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Biomedical subjects

P Geyer

Publications and source records attributed to P Geyer.

18 recordsLinked to original sources
PubMed2003

Sustained elevation of NF-kappaB DNA binding activity in radiation-induced lung damage in rats.

PURPOSE: To characterize the cellular distribution and DNA binding activity of the nuclear factor kappaB (NF-KappaB) in a model of radiation-induced lung damage in the rat. MATERIAL AND METHODS: The right lung of Fischer rats was irradiated with a single dose of 20 Gy. The cellular distributions of NF-KappaB proteins and mRNA were detected with immunohistochemistry and in-situ hybridization respectively. The DNA binding activity of NF-KappaB, nuclear and cytoplasmic levels of NF-KappaB proteins, and kinase activity towards IkappaBalpha (IKappaBAlpha) were determined using electrophoretic mobility shift assays (EMSA), Western blots and kinase assays, respectively. The mRNA level of interleukin 6 (IL-6) was determined using quantitative room temperature polymerase chain reaction. RESULTS: There was a continuous elevation of NF-KappaB DNA binding activity in the rat lung after ionizing irradiation over 6 months. The irradiated lung tissue exhibited an increased kinase activity towards IKappaBAlpha and a selective loss of nuclear IKappaBAlpha. The NF-KappaB-DNA binding complex switched from p50-p65 heterodimers in normal lung tissue to p50 homodimers in irradiated lung tissue. The increased level of IL-6 mRNA suggests transcriptional activation of NF-KappaB-dependent genes in the irradiated rat lung. CONCLUSIONS: The DNA binding activity of NF-KappaB is continuously activated after irradiation of the rat lung by loss of nuclear IKappaBAlpha. This might play a role in sustaining chronic inflammation and hyperproliferation of mesenchymal cells after irradiation.

Animals↗
PubMed2001

Patient position reproducibility in fractionated stereotactically guided conformal radiotherapy using the BrainLab mask system.

PURPOSE: Dedicated mask systems nowadays allow the use of stereotactic radiotherapy in fractionated regimes, therefore combining the advantages of high precision radiotherapy with the biological benefit of fractionation. Therefore the knowledge of institution specific isocenter accuracy is essential for decision-making about margins to be allowed to form the planning target volume. PATIENTS AND METHOD: Measurements of isocenter deviations during fractionated treatments were performed in 33 patients using the simulator Simulix-xy (Oldelft) in connection with the BrainLab angiographic localizer-box as well as port-films. In both cases repeated images were overlaid by use of anatomical landmarks with a methodical accuracy in the order of 0.5 mm. RESULTS: Both methods yield random isocenter deviations of less then 2 mm (standard deviation) in all three directions and no significant systematic deviations. These values are in the order of the accuracy of the method, obtained by comparison of two independent investigators, as well as they are comparable with the literature. CONCLUSIONS: The accuracy of less than 2 mm indicates safety margins of 3-4 mm as sufficient for clinical routine to cover the target in 95.5% of all set-ups (2 SD).

Brain Neoplasms↗
PubMed2001

Impact of the tumour bed effect on microenvironment, radiobiological hypoxia and the outcome of fractionated radiotherapy of human FaDu squamous-cell carcinoma growing in the nude mouse.

