PubMed Health⌕ Search

Biomedical subjects

O Peters

Publications and source records attributed to O Peters.

At least 19 recordsLinked to original sources
PubMed2004

Intratumoral methotrexate kinetics in a patient with intracranial anaplastic ependymoma.

Little is known about intratumoral anticancer drug concentration in childhood brain tumors. We were able to measure methotrexate (MTX) tumor concentrations directly in a cystic anaplastic ependymoma. Cyst fluid was obtained by puncture of a subgaleal Rickham reservoir connected to a catheter in the tumor cyst. MTX concentrations were determined by fluorescence polarization immunoassay and compared to serum concentrations. Maximum MTX concentrations in tumor and CSF were found at the end of MTX infusion. Twenty-four hour after MTX infusion the mean tumor concentration was significantly higher than in the serum indicating MTX retention and accumulation in the tumor cyst. An AUC(tumor)/AUC(serum) ratio of 1.95 was obtained. In response to the applied multiagent chemotherapy the clinical condition of our patient improved and the tumor showed partial response on MRI. Cystic ependymomas might benefit from high dose MTX especially because of drug retention in the tumor cyst.

Antimetabolites, Antineoplastic↗
PubMed2004

[Anaesthesia for radiation therapy of brain tumours in children. A multidisciplinary challenge].

Radiation therapy of childhood intracranial malignancies is always a challenge for radiation oncologists, anaesthetists and paediatric oncologists. Detailed knowledge of the course of the disease prior to radiation therapy and a critical evaluation of the child's actual physical status are mandatory in each case. Furthermore the anaesthetist should be informed about the child's individual preferences and aversions. The optimum prearrangement of the radiation therapy is of paramount importance. Interdisciplinary communication structures which must always involve the child's parents have to be established. Perfect adjustment of the mask that fixes the head during each radiation procedure is necessary to give the child the possibility to breathe spontaneously without an endotracheal tube or a laryngeal mask. Two case reports highlight these aspects of the complex procedure of paediatric radiation therapy which are relevant for the anaesthetist.

Anesthesia↗
PubMed2001

Hepatitis C virus transmission in a pediatric oncology ward: analysis of an outbreak and review of the literature.

Hospital-related hepatitis C virus (HCV) infections continue to occur even after the introduction of blood donor screening. We report an outbreak of HCV in nine patients of a pediatric oncology ward in 1996/1997. Sequencing of the hypervariable genomic region 1 (HVR1) of the E2/NS1 region showed near identity between HCV isolates from these patients as evidence for infection with the same virus. Despite a detailed and careful investigation, the source of infection and the mode of virus transmission could not be established. Based on a review of the current literature about nosocomial HCV infection and HCV infection in children, hypotheses for possible means of transmission in this outbreak are discussed.

Autoimmune Diseases↗
PubMed2001

Cortical spreading depression induces proinflammatory cytokine gene expression in the rat brain.

Cortical spreading depression (CSD) is characterized by reversible neuronal dysfunction in the absence of cell death. Preconditioning by CSD induces tolerance against subsequent lethal ischemia. In this study, we used quantitative reverse transcriptase-polymerase chain reaction and immunocytochemistry to analyze proinflammatory cytokine expression after CSD induced by topical application of potassium chloride (KCl) to the cortical surface of rat brains. Relative to control cortex, we found an increase of tumor necrosis factor-alpha (mean 62-fold, P < 0.001) and interleukin (IL)-1beta (mean 24-fold, P < 0.001) mRNA levels within 4 hours ipsilateral to the site of KCl application. At 16 hours cytokine expression was decreasing toward baseline levels. Ipsilateral cytokine induction was abolished by pretreatment with the noncompetitive N-methyl-d-aspartate antagonist, MK-801. In contrast to focal cortical infarction, cytokine induction in CSD was not accompanied by the expression of inducible nitric oxide synthase mRNA. In immunocytochemical studies, expression of IL-1beta protein was localized to ramified microglia in cortical layers I to III of the ipsilateral hemisphere. Our finding that NMDA receptor signaling without subsequent neuronal cell death is sufficient to induce inflammatory cytokine expression in the brain has basic implications for central nervous system immunoregulation. We postulate that cytokine expression in CSD forms part of a physiologic stress response that contributes to the development of ischemic tolerance in this and other preconditioning paradigms.

Animals↗
PubMed2001

Comparing apical preparations of root canals shaped by nickel-titanium rotary instruments and nickel-titanium hand instruments.

