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Biomedical subjects

M Delmelle

Publications and source records attributed to M Delmelle.

At least 19 recordsLinked to original sources
PubMed1997

[Belgian registry of thyroid cancer. Preliminary epidemiological characteristics revealed by a retrospective study (1988-1995). Belgian Thyroid Cancer Study Group].

The aim of a cancer registry is to study the incidence of cancer in a well-determined population and to allow epidemiological research to the setting up of diagnosis and therapeutic strategies. The Belgian Thyroid Cancer Study Group (BTCSG) was founded in 1990. In the present study we report data collected from 1988 to 1995 in 397 patients with a differentiated (papillary and follicular) thyroid carcinoma living in the french-speaking area of Belgium. The sex ratio female/male is 3.5 and the median ages at the diagnosis, is similar (45 yrs, 12-82) in both sexes. Seven cases of thyroid cancer were registered in young patients less than 18 yrs old. Thyroid carcinoma were associated with multinodular goiter in more than 50% cases. Cancer was bilateral in 17%. Papillary histological type accounts for 84% in our series while its diagnosis was established in 45% at early clinical stages (TO-T1). These observations could probably be related with 1) broader indications and more aggressive options for the surgical removal of diffuse multinodular goiter, 2) more sophisticated pathologic examinations that might have led to the detection of a greater incidence of occult carcinomas, incidentally discovered. Lymph nodes metastases were present at the time of diagnosis in 20%, especially in young patients. The risk for local and/or lateral recurrence or distant metastases is significantly related to the size of the tumor, histologically verified lymph node metastases and the values of the EORTC prognostic index (> or = 50) that additionally takes into account the differentiation of the tumor. Considering our short median follow-up time of 25 months, it is currently too early to define if the controversial attitude about the extent of surgery (total thyroidectomy plus I131 or individualized surgery) can also negatively influence the risk for recurrence. In our series, eight patients died of thyroid cancer.

Adolescent↗
PubMed1995

Survival of patients with radiation enteritis of the small and the large intestine.

We reviewed the clinical and survival data of 108 consecutive patients who presented with radiation enteritis between 1965 and 1981. One hundred and two (94%) had been irradiated for carcinoma of the cervix uteri. The median follow-up was of 11 years. The median time of occurrence of severe radiation-induced lesions (obstruction, perforation) after radiotherapy was of 18 months, against 10.5 months for mild symptoms (e.g., tenesmus) and 9 months for rectal bleeding (p < 0.001). Cox survival analysis taking into account the stage of the cancer and the age at diagnosis showed that rectal bleeding is a factor with a prognosis significantly poorer than the mild symptoms (p = 0.05), equivalent to that of the severe complications. We conclude that in the evaluation of patients who underwent radiotherapy for abdominal or pelvic tumours, rectal bleeding should be considered as a sign of serious radiation-induced complication.

Abdominal Neoplasms↗
PubMed1986

Preliminary report on the rigid disc lens.

Theoretically, a circular and lenticular implant is the most appropriate for implantation in the capsular bag. Various prototypes have led to a single-piece model in polymethylmethacrylate with a bioconvex 7-mm optic and a 9-mm total diameter. This so-called disc lens has been implanted in 61 eyes. The longest follow-up is 18 months. Thus far, the clinical results are excellent. It appears that this 9-mm disc lens permits centration without acting as a spring in the capsular bag. A large mydriasis and the use of viscoelastic material are mandatory for inserting the rigid disc lens. A circular implant appears to be an advance in IOL design adapted to the capsular bag configuration. A greater number of cases and longer follow-up are necessary to evaluate the rigid disc lens.

Equipment Design↗
PubMed1984

Adriamycin and derivatives interaction with the mitochondrial membrane: O2 consumption and free radicals formation.

Adriamycin induces the formation of semiquinone free radicals, O(2) and OH. species, in beef heart intact mitochondria, submitochondrial particles and complex I-III containing proteoliposomes. Free radicals were detected by the use of Electron Spin Resonance (ESR) spectroscopy with the spin trapping method. However, to observe transient oxygen species in intact mitochondria, a flow technique was mandatory. ESR results were compared with oxygen consumption measurements. Since free radicals could be involved in the mechanism of the adriamycin induced cardiotoxicity, it was essential to design new adriamycin derivatives which do not generate radicals. From the study of two adriamycin analogs (N-acetyl-adriamycin and 5-Iminodaunorubicin), it was shown that oxygen radicals formation require both the binding of the drug to the mitochondrial membrane and a quinone function associated with the drug structure. The data reported here might be useful in the synthesis of less cardiotoxic compounds.

Animals↗
PubMed1983

Architecture and dynamics of microvillar photoreceptor membranes of a cephalopod.

