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Biomedical subjects

T Groth

Publications and source records attributed to T Groth.

At least 109 records · Page 6Linked to original sources
PubMed1986

The membrane potential of pig aortic endothelial cells.

Membrane potential and cell number of endothelial cells from pig aorta (line BSEz-3) were determined in vitro in different phases of growth. We found different membrane potentials for mononuclear (-8.6 mV) and multinuclear (-21.9 mV) endothelial cells. In both cases the maximum membrane potential occurred on the 6th day after seeding (during the exponential growth phase). The fraction of multinuclear endothelial cells was about 2.1% in the total culture. The membrane potentials of pig aortic endothelial cells are similar to our earlier values obtained from calf aortic endothelial cells.

Animals↗
PubMed1985

Complexity of enzyme release during acute myocardial infarction in a controlled study with early nifedipine treatment.

Fifty-seven consecutive patients with acute myocardial infarction (AMI), admitted to a coronary care unit (CCU) within 6 h from onset of symptoms were included in the study and randomly allocated to nifedipine treatment or placebo. The 23 patients in the treatment group received 10 mg nifedipine orally at the onset of the study, after 30 min, and then every 6 h. Placebo was given to the 34 patients in the control group. The study was double blind. Serum time-activity curves for creatine-kinase-MB (CK-MB) and myoglobin (MG) were established from frequent determinations. The two patient groups did not differ significantly regarding average cumulative MG and CK-MB release. In both groups the range was wide, with the largest maximal individual release about 30 times larger than the smallest. In most patients the enzyme release occurred stepwise, resulting in two or more separate peaks. In the treatment group significantly fewer patients had multiple peaks of MG (P less than 0.05) and CK-MB (P less than 0.025) release. The initial peaks had a longer duration in the treatment group and total release tended to stop earlier. In the control group a highly significant correlation between cumulative MG and CK-MB release was obtained, while in the treatment group no such correlation was observed. In conclusion, oral administration of nifedipine during acute myocardial infarction appears to influence the pattern of enzyme release, although no effect on the total cumulative release could be demonstrated.

Aged↗
PubMed1984

The value of serum myoglobin determinations in the early diagnosis of acute myocardial infarction.

Myoglobin has been measured in sera from 305 consecutive patients with suspected acute myocardial infarction (AMI) to study the clinical value in relation to other diagnostic methods. On admission the frequency of false negative (i.e. the diagnostic sensitivity) myoglobin values was 28% in the AMI group as compared with 60% for serum creatine kinase (CK) and 46% for serum aspartate aminotransferase (ASAT). Four hours after admission the corresponding figures were 2, 31 and 29%. This makes the diagnostic sensitivity of the myoglobin test 0.98, which is significantly higher (p less than 0.001) than that of the two enzyme tests. The predictive value of a negative myoglobin test was 0.97 and also significantly higher (p less than 0.001 and p less than 0.01) than for CK and ASAT. S-myoglobin was further related to the number of complications and the prognosis of the patients, and high levels appeared to be an unfavourable sign, particularly in combination with an anterior wall infarct. This study has demonstrated and confirmed the superior diagnostic sensitivity of myoglobin determination in early AMI. The inclusion of S-myoglobin in the routine diagnosis of AMI warrants serious consideration.

Adult↗
PubMed1984

Size estimation of acute myocardial infarction from serial serum myoglobin observations with due consideration of individual differences in basic kinetics.

