Correlation of minimum inhibitory concentrations between human and animal antimicrobials against Escherichia coli isolated from livestock

We analyzed the correlation between minimum inhibitory concentrations (MICs) of antimicrobials used in humans and those used in animals to enable comparison of antimicrobial susceptibility between Escherichia coli isolated from humans and those from animals. We compared the following pairs of MIC data: piperacillin (PIPC) to ampicillin (ABPC), amikacin (AMK) to kanamycin (KM), minocycline (MINO) to oxytetracycline (OTC), and levofloxacin (LVFX) to enrofloxacin (ERFX) using 103 isolates of E. coli from healthy livestock (cattle, pigs, broiler chickens, and layer chickens). Kappa analysis of the agreement for resistance and susceptibility between PIPC and ABPC, AMK and KM, MINO and OTC, and LVFX and ERFX showed almost perfect (κ = 0.81), slight (κ = 0.12), fair (κ = 0.37), and moderate (κ = 0.46) agreement, respectively. Within the antimicrobial pairs, all isolates resistant to the human antimicrobial were also resistant to the veterinary antimicrobial. However, there was less agreement within the pairs for those isolates that were sensitive to the human antimicrobial. The percentage agreement for susceptibility, defined as the percentage of isolates sensitive to both antimicrobials compared with isolates sensitive to both antimicrobials, as well as those sensitive only to the human antimicrobial, was 89.9%, 87.3%, 64.0%, and 89.9% for PIPC and ABPC, AMK and KM, MINO and OTC, and LVFX and ERFX, respectively. Our results suggest that the possibility of missing the resistance for antimicrobials used in human medicine by examining MICs for the equivalent antimicrobials used in veterinary medicine is low.     

The origin of OB runaway stars

About 20% of all massive stars in the Milky Way have unusually high velocities, the origin of which has puzzled astronomers for half a century. We argue that these velocities originate from strong gravitational interactions between single stars and binaries in the centers of star clusters. The ejecting binary forms naturally during the collapse of a young (≤1 million years old) star cluster. This model replicates the key characteristics of OB runaways in our galaxy, and it explains the presence of runaway stars of ≥100 solar masses (M(⊙)) around young star clusters, such as R136 and Westerlund 2. The high proportion and the distributions in mass and velocity of runaways in the Milky Way are reproduced if the majority of massive stars are born in dense and relatively low-mass (5000 to 10,000 M(⊙)) clusters.     

Mechanisms of production of soil protease by proteolytic Bacillus subtilis in wetland rice soil

In sterile soil inoculated with proteolytic Bacillus subtilis, the correlation between variations in protease activity and cell numbers was investigated during incubation, and the results were compared with those obtained in different growth media. In sterile soil inoculated with B. subtilis, the extracted soil z-FLase activity (hydrolytic activity towards benzyloxycarbonyl-L-phenylalanyl-L-leucine extracted with 0.1 M phosphate buffer) was correlated with the extracted soil protein content (r=0.95; P<0.01) and the number of vegetative cells (r=0.88, P<0.05), while the extracted soil caseinase activity was well correlated with the number of spores (r=0.82, P<0.05) and not with the number of vegetative cells. Extracellular z-FLase activity in different growth media, inoculated with the proteolytic B. subtilis, was correlated with the extracellular protein concentration (r=0.73, P<0.01) and the number of cells (r=0.73, P<0.01), but extracellular caseinase activity was not correlated with either of these measurements. From these results, we concluded that soil z-FLase production might relate to vegetative growth of the proteolytic B. subtilis and soil caseinase might relate to B. subtilis sporulation.     

Estimate of the source of soil protease in upland fields

Selective inhibition of bacterial or fungal growth in remoistened, oven-dried, inoculated Andosols indicated that bacteria were a more important source of benzyloxycarbonyl-l-phenylalanyl-l-leucine hydrolyzing activity (z-FLase) and casein-hydrolyzing activity (caseinase) than fungi. The same test indicated that bacteria were also a more important source of soil caseinase under upland conditions in a Gray Lowland soil. Most of the proteolytic bacteria isolated from the three upland fields by azocoll agar plates (Andosol upland field, 100%; Andosol uncultivated field, 96.4%; Gray Lowland upland field, 70.0%) wereBacillus spp. Most (100%, 97.1%, and 84.0%, respectively) of the gelatin liquefiers selected from the azocoll degraders, as those with high extracellular z-FLase and caseinase, were alsoBacillus spp. We conclude thatBacillus spp. are the major source of soil protease in the three upland fields studied.     

