A note on the effect of the lactoperoxidase systems on salmonellas in vitro and in vivo

The lactoperoxidase system (LPS), a natural bactericidal system in milk, was investigated for its activity against salmonellas in vivo and in vitro. In acidified raw milk, in which the LPS was supplemented with an exogenous supply of H₂O₂, the numbers of salmonellas decreased rapidly. Different salmonella serotypes were affected to the same extent; rough strains, however, were more susceptible than smooth strains. When calves were fed on fresh milk, containing the LPS, and challenged with Salmonella typhimurium in doses of either 10⁹ or 10¹⁰, the clinical findings and salmonella excretion patterns were similar to those of control calves fed on heated milk. It was concluded that further studies, perhaps in the field, are necessary to evaluate LPS as a possible non-antibiotic system to control salmonellosis.     

A note on the effect of the lactoperoxidase systems on salmonellas in vitro and in vivo

The lactoperoxidase system (LPS), a natural bactericidal system in milk, was investigated for its activity against salmonellas in vivo and in vitro. In acidified raw milk, in which the LPS was supplemented with an exogenous supply of H2O2, the numbers of salmonellas decreased rapidly. Different salmonella serotypes were affected to the same extent; rough strains, however, were more susceptible than smooth strains. When calves were fed on fresh milk, containing the LPS, and challenged with Salmonella typhimurium in doses of either 10(9) or 10(10), the clinical findings and salmonella excretion patterns were similar to those of control calves fed on heated milk. It was concluded that further studies, perhaps in the field, are necessary to evaluate LPS as a possible non-antibiotic system to control salmonellosis.     

吡虫啉对蜜蜂行为与生理影响研究进展

蜜蜂是一种社会性昆虫,也是重要的授粉昆虫,对发展农业生产、维护生态环境和物种多样性有极其重要的意义。吡虫啉是一种活性高、杀虫谱广的新烟碱类杀虫剂,对蜜蜂等传粉昆虫造成潜在危害。本文主要从吡虫啉对蜜蜂的作用机制、暴露途径、代谢过程、行为影响等方面进行叙述,重新评估蜜蜂接触杀虫剂的"安全水平",从而确定最安全有效的施用浓度,为我国新烟碱类杀虫剂对蜜蜂安全性评价工作提供参考。     

Effects of immobilization stress in utero on the course of pregnancy in the rat and on various parameters in the newborn animals

The effects of immobilization stress applied during pregnancy on the evolution of pregnant rats and on the fetus and newborn have been studied. Results show alterations in food intake during pregnancy as well as in the weight of some measured structures in 21 day old fetuses. There was similarly found a significant increase in the number of dead newborn. The effect of immobilization stress applied in utero upon the evolution of pregnancy, fetus and newborn, is discussed.     

Evaluation in the greenhouse of the effects of fungicides on the development of mycorrhiza on leek and wheat

Summary The effect of 11 fungicides, viz Aliette, Bayleton 5, Benlate, Dithane M45, Euparene, Karathane, Orthocide 83RP, Pelt 44, Tilt C, Tilt 125 and Tripomol 80, on vesicular-arbuscular mycorrhizal symbiosis in leek and wheat growing in a calcined clay was studied in the greenhouse at four concentrations applied to the foliage. Fungicides had minimal effects when applied to leek or wheat plants with well-established mycorrhiza. Mycorrhizal infection was not drastically affected by any fungicide at any application level. However, mycorrhizal infection of leek plants was reduced by systemic fungicides, and that of wheat by non-systemic fungicides. Aliette was the only fungicide that stimulated mycorrhizal development.     

Studies on the effect of retinoids on the differentiation of teratocarcinoma stem cells in vitro and in vivo

Previous work has shown that retinoic acid can induce F9 embryonal carcinoma cells to differentiate into extraembryonic endoderm in vitro. We have investigated in detail the structureactivity relationship of various derivatives of retinoic acid, the kinetics of the cellular response, and the nature of the type of endoderm formed. These experiments demonstrate that the carboxylic acid group of retinoic acid is essential for activity, whereas the structure can be modified in the cyclohexenyl ring system with retention of effectiveness. The time course of the response of the cells shows that the amount of differentiation is proportional to the duration of treatment, and suggests that the retinoid facilitates formation of endoderm at each division. Finally, even well-differentiated cultures do not produce alpha-fetoprotein, indicating that the endoderm formed is similar to parietal, but not visceral, endoderm. We have also explored the consequence of in vivo retinoic acid treatment on the tumorigenesis of F9 embryonal carcinoma cells in 129/Sv mice. The presence of retinoic acid in the diet at 100 mg/kg significantly retarded tumor growth and lengthened the survival time of the mice. Histological analysis and assays for biochemical markers of endoderm in the tumor both suggest that the retinoid is inducing differentiation of the embryonal carcinoma cells in vivo.     

Effects of environment on the uptake and distribution of calcium in tomato and on the incidence of blossom-end rot

Studies of Ca uptake and distribution in relation to environmental variables were used to relate Ca status of tomato fruit to blossom-end rot (BER) incidence. Ca uptake was highly correlated with solar radiation and root temperature. The rate of Ca uptake decreased linearly with increasing salinity. High humidity reduced Ca import by the leaves but increased that by the fruit. While total plant dry weight was reduced more than fruit dry weight by salinity, total Ca uptake and the Ca content of the fruit were decreased similarly. Thus, the concentration of calcium in the fruit was substantially reduced by salinity. The distal half of the fruit contained less Ca than the proximal half. The lowest % Ca was found in the distal placenta and locular tissues, where BER first develops. The incidence of BER was often stimulated more by high salinity achieved with the addition of major nutrients than with NaCl. The cause of BER is usually an interaction between the effects of irradiance and ambient temperature on fruit growth and the effects of environmental stress on calcium uptake and distribution within the whole plant.