Search PubMed⌕ Search

Biomedical subjects

J P Yvert

Publications and source records attributed to J P Yvert.

At least 19 recordsLinked to original sources
PubMed1998

Elecsys TSH, FT4, T4, T-uptake, FT3 and T3. Clinical results of a multicentre study.

6 assays for the assessment of thyroid function (TSH, FT4, T4, T-uptake, FT3 and T3) were targets of the International Multicenter Study on the random access analyzer Elecsys 2010. The aim of the study was to characterize the clinical performance of the assay in method comparison and reference range studies. The assays under evaluation were compared to a broad variety of radio isotopic and non-radio isotopic assays. They are suitable for serum and plasma samples. In case of TSH the study include 2nd and 3rd generation TSH procedures. In general, good to excellent correlations were found between the Elecsys and the respective routine methods. Systematic deviations were extraordinary low in case of TSH, FT4 and T4. Regarding the analysis of T3 and FT3 some systematic deviations in terms of standardization have been observed. Results of Elecsys T4 and Elecsys FT4 were independent of the serum total protein or serum albumin concentrations. In T3 and FT3 Elecsys the results of samples from NTI (non-thyroidal-illness) patients were decreased, reflecting the physiological situation in these patients. Studies using samples from healthy euthyroid as well as untreated hypo- and hyperthyroid individuals enabled us to assess the assays reference ranges.

Humans↗
PubMed1998

Elecsys CEA, PSA and AFP. Clinical results of a multicentre evaluation.

Three tumormarker assays, Elecsys CEA, PSA and AFP, have been evaluated in an international multicentre study to characterize their clinical performance and to verify the comparability with the corresponding tests of the Enzymun-Test product line and other methods. For each of the markers results were obtained from four laboratories. On the basis of 314 and 199 specimens respectively, (preliminary) reference ranges could be established for CEA and PSA. For the prostate marker, the age dependence of the antigen level could be clearly confirmed. Mean concentrations range between 0.51 ng/ml (< 40 years) and 3.57 ng/ml (> 70 years). Referring to CEA, 95th percentiles of 4.31 ng/ml and 2.69 ng/ml were elaborated for smokers and nonsmokers. In general, good to excellent correlations (r > 0.98) were found between the Elecsys and Enzymun-Tests. Regarding the systematic comparability of both systems, most of the slopes derived from the individual method comparison studies are within the +/- 10% range of the respective standardization results. The specific distribution pattern of the individual tumormarker values elaborated with sample material of known clinical background, reflects the well established categorization of different benign and malignant diseases according to their characteristic marker levels. Of utmost importance, however, is the excellent comparability of the Elecsys assays with the corresponding Enzymun-Tests and the FDA approved AIA 1200 tests from TOSOH in follow-up studies. Almost superimposable concentration curves guarantee that identical diagnostic information is derived from all three methods. Especially for PSA, a series of measurements on sera of prostatectomized patients proved the usability and clinical value of the test also for this particular indication. For either one of the Elecsys tests, the feasibility of using plasma as sample material was verified.

Adult↗
PubMed1998

Results of the multicentre evaluation of an electrochemiluminescence immunoassay for HCG on Elecsys 2010.

