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Biomedical subjects

P Bischoff

Publications and source records attributed to P Bischoff.

At least 73 records · Page 4Linked to original sources
PubMed1995

Long-term results of low vision rehabilitation in age-related macular degeneration.

One to five years after successful low vision rehabilitation, 199 patients with age-related macular degeneration were asked by means of a questionnaire whether they still used their low vision aids and whether they were satisfied with the low vision counseling. We received feedback from 66% of the patients. 20 patients had already passed away. 74% of the 112 answering patients still use a low vision aid today. Three-quarters of them still use the originally prescribed low vision aid. Interestingly enough, the daily reading time was rather short, only 16% of the patients read more than 1 hour per day, 42% read somewhat more and 13% somewhat less than 10 minutes per day. Retrospectively, 81% of all responding patients found their low vision counseling at least a little, more of them quite or very helpful. These numbers suggest, that the initial labor of patiently examining and training older, visually handicapped patients is worthwhile.

Aged↗
PubMed1995

Immunosuppressive activities of 6(5H)-phenanthridinone, a new poly(ADP-ribose)polymerase inhibitor.

6(5H)-phenanthridinone, a recently identified poly(ADP-ribose)polymerase (PARP) inhibitor, is able, at micromolar concentrations, to inhibit concanavalin A-induced lymphocyte proliferation and to potentiate the effect of gamma radiation upon murine spleen cells. When added at the onset of a mixed lymphocyte culture, this compound strongly depresses the induction of primary allogeneic (anti-H2k) cytotoxic T-lymphocytes (CTLs). Lymphokine-activated killer (LAK) induction was also found to be impaired by the PARP inhibitor. Taken together, these results clearly indicate that PARP plays a key-role in immune reactions involving cytotoxicity and that 6(5H)-phenanthridinone could be considered as a potent immunomodulator.

Acridines↗
PubMed1995

Macular sparing as a perimetric artifact.

PURPOSE: We studied the hypothesis that the typical macular sparing of a few degrees was based on an unstable fixation coupled with a nystagmiform searching movement in the direction of the seeing hemiretina. METHODS: By means of microperimetry with a scanning laser ophthalmoscope, we recently tested the visual fields of 15 hemianoptic patients, through direct visual control of the retina. The tests provided us with accurate information about all fixation shifts that occurred. RESULTS: Twelve patients showed macular sparing of 1 to 5 degrees both in the Goldmann visual field and in the scanning laser ophthalmoscope field. Their fixation shifted regularly 1 to 10 degrees toward the seeing hemiretina one to two times per second, then returned rapidly to the foveola. Conversely, three patients showed greater macular sparing, and they all had particular characteristics--extensive fixation shifts, dual fixation, and limited quadrantanopsia. CONCLUSIONS: We believe that macular sparing could be interpreted as a perimetric (not an anatomic) artifact, provided that the results of these tests on 15 patients are confirmed by further similar studies.

Adolescent↗
PubMed1995

Oxysterol-induced apoptosis in human monocytic cell lines.

Oxysterols constitute a large family of natural compounds, endowed with various biological activities including cholesterol regulation, immunosuppression and antitumoral potency. In the present study, we examine and compare the cytotoxic effects of two representative members of this family: 7 beta-hydroxycholesterol (7 beta-OH) and 25-hydroxycholesterol (25-OH), in two human monocytic cell lines, U-937 and HL-60. In both cell lines 7 beta-OH at 30 mu M induces cell death by apoptosis within the first hours of treatment. Under the same conditions and in contrast with results previously obtained with lymphoma cells, 25-OH is cytostatic only. It is interesting to note that the simultaneous treatment of U-937 cells by equimolar concentrations of 7 beta-OH and 25-OH leads to a considerably decreased induction of apoptosis. Such an effect is not observed with HL-60 cells. Taken together, these results indicate for the first time that: 1) oxysterols hydroxylated on the sterol nucleus are also able to induce apoptosis, 2) apoptosis can be induced by these substances in cells belonging to the myeloid lineage and 3) as far as apoptosis is concerned, a combined treatment with 7 beta-OH and 25-OH can lead to opposite effects depending on the cell type.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1995

[Low dosage radiotherapy of subfoveal neovascularization in age-related macular degeneration. Preliminary results].

