Effect of protein synthesis inhibitors on sensitization of defence reaction and on cholinosensitivity of command neurons in Helix lucorum

We studied influence of protein synthesis inhibitors on short-term sensitization of Helix escape reaction and potentiation cholinosensitivity in command neurons. Inhibitor of protein synthesis anisomycin does not prevent behavioral sensitization. Anisomycin and irreversible inhibitor of protein synthesis saporin change the dynamics of cholinosensitivity potentiation in command neurons. The results Suggest that investigated sensitization of Helix escape reaction does not require synthesis of new proteins.     

Inhibitor of protein synthesis blocks long-term behavioral sensitization in the isolated gill-withdrawal reflex of Aplysia

To study the effects of protein synthesis inhibition on long-term sensitization of the gill- and siphon-withdrawal reflex of Aplysia, we have developed an isolated reflex preparation in which we could expose the inhibitor to only that part of the central nervous system involved in mediating the reflex and not to the other parts of the animal's central nervous system, thus minimizing the possible systemic side effects. We have found that long-term sensitization can be obtained in the isolated gill reflex, and that this long-term process, but not the short-term process, is blocked selectively by anisomycin, a reversible inhibitor of protein synthesis. Moreover, to obtain this blockade of long-term sensitization, this drug need only be applied during the training procedure.     

Participation of protein synthesis in brain cell structures in the action of antifeins on long-term memory]

Incorporation of 3H-leucine into proteins of rat brain cell structures during application of antifeins (compounds of alternative action on memory processes) has been studied. No correlation was observed between changes in protein synthesis in nuclei, mitochondria, components of endoplasmic reticulum and memory effects of ethyl-, allyl- and propylnorantifeins. Only M1 and M2-demethylated structural analogs of ethylnorantifeins (exerting the most effective action on RNA synthesis and retention of conditional reflexes) enhanced the synaptosomal protein synthesis.     

Mechanism of corticotropin action on adrenal protein synthesis. The effects of inhibitors of protein synthesis and calcium chelators

We have recently shown that beside a general stimulation of most adrenal proteins, corticotropin induces a marked increase in a specific adrenal cytosolic protein, protein E, in intact and hypophysectomized rats. To further clarify the mechanisms by which corticotropin exerts its trophic action we have investigated the effects of cycloheximide, calcium and calcium chelator administration on intact and hypophysectomized animals. These substances were injected in rats with or without corticotropin, and slices of adrenal glands from control and treated animals were removed 5 h later, incubated with [14C]- or [3H]-leucine for 2 h, and cytosolic proteins analyzed by polyacrylamide gel electrophoresis using a dual labelling technique. When high doses of cycloheximide (higher than 500 micrograms) were injected in rats, incorporation of labelled leucine in adrenal slices of control and corticotropin-treated animals was inhibited. With 500 micrograms cycloheximide per rat, incorporation of labelled leucine in adrenal slices of control animals was normal, but the corticotropin stimulation of both protein E and total protein synthesis was inhibited. Lower doses of cycloheximide (100 micrograms per rat) completely inhibited the stimulatory effect of corticotropin on total protein synthesis but did not affect protein E synthesis, while after 50 micrograms per rat both stimulatory effects were preserved. The two higher doses of cycloheximide (500 and 100 micrograms per rat) could not completely block the steroidogenic effect of the hormone. The effects of calcium and calcium chelators were studied in 1-day hypophysectomized rats. Calcium alone or injected simultaneously with corticotropin has no effect. Calcium chelators injected simultaneously with corticotropin partially inhibited the stimulatory effects of corticotropin on steroidogenesis but totally inhibited stimulation of total protein synthesis, while the stimulation of protein E persisted. Our results show that after corticotropin, stimulation of protein E synthesis correlates better with steroidogenesis than with total protein synthesis.     

Beta blockers in heart failure haemodynamics,clinical effects and modes of action

Treatment for heart failure may be directed at relieving symptoms and/or improving prognosis. One of the primary aims of research in heart failure is to alter the progressive decline in pump function and thereby improve prognosis.For many years, diuretics have been known as therapeutics in heart failure and they are very effective in symptom relief. Vasodilators and inotropes also have beneficial effects on symptom relief especially in the acute phase through changes in cardiac output, filling pressures and renal perfusion. However, although these treatments produce short-term relief, none have been shown to influence the disease process and thereby improve mortality. Indeed, many of these drugs may even lead to untoward long-term clinical outcomes as has been shown for example for milrinone and ibopamine.There is overwhelming evidence that drugs interfering with the neurohormonal activation in heart failure not only produce symptomatic relief but are also capable of attenuating disease progression with concomitant reductions in both morbidity and mortality. About a decade ago, convincing and large-scale evidence showed that ACE inhibitors produced favourable effects by antagonising the activated renin-angiotensin system. More recently, β-blockers, which antagonise the activated sympathetic system, were shown to be beneficial in the long term in moderate severe heart failure in terms of significant improvements in both morbidity and mortality. The RALES study further amplified the concept that drugs that interact in the neurohormonal system have beneficial effects. In this study, spironolactone, a weak, potassium-sparing diuretic counteracting aldosterone showed a reduction in mortality in more severe forms of heart failure.     

