PubMed Health⌕ Search

Biomedical subjects

B Bubeck

Publications and source records attributed to B Bubeck.

At least 19 recordsLinked to original sources
PubMed2000

[D2-dopamine receptor upregulation and treatment response under neuroleptic therapy].

Animal and post mortem studies indicate that neuroleptic therapy may induce D2-dopamine receptor upregulation in the basal ganglia. To address this phenomenon in a clinical study, we investigated the D2-dopamine receptor binding in 15 DSM-III-R schizophrenics in the drug-naive state and three days after completion of a standardized neuroleptic therapy (benperidol 12-16 mg/d for 25 days) using single photon emission computed tomography (SPECT). SPECT scans were obtained 2 h after intravenous injection of 185 MBq 123I-IBZM. For analysis, basal ganglia to frontal cortex (BG/FC) ratios were calculated and the patient sample was subgrouped into patients with a favourable versus a poor treatment response. Neuroleptic treatment led to decreased BG/FC ratios in patients with a favourable response, but increased ratios in the poor responders (df = 1, F = 4.1, p = 0.06). Changes of BG/FC ratios were significantly correlated with extrapyramidal side effects, but not with neurological soft signs (NSS). Our findings indicate that neuroleptic therapy induces D2-dopamine receptor upregulation in a subgroup of patients characterized by poor treatment response and pronounced extrapyramidal side effects.

Antipsychotic Agents↗
PubMed1999

Report of the Radionuclides in Nephrourology Committee for evaluation of transplanted kidney (review of techniques).

Comprehensive evaluation of renal transplants has been important in differential diagnosis of medical and surgical complications in the early post-transplantation period and in the long-term follow-up. If performed well, it yields excellent functional and good anatomic information about the graft that can be effectively used in the patient. That includes selection of patients for biopsy and for various drug regimens. This is true especially in patients with anuric acute tubular necrosis (ATN) and in patients with developing chronic rejection. Improving indices of renal function (effective renal plasma flow, uptake of tubular tracers) can indicate resolution of tubular injury (ATN) while there is still no improvement in plasma creatinine. In patients with chronic rejection, plasma creatinine increases only after approximately 30% of renal function is lost due to graft fibrosis. Early recognition of this condition could permit treatment and delay of retransplantation. The protocol recommended at the Copenhagen meeting includes a flow study, scintigram of the kidneys, prevoid and postvoid bladder image, injection site image (quality control), time/activity curves of the graft and bladder, and quantitative data of perfusion, function, and tracer transit. The flow study obtained during the initial transit of the bolus through the graft could be performed either with 99mTc mercaptoacetyltriglycine, or 99mTc diethylenetriaminepentaacetate (DTPA). Quantitative analysis of perfusion facilitates interpretation of the study during the early post-transplantation period. ATN, common in cadaver transplants, typically shows adequate perfusion. The function phase should include images and time/activity curves. Images alone are insufficient. Quantitative data such as clearance or other indices of function and indices of tracer transit are essential for correct interpretation of the results. Normal images and normal graft function reliably exclude clinically important complications. A single scintigram demonstrating prolonged tracer transit with decreased function cannot separate acute rejection and ATN. On serial studies, decline in function and poor perfusion are indicative of acute rejection. A normally appearing scintigram without cortical retention, but with low function, is consistent with chronic rejection. Pharmacological intervention to exclude obstruction (diuretic renogram) or hemodynamically significant renal artery stenosis (angiotensin converting enzyme challenge) should be used whenever indicated.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

D2 dopamine receptor up-regulation, treatment response, neurological soft signs, and extrapyramidal side effects in schizophrenia: a follow-up study with 123I-iodobenzamide single photon emission computed tomography in the drug-naive state and after neuroleptic treatment.