This study measured displacement of canal centers in extracted human teeth after preparation by Lightspeed and nickel-titanium K-files. The specimens were divided into two groups (n = 11), after radiographing the roots from the buccolingual and mesiodistal planes with pathfinding files in situ. More strongly and less strongly curved canals were, respectively, assigned to the Lightspeed and nickel-titanium K-file groups. Using a reassembly technique, cross-sections at 1.25 mm, 3.25 mm, and 5.25 mm from the apices were made of the experimental roots embedded in clear plastic. Stereomicroscopic 35-mm slides were taken of the uninstrumented sectioned canals. The sections were reassembled and then prepared to size 50 Master Apical Rotary and size 40 Master Apical Files, for the Lightspeed and K-file groups, respectively. Similar 35-mm slides of the instrumented canals were taken and electronically superimposed over their uninstrumented counterparts. Displacements of root canal centers after preparation and increases in cross-sectional areas of the prepared root canals were evaluated at specific levels. No significant differences in displacement of canal centers or between the mean cross-sectional areas of the instrumented root canals were recorded between the Lightspeed and K-file groups. Both types of instruments produced similar displacement of canal centers after preparation.

Anatomy, Cross-Sectional↗
PubMed2001

Jaundice caused by a pancreatic mass: an exceptional presentation of Crohn's disease.

It is well known that Crohn's disease can involve the pancreas. However, granulomatous inflammation of the pancreas causing jaundice is extremely rare. In this report, we describe a patient presenting with jaundice in whom a Whipple procedure was performed because of the suspicion of a malignant pancreatic tumor. However, on histologic examination a benign granulomatous pancreatic mass was found. Further investigations revealed no other organ involvement and no underlying disease could be identified. Therefore, the tentative diagnosis of an idiopathic inflammatory pseudotumor was made. Only 6 months later, when the patient developed bloody diarrhea, Crohn's disease was diagnosed. This case stresses that, especially in young patients, Crohn's disease should be included in the differential diagnosis of benign common bile duct strictures even if no other symptoms of Crohn's disease are present.

Adult↗
PubMed2000

Effect of eugenol-containing sealer on marginal adaptation of dentine-bonded resin fillings.

AIM: Eugenol is claimed to interfere with the polymerization of composite resins and to affect shear bond strengths of dentine-bonded composite restorations. Eugenol-based sealers are used during root canal treatment in teeth that may require build-ups or extensive restorations. Unfortunately, the adverse effect of eugenol has mostly been assessed in shear bond tests and this variable may be clinically inappropriate. The current study evaluate the effect of eugenol in a eugenol-based endodontic sealer on marginal adaptation of composite resin restorations with and without thermo-mechanical stress. METHODOLOGY: Thirty Class V cavities with half of the cavity margins in dentine and half of the cavity margins in enamel were prepared in extracted human premolars and then divided into 5 groups. Teeth in group 1 were not contaminated with eugenol. Cavities in groups 2-4 were contaminated with a eugenol-based sealer (Tubli-Seal, Kerr) and cleaned with: (i) sandblasting, (ii) bur finishing alone or (iii) bur finishing combined with swabbing with alcohol. These 4 groups were temporized for 6 weeks (Ketac, ESPE), whilst group 5 received no eugenol, was not temporized and acted as the control. Cavities were restored with Tetric Ceram using Syntac Classic (Vivadent) as a dentine-bonding agent. The specimens were then thermo-mechanically stressed. The percentages of marginal adaptation in dentinal and enamel margins were assessed in a SEM at x200 magnification before and after stress using a replica method. Mean percentages of marginal adaptation were calculated and compared using a two way-ANOVA (influence of eugenol and cleaning procedure) and non-parametric tests. RESULTS: Marginal adaptation in enamel exceeded 95% and 92% in all specimens before and after thermo-mechanical stress, respectively. Before stress, marginal adaptation in dentine ranged from 92.3 +/- 7.9% to 95.7 +/- 6.2% in groups 1-5. After stress, the percentage of marginal adaptation in dentine decreased significantly overall (P < 0.05, range 39.8 +/- 21.1% to 82.9 +/- 13.7%). The effect of contamination with eugenol was not significant (P > 0.05): in contrast, there was a significantly beneficial effect when the entire cavity was finished with burs (P < 0.01). CONCLUSIONS: Under the conditions of this study, the eugenol containing sealer did not significantly impair marginal adaptation in dentinal margins of mixed Class V restorations when bur finishing was employed before placement. However, no other cleaning method was sufficient to produce acceptable figures of marginal adaptation.

