Neoantigen Targetability in Progressive Advanced Melanoma

PURPOSE

The availability of (neo)antigens and the infiltration of tumors by (neo)antigen-specific T cells are crucial factors in cancer immunotherapy. In this study, we aimed to investigate the targetability of (neo)antigens in advanced progessive melanoma and explore the potential for continued T-cell-based immunotherapy.

EXPERIMENTAL DESIGN

We examined a cohort of eight patients with melanoma who had sequential metastases resected at early and later time points. Antigen-presenting capacity was assessed using IHC and flow cytometry. T-cell infiltration was quantified through multiplex immunofluorescence. Whole-exome and RNA sequencing were conducted to identify neoantigens and assess the expression of neoantigens and tumor-associated antigens. Mass spectrometry was used to evaluate antigen presentation. Tumor recognition by autologous T cells was assessed by coculture assays with cell lines derived from the metastatic lesions.

RESULTS

We observed similar T-cell infiltration in paired early and later metastatic (LM) lesions. Although elements of the antigen-presenting machinery were affected in some LM lesions, both the early and later metastasis-derived cell lines were recognized by autologous T cells. At the genomic level, the (neo)antigen landscape was dynamic, but the (neo)antigen load was stable between paired lesions.

CONCLUSIONS

Our findings indicate that subsequently isolated tumors from patients with late-stage melanoma retain sufficient antigen-presenting capacity, T-cell infiltration, and a stable (neo)antigen load, allowing recognition of tumor cells by T cells. This indicates a continuous availability of T-cell targets in metastases occurring at different time points and supports further exploration of (neo)antigen-specific T-cell-based therapeutic approaches for advanced melanoma.

Identification of a neo-epitope dominating endogenous CD8 T cell responses to MC-38 colorectal cancer

The murine MC-38 colorectal cancer model is a commonly used model for cancer with high mutational burden, which is sensitive for immune checkpoint immunotherapy. We set out to analyze endogenous CD8+ T cell responses to MC-38 neo-antigens in tumor-bearing mice and after anti-PD-L1 checkpoint therapy. Through combination of whole-exome sequencing analysis with mass spectrometry of MHC class I eluted peptides we could identify eight candidate epitopes. Of these, a neo-epitope encoded by a point-mutation in the sequence of the ribosomal protein L18 (Rpl18) strongly dominated the CD8+ T cell response to our MC-38 cell-line in comparison to a previously described neo-epitope in the Adpgk protein. Therapeutic vaccination with synthetic peptides induced CD8+ T cell responses against the mutated Rpl18 epitope, which controlled tumor growth in vivo. This immunologically dominant response to mutated Rpl18 is of great importance in the development and optimization of immunotherapeutic strategies with the MC-38 tumor model.

Sustained activation of the mammalian target of rapamycin nutrient sensing pathway is associated with hepatic insulin resistance, but not with steatosis, in mice

AIMS/HYPOTHESIS

Activation of nutrient sensing through mammalian target of rapamycin (mTOR) has been linked to the pathogenesis of insulin resistance. We examined activation of mTOR-signalling in relation to insulin resistance and hepatic steatosis in mice.

MATERIALS AND METHODS

Chronic hepatic steatosis and hepatic insulin resistance were induced by high-fat feeding of male C57BL/6Jico mice for 6 weeks. In addition, acute hepatic steatosis in the absence of insulin resistance was induced by pharmacological blockade of beta-oxidation using tetradecylglycidic acid (TDGA). mTOR signalling was examined in liver homogenates.

RESULTS

High-fat feeding caused obesity (p<0.001), hepatic steatosis (p<0.05) and hepatic insulin resistance (p<0.05). The phosphorylation of mTOR and its downstream targets p70S6 kinase and S6 ribosomal protein was two-fold higher in mice on a high-fat diet than in mice fed standard chow (all p<0.05) and associated with enhanced rates of protein synthesis. Acute induction of hepatic steatosis with TDGA had no effect on mTOR activity. The increased activity of the mTOR pathway in livers from mice on a high-fat diet could not be ascribed to diet-induced alterations in known modulators of mTOR activity such as circulating plasma leucine levels, phosphorylation of protein kinase B and AMP-activated protein kinase, and changes in mitochondrial function.

CONCLUSIONS/INTERPRETATION

High-fat diet induces increase of the mTOR nutrient sensing pathway in association with hepatic insulin resistance, but not with hepatic lipid accumulation as such.

Chronic hypoxia stimulates periarterial sympathetic nerve development in chicken embryo

BACKGROUND

Epidemiological findings suggest an association between low-for-age birth weight and the risk to develop coronary heart diseases in adulthood. During pregnancy, an imbalance between fetal demands and supply may result in permanent alterations of neuroendocrine development in the fetus. We evaluated whether chronic prenatal hypoxia increases arterial sympathetic innervation.

METHODS AND RESULTS

Chicken embryos were maintained from 0.3 to 0.9 of the 21-day incubation period under normoxic (21% O(2)) or hypoxic conditions (15% O(2)). At 0.9 incubation, the degree of sympathetic innervation of the embryonic femoral artery was determined by biochemical, histological, and functional (in vitro contractile reactivity) techniques. Chronic hypoxia increased embryonic mortality (32% versus 13%), reduced body weight (21.9+/-0.4 versus 25.4+/-0.6 g), increased femoral artery norepinephrine (NE) content (78.4+/-9.4 versus 57.5+/-5.0 pg/mm vessel length), and increased the density of periarterial sympathetic nerve fibers (14.4+/-0.7 versus 12.5+/-0.6 counts/10(4) microm(2)). Arteries from hypoxic embryos were less sensitive to NE (pD(2), 5.99+/-0.04 versus 6. 21+/-0.10). In the presence of cocaine, however, differences in sensitivity were no longer present. In the embryonic heart, NE content (156.9+/-11.0 versus 108.1+/-14.7 pg/mg wet wt) was also increased after chronic hypoxia.

CONCLUSIONS

In the chicken embryo, chronic moderate hypoxia leads to sympathetic hyperinnervation of the arterial system. In humans, an analogous mechanism may increase the risk for cardiovascular disease in adult life.

The diabetes-associated 3243 mutation in the mitochondrial tRNA(Leu(UUR)) gene causes severe mitochondrial dysfunction without a strong decrease in protein synthesis rate

Cells harboring patient-derived mitochondria with an A-to-G transition at nucleotide position 3243 of their mitochondrial DNA display severe loss of respiration when compared with cells containing the wild-type adenine but otherwise identical mitochondrial DNA sequence. The amount and degree of leucylation of tRNA(Leu(UUR)) were both found to be highly reduced in mutant cells. Despite the low level of leucyl-tRNA(Leu(UUR)), the rate of mitochondrial translation was not seriously affected by this mutation. Therefore, decrease of mitochondrial protein synthesis as such does not appear to be a necessary prerequisite for loss of respiration. Rather, the mitochondrially encoded proteins seem subject to elevated degradation, leading to a severe reduction in their steady state levels. Our results favor a scheme in which the 3243 mutation causes loss of respiration through accelerated protein degradation, leading to a disequilibrium between the levels of mitochondrial and nuclear encoded respiratory chain subunits and thereby a reduction of functional respiratory chain complexes. The possible mechanisms underlying the pathogenesis of mitochondrial diabetes is discussed.

