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Biomedical subjects

A Brun

Publications and source records attributed to A Brun.

At least 73 records · Page 4Linked to original sources
PubMed1996

Preoperative grading of glioma malignancy with thallium-201 single-photon emission CT: comparison with conventional CT.

PURPOSE: To compare thallium-201 single-photon emission CT with conventional CT in grading the malignancy of gliomas and to determine the reliability of each in tumor assessment. METHODS: We studied 37 patients who had gliomas (31 high grade and 6 low grade) and compared the CT findings with the thallium-201 index, which we defined as tumor uptake relative to the uptake in the contralateral hemisphere. RESULTS: Among the high-grade gliomas, we observed a significant correlation between breakdown volume of the blood-brain barrier and thallium-201 uptake. However, 8 of the high-grade gliomas had low thallium-201 uptake, in the same range as the low-grade gliomas. Of these, 2 were nonenhancing and the other 6 showed ring enhancement on CT scans. Analysis of variance showed no significant difference in thallium-201 indexes between low-grade gliomas and highly malignant (grade II-III) gliomas. Accuracy of thallium-201 imaging was lower (78%) than that of CT (84%) in identifying high-grade gliomas. CONCLUSIONS: Damage to the blood-brain barrier is a prerequisite for uptake of thallium-201 in gliomas. Tumors with central necrotic areas and moderate ring enhancement tend to be underestimated when evaluated by means of thallium-201 scintigraphy. The results indicate a need for caution when interpreting findings on images obtained with thallium-201 single-photon emission CT in preoperative evaluation of brain tumors.

Adolescent↗
PubMed1996

Frontal lobe degeneration of non-Alzheimer type. Structural characteristics, diagnostic criteria and relation to other frontotemporal dementias.

Frontal lobe degenerative dementias, the second largest degenerative dementia group after Alzheimer's disease, is dominated by frontal lobe degeneration of non-Alzheimer type. It is classified in a group also containing Pick's disease, progressive aphasia and dementia in motor neuron disease. Frontal lobe degeneration of non-Alzheimer type is clinically marked by frontal lobe symptoms and frontotemporal reduction of blood flow. From a histopathological point of view it is characterized by gliosis, microvacuolation, neuronal atrophy-loss and 40-50% loss of synapses in three superficial cortical laminae of the frontal convexity and anterior temporal cortex, while the deeper laminae are little or not changed. The structural changes of Alzheimer's disease including amyloid, Levy body dementia and Pick's disease are entirely lacking. A strong heredity points to a genetic cause as yet undefined.

Aged↗
PubMed1995

Pathological changes in the Brown Norway rat cerebellum after mercury vapour exposure.

Our previous studies have demonstrated that mercury vapour exposure of Brown Norway rats induced an autoimmune response with development of glomerulonephritis and resulted in mercury deposition in the central nervous system, particularly in the neurons. The aim of this study was to investigate the effect on the central nervous system. A loss of Purkinje cells accompanied by Bergmann glial cell proliferation was found at a brain mercury level of 0.71 micrograms/g and became even more pronounced as the exposure dose increased. At a brain mercury level of 5.0 micrograms/g, a heavy gliosis was present in the brain stem, particularly around the pontine nuclei. In comparison with our previous study, the pathological changes in the brain appeared at the same mercury exposure dose as the glomerulonephritis. However, the location of pathological changes at the mercury level of 0.71 micrograms/g was not completely in accordance with the mercury distribution in the brain, which might be due to the sequence of mercury deposition, its amount or the vulnerability of the various cells classes.

Administration, Inhalation↗
PubMed1995

A microfluorometric method for measuring ethoxycoumarin-O-deethylase activity on individual Drosophila melanogaster abdomens: interest for screening resistance in insect populations.

We developed a method for measuring ethoxycoumarin deethylase (ECOD) activity using a single Drosophila abdomen. The activities obtained were well correlated with the classic method from microsomes (r = 0.902). This new method, performed in microtitration plates, was at least six times more sensitive compared to the conventional cuvet fluorometric one. Moreover, it was possible among a large number of insects to differentiate those with low or high ECOD activities. This improved procedure has been checked upon crosses between resistant strain (with high ECOD activity) and susceptible strain (with low ECOD activity). The results demonstrate the possible separation of resistant phenotypes and emphasize the importance of this approach in assessing the spreading of insecticide resistance in natural populations of insects.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1995

Synapse loss and gliosis in the molecular layer of the cerebral cortex in Alzheimer's disease and in frontal lobe degeneration.