Specificity of interferon action in protein synthesis.

Inhibitors of elongation steps in protein synthesis such as cycloheximide and anisomycin mimic interferon treatment in that they specifically inhibit the synthesis of certain viral proteins. These specific effects are seen only at very low concentrations of the antibiotics, under conditions where host cellular protein synthesis, as well as cell viability, are not severely reduced. A qualitatively as well as quantitatively close correlation between the effects of the two types of agents has been established for encephalomyocarditis virus, vesicular stomatitis virus and murine leukemia virus protein synthesis. It is concluded that one of the primary mechanisms of interferon action may be a nonspecific retardation of one or more elongation steps, and that this may be sufficient to account for its effects on the replication of certain viruses such as encephalomyocarditis and vesicular stomatitis viruses.     

Conditioning and sensitization in the edible snail: the neurophysiological and metabolic characteristics]

Electrophysiological parameters and bound calcium (Ca(b)) level dynamics during sensitization development or conditioning of food aversion were studied in the command neurons of defense behaviour in the snail Helix lucorum. Responses evoked by a testing sensory stimulus were facilitated 50-60 min after the first sensitizing stimulation, while conditioned responses appeared 80-90 min after the first conditioning. It was the most essential electrophysiological difference between the long-term sensitization and conditioning. Analysis of the Ca(b)) dynamics in the neurons showed significant differences in calcium-dependent metabolism during the sensitization and conditioning, likely underlying the electrophysiological differences.     

Inhibition of protein synthesis during associative memory reactivation produces reversible or irreversible amnesia in the snail Helix lucorum

Effects of protein synthesis inhibitors on reactivation processes of food aversion conditioning were inverstigated in snail Helix lucorum. Protein synthesis inhibitor (PSI, anisomycin, 0.4 mg, or cycloheximede, 0.6 mg) was injected into snail body cavity 24 hours after 3-day training; then conditioned stimulus (banana) was presented and memory was tested. It was found that 2.5-3 hours after first reminding, associative food conditioning was suppressed, recovering of the conditioning was observed 4.5-5.5 hours after first reminding. In other group of snails, PSI injections were single (1.8 mg) or triple (0.6 mg with 2-hour interval). Reminding stimulus was presented after each injection. In this case, suppression of food aversion conditioning was also observed 2.5-3 hours after first reminding, while amnesia in this case lasted over 30 days. Repeated training of the group of snails recovered the food aversion conditioning only partially. In control snails (saline instead of PSI or 3 injections of PSI without reminding), foot aversion conditioning was detected 30 days after first training. Thus we found that PSI effects during reminding of food aversion conditioning produced two phases amnesia: (1) the easily suppressed by PSI transient phase lasted 2-3 hours, and (2) irreversible phase, its suppression by high doses of PSI-initiated amnesia lasting over 1 month. Second phase of amnesia was not recovered after repeated training. It was suggested that reminding induced reconsolidation of initial memory. Its suppression by protein synthesis inhibitors results in erasing of memory trace and disturbs repeated consolidation.     

Antioxidant effects and the therapeutic mode of action of calcium channel blockers in hypertension and atherosclerosis

Drugs currently known as calcium channel blockers (CCB) were initially called calcium antagonists because of their ability to inhibit calcium-evoked contractions in depolarized smooth muscles. Blocking the entry of calcium reduces the active tone of vascular smooth muscle and produces vasodilatation. This pharmacological property has been the basis for the use of CCBs in the management of hypertension and coronary heart disease. A major question is whether drugs reducing blood pressure have other effects that help prevent the main complications of hypertension, such as atherosclerosis, stroke, peripheral arterial disease, heart failure and end-state renal disease. Experimental studies that focus on this question are reviewed in the present paper.     

Self stimulation against a background of action of blockers of the synthesis of proteins and oligopeptides

The experiments on rabbits have demonstrated that blockade of protein synthesis by the administration of cycloheximide and actinomycin D abolishes self-stimulation in the central nervous system. The treatment with ACTH fragment (ACTH4-10) restored the self-stimulation. Unlike ACTH, injections of pentagastrin, Met-enkephalin, Leu-enkephalin and cholecystokinin were ineffective. The present study shows that ACTH4-10 plays an important role in genetic determination of self-stimulation behaviour.     

Mechanism of action of sparsomycin in protein synthesis.

