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Biomedical subjects

P Robin

Publications and source records attributed to P Robin.

At least 73 records · Page 4Linked to original sources
PubMed1991

Regulation of NO(3) Assimilation by Anion Availability in Excised Soybean Leaves.

The regulation of NO(3) (-) assimilation by xylem flux of NO(3) (-) was studied in illuminated excised leaves of soybean (Glycine max L. Merr. cv Kingsoy). The supply of exogenous NO(3) (-) at various concentrations via the transpiration stream indicated that the xylem flux of NO(3) (-) was generally rate-limiting for NO(3) (-) reduction. However, NO(3) (-) assimilation rate was maintained within narrow limits as compared with the variations of the xylem flux of NO(3) (-). This was due to considerable remobilization and assimilation of previously stored endogenous NO(3) (-) at low exogenous NO(3) (-) delivery, and limitation of NO(3) (-) reduction at high xylem flux of NO(3) (-), leading to a significant accumulation of exogenous NO(3) (-). The supply of (15)NO(3) (-) to the leaves via the xylem confirmed the labile nature of the NO(3) (-) storage pool, since its half-time for exchange was close to 10 hours under steady state conditions. When the xylem flux of (15)NO(3) (-) increased, the proportion of the available NO(3) (-) which was reduced decreased similarly from nearly 100% to less than 50% for both endogenous (14)NO(3) (-) and exogenous (15)NO(3) (-). This supports the hypothesis that the assimilatory system does not distinguish between endogenous and exogenous NO(3) (-) and that the limitation of NO(3) (-) reduction affected equally the utilization of NO(3) (-) from both sources. It is proposed that, in the soybean leaf, the NO(3) (-) storage pool is particularly involved in the short-term control of NO(3) (-) reduction. The dynamics of this pool results in a buffering of NO(3) (-) reduction against the variations of the exogenous NO(3) (-) delivery.

Journal Article↗
PubMed1989

In situ detection of a heat-shock regulatory element binding protein using a soluble synthetic enhancer sequence.

In various studies, enhancer binding proteins have been successfully absorbed out by competing sequences inserted into plasmids, resulting in the inhibition of the plasmid expression. Theoretically, such a result could be achieved using synthetic enhancer sequences not inserted into plasmids. In this study, a double stranded DNA sequence corresponding to the human heat shock regulatory element was chemically synthesized. By in vitro retardation assays, the synthetic sequence was shown to bind specifically a protein in extracts from the human T cell line Jurkat. When the synthetic enhancer was electroporated into Jurkat cells, not only the enhancer was shown to remain undegraded into the cells for up to 2 days, but also it was shown to bind intracellularly a protein. The binding was specific and was modulated upon heat shock. Furthermore, the binding protein was shown to be of the expected molecular weight by UV crosslinking. However, when the synthetic enhancer element was co-electroporated with an HSP 70-CAT reporter construct, the expression of the reporter plasmid was consistently enhanced in the presence of the exogenous synthetic enhancer.

Cell Line↗
PubMed1989

[Protein-losing enteropathy syndrome caused by a localization of Kaposi's sarcoma in AIDS].

A 35-year-old HIV positive patient with skin and gastrointestinal localization of a Kaposi's sarcoma was admitted for severe diffuse edema. Increased alpha-I-antitrypsin clearance (150 ml/24 h) allowed us to confirm the diagnosis of protein loosing enteropathy resulting from sarcoma infiltration in the stomach, the duodenum and the entire small bowel. At autopsy, ileal ulcerations were found. Gastrointestinal involvement occurring during Kaposi's sarcoma is common and usually symptomless. The discovery of a protein loosing enteropathy in our patient suggests that this gastrointestinal involvement could play a role in the hypoalbuminemia often found in these patients.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Cloning and expression of a cDNA for human thioredoxin.

Thioredoxin is the best representative enzyme of a group of proteins, widely distributed and possessing dithiol-disulfide oxidoreductase activity. We have constructed a cDNA library from messenger RNAs isolated from a lymphoblastoid B cell line (Epstein-Barr virus-immortalized normal human lymphocytes). Screening of this library with synthetic oligonucleotide probes, constructed from the NH2-terminal amino acid sequence of a protein produced by this line, allowed us to identify a full-length cDNA clone coding for human thioredoxin. The open reading frame (315 nucleotides long) codes for a protein of 104 amino acids (excluding the initial methionine). This protein possesses the highly conserved enzymatic active site common to plant and bacterial thioredoxins: Trp-Cys-Gly-Pro-Cys (amino acids 30-34). These data provide for the first time the complete primary sequence of a thioredoxin of mammalian origin. Recombinant human thioredoxin, expressed in Escherichia coli, possesses a dithiol-reducing enzymatic activity as assayed on mammalian and plant substrates. It is able to reduce the interchain disulfide bridges of murine pentameric IgM and porcin insulin and also to activate vegetal NADP-malate dehydrogenase. Studies of human thioredoxin mRNA expression and regulation in immunocompetent cells of human origin indicate that the protein is weakly expressed in resting lymphocytes and monocytes, but the level of human thioredoxin mRNA transcription is quite important in activated monocytes and established dividing human cell lines.

