Biomedical subjects
Publications and source records attributed to I Günther.
We used positron emission tomography and [11C]flumazenil to analyze the benzodiazepine receptor binding in symptomatic and asymptomatic carriers of the Huntington's disease gene. We found an inverse relationship between [11C]flumazenil and [11C]raclopride binding in the putamen of symptomatic patients, and interpret this result as GABA receptor upregulation.
FDOPA/PET scans were performed in one rhesus monkey to study the influence of three catechol-O-methyltransferase (COMT) inhibitors (CGP 28014, OR-611 and Ro 40-7592) on FDOPA pharmacokinetics. COMT inhibitors were administered in combination with carbidopa, a peripherally acting inhibitor of the aromatic amino acid decarboxylase (AAAD). FDOPA was administered intravenously and its metabolic fate in plasma was determined using an HPLC system with an on-line gamma-gamma coincidence detector. Cerebral tracer uptake was assessed in the striatum and in a non-dopaminergic brain region (occipital cortex). In the periphery, the pharmacokinetic efficiency of FDOPA was increased due to the combined inhibition of COMT and AAAD activity. All three COMT inhibitors reduced the FDOPA methylation rate constant in plasma, with complete suppression obtained in the case of Ro 40-7592. In the brain, specific 18F radioactivity (striatal minus brain reference radioactivity) increased as a result of the increase in FDOPA plasma availability following the administration of COMT and AAAD inhibitors. We established a significant linear correlation between striatal radioactivity and FDOPA plasma levels (r = 0.924 +/- 0.048, P < 0.0001 for total striatal and r = 0.948 +/- 0.054, P < 0.0001 for specific striatal radioactivity). Using plasma FDOPA radioactivity as input, we found that the striatal FDOPA uptake rate constant KiFD was not changed by any of the inhibitors. Thus, the enhancement of striatal radioactivity after application of enzyme inhibitors is a consequence of the increase in plasma FDOPA that becomes available for conversion to fluorodopamine in the striatal dopaminergic nerve terminals. By contrast, using the radioactivity in a non-dopaminergic region (cortex) as input, we found that the striatal FDOPA uptake rate constant Ki(ref) was significantly (P < 0.0001) increased following pretreatment with COMT inhibitors. Our analysis demonstrated that Ki(ref) and the 3-OMFD contribution to the cerebral radioactivity were inversely correlated.
The binding of the three dopamine transporter radioligands ([125I] beta-CIT, [125I] beta-CIT-FE, and [125I] beta-CIT-FP) was studied using whole-hemisphere autoradiography on postmortem human brains. The autoradiograms revealed an intense and homogeneous labeling of the nucleus caudatus and putamen but also to varying extent to serotonergic and noradrenergic transporters of neocortex and thalamus. The order of specificity estimated (striatum over neocortex ratios) was beta-CIT-FP > beta-CIT-FE > > beta-CIT, suggesting that beta-CIT-FE and beta-CIT-FP should be preferred for in vivo studies of the dopamine transporter in the human brain.
We used PET with the tracers [18F]fluorodeoxyglucose (FDG), [18F]fluorodopa (FDOPA) and [11C]raclopride (RACLO) to study striatal glucose and dopa metabolism, and dopamine D2 receptor binding, respectively, in nine patients with multiple system atrophy. Ten patients with classical Parkinson's disease were investigated with the same three PET tracers' and three separate groups, each of 10 healthy subjects, served as control populations. We found that striatal FDOPA values separated all healthy subjects from patients with parkinsonism but they were not useful in distinguishing multiple system atrophy from Parkinson's disease. Conversely, striatal RACLO as well as FDG values discriminated all multiple system atrophy from Parkinson's disease patients as well as from healthy control subjects. Metabolic and receptor binding decrements in the putamen of multiple system atrophy patients were significantly correlated. Stepwise regression analysis revealed that a linear combination of putamen RACLO and FDOPA values accurately predicted clinical measures of disease severity in the multiple system atrophy group. Our findings suggest that striatal FDG and particularly RACLO are sensitive and effective measures of striatal function and may help characterizing patients with multiple system atrophy. In contrast, FDOPA measurements are accurate in detecting abnormalities of the nigrostriatal dopaminergic system but may not distinguish among different forms of parkinsonism.
