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G Pons

Publications and source records attributed to G Pons.

At least 109 records · Page 6Linked to original sources
PubMed1988

Heterogeneous expression of protein and mRNA in pyruvate dehydrogenase deficiency.

Deficiency of pyruvate dehydrogenase [pyruvate:lipoamide 2-oxidoreductase (decarboxylating and acceptor-acetylating), EC 1.2.4.1], the first component of the pyruvate dehydrogenase complex, is associated with lactic acidosis and central nervous system dysfunction. Using both specific antibodies to pyruvate dehydrogenase and cDNAs coding for its two alpha and beta subunits, we characterized pyruvate dehydrogenase deficiency in 11 patients. Three different patterns were found on immunologic and RNA blot analyses. (i) Seven patients had immunologically detectable crossreactive material for the alpha and beta proteins of pyruvate dehydrogenase. (ii) Two patients had no detectable crossreactive protein for either the alpha or beta subunit but had normal amounts of mRNA for both alpha and beta subunits. (iii) The remaining two patients also had no detectable crossreactive protein but had diminished amounts of mRNA for the alpha subunit of pyruvate dehydrogenase only. These results indicate that loss of pyruvate dehydrogenase activity may be associated with either absent or catalytically inactive proteins, and in those cases in which this enzyme is absent, mRNA for one of the subunits may also be missing. When mRNA for one of the subunits is lacking, both protein subunits are absent, suggesting that a mutation affecting the expression of one of the subunit proteins causes the remaining uncomplexed subunit to be unstable. The results show that several different mutations account for the molecular heterogeneity of pyruvate dehydrogenase deficiency.

Acidosis, Lactic↗
PubMed1988

Cloning and cDNA sequence of the dihydrolipoamide dehydrogenase component human alpha-ketoacid dehydrogenase complexes.

cDNA clones comprising the entire coding region for human dihydrolipoamide dehydrogenase (dihydrolipoamide:NAD+ oxidoreductase, EC 1.8.1.4) have been isolated from a human liver cDNA library. The cDNA sequence of the largest clone consisted of 2082 base pairs and contained a 1527-base open reading frame that encodes a precursor dihydrolipoamide dehydrogenase of 509 amino acid residues. The first 35-amino acid residues of the open reading frame probably correspond to a typical mitochondrial import leader sequence. The predicted amino acid sequence of the mature protein, starting at the residue number 36 of the open reading frame, is almost identical (greater than 98% homology) with the known partial amino acid sequence of the pig heart dihydrolipoamide dehydrogenase. The cDNA clone also contains a 3' untranslated region of 505 bases with an unusual polyadenylylation signal (TATAAA) and a short poly(A) track. By blot-hybridization analysis with the cDNA as probe, two mRNAs, 2.2 and 2.4 kilobases in size, have been detected in human tissues and fibroblasts, whereas only one mRNA (2.4 kilobases) was detected in rat tissues.

Amino Acid Sequence↗
PubMed1988

Gentamicin monitoring in neonates.

The elimination of gentamicin (G) was studied in 103 neonates (30 premature) during the first month of life after 2.5 mg/kg i.v. (as infusion) over 20-30 min. G plasma levels, measured by EMIT assay, were obtained before and at 1, 2, 3, and 6 h after infusion. We derived individual first-order kinetic parameters and designed optimal dose regimens. G plasma clearance, half-life, and recommended dose (mg/kg/h) changed exponentially with postnatal age during the first 14 days of life. No significant changes in kinetic values were noted during the first 3 days of life; however, they varied linearly with gestational age when they were measured during this period. Apgar score at 10 min and blood urea nitrogen significantly influenced the same parameters. The predictive value of a designed dose regimen was evaluated at steady-state, after dosage adjustment using two plasma concentration values: the minimum plasma concentration was below 2 mg/L in 93% of the patients; the plasma concentration observed within 1 h after completion of the infusion was (mean +/- SD) 5.33 +/- 0.97 mg/L. Our data suggest that 2.5 mg/kg every 12 h is appropriate in most neonates except for 0-2-day-old premature infants who require 2.5 mg/kg every 18 h. Monitoring of G plasma levels is advisable in infants with low Apgar score and/or renal failure.

