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Biomedical subjects

C Duyckaerts

Publications and source records attributed to C Duyckaerts.

At least 199 records · Page 11Linked to original sources
PubMed1985

[Baló's concentric sclerosis: lesions restricted to the pons].

A clinico-pathological case of Baló's concentric sclerosis is reported. Besides the rarity of the disease, this case was interesting because of the late onset of the illness (50 years) the normality of the CSF and the localization of the lesions which were restricted to the pons.

Autopsy↗
PubMed1985

[Chiasmatic radionecrosis after multifractionated radiotherapy of a temporal glioma].

A 45-year-old male received split course multiple daily fractionated radiotherapy for an anaplastic left parieto-temporal astrocytoma. A total dose of 60 grays was delivered by 15 fractions of 2 grays given in 5 days and repeated after a rest period of 15 days. Forty grays were delivered to the whole brain and 20 grays to the tumor area. No surgery or radiosensitizer or chemotherapy were used at any time. The patient noted progressive loss of vision in both eyes and became blind 9 months after irradiation. Post-mortem study revealed 2 areas of radionecrosis in the chiasma and corpus callosum, corresponding to the dose of 57-60 grays. The necrotic area were at a distance of the tumor remnants. The high Daily Dose Multifractionation schedule may be responsible for the radionecrosis.

Astrocytoma↗
PubMed1984

Spontaneous modification of the oxoglutarate translocator in vivo.

In studying the oxoglutarate translocator of rat-heart mitochondria over many years, we have observed an unexpected decrease in its efficiency. It has been divided by 2.48 +/- 0.07, (S.E.M.) for the exchange of external oxoglutarate for internal malate at 2 degrees C when the internal-malate concentration is 4 mM and is accompanied by an increase in its concentration (multiplied by 1.61 +/- 0.02, S.E.M.). The affinity of the external sites of the translocator for the external oxoglutarate is unchanged as well as the binding and kinetic cooperativities of the external oxoglutarate. This shows that the external side of the translocator has not been modified and suggests that its central part has not been modified either. The apparent Michaelis constant of the internal malate is increased (multiplied by 1.74 +/- 0.23, S.E.M.) suggesting that the translocator has been modified on its matricial side. Some control experiments show that a change in the diet of the rats, despite its effect on the fatty-acid content of the mitoplasts, is probably not responsible for the observed modification. As it is nevertheless very likely that changes of the oxoglutarate translocator have occurred in vivo, it is proposed that the observed modification has a genetic origin. The existence of two antagonist changes which are not directly related suggests that one of them is a response of the organism against the other; thus the oxoglutarate translocator may play a regulatory rôle in certain physiological conditions.

Animals↗
PubMed1984

[Baló's concentric sclerosis].

A clinico-pathological case of concentric sclerosis (Baló type) is reported. A 30-year-old man experienced dizziness, nausea and vomiting. Twelve days later he developed gait disturbances. Neurological examination showed broad based gait, brisk tendon reflexes, bilateral extensor plantar responses, right hemihypoesthesia, cerebellar dysmetria, and a left lateral gaze palsy. CSF examination showed, 520 mg p. 100 ml protein, 7500 red blood cells, 31 lymphocytes and 9 polymorphonuclear leukocytes/mm3, 18 p. 100 gammaglobulin. Three CT scans were performed and showed a round hypodensity in the parieto-occipital white matter with contrast enhancement on one occasion, and several other hypodensities in the contralateral parieto-occipital white matter and in both frontal lobes. 23 days after the onset of the disease, the patient became comatose. A cerebral biopsy was obtained from one of the frontal lesions. He died from aspiration bronchopneumonia 2 months after the first signs. Neuropathological examination showed numerous concentric zones of demyelination which involved the white matter of both hemispheres, brain stem, and cerebellum. On light microscopy sudanophilic myelin breakdown products were numerous in the bands of demyelinisation. Astrocytic proliferation was marked, with frequent Rosenthal fibers. Edema was noted in some lesions. Myelin-axonal dissociation was obvious, but some axonal swelling were observed. Electron microscopy demonstrated the integrity of oligodendrocytes and of blood vessels and confirmed the prominent alterations of the astrocytes. Fifteen similar cases of the literature have been reviewed. The present case seems to be the first one with CT scan examination and electron microscopic study of a brain biopsy. The nosological situation of Baló's disease among the inflammatory demyelinating diseases of the group of MS is discussed.

