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Biomedical subjects

F Petit

Publications and source records attributed to F Petit.

At least 91 records · Page 5Linked to original sources
PubMed1991

Drug addicts attending specialised institutions: towards a drug addiction data bank?

In 1986, a national survey was carried out in France among 4846 drug abusers attending specialised agencies and treatment centres. Data are analysed and compared with the results of a previous study in 1972. Most French drug abusers are men (74%) ranged in age from 20 to 29 years (68%). Data suggest increasing problems with heroin (69%), cocaine (13%), solvents (5%), alcohol (26%) and multiple drug dependence. Women are younger, they have attempted suicide more often than men but have been incarcerated half as often. Concerning drug abuse trends, women appear to use increasingly sedatives in combination with other drugs. Partial data concerning HIV seropositivity reveal a rate of 48% among drug abusers having been tested.

Adolescent↗
PubMed1991

Detection of African swine fever virus by a biotinylated DNA probe: assay on cell cultures and field samples.

African swine fever virus was detected in various samples using a molecular hybridization technique. A fragment located in a constant area of the viral genome was biotin-labelled. This probe, when present at a concentration of 100 ng/ml of the hybridization solution, could detect 10 pg of target DNA immobilized on nitrocellulose with cellular DNA and RNA. The virus was evidenced after being passaged on monkey kidney cells, either 8 h post-inoculation (pi) if the multiplicity of infection (MOI) was at least 1 hemadsorbing unit (HAd) per cell, or 24 h later if the inoculum was diluted up to 10(-3) HAd per cell. When passaged on pig leukocytes with a MOI of 0.1 HAd per cell, the virus was evidenced 12 h pi, or 24 h pi with a MOI of 10(-2) HAd per cell. The probe did not hybridize with another DNA virus passaged on cells, neither did it react with non-infected blood or ham, but did so if African swine fever virus was resuspended with the samples. The spleen from uninfected pig and the lymph nodes from a pig which had died from hog cholera were found to be negative, whereas the spleen from a pig which had died of African swine fever was positive. These samples were also tested with a 32P-labelled probe whose sensitivity was 10-fold higher. A non-radioactive probe could be used both for the sensitive and specific diagnosis of African swine fever and the detection of the virus in an epidemiological survey.

African Swine Fever↗
PubMed1989

Ornithine carbamoyltransferase deficiency. A new variant with subnormal enzyme activity.

A new ornithine carbamoyltransferase variant is described with a nearly normal specific enzymatic activity. This new variant is characterized by a ten-fold increased Km value for L-ornithine (3.75 vs. 0.33 mmol/l in control) and by a normal Km value for carbamoylphosphate (0.42 vs. 0.29 mmol/l). Its pH optimum is shifted towards the alkaline side. This enzyme is highly unstable at 55 degrees C.

Amino Acids↗
PubMed1989

Metabolism of endogenous arachidonic acid in weakly activated platelets. Absence of leukocyte cooperative products in whole blood.

Human platelets were incubated alone or in whole blood with specific agonists such as thrombin or collagen, and 12-hydroxy-heptadecatrienoic (HHT) and 12-hydroxy-eicosatetraenoic (12-HETE) acids were measured by HPLC as indices of platelet cyclooxygenase and lipoxygenase activities, respectively. We found that both arachidonic acid metabolites are significantly formed at concentrations of thrombin insufficient to provoke platelet aggregation. The ratio HHT/12-HETE varied with increasing concentrations of thrombin, with an increase in the absence and a decrease in the presence of albumin in the incubation. When platelets were stimulated in whole blood, this ratio favoured HHT and the addition of albumin to isolated platelets had the same effect. The formation of oxygenated products of 12-HETE by leukocyte LTB w-hydroxylase and 5-lipoxygenase in unstimulated and stimulated leukocytes, respectively, was also investigated. We failed to detect any significant amounts of these products in whole blood incubated with relatively high concentrations of collagen in the presence or absence of the chemotactic peptide FMLP. We conclude that, although 12-HETE is a good substrate for leukocyte oxygenases when incubated at high concentration with the cells alone, its oxygenation is unlikely to occur in whole blood, making 12-HETE and/or HHT potential markers of platelet activation in vivo, provided they are not substantially degraded during passage of the blood through various organs.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1987

Use of mu and delta opioid peptides of various selectivity gives further evidence of specific involvement of mu opioid receptors in supraspinal analgesia (tail-flick test).

