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Biomedical subjects

A Guell

Publications and source records attributed to A Guell.

At least 55 records · Page 3Linked to original sources
PubMed1983

[Value of the piribedil test in diagnosing migraine. Apropos of 150 cases].

Patients with migraine show a hypersensitivity to dopamine or its agonists. One of these, piribedil, was administered as 0,1 mg/kg intravenously over 30 minutes to 150 subjects with either migraine or other types of headache. This test provoked nausea and vomiting in 94 p. cent of patients with migraine, and a rapid fall in blood pressure requiring immediate interruption of the infusion in 69 p. cent. In contrast, in those subjects with chronic non-migrainous headache the administration of piribedil had no effect in 61 p. cent and provoked a fall in blood pressure in only 16 p. cent. The piribedil test appears to possess good specificity vis-à-vis migraine, enabling a differential diagnosis from atypical periodic headache, a condition difficult to consider as migrain or psychogenic headache on clinical grounds alone.

Adult↗
PubMed1982

[Blood biorheology and ischemic cerebrovascular accidents].

Blood hyperviscosity is usually observed in ischemic stroke. Our purpose was to study relations between viscosity and the different parameters of blood that influence viscosity, and to search abnormalities of circadian rhythms. 18 stroke patients (8 females and 10 males mean 65.4 years) and 12 normal subjects (4 females and 8 males, mean 68 years) were studied. The measures were realised within the 48 hours after stroke at 6 p.m. and 12 p.m. and the fourth day at 6 p.m. and 12 p.m., by means of a Taylor-Couette type rheometer. Stroke patients have a significant increase of their blood viscosity, but without elevation of blood hematocrit or fibrinogen within 48 hours. Stroke patients have no nocturnal decrease of viscosity, and they don't present the normal circadian periodicity. Perhaps would this phenomenon explain the diurnal variations in occurrence of strokes?

Adult↗
PubMed1982

Hydroelectrolytic and hormonal modifications related to prolonged bedrest in antiorthostatic position.

The effects of prolonged bedrest in antiorthostatic position (-4 degrees head down) on electrolyte balance were studied in 4 young volunteers. An increase was noted in sodium excretion during the first 4 days. Plasma renin activity and plasma aldosterone varied in parallel manner during the same period. Potassium balance and creatinine clearance were not significantly modified. In light of these data we feel that prolonged bedrest in antiorthostatic position constitutes an effective way to simulate on earth metabolic and hormonal modifications occurring in man under weightlessness conditions.

Adult↗
PubMed1982

Changes in the loco-regional Cerebral Blood Flow (r.C.B.F.) during a simulation of weightlessness.

Experiments of prolonged bedrest in antiorthostatic position are conducted in order to simulated cardio-circulatory modifications observed in weightlessness. Until now, no studies of r.C.B.F. have been effected in these conditions. Six young, healthy volunteers (average age 23.8) were placed in strict bedrest and in antiorthostatic position -4 degrees for 7 days. The r.C.B.F. measurements were studied by 133Xe inhalation method using a 32 detectors system. Studies were made first in basal conditions, then between the 6th and 12th hr, and finally between the 72nd and the 78th hr after the beginning of the experiment. Three of the subjects received 0.450 mg of Clonidine daily during the experiment. In the subjects having taken no Clonidine, we observed a constant increase in r.C.B.F. (12, 17 and 16% respectively) in the first 12 hr; at the 72nd hour, all values had returned to basal state. This findings agrees with the well known notion of a rapid correction of hemodynamic disturbances observed in the first days of weightlessness. In the subjects treated with Clonidine, the increase of r.C.B.F. did not occur. Several mechanisms of action are possible; the Clonidine affecting either the heart by inhibiting volemic atrial receptors or the brain by direct vasoconstriction.

Adrenergic alpha-Agonists↗
PubMed1978

Hemodynamic and metabolic factors in human cerebral ischemia.

Hemodynamic and metabolic cerebral measurements (CBF, CMRO2, CMRG, CSF) were evaluated in stroke patients. To investigate the effects of chronic cerebral circulatory insufficiency, CBF and CMRO2 were also studied. Further nontraumatic investigations of CBF measurement will allow a better understanding of clinical cases.

Acidosis↗
PubMedDate not supplied

Status of vestibular function after prolonged bedrest.

6 young, healthy, male volunteers were submitted to one week of head down (-4 degrees) bedrest. This position simulates the cerebral hemodynamic conditions in weightlessness. Measurements of vestibular equilibrium and of oculomotor system function were made before and after the prolonged bedrest. Analysis of the results indicates that vestibular responses, as measured by the maximal speed of the slow phase of the provoked nystagmus (caloric and sinusoidal rotatory stimulations), are decreased after prolonged bedrest. This statistically significant diminution requires confirmation with a greater number of cases. The reflex conflicting or interacting with the cervico-ocular and optokinetic reflexes on the one hand and the foveal vision on the other, is one of several possible explanations for the observed changes.

Adult↗
PubMedDate not supplied

Leg venous hemodynamics and leg volumes during a 42 day -6 degrees head-down bedrest.

