Acid release at meiotic maturation of oocytes in the polychaete annelid Sabellaria alveolata.

ABout 1 pmole of acid per egg is released when prophasic oocytes undergo maturation under the action of sperm, proteases or ionophore A 23187. No similar acid release occurs at fertilization of matured oocytes. These findings are compared with data on Urechis and sea urchin.     

Acid release at meiotic maturation of oocytes in the polychaete annelidSabellaria alveolata

Summary About 1 pmole of acid per egg is released when prophasic oocytes undergo maturation under the action of sperm, proteases or ionophore A 23187. No similar acid release occurs at fertilization of matured oocytes. These findings are compared with data onUrechis and sea urchin.     

Protein synthesis inhibition induced by dimethylnitrosamine and diethylnitrosamine on isolated rat hepatocytes.

Time- and dose-dependent protein synthesis inhibition takes place following exposure to high doses of dimethylnitrosamine (DMN) or diethylnitrosamine (DENA) in isolated rat hepatocytes. The ability of DENA to depress protein synthesis is 5-fold higher than that of DMN. Cells inhibited by 60 min exposure to DMN or DENA, and then incubated in a nitrosamine-free medium, regain their initial rate of protein synthesis. This recovery is faster and more complete for DENA-treated cells.     

Protein synthesis inhibition induced by dimethylnitrosamine and diethylnitrosamine on isolated rat hepatocytes

Summary Time- and dose-dependent protein synthesis inhibition takes place following exposure to high doses of dimethylnitrosamine (DMN) or diethylnitrosamine (DENA) in isolated rat hepatocytes. The ability of DENA to depress protein synthesis is 5-fold higher than that of DMN. Cells inhibited by 60 min exposure to DMN or DENA, and then incubated in a nitrosamine-free medium, regain their initial rate of protein synthesis. This recovery is faster and more complete for DENA-treated cells.     

Calcium activity and post-ischemic suppression of protein synthesis

Increase in intracellular calcium concentration is a prominent feature of ischemia and has been considered a major factor in the initiation of ischemic pathology, which involves inhibition of protein synthesis. A reduction of calcium ion activity during and immediately after in vitro ischemia did not prevent inhibition of protein synthesis in hippocampae slices. When slices were overloaded with calcium by NMDA receptor activation or by the calcium ionophore A23187, no significant inhibition of protein synthesis was observed. We conclude that calcium overload plays only a limited role in ischemic inhibition of protein synthesis.     

Végétalisation de l'œuf de l'oursinParacentrotus lividus par l'hydrazide de l'acide isonicotinique (isoniazide)

Summary Isonicotinic acid hydrazide (isoniazid) causes vegetalization of whole larvae of the sea urchinParacentrotus lividus. The effects of isoniazid are compared with those of chloramphenicol and lithium ions. The protein synthesis during the phase of reversible determination, i.e. to the late blastula stage, appears to be of paramount importance in the differentiation of larvae. It is suggested that the protein synthesis connected with the determination of ectodermal structures is more sensitive to the action of vegetalizing agents than the protein synthesis connected with the determination of entomesodermal structures.     

Der Einfluss von Halothan und Chloroform auf die Feinstruktur und Proteinsynthese der Rattenleber

Summary Examinations by electron microscopic and autoradiographic techniques of whether chloroform and halothane alter protein synthesis in rat liver, demonstrate, that chloroform causes an early destruction of the granular endoplasmatic reticulum accompanied by a marked decrease of the protein synthesis in the centre of the acini. After anaesthesia with halothane, the granular endoplasmatic reticulum and the protein synthesis proved to remain unaffected.     

Inhibition of protein synthesis in ischaemic liver from phenobarbitone-treated rat.

Both ribosomal factors and cytosolic inhibitors are involved in the reduction of the rate of protein synthesis which occurs in the ischaemic hepatocyte from control and phenobarbitone-treated livers. Of these 2 factors it is the latter which seems to play a major role in determining the irreversible impairment of protein synthesis. Phenobarbitone administration has no effect on the rate of protein synthesis of ischaemic and post-ischaemic hepatocyte.     

Activation of GCN2 upon HIV-1 infection and inhibition of translation

Higher eukaryotic organisms have a variety of specific and nonspecific defense mechanisms against viral invaders. In animal cells, viral replication may be limited through the decrease in translation. Some viruses, however, have evolved mechanisms that counteract the response of the host. We report that infection by HIV-1 triggers acute decrease in translation. The human protein kinase GCN2 (eIF2AK4) is activated by phosphorylation upon HIV-1 infection in the hours following infection. Thus, infection by HIV-1 constitutes a stress that leads to the activation of GCN2 with a resulting decrease in protein synthesis. We have shown that GCN2 interacts with HIV-1 integrase (IN). Transfection of IN in amino acid-starved cells, where GCN2 is activated, increases the protein synthesis level. These results point to an as yet unknown role of GCN2 as an early mediator in the cellular response to HIV-1 infection, and suggest that the virus is able to overcome the involvement of GCN2 in the cellular response by eliciting methods to maintain protein synthesis.     