The tail-flick assay in chronic implanted rats was used to test the analgesic potency of agonists selective for mu opioid receptors: [D-Ala2,MePhe4,Gly-ol5]enkephalin (DAGO), Tyr-D-Ala-Gly-NH(CH2)2-CH(CH3)2 (TRIMU 5) and for delta receptor subtypes: [D-Ser2,Leu5]enkephalyl-Thr6 (DSLET), [D-Thr2,Leu5]enkephalyl-Thr6 (DTLET) and cyclic [D-Pen2,L-Pen5]enkephalin (DPLPE). DAGO produced an analgesic response at a concentration 500 times lower than DPLPE. The relative activity of these compounds was significantly correlated with their affinity for central or peripheral mu receptors but not with their delta receptor affinity. Diffusion studies of tritiated mu and delta agonists showed that after i.c.v. injection, these enkephalin analogues remained essentially localized within supraspinal structures. Taken together these results suggest strongly that the analgesia produced at the supraspinal level by opioid peptides is related to mu receptor stimulation.

Analgesia↗
PubMed1986

Further evidence for a role of delta-opiate receptors in the presynaptic regulation of newly synthesized dopamine release.

The effects of the specific delta-agonist of opiate receptors, DTLET (Tyr-D-Thr-Gly-Phe-Leu-Thr), the specific mu-agonist DAGO (Tyr-D-Ala-Gly-(Me)Phe-Gly-ol) and of kelatorphan (N-((2R)-3-(hydroxyaminocarbonyl-2-benzyl-1-oxopropyl)-L-alanine), a potent inhibitor of the enkephalin-degrading enzymes, on the spontaneous release of [3H]dopamine ([3H]DA) synthesized from [3H]tyrosine were examined in rat striatal slices. DTLET (10(-7) M, 10(-6) M) and kelatorphan (5 X 10(-6) M) enhanced markedly the release of newly synthesized [3H]DA, while DAGO (10(-6) M) was inactive. The stimulatory effects of DTLET (10(-7) M) and kelatorphan (5 X 10(-6) M) were prevented in the presence of naloxone (3 X 10(-6) M; 10(-4) M respectively) or ICI 154,129 (10(-5) M), a selective antagonist of delta-opiate receptors. While DTLET (10(-7) M) stimulated the 30 mM potassium-evoked release of newly synthesized [3H]DA, it did not affect the potassium-evoked release of [3H]DA previously synthesized in tissues. A higher concentration of DTLET (10(-6) M) was required in the latter case. In contrast to the release observed with striatal slices, DTLET (10(-7) M), 10(-6) M) or DAGO (10(-6) M) did not affect the spontaneous release of newly synthesized [3H]DA from nucleus accumbens slices. In addition, DTLET (10(-6) M) was without effect on the potassium-evoked release of newly synthesized [3H]DA in this structure. The present results confirmed that delta-opiate receptors are involved in the presynaptic regulation of [3H]DA release.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Stimulatory effect of substance P on the spontaneous release of newly synthesized [3H]dopamine from rat striatal slices: a tetrodotoxin-sensitive process.

Striatal slices from the rat were continuously superfused with [3H]tyrosine in order to estimate the release of newly synthesized [3H]dopamine [( 3H]DA). Substance P (SP) and neuromedin K (NKB) stimulated the spontaneous release of [3H]DA when used in concentrations (from 10(-9) M to 10(-7) M). The stimulatory effect of substance P (10(-8) M) was prevented completely when slices were superfused with tetrodotoxin (10(-7) M) or the substance P antagonist (D-Arg1,D-Pro2,D-Trp7,9,Leu11) substance P (10(-5 M) indicating that the response evoked by substance P was mediated by substance P receptors but that these were not located on DA nerve terminals. In addition, substance P did not modify the stimulatory effect of acetylcholine (ACh) (10(-5) M) on the spontaneous release of [3H]DA since the effects of substance P (10(-7) M) and ACh (10(-5) M) were additive.

