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Biomedical subjects

H Keller

Publications and source records attributed to H Keller.

At least 181 records · Page 10Linked to original sources
PubMed1990

Batch production and secretion kinetics of hybridomas: pulse-chase experiments.

Pulse chase experiments of two mouse hybridoma lines were conducted in order to elucidate the kinetics of monoclonal antibody (mAb) production and secretion during different stages of batch cultures. The results indicate that a stock of cytoplasmic IgG exists in hybridoma cells and that the concentration of this stored IgG depends on the cell line used and the stage of the culture. This stored IgG can be released by dying cells, and a certain quantity of the secreted IgG is derived from this source. However, only between 0.3 and 9.3% of the released IgG of U0208 (average: 2.08%) and between 2.08 and 25.8% of the IgG, released from I.13.17 (average: 6.95%), were of storage origin, calculated on culture viability and intracellular IgG-stock. Comparing the accumulation of radio-labelled IgG (IgG*) in the supernatant with the reduction of cytoplasmic IgG* during the chase experiments, the percentages range between 14 and 50%, somewhat higher values probably caused by changes in the culture conditions. These changes led to a release of IgG during the chase experiments, which accounts for about 20-25% of the totally secreted IgG. It could be established that during the logarithmic growth phase of batch cultures a certain percentage of synthesized IgG was not released but stored within the cells: for U0208: 0.3-4.5%, for I.13.17: 1-7.6%. During the stationary and death phase, this percentage ranged between 1.5 and 20% for U0208 and between 0.5 and 8.1% for I.13.17. Finally, the chase experiments also revealed that the time of synthesis, assembly, and secretion of mAbs does not vary much during the different phases of batch cultures, and is within the range of 1.5 and 3 hrs.

Animals↗
PubMed1990

Morphological quantification and differentiation of left ventricular hypertrophy in hypertrophic cardiomyopathy and hypertensive heart disease. A two dimensional echocardiographic study.

Differentiation between hypertrophic cardiomyopathy and hypertensive heart disease is a diagnostic challenge. M-mode echocardiography only permits assessment of hypertrophy in limited areas of the left ventricular wall. 2-D echocardiography allows visualization of most of the myocardium. To assess the reliability of conventional M-mode echocardiographic and 2-D echocardiographic criteria in patients with hypertrophic cardiomyopathy (HCM) and hypertensive heart disease (HY), 30 patients with hypertrophic cardiomyopathy and 30 patients with hypertension and severe cardiac hypertrophy were examined using M-mode and 2-D echocardiography. Although the M-mode echocardiographic features showed statistically significant differences between the mean values in the two groups, the degree of overlap made the differentiation of the individual patients difficult. The diagnostic sensitivity and specificity of classic echocardiographic features were assessed: ventricular septal thickness greater than or equal to 1.5 cm, 90% and 43% (sensitivity and specificity, respectively); ventricular septal thickness to posterior wall ratio greater than or equal to 1.5, 83% and 56%; cross-sectional area at papillary level greater than 21 cm2m-2, 80% and 73%; septal segment of the myocardial ring at papillary level greater than 6.5 cm2m-2, 80% and 87%; and the combined criteria of cross-sectional area at papillary level greater than 21 cm2m-2 and septal segment greater than 6.5 cm2m-2, 77% and 93%. Quantitative 2-D echocardiography is useful to differentiate patients with hypertrophic cardiomyopathy from those with secondary myocardial hypertrophy due to hypertension. Hypertrophic cardiomyopathy is characterized by a spectrum of different morphological patterns of hypertrophy. Patients with the predominant region of hypertrophy in the anterolateral free wall or the apical region of the left ventricle were not detected with our quantitative method. Patients with this type of hypertrophy are relatively rare in the western population.

Adult↗
PubMed1990

Normalization of enhanced hepatic gluconeogenesis by the antiglucocorticoid RU 38486 in acutely uraemic rats.

Hepatic amino acid uptake, urea and glucose production are increased in acute uraemia. It has been shown that this metabolic pattern is mediated by glucocorticoids. Accordingly, the administration of the antiglucocorticoid RU 38486 to acutely uraemic rats resulted in a reduction of serum urea-N and glucose levels. To clarify whether this effect is due to a reduction in hepatic gluconeogenesis we examined the effect of the antiglucocorticoid RU 38486 on urea and glucose formation in isolated hepatocytes from sham-operated (SHAM) and bilaterally nephrectomized (BNX) rats receiving RU 38486 or the vehicle only. Hepatic glucose production in BNX rats was considerably increased from Na-pyruvate (+79%), alanine (+174%), glutamine (+158%), and serine (+87%) compared with SHAM animals. Concomitantly, hepatic urea formation was also enhanced from amino acid substrates in acutely uraemic rats. When uraemic animals were treated with RU 38486, glucose production from amino acids and Na-pyruvate was reduced to the range of SHAM animals or even lower. This effect could not be demonstrated in SHAM-operated controls. A comparable decrement in hepatic urea production was observed in BNX rats treated with the antiglucocorticoid. Thus, glucocorticoids appear to play a key role in the abnormal hepatic urea and glucose production of acutely uraemic rats.