This study evaluated the performance of the HCG STAT Elecsys assay in 8 European laboratories using the Elecsys 2010 system. Analytical sensitivity was < 0.5 mlU/mL. The analysis of concentration series prepared by mixing serum pools with high and low HCG concentrations proved linearity up to 10.000 mIU/mL. A high-dose hook effect was not seen up to HCG concentrations of 430.000 mIU/mL. The medians of the within-run CVs (n = 21, 3 series) were 3.0% (2.1-5.8% CV; 10.4-14.4 mIU/mL), 2.4% (1.7-6.1% CV; 35.6-88.6 mIU/mL) and 2.3% (1.7-6.1% CV; 282.3-643.8 mIU/mL). The medians of the between-day imprecisions (n = 10-21) were 7.0% CV (5.2-12.0% CV; 4.0-14.0 mIU/mL), 5.5% CV (3.1-7.2% CV; 35.4-92.7% mIU/mL) and 4.1% CV (2.8-5.1% CV; 270.8-658.0 mIU/mL). The median recovery of two external quality control samples with assigned values of 9.39 and 10.40 mIU/mL) were 101.2 and 104.3% (ranges: 94.8-116.1%, 98.6-117.8%, n = 10). The assay was compared with five non-isotopic automated routine immunoassay systems (x). Slopes ranged from 0.87 to 1.15 and intercepts from-0.53 to 12.50 mIU/mL. The coefficients of correlation were with one exception (0.898) > or = 0.960. The distribution of HCG in samples from non-pregnant women and healthy men was very similar to that observed with other automated routine methods. The HCG Elecsys assay is very specific for the intact holo-hormone. Nicked HCG dimer, nicked and non-nicked beta-subunits are weakly recognised or not detected. Hemoglobin, bilirubin and lipemia (tested up to: Hb, 3.7 g/L; bilirubin, 500 mumol/L; triglyceride, 37.6 mmol/L) did not interfere the assay. The HCG Elecsys assay is well suited for the early and fast diagnosis of normal pregnancy and the detection of tubal pregnancy.

Adult↗
PubMed1997

Accelerated glycogenolysis in uremia and under sucrose feeding: role of phosphorylase alpha regulators.

To understand the mechanism of hepatic glycogen depletion found in uremia and under sucrose feeding, we examined net hepatic glycogenolysis-associated active enzymes and metabolites during fasting. Liver was taken 2, 7, and 18 h after food removal in uremic and pair-fed control rats fed either a sucrose or cornstarch diet for 21 days. Other uremic and control rats fasted for 18 h were refed a sucrose meal to measure glycogen increment. Glycogen storage in uremia was normal, suggesting effective glycogen synthesis. During a short fast, sucrose feeding and uremia enhanced net glycogenolysis through different but additive mechanisms. Under sucrose feeding, there were high phosphorylase alpha levels associated with hepatic insulin resistance. In uremia, phosphorylase alpha levels were low, but the enzyme was probably activated in vivo by a fall of inhibitors (ATP, alpha-glycerophosphate, fructose-1,6-diphosphate, and glucose) and a rise of Pi, as verified in vitro. Enhanced gluconeogenesis was also suggested, but excessive hepatic glucose production was unlikely in uremia. During fasting, hypoglycemia occurred in uremia due to reduced glycogenolysis, inefficient hepatic gluconeogenesis, and impaired renal gluconeogenesis. This may be relevant to poor fasting tolerance in uremia, which could be aggravated under excessive sucrose intake.

Animals↗
PubMed1996

Acidosis prevents growth hormone-induced growth in experimental uremia.

The effects of 2 weeks of a daily injection (2 IU/day) of recombinant human growth hormone (GH) were studied in young (60-g) growing rats in two experiments. Experiment 1 was performed in uremic animals (mean plasma creatinine 65-71 mumol/l) who were either acidotic (mean bicarbonate 11.5 mmol/l) or had acidosis corrected (mean bicarbonate 26 mmol/l) by addition of sodium bicarbonate to the diet. Experiment 2 used rats with normal renal function (plasma creatinine 25 mumol/l) who were either non-acidotic but restricted to the dietary intake of uremic rats or rendered acidotic by ammonium chloride. GH induced an increase in body weight and length in non-acidotic uremic (+33% and +41%) and in non-acidotic food-restricted (+13% and +42%) rats, associated with an increased rate of protein synthesis and little change in plasma insulin-like growth factor 1 (IGF 1). In both acidotic rat groups, GH altered none of the parameters studied. Thus: (1) the presence of severe metabolic acidosis blunts the response to GH in uremic and non-uremic rats and (2) the increment of growth rate does not depend on a rise in plasma IGF 1.