Iron and transferrin are required for DNA synthesis and cell division. Cellular iron uptake is mediated by transferrin receptors. In order to investigate whether iron uptake in brain tumors is associated with their histological grade, we studied 24 patients (5 astrocytoma, 11 glioblastoma, 8 meningioma) using positron emission tomography and 52Fe-citrate. Tracer uptake from blood into brain and tumor tissue was assessed 1. using multiple time graphical analysis yielding a measure for unidirectional net tracer uptake (Ki) and 2.) testing a one- and two-tissue kinetic compartment model, where K1 denotes tracer uptake from blood into tissue, k2 efflux from tissue into plasma, and k3 specific tracer binding. In the plasma, 52Fe was bound to a 80 kD protein (transferrin). Ki (in units of 10(-5)/min) was higher in glioblastomas (Ki mean +/- SD 13.6 +/- 6.1) compared with astrocytomas (4.8 +/- 3.5, Mann Whitney p = 0.015) and contralateral brain (2.2 +/- 0.9, Mann Whitney p = 0.009). Highest values were found in meningiomas (no blood-brain barrier (BBB); Ki 33.4 +/- 16.5, Mann Whitney p = 0.008 compared with glioblastomas). Among the compartment models, fitting with K1 and regional plasma volume explained the data best (one-tissue model), data fits were not significantly improved by addition of a k2 or k3 parameter. K1 and Ki values were significantly correlated (Spearman Rank, p = 0.0006). We conclude that 52Fe accumulation in tumors is governed by tracer uptake at the BBB, and does not reflect number of transferrin receptors at the level of tumor cells.
OBJECTIVE: To assess the relationship between striatal dopa decarboxylase capacity, D2 dopamine receptor binding, and energy metabolism in Parkinson's disease (PD). DESIGN: Positron emission tomographic (PET) studies of glucose and dopa metabolism and D2 dopamine receptor binding in the caudate nucleus and putamen of patients with PD at different Hoehn and Yahr (HY) stages using PET and the tracers 18F-fluorodeoxyglucose (FDG), 6-18F-fluoro-L-dopa (FDOPA), and 11C-raclopride (RACLO). SETTING: Positron emission tomography research program at the Paul Scherrer Institute. SUBJECTS: Twenty patients with PD at different stages of the disease (HY stages I through IV; five patients for each stage) compared with separate groups of age-matched healthy subjects. MAIN OUTCOME MEASURES: Influx constant (Ki) for specific FDOPA uptake; uptake index ratio for RACLO binding to D2 dopamine receptors; normalized to global FDG metabolic rate for glucose consumption; and semiquantitative score for assessment of tremor, rigidity, and bradykinesia in PD. RESULTS: Patients with PD at HY stages I to II (hereafter HY-I-II PD) revealed reduced FDOPA metabolism, particularly in the putamen. The FDOPA uptake in the putamen and caudate nucleus declined with increasing HY staging and scoring for bradykinesia and rigidity. Putamen RACLO binding to D2 dopamine receptors was up-regulated in patients with HY-I-II PD but declined toward control values, with increasing disease severity. Putamen side-to-side asymmetries of FDOPA metabolism and RACLO binding revealed a significant correlation. Putamen FDG metabolism showed a relative increase in all patients with PD. CONCLUSIONS: Our results show that FDOPA, RACLO, and FDG PET measurements provide complementary information to characterize metabolic and receptor changes in the striatum of PD with different degrees of motor disability. The FDOPA uptake reflects the best motor-related pathologic features, as indicated by the significant correlation between Ki values and clinical scores. The significant association between RACLO and FDOPA in the putamen suggests that D2 dopamine receptor changes are related to the reduction of presynaptic dopaminergic nerve terminals. Putamen FDG increase is probably the result of more complex feedback mechanisms that are primarily induced by striatal dopamine deficiency.
We compared the influence of three different catechol-O-methyltransferase (COMT) inhibitors (CGP 28014, OR-611 and Ro 40-7592) on the metabolism of no-carrier-added (NCA) 6-[18F]fluoro-L-dopa (6-FDOPA) in one Rhesus monkey. All three COMT inhibitors improved 6-FDOPA availability in plasma, increased the specific uptake in the brain and thus improved 6-FDOPA uptake measurements using positron emission tomography (PET). Best results were obtained with Ro 40-7592.
Catechol-O-methyl-transferase inhibitors are promising drugs in Parkinson's disease since these drugs enhance levodopa effects and increase their duration. However, since these compounds block a pathway for the peripheral metabolism of catecholamines, they may also produce side effects related to elevation of catecholamines in plasma. We investigated the adverse effects of Ro 40-7592 in rabbits and the relationship of Ro 40-7592 to norepinephrine plasma levels. Intravenous administration of Ro 40-7592 in rabbits induced elevation of norepinephrine plasma levels in old animals after bolus injection of a dose three times the highest dose actually recommended to be taken orally by humans. Though Ro 40-7592 appears safe for humans, special precautions may be needed in patients with a high risk of adrenergic hyperactivity.
Two receptor binding variants of the influenza virus A/Tübingen/12/85 (H1N1) were separated by their different plaque formation in MDCK cells. Hemagglutination of variant I was restricted to red blood cells of guinea pigs, whereas variant II also hemagglutinated chicken cells. The variants differed also in their ability to bind to alpha 2,6-linked sialic acid. Evidence is presented that this difference is determined by a complex carbohydrate side chain at asparagine131 near the receptor binding site which is absent in variant II. With both variants, the arginine found at the cleavage site of all other human isolates analyzed so far was replaced by lysine.