Thirty-three consecutive patients suffering from acute myocardial infarction were studied. Serial serum myoglobin and CK-MB measurements were made, and in seven patients individual kinetic constants for myoglobin were available from previous single injection studies. A two-compartment model for myoglobin kinetics was used for infarct size estimation. Given values for the basic kinetic constants (elimination rate constant, exchange rate constants, and distribution volume), the adjustment of a flexible, parameterized 'blood-appearance rate-function', phi AMI (mg X h-1), allowed estimation of start-time (t0), peak-time (tpeak) and end-time (tend) of myoglobin inflow into blood from the infarct area, in addition to the total cumulative release (A), which was used as a measure of infarct size. Use of patient-mean values for the kinetic constants caused a mean difference in estimated 'infarct size' of 34% (n = 7). Individual estimation of the elimination rate constant from the 'final slope' of the serum myoglobin curve could neither be recommended from a theoretical point of view nor from the practical outcome of numerical calculations; the 'true' elimination rate constant is underestimated by a factor of about 10 on average. Good correlation was found between our myoglobin estimates of 'infarct size' (using patient-mean kinetic constants), and independent estimates from serial serum CK-MB data, as calculated by the use of the method by Sobel et al.. Large inter-individual variations were found in the estimated infarct parameters, a circumstance which is of special interest in evaluation of therapeutic intervention studies on AMI-patients, and in infarct size prediction calculations.

Creatine Kinase↗
PubMed1984

Potential use of computer simulation in treatment of burns with special regard to oedema formation.

The potential usefulness of computer-based 'patient-simulators' in burn care is discussed and illustrated in the special case of oedema formation in three patients with severe thermal injuries. The present model was derived from a model by Wiederhielm (1978), and modified to be applicable to thermal injuries. The model seems to describe accurately the oedema formation as well as the distribution and composition of local and general oedema. Following thermal injuries the general oedema is characterized by typical disturbances in the circulatory state variables such as capillary pressure and plasma colloid osmotic pressure. The net water flow is increased because of an increase in filtration rate and a decrease in reabsorption rate. The resulting interstitial oedema leads to dilution of the free water proteins and a decrease in interstitial colloid osmotic pressure. The elevation of interstitial pressure leads to an increase in lymph flow. The local oedema is caused by changes in both the circulatory system and the interstitial space. There is an increase in both water and protein net flows. The latter is due to increased protein leakage to the interstitium. This results in an interstitial oedema with a higher protein concentration in free water than in general oedema. Because of the higher protein concentration in free water, the interstitial colloid osmotic pressure is at all times larger than the corresponding pressure in general oedema. In all three patients the general shape of the simulated and measured oedema curve were the same, but with minor differences in numerical values. It is interesting to note that the general oedema was larger than the local oedema in all three extensively burned patients. The results from the present investigation indicate the importance of monitoring either the total plasma protein concentration or the plasma colloid osmotic pressure and small vein pressure for guidance of a proper fluid resuscitation. The steady state 'oedema vs. venous pressure'-diagram obtained may also be used for evaluating the dynamic effects on general oedema formation due to changes in venous pressure and plasma protein concentration. It thus turned out that for a typical thermal injury with a decreased small vein pressure a continuous colloid infusion is to be preferred instead of an intermittent model of administration.

Blood Proteins↗
PubMed1984

Principles for developing improved quality control procedures.

Achieving quality goals in the clinical chemistry laboratory requires a comprehensive understanding of the many critical components and factors that are involved in a quality assurance program. The present paper has therefore been divided into sections dealing with quality goals as a rational starting point, determinants of quality for an analytical procedure, assessing the quality of a measurement procedure, assessing the quality of an internal control procedure, improving the quality of internal control procedures, designing an internal control procedure to provide a specified level of quality, strategy for implementing high power control procedures, implications of frequency of errors and predictive value theory on design of control procedures, role of external quality assessment in achieving quality goals, tools needed to improve quality control, and further considerations in achieving quality goals. In designing control procedures we have focused mainly on internal statistical control, emphasizing the new aspects of frequency of analytical disturbances. Less detailed consideration has been given to external quality assessment, though this problem area is also essential to a quality assurance program. Many other aspects have not been discussed, e.g., requirements for control materials, and use of patient specimens for control purposes, though both aspects are obviously very important. Even with these limitations, we think that quality control can be improved by development of better control procedures following the principles outlined here.

Chemistry, Clinical↗
PubMed1984

A quality control simulator for design and evaluation of internal quality control procedures.