RNA polymerase of vesicular stomatitis virus specifically associates with translation elongation factor-1 alphabetagamma for its activity

An RNA-dependent RNA polymerase is packaged within the virions of purified vesicular stomatitis virus, a nonsegmented negative-strand RNA virus, which carries out transcription of the genome RNA into mRNAs both in vitro and in vivo. The RNA polymerase is composed of two virally encoded polypeptides: a large protein L (240 kDa) and a phosphoprotein P (29 kDa). Recently, we obtained biologically active L protein from insect cells following infection by a recombinant baculovirus expressing L gene. During purification of the L protein from Sf21 cells, we obtained in addition to an active L fraction an inactive fraction that required uninfected insect cell extract to restore its activity. The cellular factors have now been purified, characterized, and shown to be beta and gamma subunits of the protein synthesis elongation factor EF-1. We also demonstrate that the alpha subunit of EF-1 remains tightly bound to the L protein in the inactive fraction and betagamma subunits associate with the L(alpha) complex. Further purification of L(alpha) from the inactive fraction revealed that the complex is partially active and is significantly stimulated by the addition of betagamma subunits purified from Sf21 cells. A putative inhibitor(s) appears to co-elute in the inactive fraction that blocked the L(alpha) activity. The purified virions also package all three subunits of EF-1. These findings have a striking similarity with Qbeta RNA phage, which also associates with the bacterial homologue of EF-1 for its replicase function, implicating a possible evolutionary relationship between these host proteins and the RNA-dependent RNA polymerase of RNA viruses.

A positive and reversible relationship between adrenergic nerves and alpha-1A adrenoceptors in rat arteries

We evaluated the relationship between the presence of adrenergic nerves and the presence of alpha-1 adrenoceptors (alpha-1 AR) in the arterial tree of the rat. The thoracic aorta and the carotid, mammary, renal and femoral arteries were isolated from 20-week-old male WKY rats, along with the superior mesenteric artery and small (first order) and resistance-sized (third order) side branches of this vessel. Norepinephrine content ([NE]) and specific binding of 300 pM [3H]prazosin were determined. To estimate the total density of alpha-1 AR ([alpha-1 AR]) as well as the density of alpha-1A AR ([alpha-1A AR]), binding experiments were performed with and without pretreatment of the preparations with the irreversible alpha-1B AR and alpha-1D AR antagonist chloroethylclonidine and in the absence and presence of the alpha-1A AR selective ligand (+)-niguldipine (30 nM). Also the presence of mRNA for alpha-1A AR was evaluated by use of reverse transcriptase-polymerase chain reaction (RT-PCR). In intact rats, arterial [NE] ranged between 0.1 and 15 ng/microgram DNA, arterial [alpha-1 AR] ranged between 12.4 and 46.8 fmol/mg protein and [alpha-1A AR] ranged between 0.05 and 27.9 fmol/mg protein. There was no significant correlation between [alpha-1 AR] and [NE]. However, with respect to the [alpha-1A AR] a significant correlation between [NE] and [alpha-1A AR] was observed. RT-PCR analysis confirmed the expression of alpha-1A AR in the densely innervated mesenteric resistance-sized arteries. Two weeks after chemical sympathectomy of the rats with 6-hydroxydopamine (i) arterial [NE] was markedly reduced, and (ii) a distinct reduction in the [alpha-1A AR] as percentage of the total [alpha-1 AR] density in mesenteric artery side branches was noted. These findings indicate that there is a positive and reversible relationship between the presence of adrenergic nerves and that of alpha-1A AR in rat arteries.

Termination of quiescence in crustacea. The role of transfer RNA aminoacylation in the brine shrimp Artemia

In quiescent embryos of the brine shrimp Artemia, the level of aminoacylation of transfer RNAs is low. During resumption of development the charging level of transfer RNAs increases, concomitant with the activation of protein synthesis. The total level of charging rises dramatically from an average of 4% to 50% within a period of 24 h of development. The restriction of in vitro translation of the quiescent embryo extract can be partially released by the addition of charged aminoacyl-tRNA, which apparently starts the flow of ribosomes into polyribosome structures. Complete reactivation of translation by aminoacyl-tRNA occurs when mRNA from preformed mRNA-ribosome complexes, like the polyribosomes extracted from developing embryos or poly(U)-programmed ribosomes, are offered to quiescent embryo extracts. With respect to the mechanism of in vivo recharging of tRNAs, we observed that the level of several aminoacyl-tRNA synthetases increase during development. Methionyl-tRNA synthetase rises more than 10-fold. In the case of valyl-tRNA synthetase, the activation is lower and shown to be due to the de novo synthesis of its mRNA and the corresponding protein product as well. We conclude that protein synthesis and thereby the gradual animation of cryptobiotic Artemia embryos is determined to a large extent by the rate by which aminoacyl-tRNAs are replenished during development at both the initiation and elongation level.

Reduced responsiveness of rat mesenteric resistance artery smooth muscle to phenylephrine and calcium following myocardial infarction

1. We evaluated responses of peripheral resistance arterial smooth muscle to alpha 1-adrenoceptor stimulation in a rat model of heart failure in relation to neurohumoral changes, wall structure, receptor density and cellular calcium handling. 2. Plasma samples and third order mesenteric artery side-branches were obtained from Wistar rats after induction of left ventricular infarction (M1) or sham surgery. Vessels were denuded of endothelium, sympathectomized, depleted of neuropeptides, and mounted in a myograph for recording of isometric force development in response to calcium, agonist and high potassium. Also, the morphology of these preparations was determined. Separate vessel segments were used in radioligand binding assays with [1H]-prazosin. 3. At 1 week after MI, circulating plasma levels of adrenaline, angiotensin II, atrial natriuretic factor (ANF) and vasopressin were significantly elevated. At 5 weeks only a significant elevation of ANF persisted. 4. At 5 weeks after MI, the structure of the vessels and responsiveness to high potassium or Bay K 8466 (10(6) mol l-1) were not modified. Yet, at this stage, sensitivity to phenylephrine was increased (pD2: 6.24 +/- 0.04 vs 5.98 +/- 0.04 for controls) while maximal contractile responses to phenylephrine in the presence of 2.5 mmol l-1 calcium (2.26 +/- 0.28 vs 3.53 +/- 0.34 N m-1) and the sensitivity to calcium in the presence of phenylephrine (pD2: 2.81 +/- 0.22 vs 3.74 +/- 0.16) were reduced. Responses to the agonist in calcium-free solution and the calcium sensitivity in the presence of 125 mmol l-1 potassium or of phorbol myristate acetate (PMA, 10(-6) mol l-1) were not altered. 5. At 5 weeks after MI, the density of prazosin binding sites was not reduced (4.04 +/- 1.40 vs 2.29 +/- 0.21 fmol microgram-1 DNA in controls). 6. In conclusion, myocardial infarction leads in the rat to a reduction of contractile responses of mesenteric resistance arterial smooth muscle to alpha 1-adrenoceptor stimulation. This seems to involve impaired agonist-stimulated calcium influx.

