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Biomedical subjects

S Bonnet

Publications and source records attributed to S Bonnet.

At least 37 records · Page 2Linked to original sources
PubMed1999

Radiation-induced changes in nucleotide metabolism of two colon cancer cell lines with different radiosensitivities.

PURPOSE: To investigate changes in nucleotide metabolism after irradiation. MATERIALS AND METHODS: HT29 and SW48 human colon carcinoma cells were exposed to 60Co gamma-rays at doses ranging from 0 to 7.5 Gy. At different times after irradiation, the activities of nine enzymes involved in nucleotide metabolism were measured, the levels of thymidine kinase and deoxycytidine kinase proteins were evaluated by Western blot, and cell-cycle kinetics were analysed by flow cytometry. RESULTS: Changes in enzyme activities concerned not purine but pyrimidine metabolism and essentially the salvage pathway for deoxyribonucleotide synthesis. They were greater in the less radiosensitive HT29 cells. The levels of thymidine kinase and deoxycytidine kinase proteins changed in parallel with their activities. The metabolic changes in irradiated cells did not seem to be due to S-phase transition and the pattern of enzyme activity changes was different from that observed in proliferative cells. CONCLUSIONS: Radiation-induced changes in the salvage pathway for pyrimidine deoxyribonucleotide synthesis were observed. These findings could be exploited in cancer therapy because higher enzyme activities after irradiation suggest that radiation exposure may render cells more sensitive to the drugs activated by these enzymes.

Cell Cycle↗
PubMed1999

Effect of ligand and DNA binding on the interaction between human transcription intermediary factor 1alpha and estrogen receptors.

Hormonal regulation of gene activity is mediated by nuclear receptors acting as ligand-activated transcription factors. To achieve efficient regulation of gene expression, these receptors must interact with different type of molecules: 1) the steroid hormone, 2) the DNA response element, and 3) various proteins acting as transcriptional cofactors. In the present study, we have investigated how ligand and DNA binding influence the in vitro interaction between estrogen receptors (ERs) and the transcription intermediary factor hTIF1alpha (human transcriptional intermediary factor 1alpha). We first optimized conditions for the coactivator-dependent receptor ligand assay to lower ED50, and we then analyzed the ability of various natural and synthetic estrogens to allow the binding of the two types of proteins. Results were compared with the respective affinities of these ligands for the receptor. We then developed a protein-protein-DNA assay allowing the quantification of cofactor-ER-estrogen response element (ERE) complex formation in the presence of ligand and used measurements of fluorescence anisotropy to define the equilibrium binding parameters of the interaction. We demonstrated that the leucine-charged domain of hTIF1alpha is sufficient to interact with ERE-bound ERalpha in a ligand-dependent manner and showed that binding of ERalpha onto DNA does not significantly affect its hormone-dependent association with TIF1alpha. Finally, we show that, mainly in the absence of hormone, hTIF1alpha interacts better with ERbeta than with ERalpha independently of the presence of ERE.

Binding Sites↗
PubMed1999

[Preservation of the native aortic valve in the treatment of aortic aneurysmal dilatation].

Mechanical valve conduit replacement of the aortic root is a durable and appropriate procedure for aortic root dilatation with or without aortic aortic insufficiency. But this procedure may sacrifice an anatomically salvageable aortic valve and requires a life-long anticoagulation with its attendant thromboembolic versus haemorrhagic risks, which is not ideal for young active patients. Recently, two techniques of aortic root replacement with aortic valve sparing have been described, based on experimental data. The first one is Yacoub's procedure (1983), where the correction of the aortic root is performed by correcting the sinotubular junction and replacement of the aortic sinuses with an appropriately tailored Dacron graft (remodelling). The second technique was described by David (1992). In this one, the aortic root reconstruction is performed by reimplanting the aortic valve in a tubular Dacron graft (reimplantation). Since 1993, we have been interested in these procedures and the aim of this study was to examine the perioperative and intermediate term results of these techniques. From 1993 to 1998, 14 patients had either reimplantation of the aortic valve (3 patients) or remodelling of the aortic root (11 patients). Patients' ages ranged from 17 to 57 years (40.2 +/- 7.9 years). Four patients had Marfan's syndrome (29%). There were 11 cases of aortic insufficiency, three 1+ (21.4%), 3+ (21.4%), seven 2+ (50%) and one 3+ (7.2%). All the patients had morphologically normal aortic leaflets. The mean diameter of the sinuses was 57 +/- 4 mm. There was no acute or chronic dissection. The left ventricular function was measured as the percentage of the fractional shortening of the left ventricular diameter. The mean of the fractional shortening was 38.3 +/- 4%. There was no mortality and all patients underwent early and late follow-up echocardiography. The 14 patients have only mild or no insufficiency, which has not progressed in any patient. No other valve-related complication has occurred. Aortic valve-sparing replacement of the aortic root is an excellent procedure for patients with aortic root dilatation and anatomically salvageable valves. The long-term results are still unknown but it seems an attractive alternative to composite replacement of the aortic valve and descending aorta. Morbidity and mortality rates are very low, even lower than a Bentall procedure, while the savings in cost and human lives due to the absence of a mechanical valve prosthesis are significant.