Amino Acid Sequence↗
PubMed1988

Intramitochondrial factors controlling hepatic fatty acid oxidation at weaning in the rat.

Fatty acid oxidation was studied in isolated liver mitochondria of rats during the suckling-weaning transition. The oxidation rate of oleyl-CoA and palmitoylcarnitine was reduced 2.5-fold in rats weaned on a high-carbohydrate diet compared to suckling rats, when acetyl-CoA produced by beta-oxidation was directed towards ketone-body synthesis. Weaning on a high-fat diet minimized this change. Channeling of acetyl-CoA towards citrate synthesis doubled the oxidation rate of both substrates in HC-weaned rats. Thus, in addition to changes in carnitine palmitoyltransferase I activity, the beta-hydroxymethylglutaryl-CoA synthase pathway is also involved in the decreased fatty acid oxidation at weaning. This was confirmed by measurement of beta-hydroxymethylglutaryl-CoA synthase pathway activity.

Acetyl Coenzyme A↗
PubMed1988

[Comparative serum pharmacokinetics of prednisone and prednisolone methylsulfobenzoate after oral administration].

Pharmacokinetic values of prednisone and prednisolone were measured in the serum of 6 healthy volunteers after oral administration of either prednisolone methylsulfobenzoate 30 mg or prednisone 30 mg. Peak serum concentrations of prednisolone obtained after dosing with prednisone occurred earlier and were higher (473 +/- 106 ng/ml) than those obtained after dosing with prednisolone methylsulfobenzoate (232 +/- 70 ng/ml; P less than 0.01). Similarly, areas under the 0-8 h concentration curves were significantly greater after dosing with prednisone than after dosing with prednisolone methylsulfobenzoate (prednisolone: P less than 0.001; prednisone: P less than 0.02). The differences may be due to prednisolone methylsulfobenzoate not being absorbed as well as prednisone. These kinetic data may warrant a reappraisal of the therapeutic equivalence of the two drugs taken for granted in France.

Administration, Oral↗
PubMed1988

Decreased hepatic fatty acid oxidation at weaning in the rat is not linked to a variation of malonyl-CoA concentration.

In rats weaned on a high-carbohydrate diet, hepatic fatty acid oxidation capacity is decreased when compared to suckling rats. Previous studies (Benito et al., 1979) suggested that a malonyl-CoA-dependent mechanism could be at the origin of this decrease. Studies on isolated hepatocytes show that despite, respectively, a low and a high lipogenic rate in suckling and weaned rats, malonyl-CoA concentrations are similar in the two groups. This might be due to the lower ratio fatty acid synthetase/acetyl-CoA carboxylase (EC 6.4.1.2) activities during suckling than after weaning. Different rates of hepatic fatty acid oxidation despite similar malonyl-CoA concentrations can be explained by the 2.5-fold higher carnitine palmitoyltransferase I (EC 2.3.1.21) activity in suckling rats together with a 7-fold higher Ki for malonyl-CoA. This precludes a tight control of fatty acid oxidation by [malonyl-CoA] in suckling rats. Weaning on a high-fat carbohydrate-free diet abolishes the changes previously described for the kinetic characteristics of carnitine palmitoyltransferase I suggesting that nutritional modifications rather than a developmental stage are involved. Thus, during the suckling-weaning transition, a variation of [malonyl-CoA] is not responsible for the decrease in hepatic fatty acid oxidation. It involves, in addition, a decrease in carnitine palmitoyltransferase I activity and an increase of the sensitivity of this enzyme to malonyl-CoA.

ATP Citrate (pro-S)-Lyase↗
PubMed1988

[Limitations of scintigraphy using metaiodobenzylguanidine for locating pheochromocytomas. Apropos of 2 cases].

