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Biomedical subjects

P Aymard

Publications and source records attributed to P Aymard.

At least 19 recordsLinked to original sources
PubMed1996

The effect of temperature and ionic strength on the dimerisation of beta-lactoglobulin.

Bovine beta-lactoglobulin is a globular whey protein that associates partly and reversibly in dimers in the native state. Static and dynamic light scattering techniques have been used to determine the relative amount of monomers and dimers, and to estimate their size and shape in different conditions. The effect of the ionic strength on the dimerisation has been studied at pH 2, where the protein is highly charged. A simple model, taking into account the monomer-dimer equilibrium and virial interactions has been used. The strength of the interactions depends on the amount of added salt, i.e. ionic strength, and influences the dimer dissociation. When the ionic strength decreases, the equilibrium is shifted towards the monomeric form. The dissociation, however, is only complete at very low concentration. The effect of temperature has been studied at pH 7 and low concentration where virial interactions are negligible. The dissociation increases with increasing temperature (5 degrees C - 76 degrees C). At high temperatures, protein-protein aggregation is fast, even at low concentration. The temperature dependence can be described using a simple Van't Hoff model, even at temperatures where aggregation occurs. The ionic strength and temperature dependence both indicate that beta-lactoglobulin solutions have to be considered as a mixture of monomers and dimers.

Hydrogen-Ion Concentration↗
PubMed1996

Sucrase-isomaltase deficiency: changing pattern over two decades.

Twenty-two cases of sucrase-isomaltase deficiency (SID) were observed over a period of 20 years. Since 1977 delay of introduction of sucrose and its decrease in infants' diets have modified the symptomatology. In general, onset of diarrhea has not taken place immediately but 15 days to 2 months after introduction of sucrose. Out of 12 cases with dehydration, five occurred 3 to 7 months after the beginning of sucrose diet. Hypotrophy was not constant (11 of 22 cases), thus diagnosis was delayed in 17 of 22 cases. A yellow complexion due to rising carotene levels in the blood is a striking feature. Because of falsely positive sucrose load tests (four out of 14 nonSID infants) and failure of the hydrogene breath test (one out of five studied cases), disaccharidase determination remains the key to diagnosis. Despite the genetic difference symptoms seem to depend on infant feeding practices.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1995

Determination of iodide in serum and urine by ion-pair reversed-phase high-performance liquid chromatography with coulometric detection.

An HPLC method is described for the determination of iodide in serum and urine using ion-pair chromatography with coulometric detection. After adding hexadecyltrimethylammonium chloride, the ions pairs formed with the iodide in the sample are extracted using an organic solvent. The solvent is then evaporated and the dry residue obtained is mixed with an appropriate volume of mobile phase so as to concentrate the sample prior to injection into the chromatograph. For a sample of 0.5 ml of serum, the method features a limit of detection (signal-to-noise ratio of 3) of 0.2 microgram l-1, sufficient to be applied in paediatric assays for the diagnosis of both iodide deficiency and excess.

Child↗
PubMed1995

Evaluation of human IgG subclass assays on Beckman array.

Automated immunonephelometric assays were developed to measure human IgG subclasses in serum, on the Beckman Array Protein System (APSR), with sheep antihuman IgG subclass antisera. The interassay imprecision was judged to be satisfactory in each case (CV: IgG1: 2.3%; IgG2: 2.9%; IgG3: 4.0% and IgG4 5.4%). The standard curves were found to be linear in the ranges 1.5-30.0 g/L for IgG1, 1.5-15.0 g/L for IgG2, 0.1-1.0 g/L for IgG3 and 0.1-1.0 g/L for IgG4. The lower limit for quantification of the immunephelometric assays was 0.5 g/L for IgG1, 0.04 g/L for IgG2, 0.06 g/L for IgG3 and 0.03 g/L for IgG4. We found no antigen excess to at least 60.0 g/L for IgG1 and IgG2, 3.5 g/L for IgG3 and 2.0 g/L for IgG4. Nephelometric results correlated with those of radial immunodiffusion (r = 0.96 for IgG1, r = 0.93 for IgG2, r = 0.90 for IgG3 and r = 0.96 for IgG4). The reaction monitored by the Beckman Array Protein System is easy to perform, rapid and precise. The performance makes the immunonephelometric method suitable for the determination of IgG subclass concentrations in routine analysis.