Analysis of Variance↗
PubMed1999

Wear of nickel-titanium lightspeed instruments evaluated by scanning electron microscopy.

Used rotary nickel-titanium instruments require frequent replacing. This laboratory study evaluated defects of Lightspeed cutting tips before and after usage. The instruments were fixed into custom-made holders, the cutting heads photographed in a scanning electron microscope at x120 to x400 magnification at preset points around the cutting tip (90, 180, 270 and 360 degrees) and head-on. Instrument sizes 20 to 32.5, 35 to 60, and 65 to 100 were used in 9, 18, and 36 canals, respectively, and autoclaved after shaping every third root canal. The used instruments were cleaned and then reexamined in a scanning electron microscope as before. The presence of 11 types of conditions was scored from the pre- and postusage photographs. No instruments fractured during the test, but all the cutting heads had one or more imperfections, even before usage. The presence of debris, pitting, and metal strips changed significantly. Imperfections were found on new and used Lightspeed cutting heads, indicating the general difficulty in machining defect-free nickel-titanium rotary instruments. However, high quality should remain a goal to improve instrument efficiency.

Corrosion↗
PubMed1999

Apical transportation revisited or 'where did the K-file go'?

CASE REPORT: This case report describes the outcome of a number of retreatments on a failed root filling in a maxillary first molar. The patient wanted all amalgams replaced by tooth-coloured Cerec restorations, including one in a symptomless maxillary molar. This tooth had a pulpotomy or a poorly done root-canal treatment 10 years earlier. The molar was root-canal retreated before placing the Cerec restoration and the palatal canal was filled 5 mm short of the radiographic apex. About 1 year later the patient presented with pain. Suspecting that a second mesiobuccal canal (MB-2) had not been located, a second non-surgical retreatment was instituted. MB-2 was not found and the palatal canal was retreated a third time, setting the working length 2 mm short of the radiographic apex. Because pain persisted palatally an apicectomy was performed and the tooth became symptomless. The resected palatal root apex was subsequently serially cross-sectioned, photographed and the canals analysed. Obvious apical transportation occurred during the cleaning and shaping procedures. Analyses of the canals showed that despite the retreatments, 11% of the canal cross-sectional area remained uncleaned although 7% of the root area was 'shaped'. Radiographically, the obturated palatal canal appeared reasonably well centred. However, this was disproved by the cross-sections, indicating that in this case, the clinician did not know where the K-Files had 'gone'. Apically, the obturated canal was certainly not within the natural canal. The pain located palatally was probably due to inadequate cleaning and shaping of the apical part of the root canal and its accessory canals.

Apicoectomy↗
PubMed1999

Effects of Nd:YAG lasers on root canal walls: a light and scanning electron microscopic study.

OBJECTIVE: This study evaluated amounts of debris, smear layer, and recrystallized dentin on root canal walls treated with an Nd:YAG laser. The presence of carbonized material was also assessed. METHOD AND MATERIALS: The root canals of 36 extracted incisors were prepared by stepdown and stepback techniques and divided into 4 groups. One group was not treated further, while 3 others were exposed to the laser beam at an energy density of 159, 239, or 318 J/cm2. The roots were split longitudinally, photographed, and examined using a scanning electron microscope. The amounts of debris, smear layer, and recrystallized dentin were recorded from horizontal bands around the root, 2, 6, and 10 mm from the apices. RESULTS: Mean smear layer scores were similar for all groups at the 3 levels examined, ranging from 2.157 to 2.851 on a scale of 0.0 to 3.0. Mean debris scores were similar for all groups at the 3 levels examined, ranging from 0.774 to 1.408 on a scale of 0.0 to 3.0. Recrystallized dentin was recorded in all 3 irradiated groups at the 2-mm level, but only in the group irradiated with 318 J/cm2 at the 6- and 10-mm levels. Severe carbonization was recorded at the 2-mm level. CONCLUSION: Use of the Nd:YAG laser did not reduce the mean amounts of debris and smear layer compared to a nonirradiated group. Carbonization was recorded in the apical part of the canal, but this is not obvious when only scanning electron photomicrographs are examined.

Dental Pulp Cavity↗
PubMed1998

Increased formation of reactive oxygen species after permanent and reversible middle cerebral artery occlusion in the rat.