PURPOSE: To investigate the impact of the tumour bed effect (TBE) on histological parameters of the micromilieu, radiobiological hypoxic fraction and local control after fractionated irradiation in FaDu squamous-cell carcinoma in the nude mouse. This tumour has previously shown a clear-cut TBE caused by increased necrotic cell loss at a constant cell production rate in the viable tumour compartment. MATERIALS AND METHODS: Human FaDu tumours were studied in the NMRI nude mouse. Tumours were transplanted either into unirradiated subcutaneous (s.c.) tissues (controls) or s.c. tissues pre-irradiated with 12.5 Gy (TBE group). In both groups we measured the volume doubling time (VDT), potential doubling time (T(pot)), relative necrotic area, and in the viable tumour compartment the relative vascular area (9F1 mAb), relative hypoxic area (NITP or pimonidazole), relative perfused area (Hoechst 33342), and the perfused fraction of vasculature. The tumour control dose 50% (TCD 50), radiobiological hypoxic fraction (rHF) and dose-modifying factors (DMF) for the comparison of tumours in the TBE and control groups were determined from local tumour control data after treatment with single doses under ambient conditions or under clamp hypoxia, and after irradiation with 30 fractions under ambient conditions within 6 weeks using maximum-likelihood analysis. RESULTS: A clear-cut TBE (VDT = 4.0 days (95%CI 2.9;4.4) for the control group versus 7.2 days (6.4;8.9) for the TBE group; p <0.0001) caused by increased necrosis (mean relative necrotic area of 12% (5;20)) versus 33% (10;41); p = 0.07) at a constant cell production rate (T(pot) = 2.2 days (1.4;2.3) versus 2.2 days (1.7;2.6); p = 0.30) was confirmed. Histological analysis of the micromilieu within the vital subarea revealed no systematic differences between the TBE and control groups. The rHF of 2% (0.1;27) for control tumours was lower than the 15% (95% CI 2;91) for the TBE group, but this difference was nonsignificant (p = 0.12). Compared with control tumours, the TCD50 for irradiation under clamped hypoxia was in a statistical trend lower for tumours in the TBE group (DMF 1.11 (0.98;1.28), p = 0.09). After fractionated irradiation, tumours of the TBE group were significantly more radiosensitive (TCD50 56.6 Gy (46;70) versus 78.7 Gy (63;100); p = 0.003). CONCLUSIONS: The results on FaDu tumours growing in pre-irradiated tissues indicate that increased necrosis caused by impairment of the vascular supply may increase the radiosensitivity of tumours treated by fractioned irradiation.

Animals↗
PubMed2000

Lack of effect of small high-dose volumes on the dose-response relationship for the development of fibrosis in distant parts of the ipsilateral lung in mini-pigs.

PURPOSE: Multi-field radiation therapy for intrathoracic tumours results in a heterogeneous dose distribution in lung tissue. This study investigated whether irradiation of small lung volumes with high fibrogenic doses affects the dose-response relationship for development of fibrosis in distant parts of the ipsilateral lung of mini-pigs. MATERIALS AND METHODS: The whole right lung of 26 'Mini-Lewe' pigs was irradiated with homogeneous doses of between 25 Gy and 40 Gy given in five equal fractions using opposing anterior-posterior portals and a linear accelerator. Another 32 animals were irradiated with a constant dose of 35 Gy to a small house-shaped high-dose field (base 3.0 cm, height 4 cm) located 3 cm caudolateral to the right hilus, while the surrounding right lung received either no irradiation or homogeneous doses of between 20 Gy and 30 Gy. The radiation fields were simulated and port films were obtained for each of the 10 fields in all pigs. Fibrosis was quantified 9 months after irradiation by determination of the hydroxyproline (HP) content of the 32 high-dose volumes and in the lung apex and the basolateral lung of all 58 pigs. Based on the reference value for the HP-ratio, i.e. the HP-concentration of the right lung over the left lung, obtained in 12 unirradiated control animals, the experimental results were converted into quantal data for probit analysis, a responder being an animal with an HP-ratio > 1.33. RESULTS: A dose-response relationship for the HP-ratio was obtained in the different lung sites and irradiation groups. For a given dose level the mean HP-ratios and response rates did not differ systematically between the lung apex and the basolateral lung. Probit analysis of the pooled data produced ED50 values of 21.8 Gy (95% CI 12-37) for irradiation without a high-dose volume and 25.9 Gy (24-28) for irradiation with a high-dose volume. These values are not significantly different. The results from both irradiation groups could be well fitted by a common dose-response curve with an ED50 value of 26.1 Gy. Unexpectedly, the response rates in the high-dose volume increased with increasing dose to the surrounding right lung. Analysis of the port films provided an explanation for this finding: inaccuracies in daily field positioning. When this error was corrected for by use of the mean dose to the high-dose volume, a dose-response curve with an ED50 of 25.2 Gy (22-29) was determined for the high-dose volume. CONCLUSIONS: The results of the study indicate that the irradiation of a small lung volume with high fibrogenic doses does not affect the dose-response relationship for development of fibrosis in distant parts of the ipsilateral lung.

