Editorial

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The effects of lead on algae

The effects of lethal and sublethal concentrations of PbCl₂ on reproduction , viability, and motility of a marine unicellular green flagellate alga, Platymonas subcordiformis, were studied under controlled laboratory conditions. The severity of the effects depended primarily upon the concentration of Pb⁺⁺ and the duration of treatment. Log phase cells were more sensitive than stationary phase cells. Sublethal amounts of Pb (2.5 and 10 mg l^?1 Pb⁺⁺) tended to retard population growth by delaying cell division and daughter cell separation. A lethal amount of Pb (60 mg I^?1 Pb⁺) caused inhibition of growth and cell death. Various intracellular abnormalities resulted from Pb treatment. The flagella were shed or altered in a variety of ways, depending on Pb concentration; motility was least affected by low Pb and completely impaired by high Pb. Normal wild-type cells appeared to be more sensitive to Pb than mechanically sheared (flagella-less) cells and cells of a non-flagellate mutant of Platymonas. Exposure of cells to Pb in non-growth conditions of dark and cold (2°C) had little negative effect.     

Does crumb morphology affect water migration and crispness retention in crispy breads?

Crispness of bread is rapidly lost because of water migration inside the crumb towards the crust. How crumb properties determine this process independent of crust properties has not been examined before. Therefore, the aim of this study was to analyze and explain the influence of crumb morphology on the overall crispness retention. Crispness retention was determined by analyzing the acoustic emission of breads differing in either crust or crumb morphology. When crumb morphology is coarse with a lower number of large connections between the air cells, the effective diffusion coefficient is reduced. This effective diffusion coefficient of crumb, which equals approximately half the value of air, was estimated using X-ray micro-computer tomography images of crumb pieces. If the crumb has a lower effective diffusion coefficient, bread with similar crust properties has significantly longer crispness retention. Despite this, our data show that variations in properties of crust, which has 30 times higher permeability than crumb, have a larger impact on crispness retention than variations in properties of crumb.     

Formation of furan and methylfuran by maillard-type reactions in model systems and food

The formation of furan and 2-methylfuran was studied in model systems based on sugars and selected amino acids. Both compounds were preferably formed under roasting conditions in closed systems yielding up to 330 micromol of furan and 260 micromol of 2-methylfuran per mol of precursor. The amounts obtained under pressure cooking conditions were much lower, usually below 20 micromol/mol, except for 2-furaldehyde, which yielded 70-100 micromol/mol of furan. Labeling studies indicated two major formation pathways for both furans: (i) from the intact sugar skeleton and (ii) by recombination of reactive C(2) and/or C(3) fragments. Under roasting conditions in the absence of amino acids, furan was mainly formed from the intact sugar skeleton. Formic and acetic acid were identified as byproducts of sugar degradation, indicating the split off of C(1) and/or C(2) units from hexoses. The presence of alanine, threonine, or serine promoted furan formation by the recombination of C(2) fragments, such as acetaldehyde and glycolaldehyde, which may originate from both sugars and amino acids. In aqueous solution, about half of furan was generated by the recombination of sugar fragments. 2-Methylfuran was preferably formed in the presence of amino acids by aldol-type reactions of C(2) and C(3) fragments with lactaldehyde as a key intermediate, the Strecker aldehyde of threonine. The total furan levels in cooked vegetables were increased by spiking with hexoses. However, in pumpkin puree, only about 20% of furan was formed from sugars, preferably from the intact carbon skeleton.     

Mycobacterium fortuitum infection interference with Mycobacterium bovis diagnostics: natural infection cases and a pilot experimental infection

Mycobacterium fortuitum and at least 1 unidentified species of soil mycobacteria were isolated from lymph nodes from 4 of 5 African buffalo (Syncerus caffer) that had been culled because of positive test results using the Bovigam assay. The buffalo were part of a group of 16 free-ranging buffalo captured in the far north of the Kruger National Park (South Africa) assumed to be free of bovine tuberculosis. No Mycobacterium bovis was isolated. To investigate the possible cause of the apparent false-positive diagnosis, the Mycobacterium isolates were inoculated into 4 experimental cattle and their immune responses monitored over a 13-week period, using the gamma interferon assay. The immune reactivity was predominantly directed toward avian tuberculin purified protein derivative (PPD) and lasted for approximately 8 weeks. During that period 3 of 4 cattle yielded positive test results on 1 or 2 occasions. The immune responsiveness was boosted when the inoculations were repeated after 15 weeks, which led to 2 subsequent positive reactions in the experimental animal that did not react previously. Including an additional stimulatory antigen, sensitin prepared from M. fortuitum in the gamma interferon assay, showed that it was able to elicit a detectable gamma interferon response in all 4 experimentally inoculated cattle when applied in parallel with bovine and avian tuberculin PPD for the stimulation of blood samples. The implications of occasional cross-reactive responses in natural cases of infection with environmental mycobacteria in the diagnosis of bovine tuberculosis in African buffalo and cattle in South Africa are discussed.     

