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Biomedical subjects

A Dwenger

Publications and source records attributed to A Dwenger.

At least 55 records · Page 3Linked to original sources
PubMed1986

Bronchoalveolar lavage fluid and plasma proteins, chemiluminescence response and protein contents of polymorphonuclear leukocytes from blood and lavage fluid in traumatized patients.

The technique of bronchoalveolar lavage was used to obtain serial samples of lavage every two days from non-contused lung areas of seven traumatized patients and four normals; blood was drawn simultaneously. Urea, total protein, albumin, alpha 1-proteinase inhibitor, alpha 2-macroglobulin, lactate dehydrogenase, beta-N-acetyl-glucosaminidase, myeloperoxidase, and elastase enzyme activity, as well as complexed and total elastase concentrations were determined in bronchoalveolar lavage fluids and plasma samples. Lavage fluid cell pattern was counted. Polymorphonuclear leukocytes were isolated from lavage fluids and blood samples. Granulocyte contents of elastase enzyme activity, complexed and total elastase concentrations, and myeloperoxidase and lactate dehydrogenase activity were determined. Polymorphonuclear leukocyte stimulatory functions were measured by luminol-enhanced chemiluminescence. The following results were obtained for the patient group: Patterns of lavage fluid cells were shifted in favour of polymorphonuclear leukocytes and lymphocytes. The protein determinations of bronchoalveolar lavage fluids and plasma samples gave information about the extent of alterations of permeability of the capillary-interstitial-alveolar space (albumin/urea and alpha 1-proteinase inhibitor/urea ratios) as well as about the amounts of cytoplasmic and lysosomal enzymes released by phagocytes (lactate dehydrogenase/urea, beta-N-acetylglucosaminidase/urea, elastase/urea ratios). Polymorphonuclear leukocytes isolated from bronchoalveolar lavage fluids contained a decreased content of myeloperoxidase and elastase enzyme activities and total elastase concentration; the content of complexed elastase was found to be increased more than 100 fold. From chemiluminescence measurements there was evidence for decreased zymosan-induced stimulatory function, while the photon emission rate of polymorphonuclear leukocytes after passage into the alveolar space was increased.

Blood Proteins↗
PubMed1986

Evaluation of elastase and alpha 1-proteinase inhibitor-elastase uptake by polymorphonuclear leukocytes and evidence of an elastase-specific receptor.

Neither resting nor stimulated isolated human polymorphonuclear leukocytes did bind or ingest preformed complexes of alpha 1-proteinase inhibitor and unlabeled/125I-labeled human leukocyte elastase. In contrast, granulocytes bound unlabeled/125I-labeled elastase and the extent of binding was reduced in the presence of respiratory burst stimulators, such as 4 beta-phorbol 12 beta-myristate 13 alpha-acetate, E. coli endotoxin, and N-formyl-L-methionyl-L-leucyl-L-phenylalanine. In association/dissociation and competition inhibition experiments it was demonstrated that granulocyte-elastase binding was specific and saturable. From Scatchard and non-linear regression analysis there was evidence of a two-class receptor model with independent binding sites. Calculated by the non-linear regression method assuming a two-class receptor model the characteristics of the high affinity/low capacity binding site were K1 = 216 +/- 129 X 10(6) l X mol-1 (means +/- s; n = 3) and R1 = 1.38 +/- 0.95 nmol X l-1 corresponding to 0.083 X 10(6) receptors per cell, whereas the low affinity/high capacity binding site had the characteristics K2 = 0.50 +/- 0.09 X 10(6) l X mol-1 and R2 = 237 +/- 103 nmol X l-1 corresponding to 14.3 +/- 6.2 X 10(6) receptors per cell.

Binding Sites↗
PubMed1984

Insulin binding and degradation studies on erythrocytes at different temperatures.

Insulin binding of human erythrocytes has been investigated between 0 and 37 degrees C using porcine 125I-insulin/unlabeled porcine insulin and mono [125I] (Tyr-A14)biosynthetic human insulin/ unlabeled biosynthetic human insulin, respectively. Either system exhibited a regular thermodynamical behavior between 0 and 22 degrees C, giving unitary free-energy changes of about -58/ -59 kJ/mol, unitary entropy changes of about +55/ +70 J/K per mol and a reaction heat of -43.1/ -38.3 kJ/mol. From 22 up to 37 degrees C an irregular thermodynamical behavior could be observed, which can be partially explained by an increased insulin degradation during incubation and an additional time-dependent binding of the degradation products.

