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Biomedical subjects

C Kopp

Publications and source records attributed to C Kopp.

At least 19 recordsLinked to original sources
PubMed1992

[The coronary sinus as a source of activated T-lymphocytes in patients after orthotopic heart transplantation].

Mononuclear cells are the component of blood responsible for allograft recognition, rejection and acceptance. Shifts in the patterns of various mononuclear cell subpopulations were often used as a diagnostic tool in detection of heart rejection. The specificity of mononuclear cell monitoring has remained a controversial point until today, because infections led to similar changes as organ rejection. In this study we investigated whether mononuclear cells taken from coronary sinus blood give more information about the immunological status of the transplanted heart than those taken from central verous blood. After endomyocardial biopsy, coronary sinus blood was sampled by catheterization under X-ray control. Blood from the right atrium was taken for control measurement. Mononuclear cells obtained by density gradient cytocentrifugation were stained with monoclonal fluorescein conjugated antibodies detecting CD4- (T helper)-, CD8- (T suppressor)-, CD25- (Interleukin-2 receptor), and the CD71- (Transferrin receptor) antigens. Endomyocardial biopsies were graded according to the Billingham scheme. In the absence of rejection, the phenotypes of mononuclear cells from the coronary sinus did not differ from those of right atrial cells. Mild rejection led to a statistically insignificant increase of CD4- CD25- and CD7-antigen bearing cells in the coronary sinus blood, whereas the CD8 positive cells remained stable as compared to mononuclear cells from the right atrium. However, patients with moderate rejection showed a significant elevation of CD4 positive cells and activated T-cells (CD15-, CD71-positive cells) in the coronary sinus as compared with cells from the right atrium. The T helper/suppressor ratio (Th/s-ratio) shifted towards the T-helper population.(ABSTRACT TRUNCATED AT 250 WORDS)

CD4-CD8 Ratio↗
PubMed1992

Mechanics of the cupula: effects of its thickness.

Mechanical aspects of the ampullar diaphragm, that is the crista ampullaris and the cupula, related to its thickness, are studied by a numerical method. Numerical methods are able to go beyond the limits of analytical approaches and are the only methods able to take into account this thickness. A finite elements method is applied to the median plane slice of the ampullar diaphragm. One assumes that the cupula sticks firmly without slipping, to the ampullar wall and to the crista ampullaris. The computation takes into account the pressures on the liquid interfaces and the deformations of the ampulla. So the volume swept over by the cupula during quasi-static deformations can be evaluated and the global elasticity coefficient of the human cupula can be calculated. The related value of the long time constant of the semicircular canal is close to the value obtained when measuring, in vivo, the activity on the vestibular nerve in animals. The thick cupula model clearly shows two different spatial distributions of strain on the hairs of the sensory cells, leading to a discrimination between the vestibular inflating pressure and the transcupular pressure difference. This result matches recent neurophysiological data and brings a new insight in the mechanics of the vestibular angular accelerometer and its regulation.

Animals↗
PubMed1991

Modelling the action of caloric stimulation of the vestibule. II. The mechanical model of the semi-circular canal considered as an inflatable structure.

In order to explain the mechanical effects that arise when a semi-circular canal is thermally stimulated in the horizontal position (i.e. in the absence of gravity effects) a physical model was used. The duct (corresponding to the canal) is deformable, the pressure transducer (corresponding to the ampulla) is not deformable. There is no thermal similarity but a dynamical similarity has been respected, so the mechanical phenomena occurring in the semi-circular canal and in the model are identical. The time scale is close to one. The physical model showed that the relative volume variations (fluid/duct) due to caloric stimulation lead to a pressure variation measured by the pressure transducer at the place of the ampulla and the cupula. The time history and the value of this pressure depend on the mechanical and thermal properties of the duct and the fluid. The qualitative responses of the physical model and of the vestibulo-ocular reflex after caloric stimulation were coherent. A numerical model simulating the same mechanisms yielded a quantitative estimation of the transcupular pressure arising in a horizontal semi-circular canal (i.e. without gravity dependent effects) during caloric stimulation. The physical model and the numerical simulation take no account of the inflating pressure variation.

Caloric Tests↗
PubMed1991

Modelling the action of caloric stimulation of vestibule. III. Caloric nystagmus induced by osmotic pressure variation.

