Identification of distinct pathological signatures induced by patient-derived α-synuclein structures in nonhuman primates

Dopaminergic neuronal cell death, associated with intracellular α-synuclein (α-syn)-rich protein aggregates [termed "Lewy bodies" (LBs)], is a well-established characteristic of Parkinson's disease (PD). Much evidence, accumulated from multiple experimental models, has suggested that α-syn plays a role in PD pathogenesis, not only as a trigger of pathology but also as a mediator of disease progression through pathological spreading. Here, we have used a machine learning-based approach to identify unique signatures of neurodegeneration in monkeys induced by distinct α-syn pathogenic structures derived from patients with PD. Unexpectedly, our results show that, in nonhuman primates, a small amount of singular α-syn aggregates is as toxic as larger amyloid fibrils present in the LBs, thus reinforcing the need for preclinical research in this species. Furthermore, our results provide evidence supporting the true multifactorial nature of PD, as multiple causes can induce a similar outcome regarding dopaminergic neurodegeneration.

DYRK1A promotes dopaminergic neuron survival in the developing brain and in a mouse model of Parkinson's disease

In the brain, programmed cell death (PCD) serves to adjust the numbers of the different types of neurons during development, and its pathological reactivation in the adult leads to neurodegeneration. Dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A (DYRK1A) is a pleiotropic kinase involved in neural proliferation and cell death, and its role during brain growth is evolutionarily conserved. Human DYRK1A lies in the Down syndrome critical region on chromosome 21, and heterozygous mutations in the gene cause microcephaly and neurological dysfunction. The mouse model for DYRK1A haploinsufficiency (the Dyrk1a(+/-) mouse) presents neuronal deficits in specific regions of the adult brain, including the substantia nigra (SN), although the mechanisms underlying these pathogenic effects remain unclear. Here we study the effect of DYRK1A copy number variation on dopaminergic cell homeostasis. We show that mesencephalic DA (mDA) neurons are generated in the embryo at normal rates in the Dyrk1a haploinsufficient model and in a model (the mBACtgDyrk1a mouse) that carries three copies of Dyrk1a. We also show that the number of mDA cells diminishes in postnatal Dyrk1a(+/-) mice and increases in mBACtgDyrk1a mice due to an abnormal activity of the mitochondrial caspase9 (Casp9)-dependent apoptotic pathway during the main wave of PCD that affects these neurons. In addition, we show that the cell death induced by 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP), a toxin that activates Casp9-dependent apoptosis in mDA neurons, is attenuated in adult mBACtgDyrk1a mice, leading to an increased survival of SN DA neurons 21 days after MPTP intoxication. Finally, we present data indicating that Dyrk1a phosphorylation of Casp9 at the Thr125 residue is the mechanism by which this kinase hinders both physiological and pathological PCD in mDA neurons. These data provide new insight into the mechanisms that control cell death in brain DA neurons and they show that deregulation of developmental apoptosis may contribute to the phenotype of patients with imbalanced DYRK1A gene dosage.

Optic atrophy 1 mediates mitochondria remodeling and dopaminergic neurodegeneration linked to complex I deficiency

Mitochondrial complex I dysfunction has long been associated with Parkinson's disease (PD). Recent evidence suggests that mitochondrial involvement in PD may extend beyond a sole respiratory deficit and also include perturbations in mitochondrial fusion/fission or ultrastructure. Whether and how alterations in mitochondrial dynamics may relate to the known complex I defects in PD is unclear. Optic atrophy 1 (OPA1), a dynamin-related GTPase of the inner mitochondrial membrane, participates in mitochondrial fusion and apoptotic mitochondrial cristae remodeling. Here we show that complex I inhibition by parkinsonian neurotoxins leads to an oxidative-dependent disruption of OPA1 oligomeric complexes that normally keep mitochondrial cristae junctions tight. As a consequence, affected mitochondria exhibit major structural abnormalities, including cristae disintegration, loss of matrix density and swelling. These changes are not accompanied by mitochondrial fission but a mobilization of cytochrome c from cristae to intermembrane space, thereby lowering the threshold for activation of mitochondria-dependent apoptosis by cell death agonists in compromised neurons. All these pathogenic changes, including mitochondrial structural remodeling and dopaminergic neurodegeneration, are abrogated by OPA1 overexpression, both in vitro and in vivo. Our results identify OPA1 as molecular link between complex I deficiency and alterations in mitochondrial dynamics machinery and point to OPA1 as a novel therapeutic target for complex I cytopathies, such as PD.