Acetylcholine↗
PubMed1986

Effects of organic acids on the synthesis of citrulline by intact rat liver mitochondria.

Citrulline synthesis, mostly regulated at the carbamoyl-phosphate synthase I (EC 6.3.4.16) step by the intramitochondrial concentration of ATP and/or N-acetylglutamate is tested with four organic acids: propionate, alpha-ketobutyrate, dipropyl-acetate and 4-pentenoate. In the presence of 10 mM succinate, as the oxidizable substrate, citrullinogenesis was only inhibited by propionate and 4-pentenoate. With 10 mM L-glutamate, a significant inhibition was observed with the four acids. After the addition of ATP and N-acetylglutamate to uncoupled mitochondria, no inhibition could be demonstrated with dipropylacetate and 4-pentenoate. However, a slight inhibition remained with propionate and alpha-ketobutyrate. When mitochondria were incubated with 10 mM L-glutamate, ATP decreased with propionate, dipropylacetate and 4-pentenoate. Under the same conditions, N-acetylglutamate synthesis was strongly inhibited by each organic acid. The decrease of N-acetylglutamate synthesis was related to the constant diminution of intramitochondrial acetyl-coenzyme A (CoA) and to the increase of propionyl-CoA with propionate and alpha-ketobutyrate. Acetyl-CoA and propionyl-CoA are respectively substrate and competitive inhibitor of the N-acetylglutamate synthase (EC 2.3.1.1). Each acid displayed its optimum inhibition at concentrations between 1 and 2 mM. At these acid concentrations, mitochondria had the lowest acetyl-CoA content and the highest propionyl-CoA content.

Acetyl Coenzyme A↗
PubMed1985

Impairment of citrulline synthesis during late pregnancy and lactation in rats.

Synthesis of citrulline by rat liver mitochondria was investigated during late pregnancy and early lactation. It was strongly decreased over all the period studied except during delivery, where a sudden rise was observed. The mitochondrial enzymes carbamoylphosphate synthetase I (ammonia) (EC 6.3.4.16) and ornithine carbamoyltransferase (EC 2.1.3.3) did not fall significantly during this period, although carbamoylphosphate synthetase I (ammonia) was slightly decreased antepartum. Citrulline synthesis was found significantly correlated to N-acetylglutamate concentration in mitochondria throughout the period considered. On the other hand, low levels of N-acetylglutamate could be explained by low activity of N-acetylglutamate synthase (EC 2.3.1.1).

Acetyltransferases↗
PubMed1985

Isolation of polysomes from permissive and non-permissive invertebrate cell lines infected with chilo iridescent virus.

Chilo Iridescent virus (Iridovirus type 6 or CIV) infection results in a disaggregation of the heavy polyribosomes both in permissive and non-permissive invertebrate cell lines. The integrity of the viral genome is not involved in this event, as shown by the polysome absorbance profile on sucrose gradient, prepared from cells infected with UV treated virus. Heavy polysomes reappeared in permissive infected cells during the viral replication cycle.

Aedes↗
PubMed1983

Radioisotopic assay of picomolar amounts of coenzyme A.

A two-step method of determining reduced coenzyme A (CoASH) concentrations in tissue or cell extracts is described. In the first step, CoASH is reacted with acetylphosphate in a reaction catalyzed by phosphotransacetylase to yield acetyl-CoA. Acetyl-CoA is then condensed with [14C]oxaloacetate by citrate synthase to give [14C]citrate. This method allows the measurement of 10-200 pmol of CoASH. By omitting the phosphotransacetylase step, measurement of the same amount of acetyl-CoA is possible.

Acetyl Coenzyme A↗
PubMed1983

Inhibition of ureagenesis by valproate in rat hepatocytes. Role of N-acetylglutamate and acetyl-CoA.