Alpha 1-adrenoceptor subtypes in rat aorta and mesenteric small arteries are preserved during left ventricular dysfunction post-myocardial infarction

OBJECTIVE

In heart failure, homologous downregulation of beta-adrenoceptors contributes to impaired adrenergic responsiveness of the myocardium. We evaluated alpha 1-adrenoceptors (alpha 1-AR) in a sparsely innervated and a densely innervated peripheral artery in an experimental model of left ventricular dysfunction post-myocardial infarction.

METHODS

[3H]Prazosin binding was determined in arterial segments of Wistar-Kyoto rats (WKY), and of Wistar rats 5 weeks after myocardial infarction (MI) or sham operation (SHAM).

RESULTS

In the thoracic aorta (TAO) of WKY, specific prazosin binding was: (i) prevented by the irreversible alpha 1B-AR and relatively selective alpha 1D-AR antagonist, chloroethylclonidine (CEC); (ii) displaced with low affinity (pKi 6.25) by the alpha 1A-AR selective ligand, (+)-niguldipine; and (iii) displaced with both high (pKi 10.4) and low (pKi 7.37) affinity by the alpha 1D-AR antagonist, BMY 7378. In mesenteric small arteries (MSA) of WKY, prazosin binding was: (i) reduced 50% by CEC; (ii) displaced in a biphasic fashion by (+)-niguldipine (pKi 8.60 and pKi 6.22); and (iii) displaced by BMY 7378 with low affinity only (pKi 6.86). Also in TAO of SHAM. prazosin binding was prevented by CEC, but neither 30 nM (+)-niguldipine nor 1 nM BMY 7378 affected it. In MSA of SHAM, prazosin binding was virtually abolished in the presence of 30 nM (+)-niguldipine and was not reduced by 1 nM BMY 7378. In TAO and MSA of MI, compared to SHAM, the density of binding sites tended to be increased rather than decreased and neither the affinity for the ligand nor the effects of alpha 1-AR subtype selective tools were significantly modified.

CONCLUSIONS

These findings indicate that: (i) radioligand binding can be applied in intact arterial segments to quantify and characterize alpha 1-AR; (ii) although differences seem to exist between rat strains, alpha 1B-AR and alpha 1D-AR predominate in rat thoracic aorta and alpha 1A-AR and alpha 1B-AR in mesenteric small arteries; and (iii) alpha 1-AR density is not reduced in the poorly innervated aorta and the densely innervated mesenteric small arteries of rats with heart failure due to myocardial infarction.

Immunofluorescence studies of human fibroblasts demonstrate the presence of the complex of elongation factor-1 beta gamma delta in the endoplasmic reticulum

The eukaryotic elongation factor-1 (EF-1) consists of four subunits, EF-1 alpha, EF-1 beta, EF-1 gamma and EF-1 delta which induce efficient transfer of aminoacyl-tRNA to the ribosome. In this process EF-1 alpha.GTP acts as the carrier of the aminoacyl-tRNA on its way to the ribosome. After release of aminoacyl-tRNA to the ribosome under concomitant hydrolysis of GTP, the inactive EF-1 alpha.GDP form is recycled to EF-1 alpha.GTP by EF-1 beta gamma delta. In eukaryotic cells the concentration of EF-1 alpha exceeds that of the complex beta gamma delta by a factor of 5–10. In order to delineate the intracellular localization of the different subunits of EF-1, antibodies against the EF-1 subunits have been elicited and indirect immunofluorescence microscopy experiments were performed. In human fibroblasts, the guanine nucleotide exchange part of EF-1, EF-1 beta gamma delta, was found to co-localize with the endoplasmic reticulum (ER), displaying a distinct fine-structure in its staining pattern. The guanine nucleotide-binding subunit of EF-1, EF-1 alpha, shows a more diffuse distribution throughout the cytoplasm and is, in addition, associated with the nucleus.

Valyl-tRNA synthetase from Artemia. Purification and association with elongation factor 1

Two components of the protein biosynthetic machinery, valyl-transfer RNA synthetase (VRS) and elongation factor 1 (EF-1), have been isolated as a complex from several mammalian tissues. However, yeast VRS, which lacks an amino-terminal extension, does not associated with EF-1. We purified VRS from the brine shrimp Artemia and investigated its interaction with EF-1. Western blotting of crude Artemia extracts revealed the presence of two forms of VRS, differing in size and capacity to associate with EF-1. About 80% of the total VRS corresponds to a polypeptide of 130 kDa which behaves as a monomer upon gel filtration. Only the larger form of 140 kDa coelutes, cosediments and co-immunoprecipitates with the EF-1 alpha 2 beta gamma delta complex. The ratio of the two forms of VRS remains constant throughout early development. The possible origin and mode of expression of the two forms of VRS present in Artemia are discussed.

The subunit structure of elongation factor 1 from Artemia. Why two alpha-chains in this complex?

Elongation factor 1 (EF-1) regulates the specific interaction of aminoacyl-tRNA with the ribosome during the elongation phase of protein biosynthesis. Although individual functions of its separate chains have been well defined, to date there is hardly information about the structure and function of the whole complex. We describe here the complete subunit structure of elongation factor 1, and discuss its change during development of Artemia. Elongation factor 1 consists of a pentameric complex, composed of four different subunits alpha, beta, gamma, and delta in a molar ratio of 2:1:1:1. Although one molecule of EF-1 alpha dissociates easily from the complex EF-1 alpha 2 beta gamma delta under the influence of aminoacyl-tRNA and GTP, the second molecule of EF-1 alpha was found to remain firmly attached. Thus, in eukaryotic protein synthesis, movement of transfer RNAs to the ribosome seems under the influence of two distinct molecules of EF-1 alpha, a result possibly related to the presumed consumption of two molecules of GTP by EF-Tu during the elongation step of prokaryotic protein synthesis.

Effects of a 10-month endurance-training program on performance of speeded perceptual-motor tasks

This study investigated the effects of a 10-mo. endurance-training program (running) on speeded psychometric skills. On a weekly basis the experimental group of 36 subjects participated in one supervised and three unsupervised training sessions. The control group of 22 subjects engaged in no structural training activities during this period. Subjects' performance on a simple reaction-time task, a choice reaction-time task, and a letter-recognition task was assessed before and after the training intervention. Analysis indicated that a 20% improvement in aerobic fitness in the trained group was not accompanied by a significant improvement in psychometric performance. This result is discussed in terms of the relationship between aerobic fitness and cognitive performance. It is concluded that improved physical fitness is not necessarily accompanied by improved perceptual-motor skills.

DNA synthesis in isolated arteries of normotensive and hypertensive rats: effects of the endothelium

OBJECTIVES

To compare DNA synthesis in isolated arteries of normotensive and hypertensive rats and to evaluate whether removal of the endothelium affects this process.