AIM OF THE STUDY: The aim of this study is to test the effect of low dose radiation on the subfoveal neovascular membranes (SNVM) and to analyse visual acuity in age-related macular degeneration. METHODS AND PATIENTS: From November 1993 through to August 1994, 10 patients, on the one hand, were given a dose of 5 Gy followed by controls 6 weeks and 6 months later. On the other hand, 21 patients were treated with a dose of 8 Gy and were subjected to controls 6 weeks later. Before the radiotherapy and during the control sessions, all patients were required to be measured for different parameters of visual acuity and to receive a simultaneous fluorescein and indocyanine green angiography. The radiotherapy was done by a linear accelerator 6 MeV and through a lateral port 3 x 4 cm in half beam technic. RESULTS: In the 5 Gy group, no changes in the parameters for visual acuity were noted in most cases after 6 months. In 9 of the cases, the membranes had increased in size and in 1 case, they had remained unchanged. In the 8 Gy group, no changes in the visual acuity or in the membrane size were diagnosed. Of all the patients treated, only one refused the angiography control. DISCUSSION AND CONCLUSIONS: Given the low dose used and the period of observation, the visual acuity of all patients remained stable. The size of the membranes increased in most cases for those 5 Gy patients and in this respect, no changes at all were noted in the 8 Gy patients. In order to better evaluate the potential of radiotherapy, this study must be pursued and coupled with further studies analysing the effect of different doses on patients.

Aged↗
PubMed1995

Microsatellite instability in adenocarcinomas of the upper gastrointestinal tract. Relation to clinicopathological data and family history.

We analyzed 66 adenocarcinomas arising in the upper gastrointestinal tract for microsatellite instability at eight microsatellite loci to investigate the role of these genetic alterations in the etiology of these tumors. We identified alterations in at least one locus in 11/46 adenocarcinomas of the stomach, in 2/15 adenocarcinomas arising in Barrett's esophagus, and in 1/5 adenocarcinomas of the duodenum and jejunum. Microsatellite instability in gastric tumors was found in 5/22 of intestinal, 1/3 of mixed, and 5/21 of diffuse type tumors. No relationship to the tumor stage (TNM), age, and survival time of the patients was observed. One patient had two synchronous gastric tumors both exhibiting microsatellite instability at multiple loci. His family history revealed four individuals in the maternal line afflicted with gastric carcinoma in three generations. Our data show that microsatellite instability is a genetic event in 11 to 24% of tumors of the upper gastrointestinal tract. The observation of microsatellite instability and a familial clustering of gastric tumors may suggest a genetic predisposition for a subset of gastric tumors, which may be identified by microsatellite analysis.

Adenocarcinoma↗
PubMed1994

[Perioperative EEG monitoring: studies of the electrophysiological arousal mechanism].

Electroencephalogram recordings have been advocated for assessment of changes in cerebral function during anaesthesia. Controversy exists on the specificity of EEG parameters indicating depth of anaesthesia, because cortical electrical activity is modulated not only by drugs but also by a variety of exogenous and endogenous stimuli. In clinical practice, EEG measures often fail to accurately predict anaesthetic depth since the effects of nociceptive stimulation on the EEG are still not well defined. Previous reports indicate that in anaesthetised patients sensory stimulation may induce a shift to a dominant EEG frequency with faster waves similar to patterns seen during emergence from anaesthesia under certain circumstances. This electrophysiological arousal (EEG desynchronisation) may be associated with clinical arousal phenomena such as movement and increases in haemodynamic and respiratory activity. However, the mechanism of arousal during emergence from anaesthesia may be quite different from arousal reactions induced by noxious stimulation. Recent studies indicate that surgical stimulation can induce increases in slow wave EEG-activity ("reverse" or "paradoxical" arousal) associated with clinical arousal phenomena. Stimulus related delta patterns also were observed after acoustical or painful stimulation in head injured patients. The occurrence of slow EEG wave patterns may be related to functional blockade of the ascending activating system of the brain stem. In contrast, slowing of the EEG is comparable to EEG changes seen with increasing concentrations of anaesthetics. This indicates the difficulty to discriminate arousal phenomena from drug effects using EEG monitoring alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia Recovery Period↗
PubMed1994