Adult↗
PubMed1983

Conformational changes and possible structure of the oxoglutarate translocator of rat-heart mitochondria revealed by the kinetic study of malate and oxoglutarate uptake.

Initial rates of the exchanges [14C]malateout:malatein, ([14C]oxoglutarate + malate)out:malatein and ([14C]malate + oxoglutarate)out:malatein catalysed by the oxoglutarate carrier of rat-heart mitochondria have been studied under conditions where internal and external substrates may be varied. It is shown that contrary to external oxoglutarate which induces a conformational change of the translocator subunit to which it binds, external malate does not induce conformational changes during its binding and is a Michaelian substrate. The study of the effect of external malate on the rate of oxoglutarate uptake shows that external malate and external oxoglutarate are competitive. External oxoglutarate affects the catalytic rate constant of malate uptake in a modulated way. After substrate binding, the exchange reaction between an external dicarboxylate and an internal dicarboxylate is accompanied by conformational changes. The particular form of the rate equation strongly suggests that during a first step the external substrate bound to an external binding subunit at the external surface of the membrane, and the internal substrate bound to an internal binding subunit at the internal surface of the membrane, are transferred to a catalytic subunit (channel?) deeper in the membrane. Two models, one with a single channel, and the other with several associated channels, are proposed. It is demonstrated that a binding subunit which has transferred its substrate to a catalytic subunit is left in a conformation which does not depend on the substrate that has 'passed through it'. It is also demonstrated that all the catalytic subunits are identical. These theoretical deductions allow a simple description of the complicated effect that external oxoglutarate has on the rate of malate uptake. The fact that all the external binding subunits are equivalent regarding external malate binding and that all the catalytic subunits are identical support the view that the mitochondrial preparation contains a single species of oxoglutarate translocator and not an isozymic mixture.

Animals↗
PubMed1983

Status spongiosus in the course of treatment of malignant gliomas.

Two cases of fatal encephalopathy which appeared in the course of treatment of malignant gliomas are described. CT scan showed diffuse, low density, non-enhanced lesions of the white matter. Pathological findings showed that the CT scan aspects corresponded to status spongiosus without demyelination. We were unable to find similar reports in the literature.

Brain↗
PubMed1982

Interaction of clavulanate with the beta-lactamases of Streptomyces albus G and Actinomadura R39.

The reactions of beta-lactamases of Actinomadura R39 and Streptomyces albus G with clavulanate proceed along branched pathways. Both enzymes perform the hydrolysis of this beta-lactam with rather high efficiencies (kcat. = 18s-1 and 52s-1 respectively). If large clavulanate/enzyme ratios are used, complete inactivation of the enzymes is observed. At lower ratios, inactivation is only partial. Irreversible inactivation occurs after 400 and 20000 turnovers for the A. R39 and S. albus G enzymes respectively. With the A. R39 beta-lactamase, a transiently inhibited complex is also formed that remains undetectable with the S. albus G beta-lactamase. Kinetic models are presented and studied for the interaction between clavulanate and both enzymes. A tentative general reaction scheme is also discussed.

Actinomycetaceae↗
PubMed1982

Interaction of beta-iodopenicillanate with the beta-lactamases of Streptomyces albus G and Actinomadura R39.

