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Biomedical subjects

R Sauter

Publications and source records attributed to R Sauter.

At least 19 recordsLinked to original sources
PubMed1992

[The proton MR spectroscopy of intracranial tumors. The differential diagnostic aspects for gliomas, metastases and meningiomas].

Twenty-two patients with intracranial tumours were examined by MR images and in vivo proton-MR-spectroscopy. The changes of relative concentrations of NAA, PCr/Cr, Cho, and Ins were measured spectroscopically and the amount of these metabolites were related to different tumour groups. Analysis of the results has shown that the spectra from all the tumours differed from normal spectra. All cerebral tumours showed marked reduction of the Pcr/Cho quotient and the NAA/Cho quotient was also reduced. The Ins/Cho quotient for meningiomas and metastases was also lower than in normals; in gliomas of low malignancy the quotient was slightly raised and in gliomas of greater malignancy it was significantly higher than normal. The spectra of cerebral metastases showed unusual high lipid signals of 0.9 ppm and 1.25 ppm. The only common feature for meningiomas was marked reduction of NAA concentration. In summary, localised in vivo proton-MR-spectroscopy can be used clinically to obtain valuable information for the differential diagnosis of gliomas and intracerebral metastases.

Brain Neoplasms↗
PubMed1992

Combined magnetic resonance imaging and proton magnetic resonance spectroscopy of patients with acute stroke.

BACKGROUND AND PURPOSE: The prospect for a therapeutic window for treatment of ischemic stroke encourages the noninvasive investigation of metabolic changes in acute ischemia. Recently, localized proton spectroscopy became available at 1.5-T magnetic resonance systems. In this study we evaluated the usefulness of combined magnetic resonance imaging and spectroscopy on the diagnosis of acute and chronic infarctions. METHODS: Combined magnetic resonance imaging and spectroscopy investigations were carried out with a 1.5-T system in 16 volunteers, eight patients with chronic infarction (greater than 8 months), and 10 patients with acute ischemic stroke (less than 8 hours). We used a stimulated echo sequence to acquire localized spectra from image-guided volumes of interest (16-27 ml). RESULTS: There were no significant interindividual differences of choline, creatine, phosphocreatine, and N-acetyl aspartate resonances in the spectra from volunteers. In chronic infarctions, N-acetyl aspartate was decreased in relation to choline. Acute ischemic infarctions were characterized by decreased N-acetyl aspartate resonances and elevation of lactate. CONCLUSIONS: The study demonstrates the feasibility of proton spectroscopy in stroke patients. Metabolic alterations in ischemic tissue can be monitored and can distinguish acute from chronic lesions.

Aged↗
PubMed1992

Presentation of results from bioequivalence studies.

Based on general guidelines and requirements for the design and analysis of bioequivalence studies, specific recommendations are made for the presentation of results, both in tabular and graphical form. This is done by means of two examples, one of a single-dose study and one of a multiple-dose study. The recommendations in this paper are twofold. Firstly, a complete and rather detailed presentation of results is given, which practically corresponds to the standard of research reports. Secondly, a subset of this is suggested for publication. It gives the essential results for bioequivalence assessment in a standardized form. From an editorial point of view, it would be highly appreciated if the papers submitted for publication were always accompanied by a complete presentation including the individual concentration/time data and the various steps of calculation. This would speed up peer review and ultimately improve and harmonize the standard of bioequivalence publications.

Adult↗
PubMed1992

[Neonatal heart tumor. Early symptom of tuberous sclerosis].

Congenital heart tumors are rare. About 60% of them are intramurally growing rhabdomyomas. They represent an early symptom of tumerous sclerosis in about 50% of patients. The following report shows that fetal brady arrhythmia led towards the correct diagnosis.

Echocardiography↗
PubMed1992

Bioequivalence studies: single vs multiple dose.

Bioequivalence of different preparations of the same drug substance has gained considerable importance over the last few years due to increasing generic substitution. The procedure that the manufacturer of the generic test preparation has to show bioequivalence with an appropriate reference preparation is scientifically accepted and laid down in international regulations. However, the necessity of single- vs multiple-dose bioequivalence studies has not been discussed in detail with the exception of the Dutch and US guidelines on sustained-release theophylline formulations, where multiple-dose studies are specifically required. This paper compares the conclusions drawn from single- and multiple-dose studies in the same subjects and recommends appropriate pharmacokinetic characteristics.

Chemistry, Pharmaceutical↗
PubMed1992

Presentation of results from bioequivalence studies.