The properties of the membranous wall of the semi-circular canal and of the labyrinthine fluids give as a result the inflating pressure of this inflatable structure. The difference of osmotic pressure between perilymph and endolymph, which is involved in this problem, depends on temperature. Therefore, a caloric stimulation leads to a change in the inflating pressure. A numerical model, similar to the model used to study the effects of relative volume variations, gives a quantitative estimation of the transcupular pressure arising in a horizontal semi-circular canal (i.e. without gravity dependent effects) during a caloric stimulation, according to the inflating pressure change. As a consequence, it appears that rotational and caloric stimulations are not quite similar. The caloric stimulation leads not only to a transcupular pressure difference but also to a change in inflating pressure. As a result of the change in inflating pressure, the stiffness of the cupula varies. This modifies the gain and the dynamics of the vestibulo-ocular reflex, and may explain the asymmetry between hot and cold stimulations.

Caloric Tests↗
PubMed1991

Modelling the action of caloric stimulation of the vestibule. IV. The global mechanical model.

Caloric stimulation acts on the bio-accelerometer (the semi-circular canal), as on engineered ones, through second order type multiple pathways. Three temperature induced peripheral actions have been described in our previous reports. The hydrostatic mechanism induces in the endolymph a gravity dependent transcupular stationary pressure difference. The differential expansion of the membranous duct and its content creates a local volume variation, while the modification of the transmembranous exchanges causes a local pressure variation. These two last mechanisms are gravity independent. They depend on parameters of the membrane, and induce a transcupular transient pressure difference and a stationary variation of the inflating pressure. It seems reasonable to assume the independency of these three mechanisms. If this assumption is true, than the global effect of caloric stimulation should be the sum of the effects of the three partial mechanisms. It is shown here that, for the physical model, this assumption holds. For humans, in the more general frame of the caloric vestibulo-ocular reflex experiments reported in the first paper, qualitatively and quantitatively this assumption holds, too. The model predicts a percentage of gravidity dependent effects of about 75%. It is shown that the reported human experiments lead to compatible estimates of this percentage. For humans in the earth gravity field, enduring the caloric stimulation it is not necessary to include neither otolithic interactions, nor significant modifications of the mecano-neural transduction, in the limits of precision of today's experimentation.

Caloric Tests↗
PubMed1991

[Vestibular test in Menière's disease].

When it is well known that the electronystagmographic examination cannot diagnose the Meniere's disease, it is very useful to ensure that no other pathology is involved and for the follow up of the patients. The vestibulo-oculogram, on the other hand, suggests the presence of hydrops, according to the mechanical model.

Electronystagmography↗
PubMed1991

[Modeling of the semi-circular canal, application to labyrinthine hydrops].

The angular accelerometer of vertebrates, the semi circular canal, is a pressure gage. The transformation, acceleration to pressure, is due to the inertia of the endolymph. In the 0 to 1 Hz frequency interval, the endolymph-cupula system can be described by a second order, localised parameter model with two real time constants. This mechanical model explains the occurr]nces of the vestibular-ocular reflex during rotatory stimulations. However, some features of the response to caloric stimulations cannot be explained from this unique point of view. To correspond to these features, the SCC has to be considered as an inflatable structure, sensitive to weak pressure variations between the endolymph and perilymph. Different parameters of the mechanical model, the internal radius of the membranous canal, the dimension of the cupula and its elasticity coefficient depend on the inflating pressure. Ménière's disease is caracterised by hydrops, i.e. an increase of the pressure in the membranous SCC. The different mechanisms related to this hydrops, in particular introducing the inflating pressure as a second input to the ampular system, associated to a new concept of the mechanoneural transduction can explain the classical vestibular symptoms of Ménière's disease. Therefore, this overall mechanical model of the SCC indicates that hydrops is the mechanical cause of Ménière's disease and the primary cause is more likely to be a defect in the regulation loop of the inflating pressure.

Biophysical Phenomena↗
PubMed1988

[Computer-assisted vestibular tests].

The labyrinth is a sensor of vibration. Therefore, multifrequency vestibular stimulation proves indispensable in obtaining a more accurate study of the VOR. We chose to use a pseudo-random binary sequence, generated on a mini computer. The angular velocity instructions are made up of eight repetitive sequences, the spectrum of energy in which is adapted to the frequency range of VOR. A process eliminating the quick phases, the blinking and other artefacts is applied to the nystagmic response, in order to observe only the slow phase velocity. The velocity of eye and chair are compared and the transfer function of VOR is performed. Gain, phase, coherence function and predominance of the mean slow phase velocity between left and right responses are the four indices which define VOR function. The multifrequency rotatory test is interesting for topographic diagnosis, and makes out three diagnostic ranges: a mechanical peripheral, a neurosensory peripheral and a central one. Two practical measures could help the propagation of this method: a simpler vestibular stimulation in order to suppress the rotatory chair, a simplified method of data processing using a personal computer.