The beta-lactamases of Streptomyces albus G and Actinomadura R39 are inactivated by beta-iodopenicillanate. However, in contrast with the beta-lactamase I from Bacillus cereus, they also efficiently catalyse the hydrolysis of the inactivator; with the S. albus G enzyme, kcat. is larger than 25s-1 and the number of turnovers before inactivation is 515. With the A. R39 enzyme, kcat. is larger than 50s-1 and the number of turnovers before inactivation is 80. After hydrolysis of the beta-lactam amide bond, the product rearranges into 2.3-dihydro-2,2-dimethyl-1,4-thiazine-3,6-dicarboxylate, which exhibits an absorption maximum at 305 nm.

Actinomycetaceae↗
PubMed1981

[Clinical symptoms and anatomical locations in primary haemorrhages of the basal ganglia. A neuropathological study of 64 cases (author's transl)].

The signs, symptoms and courses of 64 cases of "primary" haematoma of the basal ganglia have been retrospectively studied, and the main clinical data have been analyzed in relation to the location and extent of the bleeding. Onset with hemiplegia, accompanied or not by impaired consciousness, was more frequent with intermediate and lateral haematomas than with medial haematomas (p less than 0.001). Among patients with initial hemiplegia, impaired consciousness was more frequent with intermediate and medial haematomas than with lateral haematomas (p less than 0.005). At a later stage, patients with intermediate and lateral haematomas more often went into deep coma than those with medial haematomas (p less than 0.01). There were no statistically significant differences between the three anatomical groups with regard to frequency of other signs and symptoms or duration of the disease before death occurred.

Basal Ganglia↗
PubMed1980

Kinetic mechanism of the exchanges catalysed by the adenine-nucleotide carrier.

Initial rates of the exchange ADPin/ADPout catalysed by the adenine-nucleotide carrier of rat-heart mitochondria have been studied under conditions where internal and external ADP may be varied. The initial rate was measured within 1 s by the carboxyatractyloside-stop method, using a rapid-mixing technique. The double-reciprocal plots v0(-1) versus [ADP]out-1 at different internal-ADP concentrations and v0(-1) versus [ADP]in-1 at different external-ADP concentrations exhibit straight-line relationships having a common point of intersection on the axis of ordinates. These results demonstrate the essential role of a ternary complex and thus exclude the ping-pong mechanism generally accepted. The kinetic equation implies a strong positive cooperativity in the binding of the two substrates. Two models are proposed: (a) the ternary complex performs the exchange and the transport of the substrates in a single step; (b) the carrier is mobile and transports the substrates one by one, the formation of a ternary complex being needed to release the first product.

Adenosine Diphosphate↗
PubMed1979

Kinetic and binding properties of the oxoglutarate translocator of rat-heart mitochondria.

The kinetic study of the oxoglutarateout/malatein exchange through the inner mitochondrial membrane of rat-heart mitochondria has been compelted and extended to higher external-oxoglutarate and to lower internal-malate concentrations. It has been found that the external oxoglutarate inhibits the exchange at high concentration. This excess-substrate inhibition is preceded by four jumps. The kinetic-saturation curve by the internal malate presents an apparent positive cooperativity that may be interpreted in different ways. The independence of the effects of the two substrates on the initial rate has been observed again and supports the conclusions reached in previous work. A method for the determination of oxoglutarate binding to the external face of the inner membrane is described. The binding curve shows four intermediary plateau regions that reflect significant apparent K-effects, alternatively negative and positive. For external-oxoglutarate concentrations below the region of excess-substrate inhibition, the binding-saturation curve and the kinetic-saturation curve are similar, demonstrating that K-effects are predominant. A particularly wide intermediary plateau that seems to correspond to half saturation of the active sites is common to both saturation curves. A clear lack of proportionality between the two curves at low oxoglutarate concentrations seems to indicate that more than one catalytic-rate constant is implied in the exchange kinetics. Two models of the oxoglutarate carrier are presented. Both lead to a minimum degree of 10:10 for the equation of the binding of oxoglutarate to the catalytic sites. In the first model this corresponds to ten subunits associated into a single oligomer while in the second model this results from a mixture of monomeric, dimeric, trimeric and tetrameric associations.

Animals↗