Protein synthesis in vivo in muscles of the growing lamb]

The relationship between incorporation of intravenously injected 14C lysine and specific radio-activity of precursor was used to estimate protein synthesis in muscle of growing lambs. The rate of protein synthesis per unit of muscle weight in Supraspinatus and Extensor digitorum longus decreased strongly from one week of age to puberty (10 weeks); afterwards it decreased in supraspinatus and increased slightly in Extensor digitorum longus. The rate of protein synthesis increase in muscle protein weight was constant during the whole experiment (1 week-16 weeks). In preruminant Lambs )1 week-5 weeks) the rate of protein synthesis per unit of muscle weight decreased; however, due to the increase in muscle weight, the rate of protein synthesis in whole muscle remained relatively constant. In order Lambs the rate of protein synthesis in whole muscle decreased. The turnover time of protein increased with age. These results give some explanation on muscular development of Lambs.     

Comparison of protein synthesis profiles in chronic lymphocytic leukaemia cells and B-lymphocytes from peripheral blood,cord blood and tonsil

2D-gel electrophoresis was used to investigate protein synthesis in leukaemic cells from a series of 15 chronic lymphocytic leukaemia (CLL) patients, and in non-malignant B-cell populations from different sources. The protein synthesis profiles of CD5+ B-cells from umbilical cord blood and from tonsil were determined, and the levels of expression of their proteins were observed to be similar to the CLL cells. The CD5-cells from cord blood resembled peripheral blood B-lymphocytes, and the protein synthesis profile of CD5-cells from tonsils was very complex. One protein was also identified which consistently appeared to be synthesised at a low level in CD5+ B-cells from tonsil but which was always more prominant in CLL cells and other non-malignant B-lymphocytes. On the basis of these data it is possible that the closest non-malignant counterpart to CLL is the CD5+ B-lymphocyte from cord blood.     

Eiweissvermehrung in ein- und zweikernigen systemen vonAcetabularia

Summary (1) The rate of protein synthesis was found to be different inAcetabularia crenulata andAcetabularia mediterranea the higher cytoplasmic protein synthesis inA. crenulata depending upon the diameter of the stalk.(2) In systems containing one or two nuclei, there was no difference in the rate of cytoplasmic synthesis of proteins. This corresponds to the diminution of size and efficiency of the nuclei in binucleated systems.(3) In interspecific grafts, the rate of cytoplasmic protein synthesis corresponds nearly to the rate of protein synthesis ofAcetabularia crenulata. Corresponding to morphogenetic processes, thecren-action is prevalent.     

Effect of acute administration of triiodothyronine in chicken. Liver glycogen depletion and amino acid incorporation to proteins

Summary Single injections of thyroid hormone (T₃) produce liver glycogen depletion in chickens. This effect cannot be suppressed by protein synthesis inhibitors and is previous to the hormone-induced increase in protein synthesis.     

The effect of temperature and protein synthesis on the renaturation of firefly luciferase in intact H9c2 cells

A mild increase in temperature that does not exert an effect on tolerance development or synthesis of heat shock proteins (Hsps) in control cells can stimulate these processes when applied to cells that have previously been heat shocked. To study the underlying mechanism of this effect, H9c2 cells were stably transfected with the gene encoding firefly luciferase (Luc). Heat-shock-induced inactivation of Luc and its subsequent reactivation is frequently used as a model for cellular protein denaturation and renaturation. Luc reactivation was determined following a damaging heat shock (43 or 44 degrees C for 30 min) in cells that were subsequently exposed to either control temperatures (37 degrees C) or various mild hyperthermic conditions (from 38.5 to 41.5 degrees C for 1 h). To prevent changes in Luc activity consequent to new synthesis of Luc, Luc reactivation was monitored in the presence of cycloheximide, an inhibitor of protein synthesis. The results showed that reactivation of Luc was inhibited when heat-treated cells were post-treated under mild hyperthermic conditions. The observed increase in Hsp synthesis under mild hyperthermic post-heat shock conditions therefore appears to be the result of an increase in the period during which denatured proteins are present. In addition, we studied Luc reactivation in the absence of protein synthesis inhibitors. This condition led to much higher Luc activity. By estimating half-life times of Luc, the contribution of new Luc synthesis in this recovery could be determined, and only partially explained the observed increase in Luc reactivation after heat shock. Thus the synthesis of other proteins must be important for the renaturation of heat-damaged proteins.     

Memory formation and the regulation of gene expression

On a cellular level, formation of memory is based on a selective change in synaptic efficacy that is both fast and, in case of important information, long-lasting. Rapidity of cellular changes is achieved by modifying preexisting synaptic molecules (receptors, ion channels), which instantaneously alters the efficacy of synaptic transmission. Endurance, that is the formation of long-term memory (LTM), is based on transient and perhaps also long-lasting changes in protein synthesis. A number of different methods exist to interfere with the synthesis of specific proteins or proteins in general. Other methods, in turn, help to identify proteins whose synthesis is changed following learning. These mostly molecular methods are briefly described in the present review. Their successful application in a variety of memory paradigms in invertebrates and vertebrates is illustrated. The data support the importance of selective changes in gene expression for LTM. Proteins newly synthesized during memory consolidation are likely to contribute to restructuring processes at the synapse, altering the efficiency of transmission beyond the scope of STM. Increased or, less often, decreased synthesis of proteins appears during specific time windows following learning. Recent evidence supports older data suggesting that two or even more waves of protein synthesis exist during the consolidation period. It is expected that the new molecular methods will help to identify and characterize molecules whose expression changes during LTM formation even in complex vertebrate learning paradigms.     