Changes in density of synapses and astrocytes in the molecular layer of the frontal and parietal cortex were compared in Alzheimer's disease (AD) and frontal lobe degeneration of non-Alzheimer type (FLD). The investigation was limited to the molecular layer because it is possible in this part of the cortex to measure changes in synapses and astrocytes without contamination by nerve cell body changes. In the frontal pole synapse density declined by 40% in both FLD and AD whereas in the parietal area there was a 50% decrease in synapse density in AD but no significant change in FLD. Number of astrocytes showed an inverse relationship to synapse density. There was a significant increase in astrocytes in the frontal cortex in both FLD and AD but in the parietal cortex such an increase was seen only in AD. These results confirm previous reports of synapse loss in AD and demonstrate a similar loss in FLD in the frontal, but not parietal cortex. The findings underscore the regional pattern changes of FLD, previously shown for other parameters, and its difference from that of AD. We propose that these changes in molecular layer may be representative of the pathology (and the functional deficit) within the underlying cortical layers.

Aged↗
PubMed1995

The RG2 rat glioma model.

The ethylnitrosourea-induced cell line RG2 grows very well in infinite cell culture in vitro, and provides a simple, reproducible glioma model when inoculated into the brains of syngeneic Fischer 344 rats. We have used this tumor model in a series of therapy studies. We here report our experiences of the untreated (= tumor bearing control) animals, e.g. in terms of the techniques employed and also the growth, histology and effects upon the blood-brain barrier of the tumors. Weight loss as a measure of systemic effects during tumor development is also described. The RG2 model has considerable potential as a suitable tool for experimental neuro-oncology.

Animals↗
PubMed1995

Growth inhibition of rat glioma cells in vitro and in vivo by aspirin.

The effect of non-steroidal anti-inflammatory drugs (NSAIDs), acetylsalicylic acid (commonly known as aspirin), salicylic acid, piroxicam and indomethacin on the growth of rat glioma cells (RG 2) in vitro and aspirin in vivo was studied. The in vitro studies reveal that aspirin and salicylic acid strongly inhibit growth of rat glioma (RG 2) cells in concentrations used in medicine for treatment of rheumatic diseases. On the other hand, indomethacin and piroxicam had no effect, indicating that the inhibitory effect on tumor growth is not due to the inhibition of prostaglandin synthesis. The synthesis of ATP was markedly reduced (34% of control) in the presence of drugs, whereas protein synthesis measured as 3H-leucine incorporation was slightly more inhibited (73% of control) than cell growth. Aspirin administered to Fischer 344 rats inhibited growth of RG 2 cells inoculated into the caudate nucleus in vivo, both when administered the day before inoculation of tumor cells and when tumors had formed, i.e. 5 days post inoculation.

Adenosine Triphosphate↗
PubMed1995

A stochastic model for subcellular dosimetry in boron neutron capture therapy.

The therapeutic effectiveness of boron neutron capture therapy is highly dependent on the microscopic distribution of the administered boron compound. Two boron compounds with different uptake mechanisms in the tumour cells may thus cause effects of different degrees even if the macroscopic boron concentrations in the tumour tissue are the same. This difference is normally expressed quantitatively by the so-called relative local efficiency (RLE). In this work, a stochastic model for the subcellular dosimetry has been developed. This model can be used to calculate the probability for an energy deposition above a certain threshold level in the cell nucleus due to a single neutron capture reaction. If a threshold cell-kill function is assumed, and if the dose is low enough that multiple energy depositions are rare, the model can also be applied to calculations of the survival probability for a cell population. Subcellular boron distributions in rats carrying RG 2 rat gliomas were measured by subcellular fractionation after administration of two different boron compounds: a sulphydryl boron hydride (BSH) and a boronated porphyrin (BOPP). Based on these data, the RLE factors were then calculated for these compounds using the stochastic model.

Animals↗
PubMed1995

Incidence and prognostic significance of t(14;18) translocation in follicle center cell lymphoma of low and high grade. A report from southern Sweden.

BACKGROUND: The t(14;18)(q21;q32) is the most common recurrent genetic defect in follicle center cell lymphoma (FCC). Conflicting reports exist in regard to a possible prognostic significance for the translocation. PATIENTS AND METHODS: In a single center, 102 patients with either low-grade (n = 50) or high-grade (n = 52) FCC (Kiel classification) and a median follow-up of 82 months were retrospectively studied to determine survival in relation to t(14;18) as shown by either PCR of the bcl-2 rearrangement in paraffinized tissue or karyotype analysis. RESULTS: t(14;18) was detected in 30 of 50 (60%) low-grade FCC and in 12 of 52 (23%) high-grade FCC. The presence of the t(14;18) was not related to morphologic bone marrow involvement or other clinical parameters, but it was related to age: in low-grade FCC, patients with t(14;18) were an average of 17 years younger (p = 0.002) than those without the translocation. In the group with high-grade histology, 30% survived beyond 60 months regardless of t(14;18) status (p = 0.92). Patients with low-grade histology and t(14;18) fared better than those without, irrespective of age (p = 0.01). No significant difference in disease-free survival related to t(14;18) was found in either low- or high-grade FCC. CONCLUSIONS: The incidence of t(14;18) is in accord with that of other European reports. T(14;18) does not define a prognostic subset of high-grade FCC, but is significantly correlated with a better survival in low-grade FCC. The association of t(14;18) with younger age and indolent lymphoma is perplexing in light of recent findings of an age-related increase in t(14;18) in normal subjects.