Acidosis↗
PubMed1996

Growth hormone action is blunted by acidosis in experimental uremia or acid load.

The effects of rhGH (H) daily injection (2 IU/d) and of vehicle (V) during two weeks were studied in young (60 g) growing rats. Experiment I was performed in uremic rats (mean plasma creatinine: 65-71 mumol/l) either acidotic (mean HCO3-:11.5 mmol/l: UAH, n = 20; UAV, n = 18), or with corrected acidosis by addition of NaHCO3 in the diet (mean HCO3-:26 mmol/l: UBH, n = 25; UBV, n = 23). Experiment II used rats with normal renal function (plasma creatinine: 25 mumol/l), either non-acidotic but food restricted to the dietary intake of uremic rats (CRH: n = 18, CRV: n = 18), or rendered acidotic by NH4Cl (CAH: n = 16, CAV: n = 16). GH induced an augmentation of body weight and length gains in non-acidotic uremic rats (+33% and +41%: p < 0.01), and in non-acidotic food restricted rats (+13% and 42%: p < 0.05 and p < 0.0001). This was associated with increased protein synthesis rate in muscle and with little change of food intake as well as of plasma IGF 1. Plasma IGF 1 kept the same relationship to food intake, regardless of treatment, but length gain for each level of plasma IGF 1 was enhanced by GH in GH responding groups. In both acidotic rat groups, GH altered none of the parameters studied. Thus: 1) the presence of severe metabolic acidosis blunts the response to GH in uremic and non-uremic rats. 2) The increment of growth rate does not depend on a rise of plasma IGF 1.

Acidosis↗
PubMed1995

[Modification of hemorheological parameters in microvascular complications of diabetes].

The aim of the present study was to assess the possible modifications in the parameters of red cell aggregation and blood and plasma viscosity in 92 diabetic patients compared to 82 non diabetic control subjects. Based on the presence of microalbuminuria (> 30 mg/24 h) and/or retinopathy each group of diabetic patients was divided into two subgroups. This study shows increased red cell aggregation and blood viscosity among diabetic patients with microangiopathy. There was a very good correlation between fibrinogen level and the different rheological measurements. The results of this study confirm the importance of the blood rheology abnormalities observable in diabetes. These disorders increase peripheral vascular resistances and ischemia and therefore worsen diabetic nephropathy and retinopathy.

Adult↗
PubMed1994

In vivo unaltered muscle protein synthesis in experimental chronic metabolic acidosis.

Chronic metabolic acidosis (CMA) is a major cause of growth defect, implying disturbances of protein metabolism. Previously, in vivo studies performed in the fasting state showed enhanced whole body protein turnover, whereas in vitro studies showed unchanged muscle protein synthesis. The present study is the first to determine the effects of CMA on muscle protein synthesis and degradation in vivo. Two studies were performed in 60 g male rats fed a 30% casein diet. In study I, one group was sham-operated (C rats), and two groups underwent subtotal nephrectomy. One of them developed acidosis (UA rats) which was corrected in the other by NaHCO3 in the diet (UNA rats). Study II compared sham-operated rats rendered acidotic by NH4Cl in the drinking water (CA rats) and normal pair-fed (CNA) rats. Fractional protein synthesis rate (FSR) was determined in gastrocnemius muscle after injection of 3H-phenylalanine. Fractional protein degradation rate (FDR) was calculated as FSR minus fractional rate of muscle growth (FGR). In study I, UA rats had lower growth and N balance (163 +/- 12 vs. 216 +/- 11 mg N/day; P < 0.001) than UNA rats, despite identical food intake (11 g/day). This was associated with identical FSR (10.4 +/- 0.5 vs. 10.9 +/- 0.5%/day), but enhanced protein degradation (6.30 +/- 0.99 vs. 5.10 +/- 0.71%/day; P < 0.05). Plasma insulin, C peptide, PTH and corticosterone did not differ in UA and UNA rats, whereas plasma IGF-I was markedly reduced (147 +/- 21 vs. 283 +/- 27 ng/ml; P < 0.01) in UA rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1993

[Simultaneous multiple immunoassays: current data].