BACKGROUND: Animal and postmortem studies indicate that neuroleptic therapy may induce D2 dopamine receptor up-regulation in the basal ganglia. METHODS: To address this phenomenon in a clinical study, we investigated the D2 dopamine receptor binding in 15 DSM-III-R schizophrenics in the drug-naive state and 3 days after completion of a standardized neuroleptic therapy (benperidol 12-16 mg/day, for 25 days) using single photon emission computed tomography (SPECT). SPECT scans were obtained 2 hours after intravenous injection of 185 MBq 123I-iodobenzamide. For analysis, basal ganglia to frontal cortex (BG/FC) ratios were calculated and the patient sample was subgrouped into patients with a favorable versus a poor treatment response. RESULTS: Neuroleptic treatment led to decreased BG/FC ratios in patients with a favorable response, but increased ratios in the poor responders (df = 1, F = 4.1, p = .06). Changes of BG/FC ratios were significantly correlated with extrapyramidal side effects but not with neurological soft signs. CONCLUSIONS: Our findings suggest that neuroleptic therapy may induce D2 dopamine receptor up-regulation in a subgroup of patients characterized by poor treatment response and pronounced extrapyramidal side effects.

Adult↗
PubMed1997

Gender differences in D2 dopamine receptor binding in drug-naive patients with schizophrenia: an [123I]iodobenzamide single photon emission computed tomography study.

Recent studies have described a left lateralized striatal asymmetry of D2 dopamine receptors in male patients with schizophrenia. To replicate this finding and to explore its potential functional consequences, we investigated the D2 dopamine receptor system in 23 drug-naive patients with schizophrenia using single photon emission computed tomography (SPECT). Patients were examined in the drug-naive state and 72 h after completing a standardized neuroleptic treatment with benperidol (12-16 mg/day) for 25 days. Each SPECT examination comprised two scans: the first scan was taken 2 h after intravenous injection of 185 MBq [123I]iodobenzamide. After completion of the first scan, patients received benperidol (8 mg) intravenously. The second scan was started 20 min later. For analysis, basal ganglia to frontal cortex ratios were calculated. Fifteen of the 23 patients originally recruited completed the study on day 28. When compared to female patients, male patients showed a left lateralized asymmetry of striatal D2 dopamine receptor binding in the drug-naive state with an almost significant (P = 0.07) sex x hemisphere interaction. In the male patients, benperidol challenge led to a reversal of asymmetry patterns. These findings support previous reports of a left lateralized striatal D2 receptor binding in drug-naive male patients with schizophrenia and suggest that this asymmetry may affect the binding of conventional neuroleptics such as benperidol at the D2 dopamine receptor.

Adolescent↗
PubMed1997

Benzodiazepine receptor distribution and diazepam binding in schizophrenia: an exploratory study.

Clinical studies indicate that patients with acute schizophrenia may benefit from benzodiazepine treatment. Therefore we investigated the benzodiazepine receptor distribution and diazepam binding in 20 patients with DSM-III schizophrenia using single photon emission computed tomography (SPECT) with iomazenil as the ligand. In each patient, two SPECT images were obtained: SPECT 1 was obtained 2 h after intravenous injection of 200 MBq I-123-iomazenil. Following SPECT 1, patients received 10 mg diazepam intravenously. Twenty min later, SPECT 2 was started. The highest iomazenil uptake was found in the occipital cortex followed by the frontal and temporal cortices. Baseline iomazenil uptake in the medial frontal cortex was significantly (P < 0.05) correlated with the BPRS total score (r = 0.46). Diazepam injection led to a significant activity decrease in iomazenil binding which was greatest in the frontal regions of interest. With respect to the medial frontal cortex, this effect was significantly (P < 0.05) more pronounced in patients with a remitting than a chronic course of the disorder. These findings suggest that changes of the benzodiazepine receptor system in the frontal cortex may be associated with severity and chronicity of schizophrenia.

Adult↗
PubMed1997

Recurrent mediastinal mass in a child with Hodgkin's disease following successful therapy: a diagnostic challenge.

The case of an 11-year-old girl with mediastinal stage III B-E Hodgkin's disease is described. She achieved complete remission with combined chemoradiotherapy according to the Swiss Pediatric Oncology Group-HD Protocol 1985. Six months after all therapy was stopped, a slowly growing retrosternal mass was detected. Computed tomography (CT) and gallium-67 single-photon emission CT (SPECT) could not elucidate the true origin of the tumor, nor did ultrasound-guided transthoracic fine-needle puncture. Open biopsy with histologic examination of the lesion has successfully identified the mass as thymic hyperplasia, a rebound immunologic reaction after chemoradiotherapy that mimicked tumor regrowth.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Pharmacokinetics of iodine-123-IMBA for melanoma imaging.

