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Biomedical subjects

E K Boon-Niermeijer

Publications and source records attributed to E K Boon-Niermeijer.

5 recordsLinked to original sources
PubMed2000

Phyto-adaptogens protect against environmental stress-induced death of embryos from the freshwater snail Lymnaea stagnalis.

The main purpose of the studies presented in this paper is twofold: 1) to evaluate whether phyto-adaptogens (Acanthopanax senticosus and Rhodiola rosea) are able to exert a protective action against stress-induced death of embryos of the pond snail Lymnaea stagnalis; and 2) whether a possible protective action by phyto-adaptogens can be explained by the induction of heat shock proteins. Enhancement in resistance by phyto-adaptogens was studied by applying plant extracts for a period of 20 hours to 3-day old larvae of the pond snail Lymnaea stagnalis. Subsequently they were exposed to a high and toxic dose of different environmental stressors. The following stress conditions were selected: a physical stress condition (heat shock: 43 degrees C for 4 minutes), an oxidative stress condition (superoxide radicals induced by menadione (600 microM for 2 hours)) and heavy metal-induced stress (copper (150 microM for 1 hour) or cadmium (20 microM during 1 hour)). Both Acanthopanax and Rhodiola exert a strong protective action against a lethal heat shock. These adaptogens also significantly protect against the negative effect of superoxide radicals as induced by menadione. With respect to the protective action against exposure to heavy metals a small but significant protection was observed against intoxication with copper or cadmium by the phyto-adaptogens. In summary, there appears to be a difference in efficiency in enhancing resistance to the various stress conditions used (heat shock>menadione>copper>cadmium). Based on the results presented in this paper, we can conclude that phyto-adaptogens are able to enhance the resistance against the different stress conditions tested in developing individuals of Lymnaea. Although the degree to which resistance is enhanced appears to depend on the type of stressor applied, our results confirm the definition of phyto-adaptogens as being universal enhancers of non-specific resistance against different kinds of stress conditions. With respect to the mechanism of enhanced resistance, the question was asked whether this protective action is caused by an induction of heat shock proteins (hsps), which are known to be involved in tolerance and adaptation. The phyto-adaptogens did not induce the synthesis of any of the hsps, nor did they modulate the normal heat shock induced synthesis of these stress proteins. We conclude that it is unlikely that hsps play a major role in obtaining an enhanced state of resistance provided by phyto-adaptogens.

Animals↗
PubMedDate not supplied

Evidence for two states of thermotolerance.

The phenomenon of thermotolerance has been studied in three-day-old larvae of Lymnaea stagnalis (Pulmonata, Mollusca). The lethality of a test treatment (TT) of 1 h, 40.0 degrees C is greatly reduced by pretreatment at elevated temperatures. The induced thermotolerance shows characteristics which are dependent on duration and temperature of the pretreatment (conditioning treatment; CT). Thermotolerance induced by a CT of 1 h at greater than 38.0 degrees C is stable at least during 2 h at 25 degrees C, whereas thermotolerance induced by the lower temperatures decays partly. Five minute CTs at 33 and 35 degrees C induce thermotolerance as well; however, this fades completely within 1 h at 25 degrees C. The same level of tolerance is present after a 5 min CT at 38 degrees C, but this level continues to rise during 1 h at 25 degrees C. The induction of thermotolerance (CT 1 h) is suppressed only partly when protein synthesis is inhibited by puromycin. The effect of puromycin is relatively weaker at the lower conditioning temperatures. Furthermore, puromycin slows down the decay of thermotolerance. The influence of duration and temperature of heat treatment on the pattern of protein synthesis has been investigated by gel electrophoresis after incubation in [35S]methionine. Heat-shock proteins (hsp) are synthesized during 1 h incubation at 35, 37, and 38 degrees C, but not at 33 degrees C. Twenty-four hours at 33 degrees C does induce the synthesis of hsp. It is proposed that thermotolerance in Lymnaea is based on two states, a rather unstable one which is independent of hsp synthesis, and another more stable one, accompanied by hsp synthesis.

Adaptation, Physiological↗
PubMedDate not supplied

Thermotolerance induced by 2,4-dinitrophenol.

The capacity of 2,4-dinitrophenol (DNP) to induce thermotolerance in 3-day-old larvae of Lymnaea has been investigated. Induction of thermotolerance is dependent on the DNP concentration, the duration of treatment, and on the pH of the medium. Optimal conditions for the induction of thermotolerance are 10 min, 2.5 mM DNP at pH 4.7. Thermotolerance has been expressed in percentages of survival. Thermotolerance is maximal at 15 min after DNP treatment and decreases subsequently. DNP suppresses protein synthesis. Recovery starts 20 min after treatment, when thermotolerance is decreasing already. DNP does not induce the synthesis of the typical heat shock proteins (HSPs). It is concluded that DNP induces a state of thermotolerance of short duration, which is not accompanied by HSP synthesis.

2,4-Dinitrophenol↗
PubMedDate not supplied

Thermotolerance induced by heat and ethanol.

The effect of ethanol and heat on the thermosensitivity of 3-day-old larvae of the fresh water snail Lymnaea stagnalis is investigated, especially with regard to the kinetics of thermotolerance, the effect on protein synthesis and the pattern of proteins synthesized. Both stress factors, in a mild dose, induce a state of thermotolerance with the following characteristics: (i) it is not accompanied by an enhanced synthesis of HSPs, (ii) it needs only 10-30 min to develop maximally, and (iii) it decays within 60-90 min after it has been triggered. At a higher dose both factors induce an enhanced synthesis of the HSP 65, HSP 70, and HSP 87, and also a more stable state of thermotolerance beside the thermotolerant state present shortly after the trigger. It appears that the synthesis of HSPs is enhanced only when the overall protein synthesis is depressed. The data are discussed in relation to the putative functions of heat shock proteins. It is suggested that the constitutive levels of the HSPs provide the rapid protection against heat. An induced level of HSPs is necessary for the extension of the thermotolerant state.

Animals↗