Animals↗
PubMed1984

Radioimmunoassay: an overview.

The historical development, principle and theory of the radioimmunological test are described, together with the necessary test components, separation techniques and experimental procedure. The emphasis on different areas of diagnosis that rely on radioimmunoassay is compared for two institutions. Methods for the determination and presentation of reliability criteria are described, and the current status of quality control of radioimmunological methods is discussed. Three high grade mechanized systems and five fully mechanized or automated systems for radioimmunological assays are presented. Future trends in the development of radioimmunoassay can be predicted with the aid of general growth criteria.

Antibodies↗
PubMed1983

Insulin binding to erythrocytes before and after changing from porcine to biosynthetic human insulin in children with type-I diabetes.

The binding of [125I]insulin to isolated erythrocytes from diabetic children (n = 27) before (group a) as well as one and five months after changing from porcine to biosynthetic human insulin (groups b and c) was investigated. An analysis of variance of the binding parameters, determined by a nonlinear regression procedure, yielded statistically significant differences between the receptor affinities Ka as well as between the receptor concentrations Xo of the groups a and b, a and c and b and c. (formula: see text). The results suggest that the change from porcine insulin to biosynthetic human insulin induces a short-term as well as long-term increase in the affinity, and a decrease in the concentration of the erythrocyte insulin receptors.

Adolescent↗
PubMed1983

Insulin binding to erythrocytes in children with type-I diabetes mellitus.

Specific binding of [125I]insulin to isolated erythrocytes was investigated in four groups of children (A) Healthy children under 10 years of age (n = 20) (B) Healthy children over 10 years of age (n = 13) (C) Diabetic children under 10 years of age (n = 12) (D) Diabetic children over 10 years of age (n = 63). In addition, all diabetic children (n = 75) were subdivided into four groups according to the duration of diabetes. (E) less than 2 years, (F) 2--4 years, (G) 4--6 years, and (H) greater than 6 years. By means of a nonlinear regression analysis for the extraction of binding parameters (assuming a single receptor class model with independent receptor sites) and methods of variance analysis, statistically significant differences were observed for the receptor affinities Ka (10(8) l/mol) and the receptor concentrations X0 (nmol/l) between groups A and C, B and D, C and D, but not between A and B. The affinities of groups C and D were found to be higher than the corresponding values of groups A and B, whereas the receptor concentrations exhibited an inverse behaviour. A significant increase of the receptor concentration and decrease of the receptor affinity depending on the duration of diabetes could only be proved to exist during the first 2 years of the disease.

Adolescent↗
PubMed1983

[Effect of total hormone concentration on the determination of amount of binding in the hormone/receptor interaction between erythrocytes and insulin].

The interaction of erythrocytes and [125I]insulin/insulin were studied up to a total insulin concentration of 409 mumol/l. Assuming a single class receptor model the evaluation of receptor affinity Ka and concentration R0 may be performed either by non-linear regression analyses with iteration procedures of R0, Ka and U (nonspecific binding), or by a linear regression analysis of the initial part of the Scatchard plot. Nonlinear fitting of data to a two class receptor model gives results that are reliable only for the high affinity receptor site. The non-definable step of R0 determination leads to uncertainties in results determined by the negative cooperativity model. From the results of this investigation and from considerations of signal modulation by receptor occupancy, some recommendations have been formulated for the evaluation of binding parameters; these should contribute to an improvement in the comparability of studies on the interactions of erythrocytes and insulin.

Erythrocytes↗
PubMed1982

Insulin binding to erythrocytes after acute 16-methyleneprednisolone ingestion.

The binding of [125I]insulin to erythrocytes, glucose and insulin were determined before and 1, 7 and 35 days after ingestion of 2 X 60-methyleneprednisolone. None of two groups of volunteers (7 males, 4 females showed clear alterations of the insulin binding parameters (Ka and R0), or of the fasting cortisol, glucose and insulin concentrations. These results exclude the possibility that the diabetogenic effect of glucocorticoides is accompanied by an alteration of the insulin receptor characteristics of erythrocytes.

Blood Glucose↗
PubMed1982

Insulin binding to erythrocytes from pregnant, postpartum, follicular and luteal states.