Two cases of MIBG (metaiodobenzylguanidine) scintigraphy are reported: the first case concerns a female patient hospitalized for high blood pressure (HBP) with symptoms evocative of pheochromocytoma. Urinary titration of catecholamines metabolites, which are usually abnormally high, and tomodensitometry permit the visualization of a left adrenal tumor. On the contrary, the MIBG scintigraphy does not show any abnormal fixation. After resection, the pathological examination confirms the diagnosis of pheochromocytoma. The second case concerns a female patient hospitalized for HBP with, on the chest X-Ray, a left postero-inferior density. Serum and urinary catecholamine levels are normal. Tomodensitometry confirms the tumor of the posterior mediastinum and the MIBG scintigraphy demonstrates a focus of thoracic opposite the tumor. After resection, the pathological examination shows an ectopic supernumerary bronchial bud. These two cases illustrate the limitations of MIBG scintigraphy to locate pheochromocytomas. There are false negative (10%) which may be explained by an insufficient uptake of the tracer by the tumor, by an insufficient image formation or by medication interferences. On the contrary, there may be false positives because of histochemical similarities between the chromaffin tissues and certain glandular or neural tumors. Nevertheless, in spite of serious limitations, which we must be aware of, MIBG scintigraphy remains the best primary examination for the location of pheochromocytomas.

3-Iodobenzylguanidine↗
PubMed1986

Evidence that the development of hepatic fatty acid oxidation at birth in the rat is concomitant with an increased intramitochondrial CoA concentration.

The development of hepatic fatty acid oxidation during the perinatal period in the rat was studied using isolated mitochondria. Ketone body synthesis from substrates entering at different levels of beta-oxidation was 2-3 times lower in mitochondria isolated from term-fetal liver than in 16-h-old newborn or adult liver mitochondria. The low rate of palmitoyl-L-carnitine oxidation in term-fetal mitochondria was linked neither to the low capacity of the respiratory chain nor to the removal of acetyl-CoA in the hydroxymethylglutaryl-CoA synthase pathway. The 2.5-times lower concentration of CoA found in term-fetal liver mitochondria when compared to 16-h-old or adult liver mitochondria might be the factor responsible for the low rate of fatty acid oxidation in term-fetal liver mitochondria.

2,4-Dinitrophenol↗
PubMed1986

Purification to homogeneity and NH2-terminal amino acid sequence of a novel interleukin 1 species derived from a human B cell line.

A subclone, referred to as 3B6, derived from a DR-negative EBV-transformed B cell line, has been found to spontaneously produce IL 1. 3B6-IL 1 displays a pI of 5 on FPLC chromatofocusing. It has been purified to homogeneity by a sequence of ion-exchange chromatography and affinity chromatography on procion red agarose. The homogeneous material migrated with an apparent m.w. of 13,500 on SDS-PAGE. The overall recovery of IL 1 activity was estimated at 57%. The final material had a specific activity of 7.8 X 10(6) half-maximal units/mg and represented a 50,000-fold purification. A partial NH2-terminal amino acid sequence has been obtained that is different from those reported from monocytic IL 1. However, this molecule can formally be identified as IL 1 on its spectrum of biologic activities. In addition to inducing the proliferation of murine thymocytes in the co-stimulator assay. 3B6-IL 1 is active on both human T and B cells, respectively, in inducing IL 2 synthesis by cells from a subcloned HSB 2 line and promoting the proliferation of anti-IgM-stimulated human peripheral blood B lymphocytes. Furthermore, 3B6-IL 1 acts as a growth factor for normal human fibroblasts and for the 3B6 line itself. However, 3B6-IL 1 is not pyrogenic in rabbits. Thus, the 3B6 cell line was shown to produce a new molecular species of IL 1, with respect to its NH2-terminal sequence, which shared all of the studied biologic activities of monocytic IL 1 except for pyrogenicity.

Amino Acid Sequence↗
PubMed1986

Nitrate Reduction in Roots and Shoots of Barley (Hordeum vulgare L.) and Corn (Zea mays L.) Seedlings: I. N Study.

Nitrate reduction in roots and shoots of 7-day-old barley seedlings, and 9-day-old corn seedlings was investigated. The N-depleted seedlings were transferred for 24 h or 48 h of continuous light to a mixed nitrogen medium containing both nitrate and ammonium. Total nitrate reduction was determined by (15)N incorporation from (15)NO(3) (-), translocation of reduced (15)N from the roots to the shoots was estimated with reduced (15)N from (15)NH(4) (+) assimilation as tracer, and the translocation from the shoots to the roots was measured on plants grown with a split root system. A model was proposed to calculate the nitrate reduction by roots from these data. For both species, the induction phase was characterized by a high contribution of the roots which accounted for 65% of the whole plant nitrate reduction in barley, and for 70% in corn. However, during the second period of the experiment, once this induction process was finished, roots only accounted for 20% of the whole plant nitrate reduction in barley seedlings, and for 27% in corn. This reversal in nitrate reduction localization was due to both increased shoot reduction and decreased root reduction. The pattern of N exchanges between the organs showed that the cycling of reduced N through the plant was important for both species. In particular, the downward transport of reduced N increased while nitrate assimilation in roots decreased. As a result, when induction was achieved, the N feeding of the roots appeared to be highly dependent on translocation from the leaves.

Journal Article↗