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Deimination or citrullination, is a post-translational modification with many facets. It is involved in several basic cellular processes, including gene regulation, embryonic development and terminal differentiation, and also in various pathophysiological mechanisms linked to severe human diseases such as multiple sclerosis and rheumatoid arthritis. Deimination, the calcium-dependent enzymatic conversion of peptidyl-arginine to peptidyl-citrulline, induces a decrease in the charge of the modified proteins with major consequences on their conformation, stability and/or interactions, and therefore on their functions. Five isotypes of peptidylarginine deiminases (1-4 and 6), exist in humans with a variable tissue expression. These highly conserved enzymes are closely regulated at transcriptional and post-transcriptional levels, probably including auto-deimination.

Arterial ageing - arteriosclerosis - is characterised by both thickening and stiffening of the walls of large and medium arteries. The molecular and cellular mechanisms (i.e. endothelial dysfunction, matrix remodelling, ...) involved in this process are complex, and at least in part common to atherosclerotic injury. Arterial stiffness is strongly associated with cardiovascular disease and an increased risk of morbidity and mortality. The aim of this review is to provide an update on the pathophysiology and the biological process of arterial ageing and to underline the main difference with atherosclerosis damage process in particularly during the calcification step.

Arginine, a semi-essential amino acid, plays a major nutritional and metabolic role. In particular, arginine is the precursor of nitric oxide which is involved in the endothelial function. Several factors, such as hypercholesterolemia, diabetes, ageing and hypertension are established risk factors for atherosclerosis, in particular by decreasing the availability of nitric oxide. Thus, endothelial nitric oxide synthase has a pivotal role against atherosclerosis. A suitable amount of cofactor and a sufficient intake of arginine have been shown to modulate nitric oxide-induced vasodilatation: despite the fact that the intracellular concentration of arginine is well above the Km of endothelial nitric oxide synthase, an arginine supplemented-diet is effective in increasing the production of nitric oxide. Several mechanisms have been proposed to explain this "arginine paradox": co-localization of the arginine transporter with endothelial nitric oxide synthase, intracellular arginine regeneration from citrulline, balance between endothelial arginase and nitric oxide synthase. Statins which are HMG-CoA reductase inhibitors inhibit the synthesis of mevalonate, and thus that of cholesterol. In addition, statins increase the stabilization of endothelial nitric oxide synthase mRNA. The co-operation between cholesterol synthesis and the upregulation of caveolin-1 on the one hand, and the activation of endothelial nitric oxide synthase on the other hand, is very tight. A depletion of cholesterol in the caveolae induces a decrease in caveolin-1 at the cell surface allowing NOS activation. Thus statins improve nitric oxide production and vasodilatation. In a recent work in the hypercholesterolemic Watanabe rabbit, we have demonstrated that the combination of arginine with a statin, namely atorvastatin, significantly hinders the spreading of atherosclerotic plaques as compared with monotherapies. Such association of a nutriment and a drug open a new area of therapeutic strategy.

VASOPRESSIN: The action of vasopressin (AVP) is not limited to regulating water excretion but also plays an essential role in regulating the corticotropic axis during stress. PHYSIOLOGY: Vasopressin is synthesized in the hypothalamus and stored in the posterior pituitary. It acts on 3 types of receptors (RV). RV1a are vascular receptors mediating the vasoconstrictor and glycogenolytic effects of the hormone. Anterior pituitary RV1b or V3 mediate stimulating effects on the corticotropic axis. Renal RV2 regulate water and urea excretion. Hypothetical extrarenal RV2 would be responsible for the vasodilator and procoagulant effects of the hormone. MODIFICATIONS IN ENDOCRINE DISEASES: Pituitary or adrenal hypocorticism syndromes include hyponatremia with secondary plasma hypoosmolality and reduced glomerular filtration due to the direct effect of glucocorticoids and also the effect of vasopressinism. Certain endogenous hypercorticisms appear to be related to an overexpression of RV: in ACTH-independent Cushingís syndrome, adrenal overexpression of eutopic RV1a, and in ACTH-dependent Cushingís syndrome, pituitary overexpression of eutopic RV1b or ectopic RV2. In addition, inappropriate secretion of antidiuretic hormone is frequent after transphenoidal surgery, particularly for corticotropic adenomas. DYNAMIC TESTS: The physiological response of ACTH and also AVP to corticotropin releasing hormone (CRH) in the petrous sinus, the unusual responses of certain corticotropic tumors to dDAVP, or certain forms of ACTH-independent hypercortisolism to lysine vasopressin (LVP) suggest excessive or ectopic expression of RV in corticotropic or adrenal cells: tumorgenesis of these cells could also depend, at least partially, on AVP.