A computer simulation program has been developed to aid clinical chemists in the design and theoretical evaluation of statistical control procedures. This "QC simulator" permits the user to study the effects of different parameters characterizing the measurement procedure (method standard deviation, components of variation, rounding of results) and parameters of the control procedure (decision criteria, control limits, number of observations). The performance of control procedures is characterized by the probability for rejection, estimated at several different levels of random and systematic error. Predictive values for reject and accept signals are also calculated at different error incident rates, given a specified error model. The relative performance of different control procedures can be compared based on these performance characteristics. Another important application of the program is the design of control procedures to assure that a specified level of analytical quality is achieved in routine analyses. Various optimization criteria may be applied, e.g., in terms of test yield and cost.

Chemistry, Clinical↗
PubMed1984

Data base management systems for evaluation of analytical procedures.

The present paper gives a short introduction to data base management systems, and their application in the clinical laboratory for evaluating the quality of analytical procedures. Two applications based on the MIMER relational data base management system are described in some detail: An internal quality control data base under development at the clinical chemistry laboratory of the University Hospital in Uppsala, and a data base system for external quality assessment developed in a previous NORDKEM project.

Chemistry, Clinical↗
PubMed1984

Workshops for teaching quality control to laboratory personnel: objectives and guidelines.

The educational aspects are crucial for a successful implementation of new control procedures in the clinical laboratory. The initial effort can take the form of workshops directed to laboratory directors and supervisors on one hand, and to laboratory analysts on the other. The present paper gives an outline of objectives and guidelines for teaching quality control to these two groups of laboratory personnel.

Allied Health Personnel↗
PubMed1984

The quality-costs of an analytical process: 1. Development of quality-costs models based on predictive value theory.

General considerations are presented for the development of quality-costs models based on predictive value theory [12]. Quality-costs include costs for prevention, appraisal (surveillance), and failure [1]. Failure-costs are due to incorrect analytical runs (medically important analytical errors by the measurement procedure) and incorrect decisions on the status of analytical runs (misclassifications by the control procedure). Failure-costs depend on characteristics of the measurement procedure (f, frequency of medically important analytical errors) and characteristics of the control procedure (ped, probability for error detection; pfr, probability for false rejection). An approach is presented for developing quantitative relationships to predict failure-costs based on these critical process characteristics. Efforts to provide cost effective analytical processes should be aided by models which can relate quality-costs to characteristics of the measurement and control procedures.

Chemistry, Clinical↗
PubMed1984

The quality-costs of an analytical process: 2. A test yield formulation of the predictive value quality-costs model.

A quality-costs model has been developed to predict the cost effectiveness of a batch analytical process subject to intermittent analytical errors. The process test yield (the proportion of analytical measurements in an analytical run that are reportable as patient test results) provides a useful measure of the efficiency of an analytical process and can be related to critical characteristics of the measurement and control procedures. Equations are provided to estimate test yield from the measurement procedure's frequency of medically important errors (f) and the control procedure's probabilities for error detection (ped) and false rejection (pfr). Examples illustrate how losses in process output depend on the characteristics of the measurement and control procedures, and how increased control efforts may actually improve the yield of analytical processes when the frequency of errors is high. The test yield formulation of the quality-costs model should aid efforts to provide more cost effective analytical processes.

Chemistry, Clinical↗
PubMed1984

Nested control procedures for internal analytical quality control. Theoretical design and practical evaluation.

A quality control system has been developed and evaluated for three Greiner automatic analyzers. The control system was built in a hierarchical way with different statistical rules for different stages of the analytical process. Computer simulation techniques were found to be very helpful in grasping the quantitative aspects of various design features. In the practical evaluation of the control system the calculated rates of false rejections were of the same order as the theoretical value of 0.01 in most cases, and the estimated frequencies of analytical disturbances varied between 0 and 0.25.

Autoanalysis↗
PubMed1983

A predictive value model for quality control: effects of the prevalence of errors on the performance of control procedures.