[Does indocyanine green angiography aid in deciding indications for laser therapy of exudative senile macular degeneration?].

BACKGROUND: Only a few patients with neovascularized age-related macular degeneration (AMD) have clinical and fluorescein angiographic manifestations that meet eligibility criteria for photocoagulation therapy. Angiography with indocyanine green (ICG) may expand those criteria. MATERIAL AND METHODS: Fifty-two patients with exudative AMD were studied by fluorescein and ICG angiography (using the Rodenstock scanning laser ophthalmoscope). The ICG-angiograms were studied in relation to the questions, how often subretinal neovascularizations (SNV) were visible and how often the results were helpful for laser treatment. RESULTS: In 18 cases (about one third) a SNV was detected by ICG-angiography and in 8 (15%) the result allowed a laser treatment. "Ideal" SNV presented as neovascular trees with a visible feeder-vessel. Other cases showed a circumscribed area of diffuse hyperfluorescence especially in the late phase. Macular edema often prevented the resolution of subretinal membranes. CONCLUSIONS: Only randomised studies will be able to show whether the combination of fluorescein and ICG angiography allows the possibility of treating more patients with SNV than fluorescein angiography alone. In the following circumstances this might be the case: 1. If in subfoveal SNV a feeder-vessel could be delineated with ICG-angiography that might be treated selectively. 2. If an occult SNV might be reclassified as manifest SNV due to findings provided by ICG-angiography. 3. Examination of patients with ICG-angiography immediately after laser photocoagulation might be a way of proving the completeness of the treatment.

Aged↗
PubMed1994

[The right foreign body at the wrong site].

In ophthalmology like in any other medical field, some natural tissue or a piece of artificial material may be found in an unusual location. We are going to describe two extraordinary clinical cases: a tuft of hair in the conjunctiva and a luxated posterior chamber lens.

Aged↗
PubMed1994

[Pseudallescheria boydii fungal endophthalmitis. 6 years after trabeculectomy].

A case is reported of a 67-year-old female patient, in whom a fungal endophthalmitis occurred 6 years after trabeculectomy. Pseudallescheria Boydii was isolated. This organism is a rare cause of infection. In the literature only 14 cases of keratitis and 8 cases of endophthalmitis have been reported. Miconazole is the therapy of choice. However in 55% of the published cases, (as in the one reported here), an exenteration or enucleation of the affected bulbus was necessary.

Aged↗
PubMed1994

[How accurate is video refraction measurement in infants in comparison with skiascopy? How much do the values change within a half a year?].