Specific binding of [125I] insulin to isolate erythrocytes from four groups of women was investigated: (A) pregnant subjects between weeks 38 and 40 of pregnancy (n = 18), (B) postpartum subjects within 6 days after delivery (n = 20), (C) normal women during the follicular phase of the menstrual cycle (n = 12) and (D) normal women during the luteal phase of the menstrual cycle (N = 11). Specific [125I] insulin binding (fraction), fasting plasma glucose concentrations (mmol/l) and the corresponding insulin concentrations (mU/l) were 0.074 +/- 0.012 / 4.00 +/- 0.58 / 29.4 +/- 21.4 for group A, 0.065 +/- 0.016 / 4.40 +/- 0.75 / 41.5 +/- 26.2 for group B, 0.052 +/- 0.008 / 4.58 +/- 0.62 / 6.7 +/- 4.0 for group C and 0.054 +/- 0.011 / 4.49 +/- 0.63 / 8.3 +/- 5.9 for group D. By using a modified Scatchard analysis, statistically significant differences were observed between the receptor affinities of the groups A and D, B and D, A and C. The receptor affinities and concentrations were not significantly different between the follicular and the luteal phases. From the data, no inverse correlation between the plasma insulin concentration and receptor binding was seen, i.e. the phenomenon of downregulation of insulin receptor concentration with hyperinsulinaemia seemed not to apply to erythrocytes.

Adult↗
PubMed1982

[Effects of haemolysis, urea and bilirubin on the precision of digoxin and insulin radioimmunoassays (author's transl)].

The influence of haemolysis, uraemia and hyperbilirubinaemia on the radioimmunoassay for both digoxin and insulin has been investigated for five separation techniques (dextran/charcoal; coated tube; polyethyleneglycol 4000; sodium sulphite; double antibody). Recoveries, and intra- and interassay precision were calculated. It was demonstrated that even in serum samples with a rather high degree of haemolysis (haemoglobin up to 50 g/l)digoxin can be measured by using each of the five separation techniques without any significant interference. Visible haemolysis (haemoglobin above 200 mg/l) leads either to disturbance or to a complete failure of insulin radioimmunoassays with all separation techniques. This effect can be largely neutralized, and precision improved, by using N-ethylmaleimide. With the exception of the coated tube separation technique the intraassay precision has a CV of less than 10%, and the interassay CV is between 10 and 20%. Elevated urea concentrations interfered in the digoxin radioimmunoassay only when the coated tube technique was used. The insulin radioimmunoassay, however was affected by high urea when either the double antibody or the coated tube technique was used. Here the intraassay precision also has a coefficient of variation less than 10%, the interassay CV lying between 10 and 20%. Bilirubin influenced the digoxin test when the sodium sulphite separation was used, and it affected the insulin determinations with polyethyleneglycol 4000 and sodium sulphite. The intra- and interassay precision were however also around 10% and between 10 and 20% respectively. Compared with the interassay precision of 15% CV for digoxin and 13% for insulin for a pool-serum from blood donors, the decrease of interassay precision caused by haemolysis, uraemia and hyperbilirubinaemia was insignificant.

Animals↗
PubMed1978

[A system for the mechanized radioimmunological determination of digoxin].

Because of the increased number of samples to be processed in digoxin radioimmunoassay for clinical diagnosis and pharmacokinetic studies these analyses require mechanization to a certain extent. A newly developed modular analyzer system is described which is capable of mechanizing radioimmunoassays for digoxin, for example, independent on the kind of reagent kits as well as the separation technique. In dependence on the number of replicates from 60 to 240 samples per hour can be processed. The reaction vessels are placed in belts during the whole assay including centrifugation. The final separation of the liquid and the solid phase after centrifugation can be performed in two different ways: 1. If a conventional automatic gamma counter is used an aliquot of the supernatant is automatically dispensed into the counting vials which are to be closed manually and transferred into the counting device. 2. Further reduction of manual working steps can be achieved by employment of a newly developed discontinuous flow-through gamma counter which is part of the modular analyzer system. An aliquot of the supernatants is automatically flushed into a measuring cuvette installed into a conventional crystal detector. After measurement of the radioactivity and data output the cuvette is rinsed thoroughly. Thereafter the following sample is delivered.

Autoanalysis↗