Diagnosis, Computer-Assisted↗
PubMed1979

[Presurgical determination of lung function in patients with bronchogenic carcinoma].

90 out of 202 lung cancer patients hospitalized for preoperative investigations were scheduled for radical surgery. 15 patients were not operated on because of insufficient lung function data. The operation was performed in 75 patients. The complication rate was 11% and mortality 8%. 7 out of 8 patients who subsequently developed severe complications had fulfilled the criteria for lung resection only after intensive antibronchitic treatment. Nearly all the survivors showed the predicted preoperative minimal lung function values after the operation. The limit of 1000 ml for postoperative FEV1 is justified, since patients with these or larger functional reserves nearly all had a favourable early and late postoperative course, and also because lung function values continuously deteriorate in chronic obstructive lung disease.

Aged↗
PubMed1979

[Thorascopy as a diagnostic and therapeutic precaution in lung and pleural diseases].

Thoracoscopy is a method involving little discomfort for the patient but of high diagnostic effectiveness for pleural alterations. A histological diagnosis was established in 56 cases out of a total of 60 pleural effusions of unknown origin. In 10 pleural or pleuropulmonary diseases, anatomical classification was possible in all cases. In cases of pneumothorax (21 patients) the bronchopleural fistula could very often be seen and closure by detaching of pleural adhesions or cauterization was possible. These manipulations are usually followed by insufflation of sterile talcum powder through the thoracoscope. Suspicion of ruptured diaphragm due to accident was easily and quickly verified. No complications occurred in our 100 thoracoscopic examinations.

Female↗
PubMed1979

[Therapeutic recommendations in idiopathic spontaneous pneumothorax].

The treatment of spontaneous pneumothorax is still controversial. To evaluate pleural drainage with a chest tube the therapeutic results in 73 patients with benign pneumothorax were reviewed. Benign spontaneous pneumothorax treated with a thick chest tube size Charrière 18-22 disappeared within an average of only 6.6 days. On the other hand, the high recurrence rate of 24% after the initial pneumothorax and 37% after the first recurrence is comparable with the results of conservative management in other pneumothorax series in the literature. Small pneumothorax without severe symptoms should therefore be supervised conservatively on an outpatient basis. The more extended forms of pneumothorax should be treated with thick chest tubes. Failure of therapeutic effect, second ipsilateral relapse or the first contralateral pneumothorax are indications for parietal pleurectomy.

Adult↗
PubMed1978

[Lung circulation in emphysema].

Pulmonary emphysema is regularly complicated by pulmonary hypertension which is, however, mostly of minor degree. As long as pulmonary capillary pressure and cardiac output remain within normal limits, the elevated pressure in the pulmonary artery is due to an increase of vascular resistance for which hypoxia is responsible in the first place, while rarefaction of vascular ramifications due to the emphysematic destructive process in the pulmonary parenchyma plays only a secondary role. Breathing of oxygen decreases pulmonary hypertension, an effect which is reinforced by combination of oxygen with IPPB. Phentolamine lowers both vascular resistance and pressure in the pulmonary artery in short-term administration. The effect of hemodilution on pulmonary hypertension in emphysematic patients with hypoxic polycythemia is, however, somewhat disappointing if the hematocrit value remains below 60%. Some rheological causes for this therapeutic failure are discussed.

Bloodletting↗
PubMed1977

[Prevention and therapy of chronic cor pulmonale (author's transl)].

First prophylactic and therapeutic possibilities in cor pulmonale are shown on the basis of its pathogenesis. Our own results illustrate the effect of therapy of the underlying lung disease and of the concomitant respiratory insufficiency on the pulmonary arterial hypertension. The relationship between pulmonary artery pressure (PAp), arterial oxygen tension, forced expiratory volume of 1 second (FEV1%VC) and slow inspired viral capacity (VC) is analysed. In obstructive respiratory disorders the PAp rises when FEV1 falls below 40% of VC, in restrictive disorders when VC falls below 70% of predicted rate. 27 patients with chronic obstructive lung disease were treated with bronchodilator aerosols by intermittent positive pressure breathing (IPPB) during 2 years after a control period of 2 years: VC and FEV1 improved, the increase of total lung capacity and the deterioration of arterial blood gases came to a halt. The elevated PAp was always significantly reduced by oxygen therapy or IPPB or the combination of both. Finally, the rationale for avoiding physical stress in established cor pulmonale is illustrated: in healthy men PAp increases by less than 20% when cardiac output is doubled. In patients with cor pulmonale PAp rises to three times the initial value under the same conditions.

Adrenergic beta-Agonists↗