Adult↗
PubMed1995

Necrosis of malignant gliomas after intratumoral injection of 201Tl in vivo in the rat.

Fourteen adult Fischer 344 rats were inoculated in vivo unilaterally in the caudate nucleus in the brain with malignant RG 2 glioma cells. By 3 weeks a tumor with a diameter of 3-6 mm normally develops. Ten animals which survived the repeated periods of anesthesia and thallium (Tl) injections (intratumorally three times of 201Tl, 15-23 days after inoculation) showed a prolonged retention of radioactivity at the site of injection with no uptake in other organs except for the kidneys. Singular circumscribed necroses were found post-mortem at the site of injection, comprising malignant glioma tumor tissue, which in six animals was absent, in three animals was markedly reduced in size compared with controls and in one animal had the expected size. In four animals metastases were found in distant locations in the brain; in three of these cases there was a retention of radioactivity in the tumor. The selective necrotizing effect on the tumor cells is interpreted as mainly due to emission of Auger electrons from intracellularly accumulated 201Tl, giving rise to very high energy deposition in the vicinity of the cell nucleus. The results should also have implications for the treatment of human malignant gliomas.

Animals↗
PubMed1995

Scanning gel densitometry of amniotic fluid acetylcholinesterase and butyrylcholinesterase: quantification of 'faint-positive' bands in fetal malformations.

The quantification of 'faint-positive' cholinesterases in amniotic fluid was performed in 40 patients with positive acetylcholinesterase (AchE) tests. Fetuses with anencephaly and open spina bifida presented an AchE/butyrylcholinesterase (A/B) ratio of more than 0.3 with clearly dense bands. Fetuses with gastroschisis showed a 'faint-positive' AchE band (A/B < 0.3). In 5 fetuses (1 teratoma, 3 open spina bifida, 1 unaffected) we found faint AchE and butyrylcholinesterase bands.

Acetylcholinesterase↗
PubMed1995

Performance of sulfhydryl boron hydride in patients with grade III and IV astrocytoma: a basis for boron neutron capture therapy.

This study investigated the rationale of boron neutron capture therapy (BNCT) for the treatment of Grade III and IV astrocytoma. The European Community joint research program on BNCT plans to use sulfhydryl boron hydride (BSH) in clinical trials. The work presented here, examines the performance of BSH in eight patients with Grade III and IV astrocytoma using a measurement technique which precisely correlates the boron uptake with the histology of the tumor and the peritumoral brain. Astrocytomas are exceptionally heterogeneous and spread migrating tumor cells into the surrounding brain. The patients were infused with 50 mg BSH per kilogram of body weight at 12, 18, 24 or 48 hours before surgery. At the time of operation, specimens were obtained of the tumor, skin, muscle, dura, blood, urine, and, when surgically possible, the brain adjacent to tumor. In three patients the intracellular boron distribution was investigated by subcellular fractionation. The blood clearance was biphasic with half-lives of 0.6 and 8.2 hours. After 3 days, approximately 70% of the dose injected was excreted in the urine. The maximum boron concentration in the tumor was 20 ppm, 12 hours after the infusion. The tumor-to-blood ratios ranged between 0.2 and 1.4, with the highest values after 18 to 24 hours. In the brain specimens the boron concentration never exceeded 1 ppm. This work confirms a selective uptake of boron in the tumor compared to the surrounding brain and that boron, to some extent, is incorporated in the tumor cells.

Astrocytoma↗
PubMed1995

A comparative study on the pharmacokinetics and biodistribution of boronated porphyrin (BOPP) and sulfhydryl boron hydride (BSH) in the RG2 rat glioma model.