Adolescent↗
PubMed1994

Effects of administration of branched-chain amino acids vs. glucose during acute exercise in the rat.

Several studies of the relationship of food intake to physical exercise strongly suggest that the two are closely linked. Serotonin transmission seems to be particularly important in the regulation of both appetite and central fatigue. Thus, the ingestion of branched-chain amino acids has been reported to decrease serotonin production and to improve physical performance. In the present study, the effects of three treatments (water, glucose, and branched-chain amino acids) were compared in 34 male Wistar rats. Maximal exercise duration, blood insulin, and glucose levels were measured. Results showed that following the ingestion of branched-chain amino acids, physical performance is lower and blood insulin level is higher than after glucose administration.

Amino Acids↗
PubMed1994

Duodenal calcium binding protein and active calcium transport in rats: are they functionally related?

The effects of calcitriol and a novel calcitriol analogue, 22-oxacalcitriol (OCT) on duodenal Ca transport, calbindin-D9k mRNA, and calbindin-D9k content were studied in two animal models reflecting common human pathologies, namely arterial hypertension and chronic renal failure, as well as in normal rats. The hormone or its analogue were administered intraperitoneally to vitamin-D-replete rats. Active Ca transport was increased in both spontaneously hypertensive rats (SHR) and in normotensive control WKY rats 5 h after calcitriol dosing of either 60 and 600 ng per rat. In WKY, calbindin-D9k content was slightly increased after the injection of 60 ng calcitriol, but not of 600 ng calcitriol whereas calbindin-D9k mRNA stayed essentially unchanged. In contrast, active Ca transport was significantly stimulated after the higher dose of 600 ng calcitriol. In SHR, while both doses of calcitriol increased active Ca transport, they had no stimulatory effect on calbindin-D9k mRNA or protein. In chronically uraemic rats, active Ca transport, duodenal calbindin-D9k and calbindin-D9k mRNA were stimulated after the injection of two subsequent doses of 300 ng calcitriol per rat. OCT treatment at same dosage led to a similar stimulation of calbindin-D9k and calbindin-D9k mRNA, but failed to induce an increase in active Ca transport. These results show that the stimulation of intestinal active Ca transport and calbindin-D9k can be entirely dissociated at the protein synthesis and the mRNA expression level (1) after calcitriol administration to normal and hypertensive rats, and (2) after OCT administration to uraemic rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Impaired duodenal response to short-term dietary calcium restriction in adolescent spontaneously hypertensive rats.

The response pattern of plasma calcitriol level and related intestinal adaptation to short-term moderate calcium (Ca) restriction was examined in adolescent male, spontaneously hypertensive rats (SHR) and normotensive WKY control rats. Twelve-week-old SHR and WKY fed a low (0.1%) Ca diet for 3, 6, or 12 days were compared with rats of either strain fed a normal (1.0%) Ca diet. Plasma calcitriol response was measured and duodenal adaptation to Ca restriction was investigated by evaluating active Ca transport, calbindin-D9K (CaBP9K) protein, CaBP9K mRNA, and alkaline phosphatase activity (ALP). Under the normal Ca diet, no significant difference between strains was observed for all five parameters. In response to the low Ca diet, the SHR and WKY showed a similar increase (nearly 50%) in plasma calcitriol, starting at day 3 of this diet. However, only the WKY displayed the expected duodenal adaptation: active Ca transport increased at day 6 and CaBP9K as well as ALP increased at day 3 of the low Ca diet. The stimulation of the latter three parameters was maintained until day 12 of Ca restriction. Moreover, CaBP9K mRNA was increased in WKY after 3 days of Ca restriction. In contrast, the SHR had either no or only a minor increase of duodenal parameters in response to Ca restriction. Finally, a significant and positive correlation between Ca transport and plasma calcitriol and between Ca transport and CaBP9K was found in WKY but not in SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1992

Different forms of alkaline phosphatase in adult rat femur. Effect of a vitamin D3-deficient diet and of a sorbitol-enriched diet.