DESIGN

Carotid and renal artery segments were isolated from normotensive Wistar, Wistar-Kyoto (WKY) and Sprague-Dawley rats, and from spontaneously hypertensive rats (SHR), transgenic Sprague-Dawley rats harbouring the mouse Ren-2 gene and from WKY rats rendered hypertensive by aortic coarctation.

METHODS

Artery segments were exposed in vitro to serum with or without previous gentle removal of the endothelium. Nuclear incorporation of the thymidine analogue 5-bromo-2'-deoxyuridine was visualized by immunocytochemistry and the percentage of labelled medial nuclei was determined.

RESULTS

In both types of artery, obtained from 6-week-old WKY rats and from 6-week-old SHR, removal of endothelium increased the percentage of 5-bromo-2'-deoxyuridine-labelled medial nuclei (L%). Also, in the arteries of 20-week-old Wistar rats, WKY rats and WKY rats rendered hypertensive by aortic coarctation and in vessels of 11-week-old Sprague-Dawley rats and Sprague-Dawley rats harbouring the mouse Ren-2 gene, removal of endothelium increased L%. Conversely, in the arteries of 20-week-old SHR removal of the endothelium did not alter L%. Furthermore, maximally stimulated DNA synthesis was considerably smaller in de-endothelialized arteries of adult SHR than in denuded vessels from the other strains and models.

CONCLUSION

These findings confirm that the endothelium can reduce DNA synthesis in the intact rat arterial smooth muscle. This effect is not modified by hypertension, but is selectively reduced in the arteries of adult SHR.

Prolonged endurance exercise and blood coagulation: a 9 month prospective study

To study the long-term overall effect of physical exercise on blood coagulation, 20 sedentary males and 15 sedentary females were trained three to four times a week with increasing intensity for 9 months. After 24 and 36 weeks all subjects ran a 15 km and a half-marathon (21 km) race, respectively. Blood samples were drawn before the training programme, 5 days before both races and 5 days after the half-marathon run. Plasma factor VIII coagulant activity and von Willebrand factor antigen concentration did not increase during the training programme. In both males and females plasma fibrinogen concentration was not enhanced after 24 weeks of training but increased in preparation for the 21 km race and was still raised significantly (P < 0.01) 5 days later. No significant changes in plasma thrombin-antithrombin III concentrations were observed in either group during the training programme. The results of this study demonstrate that an exercise programme of increasing intensity induces physical stress which has significant effects on plasma fibrinogen concentrations, even at rest. However, in contrast to acute post-exercise effects, a regular physical fitness programme does not induce a long-term activation of the haemostatic system.

Statistical evidence for remnants of the primordial code in the acceptor stem of prokaryotic transfer RNA

The specificity of interaction of amino acids with triplets in the acceptor helix stem of tRNA was investigated by means of a statistical analysis of 1400 tRNA sequences. The imprint of a prototypic genetic code at position 3-5 of the acceptor helix was detected, but only for those major amino acids, glycine, alanine, aspartic acid, and valine, that are formed by spark discharges of simple gases in the laboratory. Although remnants of the code at position 3-5 are typical for tRNAs of archaebacteria, eubacteria, and chloroplasts, eukaryotes do not seem to contain this code, and mitochondria take up an intermediary position. A duplication mechanism for the transposition of the original 3-5 code toward its present position in the anticodon stem of tRNA is proposed. From this viewpoint, the mode of evolution of mRNA and functional ribosomes becomes more understandable.

Endothelial modulation of DNA synthesis in isolated arteries of the rat

The endothelium can modulate the supply of growth factors to the underlying smooth muscle. In vitro experiments suggest that it may also influence the responsiveness of arterial smooth muscle to mitogens. In these experiments, we measured DNA synthesis in segments of carotid and renal arteries that were isolated from Wistar-Kyoto (WKY) rats and exposed to serum. Nuclear incorporation of the thymidine analogue, 5-bromo-2'-deoxyuridine (BrdUrd), was visualized by immunocytochemistry and the percentage of labeled nuclei (BrdUrd L%) was determined in the tunica media. In both types of artery isolated from 6- and 20-week-old WKY rats, mechanical removal of endothelium increased the BrdUrd L% in the tunica media. In carotid arteries of 20-week-old WKY rats, gentle denudation increased the incorporation of [3H]thymidine but not [14C]leucine. In denuded renal arteries of adult WKY rats, exogenous prostaglandin E2, iloprost, and transforming growth factor-beta (TGF-beta) reduced media labeling, which was not affected by Na nitroprusside. In renal arteries with endothelium, methylene blue and indomethacin did not affect medial DNA synthesis. These findings demonstrate that in arteries of young and adult rats, the endothelium reduces stimulated DNA synthesis. It is unlikely that basal production of nitric oxide or prostaglandins is involved herein. Endothelial inhibition of DNA synthesis but not protein synthesis in arteries indicates that the endothelium may influence the extent of arterial smooth muscle hypertrophy and hyperplasia.

Changes in blood glutathione concentrations, and in erythrocyte glutathione reductase and glutathione S-transferase activity after running training and after participation in contests

Previously sedentary men (n = 23) and women (n = 18) were trained to run a half marathon contest after 40 weeks. Total blood glutathione had increased by 20 weeks of training and had returned to normal after 40 weeks. Erythrocyte glutathione reductase activity had increased by 20 weeks and remained elevated after 40 weeks. This effect was accompanied by decreases in glutathione reductase coefficients, which indicated that increases in the presence of riboflavin may have been responsible for the changes in reductase activity. Erythrocyte glutathione S-transferase activity had increased slightly after 20 weeks of training and a much more marked increase was found after 40 weeks. This may have been indicative of the occurrence of lipid peroxidation in this phase of training. The participants ran a 15-km race after the first 20 weeks of training and a half marathon after 40 weeks. Blood glutathione tended to decrease after the 15-km race and increased after the half marathon. In both cases it had returned to normal values 5 days after the race. Erythrocyte glutathione reductase was elevated 1 day after the races, and had returned to normal after 5 days. This could also have been explained from concurrent changes in the riboflavin content of the erythrocytes. Erythrocyte glutathione S-transferase activity decreased after both races, but was restored 5 days after the half marathon while such was not the case after the 15-km race.

A major substrate of maturation promoting factor identified as elongation factor 1 beta gamma delta in Xenopus laevis

Protein synthesis is believed to be under control of the cell cycle during meiosis and mitosis. Any relationship between substrates for cdc2 kinase and components of the protein synthetic apparatus would therefore be of prime importance. During meiosis of Xenopus laevis oocytes one of the substrates for this kinase is a p47 protein, which is complexed to two other proteins, P36 and P30. Judged from partial amino acid sequence data on P47 and P30, the P30 and P47 proteins were reported to resemble the protein synthetic elongation factors (EF) 1 beta and 1 gamma from Artemia salina (Bellé, R., Derancourt, J., Poulhe, R., Capony, J.P., Ozon, R., and Mulner-Lorillon, O. (1989) FEBS Lett. 255, 101-104). This paper shows that the complex composed of P30, P47, and P36 from Xenopus is identical to the complex of EF-1 beta, EF-1 gamma, and EF-1 delta from Artemia according to two criteria. 1) Both stimulate elongation factor 1 alpha-mediated transfer RNA binding to ribosomes and exchange of guanine nucleotides on elongation factor 1 alpha to a comparable degree. 2) Each of the three subunits of the protein complex P30.P47.P36 from Xenopus shows a structural homology with one of the corresponding subunits of EF-1 beta gamma delta from Artemia. Presumably the phosphorylation of EF-1 gamma, which associates with tubulin at least in vitro, is important in processes following the onset of meiosis which is accompanied by a rise of protein synthesis.