A predictive value model has been developed to describe the usefulness of results from quality control tests or procedures. The model shows that the critical parameters are the probability for false rejection, probability for error detection, and prevalence or frequency of occurrence of analytical errors. When prevalence is low, control procedures should have a low probability for false rejection. When prevalence is high, control procedures should have a high probability for error detection. The predictive value model for a quality control (QC) test is analogous to the predictive value model for a diagnostic test, thus suggesting new strategies for optimizing the performance of QC tests.

Diagnostic Errors↗
PubMed1981

Myoglobin kinetics in patients suffering from acute myocardial infarction in its early phase -as studied by the single injection method.

The turnover of myoglobin has been examined with the single injection technique in eight patients suffering from acute myocardial infarction during its early phase. All patients had elevated serum levels of myoglobin and creatine kinase-MB. The serum disappearance curve of [125I]myoglobin could be fitted adequately by a two-compartment model. The kinetic parameters did not differ form those estimated for six healthy old volunteers, previously studied with the same technique. The average elimination rate constant was 0.80 +/- 0.37 h-1 and the average turnover was 5.5 +/- 3.2 h (SD). The values are in good agreement with corresponding estimates for the retinol-binding protein, with a molecule weight (21,000) close to that for myoglobin (mol. wt 17,800). In comparison with beta 2-microglobulin, another low molecular weight protein (mol. wt 11,800), the elimination rate constant for myoglobin is significantly smaller and the turnover time is longer, as could be expected form the difference in molecular weight. Plasma protein binding of myoglobin could not be excluded, however.

Aged↗
PubMed1981

Design and evaluation of statistical control procedures: applications of a computer "quality control simulator" program.

A computer simulation program has been developed to aid in designing and evaluating statistical control procedures. This "QC stimulator" (quality control) program permits the user to study the effects of different factors on the performance of quality-control procedures. These factors may be properties of the analytical procedure, characteristics of the instrument system, or conditions for the quality-control procedure. The performance of a control procedure is characterized by its probability for rejection, as estimated at several different magnitudes of random and systematic error. These performance characteristics are presented graphically by power functions-plots of the probability for rejection vs the size of the analytical errors. The utility of this stimulation tool is illustrated by application to multi-rule single-value procedures, mean and range procedures, and a trend analysis procedure. Careful choice of control rules is necessary to minimize false rejections and to optimize error detection with multi-rule procedures. Control limits must be carefully calculated for optimum performance of mean and range procedures. The level of significance for testing control must be carefully selected for the trend analysis procedure.

Chemistry, Clinical↗
PubMed1981

Erythrocyte metabolism of purines and purine nucleosides during storage and simulated physiological conditions.

Some results from storage experiments at +4 degrees C with adenine and purine nucleosides in this laboratory are compared with incubation experiments at 37 degrees C with guanosine at pH 7.0 and 7.4 and different levels of inorganic phosphate (iP). At high iP concentration the synthesis of GTP was extremely rapid. Replacement of ATP by and ATP-GTP mixture has metabolic effects on several enzymic steps e.g. phosphofructose kinase and phosphoglycerate kinase explaining the reported beneficial effect on human erythrocytes during preservation. In order to explore the role of erythrocytes in the physiological transport of purines and purine nucleosides in vitro experiments were designed in which the substances were continuously added at the appropriate concentrations by means of a dialysis tubing. Analyses of purines, nucleosides, glucose, lactate and iP in the efferent dialysis solution and the extra- and intracellular volumes reveal the metabolic processes in the erythrocytes if the transport across the dialysis tubing is accounted for. Prior to incubation the erythrocytes were stored with NaF in order to reduce the total adenylate concentration. The rate of synthesis of adenylates was about 0.05 mmol x h(-1) (calculated per litre of erythrocytes) when adenine was supplied as source for the adenine moiety of adenylates but reached a five times higher substance rate when adenosine was supplied at a sufficiently high rate. Adenosine deaminase played an important role also at "sub-physiological" concentrations. The results indicate that the erythrocytes take part in the transport of purines between organs.

Adenine Nucleotides↗