Help in diagnosis and disease monitoring requires more and more tests with fast results: To satisfy these requirements, two approaches are possible: full automation and rapid data processing, and multiple simultaneous assays. Simultaneous assays are already commercially available with different kinds of labels (radioisotopes, enzymes, fluorophores, etc). First applications concerned simultaneous determinations of two analytes (eg FSH-LH) by two different radioisotopic (125I, 57Co), or fluorescent (Eu = Sm ...) labels. Recently, assays were described which permit simultaneous determination of more than ten analytes (membrane immunoprinting). Techniques can be classified in three groups: i) one reaction site and a single kind of signal; ii) several reaction sites and one kind of signal; iii) several reaction sites and several kinds of signal. Main applications concern antibodies, antigens and haptens determination. Simultaneous assays will be soon associated with new solid phases and detection modes in fully integrated systems, leading to simultaneous multiple determinations in a single drop of blood.

Binding Sites↗
PubMed1990

Amplify or improve detection.

Quantification with accuracy at the molecular level, by simple means, is the challenge for new generations of biospecific assays. In order to reach this goal, it is necessary to reduce the non-specific background of the current assays and further to amplify the detection signal or to expand the surface of the solid phase. For now, significant additions in performance can be achieved if we balance new ways of amplification with progressive improvements of existing procedures. For the future, new concepts derived form biosensors approach will lead to simultaneous multiple analysis on the same sample.

Biological Assay↗
PubMed1986

Correction by insulin of disturbed TG-rich LP metabolism in rats with chronic renal failure.

To define the role of insulin in lipid disturbances of chronic renal failure, chronically uremic rats (U+) were supplemented by continuous insulin infusion over a 35-day experimental period and compared with control ad libitum-fed rats (C) and uremic rats without insulin (U). Uremic rats were characterized by hypoinsulinemia, an increase in both circulating very low-density lipoprotein (VLDL) and their cholesterol concentration, a normal hepatic triglyceride secretion rate (TGSR) determined with Triton WR 1339, and a low adipose tissue lipoprotein lipase (LPL) activity. Chronic insulin infusion at low rate (0.5 IU/24 h) to U+ rats normalized serum insulin (from 17.0 +/- 0.6 mU/l in U rats to 23.4 +/- 1.7 mU/l in U+ rats), serum VLDL triglycerides (from 804 +/- 65 to 410 +/- 36 mg/l), and serum VLDL cholesterol (from 43 +/- 8 to 16 +/- 3 mg/l). Hepatic TGSR decreased significantly after insulin treatment (from 0.58 +/- 0.03 to 0.44 +/- 0.03 mumol/min). Moreover, adipose tissue LPL was restored to normal by insulin supplementation (from 460 +/- 60 to 860 +/- 150 mU per total epididymal fat in U and U+ rats, respectively). Correction of the disturbed VLDL metabolism was associated with multiple actions of insulin including 1) a decrease of peripheral lipolysis, 2) a decrease of hepatic TGSR, and 3) an increase of adipose tissue LPL activity. Because cholesterol-rich VLDL are potentially atherogenic, their normalization with insulin treatment in this animal model suggests a viable area of investigation for the prevention of accelerated atherogenesis in chronic renal failure.

Adipose Tissue↗
PubMed1986

Plasma and pituitary content of growth hormone luteinizing hormone, and prolactin in uremic rats. Effects of chronic infusion of insulin.