In vivo DNA synthesis is not uniformly increased in arterial smooth muscle of young spontaneously hypertensive rats

We compared the distribution of DNA synthesis over the arterial tree of young normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) with marginally elevated blood pressure. Six-week-old male SHR and WKY rats were therefore infused with 5-bromo-2'-deoxyuridine (BrdUrd) for 2 days and the nuclear incorporation of the thymidine analogue in the media of various arteries was determined by immunohistochemistry. In WKY rats, 2.5% of the arterial smooth muscle nuclei in elastic, muscular and resistance arteries incorporated BrdUrd. In SHR, DNA synthesis was more marked in large arteries than in resistance arteries. It was in addition significantly larger in the aorta, superior mesenteric, renal and femoral arteries of the SHR than in those of the WKY rats. However, nuclear incorporation of BrdUrd in vivo did not differ between SHR and WKY rats in aortic endothelium, carotid arterial smooth muscle, nor in mesenteric or renal resistance arteries. Between 6 and 20 weeks of age, the number of nuclear profiles per media cross-section did not increase in large arteries of WKY rats and SHR. During this period of time, however, carotid artery and thoracic aorta weight and DNA content increased. SHR large arteries gained more DNA than those of WKY rats. These data indicate that DNA synthesis is uniformly distributed over the arterial system in young WKY rats and that DNA synthesis is elevated in the smooth muscle of large arteries of 6-week-old SHR but not in their resistance arteries.

Body composition and sleeping metabolic rate in response to a 5-month endurance-training programme in adults

This study examined the effect of exercise training on body composition and sleeping metabolic rate (SMR) in 15 men and 13 women who participated in a 20-week training programme aimed at running a half marathon. Body mass (BM) was measured after waking up, fasted and with an empty bladder. Body composition was assessed using densitometry. The SMR was measured from 0300-0600 hours during an overnight sleep in a respiration chamber. Assessment of SMR was at least 36 h after the last period of exercise training. After 20 weeks of endurance training no change in BM was observed. However, body composition changed significantly. On average men lost 2.4 kg body fat (P less than 0.01) and gained 1.7 kg fat free mass (FFM) (P less than 0.01). In women fat loss averaged 0.9 kg after 20 weeks (P less than 0.01), while FFM increased by 1.0 kg (P less than 0.05). Loss of fat mass was significantly larger in males (P less than 0.05). No changes in SMR were found, either in absolute terms, or when normalised for BM or FFM. Therefore, we have concluded that exercise training has no chronic, long-term effect on SMR. A possible explanation for this outcome in view of the different findings in similar studies is discussed.

DNA synthesis in isolated arteries. Kinetics and structural consequences

We evaluated changes in DNA synthesis, structure, and mechanical activity in isolated arteries during exposure to growth factors. Renal arteries were isolated from rats, sympathectomized, denuded of endothelium, and maintained in tissue culture. Up to 4 days of culture did not affect maximal contractile responses to depolarization. From the results of nuclear incorporation of the thymidine analogue 5-bromo-2-deoxyuridine (BrdUrd), culture stimulated DNA synthesis. In the media, incorporation of BrdUrd was maximal after 3 days but fell precipitously thereafter. Culture of arterial segments did not, however, increase the cross-sectional area of the media, the ploidy of the arterial nuclei, or the number of medial cells. In contrast, new layers of cells, part of which displayed smooth musclelike properties, developed at the border of the segments. The outermost edge of this newly formed layer continued to incorporate BrdUrd for at least 2 wk. These data demonstrate that stimulation of DNA synthesis by continuous exposure of the arterial wall to exogenous growth factors is 1) transient in the media; 2) does not, at least initially, compromise contractile reactivity; 3) does not alter gross medial structure; but 4) leads to proliferation of smooth musclelike cells outside the media. These findings suggest that the number of smooth muscle cells in the arterial media is maintained constant in the presence of even strong mitogenic stimuli.

The effect of a 5-month endurance-training programme on physical activity: evidence for a sex-difference in the metabolic response to exercise

The effect of a 5-month endurance training programme on physical activity and average daily metabolic rate (ADMR) was studied. Subjects were 16 males and 16 females preparing for a half marathon. Total physical activity, measured using an accelerometer, had increased by 62% and 63% after 20 weeks in males and females, respectively. Physical activity during the non-exercise part of the day did not change although in males it tended to increase (15%, NS). The ADMR had increased significantly in males after 8 and 20 weeks (+2.3 and +3.3 MJ.day-1, respectively, P less than 0.05) and exceeded the net energy expenditure for endurance-training three to four times. In females no significant increase in ADMR was found (+1.5 and +1.3 MJ.day-1, after 8 and 20 weeks, respectively). In females the change in ADMR could be largely attributed to the net cost of running itself and a small increase (10%) in resting metabolic rate during the time of day they were awake. In males a discrepancy was observed between the increase of ADMR and the expenditure due to exercise and non-exercise activities. We suggest exercise stimulates habitual physical activity and diet-induced thermogenesis in males but not in females.

Elongation factor 1 beta of artemia: localization of functional sites and homology to elongation factor 1 delta

Elongation factor (EF)-1 beta, a 26 kDa protein, is the eukaryotic equivalent of bacterial EF-Ts, the nucleotide exchange factor in protein synthesis. EF-1 beta catalyzes the exchange of guanine nucleotides bound to EF-1 alpha; the latter protein is the eukaryotic equivalent of bacterial EF-Tu. Limited proteolytic cleavage studies on EF-1 beta lead to the following picture: the protein is composed of two domains, an aminoterminal and a carboxyterminal domain, connected to each other by a stretch of hydrophilic, charged amino acids situated in the middle of the molecule. The carboxyterminal domain supplies the catalytic site for the nucleotide exchange reaction, whereas the aminoterminal domain interacts with EF-1 gamma, the third component of elongation factor 1. The regulatory, serine phosphate residue, Ser-89, localized in the hydrophilic stretch of EF-1 beta, does not appear to be necessary for the basic exchange reaction. The fourth component of the high molecular weight elongation factor complex (EF-1H), named EF-1 delta or 28 K protein, is homologous to EF-1 beta and contains regions very similar to the carboxyterminal part. EF-1 delta was found to be active in the nucleotide exchange reaction.