UNLABELLED: The development of an effective radiopharmaceutical with affinity for malignant melanoma has been a research goal for some time. The early detection of melanoma metastases would greatly improve the therapy outcome for this disease. This article describes the synthesis of radioiodinated IMBA, N-(2-diethylaminoethyl)-3-[123I/131I]iodo-4-methoxybenzamide 8, its organ distribution, its comparison with BZA and other benzamides, and demonstrates the scintigraphic efficacy of the title compound with three melanoma patients. METHODS: The syntheses and radioiodination of eight benzamide derivatives are described. After intravenous injection into C57B16-mice subcutaneously transplanted with B16 melanoma, the organ distribution of the respective benzamides were investigated at 1 and 6 hr. n-octanol/phosphate buffer partition coefficients. The wholebody retention, erythrocyte and serum protein bound fractions of radioiodinated benzamides were measured. RESULTS: While structural changes in the amide substituents of N-(2-dialkylaminoalkyl)-4-iodobenzamides 2-7 resulted in no improvement in organ distribution compared with BZA, the 3-iodo-4-methoxyphenyl form of IMBA showed high melanoma uptake with significantly higher melanoma/nontarget tissue ratios. Compared with BZA the average ratio improved after 1 hr by a factor of eight and was still four times better after 6 hr. BZA and IMBA exhibit almost identical n-octanol/ phosphate buffer partition coefficients, however, IMBA has a faster urinary excretion facilitated by a lower affinity to erythrocytes and serum proteins; this could explain the improved tissue partinioning observed. Scintigraphy of patients with melanoma metastases confirmed the promising characteristics derived from the animal studies. CONCLUSION: Due to rapid background clearance and high melanoma affinity, IMBA showed high tumor contrast already at 4 hr after injection which makes it a promising new radiopharmaceutical for the scintigraphic detection of melanoma metastases.

Animals↗
PubMed1997

[Qualitative and quantitative kidney function testing in dogs using MAG3 clearance].

In the presented study 99mTc-MAG3 clearance measurements were undertaken in 14 dogs during renal scintigraphic examination. Of these dogs, 10 showed no renal impairment, the other 4 exhibited clinically manifested nephropathy. It was the aim of these examinations to determine if this type of clearance measurement that is routinely used in human medicine is suitable for diagnosis of canine nephropathy. An algorithm for the calculation of the MAG3-Clearance developed for humans was modified. The clearance measurement can be performed during the renal scintigraphic procedure without any difficulties. In the group of dogs with no renal impairment the clearance values ranged between 6.4 and 8.0 ml/min/kg, whereas in the group of patients exhibiting nephropathies the values ranged between 2.0 and 2.7 ml/min/kg. The suitability of the method for its use in dogs needs to be confirmed with higher patient numbers. In addition, further studies are necessary to precisely assess the correlation between measured clearance values and effective renal plasma flow in dogs.

Animals↗
PubMed1996

Hydroxylation of quinaldic acid: quinaldic acid 4-monooxygenase from Alcaligenes sp. F-2 versus quinaldic acid 4-oxidoreductases.

The N-heterocycles quinaldic acid (quinoline 2-carboxylic acid), kynurenic acid (4-hydroxyquinoline 2-carboxylic acid), 2-oxo-1,2-dihydroquinoline, and xanthine are utilized by Alcaligenes sp. F-2 as sole source of carbon and energy. Although quinoline did not serve as growth substrate, 8-hydroxy-2-oxo-1,2-dihydroquinoline and 8-hydroxycoumarin, metabolites of the 'coumarin pathway' of quinoline catabolism, were isolated from the culture fluid during growth on 2-oxo-1,2-dihydroquinoline. Contrary to Serratia marcescens 2CC-1 and Pseudomonas sp. AK-2 (Sauter et al. (1993) Biol. Chem. Hoppe-Seyler 374, 1037-1046), which possess different molybdenum-containing hydroxylases catalysing the 4-hydroxylation of quinaldic acid to kynurenic acid with incorporation of oxygen derived from water and concomitant reduction of an electron acceptor, Alcaligenes sp. F-2 contains an inducible quinaldic acid 4-monooxygenase that catalyses the very same conversion in the presence of O2 and NADH. The activity of the monooxygenase was enhanced 1.5-fold by Fe2+ ions. The extremely thermolabile enzyme (apparent molecular mass: 155 kDa) exclusively accepted quinaldic acid as substrate. The 'pseudosubstrates' menadione, 8-hydroxyquinoline, and 8-hydroxy-2-oxo-1,2-dihydroquinoline effected consumption of NADH and oxygen without being hydroxylated. Quinaldic acid 4-monooxygenase was inhibited by sulfhydryl modifying and chelating agents, and by various divalent metal ions, whereas reducing agents did not affect enzymatic activity.