Based on general guidelines and requirements for the design and analysis of bioequivalence studies, specific recommendations are made for the presentation of results, both in tabular and graphical form. This is done by means of two examples, one of a single-dose study and one of a multiple-dose study. The recommendations in this paper are twofold. Firstly, a complete and rather detailed presentation of results is given, which practically corresponds to the standard of research reports. Secondly, a subset of this is suggested for publication. It gives the essential results for bioequivalence assessment in a standardized form. From an editorial point of view, it would be highly appreciated if the papers submitted for publication were always accompanied by a complete presentation including the individual concentration/time data and the various steps of calculation. This would speed up peer review and ultimately improve and harmonize the standard of bioequivalence publications.

Delayed-Action Preparations↗
PubMed1991

Localized proton NMR spectroscopy using stimulated echoes: applications to human skeletal muscle in vivo.

Localized proton NMR spectroscopy using stimulated echoes (STEAM) has been used to study metabolites in different proximal skeletal muscles of normal volunteers at rest. Single scan water-suppressed proton NMR spectra obtained at 1.5 and 2.0 T (Siemens Magnetom) from a 64-ml volume-of-interest (VOI) yield resonances due to triglycerides, phosphocreatine plus a minor contribution from creatine, and betaines comprising carnitine and choline-containing compounds. The observation of the pH-dependent resonances of carnosine required multiple acquisitions and echo times as short as 20 ms. T1 and T2 relaxation times of muscle metabolites were obtained by varying the repetition time and echo time of the STEAM sequence, respectively. Although rather long T2 values such as 180 ms for (phospho-) creatine correspond to natural resonance linewidths of only 2 Hz, the observed linewidths of typically 10-12 Hz are entirely determined by the short T2 relaxation times (25-30 ms) of the water protons used for shimming. The spectroscopic results from 24 muscle studies on 17 young male volunteers show remarkable intra- and interindividual differences in the absolute signal intensities of mobile lipids. Further metabolic variations were observed for the relative concentrations of betaines (by a factor of 2) and carnosine (by a factor of 3) when total creatine is assumed to be constant.

Carnitine↗
PubMed1991

The influence of caffeine on the steady-state pharmacokinetics of theophylline.

During this open, two-period crossover study in eight healthy volunteers, 1200 mg anhydrous theophylline was administered as a two-stage infusion during 24 hours on day 6. During one of the 8-day periods, 300 mg caffeine, t.i.d., was administered orally. After the start of the theophylline infusion, plasma concentrations of theophylline and caffeine and urinary excretion of theophylline and four metabolites were determined frequently during 60 hours. With caffeine administration theophylline steady-state concentration and area under the curve increased by 23% and 40%, respectively, whereas the volume of distribution at steady state seemed unchanged. The cumulative urinary excretion of 1-methyluric acid and 1-methylxanthine did not reach a plateau, suggesting a capacity-limiting factor in their formation. Notwithstanding the mutual interference of theophylline and caffeine metabolism, the reduction in apparent total body clearance and elimination rate constant of theophylline by 29% and 31%, respectively, indicated a pronounced influence of concomitant administration of realistic amounts of caffeine.

Administration, Oral↗
PubMed1991

Metabolic and destructive brain disorders in children: findings with localized proton MR spectroscopy.

The diagnostic potential of volume-selective proton magnetic resonance (MR) spectroscopy in vivo was evaluated in 20 children and young adults with various neurodegenerative brain disorders. All patients were examined with MR spectroscopy in conjunction with MR imaging of the brain on a whole-body imager at 1.5 T. Comparison of spectra in our patients with those of children with normal myelination (prominent signals from N-acetylaspartate [NAA], creatine/phosphocreatine, and choline) revealed a marked decrease of NAA in 12 of 17 patients with focal or generalized demyelination. In patients with Canavan disease, NAA signal intensity was markedly increased, but no choline signal was found. Increased signal intensity from lactate occurred in patients with Leigh disease, neuroaxonal dystrophy, Schilder disease, and Cockayne disease, which indicated a disturbed energy metabolism in the examined region. These results demonstrate that proton MR spectroscopy can be applied in a clinical environment to facilitate diagnosis of hereditary and acquired brain disorders in children.

Brain↗
PubMed1991

[Chronotherapy concept and the pharmacokinetic validation of a theophylline retard preparation for once-nightly administration (Euphylong)].

Many patients with asthma often experience a deterioration of symptoms at night and in the early morning resulting in sleep disruption and possibly impaired daily performance. A bronchodilator agent which exerts its maximal effect overnight to control nocturnal symptoms, without a worsening of the disease during the daytime, should improve the treatment of asthma. In the case of theophylline, it has been shown in asthmatic patients that a chronotherapeutically optimized formulation which provides the highest serum theophylline concentrations during the critical early morning hours resulted in better airflow levels overnight than the conventional twice daily regimen without loss of airflow in the afternoon. During clinical routine, this chronotherapeutically optimized drug delivery can only be ensured if there is no food interaction. In particular, dose dumping must be excluded. One absolute prerequisite for this is the pH-independent drug release in vitro. In addition to a "state-of-the-art" biopharmaceutic formulation, an easy-to-use guidance for individualizing the theophylline dose should be provided. This in turn is only possible if the concentration/time profiles show good reproducibility between subjects, from day to day, and for different dose levels. Finally, batch-to-batch bioequivalence has to be ensured. It is shown that Euphylong satisfies all of the above requirements.

