Natural resistance

Antimicrobial Activity. The elfamycins antimicrobial specificity and lack of toxicity in animals can be explained in view of species-dependent specificity of elfamycin binding to EE-Tu. Inefficient cellular uptake or the presence of a nonresponding EE-Tu were cited as responsible factors for the natural resistance in Halohacterium cutiruhrum (67), Lactobaci//us brevis (68), and in actinomycetes (5,69). The low activity of elfamycins against S. aureus was also attributed to an elfamycin-resistant EE-Tu system (70). However, cross-resistance with other antibacterial agents has not been observed (71). 

There are two main reasons why zinc is chosen as a protective coating for iron and steel. The first is the natural resistance of zinc itself against corrosion in most atmospheric conditions, and the second is the fact that zinc is electronegative to iron and can protect it sacrificially. ... 

Structures considered are quinolizinium (187), and 1,5- (188), 1,6- (189), 1,7- (190), 1,8- (191), and 2,7- (192) naphthyridines. In the naphthyridines the 10 7r-electrons are delocalized in five bonding molecular orbitals, which are distorted by the annular nitrogens in such a way that positions ortho and para to those nitrogens are less likely to be electrophilically haloge-nated than meta carbons. Compounds with a nitrogen at the ring junction carry a positive charge and will be naturally resistant to electrophilic attack. 

Microbial Resistance to Drugs. Figure 1 MlC-distribution showing the number of isolates of one species with a certain MIC. Some bacterial species are naturally resistant (intrinsic resistance) to drugs because their natural MIC is above the breakpoint. Naturally sensitive isolates as well as naturally resistant ones can acquire resistance and with that increase their MIC (acquired or secondary resistance). 

O-phosphotransferases that modify macrolides are produced by highly macrolide resistant E. coli isolates. However, these enzymes have no clinical importance for macrolide resistance in gram-positive bacteria, and gram-negative ones are regarded as naturally resistant [2]. 

Immunological tests were performed for studying the reactive of peritoneal-exudative cells, especially peritonial macrophages, which are the main effector cells involved in natural resistance (host defence system) against bacterial infection. 

Bacterial keratitis is a broad term for a bacterial infection of the cornea. This includes corneal ulcers and corneal abscesses. The cornea in a healthy eye has natural resistance to infection, making bacterial keratitis rare. However, many factors predispose a patient to bacterial infection by compromising the defense mechanisms of the eye (Table 60-5).19... 

N4. Nathan, C., Natural resistance and nitric oxide. Cell 82, 873-876 (1995). 

Background pesticide contamination of the natural environment affects most animal species, mainly influencing their behavior and physiology [1]. For example, white rats natural resistance to plague is weakened by even the smallest dose of warfarin (0.075 mg per individual over 24 days). There are many such examples [88]. 

That the oxidative burst is directly involved in the chemical defense of these algae is clear. This reaction can be inhibited by diphenyleneiodonium, a suicide inhibitor of NADPH-oxidase which suppresses both the production of reactive oxygen species and the natural resistance to epiphytic bacteria. In addition a role in the defense against endophytes was indicated, since pre-treatment with oligomeric guluronates resulted in decreased infection of L. digitata with the pathogen Laminariocolax tomentosoides [141]. 

Nramp Natural resistance associated macrophage proteins ... 

Gruenheid, S., Pinner, E., Desjardins, M. and Gros P. (1997). Natural resistance to infection with intracellular pathogens the Nrampl protein is recruited to the membrane of the phagosome, J. Exp. Med., 185, 717-730. 

From the previously discussed studies, the oxidative burst response appears to integrate and/or orchestrate several defense responses. These provide an adaptive mechanism to counteract attacks on or injury to algal cells and thalli. As shown in Fig. 12.2, the occurrence of an oxidative burst associated with the perception of cell-free extracts of A. operculata was shown to play a crucial role in the natural resistance of C. crispus gametophytes (Bouarab et al. 1999). 

EVAs are naturally resistant to light, UV, ozone and weathering and, even more, they can be protected by addition of specific anti-UV and other protective agents. Under identical... 

Good mechanical and electrical properties rigidity fair moisture uptake fair shrinkage heat behaviour with continuous use temperatures up to 170/180°C naturally resistant to UV, light, weathering naturally fire resistant optical and UHF transparency food contact and sterilization for suitable grades. 

This kind of impact is complicated by the possible influence of these chemicals on the process of evolution itself When a chemical comes into widespread use, especially an insecticide, it is only a matter of time before the target insects develop resistance. That is, those individual insects with natural resistance (as a result of natural variation and mutation) survive successive assaults of a given chemical and reproduce broods with similar immunity, which come to be common in the whole population. In a short period of time (because insects reproduce quickly), the species becomes resistant altogether (Table 4.6). ... 

One way to avoid the use of any preservative is to use wood that is naturally resistant to decay. The heartwood of more naturally rot-resistant species, such as oak, can be used untreated. Other woods that last well without treatment are larch, which will last about 10 years in contact with the soil, or up to 20 years if not in contact with soil Western red cedar, which will give service for about 20 years and sweet chestnut, traditionally used for fence palings and posts. Untreated pine lasts for about five years. Well-seasoned wood that has been allowed to dry out evenly is more expensive than greenwood (freshly cut undried wood), but in its favor, it tends to last longer and can be less prone to distortion as it weathers. 

Anti-hepatitis B virus activity in vitro and in vivo was also found in wogonin and baicalein (Fig. 4), the major active constituents of the traditional Chinese medicine Scutellaria radix.More recently, Blach-Olszewska et al investigated the effect of baicalein and wogonin on two important mechanisms of innate immunity The secretion of cytokines, and the natural resistance of human leukocytes to viral infection. The results obtained indicate that these fiavonoids modulate cytokine production, that is they inhibit interferons-a and -y, and stimulate tumor necrosis factor-a and interleukin production. They also augment the resistance of peripheral blood leukocytes to the vesicular stomatitis virus. 

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