are indirectly involved in starch formation via degradation due to a lack of a carbohydrate sink under salinity stress. Differences in salt tolerance of the investigated crops are obviously not related to different “in vitro” properties of amylases.     

Mastitis diagnostics and performance monitoring: a practical approach

In this paper a review is given of frequently used mastitis diagnostic methods in modern dairy practice. Methods used at the quarter, cow, herd and regional or national level are discussed, including their usability for performance monitoring in udder health. Future developments, such as systems in which milk-derived parameters are combined with modern analytical techniques, are discussed. It is concluded that, although much knowledge is available and science is still developing and much knowledge is available, it is not always fully exploited in practice.     

Continuous infusion of propofol or intermittent bolus of tiletamine‐zolazepam in squirrel monkeys (Saimiri sciureus)

ObjectiveTo investigate an infusion of propofol for anesthesia in comparison to tiletamine-zolazepam anesthesia, evaluating physiological variables and recovery in squirrel monkeys.Study designProspective non-blinded randomized study.AnimalsEight healthy squirrel monkeys (Saimiri sciureus), aged 3 years and weighing 0.340–0.695 kg.MethodsPremedication was intramuscular midazolam (0.5 mg) and meperidine (4 mg). Anesthesia was induced with intravenous (IV) propofol (4 mg kg^?1 minute^?1) and maintained with propofol starting at 0.4 mg kg^?1 minute^?1 (PRO, n = 4) or IV tiletamine-zolazepam (5 mg kg^?1) and maintained with supplementary doses of TZ (TZ, n = 4). Cardiopulmonary variables were measured continuously. Arterial blood gases and lactate concentration were measured at the end of anesthesia. Quality and times of recovery were determined. Repeatedly measured data for significant differences were tested between groups with t-test and within groups by anova.ResultsMedian time for induction of anesthesia in PRO was 180 seconds. Mean maintenance infusion rate of propofol was 0.43 ± 0.05 mg kg^?1 minute^?1, varying during the 1 hour period. One monkey died after administration of TZ; others required 1, 4, or 8 supplemental doses. Cardiopulmonary variables were similar between groups, but hypotension was recorded. Recovery times to ventral recumbency in PRO (32 ± 17 minutes) and TZ (84 ± 11 minutes) and normal ambulation in PRO (58 ± 22 minutes) and TZ (358 ± 109minutes) were significantly different (p < 0.05). Recovery quality was superior in PRO, with less ataxia and fewer unsuccessful attempts to stand. Lactate concentration was not different between treatments.Conclusions and clinical relevanceCardiopulmonary variables were similar between protocols, aside from the higher incidence of hypotension in PRO, indicating that further studies with a larger number of animals are required. Compared to tiletamine-zolazepam, propofol anesthesia provided faster and superior anesthetic recovery in these animals.     

Influence of extreme K:Na ratios and high substrate salinity on plant metabolism of crops differing in salt tolerance

Mineral regulation of two soybean varieties Jackson and Lee was investigated in long term water culture experiments using saline solutions. The effects of extreme K:Na ratios using chloride and sulfate as counterions were studied in the early stages of salinity.

The growth rates of both varieties were not affected by salinization. A K⁺ stimulated, intensive acropetal Cl^‐ translocation was observed in the salt sensitive variety Jackson. The varieties did not differ in Na⁺ translocation and in the suppression of Ca²⁺ and Mg²⁺ in the leaves. But the effect of the nature of salinization indicates already differences in Na uptake and translocation of the cultivars.

The avoidance of Cl^‐, but also of Ha⁺, in connection with influences of the resulting ionic imbalance on metabolic pathways are probably the most causative factors for the different tolerance to salinity of the two soybean varieties.     

Consequences for biodiversity of reducing inputs to upland temperate pastures: effects on beetles (Coleoptera) of cessation of nitrogen fertilizer application and reductions in stocking rates of sheep

Current policies for upland pasture management in the UK encourage the integration of environmental objectives with livestock production through extensification of grazing systems. This study tested the hypothesis that a greater sward height in the summer would increase the diversity and abundance of grassland beetles (Coleoptera) as has been demonstrated for insects of indigenous grasslands. The hypothesis was tested with an experiment on an upland sheep pasture in mid‐Wales. Experimental treatments received different nitrogen fertilizer inputs (0 or 50 kg ha^?1), sheep stocking densities (12 or 9 ewes ha^?1) and average sward heights in summer were constrained to 3·5 or 5·5 cm by conserving surplus grass for silage in subplots. Five treatments, replicated in three randomized blocks, combined the two stocking densities and two sward heights without nitrogen fertilizer inputs, with the fifth combining the higher stocking density, shortest sward height and the nitrogen fertilizer input. Beetles were sampled with twelve pitfall traps in each of the fifteen plots from June to September in 1993 and 1995. In years 1 (1993) and 3 (1995) of the experiment, more Coleoptera species occurred in the tall sward (an average of nine species in addition to the forty‐one species present in the sward with the conventional sward height). Continuously grazed as opposed to ensiled subplots supported more beetle species but fewer individuals. Species composition of ground (Carabidae) and rove (Staphylinidae) beetles varied between treatments more than the arithmetic differences in species number. The experimental results supported the hypothesis but the benefits of taller swards to species diversity were small in the sown pastures of the study compared with indigenous upland grasslands (c. 33% fewer species). Inheritance effects of drainage, fertilizer and lime inputs, and the different species and management of cultivated pastures, may constrain the conservation benefits of altered pasture management compared with indigenous grasslands.