Reduction of aluminum toxicity to radish by alkaline oxygen treated kraft lignin

To obtain a soil-conditioning agent for acid soil containing excess aluminum ions (AL), kraft lignin was modified by alkaline oxygen treatment. The growth of radish root in solution and in soil containing AL with or without addition of these lignins under controlled pH was examined. We concluded the following. Growth inhibition of radish roots by AL can be removed by adding alkaline oxygentreated lignins in the range of pH 4.5–4.8 in soil. A similar result was obtained at pH 4.5 in a culture solution. The reduction of AL toxicity to plant may be due to the aggregation between AL and the modified lignin at low concentrations of modified lignin because soluble AL could not be detected. On other hand, elongation of radish root was not obviously inhibited, although the soluble AL in the solution culture was at an extremely high level when the dosage of a modified lignin was high. This suggests that the reduction in AL toxicity to plants was due to formation of a complex between AL and acidic groups of the modified lignin.Part of this report was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999 and the 44th Lignin Symposium, Gifu, October 1999     

Factors affecting fertilization and embryonic development during intracytoplasmic sperm injection in pigs

In intracytoplasmic sperm injection (ICSI) technique, a sperm was injected into ooplasm directly using a glass pipette. The fertilization physiology in ICSI is considered quite different from that of the natural fertilization. The different mechanisms for fertilization may be the causes of various results in ICSI. In this paper, we focus on the state of sperm membranes, nuclear or DNA integrity during ICSI procedure and discuss the influence of these factors on fertilization and embryonic development. We also introduce some examples in application of ICSI for new technologies in pigs.     

Characterization of a metalloproteinase component extracted from soil

Summary A metalloproteinase was found to be the main component of a protease in the extract from an Andosol collected from a tomato field. The protease has a pH optimum of 7 for benzyloxycarbonyl-L-phenylalanyl-L-tyrosyl-L-leucine with tyrosylleucine as the main reaction product. The K_m value for the substrate was 0.4 mM. Activity was inhibited by EDTA but not by pepstatin, p-chloromercuribenzoate and phenylmethanesulfonyl fluoride. After the removal of EDTA from the inactivated enzyme by dialysis and the addition of metal ions (Zn²⁺, Mn²⁺ and Fe³⁺), the enzyme activity could be recovered. The apparent isoelectric points of the metalloproteinase components were estimated to be 4.9, 4.5 and 4.1 by isoelectric focusing. A fraction with an apparent isoelectric point of 4.9 was the main component. The apparent molecular weight of the main protease component was estimated to be 4.7 × 10⁴ by gel filtration of Sephadex G-100. The enzyme hydrolyzed a natural polypeptide, angiotensin I (Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu). Main split sites in the peptide were -Tyr⁷-Ile⁵- and -Pro⁷-Phe⁸-. The former was the most sensitive site to the soil metalloproteinase concerned.     

Xenografting of gonadal tissues into mice as a possible method for conservation and utilization of porcine genetic resources

In vitro production of embryos, including in vitro maturation, fertilization of oocytes and their subsequent culture to the embryo stage, has become the most popular method of studying gametogenesis and embryogenesis in pigs. As well as their utility for basic studies, these procedures now enable us to generate viable embryos and offspring as a means of conserving genetic resources and rare animal breeds. Recently, more advanced technologies such as xenografting of gonadal (testicular and ovarian) tissues into immunodeficient experimental animals have been developed. In combination with in vitro embryo production techniques, this approach may provide many benefits. We have been carrying out studies to acquire basic information about the application of this method to porcine species, and to improve the existing techniques. Recently, we obtained oocytes from ovarian tissue xenografted and grown in nude mice that had the capacity to be fertilized and the ability to develop into early‐stage embryos. We also obtained spermatozoa from the xenografted testicular tissues and injected them intracytoplasmically into in vitro‐matured oocytes to produce piglets. Here we discuss the further possibilities of conservation and utilization of porcine gonadal tissue by xenografting into immunodeficient mice.