Animals↗
PubMed2000

Down-regulation of SP1 DNA binding activity in the process of radiation-induced pulmonary fibrosis.

PURPOSE: To determine changes in the expression and function of the transcription factor SP1 in radiation-induced pulmonary fibrosis. MATERIALS AND METHODS: The right lungs of female Fischer rats were irradiated with a fibrogenic single dose of 20 Gy gamma-irradiation. SP1 mRNA and protein expression was determined by Northern and Western blotting, respectively, between 30 min and 12 weeks after irradiation. Cellular localization of SP1 protein was characterized by immunohistochemistry (peroxidase labelling). SP1 DNA binding activity was studied with electrophoretic mobility shift assays (EMSA). RESULTS: Eight weeks after irradiation, pulmonary fibrosis was first observed. SP1 DNA binding activity showed a short-term increase from 30 min to 12 h after irradiation. Thereafter it remained quite stable until 1 month after irradiation. However, 2 months after irradiation, SP1 DNA binding activity was no longer detectable. The SP1 mRNA level was not reduced at this time, nor was there a reduction in its size. However, Western blotting revealed the occurrence of at least two slightly smaller additional bands 2 months after irradiation whereas the original SP1 band vanished. This suggests a degradation event of SP1 taking place near one or both ends of the protein. Most of the SP1 protein was found in type II pneumocytes and alveolar macrophages of the normal and fibrotic lung. Bronchial epithelial cells were also positive. In the fibrotic lung, proliferating fibroblasts also become positive. CONCLUSIONS: The functional knockout of the transcription factor SP1, in the process of irradiation-induced pulmonary fibrosis, is demonstrated. This should help elucidate the severe disturbances in transcriptional regulation, cellular proliferation and differentiation occurring in the lung at long intervals after irradiation.

Animals↗
PubMed1999

[Benign proximal esophageal stenosis--mostly a complication of gastroesophageal reflux disease].

BACKGROUND AND OBJECTIVE: Benign stenoses can occur anywhere in the oesophagus, but are most common in its distal part as a result of gastro-oesophageal reflux (GOR). It was the aim of this study to evaluate retrospectively the causes and incidence of benign stenosis of the proximal oesophagus (SPR) as well as its endoscopic and drug treatment. PATIENTS AND METHODS: Between December 1989 and December 1997 a total of 17,413 patients were referred to the authors' hospital for oesophago-gastroduodenoscopy, 1024 of them (6%) for clarification of heartburn, regurgitation and/or dysphagia. 53 of these patients (5%) were found to have benign stenosis of the oesophagus requiring bougie dilatation, located in the lower third in 29 (55%), in the middle third in six (11%) and in the upper third in 18 (34%) patients. Causes of stenosis in the upper third were peptic stricture in nine (50%), heterotopic gastric mucosa in three (17%), caustic corrosion in three (17%), post-radiation in two (11%), and the result of web formation in one (6%). Endoscopic bougie dilatation was performed in all these patients, those with GOR additionally receiving 40 mg omeprazole daily. RESULTS: In those patients with nonpeptic benign stenosis/stricture lasting improvement of symptoms was achieved with one to three dilatation. But those with GOR needed a mean of 13 dilatations during a follow-up period averaging 61 months. Barrett's oesophagus (replacement of squamous by columnar epithelium) was found in five patients. No case of dysplasia was discovered. Laparoscopic fundoplication was performed in one woman in whom bougie dilatation had failed. Remission was maintained, as needed, by bougie and omeprazole in eight patients. CONCLUSION: In benign stenosis of the upper oesophagus endoscopic dilatation is the treatment of choice. In cases of peptic aetiology the administration of proton pump inhibitors is the optimal adjuvant method.