Age Factors↗
PubMed1988

Developmental changes of caffeine elimination in infancy.

Five neonates (4 premature) and 16 infants (6 prematurely born), 15-588 days old, received caffeine as citrate salt for apnea. Plasma samples were collected 0, 2, 4, 6 h after a dose and before the next scheduled one. Patients 8 and 9 were serially studied. Caffeine plasma concentrations were determined using HPLC. The caffeine elimination half-life and clearance varied linearly with gestational age and exponentially with postnatal age, the plateau being reached during the second trimester of life. Dose regimen guidelines as a function of postnatal age were derived from individually calculated doses and dosing intervals in order to achieve, at steady state, a caffeine mean plasma concentration of 11 mg/l with a minimum of 7.5 mg/l and a maximum of 14.5 mg/l. We suggest dosing intervals for infants before 1 month, 1-2 months, 2-4 months and after 4 months to be equal to 24, 12, 8 and 6 h, respectively. The individual recommended dose varies from 2 to 10 mg/kg (as caffeine base) making caffeine monitoring mandatory in infants.

Aging↗
PubMed1988

Maturation of caffeine N-demethylation in infancy: a study using the 13CO2 breath test.

Four premature neonates and eight infants 1-19 months old received caffeine for apnea. The usual morning oral dose was substituted by 1,3,7 13C-trimethylxanthine (13C-tri CAF) as the citrate salt. Five breath samples were collected the day before (day 1) and the day of 13C-tri CAF administration (day 2). Plasma (after each breath collection) and urine were collected on day 2. 13C-CO2 exhalation was determined by isotope ratio mass spectrometry. Caffeine and its metabolites were measured using high-pressure liquid chromatography. Assessment of the labeled CO2 in the breath revealed no detectable 13C-tri CAF N-demethylation activity in infants before 45 wk postconceptional age. However, demethylation (as urinary metabolites) has been detected before that age. Two-, 4-, and 6-h cumulative excretion of 13C-tri CAF as 13C-CO2 increased with postnatal age and correlated with caffeine plasma clearance (r = 0.840, p less than 0.01). These results were consistent with those obtained for urinary metabolites. In one infant (19 months old) the cumulative excretion of 13C-CO2 while crying was 65% of the value observed during quiet breathing. The measurement of caffeine demethylation using the caffeine CO2 breath test is feasible in infants and is a safe and noninvasive method to determine age related changes in P4501-dependent N-demethylase activity.

Apnea↗
PubMed1987

Rat liver mitochondria contain two immunologically distinct dihydrolipoamide dehydrogenases.

We have raised antisera against dihydrolipoamide dehydrogenase. One antigen was isolated from purified bovine kidney pyruvate dehydrogenase complex (PDC). The other antigen was a commercial preparation of porcine heart dihydrolipoamide dehydrogenase (E3) which did not first involve purification of the alpha-keto acid dehydrogenase complex(es). Both antibody preparations cross-reacted with the E3 components of PDC, alpha-ketoglutarate dehydrogenase complex, and branched-chain keto acid dehydrogenase complex. This demonstrates the immunological identity of the E3 components. These sera totally precipitated E3 activity from the purified complexes, from purified preparations of E3, and from extracts of rat heart and kidney mitochondria. The two sera vary in their reaction with rat liver mitochondrial extracts: the anti PDC-E3 serum left residual E3 activity (approximately 50% of the original) that was precipitable by the anti-E3 anti-serum. This indicates that liver contains two immunologically distinct forms of E3. Metabolic assays measuring the differential effects of the two sera on the glycine decarboxylation reaction suggest that the form which is immunologically nonreactive with the anti-PDC-E3 serum could represent the E3 involved in the glycine cleavage system.

Animals↗
PubMed1987

Isolation of a cDNA clone for the dihydrolipoamide acetyltransferase component of the human liver pyruvate dehydrogenase complex.