BACKGROUND: Isotropic photorefraction (Atkinson et al., 1981) is a method used to screen the refraction in infants. The aim of this study is to analyze its limitations as a measuring instrument. MATERIALS AND METHODS: 215 children aged between 5 and 12 months were examined in cycloplegia. The results were subsequently compared (1) to the results of streak retinoscopy also performed at the same time and (2) to photorefraction performed a second time, 6 months later (with 145 children). RESULTS: Spherical refraction: The mean spherical values differed by 0.70 dpt through photorefraction methods, compared to retinoscopy. The standard deviation (SD) was 0.67 dpt. The values of the photorefraction differed therefore in 95% of the children within a range of 2.7 dpt (or +/- 2 SD). Compared to the second photorefractive measurement 6 months later, the average refraction showed a small myopic shift (-0.45 dpt). Astigmatism: The errors of measurement were more pronounced here. Extreme differences of up to 9 dpt were found in single cases. The mean difference, compared to retinoscopy, was 0.73 dpt. The standard deviation (SD) was 0.90 dpt. In 95% of the children, the values of photo-refraction differed therefore by a range of 3.6 dpt (or +/- 2 SD). Compared to the second photorefractive measurement 6 months later, the average refraction showed a mean change of 0.73 dpt. CONCLUSIONS: Our photorefractive measurements showed errors in the range of 1-2 dpt for the spherical refraction, and in the range of 2-3 dpt for astigmatism. In 5% of the children examined, even greater aberrations were found. As long as the aim of photorefraction is restricted to disclosing high refractive errors, this method is judged suitable for the refractive screening of infants. For more precise refraction, and for the prescription of spectacles, we believe that is should be supplemented by a second examination technique, such as retinoscopy or automated refractometry.

Astigmatism↗
PubMed1994

[Video refraction measurement in the first year of life].

BACKGROUND: 426 children were examined, using the isotropic photorefraction method (Atkinson et al. 1981). The aim of this study was to analyze whether the frequency of convergent strabismus and/or amblyopia would increase, particularly in cases of high ametropia, and whether the early prescription of spectacles would be beneficial. The preliminary results of this study are presented here. MATERIALS AND METHODS: 426 children aged between 5 and 12 months were examined. Family history, particularly involving strabismus, ametropia and amblyopia, was ascertained and taken into consideration. RESULTS: Spherical refraction: 92% of the children were emmetropic or slightly hyperopic (< or = +2.5 D). 3.4% were hyperopic (> +2.5 D spherical equivalent) and 4.6% were myopic (0.9 > or = -2.0 D). Astigmatism: 85% had no or mild (< or = 1.5 D) astigmatism. Values greater than 3.5 D were rarely seen. Anisometropia: 67% of the children had no side-difference and only 2.4% had anisometropia with values greater than 1.5 D. Family history/orthoptic findings: 2.6% of the examined population had strabismus. In 12.2% of all the cases one or more first degree relatives had strabismus. Hyperopia and strabismus were found more frequently in this latter group, namely hyperopia (> +2.5 D spherical equivalent) in 13.6% and strabismus in 11.5%. CONCLUSIONS: Refractive errors greater than 2.5 D were seldom seen in this study, and yet were more frequently detected in families with a history of strabismus. In our opinion, isotropic photorefraction is a method most suitable to screening these especially high-risk groups.

Amblyopia↗
PubMed1994

Surgical stimulation induces changes in brain electrical activity during isoflurane/nitrous oxide anesthesia. A topographic electroencephalographic analysis.

BACKGROUND: The aim of this study was to investigate topographic changes in electroencephalographic (EEG) power and frequency induced by abdominal surgery during anesthesia with 0.6% or 1.2% isoflurane in 66% nitrous oxide. METHODS: Forty-six patients (aged 41 +/- 13 yr) scheduled for elective abdominal surgery were studied. The trachea of each patient was intubated and the lungs ventilated. Patients were randomly assigned to one of four groups: anesthesia was maintained with 0.6% (group 1, n = 12; group 2, n = 11) or 1.2% end-tidal isoflurane (group 3, n = 12; group 4, n = 11) in 66% nitrous oxide. Data were recorded over 20 min. Groups 1 and 3 were studied without surgery (as controls). In groups 2 and 4 recording was started 6 min before skin incision. The EEG was acquired via 17 scalp electrodes placed in standard International 10-20 locations (reference Cz). Absolute and relative power densities were calculated in selected frequency bands. EEG maps of spectral power densities were coded according to a continuous color spectrum. RESULTS: During baseline recordings, alpha activity was dominant at frontal areas in groups 1 and 2. In comparison, in groups 3 and 4, delta and theta activities were dominant at frontal leads. In group 2, the start of surgery resulted in increases in delta activity and decreases in alpha activity that were most dominant frontally (delta +181% and alpha -61%, F3). The delta shift was attenuated at 1.2% isoflurane (group 4, delta +44%, F3), but decreases in alpha activity (-53%, F3) were comparable to those in group 2. The EEG response in all frequency bands was attenuated at parietotemporal recording sites at both isoflurane concentrations. CONCLUSIONS: The current data demonstrate graded EEG responses induced by abdominal surgery during anesthesia with 0.6% or 1.2% isoflurane in 66% nitrous oxide. Spatial heterogeneities in absolute spectral power densities were reflected by color changes in the EEG maps. The topographic EEG analysis indicates that these changes were most dominant at frontal areas. The increases in delta and decreases in alpha activities may be related to intraoperative "paradoxical" electrophysiologic arousal phenomena.