Adolescent↗
PubMed1998

Efficient reamplification of differential display products by transient ligation and thermal asymmetric PCR.

A new method for specific reamplification of DDRT-PCR products is presented. After transient ligation of the primary DDRT-PCR fragments into a T-vector, the cDNAs of interest were reamplified by hemi-nested PCR and thermally asymmetric cycles. In contrast to the originally described protocol, this method of reamplification is specific, sensitive, reproducibly gives a high yield of DNA and allows direct sequencing of the reamplified product without purification or cloning.

Animals↗
PubMed1998

[Levels of malaria transmission: methods and parameters].

Evaluation of malaria transmission levels is necessary to compare ecologically diverse areas and to assess the effectiveness of efforts to control the disease. The purpose of this report is to describe useful techniques for descriptive epidemiology and potentially pertinent indicators regarding the three links in the epidemiological chain: transmission from mosquito to man, transmission from man to mosquito, and sporogonic cycle. Standards for evaluation of transmission from mosquito to man are now well established. Techniques and resulting data, mostly entomological, have been validated in numerous multicenter and multidiscipline studies before and after implementation of control measurements. Evaluation of transmission from man to mosquito has not yet been extensively studied. Gametocyte index does not appear to be a good indicator of infectivity in mosquitoes. Two other parameters that have been proposed in the literature are rate of human infectivity to mosquitoes and probability that a bloodmeal will be infectious. However these evaluation techniques have been neither subjected to comparative study nor validated in epidemiological surveys. The third factor for evaluation of malaria transmission levels involves sexual development of the gametocytes (sporogonic cycle) in the vector. Two indicators that might be useful in this regard are quantification of early-stage parasites in the stomach of the mosquito and study of blood factors in subjects in whom inhibition transmission has been documented. Since these methods have been used only sporadically, further study will be needed to validate this approach to evaluate transmission level.

Animals↗
PubMed1997

Coloboma, mental retardation, hypogonadism, and obesity: critical review of the so-called Biemond syndrome type 2, updated nosology, and delineation of three "new" syndromes.

Biemond syndrome type 2 (BS2) is classically regarded as a recessively inherited condition (MIM 210350) comprising mental retardation, coloboma, obesity, polydactyly, hypogonadism, hydrocephalus, and facial dysostosis. Clinically, the disorder is closely related to Bardet-Biedl syndrome. Few cases have been reported, most of them before 1970. We present clinical data on three mentally retarded sporadic cases with coloboma, obesity, and hypogenitalism (in two of them), fitting as first glance a diagnosis of BS2. A review documents striking clinical variability among the patients said to have BS2. We propose a new nosology of those cases and delineate several new clinical forms. Purported BS2 cases may be divided into: (1) Bardet-Biedl syndrome with fortuitous coloboma or aniridia, (2) BS2 sensu stricto, a recessively inherited syndrome of sexual infantilism, short stature, coloboma, and preaxial polydactyly without obesity, only known from the original report, (3) a "new" dominantly inherited form of colobomatous microphthalmia occasionally associated with obesity, hypogonadism, and mental retardation, to which our observations belong. (4) cytogenetically proven Rubinstein-Taybi syndrome (one case), (5) an unclassifiable, early lethal familial syndrome resembling Buntinx-Majewski syndrome, and (6) a "new" coloboma-zygodactyly-clefting syndrome. The latter two syndromes may result from chromosomal anomaly.

Abnormalities, Multiple↗
PubMed1997

Both estradiol and tamoxifen decrease proliferation and invasiveness of cancer cells transfected with a mutated estrogen receptor.

Previous studies have shown that, after wild-type estrogen receptor (ER) transfection in ER-negative breast cancer cells, estradiol but not tamoxifen prevents growth, invasiveness and metastasis of these cells in mice. Because an ER mutation at position 400 converts the triphenylethylene antiestrogen, OH-tamoxifen into a full estrogen agonist, we transfected this mutated form of human ER in an ER-negative rat cancer cell line. This was aimed at inducing an inhibitory, estrogen-like response of tamoxifen in these cells. In two stable ER-positive transfectants, OH-tamoxifen inhibited cell growth and invasiveness in vitro as efficiently as estradiol. The pure antiestrogen, ICI 164,384, was not agonistic alone and antagonized estrogen action. In contrast, the three compounds were ineffective in control mock-transfected cells. When injected into ovariectomized nude mice, ER-negative mock-transfected cells formed tumours which were significantly stimulated by estradiol and inhibited by tamoxifen treatment. This indicates that estradiol and tamoxifen altered the growth of ER-negative tumours via a general effect on the host response. Surprisingly, the hormone responsiveness of ER-positive tumours developed from ER-transfected cells did not significantly differ from that of ER-negative (mock-transfected) tumours. We conclude that transfection of a mutated human estrogen receptor inhibited, through an estrogenic activity of tamoxifen, the growth and invasiveness of these cancer cells in vitro. However, the low expression of ER did not allowed us to obtain the same effect of tamoxifen in vivo.