Amino Acids↗
PubMed1990

[Etiology and occurrence of periodic eye inflammation of horses in the area of Berlin].

Over 130 cases of equine periodic ophthalmia (p.o.), which were treated as in-patients at the Equine Clinic of the Free University of Berlin in the last 35 years, were examined statistically in relation to the age and gender of the animals involved as well as to the development of the illness and the season in which it arose. As regards aetiology, the extraction of 71 affected Trotters was investigated. Antibodies to toxoplasmosis, leptospirosis and intestinal parasites were found only in some of the patients. Younger animals, aged between one and four years, and male animals (63.6%) were predominantly affected. The results of the examinations of faeces showed no correlation between cases of p.o. and a vermination of the horses. The examinations for antibodies to toxoplasmosis gave no indication of a participation of the toxoplasmas in the aetiology of recurrent uveitis. In contrast, the results of the examinations for antibodies to leptospirosis, of which 58.8% were positive, showed a seven to ten times higher infection than in healthy horses in Berlin. Breed analysis showed that in certain breeds of Trotters and warm-blooded horses, p.o. illnesses were frequent, supporting the hypothesis that the occurrence of p.o. is due to a hereditary, allergic reaction, triggered by various factors, in particular an infection without clinical signs.

Age Factors↗
PubMed1990

[The determination of apolipoproteins Apo A-I and Apo B. A comparative study of methods].

We compared the analytical performance of a new in house developed ELISA and the commercial TurbiTime system for the determination of Apo AI and Apo B. Six dilutions of a poolserum, whose concentration had been determined by two other independent methods, were used as test material. A serum from which the apolipoproteins had been removed by immunadsorption was used as a diluent. Six specimens with known true values of Apo AI and Apo B were thus prepared. We established the analytical precision, the regression function and the correlation with respect to the true values and we constructed precision profiles and bias profiles. We found that the precision of turbidimetry is superior for the determination of Apo AI with concentrations less than 1 g/l. With Apo B both systems are nearly equivalent, the results of the turbidimetric methods were a little too low, the results of the ELISA a little too high. Below a concentration less than 0.5 g/l both methods are unreliable.

Apolipoprotein A-I↗
PubMed1990

Multicentre evaluation of the Boehringer Mannheim/Hitachi 717 analysis system.

We conducted an European multicentre trial to assess the performance of the new Boehringer Mannheim/Hitachi 717 analysis system. The photometer response was linear up to an absorbance of 2.8. The maximal CV of photometric imprecision was 0.5% for the wavelength pair 340/405 nm within the absorbance range 0.9 to 2.4. For the 13 analytes in our study, mean within-run imprecision was less than 2%, and mean between-day imprecision less than 2.5%. The results obtained with the Hitachi 717 instrument correlated closely with those of comparison instruments. Linearity for the various tests was high and exceeded the manufacturer's claims. No drift was detected during an 8-hour work period; carry over could not be detected under the chosen experimental conditions. The new instrument was readily accepted by the evaluators because of its ease of handling and simple daily maintenance.

Blood Chemical Analysis↗
PubMed1990

[Characterization of enzyme immunoassays for T4 determination].

We compared an enzyme immunoassay for T4 (MTPT4) developed in Halle with the Enzymun-Test T4, Boehringer Mannheim (BMT4). Calculated coefficients of correlation can not be used for interpretation of the two methods. By construction of Bias-profiles the evaluation of concentration depended precision and accuracy is possible. Both methods can be used equally in laboratory work.

Bias↗
PubMed1990

[The effect of housing on the development of calluses and subcutaneous mucus cysts on the limbs of swine].

Extremities of pigs often show swelling of various size and consistency. The aim of the present investigation was to determine the cause of the swelling with special emphasis on housing conditions. A total of 168 animals kept on slatted and/or partly slatted floors and 55 pigs kept on straw were examined. The swelling was partially caused by connective tissue proliferation only, but more often consisted of non inflamed subcutaneous bursae. Skeletal changes near the periost could never be seen. In pigs kept on straw weals and subcutaneous bursae practically never developed, whereas in animals kept on concrete, these changes did occur more frequently and were more pronounced with time.

Animals↗
PubMed1990

[Methods of cholesterol determination: conventional procedure or "dry chemistry"?].