Asthma↗
PubMed1991

[24-hour lung function in asthmatic patients: chrono-optimal theophylline therapy as once-daily Euphylong administration vs conventional twice-daily administration].

In this study we examined the efficacy and pharmacokinetics of a new chrono-optimized theophylline sustained release preparation for once-daily dosing in the evening for treating bronchial asthma. In a randomized, open crossover study, Euphylong (administered once daily at 2000 hours) was compared with the same dose of a reference preparation (subdivided into two equal doses taken at 800 and 2000 hours). Administration and dosage were in accordance with prior determination of clearance. The patients were outpatients during the first six days of every phase, whereas for the following 24-hour measurement period they were admitted as inpatients for measuring the requisite pharmacokinetic and pharmacodynamic data (PEF, FEV1, PEF 25 = 75, FVC). The theophylline levels remained practically constant for 24 hours under conventional theophylline treatment with twice-daily administration. In contrast, the variations of the theophylline serum levels and the night levels were higher after once-daily dosage of Euphylong, and the daytime levels and especially at the end of the dosage interval were lower. Compared with the standard profile without medication, both sustained release preparations improved the airway obstruction significantly and comparably during a 24-hour period. However, in the early morning hours between 200 and 600 both PEF and FEV1 were significantly higher under Euphylong. Between the improvement of PEF and FEV1 and the theophylline serum concentrations there was a significant correlation between 200 and 600 under Euphylong only. It is concluded that the treatment of asthma with the chrono-optimized once-daily theophylline preparation Euphylong over night is more effective than treatment with a conventional preparation in twice-daily dosage.

Adult↗
PubMed1991

[Pharmacokinetics and pharmacodynamics of twice-daily unequal administration of theophylline retard pellets in children of various age groups].

To assess the pharmacokinetic parameters of theophylline (Euphylong as retard pellets) children were studied belonging to age groups between 9 to 13 and 5 to 9 years in twice-daily dosage with unequal distribution of the daily doses. For the older children the dose was 400 + 200 mg and for the younger ones 300 + 150 mg theophylline (these quantities represent the evening and morning doses). 16 and 14 children, respectively, completed the studies regularly. Pharmacokinetic evaluation resulted in a markedly parallel course of the individual serum theophylline profiles around the mean value. The average nocturnal concentration from 200 to 600 hours in the morning was higher than the average daytime concentration (11.4 to 10.5 mg/l or 12.3 to 11.4 mg/l). Due to the relatively stable baseline values the clinical parameters improved only slightly, but there were in particular significant changes in the peak-flow profile. In the older children we could also prove that they had a better protection against metacholine provocation. The side effects were generally mild and were in accordance with previous experiences collected with the studied preparation. The dosage scheme with unequal distribution of the total daily dose is recommended, on the basis of the present study, for all patients with rapid theophylline metabolism, i. e. children, habitually strong smokers or if the clearance is accelerated due to endogenous factors.

Adolescent↗
PubMed1991

[Multicenter study with a large number of patients for the validation of pharmacokinetic and clinical findings from controlled studies with small patient cohorts].

In 94 surgeries a total of 682 patients were included into a multicenter study. Serum theophylline concentrations were monitored in patients with obstructive pulmonary diseases, that were treated with theophylline dosages as recommended in the Euphylong professional information or as adjusted after a theophylline serum level control. Peak-flow rates and theophylline tolerance as stated by the patients were also monitored and documented. 72% of the patients already received theophylline in the past. The increase of the mean daily dosage of theophylline to 750 mg administered as a single dose in the evening raised the concentration of serum theophylline in average from 8.7 +/- 5.0 mg/l to 12.2 +/- 4.1 mg/l. No increase of the portion of patients with serum concentrations above 20 mg/l was observed. The patients additional bronchodilatory medication remained unchanged during the study. As a consequence of the improved theophylline medication morning and evening peak-flow rates increased in average from 272 +/- 99 l/min to 315 +/- 109 l/min and 278 +/- 101 l/min to 318 +/- 107 l/min, respectively. After a temporary increase during the first week of treatment the frequency of side effects decreased below the one stated at the starting point of the study. Out of 106 patients, that did not finish the study, 44 (= 6.5%) dropped out because of side effects. The overall assessment of effectiveness and tolerance of Euphylong by physicians and patients was good to very good. Herein the single dosage per day was well accepted by most of the patients. The results of the presented multicenter study with Euphylong therefore confirm the pharmacokinetic and clinical data gained from single center studies with small patient numbers hitherto.