Dihydrolipoamide acetyltransferase (E2) forms the structural core of pyruvate dehydrogenase complex. A cDNA clone (lambda E2-1) for mammalian E2 was identified from a human liver lambda gt11 library using anti-E2 serum. Affinity-selected antibodies using the fusion protein from lambda E2-1 immuno-reacted specifically with E2 of purified pyruvate dehydrogenase complex on immuno-blot analysis. The cDNA insert was approximately 2.3 kb in length with an internal EcoR1 site generating 1.4 and 0.9 kb fragments. A synthetic 17-mer oligodeoxynucleotide mixture based on the amino acid sequence surrounding the lipoic acid-containing lysine residue in bovine kidney E2 hybridized with the 2.3 kb cDNA insert and the 1.4 kb fragment.

Acetyltransferases↗
PubMed1986

Kinetic properties and essential amino acids of the 2,3-bisphosphoglycerate synthase-phosphatase from pig skeletal muscle.

Histidine, arginine and lysine residues are essential for the multifunctional 2,3-bisphosphoglycerate synthase-phosphatase purified from pig skeletal muscle. The synthase, phosphatase and phosphoglycerate mutase activities of the enzyme are concurrently lost upon treatment with diethylpyrocarbonate, phenylglyoxal and trinitrobenzenesulfonate. The phosphatase activity shows hyperbolic kinetics. In contrast, the synthase activity shows a nonhyperbolic pattern which fits to a second-degree polynomial. The Km values for glycerate 1,3-P2, glycerate 3-P and glycerate 2,3-P2 are similar to those of the enzyme from mammalian erythrocytes.

Amino Acids↗
PubMed1986

Reversed septal motion in right ventricular volume overload: false negative sign in the presence of increased septal thickness.

Paradoxical septal motion of the interventricular septum and right ventricular enlargement constitute diagnostic features of right ventricular volume overload. A diastolic septal displacement toward the left ventricle and its systolic normalization explain this phenomenon. A thick septum would, theoretically, impede such movement. One patient with a cardiac allograft and gross tricuspid regurgitation is described who, in the context of a rejection episode and in a very short interval, showed two septal motion patterns related to two different septal thicknesses. It is concluded that in a patient with large right ventricular dimension and increased septal thickness, lack of paradoxical septal motion does not rule out severe right ventricular volume overload.

Adult↗
PubMed1986

Functional characterization of the enzymes with 2,3-bisphosphoglycerate phosphatase activity from pig skeletal muscle.

In pig skeletal muscle exist four enzymes with 2,3-bisphosphoglycerate phosphatase activity. Two of them (forms I-A and I-C) are multi-functional enzymes which, in addition to the phosphatase activity, possess 2,3-bisphosphoglycerate synthase and phosphoglycerate mutase activities. The other two enzyme forms (II-A and II-B) only show the phosphatase activity. The four enzymes differ in substrate specificity. Form I-C is highly specific for glycerate 2,3-P2; form I-A also hydrolyzes the monophosphoglycerates and forms II-A and II-B are specific for phosphoester bonds adjacent to a C-1 carboxylic group. The enzymes possess similar Km, Kcat and optimum pH value, but they are differently inhibited by the reaction products. They are also differently affected by glycolate-2-P (their main activator) and by other modifiers. Probably form I-A, which corresponds to M-type phosphoglycerate mutase, is the main enzyme implicated in the breakdown of glycerate 2,3-P2 in pig muscle.

Animals↗
PubMed1985

Purification of 2,3-bisphosphoglycerate synthase-phosphatase from pig skeletal muscle.

Two enzymes which possess 2,3-bisphosphoglycerate synthase, 2,3-bisphosphoglycerate phosphatase and phosphoglycerate mutase activities have been purified from pig skeletal muscle. One of the enzymes corresponds to type M phosphoglycerate mutase. The other enzyme shows properties similar to those of the 2,3-bisphosphoglycerate synthase-phosphatase present in mammalian erythrocytes. The erythrocyte and the muscle enzyme possess the same molecular (56 000) and subunit (27 000) weights. The synthase, phosphatase and mutase activity ratio is similar in both enzymes, and they are affected by the same inhibitor (glycerate 3-P) and activators (glycolate 2-P, pyrophosphate, sulfite and bisulfite).