Before CI isomerizes to C*I, we detect a competitive phase of inhibition (Ki = k5/k4 = 0.05 microM) which eventually, by increasing the concentration of I, becomes linear mixed noncompetitive and involves C*I in place of CI. The equilibration of C and I according to reaction 2 is much slower than the equilibration between C and S in reaction 1 (time-dependent inhibition). The inactivation plots obey reaction 2 and allow us to estimate k6 as equal to 2.2 min-1. The isomerized C*I, free of excess I, can be studied as a mixture with complex C. From the kinetics of the regeneration of C from C*I, in the presence of puromycin, we can estimate k7 to be between 0.22 min-1 and 0.06 min-1. Although the isomerized C*I survives after adsorption on cellulose nitrate filter disks, it does not survive after gel chromatography on a Sepharose CL-4B column but is converted quantitatively to complex C containing D of unchanged reactivity. This result does not support the proposed [Flynn, G. A., & Ash, R. J., (1990) Biochem. Biophys. Res. Commun. 166, 673-680] chemical reaction between D and I toward new products. The isomerized C*I can be obtained not only from the already-made complex C but also de novo from D, R, and M. In the latter case, the reactions which lead to C are represented by the following hypothetical scheme: D + R + M in equilibrium with DRM or C (binding reaction). When C*I is formed de novo, this reaction is coupled to reaction 2 and the ultimate product is a mixture of C and C*I.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibitor of protein synthesis blocks longterm behavioral sensitization in the isolated gill-withdrawal reflex of Aplysia

To study the effect of protein synthesis inhibition on long-term sensitization of the gill- and siphon-withdrawal reflex of Aplysia, we have developed an isolated reflex preparation in which we could expose the inhibitor to only that part of the central nervous system involved in mediating the reflex and not to the other parts of the animal's central nervous system, thus minimizing the possible systemic side effects. We have found that long-term sensitization can be obtained in the isolated gill reflex, and that this long-term process, but not the short-term process, is blocked selectively by anisomycin, a reversible inhibitor of protein synthesis. Moreover, to obtain this blockade of long-term sensitization, this drug need only be applied during the training procedure.     

Methiothepin-sensitive serotonin receptors are involved in postsynaptic mechanism of sensitization of Helix lucorum escape reaction

Tetanic electric stimulation of Helix foot evokes sensitization of escape reaction. This behavioral sensitization and posttetanic potentiation (PTP) of acetylcholine-induced inward current (ACh-current) in command Helix neurons of escape behavior were similar. Antagonist of serotonin receptors methiothepin prevents the PTP of the ACh-current and behavioral sensitization. Serotonin disrupts the PTP of the ACh-current. It is suggested that the increase in cholinosensitivity of the command neurons with the involvement of methiothepin-sensitive serotonin receptors may be the cellular postsynaptic mechanism of behavioral sensitization of Helix escape reaction.     

The long-term effects of the radiation action and induced genome instability

The intensive studies of the long-term effects of the radiation on human and animal cells allowed to reveal the row of new positions in the radiobiology and the genetics. One of the example is the determination of the fact that the genetic effects of the radiation action are not limited by the alterations detectable directly after the corresponding influences. It was found that this and other genome alterations (the chromosome and the gene mutations, transformation the reproductive cell death, the changes of the radiosensitivity and others) can appear de novo in it's sufficiently remote generations of the surviving cells. They differ in the spectrum and in the intensity from acute influence results and now unite with notion "induced genome instability". These discoveries made the studies of the regularities and of the mechanisms of forming of the genome instability in the whole organism of the human and animals more active. In this review about radiation induced instability of genome data are systematized in the accordance with the objects of the study: cultivated cells in vitro-->posterity of laboratory animals-->children born from irradiated parents-->adult people in the remote periods after irradiation.     

Selective involvement of opioids in mechanisms of synapse-specific plasticity in Helix lucorum snail during sensitization acquisition

Effects of met-enkephalin (opioid peptide) and naloxone (opioid antagonist) on nociceptive sensitization were studied in L-RP11 Helix neurons. In control snails sensitizing stimulation produced reversible membrane depolarization and depression of neural responses evoked by sensory stimuli during the short-term stage of sensitization and facilitation of these responses at the long-term stage. Met-enkephalin (10 but not 0.1 microM) suppressed the neural responses evoked by nociceptive stimuli. Sensitizing stimulation during metenkephalin application prevented the facilitation of neural responses evoked by tactile stimulation of snail head, whereas facilitation of neural responses evoked by chemical stimulation of head or tactile stimulation of foot were similar to that in control sensitized snails. Sensitizing stimulation during met-enkephalin and/or naloxone application prevented the facilitation of neural responses evoked by chemical stimulation of snail head, whereas responses evoked by tactile stimulation of snail head or foot were facilitated (as in neurons of control sensitized snails). Opioids are suggested to be involved in regulation of nociceptive mechanisms and selective induction of long-term plasticity in L-RP11 neural inputs activated by tactile of chemical stimulation of snail head.     

Electrophysiological and neurochemical study of long-term sensitization in the snail

The long-term sensitization of avoidance reflex was produced in snail Helix pomatia, which led to the remarkable increase in the pneumostome closures period. The formation of long-term sensitization is also accompanied by increase in excitability of command neurons of this reflex. One of the possible mechanisms of this phenomenon is the depolarization of these cells. The quantitative redistribution of water-soluble proteins with relative mobility 0.54 0.42 0.40 was also observed in the identified neurons, both included in the avoidance reflex (command neurons) and non-included (bursting neurons, nerve cells of pool D). The protein with the relative mobility of 0.75 was unique for the nerve cells of neurosecretory pool D in sensitized snails, and was never found in control animals.