AGING PROCESS: There is a large body of experimental and clinical data demonstrating that endothelial dysfunction is encountered not only in disease states such as atherosclerosis, hypertension, heart failure or diabetes, but also in the normal physiological process of aging. Currently available data show that endothelium-dependent function declines with age. The fact that this same decline is observed in patients with hypertension suggests that age is an independent factor capable of provoking changes in the vascular endothelium. CAUSAL MECHANISMS: It is often suggested that altered NO synthesis from L-arginine and/or increased production of contraction factors play a role in the aggravation of endothelial and parietal lesions and would thus affect the natural history of the disease process., Human Studies: Ongoing studies in man tend to confirm experimental data obtained in animal models; treatment protocols could be adapted using compounds aimed at restoring normal endothelial function.

VASOMOTRICITY: The vascular endothelium plays a key role in vasomotricity by producing a number of factors which modulate smooth muscle relaxation and contraction. Nitric oxide (NO) has been found to be one of the most important relaxation factors. NO SYNTHESIS: Nitric oxide is synthesized from L-arginine by NO-synthetase whose activity is regulated by intracellular calcium concentration and modulated by pharmacological compounds such as acetylcholine, 5-hydroxytryptamine, bradykinin and ADP as well as the sheer forces produced by blood flow., Mode of Action: NO stimulates soluble guanylate cyclase in smooth muscles. Its action is mediated by increased intracellular cGMP which provokes smooth muscle relaxation. ACTIONS OF NO: The physiological role of NO produced by the vascular endothelium is quite complex and incompletely elucidated. NO helps maintain adequate blood supply to tissues by reacting rapidly to changes in pharmacological and mechanical stimuli. It opposes the direct vasoconstrictor effect of certain factors in the blood stream and its action on platelets and endogenous fibrinolysis helps prevent thrombus formation.

The development of highly sensitive and specific immunoassays allowed the characterization of bradykinin and desArg9-BK metabolism in vitro. The same methods were used to study the time course evolution of the tissue content of both kinins in an carragenan inflammatory model. Quantification of T-kininogen in the same animal model allowed to show an influence of BK on the neosynthesis of this acute phase protein.

Non-enzymatic protein glycosylation is the first stage of the reaction described by L.C. Maillard. When the reaction progresses beyond that stage the long half-life molecules are damaged by formation of intermolecular crosslinking. The recent discovery of pentosidine, a crosslink between lysine and arginine residues, has demonstrated that advanced Maillard reaction is accelerated in diabetic patients with severe complications. Moreover, high tissue and plasma levels of pentosidine have been found in uraemia. The formation of advanced Maillard end-products (AGE) in plasma proteins constitutes a source of cell stimulation which induces macrophages to secrete cytokines, interleukin-1 and tumoral necrosis factor. Similarly, endothelial cells are induced to increase the permeability and production of the procoagulant factor. These mechanisms are thought to play an important role in the pathogenesis of atherosclerosis, nephropathy and thromboembolic disorders of diabetes. The discovery of beneficial effects of amino-guanidine, an inhibitor of advanced Maillard reaction, in the prevention of experimental diabetic complications opens a new line of investigation and new hopes for diabetics.

In this work, we compare the energetic cost of tonic and phasic contractions of the anterior byssus retractor muscle (ABRM) of Mytilus edulis. The muscle is stimulated by six different stimulation methods and frozen when it reaches its maximal isometric response. Tonic and phasic tension developments are of similar amplitude and cause a hydrolysis of the same amount of phosphoarginine corresponding to 0.64 mumole per g of muscle and per kg/cm2 of tension (Fig. 1). As compared with the results reported in the literature the values are in good agreement with the biochemical and respiratory measurements, but they are 10 times higher than those measured by the heat production. The total arginine, octopine and alanine contents of those muscles frozen at the peak of contraction are not significantly different from those measured on the resting muscle. On the other hand, these metabolites may show seasonal variations.

From a bacteriological study of 137 strains of streptococcus agalactiae, it seems that this species is perfectly defined by bacteriological tests, the most characteristic of which is hydrolysis with hippuric acid. The brown pigment of the strains, the conditions for demonstration of which are described and discussed here, may also be an important characteristic for it is rare in streptococci. The pigment was extracted, its nature and role are discussed. The sensitivity to 12 antibiotics was studied; the beta-lactamines were the most commonly active.

The essential tyrosine residue of Lobster muscle arginine kinase, which is part of an antigenic determinant, has been modified by tetranitromethane. Cleavage of the S-carboxymethylated nitrated enzyme with cyanogen bromide gives rise to eight peptides, one of which containing the labelled essential tyrosyl group. Ion exchange chromatography on sulfoethyl-Sephadex C-25 in urea medium has been used with success for isolation and purification of the nitrated peptide. From its amino acid composition and end groups structure this peptide is the N-terminal fragment of the protein.