Adolescent↗
PubMed1991

[Localized 31 phosphorus NMR spectroscopy of the human heart--development of a measuring method and initial clinical application].

In this work, the technique of 31P-NMR-spectroscopy is applied for the first time to diagnose coronary heart disease in patients, using a suitable measuring technique. In 13 healthy volunteers we applied a method comfortable and tolerable for patients, which enabled us to examine the myocardium inside the reception area of a surface coil. Concerning myocardium-specific selectivity and sensitivity the localization techniques FROGS (Fast-ROtating-Gradient-Spectroscopy), 1-D-ISIS (1-Dimensional-Image-Selected-In-vivo-Spectroscopy) and 3-D-ISIS were compared. By a combination of the 3-D-ISIS-technique with magnetic resonance imaging, we obtained a monitored position of the volume of interest (VOI) within the myocardium, thus gaining a selective measurement. The cube-shaped VOI with a lateral length of 50 mm was placed into the apical-septal area of the myocardium. On the basis of the obtained results, we examined seven patients suffering from coronary heart disease, which was symptomatic and verified by coronary angiography. The 31P-NMR-spectra of the two examined groups were computed into numbers representing the relative content of the myocardial high-energy-phosphates. In addition, the quotients PCr/ATP and Pi/ATP were calculated and compared. With this small number of cases the evaluation of the PCr/ATP-ratios already showed a significant difference of 0.34 (p less than 0.01) between patients with coronary heart disease (0.49 +/- 0.19) and healthy volunteers (0.83 +/- 0.27). The findings suggest the conclusion that 31P-NMR-spectroscopy is able to be instrumental in the diagnostic detection assessment of the metabolic state in coronary heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1990

The human brain: localized H-1 MR spectroscopy at 1.0 T.

Localized H-1 magnetic resonance (MR) spectroscopy of the human brain in vivo was performed at a field strength of 1.0 T. Investigations with the stimulated echo acquisition mode included studies in the right frontoparietal area, occipital lobe, cerebellum, and pons of healthy volunteers, as well as studies in two patients with astrocytomas. Prior to the acquisition of the H-1 MR spectra, all examinations included fast low angle shot MR imaging in three orientations to select the volumes of interest. The tumor spectra confirmed previous findings at higher field strengths by producing characteristic alterations from the spectra of normal brain tissue: markedly reduced resonances of N-acetyl-aspartate and creatine, increased signal intensities of cholines, and a strong resonance from lactate. The authors conclude that the results of this study clearly demonstrate the feasibility of H-1 MR spectroscopy at 1.0 T without significant losses in relative spectral resolution and signal-to-noise ratio of major metabolites with singlet resonances, compared with previous studies at 1.5 and 2.0 T.

Brain↗
PubMed1989

Localized high-resolution proton NMR spectroscopy using stimulated echoes: initial applications to human brain in vivo.

Water-suppressed localized proton NMR spectroscopy using stimulated echoes has been successfully applied to detect metabolites in the human brain in vivo. The STEAM spectroscopy sequence allows single-step localization by exciting three intersecting slices. Water suppression is achieved by preceding chemical-shift-selective (CHESS) rf pulses. High-resolution (0.05 ppm) proton NMR spectra of healthy volunteers have been High-resolution (0.05 ppm) proton NMR spectra of healthy volunteers have been obtained on a conventional 1.5-T whole-body MRI system (Siemens Magnetom). Volumes-of-interest (VOI) of 64 ml (4 x 4 x 4 cm3) were localized in the occipital area of the brain and spectra were recorded within measuring times ranging from 1 s (single scan) to about 10 min. The experimental procedure is described in detail. Resonance assignments include acetate, N-acetyl aspartate, gamma-amino butyrate, glutamine, glutamate, aspartate, creatine and phosphocreatine, choline-containing compounds, taurine, and inositols. Cerebral lactate was found to be at a maximum concentration of 0.5 mM when assuming N-acetyl aspartate in white matter to be 6 mM.

Adenine Nucleotides↗
PubMed1989

Cerebral metabolism in man after acute stroke: new observations using localized proton NMR spectroscopy.

Localized proton NMR spectroscopy at 1.5 T using stimulated echoes has been applied to study metabolic alterations in the postischemic phase of patients with acute cerebral infarction. A complete depletion of N-acetyl aspartate in the area of infarction has been observed in a patient studied 4 days after stroke. This finding was paralleled by a dramatic increase in the concentration of lactic acid to about 16 mM within the lesion, indicating continued anaerobic glycolysis. The diluting effect of the edema has been estimated to reduce average metabolite concentrations by about a factor of 3.

Adult↗