The characterization of microporosity in a ploughpan by submicroscopic and quantimet techniques

Ploughpans are usually recognizable in thin sections because of their massiveness (density) when compared with adjacent parts of the soil. When pores can be measured in the ploughpan such massiveness can be documented and compared with the porosity of the underlying soil profile. Such measurements, however, concern only meso- and macropores when done by Quantimet on micrographs obtained with the light microscope. This is due to the thickness of the thin section and the necessity to work with transmitted light. The measurement of the smaller mesopores may also be problematic with the light microscopy—Quantimet technique.

The introduction of backscattered electron scanning images allows to obtain micrographs of a very thin layer and this made it possible to measure micro- and mesopores by Quantimet. If only small magnifications are used, macropores can also be measured.

In the present investigation, micro- and mesopores were quantified by a combination of backscattered electron and Quantimet techniques and the macropores by light microscopy and Quantimet. It was demonstrated that macro- and mesopores were less frequent in a ploughpan than outside, whereas capillary or micropores increased somewhat.     

A DNA vaccine coding for glycoprotein B of pseudorabies virus induces cell-mediated immunity in pigs and reduces virus excretion early after infection

Glycoproteins B (gB), gC and gD of pseudorabies virus (PRV) have been implicated as important antigens in protective immunity against PRV infection. As cell-mediated immunity plays a major role in this protective immunity, we determined the significance of these glycoproteins in the actual induction of cell-mediated immunity. We vaccinated pigs with plasmid DNA constructs coding for gB, gC or gD and challenged them with the virulent NIA-3 strain of pseudorabies virus. Vaccination with plasmid DNA coding for gB induced the strongest cell-mediated immune responses including cytotoxic T cell responses, whereas plasmid DNA coding for gD induced the strongest virus neutralising antibody responses. Interestingly, vaccination with gB-DNA reduced virus excretion early after challenge infection while vaccination with gC-DNA or gD-DNA did not.This is the first study to demonstrate that DNA vaccination induces cytotoxic T cell responses in pigs and that cell-mediated immunity induced by vaccination with gB-DNA is important for the reduction of virus excretion early after challenge infection.     

Selection of Variovorax paradoxus-like bacteria in the mycosphere and the role of fungal-released compounds

At two occasions (2004 and 2006), a similar cluster of culturable bacteria was found to be selected in the mycosphere of the basidiomycetous fungus Laccaria proxima (Agaricales, Tricholomataceae) in the field. The bacteria, identified as related to Variovorax paradoxus, comprised 7.3-9% of the total culturable bacterial community in the L. proxima mycosphere, but were not found in corresponding bulk soil (<0.3%). One strain, denoted HB44, was selected in order to unravel the basis of the V. paradoxus mycosphere competence in in vitro experiments with the former Laccaria laccata, which was recently reclassified as Lyophyllum sp. strain Karsten (Agaricales, Tricholomataceae). In liquid culture experiments, L. strain Karsten was shown to be an avid producer of glycerol, next to acetate and formate, which constituted the most abundant carbonaceous compounds released. Strain HB44 was able to grow avidly at the expense of the glycerol liberated by the fungus, as evidenced by proton NMR analysis of the fungal exudates in the medium before and after bacterial growth. In sterilized field soil, strain HB44 survived significantly better in the presence than in the absence of L. strain Karsten. Addition of a glycerol series to the sterilized soil (without the fungus) resulted in the persistence or growth of strain HB44, but only if the pH of this soil was previously set at 5.5. Thus, we provide evidence for the contention that tricholomataceous fungi can create specific niches in soil for the V. paradoxus-related strain HB44 and that glycerol may be a main carbon source that drives the selection of this organism.     

氧氟沙星药物的研究进展

通过对氧氟沙星药物近十年来的检测方法、药代动力学、药效学、耐药性及抗菌后效应、联合应用及毒理学、残留及残留的检测方法等六个方面的大量研究资料进行综述,详细介绍并论述了氧氟沙星药物在这些方面的最新研究成果,对氧氟沙星药物及其他喹诺酮类药物的进一步研究、开发和应用具有指导意义。     

Development of a sequence-specific PCR marker linked to the Ku gene which removes the vernalization requirement in narrow-leafed lupin

Wild types of Lupinus angustifolius require vernalization to promote flowering. Modern domesticated cultivars carry the early-flowering gene Ku which removes this requirement. A microsatellite-anchored fragment length polymorphism marker was identified as co-segregating with the Ku gene in a recombinant inbred line (RIL) population derived from a domesticated × wild-type cross. DNA sequencing showed that the marker contained a 7 bp insertion/deletion polymorphism, as well as a single nucleotide polymorphism. A pair of sequence-specific primers was designed and successfully converted the size polymorphism into a simple polymerase chain reaction based co-dominant marker. This marker is closely linked to the Ku gene, as it co-segregates with the Ku phenotyping in a population consisting of 106 RILs.     

