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Biomedical subjects

C Kopp

Publications and source records attributed to C Kopp.

At least 55 records · Page 3Linked to original sources
PubMed1993

Effects of interleukin-1, -2, -4, -6, interferon-gamma and granulocyte/macrophage colony stimulating factor on human vascular endothelial cells.

Human vascular endothelial cells (HUVEC) exhibit various immunological functions, i.e. expression of HLA class-II antigens after incubation with IFN-gamma or antigen presenting function. It has also been reported that HUVEC are able to produce IL-1, IL-6, GM-CSF and immunologically active cleavage products of arachidonic acid. In our study we investigated whether various cytokines, namely IL-1, IL-2, IL-6, GM-CSF and IFN-gamma, do alter the proliferative capacity of HUVEC, the production of van Willebrandt factor (vWF) and the expression of MHC class-II antigens. HUVEC were prepared by the collagenase digestion of human umbilical veins. Monolayers of cells were incubated with cytokines in different concentrations for 24 and 48 h. IFN-gamma inhibits the HUVEC [3H]thymidine uptake in a dose-dependent manner. Suppression of proliferation (40.1%) could be observed after 24 h incubation with 100 U IFN-gamma/ml. IL-1 was a more effective inhibitor of HUVEC proliferation (54% at 10 U/ml and 24 h incubation and 48.4% after 48 h) than IFN-gamma. IL-6 and GM-CSF showed an increasing effect on proliferation with 226% and 151% of the control group, respectively. IFN-gamma after an incubation period of 12 h and IL-1 after 24 h reduced the vWF content by about 30%. Bright MHC class-II expression was induced only by IFN-gamma. In conclusion, some of the immunoregulative cytokines might play an important role in the control of HUVEC proliferation.

Cell Division↗
PubMed1993

Effects of neurogenic bladder dysfunction in utero seen in neonates with myelodysplasia.

Twenty neonates with myelodysplasia were prospectively evaluated during the first month of life with urodynamic studies, contrast voiding cystourethrograms (VCUG) and renal ultrasound scans. Ten of 20 infants had abnormal VCUGs--6 with vesicoureteric reflux (VUR) and 4 with bladder trabeculation alone. Only 2/20 neonates had abnormal ultrasounds--both with hydroureteronephrosis secondary to VUR. Elevated leak point pressure (LPP) and/or detrusor sphincter dyssynergia (DSD) were present in 10/20 infants--6 with elevated LPP and DSD, 3 with elevated LPP alone and 1 with DSD alone. Eight of 10 neonates with DSD or elevated LPP had abnormal VCUGs--4 with VUR and 4 with bladder trabeculation alone. Conversely, 8/10 neonates without DSD or elevated LPP had normal VCUGs. Contrast VCUG performed shortly after birth, therefore, is essential for the discovery of bladder trabeculation and reflux. There is a strong correlation between an abnormal VCUG and the presence of DSD and elevated LPP, suggesting that neurogenic bladder dysfunction in utero can lead to these structural abnormalities.

Abnormalities, Multiple↗
PubMed1993

A highly sensitive immunoenzymometric assay for the determination of angiogenin.

A polyclonal antibody to human recombinant angiogenin was prepared in rabbits using a Pam3CysSerGly conjugate. The antibody was then used to develop the first highly sensitive enzyme-labelled immunometric assay for this vascularisation inducing and tumour associated protein. The assay was suitable for quantification of angiogenin in body fluids between 2.5 and 0.05 micrograms/l. The mean intra-assay imprecision was 6.0% and the inter-assay imprecision 7.9%. Angiogenin in human plasma was found to lie in the range of 0.38 to 0.11 mg/l with a mean of 0.25 +/- 0.07 mg/l.

Angiogenesis Inducing Agents↗
PubMed1993

[Pediatric liver transplantation and related live donor. Technical and ethical considerations].

With improved results of liver transplantation, the number of candidates is increasing. However the scarcity of suitable grafts from cadaveric donors remains a limitation. In spite of the use of full size or reduced size grafts or partial grafts from split livers, some children still die while waiting for liver transplantation. We describe a successful orthotopic liver transplantation in a 10 months old female using the left lateral lobe (segments II and III) from her 27 years old father. The child suffered from biliary atresia, her condition was deteriorating with intractable ascites and increasing jaundice. The father asked us to give a part of his own liver to his daughter. The concept of this innovative therapy had already been submitted to a research-ethics consultation which gave us favorable conclusions. After careful donor evaluation, the left lateral lobe was harvested on July 22, 1992, including the left hepatic artery, left portal vein and left hepatic vein; hepatic artery for segment IV, which arose from the right structures, was preserved, The graft was immediately transplanted orthotopically after recipient total hepatectomy with inferior vena cava preservation. Cold ischemia time was 1 hour and 45 minutes, revascularization of the graft was homogeneous from the very beginning and its early function was excellent. Thirteen days after the operation, the donor was discharged in good condition. The child was reoperated at day 9 for a small biliary leak originating from the cut surface of the liver. After resolution of an episode of rejection and an intra-abdominal abscess, the child was discharged in good health with normal liver function 1 month post-transplant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[A new approach to the mechanism of vestibular response to caloric stimulation].

Barany's classical hydrodynamic theory has been called into question by the zero-gravity Spacelab experiments, and several new hypotheses are put forth to explain the vestibular response to caloric stimulation. We have developed a mathematic model based on the analysis of an experimental model of the semicircular canal, incorporating observations done with zero-gravity and with gravity. Two purely mechanical phenomena are involved: one one hand, the modification of the hydrostatic pressure on both sides of the cupula due to a temperature variation if the semicircular canal is not in the horizontal plane in normal gravity conditions; on the other hand, local changes in endolymph pressure and volume due to the mechanical and osmotic properties of the canal, which are independent from gravity and from the position of the canal. These mechanical processes, though not exclusive, are predominant and therefore sufficient to explain the caloric response of the vestibulum in all cases.

Caloric Tests↗
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↗
PubMed1984

A new viscoelastometer for studying the rheological properties of bronchial mucus in clinical practice.

In clinical practice, a wide variety of drugs are given to modify the rheological properties of bronchial mucus but they are frequently not correctly chosen because there is not a simple apparatus available for the routine measurement of the mucus viscoelasticity. We designed a new viscoelastometer which is easy to operate and permit accurate measurement of the viscoelastic properties of mucus. The system has a Couette geometry and requires a sample of 1 ml. The outer cylinder is thermostated and rotates at a constant rate. The resulting torque is measured on the inner cylinder using a microdisplacement transducer. The inner cylinder is suspended by a special wire system which maintains a constant 0.75 mm gap between the two cylinders. The apparent viscosity is calculated up to 100 Pa.s. at a low shear rate (0.4 s-1) and the elasticity is analyzed by a stress relaxation method. The characteristics of the apparatus and the typical viscoelasticity behaviour of several sputum samples are reported.

Bronchi↗