Végétalisation de l'œuf de l'oursinParacentrotus lividus par le chloramphénicol

Summary Chloramphenicol, an inhibitor of protein synthesis, causes a strong vegetalization of whole larvae of sea urchinParacentrotus lividus. Combination of chloramphenicol and lithium causes a stronger vegetalization than either of these agents alone. Chloramphenicol suppresses the animalizing effects of Evans blue and zinc ions. The effects of chloramphenicol are compared with those of lithium and phenazone. It is suggested that vegetalizing effects of chloramphenicol are connected with its inhibitory action on protein synthesis and the perturbations of ribonucleic acid metabolism.     

Effect of nonprotein thiols on protein synthesis in isolated rat hepatocytes

The ability of nonprotein thiols to modulate rates of protein synthesis was investigated in isolated rat hepatocytes. Addition of cysteine stimulates protein labelling by [¹⁴C] Leucine. Glutahione depletion, induced by in vivod administration of L-buthionine sulfoximine and diethylmaleate, did not alter the effect of cysteine, although it decreased the rate of protein synthesis by 32%. The effect of cysteine on protein synthesis does not seem to be related to a perturbatin of the redox state of the NAD⁺/NADH system or to changes in the rate of gluconeogenic pathway. The following observations indicate that cysteine may stimulate protein syntheis by increasing intracellular levels of aspartate: 1. Amino-oxyacetate, an inhibitor of pyridoxyal-dependent enzymes, inhibits protein labelling and decreases aspartate cellular content, whereas most amino acids accumulate or remain unchanged; 2. Cysteine, in the absence or in the presence of amino-ocycetate, stimulates protein labelling and induces aspartate accumulation, although mot amino acids diminish or remain unchanged.     

Zum Proliferations-Stoffwechsel der Rattenleber nach Teilhepatektomie. Autoradiographische Untersuchungen mit3H-Cytidin,-Phenylalanin und -Thymidin

Summary During the first wave of parenchymal liver regeneration in adult rats after partial hepatectomy, the cellular synthesis and migration of RNA and the metabolism of protein were studied by autoradiography following an injection of³H-cytidine or³H-l-phenylalanine and double injections of 1 of these precursors +³H-thymidine. The following results were obtained: the synthesis and migration of RNA and the metabolism of protein are enhanced under these conditions of proliferation. In spite of this, the relation of metabolic activity in nucleolus, karyoplasm and cytoplasm remains constant. By double injection techniques it is proved that no differences exist in migration of RNA into the cytoplasm and cytoplasmic protein synthesis between cells with or without DNA synthesizing nuclei.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Antibiotic activity of organic compounds and their average quasi-valence number

Summary It is shown that the average quasi-valence numbers of antibiotics inhibiting protein synthesis are well defined and lie in the region of average quasi-valence numbers of amino acids, while the average quasi-valence numbers of antibiotics inhibiting DNA or RNA synthesis have higher values. Possible explanations of these findings and their implications on the design and selection of antibiotics are discussed.     

Altered proteostasis in aging and heat shock response in C. elegans revealed by analysis of the global and de novo synthesized proteome

Protein misfolding and aggregation as a consequence of impaired protein homeostasis (proteostasis) not only characterizes numerous age-related diseases but also the aging process itself. Functionally related to the aging process are, among others, ribosomal proteins, suggesting an intimate link between proteostasis and aging. We determined by iTRAQ quantitative proteomic analysis in C. elegans how the proteome changes with age and in response to heat shock. Levels of ribosomal proteins and mitochondrial chaperones were decreased in aged animals, supporting the notion that proteostasis is altered during aging. Mitochondrial enzymes of the tricarboxylic acid cycle and the electron transport chain were also reduced, consistent with an age-associated energy impairment. Moreover, we observed an age-associated decline in the heat shock response. In order to determine how protein synthesis is altered in aging and in response to heat shock, we complemented our global analysis by determining the de novo proteome. For that, we established a novel method that enables both the visualization and identification of de novo synthesized proteins, by incorporating the non-canonical methionine analogue, azidohomoalanine (AHA), into the nascent polypeptides, followed by reacting the azide group of AHA by ‘click chemistry’ with an alkyne-labeled tag. Our analysis of AHA-tagged peptides demonstrated that the decreased abundance of, for example, ribosomal proteins in aged animals is not solely due to degradation but also reflects a relative decrease in their synthesis. Interestingly, although the net rate of protein synthesis is reduced in aged animals, our analyses indicate that the synthesis of certain proteins such as the vitellogenins increases with age.