Adult↗
PubMed1994

Effect of 6(5H)-phenanthridinone, an inhibitor of poly(ADP-ribose) polymerase, on cultured tumor cells.

By catalyzing posttranslational modifications of nuclear proteins, poly(ADP-ribose) polymerase (PARP) controls their functions and therefore constitutes an enzyme of crucial importance in tumor development. In this study, we have investigated the action of 6(5H)-phenanthridinone, an isoquinoline derivative and one of the most potent PARP inhibitors described so far, on RDM4 murine lymphoma cells in culture. We also examined whether this compound could act synergistically with an antineoplastic drug in tumor-cell destruction. Our results demonstrate that a marked inhibition of PARP activity can be obtained in whole cells after a short incubation, and that this compound, when associated with an alkylating agent, dichloro-2,2' N-methyldiethylamine (chloromethine), leads to a marked drop in the RDM4 proliferation, indicative of a synergy between the two compounds.

Animals↗
PubMed1994

[Ketamine and evoked potentials].

Ketamine-induced changes in the spontaneous and evoked electroencephalogram have been well documented in animals and humans. In contrast to the action of hypnotics, ketamine does not result in a dose-dependent suppression of neural activity. Many studies have revealed excitatory activity with induction of synchronized high-voltage slow waves in the electroencephalogram (EEG). Somatosensory evoked responses (SEP) have been found to be enhanced following induction of anaesthesia with ketamine. However, increases in amplitude were small compared with the SEP-enhancing effects of etomidate. The increase in somatosensory evoked responses may reflect dose-dependent disinhibition and/or increased excitation of cerebral neuronal activity induced by ketamine. Attenuation of late cortical somatosensory evoked responses following stimulation of thin C- and A delta-nerve fibres has been reported in volunteers given low-dose ketamine. Changes in SEP amplitude correlated to changes in subjective pain sensation. From this it was concluded that the analgesic effect of ketamine can be assessed by electrophysiological measurement methods. Recent studies suggest that the analgesic effect of the racematic ketamine mixture can probably be related to the effects of S-(+)-ketamine isomer, which has been shown to be involved in the activation of an opioidergic mechanism. Auditory evoked responses (AEP) of short latencies with origins in the brain stem have been shown to be slightly altered by ketamine. From this it was concluded that these components may not be used for assessment of the depth of anaesthesia. In contrast to the effects of hypnotics, mid-latency AEP components may be recorded during ketamine anaesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Safety and efficacy of a new transpulmonary echo contrast agent in echocardiographic studies in patients.