[About two cases of massive hypercholesterolemia]

Two patients presented massive hypercholesterolemia related to acquired disease, intrahepatic cholangitis with cholestasis in one and nephrotic syndrome in the second. Comparison of the lipoprotein patterns demonstrated distinctive pathophysiological processes different from those operating in primary causes of hypercholesterolemia.

[Unexpected occurence of hemoglobin Athens-Georgia]

The following report concerned a 47 year old Caucasian diabetic patient. Routine HPLC of HbA1c (Variant II Biorad Laboratories - hemoglobin A1c program) resulted only in the evidence of HbF (1%) and increase in HbA1c (10%). Considering the presence of HbF a standard agarose gel electrophoresis of patient's hemoglobin was performed and revealed the presence of Hb Athens-Georgia. Consequently the occurrence of HbF during determination of HbA1c by HPLC should lead to perform a standard hemoglobin electrophoresis in order to explore an hidden, unsuspected and clinically silent occurrence of rare Hb variant or additional unsuspected increase in HbA2.

Energy and nutrient intake of elderly hospitalized patients in a steady metabolic status versus catabolic status

Protein undernutrition enhances frailty and aggravates intercurrent diseases generally observed in elderly patients. Undernutrition results from insufficient food intake and catabolic status. Daily nutrient intakes were explored for hospitalized geriatric patients. Nutrient intake (carbohydrates, lipids, proteins, and calcium) was determined in randomly selected geriatric patients (n=49) over five consecutive days by weighting food in the plate before and after meals. For each geriatric patient, catabolic status and risk factors of undernutrition were considered. Results were compared between patients in a steady status or catabolic status. In steady status patients, protein, lipid and carbohydrate intake but not calcium intake, met recommended dietary allowances (total caloric intake:1535 +/- 370 Cal/day ; protein:1+/- 0.4 g/kg/day ; carbohydrates:55 +/- 7.7 % ; lipids: 30 +/- 6.3 % ; calcium:918 +/- 341 mg/day) . Patients in catabolic status (cardiopulmonary deficiency , neurologic disease , inflammatory process) had lower total caloric intake, lower protein intake and dramatically lower calcium intake (total caloric intake : 1375 +/- 500 Cal/day ; protein :0.9 +/- 0.4 g/kg/day ; carbohydrates : 54 +/- 8.3 % ; lipids : 31 +/-6.2 % ; calcium : 866 +/- 379 mg/day). Nutrient intake was lower in elderly patients hospitalized in short stay care units, perhaps due to failure to recognize suitable nutrient requirements. Protein-caloric undernutrition should be diagnosed early during hospitalization in order to allow appropriate dietary supplementation. However the incidence of protein undernutrition among elderly patients as a cause or a consequence of adverse pathophysiological processes remains a cause of debate.

Native protein glycoxidation and aging

Structural and functional alterations of proteins are observed during aging. Glycation of long half-life proteins, involving reducing carbohydrates, leads to the formation of intra and intermolecular cross-links and the production of free radicals. These processes depend on the amount of glucose available and on molecular oxygen which contributes to the production of free radicals. These processes are observed without dysfunction of carbohydrate metabolism and progress with age. However, whether this process is a primary cause or a consequence of aging remains a question of debate. Prevention of excessive glycoxidation could be a goal of recommendations designed to control the tissular alterations occurring in aging.