The influence of chronic renal failure on pituitary content and on serum concentrations of growth hormone (GH), prolactin (PRL), and luteinizing hormone (LH) was studied in chronically uremic rats by comparison with control rats fed ad libitum and diet-restricted rats pair-fed with uremic rats. A decrease of pituitary GH content was found in uremic and diet-restricted rats, in association with a normal circulating GH level. A decrease of pituitary PRL and LH content with respectively high and normal serum values was observed in uremic but not in diet-restricted rats. These data strongly suggest that GH disturbances are related to malnutrition, whereas PRL and LH abnormalities are related to the uremic state per se. As hypoinsulinemia was observed in uremic rats, and as insulin is largely implicated in growth, we have investigated the effects of chronic infusion of insulin, using miniosmotic pumps, on pituitary hormone content. In spite of normalization of circulating insulin levels in uremic rats treated with insulin, pituitary GH, LH, and PRL contents were unaffected. Thus, insulin deficiency did not appear to be responsible for the diminished pituitary reserve of these hormones.

Animals↗
PubMed1985

Factors of increase in serum triglyceride-rich lipoproteins in uremic rats.

The possible mechanisms of the increase in serum triglycerides (TG) and TG-rich lipoproteins were studied in chronically uremic (U) rats by comparison with either ad-lib fed control (C) rats or diet-restricted (DR), sham-operated pair-fed control rats. A first series of animals was studied in the fed state and a second series after a 16-hr fast. In U animals the concentration of serum TG and TG-rich particles was lower than that of C rats in the fed state but significantly higher than that of C and DR rats after a 16-hr fast. Serum glucose and lactate concentrations in the fed or fasted state were unchanged by uremia. Serum insulin concentration was significantly decreased in U rats as compared to C and DR rats in both series. The fast did not increase the concentration of serum nonesterified fatty acids (NEFA) in U or DR animals to the same extent as in C rats, whereas the serum concentration of beta-hydroxybutyrate (BOB), which was higher than that of C rats in the fed state, was significantly lower after a 16-hr fast. In U animals, as compared to control rats of either series, a significant decrease of epididymal lipoprotein lipase (LPL) activity was observed during both nutritional states when expressing the enzymic activity per number of cells. In conclusion, our data provide evidence against hepatic over-production of TG-rich lipoproteins in rats with chronic renal failure and strongly point to an LPL-mediated defect of their peripheral catabolism, probably related to the insulin deficiency state.

3-Hydroxybutyric Acid↗
PubMed1981

[A rapid method for continuous flow measurement of cholesterol contained in high density lipoproteins (HDL) (author's transl)].

The authors utilized a reagent containing concanavalin A, a vegetal lecithin, to selectively precipitate lipoproteins containing apoprotein B, a component of VLDL, LDL, and Lp (a) which are well known for their atherogenic risk. During this precipitation "true" high density lipoproteins remain in solution. HDL cholesterol determination which constitutes an indirect indication of HDL activity or concentrations is performed by an enzymatic method using an automated continuous flow technique carried out on an Auto Analyzer II (Technicon Corp.). This rapid, easy determination obtains results comparable to other methods, particularly those chosen by the Société Française de Biologie Clinique (French Society of Clinical Biology). This technique should permit all laboratories to confirm an atherogenic index.

Apolipoproteins↗
PubMed1979

Simple, fast preparation of gallium-68-labelled human serum albumin microspheres.

Following a study of the main factors involved in the 68-Ga labelling of human serum albumin microspheres (H.S.A.M.), especially methods of production and preparation of active solution and conditions of radioelement fixation on the protein support, the practical details of a fast technique (60 min) based on the process described by Hnatowich are presented. This method gives high labelling yields (93 +/- 3%), and after washing of the microspheres leads to a radiopharmaceutical product almost without free 68Ga (less than 2%). The spheres ready for use carry a total radioactivity corresponding to about 35%, including decay, of the activity originally recovered in the generator eluate and to more than 98% of that, found in the final suspension. The labelled product is sterile, non-pyrogenic and non-toxic. When it is injected in animals by left ventrical catheterization the uptake rates in the heart, lungs, spleen, left kidney and right kidney are similar to those observed with reference 85Sr-labelled carbonized microspheres. This radiopharmaceutical, easy to prepare and having excellent biological and nuclear properties, seems ideally suited for the scanning of organs by position emission tomoscintigraphy.

Animals↗