Alcaligenes↗
PubMed1996

Absorption of vitamin B12 administered to continent ileal reservoirs for urinary diversion.

Urinary diversion through intestinal segments is a widely used method after radical cystectomy. During the last few years, new methods of bladder substitution, continent ileal neobladders, were developed. We used the method described by Hautmann et al. in 1986. 70 cm of ileum is used to form a reservoir. The ureters are implanted into the reservoir, which is then anastomosed to the urethral stump. A known problem when intestine is used for urinary diversion is the absorption of urinary solutes leading to metabolic disturbances. Therefore, the absorption of vitamin B12, instilled into the neobladders of 20 patients, was measured and related to the postoperative interval. The results show a high absorption rate 2 weeks postoperatively that is reduced quickly and significantly (p < 0.001) within the first 10 months (from more than 30 to below 5%). One year to 23 months after the operation, some neobladders absorbed no vitamin B12 at all, whereas others still absorbed significantly but only small quantities. These results may probably be attributed to the loss of villous structure as well as atrophy of the epithelial surface.

Absorption↗
PubMed1996

Report of the Radionuclides in Nephrourology Committee on renal clearance.

The need for simple and accurate methods to measure renal function is self-evident. This need increases as techniques for intervention become available. The demand for evaluation of individual kidney function has increased with its role in the diagnosis and follow-up of unilateral renal disease and in decision making for conservative or surgical treatment based on residual renal function. The role of nuclear medicine in this area has been inhibited by confusion about conflicting methodologies. This report is meant to provide guidance to those centers that would like to initiate clearance procedures but have difficulty in choosing appropriate methodology.

Glomerular Filtration Rate↗
PubMed1995

Residual 201Tl activity in irreversible defects as a marker of myocardial viability. Clinicopathological study.

BACKGROUND: The objective of the present study was to characterize the relation between the residual 201Tl activity in irreversible perfusion defects and the extent of irreversible myocardial damage indicated by the volume fraction of myocardial interstitial fibrosis in patients with chronic coronary artery disease. METHODS AND RESULTS: Stress planar 201Tl scintigraphy with tracer reinjection at rest was performed in 37 patients with > or = 75% stenosis of the left anterior descending coronary artery, and anteroseptal 201Tl activity was quantified by computer-assisted placement of regions of interest from the serial myocardial images. During coronary artery bypass grafting (performed within 6 +/- 3 weeks after scintigraphy), two transmural biopsy specimens were taken from the anterior wall of the left ventricle and the amount of interstitial fibrosis was assessed by use of light microscopic morphometry. A wide spectrum of interstitial fibrosis was obtained, ranging from 15 vol% to 60 vol%. Interstitial fibrosis was similar in patients with reversible (n = 11) or irreversible (n = 15) tracer defects in conventional stress-redistribution images. However, interstitial fibrosis was significantly lower in patients who had enhanced regional 201Tl activity after tracer reinjection compared with those who did not have enhancement of tracer activity after reinjection (28 +/- 8 vol%, n = 7, versus 41 +/- 12 vol%, n = 8; P = .031). The correlation between relative poststenotic 201Tl activity and interstitial fibrosis after tracer reinjection was significantly improved compared with conventional redistribution images (r = -.622 versus r = -.851, n = 15; P < .01). CONCLUSIONS: The present data demonstrate that the level of regional 201Tl activity in redistribution and, in particular, reinjection images is significantly related to the mass of preserved viable myocytes in poststenotic left ventricular myocardium. Therefore, the residual 201Tl activity provides information about viability within irreversible perfusion defects and may itself serve as marker of myocardial viability.

Biopsy↗
PubMed1995

Radionuclide techniques for the evaluation of renal function: advantages over conventional methodology.