Improved methods of separation, identification and determination of phosphagens have been applied to the study of monosubstituted guanidines and phosphagenes in sea urchin eggs, before and after fertilization. We have been able not only to identify in these materials phosphoarginine, but also phosphocreatine and to detect an unknown phosphagen. After fertilization, free arginine and creatine decrease, within respect to unfertilized eggs, whereas phosphocreatine undergoes a large increase; phosphoarginine remains almost constant, and an unknown phosphagen appears. These observations allow to interprete the results of some authors, who, applyng less refined methods, found only an increase in phosphoarginine in the same materials.

In addition to previous taxonomic work, eight biochemical tests have been applied to the study of 580 Bacillus strains belonging to 22 species. The attack of chitin, melibiose and amygdalin can be used for the differentiation of some species. It is the same with most of the enzymes studied here, although Tween-esterase and DNase are often present in the majority of the isolates. RNase is still more frequent, being found in nearly all the strains. On the other hand, arginin-dihydrolase appears to be very rare and ornithin-decarboxylase seems always absent.

For optimal growth, the yeast-like cells of Ustilago cynodontis 4001 (originating from the mycelium 4001 prototroph forms) require the presence of both arginine and lysine. However, in the absence of lysine, growth does occur, but two exponential growth phases can then be observed: a pseudo-lag phase during which the growth rate is slow, and a second, true exponential phase. The initial OD of the culture and the arginine concentration of the medium do not appear to affect the duration of the pseudo-lag phase. The arginine concentration does, however, affect the growth yield. Upon addition of lysine to the culture medium, the period of the pseudo-lag phase is reduced and the growth rate increased. The pseudo-lag phase can be completely suppressed by the addition of adequate amounts of lysine. In the presence of lysine and in the absence of arginine, cells are not capable of multiplication. Addition of arginine initiates growth; whether or not a lag phase occurs depends on the quantity of arginine added. The successive inoculation of cells into lysine-free medium leads to suppression of the pseudo-lag phase but only after three or four passages. Therefore it does not seem that there is selection of cells which do not require lysine during the pseudo-lag phase. It is shown that it is not the modification of the culture medium which suppresses the lysine requirement: the cells which are put to grow in the supernatant of a culture in which a pseudo-lag phase had taken place behave in the same way that when they are inoculated in a new medium. The modification of the cell metabolism itself is discussed.

An aminopeptidase was purified from the culture filtrates of a collagenolytic bacterium Empedobacter collagenolyticum. Purification of this enzyme was accomplished by ammonium sulphate precipitation, gel filtration on Sephadex-G200 and chromatography on DEAE-Sephacel. The purified enzyme seemed homogeneous on polyacrylamide gel electrophoresis. The molecular weight of the enzyme was about 100,000 daltons as determined by gel filtration on Sephadex-G200 but it was only 33,000 daltons by disc gel electrophoresis in the presence of sodium dodecyl sulphate. This enzyme selectively hydrolysed N-terminal arginine and lysine residues of peptides and arylamides substrates. The enzyme was strongly inhibited by EDTA, ZnCl2 and L-arginine.

Cycloleucinead ministration (a synthetic amino acid) to rats produces a selective hyperaminoaciduria bearing on dibasic amino acids (lysine, arginine, ornithine) and cystine. Interference of cycloleucine with tubular reabsorption of these amino acids was studied "in vitro", using rat kidney cortex slices. When dibasic amino acids and cystine are at physiological concentrations, the data indicate that cycloleucine decreases their intracellular accumulation. However, effect of cycloleucine "in vitro" is not specific whatsoever its concentration; similar results are obtained with neutral amino acids such as alpha-alanine and valine. Inhibitory effects are not modified by the presence of several amino acids in the incubation medium. The results are interpreted as evidence for a dissociation between "in vitro" cellular accumu-lation and "in vivo" transepithelial transport.

The research of lysine, ornithine and arginine decarboxylases has been made for 50 strains of fluorescent Pseudomonas (P. aeruginosa, P. fluorescens, P. putida). By thin layer chromatography, all the strains of Pseudomonas aeruginosa and the fifth of the strains of P. putida had lysine decarboxylase activity at alcaline pH (optimal pH 8) ; Pseudomonas fluorescens did not produce this decarboxylase. Arginine and ornithine decarboxylase are absent for all the strains of fluorescent Pseudomonas.

Citrulline production is demonstrated in murine bone marrow cell cultures incubated with dialyzed secondary MLC supernatant. This synthesis, proceeding from arginine, is induced by a soluble protein factor released during secondary MLC, unstable to heat, with a molecular weight of approximately 150,000 daltons.