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The gene for the ribosomal protein L5 from the archaebacterium Sulfolobus acidocaldarius has been isolated and sequenced. The gene codes for a basic protein of molecular weight 29 165 Da. This protein shows substantial similarity to the equivalent protein from other archaebacteria as well as from yeast, and considerably less similarity to the equivalent eubacterial protein. These results support the concept of the archaebacteria as a monophyletic kingdom more closely related to eukaryotes than to eubacteria.
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The gene of a cytoplasmic 18 S ribosomal RNA (18 S rDNA) of the dicotyledonous plant tomato (Lycopersicon esculentum) cv. Rentita has been cloned, and its complete primary structure has been determined. The tomato 18 S rDNA is 1805 bp long with a G + C content of 49.6%. Its sequence exhibits 94%-96% positional identity when it is colinearly aligned with the previously reported sequences of the 17-18 S rDNAs of the dicot soybean and the monocots maize and rice. A model of the secondary structure of the 18 S rRNA of angiosperms is presented and its genera-specific structural features are compared with a current eukaryotic 18 S rRNA consensus model.
A microscale procedure for the isolation and purification of viroid RNA from one gram of viroid-infected leaf tissue and for its subsequent sequencing at the cDNA level is described using potato spindle tuber viroid (PSTV) as model system. Total nucleic acids are phenol-extracted and salt-fractionated with 2 M LiCl. The viroid-containing fraction is then subjected to bidirectional polyacrylamide gel electrophoresis. This removes all co-fractionated cellular RNAs from the circular viroid RNA which is finally recovered from the gel in pure form by isotachophoresis. Thus, from one gram of PSTV-infected tomato leaf tissue, about 100-250 ng of circular PSTV RNA can be obtained and used as template for several DNA primer-directed reverse transcription reactions. From the primer-extended overlapping cDNAs the entire sequence of the viroid progeny synthesized in an individual plant or plant leaf can thus be established by Maxam-Gilbert sequencing. This renders the procedure especially suited for the routine analysis of the in vivo fate of viroid mutants constructed in vitro.
For prevention of infection we used an SD design including antibacterial (trimethoprim 480 mg/daily, sulfamerazine 720 mg/daily, and polymyxin 0.25 mg/daily) and antifungal (4-6 million IU nystatin/daily) components. We analyzed retrospectively 138 treatment periods in 108 patients. The intensified chemotherapy resulted in severe granulocytopenia below 0.1 x 10(9)/liter over 25.2 days. In 19 patients there was suspicion of major fungal infection; therefore they were given amphotericin B and 5-fluocytosine. Fourteen of them died; major fungal infections were documented in 5 cases. In 18% of all the deceased we found major fungal infections. There was a correlation between fungal infection, the late stages of the hematological malignancy, and the lesions on the oropharyngeal mucosa. However, in terms of the serological and culture findings no correlation appeared to exist between the group with and the group without fungal infection. The SD regime is meant to suppress the Candida cell concentration in the digestive tract but has no influence on Aspergillus in the respiratory tract.
Besides a literature survey own results by using the method of selective decontamination in the induction attendance of patients suffering from acute leucaemia are represented. These patients had an extreme infection disposition. The infection rate, the fever days, and the amount of systemic prescribed antibiotics could be decreased statistically significant. The results of selective decontamination, of granulocytes transfusion, and of isolation of patients in the life island achieved in our clinic are confronted. The selective decontamination is of central importance for prophylaxis in the same way as in the attendance of hospital infected defense diminished patients. Additionally, in the case of infections combinations of bactericidic antibiotics are indicated. On the other hand, granulocytes transfusion are not necessary. The effectivity of selective decontamination of the gastrointestinal tract underlines the significance of gnotobiotic methods within clinical practice.
In 89 preparations of patients with a carcinoma of the prostate and 100 preparations of patients with a hyperplasia of the prostate (adenoma of the neck of the bladder) the appearance of primarily atypical hyperplasias was investigated. In these cases in the carcinoma group in the uniform as well as in the pluriform carcinomas a coincidence of carcinoma and atypical hyperplasia of 55% was found. The coincidence is particularly high in adenocarcinomas and in carcinomas with dominating adenoid part, respectively, i. e. in more mature glandular structures. Among the various histological types of the atypical hyperplasia the microglandular/papillary clear-cellular form is dominating with 82%. In the group of the benign hyperplasia of the prostate gland a coincidence of the atypical hyperplasia of 33% was found. Though this rate, in comparison to other investigators, seems to be relatively high, it is still significantly lower than in the carcinoma. From this follows that the atypical hyperplasia, particularly its severest forms and dysplastic deformations from other hyperplasias (postatrophic hyperplasia, basal cell hyperplasia, atrophy and metaplasia of the prostate) now as ever are suspected that these cases in question are precancerous lesions. For the clinically working urologist the task is derived in such histopathological diagnoses by clinical and bioptical follow-up controls to find an already existing, but still unrecognized, or developing carcinoma of the prostate gland. In no case the diagnosis may cause surplus therapeutic consequences.
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