The 16S rRNA and mcrA gene based comparative diversity of methanogens in cattle fed on high fibre based diet

In the present study, the diversity of rumen methanogens in crossbred Karan Fries cattle was determined by constructing 16S rRNA and mcrA (methyl coenzyme-M reductase α subunit) gene libraries using specific primers. All thirteen OTUs or phylotypes from 16S rRNA library clustered with order Methanobacteriales, twelve of which aligned with Methanobrevibacter spp., whereas one OTU resemble with Methanosphaera stadtmanae. Out of eighteen OTUs identified from mcrA gene library, fifteen clustered with order Methanobacteriales, two resemble with Methanomicrobiales and remaining one grouped with Methanosarcinales. These results revealed that Methanobrevibacter phylotype was predominantly present in Karan Fries crossbred cattle fed on high fibrous diet containing wheat straw. Compared to 16S rRNA gene, mcrA gene OTUs clustered in three orders providing better insights of rumen methanogens diversity in cattle.     

Measurement and analysis of static magnetic fields that block action potentials in cultured neurons

To characterize the properties of static magnetic fields on firing of action potentials (AP) by sensory neurons in cell culture, we developed a mathematical formalism based on the expression for the magnetic field of a single circular current loop. The calculated fields fit closely the field measurements taken with a Hall effect gaussmeter. The biological effect induced by different arrays of permanent magnets depended principally on the spatial variation of the fields, quantified by the value of the gradient of the field magnitude. Magnetic arrays of different sizes (macroarray: four center-charged neodymium magnets of ?14 mm diameter; microarray: four micromagnets of the same material but of ?0.4 mm diameter) allowed comparison of fields with similar gradients but different intensities at the cell position. These two arrays had a common gradient value of ?1 mT/mm and blocked >70% of AP. Alternatively, cells placed in a field strength of ?0.2 mT and a gradient of ?0.02 mT/mm produced by the macroarray resulted in no significant reduction of firing; a microarray field of the same strength but with a higher gradient of ?1.5 mT/mm caused ?80% AP blockade. The experimental threshold gradient and the calculated threshold field intensity for blockade of action potentials by these arrays were estimated to be ?0.02 mT/mm and ?0.02 mT, respectively. In conclusion, these findings suggest that spatial variation of the magnetic field is the principal cause of AP blockade in dorsal root ganglia in vitro. © 1995 Wiley-Liss, Inc.     

Innate preference for magnetic compass direction in the Alpine newt, <Emphasis Type="Italic">Triturus alpestris</Emphasis> (Salamandridae,Urodela)?

Magnetic compass orientation was first discovered for migrating/homing birds in which all individuals of a population or species prefer a predictable magnetic direction during a particular migratory situation. If all other sensory cues are absent, the Earth’s magnetic field may serve as a reference for other orientation mechanisms. It will be demonstrated that alpine newts (Triturus alpestris, Salamandridae) spontaneously align according to the natural or the deviated magnetic field lines of the Earth. They are able to do this in the dark and by apparently seeking to maintain a specific angle with respect to the magnetic field vector. When the horizontal component of the magnetic vector was eliminated, animals became disoriented, and orientation became random. We infer that the animals observed had learned to prefer a particular magnetic direction following environmental/geographical cues. Alternatively, the magnetic directional alignments are innate as, e.g. in migrating birds, but these may be modified/altered according to season, age, hormonal status, and environmental factors such as “landmarks”, light-, sound-, or olfactory cues. Numerous observations of the aligning showed that the preference for a certain magnetic compass direction/axis was not only individual but also specific for the population-subgroups tested. Specimens roughly preferred magnetic directions close to east or west. However, the larvae were able to learn to align to obviously attractive hiding spots (tubes) that were provided in a direction that deviated with respect to the first magnetic preference. The new conditioned alignments were, again, referred to magnetically by the animals and remained stable, even if the hiding tubes were absent. Animals preferred that direction until, eventually, a new directional cue became attractive.     

Long-term changes in soils of second-growth forest following abandonment from agriculture

Aim The assembly of a forest flora on sites abandoned from agriculture is potentially limited by the physical and chemical suitability of soils. This paper describes the post‐agricultural development of soil in deciduous forest sites to gauge its importance in limiting a second‐growth forest flora. Location Northern Delaware and south‐eastern Pennsylvania, USA. Methods A chronosequence of 99 second‐growth forest sites was assembled in the Piedmont region. Stand age ranged from 0–20 to > 100 years since canopy closure, as determined from historical aerial photographs. Seventy‐four sites are likely to have experienced cultivation before regeneration of forest. The presence of large rocks or pit‐and‐mound microtopography suggests that the remaining 25 sites were not cultivated, although they were probably used as pasture and/or woodlot. Soil organic content, moisture, pH, and concentrations of extractable potassium, phosphorous, calcium, magnesium and sulphur were measured in samples from each site. Coarse woody debris, size of the largest tree, canopy openness and several microtopographic features were also recorded. Results Most soil variables fell into two separate but internally correlated groups: the first group including organic matter, moisture and sulphur; the second including pH, calcium, potassium and magnesium. In formerly cultivated sites, organic matter, moisture and sulphur increased gradually through the chronosequence, approaching values recorded in uncultivated sites at 81–100 years. Calcium, potassium, magnesium and pH declined sharply between the 21–40‐ and 41–60‐year classes – probably an indirect effect related to geographic location and selective abandonment. Phosphorous also declined with time, but the decline was not as clearly defined. Main conclusions The progress of soil recovery observed here is faster than rates implied in other studies, possibly because these sites experienced a period as pasture before reversion to forest. Sites appear to have returned to undisturbed‐forest levels as fast as or faster than the predicted accumulation of a forest flora, suggesting that assembly of second‐growth forest communities is not limited by the rate of soil development in this region.     