Seven healthy subjects were submitted to a 42-day head down bedrest, where leg venous compliance (venous distensibility index VDI) and leg volumes were assessed by mercury strain gauge plethysmography with venous occlusion and optoelectronic plethysmography, respectively. Plethysmographic and volometric measurements were made, before, during (at days 1, 4, 7, 14, 21, 26, 34 and 41), and after bedrest (days 1, 4, 7, 11 and 30 of the recovery period). Results showed a continuous decrease in leg volumes throughout bedrest, when VDI increased until day 26 of bedrest, and then decreased afterwards. The recovery period was characterized by a rapid return of VDI to prebedrest levels while leg volumes progressively normalised. These results showed that leg venous compliance changes are not always dependent upon skeletal muscle changes, and that factors other than size of muscle compartment are able to determine increases in leg venous compliance during long-term bedrest.

Adaptation, Physiological↗
PubMedDate not supplied

Biomedical program of the ALTAIR french russian flight onboard the MIR station.

One year after the achievement of the 2 weeks ANTARES french-russian mission in the MIR station in July 1992, a 22 days ALTAIR mission with a french cosmonaut has been performed in July 1993, making use of the scientific payload remaining on board. Taking benefit of the analysis of the previous mission, the experimental protocols were adapted to refine scientific objectives and gave to the scientists the opportunity to enhance quantitatively and qualitatively their results. The french biomedical program, conducted in close scientific cooperation with IMBP and associated laboratories, was composed of 8 experiments out of which 2 were new with regards to the ANTARES program. In the field of cardio-vascular physiology and fluid regulation, the experiments: ORTHOSTATISME, DIURESE have been renewed and complemented by the TISSU experiment (proposed by a german scientist) and a real-time tele-assistance program using US echography technic and ground support from the french CADMOS support control center located in Toulouse. With respect to neurosciences objectives, to the experiments VIMINAL (cognitive processes) and ILLUSIONS (study of proprioceptives cues), was added the SYNERGIES experiment to analyse the postural adjustments during movement. The IMMUNOLOGIE experiment carried on and the radiobiological experiment BIODOSE ended. Adding the results of the 2 missions ANTARES and ALTAIR, and the data obtained in between onboard with russian cosmonauts, the scientists have received a wealth of physiological data and gained reproducibility and confidence in their results.

Adaptation, Physiological↗
PubMedDate not supplied

[Influence of age on several parameters of the Doppler signal at the carotid level (author's transl)].

Doppler recordings are an interesting method of exploration of the circulatory system and more information can be obtained than is generally accepted. This study demonstrates the influence of age on the Doppler signal treated in 3 different ways. This is done in order to obtain supplementary criteria if possible, which can be used to assess arterial aging and its possible pathological character. The results show the dispersion of the resistance index R after 50 years of age, many subjects having an increased index. The influence of various factors such as hypertension, smoking..., are analyzed. Particular attention is drawn to the morphological changes in the curve. Hard echos that are usually filtered are specifically analyzed. These represent the reflexion of ultrasounds on the arterial wall and it could be possible to obtain information on flow rate and vessel wall elasticity. Preliminary results show important variations of the signal with age. Doppler recordings from the carotid vessels can be used to follow, in an approximate manner, the rapid variations of cerebral blood perfusion. The during of circulatory disturbance was studied when the cerebral circulation was exposed to a particular situation requiring rapid adaptation: in this case the squatting-standing test. Large differences were observed according to age.

Adult↗
PubMedDate not supplied

The prognostic value of noninvasive CBF measurement in subarachnoid hemorrhage.

Seventy-four measurements of cerebral blood flow (CBF) were performed using the Xenon 133 inhalation method in 50 cases of spontaneous subarachnoid hemorrhage. This method is non-traumatic, reproducible and dependable. A correlation was found between clinical condition and CBF values, but in a number of cases which cannot be dismissed, very low mean CBF values or ischemic foci were revealed where clinical state gave no indication of same. A poor correlation appeared between vasospasm seen by angiography and ischemic foci detected by isotopic technique. Patients' age influenced CBF values but not clinical evolution. CBF values, measured in the first two weeks of illness, were significantly higher in those patients having favorable outcome, whatever their clinical state at the time of CBF measurement (comas excluded). The figure of 60 ml/100g/min. for mean cortical flow seemed to be a critical level below which risk of complications was greater. Conversely, in every case where mean cortical flow measured above 70 ml, outcome was favorable. Thus, CBF measurement promises to be a valuable prognostic tool, playing an important role in the therapeutic strategy for this type of patient.

Adult↗
PubMedDate not supplied

[Study of cerebral blood flow by the xenon-133 method in 10 schizophrenic adolescents].

Regional cerebral blood flow (r CBF) was compared in ten adolescents with hebephrenia who were never treated with neuroleptics and ten normal controls using the Xenon 133 inhalation method. There were no differences in mean hemispheric blood flow. The main difference was the loss of the "hyperfrontal pattern" in the schizophrenics: the prefrontal values were only 0.7% greater than the blood flow in the rest of the hemisphere, compared with 14.6% in the controls.

Adolescent↗
PubMedDate not supplied

[Cerebral blood flow in 20 depressed adolescents].

Regional cerebral blood flow was compared in twenty depressed adolescents and ten normal controls using the Xenon 133 inhalation method. There were no differences in mean hemispheric blood flow. The main difference was the loss of the "hyperfrontal distribution" in the depressed adolescents: the prefrontal values were only 5.4% greater than the blood flow in the rest of the hemisphere, compared with 13.5% in the controls.

Adolescent↗