Anti-Ulcer Agents↗
PubMed1998

A comparison of omeprazole, lansoprazole and pantoprazole in the maintenance treatment of severe reflux oesophagitis.

BACKGROUND: Proton pump inhibitors are effective for the healing of oesophagitis. Standard doses of omeprazole, lansoprazole or pantoprazole are sufficient for healing in mild to moderate cases of oesophagitis. AIM: To compare the efficacy of double the standard doses of omeprazole, lansoprazole or pantoprazole for maintenance treatment of severe oesophagitis complicated by a stricture. METHODS: Thirty-six patients with reflux oesophagitis and stricture confirmed by endoscopy were included in a prospective study comparing three maintenance therapies. In all cases weekly dilatation of the stenosis was performed and patients were treated with omeprazole 20 mg b.d. until healing of oesophagitis and dysphagia relief were achieved. Thirty participants responded to therapy and were then randomly assigned to 4 weeks of maintenance treatment with omeprazole (20 mg b.d.; n = 10), lansoprazole (30 mg b.d.; n = 10) or pantoprazole (40 mg b.d.; n = 10). Subsequently, endoscopies were performed-the endoscopists were blinded to the therapy assignment. The endpoints were defined as the absence of oesophagitis, oesophageal stricture and complaints. RESULTS: After 4 weeks of treatment, the number of patients remaining in remission (no oesophagitis or stricture and no symptoms) was nine out of 10 (90%) in the omeprazole group, two out of 10 (20%) in the lansoprazole group (P < 0.01) and three out of 10 (30%) in the pantoprazole group (P < 0.01). CONCLUSIONS: In our study omeprazole was superior to either lansoprazole or pantoprazole in the maintenance treatment of complicated gastro-oesophageal reflux disease.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1998

Fractionation effect on radiation-induced growth retardation of tibia in rabbits and rats.

A study of the sensitivity to fractionation of the growing tibia of rabbits and rats was conducted by comparing the growth of the treated right bone to that of the untreated left side in each individual animal using radiographic measurements. The experimental endpoint was the percentage of normal growth 24 weeks after irradiation in rabbits and 14 weeks after treatment in rats. The results show clear dose-response relationships in all experimental arms. A clear-cut fractionation effect was demonstrated in both species. The alpha/beta-ratios determined by maximum likelihood analysis according to the LQ-model with graded responses were 3.2 Gy (95% C.I. 1.1; 5.6) in rabbits and 6.9 Gy (5.3; 8.7) in rats, when all data were included in the calculations. When single-dose data were excluded the alpha/beta-values were -0.6 Gy (-3.1; 2.3) in rabbits and 5.0 Gy (3.5; 7.0) in rats. Our data provide further evidence that low doses per fraction should be used when irradiation of the epiphysis cannot be avoided in pediatric patients.

Animals↗
PubMed1997

[A simple device for improving the reproducibility of patient positioning in craniospinal irradiation].

PURPOSE: For craniospinal irradiation generally 2 lateral cranial fields and 1 or more posterior spinal fields are used. The cranial and spinal fields are matched in the mobile portion of the neck. Therefore, the relative position between head and upper part of the body needs to be exactly defined. MATERIAL AND METHOD: A wooden "H"-shaped frame is attached to the base plate of the head fixation device (Figure 1). A vacuum cushion filled with polystyrene beads is used to fix the thorax. This cushion is held in place by the wooden frame (Figure 1). This assures a fixed relation between the body-cushion and the head fixation device (Figures 2 and 3). DISCUSSION: The connection between the body-cushion and the head fixation device by means of the "H"-shaped frame is easy to handle in clinical practice. The method does not interfere with any the planning or irradiation procedures. CONCLUSIONS: The "H"-frame can be used to connect a wide range of self-made or custom-made head fixation devices to body-fixation-cushions, thereby avoiding the need for individual foam shells.