Aspirin renography, a new approach for the detection of renovascular hypertension, is described and compared with captopril scintigraphy. The behaviour of the new radiopharmaceutical 99mTc-ethylenedicysteine is examined for the first time in patients with impaired renal function and compared with 99mTc-mercaptoacetyltriglycine and with orthoiodohippurate. It is not yet possible to draw final conclusions about the advantages of aspirin renography and 99mTc-ethylenedicisteine over established methods and radiopharmaceuticals, respectively. In the diagnostic evaluation of renal transplants the degree of parenchymal retention is crucial. A newly described method for its quantitation is simpler and apparently more accurate than the excretion index frequently used.

Humans↗
PubMed1993

Renal clearance determination with one blood sample: improved accuracy and universal applicability by a new calculation principle.

A sufficiently accurate quantification of renal function requiring only one plasma sample without an additional gamma camera study has until now only been possible in adults. A new principle has been developed that allows the universal application of known algorithms, irrespective of the clearance substance used, by normalizing the plasma concentrations with respect to individual body dimensions of adult as well as infant patients. In this respect, algorithms are established for clearance determinations using technetium-99m mercaptoacetyltriglycine which are based on steady-state studies as the reference. They allow the calculation of quantitative clearance values in infants and require the drawing of only one blood sample at any time between 25 and 40 minutes postinjection. The comparison with a combined-camera/two-plasma-sample technique performed in 46 children ranging in age from 9 days to 14 years (mean, 6.05 years) resulted in a standard deviation of 8.5% from the line of identity (r = 0.94). Moreover, this procedure also increases accuracy in adult patients, especially those with impaired renal function.

Adolescent↗
PubMed1992

Myocardial scintigraphy with iodine-123 phenylpentadecanoic acid and thallium-201 in patients with coronary artery disease: a comparative dual-isotope study.

To characterise the clinical usefulness of serial myocardial scintigraphy with iodine-123 phenylpentadecanoic acid (IPPA) in comparison with thallium-201, dual-isotope investigations were performed in 41 patients with angiographically documented coronary artery disease. Both tracers were administered simultaneously during symptom-limited ergometry. Planar scintigrams were acquired immediately after stress, and delayed imaging was performed after 1 h for IPPA and 4 h for 201Tl. Scintigrams were evaluated both qualitatively and quantitatively using a newly developed algorithm for automated image superposition. Initial myocardial uptake of both tracers was closely correlated (r = 0.75, p < 0.001). Both tracers also revealed a similar sensitivity for the identification of individual coronary artery stenoses > or = 75% (IP-PA: 70.0%, 201Tl: 66.3%, P = NS) with identical specificity (69.8%). The number of persistent defects, however, was significantly higher with IPPA (P = 0.021), suggesting that visual analysis of serial IPPA scintigrams may overestimate the presence of myocardial scar tissue. On the other hand, previous Q wave myocardial infarction was associated with a decreased regional IPPA clearance (29% +/- 11% vs 44% +/- 11% in normal myocardium, P < 0.05). The data indicate that serial myocardial scintigraphy with IPPA is essentially as sensitive as scintigraphy with 201Tl for the detection of stress-induced perfusion abnormalities. Quantitative analysis of myocardial IPPA kinetics, however, is required for the evaluation of tissue viability.

Algorithms↗
PubMed1992

A new principle to normalize plasma concentrations allowing single-sample clearance determinations in both children and adults.

A sufficiently accurate quantification of renal function requiring only one plasma sample without an additional gamma-camera study has, until now, only been possible in adults. A new principle will be presented here allowing the universal application of known algorithms, regardless of the clearance substance used, by normalizing the plasma concentrations with respect to the individual body dimensions of the patients--for infants as well as for adults. In this respect, algorithms are developed for clearance determinations using technetium-99m mercaptoacetyltriglycine (99mTc-MAG3), which are based on steady-state studies as the reference. They allow the calculation of quantitative clearance values in infants, requiring only one blood sampling at any time between the 25th and the 40th min postinjection. The comparison with a combined camera/two-plasma-sample technique performed in 46 children aged between 9 days and 14 years (mean 6.05 years) resulted in a standard error of 8.5% from the line of identity (r = 0.94). Moreover, this procedure also increases the accuracy of results in adults.

Adolescent↗