PAF increases phagocytic capacity and superoxide anion production in equine alveolar macrophages and blood neutrophils

Phagocytosis exerted by alveolar macrophages and neutrophils is crucial in the clearance of exogenous particles deposited in the airways. Therefore, substances that activate these phagocytes in the airways can exert important effects on the particle clearance rate. PAF, particularly, was proved to be a potent activator of several immune cells and was shown to be present in the equine lower airways in specific conditions, such as after exercise. The present study aimed to investigate if PAF is able to increase the phagocytic capacity and the production of superoxide anion in equine alveolar macrophage and blood neutrophils. The results show that PAF increased these parameters in both phagocytes even in concentrations as low as 0.1 and 1.0 nM. On that ground, the present work suggests that PAF is involved in the process of particle clearance in equine lower airways.     

Mutations in the pericentrin (PCNT) gene cause primordial dwarfism

Fundamental processes influencing human growth can be revealed by studying extreme short stature. Using genetic linkage analysis, we find that biallelic loss-of-function mutations in the centrosomal pericentrin (PCNT) gene on chromosome 21q22.3 cause microcephalic osteodysplastic primordial dwarfism type II (MOPD II) in 25 patients. Adults with this rare inherited condition have an average height of 100 centimeters and a brain size comparable to that of a 3-month-old baby, but are of near-normal intelligence. Absence of PCNT results in disorganized mitotic spindles and missegregation of chromosomes. Mutations in related genes are known to cause primary microcephaly (MCPH1, CDK5RAP2, ASPM, and CENPJ).     

Development of a Multi-Residue Method for Monitoring 44 Pharmaceuticals in Slovene Surface Water by SPE-LC-MS/MS

The article describes a novel analytical method based on solid-phase extraction and LC-MS/MS for detection of a high number (n?=?44) of selected pharmaceuticals in surface waters. The validated method showed suitable accuracy, precision, and linearity. The extraction efficiency for pharmaceuticals was mostly above 90% and the determined LOQs were generally below 5 ng/L and even down to 0.03 ng/L. The matrix effect was successfully minimized with isotopically labeled internal standards. Six river and lake samples from Slovene regions were afterwards analyzed. Forty-two of the 44 target pharmaceuticals were detected in at least two water samples; 66% of them were detected in all samples. Three analytes were present above the LOQ in all samples: caffeine (1.1–3.1 ng/L), irbesartan (0.2–9.3 ng/L), and valsartan (0.8–47 ng/L). The highest concentration was measured for valsartan. Comprehensive comparison with the literature data showed that the found concentrations of pharmaceuticals were notably lower in our study and that a number of the pharmaceuticals had not been reported previously. Comparison of the measured and predicted (calculated) environmental concentrations of pharmaceuticals in surface waters showed high discrepancy between the two approaches, clearly indicating the need for comprehensive analytical methods for routine monitoring of these newly emerging pollutants. In conclusion, our method was proven to be adequately sensitive to reliably quantify the majority of pharmaceutical contaminants even though they were found in notably lower concentrations in Slovenian surface waters than it was predicted from their consumption and from the literature.     

Measuring nitrogen fixation by <Emphasis Type="Italic">Sesbania sesban</Emphasis> planted fallows using <Superscript>15</Superscript>N tracer technique in Kenya

A field experiment was performed in eastern Kenya to estimate N₂ fixation by Sesbania sesban over an 18-month period using the ¹⁵N dilution method. The influence of three reference species, Senna spectabilis, Eucalyptus saligna and Grevillea robusta, on the estimates of N₂ fixation was also assessed. Percentage Ndfa (nitrogen derived from the atmosphere) was calculated based on foliar atom excess (FAE), above-ground atom excess (AAE) or whole tree atom excess (WAE) data. The differences in atom% ¹⁵N excess values between species and plant parts are presented and discussed. We recommend the use of several reference species for estimating %Ndfa and that the different results obtained should be carefully considered in relation to the issues being addressed. In this study, Senna was the most suitable of the three reference species because its N uptake pattern and phenology were very similar to those of Sesbania. When well established, the amount of N fixed by Sesbania accounts for more than 80% of its total N content, according to FAE-based estimates. We estimated the Ndfa by Sesbania after 18 months to between 500 and 600 kg ha⁻¹ , depending on whether FAE, AAE or WAE data were used and on the choice of reference species. The substantial accumulation of N in planted Sesbania highlighted its potential to increase the sustainability of crop production on N-limited soils. We consider the ¹⁵N dilution method to be appropriate for quantifying N₂ fixation in improved fallows in studies, similar to this one, of young trees with high N₂-fixing ability.