Synergistic mechanism

Bromley-Challenor, K.C.A. (1992). Synergistic Mechanisms of Synthetic Pyrethroids and Fungicides in Apis Mellifera. M.Sc. Thesis, University of Reading, UK. 

Phospholipase A activity was subsequently demonstrated to be present in venom, and it too required Ca (25). DEAE-cellulose fractionation yielded four proteins, two of which were phospholipase A and hemolytic, and two of which had neither phospholipase A nor hemolytic activities. Either of the latter two proteins enhanced to various degrees the hemolytic activity of either of the two phospholipases. The findings suggest considerable analogy with synergistic mechanisms underlying the hemolytic action of the venoms of a number of snakes. 

A synergistic effect is exerted by the interaction of intermediate products formed from inhibitors. Actually, inhibitory systems may combine various synergistic mechanisms. 

If degradation is due to sequential or synergistic mechanisms, then a simple extrapolation may not be reasonable. For example, in accelerating the rate of oxidation of polyethylene it may be necessary to identify the induction time and subsequent degradation time separately and to produce Arrhenius diagrams for each. The total time to failure is the sum of the two times. Figure 9.3 shows an instance of where unknowing extrapolation of the short-term results in tests on polyaramid fibres could have led to overestimates of lifetime and premature failure. 

Rubin, H., Synergistic mechanisms in carcinogenesis by polycyclic aromatic hydrocarbons and by tobacco smoke a biohistorical perspective with updates, Carcinogenesis, 22, 1903-1930, 2001. 

An extensive study was conducted on the effect of chemical and structural aspects of zeolites on the fire performance of the intumescent system, ammonium polyphosphate-pentaerythritol (APP-PER), where a marked improvement of the fire-retardant properties within different polymeric matrices has been observed.56 58 The synergistic mechanism of zeolite 4A with the intumescent materials was investigated using solid-state NMR. Chemical analysis combined with cross-polarization dipolar-decoupled magic-angle spinning NMR revealed that the materials resulting from the thermal treatment of the APP-PER and APP-PER/4A systems were formed by carbonaceous and phosphocarbonaceous species, and that the zeolite enhances the stability of the phosphocarbonaceous species. 

Cause for concern related to additive or synergistic mechanisms of activity or toxicity should be addressed in a scientifically appropriate manner in consultation with regulatory authorities as necessary. Because of the broad distribution of potential combinations and mechanisms of activity/toxicity, and the complexity of species-specificity, there is not a one size fits all approach that can be applied. Current FDA regulatory guidance in this area is limited to combination products, with the intent to co-package and/or co-market as a defined treatment [9],... 

Exposure to multiple substances can also affect the dose-response curve through antagonistic, additive [115, 116] or synergistic mechanisms. Dose-response curves can therefore show a U shape or inverted U shape (Figures 2.4b andc) [117,118]. Two NO(A)EL values may then need to be used during risk management. 

Their non-linear and often synergistic mechanical behavior which arises from their above mentioned multiphase morphology. Thus, both impact resistant plastics and thermoplastic elastomers have been bom. 

In conclusion, the data demonstrated that synergistic mechanisms of cellular disruption caused by anticholinesterase agents led to cellular dysfunction and neurodegeneration. It has also been demonstrated that preventing CF-induced neuronal hyperactivity by pretreatment with MEM and atropine blocks pathways associated with oxidative damage in rat brain. The documented abihty of MEM therapy to reduce free radical generation and lipid peroxidation, prevent HEPs and attenuate the morphological injury provides further support for the role of ROS and RNS in anticholinesterase-induced seizures. 

Syncope occurred in a hypertensive 48-year-old man who took oral chloroquine sulfate (total 600 mg base) while also taking amlodipine 5 mg/day (44). Chloroquine and amlodipine both cause vasodilatation, perhaps by release of nitric oxide, and the syncope in this case was probably due to a synergistic mechanism. Malaria itself can also provoke orthostatic reactions, which may be why syncope is not a reported adverse effect of chloroquine. However, in this patient malaria had been excluded. 

Notice that the total reaction time is reduced to 50 % if only 10 % of the cobalt is substituted by manganese. Interestingly the observed reaction times remain almost constant until a Co/Mn ratio of 9 1 is reached. This demonstrates the synergistic mechanism of the different metal ions. However, at manganese concentrations lower than 10 % of the total metal content, the reaction becomes very slow. This indicates that there is one reaction step in the oxidation sequence which is strongly catalyzed by manganese ions. 

Pt-Sn alloy formation. The synergistic mechanism model for Sn and the alkali metal are shown in Figure 5. Table 2 Electrical conductivity data of catalysts and support ... 

Figure 5 Synergistic mechanism model for Sn and alkali metal (A) addition...

Synergism with hindered amines has been less investigated. To all appearances, the first example of the synergistic mechanism of this type in the case of inhibited polypropylene oxidation was pointed out by one of the authors of the present paper as far back as 1964 (61). ... 

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