Changes in glycation of fibrous type I collagen during long-term in vitro incubation with glucose

The course of glycation of calf skin fibrous type I collagen was monitored in vitro under physiological conditions during an 8-week incubation period in order to take into account the long half-life of this protein. The formation of glycated compounds was measured by determining fructosamine, pentosidine, and carboxymethyllysine content. The incubation conditions were as physiological as possible in sterile saline phosphate buffer, except glucose concentration. With incubation medium containing 200 mmol glucose, fibrous collagen underwent solubilization; in addition an increase in fructosamine, pentosidine, and carboxymethyllysine content in both solubilized and remaining insoluble collagen was noticed. There was a spontaneous, restricted, and time-dependent native glycated state of collagen; high concentration glucose enhanced the formation of glycated compounds and induced changes in solubility and glycoxidated products. The production of pentosidine during incubation without glucose should be considered as an event resulting from the initial fructosamine. Whereas the production of carboxymethyllysine during long-term incubation with glucose provided indirect proof of an additional oxidative process after early glycated product formation. These experimental observations provide insight into the in vivo context of advanced glycation end product formation in chronic hyperglycemia and aging.

In vitro glycoxidation of insoluble fibrous type I collagen: solubilization and advanced glycation end products

The deleterious effects of glycoxidation are dependent on the half-life of proteins. Collagen, the main component of extracellular matrices, is a long live protein and thus may be sensitive to the glycoxidation process. We incubated calf skin fibrous type I collagen in PBS at 37 degrees C with glucose. The fibrous type I collagen was solubilized and an increase in the amount of advanced glycation end products of the solubilized fraction was observed. As there was no bacterial contamination and no proteolytic activities in the incubation medium, the solubilization of fibrous type I collagen is probably due to the speculative production of the free radicals in our experimental conditions. To test this hypothesis, fibrous type I collagen was incubated in PBS with AAPH (2,2'azo-bis 2-aminodinopropane) a free radicals generator. AAPH induced a dramatic and dose dependent solubilization of fibrous type I collagen.

Nutritional markers, acute phase reactants and tissue inhibitor of matrix metalloproteinase 1 in elderly patients with pressure sores

BACKGROUND

Loss of collagen and elastin is observed in the elderly. In geriatric inpatients, chronic protein malnutrition could induce susceptibility to additional morbidity such as pressure sores.

OBJECTIVE

The purpose of this study was to explore the relationship between nutritional and inflammatory status and the production of tissue inhibitor of matrix metalloproteinase 1 (TIMP-1).

METHODS

Chronically ill elderly inpatients, without or with pressure sores, were enrolled. Nutritional protein markers, acute phase reactants, and TIMP-1 were determined, and changes in these biological parameters were compared.

RESULTS

Chronic inflammatory process and protein malnutrition were observed in all enrolled patients. The severity of these two pathophysiological processes was independent of the occurrence of pressure sores. The serum prealbumin and albumin levels were lower in patients with pressure sores than in those without. In addition, the general increase in the TIMP-1 level was independent of the occurrence of pressure sores. The TIMP-1 level was mainly related to the prognostic inflammatory and nutritional index.

CONCLUSIONS

The general increase in acute-phase reactants observed in the elderly could be related to the intercurrent diseases. The generally low serum albumin level, lowest in patients with pressure sores, may be considered evidence of protein malnutrition and hypercatabolism. Regarding the morbidity, the increase in TIMP-1 levels could be explained as an adaptive process to prevent intrinsic protein expenditure of extracellular matrices.

Serum pentosidine as an indicator of Alzheimer's disease

Pentosidine, an advanced glycation end product (AGE), was assayed by HPLC in serum proteins from patients with Alzheimer type dementia (AD), patients with diabetes mellitus (D), and healthy (C) age-matched old subjects (mean age from each group = 84 years). Serum pentosidine was significantly different between the three groups despite similar renal function (serum creatinine < 160 micromol/L). In all groups of patients, pentosidine was independent of glycated hemoglobin (HbA1C) and the early glycation marker fructosamine and appeared to be an independent marker, mainly bound to serum albumin. Pentosidine could be an important factor useful for the diagnosis of Alzheimer's disease.