Cranial Irradiation↗
PubMed1997

Local production of interleukin-4 during radiation-induced pneumonitis and pulmonary fibrosis in rats: macrophages as a prominent source of interleukin-4.

Fibrosis of lung tissue is a frequent and serious consequence of radiotherapy of mammary carcinoma. The pathogenesis of radiation-induced pulmonary fibrosis remains unclear. Cytokines such as transforming growth factor beta (TGFbeta) and interleukin-4 (IL-4) have been reported to stimulate collagen synthesis in fibroblasts in vitro. The aim of this study was to document the presence of IL-4 during the development of post-irradiation lung fibrosis. Right lungs of male Fischer rats were irradiated with a single dose of 20 Gy and IL-4 expression in the irradiated lungs was monitored for a period of three months. IL-4 gene transcription as determined by ribonuclease protection assay (RPA) as well as IL-4 synthesis as shown by Western blotting increased in the irradiated lungs reaching a plateau concentration within 3 weeks after irradiation. Enhanced IL-4 production was still detected at day 84 after irradiation. The cellular origin of IL-4 was analyzed by in situ hybridization and two-color immunofluorescence on lung tissue sections and on cytospin preparations of leukocytes obtained from bronchoalveolar lavages. These experiments revealed a substantial IL-4 production by macrophages during development of post-irradiation lung fibrosis.

Animals↗
PubMed1990

[A universal verification and protocol system for teletherapy].

To increase the quality of radiotherapy a verify and record system (VPS) was developed for teletherapy equipments, that takes control of manually adjusted irradiation parameters and of recording all relevant data of radiotherapy. The VPS can be adapted to special wishes of the user and it lends itself to application on different irradiation equipments. In the represented paper especially the extent of efficiency of the system is shown which is characterized by high operating comfort, flexible reacting to exceptional cases and by high date and operating security. The testing phase on an accelerator model has been brought to a close, actually the system is installed to an electron linear accelerator "Neptun 10p" and led to clinical trial.

Humans↗
PubMedDate not supplied

[Age-related and pathophysiologic significance of capillary bed rarefaction of the hypertensive vascular system].

In spontaneously hypertensive rats (SHR), in normotensive related controls (WKY), as well as in non-related controls (NR), the rarefaction of the capillary bed in the gracilis muscle has been studied. By comparing four different in vivo and in vitro techniques for estimation of the number of capillaries, a rarefaction of about 30% in SHR, was found. The precapillary arterioles revealed a reduced rarefaction by about 25.5% or 40.2% in hypertensive, as compared with normotensive control animals. Age dependency was studied in animals of 6, 12, 24 and 48 weeks with respect to the rarefaction of the capillary bed. An age-dependent reduction of capillaries was seen from 385 to 272 cap/mm2 in NR, from 346 to 276 cap/mm2 in WKY, and an age- as well as hypertension-related rarefaction was found from 285 to 213 cap/mm2 in SHR. Under antihypertensive therapy (nifedipin, 300 mg/kg b.w.) systemic pressure was reduced significantly in all three strains studied and the capillary number changed from 674 to 1051 cap/mm2 in SHR, from 806 to 864 in WKY, and from 779 to 1019 in NR. The results indicate an age-dependency of the capillary rarefaction, which may be protracted and amplified by the hypertension disease. The pathophysiological meaning may be seen in reduction of the capillary surface area during a constantly elevated effective filtration pressure. By that, the increased transvascular fluid permeability of the capillary bed is prevented, which otherwise would cause edema formation in the hypertensive system.

Age Factors↗