Assessing in vivo Fertilizing Capacity of Liquid-Preserved Boar Semen According to the 'Hanover Gilt Model'

The goal of this study was to determine the ability of the Hanover gilt model to assess in vivo fertilizing capacity of preserved sperm and to consider whether any modifications to this model were needed. This model evaluates the fertilizing capacity of semen based on the fertilization rate, the rate of normal embryos and the accessory sperm count of 3–5‐day embryos. Its distinguishing characteristics are the use of one‐time insemination of sperm in reduced numbers, of spontaneously ovulating gilts and of ovulation detection through ultrasound examination of ovaries. Reduced sperm numbers allow for an accurate evaluation of the fertilizing potential of different semen treatments, thereby avoiding the compensatory effect of doses calibrated to maximize fertility. The model's usefulness was assessed in a trial run designed to compare the fertilizing capacity of liquid boar semen diluted into two different extenders. The diluent, the boar and the backflow, had no significant effect on any of the parameters studied. Gilts inseminated less than 24 h before ovulation had a significantly higher (p < 0.01) fertilization rate and accessory sperm cell count (p < 0.05) than those inseminated more than 24 h before ovulation. Very good/good embryos from homogeneous litters (only very good/good embryos were present) had a significantly higher (p < 0.01) accessory sperm count than those from heterogeneous litters (at least one embryo was of a different quality and/or oocytes were present). Both very good/good and degenerated/retarded embryos from heterogeneous litters had low accessory sperm numbers. This suggests that accessory sperm count is significantly related to the quality of the litter, but not to the quality of the embryo within gilts. It can be concluded that the Hanover gilt model is sensitive enough to show fertility differences (in this study, those associated with in vivo ageing of semen), while using relatively few gilts and little time.     

Amino acid and energy digestibility in ten samples of distillers dried grain with solubles fed to growing pigs

The objective of this experiment was to measure the digestibilities of energy, CP, and AA in 10 samples of corn distillers dried grain with solubles (DDGS) and in corn fed to growing pigs. Twelve growing barrows (initial BW: 34.0 +/- 1.41 kg) were allotted to an 8 x 12 Youden square design with 8 periods and 12 animals. Ten of 12 diets were based on the 10 DDGS samples (66.7%), 1 diet was based on corn (97%), and the last diet was a N-free diet based on cornstarch and sucrose. Chromic oxide (0.3%) was included in all diets as an inert marker. Pigs were provided their respective diets at a level of 3 times their estimated energy requirement for maintenance. The apparent (AID) and standardized (SID) ileal digestibilities for CP and AA were measured in the 10 samples of DDGS and in corn using the direct procedure, but the apparent total tract digestibilities for DM and GE were estimated using the difference procedure. The concentration of DE in each sample of DDGS and in corn was also calculated. The results of the experiment indicated variation among the different sources of DDGS in AID and SID for Lys, which ranged from 35.0 to 55.9% and 43.9 to 63.0%, respectively. For Met, the SID varied between 73.9 and 84.7%. However, the variability among samples in the SID for CP, and for the indispensable AA other than Lys and Met, was relatively low and ranged between 6 and 8 percentage units (i.e., from 64.0 to 70.6%, 74.1 to 80.1%, and 67.4 to 75.3% for Thr, Trp, and Ile, respectively). The SID for Trp in corn (72.8%) was lower (P < 0.05) than in DDGS, but for the remaining indispensable AA, except Arg, the SID for corn were greater (P < 0.01) than for DDGS. The DE concentration in the 10 samples of DDGS varied (P < 0.001) from 3,382 to 3,811 kcal of DE per kg of DM. For corn, the DE was 3,845 kcal per kg of DM. It is concluded that the AID and SID for Lys vary among samples of DDGS, but for most other AA the AID and SID are relatively similar and vary only 6 to 8 percentage units among different samples. Future work should focus on identifying the reasons for the variation in the digestibility of Lys to avoid processing procedures that are detrimental to Lys digestibility.