[A patient with white matter involvement and superficial hemosiderosis of the central nervous system]

We present a patient with a superficial siderosis and a white matter involvement on MRI and a demyelinating pattern on visual evoked potentials. White matter involvement is supposed to be secondary to vascular modifications induced by superficial siderosis.

Synergy between ascorbate and alpha-tocopherol on fibroblasts in culture

Ascorbate and tocopherol are important antioxidants that protect cells against oxidative stress. The interaction of ascorbate and alpha-tocopherol in cells is difficult to detect as both ascorbate and alpha-tocopherol are unstable in vitro in a biological medium. We examined the interactions between human dermal fibroblasts, ascorbate and alpha-tocopherol to determine the effects of the vitamins on growth and cell viability. The interaction of ascorbate and alpha-tocopherol was studied in a fibroblast culture medium during 48h. Ascorbate and alpha-tocopherol were detected by fluorimetry after high-performance liquid chromatography (HPLC). Cell growth and cell viability were studied by cell numeration after trypan blue staining. The ascorbate concentration fell in presence of alpha-tocopherol in cell culture medium under all experimental conditions, with or without cells. Ascorbate partly protected alpha-tocopherol but only in presence of cells. Cell viability was preserved by alpha-tocopherol whereas ascorbate enhanced fibroblast growth. The synergy between ascorbate and alpha-tocopherol corresponds to a consumption of ascorbate which spares alpha-tocopherol but only in presence of cells.

Urine glycyl-L-proline increase and skin trophicity

Glycyl-L-proline (gly-pro) is an end product of collagen metabolism that is further cleaved by prolidase (EC 3.4.13.9); the resulting proline molecules are recycled into collagen or other proteins. We postulated a relationship between defective gly-pro hydrolysis, increased collagen degradation and skin destruction. This relationship was tested using HPLC to measure the gly-pro in urine. 24 hour urine samples were collected from 27 old people (86 +/- 6 years old), of whom 15 were suffering from skin pressure sores of the sacrum or calcaneus. The urine from patients with pressure sores contained significantly more gly-pro than the urine from the control. A cut-off at 7 mumol/mmol creatinine gave the test a positive predictive value of 70%. Collagen breakdown was also increased as indicated by the increase of hydroxyproline (hyp) in the urine. But this breakdown seemed to stop at the gly-pro step.

A comparison of 15N proline and 13C leucine for monitoring protein biosynthesis in the skin

The tracers L 15N-proline and L(1-13C)-leucine were used to explore the synthesis of skin proteins in vivo in rabbits. They orally received a single dose containing an equimolecular mixture of L(1-13C)-leucine and L 15N-proline. The changes in the amounts of these tracers in blood and skin were monitored for a total of 8 h. The data showed the appearance of the two tracers in blood within 15 min and their clearance in 8 h. They were both rapidly (15 min) incorporated into skin proteins, but more proline was incorporated than leucine. We therefore consider L 15N-proline to be a better tracer than L(1-13C)-leucine for studying protein metabolism in the skin.

Residual inflammatory process after aortoiliac reconstructive surgery

BACKGROUND

The aim of the present study was to investigate the inflammatory reaction and its evolution in patients who underwent a prosthetic vascular procedure. Moreover the participation of this chronic process, during the follow-up, as a promoting or a consequence of vascular injury must be discussed.

METHODS

Thirty-four patients were enrolled in the study. All patients had an aortic disease and underwent a prosthetic vascular procedure. Preoperative exclusion criteria were an emergency situation, diabetes, infection, chronic inflammatory disease, cancer and hemopathy. Postoperative exclusion criteria were the same together with abdominal complications and additional surgery during the follow-up. The inflammatory process was investigated with the measurement of blood acute phase proteins, haptoglobin, alpha1-glycoprotein acid, C-reactive protein and interleukin-6, before, immediately after surgery and several months after surgery.