The search for the cardiovascular risk factor cholesterol should essentially be done in the physicians' laboratory. The majority of such analyses is performed by 'dry' chemistry tests. This review compares this technique with conventional methods for the determination of cholesterol. The reagents and the reaction mechanisms are principally the same for both techniques, i.e. fully enzymatic methods are used. In 'dry' chemistry the reagents are fixed on a solid carrier. The reactive state is provided by the liquid of the specimen. Two principles are employed: the technique of strips which is already utilised in urinary analysis and the system of multiple film layers as it is common in color-film technique. Three already introduced systems are discussed: the Seralyzer (Ames), the Ektachem (Kodak), and the Reflotron (Boehringer, Mannheim), and one system which is still in evaluation (the Clinistat, Ames). All the systems give a good agreement provided that they are operated by well-trained operators. Problems arise with quality control, since matrix effects are particularly important. The exactitude of the results depends on the calibration. Both, the Reflotron and the Clinistat are calibrated by the manufactories himself, the employer has no influence and is entirely dependent on the reliability of the producer. Although clinical chemistry analyses are facilitated by 'dry' chemistry it is by no means devoid of risks because the errors are more difficult to recognize.

Blood Chemical Analysis↗
PubMed1989

Impaired fibrinolytic capacity and tissue plasminogen activator release in patients with restenosis after percutaneous transluminal coronary angioplasty (PTCA).

To assess the role of the fibrinolytic system in the pathogenesis of restenosis after percutaneous transluminal coronary angioplasty (PTCA), we determined the components of this system in a retrospective study, including 16 patients with restenosis (gr. A) and 19 patients with long-term success (gr. B). In both groups at baseline fibrinolytic activity (FA) is unchanged, whereas tissue plasminogen activator antigen (tPA-Ag) is significantly increased (gr. A: 147.0%; gr. B: 139.8%; p less than 0.01). Fibrinolytic capacity (FC) and tPA-Ag release are significantly reduced in the restenosis group (FC: 46.5%, p less than 0.05; tPA-Ag release: 48.3%, p less than 0.01) compared to normal controls as well as to gr. B (FC: 84.3%, p less than 0.05; tPA-Ag release: 79.0%, p less than 0.05). Relating to the contact activation system, F XII (79.5%, p less than 0.05) is significantly, and F XI (82.3%) is clearly reduced in gr. A. Protein C (PC) is significantly elevated in gr. B (117.5%, p less than 0.05). There is a negative correlation between plasminogen activator inhibitor (PAI 1) and HDL-cholesterol (r = 0.37, p less than 0.05). It appears, that there is a typical pattern of defective fibrinolysis in patients with restenosis after PTCA and that this might be a pathogenetic factor in the development of restenosis.

Angioplasty, Balloon, Coronary↗
PubMed1989

Performance profiles: new tools for characterization and comparison of clinical chemical results.

It is current practice to record the performance of immunoassays by means of precision profiles (according to Ekins), in which the variation coefficient (relative standard deviation) is plotted against the analyte concentration. On the other hand, precision profiles are only occasionally used for evaluating the performance of conventional clinical-chemical methods. It is relatively uncommon to find bias plotted against analyte concentration, presumably because this type of analysis requires reference specimens, whose true analyte concentrations are known or guaranteed by reference methods. If the relative systematic variations are plotted against the true analyte concentrations, and a confidence interval is added to the resulting regression curve, the result is a "bias profile"; if tolerance limits are added, the result is a "deviation profile". The present work describes the preparation of specimens, which can be used to provide experimental data for the three performance profiles. A computer program is used to construct the precision profile, bias profile and/or deviation profile. The mathematical-statistical basis of the program is described in detail. For evaluation of the statistical procedure, three analytes and six methods were used: determination of sodium activity/concentration with an ion sensitive electrode and by flame photometry; determination of creatinine by a manual enzymic and a mechanized Jaffé method; determination of thyrotropin by radioimmunoassay and by luminescence immunoassay. Different purposes are served by bias and deviation profiles. Thus, bias profiles can be used to compare the bias of two methods, whereas a deviation profile can be used to define the analytical range of a method. If the acceptable limits of deviation are added to the deviation profile, then the useful analytical range of the method is immediately apparent.

Chemistry, Clinical↗
PubMed1989

[Ultrasound versus abdominal visualization of a problem abdomen in a young patient? An unusual cause of epigastric pain].

The case of a 24-year-old woman with epigastric pain is reported. A past history of slight abdominal pain for 4 weeks was recorded in the patient's history; no other illnesses were reported. Sonography revealed an unrecognizable longitudinal structure and extraenteric fluid. In view of the patient's age and the possibility of a pregnancy an abdominal X-ray examination was performed 3 h after admission, revealing a foreign body in the duodenum. A 15-cm-long pencil was removed by surgical operation; it had penetrated the duodenum with its hard end.

Abdomen↗