Animals↗
PubMed1997

Effect of high ambient temperature on feed digestibility in broilers.

The effect of chronic heat exposure on feed digestibility of broilers was investigated. Eighty 4-wk-old male chickens were brooded in individual battery cages in two controlled-environment rooms at a constant ambient temperature (22 or 32 C) until 6 wk of age. They were equally distributed into three treatments: 22 C, ad libitum feed consumption (22AL); 32 C, ad libitum feed consumption (32AL), and 22 C, pair-feeding on the daily feed intake of heat-exposed chickens (22PF). Broilers were fed either a standard corn-soybean meal diet (control diet) or a practical seasonal diet containing several ingredients including wheat, spring pea, and animal fat (summer diet). Digestibility of energy, dry matter, protein, fat, starch, and nitrogen, and total mineral balances were measured between 38 and 42 d of age. Apparent metabolizable energy content of summer diet was significantly decreased in 32AL compared to 22AL, whereas AME of the control diet did not change. Nitrogen retention was significantly reduced in 32AL birds compared to 22AL and 22PF birds, irrespective of the diet. Taking into account these differences in nitrogen balance, AMEn was reduced under hot exposure: -72 and -155 kcal for control and summer diets respectively, in 32AL compared to 22PF chickens. This reduction could be explained by a significant decrease of nutrient digestibility:protein: -4.2 percentage units irrespective of the diet, fat: -1.7 and -5.2 percentage units for control and summer diets respectively, and starch: -4.2 percentage units for summer diet. It thus appears worthwhile to take into account such reduction in digestibility to formulate practical diets for brooding under hot conditions. High quality oil and protein sources should also be used instead of low quality feedstuffs, like animal sources, in such conditions.

Animal Feed↗
PubMed1997

[Orthodontic contribution in sleep apnea].

This study details the role that the orthodontist can play, when faced with sleeping obstructive apneas and snoring phénomena. Of special importance are knowledge of cranio-facial growth, radiographic exam and cephalometric analysis: they mainly help to understand all the aspects of this specific syndrome, and reveal the interest for a neuro-orthodontic or a neuro-surgical orthodontic approach.

Adult↗
PubMed1997

[How to correct astigmatism?].

The total astigmatism is measured by an automatic refractor. The astigmatism is corrected by a cylindric lens. For children cycloplegia is required. For children below school age an astigmatism is corrected only if it exceeds 2d. Children older than 6 years will benefit from correction of astigmatism if this is more than 1d. Prescription will be progressive to be supported.

Adult↗
PubMed1997

[Colored filters in the treatment of severe photosensitivities. Introduction to a pilot study].

Among photosensitive patients, the use of colored filters sometimes leads to a clear improvement of comfort. After a general review of theory, we start on the way we take care of these patients and the way filters are fitted and made. We only present here a preliminary work. A subsequent study or accurate informations of colored filters will be published later. The aim is to set up a methodic procedure in order to find the best selection of the recommended spectral curve and the best way to follow the progress of the patient as regards the wearing and the effect of the filter. An overview of our cases is presented.

Color↗
PubMed1996

A comparison of the energy availability for chickens of ground and whole grain samples of two wheat varieties.

1. The objective of this study was to examine whether the energy availabilities of two wheat samples, which differed in endosperm hardness, were changed when they were fed ground or as whole grains to chickens. Wheat samples of a variety Haven (hard endosperm) and a variety Riband (soft endosperm), both harvested in 1993 from the same growing site, were used in the experiment. 2. True metabolisable energy (TMEn) was measured in a flock of 24 adult cockerels and the mean of all the samples was 14.68 MJ/kg dry matter (DM). The TMEn of ground wheat was 0.306 MJ/kg DM greater (P < 0.05) than whole grain. There was no significant difference (P > 0.05) in TMEn between the Riband and Haven wheat samples and there were no (P > 0.05) variety x wheat form interactions. 3. The apparent metabolisable energy (AMEn) of the wheat samples was determined with 96 broiler chickens from 19 to 27 d of age. Different amounts of either whole or ground wheat samples were added to a basal diet. Extrapolation of the regression lines indicated AMEn concentrations (MJ/kg DM) of ground Haven 14.33, whole Haven 14.28 ground Riband 14.33 and whole Riband 14.51. There was no evidence (P > 0.05) that whole grain wheat had a different AMEn than ground wheat. 4. A feeding trial used 192 broiler chickens in 48 cages from 24 to 42 d of age. They were fed on a broiler grower diet either mixed with ground wheat before pelleting or with the pelleted grower diet loosely mixed with the whole wheat. There were no differences (P > 0.05) between the 2 wheat varieties or the diet form in growth rates or food conversion ratios. The growth rates of the broilers given a conventional grower and finisher dietary regimen tended (P > 0.05) to be slightly greater than the broilers given the wheat-diluted diets.

Animal Feed↗