Transfer RNAs for primordial amino acids contain remnants of a primitive code at position 3 to 5

Analysis of the nucleotide sequence of 1,400 transfer RNAs has revealed the imprint of a prototypic genetic code in position 3-4-5 of the acceptor stem. It appears only in the transfer RNAs for the primordial amino acids ie those found by chemical condensation of a nitrogen-methane-water-ammonia mixture. The model for primitive protein synthesis as mentioned by Crick assumes a direct interaction between the amino acid and a prototypic adaptor oligonucleotide. This has hitherto appeared irreconcilable with the large spatial separation between the aminoacylation site and the anticodon in present day transfer RNAs. The observations reported here show how this paradox can be resolved by a process of duplication and cleavage of a prototypic adaptor.

Plasma activity of muscle enzymes: quantification of skeletal muscle damage and relationship with metabolic variables

One hundred fourteen sedentary volunteers (34 +/- 8 years) took part in an endurance training study to be completed after 18-20 months with a marathon. Ultimately, 60 males and 18 females achieved that goal. The training program, carefully supervised, was divided into three periods with a maximum of 45-, 70-, and 110-km week training volume and concluded with a performance race of 15, 25, and 42.2 km, respectively. Three days before and 3 and 5 days after each race, 35 subjects were selected to perform a progressive treadmill test and the remaining subjects participated in field tests of 400 and 1000 m. A significant decrease in half-life time of CK enzyme plasma activity after running long distances in the course of the study from 20 h to 13 h was observed. Based on plasma enzyme activity and supposing that the total enzyme content left the muscle fiber, the estimated amount of muscle damage was found to be small. A gender difference in plasma enzyme activity increase (females demonstrated a lower increase) occurred only after the marathon.

Changes in basal plasma testosterone, cortisol, and dehydroepiandrosterone sulfate in previously untrained males and females preparing for a marathon

In the present study 25 males and 11 females were monitored for an 18- to 20-month training period during which the training distance was gradually increased. The training period was divided into three periods of 6, 5, and 7 months, respectively. The first, second, and third period were concluded with a 15-, 25-, and 42-km road race, respectively. The competitive distance always exceeded the maximal distance covered in any previous training session. Before and after three contests of 15, 25, and 42.195 km, the plasma concentration of testosterone, cortisol, and dehydroepiandrosterone sulfate (DHEAS) were determined. The decrease of plasma testosterone concentration in males was dependent on the distance of the contests. Moreover, the plasma testosterone concentration was increased in males during the course of the training period. In females no clear relation between plasma testosterone levels and the contests could be observed, and no changes in basal levels were found in the course of the training period. DHEAS seems to be a more useful stress marker than the plasma cortisol concentration. The plasma levels of this hormone remained elevated both in males and females for 1-2 days after the contests. The amplitude of DHEAS increments, however, was greater after the marathon.

Platelet system changes associated with a training period of 18-20 months: a transverse and a longitudinal approach

The effect of training for a 42-km run was investigated for the platelet count, the platelet distribution width (PDW), the mean platelet volume (MPV), and the plateletcrit (PCT). The measuring points were the start and 1 week before and 1 week after each contest (15, 25, and 42 km). For the starting position we reassessed the reference value for each platelet parameter. The results of all measuring points were compared transversely and longitudinally. As a result of the transverse approach, we found a significant decrease of the platelet count and of the MPV, which means a decrease of total thrombocytic clotting capacity with increasing training intensity. The longitudinal approach showed large intraindividual variations for all platelet parameters during the course of the study, expressed as high values for Nvar and CVp90.

Plasma urea, creatinine, uric acid, albumin, and total protein concentrations before and after 15-, 25-, and 42-km contests

One hundred fourteen volunteers (34 +/- 8 years) took part in an endurance training study to be completed after 18-20 months with a marathon. Ultimately, 60 males and 18 females achieved that goal. The training program, carefully supervised, was divided into three periods with a maximum of 45, 70, and 110 km/week training volume and concluded with contests of 15, 25, and 42.2 km, respectively. The competitive distance always exceeded the maximal distance covered in any previous training session. Three days before and 3 and 5 days after each race 35 subjects were selected to perform a progressive treadmill test and the remaining subjects participated in field tests of 400 and 1000 m. Before and after three contests of 15, 25, and 42.195 km the plasma concentration of urea, creatinine, uric acid, albumin, and total protein were determined. Both sexes demonstrated an increase of the plasma concentrations of urea, creatinine, and uric acid after the contests. Plasma albumin concentration decreased 2 days after the contests and total protein did not change. In females the decrease of the elevated plasma urea concentration after the marathon from the 1st day to the 3rd day post-exercise was faster than in males. The increase of plasma creatinine and uric acid concentrations were hardly dependent on the contest's distance.

Effect of training on red blood cell parameters and plasma ferritin: a transverse and a longitudinal approach

In the present study 60 males and 18 females were monitored during an 18- to 20-month training period, during which the training distance was gradually increased. The training period was divided into three periods of 6, 5, and 7 months, respectively. The first, second, and third periods were concluded with a 15-, 25-, and 42-km road race, respectively. The competitive distance always exceeded the maximal distance covered in any previous training session. The effect of training was investigated for erythrocyte count, hematocrit (Ht), hemoglobin (Hb), mean cell volume (MCV), mean cell hemoglobin (MCH), mean cellular hemoglobin content (MCHC), the red cell distribution width (RDW), and ferritin content. The measuring points were the start of the study (used as a reference value) and 1 week before and 1 week after the three contests (15, 25, and 42 km). The results of all measuring points were compared transversely and longitudinally. We found a significant decrease of plasma ferritin content in the first period of the study which further remained constant. Also, other red cell parameters were decreased but remained within the normal range. During the whole training period larger intraindividual variations for most of the red cell parameters were observed compared with non-endurance-trained people.

Statistical methods used in the marathon study

In this note an outline is given of the statistical methods which were used in the marathon study. The techniques are: box-and-whisker plots, several nonparametric tests, and methods for assessing the intraindividual variations and critical differences.

Effect of training and 15-, 25-, and 42-km contests on the skeletal muscle content of adenine and guanine nucleotides, creatine phosphate, and glycogen

Thirty-four nonathletic volunteers (23 males and 11 females) were subjected to a training program aimed at completing a marathon run within 18-20 months after the onset of training. During the course of the training the content of ATP, creatine phosphate, GTP, GDP, NAD+, purine bases, and glycogen in biopsyspecimens of m. vastus lateralis increased. No major gender differences were observed. The tissue content of adenine and guanine nucleotides such as ATP, ADP, AMP, GTP, and GDP did not change when measured within 6 h after a 15-, 25-, or 42-km contest. During 9 days after the 42-km contest the muscle content of the adenine nucleotides showed a slight, but significant decrease. Glycogen levels were found to be decreased to 90%, 60%, and 62% of their pre-contest values after the 15-, 25-, and 42-km contests, respectively. Nine days after the expenditures supranormal levels were only measured following the 15-km contest. The tissue content of glycogen returned to pre-contest levels after the 25- and 42-km races. The present findings indicate that, from a biochemical point of view, expenditures such as 15-, 25-, and 42-km contests are very well tolerated by the m. vastus lateralis in recreative runners subjected to a training with a maximal duration of 18-20 months.