In the femoral extremities of the adult rat containing the metaphysis, the epiphyseal cartilage, and the epiphysis, four alkaline phosphatase (AP) forms were distinguished on polyacrylamide gel electrophoresis. Two soluble forms were present in the 160,000 g supernatant: one of Mr 165 kDa and another of Mr 110-115 kDa, which exhibited a strong catalytical activity. Moreover, from the pellet, three membrane-bound forms of Mr 130, 110-115, and 100 kDa could be extacted with sodium deoxycholate. When denaturated AP was visualized by postelectrophoretic autoradiography of the phosphorylated intermediates, subunits always appeared as three monomers of Mr 75-80, 60-70, and 50-60 kDa. As four native forms but only three types of subunits were found to be present in the femur, it seems that, apart from homodimers, some heterodimers could also occur. Three types of diets were administered to three groups of rats for 5 weeks. Two are known to disturb bone mineralization: (1) a vitamin D3-deficient diet, and (2) the same as (1) but enriched with 12% sorbitol. The third was a normal diet containing vitamin D3. Concerning the effects on AP of dietary sorbitol and the vitamin D3-deficient diet, it was found that rats receiving the diet supplemented with sorbitol showed a substantial rise in the activity of the Mr 165 kDa form with the concomitant appearance of a new monomer of Mr 100 kDa. In contrast, rats fed the vitamin D3-deficient diet always displayed an increase in enzyme activity, principally of the Mr 100 and 110 kDa forms.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1992

In vitro inhibition of alkaline phosphatase activities from intestine, bone, liver, and kidney by phenobarbital.

A kinetic study of the inhibition of several alkaline phosphatase (AP isoenzyme activities by phenobarbital was carried out using p-nitrophenylphosphate (10 mM) as a substrate at pH 9.8 in a 300-mM Hepes buffer. AP from bovine kidney, calf intestine, bovine liver, and rat bone was used. Over a phenobarbital concentration range of 20-400 mM, all these isoenzymes were inhibited in an uncompetitive manner with a Ki of 200 mM for intestinal AP, and in a linear mixed-type manner for all the other isoenzymes tested. The Ki values were 10, 40 and 55 mM for kidney, bone and liver AP, respectively. The use of 15 mM carbonate-bicarbonate or 400 mM diethanolamine buffer did not modify the degree of inhibition of intestinal AP activity. Dixon plots of the reciprocal of reaction velocity versus inhibitor concentration either at different substrate concentration or at different DEA concentration indicate uncompetitive inhibition for the intestinal enzyme. This in vitro inhibitory effect of phenobarbital is in contrast to its in vivo stimulating action on AP. However, in the whole animal, the effects of phenobarbital administration probably represent the sum of multiple effects.

Alkaline Phosphatase↗
PubMed1991

Enzyme immunoassay of serum erythropoietin in healthy children: reference values.

A solid phase enzyme immunoassay for erythropoietin which required only a small specimen of blood was evaluated. It permitted measurement up to 150 IU/L. Recovery was between 86.2% and 110.0% and between-batch precision between 4.7% and 5.7%. We determined the levels of erythropoietin in infants aged 10 months (geometric mean 11.2 IU/L; 95% range 3.6-34.9) and in children aged 2 years (geometric mean 10.5 IU/L; 95% range 4.3-25.8). Both were significantly higher than the values found in children aged 4 years (geometric mean 7.2 IU/L; 95% range 2.4-21.8). There were no differences between the values in children at 4 years, those aged 4-15 years and adults.

Adolescent↗
PubMed1990

Usefulness of a prognostic inflammatory and nutritional index in pediatric clinical practice.