RESULTS

An increase in acute phase proteins was not observed to the same extent for all the studied patients. Before the surgical procedure, chronic inflammatory process was revealed by an increase in haptoglobin (52.9 p 100) and alpha1 glycoprotein acid (52.9 p 100) whereas increase in C-reactive protein (26.4 p 100) and interleukin-6 (92 p 100) are related to an acute process. Later after surgery, the chronic inflammatory process remained but differed from the observed process before surgery only by haptoglobin (61.7 p 100) and interleukin-6 (47 p 100).

CONCLUSIONS

The presented results, observed during the follow-up of vascular surgery focused on persistent inflammatory process and the surgical procedure did not modify the time course of this process. The evolutionary disease could be considered as chronic and independent of the local effect.

Enzyme adaptations of human skeletal muscle during bicycle short-sprint training and detraining

The effect of sprint training and detraining on supramaximal performances was studied in relation to muscle enzyme adaptations in eight students trained four times a week for 9 weeks on a cycle ergometer. The subjects were tested for peak oxygen uptake (VO2peak), maximal aerobic power (MAP) and maximal short-term power output (Wmax) before and after training and after 7 weeks of detraining. During these periods, biopsies were taken from vastus lateralis muscle for the determination of creatine kinase (CK), adenylate kinase (AK), glycogen phosphorylase (PHOS), hexokinase (HK), phosphofructokinase (PFK), lactate dehydrogenase (LDH) and its isozymes, 3-hydroxy-acyl-CoA dehydrogenase (HAD) and citrate synthase (CS) activities. Training induced large improvements in Wmax (28%) with slight increases (3%) in VO2peak (P < 0.10). This was associated with a greater glycolytic potential as shown by higher activities for PHOS (9%), PFK (17%) and LDH (31%) after training, without changes in CK and oxidative markers (CS and HAD). Detraining induced significant decreases in VO2peak (4%), MAP (5%) and oxidative markers (10-16%), while Wmax and the anaerobic potential were maintained at a high level. This suggests a high level in supramaximal power output as a result of a muscle glycogenolytic and glycolytic adaptation. A long interruption in training has negligible effects on short-sprint ability and muscle anaerobic potential. On the other hand, a persistent training stimulus is required to maintain high aerobic capacity and muscle oxidative potential. This may contribute to a rapid return to competitive fitness for sprinters and power athletes.

Study of basement membrane formation in dermal-epidermal recombinants in vitro

Two different dermal-epidermal recombinants were prepared in vitro and used to study the synthesis and formation of basement membrane. The first was obtained by culturing keratinocytes on the surface of a collagen lattice populated by fibroblasts. The second was prepared by coculture of both keratinocytes and fibroblasts in a collagen lattice. After 6 weeks of culture, the basal lamina was observed with electron microscopy only if keratinocytes were cultivated on top of the collagen lattice populated by fibroblasts. In the second model, however, type IV collagen, laminin, and pemphigoid bullosa antigen could be detected by immunofluorescence as well as synthesis of type IV collagen in the culture, but no basement membrane was observed by electron microscopy. These data demonstrate that, in vitro, basement membrane formation depends not only on the presence of the macromolecular components but also on the culture conditions.

Accumulation of glycolic acid and glyoxylic acid in serum in cases of transient hyperglycinemia after transurethral surgery

Experimental data are presented here proving the accumulation of glycine in serum after transurethral prostatectomy and increased production of glycine metabolites: serine, alanine, glyoxylic acid, and glycolic acid. The presence of the metabolites glyoxylic acid and glycolic acid was demonstrated by gas-liquid chromatography and mass spectrometry. Glycine, glyoxylic acid, and glycolic acid possess neurological activity, so we examined the pathophysiology of the transurethral prostatectomy syndrome in view of the transient accumulation of these compounds in serum.