Microvillar membranes of cephalopod photoreceptors, Eledone aldrovandii were analysed with respect to their protein and lipid composition. Molecular dynamics of this membrane type were investigated by ESR measurements using frog rod outer segment membranes as a reference system. The photoreceptor membrane is composed of about 56 wt% protein and 44 wt% lipid. Rhodopsin (mol wt 51 000) represents at least 70% of the membrane protein. The molar ratio of phospholipid to cholesterol to rhodopsin is about 55:24:1. Phosphatidylcholine (28.9 mol%) and phosphatidylethanolamine (27.8 mol%) are the major phospholipids. The ESR measurements suggest that the cephalopod photoreceptor membrane is less fluid than from rod outer segment membranes although the major phospholipids show remarkable high levels of polyunsaturated fatty acids (e.g. 88 mol% in phosphatidylethanolamine). It is concluded that the lower fluidity of microvillar membranes results in part from high cholesterol content and that a restricted mobility of rhodopsin in this membrane does not result only from the fact that the membrane is rolled into a microvillar structure.

Animals↗
PubMed1983

Photoacoustic spectroscopy of bacteriorhodopsin photocycle.

Photoacoustic spectroscopy was applied to study the energetics and the kinetics of the slow intermediates of the bacteriorhodopsin photocycle. An analysis of the modulation frequency dependence of the photoacoustic signal allowed us to estimate the enthalpy changes and the kinetic parameters associated with those intermediates. The effects of pH, salt concentration, and protein aggregation were studied. Three photoacoustic transitions were found. The two low frequency transitions were attributed to O660 and M412, respectively. The third transition was interpreted as resulting from a protein conformational change undetected spectrophotometrically. The frequency spectra were simulated between 5 and 180 Hz at pH's 5.1, 7.0, and 8.9 assuming a branching in the bacteriorhodopsin photocycle at the M412 level. The enthalpy changes associated with M412 and O660 were computed and compared with the experimental values.

Acoustics↗
PubMed1982

Fusion and lipid exchange in vesicles containing lipophilic spin labels.

Lipophilic non-electrolyte spin labels greatly accelerate the fusion of unilamellar vesicles of dipalmitoylphosphatidylcholine when the system is maintained below the lipid phase transition. Differential scanning calorimetry and centrifugation measurements show that the transformed vesicles are large and probably unilamellar. Differential scanning calorimetry and fluorescence depolarization measurements were also carried out on mixtures of labeled dipalmitoylphosphatidylcholine vesicles and of vesicles composed of pure dimyristoylphosphatidylcholine. A mixing of the membrane components is observed when the vesicles are incubated above the transition temperature of the two constituent lipids. However, the process does not involve a real fusion of the entire vesicles. An exchange of lipid and label monomers between the two lipid phases seems to occur. These observations are discussed in view of the molecular organization of the spin label within the dipalmitoylphosphatidylcholine matrix below and above the lipid transition temperature.

Liposomes↗
PubMed1981

Effect of compression on rat-liver mitochondrial membranes. A biochemical and morphological study.

When rat-liver mitochondria are subjected to compression at 0 degrees C, they become permeable to sucrose and the latency of malate dehydrogenase disappears. Freeze fracture electron microscopy shows smooth areas devoid of particles in fracture faces of the membranes. The effects of pressure can be inhibited as the temperature increases. Such results are explained by supposing that compression increases the transition temperature of mitochondrial membrane lipids above 0 degrees C and causes their freezing.

Animals↗
PubMed1980

Imipramine and lipid phase transition in inner mitochondrial membrane.

As ascertained by freeze-fracture electron microscopy, imipramine prevents lateral phase separation from taking place in inner mitochondrial membranes at sub-zero temperatures. Electron spin resonance (ESR) measurements performed on mitochondrial membranes labeled with the N-oxyl-4',4'-dimethyloxazolidine derivative of 16-ketostearic acid, show that the spin probe motion is markedly inhibited below 0 degree C and that 5 mM imipramine attenuates the temperature effect. These results are explained by supposing that imipramine is able to decrease the transition temperature of the inner mitochondrial membrane lipids as it does for simple lipid systems.

Animals↗
PubMed1980

Spin label partitioning in lipid vesicles. A model study for drug encapsulation.

In this paper we attempt to outline some features which determine the encapsulation of small molecules into lipid vesicles. Spin labels derived from five carboxylic acids of different lengths were synthesized and incorporated in varying amounts into multilamellar and unilamellar vesicles made up of four different phosphatidylcholines. The influence on the release process of the bilayer rigidity and of the hydrophobicity of the entrapped molecule was systematically studied. The hydrophobicity is of critical importance and was estimated by measuring the partition coefficient (P) between octanol and buffer. In multilamellar vesicles, molecules characterized by extreme P values (log P less than -0.3 and log P greater than 5) can be efficiently entrapped. The rate of leakage is related to the P value according to a bell-shaped curve. Moreover, gel state of the bilayer and long acyl chains of the lipids are properties which favor a good entrapment. Small unilamellar vesicles may be formed in the presence of high concentrations of hydrophilic and lipophilic spin labels. However, the formation of unilamellar vesicles produces a significant reduction of the internal volume and of the entrapped water-soluble spin lables. High fractions of lipid-soluble spin labels can be incorporated in unilamellar vesicles but the vesicle stability is diminished.

Carboxylic Acids↗