Animals↗
PubMed1985

Hybrid forms of phosphoglycerate mutase and 2,3-bisphosphoglycerate synthase-phosphatase.

Purified phosphoglycerate mutase from pig skeletal muscle and 2,3-bisphosphoglycerate synthase-phosphatase from pig erythrocytes were hybridized "in vitro". The hybrid showed a behaviour on electrophoresis and on ion-exchange chromatography similar to that of a naturally occurring enzyme with phosphoglycerate mutase, 2,3-bisphosphoglycerate synthase and 2,3-bisphosphoglycerate phosphatase activities present in pig skeletal and heart muscle. Both the hybrid and the muscle enzyme possess similar activities ratio. From these and previous data it is suggested that the six enzymatic forms with phosphoglycerate mutase, 2,3-bisphosphoglycerate synthase and 2,3-bisphosphoglycerate phosphatase activities detected in mammalian tissues (Carreras et al. 1981, Comp. Biochem. Physiol. 70B, 477-485) result from combination of three subunits (types M, B and E).

Animals↗
PubMed1985

Metabolism of glycerate-2,3-P2--VII. Enzymes involved in the metabolism of glycerate-2,3-P2 in cat tissues.

The levels of the enzymes involved in the metabolism of glycerate-2,3-P2 (phosphoglycerate mutase, bisphosphoglycerate synthase-phosphatase and bisphosphoglycerate phosphatase) in cat and in pig tissues are different. The main difference is the low level of bisphosphoglycerate synthase-phosphatase in cat tissues. As a consequence, in contrast with pig erythrocytes, in cat erythrocytes, both the synthesis and the breakdown of glycerate-2,3-P2 are mainly controlled by phosphoglycerate mutase.

2,3-Diphosphoglycerate↗
PubMed1984

[Hypercalcemia associated with tumors in children. 20 cases].

Thirty episodes of hypercalcemia were observed in 20 children with solid tumors: principally 9 cases of non Hodgkin's lymphomas, 4 cases of rhabdomyosarcomas and 4 cases of Wilms' tumors. The 2 children with neurological manifestations and hypertension had the most severe symptoms secondary to the high calcium levels. However, hypercalcemia was asymptomatic in 8 of the 20 children. Focal seizures and metastatic calcifications subsequently occurred in 6 children. Emergency treatment of hypercalcemia often had partial or transient efficiency. In contrast, high calcium levels always returned to normal after anti-tumoral treatment.

Adolescent↗
PubMed1983

Metabolism of glycerate-2,3-P2--IV. Effect of Hg2+ on the enzymes involved in the metabolism of glycerate-2,3-P2 in pig skeletal muscle.

Type M phosphoglycerate mutase and skeletal muscle bisphosphoglycerate synthase-phosphatase from pig are similarly affected by Hg2+. Both enzymes lose the phosphoglycerate mutase and the glycerate-2,3-P2 synthase activities, and increase the glycerate-2,3-P2 phosphatase activity upon Hg2+-treatment. In contrast, bisphosphoglycerate phosphatase from pig skeletal muscle is inactivated by Hg2+. These results confirm the similarity between phosphoglycerate mutase and bisphosphoglycerate synthase-phosphatase. In addition they support the existence of separate binding sites for monophosphoglycerates and for bisphosphoglycerates at the phosphoglycerate mutase active site.

2,3-Diphosphoglycerate↗
PubMed1983

The adult respiratory distress syndrome.

The adult respiratory distress syndrome (ARDS) is an extreme form of noncardiogenic pulmonary edema associated with alveolar-capillary damage. Clinical features include acute respiratory distress, dyspnea and tachypnea, severe hypoxemia refractory to oxygen therapy, and diffuse bilateral pulmonary infiltrates. Any number of serious disorders can cause ARDS, but the processes leading to the alveolar permeability defect are not understood. Therefore, therapy remains nonspecific and supportive. Treatment includes positive end-expiratory pressure, careful fluid management, steroid therapy, and adequate nutrition. Unfortunately, even with the most sophisticated intensive care, the mortality of ARDS is still greater than 50%.

Adult↗