In barbiturate-anesthetized rats, we induced 3 hours of permanent middle cerebral artery occlusion (MCAO) by an intraluminal thread (n = 6), or 1 hour MCAO followed by 2 hours of reperfusion (n = 6). Through a closed cranial window over the parietal cortex, the production of reactive oxygen species (ROS) was measured in the infarct border using online in vivo chemiluminescence (CL) while monitoring the appearance of peri-infarct depolarizations (PID). The borderzone localization of the ROS and direct current (DC) potential measurements was confirmed in additional experiments using laser-Doppler scanning, mapping regional CBF changes through the cranial window after permanent (n = 5) or reversible (n = 5) MCAO. CL measurements revealed a short period (10 to 30 minutes) of reduced ROS formation after vessel occlusion, followed by a significant increase (to 162 +/- 51%; baseline = 100%; P < .05) from 100 minutes of permanent MCAO onward. Reperfusion after a 1-hour period of MCAO led to a burst-like pattern of ROS production (peak: 489 +/- 330%; P < .05). When the experiments were terminated 3 hours after induction of MCAO, CL was still significantly increased above baseline after permanent and reversible MCAO (to 190 +/- 67% and 211 +/- 64%, respectively; P < .05). Simultaneous DC potential recordings detected 6.4 +/- 2.7 PID in the first, 4.7 +/- 2.3 in the second, and 2.8 +/- 2.0 in the third hour after permanent MCAO. In animals with reversible MCAO, PID were abolished from 15-minutes recirculation onward. There was no temporal relationship between ROS production and peri-infarct DC potential shifts. In conclusion, using a high temporal resolution ROS detection technique (CL), we found that permanent MCAO (after an initial decrease) was accompanied by a steady increase of ROS production during the 3-hour observation period, while reperfusion after 1 hour of MCAO produced a burst in ROS formation. Both patterns of ROS production were not related to the occurrence of PID.

Acridines↗
PubMed1997

Randomised controlled trial of acetate in preterm neonates receiving parenteral nutrition.

AIMS: To determine whether by partly replacing chloride with acetate in parenteral nutrition, hyperchloraemia, metabolic acidosis, and the subsequent use of interventions such as colloid infusion, alkali treatment, increased assisted ventilation, would be reduced. METHODS: Fifty eight neonates of less than 32 weeks gestation, receiving parenteral nutrition from days 3 to 10, were given either standard parenteral nutrition or a novel formulation with replacement of any chloride dose > 3 mmol/kg/day as acetate. RESULTS: Acetate (0 to 14.2 mmol/kg/day) reduced the incidence of hyperchloraemia from 77% to 25%, and caused an increase in base excess from day 5 onwards (mean intergroup difference 3.6 to 9.9 mmol/l), an increased pH (day 8, 7.34 vs 7.26), with an increased pCO2 (1 kPa). The acetate group received less bicarbonate (median 0 mmol vs 4.8 mmol) and less colloid (41 ml/kg vs 204 ml/kg). There was no difference in any parameter of assisted ventilation. CONCLUSION: Acetate in neonatal parenteral nutrition reduces metabolic acidosis and hyperchloraemia.

Acidosis↗
PubMed1996

Oesophageal motility disorders in patients with psychiatric disease.

Clinical and experimental observations indicate that the motility of the oesophagus may be affected by emotional stimuli. The aim of this study was to evaluate the incidence of oesophageal contractility impairment in patients suffering from a psychiatric disorder. Fifty-one patients admitted to the psychiatric department were submitted to an oesophageal transit study by means of krypton-81m. All patients with an abnormal oesophageal transit underwent manometry and endoscopy. The level of depression and anxiety was evaluated by the treating psychiatrist, using the Hamilton Depression and Anxiety Rating Scales. The oesophageal transit was abnormal in 13 patients. Two of these 13 patients refused manometric investigation. In ten of the 11 remaining patients, the manometry revealed functional motor abnormalities. Endoscopy, performed in all these ten patients, was normal. In conclusion, a high percentage of oesophageal contractility disturbances was found in psychiatric patients complaining of anxiety and/or depression. These abnormalities were detected by scintigraphy as well as by manometry. Owing to the normal endoscopic findings, these contraction abnormalities are likely to reflect a functional motor impairment.

Anxiety↗
PubMed1996

Broncho-mediastinal fistula following perforation of the oesophagus.

We present a 63-year old female with mediastinitis following an esophageal perforation, possibly favoured by an oesophageal motility-disorder and the use of non-steroidal anti-inflammatory drugs, who developed a broncho-mediastinal fistula in the left main bronchus. She was successfully treated with intravenous antibiotics, a cervical oesophagostomy and secondary isoperistaltic coloplasty.

Anti-Bacterial Agents↗