Boron neutron capture therapy is a treatment modality for cancer that depends on the specific uptake of boron by the tumor cells. The infiltrative growth of malignant gliomas requires that boron reach and accumulate in migrating cells outside the margin of the tumor; thus, it is important that the biodistribution of new boron compounds is also studied in the surrounding healthy brain tissue. This study is undertaken in the present work, in which the biodistribution and pharmacokinetics of sulfhydryl boron hydride (BSH) and boronated porphyrin (BOPP) in the RG2 rat glioma model are investigated. This model mimics the characteristics of human glioma with cells migrating into the surrounding brain. The animals were infused intravenously with either BSH (25 micrograms or 175 micrograms of boron per gram of body weight) or BOPP (12 micrograms of boron per gram body weight). For the low dose of BSH, the maximum tumor-boron content was 8 ppm at approximately 9 hours after the infusion with a tumor-to-blood ratio of 0.6. At the higher dose, the corresponding figures were 15 ppm after 12 hours with a tumor-to-blood ratio of 0.5. For BOPP, a tumor-boron concentration of 81 ppm was achieved 24 hours after the infusion and sustained in that range for at least 72 hours. The tumor-to-blood ratio at 24 hours was slightly above 6, but continued to increase as the blood was cleared. These results indicate that both compounds are spread into the normal brain tissue following the same pathways as the migrating tumor cells and in this way can be taken up even in distant tumor cell foci.

Animals↗
PubMed1995

[Monitoring neurotoxic effects among laboratory personnel working with organic solvents].

The relationship between organic solvent exposure and central nervous disorders make early detection of neurophysiologic et neuropsychologic alterations in organic solvent exposed workers a priority. Moreover, the variability in the frequency of exposure and the numerous organic solvents encountered in scientific laboratories render the environmental and biological measurements used in medical surveys almost impossible. The present study was undertaken to appreciate the potential neurotoxic effects of organic solvents handling in laboratory employees. Neurophysiological and neuropsychological tests batteries were used with each worker and data were adjusted for potential confounding factors (age and education level). A Principal Components Analysis were performed to reduce the information and the first five factors corresponded to: mood states, speed coding, contrast vision in high frequencies, manual dexterity and contrast vision in low frequencies. These five factors were compared between the daily manipulators of at least one solvent (n = 75) and the non or occasional solvent users (n = 35). The results from this study showed that subjects directly in contact with solvents had a poorer mood state than those who were not or rarely exposed (p < 0.01) and that independently of the "work activity". Mood state impairment in chronic solvent exposed workers has been shown by many authors, with or without psychomotor alteration, and may reflect possible over-exposure. Detection of this instability may lead to early neurophysiologic alteration in exposed workers and permit health services to intervene before the development of irreversible effects.

Adult↗
PubMed1994

Respiration of [14C]alanine by the ectomycorrhizal fungus Paxillus involutus.

The ectomycorrhizal fungus Paxillus involutus efficiently took up exogenously supplied [14C]alanine and rapidly converted it to pyruvate, citrate, succinate, fumarate and to CO2, thus providing direct evidence for the utilisation of alanine as a respiratory substrate. [14C]alanine was further actively metabolised to glutamate, glutamine and aspartate. Exposure to aminooxyacetate completely suppressed 14CO2 evolution and greatly reduced the flow of carbon from [14C]alanine to tricarboxylic acid cycle intermediates and amino acids, suggesting that alanine aminotransferase plays a pivotal role in alanine metabolism in Paxillus involutus.

Agaricales↗
PubMed1994

Permeability of the blood-brain barrier induced by 915 MHz electromagnetic radiation, continuous wave and modulated at 8, 16, 50, and 200 Hz.

Biological effects of electromagnetic fields (EMF) on the blood-brain barrier (BBB) can be studied in sensitive and specific models. In a previous investigation of the permeability of the blood-brain barrier after exposure to the various EMF-components of proton magnetic resonance imaging (MRI), we found that the exposure to MRI induced leakage of Evans Blue labeled proteins normally not passing the BBB of rats [Salford et al. (1992), in: Resonance Phenomena in Biology, Oxford University Press, pp. 87-91]. In the present investigation we exposed male and female Fischer 344 rats in a transverse electromagnetic transmission line chamber to microwaves of 915 MHz as continuous wave (CW) and pulse-modulated with repetition rates of 8, 16, 50, and 200 s-1. The specific energy absorption rate (SAR) varied between 0.016 and 5 W/kg. The rats were not anesthetized during the 2-hour exposure. All animals were sacrificed by perfusion-fixation of the brains under chloral hydrate anesthesia about 1 hour after the exposure. The brains were perfused with saline for 3-4 minutes, and thereafter fixed in 4% formaldehyde for 5-6 minutes. Central coronal sections of the brains were dehydrated and embedded in paraffin and sectioned at 5 microns. Albumin and fibrinogen were demonstrated immunohistochemically. The results show albumin leakage in 5 of 62 of the controls and in 56 of 184 of the animals exposed to 915 MHz microwaves. Continuous wave resulted in 14 positive findings of 35, which differ significantly from the controls (P = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