White cell system changes associated with a training period of 18-20 months: a transverse and a longitudinal approach

In the present study 60 males and 18 females were monitored during an 18- to 20-month training period, during which the training distance was gradually increased. The training period was divided into three periods of 6, 5, and 7 months, respectively. The first, second, and third periods were concluded with a 15-, 25-, and 42-km road race, respectively. The competitive distance always exceeded the maximal distance covered in any previous training session. The effect of training was investigated for the number of leukocytes, number of the subpopulations, and the percentage of white cells with a higher peroxidase activity (HPX cells). The measuring points were the start of the study (used as a reference value) and 1 week before and 1 week after three contests (15, 25, and 42 km). The results of all measuring points were compared transversely and longitudinally. Transversely the leukocytes hardly changed in the course of the study both in males and females, except a decrease of HPX cells. Longitudinally it appeared that Nvar and CVp90 of the numbers of leukocytes could not be calculated in males or in females. These findings suggest that a homogeneous population of leukocytes developed with respect to number and age.

Effects of endurance training and competition on exercise tests in relatively untrained people

One hundred fourteen subjects (34 +/- 8 years) without any competition background took part in an endurance training study to be completed after 1.5 years with running a marathon. Ultimately, 60 males and 18 females achieved that goal. The training program, carefully supervised, was divided into three phases with a maximum of 45, 70, and 110 km/week training volume and concluded with a performance race of 15, 25, and 42.195 km, respectively. Three days before and 3 and 5 days after each race, 35 subjects were selected to perform a progressive treadmill test and the remaining subjects participated in performing field tests of running 400 and 1000 m. The maximal velocity achieved in the treadmill test was 4.75 +/- 0.36 m.s-1 for males and 4.18 +/- 0.28 m.s-1 for females; it remained constant throughout the study. However, the running velocity at 4 mmol.1(-1) plasma lactate concentration increased about 10% from phase 1 to 3. In the females this rise already appeared to be completed in phase 2. Heart rate showed a tendency to increase at both submaximal and maximal exercise from training phase 1 to 2 and 3, whereas plasma lactate concentration showed a decreasing tendency. Three days after the 25 km and the marathon race the maximal running velocity in the exercise test was 2%-4% lower compared with the pre-race test (P less than 0.05). Five days after the race this difference again faded away. This small decline in running performance was not reflected in changes of physiologic responses such as heart rate or plasma lactate concentration.

Muscle carnitine level in endurance training and running a marathon

Twenty sedentary volunteers (13 men and 7 women) who were subjected to an 18- to 20-month training program aimed at completing a marathon after the onset of training participated in this study. In the course of the training and after running a marathon, the content of total carnitine in the m. vastus lateralis did not change. The content of muscle total carnitine was not sex related. However, significant correlations were demonstrated between muscle total carnitine content and plasma urea and creatinine concentrations. Also a negative significant correlation was found between the content of muscle total carnitine and the plasma activity of CK before running a marathon.

Structural and ultrastructural changes in skeletal muscle associated with long-distance training and running

The histological and ultrastructural features of 21 males and 8 females were monitored during an 18- to 20-month training period, during which the training distance was gradually increased. The training period was divided into three periods of 6, 5, and 7 months, respectively. The first, second, and third periods were concluded with a 15-, 25-, 42-km road race, respectively. The competitive distance always exceeded the maximal distance covered in any previous training session. Percutaneous biopsies were taken from the vastus lateralis muscle 5 days before each contest as well as 0.5-6 h post-contest and 8-9 days post-contest. No shift in fiber type was observed during the training period from the 15-km contest until the 42-km contest nor were any changes in fiber diameter observed. Histological examination demonstrated a gradual increase in degenerative changes during the training period, which occurred in type I as well as in type II fibers. Ultrastructural examination revealed irregular Z-lines and hypercontraction immediately after exercise. No damage to the sarcolemma was detected. The number of degenerative changes after each contest was not higher than before each race. It is concluded that long-distance running is associated with transient minor pathological changes in skeletal muscle, which are related to the total distance covered per week rather than the intensity of the exercise.

Occurrence of running injuries in adults following a supervised training program

To study the occurrence of running-related injuries, a group of 115 volunteers were supervised in a training program. These subjects who had limited or no running experience were asked to keep a diary in which they registered information on the training program and injuries. Ultimately, 63% of the diaries fulfilled the criteria for inclusion into longitudinal analysis. The training program (18-20 months) consisted of three phases, each phase finished with a contest (15 km, 25 km, and a marathon, respectively). The participants were individually supervised by an experienced coach with special attention to physiologic training and injury-preventive aspects. Eighty-five percent (n = 62) of the research population sustained at least one injury during the experiment. They reported in total 174 injuries. The number of injury cases per week increased gradually over the experimental period; however, when expressed per unit of exposure time (i.e., 1000 training hours), it showed a decline. There was a significant correlation between the number of injured volunteers and the distance covered during the training at the start of the training program. The anatomic distribution of the injuries is in agreement with findings in the literature. There was also a possible preference for the localization of injuries to the lower leg and Achilles tendon on the left side of the body.

Fluid intake and gastrointestinal problems in runners competing in a 25-km race and a marathon

A group of 114 previously untrained subjects, 31 females and 83 males, was followed for 18 months while training for a marathon. Forty-four of the subjects completed a survey regarding fluid intakes and gastrointestinal (GI) disturbances during competition for both their first 25-km race (run after 1 year of training) and their first marathon. GI problems were common. Among the individuals surveyed, 25% had GI complaints in the 25-km race. In the marathon, 52% complained of GI distress. In general, fluid consumption was low (25 km means = 109 ml; marathon w = 577 ml). Body weight losses in the marathon were substantial (w = 3.2%, BW; range 1.5%-6.2%) indicating sweat losses greater than fluid replacement. These losses were greater in men than in women (men w = 3.4% BW; women w = 2.6% BW). GI complaints were not associated with larger drink intakes. In contrast, dehydration above a certain limit appears to increase the frequency of GI disorders. In the marathon, 80% of the runners who lost greater than 4% BW had GI problems. It is possible that reduced blood flow to the GI region is compromised via the exercise itself as well as by a reduced blood volume, which may disrupt normal secretion/absorption of the digestive tract. It may also be that a rising core body temperature, associated with decreased sweating at high levels of dehydration, may be related to GI dysfunction.

Food intake and body composition in novice athletes during a training period to run a marathon

The change in diet and body composition was studied in a group of 9 female and 18 male subjects, starting a training program for 18 months with the ultimate goal of running the marathon. Mean daily intakes from 7-day dietary records for macro- and micronutrients were calculated at the start, after 1 year of training, and just before running the marathon. Anthropometric measurements were taken on the same occasions. In males the body fat mass decreased 2.4 kg, while in females no change in body composition was observed over the 18-month training period. Energy intake increased significantly in males from 131 to 159 kJ/kg/day. In women no significant change was recorded (141 to 147 kJ/kg/day). However, in both sexes CHO intake was significantly higher after 18 months (males 63.7-81.7 kJ/kg, females 68.0-81.9 kJ/kg). Also En% CHO increased significantly in males from 48 to 52 EN% and in females from 47 to 55 En%. This extra energy intake of CHO in women was covered at the expense of dietary fat. These changes in food habits in both groups are favorable in relation to the nutritional guidelines for better cardiovascular health. Whether the sex difference found in economizing energy exchange as a response to an intensive training program is based on an increased food efficiency will require further investigation.

