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Biomedical subjects

A Pfister

Publications and source records attributed to A Pfister.

At least 73 records · Page 4Linked to original sources
PubMed1978

Comparative study of lesions in the brain of rats exposed to heavy ions: accelerator and stratospheric flight research.

Irradiations of rat's brain with heavy ionized particles (12/6C, 291 Mev/nucleon, 100 to 300 ions/mm2) have been carried out at the Lawrence Berkeley Laboratory. Exposures were made with slowed ions which stopped within the brain as well as with more energetic particles which passed through. Histological examination of irradiated encephalons by optical microscopy showed zones of glial reaction and an increased number of darkly staining cells. By electron microscopy, intercellular edema, various alterations of nervous cells and macrophagy were observed, especially with stopped ions.

Animals↗
PubMed1976

Expression of a mutation affecting F incompatibility in the integrated but not the autonomous state of F.

Previously we have described a mutant Hfr strain in which incompatibility between the integrated F factor and an autonomous F-prime (F') factor was abolished. The mutation (inc) was located in the integrated F factor. F-prime factors isolated from the mutant Hfr strain have the same incompatibility behavior as those isolated from normal Hfr strains. Reintegration of these F' factors into the chromosome restores the Inc- phenotype characteristic of the mutant Hfr. The inc mutation thus affects incompatibility between integrated F and autonomous F(Fi-Fa incompatibility) but not incompatibility between two autonomous F factors (Fa-Fa incompatibility). The implications of this finding for the mechanism of plasmid incompatibility are discussed.

Chromosomes, Bacterial↗
PubMed1976

Lesional effects of primary cosmic heavy ions on rat brain.

Heavy ions were detected with nuclear emulsions plates fixed on the skulls of 20 rats which were exposed to cosmic rays at an altitude of 32,000 metres. Eight cases are described of correlations between ions tracks and brain lesions. The passage of heavy ions seems to cause functional rather than destructive alterations in the cells. The metabolic disturbances give a dark aspect to the neurons. The lesions generally appear in wide areas around the track and this fact suggests a physiopathological phenomenon of amplification. An evaluation of this biological hazard during flights of long duration at high altitude will be possible when the mechanism of action of heavy ions on nervous tissue is better known, and particularly if experiments carried out in accelerators confirm the small number of results obtained in flight.

Animals↗
PubMed1975

[Cutaneous elastopathy and vascular anomalies associated with neurological disorders. Apropos of 2 cases].

The two cases described exhibited elastopathy associated with arterial stenosis (case 1) or aneurysms (case 2). The first was clearly a case of elastic pseudo-xanthoma with characteristic cutaneous lesions associated with retinal angioid streaks and severe arterial lesions, notably stenosis of the vertebral arteries (especially the left) causing disorders in the mechanism of balance. There were, in addition, mild diabetes, hyperlipidaemia and abnormal cutaneous pigmentation. The second patient, an African, had been hospitalised for an optochiasmatic syndrome which further investigation, notably by arteriography, indicated was caused by compression of the visual pathways due to massive bilateral carotid aneurysms. The patient had molluscoid pseudo-tumours of the axillae and she reported that her father was in the same condition. Although in the first case, cutaneous biopsy enabled diagnosis of systematized elastorrhexis to be confirmed, histological investigation in the second case revealed mainly hyaline sclerosis of the deep dermal layer. The diagnosis of Ehlers-Danlos disease, suggested for this second patient, could not be confirmed. These two cases emphasize the possibility of various neurological disorders occurring in the course of dystrophy of the connectivo elastic tissue.

Adult↗
PubMed1970

Current status of French research on the biological effects of heavy ions in cosmic radiation as observed in high-altitude balloons.

On casual inspection, cosmic rays may not be considered to pose a biological hazard. Nevertheless, the heavy ion component does produce a significant but very local irradiation. This has been confirmed by the hair whitening in black-haired animals. Experiments with black C 57 mice in balloons at 30,000 m altitude show white-haired tufts along the tracks of heavy ions. Histological and radioautographic studies were carried out; the results are reported. Similar investigations on black rabbits gave similar results and confirm those obtained previously with black mice. In the discussion, we report that tissue damage is amplified. This fact is not yet explained, but suggests reconsideration of the calculation of radiation dosage. The ionization distribution induced by heavy ions is analyzed. We point out that along their tracks the dosage is very important; therefore it is necessary to investigate their biological action, particle by particle, according to their energy and their charge.

Animals↗