Accumulation of glycolic acid and glyoxylic acid in serum in cases of transient hyperglycinemia after transurethral surgery

Experimental data are presented here proving the accumulation of glycine in serum after transurethral prostatectomy and increased production of glycine metabolites: serine, alanine, glyoxylic acid, and glycolic acid. The presence of the metabolites glyoxylic acid and glycolic acid was demonstrated by gas-liquid chromatography and mass spectrometry. Glycine, glyoxylic acid, and glycolic acid possess neurological activity, so we examined the pathophysiology of the transurethral prostatectomy syndrome in view of the transient accumulation of these compounds in serum.

Measurement of changes in amino acids related to total collagen in fibrotic human liver

In the liver, total collagen accumulation during the fibrotic or cirrhotic process was measured using a methodology based on the determination of collagen amino acids in liver biopsies from adults with alcoholic liver diseases or children with biliary atresia. The results obtained with this methodology were compared to histopathological findings. Thus, it was shown that generally the severity of hepatic injury was dependent on collagen accumulation. In biliary atresia, collagen accumulation increased with the children's age despite reconstructive surgery and restoration of biliary flow.

Reversal of changes in lipoprotein A and lipoprotein B cholesterol during and for a year after a detoxication treatment program in chronic alcoholism

We studied the individual and occasional changes in lipid metabolism induced by chronic alcohol abuse. In addition, the influence of a detoxication treatment program on the evolutionary changes in some serum lipidic components was studied for a one-year period. Before this program, total cholesterol was above normal, with high values for LP-A cholesterol, whereas for some patients LP-B cholesterol was increased. After the program, there was an increase in total cholesterol, LP-B cholesterol, and apolipoprotein B, with a decrease in LP-A cholesterol. These evolutionary changes continued during the one-year period after the end of the inpatient program.

Reversal of changes in lipoprotein A and lipoprotein B cholesterol during and for a year after a detoxication treatment program in chronic alcoholism

We studied the individual and occasional changes in lipid metabolism induced by chronic alcohol abuse. In addition, the influence of a detoxication treatment program on the evolutionary changes in some serum lipidic components was studied for a one-year period. Before this program, total cholesterol was above normal, with high values for LP-A cholesterol, whereas for some patients LP-B cholesterol was increased. After the program, there was an increase in total cholesterol, LP-B cholesterol, and apolipoprotein B, with a decrease in LP-A cholesterol. These evolutionary changes continued during the one-year period after the end of the inpatient program.

Evolutionary changes in acute-phase proteins in alcoholic hepatocellular diseases

We studied the pattern of acute-phase proteins (orosomucoid, C-reactive protein, and haptoglobin) in hepatocellular deficiency due to chronic alcohol consumption, characterized by a decrease in serum transferrin concentration. We found that their patterns could vary independently of hepatocellular deficiency, but depend on the progression of hepatic disease. The most useful protein for discriminating the stage of inflammatory reaction is orosomucoid. In moderate hepatocellular deficiency, acute-phase proteins are increased independently of the decrease in transferrin, whereas in severe hepatocellular deficiency the acute-phase proteins are also decreased. Thus, it is possible to distinguish the two stages of hepatocellular deficiency by following changes in the concentration of orosomucoid.

Evolutionary changes in acute-phase proteins in alcoholic hepatocellular diseases

We studied the pattern of acute-phase proteins (orosomucoid, C-reactive protein, and haptoglobin) in hepatocellular deficiency due to chronic alcohol consumption, characterized by a decrease in serum transferrin concentration. We found that their patterns could vary independently of hepatocellular deficiency, but depend on the progression of hepatic disease. The most useful protein for discriminating the stage of inflammatory reaction is orosomucoid. In moderate hepatocellular deficiency, acute-phase proteins are increased independently of the decrease in transferrin, whereas in severe hepatocellular deficiency the acute-phase proteins are also decreased. Thus, it is possible to distinguish the two stages of hepatocellular deficiency by following changes in the concentration of orosomucoid.