Valproate (0.5-5 mM) strongly inhibited urea synthesis in isolated rat hepatocytes incubated with 10 mM-alanine and 3 mM-ornithine. Valproate at the same concentrations markedly decreased concentrations of N-acetylglutamate, an essential activator of carbamoyl-phosphate synthetase I (EC 6.3.4.16), in parallel with the inhibition of urea synthesis by valproate. This compound also lowered the cellular concentration of acetyl-CoA, a substrate of N-acetylglutamate synthase (EC 2.3.1.1); glutamate, aspartate and citrulline were similarly decreased. Valproate in a dose up to 2 mM did not significantly affect the cellular concentration of ATP and had no direct effect on N-acetylglutamate synthesis, carbamoyl-phosphate synthetase I and ornithine transcarbamoylase (EC 2.1.3.3) activities.

Acetyl Coenzyme A↗
PubMed1983

Deltakephalin, Tyr-D-Thr-Gly-Phe-Leu-Thr: a new highly potent and fully specific agonist for opiate delta-receptors.

Deltakephalin, Tyr-D-Thr-Gly-Phe-Leu-Thr (DTLET) was rationally designed as pure delta-probe from proposed models of mu and delta opiate receptors. On peripheral organs, deltakephalin displays a 3000 times higher inhibitory potency on the electrically stimulated mouse vas deferens (IC50 = 0.15 nM) as on the guinea pig ileum (IC50 = 460 nM). As expected [3H]deltakephalin interacts at 35 degrees C in rat brain tissue to a single class of binding sites (delta) (Bmax = 0.115 pmole/mg protein) with a high affinity: KD = 1.35 nM from equilibrium measurements and KD = 0.43 nM from kinetic determinations. Deltakephalin occurs as the most specific ligand for delta-binding sites as shown by the following discrimination ratios KI(mu)/KI(delta): 0.31 for D-Ala2-D-Leu5-enkephalin; 0.15 for D-Ser2-Thr6-Leu-enkephalin and 0.05 for deltakephalin.

Animals↗
PubMed1983

Developmental changes of citrullinogenesis, mitochondrial N-acetylglutamate content and N-acetylglutamate synthetase in fetal and neonatal rats.

A low citrullinogenesis (less than 60 per cent of the adult value) was observed throughout the suckling period when mitochondria isolated from newborn rat liver were incubated in vitro with L-glutamate or succinate as oxidizable substrates. The adult value was reached after weaning. From birth to weaning, intact mitochondria synthesized more citrulline when supplemented with L-glutamate than with succinate. The low citrullinogenesis could not be explained by low carbamoylphosphate synthetase-I and ornithine transcarbamoylase activities that reached adult values at birth. The decreased citrullinogenesis seen for the first three days of life seemed to be related to the low intramitochondrial concentration of N-acetylglutamate, an activator of the carbamoylphosphate synthetase-I. The concentration of this activator did not differ from that reported for adult rat liver mitochondria after the fourth day of life. The discrepancy between the normal value of N-acetylglutamate concentration and the low activity of the N-acetylglutamate synthetase (15 to 30 per cent of the adult activity) is discussed on the basis of acetyl-CoA or L-glutamate availability in mitochondria isolated from newborn or young rats.

Acetyltransferases↗
PubMed1982

Acute effects of glucagon on citrulline biosynthesis.

Mitochondria isolated from livers of rats fed on different diets showed altered capacity to synthesize citrulline. Glucagon, 15 min after injection, increases citrulline biosynthesis, except after the high-protein diet. A significant correlation between citrulline biosynthesis and N-acetylglutamate content with and without glucagon treatment was shown when rats were fed on a standard or a carbohydrate diet. Different diets modified carbamoyl phosphate synthetase I (EC 6.3.4.16) and N-acetylglutamate synthase (acetyl-CoA:L-glutamate N-acetyltransferase, EC 2.3.1.1) activities. Glucagon did not modify these activities.

Animals↗