Role of the alternative sigma factor σB on Staphylococcus aureus resistance to stresses of relevance to food preservation

Aims:  To examine the role of the alternative general stress sigma factor σ^B on the resistance of Staphylococcus aureus to stresses of relevance to food preservation, with special emphasis on emerging technologies such as pulsed electric fields (PEF) and high hydrostatic pressure (HHP).
Methods and Results:  S. aureus strain Newman and its isogenic Δ sigB mutant were grown to exponential and stationary growth phases and its resistance to various stresses was tested. The absence of the σ^B factor caused a decrease in the resistance to heat, PEF, HHP, alkali, acid and hydrogen peroxide. In the case of heat, the influence of the σ^B factor was particularly important, and decreases in decimal reduction time values of ninefold were observed as a result of its deficiency. The increased thermotolerance of the parental strain as compared with the sigB mutant could be attributed to a better capacity to sustain and repair sublethal damages caused by heat.
Conclusions:  σ^B factor provides S. aureus cells with resistance to multiple stresses, increasing survival to heat, PEF and HHP treatments.
Significance and Impact of the Study:  Results obtained in this work help in understanding the physiological mechanisms behind cell survival and death in food-processing environments.     

Seed germination of agricultural weeds is promoted by the butenolide 3-methyl-2H-furo[2,3-c]pyran-2-one under laboratory and field conditions

Here we report that a synthesised form of a naturally occurring chemical (a butenolide, 3-methyl-2H-furo[2,3-c]pyran-2-one) found in smoke can stimulate seedling emergence of the economically important weed species Avena fatua L. (Poaceae), Arctotheca calendula (L.) Levyns (Asteraceae), Brassica tournefortii Gouan (Brassicaceae), and Raphanus raphanistrum L. (Brassicaceae) under field conditions at rates equivalent to 2–20 g/ha a.i. The butenolide also stimulates germination of freshly collected seeds from wild populations of these species, as well as those of Sisymbrium orientale L. (Brassicaceae), Hordeum leporinum Link (Poaceae) and Echium plantagineum L. (Boraginaceae) under laboratory conditions, consistently greater than that of smoke water. Experiments using B. tournefortii seeds collected from several locations across Western Australia and in different growing seasons found that these factors significantly influence the butenolide response, implying a role of the maternal environment in seed germination/dormancy characteristics. This research highlights the potential of butenolide as an agent for broad acre weed control and land restoration.     

CpG site DNA methylation of the CCAAT/enhancer‐binding protein,alpha promoter in chicken lines divergently selected for fatness

CCAAT/enhancer‐binding protein (C/EBP), alpha (CEBPA) is a master regulator of adipogenesis and, together with peroxisome proliferator‐activated receptor gamma (PPARG), plays a critical role in adipocyte differentiation. Previous studies have demonstrated that CEBPA is regulated by DNA methylation and involved in the osteogenesis and adipogenesis of mouse C3H10T1/2 and bone marrow stromal cells. However, it is unclear whether CEBPA is regulated by DNA methylation in adipose tissues. Thus, the objectives of the present study were to investigate CpG site methylation in a 357‐bp CEBPA promoter region and to assess the correlation between promoter CpG site methylation and CEBPA gene expression in the abdominal adipose tissues of Northeast Agricultural University broiler lines divergently selected for abdominal fat content. The results showed that the methylation percentage of the analyzed CEBPA promoter region was significantly higher in lean broilers than in fat broilers at 2 weeks (80.3% vs. 43.4%, P < 0.0001), 3 weeks (95.4% vs. 74.0%, P < 0.0001) and 7 weeks of age (82.6% vs. 57.2%, P < 0.0001). Real‐time quantitative RT‐PCR analysis showed that CEBPA expression was significantly higher in the fat vs. the lean line at 2 weeks of age (P = 0.0013) but not at 3 or 7 weeks of age. The correlation analysis showed that only at 2 weeks of age was the methylation percentage negatively correlated with CEBPA expression (Pearson's r = ?0.8312, P = 0.0029). Of all seven tested CpGs, only two, the CpGs at ?1494 and ?1478 bp, displayed a significantly negative correlation with CEBPA mRNA expression. These results suggest that the CEBPA is methylated in adipose tissue and may regulate chicken early adipose development.     

Effects of changes in farming of subalpine meadows on a grassland bird, the whinchat ( Saxicola rubetra)

The increasing intensity of farming of meadows is supposed to be the major cause for strong declines of many meadow breeding birds. The whinchat, Saxicola rubetra, a Palaearctic migratory bird, is an indicator species of open grassland farmed at a low intensity. Originally widespread throughout Switzerland, it is now restricted to mountain and subalpine grassland. We document the changes in meadow cultivation in subalpine farmland from 1988 to 2002, and the breeding performance and density of the whinchat. We explored the impact of habitat degradation on the population dynamics of this meadow bird. The cultivation of hay meadows changed markedly within the 15 years: the onset of mowing was shifted forward by about 20 days, and farmers applied new techniques such as silage and irrigation. This shift was more pronounced in the favourable farmland in the valley bottom (Pradellas) than on the slopes (Vnà). The percentage of successful whinchat broods, ranging from 5% to 78% in different years, strongly depended on mowing date on both sites. In spite of earlier mowing, birds did not change their time schedule of breeding. Breeding success in Pradellas was too low to compensate for mortality (sink population), but because of immigration the number of breeding pairs did not decrease untill 2000. Population size may therefore be a misleading indicator of local population viability. Based on the breeding schedule of whinchats at different altitudes, we recommend mowing dates in agreement with the reproductive cycle of ground nesting meadow birds.