Relationship between hemoglobin A1c and insulin C-peptide in anomalies of carbohydrate metabolism

In this paper, we have compared the results obtained for hemoglobin A1c and C-peptide concentrations, was not convenient for the diagnosis of anomalies in the regulation of carbohydrate metabolism in obesity or in latent diabetes. Nevertheless, hemoglobin A1c allowed us to check carbohydrate metabolism and to discriminate diabetes treated by oral therapy from insulin dependent diabetes; in these latter cases, hemoglobin A1c concentration varied inversely as C-peptide concentration as it was shown by the method of factor analysis in particular "principal components analysis". In the control of insulin dependent diabetes in a remission, hemoglobin A1c allowed assessment of the regulation of carbohydrate metabolism after suppression of insulin therapy. Thus, hemoglobin A1c is an index of the adaptation of insulin secretion in anomalies of carbohydrate metabolism.

Employment of gas-liquid chromatography for the analysis of collagen amino acids in biopsy tissue

In this paper, gas-liquid chromatography, adapted for the determination of collagen amino acids, is described. This technique was attractive for its sensitivity in that only a small amount of protein such as in 0.5 mg of tissue, especially as obtained from biopsy tissue, was needed for the separation and determination of proline (Pro), 4-hydroxyproline (4-Hyp), 3-hydroxyproline (3-Hyp), lysine (Lys), hydroxylysine (Hyl) and epsilon-hydroxy-norleucine (epsilon-PH-Norleu), the characteristic amino acids of collagen. Thus, without purification of collagen, by determining the ratio Hyl/4-Hyp and 4-Hyp/Pro it was possible to determine some anomalies in the collagen content of biopsy tissue (skin or liver). The ratio Hyl/4-Hyp allows an estimation of the lack of hydroxylation of polypeptidic lysine as in the Ehlers-Danlos syndrome type VI; and the ratio 4-Hyp/Pro allows measurement of variations in collagen content in relation to protein, especially in the liver, as in alcoholic cirrhosis.

[Simultaneous characterizations of 3-prolylhydroxylase and 4-prolylhydroxylase activities by ion exchange chromatography]

3-prolyl hydroxylase activity measurements have already been described by Kivirikko and al, using specific methods. The aim of the present work was to show that the specific and rapid method used for 4-prolyl hydroxylase activity measurement, involving protocollagen [3H-4] proline (measuring of tritiated water enzymatically obtained), could be used for 3-prolyl hydroxylase activity estimation on the same sample: tritiated water enzymatically produced by 4-prolyl hydroxylase was collected by distillation, and the amino acids enzymatically modified were analysed after HCl 6 N hydrolysis of dried incubation medium, by cation exchange chromatography. The characterization of enzymatically obtained 3-hydroxyproline was performed using three means. The elution peaks reported were in the same position as the elution peak of pure 3-hydroxyproline and 4-hydroxyproline. Moreover, tritiated 3-hydroxyproline and 4-hydroxyproline were obtained only after incubation of labelled substrate with crude preparation of prolyl hydroxylases from chick embryos. Some possible artefacts such as dicetopiperazines and pyrrol-2-carboxylic acid have been shown to be distinguished chromatographically from 3-hydroxyproline and 4-hydroxyproline. The high ratio of measured (Formula: see text) activities, near 5.5 p. cent, is discussed.

[Determination of free intracellular proline pool in fibroblast cultures]

By using a direct, rapid, sensitive colorimetric method, free intracellular proline pool from human adult skin fibroblasts in monolayer was determined. Thus under identical experimental conditions, free intracellular proline pool was about 20 pmol proline/micrograms cellular proteins, whatever the cell lines from human adult skin fibroblasts, the passage and the time of subculture. Besides, there was a poor correlation between collagen biosynthesis in fibroblast cultures and free intracellular proline pool.

[Study, by an enzymatic method, of the isomers of L-proline (3H-4) and of the effects of preservation]

By use of procollagen proline hydroxylas which catalyses the substitution of the hydrogen in the trans position on carbon 4 with an hydroxyl on L-proline residues of procollagen, we have shown that the L-[3H-4] proline product of C.E.N. Saclay contained 29 per cent of the trans and 71 per cent of the cis form. It was also possible to verify the molecular stability of the isomers and that a small amount of tritium was randomly linked to the whole molecule.