The clinical usefulness of a prognostic inflammatory and nutritional index (PINI) was evaluated in 47 hospitalized infants and 72 age-matched controls from 1 mth to 14 yr of age. The PINI formula is a combination of two markers each of infection (C-reactive protein and orosomucoid) and of malnutrition (albumin and transthyretin). Healthy children are identified by a PINI value less than 1 whereas sick patients are characterized by a progressive rise above 1 as the conditions worsens. The PINI scoring system provides the clinician with a sensitive and universal tool, allowing the correct follow-up of both inflammatory and nutritional poles of the disease spectrum. The formula is of particular help in pediatric practice in recognising early subclinical complications and efficacy of specific therapeutic strategies. The micromethod is simple, rapid and may be regularly repeated since it requires only 46 microliters of serum.

Adolescent↗
PubMed1989

Circadian variations and reference intervals for some enzymes in urine of healthy children.

Circadian variations of alanine aminopeptidase (EC 3.4.11.2), gamma-glutamyltransferase (EC 2.3.2.2), and N-acetyl-beta-glucosaminidase (EC 3.2.1.30) in urine were studied in 10 healthy children, ages six to 15 years. Urine specimens were collected during 24 h, grouped into four time intervals. Enzymes were measured spectrophotometrically, with automation. These enzymes all showed diurnal variation, with morning (8 a.m.-12 noon) excretion being highest. We also analyzed timed urinary specimens (8 a.m.-12 noon) from 136 healthy children, ages two to 11 years. Reference intervals are presented for these enzymes. High excretion of the three enzymes was observed in children two and three years old.

Acetylglucosaminidase↗
PubMed1989

[Optimization of the determination in urine of alanine aminopeptidase, gamma-glutamyltransferase and N acetyl-beta-D-glucosaminidase].

The authors describe the optimization of determination of alanine aminopeptidase (AAP), gamma-glutamyltransferase (GGT) and N-acetyl-beta-D-glucosaminidase (NAG) in urine by multivariate analysis. The optimal conditions found are: for AAP at 30 degrees C TRIS HCl buffer 300 mmol/l pH 7.9, L-alanine-4-nitroanilide 5.8 mmol/l, for GGT at 30 degrees C buffer glycylglycine 150 mmol/l pH 8.0, gamma-L-glutamyl-3-carboxy-4-nitroanilide 9.0 mmol/l, for NAG at 37 degrees C citrate buffer 50 mmol/l pH 5.8, m cresolsulfonphtaleinyl-N-acetyl-beta-D-glucosaminide 5.5 mmol/l. These methods are easy to perform, apply to urine without pretreatment through Sephadex: therefore complete automatization is possible. The stability of enzymatic activities in urine is of ten days at +4 degrees C in the presence of sodium azide at neutral pH. Freezing resulted in a considerable loss of activity for AAP and GGT.

Acetylglucosaminidase↗
PubMed1989

Determination of trans-phylloquinone in children's serum.

By optimizing the conditions for determining trans-phylloquinone and its metabolite, K-2,3-epoxide, in serum through a two-step HPLC process combined with fluorometric detection after coulometric reduction, we have been able to develop a method applicable to small volumes of serum (200 to 500 microL). The limit of detection (signal-to-noise ratio of 3) was 15 ng/L for trans-phylloquinone, 30 ng/L for K-2,3-epoxide. The trans-phylloquinone concentrations measured by this method in serum from 82 children, ages one to six years, whose results were normal for overall coagulation tests, ranged from 40 to 880 ng/L (median 175 ng/L). We discuss these findings and compare them with vitamin K1(20) values reported for adults.

Child↗
PubMed1989

Automated determination of urinary Na+, K+, chloride, inorganic phosphate, urea, and creatinine without sample dilution, with the "RA-XT".

We describe how concentrations of chloride, urea, inorganic phosphate, and creatinine in urine can be measured directly, without manual sample dilution, in a discrete analyzer (the Technicon "RA-XT"). These methods were accurate for concentrations of chloride up to 280 mmol/L, urea up to 500 mmol/L, inorganic phosphate up to 50 mmol/L, and creatinine up to 30 mmol/L. CVs are less than 3% nd results correlate well with those obtained by continuous-flow analysis (SMA-II). All these reagents are stable at room temperature for three weeks. Analyses are easy to perform and infrequent calibration is required.

Autoanalysis↗