Phenylbutazone-hydroxycoumarol interactions. Effects on steady state disposition, hepatocellular distribution, and biliary excretion of (S)-acenocoumarol in rats

The effect of phenylbutazone on the disposition of (S)-acenocoumarol in the rat was studied at steady state conditions of distribution and elimination. (S)-Acenocoumarol was administered by constant rate infusions (1 microgram/min). The biliary excretion of 6- and 7-hydroxylated acenocoumarol was followed and the intrahepatic distribution was investigated. Phenylbutazone (50 mg/kg) increased the plasma unbound fraction about 4-fold. (S)-Acenocoumarol plasma clearance was enhanced (2.8 +/- 0.15 vs. 1.54 +/- 0.14 ml/min) but the unbound plasma clearance was reduced by 50% (67 +/- 9 vs. 140 +/- 27 ml/min). Phenylbutazone caused an intrahepatic redistribution of (S)-acenocoumarol, i.e. the drug shifted from the cytosol to the 10,000g pellet. The cytosolic unbound concentration, however, was increased. The (S)-acenocoumarol content in the microsomal fraction was not affected. The biliary excretion rate of total metabolite (free plus conjugated) comprised 50% of the (S)-acenocoumarol infusion rate in controls and was slightly stimulated (+20%) by phenylbutazone. The biliary excretion of free metabolites, however, was greatly increased (62 +/- 7 vs. 22 +/- 6 ng/min for 6-hydroxy-acenocoumarol; 337 +/- 38 vs. 141 +/- 32 ng/min for 7-hydroxy-acenocoumarol). This effect is probably due to stimulation of a hepatic biliary transport system; the rate constant for transport of 7-hydroxy-acenocoumarol was enhanced 5-fold (0.107 +/- 0.03 vs. 0.021 +/- 0.007 min-1).

Phosphorylation of elongation factor 1 beta by an endogenous kinase affects its catalytic nucleotide exchange activity

Elongation factor 1 beta (EF-1 beta) from Artemia is phosphorylated to a high percentage at serine 89 by an endogenous kinase present in EF-1 beta gamma. Protein sequencing of EF-1 beta revealed that this serine residue is located N-terminally of an acidic cluster of amino acids, (formula; see text) which is critical for casein kinase II-type substrate recognition. A number of compounds known to influence casein kinases were studied, revealing that the kinase activity as present in EF-1 beta gamma belongs to the class of casein kinase II. The rate of nucleotide exchange on EF-1 alpha as catalyzed by EF-1 beta was found to be affected reversibly by the state of phosphorylation of EF-1 beta. In the presence of dephosphorylated EF-1 beta, the exchange rate is almost twice as large compared to the rate in the presence of phosphorylated EF-1 beta. Rephosphorylation of dephosphorylated EF-1 beta diminishes the activity of the protein again. The role of casein kinase II-type enzymes in modulating the function of proteins involved in polypeptide synthesis is discussed.

Kinetic studies on the role of elongation factors 1 beta and 1 gamma in protein synthesis

An equilibrium isotope exchange technique was used to measure in an Artemia system the catalytic influence of elongation factor (EF) 1 beta gamma on the dissociation of GDP from the complex of elongation factor 1 alpha.[3H] GDP in the presence of an excess of free GDP. The kinetic data demonstrate that, in analogy to procaryotes, dissociation of GDP occurs via the formation of a transient ternary complex of EF-1 alpha.GDP.EF-1 beta gamma. The rate constants for the dissociation of GDP from EF-1 alpha.GDP and from the ternary complex EF-1 alpha.GDP.EF-1 beta gamma were found to be 0.7 x 10(-3) and greater than or equal to 0.7 s-1, respectively. The equilibrium association constants of GDP to EF-1 alpha.EF-1 beta gamma and of EF-1 beta gamma to EF-1 alpha.GDP were found to be 2.3 x 10(5) and 4.2 x 10(5) M-1, respectively. Judged from the known elongation rate in vivo and kinetic constants of nucleotide exchange, it was estimated that the recycling of EF-1 alpha may be a rate-controlling step in eucaryotic translation. As a model for GTP exchange, the formation of the ternary EF-1 alpha.guanylyl (beta gamma-methylene)diphosphonate.EF-1 beta gamma complex was also studied. It was observed that both an increase of the level of aminoacyl-tRNA and of temperature favored the dissociation of this complex, thereby enabling EF-1 beta gamma to recycle as a catalyst. This behavior would explain the frequent occurrence of a heavy form of elongation factor 1 in extracts of the eucaryotic cell.

Elongation factor 1 beta gamma from Artemia. Purification and properties of its subunits

The guanine nucleotide exchange factor, elongation factor 1 beta gamma (EF-1 beta gamma) has been purified from Artemia cysts using an improved method. The protein consists of two distinct polypeptides with relative molecular masses of 26,000 (EF-1 beta) and 46,000 (EF-1 gamma). A nucleoside diphosphate phosphotransferase activity often found in EF-1 beta gamma preparations has been completely separated from the actual guanine nucleotide exchange stimulatory activity of EF-1 beta gamma, thus indicating that nucleotide diphosphate phosphotransferase is not an intrinsic property of EF-1 beta. Both EF-1 beta gamma and EF-1 beta have been shown to stimulate the following three reactions to a comparable degree: (a) exchange of GDP bound to EF-1 alpha with exogenous GDP; (b) EF-1 alpha-dependent binding of Phe-tRNA to ribosomes; (c) poly(U)-dependent poly(phenylalanine) synthesis. However, a significantly higher nucleotide exchange rate was observed in the presence of EF-1 beta gamma compared to EF-1 beta alone. Concerning elongation factor 1 gamma (EF-1 gamma) the following observations were made. In contrast to EF-1 beta, pure EF-1 gamma is rather insoluble in aqueous buffers, but the tendency to precipitate can be partially suppressed by the addition of detergents. In particular, EF-1 gamma partitions solely into the detergent phase of Triton X-114 solutions. EF-1 gamma is also more susceptible to spontaneous, specific fragmentation. It is remarkably that about 5% of the cellular pool of EF-1 beta gamma was found to be present in membrane fractions, under conditions where no EF-1 alpha was detectable in these fractions. Furthermore it was noted that EF-1 beta gamma copurified strongly with tubulin on DEAE-cellulose. Moreover, it was observed that from a mixture of EF-1 beta gamma and tubulin, EF-1 gamma coprecipitates with tubulin using a non-denaturating immunoprecipitation technique. These findings suggest that EF-1 gamma has a hydrophobic domain and interacts with membrane and cytoskeleton structures in the cell.