OBJECTIVES: This study was designed to investigate in patients the effect of a new transpulmonary echo contrast agent, made from 5% human serum albumin (Albunex), on systemic and pulmonary hemodynamics and the influence of the contrast doses on left ventricular opacification. BACKGROUND: New intravenous transpulmonary echo contrast agents are promising, allowing contrast stress echocardiography and myocardial contrast echocardiography. Nevertheless, some shortcomings still remain. Thus, the pulmonary hypertension observed in pigs after Albunex injection should be investigated in humans, and the optimal dose of contrast agent remains to be determined because previous experiments indicated that the left ventricular opacification and attenuation are dose dependent. METHODS: Albunex in doses of 0.08 and 0.22 ml/kg was successively injected intravenously in 20 catheterized patients; in 11 of them, anti-inflammatory drugs were withdrawn to avoid the blocking of an eventual thromboxane-mediated pulmonary artery hypertension. Systemic blood pressure and pulmonary artery, capillary wedge and right atrial pressures were continuously monitored. Cardiac output, left ventricular fractional shortening and blood gases were determined 5 min before and 5 and 10 min after each injection. The left ventricular opacification was qualitatively assessed by three independent observers using a grading scale from 0 to 3, with 0 indicating an absence of contrast effect and 3 indicating full opacification. RESULTS: No clinical, hemodynamic or respiratory adverse reactions were observed in any patient. Irrespective of doses, a left ventricular opacification grade > or = 2 was observed in 74% of the 35 injections that could be evaluated. This percentage increased to 94% when the higher dose group was considered alone. CONCLUSIONS: This first report of the effect of Albunex injected intravenously on pulmonary artery pressures in humans demonstrates that this contrast agent appears to be safe. The significant left ventricular opacification obtained in a majority of patients without an important increase in attenuation supports the use of the higher dose of the contrast agent.

Albumins↗
PubMed1993

[Alpha 2-agonists in anesthesia and intensive medicine].

The neurotransmitters adrenaline and noradrenaline are non-selective adrenergic agonists which interact with both subtypes of alpha- and beta-receptors. Clonidine, an alpha 2-adrenergic drug with a selectivity ratio of 200/1 for alpha 2/alpha 1 has been used in clinical practice for more than 20 years. Although alpha 2-agonists have vasoconstrictor properties, sympatholytic effects on the central nervous system predominate. As a result, the sympathetic outflow from the medullary pressor centres is decreased mediating the hypotensive effects of the alpha 2-agonists. These compounds also exhibit sedative, anxiolytic, analgesic, and haemodynamic stabilising properties. The identification of alpha 2-adrenoceptors has yielded information on their biochemical properties, signal transduction, modulation of the sympathetic nervous system and neurotransmission. The classification of alpha 2-receptors based on anatomical locations and identified as presynaptic alpha 2-receptors and postsynaptic alpha 1-receptors proved to be untenable after postsynaptic and extrasynaptic alpha 2-receptor locations had been identified. At least 3 isoreceptors which are heterologously distributed in the brain have been identified. Guanine nucleotide proteins (G proteins) couple the receptor to an effector mechanism (i.e. intracellular messenger cascade, ion channel). More selective for the alpha 2-adrenoceptor than clonidine is dexmedetomidine (1600/1 of alpha 2/alpha 1), a very potent agonist at the alpha 2-adrenoceptor. Imidazole derivatives (like clonidine and dexmedetomidine) also bind to other nonadrenergic receptors ("imidazoline receptors") which may produce some effects (i.e. vagotonia) previously ascribed to alpha 2-adrenoceptors. alpha 2-receptors exist in brain tissue and several peripheral organs and tissues including the liver, eye, kidney, pancreas and platelets. Anaesthetic interest has focussed on reductions in anaesthetic requirements since experimental and clinical studies have shown that alpha 2-agonists expert powerful analgesic and anaesthetic effects. The hypnotic response is probably mediated by activation of alpha 2-adrenoceptors in the locus coeruleus. Analgesia is induced by modulation of the nociceptive pathway at the level of the dorsal root neuron and other sites not yet unambiguously characterised. Dexmedetomidine reduces the anaesthetic requirements for halothane by more than 90%. Cerebral blood flow and intraocular pressure are reduced by alpha 2-agonists. Epidural, intrathecal, intravenous and transdermal application of clonidine resulted in pain reduction, during and following surgery and in patients with neurogenic or otherwise intractable cancer pain. Administration of alpha 2-agonists induces only minor respiratory effects. Salivary flow is reduced by alpha 2-agonists and gastric and small-bowel motility is decreased.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenergic alpha-Agonists↗